Foamable resin composition

Abstract

The purpose of the present invention is to provide a foamable resin composition that has high foamability and excellent foaming stability. The present invention is a foamable resin composition containing: a thermoplastic resin; thermally expandable microcapsules containing a thermosetting resin; a reactive dispersant (I) having one functional group that is reactive with the thermosetting resin per molecule; and a reactive dispersant (II) having two or more functional groups that are reactive with the thermosetting resin per molecule.

Description

[Technical Field]

[0001] The present invention relates to a foamable resin composition. [Background technology]

[0002] Plastic foams are used in a variety of applications because they can exhibit heat-shielding properties, heat insulation properties, sound insulation properties, sound absorption properties, vibration damping properties, weight reduction, etc., depending on the foam material and the state of the formed cells. Examples of methods for producing such plastic foams include a method in which a foamable resin composition containing a foaming agent is heated to foam it and then molded.

[0003] For example, Patent Document 1 describes a resin composition for foam molding that contains thermally expandable microcapsules in which a volatile expanding agent is encapsulated as a core agent in a shell containing an epoxy resin, a thermoplastic resin, and a curable compound having two or more functional groups in one molecule, each of which is at least one type selected from the group consisting of carboxyl groups, hydroxyl groups, amino groups, amide groups, and acid anhydride groups. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2012 / 091098 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the resin composition for foam molding described in Patent Document 1 is used, while a high expansion ratio can be achieved, the dispersibility of the thermally expandable microcapsules in the resin composition for foam molding is insufficient. When the dispersibility of the thermally expandable microcapsules is reduced in this way, the foaming uniformity of the resulting foam molded article is insufficient.

[0006] An object of the present invention is to provide a foamable resin composition having high foaming properties and excellent foaming stability. [Means for solving the problem]

[0007] Disclosure 1 is a foamable resin composition comprising a thermoplastic resin, thermally expandable microcapsules containing a thermosetting resin, a reactive dispersant (I) having one functional group per molecule that reacts with the thermosetting resin, and a reactive dispersant (II) having two or more functional groups per molecule that react with the thermosetting resin. Disclosure 2 is the foamable resin composition according to Disclosure 1, wherein the functional group reactive with the thermosetting resin is at least one selected from the group consisting of an amide group, an amino group, a hydroxyl group, and a carboxyl group. Disclosure 3 is the expandable resin composition according to Disclosure 1 or 2, wherein the content of the reactive dispersant (I) is 10% by weight or less. Disclosure 4 is the expandable resin composition according to any one of Disclosures 1 to 3, wherein the content of the reactive dispersant (II) is 10% by weight or less. The present disclosure 5 is the expandable resin composition according to any one of the present disclosures 1 to 4, wherein the content ratio of the reactive dispersant (I) to the reactive dispersant (II) (reactive dispersant (I) / reactive dispersant (II)) is 50 or less. The present disclosure 6 is the foamable resin composition according to any one of the present disclosures 1 to 5, wherein the thermoplastic resin is a thermoplastic elastomer and has a melt flow rate of 0.1 g / 10 min or more and 100 g / 10 min or less. The present invention will be described in detail below.

[0008] As a result of extensive research, the inventors discovered that high foaming properties and excellent foaming stability can be achieved when a foamable resin composition containing a thermoplastic resin, thermally expandable microcapsules containing a thermosetting resin, and a specified reactive dispersant is used, and this led to the completion of the present invention.

[0009] The foamable resin composition of the present invention contains a thermoplastic resin. In the present invention, by including a thermoplastic resin as the base resin, it is possible to produce a foamed molded article with good appearance quality.

[0010] Examples of the thermoplastic resin include polyolefins such as polyethylene resins and polypropylene, polystyrene (PS), acrylonitrile-styrene copolymers (AS resins), acrylonitrile-butadiene-styrene copolymers (ABS resins), acrylic resins such as polymethyl methacrylate, polyamides, polycarbonates, polysulfones (PSU resins), polyphenylsulfones (PPSU), polyethersulfones (PES resins), polyetherimides (PEI resins), polyphenylene sulfide (PPS resins), polyester resins such as polyethylene terephthalate and polybutylene terephthalate, halogen-containing resins such as chlorinated polyvinyl chloride resins (CPVC) and polyvinyl chloride resins (PVC), polyacetals, polyimides, polyphenylene ethers, polyether ether ketones, liquid crystal polymers, and thermoplastic elastomers. Of these, thermoplastic elastomers are preferred.

[0011] Examples of the thermoplastic elastomer include olefin elastomers, styrene elastomers, ester elastomers, amide elastomers, vinyl chloride elastomers, etc. Of these, olefin elastomers are preferred.

[0012] Examples of the olefin-based elastomer include copolymers containing an olefin as a main component, and examples of the olefin as a main component include α-olefin copolymers such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, etc. Among these, propylene-based elastomers and ethylene-based elastomers are preferred. The propylene-based elastomer means an elastomer containing propylene as a main component. In the above propylene-based elastomers and ethylene-based elastomers, the component other than propylene and ethylene is preferably an α-olefin (propylene-α-olefin elastomer, ethylene-α-olefin elastomer). As the α-olefin, ethylene can be used in the case of a propylene-based elastomer, and propylene can be used in the case of an ethylene-based elastomer. Furthermore, examples of the α-olefins include α-olefins having 4 to 20 carbon atoms. Examples of the α-olefins having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. These α-olefins may be used alone or in combination of two or more. Preferred α-olefins are ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene, more preferred are ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene, and even more preferred are ethylene, propylene, and 1-butene.

[0013] The polyethylene resin is not particularly limited, and examples thereof include polyethylene resins such as low-density polyethylene resin, high-density polyethylene resin, linear low-density polyethylene resin, and ultra-high molecular weight polyethylene resin. Other examples include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-dimethylaminomethyl methacrylate copolymer, ethylene-vinyl alcohol copolymer, and ethylene-vinyl alcohol copolymer. Of these, EVA and low-density polyethylene resin are preferred as the polyethylene resin.

[0014] Examples of the acrylic resin include homopolymers of acrylic monomers such as acrylic acid, methacrylic acid, and (meth)acrylic acid esters, and (meth)acrylic copolymers containing these. Examples of the (meth)acrylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate. Examples of the (meth)acrylic acid ester include n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-octyl (meth)acrylate. The term "(meth)acrylic acid" refers to either acrylic acid or methacrylic acid.

[0015] In the (meth)acrylic copolymer, other comonomers copolymerized together with the acrylic monomer include α-olefin, styrene, α-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitrile, vinyl acetate, and the like. Among these, a copolymer of an acrylic monomer and an α-olefin is preferred, and an ethylene-methyl methacrylate copolymer (EMMA) is more preferred. These comonomers can be present in the acrylic resin in the form of a random copolymer, a graft copolymer or a block copolymer.

