Biomass composite material and method for manufacturing the same

Abstract

To provide biomass composite materials with superior durability. [Solution] The present invention relates to a biomass composite material 1 in which biomass and ceramic particles are compounded, wherein the ceramic particles coat a portion of the biomass, preferably the ceramic particles are precipitated when metal ions in water react with counterions, and at the time of precipitation, the ceramic particles coat a portion of the biomass in the biomass composite material 1.

Description

Technical Field

[0001] The present invention relates to a biomass composite material and a method for producing the same, and more particularly, to a biomass composite material in which at least biomass and ceramic particles are combined and a method for producing the same.

Background Art

[0002] Biomass is an organic resource derived from animals, plants, and fungi, excluding so-called fossil resources. Since biomass is a naturally abundant and renewable resource, it has the advantage of being able to be used continuously. In addition, in the preparation of biomass resources and materials, waste biomass is always produced as waste materials. For example, in wood processing, on average, about 6% of waste wood powder is produced. The development of utilization methods for these unused resources is essential for achieving carbon neutrality.

[0003] In recent years, in order to further improve the functions of biomass or to utilize waste biomass as an unused resource, a technology for combining biomass and ceramic particles has been developed. For example, an aggregate (biomass composite material) having a size of 0.5 mm or more and containing inorganic particles (ceramic particles), fibers, and carboxymethyl cellulose or a salt thereof is known (see, for example, Patent Document 1). In addition, a fiber structure (biomass composite material) formed from composite fibers of fibers and inorganic particles (ceramic particles) is known (see, for example, Patent Document 2). In addition, a method for preparing composite fibers (biomass composite materials) including a step of concentrating composite fibers of cellulose fibers and inorganic particles (ceramic particles) to a concentration of 23 to 55% and a step of dissociating the concentrate of the composite fibers in water is known (see, for example, Patent Document 3). In addition, granules having a particle size of 0.1 to 10 mm and a water content of less than 60% and containing composite fibers of fibers and inorganic particles (ceramic particles) (biomass composite materials) are known (see, for example, Patent Document 4). Furthermore, composite fibers (biomass composites) are known in which, when an aqueous suspension of composite fibers with a solid content concentration of 0.1% is filtered through a 60-mesh sieve, the weight ratio of the amount of inorganic matter in the residue remaining on the sieve after filtration to the amount of inorganic matter in the composite fibers before treatment is 0.3 or more, or when an aqueous suspension of composite fibers with a solid content concentration of 0.3% is classified using a fiber classification analyzer under conditions of a flow rate of 5.7 L / min, a water temperature of 25 ± 1°C, and a total outflow of 22 L, the weight ratio of the amount of inorganic matter in the fraction corresponding to an outflow of 16.00 to 18.50 and an outflow time of 10.6 to 37.3 seconds to the amount of inorganic matter in the composite fibers before treatment is 0.3 or more (see, for example, Patent Document 5). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-110071 [Patent Document 2] Japanese Patent Publication No. 2020-186504 [Patent Document 3] Japanese Patent Publication No. 2021-161561 [Patent Document 4] International Publication No. 2021 / 054312 brochure [Patent Document 5] Japanese Patent Publication No. 2021-11674 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0005] Incidentally, the biomass composite materials described in Patent Documents 1-5 can be made into biomass composite materials having functions based on ceramic particles by compounding biomass with ceramic particles. However, conventional biomass composites, including those described in Patent Documents 1-5, have insufficient adhesion between the biomass and ceramic particles, and therefore cannot be said to have superior durability. Furthermore, improving the durability of biomass composite materials remains a crucial theme in the research and development of biomass composite materials.

[0006] This invention has been made in view of the above circumstances, and aims to provide a biomass composite material with excellent durability. [Means for solving the problem]

[0007] The inventors of the present invention conducted diligent research to solve the above problems and found that the above problems can be solved by using ceramic particles, which are generally highly rigid particles, to coat at least a portion of the biomass, and thus completed the present invention.

[0008] The present invention relates to a biomass composite material comprising biomass and ceramic particles, wherein the ceramic particles coat a portion of the biomass. In this case, it is preferable that the ceramic particles are precipitated when metal ions in water react with counterions, and that during this precipitation, the ceramic particles coat a portion of the biomass.

[0009] The present invention relates to a biomass composite material comprising biomass, ceramic particles, and an organic binder, wherein the organic binder is an organic polymer, a surfactant, or a lipid, and the ceramic particles coat a portion of the biomass and a portion of the organic binder, respectively. In this case, it is preferable that the ceramic particles are precipitated when metal ions in water react with counterions, and that during this precipitation, the ceramic particles coat a portion of the biomass and a portion of the organic binder, respectively.

[0010] In the biomass composite material of the present invention, it is preferable that the organic binder is at least one selected from the group consisting of proteins, peptides, polysaccharides, fatty acids, fatty acid esters, surfactants, glycolipids, sugar esters, synthetic resins, phospholipids, and phospholipid esters.

[0011] In the biomass composite material of the present invention, the biomass is cellulose fiber, chitin fiber, or chitosan fiber, the ceramic particles are particles made of metal oxide, metal hydroxide, or metal salt, the metal ions are ionized aluminum, zinc, or metals contained in alkaline earth metals, lanthanide metals, or transition metals, and the content ratio of ceramic particles to 1% by mass of biomass is preferably 0.01 to 99.9% by mass. Furthermore, it is preferable that the content ratio of the organic binder to 1% by mass of biomass is 0.01 to 50.0% by mass.

[0012] The biomass composite material of the present invention contains at least one auxiliary agent selected from the group consisting of antibacterial agents, preservatives, flame retardants, antioxidants, ultraviolet absorbers, hydrophilic agents, antistatic agents, slip agents, surfactants, colorants, conductive agents, fragrances, antifungal agents, insecticides, and excipients, and it is preferable that the auxiliary agent does not participate in the reaction.

[0013] In the biomass composite material of the present invention, it is preferable that it be in the form of blocks, sheets, pellets, or powder.

[0014] In the biomass composite material of the present invention, it is preferable that the material is porous with a porosity of 0.1 to 99.9%.

[0015] The present invention relates to a method for producing the biomass composite material described above, comprising: a kneading step of kneading biomass, a ceramic particle precursor which is a precursor of ceramic particles, and water to form a mixture; a precipitation step of reacting the ceramic particle precursor dissolved in water with a wet gas containing carbon dioxide or ammonia gas to form a composite mixture in which ceramic particles are precipitated; and a washing step of washing the composite mixture with water, wherein the ceramic particle precursor has a higher solubility in water than the ceramic particles formed from the ceramic particle precursor.

[0016] The present invention relates to a method for producing the biomass composite material described above, comprising: a kneading step of kneading biomass, an organic binder, and water to form a mixture; an adsorption step of drying the mixture and then immersing it in an aqueous solution of ceramic particle precursors in which ceramic particle precursors, which are precursors of ceramic particles, are dissolved, to adsorb the aqueous solution of ceramic particle precursors onto the entire mixture; a precipitation step of reacting the ceramic particle precursors in the aqueous solution of ceramic particle precursors with a humid gas containing carbon dioxide or ammonia gas to form a composite mixture in which ceramic particles are precipitated; and a washing step of washing the composite mixture with water, wherein the ceramic particle precursors have a higher solubility in water than the ceramic particles formed from the ceramic particle precursors.

[0017] The present invention and the like relate to a method for producing a biomass composite material, which comprises a kneading step of kneading biomass, an organic binder, an auxiliary agent, and water to form a mixture, an adsorption step of immersing the dried mixture in an aqueous solution of a ceramic particle precursor in which the ceramic particle precursor, which is a precursor of ceramic particles, is dissolved, to adsorb the aqueous solution of the ceramic particle precursor to the entire mixture, a precipitation step of reacting the ceramic particle precursor in the aqueous solution of the ceramic particle precursor with a wet gas in the presence of a wet gas containing carbon dioxide gas or ammonia gas to form a composite mixture in which the ceramic particles are precipitated, and a washing step of washing the composite mixture with water. The ceramic particle precursor has a higher solubility in water than the ceramic particles formed from the ceramic particle precursor.

[0018] In the method for producing a biomass composite material of the present invention, in the kneading step, the mixture further contains a readily soluble substance having a solubility in water of 5 g / L or more, and in the washing step, the readily soluble substance is eluted and removed with water, so that it is preferable that the biomass composite material has porosity.

[0019] In the method for producing a biomass composite material of the present invention, the precipitation step involves charging the mixture into a sealed container containing ammonium carbonate powder in a wet environment, and it is preferable that the carbon dioxide gas and ammonia gas are those released by the decomposition of ammonium carbonate.

[0020] In the method for producing a biomass composite material of the present invention, the ceramic particle precursor is preferably a chloride, hydroxide, nitrate, acetate, or lactate of calcium, and the ceramic particles are preferably calcium carbonate particles.

[0021] In the method for producing a biomass composite material of the present invention, the ceramic particle precursor is preferably a chloride, citrate, or succinate of titanium, and the ceramic particles are preferably titanium oxide particles.

[0022] In the method for producing biomass composite materials of the present invention, it is preferable that the ceramic particle precursor is a silver nitrate or sulfate, and the ceramic particles are silver oxide particles. [Effects of the Invention]

[0023] The biomass composite material of the present invention contains ceramic particles, and therefore can exhibit functions based on these ceramic particles. This allows, for example, to further improve the functions of biomass or to impart new functions to biomass. Furthermore, in biomass composite materials, by configuring the ceramic particles to cover a portion of the biomass, it is possible to achieve sufficiently excellent adhesion between the ceramic particles and the biomass. Here, since ceramic particles are generally insoluble in water and are highly rigid, the ceramic particles coat a portion of the biomass, improving water resistance and strengthening the adhesion between the ceramic particles and the biomass. As a result, the biomass composite material will have excellent durability.

[0024] In the biomass composite material of the present invention, if the ceramic particles are precipitated when metal ions in water react with counterions, the metal ions will precipitate with sufficient penetration into the biomass, thus enabling the ceramic particles to be uniformly distributed within the biomass. During precipitation, the ceramic particles solidify and gradually grow, increasing in volume. This property can be used to allow the ceramic particles to coat a portion of the biomass. As a result, the adhesion between the ceramic particles and the biomass can be further improved in biomass composite materials. As a result, biomass composite materials exhibit extremely high durability.

[0025] In the biomass composite material of the present invention, when an organic binder, which is an organic polymer, surfactant, or lipid, is further included, the ceramic particles can be configured to coat a portion of the biomass and a portion of the organic binder, respectively, thereby providing excellent adhesion between the ceramic particles and the biomass, and between the ceramic particles and the organic binder. Furthermore, as mentioned above, since ceramic particles are generally insoluble in water and are highly rigid, biomass composites exhibit improved water resistance, and the adhesion between ceramic particles and biomass, as well as between ceramic particles and organic binders, becomes stronger. In this process, the organic binder, when coated with ceramic particles, has its dissolution and decomposition suppressed, and plays a role in binding biomass particles at distant locations to each other, to ceramic particles to each other, and even to biomass particles to ceramic particles. Furthermore, the effect is even better when the organic binder is at least one selected from the group consisting of proteins, peptides, polysaccharides, fatty acids, fatty acid esters, glycolipids, sugar esters, synthetic resins, phospholipids, and phospholipid esters. As a result, biomass composite materials become significantly more durable and can also exhibit functions such as antibacterial properties.

[0026] In the biomass composite material of the present invention, if the ceramic particles are precipitated when metal ions in water react with counterions, the metal ions will precipitate with sufficient penetration into the biomass, thus enabling the ceramic particles to be uniformly distributed within the biomass. During precipitation, the ceramic particles solidify and gradually grow, increasing in volume. This property can be used to coat a portion of the biomass and a portion of the organic binder. As a result, the adhesion between the ceramic particles and the biomass, and between the ceramic particles and the organic binder, can be further improved in the biomass composite material. As a result, biomass composite materials exhibit extremely high durability.

[0027] In the biomass composite material of the present invention, when both the biomass and ceramic particles are the substances described above, by setting the content ratio of ceramic particles to 1% by mass of biomass within the above range, the functionality based on the contained ceramic particles can be fully exhibited, and sufficient durability can be achieved. Furthermore, if the material further contains an organic binder, such as an organic polymer, surfactant, or lipid, sufficient durability can be achieved by keeping the organic binder content within the above range relative to 1% by mass of biomass.

[0028] The biomass composite material of the present invention can exhibit combined effects based on the additive, which does not participate in the precipitation reaction of ceramic particles, by including an additive. Furthermore, since the ceramic particles coat the auxiliary agent, its durability is also sufficiently excellent.

[0029] The biomass composite material of the present invention can be in block form, sheet form, pellet form, or powder form, allowing the shape to be selected according to the application. For example, block-shaped materials can be suitably used as building materials, sheet-shaped materials can be suitably used as covering materials, decorative materials, antibacterial materials, etc., pellet-shaped materials can be suitably used as fillers, adsorbents, etc., and powder-shaped materials can be suitably mixed with water, etc., and used as coating materials, etc.

[0030] The biomass composite material of the present invention can be made porous with a porosity within the above range, thereby providing good breathability. For this reason, it can be applied to applications such as ventilation filters for houses and adsorbents for air purifiers.

[0031] In the present invention, a method for producing biomass composites involves mixing biomass, ceramic particles, and water in a kneading step. As a result, at least a portion of the ceramic particle precursor dissolves in the water to form metal ions, allowing the metal ions to penetrate deep into the biomass. This makes it possible to manufacture biomass composite materials with superior durability.

[0032] In the present invention, a method for producing a biomass composite material involves, in the kneading step, kneading biomass, an organic binder, and water, drying the resulting mixture, and then immersing it in an aqueous solution of ceramic particle precursors. This allows metal ions based on the ceramic particle precursors in the aqueous solution of ceramic particle precursors to penetrate deep into the biomass. This makes it possible to manufacture highly durable biomass composite materials containing organic binders. Furthermore, by including an auxiliary agent in the mixture during the kneading step, a similar penetration effect can be obtained, and a highly durable biomass composite material containing an organic binder and auxiliary agent can be manufactured.

[0033] The present invention's method for producing biomass composite materials uses a humid gas containing carbon dioxide or ammonia gas in the precipitation step, making it easy to mix with the mixture. Specifically, since the carbon dioxide or ammonia gas comes into contact with the mixture while dissolved in water vapor, the reaction between metal ions and counterions based on carbon dioxide or ammonia gas proceeds rapidly, allowing ceramic particles to be precipitated. Therefore, in the precipitation step, the synthesis and precipitation of ceramic particles and the formation of a biomass composite material (composite mixture) can be carried out simultaneously. Furthermore, by using a ceramic particle precursor with higher solubility in water than the ceramic particles formed from the ceramic particle precursor, the precipitation of ceramic particles can be accelerated.

[0034] In the present invention, a method for producing a biomass composite material is obtained by, in the kneading step, if the mixture further contains a readily soluble substance, then, after forming the composite mixture, dissolving and removing the readily soluble substance with water in the washing step, thereby obtaining a porous biomass composite material. The resulting biomass composite material can then be made to possess, for example, hygroscopic, adsorbent, and moisture-retaining properties. For this reason, it can be applied to applications such as pre-treatment air filters, ventilation filters, and adsorbents for air purifiers.

[0035] In the method for producing biomass composite materials of the present invention, if the precipitation step involves adding the mixture to a sealed container containing ammonium carbonate powder and water, the precipitation step can be performed with simple operations without requiring complex equipment. Furthermore, it will facilitate the mass production of biomass composite materials.

