JP7251106B2 - Graft copolymer, thermoplastic resin composition and molded article thereof - Google Patents

Description

The present invention provides a graft copolymer that provides a thermoplastic resin composition having excellent transparency, impact resistance, weather resistance, and fluidity, a thermoplastic resin composition containing this graft copolymer, and a molded article thereof. Regarding.

Improving the impact resistance of resin materials not only expands the use of resin materials, but also makes it possible to make molded products thinner and larger. Various methods have been proposed so far to improve the impact resistance of resin materials. Among these methods, a technique of combining a rubber-like polymer and a hard resin material to improve impact resistance while maintaining the properties of the hard resin material has already been industrialized. Such materials include acrylonitrile-butadiene-styrene (ABS) resins.

However, although the ABS resin has excellent impact resistance, it has been difficult to use it without applying decoration such as painting or film because the weather resistance of polybutadiene, which is a rubber component, is low.

In order to solve such problems with ABS resins, acrylonitrile-styrene-acrylate (ASA) resins using acrylic rubber as a rubber component have been developed and commercialized.

Moreover, methacrylic acid ester resins are widely known as hard resins having excellent transparency. However, methacrylic acid ester resins have drawbacks such as low impact resistance and fragility.

As a resin excellent in transparency and impact resistance, Patent Document 1 discloses a method of using a methacrylate ester resin as a hard resin and adding an ASA resin or an ABS resin thereto.
However, in the method described in Patent Document 1, although the impact resistance is excellent, there is a problem that the transparency is not sufficient due to the large difference in refractive index between polybutadiene or acrylic rubber and methacrylic acid ester resin. In addition, due to the low weather resistance of polybutadiene, there have been restrictions on its uses.

Patent Document 2 discloses a method of adding a polybutadiene/acrylic rubber composite having a structure in which polybutadiene particles are covered with acrylic rubber to a methacrylic acid ester resin.
According to the method described in Patent Document 2, by compounding polybutadiene, the difference in refractive index between the rubber component and the polymethacrylic acid ester resin is reduced, and the appearance is improved. However, there is a problem that the weather resistance is lowered due to the compounding of polybutadiene.

Patent Document 3 discloses a method of increasing the refractive index of acrylic rubber by copolymerizing butyl acrylate and styrene.
However, in the method described in Patent Document 3, impact resistance is remarkably lowered.

JP-A-2001-316424 JP 2009-215398 A JP 2017-88774 A

The present invention provides a graft copolymer that provides a thermoplastic resin composition having excellent transparency, impact resistance, weather resistance, and fluidity, a thermoplastic resin composition containing this graft copolymer, and a molded article thereof. The task is to provide

As a result of repeated studies to solve the above problems, the present inventors have found that a copolymer of (meth)acrylic acid alkyl ester (Aa) and (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group By using a graft copolymer (B) obtained by graft-polymerizing a vinyl monomer mixture (m1) containing a (meth)acrylic acid alkyl ester in the presence of (A), transparency and impact resistance are improved. It has been found that a thermoplastic resin composition having excellent properties and weather resistance as well as excellent fluidity can be obtained.
That is, the gist of the present invention is as follows.

[1] A (meth)acrylic acid alkyl ester (Aa) and a (meth)acrylic acid alkyl ester (Ab) having an aromatic hydrocarbon group are added to the copolymer (A). A graft copolymer (B) obtained by graft-polymerizing the vinyl-based monomer mixture (m1) containing

[2] In the total 100% by mass of the (meth)acrylic acid alkyl ester (Aa) unit and the (meth)acrylic acid ester (Ab) unit having an aromatic hydrocarbon group in the copolymer (A) (meth ) The content of alkyl acrylate (Aa) units is 55 to 85% by mass, and the content of (meth)acrylate (Ab) units having an aromatic hydrocarbon group is 15 to 45% by mass, [ 1].

[3] The copolymer (A) comprises (meth)acrylic acid alkyl ester (Aa) units, (meth)acrylic acid ester (Ab) units having an aromatic hydrocarbon group, units derived from a crosslinking agent, and / Or the graft copolymer (B) according to [1] or [2], which contains a unit derived from a graft crossing agent.

[4] The proportion of units derived from the cross-linking agent and / or graft crossing agent in the copolymer (A) is (meth)acrylic acid alkyl ester (Aa) units and aromatic hydrocarbon group-containing (meth) The graft according to [3], which is 0.1 to 3% by mass in the total 100% by mass of the acrylic acid ester (Ab) unit, the unit derived from the crosslinking agent, and/or the unit derived from the graft crossing agent. Copolymer (B).

[5] The copolymer (A) comprises a (meth)acrylic acid alkyl ester (Aa), a (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group, and a cross-linking agent and/or a graft crossing agent. , the graft copolymer (B) according to [3] or [4], which is a miniemulsion polymer of a mixture of a hydrophobic substance and an initiator.

[6] The graft copolymer according to any one of [1] to [5], wherein the copolymer (A) has a volume average particle diameter of 0.05 to 0.80 μm and a swelling degree of 2 to 15 times. Coalescence (B).

[7] The graft copolymer (B) according to any one of [1] to [6], wherein the vinyl-based monomer mixture (m1) contains 60 to 100% by mass of (meth)acrylic acid alkyl ester.

[8] A vinyl monomer mixture (m1 ) is 20 to 50% by mass and the graft ratio is 25 to 100%, the graft copolymer (B) according to any one of [1] to [7].

[9] A thermoplastic resin composition containing the graft copolymer (B) according to any one of [1] to [8].

[10] including a graft copolymer (B) and a copolymer (C) that is a polymerization reaction product of a vinyl-based monomer mixture (m2) containing a (meth)acrylic acid alkyl ester; The thermoplastic resin composition described.

[11] The vinyl-based monomer mixture (m2) contains 60 to 100% by mass of a (meth)acrylic acid alkyl ester having the same structure as the (meth)acrylic acid alkyl ester contained in the vinyl-based monomer mixture (m1). , The thermoplastic resin composition according to [10].

[12] 10 to 50% by mass of the graft copolymer (B) and 50 to 90% by mass of the copolymer (C) in a total of 100% by mass of the graft copolymer (B) and the copolymer (C) %, the thermoplastic resin composition according to [10] or [11].

