JPH09241452A - Thermoplastic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermoplastic resin composition useful for household electric appliances, automobile parts, etc., improved in surface appearance by suppressing mutual aggregation of rubber to reduce hard spots, excellent in impact resistance, moldability and processability, by blending a specific graft polymer with a styrene-based resin. SOLUTION: This composition is obtained by blending (A) 1-99 pts.wt. of a graft polymer prepared by grafting 20-50 pts.wt. of a monomer mixture composed of 10-99wt.% of an aromatic vinyl-based monomer (X1 ), 1-50wt.% of a vinyl cyanide-based monomer (X2 ) and 0-50wt.% of another copolymerizable vinyl-based monomer (X3 ) onto 50-80 pts. wt. of a diene-based rubber-like polymer and having >=15% grafting ratic, 4-30wt.% acetone-soluble content (Z) and 0.55-0.25 dl/g intrinsic viscosity of the content Z (measured in a methyl ethyl ketone solvent at 30 deg.C) with (B) 99-1 pt.wt. of a styrene based resin prepared by polymerizing a monomer (mixture) composed of 10100wt.% of the component X1 , 0-50wt.% of the component X2 and 090wt.% of the component X3 .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a graft polymer containing a rubbery polymer and a thermoplastic resin composition containing the graft polymer, which is excellent in impact resistance, moldability and surface appearance. Is.

[0002]

As a method for improving the toughness, that is, the impact resistance of a thermoplastic resin, a method of blending a rubbery polymer is generally known. A rubber-reinforced styrene resin represented by an ABS resin is improved in impact resistance by a graft polymer obtained by polymerizing a diene rubber polymer with aromatic vinyl or vinyl cyanide. Here, simply blending the rubbery polymer has poor compatibility with the resin and lacks impact resistance, so this problem is solved by graft-polymerizing aromatic vinyl and vinyl cyanide on the rubbery polymer. are doing.

Further, as a process for producing a rubber-reinforced styrene resin, a one-step graft polymerization method and a graft blend method are known. The one-step method of graft polymerization is a method for producing a resin having a desired composition by one-time graft polymerization, and the graft-blending method does not include a graft polymer component having a high rubber polymer composition and a rubber polymer. It is a method for producing a resin having a desired composition by blending polymer components.

All of the rubber-reinforced styrene resins obtained by the above method have high impact resistance and are widely used for home electric appliances, automobile parts, daily sundries and the like.

However, emulsion polymerization, which is excellent in polymerization stability and operability, is preferably used in the production of the graft polymer, and excellent productivity and economical efficiency are obtained in the production of the polymer containing no rubbery polymer. Bulk polymerization and suspension polymerization are preferably used. Therefore, when producing a resin having the same rubbery polymer composition,
The graft blend method is advantageous in terms of productivity and economy, and it is more advantageous to blend a graft polymer having a high rubbery polymer content.

[0006]

However, due to the agglomeration of rubbers with each other, a lump that can be visually observed in a resin molded product.
Tend to occur and cause deterioration of the surface appearance, and the impact resistance and other properties tend to be impaired.

An object of the present invention is to provide a composition which suppresses the agglomeration of rubbers to reduce the lumps on the surface of the molded article and is excellent in impact resistance and other physical properties.

[0008]

Means for Solving the Problems As a result of intensive studies made by the present inventors to solve the above problems, in a graft polymer having a high rubber content of 50 to 80% by weight of the rubbery polymer, the grafting of the rubbery polymer was performed. It has been found that it is effective to control the ratio, the amount of the non-grafted polymer formed in the course of the graft polymerization and its viscosity within a specific range.

