Particle board and method for manufacturing particle board

Abstract

To enable the production of a particle board that exhibits excellent surface quality, bending strength, screw withdrawal strength, and water resistance, with minimal dimensional change, without increasing cost or weight.SOLUTION: A large number of wood pieces 1,..., 1 constituting a particle board 10 are a mixture of a large number of crushed wood pieces 2,..., 2 and a large number of flaky cut wood pieces 3,..., 3 having a thickness of 0.05-0.35 mm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to particle board. [Background technology]

[0002] Traditionally, tropical plywood such as lauan plywood has been widely used. However, in recent years, tropical plywood has become difficult to obtain due to the depletion of raw materials and concerns about environmental destruction, and efforts are being made to replace it with other wood boards.

[0003] Patent Document 1 discloses that particleboard, which is made by applying adhesive to crushed wood chips obtained by crushing wood and piling them into a mat shape and then hot pressing them with a hot platen, is used as an alternative material to plywood. Particleboard is excellent as an alternative to plywood because it can use waste materials and recycled materials, and because wood can be used without waste by changing the size of the crushed wood chips used in the core layer and surface layer, it can be made relatively inexpensively. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2005 / 115705 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the particle board is made of relatively large wood fragments in order to ensure bending strength, there is a risk of the surface properties (smoothness) decreasing. Conversely, if the particle board is made of relatively small wood fragments in order not to decrease the surface properties (smoothness), it is necessary to increase the density of the wood fragments and use a large amount of adhesive in order to ensure bending strength, which may increase costs and weight. In addition, particle board has low screw pull-out strength and cannot be used as a load-bearing base surface material to be installed with screws, and also has problems such as lack of water resistance and dimensional stability due to moisture absorption.

[0006] The present invention has been made in consideration of the above-mentioned points, and its object is to provide a particle board which has excellent surface properties, bending strength, screw pull-out strength and water resistance and which exhibits little dimensional change, without increasing cost or weight. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention is based on the idea of ​​including a large number of extremely thin wood shavings in a single layer particle board.

[0008] Specifically, the first invention is based on a particle board in which a large number of wood pieces are glued together in a collective state.

[0009] The first invention is characterized in that the numerous wood pieces are a mixture of numerous crushed wood pieces and numerous shaved wood pieces having a thickness of 0.05 to 0.35 mm.

[0010] Here, crushed wood chips refer to granular wood chips formed by crushing a wood material, and shaved wood chips refer to thin flake-like wood chips formed by cutting a wood material.

[0011] In the first invention, the particleboard is made of a large number of wood pieces that are a mixture of a large number of wood crushed pieces and a large number of very thin wood shavings with a thickness of 0.05 to 0.35 mm. In this way, the particleboard contains not only the wood crushed pieces that are usually contained in the particleboard, but also very thin wood shavings with a thickness of 0.05 to 0.35 mm, thereby increasing the bending strength of the particleboard. Therefore, it is not necessary to increase the density of the wood pieces or use a large amount of adhesive in order to ensure the bending strength of the particleboard. Furthermore, compared to a case in which the large number of wood pieces are composed only of granular wood crushed pieces, the presence of the thin wood shavings makes it easier for the wood pieces to be bonded together with a small amount of adhesive. Therefore, the particleboard according to the first invention can reduce the amount of adhesive used while ensuring the bending strength of the conventional one.

[0012] Furthermore, in the particleboard according to the first aspect of the invention, extremely thin wood shavings having a thickness of 0.05 to 0.35 mm are inserted into the gaps between the granular wood chips, so that the surface is less prone to unevenness. In particular, when the thin wood shavings are folded over on the surface of the particleboard, the surface becomes smoother, resulting in excellent surface properties (smoothness).

[0013] Furthermore, the particleboard according to the first invention contains many thin wood chips that have a larger surface area than the granular crushed wood chips, so screws are less likely to come out than in conventional particleboards that are made only of granular crushed wood chips. Therefore, by including wood chips throughout the particleboard according to the first invention, the entire board is reinforced and the screw pull-out strength (wood screw holding power) is significantly improved, making it suitable for use as a load-bearing surface material for base boards to be installed with screws.

