Mitsubishi Yuka Badische Company, Ltd.

Mitsubishi Petrochemical Company Limited

Mitsubishi Chemical Basf Company Limited

Toshihiro Gotoh

Hiroshi Endo

Toshio Yagi

Masakazu Arai

Masanori Saito

Shigeki Mathuno

Masanori Tanaka

Toshihiko Sugano

Masaaki Yokoyama

Tadashi Abe

Teruya Ohkuwa

The present invention relates to an expanded resin bead comprising:

Expanded resin beads

There are provided polypropylene resin expanded particles which have a uniform bubble size, can be molded with an exceptionally low steam pressure, and can produce an expanded molded product having a good surface appearance and an excellent energy absorption property. The present particles are polypropylene resin expanded particles containing as a base resin an isotactic polypropylene resin polymerized in the presence of a metallocene polymerization catalyst.

Polypropylene resin expanded particles

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 process for producing expanded particles of a styrene-acrylonitrile-butadiene copolymer is disclosed, comprising dispersing styrene-acrylonitride-butadiene copolymer particles in water in a closed vessel, feeding a volatile blowing agent to the aqueous dispersion in the closed vessel, heating the aqueous dispersion to a temperature higher than a glass transition point of the copolymer particles by at least 20.degree. C. to impregnate the volatile blowing agent into the copolymer particles, and opening one end of the closed vessel to release the aqueous dispersion containing the expandable copolymer particles into a low pressure zone having a pressure lower than the inner pressure of the closed vessel. The resulting expanded particles have a degree of expansion of from 10 to 50.

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Yokkaichi, Japan

Toshihiro Gotoh