Wood-based resin composition for fluid molding and method for producing the same, and method for producing a wood-molded body.

Abstract

To provide a wood-based resin composition for flow molding with excellent mold transferability, surface hardness, and film moldability when made into a wood molding body.SOLUTION: A method of producing a wood-based resin composition for flow molding according to the present invention includes an impregnation process in which a thermoplastic resin is impregnated into the wood-based material by bringing the thermoplastic resin into contact with the wood-based material, a resulting composition is in one or more shapes selected from a group consisting of plates, fibers, columns, and spheres, the maximum length of the composition is 1 to 30 mm, and the wood-based material content is 50 mass% or more and less than 95 mass% and the thermoplastic resin content is more than 5 mass% and 50 mass% or less, relative to the total mass of the composition. The thermoplastic resin has one or more bonds selected from the group consisting of amide bond, ester bond, ether bond, and thioether bond in the main chain backbone of the repeating unit, or one or more terminal groups selected from the group consisting of carbonyl group, acid anhydride group, amide group, and hydroxyl group.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, against the backdrop of the depletion of underground resources, there has been a surge in technological development to highly utilize biomass resources such as wood. In particular, the creation of components and materials with performance equal to or better than metal and plastic products, using sustainably usable biomass resources as raw materials, has become a globally important and urgent issue.

[0003] The use of wood and materials containing a large amount of wood is seen as a promising measure for forest carbon sinks, and in the future, technologies for processing and handling wood are desired so that it can be used not only in buildings but also in a wider range of applications, especially as an industrial material.

[0004] While conducting basic physical property research on biomass materials such as wood, the inventors discovered that under specific temperature and pressure conditions, wood can flow and deform while remaining solid, 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, thus forming it. Compared to methods that change shape by densifying through the occlusion of the lumens of wood cells, such as compression processing, flow molding allows for greater deformation because it causes deformation through positional changes due to the sliding phenomenon between wood cells. Furthermore, flow molding enables the plastic processing of wood-based materials of any shape, which was previously impossible with compression processing alone, and damage to fibrous wood cells is suppressed, thus providing a reinforcing effect to the resulting wood-molded body. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-155394 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the low fluidity of block-shaped wood-based materials results in insufficient filling of molds during molding, leading to poor mold transferability, which poses a challenge. Furthermore, while molded bodies with a wood-like surface appearance can be obtained, the texture is not yet satisfactory, and there is room for further improvement in terms of surface hardness. Moreover, there has been no concrete study yet on applying wood-based materials to thin-film molded bodies such as films formed from metals or plastics.

[0007] The present invention has been made in view of the above circumstances, and provides a wood-based resin composition for fluid molding that is excellent in mold transferability, surface hardness, and film moldability when used as a wood-based molded body, a method for producing the same, and a method for producing a wood-based molded body using the wood-based resin composition for fluid molding. [Means for solving the problem]

[0008] In other words, the present invention includes the following embodiments. (1) A method for producing a wood-based resin composition for flow molding, The process includes an impregnation step in which a thermoplastic resin is brought into contact with a wood-based material to impregnate the wood-based material with the thermoplastic resin. The resulting wood-based resin composition for flow molding is one or more shapes selected from the group consisting of plates, fibers, columns, and spheres. The maximum length of the wood-based resin composition for fluid molding is 1 mm or more and 30 mm or less. The wood-based material content is 50% by mass or more and less than 95% by mass relative to the total mass of the wood-based resin composition for fluid molding, and the thermoplastic resin content is more than 5% by mass and 50% by mass or less. A method for producing the thermoplastic resin, wherein the main chain skeleton of the repeating unit has one or more bonds selected from the group consisting of amide bonds, ester bonds, ether bonds, and thioether bonds, or has one or more terminal groups selected from the group consisting of carbonyl groups, acid anhydride groups, amide groups, and hydroxyl groups. (2) The manufacturing method according to (1), further comprising an adjustment step of adjusting the lignin content of the wood-based material before the impregnation step. (3) The manufacturing method according to (2), further comprising a water absorption step, which occurs before the impregnation step and after the adjustment step, in which the wood-based material is brought into contact with water. (4) The manufacturing method according to any one of (1) to (3), wherein in the impregnation step, the thermoplastic resin is brought into contact with the wood-based material in the presence of a solvent to impregnate the wood-based material with the thermoplastic resin. (5) The manufacturing method according to any one of (1) to (4), wherein the thermoplastic resin is one or more resins selected from the group consisting of polyamide, polyoxymethylene, polyester, polypropylene, polyphenylene ether, and polyarylene sulfide. (6) The manufacturing method according to any one of (1) to (5), wherein the thermoplastic resin contains a polyamide. (7) The method for producing the thermoplastic resin according to any one of (1) to (6), wherein the thermoplastic resin comprises an amorphous polyamide. (8) A heating step in which a wood-based resin composition for fluid molding obtained by the manufacturing method described in any one of (1) to (4) is heated to a temperature above the melting point or glass transition temperature of the thermoplastic resin to plasticize it, A pressurized flow step is performed to flow through a pipe with a diameter of 0.5 mm or more and 3 mm or less by pressurizing the plasticized wood-based resin composition for flow molding, The process involves filling the wood-based resin composition for fluid molding, which has been passed through the fluid, into a cavity of a predetermined shape, followed by a cooling step, A method for manufacturing a wood-based molded body, comprising the elements in this order. (9) The method for producing a wood-based molded article according to (8), wherein the wood-based material is fibrous in which the fiber diameter D is 3 mm or less and the ratio L / D of the fiber length to the fiber diameter D is 3 or more. (10) The method for producing a wood-based molded article according to (8) or (9), wherein the thermoplastic resin is one or more resins selected from the group consisting of polyamide, polyoxymethylene, polyester, polypropylene, polyphenylene ether, and polyarylene sulfide. (11) A method for producing a wood-based molded article according to any one of (8) to (10), wherein the thermoplastic resin contains a polyamide. (12) A method for producing a wood-based molded article according to any one of (8) to (11), wherein the thermoplastic resin comprises an amorphous polyamide. (13) The method for producing a wood-based molded article according to any one of (8) to (12), wherein the wood-based resin composition for flow molding further contains 10% by mass or less of water relative to the total mass of the wood-based resin composition for flow molding. (14) A method for producing a wood-molded article according to any one of (8) to (13), wherein the thermoplastic resin is present within the wood cell walls of the wood-based material in the wood-based resin composition for fluid molding. (15) A first filling step in which wood-based material is plasticized by heating and pressurizing, and then filled into a cavity of a predetermined shape, A second filling step involves plasticizing a thermoplastic resin by heating and pressurizing it, and then filling it into the cavity of a predetermined shape. A cooling step for cooling the cavity filled with the thermoplastic resin, This includes them in this order, With respect to the total mass of the wood-based molded body, 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. A method for producing a wood-based molded article, wherein 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 units, or has one or more terminal groups selected from the group consisting of carbonyl groups, acid anhydride groups, amide groups, and hydroxyl groups. (16) The method for manufacturing the wood molded body according to (15), wherein the thermoplastic resin is at least one resin selected from the group consisting of polyamide, polyoxymethylene, polyester, polypropylene, polyphenylene ether, and polyarylene sulfide. (17) The method for manufacturing the wood molded body according to (15) or (16), further including an adjustment step of adjusting the lignin amount of the woody material before the first filling step. (18) The method for manufacturing the wood molded body according to any one of (15) to (17), wherein the woody material contains 1 part by mass or more of moisture with respect to 100 parts by mass of the woody material.

Advantages of the Invention

[0009] According to the woody resin composition for melt molding and the method for manufacturing the same in the above aspect, it is possible to provide a woody resin composition for melt molding and the method for manufacturing the same, which are excellent in mold transferability, surface hardness, and film formability when formed into a wood molded body. The method for manufacturing the wood molded body in the above aspect is a method using the woody resin composition for melt molding, and a wood molded body excellent in mold transferability, surface hardness, and film formability can be obtained.

Brief Description of the Drawings

[0010] [Figure 1A] Cross-sectional image (left) and Raman mapping (right) of the injection raw material taken by the microscopic Raman spectrometer in Example 1. [Figure 1B] Raman spectrum in Example 1. [Figure 2] Image showing the appearance of the molded piece in Example 1. [Figure 3] Image showing the appearance of the molded piece in Comparative Example 1. [Figure 4] Image showing the appearance of the molded piece in Comparative Example 2. [[ID=�3]]

Embodiments for Carrying Out the Invention

[0011] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). This embodiment is illustrative for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0012] ≪Method for producing wood-based resin compositions for fluid molding≫ The method for producing the wood-based resin composition for fluid molding according to this embodiment is: The process includes an impregnation step in which a thermoplastic resin is brought into contact with a wood-based material to impregnate the wood-based material with the thermoplastic resin.

[0013] The wood-based resin composition for fluid molding obtained by the manufacturing method of this embodiment is one or more shapes selected from the group consisting of plates, fibers, columns, and spheres.

[0014] The maximum length of the wood-based resin composition for fluid molding obtained by the manufacturing method of this embodiment is 1 mm or more and 30 mm or less, preferably 2 mm or more and 25 mm or less, and more preferably 3 mm or more and 10 mm or less.

