Woody resin composition for fluidization molding, method for producing same, and woody molded product

Abstract

The purpose of the present invention is to provide: a woody resin composition for fluidization molding which makes it possible to produce a woody molded product that is produced with high commercial productivity and that has excellent water resistance; a method for producing the same; and a woody molded product which is produced with high commercial productivity and which has excellent water resistance. This woody resin composition for fluidization molding includes a woody material and a thermoplastic resin, wherein: the woody resin composition for fluidization molding has at least one shape selected from the group consisting of plate shape, fiber shape, columnar shape, and spherical shape; with respect to the total mass of the woody resin composition for fluidization molding, the content of the woody material is not less than 50 mass% but less than 95 mass% and the content of the thermoplastic resin is more than 5 mass% but not more than 50 mass%; in a skeleton of the main chain of a repeating unit, the thermoplastic resin has at least one bond selected from the group consisting of an amide bond, an ester bond, an ether bond, and a thioether bond or has at least one terminal group selected from the group consisting of carbonyl groups, acid anhydride groups, amide groups, and hydroxyl groups; the thermoplastic resin exists within a cell wall and / or within a cell lumen of the woody material; and even after extraction with a solvent in which the thermoplastic resin is soluble, the thermoplastic resin remains within a cell wall and / or within a cell lumen of the woody material.

Description

Wood-based resin composition for flow molding, its manufacturing method, and wood-based molded product

[0001] The present invention relates to a wood-based resin composition for flow molding, a method for producing the same, and a wood-based molded article obtained by molding the wood-based resin composition for flow molding.

[0002] In recent years, against the backdrop of the problem of depletion of underground resources, there has been active development of technologies for the advanced utilization of biomass resources such as wood. In particular, the creation of parts and materials made from sustainably usable biomass resources that have performance equal to or better than that of metal or plastic products has become an important and urgent issue worldwide.

[0003] The use of wood and wood-rich materials is seen as a promising way to protect forest carbon sinks, and there is a need for technologies to process and process wood so that it can be used for a wider range of purposes, not just in buildings, especially as an industrial material.

[0004] While conducting research into the fundamental properties of biomass materials such as wood, the inventors discovered that wood can flow and deform while remaining solid under certain temperature and pressure conditions, and have developed a wood flow molding technology that utilizes this phenomenon (see, for example, Patent Document 1). Wood flow molding is a technology in which a block of wood-based material is placed in a mold of any size and pressure is applied to cause it to flow and fill the mold. Compared to compression processing, which involves densifying the wood cell lumen by blocking it, resulting in a shape change, the deformation is caused by positional changes due to sliding between wood cells, allowing for greater deformation. Furthermore, flow molding enables plastic processing of wood-based materials into arbitrary shapes that was previously impossible using compression processing alone, and minimizes damage to the fibrous wood cells, thereby imparting a reinforcing effect to the resulting wood-based molded product.

[0005] Furthermore, wood materials impregnated with resins have also been developed to impart higher flow moldability to wood materials so that they can be used in the production of molded articles with more complex shapes. For example, Patent Document 2 describes a molded article obtained by side extrusion molding of a thermoplastic wood material obtained by impregnating a wood material with a methyl methacrylate (MMA) resin monomer and polymerizing the impregnated wood material. It describes that the thermoplastic wood material is capable of flow between and within the cellular tissues of the wood material and re-adhesion after flow, making it easy to re-deform and recycle. It also describes that the wood material can be imparted with flow moldability through cell wall deformation and intercellular layer peeling, and shape retention at the cellular level through the thermoplastic resin, which allows the wood material to be molded into complex shapes. Patent Document 3 also describes a wood molded article obtained by backward extrusion molding of a flow moldable wood material impregnated with a polyethylene glycol aqueous solution or a water-soluble urethane resin. It describes that the wood molded article has a woody appearance and excellent shape stability. Furthermore, Patent Document 4 describes an acoustic diaphragm obtained by uniaxially pressing a wood-based material that has been impregnated with a water-soluble phenolic resin, and describes that the acoustic diaphragm satisfies the properties required of a material used for an acoustic diaphragm (thin wall, high specific elastic modulus, appropriate sound propagation velocity, large internal loss, no deterioration due to changes in humidity, high durability, etc.).

[0006] JP 2010-155394 A JP 2014-166711 A International Publication No. 2022 / 004796 JP 2015-095819 A

[0007] However, the thermoplastic wood-based material described in Patent Document 2 requires the use of a solvent other than water to produce a wood-based resin composition, which necessitates the need for solvent recovery equipment, resulting in low commercial productivity. Furthermore, the wood-based molded products described in Patent Documents 3 and 4 contain a water-soluble resin, which can cause the molded products to disintegrate when they come into contact with water, resulting in a problem in terms of water resistance.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a wood-based resin composition for flow molding that can be used to produce wood-based molded bodies that are highly commercially productive and have excellent water resistance, a method for producing the same, and wood-based molded bodies that are highly commercially productive and have excellent water resistance.

[0009] That is, the present invention includes the following aspects: [1] A woody resin composition for flow molding comprising a woody material and a thermoplastic resin, wherein the woody resin composition for flow molding is in the form of one or more shapes selected from the group consisting of a board, a fiber, a pillar, and a sphere, the content of the woody material is 50% by mass or more and less than 95% by mass, and the content of the thermoplastic resin is more than 5% by mass and 50% by mass or less, based on the total mass of the woody resin composition for flow molding, the thermoplastic resin has one or more bonds selected from the group consisting of an amide bond, an ester bond, an ether bond, and a thioether bond in the main chain skeleton of the repeating unit, or one or more terminal groups selected from the group consisting of a carbonyl group, an acid anhydride group, an amide group, and a hydroxyl group, and the thermoplastic resin is present in the woody cell walls and / or the woody cell cavities of the woody material in the woody resin composition for flow molding, A flow-molding wood-based resin composition, characterized in that the thermoplastic resin remains within the wood cell walls and / or wood cell cavities of the wood-based material even after the flow-molding wood-based resin composition is extracted with a solvent capable of dissolving the thermoplastic resin. [2] The flow-molding wood-based resin composition according to [1], wherein the thermoplastic resin comprises one or more resins selected from the group consisting of polyamide, polyoxymethylene, polyester, polypropylene, polyphenylene ether, and polyarylene sulfide. [3] The flow-molding wood-based resin composition according to [1] or [2], wherein the thermoplastic resin comprises a polyamide. [4] The flow-molding wood-based resin composition according to any one of [1] to [3], wherein the thermoplastic resin comprises an amorphous polyamide. [5] The flow-molding wood-based resin composition according to any one of [1] to [4], wherein the wood-based material is fibrous, having a fiber diameter D of 3.0 mm or less and a ratio L / D of the fiber length L to the fiber diameter D of 3 or more. [6] The wood-based resin composition for flow molding according to any one of [1] to [5], further comprising 1 mass% or more of water based on the total mass of the wood-based resin composition for flow molding. [7] The wood-based resin composition for flow molding according to any one of [1] to [6], wherein the lignin content of the wood-based material is 3 mass% or more.[8] A method for producing a flow-molding wood-based resin composition, comprising: an impregnation step of contacting a wood-based material with a thermoplastic resin monomer to impregnate the wood-based material with the thermoplastic resin monomer; and a polymerization step of polymerizing the thermoplastic resin monomer impregnated into the wood-based material to synthesize a thermoplastic resin; wherein the obtained flow-molding wood-based resin composition has one or more shapes selected from the group consisting of boards, fibers, pillars, and spheres; the content of the wood-based material is 50% by mass or more and less than 95% by mass, and the content of the thermoplastic resin is more than 5% by mass and 50% by mass or less, based on the total mass of the flow-molding wood-based resin composition; and the thermoplastic resin has one or more bonds selected from the group consisting of amide bonds, ester bonds, ether bonds, and thioether bonds in the main chain skeleton of the repeating unit, or one or more terminal groups selected from the group consisting of carbonyl groups, acid anhydride groups, amide groups, and hydroxyl groups. A method for producing a wood-based resin composition for flow molding, characterized in that the thermoplastic resin is present in the wood cell walls and / or wood cell cavities of the wood-based material in the wood-based resin composition for flow molding, and the thermoplastic resin remains in the wood cell walls and / or wood cell cavities of the wood-based material even after the wood-based resin composition for flow molding is extracted with a solvent capable of dissolving the thermoplastic resin. [9] A method for producing a wood-based resin composition for flow molding according to [8], further comprising an adjustment step of adjusting the lignin content of the wood-based material before the impregnation step.

[10] A method for producing a wood-based resin composition for flow molding according to [9], further comprising a hydration step of contacting the wood-based material with water before the impregnation step and after the adjustment step.

[11] A method for producing a wood-based resin composition for flow molding according to any of [8] to

[10] , wherein the thermoplastic resin comprises one or more resins selected from the group consisting of polyamide, polyoxymethylene, polyester, polypropylene, polyphenylene ether, and polyarylene sulfide.

[12] The method for producing a flow molding wood-based resin composition according to any one of [8] to

[11] , wherein the thermoplastic resin contains polyamide.

[13] A method for producing a flow-molding wood-based resin composition according to any one of [8] to

[12] , wherein the thermoplastic resin comprises an amorphous polyamide.

[14] A method for producing a flow-molding wood-based resin composition according to any one of [8] to

[13] , wherein the wood-based material is fibrous, having a fiber diameter D of 3.0 mm or less and a ratio L / D of the fiber length L to the fiber diameter D of 3 or more.

[15] A method for producing a flow-molding wood-based resin composition according to any one of [8] to

[14] , wherein the flow-molding wood-based resin composition further contains 1% by mass or more of water relative to the total mass of the flow-molding wood-based resin composition.

[16] A method for producing a flow-molding wood-based resin composition according to any one of [8] to

[15] , wherein the wood-based material has a lignin content of 3% by mass or more.

[17] A woody molded body obtained by molding a flow-molding woody resin composition containing a woody material and a thermoplastic resin, wherein the content of the woody material is 50% by mass or more and less than 95% by mass, and the content of the thermoplastic resin is more than 5% by mass and 50% by mass or less, relative to the total mass of the woody molded body; the thermoplastic resin has one or more bonds selected from the group consisting of amide bonds, ester bonds, ether bonds, and thioether bonds in the main chain skeleton of the repeating unit, or one or more terminal groups selected from the group consisting of carbonyl groups, acid anhydride groups, amide groups, and hydroxyl groups; the thermoplastic resin is present in the woody cell walls and / or wood cell cavities of the woody material, and the thermoplastic resin remains in the woody cell walls and / or wood cell cavities of the woody material even after the woody molded body is extracted with a solvent capable of dissolving the thermoplastic resin.

[18] The woody molded product according to

[17] , which is obtained by injection molding the woody resin composition for flow molding.

[19] The woody molded product according to

[18] , which is obtained by press molding the woody resin composition for flow molding.

[0010] According to the present invention, it is possible to provide a wood-based resin composition for flow molding that can be used to produce wood-based molded articles that are highly commercially productive and have excellent water resistance, a method for producing the same, and wood-based molded articles that are highly commercially productive and have excellent water resistance.

