JPS6332823B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermoplastic resin composition containing a heat-resistant copolymer containing a high content of α-methylstyrene and having excellent heat resistance, impact resistance, and fluidity. ABS resin is used in large quantities in the automobile and electrical equipment fields, but in recent years there has been a trend toward thinner products due to the desire to make products lighter.
Demand for improving the heat resistance of ABS resin is increasing significantly. As a method of increasing the heat resistance of ABS resin, heat-resistant ABS resin that is a mixture of α-methylstyrene-acrylonitrile copolymer and ABS resin, as described in Japanese Patent Publication No. 35-18194, is available. The heat-resistant ABS resin obtained by
Further, in applications requiring heat resistance, restrictions have been forced. In order to improve this, attempts have been made to emulsion polymerize a copolymer of α-methylstyrene and acrylonitrile using methyl methacrylate as the third vinyl monomer. For example, in Japanese Patent Publication No. 45-18016, a copolymer of α-methylstyrene, acrylonitrile, and methyl methacrylate within a certain composition range, a diene rubber-like polymer, and a copolymer of acrylonitrile and α-methylstyrene within a certain composition range are proposed. It is stated that by mixing a graft copolymer, a heat-resistant resin with low heat resistance, particularly a low high-temperature shrinkage rate of molded products, can be obtained. However, a mixture of the above-mentioned copolymer and graft copolymer has slightly higher heat resistance than a graft copolymer obtained by graft copolymerizing acrylonitrile and α-methylstyrene onto a diene-based rubbery polymer; The problem is that they lack flexibility and fluidity, and in particular, lack of balance between heat resistance and fluidity. The index of heat resistance is often indicated by the heat distortion temperature of ASTMD-648 or the softening temperature of ASTMD-1525, but many products have complex shapes and uneven wall thickness. Therefore, since the residual strain of the product after injection molding is not constant, it is insufficient to judge the heat resistance of the product by the above-mentioned measurement alone.
The current situation is to conduct a heat resistance test. In that case, if the heat-resistant ABS resin has poor fluidity,
Because molding distortion remaining in the product becomes large, in heat resistance tests of molded products under no load, the temperature at which deformation begins is higher than the heat distortion temperature of heat-resistant ABS resin according to ASTMD-648 or the Vikatsu softening temperature according to ASTMD-1525. Since the temperature decreases by about 5 to 10°C, if the fluidity is insufficient as described above, there is a drawback that the practical heat resistance temperature becomes low. As a result of intensive study on how to improve the balance between heat resistance and fluidity, the inventors of the present invention found that (A) a copolymer of α-methylstyrene, acrylonitrile, and methyl methacrylate; B) A mixture of a graft copolymer obtained by polymerizing a diene-based rubbery polymer with a monomer mixture of α-methylstyrene, acrylonitrile, and/or methyl methacrylate, and (C) in the presence of a rubbery polymer. It consists of a resin mixture with a graft copolymer obtained by polymerizing a monomer mixture of styrene and acrylonitrile, and each component has a melt index [melt flow rate,
We found that a thermoplastic resin composition with a load of 5 kg at 230°C in the range of 0.1 to 3.0 maintains a balance of impact strength and fluidity without impairing heat resistance.
The invention has been completed. That is, the present invention provides (A) a copolymer consisting of 50 to 85% by weight of α-methylstyrene, 10 to 35% by weight of acrylonitrile, 3 to 20% by weight of methyl methacrylate, and 0 to 25% by weight of styrene,
Presence of 5 to 40% by weight of a copolymer obtained by additionally adding acrylonitrile or styrene to complete the polymerization in producing the copolymer, and (B) 10 to 50% by weight of a diene rubber-like polymer. Obtained by reacting α-methylstyrene or a monomer mixture of 50 to 95% by weight of styrene, 5 to 30 parts by weight of acrylonitrile, and 0 to 20% by weight of a vinyl monomer copolymerizable with it. Graft copolymer 30~
90% by weight and (C) polybutadiene rubber and styrene.
A mixture of styrene and acrylonitrile monomers 40~60% by weight of a mixture of butadiene copolymer rubber
A thermoplastic resin comprising a mixture with 5-30% by weight of a graft copolymer obtained by reacting 70% by weight, and characterized in that the mixture contains 5-40% by weight of a diene-based rubbery polymer. It is a composition. In the copolymer (A) used in the present invention, it is particularly important to avoid lengthening of the α-methylstyrene-methyl methacrylate chain during polymerization and to the extent that thermal stability is not adversely affected.