[0036] In the method for producing biomass composite materials of the present invention, for example, if the ceramic particle precursor is a calcium chloride, hydroxide, acetate, nitrate, or lactate, it can react with carbonate ions produced by carbon dioxide to precipitate calcium carbonate particles. That is, the ceramic particles can consist of calcium carbonate particles. In this case, the resulting biomass composite material will have excellent strength. Furthermore, in the method for producing biomass composite materials of the present invention, when the ceramic particle precursor is titanium chloride, citrate, or succinate, it reacts with ammonium ions produced by ammonia gas, and the resulting basic conditions due to the ammonium ions allow for the precipitation of titanium oxide particles. In other words, the ceramic particles can consist of titanium oxide particles. In this case, the resulting biomass composite material will have excellent strength and can exhibit functions such as antibacterial properties and photocatalytic functions. Furthermore, in the method for producing biomass composite materials of the present invention, if the ceramic particle precursor is a silver nitrate or sulfate, it reacts with ammonium ions caused by ammonia gas, and the resulting basic conditions due to the ammonium ions allow for the precipitation of silver oxide particles. In other words, the ceramic particles can consist of silver oxide particles. In this case, the resulting biomass composite material can be used as an antibacterial material. [Brief explanation of the drawing]

[0037] [Figure 1] Figure 1 is a photograph showing an example of a biomass composite material according to the first embodiment, and is a photograph showing Sample 1 in Example 1. [Figure 2] Figure 2 is a photograph showing an example of a biomass composite material according to the second embodiment. [Figure 3] Figure 3 is a flowchart showing a first embodiment of the method for producing a biomass composite material according to the present invention. [Figure 4] Figure 4 is a flowchart showing a second embodiment of the method for producing a biomass composite material according to the present invention. [Figure 5] Figure 5(a) is an SEM image of Sample 1 in Example 1, Figure 5(b) is an EDS mapping of calcium atoms in Sample 1 in Example 1, Figure 5(c) is an EDS mapping of carbon atoms in Sample 1 in Example 1, and Figure 5(d) is an EDS mapping of oxygen atoms in Sample 1 in Example 1. [Figure 6] Figure 6(a) shows the XRD pattern of Sample 1 in Example 1, and Figure 6(b) shows the XRD pattern of only calcium carbonate particles as a blank. [Figure 7] Figure 7 shows the FT-IR spectra of Sample 1 in Example 1, cellulose powder as a blank in Example 1, and calcium carbonate particles as a blank in Example 1. [Figure 8]Figures 8(a) to 8(c) are micro-CT images of Sample 1 in Example 1, where 8(a) shows the external view, 8(b) shows a cross-section, and 8(c) shows a longitudinal section. [Figure 9] Figure 9(a) is a photograph of Sample 2 when 4 mmol of calcium chloride was used in Example 2, and Figure 9(b) is a photograph of Sample 2 when 8 mmol of calcium chloride was used in Example 2. [Figure 10] Figure 10(a) is an SEM image of Sample 2 when 8 mmol of calcium chloride was used in Example 2, Figure 10(b) is the EDS mapping of calcium atoms in Sample 2, Figure 10(c) is the EDS mapping of carbon atoms in Sample 2, Figure 10(d) is the EDS mapping of oxygen atoms in Sample 2, Figure 10(e) is the EDS mapping of chlorine atoms in Sample 2, and Figure 10(f) is the EDS mapping of nitrogen atoms in Sample 2. [Figure 11] Figure 11(a) shows the XRD pattern of Sample 2 when 0.4 mmol of calcium chloride was used in Example 2, Figure 11(b) shows the XRD pattern of Sample 2 when 4 mmol of calcium chloride was used in Example 2, Figure 11(c) shows the XRD pattern of Sample 2 when 8 mmol of calcium chloride was used in Example 2, and Figure 11(d) shows the XRD pattern of only calcium carbonate particles as a blank for Example 2. [Figure 12] Figure 12 shows the FT-IR spectra of the following samples from Example 2: cedar powder as a blank for Example 2, calcium carbonate particles as a blank for Example 2, Sample 2 where 0.4 mmol of calcium chloride was used per 1 g of cedar powder, Sample 2 where 4 mmol of calcium chloride was used per 1 g of cedar powder, and Sample 2 where 8 mmol of calcium chloride was used per 1 g of cedar powder. [Figure 13]Figures 13(a) to (c) are micro-CT images of Sample 2 when 8 mmol of calcium chloride was used in Example 2. Figure 13(a) shows the external appearance, Figure 13(b) shows a cross-section, and Figure 13(c) shows a longitudinal section. [Figure 14] Figure 14(a) is a photograph of the blank sample in Example 3 when no casein was used, Figure 14(b) is a photograph of Sample 3 when a 10 g / L casein aqueous solution was used in Example 3, Figure 14(c) is a photograph of Sample 3 when a 50 g / L casein aqueous solution was used in Example 3, and Figure 14(d) is a photograph of Sample 3 when a 100 g / L casein aqueous solution was used in Example 3. [Figure 15] Figure 15(a) is an SEM image of Sample 3 when a 100 g / L casein aqueous solution was used in Example 3, Figure 15(b) is the EDS mapping of calcium atoms in Sample 3, Figure 15(c) is the EDS mapping of carbon atoms in Sample 3, Figure 15(d) is the EDS mapping of oxygen atoms in Sample 3, and Figure 15(e) is the EDS mapping of chlorine atoms in Sample 3. [Figure 16] Figure 16(a) shows the XRD pattern when no casein is used as the blank for Example 3, Figure 16(b) shows the XRD pattern of Sample 3 when a 10 g / L casein aqueous solution is used in Example 3, Figure 16(c) shows the XRD pattern of Sample 3 when a 50 g / L casein aqueous solution is used in Example 3, and Figure 16(d) shows the XRD pattern of Sample 3 when a 100 g / L casein aqueous solution is used in Example 3. [Figure 17] Figure 17 shows the FT-IR spectra of Sample 3 when no casein was used as a blank for Example 3, Sample 3 when a 10 g / L casein aqueous solution was used in Example 3, Sample 3 when a 50 g / L casein aqueous solution was used in Example 3, and Sample 3 when a 100 g / L casein aqueous solution was used in Example 3. [Figure 18]Figures 18(a) to (c) are microCT images of Example 3 when no casein was used as a blank, with Figure 18(a) showing the external appearance, Figure 18(b) showing a cross-section, and Figure 18(c) showing a longitudinal section. Figures 18(d) to (f) are microCT images of Sample 3 when a 100 g / L casein aqueous solution was used in Example 3, with Figure 18(d) showing the external appearance, Figure 18(e) showing a cross-section, and Figure 18(f) showing a longitudinal section. [Figure 19] Figure 19 is a graph showing the DTS intensity of Sample 3 when no casein was used as the blank for Example 3, when a 10 g / L casein aqueous solution was used in Example 3, when a 50 g / L casein aqueous solution was used in Example 3, and when a 100 g / L casein aqueous solution was used in Example 3. [Figure 20] Figure 20 is a photograph of the dried mixture in Example 4. [Figure 21] Figure 21(a) is a photograph of Sample 8 of Comparative Example 1, Figure 21(b) is a photograph of Sample 4 when a 0.1 mol / L calcium chloride aqueous solution was used in Example 4, Figure 21(c) is a photograph of Sample 4 when a 1.0 mol / L calcium chloride aqueous solution was used in Example 4, Figure 21(d) is a photograph of Sample 4 when a 2.0 mol / L calcium chloride aqueous solution was used in Example 4, and Figure 21(e) is a photograph of Sample 4 when a 5.0 mol / L calcium chloride aqueous solution was used in Example 4. [Figure 22] Figure 22(a) is an SEM image of Sample 4 when a 2 mol / L aqueous calcium chloride solution was used in Example 4, Figure 22(b) is the EDS mapping of calcium atoms in Sample 4, Figure 22(c) is the EDS mapping of carbon atoms in Sample 4, Figure 22(d) is the EDS mapping of oxygen atoms in Sample 4, and Figure 22(e) is the EDS mapping of chlorine atoms in Sample 4. [Figure 23]Figure 23(a) shows the XRD pattern of Sample 8 in Comparative Example 1, Figure 23(b) shows the XRD pattern of Sample 4 when a 0.1 mol / L calcium chloride aqueous solution was used in Example 4, Figure 23(c) shows the XRD pattern of Sample 4 when a 0.5 mol / L calcium chloride aqueous solution was used in Example 4, Figure 23(d) shows the XRD pattern of Sample 4 when a 1.0 mol / L calcium chloride aqueous solution was used in Example 4, Figure 23(e) shows the XRD pattern of Sample 4 when a 2.0 mol / L calcium chloride aqueous solution was used in Example 4, and Figure 23(f) shows the XRD pattern of Sample 4 when a 5.0 mol / L calcium chloride aqueous solution was used in Example 4. [Figure 24] Figure 24 shows the FT-IR spectra of Sample 8 from Comparative Example 1, Sample 4 when a 0.1 mol / L calcium chloride aqueous solution was used in Example 4, Sample 4 when a 0.5 mol / L calcium chloride aqueous solution was used in Example 4, Sample 4 when a 1.0 mol / L calcium chloride aqueous solution was used in Example 4, Sample 4 when a 2.0 mol / L calcium chloride aqueous solution was used in Example 4, and Sample 4 when a 5.0 mol / L calcium chloride aqueous solution was used in Example 4. [Figure 25] Figures 25(a) to (c) are micro-CT images of the dried mixture obtained by kneading 1 g of cedar wood powder and 100 g / L of casein aqueous solution in Example 4 and drying it. Figure 25(a) shows the external appearance, Figure 25(b) shows a cross-section, and Figure 25(c) shows a longitudinal section. Figures 25(d) to (f) are micro-CT images of Sample 4 obtained using 2 M calcium chloride in Example 4. Figure 25(d) shows the external appearance, Figure 25(e) shows a cross-section, and Figure 25(f) shows a longitudinal section. [Figure 26]Figure 26 is a graph showing the DTS intensity of Sample 8 from Comparative Example 1, Sample 4 when a 0.1 mol / L calcium chloride aqueous solution was used in Example 4, Sample 4 when a 1.0 mol / L calcium chloride aqueous solution was used in Example 4, Sample 4 when a 2.0 mol / L calcium chloride aqueous solution was used in Example 4, and Sample 4 when a 5.0 mol / L calcium chloride aqueous solution was used in Example 4. [Figure 27] Figure 27(a) is a photograph of Sample 5 when sodium chloride is not used as the blank in Example 5, Figure 27(b) is a photograph of Sample 5 when 0.5 g of sodium chloride is used in Example 5, Figure 27(c) is a photograph of Sample 5 when 1.0 g of sodium chloride is used in Example 5, Figure 27(d) is a photograph of Sample 5 when 2.0 g of sodium chloride is used in Example 5, and Figure 27(e) is a photograph of Sample 5 when 3.0 g of sodium chloride is used in Example 5. [Figure 28] Figure 28(a) is an SEM image of Sample 5 when 3 g of sodium chloride was used in Example 5, Figure 28(b) is the EDS mapping of calcium atoms in Sample 5, Figure 28(c) is the EDS mapping of carbon atoms in Sample 5, and Figure 28(d) is the EDS mapping of oxygen atoms in Sample 5. [Figure 29] Figure 29(a) shows the XRD pattern of Sample 5 when 0.5 g of sodium chloride was used in Example 5, Figure 29(b) shows the XRD pattern of Sample 5 when 1.0 g of sodium chloride was used in Example 5, Figure 29(c) shows the XRD pattern of Sample 5 when 2.0 g of sodium chloride was used in Example 5, and Figure 29(d) shows the XRD pattern of Sample 5 when 3.0 g of sodium chloride was used in Example 5. [Figure 30]Figure 30 shows the FT-IR spectra of Sample 5 when sodium chloride is not used as the blank in Example 5, when 0.5 g of sodium chloride is used in Example 5, when 1.0 g of sodium chloride is used in Example 5, when 2.0 g of sodium chloride is used in Example 5, and when 3.0 g of sodium chloride is used in Example 5. [Figure 31] Figures 31(a) to (c) are micro-CT images of Sample 5 when 0.5 g of sodium chloride was used in Example 5, with Figure 31(a) showing the external appearance, Figure 31(b) showing a cross-section, and Figure 31(c) showing a longitudinal section. Figures 31(d) to (f) are micro-CT images of Sample 5 when 3.0 g of sodium chloride was used in Example 5, with Figure 31(d) showing the external appearance, Figure 31(e) showing a cross-section, and Figure 31(f) showing a longitudinal section. [Figure 32] Figure 32 is a graph showing the DTS intensity of Sample 5 when sodium chloride is not used as the blank in Example 5, when 0.5 g of sodium chloride is used in Example 5, when 1.0 g of sodium chloride is used in Example 5, when 2.0 g of sodium chloride is used in Example 5, and when 3.0 g of sodium chloride is used in Example 5. [Figure 33] Figure 33(a) is a photograph of Sample 6 in Example 6, Figure 33(b) is a photograph of Sample 7 when a 1.0 mol / L titanium tetrachloride aqueous solution was used in Example 7, and Figure 33(c) is a photograph of Sample 7 when a 1.4 mol / L titanium tetrachloride aqueous solution was used in Example 7. [Figure 34] Figure 34(a) is an SEM image of sample 6 in Example 6, Figure 34(b) is the EDS mapping of silver atoms in sample 6, Figure 34(c) is the EDS mapping of carbon atoms in sample 6, Figure 34(d) is the EDS mapping of oxygen atoms in sample 6, and Figure 34(e) is the EDS mapping of nitrogen atoms in sample 6. [Figure 35]Figure 35 shows the XRD pattern of sample 6 in Example 6. [Figure 36] Figure 36 shows the FT-IR spectra of Sample 6 in Example 6, Sample 7 in Example 7 using a 1.0 mol / L titanium tetrachloride aqueous solution, and Sample 7 in Example 7 using a 1.4 mol / L titanium tetrachloride aqueous solution. [Figure 37] Figures 37(a) to (c) are micro-CT images of the dried mixture in Example 6, with Figure 37(a) showing the external appearance, Figure 37(b) showing a cross-section, and Figure 37(c) showing a longitudinal section. Figures 37(d) to (f) are micro-CT images of the dried mixture in Example 7 when a 1.0 mol / L titanium tetrachloride aqueous solution was used, with Figure 37(d) showing the external appearance, Figure 37(e) showing a cross-section, and Figure 37(f) showing a longitudinal section. Figures 37(g) to (i) are micro-CT images of Sample 7 in Example 7 when a 1.0 mol / L titanium tetrachloride aqueous solution and a 2.0 mol / L calcium chloride aqueous solution were used, with Figure 37(g) showing the external appearance, Figure 37(h) showing a cross-section, and Figure 37(i) showing a longitudinal section. [Figure 38] Figure 38 is a graph showing the DTS intensity of Sample 6 in Example 6, Sample 7 in Example 7 when a 1.0 mol / L titanium tetrachloride aqueous solution was used, and Sample 7 in Example 7 when a 1.4 mol / L titanium tetrachloride aqueous solution was used. [Figure 39] Figure 39(a) is an SEM image of Sample 7 when a 1.0 mmol / L titanium tetrachloride aqueous solution was used in Example 7, Figure 39(b) is the EDS mapping of titanium atoms in Sample 7, Figure 39(c) is the EDS mapping of carbon atoms in Sample 7, Figure 39(d) is the EDS mapping of oxygen atoms in Sample 7, Figure 39(e) is the EDS mapping of nitrogen atoms in Sample 7, and Figure 39(f) is the EDS mapping of chlorine atoms in Sample 7. [Figure 40]Figure 40(a) is an SEM image of Sample 7 when a 1.0 mmol / L titanium tetrachloride aqueous solution and a 2.0 mmol / L calcium chloride aqueous solution were used in Example 7; Figure 40(b) is the EDS mapping of calcium atoms in Sample 7; Figure 40(c) is the EDS mapping of carbon atoms in Sample 7; Figure 40(d) is the EDS mapping of oxygen atoms in Sample 7; Figure 40(e) is the EDS mapping of chlorine atoms in Sample 7; and Figure 40(f) is the EDS mapping of titanium atoms in Sample 7. [Figure 41] Figure 41(a) shows the XRD pattern when a 1.0 mol / L titanium tetrachloride aqueous solution was used in the dry mixture of Example 7; Figure 41(b) shows the XRD pattern when a 1.4 mol / L titanium tetrachloride aqueous solution was used in the dry mixture of Example 7; Figure 41(c) shows the XRD pattern of Sample 7 when a 0.5 mol / L titanium tetrachloride aqueous solution and a 2.0 mol / L calcium chloride aqueous solution were used in Example 7; and Figure 41(d) shows the XRD pattern of Sample 7 when a 1.0 mol / L titanium tetrachloride aqueous solution and a 2.0 mol / L calcium chloride aqueous solution were used in Example 7. [Figure 42] Figures 42(a) to 42(c) are photographs showing the results of the water resistance evaluation of Sample 8 in Comparative Example 1. Figure 42(a) is a photograph taken immediately after impregnation in distilled water, Figure 42(b) is a photograph taken 2 hours after impregnation, and Figure 42(c) is a photograph taken 12 hours after impregnation. [Modes for carrying out the invention]

[0038] Preferred embodiments of the present invention will be described in detail below, with reference to the drawings as necessary. In the drawings, the same elements will be denoted by the same reference numerals, and redundant explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Moreover, the dimensional ratios in the drawings are not limited to those shown.

