JP7792923B2 - Wood chipboards and flooring - Google Patents

Description

The present invention relates to shaved wood flakes and flooring materials that use the shaved wood flakes as a base material.

Oriented strand board (OSB, JIS A 5908:2022) is a known type of wood board made by mixing small or thin pieces of wood with an adhesive, assembling them, and then thermocompressing them together. OSB is a type of structural panel specified by the JAS, but in light of the depletion of wood resources in recent years, there has been ongoing research into using OSB for purposes other than structural panels, such as as a base material for decorative panels.

Special Publication No. 2007-521163

[0003] Conventional OSB is generally produced by drying wood shavings (strands) about 0.65 to 1.20 mm thick, applying an adhesive, and piling the wood shavings with the grain direction set in a generally uniform direction, followed by pressure molding. Its physical properties include a density of 0.60 to 0.70 g/cm ³ , a bending strength of 25 to 35 N/mm ² , and a bending Young's modulus of about 3500 to 5000 N/mm ^{2 .} However, due to uneven distribution of the adhesive and uneven press load, some of the wood shavings often appear curled up on the surface, resulting in poor surface smoothness, making it practically difficult to directly apply decorative materials such as veneer or decorative sheet to the surface of OSB. Therefore, when using OSB as a substrate for decorative boards, a surface material with excellent surface smoothness, such as MDF, is applied to the surface, and then a decorative material such as veneer or decorative sheet is applied to that surface to form the decorative board. OSB has not previously been used alone as a base material for decorative boards.

Plywood has long been used as a base material for decorative boards, 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 boards because it has excellent strength, little deflection, is easy to install, and exhibits little deformation such as warping after installation. However, it lacks sufficient surface smoothness (the maximum height indicating surface roughness exceeds 200 μm). When a decorative material such as a thin veneer is directly applied to it, the unevenness of the plywood surface becomes visible on the surface of the veneer, resulting in poor surface quality and a poor walking feel when used as a floorboard. Therefore, when applying a decorative material to a plywood base material, it is necessary to fill in the unevenness of the plywood surface with putty to achieve a smooth surface finish. On the other hand, while MDF has excellent surface smoothness, it lacks bending strength, especially in the longitudinal direction.

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 greater than that of MDF, and that can be used as a base material for directly attaching decorative materials such as veneer or decorative sheeting to create a decorative panel.

In order to solve this problem, the invention of claim 1 of the present application is a shaved wood board obtained by mixing and accumulating wood shavings and adhesive, and then thermo-compressing and integrating them, characterized in that the wood shavings have a tree species density of 0.6 g/cm3 ^or less, the board density is 0.5 g/cm3 ^or more and 0.9 g/cm3 ^or less, and in areas where the wood shavings on the surface of the shaved wood board overlap each other, both or at least one of the wood shavings are deformed or compressed so that the wood shavings become approximately flush with each other, and at least one surface has a maximum height of 200 μm or less, indicating the surface roughness defined in Japanese Industrial Standard JIS B 0601:2013.

The invention according to claim 2 of the present application is characterized in that in the shaved wood board according to claim 1, the wood shavings have a tree species density of 0.6 g/cm ³ or less.

The invention according to claim 3 of the present application is characterized in that the shaved wood flake board according to claim 1 has a board density of 0.5 g/cm ³ or more and 0.9 g/cm ³ or less.

The invention of claim 4 of this application is characterized in that, in the wood shavings board described in claim 1, the wood shavings have a thickness of 0.1 mm or more and 0.6 mm or less.

The invention of claim 5 of the present application is characterized in that, in the wood shavings board described in any one of claims 4, 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.

The invention of claim 6 of this application is characterized in that the shaved wood board of claim 1 is made up of three layers: a surface layer, a core layer, and another surface layer.

The invention of claim 7 of the present application is characterized in that, in the shaved wood flake board described in claim 6, the orientation of the core layer is approximately perpendicular to the longitudinal direction of the shaved wood flake board, and the orientation of the two surface layers is approximately parallel to the longitudinal direction of the shaved wood flake board.

The invention according to claim 8 of the present application is a flooring material formed by laminating a decorative material on the surface of the shaved wood flake board according to any one of claims 1 to 7, which has a maximum height indicating the surface roughness of 200 μm or less, and is characterized in that the bending strength is 30 to 80 N/mm ² and the bending Young's modulus is 3000 to 8500 N/mm ² .