[0014] Furthermore, with the particleboard according to the first invention, many large gaps would be formed between the granular wood chips alone, but the mixed in flaky wood cuttings fill in these gaps, making them smaller and fewer. Therefore, the particleboard according to the first invention is more resistant to moisture penetration and has excellent water resistance compared to conventional particleboards made only of granular wood chips.

[0015] Furthermore, in conventional particle boards made only of granular crushed wood chips, the crushed wood chips are crushed during press molding, and when moisture penetrates inside, it becomes more likely to absorb moisture, which may result in significant dimensional changes (changes in length and thickness).In contrast, the particle board according to the first invention has a structure that makes it more difficult for moisture to penetrate inside than conventional particle boards, as described above, and therefore does not absorb moisture and therefore does not undergo significant changes in dimensions (length and thickness).

[0016] As described above, according to the first aspect of the present invention, a particle board that is excellent in surface properties, bending strength, screw pull-out strength and water resistance and has small dimensional change can be provided without increasing cost and weight.

[0017] The second invention is characterized in that, in the first invention, the wood cutting pieces are produced from the wood material during the formation of a wood board, which is made by gluing together a large number of first small wood flakes selected by classification from a large number of small wood flakes obtained by cutting a wood material and grinding a large number of wood flakes having a thickness of 0.05 to 0.35 mm.

[0018] The third invention is characterized in that, in the second invention, the wood cutting pieces are the small wood flakes and are before the first small wood flakes are selected by classification.

[0019] The fourth invention is characterized in that, in the second invention, the wood cutting pieces are the small wood flakes other than the first small wood flakes selected by classification.

[0020] In the second to fourth inventions, the wood shavings are generated when wood material is processed to form other wood boards. Therefore, even if a material (wood shavings) different from the material (ground wood chips) used for normal particle boards is used, it can be easily procured because the different material is generated during material processing for other wood boards. Therefore, according to the second to fourth inventions, particle boards that are excellent in surface properties, bending strength, screw pull-out strength, and water resistance and have little dimensional change can be easily and relatively inexpensively provided.

[0021] In particular, in the fourth invention, wood chips are those (second and third small wood chips) other than the first small wood chips that are selected by classifying the small wood chips. In this way, 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 particle boards, making it possible to form particle boards more inexpensively. In addition, since the wood material of other wood boards is used without waste, this leads to effective use of wood resources. Effect of the Invention

[0022] As described above, according to the present invention, a single layer of particle board is made to contain a large number of extremely thin wood shavings, so that a particle board having excellent surface properties, bending strength, screw pull-out strength and water resistance and small dimensional change can be provided without increasing cost or weight. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a cross-sectional view showing a part of the particle board according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing the process of producing ground wood pieces. [Diagram 3] FIG. 3 is a diagram showing the process of producing wood cutting pieces. [Figure 4] FIG. 4 is an enlarged perspective view showing a first small wood piece. [Diagram 5] FIG. 5 is a diagram showing the manufacturing process of particle board. [Figure 6] 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. The following description of the embodiments is merely illustrative in nature and is not intended to limit the present invention, its application, or its uses.

[0025] 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.

[0026] Particleboard 10 is made up of numerous wood pieces 1, ..., 1 glued together in a collected state. Particleboard 10 contains numerous wood pieces 1, ..., 1 and an adhesive. The feature of the present invention lies in the constituent material (wood pieces 1) of particleboard 10, and there are no particular limitations on the thickness or density, but particleboard 10 may, for example, have a thickness of 3 mm to 25 mm and a density of 500 kg / m 3 More than 800kg / m 3 It is configured as follows:

[0027] <Wood piece> In the present embodiment 1, the numerous wood pieces 1, ..., 1 constituting the particle board 10 are a mixture of numerous crushed wood pieces 2, ..., 2 and numerous shaved wood pieces 3, ..., 3. The crushed wood pieces 2, ..., 2 are used as wood pieces in conventional particle boards, and the shaved wood pieces 3, ..., 3 are used as constituent materials for another wood board 50, which will be described later. That is, in the present embodiment 1, a mixture of the crushed wood pieces 2, ..., 2 used in conventional particle boards and the shaved wood pieces 3, ..., 3 used as constituent materials for another wood board 50 is used as the numerous wood pieces 1, ..., 1. The shaved wood pieces 3, ..., 3 are mixed at a ratio of 10 to 90% by weight with respect to the total weight of the wood pieces 1, ..., 1.

