Wood base material, decorative material, and method for producing wood base material

Abstract

To provide a wooden base material which does not contain a harmful substance causing a sick house syndrome, and has practical mechanical strength and water resistance, a decorative material, and a method for manufacturing a wooden base material.SOLUTION: A wooden base material 10 contains a wooden material 4 having at least one of a powder shape and a chip shape, and a thermoplastic resin composition 5, wherein the wooden base material 10 includes a skin layer 11 and a core layer 12, and standardization C-H areas calculated from absorption spectra by Fourier type infrared spectroscopy for the skin layer 11 and the core layer 12 are within a range of 0.07 or more and 1.00 or less, respectively.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wood substrate, a decorative material, and a method for producing a wood substrate. [Background technology]

[0002] Wood substrates are obtained by heating and pressurizing a mixture of wood materials such as wood flour, wood chips, and wood fibers with an adhesive. These wood substrates are called particle boards, medium density fiberboards, etc., depending on the type of wood material, and are used for a wide range of purposes, such as undercoats for floors and walls, fittings, and furniture. Conventionally, urea resin adhesives, melamine resin adhesives, or phenol resin adhesives have been used as adhesives for wood substrates together with hardeners containing formaldehyde. Since formaldehyde is a harmful substance that causes sick house syndrome, its emission from wood substrates has become a problem, and various measures to reduce the amount of emission have been considered. However, with conventional techniques, it has been difficult to completely suppress the emission of formaldehyde. In response to this, a method has been proposed in the past to use an adhesive containing powdered sugars and powdered polycarboxylic acid as its main components as a formaldehyde-free adhesive, mix this with plant fibers, and mold it under heat and pressure to produce a fiberboard (see paragraph

[0017] of Patent Document 1). Also, a method has been proposed in the past to use an adhesive containing polyvinyl alcohol and water as a formaldehyde-free adhesive to produce a laminate containing a wood substrate (see paragraph

[0015] and Figure 1 of Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-55620 A [Patent Document 2] Patent No. 5553279 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the wood substrates using the above-mentioned conventional adhesives are not practically sufficient in terms of mechanical properties such as bending strength and water resistance. Therefore, an object of the present invention is to provide a wood base material that does not contain harmful substances that cause sick house syndrome and has practical mechanical strength and water resistance, a decorative material that includes this wood base material, and a method for producing this wood base material. [Means for solving the problem]

[0005] A wood base material according to one embodiment of the present invention comprises a wood material having at least one of a powdered and chipped form and a thermoplastic resin composition, the wood base material comprising a skin layer and a core layer, and characterized in that the normalized CH area of ​​each of the skin layer and the core layer, calculated from the absorption spectrum obtained by Fourier infrared spectroscopy measurement using the following formula (1), is within the range of 0.07 to 1.00. Standardized CH area=S C-H / (S O―H +S C-OH )...Equation (1) (Here, in formula (1), S C-H is a wave number of 2700 cm -1 More than 3000cm -1 The area value of the peak derived from either the CH2 group or the CH3 group in the following region, S O-H is a wave number of 3000 cm -1 More than 3500cm -1 The area value of the peak derived from the OH group in the following region, S C-OH is a wave number of 900 cm -1 More than 1200cm -1 The area values ​​of the peaks derived from C-OH groups in the following regions are shown below.)

[0006] In addition, the wood base material according to one embodiment of the present invention is characterized in that the normalized C-H area measured for each of the skin layer and the core layer is within the range of 0.08 to 0.35. Furthermore, a wood base material according to one embodiment of the present invention is characterized in that the wood base material sequentially comprises the skin layer, the core layer, and the skin layer, and the thickness ratio of each of the layers (skin layer:core layer:skin layer) is within the range of 1:0.1:1 to 1:18:1. In addition, the wood base material according to one embodiment of the present invention is characterized in that the thickness of the skin layer is within the range of 2 mm or more and 19 mm or less. In addition, in one embodiment of the wood base material of the present invention, the normalized CH area of ​​the skin layer is A S , the normalized CH area of ​​the core layer is A C In this case, A S >A C It is characterized in that: In addition, in one embodiment of the wood base material of the present invention, the skin layer and the core layer each have a mass ratio of the wood material to the thermoplastic resin composition (wood material / thermoplastic resin composition) within the range of 95 / 5 to 70 / 30. A wood base material according to one embodiment of the present invention is characterized in that it contains a mushroom bed as a raw material. In addition, a wood substrate according to one embodiment of the present invention is characterized in that the thermoplastic resin composition contains polyethylene. In addition, a wood substrate according to one embodiment of the present invention is characterized in that the thermoplastic resin composition contains an acid-modified polyolefin.

[0007] A decorative material according to one aspect of the present invention is characterized in that a decorative substrate is laminated onto the above-mentioned wood substrate.

[0008] Furthermore, a method for producing a wood substrate according to one embodiment of the present invention is a method for producing the above-mentioned wood substrate, and is characterized by comprising the steps of: mixing a wood material having at least one of a powdered and chipped form with a thermoplastic resin composition to obtain a raw material mixture for the wood substrate; and heating and pressurizing the raw material mixture to form the wood substrate. Effect of the Invention

[0009] According to one aspect of the present invention, it is possible to provide a wood base material that does not contain harmful substances that cause sick building syndrome and has practical mechanical strength and water resistance, a decorative material that includes this wood base material, and a method for manufacturing this wood base material. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a method for producing a wood base material according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic cross-sectional view showing the structure of a wood base material according to a first embodiment of the present invention. [Diagram 3] 1 is an infrared absorption spectrum of a typical wood material. [Figure 4] 1 shows an infrared absorption spectrum of a wood base material according to a first embodiment of the present invention. [Diagram 5] FIG. 4 is a schematic cross-sectional view showing the structure of a decorative material according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Here, the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc. are different from the actual ones. Furthermore, the embodiments shown below are examples of configurations for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not specify the materials, shapes, structures, etc. of the components as described below. The technical idea of ​​the present invention can be modified in various ways within the technical scope defined by the claims.

[0012] [First embodiment] A schematic diagram for explaining a method for manufacturing a wood substrate according to an embodiment of the present invention is shown in Fig. 1. A metal plate 2 is placed on the bottom surface of a jig 1 for manufacturing a wood substrate, which has a storage section cut out to a predetermined size (for example, a 10 cm x 10 cm square), and a releasable metal plate 3 is placed on top of the metal plate 2. Next, a raw material mixture 6 containing a wood material 4 having at least one of a powder and chip form and a powdered thermoplastic resin composition 5 is placed in the storage portion of the jig 1 for producing a wood substrate, and a releasable metal plate 3 is placed on the raw material mixture 6. Next, a thickness adjusting metal plate 7 is placed on the jig 1 for producing a wooden base material, and the raw material mixture 6 is pressed down from above with a metal weight 8 via a releasable metal plate 3 . Finally, a press top plate 9 set under predetermined conditions is heated and pressurized from above the raw material mixture 6 via a metal weight 8, forming a skin layer 11 according to this embodiment. Another skin layer 11 is also formed in a similar manner. After the pair of skin layers 11 are thus formed, the metal plate 2, the releasable metal plate 3, and the skin layer 11 are layered in this order on the bottom surface of the jig 1 for producing a wooden substrate. Next, a raw material mixture 6 containing a wood material 4 having at least one of a powdered and chipped form and a powdered thermoplastic resin composition 5 is placed in the storage portion of the jig 1 for producing a wooden substrate, and a skin layer 11 and a release metal plate 3 are placed in this order on the raw material mixture 6. Here, the raw material mixture 6 sandwiched between the skin layers 11 becomes the core layer 12 in the wooden substrate 10. Next, the thickness adjusting metal plate 7 is placed on the jig 1 for producing the wooden base material, and the raw material mixture 6 is pressed down from above with a metal weight 8 via the skin layer 11 and the releasable metal plate 3 . Finally, a press top plate 9 set under predetermined conditions is used to apply heat and pressure from above the raw material mixture 6 via a metal weight 8, forming the wood base material 10 according to this embodiment.

