阅读说明：本技术 利用包含羟基的脂肪族聚合物制造金属铸件或硬化模制件的方法 (Method for producing metal castings or hardened moldings using aliphatic polymers containing hydroxyl groups ) 是由 克劳斯·里曼 尼古拉·曼奇尼 格拉尔德·拉德古尔迪耶 赫尔曼·利伯 尼尔斯·齐默尔 于尔根 于 2018-12-18 设计创作，主要内容包括：描述了一种(i)用于制造金属铸件或(ii)制造用于铸造金属铸件的硬化模制件的方法。另外,描述了一种包含含有羟基的结构单元且已借助于醚化交联的脂肪族聚合物作为用于铸造金属铸件的模制件的粘合剂的用途。同样描述了一种用于铸造金属铸件的模制件,其包含至少一种模制原料及包含脂肪族聚合物或由其构成的硬化粘合剂,该脂肪族聚合物包含含有羟基的结构单元且已借助于醚化交联。另外,描述了一种可按照根据本发明的方法制造的硬化模制件以及用于在根据本发明的方法中使用的模制材料混合物。(A method is described for (i) producing a metal casting or (ii) producing a hardened molding for casting a metal casting. Furthermore, the use of an aliphatic polymer which contains hydroxyl-containing structural units and has been crosslinked by means of etherification as a binder for moldings for casting metal castings is described. Also described is a molding for casting metal castings, comprising at least one molding base material and a hardening binder which comprises or consists of an aliphatic polymer which comprises hydroxyl-containing structural units and has been crosslinked by means of etherification. Furthermore, a hardened molded part that can be produced according to the method according to the invention and a molding material mixture for use in the method according to the invention are described.)

1. A method for (i) producing a metal casting or (ii) for producing a hardened molded part for use in casting a metal casting, the molded part being selected from a mold, a core and a riser, comprising the steps of:

-providing or manufacturing a moulding raw material,

-providing or manufacturing (a) an aqueous mixture comprising one or more aliphatic polymers, each comprising a hydroxyl-containing structural unit of formula (i),

–CH2-CH(OH)-(i)，

-providing or producing (b) an aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors as a catalyst for etherification of the hydroxyl groups of the one or more aliphatic polymers,

combining the moulding raw material with (a) the aqueous mixture comprising one or more aliphatic polymers and (b) the aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors to a moulding material mixture,

-shaping the moulding material mixture,

and is

Hardening the shaped molding material mixture into a hardened molded part,

heating the shaped molding material mixture so that

-the thermally unstable acid precursor present in the moulding material mixture decomposes and releases acid

And/or

-the hydroxyl groups of the one or more aliphatic polymers are crosslinked in the presence of the one or more acids to etherify the hydroxyl groups,

and is

-removing water from the heated, shaped molding material mixture.

2. The method of claim 1, wherein

-before or while shaping the moulding material mixture, setting the total moisture content of the moulding material mixture such that a moulding material mixture is produced which can be blown into a moulded part, preferably a riser or core, and/or a moulding material mixture which can be punched into a moulded part, preferably a mould;

and/or

-hardening the shaped molding material mixture by at least the following steps: by heating the shaped molding material mixture and removing water from the heated shaped molding material mixture until a water-resistant hardened molded part is produced,

and/or

Shaping the moulding material mixture by blowing, preferably in a blow-moulding machine, or by introduction into a moulding box,

and/or

The moulding material mixture contains sand, preferably selected from the group consisting of silica sand, zircon sand, olivine sand, chromite sand, mullite sand and mixtures thereof, and the moulding material has a solids fraction of more than 95 wt. -% based on the total mass of the moulding material mixture,

and/or

-minimizing or avoiding foam formation or bubble formation in the moulding material mixture when performing the method, preferably in one or two steps selected from the group consisting of:

-combining the moulding feedstock with (a) the aqueous mixture comprising one or more aliphatic polymers and (b) the aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors into a moulding material mixture, preferably free of aromatic compounds and/or free of phenolic resins

And is

-shaping the moulding material mixture.

3. The method of any of the preceding claims, wherein

Heating of the shaped molding material mixture to a temperature in the range from 100 ℃ to 300 ℃, preferably in the range from 150 ℃ to 250 ℃, particularly preferably in the range from 180 ℃ to 230 ℃,

and/or

-removing water from the heated, shaped molding material mixture by one or more measures selected from the group consisting of: is conducted through a heated gas, evacuated and dried in a drying device,

preferably by conducting heated gas through the molding material mixture, particularly preferably by conducting heated air through the molding material mixture.

4. The process according to any of the preceding claims, wherein the aliphatic polymer used

Can be produced by means of at least partial hydrolysis of polyvinyl acetate,

and/or

Dissolved in the aqueous mixture comprising it, preferably at least 90% by weight, particularly preferably at least 95% by weight, based on the total mass of the aliphatic polymer used.

5. The method of any of the above claims, wherein the one or more aliphatic polymers comprise one or more polyvinyl alcohols,

the polyvinyl alcohol used is preferably used as a whole

Having a degree of hydrolysis of >50 mol% (i.e. in the range of 50.1 mol% to 100 mol%), which is preferably determined according to the method as described in the document DE 102007026166A 1 paragraphs [0029] to [0034],

particularly preferably having a degree of hydrolysis in the range from 70 mol% to 100 mol%, more particularly preferably in the range from 80 mol% to 100 mol%, which is preferably determined according to the method according to DIN EN ISO 15023022017-02 draft, appendix D,

and/or

-has a dynamic viscosity in the range from 0.1 to 30 mPas, preferably in the range from 1.0 to 15 mPas, particularly preferably in the range from 2.0 to 10 mPas, determined according to DIN 53015:2001-02 at 20 ℃ using a 4% (w/w) aqueous solution of the total polyvinyl alcohol, respectively.

6. The method according to any one of the preceding claims,

wherein the molding stock comprises:

-one or more particulate refractory solids selected from:

oxides, silicates and carbides, respectively, containing one or more of the following elements: mg, Al, Si, Ca, Ti, Fe and Zr;

mixed oxides, mixed carbides and mixed nitrides, each containing one or more of the following elements: mg, Al, Si, Ca, Ti, Fe and Zr;

and

-graphite

And/or

-one or more particulate light fillers, preferably selected from:

core-shell particles, preferably having a glass core and a refractory shell, particularly preferably having a bulk density in the range of 470g/l to 500 g/l; preferably as described in document WO 2008/113765;

-spheres, preferably spheres consisting of fly ash;

-composite particles, preferably as described in document WO2017/093371a1, living as manufactured according to document WO2017/093371a 1;

-perlite, preferably expanded perlite, particularly preferably closed cell microspheres consisting of expanded perlite, preferably as described in document WO 2017/174826;

rice hull ash, preferably as described in document WO 2013/014118;

-an expanded glass,

-a hollow glass sphere,

and

hollow ceramic spheres, preferably hollow α -alumina spheres.

7. The method of any of the preceding claims, wherein

The ratio of the total mass of the aliphatic polymer used to the total mass of the moulding raw material used is in the range from 0.2:100 to 13:100, preferably in the range from 0.3:100 to 10:100, particularly preferably in the range from 0.5:100 to 9:100,

and/or

-the ratio of the total mass of the used aqueous mixture (a) comprising one or more aliphatic polymers and the sum of the total mass of the used aqueous mixture (b) comprising one or more acids and/or one or more thermally labile acid precursors to the total mass of the used molding raw materials is in the range of 1:100 to 50:100, preferably in the range of 1.5:100 to 40:100, particularly preferably in the range of 2:100 to 35: 100;

and/or

The ratio of the total mass of the acid and/or thermally labile acid precursors used to the total mass of the aliphatic polymer used is in the range from 1:5 to 1:50, preferably in the range from 1:10 to 1:50, particularly preferably in the range from 1:20 to 1:40 and very particularly preferably in the range from 1:25 to 1: 35.

8. The method according to any one of the preceding claims, wherein the one or more acids and/or the one or more thermally labile acid precursors are selected from the following:

inorganic, preferably water-soluble, protic acids having a pKa value of ≦ 7, preferably a pKa value ≦ 5, particularly preferably a pKa value ≦ 3,

-an organic protic acid, preferably a monoprotic organic protic acid, having a pKa value of ≦ 7, preferably a pKa value ≦ 5, and particularly preferably selected from: methanesulfonic acid, formic acid, acetic acid, lactic acid and ascorbic acid,

-lewis acids, preferably water-soluble lewis acids, particularly preferably selected from: boron trifluoride and the chlorides and bromides of boron, aluminum, phosphorus, antimony, arsenic, iron, zinc and tin,

and

salts which can be thermally decomposed into acids (thermally labile acid precursors), preferably selected from:

ammonium salts of mineral acids, e.g. NH₄NO3, preferably NH₄Cl，

Sulfates and chlorides of trivalent metal ions, preferably FeCl₃、AlCl₃、Fe₂(NO₃)₃、Al₂(NO₃)₃、Fe2(SO4)₃And Al₂(SO₄)₃，

And

sulfates of alkanolamines, preferably monoethanolamine.

9. The method according to any of the preceding claims, preferably according to claim 8, wherein the one or more acids and/or the one or more thermally labile acid precursors, preferably one or at least one of the acids of the plurality of acids, is selected from the group consisting of:

inorganic, preferably water-soluble, protonic acids having a pKa value of ≤ 3

And/or

Phosphoric acid and sulfuric acid.

10. The method (i) according to any of the preceding claims, having the additional step of:

contacting the hardened molded article with a cast metal to produce a metal casting, wherein the cast metal preferably hardens upon contact with the hardened molded article.

11. The method according to any of the preceding claims, preferably according to claim 10, wherein

-the cast metal is selected from: aluminum, magnesium, tin, zinc and alloys thereof

And/or

-the temperature of the cast metal during casting is not higher than 900 ℃ and the temperature of the cast metal during casting is preferably in the range of 600 ℃ to 900 ℃.

12. Use of an aliphatic polymer cross-linked by etherification, preferably of a correspondingly cross-linked polyvinyl alcohol, in the casting of metal castings, said aliphatic polymer comprising in each case a hydroxyl-containing structural unit of the formula (i):

–CH2-CH(OH)-(i)

it is used as an adhesive for moulded parts selected from moulds, cores and risers.

13. A molded article selected from a mold, a core and a riser for use in casting a metal casting, said molded article comprising:

-at least one moulding raw material,

and

a hardened binder comprising or consisting of an aliphatic polymer crosslinked by etherification, said aliphatic polymer comprising hydroxyl-containing structural units of the formula (i),

–CH2-CH(OH)-(i)

preferably comprising or consisting of polyvinyl alcohol crosslinked by etherification,

wherein it is preferred that, among others,

the ratio of the total mass of the hardened binder to the total mass of the molding material used is in the range from 0.2:100 to 13:100, preferably in the range from 0.3:100 to 10:100, particularly preferably in the range from 0.5:100 to 9: 100.

14. A hardened molded part, preferably according to claim 13, which is or can be produced according to the method (ii) according to any of claims 1 to 11, preferably according to any of claims 1 to 9.

15. A molding material mixture for making a hardened molded article for use in casting a metal casting, the molded article selected from a mold, a core and a riser, the molding material mixture comprising:

-at least one moulding raw material,

-one or more aliphatic polymers, each comprising a hydroxyl-containing structural unit of formula (i),

–CH2-CH(OH)-(i)

-one or more acids and/or one or more thermally labile acid precursors selected from:

inorganic, preferably water-soluble, protic acids having a pKa value of ≦ 7, preferably a pKa value ≦ 5, particularly preferably a pKa value ≦ 3,

-monoprotic organic protic acids having a pKa value of ≦ 7, preferably a value pKa ≦ 5, and particularly preferably selected from: methanesulfonic acid, formic acid, acetic acid, lactic acid and ascorbic acid,

-lewis acids, preferably water-soluble lewis acids, particularly preferably selected from: boron trifluoride and the chlorides and bromides of boron, aluminum, phosphorus, antimony, arsenic, iron, zinc and tin,

and

salts which can be thermally decomposed into acids (thermally labile acid precursors), preferably selected from:

ammonium salts of mineral acids, e.g. NH₄NO3, preferably NH₄Cl，

Sulfates and chlorides of trivalent metal ions, preferably FeCl₃、AlCl₃、Fe₂(NO₃)₃、Al₂(NO₃)₃、Fe2(SO4)₃And Al₂(SO₄)₃，

And

-sulfates of alkanolamines, preferably monoethanolamine,

and

-water.

Technical Field

The invention relates to a method for producing (i) a metal casting or (ii) a hardened molded part for casting a metal casting. The invention further relates to the use of aliphatic polymers which contain hydroxyl-containing structural units and have been crosslinked by means of etherification as binders for moulded parts for casting metal castings. The invention also relates to a molded part for casting metal castings, comprising at least one molding material and comprising or consisting of a hardening binder of an aliphatic polymer which comprises hydroxyl-containing structural units and has been crosslinked by means of etherification. The invention further relates to a hardened molded part that can be produced by the method according to the invention and to a molding material mixture for use in the method according to the invention.

