JP2002210711A - Method for bleaching wood veneer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out uniformly in a good productivity bleaching processing of wood veneer. SOLUTION: A laminate of wood veneers into which a bleaching solution containing hydrogen peroxide is permeated, is put into a hermetically sealed container so that a volume of the laminate attains a volume rate of >=60% to the volume of the hermetically sealed container, and the hermetically sealed container is heated at 90 deg.C to 120 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for bleaching wood veneers which can bleach wood veneers uniformly and with good productivity.

[0002]

2. Description of the Related Art Conventionally, decorative wood veneers have been bonded to wood materials such as plywood, LVL, MDF, hard board, particle board, OSB, glued wood, and inorganic boards such as calcium silicate boards and gypsum boards. Such decorative panels are well known and widely used as floor materials, wall materials, ceiling materials, doors, stairs, etc. of buildings such as houses, and surface materials of furniture.

Further, such a wood veneer is produced by thinly slicing natural wood, and even wood of the same kind usually has various colors. Furthermore, in recent years, there has been a decrease in the quality of high-quality wood with high decorativeness, and it has become necessary to use wood with a different color tone or wood with some drawbacks such as jasper.

[0004] For this reason, bleaching is generally performed in order to make the color tone of the wood veneer uniform or to make defects inconspicuous, and after the bleached wood veneer is bonded to a substrate. For example, a method of applying a colored and transparent paint on the surface thereof has been used to make the color tone uniform or to make the defective portion inconspicuous.

[0005] Hydrogen peroxide is used for such a bleaching treatment. Generally, this hydrogen peroxide and hydrogen peroxide are converted into hydrogen ions (H ⁺ ) and perhydroxy ions (HO
An alkaline substance such as sodium hydroxide or sodium metasilicate for accelerating dissociation into O ⁻ ) is mixed with water and used as a bleaching solution. Has been bleached. However, in the case of this method, alkalis remain in the veneer after the bleaching treatment, and there is a disadvantage that the veneer is darkened later due to the alkali content. There is a problem that the components must be sufficiently washed or neutralized with a washing solution or a neutralizing solution.

Further, in order to eliminate the above-mentioned alkali content remaining in a veneer veneer, for example, Japanese Patent Publication No. 4-42162
As described in the above item, a simple mixture of applying a mixture of 20 to 30% hydrogen peroxide and 5 to 10% ammonia water to a predetermined portion of a veneer veneer and leaving at room temperature for bleaching. A method has also been proposed, but the ammonia used diffuses into the air, deteriorating the surrounding working environment.Also, bleaching by partial coating makes it difficult to perform bleaching with uniform color over the entire surface, resulting in increased productivity. Was also low.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional disadvantages, an object of the present invention is to bleach wood veneers, which can be uniformly and efficiently bleached with a bleaching solution containing hydrogen peroxide. It is to provide a method.

[0008]

To achieve the above object, a method for bleaching wood veneer according to the first aspect of the present invention comprises the steps of: providing a laminate of wood veneer impregnated with a bleaching solution containing hydrogen peroxide. ,
The laminate is placed in an airtight container so that the volume ratio of the laminate is 60% or more of the volume of the airtight container, and the airtight container is heated to 90 ° C to 120 ° C.

[0009] According to this method, since a laminate of wood veneers impregnated with the bleaching solution is processed in a closed container, a large number of wood veneers can be processed at a time, and hydrogen peroxide and other added chemicals can be treated. The working environment is very good without leaking outside. Further, the ratio of the volume of the laminate to the volume of the closed container is set to 60% or more,
Since the heating temperature is 90 ° C. to 120 ° C., when heating to a high temperature in a closed vessel, the amount of steam evaporating from the veneer can be reduced as much as possible. As a result, the bleaching efficiency by hydrogen peroxide can be increased. In addition, it is possible to reduce the amount of the bleaching solution to be permeated, and to prevent the problems such as cracks and rashes caused by shrinkage due to excessive drying of the wooden veneer. Further, since the treatment can be performed at a high temperature, the bleaching action can be promoted and the bleaching can be performed in a short time. Furthermore, since the pH of the water in the veneer drops to 4 to 7 after bleaching, a washing step and a neutralization step are not required. This is because the high temperature treatment consumes the alkali component due to the reaction between the alkali component in the bleaching solution and the lignin in the veneer, or the neutralization reaction with the organic acid extracted from the veneer. Conceivable.

