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

Foamable resin composition

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

[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.

[0004] International Publication No. 2012 / 091098

[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.

[0007] Disclosure 1 relates to a foamable resin composition comprising a thermoplastic resin, thermally expandable microcapsules containing a thermosetting resin, a reactive dispersant (I) having one functional group reactive with the thermosetting resin per molecule, and a reactive dispersant (II) having two or more functional groups reactive with the thermosetting resin per molecule. Disclosure 2 relates to 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 relates to the foamable resin composition according to Disclosure 1 or 2, wherein the content of the reactive dispersant (I) is 10% by weight or less. Disclosure 4 relates to the foamable 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. Disclosure 5 is the foamable resin composition according to any one of 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. Disclosure 6 is the foamable resin composition according to any one of 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 is 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 containing a thermoplastic resin as a base resin, a foam molded article having good appearance quality can be produced.

[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 primary component. Examples of the olefin as a primary component include α-olefin copolymers such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene. Among these, propylene-based elastomers and ethylene-based elastomers are preferred. The propylene-based elastomer refers to an elastomer containing propylene as a primary component. In the 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). In the case of propylene-based elastomers, ethylene can be used as the α-olefin, and in the case of ethylene-based elastomers, propylene can be used. Examples of the α-olefin 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, with ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene being more preferred, and ethylene, propylene, and 1-butene being even more preferred.

[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, as well as (meth)acrylic copolymers containing these. Examples of the (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate. Examples of the (meth)acrylic acid esters include n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-octyl (meth)acrylate. Note that the term "(meth)acrylic acid" refers to either acrylic acid or methacrylic acid.

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

[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 the MFR to 100 g / 10 min or less, the appearance of the resulting molded product 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 indicating the fluidity of a resin. It is expressed as the amount of resin extruded per 10 minutes from an opening (nozzle) at the bottom of a cylindrical container heated by a heater, heated to a predetermined temperature (e.g., 190°C) and pressurized with a predetermined load (e.g., 2.16 kg) in the container. 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 rubbers 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. By including such thermally expandable microcapsules, a high expansion ratio can be achieved. The thermally expandable microcapsules have a shell encapsulating a volatile expanding agent as a core agent.

[0021] The thermosetting resin is preferably contained in the shell of the thermally expandable microcapsule. Examples of the thermosetting resin include epoxy resin, phenol resin, melamine resin, urea resin, polyimide resin, bismaleimide resin, and thermosetting acrylic resin. 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 preferably used 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 (meth)acrylic acid ester compounds obtained by reacting (meth)acrylic acid with a compound having a hydroxyl group, epoxy (meth)acrylates obtained by reacting (meth)acrylic acid with an epoxy resin, and urethane (meth)acrylates obtained by reacting an isocyanate compound with a (meth)acrylic acid derivative having a hydroxyl group. Examples of the (meth)acrylic acid ester compounds 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 can 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 a glycidyl group, a phenol group, a methylol group, an amino group, and an acrylic group. Of these, a glycidyl group is preferred. The functional groups that react with the carboxyl group may be the same or two or more different groups.

[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 wt %, and the preferred upper limit is 30 wt %. By setting the content of the thermosetting resin to 0.01 wt % or more, compression resistance during thermal foaming can be improved. By setting the content of the thermosetting resin to 30 wt % or less, the gas barrier properties of the shell are improved and foaming properties are enhanced. A more preferred lower limit is 0.1 wt %, a more preferred upper limit is 15 wt %, an even more preferred lower limit is 1 wt %, and an even more preferred upper limit is 10 wt %. That is, the content of the thermosetting resin is preferably 0.01 to 30 wt %, more preferably 0.1 to 15 wt %, and even more preferably 1 to 10 wt %. The monomer composition is a composition containing raw material monomers 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, and the polymer is preferably a polymer of a monomer composition containing a nitrile-based 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, thereby improving the expansion ratio. By making it 90% by weight or less, it is possible to improve heat resistance and prevent yellowing. 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] Examples of the carboxyl group-containing monomer include a radically polymerizable unsaturated carboxylic acid monomer having a carboxyl group and 3 to 8 carbon atoms. Specific examples include unsaturated monocarboxylic acids, unsaturated dicarboxylic acids, their anhydrides, and monoesters of unsaturated dicarboxylic acids. These may be used alone or in combination of two or more. Examples of the unsaturated carboxylic acids 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 monoesters of unsaturated dicarboxylic acids include monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate, and monobutyl itaconate. Among 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 setting the content to 5% by weight or more, the maximum foaming temperature can be increased, and by setting the content to 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] Examples of the crosslinkable monomer include monomers having two or more radically polymerizable double bonds, and specific examples include divinylbenzene, di(meth)acrylate, and tri- or higher functional (meth)acrylates. 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, 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 provide relatively uniform crosslinking to the acrylonitrile-based shell.

