JPH0251937B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention is a heat-resistant resin comprising N-aromatic maleimide, a vinyl aromatic compound, and a vinyl cyanide compound and having excellent heat resistance and high temperature stability.
This invention relates to a heat-resistant resin composition whose main component is a mixture with ABS resin. "Prior Art" A copolymer consisting of a vinyl aromatic compound, especially styrene, and maleic anhydride (hereinafter referred to as SMA resin) is a styrene-acrylonitrile copolymer (hereinafter referred to as AS resin). It is known that it has good compatibility with styrene-acrylonitrile-rubber elastomer graft copolymer (hereinafter referred to as ABS resin), and has a high heat distortion temperature (good heat resistance) (for example, , special public official 1977-
(Refer to Publication No. 50775 and Japanese Patent Publication No. 48-859). Therefore, a composition that is a blend of SMA resin, AS resin, and ABS resin provides a molded article with excellent heat resistance and good solvent resistance. However, its stability at high temperatures is poor; for example, when heated above 230°C, it causes discoloration, foaming, weight loss, crosslinking, etc. Therefore, when used as a normal injection molding material that is heated above 230°C, the commercial value is low. It has been difficult to obtain molded products with high . In order to improve the high-temperature stability of such compositions of SMA resin, AS resin, and ABS resin, attempts have been made to incorporate phenol-based, amine-based, or phosphorus-based antioxidants, etc. Practically satisfactory results have not been obtained. As described above, there has been a desire for a heat-resistant resin composition that solves the drawback of poor high-temperature stability caused by conventional SMA resins. "Problem to be Solved by the Invention" In order to provide a resin composition with excellent heat resistance and high temperature stability, the inventor of the present invention has conducted intensive research and found that maleic anhydride residues contained in SMA resin have been improved. The present invention was achieved by discovering that the above-mentioned problems can be solved by imidization using a specific method. "Means for Solving the Problems" The gist of the present invention is to provide a heat-resistant resin produced by a bulk-suspension polymerization method and comprising an N-aromatic maleimide, a vinyl aromatic compound, and a vinyl cyanide compound; In the heat-resistant resin composition containing the resin, by copolymerizing maleic anhydride and a vinyl aromatic compound monomer in bulk, the maleic anhydride component is 20 to 35% by weight, and the remainder is vinyl aromatic. 65 to 40% by weight of a copolymer consisting of group compound monomer components,
A first step of obtaining a syrup mixed with 35 to 60% by weight of unreacted monomers, and adding the first step to the syrup obtained in the first step.
10 to 10 parts by weight of the total amount of vinyl aromatic compound monomers added to the polymerization system in the process.
25 parts by weight of the vinyl cyanide compound monomer are added and mixed, and then the mixture of the syrup and the vinyl cyanide compound monomer is suspended in water, and the unreacted monomers contained in the syrup are suspended in water. Copolymerizing the vinyl cyanide compound monomer and the above-mentioned vinyl cyanide compound monomer, and using an aromatic amine in an amount of 0.8 to 1.5 times in molar ratio relative to the total amount of maleic anhydride added in the first step, a second step of imidizing at least 60 mol% of the maleic anhydride residues contained in the copolymer chains obtained in the first step; 10 to 90 parts by weight of resin and
A heat-resistant resin composition characterized in that the main component is a mixture obtained by mixing ABS resin at a mixing ratio of 90 to 10 parts by weight. The heat-resistant resin constituting the resin composition according to the present invention is manufactured through a first step and a second step described later. This heat-resistant resin is composed of N-aromatic maleimide, a vinyl aromatic compound, and a vinyl cyanide compound, and has excellent heat resistance and high temperature stability. The first step for producing a heat-resistant resin in the present invention is to copolymerize maleic anhydride and a vinyl aromatic compound monomer in bulk to form a copolymer containing 20 to 35% by weight of the maleic anhydride component. This is the process of producing a syrup containing 65-40% by weight of combined monomers and 35-60% by weight of unreacted monomers. The copolymer of maleic anhydride and vinyl aromatic compound monomer (hereinafter abbreviated as SMA copolymer) contained in the syrup obtained in this first step is imidized in a later step and becomes heat resistant. and a precursor for producing a copolymer with excellent high-temperature stability. Syrup in the present invention refers to SMA copolymer
