PROCESS FOR PREPARING A WOOD CHIP BOARD

Abstract

The present invention relates to a process for preparing a wood chip board comprising drying a cut raw material, classifying the dried material into several portions, gluing at least one of said portions with a resin and compressing the chip material under pressure and heat to form a board. The present invention also relates to a wood chip board and its use.

Claims

1. A process for preparing a wood chip board comprising drying a cut raw material, classifying the dried material into several portions, gluing at least one of said portions with a resin and compressing the chip material under pressure and heat to form a board, characterized in that the method comprises the following steps: i) providing a first outer layer comprising a mixture of glue and classified, dried wood material; ii) providing a core layer comprising a mixture of glue, classified, dried wood material and a particle foam polymer beads; iii) providing a second outer layer comprising a mixture of glue and classified, dried wood material; iv) forming a composite plate, comprising said first outer layer, said core layer and said second outer layer; v) compressing said composite plate under pressure and heat to form said wood chip board.

2. A process according to claim 1, wherein step v) comprises two individual steps, namely a first compressing step va) wherein said composite plate is compressed at ambient temperature and a pressure in the range of 0.5-0.7 N/mm.sup.2, followed by a second compressing step vb) wherein said composite plate is compressed in a temperature range of 200-250 C. and a pressure in the range of 1-5 N/mm.sup.2.

3. A process according to any one of the preceding claims, wherein the amount of particle foam polymer beads in said mixture for the core layer is in a range of 1-50% by weight, preferably 3-50% by weight, more preferably 5-35% by weight, on basis of the total weight of said mixture for the core layer.

4. A process according to any one of the preceding claims, wherein the wood chip board obtained after step v) is provided with a decorative sheet.

5. A process according to any one of the preceding claims, wherein said polymer beads are particle foam polymer beads chosen form the group of polystyrene (PS), polystyrene-(poly(p-fenylene oxide) (PS/PPO), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polylactic acid (PLA), mixtures of polylactic acid and starch (PLA/starch), poly(butylene adipate-co-terephthalate)-polylactic acid (PLA/PBAT), polylactic acid-polyhydroxyalkanoate (PLA/PHA), starch, polybutylene succinate (PBS) granulates of cellulose acetate butyrate (CAB), and resol, or combinations thereof.

6. A process according to claim 5, wherein in the poly(butylene adipate-co-terephthalate)-polylactic acid (PLA/PBAT) the amount of PBAT is in a range of 5-95 wt. %, preferably 15-85 wt. %, on basis of the total amount of poly(butylene adipate-co-terephthalate)-polylactic acid (PLA/PBAT).

7. A process according to claim any one of claims 5-6, wherein polylactic acid (PLA) is a copolymer of PLA and another biobased monomer, such as polyethylene glycol (PEG), poly(lactic-co-glycolic acid) (PLGA) and poly(-caprolactone) (PCL).

8. A process according to claim 7, wherein said copolymer is chosen from the group of poly(d,l-lactide) with poly(ethylene glycol) with hydroxyl end, poly(d,l-lactide) with poly(ethylene glycol) with carboxylic acid end, poly(d,l-lactide) with poly(ethylene glycol) with maleimide end, poly(d,l-lactide) with poly(ethylene glycol) with amine end, poly(lactide/glycolide) with poly(ethylene glycol) with COOH end, poly(lactide/glycolide) with poly(ethylene glycol) with maleimide end and poly(lactide/glycolide) with poly(ethylene glycol) with amine end.

9. A process according to any one of the preceding claims, wherein polymer beads having a density in a range of 5-250 kg/m.sup.3, preferably 10-100 kg/m.sup.3, more preferably 20-40 kg/m.sup.3 are used.

10. A process according to any one of the preceding claims, wherein in step ii) polymer beads of the type unexpanded polymer beads loaded with a blowing agent are used.

11. A process according to claim 10, wherein as a blowing agent CO.sub.2 is used.

12. A process according to any one of the claims 1-11, wherein polymer beads having a particle size chosen in a range of the group 2.0-1.6 mm, 1.0-1.6 mm, 0.7-1.0 mm or 0.7-0.4 mm, or a combination thereof are used.

13. A process according to any one of the claims 5-12, wherein the amount of particle foam polymer beads based on polylactic acid (PLA) in said mixture for the core layer is in a range of 1-8 wt. %, preferably in a range of 2-6 wt. %, more preferably in a range of 3-5 wt. %, on basis of the total weight of said mixture for the core layer.

14. A wood chip board provided with a core layer based on particle foam polymer beads, sandwiched between a first outer layer and a second outer layer, wherein both said first and second outer layer are based on wood material, wherein the amount of particle foam polymer beads based on polylactic acid (PLA) in said core layer is in a range of 1-8 wt. %, preferably in a range of 2-6 wt. %, more preferably in a range of 3-5 wt. %, on basis of the total weight of the core layer.

15. A wood chip board according to claim 14, wherein the density of the core layer is 660-500 kg/m.sup.3, preferably 600-550 kg/m.sup.3, more preferably 570-580 kg/m.sup.3.

16. A wood chip board according to any one or more of claims 14-15, wherein no wood material based first outer layer and second outer layer are present.

17. The use of a wood chip board according to any one or more of the claims 14-16 in construction panels, furniture, kitchen cupboards, tables and/or composites.

