JPH0471087B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a styrenic resin composition having excellent molding performance. Conventionally, general-purpose polystyrene resin or impact-resistant polystyrene resin has been used in a wide range of fields, including food containers such as frozen dessert containers and lactic acid bacteria beverage containers, and light electrical equipment such as stereo and TV housings and compact cassette halves and cases. Most of these are molded using injection molding machines and are available for demand. In recent years, the performance of injection molding machines has improved, and molded products can now be obtained at high speeds, and styrene resins are now required to have better moldability. Various methods have been known to improve the moldability of styrenic resins. for example,
Lowering the molecular weight of the styrenic polymer by using a molecular weight regulator such as mercaptans is also a means of improving moldability, but this is not preferred as it also results in poor mechanical strength. In addition, the use of plasticizers such as butyl stearate and white mineral oil is also effective in improving moldability, but all of these conventionally used plasticizers temperature,
The temperature was below 200°C, mostly 160-170°C. on the other hand,
Thanks to the high speed and precision of injection molding machines, the initial boiling temperature of 160 to 170℃ under 10mmHg reduced pressure is much higher than 250℃.
Molding is often performed at molding temperatures higher than 100%, so when using conventional plasticizers, some of the plasticizer vaporizes inside the molding machine, and when it is injected with the resin into a cooled mold, it separates from the resin. and distills out as an oily substance. This has the drawback of accumulating on the surface and grooves of the mold, combing or adhering to the molded product, and causing defective phenomena called ``oil stains'' or ``sweat staining'' that impair the appearance of the molded product. That is,
The white mineral oil conventionally used as a plasticizer for styrenic resins has an initial distillation temperature of around 160°C under a reduced pressure of 10 mmHg, and a distillation end temperature of 290°C. The oil remains in the grooves and surfaces of the mold, and if injection molding is continued for a long time, the oil will adhere to the surface of the molded product and cause it to become dirty, making it unavoidable. For this reason, in the past, the molding machine had to be stopped for a short period of time, even every hour, and the oil in the mold was wiped off, which resulted in an economic disadvantage of poor birthability. As a result of intensive research, the present inventor determined that the initial boiling temperature of white mineral oil blended as a plasticizer at 110 mmHg was 200 mmHg.
The present invention was completed based on the knowledge that the sweating phenomenon can be eliminated by setting the temperature above .degree. That is, the present invention is directed to a styrenic monomer or a mixture of a rubber-like polymer dissolved in a styrene monomer in the presence of 0.1 to 10 parts by weight of white mineral oil having an initial distillation temperature of 200° C. or higher under a reduced pressure of 10 mmHg. Alternatively, a method for producing a styrenic resin composition, comprising polymerizing 100 parts by weight of a mixture of the monomer or the mixture with another vinyl monomer copolymerizable with the styrenic monomer. be. In the present invention, the styrene resin is not only a polymer obtained by polymerizing a styrene monomer, but also a copolymer containing a styrene monomer as a main component with other copolymerizable vinyl monomers, and , a copolymer obtained by polymerizing a styrenic monomer or a styrenic monomer and another copolymerizable monomer in the presence of a rubbery polymer. Here, the styrenic monomer refers to one or more types of styrene, α-methylstyrene, tertiary-butylstyrene, nuclear-substituted styrene such as p-methylstyrene, and the like. Examples of other vinyl monomers copolymerizable with this monomer include acrylonitrile, methacrylic esters, acrylic esters, maleic anhydride, and the like. In addition, rubber-like polymers include conjugated 1,3 diene polymers such as butadiene, isoprene, and chloroprene, butadiene-styrene copolymers, butyl rubber, and ethylene-propylene terpolymers (EPDM). Use more than one species. When copolymerizing the styrene monomer with other vinyl monomers or rubber-like substances, the styrene monomer must account for at least 50% by weight of the copolymer. Further, when a rubbery polymer is used, the amount used is usually 1 to 20% by weight based on the styrenic polymer. If this value is exceeded, the viscosity of the styrenic monomer solution of the rubbery polymer increases,
The stirring power of the polymerization apparatus becomes extremely large, which is undesirable from the viewpoint of the apparatus. In the present invention, the amount of white mineral oil whose initial distillation temperature under 10 mmHg reduced pressure is 200°C or higher is styrenic monomer, or a mixture of styrene monomer and rubbery polymer dissolved therein, or For 100 parts by weight of a mixture of styrenic monomer and other vinyl monomers copolymerizable with styrenic monomer or the mixture,
The amount is 0.1 to 10 parts by weight, preferably 0.5 to 6.5 parts by weight. In the present invention, the polymerization method is not particularly limited, and polymerization methods such as bulk-suspension or bulk-suspension are preferred, but are not limited to these.
