Producing foam layer that is useful in interior trim part of vehicle, by introducing reactive mixture in fluid sealed cavity, and enlarging cavity so that it has height corresponding to thickness of layer before/during expansion of mixture

The process comprises introducing a reactive mixture in a fluid sealed cavity having a height that is less than a thickness of a foam layer (14) to be produced, where the reactive mixture is designed to generate a plastic material and a gas constituting products of a chemical reaction of the reaction mixture so that a foam is formed from the plastic, enlarging the cavity so that the cavity has a height corresponding to the thickness of the foam layer to be produced before or during the expansion of the mixture, and standing until the mixture is expanded and hardened. The process comprises introducing a reactive mixture in a fluid sealed cavity having a height that is less than a thickness of a foam layer (14) to be produced, where the reactive mixture is designed to generate a plastic material and a gas constituting products of a chemical reaction of the reaction mixture so that a foam is formed from the plastic, enlarging the cavity so that the cavity has a height corresponding to the thickness of the foam layer to be produced before or during the expansion of the mixture, standing until the mixture is expanded and hardened, and withdrawing the foam layer from the cavity. The foam layer has a thickness of 3-8 mm, and a volume density of the less than 150 g/l. The enlarging step occurs at the same time as the expansion step so that the cavity is enlarged under the effect of the pressure produced during the reaction. The enlarging step is performed before the formation of a quantity of gas that corresponds, under a normal pressure, to 20-10 vol.% of the mixture before the expansion of the mixture, and/or is completely terminated before the end of the reticulation of the plastic material. A pressure, produced during of the expansion of the mixture in the cavity, is less than 5 or 3 bars. The enlarging step begins at less than 20 seconds or 10 seconds after the introduction of the mixture. The cavity is filled with 50 or 80% of the reaction mixture before expansion. During introduction step, the reaction mixture has a viscosity of less than 1500 MPa.s. A decoration layer and/or a support is disposed in the cavity after the introduction step. An independent claim is included for a foam layer. L'invention concerne un procédé de réalisation d'une couche de mousse comportant les étapes : - introduction d'un mélange réactif (11) dans une cavité (4) étanche aux fluides, qui possède une hauteur inférieure à une épaisseur de la couche de mousse à réaliser, ledit méla