Wood chipboards and flooring

Abstract

To provide a woody board which has surface smoothness more superior than a conventional OSB and almost equivalent to that of an MDF, and has excellent bending strength compared with a plywood, and can be suitably used as a base material to be a decorative plate by directly pasting a decorative material thereon.SOLUTION: A cut wood thin plate is obtained by mixing cut wood flakes and an adhesive and accumulating them to integrate by hot pressing, in which a tree kind density (a) of the cut wood flake is 0.6 g / cm3 or less, a density (b) of the cut wood thin plate is 0.5 g / cm3 or more and 0.9 g / cm3 or less, and a density ratio (b / a) of the tree kind density (a) of the cut wood flake to the density (b) of the cut wood thin plate is 1.2 or more. In the cut wood flake, preferably, the thickness is 0.1 mm or more and 0.6 mm or less, the width is 1.0 mm or more and 50 mm or less, and the length is 15 mm or more and 200 mm or less. The cut wood thin plate can be suitably used as a base material to be a decorative plate 5 by directly pasting a decorative material 4 such as a veneer or a decorative sheet thereon.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a shaved wood flake board and a flooring material using the shaved wood flake board as a base material. [Background technology]

[0002] Oriented strand board (OSB, Japanese Industrial Standard JIS A 5908:2022) is a type of wood board made by mixing small or thin pieces of wood with adhesive, assembling them, and then combining them under heat and pressure. OSB is a type of structural panel specified in the Japanese Agricultural Standards (JAS), but in light of the depletion of wood resources in recent years, there has been research into using OSB for purposes other than structural panels, such as as a base material for decorative panels. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2007-521163 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional OSB is generally manufactured by drying thin wood shavings (strands) of approximately 0.65 to 1.20 mm in thickness, applying adhesive, stacking the thin wood shavings with the grain direction set in a roughly fixed direction, and then pressurizing them into a mold. It has a density of 0.60 to 0.70 g / cm. 3 , bending strength 25~35N / mm 2 , Young's modulus of bending 3500~5000N / mm 2Although OSB has similar physical properties, uneven distribution of adhesive and uneven press loads often cause thin wood flakes to appear on the surface, resulting in poor surface smoothness, making it practically difficult to directly adhere decorative materials such as veneer or decorative sheeting to the surface of OSB. Therefore, when using OSB as a substrate for decorative boards, the current practice is to adhere a surface material with excellent surface smoothness, such as MDF, to the surface, and then adhere a decorative material such as veneer or decorative sheeting to that surface, and OSB has not previously been used alone as a base material for decorative boards.

[0005] Plywood has long been used as a base material for decorative panels, but in recent years, as high-quality veneers have become difficult to obtain, wood fiberboards such as MDF have become more widely used. Plywood has been recognized as a suitable material for use as a base material for decorative panels due to its excellent strength, low deflection, ease of application, and minimal warping or other deformation after application. However, its surface is not sufficiently smooth (as described below, its maximum height, which indicates surface roughness, exceeds 200 μm). When a thin veneer or other decorative material is applied directly to it, the unevenness of the plywood surface becomes visible on the veneer, resulting in poor surface finish and a poor walking feel when used as a flooring board. Therefore, when applying a decorative material to a plywood substrate, it is necessary to fill the unevenness of the plywood surface with putty to achieve a smooth surface. On the other hand, while MDF has excellent surface smoothness, it lacks bending strength, especially in the longitudinal direction.

[0006] Therefore, the problem that this invention aims to solve is to provide a wood board that has surface smoothness equivalent to that of MDF and bending strength superior to that of plywood, and that can be suitably used as a base material for directly attaching decorative materials such as veneer or decorative sheeting to the board to make a decorative panel.

[0007] To solve this problem, the inventors conducted tests to produce various types of shaved wood boards by varying the tree species of the shaved wood used as raw materials in shaved wood boards obtained by mixing and accumulating shaved wood and adhesive, and then thermo-combining the shaved wood boards. They discovered that the density of the shaved wood board and the tree species density of the shaved wood boards have a significant relationship with the surface smoothness of the resulting shaved wood boards. Based on this knowledge, they conducted further tests and studies, and as a result, they have completed the present invention. [Means for solving the problem]

[0008] That is, the invention according to claim 1 of the present application is a shaved wood board obtained by mixing and accumulating wood shavings and adhesive, and then integrating them under heat and pressure, and the wood species density a of the shaved wood is 0.6 g / cm 3 The density b of the wood chipboard is 0.5 g / cm 3 More than 0.9g / cm 3 The density ratio b / a between the density a of the wood shavings and the density b of the wood shavings board is 1.2 or more; At the part where the wood shavings on the surface of the wood shavings board overlap each other, both or at least one of the wood shavings is deformed or compressed so that the wood shavings are approximately flush with each other, and at least one surface has a maximum height of 200 μm or less, which indicates the surface roughness defined in the Japanese Industrial Standard JIS B 0601:2013. It is characterized by:

[0009] The invention according to claim 2 of the present application is characterized in that in the shaved wood board according to claim 1, the thickness of the shaved wood is 0.1 mm or more and 0.6 mm or less.