Background

Cast moldings (hereinafter referred to simply as "moldings"), in particular cores (Kerne), molds and risers (including riser caps and riser shells or riser jackets) for use in metal castings are generally composed of a refractory molding material which, depending on the purpose of use, contains one or more refractory solids, for example silica sand, and/or one or more particulate light fillers, for example spheres composed of fly ash, and a suitable binder which imparts sufficient mechanical strength to the moldings after they have been removed from the molding tool (for example a molding core box, such as a core box or molding box, see below). In the uncured state, the mixture of molding material and binder, which optionally can contain further additives, is referred to as molding material mixture.

The refractory solid is preferably present in particulate and free-flowing form, so that it can be introduced into a suitable hollow mold (molding tool, see above) after incorporation into the molding material mixture and densified there. For this purpose, the risers and cores are generally introduced under pressure, i.e. "blow shot", into the mould in a core shooting machine. Smaller molded parts are usually also blown, while larger molded parts, in particular larger molds, are usually formed in a molding box by means of stamping. In general, all molded parts can also be produced by stamping in corresponding molds, for example by hand molding. To obtain a blowable or stampable moulding material mixture, its moisture content, in particular in the case of water-based binders, must be set accordingly, so that the moulding material mixture has sufficient form stability for the respective moulding process, or the ratio of the liquid component of the moulding material mixture to its solid component must be set accordingly.

Molded parts, such as molds, cores and risers, must meet the various typical requirements of a foundry. The manner and extent to which these requirements are met depends essentially on the adhesive used for its manufacture:

after the production of the molded part, i.e. shortly after the removal of the molded part from the production tool, it should have as high a strength as possible. The strength at this point in time ("initial strength") is particularly important for safe handling of the core, mold or riser when removed from the molding tool.

High so-called final strength of the molded part (i.e. the strength of the molded part after complete hardening) and high heat resistance during the actual casting of the metal are also important, in particular for the core and the mold, so that the molded part does not deform under the weight of the cast metal (i.e. retains good shape stability during the casting process, also referred to as "casting strength") and the metal castings produced thereby can be produced as free of casting defects as possible. In this context, it is also important that the moldings used have as clean or smooth as possible, distortion-free or the like surfaces, since surface defects of the moldings are otherwise transferred to the surface of the metal castings produced therewith.

In addition, the high moisture resistance of the molded parts is a great advantage. In general, such high moisture resistance permits a long shelf life of the molded parts, even under conditions which require high climatic conditions (hot, humid climates) and ideally for days or weeks, which makes the production of the molded parts easy or simple to carry out for the first time for inventory and storage thereof. In this way, significant flexibility is achieved in the industry in using these molded parts to make metal castings. It has also been found that in the case of all molded parts for casting metals, in particular in the case of risers, water absorption (for example by absorption of moisture out of the air during storage) can lead to the formation of steam bubbles from the respective water reservoir at high temperatures during the casting of the metal, which steam bubbles can lead to the formation of shrinkage cavities in the metal casting, as a result of which the metal casting then becomes unusable. In extreme cases, an explosion may even occur due to the sudden formation of water vapor. The high moisture resistance of the molded parts is likewise advantageous, since it allows, for example, the use of different types of coating slips and in particular also the use of water-based coating slips. Pasting is a ceramic-based mold release agent, which in some cases should prevent direct contact between the molded part, for example the core, and the metal melt, whereby the molded part can better withstand high thermal stresses during casting of the metal.

In the context of high metal casting quality, it is also desirable that the molded part extracts as little thermal energy as possible from the metal melt, for example due to the reaction of the binder, which may occur, for example, in the known melting reaction of water glass binders. This extraction of thermal energy can cause premature solidification of the metal melt resulting in an incomplete casting. The binder is also characterized by its own absorption of thermal energy, also referred to as its "quenching properties". In particular, in the case of risers, particularly good thermal insulation is desired or required in order to keep the metal melt in the liquid state for as long as possible in the cast metal and to achieve as little shrinkage cavity formation as possible in the metal casting, wherein the shrinkage cavity formation that may occur allows to occur as far as possible outside the finished metal casting (for example only in the riser).

After the casting process is complete, the molded part should then be decomposed as far as possible by the heat emitted from the cast metal, so that it loses its mechanical strength, i.e. the adhesion between the individual particles of the molding material is lost. Ideally, the molded part then disintegrates again into fine particles of the molding material, which can be removed easily and with little residue in the metal cast part. If the molded part is a core, this advantageous disintegration property leads to a particularly good decorability of the metal casting.

In this connection, it is also particularly desirable for the decomposition of the molding, which is usually accompanied by thermal decomposition of the binder, to take place as emission-free as possible, i.e. without emission of unpleasant odours and/or substances harmful to health, in order to keep disturbances or health hazards to personnel working in the foundry as low as possible, to reduce them or, in the ideal case, to prevent them. Such disturbances due to bad odours and/or substances harmful to health can occur in particular when casting is carried out with hot metal melts, in which case, in particular, the risers which usually protrude from the casting mould form the main cause, but can still occur after solidification of the metal casting if it is released ("unpacked" or "demolded") from the casting mould.

Various organic and inorganic binders are known for the production of moulded parts for the foundry industry, all of which have typical limitations or disadvantages.

In the field of organic binders and binder systems, organic binders and binder systems are known which are capable of achieving hardening by cold or hot methods, respectively.

In the case of the thermosetting method, the molding material mixture is heated after shaping, for example by means of a heated molding tool, to a sufficiently high temperature in order to drive off the solvent present in the binder and/or to initiate a chemical reaction which hardens the binder. One example of such a thermal hardening process is the "hot box process". Which is currently used primarily for mass production of cores.

The method, which is carried out essentially without heating the moulding tool for core production, is generally carried out at room temperature or at a temperature due to possible reactions, for example chemical reactions, is referred to herein as a cold-hardening method. For example, the hardening is effected by means of a gas which is conducted through the molding material mixture to be hardened and triggers a corresponding chemical reaction there. One example of such a cold-hardening process is the "cold-box process", which is currently widely used in the foundry industry.

However, both the hot-box process and the cold-box process utilize organic binders based on phenolic resins. Regardless of the composition, the binder has the disadvantage that it sometimes releases large amounts of harmful substances, such as benzene, toluene and xylene, also referred to simply as "BTX", when it decomposes as desired due to the temperatures present during casting of the metal. In addition, casting metals with such organic binders often causes undesirable emissions of odors and fumes or fumes. In the case of some such binder systems, undesirable emissions can even occur during the manufacture and/or storage of the moldings.

As an alternative to the organic binders mentioned above, corresponding inorganic binders are known which have none or only to a much smaller extent during the casting of metals the above-mentioned phenomenon of the release of undesirable odorous or harmful substances. An example of such an inorganic binder is water glass. The corresponding molding material mixture consists essentially of molding material (e.g. silica sand) and water glass (as an aqueous solution of alkali metal silicate). For example by exposure to CO₂The gas hardens the shaped molding material mixture.

However, the use of these inorganic binders involves other typical disadvantages, since the moldings produced from inorganic binders generally have only low strength. This disadvantage is particularly evident shortly after removal of the moulded part from the tool. In addition, the often low moisture resistance of these binders limits the storage capacity of the moldings produced by means of these binders. In addition, inorganic binders often do not exhibit satisfactory disintegration properties, whereby it is then necessary to costly reprocess the metal castings produced with the aid of these moldings. It is also known that water glass bonded risers generally have inferior insulating properties to risers bonded with organic adhesives. Finally, inorganic binder systems, such as water glass, are also known for their considerable self-absorption during the casting of metals, i.e. for the consumption of large amounts of thermal energy, whereby the solidification of the metal melt takes place relatively early, so that casting defects can occur. This applies in particular to the casting of iron and steel.

In the prior art, a series of binders, which may also be organic, have been discussed and methods for producing molded parts using these binders have been proposed:

the document DE-OS 2615714 relates to a molding sand for metal castings.

Document DE 3928858A 1 describes crosslinked hydrogels and a process for their production.

Document US 4487868 relates to compositions for casting cores.

Document EP 0743113 a1 teaches a method of manufacturing inorganic molds.

DE 102007026166A 1 relates to a process for the thermoplastic shaping of polyvinyl alcohol and to the shaped bodies or pellets produced in this way.

Document EP 1721689 a1 describes a method for producing castings.

Document EP 1769860 a1 describes a molding process and a mold produced by said process.

Document WO 2008/110378 a1 teaches a composition for making risers.

Document WO 2017/084851 a1 shows a mould, a method for its manufacture and its use.

Document EP 0608926B 1 (corresponding to DE 69404687T 2) describes a core for a casting process.

However, according to the prior art, there is still a need for a method for producing metal castings or for producing hardened molded parts for use in casting metal castings which achieves one, more and ideally all of the following characteristics:

high initial strength of the moulded part produced by the method;

high final strength of the moulded part produced by the method; if the molded part is produced in fully hardened form by means of its production method, the initial strength can correspond to the final strength;

high casting or heat resistance of the moulded part produced by means of said method;

-a clean and smooth surface of the moulded part produced by means of said method;

the extremely high moisture resistance or extremely high water resistance of the molded parts produced by means of the method results in the best possible or long storage capacity of the molded parts, in particular even under various climatic conditions, and/or the molded parts can be used by means of a water-based slip;

as low a thermal energy absorption as possible and ideally good thermal insulation of the molded part produced according to the method during the casting of metal;

the emission of odorous and/or harmful substances and fumes or fumes from the molded parts produced according to the method is as low as possible during the casting of light metals and their alloys and during the casting of cast iron and steel, in particular under the conditions of metal casting.

In addition, there is a need for binders for molded articles when casting metal castings that have or cause one, more, or ideally all of the advantageous relevant properties described above. Finally, a need arises for a molded article having one, more and ideally all of the relevant properties mentioned in connection with the above-mentioned method.

Disclosure of Invention

It is therefore a primary object of the present invention to provide a method of producing a metal casting or of producing a hardened molded part for use in casting a metal casting, which method results in or has one, more and ideally all of the advantageous properties mentioned above.

Likewise, another object of the invention is to provide a binder for molded parts in the casting of metal castings which has or causes one, more and ideally all of the mentioned relevant properties; and a molding material mixture for use in the above method.

It is also an object of the present invention to provide a moulded article for use in casting metal castings having one, more and ideally all of the relevant properties mentioned in connection with the above method.

It has now surprisingly been found that the main object of the invention, together with further objects and/or sub-objects, is achieved by a method according to the invention for (i) producing a metal casting, or (ii) producing a hardened molded part, for use in casting a metal casting, the metal casting being selected from a casting mould, a core and a riser, the method having the steps of:

-providing or producing a preferably particulate moulding raw material,

-providing or manufacturing (a) an aqueous mixture comprising one or more aliphatic polymers, each comprising a hydroxyl-containing structural unit of formula (I)

-CH2-CH(OH)-(I)，

Providing or manufacturing (b) an aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors as a catalyst for etherification of hydroxyl groups of one or more aliphatic polymers,

combining a molding raw material with (a) an aqueous mixture comprising one or more aliphatic polymers and (b) an aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors to obtain a molding material mixture which is preferably free of aromatic and/or phenolic resins,

-shaping the moulding material mixture,

and is

-hardening the shaped moulding material to obtain a hardened moulded article,

heating the shaped molding material mixture so that

The thermally labile acid precursors present in the molding material mixture decompose and release acid (if thermally labile acid precursors are used in the process according to the invention)

And/or

The hydroxyl groups of the one or more aliphatic polymers are crosslinked with one another in the presence of one or more acids and the hydroxyl groups are (at least partially) etherified,

and is

-removing water from the heated, shaped molding material,

preferably, a hardened molded part selected from the group consisting of a casting mold, a core and a riser is thus produced.

By means of the method according to the invention, molded parts, in particular molds, cores and risers, for the casting industry can be produced with a large number of advantageous properties described below. In the context of the present invention, the term "riser" is also understood here to mean, in addition to the riser, a riser housing, a riser insert and a riser cover.

Therefore, even during casting of iron or steel, the molded article produced by the method according to the present invention has high final strength (after drying or hardening), as well as high casting resistance and high heat resistance. The advantageous smooth and clean surface structure of the molded parts produced by means of the method according to the invention is also of interest. In addition, it can also be shown that the moldings produced by means of the process according to the invention have excellent moisture and water resistance, so that they are extremely suitable for long-term storage for days or weeks, even under difficult climatic conditions (hot humid climates). Furthermore, the molded parts produced by means of the method according to the invention exhibit only a low absorption of thermal energy during the metal casting, which is reflected in a low degree of shrinkage cavity formation, which also occurs only in regions of the cast metal that are relatively far from the actual metal casting (for example in the riser sockets). This property makes the method according to the invention particularly suitable for producing risers, in particular insulated risers. After the metal casting, the molded part produced by means of the method according to the invention is also characterized by an exceptionally advantageous unpacking form, since it disintegrates to a large extent under the effect of the heat released during the metal casting, thereby considerably simplifying the further processing of the metal cast part produced accordingly, since fewer or ideally no further processing steps are required in the metal cast part produced.

