JPH0742381B2 - Rubber modified polystyrene resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber-modified polystyrene resin composition having excellent surface gloss and good impact resistance, and more specifically to a methacrylic acid ester-based copolymer having a specific particle size. The present invention relates to a rubber-modified polystyrene resin composition obtained by blending a polymer and / or an acrylic acid ester-based copolymer in a predetermined ratio.

[Problems to be Solved by Prior Art and Invention]

Conventionally, as one means for improving the mechanical strength of polystyrene, a method of polymerizing styrene in which a rubber-like substance is dissolved to produce a so-called graft type rubber-modified polystyrene is known. However, the graft-type rubber-modified polystyrene is vulnerable to whitening and cracks when molding the product, and to the impact of dropping,
It has the drawback that the added rubber-like substance reduces the surface gloss. In recent years, rubber-modified polystyrene has been required to have the same gloss as acrylonitrile-butadiene-styrene resin (ABS). On the other hand, although the microstructure of rubber-modified polystyrene such as rubber particle size and gel amount has been investigated and attempts have been made to improve gloss and impact resistance, it has not been enough to satisfy both of them. .

Therefore, as a result of intensive studies, the present inventors have made a resin composition in which a methacrylic acid ester-based copolymer having a specific particle diameter and / or an acrylic acid ester-based copolymer is mixed with a rubber-modified polystyrene having a specific rubber particle diameter. It was found that the product has excellent gloss and impact resistance, and based on such findings, the present invention was completed.

[Means for solving problems]

That is, in the present invention, (A) a rubber content of 3 to 15% by weight, 100 parts by weight of a rubber-modified polystyrene having an average rubber particle diameter of 0.5 to 1.5 μ, and (B) (a) a methacrylic acid ester monomer. And / or acrylic acid ester monomer,
(B) A rubber-modified polystyrene resin composition comprising 3 to 25 parts by weight of a copolymer having an aromatic vinyl monomer and (C) a diene monomer and having a particle diameter of 0.5 μm or less. Is provided.

The rubber-modified polystyrene used as the component (A) in the present invention is a bulk, suspension or bulk-suspension two-stage polymerization method of styrene in which a rubber-like substance (for example, polybutadiene rubber, styrene-butadiene copolymer rubber, etc.) is dissolved. It is produced by the conventional graft polymerization method. In this case, the rubber content is preferably 3 to 15% by weight, preferably 4 to 10% by weight, and the average rubber particle size is preferably 0.5 to 1.5 μm. If the average rubber particle diameter is 1.5 μm or more, the gloss is poor, and if it is less than 0.5 μm, the resin composition has poor impact resistance. The average rubber particle diameter can be variously adjusted depending on the number of revolutions of the stirrer, the amount of chain transfer agent used, the reaction temperature, and the like.

Next, the copolymer which is the component (B) of the present invention is (a) a methacrylic acid ester monomer and / or an acrylic acid ester monomer, (b) an aromatic vinyl monomer and (c).
It is obtained by reacting a diene monomer.

Here, the methacrylic acid ester monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and the like, and the acrylate ester monomers include methyl acrylate, ethyl acrylate, and acrylic acid. Butyl acid and the like are used, and these are used alone or in combination of two or more kinds. Of these, methyl methacrylate and butyl methacrylate are preferable.

Aromatic vinyl monomers include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dichlorostyrene, 2,5-dichlorostyrene, dimethylstyrene, etc. The styrene derivative of can also be used.

Further, as the diene monomer, propadiene, 1,2-butadiene, 1,3-butadiene, isoprene, chloroprene, 1,3
-Pentadiene and the like, of which butadiene or its derivatives are preferred. The diene monomer may be used after being polymerized alone before the copolymerization reaction with other components.

The copolymer of the component (B) in the present invention can be produced by various methods using each of the above monomers, and one example thereof is obtained by polymerizing the (c) diene monomer. In the presence of a diene rubber or a mixture thereof, (a) a methacrylic acid ester monomer and / or an acrylic acid ester monomer, and (b) an aromatic vinyl monomer are subjected to an emulsion polymerization method, a suspension polymerization method, a solution polymerization method, There is a method of copolymerization by a known means such as a bulk-suspension polymerization method. In addition, for example, it can be produced by adding styrene and methyl methacrylate to a rubber latex obtained by copolymerizing butyl methacrylate and butadiene and graft-polymerizing. Among the components (B) thus obtained, the content of (a) methacrylic acid ester monomer and / or acrylic acid ester monomer is 5 to 40% by weight, and (b) aromatic vinyl monomer. It is preferable that the content is 5 to 40% by weight and the content of the (C) diene monomer is 30 to 80% by weight.

