Manufacturing method for three-dimensional molded product and manufacturing method for diaphragm

Abstract

To provide a solid molded article that can be manufactured with a simple and short tact by using a naturally-derived material without requiring large scale facilities, and to provide a diaphragm and manufacturing methods of them.SOLUTION: A solid molded article is molded by mixing wood meal whose maximum grain size is 1000 μm or less, cellulose nanofiber and water and then heat-pressing. A manufacturing method of the solid molded article includes: a mixing step (S1) for mixing the wood meal whose maximum grain size is 500 μm or less, 0.1-50 wt.% of the cellulose nanofiber with respect to 100 wt.% of the wood meal in terms of solid content, and water; a forming step (S2) for forming the material mixed in the mixing step (S1) into a metal mold; a heating press step (S3) for heat-pressing by the metal mold; and a taking-out step (S4) for taking out the molded article from the metal mold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a cellulose nanofiber-based composite material by mixing wood flour, cellulose nanofibers, and water, and then hot-pressing the mixture to form a cellulose nanofiber composite material. R , three-dimensional molded product A method for producing diaphragm Manufacturing method and a powder consisting of leaf powder, stem powder, seed powder or grass powder, or a mixed powder of said powder and wood flour, mixed with cellulose nanofibers and water, and molded by hot pressing. Ru, Three-dimensional molding Quality Regarding the manufacturing method. [Background technology]

[0002] The large amounts of wood waste, such as sawdust, generated at sawmills and other facilities are primarily used as fertilizer and solid fuel, and much of it is currently discarded. Meanwhile, molding techniques have been proposed that use woody biomass, which is more environmentally friendly than petrochemical products such as plastics, as a material (see, for example, Patent Document 1 and Non-Patent Document 1). Furthermore, for diaphragms of earphones, headphones, speakers, and other three-dimensional molded products, a manufacturing method has been proposed in which an isocyanate-based binder is added to wood flour, the mixture is kneaded, and the mixture is heated and pressed to form a mold (see, for example, Patent Document 2).

[0003] The method for producing a molded product described in Patent Document 1 involves bringing a wood-based material containing a fluidization promoter such as polyethylene glycol into contact with steam, followed by drying, crushing, and hot pressing to obtain a three-dimensional molded product. However, the method for producing a molded product described in Patent Document 1 has problems in that it requires large-scale or special equipment for supplying steam, as well as complicated processes such as drying.

[0004] The three-dimensional molding technology described in Non-Patent Document 1 is a manufacturing method for obtaining three-dimensional molded products using only wood-based materials by injection molding or backward extrusion molding wood-based powder, taking advantage of the flow and self-adhesive properties of wood-based materials. However, the three-dimensional molding technology described in Non-Patent Document 1 requires an extremely long molding cycle time and requires an expensive, large-scale press with high pressure capacity.

[0005] Furthermore, the method for manufacturing a diaphragm described in Patent Document 2 uses a chemically synthesized binder, which is not environmentally friendly. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-261159 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-044966 [Non-patent literature]

[0007] [Non-Patent Document 1] Shohei Kajikawa, "Three-dimensional molding processing technology using flow and self-adhesion of wood-based powder", [online], May 18, 2017, New Technology Briefing at the University of Electro-Communications, [Retrieved February 2, 2021], Internet<URL:https: / / shingi.jst.go.jp / kobetsu / uec / 2017_uec / tech_property.html#pbBlock49846> Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above circumstances, the present invention provides a three-dimensional molded product that can be manufactured using naturally occurring materials, without requiring large-scale equipment, and in a simple and short molding cycle. A method for producing vibration Board The object is to provide a manufacturing method. [Means for solving the problem]

[0010] In the present invention The types of three-dimensional molded products are not particularly limited, and include various parts such as automobile interior parts, tableware, miscellaneous goods, and various small items. Furthermore, cellulose nanofibers in the present application refer to cellulose fibers with a nano-sized fiber diameter. The fiber diameter (average fiber diameter) of cellulose nanofibers is, for example, 2 nm to 100 nm. The length (average length) of cellulose nanofibers is, for example, 0.1 μm to 100 μm. The aspect ratio (length / diameter) of cellulose nanofibers is, for example, 50 to 1000. Furthermore, wood flour in the present application refers to powder obtained by finely pulverizing wood, and may be sawdust produced when cutting wood with a saw.

