JPH0260481B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for bending wood, particularly for bending wood with small curvatures.

In order to bend wood, especially bending with a small curvature, the wood must contain a certain amount of moisture to soften and swell the wood. For this purpose, semi-dry wood or dry wood impregnated with moisture is used, but it is difficult to adjust the moisture content of semi-dry wood to the desired level, and it is also difficult to store it for a long period of time. Of course, the moisture content changes during storage. Furthermore, since the core of semi-dried wood is almost always brittle, it cannot be used for molding with a small curvature, resulting in a large number of scraps. Furthermore, semi-dried wood contains a large amount of water within its structure, making it difficult to dry and easily discolored. Therefore, a method in which dry wood is easily stored for a long period of time and has consistent material quality and is hydrated during molding is highly recommended. In the above method, dry wood is conventionally hydrated by steam curing or water impregnation. However, these methods require a long time to soften and swell the wood to the point where it can be easily bent.
The disadvantages are that the moisture content is uneven, that it is difficult to adjust the moisture content to a predetermined level, and that moisture is contained not only in the wood conduits but also in the tissue, and it takes a long time to dry during molding. exist. When molding wood, it is extremely important to uniformly adjust the moisture content to a predetermined level so that only the conduits are selectively hydrated. The higher the moisture content, the better the moldability of the wood, but if the moisture content in the structure becomes too high, drying becomes extremely difficult, and the wood will still contain a large amount of moisture even after molding. Therefore, it takes a long time to dry after molding, and the molded product is likely to be distorted due to volatilization of a large amount of water after molding, and the molded product is colored, reducing its commercial value. If the drying temperature is increased in order to dry in a short time, the moisture in the structure will rapidly evaporate, which will not only cause greater distortion in the molded product but also may cause cracks and cleavage.

The present invention solves the above-mentioned conventional drawbacks, allows a predetermined amount of water to be selectively and uniformly contained in the wood conduit, and facilitates bending with a small curvature.
The aim is to dry the molded product smoothly without causing distortion, cracking, or splitting, and the main idea is to impregnate the wood with moisture under reduced pressure and heat it at the same time.

BACKGROUND ART When injecting chemical solutions such as preservatives, antifungal agents, and flame retardants into wood, it has been conventionally done under reduced pressure. However, the present invention is the first to impregnate water under reduced pressure when bending wood, and this new method makes wood highly plasticized, which has been an unsolved problem in wood bending for many years. For the first time, it became possible to improve yields, which had been a problem.

The present invention will be explained in detail below.

It goes without saying that dried wood is used in the present invention, but the dried wood generally has a moisture content of 15%.
The following is preferably 10% or less wood, and Step 1
In this process, wood is cut into a predetermined shape, such as a plate, square, or round shape, and then placed in an airtight container 1 shown in FIG. In the figure, 10 is a wood material to be molded. Next, the vacuum pump (2) is operated to reduce the pressure inside the closed container 1. In this case, the degree of vacuum within the closed container 1 is easily adjusted by the operating time of the vacuum pump 2. The appropriate degree of vacuum is not necessarily determined uniformly depending on the material of the material to be molded 10, so it must be determined in advance for each material, but it is approximately 0 to 50 mm.
It is about Hg. Next, the pressure pump 3 is operated to force water 4 into the closed container 1. Agents such as preservatives and flame retardants may be dissolved in the water 4. In addition, water 4 is applied to the molding material 1 by spraying or the like.
0 may be contacted. In this way, under reduced pressure, the air existing in the conduit of the material to be molded 10 is expelled and comes into contact with water, so water is instantaneously and selectively impregnated into the conduit of the material to be molded 10. The moisture content of the material to be molded 10 is determined by the degree of vacuum inside the sealed container 1, but is almost 100%.
It is desirable to contain water in excess up to almost the same level. The water absorption rate in step 1 is almost 10 times that of the conventional method.

In step 2, the molding material 10 impregnated with a predetermined amount of water in step 1 is heated with steam, preferably under reduced pressure. According to such steam heating, the moisture contained in the steam causes
In this case, the amount of water that has been impregnated into the molding material 10 evaporates is regulated, and the water content is maintained at a predetermined level. By such heating, the material to be formed 10
The lignin and hemicellulose in the molding material 10 swell and soften due to the water selectively contained in the conduit, thereby making the molding material 10 highly plasticized.