It refers to a mixture of 65-40% by weight and 35-60% by weight of unreacted monomers. Here, the unreacted monomer means that in the first step, most of the maleic anhydride is consumed as a SMA copolymer through the polymerization reaction, so it is substantially more than just the vinyl aromatic compound monomer. It is what it is. In the present invention, the vinyl aromatic compound monomer is generally styrene, but examples include halogenated styrenes such as α-methylstyrene, t-butylstyrene, o-chlorostyrene, and p-chlorostyrene. These may be used alone or in a mixture of two or more. In the first step of the present invention, the SMA copolymer can be easily produced by the following two bulk copolymerization methods. A copolymerization method in which a vinyl aromatic compound monomer such as styrene is present in a bulk polymerization system, and a mixture of the vinyl aromatic compound monomer and maleic anhydride is continuously added to the polymerization system. A mixture of maleic anhydride and a vinyl aromatic compound monomer containing 5% by weight or less, preferably 1 to 3% by weight of maleic anhydride is present in the bulk polymerization system, and maleic anhydride is then added to the polymerization system. Copolymerization method in which continuous addition is made from In addition, in any of the above copolymerization methods, in the first step during the production of heat-resistant resin, a monomer mixture of vinyl aromatic compound monomer and maleic anhydride present in the polymerization system is added. The copolymerization is preferably carried out while maintaining the proportion of maleic anhydride in the range of 5% by weight or less, preferably 1 to 3% by weight. In the case of the above method, the maleic anhydride and vinyl aromatic compound monomers are mixed at a concentration of 20 to 35% by weight based on 100 parts by weight of the vinyl aromatic compound monomer initially present in the polymerization system. It is preferable to add 70 to 170 parts by weight of the mixture consisting of the following. The amount of these mixtures added is determined by the content of the desired maleic anhydride component in the SMA copolymer to be produced, but since the solubility of maleic anhydride in vinyl aromatic compound monomers is not high, , it is not preferable to increase the concentration of maleic anhydride. In other words, when the concentration of maleic anhydride exceeds 35% by weight, maleic anhydride tends to precipitate from the solution of the mixture unless the mixture is kept at a temperature of 40°C or higher.Furthermore, if the mixture is kept at too high a temperature, maleic anhydride and vinyl aromatic compounds This is not preferable because thermal polymerization with the monomer tends to occur, and both cause clogging of the charging piping of the polymerization system. Furthermore, if the concentration of maleic anhydride in the monomer mixture is less than 20% by weight, it will be difficult to increase the content of the maleic anhydride component in the SMA copolymer, and the heat-resistant resin of the present invention will This is not preferred because the improvement in heat resistance becomes insufficient. The above-mentioned method is preferably carried out by thermal polymerization, in which the polymerization system is heated to 100 to 130 DEG C., and proceeds without the use of an initiator. When the addition of the mixture of maleic anhydride and vinyl aromatic compound monomer is completed, the maleic anhydride in the polymerization system is rapidly consumed, and the contents of the polymerization system are the vinyl aromatic compound monomer and anhydride. Copolymerized with maleic acid
A syrup is obtained in which the SMA copolymer is dissolved in unreacted vinyl aromatic compound monomer. The method described above is suitable for producing an SMA copolymer containing a high concentration of maleic anhydride because it does not cause problems such as precipitation of maleic anhydride or clogging of charging piping due to polymers. The concentration of maleic anhydride initially present in the polymerization system affects the polymerization rate and the content of maleic anhydride component in the SMA copolymer.
It is suitably 5% by weight or less, more preferably 1 to 3% by weight. In the above method, 10 to 25 parts by weight of maleic anhydride is continuously added in small amounts to 100 parts by weight of the mixture of maleic anhydride and vinyl aromatic compound monomer initially present in the polymerization system. It is preferable to add The amount of maleic anhydride added later is determined by the desired amount of maleic anhydride component in the SMA copolymer. Since the content of the maleic anhydride component in the SMA copolymer is selected from the range of 20 to 35% by weight, the above addition amount is appropriate. The polymerization reaction is preferably carried out by heating to 100 to 130°C for thermal polymerization. In addition, the rate of addition of maleic anhydride to the polymerization system is high at the beginning of polymerization when the viscosity of the polymerization system is low, and as the polymerization progresses and the viscosity of the system increases.
