JP2022163565A - Wooden base material, decorative material and method for manufacturing wooden base material - Google Patents

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 20 contains a wooden material 11 having at least one of a powder shape and a chip shape, and a thermoplastic resin composition 12, wherein the wooden base material 20 sequentially includes a skin layer 21, a core layer 22 and the skin layer 21, and when the density of the skin layer 21 is represented by ρs and the density of the core layer 22 is represented by ρc, ρs/ρc is within a range of 1.0 or more and 2.4 or less, and each of the ρs and the ρc is within a range of 0.5 g/cm3 or more and 1.2 g/cm3 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wooden base material, a decorative material, and a method for producing a wooden base material.

The wood base material is a base material obtained by heating and pressurizing a mixture of a wood material such as wood flour, wood chips, and wood fiber with an adhesive. This wooden base material is called particle board or medium density fiberboard depending on the type of wood material, and is used in a wide range of applications such as base material for floors and walls, fittings and furniture.
Conventionally, urea resin-based adhesives, melamine resin-based adhesives, or phenolic resin-based adhesives have been used as adhesives for wooden substrates together with curing agents containing formaldehyde. Since formaldehyde is a harmful substance that causes sick building syndrome, its emission from wooden substrates is a problem, and various measures for reducing the amount of emission are being studied. However, in the prior art, it was difficult to completely suppress the diffusion of formaldehyde.

On the other hand, conventionally, as an adhesive that does not contain formaldehyde, an adhesive mainly composed of powdered sugar and powdered polycarboxylic acid is used. A method for manufacturing a fiber board has been proposed (see paragraph [0017] of Patent Document 1). As a formaldehyde-free adhesive, conventionally, a method for producing a laminate containing a wooden substrate using an adhesive made of polyvinyl alcohol and water has been proposed (Patent Document 2, paragraph [0017], and See Figure 1).

JP 2016-55620 A Japanese Patent No. 5553279

However, wood base materials using the above-described conventional adhesives are not practically sufficient in mechanical properties such as bending strength and water resistance.
Therefore, the present invention provides a woody base material that suppresses the emission of harmful substances that cause sick house syndrome such as formaldehyde and has practical mechanical strength and water resistance, a decorative material that includes the woody base material, and a An object of the present invention is to provide a method for producing the wooden base material.

A woody base according to an aspect of the present invention is a woody base containing a woody material having at least one of powdery and chip-like shapes and a thermoplastic resin composition, wherein the woody base is , a skin layer, a core layer, and a skin layer in sequence, where ρs is the density of the skin layer and ρc is the density of the core layer, ρs/ρc is in the range of 1.0 or more and 2.4 or less, Each of ρs and ρc is in the range of 0.5 g/cm ³ or more and 1.2 g/cm ³ or less.

Further, in the wood base material according to one aspect of the present invention, each of the skin layers and the core layer is obtained by using the following formula (1) from the absorption spectrum obtained by Fourier infrared spectrometry. The calculated normalized C-H area is in the range of 0.07 or more and 1.00 or less, and the normalized C-H area of the skin layer is A _S and the normalized C-H area of the core layer is A If _C , it is characterized by A _S > _AC .
Normalized C-H area=S _C-H /(S _O-H +S _C-OH ) Formula (1)
(Here, in formula (1), S _C-H is the area value of the peak derived from either a CH ₂ group or a CH ₃ group in the wavenumber region of 2700 cm ^-1 or more and 3000 cm ^-1 or less, and S _O-H is The area value of the peak derived from the OH group in the wavenumber region of 3000 cm ^-1 or more and 3500 cm ^-1 or less, and the area value of the peak derived from the _C -OH group in the wavenumber region of 900 cm ^-1 or more and 1200 cm ^-1 or less. indicates.)

Further, in the wooden base material according to one aspect of the present invention, the skin layer, the core layer, and the thickness ratio of each layer (skin layer: core layer: skin layer) of the skin layer is 1:0.1: It is characterized by being in the range of 1 to 1:18:1.
Further, in the wooden base material according to one aspect of the present invention, the thickness of the skin layer is in the range of 2 mm or more and 19 mm or less.
Further, in the wood base material according to one aspect of the present invention, each of the skin layers and the core layer has a mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition ) is in the range of 95/5 to 70/30.
In addition, a wooden base material according to an aspect of the present invention is characterized by including a fungal bed as a raw material.
Moreover, the wooden base material according to one aspect of the present invention is characterized in that the thermoplastic resin composition contains a polyolefin resin.
Moreover, the wooden base material according to one aspect of the present invention is characterized in that the thermoplastic resin composition contains an acid-modified polyolefin.

In addition, a decorative material according to an aspect of the present invention is characterized by laminating a designable base material on the woody base material described above.

Further, a method for producing a woody base material according to an aspect of the present invention is a method for producing a woody base material described above, wherein the woody material has at least one of a powder-like shape and a chip-like shape. and 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.

According to one aspect of the present invention, a wooden base material that suppresses the emission of harmful substances that cause sick building syndrome such as formaldehyde and that has practical mechanical strength and water resistance, and the wood base material It is possible to provide a decorative material and a method for producing the wooden base material.

It is a schematic diagram which shows the manufacturing method of the wooden base material which concerns on embodiment of this invention. 1 is a schematic cross-sectional view showing the structure of a wooden base material according to a first embodiment of the present invention; FIG. Infrared absorption spectra of common wood materials. 4 is an infrared absorption spectrum of the wood base material according to the first embodiment of the present invention; FIG. 5 is a schematic cross-sectional view showing the structure of a decorative material according to a second embodiment of the present invention;

An embodiment of the present invention will be described below with reference to the drawings.
Here, the drawings are schematic, and the relationship between the thickness and the planar dimension, the ratio of the thickness of each layer, and the like are different from the actual ones. Further, the embodiments shown below are examples of configurations for embodying the technical idea of the present invention. It does not specify anything. Various modifications can be made to the technical idea of the present invention within the technical scope defined by the claims.

[First embodiment]
FIG. 1 shows a schematic diagram for explaining a method for producing a wooden base material according to an embodiment of the present invention. FIG. 2 also shows a wooden base material 20 according to the first embodiment of the present invention. The wooden base material 20 is called a particle board or a medium density fiberboard depending on the type of the wooden material 11, and is used in a wide range of applications such as base material for floors and walls, fittings and furniture.
As shown in FIG. 1, the wood base material 20 is made by heating a raw material mixture 10 containing a wood material 11 having at least one of powdery and chip-like shapes and a powdery thermoplastic resin composition 12. Formed by pressing. The wooden base material 20 does not contain harmful substances that cause sick house syndrome, such as formaldehyde. Therefore, it is possible to suppress the diffusion of harmful substances that cause sick house syndrome, such as formaldehyde, from inside the wooden base material 20 .

