JP3924190B2 - Manufacturing method of wood-based composite material - Google Patents

Description

【００２５】
【発明の効果】
蒸気噴射が可能なプレス機を用いて、所定の時間伝熱方式による加熱・加圧処理を行った後、さらに蒸気噴射方式で加熱・加圧処理を行ったことで、表層付近の木質材片が劣化することなく、厚み方向で表層の密度が高く中心の密度が低い密度分布をもった木質系複合材料を短時間で作ることが可能となる。
従って、表層の密度が高く、中心の密度が低い密度分布をもった複合材料を短時間で得ることが出来、これらは曲げ強度の高い成形体としての特性を有するものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a wood-based composite material.
[0002]
[Prior art]
A wood-based composite material, for example, a wood-based structural material (for example, Japanese Patent Publication No. 50-17512) obtained by laminating a mixture of elongated wood material pieces and a binding material in the longitudinal direction, and applying pressure and heat treatment. ) And a wood-based structural material obtained by laminating wooden material pieces in the length direction, forming a mat, and then applying pressure and heat treatment (Japanese Patent No. 2527761).
[0003]
In the process of heating / pressurizing the above wood-based material, in the case of heat treatment by the so-called heat transfer method in which the wood material is sandwiched and pressed by a hot plate, in the case of a thick wood-based composite material, the surface layer in contact with the hot platen The density of the part is high, and the density tends to decrease toward the center. This is because the wooden piece in contact with the hot plate is softened and compressed by heat, but in the center the softening of the wooden piece is delayed and the amount of compression is reduced. Compared to a material that is homogeneous in the thickness direction, the physical properties of the bending strength are improved. However, when a thick product is produced due to heating by heat conduction, the heat treatment takes time, and if the treatment time is too long, the wood material pieces near the surface layer may be deteriorated.
[0004]
On the other hand, in the steam press method using steam injection for heating, heat is transferred to the center of the material at a stretch, so it is possible to create a homogeneous product in a short time, but the density of the surface layer in the thickness direction as in the heat transfer press However, it is difficult to produce a composite material having a high density and a density distribution with a low center density, and the physical properties of bending strength are not as good as those of the heat transfer system.
[0005]
[Problems to be solved by the invention]
The object of the present invention has been made in view of the above problems in the conventional method for producing a wood-based composite material, and the object of the present invention is a wood-based composite having a density distribution in the thickness direction in a short time. The object is to provide a method enabling the production of materials.
[0006]
[Means for Solving the Problems]
The present invention comprises a mixture of elongated wooden pieces and a binder, and the elongated wooden pieces are laminated while being oriented in one direction to form a wooden mat, and this mat is subjected to a heating and pressing process. In the method for producing a wood-based composite material to be molded, the heating / pressurizing step includes a step of performing a heat treatment by a steam injection method after performing a heating / pressurization treatment by a heat transfer method. It is a manufacturing method of a composite material.
[0007]
Tree species of the above-mentioned wood lumber include conifers such as cedar, cypress, spruce, fur, and radiatapine, and broad-leaved trees such as birch, apton, chamelere, sengonlaut, and aspen, but only plant materials produced from these forests In addition, plant materials produced outside the forest, such as bamboo and sorghum, can also be included.
[0008]
Available forms include logs of the above tree species, raw materials such as thinned wood, scraps generated at factories and residential building sites, waste pallet materials discarded after transportation of members, demolition waste materials generated at the time of building demolition, etc. . Any material can be used as long as the raw material is cut into pieces of about 1 mm to several hundred mm.
[0009]
As a method of processing the above raw materials into elongated wooden pieces, a hammer mill, a uniaxial crusher that crushes wood by rotating a roll with a blade on the surface, a biaxial or multiaxial crusher with a structure in which rotating blades are engaged However, it is also possible to use a rotary cutter that makes a veneer processed stick into a stick shape, a flaker that cuts a log or the like with a rotary blade into a strand, and the like. In particular, when a recycled material is used as a raw material, a crusher is preferable in that foreign matters are easily mixed and the durability of the blade is high.
[0010]
Since the elongated wooden piece obtained by the above method has a variation in size, a wooden piece of a predetermined size is obtained by a classification process. As the classification method, there are a roller screen method, a vibrating mesh method, a wind selection method, and the like, which may be used properly as necessary.
[0011]
It is preferable that the classified and slender wood pieces are placed with the moisture content adjusted to a certain range. By keeping the moisture content constant, there is no variation in the quality of the molded product during production. A preferable water content is 0 to 14%.
[0012]
The long and slender wood pieces that have been classified and adjusted in water content are mixed with the binder. Although the amount of the binder to be mixed depends on the density, shape and surface state of the wood piece, it is usually preferably 1 to 20% by weight with respect to the weight of the wood piece.
[0013]
Examples of the binder include phenol resins, urea resins, isocyanates, wood industry adhesives used for plywood and particle boards, and these binders may be used alone or in combination.
[0014]
Examples of the means for mixing the wood piece and the binder include a method in which the wood piece and the binder are put into a mixer such as a Henschel mixer and mixed. However, when the binder is liquid, it is on a conveyor or in a drum blender. When a binder is attached to the surface of the wood material piece by using an application means such as spray on the wood material piece, etc., a structural material having a uniform and stable strength can be obtained.
[0015]