[0011] 1 is a photograph of a cross section of the flow molding wood-based resin composition of Example 1, observed with an optical microscope. The photograph on the left is before solvent extraction, and the photograph on the right is after solvent extraction.

[0012] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0013] <Wood-based resin composition for flow molding> The wood-based resin composition for flow molding of this embodiment (hereinafter simply referred to as "wood-based resin composition") contains a wood-based material and a thermoplastic resin. The shape of the wood-based resin composition for flow molding is one or more selected from the group consisting of board, fiber, pillar, and sphere. The size of the wood-based resin composition for flow molding is not particularly limited. For example, when flow molding is performed by injection molding, the maximum length is preferably 1 mm to 30 mm, more preferably 2 mm to 25 mm, and even more preferably 3 mm to 10 mm, from the viewpoint of easily obtaining a wood-based molded product with excellent shape stability. Furthermore, when flow molding is performed by press molding, the size of the wood-based resin composition for flow molding can be appropriately set depending on the size of the desired wood-based molded product. For example, the maximum length may be 1 mm to 30 mm.

[0014] The components of the flow molding wood-based resin composition of this embodiment will be described in detail below.

[0015] [Wood-based Material] The wood-based material contained in the flow-molding wood-based resin composition of this embodiment is derived from plants having cell walls, such as wood (conifers such as cedar, cypress, and pine; broad-leaved trees such as poplar, beech, oak, and birch), bamboo, flax (jute, kenaf, flax, hemp, ramie, and sisal), and herbs, and may be the plant itself (sawn board, veneer, plywood, etc.), waste material thereof, or chemically treated products thereof.

[0016] The shape of the wood-based material is not particularly limited and may be set appropriately depending on the desired shape of the wood-based resin composition for flow molding. For example, it may be any of regular and irregular shapes such as boards, fibers, pillars, and spheres. The size of the wood-based material is not particularly limited and may be set appropriately depending on the desired size of the wood-based resin composition for flow molding. For example, when flow molding is performed by injection molding or press molding, the wood-based resin composition for flow molding is placed in a mold and molded. From the viewpoint of easily obtaining a wood-based molded product with excellent shape stability, a shape containing fibers with a length of 5 mm or more is preferred. Furthermore, when the wood-based material is fibrous, it is preferred that the fiber diameter D is 3.0 mm or less and the ratio L / D of the fiber length L to the fiber diameter D is 3 or more. When the fiber diameter D and L / D are within the above ranges, the shape of the resin composition is stable, and plasticization and handling during molding tend to be favorable.

[0017] The wood-based material is preferably one in which the amount of lignin therein has been adjusted by delignification treatment. The lignin content does not necessarily have to be low; it is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and may even be 20% by mass or more. When the lignin content is 20% by mass or more, the mechanical properties of the resulting woody molded body are equivalent to those of untreated wood-based materials, but the woody material has superior fluidity, allowing for greater deformation than untreated wood-based materials, resulting in a woody resin composition for flow molding with superior productivity for woody molded bodies. In this specification, fluidity refers to the positional change due to the sliding phenomenon between woody cells. Furthermore, when the lignin content is 3% by mass or more but 15% by mass or less, the mechanical properties of the resulting woody molded body are significantly improved compared to untreated wood-based materials, and the molding material can be used with superior productivity for woody molded bodies. The upper limit of the lignin content is preferably 15% by mass from the viewpoint of the mechanical properties of the resulting woody molded product, but may exceed 15% by mass if the mechanical properties are to be equivalent to those of untreated woody material, and is usually the content of the woody material itself before delignification. Note that the lignin content varies depending on the type of woody material, the growing environment, and even the location of the same individual material, so it is not possible to specify a uniform upper limit as a specific numerical value.

[0018] The lignin content can be measured by the acetyl bromide method, which involves decomposing powdered woody materials in a solution of acetyl bromide in acetic acid and converting the amount of dissolved lignin into UV absorbance (see K. Iiyama et al., "An improved acetyl bromide procedure for determining lignin in woods and wood pulps," Wood Science and Technology, 1988, 22: pp. 271-280).

[0019] When wood-based materials are subjected to the above-mentioned delignification treatment, the degree of lignin condensation decreases, resulting in a relaxed state within the cell walls. Therefore, the wood-based materials obtained in this manner can exhibit improved intercellular sliding during flow molding compared to those obtained by adding water to untreated plant matter or applying strain to untreated plant matter to relax the bonds between the polymer chains of the amorphous polymers hemicellulose and lignin, thereby exhibiting fluidity, as described in, for example, JP 2006-247974 A. This allows for a wood-based resin composition for flow molding that allows for superior productivity in producing wood-based molded products.

[0020] The content of the woody material in the flow molding wood-based resin composition is 50% by mass or more but less than 95% by mass, preferably 50% by mass or more but 90% by mass or less, and more preferably 50% by mass or more but 80% by mass or less, based on the total mass of the flow molding wood-based resin composition. Having the content of the woody material within this range not only increases the bio-derived component ratio and contributes to the environment, but also allows the flow of the flow molding wood-based resin composition to be improved by the heat of the wood material itself, rather than by the fluidity of the resin as in conventional compositions, thereby imparting a highly woody appearance to the resulting wood-based molded article.

[0021] [Thermoplastic Resin] The thermoplastic resin contained in the flow molding wood-based resin composition of this embodiment has, in the main chain skeleton of the repeating unit, one or more bonds selected from the group consisting of amide bonds, ester bonds, ether bonds, and thioether bonds, or one or more terminal groups selected from the group consisting of carbonyl groups, acid anhydride groups, amide groups, and hydroxyl groups. The thermoplastic resin may be a single type or a combination of two or more types.

[0022] The content of the thermoplastic resin in the flow-molding wood resin composition is more than 5% by mass and not more than 50% by mass, preferably 10% by mass to 50% by mass, and more preferably 20% by mass to 50% by mass, based on the total mass of the flow-molding wood resin composition. By keeping the thermoplastic resin content within this range, the contribution of the thermoplastic resin to the fluidity of the flow-molding wood resin composition can be reduced, and the resulting woody molded article can be given a high level of woody appearance.

[0023] Specific examples of such thermoplastic resins include, but are not limited to, polyamide, polyoxymethylene, polyester, polypropylene, polyphenylene ether, polyarylene sulfide, etc. Among these, polyamide is preferred, and amorphous polyamide is more preferred.

[0024] Polyamides have excellent heat resistance and mechanical strength, and because of the presence of hydrogen bonds within their molecular structure, they have a high affinity with wood-based materials. Furthermore, amorphous polyamides, which lack a crystalline layer, are capable of penetrating even the finest regions within the cell walls of wood-based materials, which tends to increase the content of wood-based materials in flow molding wood-based resin compositions. In this specification, "polyamide" refers to a polymer having an amide (—NHCO—) group in the main chain. In this specification, "amorphous polyamide" refers to a polyamide having a crystallization enthalpy ΔH of 15 J / g or less when measured at 20°C / min using a differential scanning calorimeter. The crystallization enthalpy of amorphous polyamides is preferably 10 J / g or less, more preferably 5 J / g or less, and even more preferably 0 J / g. Meanwhile, "crystalline polyamide" refers to a polyamide having a heat of fusion of crystalline crystalline ΔH of 4 J / g or more when measured at 20°C / min using a differential scanning calorimeter. The crystallization enthalpy ΔH and the heat of fusion of the crystals can be measured, for example, in accordance with JIS-K7121 using a measuring device such as Diamond-DSC manufactured by PERKIN-ELMER.

[0025] The amorphous polyamide is not particularly limited as long as it has a crystallization enthalpy ΔH of not more than the above upper limit, but may be, for example, a semi-aromatic polyamide. When the amorphous polyamide is a semi-aromatic polyamide, it is preferably a polyamide containing diamine units and dicarboxylic acid units.

[0026] The amorphous polyamide is preferably a polyamide containing dicarboxylic acid units containing at least 50 mol% isophthalic acid units and diamine units containing at least 50 mol% diamine units having 4 to 10 carbon atoms. The total amount of the isophthalic acid units and diamine units having 4 to 10 carbon atoms is preferably 75 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, and even more preferably 100 mol%, based on the total amount of all structural units of the amorphous polyamide. In this specification, the proportion of a predetermined monomer unit constituting the amorphous polyamide can be measured by nuclear magnetic resonance spectroscopy (NMR) or the like.

[0027] In the dicarboxylic acid units, the content of isophthalic acid units relative to the total molar amount of dicarboxylic acid units is preferably 50 mol% or more, more preferably 75 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, and particularly preferably 100 mol%. When the content of isophthalic acid units relative to the total molar amount of dicarboxylic acid units is equal to or more than the above lower limit, the resulting polyamide tends to be more satisfactory in mechanical properties, moldability, surface appearance, etc.

[0028] The dicarboxylic acid unit may contain an aromatic dicarboxylic acid unit other than an isophthalic acid unit, an aliphatic dicarboxylic acid unit, or an alicyclic dicarboxylic acid unit. The dicarboxylic acid unit other than an isophthalic acid unit preferably contains an aromatic dicarboxylic acid unit, and more preferably contains an aromatic dicarboxylic acid unit having 6 to 12 carbon atoms.

[0029] Examples of aromatic dicarboxylic acids constituting the aromatic dicarboxylic acid unit other than the isophthalic acid unit include, but are not limited to, dicarboxylic acids having a phenyl group or a naphthyl group. The aromatic group of the aromatic dicarboxylic acid may be unsubstituted or substituted. Examples of the substituent include, but are not limited to, alkyl groups having from 1 to 4 carbon atoms, aryl groups having from 6 to 10 carbon atoms, arylalkyl groups having from 7 to 10 carbon atoms, halogen groups such as chloro groups and bromo groups, silyl groups having from 1 to 6 carbon atoms, and sulfonic acid groups and salts thereof (such as sodium salts). Specific examples of aromatic dicarboxylic acids constituting the aromatic dicarboxylic acid unit include, but are not limited to, aromatic dicarboxylic acids having from 8 to 20 carbon atoms that are unsubstituted or substituted with a specific substituent, such as terephthalic acid, naphthalenedicarboxylic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, and 5-sodium sulfoisophthalic acid. Among these, terephthalic acid is preferred. The aromatic dicarboxylic acids constituting the aromatic dicarboxylic acid unit may be used alone or in combination of two or more.

[0030] Examples of aliphatic dicarboxylic acids constituting the aliphatic dicarboxylic acid unit include, but are not limited to, linear or branched saturated aliphatic dicarboxylic acids having 3 to 20 carbon atoms, such as malonic acid, dimethylmalonic acid, succinic acid, 2,2-dimethylsuccinic acid, 2,3-dimethylglutaric acid, 2,2-diethylsuccinic acid, 2,3-diethylglutaric acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid, and diglycolic acid. The aliphatic dicarboxylic acids constituting the aliphatic dicarboxylic acid unit may be one type alone or a combination of two or more types.