Description

EXAMPLE 1

[0044] A standard particle board having a bottom layer, core layer and surface layer was prepared according to the method disclosed above resulting in a density of 670 kg/m.sup.3.

EXAMPLE 2

[0045] The Example 1 was repeated except for the core layer. Polylactic micro beads (PLA) made by Synbra of 1.0-1.6 mm diameter were impregnated with CO.sub.2 of 20 bar and expanded in a pre-expander to become E-PLA with a density of 30 kg/m.sup.3. These expanded PLA beads were mixed with a mechanical mixer to become a homogenous part of the core layer. The composition of both the surface layer and the bottom layer were according to Example 1.

[0046] The wood chip board so obtained had a density of 610 kg/m.sup.3.

EXAMPLE 3

[0047] A one off lab experiment with a PBAT/PLA expandable bead with a diameter of 1.5 mm with 6% pentane present as a blowing agent was added with a weight of 3% mixed in the central wood mixture and was found to not show a discernible difference from the properties of a reference sample. As it contains pentane it was deemed to be less suitable anyhow, as it may present safety issues in handling in the plant.

ADDITIONAL EXAMPLES

[0048] Additional examples of the present wood chip board have been manufactured according to the method disclosed above. The composition of the panels (indicated by plate numbers) have been summarized in the Table (see the enclosed FIG. 4). The Table especially refers to the composition of the core layer, namely the amount of wood (g), the amount of Bio-Foam (polylactic acid beads), density (g/l), wt. % BioFoam in core layer, CO.sub.2 impregnation conditions (time), and CO.sub.2 aging (time).

[0049] The results of these experiments have been shown in the FIGS. 1A-1G (internal bonding, IB), 2A-2G (screw face) and, 3A-3G (surface strength, SS).

[0050] The test for internal bonding (IB) is a tensile strength test for measuring the inner layer. A block to be tested is glued at both sides to a sample piece and positioned in a tensile testing machine.

[0051] The screw face test refers to test wherein a screw is screwed in a wood chip board. A force is applied on the screw and the force for withdrawing the screw from the board is measured.

[0052] The test for measuring the surface strength (SS) refers to the force needed for detaching the outer layer from the core layer. In that context a small round button is glued on the surface of the layer. The whole assembly is positioned in a tensile testing machine and the force for withdrawing the button from the surface is measured.

[0053] The FIGS. 1A, 2A and 3A disclose the effect of the use of microbeads compared to a blanc, i.e. a core layer without any particle foam polymer beads. The FIGS. 1B, 2B and 3B relate to BioFoam having a density of 140 g/l. The FIGS. 10, 2C and 3C relate to BioFoam having a density of 140 g/l and impregnation with CO.sub.2. The FIGS. 1D, 2D and 3D relate to BioFoam having a density of 75 g/l. The FIGS. 1E, 2E and 3E relate to BioFoam having a density of 75 g/l and impregnation with CO.sub.2. The FIGS. 1F, 2F and 3F relate to BioFoam having a density of 35 g/l. The FIGS. 1G, 2G and 3G relate to BioFoam having a density of 35 g/l and impregnation with CO.sub.2.

[0054] From the experimental results one can learn that for the internal bonding (IB) the amount of BioFoam is within a range of 1-8 wt. %, preferably in a range of 2-6 wt. %, more preferably in a range of 3-5 wt. %. The experimental results with regard to screw face and surface strength show a similar result.

[0055] The BioBeads used here are either 1.0-1.6 of 0.7-1.0 mm type Synterra type BF2004 (BioFoam) with a D content of 4% and a Molecular weight Mw van 200 kDa, relative to polystyrene.

[0056] The expanded BioFoam (E-PLA) was made from Biobeads Synterra type BF2005 0.7-1.0 mm with a D content of 5% with a molecular weight of 200 kDa (relative to polystyrene) and expanded to the indicated densities by using CO.sub.2 impregnation and expansion in a pre-expander.

[0057] There is no pointer in the prior art about the preferred range for the amount of particle foam polymer beads in a wood chip board comprising a core layer comprising particle foam polymer beads.

[0058] The present inventors wanted to manufacture a recycled wood particle board with a density of about 550 kg/m.sup.3 with the strength and properties of a recycled wood particle board of about 680 kg/m.sup.3. To achieve this density a reduction of the amount of wood in the core layer has been applied according to the present invention. The outside fine wood layers are kept the same. To achieve a somewhat similar strength as the heavy board a foam will be added according to the present invention. First trails were done on a lab scale. The test panel had a dimension of 30030018 mm. Internal bonding (IB) and screw face test (SF) are important factors to test the core layer of the final plate. A first set of tests was done with adding foamed beads to the core layer in different densities, 30-140 g/L. Secondly adding impregnated foamed beads in the same density range and impregnated Biobeads. Concentration ranges from 3% to 10% wt %. The addition of the 3% Biobeads showed the most interesting result on performance as well on cost. An additional set of tests was carried out to narrow the concentration of impregnated Biobeads and see the 1-3% range. Also included in the test was a difference between bead size. Sizes in the range of 0.7-1.0 mm and 1.0-1.6 mm Biobead fraction were tested. The 1.0-1.6 mm range showed a slight advantage. A third test was to see if the impregnation could be done at the premises of Synbra Technology (NL) and the impregnated Biobeads could be shipped on dry ice and foamed in the lab trails. Same results were measured with the transported beads as with the impregnated beads on site of Synbra Technology.