JP4981874B2 - Method for reducing emissions and method for manufacturing wood products - Google Patents

Description

  The present invention relates to a method for reducing emissions from bonded wood products. The present invention also relates to a method for producing a laminated wood product, a product obtained by the method, and a low-release laminated wood product.

  The emissions of gaseous substances from wood products can have different sources. Solid wood may itself release substances such as terpenes and aldehydes (usually called volatile organic compounds (VOCs)) and some adhesive systems used to bond wood are adhesive Various substances can be released from the agent layer. Such emissions can be, for example, formaldehyde from phenolic or amino resin based adhesive systems, and isocyanates from emulsion polymer isocyanate (EPI) adhesive systems.

  There is an increasing interest in the release of materials, especially formaldehyde, in general, from building materials made from glued wood, such as laminated beams.

  When manufacturing laminated beams, a curable adhesive system is usually applied to the wood lamella, which is subsequently placed in the lamella assembly. The assembly is then pressed, usually under thermal or high frequency electromagnetic fields, to cure the adhesive system. After pressing this assembly, a planing process is usually performed on the surface next to the plane of the adhesive application to remove excess adhesive and any unevenness resulting from assembling the individual lamellae. The final laminated beam will have a freshly chopped wood surface as well as multiple adhesive layers exposed to open air. It has been found that this exposed adhesive layer can release a gaseous material, such as a significant amount of formaldehyde. In addition, freshly chopped wood surfaces can release gaseous substances such as terpenes and aldehydes.

  WO02 / 072323A1 and WO02 / 072324A1 disclose methods for reducing formaldehyde emissions from laminated products, but do not deal with emissions from exposed adhesive layers.

  It is an object of the present invention to provide a method for reducing emissions from bonded wood products and to provide a method for producing wood products having a low emission of gaseous substances. It is a further object of the present invention to provide a laminated wood product obtained by the method and a wood product having a low release of aldehyde or terpene, and finally a liquid treatment composition for use in these methods. .

  Wood is used herein to mean any type of material derived from wood. This includes both solid wood and materials made from, for example, wood fibers, particles, and chips.

  Surprisingly, according to the present invention, at least one of the surfaces having the exposed adhesive layer is hung, and then the at least one hung surface is reactive to one or more gaseous substances. It is possible to achieve the above object by a method for reducing emissions of one or more gaseous substances from an assembly of at least two pieces of wood bonded together, characterized by being treated with the above treatment substances. all right. The piece of wood is preferably a wood lamella. It is preferable that at least one of the gas substances is released from the exposed adhesive layer. In addition, it is preferable that at least one of the gas substances is released from the surface of the solid wood.

  Also, according to the present invention, surprisingly, the step of applying an adhesive system to one or more wood lamellas, the step of assembling two or more wood lamellas into an assembly, the step of pressing the assembly, exposed Staking at least one of the surfaces of the assembly having the adhesive layer, and reacting the one or more squeezed surfaces to one or more gaseous substances released from the at least one squeezed surface. It has been found that the above-mentioned object can be achieved by a method for producing a wood product characterized by including a step of treatment by applying one or more treatment substances having sex. The wood product is preferably a laminated wood product.

  “Reactive to one or more gaseous substances” means that the total emissions can be reduced by at least 5%, preferably at least 10%, more preferably at least 25%, most preferably at least 50%.

  The present invention is not limited to the use of any special type of adhesive system. Adhesive systems suitable for use in the method of the present invention are curable adhesive systems such as amino resin based adhesive systems, phenolic resin based adhesive systems and isocyanate based adhesive systems. Examples of amino resin based adhesive systems are melamine-formaldehyde based adhesive systems, melamine-urea-formaldehyde based adhesive systems, and urea-formaldehyde based adhesive systems. Examples of phenolic resin based adhesive systems are phenol-formaldehyde based adhesive systems, phenol-resorcinol-formaldehyde based adhesive systems and resorcinol-formaldehyde based adhesive systems. Examples of isocyanate based adhesive systems are polyurethane based adhesive systems and emulsion polymer isocyanate (EPI) based adhesive systems. This adhesive is preferably cured during or during the pressing process. However, non-curable adhesive systems such as adhesive systems based on vinyl ester polymers can also be used. Examples of adhesive systems based on vinyl esters are adhesive systems based on polyvinyl acetate, adhesive systems based on ethylene-vinyl acetate and adhesive systems based on polyvinyl propionate.

  The application of the adhesive to the lamella and all lamella assemblies is preferably performed in a separate process. It is also preferred that each lamella is applied in an adhesive system at different times and the assembly is gradually attached with the lamella most recently applied in the adhesive system.

