JP7615718B2 - Wood base material, decorative material, and method for manufacturing wood base material - Google Patents

Description

The present invention relates to wood substrates, decorative materials, and methods for producing wood substrates.

Wood-based substrates are made by heating and pressurizing a mixture of wood materials such as wood flour, wood chips, and wood fibers with adhesive. These wood-based substrates are called particle boards or medium-density fiberboards depending on the type of wood material, and are used for a wide range of applications, such as undercoats for floors and walls, and for building materials and furniture.

Conventionally, urea resin adhesives, melamine resin adhesives, or phenol resin adhesives have been used as adhesives for wood substrates, along with hardeners containing formaldehyde. Formaldehyde is a harmful substance that causes sick house syndrome, so its emission from wood substrates has become a problem, and various measures to reduce the amount of emission have been considered. However, with conventional technology, 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 acids 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 [0017] and Figure 1 of Patent Document 2).

JP 2016-55620 A Patent No. 5553279

However, wood substrates using the above-mentioned conventional adhesives are not sufficient for practical use in terms of mechanical properties such as bending strength, water resistance, cold resistance, and heat resistance.
Therefore, an object of the present invention is to provide a wood base material that suppresses the emission of harmful substances such as formaldehyde that cause sick house syndrome and has practical water resistance, a decorative material that includes this wood base material, and a method for producing this wood base material.

The wood substrate according to one aspect of the present invention is a wood substrate comprising a wood material having at least one of a powdered and chipped form and a thermoplastic resin composition, the thermoplastic resin composition comprising a thermoplastic resin and an acid-containing resin containing at least one of a carboxylic acid and a carboxylic acid anhydride, the thermoplastic resin being a polyolefin resin having a melting point in the range of 120°C to 140°C, and the content of the acid-containing resin being in the range of 5 parts by mass to 50 parts by mass per 100 parts by mass of the thermoplastic resin.

The thermoplastic resin of the wood substrate according to one embodiment of the present invention is characterized in that it is a polyolefin resin having a density of 0.93 g/ ^cm3 or more.
The thermoplastic resin of the wood substrate according to one embodiment of the present invention is characterized in that it has a melt flow rate in the range of 1 g/10 min to 30 g/10 min when measured by Method A under conditions of a temperature of 190° C. and a load of 21.18 N in accordance with the method specified in JIS K7210-1:2014.

The wood base material according to one embodiment of the present invention is characterized in that the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) is within the range of 95/5 to 70/30.
In one aspect of the present invention, the acid-containing resin in the wood substrate is a maleic anhydride-modified polyolefin.

In one embodiment of the present invention, the wood substrate is characterized in that the thermoplastic resin composition further contains an organic peroxide, and the content of the organic peroxide is in the range of 0.01 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the thermoplastic resin.
A wood base material according to one aspect of the present invention is characterized in that the wood material contains a mushroom bed as a raw material.
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.

A method for producing a wood substrate according to one aspect of the present invention includes a step of forming a wood substrate by heating and pressurizing a raw material mixture containing a wood material having at least one of a powdered and chipped shape and a powdered thermoplastic resin composition, the thermoplastic resin composition containing a thermoplastic resin and an acid-containing resin containing at least one of a carboxylic acid and a carboxylic acid anhydride, the thermoplastic resin being a polyolefin resin having a melting point in the range of 120°C to 140°C, and the content of the acid-containing resin being in the range of 5 parts by mass to 50 parts by mass per 100 parts by mass of the thermoplastic resin.

According to one aspect of the present invention, it is possible to provide a wood substrate that suppresses the emission of harmful substances such as formaldehyde that cause sick house syndrome and has practical water resistance, a decorative material that includes the wood substrate, and a method for manufacturing the wood substrate.

FIG. 2 is a schematic diagram illustrating a manufacturing process of a wood base material according to the first embodiment of the present invention. 4 is a schematic cross-sectional view showing the configuration of a decorative material according to a second embodiment of the present invention. FIG.

[First embodiment]
1 shows a wood substrate 20 according to a first embodiment of the present invention. The wood substrate 20 is called a particle board, a medium density fiberboard, or the like depending on the type of wood material 11, and is used for a wide range of applications such as underlayment for floors and walls, fittings, and furniture.
As shown in Fig. 1, the wood substrate 20 is formed by heating and pressurizing a raw material mixture 10 containing a wood material 11 having at least one of a powdered and chipped shape and a powdered thermoplastic resin composition 12. The wood substrate 20 does not contain harmful substances such as formaldehyde that cause sick house syndrome. Therefore, it is possible to suppress the emission of harmful substances such as formaldehyde that cause sick house syndrome from inside the wood substrate 20.
The wood material 11 and the thermoplastic resin composition 12 that constitute the wood substrate 20 will be described below.