[13] A molded article obtained by molding the thermoplastic resin composition according to any one of [9] to [12].

ADVANTAGE OF THE INVENTION According to this invention, the thermoplastic resin composition which is excellent in transparency, impact resistance, weather resistance, and fluidity|liquidity, and its molded article are provided.

Embodiments of the present invention will be described in detail below.
In the present invention, "(meth)acrylic acid" means one or both of "acrylic acid" and "methacrylic acid", and the same applies to "(meth)acrylate".
In addition, "unit" means a structural portion derived from a compound (monomer, i.e. monomer) before polymerization contained in a polymer, for example, "(meth)acrylic acid alkyl ester (Aa) unit ” means “a structural portion derived from the (meth)acrylic acid alkyl ester (Aa) and contained in the copolymer (A)”. The content ratio of each monomer unit in the polymer corresponds to the content ratio of the monomer in the monomer mixture used to produce the polymer.

[Graft copolymer (B)]
The graft copolymer (B) of the present invention is a copolymer (A) (hereinafter referred to as , sometimes referred to as "the copolymer (A) of the present invention".) obtained by graft polymerization of a vinyl monomer mixture (m1) containing a (meth)acrylic acid alkyl ester is.

<Copolymer (A)>
The copolymer (A) of the present invention is a copolymer of (meth)acrylic acid alkyl ester (Aa) and (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group.

As the (meth)acrylic acid alkyl ester (Aa), a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms is preferable. Among them, n-butyl acrylate, 2-ethylhexyl acrylate, and ethyl acrylate are particularly preferred because the resulting thermoplastic resin composition containing the graft copolymer (B) has excellent impact resistance. The (meth)acrylic acid alkyl ester (Aa) can be used alone or in combination of two or more.

The (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group may be a (meth)acrylic acid ester having an aromatic hydrocarbon group such as a phenyl group or a benzyl group or a group containing an aromatic hydrocarbon group. For example, (meth)acrylic acid aryl esters, (meth)acrylic acid aryloxy esters, and (meth)acrylic acid alkyl esters having an aryl group such as a phenyl group or an aryloxy group such as a phenoxy group as a substituent of the alkyl ester moiety However, it is not limited to these at all. As the (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group, benzyl acrylate is used because the thermoplastic resin composition containing the obtained graft copolymer (B) has excellent impact resistance. , and 2-phenoxyethyl acrylate are particularly preferred. The (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group can be used singly or in combination of two or more.

The content of the (meth)acrylic acid alkyl ester (Aa) unit and the content of the (meth)acrylic acid ester (Ab) unit having an aromatic hydrocarbon group in the copolymer (A) are determined by the resulting graft copolymerization. Since the thermoplastic resin composition obtained by blending the coalescence (B) has excellent transparency and impact resistance, (meth) acrylic acid alkyl ester (Aa) units and (meth) acrylic having an aromatic hydrocarbon group In a total of 100% by mass of the acid ester (Ab) units, the (meth)acrylic acid alkyl ester (Aa) unit is 55 to 85% by mass, and the (meth)acrylic acid ester (Ab) unit having an aromatic hydrocarbon group is It is preferably 15 to 45% by mass, (meth)acrylic acid alkyl ester (Aa) unit is 60 to 80% by mass, and (meth)acrylic acid ester (Ab) unit having an aromatic hydrocarbon group is 20 to It is more preferably 40% by mass, the (meth)acrylic acid alkyl ester (Aa) unit is 65 to 75% by mass, and the (meth)acrylic acid ester (Ab) unit having an aromatic hydrocarbon group is 25 to 35 % by mass is more preferred. If the content of the (meth)acrylic acid alkyl ester (Aa) is less than 55% by mass, the transparency and impact resistance tend to decrease. If it exceeds 85% by mass, the transparency tends to decrease.

The content of (meth)acrylic ester (Ab) units in the copolymer (A) and (meth)acrylic ester (Ab) units having an aromatic hydrocarbon group is After decomposing into monomer units by heating the polymer (B), or a thermoplastic resin composition containing the graft copolymer (B) and the below-described copolymer (C), and a molded article thereof at 600 ° C. , It can be calculated by component analysis with a GC-MS device, but as described above, the (meth)acrylic acid alkyl ester (Aa) and the aromatic hydrocarbon group used in the production of the copolymer (A) are The content ratio of each of the (meth)acrylic acid alkyl ester (Aa) and the (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group in the total of the (meth)acrylic acid ester (Ab) having , corresponds to the content of the (meth)acrylic acid alkyl ester (Aa) unit and the (meth)acrylic acid ester (Ab) unit having an aromatic hydrocarbon group in the copolymer (A).

The copolymer (A) of the present invention comprises a (meth)acrylic acid alkyl ester (Aa), a (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group, units derived from a crosslinking agent, and graft It is preferably a copolymer having either one or both of the units derived from the cross-linking agent. The effect of further improving the impact resistance of the thermoplastic resin composition containing the copolymer (B) is exhibited.

Graft crossing agents include allyl compounds, specifically allyl methacrylate, triallyl cyanurate, triallyl isocyanurate and the like. These may be used alone or in combination of two or more.
Examples of the cross-linking agent include dimethacrylate-based compounds such as ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, and 1,4-butylene glycol dimethacrylate. These may be used alone or in combination of two or more.

When a cross-linking agent and/or a graft crossing agent is used, the proportion of units derived from the cross-linking agent and/or the graft crossing agent in the copolymer (A) is adjusted to the proportion of units derived from the cross-linking agent and/or the graft crossing agent obtained by blending the resulting graft copolymer (B). Since the impact resistance of the thermoplastic resin composition is excellent, the (meth)acrylic acid alkyl ester (Aa) unit, the (meth)acrylic acid ester (Ab) unit having an aromatic hydrocarbon group, and the crosslinking agent It is preferably 0.1 to 3% by mass, more preferably 0.2 to 2% by mass, based on the total 100% by mass of the units derived from the graft crossing agent and/or the units derived from the graft crossing agent.

