阅读说明：本技术 发泡成形用母料和发泡成形体 (Master batch for foam molding and foam molded body ) 是由 内山裕作 于 2018-09-28 设计创作，主要内容包括：本发明的目的在于,提供对于施加强剪切力的成形、要求低成形温度的成形也能够适于使用并且能够制造发泡倍率高且外观品质良好的发泡成形体的发泡成形用母料；以及使用了该发泡成形用母料的发泡成形体。本发明是一种发泡成形用母料,其为含有基础树脂、热膨胀性微囊的发泡成形用母料,其中,所述发泡成形用母料的真比重为0.80g/cm<Sup>3</Sup>以上,门尼粘度ML1+4(100℃)为20～90,上述基础树脂含有EPDM树脂,相对于上述基础树脂100重量份,含有40～300重量份的上述热膨胀性微囊。(Objects of the inventionDisclosed is a master batch for foam molding, which can be suitably used for molding that applies a strong shearing force or molding that requires a low molding temperature, and which can produce a foam molded article having a high expansion ratio and good appearance quality; and a foam molded article using the master batch for foam molding. The invention provides a master batch for foam molding, which contains a base resin and heat-expandable microcapsules, wherein the true specific gravity of the master batch for foam molding is 0.80g/cm 3 The Mooney viscosity ML1+4(100 ℃) is 20-90, the base resin contains EPDM resin, and the heat-expandable microcapsules are contained in 40-300 parts by weight relative to 100 parts by weight of the base resin.)

1. A master batch for foam molding which comprises a base resin and heat-expandable microcapsules, wherein,

the master batch for foam molding has a true specific gravity of 0.80g/cm³The Mooney viscosity ML1+4 is 20 to 90 at 100 ℃,

the base resin contains an EPDM resin,

the thermally expandable microcapsules are contained in an amount of 40 to 300 parts by weight based on 100 parts by weight of the base resin.

2. A masterbatch for foam molding according to claim 1 wherein the EPDM resin has an ethylene content of 50 to 72% by weight.

3. The masterbatch for foam molding according to claim 1 or 2, wherein the diene content of the EPDM resin is 2.3 to 9.5 wt%.

4. A master batch for foam molding according to claim 1, 2 or 3, wherein the heat-expandable microcapsules contain a volatile expansion agent as a core agent in a shell containing a polymer,

the shell includes a polymer obtained by polymerizing a monomer mixture containing a polymerizable monomer including at least 1 selected from the group consisting of acrylonitrile, methacrylonitrile, and vinylidene chloride.

5. A masterbatch for foam molding according to claim 1, 2, 3 or 4, wherein the maximum foaming temperature of the thermally-expansible microcapsules is 180 ℃ or lower.

6. A foam-molded article produced by using the master batch for foam molding according to claim 1, 2, 3, 4 or 5.

Technical Field

The present invention relates to a master batch for foam molding, which can be suitably used for molding with a strong shearing force or molding requiring a low molding temperature, and which can produce a foam molded article having a high expansion ratio and good appearance quality. Also disclosed is a foam molded article using such a master batch for foam molding.

Background

Plastic foams can exhibit heat insulation, sound absorption, vibration isolation, and weight reduction depending on the material of the foam and the state of the formed cells, and thus can be used in various applications. Examples of the method for producing such a plastic foam include: a method of foaming and molding by heating a master batch containing a chemical foaming agent. However, a master batch containing a chemical foaming agent may not foam even when heated, and may have a problem that the foaming agent may be rapidly decomposed in an injection foam molding machine, and the operation is difficult. In addition, depending on the type of resin, a sufficient expansion ratio cannot be obtained, and it may be difficult to obtain a desired hardness as a molded article.

On the other hand, patent document 1 describes that by using master batch particles of an ethylene- α -olefin copolymer containing a chemical blowing agent, an injection foam molded article having high hardness and expansion ratio and formed with uniform cells can be obtained regardless of the type of resin.

However, the chemical foaming agent generates decomposition gas and foaming residue at the same time when it is decomposed by heating, and the residue remaining in the molded article may affect the adhesion performance of the molded article. Further, when a chemical foaming agent is used, all of the bubbles cannot be formed independently, and in any case, a portion where continuous bubbles are formed is generated, and there is a problem that it is difficult to obtain a foam molded product having high airtightness.

Patent document 2 describes a foamed resin master batch in which a polyolefin resin or a styrene resin is used as a base resin and a thermally expandable microcapsule is used as a foaming agent instead of a chemical foaming agent.

However, when the thermally expandable microcapsules described in patent document 2 are used, the expansion ratio of the obtained foam is low, and it is difficult to form closed cells of the obtained foam to have a constant size.

In view of the above, patent document 3 describes the following method: the foamed composite board is produced by foaming and molding a resin composition obtained by mixing a master batch containing thermally expandable microcapsules and a master batch containing a chemical foaming agent.

However, even when this method is used, although it is confirmed that the expansion ratio is slightly increased, the expansion ratio of the molded article is still low, and the desired properties such as lightness and heat insulation properties cannot be obtained. In addition, it is difficult to obtain a molded article having good appearance quality.

