Patent GB-763645-A (GB)
Title: Improved rubber composition
IPC: C08L7/00
Filed: 1954-05-07
Abstract: A vulcanized rubber composition comprises natural rubber and a copolymer obtained by polymerizing a monovinyl aromatic compound in the presence of a small proportion of a copolymerizable cross-linking agent.  The monovinyl aromatic compound is preferably styrene or an alkyl (of not more than 4 carbon atoms)-substituted derivative, e.g. a vinyl toluene or ethyl styrene, or a mixture of such compounds may be used.  The cross-linking agent, preferably 1-5 per cent by weight of the aromatic compound, may comprise a di-vinyl or trivinyl benzene, naphthalene, anthracene, phenanthrene, carbazole, or pyridine, di-isopropenyl benzene, or naphthalene, an ether or ester containing at least two ethylenically unsaturated groups, e.g. an allyl or vinyl ester of phthalic, succinic, oxalic, maleic, fumaric, itaconic, citraconic, acrylic, or methacrylic acid, or an ester of a polyhydric alcohol with an unsaturated acid, e.g. a di-acrylate or methacrylate derived from ethylene, propylene, butylene, diethylene or di-propylene glycol.  A batch is first prepared by mixing 1 part rubber and 1 to 3 parts cross-linked polymer at 150 DEG  C. in the presence of a plasticizer, e.g. di-butyl, or dioctyl phthalate, or tricresyl phosphate.  This batch is then incorporated into more rubber with vulcanizing agents and vulcanized to give a composition comprising 5 to 25 parts of crosslinked polymer per 100 parts rubber. In examples, compositions are prepared using pale crepe rubber and styrene-divinyl benzene, vinyl toluene-divinyl benzene, styrene-diisopropenyl benzene and styrene-ethylene glycol dimethacrylate copolymers together with zinc oxide, sulphur, stearic acid and cyclohexyl benzthiazyl sulphenamide.ALSO:A vulcanized rubber composition comprises natural rubber and a cross-linked aromatic compound polymer obtained by polymerizing a monovinyl aromatic compound in the presence therein of a small proportion of a copolymerizable cross-linking agent.  The monovinyl aromatic compound is preferably styrene or an alkyl (of less than 5 carbon atoms)-substituted derivative, e.g. a vinyl toluene or ethyl styrene, or a mixture of such compounds may be used.  The cross-linking agent may comprise a di-vinyl or tri-vinyl benzene, naphthalene, anthracene, phenanthrene, carbazole, di-isopropenyl benzene, naphthalene, an ether or ester containing at least two ethylenically unsaturated groups, e.g. an allyl or vinyl ester of phthalic, succinic, oxalic, maleic, fumaric, itaconic, citraconic, acrylic, or methacrylic acid, or an ester of a polyhydric alcohol with an unsaturated acid, e.g. a di-acrylate or methacrylate derived from ethylene, propylene, butylene, di-ethylene, or di-propylene glycol. The amount of cross-linking agent used in the polymerization of the mono-vinyl aromatic compound preferably comprises 1 to 5 per cent by weight of the latter.  To avoid damage to the rubber composition by excessive heating during the incorporation of the cross-linked polymer therein, a batch is first prepared by mixing 1 part rubber and 1 to 3 parts cross-linked polymer at about 150 DEG C. in the presence of a plasticizer, e.g. di-butyl or di-octyl phthalate, or tricresyl phosphate.  This batch is then incorporated into a vulcanizable rubber mix in an amount such that the resulting composition comprises 5 to 25 parts of cross-linked polymer per 100 parts rubber.  In examples batches are prepared using pale crepe rubber and styrene polymerized in the presence of di-vinyl or di-isopropenyl benzene or ethylene glycol dimethacrylate, or pale crepe rubber and vinyl toluene polymerized in the presence of divinyl benzene.