Polychloroprene has a long history in the world of adhesives. It has been the primary choice when fast, high-strength, and permanent bonds are needed in variety of applications, from shoe soles to foam bonding. Historically, polychloroprene adhesives have been solvent borne, but environmental and occupational safety reasons have recently caused a shift toward waterborne polychloroprene adhesives. One of the challenges in waterborne polychloroprene dispersion adhesives has been related to the thickening of these high pH systems, as well as the storage stability.
Typical thickeners used for waterborne polychloroprene dispersions include methylcellulose, carboxymethylcellulose, and acrylate thickeners. The purpose of the thickener is to increase the viscosity of the finished adhesive to provide enough sag resistance, as well as to control the level of penetration of the adhesive into the substrate (e.g., in the case of foam bonding). Thickeners are also added in order to prevent the settling of pigments, fillers, or metal oxides such as zinc oxide.