Rubber surface identification coating and rubber products prepared therefrom

A method of manufacturing a rubber product comprises the steps of (A) providing a marked diene rubber composition component containing carbon black and sulfur based curative therefor and having an identifying contrastingly white colored marking coating composition thereon, (B) assembling two or more rubber components consisting of at least one of said marked rubber composition components together to form a composite product of two or more rubber components, and (C) curing said article under conditions of an elevated pressure and a temperature of at least about 135.degree. C.;

• wherein said contrasting color of the marking composition remains visible after said curing;
• wherein said marking composition consists essentially of (i) 100 parts by weight of particulate zinc oxide, and (ii) as a binder therefor, about 20 to about 25 parts by weight of polybutadiene prepared by aqueous emulsion polymerization and containing an alkyl aryl sulfonate emulsifier;
• and wherein said marking composition is applied to said rubber composition component by (1) coating a surface of said diene rubber component with an aqueous mixture/dispersion coating composition having a pH in a range of about 9.4 to about 10.5 and comprised of a blend of polybutadiene latex, utilizing and containing a synthetic anionic emulsifier, and an aqueous dispersion of zinc oxide, and (2) drying the applied marking composition on the surface of said rubber component.