Mitsubishi Yuka Badische Company, Ltd.

Shigeki Mathuno

Hiroshi Endo

Masakazu Arai

Masanori Saito

Toshio Yagi

Toshihiro Gotoh

Masanori Tanaka

Masahiro Tanaka

Kunikazu Nagasaki

Shigeo Nishikawa

Foamed particles of a propylene resin are described which comprises, as a base resin, a random copolymer of propylene and 1-butene, said random copolymer having a 1-butene content of from 3 to 12% by weight. A foamed mold article is also described which is composed of a random copolymer of propylene and 1-butene, and having a density of from 0.015 to 0.09 g/cm.sup.3. A bumper core material for use in automobile bumpers is also described which is composed of a foamed mold article of a random copolymer of propylene and 1-butene, said random copolymer having a 1-butene content of from 3 to 12% by weight, said foamed mold article having a density of from 0.02 to 0.08 g/cm.sup.3, a compression stress at 50% compression as measured at 20.degree. C. of 2.5 to 10 kg/cm.sup.2, and an energy absorption efficiency as measured at 20.degree. C. of 60 to 90%, the ratio (E.sub.80 /E.sub.20) of the amount of the energy absorption of said foamed mold article as measured at 80.degree. C. (E.sub.80) to the amount of the energy absorption of said foamed mold article as measured at 20.degree. C. (E.sub.20) being 0.5 to 0.9.

Propylene resin foamed particles and foamed mold article

Foamed particles of a propylene resin are described which comprises, as a base resin, a random copolymer of propylene and 1-butene, said random copolymer having a 1-butene content of from 3 to 12% by weight. A foamed mold article is also described which is composed of a random copolymer of propylene and 1-butene, and having a density of from 0.015 to 0.09 g/cm.sup.3. A bumper core material for use in automobile bumpers is also discribed which is composed of a foamed mold article of a random copolymer of propylene and 1-butene, said random copolymer having a 1-butene content of from 3 to 12% by weight, said foamed mold article having a density of from 0.02 to 0.08 g/cm.sup.3, a compression stress at 50% compression as measured at 20.degree. C. of 2.5 to 10 kg/cm.sup.2, and an energy absorption efficiency as measured at 20.degree. C. of 60 to 90% the ratio (E.sub.80 /E.sub.20) of the amount of the energy absorption of said foamed mold article as measured at 80.degree. C. (E.sub.80) to the amount of the energy absorption of said foamed mold article as measured at 20.degree. C. (E.sub.20) being 0.5 to 0.9.

A method of producing a polypropylene resin molded product from foamed polypropylene particles is disclosed, which comprises introducing a pressurizing gas into foamed polypropylene particles having closed cells so that the particles have an internal gas pressure of from 0.3 to 2.5 Kg/cm.sup.2 G, charging the particles in a mold cavity while compressing the particles with a pressurizing inorganic gas until the initial apparent volume of the particles is reduced to 50 to 99%, removing the gas from the mold cavity while keeping the foamed particles in a compressed state, and introducing steam in the cavity to cause adhesion of the compressed foamed particles. The method produces a molded product having satisfactory appearance and excellent adhesion among particles in a shortened molding cycle.

Methods of producing molded products from foamed polypropylene particles

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Mie, Japan

Shigeki Mathuno