TWI631157B - Thermal expansion microcapsules and foamed shaped bodies - Google Patents

Abstract

The present invention provides a heat-expandable microcapsule which has excellent heat resistance and a high expansion ratio, and which can produce a foamed molded article having an excellent appearance which is not easily yellowed, and a foamed molded article using the heat-expandable microcapsule.

The present invention relates to a heat-expandable microcapsule comprising a volatile expansion agent as a nucleating agent in a shell composed of a polymer, and the shell is composed of a polymer obtained by polymerizing a monomer composition described below. The monomer composition contains 44 to 63% by weight of a polymerizable monomer (I) composed of at least one selected from the group consisting of acrylonitrile and methacrylonitrile, and a radical polymerization property having a carboxyl group and having a carbon number of 3 to 8. 15 to 30% by weight of the saturated carboxylic acid monomer (II), 0.1 to 3.0% by weight of the crosslinkable monomer (III) having two or more double bonds in the molecule, and from a (meth) acrylate selected from The polymerizable monomer (IV) composed of at least one of dichloroethylene, vinyl acetate and a styrene monomer is 21 to 40% by weight.

Description

Thermal expansion microcapsules and foamed shaped bodies

The present invention relates to a heat-expandable microcapsule which has excellent heat resistance and a high expansion ratio, and which can produce a foamed molded article having an excellent appearance which is not easily yellowed, and a foamed molded article using the heat-expandable microcapsule.

The heat-expandable microcapsules are used as a designing agent or a lightening agent for a wide range of applications, and are also used for coating materials such as foamed inks and wallpapers for weight reduction.

Such a heat-expandable microcapsule is widely known in the thermoplastic shell polymer in which a volatile expander which becomes a gas at a temperature lower than a softening point of the shell polymer is known. For example, Patent Document 1 discloses a method in which An oily mixed liquid obtained by mixing a volatile expansion agent such as a low-boiling aliphatic hydrocarbon with a monomer is added to an aqueous dispersion medium containing a dispersant while stirring, and is suspended and polymerized to produce a liquid. A heat-expandable microcapsule containing a volatile expansion agent.

However, the heat-expandable microcapsules obtained by the method can thermally expand at a relatively low temperature of about 80 to 130 ° C, but have the following disadvantages: if heated at a high temperature or for a long time, the expanded microcapsules may be broken or Since shrinkage and expansion ratio are lowered, heat-expandable microcapsules excellent in heat resistance cannot be obtained.

On the other hand, Patent Document 2 discloses a method in which a polymerization component containing 80 to 97% by weight of a nitrile-based monomer, 20 to 3% by weight of a non-nitrile monomer, and 0.1 to 1% by weight of a trifunctional crosslinking agent is used. The obtained polymer was used as a shell to produce a heat-expandable microcapsule containing a volatile expander.

Further, Patent Document 3 discloses a heat-expandable microcapsule which uses a polymerization component containing 80% by weight or more of a nitrile-based monomer, 20% by weight or less of a non-nitrile monomer, and 0.1 to 1% by weight of a crosslinking agent. The obtained polymer contains a volatile expander, and the non-nitrile monomer is a methacrylate or an acrylate.

The heat-expandable microcapsules obtained by the above methods are superior in heat resistance to the conventional microcapsules, and are said to not foam at 140 ° C or lower, but actually if they are continuously heated at 130 to 140 ° C for about 1 minute, A part of the microcapsules thermally expand, and it is difficult to obtain a heat-expandable microcapsule having an excellent heat resistance of a maximum foaming temperature of 180 ° C or more.

Further, in Patent Document 4, in order to obtain a heat-expandable microcapsule having a maximum foaming temperature of 180 ° C or higher, preferably 190 ° C or higher, 85% by weight or more of the ethylenically unsaturated monomer having a nitrile group is used. A heat-expandable microcapsule composed of a shell polymer composed of a homopolymer or a copolymer and 50% by weight or more of a foaming agent having isooctane.

In such a heat-expandable microcapsule, although the maximum foaming temperature is a very high value, it cannot maintain the subsequent expanded state, and it is difficult to use it for a long time in a high temperature region.

Further, in Patent Documents 5 to 9, it is disclosed that a monomer having a shell constituting a heat-expandable microcapsule has a good foaming property in a wide range of foaming temperature regions, particularly a high temperature region (160 ° C or higher). The heat-expandable microcapsules which further improve heat resistance. However, although the maximum expansion temperature of the heat-expandable microcapsules shows a high value, it is used for strong application. In the case of forming, such as kneading, calendering, extrusion molding, and injection molding, especially in the case of injection molding, in the melt-kneading step, heat-expandable microcapsules may be generated due to heat resistance or strength. The phenomenon of "aging" is either crushed and the resulting shaped body is yellowed. In addition, in the step of foaming the heat-expandable microcapsules, the expansion ratio is low, and the expansion ratio is different, so that the heat-expandable microcapsules are not sufficiently foamed, and the obtained molded body has functions such as appearance and light weight. The aspect of sex is poor.