(Wood Materials 11)
The wood material 11 has at least one of a powder and chip shape. Here, there is generally no definition of size or shape for "powder" and "chip shape." In this embodiment, the size (average particle size) is generally in the range of several tens of microns to several centimeters. The average particle size of the wood material 11 in this embodiment is, for example, in the range of 10 μm to 10 mm.

Examples of the wood material 11 include wood powder, 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 be used as the wood material 11, such as bamboo, hemp, coconut fiber, and walnut shells, as long as they contain cellulose components similar to wood.

As a raw material for the wood material 11, for example, used mushroom beds, which are generated in large quantities during mushroom cultivation, are suitable. The mushroom beds are a culture medium used in mushroom cultivation, and are 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.

In this embodiment, when a mushroom bed is used as the wood material 11, the ratio of the mushroom bed to the total volume of the wood material 11 may be within the range of 1% to 100%, and preferably within the range of 50% to 100%. If the mushroom bed content is within the above numerical range, the production cost can be reduced compared to when ordinary wood chips are used.

(Mass ratio of wood material 11 to thermoplastic resin composition 12)
The mass ratio of the wood material 11 to the thermoplastic resin composition 12 (wood material/thermoplastic resin composition) is preferably within the range of 95/5 to 70/30.
If the content of the wood material 11 is greater than the above-mentioned value (95/5), sufficient mechanical strength cannot be imparted to the wood base material 20. On the other hand, if the content of the wood material 11 is less than the above-mentioned value (70/30), the wood base material 20 is likely to deform when heated and pressed, which is not preferable.

(Thermoplastic resin composition 12)
The thermoplastic resin composition 12 is in the form of powder and is a composition containing a thermoplastic resin and an acid-containing resin. The average particle size of the thermoplastic resin composition 12 in this embodiment is For example, the thickness is in the range of 10 μm to 1 mm.

(Thermoplastic resin)
The thermoplastic resin is preferably a polyolefin resin, more preferably polypropylene or polyethylene, and even more preferably polyethylene, because it can impart mechanical strength, heat resistance, and cold resistance to the wood substrate 20 and is less likely to deform when heated and pressurized. The thermoplastic resin is more preferably a polyolefin resin having a density of 0.93 g/ ^cm3 or more and a melting point in the range of 120°C to 140°C, and even more preferably a polyolefin resin having a density of 0.94 g/cm3 ^or more and a melting point in the range of 125°C to 135°C.

If the density is less than 0.93 g/cm ³ , the heat resistance of the wood base material 20 may decrease, which is undesirable.
If the melting point is less than 120° C., the wood base material 20 cannot have sufficient heat resistance and the mechanical strength is often reduced, which is not preferable. On the other hand, if the melting point is more than 140° C., the wood base material 20 cannot have sufficient cold resistance and is likely to deform when heated and pressed, which is not preferable.

In this embodiment, the upper limit of the density of the thermoplastic resin is not limited, but is 1.00 g/cm3 ^or less, and preferably 0.97 g/cm3 ^or less. This is because thermoplastic resins with a density exceeding 1.00 g/ ^cm3 do not substantially exist, and even if they exist, they are extremely difficult to obtain.

In addition, if the wood substrate 20 contains a thermoplastic resin, the high water resistance of the thermoplastic resin can impart excellent water resistance to the entire wood substrate 20. Specifically, since the thermoplastic resin with excellent water resistance covers the surface of the wood material 11, the water absorption and expansion of the entire wood substrate 20 can be suppressed, and excellent water resistance can be imparted to the entire wood substrate 20.

In addition to the above-mentioned polyethylene and polypropylene, examples of polyolefin resins that can be used in this embodiment include polyolefin resins such as polymethylpentene, polybutene, ethylene-propylene copolymer, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer, as well as polyolefin-based resins such as olefin-based copolymer resins such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-(meth)acrylic acid (ester) copolymer, and ethylene-unsaturated carboxylic acid copolymer metal neutralized product (ionomer), or mixtures, copolymers, composites, laminates, and the like of two or more of these.

Examples of polypropylene-based resins that are homopolymers or copolymers mainly composed of propylene include homopolypropylene resins, random polypropylene resins, block polypropylene resins, etc., or resins obtained by appropriately blending these resins with atactic polypropylene. Copolymers containing olefin monomers other than propylene are also acceptable, and examples thereof include propylene-α-olefin copolymers having polypropylene crystal parts and containing 15 mol% or more of one or more comonomers of α-olefins having 2 to 20 carbon atoms other than propylene, preferably ethylene, butene-1, 4-methylpentene-1, hexene-1, or octene-1. Modifiers such as low-density polyethylene, ethylene-α-olefin copolymers, ethylene-propylene copolymer rubber, ethylene-propylene-non-conjugated diene copolymer rubber, styrene-butadiene copolymers, or hydrogenated products thereof, which are usually used to soften polypropylene-based resins, can be appropriately added. Here, the above-mentioned "main component" refers to a state in which the propylene component accounts for 50 mass % or more of the total mass of the polypropylene-based resin.
Among the above-mentioned materials, high density polyethylene (HDPE) is particularly preferable as the polyolefin resin of this embodiment in terms of density and melting point.

