Particle board

Abstract

To provide a particle board excellent in dimensional stability at the time of wetting.SOLUTION: By using the semi-carbonized wood heat-treated at a temperature (for example, 200 °C (150 °C) to 300 °C) lower than the carbonizing temperature as the particle material for manufacturing the particle board, the water-absorption thickness expansion coefficient can be made lower than that of the non-semi-carbonized particle board manufactured using the general-purpose wood, and the particle board having excellent dimensional stability at the time of wetting can be provided.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a particle board made from semi-carbonized wood. [Background technology]

[0002] Today, particle boards are known, which are made from chipped wood (particle material) and processed into boards by heat compression molding using a synthetic resin adhesive, and are widely used not only as housing materials but also in various fields such as furniture and packaging materials. Furthermore, such particle boards are highly convenient and are widely used, in part because the thickness, size, etc., can be freely adjusted. In contrast, strand boards are known that are made from wood pieces (strand material) that are larger than the particle material that is the raw material for particle boards, and such strand boards have strength advantages because the strand material is larger than the particle material, and are therefore often used as structural materials for wooden structures such as houses.In such strand boards, it has been proposed to use semi-carbonized wood (semi-carbonized wood) as the strand material in order to reduce the expansion rate (water absorption thickness expansion rate) when the strand board absorbs water (see, for example, Patent Document 1). The semi-carbonized wood is a modified wood that has been thermally modified by exposing it to a relatively low temperature range of approximately 200°C (or 150°C) to 300°C. It has a high energy density, excellent VOC (volatile organic compound) suppression effect, and excellent water resistance. Utilizing the properties of semi-carbonized wood, it has been proposed to manufacture strand boards using the semi-carbonized wood as strand material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6622423 Summary of the Invention [Problem to be solved by the invention]

[0004] However, strand board is made using strand material (chip material) with large particle sizes, and is different not only in characteristics but also in uses from particle board made using particle material with small particle sizes, so it goes without saying that semi-carbonized particle board cannot be made using semi-carbonized strand material as is. Furthermore, there have been no attempts to use semi-carbonized wood as the particle material that is the raw material for particle board, and the problem to be solved by this invention is whether particle board can actually be manufactured using semi-carbonized wood as the particle material, and if it can be manufactured, verifying the differences in properties between semi-carbonized wood and general-purpose particle board that does not use semi-carbonized wood, and examining the advantages of particle board using semi-carbonized wood, thereby determining whether particle board with unprecedented properties can be provided. [Means for solving the problem]

[0005] The present invention was created in view of the above-mentioned circumstances and with the aim of solving these problems. The invention of claim 1 is a semi-carbonized particle board made by applying adhesive to the surface of particle material cut from wood chips and molding the material under high-temperature and pressurized conditions, in which all or part of the particle material is semi-carbonized particle material made from semi-carbonized wood. The invention of claim 2 is a semi-carbonized particle board according to claim 1, characterized in that the semi-carbonized particle material is made by crushing biomass wood into chips, cutting them, and then semi-carbonizing them. The invention of claim 3 is the semi-carbonized particle board according to claim 1, characterized in that the semi-carbonized particle board has a water absorption thickness swelling rate superior to that of a non-semi-carbonized particle board that does not use semi-carbonized particles. [Effects of the Invention]

[0006] By adopting the invention of claim 1, semi-carbonized wood is used as particle material, and a particle board can be provided that is excellent in bending when wet and in thickness expansion rate upon water absorption. By adopting the invention of claim 2, it is possible to effectively utilize biomass wood to create semi-carbonized particle board. By adopting the invention of claim 3, it is possible to provide a product that is superior to non-semi-carbonized particle boards. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a process diagram showing the particle board manufacturing process. [Figure 2] (A) and (B) are photographs of non-torrefied particleboard and torrefied particleboard. [Figure 3] FIG. 1 is a table showing the physical properties of torrefied and non-torrefied particleboards with varying thicknesses. [Figure 4] FIG. 1 is a graph showing the relationship between the thickness of torrefied and non-torrefied particle boards and the water absorption thickness swelling rate. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail. The particle board embodying the present invention uses particulate material made from semi-carbonized wood chips as part or all of the raw material. Particle boards generally have a three-layer structure consisting of a central core layer sandwiched between two surface layers, with the particle material for the core layer being sieved through a mesh of 1.00mm to 4.00mm, and the particle material for the surface layer being sieved through a mesh of 0.25mm to 1.00mm.

[0009] On the other hand, semi-carbonized wood is modified wood that has been altered by treating (exposing) wood to the aforementioned temperature of 200°C (or 150°C) to 300°C, which is lower than the normal carbonization temperature (600°C to 1000°C), and under atmospheric pressure. The treatment conditions for semi-carbonization, such as temperature and treatment time, are adjusted appropriately depending on the type, size, moisture content, quality, etc. of the wood used as raw material. The wood used as the raw material for this semi-carbonized wood can be so-called woody biomass, such as thin trees and branches generated when forests are cut down or trees are pruned, sawmill scraps generated from sawmills, and wood generated during the construction and demolition of houses.

[0010] A more specific method is explained using Figure 1. First, the raw material wood chips are cut into particles (chipped). The particles are then sieved as described above to obtain particle materials with average particle sizes of approximately 3.00 mm and 0.7 mm for the core layer and surface layer. In this embodiment, of the obtained particle materials for the core layer and the surface layer, only the particle materials for the core layer were semi-carbonized. The core layer particle material was then placed in a drying furnace and heat treated for approximately 15 to 30 minutes at an internal temperature of 280°C under atmospheric pressure to produce semi-carbonized wood. In particular, the particle material for semi-carbonization used in the present invention is small pieces with an average particle size of approximately 3.00 mm that are retained when sieved through a 1.00 mm mesh screen and fall off when sieved through a 4.00 mm mesh screen. Therefore, the particles are efficiently semi-carbonized to the core through a short heating and pressure treatment, and can exhibit uniform performance as semi-carbonized particle material. Incidentally, the surface of semi-carbonized wood is brown, and therefore, when the particle material for the surface layer is semi-carbonized, the semi-carbonized particle board produced has a brown surface, which impairs visibility. For this reason, only the particle material for the core layer is used as semi-carbonized particle material, but it goes without saying that the particle material for the surface layer may also be semi-carbonized.

