JPH0548779B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a thermoplastic resin composition, and more particularly, it contains a high content of ethylene/propylene/non-conjugated diene copolymer rubber having a high gel content, and has particularly high impact resistance and heat resistance. The present invention relates to a thermoplastic resin composition that provides molded products with excellent properties and surface gloss. Prior Art Graft copolymers obtained by copolymerizing ethylene/propylene/non-conjugated diene copolymer rubber with styrene and acrylonitrile, and styrene and acrylonitrile, which are called rigid components, are added to this graft copolymer. A rubber-reinforced resin composition prepared by mixing a copolymer with is conventionally known as AES resin. Although these resins have improved impact resistance compared to polystyrene and styrene-acrylonitrile copolymers, and improved weather resistance compared to ABS resin, their heat resistance and surface gloss are still insufficient. isn't it. Conventionally, to obtain such AES resin,
A known method is to graft copolymerize styrene, acrylonitrile, etc. onto ethylene/propylene/nonconjugated diene copolymer rubber by suspension polymerization, solution polymerization, or bulk polymerization, but the stability of the reaction system during polymerization, Graft copolymerization by solution polymerization is currently the mainstream method in view of the physical properties of the resulting AES resin and economic efficiency. however,
When using the solution polymerization method, it is difficult to obtain a copolymer containing a high content of ethylene/propylene/nonconjugated diene copolymer rubber and having an excellent balance of physical properties due to its polymerization form. Therefore, the production of AES resin by emulsion polymerization is also
For example, as described in Japanese Patent Publication No. 49-14549, various proposals have been made, but even with conventionally known emulsion polymerization methods, ethylene, propylene, and non-conjugated diene having a high gel content cannot be used. It is difficult to stably and reproducibly produce an AES resin containing a high content of copolymer rubber. On the other hand, JP-A-61-238844 discloses a method of emulsifying and grafting an aromatic vinyl compound and a vinyl cyanide monomer to an ethylene/propylene/non-conjugated diene copolymer rubber having a gel content of 40 to 95% by weight. It is described that a thermoplastic graft copolymer having excellent impact resistance, weather resistance, surface gloss, etc. can be obtained by polymerization. However, even when using this method, when α-methylstyrene is used for the purpose of improving the heat resistance of the resin, the monomer conversion rate is not high and the polymerization stability is not necessarily sufficient. can get
AES resin also has insufficient impact resistance. Furthermore, in order to improve the physical properties of AES resin, for example, JP-A-57-70148 and JP-A-59-
As described in Publication No. 184243, etc., a graft copolymer to a rubber-like polymer and a rigid component as a copolymer consisting of an aromatic vinyl compound, acrylonitrile, N-phenylmaleimide, etc. are mixed. Various thermoplastic resin compositions have also been proposed. However, in terms of impact resistance,
However, this is not satisfactory, and therefore a high-performance resin composition with well-balanced physical properties cannot be obtained. Problems to be Solved by the Invention The present inventors have conducted extensive research to solve the above-mentioned problems with conventional thermoplastic resin compositions made of AES resin and rigid components. A predetermined amount of an aromatic vinyl compound and a vinyl cyanide monomer are co-emulsified and grafted onto an ethylene/propylene/non-conjugated diene copolymer rubber at high temperature in the absence of a chain transfer agent using a predetermined redox initiator. By polymerization, AES resin can be obtained stably at a high conversion rate, and furthermore, this AES resin can be combined with a predetermined aromatic vinyl compound, vinyl cyanide monomer, and N-phenyl. It has been discovered that when mixed with a rigid component consisting of a copolymer with maleimide to form a thermoplastic resin composition, this resin composition provides a molded product with particularly excellent impact resistance, heat resistance, and surface gloss. , which led to the present invention. Means for Solving the Problems The thermoplastic resin composition according to the present invention comprises: (a) 40 to 80 parts by weight of an ethylene/propylene/nonconjugated diene copolymer rubber latex having a gel content of 40 to 95% by weight; Group vinyl compounds 60-76
60 to 20 parts by weight of a vinyl monomer mixture consisting of 40 to 24 parts by weight of cumene hydroperoxide, ferrous sulfate, and sodium pyrophosphate in a total amount of 100 parts by weight. and in the absence of a chain transfer agent in the presence of a redox initiator consisting of dextrose and dextrose.
React at a temperature of 70 to 95°C, and at that time,
Add a polymerization activator consisting of ferrous sulfate, sodium pyrophosphate, and dextrose at a ratio of 0.3 to 0.8 to the total amount to the above latex all at once at the start of the reaction, and add for at least 1 hour from the start of the reaction. The entire amount of the vinyl monomer mixture and cumene hydroperoxide is continuously added to the latex over the addition time of the vinyl monomer mixture and cumene hydroperoxide, and the remainder of the polymerization activator and emulsifier are added to the latex over the addition time of the vinyl monomer mixture and cumene hydroperoxide. Graft copolymer 10 to 60 obtained by continuously adding to the above latex over a period of 30 minutes or more than
