Stress reducing agent and resin composition

Abstract

The present invention provides a stress reducing agent (i) which has excellent dispersibility in a matrix resin, and (ii) which enables the achievement of a cured product that has a good linear expansion coefficient. The above is achieved by means of a stress reducing agent which contains polymer fine particles (A), wherein: the polymer fine particles (A) contain a rubber-containing graft copolymer which comprises an elastic body and a graft part that is grafted to the elastic body; the elastic body contains an organosiloxane rubber; the elastic body is contained in an amount of more than 70% by weight but not more than 97% by weight relative to 100% by weight of the polymer fine particles (A); the graft part comprises an epoxy group-containing constituent unit; the epoxy group-containing constituent unit in the graft part is contained in an amount of 0.5% by weight to 4.0% by weight relative to 100% by weight of the rubber-containing graft copolymer; and this stress reducing agent is in the form of a particulate matter.

Description

Stress reducing agent and resin composition

[0001] The present invention relates to a stress reducing agent and a resin composition.

[0002] The encapsulant used mainly for semiconductor materials is one containing epoxy resin and silica. If the encapsulant is exposed to heat or light for a long period of time, cracks may occur inside the encapsulant. Therefore, a method of adding a stress reducing agent to the encapsulant is widely used to ensure the long-term reliability of the encapsulant.

[0003] As such a stress reducing agent, a graft copolymer may be used.

[0004] For example, Patent Document 1 discloses a graft copolymer obtained by polymerizing a grafting vinyl monomer to a rubber containing a polyorganosiloxane and a poly(meth)acrylic acid alkyl ester, which was developed for the purpose of reducing the elastic modulus of a curable resin composition and a molded article and improving stress relaxation ability, and in which the poly(meth)acrylic acid alkyl ester in the rubber contains (meth)acrylic acid alkyl ester units in which the alkyl group has 5 to 13 carbon atoms.

[0005] Patent Document 2 discloses a liquid epoxy resin composition for sealing that uses a graft copolymer having a relatively low rubber content.

[0006] Although not a technology relating to a stress-reducing agent, the polymer particles disclosed in Patent Document 3 are also graft copolymers.

[0007] Japanese Patent Publication No. 2015-172185 International Publication No. 2017 / 188286 Pamphlet Japanese Patent Publication No. 2018-035210

[0008] However, the above-mentioned conventional stress-reducing agents have room for further improvement in terms of (i) dispersibility in a matrix resin and (ii) the linear expansion coefficient of a cured product of a resin composition containing the stress-reducing agent and a matrix resin.

[0009] An object of one aspect of the present invention is to provide a stress-reducing agent that (i) has excellent dispersibility in a matrix resin, and (ii) is capable of providing a cured product having a good linear expansion coefficient when a resin composition containing the stress-reducing agent and a matrix resin is cured.

[0010] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0011] That is, one embodiment of the present invention includes the following configuration.

[0012] A stress-reducing agent according to one embodiment of the present invention is a stress-reducing agent containing polymer fine particles (A), wherein the polymer fine particles (A) comprise a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, the proportion of the elastomer in the polymer fine particles (A) being greater than 70% by weight and not more than 97% by weight based on 100% by weight of the polymer fine particles (A), the elastomer comprises an organosiloxane rubber, the graft portion comprises an epoxy group-containing structural unit, and the epoxy group-containing structural unit in the graft portion is contained in an amount of 0.5% by weight to 4.0% by weight based on 100% by weight of the rubber-containing graft copolymer, and the stress-reducing agent is in the form of a powder or granule.

[0013] In another embodiment of the present invention, a stress-reducing agent is a stress-reducing agent containing polymer microparticles (A), wherein the polymer microparticles (A) comprise a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, the proportion of the elastomer in the polymer microparticles (A) being more than 70% by weight and not more than 97% by weight, relative to 100% by weight of the polymer microparticles (A), the elastomer comprises an organosiloxane rubber, the graft portion comprises an epoxy group-containing structural unit, and the epoxy group-containing structural unit in the graft portion is contained in an amount of 3.3% by weight to 26.7% by weight, relative to 100% by weight of the graft portion in the rubber-containing graft copolymer, and the stress-reducing agent is in the form of a powder or granule.

[0014] According to one aspect of the present invention, it is possible to provide an effect of providing a stress-reducing agent that (i) has excellent dispersibility in a matrix resin, and (ii) is capable of providing a cured product having a good linear expansion coefficient when a resin composition containing the stress-reducing agent and the matrix resin is cured.

[0015] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by appropriately combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic literature and patent documents described in this specification are incorporated herein by reference. Furthermore, unless otherwise specified in this specification, the term "A to B" representing a numerical range means "greater than or equal to A (including and greater than A) and less than or equal to B (including and less than B)."

[0016] [1. Technical Concept of an Embodiment of the Invention] A stress-reducing agent added to an encapsulant (resin composition) to ensure long-term reliability may be required to have the function of reducing the elastic modulus of the encapsulant. Meanwhile, a reduction in the elastic modulus of the encapsulant due to a stress-reducing agent often leads to a deterioration in the linear expansion coefficient of the encapsulant. In other words, in the past, a reduction in the elastic modulus of the encapsulant due to a stress-reducing agent and maintaining the linear expansion coefficient of the encapsulant (reducing the deterioration in the linear expansion coefficient) were in a trade-off relationship, and it was difficult to achieve both. Here, a deterioration in the linear expansion coefficient refers to the encapsulant expanding due to an increase in temperature, in other words, an increase in the linear expansion coefficient.

[0017] In light of this situation, the present inventors have conducted extensive research to provide a stress-reducing agent that can provide a cured product having a low elastic modulus and reduced deterioration in the linear expansion coefficient (in other words, a good linear expansion coefficient).

[0018] Through intensive research, the present inventors independently discovered the following novel findings: (1) A stress-reducing agent containing polymer microparticles including a rubber-containing graft copolymer having an elastomer containing an organosiloxane rubber and a graft portion graft-bonded to the elastomer can surprisingly provide a cured product having a low elastic modulus and reduced deterioration in the linear expansion coefficient, i.e., a good linear expansion coefficient; and (2) When the graft portion of the polymer microparticles contains an epoxy group-containing structural unit, it can surprisingly provide a cured product having a low elastic modulus and further reduced deterioration in the linear expansion coefficient, i.e., a good linear expansion coefficient.

[0019] Conventionally, diene rubbers have been used as the elastomers of the rubber-containing graft copolymers contained in stress-reducing agents. In stress-reducing agents containing rubber-containing graft copolymers containing elastomers containing diene rubbers, the effect of the epoxy group-containing structural units in the graft moieties in reducing the deterioration of the linear expansion coefficient of the cured product was small. That is, the effect of the epoxy group-containing structural units in the graft moieties in reducing the deterioration of the linear expansion coefficient of the cured product was first discovered by the present inventors in the course of extensive research when an elastomer containing an organosiloxane rubber was used, and it was a unique effect that could not easily be arrived at based on conventional technical common sense.

[0020] Furthermore, in the course of intensive research, the present inventors independently and surprisingly discovered the novel finding that when the amount of epoxy group-containing structural units contained in the graft moiety exceeds a certain amount, the dispersibility of the stress-reducing agent in the matrix resin decreases. Dispersibility in the matrix resin may also be required for the stress-reducing agent. Therefore, the present inventors further intensively researched to provide a stress-reducing agent that has excellent dispersibility in the matrix resin and can provide a cured product having a low elastic modulus and a good linear expansion coefficient.

[0021] As a result, the inventors independently discovered the following novel finding, which led to the completion of the present invention: a stress-reducing agent containing polymer microparticles that include a rubber-containing graft copolymer having an elastomer containing an organosiloxane-based rubber and a graft portion grafted to the elastomer and containing a specific amount of epoxy group-containing structural units can surprisingly provide a resin composition that (i) has excellent dispersibility in a matrix resin and (ii) is capable of providing a cured product that has a low elastic modulus and a good linear expansion coefficient.

[0022] [2. Stress-Reducing Agent] A stress-reducing agent according to one embodiment of the present invention is a powdery material and contains polymer microparticles (A). The polymer microparticles (A) contain a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer. The proportion of the elastomer in the polymer microparticles (A) is more than 70% by weight and not more than 97% by weight, based on 100% by weight of the polymer microparticles (A). The elastomer contains an organosiloxane rubber, and the graft portion contains an epoxy group-containing structural unit. The epoxy group-containing structural unit in the graft portion is contained in an amount of 0.5% by weight to 4.0% by weight, based on 100% by weight of the rubber-containing graft copolymer.

[0023] Alternatively, in one embodiment of the present invention, the polymer microparticles (A) comprise a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, the proportion of the elastomer in the polymer microparticles (A) being more than 70% by weight and not more than 97% by weight based on 100% by weight of the polymer microparticles (A), the elastomer comprises an organosiloxane rubber, the graft portion comprises an epoxy group-containing structural unit, and the epoxy group-containing structural unit in the graft portion is contained in an amount of 3.3% by weight to 26.7% by weight based on 100% by weight of the graft portion in the rubber-containing graft copolymer.

[0024] Hereinafter, the "stress-reducing agent according to one embodiment of the present invention" may also be referred to as "the present stress-reducing agent." Because the present stress-reducing agent has the above-described configuration, it has the advantage of excellent dispersibility of polymer microparticles (A) in a matrix resin. In other words, because the present stress-reducing agent has the above-described configuration, it has the advantage that by mixing the stress-reducing agent with a matrix resin, a resin composition can be provided in which polymer microparticles (A) are uniformly dispersed in the matrix resin. Furthermore, the present stress-reducing agent has the advantage that by curing a resin composition containing the stress-reducing agent and a matrix resin, a cured product having a low elastic modulus and a good linear expansion coefficient can be provided. In this specification, "reduced deterioration in the linear expansion coefficient of the cured product" may also be expressed as "the cured product has a good linear expansion coefficient."

[0025] (2-1. Polymer Fine Particles (A)) The polymer fine particles (A) contain a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer.

[0026] (2-1-1. Elastomer) The elastomer contains an organosiloxane-based rubber. When the elastomer contains an organosiloxane-based rubber, the stress reducing agent can provide a cured product with a low elastic modulus and a good linear expansion coefficient. Furthermore, when the elastomer contains an organosiloxane-based rubber, the resin composition can provide a cured product with sufficient heat resistance and excellent impact resistance at low temperatures. The elastomer can also be referred to as an elastic portion or rubber particles.

[0027] Examples of the organosiloxane rubber include (a) organosiloxane polymers composed of alkyl or aryl di-substituted silyloxy units, such as dimethylsilyloxy, diethylsilyloxy, methylphenylsilyloxy, diphenylsilyloxy, and dimethylsilyloxy-diphenylsilyloxy, and (b) organosiloxane polymers composed of alkyl or aryl mono-substituted silyloxy units, such as organohydrogensilyloxy in which some of the alkyl groups in the side chains have been substituted with hydrogen atoms. These organosiloxane polymers may be used alone or in combination of two or more.

[0028] Cyclic siloxanes composed of multiple dimethylsilyloxy units may be used as raw materials for organosiloxane-based rubbers. Examples of the cyclic siloxanes include octamethylcyclotetrasiloxane (also known as "D4") having four dimethylsilyloxy units, decamethylcyclopentasiloxane (also known as "D5") having five dimethylsilyloxy units, and dodecamethylcyclohexasiloxane (also known as "D6") having six dimethylsilyloxy units.

[0029] In this specification, for example, a polymer composed of dimethylsilyloxy units is referred to as a dimethylsilyloxy rubber, a polymer composed of methylphenylsilyloxy units is referred to as a methylphenylsilyloxy rubber, and a polymer composed of dimethylsilyloxy units and diphenylsilyloxy units is referred to as a dimethylsilyloxy-diphenylsilyloxy rubber. The organosiloxane rubber is more preferably one or more selected from the group consisting of dimethylsilyloxy rubber, methylphenylsilyloxy rubber, and dimethylsilyloxy-diphenylsilyloxy rubber, because (a) the linear expansion coefficient of the cured product is more favorable and the resulting resin composition can provide a cured product with excellent heat resistance, and (b) dimethylsilyloxy rubber is even more preferable because it is easily available and economical.

[0030] When preparing the organosiloxane rubber, a monomer containing (a) one or more hydrolyzable silyl groups and (b) one or more ethylenically unsaturated groups and / or mercapto groups in the molecule (hereinafter also referred to as "monomer M") may be used as a raw material. In other words, the organosiloxane rubber may contain a structural unit derived from monomer M (hereinafter also referred to as "structural unit M").

[0031] The hydrolyzable silyl group contained in the monomer M is not particularly limited. Examples of the hydrolyzable silyl group include a halogenosilyl group, an acyloxysilyl group, an amidosilyl group, an aminosilyl group, an alkenyloxysilyl group, an aminoxysilyl group, an oximesilyl group, an alkoxysilyl group, a thioalkoxysilyl group, and a silanol group. Because of their high polymerization reactivity and ease of handling, alkoxysilyl groups are more preferred as the hydrolyzable silyl group. When the monomer M contains two or more hydrolyzable silyl groups in its molecule, the multiple hydrolyzable silyl groups may be the same or different from each other.

[0032] Specific examples of the monomer M include vinylsilanes such as vinylmethyldimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and tetramethyltetravinylcyclotetrasiloxane; β-methacryloyloxyethyldimethoxymethylsilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyldimethoxymethylsilane, 3-(meth)acryloyloxypropylmethoxydimethylsilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropyldiethoxymethylsilane, and 3-(meth)acryloyloxypropyldiethoxymethylsilane. (meth)acryloyloxyalkylsilanes such as 3-(meth)acryloyloxypropylethoxydimethylsilane, 3-(meth)acryloyloxypropylethoxydiethylsilane, and δ-(meth)acryloyloxybutyldiethoxymethylsilane; and mercaptoalkylsilanes such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropylmethoxymethidylsilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldiethoxymethylsilane, and 3-mercaptopropyldiethoxyethylsilane. Specific examples of the monomer M include p-vinylphenylmethyldimethoxysilane, 2-(m-vinylphenyl)ethylmethyldimethoxysilane, 1-(m-vinylphenyl)methyldimethylisopropoxysilane, 2-(p-vinylphenyl)ethylmethyldimethoxysilane, 3-(p-vinylphenoxy)propylmethyldiethoxysilane, 3-(p-vinylbenzoyloxy)propylmethyldimethoxysilane, 1-(o-vinylphenyl)-1,1,2-trimethyl-2,2-dimethoxydisilane, 1-(p-vinylphenyl)-1,1-diphenyl-3-ethyl-3,3-diethoxydisiloxane, m-vinylphenyl-[3-(triethoxysilyl)propyl]diphenylsilane, and [3-(p-isopropenylbenzoylamino)propyl]phenyldipropoxysilane. These monomers M may be used alone or in combination of two or more.

