JPH09155813A - Compressed wood material and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep a compressed state by providing a thin high specific gravity layer compressed by heating compression to the upper and rear surfaces of a wooden material of which the water content is adjusted to a fiber saturated point or less. SOLUTION: A wooden material of which both upper and rear surfaces are high in temp. is inserted into the gap between the upper and lower hot plates of a hot press device having a thickness prescribing jig attached thereto to be compressed under heating and pressure to form thin high specific gravity layers to both upper and rear surfaces of the wooden material by heating compression. Thin high specific gravity layers 2, 2 compressed by heating compression are provided to the upper and lower surfaces of the wooden material of which the water content is adjusted to a fiber saturated point or less. By this method, a compressed wooden material 1 is obtained. Since the thin high specific gravity layers are formed on the upper and rear surfaces of the wooden material, bending strength, surface smoothness and surface hardness are enhanced in spite of light wt. Since inside and outside balance is kept, the compressed wooden material generating no warpage or twist is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a compressed wood material obtained by heating and compressing wood material.

[0002]

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

The above-mentioned prior art is to obtain a compressed wood material by heating and compressing it at a high temperature in the presence of a large amount of water in the wood material, and softening wood components such as cellulose, hemicellulose and lignin, Especially for hemicellulose and lignin, which are non-crystalline components, water acts as a plasticizer to lower the softening temperature of each to about 60 ° C, and heat compression is performed while increasing the plasticity of the wood material. 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 It is an object of the present invention to provide a novel compressed wood material and a method for producing the same, which can solve the above problems of the prior art.

That is, the compressed wood material according to the present invention is characterized in that a thin 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. To do.

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 increase the front and back material temperatures, and It is characterized by forming a compressed thin high specific gravity layer on the front and back surfaces of wood by heating and compressing at a temperature above the softening point of cellulose, which is the crystalline component of wood, and then decompressing and cooling. To do.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As the wood material, a processed material such as sawn wood or laminated wood, laminated veneer wood, plywood, particle board and fiber board is used.

As the wood materials, both softwood and hardwood can be used, and particularly soft wood and low specific gravity wood are preferably 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 the wood material, it is obtained by drying the wood before sawing it into a sawn sawn timber, or without drying it into a sawn timber and then drying. When a processed material is used, the water content is adjusted to a fiber saturation point or lower during the manufacturing process.

At least the front and back surfaces of a wood material whose water content has been adjusted to a temperature below the fiber saturation point are preheated to raise the temperature of the front and back materials.

Preheating is performed by an arbitrary method such as putting a wood material in a dryer or sandwiching it between hot plates to raise the temperature of the front and back materials. Preferably the material temperature on the front and back is 80 ° C
Preheating is performed so as to become the above.

Next, while the material temperature was high, preheating was performed between the hot plates of the hot press machine to which a thickness regulating jig (generally called a distance bar) for regulating the interval between the upper and lower hot plates was attached. Insert wood.

A jig having a thickness of 60 to 95% of the thickness of the wood material, more preferably 65 to 92%, is preferably used as the thickness control jig between the heating plates. In other words, the thickness regulating jig is attached so that the compressibility of the wood material is 5 to 40%, more preferably 8 to 35%.

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.

By inserting a wood material having a high material temperature on both the front and back sides into the upper and lower hot plates of a hot press equipped with the above-mentioned thickness regulating jig and hot-pressing it, the front and back surfaces are thinned by heating and compression. A high specific gravity layer is formed.

When the wood material is preheated by the hot platen, the wood material is inserted between the hot plates of the hot press machine, and a slight pressure is applied without applying pressure to the hot plate or the wood material is not deformed. To contact the wood material, preheat while maintaining this contact state, then apply the pressure necessary to give a predetermined compressibility to the wood material to the hot platen and hot press it, A compressed high specific gravity layer can be formed on both front and back surfaces.

As described above, according to the compression method in which the preheating and the heat compression by the hot press device are performed in one cycle,
It is not necessary to convey a wood material, and it can be easily performed only by setting the press schedule of the hot press device. Therefore, the wood material is not damaged, the thermal efficiency is good, the equipment is simplified, the setting of the press schedule can be easily changed, and it can be applied to various wood materials. The specifications can be easily changed, and the advantages such as excellent production efficiency and good yield are exhibited.

The hot-pressing of the wood material 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 150 ° C., respectively.
However, at a water content of 35%, which is the fiber saturation point of the wood material, the softening point temperature decreases to around 60 ° C. 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.

The pressing time and the pressing pressure are arbitrarily set according to the type of wood material to be used, the type of wood, the specific gravity of the material itself, the softness, etc. In order to obtain the required compression rate according to (1), it is generally preferable to set a pressing time of 1 to 7 minutes and a pressing pressure of 5 to 25 kg / cm 2.

The wood material which is heated and compressed between the upper and lower hot plates of the hot press machine is preheated on both the front and back sides in advance so that the front and back material temperatures are high. However, since heat softening and compression by the compression force proceed in the front and back parts, the heat transfer is relatively slow because the water content is adjusted to the fiber saturation point or lower, and therefore the front and back surfaces of the wood material are Only the part is compressed.

In this way, the temperature of the entire wood material does not rise even during hot pressing, so it is easily cooled by subsequent decompression.

Moreover, since it is hot-pressed at a temperature equal to or higher than the softening point of cellulose, which is a crystalline component in the woody tissue, the fibrous cellulose softened during hot pressing is fixed in a deformed state by cooling after decompression. To be done. Furthermore, since hemicellulose, which is an amorphous component, lignin also softens and melts by heat pressure and acts as an adhesive to cellulose, springback of the wood material due to decompression after hot pressing is suppressed to a minimum, A compressed thin high specific gravity layer is formed on both front and back surfaces.

The thin high specific gravity layers formed by compression on both front and back surfaces of the wood material preferably have a specific gravity of 0.7 or more.

The hardness of the high specific gravity layer is JIS Z-
1.5 kgf in the hardness test method of wood according to 2007
/ Mm2 or more is preferable, whereby the impact resistance of the surface is sufficient, scratches are less likely to occur, the bending strength of the material itself is improved, and the hydrophobicity, swelling ratio,
Improves dimensional stability as a wood material by reducing water absorption.

As described above, the thin high specific gravity layers 2 and 2 which are compressed by heat compression are provided on the front and back surfaces of the wood material whose water content is adjusted to the fiber saturation point or lower. The compressed wood material 1 of the present invention is obtained (FIG. 1).

[0033]

According to the present invention, thin high specific gravity layers are formed on the front and back surfaces of a wood material without increasing the overall specific gravity. Therefore, the bending strength, surface smoothness, and surface hardness are improved while being lightweight. Moreover, since the front and back surfaces are kept in balance, a compressed wood material that does not warp or twist can be obtained.

The high specific gravity layers on both the front and back sides are formed by softening cellulose, which is a crystalline component of wood, and softening and melting non-crystalline components, hemicellulose and lignin, and then compressing and hardening them to a high specific gravity. Since it is a material, it becomes a hydrophobic film, and coupled with the reduction of hydrophilicity due to compression,
The swelling rate and the water absorption rate can be reduced, and the dimensional stability of the wood material is significantly improved.

[Brief description of the 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 thin 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 fiber saturation point or lower to preheat the front and back surfaces of the wood material to raise the temperature of the front and back materials, and soften cellulose which is a crystalline component of the wood material while the wood temperature is high. A method for producing a compressed wood material, which comprises forming a compressed thin high specific gravity layer 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.