KR101233587B1 - Core-shell structure butadiene impact modifier for polycarbonate and thermoplastic resin composition thereof - Google Patents

Abstract

The present invention relates to a thermoplastic resin composition, and more particularly, butadiene-based impact modifiers prepared by grafting alkyl methacrylate-based monomers, ethylenically unsaturated aromatic compounds, and other copolymerizable one or more vinyl-based compounds to large-diameter rubber latex. It relates to a thermoplastic resin composition to contain. According to the present invention, there is an effect of providing a thermoplastic resin composition with improved low-temperature impact strength and colorability.

Thermoplastic resin composition, core-shell structure, butadiene impact modifier, low temperature impact strength, colorability

Description

Core-shell structure butadiene impact modifier for polycarbonate and thermoplastic resin composition using same

The present invention relates to a thermoplastic resin composition, and more particularly to a butadiene-based impact modifier having a core-shell structure for polycarbonate and a thermoplastic resin composition containing the same.

Polycarbonate (PC) is known as a resin having excellent impact resistance, electrical properties, and heat resistance, and is widely used for manufacturing molded articles of electric / electronic products including automobiles. However, polycarbonate has disadvantages such as high melt viscosity, poor moldability and impact resistance thickness dependency. Various studies have been made to make up for these drawbacks.

JPA S56 (1981) -45946 and JPA S56 (1981) -45947, EP465792 produce and mix an acrylic impact modifier for the purpose of improving impact resistance. However, in the case of the acrylic impact modifier, the glass transition temperature is higher than that of other butadiene-based and silicone-based impact modifiers, so that the effect of improving the low temperature impact strength is insufficient and the colorability is also deteriorated.

Korean Laid-Open Patent Publication No. 2006-0036523 discloses a method for improving low-temperature impact strength and colorability by providing a silicone-acrylic impact modifier using a silicone-based rubber seed, and the colorability is improved compared to the existing one, but is not satisfactory.

In addition, polyester resins such as PET or PBT may be mixed in JPB S36 (1961) -14035 and JPA S48 (1973) -54160 to supplement the chemical resistance of polycarbonate. However, the impact resistance is low and requires the combination of an impact modifier.

JPB H1 (1989) -34463 discloses a method of improving the impact strength and colorability by adding an acrylic impact modifier with a multilayer structure to a polycarbonate and polyester resin mixture. However, the coloring properties and the low temperature impact strength improving effect are insufficient.

Korean Laid-Open Patent Publication No. 2001-0070975 provides a resin composition having excellent impact resistance and molding appearance through particle size distribution control and rubber content control of an impact modifier. However, there is no mention of low temperature impact strength improvement effect and colorability.

In order to solve the problems of the prior art as described above, an object of the present invention is to provide a butadiene-based impact modifier of the core-shell structure having an effect of providing a thermoplastic resin composition excellent in low-temperature impact strength and colorability.

In addition, an object of the present invention is to provide a thermoplastic resin composition excellent in low-temperature impact strength and colorability.

The above and other objects of the present invention can be achieved by the present invention described below.

In order to achieve the above object, the present invention, in the butadiene-based impact modifier included in the thermoplastic resin composition, 60 to 80 parts by weight of the butadiene-based core rubber polymer adjusted to a particle diameter of 280 ~ 330 nm, gel content 65 ~ 95% ,

Iii) 73-95 weight percent of alkyl methacrylate monomers;

Ii) 5-25% by weight of ethylenically unsaturated aromatic compounds; And

Iii) 0 to 2% by weight of one or more copolymerizable vinyl compounds other than iv) and ii) above; It provides a butadiene-based impact modifier comprising 20 to 40 parts by weight of the shell graft polymerized monomer mixture containing.

In addition, the present invention provides a thermoplastic resin composition having excellent low temperature impact strength and colorability, including 95 to 98% by weight of a thermoplastic resin and 2 to 5% by weight of the butadiene-based impact modifier.

As described above, according to the present invention, there is an effect of providing a thermoplastic resin composition excellent in low temperature impact strength and colorability.

Hereinafter, the present invention will be described in detail.

