RUBBER COMPOSITION FORMULATED FOR FOAMING

摘要

PROBLEM TO BE SOLVED: To obtain a foaming rubber composition capable of readily controlling a multiplying power of foaming and providing a foamed rubber molding having good surface skin by blending a thermally decomposing type foaming agent as compounded fine particles in which an inorganic carrier is absorbed and carried. SOLUTION: In a rubber composition for foam, a thermally decomposing type foaming agent (e.g. azodicarbonamide or 2, 2'-azobisisobutylonitrile) is blended with an inorganic carrier (preferably diatomaceous earth from the viewpoint of surface appearance) in which an inorganic carrier is absorbed and carried. The inorganic carrier is preferably mixed with the thermally decomposing type foaming agent using a mechanical particle compounding apparatus (a compression type mixer) based on principles of compression, shearing and friction in order to absorb and carry the foaming agent into the inorganic carrier. The content of the foaming agent in a compounded fine particles is preferably 5-20wt.% and blend amount of the compounded fine particles to a rubber composition is usually 1-20phr. Furthermore, e.g. ethylene-propylene- based rubber used when window frame rubber is subjected to extrusion molding is exemplified as rubber polymer.