Cut wood thin plate and floor material

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 obtained by mixing small or thin pieces of wood with adhesive, piling them up, and integrating them under heat and pressure. OSB is a type of structural panel specified by the Japanese Agricultural and Forestry Standards (JAS), but in light of the recent depletion of wood resources, 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 about 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 pressurizing them to form a sheet. 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 it has physical properties of about the same level, due to uneven distribution of adhesive and non-uniform press load, some shavings of wood tend to be rolled up and exposed on the surface, and because of its poor surface smoothness, it has been practically difficult to directly attach decorative materials such as veneer or decorative sheet to the surface of OSB. Therefore, when using OSB as a base for decorative boards, the current situation is that a surface material with excellent surface smoothness, such as MDF, is attached to the surface, and then a decorative material such as veneer or decorative sheet is attached to the surface to make a decorative board, 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 boards, but in recent years, when it has become difficult to obtain high-quality veneers, wood fiberboards such as MDF have been widely used. Plywood has excellent strength, is easy to install with little deflection, and is less likely to warp or deform after installation, so it has been recognized as a material suitable for use as a base material for decorative boards. However, it does not have sufficient surface smoothness (as described below, the maximum height indicating surface roughness is over 200 μm), and when a decorative material such as a thin veneer is directly attached to it, the unevenness of the plywood surface appears on the surface of the veneer, resulting in poor surface properties and a poor feeling when used as a floorboard. Therefore, when attaching a decorative material to a plywood base material, it is necessary to fill the unevenness of the plywood surface with putty to give it a smooth surface. On the other hand, although MDF has excellent surface smoothness, it has insufficient bending strength, especially in the longitudinal direction.

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

[0007] In order to solve this problem, the inventors conducted tests to produce various types of shaved wood boards by mixing and accumulating wood shavings with adhesive and combining them under heat and pressure. The inventors discovered that the density of the shaved wood board and the tree species density of the wood shavings are significantly related to the surface smoothness of the resulting shaved wood boards. Based on this discovery, the inventors conducted further tests and studies, which led to the completion of 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 shaved wood and adhesive, and 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 shaved wood board is 0.5 g / cm 3 More than 0.9g / cm 3 or less, and is characterized in that the density ratio b / a of the wood species density a of the shaved wood flakes to the density b of the shaved wood flake board is 1.2 or more.

[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 shavings board described in claim 1, 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.

[0011] The invention according to claim 4 of the present application is a flooring material comprising a decorative material laminated on at least one surface of the shaved wood chip 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 It is characterized in that: Effect 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 according to the present invention can be suitably used as a substrate for directly attaching a decorative material such as veneer or decorative sheet onto the shaved wood flake board, instead of conventionally used MDF, etc.

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

[0014] A flooring material formed by laminating a decorative material such as veneer onto the smooth surface of this shaved wood flake board has good density and bending Young's modulus, and provides a flooring material with excellent strength, rigidity, scratch resistance, and the like. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a side view showing a schematic diagram of a shaved wood board according to the present invention. [Diagram 2] FIG. 1 is a side view showing a flooring material using the shaved wood board according to the present invention as a base material. [Diagram 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 a thick wood shavings with low tree species density (a), a thin wood shavings with low tree species density (b), a thick wood shavings with high tree species density (d), and a thin wood shavings with high tree species density (e), as well as schematic cross-sectional views (c, f) of thin wood shavings (b, e) after compression. [Diagram 5]Schematic cross-sectional views showing (a) mats made of accumulated wood shavings with a low tree species density and (b) the state in which these mats have been compressed and both ends in the width direction cut vertically, and (c) mats made of accumulated wood shavings with a high tree species density and (d) the state in which these mats have been compressed and both ends in the width direction cut vertically. [Figure 6] FIG. 1 is a schematic cross-sectional view showing the surface condition (a) of a portion where wood shavings with low wood species density overlap each other before compression and the surface condition (b) of the portion where wood shavings with high wood species density overlap each other before compression and the surface condition (c) of the portion where wood shavings with high wood species density overlap each other before compression and the surface condition (d) of the portion where wood shavings with high wood species density overlap each other before compression and the surface condition after compression. [Figure 7] 1 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 the board has an approximately constant board density produced from shaved wood boards of several tree species with different densities. [Figure 8] 1 is a graph showing the correlation between board density and maximum height indicating surface roughness of shaved wood boards when shaved wood boards having different board densities are produced 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 density ratios are determined by the presence or absence or degree of compression. BEST MODE FOR CARRYING OUT THEINVENTION