[0015] In the wood-based resin composition for fluid molding obtained by the manufacturing method of this embodiment, the content of wood-based material is 50% by mass or more and less than 95% by mass, preferably 50% by mass or more and 90% by mass or less, and more preferably 50% by mass or more and 80% by mass or less, based on the total mass of the wood-based resin composition for fluid molding. By keeping the wood-based material content within the above range, it is possible to increase the proportion of bio-derived components and contribute to the environment. Furthermore, unlike conventional compositions, the composition does not flow due to the fluidity of the resin, but rather flows due to the improved fluidity effect of the heat of the wood material itself, thereby imparting a high wood-like appearance to the resulting molded product.

[0016] The content of thermoplastic resin is more than 5% by mass and 50% by mass or less relative to the total mass of the wood-based resin composition for fluid molding, preferably 10% by mass or more and 50% by mass or less, and more preferably 20% by mass or more and 50% by mass or less. By keeping the thermoplastic resin content within the above range, the contribution of the thermoplastic resin to the fluidity of the composition can be reduced, and the resulting molded article can be given a high wood-like appearance.

[0017] 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 units, or has one or more terminal groups selected from the group consisting of carbonyl groups, acid anhydride groups, amide groups, and hydroxyl groups.

[0018] The method for producing the wood-based resin composition for fluid molding according to this embodiment, having the above configuration, yields a wood-based resin composition for fluid molding that exhibits excellent mold transferability, surface hardness, and film moldability when formed into a wood-based molded body.

[0019] In this specification, "mold transferability" refers to the property of forming a molded body with a fine structure and maintaining a shape that reflects the structure of the mold.

[0020] Furthermore, in this specification, "film moldability" specifically refers to the property that the entire composition, including not only the resin but also the woody components, can flow into and solidify in narrow gaps of 500 μm or less in thickness.

[0021] Furthermore, in this specification, "surface hardness" refers to the property of a molded body exhibiting excellent scratch resistance when in contact with a hard material. Surface hardness can be evaluated by measuring scratch hardness (pencil method) in accordance with ISO 15184:1996.

[0022] Next, the steps for the manufacturing method of the wood-based resin composition for fluid molding according to this embodiment will be described in detail below.

[0023] <Impregnation process> In the impregnation process, the thermoplastic resin is brought into contact with the wood-based material to impregnate the wood-based material with the thermoplastic resin.

[0024] Impregnation methods include, but are not limited to, methods in which only thermoplastic resin is brought into contact with the wood-based material, or methods in which thermoplastic resin is brought into contact with the wood-based material in the presence of a solvent.

[0025] In a method where only thermoplastic resin is brought into contact with wood-based materials, the thermoplastic resin can be impregnated into the wood-based materials by bringing them into contact under a heated and pressurized environment.

[0026] The heating temperature is preferably above the melting temperature of the resin. For example, if the thermoplastic resin is a crystalline resin, the temperature can be above its melting point, preferably 10°C or more above the melting point, and more preferably 20°C or more above. If the thermoplastic resin is an amorphous resin, the temperature can be above its glass transition temperature, preferably 30°C or more above the glass transition temperature, and more preferably 50°C or more above. Furthermore, the upper limit of the heating temperature is preferably 220°C or less, and more preferably 200°C or less, because wood decomposition becomes significant otherwise.

[0027] The melting point of thermoplastic resins can be measured in accordance with ISO 11357-1~6:2016. Furthermore, the glass transition temperature of thermoplastic resins can be measured using a dynamic viscoelasticity measuring device. Typical measurement conditions include a strain within the linear region, a measurement frequency of 10 Hz, and a heating rate of 2°C / min.

[0028] The applied pressure can be, for example, above atmospheric pressure, preferably 0.2 MPa or higher, more preferably 0.5 MPa or higher, and even more preferably 0.8 MPa or higher. The upper limit of the applied pressure is preferably 5.0 MPa or lower, more preferably 3.0 MPa or lower, and even more preferably 2.0 MPa or lower.

[0029] The heating and pressurizing time should be sufficient for the resin to penetrate the wood-based material completely, but it can be, for example, 20 minutes or more, preferably 30 minutes or more, and more preferably 40 minutes or more. The upper limit of the heating and pressurizing time is preferably 5 hours or less, and more preferably 3 hours or less.

[0030] In a method of contacting a thermoplastic resin with a wood-based material in the presence of a solvent, it is preferable to use a solvent that can dissolve or disperse the thermoplastic resin.

[0031] As a solvent for dissolving the thermoplastic resin, a solvent capable of dissolving the thermoplastic resin can be selected at a concentration of at least 0.5% by mass, more preferably 1% by mass or more, even more preferably 3% by mass or more, and even more preferably 5% by mass or more. Specifically, for example, when the thermoplastic resin is polyamide, examples include formic acid, sulfuric acid, hexafluoroisopropanol, and aqueous calcium chloride solutions. Alternatively, for example, when the thermoplastic resin is polyoxymethylene, examples include formic acid. Alternatively, for example, when the thermoplastic resin is polypropylene, examples include aromatic organic solvents such as xylene and toluene. Alternatively, for example, when the thermoplastic resin is polyphenylene ether, examples include halogen-containing solvents such as chloroform and methylene chloride, and aromatic organic solvents such as xylene and toluene. Alternatively, for example, when the thermoplastic resin is polyarylene sulfide, since there is no suitable solvent, a method of contacting only the thermoplastic resin with a wood-based material is preferred.

[0032] Furthermore, in the case of a method in which a thermoplastic resin is brought into contact with a wood-based material in the presence of a solvent, the thermoplastic resin can be impregnated into the wood-based material by the solution displacement method or the drying and impregnation method described in International Publication No. 2022 / 004796.

[0033] In the solution displacement method, specifically, a wood-based material swollen with water is immersed in an impregnation solution containing a thermoplastic resin and a solvent at a temperature of 20°C to 40°C, preferably 30°C to 40°C, under atmospheric pressure, under pressurized or reduced pressure conditions. The immersion time can be appropriately set depending on the shape, size, or mass of the wood-based material; for example, it can be 1 hour to 200 hours per 10 g of dry wood-based material.

[0034] In the drying and impregnation method, specifically, wood-based materials that are swollen with water are dehydrated by forced-air drying, reduced-pressure drying, or high-temperature drying, and then immersed at a temperature of 20°C to 40°C (preferably 30°C to 40°C), under atmospheric pressure, under pressurized or reduced-pressure conditions. The immersion time can be appropriately set depending on the shape, size, or mass of the wood-based material; for example, it can be 1 minute to 24 hours per 10 g of dry wood-based material.

[0035] <Other processes> The method for producing the wood-based resin composition for fluid molding according to this embodiment may include, in addition to the impregnation step, other steps such as a conditioning step and a water absorption step before the impregnation step.

[0036] [Adjustment process] In the adjustment process, the lignin content of the wood-based material is adjusted before the impregnation process.

[0037] Methods for adjusting the lignin content in wood-based materials include known lignin treatment methods such as the Klaudiz method, Wize method, Kraft pulping method, soda method, phenol pulping method, organic acid pulping method, organosolve pulping method, ASAM method, and bleaching treatment. Among these, the Klaudiz method is preferred as the adjustment method.

[0038] Details regarding the lignin content in wood-based materials and the methods for measuring it will be described later in the section "Wood-based materials" below.

[0039] [Water-containing process] In the water absorption process, the wood-based material is brought into contact with water before the impregnation process and after the conditioning process.

[0040] By impregnating the wood-based material with water, water molecules can penetrate between the hydrogen bonds of cellulose and hemicellulose, the main components of the wood-based material, making it easier to replace them with resin during the impregnation process. Furthermore, since the water in the wood-based material acts as a plasticizer, the fluidity of the resulting wood-based resin composition for fluid molding can be further improved during molding.

[0041] Methods for hydration include, but are not limited to, methods of bringing saturated water vapor into contact with wood-based materials, methods of humidifying wood-based materials under a constant relative humidity environment, and methods of immersing wood-based materials in water.

[0042] <Raw materials> Next, the raw materials used in the method for producing the wood-based resin composition for fluid molding according to this embodiment will be described in detail below.

[0043] [Wood-based materials] Wood-based materials are derived from plant bodies with cell walls, such as wood (coniferous trees like cedar, cypress, and pine; broad-leaved trees like poplar, beech, oak, and birch), bamboo, hemp (jute, kenaf, flax, hemp, ramie, sisal, etc.), and herbaceous plants. They may be the plant bodies themselves (sawn boards, veneers, etc.), their waste materials, or chemically treated products thereof.

[0044] The shape and size of the wood-based material are not particularly limited, but since flow molding is a molding method in which a molded body is manufactured with a wood-based resin composition for flow molding contained in a mold, when using wood-based material as one of the raw materials for a wood-based resin composition for flow molding and aiming to obtain a wood-based molded body with excellent shape stability, it is preferable that the material be in the form of chips containing fibers with a length of at least 5 mm. The shape of the wood-based material is not particularly limited and may be fixed or irregular in shape, such as a board, fiber, column, or sphere.