[0028] [Crushed wood chips] As shown in Fig. 2, the pulverized wood pieces 2, ..., 2 are obtained by pulverizing a wood material A into granules using a known pulverizing device (chipper) such as a hammer mill, a pin mill, or a jet mill. In the particle board 10 of the present embodiment 1, as shown in Fig. 2, wood granular pieces 2a, ..., 2a obtained by pulverizing the wood material A are classified using two types of sieves, one large and one small, and the first wood granular pieces 2b, ..., 2b selected by classification are used as the pulverized wood pieces 2, ..., 2. Granular pieces having a particle size (maximum diameter) of 0.5 mm or more and 5 mm or less are selected as the first wood granular pieces 2b, ..., 2b.

[0029] The pulverized wood pieces 2,...,2 used in the particle board 10 are not limited to the first wood granular pieces 2b,...,2b. The pulverized wood pieces 2,...,2 may be second wood granular pieces 2c,...,2c that are finer than the first wood granular pieces 2b,...,2b that have passed through both types of sieves, or third wood granular pieces 2d,...,2d that are coarser than the first wood granular pieces 2b,...,2b that have not passed through both types of sieves. In addition, the wood granular pieces 2a, ..., 2a before classification may be used as the ground wood pieces 2, ..., 2, or all, any two or any three of the wood granular pieces 2a, ..., 2a, the first wood granular pieces 2b, ..., 2b, the second wood granular pieces 2c, ..., 2c and the third wood granular pieces 2d, ..., 2d may be combined and used as the ground wood pieces 2, ..., 2. In other words, at least one of the wood granular pieces 2a, ..., 2a, the first wood granular pieces 2b, ..., 2b, the second wood granular pieces 2c, ..., 2c and the third wood granular pieces 2d, ..., 2d can be used as the ground wood pieces 2, ..., 2.

[0030] Also, as shown in Figure 2, the third wood granules 2d, ..., 2d which are coarser than the first wood granules 2b, ..., 2b may not be used as wood crushed pieces 2, ..., 2 but may be returned to the chipper device and crushed again.

[0031] The species of the wood material A is not particularly limited, and any species of tree can be used as the wood material A. For example, fir materials such as cedar, cypress, and Douglas fir, acacia, aspen, poplar, pine (hard pine, soft pine, radiata pine, etc.), birch, rubber (rubber tree), and the like can be used as the wood material A. In addition, domestic materials such as Abies sachalinensis, larch, Yezo spruce, sawara, hiba, kaya, tsuga, cypress, various pines, paulownia, maple, birch (white birch), shiitake, beech, oak, fir, Japanese oak, camphor, and zelkova; North American materials such as American cypress, American hiba, American cedar, American fir, spruce, American tsuga, and redwood; South Sea materials such as agathis, terminalia, lauan, meranti, junkon, chamerele, carampayan, amberoi, melina, teak, apitong, and sengon laut; and other foreign materials such as balsa, cedar, mahogany, lignum vitae, acacia mangium, Mediterranean pine, sorghum, and chamerele. In addition to logs and thinned wood, scraps and waste materials generated at construction sites, waste pallet materials, recycled materials, and the like may be used as the wood material A.

[0032] [Wood cuttings] The wood cutting pieces 3, 3 are produced from a wood material B when a wood board 50 different from the particle board 10 according to the present invention is formed. As shown in Fig. 3, the wood board 50 is produced by cutting a wood material B with a known cutting device (strander) to produce a large number of wood flakes 3a, 3a having a thickness of 0.05 to 0.35 mm, which are then crushed with a known crushing device to form a large number of small wood flakes 3b, 3b, which are then classified using two types of sieves, one large and one small, and the first small wood flakes 3c, 3c selected by the classification are bonded together in an aggregated state.