In addition, the melt flow rate of the thermoplastic resin is preferably in the range of 1 g/10 min to 30 g/10 min when measured by Method A under conditions of a temperature of 190° C. and a load of 21.18 N in the method specified in JIS K7210-1:2014.
If the melt flow rate is less than 1 g/10 min, it is not preferable because it is difficult to blend with wood substrates, etc. If the melt flow rate exceeds 30 g/10 min, it is not preferable because it becomes difficult to mold the composition by applying heat and pressure.

(Acid-containing resin)
The acid-containing resin used is a resin containing at least one of a carboxylic acid and a carboxylic acid anhydride in order to improve the adhesiveness between the wood material 11 and the thermoplastic resin.
Examples of the acid-containing resin that can be used include maleic anhydride-modified polyolefins such as maleic anhydride-modified polyethylene and maleic anhydride polypropylene, ethylene (meth)acrylic acid copolymers, and itaconic anhydride-modified polyethylene. From the viewpoint of compatibility with the wood material 11 containing cellulose (in terms of adhesiveness), maleic anhydride-modified polyolefins are preferred, and maleic anhydride-modified polyethylene is even more preferred.

(Amount of Acid-Containing Resin Added)
The amount of the acid-containing resin added is preferably in the range of 5 parts by mass to 50 parts by mass, and more preferably in the range of 10 parts by mass to 40 parts by mass, per 100 parts by mass of the thermoplastic resin.
If the amount of the acid-containing resin added is less than 5 parts by mass, the adhesion between the wood material 11 and the thermoplastic resin will be insufficient, making it impossible to impart sufficient strength to the wood substrate 20. If the amount of the acid-containing resin added is more than 50 parts by mass, the strength of the wood substrate 20 will often decrease, which is not preferable.

When the adhesion between the wood material 11 and the thermoplastic resin is insufficient, the entire surface of the wood chips and other components that make up the wood material 11 cannot be covered with thermoplastic resin, and moisture that has penetrated into the wood material 11 causes the entire wood base material 20 to absorb water and expand, reducing the water resistance of the entire wood base material 20.

(Organic peroxides)
The thermoplastic resin composition 12 may further contain an organic peroxide.
The organic peroxide may be used for radical crosslinking between thermoplastic resins in the heating and pressurizing step of the raw material mixture 10. In addition, if a material having radical crosslinking properties is used for the acid-containing resin, crosslinking can be caused between the acid-containing resin and the thermoplastic resin by adding an organic peroxide to the thermoplastic resin composition 12. When radical crosslinking is formed between thermoplastic resins or between the acid-containing resin and the thermoplastic resin, the mechanical strength of the entire wood substrate 20 is improved due to the crosslinked structure.

The organic peroxide is not particularly limited, and may be appropriately selected from existing materials such as peroxyketals, dialkyl peroxides, diacyl peroxides, and peroxyesters, taking into consideration their reactivity and stability.
The organic peroxide is a type of radical crosslinking agent, and examples thereof include hydroperoxides, diacyl peroxides, peroxydicarbonates, peroxyesters, peroxycarbonates, dialkyl peroxides, and ketone peroxides.

(Amount of organic peroxide added)
The amount of the organic peroxide added is desirably within the range of 0.01 parts by mass to 3 parts by mass relative to 100 parts by mass of the thermoplastic resin.
If the amount of organic peroxide added is less than 0.01 parts by mass, the reactivity of the raw material mixture when heated and pressurized is insufficient, and therefore the strength of the wood substrate is not improved. If the amount of organic peroxide added is more than 3 parts by mass, the amount of decomposition products during the reaction increases, which may cause deformation of the wood substrate, and is therefore undesirable.

Furthermore, by adding an organic peroxide to the thermoplastic resin composition 12, it becomes possible to form a three-dimensional network (bonds) by radical crosslinking between the thermoplastic resin, the acid-containing resin, and the wood material 11. This improves the mechanical strength of the entire wood substrate 20.

(Method of Preparing Thermoplastic Resin Composition 12)
The thermoplastic resin composition 12 containing an organic peroxide and an acid-containing resin can be produced by various known methods. For example, the acid-containing resin and the organic peroxide can be heated and kneaded together with the thermoplastic resin using a single-axis kneader or a batch kneader, and then powdered by a method such as mechanical crushing or freeze crushing.

(Production method by heating and pressurizing raw material mixture 10)
The raw material mixture 10 can be heated and pressurized by various known methods, but press molding using a mold is preferred.
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, but if the heating temperature exceeds 250° C., significant thermal degradation of the wood material 11 may occur. The pressing pressure is usually within the range of 10 kgf/ ^cm2 to 400 kgf/ ^cm2 , and an appropriate value is used depending on the desired density of the wood base material.

