JP2008189860A - Silicone rubber graft copolymer and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicone rubber graft copolymer having excellent low-temperature impact resistance and solvent resistance as well and to provide its production method. <P>SOLUTION: The silicone rubber graft copolymer is one comprising a core (1) formed from a polyorganosiloxane, an intermediate layer (2) formed from a rubber-like polymer formed from an alkyl (meth)acrylate with a 2-8C alkyl, and an outermost layer (3) made from a polymer formed from one or more vinyl monomers, wherein the outermost layer is crosslinked with a crosslinking monomer in an amount of 0.5-20 wt.% based on the entire weight of the monomer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a silicone rubber graft copolymer having excellent low temperature impact resistance and at the same time having excellent solvent resistance, and a method for producing the same.

  It has been widely practiced to improve the impact resistance performance, particularly impact resistance performance at a low temperature of 0 ° C. or lower by blending graft copolymer particles containing a silicone rubber component with a thermoplastic resin. For example, it is known to use graft copolymer particles obtained by graft-polymerizing a vinyl monomer to a composite rubber composed of a core of crosslinked silicone rubber particles and a shell of crosslinked acrylic rubber (Patent Document 1).

  Also known is a graft copolymer particle obtained by graft-polymerizing a vinyl monomer to a composite rubber comprising a core of a crosslinked acrylic rubber particle and a shell of a crosslinked silicone rubber (Patent Document 2).

  Furthermore, the graft copolymer particles obtained by graft-polymerizing a vinyl monomer to a composite rubber having a structure in which a polyorganosiloxane rubber component and a polyalkyl (meth) acrylate rubber component are intertwined so that they cannot be separated from each other have already been obtained. Known (Patent Documents 3, 4 and 5).

JP-A-62-280210 JP-A 64-6012 Japanese Patent Laid-Open No. 4-100812 JP-A-1-190746 Japanese Patent Laid-Open No. 1-279954

However, a resin composition obtained by kneading a graft copolymer containing a silicone rubber described in the above-mentioned patent document as an impact-resistant modifying resin into a thermoplastic resin has poor pigment colorability and has a gloss derived from a silicone rubber component. Only a molded product with a surface appearance with no surface can be obtained. As a method for improving this problem, coloring is not performed by adding a pigment but by spraying a paint on the surface of the resin composition. However, since most of the paint used at this time is a solvent-based paint, the impact-resistant modified resin swells or deteriorates due to the solvent. This causes a decrease in the adhesion and strength of the paint film, and the paint film sprayed by an impact such as dropping may peel off. Therefore, there is a strong demand for the development of an impact-resistant modified resin that has excellent solvent resistance without impairing impact resistance over a wide temperature range, particularly at low temperatures.

As a result of intensive studies to solve the above problems, the present inventors have
Resin obtained by seed polymerizing alkyl (meth) acrylate monomer on polyorganosiloxane core and graft polymerizing vinyl monomer containing crosslinkable monomer to the resulting particles Knew that the problem could be solved, and further research was completed to complete the present invention.
That is, the present invention
1. A core (1) formed of polyorganosiloxane, an intermediate layer (2) composed of a rubbery polymer formed by polymerization of an alkyl (meth) acrylate monomer having an alkyl group with 2 to 8 carbon atoms, a kind Or it has the outermost layer (3) which consists of a polymer formed by superposition | polymerization of 2 or more types of vinylic monomers, and an outermost layer (3) is 0.5-20 weight with respect to the whole quantity of the monomer. % Silicone rubber graft copolymer crosslinked with a crosslinkable monomer.
2. An intermediate comprising a rubbery polymer formed by polymerization of an alkyl (meth) acrylate monomer having a core (1) formed by polyorganosiloxane of 5 to 70% by weight and an alkyl group having 2 to 8 carbon atoms. 2. The silicone according to 1, wherein the layer (2) is 15 to 80% by weight, and the outermost layer (3) made of a polymer formed by polymerization of one or more vinyl monomers is 10 to 30% by weight. Rubber graft copolymer.
3. 3. The silicone rubber graft copolymer of 1 or 2 above, wherein the outermost layer (3) is a styrene-acrylonitrile copolymer.
It is.

  First, a core (1) formed of polyorganosiloxane, that is, silicone rubber seed fine particles is produced. This polyorganosiloxane (1) is a copolymer of silicone rubber-forming components comprising an organosiloxane (1-1), a polyfunctional silane compound (1-2) and a silane compound (1-3) having a vinyl polymerizable group. Is obtained.