That is, in the present invention, "(A) 10 to 99% by weight of an aromatic vinyl monomer and 1 to 100% of a vinyl cyanide monomer in the presence of 50 to 80 parts by weight of a diene rubber polymer. Fifty
% By weight and other vinylic monomers copolymerizable therewith 0
A graft polymer obtained by polymerizing 20 to 50 parts by weight of a monomer mixture of 50 to 50% by weight and satisfying the conditions (a), (b) and (c), and (B) an aromatic vinyl-based polymer. By polymerizing a monomer mixture comprising 10 to 100% by weight of a monomer, 0 to 50% by weight of a vinyl cyanide-based monomer, and 0 to 90% by weight of another vinyl-based monomer copolymerizable therewith. The styrene-based resin is a graft polymer (A) 1
A thermoplastic resin composition prepared by mixing 99 parts by weight and 99 to 1 parts by weight of the styrene resin (B). (A) Graft ratio of the graft polymer is 15% or more. (B) Acetone soluble content of the graft polymer is 4 to 30% by weight. (C) Intrinsic viscosity of the soluble content (methyl ethyl ketone solvent,
(Measured at 30 ° C.) is 0.05 to 0.25 dl / g ”,“ 10 to 99 wt% of aromatic vinyl monomer, vinyl cyanide simple substance in the presence of 50 to 80 parts by weight of diene rubbery polymer. Monomer mixture 20 to 5 comprising 1 to 50% by weight of a monomer and 0 to 50% by weight of another vinyl monomer copolymerizable therewith
Polymerizing 0 parts by weight and obtaining a graft polymer (A) satisfying the conditions (a), (b) and (c).
And a monomer comprising 10 to 100% by weight of an aromatic vinyl monomer, 0 to 50% by weight of a vinyl cyanide monomer, and 0 to 90% by weight of another vinyl monomer copolymerizable therewith. A step of polymerizing the mixture to obtain a styrene resin (B), 1 to 99 parts by weight of the graft polymer (A), the styrene resin (B), and the styrene resin (B). ) A method for producing a thermoplastic resin composition, which comprises the step of mixing at a ratio of 99 to 1 part by weight. (A) Graft ratio of the graft polymer is 15% or more. (B) Acetone soluble content of the graft polymer is 4 to 30% by weight. (C) Intrinsic viscosity of the soluble content (methyl ethyl ketone solvent,
0.05 to 0.25 dl / g "at 30 ° C.) and 10 to 99% by weight of the aromatic vinyl monomer and vinyl cyanide monomer in the presence of 50 to 80 parts by weight of the diene rubbery polymer. Monomer mixture 2 consisting of 1 to 50% by weight of a monomer and 0 to 50% by weight of another vinyl monomer copolymerizable therewith
Graft polymer (A) obtained by polymerizing 0 to 50 parts by weight, aromatic vinyl monomer 10 to 100% by weight, vinyl cyanide monomer 0 to 50% by weight, and copolymerizable with these Styrene resin (B) obtained by polymerizing a monomer mixture consisting of 0 to 90% by weight of another vinyl monomer, 1 to 99 parts by weight of a graft polymer (A), and a styrene resin (B ) A method for producing a thermoplastic resin composition, which comprises the step of mixing at a ratio of 99 to 1 part by weight. (A) Graft ratio of the graft polymer is 15% or more. (B) Acetone soluble content of the graft polymer is 4 to 30% by weight. (C) Intrinsic viscosity of the soluble content (methyl ethyl ketone solvent,
(Measured at 30 ° C.) is 0.05 to 0.25 dl / g ”.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below. In the present invention, weight means mass.

As the diene rubbery polymer used in the graft polymer of the present invention, a polymer or copolymer containing a conjugated diene as a main component is preferable. The content of conjugated diene in the diene rubber polymer used is 75% by weight.
Above all, particularly preferably 85% by weight or more. Specifically, polybutadiene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, butyl acrylate-
Butadiene copolymer and isoprene rubber can be used.

The average particle size of these diene rubbery polymers is preferably 0.10 to 0.60 μm, more preferably 0.15 to 0.50 μm.

In the present invention, the monomer that is graft-polymerized in the presence of the rubbery polymer is an aromatic vinyl-based monomer, a vinyl cyanide monomer, and, if necessary, other copolymerizable with these. It is a mixture of monomers.

Aromatic vinyl monomers are styrene,
α-methylstyrene, p-methylstyrene, vinyltoluene, t-butylstyrene, o-ethylstyrene, o-
Examples thereof include chlorostyrene and o, p-dichlorostyrene, and styrene is particularly preferably used. These may be used alone or in combination of two or more.

Examples of vinyl cyanide-based monomers include acrylonitrile, methacrylonitrile and ethacrylonitrile, with acrylonitrile being particularly preferred.

Other monomers copolymerizable with them include unsaturated carboxylic acid type monomers, unsaturated carboxylic acid anhydride type monomers, unsaturated carboxylic acid ester type monomers,
Alternatively, a maleimide-based monomer or the like can be used.
Specifically, (meth) acrylic acid, maleic anhydride,
Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, Chloromethyl (meth) acrylate, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide can be used.

