Nissan Motor Company Limited

Mitsubishi Petrochemical Company Limited

Takashi Sugimoto

Masahiro Terada

Toshiro C Watanabe

Yukio Okada

Masashi Ohno

Nobuji Sugimoto

Yujiro Kawamura

Toyo Kawase

A plastic bumper for an automotive vehicle, of the type having so-called floating ribs for the purpose of weight-lightening and preventing surface sinkage due to resin shrinkage. The bumper is formed of a composition comprising (a) propylene-ethylene block copolymer in an amount ranging from 51 to 60 weight %, the block copolymer containing a content soluble in xylene at ordinary temperature, the content ranging from 3 to 8 weight %, and ethylene in an amount ranging from 3 to 8 mol %, the block copolymer having a MFR ranging from 20 to 40 g/10 min; (b) ethylene-propylene based copolymer rubber in an amount ranging from 20 to 30 weight %, the copolymer rubber having a MFR ranging from 0.1 to 2 g/10 min; and (c) talc in an amount ranging from 17 to 25 weight %, said talc having an average particle size ranging from 1.0 to 2.5 .mu.m. Additionally, the composition has (I) a flexural elastic modulus (at 23.degree. C.) not lower than 17000 Kg/cm.sup.2, (II) an Izod impact value (at -30.degree. C.) not lower than 6 kg-cm/cm, (III) a coefficient of linear expansion (3 mm thickness, 45 mm length, at 23.degree. to 80.degree. C.) not higher than 7.0.times.10.sup.-5 (cm/cm/.degree.C.), and (IV) a MFR not lower than 7 g/10 min.

Plastic automotive bumper

A large-sized exterior part of an automotive vehicle, injection-molded and formed of a polymer material comprises: (A) polypropylene in an amount ranging from 50 to 70 by weight %, the polypropylene containing ethylene in an amount not more than 15 weight % relative to the polypropylene and having a MFR (at 230.degree. C.) ranging from 5 to 60 g/10 min.; (B) ethylene-propylene copolymer rubber polymerized in the presence of a vanadium-based catalyst, in an amount ranging from 5 to 30 weight %, the copolymer containing propylene in an amount ranging from 20 to 40 weight % relative to the ethylene-propylene copolymer rubber and having a Mooney viscosity ML.sub.1+4 (100.degree. C.) ranging from 20 to 80; (C) ethylene-propylene copolymer rubber polymerized in the presence of a titanium-based catalyst, in an amount ranging from 5 to 45 weight %, the copolymer containing propylene in an amount ranging from 30 to 70 weight % relative to the ethylene-propylene copolymer rubber and having a Mooney viscosity ML.sub.1+4 (100.degree. C.) ranging from 20 to 75; and (D) polyethylene in an amount not more than 10 weight %, the polyethylene having a MFR (at 190.degree. C.) ranging from 5 to 50 g/10 min. The injection-molded article has an average thickness ranging from 2 to 6 mm, a flexural elastic modulus ranging from 3000 to 6000 kg/cm.sup.2, and a coefficient of linear expansion not higher than 8.times.10.sup.-5 /.degree.C.

Injection-molded article

Disclosed is an automobile bumper which is formed of a thermoplastic multicomponent resin composition and which is improved in weatherability and impact resistance at low temperatures and also in surface glossiness. Essentially the resin composition is a blend of 22-28 wt % of a hydrogenated block copolymer of an aromatic vinyl compound such as styrene and a conjugated diene such as butadiene, 32-56 wt % of a propylene-ethylene block copolymer in which the content of ethylene is 1-10 wt % and 22-28 wt % of an ethylene-propylene copolymer rubber. Optionally, up to 5 wt % of talc and/or up to 7 wt % of low-pressure low-density polyethylene may be added. Some physical properties of the ingredients are specified such that the resin composition has a melt index not lower than 5 g/10 min at 230.degree. C. under load of 2.16 kg and a modulus of elasticity in bending in the range from 2000 to 4000 kg/cm.sup.2.

Automobile bumper formed of thermoplastic multicomponent resin

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Mie, Japan

Takashi Sugimoto