[0013] FIG. 2 is a schematic cross-sectional view showing the structure of the wood substrate 10 according to this embodiment. 2, the wood substrate 10 according to this embodiment is configured to include skin layers 11 that form the front and back surfaces of the wood substrate 10, and a core layer 12 that is located at the center of the wood substrate 10 and is sandwiched between the skin layers 11. That is, the wood substrate 10 according to this embodiment includes a skin layer 11 formed from a wood material 4 and a thermoplastic resin composition 5, and a core layer 12 formed from a wood material 4 and a thermoplastic resin composition 5. In the wood substrate 10, it is preferable that the skin layer 11 and the core layer 12 are in contact with each other. The wood base material 10 is called particle board, medium density fiberboard, etc. depending on the type of wood material 4, and is used for a wide range of purposes such as underlayment for floors and walls, fittings, and furniture. As described above, the wood base material 10 according to this embodiment does not contain harmful substances such as formaldehyde that cause sick house syndrome, and therefore, it is possible to suppress the emission of harmful substances such as formaldehyde that cause sick house syndrome from inside the wood base material 10. The materials constituting the wood base material 10 will now be described.

[0014] (wood material 4) The wood material 4 has at least one of a powder and chip shape. Here, the terms "powder" and "chip" do not generally have definitions of size or shape. In this embodiment, the term refers to a size (average particle size) in the range of approximately several tens of microns to several centimeters. To stably produce the wood base material 10, it is desirable for the average particle size of the wood material 4 to be in the range of 1 to 5 mm. Examples of the wood material 4 include wood flour, wood fiber, and wood crushed into chips, and examples of the raw material that can be used include thinned wood, sawdust, and waste wood. Furthermore, materials other than wood may also be used as the wood material 4, such as bamboo, hemp, coconut fiber, and walnut shells, as long as they contain cellulose components similar to wood. A suitable raw material for the wood material 4 is, for example, used mushroom beds that are generated in large quantities during mushroom cultivation. The mushroom bed is a culture medium used in mushroom cultivation, and is made by mixing wood chips and sawdust with nutrients such as bran and rice bran. It is estimated that around 300,000 tons of mushroom beds are discarded annually in Japan after mushroom cultivation, making them a promising source of biomass, but recycling is currently not progressing well, and using them as a wood raw material (wood material 4) is beneficial in reducing the environmental burden. As the wood substrate 10 containing a mushroom bed, the mushroom bed may be used alone as the wood material 4, or the mushroom bed may be mixed with other wood materials 4. Here, the term "wood substrate containing a mushroom bed" refers to a wood substrate 10 in which the proportion of the mushroom bed in the total volume of the wood material 4 is within the range of 1% to 100%.

[0015] (Manufacturing method of wood material 4) For example, when trying to obtain wood material 4 from waste wood, many foreign objects such as concrete fragments, metal fragments, paper, etc. can be contained. The foreign objects can be removed by known methods such as magnetic sorting, air sorting, and specific gravity sorting. In addition, the size of coarse particles is adjusted by known methods such as cutting and crushing, and those in the range of approximately several tens of microns to several centimeters are used. Furthermore, when attempting to obtain the wood material 4 from a mushroom bed, it is desirable to sterilize it by a known method before use.

[0016] (Mass ratio of wood material 4 to thermoplastic resin composition 5) The mass ratio of the wood material 4 to the thermoplastic resin composition 5 (wood material / thermoplastic resin composition) is preferably in the range of 95 / 5 to 70 / 30 in each of the skin layer 11 and the core layer 12. If the content of the wood material 4 is greater than the above value (95 / 5), sufficient bending strength cannot be imparted to the wood substrate 10. On the other hand, if the content of the wood material 4 is less than the above value (70 / 30), the wood substrate 10 is likely to deform when heated and pressed, which is not preferable. The mass ratio of the wood material 4 to the thermoplastic resin composition 5 (wood material / thermoplastic resin composition) is more preferably in the range of 85 / 15 to 70 / 30 in each of the skin layer 11 and the core layer 12. By setting the content of the wood material 4 within the above numerical range, a wood substrate 10 with greater bending strength can be obtained.

[0017] Regarding the mass ratio between the wood material 4 and the thermoplastic resin composition 5 (wood material / thermoplastic resin composition), it is desirable to increase the proportion of the thermoplastic resin composition 5 in the skin layer 11 more than in the core layer 12. Increasing the proportion of the thermoplastic resin composition 5 improves the water resistance of the skin layer 11 (particularly the skin layer 11 that constitutes the surface layer of the wood substrate 10). Furthermore, for example, the content of the thermoplastic resin composition 5 in the skin layer 11 is desirably in the range of 1.1 to 2 times the content of the thermoplastic resin composition 5 in the core layer 12, and more desirably in the range of 1.3 to 1.8 times.

[0018] (Thermoplastic resin composition 5) The thermoplastic resin composition 5 is a powder-like composition having an average particle size of several tens of microns to 1 mm. The particle size of the thermoplastic resin composition 5 is not particularly limited, but it is preferable that the particle size is similar to that of the wood material 4, since it is easier to mix with the wood material 4. If the particle size of the thermoplastic resin composition 5 is too small, it will slip through the wood material 4 and accumulate at the bottom, and if it is too large, it will accumulate at the top of the wood material 4, resulting in a non-uniform wood substrate 10, which is undesirable. Therefore, the particle size (average particle size) of the thermoplastic resin composition 5 is more preferably within the range of 1 micron (μm) to 1 mm. In addition, the particle size (average particle size) of the thermoplastic resin composition 5 is preferably within the range of 30 microns (μm) to 300 microns (μm) in consideration of ease of handling, etc. The thermoplastic resin composition 5 can be made of various materials such as polyester, polyamide, polyolefin, ethylene-propylene-diene rubber, ethylene vinyl acetate, and silicone rubber. From the viewpoint of the mechanical strength and water resistance of the wood base material 10, polyethylene is preferable. The thermoplastic resin composition 5 may be used alone or in combination with multiple types. In terms of the mechanical strength of the wood substrate 10, it is preferable that the thermoplastic resin composition 5 contains polyethylene in an amount of 50 parts by mass to 100 parts by mass, based on 100 parts by mass of the entire thermoplastic resin composition 5. It is more preferable that the thermoplastic resin composition 5 contains polyethylene in an amount of 80 parts by mass to 100 parts by mass. The polyethylene added to the thermoplastic resin composition 5 is not particularly limited, and may be appropriately selected from existing materials such as high density polyethylene (polyethylene with a specific gravity of about 0.92 to 0.96), low density polyethylene (polyethylene with a specific gravity of about 0.91 to 0.92), very low density polyethylene (polyethylene with a specific gravity of less than 0.9), and linear low density polyethylene (polyethylene with a specific gravity of less than 0.94) in consideration of reactivity during heating and pressurization and the fluidity of the raw material mixture 6. Of the above-mentioned materials, it is more desirable to use high density polyethylene in order to obtain a wood substrate 10 with high bending strength.

