CA2244005C - Wood/plastic composites, their production and use - Google Patents
Wood/plastic composites, their production and use Download PDFInfo
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- CA2244005C CA2244005C CA 2244005 CA2244005A CA2244005C CA 2244005 C CA2244005 C CA 2244005C CA 2244005 CA2244005 CA 2244005 CA 2244005 A CA2244005 A CA 2244005A CA 2244005 C CA2244005 C CA 2244005C
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
- B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
- B27N3/005—Manufacture of substantially flat articles, e.g. boards, from particles or fibres and foam
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- Wood Science & Technology (AREA)
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- Dry Formation Of Fiberboard And The Like (AREA)
- Polyurethanes Or Polyureas (AREA)
- Compositions Of Macromolecular Compounds (AREA)
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 materials, 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
Wood/plastic Composites, their Production and Use FIELD OF THE INVENTION
This invention relates to formaldehyde-free plastic/wood composites having improved resistance to water, to their production and to their use.
BACKGROUND OF THE INVENTION
According to Ullmann, Enzyklopadie der technischen Chemie, 4th Edition, Vol. 12, pages 709 et seq, wood-based materials may be divided into the following classes of semi-finished products:
Wood chip boards or particle boards are generally understood to be boards of mechanically produced chips of wood or wood-containing parts which are made by gluing under pressure with a binder. The synthetic resins or binders used are selected from urea resins or aminoplastics, phenolic resins or mixed resins of urea, melamine, phenol and formaldehyde.
Isocyanates, particularly those based on diphenylmethane diisocyanate, and crosslinkable polymers are also used. The properties of chipboards can be varied through the size, shape and arrangement of the chips and the amount of synthetic resin or binder used (ca. 5 - 10%). High-quality boards comprise several layers with a surface layer of particularly fine particles. For use in furniture making, chipboards can be coated with decorative films, priming films and veneers. Here, a density-based distinction is drawn between flat-pressed boards with a medium density of 500 to 800 kg/m3 and light flat-pressed boards with a density of about 300 kg/m3.
Japanese Publication No. 58-185670, published October 29, 1983, describes binders for chipboards based on a 4,4'-diphenylmethane diisocyanate fraction. According to this document, the chipboards are moistened with water so that the diisocyanate mentioned can be reacted during hot pressing at 150 C/25 kp/cm2. The polyurethane-containing chipboards obtained have improved flexural strength.
DOCSTOR: 1111600U
This invention relates to formaldehyde-free plastic/wood composites having improved resistance to water, to their production and to their use.
BACKGROUND OF THE INVENTION
According to Ullmann, Enzyklopadie der technischen Chemie, 4th Edition, Vol. 12, pages 709 et seq, wood-based materials may be divided into the following classes of semi-finished products:
Wood chip boards or particle boards are generally understood to be boards of mechanically produced chips of wood or wood-containing parts which are made by gluing under pressure with a binder. The synthetic resins or binders used are selected from urea resins or aminoplastics, phenolic resins or mixed resins of urea, melamine, phenol and formaldehyde.
Isocyanates, particularly those based on diphenylmethane diisocyanate, and crosslinkable polymers are also used. The properties of chipboards can be varied through the size, shape and arrangement of the chips and the amount of synthetic resin or binder used (ca. 5 - 10%). High-quality boards comprise several layers with a surface layer of particularly fine particles. For use in furniture making, chipboards can be coated with decorative films, priming films and veneers. Here, a density-based distinction is drawn between flat-pressed boards with a medium density of 500 to 800 kg/m3 and light flat-pressed boards with a density of about 300 kg/m3.
Japanese Publication No. 58-185670, published October 29, 1983, describes binders for chipboards based on a 4,4'-diphenylmethane diisocyanate fraction. According to this document, the chipboards are moistened with water so that the diisocyanate mentioned can be reacted during hot pressing at 150 C/25 kp/cm2. The polyurethane-containing chipboards obtained have improved flexural strength.
DOCSTOR: 1111600U
Wood-fiber chipboards are made from wood fibers or lignocellulose-containing material. Under the effect of heat, moisture and mechanical pressure in fiberizing machines, the lignin-, cellulose and hemicellulose-containing raw material is broken down into its fiber-like, anatomical basic elements in the form of individual fibers and fiber bundles. In the course of the manufacturing process, the fibrous material is shaped, compacted and pressed. The matting of the fibers and the natural binding forces are primarily used for this purpose. The binding forces can be increased by adding binding and hydrophobicizing agents and by thermal and other aftertreatments. The physical and strength properties can thus be adapted to the intended application.
According to German Institute for Standardization Document No. DIN
68 753 published January, 1976, wood-fiber chipboards are divided into hard boards with a density of more than 800 kg/m3, medium-hard boards with a density of more than 350 kg/m3 to 800 kg/m3 and porous boards with a density of 230 to 350 kg/m3. Both in the wet process and in the dry process, up to 25 kg of resin and 1.5 to 20 kg of paraffin - per tonne of wood-fiber chipboard produced - are required for binding and hydrophobicizing. In the wet process predominantly in use today, the process water has to be circulated with a content of soluble material of up to 2.0-2.5% which is highly energy-intensive at a water temperature of up to 65 C. In addition, formaldehyde has to be added in a quantity of 0.02 to 0.2% to avoid troublesome staining of the wood-fiber chipboards by the highly concentrated circuit water.
At the present time, medium-hard wood-fiber chipboards are mainly marketed in semifinished form as medium-density fiberboards (MDFs) which are made with formaldehyde-containing condensation resins. However, through the continuous emission of carcinogenic formaldehyde vapors, in some cases for several years, products such as these are no longer wanted on ecological grounds. In the furniture industry, the situation is remedied by giving MDFs an additional coating to bring the emission of formaldehyde below the legally specified limits. In addition, although MDFs have better dimensional stability than natural wood at typical air humidity levels of 35 to DOCSTOR: 1111600\1 85%, it is still not good enough for certain applications. In addition, MDFs made with synthetic urea-formaldehyde binders are not suitable for use in high-humidity environments, particularly in water.
