Method of producing a thermoplastically moldable fiber-reinforced semifinished product

A continuous process for the preparation of a porous thermoformable semifinished product having a porosity of from 25 volume percent to 75 volume percent from thermoplastic fibers and reinforcing fibers, comprising the steps of:

• a) blending from 10 to 80 weight percent of thermoplastic fibers with 90 to 20 weight percent of reinforcing fibers, said reinforcing fibers supplied as individual fibers or as multi-fiber strands which are opened into individual fibers during blending, to form a lofty, continuous non-woven mat;
• b) consolidating the lofty non-woven mat of step a) by needling or by thermal treatment which melts the thermoplastic fibers only partially to form a porous and flexible but handleable consolidated mat;
• c) heating the consolidated mat to a temperature above the melting point of the thermoplastic fibers;
• d) compressing the consolidated mat while still hot in a heated zone of a double band press at a pressure of 0.05 bar to 0.5 bar or less for a period of at least 3 seconds to form a densified but still porous product containing reinforcing fibers and molten thermoplastic;
• and
• e) cooling said densified porous product at a pressure of 0.5 bar or less, in a cool zone of a double band press maintained at a temperature below the melt temperature of the thermoplastic fibers, for a time period sufficient to allow the thermoplastic to solidify and form a porous semifinished intermediate product, and removing a stiff semifinished product.