JPH0140722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for compressing wood materials to significantly increase their strength.

Conventionally, in order to obtain such compressed wood, wood materials are compressed while being heated externally using a hot press, etc., but with this method, it takes a long time to heat the wood to the center. This method has disadvantages in that productivity is poor due to the high temperature required, and moisture in the surface layer of the wood material evaporates during the heating process, resulting in surface hardening and cracking.

In particular, it was difficult to significantly deform and compress the wood cells in the center of the wood material because they were hardly plasticized by short-time heat treatment.

Further, after the compression treatment, large restoration occurs due to water absorption, etc., and there are problems such as the wooden material cannot maintain the desired compressed thickness.

In order to eliminate such problems, the present invention has the following features:
By making the wood absorb moisture above the equilibrium moisture content and impregnating at least the surface layer with a thermosetting synthetic resin liquid with a curing temperature of 120°C or higher, irradiation with microwaves extends from the surface layer to the inside of the wood material. To provide a compression processing method for a wood material, characterized in that the thermosetting synthetic resin liquid impregnated is uniformly and sufficiently plasticized, and then compressed while the impregnated thermosetting synthetic resin liquid is not yet cured, and is dried and solidified. It is something.

An embodiment of the present invention will be described with reference to the drawings. A wooden material 1 having an appropriate thickness such as a plate shape or a square shape
The material is soaked in water, sprayed with water, or steamed to retain moisture.

This water-retaining treatment is necessary in order to impart sufficient plasticity to the wood material 1 by microwave irradiation that will be performed later, and is to absorb water sufficiently to the center of the wood material 1. Saturation point (25%)
In other words, it is used by retaining water so that the water content is equal to or higher than the equilibrium water content.

Note that if the wood material 1 is a raw material, it may contain a large amount of moisture and may be used as is.

Next, this water-containing wood material 1 is impregnated with a synthetic resin liquid by dipping, injecting, or coating. Although the impregnation with the synthetic resin liquid may be carried out to the inside of the wood material 1, it is sufficient that at least the surface layer thereof is impregnated with the synthetic resin liquid.

Further, when impregnating the inside of the wood material 1 with the thermosetting synthetic resin liquid, a water-soluble thermosetting synthetic resin may be diluted with water and impregnated simultaneously with the water absorption treatment.

In addition, since the hydrated wood material 1 is heated to a temperature of 100 to 120°C by subsequent microwave irradiation to plasticize it and then compressed, the synthetic resin used does not harden before the compression process. That is, the curing temperature is
A thermosetting synthetic resin having a temperature of 120°C or higher is used, and examples of such synthetic resin include phenol, unsaturated polyester, melamine, and urea.

After impregnating at least the surface layer of the water-containing wood material 1 with the thermosetting synthetic resin liquid, the wet wood material 1 is placed in a microwave irradiation furnace and the wood material 1 is irradiated with microwaves 2. , the temperature of the wood material 1 is increased.

This temperature increase due to microwave irradiation utilizes the heat generation phenomenon caused by dielectric loss when a polar material is placed in a high frequency electric field, and microwaves (300MHz to 300KMHz) are used as the high frequency.

Here, the reason for using microwaves is that when the wooden material 1 is irradiated with microwaves 2, heat can be generated evenly from inside the wooden material 1, unlike hot air heating or heating between hot plates. The moisture retained in the wood material 1 actively moves not only in the surface layer of the wood material but also in the center of the wood material 1.
This is because the plasticization phenomenon can be caused throughout the wood material.

Also, the reason we used microwaves instead of normal high frequencies (10MHz to 100MHz) is because the frequency at which the dielectric loss factor of the wood material 1 in a wet state is at its maximum is in the microwave region, so the dielectric loss factor and frequency are different. This is because the amount of heat involved in the product is significantly larger in the microwave range than in the normal high frequency range, and the heat generation is rapid and the wood material 1 can be plasticized in a short time.

