Patent ID: 6593432
Filing Date: 2003-07-15
Classification: C08K,C08L

Abstract:
A sulfur vulcanizing system rubber composition suitable for a cooling system hose and comprising an ethylene-propylene-diene terpolymer (EPDM) as a base material, a vulcanizing accelerator and zinc, wherein the vulcanizing accelerator comprises a combination of at least one first accelerator capable of controlling dissolution of zinc when at least 0.005 mol of said accelerator is incorporated in said composition, and at least one second accelerator classified as an ultra-accelerator;the first accelerator being such that, when at least 0.005 mol thereof is incorporated in the composition and a vulcanized sheet of said composition is left to stay for 24 hours at a normal ambient temperature in an aqueous solution containing 50% by volume of a long-life coolant in a volume of 10 times the volume of the vulcanized sheet, the amount of zinc dissolved in said coolant is less than 1 ppm; the rubber composition containing a total of from 2.0 to 7.0 parts by weight of said vulcanization accelerator, including from 0.1 to 3.0 parts by weight of the first accelerator, each per 100 parts by weight of EPDM; the first accelerator comprising a thiazole type accelerator selected from the group consisting of 2-mercaptobenzothiazole, a zinc salt thereof and dibenzothiazyldisulfide, and the second accelerator comprising a thiuram type accelerator selected from the group consisting of tetramethylthiuram monosulfide, tetraethylthiuram disulfide and tetrabutylthiuram disulfide.