KR20020039853A - Method for preparing of acrylonitrile-butadiene-styrene latex graft latex havng superior stability - Google Patents

Abstract

PURPOSE: Provided is a process for producing acrylonitrile-butadiene-styrene(ABS) graft copolymers excellent in stability, impact strength, polymerization stability, and storage stability. CONSTITUTION: The process comprises the steps of: emulsion-polymerizing 50-80pts.wt. of a diene rubber latex, 30-64pts.wt. of an aromatic vinyl compound, and 10-32pts.wt. of a vinyl cyan compound in the presence of 0.1-3pts.wt. of a reactive emulsifier; melting and mixing the polymers with 20-80pts.wt. of styrene-acrylonitrile copolymers. The diene rubber latex is a rubber latex mixture containing a large caliber diene or alkyl acrylate rubber latex having an average particle diameter of 0.27-0.33 micrometer and the gel content of 70-90% and a large caliber diene or alkyl acrylate rubber latex having an average particle diameter of 0.27-0.33 micrometer and the gel content of 55-75%.

Description

Method for preparing acrylonitrile-butadiene-styrene graft copolymer having excellent stability {METHOD FOR PREPARING OF ACRYLONITRILE-BUTADIENE-STYRENE LATEX GRAFT LATEX HAVNG SUPERIOR STABILITY}

[Industrial use]

The present invention relates to a method for preparing acrylonitrile-butadiene-styrene (hereinafter referred to as ABS) graft copolymer, in particular, a diene rubber latex having a mono alkenyl monomer, a vinyl cyan monomer, and a maleic anhydride monomer. The present invention relates to a method for producing an acrylonitrile-butadiene-styrene graft copolymer by melt-kneading by adding at least one selected monomer, to produce a latex having excellent stability.

[Prior art]

In general, when preparing acrylonitrile-butadiene-styrene resins or similar resins, diene-based rubber components such as polystyrene, polystyrene, and polymethyl methacrylate may be used in thermoplastic resins such as styrene-acrylonitrile copolymer (SAN). It is already well known to graft copolymer rubber latexes such as butadiene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, and then add them to the thermoplastic resins to enhance impact resistance.

In order to improve the impact resistance of the conventional ABS, the graft ratio is improved, the average particle size of the diene rubber component being used is increased, or the third component other than the above-mentioned thermoplastic resin or the monomer of the diene rubber component. We tried to overcome this by introducing.

However, in applying this technique, it is difficult to expect improvement in impact resistance as it is limited to improve the graft rate as the content of the rubber component increases, and when increasing the average particle size of the rubber component, The polymerization stability and storage stability of the latex itself were lowered in the content. In addition, the polymer prepared under the above conditions was more impossible to exhibit high impact strength and improved physical properties.

In addition, in mass production of such ABS resin, it is necessary to achieve high polymerization conversion rate in a short time in order to increase productivity. In general, to achieve this in emulsion polymerization, it is necessary to ensure latex stability at high temperatures. In the prior art, when the polymerization is carried out under a short reaction time of about 2 hours and a high temperature reaction condition, it causes a decrease in graft efficiency and an increase in polymerization coagulation due to the generation of many free SANs. As shown in the following, there is a problem of deteriorating the physical properties of the final resin.

In view of the problems of the prior art, an object of the present invention is to provide a method for producing acrylonitrile-butadiene-styrene graft copolymer having excellent stability.

It is another object of the present invention to provide a method for producing an acrylonitrile-butadiene-styrene graft copolymer which is excellent in impact strength, polymerization stability, and storage stability, and excellent in stability at high speed even at high rubber content. The purpose.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a method for producing an acrylonitrile-butadiene-styrene graft copolymer having excellent stability,

a) iii) diene rubber latex;

Ii) aromatic vinyl compounds; And

Iii) vinyl cyan compound

Iii) polymerizing by emulsion polymerization under addition of a reactive emulsifier; And

b) melt polymerization with the styrene-acrylonitrile copolymer

Consecutive steps

It provides a method for producing an acrylonitrile-butadiene-styrene graft copolymer comprising a.

Hereinafter, the present invention will be described in detail.