[0010] The invention of claim 3 of the present application is characterized in that, in the wood shavings board described in claim 1, the width of the wood shavings is 1.0 mm or more and 50 mm or less, and the length of the wood shavings is 15 mm or more and 200 mm or less.

[0011] The invention according to claim 4 of the present application is a flooring material obtained by laminating a decorative material on at least one surface of the shaved wood chipboard according to any one of claims 1 to 3, and having a bending strength of 30 to 80 N / mm 2 and the bending Young's modulus is 3000 to 8500 N / mm 2 It is characterized in that: [Effects of the Invention]

[0012] According to the present invention, a shaved wood flake board is provided which has a surface smoothness that is significantly improved over conventional OSB, is comparable to or better than MDF, which is known to have good surface smoothness, and has excellent physical properties. Therefore, the shaved wood flake board of the present invention can be suitably used instead of conventional MDF, etc., as a substrate for directly attaching a decorative material such as veneer or decorative sheet to the board to make a decorative board.

[0013] Even if the wood shavings of the present invention are randomly stacked without giving the wood shavings a specific orientation, by adjusting the tree species density of the wood shavings and the board density, they can have various physical properties such as bending strength suitable for use as a base material for decorative boards. In a three-layer laminate structure, by giving the core layer an orientation that is approximately perpendicular to the longitudinal direction of the wood shavings and the two surface layers an orientation that is approximately parallel to the longitudinal direction of the wood shavings, the bending strength can be further increased and the length expansion rate can be reduced, thereby improving dimensional stability.

[0014] A flooring material made by laminating a decorative material such as veneer on the smooth surface of this shaved wood flake board has good density and bending Young's modulus, and is excellent in strength, rigidity, scratch resistance, etc. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a side view schematically showing a shaved wood board according to the present invention. FIG. [Figure 2] 1 is a side view schematically showing a flooring material using the shaved wood flake board according to the present invention as a base material. [Figure 3] FIG. 1 is a diagram showing measurement points for a surface roughness test in a test example. [Figure 4] Schematic cross-sectional views of thick wood shavings with low tree species density (a), thin wood shavings with low tree species density (b), thick wood shavings with high tree species density (d), and thin wood shavings with high tree species density (e), as well as schematic cross-sectional views of thin wood shavings (b, e) after compression (c, f). [Figure 5]Schematic cross-sectional views showing (a) a mat made of wood shavings with a low tree species density and (b) the state in which these mats have been compressed and both ends of the width cut vertically, and (c) a mat made of wood shavings with a high tree species density and (d) the state in which these mats have been compressed and both ends of the width cut vertically. [Figure 6] Schematic cross-sectional views showing the surface condition (a) of a portion where wood shavings with a low species density overlap each other before compression and the surface condition (b) of that portion after compression, and the surface condition (c) of a portion where wood shavings with a high species density overlap each other before compression and the surface condition (d) of that portion after compression. [Figure 7] This is a graph showing the correlation between the tree species density and the maximum height indicating the surface roughness of a shaved wood board when a shaved wood board having a substantially constant board density is manufactured from shaved wood boards of several tree species with different densities. [Figure 8] 10 is a graph showing the correlation between board density and maximum height indicating the surface roughness of shaved wood boards when shaved wood boards having different board densities are manufactured from shaved wood boards of the same tree species. [Figure 9] This is a graph showing the correlation between the density ratio (board density / tree species density) and the maximum height, which indicates the surface roughness of shaved wood boards, when various shaved wood boards are produced from shaved wood boards of several tree species with different densities. [Figure 10] This diagram compares shaved wood boards and solid wood boards of the same tree species and volume, and explains how the density ratio is affected by whether or not they have been crushed (compressed) or by the degree of compression. BEST MODE FOR CARRYING OUT THE INVENTION

[0016] The present invention relates to a shaved wood board obtained by mixing and accumulating wood shavings with an adhesive, and then thermocompressing and integrating them. Fig. 1 is a cross-sectional view showing this shaved wood board 1 alone, with the reference numeral 2 indicating wood shavings. Fig. 2 is a cross-sectional view showing a flooring material 4 (decorative board) in which this shaved wood board 1 is used as a substrate and veneer 3 (decorative material) is laminated and bonded onto its smooth surface.