Further, the particle size of the copolymer must be 0.5 μm or less. If the particle size exceeds 0.5 μ, high gloss cannot be obtained, which is not desirable. A typical example of the component (B) is methyl methacrylate-butadiene-styrene resin (MBS) resin).

The component (B) as described above is used in a proportion of 3 to 25 parts by weight, preferably 4 to 15 parts by weight, per 100 parts by weight of the rubber-modified polystyrene of the component (A). Here, the mixing ratio of component (B) is 25
If it exceeds 5 parts by weight, the melt viscosity is high and molding is difficult.

The rubber-modified polystyrene resin composition of the present invention can be produced by kneading the above-mentioned components (A) and (B) by a conventional method. In addition, if necessary, an auxiliary component such as an antioxidant, a release agent, and silicone oil can be added as appropriate.

〔Example〕

 Next, the present invention will be described in detail with reference to Examples.

Production Example A rubber-modified polystyrene used in the present invention was produced as follows. 92 parts by weight of styrene, polybutadiene (made by Asahi Kasei Corp., NF35)
AS) 8 parts by weight and 250 ppm of normal dodecyl mercaptan as a chain transfer agent are added, and the temperature is 140 ° C and the rotation speed is 500 rpm.
Was reacted for 2 hours to obtain a prepolymer having a styrene conversion of 42% by weight.

Then, the prepolymer prepared above was put into a 10 stainless steel autoclave at a prepolymer / water phase ratio of 1/1, and polyvinyl alcohol was added in an amount of 0.25% by weight based on the water phase and benzoyl peroxide 2000 ppm (based on the prepolymer). ), 1000 ppm of dicumyl peroxide (relative to the prepolymer) were added, and the rotation speed of the stirring blade was 50
At 0 rpm, the temperature is raised from 60 ℃ at a rate of 20 ℃ per hour, and
The reaction was carried out at 0 ° C for 3 hours. After the reaction was completed, the temperature was lowered and the aqueous phase was separated to obtain rubber-modified polystyrene.

The average rubber particle diameter in this rubber-modified polystyrene was measured by an electron microscope photograph and found to be 0.9 μ (the average value of 1000 averages of the major axis and the minor axis).

In the above manufacturing method, the amount of the chain transfer agent, the rotation speed of stirring,
By adjusting the amount of rubber added, rubber-modified polystyrene having various average rubber particle diameters and rubber contents used in Examples and Comparative Examples was produced.

Example 1 100 parts by weight of rubber-modified polystyrene having an average rubber particle diameter of 0.9 μ and a rubber content of 8% by weight was mixed with methyl methacrylate-butadiene-styrene resin (MBS resin) [Kaneace B56 manufactured by Kanegafuchi Chemical Industry Co., Ltd.]. , Average particle size 0.2 μ] were mixed and kneaded at 180 ° C. with a single-screw extruder to obtain a resin composition.

The obtained resin composition was molded into a molded product having a width of 70 mm, a thickness of 3 mm and a length of 270 mm, and the gloss measurement and the falling weight strength test were performed.
The results are shown in Table 1. Examples 2-9 and Comparative Example 1
4 In the same manner as in Example 1 except that the average rubber particle diameter and the rubber content in the rubber-modified polystyrene were changed and the mixing ratio of the MBS resin was changed as shown in Table 1. A resin composition was obtained, and this resin composition was similarly molded and tested. The results are shown in Table 1.

[Advantages of the Invention] The rubber-modified polystyrene resin composition of the present invention has excellent gloss and impact resistance.

Therefore, the rubber-modified polystyrene resin composition of the present invention is widely used in the production of products useful in the fields of home appliances, office equipment housings, etc. by extrusion molding, injection molding and the like.

Claims (1)

[Claims] 1. A rubber content of (A) is 3 to 15% by weight,
(B) (a) methacrylic acid ester monomer and / or acrylic acid ester monomer, (b) in 100 parts by weight of rubber-modified polystyrene having an average rubber particle diameter of 0.5 to 1.5 μm
A rubber-modified polystyrene resin composition comprising 3 to 25 parts by weight of a copolymer comprising an aromatic vinyl monomer and a (c) diene monomer and having a particle diameter of 0.5 µ or less.