[Action]

The present invention adds an aromatic vinyl compound and a vinyl cyan compound to the diene rubber latex to emulsify and polymerize it under the addition of a reactive emulsifier, and add styrene-acrylonitrile copolymer to melt kneading to effect impact strength, polymerization stability, and storage. It is possible to provide an acrylonitrile-butadiene-styrene graft copolymer having excellent stability and excellent stability that can be produced at high speed even at high rubber content.

To this end, the acrylonitrile-butadiene-styrene graft copolymer is

a) i) 50 to 80 parts by weight of diene rubber latex;

Ii) 10 to 40 parts by weight of an aromatic vinyl compound; And

Iii) 10-25 parts by weight of a vinyl cyan compound

Iii) emulsion polymerization under addition of 0.1 to 3 parts by weight of a reactive emulsifier; And

b) in the polymer of step a) iii) in styrene-acrylonitrile copolymer 20 to 80

It is prepared through the step of melt-kneading by adding the amount.

The diene rubber latex of i)

A) a diene type having an average particle diameter of 0.27 to 0.33 µm and a gel content of 70 to 90%, or an alkyl acryl

Latex rubber latex; And

B) a diene type having an average particle diameter of 0.27 to 0.33 µm and a gel content of 55 to 75%, or an alkyl acryl

Latex Rubber Latex

A rubber latex mixture is preferable, and in particular, a) a large diameter diene type, or an alkyl acrylate rubber latex and b) a large diameter diene type, or an alkyl acrylate rubber latex is mixed in a weight ratio of 20:80 to 80:20. It is desirable to be.

In the emulsion polymerization, the aromatic vinyl compound and the vinyl cyan compound, which are added as monomers, are divided into two portions, and a redox initiator and an emulsifier are added thereto, and then the temperature is raised to increase the reaction conversion rate so that polymerization can be efficiently performed. .

More specifically,

a) in the reactor

50 to 80 parts by weight of diene rubber latex of i);

Ii) aromatic vinyl compound monomers 10 to 40 Parts by weight;

(Iii) Vinyl cyan compound monomers 10-25 Parts by weight; And

0.1-1 part by weight of reactive emulsifier of i)

A first reaction after the batch;

b) at the point where the first reaction of step a) is heated from 45 ° C. to 70 ° C .;

a) in the reactor of step

10 to 40 parts by weight of the aromatic vinyl compound monomer of ii); And

10-25 parts by weight of the vinyl cyan compound monomer of i)

Remaining monomers of; And

0.1-1 part by weight of reactive emulsifier of i)

Performing a secondary reaction by continuously introducing;

c) in the reactor of step b).

0.1-1 weight part of remaining reactive emulsifier of viii)

After the batch is injected, and then b) raising the temperature of about 10 ℃ than step b)

step; And

d) to the ABS latex prepared by the steps a), b), and c)

Iii) 20 to 80 parts by weight of styrene-acrylonitrile copolymer

Melting and kneading by adding

To prepare an acrylonitrile-butadiene-styrene graft copolymer in a method comprising a.

Unlike the non-reactive emulsifier, the reactive emulsifier used in the method for preparing the acrylonitrile-butadiene-styrene graft copolymer of the present invention has an unsaturated double bond in the emulsifier itself, which enables direct reaction with the monomer. . This indicates that an unreacted emulsifier, such as potassium rosinate, can impart latex stability through chemical bonding, rather than physical adsorption, which is a method of stabilizing the latex. It is also possible to reduce the desorption of emulsifiers and the generation of bubbles due to the excess emulsifiers remaining in the water phase, while the coagulation of the graft polymer and the flocculation from the dehydration process and the outflow of the emulsifier into the wash water. It can prevent water pollution.

The reactive emulsifier as described above may be an anionic emulsifier having an allyl group, a (meth) acryloyl group, and a propenyl group, or a neutral emulsifier.

The anionic emulsifier having an allyl group may be representative of sulfate salts of polyoxyethylene allylglycidyl nonylphenyl ether. Examples of useful anionic emulsifiers include ADEKARIA SOAP SE series (manufactured by Asahi Denka), and neutral allyl groups. Systemic emulsifiers are polyoxyethylene allylglycidyl nonylphenyl ether series, and useful in the market include ADEKARIA SOAP NE series (manufactured by Asahi Denka). Useful in the market as an anionic emulsifier having a (meth) acryloyl group are ELEMINOL RS series (manufactured by Sanyo kasei), and a neutral emulsifier includes a RMA-560 series (manufactured by Nippon Surfactant). In addition, anionic emulsifiers having a propene group may be representative of the almonium sulfate salts of polyoxyethylene allylglycidyl nonyl propenyl phenyl ether, and useful in the market are AQUARON HS series (product of Daiichi Kogyo Seiyaku) and LATEMUL S There is a series (Kao), and the neutral emulsifier is AQUARON BC (product of Daiichi kogyo Seiyaku). One or more of these reactive emulsifiers may be selected or used in combination with a non-reactive emulsifier.