The configuration of the wooden base material 20 according to this embodiment will be described in detail below.
As shown in FIG. 2, the wooden base material 20 according to the present embodiment includes a skin layer 21 that constitutes the front surface and the back surface of the wooden base material 20, and a central portion of the wood base material 20 that is sandwiched between the skin layers 21. and a core layer 22 located at the That is, the wood base material 20 according to the present embodiment includes the skin layer 21 formed by including the wood material 11 and the thermoplastic resin composition 12, and the wood material 11 and the thermoplastic resin composition 12. and a core layer 22 . In the wooden base material 20, the skin layer 21 and the core layer 22 are preferably in contact with each other.
Thus, the wooden base material 20 according to the present embodiment does not contain harmful substances such as formaldehyde that cause sick house syndrome. Therefore, it is possible to suppress the diffusion of harmful substances that cause sick house syndrome, such as formaldehyde, from inside the wooden base material 20 .
Each material constituting the wooden base material 20 will be described below.

(Density of wooden base material 20)
The density of the wood base material 20 is such that ρs/ρc is in the range of 1.0 to 2.4, where ρs is the density of the skin layer 21 and ρc is the density of the core layer 22. It is preferably in the range of 0.0 or less, more preferably in the range of 1.0 to 1.5. If ρs/ρc exceeds 2.4, the weight of the skin layer 21 increases, possibly causing substrate deformation. If ρs/ρc is less than 1, the strength of the skin layer 21 is so low that the mechanical strength may be insufficient.
Further, the density ρs of the skin layer 21 and the density ρc of the core layer 22 are within the range of 0.5 g/cm ³ or more and 1.2 g/cm ³ or less, and 0.6 g/cm ³ or more and 1.1 g/cm 3 or more. A range of ³ or less is preferable. If ρs and ρc each do not satisfy 0.5 g/cm ³ , the wooden base material 20 may not have sufficient strength.
Also, if ρs and ρc are each greater than 1.2 g/cm ³ , the weight of the wooden base material 20 is too large, which may make it difficult to handle during construction.

(wood material 11)
The wooden material 11 has at least one of powdery and chip-like shapes. Here, there is generally no definition of size and shape for "powder" and "chip". In this embodiment, the size (average particle size) is generally in the range of several tens of microns to several centimeters. It is desirable that the average particle size of the wooden material 11 in the present embodiment is, for example, within the range of 10 μm or more and 3 mm or less.

The wood material 11 includes, for example, wood flour, wood fibers, and chips obtained by crushing wood, and thinned wood, sawdust, and waste wood, for example, can be used as raw materials.
In addition, the wooden material 11 may be a candidate other than wood if it contains a cellulose component like wood, such as bamboo, hemp, coconut fiber, and walnut shell.

As a raw material for the wooden material 11, for example, a large amount of used mushroom bed generated during mushroom cultivation is suitable. The mushroom bed is a medium used for mushroom cultivation, and is made by mixing nutrients such as bran and rice bran with wood chips and sawdust. It is estimated that about 300,000 tons of mushroom beds are discarded annually in Japan after mushroom cultivation, and they are promising as biomass, but the current situation is that recycling is not progressing.
In this embodiment, when the fungus bed is used as the wooden material 11, the ratio of the fungal bed to the entire volume of the wooden material 11 may be in the range of 1% or more and 100% or less, preferably 50%. % or more and 100% or less. If the content of the fungal bed is within the above numerical range, the manufacturing cost can be reduced as compared with the case of using ordinary wood chips.

(Manufacturing method of wooden material 11)
For example, when trying to obtain the wooden material 11 from waste wood, many foreign substances such as concrete pieces, metal pieces, and papers are included. Foreign matter can be removed by known methods such as magnetic separation, air separation, gravity separation, and the like. In addition, the size of coarse particles is adjusted by a known method such as cutting and crushing, and those in the range of approximately several tens of microns to several centimeters are used.
Furthermore, when trying to obtain the woody material 11 from the fungal bed, it is desirable to sterilize it by a known method before using it.

(Mass ratio of wooden material 11 and thermoplastic resin composition 12)
The mass ratio of the woody material 11 and the thermoplastic resin composition 12 (woody material/thermoplastic resin composition) is in the range of 95/5 to 70/30 in each of the skin layer 21 and the core layer 22. is desirable.
If the content of the wooden material 11 exceeds the numerical value (95/5) described above, it is not possible to impart sufficient bending strength (mechanical strength) to the wooden base material 20 . On the other hand, if the content of the wooden material 11 is smaller than the above numerical value (70/30), deformation of the wooden base material 20 tends to occur during heating and pressurization, which is not preferable.
The mass ratio (woody material/thermoplastic resin composition) of the woody material 11 and the thermoplastic resin composition 12 is preferably in the range of 85/15 to 70/30 in each of the skin layer 21 and the core layer 22 . By setting the content of the woody material 11 within the above numerical range, the woody base material 20 having a higher bending strength can be obtained.

As for the mass ratio of woody material 11 and thermoplastic resin composition 12 (woody material/thermoplastic resin composition), it is desirable that skin layer 21 contains more thermoplastic resin composition 10 than core layer 22 . By increasing the proportion of the thermoplastic resin composition 10, the water resistance of the skin layer 21 (particularly, the skin layer 21 constituting the surface layer of the wooden base material 20) is improved. Further, for example, the content of the thermoplastic resin composition 10 in the skin layer 21 is preferably in the range of more than 2 times or less than the content of the thermoplastic resin composition 10 in the core layer 22, preferably 1.3 times. It is more desirable if it is in the range of 1.8 times or less.

(Thermoplastic resin composition 12)
The thermoplastic resin composition 12 is a powdery composition with an average particle size of several tens of microns to 1 millimeter. Although the particle size of the thermoplastic resin composition 12 is not particularly limited, it is preferable that the particle size of the thermoplastic resin composition 12 is about the same when mixing with the woody material 11 because mixing is easy. If the particle size of the thermoplastic resin composition 12 is too small, it will pass through the wood material 11 and deposit on the bottom. Therefore, the particle size (average particle size) of the thermoplastic resin composition 12 is more preferably in the range of 1 to 5 millimeters. The particle size (average particle size) of the thermoplastic resin composition 12 is desirably in the range of 30 microns (μm) or more and 300 microns (μm) or less in consideration of ease of handling.
For the thermoplastic resin composition 12, various materials such as polyester, polyamide, polyolefin, ethylene-propylene-diene rubber, ethylene vinyl acetate, and silicone rubber can be used. is preferred.
Polyolefin resins that can be used in the present embodiment include, in addition to polyethylene and polypropylene, polymethylpentene, polybutene, ethylene-propylene copolymers, ethylene-α-olefin copolymers, and propylene-α-olefin copolymers. Polyolefin resins such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-(meth)acrylic acid (ester) copolymer, ethylene-unsaturated carboxylic acid copolymer metal neutralized product ( polyolefin resins such as olefin copolymer resins such as ionomers), or mixtures, copolymers, composites, laminates, etc. of two or more of these.
The thermoplastic resin composition 12 may be used alone, or may be used by mixing a plurality of types. From the viewpoint of the mechanical strength of the wooden base material 20, it is desirable that the thermoplastic resin composition 12 contains 50 parts by mass or more and 100 parts by mass or less of a polyolefin resin or the like with respect to 100 parts by mass of the total mass of the thermoplastic resin composition 12. More preferably, it contains polyolefin resin and the like in the range of 80 parts by mass or more and 100 parts by mass or less.
The polyethylene added to the thermoplastic resin composition 12 is not particularly limited, and may be high-density polyethylene (polyethylene having a specific gravity of about 0.92 to 0.96), low-density polyethylene (having a specific gravity of 0.91 to 0.96). 92 polyethylene), ultra-low density polyethylene (polyethylene with a specific gravity of less than 0.9), linear low density polyethylene (polyethylene with a specific gravity of less than 0.94), etc. They are appropriately selected and used in consideration of reactivity during pressurization, fluidity of the raw material mixture 10, and the like. Among the materials described above, it is more preferable to use high-density polyethylene in order to obtain the wooden base material 20 having high bending strength.

