PRODUCTION OF A LIGNOCELLULOSE-CONTAINING, PLASTIC-COATED AND PRINTABLE MOLDING

Abstract

A process for producing a lignocellulose-containing, plastic-coated and printable molding (26), in particular in sheet form, comprising the steps of: a) producing a layer (A, B′) containing lignocellulose-containing particles according to the shape of the molding to be produced (26); b) applying a layer (C) of particles containing electron beam-reactive thermoplastic onto the layer produced according to the preceding feature; c) heating the layers (A, C) produced according to the preceding features such that thermoplastic particles melt into the layer containing lignocellulose-containing particles (Cs); d) pressing the layers heated according to feature (1c); and e) irradiating the layers pressed according to feature (1d) with electrons in the energy range from 1 MeV to 10 MeV. The process is for example elucidated with reference to an MDF sheet one-sidedly provided with a polymer layer.

Claims

1. A process for producing a lignocellulose-containing, plastic-coated and printable molding (26), in particular in sheet form, comprising the following steps: a) producing a layer (A, B′) containing lignocellulose-containing particles according to the shape of the molding (26) to be produced; b) applying a layer (C) of particles containing electron-beam-reactive thermoplastic to the layer produced according to the preceding feature; c) heating the layers (A, C) produced according to the preceding features such that thermoplastic-containing particles melt into the layer containing lignocellulose-containing particles (Cs); d) pressing the layers heated according to feature (1c); and e) irradiating the layers pressed according to feature (1d) with electrons in the energy range from 1 MeV to 10 MeV. (FIGS. 9, 10; MDF, on one side, thermoplastic, on the top).

2. The process as claimed in claim 1, wherein, prior to step 1a), a layer (C′) of particles containing electron-beam-reactive thermoplastic is produced, to which there is applied the layer containing lignocellulose-containing particles according to step 1a). (FIGS. 7, 8; MDF, thermoplastic on both sides).

3. The process as claimed in either claim 1 or claim 2, wherein the layer produced according to feature 1a) contains electron-beam-reactive thermoplastic polymer in powder form with powder particle sizes < 2000 micrometers (.Math.m) or a liquid containing electron-beam-reactive polymer.

4. The process as claimed in claim 2, wherein step 1b) is omitted. (MDF, on one side, thermoplastic on the bottom).

5. The process as claimed in any one of the preceding claims, wherein the mentioned layers are produced by spreading particles.

6. The process as claimed in either claim 1 or claim 3, wherein the order of process steps 1a) and 1b) is reversed. (MDF, thermoplastic on one side, on the bottom).

7. The process as claimed in any one of claims 1 to 5, wherein the layer (B′) produced according to feature 1a) contains fine lignocellulose-containing particles, and the following steps are carried out after step 1a) and before step 1b): aa) application of a layer (A′) containing coarse lignocellulose-containing particles; and ab) application of a layer (B′) containing fine lignocellulose-containing particles. (FIGS. 5, 6; chipboard, thermoplastic on one side, on the top).

8. The process as claimed in claim 7, wherein the layers applied according to feature 7aa) and/or according to feature 7ab) contain thermoplastic polymer in powder form with powder particle sizes < 2000 micrometers (.Math.m) or a liquid containing electron-beam-reactive polymer.

9. An apparatus for producing a lignocellulose-containing, plastic-coated and printable molding (26), in particular in sheet form, comprising the following: a) a particle spreader (32) for producing a layer (A, B′) containing lignocellulose-containing particles according to the shape of the molding (26) to be produced; b) a particle spreader (30) for applying a layer (C) of particles containing electron-beam-reactive thermoplastic to the layer produced according to the preceding feature; c) a heater (18) for heating the layers (A, C) produced according to the preceding features such that thermoplastic-containing particles melt into the layer containing lignocellulose-containing particles (Cs); d) a press (20) for pressing the layers heated according to feature (1c); and e) an electron emitter (22) for irradiating the layers pressed according to feature (1d) with electrons in the energy range from 1 MeV to 10 MeV. (FIGS. 9, 10; MDF, on one side, thermoplastic, on the top).

10. The apparatus as claimed in claim 9, wherein there is arranged upstream of the particle spreader according to feature 9a) a particle spreader (30) for producing a layer (C′) of particles containing electron-beam-reactive thermoplastic. (FIGS. 7, 8; MDF, thermoplastic, on both sides).

11. The apparatus as claimed in either claim 9 or claim 10, wherein the layer produced by the particle spreader according to feature 9a) contains electron-beam-reactive thermoplastic polymer in powder form with powder particle sizes < 2000 micrometers (.Math.m) or a liquid containing electron-beam-reactive powder.

12. The apparatus as claimed in claim 10, wherein the particle spreader according to feature 9b) is omitted.

13. The apparatus as claimed in either claim 9 or claim 11, wherein the order in which the particle spreaders according to features 9a) and 9b) are arranged is reversed.