The density and shape of the wood substrate 20 obtained as described above are appropriately determined depending on the application, but the density is preferably in the range of 0.5 g/ ^cm3 to 1.2 g/ ^cm3 , and more preferably in the range of 0.6 g/ ^cm3 to 1.1 g/ ^cm2 . If the density of the wood substrate 20 is within the above numerical range, the mechanical strength of the entire wood substrate 20 is further improved. Furthermore, if the density of the wood substrate 20 is within the above numerical range, the pore volume contained in the entire wood substrate 20 is reduced, and therefore the heat resistance and cold resistance are also improved.

[Second embodiment]
The second embodiment will be described with reference to FIG.
The second embodiment is a decorative material 30 in which a decorative substrate 31 having a design is laminated on the wood substrate 20 according to the first embodiment described above with reference to FIG.
According to this embodiment, by laminating the decorative substrate 31 on the wood substrate 20, a decorative feature can be imparted.

That is, the wood base material 20 can be used as a decorative material by itself, but in order to impart even more excellent design to the wood base material 20, a decorative base material 31 such as paper or film with a design such as a picture may be laminated onto the wood base material 20 as shown in FIG. 2 to form the decorative material 30.

[Effects of this embodiment]
The wood substrate 20 of this embodiment comprises a wood material 11 having at least one of a powder and chip form, and a thermoplastic resin composition 12. The thermoplastic resin composition 12 contains a thermoplastic resin and an acid-containing resin containing at least one of a carboxylic acid and a carboxylic acid anhydride. The thermoplastic resin is a polyolefin resin having a melting point in the range of 120°C or more and 140°C or less, and the content of the acid-containing resin is in the range of 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the thermoplastic resin.

With this configuration, the wood base material 20 does not contain harmful substances that cause sick house syndrome, such as formaldehyde, and therefore the emission of harmful substances that cause sick house syndrome, such as formaldehyde, can be suppressed. In addition, since the wood base material 20 contains a thermoplastic resin, the high water resistance of the thermoplastic resin can impart excellent water resistance to the wood base material 20.

The thermoplastic resin of the present embodiment may be a polyolefin resin having a density of 0.93 g/cm ³ or more.
With this configuration, the heat resistance of the wood base material 20 can be further improved.

In addition, the thermoplastic resin of this embodiment has a melt flow rate in the range of 1 g/10 min or more and 30 g/10 min or less when measured by Method A under conditions of a temperature of 190 ° C. and a load of 21.18 N in the method specified in JIS K7210-1:2014. It may have a melt flow rate of 1 g/10 min or more and 30 g/10 min or less.
With such a structure, the thermoplastic resin easily blends with the wood substrate and the like, facilitating molding by heating and pressurization.

The mass ratio of the wood material 11 to the thermoplastic resin composition 12 in this embodiment (wood material/thermoplastic resin composition) may be within a range of 95/5 to 70/30.
With this configuration, it is possible to impart sufficient mechanical strength to the wood base material 20 while reducing deformation of the wood base material 20 when heated and pressurized.

The acid-containing resin of the present embodiment may be a maleic anhydride-modified polyolefin.
With this configuration, the adhesion between the wood material 11 and the thermoplastic resin can be further improved.

In addition, the thermoplastic resin composition 12 of this embodiment further contains an organic peroxide, and the content of the organic peroxide may be in the range of 0.01 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the thermoplastic resin.
Such a configuration improves the strength of the wood substrate 20 and reduces deformation of the wood substrate 20. Furthermore, such a configuration makes it possible to form a three-dimensional network (bonds) by radical crosslinking between the thermoplastic resin, the acid-containing resin, and the wood material 11, thereby improving the mechanical strength of the wood substrate 20.

Furthermore, the wood material 11 of this embodiment may contain a mushroom bed as a raw material.
With this configuration, the wood material 11 can be manufactured in an environmentally friendly manner.

The decorative material 30 of this embodiment may be formed by laminating a decorative substrate 31 onto a wood substrate 20 .
With this configuration, the design of the wood base material 20 can be improved.

The manufacturing method of the wood substrate 20 of this embodiment includes a step of forming the wood substrate 20 by heating and pressurizing a raw material mixture 10 containing a wood material 11 having at least one of a powdered and chipped shape and a powdered thermoplastic resin composition 12, the thermoplastic resin composition 12 containing a thermoplastic resin and an acid-containing resin containing at least one of a carboxylic acid and a carboxylic acid anhydride, the thermoplastic resin being a polyolefin resin having a melting point in the range of 120°C to 140°C, and the content of the acid-containing resin being in the range of 5 parts by mass to 50 parts by mass per 100 parts by mass of the thermoplastic resin.

With this configuration, the manufactured wood base material 20 does not contain harmful substances such as formaldehyde that cause sick house syndrome, and therefore the emission of harmful substances such as formaldehyde that cause sick house syndrome can be suppressed. In addition, since the manufactured wood base material 20 contains a thermoplastic resin, the high water resistance of the thermoplastic resin can impart excellent water resistance to the wood base material 20.