In addition, the reactive emulsifier is preferably added when the emulsion polymerization of 0.1 to 3.0 parts by weight based on 100 parts by weight of ABS.

The non-reactive emulsifier is preferably added 5 parts by weight or less, and may be selected from the group consisting of potassium rosin, sodium rosin, potassium oleate, sodium stearate, and alkyl arylsulfonates.

The styrene-acrylonitrile copolymer (SAN) of d) iii) improves the graft ratio by increasing the size of rubber particles by occluding in rubbery latex particles, and examples thereof include mono alkenyl monomer and vinyl cyan. It is preferable that 2 or more types are selected from the group which consists of a monomer and a maleic anhydride monomer, and they were manufactured by copolymerizing in the weight ratio of 20: 80-40: 60.

In the production method of the present invention, an acrylonitrile-butadiene-styrene graft copolymer may be prepared by adding a molecular weight regulator and a polymerization initiator used in conventional emulsion polymerization.

Specifically, the molecular weight modifier is preferably added 0.1 to 2 parts by weight, consisting of t-dodecylmercaptan, n-dodecylmercaptan, tabinolten, dipentene, t-tyrphyene, chloroform, and carbon tetrachloride One or more species may be selected from the group.

In addition, the polymerization initiator may be selected from the group consisting of silicate hydroperoxide, diisopropyl benzene hydroperoxide, t-butyl peroxy pivalate, potassium persulfate, ammonium persulfate, and t-alkyl hydroperoxide The redox catalyst can be used.

Hereinafter, the rubber latex mixture used to prepare the acrylonitrile-butadiene-styrene graft copolymer will be described.

The large diameter diene type or alkyl acrylate rubber latex having a mean particle diameter of 0.27 to 0.33 µm, a gel content of 70 to 90%, or an alkyl acrylate rubber latex used in the method of the present invention is 0.07 to 0.15 prepared by a conventional emulsion polymerization method. A small-diameter rubber latex having a 탆, a gel content of 90% or more, and a swelling index of 20 or less was prepared by an agglomeration method with an acid.

In addition, the average particle diameter of (b) is 0.27 ~ 0.33 ㎛, the large diameter diene type, or the alkyl acrylate rubber latex having a gel content of 55 ~ 75%, the average particle diameter of 0.07 ~ 0.115 ㎛, gel content 90 prepared by conventional emulsion polymerization method A small diameter rubber latex having a% or more and a swelling index of 20 or less was prepared by an agglomeration method with an acid.

The small-diameter rubber latex is a polybutadiene and butadiene copolymer, and examples thereof include aromatic vinyl compounds such as styrene, alphamethylstyrene and vinyltoluene, and cyanvinyl compounds such as acrylonitrile and methacrylonitrile.

Aggregation with the acid is influenced by the amount of emulsifier, pH, temperature, and amount of solids.

In the present invention, by using the water-soluble initiator in one step to increase the whiteness, the monomer reduced due to the increase in the content of the rubbery polymer is efficiently grafted to have a high impact strength, the second step in the graft efficiency using the oil-soluble initiator Raised.

The acrylonitrile-butadiene-styrene graft copolymer emulsion-polymerized by the preparation method of the present invention is coagulated using 25% CaCl ₂ , an inorganic metal flocculant such as MgSO ₄ , and an organic compound flocculant such as sulfuric acid, and washed. And dried to prepare a powdery graft copolymer.

The swelling index and the gel content measurement defined in the present invention, after the rubber latex solidified wash, dried in a vacuum oven at 40 ℃ for one day, 1 g of rubber in 100 g of toluene and left for 48 hours, the dissolved part The weight of the undissolved portion was measured and measured by the method of Equations 1 and 2 below.