The polyethylene used in this 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 a raw material monomer, the polymerized polyethylene is biomass-derived. The raw material monomer for polyethylene may not contain 100% by mass of biomass-derived ethylene.

The thermoplastic resin composition 12 may be used alone, or a mixture of known thermoplastic resin compositions 12 may be used. Materials to be mixed with the thermoplastic resin composition 12 are not particularly limited, but examples thereof include acid-modified resins and organic peroxides.

(Acid-modified resin)
The acid-modified resin is used to improve adhesion between the wood material 11 and the thermoplastic resin composition 12 .
As the acid-containing resin, for example, maleic anhydride-modified polyethylene, maleic anhydride-modified polyolefin such as maleic anhydride polypropylene, ethylene (meth)acrylic acid copolymer, or itaconic anhydride-modified polyethylene can be used. Among the materials described above, maleic anhydride-modified polyolefin is preferable as the acid-containing resin, and maleic anhydride-modified polyethylene is more preferable, from the viewpoint of compatibility (adhesiveness) with the wood material 11 containing cellulose.

(Addition amount of acid-modified resin)
The amount of the acid-containing resin to be added is preferably 5 parts by mass or more and 50 parts by mass or less, more preferably 10 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the total thermoplastic resin composition.
If the amount of the acid-containing resin added is less than 5 parts by mass, the adhesiveness between the wood material 11 and the thermoplastic resin composition 12 is insufficient, and sufficient strength cannot be imparted to the wood base material 20 . Moreover, if the amount of the acid-containing resin added exceeds 50 parts by mass, the strength of the wooden base material 20 is often lowered, which is not preferable.
When the adhesion between the wood material 11 and the thermoplastic resin composition 12 is insufficient, the thermoplastic resin composition 12 cannot cover the entire surface of the wood chips constituting the wood material 11. Moisture that has entered the wooden material 11 causes the entire wooden base material 20 to absorb water and swell, thereby reducing the water resistance of the entire wooden base material 20 .

(organic peroxide)
The thermoplastic resin composition 12 may further contain an organic peroxide.
The organic peroxide may be used for radically cross-linking the thermoplastic resins contained in the thermoplastic resin composition 12 in the step of heating and pressurizing the raw material mixture 10 . Moreover, if a material having radical crosslinkability is used for the acid-containing resin, the acid-containing resin and the thermoplastic resin can be crosslinked by adding an organic peroxide to the thermoplastic resin composition 12. When radical cross-linking is formed between thermoplastic resins or between an acid-containing resin and a thermoplastic resin, the cross-linking structure improves the mechanical strength of the wood base material 20 as a whole.

The organic peroxide is not particularly limited, and can be appropriately selected from existing materials such as peroxyketals, dialkyl peroxides, diacyl peroxides, and peroxyesters in consideration of reactivity and stability. be done. Organic peroxides are a kind of radical cross-linking agents, and examples thereof include hydroperoxides, diacyl peroxides, peroxydicarbonates, peroxyesters, peroxycarbonates, dialkyl peroxides, ketone peroxides, and the like. be.

(Addition amount of organic peroxide)
The amount of the organic peroxide to be added is preferably in the range of 0.01 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the total thermoplastic resin composition.
If the amount of the organic peroxide to be added is less than 0.01 part by mass, the reactivity of the raw material mixture 10 during heating and pressurization is insufficient, so that it does not contribute to improving the strength of the wooden base material 20 . Moreover, if the amount of the organic peroxide added exceeds 5 parts by mass, the amount of decomposition products during the reaction increases, which may cause deformation of the wooden base material 20, which is not preferable.
Furthermore, by adding an organic peroxide to the thermoplastic resin composition 12, the thermoplastic resin contained in the thermoplastic resin composition 12, the acid-containing resin, and the woody material 11 are three-dimensionally interconnected by radical cross-linking. Networks (bonds) can be formed. As a result, the mechanical strength of the wooden base material 20 as a whole is improved.

(Additive)
The thermoplastic resin composition 12 may be mixed with additives such as wax. By adding wax as an additive, the water resistance of the wooden base material 20 is further improved. Additives such as wax also serve as lubricants for uniformly mixing the wood material 11 and the thermoplastic resin composition 12 or a plurality of types of thermoplastic resin compositions 12 .

(Method for producing thermoplastic resin composition 12)
The thermoplastic resin composition 12 can be produced by various known methods.
For example, the particulate thermoplastic resin composition 12 may be welded together by heating during mixing. However, if the particles are larger than 150 μm, the number of particles decreases and the surface area becomes smaller, which makes it difficult to uniformly mix the particles with the woody material 11, which is not desirable.
Moreover, the thermoplastic resin composition 12 can also be pulverized by a known method such as mechanical pulverization or freeze pulverization from resin pellets produced by a known method. When a thermoplastic resin composition containing a mixture of resin pellets and powder is mixed, the resin pellets and powder may be mixed and then pulverized, or may be pulverized and then mixed. For example, if polyethylene powder and acid-modified polyolefin powder are mixed, processing such as freeze-grinding is unnecessary when the thermoplastic resin composition 12 is pulverized, and the thermoplastic resin composition 12 can be easily produced. A powder can be obtained.

For the thermoplastic resin composition 12, for example, using a uniaxial kneader or a batch type kneader, a plurality of types of thermoplastic resin pellets are heated and kneaded, and then pulverized by a method such as mechanical pulverization or freeze pulverization. be able to. For example, polyethylene pellets and acid-modified polyolefin pellets are heated and kneaded in a uniaxial kneading extruder, pelletized, and the kneaded pellets are freeze-pulverized to obtain a powder of the thermoplastic resin composition 12. can. That is, the powder of the thermoplastic resin composition 12 may be obtained by kneading a plurality of types of the thermoplastic resin composition 12 by an extrusion method. In addition, by mixing a plurality of types of powdery thermoplastic resin composition 12, the thermoplastic resin composition 12 can be mixed more uniformly. A substrate 20 can be obtained.