Wood/plastic composites are understood to be wood/plastic combinations which are obtained by treating wood with monomers or prepolymers. They are composite materials where the wood is impregnated with the liquid starting material and the monomer deposited in the wood is subsequently polymerized. Liquid monomers and solutions, for example methacrylate prepolymers or unsaturated polyesters dissolved in styrene, are preferably used in practice. The polymers primarily increase the strength of the wood, above all its hardness and its compressive strength. Finally, the aesthetic effect of natural wood not only is not impaired, it is actually enhanced in many cases. Despite these advantages, wood/plastic composites have hitherto been used to only a very limited extent for special applications, for example for parquet floors, sports equipment, kitchen utensils and tool handles.
In contrast to the pure impregnating process for making wood/plastic composites, the skinpreg process comprises surface impregnation with plastics which penetrate into the wood to different depths under light pressure without completely impregnating it.
Japanese Publication No. 64-045440, published February 17, 1989, describes isocyanate- or formaldehyde-based wood/foam compositions which contain sawdust as filler. The foam obtained, with a density of 0.35 g/cm3, possesses very high strength. The sawdust or wood powder is normally very finely size-reduced wood which is used as a filter aid, as a filler, as an additive for rough fiber coatings, etc. However, there is nothing in the literature reference in question to suggest that the foam is produced under high pressure. Solvents are used.
Japanese Publication No. 63-303703, published December 12, 1988, describes composites of fine vegetable fibers or vegetable particles, more particularly wood powder, and a urethane prepolymer which are contacted with water or steam before or after molding. A composite of this type has a DOCSTOR: 1111600\1 density of 0.29 g/cm3, a compressive strength of 5.3 kg/cm2 and a tensile strength of 3.4 kg/cm2. However, there is nothing in this literature reference which directly or indirectly suggests that the composites are produced at above-atmospheric pressure. Solvents are used.
SUMMARY OF THE INVENTION
Accordingly, the problem addressed by the present invention was to provide a new wood/plastic composite which would avoid the use of the formaldehyde-containing binders still absolutely essential in the MDFs mainly in use today and which would also have advantageous performance properties.
Accordingly, the present invention relates to a wood/plastic composite based on wood particles and/or cellulose-containing material and at least one binder, the binder being a carbon-dioxide-eliminating two-component polyurethane binder of a polyol, water and a polyisocyanate, characterized in that the binder is present 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, the composite being obtainable by reaction of the wood particles and/or the cellulose-containing material and the binder under a pressure of at least I
kp/cm2 and, more particularly, in the range from 50 to 100 kp/cm2.
In one aspect of the invention, the polyisocyanate is selected from the group consisting of: aliphatic, alicyclic, and aromatic di- and triisocyanates, and reaction products of monomeric diisocyanates with low molecular weight diols.
In view of the marked increase in the hardness of the wood, even in the interior of the composite, it is assumed that - depending on the ratio by weight of wood to binder, the size of the wood particles and the pressure applied - the wood is strengthened by the polyurethane at its surface or throughout, i.e.
the wood is present as a wood/plastic composite.
The wood/plastic composite has the following advantages over the prior art:
- In contrast to the known wood-based materials mentioned above, it can be made in any form, i.e. made-to-measure, for example in the form of boards, strips, cubes, squares, etc.
- It is suitable as a lightweight building material because it normally has a density of 0.40 to 0.65 g/cm3. It is therefore a substitute for light and medium flat-pressed boards or medium-hard wood-fiber chipboards, but without the attendant formaldehyde problems.
- It does not swell in water at room temperature, i.e. its increase in thickness after 24 hours in water at 20 C is <4 or 1% for thicknesses of 6 to 12 or >35 mm.
- In contrast to many of the wood-based materials and MDF boards still in use today, it is formaldehyde-free and flame-retardant.
- The composites are so elastic that 5 mm diameter timber screws can be screwed in without any splintering.
- The composites are also so dimensionally stable that threads can be cut for SpaxTM screws, i.e. screws with a broad thread.
- By virtue of the polyurethane present, the composites may readily be painted.
- Finally, the composites are characterized by their homogeneity, i.e. there is none of the otherwise usual layer formation; in particular, there is no inner layer and outer layer.
In one preferred embodiment of the wood/plastic composite according to the invention, soft woods, for example woods of the spruce, pine, fir, larch, birch, alder, horse chestnut, aspen, willow, poplar and lime, are used as the wood starting material. However, hard woods, for example beech, hawthorn, blackthorn, ash, maple, walnut, apple, pear, yew or oak, may also be used.
Mixtures of soft wood and hard wood may also be used.
In another preferred embodiment, vegetable fibers, for example cotton, jute, flax, hemp, bast, sisal, ramie, coconut fibers, yucca fibers or manila, or chemically modified fibers, such as the viscose fibers rayon and rayon staple, cuoxam fibers, acetate fibers, and paper and cellulose yarns, may be used as the cellulose-containing material in the composite according to the invention.
In another aspect of the present invention, a process is provided comprising the steps of:
a) mixing the particles with the polyol component;
b) adding the polyisocyanate in excess and water to yield a mixture and homogenizing said mixture;
c) introducing the mixture a closable pressure-tight mold optionally coated with release agents and the mixture is reacted under a pressure of at least 1 kg/cm3 and d) removing the molding from the mold.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The wood particles are present in the composite according to the invention in the form of wood chips and/or wood particles or as cellulose-containing material in particle sizes of at most 5 mm (thickness) x 20 mm (width) x 50 mm (length). A thickness range of 0.5 to 3 mm, a width range of 1 to 15 mm and a length range of 3 to 40 mm are preferred.
