EP3852988A1

EP3852988A1 - Method and device for producing products by using lignocellulose-containing particles

Info

Publication number: EP3852988A1
Application number: EP19766281.0A
Authority: EP
Inventors: Max Zaher; Wolfgang Schwarz; Volker Thole
Original assignee: Polymertrend LLC
Current assignee: Polymertrend LLC
Priority date: 2018-09-18
Filing date: 2019-09-17
Publication date: 2021-07-28
Also published as: US20220033656A1; WO2020058275A1; US20240309210A1; EP3626418A1

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 MeV and also with appropriately chosen dosages and dosing rates.

Description

METHOD AND DEVICE FOR PRODUCING PRODUCTS USED

LIGNOCELLULOSE-CONTAINING PARTICLE

The invention relates to methods and devices for the production of products using lignocellulose-containing particles. In particular, the invention relates to a method for producing a mixture of lignocellulose-containing particles with electron beam-reactive synthetic polymers in powder form and / or electron beam-reactive synthetic and / or bio-based partially synthetic polymeric liquids, a method for producing a lignocellulose-containing molded part, a device for pretreating and for mixing with electron-beam reactive Powder made of a polymer and / or a liquid containing electron beam reactive polymer suitable lignocellulose-containing particles and a device for producing a composite material using lignocellulose-containing particles.

Suitable lignocellulose-containing particles here are, in particular, substances from wood or from plants which do not contain wood, or also a mixture of such, for. B. in the form of chips, fibers, so-called strands or flakes. The particles mentioned here include in particular wood-containing and wood-like chips and fibers.

Wood chips or wood fibers or wood-like chips or fibers are to be understood here in particular as native cellulose-containing raw materials, such as wood of various tree types and provenance (fresh, old or recycled).

Further examples of wood-like chips or fibers in the sense of this description are bamboo, straw from corn or cereals, fiber plants such as flax or jute.

The use of ionizing radiation for the treatment, in particular for the digestion of native cellulose-containing raw materials for various further processing purposes is known as such. Examples are pest decontamination, facilitating so-called refining or pulping in papermaking, or accelerating saccharification and fermentation, e.g. B. in the production of bioethanol.

In particular, the invention relates to the production of chipboard and MDF / HDF boards.

For this purpose, it is known in the prior art to use a chopper for comminuting the wood-like starting materials, a chipper for producing chips, and a sieve for Determination of the chip or fiber sizes, a washing system, a so-called defibrator (in the case of MDF production), a dryer, a mixer for mixing the chips or fibers with a binder, in particular the formaldehyde component, a system for producing nonwovens, a pre-press, and one Open full press with heating. B. 220 ° C and means for post-treatment of the chipboard or MDF / HDF boards.

The use of formaldehyde is problematic with regard to health protection and fire risk.

US 2011 / 060133A1 describes irradiation of wood / plastic mixtures with electrons in the MeV range.

The state of the art is to be improved in particular with regard to the following properties and parameters:

Productivity in production, energy consumption, required temperatures, mixing and binding times, cooling times, swelling in thickness, abrasion and bending strength (E-Modui), transverse tensile strength, ease of further processing, UV protection, climate and moisture resistance, bioresistance of the products against spores, Fungi, insects, fire protection,

Health protection, etc.

The invention has for its object to provide methods and devices with which some of the above objectives in the processing of wood-like chips and fibers to wood composites are at least partially achieved.

First of all, the invention relates to a method and a device for producing an intermediate product in the production of wood composite materials, namely the production of wood or wood-like chips or fibers which can be mixed with an electron beam reactive powder made of a synthetic polymer and / or for mixing with a liquid electron beam reactive synthetic or bio-based polymer.

For this purpose, the invention teaches irradiation of the chips or fibers with the dose required by high-energy electrons, preferably under normal pressure in air.

One of the findings on which the invention is based is that with such radiation the chips or fibers are particularly well prepared in order to be able to be mixed with a thermoplastic in the production of a wood composite material such as chipboard or MDF / HDF boards. Irradiation with electrons in the dose range from 50 to 150 kGy in air has proven to be particularly suitable. Such an energy input leads to the splitting of fiber bundles, to bond breaks on and between molecular chains with the formation of new oxygen-containing groups, to the cleavage of low molecular fragments and to new molecular chains between the different wood components (cellulose, hemicelluloses, lignin). As a result, simultaneous exposure to ozone on the enlarged and increasingly hydrophilic fiber surfaces can facilitate the adhesion of admixed special polymers in powder or liquid form. Their selection is aimed at being particularly easy to fragment under subsequent electron irradiation and to form new, preferably three-dimensional bonds or stable networks (“crosslinking”).

