JPH09290407A - Compressed wooden material and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the bending strength, the surface smoothness, the surface hardness, and the dimensional stability, etc., without increasing the specific gravity of the whole body. SOLUTION: The front and rear material temperatures are increased by pre-heating a wooden material of which the moisture content is adjusted to be at the fiber saturation point or less, and after applying water on the front and rear surfaces, a heat-compression is performed at a temperature which is the softening point of cellulose, being the crystalline component of the wooden material, or higher, and then, the pressure is released, and the wooden material is cooled. By doing so, this compressed wooden material 1 for which a high specific gravity layer 2 being compressed by the heat-compression, is respectively provided on the front and rear surfaces, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressed wood material obtained by heating and compressing a wood material and a method for producing the same.

[0002]

2. Description of the Related Art A conventional compressed wood material is manufactured by humidifying and heating a wood material in a wet state or in a steam atmosphere to obtain a high water content and high temperature state, and then heating and compressing the wood material.

[0003] The above-mentioned prior art is to obtain a compressed wood material by heating and compressing the wood material at a high temperature in a state where a large amount of moisture is present in the wood material. In particular, for hemicellulose and lignin, which are non-crystalline components, moisture largely acts as a plasticizer to lower their softening temperatures to about 60 ° C., respectively, and to perform heat compression while increasing the plasticity of wood. is there.

[0004]

However, in the case of the prior art in which a wooden material is heated and compressed in a high water content state,
The high steam pressure of water present inside the wood material acts as a force to restore the compressed state when the pressure is released, and it is difficult to maintain the compressed state in combination with the springback phenomenon due to the pressure release. .

[0005] Particularly, in the case of wood materials having a low specific gravity,
Although compression is easily performed, puncturing (delamination) may occur due to the instantaneous release of the high steam pressure of water when the compression is released.

In order to prevent the effect of high steam pressure, cooling may be considered while maintaining the compression-compressed state, but it is not practical because productivity is extremely low and cost is greatly increased.

[0007] Further, even if the compressed state can be maintained, the wood material is compressed over the entire wood material in a high water content state, so that the wood material has a high specific gravity. This means that the volume is reduced by maintaining the compressed state,
This means lower product yields and significantly higher costs.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel compressed wood material capable of solving the above-mentioned problems of the prior art and a method for producing the same.

That is, the compressed wood material according to the present invention is characterized in that a high specific gravity layer compressed by heat compression is provided on the front and back surfaces of the wood material whose water content is adjusted to a fiber saturation point or lower. .

In the method for producing a compressed wood material according to the present invention, the wood material whose water content is adjusted to the fiber saturation point or lower is preheated to raise the temperature of the front and back materials, and water is applied to the front and back surfaces of the wood material. By heating and compressing at a temperature equal to or higher than the softening point of cellulose, which is a crystalline component of the wood material, and then decompressing and cooling, high specific gravity layers compressed by heat compression are formed on the front and back surfaces of the wood material. It is characterized by

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Wood materials include sawn or glued wood, laminated veneer, plywood, particle board, and the like.
A processing material such as a fiberboard is used.

As these wood materials, both softwood materials and hardwood materials can be used, and particularly soft materials and low specific gravity materials are suitably used.

Wood materials have a water content below the fiber saturation point,
Preferably, it is adjusted to 35% or less. For this reason, when a sawn timber is used as a wood material, it is obtained by drying the sawn timber before sawing, or turning it into a sawn timber without drying. When a processed material is used, the water content is adjusted to a fiber saturation point or lower during the manufacturing process.

The wood material whose water content is adjusted to a temperature below the fiber saturation point is preheated to raise the temperature of the front and back materials. Preheating is
It can be carried out by any method such as putting the wood material in a dryer or sandwiching it between heating plates, and preferably the front and back material temperature of the wood material is 80 ° C. or higher.

Water is applied to the front and back surfaces of the wood material whose front and back material temperatures have been raised by preheating. The application of water is performed by using a roll coater, a spray, or the like, which increases the surface water content of the wood material and promotes the subsequent compression of the wood material by heat and pressure.

The water may be used at room temperature, hot water, hot water, or the like. Since water is applied in a state where the front and back materials are heated by the preheating, the water permeates into the surface of the wood material favorably and the surface water content increases. To further enhance the penetration of water into the wood surface, a penetration aid such as a surfactant can be admixed. Alternatively, it is possible to promote the permeation of water by engraving minute concave grooves or kerfs on the surface of the wood material.

Next, the temperature of the front and back materials is increased by preheating between the hot plates of the hot press machine to which a thickness control jig (generally called a distance bar) for controlling the distance between the upper and lower hot plates is attached. Insert wood material whose water content on the front and back has been increased by applying.

The thickness-regulating jig that is used by being mounted between the heating plates at the time of heating and compression is assumed to have a thickness substantially the same as the thickness of the compressed wood material to be finally obtained, and the compression ratio of the wood material is 5 It is suitable to be provided so as to be -40%, more preferably 8-35%. In other words, a thickness control jig having a thickness of 60 to 95%, more preferably 65 to 92% of the thickness of the wood material is preferably used.

If the compressibility of the wood material is less than 5%, the compression on both the front and back surfaces becomes insufficient, and the strength required for the high specific gravity layer cannot be obtained. Conversely, the compression rate is 40%
If it exceeds the above, the front and back surfaces will be sufficiently compressed to obtain the required strength as a high specific gravity layer, but the overall specific gravity will increase, leading to an increase in weight, and a decrease in volume due to an excessive compression ratio. That is, since the loss of raw materials increases, the yield decreases, which causes an increase in cost, which is not preferable.