[0045] The wood-based material is preferably one whose lignin content has been adjusted by the adjustment process described above. The lignin content is not necessarily low, but is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more. The lignin content may be 20% by mass or more. When the lignin content is 20% by mass or more, the mechanical properties of the resulting wood-based molded article are equivalent to those of an untreated wood-based material, but because the flowability of the wood-based material is excellent, it can be subjected to greater deformation than an untreated wood-based material, resulting in a wood-based resin composition for flow molding with excellent productivity of wood-based molded articles. Furthermore, when the lignin content is 3% by mass or more and 15% by mass or less, the mechanical properties of the resulting wood-based molded article are greatly improved compared to an untreated wood-based material, and it can be a molding material with excellent productivity of wood-based molded articles. The upper limit of the lignin content is preferably 15% by mass, from the viewpoint of the mechanical properties of the resulting woody molded body. However, it may exceed 15% by mass if the mechanical properties are equivalent to those of untreated woody material, and is usually the same as the lignin content of the woody material itself before delignin treatment. It should be noted that the upper limit varies depending on the type of woody material, the growing environment, and differences in parts even within the same individual, so it is not possible to indicate a uniform upper limit with a specific numerical value.

[0046] Lignin content can be measured by the acetyl bromide method. The acetyl bromide method is a technique in which powdered wood-based material is decomposed with an acetic acid solution of acetyl bromide, and the amount of lignin dissolved is converted into ultraviolet 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).

[0047] When wood-based materials are subjected to the lignin content adjustment treatment described above, the degree of lignin condensation decreases, and a relaxed state can be formed within the cell walls. Therefore, the wood-based materials obtained in this way can further improve the intercellular sliding of wood cells in the wood-based material during flow molding compared to those obtained by methods such as adding water to untreated plant material or applying strain to untreated plant material to relax the bonds between polymer chains in amorphous polymers such as hemicellulose and lignin, as described in Japanese Patent Application Publication No. 2006-247974, in order to exhibit fluidity. This makes it possible to provide a wood-based resin composition for flow molding with superior productivity of wood-based molded products.

[0048] [Thermoplastic resin] Thermoplastic resins have 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 repeating units, or have one or more terminal groups selected from the group consisting of carbonyl groups, acid anhydride groups, amide groups, and hydroxyl groups.

[0049] Examples of such thermoplastic resins include, but are not limited to, polyamides, polyoxymethylenes, polyesters, polypropylenes, polyphenylene ethers, and polyarylene sulfides. Among these, polyamides are preferred, and amorphous polyamides are more preferred. Polyamides have the characteristics of heat resistance, mechanical strength, and high affinity with wood-based materials due to the presence of hydrogen bonds in their molecular structure. Furthermore, by using amorphous polyamides that do not have a crystalline layer, the resin can penetrate even finer regions within the cell walls of wood, making it possible to include wood components at a higher concentration.

[0050] In this specification, "polyamide" means a polymer having an amide (-NHCO-) ​​group in its main chain.

[0051] Furthermore, "amorphous polyamide" refers to a polyamide whose crystallization enthalpy ΔH is 15 J / g or less when measured by differential scanning calorimeter at 20°C / min. (B) The crystallization enthalpy of amorphous polyamide is preferably 10 J / g or less, more preferably 5 J / g or less, and even more preferably 0 J / g.

[0052] On the other hand, "crystalline polyamide" refers to a polyamide whose heat of fusion of the crystals is 4 J / g or more when measured at 20°C / min using a differential scanning calorimeter.

[0053] Furthermore, the crystallization enthalpy ΔH and the heat of fusion of the crystal can be measured, for example, using a measuring device such as the Diamond-DSC manufactured by PERKIN-ELMER, in accordance with JIS-K7121.

[0054] (Amorphous polyamide) The amorphous polyamide is not particularly limited as long as it is a polyamide whose crystallization enthalpy ΔH is less than or equal to the above upper limit, but it may be a semi-aromatic polyamide.

[0055] When the amorphous polyamide is a semi-aromatic polyamide, it is preferable that it is a polyamide containing diamine units and dicarboxylic acid units.

[0056] 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.

[0057] The total amount of 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%, relative to the total amount of all constituent units of the amorphous polyamide.

[0058] In this invention, the proportion of predetermined monomer units constituting the amorphous polyamide can be measured by nuclear magnetic resonance spectroscopy (NMR) or the like.

[0059] In 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, particularly preferably 75 mol% to 100 mol%, even more preferably 90 mol% to 100 mol%, and particularly preferably 100 mol%.

[0060] By ensuring that the content of isophthalic acid units relative to the total number of moles of dicarboxylic acid is above the above lower limit, a polyamide that satisfies mechanical properties, moldability, surface appearance, etc., can be obtained.

[0061] The dicarboxylic acid units may also contain aromatic dicarboxylic acid units other than isophthalic acid units, aliphatic dicarboxylic acid units, and alicyclic dicarboxylic acid units.

[0062] Aromatic dicarboxylic acids that constitute aromatic dicarboxylic acid units other than isophthalic acid units are not limited to the following, but examples include dicarboxylic acids having a phenyl group or a naphthyl group. The aromatic group of the aromatic dicarboxylic acid may be unsubstituted or have substituents.

[0063] The substituents are not particularly limited, but examples include alkyl groups having 1 to 4 carbon atoms, aryl groups having 6 to 10 carbon atoms, arylalkyl groups having 7 to 10 carbon atoms, halogen groups such as chloro and bromo groups, silyl groups having 1 to 6 carbon atoms, sulfonic acid groups and their salts (such as sodium salts).

[0064] Specifically, examples include, but are not limited to, terephthalic acid, naphthalenedicarboxylic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5-sodium sulfisoisophthalic acid, and other aromatic dicarboxylic acids having 8 to 20 carbon atoms, either unsubstituted or substituted with a predetermined substituent. Among these, terephthalic acid is preferred.

[0065] The aromatic dicarboxylic acids that make up the aromatic dicarboxylic acid unit may be used individually or in combination of two or more types.

[0066] Examples of aliphatic dicarboxylic acids that constitute an aliphatic dicarboxylic acid unit include, but are not limited to, 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, dodecanediic acid, tetradecanediic acid, hexadecanedioic acid, octadecanediic acid, eicosanedioic acid, diglycolic acid, and other linear or branched saturated aliphatic dicarboxylic acids having 3 to 20 carbon atoms.

[0067] The alicyclic dicarboxylic acids that constitute the alicyclic dicarboxylic acid unit (hereinafter also referred to as "alicyclic dicarboxylic acid unit") are not limited to the following, but examples include alicyclic dicarboxylic acids with 3 to 10 carbon atoms in the alicyclic structure, and alicyclic dicarboxylic acids with 5 to 10 carbon atoms in the alicyclic structure are preferred.

[0068] 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. Among these, 1,4-cyclohexanedicarboxylic acid is preferred.

[0069] Furthermore, the alicyclic dicarboxylic acids that constitute the alicyclic dicarboxylic acid unit may be used individually or in combination of two or more types.

[0070] The alicyclic group of an alicyclic dicarboxylic acid may be unsubstituted or substituted. Examples of substituents include alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl groups, but are not limited to those listed below.

[0071] In addition to isophthalic acid units, the dicarboxylic acid units preferably include aromatic dicarboxylic acid units, and more preferably include aromatic dicarboxylic acids having 6 to 12 carbon atoms.

[0072] Using such dicarboxylic acids tends to improve the mechanical properties, fluidity, and surface appearance of polyamides.

[0073] In amorphous polyamides, the dicarboxylic acid constituting the dicarboxylic acid unit is not limited to the compounds described above as dicarboxylic acids, but may be equivalent compounds to the dicarboxylic acids.

[0074] Here, "compounds equivalent to dicarboxylic acids" refers to compounds that can have a dicarboxylic acid structure similar to the dicarboxylic acid structure derived from the above-mentioned dicarboxylic acid. Examples of such compounds, though not limited to those listed below, include anhydrides and halides of dicarboxylic acids.

[0075] Furthermore, amorphous polyamides may optionally contain units derived from trivalent or higher polycarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid.

[0076] The aforementioned polycarboxylic acids with a valency of three or more may be used alone or in combination of two or more types.

[0077] The diamine units constituting the amorphous polyamide preferably contain at least 50 mol% of diamine units having 4 to 10 carbon atoms. Examples of such units include, but are not limited to, aliphatic diamine units, alicyclic diamine units, aromatic diamine units, and the like.

[0078] The aliphatic diamines that constitute the aliphatic diamine unit are not limited to the following, but include, for example, linear saturated aliphatic diamines with 2 to 20 carbon atoms such as ethylenediamine, propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, and tridecamethylenediamine.

[0079] The alicyclic diamines that constitute the alicyclic diamine unit (hereinafter also referred to as "alicyclic diamines") are not limited to the following, but examples include 1,4-cyclohexanediamine, 1,3-cyclohexanediamine, and 1,3-cyclopentanediamine.

[0080] The aromatic diamines that constitute the aromatic diamine unit are not limited to those listed below, as long as they are diamines containing aromatics, but examples include metaxylylenediamine.

[0081] Among these, aliphatic diamine units are preferred, diamine units having a linear saturated aliphatic group with 4 to 10 carbon atoms are more preferred, diamine units having a linear saturated aliphatic group with 6 to 10 carbon atoms are even more preferred, and hexamethylenediamine units are particularly preferred.

[0082] Using such diamines tends to result in polyamides with superior mechanical properties, fluidity, and surface appearance.

[0083] The diamine may be used alone or in combination of two or more types.

[0084] As amorphous polyamides, polyamide 6I, 6I / 6T, 9I, or 10I are preferred, 6I or 6I / 6T are more preferred, and 6I is the most preferred.

[0085] Furthermore, amorphous polyamides may optionally contain trivalent or higher polyhydric aliphatic amines such as bispentamethylenetriamine and bishexamethylenetriamine.