In addition, the copolymer (A) includes (meth)acrylic acid alkyl ester (Aa) units, aromatic hydrocarbon group-containing (meth)acrylic acid ester (Ab) units, and It may contain monomeric units other than the units derived from the cross-linking agent and/or graft crossing agent used as necessary. Other monomer units that may be contained in the copolymer (A) include (meth)acrylic acid alkyl ester (Aa) and aromatic carbonization contained in the vinyl-based monomer mixture (m1) described later. One or more vinyl monomers other than the (meth)acrylic acid ester (Ab) having a hydrogen group may be used. The content of the monomer unit is preferably 20% by mass or less, particularly 10% by mass or less, based on 100% by mass of the copolymer (A).

The method for producing the copolymer (A) is not particularly limited, but a (meth)acrylic acid alkyl ester (Aa), an aromatic hydrocarbon group-containing (meth)acrylic acid ester (Ab), a cross-linking agent and/or Alternatively, a method of subjecting a mixture containing a graft crossing agent to emulsion polymerization or mini-emulsion polymerization is preferable, and a method of mini-emulsion polymerization is preferable because the resulting resin composition containing the graft copolymer (B) has excellent physical properties. Especially preferred.

As a method for producing the copolymer (A) by emulsion polymerization, a radical initiator, a (meth)acrylic acid alkyl ester (Aa), and an aromatic hydrocarbon group-containing (meth)acrylic acid ester ( Ab) and a cross-linking agent and/or a graft crossing agent are added and copolymerized in the presence of an emulsifier.
The method of adding the radical initiator, the (meth)acrylic acid alkyl ester (Aa), the (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group, the cross-linking agent and/or the graft crossing agent is collectively It can be divided or continuous.

The mini-emulsion polymerization for producing the copolymer (A) is, but not limited to, for example, (meth)acrylic acid alkyl ester (Aa) and (meth)acrylic acid having an aromatic hydrocarbon group Ester (Ab), a cross-linking agent and/or graft crossing agent, a hydrophobic substance, and an initiator are mixed, water and an emulsifier are added to the resulting mixture, and a shear force is applied to form a pre-emulsion ( making a mini-emulsion), and heating the mixture to the polymerization initiation temperature to polymerize it.

In the process of forming a mini-emulsion, for example, by performing a shearing process using ultrasonic irradiation, the monomer is torn off by the shearing force to form monomer micro oil droplets covered with an emulsifier. After that, by heating to the polymerization initiation temperature of the initiator, the monomer fine oil droplets are polymerized as they are to obtain polymer fine particles. Any known method of applying a shearing force to form a mini-emulsion can be used, and examples of high-shearing devices capable of forming a mini-emulsion include, but are not limited to, high-pressure pumps and There are emulsifying devices that consist of interaction chambers, and devices that form mini-emulsions using ultrasonic energy or high frequencies. Examples of the emulsifying device consisting of a high-pressure pump and an interaction chamber include "Pressure Homogenizer" manufactured by SPX Corporation APV, "Microfluidizer" manufactured by Powrex Co., Ltd., and the like. Examples of forming apparatuses include Fisher Scient's "Sonic Dismembrator" and Nippon Seiki Seisakusho's "ULTRASONIC HOMOGENIZER", but are not limited to these.

From the viewpoint of workability, stability, manufacturability, etc., the amount of the water solvent used when forming the mini-emulsion is such that the solid content concentration of the reaction system after polymerization is about 5 to 50% by mass. It is preferably about 100 to 500 parts by mass with respect to 100 parts by mass of the mixture other than.

When the copolymer (A) is produced by mini-emulsion polymerization, it is preferable to use a hydrophobic substance in a predetermined proportion. When the pre-emulsion is formed, the addition of a hydrophobic substance tends to further improve the production stability of the mini-emulsion polymerization, making it possible to produce the copolymer (A) suitable for the present invention.

Hydrophobic substances include, for example, hydrocarbons having 10 or more carbon atoms, alcohols having 10 or more carbon atoms, hydrophobic polymers having a mass average molecular weight (Mw) of less than 10000, and hydrophobic monomers such as alcohols having 10 to 30 carbon atoms. vinyl ester, vinyl ether of alcohol having 12 to 30 carbon atoms, alkyl (meth)acrylate having 12 to 30 carbon atoms, vinyl carboxylate ester having 10 to 30 carbon atoms (preferably 10 to 22 carbon atoms), p-alkylstyrene , hydrophobic chain transfer agents, hydrophobic peroxides, and the like. These may be used individually by 1 type, and may be used in mixture of 2 or more types.

Hydrophobic substances more specifically include hexadecane, octadecane, icosane, liquid paraffin, liquid isoparaffin, paraffin wax, polyethylene wax, olive oil, cetyl alcohol, stearyl acrylate, lauryl acrylate, stearyl acrylate, and lauryl methacrylate. , stearyl methacrylate, polystyrene having a number average molecular weight (Mn) of 500 to 10,000, poly(meth)acrylic acid ester, and the like.

The hydrophobic substance is a (meth)acrylic acid alkyl ester (Aa), a (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group, a crosslinking agent and / or a graft crossing agent, based on a total of 100 parts by mass , preferably 0.1 to 10 parts by mass, more preferably 1 to 3 parts by mass, from the viewpoint of controlling the particle size of the copolymer (A).

Emulsifiers used in the production of the copolymer (A) of the present invention include carboxylic acid-based emulsifiers exemplified by oleic acid, palmitic acid, stearic acid, alkali metal salts of rosin acid, and alkali metal salts of alkenylsuccinic acid. Emulsifiers, alkyl sulfates, sodium alkylbenzene sulfonate, sodium alkyl sulfosuccinate, anionic emulsifiers selected from sodium polyoxyethylene nonylphenyl ether sulfate, etc. Use known emulsifiers alone or in combination of two or more. can do.

The amount of the emulsifier to be added is 100 parts by mass in total of the (meth)acrylic acid alkyl ester (Aa), the (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group, and the cross-linking agent and/or graft crossing agent. 0.01 to 3.0 parts by mass, more preferably 0.05 to 2.0 parts by mass, for controlling the particle size of the copolymer (A).

The initiator used in the production of the copolymer (A) is a radical polymerization initiator for radical polymerization, and the type thereof is not particularly limited. compounds, organic peroxides, and redox initiators in which organic peroxides, transition metals, and reducing agents are combined. Among these, azo polymerization initiators, inorganic peroxides, organic peroxides, and redox initiators, which can initiate polymerization by heating, are preferred. These may be used alone or in combination of two or more.