The present invention provides a shaved wood flake board that has significantly improved surface smoothness over conventional OSB, a surface smoothness comparable to or equal to that of MDF, which is known to have good surface smoothness, and excellent physical properties. Therefore, the shaved wood flake board of the present invention can be suitably used in place of conventionally used MDF, etc., as a substrate for making a decorative board by directly attaching a decorative material such as veneer or decorative sheet onto it.

Even if the wood shavings of the present invention are randomly accumulated without any specific orientation, they can be made to 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 wood shavings and the board density. However, 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, bending strength can be further increased and the length expansion rate can be reduced, improving dimensional stability.

Flooring materials made by laminating decorative materials such as veneer onto the smooth surface of this wood chipboard have good density and bending Young's modulus, and are excellent in strength, rigidity, scratch resistance, etc.

1 is a side view schematically showing a shaved wood board according to the present invention. FIG. 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. FIG. 1 is a diagram showing measurement points for a surface roughness test in a test example. 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) compressed (c, f). Schematic cross-sectional views showing a mat (a) made of accumulated wood shavings with a low tree species density and its compressed state (b), and a mat (c) made of accumulated wood shavings with a high tree species density and the state (d) in which these mats have been compressed and both ends of the width direction cut vertically. Schematic cross-sectional views showing the surface condition (a) of a portion where wood shavings with a low tree species density overlap each other before compression and the surface condition (b) of the portion where wood shavings with a high tree species density overlap each other before compression and the surface condition (d) of the portion where wood shavings with a high tree species density overlap each other before compression and the surface condition (c) of the portion where wood shavings with a high tree species density overlap each other before compression and the surface condition (d ... 1 is a graph showing the correlation between the density of the tree species used as the wood shavings and the maximum height indicating the surface roughness of the resulting wood shavings board. 1 is a graph showing the correlation between the board density of shaved wood flake board and the maximum height indicating the surface roughness.

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

Wood shavings are made by thinly cutting hardwood or softwood logs with a strander. Wood shavings can also be obtained from planted renewable hardwoods and softwoods.

The wood shavings used in the wood shavings board of the present invention 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.

If the thickness of the wood shavings is less than 0.1 mm, wood shaving production capacity will decrease, and if it exceeds 0.6 mm, the surface smoothness of the resulting wood shavings board will decrease and the rigidity will be uneven. If the thickness of the wood shavings is within the range of 0.1 mm to 0.6 mm, a wood shavings board with excellent surface smoothness and uniform rigidity can be obtained.

If the width of the wood shavings exceeds 50 mm, not only will the handling and transportability be reduced, but the wood shavings will be prone to curling, making them less compatible with adhesives. If the width of the wood shavings is less than 1 mm , the rigidity of the resulting wood shavings board will be reduced. 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.

If the length of the wood shavings exceeds 200 mm, not only will handling and transport be impaired, but the wood shavings will also be more likely to curl, 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 the required rigidity will be easier to achieve.

The moisture content of the wood shavings is preferably 15% by weight or less, and they are dried to this moisture content 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 pressing during pressure molding and results in uneven rigidity of the resulting wood shavings board. From this perspective, it is more preferable that the moisture content of the wood shavings be 3% by weight or less. The moisture content MC of the wood shavings can be calculated using the formula MC = (m ₁ -m ₀ ) x 100/m ₀ in accordance with Japanese Industrial Standard JIS A 5905:2022 7.5. Here, m ₁ is the mass (g) of the wood shavings sample before drying, and m ₀ is the mass (g) of the wood shavings sample when placed in an air dryer at 103°C and brought to constant weight.

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 appropriate mixtures. However, 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 amount 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.

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. If an isocyanate compound is used as the adhesive, the solids content should preferably be 4 to 12 parts by weight, and if a melamine urea resin is used, the solids content should preferably be 10 to 30 parts by weight.

Next, we will explain the method for manufacturing shaved wood boards according to the present invention. Generally speaking, shaved wood boards according to the present invention are manufactured by drying shaved wood, applying adhesive, randomly stacking the shaved wood boards without specifying the grain direction, and then pressure-molding this stack (mat). This will be explained in more detail below.

A plantable hardwood or softwood log, waste wood, sawmill waste, recycled material, etc., is prepared and cut with a strander (cutting machine) to produce wood shavings. As described above, the wood shavings used in the wood shavings board of the present invention 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, and are cut to satisfy these dimensional conditions to produce wood shavings.