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

[0017] Wood shavings are prepared by cutting hardwood or softwood logs into thin strips using a strander. Wood shavings may also be obtained from planted, renewable hardwood or softwood trees.

[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 decreases, and if it exceeds 0.6 mm, the surface smoothness of the resulting wood shavings board decreases and the rigidity tends to become non-uniform. If the thickness of the wood shavings is within the range of 0.1 mm to 0.6 mm, a wood shavings board having excellent surface smoothness and uniform rigidity can be obtained.

[0020] If the width of the wood shavings exceeds 50 mm, not only will the handling and transportability decrease, but the wood shavings will also be prone to curling, making the adhesive less likely to adhere to them. If the width of the wood shavings is less than 1 mm, the stiffness 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 stiffness can be obtained.

[0021] If the length of the wood shavings exceeds 200 mm, not only will the handling and transportability decrease, but the wood shavings will also be more likely to curl, and when heated and pressed, localized cavities (core voids) will form, reducing strength and causing punctures. If the length of the wood shavings is less than 15 mm, the rigidity of the resulting shaved wood board will decrease. If the length of the wood shavings is within the range of 15 mm to 200 mm, the productivity of the shaved wood board will be excellent and the required rigidity will be easier to obtain.

[0022] The moisture content of the wood shavings is preferably 15% by weight or less, and the wood shavings are dried until the moisture content is 15% by weight or less before entering the manufacturing process of the wood shavings board. If the moisture content exceeds 15% by weight, an extremely high density layer is likely to be formed on the surface of the wood shavings board, which requires a long time for pressing during pressure molding and makes the rigidity of the obtained wood shavings board uneven. From this viewpoint, it is more preferable that the moisture content of the wood shavings is 3% by weight or less. The moisture content MC of the wood shavings can be calculated from 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 a constant weight.

[0023] The adhesive to be applied to the wood chips can be a thermosetting resin such as urea resin, melamine urea resin, phenol resin, polyurethane resin, or epoxy resin, either alone or in a suitable mixture. In particular, a mixture of these with polyisocyanate is preferred, since it reduces the amount of formaldehyde released and improves physicochemical properties such as bending strength. Polyisocyanate is a compound that has two or more isocyanate groups in one molecule, and includes diisocyanate compounds such as 4,4'-diphenylmethane diisocyanate (MDI) and compounds obtained by reacting an excess amount of a diisocyanate compound with a polyol. One example of polyisocyanate is polymeric MDI (polymethylene polyphenyl polyisocyanate: a mixture of monomeric MDI and high molecular weight polyisocyanate, also known as crude MDI), which has the property of reacting with moisture to harden or foam.

[0024] The amount of adhesive used is preferably 4 to 30 parts by weight in terms of solid content per 100 parts by weight of the bone dry weight of the wood shavings. If the amount of adhesive solid content per 100 parts by weight of the bone dry weight of the wood shavings is less than 4 parts by weight, the bending strength of the wood shavings board decreases, and if it exceeds 30 parts by weight, it becomes an excessive amount, and the rigidity increases excessively, which is economically disadvantageous. When an isocyanate compound is used as the adhesive, the solid content is preferably 4 to 12 parts by weight, and when a melamine urea resin is used, the solid content is preferably 10 to 30 parts by weight.

[0025] Next, the method for manufacturing the 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 adhesive, randomly stacking the shaved wood without setting the grain direction, and pressurizing the stack (mat). The following will be described in more detail.