and (b) 30 to 55 weight % of α-methylstyrene, 0 to 20 weight % of styrene, 10 to 35 weight % of acrylonitrile, and N so that the total amount with the above graft copolymer is 100 parts by weight. -Phenylmaleimide 1
It is characterized by comprising 40 to 90 parts by weight of a copolymer having a monomer composition of 25% by weight. The ethylene-propylene-nonconjugated diene copolymer rubber containing the gel used in the present invention is already known, for example, as described in the above-mentioned Japanese Patent Application Laid-Open No. 61-238844. However, in the present invention, the ethylene/propylene/non-conjugated diene copolymer rubber must have a gel content of 40 to 95% by weight, defined as the rubber content insoluble in toluene, and in particular, 50
It is preferred to have a gel content in the range of ~80% by weight. When the gel content is less than 40% by weight,
When the resulting AES resin was mixed with a rigid component to form a thermoplastic resin composition, the desired high impact resistance and excellent molded appearance could not be obtained.
On the other hand, if the gel content is more than 95% by weight, the resulting resin composition will be significantly inferior in impact resistance. Further, in the ethylene/propylene/non-conjugated diene copolymer rubber, the weight ratio of ethylene to propylene is preferably in the range of 85:15 to 30:70, and the non-conjugated diene component is preferably 1,
These include 4-hexadiene, 5-ethylidene-2-norbornene, 5-vinylnorbornene, and dicyclopentadiene. In the present invention, the vinyl monomer to be graft copolymerized to the ethylene/propylene/nonconjugated diene copolymer rubber is a mixture of an aromatic vinyl compound and a vinyl cyanide compound, and examples of the aromatic vinyl compound include: Styrene and α-methylstyrene are preferably used, and as the vinyl cyanide monomer, acrylonitrile and methacrylonitrile are preferably used. In the above monomer mixture, the aromatic vinyl compound is in the range of 60 to 76% by weight, and the cyanide vinyl compound is in the range of 40 to 76% by weight.
It is necessary that the content be in the range of 24% by weight. 60% by weight of aromatic vinyl compounds in the monomer mixture
If the amount is less than 76% by weight, the resulting resin composition will be significantly inferior in thermal stability, while if it exceeds 76% by weight, the resulting resin composition will be inferior in heat resistance and impact resistance. According to the present invention, 60 to 20 parts by weight of the monomer mixture is grafted onto 40 to 80 parts by weight of the ethylene/propylene/nonconjugated diene copolymer rubber containing the gel so that the total amount is 100 parts by weight. Polymerize. In this graft copolymerization reaction, when the amount of the copolymer rubber is less than 40 parts by weight, the resulting resin composition is inferior in impact resistance and heat resistance, while when it is more than 80 parts by weight, the resin composition This is because the object will have poor impact resistance. In the present invention, particularly as a polymerization initiator,
A redox initiator consisting of cumene hydroperoxide, ferrous sulfate, sodium pyrophosphate and dextrose is used. According to the method of the present invention, the redox initiator thus specified is used, and as described below, a polymerization activator consisting of ferrous sulfate, sodium pyrophosphate, and dextrose, and cumene hydropere are also used in the polymerization reaction. Adjusting the amount of oxide, vinyl monomer mixture and emulsifier added, timing of addition to latex, addition time, etc. according to the present invention,
Furthermore, by conducting the reaction at a predetermined reaction temperature in the absence of a chain transfer agent, the amount of emulsifier used can be reduced to about 1/3 of the conventional amount, resulting in a high monomer conversion rate. In addition, it is possible to significantly improve polymerization stability and obtain an AES resin having the desired excellent properties. For example, when using an initiator other than those specified in the present invention, the monomer conversion rate is usually low or the latex stability is poor, resulting in the reaction system solidifying during the reaction, or The resin composition has poor impact resistance and molded appearance. In the present invention, a polymerization activator consisting of ferrous sulfate, sodium pyrophosphate, and dextrose is added to the latex in a quantity ratio of 0.3 to 0.8 to the total amount at the start of the reaction, and
The entire amount of vinyl monomer mixture and cumene hydroperoxide is continuously added to the latex over an addition period of at least one hour from the start of the reaction. Furthermore, the remainder of the polymerization activator and the entire amount of the emulsifier are continuously added to the latex from the start of the reaction over a period of at least 30 minutes longer than the addition time of the vinyl monomer mixture and cumene hydroperoxide. . For example, when adding the entire amount of polymerization activator and emulsifier to the latex at once before adding the vinyl monomer mixture, the stability of the latex during the polymerization reaction is poor and the amount of coagulated material precipitated increases. Moreover, the monomer conversion rate is low. If the amount of emulsifier used is increased, other conditions being the same, the stability of the latex is improved and the monomer conversion rate is also increased, but the resulting resin is inferior in impact strength.