(wood base material 20)
The wood base material 20 is formed by heating and pressing a raw material mixture 10 containing a wood material 11 having at least one of powdery and chip-like shapes and a powdery thermoplastic resin composition 12 . The wooden base material 20 thus formed has a multi-layer structure having at least one skin layer 21 and at least one core layer 22, as shown in FIG. Here, the skin layer 21 is a layer having water resistance. By providing this skin layer 21, the water absorption in the core layer 22 is reduced, and it is possible to prevent the entire wooden base material 20 from expanding and deforming.
If it is considered that the absorption of water from both sides of the wood base material 20 occurs at the same time, warping of the wood base material 20 due to swelling becomes a problem. It is desirable to have a three-layer structure with a skin layer 21 having a
The thickness of the wooden base material 20 is desirably in the range of 5 mm or more and 40 mm or less. If the thickness of the wooden base material 20 is less than 5 mm, the bending strength of the wooden base material 20 is weak (low) and impractical. Also, if the thickness of the wooden base material 20 is greater than 40 mm, the weight of the wooden base material 20 is heavy and it becomes difficult to handle during construction work.
The thickness of the skin layer 21 on one side (for example, the front surface) of the wooden base material 20 may be thicker than the thickness of the skin layer 21 on the other side (for example, the back surface) of the wooden base material 20. , can be thin. Also, the thickness of the skin layer 21 on one side (eg, front surface) of the wooden base material 20 and the thickness of the skin layer 21 on the other side (eg, back surface) of the wooden base material 20 may be the same.

It is desirable that each of the skin layer 21 and the core layer 22 constituting the wooden substrate 20 has a thickness of 2 mm or more. If each thickness of the skin layer 21 and the core layer 22 is less than 2 mm, it will be too thin and it will be difficult to prepare the skin layer 21 and the core layer 22 uniformly. As shown in FIG. 2, in the case of a three-layer structure having the skin layers 21 on the front and back sides of the wooden base material 20, the thickness ratio between the skin layer 21 and the core layer 22 (skin layer 21:core layer 22) is 1. : desirably in the range of 0.1 to 1:18. That is, as shown in FIG. 2, when the wooden base material 20 has a structure in which the skin layer 21, the core layer 22, and the skin layer 21 are sequentially provided, the thickness ratio of each layer (skin layer 21:core layer 22: The skin layer 21) is preferably in the range of 1:0.1:1 to 1:18:1.
In addition, since the total thickness of the wooden base material 20 including the skin layer 21 and the core layer 22 is desirably 40 mm or less, the skin layer 21 is desirably 19 mm or less.

The skin layer 21 and the core layer 22 that constitute the woody base material 20 are defined as follows: A S is the normalized CH area of the skin layer 21 calculated from the absorption spectrum obtained in Fourier infrared spectroscopy, and A _S is the core If the normalized CH area of layer 22 is A _C , it is desirable to adjust A _S >A _C . The size of each normalized CH area is qualitatively proportional to the amount (content ratio) of the thermoplastic resin composition 12 added to the skin layer 21 and the core layer 22, respectively. Therefore, even if the component amount (content ratio) of the thermoplastic resin composition 12 in the core layer 22 is the same as the component amount (content ratio) of the thermoplastic resin composition 12 in the skin layer 21, the problem of the present application is solved. can. However, in that case, the amount (content ratio) of the thermoplastic resin composition 12 in the core layer 22 becomes more than necessary (increases), which may increase the manufacturing cost. Therefore, by adjusting the component amount (content ratio) of the thermoplastic resin composition 12 so that _{A S} >AC, the manufacturing cost is reduced while maintaining both the mechanical strength and water resistance functions. be able to.

Here, Fourier infrared spectroscopy will be described. First, infrared spectroscopy is based on the principle that the amount of infrared light with a wavelength of 2.5 μm to 25 μm absorbed by a substance changes based on the vibration and rotational motion of the substance's molecules. is a measurement method for obtaining information on the chemical structure and state of a substance by measuring the infrared light absorbed by the substance. A specific measurement method is to irradiate a substance with infrared light from a light source, generate an interference wave by synthesizing the divided transmitted light and reflected light, and calculate the signal strength of the interference wave for each wave number. The infrared spectrum is measured by calculating the light intensity of the components. In particular, in the present embodiment, the interference wave is calculated using the Fourier transform method and measured by Fourier infrared spectrometry, which is a method for measuring the infrared spectrum. A graph in which the wavenumber 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. be done. At this time, the absorbance on the vertical axis changes in proportion to the concentration and thickness of the substance, and in the case of a crystalline substance, the amount of the crystalline part or the amorphous part, so that the value of the peak intensity at a predetermined wave number changes. Quantitative analysis can also be performed from peak heights and areas.

FIG. 3 shows an infrared absorption spectrum of a general wooden material 11 alone as an example. In the woody material 11, the peak of the OH group derived from cellulose strongly exists in the wave number region of 3000 cm ⁻¹ to 3500 cm ⁻¹ and the peak of the C—OH group strongly exists in the wave number region of 900 cm ⁻¹ to 1200 cm ⁻¹ . The area values of the peaks are indicated as S _{0 -H and} S _{C -OH} , respectively, and corrected with the baseline indicated by the dashed line as the background. That is, each range surrounded by a solid line and a dashed line shown in FIG. 3 is defined as the area value of each peak of the OH group and the C—OH group.
In this embodiment, the area value of each peak is a value obtained by averaging the values obtained by measuring at ten different measurement positions within the same sample.

FIG. 4 shows an example of the infrared absorption spectrum of the wooden base material 20 of this embodiment. In addition to the peaks derived from the woody material 11, the peaks of CH ₂ groups and CH ₃ groups derived from the thermoplastic resin composition 12 are strongly present in the wave number range of 2700 cm ⁻¹ to 3000 cm ⁻¹ . The area value of the peak is labeled as S _C-H and corrected with the baseline indicated by the dashed line as the background. That is, each range surrounded by a solid line and a broken line shown in FIG. 4 is defined as the area value of each peak of OH group, C—OH group, and CH ₂ group and CH ₃ group.

The normalized C-H area A _S of the skin layer 21 and the normalized C-H area A _c of the core layer 22 calculated using the following formula (1) from the area value of each peak is 0.07 or more 1 It is desirable to adjust it so that it falls within the range of 0.00 or less. Specifically, the content ratio between the wooden material 11 and the thermoplastic resin composition 12 is adjusted to adjust the values of the normalized CH area A _S and the normalized CH area A _c .
Normalized C-H area=S _C-H /(S _O-H +S _C-OH ) Formula (1)
If the normalized C—H area A _S and the normalized C—H area A _c are each less than 0.07, the ratio of the wooden material 11 is too high to impart practically necessary bending strength and water resistance. becomes difficult. On the other hand, when the normalized C—H area A _S and the normalized C—H area A _c each exceed 1.00, the proportion of the thermoplastic resin composition 12 is too high, and the wooden base material 20 is reduced during heating and pressurization. Deformation tends to occur, which is not preferable. In addition, if the wood material 11 and the thermoplastic resin composition 12 are not uniformly mixed, the normalized C—H area A _S and the normalized C—H area A _c are locally greater than 1.00. There is If the woody material 11 and the thermoplastic resin composition 12 are not uniformly mixed, the bending strength and water resistance of the woody base material 20 will vary, which is undesirable.

