Binder and method for manufacturing molded body

Abstract

To provide a binder which, when used as a binding material in the production of a molded body by binding fibers, etc., produces a molded body with sufficient strength.SOLUTION: A binder C10 includes an inorganic oxide particle C3 and a binding material particle C2 containing a binding material to mutually bind fibers when water is provided. The binder C10 includes a composite particle C1 in which the binding material particle C2 and the inorganic oxide particle C3 are integrated, the inorganic oxide particle C3 contains carbon, and the content of the carbon is 2 mass% or more relative to the mass of the inorganic oxide particle C3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a binder and a method for producing a molded body. [Background technology]

[0002] As a method for producing a molded body such as a cushioning material from recycled waste paper without using a large amount of water as in the papermaking method, a method for producing a molded body has been proposed in which waste paper is defibrated into a cotton-like material, and then atomized water is added to the cotton-like material, and a powdered or granular paste material is further added to produce the molded body (see, for example, Patent Document 1).This method for producing a molded body has the advantage that it can produce a molded body using only a small amount of water compared to the papermaking method, thereby saving energy and time spent on dehydration, drying, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-246465 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned manufacturing method of a molded body, even if a powdery glue material is simply mixed with fibers, it is difficult to distribute the glue material uniformly in the molded body, and it may be difficult to ensure sufficient strength of the resulting molded body. In particular, when a sheet-like molded body such as recycled paper is manufactured as the molded body, if there is an area where the amount of glue material is low, there is a problem that the molded body will break starting from that area, and the strength of the sheet will decrease. [Means for solving the problem]

[0005] The binder contains inorganic oxide particles and binder particles, the binder particles containing a binder that bonds fibers together when moisture is added, and the binder contains composite particles in which the binder particles and the inorganic oxide particles are integrated together, and the inorganic oxide particles contain carbon, and the carbon content is 2 mass% or more relative to the mass of the inorganic oxide particles.

[0006] The method for manufacturing a molded body includes a depositing step of depositing a mixture containing fibers and the binder, a humidifying step of adding moisture to the deposited mixture, and a molding step of heating and pressurizing the moistened mixture to obtain a molded body. [Brief explanation of the drawings]

[0007] [Figure 1] Schematic diagram of a binder according to an embodiment. [Figure 2] FIG. 1 is a schematic side view showing the configuration of a manufacturing apparatus suitable for carrying out a method for manufacturing a molded body. DETAILED DESCRIPTION OF THE INVENTION

[0008] 1.Binding material 1, the binder C10 includes inorganic oxide particles C3 and binder particles C2, which include a binder that binds fibers together when moisture is added, and composite particles C1 in which the binder particles C2 and the inorganic oxide particles C3 are integrated. The inorganic oxide particles C3 include carbon, and the carbon content is 2 mass% or more relative to the mass of the inorganic oxide particles C3.

[0009] As a result, when fibers are bonded together using the binder C10 to produce a molded body, a molded body having sufficient strength can be obtained. Specifically, the inorganic oxide particles C3 contained in the composite particles C1 contain 2 mass% or more of carbon relative to the mass of the inorganic oxide particles C3, thereby effectively reducing the surface free energy of the inorganic oxide particles C3. As a result, the binder C10 can be more suitably applied to the surface of the fibers. This improves the adhesion between the fibers and the binder C10 in the final molded body, thereby improving the strength of the molded body. Furthermore, since the binder C10 of the present invention has excellent dispersibility, it is possible to effectively prevent unintended aggregation of the binder C10 during storage of the binder C10 or during transportation of the binder C10 in the molded body production process.

[0010] In the present invention, a state in which at least some of the inorganic oxide particles C3 are attached to the surface of the binding material particles C2 or at least some of the inorganic oxide particles C3 are contained inside the binding material particles C2 to form composite particles C1 is referred to as a "composite particle C1 in which the binding material particles C2 and the inorganic oxide particles C3 are integrated." In other words, this does not exclude the binder C10 from containing binding material particles C2 and inorganic oxide particles C3 that do not form composite particles C1.

[0011] In the illustrated configuration, composite particles C1 contained in binder C10 have inorganic oxide particles C3 attached to the surfaces of binder material particles C2.

[0012] This creates a repulsive force between the inorganic oxide particles C3, making it difficult for the binding material particles C2 to aggregate together. The arrangement of the inorganic oxide particles C3 can be confirmed, for example, by using various electron microscopes.

[0013] 1.1. Composite particles The composite particle C1 contained in the binder C10 may be a single binder material particle C2 having a single inorganic oxide particle C3 attached to the surface thereof, but it is preferable that the binder C10 contains, as the composite particle C1, a particle having a single binder material particle C2 having multiple inorganic oxide particles C3 attached to the surface thereof.