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 their surface. One suitable method for applying the adhesive is to place the wood shavings inside a rotating drum rotating at a low speed (approximately 30 rpm), and then spray the adhesive onto the wood shavings as they fall naturally inside the drum.

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 wood shavings board. The thermocompression temperature varies depending on the type of adhesive used, but is generally between 190 and 220°C.

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

The shaved wood flake board produced in this manner preferably has a density of 0.5 to 0.9 g/cm ^3. If the density is less than 0.5 g/cm ³ , the strength of the shaved wood flake board will be insufficient, while if the density is greater than 0.9 g/cm ³ , the weight of the entire shaved wood flake board will increase, making it difficult to handle. If the density is within the range of 0.5 to 0.9 g/cm ³ , various properties suitable for use as flooring materials and other indoor interior materials can be obtained.

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 mat during hot pressing, it is possible to keep the density distribution within the range of 0.5 to 0.9 g/cm ³ , and it is possible to produce a shaved wood board with a uniform density distribution. The density distribution (density profile) in the thickness direction can be measured using a density distribution measuring instrument (DAX5000, manufactured by Grecon GmbH, Germany).

Furthermore, the shaved wood flake board preferably has a bending strength of 25 to 90 N/mm ² and a bending Young's modulus of 3000 to 8500 N/mm ^2. If the bending strength is less than 25 N/mm ² and/or the bending Young's modulus is less than 3000 N/mm ² , the amount of deflection, particularly when used as a base material for flooring, will be greater than the deflection standard (3.5 mm or less; details will be described later) specified in the JAS wood flooring standard, making it unsuitable for use as a flooring material. On the other hand, if the bending strength exceeds 90 N/mm ² and/or the bending Young's modulus exceeds 8500 N/mm ² , the elasticity required for walking when used as a flooring material will be insufficient, resulting in an inferior walking feel. If the bending strength is within the range of 25 to 90 N/mm ² and the bending Young's modulus is within the range of 3000 to 8500 N/mm ² , the shaved wood flake board can be made suitable for use as a base material for flooring.

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 in Table 3 of Japanese Industrial Standard JIS A 5536:2015 "Adhesives for Floor Finishing Materials." A coating layer of approximately 20 to 80 μm thick, such as a urethane coating, 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 this smooth surface also has a smooth surface and possesses appropriate physical properties such as strength, elasticity, and flexure, making it an ideal flooring material.

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 to 0.6 mm thick, 15 to 200 mm long, and 1 to 50 mm wide, were prepared by thinly shaving cypress logs using a strander (a cutting machine). These samples were weighed to a predetermined weight ratio and divided into three groups (top layer sample a, core layer sample b, and bottom layer sample c). In Example 1, the top layer sample a was 30%, the core layer sample 40%, and the bottom layer sample 30% by bone-dry weight. In Example 2, the top layer sample was 25%, the core layer sample 50%, and the bottom layer sample 25% by bone-dry weight.

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 for the upper layer sample a, the core layer sample b, and the lower layer sample c. The application was performed using a spray method, with the wood shavings of sample a placed inside a rotating drum rotating at a low speed (approximately 30 rpm), and the resin adhesive containing polyisocyanate sprayed onto the wood shavings as they naturally fell inside the drum. The adhesive was sprayed onto samples b and c in the same manner.

The upper layer sample a, the core layer sample b, and the lower layer sample c were each stacked in a mat shape to form an upper layer mat A, a core layer mat B, and a lower layer mat C. These were then stacked in order and hot-pressed for 2 to 4 minutes under hot-press conditions of a surface pressure of 3 to 10 N/mm ² and a temperature of 190 to 220°C to obtain a shaved wood flake board specimen (Examples 1 and 2) measuring 300 mm long, 300 mm wide, and 12 mm thick.

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 also the same as in Examples 1 and 2: 300 mm x 300 mm x 12 mm thick.

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). These measurement results 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, with the centers of each region 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-long 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 apex of the highest protrusion, Rz = Rv + Rq), and the average maximum height measured at each measurement point is shown in Table 1.

Furthermore, each of these test specimens was used as a base material, and a 0.2 mm thick 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 base material surface visible, a triangle indicates that the veneer surface was in a slightly poor condition with only slight irregularities from the base material surface visible, and an cross indicates that the veneer surface was in a poor condition with many irregularities from the base material surface visible.