On the other hand, when the entire amount of polymerization activator and emulsifier is added continuously to the latex, an induction period appears in the reaction;
Moreover, the resulting resin will have poor physical properties. Furthermore, when the entire amount of the polymerization activator is added to the latex at once at the start of the reaction and the emulsifier is added continuously, the stability of the latex is improved, but the monomer conversion rate is low. Furthermore, when the addition time of the polymerization activator, emulsifier, and water is shorter than the monomer addition time, the monomer conversion rate is low. Furthermore, according to the method of the present invention, it is necessary to graft-copolymerize the monomer mixture onto the ethylene-propylene-nonconjugated diene copolymer rubber in the absence of a chain transfer agent such as t-dodecylmercaptan. It is. In addition, in the method of the present invention, the reaction temperature is 70~
In particular, the reaction temperature is 80 to 90°C from the viewpoint that the latex has high stability during the polymerization reaction and furthermore, it can impart excellent impact resistance to the resulting resin composition. A range of is preferred. In particular, in the method of the present invention, the monomer mixture is added continuously from the start of the reaction, preferably over a period of 1 to 3 hours, at a temperature of 70 to 90°C, preferably
It is desirable to carry out the reaction at a temperature of 80-90°C. The thermoplastic resin composition according to the present invention can be obtained by mixing a rigid component as a copolymer of monomers having a predetermined composition with the AES resin obtained as described above. That is, the thermoplastic resin composition according to the present invention contains 10 to 60 parts by weight of the above AES resin, 30 to 55% by weight of α-methylstyrene, 0 to 20% by weight of styrene, 10 to 35% by weight of acrylonitrile, and N-phenyl. It consists of 40 to 90 parts by weight of a copolymer having a monomer composition of 1 to 25% by weight of maleimide, and the total amount is 100% by weight.
Constitutes the weight part. In 100 parts by weight of the resin composition, 10 parts of AES resin
When the amount is less than 60 parts by weight, the resin composition has poor impact resistance, while when it exceeds 60 parts by weight, the resin composition has poor heat resistance. Furthermore, when the monomer component of the rigid copolymer contains less than 30% by weight of α-methylstyrene or more than 20% by weight of styrene, the heat resistance decreases;
When it exceeds 35%, the resin becomes noticeably colored.
In addition, when N-phenylmaleimide is less than 1% by weight, the resin composition does not have sufficient heat resistance, while when it is more than 25% by weight, the resulting resin composition has poor impact resistance. With,
This is not preferable since resin coloring also becomes noticeable. The above-mentioned rigid component can be obtained by conventional methods such as emulsion polymerization, suspension polymerization, solution polymerization, and bulk polymerization, as is conventionally known. In addition, in the production of this rigid component, by using an appropriate amount of a chain transfer agent as a molecular weight regulator, such as t-dodecyl mercaptan or α-methylstyrene dimer, a product having the required molecular weight can be obtained. be able to. The AES resin and such rigid components are mixed together with antioxidants, lubricants, processing aids, pigments, fillers, etc. as necessary, and kneaded using, for example, an extruder, a Banbury mixer, a kneading roll, etc. A thermoplastic resin composition can be obtained by pelletizing. Effects of the Invention As described above, the thermoplastic resin composition according to the present invention is an AES resin in which a predetermined amount of an aromatic vinyl compound and cyanide are added to an ethylene propylene non-conjugated diene copolymer rubber having a high gel content. A graft copolymer of a monomer mixture consisting of vinyl monomers is used, and a rigid component having a predetermined composition is mixed with the AES resin.
In particular, it has excellent impact resistance, heat resistance, and surface gloss.
To provide a high-performance thermoplastic resin composition with well-balanced physical properties. Therefore, the resin composition containing the graft copolymer according to the present invention can be suitably used as a molding material in the fields of automobile parts, building materials, etc., for example. EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way. In the following, the gel content of the ethylene/propylene/non-conjugated diene copolymer rubber is determined by coagulating the copolymer rubber latex with dilute sulfuric acid, washing with water, drying, taking 1 g of this, and adding 40% of the copolymer rubber latex to 200 ml of toluene. It was determined by soaking for an hour, then filtering through a 200-mesh stainless wire mesh, and drying the residue. Example 1 In a reaction vessel equipped with a stirrer, distilled water, the non-conjugated diene component was 5-ethylidene-2-norbornene, and the gel content was 72% by weight were added as shown in Table 1.
ethylene propylene non-conjugated diene copolymer rubber (average particle size 0.5 μm), sodium hydroxide, sodium pyrophosphate, ferrous sulfate, and dextrose (this preparation is referred to as composition A), 80 The temperature was raised to ℃. Separately, a mixture consisting of acrylonitrile, styrene and cumene hydroperoxide in predetermined amounts shown in Table 1 was prepared (this mixture is referred to as composition B), and together with this, each of
Ferrous sulfate, sodium pyrophosphate in the prescribed amounts shown in the table.