[0014] This effectively generates a repulsive force between the inorganic oxide particles C3, making it more difficult for the binding material particles C2 to aggregate.

[0015] The average particle size of the composite particles C1 is preferably 1.0 μm or more and 100.0 μm or less, more preferably 2.0 μm or more and 70.0 μm or less, and even more preferably 3.0 μm or more and 50.0 μm or less, which makes it easier to distribute the composite particles C1 uniformly in the molded body.

[0016] In this specification, the average particle size refers to the median diameter (D50 value of cumulative 50% frequency) unless otherwise specified. The average particle size can be determined, for example, by measurement using a Microtrac UPA (manufactured by Nikkiso Co., Ltd.). 1.1.1.Binding material particles The binder particles C2 contain a binder that binds the fibers together when moisture is added.

[0017] Examples of the binding material constituting the binding material particles C2 include naturally occurring components such as starch, dextrin, glycogen, amylose, hyaluronic acid, kudzu, konjac, potato starch, etherified starch, esterified starch, natural gum paste (etherified tamarind gum, etherified locust bean gum, etherified guar gum, acacia arabic gum), fiber-derived paste (etherified carboxymethylcellulose, hydroxyethylcellulose), seaweed (sodium alginate, agar), animal protein (collagen, gelatin, hydrolyzed collagen, sericin), polyvinyl alcohol, polyacrylic acid, polyacrylamide, etc. One or more of these may be used in combination, but naturally occurring components are preferred, and starch is more preferred.

[0018] By using natural product-derived components as binding materials, the use of petroleum-derived materials can be reduced, leading to a reduction in CO2 emissions.Naturally derived materials also have excellent biodegradability.

[0019] In particular, starch is a material that exhibits favorable bonding strength as gelatinization proceeds when heated after adding moisture, i.e., a binding material that exhibits favorable bonding strength to bind fibers together when added with moisture. Furthermore, starch exhibits bonding strength through non-covalent bonds such as hydrogen bonds with fibers, particularly fibers made of materials having functional groups such as hydroxyl groups, such as cellulose fibers, and exhibits excellent bonding strength with fibers and excellent covering properties for fibers, thereby improving the strength, etc. of molded articles produced using the binder C10.

[0020] The binder material preferably contains starch having a weight average molecular weight of 50,000 or more and 400,000 or less, more preferably 70,000 or more and 300,000 or less, and even more preferably 80,000 or more and 200,000 or less.

[0021] This improves the water absorption efficiency of the binder C10, and allows the production of molded articles with sufficient strength. More specifically, even when a small amount of water is added, the gelatinization of starch by heating proceeds favorably, and the productivity of molded articles using the binder C10 can be improved. In addition, the strength of the molded articles produced can be improved. Furthermore, starch having a weight-average molecular weight within the above range is less likely to be undesirably denatured by the addition of water.

[0022] The weight-average molecular weight of starch can be determined by gel permeation chromatography. The weight-average molecular weights shown in the examples described below are also values ​​determined by gel permeation chromatography.

[0023] Starch with a weight-average molecular weight controlled to a predetermined range can be conveniently obtained as follows. For example, natural starch is suspended in water and then treated with sulfuric acid, hydrochloric acid, or sodium hypochlorite under conditions that do not gelatinize the starch, thereby obtaining starch with a weight-average molecular weight controlled to a predetermined range. Alternatively, natural starch can be added directly or diluted with a small amount of volatile acid such as hydrochloric acid in water, thoroughly mixed, aged, dried at low temperature, and then heated to 120 to 180°C to obtain starch with a weight-average molecular weight controlled to a predetermined range. Alternatively, starch with a weight-average molecular weight controlled to a predetermined range can be conveniently obtained by subjecting a paste obtained by heating natural starch with water to a treatment of hydrolysis with an acid or enzyme.

[0024] Starch is a polymeric material formed by the polymerization of multiple α-glucose molecules via glycosidic bonds, and contains at least one of amylose and amylopectin.

[0025] The binder particles C2 may contain, in addition to the binder, components other than the binder, i.e., components that do not exert a bonding force to bond fibers together even when moisture is added, such as fiber materials, pigments, dyes, and coloring materials such as toner.

[0026] The content of the binder material in the binder particles C2 is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0027] The average particle size of the binder material particles C2 is preferably 1.0 μm or more and 50.0 μm or less, more preferably 3.0 μm or more and 30.0 μm or less, and even more preferably 5.0 μm or more and 15.0 μm or less.