  The organosiloxane (1-1) is a component for constituting the main skeleton of the silicone rubber (1), and as a specific example thereof, a linear or branched one can be used. Cyclic siloxane is preferred from the viewpoint of applicability of the polymerization system and economy. Specific examples thereof include 6- to 12-membered hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and the like. These may be used alone or in combination of two or more.

  The compound (1-2) is a component that is copolymerized with the organosiloxane (1-1), functions as a crosslinking agent that introduces a crosslinking bond into the silicone rubber (1), and exhibits rubber elasticity. Specific examples thereof include tetramethoxysilane, tetraethoxysilane, triethoxymethylsilane, triethoxyethylsilane and the like.

  The compound (1-3) functions as a graft crossing agent and is a component for providing a graft active point of the alkyl (meth) acrylate monomer (2-1) described later. Further, it is a component that can be used as a crosslinking agent because a radical reaction can be caused between the graft active sites by a normal radical polymerization initiator to form a crosslinking bond. Even when cross-linking is carried out by radical reaction, grafting is possible because part of the graft active site remains. Specific examples of the compound (1-3) include β-methacryloyloxyethyldimethoxymethylsilane, γ-methacryloyloxypropylmethoxydimethylsilane, γ-methacryloyloxypropyldimethoxymethylsilane, γ-methacryloyloxypropyltrimethoxysilane, and γ-methacryloyl. Examples include oxypropylethoxydiethylsilane, γ-methacryloyloxypropyldiethoxymethylsilane, and δ-methacryloyloxybutyldiethoxymethylsilane. In addition, what a silane compound (1-3) is a trialkoxysilane type has also the function of the said compound (1-2), Therefore It can be used as a graft crossing agent and a crosslinking agent. In addition to these, cyclic siloxanes having a vinyl polymerizable group in the molecule, such as tetravinyltetramethylcyclotetrasiloxane and tetramethacryloyloxypropyltetramethylcyclotetrasiloxane, can also be used.

  The compound (1-1) is used in a proportion of 70 to 99.9% of the compound (1-1) used as the component for forming the silicone rubber (1). -2) is 0 to 15%, compound (1-3) is 0 to 15% ((1-2) and (1-3) are not 0% at the same time. %), The total amount of these is adjusted to 100%. Moreover, it is preferable that a compound (1-1) is 80 to 99.8%, a compound (1-2) is 0.1 to 10%, and a compound (1-3) is 0.1 to 10%, More preferably, the compound (1-1) is 90 to 99%, the compound (1-2) is 0.3 to 5%, and the compound (1-3) is 0.3 to 5%.

  When the amount of the organosiloxane (1-1) is too small, characteristics such as flexibility of the obtained silicone rubber tend to be difficult to express, and therefore usually 70% or more, preferably 80% or more, more preferably Is 90% or more. In addition, when the amount of the organosiloxane (1-1) is too large, the amount of the other compounds (1-2) and (1-3) becomes too small and the effect of using these compounds is manifested. Therefore, it is usually 99.9% or less, preferably 99.8% or less, and more preferably 99% or less.

  When neither the compound (1-2) nor the compound (1-3) is used, the impact resistance tends to decrease, and either one is 0.1% or more, preferably both are 0.2% or more, More preferably, both use 0.3% or more. Moreover, if any compound is used too much, the properties such as the flexibility of the silicone rubber are hardly expressed, and it is usually 15% or less, preferably 10% or less, more preferably 5% or less.

  The polymerization of each forming component of the silicone rubber (1) is carried out by a method in which each forming component of the silicone rubber (1) is emulsified and dispersed in water by mechanical shearing in the presence of an emulsifier and heated and stirred in an acidic state to polymerize. A means known per se can be employed.

  As the emulsifier, an anionic emulsifier is preferable, and a nonionic emulsifier can be used in combination. As the anionic emulsifier, those selected from sodium alkylbenzene sulfonate, sodium lauryl sulfonate, sodium sulfosuccinate and the like are used. Examples of nonionic emulsifiers include polyoxyethylene alkyl ether, poxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester and the like. In the present invention, it is particularly preferable to use a sulfonic acid-based emulsifier such as sodium alkylbenzene sulfonate and sodium lauryl sulfonate.

  These emulsifiers are used in the range of about 0.5 to 5 parts by weight with respect to 100 parts by weight of the total amount of the organosiloxane monomer. If the amount used is small, the dispersion state becomes unstable and the emulsified state with a minute particle size cannot be maintained. Further, when the amount used is large, coloring due to the emulsifier of polyorganosiloxane may occur.