A particular advantage of the moldings produced by means of the process according to the invention is their emission properties, in particular during the casting of metals and the unpacking of metal castings which have been produced by means of the moldings produced according to the invention, as a result of which no or hardly any formation of soot or smoke, no or hardly any occurrence of unpleasant odours and/or no or hardly any emission of potentially health-hazardous substances, as frequently occurs when conventional organic casting binders, in particular containing aromatic compounds, for example containing phenolic resins, are used when casting light metals and their alloys, for example when casting aluminum, and when casting iron or steel or when unpacking metal castings produced in this way. This applies in particular to the production of risers according to the method according to the invention. The production of an insulated feeder according to the method according to the invention also shows that there is no or hardly any undesired emission at the relatively low temperatures of the light metal casting. The exothermic riser produced according to the method according to the invention also shows no or hardly any undesirable emissions (e.g. escaping smoke) during or after combustion.

The invention and preferred combinations according to the invention of parameters, characteristics and/or components according to the invention are defined in the appended claims. Preferred aspects of the invention are also illustrated and defined in the following description and examples.

In the above-described process according to the invention, the step of combining the moulding raw material with (a) an aqueous mixture comprising one or more aliphatic polymers and (b) an aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors to obtain the moulding material mixture can be carried out in any technically feasible manner.

Thus, the moulding raw material may first be combined, preferably mixed, with (a) the aqueous mixture comprising the one or more aliphatic polymers, and subsequently (after completion of the above-mentioned combination) the aqueous mixture comprising the one or more acids and/or the one or more thermally labile acid precursors may be combined (b) with the initial charge formed by means of this combination, preferably mixed therewith.

Likewise, it is also possible to first combine, preferably mix, the molding starting material with (b) the aqueous mixture comprising one or more acids and/or one or more thermally unstable acid precursors, in reverse order, and subsequently (after the above-mentioned combination has been completed) to combine (a) the aqueous mixture comprising one or more aliphatic polymers with the initial charge formed by means of this combination, preferably with it.

In addition, it is also possible according to the invention to combine alternately, preferably to mix the molding material with (a) an aqueous mixture comprising one or more aliphatic polymers; and (b) an aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors.

In many cases, a process according to the invention, preferably a process (ii) according to the invention, is also preferred, wherein the aqueous mixture (a) comprising one or more aliphatic polymers and the aqueous mixture (b) comprising one or more acids and/or one or more thermally labile acid precursors are provided or produced by:

-providing or manufacturing an aqueous binder system comprising:

(a) comprising one or more aliphatic polymers

And

(b) an aqueous mixture of one or more acids and/or one or more thermally labile acid precursors, wherein, for the production of a molding material mixture, a molding material and an aqueous binder system are combined, preferably mixed, to give a molding material mixture.

The aqueous binder system preferably comprises one or more aliphatic polymers, each of which comprises hydroxyl-containing structural units of the formula (I), in a total amount in the range from 10 to 40% by weight, preferably in the range from 15 to 35% by weight and particularly preferably in the range from 20 to 30% by weight, based on the total mass (or total weight) of the abovementioned aqueous binder system to be used in the process according to the invention.

The aqueous binder system preferably comprises one or more acids and/or one or more thermally labile acid precursors in a total amount in the range from 0.2 to 10% by weight, preferably in the range from 0.3 to 5% by weight and particularly preferably in the range from 0.4 to 2.5% by weight, based on the total mass (or total weight) of the abovementioned aqueous binder system to be used in the process according to the invention.

In addition to the components mentioned above, i.e. the one or more aliphatic polymers each comprising a structural unit containing hydroxyl groups of the formula (I) and the one or more acids and/or one or more thermally labile acid precursors, the abovementioned aqueous binder system to be used in the process according to the invention preferably comprises only water as further component, so that the components present therein, i.e. the one or more aliphatic polymers each comprising a structural unit containing hydroxyl groups of the formula (I), the one or more acids and/or one or more thermally labile acid precursors and water, in this preferred variant, each amount to 100% by weight.

The moulding raw materials, the aqueous mixture (a) comprising one or more aliphatic polymers, the aqueous mixture (b) comprising one or more acids and/or one or more thermally labile acid precursors and/or the binder system (as explained above) can be combined in a mixed form in a manner known to the person skilled in the art using a stirrer suitable for this purpose.

The choice of which variant is used for the step of combining the molding material with (a) an aqueous mixture comprising one or more aliphatic polymers and (b) an aqueous mixture (or aqueous binder system) comprising one or more acids and/or one or more thermally labile acid precursors to obtain a molding material mixture depends mainly on the state of the individual cases:

if, for example, an aqueous mixture comprising one or more aliphatic polymers (a) having a high dynamic viscosity is used, the highly viscous aqueous mixture (a) is preferably combined first with the molding starting material (and this mixture is then combined with the aqueous mixture (b) comprising one or more acids and/or one or more thermally labile acid precursors) or with a premix obtained by combining the molding starting material with (b) an aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors as described above.

The manufacture of a premix comprising an aqueous mixture of one or more aliphatic polymers (a), for example as a binder system as described above, by combination with an aqueous mixture (b) comprising one or more acids and/or one or more thermally labile acid precursors, is especially preferred if the premix or the binder system is further processed shortly after its manufacture by means of the process according to the invention in that storage of such a premix or such a binder system over a longer period of time leads to a deterioration in quality when such a premix or such a binder system contains one or more free acids.

By making a premix of the aqueous mixture (a) comprising one or more aliphatic polymers, for example as a binder system as described above, in combination with an aqueous mixture (b) comprising one or more thermally labile acid precursors (b) but no one or more acids, it is therefore also preferred if the premix is not further treated according to the process according to the invention shortly after manufacture, since this premix or this binder system without any free acid or acids can be stored even over a longer period of time without or without significantly deteriorating the quality of the premix or the binder system. This is a particular advantage according to a variant of the process according to the invention which comprises providing or producing (b) an aqueous mixture comprising one or more thermally labile acid precursors as a catalyst for etherification of the hydroxyl groups of one or more aliphatic polymers.

The aqueous binder system comprising one or more aliphatic polymers, which in each case comprise hydroxyl-containing structural units of the formula (I), preferably comprises one or more aliphatic polymers in a total amount (concentration) in the range from 10 to 40% by weight, preferably in the range from 15 to 35% by weight and in particular in the range from 20 to 30% by weight, based on the total mass (or total weight) of the aqueous binder system to be used in the process according to the invention, which aqueous binder system comprises one or more aliphatic polymers, which in each case comprise hydroxyl-containing structural units of the formula (I).

The aqueous binder system comprising one or more acids and/or one or more thermally labile acid precursors preferably comprises one or more acids and/or one or more thermally labile acid precursors in a total amount (concentration) in the range of from 0.2 to 10 wt. -%, preferably in the range of from 0.3 to 5 wt. -% and particularly preferably in the range of from 0.4 to 2.5 wt. -%, based on the total mass (or total weight) of the aqueous binder system to be used in the process according to the invention comprising one or more acids and/or one or more thermally labile acid precursors.

In the above-described method according to the invention, the substep of heating the shaped molding material mixture to obtain a hardened molded article during hardening of the shaped molding material mixture is carried out such that the thermally unstable acid precursors present in the molding material mixture are decomposed under the effect of heat to release acid, as long as these thermally unstable acid precursors are used in the method according to the invention. The acid released in this way then likewise serves as the corresponding (at least partially etherified) crosslinking acid in the substep of heating the shaped molding material mixture during hardening of the shaped molding material mixture to give a hardened molded part.

As a result of the catalytic effect of the hydroxyl groups of the aliphatic polymer(s) by means of the acid(s) used, including the acid(s) released by means of thermal action from the thermally labile acid precursor (if present), and at the same time the (at least partial etherification) crosslinking takes place upon heating (under the conditions or preferred conditions according to the process of the invention) and removal of water (under the conditions or preferred conditions according to the process of the invention), the molding material is mixed and, in particular, sufficiently hardened to give a hardened molded part, so that the abovementioned advantageous properties of such a molded part, in particular good moisture resistance or good water resistance, result. It can be assumed that at least partially etherifying the hydroxyl groups of the aliphatic polymer or polymers with one another significantly contributes to the overall and preferably water-resistant hardening of the shaped molding material mixture into a hardened molded part according to the method according to the invention. See below for preferred temperature, acid and thermally labile acid precursors.

Also preferred is a process according to the invention as described hereinbefore, preferably the process (ii) according to the invention (or referred to as preferred process according to the invention in the present context), wherein

Setting the total moisture content, preferably the total moisture content, of the molding material mixture before or during shaping of the molding material mixture, such that a molding material mixture is produced which can be blown into a molded part, preferably a riser or core, and/or can be punched into a molded part, preferably a mold;

and/or

-at least the step of hardening the shaped molding material mixture by heating the shaped molding material mixture and removing water from the heated shaped molding material mixture is performed until a water-resistant, preferably all-round water-resistant hardened molded part is produced,

preferably the temperature is in the range of from 100 ℃ to 300 ℃, preferably in the range of from 150 ℃ to 250 ℃, particularly preferably in the range of from 180 ℃ to 230 ℃;

and/or

Shaping the moulding material by blowing, preferably in a blow-moulding machine, or by introduction into a moulding box, and/or

The moulding material mixture contains sand, preferably selected from the group consisting of silica sand, zircon sand, olivine sand, chromite sand, mullite sand and mixtures thereof, and has a solids fraction of more than 95 wt. -% based on the total mass of the moulding material mixture,

and/or

-minimizing or avoiding foam-like or bubble formation in the moulding material when the method is performed in one or both of the steps preferably selected from:

-combining a molding raw material with an aqueous mixture of (a) an aqueous mixture comprising one or more aliphatic polymers and (b) an aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors to obtain a molding material mixture, preferably free of aromatic compounds and/or free of phenolic resins;

and is

-shaping the moulding material mixture.

In the context of the present invention, the term "moulding tool" is intended to mean any tool used in the casting industry for shaping moulded articles, preferably selected from the group consisting of moulds, cores and risers (including riser caps and riser jackets), in particular moulded article boxes and blow-moulding machines for blow-moulding moulded articles, in particular cores and risers, including core-blowing blow-moulding machines.

In the context of the present invention, the term "moulding box" covers any tool suitable for forming a cast moulding selected from the group consisting of moulds, cores and risers (including riser caps and riser jackets), in particular moulding boxes and core boxes.

In the context of the present invention, the total moisture content of the molding material mixture is understood to be the total content in the molding material mixture of components in liquid form (i.e. in liquid form minus any solids dissolved therein) which are added to or combined with the molding material, expressed in percent by weight based on the total mass (or total weight) of the molding material mixture. The total moisture content of the moulding material mixture comprises the total moisture content and additionally the content of other components, if present, added in liquid form, for example the content of one or more acids added in liquid form.

In the context of the present invention, the total water content of the molding material mixture is therefore understood as the total content of water added to or combined with the molding material (minus any solids dissolved therein) in the molding material mixture, expressed in percent by weight, based on the total mass (or total weight) of the molding material mixture.

Before or during the shaping of the molding-material mixture, the total moisture content, preferably the total moisture content, of the molding-material mixture can be set, for example, in the following manner: correspondingly, a greater or lesser volume of the aqueous component(s) of the molding material mixture, which are (a) the aqueous mixture comprising the aliphatic polymer(s), (b) the aqueous mixture comprising the acid(s) and/or the thermally labile acid precursor(s) and, if present, the aqueous binder system, is combined with the molding starting materials, wherein the concentration of the so-called aqueous component(s) of the molding material mixture, respectively, can be varied or adjusted accordingly by the person skilled in the art, so that in any case the total amount of aliphatic polymer(s) or acid(s) and/or thermally labile acid precursor(s) required or desired for forming the molding material mixture is used. This is possible even during the combining of the moulding raw material with the aqueous mixture, for example when combining the aqueous component with the moulding raw material in portions. Too low a total moisture content or a total moisture content in the molding material mixture can be brought to a suitable value by adding suitable amounts of water.

Prior to or when shaping the molding material mixture, the person skilled in the art can readily set the concentration of the above-mentioned aqueous mixture (or aqueous binder system) and also the total moisture content, preferably the total moisture content, of the molding material mixture with his expert knowledge (for example by varying the amount and type of molding raw material to be used compared to the used aqueous component of the molding material mixture) so that a molding material mixture is produced which can be blow-injected into a molded part, preferably a riser or core, and/or which can be stamped into a molded part, preferably a mold.

The total moisture content, preferably the total moisture content, of the molding material mixture is not allowed to be so high that molding material mixtures are produced which are not sufficiently stable in shape, too soft or even deliquescent for blowing (in particular in molded part blowing machines) or for stamping. However, the total moisture content, preferably the total moisture content, of the molding material mixture is also not allowed to be so low that particles of the molding material of the microparticles cannot be present in the molding material mixture which adhere together sufficiently dimensionally stable for blowing (in particular in a core shooter) or for stamping.

The embodiments described herein provide those skilled in the art with further indications as follows: how the total moisture content, preferably the total moisture content, suitable for the process according to the invention has to be selected to produce the moulding material mixture to be used in the process according to the invention. By setting the total moisture content, preferably the total moisture content, of the molding material mixture in the manner explained hereinabove, the method according to the invention can be advantageously used for the manufacture of various molded parts (molds, cores and risers) and is carried out with customary tools in the casting industry. The method according to the invention can thus be integrated into customary programs already in operation, so that no or no significant changes in the assembly or progress are required in the foundry.

In the context of the present invention, the term "shape-stable molding material mixture" preferably means that, after shaping of the molding material mixture (in particular in a molding tool selected from the group consisting of a molding box, a core box and a corresponding tool as a component of a blow-molding machine) and removal of the molding tool, the molding material mixture retains its shape obtained by shaping for at least 30 minutes (at 20 ℃ and atmospheric pressure), without, for example, deliquescing or disintegrating.