The mixture of the wood piece and the binder is laminated while being oriented in a certain direction to form a wood mat. Specifically, it can be performed by putting wooden pieces into a mold and laminating them. In order to orient in one direction, an orientation laminating apparatus such as a forming type divided at regular intervals or a disk orienter used in the manufacture of an oriented strand board (OSB) or the like is used.
[0016]
In the present invention, a wood-based composite material is produced by heating and pressure-molding the above-mentioned wood-based mat. As a method used for heating and pressure-molding, heat is applied from the surface of the wood material piece to the inside by a hot platen or the like. A heat transfer system that transmits heat and a steam injection system that directly heats the inside of the material are used. By performing heat treatment and heat treatment by heat transfer method and then heat treatment by steam injection method, the density of the surface layer part is high, and a wood-based composite material that decreases in density toward the center is obtained, and in a short time Heating and pressurization can be performed.
[0017]
As for the said heating conditions, 100-250 degreeC is preferable. The pressure condition is preferably 1 to 10 MPa. The heating / pressurizing treatment time may be performed only for the time during which the binder is cured.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Example 1
A molded body made of a wood-based composite material was prepared by the following process.
Using the web roller type classifier (web roller screen, manufactured by Taihei Co., Ltd.), the wooden piece of board purchased from a wood waste disposal contractor is classified into a wooden piece of 1 to 15 mm in thickness, and the above wooden piece The water content of the piece was adjusted in a heating oven (50 ° C., 24 hours) (water content was 5.2%).
[0019]
Next, the wooden piece and the binder were blended using a drum blender. First, a wooden piece was put into a drum blender, and an isocyanate adhesive (5% with respect to the wooden piece) was applied as a binder. Next, the blended binder and the wood piece were put into a wood piece supply apparatus, and forming (orientation / laminating) was performed. The forming mold had a length of 2000 mm, a width of 500 mm, and a height of 100 mm, and was divided into 10 equal portions at intervals of 50 mm using a metal orientation plate (steel, thickness 2 mm). As a result, a woody mat having a thickness of about 100 mm was obtained.
[0020]
Next, the forming mold was removed and the wood mat was put into a heating press. A metal mold having a length of 2500 mm, a width of 500 mm, and a height of 150 mm was used as the heating press machine, and a heat transfer type (300 t press machine manufactured by Kawasaki Yoko Co., Ltd.) was used. The treatment conditions by the heat transfer method were 5 minutes at a temperature of 180 ° C. and a pressure of 3 MPa. Thereafter, 0.9 MPa, 180 ° C. steam was injected under a constant pressure, and the vapor pressure was maintained for 1 minute to obtain a molded body of a wood-based composite material. Next, the molded body was cut into six faces to obtain a molded body of 1500 × 400 × 25 mm. When the cross section of the molded product was observed, the density of the surface layer portion was about 0.8, the density of the central portion was about 0.7, and the overall density was 0.75.
[0021]
(Example 2)
In Example 1 above, after the heating / pressurizing process by the heat transfer method, the pressure is once released and 0.9 MPa of steam is injected, and at the same time, pressurization is started again, and the heat transfer method is performed at 180 ° C. and 3 MPa. Except that it was molded, a wood-based composite material molded body was obtained in the same manner as in Example 1. When the cross section of the molded product was observed, the density of the surface layer portion was about 0.8, the density of the central portion was about 0.7, and the overall density was 0.76.
[0022]
(Comparative Example 1)
It carried out similarly to Example 1 except not having performed the heating and pressurizing process by the heat-transfer system. That is, 0.9 MPa, 180 ° C. steam was injected, and the vapor pressure was maintained for 1 minute to obtain a molded body of a wood-based composite material. The molded product had no density distribution and was homogeneous throughout, and the density was 0.76.
[0023]
(Comparative Example 2)
In Example 1, the processing time by the heat transfer method is performed for 30 minutes, and the molding of the wood-based composite material is performed in the same manner as in Example 1 except that the heating / pressurizing process by the steam injection method is not performed. Got the body. When the cross section was observed, the density of the surface layer portion was about 0.8, the density of the central portion was about 0.7, and the density as a whole was 0.75. The bending strength and elastic modulus of the sample were evaluated, and the results are shown in Table 1. In addition, the measurement of a density, bending strength, and a bending elastic modulus was measured based on JISZ2101.
[0024]
[Table 1]

[0025]
【The invention's effect】
Using a press machine capable of steam injection, after heating and pressurizing treatment by heat transfer method for a predetermined time, and further by heating and pressurizing treatment by steam injection method, wood material pieces near the surface layer It is possible to make a wood-based composite material having a density distribution in which the surface layer density is high and the center density is low in the thickness direction without deterioration.
Accordingly, a composite material having a density distribution with a high surface layer density and a low density at the center can be obtained in a short time, and these have properties as a molded article having a high bending strength.

Claims (1)

A wood system consisting of a mixture of elongated wood pieces and a binder, and the elongated wood pieces are laminated while being oriented in one direction to form a wood-based mat, and this mat is formed through a heating and pressing process. In the method for producing a composite material,
The method for producing a wood-based composite material, wherein the heating / pressurizing step includes a step of performing a heat treatment by a steam injection method after performing a heating / pressurization treatment by a heat transfer method.