Novel Foamable Compositions and Rotational MOlded ARticles Made THerefrom
Publication Date: 2002-May-17
The IP.com Prior Art Database
This invention describes foamable thermoplastic compositions and rotational molded articles made therefrom in which the blowing agents are dispersed uniformly and activate relatively slowly, preferably after fusion has been substantially completed, resulting in foamed articles with uniform cell structure and properties. Conventional rotomolded foams are made by dry-blending thermoplastic powder with chemical blowing agents (CBA) followed by biaxial rotational molding at zero shear rate to melt and sinter the powder particles. The blowing agents generate a lot of energy and decompose very fast at peak temperatures of about 190°C or less, before fusion of the thermoplastic powder has been completed. Hence, the foamed rotomolded articles made with conventional chemical blowing agents typically contain a lot of irregular sized voids.