[0033] Among these, the compounds exemplified above as specific examples of (meth)acryloyloxyalkylsilanes are more preferred as the monomer M, and 3-(meth)acryloyloxypropyltrimethoxysilane and 3-(meth)acryloyloxypropyldimethoxymethylsilane are even more preferred. This configuration has the advantage of enabling efficient polymerization of the graft-forming monomer mixture in the presence of the organosiloxane rubber.

[0034] The organosiloxane rubber preferably contains 0.001 to 10.0% by weight, more preferably 0.001 to 5.0% by weight, even more preferably 0.01 to 5.0% by weight, and particularly preferably 1.0 to 5.0% by weight of the structural unit M, based on 100% by weight of the organosiloxane rubber. This configuration has the advantage of enabling efficient polymerization of the graft-forming monomer mixture in the presence of the organosiloxane rubber.

[0035] The organosiloxane-based rubber contained in the elastomer may be composed of only one type of polyorganosiloxane-based rubber having the same composition of constituent units, or may be composed of two or more types of polyorganosiloxanes having different compositions (types and content ratios) of constituent units.

[0036] The polymer microparticles (A) preferably contain 60% by weight to 100% by weight of the organosiloxane rubber, more preferably 70% by weight to 100% by weight, even more preferably 80% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, and particularly preferably 95% by weight to 100% by weight, based on 100% by weight of the elastomer contained in the polymer microparticles (A). According to this configuration, the stress reducing agent can provide a cured product with a better linear expansion coefficient. The polymer microparticles (A) may contain 100% by weight of the organosiloxane rubber in the elastomer contained in the polymer microparticles (A), i.e., the elastomer may be composed solely of the organosiloxane rubber.

[0037] The elastomer may contain one or more other rubbers in addition to the organosiloxane rubber described above, as long as the effect of one embodiment of the present invention is not impaired. Examples of the other rubbers include diene rubbers, (meth)acrylate rubbers, and natural rubbers. The total content of the other rubbers is less than 40% by weight, more preferably less than 30% by weight, more preferably less than 20% by weight, even more preferably less than 10% by weight, and particularly preferably less than 5% by weight, based on 100% by weight of the elastomer contained in the polymer microparticles (A).

[0038] Examples of the diene rubber include butadiene rubber (also referred to as polybutadiene rubber) consisting of structural units derived from 1,3-butadiene, and butadiene-styrene rubber (also referred to as polystyrene-butadiene) which is a copolymer of 1,3-butadiene and styrene.

[0039] Examples of the (meth)acrylate rubber include ethyl (meth)acrylate rubber, butyl (meth)acrylate rubber, and 2-ethylhexyl (meth)acrylate rubber.

[0040] (Crosslinked Structure of Elastomer) It is more preferable that a crosslinked structure is introduced into the elastomer, since this allows the dispersion stability of the polymer microparticles (A) in the matrix resin to be maintained. By using a polyfunctional alkoxysilane compound and / or a polyfunctional monomer during the preparation (polymerization) of the organosiloxane rubber, a crosslinked structure can be introduced into the organosiloxane rubber. Therefore, the polyfunctional alkoxysilane compound and the polyfunctional monomer used in the preparation of the organosiloxane rubber can also be said to be crosslinking agents for the organosiloxane rubber.

[0041] Examples of polyfunctional alkoxysilane compounds include tetramethoxysilane, tetraethoxysilane (TEOS), tetraisopropoxysilane, tetrabutoxysilane, tetraoctylsilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, methyltriisopropoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, and dimethyldimethoxysilane.

[0042] A polyfunctional monomer can also be said to be a monomer having two or more radically polymerizable reactive groups in the same molecule. The radically polymerizable reactive group is preferably a carbon-carbon double bond. Examples of polyfunctional monomers include (meth)acrylates having an ethylenically unsaturated double bond, such as allyl alkyl (meth)acrylates and allyloxy alkyl (meth)acrylates, and do not include butadiene. Examples of monomers having two (meth)acrylic groups include ethylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, and polyethylene glycol di(meth)acrylates. Examples of the polyethylene glycol di(meth)acrylates include triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and polyethylene glycol (600) di(meth)acrylate. Examples of monomers having three (meth)acrylic groups include alkoxylated trimethylolpropane tri(meth)acrylates, glycerol propoxy tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate. Examples of the alkoxylated trimethylolpropane tri(meth)acrylates include trimethylolpropane tri(meth)acrylate and trimethylolpropane triethoxy tri(meth)acrylate. Further, examples of monomers having four (meth)acrylic groups include pentaerythritol tetra(meth)acrylate and ditrimethylolpropane tetra(meth)acrylate.Further, examples of monomers having five (meth)acrylic groups include dipentaerythritol penta(meth)acrylate.Further, examples of monomers having six (meth)acrylic groups include ditrimethylolpropane hexa(meth)acrylate.The polyfunctional monomers also include diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, divinylbenzene, and the like.

[0043] (Glass Transition Temperature of Elastomer) The glass transition temperature of the elastomer is preferably 80°C or lower, more preferably 70°C or lower, more preferably 60°C or lower, more preferably 50°C or lower, more preferably 40°C or lower, more preferably 30°C or lower, more preferably 20°C or lower, more preferably 10°C or lower, more preferably 0°C or lower, more preferably -20°C or lower, more preferably -40°C or lower, more preferably -45°C or lower, more preferably -50°C or lower, more preferably -55°C or lower, more preferably -60°C or lower, more preferably -65°C or lower, more preferably -70°C or lower, more preferably -75°C or lower, more preferably -80°C or lower, more preferably -85°C or lower, more preferably -90°C or lower, more preferably -95°C or lower, more preferably -100°C or lower, more preferably -105°C or lower, more preferably -110°C or lower, more preferably -115°C or lower, even more preferably -120°C or lower, and particularly preferably -125°C or lower. In this specification, "glass transition temperature" is sometimes referred to as "Tg." This configuration allows for the production of polymer microparticles (A) having a low Tg and a stress-reducing agent having a low Tg. As a result, a resin composition containing the resulting stress-reducing agent can provide a cured product with excellent toughness. Furthermore, this configuration allows for the viscosity of the resulting resin composition containing the stress-reducing agent to be further reduced. The Tg of the elastomer can be obtained by performing viscoelasticity measurements using a flat plate made of polymer microparticles (A). Specifically, the Tg can be measured as follows: (1) A dynamic viscoelasticity measurement is performed under tensile conditions on a flat plate made of polymer microparticles (A) using a dynamic viscoelasticity measuring device (e.g., DVA-200, manufactured by IT Measurement & Control Co., Ltd.) to obtain a tan δ graph; (2) The peak temperature of tan δ on the obtained tan δ graph is taken as the glass transition temperature. Here, if multiple peaks are obtained in the tan δ graph, the lowest peak temperature is taken as the glass transition temperature of the elastomer.

[0044] On the other hand, since this can reduce the decrease in the modulus of elasticity (rigidity) of the resulting cured product, i.e., a cured product having sufficient modulus of elasticity (rigidity) can be obtained, the Tg of the elastic body is preferably higher than 0°C, more preferably 20°C or higher, even more preferably 50°C or higher, particularly preferably 80°C or higher, and most preferably 120°C or higher.

[0045] The Tg of the elastomer can be determined by the composition of the structural units contained in the elastomer, etc. In other words, the Tg of the resulting elastomer can be adjusted by changing the composition of the monomers used when producing (polymerizing) the elastomer.

[0046] Here, when a homopolymer is prepared by polymerizing only one type of monomer, a group of monomers that provides a homopolymer having a Tg greater than 0°C is referred to as monomer group a. Furthermore, when a homopolymer is prepared by polymerizing only one type of monomer, a group of monomers that provides a homopolymer having a Tg less than 0°C is referred to as monomer group b. An elastomer containing 50 to 100 wt% (more preferably, 65 to 99 wt%) of structural units derived from at least one monomer selected from monomer group a and 0 to 50 wt% (more preferably, 1 to 35 wt%) of structural units derived from at least one monomer selected from monomer group b is referred to as elastomer X. Elastomer X has a Tg greater than 0°C. Furthermore, when the elastomer contains elastomer X, the resulting resin composition containing the stress-reducing agent can provide a cured product with sufficient rigidity.

[0047] It is also preferable that a crosslinked structure be introduced into the elastic body when the Tg of the elastic body is higher than 0° C. Methods for introducing a crosslinked structure include the methods described above.

[0048] Monomers that can be included in the monomer group a include, but are not limited to, unsubstituted vinyl aromatic compounds such as styrene and 2-vinylnaphthalene; vinyl-substituted aromatic compounds such as α-methylstyrene; ring-alkylated vinyl aromatic compounds such as 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,5-dimethylstyrene, and 2,4,6-trimethylstyrene; ring-alkoxylated vinyl aromatic compounds such as 4-methoxystyrene and 4-ethoxystyrene; ring-halogenated vinyl aromatic compounds such as 2-chlorostyrene and 3-chlorostyrene; ring-ester-substituted vinyl aromatic compounds such as 4-acetoxystyrene; and ring-hydroxylated vinyl aromatic compounds such as 4-hydroxystyrene. vinyl halides such as vinyl chloride; aromatic monomers such as acenaphthalene and indene; alkyl methacrylates such as methyl methacrylate, ethyl methacrylate and isopropyl methacrylate; aromatic methacrylates such as phenyl methacrylate; methacrylates such as isobornyl methacrylate and trimethylsilyl methacrylate; methacrylic monomers including methacrylic acid derivatives such as methacrylonitrile; certain acrylic acid esters such as isobornyl acrylate and tert-butyl acrylate; acrylic monomers including acrylic acid derivatives such as acrylonitrile, etc. Further, examples of monomers that can be included in the monomer group a include acrylamide, isopropylacrylamide, N-vinylpyrrolidone, isobornyl methacrylate, dicyclopentanyl methacrylate, 2-methyl-2-adamantyl methacrylate, 1-adamantyl acrylate, and 1-adamantyl methacrylate, which, when made into a homopolymer, can provide a homopolymer having a Tg of 120° C. or higher. These monomers a may be used alone or in combination of two or more.

[0049] Examples of the monomer b include ethyl acrylate, butyl acrylate (also known as butyl acrylate), 2-ethylhexyl acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, 2-hydroxyethyl acrylate, and 4-hydroxybutyl acrylate. These monomers b may be used alone or in combination of two or more. Among these monomers b, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate are particularly preferred.

[0050] (Volume Average Particle Diameter of Elastomer) The volume average particle diameter of the elastomer is preferably 0.03 μm to 50.00 μm, more preferably 0.05 μm to 10.00 μm, more preferably 0.08 μm to 2.00 μm, even more preferably 0.10 μm to 1.00 μm, even more preferably 0.10 μm to 0.80 μm, and particularly preferably 0.10 μm to 0.50 μm. When the volume average particle diameter of the elastomer is (a) 0.03 μm or more, an elastomer having the desired volume average particle diameter can be stably obtained, and when (b) 50.00 μm or less, the heat resistance and impact resistance of the resulting cured product are excellent. The volume average particle diameter of the elastomer can be measured using a dynamic light scattering particle size distribution analyzer or the like, using an aqueous latex containing the elastomer as a sample. The method for measuring the volume average particle diameter of the elastomer is described in detail in the Examples below.

[0051] (Proportion of Elastomer) The proportion of the elastomer in the polymer microparticles (A), based on 100% by weight of the entire polymer microparticles (A), is preferably more than 70% by weight but not more than 97% by weight, more preferably more than 70% by weight but not more than 95% by weight, and even more preferably more than 70% by weight but not more than 93% by weight. When the proportion of the elastomer is more than 70% by weight, the resulting resin composition containing the stress-reducing agent can provide a cured product with excellent toughness and impact resistance. When the proportion of the elastomer is 97% by weight or less, the polymer microparticles (A) do not easily aggregate (are less likely to aggregate), so the resulting resin composition containing the stress-reducing agent does not become highly viscous. As a result, the resin composition can be easily handled. Conventionally, when the proportion of the elastomer in the polymer microparticles (A) is more than 70% by weight, the high proportion of the elastomer effectively reduces the elastic modulus of the cured product, but the low proportion of graft moieties tends to make the powder / particle less dispersible in the matrix resin. However, in one embodiment of the present invention, even if the proportion of the elastomer in the polymer microparticles (A) exceeds 70% by weight, the polymer microparticles (A) can be well dispersed in the matrix resin, and stress reduction can be achieved in the cured product of the resin composition containing the stress-reducing agent and the matrix resin.

[0052] (Gel Content of Elastomer) The elastomer is preferably one that can swell in an appropriate solvent but is substantially insoluble in the matrix resin used.

[0053] The elastic body preferably has a gel content of 60% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. When the gel content of the elastic body is within the above range, the resulting resin composition containing the stress reducing agent can provide a cured product with excellent toughness.

[0054] In this specification, the gel content is calculated as follows. First, an aqueous latex containing polymer microparticles (A) is obtained, and then a powder of polymer microparticles (A) is obtained from the aqueous latex. The method for obtaining a powder of polymer microparticles (A) from the aqueous latex is not particularly limited, but examples thereof include (i) agglomerating the polymer microparticles (A) in the aqueous latex, (ii) dehydrating the obtained agglomerates, and (iii) further drying the agglomerates to obtain a powder of polymer microparticles (A). Next, 2.0 g of the powder of polymer microparticles (A) is dissolved in 50 mL of methyl ethyl ketone (MEK). Thereafter, the obtained MEK solution is separated into a component soluble in MEK (MEK solubles) and a component insoluble in MEK (MEK insolubles). Specifically, the obtained MEK dissolved material is centrifuged using a centrifuge (CP60E, manufactured by Hitachi Koki Co., Ltd.) at a rotation speed of 30,000 rpm for 1 hour to separate the dissolved material into MEK-soluble and MEK-insoluble components. Three sets of centrifugation are performed in total. The weights of the obtained MEK-soluble and MEK-insoluble components are measured, and the gel content is calculated using the following formula: Gel content (%) = (weight of methyl ethyl ketone-insoluble component) / {(weight of methyl ethyl ketone-insoluble component) + (weight of methyl ethyl ketone-soluble component)} × 100.

[0055] In one embodiment of the present invention, the "elastic body" of the polymer microparticles (A) may be composed of only one type of elastomer having the same composition of structural units. In this case, the "elastic body" of the polymer microparticles (A) is one type selected from organosiloxane rubbers.

[0056] In one embodiment of the present invention, the "elastic body" of the polymer microparticles (A) may be composed of multiple types of elastomers each having a different composition of structural units. In this case, the "elastic body" of the polymer microparticles (A) may be two or more types selected from organosiloxane rubbers, or may be a mixture of one type selected from organosiloxane rubbers and one or more types selected from the other rubbers such as diene rubbers and (meth)acrylate rubbers.