Examples of azo polymerization initiators include 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′- Azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl) azo]formamide, 4,4'-azobis(4-cyanovaleric acid), dimethyl 2,2'-azobis(2-methylpropionate), dimethyl 1,1'-azobis(1-cyclohexanecarboxylate) ), 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2′-azobis(N-butyl-2-methylpropionamide), 2,2′-azobis ( N-cyclohexyl-2-methylpropionamide), 2,2′-azobis[2-(2-imidazolin-2-yl)propane], 2,2′-azobis(2,4,4-trimethylpentane), etc. mentioned.

Examples of inorganic peroxides include potassium persulfate, sodium persulfate, ammonium persulfate, and hydrogen peroxide.

Examples of organic peroxides include peroxyester compounds, specific examples of which include α,α'-bis(neodecanoylperoxy)diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3, 3-tetramethylbutyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, 1- Cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy 2-hexylhexanoate, t-butylperoxy 2-hexylhexanoate, t-butylperoxyisobutyrate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy 3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-bis(m-toluoylperoxy ) hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy 2-ethylhexylmonocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, t-butylperoxyacetate, t-butylperoxy-m-toluoylbenzoate, t-butylperoxybenzoate, bis(t-butylperoxy)isophthalate, 1,1-bis(t-hexylperoxy)3,3,5-trimethylcyclohexane, 1,1 -bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t -butylperoxy)cyclododecane, 2,2-bis(t-butylperoxy)butane, n-butyl 4,4-bis(t-butylperoxy)valerate, 2,2-bis(4,4-di-t- Butylperoxycyclohexyl)propane, α,α'-bis(t-butylperoxide)diisopropylbenzene, dicumylperoxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, t-butylcumylperoxide , di-t-butyl peroxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, dilauroyl peroxide, diisononanoyl peroxide, t-butyl hydroperoxide, benzoyl peroxide, lauroyl peroxide, dimethylbis(t-butylperoxy)-3- Hexyne, bis(t-butylperoxyisopropyl)benzene, bis(t-butylperoxy)trimethylcyclohexane, butyl-bis(t-butylperoxy)valerate, t-butyl 2-ethylhexaneperoxyate, dibenzoyl peroxide, para-menthane hydro and peroxides and t-butyl peroxybenzoate.

As the redox initiator, a combination of an organic peroxide, ferrous sulfate, a chelating agent and a reducing agent is preferred. For example, one consisting of cumene hydroperoxide, ferrous sulfate, sodium pyrophosphate, and dextrose, or a combination of t-butyl hydroperoxide, sodium formaldehyde sulfoxylate (Rongalite), ferrous sulfate, and disodium ethylenediaminetetraacetate. etc.

Among these, organic peroxides are particularly preferred as initiators.

The amount of the initiator added is a total of 100 mass of the (meth)acrylic acid alkyl ester (Aa), the (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group, and the cross-linking agent and/or graft crossing agent. It is usually 5 parts by mass or less, preferably 3 parts by mass or less, for example 0.001 to 3 parts by mass.

The process of preparing the pre-emulsion is usually carried out at normal temperature (about 10 to 50°C), and the process of mini-emulsion polymerization is carried out at 40 to 100°C for about 30 to 600 minutes.

The average particle size of the copolymer (A) of the present invention dispersed in the aqueous dispersion is such that the molded article made of the thermoplastic resin composition containing the obtained graft copolymer (B) has excellent physical properties. Therefore, it is preferably 0.05 to 0.80 μm, more preferably 0.10 to 0.60 μm, even more preferably 0.25 to 0.45 μm.
Methods for controlling the average particle size of the copolymer (A) include, but are not limited to, adjusting the type or amount of emulsifier used.
Here, the average particle size of the copolymer (A) is the volume average particle size measured by the method described in Examples below.

Further, the degree of swelling of the copolymer (A) of the present invention is preferably 2 to 15 times because the thermoplastic resin composition obtained by blending the graft copolymer (B) has excellent impact resistance. , more preferably 4 to 10 times.
The degree of swelling of the copolymer (A) is measured by the method described in the Examples section below.

<Graft copolymer (B)>
The graft copolymer (B) is a graft copolymer obtained by graft-polymerizing a vinyl-based monomer mixture (m1) containing a (meth)acrylic acid alkyl ester to the copolymer (A).
The graft copolymer (B) is obtained by polymerizing a vinyl-based monomer mixture (m1) containing a (meth)acrylic acid alkyl ester in the presence of the copolymer (A).

The (meth)acrylic acid alkyl ester contained in the vinyl-based monomer mixture (m1) preferably has an alkyl group having 1 to 20 carbon atoms, particularly preferably 1 to 10 carbon atoms, and the alkyl group may be a linear alkyl group. , a branched alkyl group or a cycloalkyl group, preferably a linear alkyl group. Examples of (meth)acrylic acid alkyl esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, acrylic Acrylic acid alkyl esters such as amyl acid, isoamyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, pentyl acrylate, and benzyl acrylate; methacrylic acid Methyl, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, octyl methacrylate, methacrylic acid Alkyl methacrylates such as 2-ethylhexyl, decyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate and benzyl methacrylate. Among these, methyl acrylate, methyl methacrylate, methyl acrylate, methyl methacrylate, Ethyl methacrylate is preferred, and methyl methacrylate and ethyl methacrylate are more preferred.

These (meth)acrylic acid alkyl esters may be used alone or in combination of two or more. For example, it is preferable to use methyl methacrylate and methyl acrylate together at a ratio of 1:0.01 to 0.2 (mass ratio) because depolymerization of the graft polymer can be suppressed.

The (meth)acrylic acid alkyl ester contained in the vinyl monomer mixture (m1) has the same structure as the (meth)acrylic acid alkyl ester contained in the vinyl monomer mixture (m2) described later. It is particularly preferable in terms of transparency, impact resistance and weather resistance of the thermoplastic resin composition and its molded article.

The content of the (meth)acrylic acid alkyl ester contained in the vinyl-based monomer mixture (m1) is not particularly limited, but a content of 60 to 100% by mass is preferable for the thermoplastic resin composition and its molded article. It is preferable in terms of excellent balance between impact resistance and transparency, and more preferably 70 to 100% by mass.

