JP2005199638A - Modified wood and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which enables production of a modified wood excellent in dimensional stability, water resistance, light resistance and anti-rotting properties and also holding characteristics as a wood by solving the problems with a conventional modified wood. <P>SOLUTION: This modified wood production method comprises the steps of adding an apatite-coated photocatalyst to a resinous liquid containing, as main components, a monomer, oligomer and prepolymer of synthetic polymers such as a vinyl resin, e.g. an acrylic oligomer and the like, uniformly stirring the mixture to obtain an impregnating liquid in which the photocatalyst is completely dispersed in the resinous liquid, impregnating a wood with the impregnating liquid by a pressure reduction/pressurizing method, polymerizing to solidify, and then coating the wood surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to modified wood and a method for producing the same. More specifically, the present invention relates to a so-called WPC (wood plastic combination) in which various properties of wood are improved by impregnating a surface layer of wood with an impregnating solution containing a resin or the like as a main component and then polymerizing and fixing, and a method for producing the same.

  Painting is generally used as a method for protecting wood, but this is protection of only the surface layer. As a method for protecting the inner layer, a method of impregnating and injecting a preservative mainly composed of heavy metal ions, a method of impregnating and injecting a synthetic resin solution to polymerize and harden the inside of the wood, and a direct reaction with the wood part (cellulose). There are methods such as addition polymerization and chemical modification.

  In the chemical injection process, wood is discolored due to the unique color of heavy metal ions as the main component, and environmental problems such as long-term chemical leaching have been pointed out.

  On the other hand, a wood plastic composite in which wood is impregnated with an impregnating solution made of a resin such as the vinyl monomer is called WPC, and it is widely known that performances such as dimensional stability and water resistance are remarkably improved. On the other hand, the improvement in light resistance due to ultraviolet rays or the like is small, and it is difficult to use it as an exterior building material in a state of being impregnated, cured and fixed.

  In order to solve this problem, an ultraviolet absorber or a heat stabilizer may be added. However, a polymerization initiator for initiating graft polymerization is added to the impregnating solution, and there is a problem that polymerization inhibition is caused by adding an ultraviolet absorber or the like.

  In addition, there is a method of applying a light-resistant paint to the modified wood, but it is necessary to increase the thickness of the coating film. In the case where the modified wood comes in direct contact with the outside after peeling, the modified wood is weathered and deteriorated due to the influence of ultraviolet rays.

  Therefore, the present inventors added a photocatalyst such as titanium dioxide to a resin liquid mainly composed of monomers, oligomers, and prepolymers and injected it into the resin liquid wood to cause a polymerization reaction. Due to its strength, there is a problem that if it is mixed with a base material made of an organic material such as paint or resin, the base material itself is broken and the deterioration proceeds rapidly.

  The object of the present invention is to solve the above-mentioned conventional problems, and to stabilize the wooden member without causing problems of polymerization inhibition or discoloration deterioration due to addition of an ultraviolet absorber or the like, or deterioration of the substrate itself due to the oxidizing power of the photocatalyst An object of the present invention is to provide a modified wood capable of ensuring the light resistance essential as a building material for exterior use, and a method for producing the same.

  In order to achieve the above object, as a result of earnest research, the present inventors added an apatite-coated photocatalyst obtained by coating a photocatalyst such as titanium dioxide with apatite to a resin liquid mainly composed of monomers, oligomers and prepolymers. The impregnating solution is produced by uniformly stirring and impregnating the impregnating solution into the wood by the reduced pressure method, followed by polymerization and fixing, providing excellent weather resistance and decay resistance, as well as conventional modified wood such as texture. The present inventors have found that modified wood having the characteristics can be obtained, and have reached the present invention.

  That is, the modified wood according to claim 1 of the present invention is characterized in that an impregnating solution obtained by adding a photocatalyst coated with apatite to a resin solution for WPC production and uniformly stirring is impregnated into the wood and polymerized and fixed. .

  The method for producing modified wood according to claim 2 is characterized in that dried wood is placed under reduced pressure, and then a photocatalyst coated with apatite is added to a resin liquid mainly composed of monomers, oligomers, and prepolymers, and this is uniformly performed. Immerse the wood in an impregnating solution that is stirred in a vacuum and further pressurize it to impregnate the wood with the impregnating solution, then polymerize the impregnated resin solution to cure and fix the resin to the wood surface layer. It is characterized by making it.

  The method for producing a modified wood according to claim 3 is characterized in that the photocatalyst is titanium dioxide and is added in an amount of 1 to 20% by weight with respect to 100% by weight of the impregnating liquid.

As the photocatalyst, for example, zirconium oxide (ZrO ₂ ), zinc oxide (ZnO), potassium tantalate (KTaO ₃ ), strontium titanate (SrTiO ₃ ) and the like can be used in addition to titanium dioxide (TiO ₂ ). .

  Examples of the synthetic polymer include vinyl monomers such as styrene (St), methyl methacrylate (MMA), vinyl acetate (VAc), and acrylonitrile (AN), acrylic oligomers, polyethylene terephthalate (PET), and polybutylene. Polyester such as terephthalate (PBT) or ultra high molecular polyethylene (UPE), polyurethane, phenolic resin, urea resin, polyethylene glycol, or the like can be used.

  The synthetic resin containing the apatite-coated photocatalyst can be impregnated on the surface by the above production method. The resulting modified wood can be used as building materials for outdoor use, and the synthetic resin layer covering the wood surface is removed to expose the woody part and the photocatalyst is exposed to the outside air, so that it has an adsorption decomposition action and dimensional stability. It can also be used as a building material.