[0026] Plantation-renewable hardwood or softwood logs, waste wood, lumber waste, recycled materials, etc. are prepared, and cut with a strander (cutting machine) to produce shaved wood flakes. As described above, the shaved wood flakes used in the shaved wood flake board of the present invention are preferably 0.1 mm to 0.6 mm thick, 1 mm to 50 mm wide, and 15 mm to 200 mm long, so that the shaved wood flakes are cut to satisfy these dimensional conditions.

[0027] Next, the wood shavings are dried in a dryer to adjust the moisture content to 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, and a suitable method is to put the wood shavings into a rotating drum rotating at a low speed (about 30 rpm) and spray the adhesive onto the wood shavings as they fall naturally inside the rotating drum.

[0028] Next, the adhesive-coated wood shavings are 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 wood shavings board. The thermocompression process temperature varies depending on the type of adhesive used, but is generally between 190 and 220°C.

[0029] When accumulating the wood shavings to form a mat, they may be formed into a single mat, but the wood shavings may also 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 the board into multiple layers, the unevenness in the wood shavings can be dispersed or eliminated, resulting in uniform strength and rigidity.

[0030] The shaved wood 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 it is less than 0.9 g / cm3, the strength of the shaved wood board will be insufficient, while the density will be 0.9 g / cm3. 3 If it is larger than this, the weight of the entire wood chip board increases and handling becomes difficult. 3 More than 0.9g / cm 3 Within the following ranges, suitable performance properties for use as flooring and other indoor interior materials can be obtained.

[0031] Regarding the density distribution of the shaved wood board, by using shaved wood 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 mat 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 manufacture shaved wood boards having 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, Germany).

[0032] In addition, the bending strength of shaved wood board is 25 to 90 N / mm 2 , bending Young's modulus is 3000~8500N / mm 2It is preferable that the bending strength is 25N / 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 shavings are used as a base material for flooring, making it unsuitable for use as a flooring material. 2 and / or bending Young's modulus is 8500N / mm 2 If it exceeds 25-90N / mm, the elasticity required for walking will be insufficient when used as a flooring material, 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 shavings can be made suitable for use as a base material for flooring.

[0033] Furthermore, a flooring material can be manufactured by laminating and adhering a decorative material such as a veneer, a decorative sheet, or a decorative paper having a thickness of about 0.1 to 0.2 mm on the surface of the shaved wood board as a substrate using an adhesive of F☆☆☆☆ grade in Table 3 of the Japanese Industrial Standard JIS A 5536:2015 "Adhesives for Floor Finishing Materials". A coating layer such as a urethane coating having a thickness of about 20 to 80 μm may be further formed on the surface of the decorative material. Since the surface of the shaved wood board is obtained smoothly, the flooring material obtained by laminating and adhering a decorative material on the smooth surface also has a smooth surface, and is a suitable flooring material having physical properties such as moderate strength, elasticity, and deflection.

[0034] The following describes the examples and comparative examples of the present invention with reference to test examples. In this test example, a large number of wood shaving samples with thicknesses of 0.1 mm to 0.6 mm, lengths of 15 mm to 200 mm, and widths of 1 mm to 50 mm were prepared by thinly cutting each cypress log with a strander (cutting machine), and these were weighed to a predetermined weight ratio and divided into three groups (upper layer sample Sa, core layer sample Sb, and lower layer sample Sc). In Example 1, the upper layer sample Sa was distributed at 30%, the core layer sample Sb was distributed at 40%, and the lower layer sample Sc was distributed at 30% in terms of the bone dry weight ratio of the wood shaving samples, and in Example 2, the upper layer sample Sa was distributed at 25%, the core layer sample Sb was distributed at 50%, and the lower layer sample Sc was distributed at 25% in terms of the bone dry weight ratio of the wood shaving samples.

[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. A spray method was used for application, and the wood shavings of sample Sa were placed in a rotating drum rotating at a low speed (approximately 30 rpm), and the resin adhesive containing polyisocyanate was sprayed on as the wood shavings naturally fell inside the rotating drum. The adhesive was sprayed on samples Sb and Sc in the same manner.