【table】

[Table] A mixture consisting of dextrose, dextrose, sodium oleate, and water was prepared (this mixture is referred to as composition C), and each of these was added to the above reaction vessel.
It was added continuously over 150 minutes and 180 minutes, after which the reaction was continued for an additional 60 minutes at 80°C. The obtained latex was coagulated, washed and dried to obtain a graft copolymer according to the present invention and a graft copolymer as a comparative example, as shown in Table 1.
That is, AES resins 1-8 were obtained from AES resins 1-1. Table 1 shows the conversion rate of the vinyl monomer mixture in this graft copolymerization reaction and the stability of the latex in terms of the amount of coagulated material precipitated at the end of the reaction. Separately, after thoroughly purging the inside of an autoclave equipped with a stirrer with nitrogen, predetermined amounts of monomers, distilled water, surfactants, organic peroxides, etc. were charged, as shown in Table 2, and the autoclave was heated at 350 rpm. While stirring in proportion,
The internal temperature was raised to 80°C, and polymerization was carried out at this temperature for 9 hours. Next, the internal temperature was raised to 120°C over 2.5 hours, and the reaction was carried out at this temperature for 2 hours. The obtained slurry was washed and dried to obtain copolymers 2-1 to 2-4 as rigid components. Next, as shown in Table 3, 2-1 of the above rigid components were added so that the amount of ethylene-propylene-nonconjugated diene copolymer rubber in the resulting resin composition was constant (24.5% by weight). The above
AES resin, calcium stearate 0.5 parts by weight,
and N,N'-ethylene bisstearylamide 1.5
The powder was mixed with parts by weight, kneaded in a Banbury mixer, and then pelletized. This pellet was molded using a 2-ounce injection molding machine with a cylinder temperature of 260°C to obtain resin molded products 3-1 to 3-8. Table 3 shows the measurement results of the physical properties of these. It is clear that molded articles made from resin compositions containing AES resins according to the method of the present invention are particularly excellent in Izod impact value, heat distortion temperature and molded appearance.

【table】

[Table] Example 2 The AES resin 1-6 obtained in Example 1 and the rigid components 2-1 to 2-4 were mixed in the proportions shown in Table 4 to obtain a resin composition. is pelletized and injection molded to obtain the resin molded product 3.
-6, 3-11 was obtained from 3-9. Table 4 shows the measurement results of the physical properties of these. It is understood that the resin composition containing the AES resin produced by the method of the present invention has an excellent heat distortion temperature and an excellent balance between impact resistance and heat resistance. Example 3 First, for comparison, using groups A, B, and C shown in Table 5, a method of adding a polymerization activator and an emulsifier to a latex at the start of the reaction, and a method of adding a polymerization activator and an emulsifier to a latex at the start of the reaction. AES Resin 1 as a comparative example
1-14 were obtained from ~9. Next, in the same manner as in Example 1, as shown in Table 6,

【table】

【table】

【table】

【table】

[Table] Hydroperoxide.