  According to the method of the present invention, the cutting is preferably performed on two sides of the assembly having the exposed adhesive layer.

  It is preferred that the one or more treatment substances are reactive with the one or more gas substances released from the adhesive layer. It is also preferred that the one or more treatment substances are reactive to one or more gas substances released from the solid wood.

  The gas substances of the present invention may be of different types. One group of substances that may be released from the adhesive layer are aldehydes such as acetaldehyde, formaldehyde, glutaraldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, hexanal and furfural. Another group of materials that may be released from the adhesive layer are isocyanates such as methyl isocyanate, hexamethylene-1,6-diisocyanate, 4,4-methylene diphenyl isocyanate, toluene 2,4-diisocyanate, and isophorone diisocyanate. It is. Gaseous substances that can be released from solid wood are, for example, terpenes such as monoterpenes α-pinene and β-pinene, 3-carene and limonene as well as aldehydes such as acetaldehyde, propanal, butanal. , Pentanal, hexanal and benzaldehyde.

  In the first aspect of the method of the present invention, it is preferred that the kind of gaseous substance is an aldehyde, preferably formaldehyde. At that time, it is preferred that the one or more treatment substances are reactive to aldehydes, preferably formaldehyde. The one or more treatment substances preferably contain an amino group or an amide group. Examples of these substances are guanamine, urea, thiourea, biuret, semicarbazide, succinamide, hexamethylenediamine, ethanolamine, ethyleneamine, protein, peptide. Hydrazides and ammonium salts, such as ammonium carbonate, monoammonium phosphate and diammonium phosphate, ammonium sulfide, and ammonium sulfite. Other sulfites such as potassium sulfite or sodium sulfite may also be used. Also, proteins such as glutenin, casein, and zein, or protein-containing materials such as flour, whey and protein-containing starch may be used. Hydroxy group-containing materials such as alcohol and polyvinyl alcohol may also be used as treatment materials. Carbohydrates such as monosaccharides, disaccharides and polysaccharides can also be used. An amino group-containing substance or an amide group-containing substance is preferably used. Most preferably, the at least one treatment substance is urea or a urea derivative.

  In the second aspect of the method of the present invention, the one kind of gas substance is preferably an isocyanate. At that time, it is preferred that the one or more treatment substances are reactive to the isocyanate. Suitable treating substances include substances containing amino or amide groups, examples of which are guanamine, urea, thiourea, biuret, semicarbazide, succinamide, hexamethylenediamine, ethanolamine, ethyleneamine, protein, peptide, Hydrazides and ammonium salts such as ammonium carbonate, ammonium sulfide, and ammonium sulfite. Hydroxy group-containing materials such as alcohol and polyvinyl alcohol may also be used as treatment materials. Carbohydrates such as monosaccharides, disaccharides and polysaccharides can also be used. A further suitable treatment material is water. The at least one treatment substance is preferably a substance containing an amino group or an amide group.

  In a further aspect of the method of the invention, it is preferred that the gaseous substance belongs to the group of terpenes. The one or more treatment materials are then preferably reactive to terpenes. This treatment material preferably belongs to the group of unsaturated aldehydes such as alkenals and alkadienals, or hydroxy group-containing materials such as alcohols and polyvinyl alcohols. This at least one treatment substance is preferably an unsaturated aldehyde, for example pentenal, hexenal or octenal.

  The treatment material may be used in the method of the present invention as a single component. However, it is preferred that the one or more treatment substances are components of the treatment composition. The treatment composition of the method of the present invention is preferably a liquid and preferably comprises a solvent for the one or more treatment materials. Suitable solvents are water, alcohols such as methanol, ethanol and glycol, and esters such as butyl diglycol acetate. It is preferred that water is used as the solvent. Mixtures of solvents may also be used. This choice of solvent can in some cases affect fiber swelling at the wood surface. Preferred solvents in these cases include alcohol, glycol, or glycolic acid. The treatment composition is suitably one or more from about 0.01% to about 99%, preferably from about 1% to about 80%, most preferably from about 10% to about 60% by weight. Of processing substances. Suitably the treatment composition comprises an agent for improving the film-forming properties of the composition when applied to a surface, preferably a wood surface. The treatment composition preferably comprises a polymer as a film-forming modifier, preferably in the form of a polymer dispersion. The polymer dispersion is preferably a polyvinyl ester, such as polyvinyl acetate or a derivative thereof, such as a dispersion of polyvinyl alcohol, or a polyacrylate dispersion, most preferably a polyvinyl alcohol dispersion. The dry content of the film-forming modifier in the treatment composition is suitably from about 0.01% to about 50%, preferably from about 0.02% to about 10%, most preferably about 0%. 0.03% to about 2% by weight.