  Mechanical shearing can be obtained by using a high-speed stirrer such as a homomixer, or a disperser such as a high-pressure homogenizer or an ultrasonic disperser.

  The acidic state can be obtained by adding inorganic acids such as sulfuric acid and hydrochloric acid and organic acids such as alkylbenzene sulfonic acid, alkyl sulfonic acid, and trifluoroacetic acid to the system, and the pH does not corrode the production equipment and has an appropriate polymerization rate. It is preferable to adjust to 1.0 to 3.0 in terms of being obtained, and it is more preferable to adjust to 1.2 to 2.5.

  The heating for the polymerization is preferably 60 to 120 ° C, more preferably 70 to 100 ° C in that an appropriate polymerization rate can be obtained.

  In addition, since the Si—O—Si bond forming the skeleton of the silicone rubber is in an equilibrium state of cleavage and formation under an acidic state, sodium hydroxide, It is preferable to neutralize by adding an alkaline aqueous solution such as potassium hydroxide or sodium carbonate. Furthermore, this equilibrium proceeds to the production side as the temperature becomes lower, and it becomes easier to produce a polymer having a high molecular weight or a high degree of cross-linking. After carrying out at 60 degreeC or more, it is preferable to neutralize, after cooling to below room temperature and hold | maintaining for about 5 to 100 hours.

  An alkyl (meth) acrylate monomer having an alkyl group having 2 to 8 carbon atoms and a polyfunctional alkyl (meth) in the aqueous dispersion of polysiloxane seed fine particles, that is, the core (1) thus obtained. A silicone-acrylic composite rubber can be obtained by adding an acrylate monomer and radical polymerization in one or more stages.

  As the polymerization initiator, a peroxide, an azo initiator, or a redox initiator combined with an oxidizing agent / reducing agent is used. In this, a redox-type initiator is preferable, and the initiator which combined ferrous sulfate, ethylenediaminetetraacetic acid disodium salt, L-ascorbic acid, and hydroperoxide is especially preferable.

  The acrylic rubber intermediate layer (2) is at least one monomer selected from the group consisting of acrylic acid alkyl ester monomers having 2 to 8 carbon atoms in the alkyl group (hereinafter referred to as monomer (2). -1)) and a polyfunctional alkyl (meth) acrylate monomer (hereinafter also referred to as monomer (2-2)).

  The acrylic rubber intermediate layer (2) does not need to be formed of only one layer, and is a two-layer obtained by radical polymerization of the monomer (2-1) and the monomer (2-2) stepwise. Alternatively, it may be composed of a plurality of layers having a three-layer structure.

  Specific examples of the monomer (2-1) include alkyl acrylates having 2 to 8 carbon atoms such as ethyl acrylate, propyl acrylate, n-butyl acrylate, and ethyl methacrylate, propyl methacrylate, n- Examples thereof include alkyl methacrylate having a C 2-8 alkyl group such as butyl methacrylate. These monomers (2-1) may be used independently and may use 2 or more types together. Among these, n-butyl acrylate is preferable from the viewpoint of low Tg of the obtained polymer and economical efficiency.

  Specific examples of the polyfunctional alkyl (meth) acrylate monomer (2-2) include allyl methacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, and 1,4-butylene. A glycol dimethacrylate etc. are mentioned, It can use individually or in combination of 2 or more types. The usage-amount of polyfunctional alkyl (meth) acrylate (2-2) is 0.1-20 weight% normally with respect to the total amount of an alkyl (meth) acrylate monomer, Preferably it is 0.5-10 weight %.

  A composite rubber in which a vinyl monomer (3-1) is further graft-polymerized to the composite rubber particles produced as described above, and a polymer of a vinyl monomer is grafted onto the composite rubber particles. Containing graft copolymer particles (3) (hereinafter also referred to as graft copolymer particles) are obtained.

  The vinyl monomer (3-1) improves the compatibility of the resulting graft copolymer particles (3) with the thermoplastic resin blended, and the graft copolymer particles are uniformly dispersed in the thermoplastic resin. It is used to make it.

  The average particle diameter of the graft copolymer particles (3) is preferably 0.03 μm or more, more preferably 0.06 μm or more, and preferably 1.2 μm or less, more preferably 1 μm or less. When the particle size is smaller or larger than that, the impact resistance tends to decrease.

