Combination blowing agent and filler for thermoplastic foams

A process for the preparation of an alkenyl aromatic polymeric foam body, the steps of the method comprising:

• (1) heat plastifying an alkenyl aromatic polymeric material;
• (2) adding to the heat plastified polymeric material, under a pressure sufficient to prevent foaming, a volatile organic fluid foaming agent and an amount of finely-divided, water-containing organic vegetable matter, to provide a foaming agent/polymeric material, mixture;
• (3) mixing the volatile organic fluid foaming agent and the finely-divided, water-containing organic vegetable matter with the heat plastified polymeric material to form a blowable mixture;
• (4) reducing the temperature of the blowable mixture to a temperature such that when the pressure is reduced thereon, an alkenyl aromatic polymeric foam of desirable quality is formed;
• and
• (5) extruding the blowable mixture into a zone of lower pressure to thereby cause the blowable mixture to form a foam of desirable quality.