[0016] The thermoplastic resin preferably has a weight-average molecular weight of 10,000 or more and 1,000,000 or less, and more preferably 12,000 or more and 500,000 or less. By setting the weight-average molecular weight within the above range, a molded product with excellent appearance can be obtained. The weight average molecular weight (Mw) is measured as a polystyrene-equivalent molecular weight by gel permeation chromatography (GPC).

[0017] The melt flow rate (MFR) of the thermoplastic resin is preferably 0.1 g / 10 min or more and 100 g / 10 min or less. By setting the MFR to 0.1 g / 10 min or more, the moldability of the masterbatch can be improved, and by setting it to 100 g / 10 min or less, the appearance of the resulting molded article can be improved. The thermoplastic resin is particularly preferably a thermoplastic elastomer having a melt flow rate of 0.1 g / 10 min or more and 100 g / 10 min or less. The melt flow rate is an index that indicates the fluidity of a resin, and is expressed as the amount of resin extruded from an opening (nozzle) at the bottom of a cylindrical container heated by a heater, heated to a specified temperature (e.g., 190°C), and pressurized with a specified load (e.g., 2.16 kg) in 10 minutes. The unit is g / 10 min, and it is measured according to the measurement method specified in JIS K7210-1.

[0018] Examples of the other resin components include rubber components. Examples of the rubber components that can be used include natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), chloroprene rubber (CR), urethane rubber (U), and silicone rubber (Si). One or more types selected from the above rubber components can be used in combination.

[0019] The preferred lower limit of the content of the thermoplastic resin in the foamable resin composition of the present invention is 30% by weight, and the preferred upper limit is 80% by weight. When the content of the thermoplastic resin is 30% by weight or more, the thermally expandable microcapsules can be dispersed well, and when the content of the thermoplastic resin is 80% by weight or less, the desired expansion ratio can be obtained. The more preferred lower limit of the content of the thermoplastic resin is 40% by weight, and the more preferred upper limit is 75% by weight.

[0020] The foamable resin composition of the present invention contains thermally expandable microcapsules containing a thermosetting resin, and by containing such thermally expandable microcapsules, a high expansion ratio can be achieved. The thermally expandable microcapsules have a shell containing a volatile expanding agent as a core agent.

[0021] The thermosetting resin is preferably contained in the shell of a thermally expandable microcapsule. Examples of the thermosetting resin include epoxy resin, phenol resin, melamine resin, urea resin, polyimide resin, bismaleimide resin, thermosetting acrylic resin, etc. Among these, epoxy resin and phenol resin are preferred.

[0022] The epoxy resin is not particularly limited, and examples thereof include bisphenol-type epoxy resins such as bisphenol A, bisphenol F, bisphenol AD, and bisphenol S; novolac-type epoxy resins such as phenol novolac and cresol novolac; aromatic epoxy resins such as resorcinol-type epoxy resins and trisphenolmethane triglycidyl ether; alicyclic epoxy resins; naphthalene-type epoxy resins; fluorene-type epoxy resins; dicyclopentadiene-type epoxy resins; polyether-modified epoxy resins such as epoxy resins having a polyether skeleton; NBR-modified epoxy resins; CTBN-modified epoxy resins; and hydrogenated versions thereof. Among these, hydrogenated bisphenol-type epoxy resins and epoxy resins having a polyether skeleton are preferred as the cationically curable resin contained in the resin composition used to form the second resin layer. These epoxy resins may be used alone or in combination of two or more.

[0023] The epoxy resin preferably has an epoxy equivalent of 0 or more and 5,000 or less, more preferably 50 or more and 1,000 or less. When the epoxy equivalent is within the above range, the distance between crosslinking points of the epoxy resin becomes an appropriate range, and foaming properties can be further improved. The epoxy equivalent is defined as "the mass of the resin containing 1 equivalent of epoxy groups" and is measured by a method in accordance with JIS K7236.

[0024] The hydrogenated bisphenol epoxy resin is preferably a hydrogenated bisphenol A epoxy resin containing a hydrogenated bisphenol A skeleton. The hydrogenated bisphenol epoxy resin may be a multimer such as a dimer. The hydrogenated bisphenol epoxy resin preferably has an epoxy equivalent of 100 or more and 2000 or less. By having the epoxy equivalent of 100 or more and 2000 or less, the crosslinking density of the epoxy resin can be controlled within a preferred range, thereby further improving impact resistance. The epoxy equivalent is defined as "the mass of the resin containing one equivalent of epoxy groups" and is measured according to a method in accordance with JIS K7236.

[0025] Examples of the alicyclic epoxy resin include 3',4'-epoxycyclohexylmethyl, 3,4-epoxycyclohexanecarboxylate, ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl, 3,4-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexyl)adipate, 1,2-epoxy-4-vinylcyclohexane, 1,4-cyclohexanedimethanol diglycidyl ether, epoxyethyldivinylcyclohexane, diepoxyvinylcyclohexane, 1,2,4-triepoxyethylcyclohexane, limonene dioxide, and alicyclic epoxy group-containing silicone oligomers. These alicyclic epoxy resins may be used alone or in combination of two or more.

[0026] The epoxy resin may be an epoxy resin that is liquid at room temperature (23°C) or an epoxy resin that is solid at room temperature, or an appropriate combination of these may be used. The epoxy resin preferably contains at least one epoxy resin that is liquid at room temperature, and for example, a hydrogenated bisphenol epoxy resin that is liquid at room temperature or an epoxy resin having a polyether skeleton that is liquid at room temperature is preferably used.

[0027] Examples of the phenolic resin include novolac type phenolic resin, resol type phenolic resin, benzylic ether type phenolic resin, etc. Among these, novolac type phenolic resin is preferred.

[0028] Examples of the thermosetting acrylic resin include a (meth)acrylic acid ester compound obtained by reacting a compound having a hydroxyl group with (meth)acrylic acid, an epoxy (meth)acrylate obtained by reacting (meth)acrylic acid with an epoxy resin, and a urethane (meth)acrylate obtained by reacting an isocyanate compound with a (meth)acrylic acid derivative having a hydroxyl group. Examples of the (meth)acrylic acid ester compound include 2-hydroxyethyl (meth)acrylate, 2-(acetoacetoxy)ethyl (meth)acrylate, 2-aminoethyl (meth)acrylate, allyl (meth)acrylate, cholesteryl (meth)acrylate, t-butyldimethylsilyl (meth)acrylate, diethylene glycol monomethyl ether (meth)acrylate, 2-(dimethylamino)ethyl (meth)acrylate, and ethylene glycol monomethyl ether (meth)acrylate.

[0029] The thermosetting resin preferably has two or more functional groups per molecule that react with the reactive dispersant described below. This makes it possible to further strengthen the curing properties of the thermosetting resin. The thermosetting resin preferably does not have a radically polymerizable double bond. Examples of functional groups that react with the reactive dispersant include glycidyl groups, phenol groups, methylol groups, amino groups, and acrylic groups. Of these, glycidyl groups are preferred. The functional groups that react with the carboxyl groups may be the same or two or more types.