The moisture content of the wood particles or cellulose-containing material in the composite according to the invention is normally from 5 to 20%
by weight. If desired, it may 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 composites according to the invention may contain wires, cables, wire nets, rods or the like, for example for stabilization.
The two-component polyurethane binder used in the composite according to the invention consists of a reaction product of at least one polyol with at least one polyisocyanate.
The quantity in which the two reactants are used is always selected so that the polyisocyanate is present in excess, i.e. the equivalent ratio of NCO
groups to OH groups is 5:1 and preferably 2:1 to 1.2:1.
The polyisocyanate used is normally an aliphatic, alicyclic or aromatic diisocyanate or triisocyanate.
The polyisocyanates 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 (H12MDI), xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI), 4,4'-diphenyl dimethyl methane diisocyanate, di- and tetraalkyl diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, the isomers of tolylene diisocyanate (TDI), optionally in admixture, 1-methyl-2,4-diisocyanatocyclohexane, 1,6-diisocyanato-2,2,4-trimethyl hexane, 1,6-diisocyanato-2,4,4-trimethyl hexane, 1-isocyanato-methyl-3-isocyanato-1,5,5-trimethyl cyclohexane (IPDI), chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4,4'-diisocyanatophenyl perfluoroethane, tetramethoxybutane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-diisocyanate (HDI), dicyclohexyl-methane diisocyanate, cyclohexane-1,4-diisocyanate, ethylene diisocyanate, phthalic acid-bis-isocyanatoethyl ester. Other important diisocyanates are trimethyl hexamethylene diisocyanate, 1,4-diisocyanatobutane, 1,12-diisocyanatododecane and dimer fatty acid diisocyanate. Also of interest are partly masked polyisocyanates which enable self-crosslinking polyurethanes to be formed, for example dimeric tolylene diisocyanate. Finally, prepolymers, i.e. oligomers containing several isocyanate groups, may also be used.
Prepolymers are obtained using a large excess of monomeric polyisocyanate, for example in the presence of diols. Isocyanuratization products of HDI and biuretization products of HDI may also be used.
The diisocyanates or polyisocyanates preferably used are aromatic isocyanates, for example diphenylmethane diisocyanate, either in the form of the pure isomers or in the form of a mixture of the 2,4'- and 4,4'-isomers, or even carbodiimide-liquefied diphenylmethane diisocyanate (MDI) which is commercially available, for example, as Isonate 143 L. The so-called "crude MDI", i.e. the isomer/oligomer mixture of MDI commercially available, for example, as PAPI or Desmodur VK may also be used. In addition, so-called "quasi prepolymers", i.e. reaction products of MDI or tolylene diisocyanate (TDI) with low molecular weight diols, for example ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol or triethylene glycol, are also suitable.
Preferred diols and/or polyols for the binder are the liquid polyhydroxy compounds containing two or three hydroxyl groups per molecule, for example difunctional and/or trifunctional polypropylene glycols with molecular weights in the range from 200 to 6,000 and preferably in the range from 400 to 3,000. Statistical and/or block copolymers of ethylene oxide and propylene oxide may also be used. Another group of preferred polyether polyols are the polytetramethylene glycols which are obtained, for example, by acidic polymerization of tetrahydrofuran. The molecular weight of the polytetramethylene glycols is in the range from 200 to 6,000 and preferably in the range from 40 to 4,000.
Other suitable polyols are the liquid polyesters which may be obtained by condensation of di- and tricarboxylic acids, for example adipic acid, sebacic acid and glutaric acid, with low molecular weight diols and triols, for example ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, butane-1,4-diol, hexane-1,6-diol, glycerol or trimethylol propane.
Another group of polyols suitable for use in accordance with the invention are the polyesters based on s-caprolactone which are also known as "polycaprolactones".
However, polyester polyols of oleochemical origin may also be used.
Oleochemical polyester polyols may be obtained, for example, by complete ring opening of epoxidized triglycerides of an at least partly olefinically unsaturated fatty-acid-containing fatty mixture with one or more alcohols containing 1 to 12 carbon atoms and subsequent partial transesterification of the triglyceride derivatives to form alkyl ester polyols containing 1 to 12 carbon atoms in the alkyl group. Other suitable polyols are polycarbonate polyols and dimer diols (Henkel KGaA) and, in particular, castor oil and derivatives thereof. The hydroxyfunctional polybutadienes commercially obtainable, for example as "Poly-bd" may also be used as polyols for the composites according to the invention.
The present invention also relates to a process for producing the wood/plastic composites in which the wood particles and/or the cellulose-containing material are/is first mixed with the polyol component, the other component(s), more particularly the polyisocyanate in excess, is/are added to the resulting mixture, the mixture is homogenized and then introduced into a closable, pressure-tight mold optionally coated with release agents, the reaction mixture is reacted under a pressure of at least 1 kp/cm2 and the composite is removed or freed from the mold after cooling.
The mixing and reaction steps mentioned above are carried out at temperatures of 10 to 30 C and more particularly at room temperature (18 to 25 C). The pressure treatment in the process according to the invention is sourced by the reaction of the reaction mixture under the natural reaction pressure. If necessary, however, pressure may also be supplied from outside in known manner in the form of an inert gas or even steam.
In the process according to the invention, the reaction in the mold and hence the formation of the composite takes 5 to 30 minutes and preferably 10 to 20 minutes.
Closable pressure-tight molds are used in the process according to the invention.
There is normally no need to provide a release agent, more particularly in the form of a Teflon coating, between the pressure reactor and the composite. In certain cases, however, type 39-5001, 39-4487, 37-3200 and 36-3182 Acmos release agents for PUR are preferably used.