[0028] This allows the fibers and binder C10 to be mixed more uniformly in the process of mixing the fibers and binder C10 when producing a molded body by binding the fibers with binder C10. Furthermore, when moisture is added to the mixture of fibers and binder C10, moisture absorption proceeds more smoothly, resulting in improved strength and reliability of the final molded body. In particular, when the particle size of the binder material particles C2 is relatively small, the surface area per unit mass of the binder material particles C2 increases, resulting in improved water absorption efficiency by the binder. As a result, a molded body with sufficient strength can be produced even when a small amount of moisture is added.

[0029] Furthermore, in the binder C10, when the binder particles C2 having such a small average particle size are not present together with the inorganic oxide particles C3, aggregation of the binder particles C2 often occurs. However, in the present invention, by forming composite particles C1 in which the binder particles C2 and the inorganic oxide particles C3 are integrated, aggregation of the binder particles C2 can be effectively prevented. That is, even when aggregation of the binder particles C2 is likely to occur because the average particle size of the binder particles C2 is within the above range, aggregation of the binder particles C2 can be suppressed by forming composite particles C1 in which the binder particles C2 and the inorganic oxide particles C3 are integrated.

[0030] The binder C10 may contain binder particles C2 that do not have inorganic oxide particles C3 attached, in other words, binder particles C2 that do not constitute composite particles C1, but the proportion of binder particles C2 that constitute composite particles C1 in the total binder particles C2 contained in the binder C10 is preferably 50 mass% or more, more preferably 60 mass% or more, and even more preferably 70 mass% or more.

[0031] This makes it possible to more effectively suppress the aggregation of the binder particles C2, and to produce a molded article having excellent strength.

[0032] 1.1.2. Inorganic oxide particles The binder C10 contains inorganic oxide particles C3. The binder C10 also contains composite particles C1, in which the inorganic oxide particles C3 and binder material particles C2 are integrated. This prevents the composite particles C1 from aggregating and maintains a highly dispersed state when fibers are bonded together to produce a molded article. This allows the particle surface of the composite particles C1, which serves as the charged site, to be broadened. Furthermore, the inclusion of inorganic oxide particles C3 in the composite particles C1 keeps the surface of the composite particles C1 dry, preventing the loss of charge due to moisture. As a result, the binder C10 can be efficiently charged, increasing the adhesive strength of the binder C10 to the fibers and the bonding strength between the fibers, resulting in the production of a molded article with excellent strength.

[0033] The inorganic oxide particles C3 are mainly composed of inorganic oxides. Examples of materials constituting the inorganic oxide include metal oxides such as silica, alumina, zirconia, titania, and magnetite. Among these, silica, alumina, and titania are preferred, and silica is more preferred, in terms of their excellent chemical and thermal stability.

[0034] Since the inorganic oxide particles C3 are mainly composed of silica, the dispersibility of the composite particles C1 is further improved. As a result, the binder C10 is effectively prevented from undesirably agglomerating during storage of the binder C10 or during transport of the binder C10 in the manufacturing process of a molded body. Furthermore, since silica has a relatively low specific gravity among inorganic oxides, the fluidity of the composite particles C1 is improved. Furthermore, silica is a material that is unlikely to adversely affect the color of a molded body manufactured using the binder C10. This effect is particularly pronounced when the molded body is paper.

[0035] The inorganic oxide particles C3 contain carbon in addition to an inorganic oxide. This effectively reduces the surface free energy of the inorganic oxide particles C3. As a result, when the binder C10 is used to manufacture a molded body, the binder C10 can be suitably applied to the surface of the fibers. This allows the binder C10 to be uniformly distributed throughout the molded body, thereby improving the strength of the molded body.

[0036] The carbon contained in the inorganic oxide particles C3 is preferably carbon derived from a hydrocarbon group. More specifically, the inorganic oxide particles C3 are preferably hydrophobized inorganic oxide particles C3 in which base particles composed of an inorganic oxide are treated with a surface treatment agent having a hydrocarbon group. That is, the carbon contained in the hydrophobized inorganic oxide particles C3 is preferably derived from a hydrocarbon group imparted to the surface of the inorganic oxide by the surface treatment. When the inorganic oxide particles C3 are such hydrophobized inorganic oxide particles C3, the surface free energy of the inorganic oxide particles C3 can be more effectively reduced. As a result, when fibers are bonded together using the binder C10 to produce a molded body, the binder C10 can be more suitably blended with the fiber surface. This allows the binder C10 to be uniformly distributed throughout the entire molded body, thereby improving the strength of the molded body.