[0057] In one embodiment of the present invention, the "elastic body" of the polymer fine particles (A) is made up of a plurality of types of elastomers each having a different composition of structural units. In this case, each of the plurality of types of elastomers is referred to as an elastomer. １ , elastic body ２ , ..., and elastic body ｎ Here, n is an integer of 2 or more. The "elastic bodies" of the polymer fine particles (A) are elastomers polymerized separately. １ , elastic body ２ , ..., and elastic body ｎ The "elastic body" of the polymer fine particles (A) may contain a composite of the following: １ , elastic body ２ , ..., and elastic body ｎ The polymerizable composition may include a single elastomer obtained by sequentially polymerizing each of the above elastomers. Such sequential polymerization of multiple elastomers (polymers) is also referred to as multistage polymerization. A single elastomer obtained by multistage polymerization of multiple types of elastomers is also referred to as a multistage polymerized elastomer. The method for producing a multistage polymerized elastomer will be described in detail later.

[0058] Elastic body １ , elastic body ２ , ..., and elastic body ｎ In the multi-stage polymerized elastomer, the elastomer ｎ is an elastic body ｎ－１ or an elastic body ｎ－１ In the multi-stage polymerized elastomer, ｎ Part of the material is elastic ｎ－１ Sometimes it penetrates inside the

[0059] In the multi-stage polymerized elastomer, each of the plurality of elastomers may form a layer structure. １ , elastic body ２ , and elastic body ３ If it consists of an elastic body １ forms the innermost layer, and the elastic body １ Elastic body on the outside ２ A layer of elastic material is formed. ２ Elastic on the outside of the layer ３An embodiment in which the layer is formed as the outermost layer of the elastomer is also one aspect of the present invention. In this way, a multistage polymerized elastomer in which each of a plurality of elastomers forms a layer structure can also be called a multilayer elastomer. That is, in one embodiment of the present invention, the "elastic body" of the polymer fine particles (A) may include (a) a composite of a plurality of elastomers, (b) a multistage polymerized elastomer, and / or (c) a multilayer elastomer.

[0060] (2-1-2. Graft Moiety) In this specification, the polymer grafted to the elastomer is referred to as the graft moiety. The polymer microparticles (A) contain a rubber-containing graft copolymer having the elastomer and a graft moiety grafted to the elastomer. The graft moiety can play various roles. Examples of the "various roles" include (a) improving the compatibility between the matrix resin and the polymer microparticles (A), (b) improving the dispersibility of the polymer microparticles (A) in the matrix resin, and (c) enabling the polymer microparticles (A) to be dispersed in the form of primary particles in the resulting resin composition containing the stress-reducing agent or in the cured product.

[0061] The graft portion contains an epoxy group-containing structural unit, in other words, a structural unit having an epoxy group, as a structural unit. When the graft portion contains a structural unit derived from an epoxy group-containing monomer such as glycidyl methacrylate, the stress-reducing agent has the advantage of being able to provide a cured product with a better linear expansion coefficient. In preparing the graft portion, a mixture containing a monomer having an epoxy group (a graft portion-forming monomer mixture) is used (polymerized) to obtain a graft portion containing an epoxy group-containing structural unit.

[0062] Specific examples of the monomer having an epoxy group include glycidyl group-containing vinyl monomers such as glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and allyl glycidyl ether. These may be used alone or in combination of two or more. Glycidyl methacrylate is more preferred as the monomer having an epoxy group because it is easily available and economical.

[0063] The graft portion preferably contains 0.5 wt% to 4.0 wt%, more preferably 0.6 wt% to 3.8 wt%, more preferably 0.7 wt% to 3.5 wt%, even more preferably 0.8 wt% to 3.3 wt%, still more preferably 0.8 wt% to less than 3.2 wt%, even more preferably 0.9 wt% to 3.0 wt%, and particularly preferably 1.0 wt% to less than 3.0 wt%, of epoxy group-containing structural units relative to 100 wt% of the rubber-containing graft copolymer. When the graft portion contains 0.5 wt% or more of epoxy group-containing structural units relative to 100 wt% of the rubber-containing graft copolymer, the linear expansion coefficient of the cured product of the resin composition obtained by adding the stress-reducing agent to the matrix resin is significantly reduced, i.e., the stress-reducing agent has the advantage of being able to provide a cured product with a better linear expansion coefficient. Furthermore, if the epoxy group-containing constitutional unit in the graft portion is 4.0% by weight or less relative to 100% by weight of the rubber-containing graft copolymer, the stress-relieving agent has the advantage of being excellent in dispersibility in the matrix resin.

[0064] Furthermore, the graft portion preferably contains 3.3 wt% to 26.7 wt% of epoxy group-containing structural units, based on 100 wt% of all structural units in the graft portion of the rubber-containing graft copolymer, more preferably 4.0 wt% to 25.0 wt%, even more preferably 5.0 wt% to 22.0 wt%, and particularly preferably 6.0 wt% to 20.0 wt%. When the graft portion contains 3.3 wt% or more of epoxy group-containing structural units, based on 100 wt% of all structural units in the graft portion, the linear expansion coefficient of the cured product of the resin composition obtained by adding the stress-reducing agent to a matrix resin is significantly reduced. In other words, the stress-reducing agent has the advantage of being able to provide a cured product with a better linear expansion coefficient. Furthermore, when the epoxy group-containing structural units in the graft portion are 26.7 wt% or less, based on 100 wt% of all structural units in the graft portion, the stress-reducing agent has the advantage of excellent dispersibility in the matrix resin.

[0065] In particular, it is more preferable that the graft portion contains epoxy group-containing structural units within the above range relative to 100% by weight of the rubber-containing graft copolymer, and that the graft portion contains epoxy group-containing structural units within the above range relative to 100% by weight of all structural units of the graft portion in the rubber-containing graft copolymer.

[0066] Furthermore, the graft portion may contain, as a structural unit, a structural unit derived from one or more monomers selected from the group consisting of an aromatic vinyl monomer not containing an epoxy group, a vinyl cyan monomer not containing an epoxy group, and a (meth)acrylate monomer not containing an epoxy group, as a non-epoxy group-containing structural unit.

[0067] The one or more monomers selected from the group consisting of the aromatic vinyl monomer, the vinyl cyan monomer, and the (meth)acrylate monomer may be used alone or in combination of two or more.

[0068] The graft portion preferably contains, as structural units, structural units derived from aromatic vinyl monomers containing no epoxy groups, structural units derived from vinyl cyan monomers containing no epoxy groups, and structural units derived from (meth)acrylate monomers containing no epoxy groups in a total amount of 10 to 97% by weight, more preferably 30 to 96% by weight, even more preferably 50 to 95% by weight, particularly preferably 60 to 94% by weight, and most preferably 70 to 94% by weight, based on 100% by weight of all structural units in the graft portion.

[0069] The graft moiety may contain, as a structural unit, a structural unit derived from a monomer having a reactive group other than an epoxy group. Examples of the monomer having a reactive group other than an epoxy group include a monomer having an oxetane group, a hydroxyl group, an amino group, an imide group, a carboxylic acid group, a carboxylic anhydride group, a cyclic ester, a cyclic amide, a benzoxazine group, and a cyanate ester group.

[0070] The graft moiety may contain a structural unit derived from a polyfunctional monomer. When the graft moiety contains a structural unit derived from a polyfunctional monomer, the following advantages are obtained: (a) swelling of the polymer fine particles (A) can be prevented in the resin composition containing the obtained stress-reducing agent, (b) the viscosity of the resin composition containing the obtained stress-reducing agent is reduced, which tends to improve the handleability of the resin composition, and (c) the dispersibility of the polymer fine particles (A) in the matrix resin in the resin composition is improved.

[0071] When the graft portion does not contain a structural unit derived from a polyfunctional monomer, the resulting resin composition containing the stress-reducing agent can provide a cured product with superior toughness and impact resistance, compared to when the graft portion contains a structural unit derived from a polyfunctional monomer.

[0072] Specific examples of the polyfunctional monomer are the same as those explained in the section (Crosslinked structure of elastic body) above, so the explanation therefor is omitted here and the explanation is incorporated herein by reference.

[0073] The graft portion may contain, as a structural unit, a structural unit derived from another monomer in addition to the structural units derived from the above-mentioned monomers.

[0074] (Glass Transition Temperature of Graft Portion) The glass transition temperature of the graft portion is preferably 190°C or lower, more preferably 160°C or lower, more preferably 140°C or lower, more preferably 120°C or lower, preferably 80°C or lower, more preferably 70°C or lower, more preferably 60°C or lower, more preferably 50°C or lower, more preferably 40°C or lower, more preferably 30°C or lower, more preferably 20°C or lower, more preferably 10°C or lower, more preferably 0°C or lower, more preferably -20°C or lower, more preferably -40°C or lower, more preferably -45°C or lower, and More preferably 0°C or lower, more preferably -55°C or lower, more preferably -60°C or lower, more preferably -65°C or lower, more preferably -70°C or lower, more preferably -75°C or lower, more preferably -80°C or lower, more preferably -85°C or lower, more preferably -90°C or lower, more preferably -95°C or lower, more preferably -100°C or lower, more preferably -105°C or lower, more preferably -110°C or lower, more preferably -115°C or lower, even more preferably -120°C or lower, and particularly preferably -125°C or lower.

[0075] The glass transition temperature of the graft portion is preferably 0°C or higher, more preferably 30°C or higher, more preferably 50°C or higher, more preferably 70°C or higher, even more preferably 90°C or higher, and particularly preferably 110°C or lower.

[0076] The Tg of the graft portion can be determined by the composition of the structural units contained in the graft portion, etc. In other words, the Tg of the resulting graft portion can be adjusted by changing the composition of the monomers used when producing (polymerizing) the graft portion.

[0077] The Tg of the graft portion is determined by obtaining a tan δ graph in the same manner as in the measurement of the Tg of the elastomer. If multiple peaks are obtained in the obtained tan δ graph, the highest peak temperature is taken as the glass transition temperature of the graft portion.

[0078] (Graft ratio of graft moiety) In one embodiment of the present invention, the polymer microparticles (A) may contain a polymer having the same structure as the graft moiety but not grafted to the elastomer. In this specification, a polymer having the same structure as the graft moiety but not grafted to the elastomer is also referred to as a non-graft polymer. The non-graft polymer can also be said to be a polymer produced in the polymerization of the graft moiety but not grafted to the elastomer.

[0079] In this specification, the proportion of the polymer grafted to the elastomer, i.e., the proportion of the grafted portion, among the polymers produced in the graft portion preparation step, is referred to as the graft ratio. The graft ratio can also be expressed as the value expressed by (weight of the grafted portion) / {(weight of the grafted portion)+(weight of the non-grafted polymer)}×100.

[0080] In the preparation process of the grafted portion, soluble components may also be present in addition to the grafted portion and the non-grafted polymer. The soluble components include unpolymerized monomers and secondary raw materials such as initiators.

[0081] As a method for determining whether a polymer is the graft copolymer (A), a non-graft polymer, or a soluble component, for example, a method for determining whether the polymer is soluble or insoluble in a solvent can be mentioned, such as (i) determining that the polymer is insoluble in MEK as the graft copolymer (A), (ii) determining that the polymer is soluble in MEK and insoluble in methanol as the non-graft polymer, or (iii) determining that the polymer is soluble in MEK and soluble in methanol as the soluble component.

[0082] The graft ratio of the graft portion is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. A graft ratio of 70% or more has the advantage that the viscosity of the resulting resin composition containing the stress-reducing agent does not become too high.

[0083] As described above, the polymer fine particles (A) and the non-grafted polymer can be separated using a solvent, but in this specification, the non-grafted polymer also constitutes a part of the polymer fine particles (A) according to one embodiment of the present invention. For example, when referring to the weight of the polymer fine particles (A) in one embodiment of the present invention, the "weight of the polymer fine particles (A)" refers to the total weight of the polymer fine particles (A) which are MEK-insoluble and the non-grafted polymer which is MEK-soluble and methanol-insoluble.

[0084] The weight of the polymer in the graft portion is the amount of the monomer constituting the polymer in the graft portion. In calculating the graft ratio, the method for coagulating the polymer fine particles (A) is not particularly limited, and a method using a solvent, a method using a coagulant, a method using an aqueous latex, or the like can be used.

[0085] (Modifications of the Graft Portion) In one embodiment of the present invention, the graft portion may consist of only one type of graft portion having structural units of the same composition. In one embodiment of the present invention, the graft portion may consist of multiple types of graft portions each having a structural unit of a different composition.

[0086] In one embodiment of the present invention, the graft portion is composed of a plurality of types of graft portions. In this case, each of the plurality of types of graft portions is １ , graft part ２ , ..., graft part ｎ (n is an integer of 2 or more). The graft moieties are each polymerized separately. １ , graft part ２ , ..., and the graft portion ｎ The graft portion may comprise a composite of １ , graft part ２ , ..., and the graft portion ｎ The polymer obtained by multistage polymerization of a plurality of types of graft moieties is also referred to as a multistage polymerization graft moiety. The method for producing the multistage polymerization graft moiety will be described in detail later.

[0087] When the graft portion is composed of multiple types of graft portions, not all of these multiple types of graft portions need to be graft-bonded to the elastomer. It is sufficient that at least a portion of at least one type of graft portion is graft-bonded to the elastomer, and the other types (multiple other types) of graft portions may be graft-bonded to graft portions that are graft-bonded to the elastomer. Furthermore, when the graft portion is composed of multiple types of graft portions, it may also have multiple types of polymers (multiple types of non-graft polymers) that have the same structure as the multiple types of graft portions and are not graft-bonded to the elastomer.

[0088] Graft area １ , graft part ２ , ..., and the graft portion ｎ In the multi-stage polymerization graft portion, ｎ is the graft area ｎ－１ or a graft portion. ｎ－１ In the multi-stage polymerization graft portion, ｎ Part of the graft ｎ－１ Sometimes it penetrates inside the

[0089] In the multi-stage polymerization graft portion, each of the plurality of graft portions may form a layer structure. For example, the multi-stage polymerization graft portion may be １ , graft part ２ , and the graft portion ３ If it consists of １ forms the innermost layer of the graft portion, １ The graft part is located on the outside of the ２ A layer of graft tissue is formed. ２ The graft area is located on the outside of the layer. ３An embodiment in which the layer (a) is formed as the outermost layer is also one aspect of the present invention. In this way, a multi-stage polymerization graft portion in which each of a plurality of graft portions forms a layer structure can also be called a multi-layer graft portion. That is, in one embodiment of the present invention, the graft portion may include (a) a mixture of a plurality of types of graft portions, (b) a multi-stage polymerization graft portion, and / or (c) a multi-layer graft portion.

[0090] When the elastomer and the graft moiety are polymerized in this order in the production of polymer microparticles (A), at least a portion of the graft moiety can cover at least a portion of the elastomer in the resulting polymer microparticles (A). Polymerization of the elastomer and the graft moiety in this order can be said to be multistage polymerization of the elastomer and the graft moiety. The polymer microparticles (A) obtained by multistage polymerization of the elastomer and the graft moiety can also be said to be multistage polymers.