[0017] Wood shavings are prepared by thinly cutting hardwood or softwood logs with a strander. Wood shavings may also be obtained from planted, renewable hardwoods or softwoods.

[0018] The shaved wood flakes used in the shaved wood board of the present invention preferably have a thickness of 0.1 mm to 0.6 mm, a width of 1 mm to 50 mm, and a length of 15 mm to 200 mm.

[0019] If the thickness of the wood shavings is less than 0.1 mm, the production capacity of the wood shavings will decrease, and if it exceeds 0.6 mm, the surface smoothness of the resulting wood shavings board will decrease and the rigidity will tend to be uneven.If the thickness of the wood shavings is within the range of 0.1 mm to 0.6 mm, the wood shavings board will have excellent surface smoothness and uniform rigidity.

[0020] If the width of the wood shavings exceeds 50 mm, not only will they be difficult to handle and transport, but they will also be prone to curling, making them less adhesive. If the width of the wood shavings is less than 1 mm, the rigidity of the resulting wood shavings board will decrease. If the width of the wood shavings is within the range of 1 mm to 50 mm, a wood shavings board with excellent surface smoothness and uniform rigidity can be obtained.

[0021] If the length of the wood shavings exceeds 200 mm, not only will handling and transportability be impaired, but the wood shavings will also be prone to curling, which will create localized cavities (core voids) when heated and pressed, reducing strength and causing punctures. If the length of the wood shavings is less than 15 mm, the rigidity of the resulting wood shavings board will be reduced. If the length of the wood shavings is within the range of 15 mm to 200 mm, the productivity of the wood shavings board will be excellent and it will be easier to achieve the required rigidity.

[0022] The moisture content of the wood shavings is preferably 15% by weight or less, and they are dried until the moisture content reaches 15% by weight or less before entering the wood shavings board manufacturing process. If the moisture content exceeds 15% by weight, an extremely high-density layer is likely to form on the surface of the wood shavings board, which requires a long time for pressure molding and results in uneven rigidity of the resulting wood shavings board. From this perspective, it is more preferable for the moisture content of the wood shavings to be 3% by weight or less. The moisture content MC of the wood shavings can be calculated using the formula MC = (m1 - m0) x 100 / m0 in accordance with Japanese Industrial Standard JIS A 5905:2022 7.5. Here, m1 is the mass (g) of the wood shavings sample before drying, and m0 is the mass (g) of the wood shavings sample when it is placed in an air dryer at 103°C and reaches constant weight.

[0023] The adhesive applied to the wood shavings can be thermosetting resins such as urea resin, melamine urea resin, phenolic resin, polyurethane resin, or epoxy resin, either alone or in combination. Mixing these with polyisocyanates is particularly preferable, as it reduces formaldehyde emissions and improves physicochemical properties such as bending strength. Polyisocyanates are compounds containing two or more isocyanate groups per molecule, such as diisocyanate compounds like 4,4'-diphenylmethane diisocyanate (MDI) and compounds obtained by reacting an excess of a diisocyanate compound with a polyol. One example of a polyisocyanate is polymeric MDI (polymethylene polyphenyl polyisocyanate: a mixture of monomeric MDI and high-molecular-weight polyisocyanate, also known as crude MDI), which hardens or foams upon reaction with moisture.

[0024] The amount of adhesive used is preferably 4 to 30 parts by weight in solids per 100 parts by weight of bone-dry wood shavings. If the amount of adhesive solids per 100 parts by weight of bone-dry wood shavings is less than 4 parts by weight, the bending strength of the wood shavings board will decrease, and if it exceeds 30 parts by weight, it will be an excessive amount, causing excessive rigidity and being economically disadvantageous. When an isocyanate compound is used as the adhesive, the solids content should preferably be 4 to 12 parts by weight, and when a melamine urea resin is used, the solids content should preferably be 10 to 30 parts by weight.

[0025] Next, a method for manufacturing a shaved wood board according to the present invention will be described. Generally speaking, the shaved wood board according to the present invention is manufactured by drying the shaved wood, applying an adhesive, randomly stacking the shaved wood without specifying the grain direction, and then pressurizing and molding this stack (mat). This will be described in more detail below.

[0026] Plantable hardwood or softwood logs, waste wood, sawmill waste, recycled materials, etc. are prepared and cut with a strander (cutting machine) to produce shavings. As mentioned above, the shavings used in the shavings board of the present invention preferably have a thickness of 0.1 mm to 0.6 mm, a width of 1 mm to 50 mm, and a length of 15 mm to 200 mm, so the shavings should be cut to meet these dimensional requirements.