[0019] The polyethylene used in the present embodiment may be biomass-derived polyethylene. Biomass-derived polyethylene is obtained by polymerizing a monomer containing biomass-derived ethylene. Since biomass-derived ethylene is used as the raw material monomer, the polymerized polyethylene is derived from biomass. Note that the raw material monomer of polyethylene may not contain 100% by mass of biomass-derived ethylene.

[0020] The thermoplastic resin composition 5 may be a single substance, or may be mixed with a known thermoplastic resin composition 5. The material to be mixed with the thermoplastic resin composition 5 is not particularly limited, but examples thereof include an acid-modified resin and an organic peroxide.

[0021] (Acid-modified resin) The acid-modified resin is used to improve the adhesion between the wood material 4 and the thermoplastic resin composition 5. When the main component of the thermoplastic resin composition 5 is polyethylene, the acid-modified resin is preferably an acid-modified polyolefin because of its ease of compatibility (high compatibility). In particular, maleic acid-modified polyethylene is preferably used as the acid-modified resin. Here, the above-mentioned "main component" refers to a component that accounts for 50% by mass or more of the total mass of the thermoplastic resin composition 5.

[0022] (Amount of acid-modified resin added) The amount of the acid-modified resin added is preferably within the range of 3 parts by mass to 40 parts by mass based on 100 parts by mass of the total thermoplastic resin composition. If the amount of the acid-modified resin added is less than 3 parts by mass, the effect of improving the adhesion between the wood material 4 and the thermoplastic resin composition 5 is insufficient, and sufficient strength may not be imparted to the wood substrate 10. If the amount of the acid-modified resin added exceeds 40 parts by mass, the effect of improving the adhesion is limited and only a slight improvement can be confirmed. The amount of the acid-modified resin added is more preferably within the range of 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the entire thermoplastic resin composition.

[0023] (organic peroxide) The organic peroxide may be used to radically crosslink the thermoplastic resins contained in the thermoplastic resin composition 5 when the raw material mixture 6 is heated and pressurized. In addition, if a material having radical crosslinking properties is used for the acid-containing resin, the addition of the organic peroxide to the thermoplastic resin composition 5 can reliably cause crosslinking between the acid-containing resin and the thermoplastic resin. When radical crosslinking is formed between the thermoplastic resins themselves or between the acid-containing resin and the thermoplastic resin, the crosslinked structure improves the mechanical strength of the entire wood substrate 10. In other words, the addition of the organic peroxide to the thermoplastic resin composition 5 makes it possible to form a three-dimensional network (bond) by radical crosslinking between the thermoplastic resin contained in the thermoplastic resin composition 5, the acid-containing resin, and the wood material 4. This improves the mechanical strength of the entire wood substrate 10. The organic peroxide is not particularly limited, and may be appropriately selected from existing materials such as peroxyketals, dialkyl peroxides, diacyl peroxides, peroxyesters, etc., taking into consideration reactivity and stability. Organic peroxides are a type of radical crosslinking agent, and examples of such organic peroxides include hydroperoxides, diacyl peroxides, peroxydicarbonates, peroxyesters, peroxycarbonates, dialkyl peroxides, and ketone peroxides.

[0024] (Amount of organic peroxide added) The amount of the organic peroxide added is preferably within the range of 0.01 parts by mass or more and 5 parts by mass or less based on 100 parts by mass of the entire thermoplastic resin composition. If the amount of organic peroxide added is less than 0.01 parts by mass, the raw material mixture 6 will not be sufficiently reactive when heated and pressurized, and will not contribute to improving the strength of the wood base material 10. If the amount of organic peroxide added is more than 5 parts by mass, the amount of decomposition products produced during the reaction will increase, which may cause deformation of the wood base material 10, and is therefore undesirable.

[0025] (Additives) An additive such as wax may be mixed into the thermoplastic resin composition 5. Adding wax as an additive further improves the water resistance of the wood substrate 10. In addition, an additive such as wax also serves as a lubricant to uniformly mix the wood material 4 and the thermoplastic resin composition 5, or multiple types of thermoplastic resin compositions 5.

[0026] (Method of producing thermoplastic resin composition 5) The thermoplastic resin composition 5 can be made into a powder form by a known method. When a plurality of types of materials are mixed with the thermoplastic resin composition 5, they are mixed by a known method. The particles of the thermoplastic resin composition 5 may be heated during mixing to weld them together. However, if the particles are larger than 150 μm, the number of particles decreases and the surface area decreases, making it difficult to mix uniformly with the wood material 4, which is not desirable. In addition, the thermoplastic resin composition 5 can be prepared by powdering resin pellets produced by a known method using a known method such as mechanical crushing or freeze crushing. When mixing a thermoplastic resin composition containing a mixture of resin pellets and powder, the resin pellets and powder may be mixed and then crushed, or the resin pellets may be crushed and then mixed into powder. For example, if a powder of polyethylene and a powder of an acid-modified polyolefin are mixed, a process such as freeze crushing is not required when crushing the thermoplastic resin composition 5, and a powder of the thermoplastic resin composition 5 can be easily obtained.

[0027] The thermoplastic resin composition 5 can be powdered by a method such as mechanical crushing or freeze crushing after heating and kneading multiple types of thermoplastic resin pellets using, for example, a single-screw kneader or a batch kneader. For example, polyethylene pellets and acid-modified polyolefin pellets are heated and kneaded in a single-screw kneading extruder, pelletized, and the kneaded pellets are freeze-pulverized to obtain a powder of the thermoplastic resin composition 5. In other words, multiple types of thermoplastic resin compositions 5 may be kneaded by an extrusion method to obtain a powder of the thermoplastic resin composition 5. In addition, by mixing multiple types of powdered thermoplastic resin compositions 5, the thermoplastic resin compositions 5 can be mixed more uniformly, so that a wood substrate 10 with excellent in-plane uniformity of bending strength can be obtained.