The compressibility of the wood material is within the above range,
It can be arbitrarily selected according to the tree species of the wood material to be used, the specific gravity, the hardness of the front and back surfaces to be obtained, etc., and the thickness regulating jig is set according to the selected compression rate.

The pressing time and the pressing pressure are arbitrarily set according to the type of wood material used, the type of wood, the specific gravity of the material itself, the softness, etc., but generally, the pressing time is 1 to 7 minutes. The pressure is preferably 5 to 25 kg / cm ² .

The hot pressing of the wood material in the hot press machine is carried out at a hot pressing temperature which is equal to or higher than the softening point of cellulose which is a crystalline component of the wood material.

The softening point temperature of cellulose, which is a crystalline component in wood, is about 20 although it varies slightly depending on the tree species.
The temperature is 0 to 250 ° C. and is almost constant regardless of the water content of the wood material. Therefore, in the present invention, the hot pressing temperature is set to 2
It is necessary to clamp at a temperature of 00 ° C or higher.

The softening point temperatures of hemicellulose and lignin, which are non-crystalline components of wood, vary greatly depending on the water content of the wood, and the softening temperatures of hemicellulose and lignin in an absolutely dry state are about 180 ° C. and about 15 °, respectively.
Although the temperature is 0 ° C., the softening point temperature decreases to around 60 ° C. at the water content of 35% which is the fiber saturation point of the wood material. Therefore, in the present invention using a wood material whose water content is adjusted to a fiber saturation point or lower, by hot pressing at a temperature equal to or higher than the softening point of cellulose, the cellulose that is a crystalline component is thermally softened, and at the same time, an amorphous component is used. Certain hemicelluloses and lignin also soften and melt.

In the wood material which is heated and compressed between the upper and lower hot plates of the hot press machine, the heat of the hot plate is transmitted to the front and back parts, and thermal softening and compression by compression force proceed in the front and back parts. Is adjusted to a water content below the fiber saturation point, the heat transfer is transferred to the inside at a relatively slow speed, so that only the front and back parts of the wood material are compressed early. In particular, in the present invention, since the front and back material temperature is increased by preheating before hot pressing and the water content of the front and back parts of the wood material is increased by applying water, the front and back parts of the wood material due to heat pressure are increased. Is efficiently and early compressed.

It should be noted that, particularly when normal temperature water is used as the water to be applied to the front and back surfaces of the wood material, it can be said that preheating is performed, but this application may lower the material temperature of the wood material itself. Since heat compression is performed in a state where the surface water content is increased, heat transfer is rapid in the front and back parts, and in combination with a decrease in the softening point temperature of the amorphous component,
It is possible to significantly reduce the clamping time.

After the heating and compression are performed as described above, the pressure and cooling are performed.

The hardness of the high specific gravity layers on the front and back of the wood material is JIS
1.5 in wood hardness test method according to Z-2007
It is preferably at least kgf / mm ² . As a result, the impact resistance of the surface is sufficient and scratches are less likely to occur, the bending strength of the material itself is improved, and the dimensional stability as a wood material is improved by reducing the hydrophobicity, swelling rate and water absorption rate. Let The hardness values obtained by the above test method are measured with the respective high specific gravity layers exposed to the outer surface by grinding or the like.

As described above, the book is characterized in that the high specific gravity layers 2 and 2 respectively compressed by heat compression are provided on the front and back surfaces of the wood material whose water content is adjusted to be below the fiber saturation point. The compressed wood material 1 of the invention is obtained (FIG. 1).

Such a wooden board may be provided on the surface thereof with a direct makeup such as a base treatment, a color coating, a pattern pattern printing, and a top coating, or a decorative material such as a veneer, a decorative paper or a synthetic resin film, if necessary. It is suitably used as a base material for a decorative board on which overlay makeup is applied according to 1., and the decorative board is effectively used as a building material, a fitting, or a furniture material.

[0031]

EFFECTS OF THE INVENTION According to the present invention, since high specific gravity layers are formed on the front and back surfaces of a wood material and at the center in the thickness direction thereof without increasing the overall specific gravity, it is lightweight, yet flexural strength and surface smoothness are achieved. Since the properties and surface hardness are improved, and the balance between the front and back is maintained, a compressed wood material that does not warp or twist can be obtained.

The high specific gravity layers formed on the front and back surfaces of the wood material have a high specific gravity obtained by softening the cellulose, which is a crystalline component of the wood material, and softening and melting the amorphous components, hemicellulose and lignin. Since it is hardened to form, it becomes a hydrophobic film, and the swelling rate and water absorption rate can be reduced together with the reduction of hydrophilicity due to compression, and the dimensional stability of wood material is greatly improved. Let

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a compressed wood material according to the present invention.

[Explanation of symbols]

 1 Compressed wood 2 High specific gravity layer

Claims (2)

[Claims] 1. A compressed wood material, characterized in that a high specific gravity layer compressed by heat compression is provided on the front and back surfaces of the wood material whose water content is adjusted to a fiber saturation point or lower. 2. A wood material whose water content is adjusted to a point below the fiber saturation point is preheated to raise the temperature of the front and back materials, water is applied to the front and back surfaces of the wood material, and then the cellulose, which is a crystalline component of the wood material, is softened. A method for producing a compressed wood material, characterized in that a high specific gravity layer compressed by heat compression is formed on the front and back surfaces of the wood material by heating and compressing at a temperature above a point and then decompressing and cooling. .