The steam pressure applied in step 2 is 0.3~2
Kg/cm ² and the final moisture content of the molded material 10 is generally 40-100% by weight.

In step 3, the material to be formed 10, which contained a predetermined amount of water and was heated in steps 1 and 2, is bent by a pressing die 5 consisting of an upper die 5A and a lower die 5B as shown in FIG. conduct. At this time, the material to be molded 10 is usually placed on the tonette 6, but
In the case of the present invention, since the molded material 10 has an appropriate and uniform moisture content and is highly plasticized,
It becomes unnecessary to use the tonette 6 until the bending process has a considerably small curvature. Since the material to be molded 10 is heated during the above-mentioned press molding, the moisture contained in the conduit of the material to be molded 10 rapidly evaporates to the outside world and approaches a dry state. In order to bring the material to be molded 10 closer to a highly dry state during press molding, press molding is performed in a high temperature heated state. According to such high-temperature heating and press molding, the moisture contained in the conduit of the material to be molded 10 evaporates to the outside more rapidly and becomes dry in a short time. However, when semi-dried wood is used, or even when dry wood is used and moisture is impregnated without applying reduced pressure, if a large amount of moisture is included in the structure of the material to be molded 10, high temperature heating and pressing is required. When molding is performed, water in the structure rapidly evaporates, resulting in cracks and even cleavages in the material to be molded. Therefore, if drying is carried out at a low temperature of about 80°C or lower, the evaporation of water is slow and a large amount of water remains after molding, resulting in poor shape stability after molding and coloring of the wood molded product.

In this way, a substantially completely dried wood molded product 11 as shown in FIG. 3 is obtained, but according to the present invention, the water absorption rate is 10 times that of the conventional product, and most of the products with a defect rate of 30 to 50% in the past have been improved. The defective rate was 0, and thus it can be said that the effects of the present invention are tremendous.

Tests to further clarify the effects of the present invention are shown below.

Beech wood with a moisture content of 5% as dry wood (thickness 20
mm) is used. When the beech wood is placed in a sealed container 1 and pressurized under a reduced pressure of 10 mmHg, its moisture content decreases in 1 minute.
Reach 100%. The beech wood was again placed under reduced pressure and heated with steam, and then bent to a radius of curvature of 35 mm using a press mold heated to 120°C. After a molding time of 20 minutes, the molded product is removed from the press mold. The molded product had a water content of 10%, did not require any subsequent drying, was free from distortion, cracking, cleavage, and discoloration, and had an extremely high market value.

For comparison, when semi-dry wood with a moisture content of 20% is bent using a press mold heated to 120°C in the same manner as above, the beech wood splits and cannot be formed. Therefore, the temperature of the press molding mold was set to 80℃.
After 20 minutes of bending, the resulting molded product has 17
When dried in a drying room at 80°C, it takes about 24 hours to reduce the moisture content to 10% or less, during which time the molded product loses its shape and becomes discolored.

Furthermore, as a comparison, when steam curing is performed on beech wood with a moisture content of 5% without reducing the pressure, the moisture content finally reaches 20% after 6 hours, but the moisture content is uneven. When this beech wood is bent, it has almost the same effect as the semi-dried wood described above.

[Brief explanation of the drawing]

The figure shows one embodiment of the present invention.
The figure is a schematic side sectional view showing process 1, and the figure 2 is process 3.
FIG. 3 is a side view showing the obtained molded wood product. In the figure, 1... Airtight container, 2... Vacuum pump, 3
... Nozzle, 5 ... Pressing die, 10 ... Material to be molded, 11 ... Wood molded product.

Claims (1)

[Scope of Claims] 1. By reducing the pressure of a sealed container containing dried wood, and then injecting water into the sealed container to bring the water into contact with the dried wood, selectively entering the conduit of the wood. Step 1 of impregnating the wood with water; Step 2 of heating the water-impregnated wood with steam to soften and swell the wood; Press molding the wood that has been softened and swollen by heating; and A wood bending method consisting of step 3 of drying, and steps 1, 2, and 3 above.