[0036] The upper layer sample Sa, the core layer sample Sb, and the lower layer sample Sc, each coated with adhesive, are stacked in a mat shape to form an upper layer mat Ma, a core layer mat Mb, and a lower layer mat Mc, which are then stacked in order at a surface pressure of 3 to 10 N / mm 2 The pieces were then molded under heat and pressure 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 in length, 300 mm in width, and 12 mm in thickness.

[0037] For comparison, plywood, which has been widely used as a base material for flooring materials, and commercially available OSB (made from shaved wood flakes 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, these are collectively referred to as "test specimens"), the density, longitudinal bending strength, longitudinal bending Young's modulus, and maximum height measured by a surface roughness measuring instrument (JIS B 0651:2001, Surftest SJ-310, manufactured by Mitutoyo Corporation) were measured. The results of these measurements are shown in Table 1. As shown in FIG. 3, the test specimen with planar dimensions of 300 mm x 300 mm was divided into nine regions of 100 mm x 100 mm, and the centers of each region were designated as measurement points 1 to 9. Specifically, a measurement instrument was placed on the surface of each test specimen, and the uneven shape was automatically measured at a pitch of 0.01 mm while a stylus set at each measurement point moved within a linear range of 15 mm in length. 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 of the maximum heights measured at each measurement point is shown in Table 1.

[0039] [Table 1]

[0040] Each of these test specimens was used as a base material, and a 0.2 mm thick veneer was laminated and bonded to the surface to obtain flooring materials, and 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 no irregularities of the base material surface were visible on the veneer surface, and a good surface condition was observed, a triangle indicates that only slight irregularities of the base material surface were visible on the veneer surface, and a cross indicates that many irregularities of the base material surface were visible on the veneer surface, and a poor surface condition was observed.

[0041] As can be seen from the results shown in Table 1, the maximum height indicating the surface roughness of the shaved wood flake boards of Examples 1 and 2 of the present invention is 114 μm and 118 μm, and has a surface smoothness far superior to that of the plywood and OSB of the comparative example. Therefore, even if this is used as a base material and a thin veneer is attached to the surface to make a flooring material, it was confirmed that a good surface condition can be obtained without unevenness appearing on the veneer surface. In addition, the maximum height indicating the surface roughness of MDF is about 40 μm, and although the shaved wood flake boards of Examples 1 and 2 of the present invention are not as good as MDF, a good surface condition is obtained in which unevenness does not appear on the veneer surface when the veneer is attached to the surface of the flooring material (◯ mark), and it has sufficient surface smoothness in practice, and Tables 2 and 3 shown later include ones with surface smoothness equal to or greater than that of MDF.

[0042] In addition, the wood shavings of Examples 1 and 2 of the present invention are also excellent in 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 with a width of 300 mm x length of 1800 mm x thickness of 12 mm is supported with 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 amount D1 is measured when a load of 9 kg is applied, and the difference in the displacement amount D1-D2 is 3.5 mm or less) was tested, and the result was D1-D2 = 1.9 mm, which fully cleared 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 base material for flooring.

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

[0044] More specifically, the compressive deformation of the wood shavings will be explained with reference to Fig. 4. As shown in Figs. 4(a)-(c), when the tree species density is low, the proportion of the woody parts 2a in the wood shavings is relatively small and the proportion of the voids 2b is large, so the wood shavings are easily compressed. When cut thinly (Fig. 4(b)), the presence of the voids tends to cause unevenness on the surface, but the voids are crushed by compression, so the unevenness on the surface becomes smaller (Fig. 4(c)). On the other hand, as shown in Figs. 4(d)-(f), when the tree species density is high, the proportion of the voids 2b in the wood shavings becomes small and the woody parts 2a occupy the majority, so the strength increases, and the wood shavings are not easily compressed (Fig. 4(f)) even when the wood shavings are thin (Fig. 4(e)).