Further, patent document 4 discloses a synthetic resin composition containing a thermally expandable microcapsule and a base resin, and a method for producing the same. In such a synthetic resin composition, by using a base resin having a melt flow rate within a predetermined range, the heat-expandable microcapsules and the base resin can be made excellent in miscibility and affinity without damaging the shell of the heat-expandable microcapsules.

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide a master batch for foam molding, which can be suitably used for molding in which a strong shearing force is applied or molding in which a low molding temperature is required, and which can produce a foam molded article having a high expansion ratio and good appearance quality. It is another object of the present invention to provide a foam molded article using the master batch for foam molding.

Means for solving the problems

The invention provides a master batch for foam molding, which contains a base resin and heat-expandable microcapsules, wherein the true specific gravity of the master batch for foam molding is 0.80g/cm³The Mooney viscosity ML1+4(100 ℃) is 20-90, the base resin contains EPDM resin, and the heat-expandable microcapsules are contained in 40-300 parts by weight relative to 100 parts by weight of the base resin.

The present invention is described in detail below.

The present inventors have conducted intensive studies and, as a result, have found that: when the EPDM resin is used as the base resin, the thermally expandable microcapsules are used as the foaming component, and the contents of the thermally expandable microcapsules and the base resin and the mooney viscosity are set to be within specific ranges, the EPDM resin can be suitably used for molding in which a strong shearing force is applied and molding in which a low molding temperature is required. In addition, it was found that: the present inventors have completed the present invention by obtaining a foam molded article having a high expansion ratio and good appearance quality.

The master batch for foam molding of the present invention contains a base resin.

In the present invention, an EPDM resin (ethylene-propylene-diene rubber) is used as the base resin. This enables production of a foam molded article having good appearance quality.

The preferable lower limit of the Mooney viscosity ML1+4(100 ℃) of the EPDM resin is 5, and the preferable upper limit thereof is 70.

By setting the mooney viscosity to 5 or more, the handleability of the foam molding masterbatch can be improved, and by setting the mooney viscosity to 70 or less, the processability of the foam molding masterbatch can be improved.

A more preferable lower limit and a more preferable upper limit of the Mooney viscosity are 10 and 60, respectively.

The mooney viscosity is measured by a method specified in JIS K6300 and used as an index representing the viscosity. In ML1+4, M refers to mooney M, L refers to rotor shape L, (1+4) refers to preheating time 1 minute and rotation time of rotor 4 minutes. Further, "(100 ℃ C.)" means that the measurement is performed at 100 ℃.

The ethylene content (weight% of the ethylene component with respect to the entire EPDM resin) of the EPDM resin preferably has a lower limit of 50 wt% and an upper limit of 72 wt%.

By using the EPDM resin having an ethylene content within the above range, moldability and dispersibility of the thermally expandable microcapsules can be improved. The lower limit of the ethylene content is more preferably 55% by weight, and the upper limit is more preferably 65% by weight.

The EPDM resin preferably has a propylene content (wt% of the propylene component with respect to the entire EPDM resin) of 20 to 50 wt%.

The preferable lower limit of the diene content (the weight% of the diene component with respect to the entire EPDM resin) of the EPDM resin is 2.3 wt%, and the preferable upper limit is 9.5 wt%.

By using the EPDM resin having the diene content within the above range, the weather resistance can be improved. The diene content has a more preferable lower limit of 4% by weight and a more preferable upper limit of 5.5% by weight.

Examples of the diene component constituting the EPDM resin include norbornenes such as 5-ethylidene-2-norbornene (ENB), 5-methylene-2-norbornene, 5-n-propylidene-2-norbornene, 5-isobutylidene-2-norbornene, and 5-n-butylidene-2-norbornene. Further, non-conjugated dienes such as dicyclopentadiene (DCPD), 1, 4-Hexadiene (HD), bicyclo [2.2.1] heptadiene and the like are exemplified. Of these, 5-ethylidene-2-norbornene is particularly preferable.

The EPDM resin preferably has a ratio of an ethylene component to a diene component (ethylene component: diene component) of 80: 20 to 98: 2, and more preferably 84: 16 to 96: 4.

The weight average molecular weight of the EPDM resin preferably has a lower limit of 1 ten thousand and an upper limit of 100 ten thousand. The EPDM resin may be oil-extended or non-oil-extended.

The EPDM resin may be 100 wt% of the base resin, and 1 or 2 or more other resin components may be appropriately mixed in addition to the EPDM resin.

When the other resin component is used, the proportion of the EPDM resin is preferably 80 wt% or more, and more preferably 90 wt% or more.

Examples of the other resin component include rubber components, and as the rubber component, Ethylene Propylene Rubber (EPR), Natural Rubber (NR), Butadiene Rubber (BR), Styrene Butadiene Rubber (SBR), Isoprene Rubber (IR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), and the like can be used. Chloroprene Rubber (CR), acrylic rubber (ACM, ANM), urethane rubber (U), silicone rubber (Si), and the like may be used, and 1 or 2 or more selected from the above rubber components may be used in combination.

As the other resin component, a general thermoplastic resin can be used.