More preferably, the normalized CH area A _S of the skin layer 21 and the normalized CH area A _c of the core layer 22 are within the range of 0.08 or more and 0.35 or less. If each normalized C-H area is within the above numerical range, it is possible to obtain a good wood base material 20 with higher bending strength, improved water resistance, and less deformation of the wood base material 20. Become.
In addition, the area ratio (A _S /A _c ) of the normalized C-H area A _S to the normalized C-H area A _c is preferably in the range of more than 1 and 4 or less, and in the range of 1.5 or more and 3 or less. Inside is preferable. If the normalized CH area ratio (A _S /A _c ) is within the above numerical range, the thermoplastic resin composition added to the core layer 22 while imparting excellent water resistance to the entire wooden base material 20. Since the amount of addition of 12 can be minimized, the manufacturing cost can be reduced.

(Manufacturing conditions for the wooden base material 20)
Various known methods can be used for the heating and pressurizing method used when manufacturing the wooden base material 20. For the manufacturing of the wooden base material 20, a press using a frame mold as shown in FIG. Molding is preferred. The heating temperature is usually in the range of 120° C. or higher and 250° C. or lower, and must be equal to or higher than the melting point of the thermoplastic resin composition 12. However, if the heating temperature exceeds 250° C., the wooden material 11 will be thermally deteriorated. It may occur markedly. The applied pressure is usually in the range of 10 kgf/cm ² or more and 400 kgf/cm ² or less, and a value appropriately set according to the desired density of the wooden base material 20 is used.

FIG. 1 shows a schematic diagram for explaining a method for producing a wooden base material according to an embodiment of the present invention. A metal plate 2 is laid on the bottom surface of a jig 1 for preparing a wooden base material, which has an accommodating portion hollowed out to a predetermined size (for example, a square of 10 cm×10 cm), and a releasable metal plate 3 is placed thereon.
Next, a raw material mixture 10 containing a woody material 11 having at least one of powdery and chip-like shapes and a powdery thermoplastic resin composition 12 is put into the accommodating portion of the jig 1 for producing a woody base material. , the releasable metal plate 3 is placed on the raw material mixture 10 .
Next, the metal plate 7 for adjusting the thickness is placed on the jig 1 for producing the wooden base material, and the raw material mixture 6 is pressed from above with the metal weight 8 via the releasable metal plate 3 .
Finally, the pressing machine top plate 9 set to predetermined conditions is heated and pressed from above the raw material mixture 6 via a metal weight 8 to form the skin layer 21 according to the present embodiment. Another skin layer 21 is also formed in a similar manner.
After forming a pair of skin layers 21 in this manner, the metal plate 2, the releasable metal plate 3, and the skin layer 21 are stacked in this order on the bottom surface of the jig 1 for producing a wooden substrate.
Next, a raw material mixture 10 containing a woody material 11 having at least one of powdery and chip-like shapes and a powdery thermoplastic resin composition 12 is put into the accommodating portion of the jig 1 for producing a woody base material. , the skin layer 21 and the releasable metal plate 3 are placed on the raw material mixture 10 in this order. Here, the raw material mixture 10 sandwiched between the skin layers 21 becomes the core layer 22 of the wooden base material 20 .
Next, the metal plate 7 for adjusting the thickness is placed on the jig 1 for producing the wooden base material, and the raw material mixture 10 is spread from above the raw material mixture 10 with a metal weight 8 through the skin layer 21 and the releasable metal plate 3 . hold down.
Finally, the pressing machine top plate 9 set to predetermined conditions is heated and pressurized from above the raw material mixture 10 via the metal weight 8 to form the wooden base material 20 according to the present embodiment.

A releasable metal plate 3 as shown in FIG. 1 may be used when manufacturing the wooden base material 20 . As the material of the releasable metal plate 3, a film having releasability may be used, but if smoothness of the wooden base material 20 is required, a hard metal is more desirable. The material of the releasable metal plate 3 may be any material that does not adhere to the thermoplastic resin composition 12, the metal plate 2, and the metal weight 8. For example, a fluorine-coated material is preferably used. Alternatively, fine metal particles may be thermally sprayed onto the surface of the releasable metal plate 3 to provide unevenness. Forming unevenness on the surface of the releasable metal plate 3 improves releasability. In addition, by using both the concave-convex structure and the fluorine coating on the releasable metal plate 3, it is possible to further improve the releasability.

In this embodiment, instead of the releasable metal plate 3, a non-adhesive-treated metal plate 2 or a metal weight 8 may be used. That is, the surface of the metal plate 2 or the surface of the metal weight 8 may be subjected to a non-adhesive treatment that does not adhere to the thermoplastic resin composition 12, and it is more preferable if an uneven structure is formed by fluorine coating or thermal spraying. is.

(Modification)
In the present embodiment, regarding the method of manufacturing the wooden base material 20, first, two skin layers 21 are formed by heating and pressurizing, and then the raw material mixture 10 to be the core layer 22 is sandwiched between the two skin layers 21. Although the method of manufacturing the wooden base material 20 by heating and pressurizing again in a state has been described, the present invention is not limited to this.
For example, first, the raw material mixture 10 to be the skin layer 21, the raw material mixture 10 to be the core layer 22, and the raw material mixture 10 to be the skin layer 21 are laminated in this order, and then the raw material mixture 10 of two kinds and three layers is laminated. may be heated and pressurized at the same time to manufacture the wooden base material 20 .
As described above, in the method for manufacturing the wooden base material 20 according to the present embodiment, the skin layer 21 may be formed in the first heating and pressurizing step, and the core layer 22 may be formed in the second heating and pressurizing step. Alternatively, the skin layer 21 and the core layer 22 may be formed in the first heating and pressurizing step.

[Second embodiment]
A second embodiment will be described with reference to FIG.
A feature of the second embodiment is that a decorative material 14 is formed by laminating a design layer 13 having design properties on the wooden base material 20 according to the first embodiment described above with reference to FIG.
According to this embodiment, by laminating the design layer 13 on the wooden base material 20, it is possible to impart a design property.
That is, the wooden base material 20 can be practically used as a decorative material even when the base material is used alone. The design layer 13 such as paper or film may be laminated on the wooden base material 20 to form the decorative material 14 .