The graft polymer of the present invention has a diene rubbery polymer / monomer mixture weight ratio of 50/50 to 80/2.
It is obtained by graft polymerization under the condition of 0, preferably 60/40 to 75/25. When the amount of the rubber-like polymer is large, the graft ratio is lowered due to the relative decrease of the monomer mixture, so that the surface appearance properties and impact resistance of the resin tend to be deteriorated. On the other hand, if the amount is small, the ratio of the non-grafted polymer generated in the graft polymerization process to the resin increases,
Affects physical properties.

The graft ratio is the percentage by weight of the grafted monomer mixture with respect to the weight of the diene rubber polymer.

The proportion of the aromatic vinyl monomer is 10 to 99% by weight, preferably 60 to 99% by weight based on the monomer mixture.
90% by weight, more preferably 65-80% by weight,
When the amount is small, the mechanical properties of the thermoplastic resin deteriorate, and when the amount is large, the chemical resistance and the affinity with other polymers tend to decrease.

The proportion of vinyl cyanide-based monomer is from 1 to 50% by weight, preferably from 10 to 40% by weight, based on all the monomers.
It is more preferably from 20 to 35% by weight, and when it is large, the moldability and surface appearance of the thermoplastic resin are deteriorated, and when it is small, the chemical resistance tends to be low and the affinity with other polymers tends to be low. .

Further, other vinyl-based monomers copolymerizable with these can achieve the object of the present invention if used in an amount of less than 50% by weight.

The method for producing the graft copolymer (A) is not particularly limited, but emulsion polymerization is preferably used. Various methods can be adopted as a method for adding components such as a monomer mixture, an emulsifier, a polymerization initiator and a chain transfer agent in emulsion polymerization. That is, there may be mentioned a method of adding the whole amount at the initial stage of polymerization, a method of adding a part of the mixture initially and the rest, a method of continuously adding the whole amount, a method of adding in two or more portions.

The types of emulsifier, polymerization initiator and chain transfer agent used are not particularly limited, and reagents used in ordinary emulsion polymerization can be used. Representative emulsifiers include potassium rosinate, potassium stearate, potassium oleate, and the like, and as a polymerization initiator, a combination system of organic hydroperoxide and sugar-containing pyrophosphate-ferrous sulfate, a persulfate, and the like, Examples of the chain transfer agent include alkyl thiol compounds.

The graft ratio in the graft polymer obtained by the above method is 15% by weight or more, preferably 1
It is 8% by weight or more, more preferably 20% by weight or more.
If the graft ratio is low, the surface appearance and impact resistance of the resin tend to be reduced.

When emulsion polymerization is carried out by the above method, a polymer which does not graft is formed at the same time as grafting. The polymer not grafted means a soluble component when the graft polymer is treated with acetone. Particularly, when the total amount of the rubber chamber polymer and the monomer mixture is 100 parts by weight, when the rubbery polymer is 50 to 80 parts by weight, the methyl ethyl ketone solvent of the polymer not grafted, the intrinsic viscosity measured at 30 ° C. 0.05-0.25 dl / g, preferably 0.70
-0.23 dl / g, more preferably 0.10-0.2
0 dl / g. When the viscosity is high, the graft polymers are likely to aggregate with each other, so that the surface appearance and impact resistance of the resin tend to be lowered, and when the viscosity is low, sufficient impact resistance may not be obtained.

The amount of the non-grafted polymer is 4 to 30% by weight, preferably 6 to 25% by weight, more preferably 10 to 20% by weight, as an acetone-soluble content. The mechanical properties such as impact resistance of the resin tend to deteriorate when the amount is large. The graft ratio and the intrinsic viscosity of the polymer not grafted are the ratio of the rubbery polymer and the monomer mixture, the kind of the polymerization initiator. And the amount, and the type and amount of the chain transfer agent can be adjusted.

Styrenic resin (B) used in the present invention
Can be obtained by polymerizing a mixture of an aromatic vinyl-based monomer, a vinyl cyanide monomer, and, if necessary, another monomer copolymerizable therewith.

