阅读说明：本技术 铸型材料和其制造方法以及铸型的制造方法 (Casting material, method for producing same, and method for producing casting ) 是由 高间智宏 浦哲也 于 2018-12-28 设计创作，主要内容包括：提供：能更进一步改善流动性、进而改善铸型造型时对成型模的填充率的铸型材料；而且还提供：能有利地提供使铸造品的铸件表面良好、进而能有效地改善对铸造品的砂附着的、强度优异的铸型的铸型材料。以湿态的覆膜砂的形式构成铸型材料,所述湿态的覆膜砂是向耐火性骨料,至少混合粘度为1000cP以下的液态的水溶性无机粘结剂和拒粘结剂性的球状有机硅树脂颗粒,且使上述球状有机硅树脂颗粒存在于表面而成的湿态的覆膜砂。(Providing: a casting material which can further improve the fluidity and further improve the filling rate of a forming die during the casting of the casting; and also provides: the casting material for a mold is advantageously provided which has excellent strength and can improve the surface of a cast product and effectively improve the adhesion of sand to the cast product. The casting material is constituted as wet coated sand in which at least a liquid water-soluble inorganic binder having a viscosity of 1000cP or less and binder-repellent spherical silicone resin particles are mixed with a refractory aggregate, and the spherical silicone resin particles are present on the surface.)

1. A casting mold material characterized by being formed as wet coated sand in which a refractory aggregate, a liquid water-soluble inorganic binder having a viscosity of 1000cP or less, and binder-repellent spherical silicone resin particles are mixed together, and the spherical silicone resin particles are present on the surface.

2. The casting mold material according to claim 1, wherein the spherical silicone resin particles have the following characteristics: in the thermogravimetric differential thermal analysis device, the weight loss rate is 5-50% when the temperature is applied from room temperature to 700 ℃ in an air atmosphere.

3. The casting mold material according to claim 1 or claim 2, wherein the spherical silicone resin particles have an average particle diameter of 0.01 μm to 50 μm.

4. The casting mold material according to any one of claims 1 to 3, wherein the content of the spherical silicone resin particles is 0.1 to 500 parts by mass with respect to 100 parts by mass of a solid content of a water-soluble inorganic binder in the casting mold material.

5. The casting mold material according to any one of claims 1 to 4, wherein the silicone resin particles are resin particles containing organopolysiloxane as a main component.

6. The casting mold material as recited in claim 5, wherein the organopolysiloxane comprises silsesquioxane.

7. The casting mold material of claim 6, wherein the silsesquioxane is polymethylsilsesquioxane.

8. A casting mold material according to any one of claims 1 to 7, wherein the spherical silicone resin particles have the following binder repellency: the contact angle when the liquid water-soluble inorganic binder is dropped on a horizontal surface formed by the silicone resin particles is 90 ° or more.

9. The casting mold material according to any one of claims 1 to 8, wherein at least one nitrate selected from the group consisting of alkali metal salts and alkaline earth metal salts of nitric acid is further mixed.

10. The casting mold material according to any one of claims 1 to 9, wherein the water-soluble inorganic binder contains water glass as a main component.

11. A method for producing a casting material, characterized by adding a liquid water-soluble inorganic binder having a viscosity of 1000cP or less and binder-repellent spherical silicone resin particles to a refractory aggregate, and kneading or mixing the mixture at normal temperature to produce wet-state coated sand in which the spherical silicone resin particles are present on the surface.

12. The method for producing a mold material according to claim 11, wherein the liquid water-soluble inorganic binder having a viscosity of 1000cP or less is formed by separately adding a predetermined amount of water and a predetermined amount of water.

13. A method for producing a casting mold, characterized in that a target casting mold is obtained by filling the casting mold material according to any one of claims 1 to 10 into a heated mold, and then holding the mold in the mold to cure or harden the material.

Technical Field

The present invention relates to a mold material and a method for producing the same, and a method for producing a mold, and more particularly, to a mold material and a method for producing the same, which can be advantageously molded into a target mold, and further, to a method for advantageously producing a mold having excellent characteristics by using such a mold material.

Background

Conventionally, as one of the molds used for casting molten metal, a mold obtained by: the mold is obtained by molding a casting sand (mold material) made of a foundry sand made of a refractory aggregate with a predetermined binder into a desired shape. As the binder in such coated sand, in addition to an inorganic binder such as water glass, an organic binder made of a resin such as a phenol resin, a furan resin, or a urethane resin is used, and a method of molding a self-hardening mold using the binder is also put into practical use.

However, the following problems are inherent to the coated sand obtained using the above binder: the presence of the binder tends to lower the fluidity of the coated sand, and there are problems that a filling failure occurs in a molding cavity of a mold (mold) used for molding a mold, and that the strength of the obtained mold is not sufficient. Among these binders, in particular, coated sand using an organic binder is concerned in the production thereof and in the molding of a mold using the coated sand, as follows: volatile components remaining in the organic binder are released to the outside to generate odor, or when casting of molten metal is performed using a mold formed of such coated sand, the organic components in the organic binder are decomposed to generate gas, which causes problems such as gas defects in the formed cast product, and deterioration of the working environment.

Therefore, in recent years, attention has been paid to an inorganic binder as a binder free from such an organic component, but the following problems are inherent in coated sand obtained using such an inorganic binder: the mold formed therefrom has insufficient disintegratability after casting, and the mold strength is lowered by moisture absorption.

Therefore, in Japanese patent application laid-open No. 2008-511447, the following mold materials are explained: a molding material mixture for use in the production of a mold for metal working, which comprises at least one refractory molding base material and at least one binder made of water glass, wherein a particulate metal oxide selected from the group consisting of silica, alumina, titanium oxide and zinc oxide is added to the binder at a predetermined ratio. But also brings the following advantages: by adding such a particulate metal oxide, the initial strength (strength immediately after production) of the mold, the strength after long-term storage, and the moisture resistance are improved.