The goal is to incorporate as many of them as possible. For this purpose, it is difficult to control the polymerization conversion rate as it becomes high, so the copolymer (A) of the present invention must be
In this case, the thermal stability is improved by adding acrylonitrile or a monomer consisting of it and styrene in the latter half of the polymerization to complete the polymerization reaction. Furthermore, when a mixture of methyl methacrylate, styrene, and acrylonitrile is polymerized in an area where the amount of α-methylstyrene is 50% by weight or more, as the polymerization progresses, the amount of α-methylstyrene in the unreacted monomer increases, resulting in thermal stability. It becomes easier to create polymer chains with poor properties. In the copolymer (A) of the present invention, 50 to 85% by weight of α-methylstyrene, 3 to 85% by weight of methyl methacrylate,
Monomer consisting of a mixture of 20% by weight, 10-35% by weight of acrylonitrile, and 0-25% by weight of styrene.
Polymerization is started using 65 to 85 parts by weight, and during the polymerization, preferably from a point at which the polymerization conversion rate is 10 to 50%, 15 to 35 parts by weight of acrylonitrile or a monomer consisting of it and styrene is added continuously or The thermal stability is improved by using the intermittent addition method. In the copolymer (A) of the present invention, if the amount of α-methylstyrene is less than 50% by weight, the heat resistance will be low, and if it exceeds 85% by weight, a product with good thermal stability will not be obtained. If the amount of acrylonitrile is less than 10% by weight, impact resistance will decrease, and if it exceeds 35% by weight, polymerization stability will deteriorate and heat resistance will decrease. If the amount of methyl methacrylate is less than 3% by weight, the heat resistance will decrease, and the heat resistance of the final resin composition, especially the heat shrinkage rate of the molded product, will deteriorate, and if it exceeds 20% by weight, the heat stability will deteriorate. is inferior. The copolymer (B) used in the present invention is a radical initiator in which α-methylstyrene or a monomer mixture consisting of α-methylstyrene and styrene, acrylonitrile, and/or methyl methacrylate is used in the presence of a diene-based rubbery polymer latex. It can be obtained by emulsion polymerization using, for example, The diene-based rubbery polymer latex of the present invention is a butadiene polymer or a butadiene-based rubber latex.
Examples include copolymer latexes containing 50% by weight or more of butadiene and other copolymerizable monomers. Preferably, it is a butadiene polymer or a styrene-butadiene copolymer with a styrene content of 40% by weight or less. Further, examples of the radical initiator include potassium persulfate, sodium persulfate, ammonium persulfate, and redox catalysts such as cumene hydroperoxide and diisopropyl hydroperoxide. Preferably, radical initiators are water-soluble initiators. Potassium sulfate or sodium persulfate. As the emulsifier used in emulsion polymerization, any commonly used emulsifier can be used, but anionic emulsifiers are preferred, and sodium lauryl sulfate is particularly preferred. In addition, in order to obtain good impact resistance, it is desirable that the particle size of the butadiene rubber latex is relatively large, and in order to achieve the object of the present invention, the butadiene rubber latex used is
The polymerization fraction of diene rubber with a diameter of 400 to 900 Å is
It needs to be 10 to 50% by weight, and if this amount is less than 10% by weight, the efficiency of adding the rubbery polymer will be insufficient and the impact resistance of the final resin composition will be poor. . On the other hand, if it exceeds 50% by weight, the stability of the graft polymerization reaction deteriorates, making it impossible to obtain the desired graft polymer. The composition of the monomers used in the graft copolymer (B) of the present invention is 50 to 95% by weight of α-methylstyrene or styrene, 5 to 30% by weight of acrylonitrile, and 0% of a copolymerizable vinyl monomer. ~20% by weight. Examples of copolymerizable vinyl monomers include lower alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate. The graft copolymer (C) used in the present invention is obtained by graft copolymerizing a monomer mixture consisting of styrene and acrylonitrile in the presence of polybutadiene rubber and styrene-butadiene rubber. Rubbers used in graft copolymer (C) include:
Examples include butadiene polymers and copolymer latexes of butadiene and styrene containing 50% by weight or more, preferably 60% by weight or more of butadiene. The usage ratio of butadiene polymer and styrene-butadiene copolymer is in the range of 70/30 to 95/5,
