EP0839083A1

EP0839083A1 - Polymer timber mouldings, their production and use

Info

Publication number: EP0839083A1
Application number: EP96925696A
Authority: EP
Inventors: Hans Reinhard Striewski; Lothar Thiele; Hans-Peter Kohlstadt
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 1995-07-17
Filing date: 1996-07-10
Publication date: 1998-05-06
Anticipated expiration: 2016-07-10
Also published as: JP3874203B2; CA2244005C; WO1997003794A1; JPH11509149A; EP0839083B1; DE59606806D1; DE19526032A1; CA2244005A1

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

Molded polymer wood, its manufacture and use

The present invention relates to formaldehyde-free wood-polymer forming body having improved water resistance, their preparation and application _^ Ver.

In the case of wood-based materials, a distinction is usually made according to Ullmann, Encyclopedia of Industrial Chemistry, 4th edition, Volume 12, pp. 709 ff.

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 kg / m ³ and light flat pressed sheets with a density of around 300 kg / m 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. The raw material containing lignin, cellulose and hemicellulose is broken down into its fibrous, anatomical basic elements in the form of individual fibers and fiber bundles by the action of heat, moisture and mechanical pressure in fiberizing plants. In the course of the manufacturing process, the fiber material is shaped, compressed and pressed. Here the felting of the fibers and the natural binding forces are primarily used. The binding forces can be increased by adding binders and water repellents as well as by thermal and other post-treatments. So the physical and strength properties can 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 form a disturbing stain on the fibreboard due to the highly concentrated circulating water avoid adding formaldehyde in an amount of 0.02 - 0.2%.

In today's world, the medium-hard wood fiber boards are mainly offered in the form of medium density fiber boards (MDF) as semi-finished products, which are manufactured with formaldehyde-containing condensation resins. Such products are no longer desirable for ecological reasons due to the continuous, sometimes years-long, evaporation of cancerogenic formaldehyde vapors. It helps in the furniture industry that the MDF is given an additional coating in order to lower the formaldehyde emission below the limit values required by the legislator. In addition, MDF has an improved dimensional stability compared to natural wood with a normal air humidity of between 35 and 85%, which, however, is not sufficient for certain applications. Furthermore, MDF produced with synthetic urea-formaldehyde binders are not suitable for use under high atmospheric humidity, especially in water.

Polymer wood (wood-plastic-composites) means wood-plastic combinations as obtained by treating wood with monomers or prepolymers. It is a composite material in which the wood is soaked with the liquid starting material and then the monomer deposited in the wood is polymerized. In practice, liquid monomers and solutions are preferably used, for example methacrylate prepolymers or unsaturated polyesters dissolved in styrene. The polymers primarily increase the strength of the wood, especially its hardness and pressure resistance. Finally, the aesthetic effect of the natural wood is not only not impaired, but in many cases even increased. Despite these advantages, polymer wood has so far only been used to a very limited extent for special goods, for example for parquet, sports equipment, kitchen appliances and tool handles. In contrast to the pure impregnation process for the production of polymer wood, the Skinpreg process can be used to impregnate the surface with plastics, which penetrate deeply into the wood under low pressure 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, which 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 from 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 providing a novel molded wood body which avoids the use of binders containing formaldehyde, as is still absolutely necessary in the MDF which is usually mainly used today, and also has advantageous application properties.

This object is solved by the features of claim 1. The present invention therefore relates to a molded article based on wood particles and / or cellulose-containing material and at least one binder, the binder being a two-component polyurethane binder which releases carbon dioxide and consists of a polyol, water and a polyisocyanate, characterized in that that the binder is contained in an amount of 10 to 200 parts by weight, based on 100 parts by weight of the wood particles and / or the cellulose-containing material, the shaped body by reaction of the wood particles and / or the cellulose-containing material and the binder is obtained under a pressure of at least 1, in particular 50 to 100 kp / cm ² .

Because of the significant increase in the hardness of the wood even inside the molded body, it is assumed that the wood, depending on the mass ratio of wood: binder, the size of the wood chips and the pressure, is superficially to completely reinforced with the polyurethane, i.e. the wood as a polymer -Wood is present.

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

It can be different from the predisputed wood materials of the

State of the art in any shape, that is tailor-made, for example in the form of plates, moldings, cubes, cuboids, etc.

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, i.e. his

Thickness increase 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 boards that are still used today, it is formaldehyde-free and flame-retardant.

The shaped bodies are so elastic that wood screws with a 0 of 5 mm can be screwed in without splinters. It is also so dimensionally stable that you can cut threads for Spax screws, i.e. Wide thread screws. Due to the polyurethane content in the molded body, it can be easily painted.

