JPH0471940B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a styrenic resin composition that has excellent mechanical strength at low temperatures. (Prior art) Conventionally, general-purpose polystyrene resin or impact-resistant polystyrene resin has been used in a wide range of fields, such as containers for frozen desserts such as pudding and ice cream, food containers such as lactic acid drink containers, meat plates in refrigerators, and vegetable boxes. These materials are used in low-temperature environments, and mechanical strength at low temperatures is important in addition to general mechanical strength at room temperature. Conventionally, in the above-mentioned application fields using general-purpose polystyrene resin or impact-resistant polystyrene resin, in order to improve low-temperature mechanical strength,
Rather than improving the resin, the wall thickness of the molded product has been increased to cover the problem. Naturally, when the wall thickness of a molded product is increased, it is necessary to lengthen the cooling time during molding, which lengthens the molding cycle and reduces the tolerance. Also, if the wall thickness is increased, molded product 1
This increased the weight of each piece, which was a major disadvantage from an economic standpoint. (Problems to be Solved by the Invention) The present invention was made with the object of obtaining a styrenic resin composition having excellent mechanical strength at low temperatures. (Means for solving the problem) As a result of intensive research, the present inventor has discovered that as a plasticizer,
The present invention was completed based on the knowledge that a styrenic resin composition with excellent mechanical strength at low temperatures can be obtained by using a so-called white mineral oil having a pour point of -20°C or lower and a viscosity index of 85 or higher. I reached it. That is, the present invention provides a polymer of styrene or a nuclear substituted styrene, a copolymer of styrene or a nuclear substituted styrene, or a polymer of styrene or a nuclear substituted styrene in the presence of a rubbery polymer, if necessary. Copolymers obtained by copolymerizing with monomers (these polymers are called "styrenic polymers")
Mineral oil (white mineral oil) obtained by dewaxing and hydrogenating a fraction obtained by distilling crude oil per 100 parts by weight, and having a pour point of -20°C or lower and a viscosity index of 85 or higher. The present invention relates to a styrenic resin composition characterized by containing 0.1 to 10 parts by weight of oil. In the present invention, the styrenic polymer is not only a polymer obtained by polymerizing a styrenic monomer, but also a copolymer containing a styrenic monomer as a main component with other copolymerizable vinyl monomers, and includes 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 that can be copolymerized with the core monomer include:
Examples include acrylonitrile, methacrylic ester, acrylic ester, and maleic anhydride. or,
Examples of rubbery 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 vinyl monomers or rubber-like substances in addition to styrene monomers, the styrene monomers contained in the copolymer are at least
It is necessary to account for 50% by weight or more. Further, when a rubbery polymer is used, the amount used is usually 1 to 20% by weight based on the styrenic polymer. If it exceeds this range, the viscosity of the styrene monomer solution of the rubbery polymer will increase, and the stirring power of the polymerization apparatus will become very large, which is not desirable from the viewpoint of the apparatus. The pour point of the white mineral oil used in the composition of the present invention is -20°C or lower. Low-temperature strength is weak at temperatures higher than -20℃. Also, the viscosity index needs to be 85 or higher. If it is less than 85, the low temperature strength is similarly insufficient. In the composition of the present invention, the content of white mineral oil having a pour point of -20°C or lower and a viscosity index of 85 or higher is 0.1 parts by weight per 100 parts by weight of the styrenic polymer.
~10 parts by weight, preferably 0.5 to 6.5 parts by weight. The white mineral oil that meets the purpose of the present invention can be obtained by sufficiently performing dewaxing treatment, for example, crude oil is distilled under normal pressure, then distilled under reduced pressure, the resulting fraction is dewaxed, and then this is hydrotreated. do. It is then obtained by further fractional distillation, solvent dewaxing, and hydrogenation treatment. The method for producing the styrenic resin composition of the present invention includes mechanical mixing such as kneading the white mineral oil into the styrenic polymer, and mixing during the polymerization process to obtain the styrenic polymer, preferably after the devolatilization process. Preferably, a production method using an addition method in which the styrenic polymer is mixed with the styrene monomer in advance during polymerization is preferable. There are no particular restrictions on the polymerization method; bulk,
