Patent GB-939778-A (GB)
Title: Cellular material
IPC: C08J9/00
Filed: 1961-12-04
Abstract: The invention comprises a vulcanized cellular material derived from amorphous polypropylene, a minor proportion by weight of a vulcanizable olefin polymer or copolymer or a rubber, and sulphur as a vulcanization agent.  The material can be prepared by a process in which the constituents are mixed in the desired proportions with a blowing agent, heated (e.g. at 100 DEG  to 200 DEG C.) under pressure, expanded, and vulcanized at a higher temperature than that of the heating generally between 110 DEG  and 230 DEG C. Alternatively a gas such as nitrogen may be introduced at 5 to 150 atmospheres into the mass, which is made plastic at the operating temperature.  The vulcanizable olefin polymer is preferably a butadiene polymer, such as polybutadiene produced with a sodium catalyst, polyisoprene, polyisobutylene, a butadiene-styrene copolymer or an ethylene-propylene or ethylene-butene copolymer.  In Example (1) a homogenized mix of amorphous polypropylene, polybutadiene, silica, p,p1-oxy-bis(benzenesulphonyl hydrazide), sulphur and zinc oxide is heated in a sealed mould firstly at 135 DEG C. and then at 160 DEG C. to give a product of apparent density 0,25 g. per c.c.  In other examples there are used mixes of amorphous polypropylene with (2) ethylenepropylene copolymer, silica, p,p1-oxy-bis(benzenesulphonyl hydrazide), sulphur and dicumyl peroxide, (3) GRS rubber, silica, sulphur, zinc oxide and zinc dimethyl dithiocarbamate.  In a comparison experiment the mixture used comprises amorphous polypropylene, 2,6-ditert. butyl phenol (antioxidant) and azodicarbamide blowing agent.ALSO:The invention comprises a vulcanized cellular material derived from amorphous polypropylene, a minor proportion by weight of a vulcanizable olefin polymer or copolymer or a rubber and sulphur as a vulcanization agent.  The material can be prepared by a process in which the constituents are mixed in the desired proportions, with a blowing agent, heated (e.g. at 100 DEG C. to 200 DEG C.) under pressure, expanded, and vulcanized at a higher temperature than that of the heating generally between 110 DEG C. and 230 DEG C.  Alternatively a gas such as nitrogen may be introduced at 5 to 150 atmospheres into the mass, which is made plastic at the operating temperature.  The vulcanizable olefin polymer is preferably a butadiene polymer, such as polybutadiene produced with a sodium catalyst, polyisoprene, polyisobutylene, a butadiene-styrene copolymer or an ethylene-propylene or ethylene-butene copolymer.  In Example (1) a homogenised mix of amorphous polypropylene, polybutadiene, silica p, p1-oxy-bis (benzene sulphonyl hydrazide), sulphur and zinc oxide is heated in a sealed mould firstly at 135 DEG C. and then at 160 DEG C. to give a product of apparent density 0,25 g per cc.  In other examples there are used mixes of amorphous polypropylene with (2) ethylene-propylene copolymer, silica, p, p1-oxy-bis (benzene sulphonyl hydrazide), sulphur and dicumyl peroxide, (3) GRS rubber, silica, sulphur, zinc oxide and zinc dimethyl dithiocarbamate.  In a comparison experiment the mixture used comprises amorphous polypropylene, 2, 6- di-trt butyl phenol (antioxidant) and azo-dicarbamide blowing agent.