Further, white spots caused by aggregation of the heat-expandable microcapsules are generated on the surface of the foamed molded body, and the appearance of the foamed molded body is remarkably impaired.

Therefore, the industry needs to have excellent heat resistance and expansion ratio, and it is possible to produce a heat-expandable microcapsule having a foamed molded article having an excellent appearance which is not easily yellowed.

Patent Document 1: Japanese Patent Publication No. Sho 42-26524

Patent Document 2: Japanese Special Fair 5-15499

Patent Document 3: Japanese Patent No. 2894990

Patent Document 4: European Patent Application Publication No. 1149628

Patent Document 5: International Publication No. 2003/099955

Patent Document 6: Japanese Laid-Open Patent Publication No. 2009-113037

Patent Document 7: Japanese Laid-Open Patent Publication No. 2009-299071

Patent Document 8: JP-A-2013-32542

Patent Document 9: Japanese Patent Laid-Open Publication No. 2013-28818

It is an object of the present invention to provide a heat-expandable microcapsule which has excellent heat resistance and a high expansion ratio, and which can produce a foamed molded article having an excellent appearance which is not easily yellowed, and foam molding using the heat-expandable microcapsule body. In addition, "not easy to yellow" means "not susceptible to yellowing caused by the addition of heat-expandable microcapsules".

The present invention relates to a heat-expandable microcapsule comprising a volatile expansion agent as a nucleating agent in a shell composed of a polymer, and the shell is composed of a polymer obtained by polymerizing a monomer composition described below. The monomer composition contains 44 to 63% by weight of a polymerizable monomer (I) composed of at least one selected from the group consisting of acrylonitrile and methacrylonitrile, and a radical polymerization property having a carboxyl group and having a carbon number of 3 to 8. 15 to 30% by weight of the saturated carboxylic acid monomer (II), 0.1 to 3.0% by weight of the crosslinkable monomer (III) having two or more double bonds in the molecule, and from a (meth) acrylate selected from The polymerizable monomer (IV) composed of at least one of dichloroethylene, vinyl acetate and a styrene monomer is 21 to 40% by weight.

Hereinafter, the present invention will be described in detail.

The inventors of the present invention have conducted intensive studies and found that they contain a polymerizable monomer (I), a radically polymerizable unsaturated carboxylic acid monomer (II), a crosslinking monomer (III), and a polymerizable monomer (IV). When the ratio of each monomer is within a specific range, stable foaming performance can be achieved in a high temperature region, a high expansion ratio can be obtained, and thermal expansion property of a foamed molded article having an excellent appearance can be produced. Microcapsules, thereby completing the present invention.

The shell constituting the heat-expandable microcapsule of the present invention is composed of a polymer obtained by polymerizing a monomer composition containing at least one selected from the group consisting of acrylonitrile and methacrylonitrile. The monomer (I) is 44 to 63% by weight, the radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxyl group and having a carbon number of 3 to 8 is 15 to 30% by weight, and has two in the molecule. The crosslinkable monomer (III) of the upper double bond is 0.1 to 3.0% by weight, and the polymerization is composed of at least one selected from the group consisting of (meth) acrylate, vinylidene chloride, vinyl acetate, and styrene monomer. The monomer (IV) is 21 to 40% by weight.

The polymerizable monomer (I) is composed of at least one selected from the group consisting of acrylonitrile and methacrylonitrile.

By adding the above polymerizable monomer (I), the gas barrier properties of the shell can be improved.

The lower limit of the content of the polymerizable monomer (I) in the monomer composition is 44% by weight, and the upper limit is 63% by weight. If it is less than 44% by weight, the gas barrier properties of the shell become low, and the expansion ratio is lowered. When it exceeds 63% by weight, heat resistance does not improve, or yellowing is likely to occur. A preferred lower limit is 50% by weight, and a preferred upper limit is 60% by weight.

As the radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxyl group and having a carbon number of 3 to 8, for example, one or more free carboxyl groups for ion-crosslinking each molecule can be used, specifically For example, unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid, maleic acid, itaconic acid, fumaric acid, and methylbutylene may be mentioned. An unsaturated dicarboxylic acid such as diacid or chlorinated maleic acid or an anhydride thereof, or monomethyl maleate, monoethyl maleate, monobutyl maleate or reversed a monoester of an unsaturated dicarboxylic acid such as monomethyl methacrylate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate or monobutyl itaconate or a derivative thereof, These may be used alone or in combination of two or more. Among these, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and itaconic acid are particularly preferable.