Finally, its homogeneity, i.e. the usual layer formation does not occur, and in particular there is no inner or outer layer either.

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

It is further preferred as the cellulose-containing material in the molded article according to the invention, vegetable fibers, for example cotton, jute, flax, hemp, bast, sisal, ramie, coconut fibers, yucca fibers or manila, or chemically modified fibers such as rayon and cellulose viscose fibers, cuoxam fibers , Acetate fibers and paper and cellulose game.

In the shaped body according to the invention, the wood particles are in the form of wood chips and / or wood flour or as cellulose-containing material in particle sizes of a maximum of 5 mm thick, 20 mm wide and 50 mm Length before. A thickness range from 0.5 to 3 mm, a width range from 1 to 15 mm and a length range from 3 to 40 mm are preferred.

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

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

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

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

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

They preferably contain on average 2 to at most 4 NCO groups. Examples of suitable isocyanates include: 1, 5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MD!), Hydrogenated MDI (H ₁₂ MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), 4,4'-diphenyldimethylmethane diisocyanate , Di- 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 -diisocyanato- cyclohexane, 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, 1-tetramethoxybutane, 4-diisocyanate, 1-butane, 4-diisocyanate, 1-hexane, 6-diisocyanate (HDI), dicylohexyl -methane diisocyanate, cyclohexane-1, 4-diisocyanate, ethylene diisocyanate, phthalic acid bis-isocyanatoethlester. Other important diisocyanates are trimethylhexamenthylene diisocyanate, 1,4-diisocyanatobutane, 1,2-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 isocyanuration products and HDI biuretization products are also possible.

Aromatic isocyanates are preferably used as di- or polyisocyanates, e.g. Diphenylmethane diisocyanate, either in the form of the pure isomers, as an isomer mixture of the 2,4 '- / 4,4'-isomers, or also the diphenylmethane diisocyanate (MDI) liquefied with carbodiimide, which e.g. is known under the trade name Isonate 143 L. In addition, the so-called "raw MDI", i.e. the isomer / oligomer mixture of the MDI can be used, such as are commercially available, for example, under the trade names PAPI or Desmodur VK. Furthermore, so-called "quasi-prepolymers", i.e. Reaction products of MDI or tolylene diisocyanate (TDI) with low molecular weight diols, such as Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol or triethylene glycol can be used.

The liquid polyhydroxy compounds having two or three hydroxyl groups are preferably suitable as diols and / or polyols for the binder per molecule, such as di- and / or trifunctional polypropylene glycols in the molecular weight range from 200 to 6000, preferably in the range from 400 to 3000. Statistical and / or block copolymers of ethylene oxide and propylene oxide can also be used. Another group of polyether polyols which are preferably to be used are the polytetramethylene glycols which are prepared, for example, by the acidic polymerization of tetrahydrofuran. The molecular weight range of the polytetramethylene glycols is between 200 and 6000, preferably in the range from 40 to 4000.

Also suitable as polyols are the liquid polyesters which are obtained by condensation of di- or tricarboxylic acids, e.g. Adipic acid, sebacic acid and glutaric acid, with low molecular weight diols or triols, e.g. Ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, 1, 4-butanediol, 1, 6-hexanediol, glycerol 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 called “polycaprolactones”.

However, polyester polyols of oleochemical origin can also be used. Such polyester polyols can, for example, by completely ring opening epoxidized triglycerides of an at least partially olefinically unsaturated fatty acid-containing fat mixture with one or more alcohols with 1 to 12 C atoms and then partial re-esterification of the triglyceride derivatives to alkyl ester polyols with 1 to 12 C atoms in the alkyl radical getting produced. Other suitable polyols are polycarbonate polyols and dimer diols (from Henkel) and in particular castor oil and its derivatives. Hydroxy-functional polybutadienes, such as are available, for example, under the trade name “Poly-bd”, can also be used as polyols for the compositions according to the invention. Another object of the present invention is to provide a manufacturing process for such a shaped body, wherein the wood particles and / or the cellulose-containing material is first mixed with the polyol component, to this mixture the other component (s), in particular the polyisocyanate in excess adds, this mixture is homogenized, this mixture is placed in a sealable, pressure-tight mold which may have a release agent, the reaction mixture is reacted under a pressure of at least 1 kp / cm ² and the mold is removed after the mold has cooled or freed from the mold.

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

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

In the process according to the invention, sealable, pressure-tight molds are used.