[0038] When a crosslinkable monomer is contained in the monomer composition, the preferred lower limit of the crosslinkable monomer content is 0.001 wt %, and the preferred upper limit is 1.0 wt %. By setting the crosslinkable monomer content to 0.001 wt % or more, the effect as a crosslinking agent can be fully exerted, and by setting the crosslinkable monomer content to 1.0 wt % or less, the expansion ratio of the thermally expandable microcapsules can be improved. The more preferred lower limit of the crosslinkable monomer content is 0.0015 wt %, and the more preferred upper limit is 0.9 wt %. That is, the content of the crosslinkable monomer is preferably 0.001 to 1.0 wt %, and more preferably 0.0015 to 0.9 wt %.

[0039] The monomer composition preferably contains other monomers in addition to the nitrile monomer, the carboxyl group-containing monomer, and the crosslinkable monomer. The inclusion of the other monomers improves the miscibility of the thermally expandable microcapsules with matrix resins such as thermoplastic resins, resulting in foamed molded articles using the thermally expandable microcapsules with 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, with alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate, and alicyclic, aromatic, and heterocyclic methacrylates such as cyclohexyl methacrylate, benzyl methacrylate, and isobornyl methacrylate being particularly 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. A more preferred lower limit of the content of the other monomer is 0.3 wt %, and a 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 monomer. Suitable examples of the polymerization initiator include dialkyl peroxides, diacyl peroxides, peroxyesters, peroxydicarbonates, and azo compounds. Examples of the dialkyl peroxides include methyl ethyl peroxide, di-t-butyl peroxide, isobutyl peroxide, and dicumyl peroxide. Examples of the diacyl peroxides include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and 3,5,5-trimethylhexanoyl peroxide. Examples of the peroxyesters include t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, 1-cyclohexyl-1-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 a low-boiling organic solvent is suitable. 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 chlorofluorocarbons include CCl ３ F, CCl ２ F ２ , CClF ３ , CClF ２ -CClF ２ 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 expanding agents may be used alone or in combination of two or more. Furthermore, a thermally decomposable compound that decomposes thermally upon heating to become gaseous may also be used as the volatile expanding agent.

[0045] Among the above-mentioned volatile expanding agents, it is preferable to use low-boiling-point hydrocarbons having 5 or less carbon atoms in the thermally expandable microcapsules. By using such hydrocarbons, it is possible to obtain thermally expandable microcapsules with a high expansion ratio and rapid expansion start. Furthermore, a thermally decomposable compound that is thermally decomposed into a gaseous form by heating 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. 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% by weight, it becomes 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 as a lower limit and 230°C as an upper limit. A maximum foaming temperature of 160°C or higher increases heat resistance, thereby 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. A more preferred lower limit of the maximum foaming temperature is 170°C, and a more preferred upper limit is 220°C. In this specification, the maximum foaming temperature refers to the temperature at which the diameter of the thermally expandable microcapsules reaches its maximum (maximum displacement) when the diameter is measured while heating the thermally expandable microcapsules from room temperature.

[0048] The maximum displacement (Dmax) of the thermally expandable microcapsules measured by thermomechanical analysis preferably has a lower limit of 500 μm and an upper limit of 2000 μm. The maximum displacement refers to the value at which the diameter of a predetermined amount of thermally expandable microcapsules is maximized when the diameter of the entire thermally expandable microcapsules is measured while heating the microcapsules 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 refers to the temperature at which the thermally expandable microcapsules reach their maximum displacement when the diameter of the thermally expandable microcapsules is measured while heating the microcapsules 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 body can be sufficiently expanded, and when the average particle size is 35 μm or less, the resulting molded body can have sufficient strength. A more preferred lower limit of the average particle size is 18 μm, and a more preferred upper limit is 30 μm. Note that 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 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 The true specific gravity refers to the specific gravity of the material only excluding pores, and can be measured, for example, by putting a predetermined amount of thermally expandable microcapsules into 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 thermally expandable microcapsules is not particularly limited, but for example, they can be produced 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 monomer. The monomer composition can contain, in addition to the thermosetting resin, the nitrile monomer, a monomer having a carboxyl group, a crosslinkable monomer, or other monomers.