Finally, the present invention relates to the use of composites of the type mentioned above or produced by the process described above in the form of boards, strips, cubes, squares etc., more particularly in humid environments or outdoors. The present invention also relates to the use of the composites obtainable by the process described above as semi-finished products or for cladding purposes in the building industry. The composites according to the invention may also be used as a packaging material, as a floor covering, as stairs or as ornamental beams. These uses of the composites preferably involve the interior fitting-out of vehicles, more particularly motor vehicles, such as automobiles and camping vehicles, but also caravans, ships and aircraft. Altematively, the composites according to the invention may be used for decorative purposes outdoors or in the domestic and institutional sectors, more particularly in kitchens and bathrooms.
The invention is illustrated by the following non-limiting Examples.
EXAMPLES
Example 1:
A) Starting products a) Polyol component:
trifunctional polyether polyol based on glycerol, ethylene oxide and propylene oxide 83.8 glycerol 6.0 soya polyol modified with ethylene oxide 6.0 water 2.2 Tegostab B 8404 (Goldschmidt) 1.3 dibutyl tin dilaurate 0.7 b) Isocyanate component:
diphenylmethane-4,4'-diisocyanate 100 (crude MDI with a viscosity of 200 to 220 mPas) B) Production 1500 g of wood chips (pine) up to 4 cm in length are intensively mixed with 1,000 g of the polyol component of the foam system. After addition of 1,000 g of the isocyanate and remixing, the mixture was quickly introduced into a metal mold around 6.5 dm3 in size. The mold was immediately closed with a cover. After 30 minutes the foam-containing wood/plastic composite is removed from the mold.
The composite obtained has a density of 0.6 g/cm3 and a smooth surface and can be mechanically treated like wood, for example sawn, planed, sanded and drilled. Threads can also be cut into the material.
C) Application The composite obtained in accordance with the Production Example was compared for quality with a medium-density fiberboard (MDF board) which had been produced with formaldehyde-containing condensation resins and had exactly the same thickness. It was found above all that the composite according to the invention has significantly lower water absorption than the MDF board.
Table :
Water absorption and swelling of the composites according to the invention compared with MDF boards Density Water absorption Increase in thickness [g/cm] [%] [%]
After storage in water for 24 h Board thickness 6-12 >35 6-12 >35 [mm]
MDF board 0.72 20 16 8 5 Composite 0.60 14 7.5 4 1 according to the invention
According to German Institute for Standardization Document No. DIN
68 753 published January, 1976, wood-fiber chipboards are divided into hard boards with a density of more than 800 kg/m3, medium-hard boards with a density of more than 350 kg/m3 to 800 kg/m3 and porous boards with a density of 230 to 350 kg/m3. Both in the wet process and in the dry process, up to 25 kg of resin and 1.5 to 20 kg of paraffin - per tonne of wood-fiber chipboard produced - are required for binding and hydrophobicizing. In the wet process predominantly in use today, the process water has to be circulated with a content of soluble material of up to 2.0-2.5% which is highly energy-intensive at a water temperature of up to 65 C. In addition, formaldehyde has to be added in a quantity of 0.02 to 0.2% to avoid troublesome staining of the wood-fiber chipboards by the highly concentrated circuit water.
At the present time, medium-hard wood-fiber chipboards are mainly marketed in semifinished form as medium-density fiberboards (MDFs) which are made with formaldehyde-containing condensation resins. However, through the continuous emission of carcinogenic formaldehyde vapors, in some cases for several years, products such as these are no longer wanted on ecological grounds. In the furniture industry, the situation is remedied by giving MDFs an additional coating to bring the emission of formaldehyde below the legally specified limits. In addition, although MDFs have better dimensional stability than natural wood at typical air humidity levels of 35 to DOCSTOR: 1111600\1 85%, it is still not good enough for certain applications. In addition, MDFs made with synthetic urea-formaldehyde binders are not suitable for use in high-humidity environments, particularly in water.
Wood/plastic composites are understood to be wood/plastic combinations which are obtained by treating wood with monomers or prepolymers. They are composite materials where the wood is impregnated with the liquid starting material and the monomer deposited in the wood is subsequently polymerized. Liquid monomers and solutions, for example methacrylate prepolymers or unsaturated polyesters dissolved in styrene, are preferably used in practice. The polymers primarily increase the strength of the wood, above all its hardness and its compressive strength. Finally, the aesthetic effect of natural wood not only is not impaired, it is actually enhanced in many cases. Despite these advantages, wood/plastic composites have hitherto been used to only a very limited extent for special applications, for example for parquet floors, sports equipment, kitchen utensils and tool handles.
In contrast to the pure impregnating process for making wood/plastic composites, the skinpreg process comprises surface impregnation with plastics which penetrate into the wood to different depths under light pressure without completely impregnating it.
Japanese Publication No. 64-045440, published February 17, 1989, describes isocyanate- or formaldehyde-based wood/foam compositions which contain sawdust as filler. The foam obtained, with a density of 0.35 g/cm3, possesses very high strength. The sawdust or wood powder is normally very finely size-reduced wood which is used as a filter aid, as a filler, as an additive for rough fiber coatings, etc. However, there is nothing in the literature reference in question to suggest that the foam is produced under high pressure. Solvents are used.
Japanese Publication No. 63-303703, published December 12, 1988, describes composites of fine vegetable fibers or vegetable particles, more particularly wood powder, and a urethane prepolymer which are contacted with water or steam before or after molding. A composite of this type has a DOCSTOR: 1111600\1 density of 0.29 g/cm3, a compressive strength of 5.3 kg/cm2 and a tensile strength of 3.4 kg/cm2. However, there is nothing in this literature reference which directly or indirectly suggests that the composites are produced at above-atmospheric pressure. Solvents are used.