[0010] The bleaching method of the veneer of the second aspect of the invention is characterized in that, in the first aspect of the invention, high-frequency heating is used for the heating means. According to this, the inside of the laminated wood veneer can be quickly raised to a predetermined temperature, and many wood veneers including hydrogen peroxide can be laminated and bleached, so that the bleaching process can be performed with higher productivity. It can be performed.

Further, the bleaching method of the veneer of the third aspect of the present invention is characterized in that, in the first or second aspect of the present invention, the closed container used has a rectangular parallelepiped shape. According to this, since the laminated body of the wood veneer has a rectangular parallelepiped shape, it is possible to efficiently put the laminated body into the closed container at a rate of 60% or more as compared with the cylindrical closed container. This is desirable because the above-described effects can be further enhanced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for bleaching a veneer of the present invention will be described with reference to FIG. 1 showing an example of an embodiment.

FIG. 1 schematically shows an apparatus used in a method for bleaching a veneer of the present invention, wherein 1 denotes a laminate of a veneer 1a in which a bleaching solution 4 containing hydrogen peroxide has been impregnated. 2 is a rectangular parallelepiped closed container, 3 is a storage tank for storing the bleaching liquid 4, 4 is the bleaching liquid stored in the storage tank 3, and 5 is a piping means for supplying the bleaching liquid 4 to the closed container 2. , 6 are piping means for supplying heated steam connected to a boiler for heating the inside of the closed vessel 2, 7 are piping means for collecting the bleaching solution 4 staying in the closed vessel 2, and 8 is a depressurizing means inside the closed vessel 2. Piping means for connecting to at least one of unillustrated decompression means for increasing or decreasing pressure or returning to normal pressure, pressurization means, and atmosphere opening means, and 9 is a table on which the laminate 1 of the veneer veneer la is mounted. It is.

Here, since the above-mentioned apparatus is entirely cuboid, the laminate 1 of the same cuboid wood veneer 1a can be accommodated in the apparatus at a high volume ratio, which is desirable. The shape is not limited to a shape, and may be a cylindrical shape or another shape. The lid may be provided not only at the upper part but also at the front part, for example.

The above-mentioned apparatus has a function of penetrating the bleaching liquid 4 into the wood veneer 1a, and a function of penetrating the wood veneer 1a into which the bleaching liquid 4 has penetrated.
Although the example provided with the function of bleaching the laminate 1 of Example 1a, the bleaching liquid 4 may be permeated into the veneer veneer 1a by another device. In this case, the veneer veneer may be used. A storage tank 3 for the bleaching liquid 4 which is a means for infiltrating the bleaching liquid 4 into 1a
A piping means 5 for supplying the bleaching liquid 4 from the liquid storage tank 3 to the closed container 2, or a pressure reducing means (not shown) for depressurizing, pressurizing, or returning to normal pressure in the closed container 2;
Piping means 8 for connecting to pressurizing means and atmosphere opening means
Need not be provided.

Further, in the above-described apparatus, the case where steam is used as a heating means for heating the inside of the closed vessel 2 is exemplified, but a high-frequency heating apparatus may be used. When such a high-frequency heating device is used, when the wood veneers 1 a are directly and densely stacked without leaving a gap to form the laminate 1,
It is particularly desirable because it can be efficiently heated. In this case,
There is no particular need to provide the heating steam supply piping means 6.