The lower limit of the content of the segment derived from the above-mentioned radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxyl group and having 3 to 8 carbon atoms in the monomer composition is 15% by weight, and the upper limit is 30% by weight. If it is less than 15% by weight, the maximum foaming temperature becomes less than 175 ° C. When it exceeds 30% by weight, although the maximum foaming temperature is increased, the expansion ratio is lowered. A preferred lower limit is 17% by weight, and a preferred upper limit is 28% by weight.

The monomer composition contains a crosslinkable single having two or more double bonds in the molecule Body (III). The above crosslinkable monomer (III) has a function as a crosslinking agent. By containing the above crosslinkable monomer (III), the strength of the shell can be strengthened, and the microcell walls become difficult to break when thermally expanded.

Examples of the crosslinkable monomer (III) include two or more radical polymerizations. Specific examples of the monomer of the conjugated double bond include divinylbenzene, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(a). Acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-anthracene Alcohol di(meth)acrylate, di(meth)acrylate of polyethylene glycol having a weight average molecular weight of 200-600, glycerol di(meth)acrylate, trimethylolpropane di(meth)acrylic acid Ester, trimethylolpropane tri(meth)acrylate, ethylene oxide modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, triallyl Formal tris(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylic acid Ester and the like. Among these, a trifunctional group such as trimethylolpropane tri(meth)acrylate or a difunctional (meth)acrylate such as polyethylene glycol is preferably used because of the use of acrylonitrile. The shell of the main body is relatively uniformly crosslinked, and even in a high temperature region exceeding 200 ° C, the microcapsules which are thermally expanded are not easily shrunk, and the state of swelling is easily maintained, so that the phenomenon of "aging" can be suppressed.

The lower limit of the content of the above crosslinkable monomer (III) in the above monomer composition is 0.1% by weight, the upper limit is 3.0% by weight. When the content of the crosslinkable monomer (III) is less than 0.1% by weight, the effect of the crosslinking agent is not exhibited, and the addition is more than 3.0% by weight. In the case of the crosslinkable monomer (III), the expansion ratio of the heat-expandable microcapsules is lowered. A preferred lower limit of the content of the crosslinkable monomer (III) is 0.15% by weight, and a preferred upper limit is 2.0% by weight.

The monomer composition contains a polymerizable monomer (IV) composed of at least one selected from the group consisting of (meth) acrylate, vinylidene chloride, vinyl acetate, and a styrene monomer. By containing the polymerizable monomer (IV), the miscibility of the heat-expandable microcapsules with a matrix resin such as a thermoplastic resin is improved, and the foam molded article using the heat-expandable microcapsules has an excellent appearance.

Among them, preferred is (meth) acrylate, and more preferably alkyl methacrylate such as methyl methacrylate, ethyl methacrylate or n-butyl methacrylate, or cyclohexyl methacrylate. A methacrylate containing an alicyclic ring, an aromatic ring or a heterocyclic ring such as benzyl methacrylate or isodecyl methacrylate.

The upper limit of the content of the polymerizable monomer (IV) in the monomer composition is 21% by weight, and the lower limit is 40% by weight. When the content of the polymerizable monomer (IV) is less than 21% by weight, the appearance of the foamed molded article using the heat-expandable microcapsules is deteriorated, and when it exceeds 40% by weight, the gas barrier properties of the microcell walls are lowered. The thermal expansion property is easily deteriorated. A preferred lower limit of the content of the above polymerizable monomer (IV) is 22% by weight, and a preferred upper limit is 35% by weight. The lower limit of the content of the above polymerizable monomer (IV) is preferably 23% by weight, and more preferably 30% by weight.

By adjusting the content of the above polymerizable monomer (I) in the monomer composition with respect to the content of the polymerizable monomer (IV), a foamed molded article having less yellowing can be obtained.

A preferred upper limit of the ratio of the above polymerizable monomer (I) to the polymerizable monomer (IV) is 3.0. When the ratio of the polymerizable monomer (I) to the polymerizable monomer (IV) exceeds 3.0, the foamed molded article using the heat-expandable microcapsules may be yellowed.

A more preferable upper limit of the ratio of the above polymerizable monomer (I) to the polymerizable monomer (IV) is 2.7. Further, a preferred lower limit of the ratio of the polymerizable monomer (I) to the polymerizable monomer (IV) is 1.0.

The above monomer composition preferably contains a metal cation salt.