[0031] Examples of alicyclic dicarboxylic acids constituting the alicyclic dicarboxylic acid unit include, but are not limited to, alicyclic dicarboxylic acids having an alicyclic structure with 3 to 10 carbon atoms, with alicyclic dicarboxylic acids having 5 to 10 carbon atoms being preferred. Examples of such alicyclic dicarboxylic acids include, but are not limited to, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,3-cyclopentanedicarboxylic acid. Of these, 1,4-cyclohexanedicarboxylic acid is preferred. The alicyclic group of the alicyclic dicarboxylic acid may be unsubstituted or substituted. Examples of the substituent include, but are not limited to, alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl. The alicyclic dicarboxylic acids constituting the alicyclic dicarboxylic acid unit may be used alone or in combination of two or more.

[0032] When the amorphous polyamide contains the dicarboxylic acid units described above, the mechanical properties, fluidity, surface appearance, etc. tend to be more excellent.

[0033] The dicarboxylic acid unit may be one type alone or a combination of two or more types.

[0034] In amorphous polyamides, the dicarboxylic acid constituting the dicarboxylic acid unit is not limited to the compounds described above as dicarboxylic acids, but may also be a compound equivalent to the dicarboxylic acid. Here, "a compound equivalent to a dicarboxylic acid" refers to a compound that can form a dicarboxylic acid structure similar to the dicarboxylic acid structure derived from the dicarboxylic acid. Examples of such compounds include, but are not limited to, anhydrides and halides of dicarboxylic acids.

[0035] Furthermore, the amorphous polyamide may further contain units derived from a trivalent or higher polycarboxylic acid such as trimellitic acid, trimesic acid, or pyromellitic acid, as necessary. The trivalent or higher polycarboxylic acid may be used alone or in combination of two or more.

[0036] The diamine units constituting the amorphous polyamide preferably contain at least 50 mol% of diamine units having from 4 to 10 carbon atoms. Examples of diamine units include, but are not limited to, aliphatic diamine units, alicyclic diamine units, and aromatic diamine units.

[0037] Examples of aliphatic diamines constituting the aliphatic diamine unit include, but are not limited to, linear saturated aliphatic diamines having 2 to 20 carbon atoms, such as ethylenediamine, propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, and tridecamethylenediamine. The aliphatic diamines constituting the aliphatic diamine unit may be one type alone or a combination of two or more types.

[0038] Examples of alicyclic diamines constituting the alicyclic diamine unit include, but are not limited to, 1,4-cyclohexanediamine, 1,3-cyclohexanediamine, 1,3-cyclopentanediamine, etc. The alicyclic diamines constituting the alicyclic diamine unit may be one type alone or a combination of two or more types.

[0039] The aromatic diamine constituting the aromatic diamine unit is not limited to the following as long as it is a diamine containing an aromatic group, and examples thereof include metaxylylenediamine, etc. The aromatic diamine constituting the aromatic diamine unit may be one type alone or a combination of two or more types.

[0040] Among these, an aliphatic diamine unit is preferred, a diamine unit having a linear saturated aliphatic group having from 4 to 10 carbon atoms is more preferred, a diamine unit having a linear saturated aliphatic group having from 6 to 10 carbon atoms is even more preferred, and a hexamethylenediamine unit or a decamethylenediamine unit is particularly preferred.

[0041] When the diamine unit is contained as described above, the amorphous polyamide tends to be superior in mechanical properties, flowability, surface appearance, and the like.

[0042] The diamine unit may be one type alone or a combination of two or more types.

[0043] Furthermore, the amorphous polyamide may further contain, as necessary, units derived from a trivalent or higher polyvalent aliphatic amine such as bispentamethylenetriamine, bishexamethylenetriamine, etc. The trivalent or higher polyvalent aliphatic amine may be used alone or in combination of two or more.

[0044] The amorphous polyamide is preferably polyamide 6I, 6I / 6T, 9I, or 10I, more preferably 6I, 6I / 6T, or 10I, and most preferably 6I or 10I.

[0045] The amorphous polyamide may further contain at least one unit selected from the group consisting of lactam units and aminocarboxylic acid units. By including such units, the resulting polyamide tends to have better toughness. Here, the lactam and aminocarboxylic acid constituting the lactam unit and aminocarboxylic acid unit refer to lactam and aminocarboxylic acid capable of being polymerized (condensed).

[0046] The lactam and aminocarboxylic acid constituting the lactam unit and aminocarboxylic acid unit are not limited to the following, but for example, lactams and aminocarboxylic acids having from 4 to 14 carbon atoms are preferred, and lactams and aminocarboxylic acids having from 6 to 12 carbon atoms are more preferred.

[0047] Examples of lactams constituting the lactam units include, but are not limited to, butyrolactam, pivalolactam, ε-caprolactam, caprylolactam, enantholactam, undecanolactam, and laurolactam (dodecanolactam). Among these, ε-caprolactam or laurolactam is preferred, and ε-caprolactam is more preferred. By including such a lactam, the resulting polyamide tends to have better mechanical properties.

[0048] The aminocarboxylic acid constituting the aminocarboxylic acid unit is not limited to the following, but examples thereof include ω-aminocarboxylic acids, which are compounds formed by ring-opening of lactams, and α,ω-amino acids.

[0049] The aminocarboxylic acid is preferably a linear or branched saturated aliphatic carboxylic acid having from 4 to 14 carbon atoms and substituted with an amino group at the ω position. Examples of such aminocarboxylic acids include, but are not limited to, 6-aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Other examples of aminocarboxylic acids include para-aminomethylbenzoic acid.

[0050] The lactam and aminocarboxylic acid constituting the lactam unit and aminocarboxylic acid unit may each be one type alone or a combination of two or more types.

[0051] The total proportion (mol %) of lactam units and aminocarboxylic acid units is preferably 0 mol % or more and 20 mol % or less, more preferably 0 mol % or more and 10 mol % or less, and even more preferably 0 mol % or more and 5 mol % or less, based on the entire polyamide.

[0052] When the total ratio of lactam units and aminocarboxylic acid units is within the above range, effects such as improved fluidity tend to be obtained.

[0053] The amorphous polyamide may be end-capped with an end-capping agent, which may also be added as a molecular weight modifier when producing the polyamide from the dicarboxylic acid, diamine, and, optionally, at least one compound selected from the group consisting of lactams and aminocarboxylic acids.

[0054] Examples of the end-capping agent include, but are not limited to, monocarboxylic acids, monoamines, acid anhydrides (such as phthalic anhydride), monoisocyanates, monoacid halides, monoesters, and monoalcohols.

[0055] Among these, monocarboxylic acids or monoamines are preferred. By capping the ends of the polyamide with an end-capping agent, the polyamide tends to have better thermal stability.

[0056] The end-capping agent may be used alone or in combination of two or more.

[0057] The monocarboxylic acid usable as the end-capping agent may be any monocarboxylic acid that is reactive with amino groups that may be present at the terminals of the polyamide. Specific examples of the monocarboxylic acid include, but are not limited to, aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, and aromatic monocarboxylic acids.

[0058] Examples of aliphatic monocarboxylic acids include, but are not limited to, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid.

[0059] Examples of alicyclic monocarboxylic acids include, but are not limited to, cyclohexanecarboxylic acid.

[0060] Examples of aromatic monocarboxylic acids include, but are not limited to, benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid.

[0061] These monocarboxylic acids may be used alone or in combination of two or more.

[0062] The monoamine usable as the end-capping agent may be any monoamine that is reactive with carboxyl groups that may be present at the terminals of the polyamide, and specific examples of the monoamine include, but are not limited to, aliphatic monoamines, alicyclic monoamines, and aromatic monoamines.

[0063] Examples of aliphatic amines include, but are not limited to, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine.

[0064] Examples of alicyclic amines include, but are not limited to, cyclohexylamine and dicyclohexylamine.

[0065] Examples of aromatic amines include, but are not limited to, aniline, toluidine, diphenylamine, naphthylamine, and the like.

[0066] These monoamines may be used alone or in combination of two or more.

[0067] Polyamides end-capped with an end-capping agent tend to have better flowability, low water absorption, moldability, and surface appearance.

[0068] When preparing a polyamide such as an amorphous polyamide, the amount of dicarboxylic acid added and the amount of diamine added are preferably approximately the same molar amount. Taking into consideration the amount of diamine that escapes to the outside of the reaction system during the polymerization reaction, the molar amount of the total diamine relative to the molar amount of the total dicarboxylic acid is preferably 0.9 to 1.2, more preferably 0.95 to 1.1, and even more preferably 0.98 to 1.05.

[0069] The polymer terminals of polyamides are not particularly limited, but can be classified and defined as follows (1) to (4): (1) amino terminals, (2) carboxy terminals, (3) terminals formed by a capping agent, and (4) other terminals. (1) Amino terminals are terminals formed by an amino group (-NH ２ (2) Carboxy terminals are polymer terminals having a carboxy group (-COOH group) and are derived from dicarboxylic acid. (3) Terminals formed by a capping agent are terminals formed when a capping agent is added during polymerization. Examples of the capping agent include the terminal capping agents described above. (4) Other terminals are polymer terminals that cannot be classified into the above categories (1) to (3). Specific examples of other terminals include terminals formed by deammoniating amino terminals and terminals formed by decarboxylating carboxy terminals.

[0070] Examples of methods for producing polyamide include the methods exemplified in the "Polymerization step" in the "Method for producing a wood-based resin composition for flow molding" described below.

[0071] The number-average molecular weight Mn of the polyamide is preferably 40,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, and particularly preferably 15,000 or less. When the number-average molecular weight Mn is equal to or less than the upper limit, the permeability into wood-based materials tends to be enhanced. On the other hand, the number-average molecular weight Mn of the polyamide is preferably 3,000 or more, more preferably 5,000 or more. When the number-average molecular weight Mn is equal to or greater than the lower limit, the strength of the resulting molded body is more easily maintained. Furthermore, the weight-average molecular weight Mw of the polyamide is preferably 90,000 or less, more preferably 50,000 or less, even more preferably 30,000 or less, and particularly preferably 25,000 or less. When the weight-average molecular weight is equal to or less than the upper limit, the permeability into wood-based materials tends to be enhanced. On the other hand, the weight-average molecular weight Mw of the polyamide is preferably 10,000 or more, more preferably 11,000 or more, and even more preferably 12,000 or more. When the weight-average molecular weight Mw is equal to or greater than the lower limit, the strength of the resulting molded article is more easily maintained. The molecular weight distribution Mw / Mn of the polyamide is preferably 2.0 or more and 2.5 or less, regardless of the molecular weight. The number-average molecular weight Mn and weight-average molecular weight Mw of the polyamide can be calculated based on a calibration curve prepared from the number-average molecular weight measured in advance by gel permeation chromatography (GPC) using hexafluoroisopropanol (HFIP) as a solvent and converted into a polymethyl methacrylate (PMMA) standard sample (manufactured by Polymer Laboratory Co., Ltd.).