The acceleration energy of the electrons (in MeV) is the decisive parameter for their penetration depth into the bulk material to be irradiated or into a solid. The penetration depth is inversely proportional to the density of the respective radiation material, but the electrons are subject to increasing deceleration in this way. The higher the acceleration energy, the more product quantity or solid thickness can be recorded and enforced. If, for example, a material density of 1 / cm ³ is used for wood-like materials, the effective penetration depth at 1 MeV acceleration energy is approximately 2.8 mm, and with double-sided irradiation approximately 7 mm. With 10 MeV one detects 32 mm, double-sided about 80 mm thickness due to mutually crossing residual electron currents.

The amount of electrons generated, the beam current (unit of measurement in milliampere mA), is the source of the radiation dose: it characterizes the amount of energy in kGy that the electrons release to the target material in the course of their penetration and deceleration, and increases with increasing depth from. Ultimately, it falls below a threshold for chemical ineffectiveness or the desired process relevance. In particular, the radiation dose has to be experimentally optimized for the product target: what is important is the sensitivity of the radiation-crosslinking polymers or their mixtures selected as binders to the wood, their crosslinking behavior with one another and the resulting product quality. The dose input per time, the dose rate, depends on the performance of the electron gun, the dose rate has an influence on the chemical reaction, but essentially it is economically noteworthy. Electron emitters as such are well known in the art and have long been present in numerous market economy applications. Depending on the area of application, a distinction is made between low-energy up to approx. 300 keV, then medium, and from approx. 3-5 MeV high-energy radiators. Accordingly, they serve (for thin layers) e.g. to

Surface sterilization or paint hardening, with deeper material treatment (with MeV) also for sterilization / decontamination (packages), for pollutant degradation in waste water, degradation dation of vegetable raw materials, for example for bioethanol production or for polymer crosslinking, such as composite materials (WPC), car tires or polyethylene tubes.

The construction principle consists of a hot cathode, from which electrons are emitted in a high vacuum and accelerated in a focused manner as a beam via a high-voltage potential cascade to the anode. The beam is mostly pulsed and can deliver several hundred milliwatts per pulse. Due to electromagnetic deflection at the highest possible frequencies, the beam is scanned in a beam funnel for the desired working widths and penetrates through an electron exit window, usually made of titanium foil, into the process chamber in order to develop its effect in a normal pressure atmosphere. High-energy emitters in particular require extensive protection against the simultaneously generated X-rays; i.e.: separate thick-walled buildings with multiple-angled import and export transport routes for the goods to be irradiated.

Protective measures also require the ozone gas that is generated in air from electron radiation, which is highly corrosive and harmful to health.

There are different versions for efficient industrial-technical applications, where the emitters have to deliver powerful beam currents (dose, dose rate) and large depths of penetration (MeV) into the targets. The types offered require power consumption of up to several hundred kilowatts; they deliver appropriate acceleration energies (MeV) and jet currents as required.

Linear accelerators (LINACs) with up to 10 MeV, rhodotrons (7 MeV / 700 kW or 10 MeV / 200 kW) or dynamitrons with 5 MeV / 300 kW are on the market.

The wood or wood-like chips and fibers prepared in this way with electron radiation are used for a process for producing a wood composite material.

The method contains at least the following steps: a) irradiation of wood or wood-like chips or fibers in air with electrons in the energy range> 1 MeV;

b) mixing the pretreated irradiated chips or fibers with an electron beam reactive synthetic polymer powder, in particular a thermoplastic, with powder particle sizes <2000 micrometers (pm) and / or with a liquid electron beam reactive synthetic or bio-based polymer;

c) shaping the mixture produced in accordance with the shape of the wood composite material to be produced, in particular shapes to form a fleece; d) heating the molded mixture to 100-180 ° C;

e) pressing the molded mixture without significant heating; and

f) irradiation of the compression-molded mixture with electrons in the energy range from 1 MeV to 10 MeV.

A large number of chemical compounds in liquid or solid form are known and can be replaced as "electron beam reactive" in the sense of the process for the mixture with the irradiated chips or fibers for the purpose of producing a composite product. A common feature is that they can be easily split by means of electron beams via mostly radical reaction mechanisms chemical bonds and the efforts of the fragments for preferred two- and three-dimensional reunification (polymerization, crosslinking to 3D networks). Typical polymer types for this are, for example, low-density polyethylenes of medium molecular weights (linear chains without double bonds, LDPE) as well as polyvinyl chloride ( PVC) or ethylene vinyl acetate copolymers (EVA) The acrylates or vinyls, usually in liquid form, are suitable connecting groups with highly reactive chemical double bonds.