The concentration of hydrogen peroxide in the bleaching solution 4 can be determined in consideration of the species of the wood veneer 1a to be bleached, the aqueous solution permeability of the wood veneer 1a, and the like. Usually, it is in the range of about 0.5% by weight to 10% by weight. The pH can be adjusted to 6 or more in order to promote the bleaching action. In this case, an alkaline substance such as sodium hydroxide is added to the bleaching solution 4 as a pH adjuster. In addition, to the bleaching liquid 4, an ethylenediamine which has a function of adding a surfactant which has a function of quickly penetrating the bleaching liquid 4 into the interior of the veneer 1 a or a function of suppressing the decomposition of hydrogen peroxide in the bleaching liquid 4. Tetraacetic acid, diethylenetriaminepentaacetic acid, chelating agents for these salts, and stabilizers such as sodium metasilicate, sodium silicate, and magnesium sulfate can also be added. These additives are used for the wood species of the wood veneer 1a. It is added as necessary in consideration of the thickness, processing time, etc.

The method for infiltrating the bleaching liquid 4 into the veneer 1a to form the laminate 1 in which the bleaching liquid 4 has penetrated is not particularly limited. For example, a method of immersing the wood veneers 1a one by one in the bleaching solution 4 for a predetermined time and laminating the same to form a laminate 1; A method of arranging a rack so that a gap is opened for each sheet, a method of immersing the rack in the bleaching solution 4 for a predetermined time, and forming the laminate 1 as it is or with the wire mesh or bottle removed, and a wire mesh or U-shaped pin Wood veneer 1 without using wood
a method of slightly loosening a, a method of immersing this rack in the bleaching solution 4 for a predetermined time, or a method of immersing the rack in the closed container 2 or another closed container by a decompression method, a pressurization method, a decompression / pressure method, or the like. There is a method under permeation.

FIG. 1 shows an example in which the veneer veneers 1a are vertically stacked to form the laminated body 1. However, the present invention is not limited to this example. Needless to say, the laminate 1 can be formed by depositing the wood veneers 1a in such directions.

Next, the laminate 1 impregnated with the bleaching solution 4
When the bleaching solution 4 is permeated in the closed container 2, the bleaching solution 4 is kept as it is, and when the bleaching solution 4 is permeated in a place other than the closed container 2, the laminate 1 is placed in a closed container. Carry in 2. At this time, the laminate 1 is adjusted so that the volume of the laminate 1 becomes 60% or more of the volume of the closed container 2.
It is good to form.

Next, the laminate 1 in the closed vessel 2 is heated so that the temperature of the laminate 1 becomes 90 ° C. to 120 ° C. The heating means may be a method such as heating steam, high-frequency heating, or immersion heating using the bleaching solution 4 as a heating medium. It is preferable to laminate so as to provide a gap between a large number of wood veneers a. In the case of high-frequency heating, it is preferable to laminate the wood veneers a so as to be in close contact with each other.

The bleaching process can be performed even when the temperature of the laminate 1 is lower than 90 ° C., but it is not preferable because the processing time needs to be lengthened. May be discolored,
A range of 90C to 120C is desirable.

Further, when the pH of the bleaching solution 4 is adjusted to 6 or more and less than 11 to promote the bleaching action, the above-mentioned high-temperature heating bleaching treatment is carried out, and the bleaching solution 4 in the wood veneer 1a after bleaching is obtained. Has a pH of 4 to 7, and the washing step can be greatly reduced or made unnecessary.

[0024]

EXAMPLE 1 200 wooden veneers made of oak wood having a thickness of 0.3 mm, a width and a length of 300 mm were placed in a bleaching solution adjusted to pH 10 by adding sodium hydroxide to 2% hydrogen peroxide. Each sheet was dipped for about 10 seconds and deposited to form a laminate. Next, this laminate was placed in a stainless steel square hermetic container having a height of 60 mm, a width and a length of 350 mm, and sealed. The ratio of the volume of the laminate to the volume of the square closed container was 73%. Next, the container was heated in a 100 ° C. oil bath for 5 minutes to perform bleaching treatment, and the laminate in the container was taken out.

The wood veneer thus obtained is free from cracks and the like.
The whole was bleached with good uniformity and had a good appearance. The single veneer was folded small and immersed in 1 L of distilled water for 2 hours to measure the pH.
It was 2.