It is usually not necessary to provide a release agent, in particular a ^Teflon® layer, between the pressure reactor and the shaped body. 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 in accordance with the above type in the form of plates, moldings, cubes, cuboids, etc., in particular in wet areas or outdoors. Furthermore, the present invention also relates to the use of this shaped body, which is obtainable in the manner described above, as a semi-finished product or cladding in the construction sector. In addition, the molded body according to the invention can be used as packaging material, flooring, as steps or decorative beams. These aforementioned uses of the molded body preferably relate to the interior of vehicles, in particular motor vehicles such as passenger vehicles and camping vehicles, but also caravans, ships and aircraft. Alternatively, the shaped bodies according to the invention can be used for decorative purposes in the outdoor area or in the household and commercial area, in particular 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 molding 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 molded article obtained according to the production example was compared in terms of its quality features with a medium-density fiberboard (MDF board) which was produced with formaldehyde-containing condensation resins and had an identical thickness. Here it was found in particular that the molded body according to the invention has a significantly lower water absorption value than an MDF board.

Table: Water absorption capacity and swelling of the shaped articles according to the invention in comparison to MDF boards.

Dense water absorption Thickness swelling

[g / cm] [%] [%] after 24h water storage

Board thickness 6-12> 35 6-12> 35

[mm]

MDF board 0.72 20 16 8 5

Shaped body 0.60 14 7.5 4 1 acc.

Claims

claims

1. Shaped body based on wood particles and / or cellulose-containing material and at least one binder, the binder being a carbon dioxide-releasing two-component polyurethane binder made of a polyol, water and a polyisocyanate, characterized in that the binder in an amount of 10 to 200 Parts by weight, based on 100 parts by weight of the wood particles and / or the cellulose-containing material, is contained, and wherein the shaped body by reacting the wood particles and / or cellulose-containing material and the binder under a pressure of at least 1 kp / cm ² , in particular 50 kp / cm ² to 100 kp / cm ^{2 is} obtained.

2. Shaped body according to claim 1, characterized in that softwood species such as softwood or hardwood species such as beech or oak are used as the starting material for the wood particles.

3. Shaped body according to at least one of the preceding claims, characterized in that vegetable fibers such as cotton, jute, flax, hemp or chemically modified fibers such as rayon are used as the cellulose-containing material.

4. Shaped body according to at least one of the preceding claims, characterized in that the wood particles in the form of wood chips or wood flour with particle sizes of a maximum of 1 mm in thickness, 20 mm in width and 50 mm in length are used.

5. Shaped body according to at least one of the preceding claims, characterized in that the moisture content of the wood particles and or of the cellulose-containing material corresponds to 5 to 2% by weight.

6. Shaped body according to at least one of the preceding claims, characterized in that it further contains deposits or reinforcing means such as wires, cables, wire nets or rods.

7. Shaped body according to at least one of the preceding claims, characterized in that the polyisocyanate is a di- or triisocyanate, in particular the diphenylmethane-2,2'-diisocyanate (as a crude product).

8. Shaped body according to 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. Shaped body according to at least one of the preceding claims, characterized in that it has a density of 0.40 g / cm ³ to 0.65 g / cm ³ .

10. A method for producing a shaped body according to the preceding claims, characterized in that

a) the wood particles and / or the cellulose-containing material are first mixed with the polyol component,

b) an excess of the further component (s), in particular the polyisocyanate, is added to this mixture and this mixture is homogenized,

c) the aforementioned mixture is placed in a sealable, pressure-tight form which may have a release agent and the reaction mixture is reacted under a pressure of at least 1 kp / cm ³ and d) removes the mold from the mold or frees it from the mold

11. The method according to claim 10, characterized in that steps (a) to (c) at temperatures of 10 to 30 ° C, in particular at room temperature (18 - 25 C) are carried out.

12. The method according to claim 10, characterized in that the reaction of the reaction mixture in step (c) takes place under Eigenre¬ reaction pressure.

13. The method according to claim 10, characterized in that the reaction time in step (c) is 5 to 30 minutes, preferably 10 to 20 minutes.

14. The method according to at least one of claims 10-13, characterized in that a closable metal or plastic mold is used as the mold.

15. Use of the shaped body according to at least one of claims 1 to 9 or produced according to at least one of claims 10 to 14 in the form of plates, moldings, cubes, cuboids, etc., in particular in wet areas or outdoors.

16. Use of the shaped body according to at least one of claims 1 to 9 or manufactured according to at least one of claims 10 to 14 as a semi-finished product or cladding in the construction sector.

17. Use of the shaped body according to at least one of claims 1 to 9 or produced according to at least one of claims 10 to 14 as packaging material, floor covering, stair treads or decorative beams.

18. Use of the shaped body according to claim 17 in the interior of vehicles, in particular motor vehicles such as passenger vehicles and camping vehicles, but also of caravans, ships and planes.

19. Use of the shaped body according to claim 16 for decorative purposes outdoors or in the household and commercial area, in particular in the kitchen and sanitaryware area.