However, in the molding material mixture (mold material) containing both water glass as the binder and the particulate metal oxide, there is a problem that the water glass adheres to the particulate metal oxide by the mixing of the above components, so that the number of bonding points with the mold increases, and thus the mold obtained by molding with the mold is poor in mold release property, and the mold is broken at the time of mold release. Further, when the viscosity of the binder (water glass) is reduced to improve the mold strength, the low-viscosity binder is moved in the mold by the influence of the air pressure after the molding material mixture (mold material) is blown into the mold (molding cavity) by the air pressure at the time of mold molding, and becomes unevenly distributed on the inner peripheral surface of the cavity, and thus there is a problem that the mold release property tends to be further deteriorated, and if the filling property is high, the number of bonding points between the molding base materials (aggregates) is increased, and the disintegration property is deteriorated.

In addition, in japanese patent No. 4953511, the following casting sand composition (mold material) is explained: the refractory aggregate contains a refractory particulate aggregate and non-hollow spherical fine particles having an average particle diameter at a predetermined ratio to the average particle diameter of the refractory particulate aggregate, and the non-hollow spherical fine particles are formed using a material selected from the group consisting of silica, silicone resins, alumina glass, mullite, polyethylene, polypropylene, polystyrene, (meth) acrylic resins, and fluorine resins. Further, such a casting sand composition is improved in fluidity and is suitable for molding of a complicated mold or a high-strength mold, but in molding of a mold having a complicated shape in recent years, the fluidity of such a casting sand composition is still insufficient, and further improvement in fluidity is desired, and in casting using a mold molded therefrom, it is required to improve the casting surface of the obtained cast product and further prevent sand adhesion to the cast product.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide: a casting material which can further improve the fluidity and further improve the filling rate of a forming die during the casting of the casting; and also provides: the mold material for a mold, which is excellent in mold releasability and disintegratability, can provide a good casting surface of a cast product, can effectively improve adhesion of sand to the cast product, and is excellent in strength, and further: a method capable of advantageously producing a mold material having such excellent characteristics, and a method capable of advantageously producing a mold having excellent characteristics using such a mold material.

Means for solving the problems

In order to solve the above problems, the present invention can be suitably implemented in various ways as described below. It should be noted that aspects and/or technical features of the present invention are not limited to the following description, and can be recognized based on the inventive concept which can be grasped from the description of the specification and the attached drawings.

(1) A casting mold material characterized by being formed as wet coated sand in which a refractory aggregate, a liquid water-soluble inorganic binder having a viscosity of 1000cP or less, and binder-repellent spherical silicone resin particles are mixed together, and the spherical silicone resin particles are present on the surface.

(2) The mold material according to the above aspect (1), wherein the spherical silicone resin particles have the following characteristics: in the thermogravimetric differential thermal analysis device, the weight loss rate is 5-50% when the temperature is applied from room temperature to 700 ℃ in an air atmosphere.

(3) The mold material according to claim 1 or 2, wherein the spherical silicone resin particles have an average particle diameter of 0.01 to 50 μm.

(4) The mold material according to any one of the above aspects (1) to (3), wherein the content of the spherical silicone resin particles is 0.1 to 500 parts by mass with respect to 100 parts by mass of a solid component of the water-soluble inorganic binder in the mold material.

(5) The mold material according to any one of the above aspects (1) to (4), wherein the silicone resin particles are resin particles containing organopolysiloxane as a main component.

(6) The mold material according to the above aspect (5), wherein the organopolysiloxane comprises silsesquioxane.

(7) The mold material according to the above-described aspect (6), wherein the silsesquioxane is polymethylsilsesquioxane.

(8) The casting mold material according to any one of the foregoing aspects (1) to (7), wherein the foregoing spherical silicone resin particles have the following binder repellency: the contact angle when the liquid water-soluble inorganic binder is dropped on a horizontal surface formed by the silicone resin particles is 90 ° or more.

(9) The casting mold material according to any one of the foregoing aspects (1) to (8), wherein at least one nitrate selected from the group consisting of alkali metal salts and alkaline earth metal salts of nitric acid is further mixed.

(10) The casting mold material according to any one of the above aspects (1) to (9), wherein the water-soluble inorganic binder contains water glass as a main component.

(11) A method for producing a casting material, characterized by adding a liquid water-soluble inorganic binder having a viscosity of 1000cP or less and binder-repellent spherical silicone resin particles to a refractory aggregate, and kneading or mixing the mixture at normal temperature to produce a wet-state coated sand in which the spherical silicone resin particles are present on the surface.

(12) The method of producing a mold material according to the above-mentioned aspect (11), wherein the liquid water-soluble inorganic binder having a viscosity of 1000cP or less is formed by separately adding a predetermined amount of water to a predetermined water-soluble inorganic binder.

(13) A method for producing a mold, characterized in that a target mold is obtained by filling a heated mold with the mold material according to any one of the above aspects (1) to (10), and then holding the mold material in the mold to cure or harden the mold material.

ADVANTAGEOUS EFFECTS OF INVENTION

In this manner, the casting mold material of the present invention is obtained by mixing a liquid water-soluble inorganic binder adjusted to have a low viscosity and spherical silicone resin particles having a binder repellency, so that the spherical silicone resin particles are formed as wet coated sand in a form in which the spherical silicone resin particles are present on the surface of the water-soluble inorganic binder layer formed around the refractory aggregate, therefore, the casting materials come into contact with each other via the spherical silicone resin particles on the surface thereof, the friction between the particles of the casting materials can be effectively reduced, the fluidity of the material is obviously improved, the filling property of the casting material to the forming cavity of the forming die for casting the casting mold can be effectively improved, further, after the filling of the mold material, the mold material moves to fill gaps between the particles of the mold material, and thus the filling rate can be further improved.

Further, since such binder-repellent spherical silicone resin particles are present on the particle surface of the mold material and migrate to the surface of the water-soluble inorganic binder layer, a mold having excellent strength can be favorably formed from the mold material, and the mold release property of the formed mold can be improved.

Drawings

Fig. 1 is a schematic front view showing a parting surface of one mold half constituting a molding die for evaluating filling fluidity.

