CZ307977B6 - A method of producing composite boards from extruded PMMA and wood pieces, and a composite board produced by this method - Google Patents

Abstract

This is a method of producing composite boards from extruded PMMA and wood pieces, in which the layers of crushed extruded PMMA are gradually poured between which are alternatively placed by semi-layers if wooden pieces with humidity max. 10% by weight related on the weight of the wood in an absolutely dry state, with a total number of n + 1 layers of extruded PMMA pulp and n interlayers of wood pieces, where n is a positive integer number, then the resulting composite material is placed in a press heated to 120 to 180 °C, hot pressed to the desired thickness and cooled in air. Another subject is a composite plate made in this way.

Description

The present invention relates to the field of manufacturing plexiglass and wood composite panels and furniture.

BACKGROUND OF THE INVENTION

It is currently known to produce wood plastic composites by extrusion - extrusion at a temperature of about 200 ° C, as disclosed, for example, in WO 2016/82066, EP 2591053 or CN 101775885. In the case of patent document CN 1482166, extrusion production of a molten PMMA mix is described. (polymethyl methacrylate) with wood dust or using various elements such as sawdust, bamboo pieces, walnut shells for use in the manufacture of furniture, door panels, etc. However, the extrusion can only be achieved by a randomly directed and mostly spatially uniform arrangement of these panels.

Further, board bonding technologies are known in which one of the layers is a continuous PMMA board, and individual boards of different materials are bonded by gluing, as described in US Patent 20170197391. Similarly, US 7008700 describes making a composite of glued polycarbonate sheets between a layer of different filler materials is glued. Alternatively, sheets of different materials, one of which is PMMA, may be joined by compression molding as described in US Patent 20170144409.

In the case of the patent document WO 2015/20251, the resin-impregnated wood veneer is pressed onto another plate by means of a heated press. The disadvantage of joining materials in the form of plates is the possibility of straightening only very thin sheet fillers into a very thin layer, resulting in a 2D arrangement.

SUMMARY OF THE INVENTION

The drawbacks of the above-mentioned techniques for the production of wood-based plastics materials are eliminated by the method for producing composite boards of extruded PMMA and wood pieces according to the invention, which consists in gradually spreading layers of extruded PMMA pulp between substrates. 10% by weight, based on the weight of the wood in an absolutely dry state with a total number of n + 1 layers and n interlayers, where n is an integer positive number, then the resulting composite material is placed in a press heated to 120 to 180 ° C heat to the desired thickness and cooled freely in the air, for example in an air conditioning rack.

It is essential to keep the moisture content of the wood pieces before pressing at maximum 10% by weight, ideally up to 5% by weight, because at higher humidity a large number of bubbles are formed around the wood material and shape changes of the resulting composite board. In order to eliminate the problem of plate shape changes / deformations due to rapid temperature reduction, it is advisable to ensure uniform cooling of the plates from both sides, preferably in air conditioning racks.

In a preferred embodiment, the compression temperature is 150 to 160 ° C, most preferably 160 ° C. The higher the pressing temperature, the easier it is to melt the extruded PMMA pulp and hence the pressing, therefore it is best to use the maximum possible pressing temperature of 160 ° C, at higher temperatures than 180 ° C the wood degrades.

- 1 GB 307977 B6

In a preferred embodiment, waste crushed extruded PMMA generated as waste in the production of extruded PMMA is used. The use of waste materials saves costs. The solution according to the invention does not use a PMMA layer in the form of an embedded continuous plate, but uses waste material from the production and processing of extruded PMMA in the form of pulp from waste pieces of extruded PMMA production / processing plates. PMMA, ie 3D structures. Instead of shredded extruded Plexiglas (PMMA XT), it is not possible to use other types of Plexiglas such as Plexiglas (PMMA GS), which do not sufficiently melt the Plexiglass pulp at the temperatures used. The wood pieces can be laid in different directions on the layer of extruded PMMA, not only in the plane of one layer, but also set / stuck perpendicular to the plane. It is therefore not necessary to lay the wood pieces only in a plane parallel to the base press plates. The crushed layers of extruded PMMA are continuous and form a compact unit after compression. The interlayers with wooden pieces are discontinuous.

In a preferred embodiment, hot pressing, most preferably at 160 ° C, is carried out by heating the composite material in a press without pressure for 5 to 20 minutes under a pressure of 0.2 to 0.8 MPa, 5 to 25 minutes at a pressure of 0.2 to 0.8 MPa. pressure 1.8 to 2.6 MPa. During the last press phase, the composite material can be removed from the press for inspection and returned to the press for compression. The laminated composite material is first fed into a press heated to 160 ° C. The composite material is not pressurized at the initial stage as it would cause the wood pieces to break into smaller fragments.

