EP0839083B1 - Polymer timber mouldings, their production and use - Google Patents

Abstract

The description relates to a polymer timber moulding based on timber particles and/or cellulose-containing material and at least one binder, in which the binder is a carbon dioxide-separating two-component polyurethane binder of a polyol, water and a polyisocyanate. The binder is present in a quantity of 10 to 200 parts by weight in relation to 100 parts by weight of the timber particles and/or the cellulose-containing material, where the polymer timber moulding is obtained by reacting the timber particles and/or cellulose-containing material and the binder at a pressure of at least 1 kp/cm2 and especially 50 to 100 kp/cm2.

Description

The present invention relates to formaldehyde-free molded polymer wood articles with improved water resistance, their manufacture and use.

When it comes to wood-based materials, a distinction is usually made according to Ullmann, Encyclopedia of technical chemistry, 4th ed., Volume 12, p. 709 ff following Semi-finished product classes:

Wood chipboard or particle board is generally understood to mean plates made of mechanically produced wood shavings or woody parts, which are produced by gluing with a binder under pressure. Urea resins or aminoplasts, phenolic resins or mixed resins made from urea, melamine, phenol and formaldehyde can be used as synthetic resins or binders. Isocyanates, in particular those based on diphenylmethane diisocyanate, and crosslinkable polymers are also used. The properties of the chipboard can be varied through the size, shape and arrangement of the chips and the amount of synthetic resin or binder (approx. 5 - 10%). High-quality boards are produced in multiple layers and with particularly fine covering chips. For use in furniture construction, the chipboard can be coated with decorative films, primer films and veneers. Depending on the density, a distinction is made between flat pressed sheets with an average density of 500 - 800 kglm ³ and light flat pressed sheets with a density around 300 kglm ³ .

CA 100: 104746 relating to JP-A-58185670 discloses binders for particle boards based on a 4,4'-diphenylmethane diisocyanate fraction. There, the wood chips are moistened with water so that the aforementioned diisocyanate can be converted during hot pressing at 150 ° C and 25 kg / cm ² . The polyurethane-containing chipboard obtained has an improved flexural strength.

Wood-fiber chip boards are made from wood fibers or lignocellulose-containing material. By the action of Heat, moisture and mechanical pressure in fiberizing plants becomes the raw material containing lignin, cellulose and hemicellulose in its fibrous, anatomical basic elements in the form of Individual fibers and fiber bundles disassembled. During the manufacturing process the fiber material is shaped, compressed and pressed. Here are primarily the matting of the fibers and the natural binding forces used. By adding binders and water repellents and by The binding forces can be thermal and other post-treatments increase. So the physical and strength properties be adapted to the intended use.

According to DIN 68 753, a distinction is made between hard wood fiber boards with a bulk density of over 800 kg / m ³ , medium hard wood fiber boards with a bulk density of more than 350 kg / m ³ to 800 kg / m ³ and porous wood fiber boards with a bulk density of 230 - 350 kg / m ³ . Up to 25 kg of resin and 1.5 - 20 kg of paraffin are required as binders and water repellents in the wet process as well as in the dry process per ton of wood fiber board produced. In the wet process that is predominantly used today, the process water with a soluble content of up to 2.0-2.5% must be routed mainly in a cycle, which is very energy-intensive at a water temperature of up to 65 ° C. Furthermore, in order to avoid annoying stains on the wood fiber boards due to the highly concentrated circulating water, formaldehyde should be added in an amount of 0.02 - 0.2%.

At the present time, the medium hard fiberboard are mainly in the form of medium density fibreboard (MDF) as a semi-finished product on the Market offered that are manufactured with formaldehyde-containing condensation resins become. Such products are continual, in part Long-term evaporation of cancerogenic formaldehyde vapors no longer desired for ecological reasons. In the Furniture industry is helped that the MDF an additional Coating obtained to reduce formaldehyde emissions by law lower the required limit values. In addition, MDF an improved dimensional accuracy compared to natural wood with a conventional one Humidity between 35 and 85%, which, however, at certain Applications are not enough. Furthermore, with synthetic MDF made from urea-formaldehyde binders is not for use suitable under high air humidity, especially in water.