Preferably it is 70/30 to 90/10. Outside this range, it is difficult to maintain the impact resistance, which is a characteristic of the resin composition of the present invention. Regarding the particle size of these butadiene rubber and styrene-butadiene rubber latex, it is possible to use latexes with an average particle size of 100 to 400 Å, which are used for ordinary ABS resins, but preferably polymer particles with a particle size of 400 Å or more are used by weight of 10 to 35 Å. It is preferable to use a latex containing %. This diene-based rubbery polymer latex may be made containing 10 to 35% by weight of particles with a particle size of 400 Å or more in the same polymerization system, or it may be made using two or more types of diene-based rubber polymers with appropriate particle sizes. It may also be obtained by mixing a combined latex. By using a mixed system of butadiene polymer and styrene-butadiene copolymer as the rubber latex and by considering the balance of rubber particles, the resin composition of the present invention can achieve impact resistance without impairing heat resistance. It is possible to maintain a balance in various properties such as fluidity and fluidity. The composition of the monomers used in the graft copolymer (C) of the present invention is 30 to 60% by weight of a mixture of polybutadiene rubber and styrene-butadiene copolymer rubber, and 40 to 70% by weight of a mixture of styrene and acrylonitrile monomer. be. In the present invention, the content of the rubber component in the mixture of components (A), (B), and (C) is 5 to 40% by weight, and if it is less than 5% by weight, the impact resistance is low, and if it exceeds 40% by weight. This is not preferable because the heat resistance decreases. Melt index of each of the copolymers (A), (B), and (C) used in the present invention [melt flow rate, 230°C, load 5
Kg] ranges from 0.1 to 3.0. If it is less than 0.1, the fluidity decreases significantly, resulting in a major drawback in formability when used as a structural material in the automobile field, electrical equipment field, etc. On the other hand, if it is 3.0 or higher, although the fluidity is improved, the orientation in the flow direction becomes large during injection molding.
Sufficient impact resistance cannot be obtained. The reason is not clear, but in (A) a copolymer consisting of α-methylstyrene, acrylonitrile, and methyl methacrylate, the copolymer containing methyl methacrylate has the effect of improving heat resistance, but it is not as strong as acrylonitrile. Compared to styrene copolymers, they have poor compatibility with ABS resins, so a mixture of monomers such as α-methylstyrene and acrylonitrile and/or methyl methacrylate is added to the diene-based rubbery polymer of component (B). In a mixed system with a polymerized graft copolymer, it is thought that the rubber content is insufficiently dispersed during the heating and kneading process using a normal extruder, making it difficult for the resin to exhibit its original impact properties. It will be done. However, in a mixture of the above components (A) and (B),
By mixing a graft copolymer obtained by polymerizing a mixture of styrene and acrylonitrile monomers in the presence of a rubbery polymer containing a butadiene polymer and a styrene-butadiene copolymer as component (C),
Surprisingly, the (C) component is dispersed at the interface between both the (A) and (B) components, improving impact resistance without compromising heat resistance and maintaining a good balance of various properties such as fluidity. Get better. Furthermore, the melting index [melt flow rate, 230
Even if fluidity is improved by mixing copolymers with a difference of 3.0 or more in [°C, load 5 kg], each copolymer tends to separate into layers during extrusion molding, injection molding, etc. The impact properties of the mixture are reduced. The above components can be blended using a known method such as a kneader, roll mill or extruder. Furthermore, various additives such as coloring agents such as pigments, lubricants, plasticizers, stabilizers, and glass fibers can be blended. The method of the present invention will be explained below with reference to Examples, but the present invention is not limited to these in any way. Note that the amounts of additives shown in Examples are expressed in parts by weight and % by weight unless otherwise specified. In addition, the physical property values of the manufactured products are values measured by the following methods. Γ Melt index: Based on ASTMD-1238, the melt flow rate is 230℃ and a load of 5Kg.