[0086] The aforementioned polyvalent or higher polyhydric aliphatic amines may be used alone or in combination of two or more types.

[0087] Amorphous polyamides may further contain at least one unit selected from the group consisting of lactam units and aminocarboxylic acid units. The inclusion of such units tends to result in polyamides with superior toughness. Here, the lactam and aminocarboxylic acid constituting the lactam and aminocarboxylic acid units refer to polypolymerizable (condensable) lactams and aminocarboxylic acids.

[0088] 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 4 to 14 carbon atoms are preferred, and lactams and aminocarboxylic acids having 6 to 12 carbon atoms are more preferred.

[0089] The lactams that make up the lactam unit are not limited to the following, but examples include butyrolactam, pivalolactam, ε-caprolactam, capryloractam, enantractam, undecanolactam, and laurolactam (dodecanolactam). Among these, ε-caprolactam or laurolactam are preferred as lactams, with ε-caprolactam being more preferred. Including such lactams tends to result in polyamides with superior mechanical properties.

[0090] The aminocarboxylic acids that constitute the aminocarboxylic acid unit are not limited to the following, but examples include ω-aminocarboxylic acids and α,ω-amino acids, which are compounds in which lactam rings have been opened.

[0091] As the aminocarboxylic acid, linear or branched saturated aliphatic carboxylic acids having 4 to 14 carbon atoms, with an amino group substituted at the ω position, are preferred. Examples of such aminocarboxylic acids, though not limited to those listed below, include 6-aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Other examples of aminocarboxylic acids include para-aminomethylbenzoic acid.

[0092] The lactam and aminocarboxylic acid that constitute the lactam unit and aminocarboxylic acid unit may be used individually or in combination of two or more types.

[0093] The total proportion (mol%) of lactam units and aminocarboxylic acid units is preferably 0 mol% to 20 mol%, more preferably 0 mol% to 10 mol%, and even more preferably 0 mol% to 5 mol% relative to the total polyamide.

[0094] When the total ratio of lactam units and aminocarboxylic acid units falls within the above range, effects such as improved fluidity tend to be obtained.

[0095] Amorphous polyamides may have their ends sealed with an end-capping agent. The end-capping agent can also be added as a molecular weight modifier when producing polyamides from the dicarboxylic acid and diamine mentioned above, and at least one compound selected from the group consisting of lactams and aminocarboxylic acids, which may be used as needed.

[0096] Examples of end-cap encapsulants include, but are not limited to, acid anhydrides, monoisocyanates, monoacid halides, monoesters, monoalcohols, and the like.

[0097] Examples of acid anhydrides include monocarboxylic acids, monoamines, and phthalic anhydrides.

[0098] Among these, monocarboxylic acids or monoamines are preferred. The sealing of the polyamide's ends with a terminal encapsulant tends to result in a polyamide with superior thermal stability.

[0099] The aforementioned end-capturing agent may be used alone or in combination of two or more types.

[0100] Any monocarboxylic acid that can be used as a terminal encapsulant is one that is reactive with the amino group that may be present at the ends of the polyamide. Specifically, examples of monocarboxylic acids are not limited to the following, but include aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, aromatic monocarboxylic acids, etc.

[0101] 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, tridecyl acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid.

[0102] Examples of alicyclic monocarboxylic acids include, but are not limited to, cyclohexanecarboxylic acid.

[0103] 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.

[0104] These monocarboxylic acids may be used individually or in combination of two or more types.

[0105] Any monoamine that can be used as a terminal encapsulant is one that is reactive with the carboxyl groups that may be present at the ends of the polyamide. Specifically, examples of monoamines are not limited to the following, but include aliphatic monoamines, alicyclic monoamines, aromatic monoamines, etc.

[0106] Aliphatic amines include, but are not limited to, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine.

[0107] Examples of alicyclic amines include, but are not limited to, cyclohexylamines and dicyclohexylamines.

[0108] Aromatic amines are not limited to the following, but examples include aniline, toluidine, diphenylamine, naphthylamine, etc.

[0109] These monoamines may be used individually or in combination of two or more types.

[0110] Polyamides that are end-encapsulated with end-encapsulants tend to exhibit superior fluidity, low water absorption, moldability, and surface appearance.

[0111] When obtaining polyamides such as amorphous polyamides, it is preferable that the amount of dicarboxylic acid added and the amount of diamine added are approximately equal in molar amounts. Taking into account the escape of diamine from the reaction system during the polymerization reaction in the molar ratio, the total molar amount of diamine per molar amount of 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.

[0112] The method for producing polyamide is not limited to the following, but includes, for example, the polymerization step of (1) or (2) below. (1) A step of polymerizing a combination of a dicarboxylic acid constituting a dicarboxylic acid unit and a diamine constituting a diamine unit to obtain a polymer. (2) A step of polymerizing one or more selected from the group consisting of lactams constituting lactam units and aminocarboxylic acids constituting aminocarboxylic acid units to obtain a polymer.

[0113] Furthermore, the method for producing polyamide preferably includes a step after the polymerization step in which the degree of polymerization of the polyamide is increased. Additionally, if necessary, a sealing step may be included after the polymerization step and the sealing step in which the ends of the obtained polymer are sealed with a terminal sealant.

[0114] Specific methods for producing polyamide include the various methods exemplified in 1) to 4) below. 1) A method of polymerization by heating one or more aqueous solutions or aqueous suspensions selected from the group consisting of dicarboxylic acid-diamine salts, mixtures of dicarboxylic acid and diamine, lactams, and aminocarboxylic acids, while maintaining a molten state (hereinafter sometimes referred to as "thermal fusion polymerization"). 2) A method for increasing the degree of polymerization of polyamide obtained by thermal fusion polymerization while maintaining a solid state at a temperature below the melting point (hereinafter sometimes referred to as "thermal fusion polymerization / solid-phase polymerization"). 3) A method for polymerizing one or more substances selected from the group consisting of dicarboxylic acid-diamine salts, mixtures of dicarboxylic acid and diamine, lactams, and aminocarboxylic acids while maintaining a solid state (hereinafter sometimes referred to as "solid-phase polymerization"). 4) A method of polymerization using a dicarboxylic acid halide component equivalent to a dicarboxylic acid and a diamine component (hereinafter sometimes referred to as the "solution method").

[0115] In particular, a manufacturing method including thermal fusion polymerization is preferred for producing polyamides. Furthermore, when producing polyamides by thermal fusion polymerization, it is preferable to maintain the molten state until polymerization is complete. In order to maintain the molten state, it is necessary to manufacture polyamides under polymerization conditions suitable for polyamides. Examples of polymerization conditions include the following: First, the polymerization pressure in the thermal fusion polymerization method is set to 14 kg / cm². 2 More than 25kg / cm 2 Continue heating while controlling the pressure to the following (gauge pressure). Next, when the pressure inside the tank reaches atmospheric pressure (gauge pressure is 0 kg / cm²), continue heating. 2The blood pressure is lowered over a period of 30 minutes or more until it reaches the target value.

[0116] In the method for producing polyamide, the polymerization method is not particularly limited and may be a batch method or a continuous method.

[0117] The polymerization apparatus used in the production of polyamides is not particularly limited, and known apparatus can be used. Specific examples of polymerization apparatus include autoclave reactors, tumbler reactors, and extruder reactors (such as kneaders).

[0118] The following describes a method for producing polyamides using a batch-type thermal fusion polymerization method, but the method of producing polyamides is not limited to this.

[0119] First, an aqueous solution is prepared containing approximately 40% to 60% by mass of a combination of dicarboxylic acid and diamine, which are raw material components of polyamide, and, if necessary, at least one selected from the group consisting of lactam and aminocarboxylic acid. Next, the aqueous solution is gradually dehydrated in a concentration tank operated at a temperature of 110°C to 180°C and a pressure of approximately 0.035 MPa to 0.6 MPa (gauge pressure) to obtain a concentrated solution concentrated to approximately 65% ​​to 90% by mass.

[0120] Next, the resulting concentrated solution is transferred to an autoclave, and heating is continued until the pressure in the autoclave is between approximately 1.2 MPa and 2.2 MPa (gauge pressure).

[0121] Next, in the autoclave, the pressure is maintained at approximately 1.2 MPa to 2.2 MPa (gauge pressure) while removing at least one of the water and gas components. Then, when the temperature reaches approximately 220°C to 260°C, the pressure is reduced to atmospheric pressure (gauge pressure is 0 MPa). After reducing the pressure inside the autoclave to atmospheric pressure, the by-product water can be effectively removed by reducing the pressure as needed.

[0122] Next, the autoclave is pressurized with an inert gas such as nitrogen, and the molten polyamide is extruded from the autoclave as strands. The extruded strands are then cooled and cut to obtain polyamide pellets.

[0123] The polymer ends of the polyamide obtained by the above-described manufacturing method are not particularly limited, but can be classified and defined as follows: 1) to 4). In other words, these are 1) amino terminus, 2) carboxyl terminus, 3) terminus due to a encapsulating agent, and 4) other terminus. 1) The amino terminus is a polymer terminus that has an amino group (-NH2 group) and is derived from a diamine unit. 2) The carboxyl terminus is a polymer terminus that has a carboxyl group (-COOH group) and is derived from a dicarboxylic acid. 3) Ends formed by the encapsulant are ends formed when the encapsulant is added during polymerization. Examples of encapsulants include the end encapsulants mentioned above. 4) Other ends are polymer ends that do not fall under categories 1) to 3) above. Specific examples of other ends include ends formed by the deammonia reaction of amino ends, and ends formed by the decarboxylation reaction of carboxyl ends.