[0039] (First embodiment of biomass composite material) First, a first embodiment of the biomass composite material according to the present invention will be described. Figure 1 is a photograph showing an example of a biomass composite material according to the first embodiment. The biomass composite material 1 shown in Figure 1 uses cellulose nanofibers as biomass and calcium carbonate as ceramic particles, and after composite formation, it is molded into a cylindrical shape using a mold. The details of the biomass composite material 1 according to the first embodiment will be described below.

[0040] The biomass composite material according to the first embodiment is a composite of biomass and ceramic particles. That is, biomass is used as the base material, and functional ceramic particles are added to the biomass, and the two are composited together. A composite material is a material that combines multiple materials in an integrated manner. Therefore, the biomass composite material according to the first embodiment has the characteristic of combining the functions of biomass and the functions of ceramic particles. For example, in a biomass composite material, the functions of the biomass can be further enhanced by the functions of the ceramic particles, or new functions of ceramic particles can be added to the biomass.

[0041] In the biomass composite material according to the first embodiment, the ceramic particles are preferably those precipitated by the reaction of metal ions in water with counterions. Details of this will be described later. In this case, water containing metal ions permeates uniformly into the biomass due to capillary action. Therefore, in the biomass composite material according to the first embodiment, when metal ions are reacted to precipitate ceramic particles, the ceramic particles penetrate sufficiently into the biomass and are uniformly distributed. In addition, in the biomass composite material according to the first embodiment, ceramic particles precipitate and gradually grow, increasing in volume and thus capturing biomass, resulting in a structure that covers a portion of the biomass. This results in sufficiently excellent adhesion between the ceramic particles and the biomass. Furthermore, the ceramic particles may be separated from each other and coat a portion of the biomass, or they may precipitate in an intertwined or fused state.

[0042] Furthermore, since ceramic particles are generally insoluble in water and highly rigid, they fill the voids within the biomass, resulting in improved water resistance and superior adhesion between the ceramic particles and the biomass in the biomass composite material. Therefore, the biomass composite material according to the first embodiment can exhibit functions based on ceramic particles and also has extremely excellent durability.

[0043] In the biomass composite material according to the first embodiment, the content ratio of ceramic particles to 1% by mass of biomass is preferably 0.01 to 99.9% by mass, and more preferably 0.1 to 90.0% by mass. If the content ratio of ceramic particles per 1% by mass of biomass is less than 0.1% by mass, there is a risk that the biomass composite material may not be able to adequately incorporate the functions based on the ceramic particles compared to when the content ratio is within the above range. If the content ratio of ceramic particles per 1% by mass of biomass exceeds 90.0% by mass, there is a risk that the improvement in functions based on the ceramic particles will not be observed compared to when the content ratio is within the above range, and that peeling of the ceramic particles due to excessive addition may occur.

[0044] In the biomass composite material according to the first embodiment, its shape is not particularly limited and can be appropriately deformed depending on the application. In addition, the initial shape of the biomass composite material depends on the shape of the biomass used as the base material. Among these, the biomass composite material is preferably in the form of blocks, sheets, pellets, or powder. In this case, for example, block-shaped materials can be suitably used as building materials such as plywood, sheet-shaped materials can be suitably used as covering materials, decorative materials, antibacterial materials, etc., pellet-shaped materials can be suitably used as fillers, adsorbents, etc., and powder-shaped materials can be suitably used as coating materials, etc., when mixed with water, etc. Furthermore, the biomass composite material may be processed mechanically or chemically to form chips, pellets, pastes, fibers, etc., or molded into blocks, sheets, boards, etc., using molds, etc.

[0045] The biomass composite material according to the first embodiment can be used for a variety of applications depending on the function of the ceramic particles imparted to it. For example, biomass composites can be applied to various carriers, adhesives, and other uses in addition to the applications mentioned above.

[0046] In the biomass composite material according to the first embodiment, the biomass, as described above, serves as the base material of the biomass composite material. Here, biomass refers to organic resources derived from animals, plants, and fungi. Specifically, examples of biomass that can be used include woodworking waste, wood powder, herbaceous plants, agricultural waste, pulp, arthropod exoskeletons, and fungal fibers. These can be used individually or in combination.

[0047] Suitable woodworking waste and wood powder include varieties such as cypress, cedar, and eucalyptus. As herbaceous plants, for example, Erianthus, sorghum, and switchgrass are suitable. Suitable agricultural waste materials include, for example, sugarcane bagasse, rice husks, rice bran, coconut shells, rice straw, fruit peels, and grain flour. Suitable pulps include, for example, wood pulp, non-wood pulp, and recycled paper pulp. Suitable arthropod exoskeletons include, for example, crab shells and shrimp shells. As for fungal fibers, mushrooms and the like are preferably used.

[0048] The biomass material is preferably cellulose fiber, chitin fiber, or chitosan fiber. Cellulose fibers also include cellulose defibrillants such as cellulose microfibers and cellulose nanofibers, as well as chemically modified cellulose such as surface-modified cellulose and cellulose derivatives. Chitin fibers also include chitin defibrillated materials such as chitin microfibers and chitin nanofibers, as well as chemically modified chitins such as surface-modified chitin and chitin derivatives. Chitosan fibers also include chitosan defibrillated materials such as chitosan microfibers and chitosan nanofibers, as well as chemically modified chitosan such as surface-modified chitosan and chitosan derivatives.

[0049] The biomass is preferably a defibrated substance or a chemically modified substance as described above. The method of defibration is not particularly limited; mechanical treatment, chemical treatment, etc., may be used as appropriate. Specific examples of chemical modifications include oxidation, esterification, etherification (including TEMPO(2,2,6,6-tetramethylpiperidine 1-oxyl) oxidation, acetylation, and etherification by carboxymethylation). In the biomass composite material according to the first embodiment, by using biomass defibration material as the biomass, ceramic particles precipitated between intertwined fibers are retained, thereby improving durability. Furthermore, it has the advantage of being moldable into desired shapes. On the other hand, using chemically modified biomass as biomass offers the advantage of acquiring new functions resulting from the chemical modifications.

[0050] The shape of the biomass is not particularly limited, but as mentioned above, since it serves as the base material for biomass composites, it should be shaped according to its intended use. Among these, the biomass is preferably in the form of blocks, sheets, fibers, chips, pellets, or powder, similar to the preferred shapes of the biomass composite materials described above. Furthermore, the biomass may be in the form of chips, pellets, pastes, fibers, etc., obtained by mechanical or chemical processing, or it may be molded into blocks, sheets, boards, etc., using molds or the like.

[0051] In the biomass composite material according to the first embodiment, the ceramic particles are ceramic particles. Ceramics include solid materials consisting of nonmetallic elements and inorganic compound materials which are combinations of metallic and nonmetallic elements. Examples of materials made from nonmetallic elements include silicon, graphite, and diamond. Examples of inorganic compound materials include metal oxides, metal hydroxides, metal carbides, metal salts, phosphates, metal nitrides, metal sulfates, silica, metal silicates, and metal halides. Among these, ceramics are preferably inorganic compound materials containing metal elements, as they are preferably formed by the reaction of metal ions in water with counterions, as described above. Furthermore, the ceramic particles are more preferably made of metal oxides, metal hydroxides, or metal salts, and more preferably made of water-insoluble metal oxides or water-insoluble metal salts.

[0052] Metal ions become metallic elements contained in ceramic particles through reactions with counterions. The metal ions are preferably ionized aluminum, zinc, or metals contained in alkaline earth metals, lanthanide metals, or transition metals. Among these, the metal ions are more preferably ionized calcium, magnesium, barium, aluminum, titanium, copper, zinc, or rare earth metals. Furthermore, it is even more preferable that the metal ion is an ionized form of at least one metal selected from the group consisting of calcium, silver, and titanium.

[0053] A counterion is the ion that pairs with a metal ion. When a metal ion, such as a monatomic ion, is a cation, its counterion is the corresponding anion. Conversely, when a metal ion is an anion, such as a polyatomic ion or complex ion, its counterion is the corresponding cation. Examples of counterions include countercations such as ammonium ions, halide ions, hydroxide ions, cyanide ions, nitrate ions, sulfate ions, bisulfate ions, oxalate ions, hydrogen oxalate ions, acetate ions, carbonate ions, bicarbonate ions, phosphate ions, monohydrogen phosphate ions, and dihydrogen phosphate ions. Among these, it is preferable that the metal ion is a cation and the counteranion is a hydroxide ion or a carbonate ion.

[0054] As described above, it is preferable that the metal ion is an ionized form of at least one metal selected from the group consisting of calcium, silver, and titanium, and that the counterion is preferably a hydroxide ion or a carbonate ion. Therefore, it is more preferable that the ceramic particles are obtained from a combination of these. Among these, the ceramic particles are more preferably silver oxide (metal oxide) obtained by reacting silver ions (metal ions) and hydroxide ions (counterions), titanium oxide (metal oxide) obtained by reacting titanium ions (metal ions) and hydroxide ions (counterions), or calcium carbonate (metal salt) obtained by reacting calcium ions (metal ions) and carbonate ions (counterions), from the viewpoint of ease of precipitation and functionality.

[0055] The ceramic particles are preferably precipitated. Methods of precipitation include changing the temperature of the aqueous solution, concentrating the aqueous solution, chemical reactions from highly soluble substances to less soluble substances, and adding alcohol to the aqueous solution. In this specification, solubility is measured in water at 1 atmosphere, 20°C, and pH 7. Among these, ceramic particles are preferably those precipitated by the reaction of metal ions in water with counterions, as described above. Therefore, it is preferable that they be precipitated by a chemical reaction from highly soluble ceramic particles (ceramic particle precursors) to less soluble ceramic particles.

[0056] The size and shape of a single ceramic particle are not particularly limited. For example, the particle size of the ceramic particles is 0.1 μm to 5.0 mm, preferably 1.0 μm to 1.0 mm, more preferably 5.0 μm to 200.0 μm, and even more preferably 10.0 μm to 100.0 μm. Furthermore, the shape of the ceramic particles may be self-formed according to the crystal structure of the ceramics constituting the ceramic particles, or they may be polycrystalline in shape resulting from dense aggregation, etc. They may not exhibit a clear shape and may even be a gel-like structure. Furthermore, the precipitated ceramic particles are not limited to crystals, but may also be amorphous.

[0057] (Second embodiment of biomass composite material) Next, a second embodiment of the biomass composite material according to the present invention will be described. Figure 2 is a photograph showing an example of a biomass composite material according to the second embodiment. The biomass composite material 2 shown in Figure 2 is a composite material made using wood chips as biomass, calcium carbonate as ceramic particles, and casein as an organic binder. The details of the biomass composite material 2 according to the second embodiment will be described below.

[0058] The biomass composite material according to the second embodiment is a composite of biomass, ceramic particles, and an organic binder. That is, biomass is used as the base material, and functional ceramic particles and a functional organic binder are added to the biomass, and these are then composited. Therefore, biomass composites possess the characteristic of combining the functions of biomass, ceramic particles, and organic binders.

[0059] In the biomass composite material according to the second embodiment, it is preferable that the ceramic particles are precipitated by the reaction of metal ions in water with counterions, similar to the ceramic particles in the biomass composite material according to the first embodiment. In this case, water containing metal ions penetrates uniformly into the biomass by capillary action, regardless of the presence of an organic binder. Therefore, in the biomass composite material according to the second embodiment, when metal ions are reacted to precipitate ceramic particles, the ceramic particles penetrate sufficiently into the biomass and are uniformly distributed. In addition, in the biomass composite material according to the second embodiment, ceramic particles precipitate and gradually grow, increasing in volume and capturing the biomass, resulting in a structure that coats a portion of the biomass and a portion of the organic binder. This results in excellent adhesion between the ceramic particles and the biomass, as well as between the ceramic particles and the organic binder. Furthermore, the ceramic particles may be separated from each other and coated with a portion of the biomass and an organic binder, or they may precipitate in an intertwined or fused state.

[0060] Furthermore, since ceramic particles are generally insoluble in water and are highly rigid, they fill the voids within the biomass, resulting in improved water resistance in the biomass composite material, as well as superior adhesion strength between the ceramic particles and the biomass, and between the ceramic particles and the organic binder. In this process, the organic binder, by being coated with ceramic particles, has its dissolution and decomposition suppressed, and plays a role in binding biomass particles at distant locations to each other, to ceramic particles to each other, and even to biomass particles to ceramic particles. Therefore, the biomass composite material according to the second embodiment can exhibit functions based on ceramic particles and organic binders, and also has extremely excellent durability.

[0061] In the biomass composite material according to the second embodiment, the content ratio of ceramic particles to 1% by mass of biomass is the same as that of the biomass composite material according to the first embodiment, so no explanation is given. The content ratio of the organic binder per 1% by mass of biomass is preferably 0.01 to 50.0% by mass, more preferably 0.05 to 25.0% by mass, even more preferably 0.1 to 15.0% by mass, and most preferably 0.2 to 10.0% by mass. If the content ratio of organic binder to 1% by mass of biomass is less than 0.01% by mass, there is a risk that the biomass composite material may not be able to adequately impart functions based on the organic binder compared to when the content ratio is within the above range. If the content ratio of ceramic particles to 1% by mass of biomass exceeds 50.0% by mass, there is a risk that the improvement in functions based on the organic binder will not be observed compared to when the content ratio is within the above range, and that peeling of the organic binder due to excessive application may occur.

[0062] In the biomass composite material according to the second embodiment, its shape and application are the same as those of the biomass composite material according to the first embodiment, so a description will be omitted. Furthermore, since the biomass and ceramic particles are the same as those in the biomass composite material according to the first embodiment, their description will be omitted.

[0063] In the biomass composite material according to the second embodiment, the organic binder is an organic polymer, a surfactant, or a lipid. The organic binder may be synthesized, naturally occurring, or produced by microorganisms.