[0091] When the polymer fine particles (A) are multistage polymers, the graft moieties may cover at least a part of the elastomer or may cover the entire elastomer. When the polymer fine particles (A) are multistage polymers, the graft moieties may be partially embedded inside the elastomer.

[0092] When the polymer microparticles (A) are multistage polymers, the elastomer and the graft moieties may form a layer structure. For example, one embodiment of the present invention is one in which the elastomer forms the innermost layer (also referred to as a core layer) and a layer of the graft moieties is formed as the outermost layer (also referred to as a shell layer) outside the elastomer. A structure in which the elastomer forms the core layer and the graft moieties form the shell layer can also be referred to as a core-shell structure. Thus, polymer microparticles (A) in which the elastomer and the graft moieties form a layer structure (core-shell structure) can also be referred to as a multilayer polymer or a core-shell polymer. That is, in one embodiment of the present invention, the polymer microparticles (A) may be multistage polymers and / or multilayer polymers or core-shell polymers. However, as long as the graft moieties are graft-bonded to the elastomer, the polymer microparticles (A) are not limited to the above structure.

[0093] At least a portion of the graft portion preferably covers at least a portion of the elastomer, in other words, at least a portion of the graft portion preferably exists on the outermost side of the polymer fine particles (A).

[0094] (2-1-3. Surface-Crosslinked Polymer) The rubber-containing graft copolymer may further contain a surface-crosslinked polymer in addition to the elastomer and the graft portion grafted to the elastomer. When the rubber-containing graft copolymer further contains a surface-crosslinked polymer, it is possible to improve the blocking resistance in the production of polymer microparticles (A), and (b) in the resin composition containing the obtained stress-reducing agent, it has the advantage of improving the dispersibility of the polymer microparticles (A) in the matrix resin. When the rubber-containing graft copolymer further contains a surface-crosslinked polymer, it can also have the following effects: (a) the effect of reducing the viscosity of the resin composition containing the obtained stress-reducing agent, (b) the effect of increasing the crosslink density in the elastomer, and (c) the effect of increasing the graft efficiency of the graft portion. The crosslink density in the elastomer refers to the degree of the number of crosslinked structures in the entire elastomer.

[0095] The surface cross-linked polymer is composed of a polymer containing, as structural units, 30% by weight to 100% by weight of structural units derived from polyfunctional monomers and 0% by weight to 70% by weight of structural units derived from other vinyl monomers, totaling 100% by weight.

[0096] Specific examples of the polyfunctional monomer are the same as those explained in the section (Crosslinked structure of elastic body) above, so the explanation therefor is omitted here and the explanation is incorporated herein by reference.

[0097] (2-1-4. Physical Properties of Polymer Fine Particles (A)) Hereinafter, the physical properties of the polymer fine particles (A) will be described.

[0098] (Volume Average Particle Diameter (Mv) of Polymer Microparticles (A)) The volume average particle diameter (Mv) of the polymer microparticles (A) is preferably 0.03 μm to 50.00 μm, more preferably 0.05 μm to 10.00 μm, more preferably 0.08 μm to 2.00 μm, even more preferably 0.10 μm to 1.00 μm, even more preferably 0.10 μm to 0.80 μm, and particularly preferably 0.10 μm to 0.50 μm, because this allows for the production of a resin composition having the desired viscosity and high stability. When the volume average particle diameter (Mv) of the polymer microparticles (A) is within the above range, there is also the advantage that the dispersibility of the polymer microparticles (A) in the matrix resin is improved. In this specification, the term "volume average particle diameter (Mv) of the polymer microparticles (A)" refers to the volume average particle diameter of the primary particles of the polymer microparticles (A), unless otherwise specified. The volume average particle diameter of the polymer microparticles (A) can be measured using a dynamic light scattering particle size distribution analyzer or the like, using an aqueous latex containing the polymer microparticles (A) as a sample. The volume average particle diameter of the polymer microparticles (A) will be described in detail in the Examples below. The volume average particle diameter of the polymer microparticles (A) can also be measured by cutting a cured resin composition, photographing the cut surface using an electron microscope or the like, and using the obtained photographed data (photographed image).

[0099] The number distribution of the volume average particle diameter of the polymer fine particles (A) in the matrix resin preferably has a half-value width of 0.5 to 1 times the volume average particle diameter, since this results in a resin composition that is low in viscosity and easy to handle.

[0100] (2-1-5. Method for Producing Polymer Microparticles (A)) The polymer microparticles (A) can be produced by polymerizing an elastomer, and then graft-polymerizing a polymer that will form a graft moiety onto the elastomer in the presence of the elastomer.

[0101] The polymer microparticles (A) can be produced by known methods, such as emulsion polymerization, suspension polymerization, and microsuspension polymerization. Specifically, the polymerization of the elastomer in the polymer microparticles (A), the polymerization of the graft moiety (graft polymerization), and the polymerization of the surface-crosslinked polymer can be carried out by known methods, such as emulsion polymerization, suspension polymerization, and microsuspension polymerization. Among these, emulsion polymerization is particularly preferred as a method for producing the polymer microparticles (A). The emulsion polymerization method has the advantages of (a) easy compositional design of the polymer microparticles (A), (b) easy industrial production of the polymer microparticles (A), and (c) easy production of an aqueous latex of the polymer microparticles (A) that can be suitably used in the production of the present resin composition described below. Below, the elastomer, graft moiety, and method for producing a surface-crosslinked polymer of any configuration that can be contained in the polymer microparticles (A) will be described.

[0102] (Method for Producing Elastic Body) The method for preparing the organosiloxane-based rubber is not particularly limited, and a known emulsion polymerization method can be used. Specific examples of the method for preparing the organosiloxane-based rubber include a method in which an organosiloxane and the monomer M are emulsion-polymerized in the presence of an acidic emulsifier.

[0103] As the organosiloxane raw material used in preparing the organosiloxane rubber, various organosiloxane cyclic compounds having three or more members, such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane, tetradecamethylcycloheptasiloxane, and dimethylcyclics (mixtures of dimethylsiloxane cyclic oligomers trimer to heptamer), are preferred because they are easily available and can be used to prepare organosiloxane rubber.

[0104] The acidic emulsifier is not particularly limited, but when using an organosiloxane cyclic compound, it is preferable to use one that can open the ring of the organosiloxane cyclic compound.As the acidic emulsifier, for example, dodecylbenzenesulfonic acid is preferably mentioned.The amount of the acidic emulsifier used is not particularly limited, and can be appropriately set according to (a) the desired volume average particle size of the organosiloxane rubber and the polymer microparticles (A), (b) the solid content (monomer mixture) concentration in the reaction solution, (c) polymerization conditions such as polymerization temperature, and (d) whether or not additives such as surfactants are used and the amount used.

[0105] The volume average particle size of the resulting organosiloxane rubber can be controlled by (a) the degree of pre-dispersion of the raw materials, (b) the amount of emulsifier used, (c) the polymerization temperature, and (d) the method of supplying the raw materials.

[0106] When an organosiloxane rubber is obtained by emulsion polymerization in the presence of an acidic emulsifier, the resulting aqueous latex is strongly acidic, and therefore it is preferable to neutralize it after the polymerization reaction is completed. The basic compound used for neutralization is not particularly limited, and examples thereof include sodium hydroxide, potassium hydroxide, ammonia, and triethylamine. The aqueous latex can be neutralized by adding these basic compounds directly or in the form of an aqueous solution to the aqueous latex containing the organosiloxane rubber.

[0107] The organosiloxane rubber can be prepared, for example, by the method described in WO2006 / 070664.

[0108] When the elastomer contains at least one selected from the group consisting of diene rubbers and (meth)acrylate rubbers, these elastomers can be produced by a method such as emulsion polymerization, suspension polymerization, or microsuspension polymerization, and the production method can be, for example, the method described in WO 2005 / 028546.

[0109] (Method for producing the graft portion) The graft portion can be formed, for example, by polymerizing the monomer used to form the graft portion by known radical polymerization. When (a) the elastomer or (b) the polymer microparticle precursor containing the elastomer and the surface-crosslinked polymer is obtained as an aqueous latex, it is preferable to carry out the polymerization of the graft portion by emulsion polymerization. The graft portion can be produced, for example, according to the method described in WO2005 / 028546.

[0110] When the graft moiety is composed of a plurality of types of graft moieties, the graft moieties having the plurality of types of graft moieties may be polymerized, and then the graft moieties may be graft polymerized onto an elastomer to produce polymer fine particles (A).The polymer fine particles (A) may also be produced by sequentially graft polymerizing the plurality of types of polymers constituting the graft moieties onto the elastomer in the presence of the elastomer through multistage graft polymerization.

[0111] When emulsion polymerization is used as a method for preparing the diene rubber and (meth)acrylate rubber and / or a method for preparing the graft moiety, a known emulsifier (dispersant) can be used.

[0112] Examples of emulsifiers include anionic emulsifiers, nonionic emulsifiers, polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, polyacrylic acid derivatives, etc. Examples of anionic emulsifiers include sulfur-based emulsifiers, phosphorus-based emulsifiers, sarcosinic acid-based emulsifiers, and carboxylic acid-based emulsifiers. Examples of sulfur-based emulsifiers include sodium dodecylbenzenesulfonate (abbreviated as SDBS). Examples of phosphorus-based emulsifiers include sodium polyoxyethylene lauryl ether phosphate.

[0113] When emulsion polymerization is used to prepare the diene rubber and (meth)acrylate rubber, and / or the graft portion, a thermally decomposable initiator can be used. Examples of the thermally decomposable initiator include known initiators such as (a) 2,2'-azobisisobutyronitrile and (b) peroxides, such as organic peroxides and inorganic peroxides. Examples of the organic peroxides include t-butylperoxyisopropyl carbonate, paramenthane hydroperoxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, and t-hexyl peroxide. Examples of the inorganic peroxides include hydrogen peroxide, potassium persulfate, and ammonium persulfate.

[0114] When emulsion polymerization is used to prepare the diene rubber and (meth)acrylate rubber and / or the graft portion, a redox initiator can also be used. The redox initiator is an initiator that combines (a) a peroxide, such as an organic peroxide or an inorganic peroxide, with (b) a reducing agent, such as a transition metal salt, such as iron (II) sulfate, sodium formaldehyde sulfoxylate, or glucose. If necessary, a chelating agent, such as disodium ethylenediaminetetraacetate, and a phosphorus-containing compound, such as sodium pyrophosphate, may also be used in combination.

[0115] When a redox initiator is used, polymerization can be carried out even at a low temperature where the peroxide does not substantially decompose thermally, and the polymerization temperature can be set over a wide range. Therefore, it is preferable to use a redox initiator. Among redox initiators, redox initiators using organic peroxides such as cumene hydroperoxide, dicumyl peroxide, paramenthane hydroperoxide, and t-butyl hydroperoxide as the peroxide are preferred. The amount of the initiator used, and when a redox initiator is used, the amounts of the reducing agent, transition metal salt, chelating agent, etc. used can be within known ranges.

[0116] When a polyfunctional monomer is used in preparing the elastomer and / or the graft portion, a known chain transfer agent can be used in a known amount range. By using the chain transfer agent, the molecular weight and / or the degree of crosslinking of the resulting elastomer, the graft portion, or the surface-crosslinked polymer can be easily adjusted.

[0117] In addition to the above-mentioned components, a surfactant may be used in the production of the polymer microparticles (A). The type and amount of the surfactant used are within known ranges.

[0118] In the production of the polymer fine particles (A), conditions within known numerical ranges can be appropriately applied as polymerization conditions such as polymerization temperature, pressure, and deoxidation.

[0119] (2-2. Resin (B)) The stress-reducing agent may further contain a resin (B) in addition to the polymer fine particles (A). When the stress-reducing agent contains the resin (B), it has the advantage of providing better dispersibility of the polymer fine particles (A) in the matrix resin.

[0120] Resin (B) may be, for example, a thermosetting resin, a thermoplastic resin, or any combination of a thermosetting resin and a thermoplastic resin.

[0121] (2-2-1. Thermosetting Resin) The thermosetting resin in resin (B) is not particularly limited, but preferably contains at least one selected from the group consisting of resins containing polymers obtained by polymerizing ethylenically unsaturated monomers, epoxy resins, phenolic resins, polyol resins, and amino-formaldehyde resins. Examples of thermosetting resins in resin (B) include resins containing polymers obtained by polymerizing aromatic polyester raw materials. Resin (B) may use one type of thermosetting resin, or two or more types may be used in combination.

[0122] (Epoxy Resin) The epoxy resin is not particularly limited as long as it has at least one epoxy group in the molecule.

[0123] Specific examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD ​​type epoxy resins, bisphenol S type epoxy resins, glycidyl ester type epoxy resins, glycidylamine type epoxy resins, novolac type epoxy resins, glycidyl ether type epoxy resins of bisphenol A propylene oxide adducts, hydrogenated bisphenol A (or F) type epoxy resins, fluorinated epoxy resins, rubber-modified epoxy resins containing polybutadiene or NBR, flame-retardant epoxy resins such as glycidyl ether of tetrabromobisphenol A, p-oxybenzoic acid glycidyl ether ester type epoxy resins, m-aminophenol type epoxy resins, diaminodiphenylmethane-based epoxy resins, urethane-modified epoxy resins having a urethane bond, various alicyclic epoxy resins, glycidyl ethers of polyhydric alcohols, hydantoin type epoxy resins, epoxidized products of unsaturated polymers such as petroleum resins, and amino-containing glycidyl ether resins. Examples of the polyhydric alcohol include N,N-diglycidylaniline, N,N-diglycidyl-o-toluidine, triglycidyl isocyanurate, polyalkylene glycol diglycidyl ether, and glycerin. Examples of the epoxy resin include epoxy compounds obtained by subjecting the above-mentioned epoxy resins to an addition reaction with bisphenol A (or F), polybasic acids, or the like. The epoxy resin is not limited to these, and commonly used epoxy resins can be used. These epoxy resins may be used alone or in combination of two or more.

[0124] Among the above-mentioned epoxy resins, those having at least two epoxy groups per molecule are preferred because they have high reactivity during curing of the resin composition and the resulting cured product easily forms a three-dimensional network. Furthermore, among epoxy resins having at least two epoxy groups per molecule, those containing bisphenol-type epoxy resin as the main component are preferred because of their excellent economic efficiency and ease of availability.

[0125] (2-2-2. Thermoplastic Resin) Examples of the thermoplastic resin in resin (B) include acrylic polymers, vinyl copolymers, polycarbonates, polyamides, polyesters, polyphenylene ethers, polyurethanes, and polyvinyl acetates. These may be used alone or in combination of two or more.

[0126] Resin (B) may be the same resin (resin having the same composition) as the matrix resin to be mixed, which will be described later, or may be a resin different from the matrix resin. In the resin composition, it is preferable that the matrix resin and resin (B) are not phase-separated. Resin (B) is preferably a resin that is compatible with the matrix resin.

[0127] When resin (B) is the same resin as the matrix resin to be mixed, which will be described later, there is an advantage that resin (B) does not affect the various physical properties of the resulting resin composition containing the stress-reducing agent or the cured product.