[0072] [Other Raw Materials] In addition to the wood-based material and thermoplastic resin, the flow-molding wood-based resin composition of this embodiment may further contain additives such as plasticizers, antioxidants, UV absorbers, antioxidants, fillers, antibacterial agents, preservatives, antistatic agents, lubricants, mold release agents, etc. These additives can be mixed in advance with the monomers of the thermoplastic resin in the production method of the flow-molding wood-based resin composition described below.

[0073] The wood-based resin composition for flow molding of this embodiment preferably further contains 1% by mass or more of water relative to its total mass, more preferably 2% by mass or more, and even more preferably 3% by mass or more. If the water content is equal to or greater than the lower limit, the water acts as a plasticizer, tending to further improve the fluidity of the wood-based material. On the other hand, the upper limit of the water content is not particularly limited, but can be, for example, 30% by mass or less.

[0074] In the wood-based resin composition for flow molding of this embodiment, the thermoplastic resin is present within the wood cell walls and / or the wood cell cavities of the wood-based material. Because the wood-based resin composition for flow molding is in this state, a wood-based molded product can be obtained that exhibits excellent shape retention upon moisture absorption and drying. The presence of the thermoplastic resin within the wood cell walls and / or the wood cell cavities of the wood-based material can be confirmed, for example, using an optical microscope. Specifically, a section (approximately 25 μm thick) cut perpendicular to the fiber direction of the wood-based material of the wood-based resin composition for flow molding is observed using an optical microscope (e.g., Keyence Corporation's "VHX-970F") with a field of view that allows observation of the cell walls and the cell cavities. A darker color in the image after in situ polymerization compared to the image before in situ polymerization indicates the presence of the thermoplastic resin, which allows confirmation of the presence or absence of the thermoplastic resin within the wood cell walls and / or the wood cell cavities.

[0075] In the wood-based resin composition for flow molding of this embodiment, even after solvent extraction of the wood-based resin composition for flow molding using a solvent capable of dissolving the thermoplastic resin, the thermoplastic resin remains within the wood cell walls and / or wood cell cavities of the wood-based material. This results in a strong bond between the wood-based material and the thermoplastic resin, excellent shape retention during moisture absorption and drying, reduced pressure during molding flow, and improved molding fluidity. This makes it possible to obtain thin wood-based molded products while maintaining their toughness. Whether or not the thermoplastic resin remains within the wood cell walls and / or wood cell cavities of the wood-based material in the wood-based resin composition for flow molding after solvent extraction can be confirmed, for example, using the optical microscope described above.

[0076] Furthermore, the presence of thermoplastic resin in the wood cell walls and / or wood cell cavities of the wood-based material was confirmed by the optical microscope observation, and the wood-based resin composition for flow molding after the solvent extraction was analyzed using a solid-state NMR device. １３ By performing C-NMR measurement, the presence of thermoplastic resin within wood cell walls and / or wood cell cavities after solvent extraction can be quantitatively confirmed. For example, the presence of polyamide within wood cell walls and / or wood cell cavities after solvent extraction can be determined from signal A at the highest magnetic field, CH2 (near 28 ppm). Therefore, the presence of polyamide after solvent extraction can be quantitatively confirmed by calculating signal A / signal B (percentage), where B is the signal derived from cellulose C1 in the wood-based material (near 105 ppm). The value of signal A / signal B (percentage) is preferably greater than 0%, more preferably 10% or greater, and even more preferably 20% or greater. By satisfying the above range, it is possible to obtain a woody molded product with a thinner molded product thickness while maintaining greater toughness.

[0077] As the solvent for solvent extraction, a solvent capable of dissolving the thermoplastic resin at a concentration of preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 3% by mass or more, and even more preferably 5% by mass or more can be selected. Specifically, for example, when the thermoplastic resin is polyamide, formic acid, sulfuric acid, hexafluoroisopropanol (HFIP), calcium chloride aqueous solution, etc. can be used. Alternatively, for example, when the thermoplastic resin is polyoxymethylene, formic acid can be used. For polypropylene, aromatic organic solvents such as xylene and toluene can be used. For polyphenylene ether, halogen-containing solvents such as chloroform and methylene chloride, and aromatic organic solvents such as xylene and toluene can be used. Furthermore, for example, when the thermoplastic resin is polyarylene sulfide, there is no suitable solvent, so a method in which only the thermoplastic resin is brought into contact with the wood-based material is preferred. The extraction conditions (temperature, time, etc.) can be set appropriately depending on the shape, size, and mass of the wood-based resin composition for flow molding, the type of thermoplastic resin, etc., so long as the thermoplastic resin is sufficiently extracted. For example, if the thermoplastic resin is polyamide, the composition can be immersed in a solvent at 0 to 50°C for 2 to 5 days.

[0078] <Method for producing a wood-based resin composition for flow molding> The method for producing a wood-based resin composition for flow molding of this embodiment includes an impregnation step in which a thermoplastic resin monomer is brought into contact with a wood-based material to impregnate the wood-based material with the thermoplastic resin monomer, and a polymerization step in which the thermoplastic resin monomer impregnated into the wood-based material is polymerized to synthesize a thermoplastic resin. By having these steps, the method for producing a wood-based resin composition for flow molding of this embodiment can produce a wood-based resin composition for flow molding that has excellent color tone, commercial productivity, mold transferability, surface hardness, and film formability when made into a wood-based molded product.

[0079] As used herein, "color tone" refers to the degree of shading or brightness of the color of the surface of a molded product. Furthermore, as used herein, "commercial productivity" can be evaluated based on the manufacturing cost of the molded product (the cost of raw materials, solvents, etc. used) and the need for equipment to recover used solvents. The lower the manufacturing cost and the less equipment is needed to recover used solvents, the better the commercial productivity. Furthermore, as used herein, "mold transferability" refers to the ability to mold a molded product with a fine structure and retain a shape that reflects the mold structure. Furthermore, as used herein, "surface hardness" refers to the ability to provide excellent scratch resistance when the molded product comes into contact with a hard substance. Surface hardness can be evaluated by measuring scratch hardness (pencil method) in accordance with ISO 15184:1996. Furthermore, as used herein, "film formability" specifically refers to the ability of the entire composition, including not only the resin but also the wood components, to flow and solidify in a narrow gap of 500 μm or less in thickness.

[0080] Each step of the method for producing the flow molding wood-based resin composition of this embodiment will be described in detail below.

[0081] [Impregnation Step] In the impregnation step, a thermoplastic resin monomer is brought into contact with a wood-based material to impregnate the wood-based material with the thermoplastic resin monomer. The impregnation method is not particularly limited as long as it can impregnate the wood-based material with the thermoplastic resin monomer. For example, a method of immersing the wood-based material in an aqueous solution of the thermoplastic resin monomer (aqueous monomer solution) is possible. Examples of aqueous monomer solutions include aqueous solutions of monomer salts. For example, when the thermoplastic resin is a polyamide, an aqueous solution of a salt of a diamine and a dicarboxylic acid that constitutes the polyamide (aqueous dicarboxylic acid-diamine salt solution) can be used. The concentration of the aqueous monomer solution may be adjusted appropriately taking into account the resin content in the resulting wood-based resin composition, but can be, for example, 5% by mass or more and 90% by mass or less.

[0082] The immersion temperature may be room temperature (23°C ± 2°C), but for example, if the monomer salt does not dissolve in the aqueous solution of the monomer salt, the temperature at which the monomer salt dissolves may be used (e.g., 110°C for a monomer salt of sebacic acid and decamethylenediamine). The immersion time is not particularly limited and can be set appropriately depending on the shape, size, and mass of the wood-based material. For example, it may be 1 hour to 200 hours, 20 hours to 190 hours, or 40 hours to 180 hours per 10 g of dry wood-based material. The immersion pressure is not particularly limited and may be atmospheric pressure, elevated pressure, or reduced pressure.

[0083] (Wood-based material) As the wood-based material, the same wood-based materials as exemplified in the above-mentioned <Wood-based resin composition for flow molding> can be used.

[0084] (Thermoplastic Resin Monomer) As the thermoplastic resin monomer, the same ones as those exemplified for the thermoplastic resin in the above <Wood-based resin composition for flow molding> can be used.

[0085] [Polymerization Step] In the polymerization step, the wood-based material impregnated with the thermoplastic resin monomer obtained in the impregnation step is used, and the thermoplastic resin monomer impregnated in the wood-based material is polymerized (in situ polymerization). The polymerization conditions may be appropriately set depending on the type of thermoplastic resin and its monomer.

[0086] The polymerization apparatus used for polymerizing the thermoplastic resin is not particularly limited, and known apparatuses can be used, such as autoclave-type reactors and tumbler-type reactors.

[0087] As a specific example, a method for polymerizing polyamide will be described in detail below.

[0088] (Polyamide Polymerization Method) Specific polyamide polymerization methods include, for example, the following methods (1) and (2). (1) A method in which a wood-based material impregnated with an aqueous solution of polyamide monomers (an aqueous solution of one or more selected from the group consisting of a dicarboxylic acid-diamine salt, a mixture of dicarboxylic acid and diamine, a lactam, and an aminocarboxylic acid) is heated to polymerize the monomers while maintaining the molten state (hereinafter, this may be referred to as a "thermal melt polymerization method"). (2) A method in which the degree of polymerization of the polyamide obtained by the thermal melt polymerization method is increased while maintaining the solid state at a temperature below the melting point (hereinafter, this may be referred to as a "thermal melt polymerization / solid-state polymerization method"). When polymerizing polyamide by the thermal melt polymerization method, it is preferable to maintain the molten state until the polymerization is completed. Polymerization conditions for maintaining the molten state include, for example, the following conditions. First, the polymerization pressure in the thermal melt polymerization method is set to 14 kg / cm. ２ More than 25kg / cm ２ Heating is continued while controlling the pressure in the vessel to atmospheric pressure (gauge pressure is 0 kg / cm ２ ) and reduce the blood pressure over 30 minutes or more until the blood pressure reaches a normal level.

[0089] Specific examples of methods for polymerizing polyamide by thermal melt polymerization are shown below.

[0090] The wood-based material impregnated with an aqueous polyamide monomer solution and the aqueous polyamide monomer solution are transferred to an autoclave and heated to a temperature of 150°C to 280°C. When the internal pressure of the autoclave reaches 1.0 MPa (gauge pressure), the pressure is maintained at 0.5 MPa to 2.2 MPa (gauge pressure) while removing at least one of water vapor and gas components, allowing the reaction to proceed. The pressure inside the autoclave is then reduced to atmospheric pressure, and the by-product water can be effectively removed by cooling as necessary. The autoclave is then pressurized with an inert gas such as nitrogen, and the autoclave is then cooled to obtain a wood-based resin composition.

[0091] The polyamide polymerization method of the present embodiment may further include a step of increasing the degree of polymerization of the polyamide after polymerization of the polyamide, for example, a step of performing solid-state polymerization. Furthermore, if necessary, additives such as an end-capping agent and a polymerization catalyst may be contained in the aqueous monomer solution.

[0092] The method for producing the flow molding wood-based resin composition of this embodiment may include, in addition to the impregnation step and polymerization step, other steps such as an adjustment step and a water-containing step before the impregnation step.

