JPS636106B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an impact-resistant thermoplastic resin composition with excellent heat resistance. More specifically, styrene, α-
A graft copolymer obtained by polymerizing a monomer mixture consisting of methylstyrene, a vinyl cyanide compound, and methyl methacrylate, and a monomer mixture consisting of α-methylstyrene, a vinyl cyanide compound, and methyl methacrylate. The present invention relates to a thermoplastic resin composition having excellent heat resistance and impact resistance obtained by mixing the present invention with a copolymer of Conventionally, a graft copolymer (commonly known as ABS resin) obtained by polymerizing a monomer mixture of styrene and acrylonitrile in the presence of a diene rubber polymer.
has good processability and excellent impact resistance, but generally has the disadvantage of low heat resistance.
Many methods have been proposed to improve its heat resistance. However, most of them lack heat resistance and/or impact resistance. Furthermore, even if these materials have excellent mechanical properties, they have low polymerization conversion and polymerization rate, poor homopolymerizability, and there is a shortage of molds, making it difficult to utilize them widely. For example, Japanese Patent Publication No. 35-18194 states that a composition having heat resistance and impact resistance can be obtained by mixing a copolymer of α-methylstyrene and acrylonitrile with a graft copolymer of styrene and acrylonitrile to polybutadiene. However, the heat distortion temperature of this composition is slightly over 100°C, so it cannot be said that the heat resistance is sufficient. In addition, in Japanese Patent Publication No. 37-697, the excellent heat resistance of α-methylstyrene and methyl methacrylate copolymer was utilized, and α-methylstyrene and methacrylate in which a small amount of polybutadiene was dissolved were used to further impart impact resistance. A method of polymerizing a monomer mixture consisting of methyl acid has been proposed, but the impact resistance is insufficient and the polymerization rate is slow, making it extremely disadvantageous for industrial production. To improve this, α-methylstyrene,
Attempts have been made to copolymerize methyl methacrylate by using acrylonitrile as the third vinyl monomer to carry out emulsion polymerization. For example, special public relations
In No. 37415, a copolymer of α-methylstyrene, acrylonitrile, and methyl methacrylate within a certain composition range, and a graft copolymer of styrene, methyl methacrylate, and acrylonitrile within a certain composition range are mixed with diene-based synthetic rubber. It is stated that a resin having heat resistance and impact resistance was obtained by the method, but since the heat resistance of the graft copolymer is low, it has the disadvantage that the heat resistance of the composition after mixing is reduced. are doing. In addition, in Japanese Patent Publication No. 18016/1986, a copolymer of α-methylstyrene, acrylonitrile, and methyl methacrylate within a certain composition range, and a graft copolymerization of α-methylstyrene and acrylonitrile within a certain composition range to a butadiene polymer are disclosed. It is stated that by mixing these materials, an impact-resistant resin with high heat resistance, especially a low high-temperature shrinkage rate of molded products, can be obtained. However, although the graft copolymer obtained by graft copolymerizing α-methylstyrene and acrylonitrile described in the invention has slightly higher heat resistance than the graft copolymer obtained by graft copolymerizing styrene, methyl methacrylate, and acrylonitrile, It has the drawbacks of low grafting efficiency and insufficient impact resistance of the composition after mixing. In view of these circumstances, the inventors of the present invention have conducted intensive studies on thermoplastic resins that have excellent heat resistance and impact resistance, and can be produced extremely advantageously in industrial production. A graft copolymer (A) obtained by graft copolymerizing a monomer mixture in a certain range of amounts consisting of styrene, α-methylstyrene, a vinyl cyanide compound, and methyl methacrylate in a certain composition range in the presence of a coalesced latex. A copolymer obtained by polymerizing a monomer mixture consisting of α-methylstyrene, vinyl cyanide compound, and methyl methacrylate within a certain composition range.