  Specific examples of the vinyl monomer (3-1) include aromatic vinyl monomers such as styrene, α-methyl styrene and paramethyl styrene, and vinyl cyanide monomers such as acrylonitrile and methacrylonitrile. Methacrylic acid such as vinyl chloride, vinylidene chloride, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, glycidyl methacrylate, hydroxyethyl methacrylate, etc. Examples thereof include acid monomers, acrylic acid, methyl acrylate, butyl acrylate, glycidyl acrylate, acrylic acid monomers such as hydroxyethyl acrylate, and acrylic acid monomers composed of esters thereof. According to the present invention, the hard outermost layer (3) subjected to crosslinking is particularly preferably composed mainly of a styrene-acrylonitrile copolymer.

  The amount of the vinyl monomer used is preferably 60 to 95% by weight, more preferably 70 to 90% by weight of the composite rubber particles composed of the core (1) and the intermediate layer (2). Preferably, it is 5 to 40% by weight, more preferably 10 to 30% by weight so that the total amount becomes 100% by weight. When the amount of the vinyl monomer used is too large, the rubber component content tends to be too small to exhibit sufficient impact resistance. Therefore, the compatibility with the thermoplastic resin, which is a matrix resin, deteriorates when blended with a thermoplastic resin, and the impact resistance tends to decrease.

  In the present invention, 0.5 to 20% by weight, preferably 1 to 15% by weight, more preferably 2 to 10% by weight of the crosslinkable monomer based on the total amount of the vinyl monomer forming the outermost layer (3). The body (3-2) is mixed and polymerized. This cross-linking agent introduces a cross-linking bond into the vinyl monomer to form a network structure to express rubber elasticity and solvent resistance, and also acts as a graft crossing agent. It is also a component for providing a graft active point of a vinyl monomer used when obtaining polymer particles. Specific examples thereof include divinylbenzene, allyl methacrylate, diallyl phthalate, and ethylene glycol dimethacrylate. Of these, divinylbenzene is preferably used. Moreover, these crosslinkable monomers may be used independently and may use 2 or more types together.

  The graft polymerization can be performed by using a usual emulsion polymerization method. As the radical polymerization initiator used for the polymerization, a peroxide or an azo initiator can be used. In the case of using an emulsifier, those that can be used in the production of the silicone rubber can be used.

  A preferred form of graft polymerization is a method in which a mixture of a vinyl monomer and a radical polymerization initiator is dropped into an emulsion of composite rubber particles (2) for polymerization.

  In the polymerization of the vinyl monomer in the presence of the composite rubber particle emulsion, the portion corresponding to the branch of the graft copolymer (here, the polymer of the vinyl monomer) is the trunk component (here, the composite rubber particle). In other words, a so-called free polymer obtained by polymerizing only the branch component alone without grafting is obtained as a by-product, and is obtained as a mixture of the graft copolymer and the free polymer. It is called a polymer.

  The graft copolymer particles after polymerization may be used by separating the polymer from the emulsion when blended with a thermoplastic resin, or may be used as an emulsion. Methods for separating the polymer include known methods such as adding a metal salt such as calcium chloride, magnesium chloride, and magnesium sulfate to the emulsion, and freezing and thawing the emulsion to solidify, separate, wash, dehydrate the emulsion, The method of drying is mention | raise | lifted. A spray drying method can also be used.

  A core (1) formed of polyorganosiloxane, an intermediate layer (2) made of a rubber-like polymer formed of an alkyl (meth) acrylate monomer having an alkyl group with 2 to 8 carbon atoms, Crosslinkability having an outermost layer (3) made of a polymer formed of two or more kinds of vinyl monomers, and the outermost layer accounts for 0.5 to 20% by weight with respect to the total amount of the monomers The amount of (1), (2) and (3) used in the silicone rubber graft copolymer crosslinked with the monomer is such that (1) is 5 to 70% by weight, preferably 5 to 50% by weight (2 ) Is 15 to 80% by weight, preferably 30 to 70% by weight (3) is 10 to 30% by weight, preferably 15 to 25% by weight.

  The silicone rubber graft copolymer can be used by blending with a thermoplastic resin. Specific examples of the thermoplastic resin include polyvinyl chloride resin, polystyrene resin, styrene-acrylonitrile copolymer resin, styrene-acrylonitrile. -N-phenylmaleimide copolymer resin, α-methylstyrene-acrylonitrile copolymer resin, polymethyl methacrylate resin, methyl methacrylate-styrene copolymer resin, polycarbonate resin, polyamide resin, polyethylene terephthalate, polybutylene terephthalate, and other polyester resins Etc.