Polymer wood (wood-plastic-composites) means wood-plastic combinations, how to treat them with wood Monomers or prepolymers. This is one Composite material, in which the wood with the liquid starting material soaks and then polymerizes the monomer deposited in the wood. In practice, liquid monomers and solutions are preferred used, for example methacrylate prepolymers or dissolved in styrene unsaturated polyester. The polymer is primarily the strength of the wood increased, especially its hardness and Pressure resistance. Finally, the aesthetic impact of natural wood not only not impaired, but in many cases even increased. Despite these advantages, polymer wood has so far only been used in very limited quantities Scope used for special goods, e.g. for parquet, sports equipment, Kitchen appliances and tool handles.

Deviating from the pure impregnation process for the production of polymer wood can be surface impregnated using the Skinpreg process made with plastics that differ under low pressure penetrate the wood without completely soaking it.

CA 111: 59849 relating to JP-A-01045440 discloses wood-foam compositions based on isocyanates or formaldehyde which contain sawdust as a filler. The foam obtained with a density of 0.35 g / cm ³ has good strength. Wood flour or sawdust is usually very finely chopped wood that is used as a filter aid, filler, admixture in woodchip coatings, etc. There, however, is not described or suggested to produce this foam under high pressure. Solvents are used.

CA 111: 9171 relating to JP-A-63303703 discloses moldings made of fine plant fibers or plant particles, in particular wood flour and a urethane prepolymer, which are contacted with water or steam before or after shaping. Such a shaped body has a density of 0.29 g / cm ³ , a compressive strength of 5.3 kg / cm ² and a tensile strength of 3.4 kg / cm ² . There, however, it is neither disclosed nor suggested that the molding should take place at a superatmospheric pressure. Solvents are used.

The present invention is therefore based on the object of a novel Provide wood moldings, the use of avoids formaldehyde-containing binders, as is customary with today's mainly used MDF is still mandatory is, and also has advantageous application properties.

This object is solved by the features of claim 1.

The present invention therefore relates to a molded body according to claim 1.

Because of the significant increase in the hardness of the wood also inside the Shaped body is assumed that the wood depending on Mass ratio wood: binder, on the size of the wood chips and from superficial to completely reinforced with polyurethane, that the wood is thus available as polymer wood.

• Er kann anderes als die vordiskutierten Holzwerkstoffe des Standes der Technik in beliebiger Form, also maßgeschneidert, beispielsweise in Form von Platten, Leisten, Würfeln, Quadern usw. hergestellt werden.
• Er ist als Leichtbaustoff geeignet, da er üblicherweise eine Dichte von 0,40 - 0,65 g/cm³ aufweist. Er ist daher ein Substitut für leichte und mittlere Flachpreßplatten oder mittelharte Holzfaserplatten allerdings ohne die entsprechenden Formaldehydprobleme.
• Er ist bei Raumtemperatur nicht quellbar in Wasser, d.h. seine Dickenzunahme nach 24 Stunden in Wasser bei 20 °C ist < 4 bzw. 1 Prozent bei Dicken von 6 bis 12 bzw. > 35 mm.
• Anders als ein Großteil der heute noch eingesetzten Holzwerkstoffe sowie MDF-Platten ist er formaldehydfrei und schwer brennbar.
• Die Formkörper sind so elastisch, daß sich Holzschrauben mit einem Ø von 5 mm splitterfrei einschrauben lassen.
• Er ist weiter so formstabil, daß man Gewinde hineinschneiden kann für Spax-Schrauben, d.h. Schrauben mit einem breiten Gewinde.
• Bedingt durch den Polyurethananteil im Formkörper ist er ohne weiteres lackierbar.
• Hervorzuheben ist schließlich seine Homogenität, d.h. es kommt nicht zu der sonst üblichen Schichtenbildung, insbesondere findet man auch nicht eine Innen- und Außenschicht.

The molded body according to the invention has the following advantages over the prior art:

• It can be manufactured in any shape, ie tailor-made, for example in the form of boards, moldings, cubes, cuboids, etc., other than the predisputed wood-based materials of the prior art.
• It is suitable as a lightweight material because it usually has a density of 0.40 - 0.65 g / cm ³ . It is therefore a substitute for light and medium-sized flat pressed boards or medium-hard wood fiber boards, but without the corresponding formaldehyde problems.
• It is not swellable in water at room temperature, ie its increase in thickness after 24 hours in water at 20 ° C is <4 or 1 percent for thicknesses from 6 to 12 or> 35 mm.
• Unlike most of the wood-based materials and MDF panels that are still used today, it is formaldehyde-free and flame-retardant.
• The moldings are so elastic that wood screws with a diameter of 5 mm can be screwed in without splintering.
• It is also so dimensionally stable that you can cut threads for Spax screws, ie screws with a wide thread.
• Due to the polyurethane content in the molded body, it can be easily painted.
• Finally, its homogeneity should be emphasized, ie the usual layer formation does not occur, and in particular there is also no inner and outer layer.