(B) in a certain range of ratios, it was discovered that resin compositions having various heat resistance and impact resistance depending on the composition of each component can be obtained, and the present invention was completed. That is, the gist of the present invention is that the particle size is
In the presence of 30 to 60 parts by weight (solid content) of a butadiene-based rubbery polymer latex containing 10 to 35 weight % of particles of 0.4μ or larger, 55 to 80 weight % of a mixture of styrene and α-methylstyrene, and vinyl cyanide. compound 15
~35% by weight and 5-20% by weight of methyl methacrylate
70 to 40 parts by weight of a monomer mixture containing styrene in a proportion of 20 to 50% by weight based on the rubbery polymer are subjected to emulsion polymerization. Obtained graft copolymer (A)
and a copolymer (B) obtained by emulsion polymerization of a monomer mixture consisting of 55 to 75% by weight of α-methylstyrene, 10 to 25% by weight of a vinyl cyanide compound, and 3 to 30% by weight of methyl methacrylate. The rubbery polymer is mixed in a thermoplastic resin composition in which the rubbery polymer content is 5 to 30% by weight in the resin composition. Next, the present invention will be explained in detail. The graft copolymer (A) of the present invention is produced by producing styrene,
It is obtained by graft copolymerizing a monomer mixture consisting of α-methylstyrene, a vinyl cyanide compound, and methyl methacrylate. The butadiene-based rubbery polymer latex of the present invention may be polybutadiene latex or butadiene containing 50% by weight.
Examples include copolymer latexes containing butadiene and other copolymerizable monomers. Monomers that can be used to copolymerize with butadiene include, for example, vinyl aromatic compounds such as styrene, acrylic compounds such as butyl acrylate, and vinyl cyanide compounds such as acrylonitrile. These butadiene-based rubbery polymer latexes may be crosslinked with a crosslinking agent such as divinylbenzene, but the gel content
80% or less is preferable. In addition, in order to obtain good impact resistance, it is desirable that the particle size of the butadiene rubber latex is relatively large.In order to achieve the object of the present invention, the butadiene rubber polymer latex used should be It is necessary that the weight fraction of particles with a particle size of 0.4μ or more is 10 to 35% by weight, and if this amount is less than 10% by weight, the addition efficiency of the rubbery polymer is insufficient, The impact resistance of the final resin composition is poor. On the other hand, if it exceeds 35% by weight, the stability of the graft polymerization reaction deteriorates, a large amount of coagulum is produced, and the desired graft copolymer cannot be obtained. The composition of the monomers subjected to the graft copolymerization of the present invention is a mixture of styrene and α-methylstyrene, 55 to 80%
% by weight, 15-35% by weight of vinyl cyanide compound, and 5-20% by weight of methyl methacrylate. In order to achieve the object of the present invention, it is necessary to increase the composition ratio of α-methylstyrene, which contributes to the heat resistance of the graft copolymer, but increasing the composition ratio significantly reduces the polymerization rate. decreases,
This leads to a decrease in grafting efficiency, and the impact resistance of the finally obtained resin composition decreases. In order to avoid such drawbacks and increase the composition ratio of α-methylstyrene as much as possible, it is necessary to
Styrene, which is susceptible to graft reactions, must be used in an amount of 20 to 50% by weight based on the rubbery polymer, and the mixture of styrene and α-methylstyrene must be used in a proportion of 20 to 50% by weight based on the total monomer content to be subjected to graft copolymerization. It should be 55-80% by weight of the body. The weight fraction of styrene to the rubbery polymer during graft copolymerization is less than 20% by weight, or the weight fraction of the mixture of styrene and α-methylstyrene in the total monomers subjected to graft copolymerization is 80% by weight. If it exceeds %,
The polymerization rate becomes slow, the grafting efficiency decreases, and the impact resistance of the finally obtained resin composition decreases.