[0013] Book The diaphragm of the present invention can be used for diaphragms of earphones, headphones, speakers, etc. Furthermore, the wood flour is not particularly limited, and for example, sawdust from cedar, cypress, pine, etc. can be used, or a mixture of these can be used. From the perspective of acoustic properties, it is preferable to use wood flour with a maximum particle size of 250 μm or less. Furthermore, to improve strength, natural pulp can be mixed as an aggregate. Furthermore, the wood flour used may have an average particle size of 125 μm or more and 250 μm or less. The average particle size of wood flour in this application refers to the reading of the value of the opening size corresponding to 50 weight % when a cumulative weight % curve against the opening size is created by classifying the powder through a sieve.

[0015] The method for producing a three-dimensional molded product according to the present invention, which achieves the above object, comprises: wood flour having a maximum particle size of 1000 μm or less; cellulose nanofibers in an amount of 0.1% by weight to 50% by weight, calculated as a solid content, relative to 100% by weight of the wood flour; The weight ratio of the wood flour and the cellulose nanofiber is 3 to 7 times a mixing step of mixing the above-mentioned ingredients with water; a forming step of forming the material mixed in the mixing step into a mold; a heat pressing step of heat pressing using the mold; a removal step of removing a molded product from the mold; The present invention is characterized by having the following.

[0016] Here, in the mixing step, it is more preferable that the cellulose nanofibers are mixed in an amount of 0.1% by weight to 30% by weight relative to 100% by weight of the wood flour, and even more preferable that the cellulose nanofibers are mixed in an amount of 0.1% by weight to 10% by weight relative to 100% by weight of the wood flour.

[0017] According to the method for producing a three-dimensional molded product of the present invention, the cellulose nanofibers penetrate the wood flour when it absorbs moisture during the hot-pressing process, reinforcing hydrogen bonds. This is thought to be why the cellulose nanofibers act as a so-called hydrogen-bond strengthener (binder). This allows for the production of three-dimensional molded products with sufficient mechanical strength using naturally derived materials, without the need for large-scale equipment, and with a simple and short molding cycle. In particular, adding water during the mixing process makes it possible to heat-press while retaining moisture during the hot-pressing process, which is thought to prevent aggregation of the cellulose nanofibers and reduce variations in mechanical strength.

[0018] The method for manufacturing a diaphragm in the present invention that achieves the above object comprises: wood flour having a maximum particle size of 500 μm or less; cellulose nanofibers in an amount of 0.1% by weight to 50% by weight, calculated as a solid content, relative to 100% by weight of the wood flour; The weight ratio of the wood flour and the cellulose nanofiber is 3 to 7 times a mixing step of mixing the above-mentioned ingredients with water; a forming step of forming the material mixed in the mixing step into a mold; a heat pressing step of heat pressing using the mold; a removal step of removing a molded product from the mold; The present invention is characterized by having the following.

[0019] Here, it is more preferable that the cellulose nanofibers be mixed in an amount of 3% by weight to 10% by weight based on 100% by weight of the wood flour in the mixing step. If the amount of the cellulose nanofibers mixed is less than 3% by weight based on 100% by weight of the wood flour, it may be difficult to maintain the shape or the mechanical strength of the diaphragm may be insufficient. On the other hand, if the amount of the cellulose nanofibers mixed is more than 10% by weight based on 100% by weight of the wood flour, it may be disadvantageous in terms of cost.

[0020] In the mixing step, the wood flour preferably has a maximum particle size of 250 μm or less in terms of acoustic properties. Furthermore, to improve strength, natural pulp may be mixed as an aggregate. The wood flour may have an average particle size of 125 μm or more and 250 μm or less.

[0021] In the mixing step, water is mixed in an amount of 3 to 7 times by weight of the wood flour and the cellulose nanofibers. do. If the amount of water to be mixed is less than three times the weight of the wood flour and the cellulose nanofibers, mixing may be difficult and the mixture may not be uniform (the water may not penetrate the wood flour and the cellulose nanofibers).On the other hand, if the amount of water to be mixed is more than seven times the weight of the wood flour and the cellulose nanofibers, problems may arise such as difficulty in removing the moisture during the heat pressing step.