In a preferred embodiment, to facilitate layering of the composite material, an auxiliary bounding frame is removed prior to layering around the future layers, which is removed prior to pressing, and press stops are positioned around the perimeter of the resulting composite material to set the pressing thickness. Depending on the desired size of the resulting composite board, the sub-frame is always with a certain excessively delimited place for laying individual layers of PMMA extruded pulp and interlayer of wood pieces.

In a preferred embodiment, release paper is sandwiched between the outer layers of the extruded PMMA crumb and the backing sheet. Separation paper ensures a simple separation of the pressed composite plate from the base press plates.

In a preferred embodiment, the press plates are sheet metal or tempered glass.

In a preferred embodiment, the thicknesses of the extruded PMMA layers are made such that the resulting distribution of the thicknesses of the individual layers from the center to the base press plates is symmetrical, which is suitable to minimize the deflection of the resulting composite plates.

In a preferred embodiment, the wood pieces with the backing plate are substantially parallel elongated wood strips or leaf chips that are directed in each additional interlayer added in a direction approximately perpendicular to the direction used in the last interlayer added last. Such folding will ensure an even distribution of weight, even for an odd number of interlayers made of wood pieces, even symmetry from the center to the surface layers as well as the orientation of the wood particles and interlayers in the longitudinal and transverse directions. Any kind of wood can be used to make composite boards. The wood pieces are, for example, in the form of sheet chips or preferably pieces produced as waste are used in the production of veneers in the form of strips. The maximum dimensions of the wooden pieces depend on the spatial arrangement and dimensions of the board. The dimensions of the wood pieces are suitably selected and these pieces are laid so that they do not protrude from the resulting composite board, i.e., selected with respect to the laying direction of the wood piece, the local location of the wood piece and the dimensions of the resulting composite board.

Preferably, the wood pieces are placed at least 0.5 mm from the walls of the resulting composite board.

-2GB 307977 B6

The backing press plates have a smooth or shaped surface that forms the surface structure of the composite board during the press.

Another object of the present invention are composite sheets of alternately layered extruded PMMA and wood pieces produced by the above process.

The composite sheets produced in this way are characterized in that they are waterproof and contain real wood which can be used in damp areas. The surface of the PMMA plate can be shaped by a structure that can be applied to the upper and possibly lower backing plate during molding.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be further elucidated by means of exemplary embodiments. In one exemplary embodiment, first, a release paper was placed on the lower backing sheet and a sub-frame of desired size was placed around it. The first continuous layer of PMMA waste extruded PMMA of 2 mm thickness was poured onto the release paper and the first interlayer with mutually parallel wood chips from spruce wood with a maximum moisture content of 5% by weight was applied to the separating paper. and at approximately the same spacing, the chip dimensions being approximately 1 mm x 15 mm x 200 mm. Next, a second continuous layer of 1.8 mm thick PMMA waste extruded grit was added by sprinkling and a second interlayer with wood chips this time oriented from front to back, ie perpendicular to the previous direction, was placed on it. This was followed by a third loose continuous layer of 1.8 mm thick PMMA waste extruded material and a third interlayer with wood chips this time from left to right as in the first interlayer. The wood chips were laid in all interlayers parallel to the base press plate. The third interlayer of wood chips was covered with a fourth continuous continuous layer of PMMA waste extruded 2 mm thick. The auxiliary bounding frame was removed and then pressing stops of 7 mm compression thickness along the perimeter of the laminated composite material. Separation paper was placed on the fourth layer of PMMA waste extruded crumb and on top of the press plate. The layered composite material was placed in a press heated to 160 ° C and left in the first phase for 15 minutes at rest, only being heated without applying press pressure. In the second phase, compression was carried out at a pressure of 0.5 MPa at 160 ° C for 10 minutes. In the third stage, compression was continued at a pressure of 2.2 MPa at 160 ° C for 10 minutes. The compressed composite plate was removed from the quality control press, the release paper was replaced with a new one, and then the composite plate was returned to the press where the third phase was continued by pressing at 2.2 MPa for 5 minutes at 160 ° C. Subsequently, the composite plate was removed from the press and placed in an air conditioning rack, where it was left in the air for 2 h. Both base press plates had a smooth surface. Η + 1 = 4 layers of PMMA waste extruded grit and n = 3 wood-chip interlayers were used. The resulting board had dimensions of 350 mm x 350 mm x 7 mm.