SUMMARY OF THE INVENTION
Accordingly, the problem addressed by the present invention was to provide a new wood/plastic composite which would avoid the use of the formaldehyde-containing binders still absolutely essential in the MDFs mainly in use today and which would also have advantageous performance properties.
Accordingly, the present invention relates to a wood/plastic composite based on wood particles and/or cellulose-containing material and at least one binder, the binder being a carbon-dioxide-eliminating two-component polyurethane binder of a polyol, water and a polyisocyanate, characterized in that the binder is present 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, the composite being obtainable by reaction of the wood particles and/or the cellulose-containing material and the binder under a pressure of at least I
kp/cm2 and, more particularly, in the range from 50 to 100 kp/cm2.
In one aspect of the invention, the polyisocyanate is selected from the group consisting of: aliphatic, alicyclic, and aromatic di- and triisocyanates, and reaction products of monomeric diisocyanates with low molecular weight diols.
In view of the marked increase in the hardness of the wood, even in the interior of the composite, it is assumed that - depending on the ratio by weight of wood to binder, the size of the wood particles and the pressure applied - the wood is strengthened by the polyurethane at its surface or throughout, i.e.
the wood is present as a wood/plastic composite.
The wood/plastic composite has the following advantages over the prior art:
- In contrast to the known wood-based materials mentioned above, it can be made in any form, i.e. made-to-measure, for example in the form of boards, strips, cubes, squares, etc.
- It is suitable as a lightweight building material because it normally has a density of 0.40 to 0.65 g/cm3. It is therefore a substitute for light and medium flat-pressed boards or medium-hard wood-fiber chipboards, but without the attendant formaldehyde problems.
- It does not swell in water at room temperature, i.e. its increase in thickness after 24 hours in water at 20 C is <4 or 1% for thicknesses of 6 to 12 or >35 mm.
- In contrast to many of the wood-based materials and MDF boards still in use today, it is formaldehyde-free and flame-retardant.
- The composites are so elastic that 5 mm diameter timber screws can be screwed in without any splintering.
- The composites are also so dimensionally stable that threads can be cut for SpaxTM screws, i.e. screws with a broad thread.
- By virtue of the polyurethane present, the composites may readily be painted.
- Finally, the composites are characterized by their homogeneity, i.e. there is none of the otherwise usual layer formation; in particular, there is no inner layer and outer layer.
In one preferred embodiment of the wood/plastic composite according to the invention, soft woods, for example woods of the spruce, pine, fir, larch, birch, alder, horse chestnut, aspen, willow, poplar and lime, are used as the wood starting material. However, hard woods, for example beech, hawthorn, blackthorn, ash, maple, walnut, apple, pear, yew or oak, may also be used.
Mixtures of soft wood and hard wood may also be used.
In another preferred embodiment, vegetable fibers, for example cotton, jute, flax, hemp, bast, sisal, ramie, coconut fibers, yucca fibers or manila, or chemically modified fibers, such as the viscose fibers rayon and rayon staple, cuoxam fibers, acetate fibers, and paper and cellulose yarns, may be used as the cellulose-containing material in the composite according to the invention.
In another aspect of the present invention, a process is provided comprising the steps of:
a) mixing the particles with the polyol component;
b) adding the polyisocyanate in excess and water to yield a mixture and homogenizing said mixture;
c) introducing the mixture a closable pressure-tight mold optionally coated with release agents and the mixture is reacted under a pressure of at least 1 kg/cm3 and d) removing the molding from the mold.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The wood particles are present in the composite according to the invention in the form of wood chips and/or wood particles or as cellulose-containing material in particle sizes of at most 5 mm (thickness) x 20 mm (width) x 50 mm (length). A thickness range of 0.5 to 3 mm, a width range of 1 to 15 mm and a length range of 3 to 40 mm are preferred.
The moisture content of the wood particles or cellulose-containing material in the composite according to the invention is normally from 5 to 20%
by weight. If desired, it may 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 composites according to the invention may contain wires, cables, wire nets, rods or the like, for example for stabilization.
The two-component polyurethane binder used in the composite according to the invention consists of a reaction product of at least one polyol with at least one polyisocyanate.
The quantity in which the two reactants are used is always selected so that the polyisocyanate is present in excess, i.e. the equivalent ratio of NCO
groups to OH groups is 5:1 and preferably 2:1 to 1.2:1.
The polyisocyanate used is normally an aliphatic, alicyclic or aromatic diisocyanate or triisocyanate.
The polyisocyanates 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 (H12MDI), xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI), 4,4'-diphenyl dimethyl methane diisocyanate, di- and tetraalkyl diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, the isomers of tolylene diisocyanate (TDI), optionally in admixture, 1-methyl-2,4-diisocyanatocyclohexane, 1,6-diisocyanato-2,2,4-trimethyl hexane, 1,6-diisocyanato-2,4,4-trimethyl hexane, 1-isocyanato-methyl-3-isocyanato-1,5,5-trimethyl cyclohexane (IPDI), chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4,4'-diisocyanatophenyl perfluoroethane, tetramethoxybutane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-diisocyanate (HDI), dicyclohexyl-methane diisocyanate, cyclohexane-1,4-diisocyanate, ethylene diisocyanate, phthalic acid-bis-isocyanatoethyl ester. Other important diisocyanates are trimethyl hexamethylene diisocyanate, 1,4-diisocyanatobutane, 1,12-diisocyanatododecane and dimer fatty acid diisocyanate. Also of interest are partly masked polyisocyanates which enable self-crosslinking polyurethanes to be formed, for example dimeric tolylene diisocyanate. Finally, prepolymers, i.e. oligomers containing several isocyanate groups, may also be used.