Conversely, when the weight fraction of styrene during graft copolymerization with respect to the rubbery polymer exceeds 50% by weight, or when the weight fraction of the mixture of styrene and α-methylstyrene in the total monomers subjected to graft copolymerization is If it is less than 55% by weight, the heat resistance of the graft copolymer will be lowered, and the heat resistance of the finally obtained resin composition will be lowered. The vinyl cyanide compound, which is an essential component of the graft copolymer of the present invention, is represented by acrylonitrile, methacrylonitrile, etc., and is present in an amount of 15 to 35% by weight based on the total monomers used in the graft copolymerization. If the vinyl cyanide compound is less than 15% by weight, the impact resistance and chemical resistance of the final resin composition will be poor, and if it exceeds 35% by weight, polymerization stability will be poor and agglomerates may form. It is produced in large quantities and graft copolymerization cannot be completed. Furthermore, the monomer composition of methyl methacrylate, which is an essential component of the graft copolymer, is 5 to 20% by weight. If the content of methyl methacrylate is less than 5% by weight, the heat resistance of the finally obtained resin composition, particularly the heat shrinkage rate of the molded product, will decrease. On the other hand, if it exceeds 20% by weight, polymerization stability deteriorates, a large amount of coagulum is produced, and the graft copolymerization cannot be completed. The ratio of the butadiene rubbery polymer latex and the monomer mixture used in the graft copolymerization is 70 to 40 parts by weight of the monomer mixture to 30 to 60 parts by weight of the rubbery polymer latex (in terms of solid content). If the butadiene-based rubbery polymer latex is less than 30 parts by weight, the mixture of the highly heat-resistant copolymer (B) consisting of α-methylstyrene, acrylonitrile, and methyl methacrylate will be reduced, resulting in a reduced amount of the final resin obtained. The heat resistance of the composition decreases. 60 on the contrary
If the amount exceeds 1 part by weight, the monomer available for graft copolymerization will decrease, leading to a decrease in the grafting ratio and resulting in poor impact resistance of the final composition. The copolymer (B) of the present invention is α-methylstyrene 55
It is obtained by copolymerizing a monomer mixture consisting of ~75% by weight, 10~25% by weight of a vinyl cyanide compound, and 3~30% by weight of methyl methacrylate. In general, α-methylstyrene contributes to improving the heat resistance of the copolymer, but if α-methylstyrene exceeds 75% by weight, the polymerization rate decreases significantly, which leads to a decrease in polymerization conversion. Furthermore, it becomes difficult to remove the residual monomer. On the other hand, if it is less than 55% by weight, the heat resistance of the copolymer will decrease, and the heat resistance of the resin composition finally obtained will also decrease. Methyl methacrylate is 3-30% by weight. When the content of methyl methacrylate is less than 3% by weight, the heat resistance of the copolymer decreases, and the heat resistance of the finally obtained resin composition, particularly the heat shrinkage rate of the molded product, deteriorates. On the other hand, if it exceeds 30% by weight, the thermal stability of the final resin composition will deteriorate, causing a decrease in heat resistance. The amount of vinyl cyanide compounds represented by acrylonitrile, methacrylonitrile, etc. is 10 to 25% by weight. If the vinyl cyanide compound is less than 10% by weight, the impact resistance of the copolymer will decrease, and the impact resistance of the final resin composition will decrease. 25 on the contrary
If it exceeds % by weight, polymerization stability deteriorates and a large amount of coagulum is produced. Moreover, the heat resistance of the copolymer is lowered, and the heat resistance of the resin composition finally obtained is lowered. The graft copolymer (A) and copolymer (B) of the present invention are produced by an emulsion polymerization method, and examples of emulsifiers that can be used at this time include alkali metal salts of fatty acids and fatty acid sulfuric esters. and alkali metal salts of disproportionated rosin acids. As the polymerization catalyst, it is possible to use a redox catalyst consisting of a combination of a persulfate and an organic peroxide with a reducing agent. Mercaptans, terpenes, halides, etc. are used as polymerization regulators. Regarding the method of adding monomers in the polymerization reaction of the graft copolymer, it is preferable to add the monomers in two parts with characteristics of the monomer component composition as shown below. It is possible to adopt either a method of adding the entire amount at once, or a method of adding each monomer mixture in two or more portions or continuously. In addition, the method of adding monomers in the polymerization reaction of the copolymer can be either adding the entire amount at once, changing the composition of the three components and adding them in two or more times, or adding them continuously, or continuously adding only a specific component. It is possible. In producing the graft copolymer (A) of the present invention, a preferred method is two-step polymerization, in which a butadiene-based rubbery polymer latex containing 10 to 35% by weight of particles having a particle size of 0.4μ or more is used.