[0030] The shell constituting the thermally expandable microcapsules is formed by reacting a monomer composition. The preferred lower limit of the content of the thermosetting resin in the monomer composition is 0.01% by weight, and the preferred upper limit is 30% by weight. By setting the content of the thermosetting resin to 0.01% by weight or more, compression resistance during heat foaming can be improved. By setting the content of the thermosetting resin to 30% by weight or less, the gas barrier properties of the shell are improved and foaming properties are enhanced. A more preferred lower limit is 0.1% by weight, a more preferred upper limit is 15% by weight, an even more preferred lower limit is 1% by weight, and an even more preferred upper limit is 10% by weight. That is, the content of the thermosetting resin is preferably 0.01 to 30% by weight, more preferably 0.1 to 15% by weight, and even more preferably 1 to 10% by weight. The monomer composition is a composition containing a raw material monomer and a thermosetting resin, and the content in the monomer composition is synonymous with the content in the shell.

[0031] The shell constituting the thermally expandable microcapsules preferably contains a polymer in addition to the thermosetting resin. The polymer is preferably a polymer of a monomer composition containing a nitrile monomer and a monomer having a carboxyl group.

[0032] The nitrile monomer is not particularly limited, and examples thereof include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile, and mixtures thereof. Among these, acrylonitrile and methacrylonitrile are particularly preferred. These may be used alone or in combination of two or more.

[0033] The preferred lower limit of the content of the nitrile monomer in the monomer composition is 30% by weight, and the preferred upper limit is 90% by weight. By making it 30% by weight or more, the gas barrier properties of the shell can be improved, and the expansion ratio can be increased. By making it 90% by weight or less, heat resistance can be improved and yellowing can be prevented. A more preferred lower limit is 40% by weight, and a more preferred upper limit is 80% by weight. That is, the content of the nitrile monomer is preferably 30 to 90% by weight, and more preferably 40 to 80% by weight.

[0034] As the monomer having a carboxyl group, for example, a radically polymerizable unsaturated carboxylic acid monomer having a carboxyl group and 3 to 8 carbon atoms can be used. Specific examples include unsaturated monocarboxylic acids, unsaturated dicarboxylic acids, anhydrides thereof, and monoesters of unsaturated dicarboxylic acids, which may be used alone or in combination of two or more. Examples of the unsaturated carboxylic acid include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid, and unsaturated dicarboxylic acids such as 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, and monobutyl itaconate. Of these, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and itaconic acid are particularly preferred.

[0035] The preferred lower limit of the content of the carboxyl group-containing monomer in the monomer composition is 5% by weight, and the preferred upper limit is 70% by weight. By making it 5% by weight or more, the maximum foaming temperature can be increased, and by making it 70% by weight or less, the foaming ratio can be improved. A more preferred lower limit is 10% by weight, and a more preferred upper limit is 50% by weight. That is, the content of the carboxyl group-containing monomer is preferably 5 to 70% by weight, and more preferably 10 to 50% by weight.

[0036] The monomer composition preferably does not contain a crosslinkable monomer having two or more double bonds in the molecule.

[0037] The crosslinkable monomer may be a monomer having two or more radically polymerizable double bonds, and specific examples thereof include divinylbenzene, di(meth)acrylate, tri- or higher functional (meth)acrylate, and the like. Examples of the di(meth)acrylate include 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. Other examples include 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, trimethylolpropane di(meth)acrylate, and dimethylol-tricyclodecane di(meth)acrylate. Furthermore, a di(meth)acrylate of polyethylene glycol having a weight-average molecular weight of 200 to 600 may also be used. Examples of the trifunctional (meth)acrylate include trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, triallyl formal tri(meth)acrylate, etc. Examples of the tetrafunctional or higher (meth)acrylate include pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc. Among these, trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate and bifunctional (meth)acrylates such as polyethylene glycol are crosslinked relatively uniformly in the shell mainly composed of acrylonitrile.

[0038] When the monomer composition contains a crosslinkable monomer, the preferred lower limit of the crosslinkable monomer content is 0.001% by weight, and the preferred upper limit is 1.0% by weight. By setting the crosslinkable monomer content to 0.001% by weight or more, the crosslinkable monomer can fully exert its effect as a crosslinking agent, while setting the crosslinkable monomer content to 1.0% by weight or less can improve the expansion ratio of the thermally expandable microcapsules. The more preferred lower limit of the crosslinkable monomer content is 0.0015% by weight, and the more preferred upper limit is 0.9% by weight. That is, the content of the crosslinkable monomer is preferably 0.001 to 1.0% by weight, and more preferably 0.0015 to 0.9% by weight.

[0039] The monomer composition preferably contains other monomers in addition to the nitrile monomer, the carboxyl group-containing monomer, and the crosslinkable monomer, which improves the compatibility of the thermally expandable microcapsules with the matrix resin, such as a thermoplastic resin, and provides a foamed molded article using the thermally expandable microcapsules with an excellent appearance. Examples of the other monomers include (meth)acrylic acid esters as well as vinyl monomers such as vinyl chloride, vinylidene chloride, vinyl acetate, and styrene. These may be used alone or in combination of two or more. Among these, (meth)acrylic acid esters are preferred, and in particular, methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate, or alicyclic, aromatic, or heterocyclic methacrylic acid esters such as cyclohexyl methacrylate, benzyl methacrylate, and isobornyl methacrylate are preferred.

[0040] The preferred lower limit of the content of the other monomer in the monomer composition is 0.1 wt %, and the preferred upper limit is 35 wt %. By setting the content of the other monomer to 0.1 wt % or more, the dispersibility of the composition using thermally expandable microcapsules can be improved, and by setting the content to 35 wt % or less, the gas barrier properties of the cell walls can be improved, thereby improving thermal expandability. The more preferred lower limit of the content of the other monomer is 0.3 wt %, and the more preferred upper limit is 32 wt %. That is, the content of the other monomer is preferably 0.1 to 35 wt %, and more preferably 0.3 to 32 wt %.

[0041] The monomer composition contains a polymerization initiator to polymerize the monomers. As the polymerization initiator, for example, dialkyl peroxide, diacyl peroxide, peroxyester, peroxydicarbonate, azo compound, etc. are preferably used. Examples of the dialkyl peroxide include methyl ethyl 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 peroxyester include t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, and 1,1,3,3-tetramethylbutyl peroxyneodecanoate. Examples of the peroxydicarbonate include bis(4-t-butylcyclohexyl)peroxydicarbonate, di-n-propyl-oxydicarbonate, diisopropyl peroxydicarbonate, di(2-ethylethylperoxy)dicarbonate, and dimethoxybutyl peroxydicarbonate. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 1,1'-azobis(1-cyclohexanecarbonitrile).

[0042] The weight-average molecular weight of the polymer other than the thermosetting resin that constitutes the shell preferably has a lower limit of 100,000 and an upper limit of 2,000,000. If the weight-average molecular weight is less than 100,000, the strength of the shell may decrease, whereas if the weight-average molecular weight exceeds 2,000,000, the strength of the shell may become too high, resulting in a decrease in the expansion ratio.