[Equation 1]

[Equation 2]

The present invention will be described in more detail with reference to the following examples and comparative examples. However, an Example is for illustrating this invention and is not limited only to these. The physical properties measured in Examples and Comparative Examples of the present invention were carried out in the following manner.

A. Izod impact strength test

It measured according to the method of ASTM D256. The thickness of the specimen is ¼.

B. Tensile Test

Tensile strength was measured by ASTM D638 method.

C. Melt Flow Index (MI)

It measured by the ASTM D1238 method under the conditions of 220 degreeC and 10 kg.

D. Foaming Volume

After putting 450 g of latex into a 1000 mL beaker, the mixture was run for 10 minutes at 10000 rpm with a Homo mixer, and then the height of the foam was measured.

E. Whiteness (W)

It was measured using a Suga color computer (SUGA Co.).

F. Graft Rate

After dissolving the graft copolymer powder obtained in the above for 24 hours with acetone, using a centrifugal separator at a low temperature to separate the solid content, and dried the separated solid content to determine the graft rate by the following equation (3). In addition, the part dissolved in acetone was precipitated using water, and then dissolved in RHF again to measure the molecular weight.

[Equation 3]

G.% Coagulum (Goagulum)

After the reaction was completed, the coagulum was filtered through a 50 mesh net, and then dried and expressed in weight% based on the total solids and monomers contained during the reaction.

The specimen used in measuring the physical properties was produced by injection molding at 220 ℃, the prepared specimen was used after being left at room temperature for 24 hours.

EXAMPLE

Example 1

20 parts by weight of large-diameter rubber latex (a) with an average particle diameter of 0.25 to 0.35 μm, gel content of 70 to 90%, 35 parts by weight of large-diameter rubber latex (b) with an average particle diameter of 0.25 to 0.35 μm and a gel content of 55 to 75%, ion exchange 94 parts by weight of water, 15.75 parts by weight of styrene monomer, 6.75 parts by weight of acrylonitrile, 0.3 part by weight of t-dodecylmercaptan, 0.06 part by weight of t-butylhydroperoxide into the reactor, 0.12 part by weight of dextrose, and 0.1% of sodium pyrrolate Part by weight and 0.003 parts by weight of ferrous sulfate were added at a temperature of 45 ° C, and the reaction was carried out for 30 minutes while the temperature was raised to 70 ° C.

An emulsion comprising 6 parts by weight of ion-exchanged water, 1.6 parts by weight of HITENOL HS-10, 15.75 parts by weight of styrene monomer, 6.75 parts by weight of acrylonitrile, and 0.2 parts by weight of 80% cumene hydroperoxide was continuously charged for 40 minutes. 1.35 parts by weight of exchanged water, 0.04 part by weight of dextrose, 0.03 part by weight of sodium pyrolate, 0.0007 part by weight of ferrous sulfate, and 0.0351 part by weight of t-butylhydroperoxide were collectively added to the reactor to raise the temperature to 80 ° C. The reaction was terminated and the reaction was terminated. The reaction conversion was 98%.

Example 2

20 parts by weight of large-diameter rubber latex (a) with an average particle diameter of 0.25 to 0.35 μm, gel content of 70 to 90%, 35 parts by weight of large-diameter rubber latex (b) with an average particle diameter of 0.25 to 0.35 μm and a gel content of 55 to 75%, ion exchange 92 parts by weight of water, 15.75 parts by weight of styrene monomer, 6.75 parts by weight of acrylonitrile, 0.3 part by weight of t-dodecyl mercaptan, 0.06 part by weight of t-butylhydroperoxide, and 0.06 part by weight of dextrose at 45 ° C. 0.04 parts by weight of sodium pyrolate, 0.0008 parts by weight of ferrous sulfate, and 2 parts by weight of ion-exchanged water were added, and the polymerization was carried out for 1 hour while the temperature was raised to 70 ° C.

An emulsion consisting of 16 parts by weight of ion-exchanged water, 0.15 parts by weight of HITENOL HS-10, 1 part by weight of potassium rosinate, 15.75 parts by weight of styrene monomer, 6.75 parts by weight of acrylonitrile, and 0.2 parts by weight of 80% cumene hydroperoxide was dexted. The solution was continuously added with 0.06 parts by weight of troz, 0.04 parts by weight of sodium pyrolate, and 0.0008 parts by weight of ferrous sulfate, and was added while maintaining the temperature at 70 ° C. for 50 minutes.