[0128] As an example, consider the case where resin (B) is the same type of resin as the matrix resin. In this case, it is impossible to distinguish between the matrix resin and resin (B) in the resulting resin composition containing the stress-reducing agent. Therefore, from the outside, the resulting resin composition containing the stress-reducing agent appears to contain only resin (B) or only the matrix resin in addition to the polymer microparticles (A). Next, consider the case where resin (B) is a different type of resin from the matrix resin. In this case, it is possible to distinguish between the matrix resin and resin (B) in the resulting resin composition containing the stress-reducing agent. In this case, the finally obtained resin composition containing the stress-reducing agent may contain, in addition to the polymer microparticles (A), resin (B) as a resin other than the matrix resin.

[0129] (2-2-3. Others) In this specification, fats and oils and fatty acid esters are also included in resin (B). Examples of fats and oils that can be suitably used as resin (B) include epoxidized fats and oils such as epoxidized soybean oil and epoxidized linseed oil. Commercially available epoxidized soybean oils can also be used, and examples include Adekaiser O-130P manufactured by ADEKA Corporation. Examples of fatty acid esters that can be suitably used as resin (B) include epoxidized fatty acid esters such as epoxidized fatty acid butyl, epoxidized fatty acid 2-ethylhexyl, epoxidized fatty acid octyl ester, and epoxidized fatty acid alkyl ester.

[0130] Epoxidized fats and oils and epoxidized fatty acid esters are sometimes referred to as epoxy plasticizers. That is, in this specification, epoxy plasticizers are also included in resin (B). Examples of epoxy plasticizers other than epoxidized fats and oils and epoxidized fatty acid esters include diepoxystearyl epoxyhexahydrophthalate and di-2-ethylhexyl epoxyhexahydrophthalate.

[0131] The above-mentioned thermosetting resin, thermoplastic resin, mixture of thermosetting resin and thermoplastic resin, oils and fats, and fatty acid esters can each be used in combination with an antioxidant. In this specification, the antioxidant is considered to be part of resin (B) only when used in combination with each of the above-mentioned substances. When the antioxidant is used alone, it is not considered to be part of resin (B). The following describes the use of only an antioxidant instead of resin (B). Because the antioxidant is a component that does not contribute to crosslinking, when the resulting stress-reducing agent is mixed with a matrix resin, the physical properties of the final product (i.e., the final product; for example, if the matrix resin is a thermosetting resin, the cured product) tend to be inferior. For example, the Tg of the final product may be lowered or the impact resistance may be poor.

[0132] The antioxidant is not particularly limited and examples thereof include (a) primary antioxidants such as phenol-based antioxidants, amine-based antioxidants, lactone-based antioxidants, and hydroxylamine-based antioxidants, and (b) secondary antioxidants such as sulfur-based antioxidants and phosphorus-based antioxidants.

[0133] Other conventionally known substances may also be used as the antioxidant, including various substances described in "Antioxidant Handbook" published by Taiseisha (first edition published on October 25, 1976) and "Polymer Additives Handbook" published by CMC Publishing (edited by Toru Haruna, first edition published on November 7, 2010).

[0134] The resin (B) is preferably one or more selected from the group consisting of a thermosetting resin, a mixture of a thermosetting resin and an antioxidant, a thermoplastic resin, a mixture of a thermoplastic resin and an antioxidant, an oil or fat, a mixture of an oil or fat and an antioxidant, a fatty acid ester, a mixture of a fatty acid ester and an antioxidant, an epoxy curing agent, and a mixture of an epoxy curing agent and an antioxidant, more preferably one or more selected from the group consisting of an epoxy resin, an acrylic polymer, a mixture of an epoxy resin and an antioxidant, a mixture of an acrylic polymer and an antioxidant, and a mixture of an epoxy plasticizer and an antioxidant, still more preferably one or more selected from the group consisting of a mixture of an epoxy resin and an antioxidant, a mixture of an acrylic polymer and an antioxidant, and a mixture of an epoxy plasticizer and an antioxidant, and particularly preferably a mixture of an epoxy plasticizer and an antioxidant. This configuration has the advantages of (a) providing a cured product with excellent heat resistance from the resulting resin composition containing the stress reducing agent, and (b) improving the dispersibility of the polymer fine particles (A) in the matrix resin.

[0135] (2-2-4. Physical Properties of Resin (B)) Resin (B) is not particularly limited in other properties as long as it is a liquid, semi-solid, or solid having a viscosity of 100 mPa·s to 1,000,000 mPa·s at 25°C. In this specification, "resin (B) has a viscosity of 100 mPa·s to 1,000,000 mPa·s at 25°C" means "resin (B) at 25°C has a viscosity of 100 mPa·s to 1,000,000 mPa·s."

[0136] When the resin (B) is a liquid, the viscosity of the resin (B) is preferably 750,000 mPa·s or less at 25° C. According to the above-described configuration, the stress-reducing agent has the advantage of excellent fluidity.

[0137] The viscosity of the resin (B) at 25°C is more preferably 200 mPa·s or more, and even more preferably 300 mPa·s or more. According to this configuration, the resin (B) does not impregnate the polymer microparticles (A), but penetrates between the particles of multiple polymer microparticles (A) and can remain near the surfaces of the polymer microparticles (A). As a result, the resin (B) can prevent the polymer microparticles (A) from fusing together.

[0138] The viscosity of resin (B) at 25°C is more preferably 100 mPa·s to 750,000 mPa·s, more preferably 100 mPa·s to 700,000 mPa·s, more preferably 100 mPa·s to 350,000 mPa·s, more preferably 100 mPa·s to 300,000 mPa·s, more preferably 100 mPa·s to 50,000 mPa·s, even more preferably 100 mPa·s to 30,000 mPa·s, and particularly preferably 100 mPa·s to 15,000 mPa·s.

[0139] When resin (B) is semi-solid at 25° C., it can also be said that resin (B) is semi-liquid at 25° C., and that resin (B) has a viscosity of greater than 1,000,000 mPa s at 25° C. When resin (B) is semi-solid or solid at 25° C., the resulting resin composition containing the stress-reducing agent has the advantage of being less sticky and easier to handle.

[0140] The content of resin (B) in the stress-reducing agent is 50 to 99% by weight of the polymer microparticles (A) and 1 to 50% by weight of the resin (B), assuming the total of the polymer microparticles (A) and the resin (B) to be 100% by weight. The content of resin (B) can be appropriately set within the above-mentioned numerical range and within the range in which a stress-reducing agent can be obtained, depending on the type of resin (B) and its physical properties (solid, semi-solid, liquid, viscosity, etc.). If resin (B) is a liquid at 25°C and the content of resin (B) in the stress-reducing agent is high, the stress-reducing agent may not be obtained. If resin (B) is a liquid at 25°C and the content of resin (B) in the stress-reducing agent is high, the fluidity (smoothness) of the stress-reducing agent may be impaired.

[0141] The content of the resin (B) in the stress reducing agent will be explained from the viewpoint of excellent blocking resistance. When the total of the polymer fine particles (A) and the resin (B) is 100% by weight, it is more preferable that the polymer fine particles (A) be 55 to 99% by weight and the resin (B) be 1 to 45% by weight, it is more preferable that the polymer fine particles (A) be 60 to 99% by weight and the resin (B) be 1 to 40% by weight, it is more preferable that the polymer fine particles (A) be 65 to 99% by weight and the resin (B) be 1 to 35% by weight, it is more preferable that the polymer fine particles (A) be 70 to 99% by weight and the resin (B) be 1 to 30 ... It is more preferable that the polymer fine particles (A) are 75 to 99% by weight and the resin (B) is 1 to 25% by weight, it is more preferable that the polymer fine particles (A) are 80 to 99% by weight and the resin (B) is 1 to 20% by weight, it is even more preferable that the polymer fine particles (A) are 85 to 99% by weight and the resin (B) is 1 to 15% by weight, it is even more preferable that the polymer fine particles (A) are 90 to 99% by weight and the resin (B) is 1 to 10% by weight, it is particularly preferable that the polymer fine particles (A) are 95 to 99% by weight and the resin (B) is 1 to 5% by weight.

[0142] The content of resin (B) in the stress reducing agent will be explained from the viewpoint of improving the dispersibility of polymer fine particles (A) in the matrix resin. When the total of polymer fine particles (A) and resin (B) is 100% by weight, the polymer fine particles (A) are preferably 50 to 97% by weight and the resin (B) is 3 to 50% by weight, more preferably 50 to 95% by weight and the resin (B) is 5 to 50% by weight, still more preferably 50 to 92% by weight and the resin (B) is 8 to 50% by weight, still more preferably 50 to 90% by weight and the resin (B) is 10 to 50% by weight, and still more preferably 50 to 92% by weight and the resin (B) is 8 to 50% by weight. It is more preferable that the polymer microparticles (A) are 0 to 87% by weight and the resin (B) is 13 to 50% by weight, it is more preferable that the polymer microparticles (A) are 50 to 85% by weight and the resin (B) is 15 to 50% by weight, it is even more preferable that the polymer microparticles (A) are 50 to 82% by weight and the resin (B) is 18 to 50% by weight, it is even more preferable that the polymer microparticles (A) are 50 to 80% by weight and the resin (B) is 20 to 50% by weight, it is particularly preferable that the polymer microparticles (A) are 60 to 80% by weight and the resin (B) is 20 to 40% by weight.

[0143] (2-3. Anti-blocking Agent) The stress reducing agent preferably further contains an anti-blocking agent. According to this configuration, the resulting stress reducing agent has (a) excellent blocking resistance and (b) excellent dispersibility of the polymer fine particles (A) in the matrix resin.

[0144] The antiblocking agent is not particularly limited as long as it exhibits the effects of one embodiment of the present invention. Examples of the antiblocking agent include antiblocking agents composed of inorganic fine particles such as silicon dioxide, titanium oxide, aluminum oxide, zirconium oxide, aluminum silicate, diatomaceous earth, zeolite, kaolin, talc, calcium carbonate, calcium phosphate, barium sulfate, and magnesium hydrosilicate; antiblocking agents composed of organic fine particles; and oil-based antiblocking agents such as polyethylene wax, higher fatty acid amide, metal soap, and silicone oil. Among these, antiblocking agents composed of fine particles are preferred, and antiblocking agents composed of organic fine particles are more preferred. As the antiblocking agent composed of organic fine particles, antiblocking agents composed of organic fine particles of a polymer containing, as a constituent unit, a constituent unit derived from one or more monomers selected from aromatic vinyl monomers, vinyl cyan monomers, and (meth)acrylate monomers are particularly preferred.

[0145] Antiblocking agents consisting of fine particles are generally in the form of fine particles dispersed in a liquid or in a colloidal state. The fine particles in the antiblocking agent typically have a volume average particle diameter (Mv) of 10 μm or less, preferably 0.05 μm to 10.00 μm. The content of the antiblocking agent is preferably 0.01 wt % to 5.00 wt %, more preferably 0.50 wt % to 3.00 wt %, based on the total weight (100 wt %) of the stress-reducing agent.

[0146] (2-4. Other Optional Components) The stress-reducing agent may contain other optional components in addition to the components described above, as necessary. Examples of other optional components include the various components described in the section (4-4. Other Optional Components) below.

[0147] The antiblocking agent and other optional components can be added as appropriate in any step in the production method of the stress-reducing agent. For example, the antiblocking agent and other optional components can be added to the aqueous suspension (aqueous latex) of the polymer fine particles (A) or the polymer fine particles (A) and the resin (B) before or after coagulation. The antiblocking agent and other optional components can also be added to the stress-reducing agent containing the polymer fine particles (A), the resin (B), or the polymer fine particles (A) and the resin (B).

[0148] [3. Method for producing stress-reducing agent] In one embodiment of the present invention, the method for producing the stress-reducing agent is not particularly limited. Hereinafter, an example of a method for producing a stress-reducing agent will be described, taking as an example a case where the stress-reducing agent contains polymer fine particles (A) and a resin (B). Note that if the resin (B) is not used in the following production method, a stress-reducing agent containing polymer fine particles (A) but not resin (B) can be obtained.

[0149] In one embodiment of the present invention, the method for producing a stress-reducing agent comprises a resin (B) addition step of adding a resin (B) to an aqueous latex containing polymer fine particles (A), an aggregation step of preparing aggregates containing the polymer fine particles (A) and the resin (B) using the obtained aqueous latex, and a recovery step of recovering the aggregates. In this specification, the terms "aggregation," "coagulation," and "coagulation" have the same meaning and are interchangeable.

[0150] The resin (B) addition step is a step of obtaining an aqueous latex containing polymer microparticles (A) and resin (B). The resin (B) addition step can also be said to be a step of mixing polymer microparticles (A) and resin (B). The specific method of adding resin (B) to the aqueous latex containing polymer microparticles (A) is not particularly limited, and examples include a method of directly adding resin (B) to the aqueous latex containing polymer microparticles (A), a method of adding resin (B) in an aqueous emulsion state, and a method of adding resin (B) in a solution state. In the resin (B) addition step, it is preferable to add resin (B) in an aqueous emulsion state to the aqueous latex containing polymer microparticles (A).

[0151] The aggregation step is a step for aggregating the polymer microparticles (A) in the aqueous latex together with the resin (B). In the aggregation step, aggregates containing the polymer microparticles (A) and the resin (B) can be obtained. The method for aggregating the polymer microparticles (A) together with the resin (B) is not particularly limited, but for example, a method using a solvent, a method using an aggregating agent (also referred to as a coagulant or a coagulant), a method of spraying an aqueous latex containing the polymer microparticles (A) and the resin (B), etc. can be used.

[0152] The aggregation step preferably includes a step of preparing aggregates containing polymer fine particles (A) and the resin (B) using an aggregating agent. This configuration eliminates the need for a solvent, making it possible to obtain powders and granules for thermosetting resins with a low environmental impact. Furthermore, this configuration does not require special facilities for spraying, making it possible to easily obtain powders and granules for thermosetting resins.

[0153] The recovery step is a step of removing water from the aqueous latex to obtain aggregates containing polymer microparticles (A) and resin (B). The recovery step can also be described as a step of separating the aggregates containing polymer microparticles (A) and resin (B) from the water component from the aqueous latex. The water component is a mixture containing water as the main component, as well as emulsifier, non-aggregated polymer microparticles (A), resin (B), etc. The method for recovering the aggregates containing polymer microparticles (A) and resin (B) is not particularly limited, and examples thereof include filtration, centrifugation, etc.

[0154] The aggregate obtained through the resin (B) adding step, the aggregating step, and the recovering step can be used as a stress reducing agent.

[0155] In one embodiment of the present invention, the method for producing a stress-reducing agent may further include a washing step.

[0156] The washing step is a step of washing the aggregates containing the polymer fine particles (A) and the resin (B) obtained in the recovery step. By washing the aggregates, powders and granules for thermosetting resins with a low content of impurities and the like can be obtained. In the washing step, the aggregates are preferably washed with water, and more preferably washed with ion-exchanged water or pure water.

