JP5849219B2 - Method for suppressing discoloration of wooden decorative board - Google Patents

Description

  The present invention relates to a wooden decorative board used for building materials for houses such as floors, walls, doors and the like, and more particularly to a wooden decorative board in which a decorative veneer is attached to the surface of a wooden board containing a nitrogen compound.

  Conventionally, wood boards such as particle board and MDF (medium density fiber board) are widely used in addition to plywood as a base material for residential building materials such as floors, walls and doors.

  Wood boards such as particle board and MDF are manufactured by mixing wood elements and wood board adhesives to form a mat, and then hot pressing. As the wood board adhesive, a type cured with formaldehyde such as a urea resin adhesive, a melamine resin adhesive, and a phenol resin adhesive is used.

  And the wooden decorative board used for the building materials for houses, etc. is manufactured by sticking a decorative veneer on the surface of a wooden board with the adhesive for decorative veneer sticking.

  In recent years, the problem of the indoor environment has become apparent, and in particular, it has been demanded to suppress the amount of unreacted formaldehyde emitted from the wood board adhesive. For this reason, urea or nitrogen compounds such as hydrazine compounds such as succinic acid dihydrazide and adipic acid dihydrazide are added to the wood board as a formaldehyde catcher. Among these, urea is widely used because it is inexpensive and has a slow reaction with formaldehyde, so that the decrease in the adhesive strength of the wooden board is small (see Patent Documents 1 to 3).

  Moreover, the wooden board contains a nitrogen compound in addition to the catcher agent. For example, wood board adhesives such as urea resin adhesives and melamine resin adhesives contain nitrogen compounds. In addition, a fatty acid amide that is a nitrogen compound may be used as a wax for imparting water resistance to the wooden board. Furthermore, the wood, which is the raw material for the wooden board, contains protein as a nitrogen compound in a small amount.

  Therefore, many wooden decorative boards contain nitrogen compounds in the wooden boards.

JP 2001-79806 A JP 2001-164235 A JP 2005-179474 A

  However, if the wooden board contains a nitrogen compound, the nitrogen compound is hydrolyzed and ammonia is generated when the wooden decorative board is exposed to a hot and humid environment. In a high temperature and humidity environment, microorganisms such as molds and bacteria easily propagate, and these microorganisms decompose nitrogen compounds, so that the amount of ammonia generated increases at an accelerated rate. Urea is particularly susceptible to hydrolysis and microbial degradation due to its simple structure.

  Since the generated ammonia is basic, when it comes into contact with the decorative veneer on the surface of the wooden decorative board, it reacts with the tannin component in the decorative veneer and turns black.

  Furthermore, particle board and MDF have a large amount of adhesive for wood board because wood elements are smaller than plywood. Therefore, the amount of nitrogen compounds in the catcher agent also increases. In the case of plywood, since the adhesive is applied between the laminated single plates, it is considered that the plywood face layer under the decorative veneer on the surface serves as a buffer layer to alleviate discoloration of the decorative veneer. However, since the particle board and MDF do not have such a buffer layer, discoloration of the decorative veneer is likely to occur.

  In particular, when the decorative veneer is wood containing a large amount of tannin components, such discoloration becomes significant.

  Moreover, even when it does not contain a nitrogen compound as a catcher agent, as described above, it contains a nitrogen compound in the wood board adhesive or wax, or contains wood in the wood that is the raw material of the wood board. There is a case. In such a case, these nitrogen compounds are decomposed by microorganisms to generate ammonia, and the decorative veneer may turn black as in the case of containing the nitrogen compound as a catcher agent.

  The present invention has been made in view of the circumstances as described above, and provides a wooden decorative board capable of suppressing discoloration of a decorative veneer caused by ammonia generated by decomposition of a nitrogen compound contained in a wooden board. The challenge is to do.

  In order to solve the above problems, the wooden decorative board of the present invention is a wooden decorative board in which a decorative veneer is attached to the surface of a wooden board containing a nitrogen compound that generates ammonia by an adhesive for applying a decorative veneer. The decorative veneer adhesive contains at least one selected from weakly acidic chelating agents and antibacterial agents.

  In this woody decorative board, the decorative veneer adhesive preferably contains disodium ethylenediaminetetraacetate as a weakly acidic chelating agent.