[0064] The organic polymer is preferably a protein, peptide, polysaccharide, sugar ester, synthetic resin, fatty acid, or fatty acid ester. Here, a protein refers to a molecule in which multiple amino acids are linked together in a linear chain by peptide bonds. Proteins may also have molecules such as phosphate or sugar attached to their side chains. In other words, examples of proteins include simple proteins such as globular proteins and fibrous proteins, or complex proteins such as glycoproteins, phosphoproteins, metalloproteins, lipoproteins, pigment proteins, and nucleoproteins. Specifically, the proteins include gelatin, collagen, elastin, actin, myosin, albumin, globulin, lysozyme, keratin, fibrin, casein, conchiolin, lectin, cadherin, amyloid, mucin, hemoglobin, hemagglutinin, kinesin, calmodulin, myoglobin, ferritin, hormones, histones, chaperones, heat shock proteins, clathrin, capsid proteins, fluorescent proteins, luciferase, protein A, carbohydrate-degrading enzymes, glycosyltransferases, acyltransferases, acetyltransferases, sulfotransferases, isomerases, oxidases, amino acid synthases, dehydrogenases, and oxidative enzymes. Examples include enzymes, esterases, phosphorylases, hydrogenases, nitrogenases, catalases, dehalogenases, transposases, ferredoxin, peroxidases, monooxygenases, secretases, polymerases, nucleases, proteases, peptidases, lipases, kinases, phosphatases, ligases, helicases, zinc fingers, exosomes, DNA methyltransferases, RNA capping enzymes, transcription factors, elongation factors, membrane transport-related proteins, receptor proteins, rhodopsin, transcriptases, reverse transcriptases, insulin, RNA polymerases, photosystems, antifreeze proteins, and artificially designed proteins. These may be used individually or in combination. Among these, the protein is preferably casein. A peptide is a molecule in which two to several dozen amino acids are linked together by peptide bonds.

[0065] Polysaccharides are high-molecular-weight compounds formed by the polymerization of numerous monosaccharide molecules through glycosidic bonds. Polysaccharides may also have other functional groups modified in their side chains, and may exist in the form of salts. Specifically, the polysaccharides include starch, dextran, dextrin, amylose, gellan gum, chondroitin, chondroitin sulfate, amylopectin, glycogen, cellulose, carboxymethylcellulose, curdlan, paramylon, chitin, α-1,3-glucan, nigella, agarose, carrageenan, heparin, alginic acid, hyaluronic acid, pectin, xyloglucan, xylan, glucomannan, levan, gum arabic, arabinoxylan, propylene glycol alginate, α-1,3-glucan, inulin, excel chitosan, curdlan, carrageenan, galactan, karaya gum, callose, xanthan gum, and k Examples include silane, xyloglucan, chitin, chitosan, guar bean enzyme hydrolysate, guar gum, glycocalyx, glycogen, glycosaminoglycan, glycosylphosphatidylinositol, chrysolaminarin, glucan, glucuronoxylan, galactomannan, glucomannan, keratan sulfate, sacran, cellulose, tamarind gum, low molecular weight heparin, indigestible dextrin, parnaparin, fucoidan, fructan, pullulan, pectin, β-glucan, heparin, hemicellulose, polydextrose, porphyran, maltodextrin, mutilege, laminaran, rhamnan sulfate, lichenin, levan, lentinan, etc. These may be used individually or in combination.

[0066] Sugar esters are compounds formed by esterifying fatty acids and sugars. Specifically, examples of sugar esters include sucrose fatty acid esters, inositol phosphates, and glycerol fatty acid esters. These may be used individually or in combination.

[0067] Synthetic resins are substances that are artificially and industrially manufactured, consisting mainly of polymer compounds made up of carbon chains. In this invention, it is desirable that the synthetic resin mixes well with water and forms a solution. Specifically, examples of synthetic resins include polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, iodized polyvinylpyrrolidone, polyethylene glycol, polyacetal, polyacrylic acid, polyvinylamide, and polymannuronic acid. These can also be used in salt form. These can be used individually or in mixtures.

[0068] Fatty acids are monovalent carboxylic acids, which have a carboxyl group attached to a hydrocarbon chain. These fatty acids are preferably highly viscous liquids or solids at room temperature and pressure. Specifically, fatty acids include saturated fatty acids such as capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, henicosyl acid, behenic acid, tricosylic acid, and lignoceric acid; monounsaturated fatty acids such as crotonic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid, erucic acid, and nervonic acid; and diunsaturated fatty acids such as linoleic acid, eicosadienoic acid, and docosadienoic acid. Examples include fatty acids, triunsaturated fatty acids such as alpha-linolenic acid, gamma-linolenic acid, pinolenic acid, alpha-eleostearic acid, beta-eleostearic acid, meadic acid, dihomo-gamma-linolenic acid, and eicosatrienoic acid; tetraunsaturated fatty acids such as stearidonic acid, arachidonic acid, eicosatetraenoic acid, and adrenaline; pentaunsaturated fatty acids such as boseopentaenoic acid, eicosapentaenoic acid, osbondic acid, sardine acid, and tetracosapentaenoic acid; hexaunsaturated fatty acids such as docosahexaenoic acid and herringic acid; branched fatty acids; cyclic fatty acids; and hydroxy fatty acids. These may be used individually or in combination.

[0069] A fatty acid ester is a compound in which the carboxyl group of a fatty acid is bonded to an alcohol via an ester bond. Specifically, fatty acid esters include methanol, ethanol, propan-1-ol, butan-1-ol, pentan-1-ol, hexane-1-ol, heptan-1-ol, octan-1-ol, nonan-1-ol, decane-1-ol, undecane-1-ol, dodecane-1-ol, tridecane-1-ol, tetradecane-1-ol, pentadecane-1-ol, hexadecane-1-ol, heptadecane-1-ol, octadecane- 1-ol, nonadecan-1-ol, eicosan-1-ol, heneicosan-1-ol, docosan-1-ol, tricosan-1-ol, tetracosan-1-ol, pentacosan-1-ol, hexacosan-1-ol, heptacosan-1-ol, octacosan-1-ol, nonacosan-1-ol, triacontan-1-ol, policosanol, 2-methyl:2-methylpropane-1-ol, 3-methyl:3-methylbutan-1-ol, etc. Primary alcohols, propan-2-ol, butan-2-ol, pentan-2-ol, hexane-2-ol, heptan-2-ol, 2-methyl:2-methylbutan-1-ol, cyclohexanol (C6), and other secondary alcohols, 2-methyl:2-methylpropan-2-ol, 2-methylbutan-2-ol, 2-methylpentan-2-ol, 2-methylhexane-2-ol, 2-methylheptan-2-ol, 3-methyl:3-methylpentan-3 -ol, tertiary alcohols such as 3-methyloctan-3-ol, Cis-butene-1,4-diol, P-menthane-3,8-diol, acetylenediol, iopidolu, xylosan, dihydroxymethylidene, dianhydrohexitol, 1,3-butanediol, 1,3-propanediol, 2,3-butanediol, ethylene glycol, pinacol, 1,2-butanediol, 1,4-butanediol, butanediol, propylene glycol, 1,Examples include esters of diols such as 5-pentanediol, geminaldiol, orthocarbonate, saxitoxin, dodecahydroxycyclohexane, ninhydrin, chloral hydrate, and methanediol, or polyols such as glycerin, inositol, 3-methoxy-4-hydroxyphenyl glycol, avocatin B, ingenol 3-angelate, ouabagenin, ethylene glycol, enanthotoxin, gamithromycin, glycerin, diethylene glycol, cicutoxin, sorbitan, daphnetoxin, palytoxin, falcarindiol, phytantriol, philipin (compound), bronopol, propylene glycol, polyvinyl alcohol, terminal hydroxyl group polybutadiene, miglitol, mezelein, and momordicin, with the aforementioned fatty acids. These may be used individually or in combination.

[0070] The type of surfactant is not particularly limited and is arbitrary. Examples of surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. Examples of anionic surfactants include carboxylate types such as sodium fatty acid and alkyl ether carboxylates, sulfonate types such as linear alkylbenzene sulfonates, α-sulfo fatty acid methyl esters, α-olefin sulfonates, and sulfosuccinates, sulfate ester types such as alkyl sulfates and polyoxyethylene alkyl sulfates, and phosphate ester types such as lauryl phosphate, sodium lauryl phosphate, and potassium lauryl phosphate. Examples of cationic surfactants include amine salt types such as monoamine hydrochloride, diamine hydrochloride, and triamine hydrochloride, and quaternary ammonium salt types such as alkyltrimethylammonium salt and alkylbenzyldimethylammonium salt. Examples of amphoteric surfactants include amino acid types such as sodium laurylaminopropionate, betaine types such as lauryldimethylbetaine and laurylimidazolinium betaine, sulfate ester types, sulfonate types, phosphate ester types, and natural types such as lecithin. Examples of nonionic surfactants include ester-type surfactants such as glycerin fatty acid esters, sorbitan fatty acid esters, and sucrose fatty acid esters; ether-type surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene polyoxypropylene glycol; and ester / ether-type surfactants such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monooleate. These may be used individually or in combination. Among these, the surfactant is preferably a quaternary ammonium salt type or a sucrose fatty acid ester.

[0071] The lipids are preferably glycolipids, phospholipids, or phospholipid esters. Glycolipids are substances in which a sugar is further bonded to a substance formed by an ester bond between a fatty acid and an alcohol. Sugars, on the other hand, are compounds that have one formyl group (-CHO) or carbonyl group (>C=O) in their basic molecular structure. Specifically, the glycolipids include glycolaldehyde, ketotriose (dihydroxyacetone), aldotrioose (glyceraldehyde), ketotetrose (erythrolose), aldotetrose (erythrose-threose), ketopentose, ribulose, xylulose, aldopentose, ribose, arabinose, xylose, lyxose, deoxyribose, ketohexose, psicose (allulose), fructose, sorbose, tagatose, and aldohexose. Examples include monosaccharides such as xose, allose, altrose, glucose, mannose, growth, idose, galactose, talose, fucose, fuculose, rhamnose, heptose, mannoheptulose, and sedoheptulose; disaccharides such as sucrose, lactose, maltose, trehalose, turanose, and cellobiose; trisaccharides such as raffinose, melegitose, and maltotriose; or tetrasaccharides such as acarbose and stachyose, which are bound to lipids. These may be used individually or in combination.

[0072] Phospholipids or phospholipid esters are lipids that have a phosphate ester moiety in their molecular structure. Specifically, examples of phospholipids or phospholipid esters include DL-phosphatidylcholine, PO-phosphatidylcholine, N-acylphosphatidylethanolamine, erythritol, glycosylphosphatidylinositol, distearoylphosphatidylcholine, dipalmitoylphosphatidylcholine, sphingomyelin, plasmalogen, phosphatidylinositol-3,4,5-trisphosphate, phosphatidylinositol-3,4-bisphosphate, phosphatidylinositol, phosphatidylinositol-4,5-bisphosphate, phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, phosphatidic acid, lysophosphatidic acid, lipid A, lipoteichoic acid, lipopolysaccharide, lecithin, phospholipase, phospholipase A1, phospholipase A2, phospholipase C, etc. These may also be used in salt form. These may be used individually or in combination.

[0073] Here, in the case of the polysaccharides, synthetic resins, or phospholipids or phospholipid esters mentioned above, the salt state refers to the presence of an ion with a corresponding charge as charge compensation when these are ionic. Specifically, examples of paired charges include alkali metal salts such as sodium, potassium, and cesium salts; alkaline earth metal salts such as calcium, magnesium, and barium salts; rare earth salts such as lanthanum, cerium, and yttrium salts; transition metal salts such as iron, copper, and titanium salts; quaternary amine salts such as pyridine and choline salts; cations such as ammonium salts; halogen salts such as chlorides, bromides, fluorides, and iodides; monocarboxylates such as sulfates, nitrates, acetates, lactic acid, and propionates; dicarboxylates such as succinates, malates, and thiomalates; and tricarboxylates such as citrates.

[0074] Among these, the organic binder is preferably at least one selected from the group consisting of proteins, peptides, polysaccharides, fatty acids, fatty acid esters, surfactants, glycolipids, sugar esters, synthetic resins, phospholipids, and phospholipid esters. In this case, the organic binder has the effect of more strongly binding biomass particles to each other, ceramic particles to each other, and even biomass and ceramic particles together, thereby improving the durability of the biomass composite material.

[0075] The organic binder is preferably insoluble or sparingly soluble in water, or, even if readily soluble, does not participate in the reaction between metal ions and counterions. Furthermore, from the viewpoint of durability, the organic binder is preferably insoluble or sparingly soluble in water. Furthermore, if the organic binder is insoluble or sparingly soluble in water, it is preferable that the organic binder be in particulate form.

[0076] (Third embodiment of biomass composite material) Next, a third embodiment of the biomass composite material according to the present invention will be described. The biomass composite material according to the third embodiment is a composite of biomass, ceramic particles, an organic binder, and an auxiliary agent. That is, biomass is used as the base material, and functional ceramic particles, a functional organic binder, and a functional auxiliary agent are added to the biomass, and these are then composited. Therefore, biomass composites possess the characteristic of combining the functions of biomass, ceramic particles, organic binders, and additives.

[0077] In the biomass composite material according to the third embodiment, it is preferable that the ceramic particles are precipitated by the reaction of metal ions in water with counterions, similar to the ceramic particles in the biomass composite material according to the first embodiment. In this case, water containing metal ions penetrates uniformly into the biomass by capillary action, regardless of the presence of auxiliary agents. Therefore, in the biomass composite material according to the third embodiment, when metal ions are reacted to precipitate ceramic particles, the ceramic particles penetrate sufficiently into the biomass and are uniformly applied. In addition, in the biomass composite material according to the third embodiment, ceramic particles precipitate and gradually grow, increasing in volume and capturing the biomass, resulting in a structure that coats a portion of the biomass, a portion of the organic binder, and a portion of the auxiliary agent. This results in sufficiently excellent adhesion between the ceramic particles and the biomass, the ceramic particles and the organic binder, and the ceramic particles and the auxiliary agent. Furthermore, since ceramic particles are generally insoluble in water and are highly rigid, they fill the voids within the biomass, resulting in improved water resistance in the biomass composite material, as well as superior adhesion strength between the ceramic particles and biomass, the ceramic particles and organic binder, and the ceramic particles and auxiliary agents. Therefore, the biomass composite material according to the third embodiment can exhibit functions based on ceramic particles, an organic binder, and an additive, and also has extremely excellent durability.

[0078] In the biomass composite material according to the third embodiment, the content ratio of ceramic particles to 1% by mass of biomass is the same as that of the biomass composite material according to the first embodiment, so no explanation is given. Furthermore, the content ratio of the organic binder to 1% by mass of biomass is the same as that of the biomass composite material according to the second embodiment, so no explanation is provided. The proportion of the additive per 1% by mass of biomass is preferably 0.01 to 50.0% by mass, and more preferably 0.05 to 25.0% by mass. If the additive content is less than 0.01% by mass per 1% by mass of biomass, there is a risk that the biomass composite material may not be able to adequately incorporate the additive-based functions compared to when the content is within the above range. Conversely, if the ceramic particle content exceeds 50.0% by mass per 1% by mass of biomass, there is a risk that the improvement in functions based on the additive will not be observed compared to when the content is within the above range, and that the additive may peel off due to excessive application.

[0079] In the biomass composite material according to the third embodiment, its shape and application are the same as those of the biomass composite material according to the first embodiment, so a description will be omitted. Furthermore, since the biomass and ceramic particles are the same as those in the biomass composite material according to the first embodiment, their description will be omitted. Furthermore, the organic binder is the same as the organic binder in the biomass composite material according to the second embodiment, so its explanation will be omitted.

[0080] In the biomass composite material according to the third embodiment, the auxiliary agent is at least one selected from the group consisting of antibacterial agents, preservatives, flame retardants, antioxidants, ultraviolet absorbers, hydrophilic agents, antistatic agents, slip agents, surfactants, colorants, conductive agents, fragrances, chelating agents, fungicides, insecticides, and excipients. These may be used individually or in combination. Known auxiliary agents may be appropriately selected.