[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 the auxiliary stabilizer is not particularly limited, and examples thereof include a combination of colloidal silica and a condensation product, a combination of colloidal silica and a water-soluble nitrogen-containing compound, and a combination of magnesium hydroxide or calcium phosphate and an emulsifier. Among these, a 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 polydimethylaminopropyl acrylamide and polydimethylaminopropyl methacrylamide. 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 a preferred 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 an oily mixture containing a monomer composition and a volatile expanding agent in an aqueous dispersion medium is carried out. Specifically, a step of dispersing an oily mixture containing a monomer composition and a volatile expanding agent in an aqueous dispersion medium is carried out. In this step, the monomer composition and the volatile expanding agent may be added separately to the aqueous dispersion medium to prepare the oily mixture in the aqueous dispersion medium, but typically the two are mixed together to form an oily mixture before adding it 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 and mixing in the separate containers, and then added to the polymerization reaction vessel. In this step, an inorganic compound is present at the interface between the oil droplets of the oily mixture and the aqueous dispersion medium, resulting in the inorganic compound being 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 dispersion 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 reactive with the thermosetting resin per molecule and a reactive dispersant (II) having two or more functional groups reactive with the thermosetting resin per molecule, whereby the dispersant chemically bonds to the shell surface of the thermally expandable microcapsules, enabling good dispersion in the foamable resin composition, while also highly crosslinking the shell, thereby providing 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 carboxyl group-containing compounds such as aromatic monocarboxylic acids such as phenylacetic acid, benzoic acid, γ-phenylbutyric acid, and o-toluic acid; 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 1000 or less. This makes it possible to achieve both high foamability and excellent foam 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 1000 or less, 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 setting the content of the reactive dispersant (I) to 0.01% by weight or more, the thermally expandable microcapsules can be dispersed well. By setting the content of the reactive dispersant (I) to 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 1000 or less. This makes it possible to achieve both high foamability and excellent foam 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 2000 or less, more preferably 80 or more and 1000 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 setting the content of the reactive dispersant (II) to 0.01% by weight or more, the expansion ratio of the thermally expandable microcapsules can be improved. By setting the content of the reactive dispersant (II) to 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 reactive with the thermosetting resin. This allows for better foaming stability. Examples of dispersants that do not have a functional group reactive with the thermosetting resin include esters of aliphatic monocarboxylic acids and monools, such as liquid paraffin, palmitic acid methyl ester, palmitic acid ethyl ester, palmitic acid hexyl ester, 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 reactive 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. When a chemical foaming agent such as sodium bicarbonate is used, the inclusion of the chemical foaming agent reduces CO 2 generated during decomposition. ２ 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 as a lubricant 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, the foamable resin composition can be produced by carrying out 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 mixing process include connecting two or more feeders to the extruder's feed port, feeding the base resin and the thermally expandable microcapsules into the extruder from separate feeders, and mixing them by kneading in the extruder, and then feeding them into the extruder after pre-mixing. Examples of extruders used in the mixing process include those equipped with a feed port, vent, screw, temperature control function, and discharge port (head). The extruder can be of various extrusion types, such as single-screw, twin-screw, and multi-screw, but twin-screw extrusions are preferred. Furthermore, twin-screw extrusions can be counter-rotating or co-rotating (conical or parallel), but the co-rotating (either conical or parallel) type is preferred in the manufacturing 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 inside of 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. In addition, the screw rotation speed in the mixing step is preferably set within a range of 270 to 330 rpm (in this case, the output is approximately 100 kg / hour).

[0084] When producing a foamable masterbatch as the foamable resin composition of the present invention, the 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 cutting method). Alternatively, a method in which the cutting step is performed without performing the cooling step after the mixing step (hot cutting method) may be used. Furthermore, a method in which the mixture is extruded into a sheet and then the cooling step and cutting step are performed (sheet cutting method) may be used.

[0085] The cooling method for the strand in the cooling step can be an air-cooling method or a water-cooling method, but it is preferable to use the water-cooling method. Furthermore, when the water-cooling method is adopted, it is desirable to install a drainer or a dryer before the pelletizer that cuts the strand in order to remove water adhering to the strand. An example of a cooling method using the water-cooling method is a method in which the strand is cooled by contacting it with water while being conveyed toward a cutter. In the cooling method using the water-cooling method, the submersion distance (water-cooling distance) is preferably 60 to 200 cm when the discharge rate is around 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, as well as building materials such as wood powder plastics, shoe soles, and artificial cork.

[0091] According to the present invention, a foamable resin composition having high expandability (expansion ratio) can be provided. Furthermore, a foamable resin composition having excellent foaming stability and capable of producing foamed molded articles with little variation in expansion ratio and tensile strength can be provided. Additionally, a foamable resin composition having little fusion and excellent handling during molding can be provided. This reduces fusion between masterbatches after drying, for example, when used as a masterbatch. This is thought to be because the reactive dispersant reacts with the thermally expandable microcapsules, reducing elution of the reactive dispersant due to heating during drying. Furthermore, a foamable resin composition having excellent moldability and reduced defects such as die buildup can be provided.