[Example]
Below, examples 1 to 28 of wood base materials according to the first embodiment of the present invention and comparative examples 1 to 4 will be described. Note that the present invention is not limited to the following examples 1 to 28.

Example 1
The components and masses of the thermoplastic resin composition of Example 1 are as follows.
(1) High density polyethylene resin 100 parts by mass (melting point 129°C, density 0.952 g/ ^cm3 , MFR (190°C, under a load of 2.16 kg) 21 g/10 min)
(2) Maleic anhydride modified polyethylene: 25 parts by weight (3) Organic peroxide (peroxyketal): 1 part by weight The above (1) to (3) were heated and kneaded in a batch kneader, and then mechanically pulverized to obtain a powdered thermoplastic resin composition.

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 base material.
This raw material mixture was introduced into an aluminum mold and heated and pressed in a hot press to obtain the wood substrate of this example (pressing conditions: 40 kgf/cm ² , 200° C. for 10 minutes, substrate thickness: 10 mm, substrate density: 0.8 g/cm ³ ).

As described above, the manufacturing process of the wood base material of this embodiment does not use harmful substances such as formaldehyde that cause sick house syndrome. Therefore, the wood base material of this embodiment can suppress the emission of harmful substances such as formaldehyde that cause sick house syndrome.

Example 2
In Example 2, the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was changed from "85/15" in Example 1 to "70/30," and otherwise a wood base material was obtained in the same manner as in Example 1.

Example 3
In Example 3, the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was changed from "85/15" in Example 1 to "95/5," and otherwise a wood base material was obtained in the same manner as in Example 1.

Example 4
In Example 4, the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was changed from "85/15" in Example 1 to "60/40," and otherwise a wood base material was obtained in the same manner as in Example 1.

Example 5
In Example 5, the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was changed from "85/15" in Example 1 to "97/3," and otherwise a wood base material was obtained in the same manner as in Example 1.

Example 6
In Example 6, the (1) high-density polyethylene in the thermoplastic resin composition was changed to a linear low-density polyethylene having a melting point of 124°C, a density of 0.940 g/ ^cm3 , and an MFR (190°C, under a load of 2.16 kg) of 20 g/10 min, and the rest of the wood base material was obtained in the same manner as in Example 1.

(Example 7)
In Example 7, the (1) high-density polyethylene in the thermoplastic resin composition was changed to a linear low-density polyethylene having a melting point of 120°C, a density of 0.919 g/ ^cm3 , and an MFR (190°C, under a load of 2.16 kg) of 20 g/10 min, and the rest of the wood base material was obtained in the same manner as in Example 1.

(Example 8)
In Example 8, a wood base material was obtained in the same manner as in Example 1, except that the amount of (2) the acid-containing resin in the thermoplastic resin composition was changed to 5 parts.
(Example 9)
In Example 9, a wood base material was obtained in the same manner as in Example 1, except that the amount of (2) the acid-containing resin in the thermoplastic resin composition was changed to 50 parts.

(Example 10)
In Example 7, a wood base material was obtained in the same manner as in Example 1, except that (1) the high-density polyethylene in the thermoplastic resin composition was changed to a high-density polyethylene having a melting point of 130°C, a density of 0.960 g/ ^cm3 , and an MFR (190°C, under a load of 2.16 kg) of 13 g/10 min.

Example 11
In Example 11, a wood base material was obtained in the same manner as in Example 1, except that the (3) organic peroxide in the thermoplastic resin composition was not blended.
Example 12
In Example 12, a wood base material was obtained in the same manner as in Example 1, except that 5 parts of (3) an organic peroxide was added to the thermoplastic resin composition.

Example 13
In Example 13, a wood substrate was obtained in the same manner as in Example 1, except that (1) the high-density polyethylene in the thermoplastic resin composition was changed to a high-density polyethylene having a melting point of 130°C, a density of 0.945 g/ ^cm3 , and an MFR (190°C, under a load of 2.16 kg) of 0.05 g/10 min.

(Example 14)
In Example 14, a wood base material was obtained in the same manner as in Example 1, except that (1) the high-density polyethylene in the thermoplastic resin composition was changed to a high-density polyethylene having a melting point of 133°C, a density of 0.960 g/ ^cm3 , and an MFR (190°C, under a load of 2.16 kg) of 40 g/10 min.

(Example 15)
In Example 15, (1) the high-density polyethylene in the thermoplastic resin composition was changed to a low-density polyethylene with a melting point of 122°C, a density of 0.922 g/ ^cm3 , and an MFR (190°C, under a load of 2.16 kg) of 0.6 g/10 min, (2) the acid-containing resin was changed to "maleic anhydride polypropylene" and its amount was set to 5 parts, (3) no organic peroxide was added, the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was set to "60/40", and the wood material was changed to "wood chips (average particle size 2 mm)", and otherwise a wood base material was obtained in the same manner as in Example 1.