[0028] (wood base material 10) The wood substrate 10 is formed by heating and pressurizing a raw material mixture 6 containing a wood material 4 in at least one of a powdered and chipped form and a powdered thermoplastic resin composition 5. The wood substrate 10 thus formed has a multilayer structure having at least one skin layer 11 and one core layer 12. The skin layer 11 is a water-resistant layer. The provision of this skin layer 11 reduces water absorption in the core layer 12, and prevents the entire wood substrate 10 from expanding and deforming. In addition, if it is considered that moisture absorption occurs simultaneously from the front and back of the wood base material 10, warping of the wood base material 10 due to swelling becomes a problem, so it is desirable to use a three-layer structure as shown in Figure 2, with skin layers 11 having the same properties on the front and back of the wood base material 10. The thickness of the wood base material 10 is preferably within a range of 5 mm to 40 mm. If the thickness of the wood base material 10 is thinner than 5 mm, the bending strength of the wood base material 10 is weak (low) and is not practical. If the thickness of the wood base material 10 is thicker than 40 mm, the weight of the wood base material 10 is heavy and difficult to handle during construction work. The thickness of the skin layer 11 on one side (e.g., the front side) of the wooden substrate 10 may be thicker or thinner than the thickness of the skin layer 11 on the other side (e.g., the back side) of the wooden substrate 10. The thickness of the skin layer 11 on one side (e.g., the front side) of the wooden substrate 10 and the thickness of the skin layer 11 on the other side (e.g., the back side) of the wooden substrate 10 may be the same.

[0029] The thickness of each of the skin layer 11 and the core layer 12 constituting the wood substrate 10 is preferably 2 mm or more. If the thickness of each of the skin layer 11 and the core layer 12 is less than 2 mm, it is difficult to produce a uniform skin layer 11 and a core layer 12 because they are too thin. As shown in FIG. 2, when the wood substrate 10 has a three-layer structure with the skin layer 11 on the front and back sides, the thickness ratio of the skin layer 11 to the core layer 12 (skin layer 11:core layer 12) is preferably within a range of 1:0.1 to 1:18. In other words, as shown in FIG. 2, when the wood substrate 10 has a structure in which the skin layer 11, the core layer 12, and the skin layer 11 are sequentially provided, the thickness ratio of each layer (skin layer 11:core layer 12:skin layer 11) is preferably within a range of 1:0.1:1 to 1:18:1. Moreover, since the total thickness of the wood base material 10, which is the sum of the skin layer 11 and the core layer 12, is desirably 40 mm or less, it is desirable for the skin layer 11 to be 19 mm or less.

[0030] The skin layer 11 and the core layer 12 constituting the wood substrate 10 are formed by measuring the normalized CH area of ​​the skin layer 11 calculated from the absorption spectrum obtained by Fourier infrared spectroscopy, which will be described later, as A S , the normalized CH area of ​​the core layer 12 is A C In this case, A S >A CIt is desirable to adjust the normalized CH area so that it is equal to or smaller than the amount of the thermoplastic resin composition 5 added to the skin layer 11 and the core layer 12. The size of each normalized CH area is qualitatively proportional to the amount (content ratio) of the thermoplastic resin composition 5 added to the skin layer 11 and the core layer 12, respectively. Therefore, the problem of the present application can be solved even if the amount (content ratio) of the thermoplastic resin composition 5 in the core layer 12 is made the same as the amount (content ratio) of the thermoplastic resin composition 5 in the skin layer 11. However, in that case, the amount (content ratio) of the thermoplastic resin composition 5 in the core layer 12 becomes larger than necessary, which may increase the production cost. Therefore, the amount (content ratio) of the thermoplastic resin composition 5 is adjusted to be equal to or smaller than the amount (content ratio) of the thermoplastic resin composition 5 added to the skin layer 11 and the core layer 12. S >A C By adjusting the thickness so as to be equal to or smaller than the thickness of the resin, it is possible to reduce the manufacturing cost while maintaining both the mechanical strength and the water resistance.

[0031] Here, Fourier infrared spectrometry will be described. First, infrared spectrometry is a measurement method that obtains information about the chemical structure and state of a substance by measuring infrared light absorbed by the substance, utilizing the principle that the amount of infrared light, which is light with a wavelength of 2.5 μm to 25 μm, absorbed by the substance changes based on the vibration and rotational motion of the molecules of the substance. A specific measurement method is to irradiate the substance with infrared light from a light source, generate an interference wave by synthesizing the divided transmitted light and reflected light, and calculate the light intensity of each wave number component from the signal intensity of the interference wave to measure the infrared spectrum. Particularly, in this embodiment, the calculation of the interference wave is performed using the Fourier transform method, and the measurement is performed by Fourier infrared spectrometry, which is a method for measuring an infrared spectrum. A graph in which the wave number obtained by the above method is plotted on the horizontal axis and the measured absorbance (or transmittance) on the vertical axis is called an infrared absorption spectrum (or infrared transmission spectrum), and a unique pattern is recognized for each substance. In this case, the absorbance on the vertical axis changes as the peak intensity value at a given wavenumber in proportion to the concentration or thickness of the substance, or, in the case of a crystalline substance, the amount of crystalline or amorphous parts, making it possible to perform quantitative analysis from the height or area of ​​the peak.

[0032] As an example, Figure 3 shows the infrared absorption spectrum of a typical single wood material 4. Wood material 4 has a peak due to the OH group derived from cellulose at a wave number of 3000 cm. -1 More than 3500cm -1 The C-OH group peak at wavenumber 900 cm is in the following region. -1 More than 1200cm -1 The peak areas are S O-H、 S C-OH The baseline shown by the dashed line is used as the background for correction. In other words, the ranges enclosed by the solid and dashed lines in Figure 3 are the area values ​​of the peaks of the OH group and the C-OH group. In this embodiment, the area value of each peak was calculated by averaging values ​​obtained by measuring at 10 different measurement positions within the same sample.

[0033] 4 shows an example of the infrared absorption spectrum of the wood substrate 10 of this embodiment. In addition to the peak derived from the wood material 4, the peaks of the CH2 group and CH3 group derived from the thermoplastic resin composition 5 are observed at a wave number of 2700 cm. -1 More than 3000cm -1 It is strongly present in the following region. The area value of the peak is S C-H The baseline shown by the dashed line is used as the background for correction. In other words, the areas surrounded by the solid and dashed lines in Figure 4 represent the area values ​​of the peaks of the OH group, the C-OH group, the CH2 group, and the CH3 group.

[0034] The normalized CH area A of the skin layer 11 calculated from the area values ​​of each peak using the following formula (1) S and the normalized CH area A of the core layer 12 c Specifically, the content ratio of the wood material 4 and the thermoplastic resin composition 5 is adjusted so that the normalized CH area A S and normalized CH area A c Adjust the values ​​of each. Standardized CH area=S C-H / (S O―H +S C-OH )...Equation (1) Normalized CH area A S and normalized CH area A c When the normalized CH area A is less than 0.07, the proportion of the wood material 4 is too high, making it difficult to provide the bending strength and water resistance required for practical use. S and normalized CH area A c When each of the normalized CH area A and the normalized CH area B exceeds 1.00, the proportion of the thermoplastic resin composition 5 is too high, which is undesirable since the wood substrate 10 is likely to deform when heated and pressurized. S and normalized CH area A c may each be greater than 1.00. If the wood material 4 and the thermoplastic resin composition 5 are not mixed uniformly, the bending strength and water resistance of the wood base material 10 will vary, which is not preferable.