  In this wood decorative board, the wood board preferably contains urea as a catcher agent as a nitrogen compound.

  In this wooden decorative board, the decorative veneer is preferably a single veneer of wood selected from oak, oak, walnut, and walnut.

  According to the wood decorative board of the present invention, discoloration of the decorative veneer due to ammonia generated by the decomposition of the nitrogen compound contained in the wood board can be suppressed.

It is a longitudinal cross-sectional view of the wooden decorative board of Example 1.

  The present invention is described in detail below.

  The wooden decorative board of the present invention contains a nitrogen compound that generates ammonia by its decomposition in the wooden board. The adhesive for adhering the decorative veneer for adhering the wood board and the decorative veneer includes at least one selected from weakly acidic chelating agents and antibacterial agents.

  By containing at least one selected from weakly acidic chelating agents and antibacterial agents in the veneer adhesive for decorative veneer, it is possible to suppress the growth of microorganisms such as fungi and bacteria that generate ammonia by decomposition of nitrogen compounds. . Therefore, discoloration of the decorative veneer due to ammonia can be suppressed.

  Chelating agents have a function of suppressing the growth of molds and bacteria. Specifically, it is said that the divalent metal ions bound to lipopolysaccharide, which is a component of bacterial cell wall, are removed by chelation to damage the outer membrane and inactivate the enzyme. . Antimicrobial agents also inhibit the growth of these microorganisms.

  When a weakly acidic chelating agent or antibacterial agent is added to the adhesive for adhering the decorative veneer that bonds the wooden veneer and the veneer veneer, many of these are present on the surface layer of the wooden veneer. Therefore, generation | occurrence | production of ammonia by decomposition | disassembly of the nitrogen compound in the surface layer vicinity of a wooden board can be suppressed. That is, since it is considered that the ammonia generated on the surface of the wooden board is greatly affected by the discoloration of the decorative veneer, it is effective to add a weakly acidic chelating agent or antibacterial agent to the adhesive for adhering the decorative veneer. . Moreover, by adding a weakly acidic chelating agent or antibacterial agent to the adhesive for adhering to the decorative veneer, it is possible to omit the trouble of applying and drying these in a separate step, and productivity is improved.

  In the woody decorative board of the present invention, it is necessary to use a weakly acidic chelating agent. When a strong acid is used as the chelating agent, the decorative veneer may be discolored by a so-called “acid burn phenomenon” or the coating equipment may be rusted. Further, if the chelating agent is acidic, ammonia can be neutralized. However, when a basic chelating agent is used, the decorative veneer may be discolored by the base.

  The discoloration of the decorative veneer is considered to be caused by alkali contamination caused by the tannin component contained in the decorative veneer and ammonia generated from the wooden board. Therefore, when the decorative veneer is a wood veneer containing a lot of tannin components such as oak, oak, walnut, and walnut, the discoloration suppression by the weakly acidic chelating agent and antibacterial agent contained in the wooden board is more remarkable. It becomes.

  In the present invention, as the wood board, for example, a material mainly composed of plant-based particles (small pieces) and plant fibers and hot-pressed into a plate shape with a certain area and thickness using a wood board adhesive is used. Can do.

  For example, a particle board can be used as the wood board composed mainly of plant-based particles.

  The particle board is a plant-based particle, for example, a softwood such as pine, cedar or cypress, or a broad-leaved tree such as lauan, capol, or poplar, or a kenaf core. What was made into (a piece of wood chip) can be used.

  Examples of the particle board include a single layer board, a three layer board, and a multilayer board. Of these, the three-layer board has a three-layer structure including a core layer containing coarse pieces as plant particles and a surface layer containing fine pieces as plant particles on both sides thereof. With this configuration, the surface layer becomes dense and the core layer becomes rough. Therefore, the smoothness of the surface can be increased, the overall density can be lowered, and the bending strength can be increased.

  The particle board can be manufactured, for example, by a conventionally known method. For example, the production of the particle board by the production line is performed through raw material fragmentation, small piece drying, addition of a wood board adhesive, mat forming (foaming), hot pressing, and finishing steps.