These in turn can be combined with a variety of chemical partners such as epoxy acrylates or reactive organosilicon compounds. In addition, there are a variety of bio-based products or natural products, such as native or processed (bio-based) oils, which in particular have double bonds and also tend to polymerize and / or crosslink by initiation with electron beams.

If necessary, small additional quantities such as e.g. come to improve the quality of the end product. Adhesion improver on the base material (wooden surfaces), flame retardants, electrical conductivity, hydrophobic additives and / or UV stabilizers.

It has been shown that powder particle sizes of less than 2000 micrometers (pm) are suitable for admixing a powdery synthetic polymer, in particular thermoplastic, in particular particle sizes in the range from 1000 to 1500 micrometers.

An advantage of the invention is that the phenol or urea resins typically used in the prior art and provided with the health-critical formaldehyde can be dispensed with. Another advantage of the invention in terms of energy expenditure and productivity is that in the production of the wood composite material according to feature 3e)

Pressing can take place without significant heating, especially cold. The subsequent irradiation of the compressed mixture with electrons takes place in the

Electron energy range from I to 10 MeV, preferably powerful in the energy range from 5 to 10 MeV for crosslinking the polymer in appropriate layers. The dose range is preferably 50 to 150 kGy. The parameters regarding energy, dose and dose rate have to be experimentally optimized for the given system; depending on z. B. the type of wood, the preparation of the chips and fibers, the moisture content, the type of polymer that can be cross-linked by electron beams, the mixing ratio

Polymer wood as well as the types of polymer used among each other, parameters of the previous pressing, the residual temperature and the specific product target or its product quality.

The invention also relates to a wood composite material which is produced by the method according to the invention, in particular a particle board or an MDF / HDF board (MDF: medium density fiberboard; HDF: high density fiberboard). Further wood composite materials in the sense of the invention are the so-called OSB (Oriented Strand Board) and the composite material WPG (Wood-Plastics-Composites).

Optionally, the pressed plate can be shaped three-dimensionally before the final irradiation with electrons. The invention also includes devices according to claims 12 to 15.

Exemplary embodiments of the invention are described in more detail below with reference to the figures. FIGS. 1 to 3 explain a method and a device for producing chipboard.

FIGS. 4 and 5 explain a method and an apparatus for producing MDF / HDF boards.

Two exemplary embodiments of the invention are described in more detail below, namely the production of wood composite materials in the form of chipboard and in the form of MDF / HDF boards.

Figures 1 to 3 each show a section of the method or the device in the temporal-spatial sequence.

A chopper (10) chops raw wood. A chipper (12) then processes the chopped wood into chips. These are washed in a washer (16), then sieved and dried if necessary. A minimum humidity can be maintained to promote the effect of the subsequent electron radiation. When shredding recycled or used wood, an additional device (magnet) is used to remove metallic

Foreign bodies for use.

Small amounts of additives, e.g. B. for hydrophobing or flame retardant.

The irradiated chips are then fed to a dryer (18). As such, the dryer has a conventional structure.

The chips prepared in this way are then irradiated in an electron beam accelerator (20) with acceleration energies in the range between 5 and 10 MeV; with parameters chosen as appropriate with regard to the starting raw material and the operational throughput (bulk quantity and bulk density). The dose is optimized 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 material mixture.

Dryers and electron beam accelerators can be exchanged. The irradiation can therefore take place before and / or after drying. This depends on the moisture content of the chips. Irradiation is more effective when the chips are around 10-20% moist.

The output (20a) of the electron beam accelerator (20) is connected to a sieve tray (22) and the dried chips are divided into 3 size-dependent fractions via sieves (22a, 22b), which are shaken in the horizontal plane by a drive. A coarse fraction is discharged via an outlet (24a), a middle fraction via an outlet (24b) and a small fraction via an outlet (24c).

A conveyor (26) feeds the coarse and medium fractions to a chip dispenser (32), the fine fraction reaches a chip metering device (30) via a conveyor (28). The respective chips come from these dispensers into a hot screw conveyor

(34 and 36). The respective ones come from these screw conveyors (34 and 36)

Fractions (fine, medium and coarse) in the appropriately allocated mixer (42) for

Fine or in the mixer (44) for medium and coarse chips.

Thermoplastic powder particles are also added from a metering device (40)

Particle sizes in the range between 1000 and 1500 pm in the mixer (42, 44), where chips and thermoplastic powder are mixed.

Binders such as paraffin or starch can be added in the metering device or in the mixer.