[0027] Next, the wood shavings are dried in a dryer to a moisture content of 15% or less, preferably 3% or less, and then an adhesive is applied to the surface. The adhesive can be applied, for example, by a spray method, for example, by putting the wood shavings into a rotating drum rotating at a low speed (about 30 rpm) and spraying the adhesive onto the wood shavings as they fall naturally inside the rotating drum.

[0028] The adhesive-coated wood shavings are then piled up and formed into a mat, which is then thermocompressed in a press. The heat from the thermocompression process hardens the thermosetting resin in the adhesive, firmly bonding the wood shavings together to produce a shaved wood board. The thermocompression temperature varies depending on the type of adhesive used, but is generally between 190 and 220°C.

[0029] When collecting and forming wood shavings into a mat, they may be formed into a single mat, or they may be divided into multiple groups, for example, three groups, and each group may be formed into a mat, which may then be stacked and thermo-compressed to produce a wood shavings board consisting of three layers: an upper layer, a core layer, and a lower layer. Wood shavings boards produced by thermo-compressing a single-layer mat may have unevenness in the wood shavings, but by forming multiple layers, the unevenness in the wood shavings can be dispersed or eliminated, resulting in uniform strength and rigidity.

[0030] The wood chip board of the present invention has a density of 0.5 g / cm 3 More than 0.9g / cm 3 It is manufactured to have a density of 0.5 g / cm 3 If the thickness is less than 0.9 g / cm3, the strength of the wood chip board will be insufficient, while the density will be 3 If the density is larger than 0.5g / cm, the weight of the entire wood chipboard increases and handling becomes difficult. 3 More than 0.9g / cm 3 Within the following ranges, various properties suitable for flooring and other indoor interior materials can be obtained.

[0031] Regarding the density distribution of the shaved wood board, by using shaved wood boards with a moisture content of 15% by weight or less, more preferably 3% by weight or less, it is possible to effectively prevent the formation of a high-density layer on the surface of the shaved wood board, and by adjusting the timing and pressure at which the hot platen is brought into contact with the shaved wood board during hot pressing, it is possible to achieve a density distribution of 0.5 g / cm. 3 More than 0.9g / cm 3 It is possible to produce shaved wood flake boards with a uniform density distribution that is approximately uniform within the following range. The density distribution (density profile) in the thickness direction can be measured using a density distribution measuring device (DAX5000, manufactured by Grecon GmbH, Germany).

[0032] In addition, the bending strength of wood flakes is 25 to 90 N / mm 2 , bending Young's modulus is 3000~8500N / mm 2It is preferable that the bending strength is 25 N / mm 2 and / or bending Young's modulus is less than 3000N / mm 2 If the bending strength is less than 90N / mm, the deflection will be greater than the deflection standard (3.5mm or less, see below) set by the Japanese Agricultural Standards (JAS) wood flooring standard, especially when the wood chipboard is used as a base material for flooring, making it unsuitable for use as a flooring material. 2 and / or bending Young's modulus 8500N / mm 2 If the bending strength is more than 25-90N / mm, the elasticity required for walking when used as a flooring material will be insufficient, resulting in a poor walking feel. 2 The Young's modulus of bending is within the range of 3000 to 8500 N / mm 2 Within this range, the wood flake board can be made suitable for use as a base material for flooring.

[0033] Furthermore, flooring can be produced by using the shaved wood flakes produced as described above as a substrate and laminating and adhering a decorative material, such as veneer, decorative sheet, or decorative paper, approximately 0.1 to 0.2 mm thick onto its surface using an F☆☆☆☆ grade adhesive as specified in Table 3 of the Japanese Industrial Standard JIS A 5536:2015 "Adhesives for Floor Finishes." A coating layer, such as a urethane coating, approximately 20 to 80 μm thick may also be formed on the surface of the decorative material. Because the surface of the shaved wood flakes is smooth, the flooring obtained by laminating and adhering a decorative material onto the smooth surface also has a smooth surface, resulting in a suitable flooring material with appropriate physical properties such as strength, elasticity, and flexure.

[0034] The following test examples will explain the present invention and comparative examples. In these test examples, a large number of wood shaving samples, each 0.1 mm to 0.6 mm thick, 15 mm to 200 mm long, and 1 mm to 50 mm wide, were prepared by thinly shaving cypress logs using a strander (cutting machine). These samples were weighed to a predetermined weight ratio and divided into three groups (top layer samples Sa, core layer samples Sb, and bottom layer samples Sc). In Example 1, the top layer samples Sa were 30%, the core layer samples Sb were 40%, and the bottom layer samples Sc were 30% by bone-dry weight of the wood shavings. In Example 2, the top layer samples Sa were 25%, the core layer samples Sb were 50%, and the bottom layer samples Sc were 25% by bone-dry weight of the wood shavings.

