Wooden material panel, in particular in the form of a wood-plastic composite material, and a method for producing the same

Abstract

The present invention relates to a wooden material panel, in particular a wood-plastic composite material, including particles of wood and at least one plastic that is functionalized with at least one organic compound. At least one decorative layer is provided on at least one side of the wooden material panel.

Claims

1. A process for the production of a wooden board, in the form of a wood-plastic composite, comprising the steps of: providing wood fibers with a wood fiber moisture content of from 6 to 15% and polymer fibers; forming a mixture of the wood fibers and the polymer fibers in a blow line with a mixing ratio of from 70% by weight of wood fibers/30% by weight of polymer fibers to 40% by weight of wood fibers/60% by weight of polymer fibers; intermediately buffering or intermediately storing the mixture in a feeder; blowing the mixture onto a first roll to form a first preliminary mat (airlay); defibrating the first preliminary mat and once again blowing the mixture onto a second roll to form a second preliminary mat (airlay); transferring the second preliminary mat onto a transport belt and introducing the second preliminary mat into at least one heat-conditioning oven for preliminary consolidation by thermal bonding to give a pre-consolidated mat, wherein the temperatures in the heat treatment in the heat-conditioning oven are maintained by blowing in hot air and the core temperature of the second preliminary mat is within a range between 100 and 150 C.; transfer of the pre-consolidated mat into at least one twin-belt press for compaction to give a wooden board; and cooling of the compacted wooden board in at least one cooling press to temperatures of from 10 to 70 C.

2. The process according to claim 1, wherein the polymer is a thermoplastic.

3. The process according to claim 1, wherein the polymer used comprises bicomponent fibers.

4. The process according to claim 1, wherein the polymer used comprises thermoplastics selected from the group consisting of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), or polyester.

5. The process according to claim 1, wherein the second preliminary mat made of wood particles and plastic is pre-consolidated in the at least one heat-conditioning oven at temperatures of from 130 to 200 C.

6. The process according to claim 1, wherein a density of the pre-consolidated mat after discharge from the heat-conditioning oven is from 40 to 200 kg/m.sup.3.

7. The process according to claim 1, wherein after leaving the heat-conditioning oven the pre-consolidated mat is cooled and subjected to finishing processes.

8. The process according to claim 1, wherein in the at least one twin-belt press the pre-consolidated mat is compacted to a thickness of from 2 to 20 mm.

9. The process according to claim 1, wherein in the at least one twin-belt press the pre-consolidated mat is compacted at temperatures of from 150 to 250 C.

10. The process according to claim 1, wherein in the at least one twin-belt press the pre-consolidated mat is compacted at a pressure of from 2 MPa to 10 MPa.

11. The process according to claim 1, wherein in the at least one cooling press the compacted wooden board is cooled to temperatures of from 20 to 40 C.

12. The process according to claim 1, wherein in the at least one cooling press the compacted wooden board is cooled at a pressure which is the same as the pressure in the twin-belt press.

13. The process according to claim 1, wherein a thickness of the compacted wooden board after leaving the cooling press is from 2 to 15 mm.

14. The process according to claim 1, wherein a density of the compacted wooden board is from 500 to 1500 kg/m.sup.3.

15. The process according to claim 1, wherein the pre-consolidated mat is transferred into the at least one twin-belt press with simultaneous application of at least one decorative finish film to the top side of the pre-consolidated mat for further consolidation.

16. The process according to claim 15, wherein at least one separation ply is simultaneously applied above the decorative finish film during the transfer of the pre-consolidated mat into the at least one twin-belt press.

17. The process according to claim 1, comprising: providing the wooden board; applying a decorative layer to the top side of the board, and compressing under the action of pressure and temperature to form a laminate.

18. The process according to claim 2, wherein the polymer is in the form of thermoplastic granulates or synthetic fibers.

19. The process according to claim 4, wherein the polymer used comprises polyethylene terephthalate.

20. The process according to claim 1, wherein at least one decorative finish film comprising an amino resin-filled decorative paper and at least one varnish layer is laminated onto the wooden board using at least one adhesive.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention is elucidated in detail hereinafter with reference to the figures of the drawing with reference to several working examples. The figures show:

(2) FIG. 1 a schematic diagram of a first embodiment of the present process, and

(3) FIG. 2 a schematic diagram of a second embodiment of the present process.

DETAILED DESRCIPTION OF THE INVENTION

(4) The process flow diagram shown in FIG. 1 comprises a mixing apparatus 1, into which are introduced wood fibers H and polymer K, for example maleic anhydride-functionalized bicomponent fibers. The mixing apparatus 1 may take the form, for example, of a blow line in which the air blown in results in intensive mixing of the wood fibers and the functionalized bicomponent fibers.

(5) From the mixing apparatus 1, the fiber mixture arrives in a scattering apparatus 2 from which the fiber mixture is mechanically discharged and scattered onto a transport belt 3 to form a preliminary mat. The scattering apparatus 2 may take the form, for example, of a roll-type scattering head. Below the transport belt may be arranged a balance, for example in the form of a belt balance, which continuously determines the weight of the preliminary mat.