[0081] The auxiliary agent is preferably insoluble or sparingly soluble in water, or, even if readily soluble, does not participate in the reaction between the metal ions and counterions. Furthermore, from the viewpoint of durability, it is preferable that the auxiliary agent be insoluble or sparingly soluble in water. Furthermore, if the auxiliary agent is insoluble or sparingly soluble in water, the shape of the auxiliary agent is not particularly limited, but it is preferable that it be uniformly compoundable, such as in particulate or fibrous form.

[0082] (Fourth embodiment of biomass composite material) Next, a fourth embodiment of the biomass composite material according to the present invention will be described. The biomass composite material according to the fourth embodiment is a composite of biomass, ceramic particles, and an organic binder, and is a porous body having pores. In other words, the biomass composite material according to the fourth embodiment is the same as the biomass composite material according to the second embodiment, except that it is a porous body having pores.

[0083] In the biomass composite material according to the fourth embodiment, the porosity is 0.1 to 99.9%, preferably 10.0 to 99.0%, more preferably 20.0 to 95.0%, even more preferably 30.0 to 90.0%, even more preferably 40.0 to 85.0%, particularly preferably 50.0 to 80.0%, and extremely preferably 60.0 to 75.0%. As a result, the biomass composite material has sufficient breathability and can be applied to applications such as ventilation filters for houses and adsorbents for air purifiers. Furthermore, if the porosity is less than 10.0%, the benefits of creating pores will not be fully realized compared to when the porosity is within the above range, and if the porosity exceeds 99.0%, there is a risk that durability such as tear strength will be insufficient compared to when the porosity is within the above range.

[0084] (First embodiment of a method for manufacturing biomass composite materials) Next, a first embodiment of the method for producing biomass composite materials according to the present invention will be described. Figure 3 is a flowchart showing a first embodiment of the method for producing a biomass composite material according to the present invention. As shown in Figure 3, the method for producing a biomass composite material according to the first embodiment comprises a kneading step S1 for producing a mixture of biomass, a ceramic particle precursor, and water; a precipitation step S2 for producing a composite mixture in which ceramic particles have been precipitated; and a washing step S3 for washing with water. According to the method for manufacturing biomass composite materials according to the first embodiment, the biomass composite material according to the first embodiment described above can be manufactured.

[0085] In the method for producing a biomass composite material according to the first embodiment, the kneading step S1 is a step in which biomass, ceramic particle precursor, and water are kneaded together to form a mixture. In the mixing step S1, at least a portion of the ceramic particle precursor is dissolved in water to release metal ions. If necessary, the mixture may be subjected to stirring, temperature changes, pressure changes, etc. This allows the aqueous solution containing metal ions to penetrate into the biomass. It is not necessary to dissolve all of the ceramic particle precursor in water, but if it is not completely dissolved, it is preferable to disperse the undissolved ceramic particle precursor as uniformly as possible in the mixture.

[0086] Here, a ceramic particle precursor is a substance that serves as a precursor for ceramic particles, and becomes a ceramic particle through a reaction with counterions. In other words, the metallic portion is the same in both the ceramic particle precursor and the ceramic particle itself.

[0087] The ceramic particle precursor may be readily soluble, soluble, slightly soluble, or sparingly soluble in water, but it is preferable that its solubility in water is higher than that of the ceramic particles formed from the ceramic particle precursor. Furthermore, it is more preferable that the ceramic particles are insoluble in water, rather than the ceramic particle precursor being insoluble in water. In this case, ceramic particles can be easily precipitated. That is, when the metal ions of the ceramic particle precursor are reacted with a counterion different from the counterion of the ceramic particle precursor, the resulting ceramic particles have low solubility and therefore precipitate outside the reaction system.

[0088] As mentioned above, any material other than metal salts that are insoluble in water can be used as the ceramic particle precursor. Specifically, examples of such metal salts include carbonates, sulfates, bicarbonates, hydrogen sulfates, phosphates, monohydrogen phosphates, dihydrogen phosphates, silicates, hydrogen silicates, fluorides, hexafluorophosphates, manganese salts, titanates, tungstates, molybdates, iron salts, chromates, etc. These may be used individually or in combination. When using a combination, the metals of the target ceramic particles may be the same or different.

[0089] Among these, the ceramic particle precursor is preferably a metal salt that triggers a reaction upon exposure to carbon dioxide or ammonia, or a resulting change in solution conditions, as described later. For example, when using calcium carbonate particles as ceramic particles, readily soluble salts such as calcium chloride, hydroxide, nitrate, acetate, and lactate can be used as ceramic particle precursors. By adding carbonate ions to these precursors, calcium carbonate is precipitated. In this case, the resulting biomass composite material will have superior strength. Furthermore, when titanium dioxide particles are used as ceramic particles, readily soluble salts of titanium, such as chloride, citrate, and succinate, can be used as ceramic particle precursors. By adding hydroxide ions to these, that is, by making the aqueous solution basic, titanium dioxide is precipitated. In this case, the resulting biomass composite material will have excellent strength and may also exhibit functions such as antibacterial properties and photocatalytic functions. Furthermore, when using silver oxide particles as ceramic particles, readily soluble silver salts such as silver nitrate and sulfate can be used as ceramic particle precursors. By adding hydroxide ions to these, i.e., making the aqueous solution basic, silver oxide is precipitated. In this case, the resulting biomass composite material can be used as an antibacterial agent.

[0090] In the method for producing a biomass composite material according to the first embodiment, the precipitation step S2 is a step in which a ceramic particle precursor dissolved in water is reacted with a wet gas containing carbon dioxide or ammonia gas in the presence of the wet gas to obtain a composite mixture in which ceramic particles are precipitated. In precipitation step S2, a humid gas containing carbon dioxide or ammonia gas is used. In other words, a gas containing carbon dioxide or ammonia gas and water vapor is used. This results in liquid phases, making it easier for the humid gas and the mixture to mix.

[0091] A moist gas contains carbonate ions formed when carbon dioxide is dissolved in water vapor, or a large amount of ammonium ions formed when ammonia gas is dissolved in water vapor, and hydroxide ions produced when the aqueous solution becomes basic due to the presence of ammonium ions. In the precipitation step S2, the wet gas comes into contact with the mixture, causing the ceramic particle precursor dissolved in water to react with the wet gas. For example, if the metal ion released when the ceramic particle precursor dissolves in water is a cation, it reacts with a counteranion such as a carbonate ion or a counteranion such as a hydroxide ion. As a result, ceramic particles are precipitated in the precipitation step S2. In other words, the mixture prepared in the kneading step S1 becomes a composite mixture through reaction with the wet gas. Therefore, in precipitation step S2, the synthesis and precipitation of ceramic particles and the formation of the biomass composite material are carried out simultaneously.

[0092] The wetting gas preferably contains carbon dioxide and ammonia gas. In this case, the wetting gas offers excellent versatility in the reaction for precipitating ceramic particles, as it can accommodate a wide range of metal ions. Furthermore, if the humid gas contains carbon dioxide and ammonia gas, it is preferable that the precipitation step S2 involves adding the mixture prepared in the kneading step S1 to a sealed container containing ammonium carbonate powder in a humid environment. Note that the ammonium carbonate decomposes in the air, releasing carbon dioxide and ammonia gas. In this case, the precipitation step S2 can be performed with simple operations without requiring complex equipment. Therefore, mass production of biomass composites becomes easier.

[0093] At this time, the reaction temperature in the sealed container is not particularly limited, but if the reaction is carried out at 80°C or higher, the internal pressure will become too high and the risk of rupture will increase, so the temperature should be 0°C to 80°C, preferably 4°C to 60°C, more preferably 10°C to 50°C, even more preferably 15°C to 45°C, and most preferably 20°C to 40°C. Furthermore, the reaction time is not particularly limited and can be arbitrarily set between 1 minute and 168 hours depending on the progress of the reaction (degree of precipitation).

[0094] In the precipitation step S2, it is preferable to expose the mixture, which has been filled into a predetermined mold, to the presence of a humid gas containing carbon dioxide or ammonia gas. This allows the mixture to be transformed into a composite mixture and into a predetermined shape.

[0095] In the method for producing a biomass composite material according to the first embodiment, the washing step S3 is a step of washing with water to remove impurities. In the washing step S3, impurities contained in the composite mixture prepared in the precipitation step S2 are removed. These impurities include residues and by-products of the ceramic particle precursor. In this way, a biomass composite material is obtained in which biomass and ceramic particles are combined.

[0096] (Second embodiment of the method for manufacturing biomass composite materials) Next, a second embodiment of the method for producing biomass composite materials according to the present invention will be described. Figure 4 is a flowchart showing a second embodiment of the method for producing a biomass composite material according to the present invention. As shown in Figure 4, the method for producing a biomass composite material according to the second embodiment comprises a kneading step S11 for preparing a mixture of biomass, an organic binder, and water; an adsorption step S12 for adsorbing an aqueous solution of ceramic particle precursors onto the entire mixture; a precipitation step S13 for preparing a composite mixture in which ceramic particles have been precipitated; and a washing step S14 for washing with water. According to the method for manufacturing biomass composites of the second embodiment, the biomass composites of the second embodiment described above can be manufactured.

[0097] In the method for producing a biomass composite material according to the second embodiment, the kneading step S11 is a step in which biomass, an organic binder, and water are kneaded together to form a mixture. In the mixing step S11, the biomass, organic binder, and water are simply mixed together. If necessary, the mixture may be subjected to stirring, temperature changes, pressure changes, etc. Incidentally, if the organic binder is insoluble in water, it is preferable to disperse the organic binder as uniformly as possible in the mixture.

[0098] In the method for producing a biomass composite material according to the second embodiment, the adsorption step S12 is a step in which, after drying the mixture, it is immersed in an aqueous solution of ceramic particle precursors in which ceramic particle precursors, which are precursors of ceramic particles, are dissolved, so that the aqueous solution of ceramic particle precursors is adsorbed over the entire mixture. In the adsorption step S12, the mixture is first dried. This allows the organic binder to adhere to the biomass fibers in a way that it becomes entangled. Furthermore, it facilitates the penetration of the ceramic particle precursor aqueous solution, described later, into the biomass.

[0099] The ceramic particle precursor is the same as the ceramic particle precursor in the method for producing biomass composite material according to the first embodiment, so its description is omitted. A ceramic particle precursor aqueous solution is an aqueous solution in which at least a portion of the ceramic particle precursor is dissolved in water. In other words, a ceramic particle precursor aqueous solution is an aqueous solution containing metal ions derived from the ceramic particle precursor. It is not necessary to dissolve all of the ceramic particle precursor in water, but if it is not completely dissolved, it is preferable to disperse the undissolved ceramic particle precursor as uniformly as possible in the mixture. Next, the mixture is immersed in an aqueous solution of ceramic particle precursors. If necessary, the mixture may be subjected to stirring, temperature changes, pressure changes, etc. This allows the aqueous solution containing metal ions to penetrate deep into the biomass.

[0100] In the method for producing biomass composite material according to the second embodiment, the precipitation step S13 and the washing step S14 are the same as the precipitation step S2 and the washing step S3 in the method for producing biomass composite material according to the corresponding first embodiment, so their explanation is omitted. In addition, in the precipitation step S13, the mixture contains an organic binder, but it is preferable that this organic binder does not participate in the reaction that precipitates the ceramic particles. Furthermore, in the washing step S14, since the organic binder is coated with ceramic particles, its leakage during washing with water is suppressed. In this way, a biomass composite material is obtained in which biomass, ceramic particles, and an organic binder are combined.

[0101] (Third embodiment of the method for manufacturing biomass composite materials) Next, a third embodiment of the method for producing biomass composite materials according to the present invention will be described. The method for producing a biomass composite material according to the third embodiment comprises a kneading step of preparing a mixture of biomass, an organic binder, an auxiliary agent, and water; an adsorption step of adsorbing an aqueous solution of ceramic particle precursors onto the entire mixture; a precipitation step of preparing a composite mixture in which ceramic particles have precipitated; and a washing step of washing with water. In other words, the method for producing a biomass composite material according to the third embodiment is the same as the method for producing a biomass composite material according to the second embodiment, except that an auxiliary agent is included in the mixture in the kneading step. According to the method for manufacturing biomass composite materials of the third embodiment, the biomass composite material of the third embodiment described above can be manufactured.

[0102] In the method for producing a biomass composite material according to the third embodiment, the kneading step is a step of kneading biomass, an organic binder, an auxiliary agent, and water to form a mixture. In the mixing step, the biomass, organic binder, auxiliary agent, and water are simply mixed together. If necessary, the mixture may be subjected to stirring, temperature changes, pressure changes, etc. Furthermore, if the organic binder and auxiliary agents are insoluble in water, it is preferable to disperse them as uniformly as possible in the mixture.

[0103] In the method for producing a biomass composite material according to the third embodiment, the adsorption step, the precipitation step, and the washing step are the same as the adsorption step S12, the precipitation step S13, and the washing step S14 in the method for producing a biomass composite material according to the corresponding second embodiment, so their explanation is omitted. Furthermore, in the adsorption step, the mixture is dried once, allowing the organic binder and auxiliary agents to adhere to the biomass fibers in a way that they become entangled. Furthermore, in the precipitation step, the mixture contains an organic binder and an auxiliary agent, but it is preferable that the organic binder and auxiliary agent do not participate in the reaction that precipitates the ceramic particles. Furthermore, in the washing step, since the organic binder and auxiliary agents are coated with ceramic particles, their leaching out by washing with water is suppressed. In this way, a biomass composite material is obtained in which biomass, ceramic particles, an organic binder, and an auxiliary agent are combined.

[0104] (Fourth embodiment of the method for manufacturing biomass composite materials) Next, a fourth embodiment of the method for producing biomass composite materials according to the present invention will be described. The method for producing a biomass composite material according to the fourth embodiment comprises a kneading step of preparing a mixture of biomass, an organic binder, a readily soluble substance, and water; an adsorption step of adsorbing an aqueous solution of ceramic particle precursors onto the entire mixture; a precipitation step of preparing a composite mixture in which ceramic particles have been precipitated; and a washing step of washing with water. In other words, the method for producing a biomass composite material according to the fourth embodiment is the same as the method for producing a biomass composite material according to the second embodiment, except that the readily soluble substance is included in the mixture in the kneading step. According to the method for manufacturing biomass composites according to the fourth embodiment, the biomass composites according to the fourth embodiment described above can be manufactured.

[0105] In the method for producing a biomass composite material according to the fourth embodiment, the kneading step is a step of kneading biomass, an organic binder, a readily soluble substance, and water to form a mixture. In the mixing step, the biomass, organic binder, easily soluble substance, and water are simply mixed together. If necessary, the mixture may be subjected to stirring, temperature changes, pressure changes, etc.

[0106] Easily soluble substances are substances that are easily soluble in water with a solubility of 5 g / L or more, and may be organic or inorganic substances. They may also be solid or liquid at room temperature. Furthermore, it is preferable that the readily soluble substance does not participate in the reaction between metal ions and counterions. Specific examples of easily soluble substances include alkali metal halides such as sodium chloride, potassium chloride, and lithium chloride; polyhydric alcohols such as ethylene glycol, glycerin, and polyethylene glycol; and sugars such as sucrose, glucose, fructose, mannose, xylitol, pentanol, and erythritol.

