METHOD AND DEVICE FOR PRODUCING PRODUCTS BY USING LIGNOCELLULOSE-CONTAINING PARTICLES

Abstract

The invention relates to a method and devices for producing products (65) by using cellulose-containing particles, with which the following steps are carried out: a) irradiating the particles with electrons in the energy range >1 MeV: b) mixing the irradiated particles with electron-beam-reactive powder of a synthetic polymer, in particular a thermoplastic, having powder particle sizes <2000 micrometres and/or with a liquid electron-beam-reactive synthetic or bio-based polymer; c) forming the mixture created in a way corresponding to the form of the product to be produced, in particular forming it into a nonwoven (56): d) heating the formed mixture to 100-180° C.; e) pressing the formed mixture without heating; and f) irradiating the pressed mixture with electrons in the energy range of 1 MeV to 10 Me V and also with appropriately chosen dosages and dosing rates.

Claims

1. Method for producing a formed part containing lignocellulose, the method having the following steps: a) irradiation of lignocellulose-containing particles in the energy range between 1 MeV and 10 MeV, preferably >3 MeV <8 MeV; b) mixing the irradiated lignocellulose-containing particles with an electron-beam-reactive polymer in powder form, in particular a thermoplastic, with powder particle sizes <2000 micrometres (μm), and/or with a liquid containing electron-beam-reactive polymer; c) forming of the mixture produced in a way corresponding to the form of the formed part to be produced, in particular forming it into a nonwoven; d) conveying the formed mixture to a preheating device; e) heating the formed mixture to 100-180° C.; f) pressing the formed mixture without significant heating; and g) irradiating the pressed mixture with electrons in the energy range from 1 MeV to 10 MeV.

2. Method according to claim 1, characterised in that in step a) irradiation takes place with a dosage between 50 and 150 kGy, in particular with a dosage input of 100 kGy plus/minus 20 kGy.

3. Method according to claim 1, characterised in that in step f) irradiation takes place according to the specified mixture recipe and selected product aim with a dosage from 50 to 250 kGy, in particular 100 kGy plus/minus 20 kGy.

4. Method according to claim 1, characterised in that in step e) a nonwoven is pressed to form a board.

5. Method according to claim 1, characterised in that in step b) the particle sizes are in the range from 1000 to 1500 micrometres (μm).

6. Method according to claim 1, characterised in that in step b) to produce a wood material, 5% to <30% proportions by mass of a polymer are added.

7. Method according to claim 1, characterised in that in step b) to produce a WPC 30% to 60% proportions by mass of a polymer are added.

8. Method according to claim 1, characterised in that in step a) the energy range is between 5 and 10 MeV.

9. Method according to claim 1, characterised in that in step b) the lignocellulose-containing particles are heated before or during the addition of the thermoplastic powder to a temperature from 60° C. to 160° C., preferably to 80° C. to 120° C.

10. Method according to claim 1, characterised in that before or in step b) the lignocellulose-containing particles are acted upon by an adhesive agent before the addition of the thermoplastic powder.

11. Method according to claim 10, characterised in that adhesives and/or paraffins, starches and/or albuminous substances are used as adhesive agents.

12. Device for producing a composite containing lignocellulose-containing particles having: a) an electron beam accelerator designed to irradiate the particles with electrons in the energy range >1 MeV; b) at least one mixer designed to mix the irradiated particles with electron-beam-reactive powder of a synthetic polymer, in particular a thermoplastic, with powder particle sizes <2000 micrometres (μm), and/or with a fluid containing electron-beam-reactive synthetic polymer; c) a device designed to form the mixture produced in a way corresponding to the form of the composite to be produced, in particular to the form of a nonwoven; d) a conveyor for conveying the formed mixture to a preheating device, wherein e) the preheating device is designed to heat the formed mixture to 100° C. to 180° C.; f) a press designed to press the formed mixture without heating; and g) a high-energy electron beam accelerator in the energy range from 1 MeV to 10 MeV, designed in an outwardly radiation-protected process chamber to irradiate the pressed and formed mixture carried past by means of a transport device.

13. Device according to claim 12, characterised in that the electron beam accelerator according to feature f) is designed for uniform irradiation of the pressed and formed mixture carried past with a dosage of 50 to 250 kGy, in particular with a dosage of 100 kGy plus/minus 20 kGy.

14. Device according to claim 12, characterised in that the electron beam accelerator according to feature a) is designed for uniform irradiation with a dosage of 50 to 150 kGy, in particular with a dosage of 100 kGy plus/minus 20 kGy.

15. Device according to claim 12, characterised in that the mixing device is a universal mixer, a turbomixer, a plough blade mixer, a free fall mixer or similar.

16. Method according to claim 2, characterised in that in step f) irradiation takes place according to the specified mixture recipe and selected product aim with a dosage from 50 to 250 kGy, in particular 100 kGy plus/minus 20 kGy.

