Abstract: A coating composition is based on polyvinyl chloride plastisol containing thermoplastic microspheres and is suitable for use as underbody compound for vehicles. The coating composition contains a mixture of expandable and expanded microspheres, in which the expandable microspheres expand at a temperature in the vicinity of the temperature at which the expanded microspheres begin to collapse. The mixture of microspheres solves the problem of a varying density of the coating when the plastisol is gelatinated.

Abstract: A coating composition suitable as an undercoating for cars contains vinyl-chloride-polymer-based plastisol and expandable thermoplastic microspheres. The expandable thermoplastic microspheres have a substantially halogen-free polymer shell which comprises a copolymer of halogen-free monomers and, in an amount of at least about 80% by weight, nitrile-containing monomers. Preferably, the polymer shell of the thermoplastic microspheres contains from about 85% by weight to about 97% by weight of nitrile-containing monomer. A method for spray-coating a surface with the coating composition by airless spraying is also disclosed.