[0011] The particle material thus obtained is used to make particle boards, which requires applying an adhesive to the surface of each particle material for the core layer and the surface layer. The adhesive used in this case is one or a mixture of adhesives selected from the adhesives used in ordinary particle board manufacturing, such as formaldehyde resin adhesives and urethane adhesives, which are polymer resin adhesives. In this embodiment, a urethane adhesive is used. Incidentally, the present embodiment employs an adhesive that does not contain any wax to improve the water resistance of the particle material, but even when such an adhesive is used, it exhibits performance equivalent to that of an adhesive that contains wax.

[0012] The particle material for the core layer and the surface layer coated with adhesive in this way is spread onto a wooden mold to form a particle board measuring 400 mm x 400 mm x thickness.To do this, first the particle material for the surface layer is spread onto the bottom of the mold to a specified thickness, then the particle material for the core layer is spread to a specified thickness, and finally the particle material for the surface layer is spread to a specified thickness. In this embodiment, the particle board to be manufactured is first prepared to have a thickness of 9.00 mm and a density of 0.78 g / cm. 3 The particle materials for the surface layer and the core layer were scattered on the wooden mold so that the surface layer ratio was 40% (surface layer 20%, core layer 60%, surface layer 20%). Then, the temperature was 210°C and the pressure was 3.43 × 10 6 Pa (surface pressure 35kgf / cm 2 ) was heated and pressed under the same heat and pressure conditions as for making ordinary particle boards for 100 seconds, then allowed to cool naturally, and the necessary finishing processes such as polishing the front and back surfaces were carried out to make semi-carbonized particle boards, and the physical properties of the boards were examined. For comparison, a non-carbonized particleboard was produced as a control (standard) using ordinary non-carbonized particle material under the same conditions as the semi-carbonized particleboard manufacturing process, except that no semi-carbonized wood was used, and its physical properties were measured in the same way. Photographs of the non-carbonized particle board and semi-carbonized particle board prepared above are shown in Figure 2(A) and (B).

[0013] The 9mm-thick torrefied and non-torrefied particleboards were measured for density and bending strength after standing at room temperature, density, bending strength (wet bending strength), and peel strength after 2 hours of immersion in 70°C hot water followed by 1 hour of immersion in 20°C cold water. The density and water-absorption thickness swelling coefficient were also measured after 24 hours of immersion in 20°C ± 1°C water approximately 3 cm below the water surface. The results are shown in Figure 3. Regarding bending strength and wet bending strength, multiple samples were prepared from each of the torrefied and non-torrefied particleboards, and the density, bending strength, and wet bending strength were measured and averaged. Similarly, multiple samples were prepared from each of the torrefied and non-torrefied particleboards, and the density, bending strength, and peel strength after standing were measured and averaged. The results are shown in the table in Figure 3, in the column for "test piece thickness" of 9 mm. Incidentally, for these measurement items, those described in JIS A5908:2022 were followed.

[0014] According to this, the bending strength is roughly the same when left at room temperature and when immersed in water at 20°C±1°C at a depth of about 3 cm for 24 hours. In contrast, the water absorption rate and water absorption thickness expansion rate of the torrefied particleboard were both lower than those of the non-tomrefied particleboard, and it is therefore concluded that the torrefied particleboard has better wettability properties than the non-tomrefied particleboard.

[0015] Furthermore, we investigated whether the thickness of particleboard affects the properties. Torrefied and non-torrefied particleboards were produced under the same conditions as those used for producing particleboards in the above-described embodiment, except for thicknesses of 12 mm, 15 mm, 20 mm, 25 mm, and 30 mm. Multiple sample pieces were similarly taken from each of these particleboards, and each was measured for density and bending strength after standing at room temperature, density and bending strength after immersion under the above-described conditions (wet bending strength), density and thickness swelling after water absorption under the above-described conditions, and peel strength after standing. The average values ​​of these measurements are shown in the table in Figure 3. Furthermore, the graph in Figure 4 plots the measurements for each test piece for different board thicknesses and the relationship between thickness swelling and water absorption.

[0016] From these tables and graphs, it can be seen that when comparing torrefied particleboard with non-torrefied particleboard, the torrefied particleboard has slightly weaker bending strength under normal conditions, but when the board is thin, the torrefied particleboard has weaker bending strength under wet conditions, but when the board is thicker, the torrefied particleboard is stronger. It was also confirmed that the torrefied particleboard had a lower water absorption thickness swelling rate and water absorption rate, making it possible to provide particleboard with unprecedented properties. [Industrial Applicability]

[0017] The present invention can be used as a particle board using semi-carbonized wood.

Claims

1. This semi-carbonized particle board is made by applying adhesive to the surface of particle material made by cutting wood into chips, and molding the material under high-temperature and pressure conditions, and all or part of the particle material is semi-carbonized particle material made from semi-carbonized wood.

2. 2. The semi-carbonized particle board according to claim 1, wherein the semi-carbonized particle material is obtained by crushing biomass wood into chips, cutting the chips, and then semi-carbonizing the chips.

3. 2. The torrefied particle board according to claim 1, characterized in that the torrefied particle board has a water absorption thickness swelling rate superior to that of a non-torrefied particle board not using torrefied particles.

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