(Butadiene rubber core polymer)

In order to achieve the above object,

(a) 60 to 70 parts by weight of the total 100 parts by weight of the conjugated diene compound, 1 to 4 parts by weight of the emulsifier, 0.2 to 0.4 parts by weight of the polymerization initiator, 0.2 to 2.0 parts by weight of the electrolyte, 0.1 to 0.5 parts by weight of the molecular weight regulator, ion exchange water 75 to 100 parts by weight of a batch to react at 55 ~ 75 ℃;

(b) 15 to 20 parts by weight of the conjugated diene compound and 0.5 to 1.5 parts by weight of an emulsifier are reacted at 65 to 75 ° C. at the time when the polymerization conversion rate of step (a) is 30 to 40%; And

(c) reacting the remaining conjugated diene compound in batch or successively after the time point at which the polymerization conversion rate in step (b) is 50 to 60%; It provides a large diameter rubber latex excellent in stability by the production method comprising a.

In the method for preparing the rubbery polymer latex, the polymerization may be terminated by adding a polymerization inhibitor at the time when the polymerization conversion rate of the step (c) is 80 to 95%.

As the conjugated diene compound, 1,3-butadiene, isoprene, chloroprene and pyrrylene may be used alone or copolymerized with a comonomer. Here, as the comonomer, aromatic vinyl compounds such as styrene and α-methyl styrene, and vinyl cyan compounds such as acrylonitrile, methacrylonitrile and ethacrylonitrile can be used. The comonomer is preferably used in 0 to 20 parts by weight based on 100 parts by weight of the total monomer content.

As the emulsifier, alkyl aryl sulfonates, alkali methyl alkyl sulfates, sulfonated alkyl esters, fatty acid soaps, or alkali salts of rosin acids may be used alone or in combination of two or more thereof.

As said polymerization initiator, water-soluble persulfate initiators, such as potassium persulfate, sodium persulfate, or ammonium persulfate, can be used.

As the electrolyte, KCl, NaCl, KHCO ₃ , NaHCO ₃ , K ₂ CO ₃ , Na ₂ CO ₃ , KHSO ₃ , NaHSO ₃ , K ₄ P ₂ O ₇ , Na ₄ P ₂ O ₇ , K ₃ PO ₄ , Na ₃ PO ₄ , K ₂ HPO ₄ or Na ₂ HPO ₄ may be used alone or in combination of two or more thereof.

As the molecular weight regulator, mercaptans can be mainly used.

The conjugated diene compound of step (a) is preferably used at 60 to 70 parts by weight based on 100 parts by weight of the total monomers used. When the content is less than 60 parts by weight, the number of particles initially generated is extremely small, and the latex particles may not be fused due to a decrease in particle surface coverage of the emulsifier due to the growth of particles. There is no problem. By using the content less than 60 parts by weight, using a small amount of emulsifier or increasing the total solid content and using a large amount of electrolyte may cause fusion of latex particles. However, these methods may be possible in a small reactor without the generation of coagulum, but when the production is carried out in a large reactor with a large capacity, a large amount of coagulum is generated, thereby lowering the polymerization productivity. In addition, when the content exceeds 70 parts by weight, there is a problem in that the heat removal capacity is lowered by the increased heat of polymerization to cause a runaway reaction.

The conjugated diene compound of step (b) is preferably used in an amount of 15 to 25 parts by weight when the polymerization conversion rate of step (a) is 30 to 40%. Since the fusion of the latex particles is completed when the polymerization conversion rate is 30 to 40%, it is preferable to collectively administer the conjugated diene compound monomer. In addition, at this point, it is preferable to stop the progress of the fusion of the extra particles by adding an emulsifier in sufficient amount to stabilize the coating of the particle surface to the particles undergoing fusion before the monomer administration.

The emulsifier added in the step (b) may be a disproportionated rosin acid emulsifier, it is more preferable to use an emulsifier having a linear chain such as oleic acid, stearic acid. By adding the emulsifier, an atmosphere in which the monomers can generate new particles is formed, and after this time, the reaction rate increases with the growth of newly generated particles. In addition, the particles having a large particle size and particles having a small particle size coexist and grow to reduce latex viscosity, thereby securing latex stability.