Prepolymers are obtained using a large excess of monomeric polyisocyanate, for example in the presence of diols. Isocyanuratization products of HDI and biuretization products of HDI may also be used.
The diisocyanates or polyisocyanates preferably used are aromatic isocyanates, for example diphenylmethane diisocyanate, either in the form of the pure isomers or in the form of a mixture of the 2,4'- and 4,4'-isomers, or even carbodiimide-liquefied diphenylmethane diisocyanate (MDI) which is commercially available, for example, as Isonate 143 L. The so-called "crude MDI", i.e. the isomer/oligomer mixture of MDI commercially available, for example, as PAPI or Desmodur VK may also be used. In addition, so-called "quasi prepolymers", i.e. reaction products of MDI or tolylene diisocyanate (TDI) with low molecular weight diols, for example ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol or triethylene glycol, are also suitable.
Preferred diols and/or polyols for the binder are the liquid polyhydroxy compounds containing two or three hydroxyl groups per molecule, for example difunctional and/or trifunctional polypropylene glycols with molecular weights in the range from 200 to 6,000 and preferably in the range from 400 to 3,000. Statistical and/or block copolymers of ethylene oxide and propylene oxide may also be used. Another group of preferred polyether polyols are the polytetramethylene glycols which are obtained, for example, by acidic polymerization of tetrahydrofuran. The molecular weight of the polytetramethylene glycols is in the range from 200 to 6,000 and preferably in the range from 40 to 4,000.
Other suitable polyols are the liquid polyesters which may be obtained by condensation of di- and tricarboxylic acids, for example adipic acid, sebacic acid and glutaric acid, with low molecular weight diols and triols, for example ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, butane-1,4-diol, hexane-1,6-diol, glycerol or trimethylol propane.
Another group of polyols suitable for use in accordance with the invention are the polyesters based on s-caprolactone which are also known as "polycaprolactones".
However, polyester polyols of oleochemical origin may also be used.
Oleochemical polyester polyols may be obtained, for example, by complete ring opening of epoxidized triglycerides of an at least partly olefinically unsaturated fatty-acid-containing fatty mixture with one or more alcohols containing 1 to 12 carbon atoms and subsequent partial transesterification of the triglyceride derivatives to form alkyl ester polyols containing 1 to 12 carbon atoms in the alkyl group. Other suitable polyols are polycarbonate polyols and dimer diols (Henkel KGaA) and, in particular, castor oil and derivatives thereof. The hydroxyfunctional polybutadienes commercially obtainable, for example as "Poly-bd" may also be used as polyols for the composites according to the invention.
The present invention also relates to a process for producing the wood/plastic composites in which the wood particles and/or the cellulose-containing material are/is first mixed with the polyol component, the other component(s), more particularly the polyisocyanate in excess, is/are added to the resulting mixture, the mixture is homogenized and then introduced into a closable, pressure-tight mold optionally coated with release agents, the reaction mixture is reacted under a pressure of at least 1 kp/cm2 and the composite is removed or freed from the mold after cooling.
The mixing and reaction steps mentioned above are carried out at temperatures of 10 to 30 C and more particularly at room temperature (18 to 25 C). The pressure treatment in the process according to the invention is sourced by the reaction of the reaction mixture under the natural reaction pressure. If necessary, however, pressure may also be supplied from outside in known manner in the form of an inert gas or even steam.
In the process according to the invention, the reaction in the mold and hence the formation of the composite takes 5 to 30 minutes and preferably 10 to 20 minutes.
Closable pressure-tight molds are used in the process according to the invention.
There is normally no need to provide a release agent, more particularly in the form of a Teflon coating, between the pressure reactor and the composite. In certain cases, however, type 39-5001, 39-4487, 37-3200 and 36-3182 Acmos release agents for PUR are preferably used.
Finally, the present invention relates to the use of composites of the type mentioned above or produced by the process described above in the form of boards, strips, cubes, squares etc., more particularly in humid environments or outdoors. The present invention also relates to the use of the composites obtainable by the process described above as semi-finished products or for cladding purposes in the building industry. The composites according to the invention may also be used as a packaging material, as a floor covering, as stairs or as ornamental beams. These uses of the composites preferably involve the interior fitting-out of vehicles, more particularly motor vehicles, such as automobiles and camping vehicles, but also caravans, ships and aircraft. Altematively, the composites according to the invention may be used for decorative purposes outdoors or in the domestic and institutional sectors, more particularly in kitchens and bathrooms.
The invention is illustrated by the following non-limiting Examples.
EXAMPLES
Example 1:
A) Starting products a) Polyol component:
trifunctional polyether polyol based on glycerol, ethylene oxide and propylene oxide 83.8 glycerol 6.0 soya polyol modified with ethylene oxide 6.0 water 2.2 Tegostab B 8404 (Goldschmidt) 1.3 dibutyl tin dilaurate 0.7 b) Isocyanate component:
diphenylmethane-4,4'-diisocyanate 100 (crude MDI with a viscosity of 200 to 220 mPas) B) Production 1500 g of wood chips (pine) up to 4 cm in length are intensively mixed with 1,000 g of the polyol component of the foam system. After addition of 1,000 g of the isocyanate and remixing, the mixture was quickly introduced into a metal mold around 6.5 dm3 in size. The mold was immediately closed with a cover. After 30 minutes the foam-containing wood/plastic composite is removed from the mold.
The composite obtained has a density of 0.6 g/cm3 and a smooth surface and can be mechanically treated like wood, for example sawn, planed, sanded and drilled. Threads can also be cut into the material.
C) Application The composite obtained in accordance with the Production Example was compared for quality with a medium-density fiberboard (MDF board) which had been produced with formaldehyde-containing condensation resins and had exactly the same thickness. It was found above all that the composite according to the invention has significantly lower water absorption than the MDF board.
