Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-08-22
2000-02-29
Henderson, Christopher
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C08L 5104
Patent
active
060310502
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a rubber-modified styrenic resin composition having an excellent mechanical strength and gloss as well as an excellent coloring property.
BACKGROUND ART
Conventional rubber-modified styrenic resins (HIPS) have had the problems that they have a low impact resistance and are inferior in a surface gloss of the molded articles and in a hue obtained by toning with a dye or a pigment as compared with those of an ABS resin. Accordingly, a method has recently been proposed in which the particle diameter of rubber is decreased and the impact resistance is supplemented by silicon oil for the purpose of improving a balance between the impact resistance and the gloss, whereby it is brought close to the characteristic of an ABS resin. However, an HIPS composition obtained by such method has not necessarily been satisfactory in terms of a coloring property while a balance between the impact resistance and the gloss is improved.
In order to improve this defect, methods are proposed in Japanese Patent Publication No. Hei 3-62723 and Japanese Patent Publication No. Hei 1-34453, in which the particle diameter of an aromatic monovinyl polymer included in a dispersed rubber particle is made fine and uniform to thereby improve the coloring property and the mechanical properties. These methods are characterized by using specific polybutadiene and making the particle diameter of an aromatic monovinyl polymer included in a dispersed rubber particle fine to 0.13 micron or less and so uniform that 90% of the number thereof falls in the range of .+-.0.04 micron.
The coloring property is certainly improved by these methods. On the other hand, the mechanical strength, particularly tensile elongation and drop impact strength are notably reduced. A reduction in these mechanical strength has brought about the problem that the injection-molded article is liable to be broken when it is released from a mold or dropped, and therefore the improvement has been desired.
DISCLOSURE OF THE INVENTION
An object of the present invention is to overcome such a defect and to provide a rubber-modified styrenic resin composition having an excellent coloring property without deteriorating a balance between the gloss and the mechanical strength.
The present inventors have found that HIPS capable of being suited to the object described above can be obtained by controlling the number average particle diameter and the particle diameter distribution of a styrenic polymer included in rubber particles of the HIPS to the specific ranges and thus have come to complete the present invention based on this knowledge.
That is, the present invention relates to a rubber-modified styrenic resin composition comprising 80 to 96% by weight of a styrenic polymer and 20 to 4% by weight of the rubber-like polymer which is obtained by graft-polymerizing a styrenic monomer dissolving a rubber-like polymer, wherein: the form of particles having a volume average particle diameter falling in the range of 0.5 to 1.6 .mu.m, salami structure in which a part of the styrenic polymer having a number average particle diameter falling in the range of 0.13 .mu.m or more and up to 0.20 .mu.m and a particle diameter distribution falling in the range of 1.15 to 1.35 is dispersed and included in the rubber-like polymer particles, and ratio falling in the range of 7 to 12 in toluene.
The present invention shall be explained below in detail.
The styrenic monomer constituting the rubber-modified styrenic resin composition of the present invention includes, as well as the styrenic monomer alone, other vinyl monomers copolymerizable with the styrenic monomer which are used in combination therewith. The styrenic monomer includes aromatic monovinyl compounds such as styrene, .alpha.-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinylethylbenzene, vinylxylene and vinylnaphthalene. The vinyl monomers copolymerizable with the styrenic monomer include, for example, methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl ac
REFERENCES:
patent: 4308354 (1981-12-01), Jung
Fujita Masanari
Nozawa Masayuki
Shichijo Yasuji
Henderson Christopher
Nippon Steel Chemical Co., Ltd
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