[0033] In the particle board 10 of this embodiment 1, when forming the above-mentioned wood board 50, a large number of small wood flakes 3b, ..., 3b obtained by further crushing a large number of wood flakes 3a, ..., 3a having a thickness of 0.05 to 0.35 mm, which are obtained by cutting the wood material B, can be used as the wood cutting pieces 3, ..., 3.

[0034] The thickness t of the wood flakes 3a is 0.05 mm or more and 0.35 mm or less, preferably 0.10 mm or more and 0.30 mm or less, more preferably 0.15 mm or more and 0.25 mm or less, and even more preferably 0.15 mm or more and 0.20 mm or less. The thickness t of the wood flakes 3a is an average value. Since the small wood flakes 3b are obtained by pulverizing the wood flakes 3a, the small wood flakes 3b also have the same thickness t as the wood flakes 3a.

[0035] The first small woody flakes 3c used to form the wood board 50 will be described in detail. As shown in an enlarged view in FIG. 4, the first small woody flakes 3c have a long and slender shape (strip shape) in which the fiber direction dimension d1 in the direction along the fibers a due to vessels, tracheids, etc. is longer than the fiber orthogonal direction dimension d2 in the direction perpendicular to the fiber direction. If the fiber direction dimension d1 is the length and the fiber orthogonal direction dimension d2 is the width, the length d1 is 40 mm or less, preferably 35 mm or less, more preferably 30 mm or less, even more preferably 25 mm or less, and even more preferably 10 mm or more and 20 mm or less. The width d2 is 35 mm or less, preferably 15 mm or less, and more preferably 0.5 mm or more and 5 mm or less. The length d1 and width d2 of the first small woody flakes 3c are both average values.

[0036] The first woody small flakes 3c, ..., 3c having such thickness, shape and size are selected by classifying the many woody small flakes 3b, ..., 3b using two types of sieves, large and small, appropriately selected as described above. This classification not only selects the many first woody small flakes 3c, ..., 3c, but also obtains the second woody small flakes 3d, ..., 3d that are finer than the first woody small flakes 3c, ..., 3c that have passed both types of sieves, and the third woody small flakes 3e, ..., 3e that are coarser than the first woody small flakes 3c, ..., 3c that have not passed both types of sieves.

[0037] In the first embodiment, as described above, the numerous small wood flakes 3b, ..., 3b after crushing and before classification can be used as the wood shavings 3, ..., 3 in the particle board 10. However, the wood shavings 3, ..., 3 constituting the particle board 10 are not limited to the small wood flakes 3b, ..., 3b. The first small wood flakes 3c, ..., 3c used in the wood board 50, and the second small wood flakes 3d, ..., 3d and the third small wood flakes 3e, ..., 3e not used in the wood board 50 may be used as the wood shavings 3, ..., 3 constituting the particle board 10. Also, the wood slices 3a, ..., 3a after cutting and before grinding may be used as the wood cutting pieces 3, ..., 3, or all or any two, three or four of the wood slices 3a, ..., 3a, the small wood slices 3b, ..., 3b, the first small wood slices 3c, ..., 3c, the second small wood slices 3d, ..., 3d and the third small wood slices 3e, ..., 3e may be combined and used as the wood cutting pieces 3, ..., 3. In other words, at least one of the wood slices 3a, ..., 3a, the small wood slices 3b, ..., 3b, the first small wood slices 3c, ..., 3c, the second small wood slices 3d, ..., 3d and the third small wood slices 3e, ..., 3e can be used as the wood cutting pieces 3, ..., 3.