[Table] These AES resins are combined with the rigid component 2-
1, 0.5 parts by weight of calcium stearate, and N,
A resin composition was obtained by powder mixing with 1.5 parts by weight of N'-ethylenebisstearylamide, which was kneaded in a Banbury mixer and pelletized. This pellet was molded using a 2-ounce injection molding machine with a cylinder temperature of 260°C to obtain resin molded product 3-12.
The physical properties of 3-17 were measured. The results are shown in Table 6. As shown in Tables 5 and 6, AES resin 1-
According to 9 and 1-10, since the entire amount of the polymerization activator and emulsifier was added all at once before adding the vinyl monomer mixture to the latex, the stability of the latex was poor and the amount of precipitated coagulum was low. The final monomer conversion rate is also low. When polymerizing under the same conditions as above except for increasing the amount of emulsifier added,
As seen in AES Resin 1-11, although the stability of the latex is improved and the monomer conversion rate is also increased, the impact strength of the resulting resin is low. Furthermore, as seen in AES Resin 1-12, adding the entire amount of polymerization activator and emulsifier to the latex continuously improves the stability and monomer conversion of the latex, but increases the induction period in the reaction. In addition, the physical properties of the resin obtained also deteriorate. When the entire amount of polymerization activator is charged at once and only the emulsifier is added continuously, the stability of the latex is improved, as seen in AES resin 1-13, but the monomer conversion rate is low. . When adding the polymerization activator and emulsifier within a time shorter than the continuous addition time of the monomer, as seen in AES resin 1-14,
Monomer conversion rate decreases. Next, in the same manner as in Example 1, using compositions A, B, and C shown in Table 7, AES resins according to the present invention with various gel contents in ethylene-propylene-nonconjugated diene copolymer rubber and comparative AES resins 1-6 and 1-15 to 1-20 as examples
was prepared. Next, as shown in Table 8, in the same manner as in Example 1, these AES resins were added to the rigid component 2-
1, 0.5 parts by weight of calcium stearate, and N,
A resin composition was obtained by powder mixing with 1.5 parts by weight of N'-ethylene bisstearylamide, which was kneaded in a Banbury mixer and pelletized. This pellet is heated to a cylinder temperature of 260℃.
Molded with an ounce injection molding machine to form a resin molded product 3-
In addition to 6, the physical properties of 3-18 to 3-23 were measured. The results are shown in Table 8. It is clear that resin moldings made from resin compositions containing AES resins according to the method of the invention have particularly good Izod impact values, gloss and molded appearance. Example 4 As shown in Table 9, in compositions A, B, and C, the polymerization initiator was variously changed, and acrylonitrile and acrylonitrile were added to ethylene propylene non-conjugated diene copolymer rubber at the reaction temperature shown in Table 9. AES resins 1-21 to 1-25 according to comparative examples were obtained by emulsion graft copolymerization with styrene. The latex stability and monomer conversion in this reaction are shown in Table 9 together with the results for the AES resins 1-6 according to the present invention.

【table】

[Table] Peroxide.

【table】

【table】

【table】

[Table] According to the method of the present invention, it is possible to graft-copolymerize a monomer into an ethylene/propylene/non-conjugated diene copolymer rubber at a high conversion rate while maintaining the stability of the latex. Next, as shown in Table 10, the above AES resin and the above rigid component 2-1 are mixed at a predetermined ratio to obtain a resin composition, which is pelletized and injection molded to form a resin molded product. Along with 3-6, we got 3-24 to 3-26. Table 10 shows the measurement results of the physical properties of these resin molded products. It is understood that the resin composition containing the AES resin produced by the method of the present invention has excellent impact resistance, heat resistance, and appearance, and provides a well-balanced molded product. Example 5 Using compositions A, B, and C shown in Table 11 and varying the reaction temperature, AES resins 1-6, 1-26 to 1 were prepared according to the present invention and comparative examples as shown in Table 11. I got -29. Table 11 shows the latex stability and monomer conversion in this reaction. According to the method of the present invention, it is possible to graft copolymerize a monomer into an ethylene/propylene/nonconjugated diene copolymer rubber at a high conversion rate while maintaining the stability of the latex. Next, the AES resin obtained in this way was
As shown in Table 12, it is mixed with the rigid component 2-1 at a predetermined ratio, pelletized, and injection molded.
Resin moldings 3-30 were obtained from resin moldings 3-6 and 3-27. Table 12 shows the measurement results of the physical properties of these. It is understood that the resin composition containing the AES resin produced by the method of the present invention not only has particularly excellent impact resistance, but also excellent heat resistance and molded appearance, thus giving a well-balanced molded product. Example 6 Using compositions A, B, and C shown in Table 13, the reaction temperature was 80°C, and the monomer mixture was added all at once at the start of the reaction, or the time for continuous addition was varied. As shown in Table 13, AES resins 1-6 and 1-30 according to the present invention and comparative examples

