Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
  • B27N3/02—Manufacture of substantially flat articles, e.g. boards, from particles or fibres from particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
  • B27N3/06—Making particle boards or fibreboards, with preformed covering layers, the particles or fibres being compressed with the layers to a board in one single pressing operation

Definitions

• the present invention relates to a three-layer particle board and a method for manufacturing particle board.
• three-layer particleboard uses fine ground wood chips for the surface layer, it has improved surface properties (smoothness) compared to single-layer particleboard made of coarse ground wood chips, but its bending strength is lower. Increasing the density of the surface layer to ensure a certain level of bending strength in three-layer particleboard creates the problem of increased weight and the use of more adhesive. Three-layer particleboard also has the problem of low peel strength, and poor water resistance and dimensional stability due to moisture absorption.
• the present invention uses a surface layer of ground wood chips that are finer than the core layer of a three-layer particle board, and contains a large number of extremely thin shaved wood chips.
• the first invention is based on a three-layer particleboard in which the surface layer is made of finer wood chips than the core layer.
• the first invention is characterized in that the surface layer contains numerous thin wood chips having a uniform thickness of 0.05 mm or more and 0.35 mm or less.
• ground wood chips refer to wood chips of various shapes and of non-uniform thickness, which are formed by finely grinding wood material with a known grinding device until it passes through a sieve with a specified mesh size installed at the discharge outlet of the grinding device.
• shaved wood chips refer to thin, flake-like wood chips of uniform thickness, which are formed by cutting wood material into a thin, uniform thickness with a known cutting device having a blade that cuts material into a thin, uniform thickness. Note that "shaved wood chips have a uniform thickness” allows for thickness variations due to processing errors of the cutting device, for example, a thickness variation of about ⁇ 20% is allowed.
• the surface layer of the three-layer particle board contains not only the fine wood chips that are usually included, but also wood chips with an extremely thin and uniform thickness of 0.05 mm to 0.35 mm, which are produced by cutting.
• This configuration increases the bending strength of the surface layer of the particle board. Therefore, there is no need to increase the density of the surface layer or use a large amount of adhesive to ensure the bending strength of the particle board.
• the presence of thin wood chips makes it easier to bond the wood pieces (wood chips and wood chips) together with a small amount of adhesive. Therefore, with the three-layer particle board of the first invention, it is possible to reduce the amount of adhesive used while ensuring bending strength.
• wood chips are mixed into a large number of surface wood chips at a ratio of 20% to 90% by weight of the total weight of the surface wood chips.
• the fourth invention is a method for manufacturing a particleboard having a three-layer structure in which fine wood chips are used for the surface layer than for the core layer, comprising a first crushing step in which a first wood material is crushed to produce a large number of wood chips, and a second sieve in which the large number of wood chips are sieved using a first sieve having a mesh size of 16 mm or less and a second sieve having a mesh size of 0.5 mm or more and smaller than the first sieve to produce a large number of first wood chips that pass through the first sieve but not the second sieve, a large number of second wood chips that pass through both the first and second sieves, and a large number of wood chips that pass through the first and second sieves.
• a first classification step in which the first wood chips are classified into a number of pulverized wood chips for a core layer and a number of pulverized wood chips for a surface layer, the first wood chips being classified into a number of pulverized wood chips for a core layer and a number of pulverized wood chips for a surface layer; a cutting step in which the second wood material is cut so that the fibers are linearly present on the surface to produce a number of thin wood flakes having a uniform thickness of 0.05 mm to 0.35 mm; and a second crushing step in which the number of thin wood flakes and the number of thin wood flakes are crushed so that they are broken along the fiber direction to produce a number of small wood flakes having an elongated shape, and a number of small wood flakes produced by the above-mentioned number of thin wood flakes and the number of small wood flakes.
• crushing the first wood material means using a known crushing device to crush the first wood material finely until it passes through a sieve with a specified mesh size installed at the discharge outlet of the crushing device, and crushing forms wood chips of various shapes with non-uniform thickness.
• cutting the second wood material means cutting the second wood material thinly and uniformly by a known cutting device having a blade that cuts material thinly and uniformly, and cutting forms flake-like wood cutting pieces with uniform thickness. Note that "wood cutting pieces with uniform thickness” means that thickness variations due to processing errors are allowed, for example, thickness variations of about ⁇ 20% are allowed.
• the fourth invention makes it possible to provide a three-layer particleboard that has excellent surface properties, water resistance, bending strength, and peel strength, and has little dimensional change, without increasing cost or weight.
• the sixth invention is the fifth invention, characterized in that in the selection process, the numerous first woody thin pieces are selected as the numerous woody cutting pieces for the surface layer.