Examples of the thermoplastic resin include general thermoplastic resins such as polyvinyl chloride, polypropylene oxide, low-density polyethylene, high-density polyethylene, and polystyrene, and engineering plastics such as polybutylene terephthalate, nylon, polycarbonate, and polyethylene terephthalate. Among these, at least 1 selected from the group consisting of low density polyethylene, high density polyethylene, polypropylene and polystyrene is preferable.

The lower limit of the content of the base resin in the master batch for foam molding of the present invention is preferably 30% by weight, and the upper limit is preferably 70% by weight. If the content of the base resin is less than 30% by weight, foaming may not be performed during preparation of a master batch, and if the content of the base resin exceeds 70% by weight, a desired expansion ratio may not be obtained.

The master batch for foam molding of the present invention contains heat-expandable microcapsules.

The lower limit of the content of the thermally expandable microcapsules in the master batch for foam molding of the present invention is 40 parts by weight and the upper limit is 300 parts by weight with respect to 100 parts by weight of the base resin. By setting the content of the thermally expandable microcapsules to 40 parts by weight or more, a desired expansion ratio can be obtained. By setting the content of the thermally expandable microcapsules to 300 parts by weight or less, foaming at the time of producing a master batch can be prevented, and as a result, the expansion ratio of the foam-molded article can be increased. The lower limit of the content of the thermally expandable microcapsules is preferably 65 parts by weight, and the upper limit is preferably 150 parts by weight.

The shell constituting the thermally-expansible microcapsules preferably contains a polymer obtained by polymerizing a monomer mixture containing a polymerizable monomer containing at least 1 selected from the group consisting of acrylonitrile, methacrylonitrile, and vinylidene chloride.

The addition of the polymerizable monomer can improve the gas barrier property of the shell.

The lower limit of the content of the polymerizable monomer in the monomer mixture is preferably 40% by weight, and the upper limit is preferably 98% by weight. If the content of the polymerizable monomer in the monomer mixture is less than 40% by weight, the gas barrier property of the shell is lowered, and therefore the expansion ratio may be lowered. If the content of the polymerizable monomer in the monomer mixture exceeds 98% by weight, the heat resistance may not be improved. The lower limit of the content of the polymerizable monomer in the monomer mixture is more preferably 50% by weight, and the upper limit is more preferably 97% by weight.

The monomer mixture preferably contains a crosslinkable monomer having 2 or more double bonds in the molecule. The crosslinkable monomer has a function as a crosslinking agent. By containing the crosslinkable monomer, the strength of the shell can be enhanced, and the cell wall is less likely to be broken during thermal expansion.

Examples of the crosslinkable monomer include monomers having 2 or more radical polymerizable double bonds. Specific examples thereof include divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and 1, 4-butanediol di (meth) acrylate. Further, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, di (meth) acrylate of polyethylene glycol having a weight average molecular weight of 200 to 600, glycerin di (meth) acrylate, trimethylolpropane di (meth) acrylate, and the like can be mentioned. Further, trimethylolpropane tri (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, triallylformal tri (meth) acrylate, and the like can be mentioned. Further, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate and the like can be mentioned.

The lower limit of the content of the crosslinkable monomer in the monomer mixture is preferably 0.0 wt%, and the upper limit is preferably 3.0 wt%. By setting the content of the crosslinkable monomer to 3.0 wt% or less, the expansion ratio of the thermally expandable microcapsule can be increased. The lower limit of the content of the crosslinkable monomer is more preferably 0.0% by weight, and the upper limit is more preferably 2.0% by weight.

Examples of the monomer other than the polymerizable monomer and the crosslinkable monomer containing at least 1 kind selected from the group consisting of acrylonitrile, methacrylonitrile, and vinylidene chloride include unsaturated monocarboxylic acid, unsaturated dicarboxylic acid or anhydride thereof, monoester of unsaturated dicarboxylic acid or derivative thereof, (meth) acrylic acid ester, vinyl acetate or derivative thereof, and the like.

Examples of the unsaturated monocarboxylic acid include acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid. Examples of the unsaturated dicarboxylic acid include maleic acid, itaconic acid, fumaric acid, citraconic acid, and chloromaleic acid. Examples of the monoester of the unsaturated dicarboxylic acid include monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, and the like. These can be used alone, also can be used in combination of more than 2.

In order to polymerize the monomer, a polymerization initiator is added to the monomer composition containing the monomer mixture. As the polymerization initiator, for example, dialkyl peroxides, diacyl peroxides, peroxyesters, peroxydicarbonates, azo compounds, and the like are suitably used.

Examples of the dialkyl peroxide include methylethyl peroxide, di-t-butyl peroxide, isobutyl peroxide, and dicumyl peroxide.

Examples of the diacyl peroxide include benzoyl peroxide, 2, 4-dichlorobenzoyl peroxide, and 3, 5, 5-trimethylhexanoyl peroxide.

Examples of the peroxyesters include t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, and 1, 1, 3, 3-tetramethylbutyl peroxyneodecanoate.

Examples of the peroxydicarbonate include bis (4-t-butylcyclohexyl) peroxydicarbonate, di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, bis (2-ethylperoxyl) dicarbonate, and dimethoxybutylperoxydicarbonate.

