JPH0752112A - Manufacture of wooden plate - Google Patents

Abstract

PURPOSE:To prevent the invasion of moisture into wooden chips by a method wherein the whole surfaces of wooden chips are plasticated so as to have bonding property and the wooden chips are bonded mutually and strongly while the wooden chips are coated by resin films. CONSTITUTION:Mixed solution of phenol and sulfuric acid is poured onto wooden chips 1 to plasticize the wooden chips thermally. Next, the water solution of sodium hydroxide is poured and mixed under heating in order to provide the heat-plasticized wooden chips 1 with alkalified nature. Then, the chips are heated utilizing thermal inertia whereby the surfaces of the wooden chips 1 are alkalified. Next, formaldehyde solution is added to the alkalified wooden chips to make resol resin on the surfaces of the wooden chips 1. Then, the wooden chips 1, whose surfaces are changed into resol resin, are foamed by a foaming machine, then, hot pressing is effected by a hot press to obtain an objective plate type body. Accordingly, the whole surfaces of the wooden chips are changed into adhesive agent whereby the wooden chips are bonded mutually and strongly while the wooden chips 1 are coated by resin whereby moisture can not invade easily into the chips.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving dimensional stability and surface smoothness of a wooden board.

[0002]

2. Description of the Related Art A wood board such as particle board is formed by chipping wood or mechanically crushing it to a state close to wood powder and then spraying an adhesive such as urea formaldehyde or melamine formaldehyde. It was manufactured by hot pressing with a hot press.

[0003]

However, in such a method, since the adhesive is sprayed or sprayed on the surface of the wood chips, the adhesion of the adhesive becomes partial and non-uniform as shown in FIG. As the adhesion between the chips weakened, moisture easily entered into the wood chips not covered with the adhesive and into the gaps between the wood chips, and the wood board was accompanied by a significant dimensional change. Also, due to the uneven application of the adhesive to the wood chips, after hot pressing molding,
Since the surface of the wooden board was not smooth, it was necessary to sand it, and the yield of the material was also reduced.

[0004]

In order to solve the above problems, the present invention is directed to a step of adding a mixed solution of phenol and sulfuric acid to wood chips, stirring and heating, and then adding an aqueous sodium hydroxide solution. A method of sequentially performing a step of stirring and heating, a step of adding an aqueous formaldehyde solution, stirring and heating, and a step of forming and molding with a hot press were adopted.

The above means will be described in detail below.

First, wood chips are obtained. As the wood chips, generally used waste materials of hardwoods and conifers from lumber factories and plywood factories are mainly used. As a size, it is formed into a chip shape with a thickness of 0.1 to 0.5 mm, a length of about 10 to 20 mm and a width of about 1.0 to 3.0 mm by a crusher. The obtained wood chips are placed in a container, and the water content thereof is adjusted to about 30 to 40% so that a mixed solution of phenol and sulfuric acid described later is uniformly attached to the surface of the wood chips.

Next, a mixed liquid of phenol and sulfuric acid is added to the wood chips to make the wood chips thermoplastic. The mixing ratio of phenol and sulfuric acid is 1: 0.03 to 0.10 (weight ratio), and the addition ratio of the mixing liquid of phenol and sulfuric acid is 0.5 to 1.5 (weight ratio) with respect to the wood chips 10. After addition, stir and heat. The heating temperature is 90 to 100 ° C. and the time is about 30 minutes.

Next, in order to make the thermoplastic (acidic) wood chips alkaline, an aqueous sodium hydroxide solution is added and stirred and heated. The addition ratio of the sodium hydroxide aqueous solution is 0.5 to 1.5 (weight ratio) with respect to the wood chips 10. Then, the residual heat (80-9
It heats for about 30 minutes using (0 degreeC). This makes the surface of the wood chips alkaline.

Next, an aqueous formaldehyde solution is added to the wood pieces made alkaline to convert the surface of the wood chips into a resole resin (adhesive). The addition ratio of the 37% formaldehyde aqueous solution was 1.0 to 1.
5 (weight ratio). The heating temperature is 80 to 90 ° C. and the time is about 30 minutes. As a result, the surface of the wood chips is made into a thermosetting resol resin.

It is preferable that the stirring operation in the above steps is continuously carried out by a screw feeder or the like because the processing efficiency is improved.

Then, the wood chips, which have been made into a resole resin in the above process, are formed by a forming machine,
Hot press molding is performed with a hot press to obtain the desired plate-shaped body. The hot press conditions are a temperature of 150 to 170 ° C., a pressure of 20 to 30 kg / cm ² , and a time of 10 to 15 minutes.

[0012]

In the present invention, the above-mentioned method is adopted in order to make the entire surface of the wood chips resinous so as to have an adhesive property as shown in FIG. However, this is to prevent water from entering the wood chips.

Examples of the present invention will be shown below.

[0014]

EXAMPLE A mixed solution of phenol and sulfuric acid having a mixing ratio of 1: 0.03 was added to wood chips adjusted to have a water content of 40%, stirred and heated to 90 ° C. Subsequently, an aqueous sodium hydroxide solution was added at a ratio of 1 to 10 wood chips,
The mixture was stirred and heated to 80 ° C. using the residual heat of the above process.
Next, add 37% formaldehyde solution to wood chips 1
It was added at a ratio of 1 to 0, stirred and heated to 80 ° C. Next, forming wood chips at 160 ℃,
Hot pressing was performed with a hot press under the conditions of 20 kg / cm ² and 10 minutes. By the above method, wood boards having resin rates of 15% and 20% (each having a thickness of 9 mm) with respect to wood chips were manufactured.

As comparative examples, two types of 12 mm thick melamine resin type three-layer particle board (M type) and 9 mm thick phenol resin type single layer particle board (P type) manufactured by the conventional method are prepared. Then, the following comparative test was performed.

[0016]

[Table 1]

The dimensional change rate was calculated by first measuring the dimension L _o of a wood board dried at 60 ° C. for 24 hours and then leaving the wood board at 40 ° C. and a humidity of 90% for 6 days. The dimension L _g was measured and determined by the formula of (L _g −L _o ) / L _o × 100.

From the above results, it can be seen that the wood board manufactured according to the present invention (especially 20% resin rate type) has a small dimensional change and a bending strength comparable to that of a three-layer particle board having a thickness of 12 mm.

[0019]

According to the present invention, the entire surface of the wood chips is made into an adhesive agent, the wood chips are firmly adhered to each other, and the wood chips are covered with the resin so that water cannot easily enter. A wood board with excellent dimensional stability against moisture can be obtained. In addition, since the surface of the wood chips is completely covered with resin, even though the chips for the core layer used for manufacturing the conventional three-layer or multilayer particle board are used, The surface of the wood board is finished in a smooth shape like a plastic board, and it is not necessary to sand, and the material yield is improved.

[Brief description of drawings]

FIG. 1 is a view showing a state of adhesion of an adhesive on the surface of a conventional wood chip.

FIG. 2 is a diagram showing a state of adhesion of an adhesive agent on the surface of the wood chip of the present invention.

[Explanation of symbols]

 1 Wood chip 2 Adhesive

Claims (1)

[Claims] 1. A step of adding a mixed solution of phenol and sulfuric acid to wood chips, stirring and heating, then adding an aqueous sodium hydroxide solution, stirring and heating, and then adding an aqueous formaldehyde solution, stirring and heating A method of manufacturing a wood board, which comprises sequentially performing the step of forming, and then forming and hot-pressing.