According to a preferred embodiment of the shaped body according to the invention softwood species, e.g. woods of the Spruce, pine, fir, larch, birch, alder, horse chestnut, pine, aspen, Willow, poplar and linden are used. But also hardwood types, such as beech, hawthorn, sloe, ash, maple, walnut, Apple, pear, yew or oak can be used. Also Mixtures of any kind of softwood with hardwood can be used.

It is further preferred as the cellulose-containing material in the invention Moldings of vegetable fibers, for example cotton, jute, Flax, hemp, bast, sisal, ramie, coconut fiber, yucca fibers or manila or chemically modified fibers such as rayon and rayon viscose fibers, Cuoxam fibers, acetate fibers and paper and cellulose yarns.

The wood particles are in shape in the molded body according to the invention of wood chips and / or wood flour or as cellulosic material in Particle sizes of maximum 5 mm thick, 20 mm wide and 50 mm Length before. A thickness range of 0.5 to 3 mm, a width range is preferred from 1 to 15 mm and a length range from 3 to 40 mm.

The moisture or the moisture content of the wood particles or the cellulosic Material in the molded body according to the invention is usually 5 to 20% by weight. If necessary, it can be moistened with Water or steam increased or by drying at elevated Temperature can be lowered. The moisture content preferably corresponds but the equilibrium moisture content of the material at ambient temperature.

The moldings according to the invention can e.g. for stabilization Contain wires, cables, wire nets, rods or the like.

The two-component polyurethane binder used in the molding according to the invention consists of a reaction product at least one polyol with at least one polyisocyanate.

The amount of the two reactants is always chosen so that that the polyisocyanate is used in excess, i.e. it is a Equivalence ratio of NCO to OH groups of 5 to 1, preferably but from 2: 1 to 1.2: 1.

An aliphatic, alicyclic is usually used as the polyisocyanate or aromatic di- or triisocyanate.

They preferably contain on average 2 to at most 4 NCO groups. Examples of suitable isocyanates are: 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), hydrogenated MDI (H ₁₂ MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), 4,4'-diphenyldimethylmethane diisocyanate, and tetraalkyldiphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, the isomers of tolylene diisocyanate (TDI), optionally in a mixture, 1-methyl-2,4-diisocyanatocyclohexane, 1,6-diisocyanato 2,2,4-trimethylhexane, 1,6-diisocyanato-2,4,4-trimethylhexane, 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (IPDI), chlorinated and brominated diisocyanates, phosphorus-containing diisocyananates, 4 , 4'-diisocyanatophenylperfluoroethane, tetramenthoxybutane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-diisocyanate (HDI), dicylohexylmethane diisocyanate, cyclohexane-1,4-diisocyanate, ethylene diisocyanate , Phthalic acid bis-isocyanatoethlester. Other important diisocyanates are trimethylhexamenthylene diisocyanate, 1,4-diisocyanatobutane, 1,12-diisocyanatododecane and dimer fatty acid diisocyanate. Interesting partially masked polyisocyanates, which allow the formation of self-crosslinking polyurethanes, such as dimeric tolylene diisocyanate. Finally, prepolymers can also be used, ie oligomers with several isocyanate groups. As is known, they are obtained with a large excess of monomeric polyisocyanant in the presence of, for example, diols. HDI isocyanuratization products and HDI biuretization products are also possible.

Aromatic are preferred as di- or polyisocyanates Isocyanates used, e.g. Diphenylmethane diisocyanate, either in the form the pure isomers, as an isomer mixture of the 2,4 '- / 4,4'-isomers or also diphenylmethane diisocyanate (MDI) liquefied with carbodiimide, that e.g. is known under the trade name Isonate 143 L. Moreover the so-called "raw MDI", i.e. the isomer / oligomer mixture of the MDI are used, e.g. under the trade name PAPI or Desmodur VK are commercially available. Can continue so-called "quasi-prepolymers", i.e. Implementation products of the MDI or of tolylene diisocyanate (TDI) with low molecular weight diols, such as e.g. Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol or Triethylene glycol.