Thus, preferred is a process (ii) according to the invention as described hereinbefore (or referred to herein as a preferred process according to the invention) comprising the steps of:

-combining a moulding raw material with (a) an aqueous mixture comprising one or more aliphatic polymers and (b) an aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors into a shape-stable moulding material mixture.

Preferably, the step of hardening the shaped molding material mixture by heating the shaped molding material mixture and removing water from the heated shaped molding material mixture, preferably in the range of 150 ℃ to 250 ℃, particularly preferably in the range of 180 ℃ to 230 ℃, as given herein, is preferably carried out as explained above until a water-resistant, preferably all-round water-resistant hardened molded part is produced. The time to be selected for carrying out the method until a water-resistant hardened molded part (or an all-round water-resistant hardened molded part) is obtained depends mainly on the size of the molded part to be produced, in particular its wall thickness or volume. Thus, under the conditions of the method according to the invention, it is possible, for example, to harden smaller molded parts, for example, risers or riser caps, to a water-resistant state (or a state of all-round water resistance) already after about 60s to 90s, whereas under the conditions of the method according to the invention, larger molded parts, for example, large cores or molds, are not hardened to a water-resistant state (or all-round water-resistant state) until after a longer period of time, for example, a few minutes, approximately 30 minutes. The precise process conditions, in particular the process times, which are suitable for the purpose of the particular molded part can be selected very easily by the person skilled in the art with the aid of the general technical knowledge and the additional description provided herein. If desired, appropriate simple preliminary tests can be performed to determine appropriate parameters.

In this connection and within the scope of the present invention, the term "molded part hardened to a water-resistant state" preferably means that the molded part produced by the process according to the invention remains form-stable and does not disintegrate (even after removal from water) after complete immersion (i.e. total time of exactly complete immersion for 30 minutes) in deionized water for 30 minutes (horse table) at 20 ℃ and atmospheric pressure; the disintegration is preferably a disintegration without additional external forces. Particularly preferred are water-resistant hardened mouldings, in which the penetration depth measured immediately after their immersion test (under the conditions mentioned above) by means of a core hardness tester GM-578 (from Simpson Technologies GmbH, Switzerland) (according to the operating instructions of the core hardness tester) does not exceed 4mm, preferably 3 mm.

In this connection and within the scope of the present invention, the term "molded article which has hardened to a state of all-round water resistance" means in particular a molded article which is produced according to the process of the present invention in which all internal volume regions (i.e. volume regions which are not adjacent to the outer surface of the molded article) have hardened to a state of water resistance (as defined above). Such an inner volume region can be accessed for inspection purposes, for example, by sawing.

According to a preferred embodiment described hereinbefore, the method according to the invention is carried out at least as far as producing a water-resistant hardened moulding, preferably an all-round water-resistant hardened moulding. After the production of a water-resistant hardened molded part, preferably an all-round water-resistant hardened molded part, under the conditions of the method according to the invention, the hardening by heating the shaped molding material mixture and removing water from the heated, shaped molding material mixture is preferably interrupted immediately. Since it has been found in experiments that prolonged heating of the shaped molding material mixture after a water-resistant hardened molding, preferably an omnidirectionally water-resistant hardened molding, has been obtained and removal of water from the heated, shaped molding material mixture leads to a deterioration of the properties of such excessively heated molding, possibly due to the onset of decomposition of the binder used, i.e. the aliphatic polymer which initially contains hydroxyl groups and has been crosslinked by means of an acid. In order to set suitable process parameters, such as the duration of the step of hardening (in particular heating) the shaped molding material mixture, for the production of a particular molded part by the process according to the invention, such suitable parameters can be determined, for example, in preliminary tests and subsequently used for the mass production of molded parts. The process procedure described hereinbefore ensures that the moldings produced according to the invention acquire or retain their advantageous properties, in particular their good moisture resistance or their good water resistance.

In the above-described preferred embodiment of the method according to the invention, the molding material mixture is shaped by blowing, preferably in a blowing machine (for example a core shooter), or by introducing the molding material mixture into the molding box and preferably punching the molding material mixture in the molding box.

According to the invention, a blow-moulding machine with a heatable moulding box, for example a core shooting machine with a heatable core box, such as a core shooting machine known per se for treating hot-box binders or heat-setting water-glass binders, for example suitable for blow-moulding a moulding material mixture, is provided. The blow-injection machine preferably also has means for passing a gas, preferably warm or hot air, through the shaped molding material mixture.

The molding material mixture that has been blown by means of the blow-molding machine can then be hardened while being heated (by heating and/or by warm or hot air) in a heatable molded part box (e.g. a core box) and the water removed (e.g. by warm or hot air) to obtain a (preferably water-resistant) hardened molded part. If a blow-injection machine with a heatable molding box is not used, the injected molding material mixture can also be cured in another manner, for example (together with the molding tool) in a drying oven, in order to obtain a (preferably water-resistant) cured molded part. The correspondingly suitable method of shaping can be selected by the person skilled in the art depending on the state of the individual case. The molding material mixture for producing the smaller molded parts (e.g. risers or riser caps or smaller cores or molds) is therefore advantageously blown in a blow-injection machine, particularly preferably in a core shooting machine. Advantageously, larger molded parts, such as larger cores or larger dies, are shaped by introducing a suitable molding material mixture into the molding box (or core box) and compacted, preferably by stamping. In the production of such larger moldings, the molded molding material mixture is preferably hardened in the core box or molding box in which it is present to give a hardened (preferably water-resistant) molding.

Preferably, in carrying out the method according to the invention, foam formation or bubble formation in the moulding material mixture can preferably be avoided in the step of combining the moulding raw material with (a) the aqueous mixture comprising one or more aliphatic polymers and (b) the aqueous mixture comprising one or more acids and/or one or more thermally labile acid precursors as a moulding material mixture, preferably free of aromatic compounds and/or free of phenolic resins, and/or in the step of "shaping the moulding material mixture", preferably by minimizing or avoiding the introduction of air or other gases into the moulding material mixture as much as possible in one or both of such steps. Some aliphatic polymers comprising hydroxyl containing structural units of formula (I) may tend to form foam or form bubbles; however, this foam formation or bubble formation is undesirable when producing hardened moldings according to the method according to the invention for use in casting metal castings, for example because the foam-or bubble-containing molding material mixture has a porous structure when hardening to a hardened molding, so that the desired strength and/or heat resistance of the resulting molding is impaired.

Also preferred is a process according to the invention as illustrated hereinbefore, preferably a process (ii) according to the invention (or a process according to the invention as described herein as preferred),

-wherein the shaped molding material mixture is heated to a temperature in the range of 100 ℃ to 300 ℃, preferably in the range of 150 ℃ to 250 ℃, particularly preferably in the range of 180 ℃ to 230 ℃, and/or

-wherein the removal of water from the heated, shaped molding material mixture is effected by means of one or more measures selected from the group consisting of: leading through heated gas, evacuating and drying in a drying device,

preferably by conducting heated gas, particularly preferably by conducting heated air.

The drying means described hereinbefore are preferably selected from the following: drying ovens, convection drying ovens, belt dryers, continuous dryers, tunnel dryers, and drying belts. The drying means is preferably a convection drying oven.

It has been found that the molded parts produced according to the method according to the invention can be hardened in the temperature range specified above, in particular sufficiently and in a relatively short period of time (preferably to a water-repellent state), so that short cycle times can advantageously be used in the production of the molded parts, without the molded parts losing their advantageous properties completely or in part (see above, also from overheating).

It has also been found that by heating the molding material mixture by conducting a heated gas, preferably heated air, through the molded molding material mixture, according to the method according to the invention, water can be removed from the molded molding material mixture in a particularly effective and advantageous manner in combination with the heating of the molding material mixture. In this way, the shaped molding material mixture hardens particularly quickly and completely (also in its interior) to give a hardened molded part. It can be assumed that: the removal of water from the heated, shaped molding material mixture may promote at least partial etherification of the hydroxyl groups of the aliphatic polymer(s), for example by means of shifting the reaction to the desired side (le chatel principle) as known to the person skilled in the art. Sulfuric acid is thus the preferred acid for use in the process according to the invention.

In general, the precise process parameters of hardening the shaped molding material mixture to give a hardened molded part, such as the heating duration, the temperature of the drying oven or of the heated gas, the flow-through time of the heated gas (i.e. the duration of the introduction of the heated gas) and, if used, the pressure of the heated gas) are set largely dependent on the geometry of the molded part to be produced by hardening (for example its size), its weight, its volume and/or its wall thickness. For the suitability of the preliminary tests for determining the parameters suitable for carrying out the method according to the invention, see above.

Also preferred is a process according to the invention as illustrated hereinbefore, preferably the process (ii) according to the invention (or a process according to the invention as described herein as preferred) wherein an aliphatic polymer is used

Can be produced by at least partially hydrolyzing polyvinyl acetate,

and/or

-dissolved in the aqueous mixture comprising it, preferably at least 90 wt.%, particularly preferably at least 95 wt.%, based on the total mass (or total weight) of the aliphatic polymer used.

Also preferred is an inventive process as illustrated hereinbefore, preferably a process (ii) according to the invention (or a process according to the invention as described herein as preferred) wherein the one or more aliphatic polymers comprising hydroxyl-containing structural units of formula (I) comprise one or more polyvinyl alcohols,

the polyvinyl alcohol used is preferably used as a whole

Having a degree of hydrolysis of >50 mol% (i.e. in the range of 50.1 mol% to 100 mol%), as preferably determined by a method as described in paragraphs [0029] to [0034] of document DE 102007026166A 1,

and particularly preferably has a degree of hydrolysis in the range from 70 mol% to 100 mol%, more particularly preferably in the range from 80 mol% to 100 mol%, preferably determined by the method according to DIN EN ISO 15023-022017-02, draft appendix D,

and/or

-has a dynamic viscosity in the range from 0.1 to 30 mPa-s, preferably in the range from 1.0 to 15 mPa-s, particularly preferably in the range from 2.0 to 10 mPa-s, determined using a 4% (w/w) aqueous solution of the total polyvinyl alcohol at 20 ℃ according to DIN 53015:2001-02, respectively.

It has been found that the aliphatic polymer(s) specified above, particularly preferably the polyvinyl alcohol(s) specified above, contribute significantly to the advantageous properties of the molded parts produced according to the invention (when they are treated by the process according to the invention), particularly to the good moisture or water resistance, final strength and casting resistance of the molded parts produced according to the invention.

In addition, it can be assumed that the aliphatic polymer(s) specified hereinabove, particularly preferably the polyvinyl alcohol(s) specified hereinabove, contribute significantly to the advantageous emission properties of the molded articles produced according to the invention or even for their reason (possibly since the aliphatic polymer(s) to be used in the invention do not contain any aromatic components, such as phenolic resins, which are usually mentioned as being responsible for harmful emissions), in particular that little or no smoke or fumes and/or odorous materials and/or harmful substances are emitted during or after the metal casting and that also little or no odorous materials and/or harmful substances are emitted when the molded articles are produced or stored.

The aliphatic polymer or polymers to be used in the present invention are therefore preferably free of aromatic-containing and/or phenolic-containing resin components and/or other components which, under the conditions of the process according to the invention, significantly cause smoke, fumes, odours and/or emissions of harmful substances.

For the reasons explained hereinbefore, the process according to the invention is preferably not carried out in the presence of an organic compound containing an aromatic compound and/or a phenolic resin, or the moulding material mixture produced in the process according to the invention is free of aromatic compound and/or phenolic resin (i.e. the moulding material mixture produced in the process according to the invention preferably does not contain any aromatic compound containing organic compound, such as phenolic resin).

The process according to the invention is preferably not carried out in the presence of furan-containing organic compounds or the molding material mixtures produced in the process according to the invention do not contain any furan-containing organic compounds.

The process according to the invention is preferably not carried out in the presence of alkoxy silicon based compounds or the moulding material mixtures produced in the process according to the invention do not contain any alkoxy silicon based compounds.

Thus, preferred is also a method (ii) according to the invention as illustrated above (or a method according to the invention described herein as preferred), wherein the molding material mixture consists of (or wherein the method is performed such that a molding material mixture consisting of) the following components is produced:

a molding material (preferably particulate),

-one or more aliphatic polymers, each comprising a hydroxyl-containing structural unit of formula (I),

-one or more acids and/or one or more thermally labile acid precursors,

and

-water.

Further, preferred is a process according to the invention as illustrated hereinbefore, preferably a process (ii) according to the invention (or as described herein as preferred according to the invention), wherein the moulding feedstock comprises:

-one or more particulate refractory solids selected from:

oxides, silicates and carbides, respectively, containing one or more of the following elements: mg, Al, Si, Ca, Ti, Fe and Zr;

-mixed oxides, mixed carbides and mixed nitrides, respectively comprising one or more of the following elements: mg, Al, Si, Ca, Ti, Fe and Zr;

and

-graphite

And/or

-one or more particulate light fillers, preferably selected from the following:

core-shell particles, preferably having a glass core and a refractory shell, particularly preferably having a bulk density in the range 470g/l to 500g/l, preferably as described in document WO 2008/113765;

-spheres, preferably spheres consisting of fly ash;

-composite particles, preferably as described in or manufactured according to document WO2017/093371a 1;

-perlite, preferably expanded perlite, particularly preferably closed cell microspheres consisting of expanded perlite, preferably as described in document WO 2017/174826 a 1;

rice hull ash, preferably as described in document WO 2013/014118 a 1;

-an expanded glass,

-a hollow glass sphere,

and

hollow ceramic spheres, preferably hollow α -alumina spheres.