[0093] [Adjustment Step] In the adjustment step, a delignification treatment is performed before the impregnation step to adjust the lignin content of the wood-based material. Examples of methods for adjusting the lignin content of wood-based materials (delignification treatment methods) include known lignin treatment methods such as the Klaudiz method, Wize method, kraft pulping method, soda method, phenol pulping method, organic acid pulping method, organosolv pulping method, ASAM method, and bleaching treatment. Among these, the Klaudiz method is preferred as the adjustment method. Details of the lignin content of wood-based materials and the method for measuring it may be the same as those described in the [Wood-based Material] section of the flow molding wood-based resin composition of this embodiment.

[0094] [Moisture-imparting step] In the moisture-imparting step, the wood-based material is brought into contact with water before the impregnation step and after the conditioning step. By impregnating the wood-based material with water, water molecules can penetrate between the hydrogen bonds of cellulose and hemicellulose, the main components that make up the wood-based material, facilitating substitution with resin in the impregnation step. Furthermore, the moisture in the wood-based material acts as a plasticizer, further improving the fluidity of the resulting wood-based resin composition for flow molding during molding. Moisture-imparting methods include, but are not limited to, contacting the wood-based material with saturated water vapor, conditioning the wood-based material in a constant relative humidity environment, and immersing the wood-based material in water.

[0095] <Woody Molded Body> The woody molded body of this embodiment is a molded body obtained by molding a woody resin composition for flow molding that contains a woody material and a thermoplastic resin. The woody resin composition for flow molding, which is the raw material for the woody molded body of this embodiment, can be the same as those exemplified in the above <Woody Resin Composition for Flow Molding>.

[0096] The content of wood-based material in the wood-based molded product is 50% by mass or more but less than 95% by mass, preferably 50% by mass or more but less than 90% by mass, and more preferably 50% by mass or more but less than 80% by mass, based on the total mass of the wood-based molded product. By having the content of wood-based material within the above range, the wood-based molded product has a high proportion of bio-derived components, which is not only environmentally friendly but also has a high wood-like appearance. It can be said that the content of wood-based material in the wood-based molded product is equivalent to the value in the wood-based resin composition for flow molding, which is the raw material for the wood-based molded product.

[0097] The content of the thermoplastic resin in the woody molded product is more than 5% by mass and not more than 50% by mass, preferably 10% by mass to 50% by mass, and more preferably 20% by mass to 50% by mass, based on the total mass of the woody molded product. By ensuring that the content of wood-based material falls within the above range, the woody molded product has a highly woody appearance. The content of the thermoplastic resin in the woody molded product can be said to be equivalent to the value in the woody resin composition for flow molding, which is the raw material for the woody molded product.

[0098] In the woody molded product of this embodiment, a thermoplastic resin is present within the wood cell walls and / or the wood cell cavities of the wood-based material. Therefore, the woody molded product has excellent shape retention upon moisture absorption and drying. The presence of a thermoplastic resin within the wood cell walls and / or the wood cell cavities of the wood-based material can be confirmed, for example, using an optical microscope, as in the case of the flow molding woody resin composition of this embodiment described above.

[0099] In the woody molded product of this embodiment, even after solvent extraction of the woody molded product using a solvent capable of dissolving the thermoplastic resin, the thermoplastic resin remains within the wood cell walls and / or wood cell cavities of the wood-based material. In other words, the bonding strength between the woody material and the thermoplastic resin is strong, and the shape retention during moisture absorption and drying is excellent. This makes it possible to obtain a thin woody molded product while maintaining its toughness. Whether or not the thermoplastic resin remains within the wood cell walls and / or wood cell cavities of the woody material in the woody molded product after solvent extraction can be confirmed, for example, using an optical microscope, in the same way as for the woody resin composition for flow molding of this embodiment described above.

[0100] The solvent for solvent extraction can be the same as that used for the wood-based materials exemplified in the above-mentioned "Wood-based resin composition for flow molding." The extraction conditions (temperature, time, etc.) can be set appropriately depending on the shape, size, and mass of the wood-based molded body, the type of thermoplastic resin, etc., so long as the thermoplastic resin is sufficiently extracted. For example, if the thermoplastic resin is polyamide, the wood-based molded body can be immersed in the solvent at 0 to 50°C for 2 to 5 days.

[0101] <Method for manufacturing woody molded body> The method for manufacturing the woody molded body of this embodiment is not particularly limited, and examples include extrusion molding, injection molding, press molding, etc. Among these, injection molding and press molding are preferred. Examples of molding machines used in the method for manufacturing the woody molded body of this embodiment include extrusion molding machines such as film molding machines and sheet molding machines, inflation molding machines, blow molding machines, injection molding machines, press molding machines, etc.

[0102] (Injection Molding) The injection molding method for the woody molded body of this embodiment is not limited to the following, but may include, for example, a method comprising, in this order: a heating step in which a flow-molding woody resin composition is heated to or above the melting point or glass transition temperature of the thermoplastic resin contained in the flow-molding woody resin composition to plasticize it; a pressurized flow step in which the plasticized flow-molding woody resin composition is pressurized to flow through a tube with a diameter of 0.5 mm to 3 mm; and a cooling step in which the flow-molded woody resin composition is filled into a cavity of a predetermined shape and then cooled. Injection molding with the above configuration tends to produce woody molded bodies that have excellent shape retention when absorbing moisture and drying, film formability, and surface appearance.

[0103] Each step of the injection molding will now be described in detail.

[0104] -Heating Step- In the heating step, the wood-based resin composition for flow molding is heated to or above the melting point or glass transition temperature of the thermoplastic resin contained in the wood-based resin composition for flow molding to plasticize it. The heating temperature can be set appropriately depending on the type of thermoplastic resin. For example, the heating temperature can be set to or above the flow initiation temperature of the thermoplastic resin, and is preferably at least 10°C higher than the flow initiation temperature, and more preferably at least 20°C higher. Note that the flow initiation temperature refers to the melting point of the thermoplastic resin if it is a crystalline resin, and to the glass transition temperature if it is an amorphous resin. The upper limit of the heating temperature is preferably 220°C or lower, more preferably 200°C or lower, from the viewpoint of suppressing decomposition of the wood-based material. The heating time can be, for example, 60 minutes or less, preferably 30 minutes or less, more preferably 20 minutes or less, even more preferably 15 minutes or less, and particularly preferably 10 minutes or less. On the other hand, the lower limit of the heating time can be, for example, 1 minute or more, and preferably 2 minutes or more.

[0105] -Pressure flow process- In the pressure flow process, the plasticized wood-based resin composition for flow molding is pressurized to flow through a tube with a diameter of 0.5 mm to 3 mm. The pressure can be anything, as long as it is high enough to cause flow. The lower the pressure, the less energy is required, which is preferable. For example, it may be 50 MPa or more. Furthermore, since the upper limit of injection pressure in typical injection molding machines is often around 250 MPa, the pressure is preferably 250 MPa or less, more preferably 200 MPa or less, and even more preferably 150 MPa or less.

[0106] -Cooling Process- In the cooling process, the flow-molded wood-based resin composition is filled into a cavity of a predetermined shape and then cooled. The cavity refers to a hollow portion for solidifying the flow-molded wood-based resin composition that has been poured into the mold, and a cavity of the desired shape can be appropriately selected. Typical cooling methods can be used, such as air-cooling or liquid-cooling the mold itself. A preferred method is to control the temperature of the mold with water or oil to remove heat from the flow-molded wood-based resin composition. The cooling time depends on the type of equipment used, but can be appropriately selected from a range of 4 hours or less. For typical injection molding, the cooling time is generally 1 minute or less.

[0107] (Press Molding) The press molding method for the woody molded body of this embodiment is not limited to the following, but may include, for example, a method comprising, in this order: a heating step in which a flow-molding woody resin composition is heated to or above the melting point or glass transition temperature of the thermoplastic resin contained in the flow-molding woody resin composition to plasticize it; a pressing step in which the plasticized flow-molding woody resin composition is placed in a cavity of a predetermined shape and clamped; and a cooling step in which the clamped flow-molding woody resin composition is cooled. Press molding with the above configuration tends to produce woody molded bodies that have excellent shape retention during moisture absorption and drying, film formability, and surface appearance. Furthermore, press molding is more likely to retain the wood grain of the woody material than other molding methods such as injection molding, making it easier to produce molded bodies with a more wood-like texture.

[0108] Each step of the press molding will now be described in detail.

[0109] Heating Step: In the heating step, the wood-based resin composition for flow molding is heated to or above the melting point or glass transition temperature of the thermoplastic resin contained in the wood-based resin composition for flow molding to plasticize it. The heating temperature and heating time may be the same as those exemplified for the heating step in injection molding described above. The wood-based resin composition for flow molding may be heated in the heating step while placed in a cavity of a predetermined shape, and then may be directly transferred to the pressing step (i.e., the mold may be clamped as is).

[0110] - Pressing Process - In the pressing process, the plasticized wood-based resin composition for flow molding is placed in a cavity of a predetermined shape and clamped. The cavity refers to the hollow portion of the mold used to solidify the placed wood-based resin composition for flow molding, and a mold of the desired shape can be appropriately selected. The clamping force is not particularly critical as long as it applies the pressure necessary for flow within the cavity. The lower the clamping force, the less energy is required, making it preferable. For example, it may be 1 MPa or more. Furthermore, the upper limit of the clamping force is often around 500 MPa in a typical press molding machine, so it is preferably 400 MPa or less, more preferably 300 MPa or less, and even more preferably 200 MPa or less.

[0111] -Cooling Step- In the cooling step, the mold-closed wood-based resin composition for flow molding is cooled. The cooling method and cooling time may be the same as those exemplified for the cooling step in injection molding described above.

[0112] The present invention will be described in detail below with reference to specific examples and comparative examples, but the present invention is not limited to the following examples.

[0113] <Measurement and Evaluation Methods> Measurement and evaluation methods used in the examples and comparative examples will be described below.

[0114] [Structural Analysis] The obtained wood-based resin composition for flow molding was subjected to solid-state NMR analysis using a solid-state NMR device (400 MHz NMR manufactured by Varian) with a waiting time of 5 seconds and an accumulation number of 1024 times by the CP / MAS method. １３ C-NMR measurement was carried out.

[0115] [Weight-average molecular weight] The weight-average molecular weight of the resin in the obtained wood-based resin composition for flow molding was calculated based on a calibration curve prepared using a gel permeation chromatograph (GPC) ("HLC-8020" manufactured by Tosoh Corporation) and a hexafluoroisopropanol (HFIP) solvent, converted into weight-average molecular weights of polymethyl methacrylate (PMMA) standard samples (manufactured by Polymer Laboratory Co., Ltd.) in advance. The GPC columns used were TSK-GEL GMHHR-M and G1000HHR.