Table :
Water absorption and swelling of the composites according to the invention compared with MDF boards Density Water absorption Increase in thickness [g/cm] [%] [%]
After storage in water for 24 h Board thickness 6-12 >35 6-12 >35 [mm]
MDF board 0.72 20 16 8 5 Composite 0.60 14 7.5 4 1 according to the invention
Claims (29)
1. Wood-plastic composites comprising:
particles selected from the group consisting of wood particles, cellulose-containing material particles and mixtures thereof; and at least one binder, the binder being a carbon-dioxide-eliminating two-component polyurethane binder comprising a polyol, water and a polyisocyanate, the polyisocyanate selected from the group consisting of:
aliphatic, alicyclic and aromatic di- and triisocyanates, and reaction products of monomeric diisocyanates with low molecular weight diols;
wherein the binder is present in a quantity of 10 to 200 parts by weight, based on 100 parts by weight of the particles, the composite being obtainable by reaction of the particles and the binder under a pressure of at least about kp/cm2.
particles selected from the group consisting of wood particles, cellulose-containing material particles and mixtures thereof; and at least one binder, the binder being a carbon-dioxide-eliminating two-component polyurethane binder comprising a polyol, water and a polyisocyanate, the polyisocyanate selected from the group consisting of:
aliphatic, alicyclic and aromatic di- and triisocyanates, and reaction products of monomeric diisocyanates with low molecular weight diols;
wherein the binder is present in a quantity of 10 to 200 parts by weight, based on 100 parts by weight of the particles, the composite being obtainable by reaction of the particles and the binder under a pressure of at least about kp/cm2.
2. The composite of claim 1, wherein the pressure is from about 50 to about 100 kp/cm2.
3. Composites as claimed in claim 1, wherein soft wood is the wood starting material for the wood particles.
4. Composites as claimed in claim 3, wherein the soft wood is coniferous wood.
5. Composites as claimed in claim 1, wherein hard wood is the wood starting material for the wood particles.
6. Composites as claimed in claim 5, wherein the hard wood is selected from the group consisting of beech, oak and mixtures thereof.
7. Composites as claimed in claim 1, wherein the cellulose-containing material particles are selected from the group consisting of vegetable fibers, chemically modified fibers and mixtures thereof.
8. Composites as claimed in claim 7, wherein the vegetable fibers are selected from the group consisting of cotton, jute, flax, hemp and mixtures thereof.
9. Composites as claimed in claim 7, wherein the chemically modified fibers are rayon staple.
10. Composites as claimed in claim 1, wherein the wood particles are in the form of wood chips or wood powder with particle sizes of at most about 1 mm thickness × about 20 mm width × about 50 mm length.
11. Composites as claimed in claim 1, wherein the moisture content of the particles is between about 5 and about 2% by weight.
12. Composites as claimed in claim 1, further comprising strengtheners.
13. Composites as claimed in claim 12, wherein said strengthners are selected from the group consisting of wires, cables, wire nets, rods and mixtures thereof.
14. Composites as claimed in claim 1, wherein the polyisocyanate is selected from the group consisting of diisocyanates, triisocyanates and mixtures thereof.
15. Composites as claimed in claim 1, wherein the polyisocyanate is crude diphenylmethane-2,2'-diisocyanate.
16. Composites as claimed in claim 1, wherein the polyol is a diol/triol mixture of polyether and polyester polyols with water.
17. Composites as claimed in claim 1, wherein said composite has a density of about 0.40 g/cm3 to about 0.65 g/cm3.
18. A process for the production of the composites claimed in claim 1, comprising the steps of:
a) mixing the particles with the polyol component;
b) adding the polyisocyanate in excess and water to yield a mixture and homogenizing said mixture;
c) introducing the mixture a closable pressure-tight mold optionally coated with release agents and the mixture is reacted under a pressure of at least 1 kg/cm3; and d) removing the molding from the mold.
a) mixing the particles with the polyol component;
b) adding the polyisocyanate in excess and water to yield a mixture and homogenizing said mixture;
c) introducing the mixture a closable pressure-tight mold optionally coated with release agents and the mixture is reacted under a pressure of at least 1 kg/cm3; and d) removing the molding from the mold.
19. The process as claimed in claim 18, wherein steps (a) to (c) are carried out at temperatures of about 10 to about 30°C.
20. The process as claimed in claim 18, wherein steps (a) to (c) are carried out at temperatures of about 18 to about 25°C.
21. The process as claimed in claim 18, wherein the reaction of the mixture in step (c) takes place under the natural reaction pressure.
22. The process as claimed in claim 18, wherein the reaction time in step (c) is about 5 to about 30 minutes.
23. The process as claimed in claim 18, wherein the reaction time in step (c) is about 10 to about 20 minutes.
24. A process as claimed in claim 18, wherein a closable metal or plastic mold is used as the mold.
25. A process for exposing boards, strips, cubes and squares to humid or outdoor environments, wherein the improvement comprises molding composite boards, strips, cubes and squares with the process of claim 18.
26, Articles of manufacture, composite semi-finished products or composite cladding in the building industry, produced by the process claimed in claim 18.
27. Articles of manufacture, composite packaging material, floor covering, stairs or decorative beams, produced by the process claimed in claim 18.
28. A process for the interior fitting out of vehicles, more particularly motor vehicles, such as automobiles and camping vehicles but also caravans, ships and aircraft, wherein the improvement comprises fitting out said vehicles with composites produced by the process of claim 18.