[0124] Furthermore, the number-average molecular weight 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 is below the above upper limit, the permeability into wood-based materials tends to be higher. On the other hand, the number-average molecular weight of the polyamide is preferably 3,000 or more, and more preferably 5,000 or more. When the number-average molecular weight is above the lower limit, it becomes easier to maintain the strength of the resulting molded article.

[0125] The molecular weight distribution (Mw / Mn) of the polyamide is preferably in the range of 2.0 to 2.5, regardless of the molecular weight.

[0126] The number-average molecular weight and weight-average molecular weight of polyamides can be calculated based on a calibration curve created using the number-average molecular weight previously measured by gel permeation chromatography (GPC) with hexafluoroisopropanol solvent, converted to PMMA (polymethyl methacrylate) standard samples (manufactured by Polymer Laboratory).

[0127] [Other ingredients] In the method for producing the wood-based resin composition for fluid molding according to this embodiment, in addition to the wood-based material and thermoplastic resin, additives such as plasticizers, antioxidants, ultraviolet absorbers, anti-aging agents, fillers, antibacterial agents, preservatives, antistatic agents, lubricants, and mold release agents may be used as raw materials. These additives can be used after being mixed with the thermoplastic resin beforehand.

[0128] The wood-based resin composition for fluid molding obtained by the manufacturing method of this embodiment preferably further contains 1% by mass or more of water relative to the total mass of the wood-based resin composition for fluid molding. By including water above the lower limit, the water acts as a plasticizer, further improving the fluidity of the wood-based material. On the other hand, there is no particular upper limit for the water content, but for example, it can be 30% by mass or less.

[0129] Furthermore, in the wood-based resin composition for fluid molding obtained by the manufacturing method of this embodiment, it is preferable that the thermoplastic resin is present within the wood cell walls of the wood-based material. This makes it possible to further improve the moisture absorption and shape retention during drying when it is made into a wood-based molded body.

[0130] The presence of the thermoplastic resin within the wood cell walls of wood-based materials can be confirmed, for example, using Raman spectroscopy. Specifically, a cross-section of a wood-based material of a wood-based resin composition for fluid molding or a molded body is subjected to micro-Raman spectroscopy (HR-800MX, Horiba, Ltd.) using a 50x objective lens, with a field of view that allows observation of the inside of the cell walls, approximately 40 μm in size. 2Mapping measurements are performed at 0.3 μm intervals on the area (an argon laser with a wavelength of 514 nm is irradiated for an exposure time of 0.3 seconds, with a pinhole diameter of 300 μm and a slit width of 100 μm, and the number of integrations is 3), and the spectrum is obtained. Subsequently, mapping is obtained based on the intensity of the absorption peak characteristic of the resin, for example, the absorption intensity in the range of 978 to 1030 nm for PA6I, and the presence or absence of resin components inside the cell wall can be confirmed.

[0131] ≪Method for manufacturing wood-based molded bodies≫ Wood-based molded bodies can be manufactured, for example, using the method shown below.

[0132] <First Embodiment> The method for manufacturing a wood-based molded body in this embodiment includes a heating step of heating the wood-based resin composition for fluid molding obtained by the manufacturing method described above to a temperature above the melting point or glass transition temperature of the thermoplastic resin to plasticize it, A pressurized flow step is performed to flow through a pipe with a diameter of 0.5 mm or more and 3 mm or less by pressurizing the plasticized wood-based resin composition for flow molding, The process involves filling the wood-based resin composition for fluid molding, which has been passed through the fluid, into a cavity of a predetermined shape, followed by a cooling step, It includes them in this order.

[0133] The manufacturing method for the wood-based molded body of this embodiment, having the above configuration, yields a wood-based molded body with excellent shape retention during moisture absorption and drying, film moldability, and surface appearance.

[0134] Next, the steps for manufacturing the wood-based molded body according to this embodiment will be described in detail below.

[0135] [Heating process] In the heating step, the wood-based resin composition for fluid molding obtained by the manufacturing method described above is heated to a temperature above the melting point or glass transition temperature of the thermoplastic resin to plasticize it.

[0136] The heating temperature can be set appropriately depending on the type of thermoplastic resin, but for example, it can be set to a temperature at or above the flow initiation temperature of the thermoplastic resin, preferably at least 10°C higher than the flow initiation temperature, and more preferably at least 20°C higher. The flow initiation temperature is the melting point if the thermoplastic resin is a crystalline resin, and the glass transition temperature if it is an amorphous resin. Furthermore, the upper limit of the heating temperature is preferably 220°C or lower, and more preferably 200°C or lower, from the viewpoint of suppressing the decomposition of wood.

[0137] 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 heating time can be, for example, 1 minute or more, preferably 2 minutes or more.

[0138] [Pressurized fluidization process] In the pressurized fluidization process, a plasticized wood-based resin composition for fluid molding is pressurized to flow through a pipe with a diameter of 0.5 mm to 3 mm.

[0139] Regarding the applied pressure, for example, there is no particular problem as long as the pressure necessary for flow is applied, and a lower pressure is preferable as it reduces the energy required. However, in general injection molding machines, for example, the upper limit of injection pressure is often around 250 MPa, so it is preferable that the pressure be 250 MPa or less.

[0140] [Cooling process] In the cooling process, the wood-based resin composition for fluid molding, which has been passed through the fluid, is filled into a cavity of a predetermined shape and then cooled.

[0141] A cavity refers to a hollow space into which mold resin flows and solidifies, and a cavity of the desired shape can be appropriately selected and used.

[0142] As for the cooling method, general cooling methods can be used, such as air cooling or liquid cooling of the mold itself. Preferably, the temperature of the mold is controlled with water or oil to remove heat from the wood-based resin composition for fluid molding.

[0143] The cooling time depends on the type of equipment, but can be appropriately selected from, for example, 4 hours or less. For typical injection molding, the cooling time is generally 1 minute or less.

[0144] Examples of molding equipment used in the manufacturing method of the wood-based 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, and the like.

[0145] <Second Embodiment> The method for manufacturing a wood-based molded body of this embodiment includes a first filling step in which a wood-based material is plasticized by heating and pressurizing, and then filled into a cavity of a predetermined shape, A second filling step involves plasticizing a thermoplastic resin by heating and pressurizing it, and then filling it into the cavity of a predetermined shape. A cooling step for cooling the cavity filled with the thermoplastic resin, It includes them in this order.

[0146] The wood-based material content of the wood-based molded body obtained by the manufacturing method of this embodiment is 50% by mass or more and less than 95% by mass, preferably 50% by mass or more and 90% by mass or less, and more preferably 50% by mass or more and 80% by mass or less, relative to the total mass. By keeping the wood-based material content within the above range, it is possible to increase the proportion of bio-derived components and contribute to the environment. Furthermore, unlike conventional compositions, the composition does not flow due to the fluidity of the resin, but rather flows due to the improved fluidity effect of the heat of the wood material itself, thereby imparting a high wood-like appearance to the resulting molded product.

[0147] The thermoplastic resin content is more than 5% by mass and 50% by mass or less relative to the total mass of the wood-based molded body, preferably 10% by mass or more and 40% by mass or less, and more preferably 20% by mass or more and 30% by mass or less. By keeping the thermoplastic resin content within the above range, the contribution of the thermoplastic resin to the fluidity of the composition can be reduced, and the resulting molded article can be given a high wood-like appearance.

[0148] 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 units, or has one or more terminal groups selected from the group consisting of carbonyl groups, acid anhydride groups, amide groups, and hydroxyl groups. Specific examples of such thermoplastic resins are the same as those exemplified in the "Wood-based Resin Composition for Flow Molding" described above.

[0149] The manufacturing method for the wood-based molded body of this embodiment, having the above configuration, yields a wood-based molded body with excellent shape retention during moisture absorption and drying, film moldability, and surface appearance.

[0150] Next, the steps for manufacturing the wood-based molded body according to this embodiment will be described in detail below.

[0151] [First filling process] In the first filling process, wood-based material is plasticized by heating and pressurizing, and then filled into a cavity of a predetermined shape.

[0152] The heating temperature can be, for example, 50°C or higher, preferably 70°C or higher, more preferably 90°C, and even more preferably 100°C. On the other hand, the heating temperature can be, for example, less than 200°C, preferably 180°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower. Setting the heating temperature above the lower limit can further increase the fluidity of the wood-based material, while setting it below the upper limit can further suppress discoloration.

[0153] The applied pressure can be, for example, 200 MPa or less, preferably 180 MPa or less, more preferably 160 MPa or less, and even more preferably 150 MPa or less. By keeping the applied pressure below the above upper limit, shear heat generation in the wood-based material during molding is further suppressed, and discoloration can be further suppressed. On the other hand, there is no particular preferred lower limit for the applied pressure, but it is generally 20 MPa or more.

[0154] The heating and pressing time can be, for example, 5 minutes or less, preferably 3 minutes or less, more preferably 1 minute or less, and even more preferably 30 seconds or less. By keeping the heating and pressing time below the above upper limit, excessive heating of the wood-based material during molding is further suppressed, and discoloration can be further suppressed. On the other hand, there is no particular preferred lower limit for the heating and pressing time, but it is generally around 5 seconds.