(Example 16)
In Example 16, a wood base material was obtained in the same manner as in Example 15, except that (1) the low-density polyethylene in the thermoplastic resin composition was changed to a low-density polyethylene having a melting point of 122°C and (2) the amount of the acid-containing resin was changed to 50 parts.

(Example 17)
In Example 17, the (1) low-density polyethylene in the thermoplastic resin composition was changed to a low-density polyethylene having a melting point of 131°C, a density of 0.949 g/ ^cm3 , and an MFR (190°C, under a load of 2.16 kg) of 0.05 g/10 min, and the rest of the wood base material was obtained in the same manner as in Example 15.

(Example 18)
In Example 18, the (1) low-density polyethylene in the thermoplastic resin composition was changed to a low-density polyethylene having a melting point of 131°C, a density of 0.949 g/ ^cm3 , and an MFR (190°C, under a load of 2.16 kg) of 0.05 g/10 min, and the rest of the wood base material was obtained in the same manner as in Example 16.

(Example 19)
In Example 19, the (1) low-density polyethylene in the thermoplastic resin composition was changed to a low-density polyethylene having a density of 0.923 g/cm ³ and an MFR (190°C, under a load of 2.16 kg) of 1.00 g/10 min, and the rest of the wood base material was obtained in the same manner as in Example 15.

(Example 20)
In Example 20, the (1) low-density polyethylene in the thermoplastic resin composition was changed to a low-density polyethylene having a melting point of 123°C, a density of 0.923 g/ ^cm3 , and an MFR (190°C, under a load of 2.16 kg) of 30.00 g/10 min, and the rest of the wood base material was obtained in the same manner as in Example 16.

(Example 21)
In Example 21, a wood base material was obtained in the same manner as in Example 15, except that the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was 95/5.
(Example 22)
In Example 22, a wood base material was obtained in the same manner as in Example 16, except that the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was set to "70/30."

(Example 23)
In Example 23, a wood base material was obtained in the same manner as in Example 15, except that (2) the acid-containing resin in the thermoplastic resin composition was changed to “maleic anhydride-modified polyethylene.”
(Example 24)
In Example 24, a wood base material was obtained in the same manner as in Example 16, except that (2) the acid-containing resin in the thermoplastic resin composition was changed to “maleic anhydride-modified polyethylene.”

(Example 25)
In Example 25, a wood base material was obtained in the same manner as in Example 15, except that the amount of (2) organic peroxide (peroxyketal) in the thermoplastic resin composition was 0.01 part.
(Example 26)
In Example 26, a wood base material was obtained in the same manner as in Example 16, except that the amount of (2) organic peroxide (peroxyketal) in the thermoplastic resin composition was 3.00 parts.

(Example 27)
In Example 27, a wood base material was obtained in the same manner as in Example 15, except that the wood material was changed to a "harvested mushroom bed (average particle size 2 mm)".
(Example 28)
In Example 28, a wood base material was obtained in the same manner as in Example 16, except that the wood material was changed to a "harvested mushroom bed (average particle size 2 mm)".

(Comparative Example 1)
In Comparative Example 1, a wood base material was obtained in the same manner as in Example 1, except that (1) the high density polyethylene in the thermoplastic resin composition was replaced with homopolypropylene having a melting point of 163° C. and a density of 0.910 g/cm ³ .

(Comparative Example 2)
In Comparative Example 2, the (1) high-density polyethylene in the thermoplastic resin composition was replaced with a low-density polyethylene having a melting point of 106°C, a density of 0.918 g/ ^cm3 , and an MFR (190°C, under a load of 2.16 kg) of 7 g/10 min, and the rest of the wood base material was obtained in the same manner as in Example 1.

(Comparative Example 3)
In Comparative Example 3, a wood base material was obtained in the same manner as in Example 1, except that the amount of (2) the acid-containing resin in the thermoplastic resin composition was 60 parts.
(Comparative Example 4)
In Comparative Example 4, a wood base material was obtained in the same manner as in Example 1, except that the amount of (2) the acid-containing resin in the thermoplastic resin composition was 3 parts.

(Evaluation of wood-based materials)
The physical properties of the wood base material were evaluated based on the following five points: (1) mechanical strength, (2) water resistance, (3) substrate deformation, (4) cold resistance, and (5) heat resistance.
(Mechanical strength)
The mechanical strength was measured as bending strength by a method conforming to JIS A 5908. The evaluation criteria for mechanical strength with respect to the measured values (unit: N/mm ² ) were set as follows, based on the standard values of the JIS.
The mechanical strength was evaluated according to the following three-level scale of "good", "defective", and "bad", with "good" and "defective" being acceptable and "bad" being unacceptable.
○: 13 or more (pass)
△: 8 or more but less than 13 (pass)
×: Less than 8 (failed)