It is preferable to reduce it in proportion to the amount of SMA copolymer produced. In this way, heat removal becomes easy and the polymerization time can be further shortened. In addition, in the present invention, a part of the vinyl aromatic compound monomer initially present in the polymerization system in the first step may be acrylic acid alkyl ester, methacrylic acid ester such as methyl methacrylate, or ethyl methacrylate, acrylonitrile, It can be replaced with a monomer copolymerizable with maleic anhydride and vinyl aromatic compound monomers, such as methacrylonitrile. In the present invention, the syrup obtained in the first step of producing a heat-resistant resin contains 35 to 60% by weight of unreacted vinyl aromatic compound monomer, 20 to 35% by weight of maleic anhydride component, and the remainder. and 65 to 40% by weight of an SMA copolymer consisting of a vinyl aromatic compound monomer component. In the second step for producing the heat-resistant resin of the present invention, a total amount of 100 parts by weight of the vinyl aromatic compound monomer added to the polymerization system in the first step is added to the syrup obtained in the first step. 10 to 25 parts by weight of the vinyl cyanide compound monomer are added and mixed, and then the mixture of the above syrup and the above vinyl cyanide compound monomer is suspended in water, and added to the above syrup in a suspended state. The unreacted monomers contained are copolymerized to obtain a vinyl aromatic compound/vinyl cyanide compound copolymer, and the above-mentioned first
Maleic anhydride residues contained in the copolymer chain obtained in the first step are reduced by aromatic amine in an amount of 0.5 to 1.5 times in molar ratio relative to the total amount of maleic anhydride added in the step. A heat-resistant resin comprising N-aromatic maleimide, vinyl aromatic compound, and vinyl cyanide compound is produced by imidizing 60 mol% or more of . In this second step, a vinyl cyanide compound monomer is first added to the syrup obtained in the first step, and the mixture is stirred at a temperature of 70 to 130°C for 5 to 60 minutes.
In this second step, an aromatic amine is added to the polymerization system, and the time of addition of this amine may be at the same time as the addition of the vinyl cyanide compound monomer,
The polymerization mixture may be added after being suspended in water. In the present invention, examples of the vinyl cyanide compound monomer include acrylonitrile and methacrylonitrile. These may be one type or a mixture of two types. In the second step for producing the heat-resistant resin of the present invention, as the aromatic amine, aniline is industrially easily available and is most suitable; however, halogenated aniline, nitroaniline, toluidine,
Examples include aromatic primary amines such as α-naphthylamine and phenylenediamine. These may be one type or a mixture of two or more types. In the second step, the amount of vinyl cyanide compound monomer to be added and mixed is 10 to 25 parts by weight, with the total amount of vinyl aromatic compound monomers added to the polymerization system in the first step being 100 parts by weight. range. Also,
The amount of aromatic amine added is in molar ratio to the total amount of maleic anhydride added in the first step.
The amount ranges from 0.8 to 1.5 times. Adding aromatic amines, especially aniline,
Maleic anhydride residues contained in the SMA copolymer react with aniline to produce a monoamide. Subsequently, the polymerization system is suspended in water. In this case, it is preferable to add a suspending agent and a polymerization initiator to the polymerization mixture. Examples of suspending agents include polyvinyl alcohol, polyacrylamide, barium sulfate, and the like. Examples of the polymerization initiator include those commonly used in suspension polymerization, such as azobisisobutyronitrile and benzoyl peroxide. Through the suspension polymerization reaction, the unreacted vinyl aromatic compound monomer and the added mixed vinyl cyanide compound monomer are copolymerized, forming a vinyl aromatic compound/vinyl cyanide compound copolymer (AS resin). , imidized and/or monoamidated SMA copolymer are produced in a uniformly mixed state. This suspension polymerization reaction is carried out at a temperature of 60 to 120°C, 1 to 5
It takes place over a period of time. Thereafter, the temperature is raised to a slightly higher temperature of 120 to 190°C to carry out the N-aromatic maleimidation reaction. In this case, the higher the temperature is, the more the monoamidized SMA copolymer is dehydrated and becomes an imidized product, and the imidization rate becomes higher. In the imidization reaction, if a basic substance such as triethylamine is used as a catalyst, as described in Japanese Patent Publication No. 47-24024, the imidization rate can be improved at a relatively low temperature. The higher the amount of aromatic amine added, the better the imidization rate will be, but since the treatment of the aromatic amine present in excess after the reaction is a problem, the above range is appropriate. Through the second step, 60 mol% or more of the maleic anhydride residues contained in the SMA copolymer are imidized. The heat-resistant resin in the present invention is obtained in a state in which the imidized SMA copolymer and the AS resin are already uniformly dispersed and mixed in the polymerization system through the first and second steps. When blended as a composition, it has excellent miscibility, moldability, and fluidity. In the present invention, ABS resin refers to a continuous phase consisting of a copolymer mainly composed of acrylonitrile, styrene, and their derivatives, conventionally known as acrylonitrile-butadiene-styrene resin, and polybutadiene rubber, styrene-butadiene rubber, A synthetic resin consisting of a phase in which acrylonitrile-butadiene rubber, etc. is dispersed. this
ABS resin can be produced by a graft polymerization method, a blend method, or a graft polymerization-blend method. The ABS resin according to the present invention functions to improve the impact resistance of the resin composition according to the present invention and to significantly improve the impact strength. The mixing ratio of ABS resin is
It is preferable to select within a range that improves the impact resistance of the resin composition according to the present invention. Specifically, the resin composition according to the present invention includes a heat-resistant resin and an ABS resin in a mixing ratio of 10 to 90 parts by weight of the heat-resistant resin and 90 to 10 parts by weight of the ABS resin (total is 100 parts by weight). It is preferable that the main component be a mixture selected from the range of .). This mixing ratio is based on SMA resin, which has excellent impact resistance but poor high temperature stability, and ABS resin, as described in the ``Prior Art'' column above.