  Further, the modified wood obtained by the present invention has improved stain resistance, decay resistance, and weather resistance in addition to the performance of the modified wood obtained by the conventional treatment. Durability is further improved by the extremely simple task of painting the material.

  Further, since the energy of ultraviolet rays is converted into heat in a general organic ultraviolet absorber, it deteriorates with discoloration, but the photocatalyst suppresses discoloration because it converts ultraviolet energy into electric energy. In addition, although the substance adsorbed by this electric energy is oxidatively decomposed and rendered harmless, decomposition products such as water and carbon dioxide are released into the atmosphere, so that the adsorption performance is restored and super light resistance is exhibited.

  In addition, since protein is also decomposed, it is possible to obtain an antiseptic and antifungal effect without adding a preservative, and because of the superhydrophilicity of the photocatalyst, nitrogen oxides and wood adhering to the wood surface and cracks generated on the wood Wash away deterioration-promoting substances such as decaying fungi and dirt.

  In addition, light resistance has been obtained by thickening the coating film so far, but even if the coating film is thinned by forming a layer with excellent light resistance on the wood part, light resistance performance higher than conventional can be obtained, Simplification of painting can reduce the number of processes and work time.

Hereinafter, a method for producing the modified wood will be described.
First, the wood used for the impregnation treatment is dried until the moisture content becomes 8 to 20%. Cut the wood into the desired dimensions and shape. Although the kind of wood is not specifically limited, For example, they are hinoki, sawara, hiba, cedar, red pine, beech, mizunara, firewood, tammo, hoo.

  Next, the wood is put in a heat-resistant and pressure-resistant container such as an autoclave, and the pressure is reduced. The wood is left under a reduced pressure for a predetermined time to remove air contained in the wood. Then, an impregnating liquid (a liquid obtained by adding a photocatalyst coated with apatite such as titanium dioxide to a resin liquid mainly composed of monomers, oligomers, and prepolymers and uniformly stirring the liquid) is poured into the container, Immerse in this solution and let stand for a predetermined time. Thereafter, the wood is impregnated with the impregnating liquid by standing for a predetermined time under normal pressure or under pressure.

  A photocatalyst coated with apatite is added to the impregnation liquid. When the added amount of the photocatalyst is increased, the viscosity increases and the permeability of the impregnating liquid to the wood decreases. When the added amount is small, sufficient adsorption decomposition performance cannot be obtained. 1 to 20% by weight. Since titanium dioxide has a strong oxidizing power, when using apatite-coated titanium dioxide, the amount of splash added should be 2 to 5% by weight. In addition, when the apatite-coated titanium dioxide has a large particle size, it is difficult for the particles to penetrate into the voids of the wood, and a rough feeling is generated on the treated wood surface.

  In addition to the apatite-coated photocatalyst, for example, a stabilizer such as a heat stabilizer, an antioxidant, an ultraviolet absorber, and an ultraviolet stabilizer, a flame retardant, an antifoaming agent, a surfactant, and the like are added to the impregnating liquid. However, it is necessary to sufficiently stir with a stirrer or the like so that they are uniformly dispersed in the impregnation liquid and so that no precipitate is formed in the impregnation liquid to which they are added.

  Next, when the amount of the impregnation liquid impregnated into the wood reaches a desired value, the surplus impregnation liquid is recovered and then polymerized by radiation, light, heat, water vapor or the like to be cured and fixed to the wood surface layer. The polymerization method may be any of known methods such as radiation irradiation, ultraviolet irradiation, and heating.

  The impregnating solution is obtained by adding 4% by weight of apatite-coated titanium dioxide to 100% by weight of a resin solution mainly composed of an acrylic oligomer and stirring the solution.

First, a sufficiently dried wood block piece (60 × 25 × 90 mm) is introduced into a pressure-resistant and heat-resistant container and left under a reduced pressure of 30 mmHg for 30 minutes, and then the impregnating solution is injected and left standing in an immersed state for 30 minutes. . Thereafter, the container is left to stand for 60 minutes under a pressure of 7 kgf / cm ² .
In the subsequent curing step, treatment was performed by combining curing with ultraviolet light and curing with heating.

  In this way, the surface of the wood can be impregnated with an acrylic resin containing apatite-coated titanium dioxide. This apatite-coated titanium dioxide has both apatite adsorption action and titanium dioxide resolution, and the adsorption action and decomposition action last semipermanently. Performance is significantly improved.

The modified wood is usually coated with a paint added with an ultraviolet absorber, etc. to provide an aesthetic appearance and block UV rays to improve durability, but conventional modified wood has a coating film formed on the surface. If peeled off, the building material will be damaged or corroded from the exposed wood. However, in the modified wood obtained by this example, even if the coating film peeled off and the wood part was exposed, the surface of the modified wood was coated with an acrylic resin containing apatite-coated titanium dioxide. Can suppress wood damage and corrosion.

Claims (3)

  A modified wood obtained by impregnating wood with an impregnating solution obtained by adding a photocatalyst coated with apatite to a resin solution for WPC production and stirring uniformly. Place the dried wood under vacuum,
Thereafter, a photocatalyst coated with apatite is added to a resin liquid mainly composed of monomers, oligomers, and prepolymers, and the wood is immersed in an impregnating liquid obtained by uniformly stirring the liquid while maintaining a reduced pressure state.
After further pressurizing and impregnating the wood with the impregnating liquid,
A method for producing a modified wood, comprising polymerizing an impregnated resin solution to cure and fix the resin to a wood surface layer. The method for producing a modified wood according to claim 2, wherein the photocatalyst is titanium dioxide and is added in an amount of 1 to 20% by weight based on 100% by weight of the impregnating liquid.