(water resistance)
The water resistance was measured by measuring the water absorption thickness swelling rate according to a method in accordance with JIS A 5908. The evaluation criteria for water resistance for the measured value (unit: %) were set as follows, based on the standard values of the JIS.
The water resistance was evaluated according to the following three-level scale of "good", "defective" and "bad", with "good" and "defective" representing pass and "bad" representing fail.
○: Less than 8 (pass)
△: 8 or more but less than 12 (pass)
×: 12 or more (fail)

(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 the substrate deformation were as follows: 3-level evaluation of "good", "defective", and "bad", with "good" and "defective" representing pass and "bad" representing fail.
○: No voids (passed)
△: Traces of voids (passed)
×: Voids present (failed)

(Cold resistance)
For cold resistance, the specimen was placed in a 5° C. environment for 1 hour, and then the bending strength was measured by a method conforming to JIS A 5908. The evaluation criteria for mechanical strength with respect to the measured value (unit: N/mm ² ) were set as follows, based on the standard values of the JIS.
The mechanical strength was evaluated according to the following three-level scale of "good", "defective", and "bad", with "good" and "defective" being acceptable and "bad" being unacceptable.
○: 13 or more (pass)
△: 8 or more but less than 13 (pass)
×: Less than 8 (failed)

(Heat resistance)
Heat resistance was measured by placing the sample in a 70° C. environment for 1 hour, and then measuring the bending strength by a method conforming to JIS A 5908. The evaluation criteria for mechanical strength with respect to the measured value (unit: N/mm ² ) were set as follows, based on the standard values of the JIS.
The mechanical strength was evaluated according to the following three-level scale of "good", "defective", and "bad", with "good" and "defective" being acceptable and "bad" being unacceptable.
○: 8 or more (pass)
△: 3 or more but less than 8 (pass)
×: Less than 3 (failed)

(Evaluation Results) The evaluation results of the wood base materials are as shown in Table 1 below.
In the table, "Amount of acid-containing resin" and "Amount of organic peroxide" respectively indicate the amount of each component per 100 parts by mass of thermoplastic resin, "Blending ratio" indicates "wood material/thermoplastic resin composition," and "MFR" indicates the value measured under the conditions of JIS K7210:2014, 190°C, 2.16 kg.

Examples 1 to 28 were "passed" in all five physical property evaluations, while Comparative Examples 1 to 4 included one or more failures.

(Mechanical strength evaluation results)
The three comparative examples, Comparative Example 2, Comparative Example 3 and Comparative Example 4, failed in terms of mechanical strength.
It is presumed that the cause is that low-density polyethylene was used as the thermoplastic resin in Comparative Example 2, that the amount of "acid-containing resin" added was too large in Comparative Example 3, and that the amount of "acid-containing resin" added was too small in Comparative Example 4. In other words, it is presumed that the mechanical strength decreases depending on the type of "thermoplastic resin" and whether the "acid-containing resin" is used in an excessive or small amount.

(Water resistance evaluation results)
Although there were no samples that failed the water resistance test, Examples 8, 11, 15 to 25, 27, and 28, and Comparative Example 4 were relatively poor in water resistance even among the samples that passed the test.
It is presumed that the water resistance is reduced due to the small amount of "acid-containing resin" in Examples 8, 15, 17, 19, 21, 23, 25, 27, and Comparative Example 4. It is presumed that the water resistance is reduced due to the small amount of "acid-containing resin" in Examples 11, 16, 18, 20, 22, 24, and 28 because "organic peroxide" is not used.

(Evaluation results of substrate deformation)
Only one example, Comparative Example 1, failed in terms of substrate deformation.
It is presumed that this is because in Comparative Example 1, the "thermoplastic resin" was a polyolefin resin with a melting point of 140°C or higher.

(Cold resistance)
Only one sample, Comparative Example 1, failed the cold resistance test.
It is presumed that this is because in Comparative Example 1, the "thermoplastic resin" was a polyolefin resin with a melting point of 140°C or higher.

(Heat resistance)
Only one example, Comparative Example 2, failed in terms of heat resistance.
It is presumed that this is because in Comparative Example 2, the "thermoplastic resin" was a polyolefin resin with a melting point of 120°C or lower.

(Evaluation Results of Examples 1 to 28)
The evaluation results for Examples 1 to 28 were "pass" for all five physical property evaluations.
The evaluation results for mechanical strength including "Δ" were given to 18 examples, namely, Examples 5, 8, 9, and 14 to 28.
In Example 5, it is presumed that the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was changed from "85/15" in Example 1 to "97/3". In Examples 8, 15, 17, 19, 21, 23, 25, and 27, it is presumed that the amount of the acid-containing resin was reduced from 25 parts by mass in Example 1 to 5 parts by mass. In Examples 9, 16, 18, 20, 22, 24, 26, and 28, it is presumed that the amount of the acid-containing resin was increased from 25 parts by mass in Example 1 to 50 parts by mass. In Example 14, it is presumed that the MFR is high.