Furthermore, in the present invention, mercaptans,
It is also possible to add a molecular weight regulator such as α-methylstyrene dimer. In the present invention, the polymerization temperature is preferably 80 to 200°C, and although a styrenic resin can be obtained even if it is lower than 80°C, it takes time to complete the polymerization reaction and the yield per unit time is undesirable. Also
When the temperature exceeds 200°C, the reaction rate becomes extremely high, making it difficult to smoothly control polymerization. In order to obtain a styrenic resin composition having excellent molding performance, which is one of the objectives of the present invention,
As mentioned above, 10mmHg during polymerization of styrene resin.
A specific amount of white mineral oil having an initial distillation temperature of 200° C. or higher under reduced pressure may be present. Furthermore, the properties of the white mineral oil used are such that the initial distillation temperature under a reduced pressure of 10 mmHg is 200°C or higher, and n
When the naphthene component (Cn) determined by the -dM ring analysis method is at least 28% or more, preferably 30% to 40%, the resulting styrenic resin composition not only has excellent molding performance, but also It has been found that in the case of a transparent styrene resin composition that does not contain a rubbery polymer, a styrenic resin composition with good transparency can be obtained. That is, according to the present invention, furthermore, 10 mmHg
The initial distillation temperature under reduced pressure is 200℃ or higher, and n
- A styrenic monomer or a rubbery polymer is dissolved in a styrenic monomer in the presence of 0.1 to 10 parts by weight of a white mineral oil containing at least 28% naphthene component by dM ring analysis method. A method for producing a styrenic resin composition, comprising polymerizing 100 parts by weight of the mixture or the monomer, or a mixture of the mixture and another vinyl monomer copolymerizable with the styrenic monomer. is provided. The ndM ring analysis method is a method for testing the composition of high-boiling petroleum fractions, and it determines the carbon distribution of each hydrocarbon. Carbon distribution is the content of carbon atoms in aromatic rings (%Ca), the content of carbon atoms in naphthene rings (%Cn), and the content of carbon atoms in paraffin chain structures (%Cp). These calculations are
It is called the ndM method because it is obtained by a mathematical formula from the refractive index (n) according to JIS K2421, the density (d) according to JIS K2249, and the molecular weight (M) known from molecular weight measurement. Next, the present invention will be further explained using examples. However, the present invention is not limited to these examples. Example 1 In an autoclave with an internal volume of 230 mm, 100 kg of pure water, 3 g of sodium dodecylbenzenesulfonate, and 3.
600 g of calcium phosphate was added and stirred at 150 rpm. Next, add 90kg of styrene mixed in advance and 2.7kg of white mineral oil, and add 207g of benzoyl peroxide.
and tert-butyl peroxybenzoate 45
g was added, the inside of the autoclave was purged with nitrogen gas, and then the autoclave was sealed. The properties of the white mineral oil used here were that the initial distillation temperature was 202°C under a reduced pressure of 10 mmHg, and the n-d-M
The naphthenic content was 30% by ring analysis. The autoclave was heated to 90°C for 6 hours and 30 minutes at 115°C.