[0035] Normalized CH area A of skin layer 11 S and the normalized CH area A of the core layer 12 c More preferably, each of the normalized CH areas is within the range of 0.08 to 0.35. If each normalized CH area is within the above numerical range, it is possible to obtain a good wood base material 10 that has a higher bending strength, is more water resistant, and is less prone to deformation. In addition, the normalized CH area A S and the normalized CH area A c The area ratio (A S / A c The normalized CH area ratio (A) is preferably in the range of more than 1 and not more than 4, and more preferably in the range of 1.1 to 1.8. S / A c ) within the above-mentioned range, excellent water resistance can be imparted to the entire wood base material 10, while the amount of thermoplastic resin composition 5 added to the core layer 12 can be reduced to the minimum necessary, thereby reducing production costs.

[0036] (Manufacturing conditions for wood base material 10) Various known methods of heating and pressing can be used to manufacture the wood substrate 10, but press molding using a frame mold as shown in Fig. 1 is suitable for manufacturing the wood substrate 10. The heating temperature is usually within the range of 120°C to 250°C, and must be equal to or higher than the melting point of the thermoplastic resin composition 5. However, if the heating temperature exceeds 250°C, significant thermal degradation of the wood material 4 may occur. The pressing pressure is usually 10 kgf / cm 2 More than 400kgf / cm 2 The value is within the following range and is appropriately set depending on the desired density of the wood base material 10. The density and shape of the wood substrate 10 obtained above are appropriately determined depending on the application. 3 More than 1.2g / cm 3 Within the following range, especially 0.6 g / cm 3 More than 1.1g / cm 3 The density of the wood base material 10 is preferably within the following range: 3 If the density of the wood base material 10 is less than 1.2 g / cm, the bending strength is significantly reduced and it is not practical. 3 If it is larger, the weight of the wood base material 10 becomes too large, making it difficult to handle during construction.

[0037] When manufacturing the wood substrate 10, a releasable metal plate 3 as shown in FIG. 1 may be used. The material of the releasable metal plate 3 may be a film having releasability, but when smoothness of the wood substrate 10 is required, a hard metal material is more preferable. The material of the releasable metal plate 3 may be any material that does not adhere to the thermoplastic resin composition 5, the metal plate 2, and the metal weight 8, and for example, a fluorine-coated material is preferably used. In addition, fine metal particles may be sprayed onto the surface of the releasable metal plate 3 to provide irregularities. The releasability is improved by forming an irregular structure on the surface of the releasable metal plate 3. In addition, the releasability can be further improved by using an irregular structure and a fluorine coating on the releasable metal plate 3.

[0038] In this embodiment, a metal plate 2 or a metal weight 8 that has been subjected to a non-adhesive treatment may be used instead of the releasable metal plate 3. In other words, the surface of the metal plate 2 or the surface of the metal weight 8 may be subjected to a non-adhesive treatment that prevents the thermoplastic resin composition 5 from adhering thereto, and it is more preferable that an uneven structure is formed by fluorine coating or thermal spraying.

[0039] (Modification) In this embodiment, the method for producing the wood base material 10 includes first creating two separate skin layers 11 by heating and pressurizing, and then sandwiching the raw material mixture 6 that will become the core layer 12 between the two skin layers 11 and heating and pressurizing again to produce the wood base material 10, but the present invention is not limited to this method. For example, first, the raw material mixture 6 that will become the skin layer 11, the raw material mixture 6 that will become the core layer 12, and the raw material mixture 6 that will become the skin layer 11 may be laminated in this order, and then the two types and three layers of raw material mixture 6 may be heated and pressurized simultaneously to produce the wood base material 10. Thus, in the manufacturing method of wood substrate 10 according to this embodiment, skin layer 11 may be formed in a first heating and pressing process and core layer 12 may be formed in a second heating and pressing process, or skin layer 11 and core layer 12 may be formed in the first heating and pressing process.

[0040] [Second embodiment] The second embodiment will be described with reference to FIG. The second embodiment is a decorative material 14 in which a decorative layer 13 having a design property is laminated on the wood base material 10 according to the first embodiment described above with reference to FIG. According to this embodiment, by laminating the design layer 13 on the wood base material 10, it is possible to impart design properties. That is, the wood base material 10 can be used as a decorative material by itself, but in order to impart even more excellent design to the wood base material 10, a design layer 13 such as paper or film having a design such as a picture may be laminated onto the wood base material 10 to form a decorative material 14, as shown in Figure 5.

[0041] <Other effects> (1) The wood base material 10 of this embodiment includes a wood material 4 having at least one of a powder and chip shape, and a thermoplastic resin composition 5. The wood base material 10 has a skin layer 11 and a core layer 12. The normalized CH area of ​​each of the skin layer 11 and the core layer 12, calculated from the absorption spectrum obtained by Fourier infrared spectroscopy measurement using the following formula (1), is within the range of 0.07 to 1.00. Standardized CH area=S C-H / (S O―H +S C-OH )...Equation (1) Here, in formula (1), S C-H is a wave number of 2700 cm -1 More than 3000cm -1 The area value of the peak derived from either the CH2 group or the CH3 group in the following region, S O-H is a wave number of 3000 cm -1 More than 3500cm -1 The area value of the peak derived from the OH group in the following region, S C-OH is a wave number of 900 cm -1 More than 1200cm -1 The area values ​​of the peaks derived from C-OH groups in the following regions are shown. With this configuration, since the thermoplastic resin composition 5 is used as an adhesive instead of formaldehyde, which causes sick house syndrome, it is possible to provide a wood base material 10 that does not emit harmful substances. Furthermore, since the wood base material 10 contains the thermoplastic resin composition 5, the thermoplastic resin composition 5 itself has high water resistance, which imparts excellent water resistance to the wood base material 10. Furthermore, since the wood base material 10 is a laminated structure including at least the skin layer 11 and the core layer 12, it has excellent mechanical properties such as bending strength.

[0042] (2) The wood substrate 10 of this embodiment has a normalized CH area A measured for each of the skin layer 11 and the core layer 12. S , A C may be within the range of 0.08 or more and 0.35 or less. With this configuration, since a thermoplastic resin composition is used as an adhesive instead of formaldehyde, which causes sick house syndrome, it is possible to provide a wood base material 10 that does not emit harmful substances. In addition, the normalized CH area A S , A C If is within the above-mentioned range, it is possible to obtain a favorable wood substrate 10 that has a higher bending strength, is more water-resistant, and is less prone to deformation.

[0043] (3) The wood base material 10 of this embodiment includes a skin layer 11, a core layer 12, and a skin layer 11 in that order, and the thickness ratio of each layer (skin layer:core layer:skin layer) may be within a range of 1:0.1:1 to 1:18:1. With such a structure, the wood substrate 10 has a multi-layer structure and is therefore excellent in bending strength and water resistance.