[0038] The species of the wood material B is not particularly limited, and any species of tree can be used as the wood material B. For example, fir materials such as cedar, cypress, and Douglas fir, acacia, aspen, poplar, pine (hard pine, soft pine, radiata pine, etc.), birch, rubber (rubber tree), and the like can be used as the wood material B. In addition, domestic materials such as Abies sachalinensis, larch, Yezo spruce, sawara, hiba, kaya, tsuga, cypress, various pines, paulownia, maple, birch (white birch), shiitake, beech, oak, fir, Japanese oak, camphor, and zelkova; North American materials such as American cypress, American hiba, American cedar, American fir, spruce, American tsuga, and redwood; South Sea materials such as agathis, terminalia, lauan, meranti, junkon, chamerele, carampayan, amberoi, melina, teak, apitong, and sengon laut; and other imported materials such as balsa, cedar, mahogany, lignum vitae, acacia mangium, Mediterranean pine, sorghum, and chamerele. In addition to logs and thinned wood, scraps and waste materials generated at construction sites, waste pallet materials, recycled materials, etc. may also be used as the wood material B.

[0039] By mixing the above-mentioned ground wood chips 2, ..., 2 and shaved wood chips 3, ..., 3, a large number of wood chips 1, ..., 1 that make up the particle board 10 are formed.

[0040] Regarding the physical properties of the wood pieces 1 (ground wood pieces 2, wood cutting pieces 3), their density is preferably 250 kg / m 3 More preferably, 300 kg / m 3 More preferably, it is 800 kg / m 3 Less than or equal to 500 kg / m 3 Less than 400 kg / m, more preferably 400 kg / m 3 Density is 250kg / m or less. 3 If the density of the wood piece 1 is less than 800 kg / m, the thickness of the mat required to form the particle board 10 having the same density and bending strength becomes large, and the pressing pressure in the hot pressing process in the press molding step must be increased. 3 However, it is difficult to obtain such a wood piece 1. 3If it is easy to obtain wood chips 1 exceeding this value, the upper limit of density is 800 kg / m 3 It is not limited to this and may be a higher value.

[0041] Furthermore, the moisture content of the wood pieces 1 (ground wood pieces 2, shaved wood pieces 3) is preferably 2% or more and 20% or less, and more preferably 2% or more and 8% or less. If the moisture content is less than 2%, it may take a long time to soften the wood pieces in the hot press process in the press molding step, which may lengthen the pressing time and reduce the bending strength. On the other hand, if the moisture content of the wood pieces 1 exceeds 20%, it may take a long time to heat and compress the wood pieces in the hot press process, and furthermore, the hardening of the adhesive may be inhibited, which may reduce the bending strength.

[0042] <Adhesive> The adhesive used for the particle board 10 is not particularly limited as long as it is a thermosetting adhesive. For example, an isocyanate-based adhesive can be used. Other adhesives that can be used include amine-based adhesives such as phenolic resin, urea resin, and melamine resin, and natural adhesives. The adhesive is applied to the wood pieces 1, ..., 1 before they are piled up, and hardens when the mat on which the wood pieces 1, ..., 1 are piled up is hot-pressed. This causes the numerous wood pieces 1, ..., 1 to be bonded together in a collective state.

[0043] -Manufacturing method of particle board- Next, a description will be given of a method for manufacturing the particle board 10. As shown in Fig. 5, the method for manufacturing the particle board 10 includes a wood piece preparation step S1, an adhesive application step S2, a mat forming step S3, and a heat pressing step S4.

[0044] <Wood piece production process S1> The wood piece producing process S1 includes a wood crushed piece producing process S11, a wood cutting piece producing process S12, and a wood piece mixing process S13.

[0045] [Wood chip production process S11] The wood pulverized piece preparation process S11 includes a material preparation process S111, a pulverization process S112, and a classification process S113.

[0046] (Material preparation process S111) First, prepare wood material A. When using logs, thinned wood, or other raw wood, cut them into short pieces and remove the bark to prepare wood material A. When using scraps or waste wood generated at construction sites, waste pallet materials, recycled materials, etc., cut them into short pieces to prepare wood material A.

[0047] (Crushing process S112) Next, the prepared wood material A is crushed into granules by a known crushing device (chipper) such as a hammer mill, a pin mill, a jet mill, etc. By crushing the wood material A, wood granule pieces 2a, ..., 2a are obtained.