17. Method according to claim 2, characterised in that in step e) a nonwoven is pressed to form a board.

18. Method according to claim 3, characterised in that in step e) a nonwoven is pressed to form a board.

19. Method according to claim 2, characterised in that in step b) the particle sizes are in the range from 1000 to 1500 micrometres (μm).

20. Method according to claim 3, characterised in that in step b) the particle sizes are in the range from 1000 to 1500 micrometres (μm).

Description

[0039] Exemplary embodiments of the invention are described below in greater detail with reference to the figures.

[0040] FIGS. 1 to 3 explain a method and a device for producing chipboard.

[0041] FIGS. 4 and 5 explain a method and a device for producing MDF/HDF sheets.

[0042] Two exemplary embodiments of the invention are described in greater detail below, namely the production of wood composites in the form of chipboard and in the form of MDF/HDF sheets.

[0043] FIGS. 1 to 3 each show a section of the method or of the device in a temporal-spatial sequence.

[0044] A chopper (10) chops raw wood. A chipper (12) then processes the chopped wood into chips. These are washed in a washer (16), then screened, and dried if required. A minimal moisture level can be retained in this case to promote the effect of the subsequent electron irradiation. When crushing recycled or used wood, an additional device (magnet) is used to remove metal foreign bodies.

[0045] Small quantities of additives, e.g. for hydrophobisation or flame retardancy, can be added if necessary.

[0046] The irradiated chips are then supplied to a dryer (18). The dryer as such has a conventional design.

[0047] Thus prepared, the chips are then irradiated in an electron beam accelerator (20) using acceleration energies in the range between 5 and 10 MeV; with suitably selected parameters in each case with regard to the initial raw material and the operational throughput (bulk quantity and bulk density). The dosage is optimised in the range from 50 to 150 kGy according to the treatment parameters determined as necessary for the subsequent preparation of the desired wood composite mixture.

[0048] Dryers and electron beam accelerators can be interchanged. Irradiation can thus take place before and/or after drying. This depends on the moisture content of the chips. Irradiation is more effective if the chips contain roughly 10-20% moisture.

[0049] The output (20a) of the electron beam accelerator (20) is connected to a screening repository (22) and the dried chips are split into 3 size-dependent fractions via screens (22a, 22b), which are shaken in the horizontal plane via a drive. A coarse fraction is discharged via an outlet (24a), a medium fraction via an outlet (24b) and a small fraction via an outlet (24c).

[0050] A conveyor (26) carries the coarse and medium fractions to a chip dosing unit (32), while the fine fraction passes via a conveyor (28) to a chip dosing unit (30). From these dosing units the respective chips enter a hot screw conveyor (34 and 36). From these screw conveyors (34 and 36) the respective fractions (fine, medium and coarse) enter the correspondingly assigned mixer (42) for fine chips and mixer (44) for medium and coarse chips.

[0051] From a dosing unit (40) thermoplastic powder particles with particle sizes in the range between 1000 and 1500 μm enter the mixers (42, 44), where chips and thermoplastic powder are mixed.

[0052] Binding agents such as paraffin or starch can be added in the dosing unit or in the mixer.

[0053] The fine chip/thermoplastic powder mixture is transferred from the mixer (42) to a deagglomerator (loosener) (46), the medium/coarse chip mixture is transferred from the mixer (44) to a deagglomerator (48).

[0054] To produce a nonwoven, the mixture is conveyed from the deagglomerator (46) (fine fraction) both to a bottom-layer spreader (50) via its inlet (50a) and to a top-layer spreader (54) via its inlet (54a). The outlet of the other deagglomerator (48) is connected to the inlet (52a) of a middle-layer spreader (52).

[0055] The bottom-layer spreader, middle-layer spreader and top-layer spreader are controlled timewise and spatially such that a nonwoven is formed among them with a bottom layer (fine chip), a middle layer (medium and coarse chip) above this and a top layer (fine chip).

[0056] The nonwoven (56) passes via a conveyor (58) to a preheating facility (60). The heating temperatures depend on the given system. For example, the heating can take place via HF (high frequency), IR (infrared) or MW (microwave).

[0057] The nonwoven is then supplied to a press (62), which is a cooling press in the exemplary embodiment depicted and thus (in contrast to the prior art) does not require any energy- and time-consuming heating. In the press (62), the nonwoven is formed into sheets (65) and then cut to size. (Further forming can optionally take place into three-dimensional constructional products.) The sheets formed by pressing (products) (65) are then transferred via special transport passages necessitated by X-ray protection to the process chamber of an electron beam accelerator (64) and irradiated there using high-energy electrons in the energy range from 1 to 10 MeV and with a suitably selected dosage or dosing rate in air to carry out crosslinking within the reactive synthetic or partly synthetic polymer mixture (in particular thermoplastic powder and/or liquid polymers) as well as to bring about adhesion or also chemical combination of same with the crushed and pretreated wood raw material and its constituents (cellulose, lignin) etc.