[0043] The shell may further contain, as necessary, a stabilizer, an ultraviolet absorber, an antioxidant, an antistatic agent, a flame retardant, a silane coupling agent, a coloring agent, and the like.

[0044] The thermally expandable microcapsules have a volatile expanding agent encapsulated in the shell as a core agent. The volatile expanding agent is a substance that becomes gaseous at a temperature below the softening point of the polymer that constitutes the shell, and is preferably a low-boiling organic solvent. Examples of the volatile expanding agent include low molecular weight hydrocarbons, chlorofluorocarbons, and tetraalkylsilanes. Examples of the low molecular weight hydrocarbons include ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, isooctane, and petroleum ether. Examples of the chlorofluorocarbon include CCl3F, CCl2F2, CClF3, and CClF2-CClF2. Examples of the tetraalkylsilane include tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane. Among these, isobutane, n-butane, n-pentane, isopentane, n-hexane, isooctane, petroleum ether, and mixtures thereof are preferred. These volatile blowing agents may be used alone or in combination of two or more. Furthermore, a thermally decomposable compound that is thermally decomposed into a gaseous form by heating may also be used as the volatile expanding agent.

[0045] In the thermally expandable microcapsules, among the above-mentioned volatile expanding agents, it is preferable to use low-boiling-point hydrocarbons having a carbon number of 5 or less. By using such hydrocarbons, it is possible to obtain thermally expandable microcapsules that have a high expansion ratio and start expanding quickly. Furthermore, a thermally decomposable compound that is thermally decomposed into a gaseous form when heated may be used as the volatile expanding agent.

[0046] In the thermally expandable microcapsules, the preferred lower limit of the content of the volatile expanding agent used as the core agent is 10% by weight, and the preferred upper limit is 25% by weight. The thickness of the shell varies depending on the content of the core agent, but if the content of the core agent is reduced and the shell becomes too thick, the foaming performance decreases, and if the content of the core agent is increased, the strength of the shell decreases. When the content of the core agent is set to 10 to 25 wt%, it is possible to prevent the thermally expandable microcapsules from collapsing and improve the foaming performance at the same time.

[0047] The maximum foaming temperature (Tmax) of the thermally expandable microcapsules is preferably 160°C in lower limit and 230°C in upper limit. By setting the maximum foaming temperature to 160°C or higher, heat resistance is increased, preventing the thermally expandable microcapsules from bursting or shrinking in high temperature regions or during molding. Furthermore, foaming due to shear during masterbatch production is prevented, enabling stable production of unfoamed masterbatches. The maximum foaming temperature is more preferably 170°C in lower limit and 220°C in upper limit. In this specification, the maximum foaming temperature means the temperature at which the diameter of a thermally expandable microcapsule becomes maximum (maximum displacement) when the diameter of the thermally expandable microcapsule is measured while being heated from room temperature.

[0048] The thermally expandable microcapsules preferably have a maximum displacement (Dmax) measured by thermomechanical analysis of 500 μm in lower limit and 2000 μm in upper limit. The maximum displacement is the value at which the diameter of a predetermined amount of thermally expandable microcapsules reaches its maximum when the diameter of the predetermined amount of thermally expandable microcapsules is measured while being heated from room temperature. The foaming initiation temperature (Ts) preferably has a lower limit of 140°C, a preferred upper limit of 200°C, a more preferred lower limit of 150°C, and a more preferred upper limit of 190°C. In this specification, the maximum foaming temperature means the temperature at which the thermally expandable microcapsules have reached their maximum displacement when their diameters are measured while being heated from room temperature.

[0049] The preferred lower limit of the average particle size of the thermally expandable microcapsules is 15 μm, and the preferred upper limit is 35 μm. When the average particle size is 15 μm or more, the resulting molded article can be sufficiently expanded, and when the average particle size is 35 μm or less, the resulting molded article can have sufficient strength. The more preferred lower limit of the average particle size is 18 μm, and the more preferred upper limit is 30 μm. The average particle size of the thermally expandable microcapsules refers to the volume average particle size measured using a particle size distribution diameter measuring instrument or the like.

[0050] The preferred lower limit of the true specific gravity of the thermally expandable microcapsules is 0.95 g / cm 3 The true specific gravity is 0.95 g / cm 3 If the ratio is more than this, a molded product with high expandability can be obtained. A more preferable lower limit of the true specific gravity is 1.0 g / cm 3 , the preferred upper limit is 1.10 g / cm 3 is. The true specific gravity refers to the specific gravity of the material alone excluding pores, and can be measured, for example, by placing a predetermined amount of thermally expandable microcapsules in a dry automatic density meter.

[0051] The preferred lower limit of the content of the thermally expandable microcapsules in the foamable resin composition of the present invention is 20% by weight, and the preferred upper limit is 60% by weight. By setting the content of the thermally expandable microcapsules to 20% by weight or more, a desired expansion ratio can be obtained. By setting the content of the thermally expandable microcapsules to 60% by weight or less, foaming during the preparation of the foamable resin composition can be prevented, and as a result, the expansion ratio of the foam-molded product can be improved. The more preferred lower limit of the content of the thermally expandable microcapsules is 25% by weight, and the more preferred upper limit is 55% by weight.

[0052] The method for producing the above-mentioned thermally expandable microcapsules is not particularly limited, but they can be produced, for example, by carrying out the steps of preparing an aqueous dispersion medium containing an inorganic compound, dispersing a monomer composition and an oily mixture containing a volatile expanding agent in the aqueous dispersion medium, and polymerizing the above-mentioned monomer. The monomer composition may contain the above-mentioned nitrile monomer, a monomer having a carboxyl group, a crosslinkable monomer, and other monomers in addition to the thermosetting resin.

[0053] When producing the thermally expandable microcapsules, the first step is to prepare an aqueous dispersion medium. Specifically, for example, water, a dispersion stabilizer, and optionally a co-stabilizer are added to a polymerization reaction vessel to prepare an aqueous dispersion medium containing the dispersion stabilizer. Furthermore, alkali metal nitrite, stannous chloride, stannic chloride, potassium dichromate, etc. may also be added as needed.

[0054] Examples of the dispersion stabilizer include silica, calcium phosphate, magnesium hydroxide, aluminum hydroxide, ferric hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, barium carbonate, and magnesium carbonate.

[0055] The amount of the dispersion stabilizer to be added is not particularly limited and is determined appropriately depending on the type of dispersion stabilizer, the particle size of the thermally expandable microcapsules, etc., but the preferred lower limit is 0.1 parts by weight and the preferred upper limit is 20 parts by weight per 100 parts by weight of the monomer.

[0056] Examples of the auxiliary stabilizer include a condensation product of diethanolamine and an aliphatic dicarboxylic acid, a condensation product of urea and formaldehyde, etc. Further examples include polyvinylpyrrolidone, polyethylene oxide, polyethyleneimine, tetramethylammonium hydroxide, gelatin, methylcellulose, polyvinyl alcohol, dioctyl sulfosuccinate, sorbitan ester, various emulsifiers, etc.