  For example, when the raw material is a log, a drum flaker can be used. When the raw material is a waste chip, a ring flaker can be used. In the case of a three-layer board, the coarse piece of the core layer has a thickness of about 0.5 mm and a length of 10 to 20 mm, for example. The fine particles on the surface layer are further finely pulverized.

  Small piece drying is a process necessary for suppressing puncture during hot pressing.

  Moreover, as a wood board comprised by vegetable fiber as a main component, fiber boards, such as MDF, can be used, for example.

  Since fiber boards such as MDF are dense with fibers as raw materials, bending strength, peel strength, and the like can be increased.

  The fiber board should be processed with heating and pressurizing wood fiber obtained by decomposing softwood such as pine, cedar and cypress or broad-leaved trees such as lauan, capol and poplar at high temperature and pressure. Can do.

  The fiber board can be manufactured by a conventionally known method. For example, MDF production using the MDF production line includes chip yard collection, chip cleaning, chip steaming, fiberization by refiner, addition of wood board adhesive, fiber drying with hot air, mat molding (forming) ), Hot pressing and finishing. In these processes, the chips and fibers are pumped by air, for example.

  As an adhesive for a wooden board used for a wooden board such as a particle board or a fiber board, a synthetic resin adhesive according to the type of the wooden board can be used. For example, a urea resin adhesive, a melamine resin adhesive, a urea / melamine cocondensation resin adhesive, a phenol resin adhesive, and the like can be used. Isocyanate resin adhesives such as MDI (diphenylmethane diisocyanate), TDI (tolylene diisocyanate), MDI prepolymer, and TDI prepolymer can also be used. These may be used in combination of two or more. Moreover, the curing catalyst according to the kind of synthetic resin adhesive can also be used together. For example, specific examples of the curing catalyst for urea resin adhesive, melamine resin adhesive, and urea-melamine cocondensation resin adhesive include ammonium sulfate and ammonium chloride.

  Of the wood board adhesives exemplified above, for example, urea resin adhesives, melamine resin adhesives, and urea / melamine cocondensation resin adhesives contain nitrogen compounds that generate ammonia. However, in the present invention, the decorative veneer adhesive contains at least one selected from a weakly acidic chelating agent and an antibacterial agent. Discoloration of a single plate can be suppressed.

  The mat mixture used for the mat for forming is prepared by mixing plant particles or plant fibers and an adhesive for wood board.

  The mat mixture is preferably mixed with a formaldehyde catcher agent. As the catcher agent, for example, urea or hydrazine compounds such as succinic dihydrazide and adipic dihydrazide can be used. These catcher agents can effectively capture and detoxify formaldehyde generated from the produced wood board.

  Of these, urea is preferable as the catcher agent. Since urea is inexpensive and has a slow reaction with formaldehyde, the decrease in the adhesive strength of the wooden board is small. However, since urea has a simple structure as a nitrogen compound, it easily undergoes hydrolysis or decomposition by microorganisms to easily generate ammonia. However, in the present invention, since the adhesive for applying a decorative veneer contains at least one selected from a weakly acidic chelating agent and an antibacterial agent, generation of ammonia due to decomposition of urea is suppressed, and Discoloration can be suppressed.

  Moreover, other additives can be mix | blended with the mixture for mats within the range which does not impair the effect of this invention. Examples of such additives include waxes such as fatty acid amides.

  The mixture for mats can be prepared, for example, by blending each of the above components and stirring and mixing in a blender.

  The mixture of the catcher agent into the mat mixture can be carried out, for example, by spraying in the form of an aqueous solution such as urea water together with the wood board adhesive while stirring the plant particles and plant fibers in a blender. In addition, it can be contained in the wooden board by a method of impregnating the wooden board after hot pressing in the form of a diluent.

  Although the compounding quantity of the adhesive agent for wooden boards in manufacture of particle board is not specifically limited, For example, in the case of 3 layer board, 10-15 mass parts of surface layers with respect to 100 mass parts of plant particles of a dry state, inner layer 5 The amount can be 10 parts by mass.

  The blending amount of the wood board adhesive in the production of fiber boards such as MDF is not particularly limited. For example, in the case of MDF, in consideration of plane tensile strength, bending strength, water resistance, etc., dried plant fibers It can be 5-25 mass parts with respect to 100 mass parts.