[0026]

Example 2 200 wooden veneers made of birch having a thickness of 0.6 mm, a width and a length of 300 mm were placed in a bleaching solution adjusted to pH 9 by adding sodium metasilicate to 5% hydrogen peroxide. Each sheet was immersed for about 10 seconds and deposited to form a laminate. Next, this laminate was placed in the same rectangular closed container used in Example 1 and sealed. The ratio of the volume of the laminate to the volume of the square closed container was 66%. Next, the container was heated in a 110 ° C. oil bath for 5 minutes to perform bleaching treatment, and the laminate in the container was taken out.

The obtained wood veneer is free from cracks and the like.
The whole was bleached with good uniformity and had a good appearance. Further, when this single veneer was folded small and immersed in 1 L of distilled water for 2 hours to measure pH, it was found that pH 5.5.
It was 4.

[0028]

Example 3 A bleaching treatment was performed in the same manner as in Example 1 except that heating was performed by a high-frequency heating device for 3 minutes instead of heating in an oil bath. The center temperature of the wood veneer during high frequency heating was 97 ° C.

The obtained wood veneer is free from cracks and the like.
The whole was bleached with good uniformity and had a good appearance. Further, when this single veneer was folded small and immersed in 1 L of distilled water for 2 hours to measure pH, it was found that pH 5.5.
Nine.

[0030]

Comparative Example 1 A bleaching process was performed in the same manner as in Example 1 except that the number of veneer veneers was 140 (the ratio of veneer volume to container volume was 51%). Was done. The obtained wood veneer had insufficient bleaching degree as a whole and was insufficient.

[0031]

Comparative Example 2 A bleaching treatment was performed in the same manner as in Example 2 except that the heating was performed in a water bath at 60 ° C. The obtained wood veneer had insufficient bleaching degree as a whole and was insufficient. This single veneer is folded small 1
L was immersed in distilled water for 2 hours and the pH was measured.
pH 8.2.

[0032]

Comparative Example 3 A bleaching treatment was performed in the same manner as in Example 2 except that the heating was performed in an oil bath at 130 ° C. The obtained wood veneer was blackish as a whole, and the blackness in the peripheral part was particularly remarkable. This single veneer was folded small and immersed in 1 L of distilled water for 2 hours to measure the pH.

[0033]

As is clear from the above description, according to the invention of claim 1 of the present invention, a laminate of wood veneers impregnated with a bleaching solution is treated in a closed vessel, so that a large number of wood veneers are treated at once. The plate can be processed and the working environment is very good without hydrogen peroxide and other added chemicals leaking out. In addition, since the ratio of the volume of the laminate to the volume of the closed container is set to 60% or more and the heating temperature is set to 90 ° C. to 120 ° C., when heating to a high temperature in the closed container, the amount of steam evaporating from the wood veneer is reduced. As a result, the efficiency of bleaching with hydrogen peroxide can be increased, the amount of bleaching solution to be permeated can be reduced, and problems such as cracking and rash due to shrinkage due to overdrying of the veneer wood. Can be prevented. In addition, since the treatment can be performed at a high temperature, the bleaching action can be accelerated and the bleaching treatment can be performed in a short time.

According to the invention of claim 2, according to claim 1,
In the invention, since the high-frequency heating is used as the heating means, the inside of the laminated wood veneer can be quickly raised to a predetermined temperature, and many wood veneers including hydrogen peroxide are laminated and bleached. The bleaching process can be performed with higher productivity.

Further, according to the invention of claim 3, according to claim 1,
In the invention of the second aspect, since the closed container used is made into a rectangular parallelepiped, it is possible to efficiently put the laminate into the closed container at a rate of 60% or more as compared with the cylindrical closed container. The effect can be further enhanced.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for explaining an embodiment of a method of the present invention.

[Explanation of symbols]

 1. Laminated material 2. Airtight container 3. Storage tank 4. Bleaching liquid 5-8.

Claims (3)

[Claims] 1. A laminated wooden veneer impregnated with a bleaching solution containing hydrogen peroxide is placed in a closed container so that the volume of the laminated product is 60% or more of the volume of the closed container. A method for bleaching wood veneers, comprising heating the sealed container to 90 ° C to 120 ° C. 2. The method according to claim 1, wherein the heating means is high-frequency heating. 3. The method according to claim 1, wherein the closed container has a rectangular parallelepiped shape.