The diols and / or polyols for the binder are preferably suitable liquid polyhydroxy compounds with two or three hydroxyl groups per molecule, e.g. di- and / or trifunctional polypropylene glycols in Molecular weight range from 200 to 6000, preferably in the range from 400 to 3000. Statistical and / or block copolymers can also be used of ethylene oxide and propylene oxide are used. Another The group of polyether polyols to be used preferably are Polytetramethylene glycols, e.g. through the acidic polymerization of Tetrahydrofuran can be produced. Here lies the Molecular weight range of the polytetramethylene glycols between 200 and 6000, preferably in the range of 40 to 4000.

Also suitable as polyols are the liquid polyesters which pass through Condensation of di- or tricarboxylic acids, e.g. Adipic acid, sebacic acid and glutaric acid, with low molecular weight diols or triols, such as. Ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, Dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerin or trimethylolpropane, can be produced.

Another group of the polyols to be used according to the invention are the polyesters based on ε-caprolactone, also "polycaprolactones" called.

However, polyester polyols of oleochemical origin can also be used become. Such polyester polyols can, for example, by complete ring opening of epoxidized triglycerides at least one partially olefinically unsaturated fatty acid-containing fat mixture with one or more alcohols with 1 to 12 carbon atoms and subsequent partial change of the triglyceride derivatives Alkyl ester polyols with 1 to 12 carbon atoms in the alkyl radical are prepared. Other suitable polyols are polycarbonate polyols and dimer diols (Fa. Henkel) and in particular castor oil and its derivatives. Also Hydroxy-functional polybutadienes, e.g. under the Trade names "Poly-bd" are available for the invention Compositions are used as polyols.

Another object of the present invention is to provide a manufacturing process for such a shaped body with the features of claim 10.

In this context, it is preferred that the aforementioned mixing and reaction steps at temperatures of 10 to 30 ° C, in particular at room temperature (18 - 25 ° C). The pressure treatment is carried out using the method according to the invention by reacting the reaction mixture under its own reaction pressure. Under certain circumstances, however, can also be done in a manner known per se Inert gas or water vapor pressure can be supplied from the outside.

In the process according to the invention, the reaction time is in the mold and thus the formation of the shaped body 5 to 30 minutes, preferably 10 to 20 minutes.

In the method according to the invention, sealable pressure-tight seals are used Forms. Usually it is not necessary between the pressure reactor and to provide a mold release agent, in particular a Teflon® layer. In certain cases, however, it is preferred to use Acmos release agents for PUR with the type designations 39-5001, 39-4487, 37-3200 and 36-3182.

Finally, the present invention relates to the use of the Shaped body of the aforementioned type or produced according to the above Kind in the form of plates, moldings, cubes, cuboids, etc., especially in the Wet area or outdoor area. The present concerns further Invention also the use of this shaped body according to is available as a semi-finished or cladding in the Construction area. In addition, the molded body according to the invention as Packaging material, flooring, as stairs or decorative beams be used. These aforementioned uses of the shaped body relate preferably to the interior of vehicles, in particular Motor vehicles such as passenger vehicles and camping vehicles, but also of caravans, ships and airplanes. Alternatively, you can the moldings according to the invention for decorative purposes in Outdoors or in the household and commercial sector, be used especially in the kitchen and sanitary area.

The invention is explained in more detail below by means of exemplary embodiments.

Example 1: A) Starting products

a) polyol component: Trifunctional polether polyol based on glycerin, 83.8 Ethylene and propylene oxide glycerin 6.0 Soy polyol modified with ethylene oxide 6.0 water 2.2 Tegostab B 8404 (Goldschmidt) 1.3 Dibutyltin dilaurate 0.7 b) Isocyanate component: Diphenymethane-4,4 'diisocyanant 100 (Raw MDI with a viscosity of 200-220 mPas)

B) Manufacturing

1500 g of wood chips from pine wood with a chip length of up to 4 cm are mixed intensively with 1000 g of the polyol component of the foam system. After adding 1000 g of the isocyanate and mixing again, the mixture was quickly placed in a metal mold of about 6.5 dm ^{3 in} size. The mold was immediately closed with a lid. After 30 minutes, the foam-containing polymer wood molded body was removed from the mold.

The molded body obtained in this way has a density of 0.6 g / cm ³ , a smooth surface and can be machined like wood, for example sawing, planing, grinding and drilling. Threads can be cut into the material.