It is preferable that the conjugated diene compound of step (c) is administered in a batch or continuous manner after the time when the polymerization conversion rate of step (b) is 50 to 60%. After the polymerization conversion rate of 50 to 60%, monomer droplets in the latex disappear and the internal pressure of the reactor decreases, so that the polymerization productivity can be stably improved by batch or continuous administration of the remaining content of the conjugated diene compound. And the particle diameter can be controlled.

The polymerization temperature for preparing the rubbery polymer latex can be controlled according to the gel content and swelling degree of the rubbery latex, and the selection time and the timing of administration of the polymerization initiator should also be considered.

In the present invention, since the particle diameter and gel content of the rubber polymer constituting the core greatly influences the physical properties such as impact strength, fluidity, and colorability of the thermoplastic resin, selection of appropriate particle diameter and gel content is important. That is, the smaller the rubber polymer particle diameter, the better the colorability and appearance characteristics, but the impact strength and fluidity are lowered, while the larger the particle diameter, the better the impact strength and flowability, but the appearance and colorability are lowered. In addition, when the gel content of the rubber polymer is low, the monomer mixture swells much in the rubber polymer during the graft reaction, so that the rubber layer becomes too hard, and the colorability is lowered. In addition, it is difficult to coat the core layer of the rubber, so it is easy to agglomerate during aggregation and drying. In addition, if the gel content is too high, the swelling is less enough to cover the core layer of the rubber with a hard polymer, but the impact absorption is lowered when the external impact is lowered, so that the impact resistance is lowered, it is important to select the appropriate gel content. Therefore, the butadiene-based rubber polymer prepared in the present invention is preferably adjusted so that the particle size is 280 to 330 nm, the gel content is 65 to 85%.

In the present invention, the butadiene-based rubber core polymer is preferably used 60 to 80 parts by weight. When the content of the rubbery polymer is less than 60 parts by weight, the impact reinforcing effect is insignificant and the colorability is poor, and when more than 80 parts by weight, the graft ratio cannot be sufficiently increased due to the decrease of the graft monomer, and the dispersibility in the matrix resin This lowers and the impact strength drops. Moreover, it is easy to agglomerate at the time of aggregation and drying after completion | finish of polymerization.

(Graft shell polymer)

60 to 80 parts by weight of the rubber polymer prepared above

Iii) 73 to 95% by weight of alkyl methacrylate monomers;

Ii) 5 to 25% by weight of ethylenically unsaturated aromatic compounds; And

Iii) 20 to 40 parts by weight of a mixture of 0 to 2% by weight of the copolymerizable one or more vinyl compounds other than iii) and ii) based on the weight of the impact modifier to prepare a shell.

The shell layer serves to give the graft copolymer compatibility with the thermoplastic resin, and the rubber polymer core layer can exert the impact strength well. It is important to wrap the shell well in order for the rubber polymer of the core to disperse well, but if the shell becomes too thick the impact cannot be transmitted to the core layer upon impact from the outside, thereby reducing the impact.

The alkyl methacrylate monomers include methyl methacrylate, butyl methacrylate, benzyl methacrylate, and methyl methacrylate is most preferred. The use range is preferably 73 to 95% by weight. Alkyl methacrylate monomers serve to increase the impact strength by providing compatibility with the matrix resin. However, when it is used at less than 73% by weight, the effect is weak, and when used at 95% by weight or more, the colorability is lowered, and the shell layer is so thick that the impact from the outside cannot be transmitted to the core layer, so that the impact strength is lowered.

The ethylenically unsaturated aromatic monomers include styrene, alphamethylstyrene, vinyltoluene, 3-4-dichlorostyrene and the like, of which styrene is most preferred. The use range is preferably 5 to 25% by weight. The ethylenically unsaturated aromatic monomer has a high refractive index and serves to improve colorability. However, when the content is less than 5% by weight, the effect of improving the colorability is insignificant. When the content is more than 25% by weight, the compatibility with the matrix resin is low, which adversely affects the impact strength.

The at least one copolymerizable vinyl-based compound other than iv) and ii) may be an alkyl acrylate-based monomer such as ethyl acrylate, propyl acrylate, isopropyl acrylate or butyl acrylate, a vinyl cyan compound such as acrylonitrile, or the like. This can be used. The use range is preferably 0 to 2% by weight.

