FUNCTIONALIZED PARTICULATE BICARBONATE AS BLOWING AGENT, FOAMABLE POLYMER COMPOSITION CONTAINING IT, AND ITS USE IN MANUFACTURING A THERMOPLASTIC FOAMED POLYMER

A chemical blowing agent for foaming a thermoplastic polymer, for example PVC plastisol or a polymer resin in an extrusion process, said chemical blowing agent comprising a functionalized particulate bicarbonate containing at least one additive, preferably excluding an exothermic blowing agent. The additive may be selected from the group consisting of rosin acids, any derivative thereof, and salts thereof; or any combinations thereof, such as comprising abietic acid, dihydroabietic acid, neoabietic acid, a rosin acid ester, or mixtures thereof. The particulate bicarbonate may be preferably functionalized by spray-coating, extrusion or co-grinding with at least one additive. The functionalized particulate bicarbonate may comprise 50 wt % to less than 100 wt % of the bicarbonate component, and 0.02-50 wt % of the additive. The functionalized particulate bicarbonate may further comprise 0.1-5 wt % silica. A foamable polymer composition comprising such chemical blowing agent. A process for manufacturing a foamed polymer, such as foamed PVC, comprising shaping and heating the foamable polymer composition, and a foamed polymer obtained by such process.