In a composition blended with a resin, for example,
A composition containing 10 to 90 parts by weight of SMA resin and 90 to 10 parts by weight of ABS resin (see, for example, Japanese Patent Publication No. 47-50775) is well known.
By producing such a known SMA resin by the methods of the first and second steps of the present invention and further imidizing it, a resin composition having a mixing ratio within the range of the present invention can be obtained. As explained above, the resin composition according to the present invention includes a heat-resistant resin comprising an N-aromatic maleimide, a vinyl aromatic compound, and a vinyl cyanide compound;
By using a mixture with ABS resin as the main component, a thermoplastic resin composition with an excellent balance of heat resistance, impact resistance, and moldability can be obtained. In order to obtain the resin composition according to the present invention, generally known mixing and kneading methods may be used. For example, powder,
A method may be used in which predetermined amounts of two types of resins in the form of beads or pellets are weighed and mixed, and the resulting mixture is melted and kneaded. When melt-kneading, an extruder such as a single-screw extruder or a twin-screw extruder, or a kneading machine such as a Banbury mixer, a pressure kneader, or a two-roll mill may be used. The resin composition thus produced has good stability at high temperatures, heat resistance, impact resistance, and physical strength, and is excellent in moldability. The resin composition according to the present invention can be used as a raw material for manufacturing molded products as it is. In addition, impact resistance can be improved by blending with other resins such as ABS resin, AAS resin, AES resin, etc. Furthermore, reinforcing agents such as glass fibers, carbon fibers, talc, and calcium carbonate, fillers, and lubricants of a type and amount that do not impede the properties of the resin, mold release agents, colorants, ultraviolet absorbers, light resistance stabilizers, Other additives such as heat-resistant stabilizers and flame retardants can be blended. The resin composition according to the present invention can be produced by various processing methods such as injection molding, extrusion molding, and compression molding.
It can be used in applications requiring excellent heat resistance, high temperature stability, and impact resistance. "Effects of the Invention" The present invention has been described above, and has particularly remarkable effects as described below, and its industrial utility value is extremely large. (1) Even when the resin composition according to the present invention is heated at a temperature of 270°C for 1 hour, it does not cause foaming, weight loss, or discoloration in appearance.
No crosslinking occurs, and it exhibits excellent high temperature stability.
Since the molded product does not become foamed during molding, it is possible to obtain a molded product with an excellent appearance. (2) The resin composition according to the present invention includes a heat-resistant resin and
Since the compatibility between ABS resins is good, the resin composition has an excellent balance of physical properties between impact resistance and heat resistance. (3) The resin composition according to the present invention has good physical strength, heat resistance, and moldability, and has an excellent balance among these. (4) The resin composition according to the present invention can be kneaded and mixed with other thermoplastic resins and the like to produce a different type of resin composition with excellent heat resistance. "Examples" Next, the present invention will be specifically explained based on Examples and Comparative Examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Production example 1 (1st step) 296 g of styrene was placed in a 21 autoclave equipped with a stirring blade, a raw material auxiliary addition device, and a nitrogen gas supply port, and while stirring and purging with nitrogen gas, the autoclave was heated from the outside and heated from the inside. The temperature was raised to 100°C. A monomer mixture consisting of 280 g of styrene and 120 g of maleic anhydride was added to this polymerization system for 4 hours.