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

To produce a nonwoven, the mixture from the deagglomerator (46) (fine fraction) is conveyed both into a lower-layer spreader (50) via its entrance (50a) and into an upper-layer spreader (54) - via its entrance (54a). The outlet of the other deagglomerator (48) is connected to the inlet (52a) of a middle layer spreader (52).

Lower-layer spreaders, middle-layer spreaders and upper-layer spreaders become temporal

and spatially controlled in such a way that a fleece (56) is formed below them with a lower layer (fine chipboard), above a middle layer (medium and coarse chipboard) and an upper layer (fine chipboard).

The fleece (56) reaches a preheater (60) via a conveyor (58). The heating temperatures depend on the given system. For example, heating can take place via HF (high frequency), IR (infrared) or MW (microwave).

The fleece is then fed to a press (62) which, in the exemplary embodiment shown, is a cooling press and therefore (in contrast to the prior art) does not require any energy-consuming and time-consuming heating. The fleece is formed into plates (65) in the press (62) and then cut to size. (Optionally, further deformation into three-dimensional structural products can take place). The plates (products) (65) formed by the pressing are then transported in via special transport routes which are caused by X-ray protection transferred to the process space of an electron beam accelerator (64) and irradiated there with high-energy electrons in the energy range from 1 to 10 MeV and with a correspondingly selected dose or dose rate in air in order to crosslink within the reactive synthetic or partially synthetic polymer mixture (in particular thermoplastic powder and / or liquid polymers ) as well as to bring about a liability or chemical connection of the same with the chopped and pretreated wood raw material or its components (cellulose, lignin) etc.

The result of this production technology is a particle board (or a specially shaped product) with very good properties, especially with regard to resistance to climatic changes, hydrophobicity, dimensional stability, bending strength, transverse tensile strength, health protection and recyclability.

The method is particularly advantageous in terms of energy saving (low heating requirement), productivity (low time expenditure) and environmental compatibility etc.

A method and an apparatus for producing MDF / HDF boards and WPC wood composite materials are now described in more detail with reference to FIGS. 4 and 5.

In the figures, the same reference numerals relate to components that correspond to one another.

Chopper (10), chipper (12), screening plant (14), washer (16) and electron emitter (18) essentially correspond to the exemplary embodiment according to FIG. 1, the process parameters (chipper 12) now being set such that wood fibers or fibers are made of wood-like material for MDF / HDFPI panels or WPC wood composite materials.

The electron-irradiated fibers are fed via a conveyor (38) to a so-called defibrator (fiber loosener) (66) (known as such in the prior art), from where the fibers come into a dryer (20).

According to FIG. 5, the dried fibers are transferred from the dryer 20 to a fiber spreader (72), where they are loosened further and metered to a screw conveyor (74), which is preferably heated. From there, the fibers enter a mixer (76).

Connected to the mixer (76) are on the one hand a metering device (68) with an electron beam-reactive synthetic or bio-based polymer liquid and on the other hand a Dispenser (70) with a thermoplastic powder mixture as a common binder mixture for the wood chips.

Depending on the desired properties of the MDF / HDF board to be produced, the control enables liquid and / or powder to be fed into the mixer (76).

If, for example, only powder is supplied to produce an M DF board, this can be done with 10 to 20%, based on the total mass. On the other hand, for a WPC composite, the powder content can be measured at 30 to 35%. (WPC: Wood-Polymer-Composites)

The mixture comes from the mixer (76) into a deagglomerator (78), which can be cooled. From the deagglomerator (78) the mixture reaches a fiber spreader (80) which (in a manner known per se) forms the fleece, which is prepared for the pressing process in a further fleece forming station (82).

A preheater (84), e.g. B. HF / MW, heats the fleece, which is then pressed in a press (86). The pressing is preferably carried out without heating (cool). The plates are then cut to size (optionally shaped into special products) and irradiated with electrons in an electron beam accelerator (90), for example in the energy or dose range specified above, for the purpose of crosslinking the electron beam-reactive polymer mixtures, including binding to the wood components or their surfaces . The MDF / HDF boards or WPC composite materials produced in this way have similar advantages to the chipboard described above.

