Kureha Kagaku Kogyo Kabushiki Kaisha

Kureha Kagaku Kogyo K.k.

Katsumi Suzuki

Haruhiko Yusa

Masanori Oota

Takayuki Katto

Yoshikatsu Satake

Mitsuru Hoshino

Toshio Hosokawa

Hiroshi Hagiwara

A graft copolymer is formed by graft-polymerizing 10-95 wt. parts of a vinyl monomer onto 5-90 wt. parts of the rubber polymer which comprises 40-99 wt. % of butadiene and 1-60 wt. % of an aromatic polycyclic vinyl monomer represented by the following formula (I) or (II): ##STR1## wherein R denotes a hydrogen atom or a methyl group. The graft copolymer is characterized by the rubber polymer having a high refractive index as well as a low glass transition temperature due to the use of the aromatic polycyclic vinyl monomer. Accordingly, the graft copolymer per se may be used as a thermoplastic resin having good transparency and impact resistance at a low rubber polymer content and may also be added to a transparent thermoplastic resin inclusive of a vinyl chloride resin and a styrene-acrylonitrile copolymer resin to provide the thermoplastic resin with an improved impact resistance while retaining a good transparency.

Impact-resistant graft copolymer and thermoplastic resin composition

A polyvinyl chloride resin composition comprises 3-30 wt. % of a graft copolymer and 97-70 wt. % of a polyvinyl chloride resin and has highly-balanced properties between impact resistance, transparency and stress-whitening resistance and excellent processing characteristics. The graft copolymer is obtained by graft-polymerizing, in the presence of a latex containing greater than 75 but not exceeding 85 parts by weight of a rubbery butadiene-styrene copolymer formed of 65-85 wt. % of butadiene, 15-35 wt. % of styrene and 0-3 wt. % of crosslinkable monomer, (i) 5-24 parts by weight of a first monomer mixture as a first-stage component, said first monomer mixture being composed of 70-97 wt. % of methyl methacrylate and 30-3 wt. % of an alkyl acrylate whose alkyl group has 1-8 carbon atoms; and then (ii) 3-21 parts by weight of a second monomer mixture as a second-stage component, said second monomer mixture being composed of 97-100 wt % of styrene and 0-3 wt. % of crosslinkable monomer. The sum of the first and second monomer mixtures and the rubbery butadiene-styrene copolymer is 100 parts by weight. The monomers grafted in the first stage amount to 30-80 wt. % of the sum of the grafted monomers.

Polyvinyl chloride resin composition

A latex of a highly crosslinked butadiene rubber polymer comprising not less than 50% of butadiene, 1.0 to 10% of a crosslinking agent and a remainder of an ethylenically unsaturated monomer copolymerizable with butadiene, and having a particle size of 600 to 3,000 .ANG. and a degree of swelling of not greater than 7 is obtained by one or more stages of emulsion polymerization. By polymerizing 15 to 30 parts of a monomer mixture of an alkyl methacrylate, an aromatic vinyl monomer, and optionally a crosslinking agent and an unsaturated nitrile in the presence of 85 to 70 parts of the rubber polymer, a graft copolymer is obtained. A composition comprising 2 to 40% of this graft copolymer and 98 to 60% of a vinyl chloride resin possesses high impact resistance coupled with improved stress-whitening resistance, which properties cannot be easily obtained at the same time in conventional resin compositions.

Vinyl chloride resin composition

Graft-copolymers for improving impact strength comprising a relatively large quantity of an elastomeric trunk polymer, such as acrylonitrile/styrene/butadiene resins and methyl methacrylate/styrene/butadiene resins, have some undesirable powder characteristics, for example, poor fluidity and an easily blocking property. However, by blending a graft-copolymer of this type with a graft-copolymer comprising a relatively small quantity of an elastomeric trunk polymer in slurry form or dry state, it is possible to obtain a graft-copolymer blend with improved powder characteristics without significantly lowering the effect of improving the impact strength of the former graft-copolymer. The graft-copolymer blend thus obtained, when blended with a hard resin such as polyvinyl chloride, provides a resin composition with high impact strength.

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Iwaki, Japan

Katsumi Suzuki