[0116] [Presence or absence of thermoplastic resin within wood cell walls and / or cell cavities] The presence or absence of thermoplastic resin within the wood cell walls and / or cell cavities of the resulting flow-molding wood-based resin composition was confirmed using an optical microscope. Specifically, sections (approximately 25 μm thick) of the flow-molding wood-based resin composition cut perpendicular to the fiber direction of the cypress veneer were observed using an optical microscope (Keyence Corporation, "VHX-970F") in a field of view that allowed observation of the cell walls and cell cavities. If the images after in situ polymerization and solvent extraction were darker in color than the images before in situ polymerization, it was determined that a thermoplastic resin was present. (Solvent Extraction) The wood-based resin composition for flow molding, in which the presence of resin components within the cell walls and / or cell cavities was confirmed by optical microscopy, was cut into pieces approximately 2 mm long in the fiber direction and immersed in a good solvent for the resin contained in the wood-based resin composition for flow molding (HFIP in the case of polyamide) for 72 hours at 23°C while stirring, to perform solvent extraction of the thermoplastic resin in the wood-based resin composition for flow molding. The wood-based resin composition for flow molding after solvent extraction was observed under the optical microscope in the same manner as before solvent extraction to confirm the presence or absence of thermoplastic resin within the wood cell walls and / or cell cavities. (Presence of thermoplastic resin in wood cell walls and / or wood cell cavities after solvent extraction) The presence of resin components in the cell walls and / or cell cavities was confirmed by the optical microscope observation. After the solvent extraction, the wood-based resin composition for flow molding was analyzed by solid-state NMR using a solid-state NMR device (400 MHz NMR manufactured by Varian) with a waiting time of 5 seconds and an accumulation number of 1024 times. １３ For example, the presence of polyamide within wood cell walls and / or wood cell cavities after solvent extraction can be determined from signal A at CH2 (near 28 ppm) in the highest magnetic field. Therefore, the presence of polyamide after solvent extraction was quantitatively confirmed by calculating signal A / signal B (percentage), where signal B is derived from cellulose C1 in the wood (near 105 ppm).

[0117] [Moisture content before molding] The mass (Wｗｅｔ ) and the mass (W ｄｒｙ ) were measured, and the moisture content (mass%) before molding was calculated using the following formula: Moisture content (mass%) before molding = (W ｗｅｔ -W ｄｒｙ ) x 100 / W ｄｒｙ

[0118] [Color Tone] The color tone of the obtained gear molding was visually confirmed. The better the thermal stability, the more suppressed the coloring and the brighter the color tone tended to be.

[0119] [Commercial productivity] When producing wood-based resin compositions, the commercial productivity was evaluated using the following three-point scale based on the cost of the solvent used and the need for equipment to recover used solvents. (Evaluation criteria) 3: No solvent is required, and no solvent recovery equipment is needed. 2: Solvent is required, and small-scale used solvent recovery equipment is needed. 1: Solvent is required, and large-scale used solvent recovery equipment is needed.

[0120] [Mold Transferability] The mold transferability of the obtained gear molded body was evaluated on the following 5-point scale. (Evaluation Criteria) 5: The shape of the gear teeth forms the same right angles as the mold, and the molded body has a gloss over the entire surface. 4: The shape of the gear teeth forms the same right angles as the mold, but the molded body has no gloss in part. 3: The shape of the gear teeth forms the same right angles as the mold, but the molded body has no gloss at all. 2: The shape of the gear teeth does not reflect the mold shape, and the molded body has no gloss at all. 1: Not filled sufficiently.

[0121] [Surface Hardness] The surface hardness of the molded product was measured by scratch hardness (pencil method) in accordance with ISO 15184:1996.

[0122] [Water resistance] The obtained molded body was immersed in water set at 80°C, and after 10 hours, the change in appearance was checked and evaluated on the following 4-point scale. (Evaluation criteria) 4: No change in appearance. 3: The molded body was slightly deformed (swelled) due to water absorption. 2: The molded body was partially collapsed due to water absorption. 1: The molded body no longer retained its original shape.

[0123] [Film formability] Film formability was evaluated on the following five-point scale based on the amount of raw material flowing into the burr-like clearance (100-200 μm) between the piston and cylinder during injection molding and toughness. (Evaluation criteria) 5: The flow length of the resin-impregnated raw material containing wood cells is 10 mm or more, and the burr is tough and does not crumble easily. 4: The flow length of the resin-impregnated raw material containing wood cells is 8 mm or more but less than 10 mm, and the burr is tough and does not crumble easily. 3: The flow length of the resin-impregnated raw material containing wood cells is 5 mm or more but less than 8 mm, and the burr is tough and does not crumble easily. 2: The flow length of the resin-impregnated raw material containing wood cells is less than 5 mm, or the burr is brittle and crumbles easily. 1: There is almost no flow of the resin-impregnated raw material containing wood cells, or it is so brittle that it cannot maintain its shape.

[0124] <Raw Materials> Raw materials used in the examples and comparative examples will be described below.

[0125] [Wood material] Hinoki veneer: A rotary veneer was peeled from a Hinoki log to a thickness of 4 mm (radial direction: R), and then cut into disks of approximately 25 mm diameter using a hole saw with an inner diameter of 26 mm, obtaining a large number of Hinoki veneers with a diameter of approximately 25 mm on the tangential surface (LT surface) and a thickness (R) of 4 mm.

[0126] <Lignin Adjustment Method> The lignin amount of cypress veneer was adjusted (delignification treatment) by a method based on the Klaudiz method (Reference 1: "Takahide Sakaguchi et al.: "Wood Chemistry", Bun'ei-do Shuppan, 1985, pp. 69-70"). Specifically, the dried cypress veneer was immersed in a 4 mass % aqueous solution of sodium chlorite set at 45°C for 6 hours to obtain a cypress veneer with an adjusted lignin amount (delignification treatment). After treatment, the cypress veneer was immersed in water for several times to wash and saturated with water. The preheated treatment solution was injected under reduced pressure to ensure that it would quickly penetrate and react inside the cypress veneer. The delignified cypress veneer was stored in a saturated state until the next resin impregnation. A portion of the resulting delignified cypress veneer was dried, and the weight loss rate from the dried cypress veneer before lignin treatment was measured, which was 6.8% by mass.

[0127] <Monomer Salt Impregnation Method> Delignified cypress veneers were immersed in a 50% by mass equimolar homogeneous aqueous solution of raw material monomers (monomer salt aqueous solution) at atmospheric pressure and 23°C for one week or more. If the monomer salt aqueous solution became a slurry and the raw material monomer salt did not dissolve, the veneer was immersed at a temperature at which the raw material monomer salt would dissolve for one week or more. For example, in the case of raw material monomer salts of sebacic acid and decamethylenediamine, the veneer was immersed at a temperature of 110°C for one week or more.

[0128] <Production of Woody Molded Articles> [Example 1] (Preparation of Flow Molding Wood-Based Resin Composition (Injection Raw Material)) 1,500 g of an equimolar salt of isophthalic acid and hexamethylenediamine was dissolved in 1,500 g of distilled water to prepare a 50% by mass equimolar homogeneous aqueous solution of raw material monomers (monomer salt aqueous solution). Delignified cypress veneers, the lignin content of which had been adjusted using the lignin adjustment method described above, were immersed in the monomer salt aqueous solution using the monomer salt impregnation method described above. The concentration of the monomer salt aqueous solution was adjusted so that the resin content, calculated from the mass of the dry delignified cypress veneer and the mass (calculated value) of the resin composition in the resulting wood-based resin composition, would be 30% by mass. The impregnated cypress veneer and the monomer salt aqueous solution were transferred to an autoclave, heated to 240°C, and the water vapor was gradually released when the internal pressure reached 1.0 MPa. The reaction was allowed to proceed for 1 hour. Next, the pressure was reduced over 30 minutes, and then the autoclave was depressurized to 0.02 MPa using a vacuum device and maintained for 10 minutes. The autoclave was then pressurized with nitrogen and cooled to obtain a wood-based resin composition for flow molding. CP / MAS NMR analysis confirmed that polyamide 6I was polymerized in situ and contained in the wood-based resin composition for flow molding. GPC analysis revealed that the weight-average molecular weight of polyamide 6I was 16,000. The wood content in the wood-based resin composition for flow molding was calculated from the mass of the wood-based resin composition for flow molding and the estimated mass of the dry delignified cypress veneer, calculated from the weight loss rate of the cypress veneer due to delignification (6.8% by mass), and was found to be 70% by mass (resin content: 30% by mass). The form of the flow-molding wood-based resin composition was the same as that of the original cypress veneer, maintaining the wood board shape, and exhibiting a structure in which the synthesized resin was impregnated into the cypress veneer structure. Observation with an optical microscope confirmed the presence of thermoplastic resin within the wood cell walls and / or cell cavities both before and after solvent extraction. Figure 1 shows a photograph of the cross section of the wood-based molded body observed with an optical microscope. The photograph on the left is before solvent extraction, and the photograph on the right is after solvent extraction. CP / MAS NMR measurement after solvent extraction showed that the signal A / signal B of polyamide 6I after solvent extraction was 37%.(Injection Molding) A vertical injection unit with a 3 mm diameter x 10 mm long capillary hole at the tip of a mold having a piston with an outer diameter of 29.7 mm and a cylinder with an inner diameter of 30.0 mm was placed between the heating plates of a press molding machine. A gear mold with a gear-shaped cavity was installed at the bottom of the injection unit. The mold was heated by heat transfer from the heating plate until the surface temperature of the cylinder reached 150°C. Then, several sheets of wood-based resin composition (approximately 10 g) were placed in the cylinder and preheated over 5 minutes while slowly compressing. The heating plate was then lowered at a rate of 10 mm / min to apply pressure to the wood-based resin composition in the cylinder, fluidizing it and allowing it to pass through the capillary and move into the mold cavity. Once the wood-based resin composition had completely moved into the mold cavity, heating was stopped. The mold temperature was confirmed to be below 100°C, and the molded body was removed. The piston pressure and mold clamping pressure were 212 MPa. During this molding, the pressure at which the wood-based resin composition in the cylinder flows out (flow pressure) was recorded as the pressure applied to the piston when the distance from the tip of the piston to the capillary reached 4 mm. The results of the measurements and evaluations are shown in Table 1.

[0129] Example 2: A woody molded body was produced in the same manner as in Example 1, except that untreated cypress veneer that had not undergone lignin group treatment using the above-described lignin preparation method was used. CP / MAS NMR measurements confirmed that polyamide 6I was polymerized in situ and contained in the flow molding wood-based resin composition. GPC measurements revealed that the weight-average molecular weight of polyamide 6I was 15,000. The wood content in the wood-based resin composition, calculated as in Example 1, was 70% by mass (resin content: 30% by mass). The morphology of the wood-based resin composition was identical to that of the original cypress veneer, maintaining the wooden board shape, and exhibiting a structure in which the synthesized resin was impregnated within the cypress veneer structure. The results of each measurement and evaluation are shown in Table 1.

