B29C 44/0461

Shaping by internal pressure generated in the material, e.g. swelling or foaming {; Producing porous or cellular expanded plastics articles} for articles of definite length, i.e. discrete articles consisting of at least two parts of chemically or physically different materials, e.g. having different densities {by having different chemical compositions in different places, e.g. having different concentrations of foaming agent, feeding one composition after the other}