[0155] [Second filling process] In the second filling step, the thermoplastic resin is plasticized by heating and pressurizing, and then filled into the cavity of a predetermined shape.

[0156] The heating temperature is preferably above the melting temperature of the resin. For example, if the thermoplastic resin is a crystalline resin, the temperature can be above its melting point, preferably 10°C or more above the melting point, and more preferably 20°C or more above. If the thermoplastic resin is an amorphous resin, the temperature can be above its glass transition temperature, preferably 30°C or more above the glass transition temperature, and more preferably 50°C or more above. Furthermore, the upper limit of the heating temperature is preferably 220°C or less, and more preferably 200°C or less, from the viewpoint of suppressing the decomposition of the wood.

[0157] The applied pressure can be any pressure commonly used in resin injection molding, for example, 200 MPa or less, preferably 180 MPa or less, more preferably 160 MPa or less, and even more preferably 150 MPa or less. By keeping the applied pressure below the above upper limit, molding can be performed with less energy. There is no particular preferred lower limit for the applied pressure, but it is generally 20 MPa or more.

[0158] The heating and pressing time can be any time used in general resin injection molding, for example, it can be 1 minute or less, preferably 30 seconds or less, more preferably 20 seconds or less, and even more preferably 15 seconds or less. By keeping the heating and pressing time below the above upper limit, productivity can be further increased. There is no particular preferred lower limit for the heating and pressing time, but it can be 1 second or more.

[0159] [Cooling process] In the cooling process, the cavity filled with thermoplastic resin is cooled.

[0160] As for the cavity, one of the desired shape can be appropriately selected and used.

[0161] As for the cooling method, general cooling methods can be used, such as air cooling or liquid cooling of the mold itself. Preferably, the temperature of the mold is controlled with water or oil to remove heat from the wood-based resin composition for fluid molding.

[0162] The cooling time can be, for example, between 10 seconds and 1 minute. After the cooling process has reduced the surface temperature of the molded body to a temperature at which the resin can maintain its shape, the wood-based molded body is removed from the cavity.

[0163] [Adjustment process] The method for manufacturing a wood-based molded body according to this embodiment may further include an adjustment step to adjust the lignin content of the wood-based material before the first filling step. The adjustment process can be carried out in the same manner as the adjustment process described in the "Method for Manufacturing Wood-Based Resin Composition for Flow Molding" above.

[0164] Examples of molding equipment used in the manufacturing method of the wood-based 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, and the like.

[0165] The wood-based material and thermoplastic resin used in the method for manufacturing the wood-based molded article of this embodiment can be the same as those exemplified in the "Method for Manufacturing a Wood-Based Resin Composition for Flow Molding" described above.

[0166] In particular, the wood-based material preferably contains 1 part by mass or more of water per 100 parts by mass of the wood-based material. By containing water above the lower limit, water molecules can enter between the hydrogen bonds of cellulose and hemicellulose, which are the main components of the wood material, and the substitution with resin can be easily carried out in the impregnation process. In addition, since the water in the wood-based material acts as a plasticizer, the fluidity when molding the resulting wood-based resin composition for fluid molding can be further improved. On the other hand, there is no particular upper limit to the water content, but it is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 5 parts by mass or less. [Examples]

[0167] 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.

[0168] <Ingredients> The raw materials used in the examples and comparative examples are described below.

[0169] [Thermoplastic resin] (Polyamide 6 (PA6)) UBE Nylon SF1013A (Number average molecular weight: 14000, Melting point: 220℃) manufactured by Ube Industries, Ltd.

[0170] (Polyamide 6I (PA6I)) Polyamide 6I was synthesized using the following method. 1500 g of an equimolar salt of isophthalic acid and hexamethylenediamine, along with 1.5 mol% excess adipic acid and 0.5 mol% acetic acid relative to the total equimolar salt components, were dissolved in 1500 g of distilled water to prepare a homogeneous 50% by mass equimolar aqueous solution of the raw material monomers. The solution was concentrated by gradually removing water vapor while stirring at a temperature of 110-150°C until the solution concentration reached 70% by mass. The internal temperature was then raised to 220°C. At this time, the autoclave pressure was increased to 1.8 MPa. The reaction was continued for 1 hour, while gradually removing water vapor and maintaining the pressure at 1.8 MPa until the internal temperature reached 245°C. Next, the pressure was reduced over 30 minutes, and then the autoclave was maintained under reduced pressure of 0.087 MPa for 10 minutes using a vacuum device. At this point, the final internal temperature of polymerization was 265°C. Subsequently, the material was pressurized with nitrogen and formed into strands from the lower spindle (nozzle), then water-cooled and cut to discharge it in pellet form. The pellets were then dried at 100°C under a nitrogen atmosphere for 12 hours to obtain polyamide 6I. The obtained PA6I had a number-average molecular weight of 12,000, a weight-average molecular weight of 24,000, and a glass transition temperature of 158°C.

[0171] The number-average molecular weight and weight-average molecular weight were calculated based on a calibration curve created using the number-average molecular weight previously measured using a gel permeation chromatography (GPC) (HLC-8020, manufactured by Tosoh Corporation) and hexafluoroisopropanol solvent, converted to PMMA (polymethyl methacrylate) standard samples (manufactured by Polymer Laboratory Co., Ltd.). The GPC columns used were TSK-GEL GMHHR-M and G1000HHR.

[0172] Furthermore, the glass transition temperature was measured using a dynamic viscoelasticity measuring device. Specifically, for example, when the temperature was increased from 23°C at a heating rate of 2°C / min, the applied strain was kept within the linear region, and measurements were taken at an applied frequency of 10 Hz. The temperature at the peak of the peak where the storage modulus decreased significantly and the loss modulus was at its maximum was defined as the glass transition temperature Tg. If two or more peaks in the loss modulus appeared, the peak top temperature of the highest-temperature peak was defined as the glass transition temperature Tg. To improve measurement accuracy, measurements were taken at least once every 20 seconds.

[0173] (Polyethylene glycol (PEG)) PEG-20000, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Average molecular weight: 20,000 ± 5,000

[0174] (Acrylic resin (acrylic)) Acrylic resin emulsion (Aron T-50, sodium polyacrylate, number average molecular weight: 6000, acrylic content (solids concentration): 43% by mass) manufactured by Toagosei Co., Ltd.

[0175] [Wood material] (Hinoki veneer) From rotary veneers peeled from cypress logs to a thickness of 4 mm (radially: R), a hole saw with an inner diameter of 26 mm was used to cut out discs approximately 25 mm in diameter, yielding numerous cypress veneers with a tangential surface (LT surface) of approximately 25 mm in diameter and a thickness (R) of 4 mm.

[0176] (Small pieces of cypress wood) From a rotary veneer peeled from a cypress log to a thickness of 5 mm (radially: R), a cutting saw was used to cut it into 5 mm long and 5 mm wide pieces, obtaining small 5 mm cubic pieces.

[0177] (Cedar wood powder) Wood powder extracted from cedar wood: 178μm pass-through and 300μm on-through.

[0178] [Lignin adjustment method] The lignin content of cypress veneer was adjusted using a method in accordance with the Klaudiz method (Reference 1: "Takahide Sakaguchi et al.: "Chemistry of Wood", Bun'eido Publishing, 1985, pp. 69-70"). Specifically, dried cypress veneer was immersed in a 4% by mass aqueous solution of sodium chlorite set at 45°C for 6 hours to obtain cypress veneer with adjusted lignin content. After treatment, the veneer was washed multiple times by immersion in water to a saturated state. In addition, the treatment solution, which had been preheated, was injected under reduced pressure to ensure that the treatment solution quickly penetrated and reacted within the cypress veneer. The delignin-treated wood was stored in a saturated state until the next resin impregnation. A portion of the obtained treated cypress veneer was dried, and the weight loss rate from the untreated dry cypress veneer was measured to be 6.8% by mass.

[0179] <Method for measuring physical properties> [Presence or absence of thermoplastic resin within the wood cell wall] The end grain cross-section or wood powder portion of the cypress veneer obtained as resin-impregnated raw material was subjected to micro-Raman spectroscopy using a 50x objective lens, with a field of view that allowed observation of the inside of the cell wall, at a depth of approximately 40 μm. 2 Mapping measurements were performed on the area. The measurement involved irradiating with an argon laser with a wavelength of 514 nm for an exposure time of 0.3 seconds, setting the pinhole diameter to 300 μm and the slit width to 100 μm, and acquiring the spectrum with 3 integrations. A mapping of Raman absorption intensity in the range of 978 to 1030 nm was obtained. Subsequently, the presence or absence of resin components within the cell wall was confirmed based on the intensity of the absorption peaks characteristic of the resin. Specifically, in the raw material impregnated with polyamide 6I, 1000 cm³ -1 Because a characteristic absorption peak was found in the vicinity, mapping was performed using the absorption intensity in the range of 978 to 1030 nm.

[0180] [Moisture content before molding] Mass of raw material in a water-absorbing state (W) wet ) and the mass (W) after the raw material has been vacuum-dried at 100°C for 24 hours. dry The following parameters were measured, and the pre-molding moisture content (mass%) was calculated using the formula below.

[0181] Moisture content before forming (mass %) = (W wet - W dry ) × 100 / W dry <0**********> [Evaluation method] [Color tone] The color tone of the obtained gear molded body was visually confirmed. The better the thermal stability, the more the coloring was suppressed, and the tendency was to have a brighter color tone.