  In one preferred embodiment, the treatment composition comprises from about 0.01% to about 100%, preferably from about 1% to about 80%, most preferably from about 10% to about 60% by weight. Up to urea or urea derivatives. In a second preferred embodiment, the treatment composition comprises from about 0.01% to about 100%, preferably from about 1% to about 80%, most preferably from about 10% to about 60%. Contains up to% alcohol and ammonia reaction products. In a third preferred embodiment, the treatment composition comprises from about 0.01% to about 100%, preferably from about 1% to about 80%, most preferably from about 10% to about 60%. Contains up to% unsaturated aldehydes.

  Suitable methods for treatment with the one or more treatment substances are, for example, spraying, roll coating, curtain coating, and coating with an impregnated pad or a damp cloth. The treatment with the treatment substance is preferably performed by spraying or roll coating. When two surfaces of the assembly are treated with one or more treatment materials, it is preferred that both surfaces are treated simultaneously. In this case, the upper surface is preferably treated by spraying and the lower surface is treated by roll coating. It is also possible to apply the one or more treatment substances in the form of strands, which is to the extent of more than 50%, preferably to the extent of more than 80%, most preferably to the extent of substantially 100%. Cover the adhesive layer.

  It is also possible to treat the surface of the assembly that does not have an exposed adhesive layer with the one or more treatment materials.

The one or more treatment materials are preferably applied in an amount that provides the desired effect, the amount depending on which treatment material is used. When one treatment composition is used, this treatment composition is suitably from about 0.1 g / m ² to about 100 g / m ² , preferably from about 1 g / m ² to about 50 g / m ² , most Preferably it is applied in an amount from about 5 g / m ² to about 30 g / m ² .

  Also, a drying step may be added after the one or more treatment substances are applied. Suitable drying means are, for example, infrared irradiation, warm air blowing, and microwave heating.

  The treatment with the one or more treatment substances is preferably performed immediately after the kneading, but also at a later stage after the kneading, preferably up to about 30 days after the kneading, preferably the kneading. From about 0.1 seconds to about 5 days after hanging, more preferably from about 0.5 seconds to about 1 hour after cutting, most preferably from about 0.5 to about 60 seconds after cutting. Can be done by.

  In a preferred embodiment of the invention, the laminated beam comprises a plurality of adhesive systems based on melamine-formaldehyde, adhesive systems based on melamine-urea-formaldehyde, or adhesive systems based on phenol-resorcinol-formaldehyde. Manufactured by applying to wood lamellae. This lamella is bonded to the assembly and pressed at an elevated temperature. The resulting beam is subsequently draped on both sides with a lengthwise exposed adhesive layer, which are then treated by application of a liquid treatment composition as described above.

  The laminated wood product of the present invention is preferably a laminated beam, which also includes other laminated structural materials such as laminated veneer lumbar.

  It has also been found that it is possible to obtain products having less formaldehyde emissions than similar products made by bonding with formaldehyde-based resin-based adhesive systems. The invention therefore also relates to the product obtained by the method of the invention as described above.

  The laminated wood product obtained by the method of the present invention preferably has a formaldehyde emission of not more than about 0.5 mg / l, preferably not more than about 0.3 mg / l, in accordance with the standard for structurally bonded wood, JAS MAFF Addendum No992. It is.

  The invention further relates to a laminated wood product comprising at least two lamellae bonded with a formaldehyde based resin based adhesive system. This laminated wood product has a formaldehyde emission of about 0.5 mg / l or less, preferably about 0.3 mg / l or less, in accordance with the standard for structurally bonded wood, JAS MAFF Addendum No992.

  Furthermore, the present invention relates to a laminated wood product comprising at least two lamellae joined by an adhesive layer, the laminated wood product being a surface of a product having at least one exposed adhesive layer. Close to the surface, contains substances (other than water) reactive to aldehydes, isocyanates or terpenes.

  Each laminated wood product of the present invention is preferably a laminated beam, which also includes other laminated structural materials such as laminated veneer lumbar.

  The invention will now be further described with reference to the following examples, which should not be construed as limiting the scope of the invention.

  A low formaldehyde release adhesive system comprising melamine-urea-formaldehyde (MUF) resin and conventional acid curing agent as well as melamine-urea-formaldehyde (MUF) resin, phenol-resorcinol-formaldehyde (PRF) resin and acid was tested. .