[0048] (Classification process S113) The wood grain pieces 2a, ..., 2a obtained by crushing are classified into three sizes using two types of sieves, large and small. Specifically, the wood grain pieces 2a, ..., 2a are divided into first wood grain pieces 2b, ..., 2b of a desired particle size (for example, 0.5 mm or more and 5 mm or less) that pass through a coarse sieve but not through a fine sieve, second wood grain pieces 2c, ..., 2c that are finer than the first wood grain pieces 2b, ..., 2b that pass through both types of sieves, and third wood grain pieces 2d, ..., 2d that are coarser than the first wood grain pieces 2b, ..., 2b that do not pass through both types of sieves. The first wood grain pieces 2b, ..., 2b classified and selected in this way are called wood crushed pieces 2, ..., 2.

[0049] [Wood cutting piece production process S12] The wood cutting piece preparation process S12 includes a material preparation process S121, a cutting process S122, and a crushing process S123. As described above, in the present embodiment 1, the wood thin pieces 3b, ..., 3b generated during the formation of the wood board 50 are used as the wood cutting pieces 3, ..., 3. Therefore, the wood cutting piece preparation process S12 is a part of the method for manufacturing the wood board 50.

[0050] (Material preparation process S121) First, prepare wood material B. When using logs, thinned wood, or other raw wood, cut them into short pieces and remove the bark to prepare wood material B. When using scraps or waste wood generated at construction sites, waste pallet materials, recycled materials, etc., cut them into short pieces to prepare wood material B.

[0051] (Cutting process S122) Next, the prepared wood material B is cut by a known cutting device (strander) of outer blade type or inner blade type to form a large number of wood flakes 3a, ..., 3a of the desired thickness t. Specifically, the direction and speed at which the wood material B is fed into the cutting device are adjusted to form a large number of wood flakes 3a, ..., 3a of the desired thickness t with fibers a appearing linearly on the surface.

[0052] In addition, by producing the wood flakes 3a, ..., 3a having a thickness t in this cutting step S122, the smaller wood flakes 3b, ..., 3b obtained in the subsequent crushing step will have a desired thickness t.

[0053] (Crushing process S123) Next, the woody flakes 3a, ..., 3a obtained by cutting are crushed using a known crushing device such as a hammer, a blade (knife flaker), a hammer mill, a pin mill, a jet mill, etc., to make them smaller than the size immediately after cutting. At this time, if the woody flakes after cutting are crushed in the width direction so as to break along the fiber direction (length direction), it is possible to create small woody flakes 3b, ..., 3b with elongated shapes. In other words, if a force (impact) is applied to the woody flakes 3a, ..., 3a along the fiber orthogonal direction perpendicular to the fiber direction, they are difficult to break, but if a force is applied parallel to the fiber direction, they are easily broken. Even if the woody flakes 3a, ..., 3a are curled, they are divided into flat shapes by crushing. The direction of the force applied to the woody flakes 3a, ..., 3a is not limited to the direction parallel to the fiber direction. If a force is applied to the woody flakes 3a, ..., 3a in a random direction, the woody flakes 3a, ..., 3a usually break from the part where the force is weak (they are easily broken in the direction of the weak force). Since the force connecting each fiber of the wood flakes 3a, ..., 3a (force perpendicular to the fibers) is overwhelmingly weaker than the force in the fiber direction, if the wood flakes 3a, ..., 3a are crushed in random directions using the above-mentioned crushing device (force is applied), the wood flakes 3a, ..., 3a will split along the fiber direction and shorten in the direction perpendicular to the fibers, resulting in small, elongated wood flakes 3b, ..., 3b.

[0054] Furthermore, even if the wood flakes 3a, . . . , 3a have knots, the knots are more brittle than the other parts, so the knots are turned into powder by crushing and disappear.

[0055] In this way, by adding the crushing step S123 after the cutting step S122 rather than using only one cutting step S122, and going through two processing steps, it is possible to easily produce small wood flakes 3b, ..., 3b of the required size and without knots, and with high strength.