14. The apparatus as claimed in any one of claims 9 to 13, wherein the layer (B′) produced by the powder spreader according to feature 9a) contains fine lignocellulose-containing particles, and there are arranged in the arrangement of the mentioned particle spreaders downstream of the particle spreader according to feature 9a) and upstream of the particle spreader according to feature 9b): aa) a particle spreader (14) for applying a layer (A′) containing coarse lignocellulose-containing particles; and ab) a particle spreader (12′) for applying a layer (B′) containing fine lignocellulose-containing particles. (FIGS. 5, 6; chipboard, thermoplastic on one side, on the top).

15. The apparatus as claimed in claim 14, wherein the layers applied according to feature 14aa) and/or according to feature 14ab) contain thermoplastic polymer in powder form with powder particle sizes < 2000 micrometers (.Math.m) or a liquid containing electron-beam-reactive polymer.

16. The process or apparatus as claimed in any one of the preceding claims, characterized by printing of the molding which has been produced by laser jet printing or inkjet printing.

Description

[0041] Exemplary embodiments of the invention will be described in greater detail hereinbelow with reference to the accompanying figures.

[0042] FIG. 1 shows the production of a chipboard without a polymer coating;

[0043] FIG. 2 shows a standard chipboard in section, as has been produced with an apparatus and a process according to FIG. 1;

[0044] FIG. 3 shows the production of a chipboard with a polymer layer on both sides;

[0045] FIG. 4 shows a chipboard with polymer layers on both sides produced using an apparatus according to FIG. 3;

[0046] FIG. 5 shows the production of a chipboard with a polymer layer on one side;

[0047] FIG. 6 shows a chipboard with a polymer layer on one side produced using an apparatus according to FIG. 5;

[0048] FIG. 7 shows the production of an MDF/HDF sheet with polymer layers on both sides;

[0049] FIG. 8 shows an MDF/HDF sheet with polymer layers on both sides produced using an apparatus according to FIG. 7;

[0050] FIG. 9 shows the production of an MDF/HDF sheet with a polymer layer on one side; and

[0051] FIG. 10 shows an MDF/HDF sheet with a polymer layer on one side produced using an apparatus according to FIG. 9.

[0052] FIG. 1 explains generally an apparatus and a process 10 for producing a conventional chipboard as the starting point of the present invention.

[0053] The process proceeds in FIG. 1 temporally and spatially from left to right.

[0054] “Lignocellulose-containing particles” are by way of example “wood particles” hereinbelow.

[0055] Firstly, in a manner known per se, a fine wood particle spreader spreads fine wood particles extensively on a conveyor belt 24 to produce a layer of fine wood particles. The term “wood dust” is also commonly used for such fine wood particles.

[0056] A coarse wood particle spreader 14 spreads a layer of coarse wood particles onto the layer of fine wood particles. The coarse wood particles can also be referred to as wood chips. Subsequently, a further fine wood particle spreader 16 spreads a layer of fine wood particles onto the layer of coarse wood particles. The fine particles and the coarse particles, as they are used here, have dimensions as are conventional in the production of three-layer chipboard. The fine particles thus have smaller dimensions than the coarse particles.

[0057] The conveyor belt 24 conveys the three layers so spread one on top of the other into a preheater 18 and, from there, the layers enter a press 20. Downstream of the press 20, the pressed moldings 26 are conveyed to an electron emitter 22, where they are irradiated with electrons in the energy range between 1 MeV and 10 MeV.

[0058] FIG. 2 shows a standard chipboard so produced, with a central coarse wood particle layer A, an upper fine wood particle layer B and a lower fine wood particle layer B′.

[0059] This is the basic structure on which the present invention is based.

[0060] In the figures, mutually corresponding components are provided with the same reference signs, wherein components used in different places are optionally provided with a prime or with a double prime.

[0061] FIG. 3 shows an apparatus and a process for producing a chipboard which is provided with a polymer layer on both sides. A polymer which is thermoplastically deformable and meltable by the action of heat is referred to hereinbelow as a thermoplastic.

[0062] A thermoplastic particle spreader 30 spreads a layer of fine thermoplastic particles on the conveyor belt 24. A fine wood particle spreader 12 then spreads a layer of fine wood particles on the layer of thermoplastic particles. Then a coarse wood particle spreader spreads a layer of coarse wood particles on the mentioned layer of fine wood particles. Then a further fine wood particle spreader 12′ spreads a layer of fine wood particles on the layer of coarse wood particles. A further thermoplastic particle spreader 30′ then spreads a layer of fine thermoplastic particles on the layer of fine wood particles which has been produced.

[0063] The layer thicknesses of the mentioned thermoplastic particle layers are preferably in the range from 100 to 500 micrometers (.Math.m). Preferably, in all the two-sided coatings described here, the thickness of the polymer layers produced with the thermoplastic particles on both sides of the molding is the same. This has the advantage that warping (deformation) of the molding is counteracted (the so-called “banana effect” is avoided).

