JPH0739088B2 - Wood bleaching method and equipment used therefor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a bleaching method for wood and a device used therefor capable of bleaching thick wood such as planks and timber to the core.

[Prior Art] Conventionally, for bleaching wood, as shown in FIG. 5, a bleaching solution (for example, hydrogen peroxide solution or sodium chlorite solution) is stored in a tank 1 and a veneer 2 is placed therein. It is carried out by immersing the bleaching solution in the surface for a predetermined period of time so that the bleaching solution permeates the surface, then taking it out from the tank 1 and washing it with water to remove the pigment on the surface of the veneer 2 decomposed by the bleaching solution. Also, as shown in FIG.
It is also practiced to manually apply the bleaching solution to the veneer 2 with a brush.

[Problems to be Solved by the Invention]

However, in these methods, when a thick plate having a thickness of 50 mm or more or a lumber having a thickness of 100 mm square or more is used as the wood, the bleaching action does not reach the core part sufficiently, and as shown in FIG. As shown in FIG. 5, only the surface is bleached as indicated by the shaded line P, and the interior of the interior is in a state where the original color of the wood remains. Therefore, when coloring wood that has left unbleached parts like this, it is necessary to hide the cut surface so that the core is not on the front side, or to bleach and color the wood after molding it into a predetermined shape. It had to be devised such as to be treated, which required complicated work. Further, even if there is no problem in the appearance at the beginning of finishing, there is a problem that when deep scratches are made during use, the unbleached part inside is exposed and the repair is not easy.

Therefore, in order to uniformly bleach the wood to the inside, Japanese Patent Laid-Open No.
-212005 discloses a method for manufacturing a reinforced decorative board. In this product, a thin wood plate was impregnated with a bleaching solution under reduced pressure and pressure in advance, and the temperature inside the thin wood plate was increased by activating the bleaching agent to bleach the inside of the thin wood plate. A synthetic resin solution is poured into a thin plate and solidified.

However, in this method, the impregnation of the bleaching solution is carried out by simply impregnating under reduced pressure and pressure, so that the pressure change during pressurization and depressurization is so rapid that a load is applied to the interior of the wood and the bleaching reaction causes The resulting gas expands rapidly inside the wood during depressurization, which causes a problem that the wood tends to crack in the thick plate. Further, since the bleaching solution is impregnated with a sudden pressure, when impregnated into a thick plate, unevenness is likely to occur in the impregnated state of the bleaching solution inside the wood, and there is a problem that the bleaching is not performed uniformly. Therefore, there is still a drawback that it can only be applied to thin plates.

The present invention has been made in view of such circumstances, and an object thereof is to provide a bleaching method and an apparatus used therefor capable of sufficiently bleaching even a thick timber such as planks and timber to the core part. And

(Means for Solving the Problems) In order to achieve the above object, the present invention stores a thick wood such as a plank and a timber in a hermetically-sealed processing tank, and then sets a predetermined set value in the processing tank. After depressurizing, bleaching solution is supplied into the processing tank, and the pressure is gradually increased at a rate of 1.0 kg / cm ² or less per minute to impregnate for a predetermined time under a predetermined pressure, and a decomposition reaction by heating is allowed to proceed. The first method for bleaching wood is to gradually reduce the pressure in the tank at a rate of 1.0 kg / cm ² or less per minute.
In summary, a sealed treatment tank for containing thick wood such as planks and timber, a bleaching solution supply means for providing a bleaching solution in the treatment tank, a liquid circulation means for circulating the bleaching solution, and the above circulation. A heating means for heating the bleaching solution, and a pressure adjusting means for depressurizing the inside of the processing tank and then raising the pressure to a predetermined pressure and then lowering the pressure are provided. The second gist is a wood bleaching device provided with a control means capable of controlling the rate to be 1.0 kg / cm ² or less per minute.

[Action]

