Impregnation process for a fibrous substrate, a liquid (meth) acrylic syrup for the impregnation process, its method of polymerization and structured article obtained thereof

An impregnation process for impregnating a fibrous substrate to form a thermoplastic composite material comprising at least 20 percent by weight of said fibrous material, wherein said fibrous substrate is made of long fibres having an aspect ratio of at least 1000 and said process comprises a step of impregnating said fibrous substrate with a liquid (meth) acrylic syrup in a closed mold, said (meth)acrylic syrup comprising:

• a) from 40 weight percent to 89.99 weight percent (meth)acrylic monomer, based on the sum of (meth)acrylic monomer plus (methacrylic polymer,
• b) from 10 weight percent to 59.99 weight percent (meth)acrylic polymer, based on the sum of (meth)acrylic monomer plus (methacrylic polymer,
• containing at least 90% by weight of methyl methacrylate and dissolved in said (meth)acrylic monomer,
• c) from 0.01 weight percent to 5 weight percent of one initiator or initiating system for starting the polymerization of the (meth) acrylic monomer, based on (methacrylic monomer,
• d) from 300 ppm to 4000 ppm activator, based on (meth)acrylate monomer, wherein said activator is selected from the group consisting of tertiary amines, N,N-dimethyl-p-toluidine (DMPT), N,N-dihydroxyethyl-p-toluidine (DHEPT), organic-soluble transition metal catalysts and mixtures thereof,
• e) from 0 weight percent to 20 weight percent filler, based on the liquid (meth)acrylic syrup,
• f) from 0 weight percent to 20 weight percent additives, based on the liquid (meth)acrylic syrup;
• said liquid (meth)acrylic syrup has a dynamic viscosity of a value in the range from 10 mPa*s to 10000 mPa*s.