<Other effects>
(1) The wood base material 20 of the present embodiment includes a wood material 11 having at least one of powdery and chip-like shapes and a thermoplastic resin composition 12, and the wood base material 20 includes a skin layer. 21, a core layer 22 and a skin layer 21 are provided in sequence, and when the density of the skin layer 21 is ρs and the density of the core layer 22 is ρc, ρs/ρc is in the range of 1.0 or more and 2.4 or less, Each of ρs and ρc is within the range of 0.5 g/cm ³ or more and 1.2 g/cm ³ or less.
With such a configuration, the thermoplastic resin composition 12 is used as an adhesive instead of formaldehyde, which causes sick building syndrome, so that the wooden base material 20 can be provided without the emission of harmful substances.
Moreover, if ρs and ρc are within the above numerical ranges, it is possible to obtain a good wooden base material 20 that has a higher bending strength, a higher water resistance, and is less likely to be deformed.

(2) The wood base material 20 of the present embodiment is calculated using the following formula (1) from the absorption spectrum obtained by Fourier infrared spectroscopy for each of the skin layers 21 and the core layer 22. The normalized CH area of the skin layer 21 is A _S and the normalized CH area of the core layer 22 is A _C , A _S >A _C may hold.
Normalized C-H area=S _C-H /(S _O-H +S _C-OH ) Formula (1)
Here, in formula (1), S _C-H is the area value of the peak derived from either CH ₂ group or CH ₃ group in the region of 2700 cm ^{-1 or more and 3000 cm -1 or} less wavenumber, and S _O-H is the wavenumber. The area value of the peak derived from the OH group in the region of 3000 cm ⁻¹ or more and 3500 cm ⁻¹ or less, and S _C-OH is the area value of the peak derived from the C—OH group in the region of the wave number of 900 cm ⁻¹ or more and 1200 cm ⁻¹ or less. show.
With such a configuration, the thermoplastic resin composition 12 is used as an adhesive instead of formaldehyde, which causes sick building syndrome, so that the wooden base material 20 can be provided without the emission of harmful substances.
Further, if the normalized C—H areas A _S and A _C are within the above numerical ranges, the wood base material 20 has a higher bending strength, a higher water resistance, and a good wood base material 20 that is resistant to deformation. can be obtained.

(3) In the wooden base material 20 of the present embodiment, the skin layer 21, the core layer 22, and the thickness ratio of each layer in the skin layer 21 (skin layer:core layer:skin layer) is 1:0.1:1. It may be in the range of ~1:18:1.
With such a structure, since it is a multi-layer structure, it is possible to provide the wooden base material 20 having good bending strength and water resistance.

(4) In the wooden base material 20 of the present embodiment, the thickness of the skin layer 21 may be in the range of 2 mm or more and 19 mm or less.
To provide a woody base material 20 which sufficiently functions as a skin layer 21 with such a structure, does not increase the thickness of the whole woody base material 20 too much, and has no problem in workability during construction. can be done.

(5) In the wooden base material 20 of the present embodiment, each of the skin layer 21 and the core layer 22 has a mass ratio of the wooden material 11 and the thermoplastic resin composition 12 (wood material 11/thermoplastic resin composition 12) may be in the range of 95/5 to 70/30.
With such a configuration, it is possible to reliably provide the wooden base material 20 having a higher bending strength.

(6) In the wooden base material 20 of the present embodiment, the wooden material 11 may contain fungal bed as a raw material.
With such a configuration, it is possible to provide the wooden base material 20 that is beneficial in reducing the environmental load.

(7) In the wooden base material 20 of the present embodiment, the thermoplastic resin composition 12 may contain a polyolefin resin.
With such a configuration, it is possible to provide the wooden base material 20 having both excellent bending strength and water resistance. In addition, when biomass-derived polyethylene is included, it is possible to provide the wooden base material 20 that is beneficial in reducing the environmental load.

(8) In the wooden base material 20 of the present embodiment, the thermoplastic resin composition 12 may contain acid-modified polyolefin.
With such a configuration, it is possible to provide the wooden base material 20 having a higher bending strength.

(9) The decorative material 14 of the present embodiment is obtained by laminating a designable base material (design layer 13) having a design property on the wooden base material 20 of the present embodiment.
With such a configuration, it is possible to provide the decorative material 14 having better bending strength and water resistance than conventional decorative materials.

[Example]
Examples 1 to 23 and Comparative Examples 1 to 5 of the wooden base material according to the first embodiment of the present invention are described below. The present invention is not limited to Examples 1 to 23 below.

(Example 1)
The thermoplastic resin composition of Example 1 is a single high density polyethylene resin (HDPE) pellet. By mechanically pulverizing the resin pellets, a powdery thermoplastic resin composition was obtained.
As the woody material, a mushroom bed (average particle size: 2 mm) after harvesting mushrooms was washed and dried. The woody material and the thermoplastic resin composition were dry-mixed at a mass ratio (woody material/thermoplastic resin composition) of 85/15 to obtain a raw material mixture for a woody base material.
This raw material mixture was introduced into an aluminum mold and heat-pressed with a hot press to obtain one skin layer with a thickness of 4 mm (pressing conditions: 40 kgf/cm ² , 200° C. for 10 minutes, substrate Density: 0.8 g/cm ³ ). After obtaining another skin layer with a thickness of 4 mm in the same manner, the raw material mixture for the core layer was put between the two skin layers and the density of the core layer was adjusted to 0.8 g/cm ³ . Heated and pressurized. In this way, a three-layer wooden base material of Example 1 was obtained, in which a skin layer of 4 mm, a core layer of 4 mm, and a skin layer of 4 mm were sequentially laminated.

(Example 2)
In Example 2, the density of the skin layer was changed to 1.2 g/cm ³ and the density of the core layer was changed to 0.5 g/cm ³ .

(Example 3)
In Example 3, the density of the skin layer was changed to 0.5 g/cm ³ and the density of the core layer was changed to 0.5 g/cm ³ .

(Example 4)
In Example 4, the density of the skin layer was changed to 1.2 g/cm ³ and the density of the core layer was changed to 1.2 g/cm ³ .

(Example 5)
In Example 5, the density of the skin layer was changed to 0.9 g/cm ³ and the density of the core layer was changed to 0.75 g/cm ³ .

(Example 6)
In Example 6, the thickness of the skin layer was changed to 2 mm, and the thickness of the core layer was changed to 5 mm.

(Example 7)
In Example 7, the thickness of the skin layer was changed to 2 mm, and the thickness of the core layer was changed to 36 mm.

(Example 8)
In Example 8, the thickness of the skin layer was changed to 19 mm, and the thickness of the core layer was changed to 2 mm.

(Example 9)
The thermoplastic resin composition of Example 9 is a low-density polyethylene resin (LDPE) pellet alone. A wood base material was obtained in the same manner as in Example 1 except for the above.

(Example 10)
The thermoplastic resin composition of Example 10 is a linear low density polyethylene resin (LLDPE) pellet alone. A wood base material was obtained in the same manner as in Example 1 except for the above.

