JPH0338915B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method of painting wood materials particularly suitable for outdoor use, and the present invention relates to a method of painting wood materials particularly suitable for outdoor use. By doing so, it is possible to improve the adhesion and weather resistance of the coating film, and to facilitate the disposal of treated waste liquid.

[Conventional technology]

Traditionally, when painting wooden materials for outdoor use, taking into consideration their weather resistance, there have been methods such as painting wooden materials with opaque enamel paint, applying CCA impregnation treatment to wooden materials, and painting with weather-resistant transparent paints for outdoor use. Methods such as this are used.

[Problem that the invention seeks to solve]

However, those coated with opaque enamel paint have good weather resistance and the coating film lasts a long time, but the wood grain pattern on the surface of the wood material does not appear, which makes the use of the wood material less meaningful.

In addition, CCA impregnation treatment is a type of antiseptic and insect repellent treatment in which an aqueous solution of chromium salts, copper salts, and arsenic salts is vacuum impregnated or pressurized into the wood, but the treatment cost is high and these metal salts are not allowed to enter the wood after treatment. There are drawbacks such as the wooden material becoming discolored and lack of a high-quality feel as there is no coating.

Furthermore, when applying a weather-resistant transparent paint, the wood grain pattern of the wood material appears, and although the wood texture is obtained, the wood part and coating deteriorate due to water, ultraviolet rays, etc., and peel off from the wood part surface in a short period of time, resulting in poor durability. There are disadvantages such as lack of

For this reason, the inventor of the present invention previously applied for patent application No. 60-169140.
Prior to painting wood materials, an aqueous solution of metal oxides such as chromium oxide and zinc oxide is applied and dried.
We proposed a method to improve the adhesion and weather resistance of paint films. Although good results can be obtained with this method, since an aqueous metal oxide solution is used, wastewater treatment is indispensable, and treatment equipment must be provided, resulting in an increase in wastewater treatment costs.

[Means for solving problems]

Therefore, in the present invention, the above-mentioned problems are solved by treating the wooden material with a solution of chromium oxide dissolved in a non-aqueous solvent such as alcohol and then painting it.

This invention will be explained in detail below.

Wood materials in this invention include natural wood, plywood, verticle board, decorative veneer, decorative veneer laminated plywood, etc., and these may be colored appropriately,
Those that have been ground or processed are used.

This wood material is first adjusted to have a moisture content of 8 to 15% (weight %, the same applies hereinafter). This is to improve the penetration of the non-aqueous solvent during the subsequent process of pre-cleaning with a non-aqueous solvent and treatment with a chromium oxide solution. This moisture content adjustment can be done using a normal heating furnace,
This is done using an infrared drying device.

Next, the wood material whose moisture content has been adjusted is pre-washed with a non-aqueous solvent. As the nonaqueous solvent used here, alcohols such as methanol, ethanol, and propanol, benzene, and fluorine-based solvents that have good permeability to wood materials are used.
These can be used alone or mixed in any proportion. Pre-washing uses such a non-aqueous solvent,
Preferably, the coating is carried out in a closed system using a coating device such as a flow coater, a roll coater, or a shower coater, or by a method such as brush coating or dipping. If the treatment is carried out in a closed system, the volatile solvent can be recovered, which is preferable in terms of air pollution. This preliminary cleaning removes dirt, resin, etc. from the wood material.

The pre-cleaned wood material is then treated with a non-aqueous solvent in which chromium oxide (CrO ₃ ) is dissolved. As the non-aqueous solvent, the same non-aqueous solvent used in the previous preliminary cleaning is used. The concentration of chromium oxide is 0.5~
It is said that the amount is about 5%, and if it is less than 0.5%, a sufficient treatment effect cannot be obtained, and if it exceeds 5%, it is no longer possible to expect an increase in the treatment effect, and it is also uneconomical. The application of this chromium oxide non-aqueous solvent solution to the wood material is preferably done in a closed system, as in the previous pre-cleaning, using a coating device such as a flow coater, roll coater, or shower coater, or by brush coating. It is carried out by methods such as immersion. The amount of chromium to be applied (impregnated) to wood is approximately 1 to 10 g/m ² . Drying after treatment is not particularly necessary; the nonaqueous solvent evaporates well at room temperature, and the evaporated solvent can be recovered and reused using a condenser or the like. The processing temperature is sufficient at room temperature, and there is no need for special heating.
By adjusting the treatment time, the amount of impregnation into the wood material can be adjusted.