When the above-mentioned metal cation salt is contained, ionic crosslinking occurs between the radically polymerizable unsaturated carboxylic acid monomer (II) and the carboxyl group, so that crosslinking efficiency increases and heat resistance can be improved. As a result, it becomes possible to manufacture a heat-expandable microcapsule which does not cause cracking or shrinkage in a high temperature region for a long period of time. Moreover, since the modulus of elasticity of the shell in the high-temperature region is not easily lowered, even when a molding process such as kneading, calendering, extrusion molding, or injection molding is applied with a strong shear force, the heat-expandable microcapsules are not caused. It breaks and shrinks.

Further, by causing ion crosslinking rather than covalent bonding, the particle shape of the heat-expandable microcapsule becomes close to a sphere, and deformation is less likely to occur. The reason is considered to be that the crosslinking caused by ionic bonding is weaker than the crosslinking caused by covalent bonding, and thus the thermal expansion microcapsules are converted from a monomer to a polymer during polymerization. When the volume shrinks, it shrinks evenly.

The metal cation of the metal cation salt is not particularly limited as long as it is a metal cation which is ionically crosslinked by the reaction of the above-mentioned radically polymerizable unsaturated carboxylic acid monomer (II), and examples thereof include Na, K, and Li. , Zn, Mg, Ca, Ba, Sr, Mn, Al, Ti, Ru, Fe, Ni, Cu, Cs, Sn, Cr, Pb, etc. Among these, an ion of Ca, Zn or Al which is a metal cation of 2 to 3 valence is preferable, and an ion of Zn is particularly preferable. These metal cation salts may be used singly or in combination of two or more.

In addition, the combination in the case of using two or more kinds of the above metal cation salts is not particularly limited, and it is preferred to use an ion of an alkali metal or an alkaline earth metal in combination with a metal cation other than the above alkali metal or alkaline earth metal. By having an ion of the above alkali metal or alkaline earth metal, a functional group such as a carboxyl group can be activated to promote metal cations other than the above alkali metal. The reaction with a carboxyl group or the like is carried out. Examples of the alkali metal or alkaline earth metal include Na, K, Li, Ca, Ba, and Sr. Among them, Na, K, and the like which are more basic are preferably used.

A preferred lower limit of the content of the above metal cation salt is 0.1% by weight based on the total amount of the monomers, and a preferred upper limit is 10% by weight. If it is less than 0.1% by weight, the effect cannot be obtained in terms of heat resistance, and if it exceeds 10% by weight, the expansion ratio may be remarkably deteriorated. A more preferred lower limit is 0.5% by weight, and a more preferred upper limit is 5% by weight.

The monomer composition contains a polymerization initiator in order to polymerize the above monomer.

As the polymerization initiator, for example, a dialkyl peroxide, a dinonyl peroxide, a peroxyester, a peroxydicarbonate, an azo compound or the like is suitably used. Specific examples thereof include dialkyl peroxides such as methyl ethyl peroxide, dibutyl peroxide, and dicumyl peroxide; isobutyl peroxide, benzammonium peroxide, and peroxidation. 2,4-dichlorobenzidine, perylene diperoxide such as 3,5,5-trimethylhexyl peroxide; third butyl peroxypivalate, third hexyl peroxypivalate, Tert-butyl neodecanoate, trihexyl peroxy neodecanoate, 1-cyclohexyl-1-methylethyl peroxy neodecanoate, neodecanoic acid 1,1,3,3- Tetramethyl butyl ester, cumene peroxy neodecanoate, peroxy ester such as (α,α-bis-indoylperoxy)diisopropylbenzene; diperoxydicarbonate double (4-third butyl) Cyclohexyl) ester, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di(2-ethylethyl) peroxydicarbonate, dimethoxybutyl peroxydicarbonate, Peroxydicarbonate such as di(3-methyl-3-methoxybutyl) peroxydicarbonate; 2,2'-azobisisobutyronitrile, 2,2'-azobis(4- Methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 1,1'-azobis(1-cyclohexanecarbonitrile ) Such as azo compounds and the like.

The preferred lower limit of the weight average molecular weight of the above-mentioned polymer constituting the shell is 10 Ten thousand, the upper limit is 2 million. If it is less than 100,000, the strength of the shell is lowered. If it exceeds 2 million, the strength of the shell becomes too high, and the expansion ratio is lowered.

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

The heat-expandable microcapsule of the present invention contains a volatile expansion agent as a nucleating agent in the above shell.

The volatile expansion agent is a gas-like substance at a temperature lower than the softening point of the polymer constituting the shell, and is preferably a low-boiling organic solvent.

Examples of the above-mentioned volatile expansion agent include ethane, ethylene, propane, propylene, n-butane, isobutane, butene, isobutylene, n-pentane, isopentane, neopentane, n-hexane, and heptane. , low molecular weight hydrocarbons such as petroleum ether, isooctane, octane, decane, isododecane, dodecane, hexadecane; fluorine such as CCl ₃ F, CCl ₂ F ₂ , CClF ₃ , CClF ₂ -CClF ₂ a chlorocarbon; a tetraalkyl decane such as tetramethyl decane, trimethylethyl decane, trimethyl isopropyl decane or trimethyl n-propyl decane. Among them, isobutane, n-butane, n-pentane, isopentane, n-hexane, isooctane, isododecane, and mixtures thereof are preferred. These volatile expansion agents may be used singly or in combination of two or more.