In another exemplary embodiment, n + = 2 PMMA extruded shredded crumb layers and η = 1 interlayer with wood strips resulting from beech wood veneer waste having an inlet moisture content of no more than 3% by weight based on totally dry weight of wood. The PMMA waste extruded crumb layers were laid between the tempered glass press plates due to the need for high surface smoothness and transparency of the resulting composite plate. The wooden strips were folded in the interlayer in random directions. Pressing was carried out at a temperature of 180 ° C. First, only the laminated composite material was heated without pressing for 20 min, then pressed at 0.2 MPa for 15 min and then pressed at 1.8 MP for 25 min.

In another exemplary embodiment, the molding was performed at 150 ° C. First, only the laminated composite material was heated without pressure for 10 min, then pressurized at 0.8 MPa for 5 min and then pressurized at 2.6 MPa for 5 min. A check was carried out and then further pressed at a pressure of 2.6 MPa for 2 min.

In another exemplary embodiment, n + 1 = 6 PMMA extruded debris layers and n = 5 interlayers of wood pieces were used, using different wood species, namely beech, oak and walnut veneer strips having a maximum moisture content of 10% by weight. The wood strips were not only oriented in planes parallel to the base press plates, but were also oriented perpendicular to the base press plates. The PMMA extruded crumb layers were laid between the tempered glass press plates to provide a high surface smoothness and transparency of the plate. The compression was carried out at a temperature of 120 ° C and a maximum pressure of 2.6 MPa.

The maximum dimensions of the wooden pieces depend on the spatial arrangement and dimensions of the board, for example, the largest wooden pieces of dimensions were used: thickness 5 mm, width 50 mm and length 2000 mm.

Industrial applicability

The technical solution according to the invention can be used in the furniture industry for production of various panels of furniture, doors, partition walls of rooms, it is also suitable for damp rooms.

PATENT CLAIMS

Claims (10)

Process for producing extruded PMMA composite boards and wood pieces, characterized in that successively PMMA extruded crumb layers are interposed between the base press plates which are alternately interleaved by interleaved wood pieces with a maximum moisture content of 10% by weight based on the wood weight in an absolutely dry state, with a total of n + 1 layers of extruded PMMA pulp and n interlayers formed of wood pieces, where n is an integer positive number, then the resulting composite material is placed in a press heated to 120 to 180 ° C, heat to the desired thickness and cooled freely in the air. Method for producing extruded PMMA composite boards and wood pieces according to claim 1, characterized in that the pressing temperature is 150 to 160 ° C, most preferably 160 ° C. Method for producing composite boards of extruded PMMA and wood pieces according to any one of the preceding claims, characterized in that the crushed from extruded PMMA is waste crushed extruded PMMA. Method for producing extruded PMMA composite boards and wood pieces according to any one of the preceding claims, characterized in that the hot pressing, preferably at 160 ° C, is carried out by heating the composite material in a press without pressure for 10 to 20 minutes, 5 to 15 min under a pressure of 0.2 to 0.8 MPa, 5 to 25 min under a pressure of 1.8 to 2.6 MPa. A method for producing extruded PMMA composite panels and wood pieces according to any one of the preceding claims, characterized in that an auxiliary bounding frame is removed to facilitate lamination of the composite material, which is removed prior to compression, and stored around the periphery of the resulting composite material prior to compression. pressing stops to adjust the pressing thickness. -4GB 307977 B6 Method for producing extruded PMMA composite boards and wood pieces according to any one of the preceding claims, characterized in that the base press plates are sheet metal or tempered glass. Method for producing extruded PMMA composite boards and wood pieces according to any one of the preceding claims, characterized in that the layer thicknesses of extruded PMMA are produced such that the resulting distribution of the thicknesses of the individual layers from the center to the base press plates is symmetrical. Method for producing extruded PMMA composite boards and wood pieces according to any one of the preceding claims, characterized in that the wood pieces are substantially parallel elongated wood strips or sheets that are directed in the direction of each additional interlayer to be added in the direction of the base press plate. approximately perpendicular to the direction used in the last intermediate layer added. Method for producing extruded PMMA composite boards and wood pieces according to any one of the preceding claims, characterized in that the cooling in the open air takes place in an air conditioning rack. 10. A composite board of alternately laminated extruded PMMA and wood pieces, characterized in that it consists of n + 1 layers of extruded PMMA pulp and n interlayers made of wood pieces, where n is a positive number, and that it is produced by a method according to any of the preceding claims.