[0130] Example 3: A woody molded body was produced in the same manner as in Example 1, except that the delignified cypress veneer and the monomer salt aqueous solution were placed in the autoclave immediately before polymerization, rather than impregnated with the monomer salt aqueous solution using the monomer salt impregnation method described above. CP / MAS NMR analysis confirmed that polyamide 6I was polymerized in situ and contained in the flow molding woody resin composition. GPC analysis revealed that the weight-average molecular weight of polyamide 6I was 25,000. The woody material content in the woody resin composition was calculated as in Example 1 and was found to be 70% by mass (resin content: 30% by mass). The woody resin composition retained the same shape as the original cypress veneer, maintaining its wooden board shape, and exhibiting a structure in which the synthesized resin was impregnated into the cypress veneer structure. The results of the measurements and evaluations are shown in Table 1.

[0131] Example 4 (Preparation of Flow Molding Wood-Based Resin Composition (Injection Raw Material)) 1,500 g of an equimolar salt of sebacic acid and hexamethylenediamine was dissolved in 1,500 g of distilled water to prepare a 50% by mass equimolar homogeneous aqueous solution of raw material monomers (monomer salt aqueous solution). Delignified cypress veneers, the lignin content of which had been adjusted using the lignin adjustment method described above, were immersed in the monomer salt aqueous solution using the monomer salt impregnation method described above. The concentration of the monomer salt aqueous solution was adjusted so that the resin content, calculated from the mass of the dry delignified cypress veneer and the mass (calculated value) of the resin composition in the resulting wood-based resin composition, would be 30% by mass. The impregnated cypress veneer and the monomer salt aqueous solution were transferred to an autoclave, heated to 240°C, and the water vapor was gradually released when the internal pressure reached 0.8 MPa, allowing the reaction to proceed for 1 hour. Next, the pressure was reduced over 30 minutes, and the autoclave was then depressurized to 0.02 MPa using a vacuum device and held for 10 minutes. The autoclave was then pressurized with nitrogen and cooled to obtain a wood-based resin composition for flow molding. CP / MAS NMR analysis confirmed that polyamide 610 was polymerized in situ and contained in the wood-based resin composition for flow molding. GPC analysis revealed that the weight-average molecular weight of polyamide 610 was 19,000. The wood content in the wood-based resin composition was calculated as in Example 1 and found to be 70% by mass (resin content: 30% by mass). The wood-based resin composition retained the same shape as the original cypress veneer, maintaining its wooden board shape, and exhibiting a structure in which the synthesized resin was impregnated into the cypress veneer structure. (Injection Molding) The obtained wood-based resin composition was injection molded as in Example 1 to produce a wood-based molded body. The results of each measurement and evaluation are shown in Table 1.

[0132] Example 5 (Preparation of a Flow Molding Wood-Based Resin Composition (Injection Raw Material)) 1,500 g of an equimolar salt of adipic acid and hexamethylenediamine was dissolved in 1,500 g of distilled water to prepare a 50% by mass equimolar homogeneous aqueous solution of raw material monomers (monomer salt aqueous solution). Delignified cypress veneers, the lignin content of which had been adjusted using the lignin adjustment method described above, were immersed in the monomer salt aqueous solution using the monomer salt impregnation method described above. The concentration of the monomer salt aqueous solution was adjusted so that the resin content, calculated from the mass of the dry delignified cypress veneer and the mass (calculated value) of the resin composition in the resulting wood-based resin composition, would be 30% by mass. The impregnated cypress veneer and the monomer salt aqueous solution were transferred to an autoclave, heated to 270°C, and the water vapor was gradually released when the internal pressure reached 1.0 MPa, allowing the reaction to proceed for 1 hour. Next, the pressure was reduced over 30 minutes, and then the autoclave was depressurized to 0.02 MPa using a vacuum device and held for 10 minutes. The autoclave was then pressurized with nitrogen and cooled to obtain a wood-based resin composition for flow molding. CP / MAS NMR analysis confirmed that polyamide 66 was polymerized in situ and contained in the wood-based resin composition for flow molding. GPC analysis revealed that the weight-average molecular weight of polyamide 66 was 23,000. The wood content in the wood-based resin composition was calculated as in Example 1 and was found to be 70% by mass (resin content: 30% by mass). The wood-based resin composition retained the same shape as the original cypress veneer, maintaining its wooden board shape, and exhibiting a structure in which the synthesized resin was impregnated into the cypress veneer structure. (Injection Molding) The obtained wood-based resin composition was injection molded as in Example 1 to produce a wood-based molded body. The results of each measurement and evaluation are shown in Table 1.

[0133] Example 6 (Preparation of a Flow Molding Wood-Based Resin Composition (Injection Raw Material)) 1,500 g of an equimolar salt of sebacic acid and decamethylenediamine was dissolved in 1,500 g of distilled water to prepare a 50% by mass equimolar homogeneous aqueous solution of raw material monomers (monomer salt aqueous solution). Delignified cypress veneers, the lignin content of which had been adjusted using the lignin adjustment method described above, were immersed in the monomer salt aqueous solution using the monomer salt impregnation method described above. The concentration of the monomer salt aqueous solution was adjusted so that the resin content, calculated from the mass of the dry delignified cypress veneer and the mass (calculated value) of the resin composition in the resulting wood-based resin composition, would be 30% by mass. The impregnated cypress veneer and the monomer salt aqueous solution were transferred to an autoclave, heated to 200°C, and the water vapor was gradually released when the internal pressure reached 1.0 MPa, allowing the mixture to react for 1 hour. Next, the pressure was reduced over 30 minutes, and the autoclave was then depressurized to 0.02 MPa using a vacuum device and maintained for 10 minutes. The autoclave was then pressurized with nitrogen and cooled to obtain a wood-based resin composition for flow molding. CP / MAS NMR analysis confirmed that polyamide 1010 was polymerized in situ and contained in the wood-based resin composition for flow molding. GPC analysis revealed that the weight-average molecular weight of polyamide 1010 was 14,000. The wood content in the wood-based resin composition was calculated in the same manner as in Example 1 and was found to be 70% by mass (resin content: 30% by mass). The wood-based resin composition retained the same shape as the original cypress veneer, maintaining its wooden board shape, and exhibiting a structure in which the synthesized resin was impregnated into the cypress veneer structure. (Injection Molding) The obtained wood-based resin composition was injection molded in the same manner as in Example 1 to produce a wood-based molded body. The results of each measurement and evaluation are shown in Table 1.

[0134] Example 7 (Preparation of a Flow Molding Wood-Based Resin Composition (Injection Raw Material)) 1,500 g of an equimolar salt of isophthalic acid and decamethylenediamine was dissolved in 1,500 g of distilled water to prepare a 50% by mass equimolar homogeneous aqueous solution of raw material monomers (monomer salt aqueous solution). Delignified cypress veneers, the lignin content of which had been adjusted using the lignin adjustment method described above, were immersed in the monomer salt aqueous solution using the monomer salt impregnation method described above. The concentration of the monomer salt aqueous solution was adjusted so that the resin content, calculated from the mass of the dry delignified cypress veneer and the mass (calculated value) of the resin composition in the resulting wood-based resin composition, would be 30% by mass. The impregnated cypress veneer and the monomer salt aqueous solution were transferred to an autoclave, heated to 200°C, and the water vapor was gradually released when the internal pressure reached 0.8 MPa, allowing the reaction to proceed for 1 hour. Next, the pressure was reduced over 30 minutes, and the autoclave was then depressurized to 0.02 MPa using a vacuum device and maintained for 10 minutes. The autoclave was then pressurized with nitrogen and cooled to obtain a wood-based resin composition for flow molding. CP / MAS NMR analysis confirmed that Polyamide 10I was polymerized in situ and contained in the wood-based resin composition for flow molding. GPC analysis revealed that the weight-average molecular weight of Polyamide 10I was 18,000. The wood content in the wood-based resin composition was calculated in the same manner as in Example 1 and was found to be 70% by mass (resin content: 30% by mass). The wood-based resin composition retained the same shape as the original cypress veneer, maintaining its wooden board shape, and exhibiting a structure in which the synthesized resin was impregnated into the cypress veneer structure. (Injection Molding) The obtained wood-based resin composition was injection molded in the same manner as in Example 1 to produce a wood-based molded body. The results of each measurement and evaluation are shown in Table 1.

[0135] Example 8 (Preparation of a Flow Molding Wood-Based Resin Composition (Injection Raw Material)) 1,500 g of an equimolar salt of isophthalic acid and decamethylenediamine was dissolved in 1,500 g of distilled water to prepare a 50% by mass equimolar homogeneous aqueous solution of raw material monomers (monomer salt aqueous solution). Untreated cypress veneers that had not undergone lignin group treatment using the above-described lignin preparation method were immersed in the monomer salt aqueous solution using the above-described monomer salt impregnation method. The concentration of the monomer salt aqueous solution was adjusted so that the resin content, calculated from the mass of the dry delignified cypress veneer and the mass (calculated value) of the resin composition in the resulting wood-based resin composition, would be 50% by mass. The impregnated cypress veneer and the monomer salt aqueous solution were transferred to an autoclave and heated to 200°C. When the internal pressure reached 0.8 MPa, water vapor was gradually released, and the reaction was allowed to proceed for 1 hour. Next, the pressure was reduced over 30 minutes, and the autoclave was then depressurized to 0.02 MPa using a vacuum device and maintained for 10 minutes. The autoclave was then pressurized with nitrogen and cooled to obtain a wood-based resin composition for flow molding. CP / MAS NMR analysis confirmed that Polyamide 10I was polymerized in situ and contained in the wood-based resin composition for flow molding. GPC analysis revealed that the weight-average molecular weight of Polyamide 10I was 17,000. The wood content in the wood-based resin composition was calculated as in Example 1 and found to be 50% by mass (resin content: 50% by mass). The wood-based resin composition retained the same shape as the original cypress veneer, maintaining its wooden board shape, and exhibiting a structure in which the synthesized resin was impregnated into the cypress veneer structure. (Injection Molding) The obtained wood-based resin composition was injection molded as in Example 1 to produce a wood-based molded body. The results of each measurement and evaluation are shown in Table 1.