After volatilization of the non-aqueous solvent, the wood material is coated with a synthetic resin paint, but it is preferable to apply the coating immediately after volatilization. If left for a long time after treatment, the chromium ions will be reduced and the activity will decrease, and the desired effect may not be obtained.

The synthetic resin paint used here is preferably transparent and has good weather resistance, but opaque paints may also be used, such as polybutadiene, acrylic urethane, acrylic silicone, and fluororesin paints. Paints and light stabilizers,
Those to which ultraviolet absorbers, antioxidants, etc. are added are used. For coating, well-known coating devices such as spray, roll coater, flow coater, shower coater, and brush coating can be used. The coating film thickness after drying is approximately 50 to 500 μm depending on the application.

[Effect]

In this type of painting method, the surface of the wood material is activated by applying a non-aqueous chromium oxide solution, and then the paint is applied to this, which increases the adhesion of the paint film to the wood material, resulting in This prevents inconveniences such as peeling of the paint film from the wood and cracks and cracks in the paint film.
Improves durability.

Furthermore, since it is a non-aqueous solvent system, the solution has good permeability into the wood tissue, allowing rapid processing and increasing the amount of chromium oxide impregnated.

Furthermore, if the solvent is recovered from the waste liquid of a used chromium oxide non-aqueous solvent solution, only a small amount of residual chromium compounds and resins leached from wood materials will remain in solid form, so waste treatment is difficult. It's extremely easy to do. Furthermore, if the solvent is recovered, there will be no air pollution caused by organic solvents, and the processing cost will be low.

〔Example〕

Prepare ebony (1 x 10 x 10 cm) as a wood material,
It was immersed in 1000 ml of ethanol in an autoclave at room temperature and pressure for 1 minute. Next, after discharging the ethanol, 500 ml of a 1% chromium oxide ethanol solution was introduced into the autoclave, and the pre-washed ebony was immersed in this solution at room temperature and pressure for 2 minutes, then taken out and air-dried. Next, apply acrylic urethane paint to the surface of this object and adjust the thickness.
A coating film of 50 μm was formed and used as a test piece for weather resistance evaluation.

This specimen was exposed outdoors, and the coating film survival rate was measured over time. The outdoor exposure conditions were Hamamatsu City, Shizuoka Prefecture, facing due south, and an inclination angle of 45.

For comparison, a sample that was painted without being treated with a chromium oxide ethanol solution was also exposed outdoors in the same way.

The results are shown in the graphs in the drawing. In the graph, curve A shows the data for the sample treated with the chromium oxide ethanol solution, and curve B shows the data for the sample not treated with the chromium oxide ethanol solution. As is clear from this graph, it can be seen that the coating film treated with the chromic acid ethanol solution has a markedly improved coating film survival rate, which is of great help in improving durability.

Further, when the ethanol of the chromium oxide ethanol solution after the treatment was distilled and recovered, only a small amount of blackish brown solid residue containing chromium compounds remained. This solid residue can be easily disposed of by burying it underground.

〔Effect of the invention〕

As explained above, in the method of painting wood materials of the present invention, the surface of the wood material is modified in advance with a non-aqueous chromium oxide solution, and then regular painting is performed. This increases the adhesion of the paint, prevents problems such as peeling, cracking, and cracking of the paint film, and provides good durability even outdoors. In addition, as durability improves, it becomes possible to use transparent paint, and it also becomes possible to fully obtain the woody feel of wood. Furthermore, since it is a non-aqueous solvent system,
The solvent can be recovered by distillation and reused, and only a small amount of solid residue remains after recovery, making waste disposal extremely easy. In addition, solvent recovery does not increase processing costs and does not cause air pollution.

[Brief explanation of the drawing]

The drawing is a graph showing the results of an outdoor exposure test of Examples.

Claims (1)

[Claims] 1. A method for painting wood materials, which is characterized in that the wood materials are treated with a non-aqueous chromium oxide solution and then painted.