To obtain a foamed body in which pores and an air bubbles having an ultra fine structure are uniformly dispersed by making an unvulcanized rubber contact a super critical or subcritical liquid during a kneading and/or a vulcanizing process for the liquid to penetrate and dissolve therein and then by stopping such contact.
A supercritical or subcritical liquid is made to contact an unvulcanized rubber only in an extruding machine used for kneading the unvulcanized rubber or only in a vulcanizing machine or both in the extruding machine and the vulcanizing machine and to penetrate and dissolve in the rubber. The super critical or subcritical liquid to be used includes liquids having a supercritical or subcritical temperature not more than a vulcanizing temperature such as carbon dioxide, ethane, ethylene or the like, among which carbon dioxide is most preferable. A foamed rubber item having a foaming ratio of 1-400% is thus obtained. The unvulcanized rubber includes SBR, BR, NR and the like.
HARA YUICHI
WATANABE JIRO
KAWAMO TETSUJI
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