(Example 11)
The thermoplastic resin composition of Example 11 is a single polypropylene resin (PP) pellet. A wood base material was obtained in the same manner as in Example 1 except for the above.

(Example 12)
In Example 12, the mass ratio of the woody material and the thermoplastic resin composition (woody material/thermoplastic resin composition) of the skin layer was changed from "85/15" in Example 1 to "96/4". , to obtain a wood base material in the same manner as in Example 1.

(Example 13)
In Example 13, the mass ratio of the woody material and the thermoplastic resin composition (woody material/thermoplastic resin composition) in the skin layer was changed from "85/15" in Example 1 to "90/10". , to obtain a wood base material in the same manner as in Example 1.

(Example 14)
In Example 14, the mass ratio of the woody material and the thermoplastic resin composition (woody material/thermoplastic resin composition) for the skin layer was changed from "85/15" in Example 1 to "80/20". , to obtain a wood base material in the same manner as in Example 1.

(Example 15)
In Example 15, the mass ratio of the woody material and the thermoplastic resin composition (woody material/thermoplastic resin composition) in the skin layer was changed from "85/15" in Example 1 to "70/30". , to obtain a wood base material in the same manner as in Example 1.

(Example 16)
In Example 16, the mass ratio of the woody material to the thermoplastic resin composition (woody material/thermoplastic resin composition) for the skin layer was changed from "85/15" in Example 1 to "65/35". , to obtain a wood base material in the same manner as in Example 1.

(Example 17)
In Example 17, the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) for each of the skin layer and the core layer was changed from "85/15" in Example 1 to "70/ 30", and in the same manner as in Example 1 except for this, a wood base material was obtained.

(Example 18)
In Example 18, the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) for each of the skin layer and the core layer was changed from "85/15" in Example 1 to "65/ 35", and in the same manner as in Example 1 except for this, a wood base material was obtained.

(Example 19)
The components and weights of the thermoplastic resin composition of Example 19 are as follows.
(1) High-density polyethylene resin 97 parts by mass (2) Acid-modified polyolefin 3 parts by mass After heating and kneading the above (1) to (2) in a batch type kneading device, mechanical pulverization is performed to obtain heat in powder form. A plastic resin composition was obtained. Other than that, in the same manner as in Example 1, a wood base material of Example 19 was obtained.

(Example 20)
The components and masses of the thermoplastic resin composition of Example 20 are as follows.
(1) High-density polyethylene resin 80 parts by mass (2) Acid-modified polyolefin 20 parts by mass The above (1) to (2) are heated and kneaded in a batch type kneading device, and then mechanically pulverized to obtain heat in powder form. A plastic resin composition was obtained. Other than that, in the same manner as in Example 1, a wood base material of Example 20 was obtained.

(Example 21)
The components and masses of the thermoplastic resin composition of Example 21 are as follows.
(1) High-density polyethylene resin 60 parts by mass (2) Acid-modified polyolefin 40 parts by mass The above (1) to (2) are heated and kneaded in a batch type kneading device, and then mechanically pulverized to obtain heat in powder form. A plastic resin composition was obtained. Other than that, in the same manner as in Example 1, a wood base material of Example 21 was obtained.

(Example 22)
In Example 22, the thickness of the skin layer was changed to 2 mm, and the thickness of the core layer was changed to 40 mm.

(Example 23)
In Example 23, the thickness of the skin layer was changed to 20 mm, and the thickness of the core layer was changed to 2 mm.

(Comparative example 1)
In Comparative Example 1, the density of the skin layer was changed to 0.4 g/cm ³ and the density of the core layer was changed to 0.4 g/cm ³ .

(Comparative example 2)
In Comparative Example 2, the density of the skin layer was changed to 1.3 g/cm ³ and the density of the core layer was changed to 1.3 g/cm ³ .

(Comparative Example 3)
In Comparative Example 3, the density of the skin layer was changed to 1.3 g/cm ³ and the density of the core layer was changed to 0.5 g/cm ³ .

(Comparative Example 4)
In Comparative Example 4, the density of the skin layer was changed to 0.5 g/cm ³ and the density of the core layer was changed to 1.2 g/cm ³ .

(Comparative Example 5)
In Comparative Example 5, a wooden base material was obtained in the same manner as the so-called particle board.
Specifically, a drum-type blender is used to mix a wooden material and an adhesive, and the mixture is naturally dropped and spread without applying external force such as pressurization or suction pressure. A urea resin adhesive was used as the adhesive, and the wood material and the adhesive were mixed at a mass ratio (wood material/adhesive) of 85/15. Next, a wood base material was obtained by compacting the mixture.

(Evaluation of wooden base material)
Mechanical strength, water resistance, and substrate deformation were evaluated for Examples 1 to 23 and Comparative Examples 1 to 5 described above. Fourier-type infrared spectroscopy was performed by the following method.

(Fourier infrared spectroscopy)
For the Fourier infrared spectroscopic measurement, a Fourier infrared spectrometer (Spectrum Spotlight 400) manufactured by Perkin Elmer was used to obtain an absorption spectrum from 4000 cm ⁻¹ to 400 cm ⁻¹ . The normalized CC area of each of the skin layer and the core layer is calculated from the obtained absorption spectrum using the following formula (1).
Normalized C-H area=S _C-H /(S _O-H +S _C-OH ) Formula (1)
Here, in formula (1), S _C-H is the area value of the peak derived from either CH ₂ group or CH ₃ group in the region of 2700 cm ^{-1 or more and 3000 cm -1 or} less wavenumber, and S _O-H is the wavenumber. The area value of the peak derived from the OH group in the region of 3000 cm ⁻¹ or more and 3500 cm ⁻¹ or less, and S _C-OH is the area value of the peak derived from the C—OH group in the region of the wave number of 900 cm ⁻¹ or more and 1200 cm ⁻¹ or less. show.

(mechanical strength)
As for mechanical strength, bending strength was measured by a method based on JISA5908. The evaluation criteria for the mechanical strength with respect to the measured value (unit: N/mm ² ) were as follows based on the JIS standard values.
The evaluation criteria for mechanical strength are evaluated in four stages as follows: "◎", "〇", "△", and "×". ” was rejected.
◎: 15 or more (pass)
○: 13 or more and less than 15 (pass)
△: 8 or more and less than 13 (pass)
×: less than 8 (failed)

(water resistant)
The water resistance was determined by measuring the water absorption thickness swelling rate by a method based on JISA5908. Based on the JIS standard values, the water resistance evaluation criteria for the measured values (unit: %) are as follows.
The evaluation criteria for water resistance are evaluated in four stages of "◎", "〇", "△", and "×" as follows. ” was rejected.
◎: less than 5 (passed)
○: 5 or more and less than 8 (pass)
△: 8 or more and less than 12 (pass)
×: 12 or more (failed)

(Base material deformation)
Base material deformation is a state in which the surface of the base material is partially swollen, and is mainly caused by stagnation of gas generated inside the base material during pressing. Since the deformation of the base material is more clearly reflected by the state of the edge of the base material, the appearance of the edge of the base material was visually evaluated.
The evaluation criteria for base material deformation were evaluated in three stages of “◯”, “Δ”, and “×” as follows, and “◯” and “Δ” were accepted, and “×” was rejected.
〇: No voids (accepted)
△: Traces of voids (accepted)
×: There is a void (failed)

(Evaluation results)
The evaluation results of the wooden substrate are shown in Table 1 below.
The "raw material blending ratio" in Examples 1 to 23 and Comparative Examples 1 to 4 in the table indicates the (wood material/thermoplastic resin composition) mass ratio, and the "raw material blending ratio" in Comparative Example 5 in the table. indicates the (woody material/adhesive) mass ratio.