As can be seen from the results shown in Table 1, the maximum heights, indicating surface roughness, of the shaved wood flake boards of Examples 1 and 2 of the present invention were 114 μm and 118 μm, respectively, and had significantly better surface smoothness than the plywood and OSB of the comparative examples. Therefore, even when this was used as a base material and a thin veneer was attached to its surface to create a flooring material, it was confirmed that a good surface condition could be achieved without any unevenness appearing on the surface of the veneer.

The shaved wood flakes 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, they were tested according to the bending deflection standard of the JAS wood flooring standard (a flooring sample measuring 300 mm wide x 1,800 mm long x 12 mm thick was supported at a span of 700 mm, and a load of 21 kg was applied to a load rod placed at the center of the span. Displacement A was measured, and similarly, displacement B was measured when a load of 9 kg was applied. The difference in displacement A-B must be 3.5 mm or less). A-B = 1.9 mm, clearing the standard. These results confirm that the shaved wood flakes of Examples 1 and 2 of the present invention have physical properties suitable for use as a flooring base material.

The good surface smoothness achieved in the shaved wood boards of Examples 1 and 2 of the present invention is thought to be due to the fact that the shaved wood boards used were relatively thin, the cypress species density was low, making them easy to compress, and the shaved wood boards were manufactured by sufficiently compressing them.

More specifically, we will first explain the compressive deformation of wood shavings 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 within 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 create unevenness on the surface, but compression crushes the voids, reducing the surface unevenness (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 within the wood shavings is small, and woody parts 2a account for the majority of the wood shavings, increasing strength, so that the wood shavings are less likely to be compressed (Figure 4(f)) even when they are thin (Figure 4(e)).

Next, the deformation of the surface of a shaved wood board will be explained with reference to Figure 5. To create a shaved wood board with the same board density, if wood shavings 2c with a low tree species density are used, it is necessary to accumulate a large number of these shavings 2c to increase the mat volume (Figure 5(a)). However, a mat made of accumulated wood shavings 2c with a low tree species density 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 wood shavings 2d with a high tree species density, it is necessary to reduce the amount of these shavings 2d used to reduce the mat volume (Figure 5(c)). However, a mat made of accumulated wood shavings 2d with a high tree species density 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)).

Although it is inevitable that the surface of the shavings board will tend to become uneven where the shavings overlap, as shown in Figures 6(a) and 6(b), since the shavings 2c with a low tree species density are weak and easily compressed, it is assumed that both or at least one of the overlapping shavings 2c, 2c will deform or compress, becoming approximately flush, and the surface will maintain smoothness without large irregularities. To achieve this, it is preferable to use relatively thin shavings with a thickness of 0.1 to 0.6 mm, and when the mat containing these shavings is thermocompressed, it is preferable to compress the overlapping shavings with a compressive force sufficient to make them approximately flush, and form the shavings board into a board density of approximately 0.6 to 0.8 g/ ^cm3 . By doing so, the height of the step 5 formed at the overlapping portion of the wood shavings 2c, 2c on the surface of the wood shavings board obtained after compression is 0.2 mm or less, and it is easy to obtain a wood shavings board with a maximum height indicating surface roughness of 200 μm or less. On the other hand, when wood shavings 2d with a high tree species density overlap, as shown in Figures 6(c) and (d), the overlapping wood shavings 2d, 2d are almost undeformed 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 wood shavings board with a maximum height indicating surface roughness of 200 μm or less.

Based on these assumptions, it was thought that the surface smoothness of shaved wood boards is closely correlated with the thickness of the shaved wood used as raw material, the tree species density, and the board density. It is generally known, or easily conceivable, that overlapping relatively thin shaved wood boards reduces unevenness caused by the overlapping areas (improving surface smoothness), so the inventors investigated the effects and correlations of tree species density and board density on surface roughness.

First, the following test was conducted to confirm the effect of the tree species density of the wood shavings on surface roughness. Specifically, six types of wood shavings board specimens of different tree species were prepared in the same manner as in Example 1, using wood shavings from six different tree species: sawtooth oak, zelkova, edulis, loblolly pine, cypress, and cedar. As mentioned above, it was assumed that surface roughness would also be related to board density, so each specimen was prepared so that the board density was approximately constant (approximately 0.7 g/cm ³ ). The results of measuring the surface roughness of each specimen in the same manner as above, as well as the results of visually evaluating the surface condition of flooring materials with a 0.2 mm thick sliced veneer laminated and bonded to the surface of each specimen, are shown in Table 2. The correlation between tree species density and maximum surface roughness height is also shown in a graph in Figure 7.