Aromatic vinyl monomers are styrene,
α-methylstyrene, p-methylstyrene, vinyltoluene, t-butylstyrene, o-ethylstyrene, o-
Examples thereof include chlorostyrene and o, p-dichlorostyrene, and styrene is particularly preferably used. These may be used alone or in combination of two or more.

Examples of vinyl cyanide-based monomers include acrylonitrile, methacrylonitrile and ethacrylonitrile, with acrylonitrile being particularly preferred.

Other monomers copolymerizable therewith include unsaturated carboxylic acid monomers, unsaturated carboxylic acid anhydride monomers, unsaturated carboxylic acid ester monomers, and the like.
Alternatively, a maleimide-based monomer or the like can be used.
Specifically, (meth) acrylic acid, maleic anhydride,
Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, Chloromethyl (meth) acrylate, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide can be used.

Here, the proportion of the aromatic vinyl monomer is 10 to 100% by weight, preferably 60 to 9 based on all the monomers.
0 wt%, more preferably 65-80 wt%, 1
If it is less than wt%, the mechanical properties of the thermoplastic resin deteriorate, which is not preferable.

The proportion of the vinyl cyanide-based monomer is 0 to 50% by weight, preferably 10 to 40% by weight, based on all the monomers.
It is more preferably 20 to 35% by weight, and if it exceeds 50% by weight, the moldability and surface appearance of the thermoplastic resin deteriorate, which is not preferable.

Further, the other objects of the present invention can be achieved by using other vinyl-type monomers copolymerizable with them in an amount of less than 90% by weight.

Specific examples of the styrene resin used in the present invention include polystyrene, SAN (styrene-acrylonitrile copolymer) resin, styrene-methyl (meth) acrylate copolymer, and styrene-acrylonitrile-
Methyl (meth) acrylate copolymer, styrene- (meth) acrylic acid copolymer, styrene-acrylonitrile- (meth) acrylic acid, styrene-α-methylstyrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer And styrene-acrylonitrile-maleic anhydride copolymer, styrene-N-phenylmaleimide copolymer, styrene-acrylonitrile-N-phenylmaleimide copolymer, and the like. These may be used in combination of two or more. .

The styrene resin selected from the above is polymerized by a known method such as bulk polymerization, suspension polymerization, solution polymerization and emulsion polymerization. The intrinsic viscosity of the obtained polymer measured in a methyl ethyl ketone solvent at 30 ° C. is preferably 0.30 to 1.50 dl / g, more preferably 0.40 to 1.00 dl / g.

The method for producing the resin composition is not particularly limited, and the resin composition can be produced by a simple method such as melt-kneading with a single-screw extruder.

Further, pigments and dyes, heat stabilizers, flame retardants, antioxidants, ultraviolet absorbers, light stabilizers, lubricants and plasticizers, antistatic agents, fillers and the like can be added depending on the purpose.

[0038]

The present invention will be described in more detail with reference to the following examples.

The analysis method of the graft polymer of the present invention is shown below. -Graft ratio Acetone was added to a predetermined amount M (g) of the graft polymer, and 4
Refluxed for hours. This solution was centrifuged at 9,000 rpm for 30 minutes, and the insoluble matter was filtered. This insoluble matter was dried under reduced pressure at 60 ° C. for 5 hours, and the weight N (g) was measured. The graft ratio G was calculated by the following formula. G = (N−M × L) / (M × L) × 100 Here, L represents the content rate of the rubber-like polymer in the graft polymer. -Amount of polymer not grafted The amount (wt%) of the polymer not grafted (f-AS (meaning free acrylonitrile / styrene polymer)) was calculated by the following formula using the above symbols. (F-AS) = (M−N) / M × 100 Intrinsic viscosity of polymer not graft-polymerized [η] After filtering insolubles from the acetone solution used for measuring graft ratio, the solubles obtained were obtained. It was extracted with methanol. The extracted polymer was dried under reduced pressure at 60 ° C. for 3 hours, and then dried at about 0.
4g is precisely weighed and dissolved in methyl ethyl ketone to give 100c
A solution of c in methyl ethyl ketone was prepared. Using this solution, [η] was measured in a constant temperature bath at 30 ° C.