First, in the presence of 20 to 60 parts by weight of styrene, the total amount of styrene is 20 to 50% by weight based on the rubbery polymer, and α- Monomer mixture 10 consisting of 65 to 85% by weight of a monomer mixture consisting of methylstyrene and 15 to 35% by weight of a vinyl cyanide compound
~30 parts by weight to ensure a graft ratio of at least 15
%, then the remaining monomer mixture is added to the polymerization system, and the polymerization is carried out until the graft copolymerization is substantially completed. Also obtained graft copolymer (A) and copolymer
A known antioxidant can be added to (B). The thus obtained graft copolymer (A) and copolymer (B) are mixed so that the butadiene rubbery polymer accounts for 5 to 30% by weight in the mixed resin composition. If the rubbery polymer content is less than 5% by weight, impact resistance will decrease, and if it exceeds 30% by weight, heat resistance will decrease. These mixtures are graft copolymer (A) and copolymer
Convenient methods include mixing the respective latexes in (B) and drying the solidified product, or kneading the respective powders using a roll, Banbury mixer, or pelletizer. In addition, if necessary, it is also possible to add commonly used processing aids such as stabilizers, pigments, fillers, and plasticizers during mixing. Thus, the resin composition obtained by the present invention has unprecedented heat resistance and excellent physical properties such as impact resistance, making it suitable as a molding material for molded articles exposed to high temperatures such as automobile parts. , its utility value is extremely large. In addition, in the conventional graft copolymerization reaction in which monomers of α-methylstyrene, vinyl cyanide compound, and methyl methacrylate are added in the presence of a butadiene-based rubbery polymer, a large amount of coagulum is generated, resulting in a large amount of industrial waste. However, according to the method of the present invention, the polymerization reaction can be carried out smoothly without such difficulties, and a graft copolymer can be produced without substantially reducing heat resistance and impact resistance. Its industrial value is extremely large. Next, the present invention will be specifically explained using examples. In the following Examples and Comparative Examples, parts mean parts by weight. The large-particle polybutadiene latex, graft copolymer (A), and copolymer (B) used in Examples and Comparative Examples were produced as follows. [] Production of polybutadiene latex Using potassium oleate as an emulsifier and a redox initiator consisting of cumene hydroperoxide and ferrous sulfate-ethylenediaminetetraacetic acid sodium salt-formaldehyde sulfoxylate as an initiator, butadiene was A polybutadiene latex with agglomerated latex particles was produced by low-temperature polymerization at ~10°C and forced stirring during the polymerization. The polymerization time was 30 hours and the conversion rate was 55%. The gel content measured using toluene as a solvent was 72%, and the weight content of latex particles with a particle size of 0.4μ or more measured using a Coulter counter was 20%, with an average particle size of 0.30μ. [] Production of graft copolymer (A) Stainless steel with an internal volume of 14 equipped with a stirring device, heating jacket, reflux condenser, thermometer, nitrogen gas inlet, and continuous addition device for monomer emulsion and polymerization initiator. A prepared reactor was charged with the following mixture. Polybutadiene latex 40 parts Potassium oleate 0.5 parts Styrene 12.5 parts α-methylstyrene 2 parts Acrylonitrile 5.5 parts T-dodecyl mercaptan 0.15 parts Water (including water in the latex) 120 parts After replacing the internal air with nitrogen, jacket Pour hot water into it and heat it. Reactor internal temperature is 40℃
When the temperature reaches 20 parts of water, add sodium pyrophosphate.
0.5 parts, glucose 0.7 parts and ferrous sulfate 0.01 parts
0.2 part of cumene hydroperoxide was added to the solution, and the jacket temperature was kept at 70°C and the reaction was carried out for 1 hour in a nitrogen atmosphere. After completion of the reaction, the polymerization conversion rate was 92% and the grafting rate was 20%. The emulsified mixture described below was then added continuously to the reactor over a period of 3 hours. α-methylstyrene 26 parts Acrylonitrile 10 parts Methyl methacrylate 4 parts t-dodecyl mercaptan 0.1 part Cumene hydroperoxide 0.2 parts Potassium oleate 1.0 parts Water 50 parts After completion of the preparation, the reaction was continued for an additional hour.
The conversion rate at the end of polymerization was 97%. Furthermore, the amount of coagulum in the emulsion was as low as 0.1%. After adding 1 part of 2,6-di-t-butyl para-cresol as an anti-aging agent to this graft copolymer latex, it was coagulated, washed with water and dried to obtain a graft copolymer powder. Incidentally, the grafting rate was measured by the following method. Measurement of graft ratio: Graft copolymer powder 2
g was accurately weighed into a 100 ml Erlenmeyer flask with a stopper, then 40 ml of acetone was added, and the mixture was left to stand for 15 hours. Thereafter, the mixture was strongly agitated using a shaker for 2 hours, and separated into an acetone soluble portion and an insoluble portion using a centrifuge. The grafting rate was calculated according to the formula below. Graft rate % = Acetone insoluble area % - Rubber amount % in graft copolymer / Rubber amount % in graft copolymer x