The results shown in Table 2 and Figure 7 indicate a certain correlation 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).

More specifically, shaved wood boards made from shaved wood from tree species with a density of more than 0.6 g/ ^cm3 (oak, zelkova, and edulis) had a maximum height indicating surface roughness of more than 200 μm, and had poor surface smoothness similar to that of plywood. As a result, the surface condition of flooring materials obtained by laminating and gluing veneer onto the surface was also poor (x) or somewhat poor (△).

In contrast, shaved wood boards made from shaved wood from tree species (loblolly pine, cypress, cedar) with a density of 0.6 g/cm3 or ^less had a maximum height indicating surface roughness of 200 μm or less, and had better surface smoothness than plywood, and the surface condition of flooring materials obtained by laminating and adhering sliced veneer to the surface was also good (◯).Furthermore, shaved wood boards made from shaved wood from tree species (cypress, cedar) with a density of 0.45 g/cm3 or ^less had a maximum height indicating surface roughness of 100 μm or less, and had extremely good surface smoothness.

Next, the following test was conducted to confirm the effect of board density on surface roughness. As the above confirmed that surface roughness is related to the species density of the wood shavings, this test used cedar shavings, which have a low species density and are therefore soft and easily compressed. Nine specimens with different board densities were created in the same manner as in Example 1, except that 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 a 0.2 mm thick sliced veneer laminated and glued to the surface of each specimen are shown in Table 3. Figure 8 also shows a graph of the correlation between board density and maximum surface roughness height.

The results shown in Table 3 and Figure 8 indicate that there is a certain correlation 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).

More specifically, the test specimens (cedar 8 and 9) with a board density of less than 0.5 g/ ^cm3 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 adhering veneer to the surface was also poor (x).

In contrast, the test specimens (Cedar 1 to 7) with a board density of 0.5 g/cm3 or more ^had a maximum height indicating surface roughness of 200 μm or less, which gave them a surface smoothness better than plywood, and the surface condition of the flooring material obtained by laminating and adhering sliced 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/ ^cm3 (Cedar 1), but if the board density exceeds 0.9 g/ ^cm3 , the weight increases, making it difficult to handle and adversely affecting the walking feel when used as a flooring material, so it is preferable to set the upper limit of the board density to 0.9 g/ ^cm3 .

The present invention has been described in detail above using test examples, but the present invention can be implemented in a wide variety of modifications and variations within the scope of the invention defined by the claims.

1 Wood cut thin plate (base material)
2 Wood shavings 2a Wood part 2b Void part 2c Wood shavings with low tree species density 2d Wood shavings with high tree species density 3 Veneer (decorative material)
4. Flooring (decorative panels)
5. Steps on the surface of the wood shavings board formed at the overlapping parts of the wood shavings

Claims (8)

A shaved wood board obtained by mixing and aggregating wood shavings with an adhesive, and then thermocompressing and integrating the mixture, characterized in that the wood shavings have a tree species density of 0.6 g/cm3 ^or less, the board density is 0.5 g/cm3 ^or more and 0.9 g/cm3 ^or less, and in areas where the shaved wood flakes on the surface of the shaved wood board overlap each other, both or at least one of the shaved wood flakes are deformed or compressed so that the shaved wood flakes become 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. The shaved wood board according to claim 1, wherein the wood shavings have a species density of 0.6 g/cm ^<3> or less. 2. The shaved wood flake board according to claim 1, characterized in that it has a board density of 0.5 g/cm ³ or more and 0.9 g/cm ³ or less. The wood shavings board according to claim 1, characterized in that the wood shavings have a thickness of 0.1 mm or more and 0.6 mm or less. The wood shavings board of claim 4, characterized in that 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. The shaved wood flake board according to claim 1, characterized in that it consists of three layers: a surface layer, a core layer, and another surface layer. The shaved wood flake board of claim 6, characterized in that the orientation of the core layer is approximately perpendicular to the longitudinal direction of the shaved wood flake board, and the orientation of the two surface layers is approximately parallel to the longitudinal direction of the shaved wood flake board. A flooring material obtained by laminating a decorative material on the surface of the wood chipboard according to any one of claims 1 to 7, the maximum height of which indicates the surface roughness of which is 200 μm or less, and the bending strength is 30 to 80 N/mm ² , and the bending Young's modulus is 3000 to 8500 N/mm ² .