The vinyl-based monomer mixture (m1) comprises the above (meth)acrylic acid alkyl esters and other monomers copolymerizable therewith, such as methyl acrylate, ethyl acrylate, and other alkyl acrylates. can be included for depolymerization inhibition.

Other monomers include aromatic vinyl compounds such as styrene, α-methylstyrene, o-, m- or p-methylstyrene, vinylxylene, pt-butylstyrene, ethylstyrene, acrylonitrile, methacrylic Vinyl cyanide compounds such as lonitrile, N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-propylmaleimide, Nn-butylmaleimide, Ni-butylmaleimide, N-tert N-cycloalkylmaleimides such as -butylmaleimide and N-cyclohexylmaleimide, N-phenylmaleimides, N-alkyl-substituted phenylmaleimides, N-arylmaleimides such as N-chlorophenylmaleimide, and maleimide compounds such as N-aralkylmaleimides. These can be used singly or in combination of two or more.

The graft copolymer (B) is obtained by graft-polymerizing a vinyl-based monomer mixture (m1) containing a (meth)acrylic acid alkyl ester to the copolymer (A).
The copolymer (A) used for producing the graft copolymer (B) and the vinyl-based The monomer mixture (m1) contains 50 to 80% by mass of the copolymer (A) and 20 to 50% by mass of the vinyl monomer mixture (m1) in 100% by mass of the graft copolymer (B). Preferably.

In addition, the graft copolymer (B) has a graft ratio of 25 to 100% because the thermoplastic resin composition obtained by blending the graft copolymer (B) and the molded article thereof have an excellent balance of physical properties. Preferably. The graft ratio of the graft copolymer (B) is measured by the method described in Examples below.

The graft copolymer (B) is produced by known methods such as bulk polymerization, solution polymerization, bulk suspension polymerization, suspension polymerization and emulsion polymerization. ) is preferably blended into the thermoplastic resin composition and the molded article thereof because the balance of physical properties is good.

As the emulsion graft polymerization method, the vinyl monomer mixture (m1) is added all at once, continuously, or intermittently in the presence of an emulsion of the copolymer (A) to carry out radical polymerization. mentioned. Further, in the graft polymerization, a chain transfer agent is used for the purpose of adjusting the molecular weight of the graft polymer (B) and the degree of grafting, or a known inorganic electrolyte or the like is used for the purpose of adjusting the viscosity and pH of the latex. may be used. Moreover, in emulsion graft polymerization, various emulsifiers and radical initiators can be used as needed.
There are no particular restrictions on the types and amounts of emulsifiers and radical initiators to be added. Examples of emulsifiers and radical initiators include the emulsifiers and radical initiators exemplified above in the description of the copolymer (A).

Methods for recovering the graft copolymer (B) from the aqueous dispersion of the graft copolymer (B) include (i) aqueous dispersion of the graft copolymer (B) in hot water in which a coagulant is dissolved; A method (wet method) in which the body is charged and recovered by coagulating into a slurry state (ii) semi-directly by spraying an aqueous dispersion of the graft copolymer (B) in a heated atmosphere. A method of recovering the graft copolymer (B) (spray drying method) and the like can be mentioned.

The coagulant includes inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid, and metal salts such as calcium chloride, calcium acetate and aluminum sulfate. The coagulant is selected according to the emulsifier used in the polymerization. That is, when only carboxylic acid soaps such as fatty acid soaps and rosin acid soaps are used, any coagulant may be used. When an emulsifier such as sodium dodecylbenzenesulfonate that exhibits stable emulsifying power even in an acidic region is contained, it is necessary to use a metal salt.

The method for obtaining the dry graft copolymer (B) from the slurry graft copolymer (B) includes (i) eluting the emulsifier residue remaining in the slurry into water by washing, and then washing the slurry. Examples include a method of dehydrating with a centrifugal dehydrator or a press dehydrator and then drying with a flash dryer or the like, and (ii) a method of performing dehydration and drying simultaneously with a compression dehydrator, an extruder or the like. After drying, the graft copolymer (B) is obtained in powder or particulate form. Alternatively, the graft copolymer (B) discharged from the press dehydrator or extruder can be sent directly to the extruder or molding machine for producing the thermoplastic resin composition.

[Copolymer (C)]
The copolymer (C) is obtained by polymerizing a vinyl-based monomer mixture (m2) containing a (meth)acrylic acid alkyl ester.

The (meth)acrylic acid ester is an essential component of the vinyl-based monomer mixture (m2), since the obtained thermoplastic resin composition and its molded article are excellent in transparency and weather resistance.

Examples of the (meth)acrylic acid alkyl ester contained in the vinyl monomer mixture (m2) include those described above as the (meth)acrylic acid alkyl ester contained in the vinyl monomer mixture (m1). Among the (meth)acrylic acid alkyl esters described above, methyl acrylate, methyl methacrylate, and ethyl methacrylate are preferred from the viewpoint of increasing the transparency, impact resistance, and weather resistance of the thermoplastic resin composition and its molded article. Preferred are methyl methacrylate and ethyl methacrylate.

These (meth)acrylic acid alkyl esters may be used alone or in combination of two or more. For example, it is preferable to use methyl methacrylate and methyl acrylate together at a ratio of 1:0.01 to 0.2 (mass ratio) because depolymerization of the copolymer (C) can be suppressed.

The content of the (meth)acrylic acid alkyl ester contained in the vinyl-based monomer mixture (m2) is 60 to 100% by mass. is preferable in that it is excellent, and it is more preferable that it is 70 to 100% by mass.

The vinyl-based monomer mixture (m2) contains the above (meth)acrylic acid alkyl ester and other monomers copolymerizable therewith in an amount that does not impair the physical properties of the thermoplastic resin composition and its molded product. can be included in
Other monomers include those mentioned above as other monomers contained in the vinyl-based monomer mixture (m1), and the other monomers are used singly or in combination of two or more. can.

The weight average molecular weight of the copolymer (C) is not particularly limited, but is preferably in the range of 10,000 to 300,000, more preferably in the range of 50,000 to 200,000. If the mass average molecular weight of the copolymer (C) is within the above range, the thermoplastic resin composition will be excellent in fluidity and impact resistance.
The mass average molecular weight of the copolymer (C) is measured by the method described in Examples below.