[0056] [Wood piece mixing process S13] In the wood piece mixing process S13, a large number of wood crushed pieces 2, ..., 2 produced in the wood crushed piece production process and a large number of wood cutting pieces 3, ..., 3 produced in the wood cutting piece production process are mixed to a desired mixing ratio (the wood cutting pieces 3, ..., 3 are 10 to 90% by weight relative to the total weight of the wood pieces 1, ..., 1).

[0057] <Adhesive application process S2> The numerous wood pieces 1, ..., 1 produced in the wood piece production process S1 are carried into an adhesive applicator, where adhesive is applied. As the adhesive, for example, an isocyanate-based adhesive can be used, and other adhesives such as phenol resin, amine-based adhesives such as 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.

[0058] <Mat forming process S3> In the mat forming process S3, many wooden pieces 1, ..., 1 to which adhesive has been applied are piled up in a state where they are gathered in the thickness direction until they reach a predetermined thickness (height), forming a mat 9 of the wooden pieces 1, ..., 1 (left side of Fig. 6). For example, when forming a particle board 10 with a thickness of 9 mm, the thickness (height) of the mat 9 will be about 90 mm.

[0059] <Heat pressure process S4> The mat 9 formed in the mat forming process S3 is carried into a hot press device and set between hot platens, where the mat 9 is hot pressed and compressed at a predetermined pressure and temperature by the hot press device. At this time, the adhesive hardens, bonding and integrating the numerous wood pieces 1, ..., 1. As a result, the particle board 10 shown on the right side of Fig. 6 is formed.

[0060] At this time, as shown in FIG. 6, the above-mentioned mat 9 having a thickness of about 90 mm is compressed, for example, into a particle board 10 having a thickness of 9 mm, and the thickness is compressed to 1 / 10. The pressing temperature in the hot press process is not particularly limited, but is, for example, 160 to 220° C. The pressing pressure in the hot press process is, for example, 2 to 4 N / mm 2The pressing time is, for example, 1.5 to 3 minutes (for example, 10 to 20 seconds per mm of thickness). The pressing time varies depending on the thickness of the particle board 10, and may be completed in less than 1 minute or may require more than 3 minutes. Furthermore, a preliminary heating process using a heating device may be performed prior to the hot pressing process using the hot pressing device.

[0061] -Effects of embodiment 1- In the present embodiment 1, the particle board 10 is made of a large number of wood pieces 1, ..., 1, which are a mixture of a large number of wood crushed pieces 2, ..., 2 and a large number of very thin wood cutting pieces 3, ..., 3 with a thickness of 0.05 to 0.35 mm. In this way, the particle board 10 contains not only the wood crushed pieces 2, ..., 2 that are usually contained, but also the wood cutting pieces 3, ..., 3 with a thickness of 0.05 to 0.35 mm, which increases the bending strength of the particle board 10. Therefore, in order to ensure the bending strength of the particle board 10, it is not necessary to increase the density of the wood pieces 1, ..., 1 or use a large amount of adhesive. In addition, compared to a case in which the large number of wood pieces 1, ..., 1 are composed only of granular wood crushed pieces 2, ..., 2, the presence of the thin wood cutting pieces 3, ..., 3 makes it easier for the wood pieces 1, ..., 1 to be bonded together with a small amount of adhesive. Therefore, according to the particle board 10 of the first embodiment, it is possible to reduce the amount of adhesive used while ensuring bending strength comparable to that of conventional particle boards.

[0062] Furthermore, according to the particle board 10 of the first embodiment, the extremely thin wood shavings 3, ..., 3 having a thickness of 0.05 to 0.35 mm fit into the gaps between the granular wood crushed chips 2, ..., 2, making it difficult for unevenness to occur on the surface. In particular, when the thin wood shavings 3, ..., 3 are folded over on the surface of the particle board 10, the surface becomes smoother, resulting in excellent surface properties (smoothness).

[0063] Furthermore, the particle board 10 of this embodiment 1 contains many thin wood shavings 3, ..., 3 which have a larger area than the granular wood crushed chips 2, ..., 2, so screws are less likely to come out than in conventional particle boards composed only of granular wood crushed chips. Therefore, by including the wood shavings 3, ..., 3 throughout the particle board 10 of this embodiment 1, the entire board is reinforced and the screw pull-out strength (wood screw holding power) is significantly improved, making it suitable for use as a load-bearing subsurface material for screws.