[0035] A resin adhesive containing polyisocyanate (Sumidur 44 (registered trademark) V20, a product of Sumika Covestro Urethane Co., Ltd.) was applied to the surface of each of the wood shavings of the upper layer sample Sa, the core layer sample Sb, and the lower layer sample Sc. The application was performed using a spray method, where the wood shavings of sample Sa were placed into a rotating drum rotating at a low speed (approximately 30 rpm), and the resin adhesive containing polyisocyanate was sprayed onto the wood shavings as they naturally fell inside the rotating drum. The adhesive was sprayed onto samples Sb and Sc in the same manner.

[0036] The adhesive-coated upper layer sample Sa, core layer sample Sb, and lower layer sample Sc were each stacked in a mat shape to form an upper layer mat Ma, a core layer mat Mb, and a lower layer mat Mc, which were then stacked in order at a surface pressure of 3 to 10 N / mm 2 The wood was then hot-pressed at a temperature of 190 to 220°C for 2 to 4 minutes to obtain shaved wood flake board specimens (Examples 1 and 2) measuring 300 mm long x 300 mm wide x 12 mm thick.

[0037] For comparison, plywood, which has traditionally been widely used as a base material for flooring, and commercially available OSB (made from thin wood chips with a thickness of 0.65 to 1.20 mm) were used as comparative examples. The dimensions of these comparative examples were 300 mm long x 300 mm wide x 12 mm thick, similar to Examples 1 and 2.

[0038] For each of these examples and comparative examples (hereinafter collectively referred to as "test specimens"), the density, longitudinal bending strength, longitudinal bending Young's modulus, and maximum height were measured using a surface roughness measuring device (JIS B 0651:2001, Surftest SJ-310, manufactured by Mitutoyo Corporation). The results of these measurements are shown in Table 1. The measurement points for maximum height, which indicates surface roughness, were determined by dividing a test specimen with planar dimensions of 300 mm x 300 mm into nine 100 mm x 100 mm regions, as shown in Figure 3, and the centers of each region were designated as measurement points 1 to 9. Specifically, a measuring device was placed on the surface of each test specimen, and a stylus set at each measurement point was automatically measured to measure the unevenness at 0.01 mm intervals as it moved along a 15 mm linear range. The uneven shape was measured by calculating the maximum height within the measurement range (JIS B 0601:2013, the distance from the bottom of the deepest recess to the top of the highest protrusion, Rz = Rv + Rq), and the average value of the maximum height measured at each measurement point is shown in Table 1.

[0039] [Table 1]

[0040] Each of these test specimens was used as a substrate, and a 0.2 mm thick sliced ​​veneer was laminated and glued onto the surface to obtain flooring materials. The results of a visual evaluation of the surface condition are also shown in the rightmost column of Table 1. In this visual evaluation, a circle indicates that the veneer surface was in a good condition with no irregularities from the substrate surface visible, a triangle indicates that the veneer surface was in a slightly poor condition with only slight irregularities from the substrate surface visible, and an cross indicates that the veneer surface was in a poor condition with many irregularities from the substrate surface visible.

[0041] As can be seen from the results shown in Table 1, the maximum height of the shaved wood flakes in Examples 1 and 2 of the present invention, indicating surface roughness, was 114 μm and 118 μm, and the surface smoothness was significantly better than that of the comparative plywood and OSB. Therefore, even when this was used as a base material and a thin veneer was attached to the surface to make a flooring material, it was confirmed that the veneer surface did not show any irregularities and a good surface condition could be obtained. In addition, the maximum height indicating the surface roughness of MDF was about 40 μm, and although the shaved wood flakes in Examples 1 and 2 of the present invention were not as good as MDF, a good surface condition was obtained in which the veneer was attached to the surface of the veneer, and the surface smoothness was not uneven (marked with a circle). In fact, it has sufficient surface smoothness, and Tables 2 and 3 shown later include those with surface smoothness comparable to or better than MDF.

[0042] In addition, the wood shavings of Examples 1 and 2 of the present invention also have excellent physical properties such as density, bending strength, and bending Young's modulus. Although not shown in the table, the bending deflection standard of the Japanese Agricultural Standards (JAS) wood flooring standard (a flooring sample measuring 300 mm wide x 1800 mm long x 12 mm thick is supported at a span of 700 mm, and a load of 21 kg is applied to a load rod placed in the center of the span. The displacement D1 is measured when a load of 9 kg is applied, and the difference D1 - D2 is 3.5 mm or less) was measured. The result was D1 - D2 = 1.9 mm, which fully meets the above standard. From the above results, it was confirmed that the wood shavings of Examples 1 and 2 of the present invention have various physical properties suitable for use as a flooring base material.