(6) The transport belt 3 introduces the preliminary mat into a heat treatment oven 4, for example in the form of a conveyor oven with an advance rate of up to 15 m/min. In the heat treatment oven, preliminary consolidation of the preliminary mat proceeds at temperatures of up to 200 C., with partial melting of the bicomponent fibers, bringing about bonding of the bicomponent fibers with the wood fibers. The thickness of the preliminary mat that leaves the heat treatment oven may be between 20 and 100 mm.

(7) After leaving the heat treatment oven 4, the pre-consolidated preliminary mat is introduced directly into a double belt press 5 with an advance rate of up to 12 m/min. In the double belt press 5, there is further consolidation of the mat or preliminary mat at a pressure of, for example, 3 MPa and a temperature of, for example, 220 to a thickness between 2 and 15 mm.

(8) After the partial melting of the bicomponent fibers, the state of consolidation of the board leaving the double belt press 8 has to be kept constant until the bicomponent fibers have cooled to such an extent that the temperature has reliably gone below the softening temperature thereof, in order to prevent the consolidated board from coming apart by virtue of the reset forces of the bicomponent fibers. For this purpose, the consolidated board leaving the double belt press 8 is introduced directly into a chill press 10 in which the consolidated board is chilled to temperatures between 15 and 40 C. The chill press can be cooled, for example, by means of water cooling. The heating and cooling segments can also be integrated jointly into the double belt press and connected to one another via a shared transport belt.

(9) After leaving the chill press 10, the consolidated (WPC) board has a thickness between 2 and 12 mm and an apparent density of, for example, 800 to 1100 kg/m.sup.3. The WPC board can subsequently be processed further as desired (for example application of decorative layers) and finished.

(10) The process flow diagram shown in FIG. 2 differs from the flow diagram of FIG. 1 in that, after leaving the heat treatment oven 4, the pre-consolidated preliminary mat is introduced directly into a double belt press 8 with an advance rate of up to 12 m/min, with simultaneous application of a decorative finish film to the top side of the preliminary mat by means of the unwinding apparatus 5 and of a backing paper to the bottom side of the preliminary mat by means of the unwinding apparatus 7. As required, after application of the decorative finish film with the unwinding apparatus 5, a release paper or a release film can also be applied with the unwinding apparatus 6. In the double belt press 8, the mat or preliminary mat is consolidated further to a thickness between 2 and 15 mm, for example to 4.5 mm at a pressure of, for example, 3 MPa and a temperature of, for example, 160.

WORKING EXAMPLE 1a

Production of a First WPC Base Board

(11) Bale openers were used to provide wood fibers (44 wt %) and a mixture of bicomponent fibers (55 wt %, polyethylene terephthalate/polyethylene terephthalate-co-isophthalate) and 1 wt % of LLDPE fibers grafted with maleic anhydride, which were fed to a blow line as mixing apparatus to form a wood fiber/polymer fiber mixture. The wood fiber/polymer fiber mixture is intermediately stored in a feeder.

(12) Subsequently, the wood fiber/polymer fiber mixture is blown onto a first roll to form a first preliminary mat (airlay), the first preliminary mat is defiberized and the defiberized mixture is blown once again onto a further second roll to form a second preliminary mat (airlay).

(13) The second preliminary mat (basis weight: 4200 g/m.sup.2) is laid onto a conveyor belt in a width of 2800 mm. The advance rate of the conveyor belt was about 6 m/min.

(14) The preliminary mat was pre-consolidated in a conveyor oven at temperatures of up to 160 C. to a thickness of 35 mm to give a mat by thermal bonding. The mat here reached a core temperature of about 130 C.

(15) The mat (size format: 26502150 mm, thickness: 35 mm, basis weight: 3100 g/m.sup.2) is consolidated in a double belt press at about 220 C. and 50 bar to about 4 mm. Subsequently, the mat consolidated to a board is chilled to about 50 C. in a chilled continuous press. The boards are trimmed (size format: 26002070 mm; thickness about 4 mm) and polished.

WORKING EXAMPLE 1b Production of a Second WPC Base Board

(16) In analogy to working example 1a, the mat (pre-consolidated mat) is produced by mixing the fibers and forming a preliminary mat with subsequent thermal bonding to form a mat, in which bonding points form between the heated polymer and wood fibers.

(17) The ratio of polymer fibers to wood fibers is 56%:44%. The polymer fibers are bicomponent fibers composed of PE/PP grafted with maleic anhydride. The maleic anhydride serves as a coupler to the OH groups of the cellulose of the wood fibers.

(18) The mat (size format: 26502150 mm, thickness: 35 mm, basis weight: 3100 g/m.sup.2) is consolidated here in a double belt press at about 220 C. and 50 bar to about 4 mm. Subsequently, the consolidated mat is chilled to about 50 C. in a chilled continuous press. The boards are trimmed (size format: 26002070 mm; thickness about 4 mm) and polished.