• the seventh invention is the fifth invention, characterized in that in the selection process, the numerous second small wood flakes that pass through both the third and fourth sieves and the numerous third small wood flakes that do not pass through both the third and fourth sieves are selected as the numerous wood cuttings for the surface layer.
• the wood shavings produced when the second wood material is processed to form another wood board are used as the wood shavings in the particle board. Therefore, even if a material (wood shavings) different from the material (ground wood chips) used in normal particle boards is used, it can be easily procured because the different material is the one produced when processing the material for the other wood board. Therefore, according to the fifth to seventh inventions, a three-layer particle board with excellent surface properties, water resistance, bending strength, and peel strength and small dimensional change can be easily and relatively inexpensively provided.
• wood chips other than the first small wood chips that are selected by classifying the small wood chips are used as the wood chips.
• waste wood that is generated during the formation of other wood boards and is not used for other wood boards is used as wood chips for the surface layer of the three-layer particle board, making it possible to form the three-layer particle board more inexpensively.
• the second wood material of the other wood boards is used without waste, this leads to effective use of wood resources.
• wood chips are mixed with a large number of surface wood chips in a ratio of 20% to 90% by weight of the total weight.
• a three-layer particleboard with excellent surface properties, water resistance, bending strength, and peel strength and with little dimensional change can be provided without increasing cost or weight.
• the surface layer of the three-layer particle board is made of finer ground wood chips than the core layer, and contains a large number of extremely thin, uniformly thick shaved wood chips. This makes it possible to provide a three-layer particle board with excellent surface properties, water resistance, bending strength, and peeling strength, and with little dimensional change, without increasing cost or weight.
• FIG. 1 is a cross-sectional view showing a part of a particle board according to a first embodiment.
• FIG. 2 is a diagram showing the process of producing ground wood pieces.
• FIG. 3 is a diagram showing the process of producing wood cutting pieces.
• FIG. 4 is an enlarged perspective view showing a first small wood piece.
• FIG. 5 is a diagram showing the manufacturing process of particle board.
• FIG. 6 is a partially enlarged cross-sectional view showing in comparison the mat before the hot pressing step and the particle board formed after the hot pressing step.
• FIG. 7 shows the results of an experiment to verify the effects of the first embodiment.
• First Embodiment of the Invention - Composition of particle board - 1 shows a particle board 10 according to a first embodiment of the present invention.
• the particle board 10 can be used, for example, as a base material for building materials such as flooring, or as a component material for furniture.
• the first wood chips 2b, ..., 2b thus classified and selected are used as the ground wood chips 2, ..., 2 for the core layer 11, and the second wood chips 2c, ..., 2c obtained at the same time are used as the ground wood chips 2, ..., 2 for the surface layer 12.
• the third wood chips 2d, ..., 2d are not used as the ground wood chips 2, ..., 2 but are returned to the grinding device and ground again.
• the woody flakes 3b, ..., 3b obtained by pulverization are classified into three sizes using two types of sieves (third and fourth sieves), large and small. Specifically, the woody flakes 3b, ..., 3b are divided into first woody flakes 3c, ..., 3c of desired size that pass through the coarse third sieve and do not pass through the fine fourth sieve, second woody flakes 3d, ..., 3d that pass through both the third and fourth sieves (i.e., finer than the first woody flakes 3c, ..., 3c), and third woody flakes 3e, ..., 3e that do not pass through both the third and fourth sieves (i.e., coarser than the first woody flakes 3c, ..., 3c).
• the second small wood flakes 3d, ..., 3d and the third small wood flakes 3e, ..., 3e other than the first small wood flakes 3c, ..., 3c classified and selected in this manner are used as the wood cutting pieces 3, ..., 3 for the surface layer 12.
• ⁇ Adhesive application step S2> The wood pieces 1, ..., 1 for the core layer 11 and the wood pieces 1, ..., 1 for the surface layer 12 produced in the wood piece production process S1 are each carried into an adhesive applicator to be coated with adhesive.
• an isocyanate-based adhesive can be used, and other adhesives such as amine-based adhesives such as phenolic resin, urea resin, and melamine resin, and natural wood (tannin)-based adhesives may also be used.
• a commonly used water repellent may also be used together with the adhesive.
• ⁇ Mat forming process S3> In the mat forming process S3, as shown in the left side of Fig. 6, first, a number of wood pieces 1, ..., 1 for the surface layer 12 to which adhesive is applied are piled up in a state of being gathered in the thickness direction until they reach a predetermined thickness (height), forming a first mat 9a of wood pieces 1, ..., 1. Next, a number of wood pieces 1, ..., 1 for the core layer 11 to which adhesive is applied are piled up on the first mat 9a in a state of being gathered in the thickness direction until they reach a predetermined thickness (height), forming a second mat 9b of wood pieces 1, ..., 1.
• the thicknesses of the first to third mats 9a to 9c are adjusted to obtain the desired ratio of the thickness of the core layer 11 and each surface layer 12 to the entire particle board 10.
• the mats 9 are formed so that the thickness (height) of the first and third mats 9a, 9c that will become the surface layers 12 is about 13.5 mm, and the thickness (height) of the second mat 9b that will become the core layer 11 is about 63 mm.