Fig. 2 is a longitudinal sectional explanatory view of a sand mold for a casting test used in a disintegration test in examples.

FIG. 3 is a longitudinal sectional explanatory view of an aluminum alloy casting containing a waste core obtained in the example.

Detailed Description

However, the mold material containing a refractory aggregate and a water-soluble inorganic binder is classified into a dry mold material and a wet mold material according to the state after its preparation. The present invention is directed to a wet molding material (coated sand) in which a water-soluble inorganic binder exhibits adhesiveness and is in a wet state (appearance) as a whole. Such a wet mold material is filled into a mold (mold cavity), for example, and heated and dried in the mold to cause a curing or hardening reaction, thereby molding a target mold. The dry state or the wet state of the mold material is determined depending on the amount of the water content in the mold material relative to the amount of the solid component of the water-soluble inorganic binder, but the dry state or the wet state of the mold material differs depending on the type of the water-soluble inorganic binder. For example, when the water-soluble inorganic binder is water glass, the mold material containing moisture in an amount corresponding to 5 to 55 mass% of the solid content thereof is in a dry state, while the mold material containing moisture in an amount exceeding 55 mass% of the solid content of the water glass is in a wet state.

The wet molding material (precoated sand) of the present invention is a molding material (precoated sand) which does not have fluidity at normal temperature and in which a measured value of the dynamic repose angle cannot be obtained when the dynamic repose angle is measured, regardless of the moisture content thereof, and here, the dynamic repose angle is a molding material in which the molding material (precoated sand) is placed in a cylinder having a transparent one side and a flat surface (for example, the molding material is placed in a container having a diameter of 7.2cm × and a height of 10cm up to half the volume), the molding material is rotated at a constant speed (for example, 25rpm), the inclined surface of the layer of the molding material flowing in the cylinder is flat, and the angle formed between the inclined surface and the horizontal surface is measured.

Here, as the refractory aggregate constituting the wet mold material of the present invention, any of various refractory granular and/or powdery materials conventionally used for molds can be used as the refractory material functioning as the base material of the mold, and specifically, specific examples include silica sand, regenerated silica sand, and special sand such as alumina sand, olivine sand, zircon sand, and chromite sand, slag-based granules such as ferrochrome-based slag, ferronickel-based slag, and converter slag; and artificial particles such as alumina-based particles and mullite-based particles, and regenerated particles thereof; further, alumina balls, magnesium frits, and the like. The refractory aggregate may be fresh sand, reclaimed sand or reclaimed sand used once or more times as foundry sand in the molding of a mold, or mixed sand obtained by adding fresh sand to the reclaimed sand or reclaimed sand and mixing the same, without limitation. The refractory aggregate is generally an aggregate having a particle size of about 40 to 130 in terms of AFS index, and preferably an aggregate having a particle size of about 60 to 110.

In particular, as described above, among the refractory aggregates, spherical aggregates are recommended in order to favorably achieve the object of the present invention, and more specifically, it is desirable that the angle coefficient is 1.2 or less, and more preferably 1.0 to 1.1, as the use of the refractory aggregate having the angle coefficient of 1.2 or less, the fluidity and the filling property become good, and the number of joints between aggregates becomes large, whereby the amount of the binder and the amount of the additive required to exhibit the same strength can be reduced.

The water-soluble inorganic binder in the casting material of the present invention may be suitably selected from various known materials and used, and among them, 1 or 2 or more selected from the group consisting of water glass, sodium chloride, sodium phosphate, sodium carbonate, sodium vanadate, sodium alumina, potassium chloride, potassium carbonate, magnesium sulfate, aluminum sulfate, sodium sulfate, nickel sulfate, manganese sulfate, and the like as main components can be favorably used. Among them, water glass and water glass as a main component are particularly preferable from the viewpoints of ease of handling and strength of a mold to be finally obtained. The water glass is an aqueous solution of a soluble silicic acid compound, and examples of such silicic acid compounds include sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, and ammonium silicate. In the present invention, water glass may be used as the main component, and a water-soluble binder such as a thermosetting resin, a saccharide, a protein, a synthetic polymer, a salt, an inorganic polymer, or the like may be used. When water glass and another water-soluble binder are used in combination, the ratio of water glass in the total amount of the binder is 60 mass% or more, preferably 80 mass% or more, and more preferably 90 mass% or more.

Here, sodium silicate is generally based on SiO₂/Na₂The molar ratio of O is used in the range of 1 to 5. Specifically, sodium silicate No. 1 is SiO₂/Na₂Sodium silicate with a molar ratio of O of 2.0-2.3, and sodium silicate No. 2 being SiO₂/Na₂Sodium silicate having a molar ratio of O of 2.4 to 2.6, and further sodium silicate No. 3 is SiO₂/Na₂Sodium silicate having a molar ratio of O of 2.8 to 3.3. In addition, sodium silicate No. 4 is SiO₂/Na₂Sodium silicate with the molar ratio of O being 3.3-3.5, and the sodium silicate No. 5 is SiO₂/Na₂Sodium silicate having a molar ratio of O of 3.6 to 3.8. Among these, sodium silicate Nos. 1 to 3 are also defined in JIS-K-1408. These various sodium silicates may be used alone or in combination, or 2 or more kinds of sodium silicates may be mixed to prepare SiO₂/Na₂Molar ratio of O.

It should be noted that, in order to advantageously obtain the casting mold material of the present invention, SiO, which is a sodium silicate constituting water glass used as a binder₂/Na₂The molar ratio of O is desirably usually 1.9 or more, preferably 2.0 or more, more preferably 2.1 or more, and among the above-mentioned sodium silicates, sodium silicates corresponding to nos. 1 to 3, preferably nos. 1 to 2, more preferably No. 2 can be particularly advantageously used. The above-mentioned sodium silicates nos. 1 to 3 stably provide casting materials having good characteristics even in a wide range of the concentration of sodium silicate in water glass. In order to obtain the strength of the mold, sodium silicate nos. 1 to 2 were selected, and sodium silicate No. 2 was further selected in the total balance of moisture resistance and the like. Furthermore, SiO in such sodium silicate₂/Na₂The upper limit of the molar ratio of O may be appropriately selected depending on the characteristics of the water glass in the form of an aqueous solution, and is usually 3.5 or less, preferably 3.2 or less, and more preferably 2.7 or less. Here, SiO₂/Na₂When the molar ratio of O is less than 1.9, a large amount of alkali is present in the water glass, and therefore, the solubility of the water glass in water increases, and the mold material may be easily degraded by moisture absorption. On the other hand, SiO₂/Na₂Sodium silicate having an O molar ratio of more than 3.5 has low solubility in water, and therefore, in the finally obtained mold, there is a concern that the bonding area between the refractory aggregates is not obtained and the mold strength is lowered.