[0183] ] [Mold transferability] The mold transferability of the obtained gear molded body was evaluated in the following 5 grades.

[0184] (Evaluation criteria) 5: The shape of the gear teeth forms a right angle equivalent to the mold, and the entire surface of the molded piece has a gloss. 4: The shape of the gear teeth forms a right angle equivalent to the mold, but there is no gloss on a part of the molded piece. 3: The shape of the gear teeth forms a right angle equivalent to the mold, but there is no gloss on the molded piece at all. 2: The shape of the gear teeth does not reflect the mold shape, and there is no gloss on the molded piece at all. 1: Not fully filled

[0185] [Surface hardness] The surface hardness of the molded piece was measured by scratch hardness (pencil method) conforming to ISO 15184:1996.

[0186] <00007**********>[Film formability] The amount and toughness of the raw material flowing into the clearance (100 - 200 μm) between the piston and the cylinder during injection molding were evaluated in the following 3 grades.

[0187] (Evaluation criteria) 3: The flow length of the resin-impregnated raw material containing wood cells is 5 mm or more, and the burr has toughness and is difficult to break. 2: The flow length of the resin-impregnated raw material containing wood cells is less than 5 mm, or the burr is brittle and easy to break. 1: The resin-impregnated material containing woody cells has almost no inflow, or it is too brittle to maintain its shape.

[0188] [Recyclability] For evaluating the recyclability of the molded product, a mold was used with an inner container shape of 50 x 52 mm and flat punches and dies of the same dimensions on the top and bottom. After setting the mold surface temperature to 150°C, the molded product, punch, and die were placed inside the container, and a molding load of 8 tons (molding surface pressure: approximately 30 MPa) was applied in the vertical direction to produce a plate-shaped molded product. All mold surfaces in contact with the molded product were mirror-finished. Recyclability was evaluated in the following three stages.

[0189] (Evaluation Criteria) 3: The molded body is a plate-shaped molded product with the same dimensions and shape as the container, and has good mold transferability, resulting in a glossy surface. 2: It is a plate-shaped molded body with the same dimensions and shape as a container, but the surface of the molded body is not glossy. 1: Not sufficiently filled, or the molded product is brittle and easily crumbles (or has already crumbled).

[0190] [water resistance] The resulting molded pieces were immersed in water set at 80°C, and the changes in appearance after 10 hours were observed and evaluated on the following four-point scale.

[0191] (Evaluation Criteria) 4: Items that show no visible changes in appearance. 3: Molded products that have undergone slight deformation due to moisture absorption. 2: Molded bodies that have partially collapsed due to moisture absorption. 1: Items that no longer retain the original form of the molded product.

[0192] <Manufacturing of wood-based molded products> [Example 1] (Preparation of injection molding raw materials (wood-based resin composition for fluid molding)) An impregnation solution was prepared by dissolving polyamide 6I in hexafluoroylopropyl alcohol (HFIP) at a concentration of 10% by mass. Hinoki cypress veneers with adjusted lignin content were immersed in this impregnation solution at 35°C for 7 days, replacing the liquid inside the hinoki with the polyamide 6I HFIP solution. The resin-impregnated hinoki cypress veneers removed from the impregnation solution were 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.

[0193] The wood content in the resin-impregnated cypress veneer obtained as an injection molding raw material was calculated from the weight of the obtained raw material and the estimated weight of the delignin-treated wood in its dry state, which was calculated from the weight reduction rate of the wood due to the delignin treatment (6.8 mass%). The result was 70 mass (resin content 30 mass%). The morphology was identical to that of the original cypress veneer, maintaining a woody, board-like structure with resin impregnated into the woody material structure. Furthermore, the presence or absence of thermoplastic resin within the woody cell walls was measured for the obtained resin-impregnated raw material. For Example 1, to aid understanding, the mapping results are shown in Figure 1A (Raman mapping and Raman spectrum measurement locations) and Figure 1B (Raman spectrum) as representative examples.

[0194] (injection molding) Between the heating plates of the press molding machine, a vertical injection unit was installed, which had a piston with an outer diameter of 29.7 mm and a cylinder with an inner diameter of 30.0 mm, with a capillary hole of 3 mm in diameter and 10 mm in length at the tip of the mold. A gear mold with a gear-shaped cavity was installed at the bottom of the injection unit. After heating the mold until the surface temperature of the cylinder reached 150°C by heat transfer from the heating plates, several resin-impregnated cypress veneers (approximately 10 g each) were placed inside the cylinder and preheated for 5 minutes while slowly compacting them. Then, the plates were lowered at a rate of 10 mm / min to apply pressure to the resin-impregnated cypress veneers inside the cylinder, causing them to fluidize, pass through the capillary, and move into the mold cavity. After that, heating was stopped, and after confirming that the mold temperature had fallen below 100°C, the molded body inside (see Figure 2) was removed. The piston pressure and mold clamping pressure at this time were 212 MPa. During this molding process, the pressure applied to the piston at a position 4 mm from the tip was recorded as the flow pressure, while the pressure applied to the piston as the flow pressure was recorded as the pressure when the raw material flowed out of the cylinder.

[0195] [Example 2] (Preparation of injection molding raw materials (wood-based resin composition for fluid molding)) Polyamide 6I was immersed in water at 80°C for 100 hours to obtain saturated polyamide 6I with a water content of 4% by mass. A cypress veneer with a controlled amount of lignin, saturated with water, was placed in an autoclave, and the saturated polyamide was layered on top of it. The autoclave was then sealed after purging it with nitrogen. At this time, the ratio of cypress veneer to polyamide 6I was adjusted to 70 / 30 by dry weight.

[0196] Next, the autoclave was heated to 200°C. At this time, the pressure was increased to 1.6 MPa. After maintaining this pressure for one hour, the steam was gradually released, and the pressure was reduced to atmospheric pressure over 30 minutes, at which point the resin-impregnated cypress veneer was removed.

[0197] The obtained raw material had a shape almost identical to the original cypress veneer, maintaining a woody, board-like structure, and exhibiting a structure in which resin was impregnated within the woody material structure. Furthermore, similar to Example 1, the presence or absence of thermoplastic resin within the woody cell walls was confirmed using a micro-Raman spectrometer. As a result, the presence of polyamide 6I within the cell walls was confirmed.

[0198] (injection molding) Injection molding was performed in the same manner as in Example 1.

[0199] [Comparative Example 1] (Preparation of injection molding materials) A cypress veneer with an adjusted lignin content, in a dry state (moisture content: approximately 0%), was immersed in an aqueous solution of acrylic resin emulsion (Aron T-50, composition: sodium polyacrylate, number average molecular weight: 6000, acrylic content (solids concentration): 43% by mass) manufactured by Toagosei Co., Ltd., diluted to a solids concentration of 20% by mass. The veneer was then subjected to reduced pressure at approximately 20°C for 1 hour, followed by pressurization for 18 hours, injecting the acrylic resin emulsion into the cypress wood. The resin-impregnated cypress veneer was removed from the impregnation solution and dried at room temperature for approximately 48 hours, then air-dried at 35°C for 48 hours, and finally dried under reduced pressure for 48 hours. The wood content in the resin-impregnated cypress veneer, which was obtained as the raw material for injection molding at this time, was calculated to be 70% by mass (resin content 30% by mass). The form was identical to the original cypress veneer, maintaining a woody, board-like structure, and exhibiting a structure in which resin was impregnated within the woody material structure.

[0200] (injection molding) Injection molding was performed in the same manner as in Example 1. The cylinder temperature was set to 170°C. The appearance of the resulting molded piece is shown in Figure 3.

[0201] [Comparative Example 2] (Preparation of injection molding materials) Hinoki cypress veneers with adjusted lignin content were immersed in a 25% aqueous solution of PEG-20000 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. at room temperature for one week, replacing the internal liquid of the cypress with the PEG aqueous solution. The resin-impregnated cypress veneers removed from the impregnation solution were dried under controlled humidity conditions at 20°C and 60% RH. The wood content in the resin-impregnated cypress veneer, which was obtained as the injection molding raw material at this time, was calculated to be 60% by mass.

[0202] The form was identical to the original cypress veneer, maintaining a woody, board-like structure, and exhibiting a structure in which resin was impregnated within the woody material structure.

[0203] (injection molding) Injection molding was performed in the same manner as in Example 1. The cylinder temperature was set to 150°C. The appearance of the resulting molded piece is shown in Figure 4.

[0204] [Example 3] (Preparation of injection molding raw materials (wood-based resin composition for fluid molding)) An impregnation solution was prepared by dissolving polyamide 6 in HFIP at a concentration of 17% by mass. Hinoki cypress veneer with adjusted lignin content was immersed in this impregnation solution at 35°C for 7 days, dried at room temperature, then hot-air dried at 60°C for 2 days, and finally vacuum-dried at 80°C for 5 days.

[0205] The wood content in the resin-impregnated cypress veneer obtained as an injection molding raw material was calculated from the weight of the obtained raw material and the estimated weight of the delignin-treated wood in its dry state, which was calculated from the weight reduction rate of the wood due to the delignin treatment (6.8 mass%). The result was 50 mass (50 mass resin content).

[0206] The morphology was identical to that of the original cypress veneer, maintaining a woody, board-like structure, and exhibiting a structure in which resin was impregnated within the woody material structure. Furthermore, similar to Example 1, the presence or absence of thermoplastic resin within the woody cell walls was confirmed using a micro-Raman spectrometer. As a result, the presence of polyamide 6 within the cell walls was confirmed.