℃ for 2 hours and 135℃ for 2 hours for polymerization, and then cooled. Next, neutralize, dehydrate and dry according to conventional methods,
A styrenic resin composition was obtained in the form of ordinary pellets by extrusion. Example 2 Initial distillation temperature under 10 mmHg vacuum is 264℃, n-d-M
A styrenic resin composition was obtained in the same manner as in Example 1, except that a white mineral oil having a naphthenic content of 32% as determined by ring analysis was used. Example 3 Initial distillation temperature under 10 mmHg vacuum is 229°C, n-d-M
750 g of a white mineral oil with a naphthenic content of 40% determined by ring analysis was mixed with 25 kg of a styrene solution in which 1.5 kg of polybutadiene was dissolved, and the mixture was charged into a 30-capacity autoclave. Add 5g of benzoyl peroxide and 20g of linear dodecyl mercaptan to this,
Stirred at 200 rpm. After purging the inside of the can with nitrogen gas, it was sealed and the temperature was raised. After polymerizing at 100°C for 7 hours, the mixture was cooled to complete the prepolymerization. Then capacity 60
25 kg of pure water, 250 g of tertiary calcium phosphate, and 0.8 g of sodium dodecylbenzenesulfonate were added to an autoclave, and while stirring at 180 rpm, 37.5 g of 2,2 ditertiary butyl peroxybutane was added and Milperoxide 25g
The prepolymerization solution added with was added thereto, and after purging with nitrogen, the container was sealed, heated, polymerized at 110° C. for 6 hours, and at 135° C. for 4 hours, and then cooled. Next, a styrenic resin composition was obtained in the same manner as in Example 1. Comparative example 1 Initial distillation temperature under 10mmHg vacuum is 178℃, n-d-M
A styrenic resin composition was obtained in the same manner as in Example 1, except that a white mineral oil having a naphthenic content of 37% as determined by ring analysis was used. Comparative Example 2 A styrenic resin was obtained in the same manner as in Example 3 except that white mineral oil was not added. Example 4 Initial distillation temperature under 10 mmHg vacuum is 204℃, n-d-M
A styrenic resin composition was obtained in the same manner as in Example 1, except that a white mineral oil containing 25% naphthene as determined by ring analysis was used. Example 5 A styrenic resin composition was obtained in the same manner as in Example 1 except that the amount of white mineral oil was changed to 5.4 kg. Table 1 shows the results of measuring various physical properties of the styrenic resins or styrene resin compositions obtained in the above Examples and Comparative Examples.

[Table] The physical properties shown in the above table were measured by the following method. (1) Melt flow index: Based on JIS K-7210. (2) Haze: According to ASTM D-1003. Example 3
and Comparative Example 2 were not measured because they both contained rubber-like polymers and were opaque. (3) Mold contamination: A two-cavity plate mold with a surface plating finish was set in a 20Z inline screw injection molding machine SN-51B manufactured by Niigata Tekkosho Co., Ltd., and each sample was heated at a mold temperature of 40℃ and a molding temperature of 40℃. The oil stains around the mold air vent after 20 shot molding at 230°C are expressed in terms of area. (4) Continuous molding test: 7 on Nissei Plastics 90Z inline screw injection molding machine FS-170SE
A cassette half mold was set, and each sample was continuously molded for 10 hours at a mold temperature of 40°C and a molding temperature of 250°C, and the number of molded products with oil stains and cracks was expressed as the number of defective products. In addition, for Example 3 and Comparative Example 2, the number of pieces after 3 hours of continuous molding was converted into 10 hours and displayed.

Claims (1)

[Claims] 1. A styrenic monomer or a rubbery polymer dissolved in a styrenic monomer in the presence of 0.1 to 10 parts by weight of a white mineral oil whose initial distillation temperature is 200°C or higher under a reduced pressure of 10 mmHg. 100 parts by weight of a mixture obtained by mixing said monomer or said mixture with another vinyl monomer copolymerizable with a styrenic monomer. Production method. 2 In the presence of 0.1 to 10 parts by weight of a white mineral oil whose initial distillation temperature is 200°C or higher under a reduced pressure of 10 mmHg and whose naphthenic content is at least 28% by ND-M ring analysis, styrenic monomers are , or a mixture of a rubbery polymer dissolved in a styrenic monomer,
Or, a method for producing a styrenic resin composition, which comprises polymerizing 100 parts by weight of the monomer or a mixture obtained by mixing the mixture with another vinyl monomer copolymerizable with the styrenic monomer.