After the polymerization was completed, 1.35 parts by weight of ion-exchanged water, 0.04 part by weight of dextrose, 0.03 part by weight of sodium pyrolate, 0.0007 part by weight of ferrous sulfate, and 0.0351 part by weight of t-butylhydroperoxide were collectively added to the reactor. After the reaction was conducted for 40 minutes while the temperature was raised to 80 ° C., the reaction was terminated.

Example 3

The reaction was carried out in the same manner as in Example 2 except that 0.15 part by weight of S-180, a reactive emulsifier, and 1 part by weight of potassium rosinate were added thereto.

Example 4

The reaction was carried out in the same manner as in Example 2 except that 0.15 part by weight of S-180A, a reactive emulsifier, and 1 part by weight of potassium rosinate were added thereto.

Example 5

The reaction was carried out in the same manner as in Example 2 except that 0.5 parts by weight of HS-10, which is a reactive emulsifier, and 1 part by weight of potassium rosinate were added thereto.

Comparative Example 1

20 parts by weight of a large-diameter rubber latex (a) having an average particle diameter of 0.25 to 0.35 μm, a gel content of 70 to 90%, and 30 parts by weight of a large-diameter rubber latex (b) having an average particle diameter of 0.25 to 0.35 μm and a gel content of 55 to 75% The reaction was carried out in the same manner as in Example 2, using 3 parts by weight of potassium rosinate without adding a reactive emulsifier.

Comparative Example 2

In the same manner as in Example 2, the reaction proceeds for 1 hour by adding 0.8 parts by weight of potassium rosin in step 1, and continuously added the emulsion solution 0.8 parts by weight of potassium rosin in step 2 over 1 hour 30 minutes Then, in three steps, an initiator of the same composition ratio as in Example 1 was added to maintain the reaction for 1 hour, and then the reaction was terminated.

An antioxidant was added to the reactants of Examples 1 to 5 and Comparative Examples 1 and 2, and then agglomerated with 10% aqueous sulfuric acid solution, washed, and dried to obtain a powdery graft copolymer. After adding a weight average molecular weight of 100,000, an acrylonitrile content of 28% SAN and a lubricant, melt-kneading, extruding and injection molding to prepare a specimen with a final rubber content of about 15%. Table 1 shows.

TABLE 1

division Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Solid content (%) 50 47 47 47 47 47 47 Rubber content in the polymerized product (B / B) 35/20 35/20 35/20 35/20 35/20 30/20 30/20 Potassium rosin (parts by weight) One One One One 3 1.6 HS-10 1.6 0.15 0.5 S-180 0.15 S-180A 0.15 Total reaction time (Hr) 2 2.5 2.5 2.5 2.5 2.5 3.5 Total coagulum (%) 0.02 0.02 0.03 0.03 0.02 0.09 0.15 Izod impact strength (㎏ m / m) 29 28 27 27 28 26 25 Tensile Strength (㎏ / ㎠) 495 490 493 489 491 480 476 Liquidity Index (g / 10min) 24 23 22 22 23 20 21 Whiteness 50 48 47 47 49 43 44 Foaming degree (cm / 10 min) One 3 3 4 2 15 12

As shown in Table 1, in Examples 1, 2, 3, 4, and 5 to which a reactive emulsifier was added, polymerization coagulant and foaming were less than Comparative Examples 1 and 2, and impact and tensile strength were high. , Fluidity and whiteness were excellent. In addition, in the case of Example 1 to which only the reactive emulsifier was added, the impact strength, tensile strength, fluidity, whiteness, and It was confirmed that the degree of foaming is excellent.

The production method of the present invention can provide an acrylonitrile-butadiene-styrene graft copolymer excellent in impact strength, polymerization stability, and storage stability, and excellent in latex stability that can be produced at high speed even at high rubber content. .

