JPH0361561B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing particle board. Particle board has no anisotropy and is widely used as a large-area board material with sufficient strength for furniture, construction materials, etc., and single-layer and multi-layer particle boards are manufactured according to the purpose. . Multi-layer particle board can be explained using the mainstream three-layer particle board as an example.
It has a structure consisting of an inner layer made up of coarse particles and a smooth and hard surface layer made up of fine particles, so it has good dimensional stability, high bending strength, and an overall well-balanced party. It's a kuru board. On the other hand, with the depletion of high-quality wood resources in recent years, sawdust is also being used as a raw material for the surface layer of particle board.
It has become necessary to use so-called low-quality raw materials such as synthetic waste materials. However, the low-quality raw materials have the following drawbacks. In other words, taking sawdust as an example, sawdust is square in shape and has a form factor (L/D/W;
Since L = length, D = thickness, W = material specific gravity) is small, when used as a surface layer material of multilayer particle board as it is, it is difficult to obtain strength properties, especially bending strength. Furthermore, since the thickness swelling is large, when secondary processing is performed using water-soluble adhesives or various cosmetic materials, there is a risk that the surface smoothness will deteriorate. Moreover, even if the sawdust is subjected to some mechanical treatment, the size after treatment must be extremely small, 90% of the total weight under the sieve is 1 mm or less, so it cannot be used with ordinary crushing equipment such as refiners or hammer mills. It was difficult to adjust it to the desired shape. Due to the above-mentioned circumstances, there have been problems in using sawdust etc. as a raw material for the surface layer of a multilayer particle board, even though the raw material cost is low. The present invention has been devised in view of the above-mentioned problems, and by applying special treatment to lumber sawdust to produce adjusted sawdust, and layering the adjusted sawdust on the surface of particle board, it has a high strength and a good surface texture. An object of the present invention is to provide a method for manufacturing particle board which is excellent in quality and is inexpensive. Hereinafter, the method for manufacturing particle board of the present invention will be explained in detail. When processing lumber sawdust, first its moisture content is adjusted to about 40 to 60%. Next, the lumber sawdust having the above moisture content is fed into a closed container and compressed while being heated from the outside to raise the internal pressure and temperature, and then the compression is suddenly released to form adjusted sawdust. The heating temperature in this case is 140°C or higher, preferably 200 to 300°C. More specifically, a dry extrusion molding machine, a rice husk swelling and softening machine, etc. can be used as a closed container having a compression mechanism as described above, that is, as a processing machine. As described above, when the sawdust whose moisture content is adjusted to 40 to 60% is compressed in the processing machine, the internal pressure increases and the internal temperature increases due to the heat of compression friction. If compression is suddenly released in this state,
The water present in the sawdust tissue expands rapidly as the internal pressure drops as it exits the system. Then, the sawdust is destroyed from inside the tissue by the water expansion action, and is pulverized into the desired shape and size. The form factor of the adjusted sawdust created by the above treatment is about 15 to 30, and the form factor of the adjusted sawdust is about 15 to 30.
It is markedly improved compared to about 10 to 10, and moreover, its shape is fibrous. Therefore, the bonding strength between the fibers is improved, and the shape and size become sufficient to be used as a raw material for the surface layer of multilayer particle board. Further, when processing sawdust by the above-mentioned method, there are advantages such as less electric power is required and less fine powder is generated compared to the conventional method of pulverizing with a refiner or the like. Next, the adjusted sawdust is sieved according to the surface properties of the target particle board, and then layered on the surface of the base material of the particle board. The method for layering the above-mentioned adjusted sawdust, that is, the manufacturing method for multilayer particle board, is the same as before, but the adjusted sawdust and the chips for the inner layer prepared by the usual method are separately dispersed according to the order of the layers, and then hot-press molded. It has characteristics. As described above, according to the method for manufacturing particle board of the present invention, a particle board with excellent strength and surface quality can be produced by using lumber sawdust, which has not been suitable as a raw material for the surface layer of particle board until now. can be manufactured. Moreover, since sawdust, which is inexpensive as a raw material, is used, product costs can be reduced, and the particle board manufacturing method of the present invention has high practical effects both technically and economically. be. The present invention will be described below with reference to Examples and Comparative Examples. Example 1 Lauan wood sawdust with a moisture content of 40% was heated to
After compaction in an extruder with a temperature of 200° C., the compaction was abruptly released to obtain conditioned sawdust. The prepared sawdust was sieved through a 1.0 mm screen to form chips for the surface layer. Next, a urea resin adhesive was applied to the surface layer chip (water content 3.5%) and the inner layer chip (water content 5.5%) prepared from lauan material using a conventional method.
After applying 11.5% and 7.5% (by weight), hot pressure molding (145° C., pressure 25 Kg/cm ² ) was performed to obtain a board having a thickness of 13.5 mm. Finally, the board was cured at room temperature for about a week until it reached a thickness of 12 mm.
A three-layer particle board with mm was obtained. Comparative Example 1 A three-layer particle board with a thickness of 12 mm was obtained in the same manner as in Example 1, except that lauan sawdust having a moisture content of 3.5% was used as chips for the surface layer. Comparative Example 2 The thickness was adjusted in the same manner as in Example 1, except that pulverized material obtained by treating lauan wood sawdust with a single-disc refiner (clearance 0.2 mm) was used as surface layer chips (water content 3.5%). A three-layer particle board with 12mm was obtained. Table 1 shows the properties of the three-layer particle boards obtained in Example 1 and Comparative Examples 1 and 2.

[Table] As shown in Table 1, the three-layer particle board obtained by the manufacturing method of the present invention has particularly excellent bending strength and surface roughness.

Claims (1)

[Claims] 1. After compressing lumber sawdust in a closed container to raise the internal pressure and temperature, the compression is suddenly released to create adjusted sawdust, and the adjusted sawdust is layered on the surface of the particle board. A method for manufacturing particle board.