Method for producing an acoustic protection panel for a motor vehicle

A method for producing an acoustic protection panel (1) for a motor vehicle, said panel comprising an elastically compressible acoustic decoupling layer (2), said layer being based on elastically compressible foam flakes (3) agglomerated together by a heat-activatable binding agent (4), said method comprising the following steps:

• providing a mould provided with a die (5), said mould making it possible to successively define a first cavity (6) and a second smaller-volume cavity (7),
• providing a homogeneous mixture (8) of said flakes and said binding agent,
• arranging said mixture in said die to form a mattress (17),
• placing a first punch (12) opposite said die to define a first moulding cavity (6) that pre-compresses said mattress,
• heating said pre-compressed mattress to the activation temperature of said agent so as to ensure that said flakes are pre-maintained between them,
• placing a second punch (13) opposite said die to define a second moulding cavity (7) for over-compressing said mattress to obtain said decoupling layer,
• cooling said layer and removing it from said mould,
• said method also having the following features:
• said binding agent is formed by binding fibres, said fibres comprising a core (9) meltable at high temperature and a sheath (10) meltable at lower temperature,
• said flakes are bound together by melting said sheath, so that said layer is in the form of foam flakes agglomerated by said fibres,
• said flakes occupy between 80% and 90% by weight of said layer, so that said fibres occupy between 20% and 10% by weight of said layer.