The water glass used in the present invention is a solution of a silicic acid compound dissolved in water, and may be used in a state in which the raw solution is diluted by adding water thereto, in addition to a state in which the raw solution is directly used as a commercially available raw solution in the production of the casting material of the present invention. A nonvolatile component (water glass component) obtained by removing volatile substances such as water and a solvent from such water glass is referred to as a solid component, and corresponds to a soluble silicic acid compound such as sodium silicate. In addition, the higher the ratio of such solid components, the higher the concentration of the silicic acid compound in the water glass becomes. Therefore, when the solid content of the water glass used in the present invention is constituted only by the stock solution, the ratio obtained by subtracting the amount of water in the stock solution corresponds to the ratio obtained by diluting the stock solution with water, and when a diluted solution obtained by diluting the stock solution with water is used, the ratio obtained by subtracting the amount of water in the stock solution and the amount of water used for dilution corresponds to the solid content of the water glass used.

The solid content in the water glass is preferably contained in an appropriate ratio depending on the type of the water glass component (soluble silicic acid compound), and is preferably 20 to 50 mass%. By appropriately making the water glass component corresponding to the solid component exist in the aqueous solution, and kneading or mixing the water glass component with the refractory aggregate, a mixture in which the water glass component is uniformly dispersed in the refractory aggregate without variation can be prepared. When the concentration of the water glass component (soluble silicic acid compound) in the water glass is too low and the total amount of the water glass component (solid component) is less than 20 mass%, the heating temperature in the mold must be increased or the heating time must be prolonged for the wet mold material of the present invention, and therefore, there is a concern that problems such as energy loss may occur. On the other hand, if the ratio of the solid content in the water glass is excessively high, it becomes difficult to prepare a mixture in which the water glass component is uniformly and uniformly dispersed in the refractory aggregate, and there is a concern that a problem arises in the characteristics of the target mold, and therefore, it is desirable to prepare the water glass in the form of an aqueous solution so that the solid content becomes 50 mass% or less and the water content becomes 50 mass% or more.

In addition to the above water glass, sodium chloride, sodium phosphate, sodium carbonate, sodium vanadate, sodium alumina, potassium chloride, potassium carbonate, magnesium sulfate, aluminum sulfate, sodium sulfate, nickel sulfate, manganese sulfate, and the like used as the water-soluble inorganic binder in the present invention are known as water-soluble inorganic binders, and can be used as appropriate in order to exhibit the characteristics as disclosed in, for example, japanese patent laid-open No. 2012-76115 and the like.

Therefore, the aqueous solution of the above-described water-soluble inorganic binder used in the present invention, in other words, the liquid water-soluble inorganic binder is used as a low-viscosity liquid having a viscosity of 1000cP or less, preferably 750cP or less, more preferably 500cP or less, and still more preferably 300cP or less at 25 ℃ in order to favorably improve the strength of the mold obtained by using the mold material of the present invention. The lower limit of the viscosity of the liquid water-soluble inorganic binder is not limited as long as the viscosity is higher than water, and is usually 1cP or more, preferably 3cP or more, more preferably 5cP or more, and still more preferably 7cP or more. By using such a liquid water-soluble inorganic binder having a low viscosity, the binder-repellent spherical silicone resin particles easily move to the surface of the liquid water-soluble inorganic binder covering the surface of the refractory aggregate. The liquid water-soluble inorganic binder may be used as it is, for example, as long as it is in a liquid state such as water glass and has a viscosity within the range defined in the present invention, or may be used as it is, or in a solid state or in a state outside the range defined in the present invention (exceeding 1000cP), by further adding water to form a liquid having a viscosity of 1000cP or less. Even if the viscosity of such a liquid water-soluble inorganic binder is 1000cP or less, the strength of the resulting mold is improved when a lower viscosity is used, but conversely, the releasability is disadvantageously lowered. However, the mold material of the present invention has the following characteristics: when the viscosity of the liquid water-soluble inorganic binder is set to an arbitrary value of 1000cP or less, a mold having good strength and mold releasability can be stably molded.

Further, in the case of the various water-soluble inorganic binders, in the mold material of the present invention, the mass is preferably used in a ratio of 0.1 to 2.5 parts by mass per 100 parts by mass of the refractory aggregate in the case of a solid, and the mass in terms of solid content when considered as a solid component alone is preferably used in a ratio of 0.1 to 2.5 parts by mass per 100 parts by mass of the refractory aggregate in the case of a liquid, and among these, the ratio of 0.2 to 2.0 parts by mass is particularly favorably used. Here, the solid content was measured as follows. That is, 10g of a sample was stored in an aluminum foil container (vertical: 9cm, horizontal: 9cm, height: 1.5cm, not sealed), and weighed, to determine the mass of the sample storage container before drying. Subsequently, the sample container was placed on a hot plate maintained at 180. + -. 1 ℃ for 20 minutes, and then the sample container was inverted and placed on the hot plate for 20 minutes. Then, the sample container was taken out from the hot plate, cooled naturally in a desiccator, and weighed to determine the mass of the dried sample container, and the solid content (mass%) was calculated from the following equation.