Examples of the azo compound include 2, 2 '-azobisisobutyronitrile, 2' -azobis (4-methoxy-2, 4-dimethylvaleronitrile), 2 '-azobis (2, 4-dimethylvaleronitrile), 1' -azobis (1-cyclohexanecarbonitrile), and the like.

The weight average molecular weight of the polymer constituting the shell preferably has a lower limit of 10 ten thousand and an upper limit of 200 ten thousand. When the weight average molecular weight is less than 10 ten thousand, the strength of the shell may decrease, and when the weight average molecular weight exceeds 200 ten thousand, the strength of the shell may become too high, and the expansion ratio may decrease.

The shell may further contain a stabilizer, an ultraviolet absorber, an antioxidant, an antistatic agent, a flame retardant, a silane coupling agent, a coloring material, and the like as needed.

The thermally expandable microcapsule contains a volatile expansion agent as a core agent in the shell.

The volatile expansion agent is a substance that is in a gaseous state at a temperature not higher than the softening point of the polymer constituting the shell, and a low-boiling organic solvent is preferable.

Examples of the volatile expansion agent include low molecular weight hydrocarbons, chlorofluorocarbons, and tetraalkylsilanes.

Examples of the low molecular weight hydrocarbon include ethane, ethylene, propane, propylene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, isooctane, and petroleum ether.

Examples of the chlorofluorocarbon include CCl₃F、CCl₂F₂、CClF₃、CClF₂-CClF₂And the like.

Examples of the tetraalkylsilane include tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyln-propylsilane.

Of these, isobutane, n-butane, n-pentane, isopentane, n-hexane, isooctane, petroleum ether and mixtures thereof are preferable. These volatile swelling agents may be used alone, or 2 or more of them may be used in combination.

As the volatile expansion agent, a thermal decomposition type compound that thermally decomposes into a gaseous state by heating can be used.

In the thermally expandable microcapsule, a low boiling point hydrocarbon having 5 or less carbon atoms is particularly preferably used as the volatile expansion agent. By using such a hydrocarbon, a thermally expandable microcapsule having a high expansion ratio and rapidly starting to foam can be produced.

As the volatile expansion agent, a thermal decomposition type compound that thermally decomposes into a gaseous state by heating may be used.

In the master batch for foam molding of the present invention, the content of the volatile expansion agent used as the core agent is preferably 10% by weight at the lower limit and 25% by weight at the upper limit.

The thickness of the shell varies depending on the content of the core agent, and when the content of the core agent is reduced and the shell becomes too thick, the foaming property is lowered, and when the content of the core agent is increased, the strength of the shell is lowered. When the content of the nucleating agent is 10 to 25 wt%, both prevention of decrease in the elastic force of the thermally expandable microcapsule and improvement in the foaming performance can be achieved.

The lower limit of the maximum foaming temperature (Tmax) of the thermally expandable microcapsule is preferably 100 ℃ and the upper limit thereof is preferably 180 ℃. When the maximum foaming temperature is less than 100 ℃, the heat resistance is low, and therefore, the thermally expandable microcapsules are broken and shrunk in a high temperature region or during molding. Further, foaming occurs due to shearing when producing a master batch, and an unfoamed master batch cannot be stably produced. A more preferred lower limit of the maximum foaming temperature is 120 ℃.

In the present specification, the maximum foaming temperature means: the temperature at which the diameter of the thermally-expansible microcapsules reaches the maximum (maximum displacement amount) when the diameter of the thermally-expansible microcapsules is measured while heating the thermally-expansible microcapsules at normal temperature.

The volume average particle diameter of the thermally expandable microcapsules preferably has a lower limit of 5 μm and an upper limit of 100 μm. If the volume average particle size is less than 5 μm, the resulting molded article may have too small bubbles, and therefore the weight of the molded article may be insufficient, and if the volume average particle size exceeds 100 μm, the resulting molded article may have too large bubbles, and therefore, the strength may be problematic. The volume average particle diameter has a more preferable lower limit of 10 μm, a more preferable upper limit of 40 μm, a further more preferable lower limit of 12 μm, and a further more preferable upper limit of 25 μm.

The lower limit of the bulk density of the thermally expandable microcapsule is 0.40g/cm³. If the bulk specific gravity is less than 0.40g/cm³In particular, when a masterbatch is produced by extrusion molding, the thermally expandable microcapsules tend to foam because shear is easily applied to the thermally expandable microcapsules. As a result, a stable master batch cannot be produced due to a decrease in the true specific gravity of the master batch or the like, and thereafter, when foam molding is performed using injection molding or the like, variations in the expansion ratio are likely to occur. The preferable lower limit of the bulk density is 0.42g/cm³。

The bulk specific gravity is a specific gravity based on the volume of the thermally expandable microcapsule aggregate most densely packed in a container or the like. The bulk density can be measured according to JIS K6721.

Examples of the method for producing the thermally expandable microcapsules include the following methods: for example, a step of preparing an aqueous medium; dispersing an oily mixture containing a monomer composition and a volatile swelling agent in an aqueous medium, the monomer composition containing 40 to 98 wt% of the polymerizable monomer, 0 to 3 wt% of a crosslinkable monomer, a monomer such as vinyl acetate, and a polymerization initiator; thereafter, a step of polymerizing the monomer is performed.