For each adhesive system, the release from the bonded structure was tested according to JAS MAFF992. Two sets of bonded structures were produced for each adhesive system. Five spruce lamellae (135 × 150 × 29 mm) were assembled and glued together with a mixture of resin and hardener applied in an amount of 400 g / m ² . After pressing and conditioning (20 ° C. at 65% relative humidity), two pieces of 75 × 150 × 135 mm were cut. The butt end (opposite to the fiber direction) was sealed with aluminum foil, leaving two 75 x 150 mm surfaces with exposed adhesive layers. This bonded structure is then sandwiched on two sides with an exposed adhesive layer, one of the structures for each adhesive system containing 40% by weight urea and 0.07% by weight polyvinyl alcohol. It was treated by spraying both hung surfaces with the aqueous composition, while leaving another structure untreated. Each piece was placed in a 40 liter chamber with a beaker containing water as a sampler. The release of formaldehyde, expressed as mg / l in a sample of water, was measured for all structures according to the test method and is shown in Table 1.

  It is concluded that the present invention results in a significant reduction in formaldehyde emissions for both conventional MUF resin based adhesive systems and low release MUF / PRF resin based adhesive systems.

  The same melamine-urea-formaldehyde (MUF) and conventional acid hardener as in Example 1 were tested.

The release of formaldehyde from the bonded structure was tested according to an internal test method which is a modified JAS MAFF992 using smaller specimens. Five sprout lamellae (5 × 150 × 150 mm) were assembled and glued together with a mixture of resin and hardener applied in an amount of 380 g / m ² . After pressing and conditioning (20 ° C. with 65% relative humidity), two 75 × 25 × 10 mm pieces were cut. The butt end (opposite to the fiber direction) was sealed with aluminum foil, leaving two 75 x 25 mm surfaces with an exposed adhesive layer. Two pieces are sandwiched on two sides with an exposed adhesive layer, after which one of the pieces is both in an aqueous composition containing 40% by weight urea and 0.07% by weight polyvinyl alcohol. The treatment was carried out by spraying on a kneaded surface. Each piece was placed in a 4 liter chamber with a beaker containing water as a sampler. The release of formaldehyde, expressed as mg / l in a sample of water, was measured for both structures after 2 days and 30 days, respectively, and is shown in Table 2.

  It is concluded that the method of the present invention produces a long lasting effect on formaldehyde emission.

Claims (19)

At least two of the woods bonded together, characterized in that at least one of the surfaces with the exposed adhesive layer is planed and subsequently at least one planed side is treated with polyvinyl alcohol A method for reducing emissions of one or more gaseous substances from a piece assembly.   The method of claim 1, wherein at least one of the gaseous substances is released from the exposed adhesive layer.   The method of claim 1, wherein at least one of the gaseous substances is released from a solid wood surface. (A)-applying an adhesive system to one or more wood lamellae;
(B)-assembling two or more wood lamellae into an assembly;
(C)-pressing the assembly;
(D)-cutting at least one of the surfaces of the assembly having the exposed adhesive layer; and (f)-treating one or more of the hooked surfaces by application of polyvinyl alcohol. A method for producing a laminated wood product, comprising:   The method according to any one of claims 1 to 4, wherein the one kind of gas substance is an aldehyde.   6. The method according to any one of claims 1 to 5, wherein the one gas substance is formaldehyde.   5. A method according to any one of claims 1 to 4, wherein the one gas substance is an isocyanate.   The method according to any one of claims 1 to 4, wherein the one kind of gas substance is a terpene. 9. A method according to any one of claims 1 to 8 , wherein polyvinyl alcohol is a component of the treatment composition , the treatment composition comprising one or more further treatment substances . Wherein, one unsaturated aldehydes further processing materials, the method of claim 9. 11. A method according to claim 9 or 10 , wherein one of the further treatment substances is urea or a urea derivative. 12. A process according to any one of claims 9 to 11, wherein one of the further treatment substances is a reaction product of alcohol and ammonia. 13. A method according to any one of claims 9 to 12, wherein the treatment composition comprises from about 1% to about 80% by weight polyvinyl alcohol and / or the one or more further treatment substances. 14. A method according to any one of claims 9 to 13, wherein the treatment composition comprises from about 0.02% to about 10% by weight polyvinyl alcohol . 15. A method according to any one of claims 9 to 14, wherein the treatment composition comprises a polyvinyl alcohol dispersion.   The method according to any one of claims 4 to 15, wherein the laminated wood product is a laminated beam.   Laminated wood product obtained by the method according to any one of claims 4 to 16. In accordance with JAS MAFF Addendum No 992, a standard for structurally bonded wood, including at least two lamellae bonded in a formaldehyde-based resin-based adhesive system having a formaldehyde emission of about 0.5 mg / l or less 18. Laminated wood product according to claim 17, characterized in that 19. A laminated wood product according to claim 17 or 18 , which is a laminated beam.