The solid content (% by mass) is { [ mass (g) of the sample storage container after drying) -mass (g) of the container only ]/[ mass (g) of the sample storage container before drying) -mass (g) of the container only ] } × 100

In the wet casting mold of the present invention, if the amount of the water-soluble inorganic binder is excessively reduced, it may be difficult to prepare the casting mold as a mixture (casting mold) in which the water-soluble inorganic binder is uniformly dispersed in the refractory aggregate without variation. On the other hand, even if the amount of the water-soluble inorganic binder is excessively increased, there is a concern that the fluidity of the mold material is lowered or the mold release property is deteriorated, and therefore, there is a problem that the physical properties of the finally obtained mold are adversely affected and sand falling (removal of the solidified material of the mold material) of the core after the metal casting is formed is difficult.

Furthermore, the present invention is as follows: as described above, since the intended wet mold material is prepared by adding and mixing the liquid water-soluble inorganic binder and the binder-repellent spherical silicone resin particles to the predetermined refractory aggregate, the binder-repellent spherical silicone resin particles are used as the spherical silicone resin particles, and the spherical silicone resin particles are present on the particle surface of the obtained mold material, in other words, on the surface of the water-soluble inorganic binder layer covering the refractory aggregate, whereby the mold materials come into contact with each other via the spherical silicone resin particles when the mold material is fluidized for filling the mold material in the molding die (mold), and the friction between the particles of the mold material can be effectively reduced, and the fluidity thereof can be favorably improved. In addition, while the water-soluble inorganic binder on the surface of the mold material adheres to the paths of the pneumatic metal pressure vessel and the nozzle in the molding machine during molding of the mold, and thus the flowability also deteriorates, in the mold material of the present invention, the spherical silicone resin particles present on the particle surface are sandwiched between the metal surface of the member in the molding machine and the water-soluble inorganic binder, and the spherical silicone resin particles exert the surface protecting effect, and therefore, the adhesion of the mold material to the paths of the pneumatic pressure vessel and the nozzle in the molding machine can be effectively prevented and/or suppressed. Further, after the mold material of the present invention is filled, the mold material moves to fill the gaps between the particles, and thus the filling property can be further improved.

Further, since the surface of the spherical silicone resin particles used in the present invention is adhesive repellency, the particles easily move to the surface of the liquid water-soluble inorganic binder when mixed with the liquid water-soluble inorganic binder, and the spherical silicone resin particles are present on the surface of the water-soluble inorganic binder and are spherical, so that the mold material is more easily slid, and the fluidity can be further improved. In addition, since the adhesion of the water-soluble inorganic binder to the mold can be favorably prevented, the mold release property from the mold can be significantly improved. Further, such silicone resin particles are made binder-repellent, and when forming a bond (bridge) between the aggregate and the water-soluble inorganic binder, the silicone resin particles migrate to the surface of the water-soluble inorganic binder portion constituting the bond (around the bond), and are effectively inhibited and/or prevented from being introduced into the interior of the water-soluble inorganic binder portion, whereby the aggregates are favorably joined to each other at the water-soluble inorganic binder portion where no inclusion is present, and the strength of the mold is effectively ensured, whereby the strength can be more favorably maintained and/or improved.

The term "binder repellency" as used herein means a property of repelling a liquid water-soluble inorganic binder, and in the present invention, the spherical silicone resin particles have the following properties: after the spherical silicone resin particles are sprinkled on a predetermined support member and a horizontal surface is formed from the spherical silicone resin particles, a liquid water-soluble inorganic binder used for forming the mold material is dropped on the horizontal surface, and the contact angle of the liquid drop with the horizontal surface is 90 ° or more, preferably 100 ° or more, more preferably 120 ° or more, and further preferably 125 ° or more.

The spherical shape in the spherical silicone resin particles is a spherical shape of a degree that can be recognized in general, and is not necessarily spherical, and usually, a spherical degree of 0.5 or more is used, and preferably 0.7 or more, and more preferably 0.9 or more is used favorably. Here, the sphericity is an average value of aspect ratios (ratio of short diameter/long diameter) obtained by randomly selecting 10 single particles and projecting the particles on a scanning electron microscope.

Further, the binder-repellent spherical silicone resin particles used in the present invention desirably have the following characteristics: in the thermogravimetric differential thermal analysis device, when the device is heated from room temperature to 700 ℃ in an air atmosphere, the weight reduction rate is 5 to 50%, preferably 10 to 30%, and more preferably 10 to 20%. While a mold material using a water-soluble inorganic binder generally has the advantage of not generating gas because it contains no organic component, but has the inherent problem of deterioration in disintegration properties after casting, according to the present invention, the weight reduction ratio is preferably 5% or more in order to improve the disintegration properties of a mold by adding and blending binder-repellent spherical silicone resin particles to utilize gas generated from the organic component contained in such spherical silicone resin particles. On the other hand, in order to suppress the generation of a large amount of gas during casting and to suppress the occurrence of gas defects in the cast product, the weight reduction rate is preferably 50% or less.

Further, as the spherical silicone resin particles having the binder repellency as described above, those having a particle diameter smaller than that of the refractory aggregate are favorably used, and their average particle diameter is usually 0.01 μm or more and 50 μm or less, preferably 0.05 μm or more and 25 μm or less, more preferably 0.1 μm or more and 10 μm or less, and still more preferably 0.2 μm or more and 3 μm or less. Since the spherical silicone resin particles having such an average particle diameter have a particle diameter smaller than that of the mixed refractory aggregate, they easily enter between the refractory aggregates, can be uniformly dispersed, and can be uniformly present on the particle surface of the mold material.

In the casting mold material of the present invention, the binder-repellent spherical silicone resin particles are used in a ratio of 0.1 to 500 parts by mass, preferably 0.3 to 300 parts by mass, more preferably 0.5 to 200 parts by mass, further preferably 0.75 to 100 parts by mass, and most preferably 1 to 50 parts by mass, based on 100 parts by mass of the solid content of the water-soluble inorganic binder constituting the coating layer on the surface of the refractory aggregate. In this way, the effect of the present invention can be more advantageously enjoyed by including spherical silicone resin particles having a predetermined average particle diameter in the water-soluble inorganic binder coating layer on the surface of the refractory aggregate at a predetermined ratio. The average particle diameter of the silicone resin particles can be determined from the particle size distribution measured by a laser diffraction particle size distribution measuring apparatus or the like.