  The amount of the graft copolymer particles added to 100 parts of the thermoplastic resin is 0.5 to 50 parts, and preferably 1 to 30 parts from the viewpoint of balance of physical properties. When the addition amount is too small, the impact resistance of the thermoplastic resin is not sufficiently improved, and when it is too large, it is difficult to maintain the properties such as rigidity and surface hardness of the thermoplastic resin.

  The graft copolymer particles obtained by separating the polymer particles from the emulsion and the thermoplastic resin can be mixed by mixing with a Henschel mixer, a ribbon blender, or the like, and then melt-kneading with a roll, an extruder, a kneader, or the like. .

  In this melt-kneading, usually used compounding agents, that is, plasticizers, stabilizers, lubricants, ultraviolet absorbers, antioxidants, flame retardants, pigments, glass fibers, fillers, polymer processing aids, polymer lubricants, etc. Can be blended.

  When the thermoplastic resin is produced by an emulsion polymerization method, both the emulsion of the thermoplastic resin and the emulsion of the graft copolymer particles are blended in the state of emulsion and then co-coagulated to make the thermoplasticity. It is also possible to obtain a resin composition.

  As a molding method of the obtained thermoplastic resin composition, a molding method used for molding a normal thermoplastic resin composition, that is, an injection molding method, an extrusion molding method, a blow molding method, a calendar molding method, or the like is applied. be able to.

  The obtained molded article has excellent coating film adhesion without impairing the impact resistance even at a low temperature of −30 ° C. as compared with the one using a conventional impact modifier.

  Hereinafter, the present invention will be specifically described with reference to examples. Parts are parts by weight unless otherwise noted.

Production method of silicone core Production of polyorganosiloxane latex 1.25 parts of tetraethoxysilane, 0.75 part of γ-methacryloxypropylmethyldimethoxysilane and 98 parts of octamethyltetracyclosiloxane were mixed, and 100 parts of siloxane-based mixture was added. Obtained. To this was added 200 parts of distilled water in which 2 parts of sodium dodecylbenzenesulfonate was dissolved, and the mixture was stirred and predispersed at 1500 rpm for 30 minutes with a disper. An organosiloxane emulsion was obtained.
Next, after the emulsion was put into a separable flask equipped with a cooling condenser, a mixture of 0.20 parts of sulfuric acid and 49.8 parts of distilled water was allowed to flow down over 5 minutes. Subsequently, the temperature was maintained for 8 hours while being heated to 80 ° C., and then cooled. Subsequently, the obtained reaction product was kept at room temperature for 14 hours, and then neutralized to pH 7.5 with 10% aqueous sodium hydroxide solution. Thus, a polyorganosiloxane latex was obtained.
The latex thus obtained was dried at 160 ° C. for 1.5 hours and the solid content was determined to be 26.2%. The number average particle size of this latex was 194 nm.

Formation of Intermediate Layer 38.2 parts of the polyorganosiloxane latex obtained by the above reaction was collected in a separable flask, and 100 parts of distilled water was added thereto and mixed. Subsequently, the atmosphere in the flask was replaced with nitrogen by passing a nitrogen stream through the separable flask, and then the temperature was raised to 60 ° C. Next, a mixture consisting of 14.85 parts of butyl acrylate, 0.15 part of allyl methacrylate and 0.2 part of tertiary butyl hydroperoxide was added at once and stirred for 1 hour.
After stirring, an aqueous solution in which 0.0006 parts of ferrous sulfate and 0.32 parts of L-ascorbic acid were dissolved in 10 parts of distilled water was added to initiate radical polymerization. After confirming the exothermic peak due to the reaction, the liquid temperature was adjusted to 70 ° C., and a mixture of 54.3 parts of butyl acrylate, 0.7 part of allyl methacrylate and 0.55 part of tertiary butyl hydroperoxide was added dropwise over 2 hours. And polymerized. In order to complete the polymerization of the acrylate component, the liquid temperature was maintained at 70 ° C. for 1.5 hours to obtain a composite rubber latex composed of polybutyl acrylate using polyorganosiloxane as a seed. The latex thus obtained was dried at 160 ° C. for 1.5 hours and the solid content was determined to be 35.3%. The number average particle size of this latex was 325 nm.