Measured using a nozzle with an inner diameter of 1 mmφ. Γ Izot impact strength: Measured at 20℃ and 65%RH in accordance with ASTMD-256. Γ Vikatsu softening temperature: Measured according to ASTMD-1525. Γ Product heat resistance test: Molded product (dimensions 50mm x
A 90mm thick (3mm, 2mm, 1mm stepped color plate) was kept in a arbitrarily set hot air dryer for 3 hours, and the length of the long side was measured at the center of the short side to determine the dimensional change before and after the test. Determine the heating shrinkage rate by comparing with the dimensions before the test. Heat shrinkage rate = Dimension before test - Dimension after test / Dimension before test x 100 (%
) Reference Examples A-1 to A-2 A mixture of monomers such as α-methylstyrene, half of acrylonitrile, and methyl methacrylate, and tertiary dodecyl were placed in a reactor equipped with a stirrer and replaced with nitrogen at the composition ratio shown in Table 1. 0.4 parts of mercaptan was added and emulsified. After raising the temperature to 40°C while stirring under a nitrogen stream, sodium formaldehyde sulfoxylate, sodium ethylenediaminetetraacetate, and ferrous sulfate dissolved in ion-exchanged water were added, and cumene hydroperoxide was added to initiate a polymerization reaction. started. After preparation is complete, increase the jacket temperature further.
After polymerization was carried out at 60° C. for 1 hour, the remaining acrylonitrile was continuously added over 2 hours. After the addition was completed, water and styrene were emulsified and added, and the above-mentioned emulsifier and initiator were added, and a polymerization reaction was carried out for 2 hours to complete the polymerization. Calcium chloride was added to the obtained copolymer latex to solidify it, and the mixture was kept at a temperature of 90° C. or higher with stirring for 10 to 20 minutes, then decomposed, washed with water, and dried to obtain a resin powder. Let them be A-1 and A-2, respectively. Reference examples B-1 to B-3 At the composition ratio shown in Table 1, diene rubber latex and potassium persulfate were placed in a reactor equipped with a nitrogen-substituted stirrer, and the inside of the reaction tank was heated to 70°C and stirred. Monomer mixtures containing tertiarydodecyl mercaptan (alphamethylstyrene, styrene, acrylonitrile and methyl methacrylate)
and an aqueous solution of sodium lauryl sulfate.
Add in time. After the addition was completed, aging was performed at 70°C for 30 hours. The produced latex was coagulated with an aqueous solution of aluminum sulfate, filtered, washed with water, and dried to obtain a resin powder. Let them be B-1, B-2, and B-3, respectively. Reference Examples C-1 to C-2 1/3 of the emulsified solution (a) in which ion-exchanged water, styrene, acrylonitrile, potassium stearate, and tertiary dodecyl mercaptan were mixed and added at the composition ratio shown in Table 1. Amount and ion exchange water, polybutadiene latex and butadiene content 75%
The mixture of styrene-butadiene copolymer latex containing the styrene-butadiene copolymer latex was charged into a reactor equipped with a stirrer and purged with nitrogen, and emulsified. After raising the temperature to 40°C with stirring under a nitrogen stream, add a solution of sodium pyrophosphate, glucose, and ferrous sulfate in ion-exchanged water and cumene hydroperoxide, and maintain the jacket temperature at 70°C for 1 hour. Made it react. Next, the remainder of the emulsified solution (a) of the monomers, etc. and cumene hydroperoxide were each added to
It was added continuously into the polymerization system over time. Calcium chloride was added to the thus obtained copolymer latex to solidify it, and after holding at a temperature of 90°C or higher for 10 to 20 minutes with stirring, it was decomposed, washed with water, and dried to obtain a resin powder. Let them be C-1 and C-2. Examples 1 to 3, Comparative Examples 1 to 4 (A) Copolymer with high α-methylstyrene content (Table 1
A-1), (B) a graft copolymer with a high α-methylstyrene content (B-1 in Table 1), (C) a graft copolymer containing a mixture of polybutadiene rubber and styrene-butadiene copolymer rubber ( C-1 in Table 1 was blended in the proportions shown in Table 2 and pelletized using an extruder with a cylinder temperature of 250°C to obtain a thermoplastic resin composition. Furthermore, test pieces were prepared using an injection molding machine with a cylinder temperature of 250°C. Table 2 shows their blending ratios and various properties. The thermoplastic resin composition of the present invention comprises components A-1,
It is shown that by mixing component C-1 into the mixture system of B-1, a balance of various properties such as excellent impact resistance and fluidity can be maintained without impairing heat resistance. These characteristics are different from each resin component alone.