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

[0046] Although it is inevitable that the surface of the wood shavings board tends to become uneven at the parts where the wood shavings overlap, as shown in Figures 6(a) and (b), the wood shavings 2c with a low tree species density are weak in strength and easily compressed, so 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 the surface smoothness will be maintained without large unevenness. In order to achieve this well, the wood shavings are relatively thin, with a thickness of 0.1 to 0.6 mm, and when the mat made of accumulated 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 mold the shaved wood into a shaved wood board having a board density of about 100 μm. By doing so, the height of the step 5 formed at the part where the shaved wood pieces 2c, 2c overlap on the surface of the shaved wood board obtained after compression is 0.2 mm or less, and it is easy to obtain a shaved wood board having a maximum height indicating surface roughness of 200 μm or less. On the other hand, when the shaved wood pieces 2d having a high tree species density overlap each other, as shown in Figures 6(c) and (d), the overlapped shaved wood pieces 2d, 2d are hardly deformed and overlap as they are, leaving a step, and the height of the step 5 becomes larger than 0.2 mm, making it difficult to obtain a shaved wood board having a maximum height indicating surface roughness of 200 μm or less.

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

[0048] First, the following test was carried out to confirm the effect of the tree species density of the wood shavings on the surface roughness. That is, wood shavings from six different tree species, namely, Quercus acutissima, Zelkova, Quercus stenophylla, Loblolly Pine, Japanese Cypress, and Japanese 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 described above, it was assumed that the surface roughness is also related to the board density, so the surface roughness was measured when the board density was approximately constant (approximately 0.7 g / cm 3 The test specimens were then prepared so that the surface roughness of each specimen was measured in the same manner as above, and the results of a visual evaluation of the surface condition of the flooring material in which a 0.2 mm thick veneer was laminated and bonded to the surface of each specimen are shown in Table 2. Figure 7 also shows a graph of the correlation between the wood species density and the 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 (the better the surface smoothness), and conversely, the higher the tree species density, the larger the maximum height, which indicates the surface roughness (the lower the surface smoothness).

[0051] More specifically, the density is 0.6 g / cm 3 The shaved wood boards made from shaved wood of the most common tree species (Quercus acutissima, Zelkova, and Quercus stenophylla) had a maximum height, which indicates the surface roughness, of over 200 μm, and had a surface smoothness that was equivalent 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 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 on the surface of the board 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 a surface smoothness far superior to that of plywood.

[0053] Next, the following test was carried out to confirm the effect of board density on surface roughness. As a result of the above, it was confirmed that surface roughness is related to the tree species density of the wood shavings. Therefore, in this test, cedar wood shavings, which have a low tree species density and therefore are soft and easily compressed, were used, and nine types of test specimens with different board densities were created in the same manner as in Example 1, except that the heat and pressure conditions for the mat were changed to have various board densities. The results of measuring the surface roughness of each test specimen in the same manner as above, and the results of visually evaluating the surface condition of the flooring material in which a 0.2 mm thick veneer was laminated and bonded to the surface of each test specimen are shown in Table 3. In addition, the correlation between board density and maximum height of surface roughness is shown in a graph in FIG. 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 to be the smaller the maximum height indicating surface roughness (better surface smoothness), and conversely, the lower the board density to be the larger the maximum height indicating surface roughness (deteriorating surface smoothness).

[0056] More specifically, the board density is 0.5 g / cm 3The smaller test specimens (Cedar 1 and 2) had a maximum height indicating surface roughness exceeding 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 0.5 g / cm 3 The above specimens (cedar 3 to 9) had a maximum height indicating surface roughness of 200 μm or less, and had a surface smoothness better than that of plywood. The surface condition of the flooring material obtained by laminating and gluing veneer on the surface was also good (◯). In this test, the upper limit of the board density of the 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 0.9 g / cm, the weight increases and handling becomes difficult, and it also has a negative effect on the walking feel when used as a flooring material. 3 It is preferable to set the upper limit at .