The method for producing the copolymer (C) is not particularly limited, and includes known methods such as emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization. From the viewpoint of heat resistance of the resulting thermoplastic resin composition, suspension polymerization and bulk polymerization are preferred.

Although there is no particular limitation on the polymerization initiator used in producing the copolymer (C), examples thereof include organic peroxides.

A chain transfer agent can be used to adjust the molecular weight of the copolymer (C) during the production of the copolymer (C). Chain transfer agents are not particularly limited, but include mercaptans, α-methylstyrene dimers, terpenes and the like.

[Thermoplastic resin composition]
The thermoplastic resin composition of the present invention contains the graft copolymer (B) of the present invention described above, preferably the graft copolymer (B) of the present invention and the copolymer (C) described above. including.

The content of the graft polymer (B) of the present invention in the thermoplastic resin composition of the present invention is 10 to 10 when the total of the graft copolymer (B) and the copolymer (C) is 100% by mass. It is preferably 50% by mass, and the content of the copolymer (C) is preferably 50 to 90% by mass. When the content of the graft polymer (B) and the copolymer (C) is within the above range, the thermoplastic resin composition and its molded article have excellent transparency and impact resistance.

The thermoplastic resin composition of the present invention may contain other thermoplastic resins, if necessary, as long as the physical properties of the thermoplastic resin composition and its molded article are not impaired. Other thermoplastic resins are not particularly limited, and examples include polycarbonate resin, polybutylene terephthalate (PBT resin), polyethylene terephthalate (PET resin), polyvinyl chloride, polystyrene, polyacetal resin, modified polyphenylene ether (modified PPE resin), Ethylene-vinyl acetate copolymers, polyarylates, liquid crystal polyester resins, polyethylene resins, polypropylene resins, fluororesins, polyamide resins (nylons), and the like. These may be used alone or in combination of two or more.

The thermoplastic resin composition of the present invention contains other commonly used additives during production (during mixing) and molding of the thermoplastic resin composition within a range that does not impair the physical properties of the thermoplastic resin composition and its molded product. For example, lubricants, pigments, dyes, fillers (carbon black, silica, titanium oxide, etc.), heat-resistant agents, anti-oxidation agents, weather-resistant agents, release agents, plasticizers, antistatic agents, etc. can be added.

The thermoplastic resin composition of the present invention can be produced by known methods using known equipment. For example, there is a melt mixing method as a general method, and devices used in this method include extruders, Banbury mixers, rollers, kneaders, and the like. Mixing may be performed either batchwise or continuously. Moreover, there is no particular restriction on the mixing order of each component, as long as all the components are uniformly mixed.

[Molding]
The molded article of the present invention is obtained by molding the thermoplastic resin composition of the present invention. Examples of molding methods include injection molding, injection compression molding, extrusion, blow molding, vacuum molding, air pressure molding, calendar molding, and inflation molding. Among these, the injection molding method and the injection compression molding method are preferable because they are excellent in mass productivity and can obtain molded articles with high dimensional accuracy.

[Use]
As explained above, the thermoplastic resin composition of the present invention has excellent fluidity, and the molded article thereof has excellent transparency, impact resistance and weather resistance.
Applications of the thermoplastic resin composition of the present invention and its molded articles are not particularly limited. Also, it is useful in a wide range of fields such as OA/home appliances, vehicles/ships, housing-related fields such as furniture/building materials, sanitary goods, miscellaneous goods, stationery/toys/sports goods.

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
In the following, "parts" means "parts by mass" and "%" means "% by mass".

Various measurement and evaluation methods in the following examples and comparative examples are as follows.

<Volume average particle size of copolymer (A)>
Using Microtrac ("Nanotrac 150" manufactured by Nikkiso Co., Ltd.) and using deionized water as a measurement solvent, the volume average particle size of the copolymer (A) dispersed in the aqueous dispersion was measured.

<Swelling degree of copolymer (A)>
The copolymer (A) was dried at 80° C. for 24 hours and then vacuum-dried at 80° C. for 24 hours to prepare a film-like dried product of the copolymer (A). Let W1 be the weight of the obtained dry matter. The dried product was immersed in acetone at room temperature for 12 hours, filtered through a 200-mesh wire mesh, and the residue was weighed. Let W2 be the weight of the residual. The residue was then vacuum-dried at room temperature for 24 hours. Let W3 be the weight of the residual dry matter after vacuum drying. The swelling degree of the copolymer (A) is calculated by the following formula (1).
Degree of swelling (%) = (W2/W3) x 100 (1)

<Graft ratio of graft copolymer (B)>
Add 1 g of the graft copolymer (B) to 80 mL of acetone, heat and reflux at 65 to 70° C. for 3 hours, and centrifuge the resulting suspended acetone solution (“CR21E” manufactured by Hitachi Koki Co., Ltd.). The mixture was centrifuged at 14,000 rpm for 30 minutes to separate precipitated components (acetone-insoluble components) and an acetone solution (acetone-soluble components). Then, the precipitated component (acetone-insoluble component) was dried, its mass (Y (g)) was measured, and the graft ratio was calculated by the following formula (2). Y in the formula (2) is the mass (g) of the acetone-insoluble component of the graft copolymer (B), X is the total mass (g) of the graft copolymer (B) used in determining Y, The rubber fraction is the solid content concentration in the aqueous dispersion of the copolymer (A) used in the production of the graft copolymer (B).
Graft rate (% by mass) = {(YX x rubber fraction)/X x rubber fraction}
×100 (2)

<Mass Average Molecular Weight of Copolymer (C)>
The mass-average molecular weight of the copolymer (C) was determined by dissolving in tetrahydrofuran (THF) using gel permeation chromatography (GPC) and converting the value to standard polystyrene (PS).

