Kaneka Corporation

Nobuhisa Ota

Naruhiko Akamatsu

Tsuyoshi Mihayashi

Yutaka Yanagihara

Takeshi Satoh

There is provided pre-expanded particles of a propylene resin having a high expansion ratio and excellent molding adhesion without using a volatile blowing agent or increasing an expansion pressure. The pre-expanded particles of a propylene resin are prepared by the process comprising dispersing resin particles comprising a propylene resin composition, which contains 100 parts by weight of (A) a random copolymer of ethylene and propylene having an ethylene content of 1.5 to 4.5% by weight and 0.001 to 10 parts by weight of (B) an alkali metal salt of a copolymer of ethylene and (meth)acrylic acid, into an aqueous dispersion medium in a pressure vessel to obtain a mixture, heating the mixture to an expansion temperature higher than a softening temperature of the resin particles, introducing an inorganic gas, and releasing the mixture into a lower atmosphere than the inner pressure of the pressure vessel; said mixture is expanded after a temperature of said mixture is maintained at a temperature region of not more than the expansion temperature to at least (the expansion temperature &minus;1&deg; C.) for at least 30 minutes.

Pre-expanded particles of propylene resin, process for preparing the same and flow-restricting device

There is provided pre-expanded particles of a propylene resin having a high expansion ratio and excellent molding adhesion without using a volatile blowing agent or increasing an expansion pressure. The pre-expanded particles of a propylene resin are prepared by the process comprising dispersing resin particles comprising a propylene resin composition, which contains 100 parts by weight of (A) a random copolymer of ethylene and propylene having an ethylene content of 1.5 to 4.5% by weight and 0.001 to 10 parts by weight of (B) an alkali metal salt of a copolymer of ethylene and (meth)acrylic acid, into an aqueous dispersion medium in a pressure vessel to obtain a mixture, heating the mixture to an expansion temperature higher than a softening temperature of the resin particles, introducing an inorganic gas, and releasing the mixture into a lower atmosphere than the inner pressure of the pressure vessel; said mixture is expanded after a temperature of said mixture is maintained at a temperature region of not more than the expansion temperature to at least (the expansion temperature -1.degree. C.) for at least 30 minutes.

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Settsu, Japan

Nobuhisa Ota