[0107] In the method for producing a biomass composite material according to the fourth embodiment, the adsorption step, the precipitation step, and the washing step are the same as the adsorption step S12, the precipitation step S13, and the washing step S14 in the method for producing a biomass composite material according to the corresponding second embodiment, so their description is omitted. In the precipitation step, the mixture contains an organic binder and a readily soluble substance, but it is preferable that the organic binder and readily soluble substance do not participate in the reaction that precipitates the ceramic particles. Furthermore, during the washing step, readily soluble substances are easily dissolved and removed by water because they are readily soluble. As a result, pores are formed in the areas where the readily soluble substances have been removed. In this way, a porous biomass composite material is obtained, which is a composite of biomass, ceramic particles, and an organic binder.

[0108] Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

[0109] The biomass composite material according to the first embodiment is a composite of biomass and ceramic particles, the biomass composite material according to the second embodiment is a composite of biomass, ceramic particles and an organic binder, and the biomass composite material according to the third embodiment is a composite of biomass, ceramic particles and an organic binder and an auxiliary agent, however, it may also be a composite of biomass, ceramic particles and an auxiliary agent.

[0110] The biomass composite material according to the fourth embodiment is a composite of biomass, ceramic particles, and an organic binder, and is a porous body having pores. However, the biomass composite material formed by combining biomass and ceramic particles may be a porous body, the biomass composite material formed by combining biomass, ceramic particles, an organic binder, and an auxiliary agent may be a porous body, and the biomass composite material formed by combining biomass, ceramic particles, and an auxiliary agent may be a porous body. Furthermore, to create a porous material, for example, a readily soluble substance may be included in the mixture, similar to the method for producing the biomass composite material according to the fourth embodiment.

[0111] In the method for producing a biomass composite material according to the first embodiment, a mixture of biomass, ceramic particle precursors, and water is used, but the mixture may further include at least one selected from the group consisting of an organic binder, an auxiliary agent, and a readily soluble substance.

[0112] In the method for producing biomass composite material according to the second embodiment, a mixture of biomass, an organic binder, and water is used as the mixture, but the organic binder is not essential, and an auxiliary agent may be added instead of the organic binder.

[0113] In the method for producing a biomass composite material according to the fourth embodiment, a mixture of biomass, an organic binder, a readily soluble substance, and water is used as the mixture. However, the organic binder may not be included, and an auxiliary agent may be added instead of the organic binder. Furthermore, the organic binder and the auxiliary agent may be included together. [Examples]

[0114] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0115] (Example 1) [biomass] First, filter paper powder (manufactured by Advantec Toyo Co., Ltd.) was soaked in water to create a 5 wt% dispersion. Next, a defibration process was performed using a grinder (model number: MKCA6-2, manufactured by Masuko Sangyo Co., Ltd.) to obtain a dispersion containing cellulose nanofibers with a fiber diameter of approximately 10-200 nm, which was then used. [Ceramic particle precursor] Calcium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the ceramic particle precursor. [Mixing step] A cellulose nanofiber aqueous dispersion containing 0.2 g of solids and 20 g of calcium hydroxide were kneaded in an agate bowl. The kneaded mixture was filled into a φ6 × 3 mm silicone rubber mold using a stainless steel spatula. The ends of the mold were then covered with a 0.3 mm thick polypropylene sheet, and the ends were further sandwiched between microscope slides. The mold was then secured with clips and cured at room temperature for 1 to 24 hours. [Precipitation step] After removing both sides of the microscope slide and one side of the polypropylene sheet, the mold was placed on a polypropylene stand and set up in a sealed container along with a petri dish containing ammonium carbonate powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and a petri dish containing ultrapure water. Each sealed container was placed in a 40°C incubator and exposed to an ammonium carbonate saturated environment for 3 days. [Washing Step] The composite mixture after the carbonation reaction was removed from the sealed container, washed multiple times with distilled water, then immersed in distilled water at room temperature for 12 hours, washed several more times with distilled water, and finally dried in a forced-air dryer at 40°C, still in its mold. Thus, we obtained sample 1.

[0116] (Example 2) [biomass] The wood chips of Japanese cedar (a conifer) were coarsely crushed using a cutter mill (model number: MKCM-5, manufactured by Masuko Sangyo Co., Ltd.), and then further crushed using an air-flow type pulverizer, a selenium mirror (model number: MKCL8-15J, manufactured by Masuko Sangyo Co., Ltd.) to obtain dried cedar wood powder, which was then used. [Ceramic particle precursor] Anhydrous calcium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the ceramic particle precursor. The calcium chloride was an aqueous solution prepared to any concentration between 1 and 5 mol / L. [Mixing step] A calcium chloride aqueous solution was added to dried cedar wood powder and mixed in an agate bowl. Samples were prepared by adding 0.4 mmol, 4 mmol, or 8 mmol of calcium chloride per 1 g of dried cedar wood powder. The mixed mixture was then filled into a φ6 × 3 mm silicone rubber mold using a stainless steel spatula. The ends of the mold were then covered with a 0.3 mm thick polypropylene sheet, and the ends were further sandwiched between microscope slides and secured with clips. The mold was then cured at room temperature for 1 to 24 hours. [Precipitation step] After removing both sides of the microscope slide and one side of the polypropylene sheet, the mold was placed on a polypropylene stand and set up in a sealed container along with a petri dish containing ammonium carbonate powder and another petri dish containing ultrapure water. Each sealed container was placed in a 40°C incubator and exposed to an ammonium carbonate saturated environment for 3 days. [Washing Step] The composite mixture after the carbonation reaction was removed from the sealed container, washed multiple times with distilled water, then immersed in distilled water at room temperature for 12 hours, washed several more times with distilled water, and finally dried in a forced-air dryer at 40°C, still in its mold. Thus, we obtained sample 2.

[0117] (Example 3) [biomass] Dried cedar wood powder was used in the same manner as in Example 2. [Ceramic particle precursor] Calcium chloride dihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the ceramic particle precursor. [Organic compounds] 5 g of casein (protein, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was completely dissolved in 50 mL of 25% ammonia water (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare a 100 g / L casein aqueous solution. This casein aqueous solution was also diluted with distilled water as needed to prepare 10 g / L or 50 g / L solutions, which were also used. [Mixing step] 1 g of dried cedar wood powder, 0.2 mL of casein aqueous solution at 0 g / L (blank), 10 g / L, 50 g / L, or 100 g / L, and 0.6 mL of 6.6 mol / L calcium chloride aqueous solution were placed in an agate mortar and mixed thoroughly. The mixed mixture was filled into a φ6 × 3 mm silicone rubber mold using a stainless steel spatula. The ends of the mold were then covered with a 0.3 mm thick polypropylene sheet, and the ends were further sandwiched between microscope slides. The mold was then secured with clips and cured at 40°C for 2 hours. [Precipitation step] After removing the microscope slide and polypropylene sheet, the mold was placed on a polystyrene tray and then placed in a sealed container with ammonium carbonate powder and distilled water. Each sealed container was placed in a 40°C incubator and exposed to an ammonium carbonate saturated environment for 3 days. [Washing Step] The composite mixture after the carbonation reaction was removed from the sealed container, washed multiple times with distilled water, then immersed in distilled water at room temperature for 12 hours, washed several more times with distilled water, and finally dried in a forced-air dryer at 40°C, still in its mold. Thus, we obtained sample 3.

[0118] (Example 4) [Biomass preparation] Dried cedar wood powder was used in the same manner as in Example 2. [Preparation of ceramic particle precursors] Calcium chloride dihydrate was used in the same manner as in Example 3. [Preparation of organic compounds] Casein was used in the same manner as in Example 3. [Mixing step] 1 g of dried cedar wood powder and 4 mL of 100 g / L casein aqueous solution were placed in an agate mortar and kneaded thoroughly. The kneaded mixture was then filled into a φ6 × 3 mm silicone rubber mold using a stainless steel spatula. After covering both ends of the mold with a 0.3 mm thick polypropylene sheet, the ends were further sandwiched between microscope slides and secured with clips, and the mold was cured at 40°C for 2 hours. [Adsorption step] Next, the glass slide and polypropylene sheet were removed, and the mixture was dried in the mold at 40°C for 12 hours. After that, it was removed from the mold to obtain the dried mixture. Ten dry mixtures were immersed in 5 mL of calcium chloride aqueous solutions of 0 mol / L (blank), 0.1 mol / L, 0.5 mol / L, 1.0 mol / L, 2.0 mol / L, or 5.0 mol / L at room temperature for 2 hours. [Precipitation step] After removing excess aqueous solution, the mixture was placed on a polystyrene tray and then placed in a sealed container with ammonium carbonate powder and distilled water. Each sealed container was placed in a 40°C incubator and exposed to an ammonium carbonate saturated environment for one day. [Washing Step] The composite mixture after the carbonation reaction was removed from the sealed container, washed multiple times with distilled water, then immersed in distilled water at room temperature for 12 hours, washed several more times with distilled water, and finally dried in a forced-air dryer at 40°C, still in its mold. Thus, we obtained sample 4.

[0119] (Example 5) [Biomass preparation] Dried cedar wood powder was used in the same manner as in Example 2. [Preparation of ceramic particle precursors] Calcium chloride dihydrate was used in the same manner as in Example 3. [Preparation of organic compounds] Casein was used in the same manner as in Example 3. [Preparation of easily soluble substances] Sodium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the readily soluble substance. [Mixing step] 1 g of dried cedar wood powder, 4 mL of 100 g / L casein aqueous solution, and 0 g (blank), 0.5 g, 1.0 g, 2.0 g, or 3.0 g of sodium chloride were placed in an agate mortar and mixed thoroughly. The mixed mixture was then filled into a φ6 × 3 mm silicone rubber mold using a stainless steel spatula. After covering both ends of the mold with a 0.3 mm thick polypropylene sheet, the ends were further sandwiched between microscope slides and secured with clips, and the mold was cured at 40°C for 2 hours. [Adsorption step] Next, after removing the glass slide and polypropylene sheet, the mixed mud was dried in the mold at 40°C for 12 hours, then removed from the mold to obtain the dried mixture. Ten dry mixtures were placed in a polystyrene tray, and 5 mL of 2 mL / L calcium chloride aqueous solution was added dropwise. The tray was then left to stand for 2 hours. [Precipitation step] After removing excess aqueous solution, the mixture was placed on a polystyrene tray and then placed in a sealed container with ammonium carbonate powder and distilled water. Each sealed container was placed in a 40°C incubator and exposed to an ammonium carbonate saturated environment for one day. [Washing Step] The composite mixture after the carbonation reaction was removed from the sealed container, washed multiple times with distilled water, then immersed in distilled water at room temperature for 12 hours, and washed several more times with distilled water to remove the by-products ammonium chloride and residual sodium chloride. After that, the mold was dried in a forced-air dryer at 40°C. Thus, we obtained sample 5.

[0120] (Example 6) [Biomass preparation] Dried cedar wood powder was used in the same manner as in Example 2. [Preparation of ceramic particle precursors] Silver nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the ceramic particle precursor. [Preparation of organic compounds] Casein was used in the same manner as in Example 3. [Mixing step] 1 g of dried cedar wood powder and 4 mL of 100 g / L casein aqueous solution were placed in an agate mortar and kneaded thoroughly. The kneaded mixture was then filled into a φ6 × 3 mm silicone rubber mold using a stainless steel spatula. After covering both ends of the mold with a 0.3 mm thick polypropylene sheet, the ends were further sandwiched between microscope slides and secured with clips, and the mold was cured at 40°C for 2 hours. [Adsorption step] Next, the glass slide and polypropylene sheet were removed, and the mixture was dried in the mold at 40°C for 12 hours. After that, it was removed from the mold to obtain the dried mixture. Ten dry samples of the mixture were immersed in 5 mL of 2.0 ml / L silver nitrate aqueous solution at room temperature for 2 hours. [Precipitation step] After removing excess aqueous solution, the mixture was placed on a polystyrene tray and then placed in a sealed container with ammonium carbonate powder and distilled water. Each sealed container was placed in a 40°C incubator and exposed to an ammonium carbonate saturated environment for one day. [Washing Step] The composite mixture after the carbonation reaction was removed from the sealed container, washed multiple times with distilled water, then immersed in distilled water at room temperature for 12 hours, washed several more times with distilled water, and finally dried in a forced-air dryer at 40°C, still in its mold. Thus, we obtained sample 6.

[0121] (Example 7) [Biomass preparation] Dried cedar wood powder was used in the same manner as in Example 2. [Preparation of ceramic particle precursors] As the ceramic particle precursor, titanium tetrachloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) or titanium tetrachloride and calcium chloride dihydrate similar to that in Example 3 were used. [Preparation of organic compounds] Casein was used in the same manner as in Example 3. [Mixing step] 1 g of dried cedar wood powder and 4 mL of 100 g / L casein aqueous solution were placed in an agate mortar and kneaded thoroughly. The kneaded mixture was then filled into a φ6 × 3 mm silicone rubber mold using a stainless steel spatula. After covering both ends of the mold with a 0.3 mm thick polypropylene sheet, the ends were further sandwiched between microscope slides and secured with clips, and the mold was cured at 40°C for 2 hours. [Adsorption step] Next, the glass slide and polypropylene sheet were removed, and the mixture was dried in the mold at 40°C for 12 hours. After that, it was removed from the mold to obtain the dried mixture. Ten dry samples of the mixture were immersed for 2 hours at room temperature in either 5 mL of a 1.0 mol / L or 1.4 mol / L titanium tetrachloride aqueous solution, or 5 mL of a 0.5 mol / L or 1.4 mol / L titanium tetrachloride aqueous solution and 5 mL of a 2.0 mol / L calcium chloride aqueous solution. [Precipitation step] After removing excess aqueous solution, the mixture was placed on a polystyrene tray and then placed in a sealed container with ammonium carbonate powder and distilled water. Each sealed container was placed in a 40°C incubator and exposed to an ammonium carbonate saturated environment for one day. [Washing Step] The composite mixture after the carbonation reaction was removed from the sealed container, washed multiple times with distilled water, then immersed in distilled water at room temperature for 12 hours, washed several more times with distilled water, and finally dried in a forced-air dryer at 40°C, still in its mold. Thus, we obtained sample 7.

[0122] (Comparative Example 1) The kneading step was carried out in the same manner as in Example 4, except that a ceramic particle precursor was not used, to obtain a dry mixture. This dried mixture was designated as Sample 8. In other words, in Comparative Example 1, the adsorption step, precipitation step, and washing step were not performed.

[0123] (Evaluation method) [Scanning Electron Microscope (SEM) Observation] Scanning electron microscopy was performed to examine the morphology of each sample. The sample was fixed to the sample stage with conductive tape, and after surface conductivity treatment by osmium deposition, it was observed using a scanning electron microscope (S-4800 model, Hitachi High-Tech Corporation) at an accelerating voltage of 1 kV. Furthermore, the elemental distribution in the sample was mapped using an energy-dispersive X-ray spectroscopy (EDS) system (Octane Elect, EDAX Inc.). During EDS analysis, the accelerating voltage was adjusted to a maximum of 15 kV for observation. [X-ray diffraction (XRD)] The composition and crystal system of the ceramic particles contained in each sample were confirmed by X-ray diffraction. Approximately 100 mg of each sample was ground in an agate bowl and placed in a tablet molder. A hydraulic pump applied a pressure of 2 tons for 5 minutes to form tablets approximately 10 mm in diameter and 1 mm thick. These molded bodies were placed in a benchtop powder X-ray diffractometer (Miniflex600, manufactured by Rigaku Corporation), and CuKα rays generated by applying a tube voltage-tube current of 50 kV-300 mA to the target were irradiated onto the samples, and measured using the 2θ / θ method. Diffraction patterns for 2θ = 2-90° were obtained. [FT-IR Spectra] To investigate the chemical structure of the constituent components of each sample, FT-IR spectra were acquired using total internal reflection (ATR) measurement with an infrared spectrometer (Frontier FT-IR, PerkinElmer). For examining the composition near the surface of each sample, the sample itself was used; for the FT-IR spectrum averaged across all samples, tablets prepared by X-ray diffraction were used as the measurement sample. [3D X-ray CT (Micro-CT)] To investigate the distribution of biomass and ceramic particles, three-dimensional X-ray CT images were acquired. Using a three-dimensional X-ray microscope (SKYSCAN-2214, manufactured by Bruker Japan Co., Ltd.), a tungsten filament was used as the X-ray source, and the sample was rotated horizontally relative to the X-ray beam while transmission images were acquired at various angles and reconstructed to obtain a three-dimensional image. [Stress-strain curve and diametral tensile strength (DTS strength)] The stress-strain curves for each sample and the resulting diametral tensile strength measurements were performed using a universal testing machine (AGX, manufactured by Shimadzu Corporation) at a head speed of 1 mm / min. [water resistance] Five samples of each type were placed on a polystyrene tray, and 5 mL of distilled water was added dropwise. The tray was then left to stand at room temperature. The changes over time were observed visually.