[0044] (4) In the wood base material 10 of this embodiment, the thickness of the skin layer 11 may be within a range of 2 mm or more and 19 mm or less. With such a configuration, it is possible to provide a wood base material 10 that satisfactorily fulfills the role of the skin layer 11, the overall thickness of the wood base material 10 is not too large, and there are no problems with workability during construction.

[0045] (5) In the wood substrate 10 of this embodiment, the normalized CH area of ​​the skin layer 11 is A S , the normalized CH area of ​​the core layer 12 is A C In this case, A S >A C may be also possible. With this configuration, the thermoplastic resin composition 5 can be used as an adhesive instead of formaldehyde, which causes sick house syndrome, and the wood base material 10 has good water resistance.

[0046] (6) In the wood base material 10 of this embodiment, the mass ratio of the wood material 4 to the thermoplastic resin composition 5 (wood material 4 / thermoplastic resin composition 5) in each of the skin layer 11 and the core layer 12 may be within a range of 95 / 5 to 70 / 30. With this configuration, it is possible to reliably provide a wood substrate 10 with greater bending strength.

[0047] (7) In the wood substrate 10 of this embodiment, the wood material 4 may contain a mushroom bed as a raw material. With such a configuration, it is possible to provide a wood substrate 10 that is beneficial in reducing the environmental impact.

[0048] (8) In the wood substrate 10 of this embodiment, the thermoplastic resin composition 5 may contain polyethylene. Such a configuration can provide a wood substrate 10 that has both good bending strength and water resistance. Furthermore, when biomass-derived polyethylene is contained, a wood substrate 10 that is beneficial in reducing the environmental impact can be provided.

[0049] (9) In the wood substrate 10 of this embodiment, the thermoplastic resin composition 5 may contain an acid-modified polyolefin. With such a configuration, it is possible to provide a wood substrate 10 with better bending strength.

[0050] (10) The decorative material 14 of the present embodiment is obtained by laminating a decorative substrate (decorative layer 13) having a design onto the wood substrate 10 of the present embodiment. With this configuration, it is possible to provide a decorative material 14 that has better bending strength and water resistance than conventional decorative materials.

[0051] [Example] Below, examples 1 to 20 of the wood base material according to the first embodiment of the present invention and comparative example 1 will be described. Note that the present invention is not limited to the following examples 1 to 20.

[0052] Example 1 The thermoplastic resin composition of Example 1 was a single high-density polyethylene resin (HDPE) pellet. The resin pellet was mechanically crushed to obtain a powdered thermoplastic resin composition. The average particle size of the powdered thermoplastic resin composition was 100 μm. The wood material used was a washed and dried mushroom bed (average particle size 2 mm) after harvesting. The wood material and the thermoplastic resin composition were dry mixed in a mass ratio (wood material / thermoplastic resin composition) of 85 / 15 to obtain a raw material mixture for the wood substrate. This raw material mixture was introduced into an aluminum mold and heated and pressed with a heat press device to obtain one skin layer with a thickness of 4 mm (pressing conditions: 40 kgf / cm 2 , 200°C for 10 minutes, substrate density: 0.8g / cm 3 ) After obtaining another 4 mm skin layer in the same manner, the raw material mixture that would become the core layer was placed between the two skin layers and heated and pressurized. In this way, a three-layered wood substrate was obtained, in which a 4 mm skin layer, a 4 mm core layer, and a 4 mm skin layer were laminated in sequence, as in Example 1.

[0053] Example 2 In Example 2, a wood base material was obtained in the same manner as in Example 1, except that the thickness of the skin layer was changed to 2 mm and the thickness of the core layer was changed to 5 mm.

[0054] Example 3 In Example 3, a wood base material was obtained in the same manner as in Example 1, except that the thickness of the skin layer was changed to 2 mm and the thickness of the core layer was changed to 36 mm.

[0055] Example 4 In Example 4, a wood base material was obtained in the same manner as in Example 1, except that the thickness of the skin layer was changed to 19 mm and the thickness of the core layer was changed to 2 mm.

[0056] Example 5 The thermoplastic resin composition of Example 5 was a low-density polyethylene resin (LDPE) pellet alone, and a wood base material was obtained in the same manner as in Example 1.

[0057] Example 6 The thermoplastic resin composition of Example 6 was a linear low-density polyethylene resin (LLDPE) pellet alone. A wood base material was obtained in the same manner as in Example 1.

[0058] Example 7 The thermoplastic resin composition of Example 7 was polypropylene resin (PP) pellets alone. A wood base material was obtained in the same manner as in Example 1.

[0059] Example 8 In Example 8, the mass ratio of the wood material to the thermoplastic resin composition for the skin layer (wood material / thermoplastic resin composition) was changed from "85 / 15" in Example 1 to "96 / 4," and otherwise the wood base material was obtained in the same manner as in Example 1.

[0060] Example 9 In Example 9, the mass ratio of the wood material to the thermoplastic resin composition for the skin layer (wood material / thermoplastic resin composition) was changed from "85 / 15" in Example 1 to "90 / 10," and otherwise the wood base material was obtained in the same manner as in Example 1.

[0061] Example 10 In Example 10, the mass ratio of the wood material to the thermoplastic resin composition for the skin layer (wood material / thermoplastic resin composition) was changed from "85 / 15" in Example 1 to "80 / 20," and otherwise the wood base material was obtained in the same manner as in Example 1.

[0062] Example 11 In Example 11, the mass ratio of the wood material to the thermoplastic resin composition for the skin layer (wood material / thermoplastic resin composition) was changed from "85 / 15" in Example 1 to "70 / 30," and otherwise the wood base material was obtained in the same manner as in Example 1.

[0063] Example 12 In Example 12, the mass ratio of the wood material to the thermoplastic resin composition for the skin layer (wood material / thermoplastic resin composition) was changed from "85 / 15" in Example 1 to "65 / 35," and otherwise the wood base material was obtained in the same manner as in Example 1.

[0064] Example 13 In Example 13, the mass ratio of the wood material to the thermoplastic resin composition (wood material / thermoplastic resin composition) for each of the skin layer and core layer was changed from "85 / 15" in Example 1 to "70 / 30," and otherwise the wood base material was obtained in the same manner as in Example 1.

[0065] Example 14 In Example 14, the mass ratio of the wood material to the thermoplastic resin composition (wood material / thermoplastic resin composition) for each of the skin layer and core layer was changed from "85 / 15" in Example 1 to "65 / 35," and otherwise the wood base material was obtained in the same manner as in Example 1.

[0066] Example 15 The components and masses of the thermoplastic resin composition of Example 15 are as follows. (1) High density polyethylene resin 97 parts by weight (2) Acid-modified polyolefin: 3 parts by mass The above (1) and (2) were heated and kneaded in a batch kneader, and then mechanically pulverized to obtain a powdered thermoplastic resin composition. A wood substrate for Example 15 was obtained in the same manner as in Example 1 except for the above.

[0067] (Example 16) The components and masses of the thermoplastic resin composition of Example 16 are as follows. (1) High density polyethylene resin 80 parts by weight (2) Acid-modified polyolefin: 20 parts by mass The above (1) and (2) were heated and kneaded in a batch kneader, and then mechanically pulverized to obtain a powdered thermoplastic resin composition. A wood substrate for Example 16 was obtained in the same manner as in Example 1 except for the above.