[0057] The combination of the dispersion stabilizer and co-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, a combination of magnesium hydroxide or calcium phosphate and an emulsifier, etc. Among these, the combination of colloidal silica and a condensation product is preferred. Furthermore, as the condensation product, a condensation product of diethanolamine and an aliphatic dicarboxylic acid is preferred, and a condensation product of diethanolamine and adipic acid or a condensation product of diethanolamine and itaconic acid is particularly preferred.

[0058] Examples of the water-soluble nitrogen-containing compound include polyvinylpyrrolidone, polyethyleneimine, polyoxyethylene alkylamine, polydialkylaminoalkyl(meth)acrylate, polydialkylaminoalkyl(meth)acrylamide, polyacrylamide, polycationic acrylamide, polyamine sulfone, and polyallylamine. Examples of the polydialkylaminoalkyl(meth)acrylate include polydimethylaminoethyl methacrylate and polydimethylaminoethyl acrylate. Examples of the polydialkylaminoalkyl(meth)acrylamide include polydimethylaminopropylacrylamide, polydimethylaminopropylmethacrylamide, etc. Among these, polyvinylpyrrolidone is preferably used.

[0059] The amount of colloidal silica added is determined appropriately depending on the particle size of the thermally expandable microcapsules, with a preferred lower limit of 1 part by weight and a preferred upper limit of 20 parts by weight per 100 parts by weight of vinyl monomer. A more preferred lower limit of the amount of colloidal silica added is 2 parts by weight and a more preferred upper limit is 10 parts by weight. The amount of the condensation product or water-soluble nitrogen-containing compound added is also determined appropriately depending on the particle size of the thermally expandable microcapsules, with a preferred lower limit of 0.05 parts by weight and an upper limit of 2 parts by weight per 100 parts by weight of monomer.

[0060] In addition to the dispersion stabilizer and co-stabilizer, inorganic salts such as sodium chloride and sodium sulfate may be added. By adding an inorganic salt, it is possible to obtain thermally expandable microcapsules with a more uniform particle shape. The amount of the inorganic salt added is usually preferably 0 to 100 parts by weight per 100 parts by weight of the monomer.

[0061] The aqueous dispersion medium containing the dispersion stabilizer is prepared by blending the dispersion stabilizer and / or co-stabilizer with deionized water, and the pH of the aqueous phase is determined appropriately depending on the type of dispersion stabilizer and / or co-stabilizer used. For example, when silica such as colloidal silica is used as the dispersion stabilizer, polymerization is carried out in an acidic medium, and to make the aqueous medium acidic, an acid such as hydrochloric acid is added as necessary to adjust the pH of the system to 3 to 4. On the other hand, when magnesium hydroxide or calcium phosphate is used, polymerization is carried out in an alkaline medium.

[0062] Next, in the method for producing thermally expandable microcapsules, a step of dispersing the monomer composition and the oily mixture containing the volatile expanding agent in an aqueous dispersion medium is carried out. Specifically, a process is carried out in which an oily mixture containing a monomer composition and a volatile swelling agent is dispersed in an aqueous dispersion medium. In this process, the monomer composition and the volatile swelling agent may be added separately to the aqueous dispersion medium to prepare an oily mixture in the aqueous dispersion medium, but usually, the two are mixed in advance to form an oily mixture, which is then added to the aqueous dispersion medium. In this case, the oily mixture and the aqueous dispersion medium may be prepared in separate containers, and the oily mixture may be dispersed in the aqueous dispersion medium by stirring in a separate container, and then added to the polymerization reaction vessel. In this process, an inorganic compound is present at the interface between the oil droplets of the oily mixture and the aqueous dispersion medium, and as a result, the inorganic compound can be present on the surface of the resulting thermally expandable microcapsules. A polymerization initiator is used to polymerize the monomers. The polymerization initiator may be added to the oily mixture in advance, or may be added after the aqueous dispersion medium and the oily mixture are stirred and mixed in a polymerization reaction vessel.

[0063] Examples of a method for emulsifying and dispersing the oily mixture in an aqueous dispersion medium to a predetermined particle size include a method of stirring with a homomixer (for example, manufactured by Tokushu Kika Kogyo Co., Ltd.) or a method of passing the mixture through a static dispersion device such as a line mixer or an element-type static disperser. The aqueous dispersion medium and the polymerizable mixture may be supplied separately to the static dispersing device, or a dispersion liquid that has been mixed and stirred in advance may be supplied.

[0064] The thermally expandable microcapsules can be produced by subjecting the dispersion obtained through the above-mentioned steps to a step of polymerizing the monomers by heating, and a step of washing. The thermally expandable microcapsules produced by this method have a high maximum foaming temperature, excellent heat resistance, and do not burst or shrink even when coated at high temperatures.

[0065] The foamable resin composition of the present invention contains a reactive dispersant (I) having one functional group per molecule that reacts with the thermosetting resin, and a reactive dispersant (II) having two or more functional groups per molecule that react with the thermosetting resin, whereby the dispersant chemically bonds to the shell surface of the thermally expandable microcapsules, enabling good dispersion in the foamable resin composition, and at the same time, highly crosslinking the shell, thereby enabling high heat resistance and durability.

[0066] The functional group reactive with the thermosetting resin is preferably at least one selected from the group consisting of an amide group, an amino group, a hydroxyl group, and a carboxyl group, which allows the reaction with the thermosetting resin to proceed sufficiently.

[0067] Examples of the reactive dispersant (I) include aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, lauric acid, myristic acid, and palmitic acid, and aromatic monocarboxylic acids such as phenylacetic acid, benzoic acid, γ-phenylbutyric acid, and o-toluic acid, and other carboxyl group-containing compounds; n-propylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, and n-octylamine; amine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-octadecylamine, n-butenylamine, n-pentenylamine, n-hexenylamine, n-heptenylamine, n-octenylamine, n-nonenylamine, n-decenylamine, n-undecenylamine, n-dodecenylamine amino group-containing compounds such as aliphatic monoamines such as n-tridecenylamine, n-tetradecenylamine, n-pentadecenylamine, n-hexadecenylamine, n-heptadecenylamine, n-octadecenylamine, dimethylamine, di-n-nonylamine, methylethylamine, ethyl-n-heptylamine, and methyl-n-heptadecenylamine; amide group-containing compounds such as aliphatic monoamides such as lauric amide, palmitic amide, stearic amide, behenic amide, stearyl oleic amide, oleyl stearic amide, oleyl oleic amide, oleyl erucic amide, and stearyl erucic amide; and hydroxy group-containing compounds such as aliphatic alcohols such as undecyl alcohol, cetanol, stearyl alcohol, isostearyl alcohol, elaidyl alcohol, linoleyl alcohol, oleyl alcohol, and ceryl alcohol.

