Patent FR-2800083-A1 (FR)
Title: Production of a compound material of wood particles in a synthetic polymer matrix for injection molding or extrusion, has a chemical modification of the wood before agglomeration to prevent chemical reactions with the polymers
Inventor: POINT JACQUES
IPC: C08H8/00
Filed: 1999-10-26
Abstract: Production of a compound material of wood particles in a synthetic polymer matrix for injection molding or extrusion, has a chemical modification of the wood before agglomeration to prevent chemical reactions with the polymers. To produce a compound material of wood particles, embedded in a plastics matrix using thermoplastic or heat setting plastics materials, the wood particles (PB) are modified chemically to give compatibility with the polymers of the matrix. The wood material is initially crushed (Br) and then agglomerated (Ag) to increase the density. The wood particles are mixed with the polymer before or after the agglomerating stage.  The chemically-modified wood particles (PB) can be mixed with the synthetic polymers before agglomeration (Ag), to give a compound material which can be used for injection molding of plastics with inner wood particles. Or the chemically-modified wood particles (PB) are mixed with the synthetic polymers after agglomeration, to be augmented with minerals and additives such as stabilizing or antioxidizing colorants. It is passed through a single- or double screw extruder (Ext) to give a homogeneous compound (C1) as a semi-finished product. The mineral additive is a calcium carbonate powder at a rate of 1-5 wt.%, from waste sea shells which have been made inert and reduced to granules of 300  mu m to 1.5 mm. The compound material (C1) is composed of 55-90% of polymer matrix, 9-45% wood, 1-5% of minerals and 0.1-1.0% additives. The mixture of materials is processed in the extruder (Ext) at a rising temp. of 120-150 deg C in stages between its entry and exit, so that the polymer is completely softened. The extruder screw has a rotary speed of 50 rpm for a single-screw, and 100-200 rpm with a double-screw. The extruded material is of rushes, chopped into granules for use in an injection mold. The crushing of the synthetic polymers is at ambient temps. using a cutter chopper. The agglomeration (Ag) of the polymers and/or the mixture of polymers/wood (PB) is at a temp. which is 80-130 deg C below the polymer fusion temp. The agglomerating unit has a vat with angled blades and counter blades. The contents are chilled abruptly by cold water as the polymer is plasticized by the blades to be fragmented into granules in a size of  <= 5 mm. The agglomerator gives a plastics material or a mixture of polymer/wood in a density of 400 kg/m<3>. The synthetic polymers are waste plastics materials (DP) as films, bags, various objects which are not cleaned or separated before use. The wood particles (PB) are initially modified chemically to give a radical synthesis of a copolymer formed at least by a reactive component with the hydroxyl groups of the wood cellulose, to ensure compatibility with the matrix of thermoplastics or prevent a chemical reaction with heat setting plastics. It is also charged with at least one additive to control its hydrophobic character and resist bacteria.