  After preparing the mixture for mats, the step of forming the mat can be performed, for example, by forming performed in the manufacture of particle board or MDF.

  For example, in the case of a three-layer particle board, a mat mixture for surface layer formation is deposited on a molding belt, then a mat mixture for core layer formation is deposited thereon, and then the mat for surface layer formation is used. A mat can be obtained by depositing the mixture thereon.

  The cake-like mat thus obtained is preferably pre-compressed at room temperature or the like. The quality of the wood board can be stabilized by pre-compressing in consideration of the shape of the target wood board before or after the deposition on the forming table, the steel belt or the like, and then hot pressing.

  After forming the mat in this way, it is hot-pressed into a plate shape. The hot pressure conditions (moisture content, temperature, pressing pressure, time, etc.) at this time can be factors that determine the characteristics of the wood board, such as surface condition, bending strength, wood board adhesive, formaldehyde emission amount, and the like.

  The surface temperature and pressure of the hot platen or steel belt during hot pressing depends on the type of adhesive for the wooden board, but in the case of particle board, for example, the surface temperature may be 180 to 220 ° C. and the pressure is 3 to 5 MPa. it can.

  Examples of the hot-pressure forming press method include a continuous press using a steel belt, a flat press such as a batch-type multi-stage press and a single-stage press. Among these, in consideration of productivity, continuous pressing is preferable.

  Thereafter, in the case of a particle board, the base particle board can be manufactured through finishing processes such as trimming and surface finishing with a sander.

  In the case of fiberboard, the board after hot press molding is once loaded and cured, and then as a finishing process, surface finishing is performed with a sander, and further cut to a desired dimension to produce a base MDF or the like. it can.

  A decorative veneer is attached to the surface of the wood board thus manufactured. For adhering the decorative veneer, for example, an adhesive for adhering a decorative veneer that is conventionally used for adhering the veneer veneer can be used. Specifically, for example, a vinyl acetate adhesive, a latex adhesive, a urea resin adhesive, or the like can be used.

  Moreover, in this invention, at least 1 sort (s) chosen from a weakly acidic chelating agent and an antibacterial agent is mix | blended with the adhesive agent for sticking a decorative veneer. In the present invention, “weakly acidic” means that the pH of the aqueous solution is in the range of 3 to 6.5, preferably 4 to 5.

  Examples of weakly acidic chelating agents include disodium ethylenediaminetetraacetate (EDTA · 2Na), disodium nitrilotriacetate (NTA · H · 2Na), and disodium hydroxyethylidene diphosphonate (HEDP · 2Na). Can be used.

  Of these, disodium ethylenediaminetetraacetate is preferred. Ethylenediaminetetraacetic acid dihydrogen disodium is soluble in water, the aqueous solution is weakly acidic, and the discoloration suppressing action is also good.

  As the antibacterial agent, inorganic and organic antibacterial agents can be used. The inorganic antibacterial agent is one in which metal ions such as silver, zinc and copper are supported on an inorganic carrier such as zeolite as an antibacterial component. Depending on the type of metal ion, it is called an antibacterial agent such as silver, zinc, silver-zinc, or copper.

  An organic antibacterial agent is an antibacterial agent containing an organic compound as an active ingredient. Examples of the organic compound include triazine derivatives, 1,2-benzisothiazolin-3-one and 2-methyl-4,5-trimethylene-4-isothiazolin-3-one, and dithio-2,2- Bis (benzmethylamide), tetramethylthiuram disulfide, dimethylphenylsulfamide and the like can be mentioned. These are referred to as triazine-based, imidazole / thiazole-based, disulfide-based, sulfamide-based (for example, dimethylphenylsulfamide-based) antibacterial agents depending on the type of organic compound.

  As for the compounding quantity of a weakly acidic chelating agent, 1-40 mass% in conversion of solid content is preferable with respect to the whole quantity of the adhesive agent for decorative veneer sticking. If the blending amount of the weakly acidic chelating agent or antibacterial agent is within this range, the discoloration of the decorative veneer can be more effectively suppressed, and the decrease in the adhesiveness of the adhesive for applying the decorative veneer can also be suppressed. Can do.