[0064] Furthermore, with the particle board 10 of this embodiment 1, many large gaps would be formed between the granular wood crushed chips 2, ..., 2 alone, but the mixed in flaky wood shavings 3, ..., 3 fill in these gaps, making them smaller and fewer. Therefore, compared to conventional particle boards made only of granular wood crushed chips, the particle board 10 of this embodiment 1 is more resistant to moisture penetration and has excellent water resistance.

[0065] Furthermore, in conventional particle boards made only of granular crushed wood chips, the crushed wood chips are crushed during press molding, and when moisture penetrates inside, it becomes more likely to absorb moisture, which may result in significant dimensional changes (changes in length and thickness). In contrast, the particle board 10 of the first embodiment has a structure that makes it more difficult for moisture to penetrate inside than conventional particle boards, as described above, and therefore does not absorb moisture and therefore does not undergo significant changes in dimensions (length and thickness).

[0066] As described above, according to the first embodiment, it is possible to provide a particle board 10 that is excellent in surface properties, bending strength, screw pull-out strength, and water resistance and that is small in dimensional change, without increasing cost and weight.

[0067] In addition, in this embodiment 1, the wood shavings 3, ..., 3 are generated when the wood material B is processed to form another wood board 50. Therefore, even if a material (wood shavings 3, ..., 3) different from the material (ground wood chips 2, ..., 2) used for normal particle boards is used, it can be easily procured because the different material is generated during material processing of the other wood board 50. Therefore, according to this embodiment 1, it is possible to easily and relatively inexpensively provide a particle board 10 that has excellent surface properties, bending strength, screw pull-out strength, and water resistance and has little dimensional change.

[0068] In particular, when wood cutting pieces 3, ..., 3 are made of wood other than the first small wood flakes 3c, ..., 3c (the second small wood flakes 3d, ..., 3d and the third small wood flakes 3e, ..., 3e) selected by classifying the small wood flakes 3b, ..., 3b, waste wood that is not used for the other wood boards 50 and is generated during the formation of the other wood boards 50 is used as the wood cutting pieces 3, ..., 3 for the particle board 10, so that the particle board 10 can be formed more inexpensively. Also, since the wood material B of the other wood boards 50 is used without waste, this leads to effective use of wood resources.

[0069] Other Embodiments In the above embodiment 1, an example was described in which wood shavings generated during material processing of another wood board 50 are used as the wood shavings 3, ..., 3. However, the wood shavings 3, ..., 3 may not be generated during material processing of the other wood board 50, but may be procured for the purpose of forming the above-mentioned particle board 10. [Industrial Applicability]

[0070] The present invention is useful for particle board. [Explanation of symbols]

[0071] 1 wood piece 2 Crushed wood chips 3 wood cuttings 3a wood flakes 3b Small wood flakes 3c 1st woody flake 3d. Secondary woody flakes (other than the first secondary woody flakes) 3e. Third woody flakes (other than first woody flakes) 10. Particleboard 50 Wood Board

Claims

1. A particle board made of a large number of wood pieces glued together in a collective state, The plurality of wood pieces is a mixture of a plurality of crushed wood pieces and a plurality of shaved wood pieces having a thickness of 0.05 to 0.35 mm. A particle board characterized by:

2. The particle board according to claim 1, The wood chips are produced from the wood material when a wood board is formed by bonding together a number of first small wood chips selected by classification from a number of small wood chips obtained by cutting a wood material and crushing the resulting number of thin wood chips having a thickness of 0.05 to 0.35 mm. A particle board characterized by:

3. The particle board according to claim 2, The wood cutting pieces are the small wood pieces before the first small wood pieces are selected by classification. A particle board characterized by:

4. The particle board according to claim 2, The wood cutting pieces are the wood small pieces other than the first wood small pieces selected by classification. A particle board characterized by:

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