【table】

【table】

【table】

【table】

【table】

1-36 was obtained from [Table]. Table 13 shows the latex stability and monomer conversion in this reaction. According to the method of the present invention, it is possible to graft copolymerize a monomer into an ethylene/propylene/nonconjugated diene copolymer rubber at a high conversion rate while maintaining the stability of the latex. Next, the AES resin obtained in this way was
As shown in Table 14, it is mixed with the rigid component 2-1 at a predetermined ratio, pelletized, and injection molded.
Resin moldings 3-37 were obtained from resin moldings 3-6 and 3-31. Table 14 shows the measurement results of the physical properties of these resin molded products. The resin composition containing the AES resin produced by the method of the present invention not only has particularly excellent impact resistance, but also has excellent heat resistance and
It is understood that the molded product has excellent appearance, gloss, etc., and thus provides a well-balanced molded product. Example 7 Table 15 shows the weather resistance test results for the resin molded products 3-4 to 3-6. As molded product 3-38 for comparison, Butadier

【table】

【table】

[Table] Table 15 also shows the results for a general-purpose AES resin containing 20% by weight of the carbon component. As is clear from these results, it is clear that the resin composition containing the AES resin according to the present invention has much better weather resistance than the resin molded product according to the comparative example. In addition, in the above examples, the method of measuring the physical properties of the resin molded product is as follows. Notched Izod Impact Value Based on ASTM D 256. Heat distortion temperature According to ASTM D 648-56. Tensile strength According to ASTM D 638. Bending strength According to ASTM D 790. Gloss Conforms to JIS Z 8741 (reflectance at 60° angle of incidence). Evaluation of molded appearance Visual evaluation was performed based on the following criteria. 〇 Even pearl-like luster. △ Some unevenness of pearl-like luster is observed. × Uneven pearl-like luster is clearly observed. Fluidity Evaluation was made using the minimum filling pressure (Kg/cm ² ) during injection molding at 260°C. Weather resistance The test piece was tested using a weather meter (Suga Test Instruments Sunshine Super Long Life Xenon Weather Meter WEL-6XS-HCH-B) at a black panel temperature of 83°C (no rain) at 200°C.
Izod impact value after 400 hours (ASTM
According to D 256. -30°C, no notch) and evaluated based on this impact value.

Claims (1)

[Scope of Claims] 1 (a) An aromatic vinyl compound is added to 40 to 80 parts by weight of an ethylene/propylene/nonconjugated diene copolymer rubber latex having a gel content of 40 to 95% by weight.
Cumene hydroperoxide, ferrous sulfate, The reaction is carried out in the presence of a redox initiator consisting of sodium pyrophosphate and dextrose in the absence of a chain transfer agent at a temperature of 70 to 95°C; A polymerization activator consisting of 0.3 to 0.8 of the total amount of the polymerization activator is added to the latex at once at the start of the reaction, and the vinyl monomer mixture and cumene are added to the latex for at least 1 hour from the start of the reaction. The entire amount of hydroperoxide is continuously added to the latex, and the remainder of the polymerization activator and emulsifier are continuously added for a period of at least 30 minutes longer than the addition time of the vinyl monomer mixture and cumene hydroperoxide. Graft copolymer 10 obtained by adding to the above latex
~60 parts by weight, and (b) 30-55% by weight of α-methylstyrene, 0-20% by weight of styrene, and 10-35% by weight of acrylonitrile so that the total amount with the above graft copolymer is 100 parts by weight. and N-phenylmaleimide 1
A thermoplastic resin composition comprising 40 to 90 parts by weight of a copolymer having a monomer composition of 25% by weight.