Water-Resistant Release Coating for Uncured Rubber

Abstract Rubber is conventionally formed into sheets or slabs on a two-roll mill. These are immersed in a release agent (slab dip), followed by cooling and drying in air. The low rate of cooling associated with air limits the throughput in rubber mixers. The throughput can be significantly increased through the use of water for cooling. However, water cannot be used with conventional slab dips; it washes them from the rubber slabs, causing the slabs to stick together after stacking. A new slab dip now permits cooling rubber slabs rapidly with water. After they are dried and stacked, the slabs do not stick together. The new dip contains a unique combination of a carboxylated SBR latex, a heat sensitizer, fillers and other additives. The heat sensitizer causes the latex to gel rapidly after it contacts the hot surface of the rubber slabs; this provides a water-resistant release coating. Other additives in this slab dip control its wetting and rheological behavior. The new dip does not significantly alter ph...