That is, the present invention, when bleaching wood, rather than simply immersing the wood in a bleaching solution or brush painting as in the conventional case, first, the inside of the treatment tank containing the wood is degassed by vacuum degassing. After removing the air and water, the bleaching solution is supplied, the pressure is gradually increased at a rate of 1.0 kg / cm ² or less per minute to impregnate it under pressure to forcefully penetrate into the wood, and then heat. Then, a bleaching reaction accompanying the decomposition reaction of the bleaching solution is performed, and then the pressure is gradually reduced at a rate of 1.0 kg / cm ² or less per minute. As a result, the bleaching solution gradually permeates into the core of the wood and reaches the core evenly and sufficiently, so that no unbleached part remains and uneven bleaching does not occur. In addition, the pressure change on the wood is suppressed from the minimum to a minimum, and the gas generated by the bleaching reaction is gradually released from the wood without burdening the interior of the wood. However, it does not crack. Therefore, according to the present invention, conventionally, it is possible to uniformly bleach to the core a thick plate having a thickness of 50 mm or more and a square timber having a thickness of 100 mm square or more that could not be bleached to the core. . Further, according to the present invention, the residual solution of the bleaching solution is discharged to the outside of the tank while being pressurized, and then the heating medium is supplied into the processing tank to raise the temperature of the solution, whereby the decomposition reaction of the bleaching solution proceeds. By doing so, the residual solution of the bleaching solution that is not impregnated into the wood can be recovered and reused, so that the chemical solution can be saved, which is advantageous in terms of cost. Moreover, according to the present invention, since the impregnation of the bleaching solution and the bleaching reaction can be continuously performed in the same processing tank, there is an advantage that the working efficiency is significantly improved.

Next, the present invention will be described in detail based on examples.

〔Example〕

FIG. 1 shows an embodiment of the wood bleaching apparatus of the present invention. In the figure, reference numeral 10 denotes a horizontal cylindrical processing tank, which can be loaded with wood 2 in the horizontal direction. The inside of the processing tank 10 communicates with a circulation pipe 13 including a circulation pump 11 and a heat exchanger 12 on one end side and the other end side thereof. Further, in the circulation pipe 13 via an on-off valve 14,
A bleaching solution supply pipe 17 extending from the bleaching solution storage tank 16 is connected so that the bleaching solution can be supplied into the processing tank 10. Reference numeral 20 is a drainage pipe connected to the circulation pipe 13 via an opening / closing valve 21.

On the other hand, a pressure adjusting pipe 22 is communicated with the upper part of the processing tank 10, and a pressure reducing valve 25 and a cooling trap 26 are provided via a drain removing trap 23 and a release valve 24 for preventing drain from entering.
And a pressure reducing pipe 28 provided with a vacuum pump 27 and a pressurizing valve.
A pressurized pipe 31 which is opened and closed by 29 and communicated with a compressed air feeding means (not shown) such as a compressor is connected. In addition, the pressure adjusting pipe 22 has a pressure gauge 32, a safety valve 3
3, a pressure switch 34, a gauge sluice valve 35, a decompression meter 36, and a decompression switch 37 are provided. The opening and closing of the pressure reducing valve 25 and the pressure increasing valve 29 are controlled by a separately provided control means (not shown) such as a computer, and the rate of change in pressure during pressurization and pressure decrease 1.0k per minute
It can be set to any value up to g / cm ² .

Using the above apparatus, the wood is bleached as follows, for example. That is, first, the wood 2 is loaded into the processing tank 10 and the open / close lid is closed to seal it. Next, the vacuum pump 27 connected to the pressure adjusting pipe 22 is operated to open the pressure reducing valve 25 to make the inside of the processing tank 10 a vacuum of about 5 to 760 Torr and maintain it for a predetermined time, and then the pressure reducing valve 25 is closed. And the on-off valve 14 is opened, and the bleaching solution is supplied from the bleaching solution storage tank 16 to the processing tank 10 via the pipe 17 by utilizing the differential pressure. After that, the on-off valve 14 is closed, the circulation pump 11 is operated to circulate the bleaching solution, and the release valve of the pressure adjusting pipe 22 is released.
After opening 24 and returning the inside of processing tank 10 to normal pressure, the release valve is opened again.
24 is closed, and this time the pressurizing valve 29 is opened to pressurize the inside of the processing tank 10 to a predetermined pressure (for example, 10 to 15 kg / cm ² ). At this time, it is necessary to gradually increase the pressure so that the wood in the processing tank 10 is not cracked or the impregnation of the bleaching solution is not unevenly caused by the sudden pressurization. That is, in a general pressure impregnation treatment, the pressure in the treatment tank is rapidly applied so that there is no time loss as much as possible (for example, 3 to 15 kg / cm ² per minute). Control so that the rate of pressure change is 1.0 g / cm ² or less per minute. In this way, after gradually increasing the pressure to reach the predetermined pressure, the bleaching solution is circulated to sufficiently impregnate the inside of the wood, and then the heat exchanger 12 is activated to circulate the bleaching solution at 50 to 70 ° C. Raise the temperature. Due to the pressurized circulation of the heated bleaching solution, the wood 2 is heated to the inside, and a decomposition reaction of the impregnated bleaching solution occurs. Along with this, the wood pigment is decomposed and the bleaching reaction proceeds. Then, during the bleaching reaction, the release valve 24 of the pressure adjusting pipe 22 is opened to reduce the pressure in the processing tank 10 to the normal pressure. Again, wood 2
It is necessary to gradually reduce the pressure so that the timber 2 will not crack due to a sudden pressure change, and the rate of pressure change at that time is every minute.
Control so that it is 1.0 kg / cm ² or less. And the processing tank 10
When the inside pressure reaches normal pressure, open the on-off valve 21 and drain the drainage pipe 20.
Remove the bleach from the. This completes the bleaching process. Therefore, the bleached product is obtained by opening the open / close lid of the processing tank 10 and taking out the wood 2.