Polymerization methods such as suspension or bulk-suspension are preferred, but are not limited thereto. Further, in the present invention, it is also possible to add a molecular weight regulator represented by mercaptans, α-methylstyrene dimer, etc. during polymerization. It is also possible to add lubricants and mold release agents such as higher fatty acids and metal salts of higher fatty acids within a range that does not impair the effects of the present invention. (Example) Next, the present invention will be further explained with reference to Examples. However, the present invention is not limited to these examples. Example 1 White mineral oil with a pour point of -50.0°C and a viscosity index of 93 (Idemitsu Kosan Co., Ltd. Daphne Oil CP38G) 625
g, polybutadiene (Ube Industries, Ltd. Ubepol)
2 kg of BR15H) was mixed with 25 kg of a styrene solution and placed in a 30 capacity autoclave. To this were added 10 g of dicumyl peroxide and 12.5 g of linear dodecyl mercaptan, and the mixture was 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 110°C for 6 hours and 30 minutes, the mixture was cooled to complete the preliminary polymerization. Then add 25% pure water into an autoclave with a capacity of 60%
Kg, 25 g of tribasic calcium phosphate, and 0.8 g of sodium dodecylbenzenesulfonate were added, and while stirring at 180 rpm, added 75 g of benzoyl peroxide.
Pour the above prepolymerization solution containing 20 g of tert-butyl perbenzoate, purge with nitrogen gas, seal, raise the temperature, and heat at 90°C for 5 hours and 115°C for 2 hours.
Polymerization was carried out by holding at 135°C for 3 hours, and the mixture was cooled. The mixture was then neutralized, dehydrated, dried, and extruded by conventional methods to obtain a styrenic resin composition in the form of ordinary pellets. Example 2 In an autoclave with an internal volume of 230 mm, 100 kg of pure water, 3 g of sodium dodecylbenzenesulfonate, and a third
600 g of calcium phosphate was added and stirred at 150 rpm. Next, pre-mixed styrene 90kg and white mineral oil (Idemitsu Kosan Co., Ltd. Daphne Oil CP42NC) 3.15
72 g of 2,2-di-tert-butylperoxybutane and 45 g of ethyl 3,3-bis(tert-butylperoxy)butyrate were added, and the inside of the autoclave was purged with nitrogen gas and then sealed. The white mineral oil used here had a pour point of -42.5°C and a viscosity index of 94. The temperature of the autoclave was increased to 110℃ for 3 hours and 30 minutes, then to 120℃ for 4 hours.
Polymerization was carried out by holding at 135°C for 2 hours, and the mixture was cooled. Then, in the same manner as in Example 1, a styrenic resin composition was obtained. Example 3 A styrenic resin composition was obtained in the same manner as in Example 1, except that white mineral oil having a pour point of -22.5°C and a viscosity index of 103 was used. Comparative Example 1 A styrenic resin composition was obtained in the same manner as in Example 1, except that a white mineral oil (trade name: Gloria, manufactured by Witco Chemical) having a pour point of -17.5°C and a viscosity index of 95 was used. Comparative Example 2 A styrenic resin was obtained in the same manner as in Example 1 except that white mineral oil was not added. Comparative Example 3 A styrenic resin composition was obtained in the same manner as in Example 2, except that a white mineral oil (trade name: Kaydol, manufactured by Witco Chemical) having a pour point of -22.5°C and a viscosity index of 74 was used. Example 4 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 1375 g. Example 5 1.5 parts by weight of the white mineral oil used in Example 1 was blended with 100 parts by weight of the styrene resin obtained in Comparative Example 2 using a Henschel mixer, and then extruded using a press to obtain a styrenic resin composition. I got something. 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. The physical properties shown in the table below were measured by the following method. (1) Izot impact strength at room temperature: According to JISK7110 (2) Izot impact strength at low temperature: The test piece was conditioned at -20°C overnight and measured in a -20°C room according to JISK7110. (3) Falling weight strength: A square plate of 120 x 120 x 2 mm was formed using a molding machine Toshiba IS-12590Z at an injection pressure of SSP + 10 Kg/cm ² G mold temperature of 50°C and a molding temperature of 240°C.
A weight with a 5R tip was dropped, and the strength was expressed as the product of weight and height at which cracking occurred. Measurements were taken at room temperature and -20°C.

[Table] * Example 2 and Comparative Example 3 are general-use polystyrene resin compositions, other examples are impact-resistant
It is an impact-resistant polystyrene resin composition.

Claims (1)

[Claims] 1 Polymer of styrene or nuclear substituted styrene,
100 weight copolymers of styrene or nuclear-substituted styrene, or copolymers obtained by copolymerizing styrene or nuclear-substituted styrene optionally with other copolymerizable monomers in the presence of a rubbery polymer. 0.1% of mineral oil, which is obtained by dewaxing and hydrogenating a fraction obtained by distilling crude oil, and has a pour point of -20°C or lower and a viscosity index of 85 or higher.
A styrenic resin composition comprising ~10 parts by weight.