[0124] (Evaluation and discussion of each embodiment) 1-1. About Example 1 A photograph of Sample 1 is shown in Figure 1. As shown in Figure 1, Sample 1 clearly maintains the shape of the mold. Figure 5(a) shows the SEM image of Sample 1, Figure 5(b) shows the EDS mapping of calcium atoms in Sample 1, Figure 5(c) shows the EDS mapping of carbon atoms in Sample 1, and Figure 5(d) shows the EDS mapping of oxygen atoms in Sample 1. The XRD pattern of Sample 1 is shown in Figure 6(a), and the XRD pattern of only calcium carbonate particles as a blank is shown in Figure 6(b). Figure 7 shows the FT-IR spectra of Sample 1, cellulose powder (cellulose nanofiber raw material) as a blank, and calcium carbonate particles as a blank. In the micro-CT images of Sample 1, the external appearance is shown in Figure 8(a), the cross-section in Figure 8(b), and the longitudinal section in Figure 8(c). The DTS intensity of sample 1 was measured.

[0125] 1-2. Consideration In Sample 1, the SEM image shown in Figure 5(a) revealed that cellulose nanofibers (biomass) and calcium carbonate particles (ceramic particles) were composited. Furthermore, calcium carbonate particles were observed in both submicron and several-micrometer sizes. In Sample 1, the EDS mapping shown in Figures 5(b) to (d) indicates the presence of calcium atoms, carbon atoms, and oxygen atoms throughout, suggesting the presence of calcium carbonate crystals throughout. In Sample 1, the XRD patterns shown in Figures 6(a) and (b) yielded diffraction patterns consistent with commercially available calcium carbonate, indicating the formation of calcium carbonate calcite crystals. In other words, it was confirmed that calcium carbonate was formed by the reaction of calcium chloride with carbonate ions. In Sample 1, the FT-IR spectrum shown in Figure 7 revealed bands corresponding to calcium carbonate and bands corresponding to cellulose nanofibers. Sample 1 was observed to have an overall uniform structure, as seen in the micro-CT images shown in Figures 8(a) to (c). Five samples of Sample 1 were prepared, and their DTS intensity was measured to be 0.62 MPa.

[0126] 2-1. Regarding Example 2 In Sample 2, the photograph taken when 4 mmol of calcium chloride was used is shown in Figure 9(a), and the photograph taken when 8 mmol of calcium chloride was used is shown in Figure 9(b). Figure 10(a) shows the SEM image of Sample 2 using 8 mmol of calcium chloride, Figure 10(b) shows the EDS mapping of calcium atoms in Sample 2, Figure 10(c) shows the EDS mapping of carbon atoms in Sample 2, Figure 10(d) shows the EDS mapping of oxygen atoms in Sample 2, Figure 10(e) shows the EDS mapping of chlorine atoms in Sample 2, and Figure 10(f) shows the EDS mapping of nitrogen atoms in Sample 2. In Sample 2, the XRD pattern when 0.4 mmol of calcium chloride was used is shown in Figure 11(a), the XRD pattern when 4 mmol of calcium chloride was used is shown in Figure 11(b), the XRD pattern when 8 mmol of calcium chloride was used is shown in Figure 11(c), and the XRD pattern of only calcium carbonate particles as a blank is shown in Figure 11(d). Figure 12 shows the FT-IR spectra of Sample 2, cedar powder as a blank, calcium carbonate particles as a blank, Sample 2 using 0.4 mmol of calcium chloride per 1 g of cedar powder, Sample 2 using 4 mmol of calcium chloride, and Sample 2 using 8 mmol of calcium chloride. In Sample 2, when 8 mmol of calcium chloride was used, the external appearance is shown in Figure 13(a), the cross-section in Figure 13(b), and the longitudinal section in Figure 13(c). In Sample 2, the DTS intensity was measured using 8 mmol of calcium chloride.

[0127] 2-2. Consideration In Sample 2, the mold shape was clearly maintained, as can be seen from the photographs in Figure 9(a) and (b). In sample 2, the SEM image shown in Figure 10(a) revealed that particulate compounds were compounded around the fibers. In Sample 2, EDS mapping shown in Figures 10(b) to (f) indicates that calcium atoms, carbon atoms, and oxygen atoms were present in the particle portion of several tens of nanometers, suggesting that the particles are calcium carbonate crystals. In Sample 2, the XRD patterns shown in Figures 11(a) to (d) revealed diffraction peaks originating from calcium carbonate calcite crystals, along with diffraction peaks from the cellulose crystal (1 1 0) and (1 - 1 0) planes near 2θ=16° and the (2 0 0) plane at 2θ=23°. Furthermore, the intensity of the diffraction peaks originating from calcium carbonate increased as the amount of calcium chloride mixed in increased. In Sample 2, the FT-IR spectrum shown in Figure 12 revealed bands corresponding to calcium carbonate, as well as bands corresponding to cellulose, hemicellulose, and lignin. In sample 2, the micro-CT images shown in Figures 13(a) to (c) revealed that a particulate region with high X-ray absorption was distributed at the outer edge of sample 2. Five samples of Sample 2 were prepared, and their DTS intensity was measured to be 0.16 MPa.

[0128] 3-1. Regarding Example 3 In Sample 3, the photograph taken when no casein was used as a blank is shown in Figure 14(a), the photograph taken when a 10 g / L casein aqueous solution was used is shown in Figure 14(b), the photograph taken when a 50 g / L casein aqueous solution was used is shown in Figure 14(c), and the photograph taken when a 100 g / L casein aqueous solution was used is shown in Figure 14(d). Figure 15(a) shows the SEM image of Sample 3 using a 100 g / L casein aqueous solution, Figure 15(b) shows the EDS mapping of calcium atoms in Sample 3, Figure 15(c) shows the EDS mapping of carbon atoms in Sample 3, Figure 15(d) shows the EDS mapping of oxygen atoms in Sample 3, and Figure 15(e) shows the EDS mapping of chlorine atoms in Sample 3. In Sample 3, the XRD pattern when no casein is used as a blank is shown in Figure 16(a), the XRD pattern when a 10 g / L casein aqueous solution is used is shown in Figure 16(b), the XRD pattern when a 50 g / L casein aqueous solution is used is shown in Figure 16(c), and the XRD pattern when a 100 g / L casein aqueous solution is used is shown in Figure 16(d). Figure 17 shows the FT-IR spectra for Sample 3 when no casein was used as a blank, when a 10 g / L casein aqueous solution was used, when a 50 g / L casein aqueous solution was used, and when a 100 g / L casein aqueous solution was used. In Sample 3, the microCT images when no casein was used as a blank show the external appearance in Figure 18(a), the cross-section in Figure 18(b), and the longitudinal section in Figure 18(c). The microCT images when a 100 g / L casein aqueous solution was used show the external appearance in Figure 18(d), the cross-section in Figure 18(e), and the longitudinal section in Figure 18(f). Figure 19 shows the DTS intensity for Sample 3 when no casein was used as a blank, when a 10 g / L casein aqueous solution was used, when a 50 g / L casein aqueous solution was used, and when a 100 g / L casein aqueous solution was used.

[0129] 3-2. Consideration Sample 3 clearly maintained its mold shape regardless of the casein concentration, as shown in the photographs (a) to (d) in Figure 14. In sample 3, the SEM image shown in Figure 15(a) revealed that particulate compounds were compounded around the fibers. In Sample 3, the EDS mapping shown in Figures 15(b) to (e) indicates that calcium atoms, carbon atoms, and oxygen atoms were present in the particle portion of several tens of nanometers, suggesting that the particles are calcium carbonate crystals. From the XRD patterns shown in Figures 16(a) to (d), the peak intensity of calcium carbonate varied in Sample 3 in proportion to the concentration of the immersed casein aqueous solution. Furthermore, diffraction peaks originating from calcite and vaterite crystals were observed. The diffraction peak intensity originating from vaterite crystals increased relatively as the concentration of the casein aqueous solution increased, suggesting a higher proportion of vaterite crystals. In Sample 3, the FT-IR spectrum shown in Figure 17 indicates that even when the concentration of the immersed casein aqueous solution fluctuated, the bands corresponding to calcium carbonate and the bands corresponding to cedar wood powder did not change significantly. In sample 3, the micro-CT images shown in Figures 18(a) to (f) revealed that, regardless of the casein concentration, a particulate region with high X-ray absorption was distributed at the outer edge of sample 3. In Sample 3, no dependence of the concentration of the immersed calcium chloride solution on the intensity of Sample 3 was observed, as shown in Figure 19 of the DTS intensity.

[0130] 4-1. About Example 4 (Comparative Example 1) Figure 20 shows a photograph of the dry mixture before immersion in the calcium chloride aqueous solution during the adsorption step. In Sample 4, the photograph of Sample 8 as a blank is shown in Figure 21(a), the photograph of the case using a 0.1 mol / L calcium chloride aqueous solution is shown in Figure 21(b), the photograph of the case using a 1.0 mol / L calcium chloride aqueous solution is shown in Figure 21(c), the photograph of the case using a 2.0 mol / L calcium chloride aqueous solution is shown in Figure 21(d), and the photograph of the case using a 5.0 mol / L calcium chloride aqueous solution is shown in Figure 21(e). Figure 22(a) shows the SEM image of Sample 4 using a 2 mol / L aqueous calcium chloride solution, Figure 22(b) shows the EDS mapping of calcium atoms in Sample 4, Figure 22(c) shows the EDS mapping of carbon atoms in Sample 4, Figure 22(d) shows the EDS mapping of oxygen atoms in Sample 4, and Figure 22(e) shows the EDS mapping of chlorine atoms in Sample 4. In Sample 4, the XRD pattern of Sample 8 is shown as a blank in Figure 23(a), the XRD pattern when using a 0.1 mol / L calcium chloride aqueous solution is shown in Figure 23(b), the XRD pattern when using a 0.5 mol / L calcium chloride aqueous solution is shown in Figure 23(c), the XRD pattern when using a 1.0 mol / L calcium chloride aqueous solution is shown in Figure 23(d), the XRD pattern when using a 2.0 mol / L calcium chloride aqueous solution is shown in Figure 23(e), and the XRD pattern when using a 5.0 mol / L calcium chloride aqueous solution is shown in Figure 23(f). Figure 24 shows the FT-IR spectra for Sample 4 when Sample 8 was used as a blank, and when a 0.1 mol / L calcium chloride aqueous solution was used, when a 0.5 mol / L calcium chloride aqueous solution was used, when a 1.0 mol / L calcium chloride aqueous solution was used, when a 2.0 mol / L calcium chloride aqueous solution was used, and when a 5.0 mol / L calcium chloride aqueous solution was used. In the microCT images of the dried mixture obtained by kneading 1 g of cedar wood powder and 100 g / L of casein aqueous solution and drying, the appearance is shown in Figure 25(a), the cross section in Figure 25(b), and the longitudinal section in Figure 25(c). In the microCT images of Sample 4, obtained using 2 M calcium chloride, the appearance is shown in Figure 25(d), the cross section in Figure 25(e), and the longitudinal section in Figure 25(f). Figure 26 shows the DTS intensity for Sample 4 when Sample 8 was used as a blank, when a 0.1 mol / L calcium chloride aqueous solution was used, when a 1.0 mol / L calcium chloride aqueous solution was used, when a 2.0 mol / L calcium chloride aqueous solution was used, and when a 5.0 mol / L calcium chloride aqueous solution was used. In the water resistance evaluation of Sample 8, a photograph taken immediately after impregnation with distilled water is shown in Figure 42(a), a photograph taken 2 hours after impregnation is shown in Figure 42(b), and a photograph taken 12 hours after impregnation is shown in Figure 42(c).

[0131] 4-2. Consideration The dried mixture clearly maintained the shape of the mold, as can be seen in the photograph in Figure 20. Sample 8, as shown in the photograph in Figure 21(a), was completely disintegrated and no longer retained its original shape. On the other hand, as shown in the photographs in Figure 21(b) to (e), Sample 4, which was immersed in a calcium chloride aqueous solution with a concentration of 0.5 mol / L or higher, clearly maintained its shape. In sample 4, the SEM image shown in Figure 22(a) revealed that particulate compounds were compounded around the fibers. In Sample 4, EDS mapping shown in Figures 22(b) to (e) indicates that calcium atoms, carbon atoms, and oxygen atoms were present in the particle portion of several tens of nanometers, suggesting that the particles are calcium carbonate crystals. In Sample 4, the XRD patterns shown in Figures 23(a) to (f) indicate that the peak intensity of calcium carbonate fluctuated in proportion to the calcium chloride concentration up to 1 M of the immersed calcium chloride solution. Furthermore, compared to sample 3, sample 4 showed a relatively higher diffraction peak intensity from vaterite crystals than from calcite, suggesting a higher proportion of vaterite crystals. In Sample 4, the intensity of the band corresponding to calcium carbonate fluctuated in proportion to the concentration of the immersed calcium chloride aqueous solution, as shown in the FT-IR spectrum in Figure 24. In the dried mixture, micro-CT images shown in Figures 25(a) to (c) revealed that the cedar wood powder particles were uniformly dispersed throughout. Furthermore, in sample 4, micro-CT images shown in Figures 25(d) to (f) revealed that a particulate region with high X-ray absorption was distributed at the outer edge. On the other hand, the central part of sample 4 had a structure similar to that of a dried structure. The intensity of Sample 4 initially increased in proportion to the concentration of the calcium chloride solution in which it was immersed, as shown in Figure 26 (DTS intensity). However, when the concentration of the calcium chloride solution exceeded 2.0 mol / L, a slight decrease in intensity was observed. Furthermore, the intensity of Sample 4 immersed in a 2.0 mol / L calcium chloride solution was comparable to that of the dry mixture. In sample 8, as seen in the photographs in Figure 42 (a) to (c), it was confirmed that it expanded and disintegrated over time. This is thought to be because sample 8 does not contain calcium carbonate. Incidentally, sample 4, which contains calcium carbonate, maintained its shape even after being immersed in water for a long time during the washing step, etc. (Figure 21 (b) to (e)).