[Production of copolymer (A)]
<Production of copolymer (A-1)>
A copolymer (A-1) was produced with the following formulation.
[Formulation]
n-butyl acrylate (Aa) 42 parts 2-phenoxyethyl acrylate (Ab) 18 parts Allyl methacrylate 0.24 parts 1,3-butylene glycol dimethacrylate 0.12 parts Liquid paraffin 0.6 parts Dipotassium alkenyl succinate 0.20 parts dilauroyl peroxide 0.6 parts deionized water 406 parts

n-Butyl acrylate, 2-phenoxyethyl acrylate, liquid paraffin, allyl methacrylate, dilauroyl peroxide, ion-exchanged water, and alkenyl succinate were added to a reactor equipped with a reagent injection vessel, cooling tube, jacket heater, and stirrer. A pre-emulsion was obtained by adding dipotassium acid, and performing ultrasonic treatment for 20 minutes at an amplitude of 35 μm using an ULTRASONIC HOMOGENIZER US-600 manufactured by Nippon Seiki Seisakusho Co., Ltd. at room temperature. The volume average particle size of the obtained latex was 250 nm.
The pre-emulsion was heated to 60° C. to initiate radical polymerization. The liquid temperature rose to 78° C. due to the polymerization. The temperature was maintained at 75° C. for 30 minutes to complete the polymerization to obtain a copolymer (A-1) dispersed in an aqueous dispersion having a volume average particle size of 300 nm.

<Production of copolymers (A-2) to (A-17)>
Tables 1A and 1B show the amounts of (meth)acrylic acid alkyl ester (Aa), (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group, dipotassium alkenyl succinate, and other monomers. Copolymers (A-2) to (A-17) dispersed in an aqueous dispersion were obtained in the same manner as for copolymer (A-1), except that the procedure was changed as follows.

<Production of copolymer (A-18)>
In a stainless steel autoclave (hereinafter abbreviated as SUS autoclave), 145 parts of ion-exchanged water (hereinafter abbreviated simply as water), 1.0 part of potassium rosinate, 1.0 part of potassium oleate, sodium hydroxide 0.06 parts of sodium sulfate, 0.4 parts of t-dodecylmercaptan, and 0.3 parts of t-dodecyl mercaptan were charged, and after purging with nitrogen, 125 parts of 1,3-butadiene were charged and the temperature was raised to 60°C.
Then, an aqueous solution prepared by dissolving 0.3 parts of potassium persulfate in 5 parts of water was injected to initiate polymerization. During the polymerization, the polymerization temperature was adjusted to 65° C., and unreacted 1,3-butadiene was recovered when the internal pressure reached 4.5 kg/cm ² (gauge pressure) after 12 hours. Thereafter, the internal temperature was raised to 80° C. and held for 1 hour to obtain a butadiene rubber latex having a volume average particle size of 250 nm and a solid content of 41%.

20 parts of butadiene rubber latex in terms of solid content was charged into a 5-liter glass reactor, then 1.0 parts of dipotassium alkenyl succinate and 150 parts of water were added to replace with nitrogen, and the internal temperature was raised to 70°C. I warmed up. An aqueous solution prepared by dissolving 0.12 parts of potassium persulfate in 10 parts of water was added thereto, followed by 79.5 parts of n-butyl acrylate (Aa) previously substituted with nitrogen, 0.33 parts of allyl methacrylate, A monomer mixture consisting of 0.17 parts of 1,3-butylene glycol dimethacrylate was continuously added dropwise over 2 hours. After the completion of the dropwise addition, the internal temperature was raised to 80° C. and held for 1 hour to obtain a copolymer (A- 18) was obtained.

Tables 1A and 1B show the degree of swelling and the volume average particle size of the copolymers (A-1) to (A-18).

[Production of graft copolymer (B)]
<Production of graft copolymer (B-1)>
After producing the copolymer (A-1), while maintaining the internal temperature of the reactor at 75° C., ferrous sulfate was added to 60 parts (as a solid content) of the copolymer (A-1) at 0.00. 001 parts of ethylenediaminetetraacetic acid disodium salt, 0.003 parts of ethylenediaminetetraacetic acid disodium salt, 0.3 parts of Rongalit and 5 parts of ion-exchanged water are added, followed by 0.65 parts of dipotassium alkenylsuccinate and 10 parts of ion-exchanged water. An aqueous solution consisting of was added. Thereafter, a mixture of 39.6 parts of methyl methacrylate and 0.4 parts of methyl acrylate as a vinyl monomer mixture (m1) and 0.18 parts of t-butyl hydroperoxide were added dropwise over 1 hour and 30 minutes for grafting. polymerized.
After the dropwise addition, the internal temperature was maintained at 75°C for 10 minutes, and then cooled. When the internal temperature reached 60°C, 0.2 parts of an antioxidant (ANTAGE W500 manufactured by Yoshitomi Pharmaceutical Co., Ltd.) and alkenyl succinate were added. An aqueous solution prepared by dissolving 0.2 parts of dipotassium acid in 5 parts of deionized water was added. Then, the aqueous dispersion of the reaction product was coagulated with an aqueous sulfuric acid solution, washed with water, and dried to obtain a graft copolymer (B-1). The graft ratio of the graft copolymer (B-1) was 40%.

<Production of graft copolymers (B-2) to (B-18)>
Graft copolymers (B-2) to (B-18) were prepared in the same manner as for graft copolymer (B-1), except that the type of copolymer (A) was changed as shown in Tables 2A and 2B. ).

The graft ratios of the graft copolymers (B-2) to (B-18) were as shown in Tables 2A and 2B.

[Production of copolymer (C)]
<Production of copolymer (C-1)>
150 parts of ion-exchanged water, a mixture of 99 parts of methyl methacrylate and 1 part of methyl acrylate as a vinyl-based monomer mixture (m2), and 0.2 parts of 2,2'-azobis(isobutyronitrile) were placed in a pressure-resistant reaction vessel. 2 parts of n-octyl mercaptan, 0.45 parts of n-octyl mercaptan, 0.47 parts of calcium hydroxyapatite and 0.003 parts of potassium alkenylsuccinate were charged, the internal temperature was raised to 75° C., and the reaction was carried out for 3 hours. After that, the temperature was raised to 90° C. and held for 60 minutes to complete the reaction. The content was repeatedly washed with a centrifugal dehydrator, dewatered, and dried to obtain a copolymer (C-1) having a mass average molecular weight of 124,000.