C) Application

The quality of the molded article obtained according to the production example was compared with that of a medium-density fiberboard (MDF board) which was produced with condensation resins containing formaldehyde and had an identical thickness. Here it was found in particular that the molded article according to the invention has a significantly lower water absorption value than an MDF board. Water absorption capacity and swelling of the moldings according to the invention in comparison to MDF boards. Density [g / cm] Water absorption [%] after 24 hours Thickness swelling [%] water storage Sheet thickness [mm] 6-12 > 35 6-12 > 35 MDF board 0.72 20th 16 8th 5 Shaped body according to Erf. 0.60 14 7.5 4th 1

Claims (19)

1. Wood-plastic composites of polyurethane-bonded wood particles and/or cellulose-containing material surface-reinforced or reinforced throughout with the polyurethane, obtainable by the following process steps:

   using a carbon-dioxide-eliminating two-component polyurethane binder of the starting constituents polyol, water and polyisocyanate in a quantity of 10 to 200 parts by weight, based on 100 parts by weight of the wood particles and/or the cellulose-containing material,

   mixing the wood particles and/or the cellulose-containing material with the liquid polyol component and the water

   adding the polyisocyanate in excess, based on the polyol, and

   moulding in a closed pressure-tight mould under a pressure of 1 to 100 bar.
2. Composites as claimed in claim 1, characterized in that soft woods, for example needle woods or hard woods, for example beech or oak, are used as the wood starting material for the wood particles.
3. Composites as claimed in at least one of the preceding claims, characterized in that vegetable fibres, such as cotton, jute, flax, hemp, or chemically modified fibres, such as rayon staple, are used as the cellulose-containing material.
4. Composites as claimed in at least one of the preceding claims, characterized in that the wood particles are used in the form of wood chips or wood powder with particle sizes of at most 1 mm (thickness) x 20 mm (width) x 50 mm (length).
5. Composites as claimed in at least one of the preceding claims, characterized in that the moisture content of the wood particles and/or the cellulose-containing material is between 5 and 2% by weight.
6. Composites as claimed in at least one of the preceding claims, characterized in that they additionally contain inserts or strengtheners, for example in the form of wires, cables, wire nets or rods.
7. Composites as claimed in at least one of the preceding claims, characterized in that the polyisocyanate is a diisocyanate or triisocyanate, more particularly diphenylmethane-2,2'-diisocyanate (as the crude product).
8. Composites as claimed in at least one of the preceding claims, characterized in that the polyol is a diol/triol mixture of polyether and polyester polyols with water.
9. Composites as claimed in at least one of the preceding claims, characterized in that they have a density of 0.40 g/cm³; to 0.65 g/cm³;.
10. A process for the production of a wood-plastic composite of polyurethane-bonded wood particles and/or cellulose-containing material surface-reinforced or reinforced throughout with the polyurethane, comprising the following process steps:

    using a carbon-dioxide-eliminating two-component polyurethane binder of the starting constituents polyol, water and polyisocyanate in a quantity of 10 to 200 parts by weight, based on 100 parts by weight of the wood particles and/or the cellulose-containing material,

    mixing the wood particles and/or the cellulose-containing material with the liquid polyol component and the water

    adding the polyisocyanate in excess, based on the polyol,

    moulding in a closed pressure-tight mould under a pressure of 1 to 100 bar,

    a release agent being used in the mould and the composite being removed from the mould after polymerization.
11. A process as claimed in claim 10, characterized in that in that steps (a) to (c) are carried out at temperatures of 10 to 30°C and more particularly at room temperature (18 to 25°C).
12. A process as claimed in claim 10, characterized in that the reaction of the reaction mixture in step (c) takes place under the natural reaction pressure.
13. A process as claimed in claim 10, characterized in that the reaction time in step (c) is 5 to 30 minutes and preferably 10 to 20 minutes.
14. A process as claimed in at least one of claims 10 to 13, characterized in that a closable metal or plastic mold is used as the mold.
15. The use of the composites claimed in at least one of claims 1 to 9 or produced by the process claimed in at least one of claims 10 to 14 in the form of boards, strips, cubes, squares, etc., more particularly in humid environments or outdoors.
16. The use of the composites claimed in at least one of claims 1 to 9 or produced by the process claimed in at least one of claims 10 to 14 as a semi-finished product or as cladding in the building industry.
17. The use of the composites in at least one of claims 1 to 9 or produced by the process claimed in at least one of claims 10 to 14 as a packaging material, floor covering, stairs or decorative beams.
18. The use of composites as claimed in claim 17 for the interior fitting out of vehicles, more particularly motor vehicles, such as automobiles and camping vehicles but also caravans, ships and aircraft.
19. The use of composites as claimed in claim 16 for decorative purposes outdoors or in the domestic and institutional sectors, particularly in kitchens and bathrooms.