The emulsifier used in the graft shell polymerization is the same as that used when polymerizing the rubbery polymer, and may be selected from various kinds well known in the emulsion polymerization technique, but alkali metal salts of weak acids such as fatty acid salts are preferable. For example, fatty acid potassium salts, potassium oleate salts and the like can be used. The amount of the emulsifier is preferably 0.5 to 2.0 parts by weight. If the amount of the emulsifier is used in a smaller amount than the above range, excessive coagulum is generated during polymerization, which is not productive.

The polymerization initiators used in the graft shell polymerization are peroxides such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide and sodium formaldehyde sulfoxylate, ethylenediamine tetrasodium acetate, ferrous sulfate Oxidation-reduction catalysts such as sodium pyrophosphate and dextrose can be used.

The method of adding the monomer may be either batch or multistage, but the method of continuous administration for 2 to 5 hours is preferable in order to minimize the formation of coagulum and to improve the graft reaction such as controlling the heat of reaction and improving reproducibility. .

It is preferable to perform the said graft polymerization at the temperature of 40-80 degreeC according to the kind of initiator.

Butadiene-based impact modifier prepared by the present invention, including 2 to 5% by weight relative to 95 to 98% by weight of a thermoplastic resin such as polycarbonate resin provides a thermoplastic resin composition having excellent low-temperature impact strength and colorability.

Hereinafter, preferred examples are provided to help the understanding of the present invention, which is intended to help a specific understanding of the present invention, and the present invention is not limited to the following examples.

[Example]

Example 1

(Rubber polymer production)

75 parts by weight of ion-exchanged water, 60 parts by weight of 1,3-butadiene as monomer, 1.4 parts by weight of potassium rosin salt as emulsifier, 0.6 parts by weight of potassium oleate salt, and potassium carbonate as electrolyte in a nitrogen-substituted polymerization reactor (autoclave) K ₂ CO ₃ ) 0.9 parts by weight, 0.3 parts by weight of tertiary dodecyl mercaptan (TDDM) as a molecular weight regulator, 0.3 parts by weight of potassium persulfate (K ₂ S ₂ O ₈ ) as an initiator and polymerization at a reaction temperature of 70 ℃ After the reaction was carried out to the time of 30 to 40% conversion rate, 0.7 parts by weight of potassium oleate was first administered, and then 20 parts by weight of 1,3-butadiene was collectively reacted at 70 ° C. to the point of polymerization conversion rate of 60%, and then the remaining 1,3 20 parts by weight of butadiene was collectively heated to 80 ° C, and the reaction was terminated when the polymerization conversion was 95%. The polymerization time was 23 hours, the gel content of the obtained rubbery polymer latex was 76%, the average particle diameter was 305 nm.

In the above gel content, the rubber latex is coagulated with dilute acid or metal salt, washed, dried in a vacuum oven at 60 ° C. for 24 hours, and then chopped the obtained rubber mass with scissors, and then 1 g of rubber sections are cut. 100 g of toluene was stored in a dark room at room temperature for 48 hours, and then separated into sol and gel and measured.

(Manufacture of graft copolymer)

70 parts by weight (solid content) of the prepared rubber latex was added to a closed reactor, and the temperature was raised and maintained at 70 ° C. with nitrogen filling. 0.1 parts by weight of sodium pyrophosphate, 0.2 parts by weight of dextrose, and 0.002 parts by weight of ferrous sulfide were introduced into the reactor at once. In a separate mixing device, 25.5 parts by weight of methyl methacrylate, 4.5 parts by weight of styrene, 1.5 parts by weight of potassium oleate, 0.1 parts by weight of cumene hydroperoxide, and 20 parts by weight of ion-exchanged water were mixed to prepare a monomer emulsion. The monomer emulsion was continuously added to the reactor over 2.5 hours. 30 minutes after the completion of the addition, 0.03 parts by weight of cumene hydroperoxide was added and aged at the same temperature for 1 hour to terminate the reaction. After the completion of the polymerization, the particle size was 3200 mm 3, the polymerization conversion was 98%, and the solid content was 42%. An antioxidant was added to this latex, coagulated with an aqueous sulfuric acid solution, and then dehydrated and dried to obtain an impact modifier resin powder.

