The invention further refers to a method for the production of said material.

Background of the invention There is today an extensive production of wood composite products, like particle boards and the like. These are made by mixing wood powder with glue. The glue can be of thermoplastic or thermoset plastic type. The glue represents an essential part of the cost for the composite material. The glue cost for a thermoset glue is today about 18 SEK per kg glue.

The spray painting industry has today to a great extent changed from wet paint to powder paint. The binder in such paint is a thermoset plastic. The binder may for example be an epoxy-, polyester-or acrylic resin. Both in the manufacture and use of powder paint a certain amount of residual material is obtained. One has to get rid of this residual material in some way. Today powder remaining from the powder paint industry is left for incineration or is set and then deposited. The cost for getting rid of the residual material is today about 5 SEK per kilo. However within a near future restrictions against deposition are awaited.

Through WO 96/15891 it is known to reuse powder paint, wherein this is pressed to tablets, which are used in powder spraying procedures.

Through JP 10-330536 it is known to produce an injection moulded product by using excess powder from the spray painting industry. A filler in the form of small partcles of inorganic material, such as kaolin, is added to the powder paint. The content of powder paint in the examples is from 67% and more.

The object and most important features of the invention The object of the present invention is to provide a wood composite material in which the main component is wood particles such as powder, chips or fibers, which

are bonded together with a binder and can be made in a cost efficient way. This has according to the invention been solved by the fact that the material contains at least 50% by weight wood material in the form of wood particles such as powder, chips or fibers and mo more than 50% by weight of powder paint, which as a main component contains thermoset resin and which acts as a binder between the wood particles.

For economical reasons powder paint mainly in the form of residual material from spray painting, powder paint manufacture or the like are intended to be used.

The final material contains preferably at least 60 % by weight and preferably at least 75 % by weight wood material.

Besides wood material and powder paint a binder in which the powder paint is distributed can be contained. The binder can be a thermoset resin, which is set together with the powder paint.

The invention further refers to a method for the manufacture of a composite material, wherein at least 50% by weight of wood material in the form of wood particles such as powder, chips or fibers and no more than 50% by weight powder paint, which as a main component contains a thermoset resin, are mixed, the mixture being heated and then shaped and set.

Description of the invention The wood composite material according to the invention contains as a main component wood particles in the form of powder, chips or fibers, which have been bonded together with a binder. The amount of wood material should be at least 50, preferably at least 60 and more preferably at least 75% by weight. The wood particles are mainly residual products from the wood industry.

Powder paint is used as binder, said powder paint as a main component containing a thermoset resin. The powder paint can at least to a substantial extent contain a residual powder coming from spray painting and from the production of powder paint. When applying and manufacturing powder paint a certain amount therefore will be obtained as a residual material, which today is incinerated or alternatively is

set and deposited. This residual material is according to the invention used as a binder between wood particles, for the manufacture of a wood composite material similar to the ones that today are manufactured by mixing the wood particles with glue in the form of a thermoset resin glues or a thermoplastic glue. The powder paint/lacquer is thus used for replacing this glue. The powder paint/lacquer may of course partly of wholly also consist of first-class product, i. e. non-residual powder.

The powder paint/lacquer is optionally mixed with a liquid material, such as an additional glue, on one hand for avoiding dusting and on the other hand for making the powder to distribute better between the wood particles. The liquid material can be a thermoset glue, which sets together with the powder paint/lacquer. Examples of such thermoset glues are phenol-, epoxy-, polyester-and acrylic glues.

Further additives that may be contained in the material are for example pigment, further binders, fillers, release agents, flame guards.

The wood composite material according to the invention are produced by mixing the wood particles, which may vary in size from powder to coarse chips, with the powder paint, which optionally is mixed with a liquid material, as mentioned above.

The mixture is then heated to a suitable setting temperature, usually 130-180°C, is shaped and set. Shaping preferably takes place by pressing.

Products that may be produced from the wood composite material according to the invention are particle boards for building purposes, details for car industry, hat- racks, toilet covers and wood plugs.

Examples The examples below disclose manufacturing of cylindrical test bodies and boards according to this invention.

The start material was 70 weight-% dried wood powder and 30 weight-% powder paint based on thermoset resin. Powder paint based on thermoset resin comprises a binder and a setting agent, in this case a common commercial polyester product from the paint manufacturer Jotun (Corro-Coat) was used. The wood powder was a mixture of spruce and pine and the particle size was < 0,4 mm.

The manufacture took place in tools of aluminum with a cylindrical and a rectangular cavity. From the powder amounts 6,7 and 100 g respectively boards with a diameter of 40 mm and the thickness 4 mm and 250 x 50 x 6 mm (L x B x H) respecively were made. The tool was treated with a release agent (Lagomat) so that the boards would not stick therein. The tool was heated up to 180 °C, and then the cavity was filled with the powder mixture. The powder mixture was pressed to a board in a press in which the heating plates had a temperature of 180 °C. While the powder mixture was pressed together, molten and finally set, the pressing pressure was gradually adjusted. The parameters used at the manufacture of the cylindrical board and the properties obtained are disclosed in the table below.

Wood powder 4,7 g Powder paint 2 g Degree of compression 6 times Pressing pressure 80 bar Pressing time 20 minutes Setting temperature 180 °C Density (ISO 2781) 1300 kg/m3 Elasticity module (ISO 178) 5400 Mpa Bending strength (ISO 178) 60 Mpa Break elongation (ISO 178) 1, 11 The properties obtained are comparable with those of a hard plywood plate. The material according to the invention can however be manufactured at a considerably lower cost.