B29C 44/0469

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 provided with physical separators between the different materials, e.g. separating layers, mould walls}