WORKING EXAMPLE 2

WPC with Decorative Film Applied by Lamination

(19) The WPC size formats of working example 1a, after cooling, were bonded to a decorative polypropylene film for floor applications on the top side and to a backing based on a glued paper on the reverse side. The bonding is effected with a PU hotmelt. The amounts of the adhesive applied are 100 g/m.sup.2 on the top side and 50 g/m.sup.2 on the bottom side.

(20) The abovementioned size formats were used to produce floorboards equipped with connecting profiles of the tongue and groove type on the side faces. The panels thus obtained are suitable for covering a floor and are laid in a floating manner.

WORKING EXAMPLE 3

WPC with Decorative Paper Ply (Finish Film) Applied by Lamination and Given an Abrasion-resistant Varnish Seal

(21) The WPC base board produced in working example 1b is coated in a lamination press with a decorative, resin-filled and surface-varnished paper. A backing (paper) is laminated onto the bottom side. For the lamination, a PVAc glue is used, which is applied in liquid form on either side in an amount of about 30 g/m.sup.2. The advance rate at the lamination line is about 20 m/min. The temperature in the thermal oil is about 200 C.

(22) The decorated side of the board (size format 130013004 mm) is varnished with several applications of varnish in a varnishing line. First of all, a corundum-filled UV basecoat is applied (amount applied about 80 g/m.sup.2). The latter is partly gelated with a UV source. Thereafter, an elastic intermediate varnish, an EBC varnish, is applied (amount applied about 50 g/m.sup.2). The latter is partly cured with an electron beam source. Subsequently, an EBC topcoat is applied, provided with nanoparticles to enhance micro-scratch resistance (amount applied about 20 g/m.sup.2). This varnish is first partly surface cured with an excimer source (this is done for the purpose of matting by formation of microcreases in the varnish surface) and then the entire varnish structure is subjected to final curing, in the sense of through-curing, with an EBC emitter.

(23) The plates of large size format, after a rest period of about two days, are used to produce panels on a flooring line, these having been equipped with connecting profiles on the side faces that are suitable for glue-free connection and interlocking of such panels to give a floor covering laid in a floating manner.

WORKING EXAMPLE 4

WPC with Paper Ply (Finish Film) Applied by Direct Lamination to the Pre-consolidated MAT

(24) In analogy to working example 1a, preliminary mats or fiber cake blanks consisting of 54 wt % of polymer fibers (27 wt % of PE fibers, 25 wt % of PET bicomponent fibers and 2 wt % of LLDPE fibers grafted with maleic anhydride), 44 wt % of wood and 2 wt % of paraffin, with a basis weight of 3150 g/m.sup.2, a thickness of 35 mm and a size format of 13001400 mm are placed onto a transport belt of a double belt press. The double belt press had a heating zone having a length of three meters and a cooling zone having a length of six meters.

(25) A decorative finish film which had been varnished on the top side with a corundum-containing, radiation-curing varnish was placed onto the fiber cake from above by means of an unwinding apparatus. The weight of the varnished paper was about 200 g/m.sup.2. A second unwinding apparatus was used to apply a release paper to the decorative film. A backing paper (gram weight: 80 g/m.sup.2) was supplied to the bottom side of the fiber cake by means of an unwinding apparatus.

(26) The fiber cake then entered the double belt press and was compressed to a thickness of 4.5 mm at an advance rate of 2 m/min, a pressure of 30 bar and a temperature of the upper and lower steel belt of 160 C. An accompanying thermocouple was used to determine the temperature in the middle of the fiber cake. It was 140 C. at the end.

(27) Beyond the press, the release paper was wound up. The decorative paper and the backing paper had been pressed in a homogeneous and fold-free manner onto the WPC (=wood plastic composite) board that had formed during the pressing operation. In the cross-cut test, it was possible to peel off the decorative paper on the reverse side only with all the fibers attached, which suggests a very good bond between the film and WPC board.

WORKING EXAMPLE 5

Laminate Formed from WPC

(28) A WPC board (5 mm, apparent density: 850 kg/m.sup.2, ratio of polymer to wood fibers 56% to 44%) produced, for example, according to working examples 1a, b, is coated in a short-cycle press with a structure which is typically used for a laminate floor. This was as follows: top side overlay with melamine resin impregnation (corundum-filled), decorative paper with melamine resin impregnation bottom side backing with melamine resin impregnation

(29) The impregnated papers were the standard products in terms of resin application, VC (=content of volatile constituents) and the reactivity. The coating was executed at about 150 C. (product temperature), 40 bar and compression time 9 seconds. Subsequently, the coated board was cooled and, after a defined storage time, divided on a flooring line to give boards with a glue-free connection profile. Boards were taken from the production and subjected to an edge swell test according to DIN EN 13329. In this test, after a test duration of 24 h, edge swelling of 2.5% was found. After redrying at room temperature, this declined to 0.5%.