[0022] The diaphragm manufacturing method of the present invention uses naturally occurring materials, does not require large-scale equipment, and can produce a diaphragm with excellent vibration characteristics in a simple and short molding cycle. In particular, while a paper diaphragm (paper cone) requires a large amount of water for its manufacture, the manufacturing method of the present invention does not encounter such a problem.

[0024] The second method of manufacturing a three-dimensional molded product of the present invention that achieves the above object comprises: a powder consisting of leaf powder, stem powder, seed powder, or grass powder, each having a maximum particle size of 1000 μm or less, or a mixed powder obtained by mixing the powder with wood powder having a maximum particle size of 1000 μm or less; and cellulose nanofibers in an amount of 0.1% by weight to 50% by weight, calculated as solid content, relative to 100% by weight of the powder or the mixed powder. A weight ratio of the powder or the mixed powder to the cellulose nanofibers is 3 to 7 times a mixing step of mixing the above-mentioned ingredients with water; a forming step of forming the material mixed in the mixing step into a mold; a heat pressing step of heat pressing using the mold; a removal step of removing a molded product from the mold; The present invention is characterized by having the following. [Effects of the Invention]

[0025] According to the present invention, a three-dimensional molded product can be produced using naturally derived materials, without requiring large-scale equipment, and in a simple and short molding cycle. Manufacturing method, Beauty diaphragm It is possible to provide a method for producing the above-mentioned [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a flowchart showing an example of a method for manufacturing a diaphragm of the present invention. [Figure 2] FIG. 3 is a diagram showing the frequency characteristics of the diaphragms obtained in Example 1, Example 2, and the comparative example. [Figure 3] 1 is a graph showing the results of a Charpy impact test carried out on five test pieces taken from each of Examples 3 to 12. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The three-dimensional molded product of the present invention is not limited in its use. Therefore, in the following description, a diaphragm of the present invention, which is one of the three-dimensional molded products of the present invention, and a method for manufacturing the same will be described as an example.

[0028] The diaphragm of the present invention is manufactured using wood flour, cellulose nanofibers, and water.

[0029] The wood flour is not particularly limited, and sawdust from cedar, cypress, pine, or the like can be suitably used. Furthermore, wood flour with a maximum particle size of 500 μm or less can be used, with wood flour with a maximum particle size of 250 μm or less being more preferable in terms of the vibration characteristics of the diaphragm. Specifically, when using wood flour with a maximum particle size of 500 μm or less, wood flour that has passed through a sieve with a mesh size of 500 μm can be used, and when using wood flour with a maximum particle size of 250 μm or less, wood flour that has passed through a sieve with a mesh size of 250 μm can be used. Furthermore, wood flour with an average particle size of 125 μm or more and 250 μm or less can also be used.

[0030] The cellulose nanofibers are not particularly limited, and can be, for example, those produced by a method of defibrating cellulose. Any cellulose that can be used as a defibrated or refined material can be used. Examples include pulp, cotton, paper, regenerated cellulose fibers such as rayon, cupro, polynosic, and acetate, bacterially produced cellulose, and animal-derived cellulose such as sea squirts. These celluloses may also be chemically modified on the surface as needed.

[0031] As a method for defibrating cellulose, for example, a method can be used in which an aqueous suspension of cellulose is mechanically ground or beaten using a refiner, high-pressure homogenizer, grinder, single- or multi-screw kneader, bead mill, etc. Cellulose nanofibers may be produced by using one or a combination of these methods.

[0032] The average fiber diameter of cellulose nanofibers is preferably 3 nm or more and 150 nm or less, more preferably 3 nm or more and 100 nm or less. Here, the average fiber diameter of cellulose nanofibers refers to the average value of values ​​measured using a scanning electron microscope (SEM) for 40 randomly sampled cellulose nanofibers. Furthermore, from the viewpoint of dispersibility of cellulose nanofibers, the maximum fiber diameter of cellulose nanofibers is preferably 1000 nm or less, and particularly preferably 500 nm or less.

[0033] The lower limit of the average length of cellulose nanofibers is preferably 1 μm, more preferably 2 μm. Meanwhile, the upper limit of the average length of cellulose nanofibers is preferably 6 μm, more preferably 4 μm. Here, the average length of cellulose nanofibers refers to the average value of the values ​​measured by scanning electron microscope (SEM) for 40 randomly sampled cellulose nanofibers.