100 Samples A-2 to A shown in Table-1 in the same manner
-10 was polymerized. The amount of the monomer mixture charged in the first step was 50% by weight based on the rubbery polymer, except for A-3 and A-9. In A-3, the monomer mixture in the first step was 14 parts, and in A-9
In this case, there will be 34 parts. [] Production of copolymer (B) A stainless steel machine with an internal volume of 10, equipped with a stirring device, a heating jacket, a reflux condenser, a thermometer, a nitrogen gas inlet, and a continuous addition device for monomer emulsion and polymerization initiator. The reactor was charged with the following mixture. Water 250 parts Potassium oleate 4 parts α-methylstyrene 75 parts Methyl methacrylate 10 parts t-dodecyl mercaptan 0.3 parts Next, the atmosphere was replaced with nitrogen and the temperature was raised to 50°C while stirring under a nitrogen stream, and then added to 10 parts of water. Dissolved Sodium Formaldehyde Sulfoxylate 0.4
Sodium ethylenediaminetetraacetate
After adding 0.2 parts of ferrous sulfate and 0.01 parts of ferrous sulfate, and further adding 0.15 parts of cumene hydroperoxide, 15 parts of acrylonitrile was continuously added over 5 hours to cause a reaction. After the preparation was completed, the reaction was continued for an additional 2 hours. The polymerization conversion rate at the end of the polymerization reaction was 92%. Calcium chloride was added to the thus 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 separated, washed with water, and dried to obtain a resin powder. Similarly, Samples B-2 to B shown in Table-2
-6 was polymerized. Examples 1 to 6 40 parts of the above graft copolymer and 60 parts of copolymer and 0.2 part of dithiostearylthiopropionate,
4,4'-Butylidenebis-6-t-butyl-m-
After mixing 0.5 parts of cresol in a Henschel mixer, the mixture was pelletized at 200°C using an extruder, and a test piece was molded using the method described below to measure its physical properties. Molding of test pieces and measurement of physical properties The Izotsu impact strength was determined by molding specified test pieces at 250℃ using a 5-ounce injection molding machine, and using ASTM
Measured at 23°C according to the D250 method. Rockwell hardness was measured according to ASTM D785 using the same test piece as Izod impact strength. Measurement of heat shrinkage rate A 1/3″ x 1/2″ x 5″ test piece was made by injection molding, and after measuring the length _L0 of the longest part, it was placed in a gear aging tester at 130°C. After leaving it for 1 hour, it was taken out and left at room temperature for 1 hour, and then the length L ₁ was measured again, and the heat shrinkage rate (α) was calculated using the following formula: α=L ₀ −L ₁ /L ₀ ×100 ( %) The results of measuring various physical properties are shown in Table 3.Table-
As shown in detail in Section 3, the resin composition of the present invention has a high Izot impact strength of 12 Kgcm/cm or more, a Vicat softening temperature of 130°C or more, and a
A product with a heat shrinkage rate of 1.8% or less and excellent both heat resistance and impact resistance was obtained. Comparative Examples 1 to 6 40 parts of a graft copolymer and 60 parts of a copolymer in which one or both of the graft copolymer (A) and the copolymer (B) were produced with a monomer composition other than that of the present invention When the physical properties were measured in the same manner as in Example 1, the physical properties shown in Table 3 were obtained. As detailed in Table 3, all of these comparative examples have both impact resistance and heat resistance, or
One of them has a drawback.

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Claims (1)

[Scope of Claims] 1. Butadiene-based rubbery polymer latex 30-60 containing 10-35% by weight of particles with a particle size of 0.4μ or more
In the presence of parts by weight (calculated as solid content), styrene and α
- a monomer mixture consisting of 55-80% by weight of a methylstyrene mixture, 15-35% by weight of a vinyl cyanide compound and 5-20% by weight of methyl methacrylate, of which the amount of styrene is relative to the rubbery polymer; te20
Monomer mixture containing ~50% by weight
It consists of a graft copolymer (A) obtained by emulsion polymerization of 70 to 40 parts by weight, 55 to 75% by weight of α-methylstyrene, 10 to 25% by weight of a vinyl cyanide compound, and 3 to 30% by weight of methyl methacrylate. A thermoplastic resin composition obtained by mixing a copolymer (B) obtained by emulsion polymerization of a monomer mixture, and in which the rubbery polymer content is 5 to 30% by weight in the resin composition. 2 The graft copolymer (A) is obtained by two-stage polymerization, in which 30 to 60 parts by weight of a butadiene-based rubbery polymer latex, the total amount of styrene used first, and the styrene and α-methyl used in the first stage are added. A monomer mixture consisting of 65-85% by weight of α-methylstyrene, which accounts for 0-20% by weight of the styrene mixture, and 15-35% by weight of vinyl cyanide.
Add 10-30 parts by weight to ensure that the grafting rate is at least
The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin composition is polymerized until it reaches 15%, and then the remaining monomer mixture is added to the polymerization system and polymerized until the graft copolymerization is substantially completed. thing.