  As for the compounding quantity of an antibacterial agent, 0.1-5 mass% is preferable in conversion of solid content with respect to the whole quantity of the adhesive agent for decorative veneer sticking. If the blending amount of the antibacterial agent is within this range, the discoloration of the decorative veneer can be more effectively suppressed, and the deterioration of the adhesiveness of the adhesive for applying the decorative veneer and the adverse effect on the cost can also be suppressed. Can do.

  Weakly acidic chelating agents and antibacterial agents are uniformly added to the adhesive for decorative veneer paste by stirring and mixing the powdered or pasty powder together with the adhesive for adhering decorative veneer in a blender be able to. Or it can also add to the adhesive for decorative veneer sticking in the form of aqueous solution.

  As the decorative veneer, for example, a veneer such as oak, oak, walnut, walnut, beach or birch can be used. The discoloration of the decorative veneer is considered to be caused by alkali contamination caused by the tannin component contained in the decorative veneer and ammonia generated from the wooden board. Therefore, when the decorative veneer is a wood veneer containing a lot of tannin components such as oak, oak, walnut, and walnut, discoloration suppression by the weakly acidic chelating agent and antibacterial agent contained in the wooden board is more Become prominent.

  Joint processing can be applied to the surface of the decorative veneer. Moreover, you may stick a moisture-proof sheet | seat on the back surface on the opposite side to the decorative board of a wooden board in order to suppress water absorption or moisture absorption.

  After sticking the decorative veneer on the surface of the wooden board, the surface of the decorative veneer can be painted with a colorant to improve the design. As the colorant, for example, a wood material-based colored stain paint can be used. Also, urethane resin paint, acrylic resin paint, amino alkyd resin paint, polyester resin paint, and the like can be used. In consideration of safety in the working environment, influence on air pollution, and the like, it is preferable to use a water-based colored paint.

  The colorant can be applied with a roll coater. The roll coater supports a sponge roll that paints a paint-like colorant on a decorative veneer on the surface of a wooden board, a reverse roll that scrapes off excess colorant on the surface of the decorative veneer, and the lower surface of the wooden board. What is provided with the support roll to do can be used.

  As the sponge roll, a foamed synthetic resin, for example, a roll made of polyethylene foam, polyurethane foam or the like can be used.

  As the reverse roll, for example, a roll made of metal, urethane rubber, butyl rubber, ethylene propylene rubber or the like can be used.

  A wooden board is conveyed to a roll coating machine, and a coloring agent is supplied from a sponge roll rotating in the conveying direction to the surface of the decorative veneer on the upstream side while being applied to the surface of the decorative board while supporting the lower surface of the wooden board with a support roll. The colorant is supplied from the paint tank to the sponge roll, and the colorant is roller coated on the entire surface of the decorative veneer on the surface of the wooden board.

  And on the downstream side, the colorant is uniformly applied by scraping off the excess colorant by pressing a reverse roll that rotates in the direction opposite to the conveying direction against the surface of the veneer veneer coated with the colorant. Paint. Excess colorant is collected in a collection tank. Thereby, a coloring agent is filled in a ditch | groove, a conduit | pipe, etc., and a ditch | groove, a conduit | pipe etc. are colored.

  After the colorant is applied to the surface of the decorative veneer with a roll coater, the solvent is scattered and dried. Drying can be performed using, for example, a jet dryer or the like. For example, the drying can be performed under conditions of a drying temperature of 80 to 150 ° C. and a drying time of 30 seconds to 3 minutes.

  Thereafter, a clear paint can be applied to the entire surface of the veneer colored veneer in consideration of the surface protection and finish of the veneer veneer.

  The coating with the clear paint can be performed by, for example, multiple coatings such as undercoating, intermediate coating, and topcoating, and polishing (sanding) can be appropriately performed before and after these coatings.

  For the undercoat and intermediate coat, for example, a room temperature curable urethane resin paint, a heat curable melamine resin paint, a urea / melamine resin paint, a polyester resin paint, an acrylic resin paint, or an ultraviolet curable urethane resin paint, polyester A modified acrylic resin paint or the like can be used.

  For the top coating, for example, acrylic resin paint, aminoalkyd resin paint, vinyl resin paint, epoxy resin paint, polyurethane resin paint, and the like can be used.