Continuous addition was made at a constant rate of about 1.48 g/min over a period of minutes. After starting the continuous addition, the temperature of the polymerization system was increased from 100°C to 115°C in 15 minutes. Thereafter, while maintaining the temperature at 115° C. and continuously adding, bulk polymerization was continued to complete the first step. In the contents of the autoclave after completing the first step, the polymerization rate of the charged monomer mixture was 54% by weight, and the content of the maleic anhydride component of the SMA copolymer in the produced syrup was 30% by weight. (Second Step) Next, 104 g of acrylonitrile was added to the syrup obtained in the first step and stirred, and the internal temperature of the autoclave was lowered to 95°C. Next, 0.3 g of a polyvinyl alcohol suspending agent and 0.3 g of a polyacrylic acid ester suspending agent were added to this system.
The syrup was suspended by adding 650 g of water containing g and 3 g of sodium sulfate. Add to this 0.4 azobisisobutyronitrile (hereinafter abbreviated as AIBN).
g and kept at a temperature of 80 °C for 90 min, followed by
Suspension polymerization was carried out while raising the temperature to 155°C over 60 minutes.
In this system, 108 g of aniline and 24 g of triethylamine are added.
The second step was completed by performing imidization reaction and suspension polymerization for 120 minutes at a temperature of 155°C, and the temperature of the polymerization system was cooled to room temperature. Subsequently, the obtained bead-like polymer was separated from the water with a cloth, washed with water, and dried. The yield of bead-like polymer was 850 g. The bead-like polymer was kneaded in a vented 1-inch extruder while devolatilizing to form pellets. As a result of analysis of the separated samples by IR absorption spectra, etc., the composition of the pellets was determined to be approximately 86 mol% of the maleic anhydride residues of the SMA copolymer with a maleic anhydride content of 30% by weight converted to N-phenylmaleimide. The resulting mixture was a transparent, uniform, heat-resistant resin mixture of 55 parts by weight of the copolymer prepared in the above manner and 45 parts by weight of a styrene-acrylonitrile copolymer containing 25% by weight of acrylonitrile. Production Example 2 (First Step) 576 g of styrene and 15.4 g of maleic anhydride were placed in an autoclave, and the temperature was raised to 115° C. while stirring and purging with nitrogen gas. To this system, 104.6 g of maleic anhydride kept at 60°C was added continuously at a temperature of 115°C according to the addition rate shown in Table 1.
Bulk polymerization was carried out for 186 minutes, and the first step was completed. At the end of the first step, the polymerization rate was 54% by weight, and the maleic anhydride component content of the SMA copolymer in the resulting syrup was 30% by weight.

[Table] (Second Step) 104 g of acrylonitrile was added to the syrup obtained in the first step and stirred, and the temperature of the system was lowered to 95°C. Add to this 0.3g of polyvinyl alcohol suspending agent,
The above syrup was suspended by adding 650 g of water containing 0.3 g of a polyacrylic acid ester suspending agent and 3 g of sodium sulfate. 0.4 g of AIBN was added thereto, held at a temperature of 80°C for 90 minutes, and then suspended polymerized while raising the temperature to 155°C over 60 minutes. A mixture of 108 g of aniline and 24 g of triethylamine was added to this system, and imidization reaction and suspension polymerization were carried out at a temperature of 155° C. for 120 minutes, and then the temperature of the polymerization system was immediately cooled to room temperature. Separate the resulting bead-like polymer from the water with a cloth,
Washed with water and dried. The yield of beaded polymer is
It was 850g. The bead-like polymer was kneaded and pelletized using a vented 1-inch extruder while devolatilizing. The composition of the pellets was determined by analysis of IR spectra, etc.
Approximately 86 mol% of the maleic anhydride residues in the SMA copolymer with a maleic anhydride component content of 30% by weight are N-
56 parts by weight of a phenylmaleimide copolymer and about 44 parts by weight of a styrene-acrylonitrile copolymer with an acrylonitrile content of 25% by weight,
It was a transparent and uniform heat-resistant resin mixture. Production Example 3 In the same manner as Production Example 1, acrylonitrile was
A syrup containing 104 g was obtained. Add 0.3% polyvinyl alcohol suspending agent to this system.