Further, as the volatile expansion agent, a thermally decomposable compound which is thermally decomposed into a gas by heating can also be used.

In the heat-expandable microcapsule of the present invention, among the above-mentioned volatile expansion agents, a low-boiling hydrocarbon having a carbon number of 5 or less is preferably used. By using such a hydrocarbon, a heat-expandable microcapsule having a high expansion ratio and rapidly foaming can be obtained.

Further, as the volatile expansion agent, a thermally decomposable compound which is thermally decomposed into a gas by heating can also be used.

The maximum foaming temperature (Tmax) of the heat-expandable microcapsule of the present invention is preferably The lower limit is 175 °C. If the temperature is less than 175 ° C, the heat resistance is lowered, so that the heat-expandable microcapsules are broken and shrunk in a high temperature region or during molding. Further, when the masterbatch pellets are produced, they are foamed by shearing, and the unfoamed masterbatch pellets cannot be stably produced. A lower limit is preferably 180 ° C, and a higher limit is 240 ° C.

In the present specification, the maximum foaming temperature means a temperature at which the diameter of the heat-expandable microcapsules becomes maximum (maximum displacement amount) when the diameter of the heat-expandable microcapsules is measured while heating the temperature.

Further, a preferred upper limit of the foaming initiation temperature (Ts) is 175 °C. If it exceeds 175 ° C, In particular, in the case of injection molding, the resin temperature during the core-pulling process is formed by foaming the core back after the mold is filled with the resin material until the resin material is foamed. Reduced, the expansion ratio does not rise. A preferred lower limit is 130 ° C, and a more preferred upper limit is 160 ° C.

The preferred lower limit of the volume average particle diameter of the heat-expandable microcapsule of the present invention is 5 The μm, preferably upper limit is 100 μm. When it is less than 5 μm, the bubbles of the obtained molded body are too small, and the weight of the molded body is insufficient. When the thickness exceeds 100 μm, the bubbles of the obtained molded body become excessively large, so that the strength is high. The aspect becomes a problem. A lower limit is preferably 10 μm, and a higher limit is 45 μm.

The method for producing the heat-expandable microcapsule of the present invention is not particularly limited. For example, it can be produced by the following steps: a step of preparing an aqueous medium; and a step of dispersing an oily mixture containing a monomer composition and a volatile expansion agent in an aqueous medium containing an acrylonitrile selected from the group consisting of acrylonitrile And a radically polymerizable unsaturated carboxylic acid monomer having a carboxyl group and having a carbon number of 3 to 8 and having a carboxyl group of at least one of methacrylonitrile (I): 44 to 63% by weight 15 to 30% by weight, a crosslinkable monomer (III) having two or more double bonds in the molecule, 0.1 to 3.0% by weight, and a selected from (meth) acrylate, vinylidene chloride, vinyl acetate, and 21 to 40% by weight of the polymerizable monomer (IV) composed of at least one of styrene monomers; and a step of polymerizing the above monomers.

In the case of manufacturing the heat-expandable microcapsule of the present invention, first preparing water The steps of the medium. As a specific example, for example, an aqueous dispersion medium containing a dispersion stabilizer is prepared by adding water, a dispersion stabilizer, and, if necessary, a stabilizing aid to a polymerization reaction container. Further, an alkali metal nitrite, tin (II) chloride, tin (IV) chloride, potassium dichromate or the like may be added as needed.

Examples of the dispersion stabilizer include silica and phosphorus. Calcium acid, magnesium hydroxide, aluminum hydroxide, iron (III) hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, barium carbonate, magnesium carbonate, and the like.

The amount of the above-mentioned dispersion stabilizer to be added is not particularly limited, and it is based on a dispersion stabilizer. The type, the particle size of the microcapsules, and the like are appropriately determined, and the lower limit is preferably 0.1 part by weight, and the upper limit is 20 parts by weight, based on 100 parts by weight of the monomer.

As the above-mentioned stabilizer, for example, diethanolamine and an aliphatic dicarboxylic acid are mentioned. Condensation product, condensation product of urea and formaldehyde, polyvinylpyrrolidone, polyethylene oxide, polyethylenimine, tetramethylammonium hydroxide, gelatin, methyl cellulose, polyvinyl alcohol , dioctyl sulfosuccinate, sorbitan ester, various emulsifiers, and the like.