  By applying the colorant and clear paint, it is possible to express the natural color of the decorative veneer and create a natural atmosphere of wood.

  The wooden decorative board of the present invention contains at least one selected from a weakly acidic chelating agent and an antibacterial agent in the adhesive for adhering a decorative veneer. Thereby, discoloration of the decorative veneer due to ammonia generated by decomposition of nitrogen compounds such as urea and other nitrogen compounds contained in the wood board as a catcher agent can be suppressed. Therefore, the wooden decorative board of the present invention can be suitably used for residential building materials such as floors, walls, doors and the like.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

<Example 1>
Fine particles as plant particles, MDI and melamine resin as adhesive for wood board, wax emulsion as water resistance, and urea as formaldehyde catcher. These were sufficiently stirred and mixed to prepare a mat mixture for surface layer formation.

  On the other hand, coarse particles as plant-based particles, MDI and melamine resin as an adhesive for wood board, wax emulsion as a water-resistant agent, and urea as a formaldehyde catcher agent. These were sufficiently stirred and mixed to prepare a mat mixture for forming a core layer.

  Three layer mats by depositing a matting mixture for surface layer formation on a belt, then depositing a matting mixture for core layer formation thereon, and further depositing a mat mixture for surface layer formation thereon Got.

  After pre-compressing this mat, it was hot-press molded under conditions of 180 ° C., 4 MPa, and 3 minutes, and after a finishing process, a particle board having a three-layer structure of 300 × 300 mm in length and width and 12 mm in thickness was obtained.

  After the particle board was cured, a moisture-proof sheet was attached to the back surface, and an oak decorative veneer was attached to the front surface. A vinyl acetate adhesive was used for attaching the moisture-proof sheet. For adhering the decorative veneer, a vinyl acetate adhesive was used as an adhesive for adhering the decorative veneer, and EDTA · 2Na as a chelating agent was blended. At this time, the blending amount of EDTA · 2Na as the chelating agent was set to 10% by mass in terms of the solid content of the chelating agent with respect to the vinyl acetate adhesive (the main vinyl acetate emulsion).

  Thereafter, a light colorant was applied to the surface of the decorative veneer with a roll coater. After drying the colorant, a clear paint was applied to the surface of the decorative veneer coated with the colorant by UV coating to obtain a woody decorative board.

  FIG. 1 shows a longitudinal sectional view thereof. This wooden decorative board 1 has a decorative veneer 4 attached to the surface of a particle board (wood board 2) with a vinyl acetate adhesive (adhesive 3 for applying a decorative veneer), and a vinyl acetate adhesive 7 on the back. Thus, the moisture-proof sheet 8 is attached. The decorative veneer adhesive 3 contains a chelating agent, EDTA · 2Na. The particle board (wood board 2) has a three-layer structure including a surface layer 2b on both sides and a core layer 2a therebetween. A colorant 5 is applied to the surface of the decorative veneer 4 and a coating film 6 made of a clear paint is provided thereon.

<Example 2>
In Example 1, the amount of EDTA · 2Na added was changed to 20% by mass, and a wooden decorative board was produced in the same manner as in Example 1 except that.

<Example 3>
In Example 1, the amount of EDTA · 2Na added was changed to 30% by mass, and a wooden decorative board was produced in the same manner as in Example 1 except that.

<Example 4>
In Example 1, a wooden decorative board was produced in the same manner as in Example 1 except that the catcher agent urea was not blended with the wooden board.

<Example 5>
In Example 1, the decorative veneer was changed to a beach, and a wooden veneer was manufactured in the same manner as in Example 1 except that.

<Example 6>
In Example 1, the chelating agent was changed to NTA · H · 2Na, and a wooden decorative board was produced in the same manner as in Example 1 except that.

<Example 7>
In Example 1, the chelating agent was changed to HEDP · 2Na, and a wooden decorative board was produced in the same manner as in Example 1 except that.

<Example 8>
In Example 1, an organic antibacterial agent (dimethylphenylsulfamide type) was blended in the adhesive for applying a decorative veneer instead of a chelating agent. The compounding amount of the organic antibacterial agent was 1% by mass with respect to the vinyl acetate adhesive (main component vinyl acetate emulsion) used as the adhesive for decorative veneer. Otherwise, a wood decorative board was produced in the same manner as in Example 1.