In order to produce the thermally expandable microcapsules, first, a step of preparing an aqueous medium is performed. Specifically, for example, an aqueous dispersion medium containing a dispersion stabilizer is prepared by adding water and the dispersion stabilizer, and an auxiliary stabilizer used as needed, to a polymerization reaction vessel. Further, alkali metal nitrite, stannous chloride, stannic chloride, potassium dichromate and the like may be added as necessary.

Examples of the dispersion stabilizer include silica, calcium phosphate, magnesium hydroxide, aluminum hydroxide, iron hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, barium carbonate, and magnesium carbonate.

The amount of the dispersion stabilizer to be added is not particularly limited, and may be suitably determined depending on the kind of the dispersion stabilizer, the particle diameter of the thermally expandable microcapsules, and the like, and the lower limit is preferably 0.1 part by weight and the upper limit is preferably 20 parts by weight with respect to 100 parts by weight of the monomer.

Examples of the auxiliary stabilizer include a condensation product of diethanolamine and an aliphatic dicarboxylic acid, and a condensation product of urea and formaldehyde. Further, polyvinyl pyrrolidone, polyethylene oxide, polyethyleneimine, tetramethylammonium hydroxide, gelatin, methyl cellulose, polyvinyl alcohol, dioctyl sulfosuccinate, sorbitan ester, various emulsifiers, and the like can be exemplified.

The combination of the dispersion stabilizer and the auxiliary stabilizer is not particularly limited, and examples thereof include a combination of colloidal silica and a condensation product, a combination of colloidal silica and a water-soluble nitrogen-containing compound, and a combination of magnesium hydroxide or calcium phosphate and an emulsifier. Of these, a combination of colloidal silica and a condensation product is preferable.

Further, the condensation product is preferably a condensation product of diethanolamine and an aliphatic dicarboxylic acid, and particularly preferably a condensation product of diethanolamine and adipic acid, or a condensation product of diethanolamine and itaconic acid.

Examples of the water-soluble nitrogen-containing compound include polyvinylpyrrolidone, polyethyleneimine, polyoxyethylenealkylamine, polydialkylaminoalkyl (meth) acrylate, polydialkylaminoalkyl (meth) acrylamide, polyacrylamide, polycationic acrylamide, polyamine sulfone, and polyallylamine.

Examples of the polydialkylamino alkyl (meth) acrylate include a polydimethylaminoethyl methacrylate and a polydimethylaminoethyl acrylate.

Examples of the polydialkylamino alkyl (meth) acrylamide include a polydimethylaminopropyl acrylamide and a polydimethylaminopropyl methacrylamide. Among these, polyvinylpyrrolidone is preferably used.

The amount of the colloidal silica added may be appropriately determined depending on the particle diameter of the thermally expandable microcapsule, and is preferably 1 part by weight at the lower limit and 20 parts by weight at the upper limit to 100 parts by weight of the vinyl monomer. The amount of the colloidal silica added is more preferably 2 parts by weight at the lower limit and more preferably 10 parts by weight at the upper limit. The amount of the condensation product or the water-soluble nitrogen-containing compound added is appropriately determined depending on the particle diameter of the thermally expandable microcapsule, and is preferably 0.05 parts by weight at the lower limit and 2 parts by weight at the upper limit to 100 parts by weight of the monomer.

In addition to the dispersion stabilizer and the auxiliary stabilizer, an inorganic salt such as sodium chloride or sodium sulfate may be further added. By adding the inorganic salt, a thermally expandable microcapsule having a more uniform particle shape can be obtained. The amount of the inorganic salt added is preferably 0 to 100 parts by weight based on 100 parts by weight of the monomer.

The aqueous dispersion medium containing the dispersion stabilizer is prepared by mixing a dispersion stabilizer and an auxiliary stabilizer into deionized water, and the pH of the aqueous phase at this time can be appropriately determined depending on the kind of the dispersion stabilizer and the auxiliary stabilizer used. For example, when silica such as colloidal silica is used as a dispersion stabilizer, polymerization is carried out in an acidic medium, and an acid such as hydrochloric acid is added as necessary to adjust the pH of the system to 3 to 4 in order to make the aqueous medium acidic. On the other hand, when magnesium hydroxide or calcium phosphate is used, it is polymerized in an alkaline medium.

Next, in the method for producing the thermally expandable microcapsule, a step of dispersing an oily mixed liquid containing a monomer composition containing 40 to 98% by weight of the polymerizable monomer, 0 to 3% by weight of a crosslinkable monomer, a monomer such as vinyl acetate, and a polymerization initiator, and a volatile expanding agent in an aqueous medium is performed. In this step, the monomer and the volatile swelling agent may be added to the aqueous dispersion medium to prepare an oily mixed solution in the aqueous dispersion medium, but the monomer and the volatile swelling agent are usually mixed in advance to prepare an oily mixed solution, and then the oily mixed solution is added to the aqueous dispersion medium. In this case, the oily mixed liquid and the aqueous dispersion medium may be prepared in advance in separate containers, and the oily mixed liquid may be dispersed in the aqueous dispersion medium by mixing the oily mixed liquid and the aqueous dispersion medium while stirring the aqueous mixed liquid in a separate container, and then the resulting mixture may be added to the polymerization reaction vessel.