[0043] It is speculated that the good surface smoothness obtained in the wood shavings of Examples 1 and 2 of the present invention is due to the fact that the cypress used as the wood shavings has a low tree species density and is therefore easily compressed, and that this is compressed to a certain degree or more to produce wood shavings with an appropriate density.

[0044] More specifically, the compressive deformation of wood shavings will be explained with reference to Figure 4. As shown in Figures 4(a) to (c), when the tree species density is low, the proportion of woody parts 2a in the wood shavings is relatively small and the proportion of voids 2b is large, making the wood shavings more susceptible to compression. When wood shavings are cut thinly (Figure 4(b)), the presence of voids tends to cause surface irregularities, but the voids are crushed by compression, reducing the surface irregularities (Figure 4(c)). On the other hand, as shown in Figures 4(d) to (f), when the tree species density is high, the proportion of voids 2b in the wood shavings is small, and the woody parts 2a occupy the majority of the wood shavings, increasing the strength, making the wood shavings less susceptible to compression (Figure 4(f)) even when the wood shavings are thin (Figure 4(e)).

[0045] Next, the deformation of the surface of the shaved wood board will be explained with reference to Figure 5. In order to create a shaved wood board with the same board density, if a shaved wood board with a low tree species density (2c) is used, it is necessary to accumulate a large number of shaved wood boards (2c) to increase the mat volume (Figure 5(a)). However, a mat made of accumulated shaved wood boards with a low tree species density (2c) is easily compressed, so when it is hot-pressed, its surface conforms to the smooth press surface, resulting in a shaved wood board with a smooth surface (Figure 5(b)). On the other hand, to create a shaved wood board with the same board density using shaved wood boards with a high tree species density (2d), it is necessary to reduce the amount of shaved wood boards (2d) used and reduce the mat volume (Figure 5(c)). However, a mat made of accumulated shaved wood boards with a high tree species density (2d) is difficult to compress, so when it is hot-pressed, its surface conforms poorly to the smooth press surface, resulting in a shaved wood board with large irregularities and poor surface smoothness (Figure 5(d)).

[0046] Although it is inevitable that the surface of the wood shavings board will tend to become uneven where the wood shavings overlap, as shown in Figures 6(a) and (b), since the wood shavings 2c with a low tree species density are weak in strength and easily compressed, it is assumed that both or at least one of the overlapping wood shavings 2c, 2c will deform or compress, making them approximately flush, and maintaining the surface smoothness without generating large unevenness. To achieve this effectively, relatively thin wood shavings with a thickness of 0.1 to 0.6 mm are used, and when the mat made by accumulating these wood shavings is thermocompressed, the overlapping wood shavings are compressed with a compressive force of 0.6 to 0.8 g / cm to make them approximately flush. 3 It is preferable to form the shaved wood board into a board density of about 100 μm. By doing so, the height of the step 5 formed at the overlapping portion of the shaved wood board obtained after compression is 0.2 mm or less, making it easy to obtain a shaved wood board with a maximum height of 200 μm or less, which indicates surface roughness. On the other hand, when shaved wood boards 2d with a high tree species density overlap, as shown in Figures 6(c) and (d), the overlapping shaved wood boards 2d, 2d are barely deformed and remain overlapped, leaving a step, and the height of the step 5 becomes greater than 0.2 mm, making it difficult to obtain a shaved wood board with a maximum height of 200 μm or less, which indicates surface roughness.

[0047] Based on these assumptions, it was thought that the surface smoothness of shaved wood boards would have a significant correlation with the tree species density of the shaved wood used as raw material and the board density. Therefore, the inventors next investigated the influence or correlation of tree species density and board density on surface smoothness.

[0048] First, the following test was carried out to confirm the influence of the tree species density of the wood shavings on the surface roughness. That is, wood shavings from six types of tree species, namely, sawtooth oak, zelkova, edulis, loblolly pine, cypress, and cedar, were used individually as the wood shavings, and six types of wood shavings board specimens of different tree species were prepared in the same manner as in Example 1. As mentioned above, it was assumed that the surface roughness is also related to the board density, so the test was carried out when the board density was approximately constant (about 0.7 g / cm 3 Each specimen was prepared so that the surface roughness was measured in the same manner as above. The results of measuring the surface roughness of each specimen, and the results of visually evaluating the surface condition of flooring materials in which 0.2 mm thick sliced ​​veneer was laminated and glued to the surface of each specimen, are shown in Table 2. Figure 7 also shows a graph of the correlation between wood species density and maximum height, which indicates surface roughness.