[0064] Downstream of the thermoplastic particle spreader 30′ according to FIG. 3, the intermediate product with the mentioned five layers (plies) is conveyed into a preheater 18 where, according to the polymers or thermoplastics used, heating to temperatures in the range from 100 to 180° C., typically in the range from 160 to 170° C., takes place. The thermoplastic particles thereby melt, and molten thermoplastic partially penetrates into the adjacent layer of fine wood particles and thus produces an intimate bond between the polymer layer and the wood particle layer. The intermediate product so treated is then guided into a press 20, where the sheets are pressed with pressures of between 30 and 50 bar. The intermediate products are then guided into the electron emitter 22 and irradiated over their entire surface with electrons in the energy range between 1 MeV and 10 MeV. The sheets are then turned through 180° and the other side of the sheets is likewise irradiated with electrons in the energy range between 1 MeV and 10 MeV.

[0065] FIG. 4 shows the molding 26 so produced in section. A central coarse wood particle layer A has fine wood particle layers B on both sides. On the outside, there are polymer layers C, C′ on both sides. The outer polymer layers C, C′ are each bonded via molten bond layers Cs to the adjacent fine wood particle layer. On heating, molten thermoplastic particles flow between the fine wood particles.

[0066] FIG. 5 shows an apparatus for producing a chipboard with a polymer layer on one side. Following a first fine wood particle spreader 12, a coarse wood particle spreader 14 and a second fine wood particle spreader 12′, a thermoplastic particle spreader 30 applies an upper layer of thermoplastic particles, following which preheating and pressing are carried out by means of a preheater 18 and a press 20, and the moldings 26 are irradiated with electrons in an electron emitter 22, as described above with reference to FIG. 3.

[0067] The observations made above in connection with FIG. 3 and FIG. 4 with regard to layer thicknesses, polymers admixed with the wood parts, etc. apply to all the exemplary embodiments.

[0068] The molding 26 produced using the apparatus according to FIG. 5 is shown in section in FIG. 6. A central coarse wood particle layer A′ has fine wood particle layers B′ on both sides and a polymer layer C on one side, which polymer layer is fixedly bonded to the fine wood particle layer B′ beneath it via a molten bond layer Cs.

[0069] FIG. 7 shows an apparatus for producing an MDF/HDF sheet (medium-density fiberboard/high-density fiberboard) with a polymer layer both on the upper side and on the lower side.

[0070] A thermoplastic particle spreader 30 spreads a layer of thermoplastic particles on the conveyor belt. A wood fiber spreader 32 spreads a layer of wood fibers on the mentioned layer of thermoplastic particles. A mat former 34 shapes the two mentioned layers into a mat. A second thermoplastic particle spreader 30′ spreads a layer of thermoplastic particles on the mat. The intermediate product so produced then enters, in the manner already described, a preheater 18 and a press 20 as well as an electron emitter 22 in the manner described above with reference to FIG. 5, for example.

[0071] FIG. 8 shows the molding so produced and is self-explanatory because the reference numerals have already been explained above.

[0072] FIG. 9 shows an apparatus for producing an MDF sheet with a polymer layer on only one side. A wood fiber spreader 332 spreads a layer of wood fibers. A mat former 34 shapes the wood fiber layer so produced. A thermoplastic particle spreader 30 spreads a layer of thermoplastic particles thereon. From there, the intermediate product enters the preheater 18, the press 20 and the electron emitter 22, as described above.

[0073] FIG. 10 shows the MDF sheet so produced with a polymer layer applied to one side.

[0074] In all the exemplary embodiments described above, polymers which crosslink under electron bombardment can be added to the fine wood particle layers and the coarse wood particle layers.

[0075] The references to figures in the claims serve to facilitate correlation with the exemplary embodiments and are not part of the claims.

LIST OF REFERENCE SIGNS

[0076] 10 chipboard production [0077] 12 fine wood particle spreader [0078] 14 coarse wood particle spreader [0079] 16 fine wood particle spreader [0080] 18 preheater [0081] 20 press [0082] 22 electron emitter [0083] 24 conveyor belt [0084] 26 molding (chipboard) [0085] 30 thermoplastic particle spreader [0086] 12′ fine wood particle spreader [0087] 14′ coarse wood particle spreader [0088] 30′ thermoplastic particle spreader [0089] 12″ fine wood particle spreader [0090] 14″ coarse wood particle spreader [0091] 30″ thermoplastic particle spreader [0092] A coarse wood particle layer [0093] B fine wood particle layer [0094] B′ fine wood particle layer [0095] C polymer layer [0096] Cs molten bond layer [0097] C′ polymer layer [0098] 32 wood fiber spreader [0099] 34 mat former