The above-mentioned one or more particulate refractory solids may be utilized individually or in combination with one another and thereby form a molding material to be utilized. Likewise, the above-mentioned light-weight filler of one or more microparticles may be utilized individually or in combination with one another and thereby form the molding raw material to be utilized. Of course, it is also possible to use a combination of one or more particulate refractory solids and one or more particulate lightweight fillers as moulding material to form the moulding material to be used. Depending on the intended use of the method according to the invention, i.e. depending on the molded part to be produced, the person skilled in the art will select a correspondingly suitable molding material. For example, a simple mold can be manufactured by selecting only silica sand as a molding material. In addition, for the production of the risers, it is possible, for example, to select a mixture of silica sand with one or more particulate light-weight fillers, or else to select only one or more particulate light-weight fillers for this purpose, preferably from the light-weight fillers defined above, which are preferred.

In addition to the preferred components mentioned above, the moulding raw material to be used in the process according to the invention may contain further components preferably selected from the group of preferred microparticles consisting of: elemental metal (e.g. aluminium), an oxidant or oxygen source, preferably a metal oxide, particularly preferably an oxide of manganese and/or iron, and an ignition agent. Thus, for example, for producing exothermic risers, the moulding material to be used can contain aluminium, iron oxide, oxidizers known per se for this purpose, spheres and igniters known per se for this purpose.

Also preferred is a process according to the invention as illustrated hereinbefore, preferably a process (ii) according to the invention (or a process according to the invention as described herein as preferred), wherein

The ratio of the total mass of the aliphatic polymer used to the total mass of the moulding raw material used is in the range from 0.2:100 to 13:100, preferably in the range from 0.3:100 to 10:100, particularly preferably in the range from 0.5:100 to 9:100,

and/or

The ratio of the sum of the total mass of the aqueous mixture (a) containing one or more trace polymers used and of the total mass of the aqueous mixture (b) containing one or more acids and/or one or more thermally labile acid precursors used to the total mass of the molding raw materials used is in the range from 1:100 to 50:100, preferably in the range from 1.5:100 to 40:100, particularly preferably in the range from 2:100 to 35: 100;

and/or

The ratio of the total mass of the acid and/or thermally labile acid precursors used to the total mass of the aliphatic polymer used is in the range from 1:5 to 1:50, preferably in the range from 1:10 to 1:50, particularly preferably in the range from 1:20 to 1:40 and very particularly preferably in the range from 1:25 to 1: 35.

As explained hereinbefore, the above-mentioned (numerical) ratio of the sum of the total mass of the aqueous mixture (a) comprising one or more aliphatic polymers used and of the total mass of the aqueous mixture (b) comprising one or more acids and/or one or more thermally labile acid precursors used to the total mass of the molding raw materials used is preferably set such that a preferably shape-stable molding material mixture is produced which can be blow-injected into a molded part, preferably a riser or core, and/or can be punched into a molded part, preferably a mold. Preferably, an aqueous mixture (a) comprising one or more aliphatic polymers or an aqueous mixture (b) comprising one or more acids and/or one or more thermally labile acid precursors, each having a preferred total amount of one or more aliphatic polymers (a) or one or more acids and/or one or more thermally labile acid precursors (b) as specified above, respectively, is utilized. In this connection, it has been verified that the above-mentioned ratios (with correspondingly constant concentrations of the aqueous mixture used) also depend on the type of moulding raw material used: thus, where a molding raw material having a lower bulk density (e.g., lower than silica sand) is utilized, the suitable numerical ratio specified above is generally in the upper portion of the range (i.e., closer to the upper limit of 50:100, preferably 40:100, and particularly preferably 35:100), while where a molding raw material having a higher bulk density (e.g., silica sand) is utilized, the suitable numerical ratio mentioned above tends to be in the lower portion of the range (i.e., closer to the lower limit of 1:100, preferably 1.5:100, and particularly preferably 2: 100).

According to the invention, the ratio of the total mass of the acid and/or thermally labile acid precursors used (or to be utilized) to the total mass of the aliphatic polymer used is in a relatively low value, i.e. there is a relatively low total mass of the acid and/or thermally labile acid precursors used or to be used relative to the total mass of the aliphatic polymer used. Thus, a (significantly) sub-stoichiometric amount of the one or more acids and/or the one or more thermally labile acid precursors (relative to the amount of aliphatic polymer used) is preferably sufficient to carry out the process according to the invention, since the one or more acids preferably serve as catalysts for etherification of the hydroxyl groups of the one or more aliphatic polymers.

The one or more acids and/or one or more thermally labile acid precursors used in the present invention are preferably free of aromatic-containing components, such as phenolic resins and/or other components that cause a significant degree of smoke, odor and/or hazardous material emissions under the conditions of the process according to the present invention.

Also preferred is a process according to the invention, preferably process (ii) according to the invention (or a process according to the invention as described herein as preferred) as hereinbefore specified, wherein the one or more acids and/or one or more thermally labile acid precursors are selected from the following:

inorganic, preferably water-soluble, protic acids having a pKa value of ≦ 7, preferably a pKa value ≦ 5, particularly preferably a pKa value ≦ 3,

-organic protic acids having a pKa value of ≦ 7, preferably a value pKa ≦ 5, and particularly preferably selected from: methanesulfonic acid, formic acid, acetic acid, lactic acid and ascorbic acid,

-lewis acids, preferably water-soluble lewis acids, particularly preferably selected from: boron trifluoride and the chlorides and bromides of boron, aluminum, phosphorus, antimony, arsenic, iron, zinc and tin,

and

salts which can be thermally decomposed into acids (thermally labile acid precursors), preferably selected from:

ammonium salts of mineral acids, e.g. NH₄NO₃Preferably NH₄Cl，

Sulfates and chlorides of trivalent metal ions, preferably FeCl₃、AlCl₃、Fe₂(NO₃)₃、Al₂(NO₃)₃、Fe₂(SO₄)₃And Al₂(SO₄)₃，

And

-sulfates of alkanolamines, preferably monoethanolamine.

In the context of the present invention, "protonic acids" are based onAnd L owry, the acid group concept is classified as an acid compound.

In the context of the present invention, the term "monoprotic organic acid" means an organic acid having exactly one group (e.g. a hydroxyl or sulfonic acid group) which, in the presence of water, can donate a proton (H + ion).

The inorganic, preferably water-soluble, protic acids mentioned above are preferably selected from: phosphoric acid (including condensates thereof, such as pyrophosphoric acid and metaphosphoric acid), phosphoric esters, boric acid, boric esters, sulfuric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, and nitric acid, and are particularly preferably selected from: phosphoric acid, phosphoric ester, sulfuric acid, hydrobromic acid, and hydroiodic acid.

The one or more acids and/or one or more thermally labile acid precursors are preferably selected from the following:

inorganic, preferably water-soluble, protic acids having a pKa value of ≦ 7, preferably a pKa value ≦ 5, particularly preferably a pKa value ≦ 3,

and

-organic protic acids, preferably monoprotic organic protic acids, having a pKa value of ≦ 7, preferably a pKa value ≦ 5, and particularly preferably selected from: methanesulfonic acid, formic acid, acetic acid, lactic acid and ascorbic acid.

The one or more acids and/or the one or more thermally labile acid precursors are particularly preferably selected from:

-inorganic, preferably water-soluble, protic acids having a pKa value of ≦ 5, preferably a pKa value ≦ 3,

and

monoprotic organic protic acids having a pKa value of ≦ 5 and preferably selected from: methanesulfonic acid, formic acid, acetic acid, lactic acid and ascorbic acid.

Also preferred is a process according to the invention, preferably a process (ii) according to the invention (or a process according to the invention as described herein as preferred) as illustrated hereinbefore, wherein the one or more acids and/or one or more thermally labile acid precursors, preferably one or at least one of the plurality of acids, is selected from:

inorganic, preferably water-soluble, protonic acids having a pKa value of ≦ 3

And/or

Phosphoric acid (including condensates thereof, such as pyrophosphoric acid and metaphosphoric acid) and sulfuric acid.

The advantages of the monoprotic organic protic acids mentioned above with pKa values ≦ 5 are: because of its relatively high acid strength and because of having only one acid group in the molecule, it only to a small extent (if at all) generates or participates in a competing reaction in which the hydroxyl groups of the polymer or polymers at least partially catalyze etherification with one another.

It has been found that the above-mentioned inorganic and monoprotic organic acids having pKa values of ≦ 5 and preferably pKa values ≦ 3, respectively, allow a particularly rapid and complete hardening of the shaped molding material mixture into hardened moldings in the process according to the invention, so that the energy consumption and cycle time required for the process are lower and the number of productions per unit time is shorter (and thus higher) than, for example, when weaker acids are used, by means of the reaction time shortened in this way.

It has also been shown that when using weaker acids (e.g.pKa values >5) in the process according to the invention, the ratio of the total mass of the acids used to the total mass of the aliphatic polymer used must also be selected higher (e.g.in the range from 1:5 to 1: 10) than when using inorganic and simple protic organic acids having pKa values of ≦ 5 and preferably ≦ 3, respectively.

Sulfuric acid has proven to be a particularly preferred acid for use in the process according to the invention, notably because it has an acid strength which is particularly suitable for catalyzing the hydroxyl etherification of one or more aliphatic polymers.

Thus, preferred is the process (ii) according to the invention as illustrated hereinbefore (or the process according to the invention as described herein as preferred), wherein

The ratio of the total mass of the acid and/or thermally labile acid precursors used to the total mass of the aliphatic polymer used is in the range from 1:10 to 1:50, particularly preferably in the range from 1:20 to 1:40 and very particularly preferably in the range from 1:25 to 1:35,

and is

The one or more acids and/or one or more thermally labile acid precursors are selected from phosphoric acid and sulfuric acid.

Further, preferred is a method according to the invention, preferably method (i) according to the invention (or a method according to the invention described herein as preferred) as illustrated above, with the following additional steps:

contacting the hardened molded part with a cast metal to produce a metal casting, wherein the cast metal preferably solidifies upon contact with the hardened molded part,

preferably, such that a metal casting is produced.

In the above-described preferred method according to the invention, the cast metal is at least partially and preferably completely liquid when contacting the hardened moulding. Any castable metal or any castable metal alloy, in particular light metals and their alloys (e.g. aluminum, magnesium, tin and zinc), as well as iron and steel, are suitable as casting metals.

In its own studies it has been demonstrated that, when the hardened moulded parts produced according to the invention are brought into contact with cast metal, at most a small amount of soot or smoke or soot is formed, irrespective of the nature of the cast metal, and that in fact no (or ideally no) gaseous aromatic-containing emissions or other emissions potentially harmful to human health are formed, for example by decomposition of the cross-linking binder of the hardened moulded parts under the thermal action of the liquid cast metal. This also applies to relatively low temperatures in the range from 600 ℃ to 900 ℃, so that the above-mentioned preferred process variant (i) is very particularly suitable for producing metal castings in which the casting metal is a light metal or a light metal alloy: it is known that at the relatively low temperatures present when casting light metals (compared to the temperatures when casting iron or steel), the cold box binders currently generally used generally only decompose incompletely thermally, so that in this case, in particular, during the casting of metals and during unpacking of the molds, particularly intense smoke, soot or soot formation and intensive release of gaseous, aromatic-containing emissions occur; this process is often accompanied by unpleasant odors and potentially harmful to human health. In contrast, this disadvantage occurs only to a substantially lesser extent or ideally does not occur when using the molded parts produced by the process according to the invention or when carrying out the above-mentioned preferred process variant (i) of the invention. The above-mentioned preferred process variant (i) of the invention is particularly effective when producing the risers or riser caps (process variant (ii)) or when using them as molded parts (process variant (i)) when carrying out the process according to the invention, since there is a particularly strong risk of emission from the risers or riser caps during casting of the metal, since they are located at the contact surface between the casting mold and the ambient air.

Thus, in many cases it is preferred that the process according to the invention, preferably the process (i) according to the invention (or the process according to the invention described herein as preferred) as illustrated hereinbefore, wherein

-the cast metal is selected from: aluminum, magnesium, tin, zinc and alloys thereof

And/or

-the temperature of the cast metal is not higher than 900 ℃ during casting, and the temperature of the cast metal is preferably in the range of 600 ℃ to 900 ℃ during casting.