[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 Dai-ichi Kogyo Seiyaku Co., Ltd.) to a polymerization reaction vessel. An oily mixture consisting of the monomer, thermosetting resin, volatile expansion 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 charged into a nitrogen-purged pressure polymerization vessel (20 L), pressurized (0.2 MPa), and reacted at 60°C for 20 hours to prepare a reaction product. The resulting reaction product was repeatedly dehydrated and washed with water using a centrifuge, and then dried to obtain thermally expandable microcapsules (A-G). The thermosetting resin used was 1,2-epoxy-4-vinylcyclohexane, bisphenol A type liquid epoxy resin, or 2-hydroxyethyl acrylate.

[0094] Example 1 (Preparation of 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 having no 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 groups: 3) as a reactive dispersant (II) were added and mixed, and the mixture was fed into a twin-screw extruder (manufactured by Toshiba Machine Co., Ltd., TEM48SS, uniaxial type). The cylinder temperatures of the regions near the raw material addition portion (portion C2, portion C3) were set to 98°C for portion C2 and 99°C for portion C3, and kneading was performed. The vent installed in the extruder was opened during extrusion. Next, the extruded strand was cooled by contacting it with water (submersion distance: 80 cm) while being conveyed in the direction of a cutter. Thereafter, the strand was cut using a strand cutter to form pellets, thereby obtaining masterbatch pellets. The weight average molecular weight (Mw) of the thermoplastic resin was measured using the following apparatus and conditions. (Measurement conditions) - Apparatus: Gel permeation chromatography GPC (manufactured by JASCO Corporation) - Detector: Differential refractive index detector RI (JASCO Corporation RI-4030) - Column: Two connected Shodex LF-804 columns - Flow rate: 0.8 mL / min - Column temperature: 40°C - Injection volume: 0.200 mL - Standard sample: Monodisperse polystyrene manufactured by Tosoh Corporation

[0095] (Production of foamed molded article) 100 parts by weight of the obtained masterbatch pellets and 100 parts by weight of an olefin-based elastomer (TPV, manufactured by Mitsui Chemicals, Inc., Milastomer 7030BS) were mixed, and the resulting mixed pellets were fed into the hopper of an extruder, melt-kneaded, and extrusion-molded 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) (Preparation of Masterbatch Pellets) Masterbatches (pellets) and foam 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 shown in Tables 2 and 3 were used. In Tables 2 and 3, EVA represents ethylene-vinyl acetate copolymer, and PE represents polyethylene. Palmitic acid was used as reactive dispersant (I)-2. Furthermore, glycerol monostearate was used as reactive dispersant (II) having two reactive functional groups, and citric acid was used as reactive dispersant (II) having four reactive functional groups.

[0097] (Evaluation) The thermally expandable microcapsules (A to G), and the masterbatches and foamed 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 Diameter The volume average particle diameter was measured using a particle size distribution diameter measuring instrument (LA-910, manufactured by HORIBA Co., Ltd.).

[0099] (1-2) Foaming Initiation Temperature, Maximum Foaming Temperature, and Maximum Displacement The foaming initiation temperature (Ts), maximum displacement (Dmax), and maximum foaming temperature (Tmax) were measured using a thermomechanical analyzer (TMA) (TMAQ400, manufactured by TA Instruments). Specifically, 25 μg of a sample was placed in an aluminum container with a diameter of 7 mm and a depth of 1 mm, and heated from 80°C to 250°C at a heating rate of 5°C / min with a force of 0.1 N applied from above. The displacement in the vertical direction of the measuring probe was measured, and 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 pressurized to 0.15 to 0.18 MPa).

[0101]

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

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

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

[0105] (3) Evaluation of Molded Articles (3-1) Moldability The obtained foamed molded articles were visually inspected for the presence or absence of foreign matter (eye gunk) adhering to the surface of the foamed molded article, and were evaluated according to the following criteria: ◯: No eye gunk was observed ×: Eye gunk was observed

[0106] (3-2) Expansion Ratio The specific gravity of the obtained foam molded article was measured using a hydrometer MD-200S (manufactured by Mirage). 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: ◯: 1.5 or more ×: less than 1.5

[0107] (3-3) Expansion Variation In the measurement of the above "(3-1) Expansion Ratio," the coefficient of variation (CV value, n=10) of the expansion ratio for every 60 cm of the foam molded article was calculated and evaluated according to the following criteria: ◎: 10% or less ◯: 20% or less, more than 10% ×: more than 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, more than 10%; ×: more than 20%

[0109]

[0110]

[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 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.

2. The foamable resin composition according to claim 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.

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

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

5. The foamable resin composition according to any one of claims 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.

6. The foamable resin composition according to any one of claims 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.

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