[0068] The reactive functional group equivalent weight (molecular weight / number of reactive functional groups) of the reactive dispersant (I), which is expressed as the ratio of the molecular weight of the reactive dispersant (I) to the number of functional groups of the reactive dispersant (I) that react with the thermosetting resin [number of reactive functional groups], is preferably 40 or more and 1,000 or less. This makes it possible to achieve both high foaming properties and excellent foaming stability. The reactive functional group equivalent weight of the reactive dispersant (I) is more preferably 40 or more and 500 or less. The molecular weight of the reactive dispersant (I) is preferably 40 or more and 1,000 or less, and more preferably 40 or more and 500 or less.

[0069] The preferred lower limit of the content of the reactive dispersant (I) in the foamable resin composition of the present invention is 0.01% by weight, and the preferred upper limit is 10% by weight. By making the content of the reactive dispersant (I) 0.01% by weight or more, the thermally expandable microcapsules can be dispersed well. By making the content of the reactive dispersant (I) 10% by weight or less, the expansion ratio of the thermally expandable microcapsules can be made good. The more preferred lower limit of the content of the reactive dispersant (I) is 0.1% by weight, and the more preferred upper limit is 5% by weight.

[0070] Examples of the reactive dispersant (II) include carboxyl group-containing compounds such as aliphatic polycarboxylic acids such as succinic acid and adipic acid, and aromatic polycarboxylic acids such as phthalic acid, terephthalic acid and trimellitic acid; amino group-containing compounds or amide group-containing compounds such as diaminodiphenylmethane, diethylenetriamine, triethylenetetramine, diaminodiethyltoluene, diaminodiphenylsulfone, isophoronediamine, dicyandiamide, and polyamide resins synthesized from a linolenic acid dimer and ethylenediamine; and trimellitic anhydride. Examples of the polyol include: acid anhydride group-containing compounds such as pyromellitic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride; hydroxy acids such as lactic acid, malic acid, and citric acid; and polyols such as ethylene glycol, propylene glycol, glycerin, sorbitol, trimethylolpropane, carbonate diols, polyether diols, polyester diols, polycaprolactone diols, and glycerol monostearate.

[0071] The reactive functional group equivalent weight (molecular weight / number of reactive functional groups) of the reactive dispersant (II), which is expressed as the ratio of the molecular weight of the reactive dispersant (II) to the number of functional groups of the reactive dispersant (II) that react with the thermosetting resin [number of reactive functional groups], is preferably 40 or more and 1,000 or less. This makes it possible to achieve both high foaming properties and excellent foaming stability. The reactive functional group equivalent weight of the reactive dispersant (II) is more preferably 40 or more and 500 or less. The molecular weight of the reactive dispersant (II) is preferably 80 or more and 2,000 or less, and more preferably 80 or more and 1,000 or less.

[0072] The preferred lower limit of the content of the reactive dispersant (II) in the foamable resin composition of the present invention is 0.01% by weight, and the preferred upper limit is 10% by weight. By making the content of the reactive dispersant (II) 0.01% by weight or more, the expansion ratio of the thermally expandable microcapsules can be improved. By making the content of the reactive dispersant (II) 10% by weight or less, the dispersibility of the thermally expandable microcapsules can be improved. The more preferred lower limit of the content of the reactive dispersant (II) is 0.1% by weight, and the more preferred upper limit is 5% by weight.

[0073] In the foamable resin composition of the present invention, the content ratio of the reactive dispersant (I) to the reactive dispersant (II) (reactive dispersant (I) / reactive dispersant (II)) is preferably 50 or less. This makes it possible to achieve both high foamability and excellent foam stability. The lower limit of the reactive dispersant (I) / reactive dispersant (II) ratio is preferably 0.01, and the upper limit is more preferably 40.

[0074] In the foamable resin composition of the present invention, the content ratio of the reactive dispersant (I) to the thermosetting resin (reactive dispersant (I) / thermosetting resin) is preferably 0.01 or more and 10 or less. This makes it possible to achieve both high foamability and excellent foaming stability. The reactive dispersant (I) / thermosetting resin ratio is more preferably 2.5 or more and 6.5 or less.

[0075] The foamable resin composition of the present invention may contain, in addition to the reactive dispersant (I) and the reactive dispersant (II), a dispersant that does not have a functional group that reacts with the thermosetting resin, thereby achieving better foaming stability. Examples of dispersants that do not have a functional group that reacts with the thermosetting resin include esters of aliphatic monocarboxylic acids and monools, such as liquid paraffin, methyl palmitate, ethyl palmitate, hexyl palmitate, isopropyl palmitate, palmityl palmitate, methyl stearate, ethyl stearate, hexyl stearate, isopropyl stearate, and stearyl stearate, and esters of aliphatic monocarboxylic acids and polyols, such as tripalmitin and tristearin. The preferred lower limit of the content of the dispersant that does not have a functional group that reacts with the thermosetting resin is 0.01% by weight, and the preferred upper limit is 10% by weight.

[0076] The foamable resin composition of the present invention may contain a chemical foaming agent. By including the chemical foaming agent, for example, when a chemical foaming agent such as sodium bicarbonate is used, the foaming performance can be improved by the CO2 generated during decomposition. Furthermore, by using the thermally expandable microcapsules in combination with a chemical foaming agent, it is possible to suppress the formation of open cells, which tend to occur when a chemical foaming agent is used alone.

[0077] The chemical foaming agent is not particularly limited as long as it is in powder form at room temperature, and any conventionally commonly used chemical foaming agent can be used. Specific examples include inorganic chemical foaming agents such as sodium bicarbonate, and organic chemical foaming agents such as azodicarbonamide, N,N'-dinitrosopentamethylenetetramine, P,P'-oxybisbenzenesulfonylhydrazide, and paratoluenesulfonylhydrazide.

[0078] The foamable resin composition of the present invention may contain an additive such as a lubricant. By containing the lubricant, the shear applied to the thermally expandable microcapsules during production of the foamable resin composition is suppressed, making it difficult for micro-bubbles to occur, and the dispersibility of the thermally expandable microcapsules can be improved, making it easier to produce the foamable resin composition. As a result, a masterbatch having a high concentration of thermally expandable microcapsules can be produced stably and with good production efficiency.

[0079] The lubricant is not particularly limited as long as it dissolves at the temperature during production of the foamable resin composition, and any lubricant that has been conventionally used can be used. Specific examples include polyethylene wax having a viscosity average molecular weight of 3,000 or less, glycerin fatty acid esters such as glycerin monostearate and diglycerin stearate, fatty acids such as stearic acid, and so-called composite lubricants.

[0080] The method for producing the foamable resin composition of the present invention is not particularly limited, but for example, it can be produced by performing a mixing step in which a thermoplastic resin, thermally expandable microcapsules containing a thermosetting resin, a reactive dispersant (I), and a reactive dispersant (II) are mixed.