The polymerization initiator may be used for polymerizing the monomer, and may be added to the oil-based mixed solution in advance, or may be added after the aqueous dispersion medium and the oil-based mixed solution are stirred and mixed in a polymerization reaction vessel.

Examples of the method for emulsifying and dispersing the oil-based mixed solution in an aqueous dispersion medium with a predetermined particle diameter include the following methods: a method of stirring with a homogenizer (e.g., a special machine-made industrial company) or the like, a method of passing it through a static dispersing apparatus such as a line mixer or a unit static disperser, or the like.

The aqueous dispersion medium and the polymerizable mixture may be supplied separately to the static dispersion device, or a dispersion liquid obtained by mixing and stirring the aqueous dispersion medium and the polymerizable mixture in advance may be supplied.

The thermally expandable microcapsule can be produced by performing a step of polymerizing a monomer by, for example, heating the dispersion obtained through the above-described step.

The master batch for foam molding of the present invention may contain a chemical foaming agent. By containing the above-mentioned chemical hairThe foaming agent can utilize CO generated during decomposition when a chemical foaming agent such as sodium bicarbonate is used₂To improve foaming properties. Further, by using the thermally expandable microcapsules in combination with a chemical foaming agent, it is possible to suppress the formation of open cells which are likely to occur when the chemical foaming agent is used alone.

The chemical foaming agent is not particularly limited as long as it is in the form of a powder at room temperature, and those conventionally used as chemical foaming agents can be used. Specific examples thereof include: inorganic chemical foaming agents such as sodium bicarbonate, and organic chemical foaming agents such as azodicarbonamide, N '-dinitrosopentamethylenetetramine, P' -oxybis-benzenesulfonylhydrazide and P-toluenesulfonylhydrazide.

The master batch for foam molding of the present invention may contain additives such as lubricants and processing oils. By containing the lubricant, shearing applied to the thermally expandable microcapsules at the time of producing the master batch is suppressed, micro-foaming or the like is less likely to occur, and dispersibility of the thermally expandable microcapsules can be improved, whereby the master batch can be easily produced. As a result, a master batch having a high concentration of the thermally expandable microcapsules can be stably produced with good production efficiency.

The lubricant is not particularly limited as long as it dissolves at the temperature used in the production of the master batch, and any one commonly used as a lubricant can be used. Specifically, for example, polyethylene wax having a viscosity average molecular weight of 3000 or less, glycerin fatty acid esters such as glycerin monostearate and diglycerin stearate, fatty acids such as stearic acid, and a lubricant called a composite lubricant are included.

The process oil is not particularly limited, and a paraffinic process oil, a naphthenic process oil, an aromatic process oil, a hydrocarbon process oil obtained by mixing them, or the like can be used. Among them, paraffin-based process oils are preferable.

The content of the processing oil is preferably 40 to 200 parts by weight based on 100 parts by weight of the base resin.

The shape of the master batch for foam molding of the present invention may be any of various shapes such as powder, granule, block, strand, granule, and sheet.

The lower limit of the true specific gravity of the master batch for foam molding of the present invention is 0.80g/cm³. If the true specific gravity is less than 0.80g/cm³This means that the thermally expandable microcapsules present in the master batch expand, and therefore the expansion ratio of the molded article obtained after molding decreases.

The preferable lower limit of the true specific gravity is 0.90g/cm³Preferably, the upper limit is 1.0g/cm³。

The true specific gravity refers to the specific gravity of the raw material itself excluding the pores, and represents the ratio of the mass per unit volume of the master batch at 20 ℃ to the mass of water at 4 ℃ equivalent thereto. The true specific gravity can be measured by a method according to JIS K7112A method (underwater substitution method).

The Mooney viscosity ML1+4(100 ℃) of the master batch for foam molding of the present invention has a lower limit of 20 and an upper limit of 90.

When the mooney viscosity is 20 or more, adhesion between the master batches and the like can be prevented to improve handling properties, and when the mooney viscosity is 90 or less, kneading properties with the matrix resin can be improved. The preferred lower limit is 40 and the preferred upper limit is 85.

The method for producing the master batch for foam molding of the present invention is not particularly limited, and examples thereof include the following methods: a raw material such as a base resin containing an EPDM resin having a predetermined Mooney viscosity and various additives such as a lubricant is kneaded in advance by a pressure kneader at 50 to 100 ℃ for about 5 minutes; subsequently, the rubber composition kneaded in advance was supplied to a roll machine, molding conditions were set to 50 to 100 ℃ for the roll temperature, 20rpm for the roll speed, and 1cm for the distance between the rolls, and the rubber composition was mixed for 5 minutes to prepare a sheet-like master batch having a thickness of 1 cm. When the micro-foaming occurs at this time, it is difficult to obtain a desired expansion ratio in subsequent foaming, and the variation also increases.

Further, the following method may also be used: a method in which raw materials such as a base resin, a thermally expandable microcapsule, and a lubricant are kneaded by a batch kneader and then granulated by a granulator; a process for making a masterbatch in pellet form using an extruder and pelletizer.