The syrup was suspended by adding 650 g of water containing g, 0.3 g of a polyacrylic acid ester suspending agent, and 3 g of sodium sulfate. Add 0.4g of AIBN to this,
Hold at a temperature of 80℃ for 90 minutes, followed by 60 minutes
After the temperature was raised to 155°C and suspension polymerization was carried out at this temperature for 120 minutes, the temperature of the polymerization system was immediately cooled to room temperature. 750 g of bead-like polymer was obtained. The bead-shaped polymer was pelletized in the same manner as in Production Example 1. The composition of the obtained pellets is a transparent, uniform, heat-resistant pellet consisting of 52 parts by weight of SMA copolymer containing 30% by weight of maleic anhydride component and 48 parts by weight of styrene-acrylonitrile copolymer containing 25% by weight of acrylonitrile. It was a resin mixture. Examples 1 to 4, Comparative Examples 1 to 2 The heat-resistant resin mixture produced by the method described in Production Example 1, Production Example 2, and Production Example 3 and pelletized was
ABS resin (graft copolymer manufactured by emulsion polymerization method, styrene content 49% by weight, acrylonitrile content 17% by weight, polybutadiene content 34% by weight), AS resin (Mitsubishi Monsanto Chemical Co., Ltd. SAN -
C) was weighed in the proportions (parts by weight) listed in Table 2 and blended in a blender, and this blend was melt-kneaded in a vented extruder, extruded while removing volatile components, and pelletized. These pellets were made into test pieces for measuring physical properties by injection molding, and tensile strength, Izot impact strength, and Vicat softening point were measured. ) was carried out. The results are shown in Table 2.

[Table] From Table 2, the following becomes clear. (1) Since the resin composition according to the present invention has an optimized manufacturing method for heat-resistant resin, it does not foam even when heated to 270°C, has little weight loss at 270°C, and is therefore stable at high temperatures. Excellent properties (Example 1~
(see 4). Moreover, in Examples 1 to 4, the Vicat softening point is 110° C. or higher, and the heat resistance is particularly good. On the other hand, resin compositions that do not contain N-phenylmaleimide residues have poor high temperature stability or heat resistance (see Comparative Examples 1 and 2). (2) The resin composition according to the present invention includes a heat-resistant resin;
It has good compatibility with ABS resin and excellent impact resistance (see Examples 1 to 4). Examples 1-4
, Izotsu impact strength is 6.0Kg・cm/cm
The above results indicate particularly good impact resistance. (3) The resin composition according to the present invention has an excellent balance of physical properties (see Examples 1 to 4). Example 1~
In No. 4, the tensile strength is 400 Kg/cm ² or more, which is good.

Claims (1)

[Scope of Claims] 1. A heat-resistant resin composition produced by a bulk-suspension polymerization method and containing a heat-resistant resin made of N-aromatic maleimide, a vinyl aromatic compound, and a vinyl cyanide compound, and an ABS resin. By copolymerizing maleic anhydride and a vinyl aromatic compound monomer in bulk, a copolymer containing 20 to 35% by weight of the maleic anhydride component and the remainder consisting of the vinyl aromatic compound monomer component is produced. 65-40% by weight,
A first step of obtaining a syrup mixed with 35 to 60% by weight of unreacted monomers, and adding the first step to the syrup obtained in the first step.
10 to 10 parts by weight of the total amount of vinyl aromatic compound monomers added to the polymerization system in the process.
25 parts by weight of the vinyl cyanide compound monomer are added and mixed, and then the mixture of the syrup and the vinyl cyanide compound monomer is suspended in water, and the unreacted monomers contained in the syrup are suspended in water. Copolymerizing the vinyl cyanide compound monomer and the above-mentioned vinyl cyanide compound monomer, and using an aromatic amine in an amount of 0.8 to 1.5 times in molar ratio relative to the total amount of maleic anhydride added in the first step, a second step of imidizing at least 60 mol% of the maleic anhydride residues contained in the copolymer chains obtained in the first step; 10 to 90 parts by weight of resin and
A heat-resistant resin composition characterized in that the main component is a mixture obtained by mixing ABS resin at a mixing ratio of 90 to 10 parts by weight. 2. In the first step of manufacturing the heat-resistant resin, the proportion of maleic anhydride in the monomer mixture of vinyl aromatic compound monomer and maleic anhydride present in the polymerization system is 5% by weight. % or less by copolymerization.