Claims (10)

In the method for producing acrylonitrile-butadiene-styrene graft copolymer having excellent stability, a) iii) diene rubber latex; Ii) aromatic vinyl compounds; And Iii) vinyl cyan compound Iii) polymerizing by emulsion polymerization under addition of a reactive emulsifier; And b) melt polymerization with the styrene-acrylonitrile copolymer Lotus step Acrylonitrile-butadiene-styrene graft copolymer comprising a. The method of claim 1, a) i) 50 to 80 parts by weight of diene rubber latex; Ii) 30 to 64 parts by weight of an aromatic vinyl compound; And Iii) 10 to 32 parts by weight of a vinyl cyan compound Iii) emulsion polymerization under addition of 0.1 to 3 parts by weight of a reactive emulsifier; And b) in the polymer of step a) iii) in styrene-acrylonitrile copolymer 20 to 80 Step of melt kneading with the amount Acrylonitrile-butadiene-styrene graft copolymer comprising a. The method of claim 1, a) in the reactor 50 to 80 parts by weight of diene rubber latex of i); 10 to 40 parts by weight of the aromatic vinyl compound monomer of ii); 10-25 parts by weight of the vinyl cyan compound monomer of i); And V) 0.1 to 1 part by weight or less of reactive emulsifier A first reaction after the batch; b) at the point where the first reaction of step a) is heated from 45 ° C. to 70 ° C .; a) in the reactor of step Ii) aromatic vinyl compound monomers 10 to 40 Parts by weight; And 10-25 parts by weight of the vinyl cyan compound monomer of i) Remaining monomers of; And 0.1-1 part by weight of reactive emulsifier of i) Performing a secondary reaction by continuously introducing; c) in the reactor of step b). 0.1 to 1 remaining reactive emulsifier of i) Parts by weight After the batch is injected, and then b) raising the temperature of about 10 ℃ than step b) step; And d) to the ABS latex prepared by the steps a), b), and c) Viii) 20 to 80 parts by weight of styrene-acrylonitrile copolymer Melting and kneading by adding Acrylonitrile-butadiene-styrene graft copolymer production method comprising a. The method according to any one of claims 1 to 3, The diene rubber latex of i) A) a large diameter diene type or alkyl having an average particle diameter of 0.27 to 0.33 µm and a gel content of 70 to 90% Acrylate rubber latex; And B) large diameter diene type or alkyl having an average particle diameter of 0.27 to 0.33 µm and a gel content of 55 to 75%; Acrylate rubber latex Method for producing an acrylonitrile-butadiene-styrene graft copolymer which is a rubber latex mixture comprising a. The acrylonitrile- according to claim 4, wherein the large diameter diene type of a) or the large diameter diene type of alkyl acrylate rubber latex and b) or the acrylate rubber latex are mixed in a weight ratio of 20 to 80:80 to 20. Method for preparing butadiene-styrene graft copolymer. The method according to any one of claims 1 to 3, The method for producing an acrylonitrile-butadiene-styrene graft copolymer in which the ii) aromatic vinyl compound and iii) the vinyl cyan compound are mixed in a weight ratio of 20 to 40:60 to 80. The method according to any one of claims 1 to 3, An anionic emulsifier in which the reactive emulsifier of iii) has an allyl group of the sulfate salt of polyoxyethylene allylglycidyl nonylphenyl ether; Neutral emulsifiers having an allyl group of the polyoxyethylene allylglycidyl nonylphenyl ether series; Anionic emulsifier which has a (meth) acryloyl group; Anionic emulsifiers having a propene group of an aluminum sulfate salt of polyoxyethylene allylglycidyl nonyl propenyl phenyl ether; A method for producing an acrylonitrile-butadiene-styrene graft copolymer selected from the group consisting of neutral emulsifiers. The method according to any one of claims 1 to 3, The method for producing an acrylonitrile-butadiene-styrene graft copolymer, wherein the emulsion polymerization is carried out by further adding 5 parts by weight or less of the non-reacting emulsifier. The method of claim 7, wherein The acrylonitrile-butadiene-styrene graph is one or more selected from the group consisting of alkylaryl sulfonates, alkali methylalkyl sulfates, sulfonated alkyl esters, fatty acid soaps, and alkali salts of rosin acid. Process for the preparation of butane copolymers. The method according to any one of claims 1 to 3, (Iii) two or more styrene-acrylonitrile copolymers are selected from the group consisting of mono alkenyl monomers, vinyl cyan monomers, and maleic anhydride monomers, and are added to a weight ratio of 20:80 to 40:60 and melt-kneaded. Process for the preparation of nitrile-butadiene-styrene graft copolymers.