The kneading machine is not particularly limited as long as it can perform kneading without destroying the thermally expandable microcapsules, and examples thereof include a banbury mixer and the like.

The resin composition obtained by adding a matrix resin such as a thermoplastic resin to the master batch for foam molding of the present invention is molded by a molding method such as injection molding, and the thermally expandable microcapsules are foamed by heating at the time of molding, thereby producing a foam molded body. This foamed molded article is also one aspect of the present invention.

The foamed molded article of the present invention obtained by the above method can have a high expansion ratio and high appearance quality, can uniformly form independent cells, is excellent in light weight, heat insulation properties, impact resistance, rigidity and the like, and can be suitably used for applications such as building materials for houses, parts for automobiles, shoe soles and the like.

The matrix resin such as the thermoplastic resin is not particularly limited as long as the object of the present invention is not impaired, and for example, a general thermoplastic resin such as polyvinyl chloride, polystyrene, polypropylene oxide, polyethylene, or the like can be used. Further, engineering plastics such as polybutylene terephthalate, nylon, polycarbonate, polyethylene terephthalate, and the like can be cited. In addition, thermoplastic elastomers such as vinyl, vinyl chloride, olefin, urethane, and ester resins may be used, or these resins may be used in combination.

The matrix resin is preferably the same resin as the base resin.

The amount of the master batch for foam molding of the present invention added is preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the thermoplastic resin.

The method for molding the foamed molded article of the present invention is not particularly limited, and examples thereof include kneading molding, calendering molding, extrusion molding, and injection molding. In the case of injection molding, the method is not particularly limited, and examples thereof include a short-short method in which a part of a resin material is added to a mold and foamed, and a core back method in which the mold is opened to a state in which the resin material is filled in the mold and foamed.

Examples of applications of the molded article obtained by the method for molding a foamed molded article of the present invention include door trims, automobile interior materials such as instrument panels (instrument panels), and automobile exterior materials such as bumpers. Further, applications to building materials such as wood flour plastics, shoe soles, artificial cork, and the like are exemplified.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a master batch for foam molding which can be suitably used for molding in which a strong shearing force is applied or molding in which a low molding temperature is required and which can produce a foam molded article having a high expansion ratio and good appearance quality. In particular, when the master batch for foam molding of the present invention is used, a molded article having a smooth surface can be obtained without generating bubbles or the like on the surface of the molded article. Further, by using the master batch for foam molding of the present invention, the dispersibility of the thermally expandable microcapsules becomes good, and a foam molded article having uniform cells can be obtained.

Further, a foam molded article using the master batch for foam molding can be provided.

Detailed Description

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(preparation of thermally expandable microcapsules)

An aqueous dispersion medium was prepared by charging 300 parts by weight of water, 89 parts by weight of sodium chloride as a regulator, 0.07 part by weight of sodium nitrite as a water-soluble polymerization inhibitor, 8 parts by weight of colloidal silica (manufactured by Asahi Denka) as a dispersion stabilizer, and 0.3 part by weight of polyvinylpyrrolidone (manufactured by BASF Corp.). Next, an oily mixed liquid containing the polymerizable monomer shown in table 1, a volatile swelling agent, and a polymerization initiator was added to an aqueous dispersion medium and mixed to prepare a dispersion liquid. The total amount of the dispersion was 15 kg. The resulting dispersion was stirred and mixed by a homogenizer, and charged into a pressurized polymerizer (20L) purged with nitrogen, and pressurized (0.2MPa) to react at 60 ℃ for 20 hours, thereby preparing a reaction product. The resultant reaction product was repeatedly dehydrated and washed with water using a centrifugal separator, and then dried to obtain thermally expandable microcapsules (nos. 1 to 3).

(examples 1 to 9 and comparative examples 1 to 3)

(preparation of Master batch pellets)

The base resin, the heat-expandable microcapsules, the processing oil (Diana Process oil PW-90, manufactured by Shikino corporation, paraffinic processing oil) shown in Table 2, and 5 parts by weight of stearic acid as a lubricant were kneaded at 70 ℃ for 5 minutes by a pressure kneader. Thereafter, the kneaded mixture was mixed by a roll mill for 5 minutes under conditions of a roll temperature of 60 ℃, a roll speed of 20rpm, and an inter-roll distance of 1cm, to obtain a sheet-like master batch having a thickness of 1 cm.

The following materials were used as EPDM.

EPDM (1): mooney viscosity [ ML1+4(100 ℃ C.) ] was 8, ethylene content was 54% by weight, diene content: ENB, diene content 7.6 wt.%, propylene content 38.4 wt.%

EPDM (2): mooney viscosity [ ML1+4(100 ℃ C.) ] was 24, ethylene content was 51% by weight, diene content: ENB, diene content 8.1 wt.%, propylene content 40.9 wt.%

EPDM (3): mooney viscosity [ ML1+4(100 ℃ C.) ] was 40, ethylene content was 56% by weight, diene content: ENB, diene content 4.7 wt.%, propylene content 39.3 wt.%

EPDM (4): mooney viscosity [ ML1+4(100 ℃ C.) ] was 44, ethylene content was 50% by weight, diene content: DCPD, diene content 5.0 wt%, propylene content 45.0 wt%

Comparative example 4

(preparation of Master batch pellets)

The base resin shown in table 2 and 10 parts by weight of a fatty acid ester as a lubricant were kneaded in a banbury mixer, and when the temperature reached about 100 ℃, the resultant thermally expandable microcapsules were added in the amounts shown in table 2, and further kneaded for 30 seconds and extruded, and granulated to obtain master batch pellets. In table 2, LDPE represents low density polyethylene.