Further, the silicone resin particles used in the present invention are not particularly limited as long as they are spherical and have a binder-repellent property, and the spherical resin particles are only required to have a binder-repellent property on the surface thereof, and therefore, even when a silicone resin having a binder-repellent property is used so as to cover only the surface of the spherical particles, the same effect can be obtained. However, since there is a possibility that the spherical particles themselves are broken and the coating thereof is peeled off, it is needless to say that the spherical particles composed of a single component of the binder-repellent silicone resin are more preferably used. The silicone resin is preferably one containing an organopolysiloxane as a main component, and the organopolysiloxane more preferably contains silsesquioxane. Further, it is particularly preferable that the silsesquioxane is polymethylsilsesquioxane. When the organopolysiloxane constituting the spherical silicone resin particles is silsesquioxane, and further the silsesquioxane is polymethylsilsesquioxane, spherical particles having effective binder repellency, a high silicon content, and excellent heat resistance can be obtained. Further, by providing such characteristics, thermal decomposition and melting due to heat during mold forming are less likely to occur, so that the spherical shape can be favorably maintained during molding and casting, whereby the effects of improving filling properties and strength can be favorably maintained, and odor and smoke during molding can be suppressed, so that the effect of preventing sand adhesion and the effect of improving the surface of a cast can be more favorably exhibited during casting.

The mold material of the present invention may contain, as needed, various additives such as a curing agent and a hardening accelerator, and it is preferable that the mold material further contains at least one nitrate selected from the group consisting of alkali metal salts and alkaline earth metal salts of nitric acid in order to improve the disintegration of the mold obtained from the mold material. The nitrate is added to and mixed with the liquid water-soluble inorganic binder and the spherical silicone resin particles to the refractory aggregate, and the amount of the nitrate is preferably 0.5 to 30 parts by mass, more preferably 1 to 25 parts by mass, and particularly preferably 3 to 20 parts by mass, based on 100 parts by mass of the solid content of the water-soluble inorganic binder in the casting material. If the amount of the nitrate contained is excessively small, the above-mentioned effects may not be favorably obtained, while if the amount of the nitrate is excessively large, the effects corresponding to the amount of the nitrate are not improved, and further, it is not a good measure from the viewpoint of cost performance. Among the nitrates which can be used here, sodium nitrate and potassium nitrate are suitable as the alkali metal nitrates, and calcium nitrate and magnesium nitrate are suitable as the alkaline earth metal nitrates, and they can be used alone or in a mixture of 2 or more. In particular, when water glass is used as the water-soluble inorganic binder, alkali metal salts of nitric acid are more preferable in view of high solubility in the water glass, and among them, sodium nitrate and potassium nitrate are recommended.

In addition, the mold material of the present invention preferably further contains a moisture resistance improver together with the spherical silicone resin particles. By thus incorporating the moisture resistance improver in the mold material, a synergistic effect with the moisture resistance improver can be obtained even in the molding of the mold by the secondary effect of the binder repellency of the spherical silicone resin particles, and the moisture resistance of the finally obtained mold can be further improved.

Here, as the moisture resistance improver used in the present invention, any moisture resistance improver can be used as long as it is conventionally used in a mold material and does not interfere with the effect of the present invention. Specifically, there may be exemplified carbonates such as zinc carbonate, basic zinc carbonate, iron carbonate, manganese carbonate, copper carbonate, aluminum carbonate, barium carbonate, magnesium carbonate, calcium carbonate, lithium carbonate, potassium carbonate, sodium carbonate, etc., carbonates such as sodium tetraborate, potassium tetraborate, lithium tetraborate, ammonium tetraborate, calcium tetraborate, strontium tetraborate, silver tetraborate, sodium metaborate, potassium metaborate, lithium metaborate, ammonium metaborate, calcium metaborate, silver metaborate, copper metaborate, lead metaborate, magnesium metaborate, etc., borates such as sodium sulfate, potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate, titanium sulfate, aluminum sulfate, zinc sulfate, copper sulfate, etc., sulfates such as sodium phosphate, sodium hydrogen phosphate, potassium hydrogen phosphate, lithium hydrogen phosphate, magnesium phosphate, calcium phosphate, titanium phosphate, aluminum phosphate, zinc phosphate, etc., phosphates such as zinc phosphate, lithium hydroxide, magnesium hydroxide, calcium hydroxide, magnesium carbonate, calcium, Hydroxides such as strontium hydroxide, barium hydroxide, aluminum hydroxide and zinc hydroxide, and oxides such as silicon, zinc, magnesium, aluminum, calcium, lithium, copper, iron, boron and zirconium. Among them, especially, in the case of using water glass as a water-soluble inorganic binder, alkaline zinc carbonate, iron carbonate, lithium carbonate, sodium tetraborate, lithium tetraborate, potassium metaborate, lithium sulfate, and lithium hydroxide, the moisture resistance can be more favorably improved. Among them, carbonates and borates are preferably used because they are more likely to improve moisture resistance. The moisture resistance improver such as the above-mentioned one may be used alone, or 2 or more kinds may be used in combination. The moisture resistance improver mentioned above also includes a compound that can be used as a water-soluble inorganic binder, but when a water-soluble inorganic binder other than the above-mentioned compound is used, the above-mentioned compound can function as a moisture resistance improver.

The amount of the moisture resistance improver to be used is usually preferably about 0.5 to 50 parts by mass, more preferably 1 to 20 parts by mass, particularly preferably 2 to 15 parts by mass, based on 100 parts by mass of the solid content of the liquid water-soluble inorganic binder, in the total amount. In order to favorably enjoy the effect of adding the moisture resistance improver, the amount of 0.5 parts by mass or more is desirable, and on the other hand, if the amount of addition is too large, the bonding of the water-soluble inorganic binder is inhibited, and there is a concern that the strength of the finally obtained mold may be lowered, and therefore, 50 parts by mass or less is desirable.