As described above, according to the above bleaching method, the bleaching reaction of the wood 2 is performed by first impregnating the evacuated wood 2 with the bleaching solution under pressure and then continuously raising the temperature of the bleaching solution. The core can be fully processed. For example, in the conventional bleaching method, it was possible to perform the bleaching treatment only up to a depth of several mm from the surface, but according to the above method,
Even with a thick plate of 50 mm or more or a square material of 100 mm square or more, bleaching treatment can be sufficiently performed up to the core part. Moreover, when adjusting the pressure on the wood 2, the rate of pressure change should be 1.0 kg / cm ² per minute so as to gradually increase and decrease the pressure.
Since it is controlled as follows, the wood 2 is not cracked or cracked due to a sudden pressure change. Furthermore, since the bleaching solution gradually penetrates into the core of the wood 22 and reaches the core evenly and sufficiently, the unbleached part does not remain and uneven bleaching does not occur.

By the way, according to the flow chart shown in Fig. 2, 100 mm x 100
When bleaching was performed on mm square wood (cedar) with hydrogen peroxide solution (including alkaline agent), the core was completely bleached.

In the above example, the temperature of the bleaching solution is raised and moved from the bleaching impregnation step to the bleaching reaction step.However, at the end of the bleaching solution impregnation step, the residual solution of the bleaching solution is recovered from the bleaching solution and then water. A bleaching reaction may be caused by supplying a heating medium such as the above into the processing tank 10 and raising the temperature. In this case, as shown in FIG. 3, a device in which a heating medium supply pipe 19 extending from the heating medium storage tank 18 is connected to the circulation pipe 13 via an opening / closing valve 15 is used. That is, in the bleaching treatment by this apparatus, the material 2 is circulated and impregnated with the bleaching solution under pressure in the same manner as in the above-mentioned embodiment, and then the on-off valve 14 is opened while maintaining the above-mentioned pressurized state to open the differential pressure. Is used to collect the remaining bleaching solution in the bleaching solution storage tank 16. Next, while maintaining this pressurized state, the heating medium is supplied from the heating medium storage tank 18 into the processing tank 10 via the pipe 19. In this case, the heating medium storage tank 18 is set to a higher pressure than in the processing tank 10 and then the on-off valve is opened.
By opening 15, the heating medium can be supplied using the differential pressure. After that, the on-off valve 15 is closed, the circulation pump 11 and the heat exchanger 12 are operated, and the heating medium is heated to 50 ~
Heat to 70 ° C and circulate. By circulating this heating medium,
A decomposition reaction of the bleaching solution impregnated in the wood 2 occurs, and the bleaching reaction proceeds accordingly. During this bleaching reaction, the inside of the treatment tank 10 was gradually reduced at a rate of 1.0 kg / cm ² or less per minute to return to normal pressure, and the on-off valve 21 was opened to heat from the drainage pipe 20 as in the above-mentioned example. Eject the medium. In this way, a bleached product of wood 2 can be obtained. For example, when the bleaching treatment is performed according to the flow chart shown in FIG. 4, even in the case of a bulky thick plate or square wood, it is possible to completely bleach even the core portion, as in the above embodiment. Moreover, according to this method, the residual solution of the bleaching solution which is not impregnated in the wood 2 can be recovered and reused, so that the unimpregnated bleaching solution is heated and decomposed as compared with the previous example. It is cost effective. However, even if this device is used, if the bleaching solution is decomposable or if the impurities from the wood 2 are severely eluted, it should be discharged from the drainage pipe 21 without being collected. Good.

The wood 1 used in the present invention may be loaded into the processing tank 10 as it is, but as shown by the chain line in FIG.
The wood 2 may be loaded while being held in the multi-stage inner tank 40, or may be loaded while several woods 2 are bound by wires or the like.