In addition, it is preferred that the method (ii) according to the invention (or the method according to the invention described herein as preferred) for producing a hardened riser as explained above is used in the casting of metal castings, wherein

The molding material comprises:

-one or more particulate light fillers selected from the following:

core-shell particles, preferably having a glass core and a refractory shell, particularly preferably having a bulk density in the range 470-500g/l, preferably as described in document WO 2008/113765;

-spheres, preferably spheres consisting of fly ash;

-composite particles, preferably as described in or manufactured according to document WO2017/093371a 1;

-perlite, preferably expanded perlite, particularly preferably closed cell microspheres consisting of expanded perlite, preferably as described in document WO 2017/174826;

rice hull ash, preferably as described in document WO 2013/014118;

-an expanded glass,

-a hollow glass sphere,

and

hollow ceramic spheres, preferably hollow α -alumina spheres

And the molding material further comprises or does not comprise:

-one or more particulate refractory solids selected from:

oxides, silicates and carbides, respectively, containing one or more of the following elements: mg, Al, Si, Ca, Ti, Fe and Zr;

-mixed oxides, mixed carbides and mixed nitrides, respectively comprising one or more of the following elements: mg, Al, Si, Ca, Ti, Fe and Zr;

and

-graphite.

The invention also provides the use of aliphatic polymers which are crosslinked by etherification and which each comprise a hydroxyl-containing structural unit of the formula (I)

-CH2-CH(OH)-(I)

Preference is given to correspondingly (at least partially) crosslinked polyvinyl alcohols which are used as binders for moldings selected from the group consisting of casting molds, cores and risers when casting metal castings.

The statements made above with regard to the method according to the invention apply analogously also with regard to preferred embodiments of the use according to the invention and possible combinations of one or more relevant aspects with one another, and vice versa.

The invention further relates to a molded part selected from the group consisting of molds, cores and risers for use in casting metal castings, said molded part comprising:

at least one (preferably particulate) moulding material and

-a hardened binder comprising or consisting of an aliphatic polymer comprising in each case a hydroxyl-containing structural unit of the formula (I)

-CH2-CH(OH)-(I)

And comprises or consists of polyvinyl alcohol crosslinked (at least in part) by etherification.

Wherein

The ratio of the total mass of the hardened binder to the total mass of the mould material used is preferably in the range from 0.2:100 to 13:100, preferably in the range from 0.3:100 to 10:100, particularly preferably in the range from 0.5:100 to 9: 100.

With regard to preferred embodiments of the inventive molded part and possible combinations of one or more relevant aspects with one another, the statements made above with regard to the method according to the invention apply analogously, and vice versa.

In the moldings according to the invention, the hydroxyl groups of the crosslinked polymers are (at least for the most part) no longer present in free form as a result of crosslinking with one another by etherification, but rather participate (at least for the most part) in the formation of ether groups.

The ranges specified above for the ratio of the total mass of the hardened binder to the total mass of the molding raw material used in the molded part correspond to the ranges specified for the ratio of the total mass of the (uncrosslinked) aliphatic polymer used to the total mass of the molding raw material used. The respective mass ratios in the moldings according to the invention differ from the respective mass ratios used in the process according to the invention in individual cases and can be slightly lower in the moldings according to the invention, in particular due to condensation water released and removed during the etherification crosslinking. However, this difference is not important in practice.

Preferred are molded articles according to the invention as described above, wherein the hardened adhesive is an adhesive which has hardened to be water-resistant (as defined above), particularly preferred are adhesives which have hardened to be water-resistant on all sides (as defined above).

The present invention also provides a hardened moulded article selected from a mould, a core and a riser, which is produced by or can be produced by the method (ii) according to the invention as hereinbefore described (or the method according to the invention described as preferred herein).

With regard to preferred embodiments of the molded part produced or producible according to the invention and possible combinations of one or more relevant aspects with one another, the statements made above with regard to the method according to the invention apply analogously, too, and vice versa.

In addition, the invention also provides a molding material mixture, preferably free of aromatic compounds and/or phenolic resins, for producing hardened molded parts selected from the group consisting of casting molds, cores and risers for use in casting metal castings, which comprises or consists of (i.e. no further components other than the components mentioned below may be present):

at least one (preferably particulate) moulding material,

-one or more aliphatic polymers, each comprising a hydroxyl-containing structural unit of formula (I),

-CH2-CH(OH)-(I)

-one or more acids and/or one or more thermally labile acid precursors selected from:

inorganic, preferably water-soluble, protic acids having a pKa value of ≦ 7, preferably a pKa value ≦ 5, particularly preferably a pKa value ≦ 3,

-monoprotic organic protic acids having a pKa value of ≦ 7, preferably a pKa value ≦ 5 and particularly preferably selected from the following: methanesulfonic acid, formic acid, acetic acid, lactic acid and ascorbic acid,

-lewis acids, preferably water-soluble lewis acids, particularly preferably selected from the following: boron trifluoride and the chlorides and bromides of boron, aluminum, phosphorus, antimony, arsenic, iron, zinc and tin,

and

salts which can be thermally decomposed into acids (thermally labile acid precursors), preferably selected from the following:

ammonium salts of mineral acids, e.g. NH₄NO₃Preferably NH₄Cl，

Sulfates and chlorides of trivalent metal ions, preferably FeCl₃、AlCl₃、Fe₂(NO₃)₃、Al₂(NO₃)₃、Fe₂(SO4)₃And Al₂(SO₄)₃，

And

-sulfates of alkanolamines, preferably monoethanolamine,

and

-water.

With regard to preferred embodiments of the molding material mixture according to the invention and possible combinations of one or more relevant aspects with one another, the statements made above with regard to the method according to the invention, the use according to the invention, the molded part according to the invention and the molded part produced or producible by the method according to the invention apply analogously as well, and vice versa.

Preferred is a molding material mixture according to the invention for producing a hardened riser as described above for use in casting metal castings, wherein the molding material comprises or consists of the following components:

-one or more particulate light fillers selected from the following:

core-shell particles, preferably having a glass core and a refractory shell, particularly preferably having a bulk density in the range 470-500g/l, preferably as described in document WO 2008/113765;

-spheres, preferably spheres consisting of fly ash;

-composite particles, preferably as described in or manufactured according to document WO2017/093371a 1;

-perlite, preferably expanded perlite, particularly preferably closed cell microspheres consisting of expanded perlite, preferably as described in document WO 2017/174826;

rice hull ash, preferably as described in document WO 2013/014118;

-an expanded glass,

-a hollow glass sphere,

and

-hollow ceramic spheres, preferably hollow α -alumina spheres;

and the molding material further comprises or does not comprise:

-one or more particulate refractory solids selected from:

oxides, silicates and carbides, respectively, containing one or more of the following elements: mg, Al, Si, Ca, Ti, Fe and Zr;

-mixed oxides, mixed carbides and mixed nitrides, respectively comprising one or more of the following elements: mg, Al, Si, Ca, Ti, Fe and Zr;

and

-graphite.

The molding-material mixture according to the invention as described hereinbefore (or the preferred molding-material mixture according to the invention as described hereinbefore) is suitable and proposed for the method according to the invention as described hereinbefore.

Drawings

Fig. 1 shows the remaining components of a control standard bend test bar "B cold box" in an iron casting after casting. It can be seen that the remaining parts of the chill box standard bend test bar remain virtually completely in the iron casting and are extremely difficult to remove (poor core removal capability, see example 7).

FIG. 2 shows the remaining components of a control standard bend test bar "B-V38" in an iron casting after casting. It can be seen that the remaining parts of the standard bending test bar "B-V38" can be easily and practically completely removed from the iron casting (good core removal capability, see example 7)

Fig. 3 shows the remaining components of a standard bending test bar "B-E61.3V1" produced by the method according to the invention in an iron casting after casting. It can be seen that the remaining parts of the standard bending test bar "B-E61.3V1" can be removed very easily and practically completely from the iron casting (very good core removal capability, see example 7).

Figures 4 to 9 described below show cross sections of a cut iron casting sawn in the middle (along the support surface of a standard bending test bar) so that the cavity created by the standard bending test bar in the iron casting (after its iron casting removal) is divided in half in the middle of the length of the iron casting (see example 7 for more details). Half of the cross-section of the cavity (negative cast) made by the standard bending test bar is located in the upper half of the sawn metal casting (the "upper mold half" made during iron casting by the standard bending test bar section at the top) and half is located in the lower half of the sawn metal casting (the "lower mold half" made during iron casting by the standard bending test bar section at the bottom).

Fig. 4 shows a cross section of the upper mold half of an iron casting. Here the upper half of the cavity (cast negative) formed by the standard bending test bar B-V38 (control) after removal of the metal cast can be seen. It can be seen by means of a straight wooden screed placed on the upper side of the casting negative, the casting negative has a significant concave (away from the wooden screed) deformation in the middle, which occurs due to the deformation of the standard bending test bar B-V38 during casting using iron. Cores that are not dimensionally stable during casting cannot be used to make metal castings.

Fig. 5 shows a cross section of the lower half of the mold of an iron casting. Here can be seen the lower half of the cavity (cast negative) formed by a standard bending test bar B-V38 (control) after removal of the metal casting. As can be seen with a straight wooden screed placed on this lower side of the casting negative, the casting negative has an easily visible concave (away from the wooden screed) deformation on each side that occurs as a result of deformation of the standard bending test bars B-V38 during casting using iron.

Fig. 6 shows a cross section of the upper mold half of an iron casting. Here the upper half of the cavity (negative cast) formed by the standard bending test bar B-cold box (control) after removal of the metal cast can be seen. The casting negative was not visibly deformed so that the standard bending test bar B-cold box (control) would not be visibly deformed during casting using iron, as can be seen with the straight wooden scraper placed on this upper side of the casting negative. In addition, strong distortion can be seen in the core area. Such distortion has an adverse effect on the casting.

Fig. 7 shows a cross section of the lower half of the mold of an iron casting. Here can be seen the lower half of the cavity (negative cast) formed by the standard bending test bar B-cold box (control) after removal of the metal cast. The casting negative was not visibly deformed so that the standard bending test bar B-cold box (control) would not be visibly deformed during casting using iron, as can be seen with the straight wooden scraper placed on this lower side of the casting negative. In addition, severe distortion can be seen in the core area. Such distortion has an adverse effect on the casting.

Fig. 8 shows a cross section of the upper mold half of an iron casting. Here the upper half of the cavity (cast negative) formed by the standard bending test bar B-E61.3V1 (produced by the method according to the invention) after removal of the metal casting can be seen. The casting negative type is not visibly deformed so that the standard bending test bar B-E61.3V1 is not visibly deformed during casting using iron, as can be seen with a straight wooden scraper placed on this upper side of the casting negative type. A significantly lower distortion can also be seen compared to fig. 6 and 7.

Fig. 9 shows a cross section of the lower mold half of an iron casting. Here can be seen the lower half of the cavity (cast negative) formed by a standard bending test bar B-E61.3V1 (made by the method according to the invention) after removal of the metal casting. With the straight wooden scraper placed on this lower side of the casting negative, the casting negative does not deform visibly so that the standard bending test bar B-E61.3V1 (made by the method according to the invention) does not deform visibly during casting with iron.

Fig. 10 shows a cross section of an iron cube (1.68cm modulus) obtained in a test casting with a chill box riser made by a method not according to the invention, and the residual riser pocket consisting of iron is clearly visible at the top. It can be seen that a significant shrinkage cavity is formed in the residual riser, which extends into the metal casting (iron cube). See example 13 for additional description of fig. 10.

Fig. 11 shows a cross section of an iron cube (1.68cm modulus) obtained in a test casting with a water glass bonded riser made by a method not according to the invention, with a residual riser socket made of iron clearly visible on the top. Significant shrinkage cavities can be seen in the residual risers, extending far away from the metal casting (iron cube). See example 13 for additional description of fig. 11.

Fig. 12 shows a cross section of an iron cube (modulus 1.68cm) obtained in a test casting with risers made according to the invention ("risers B-E68.4") and a residual riser pocket made of iron is visible on top. It can be seen that no shrinkage cavities are formed in the metal casting (iron cube); shrinkage cavities appear to be present only in the residual risers. See example 13 for additional description of fig. 12.

Detailed Description

Example (c):

the following examples are intended to describe and illustrate the invention in detail without limiting its scope.

Unless otherwise stated, experiments were performed under laboratory conditions (atmospheric pressure, temperature 20 ℃, atmospheric humidity 50%) separately.

Example 1-manufacture of a molding material mixture a mixture of molding materials was manufactured using the components illustrated in table 1 below.

TABLE 1 Components of the moulding material mixtures

Silica sand BO42(CAS No. 014808-60-7) from Bodensteiner Sandwerk GmbH & Co. KG, respectively, was used as molding material.

A25% by weight solution of polyvinyl alcohol (> 93% polyvinyl alcohol) from Kuraray in water with a degree of hydrolysis of approximately 88 mol% and a dynamic viscosity in the range from 3.5 to 4.5 mPas (measured at 20 ℃ in accordance with DIN 53015 using a 4% by weight aqueous solution), a methanol content of < 3% by weight, was used as an aqueous PVA L mixture, CAS RN 25213-24-5.

A 36.5 wt% aqueous sulfuric acid solution (CAS RN 7664-93-9) was utilized as the aqueous sulfuric acid mixture.

A common polyisocyanate (activator 6324 from H ü tenes-Albertus Chemische Werke GmbH) used to make cold box adhesives (benzyl ether based polyurethanes) was utilized as cold box activator 6324.

A common phenolic resin (gas resin 7241 from H ü tenes-Albertus Chemische Werke GmbH) used to make cold box adhesives (benzyl ether based polyurethanes) was utilized as cold box gas resin 7241.

The molding material mixture was produced as explained below:

molding material mixture F-cold box: the components mentioned in Table 1 were mixed with one another in an electric mixer (Bosch Profi67), in which a molding material mixture is formed which can be blown or punched into moldings. The molding material mixture cold box is a molding material mixture for comparison purposes, which was manufactured by means of a method not according to the invention.