Comparative example 5

The base resin, the heat-expandable microcapsules, the processing oil (Diana Process oil PW-90, manufactured by Shikino corporation, paraffinic processing oil) shown in Table 2, and 5 parts by weight of stearic acid as a lubricant were kneaded at 120 ℃ for 5 minutes by a pressure kneader. Thereafter, the kneaded mixture was mixed by a roll mill for 5 minutes under conditions of a roll temperature of 80 ℃, a roll speed of 20rpm, and an inter-roll distance of 1cm, to obtain a sheet-like master batch having a thickness of 1 cm.

The following materials were used as EPDM.

EPDM (1): mooney viscosity [ ML1+4(100 ℃ C.) ] was 8, ethylene content was 54% by weight, diene content: ENB, diene content 7.6 wt.%, propylene content 38.4 wt.%

(production of foam molded article)

An EPDM composition was prepared by mixing 100 parts by weight of an EPDM resin (ethylene content 63% by weight, diene content 4.4% by weight), 335 parts by weight of other additives (zinc oxide, stearic acid, carbon black, ground calcium carbonate, paraffin oil), 1 part by weight of sulfur, and 4 parts by weight of a vulcanization accelerator. The obtained masterbatch pellets were mixed with 100 parts by weight of the EPDM composition prepared in advance, and the obtained mixed pellets were supplied to a hopper of an extruder to be melt-kneaded and extrusion-molded to obtain a sheet-shaped molded article. The extrusion conditions were set as follows: 80 ℃. The plate-shaped molded article obtained by extrusion molding was heated at 200 ℃ for 5 minutes in a hot air oven (manufactured by ESPEC corporation), thereby obtaining a foam molded article.

(evaluation)

The following properties were evaluated for the molded bodies obtained in the thermally expandable microcapsules (Nos. 1 to 3) and in examples 1 to 9 and comparative examples 1 to 5. The results are shown in tables 1 and 2. In comparative example 2, the masterbatch could not be prepared, and the following evaluation was not performed.

(1) Evaluation of thermally expandable microcapsules

(1-1) volume average particle diameter

The volume average particle diameter was measured using a particle size distribution diameter measuring instrument (LA-910, manufactured by HORIBA Co., Ltd.).

(1-2) foaming initiation temperature, maximum foaming temperature, maximum displacement amount

The foaming start temperature (Ts), the maximum displacement amount (Dmax), and the maximum foaming temperature (Tmax) were measured using a thermomechanical analyzer (TMA) (TMA2940, TA instruments). Specifically, a sample (25. mu.g) was put into an aluminum container having a diameter of 7mm and a depth of 1mm, heated from 80 ℃ to 220 ℃ at a temperature rise rate of 5 ℃/min in a state where a force of 0.1N was applied from above, and the displacement in the vertical direction of the measurement terminal was measured, and the temperature at which the displacement started to rise was referred to as the foaming start temperature, the maximum value of the displacement was referred to as the maximum displacement amount, and the temperature at the time of the maximum displacement amount was referred to as the maximum foaming temperature.

[ Table 1]

(2) Evaluation of the masterbatch

(2-1) measurement of true specific gravity

The true specific gravity of the master batch particles was measured by a method based on JIS K7112A method (displacement in water method) using a densitometer MD-200S (manufactured by MIRAGE).

(2-2) Mooney viscosity measurement

With respect to the obtained master batch pellets, the mooney viscosity at 100 ℃ was measured by a method based on JIS K6300.

(3) Evaluation of molded article

(3-1) Density and expansion ratio

The density before foaming and the density of the resulting molded article (after foaming) were measured by a method based on JIS K7112A method (underwater substitution method).

The expansion ratio was calculated from the densities of the molded article before and after the expansion.

(3-2) surface Property

The surface roughness (Rz) of the surface of the molded article was measured by a 3D shape measuring apparatus (manufactured by KEYENCE), and the measured Rz value was ○ when the Rz value was less than 50 μm, △ when the Rz value was not more than 50 μm and not more than 100 μm, and x when the Rz value was more than 100 μm.

(3-3) dispersibility

The cross section of the obtained molded body was visually observed with an electron microscope, and the dispersibility of the thermally expandable microcapsules was evaluated according to the following criteria.

○ the bubbles are uniformly dispersed.

X: the bubbles are not uniformly distributed.

[ Table 2]

Industrial applicability

According to the present invention, it is possible to provide a master batch for foam molding which can be suitably used even for molding in which a strong shearing force is applied or molding in which a low molding temperature is required, and which can obtain a foam molded article having a high expansion ratio and good appearance quality. Further, a foam molded article using the master batch for foam molding can be provided.