[0207] (injection molding) Injection molding was performed in the same manner as in Example 1.

[0208] [Example 4] (Preparation of injection molding raw materials (wood-based resin composition for fluid molding) and injection molding) Except for replacing the cypress veneer with an adjusted lignin content used in the preparation of the injection molding raw material in Example 1 with a cypress veneer without an adjusted lignin content, the procedure was carried out in the same manner as in Example 1.

[0209] [Example 5] (Preparation of injection molding raw materials (wood-based resin composition for fluid molding) and injection molding) Except for replacing the cypress veneer with an adjusted lignin content used in the preparation of the injection molding raw material in Example 2 with a cypress veneer without an adjusted lignin content, the procedure was carried out in the same manner as in Example 2.

[0210] [Comparative Example 3] (Preparation of injection molding materials) Fifty parts by mass of cedar wood powder, pre-dried for 24 hours in a vacuum dryer set to 105°C, was dry-blended with 50 parts by mass of polyamide 6 and 0.5 parts by mass of CA60 manufactured by Yumex Co., Ltd. as a compatibilizer. The mixture was then melt-kneaded at 250°C using a small Xplore kneader manufactured by DSM Corporation to obtain strip-shaped molded bodies, which were then pulverized to be used as raw materials. The resulting raw material exhibited a structure in which wood components were dispersed within the resin.

[0211] (injection molding) Injection molding was performed in the same manner as in Example 1.

[0212] [Comparative Example 4] (Preparation of injection molding materials) The procedure was carried out in the same manner as in Comparative Example 3, except that the amounts of each component were 70 parts by mass of pre-dried cedar wood powder, 30 parts by mass of polyamide 6, and 0.3 parts by mass of CA60 manufactured by Yumex Co., Ltd. as a compatibilizer. However, the thermal decomposition of the wood components was severe, and a proper melting state could not be achieved, making production impossible and thus evaluation could not be performed.

[0213] [Comparative Example 5] (Preparation of injection molding materials) Except for changing polyamide 6 to polyamide 6I in Comparative Example 4, the procedure was carried out in the same manner as in Comparative Example 4. However, similar to Comparative Example 4, the thermal decomposition of the wood component was severe, and a proper melting state was not achieved, making it impossible to manufacture the product and evaluate it.

[0214] [Example 6] (Preparation of injection molding materials) Except for changing the cypress veneer to cypress chips, the procedure was carried out in the same manner as in Example 1. The wood content in the resin-impregnated cypress veneer, which was obtained as the raw material for injection molding at this time, was calculated to be 80% by mass (resin content 20% by mass). The morphology was identical to the original cypress fragments, maintaining a woody, board-like structure, and exhibiting a structure in which resin was impregnated within the woody material.

[0215] (injection molding) Injection molding was performed in the same manner as in Example 1.

[0216] [Example 7] (Preparation of wood-based materials) The lignin content of cypress wood chips was adjusted using a method compliant with the Klaudiz method. Specifically, dried cypress wood chips were immersed in a 4% by mass aqueous solution of sodium chlorite set at 45°C for 6 hours to obtain cypress wood chips with adjusted lignin content. After treatment, the chips were washed multiple times by immersion in water to a saturated state. A portion of the treated cypress wood chips was dried, and the moisture content was measured from the weight loss rate, which was found to be 300% by mass.

[0217] (Two-color molding) Between the heating plates of the press molding machine, a vertical injection unit was installed, which had a piston with an outer diameter of 29.7 mm and a cylinder with an inner diameter of 30.0 mm, with a capillary hole of 3 mm in diameter and 10 mm in length at the tip of the mold, and a gear mold with a gear-shaped cavity was installed at the bottom of the injection unit.

[0218] After heating the mold until the cylinder surface temperature reached 120°C by heat transfer from the heating plate, several processed cypress wood pieces (approximately 8g each) were placed inside the cylinder and preheated for 5 minutes while slowly compacting them. Then, the plate was lowered at a rate of 5mm / min to apply pressure to the processed cypress wood pieces inside the cylinder, causing them to fluidize, pass through the capillary, and move into the mold cavity. At this time, the pressure applied to the piston at a position 4mm from the tip was recorded as the fluidization pressure during injection.

[0219] Subsequently, 8g of PA6I was filled into a cylinder heated to 150°C, preheated for 5 minutes while slowly compressing it, and then lowered at a plate descent rate of 5mm / min to apply pressure to the PA6I in the cylinder, causing it to fluidize, pass through the capillary, and flow into the mold cavity. At this time, the mold cavity was completely filled, so it was not possible to fill it completely with resin. Similarly, at this time, an attempt was made to record the pressure acting on the piston at a position 4mm from the tip as the pressure during flow, but the 4mm position was not reached, so the pressure just before the pressure reached its maximum value due to mold filling was taken as the pressure during flow.

[0220] In Examples 1-7 and Comparative Examples 1-3, the film moldability was evaluated based on the behavior during molding, and the resulting molded articles were evaluated for color tone, mold transferability, surface hardness, film moldability, recyclability, and water resistance. The results are shown in the table below.

[0221] [Table 1]

[0222] [Table 2]

[0223] As shown in Tables 1 and 2, in Examples 1 to 7, where molded articles were produced using injection molding raw materials in which a specific thermoplastic resin was impregnated into a wood-based material, or using a combination of a specific thermoplastic resin and a wood-based material, the articles exhibited a light brown to brown color tone, and all aspects such as mold transferability, surface hardness, film moldability, recyclability, and water resistance were good.

[0224] On the other hand, in Comparative Examples 1 and 2, where molded articles were produced using injection molding raw materials impregnated with PMMA or PEG, the color was brown or brown-brown, and all aspects such as mold transferability, surface hardness, film moldability, recyclability, and water resistance were inferior to those of Examples 1 to 7. Furthermore, in Comparative Example 3, where a molded body was produced using an injection molding material manufactured by melt-mixing cedar wood powder and resin and then extruding, the color of the wood material deteriorated significantly to a dark brown due to heating during melt-mixing. As a result, the mold transferability, surface hardness, film moldability, recyclability, and water resistance were all inferior to those of Examples 1-7. Moreover, in Comparative Examples 4-5, where the amount of cedar wood powder was increased and the cedar wood powder and resin were melt-mixed, as described above, the thermal decomposition of the wood components was significant, making it impossible to produce an injection molding material. [Industrial applicability]

[0225] The wood-based resin composition for fluid molding and its manufacturing method according to this embodiment provide a wood-based resin composition for fluid molding and its manufacturing method that exhibits excellent mold transferability, surface hardness, and film moldability when formed into a wood-based molded body.

Claims

1. A method for producing a wood-based resin composition for fluid molding, The process includes an impregnation step in which a thermoplastic resin is brought into contact with a wood-based material to impregnate the wood-based material with the thermoplastic resin. The resulting wood-based resin composition for flow molding is one or more shapes selected from the group consisting of plates, fibers, columns, and spheres. The maximum length of the wood-based resin composition for fluid molding is 1 mm or more and 30 mm or less. With respect to the total mass of the wood-based resin composition for fluid molding, 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. 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 has 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 the thermoplastic resin, wherein the thermoplastic resin includes an amorphous polyamide.

2. The manufacturing method according to claim 1, further comprising an adjustment step of adjusting the lignin content of the wood-based material before the impregnation step.

3. The manufacturing method according to claim 2, further comprising a water absorption step, which occurs before the impregnation step and after the adjustment step, in which the wood-based material is brought into contact with water.

4. The manufacturing method according to any one of claims 1 to 3, wherein in the impregnation step, the thermoplastic resin is brought into contact with the wood-based material in the presence of a solvent to impregnate the wood-based material with the thermoplastic resin.

5. The manufacturing method according to any one of claims 1 to 3, wherein the thermoplastic resin is one or more resins selected from the group consisting of polyamide, polyoxymethylene, polyester, polypropylene, polyphenylene ether, and polyarylene sulfide.

6. A heating step of heating a wood-based resin composition for fluid molding obtained by a manufacturing method according to any one of claims 1 to 3 to a temperature above the melting point or glass transition temperature of the thermoplastic resin to plasticize it, A pressurized flow step is performed to flow through a pipe with a diameter of 0.5 mm or more and 3 mm or less by pressurizing the plasticized wood-based resin composition for flow molding, The process involves filling the wood-based resin composition for fluid molding, which has been passed through the fluid, into a cavity of a predetermined shape, followed by a cooling step, A method for manufacturing a wood-based molded body, comprising the elements in this order.

7. The method for manufacturing a wood-based molded article according to claim 6, wherein the wood-based material is fibrous in which the fiber diameter D is 3 mm or less and the ratio L / D of the fiber length to the fiber diameter D is 3 or more.

8. The method for producing a wood-based molded article according to claim 6, wherein the thermoplastic resin is one or more resins selected from the group consisting of polyamide, polyoxymethylene, polyester, polypropylene, polyphenylene ether, and polyarylene sulfide.

9. The method for producing a wood-based molded article according to claim 6, wherein the wood-based resin composition for fluid molding further contains 10% by mass or less of water relative to the total mass of the wood-based resin composition for fluid molding.

10. The method for producing a wood-based molded article according to claim 6, wherein the thermoplastic resin is present within the wood cell walls of the wood-based material in the wood-based resin composition for fluid molding.

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