Process for producing motor vehicle seat cushioning

A method of making a cushion for a motor vehicle seat, the method comprising:

• providing a cover having a format of a complex comprising a layer of covering material and a sublayer of elastically compressible foam,
• setting the format in place within a mould defining a moulding cavity, the layer of covering material being disposed against a wall of the moulding cavity,
• arranging a film based on thermoplastic polyurethane over the sublayer,
• injecting an elastically compressible foam precursor mixture into the moulding cavity, making a padding block, the film having a melting point and a melt mass-flow index that breaks down when subjected to the heat released during the formation of the foam of the block, enabling overmoulding of the sublayer by the block without substantial penetration of the foam of the block into the thickness of the sublayer,
• after expanding the foam, demoulding the obtained cushion,
• the method wherein the film is provided with a reinforcing sheet directed towards the cavity, to form a two-layer barrier against the penetration of foam, the reinforcing sheet being based on thermoplastic polyurethane with a melting point higher than that of the film and with a melt mass-flow index lower than that of the film, to have an increased resistance in comparison with the film in order to be broken down with a delay under the action of the heat released during the formation of the foam of the block.