When microwaves are irradiated to wood material 1 in this way,
The wood components and moisture in the wood material 1 absorb microwaves, causing rapid heat generation due to dielectric loss, and the temperature of the wood material 1 rises to over 100℃, causing hemicellulose, lignin, etc. in the wood material to rise. As the wood components soften, moisture in the wood material actively moves inside, and the entire wood material becomes plasticized.

Next, the wood material 1, which has been plasticized with the thermosetting synthetic resin liquid impregnated into the wood material 1 while still uncured, is inserted between the hot plates 3 and 4 of a hot press, and the wood material 1 is heated by the hot press. Compression processing is performed by applying an external force in a direction perpendicular to the fiber direction.

This compression process may be performed in a microwave irradiation furnace while irradiating microwaves, or may be performed outside the microwave irradiation furnace after temporarily stopping the microwave irradiation.

In this way, if the wood material 1 is compressed while its interior is still at a high temperature, it will be compressed and deformed in a direction that closes the cell voids, and the material temperature will be maintained above the glass transition point of lignin and hemicellulose. Therefore, the cells can easily slide against each other and the wood fibers are transferred to the voids, making it possible to compress the wood to a high specific gravity in a short period of time without causing damage such as cracks.

When wood is dried with the wood cells compressively deformed in this way, new hydrogen bonds are created between the densely packed wood component molecules. In addition to obtaining wood, the solidification of the thermosetting synthetic resin further improves the dimensional stability, strength, and density of the wood material.
This results in almost no thickness recovery rate.

Note that the compression processing of the wood material 1 may be performed on the entire wood material, but it may also be performed on a portion of the wood material so as to create unevenness. can maintain its compression-molded shape.

As described above, the present invention impregnates at least the surface layer of a wood material to which water has been added above the equilibrium moisture content with a thermosetting synthetic resin liquid having a curing temperature of 120°C or higher, and then microwaves the wood material. By irradiating with Since it relates to a compression processing method for wood materials characterized by heating and compressing the wood material, curing the thermosetting synthetic resin liquid at the same time as compressing the wood material, and drying the compressed wood material, the equilibrium moisture content By irradiating the wood with moisture as described above, it is possible to sufficiently plasticize the inside of the wood in a short time, and in this state, the wood is heated and compressed using a hot press, so that the wood structure changes. It is possible to sufficiently compress the internal cell voids and densify the fibers with almost no destruction.

Furthermore, when the wood material is compressed, its temperature is kept above the glass transition point of lignin and hemicellulose, so the slippage between the cells is good, and compression processing can be performed in a short time, increasing production efficiency. In addition, the surface layer is greatly compressed and the wood grain becomes denser.Furthermore, since the heat compression is performed while the thermosetting synthetic resin impregnated into the wood material is in an uncured state, the compression At the same time, the thermosetting synthetic resin hardens and the surface density becomes even better, making it possible to obtain a wood material with excellent cosmetic properties. It is possible to obtain compressed wood that retains its compressed shape due to moisture and exhibits almost no dimensional change.

[Brief explanation of drawings]

The drawings show an embodiment of the method of the present invention.
The figure is a front view of a state where microwaves are being irradiated, and FIG. 2 is a front view of a state where compression processing is being performed. 1...Wood material, 2...Microwave, 3,4...
Hot press hot plate.

Claims (1)

[Scope of Claims] 1. After adding moisture to a wood material above the equilibrium moisture content and impregnating at least the surface layer with a thermosetting synthetic resin liquid having a curing temperature of 120°C or higher, the wood material is subjected to microwaves. By irradiating the wood, the temperature inside the wood is raised while the surface of the wood remains moist, and then the wood is heated in a hot press while the impregnated thermosetting synthetic resin liquid is still uncured. A compression processing method for wood materials, which is characterized by heating and compressing, curing a thermosetting synthetic resin liquid at the same time as compression, and drying the compressed wood materials. 2. A method for compressing a wood material according to claim 1, wherein the method for drying and solidifying the compressed wood material is performed by external heating, microwave heating, or a combination of these heating methods.