[0068] (Example 17) The components and masses of the thermoplastic resin composition of Example 17 are as follows. (1) High density polyethylene resin 60 parts by weight (2) Acid-modified polyolefin 40 parts by mass The above (1) and (2) were heated and kneaded in a batch kneader, and then mechanically pulverized to obtain a powdered thermoplastic resin composition. A wood substrate for Example 17 was obtained in the same manner as in Example 1 except for the above.

[0069] (Example 18) In Example 18, a wood base material was obtained in the same manner as in Example 1, except that the thickness of the skin layer was changed to 2 mm and the thickness of the core layer was changed to 40 mm.

[0070] (Example 19) In Example 19, a wood base material was obtained in the same manner as in Example 1, except that the thickness of the skin layer was changed to 20 mm and the thickness of the core layer was changed to 2 mm.

[0071] (Example 20) The thermoplastic resin composition of Example 20 is a single high-density polyethylene resin (HDPE) pellet. The resin pellet is mechanically pulverized to obtain a powdered thermoplastic resin composition. The average particle size of the powder of the thermoplastic resin composition is 100 μm. The wood material used was a washed and dried mushroom bed (average particle size 2 mm) after harvesting. The wood material and the thermoplastic resin composition were dry mixed in a mass ratio (wood material / thermoplastic resin composition) of 85 / 15 to obtain a raw material mixture for the wood substrate. This raw material mixture was introduced into an aluminum mold and heated and pressed with a heat press device to obtain one skin layer with a thickness of 6 mm (pressing conditions: 40 kgf / cm 2 , 200°C for 10 minutes, substrate density: 0.8g / cm 3 ) The raw material mixture was then placed on top of the skin layer and heated and pressurized. In this way, a two-layered wood substrate having a skin layer of 6 mm and a core layer of 6 mm was obtained as in Example 20.

[0072] Comparative Example 1 In Comparative Example 1, a wood base material was obtained in a manner similar to that used for producing so-called particle board. Specifically, the wood material and adhesive were mixed using a drum blender, and the mixture was allowed to fall and spread in a natural state without the application of external forces such as pressure or suction. Urea resin adhesive was used as the adhesive, and the wood material and adhesive were mixed at a mass ratio (wood material / adhesive) of 85 / 15. The mixture was then compacted to obtain a wood base material.

[0073] (Evaluation of wood-based materials) For the above Examples 1 to 20 and Comparative Example 1, Fourier infrared spectroscopy, mechanical strength, water resistance, and substrate deformation were evaluated.

[0074] (Fourier type infrared spectroscopy) The Fourier-type infrared spectroscopy was performed using a PerkinElmer Fourier-type infrared spectrometer (Spectrum Spotlight 400) at 4000 cm -1 From 400cm -1 From the obtained absorption spectrum, the normalized CC area of ​​each of the skin layer and the core layer is calculated using the following formula (1). Standardized CH area=S C-H / (S O―H +S C-OH )...Equation (1) Here, in formula (1), S C-H is a wave number of 2700 cm -1 More than 3000cm -1 The area value of the peak derived from either the CH2 group or the CH3 group in the following region, S O-H is a wave number of 3000 cm -1 More than 3500cm -1 The area value of the peak derived from the OH group in the following region, S C-OH is a wave number of 900 cm -1 More than 1200cm -1 The area values ​​of the peaks derived from C-OH groups in the following regions are shown. In the Fourier infrared spectroscopic measurement, when the normalized CH area of ​​each of the skin layer and the core layer is in the range of 0.07 to 1.00, the sample is considered to pass.

[0075] (Mechanical strength) The mechanical strength was measured by bending strength according to the method of JISA5908. Measured value (unit: N / mm 2 The evaluation criteria for mechanical strength for the above-mentioned materials are as follows, based on the JIS standard values: The mechanical strength was evaluated based on the following four-level scale: "◎", "good", "△", and "×", with "◎", "good", and "△" being pass marks and "×" being fail marks. ◎:15 or more (pass) 〇: 13 or more and less than 15 (pass) △: 8 or more but less than 13 (pass) ×: Less than 8 (failed)

[0076] (water resistance) Water resistance was measured by measuring the water absorption thickness swelling rate according to a method conforming to JISA 5908. The evaluation criteria for water resistance for the measured value (unit: %) are as follows, based on the JIS standard values. The water resistance was evaluated based on the following four-level scale: "◎", "good", "△", and "×", with "◎", "good", and "△" being acceptable and "×" being unacceptable. ◎: Less than 5 (pass) ○: 5 or more but less than 8 (pass) △: 8 or more but less than 12 (pass) ×: 12 or more (fail)

[0077] (Substrate deformation) The substrate deformation is a state in which the substrate surface is partially swollen, and is mainly caused by the retention of gas generated inside the substrate during pressing. Since the substrate deformation is clearly reflected by the state of the substrate edge, the appearance of the substrate edge was visually evaluated. The evaluation criteria for substrate deformation were as follows: 3-level evaluation of "good", "△", and "×", with "good" and "△" representing pass and "×" representing fail. 〇: No voids (passed) △: Traces of voids (passed) ×: Voids present (failed)

[0078] (Evaluation Results) The evaluation results of the wood-based substrates are as shown in Table 1 below. In addition, the "raw material mixing ratio" in the examples in the table indicates the mass ratio defined as (wood material / thermoplastic resin composition), and the "raw material mixing ratio" in the comparative examples in the table indicates the mass ratio defined as (wood material / adhesive).

[0079] [Table 1]

[0080] (Evaluation results of Fourier infrared spectroscopy) The only one that failed the evaluation of the Fourier infrared spectroscopy was Comparative Example 1. As in Examples 1 to 20, the wood base material containing a polyolefin in the thermoplastic resin composition had a 2700 cm -1 More than 3000cm -1 The normalized CH area is large for both the skin layer and the core layer because of the characteristic peaks in the following regions. In addition, the normalized CH area of ​​the wood material alone is 0.05, so 2700 cm -1 More than 3000cm -1 In the following region, almost no peaks due to the adhesive of Comparative Example 1 are detected. Comparing Examples 1 to 20, the skin layers of Examples 14 and 12, in which the amount of thermoplastic resin composition in the skin layer is large, have the largest normalized C—H area, while the skin layer of Example 8, in which the amount of thermoplastic resin composition in the skin layer is small, has the smallest normalized C—H area.

[0081] (Mechanical strength evaluation results) In terms of mechanical strength, all of Examples 1 to 20 and Comparative Example 1 passed the test. Of these, eight of Examples 4 to 9, 17, and 19 had evaluation results that included "△". In Examples 4 and 19, the core layer was extremely thinner than the skin layer, which is thought to have reduced mechanical strength. In Examples 5 to 7, LDPE, LLDPE, and PP were used as the base resin, respectively, which is thought to have reduced mechanical strength compared to HDPE. In Examples 8 to 9, the proportion of wood material in the skin layer was high, which is thought to have reduced mechanical strength. In Example 17, 40 parts of acid-modified polyolefin was blended, and the content of the base resin was relatively low, which is thought to have reduced mechanical strength.