(Production of the thermoplastic resin composition)

97 parts by weight of polycarbonate (PC 200-1 of LG-Dow), 3 parts by weight of the above-mentioned impact modifier, 0.5 parts by weight of processing additives and 0.02 parts by weight of pigment, and then twin screw extruder of Leistritz Pellets were obtained by extrusion at 200 rpm using a weighing speed of 60 kg / hr and a temperature of 250 to 320 ° C. This pellet was injected into a temperature of 250 ~ 320 ℃ using an Eng100 EC100 φ 30 injection machine was prepared as a specimen for evaluating the impact strength, colorability.

[Example 2]

In the same manner as in Example 1, 5 parts by weight of an impact modifier was added to 95 parts by weight of polycarbonate when preparing a thermoplastic resin.

[Example 3]

In the same manner as in Example 1, by reducing the rubber latex, 60 parts by weight (solids) was added, and 34 parts by weight of methyl methacrylate and 6 parts by weight of styrene were prepared as a monomer emulsion.

Example 4

In the same manner as in Example 1, the rubber latex was increased to add 80 parts by weight (solid), and 17 parts by weight of methyl methacrylate and 3 parts by weight of styrene were prepared as a monomer emulsion.

[Example 5]

In the same manner as in Example 1, 28.5 parts by weight of methyl methacrylate and 1.5 parts by weight of styrene were prepared as a monomer emulsion to reduce styrene.

[Example 6]

In the same manner as in Example 1, 22.5 parts by weight of methyl methacrylate and 7.5 parts by weight of styrene were prepared as a monomer emulsion to increase styrene.

Comparative Example 1

In the same manner as in Example 1, when the thermoplastic resin was prepared by adding 10 parts by weight of the impact modifier to 90 parts by weight of polycarbonate, the impact modifier was increased compared to Example 1.

Comparative Example 2

In the same manner as in Example 1, when the thermoplastic resin was prepared by adding 1 part by weight of the impact modifier to 99 parts by weight of polycarbonate, the impact modifier was reduced compared to Example 1.

[Comparative Example 3]

The same procedure as in Example 1, except that the particle diameter of the rubber core was 260 nm.

[Comparative Example 4]

The same procedure as in Example 1, except that the particle diameter of the rubber core was 340 nm.

[Comparative Example 5]

In the same manner as in Example 1, 50 parts by weight (solids) of rubber latex was added thereto, and 42.5 parts by weight of methyl methacrylate and 7.5 parts by weight of styrene were prepared as a monomer emulsion.

[Comparative Example 6]

In the same manner as in Example 1, 90 parts by weight (solids) of the rubber latex was added, and 8.5 parts by weight of methyl methacrylate and 1.5 parts by weight of styrene were prepared as a monomer emulsion.

[Comparative Example 7]

In the same manner as in Example 1, 30 parts by weight of methyl methacrylate was added alone as a monomer emulsion.

[Comparative Example 8]

In the same manner as in Example 1, 21 parts by weight of methyl methacrylate and 9 parts by weight of styrene were prepared by mixing the monomer emulsion to increase styrene.

[Comparative Example 9]

The same procedure as in Example 1, except that 25.5 parts by weight of methyl methacrylate and 4.5 parts by weight of ethyl acrylate were prepared as a monomer emulsion.

[Comparative Example 10]

The same procedure as in Example 1, except that 25.5 parts by weight of methyl methacrylate and 4.5 parts by weight of acrylonitrile were prepared as a monomer emulsion.

In Examples 1 to 6 and Comparative Examples 1 to 10, the Izod impact strength and colorability of the rubber latex used in the thermoplastic resin composition and the composition and content of the graft copolymer were measured and shown in Table 1 below. It was.

[Property evaluation]

Evaluation of impact strength

Impact strength was measured by making impact specimens according to ASTM D-256 standard and measuring Izod impact strengths at room temperature and -30 ° C for 1/8 inch specimens, respectively.

Evaluation of coloring

The colorability measured the CIE-Lab color value through the color tester for the specimens processed by adding the colorant during the injection molding, and showed the difference in the color values based on the specimen with the best coloration (the specimen most similar to the color of the colorant). The degree of coloring was distinguished by ΔE = (ΔL ² + Δa ² + Δb ² ) ^1/2 . 5 points for △ E value of 2 or less, 4 points for △ E value of 2 to 4, 3 points for △ E value of 4 to 6, 2 points for △ E value of 6 to 8, △ When E value exceeded 8, the method of giving 1 point was used.