[Examples 1 to 12, Comparative Examples 1 to 6]
Each component was mixed with the composition (parts by mass) shown in Tables 3A and 3B, and 0.8 part of carbon black was further mixed there, and a twin-screw extruder with a 30 mm diameter vacuum vent (“PCM30” manufactured by Ikegai Co., Ltd.) was used. The mixture was melt-kneaded at 240° C. to obtain a pellet-like thermoplastic resin composition. The melt volume rate of the obtained thermoplastic resin composition was evaluated by the following method. In addition, the transparency, impact resistance, and weather resistance of molded articles obtained by injection molding the obtained thermoplastic resin compositions were evaluated by the following methods.
Evaluation results are shown in Tables 3A and 3B.

[Each evaluation method]
<Measurement of Melt Volume Rate (MVR)>
Based on ISO 1133:1997, the MVR of the thermoplastic resin composition at 220° C. was measured with a load of 98 N (10 kg). The MVR is a measure of the fluidity of the thermoplastic resin composition, and the higher the value, the better the fluidity.

<Injection molding 1>
Pellets of the thermoplastic resin composition obtained by melt-kneading are vertically molded under the conditions of a cylinder temperature of 200 to 270 ° C. and a mold temperature of 60 ° C. by an injection molding machine (manufactured by Toshiba Machine Co., Ltd., "IS55FP-1.5A"). A molded product of 80 mm, 10 mm wide and 4 mm thick was molded and used as a molded product for Charpy impact test (molded product (Ma1)).

<Injection molding 2>
Pellets of the thermoplastic resin composition obtained by melt-kneading are vertically molded under the conditions of a cylinder temperature of 200 to 270 ° C. and a mold temperature of 60 ° C. by an injection molding machine (manufactured by Toshiba Machine Co., Ltd., "IS55FP-1.5A"). A molded product of 100 mm, 100 mm wide and 3 mm thick was molded and used as a molded product (molded product (Ma2)) for evaluation of transparency and weather resistance.

<Transparency evaluation>
The haze value (Hz) of the molded product (Ma2) was measured using a haze meter (manufactured by Murakami Color Laboratory Co., Ltd.). It was determined that the smaller the haze, the higher the transparency.

<Impact resistance evaluation: Charpy impact test>
Regarding the molded product (Ma1), in accordance with ISO 179-1: 2013 version, the Charpy impact strength of the molded product (type B1, with notch: shape A single notch) at a test temperature of 23 ° C (hitting direction: edgewise ) was measured. Higher Charpy impact strength means better impact resistance.

<Weather resistance evaluation>
The molded article (Ma2) was treated for 1,500 hours using a Sunshine Weather Meter (manufactured by Suga Test Instruments Co., Ltd.) under the conditions of a black panel temperature of 63° C. and a cycle condition of 60 minutes (12 minutes of rainfall). The haze before and after this treatment was measured with a haze meter (manufactured by Murakami Color Laboratory Co., Ltd.) to determine the change (ΔHz). The smaller the ΔHz, the better the weather resistance.

As shown in Examples 1 to 12 in Table 3A, according to each example, thermoplastic resin compositions and molded articles excellent in impact resistance, fluidity, transparency and weather resistance were obtained.
On the other hand, as shown in Table 3B, the resin compositions and molded articles obtained in Comparative Examples 1 to 6 were significantly inferior in any one of impact resistance, fluidity, transparency and weather resistance.

Claims (10)

(Meth)acrylic acid alkyl ester (Aa) and copolymer (A) of (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group, vinyl-based copolymer containing (meth)acrylic acid alkyl ester A graft copolymer (B) obtained by graft-polymerizing the monomer mixture (m1),
(Meth)acrylic acid in the total 100 mass% of the (meth)acrylic acid alkyl ester (Aa) units and the (meth)acrylic acid ester (Ab) units having an aromatic hydrocarbon group in the copolymer (A) The content of alkyl ester (Aa) units is 65 to 75 % by mass, and the content of (meth)acrylic acid ester (Ab) units having an aromatic hydrocarbon group is 25 to 35 % by mass,
The vinyl-based monomer mixture (m1) contains 99 to 100% by mass of methyl methacrylate,
The ratio of the copolymer (A) to the total 100% by mass of the copolymer (A) and the vinyl monomer mixture (m1) is 50 to 80% by mass, and the ratio of the vinyl monomer mixture (m1) is 20 to 50% by mass,
A graft copolymer (B) having a graft ratio of 25 to 100%. The copolymer (A) comprises (meth)acrylic acid alkyl ester (Aa) units, (meth)acrylic acid ester (Ab) units having an aromatic hydrocarbon group, units derived from a crosslinking agent and / or graft 2. The graft copolymer (B) according to claim 1, comprising units derived from a crossing agent. The proportion of units derived from the crosslinking agent and/or graft crossing agent in the copolymer (A) is (meth)acrylic acid alkyl ester (Aa) units and (meth)acrylic acid ester having an aromatic hydrocarbon group The graft copolymer according to claim 2, which is 0.1 to 3% by mass in the total 100% by mass of (Ab) units, units derived from the crosslinking agent and/or units derived from the graft crossing agent. (B). The copolymer (A) comprises a (meth)acrylic acid alkyl ester (Aa), a (meth)acrylic acid ester (Ab) having an aromatic hydrocarbon group, a crosslinking agent and/or a graft crossing agent, and a hydrophobic 4. The graft copolymer (B) according to claim 2 or 3, which is a miniemulsion polymerizate of a mixture of substance and initiator. 5. The graft copolymer (B ). A thermoplastic resin composition comprising the graft copolymer (B) according to any one of claims 1 to 5. The heat according to claim 6, comprising a graft copolymer (B) and a copolymer (C) that is a polymerization reaction product of a vinyl monomer mixture (m2) containing a (meth)acrylic acid alkyl ester. A plastic resin composition. The vinyl monomer mixture (m2) contains 60 to 100% by mass of a (meth)acrylic acid alkyl ester having the same structure as the (meth)acrylic acid alkyl ester contained in the vinyl monomer mixture (m1). 8. The thermoplastic resin composition according to 7. 10 to 50% by mass of the graft copolymer (B) and 50 to 90% by mass of the copolymer (C) in a total of 100% by mass of the graft copolymer (B) and the copolymer (C), The thermoplastic resin composition according to claim 7 or 8. A molded article obtained by molding the thermoplastic resin composition according to any one of claims 6 to 9.