Moreover, as a combination of the above dispersion stabilizer and a stabilizer, there is no particular limitation. The combination may, for example, be a combination of colloidal cerium oxide and a condensation product, a combination of colloidal cerium oxide and a water-soluble nitrogen-containing compound, a combination of magnesium hydroxide or calcium phosphate and an emulsifier. Among these, a combination of colloidal cerium oxide and a condensation product is preferred.

Further, the condensation product is preferably a condensation product of diethanolamine and an aliphatic dicarboxylic acid, and more 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 polyvinylpyrrolidine. a polyalkylaminoalkyl (meth)acrylate represented by a ketone, a polyethylenimine, a polyoxyethylene alkylamine, a polymethyl methacrylate or a polydimethylaminoethyl acrylate. Polydialkylaminoalkyl (meth) acrylamide represented by ester, polydimethylaminopropyl acrylamide or polydimethylaminopropyl methacrylamide, polypropylene decylamine, poly Cationic acrylamide, polyamine oxime, polyallylamine, and the like. Among these, polyvinylpyrrolidone is preferably used.

The amount of the colloidal cerium oxide added is appropriately determined depending on the particle diameter of the heat-expandable microcapsules, and the lower limit is preferably 1 part by weight, and preferably 20 parts by weight, based on 100 parts by weight of the vinyl monomer. Further preferably, the lower limit is 2 parts by weight, and further preferably, the upper limit is 10 parts by weight. In addition, the amount of the condensation product or the water-soluble nitrogen-containing compound is appropriately determined depending on the particle diameter of the heat-expandable microcapsules, and the lower limit is preferably 0.05 parts by weight based on 100 parts by weight of the monomer, and the upper limit is preferably 2 Parts by weight.

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

The aqueous dispersion medium containing the above dispersion stabilizer is prepared by dispersing a dispersion stabilizer or a stabilizer in deionized water, and the pH of the aqueous phase at this time is appropriately determined depending on the type of the dispersion stabilizer or the stabilizer. . For example, using cerium oxide such as colloidal cerium oxide In the case of a dispersion stabilizer, the polymerization is carried out in an acidic medium, and in order to make the aqueous medium acidic, an acid such as hydrochloric acid is added as needed, and the pH of the system is adjusted to 3 to 4. On the other hand, in the case of using magnesium hydroxide or calcium phosphate, the polymerization is carried out in an alkaline medium.

Then, in the method of manufacturing the heat-expandable microcapsule, the monomer group to be contained a step of dispersing an oily mixture of a product and a volatile expansion agent in an aqueous medium containing a polymerizable monomer (I) 44 composed of at least one selected from the group consisting of acrylonitrile and methacrylonitrile ~63% by weight of a radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxyl group and having 3 to 8 carbon atoms, 15 to 30% by weight, and a crosslinkable monomer having two or more double bonds in the molecule ( III) 0.1 to 3.0% by weight, and a polymerizable monomer (IV) composed of at least one selected from the group consisting of (meth) acrylate, vinylidene chloride, vinyl acetate, and styrene monomer, having a weight of 21 to 40 %By. In this step, the monomer composition and the volatile expansion agent may be separately added to the aqueous dispersion medium to prepare an oily mixture in the aqueous dispersion medium, but usually the two are mixed in advance to prepare an oily mixture. And 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 mixture may be mixed while stirring in another container, whereby the oily mixed liquid is dispersed in the aqueous dispersion medium, and then added to the polymerization reaction container. in.

Further, in order to polymerize the above monomer, a polymerization initiator may be used, and the polymerization initiator may be added to the oily mixture in advance, or the aqueous dispersion medium and the oily mixture may be stirred and mixed in a polymerization reactor. Add it.

The above oily mixture is subjected to a specific particle diameter in an aqueous dispersion medium. The method of emulsification and dispersion may be a method of stirring by a homomixer (for example, manufactured by Kosei Kogyo Co., Ltd.), or a method of passing it through a static dispersing device such as a line agitator or a component type static disperser.

Further, the aqueous dispersion medium and the polymerizable mixture may be supplied to the static dispersion device, respectively, or a dispersion liquid which is previously mixed and stirred may be supplied.

The heat-expandable microcapsule of the present invention can be produced by, for example, performing the following steps, that is, a step of polymerizing a monomer by, for example, heating the dispersion obtained through the above steps. The heat-expandable microcapsules produced by such a method have a high maximum foaming temperature and are excellent in heat resistance, and do not cause cracking or shrinkage in a high-temperature region or during molding. Further, since the heat resistance is high, the masterbatch particles are not foamed by shearing during the production of the masterbatch particles, and the unfoamed masterbatch particles can be stably produced.