[0082] (Water resistance evaluation results) The only example that failed the water resistance test was Comparative Example 1. The conventional method using an adhesive has poorer water resistance than Examples 1 to 20 of the present invention. Comparing Examples 1 to 20, there are 12 examples including Examples 1 to 9 and 18 to 20 that are marked as "△". Examples 1 to 9 and 18 to 19 are material formulations that do not contain acid-modified polyolefin, and the ratio of the thermoplastic resin composition in the skin layer in Examples 1 to 9 and 18 is 15 parts or less, so it is believed that the water resistance was insufficient. Comparing with Examples 10 to 17, it is believed that Examples 15 to 17 contain acid-modified polyolefin, so that the water resistance is improved. Examples 10 to 12 are examples in which the ratio of the thermoplastic resin composition in only the skin layer is increased to 20 parts, 30 parts, and 35 parts, and the water resistance is improved because the absorption of moisture from the front and back sides is suppressed. However, since the water resistance of the core layer is poor, the water resistance is inferior to Examples 13 and 14 in which the ratio of the thermoplastic resin composition in the core layer is also increased to 30 parts and 35 parts. Furthermore, when comparing Examples 10 and 20, the thermoplastic resin composition ratio in the skin layer in both is 20 parts, but Example 20 has a skin layer only on the surface layer, and the water resistance of the back surface is insufficient, so that the water resistance is inferior to Example 10.

[0083] (Evaluation results of substrate deformation) In terms of substrate deformation, all of Examples 1 to 20 and Comparative Example 1 passed the test. Among them, only Example 14 had an evaluation result that included "△". In Example 14, the skin layer, the core layer, and both layers contained 35 parts of thermoplastic resin composition, which is thought to have made the substrate more susceptible to deformation due to the relatively high content of thermoplastic resin composition.

[0084] (Overall evaluation results) As a comprehensive evaluation result, Examples 1 to 20 were "passed" in all evaluation items, and as is clear from Table 1, it was shown that the wood base material of the present invention has excellent mechanical strength and water resistance, and there is no problem with substrate deformation. In Examples 18 to 19, the wood base material was thick at 42 mm, and the wood base material was heavy and difficult to handle during construction work, but it was not a problem in practical use. [Explanation of symbols]

[0085] Reference Signs List 1: Jig for making wooden substrate, 2: Metal plate (bottom surface), 3: Releaseable metal plate, 4: Wooden material, 5: Thermoplastic resin composition, 6: Raw material mixture, 7: Metal plate for adjusting thickness, 8: Metal weight, 9: Press top plate, 10: Wooden substrate, 11: Skin layer, 12: Core layer, 13: Design layer, 14: Decorative material

Claims

1. A wood substrate comprising a wood material having at least one of a powder form and a chip form and a thermoplastic resin composition, The wood base material comprises a skin layer and a core layer, a normalized C-H area calculated from an absorption spectrum obtained by Fourier infrared spectrometry using the following formula (1) for each of the skin layer and the core layer is in the range of 0.07 or more and 1.00 or less, The wood base material is characterized in that, when the normalized C-H area of ​​the skin layer is AS and the normalized C-H area of ​​the core layer is AC, AS and AC are different from each other. Normalized C-H area = S Ｃ－Ｈ / (S Ｏ―Ｈ +S Ｃ－ＯＨ ) …………Formula (1) (Here, in formula (1), S Ｃ－Ｈ The wave number is 2700 cm －１ More than 3000cm －１ CH in the following areas ２ Group, CH ３ The area value of the peak derived from any one of the groups, S Ｏ－Ｈ is a wave number of 3000 cm －１ More than 3500cm －１ The area value of the peak derived from the OH group in the following region, S Ｃ－ＯＨ is a wave number of 900 cm －１ More than 1200cm －１ The area values ​​of the peaks derived from C-OH groups in the following regions are shown below.)

2. The wood base material according to claim 1, characterized in that the normalized C-H area measured for each of the skin layer and the core layer is within a range of 0.08 to 0.

35.

3. The wood base material includes the skin layer, the core layer, and the skin layer in this order, 3. The wood base material according to claim 1, wherein the thickness ratio of each layer (skin layer:core layer:skin layer) is within the range of 1:0.1:1 to 1:18:

1.

4. The wood base material includes the skin layer, the core layer, and the skin layer in this order, 3. The wood base material according to claim 1, wherein the skin layer and the core layer have different thicknesses.

5. 5. The wood base material according to claim 1, wherein the skin layer has a thickness in the range of 2 mm to 19 mm.

6. The wood base material according to any one of claims 1 to 5, characterized in that, when the normalized C-H area of ​​the skin layer is AS and the normalized C-H area of ​​the core layer is AC, AS>AC.

7. The wood base material according to any one of claims 1 to 6, characterized in that the mass ratio of the wood material to the thermoplastic resin composition (wood material / thermoplastic resin composition) in each of the skin layer and the core layer is within a range of 95 / 5 to 70 / 30.

8. The wood substrate according to any one of claims 1 to 7, characterized in that the wood material contains a mushroom bed as a raw material.

9. The wood base material according to any one of claims 1 to 8, characterized in that the thermoplastic resin composition contains polyethylene.

10. The wood substrate according to any one of claims 1 to 9, characterized in that the thermoplastic resin composition contains an acid-modified polyolefin.

11. The wood substrate according to any one of claims 1 to 9, characterized in that the thermoplastic resin composition contains only one type of acid-modified polyolefin.

12. A wood substrate comprising a wood material having at least one of a powder form and a chip form and a thermoplastic resin composition, The wood base material comprises a skin layer and a core layer, a normalized C-H area calculated from an absorption spectrum obtained by Fourier infrared spectrometry using the following formula (1) for each of the skin layer and the core layer is in the range of 0.07 or more and 1.00 or less, The wood base material is characterized in that, when the normalized C-H area of ​​the skin layer is AS and the normalized C-H area of ​​the core layer is AC, AS>AC. Normalized C-H area = S Ｃ－Ｈ / (S Ｏ―Ｈ +S Ｃ－ＯＨ ) …………Formula (1) (Here, in formula (1), S Ｃ－Ｈ The wave number is 2700 cm －１ More than 3000cm －１ CH in the following areas ２ Group, CH ３ The area value of the peak derived from any one of the groups, S Ｏ－Ｈ is a wave number of 3000 cm －１ More than 3500cm －１ The area value of the peak derived from the OH group in the following region, S Ｃ－ＯＨ is a wave number of 900 cm －１ More than 1200cm －１ The area values ​​of the peaks derived from C-OH groups in the following regions are shown below.)

13. A decorative material comprising the wood substrate according to any one of claims 1 to 12 and a decorative substrate laminated thereon.

14. A method for producing a wood substrate according to any one of claims 1 to 12, comprising the steps of: A step of mixing a wood material having at least one of a powder form and a chip form with a thermoplastic resin composition to obtain a raw material mixture for a wood base material; and heating and pressurizing the raw material mixture to form a wood base material.

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