[0157] The washing step may be any step for washing the aggregates, and the specific method is not particularly limited. Examples include a method of mixing the aggregates with water and stirring them with a stirrer, a method of kneading the aggregates with water using a kneader, a method of mixing the aggregates with water using a planetary mixer, a method of spraying water onto the aggregates, and a method of washing the cake with a pressure filter. Various kneaders can be used, such as a batch kneader, a continuous kneader, an extrusion kneader, and an extruder.

[0158] The objects to be washed include all impurities contained in the aggregates, and are not particularly limited. Examples include impurities derived from emulsifiers (e.g., phosphorus-based emulsifiers, sulfonic acid-based emulsifiers), and, when a flocculant described below is used, impurities derived from the flocculant.

[0159] Examples of emulsifiers include (a) anionic emulsifiers such as acids, alkali metal salts of the acids, or ammonium salts of the acids, as exemplified below, (b) nonionic emulsifiers such as alkyl- or aryl-substituted polyethylene glycol, and (c) polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, polyacrylic acid derivatives, etc. Examples of the acids include (a1) alkyl or aryl sulfonic acids or alkyl or aryl ether sulfonic acids, typified by dioctyl sulfosuccinic acid and dodecyl benzene sulfonic acid, (a2) alkyl or aryl sulfuric acids or alkyl or aryl ether sulfuric acids, typified by dodecyl sulfate, (a3) ​​alkyl or aryl-substituted phosphoric acids or alkyl or aryl ether-substituted phosphoric acids, (a4) N-alkyl or aryl sarcosinic acids, typified by dodecyl sarcosinic acid, and (a5) alkyl or aryl carboxylic acids or alkyl or aryl ether carboxylic acids, typified by oleic acid and stearic acid, etc. Here, the anionic emulsifiers formed from the acids described in (a1) and (a2) are referred to as sulfur-based emulsifiers, the anionic emulsifiers formed from the acids described in (a3) ​​are referred to as phosphorus-based emulsifiers, the anionic emulsifiers formed from the acids described in (a4) are referred to as sarcosinic acid-based emulsifiers, and the anionic emulsifiers formed from the acids described in (a5) are referred to as carboxylic acid-based emulsifiers. These emulsifiers may be used alone or in combination of two or more.

[0160] In one embodiment of the present invention, the method for producing a stress-reducing agent may further include a drying step. By drying the stress-reducing agent obtained by the above-mentioned method, a powdered or granular stress-reducing agent can be obtained.

[0161] The drying step is a step of drying the aggregates containing the polymer fine particles (A) and the resin (B) obtained in the recovery step or the washing step to obtain a powder or granule. The method for drying the aggregates is not particularly limited, and examples thereof include a method of drying the aggregates using a dryer, a method of placing the aggregates in a container and heating and reducing the pressure in the container, and a method of placing the aggregates in a container and bringing a dry gas into countercurrent contact with the aggregates in the container.

[0162] [4. Resin Composition] A resin composition containing the above-described stress-reducing agent and a matrix resin is also one embodiment of the present invention. Hereinafter, the "resin composition according to one embodiment of the present invention" may also be referred to as the "present resin composition." By adding the present stress-reducing agent to a matrix resin, it is possible to reduce the elastic modulus of the matrix resin and also to reduce deterioration in the linear expansion coefficient.

[0163] (4-1. Matrix Resin) The matrix resin is not particularly limited, and examples thereof include thermosetting resins, thermoplastic resins, and any combination of thermosetting resins and thermoplastic resins.

[0164] Among these, from the viewpoint of enabling the function of the present stress reducing agent to be optimally exhibited, the matrix resin is more preferably a thermosetting resin such as an epoxy resin, a phenolic resin, a polyimide resin, or an oxetane resin, or a thermoplastic resin such as a polycarbonate resin. Alternatively, the thermosetting resin and the thermoplastic resin may be the same as the thermosetting resin and the thermoplastic resin described above in the section (2-2. Resin (B)).

[0165] The matrix resin is preferably an epoxy resin. The epoxy resin may be the same as the epoxy resin described in the section (2-2. Resin (B)). The epoxy resin may be used alone, or may be used in combination with one or more matrix resins other than epoxy resins.

[0166] (4-2. Physical Properties of Matrix Resin) The properties of the matrix resin are not particularly limited. The matrix resin preferably has a viscosity of 100 mPa·s to 1,000,000 mPa·s at 25°C. The viscosity of the matrix resin at 25°C is more preferably 50,000 mPa·s or less, even more preferably 30,000 mPa·s or less, and particularly preferably 15,000 mPa·s or less. This configuration has the advantage that the matrix resin has excellent fluidity. A matrix resin having a viscosity of 100 mPa·s to 1,000,000 mPa·s at 25°C can also be said to be a liquid.

[0167] The greater the fluidity of the matrix resin, in other words, the lower the viscosity, the more difficult it becomes to disperse the polymer fine particles (A) in the form of primary particles in the matrix resin. Conventionally, it has been extremely difficult to disperse the polymer fine particles (A) in the form of primary particles in a matrix resin having a viscosity of 1,000,000 mPa·s or less at 25°C. However, the resin composition according to one embodiment of the present invention has the advantage that the polymer fine particles (A) having the above-described configuration are well dispersed in a matrix resin having a viscosity of 1,000,000 mPa·s or less at 25°C.

[0168] Furthermore, the viscosity of the matrix resin at 25°C is more preferably 100 mPa·s or more, even more preferably 500 mPa·s or more, even more preferably 1000 mPa·s or more, and particularly preferably 1500 mPa·s or more, because the matrix resin penetrates into the polymer microparticles (A) and can prevent the polymer microparticles (A) from fusing together.

[0169] The viscosity of the matrix resin at 25°C is preferably 100 mPa·s to 750,000 mPa·s, more preferably 100 mPa·s to 700,000 mPa·s, still more preferably 100 mPa·s to 350,000 mPa·s, still more preferably 100 mPa·s to 300,000 mPa·s, still more preferably 100 mPa·s to 50,000 mPa·s, still more preferably 100 mPa·s to 30,000 mPa·s, and particularly preferably 100 mPa·s to 15,000 mPa·s.

[0170] The matrix resin may have a viscosity of greater than 1,000,000 mPa s. The matrix resin may be semi-solid (semi-liquid) or solid. When the matrix resin has a viscosity of greater than 1,000,000 mPa s, the resulting resin composition containing the powder or granule has the advantage of being less sticky and easier to handle.

[0171] The matrix resin preferably has an endothermic peak of 25° C. or less in a thermogram obtained by differential scanning calorimetry (DSC), and more preferably has an endothermic peak of 0° C. or less. According to the above-mentioned configuration, the matrix resin has the advantage of excellent fluidity.

[0172] (4-3. Blending ratio of stress-reducing agent to matrix resin, etc.) When the total of the stress-reducing agent and the matrix resin is taken as 100% by weight, the blending ratio of the stress-reducing agent to the matrix resin is usually preferably 0.5 to 50% by weight and 50 to 99.5% by weight, more preferably 1 to 40% by weight and 60 to 99% by weight, even more preferably 1 to 25% by weight and 75 to 99% by weight, and particularly preferably 2.5 to 20% by weight and 80 to 97.5% by weight.

[0173] The blending ratio of the stress reducing agent to the matrix resin can be appropriately set depending on (a) the content and moisture content of components other than the polymer microparticles (A) contained in the powder or granule, and (b) the method of mixing the stress reducing agent with the matrix resin, in order to achieve the desired ratio of the content of the polymer microparticles (A) to the matrix resin in the resulting resin composition.

[0174] The content ratio of the polymer fine particles (A) to the matrix resin in the resin composition, when the total of the polymer fine particles (A) and the matrix resin is taken as 100% by weight, is usually preferably 0.5 to 50% by weight of the polymer fine particles (A) and 50 to 99.5% by weight of the matrix resin, more preferably 1 to 40% by weight of the polymer fine particles (A) and 60 to 99% by weight of the matrix resin, still more preferably 1 to 25% by weight of the polymer fine particles (A) and 75 to 99% by weight of the matrix resin, and particularly preferably 2.5 to 20% by weight of the polymer fine particles (A) and 80 to 97.5% by weight of the matrix resin.

[0175] When the matrix resin is an epoxy resin, the state of the matrix resin is not particularly limited as long as it flows when mixed with the stress-reducing agent, and it may be solid at room temperature, but is preferably liquid from the standpoint of workability.

[0176] The temperature at which the stress-reducing agent and the matrix resin are mixed is generally set to a temperature at which the matrix resin can flow. If the resin (B) in the powder or granule can flow at the temperature at which the matrix resin can flow, it becomes easy to uniformly mix the resin (B) and the matrix resin.

[0177] When the resin composition contains a thermosetting resin as a matrix resin, a cured product can be obtained by curing the resin composition. When the resin composition contains a thermoplastic resin as a matrix resin, a molded product can be obtained by molding the resin composition. A cured product obtained by curing the resin composition and a molded product obtained by molding the resin composition are also embodiments of the present invention.

[0178] The present resin composition may further contain a known thermosetting resin other than the matrix resin, or may further contain a known thermoplastic resin.

[0179] (4-4. Other Optional Components) The resin composition may contain optional components other than those described above, as necessary. The resin composition preferably contains silica as an inorganic filler. The silica may be used alone, or may be used in combination with one or more optional components other than silica. Examples of the optional components include curing agents, colorants such as pigments and dyes, extender pigments, pigment dispersants, UV absorbers, the antioxidants described above, heat stabilizers (antigelling agents), plasticizers, leveling agents, antifoaming agents, silane coupling agents, antistatic agents, flame retardants, lubricants, viscosity reducers, viscosity modifiers, thixotropy-imparting agents, shrinkage reducing agents, inorganic fillers, organic fillers, thermoplastic resins, desiccants, dispersants, thermal conductivity improvers, water binding agents, anti-sagging agents, color separation inhibitors, anti-settling agents, coating wear adjusters, surface conditioners, monobasic organic acids, camphor, and castor oil.

[0180] (4-5. Method for producing resin composition) A method for producing a resin composition according to one embodiment of the present invention is a method for producing a resin composition, which includes a step of mixing a stress-reducing agent containing polymer fine particles (A), a thermosetting resin, and an inorganic filler. The stress-reducing agent containing polymer fine particles (A) can be produced by the production method described in the above section [3. Method for producing stress-reducing agent].

[0181] The method for producing the resin composition is not particularly limited as long as it includes a step of mixing a stress-reducing agent containing polymer fine particles (A), a thermosetting resin, and an inorganic filler, but an example of such a method is to mix the stress-reducing agent and the thermosetting resin, and then add the inorganic filler and, if necessary, the other optional components described above to the resulting mixture, and mix them in a mixer, etc. The order in which the stress-reducing agent, thermosetting resin, inorganic filler, and other optional components are added is not limited to the order described above, and any order may be used.

[0182] The method for producing a resin composition according to one embodiment of the present invention is more preferably a method for producing a resin composition comprising a step of mixing a stress-reducing agent containing polymer microparticles (A), an epoxy resin, and silica. Even in the production method comprising a step of mixing a stress-reducing agent containing polymer microparticles (A), an epoxy resin, and silica, the order in which the stress-reducing agent, epoxy resin, silica, and other optional components are added may be any order. For example, a method may be used in which the stress-reducing agent and the epoxy resin are mixed, and then silica and, if necessary, the other optional components described above are added to the resulting mixture, followed by mixing with a mixer or the like.

[0183] [5. Encapsulant] An encapsulant according to one embodiment of the present invention is made using the above-described stress reducing agent or resin composition. Because of the above-described configuration, the encapsulant according to one embodiment of the present invention has the advantages of excellent toughness and impact resistance.

[0184] The sealing material according to one embodiment of the present invention is also simply referred to as the sealing material.

[0185] The uses of the present encapsulant are not particularly limited, but examples thereof include encapsulants for various electrical devices such as semiconductors and power devices.

[0186] The present encapsulant can be produced using a stress reducing agent or a resin composition. The method for producing the present encapsulant is not particularly limited, and known methods can be used.

[0187] [Summary] One embodiment of the present invention includes the following configuration.

[0188] [1] A stress-reducing agent containing polymer fine particles (A), wherein the polymer fine particles (A) comprise a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, the proportion of the elastomer in the polymer fine particles (A) being more than 70% by weight and not more than 97% by weight based on 100% by weight of the polymer fine particles (A), the elastomer comprises an organosiloxane rubber, the graft portion comprises an epoxy group-containing structural unit, and the epoxy group-containing structural unit in the graft portion is contained in an amount of 0.5% by weight to 4.0% by weight based on 100% by weight of the rubber-containing graft copolymer, and the stress-reducing agent is in the form of a powder or granule.

[0189] [2] The stress reducing agent according to [1], wherein the epoxy group-containing structural unit in the graft portion is contained in an amount of 3.3% by weight to 26.7% by weight relative to 100% by weight of the graft portion in the rubber-containing graft copolymer.

[0190] [3] A stress-reducing agent containing polymer fine particles (A), wherein the polymer fine particles (A) comprise a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, the proportion of the elastomer in the polymer fine particles (A) being more than 70% by weight and not more than 97% by weight, relative to 100% by weight of the polymer fine particles (A), the elastomer comprises an organosiloxane rubber, the graft portion comprises an epoxy group-containing structural unit, and the epoxy group-containing structural unit in the graft portion is contained in an amount of 3.3% by weight to 26.7% by weight, relative to 100% by weight of the graft portion in the rubber-containing graft copolymer, and the stress-reducing agent is in the form of a powder or granule.

[0191] [4] The stress reducing agent according to any one of [1] to [3], wherein the epoxy group-containing structural unit in the graft moiety is a glycidyl methacrylate unit.

[0192] [5] The stress reducing agent according to any one of [1] to [4], further comprising a resin (B).

[0193] [6] A resin composition comprising the stress reducing agent according to any one of [1] to [5], a thermosetting resin, and an inorganic filler.

[0194] [7] The resin composition according to any one of [1] to [6], wherein the thermosetting resin is an epoxy resin and the inorganic filler is silica.

[0195] [8] An encapsulant comprising the resin composition according to [6].

[0196] [9] An encapsulant comprising the resin composition according to [7].

[0197]

[10] A method for producing a resin composition, comprising a step of mixing a stress-reducing agent containing polymer fine particles (A), a thermosetting resin, and an inorganic filler, wherein the polymer fine particles (A) comprise a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, the proportion of the elastomer in the polymer fine particles (A) being more than 70% by weight and not more than 97% by weight, based on 100% by weight of the polymer fine particles (A), the elastomer comprises an organosiloxane rubber, the graft portion comprises an epoxy group-containing structural unit, and the epoxy group-containing structural unit in the graft portion is contained in an amount of 0.5% by weight to 4.0% by weight, based on 100% by weight of the rubber-containing graft copolymer, and the stress-reducing agent is in the form of a powder or granule.