The mold material of the present invention may contain a predetermined surfactant. The amount of the surfactant contained in the casting material of the present invention is preferably 0.1 to 20.0 parts by mass, more preferably 0.5 to 15.0 parts by mass, particularly preferably 0.75 to 12.5 parts by mass, based on 100 parts by mass of the solid content of the water-soluble inorganic binder. If the amount of the surfactant contained is too small, the above-mentioned effects may not be favorably obtained, while if the amount of the surfactant is too large, improvement of the effects according to the amount of the surfactant used is not observed, and the amount is not a good measure from the viewpoint of cost performance. In the present invention, as the surfactant, any of a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a nonionic surfactant, a silicone surfactant, and a fluorine surfactant can be used.

Specifically, the cationic surfactant includes fatty acid soap, N-acyl-N-methylglycinate, N-acyl-N-methyl- β -alaninate, N-acyl glutamate, alkyl ether carboxylate, acylated peptide, alkylsulfonate, alkylbenzene sulfonate, alkylnaphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α -olefin sulfonate, N-acyl methyl taurine, sulfated oil, higher alcohol sulfate, higher secondary alcohol sulfate, alkyl ether sulfate, higher secondary alcohol ethoxy sulfate, polyoxyethylene alkylphenyl ether sulfate, monoglyceride sulfate, fatty acid alkanolamide sulfate, alkyl ether phosphate, alkyl phosphate ester, and amphoteric surfactant includes carboxybetaine type, sulfobetaine type, amino carboxylate, imidazolinium betaine, etc., the nonionic surfactant includes polyoxyethylene surfactant, polyoxyethylene alkyl sorbitan ether, polyoxyethylene sorbitan fatty acid ester (polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene.

Among various surfactants, in particular, those having a siloxane structure as a nonpolar portion are called silicone surfactants, and those having a perfluoroalkyl group as a nonpolar portion are called fluorine surfactants. Examples of the silicone surfactant include polyester-modified silicone, acrylic-terminated polyester-modified silicone, polyether-modified silicone, acrylic-terminated polyether-modified silicone, polyglycerol-modified silicone, and aminopropyl-modified silicone. Further, examples of the fluorine-based surfactant include perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, perfluoroalkyl trimethylammonium salt, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl group-containing oligomer, and the like.

In the present invention, the above-mentioned various surfactants can be used alone or in combination of 2 or more. In particular, since the surfactant may react with the water-soluble inorganic binder and the surface active ability may decrease or disappear with the passage of time, for example, when water glass is used as the water-soluble inorganic binder, the anionic surfactant, the nonionic surfactant, and the silicone surfactant which do not react with the water glass are favorably used.

The casting material of the present invention may contain a predetermined humectant. By containing the humectant, the wettability of the mold material moistened with moisture can be stably maintained until the material is cured or hardened by heating in the molding of the mold. The content of the humectant is preferably 0.1 to 20.0 parts by mass, more preferably 0.5 to 15.0 parts by mass, per 100 parts by mass of the solid content of the water-soluble inorganic binder. As such a humectant, polyhydric alcohols, water-soluble polymers, hydrocarbons, saccharides, proteins, inorganic compounds, and the like can be used.

Specific examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, dipropylene glycol, propylene glycol, butylene glycol, 1, 2-butanediol, 1, 2-pentanediol, 1, 5-pentanediol, 1, 2-hexanediol, 2-ethyl-1, 3-hexanediol, 1, 6-hexanediol, 1, 2-heptanediol, 1, 2-octanediol, 1,2, 6-hexanetriol, thioethylene glycol, hexanediol, glycerin, trimethylolethane, and trimethylolpropane. The water-soluble polymer compound is particularly a compound having 5 to 25 alcoholic hydroxyl groups per 1000 molecular weight. Examples of the water-soluble polymer compound include polyvinyl alcohol and polyvinyl alcohol polymers such as various modified products thereof; cellulose derivatives such as alkyl cellulose, hydroxyalkyl cellulose, alkylhydroxyalkyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose; starch derivatives such as alkyl starch, carboxymethyl starch, and oxidized starch; water-absorbing polymers such as sodium polyacrylate. Examples of the hydrocarbon include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, petroleum ether, purified light-weight solvent gasoline, tetrahydronaphthalene, decahydronaphthalene, tert-amylbenzene, and dimethylnaphthalene. Examples of the saccharide include polysaccharides such as monosaccharides, oligosaccharides, and dextrins, among which monosaccharides are those that cannot be further decomposed into simple saccharides by hydrolysis, preferably three-carbon saccharides (monosaccharides having 3 carbon atoms) to ten-carbon saccharides (monosaccharides having 10 carbon atoms), and more preferably six-carbon saccharides (monosaccharides having 6 carbon atoms). In addition, examples of the protein include gelatin and the like. Examples of the inorganic compound include common salt, sodium sulfate, calcium chloride, magnesium chloride, and silicate. These various humectants may be used alone or in combination of 2 or more.

The casting material of the present invention may further contain inorganic metal oxide particles such as silica, alumina, and titania having an average particle diameter of 0.1 to 20 μm. By containing the inorganic metal oxide particles, the filling property of the molding material into the molding die (molding cavity) during molding of the mold can be improved more advantageously. The content of the inorganic metal oxide particles is preferably 0.1 to 50.0 parts by mass, particularly preferably 0.5 to 30.0 parts by mass, based on 100 parts by mass of the solid content of the water-soluble inorganic binder. The average particle diameter of the inorganic metal oxide particles can be determined from a particle size distribution measured by a laser diffraction particle size distribution measuring apparatus or the like.

Further, the inorganic metal oxide particles used in the present invention are preferably spherical, not necessarily spherical, and those having a sphericity of usually 0.5 or more, preferably 0.7 or more, and more preferably 0.9 or more are favorably used. Here, the sphericity is an average value of an aspect ratio (ratio of short diameter/long diameter) obtained by randomly selecting 10 inorganic metal oxide particles as single particles and projecting the particles on a scanning electron microscope.