The heat-expandable microcapsule of the present invention is formed by adding a resin composition or a masterbatch pellet of a matrix resin such as a thermoplastic resin to a heat-expandable microcapsule of the present invention, and the heat-expandable microcapsule is foamed by heating during molding. This makes it possible to manufacture a foamed molded body. Such a foam molded body is also one of the inventions.

The foamed molded article of the present invention obtained by such a method has high appearance quality, uniformly forms closed cells, and is excellent in lightness, heat insulation, impact resistance, rigidity, etc., and can be suitably used for residential use. Building materials, automotive components, soles, etc.

The thermoplastic resin is not particularly limited as long as it does not impair the object of the present invention, and examples thereof include general thermoplastic resins such as polyvinyl chloride, polystyrene, polypropylene, polypropylene oxide, and polyethylene; and poly terephthalic acid; Engineering plastics such as butadiene ester, nylon, polycarbonate, polyethylene terephthalate. Further, a thermoplastic elastomer such as an ethylene-based, vinyl chloride-based, olefin-based, amine-ester or ester-based resin may be used, and these resins may be used in combination.

The amount of the heat-expandable microcapsules to be added is preferably from 0.5 to 20 parts by weight, preferably from 1 to 10 parts by weight, per 100 parts by weight of the thermoplastic resin. Also, with sodium bicarbonate (small Soda) or a chemical foaming agent such as ADCA (azo) is used in combination. Further, when a molten thermoplastic resin is injected with a physical gas (such as water vapor, nitrogen gas, carbon dioxide, or the like) or a supercritical fluid (such as carbon dioxide or nitrogen gas), the thermally expandable microcapsules may be used in combination.

The method for producing the above-mentioned master batch particles is not particularly limited, and for example, In the following method, a raw material such as a matrix resin such as a thermoplastic resin or various additives is kneaded in advance using a co-axial extruder or the like. Then, after heating to a specific temperature, a foaming agent such as the heat-expandable microcapsule of the present invention is added, and further kneading is carried out, and the kneaded product thus obtained is cut into a desired size by a granulator to thereby form a pellet shape. As a masterbatch pellet. In this case, when a heat-expandable microcapsule having low heat resistance is used, there is a problem that foaming occurs due to shearing during kneading. When micro-foaming occurs at this point of time, it is difficult to obtain a desired expansion ratio in the subsequent foam molding, and the unevenness also increases. Further, a raw material such as a matrix resin such as a thermoplastic resin or a heat-expandable microcapsule may be kneaded by a batch type kneader, and then granulated by a granulator to produce pellet-shaped masterbatch particles.

The kneading machine is not particularly limited as long as it is kneaded without damaging the heat-expandable microcapsules, and examples thereof include a pressure kneader and a Banbury mixer.

The method for forming the foam molded body of the present invention is not particularly limited, and for example, Examples thereof include kneading molding, calender molding, extrusion molding, and injection molding. In the case of injection molding, the method of implementation is not particularly limited, and a short-shot method in which a part of the resin material is introduced into the mold and foamed is exemplified; or after the resin material is filled in the mold, the resin material is foamed. The core pulling method that opens the mold so far.

According to the present invention, since excellent heat resistance can be obtained, it can be made to be applied. It is also suitable for kneading, calendering, extrusion molding, injection molding, etc. with strong shearing force. Thermally expandable microcapsules for use. Further, the expansion ratio is high, and a foam molded article having desired foaming properties can be obtained. Further, the obtained foamed molded article can be made into an excellent appearance and is not easily yellowed.

Hereinafter, the embodiments of the present invention will be described in more detail with reference to the embodiments, but the present invention is not limited to the embodiments.

(Example 1)

(Production of heat-expandable microcapsules)

130 parts by weight of a solid content of 20% by weight of colloidal ceria, 6 parts by weight of polyvinylpyrrolidone, and 640 parts by weight of sodium chloride were added to 2,000 parts by weight of ion-exchanged water and mixed, and then adjusted to pH. 3.5, and prepare an aqueous dispersion medium.

238 parts by weight of acrylonitrile, 113 parts by weight of methacrylonitrile, 113 parts by weight of methacrylic acid, 287 parts by weight of methyl methacrylate, and 3 parts by weight of trimethylolpropane trimethacrylate were mixed to obtain uniformity. The monomer composition of the solution. 10 g of 2,2'-azobisisobutyronitrile and 238 parts by weight of n-pentane were added thereto, and the mixture was placed in an autoclave and mixed.

Thereafter, the aqueous dispersion medium was placed in an autoclave, stirred at 1,000 rpm for 10 minutes, and then subjected to nitrogen substitution, and allowed to react at a reaction temperature of 60 ° C for 15 hours. Stirring was carried out at 200 rpm under a reaction pressure of 0.5 MPa. The obtained polymerization slurry was pre-dehydrated by a dehydrating device (centrifuge), and then dried to obtain a heat-expandable microcapsule.