You can't get it. Hereinafter, Examples and Comparative Examples will be compared using the same amount of rubber. As in Comparative Example 1, a graft copolymer containing a mixture of (C) polybutadiene rubber and styrene-butadiene copolymer rubber in Example 1 (C- in Table 1)
It can be seen that if 1) is not mixed, the balance of various properties such as impact resistance and fluidity will be poor, making it impractical. As in Comparative Example 2, if the copolymer with a high α-methylstyrene content in Example 1 (B-1 in Table 1) is not mixed, although the impact strength and fluidity can be maintained, the heat resistance may be significantly reduced. Recognize. As in Comparative Example 3, instead of the copolymer with a high α-methylstyrene content (B-1 in Table 1) in Example 1, a copolymer containing 40% by weight of α-methylstyrene (B-3 in Table 1) was used. ), impact resistance can be maintained, but heat resistance is significantly reduced, making it impractical. As in Comparative Example 4, a graft copolymer containing a mixture of (C) polybutadiene rubber and styrene-butadiene copolymer rubber in Example 3 (C- in Table 1)
It can be seen that if Rohm &Haas' MBS resin (KM-653) is used instead of 1), the heat resistance and impact resistance will decrease, making it impractical. Example 4, Comparative Examples 5 to 7 When the high α-methyl content graft copolymer in Example 1 contains methyl methacrylate, that is, when B-2 is used instead of B-1 in Table 1. The results are shown in Example 4 in Table 2. This clearly shows that the composition maintains excellent heat resistance without impairing impact properties and fluidity. As in Comparative Example 5, a graft copolymer containing a mixture of (C) polybutadiene rubber and styrene-butadiene copolymer rubber in Example 4 (C- in Table 1)
It can be seen that if 1) is not mixed, the heat resistance does not change much compared to Example 4, but the balance of various properties such as impact resistance and fluidity is poor, making it impractical. As in Comparative Example 6, in place of (A) high α-methylstyrene content copolymer A-1 in Table 1 in Example 4, a copolymer containing 30% by weight of methyl methacrylate (Table 1) was used. Using A-2), Example 4
It can be seen that although the fluidity is slightly better than that of , the impact resistance is lower and the molded product is significantly colored, making it impractical. As in Comparative Example 7, a graft copolymer containing a mixture of (C) polybutadiene rubber and styrene-butadiene copolymer rubber in Example 4 (C- in Table 1)
When a polybutadiene-based graft copolymer (C-2 in Table 1) with a melting index (melt flow rate, 230°C, load 5 kg) of 21 and containing no styrene-butadiene copolymer rubber is used instead of 1). Although the fluidity is significantly improved, the heat resistance and impact resistance are reduced, making it impractical.

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Claims (1)

[Scope of Claims] 1 (A) A copolymer consisting of 50 to 85% by weight of α-methylstyrene, 10 to 35% by weight of acrylonitrile, 3 to 20% by weight of methyl methacrylate, and 0 to 25% by weight of styrene, , 5 to 40% by weight of a copolymer obtained by additionally adding acrylonitrile or styrene and styrene during the production of the copolymer, and (B) 10 to 50% by weight of a diene rubber-like polymer. In the presence of α-methylstyrene or it and styrene 50 ~
Graft copolymer obtained by reacting 95% by weight of a monomer mixture of 5% to 30% by weight of acrylonitrile with 50% to 90% by weight of a monomer mixture of 0% to 20% by weight of a copolymerizable vinyl monomer and 30% to 90% by weight of acrylonitrile. (C) Graft copolymer obtained by reacting 30 to 60% by weight of a mixture of polybutadiene rubber and styrene-butadiene copolymer rubber with 40 to 70% by weight of a mixture of styrene and acrylonitrile monomers.
A thermoplastic resin composition comprising a mixture of 5 to 30% by weight of a diene-based rubbery polymer in the mixture. 2. The thermoplastic resin composition according to claim 1, wherein each of the copolymers (A), (B), and (C) has a melting index [melt flow rate (230°C, load 5 kg)] of 0.1 to 3.0. thing.