Further, the kind of the bleaching solution used in the present invention is not particularly limited, and may be any one as long as it is conventionally used for bleaching the wood 2. Examples thereof include hydrogen peroxide water and sodium chlorite water. When a heating medium is used, it is necessary to use one that does not interfere with the bleaching reaction of the bleaching solution, and water is usually used. However, a solution in which a surfactant or the like is dissolved in water may be used.

Depending on the type and thickness of the wood 2, it is not always necessary to circulate the bleaching solution and the heating solution, and the treatment tank 10 may be filled with the bleaching solution and the heating water alternately.

〔The invention's effect〕

As described above, the present invention, when bleaching wood, rather than simply immersing the wood in a bleaching solution as in the past, or brush painting, first, deaeration of the treatment tank containing the wood in vacuum. After removing the air and moisture inside the wood, the bleaching solution is supplied, and the pressure is gradually increased at a rate of 1.0 kg / cm ² or less per minute to impregnate the wood to force it to penetrate into the wood. Next, after heating to perform the bleaching reaction accompanying the decomposition reaction of the bleaching solution,
The pressure is gradually reduced at a rate of 1.0 kg / cm ² or less per minute. As a result, the bleaching solution gradually permeates into the core of the wood and reaches the core evenly and sufficiently, so that no unbleached part remains and uneven bleaching does not occur. In addition, by suppressing the pressure change applied to the wood to a minimum and gently, without imposing a burden on the interior of the wood, and allowing the gas generated by the bleaching reaction to gradually escape from the interior of the wood, bulky planks and timber etc. However, it does not crack. Therefore, according to the present invention, conventionally, it is possible to uniformly bleach to the core a thick plate having a thickness of 50 mm or more and a square timber having a thickness of 100 mm square or more that could not be bleached to the core. . Further, according to the present invention, the residual liquid of the bleaching liquid is discharged to the outside of the tank while being pressurized,
Then, by supplying the heating medium into the treatment tank and raising the temperature of this, the decomposition reaction of the bleaching solution is allowed to proceed, so that the residual solution of the bleaching solution that is not impregnated into the wood is collected and reused. Therefore, the chemical solution can be saved, which is advantageous in cost. Moreover, according to the present invention, since the impregnation of the bleaching solution and the bleaching reaction can be continuously performed in the same processing tank, there is an advantage that the working efficiency is significantly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the bleaching apparatus of the present invention, FIG. 2 is a flow chart using the apparatus of FIG. 1, FIG. 3 is a block diagram showing another embodiment, and FIG. FIG. 5 is a flow chart using the apparatus of FIG. 3, FIGS. 5 and 6 are explanatory views of a conventional wood bleaching method, and FIG. 7 is an explanatory view of its problems. 2 …… Wood, 10 …… Treatment tank, 11 …… Circulation pump, 13 ……
Circulation piping, 16 ... Bleaching liquid storage tank, 17 ... Bleaching liquid supply piping,
18 …… Heating medium storage tank, 19 …… Heating medium supply pipe, 22 ……
Pressure adjustment pipe

Claims (4)

[Claims] 1. A thick wood, such as planks and timbers, is housed in a sealed processing tank, the inside of the processing tank is depressurized to a predetermined set value, and then a bleaching solution is supplied into the processing tank every minute. 1.0kg /
After gradually increasing the pressure at a rate of cm ² or less and impregnating it for a certain period of time under a predetermined pressure, allowing the decomposition reaction by heating to proceed, and then gradually reducing the pressure in the treatment tank at a rate of 1.0 kg / cm ² or less per minute. A method of bleaching wood, characterized in that 2. After impregnation with the bleaching solution, the bleaching residual solution is discharged out of the tank under pressure and then a heating medium is supplied into the processing tank to raise the temperature of the bleaching solution so that the decomposition reaction proceeds. The method for bleaching wood according to item (1). 3. A hermetically-sealed treatment tank for containing thick wood such as planks and timber, a bleaching solution supplying means for supplying a bleaching solution into the processing tank, and a liquid circulation means for circulating the bleaching solution. It comprises a heating means for heating the circulating bleaching solution and a pressure adjusting means for depressurizing the inside of the treatment tank, then raising the pressure to a predetermined pressure and then lowering the pressure, and the pressure change at the time of raising and lowering pressure by the pressure adjusting means. A bleaching apparatus for wood, which is provided with a control means capable of controlling the rate of 1.0 kg / cm ² or less per minute. 4. A wood bleaching apparatus according to claim 3, further comprising a medium supply means for supplying a heating medium into the treatment tank.