[0198]

[11] The method for producing a resin composition according to

[10] , wherein the epoxy group-containing structural unit in the graft portion is contained in an amount of 3.3% by weight to 26.7% by weight relative to 100% by weight of the graft portion in the rubber-containing graft copolymer.

[0199]

[12] A method for producing a resin composition, comprising a step of mixing a stress-reducing agent containing polymer fine particles (A), a thermosetting resin, and an inorganic filler, wherein the polymer fine particles (A) comprise a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, the proportion of the elastomer in the polymer fine particles (A) being more than 70% by weight and not more than 97% by weight, relative to 100% by weight of the polymer fine particles (A), the elastomer comprises an organosiloxane rubber, the graft portion comprises an epoxy group-containing structural unit, and the epoxy group-containing structural unit in the graft portion is contained in an amount of 3.3% by weight to 26.7% by weight, relative to 100% by weight of the graft portion in the rubber-containing graft copolymer, and the stress-reducing agent is in the form of a powder or particle.

[0200]

[13] The method for producing a resin composition according to any one of

[10] to

[12] , wherein the epoxy group-containing structural unit in the graft moiety is a glycidyl methacrylate unit.

[0201]

[14] The method for producing a resin composition according to any one of

[10] to

[13] , wherein the stress reducing agent further contains a resin (B).

[0202]

[15] The method for producing a resin composition according to any one of

[10] to

[14] , wherein the thermosetting resin is an epoxy resin and the inorganic filler is silica.

[0203] Hereinafter, one embodiment of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these. One embodiment of the present invention can be practiced with appropriate modifications within the scope of the above-mentioned or below-mentioned purpose, and all such modifications are included within the technical scope of the present invention. In the following examples and comparative examples, "parts" and "%" mean parts by weight or % by weight.

[0204] <Components> The components used in each Production Example, Example, and Comparative Example are as follows. Polymer microparticles (A) The polymer microparticles (A) obtained in the Production Examples shown below were used. Resin (B) (i) Epoxidized soybean oil (ADEKA CORPORATION, Adeka Cizer O-130P) was used alone, or (ii) a mixture of 90 parts by weight of the epoxidized soybean oil and 10 parts by weight of triethylene glycol bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate] (antioxidant) (Irganox 245, BASF Japan Ltd.) was used. Matrix resin Bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, JER828) was used.

[0205] <Evaluation Method> First, the evaluation methods for the resin compositions produced in the Examples and Comparative Examples will be described below.

[0206] (Measurement of volume average particle diameter) The volume average particle diameter (Mv) of the elastic body (elastic core layer) and polymer microparticles (A) dispersed in the aqueous latex was measured using a Nanotrac Wave II-EX150 (manufactured by Microtrackbell Co., Ltd.). A water-based latex diluted with deionized water was used as the measurement sample. The measurement was performed by inputting the refractive indexes of water, the elastic body, and the polymer microparticles, and adjusting the sample concentration so that the loading index was within the range of 1 to 10 for a measurement time of 120 seconds.

[0207] (Dispersibility of Powder and Granules in Matrix Resin) 15 parts by weight (15 g) of the powder and granules obtained in the Examples and Comparative Examples and 85 parts by weight (85 g) of bisphenol A epoxy resin, the matrix resin, were prepared. The prepared powder and bisphenol A epoxy resin were placed in a 200 mL container. The volume of the container was approximately twice the volume of the prepared powder and bisphenol A epoxy resin. The powder and bisphenol A epoxy resin were mixed using a Disper (manufactured by PRIMIX Corporation) with a stirring blade having a blade diameter of 32 mm at a rotation speed of 3,000 rpm to obtain a resin composition. The resin composition was placed on a grind meter (grind gauge), and the resin composition on the gauge was scraped with a metal scraper to visually confirm the dispersion state. The scale was read at the position where 5 to 10 granular marks created by the scraper movement appeared within a 3 mm wide band, and the time until the scale reached 0 μm was measured. The results are shown in Table 1.

[0208] (Measurement of Physical Properties of Cured Epoxy+Silica Blend) To 24.6 parts by weight of "JER828," 47.1 parts by weight of "MH-700" (trade name, manufactured by New Japan Chemical Co., Ltd.) as a curing agent, 0.471 parts by weight of 2-ethyl-4-methylimidazole as a curing accelerator, 50 parts by weight of "CMC-12S" (trade name, manufactured by Tatsumori Co., Ltd.) as silica, 0.2 parts by weight of "BYK1790" (trade name, manufactured by BYK Corporation) as a defoaming agent, and 33.3 parts by weight of a resin composition (resin composition obtained in the above section (Dispersibility of Powder Particles in Matrix Resin) after conducting a powder particle dispersibility test in the matrix resin using the powder particles obtained in the Examples and Comparative Examples) were added, and the mixture was mixed for 60 minutes at 2000 rpm in a planetary centrifugal mixer to obtain an epoxy+silica blend (resin composition). This blend was poured into a mold and heated at 100°C for 1 hour and then at 150°C for 3 hours to obtain a cured board. The cured plate was cut and subjected to a bending test at a support distance of 80 mm and a test speed of 2 mm / min. The cured plate was also cut and the coefficient of linear expansion (CTE) was measured in the range of 100°C to 130°C at a heating rate of 10°C / min using a TA7000 manufactured by Hitachi High-Tech Science Corporation.

[0209] 1. Preparation of Aqueous Latex Containing Polymer Microparticles (A) (Production Example 1-1: Preparation of Aqueous Latex (L-1) Containing Polymer Microparticles (A)) 110 parts by weight of deionized water, 0.5 parts by weight of SDS, 100 parts by weight of octamethylcyclotetrasiloxane (D4), 2 parts by weight of tetraethoxysilane, and 2 parts by weight of γ-acryloyloxypropyldimethoxymethylsilane as monomer M were charged into a pressure polymerization reactor and mixed. The resulting mixture was stirred at 10,000 rpm for 5 minutes using a homomixer to prepare an emulsion. The resulting emulsion was charged all at once into a five-neck glass container. The glass container was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and ports for adding the monomer and emulsifier. While stirring the added raw materials, (i) a 10% aqueous solution of dodecylbenzenesulfonic acid (DSA) was added to the glass container in an amount equivalent to 1 part by weight of the solids in the solution, followed by (ii) raising the temperature inside the glass container to 80°C over approximately 40 minutes, and (iii) allowing the mixture to react at 80°C for 6 hours. The temperature inside the glass container was then cooled to 25°C, and after the temperature inside the glass container reached 25°C, the mixture was left in the glass container for 20 hours. The pH of the reaction solution was then adjusted to 6.8 using sodium hydroxide to terminate the polymerization. Through these operations, an aqueous latex (R-1) containing an elastomer primarily composed of an organosiloxane rubber was obtained. The polymerization conversion rate of the monomer components was 99% or higher. The volume average particle diameter of the organosiloxane rubber-based elastomer contained in the resulting aqueous latex was 280 nm.

[0210] A glass reactor was charged with 180 parts by weight of an aqueous organosiloxane rubber latex (R-1) (containing 85 parts by weight of an elastomer primarily composed of polyorganosiloxane rubber) and 43 parts by weight of deionized water. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The raw materials were stirred at 60°C while the gas in the glass reactor was replaced with nitrogen. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate heptahydrate, and 0.11 parts by weight of SFS were added to the glass reactor and stirred for 10 minutes. Then, 2.0 parts by weight of triallyl isocyanurate and 0.5 parts by weight of cumene hydroperoxide (QHP) were added to the glass reactor and stirred for 30 minutes. Thereafter, 0.03 parts by weight of QHP was added to the glass reactor and stirred for an additional 60 minutes, yielding an aqueous latex (R-2) containing an elastomer mainly composed of a crosslinked organosiloxane rubber.

[0211] Subsequently, a mixture of 14.25 parts by weight of methyl methacrylate (MMA), 0.75 parts by weight of butyl acrylate (BA), and 0.04 parts by weight of t-butyl hydroperoxide (BHP) was continuously added to the glass reactor containing the resulting aqueous latex (R-2) over a period of 30 minutes. Then, 0.013 parts by weight of BHP was added to the glass reactor, and the mixture in the glass reactor was stirred for an additional hour to complete the polymerization. This procedure yielded an aqueous latex (L-1) containing polymer microparticles (A). The polymerization conversion rate of the monomer components was 99% or higher. The volume average particle diameter of the polymer microparticles (A) contained in the resulting aqueous latex was 290 nm.

[0212] (Production Example 1-2: Preparation of Aqueous Latex (L-2) Containing Polymer Microparticles (A)) An aqueous latex (L-2) containing polymer microparticles (A) was obtained in the same manner as in Production Example 1-1, except that a mixture of 13.5 parts by weight of MMA, 0.75 parts by weight of BA, 0.75 parts by weight of glycidyl methacrylate (GMA), and 0.04 parts by weight of t-butyl hydroperoxide (BHP) was used instead of the mixture of 14.25 parts by weight of MMA, 0.75 parts by weight of BA, 0.75 parts by weight of glycidyl methacrylate (GMA), and 0.04 parts by weight of t-butyl hydroperoxide (BHP). The polymerization conversion rate of the monomer components was 99% or more. The volume average particle diameter of the polymer microparticles (A) contained in the obtained aqueous latex was 292 nm.

[0213] (Production Example 1-3: Preparation of aqueous latex (L-3) containing polymer microparticles (A)) An aqueous latex (L-3) containing polymer microparticles (A) was obtained in the same manner as in Production Example 1-1, except that a mixture of 12.75 parts by weight of MMA, 0.75 parts by weight of BA, 1.5 parts by weight of GMA, and 0.04 parts by weight of t-butyl hydroperoxide (BHP) was used instead of the mixture of 14.25 parts by weight of MMA, 0.75 parts by weight of BA, and 0.04 parts by weight of t-butyl hydroperoxide (BHP) in Production Example 1-1. The polymerization conversion rate of the monomer components was 99% or more. The volume average particle diameter of the polymer microparticles (A) contained in the obtained aqueous latex was 290 nm.

[0214] (Production Example 1-4: Preparation of aqueous latex (L-4) containing polymer microparticles (A)) An aqueous latex (L-4) containing polymer microparticles (A) was obtained in the same manner as in Production Example 1-1, except that a mixture of 10.75 parts by weight of MMA, 0.75 parts by weight of BA, 3.5 parts by weight of GMA, and 0.04 parts by weight of t-butyl hydroperoxide (BHP) was used instead of the mixture of 14.25 parts by weight of MMA, 0.75 parts by weight of BA, 0.04 parts by weight of t-butyl hydroperoxide (BHP) in Production Example 1-1. The polymerization conversion rate of the monomer components was 99% or more. The volume average particle diameter of the polymer microparticles (A) contained in the obtained aqueous latex was 291 nm.

[0215] (Production Example 1-5: Preparation of aqueous latex (L-5) containing polymer microparticles (A)) An aqueous latex (L-5) containing polymer microparticles (A) was obtained in the same manner as in Production Example 1-1, except that a mixture of 9.75 parts by weight of MMA, 0.75 parts by weight of BA, 4.5 parts by weight of GMA, and 0.04 parts by weight of t-butyl hydroperoxide (BHP) was used instead of the mixture of 14.25 parts by weight of MMA, 0.75 parts by weight of BA, and 0.04 parts by weight of t-butyl hydroperoxide (BHP) in Production Example 1-1. The polymerization conversion rate of the monomer components was 99% or more. The volume average particle diameter of the polymer microparticles (A) contained in the obtained aqueous latex was 292 nm.

[0216] (Production Example 1-6: Preparation of aqueous latex (L-6) containing polymer fine particles (A)) 200 parts by weight of deionized water, 0.03 parts by weight of tripotassium phosphate, 0.002 parts by weight of disodium ethylenediaminetetraacetate (EDTA), 0.001 parts by weight of ferrous sulfate heptahydrate, and 1.55 parts by weight of sodium dodecylbenzenesulfonate (SDBS) were charged into a pressure-resistant polymerization vessel. Next, while stirring the charged raw materials, the gas inside the pressure-resistant polymerization vessel was replaced with nitrogen, thereby thoroughly removing oxygen from inside the pressure-resistant polymerization vessel. Thereafter, 100 parts by weight of butadiene (Bd) was charged into the pressure-resistant polymerization vessel, and the temperature inside the pressure-resistant polymerization vessel was raised to 45 ° C. Thereafter, 0.03 parts by weight of paramenthane hydroperoxide (PHP) was charged into the pressure-resistant polymerization reactor, followed by 0.10 parts by weight of sodium formaldehyde sulfoxylate (SFS) to initiate polymerization. Fifteen hours after the start of polymerization, the polymerization was terminated by devolatilization under reduced pressure to remove the remaining monomers that had not been used in the polymerization. During the polymerization, PHP, EDTA, and ferrous sulfate heptahydrate were each added to the pressure-resistant polymerization reactor in desired amounts and at desired times. This polymerization yielded an aqueous latex (R-2) containing an elastomer (core layer) primarily composed of polybutadiene rubber. The volume average particle diameter of the elastomer (core layer) contained in the resulting aqueous latex was 90 nm.

[0217] Into a pressure-resistant polymerization vessel, 7 parts by weight (solids content) of the polybutadiene rubber latex (R-2) obtained above, 200 parts by weight of deionized water, 0.03 parts by weight of tripotassium phosphate, 0.002 parts by weight of EDTA, and 0.001 parts by weight of ferrous sulfate heptahydrate were charged. Next, while stirring the charged raw materials, the gas inside the pressure-resistant polymerization vessel was replaced with nitrogen, thereby thoroughly removing oxygen from inside the pressure-resistant polymerization vessel. Thereafter, 93 parts by weight of Bd were charged into the pressure-resistant polymerization vessel, and the temperature inside the pressure-resistant polymerization vessel was raised to 45°C. Thereafter, 0.02 parts by weight of PHP was charged into the pressure-resistant polymerization vessel, followed by 0.10 parts by weight of SFS, to initiate polymerization. Thirty hours after the start of polymerization, devolatilization was carried out under reduced pressure to remove the remaining monomer not used in the polymerization, thereby terminating the polymerization. During the polymerization, PHP, EDTA, and ferrous sulfate heptahydrate were each added to the pressure polymerization reactor in desired amounts and at desired times. This polymerization yielded an aqueous latex (R-3) containing an elastomer (core layer) primarily composed of polybutadiene rubber. The volume average particle diameter of the elastomer (core layer) contained in the resulting aqueous latex was 195 nm.