[0034] FIG. 1 is a flowchart showing an example of a method 10 for manufacturing a diaphragm (three-dimensional molded product) according to the present invention.

[0035] As shown in FIG. 1, the diaphragm manufacturing method 10 begins with a mixing step (step S1). In this mixing step (S1), prepared cellulose nanofibers are first mixed with water to disperse the cellulose nanofibers. Next, prepared wood flour is mixed. The blending amounts, converted to solid content, are 0.1% by weight to 50% by weight of cellulose nanofibers relative to 100% by weight of wood flour, and the amount of water is 3 to 7 times the weight of the wood flour and cellulose nanofibers. Note that, from the perspective of achieving a balance between uniform mixing and evaporating moisture, it is preferable to use about 5 times the weight of the wood flour and cellulose nanofibers.

[0036] When pulp is mixed as an aggregate to improve strength, the pulp is first disintegrated in water, then cellulose nanofibers are mixed, and then wood flour is mixed.

[0037] Next, a forming step is carried out (step S2) in which the material mixed in the mixing step (S1) is filled (formed) into a mold using a dedicated jig.

[0038] Next, a heat pressing step is carried out in which the mixture is heat-pressed using a mold (step S3). In this heat pressing step (S3), the heating temperature is set to 130°C to 180°C, and the pressing pressure is set to, for example, 200 MPa (1.4 MPa / cm). 2 The hot pressing step (S3) may be carried out until the material filled in the mold is in a dry state, which may take from a few seconds to a few minutes depending on the weight.

[0039] Finally, a removal step is carried out to remove the molded product from the mold (step S4).

[0040] Therefore, the manufacturing method of the diaphragm of the present invention does not require large-scale or special equipment (such as an expensive, large-scale press with high pressure capacity) as in the manufacturing method of the molded body described in Patent Document 1 or the three-dimensional molding processing technique described in Non-Patent Document 1. Furthermore, compared to the three-dimensional molding processing technique described in Non-Patent Document 1, it is possible to significantly shorten the molding tact time.

[0041] Next, the frequency characteristics of a diaphragm manufactured by the diaphragm manufacturing method of the present invention will be explained in comparison with a comparative example.

[0042] Examples 1 and 2 are diaphragms manufactured using the diaphragm manufacturing method of the present invention. Specifically, the diaphragms were sized for use in speakers with a diameter of 30 mm. The diaphragms used were wood flour with a maximum particle size of 250 μm or less, 10% by weight of cellulose nanofiber relative to 100% by weight of wood flour (solid content equivalent), 10% by weight of pulp relative to 100% by weight of wood flour, and 5 times the weight of water relative to the wood flour and cellulose nanofiber. A typical paper cone of the same size was used as a comparative example.

[0043] Fig. 2 is a diagram showing the frequency characteristics of the diaphragms obtained in Example 1, Example 2, and the Comparative Example. In Fig. 2, the frequency characteristics of Example 1 are shown by a dashed line, the frequency characteristics of Example 2 are shown by a dashed line, and the frequency characteristics of the Comparative Example are shown by a solid line. In Fig. 4, the vertical axis represents output dB, and the horizontal axis represents frequency Hz.

[0044] As is clear from FIG. 2, Examples 1 and 2 have superior acoustic characteristics compared to the comparative example.

[0045] According to the present invention, it is possible to provide a three-dimensional molded product, a diaphragm, and a method for manufacturing the same, which can be manufactured using naturally occurring materials, without requiring large-scale equipment, and in a simple and short molding cycle.

[0046] The present invention is not limited to the above-described embodiments and can be modified in various ways within the scope of the claims. For example, while the above-described embodiments have been described using a diaphragm as an example, the present invention can also be applied to various parts such as automobile interior components, tableware, miscellaneous goods, and various small items, as well as three-dimensional molded products and their manufacturing methods. In particular, it is preferable to use a mixture of wood flours with different particle sizes. For example, a mixture of wood flour with a maximum particle size of 500 μm or less that passes through a 500 μm mesh sieve and long, thin wood flour with a length of 1 cm or more that falls through a 500 μm mesh sieve vertically can be used. Adopting this embodiment can improve impact strength.