(Production of foamed molded body)

70 parts by weight of dioctyl phthalate as a plasticizer, 3 parts by weight of carbon black as a black pigment, and 3 parts by weight of heat-expandable microcapsules obtained in Example 1 were mixed with 100 parts by weight of the polyvinyl chloride resin. . Then, using an injection molding machine having a clamping force of about 350 tons and a screw diameter of 60 mm, injection molding was carried out at an injection pressure of about 1860 kg/cm ² and a cylinder temperature of 190 ° C to obtain a disk-shaped hair having a diameter of 250 mm and a thickness of 3 mm. Bubble shaped body.

(Examples 2 to 7, 9, 10, and Comparative Examples 1 to 5)

Acrylonitrile, methacrylonitrile, methacrylic acid, methyl methacrylate, and trimethylolpropane trimethacrylate are mixed in the compositions shown in Tables 1 and 2 to prepare a monomer composition. In the same manner as in Example 1, a heat-expandable microcapsule and a foamed molded article were obtained.

(Example 8)

Acrylonitrile, methacrylonitrile, methacrylic acid, methyl methacrylate, and trimethylolpropane trimethacrylate were mixed in the composition shown in Table 1 to prepare a monomer composition, which was further added as The heat-expandable microcapsules and the foamed molded article were obtained in the same manner as in Example 1 except that 3.8 parts by weight of zinc hydroxide of the metal cation salt was used.

(evaluation method)

The properties of the obtained heat-expandable microcapsules and the foamed molded article were evaluated by the following methods. The results are shown in Tables 1 and 2.

(1) Evaluation of thermal expansion microcapsules

(1-1) Volume average particle size

The volume average particle diameter was measured using a particle size distribution diameter measuring instrument (LA-950, manufactured by HORIBA Co., Ltd.).

(1-2) Foaming initiation temperature, maximum foaming temperature

The foaming initiation temperature (Ts) and the maximum foaming temperature (Tmax) were measured using a thermomechanical analyzer (TMA) (TMA 2940, manufactured by TA Instruments). Specifically, 25 μg of the sample was placed in an aluminum container having a diameter of 7 mm and a depth of 1 mm, and heated from 80 ° C to 250 ° C at a temperature increase rate of 5 ° C/min while applying a force of 0.1 N from above. The displacement of the terminal in the vertical direction was measured, and the temperature at which the displacement began to rise was set as the foaming initiation temperature. Further, the expansion ratio was measured, and the temperature at which the expansion ratio was maximized was defined as the maximum expansion temperature.

(2) Evaluation of foamed molded body

(2-1) Determination of density

The density of the obtained molded body was measured by the method according to JIS K-7112 A method (aqueous substitution method).

(2-2) Appearance (surface of molded article)

The number of white spots on the surface of the molded article was visually counted.

(2-3) Yellowness (YI)

The yellowness of the surface of the molded article was measured using a color difference meter (NR-3000, manufactured by Nippon Denshoku Industries Co., Ltd.) to obtain a YI value.

[Industrial availability]

According to the present invention, it is possible to provide a heat-expandable microcapsule which has excellent heat resistance and a high expansion ratio, and which can produce a foamed molded article having an excellent appearance which is not easily yellowed, and a foamed molded article using the heat-expandable microcapsule .

Claims (4)

A heat-expandable microcapsule comprising a volatile expansion agent as a nucleating agent in a shell made of a polymer, characterized in that the shell is composed of a polymer obtained by polymerizing a monomer composition described below, The monomer composition contains 44 to 63% by weight of a polymerizable monomer (I) composed of at least one selected from the group consisting of acrylonitrile and methacrylonitrile, and a radical polymerizable unsaturated group having a carboxyl group and having a carbon number of 3 to 8. 15 to 30% by weight of the carboxylic acid monomer (II), 0.1 to 3.0% by weight of the crosslinkable monomer (III) having two or more double bonds in the molecule, and from (meth) acrylate, partial The polymerizable monomer (IV) composed of at least one of vinyl chloride, vinyl acetate and a styrene monomer is 25.2 to 40% by weight, and the content of the polymerizable monomer (I) is relative to the polymerizable monomer (IV) The ratio of the content of the film is 2.02 or less; the foaming initiation temperature of the heat-expandable microcapsule is 130 to 175 °C. The heat-expandable microcapsule according to claim 1, wherein the monomer composition contains a metal cation salt, and the content of the metal cation salt is 0.1 to 10% by weight based on the total amount of the monomers. The heat-expandable microcapsules of claim 1 or 2 have a maximum foaming temperature of 175 ° C or higher. A foamed molded article obtained by using the heat-expandable microcapsules of the first, second or third aspects of the patent application.