[0218] 260 parts by weight of the polybutadiene rubber latex (R-3) (containing 85 parts by weight of an elastomer primarily composed of polybutadiene rubber) and 50 parts by weight of deionized water were placed in a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The raw materials were stirred at 60°C while the gas in the glass reactor was replaced with nitrogen. Next, 1.8 parts by weight of 1,3-butylene glycol dimethacrylate and 0.07 parts by weight of t-butyl hydroperoxide (BHP) were added to the glass reactor and stirred for 10 minutes. Then, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate heptahydrate, and 0.13 parts by weight of SFS were added to the glass reactor and stirred for 30 minutes. Thereafter, 0.013 parts by weight of BHP was added to the glass reactor and stirred for an additional 30 minutes. Then, a mixture of 14.25 parts by weight of MMA, 0.75 parts by weight of BA, and 0.05 parts by weight of BHP was continuously added to the glass reactor over 60 minutes. Then, 0.013 parts by weight of BHP was added to the glass reactor, and the mixture in the glass reactor was stirred for an additional hour to complete the polymerization. Through the above operations, an aqueous latex (L-6) containing polymer microparticles (A) was obtained. The polymerization conversion rate of the monomer components was 99% or more. The volume average particle diameter of the polymer microparticles (A) contained in the obtained aqueous latex was 200 nm.

[0219] (Production Example 1-7: Preparation of aqueous latex (L-7) containing polymer microparticles (A)) An aqueous latex (L-7) containing polymer microparticles (A) was obtained in the same manner as in Production Example 1-6, except that a mixture of 12.75 parts by weight of MMA, 0.75 parts by weight of BA, 1.5 parts by weight of GMA, and 0.05 parts by weight of BHP was used instead of the mixture of 14.25 parts by weight of MMA, 0.75 parts by weight of BA, and 0.05 parts by weight of BHP in Production Example 1-6. The polymerization conversion rate of the monomer components was 99% or more. The volume average particle diameter of the polymer microparticles (A) contained in the obtained aqueous latex was 200 nm.

[0220] (Production Example 1-8: Preparation of aqueous latex (L-8) containing polymer microparticles (A)) An aqueous latex (L-8) containing polymer microparticles (A) was obtained in the same manner as in Production Example 1-6, except that a mixture of 9.75 parts by weight of MMA, 0.75 parts by weight of BA, 4.5 parts by weight of GMA, and 0.05 parts by weight of BHP was used instead of the mixture of 14.25 parts by weight of MMA, 0.75 parts by weight of BA, and 0.05 parts by weight of BHP. The polymerization conversion rate of the monomer components was 99% or more. The volume average particle diameter of the polymer microparticles (A) contained in the obtained aqueous latex was 200 nm.

[0221] 2. Preparation of Granular Material Example 1 Preparation of Granular Material (P-2) Water, 100 parts by weight of epoxidized soybean oil (resin (B)), and SDBS (emulsifier) ​​were mixed using a homogenizer to prepare an aqueous emulsion (S-1) (resin (B) content: 50%) in which resin (B) was emulsified. Additionally, 4 parts by weight of calcium acetate was dissolved in 600 parts by weight of ion-exchanged water adjusted to 70°C. Next, 250 parts by weight of aqueous latex (L-2) equivalent to 100 parts by weight of polymer fine particles (A) and 22.2 parts by weight of the aqueous emulsion (S-1) (equivalent to 11.1 parts by weight of resin (B)) were added to 600 parts by weight of the ion-exchanged water to obtain a slurry containing a coagulated product containing polymer fine particles (A) and resin (B). The slurry was then centrifuged to obtain a wet powder of the coagulated product. Furthermore, the wet powder obtained was subjected to a total of two cycles of adding the wet powder to 500 parts by weight of ion-exchanged water and centrifugal dehydration of the resulting mixture, to obtain a wet powder. Finally, the wet powder was dried in a dryer at 50°C for 48 hours to obtain powder (P-2). The dispersibility of the obtained powder in the matrix resin was measured using the method described above in the section (Dispersibility of powder in matrix resin). The results are shown in Table 1.

[0222] A resin composition was prepared using the powder (P-2) according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). Furthermore, a cured product was prepared using this resin composition according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). The elastic modulus and linear expansion coefficient of the obtained cured product were measured according to the methods described above. The results are shown in Table 1.

[0223] (Example 2: Preparation of powder (P-3)) ​​Powder (P-3) was obtained in the same manner as in Example 1, except that the aqueous latex (L-3) was used instead of the aqueous latex (L-2) in Example 1. The dispersibility of the obtained powder in the matrix resin was measured by the method described above in the section (Dispersibility of powder in matrix resin). The results are shown in Table 1.

[0224] A resin composition was prepared using the powder (P-3) according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). Furthermore, a cured product was prepared using this resin composition according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). The elastic modulus and linear expansion coefficient of the obtained cured product were measured according to the methods described above. The results are shown in Table 1.

[0225] (Example 3: Preparation of powdery granule (P-4)) Powdery granule (P-4) was obtained in the same manner as in Example 1, except that in Production Example 2-1, aqueous latex (L-4) was used instead of aqueous latex (L-2). The dispersibility of the obtained powdery granule in the matrix resin was measured by the method described above in the section (Dispersibility of powdery granule in matrix resin). The results are shown in Table 1.

[0226] A resin composition was prepared using the powder (P-4) according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). Furthermore, a cured product was prepared using this resin composition according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). The elastic modulus and linear expansion coefficient of the obtained cured product were measured according to the methods described above. The results are shown in Table 1.

[0227] Comparative Example 1: Preparation of Powder and Granule (P-1) Powder and granule (P-1) was obtained in the same manner as in Example 1, except that the aqueous latex (L-1) was used instead of the aqueous latex (L-2) in Example 1. The dispersibility of the obtained powder and granule in the matrix resin was measured by the method described above in the section (Dispersibility of powder and granule in matrix resin). The results are shown in Table 1.

[0228] A resin composition was prepared using the powder (P-1) according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). Furthermore, a cured product was prepared using this resin composition according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). The elastic modulus and linear expansion coefficient of the obtained cured product were measured according to the methods described above. The results are shown in Table 1.

[0229] Comparative Example 2: Preparation of Powder (P-5) Powder (P-5) was obtained in the same manner as in Example 1, except that the aqueous latex (L-5) was used instead of the aqueous latex (L-2) in Example 1. The dispersibility of the obtained powder in the matrix resin was measured by the method described above in the section (Dispersibility of powder in matrix resin). The results are shown in Table 1.

[0230] A resin composition was prepared using the powder (P-5) according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). Furthermore, a cured product was prepared using this resin composition according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). The elastic modulus and linear expansion coefficient of the obtained cured product were measured according to the methods described above. The results are shown in Table 1.

[0231] Comparative Example 3: Preparation of Granular Material (P-6) (i) Water, (ii) Resin (B), a mixture of 90 parts by weight of epoxidized soybean oil and 10 parts by weight of triethylene glycol bis[3-(-t-butyl-4-hydroxy-5-methylphenyl)propionate], and (iii) emulsifier SDBS were mixed together using a homogenizer to prepare an aqueous emulsion (S-2) (resin (B) content: 11.1%) in which Resin (B) was emulsified. Granular material (P-6) was obtained in the same manner as in Example 1, except that 22.2 parts by weight of aqueous emulsion (S-2) was used instead of 22.2 parts by weight of aqueous emulsion (S-1) and aqueous latex (L-6) was used instead of aqueous latex (L-2). The dispersibility of the obtained granular material in the matrix resin was measured using the method described above in the section (Dispersibility of granular material in matrix resin). The results are shown in Table 1.

[0232] A resin composition was prepared using the powder (P-6) according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). Furthermore, a cured product was prepared using this resin composition according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). The elastic modulus and linear expansion coefficient of the obtained cured product were measured according to the methods described above. The results are shown in Table 1.

[0233] (Comparative Example 4: Preparation of powder / granule (P-7)) Powder / granule (P-7) was obtained in the same manner as in Comparative Example 3, except that the aqueous latex (L-7) was used instead of the aqueous latex (L-6) in Comparative Example 3. The dispersibility of the obtained powder / granule in the matrix resin was measured by the method described above in the section (Dispersibility of powder / granule in matrix resin). The results are shown in Table 1.

[0234] A resin composition was prepared using the powder (P-7) according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). Furthermore, a cured product was prepared using this resin composition according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). The elastic modulus and linear expansion coefficient of the obtained cured product were measured according to the methods described above. The results are shown in Table 1.

[0235] (Comparative Example 5: Preparation of powder / granule (P-8)) Powder / granule (P-8) was obtained in the same manner as in Comparative Example 3, except that the aqueous latex (L-8) was used instead of the aqueous latex (L-6) in Comparative Example 3. The dispersibility of the obtained powder / granule in the matrix resin was measured by the method described above in the section (Dispersibility of powder / granule in matrix resin). The results are shown in Table 1.

[0236] A resin composition was prepared using the powder (P-8) according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). Furthermore, a cured product was prepared using this resin composition according to the method described above in the section (Measurement of physical properties of cured epoxy + silica blend). The elastic modulus and linear expansion coefficient of the obtained cured product were measured according to the methods described above. The results are shown in Table 1.

[0237] Comparative Example 6 In Comparative Example 6, no stress-reducing agent (powder or granule) was used. A resin composition was prepared in the same manner as described above in the section (Measurement of Physical Properties of Cured Epoxy + Silica Blend) except that no powder or granule was used, i.e., 33.3 parts by weight of bisphenol A epoxy resin was used instead of 33.3 parts by weight of the resin composition containing the powder or granule. Furthermore, a cured product was prepared using this resin composition in the same manner as described above in the section (Measurement of Physical Properties of Cured Epoxy + Silica Blend). The elastic modulus and linear expansion coefficient of the obtained cured product were measured using the same methods as described above. The results are shown in Table 1.

[0238] [Results] Table 1 reveals the following: (1) When a stress-reducing agent is prepared using the polymer microparticles (A) of Examples 1 to 3, which have an elastomer containing an organosiloxane-based rubber and a rubber-containing graft copolymer having a graft portion graft-bonded to the elastomer, the cured product has an equally low modulus of elasticity and a significantly smaller linear expansion coefficient, i.e., a better linear expansion coefficient, compared to Comparative Examples 3 to 5, which use polymer microparticles not containing an organosiloxane-based rubber as the elastomer.

[0239] (2) With regard to the polymer microparticles, when a stress-reducing agent is prepared using the polymer microparticles (A) of Examples 1 to 3 in which the graft moiety contains an epoxy group-containing structural unit, the elastic modulus of the cured product is lower and the linear expansion coefficient is better than that of Comparative Example 1 in which the polymer microparticles in which the graft moiety does not contain an epoxy group-containing structural unit are used.

[0240] (3) The polymer microparticles (A) of Examples 1 to 3, in which the content of the epoxy group-containing structural unit in the graft portion relative to the rubber-containing graft copolymer is 4.0% by weight or less, are found to have superior dispersibility in the matrix resin before curing, compared with the polymer microparticles of Comparative Example 2, in which the content is 4.5% by weight.

[0241] One embodiment of the present invention can provide a stress-reducing agent that (i) has excellent dispersibility in matrix resins and (ii) can provide a cured product with a good linear expansion coefficient. Therefore, a resin composition containing the stress-reducing agent according to one embodiment of the present invention can be suitably used as an encapsulant for electronic materials and the like.

Claims

1. A stress reducing agent containing polymer fine particles (A), the polymer fine particles (A) contain a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, a ratio of the elastomer in the polymer fine particles (A) is more than 70% by weight and not more than 97% by weight based on 100% by weight of the polymer fine particles (A), The elastic body includes an organosiloxane rubber, The graft portion contains an epoxy group-containing structural unit, the epoxy group-containing constitutional unit in the graft portion is contained in an amount of 0.5% by weight or more and less than 3.2% by weight based on 100% by weight of the rubber-containing graft copolymer; The stress reducing agent is a powder or granular material.

2. 2. The stress reducing agent according to claim 1, wherein the epoxy group-containing constitutional unit in the graft portion is contained in an amount of 3.3% by weight to 26.7% by weight relative to 100% by weight of the graft portion in the rubber-containing graft copolymer.

3. A stress reducing agent containing polymer fine particles (A), the polymer fine particles (A) contain a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, a ratio of the elastomer in the polymer fine particles (A) is 85% by weight or more and 97% by weight or less with respect to 100% by weight of the polymer fine particles (A), The elastic body includes an organosiloxane rubber, The graft portion contains an epoxy group-containing structural unit, the epoxy group-containing constitutional unit in the graft portion is contained in an amount of 3.3% by weight to 26.7% by weight based on 100% by weight of the graft portion in the rubber-containing graft copolymer; The stress reducing agent is a powder or granular material.

4. The stress reducing agent according to any one of claims 1 to 3, wherein the epoxy group-containing constitutional unit in the graft portion is a glycidyl methacrylate unit.

5. The stress reducing agent according to any one of claims 1 to 3, further comprising a resin (B).

6. A resin composition comprising the stress reducing agent according to any one of claims 1 to 3, a thermosetting resin, and an inorganic filler.

7. The resin composition according to claim 6 , wherein the thermosetting resin is an epoxy resin and the inorganic filler is silica.

8. An encapsulant comprising the resin composition according to claim 6 .

9. An encapsulant comprising the resin composition according to claim 7.

10. A method for producing a resin composition, comprising a step of mixing a stress reducing agent containing polymer fine particles (A), a thermosetting resin, and an inorganic filler, the polymer fine particles (A) contain a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, a ratio of the elastomer in the polymer fine particles (A) is more than 70% by weight and not more than 97% by weight based on 100% by weight of the polymer fine particles (A), The elastic body includes an organosiloxane rubber, The graft portion contains an epoxy group-containing structural unit, the epoxy group-containing constitutional unit in the graft portion is contained in an amount of 0.5% by weight or more and less than 3.2% by weight based on 100% by weight of the rubber-containing graft copolymer; The method for producing a resin composition, wherein the stress reducing agent is a powder or granular material.

11. The method for producing a resin composition according to claim 10, wherein the epoxy group-containing constitutional unit in the graft portion is contained in an amount of 3.3% by weight to 26.7% by weight relative to 100% by weight of the graft portion in the rubber-containing graft copolymer.

12. A method for producing a resin composition, comprising a step of mixing a stress reducing agent containing polymer fine particles (A), a thermosetting resin, and an inorganic filler, the polymer fine particles (A) contain a rubber-containing graft copolymer having an elastomer and a graft portion graft-bonded to the elastomer, a ratio of the elastomer in the polymer fine particles (A) is 85% by weight or more and 97% by weight or less with respect to 100% by weight of the polymer fine particles (A), The elastic body includes an organosiloxane rubber, The graft portion contains an epoxy group-containing structural unit, the epoxy group-containing constitutional unit in the graft portion is contained in an amount of 3.3% by weight to 26.7% by weight based on 100% by weight of the graft portion in the rubber-containing graft copolymer; The method for producing a resin composition, wherein the stress reducing agent is a powder or granular material.

13. The method for producing a resin composition according to any one of claims 10 to 12, wherein the epoxy group-containing structural unit in the graft portion is a glycidyl methacrylate unit.

14. The method for producing a resin composition according to any one of claims 10 to 12, wherein the stress reducing agent further contains a resin (B).

15. The method for producing a resin composition according to any one of claims 10 to 12, wherein the thermosetting resin is an epoxy resin, and the inorganic filler is silica.