[0058] The result of this production technology is a chipboard (or specially formed product) with very good properties, in particular in respect of temperature change resistance, hydrophobia, dimensional stability, bending resistance, transverse tensile strength, health protection and recyclability.

[0059] The method is advantageous in particular in respect of energy saving (low heating requirement), productivity (low time outlay) and environmental compatibility etc.

[0060] A method and a device for the production of MDF/HDF sheets and WPC wood composites will now be described in greater detail with reference to FIGS. 4 and 5.

[0061] In the figures, the same reference characters relate to components corresponding to one another.

[0062] Chopper (10), chipper (12), screening plant (14), washer (16) and electron emitter (18) correspond substantially to the exemplary embodiment according to FIG. 1, the process parameters (chipper 12) now being set so that wood fibres or fibres of ligneous material for MDF/HDF sheets or WPC wood composites are produced.

[0063] The electron-irradiated fibres are supplied via a conveyor (38) to a so-called defibrator (fibre loosener) (66) (known as such in the prior art), from where the fibres enter a dryer (20).

[0064] According to FIG. 5, the dried fibres are transferred from the dryer 20 to a fibre spreader (72), where they are loosened further and supplied in a metered manner to a screw conveyor (74), which is preferably heated. From there the fibres pass into a mixer (76).

[0065] Connected to the mixer (76) are on the one hand a dosing unit (68) with an electron-beam-reactive synthetic or bio-based polymer liquid and on the other hand a dosing unit (70) with a thermoplastic powder mixture as a common binding agent mixture for the wood chips.

[0066] Depending on the desired properties of the MDF/HDF sheet to be produced, the control system permits a supply of liquid and/or powder to the mixer (76).

[0067] If only powder is supplied to produce an MDF sheet, for example, this can take place with 10 to 20% related to the total mass.

[0068] On the other hand, the powder proportion can be measured at 30 to 35% for a WPC composite. (WPC: Wood-Polymer Composites)

[0069] From the mixer (76) the mixture enters a deagglomerator (78), which can be cooled. From the deagglomerator (78) the mixture passes into a fibre spreader (80), which forms (in a known manner) the nonwoven, which is prepared for the pressing process in another nonwoven forming station (82).

[0070] A preheater (84), e.g. HF/MW, heats the nonwoven, which is then pressed in a press (86). Pressing is carried out preferably without heating (cool). The sheets are then cut to size, (optionally post-formed into special products) and irradiated in an electron beam accelerator (90) by electrons, approximately in the energy and dosage range indicated above, for the purpose of crosslinking the electron-beam-reactive polymer mixtures including linkage to the wood constituents or their surfaces.

[0071] The MDF/HDF sheets or WPC composites thus produced have similar advantages to the chipboard described above.

REFERENCE CHARACTER LIST

[0072] 10 Chopper

[0073] 12 Chipper

[0074] 14 Screening plant

[0075] 26 Washer

[0076] 18 Dryer

[0077] 20 Electron beam accelerator

[0078] 20a Exit (from 20)

[0079] 22 Screening plant

[0080] 22a Screen, coarse

[0081] 22b Screen, fine

[0082] 22c Drive

[0083] 24a Chip outlet (coarse)

[0084] 24b Chip outlet (medium)

[0085] 24c Chip outlet (fine)

[0086] 26 Conveyor (for 24a, 24b)

[0087] 28 Conveyor (for 24c)

[0088] 30 Chip dosing unit

[0089] 32 Chip dosing unit

[0090] 34 Screw conveyor (hot)

[0091] 36 Screw conveyor (hot)

[0092] 38 Conveyor

[0093] 40 Dosing unit

[0094] 42 Mixer

[0095] 44 Mixer

[0096] 46 Deagglomerator (especially cooled)

[0097] 50 Bottom-layer spreader

[0098] 50a Inlet to 50 from 46

[0099] 52 Middle-layer spreader

[0100] 52a Inlet to 52 from 48

[0101] 54 Top-layer spreader

[0102] 54a Inlet to 54 from 46

[0103] 56 Nonwoven

[0104] 59 Conveyor

[0105] 60 Preheater (HF/IR/MW)

[0106] 62 Press

[0107] 64 Electron emitter (electron beam accelerator)

[0108] 65 Boards

[0109] 66 Defibrator/pulper

[0110] 68 Dosing unit for liquid

[0111] 70 Dosing unit for powder

[0112] 72 Fibre spreader

[0113] 74 Heating screw conveyor

[0114] 76 Mixer

[0115] 78 Deagglomerator

[0116] 80 Fibre spreader

[0117] 82 Nonwoven formation

[0118] 84 Preheater (HF/MW)

[0119] 86 Cooling press

[0120] 88 Conveyor

[0121] 90 Electron beam accelerator