[Table 1]

Butadiene
Impact modifier
content
(weight%) Rubber core Graft shell Izod impact strength
(Kgf-cm / cm) Coloring Particle size (nm) content
(Parts by weight) MMA
content
(Parts by weight) Comonomer
Type and content
(Parts by weight) 25 ℃ -30 ℃ Example 1 3 300 70 25.5 SM 4.5 79.8 65.4 4.5 Example 2 5 300 70 25.5 SM 4.5 78.2 64.9 4.5 Example 3 3 300 60 34 SM 6.0 77.3 64.9 4.5 Example 4 3 300 80 17 SM 3.0 76.5 63.7 4.5 Example 5 3 300 70 28.5 SM 1.5 80.7 66.2 3.5 Example 6 3 300 70 22.5 SM 7.5 79.1 62.5 5 Comparative Example 1 10 300 70 25.5 SM 4.5 76.5 58.7 4 Comparative Example 2 One 300 70 25.5 SM 4.5 77.3 51.2 4.5 Comparative Example 3 3 260 70 25.5 SM 4.5 71.3 55.3 4.5 Comparative Example 4 3 340 70 25.5 SM 4.5 70.8 56.2 4 Comparative Example 5 3 300 50 42.5 SM 7.5 74.6 57.6 3 Comparative Example 6 3 300 90 8.5 SM 1.5 73.7 56.8 4 Comparative Example 7 ^* 3 300 70 30 - 78.9 54.6 2 Comparative Example 8 3 300 70 21 SM 9 75.8 49.7 5 Comparative Example 9 ^** 3 300 70 25.5 EA 4.5 78.5 54.9 2 Comparative Example 10 3 300 70 25.5 AN 4.5 75.8 49.8 5

^{*, **} large amount of coagulum, 32% final latex solids content

In Table 1, MMA represents methyl methacrylate, SM represents styrene, EA represents ethyl acrylate, and AN represents acrylonitrile, respectively.

As shown in Table 1, it was confirmed that the impact strength and colorability of the thermoplastic resin composition were changed when the particle diameter and content of the rubber latex and the composition and content of the butadiene-based impact modifier were changed.

That is, when the contents of the butadiene-based impact modifier and the rubber latex were changed as in Examples 1 to 4, the coloring properties showed similar values, but there was an effect of improving the Izod impact strength at 70 parts by weight of the rubber latex. As described above, when a small amount of styrene was used in the manufacture of the graft shell, the impact strength was improved, but the coloring property was lowered.

In addition, in the manufacture of the graft shell as in Example 6, when the styrene was increased, the coloring property was improved, but the impact strength was lowered.

When using a small amount or an excessive amount of butadiene-based impact modifiers as in Comparative Examples 1 to 2, the effect of improving the low temperature impact strength is not large. When the particle diameter of the rubber latex was changed as in Comparative Examples 3 to 4, there was no effect of improving the impact strength. not. In the manufacture of the graft shell as in Comparative Example 7, the colorability is lowered when styrene is not used. When the styrene of the graft shell is used in excess as in Comparative Example 8, the colorability is improved, but the impact strength is lowered. In preparing the graft shell as in Comparative Example 9, the effect of improving the impact strength and the coloring property is small when the acrylate is used instead of styrene. In addition, in the manufacture of the graft shell as in Comparative Example 10, when the styrene was used instead of acrylonitrile, the colorability was improved, but it was confirmed that the impact strength was lowered.

Although the present invention has been described in detail with reference to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the scope and spirit of the present invention, and such modifications and modifications fall within the scope of the appended claims. It is also natural.