The casting material of the present invention may further contain, as necessary, various known additives in addition to the above additives. When such an additive is contained in the mold material, the following method is employed: a method of mixing a liquid water-soluble inorganic binder with a predetermined additive in advance, and then kneading or mixing the mixture with a refractory aggregate; a method of adding a predetermined additive to the refractory aggregate separately from the water-soluble inorganic binder, and uniformly kneading or mixing the whole; and the like.

In addition, it is also effective to contain, as another additive, a coupling agent for reinforcing the bond between the refractory aggregate and the water-soluble inorganic binder, and for example, a silane coupling agent, a zirconium coupling agent, a titanium coupling agent, or the like can be used. Further, it is also effective to contain a lubricant which is advantageous for improving the fluidity of the mold material, and for example, waxes such as paraffin wax, synthetic polyethylene wax, montanic acid wax, etc.; fatty acid amides such as stearamide, oleamide and erucamide; alkylene fatty acid amides such as methylene bis stearamide and ethylene bis stearamide; stearic acid, stearyl alcohol; metal stearates such as lead stearate, zinc stearate, calcium stearate, and magnesium stearate; stearic acid monoglyceride, stearic acid stearyl ester, hydrogenated oil, etc. Further, as the release agent, silicone release agents such as paraffin, wax, gas oil, engine oil, spindle oil, insulating oil, waste oil, vegetable oil, fatty acid ester, organic acid, graphite fine particles, mica, vermiculite, fluorine-based release agent, silicone oil, and the like can be used. These other additives are contained in a proportion of usually 5% by mass or less, preferably 3% by mass or less, based on the solid content in the water-soluble inorganic binder.

In the production of the wet mold material having no room-temperature fluidity according to the present invention, the following method is generally employed: the water-soluble inorganic binder in an aqueous solution state as a binder and the binder-repellent spherical silicone resin particles are kneaded or mixed with other additives as necessary to give a wet molding material (precoated sand) having no fluidity at room temperature, which is formed of a mixture in which the refractory aggregate, the water-soluble inorganic binder in an aqueous solution state, and the spherical silicone resin particles (and other additives) are uniformly mixed. The obtained wet casting material (precoated sand) having no room-temperature fluidity is produced by adjusting the moisture content of the casting material (precoated sand) to a wet level as needed so that the moisture content of the casting material (precoated sand) is more than 55 mass%, preferably 70 to 900 mass%, more preferably 95 to 500 mass%, relative to the solid content of the water-soluble inorganic binder. The wet mold material (precoated sand) adjusted to such a moisture content can be effectively prevented from hindering the filling of the mold by drying the blow gas during the filling of the mold during the molding of the mold, and can maintain the wettability as the wet mold material (precoated sand), and can also be provided with excellent characteristics in a mold molded using such a mold material (precoated sand).

Therefore, in the process for producing the wet mold material of the present invention, the binder-repellent spherical silicone resin particles may be added simultaneously with the refractory aggregate and the water-soluble inorganic binder and kneaded or mixed, or may be added separately and kneaded during the kneading, or may be kneaded with a time lag provided during the kneading. When the water-soluble inorganic binder in an aqueous solution state as a binder is used as a solid in the production of the wet casting material of the present invention, the binder is used in a state of being dissolved in water in advance. The liquid water-soluble inorganic binder may be diluted with water to adjust the viscosity thereof within the range used in the present invention. The water may be added by mixing with the water-soluble inorganic binder in advance, or by separately adding the water-soluble inorganic binder and water when kneading or mixing with the refractory aggregate. In the case where the water-soluble inorganic binder and water are separately added at the time of kneading or mixing, the viscosity of the liquid water-soluble binder in the present invention is based on the viscosity at the time of mixing the separately added water-soluble inorganic binder and water. Therefore, for example, when the solid water-soluble inorganic binder and water are separately added at the time of kneading or mixing, it is considered that a liquid water-soluble inorganic binder is used, and the viscosity of a liquid obtained by dissolving a solid water-soluble inorganic binder in water may be 1000cP or less.

Further, when the wet mold material (precoated sand) having no room-temperature fluidity of the present invention is used for molding a target mold, the following method can be advantageously employed: the casting material is filled into a cavity of a mold for providing the target mold, and the mold is heated to a temperature of 80 to 300 ℃, preferably 90 to 250 ℃, and more preferably 100 to 200 ℃ and held in the mold until the casting material filled therein is dried. By heating the molding die in advance at a temperature within such a temperature range, the wet strength of the finally obtained mold can be advantageously improved, and the drying of the mold material can be advantageously performed. In the holding of the mold material in the mold, hot air or superheated steam may be blown into the mold to promote drying, and carbon dioxide (CO) as a hardening accelerator may be used to further promote the solidification or hardening of the mold material (filling phase)₂Gas), ester, etc. are formed in a gaseous or mist state and are ventilated in the mold.

That is, since the mold material constituting the filling phase in the cavity is in a wet state by filling and holding a wet mold material (precoated sand) having no room-temperature fluidity in the cavity of the heated mold, the refractory aggregates are bonded and linked to each other by the water-soluble inorganic binder to form an aggregate (binder) of the mold material in an integrated mold shape. It should be noted that, in general, if any additive is not added, the water-soluble inorganic binder is solidified by evaporation and drying of water, and in the case where an oxide or a salt is added as a hardening agent, it is hardened. In the present invention, the aggregate (combination) of the casting material includes one obtained by simply curing and one obtained by hardening with a hardening agent. In the present specification, the expression "cured product" is understood to be used in a meaning including "cured product".

Examples of the carbon dioxide and various esters used as the hardening accelerator include methyl formate, ethyl formate, propyl formate, γ -butyrolactone, β -propiolactone, ethylene glycol diacetate, diethylene glycol diacetate, glycerol triacetate, and propylene carbonate, and these hardening accelerators may be used alone or in combination of 2 or more.

In addition to the above-described methods, various known molding methods can be suitably used as a method for producing a target mold using the mold material of the present invention, and for example, the following method of molding by stacking may be used: the layers of the mold material are sequentially laminated, and a portion corresponding to the target mold is cured to directly form a three-dimensional mold.