[0047] Next, a second embodiment of the three-dimensional molded product of the present invention will be described. In the second three-dimensional molded product of the present invention, instead of the wood flour used in the three-dimensional molded product of the present invention described above, a powder consisting of leaf powder, stem powder, seed powder, or grass powder with a maximum particle size of 1000 μm or less, or a mixed powder obtained by mixing such a powder with wood flour with a maximum particle size of 1000 μm or less, cellulose nanofibers, and water are used.

[0048] The leaf powder, stem powder, seed powder, or grass powder is not particularly limited. For example, the leaf powder can be suitably made from powder of plant leaves such as tea leaves. The stem powder can be suitably made from powder of plant stems such as sugarcane or bamboo. The seed powder can be suitably made from powder of plant seeds such as barley (beer grounds) or coffee grounds. The grass powder can be suitably made from powder of herbs such as Miscanthus. The cellulose nanofibers used may be the same as those used in the three-dimensional molded article of the present invention described above.

[0049] The method for manufacturing the second three-dimensional molded product of the present invention is the same as the method for manufacturing a three-dimensional molded product of the present invention described above with reference to Figure 1. Specifically, for example, when bamboo powder is used as the stem powder, a mixing step (step S1) is first carried out as shown in Figure 1. In this mixing step (S1), prepared cellulose nanofibers are first mixed with water to disperse the cellulose nanofibers. Next, the prepared stem powder is mixed. The blending amounts, calculated as solid content, are 0.1 to 50% by weight of cellulose nanofibers relative to 100% by weight of stem powder, and the amount of water is 3 to 7 times the weight of the stem powder and cellulose nanofibers. Note that, from the perspective of achieving a balance between uniform mixing and evaporating moisture, it is preferable to use about 5 times the weight of the stem powder and cellulose nanofibers.

[0050] Next, a forming step is carried out (step S2) in which the material mixed in the mixing step (S1) is filled (formed) into a mold using a dedicated jig.

[0051] Next, a heat pressing step is carried out in which the mixture is heat pressed using a mold (step S3). In this heat pressing step (S3), the heating temperature is set to 130°C to 180°C, and the pressing pressure is set to, for example, 1.4 MPa / cm. 2 The hot pressing step (S3) may be carried out until the material filled in the mold is in a dry state, which may take from a few seconds to a few minutes depending on the weight.

[0052] Finally, a removal step is carried out to remove the three-dimensional molded product from the mold (step S4). The same manufacturing method can be used for powders other than bamboo powder, such as stem powder, leaf powder, seed powder, and grass powder.

[0053] When using a mixed powder obtained by mixing powder made of leaf, stem, seed, or grass powder with a maximum particle size of 1000 μm or less with wood flour with a maximum particle size of 1000 μm or less, the amounts of powder made of leaf, stem, seed, or grass powder and wood flour should be approximately equal. The amounts of cellulose nanofiber and water to be mixed are, in solid content terms, 0.1% to 50% by weight of cellulose nanofiber relative to 100% by weight of the mixed powder, and the weight ratio of water is 3 to 7 times the weight of the mixed powder and cellulose nanofiber.

[0054] Next, a Charpy impact test performed on the three-dimensional molded article of the present invention and the second three-dimensional molded article of the present invention will be described.

[0055] Examples 3 to 6 are test pieces of three-dimensional molded products of the present invention, and Examples 7 to 12 are test pieces of a second three-dimensional molded product of the present invention. Specifically, Examples 3 and 4 use cypress wood flour, Example 5 uses whitewood wood flour, and Example 6 uses eucalyptus wood flour. The wood flour, which had a maximum particle size of 500 μm or less that passed through a 500 μm mesh sieve, was mixed with 10 wt% cellulose nanofibers and 15 wt% pulp, calculated as solids, and water was used in a weight ratio of approximately 5 times the amount of wood flour, cellulose nanofibers, and pulp. Note that Example 5 contained thin, elongated wood flour measuring 1 cm or longer that fell off vertically when sieved through a 500 μm mesh sieve.

[0056] Example 7 used bamboo, Example 8 used 90% bamboo and 10% bamboo charcoal, and Example 9 used bamboo charcoal stem powder.The stem powder was 100% by weight, with a maximum particle size of 500 μm or less that passed through a sieve with a mesh size of 500 μm, and in solid content terms, 10% by weight cellulose nanofiber and 15% by weight pulp were used.Water was used in a weight ratio of approximately 5 times the stem powder, cellulose nanofiber, and pulp.

