JPS6321682B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat-resistant copolymer containing α-methylstyrene, methyl methacrylate, and acrylonitrile. Conventionally, styrene has been replaced with α-methylstyrene in order to improve the heat resistance of ABS resin. Furthermore, as a method to improve heat resistance, methyl methacrylate monomer was introduced, and α-
Methylstyrene, acrylonitrile, and methyl methacrylate copolymers have been considered. For example, in JP-A No. 55-144009, polymerization is divided into two stages, in which a monomer mixture with a high α-methylstyrene content is polymerized in the first stage, and a monomer mixture with a low α-methylstyrene content is polymerized in the second stage. It is described that a thermoplastic resin with excellent heat resistance can be obtained by doing so. However, even with this method, there is a limit to the α-methylstyrene content in the resulting copolymer, and a significant improvement in its heat resistance cannot be expected. Therefore, it is difficult to obtain a thermoplastic resin with excellent heat resistance by this method. In order to overcome these drawbacks, the present inventors have conducted various studies and found that a certain range of α-methylstyrene, methyl methacrylate, and acrylonitrile copolymers have particularly excellent heat resistance. It was discovered that satisfactory impact resistance could be imparted by mixing a graft copolymer, and the present invention was completed based on this finding. Particularly important in the present invention is the composition of the α-methylstyrene, methyl methacrylate, and acrylonitrile copolymer. That is, a copolymer consisting of 50 to 90 parts by weight of a-methylstyrelene, 5 to 30 parts by weight of acrylonitrile, 5 to 30 parts by weight of methyl methacrylate, and 0 to 5 parts by weight of a copolymerizable vinyl monomer. A random copolymer (A) which is a combination and contains 30 parts by weight or more of a component having an α-methylstyrene content of 70% by weight or more. The intrinsic viscosity [η] of this copolymer is 0.2 to 1.5, preferably 0.5 to 0.8 (DMF,
23°C), and its heat resistance is significantly higher than that of conventional copolymers. Thus, a copolymer with a high content of α-methylstyrene was obtained for the first time by the method of the present invention. A particularly important point in the method of the present invention is to maintain the weight ratio of α-methylstyrene and other vinyl monomers in the polymerization system to at least 90/10, particularly preferably at least 95/5. Any copolymer has a fixed composition depending on the copolymerizability ratio of the monomers themselves and the ratio of the monomers in the polymerization system, and the resulting copolymer has a As such, it has a certain compositional distribution. In the present invention, by this method, in the composition distribution regarding the content of α-methylstyrene,
By shifting the distribution toward a higher α-methylstyrene content, they succeeded in obtaining a highly heat-resistant copolymer. Furthermore, this copolymer (A)
By mixing the graft copolymer (B) with the resin composition, a resin composition having high heat resistance and excellent impact resistance can be obtained. First, the copolymer (A) is obtained as follows. That is, α-methylstyrene monomer is first charged and made into a sufficiently emulsified state, and then acrylonitrile and methyl methacrylate monomer are added dropwise little by little, and in the polymerization system, α-methylstyrene monomer, acrylonitrile and The monomer ratio of methyl methacrylate is always adjusted to a large excess of α-methylstyrene at a weight ratio of 90/10 or more, preferably 95/5 or more until the polymerization conversion rate exceeds 30%, preferably 50%. By leaving it for a while, the desired copolymer (A) can be obtained. In this case, the amount of α-methylstyrene initially charged is 50 parts by weight or more and 90 parts by weight or less. If it is less than 50 parts by weight, heat resistance will decrease, and if it exceeds 90 parts by weight, mechanical strength will decrease. The amount of acrylonitrile and methyl methacrylate monomer to be dropped is 50 parts by weight or less10
Parts by weight or more. The α-methylstyrene monomer charged first may contain a vinyl cyanide compound, methacrylic acid, lower alkyl ester of alkyl acid, etc. in an amount of 10% by weight or less based on the α-methylstyrene monomer. The acrylonitrile and methyl methacrylate monomers added dropwise may contain a monovinyl aromatic compound, an α-substituted monovinyl aromatic compound, etc. in an amount of 15% by weight or less based on the added monomer. There is no particular restriction on the dropping of the monomer, and the monomer mixture may be dropped continuously or may be dropped in several stages by changing the mixing ratio. Copolymer (B) used in the composition according to the present invention
is a graft copolymer obtained by reacting a diene rubber, a vinyl cyanide compound exemplified by acrylonitrile and styrene, a monovinyl aromatic compound, and methyl methacrylate. The above copolymer (A) and graft copolymer (B) are
It is preferably obtained by emulsion polymerization, but is not limited to emulsion polymerization. Emulsion polymerization can be carried out by conventional methods. For example, the monomer mixture may be reacted in an aqueous dispersion in the presence of a radical initiator. Examples of the radical polymerization initiator include peroxides such as potassium persulfate, ammonium persulfate, and kyumene hydroperoxide. In addition, polymerization accelerators, polymerization degree regulators, emulsifiers, and other agents that have been commonly used in emulsion polymerization can be appropriately selected and used. In order to suitably achieve the present invention, it is preferable to mix the diene rubber in an amount of 5 to 30% by weight in the composition after mixing. Mixing may be performed by a method known per se. For example, latexes of the copolymer (A) and the graft copolymer (B) may be mixed, salted out, solidified, and dried before use. Alternatively, powders or pellets of the copolymer (A) and the graft copolymer (B) may be kneaded using a roll, screw, Banbury mixer, kneader, etc. before use. If necessary, commonly used stabilizers, pigments, lubricants, fillers, etc. may be added during mixing. The present invention will be specifically explained below with reference to Examples. In addition, all "parts" in the examples represent "parts by weight." Production of copolymer (A) The following materials were charged into a reactor equipped with a stirrer. Water 250 parts Sodium laurate 3 Sodium formaldehyde sulfoxylate 0.4 Ferrous sulfate 0.0025 Disodium ethylenediaminetetraacetate
0.01〃 After deoxygenation, the monomers () shown in Table 1 were charged after heating and stirring at 60°C in a nitrogen stream. Next, Table-1
Monomer () and monomer () shown in were added dropwise. After the dropwise addition was completed, stirring was further continued at 60°C. The resulting copolymer latex was coagulated with calcium chloride, washed with water, filtered, dried, and pelletized to measure its heat resistance. In addition, the latex was sampled during the reaction, and its composition and polymerization conversion were measured. The polymerization conversion rate, composition, and heat resistance of the copolymer (A) thus obtained were as shown in Table 1. As shown in Table 1, it can be seen that the examples have high polymerization conversion rates and extremely excellent heat distortion temperatures. 【table】

Claims (1)

[Claims] 1 Initially, 50 parts by weight or more of α-methylstyrene and 0 or 10% by weight or less of acrylonitrile or/and methyl methacrylate are added to the α-methylstyrene, and after sufficiently emulsifying the α-methylstyrene, 50 parts by weight or less of acrylonitrile or/and methyl methacrylate (methyl methacrylate is used in at least either the initial charge or subsequent addition) little by little until the polymerization conversion rate based on the total monomers used exceeds 30%. High α-methylstyrene content characterized by emulsion polymerization carried out while always maintaining the ratio of α-methylstyrene monomers and monomers other than α-methylstyrene in the system at 90/10 or higher by weight. A method for producing a thermoplastic copolymer.