The resin composition finally obtained was molded by the injection molding method, and then the physical properties were measured by the following test methods.・ Izod impact strength (MPa) ASTM D-256 1/2 inch with notch 23 ° C ・ Fall weight impact strength (J) JISK6745 ・ Number of butts By heating and pressing about 10 g of resin pellets before molding at 250 ° C, stretching A film having a thickness of 10 μm was prepared. The number of rubber-like lumps contained in this film 100 × 200 mm was visually measured. The standard for a smooth film with excellent surface appearance is 100
This is the case of 1 or less per mm ² , and the surface appearance of the molded product is not impaired if this criterion is satisfied.

Reference Example 1 Production of Graft Polymer Graft polymers A to F were polymerized by changing the composition of the diene rubber polymer. A diene rubbery polymer (PBD) latex having the composition shown in Table 1 was charged in a glass reaction vessel, and further dissolved glucose was charged in ion-exchanged water with dissolved glucose, sodium pyrophosphate, and ferrous sulfate, After replacing the inside of the container with nitrogen, the temperature inside the reaction container was raised to 65 ° C.

A liquid obtained by mixing tert-dodecyl mercaptan with a predetermined monomer (ST, AN) shown in Table 1 and an aqueous solution of cumene hydroperoxide potassium oleate were separately added to this mixed liquid over 3 to 4 hours. It was continuously added dropwise from the start of polymerization. After the addition of the monomer mixture and the potassium oleate aqueous solution were all completed, stirring was continued for 1 hour to complete the reaction, and 2,6-di-tert-butylparacresol was added as an antioxidant. The polymerization rates were all in the range of 95 to 99%.

The graft ratio and [η] shown in Table 1 were adjusted by appropriately setting the amounts of tert-dodecyl mercaptan, cumene hydroperoxide and potassium oleate to be dropped and the dropping rate.

The polymer latex thus obtained, that is, the polymer dispersion is coagulated with sulfuric acid and neutralized with sodium hydroxide.
It was washed with water, dehydrated and dried to obtain a graft polymer. Graft ratio of each graft polymer, amount of polymer not grafted (f
-AS) and the intrinsic viscosity of methyl ethyl ketone soluble components are summarized in Table 1. Among those shown in Table 1, B-4 and C-
The graft polymers of 7, C-8, D-11, D-13, and E-16 satisfy the conditions (a), (b), and (c) of the present invention.

[0045]

[Table 1]

Production of SAN Copolymer A SAN copolymer was produced by suspension-polymerizing a monomer mixture consisting of 72% styrene and 28% acrylonitrile. The intrinsic viscosity of the methyl ethyl ketone soluble component of this copolymer was 0.49 dl / g.

Examples 1 to 10 and Comparative Examples 1 to 17 Polymer composition 10 in which the graft polymers and SAN copolymers prepared in the above reference examples were blended in the proportions shown in Table 2, respectively.
0 parts by weight, 1.0 part of ethylenebisstearylamide,
0.1 part of diphenylisodecyl hofphite was added and mixed with a Henschel mixer. Next, the mixture was extruded at a kneading temperature of 220 ° C. using a 40 mmφ single screw extruder, and each was pelletized. In order to perform an Izod impact test and a falling weight impact test, each pellet was injection molded under the conditions of a molding temperature of 230 ° C. and a mold temperature of 60 ° C. to prepare each test piece. Table 2 shows the evaluation results of the physical properties thereof.

[0048]

[Table 2]

The following is clear from the examples and comparative examples.

That is, all of the resin compositions (Examples 1 to 10) containing the graft polymer within the scope of the present invention can form a smooth film, and the number of spots per 100 mm ² is 1 or less. On the other hand, in Comparative Examples 3 to 17, many spots appear and the film surface has irregularities. In particular, the higher the content of the rubbery polymer and the higher the [η] is, the larger the resin composition of the resin composition is. This tendency is noticeable when the rubber content of the resin composition is as low as 10%.

In Comparative Example 1 in which the graft polymer having a rubbery polymer content of 40% was used, although the film had few spots, Izod impact and the like were reduced. Further, comparing the falling weight impact strengths of Example 1 and Comparative Example 2 in which the graft polymer having a rubbery polymer content of 50% by weight was compared,
A superiority is recognized in the use of a graft polymer having a low intrinsic viscosity. When the content of the rubbery polymer is 85%, the surface smoothness and impact resistance of the film are remarkably lowered.