[0132] 5-1. Regarding Example 5 In Sample 5, the photographs when sodium chloride is not used as a blank are shown in Figure 27(a), the photograph when 0.5g of sodium chloride is used is shown in Figure 27(b), the photograph when 1.0g of sodium chloride is used is shown in Figure 27(c), the photograph when 2.0g of sodium chloride is used is shown in Figure 27(d), and the photograph when 3.0g of sodium chloride is used is shown in Figure 27(e). Figure 28(a) shows the SEM image of Sample 5 using 3g of sodium chloride, Figure 28(b) shows the EDS mapping of calcium atoms in Sample 5, Figure 28(c) shows the EDS mapping of carbon atoms in Sample 5, and Figure 28(d) shows the EDS mapping of oxygen atoms in Sample 5. In Sample 5, the XRD pattern when 0.5 g of sodium chloride was used is shown in Figure 29(a), the XRD pattern when 1.0 g of sodium chloride was used is shown in Figure 29(b), the XRD pattern when 2.0 g of sodium chloride was used is shown in Figure 29(c), and the XRD pattern when 3.0 g of sodium chloride was used is shown in Figure 29(d). Figure 30 shows the FT-IR spectra for Sample 5 when no sodium chloride was used as a blank, when 0.5 g of sodium chloride was used, when 1.0 g of sodium chloride was used, when 2.0 g of sodium chloride was used, and when 3.0 g of sodium chloride was used. In Sample 5, the micro-CT images obtained using 0.5 g of sodium chloride show the external appearance in Figure 31(a), the cross-section in Figure 31(b), and the longitudinal section in Figure 31(c). The micro-CT images obtained using 3.0 g of sodium chloride show the external appearance in Figure 31(d), the cross-section in Figure 31(e), and the longitudinal section in Figure 31(f). Figure 32 shows the DTS intensity for Sample 5 when no sodium chloride was used as a blank, when 0.5g of sodium chloride was used, when 1.0g of sodium chloride was used, when 2.0g of sodium chloride was used, and when 3.0g of sodium chloride was used.

[0133] 5-2. Consideration As shown in the photograph in Figure 27, Sample 5 clearly maintained its shape regardless of the amount of sodium chloride. Furthermore, under conditions where the amount of sodium chloride was 2.0 g or more, clear voids caused by sodium chloride were observed in Sample 5. In sample 5, the SEM image shown in Figure 28(a) revealed that particulate compounds were compounded around the fibers. In Sample 5, the EDS mapping shown in Figures 28(b) to (d) indicates that calcium atoms, carbon atoms, and oxygen atoms were present in the particle portion of several tens of nanometers, suggesting that the particles are calcium carbonate crystals. In Sample 5, the XRD pattern shown in Figure 29 revealed diffraction peaks originating from cellulose and calcium carbonate, regardless of the concentration of the immersed calcium chloride solution or the amount of added sodium chloride. Both calcite and vaterite crystals were formed from the calcium carbonate. In Sample 5, the FT-IR spectrum shown in Figure 30 showed that the band corresponding to calcium carbonate increased in proportion to the concentration of the immersed calcium chloride solution. In sample 5, the micro-CT image shown in Figure 31 revealed a distribution of particulate regions with high X-ray absorption at the outer edge of sample 5. On the other hand, the central part of sample 5 had a structure similar to that of a dry mixture. Furthermore, under conditions with a high sodium chloride content, a clear single-porous structure was observed even inside sample 5. In Sample 5, as shown in Figure 32, the strength (mechanical strength) of Sample 5 decreased monotonically in proportion to the amount of sodium chloride added. However, even with 3.0 g of sodium chloride, the DTS strength remained above 1.0 MPa.

[0134] 6-1. Regarding Example 6 A photograph of sample 6 is shown in Figure 33(a). The SEM image of Sample 6 is shown in Fig. 34(a), the EDS mapping of silver atoms in Sample 6 is shown in Fig. 34(b), the EDS mapping of carbon atoms in Sample 6 is shown in Fig. 34(c), the EDS mapping of oxygen atoms in Sample 6 is shown in Fig. 34(d), and the EDS mapping of nitrogen atoms in Sample 6 is shown in Fig. 34(e). The XRD pattern of Sample 6 is shown in Fig. 35. The FT-IR spectra of Sample 6 are shown in Fig. 36. In the micro-CT image of Sample 6, the appearance is shown in Fig. 37(a), the cross-section is shown in Fig. 37(b), and the longitudinal section is shown in Fig. 37(c). The DTS intensity of Sample 6 is shown in Fig. 38.

[0135] 6-2. Discussion Sample 6 clearly maintained its shape as shown in the photograph of Fig. 33(a). Also, the dry mixture immersed in the silver nitrate aqueous solution was significantly blackened. In Sample 6, from the SEM image shown in Fig. 34(a), it was observed that particulate compounds were complexed around the fibers. In Sample 6, from the EDS mappings shown in Figs. 34(b) to (e), since silver atoms and oxygen atoms were present in the particle part of several tens of nanometers, the particles were considered to be silver oxide crystals. In Sample 6, from the XRD pattern shown in Fig. 35, peaks of silver oxide were observed. In Sample 6, from the FT-IR spectra shown in Fig. 36, bands of silver oxide were observed. In Sample 6, from the micro-CT images shown in Figs. 37(a) to (c), amorphous regions with high X-ray absorbability were distributed throughout Sample 6. In Sample 6, from the DTS intensity shown in Fig. 38, when the breaking strength decreased, even when a load above the yield point was applied, it did not completely collapse and exhibited flexibility.

[0136] 7-1. Regarding Example 7 In Sample 7, a photograph of the case using a 1.0 mol / L titanium tetrachloride aqueous solution is shown in Figure 33(b), and a photograph of the case using a 1.4 mol / L titanium tetrachloride aqueous solution is shown in Figure 33(c). Figure 39(a) shows the SEM image of Sample 7 using a 1.0 mmol / L titanium tetrachloride aqueous solution, Figure 39(b) shows the EDS mapping of titanium atoms in Sample 7, Figure 39(c) shows the EDS mapping of carbon atoms in Sample 7, Figure 39(d) shows the EDS mapping of oxygen atoms in Sample 7, Figure 39(e) shows the EDS mapping of nitrogen atoms in Sample 7, and Figure 39(f) shows the EDS mapping of chlorine atoms in Sample 7. Figure 40(a) shows SEM images of Sample 7 using a 1.0 mmol / L titanium tetrachloride aqueous solution and a 2.0 mmol / L calcium chloride aqueous solution, Figure 40(b) shows the EDS mapping of calcium atoms in Sample 7, Figure 40(c) shows the EDS mapping of carbon atoms in Sample 7, Figure 40(d) shows the EDS mapping of oxygen atoms in Sample 7, Figure 40(e) shows the EDS mapping of chlorine atoms in Sample 7, and Figure 40(f) shows the EDS mapping of titanium atoms in Sample 7. In Sample 7, the XRD pattern when using a 1.0 mol / L titanium tetrachloride aqueous solution is shown in Figure 41(a), and the XRD pattern when using a 1.4 mol / L titanium tetrachloride aqueous solution is shown in Figure 41(b). Furthermore, in Sample 7, the XRD patterns when using a 0.5 mol / L titanium tetrachloride aqueous solution and a 2.0 mol / L calcium chloride aqueous solution are shown in Figure 41(c), and the XRD patterns when using a 1.0 mol / L titanium tetrachloride aqueous solution and a 2.0 mol / L calcium chloride aqueous solution are shown in Figure 41(d). Figure 36 shows the FT-IR spectra for Sample 7 when a 1.0 mol / L titanium tetrachloride aqueous solution was used and when a 1.4 mol / L titanium tetrachloride aqueous solution was used. In Sample 7, the micro-CT images obtained using a 1.0 mol / L titanium tetrachloride aqueous solution are shown in Figure 37(d) for the external appearance, Figure 37(e) for the cross-section, and Figure 37(f) for the longitudinal section. Furthermore, in Sample 7, the external appearance is shown in Figure 37(g), the cross-sectional view in Figure 37(h), and the longitudinal section in Figure 37(i) of the micro-CT images obtained using a 1.0 mol / L titanium tetrachloride aqueous solution and a 2.0 mol / L calcium chloride aqueous solution. Figure 38 shows the DTS intensity for Sample 7 when a 1.0 mol / L titanium tetrachloride aqueous solution was used and when a 1.4 mol / L titanium tetrachloride aqueous solution was used.

[0137] 7-2. Consideration As can be seen from the photographs in Figures 33(b) and (c), Sample 7 clearly maintained its shape under all aqueous solution conditions. Furthermore, the dried mixture immersed in the titanium tetrachloride aqueous solution showed a slightly yellowish-white structure on its surface. It also shrank by approximately 10% compared to before immersion. In sample 7, SEM images shown in Figure 39(a) and Figure 40(a) revealed that particulate compounds were compounded around the fibers. In Sample 7, EDS mapping shown in Figures 39(b) to (f) indicates that titanium atoms and oxygen atoms were present in the particle portion of several tens of nanometers, suggesting that the particles are titanium oxide crystals. Furthermore, EDS mappings shown in Figures 40(b) to (f) indicate that calcium atoms, carbon atoms, and oxygen atoms, as well as titanium atoms and oxygen atoms, were present in the particle portions of several tens of nanometers in size. Therefore, the particles are considered to be calcium carbonate crystals and titanium oxide crystals. In sample 7, peaks for titanium dioxide were observed in the XRD patterns shown in Figure 41(a) and (b), and peaks for titanium dioxide and calcium carbonate were observed in the XRD patterns shown in Figure 41(c) and (d). In sample 7, a titanium oxide band was observed in the FT-IR spectrum shown in Figure 36. In sample 7, micro-CT images shown in Figures 37(d) to (i) revealed that while particles with high X-ray absorption were scattered throughout the interior of sample 7, a region of particulate matter with high X-ray absorption was distributed along the outer edge of sample 7. Furthermore, the central part of sample 7 had a structure similar to that of the dried mixture before treatment. In Sample 7, the DTS intensity shown in Figure 38 was significantly increased when the sample was immersed in a 1.0 ml / L titanium tetrachloride aqueous solution compared to before immersion. [Industrial applicability]

[0138] The biomass composite material according to the present invention can be used as a substitute for biomass used in industry. For example, the biomass composite material can be applied to applications such as fillers, plywood (building materials), various carriers, adhesives, coatings, ventilation filters, and adsorbents for air purifiers. The biomass composite material according to the present invention offers improved durability compared to conventional biomass and composite materials. [Explanation of symbols]

[0139] 1,2...Biomass composite materials S1, S11... Mixing step S12... Adsorption step S2, S13... Precipitation step S3, S14... Washing steps

Claims

1. A biomass composite material in which biomass and ceramic particles are combined, A biomass composite material in which the ceramic particles coat a portion of the biomass.

2. The aforementioned ceramic particles are formed when metal ions in water react with counterions and precipitate. The biomass composite material according to claim 1, wherein, at the time of precipitation, the ceramic particles coat a portion of the biomass.

3. 0 A biomass composite material comprising biomass, ceramic particles, and an organic binder, The organic binder is an organic polymer, a surfactant, or a lipid. A biomass composite material in which the ceramic particles coat a portion of the biomass and a portion of the organic binder, respectively.

4. The aforementioned ceramic particles are formed when metal ions in water react with counterions and precipitate. The biomass composite material according to claim 3, wherein, at the time of precipitation, the ceramic particles coat a portion of the biomass and a portion of the organic binder, respectively.

5. The biomass composite material according to claim 4, wherein the organic binder is at least one selected from the group consisting of proteins, peptides, polysaccharides, fatty acids, fatty acid esters, surfactants, glycolipids, sugar esters, synthetic resins, phospholipids, and phospholipid esters.

6. The biomass is cellulose fiber, chitin fiber, or chitosan fiber. The ceramic particles are particles made of a metal oxide, a metal hydroxide, or a metal salt. The aforementioned metal ions are ionized aluminum, zinc, or metals contained in alkaline earth metals, lanthanide metals, or transition metals. The biomass composite material according to claim 2, wherein the content ratio of the ceramic particles to 1% by mass of the biomass is 0.01 to 99.9% by mass.

7. The biomass is cellulose fiber, chitin fiber, or chitosan fiber. The ceramic particles are particles made of a metal oxide, a metal hydroxide, or a metal salt. The aforementioned metal ions are ionized aluminum, zinc, or metals contained in alkaline earth metals, lanthanide metals, or transition metals. The content ratio of the ceramic particles to 1% by mass of the biomass is 0.01 to 99.9% by mass. The biomass composite material according to claim 4, wherein the content ratio of the organic binder to 1% by mass of the biomass is 0.01 to 50.0% by mass.

8. It contains at least one auxiliary agent selected from the group consisting of antibacterial agents, preservatives, flame retardants, antioxidants, UV absorbers, hydrophilic agents, antistatic agents, slip agents, surfactants, colorants, conductive agents, fragrances, antifungal agents, insecticides, and excipients. The biomass composite material according to claim 2 or 4, wherein the auxiliary agent does not participate in the reaction.

9. The biomass composite material according to claim 2 or 4, which is in the form of blocks, sheets, pellets, or powder.

10. The biomass composite material according to claim 2 or 4, wherein the porosity is 0.1 to 99.9%.

11. A method for producing a biomass composite material according to claim 2, A mixing step involves kneading the biomass, the ceramic particle precursor which is a precursor of the ceramic particles, and water to form a mixture. A precipitation step in which the ceramic particle precursor dissolved in water is reacted with the wet gas containing carbon dioxide or ammonia gas to form a composite mixture in which the ceramic particles are precipitated, A washing step of washing the composite mixture with water, Equipped with, A method for producing a biomass composite material in which the ceramic particle precursor has a higher solubility in water than the ceramic particles formed from the ceramic particle precursor.

12. A method for producing a biomass composite material according to claim 4, comprising: a kneading step of kneading biomass, an organic binder, and water to form a mixture; an adsorption step of drying the mixture and then immersing it in an aqueous solution of ceramic particle precursors in which ceramic particle precursors, which are precursors of ceramic particles, are dissolved, to adsorb the aqueous solution of ceramic particle precursors onto the entire mixture; a precipitation step of reacting the ceramic particle precursors in the aqueous solution of ceramic particle precursors with the wet gas in the presence of a wet gas containing carbon dioxide or ammonia gas to form a composite mixture in which ceramic particles are precipitated; and a washing step of washing the composite mixture with water, wherein the ceramic particle precursors have a higher solubility in water than the ceramic particles formed from the ceramic particle precursors.

13. A method for producing a biomass composite material according to claim 8, comprising: a kneading step of kneading biomass, an organic binder, an auxiliary agent, and water to form a mixture; an adsorption step of drying the mixture and then immersing it in an aqueous solution of ceramic particle precursors in which ceramic particle precursors, which are precursors of ceramic particles, are dissolved, to adsorb the aqueous solution of ceramic particle precursors onto the entire mixture; a precipitation step of reacting the ceramic particle precursors in the aqueous solution of ceramic particle precursors with the wet gas in the presence of a wet gas containing carbon dioxide or ammonia gas to form a composite mixture in which ceramic particles are precipitated; and a washing step of washing the composite mixture with water, wherein the ceramic particle precursors have a higher solubility in water than the ceramic particles formed from the ceramic particle precursors.

14. In the aforementioned kneading step, the mixture further contains an easily soluble substance having a solubility in water of 5 g / L or more. The method for producing a biomass composite material according to claim 11 or 12, wherein the easily soluble substance is dissolved and removed with water in the washing step, thereby making the biomass composite material porous.

15. The precipitation step involves adding the mixture to a sealed container containing ammonium carbonate powder in a humid environment. The method for producing a biomass composite material according to claim 11 or 12, wherein the carbon dioxide and ammonia gas are released from the decomposition of the ammonium carbonate.

16. The ceramic particle precursor is calcium chloride, hydroxide, nitrate, acetate, or lactate. A method for producing a biomass composite material according to claim 11 or 12, wherein the ceramic particles are calcium carbonate particles.

17. The ceramic particle precursor is titanium chloride, citrate, or succinate. A method for producing a biomass composite material according to claim 11 or 12, wherein the ceramic particles are titanium oxide particles.

18. The ceramic particle precursor is a silver nitrate or sulfate. A method for producing a biomass composite material according to claim 11 or 12, wherein the ceramic particles are silver oxide particles.

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