(Evaluation result of mechanical strength)
There were two failures in mechanical strength, Comparative Examples 1 and 4, which is considered to be due to the low density of the skin layer. Further, when Examples 1 to 23 and Comparative Examples 2 and 3 are compared, nine cases of Examples 3, 8 to 13, 21 and 23 include "Δ" in the evaluation results. In Example 3, it is considered that the density of the core layer and the skin layer was low. In Examples 8 and 23, the core layer was extremely thinner than the skin layer, and it is considered that the mechanical strength decreased. In Examples 9 to 11, LDPE, LLDPE, and PP were used as the base resins, respectively, so it is considered that the mechanical strength was lower than that of HDPE. In Examples 12 and 13, the ratio of the wooden material in the skin layer was large, and it is considered that the mechanical strength was lowered. In Example 21, 40 parts of acid-modified polyolefin was blended, and it is considered that the content of the base resin was relatively small, resulting in a decrease in mechanical strength.

(Evaluation result of water resistance)
Only Comparative Example 5 failed in water resistance. The conventional method using an adhesive is inferior in water resistance to Examples 1 to 23 of the present invention. Comparing Examples 1 to 23 and Comparative Examples 1 to 4, 19 cases of Examples 1 to 13, 22 to 23, and Comparative Examples 1 to 4 contain "△".
Examples 1 to 13, 22 to 23 and Comparative Examples 1 to 4 are material formulations that do not contain acid-modified polyolefin, and the thermoplastic resin composition is 15 parts or less, so it is considered that the water resistance was insufficient. be done. Compared with Example 1, Examples 19 to 21 are thought to have improved water resistance due to the acid-modified polyolefin contained. Examples 14 to 16 are examples in which the ratio of the thermoplastic resin composition was increased to 20 parts, 30 parts, and 35 parts only in the skin layer. . However, since the water resistance of the core layer is poor, the water resistance of the core layer is inferior to that of Examples 17 and 18 in which the ratio of the thermoplastic resin composition was increased to 30 parts and 35 parts.

(Evaluation result of substrate deformation)
Only Comparative Examples 2 and 3 failed in base material deformation. Examples 1 to 23 and Comparative Examples 1, 4 and 5 passed. Among them, Examples 2, 4, and 18 include "Δ" in the evaluation results.
It is considered that in Examples 2 and 4, only the skin layer or both the skin layer and the core layer have a density of 1.2 g/cm ³ . In Example 18, by containing 35 parts of the thermoplastic resin composition in both the skin layer and the core layer, the content of the thermoplastic resin composition was relatively increased, so that the base material deformation easily occurred. Conceivable.

(Comprehensive evaluation results)
As a comprehensive evaluation result, Examples 1 to 23 were "passed" in all evaluation items, and as is clear from Table 1, the wood base material of the present invention has excellent mechanical strength and water resistance. However, it was shown that there is no problem with base material deformation. In Examples 22 and 23, since the thickness of the wooden substrate exceeded 40 mm, the wooden substrate was heavy and the workability was deteriorated, but it was within a practically acceptable range.

DESCRIPTION OF SYMBOLS 1... Jig for preparing a wooden base material, 2... Metal plate (bottom surface), 3... Releasable metal plate, 7... Metal plate for thickness adjustment, 8... Metal weight, 9... Press machine top plate, 10... Raw material mixture 11 Wood material 12 Thermoplastic resin composition 13 Design layer 14 Decorative material 20 Wood substrate 21 Skin layer 22 Core layer

Claims (10)

A woody base material comprising a woody material having at least one of powdery and chip-like shapes and a thermoplastic resin composition,
The wooden base material has a skin layer, a core layer, and a skin layer in this order,
Where ρs is the density of the skin layer and ρc is the density of the core layer, ρs/ρc is in the range of 1.0 or more and 2.4 or less, and ρs and ρc are each 0.5 g/cm ³ or more and 1 .2 g/cm ³ or less of wood base material. For each of the skin layers and the core layer, the normalized CH area calculated using the following formula (1) from the absorption spectrum obtained by Fourier infrared spectroscopy is 0.07 or more. is within the range of 1.00 or less,
2. The woody material according to claim 1, wherein A _S >A _C , where A _S is the normalized C-H area of the skin layer and A _C is the normalized C-H area of the core layer. Base material.
Normalized C-H area=S _C-H /(S _O-H +S _C-OH ) Formula (1)
(Here, in formula (1), S _C-H is the area value of the peak derived from either a CH ₂ group or a CH ₃ group in the wavenumber region of 2700 cm ^-1 or more and 3000 cm ^-1 or less, and S _O-H is The area value of the peak derived from the OH group in the wavenumber region of 3000 cm ^-1 or more and 3500 cm ^-1 or less, and the area value of the peak derived from the _C -OH group in the wavenumber region of 900 cm ^-1 or more and 1200 cm ^-1 or less. indicates.) The skin layer, the core layer, and the thickness ratio of each layer (skin layer: core layer: skin layer) of the skin layer, the core layer, and the skin layer are within the range of 1:0.1:1 to 1:18:1. 3. The wooden substrate according to claim 1 or 2. 4. The wooden base material according to claim 1, wherein the skin layer has a thickness of 2 mm or more and 19 mm or less. Each of the skin layers and the core layer has a mass ratio of the woody material to the thermoplastic resin composition (woody material/thermoplastic resin composition) in the range of 95/5 to 70/30. The wood base material according to any one of claims 1 to 4, characterized in that The wooden base material according to any one of claims 1 to 5, wherein the wooden material contains fungal bed as a raw material. The wood base material according to any one of claims 1 to 6, wherein the thermoplastic resin composition contains a polyolefin resin. The wood base material according to any one of claims 1 to 7, wherein the thermoplastic resin composition contains an acid-modified polyolefin. A decorative material comprising the wooden base material according to any one of claims 1 to 8 and a designable base material laminated thereon. A method for producing a wood base material according to any one of claims 1 to 8, comprising:
a step of mixing a woody material having at least one of powdery and chip-like shapes with a thermoplastic resin composition to obtain a raw material mixture for a woody base;
A method for producing a wood base material, comprising heating and pressurizing the raw material mixture to form the wood base material.

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