[0136] Comparative Example 1 (Preparation of resin-impregnated cypress veneer (raw material for injection molding)) Polyamide 6I (weight average molecular weight: 19,000) was dissolved in HFIP at a concentration of 10% by mass to prepare an impregnation solution. A delignified cypress veneer, the lignin content of which had been adjusted using the above-mentioned lignin adjustment method, was immersed in this impregnation solution at 35°C for 7 days, and the liquid inside the cypress was replaced with the HFIP solution of polyamide 6I. The cypress veneer removed from the impregnation solution was dried at room temperature for 18 hours, then hot-air dried at 60°C for 2 days, and further dried under reduced pressure at 80°C for 5 days to obtain a resin-impregnated cypress veneer, the raw material for injection molding. The wood content of the resulting resin-impregnated cypress veneer was calculated from the mass of the resin-impregnated cypress veneer and the estimated mass of the dry delignified cypress veneer, calculated from the weight loss rate of the cypress veneer due to delignification (6.8% by mass), and was found to be 70% by mass (resin content 30% by mass). The resin-impregnated cypress veneer had the same shape as the original cypress veneer, maintaining its woody board shape and exhibiting a structure in which the resin was impregnated within the cypress veneer structure. (Injection molding) A vertical injection unit with a 3 mm diameter x 10 mm long capillary hole at the tip of a mold having a piston with an outer diameter of 29.7 mm and a cylinder with an inner diameter of 30.0 mm, and a gear mold with a gear-shaped cavity at the bottom of the injection unit were placed between the heating plates of a press molding machine. The mold was heated by heat transfer from the heating plate until the surface temperature of the cylinder reached 150°C. Several resin-impregnated cypress veneers (approximately 10 g) were then placed in the cylinder and slowly compressed over 5 minutes to preheat the resin-impregnated cypress veneers. The heating plate was then lowered at a rate of 10 mm / min, pressurizing the resin-impregnated cypress veneers in the cylinder to fluidize them and transport them through the capillary into the mold cavity. Once the wood-based resin composition had completely moved into the mold cavity, heating was stopped. The mold temperature was confirmed to be below 100°C, and the molded body was removed. The piston pressure and mold clamping pressure were 212 MPa. During this molding process, the pressure applied to the piston when the piston reached a position 4 mm from the tip of the mold was recorded as the pressure at which the resin-impregnated cypress veneers in the cylinder flowed out (flow pressure). The measurement and evaluation results are shown in Table 1.

[0137] Comparative Example 2 (Preparation of Resin-Impregnated Hinoki Veneer (Injection Raw Material)) A dry (moisture content: approximately 0%) delignified Hinoki veneer, the lignin content of which had been adjusted using the above-described lignin adjustment method, was immersed in an aqueous solution prepared by diluting an acrylic resin emulsion ("Aron T-50" manufactured by Toagosei Co., Ltd., composition: sodium polyacrylate, weight-average molecular weight: 75,000, acrylic resin content (solids concentration): 43% by mass) to a solids concentration of 20% by mass. The dried Hinoki veneer was then subjected to reduced pressure at approximately 20°C for 1 hour, followed by 18 hours of pressure application, thereby injecting the acrylic resin emulsion into the Hinoki veneer. The Hinoki veneer removed from the aqueous solution was dried at room temperature for approximately 48 hours, further air-dried at 35°C for 48 hours, and finally dried under reduced pressure for 48 hours to obtain a resin-impregnated Hinoki veneer, the injection raw material. The wood content of the obtained resin-impregnated cypress veneer was calculated in the same manner as in Comparative Example 1 and was found to be 70% by mass (resin content 30% by mass). The shape of the resin-impregnated cypress veneer was the same as the original cypress veneer, maintaining the wooden board shape and exhibiting a structure in which the resin was impregnated within the cypress veneer structure. (Injection molding) The obtained wood-based resin composition was injection molded in the same manner as in Example 1 to produce a wood-based molded body. The cylinder temperature was set to 170°C. The measurement and evaluation results are shown in Table 1.

[0138] Comparative Example 3 (Preparation of Resin-Impregnated Hinoki Veneer (Injection Raw Material)) A delignified Hinoki veneer, the lignin content of which had been adjusted using the above-described lignin adjustment method, was immersed in a 25% aqueous solution of "PEG-20000" (weight-average molecular weight: 64,000) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. at room temperature for one week, and the liquid inside the Hinoki was replaced with the PEG aqueous solution. The Hinoki veneer removed from the aqueous solution was then dried under controlled humidity conditions of 20°C and 60% RH to obtain a resin-impregnated Hinoki veneer, which is an injection raw material. The wood content of the obtained resin-impregnated Hinoki veneer was calculated in the same manner as in Comparative Example 1 and was found to be 60% by mass (resin content: 40% by mass). The resin-impregnated Hinoki veneer had the same shape as the original Hinoki veneer, maintaining its woody board shape, and exhibiting a structure in which the Hinoki veneer structure was impregnated with resin. (Injection Molding) The obtained wood-based resin composition was used to produce a woody molded body by injection molding in the same manner as in Example 1. The cylinder temperature was set to 170° C. The results of the measurements and evaluations are shown in Table 1.

[0139]

[0140] As shown in Table 1, the molded articles of Examples 1 to 6, which were produced by impregnating a wood-based material with a specific thermoplastic resin monomer and polymerizing it, exhibited a light brown to brown color tone and were good in commercial productivity, mold transferability, surface hardness, water resistance, and film formability.

[0141] On the other hand, Comparative Example 1, in which a molded body was produced by impregnating a wood-based material with an HFIP solution of PA6I, required the use of expensive HFIP as a solvent, making it impractical and inferior in terms of commercial productivity to Examples 1 to 6. Furthermore, Comparative Examples 2 and 3, in which molded bodies were produced using injection materials impregnated with PMMA or PEG, had a slightly dusky color tone of brown or brown-brown, and were inferior to Examples 1 to 6 in all aspects of commercial productivity, mold transferability, surface hardness, water resistance, and film formability.

[0142] The woody molded articles obtained using the flow-molding woody resin composition of the present invention have excellent color tone, commercial productivity, mold transferability, surface hardness, water resistance, and film formability, and are therefore suitable for a wide range of applications, including daily necessities, furniture and furnishings, building materials and construction components, housings for electrical appliances or audio equipment, and vehicle components.

Claims

1. A wood-based resin composition for melt molding, comprising a wood-based material and a thermoplastic resin, wherein the wood-based resin composition for melt molding has one or more shapes selected from the group consisting of a plate, a fiber, a column, and a sphere, wherein the content of the wood-based material is 50% by mass or more and less than 95% by mass, and the content of the thermoplastic resin is more than 5% by mass and 50% by mass or less, based on the total mass of the wood-based resin composition for melt molding, wherein the thermoplastic resin has one or more bonds selected from the group consisting of an amide bond, an ester bond, an ether bond, and a thioether bond in the main chain skeleton of the repeating unit, or has one or more end groups selected from the group consisting of a carbonyl group, an acid anhydride group, an amide group, and a hydroxyl group, wherein in the wood-based resin composition for melt molding, the thermoplastic resin is present in the wood cell wall and / or the wood cell lumen of the wood-based material, and the thermoplastic resin remains in the wood cell wall and / or the wood cell lumen of the wood-based material even after extraction with a solvent capable of dissolving the thermoplastic resin with respect to the wood-based resin composition for melt molding. A wood-based resin composition for melt molding, characterized by the above.

2. The wood-based resin composition for melt molding according to claim 1, wherein the thermoplastic resin contains one or more resins selected from the group consisting of polyamide, polyoxymethylene, polyester, polypropylene, polyphenylene ether, and polyarylene sulfide.

3. The wood-based resin composition for melt molding according to claim 1, wherein the thermoplastic resin contains polyamide.

4. The wood-based resin composition for melt molding according to claim 1, wherein the thermoplastic resin contains amorphous polyamide.

5. The wood-based resin composition for melt molding according to claim 1, wherein the wood-based material is fibrous with a fiber diameter D of 3.0 mm or less and a ratio L / D of fiber length L to fiber diameter D of 3 or more.

6. The wood-based resin composition for melt molding according to claim 1, further containing 1% by mass or more of moisture based on the total mass of the wood-based resin composition for melt molding.

7. The wood-based resin composition for melt molding according to claim 1, wherein the lignin content of the wood-based material is 3% by mass or more.

8. A method for manufacturing a wood-based resin composition for flow forming, comprising: an impregnation step of bringing a monomer of a thermoplastic resin into contact with a wood-based material to impregnate the wood-based material with the monomer of the thermoplastic resin; and a polymerization step of polymerizing the monomer of the thermoplastic resin impregnated in the wood-based material to synthesize a thermoplastic resin. The resulting wood-based resin composition for flow forming has one or more shapes selected from the group consisting of a plate, a fiber, a column, and a sphere. The content of the wood-based material is 50% by mass or more and less than 95% by mass, and the content of the thermoplastic resin is more than 5% by mass and 50% by mass or less, based on the total mass of the wood-based resin composition for flow forming. The thermoplastic resin has one or more bonds selected from the group consisting of an amide bond, an ester bond, an ether bond, and a thioether bond in the main chain skeleton of the repeating unit, or has one or more end groups selected from the group consisting of a carbonyl group, an acid anhydride group, an amide group, and a hydroxyl group. In the wood-based resin composition for flow forming, the thermoplastic resin is present in the wood cell wall and / or the wood cell lumen of the wood-based material. After extraction with a solvent capable of dissolving the thermoplastic resin with respect to the wood-based resin composition for flow forming, the thermoplastic resin remains in the wood cell wall and / or the wood cell lumen of the wood-based material. A method for manufacturing a wood-based resin composition for flow forming, characterized by the above.

9. The method for manufacturing a wood-based resin composition for flow forming according to claim 8, further comprising an adjustment step of adjusting the lignin amount of the wood-based material before the impregnation step.

10. The method for manufacturing a wood-based resin composition for flow forming according to claim 9, further comprising a water-containing step of bringing the wood-based material into contact with water after the adjustment step and before the impregnation step.

11. The method for manufacturing a wood-based resin composition for flow forming according to claim 8, wherein the thermoplastic resin contains one or more resins selected from the group consisting of polyamide, polyoxymethylene, polyester, polypropylene, polyphenylene ether, and polyarylene sulfide.

12. The method for manufacturing a wood-based resin composition for flow forming according to claim 8, wherein the thermoplastic resin contains polyamide.

13. The method for manufacturing a wood-based resin composition for flow forming according to claim 8, wherein the thermoplastic resin contains amorphous polyamide.

14. The method for producing a wood-based resin composition for flow molding according to claim 8, wherein the wood-based material is fibrous with a fiber diameter D of 3.0 mm or less and a ratio L / D of fiber length L to the fiber diameter D of 3 or more.

15. The method for producing a wood-based resin composition for flow molding according to claim 8, wherein the wood-based resin composition for flow molding further contains 1% by mass or more of moisture based on the total mass of the wood-based resin composition for flow molding.

16. The method for producing a wood-based resin composition for flow molding according to claim 8, wherein the lignin content of the wood-based material is 3% by mass or more.

17. A wood molded article formed by molding a wood-based resin composition for flow molding containing a wood-based material and a thermoplastic resin, wherein the content of the wood-based material is 50% by mass or more and less than 95% by mass, and the content of the thermoplastic resin is more than 5% by mass and 50% by mass or less, based on the total mass of the wood molded article; the thermoplastic resin has at least one bond selected from the group consisting of an amide bond, an ester bond, an ether bond, and a thioether bond in the main chain skeleton of the repeating unit, or has at least one end group selected from the group consisting of a carbonyl group, an acid anhydride group, an amide group, and a hydroxyl group; in the wood molded article, the thermoplastic resin is present in the wood cell wall and / or the wood cell lumen of the wood-based material; and the thermoplastic resin remains in the wood cell wall and / or the wood cell lumen of the wood-based material even after extraction with a solvent capable of dissolving the thermoplastic resin from the wood molded article.

18. The wood molded article according to claim 17, formed by injection molding the wood-based resin composition for flow molding.

19. The wood molded article according to claim 17, formed by press molding the wood-based resin composition for flow molding.

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