Reference list

10 chopper (debaker)

12 chippers

14 screening plant

16 washers

18 dryers

20 electron beam accelerators

20a Exit (from 20)

22 screening plant

22a screen, large

22b screen, small

22c drive

24a chip exit large

24b chip exit (medium) (chip exit medium)

24c chip output (fine) (Chip exit small)

26 conveyors (for 24a, 24b) (Conveyor for 24a, 24b)

28 conveyors (for 24c) (Conveyor for 24c)

30 chip dispensers

32 chip metering

34 screw conveyor (hot screw)

36 screw conveyor (hot screw)

38 conveyors

40 metering units

42 mixers

44 mixers

46 Deagglomerator, especially cooled (Deagglomerator, especially cooled) 50 Bottom layer scattering

50a Entrance to 50 from 46

52 mid-layer scattering

52a Entrance to 52 from 48

54 upper layer scattering

54a Entrance to 54 from 46

56 fleece (fleece mat)

58 conveyors

60 Pre-heater (HF / IR / MW)

62 Press 64 electron beam accelerator

65 plates

66 fiber (defibrator) / fiberizer (pulper)

68 Doser for liquid

70 Doser for powder

72 fiber scatterers

74 conveying heating screw

76 mixers

78 deagglomerator (deagglomerator)

80 fiber scatterers

82 mat formation

84 Preheater (HF / MW)

86 cooling press

88 conveyors

90 electron beam accelerator

Claims

1. A method for producing a molded part containing lignocellulose, comprising 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 electron beam reactive powdery polymer, in particular a thermoplastic, with powder particle sizes <2000 micrometers (pm), and / or with a liquid containing electron beam reactive polymer;

c) shaping the mixture produced in accordance with the shape of the molded part to be produced, in particular shaping to form a fleece;

d) heating the molded mixture to 100-180 ° C;

e) pressing the molded mixture without heating; and

f) irradiation of the pressed mixture with electrons in the energy range from 1 MeV to 10 MeV.

2. The method according to claim 1, characterized in that in step a) the irradiation takes place with a dose between 50 to 150 kGy, in particular with a dose entry of 100 kGy plus / minus 20 kGy.

3. The method according to any one of claims 1 or 2, characterized in that in step f) the irradiation takes place with a dose of 50 to 250 kGy, in particular 100 kGy plus / minus 20 kGy, depending on the predetermined mixture formulation and selected product target.

4. The method according to any one of claims 1 to 3, characterized in that a fleece is pressed into a plate in step e).

5. The method according to any one of claims 1 to 4, characterized in that in step b) the particle sizes are in the range from 1000 to 1500 micrometers (pm).

6. The method according to any one of claims 1 to 5, characterized in that in step b) for the production of a wood material 5% to <30% by weight of a polymer according to claim 3 are mixed.

7. The method according to any one of claims 1 to 5, characterized in that that in step b) to produce a WPC 30% to 60% by weight of a polymer according to claim 3 are mixed.

8. The method according to any one of the preceding claims, characterized in that in step a) the energy range is between 5 and 10 MeV.

9. The method according to any one of claims 1 to 8, characterized in that in step b) the lignocellulose-containing particles before or during the addition of the thermoplastic powder to a temperature of 60 ° C to 160 ° C, preferably to 80 ° C to 120 ° C be heated.

10. The method according to any one of claims 1 to 9, characterized in that before or in step b) the lignocellulose-containing particles are acted upon by an adhesive before the addition of the thermoplastic powder.

11. The method according to claim 10, characterized in that adhesives and / or paraffins, starches and / or protein-containing substances are used as adhesives.

12. A device for producing a composite material containing lignocellulose-containing particles, comprising:

a) an electron beam accelerator (18), set up to irradiate the particles with electrons in the energy range> 1 MeV;

b) at least one mixer (42, 44) set up for mixing the irradiated particles with electron beam reactive powder made of a synthetic polymer, in particular a thermoplastic, with powder particle sizes <2000 micrometers (pm), and / or with a liquid containing electron beam reactive synthetic polymer ;

c) a device (50, 52, 54) set up for shaping the mixture produced in accordance with the shape of the composite material to be produced, in particular for shaping a nonwoven;

d) a preheater (60) arranged to heat the molded mixture to 100 ° C to 180 ° C;

e) a press (62) arranged to press the molded mixture without heating; and

f) a high-energy electron beam accelerator (64) in the energy range from 1 MeV to 10 MeV, set up in a radiation-protected Process chamber for irradiating the pressed and molded mixture that is carried by a transport device.

13. The apparatus according to claim 12, characterized in that the electron beam accelerator (64) is set up according to feature f) for uniformly irradiating the pressed and molded mixture carried by with a dose of 50 to 250 kGy, in particular with a dose of 100 kGy plus / minus 20 kGy.

14. Device according to one of claims 12 or 13, characterized in that the electron beam accelerator (20) is set up according to feature a) for uniform irradiation with a dose of 50 to 150 kGy, in particular with a dose of 100 kGy plus / minus 20 kGy .

15. Device according to one of claims 12 to 14, characterized in that the mixing device is a universal mixer, a turbo mixer, a ploughshare mixer, a free-fall mixer, o. D. G. acts.