• the ratio of the thickness of the core layer 11 and each surface layer 12 to the entire particle board 10 is not limited to the above ratio and may be any ratio.
• ⁇ Heat pressing step S4> The mat 9 formed in the mat forming process S3 is carried into a hot press device and set between hot plates, where the mat 9 is compressed by hot pressing at a predetermined pressure and temperature. At this time, the adhesive hardens, bonding the numerous wood pieces 1, 1 together. As a result, the particle board 10 shown on the right side of Fig. 6 is formed.
• the presence of the thin wood cutting pieces 3, ..., 3 makes it easier to bond the wood pieces 1, ..., 1 (the wood chips 2, ..., 2 and the wood cutting pieces 3, ..., 3) to each other with a small amount of adhesive. Therefore, according to the three-layer particle board 10 of the first embodiment, it is possible to reduce the amount of adhesive used while ensuring bending strength.
• the wood chips 3 are extremely thin, with a thickness of 0.05 mm or more and 0.35 mm or less, so even if they are included in the surface layer 12, unevenness is unlikely to occur on the surface. Therefore, the surface properties (smoothness) are excellent, just like conventional particle boards.
• the inventors of the present application conducted a test to verify the effect of including extremely thin, flake-like wood shavings 3, ..., 3 with a thickness of 0.05 mm to 0.35 mm in the surface layer 12 of a three-layer particleboard 10.
• the particleboard 10 including the thin wood shavings 3, ..., 3 in the surface layer 12 has improved normal bending strength (MOR), wet bending strength (wetMOR), water absorption length change rate (LE), peel strength (IB) and water resistance (wet bending strength (wetMOR)/normal bending strength (MOR)) compared to a conventional particleboard not including the thin wood shavings 3, ..., 3 in the surface layer 12.
• the core layer 11 uses a large number of first wood chips 2b, ..., 2b that pass through a first sieve with a mesh size of 16 mm or less but do not pass through a second sieve with a mesh size of 0.5 mm or more and smaller than the first sieve, and the surface layer 12 uses fine second wood chips 2c, ..., 2c that pass through both the first and second sieves.
• the inventors of the present application have found from the results of the above verification tests that by mixing the numerous wood chips 1, ..., 1 for the surface layer 12 with wood cuttings 3, ..., 3 in a ratio of 20% by weight to 90% by weight of the total weight of the wood chips 1, ..., 1, the normal bending strength (MOR), wet bending strength (wet MOR), water absorption length change (LE) and peel strength (IB) are improved, and that the improvement rate increases as the mixing ratio of the wood cuttings 3, ..., 3 in the surface layer 12 increases.
• MOR normal bending strength
• wet MOR wet bending strength
• LE water absorption length change
• IB peel strength
• the wood cutting pieces 3, ..., 3 may be mixed with the numerous wood pieces 1, ..., 1 for the surface layer 12 in a ratio of 20% by weight to 90% by weight of the total weight of the wood cutting pieces 3, ..., 3.
• the numerous wood pieces 1, ..., 1 for the surface layer 12 with the wood cutting pieces 3, ..., 3 in such a ratio, it is possible to provide a three-layer particle board 10 that has excellent surface properties, water resistance, bending strength, and peel strength, and has little dimensional change, without increasing cost or weight.
• the particle boards 10 (specimens X1 to X4) having the wood shavings 3, ..., 3 in the surface layer 12 had improved normal bending strength (MOR) and wet bending strength (wet MOR) compared to the conventional particle board (specimen X0) that did not have the wood shavings 3, ..., 3 in the surface layer 12. Furthermore, the higher the mixing ratio of the wood shavings 3, ..., 3 in the surface layer 12, the higher the normal bending strength (MOR) and wet bending strength (wet MOR) became.
• the particle boards 10 that contain wood shavings 3, ..., 3 in the surface layer 12 also had improved peel strength (IB) compared to the conventional particle board (test specimen X0) that does not contain wood shavings 3, ..., 3 in the surface layer 12.
• the particle boards 10 (test specimens X1 to X4) that contain wood shavings 3, ..., 3 in the surface layer 12 have an index of water resistance (wet bending strength (wet MOR) / normal bending strength (MOR)) that is improved compared to the conventional particle board (test specimen X0) that does not contain wood shavings 3, ..., 3 in the surface layer 12.
• wet MOR wet bending strength
• MOR normal bending strength
• the particleboards 10 (specimens X1 to X4) containing the wood shavings 3, ..., 3 in the surface layer 12 had higher indices for normal bending strength (MOR), wet bending strength (wet MOR), peel strength (IB) and water resistance, and lower indices for water absorption length change (LE), compared to the conventional particleboard (specimen X0) not containing the wood shavings 3, ..., 3 in the surface layer 12.
• the particleboards 10 (specimens X1 to X4) containing the wood shavings 3, ..., 3 in the surface layer 12 had similar root mean square height Sq and arithmetic mean height Sa (indices of surface properties) to the conventional particleboard (specimen X0) not containing the wood shavings 3, ..., 3 in the surface layer 12.
• the two surface layers 12, 12 are configured to be thinner (height) than the core layer 11, but the two surface layers 12, 12 may also be thicker than the core layer 11.
• the present invention is useful for three-layer particle boards and methods for manufacturing particle boards.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)

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Citations (6)

• 2024
  • 2024-08-05 JP JP2024565029A patent/JPWO2025028661A1/ja active Pending
  • 2024-08-05 WO PCT/JP2024/027979 patent/WO2025028661A1/ja active Application Filing

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