[0057] In Example 10, equal amounts of tea leaf powder having a maximum particle size of 500 μm or less and cypress wood flour having a maximum particle size of 500 μm or less were mixed to form a mixed powder, and the mixed powder was 100% by weight of this mixed powder, and the cellulose nanofiber was 10% by weight and the pulp was 15% by weight, in terms of solid content. The mixed powder, cellulose nanofiber, and pulp were mixed in an amount of about 5 times the weight of the mixed powder. In Example 11, equal amounts of coffee grounds seed powder having a maximum particle size of 500 μm or less and cypress wood flour having a maximum particle size of 500 μm or less were mixed to form a mixed powder, and the mixed powder was 100% by weight of this mixed powder, and the cellulose nanofiber was 15% by weight, in terms of solid content. The mixed powder, cellulose nanofiber, and pulp were mixed in an amount of about 5 times the weight of the mixed powder.

[0058] In Example 12, 100% by weight of Miscanthus grass powder with a maximum particle size of 500 μm or less that passed through a 500 μm mesh sieve was used, with 10% by weight of cellulose nanofiber and 15% by weight of pulp converted into solid content, and water was used in an amount approximately 5 times the weight ratio of wood flour, cellulose nanofiber, and pulp. Note that in Example 12, thin grass powder with a length of 1 cm or more was mixed in, which fell out vertically when sieved through a 500 μm mesh sieve.

[0059] Then, three-dimensional molded articles were produced by the above-described production method shown in FIG. 1, and five JIS No. 4 test pieces (V-notch test pieces) were taken from the three-dimensional molded articles for each example.

[0060] FIG. 3 is a graph showing the results of a Charpy impact test carried out on five test pieces taken from each of Examples 3 to 12.

[0061] As shown in Figure 3, the three-dimensional molded products of Examples 3 to 12 have the impact strength required for various parts such as automobile interior parts, tableware, miscellaneous goods, various small items, etc. Furthermore, Example 5, which contains thin wood powder with a length of 1 cm or more, and Example 12, which contains thin grass powder with a length of 1 cm or more, showed improved impact strength.

[0062] The second three-dimensional molded product of the present invention and the manufacturing method for the second three-dimensional molded product of the present invention can also provide a three-dimensional molded product and its manufacturing method that can be manufactured using naturally occurring materials, without the need for large-scale equipment, and in a simple and short molding cycle. [Explanation of symbols]

[0063] 10 Manufacturing method of diaphragm (three-dimensional molded product) S1 Mixing process S2 forming process S3 Heat pressing process S4 Removal process

Claims

1. A mixing process for mixing wood flour having a maximum particle size of 1000 μm or less, cellulose nanofibers in an amount of 0.1% by weight to 50% by weight based on 100% by weight of said wood flour in terms of solid content, and water in an amount of 3 to 7 times by weight based on the wood flour and the cellulose nanofibers; a forming step of forming the material mixed in the mixing step into a mold; a heat pressing step of heat pressing using the mold; a removal step of removing a molded product from the mold; A method for producing a three-dimensional molded product, comprising:

2. A mixing process of mixing wood flour having a maximum particle size of 500 μm or less, cellulose nanofibers in an amount of 0.1% by weight to 50% by weight based on 100% by weight of the wood flour in terms of solid content, and water in an amount of 3 to 7 times by weight based on the wood flour and the cellulose nanofibers; a forming step of forming the material mixed in the mixing step into a mold; a heat pressing step of heat pressing using the mold; a removal step of removing a molded product from the mold; A method for manufacturing a diaphragm, comprising:

3. A mixing process of mixing a powder consisting of leaf powder, stem powder, seed powder or grass powder with a maximum particle size of 1000 μm or less, or a mixed powder obtained by mixing said powder with wood powder with a maximum particle size of 1000 μm or less, cellulose nanofibers in an amount of 0.1% by weight to 50% by weight based on 100% by weight of said powder or said mixed powder, in terms of solid content, and water in an amount of 3 to 7 times by weight based on the powder or said mixed powder and said cellulose nanofibers; a forming step of forming the material mixed in the mixing step into a mold; a heat pressing step of heat pressing using the mold; a removal step of removing a molded product from the mold; A method for producing a three-dimensional molded product, comprising:

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