[0049] [Table 2]

[0050] From the results shown in Table 2 and Figure 7, a certain correlation was found between the density of the tree species used as the wood shavings and the maximum height, which indicates the surface roughness of the wood shavings boards made using them.The lower the tree species density, the smaller the maximum height, which indicates the surface roughness (better surface smoothness). Conversely, the higher the tree species density, the larger the maximum height, which indicates the surface roughness (decreasing surface smoothness).

[0051] More specifically, a density of 0.6 g / cm 3 The shaved wood boards made from shaved wood from the most common tree species (oak, zelkova, and edulis) had a maximum height, which indicates surface roughness, of over 200 μm, and had surface smoothness that was comparable to or inferior to that of plywood (see Table 1 for the maximum height, which indicates the surface roughness of plywood).As a result, the surface condition of the flooring material obtained by laminating and gluing veneer onto the surface was also poor (×) or slightly poor (△).

[0052] In contrast, the density is 0.6 g / cm 3The shaved wood boards made from shaved wood of the following tree species (loblolly pine, cypress, and cedar) had a maximum height indicating surface roughness of 200 μm or less, and had a surface smoothness superior to that of plywood. The surface condition of the flooring material obtained by laminating and gluing veneer to the surface was also good (○). Furthermore, the density was 0.45 g / cm 3 The shaved wood boards made from shaved wood of the following tree species (cypress and cedar) had a maximum height indicating surface roughness of less than 100 μm, and had significantly better surface smoothness than plywood.

[0053] Next, the following test was conducted to confirm the effect of board density on surface roughness. Since the above confirmed that surface roughness is related to the species density of the wood shavings, nine specimens with different board densities were prepared in the same manner as in Example 1, except that cedar shavings, which have a low species density and are therefore soft and easily compressible, were used in this test, and the heat and pressure conditions on the mat were varied to achieve various board densities. The surface roughness of each specimen was measured in the same manner as above, and the results of visual evaluation of the surface condition of flooring materials with 0.2 mm thick sliced ​​veneer laminated and bonded to the surface of each specimen are shown in Table 3. The correlation between board density and maximum surface roughness height is also shown in a graph in Figure 8.

[0054] [Table 3]

[0055] From the results shown in Table 3 and Figure 8, a certain correlation was found between the board density of shaved wood flake boards and the maximum height indicating surface roughness, with a tendency for the higher the board density, the smaller the maximum height indicating surface roughness (better surface smoothness), and conversely, the lower the board density, the larger the maximum height indicating surface roughness (decreasing surface smoothness).

[0056] More specifically, board density is 0.5 g / cm 3The smaller test specimens (cedar 1 and 2) had a maximum height indicating surface roughness of over 200 μm, and had poor surface smoothness, similar to that of plywood. Therefore, the surface condition of the flooring material obtained by laminating and gluing veneer onto the surface was also poor (×).

[0057] In contrast, the board density is 0.5g / cm 3 The test specimens (cedar 3 to 9) had a maximum height of 200 μm or less, which indicates surface roughness, and had a surface smoothness better than that of plywood. The surface condition of the flooring material obtained by laminating and gluing veneer to the surface was also good (◯). In this test, the upper limit of the board density of the test specimens was set to 0.86 g / cm 3 (Cedar 9), but the board density is 0.9g / cm 3 If the board density exceeds 0.9g / cm, the weight increases and handling becomes difficult, and it also has a negative effect on the feeling of walking when used as a flooring material. 3 is preferably set as the upper limit.

[0058] Furthermore, the inventors have found that the density ratio b / a, where a is the density of the wood shavings used as raw material and b is the board density of the shavings obtained by hot-pressing the shavings, has a significant correlation with the surface smoothness of the shavings. This is demonstrated by the fact that, in Table 2, specimens with a density ratio of less than 1.2 (oak and zelkova) have poor surface smoothness, while specimens with a density ratio of 1.2 or more (Lithocarpus edulis, loblolly pine, cypress, and cedar) generally have good surface smoothness; and in Table 3, specimens with a density ratio of less than 1.2 (cedar 1) have poor surface smoothness, while specimens with a density ratio of 1.2 or more (cedars 3 to 9) have good surface smoothness. This is also demonstrated by Figure 9, which graphically illustrates the results of Tables 2 and 3. Note that cedar 2 in Table 3 satisfies the requirement for a density ratio of 1.2 or more, but has a board density of 0.49 g / cm. 3 The lower limit of the board density range of the present invention (0.5 g / cm 3 ), the desired surface smoothness was not obtained.