Fifteen examples, namely, Examples 8, 11, 15 to 25, 27, and 28, had a water resistance evaluation result of "△".
In Examples 8, 15, 17, 19, 21, 23, 25, and 27, it is presumed that the cause is that the amount of the acid-containing resin was reduced from 25 parts by mass in Example 1 to 5 parts by mass. In Examples 11, 16, 18, 20, 22, 24, and 28, it is presumed that the cause is that the amount of the organic peroxide was reduced from 1 part by mass in Example 1 to 0 part by mass.

Seventeen examples, namely, Examples 4, 12, 13, and 15 to 28, include a grade of "△" in the evaluation results for substrate deformation.
In Examples 4, 15 to 20, and 23 to 28, it is presumed that the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was changed from "85/15" in Example 1 to "60/40". In Example 22, it is presumed that the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was changed from "85/15" in Example 1 to "70/30". In Example 12, it is presumed that the amount of organic peroxide was increased from 1 part by mass in Example 1 to 5 parts by mass. In Example 13, it is presumed that the MFR of the thermoplastic resin was changed from 21 g/10 min in Example 1 to 0.05 g/10 min. In Example 21, it is presumed that the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) was changed from "85/15" in Example 1 to "95/5". That is, it is considered that in Example 21, the content of the thermoplastic resin composition was small, which caused deformation of the substrate.

(Overall evaluation results)
As a comprehensive evaluation result, all five physical property evaluations for Examples 1 to 28 were "passed." As is clear from Table 1, it was shown that the wood base material of the present invention has excellent mechanical strength, water resistance, cold resistance, and heat resistance, and there is no problem with substrate deformation.

10 Raw material mixture 11 Wood material 12 Thermoplastic resin composition 20 Wood substrate 30 Decorative material 31 Design substrate

Claims (15)

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 thermoplastic resin composition contains a thermoplastic resin and an acid-containing resin containing at least one of a carboxylic acid and a carboxylic acid anhydride,
The thermoplastic resin is a polyolefin resin having a melting point in the range of 120° C. or more and 140° C. or less,
A wood substrate comprising the acid-containing resin in an amount ranging from 5 parts by mass to 50 parts by mass relative to 100 parts by mass of the thermoplastic resin. 2. The wood base material according to claim 1, wherein the thermoplastic resin is a polyolefin resin having a density of 0.93 g/ ^cm3 or more. The wood substrate according to claim 1 or 2, characterized in that the thermoplastic resin has a melt flow rate in the range of 1 g/10 min to 30 g/10 min when measured by Method A under conditions of a temperature of 190°C and a load of 21.18 N in accordance with the method specified in JIS K7210-1:2014. The wood substrate according to any one of claims 1 to 3, characterized in that the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) is within the range of 95/5 to 70/30. The wood base material according to any one of claims 1 to 3, characterized in that the mass ratio of the wood material to the thermoplastic resin composition (wood material/thermoplastic resin composition) is within a range of 97/3 to 85/15. The wood substrate according to any one of claims 1 to 5 , wherein the acid-containing resin is a maleic anhydride-modified polyolefin. 6. The wood base material according to claim 1, wherein the acid-containing resin is an ethylene (meth)acrylic acid copolymer. The thermoplastic resin composition further comprises an organic peroxide,
The wood substrate according to any one of claims 1 to 7 , characterized in that the content of the organic peroxide is in the range of 0.01 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the thermoplastic resin. The thermoplastic resin composition further comprises an organic peroxide,
The wood substrate according to any one of claims 1 to 8, characterized in that the thermoplastic resin composition contains a peroxyketal, a diacyl peroxide, or a peroxyester as the organic peroxide. The wood substrate according to any one of claims 1 to 9 , characterized in that the wood material contains a mushroom bed as a raw material. The wood base material according to any one of claims 1 to 10, characterized in that the thermoplastic resin contains only a polyethylene resin as the polyolefin resin. 12. The wood base material according to claim 1, wherein the content of the acid-containing resin is 25 parts by mass or more per 100 parts by mass of the thermoplastic resin. The wood substrate according to any one of claims 1 to 12, characterized in that the thermoplastic resin composition does not contain a phenolic resin. A decorative material comprising the wood substrate according to any one of claims 1 to 13 and a decorative substrate laminated thereon. A method for producing a wood substrate according to any one of claims 1 to 13,
The method includes a step of heating and pressurizing a raw material mixture containing a wood material having at least one of a powdered and chipped form and a powdered thermoplastic resin composition to form a wood substrate,
The thermoplastic resin composition contains a thermoplastic resin and an acid-containing resin containing at least one of a carboxylic acid and a carboxylic acid anhydride,
The thermoplastic resin is a polyolefin resin having a melting point in the range of 120° C. or more and 140° C. or less,
A method for producing a wood substrate, wherein the content of the acid-containing resin is within a range of 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the thermoplastic resin.

Images