[0058] Furthermore, the inventors have found that the density ratio b / a between the density a of the wood shavings used as raw material and the board density b of the shavings board obtained by hot pressing the same has a large correlation with the surface smoothness of the shavings board. This is demonstrated by the fact that in Table 2, those with a density ratio of less than 1.2 (Quercus acutissima, Zelkova) have poor surface smoothness, while those with a density ratio of 1.2 or more (Lithocarpus stenophylla, Loblolly Pine, Cypress, Japanese Cedar) generally have good surface smoothness, and in Table 3, those with a density ratio of less than 1.2 (Japanese Cedar 1) have poor surface smoothness, while those with a density ratio of 1.2 or more (Japanese Cedar 3 to 9) have good surface smoothness, and by FIG. 9 which shows the results of Tables 2 and 3 in a graph. Note that Japanese Cedar 2 in Table 3 satisfies the condition of 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 ) was slightly below the required surface smoothness.

[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 found 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 smaller the tree species density, the better the surface smoothness, and the higher the tree species density, the lower the surface smoothness tends to be. This is because the board density was kept approximately constant (approximately 0.7 g / cm 3 On the other hand, from the results shown in Table 3 and Figure 8, it was confirmed that there is a certain correlation between the board density and the surface smoothness of shaved wood boards, 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 this is a test result when shaved wood boards of the same tree species (= same tree species density) were used.

[0060] In this case, when the board density is made smaller and the correlation between the tree species density and the surface smoothness is tested, it is assumed that the correlation (linear proportional relationship with a certain slope) is not as significant as the results shown in Table 2 and FIG. 7, and the tendency to improve the surface smoothness is slowed (the slope becomes gentler) even when the tree species density is made smaller, and it is assumed that it converges to a certain minimum value. Similarly, when the correlation between the board density and the surface smoothness is tested using a wood shavings with a higher tree species density, it is assumed that the correlation (linear proportional relationship with a certain slope) is not as significant as the results shown in Table 3 and FIG. 8, and the tendency to improve the surface smoothness is slowed (the slope becomes gentler) even when the board density is made larger, and it is assumed that it converges to a certain maximum value. In other words, it is believed that the tree species density and the board density not only have a large effect on the surface smoothness independently, but also that they are correlated with each other and affect the surface smoothness. From these points of view, the present inventors focused on the density ratio (board density b / tree species density a).

[0061] The density ratio (board density b / species density a) is explained further. When a solid board with volume V is obtained from a certain species of wood, its weight Wa is Wa = species density x volume V. On the other hand, when a shaved wood board with the same volume V is obtained by hot pressing shaved wood of the same species of wood, its 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 the shaved wood board is compared with the weight Wa of a solid board of the same volume obtained from the same species of wood. In other words, the density ratio is a value that indicates the degree of compression of the shaved wood board based on a solid board of the same species and volume.

[0062] In Fig. 10, a perspective view (upper left) of a shaved wood board 1 and an enlarged cross-sectional view (lower left) of a part of the board are shown, along with a perspective view (upper right) of a solid board 7 of the same wood species and volume and an enlarged cross-sectional view (lower right) of a part of the board. As described above with reference to Fig. 4, in the shaved wood board 1, the wood part 2a and the void part 2b of the shaved wood board are crushed and compressed, and the shaved wood board 1 is formed by stacking these compressed shaved wood boards in multiple layers. In contrast, in the solid board 7, the wood part 6a and the void part 6b remain uncompressed. The presence or absence or degree of this crushing (compression) is the board density b / wood 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 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 shaved wood board formed at the parts where the shaved wood pieces overlap 7 Solid wood board

Claims

1. A shaved wood board obtained by mixing and accumulating wood shavings and adhesive, and integrating them under heat and pressure, wherein the wood shavings have a density a of 0.6 g / cm ３ The density b of the shaved wood board is 0.5 g / cm ３ 0.9g / cm or more ３ The shaved wood flake board is characterized in that the density ratio b / a of the tree species density a of the shaved wood flakes to the density b of the shaved wood flake board is 1.2 or more.

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 wood shavings board according to claim 1, wherein 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.

4. A flooring material comprising a decorative material laminated on at least one surface of the shaved wood 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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