29. Articles of manufacture, outdoor, kitchen and bathroom fittings, produced by the process of claim 19.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19526032.5 | 1995-07-17 | ||
| DE1995126032 DE19526032A1 (en) | 1995-07-17 | 1995-07-17 | Polymer wood moldings, their manufacture and use |
| PCT/EP1996/003007 WO1997003794A1 (en) | 1995-07-17 | 1996-07-10 | Polymer timber mouldings, their production and use |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2244005A1 CA2244005A1 (en) | 1997-02-06 |
| CA2244005C true CA2244005C (en) | 2008-03-18 |
Family
ID=7767053
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2244005 Expired - Fee Related CA2244005C (en) | 1995-07-17 | 1996-07-10 | Wood/plastic composites, their production and use |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0839083B1 (en) |
| JP (1) | JP3874203B2 (en) |
| CA (1) | CA2244005C (en) |
| DE (2) | DE19526032A1 (en) |
| WO (1) | WO1997003794A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102712099A (en) * | 2009-12-02 | 2012-10-03 | 安德列亚斯·米哈尼克尔 | Lightweight wood material board |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19756154C1 (en) * | 1997-12-17 | 1999-10-28 | Henkel Kgaa | Moldings of wood particles and PU binders, their preparation and use |
| CN1231632C (en) * | 1998-06-17 | 2005-12-14 | 尼勒纤维纸浆和纸公司 | Arundo donax pulp, paper products and particle board |
| DE10356767A1 (en) * | 2003-12-05 | 2005-07-07 | Henkel Kgaa | Sheets and moldings based on polyurethane binders |
| DE102004019529A1 (en) * | 2004-04-22 | 2005-11-10 | Henkel Kgaa | Process for the production of moldings based on polyurethane binders and cellulose-containing material |
| DE202006009318U1 (en) * | 2006-05-08 | 2007-09-20 | Dammers, Dirk | Plate, in particular panel for covering walls or ceilings or as a floor covering |
| DE102007019416A1 (en) * | 2006-07-19 | 2008-01-24 | Pfleiderer Holzwerkstoffe Gmbh & Co. Kg | Production of base material for light-weight chipboard or fibre-board, involves mixing cellulose-containing powder, e.g. corn flour, with a hardener such as poly-isocyanate and then foaming and hardening the mixture |
| DE102007015802A1 (en) | 2007-03-30 | 2008-10-02 | Henkel Ag & Co. Kgaa | Shaped body of cellulose-containing materials |
| DE102008026266A1 (en) | 2008-06-02 | 2009-12-03 | Henkel Ag & Co. Kgaa | Molded body from granules of olive stones and crosslinked adhesive comprising reactive adhesive made of two-component epoxy adhesive, two- or one-component-polyurethane-adhesive, useful as floor covering and soundproofing molded body |
| EP2349663B1 (en) | 2008-10-21 | 2016-12-14 | Uniboard Canada Inc. | Embossed monolayer particleboards and methods of preparation thereof |
| DE102010047254B4 (en) * | 2010-10-01 | 2017-02-02 | Doka Industrie Gmbh | Wood composite |
| PL244632B1 (en) * | 2020-03-10 | 2024-02-19 | Politechnika Gdanska | Method for production of polyurethane materials from reactive polyols and obtained from waste after processing wood or wood-like waste |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1228403B (en) * | 1965-11-15 | 1966-11-10 | Novopan Ges M B H & Co Deutsch | Method and device for the production of particle boards or bodies |
| DE1653174A1 (en) * | 1966-05-10 | 1970-06-04 | Novopan Gmbh | Process for the production of chipboard or chipboard |
| US3557263A (en) * | 1967-08-15 | 1971-01-19 | Alan A Marra | Process for the preparation of rigid composite wood products |
| DE1808349A1 (en) * | 1968-11-12 | 1970-05-21 | Remy Friedr Nfg | Process for the production of lightweight bodies or panels |
| JPS57182420A (en) * | 1981-05-07 | 1982-11-10 | Gunei Kagaku Kogyo Kk | Manufacturing light particle board |
| JPS57185136A (en) * | 1981-05-09 | 1982-11-15 | Gunei Kagaku Kogyo Kk | Manufacture of particle board |
| JPS59111832A (en) * | 1982-12-17 | 1984-06-28 | Mitsui Toatsu Chem Inc | Manufacture of particle board |
-
1995
- 1995-07-17 DE DE1995126032 patent/DE19526032A1/en not_active Ceased
-
1996
- 1996-07-10 EP EP96925696A patent/EP0839083B1/en not_active Expired - Lifetime
- 1996-07-10 WO PCT/EP1996/003007 patent/WO1997003794A1/en active IP Right Grant
- 1996-07-10 CA CA 2244005 patent/CA2244005C/en not_active Expired - Fee Related
- 1996-07-10 DE DE59606806T patent/DE59606806D1/en not_active Expired - Lifetime
- 1996-07-10 JP JP50624197A patent/JP3874203B2/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102712099A (en) * | 2009-12-02 | 2012-10-03 | 安德列亚斯·米哈尼克尔 | Lightweight wood material board |
| US20120270973A1 (en) * | 2009-12-02 | 2012-10-25 | Andreas Michanickl | Light derived timber product board |
| CN102712099B (en) * | 2009-12-02 | 2015-04-22 | 克劳诺普拉斯技术有限公司 | Lightweight wood material board and its manufacture method |
| US9044876B2 (en) * | 2009-12-02 | 2015-06-02 | Kronoplus Technical Ag | Light derived timber product board |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH11509149A (en) | 1999-08-17 |
| JP3874203B2 (en) | 2007-01-31 |
| EP0839083A1 (en) | 1998-05-06 |
| DE19526032A1 (en) | 1997-02-20 |
| CA2244005A1 (en) | 1997-02-06 |
| EP0839083B1 (en) | 2001-04-18 |
| WO1997003794A1 (en) | 1997-02-06 |
| DE59606806D1 (en) | 2001-05-23 |
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