[0081] Examples of the above-mentioned mixing process include a method in which two or more feeders are connected to the supply port of the extruder, and the base resin and thermally expandable microcapsules are fed into the extruder from separate feeders and mixed by kneading in the extruder, and a method in which the components are mixed in advance and then fed into the extruder. The extruder used in the above mixing step may be one having a feed port, a vent, a screw, a temperature control function, and a discharge port (head). The extruder may be of various extrusion types such as single-screw, twin-screw, and multi-screw, but a twin-screw type is preferred. Examples of twin-screw types include counter-rotating and co-rotating types (conical and parallel types), but the co-rotating type (either conical or parallel type) is preferred for the production method of the present invention.

[0082] In the mixing step, it is preferable to replace the inside of the extruder with an inert gas such as nitrogen, or to degas the extruder through a single-stage or multi-stage vent (i.e., by opening the vent). Alternatively, forced degassing may be performed by drawing a vacuum through the vent.

[0083] In the mixing step, the cylinder temperature of the extruder is preferably set within a range of 90 to 110° C. The temperature in the region of the extruder close to the raw material addition portion is preferably set within the above range. The screw rotation speed in the mixing step is preferably in the range of 270 to 330 rpm (in this case, the discharge amount is about 100 kg / hour).

[0084] When producing a foamable masterbatch as the foamable resin composition of the present invention, the above mixing step is followed by a cooling step of cooling the strands obtained in the mixing step, and a cutting step of cutting the strands after the cooling step (cold cut method). Alternatively, a method in which the cutting step is carried out without a cooling step after the mixing step (hot cutting method) may be used, or a method in which the material is extruded into a sheet, followed by a cooling step and a cutting step (sheet cutting method) may be used.

[0085] The strands can be cooled in the cooling step by air cooling or water cooling, with water cooling being preferred. When the water cooling method is adopted, it is desirable to install a drainer or dryer before the pelletizer that cuts the strands in order to remove water adhering to the strands. The cooling method using the water cooling method may be, for example, a method in which the strand is conveyed in the direction of a cutter while being cooled by contacting the strand with water. In the cooling method using the water cooling method, the submerged distance (water cooling distance) is preferably 60 to 200 cm when the discharge amount is about 100 kg. Furthermore, the strand take-up speed is preferably about 0.2 to 0.6 m / s.

[0086] In the cutting step, the cooled strand is cut at appropriate intervals using a strand cutter or the like to form pellets. The strand cutter is not particularly limited and can be appropriately selected depending on the purpose.

[0087] A foamed molded article can be produced by molding a resin composition obtained by adding a matrix resin such as a thermoplastic resin to the foamable resin composition of the present invention using a molding method such as injection molding, and foaming the resin composition using the above-mentioned thermally expandable microcapsules by heating during molding.

[0088] The matrix resin, such as the thermoplastic resin, is not particularly limited as long as it does not impair the objectives of the present invention, and examples thereof include common thermoplastic resins such as polyvinyl chloride, polystyrene, polypropylene, polypropylene oxide, and polyethylene. Other examples include engineering plastics such as polybutylene terephthalate, nylon, polycarbonate, and polyethylene terephthalate. Thermoplastic elastomers such as ethylene-based, vinyl chloride-based, olefin-based, urethane-based, and ester-based elastomers may also be used, and these resins may be used in combination. It is preferable to use the same resin as the base resin as the matrix resin.

[0089] The molding method for the foamed molded article is not particularly limited, and examples thereof include kneading molding, calendar molding, extrusion molding, injection molding, etc. In the case of injection molding, the process is not particularly limited, and examples thereof include the short-short method in which a resin material is partially placed in a mold and foamed, and the core-back method in which the mold is fully filled with the resin material and then opened to the desired foaming point.

[0090] Examples of uses of the foamed molded article include automobile interior materials such as door trims and instrument panels, and automobile exterior materials such as bumpers. Other uses include building materials such as wood powder plastics, shoe soles, and artificial cork. [Effects of the Invention]

[0091] According to the present invention, it is possible to provide a foamable resin composition having high foamability (expansion ratio), and to provide a foamed molded article with little variation in expansion ratio and tensile strength, and to provide a foamable resin composition having excellent foaming stability. In addition, it is possible to provide a foamable resin composition that has little fusion and is easy to handle during molding. As a result, for example, when a masterbatch is formed, fusion between masterbatches after drying can be reduced. This is thought to be because the reaction between the reactive dispersant and the thermally expandable microcapsules reduces elution of the reactive dispersant due to heating during drying. Furthermore, defects such as die buildup can be reduced, and a foamable resin composition with excellent moldability can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0092] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0093] (Preparation of thermally expandable microcapsules) An aqueous dispersion medium was prepared by adding 300 parts by weight of water, 89 parts by weight of sodium chloride as a modifier, 0.07 parts by weight of sodium nitrite as a water-soluble polymerization inhibitor, 8 parts by weight of colloidal silica (manufactured by Asahi Denka Co., Ltd.) as a dispersion stabilizer, and 0.3 parts by weight of polyvinylpyrrolidone (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) to a polymerization reaction vessel. An oily mixture consisting of the monomer, thermosetting resin, volatile blowing agent, and polymerization initiator in the amounts shown in Table 1 was then added to the aqueous dispersion medium and mixed to prepare a dispersion. The total weight of the dispersion was 15 kg. The resulting dispersion was stirred and mixed using a homogenizer and then placed in a nitrogen-purged pressure polymerization vessel (20 L). The vessel was pressurized (0.2 MPa) and reacted at 60°C for 20 hours to prepare the reaction product. The resulting reaction product was repeatedly dehydrated and washed with water using a centrifuge, then dried to obtain thermally expandable microcapsules (A-G). As the thermosetting resin, 1,2-epoxy-4-vinylcyclohexane, bisphenol A type liquid epoxy resin, or 2-hydroxyethyl acrylate was used.

[0094] Example 1 (Making masterbatch pellets) 100 parts by weight of an olefin-based elastomer (TPO, propylene-based elastomer, MFR: 10 g / 10 min, weight-average molecular weight (Mw): 100,000) as a thermoplastic resin, 100 parts by weight of the obtained thermally expandable microcapsules A, 1 part by weight of liquid paraffin as a dispersant without reactive functional groups, 4 parts by weight of n-hexadecylamine [reactive dispersant (I)-1] as a reactive dispersant (I), and 5 parts by weight of trimellitic acid (reactive functional group number 3) as a reactive dispersant (II) were added and mixed, and the mixture was fed into a twin-screw extruder (Toshiba Machine Co., Ltd., TEM48SS, unidirectional). The cylinder temperatures in the regions near the raw material addition area (C2 and C3 portions) were set to 98°C for C2 and 99°C for C3, respectively, and the mixture was kneaded. The vents installed in the extruder were opened during extrusion. The extruded strand was then cooled by contacting it with water (submersion distance: 80 cm) while being conveyed toward a cutter. The strand was then cut into pellets using the strand cutter to obtain masterbatch pellets. The weight average molecular weight (Mw) of the thermoplastic resin was measured using the following equipment and conditions. (Measurement conditions) Apparatus: Gel permeation chromatograph GPC (JASCO) Detector: Differential refractive index detector RI (JASCO RI-4030) Column: Shodex LF-804, 2 columns connected ·Flow rate: 0.8mL / min Column temperature: 40℃ ·Injection volume: 0.200mL Standard sample: Tosoh monodisperse polystyrene

[0095] (Production of foam molded products) 100 parts by weight of the obtained masterbatch pellets were mixed with 100 parts by weight of an olefin-based elastomer (TPV, manufactured by Mitsui Chemicals, Inc., Milastomer 7030BS), and the resulting mixed pellets were fed into the hopper of an extruder, melt-kneaded, and extruded to obtain a plate-shaped foamed molded article. The extrusion conditions were a mold temperature of 190°C.