Formation of outermost layer Containing 14 parts of styrene (St), 5 parts of acrylonitrile (AN), 1 part of divinylbenzene (DVB) and 0.25 parts of tertiary butyl hydroperoxide while maintaining the liquid temperature of this latex at 70 ° C. The mixture was dropped and polymerized over 60 minutes. After completion of dropping, the rubber is kept at a temperature of 80 ° C. or more for 1 hour and then cooled, and a composite rubber obtained by grafting a styrene-acrylonitrile copolymer crosslinked with divinylbenzene on a composite rubber composed of polydimethylsiloxane and polybutyl acrylate. A latex of the graft copolymer was obtained. The latex thus obtained was dried at 160 ° C. for 1.5 hours and the solid content was determined to be 38.6%. The number average particle size of this latex was 345 nm.
Next, the latex was coagulated by freezing and thawing, washed with water, dehydrated, and dried to obtain a powdery composite rubber copolymer A.

Production of composite rubber copolymer B Emulsion polymerization was carried out in the same manner as in Example 1 with the composition shown in Table 1, and the resulting latex was freeze-thawed, washed with water, dehydrated and dried to obtain composite rubber copolymer B. . In the same manner, composite rubber copolymers C to I were produced according to Example 3-5 and Comparative Example 1-4.

MMA：メチルメタクリレート
EG：エチレングリコールジメタクリレート

MMA: Methyl methacrylate
EG: Ethylene glycol dimethacrylate

Solvent Swelling Test 2 g of the composite rubber copolymer obtained in a glass screw tube (35 mm × 78 mm) is weighed, tapped and densely packed, and then its bulk is measured (Amm). Thereafter, 30 g of a solvent (toluene and ethyl acetate) is added and left to stand for 24 hours, and then the bulkiness of the powder is measured again (Bmm). The degree of solvent swelling was determined by the following formula. The results are shown in Table 2.
Solvent swelling = Bmm / Amm

Manufacture of thermoplastic resin composition 5 parts of the obtained composite rubber copolymer and 100 parts of polycarbonate resin (Taflon AZ1900 manufactured by Idemitsu Kosan Co., Ltd.) are melt-kneaded at 230 to 250 ° C. with a 40 mm single-screw extruder, and pelletized Was molded into a thermoplastic resin composition.

Izod Impact Test The obtained pellets were injection molded at a cylinder temperature of 240 ° C. and a mold temperature of 70 ° C., and a V notch was made by cutting to produce an Izod impact test piece specified in JIS K7110. The Izod impact strength was measured in an atmosphere of −30 ° C. according to JIS K7110. The results are shown in Table 2.

The composite rubber copolymers of Examples 1 to 5 had good solvent resistance and excellent impact resistance at low temperatures.
On the other hand, the composite rubber copolymer of Comparative Example 1 has a high degree of solvent swelling and poor solvent resistance because the outermost layer is not crosslinked. The composite rubber copolymer of Comparative Example 2 does not function as an impact modifier at low temperatures because of the large number of crosslinks in the outermost layer. Since the composite rubber copolymer of Comparative Example 3 does not contain a polyorganosiloxane core, the impact strength at low temperatures is low. The composite rubber copolymer of Comparative Example 4 had insufficient solvent resistance because the composition of the outermost layer was only MMA and no crosslinking agent was contained.

  The thermoplastic resin composition in which the graft copolymer particles of the present invention are kneaded has excellent low-temperature impact resistance and coating film adhesion, such as mobile phones and notebook computers used at low temperatures. Excellent effect in a wide range of applications such as electrical and electronic fields such as housings.

Claims (3)

  A core (1) formed of polyorganosiloxane, an intermediate layer (2) composed of a rubbery polymer formed by polymerization of an alkyl (meth) acrylate monomer having an alkyl group with 2 to 8 carbon atoms, a kind Or it has the outermost layer (3) which consists of a polymer formed by superposition | polymerization of 2 or more types of vinylic monomers, and an outermost layer (3) is 0.5-20 weight with respect to the whole quantity of the monomer. % Silicone rubber graft copolymer crosslinked with a crosslinkable monomer.   An intermediate comprising a rubbery polymer formed by polymerization of an alkyl (meth) acrylate monomer having a core (1) formed by polyorganosiloxane of 5 to 70% by weight and an alkyl group having 2 to 8 carbon atoms. The layer (2) is 15 to 80% by weight, and the outermost layer (3) made of a polymer formed by polymerization of one or more vinyl monomers is 10 to 30% by weight. Silicone rubber graft copolymer.   The silicone rubber graft copolymer according to claim 1 or 2, wherein the outermost layer (3) is a styrene-acrylonitrile copolymer.