Molding material mixture F-V38: the components mentioned in Table 1 were mixed with one another in an electric mixer (Bosch Profi67), in which a molding material mixture is formed which can be blown or punched into moldings. Molding material mixture V38 is a molding material mixture for comparison purposes which is not produced by means of the method according to the invention or is not used in the method.

Moulding material mixture F-E61.3V the components mentioned in Table 1 are combined with one another in an electric mixer (Bosch Profi 67). for this purpose, the aqueous PVA L mixture and the aqueous sulfuric acid mixture are first combined with one another by means of mixing in a manner known per se to give a premix (or to give a binder system) and then the premix is combined with an initial charge of silica sand (moulding material) by means of mixing in an electric mixer.

Moulding material mixture F-E68.4 the components specified in Table 1 are combined with one another in an electric mixer (Bosch Profi 67). for this purpose, first the aqueous PVA L mixture and the aqueous sulfuric acid mixture are combined with one another in a manner known per se by means of mixing to give a premix (or to give a binder system) and then this premix is combined with an initial charge of silica sand (moulding raw material) by means of mixing in an electric mixer.

EXAMPLE 2 production of Standard bend test bars

The moulding material mixture described in example 1 in a manner known to the person skilled in the art was used to produce standard bending test bars (representing hardened mouldings for cast metal castings, size: 172 × × mm) for testing purposes by means of hammer peening according to the method in Verein Deutscher Gie β ereifachleute's Specification P73 (2-month release in 1996, stage 4.1) (cited hereinafter as "VDG Specification P73").

For hardening the bending test bars, the following procedure is respectively followed:

bending test bar B-cold box: the cold core box of molding material mixture (see example 1) was shaped by means of hammering in a curved rod hammer core box as described above. The shaped molding material mixture is subsequently hardened by means of the cold box method by means of the method in accordance with the VDG specification P734.3 (method a) by means of N, N-dimethylpropylamine (about 1ml of liquid, 15s) in the gaseous state (under the process conditions).

Bending test bars B-V38, B-E61.3V1, B-E68.4: in all three cases, the molding material mixture (see example 1 for manufacturing) was shaped by means of hammering in a curved rod hammer core box as described above. The shaped molding material mixture is subsequently hardened to give hardened moldings (standard bending test bars) by heating the shaped molding material mixture at 210 ℃ for 25 minutes in a drying oven and removing water from the shaped molding material mixture by means of ambient air degassing of the drying oven, respectively.

As an alternative to hardening into hardened moldings, a bent test bar (size: 187 × 22 × 22mm) B-E68.4 is shaped into the shaped molding material mixture by means of blowing in a customary core shooter (also for inorganic binders) with the molding material mixture F-E68.4 and hardened into hardened moldings by means of a tool having a temperature of 200 ℃ and by means of blowing hot air (200 ℃, pressure: 6 bar) over the length of the bent test bar.

EXAMPLE 3 Strength determination of Standard bending test bars

The standard flexural test bars produced in example 2 above were tested for final strength, respectively: for this purpose, the final strength of a standard bending test bar B-cold box was tested 24 hours after manufacture. For this purpose, the standard bending test bars B-V38, B-E613V1 and B-68.4 were each tested 30 minutes after manufacture (drying) for final strength. All standard bending test bars were stored under laboratory conditions. Final intensities were determined in triplicate using a Georg Fischer intensity test device type PFG with low pressure calculation (using motor drive), respectively, as described in VDG specification P735.2.

The bending strength of the standard bending test bars illustrated in table 2 was determined in this way:

table 2: final Strength of Standard bending test bars

n.d.: the value is not determined.

It can be seen from the values illustrated in table 2 that the moldings produced by means of the process according to the invention (standard bending test bars) B-E61.3V1 and B-E68.4 have at least comparable and even preferred final strength values compared with corresponding moldings produced by means of the customary cold box process. In contrast, the moldings B to V38 produced by means of the process not according to the invention (without catalytically active acid) showed the lowest flexural strength (final strength) under the experimental conditions.

Example 4: production of control Molding Material mixtures

The components illustrated in Table 3 were used to produce further control molding material mixtures which were produced not according to the process according to the invention but according to the process taught in document EP 1721689A 1.

Table 3: components of the control Molding Material mixture

Using a degree of hydrolysis of about 88 mol% and a dynamic viscosity in the range from 3.5 to 4.5 mPas (measured at 20 ℃ in accordance with DIN 53015 using a 4% by weight aqueous solution), a methanol content: < 3% by weight of polyvinyl alcohol (> 93%, granules) (CAS RN 25213-24-5) as polyvinyl alcohol.

Control molding material mixture F-V01: the components specified in table 3 were mixed with one another in an electric mixer (Bosch Profi67) and stirred until a foam was formed. However, a molding material mixture is formed which is deliquescent, castable, but not blowable or stampable into a molded part.

Control molding material mixture F-V02: the components specified in table 3 were mixed with one another in an electric mixer (Bosch Profi67) and stirred until a foam was formed. A molding material mixture is formed that can be blown or punched into a molded part.

Control molding material mixture F-V03: the components specified in table 3 were mixed with one another in an electric mixer (Bosch Profi67) and stirred until a foam was formed. However, a molding material mixture is formed which is deliquescent, castable, but not blowable or stampable into a molded part.

The three control molding material mixtures F-V01, F-V02, and F-V03 were then formed into shaped molding material mixtures in a curved rod hammer core box by hammer blows as described above (see example 2), respectively, if possible. Me then hardens the shaped moulding material mixture into a hardened moulded piece if feasible:

control molding material mixture F-V01: it is not possible to produce a dimensionally stable, shaped molding material mixture under the standard conditions described (hammering), so that hardened moldings cannot be produced.

Control molding material mixture F-V02: a moulding material mixture shaped as a bent test bar was obtained. It was hardened (see example 5) as described below into a molded part (bent test bar B-V02) and the result was compared with the result of the method according to the invention (see B-E61.3V1 below).

Control molding material mixture F-V03: it is not possible to produce a dimensionally stable, shaped molding material mixture under the standard conditions described (hammering). The molding material mixture was then heated at 250 ℃ for 1 minute in a bent test bar mold in a drying oven and evaluated after cooling to room temperature: the hardened molding has not yet been formed; the molding material mixture is still relatively soft. Another moulding material mixture produced in the same way was heated at 250 ℃ for 5 minutes in a bent test bar mould in a convection drying oven. This results in a hard outer shell being formed on the molded molding material mixture, but the interior of the mixture remains soft.

From the above observations, it can be seen that the control molding material mixtures F-V01 and F-V03 (corresponding to the process as described in document EP 1721689A 1) cannot be blow-molded into moldings or stamped into moldings.

In addition, it can be seen from the above observations that it is not possible to obtain moldings which harden resistant to water under the experimental conditions when using the control molding material mixtures F-V02 and F-V03.

Example 5: determination of Water resistance of Standard bending test bars

The shaped molding material mixtures F-V02 (comparative, see example 4) and F-E61.3V1 (manufactured according to the invention, see example 2) were produced and hardened to hardened moldings (standard bending test bars) in a convection drying oven under the conditions specified in Table 4 below, respectively.

After the respective hardening was completed, the flexural strength was determined according to example 3) on the molded parts which had been cooled for 30 minutes under laboratory conditions and hardened, and is likewise specified in table 4.

The hardened molded parts were then checked for water resistance according to the method described below:

first, the complete standard bending test bars were immersed in deionized water at 20 ℃ and atmospheric pressure for 30 minutes independently of each other (horse table) so that they were just completely covered with water. After 30 minutes, the standard bending test bars were quickly removed from the water and (if applicable) tested to check their consistency.

The standard bending test bars were then (if applicable) checked for residual hardness using a core hardness tester GM-578 (from Simpson Technologies GmbH, Switzerland). For this purpose, respective standard bending test bars were placed on the solid support and the penetration depth of each core hardness tester (according to the operating instructions of the core hardness tester) was measured once at one point of the outer surface (which had been in contact with water). The measurements were performed a total of three times at different points of the outer surface and the average of the three measurements is illustrated in table 4 ("penetration depth of the outer surface") respectively.

In order to also check the water resistance in the interior of the molded parts (here: standard bending test bars), the bending test bars produced in the same manner as described above with the aid of the molding material mixtures F-V02 (control, see example 4) and F-E61.3V1 (produced according to the invention, see example 2) were then each sawn in the middle of the height and just completely immersed in water for 30 minutes as described above, with the sawn-off inner cross-sectional areas of the standard bending test bars being in complete contact with water. After the bending test bar was removed from the water, the residual hardness of the bending test bar was measured again using the core hardness tester as described above, this time in the middle of the inner cross-sectional area. The measurements were again performed a total of three times at different points of the inner cross-sectional area and the average of the three measurements is illustrated in table 4 ("penetration depth of the inner cross-sectional area") respectively.

Table 4: water resistance of standard bending test bars

The notation "" not measurable "in table 4 means that it is not possible to measure any penetration depth on the corresponding bending test bar using the core hardness tester, because the bar had disintegrated during storage in water for 30 minutes.

From the measured values or comments specified in table 4, it is seen that hardened molded parts produced by means of a method not according to the invention are not water-resistant under the test conditions (after 20 minutes at 210 ℃) or are not hardened in all directions (after 30 minutes at 210 ℃). In contrast, the hardened molded parts produced by means of the method according to the invention hardened with resistance to water after only 20 minutes under the same experimental conditions (standard bending test bars do not disintegrate after removal from water) and hardened in all directions after 30 minutes (penetration depth of the core hardness tester on the inner cross-sectional area <4 mm).

Example 6: determination of Water resistance of Standard bending test bars

A standard bending test stick as manufactured in example 2 above was placed on the shelf so that only its end was supported (support area was about 1/10 of the total area of the underside of the standard bending test stick, see table 5). The rack with the standard bending test stick on it is introduced into a water-filled container so that the underside of the standard bending test stick rests completely on the water surface and can absorb water by means of capillary forces. The water resistance of the standard test bars was then visually evaluated over a 10 day period.

The results of this experiment are illustrated in table 5.

Table 5: water resistance of standard bending test bars

From the observations illustrated in table 5, it can be seen that the standard bent test bars bonded with the cold box adhesive are still completely water resistant after 10 days. The bending test bar B-E61.3V1 produced by means of the method according to the invention absorbed water after a certain time without a significant loss of water resistance. In contrast, the control bending test bars B-V38 produced by means of a method not according to the invention (polymers containing hydroxyl groups not being etherified crosslinked by acid catalysis) completely lost their water resistance and began to dissolve after only a very short time.

Example 7: properties of standard bending test bars during casting of iron

Standard bending test bars B-cold box (control), B-V38 (control) and B-E61.3V1 (manufactured by means of the process according to the invention), as manufactured in example 2 above, were coated in a manner known to the person skilled in the art with the aid of a conventional alcohol coating slip (Koalid 4087, from H ü tenes-Albertus GmbH) (conditions: running time: 17.3 s; soaking time: 7 s; drying at 110 ℃ for 40 minutes; wall thickness in the wet state: 325 μm).

The standard bending test bars coated by means of alcohol slip were then placed in furan resin moulds (size: 280 × 200 × 130mm) which had been coated undiluted with conventional zircon-containing slip (Zirkofluid 1219, from H ü tenes-Albertus GmbH) and cast iron (casting temperature approximately 1440 ℃, carbon content approximately 3.09 wt.%, silicon content approximately 1.89 wt.%, in each case based on the total mass of cast iron) was cast flatly in the moulds, so that the standard bending test bars were each completely enveloped by the iron casting and were subjected to the maximum stress on the supporting load (due to the iron as casting metal) during casting.

After the casting process, the remaining residues of the standard bending test bar were removed from the iron casting by rotating the casting so that they could fall out of the downwardly oriented openings of the cavity of the iron casting created by the standard bending test bar and the unpacking property (coring property) of the standard bending test bar was visually evaluated. Here, the following observations were obtained:

the remaining residue of the standard bending test bar B-cold box (control) could not be practically removed from the iron mold in the manner explained above; it remains virtually completely in the iron casting (see fig. 1).

The remaining residue of the standard bending test bar B-V38 (control) was easily and virtually completely removed from the iron casting in the manner described hereinabove (see fig. 2).

The remaining residues of the standard bending test bar B-E61.3V1 (manufactured by means of the method according to the invention) can be removed very easily and practically completely from the iron casting in the manner described hereinbefore (cf. fig. 3).

The iron casting was then sawn in the middle (along the support surface of the standard bending test bar) so that the cavity created by the standard bending test bar (after removal of the iron casting) was split in half just in the middle of the length of the iron casting. The cross section of the cavity created by means of the standard bending test bar is half in the upper half of the sawn metal casting (created during iron casting by means of the standard bending test bar section at the top, "upper half of the mold") and half in the lower half of the sawn metal casting (created during iron casting by means of the standard bending test bar section at the bottom, "lower half of the mold").

The upper and lower mould halves exposed in this manner were then visually evaluated to assess the casting resistance of standard bending test bars used in casting iron and their deformation due to buoyancy in the liquid iron (as can be seen in the resulting deformation of the iron casting). For this purpose, a straight wooden blade is placed along the cross section of the cavity of the upper and lower mould halves produced by standard bending test bars, and the cast negative of the upper (in the upper mould half) and lower (in the lower mould half) sides of the cavity is evaluated separately for deviations from the straight shape of the wooden blade.