Claims (23)

a) polymerizing a conjugated diene compound alone or copolymerizing a vinyl cyan compound and an aromatic vinyl compound with a comonomer to prepare a butadiene-based core rubber polymer having a particle size of 280 to 330 nm, (a) 60 to 70 parts by weight of the total 100 parts by weight of the conjugated diene compound, 1 to 4 parts by weight of the emulsifier, 0.2 to 0.4 parts by weight of the polymerization initiator, 0.2 to 2.0 parts by weight of the electrolyte, 0.1 to 0.5 parts by weight of the molecular weight regulator, ion exchange water 75 to 100 parts by weight of a batch to react at 55 ~ 75 ℃; (b) 15 to 20 parts by weight of the conjugated diene compound and 0.5 emulsifier when the polymerization conversion rate of step (a) is 30 to 40%. Reacting at 65 to 75 ° C. in batch doses of ˜1.5 parts by weight; And (c) reacting the remaining conjugated diene compound in batch or successively after the time point at which the polymerization conversion rate in step (b) is 50 to 60%; ; And b) graft copolymerization of the monomer mixture in the presence of 60 to 80 parts by weight of the butadiene core rubber polymer to form a shell on the butadiene core rubber polymer to prepare a graft shell polymer, The monomer mixture is Iii) 73-95 weight percent of alkyl methacrylate monomers; Ii) 5 to 25% by weight of ethylenically unsaturated aromatic compounds; And Iii) 0 to 2% by weight of one or more copolymerizable vinyl compounds other than iv) and ii) above; Lt; Preparing a graft shell polymer having 20 to 40 parts by weight of the shell; Characterized in that it comprises Method for producing a graft copolymer of core-shell structure for polycarbonate. The method of claim 1, The conjugated diene compound is at least one selected from the group consisting of 1,3-butadiene, isoprene, chloroprene and pyrrylene. Method for producing a graft copolymer of core-shell structure for polycarbonate. The method of claim 1, The aromatic vinyl compound is at least one selected from the group consisting of styrene and α-methylstyrene, characterized in that Method for producing a graft copolymer of core-shell structure for polycarbonate. The method of claim 1, The vinyl cyan compound is at least one selected from the group consisting of acrylonitrile, methacrylonitrile and ethacrylonitrile. Method for producing a graft copolymer of core-shell structure for polycarbonate. The method of claim 1, The comonomer used in step a) is used in an amount of 0 to 20 parts by weight based on 100 parts by weight of the total monomer content. Method for producing a graft copolymer of core-shell structure for polycarbonate. delete The method of claim 1, The alkyl methacrylate monomer is at least one member selected from the group consisting of methyl methacrylate, butyl methacrylate and benzyl methacrylate. Method for producing a graft copolymer of core-shell structure for polycarbonate. The method of claim 1, The ethylenically unsaturated aromatic compound is at least one member selected from the group consisting of styrene, alphamethylstyrene, vinyltoluene and 3-4-dichlorostyrene. Method for producing a graft copolymer of core-shell structure for polycarbonate. The method of claim 1, The at least one copolymerizable vinyl compound other than iii) and ii) is at least one member selected from the group consisting of ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate and acrylonitrile. Method for producing a graft copolymer of core-shell structure for polycarbonate. delete The method of claim 1, The butadiene-based core rubber is characterized in that the gel content of 65 ~ 95% Method for producing a graft copolymer of core-shell structure for polycarbonate. Obtained by the method of any one of claims 1 to 5 and 7 to 9, a) 60 to 80 parts by weight of a butadiene-based core rubber polymer having a particle size of 280 to 330 nm prepared by homopolymerizing a conjugated diene compound or copolymerizing a vinyl cyan compound and an aromatic vinyl compound with a comonomer, and b) 20 to 40 parts by weight of a shell formed on the butadiene-based core rubber polymer by graft copolymerization of the monomer mixture in the presence of the butadiene-based core rubber polymer, The monomer mixture is Iii) 73-95 weight percent of alkyl methacrylate monomers; Ii) 5 to 25% by weight of ethylenically unsaturated aromatic compounds; And Iii) at least one vinyl-based compound copolymerizable other than iv) and ii) ˜2 weight percent; ≪ RTI ID = 0.0 > Graft copolymer of core-shell structure for polycarbonate. delete delete delete delete delete delete delete delete delete 95 to 98% by weight of polycarbonate and 2 to 5% by weight of the graft copolymer according to claim 12 Thermoplastic resin composition. It is obtained by compression-molding the thermoplastic resin composition of Claim 22. Molded body.