<Example 9>
In Example 1, an inorganic antibacterial agent (silver-zinc type) was blended in the adhesive for applying a decorative veneer instead of a chelating agent. The compounding amount of the inorganic antibacterial agent was 1% by mass with respect to the vinyl acetate adhesive (main component vinyl acetate emulsion) used as an adhesive for decorative veneer. Otherwise, a wood decorative board was produced in the same manner as in Example 1.

<Comparative Example 1>
In Example 1, a cheeking agent was not blended with the adhesive for applying a decorative veneer, and a wooden decorative board was produced in the same manner as in Example 1 except that.

<Comparative Example 2>
In Comparative Example 1, the decorative veneer was changed to a beach, and a wooden veneer was manufactured in the same manner as in Comparative Example 1 except that.

<Comparative Example 3>
In Comparative Example 1, a wooden decorative board was produced in the same manner as in Comparative Example 1 except that urea as a catcher agent was not blended with the wooden board.

<Comparative Example 4>
In Example 1, the chelating agent was changed to basic HEDTA · 3Na, and a wooden decorative board was produced in the same manner as in Example 1 except that.

The following test was done about the wood decorative board of the Example and the comparative example.
[Discoloration test]
Put a wet cloth on the surface of the cut sample of Example and Comparative Example, seal it with a plastic bag, and leave it in a constant temperature and humidity chamber at 40 ° C. and 90% RH for 2 weeks. Evaluation based on the criteria of.

(Evaluation criteria)
◎: Almost no change ○: Slightly discolored △: Discolored ×: Large discoloration

The results are shown in Table 1.

  From Table 1, in Examples 1-9, discoloration of the decorative veneer could be suppressed by adding a weakly acidic chelating agent or antibacterial agent to the adhesive for adhering the decorative veneer.

  As the weakly acidic chelating agent, EDTA · 2Na of Examples 1 to 5 was particularly effective.

  Moreover, in the kind of decorative veneer, when Examples 1-3 and Comparative Examples 1 and 2 were contrasted, when the tannin component was large like oak, the discoloration suppressing effect was remarkably exhibited.

  When Example 4 and Comparative Example 3 are compared, even if urea as a catcher agent is not added, the discoloration suppressing action of the decorative veneer can be achieved by adding a weakly acidic chelating agent to the adhesive for applying veneer veneer. Demonstrated. This is because nitrogen compounds derived from wood board adhesives and wax, or proteins contained in the wood of the wood board raw material, are decomposed by microorganisms to generate ammonia, which may cause discoloration of the decorative veneer. This is probably because of this.

  In Comparative Examples 1 to 3, in which a weakly acidic chelating agent or antibacterial agent was not blended with the wood board, the veneer veneer turned black due to exposure to a hot and humid environment. Further, in Comparative Example 4 using a basic chelating agent, the decorative veneer was similarly discolored. This is considered to be because the reaction with tannin could not be suppressed due to insufficient growth of microorganisms such as mold and bacteria and neutralization of ammonia by urea decomposition.

1 Wood veneer 2 Wood veneer 3 Adhesive for veneer veneer 4 Veneer veneer

Claims (4)

In method for inhibiting discoloration of the wood veneer was stuck to decorative veneer by decorative veneer bonding adhesive to the surface of the wood board containing urea as a nitrogen compound that generates ammonia, the decorative veneer bonding adhesive , method for inhibiting discoloration of the wood veneer, characterized in that it makes at least one selected from weakly acidic chelating agents and antimicrobials. The method for suppressing discoloration of a woody decorative board according to claim 1, wherein the adhesive for sticking a decorative veneer contains disodium ethylenediaminetetraacetate as the weakly acidic chelating agent. The wood board is a particle or plant fibers of the plant, the wood board adhesive, to claim 1 or 2, mixture of the urea, characterized in der Rukoto those thermocompression molded into a plate The method for suppressing discoloration of the woody decorative board as described. 4. The discoloration of the wooden decorative board according to claim 1, wherein the decorative veneer is a single veneer of wood selected from oak, oak, walnut, and walnut . 5. Suppression method .

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