The following observations were obtained here:

standard bending test bar B-cold box (control): the negative casting of the upper side (in the upper half of the mold) and the lower side (in the lower half of the mold) of a standard bending test bar (B-cold box) showed no significant deviation from the straight line of the wooden screed. Therefore, the standard bending test bar B-cold box is hardly deformed when casting iron and shows high casting resistance (refer to fig. 6 and 7).

Standard bend test bars B-V38 (control): the cast negative version on the upper side (in the upper half of the mold) of the standard bending test bar B-V38 showed a significant concave (away from the wooden blade) deformation in the middle (maximum deflection height: about 5 mm). The cast negative of the underside of the standard bending test bar B-V38 (in the lower half of the die) showed significant concave (away from the wooden blade) deformation at the edge (maximum deflection height: about 7 mm). Therefore, the standard bending test bar B-V38 was significantly deformed when casting iron and showed only low casting resistance (refer to fig. 4 and 5).

Standard bending test bars B-E61.3V1 (manufactured by means of the method according to the invention): the negative casting of the upper (in the upper half of the mold) and lower (in the lower half of the mold) sides of the standard bend test bar B-E61.3V1 showed no significant deviation from the straight line of the wooden screed. Therefore, the standard bending test bar B-E61.3V1 was hardly deformed when iron was cast and showed high casting resistance (see fig. 8 and 9).

From the above observations it can be seen that the moulded parts produced by means of the method according to the invention (here: standard bending test bars represent cores, risers or moulds) show excellent decorability and high casting resistance during metal casting, and overall have properties that are significantly better than the control moulded parts.

Example 8: production of Standard test specimens (Standard bending test bars and Standard test cartridges) from insulating riser stock as a moulding material mixture

The components illustrated in table 6 were used to make molding material mixtures for insulated risers. The molding material mixture was manufactured in a manner similar to that described above in example 1.

From the resulting molding material mixture, standard bending test bars were subsequently shaped and hardened as hardened moldings analogously to the above in example 2. In addition, standard test cartridges (height: 50mm, diameter: 50mm) were produced from the molding material mixture obtained according to VDG Standard P38 by means of hammering and hardened to hardened moldings analogously to example 2 above (for standard bending test bars and standard test cartridges by means of molding material mixture F-E68.4(2), 25 minutes in a convection drying oven at 210 ℃).

The 24-hour flexural strength (final strength) of the obtained standard flexural test bars "B-cold box" (control) was then determined in a manner similar to that described above in example 3. The flexural strength (final strength) of the standard flexural test bars B-E68.4 obtained was determined under laboratory conditions (room temperature and room humidity) after the drying procedure had been completed and after storage for 30 minutes. All the above mentioned measurements are illustrated in table 6 (taking the average of 3 measurements each).

Likewise, the measured values of the gas permeability of the standard bending test bar and the standard test cylinder, respectively, and the weights thereof are illustrated in table 6. The gas permeability is an inspection value which gives information about the densification of the microstructure. In particular, in the case of risers, this is a characteristic value that can give information about the adequate derivation of the casting gas during casting.

Table 6: components of a moulding material mixture for insulating risers

The components "aqueous PVA L mixture", "aqueous sulfuric acid mixture", "cold box activator 6324", and "cold box gas resin 7241" illustrated in table 6 correspond to the components illustrated in example 1.

As can be seen from the results illustrated in table 6, the insulating riser compound produced by means of the method according to the invention has similar properties, in particular similar flexural strength (i.e. final strength), to the insulating riser compound produced by means of the known cold-box method.

Example 9: casting moulded parts from aluminium or iron

Insulated (closed at the bottom by a plate) risers were produced by blowing in a core shooter from the insulated riser charge produced in example 8 above by means of the moulding material mixture "F-cold box (2)" in a manner known to the person skilled in the art (treatment with catalyst gas N, N-dimethylpropylamine).

Insulated risers made from the insulated riser stock produced above in example 8 by means of molding material mixture "F-E68.4 (2)" were blow-shot in the same mold on a core shooter. Hardening was carried out in a drying oven (convection) at 210 ℃ for 25 minutes.

The insulated risers made in this manner were placed in a chill box type sand mold and cast using aluminum to test their properties under metal casting conditions. Other insulated risers made in this way were also placed in loose sand and cast using iron instead of aluminum.

The following observations were obtained:

when the insulated risers made with the aid of the control molding material mixture F-cold box (2) (not according to the method of the invention) were cast using aluminum, a strong soot formation was observed and this continued to occur even after the casting risers were removed from the molding sand.

When using aluminum for casting the insulated feeder produced with the aid of the molding material mixture F-E68.4(2) (method according to the invention), it was found that no soot was formed. After the casting operation, the insulated risers made according to the invention show unpacking properties that are significantly better than those made by means of the control molding material mixture F-cold box (2), i.e. they can be clearly separated from the aluminium more easily. The aluminum castings formed showed a significantly cleaner surface (i.e., no concentrate deposits) as compared to aluminum castings produced by insulated risers produced with the control molding material mixture F-cold box (2).

Soot formation and odor emission were found when the insulated feeder cast iron produced (at a temperature of 1410 ℃) with the aid of the control molding material mixture F-cold box (2) (not according to the method according to the invention) was poured.

When the insulated feeder produced with the aid of the control mold mixture F-E68.4(2) (according to the method according to the invention) was cast iron (at a temperature of 1410 ℃), no soot formation or odor emission was found, even after the casting feeder had been removed from the molding sand. After casting, the insulated risers made according to the invention show unpacking properties that are clearly superior to those of insulated risers made with the aid of the control molding material mixture F-cold box (2): the feeder head in which the iron was cast was virtually completely disintegrated when the cast sample was mechanically stretched. In addition, the iron castings formed showed a significantly cleaner surface and easier mechanical removal of sand and a smoother surface structure than the iron castings produced by means of the insulated risers produced with the aid of the control molding material mixture F-cold box (2).

Example 10: production of standard test specimens from exothermic riser material as molding material mixture

The components specified in table 7 were used to produce molding material mixtures for exothermic risers. The molding material mixture was manufactured in a manner similar to that described above in example 1.

The test specimens (standard bending test bars and standard test cartridges) were subsequently shaped from the molding material mixture obtained and hardened as (representative or exemplary) hardened moldings analogously to the above in example 2. The test specimens produced with the aid of the molding material mixture F-E68.4(3) were hardened by heating at 210 ℃ for 25 minutes in a drying oven (convection) and removing the water.

The flexural strength of the obtained standard flexural test bars was then determined in a manner similar to that described above in example 3. The results of the measurements are illustrated in table 7 (average of 3 measurements).

Likewise, the respectively determined values of the gas permeability of the standard test cartridge and the weight thereof are respectively illustrated in table 7.

TABLE 7 composition of moulding material mixtures for exothermic risers

The components "aqueous PVA L mixture", "aqueous sulfuric acid mixture", "cold box activator 6324", and "cold box gas resin 7241" illustrated in table 7 correspond to the components illustrated in example 1.

As can be seen from the results illustrated in table 7 above, the exothermic riser compound produced by means of the method according to the invention has similar properties, in particular similar flexural strength (i.e. final strength), to those produced by means of the known cold-box method.

Example 11: burnout of exothermic riser

A standard test cartridge was manufactured from the exothermic riser charge manufactured in example 10 above according to VDG standard P38 by means of hammering. In the case of exothermic riser charges with molding material mixture "F-cold box (3)", hardening was carried out in a manner known to the person skilled in the art by means of treatment with the catalyst gas N, N-dimethylpropylamine. In the case of the exothermic riser charge "F-E68.4 (3)", hardening was carried out by means of heating in a drying oven (convection) at 210 ℃ for 25 minutes and removal of water to give hardened moldings (exothermic riser).

The exothermic riser produced in this way was fired in a manner known to the person skilled in the art according to VDG standard P81 (no temperature-time measurement here). The parameters illustrated in table 8 are determined here.

Table 8: combustion parameters of exothermic riser

In addition, the following observations were obtained:

significant smoke formation was observed upon burning out the exothermic riser made with the aid of the control molding material mixture F-cold box (3) (not according to the method of the invention) (conventional cold box binder).

During the burning-out of the exothermic riser produced by means of the molding material mixture F-E68.4(3) according to the method according to the invention, virtually no soot formation was found.

From the results described above, it can be seen that the hardened moldings produced by means of the process according to the invention (here: exothermic riser) exhibit significantly reduced emissions under practical conditions compared with moldings produced by means of the conventional cold box process.

Example 12: production of aqueous adhesive systems

The components illustrated in table 9 below were used to make an aqueous binder system.

Table 9: components of aqueous adhesive systems

The components "aqueous PVA L mixture" and "aqueous sulfuric acid mixture" illustrated in table 9 correspond to the components illustrated in example 1.

The aqueous binder systems WB-E61.3V1 and WB-E68.4 are the aqueous binder systems to be used in the present invention. The aqueous binder system WB-V38 is an aqueous binder system used for the control and not for the present invention.

Example 13: test casting of iron cube

The molding material mixtures illustrated in table 10 were each shaped into risers in a core shooter.

In the case of the feeder mix "F-cold box (4)", hardening is carried out in a manner known to the person skilled in the art by means of treatment with the catalyst gas N, N-dimethylpropylamine. In the case of the "F-water glass" riser mixture, hardening was carried out in a drying oven (convection) at 210 ℃ for 25 minutes. In the case of the casting compound "F-E68.4 (4)", the hardening into hardened moldings is carried out by heating in a drying oven (convection) at 210 ℃ for 25 minutes and removing the water. The risers "riser cold boxes" and "riser water glasses" produced by means of the method not according to the invention and the risers "risers B-E68.4" produced according to the invention were produced.

Table 10: composition of molding material mixture for riser

The components illustrated in table 10 correspond to the components illustrated in example 1 and their meanings, respectively.

For the sodium water glass binder 48/50, a standard water glass binder aqueous solution (CAS RN 1344-09-8) was utilized having a water glass content (sodium silicate content) in the range of 25 to 35 wt.% and a pH in the range of 11 to 12 at 20 ℃.

The industrial availability of the above-mentioned risers, in particular the quality of their riser action, was checked by use in test castings (examples of metal castings) of iron cubes, respectively. For this purpose, risers of the same size (i.e. respectively the same modulus) were used in each case in cubic test castings having a modulus (i.e. the ratio of volume to surface area) of 1.68cm at a casting temperature of 1400 ℃ with the aid of iron (GGG 40). The quality is usually assessed by the skilled person using a cube with a modulus significantly larger than the riser to be able to obtain the best possible information about the curing from experiments. The quality of the charging action was checked via the depth of the shrinkage cavity extending into the cube: the extension of the shrinkage cavity to the depth of the cube (metal casting) represents a poor charging effect.

After casting, a test cube (halves) produced as described above was sawn in the middle and cooled to room temperature to expose its cross section and to evaluate the casting quality and the functional quality of the risers used in each case. The cross-sections obtained by sawing out the test cube with visible riser residues consisting of iron attached to the top are shown in fig. 10 (iron casting with riser "riser cold box" not manufactured according to the method of the invention), fig. 11 (iron casting with riser "riser water glass" not manufactured according to the method of the invention) and fig. 12 (iron casting with riser "riser B-E68.4" manufactured according to the invention).

It can be seen in fig. 10 that significant shrinkage cavities extending into the metal castings were formed when the chill box risers were utilized under the experimental conditions. The notation "-15 mm" (left half of the cross-section) or "-16 mm" (right half of the cross-section) shows the distance between the visible line above the picture (at the riser remnant cuff, i.e. the boundary between the metal riser remnant and the metal casting) and the visible line below the picture (the mark for the metal casting or the deepest point of the shrinkage cavity in the metal casting), respectively.

In fig. 11 it can be seen that under experimental conditions with a water glass riser not produced according to the method of the invention, a distinct shrinkage cavity is formed which extends to a far distance of the metal casting. The notation "-33" (mm) (left half of the cross-section) or "-31" (mm) (right half of the cross-section) shows the distance between the visible line above the picture (at the riser remnant cuff, i.e. the boundary between the metal riser remnant and the metal casting) and the visible line below the picture (the mark for the metal casting or the deepest point of the shrinkage cavity in the metal casting), respectively. The poor performance quality of risers incorporating water glass under experimental conditions may be attributed to the relatively high thermal energy absorption of the water glass binder (referred to as its adverse "quenching properties") and the resulting relatively early solidification of the cast metal.

In fig. 12 it can be seen that when using the riser "riser B-E68.4" manufactured according to the invention, the extension of the shrinkage cavity formed is significantly shallower than when using the known water glass bonded riser or cold box bonded riser (test cube). The notation "-3" (mm) (left half of the cross-section) or "-1" (mm) (right half of the cross-section) shows the distance between the visible line above the picture (at the riser remnant cuff, i.e. the boundary between the metal riser remnant and the metal casting) and the visible line below the picture, respectively.

From fig. 10 to 12 illustrated hereinabove, it can thus be seen that risers made according to the present invention have a significantly improved charging capacity compared to known cold box-or water glass-bonded risers used for the control.