[0096] (Examples 2 to 13, Comparative Examples 1 to 15) (Making masterbatch pellets) Masterbatches (pellets) and foamed molded articles were prepared in the same manner as in Example 1, except that the types and amounts of thermoplastic resin, thermally expandable microcapsules, and dispersant used were shown in Tables 2 and 3. In Tables 2 and 3, EVA stands for ethylene-vinyl acetate copolymer, and PE stands for polyethylene. Palmitic acid was used as the reactive dispersant (I)-2. Furthermore, glycerol monostearate was used as a reactive dispersant (II) having two reactive functional groups, and citric acid was used as a reactive dispersant (II) having four reactive functional groups.

[0097] (evaluation) The thermally expandable microcapsules (A to G), and the masterbatches and foam-molded articles obtained in the examples and comparative examples were evaluated for the following performance. The results are shown in Tables 1 to 3.

[0098] (1) Evaluation of thermally expandable microcapsules (1-1) Volume average particle size The volume average particle diameter was measured using a particle size distribution diameter measuring instrument (LA-910, manufactured by HORIBA Corporation).

[0099] (1-2) Foaming start temperature, maximum foaming temperature, maximum displacement The foaming initiation temperature (Ts), maximum displacement (Dmax), and maximum foaming temperature (Tmax) were measured using a thermomechanical analyzer (TMA) (TMAQ400, TA Instruments). Specifically, 25 μg of sample was placed in an aluminum container with a diameter of 7 mm and a depth of 1 mm, and heated from 80 to 250 °C at a heating rate of 5 °C / min under a force of 0.1 N. The vertical displacement of the measuring probe was measured. The temperature at which the displacement began to increase was defined as the foaming initiation temperature, the maximum value of the displacement as the maximum displacement, and the temperature at the maximum displacement as the maximum foaming temperature.

[0100] (1-3) True specific gravity 2.7 to 2.8 g of the obtained thermally expandable microcapsules were placed in a dry automatic density meter (Shimadzu Corporation, AccuPycII 1340) to measure the true specific gravity (air gas was used, pressurized to 0.15 to 0.18 MPa).

[0101] [Table 1]

[0102] (2) Masterbatch evaluation (2-1) Expansion Ratio The expansion ratio of the obtained master batch was measured in the same manner as in (1-2) above and evaluated according to the following criteria, where the expansion ratio was calculated by subtracting the weight of the sample used for the measurement from the maximum displacement (Dmax). ◎: 3000 or more 〇: 1000 or more, less than 3000 ×: Less than 1000

[0103] (2-2) Foaming variation (dispersibility) In the measurement of the above "(2-1) Expansion Ratio", the coefficient of variation of the expansion ratio (CV value, n=10) was calculated and evaluated according to the following criteria. ◎: 10% or less ○: 20% or less, over 10% ×: Over 20%

[0104] (2-3) Masterbatch (pellet) fusion property (fusion rate) Ten masterbatches obtained were added to a test tube and heated for 60 minutes at a temperature 10°C below the melting point of the thermoplastic resin used. After cooling, the number of fused masterbatches was counted and evaluated according to the following criteria. ◎:0 pieces 〇:2~4 pieces ×: 5~10 pieces

[0105] (3) Evaluation of the molded product (3-1) Formability The obtained foamed molded article was visually inspected for the presence or absence of foreign matter (oil deposits) adhering to the surface of the foamed molded article, and evaluated according to the following criteria. 〇: No eye discharge was observed ×: Eye discharge was confirmed

[0106] (3-2) Foaming ratio The specific gravity of the obtained foam molded article was measured using a hydrometer MD-200S (manufactured by Mirage Co., Ltd.) The specific gravity of the unexpanded thermoplastic resin used in the foam molded article was measured by underwater displacement method, and the expansion ratio was calculated by dividing the specific gravity of the unexpanded thermoplastic resin by the specific gravity of the foam molded article, and evaluated according to the following criteria. 〇: 1.5 or more ×: Less than 1.5

[0107] (3-3) Foaming variation In the measurement of the above "(3-1) Expansion Ratio," the coefficient of variation (CV value, n=10) of the expansion ratio was calculated for every 60 cm of the foamed molded article, and evaluated according to the following criteria. ◎: 10% or less ○: 20% or less, over 10% ×: Over 20%

[0108] (3-4) Tensile strength variation The tensile strength of the obtained foamed molded article was measured in accordance with JIS K 6400, and then the coefficient of variation of the tensile strength (CV value, n=10) was calculated and evaluated according to the following criteria. ◎: 10% or less ○: 20% or less, over 10% ×: Over 20%

[0109] [Table 2]

[0110] [Table 3] [Industrial Applicability]

[0111] According to the present invention, it is possible to provide a foamable resin composition having high foaming properties and excellent foaming stability.

Claims

1. A thermoplastic resin; a thermally expandable microcapsule containing a thermosetting resin; a reactive dispersant (I) having one functional group per molecule that reacts with the thermosetting resin; a reactive dispersant (II) having two or more functional groups in one molecule that react with the thermosetting resin, the functional group reactive with the thermosetting resin is at least one selected from the group consisting of an amide group, an amino group, a hydroxyl group, and a carboxyl group; the content ratio of the reactive dispersant (I) to the reactive dispersant (II) (reactive dispersant (I) / reactive dispersant (II)) is 0.01 or more and 53.33 or less; a content ratio of the reactive dispersant (I) to the thermosetting resin (reactive dispersant (I) / thermosetting resin) of 0.01 or more and 2.63 or less;

2. 2. The foamable resin composition according to claim 1, wherein the content of the reactive dispersant (I) is 10% by weight or less.

3. 3. The foamable resin composition according to claim 1, wherein the content of the reactive dispersant (II) is 10% by weight or less.

4. 3. The foamable resin composition according to claim 1, wherein the content ratio of the reactive dispersant (I) to the reactive dispersant (II) (reactive dispersant (I) / reactive dispersant (II)) is 50 or less.

5. 3. The foamable resin composition according to claim 1, wherein the thermoplastic resin is a thermoplastic elastomer and has a melt flow rate of 0.1 g / 10 min or more and 100 g / 10 min or less.

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