Further, in Comparative Example 11 in which the content of the ungrafted polymer (f-AS) in the graft polymer is less than 4%, the surface smoothness and impact strength of the film, particularly the falling weight impact strength, are reduced. This tendency is the same when the graft ratio is 15% or less.

[0053]

The graft polymer specified in the present invention is S
By blending with a styrenic resin typified by AN and the like, the surface appearance and impact strength of the molded product are remarkably improved.

Claims (5)

[Claims] (A) 10 to 99% by weight of an aromatic vinyl monomer, 1 to 50% by weight of a vinyl cyanide monomer in the presence of 50 to 80 parts by weight of a diene rubbery polymer (A), and these 20 to 50 parts by weight of a monomer mixture consisting of 0 to 50% by weight of another vinyl-based monomer copolymerizable with, and satisfying the conditions (a), (b) and (c). Graft polymer and (B) aromatic vinyl monomer 10
To 100% by weight, vinyl cyanide-based monomer 0 to 50% by weight, and other vinyl-based monomer copolymerizable with these 0 to 9%
Thermoplastic prepared by blending a styrene resin obtained by polymerizing a monomer mixture of 0% by weight in a proportion of 1 to 99 parts by weight of a graft polymer (A) and 99 to 1 parts by weight of a styrene resin (B). Resin composition. (A) Graft ratio of the graft polymer is 15% or more. (B) Acetone soluble content of the graft polymer is 4 to 30% by weight. (C) Intrinsic viscosity of the soluble content (methyl ethyl ketone solvent,
Measured at 30 ° C) is 0.05 to 0.25 dl / g 2. The intrinsic viscosity (methyl ethyl ketone solvent, measured at 30 ° C.) of styrene resin (B) is 0.30 to 1.50.
It is dl / g, The thermoplastic resin composition of Claim 1 characterized by the above-mentioned. 3. The thermoplastic resin composition according to claim 1, wherein the graft polymerization reaction on the graft polymer (A) is emulsion polymerization. 4. An aromatic vinyl monomer in an amount of 10 to 99% by weight, a vinyl cyanide monomer in an amount of 1 to 50% by weight, and a copolymerization thereof with 50 to 80 parts by weight of a diene rubbery polymer. Polymerizing 20 to 50 parts by weight of a monomer mixture consisting of 0 to 50% by weight of other possible vinyl monomers, and (a)
A step of obtaining a graft polymer (A) satisfying the conditions (b) and (c) and the aromatic vinyl monomer 1
0-100% by weight, vinyl cyanide-based monomer 0-50% by weight, and other vinyl-based monomer copolymerizable with these 0-
The step of polymerizing a monomer mixture consisting of 90% by weight to obtain a styrene resin (B), and the graft polymer (A) and the styrene resin (B) are added to the graft polymers (A) 1 to 99. Parts by weight, styrene resin (B) 99
A method for producing a thermoplastic resin composition, which comprises a step of mixing at a ratio of 1 to 1 part by weight. (A) Graft ratio of the graft polymer is 15% or more. (B) Acetone soluble content of the graft polymer is 4 to 30% by weight. (C) Intrinsic viscosity of the soluble content (methyl ethyl ketone solvent,
Measured at 30 ° C) is 0.05 to 0.25 dl / g 5. An aromatic vinyl monomer in an amount of 10 to 99% by weight, a vinyl cyanide monomer in an amount of 1 to 50% by weight, and a copolymer thereof with 50 to 80 parts by weight of a diene rubbery polymer. Graft polymer (A) obtained by polymerizing 20 to 50 parts by weight of a monomer mixture consisting of 0 to 50% by weight of other possible vinyl monomers and aromatic vinyl monomers 10 to 100
% By weight, 0 to 50% by weight of vinyl cyanide-based monomer, and 0 to 90% by weight of other vinyl-based monomer copolymerizable therewith
From the step of mixing the styrene-based resin (B) obtained by polymerizing the monomer mixture consisting of 1 to 99 parts by weight of the graft polymer (A) and 99 to 1 parts by weight of the styrene-based resin (B). Of producing the thermoplastic resin composition. (A) Graft ratio of the graft polymer is 15% or more. (B) Acetone soluble content of the graft polymer is 4 to 30% by weight. (C) Intrinsic viscosity of the soluble content (methyl ethyl ketone solvent,
Measured at 30 ° C) is 0.05 to 0.25 dl / g