[0059] The density ratio will be further explained. As mentioned above, from the results shown in Table 2 and Fig. 7, a certain correlation was recognized between the tree species density of the shaved wood flakes and the surface smoothness of the shaved wood flake board, and it was confirmed that the lower the tree species density, the better the surface smoothness, and the higher the tree species density, the lower the surface smoothness. This is because the board density was kept approximately constant (about 0.7 g / cm 3 ) are test results when the board density is 100%. On the other hand, the results shown in Table 3 and Figure 8 confirm that there is a certain correlation between the board density and the surface smoothness of the shaved wood board, and that the higher the board density, the better the surface smoothness, and that the lower the board density, the lower the surface smoothness tends to be, but these are test results when shaved wood boards of the same tree species (= same tree species density) are used.

[0060] Therefore, when the correlation between tree species density and surface smoothness is tested using a lower board density, the correlation (a linear proportional relationship with a constant slope) is not as pronounced as the results shown in Table 2 and Figure 7. It is presumed that the tendency to improve surface smoothness with decreasing tree species density becomes weaker (the slope becomes gentler) and converges to a minimum value. Similarly, when the correlation between board density and surface smoothness is tested using wood shavings with a higher tree species density, the correlation (a linear proportional relationship with a constant slope) is not as pronounced as the results shown in Table 3 and Figure 8. It is presumed that the tendency to improve surface smoothness with increasing board density becomes weaker (the slope becomes gentler) and converges to a maximum value. In other words, it is believed that tree species density and board density not only independently have a significant impact on surface smoothness, but also that they are correlated with each other and affect surface smoothness. From these perspectives, the inventors focused on the density ratio (board density b / tree species density a).

[0061] Let's further explain the density ratio (board density b / species density a). When a solid wood board with volume V is obtained from a specific tree species, its weight Wa is Wa = tree species density x volume V. On the other hand, when shaved wood boards of the same tree species are thermocompressed to obtain shaved wood boards with the same volume V, their weight Wb is Wb = board density b x volume V, so board density b / species density a = weight ratio Wb / Wa. In other words, the density ratio indicates how many times the weight Wb of a shaved wood board is compared to the weight Wa of a solid wood board of the same volume obtained from the same tree species. In other words, the density ratio is a value that indicates the degree of compression of a shaved wood board relative to a solid wood board of the same volume and tree species.

[0062] FIG. 10 shows a perspective view (upper left) of shaved wood board 1 and an enlarged cross-sectional view (lower left) of a portion thereof, as well as a perspective view (upper right) of a solid wood board 7 of the same tree species and volume as this board (upper right) and an enlarged cross-sectional view (lower right) of a portion thereof. As described above with reference to FIG. 4, in shaved wood board 1, the woody portions 2a and voids 2b of the shaved wood boards are crushed and compressed, and these compressed shaved wood boards are stacked in multiple layers to form shaved wood board 1. In contrast, in solid wood board 7, the woody portions 6a and voids 6b remain uncompressed. The presence or absence or degree of this crushing (compression) determines the board density b / tree species density a or the weight ratio Wb / Wa.

[0063] Although the present invention has been described in detail above with reference to examples and test examples, the present invention can be practiced with a wide variety of modifications and changes within the scope of the invention as defined by the claims. [Explanation of symbols]

[0064] 1 Wood cut thin plate (base material) 2 Wood cutting thin section 2a Woody part 2b Cavity 2c Wood shavings with low species density 2d Wood shavings with high species density 4. Veneer (decorative material) 5 Flooring (decorative panels) 6. Steps on the surface of the wood shavings board formed where the wood shavings overlap 7 Solid wood board

Claims

1. A shaved wood board obtained by mixing and accumulating wood shavings and adhesive, and then integrating them under heat and pressure, wherein the wood species density a of the shaved wood shavings is 0.6 g / cm ３ The density b of the shaved wood flake board is 0.5 g / cm ３ 0.9g / cm or more ３ The shaved wood board is characterized in that the density ratio b / a of the tree species density a of the wood shavings to the density b of the wood shavings board is 1.2 or more, and in the area where the wood shavings on the surface of the wood shavings board overlap each other, both or at least one of the wood shavings are deformed or compressed so that the wood shavings are approximately flush with each other, and at least one surface has a maximum height of 200 μm or less, which indicates the surface roughness defined in Japanese Industrial Standard JIS B 0601:2013.

2. 2. The wood shavings board according to claim 1, wherein the thickness of the wood shavings is 0.1 mm or more and 0.6 mm or less.

3. 2. The shavings board according to claim 1, wherein the width of the shavings is 1.0 mm or more and 50 mm or less, and the length of the shavings is 15 mm or more and 200 mm or less.

4. A flooring material obtained by laminating a decorative material on at least one surface of the shaved wood flake board according to any one of claims 1 to 3, and having a bending strength of 30 to 80 N / mm ２ and the bending Young's modulus is 3000 to 8500 N / mm ２ A flooring material characterized by:

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