[0037] The surface treatment agent can be any surface treatment agent having a hydrocarbon group, and examples thereof include fluorine-containing compounds and silicon-containing compounds. By using such a surface treatment agent, carbon can be efficiently introduced into the base particles, and the surface free energy of the inorganic oxide particles C3 can be more efficiently reduced. This improves the flowability and ease of handling of the binder C10. Furthermore, the binder C10 can be more uniformly distributed in the final molded body, improving the strength of the molded body.

[0038] Examples of the fluorine-containing compound include perfluoropolyether and fluorine-modified silicone oil.

[0039] Examples of silicon-containing compounds include silane coupling agents, titanate coupling agents, silicone oil, cyclic siloxane, hexaalkyldisilazane, and alkyldichlorosilane. Among these, treatment with hexaalkyldisilazane or alkyldichlorosilane is preferred because they have a high treatment effect and are less likely to cause leaching or seepage of the surface treatment agent. Because the above-mentioned treatment agents are highly reactive, they can introduce a required amount of carbon into the inorganic oxide particles C3 with favorable treatment efficiency, even if the amount of reactive groups such as silanol groups present on the surface of the inorganic oxide particles C3 is small.

[0040] When a surface treatment agent is used, one type of surface treatment agent may be used, or multiple types of surface treatment agents may be used.

[0041] When multiple types of surface treatment agents are used, multiple types of surface treatment agents may be used for a single base particle, or the binder C10 may contain particles treated with different surface treatment agents as the inorganic oxide particles C3.

[0042] The content of the surface treatment agent relative to 100 parts by mass of the base particles contained in the binder C10 is preferably 0.5 parts by mass or more and 7.0 parts by mass or less, and more preferably 1.0 parts by mass or more and 5.0 parts by mass or less.

[0043] By treating base particles made of inorganic oxide with a surface treatment agent having a hydrocarbon group, carbon is introduced into the base particles via chemical bonds, and inorganic oxide particles C3 containing 2% or more by mass of carbon can be obtained.

[0044] Furthermore, the inorganic oxide particles C3 contain 2.0 mass% or more of carbon relative to the mass of the inorganic oxide particles C3. The inorganic oxide particles C3 preferably contain 2.5 mass% or more, and more preferably 3.0 mass% or more of carbon relative to the mass of the inorganic oxide particles C3. The inorganic oxide particles C3 preferably contain 7.0 mass% or less, and more preferably 5.0 mass% or less of carbon relative to the mass of the inorganic oxide particles C3. The amount of carbon contained in the inorganic oxide particles C3 can be determined from the amount of mass loss when the inorganic oxide particles C3 are burned.

[0045] The average particle size of the inorganic oxide particles C3 is preferably 1.0 nm or more and 20.0 nm or less, more preferably 3.0 nm or more and 18.0 nm or less, and even more preferably 5.0 nm or more and 10.0 nm or less.

[0046] This effectively prevents excessive unevenness from occurring on the surface of the composite particles C1, where the inorganic oxide particles C3 are attached to the surfaces of the binder particles C2. Therefore, when the composite particles C1 are mixed with the fibers, the flowability of the binder C10 can be improved, and the composite particles C1 can be mixed more uniformly with the fibers. Furthermore, the inorganic oxide particles C3 can be more effectively attached to the surfaces of the binder particles C2, preventing the inorganic oxide particles C3 from unintentionally falling off the surfaces of the binder particles C2 or being unintentionally buried inside the binder particles C2.

[0047] Furthermore, since the average particle size of the inorganic oxide particles C3 is 1.0 nm or more and 20.0 nm or less, the effect obtained by integrating the binding material particles C2 and the inorganic oxide particles C3, i.e., a repulsive force acts between the inorganic oxide particles C3, which suppresses aggregation of the binding material particles C2 and improves the dispersibility of the composite particles C1, is more significantly exhibited.

[0048] The binder C10 may contain inorganic oxide particles C3 that are not attached to the binder material particles C2, in other words, inorganic oxide particles C3 that do not constitute the composite particles C1, but the proportion of the inorganic oxide particles C3 that constitute the composite particles C1 to the inorganic oxide particles C3 contained in the binder C10 is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, which suppresses aggregation of the binder material particles C2 and improves the dispersibility of the composite particles C1.

[0049] Commercially available inorganic oxide particles C3 can also be used. Examples of commercially available inorganic oxide particles C3 include fumed silica manufactured by Tokuyama Corporation under the trade names Reolosil (registered trademark) DM-30S, KS-20SC, HM-20L, HM-30S, and ZD-30ST, and fumed silica manufactured by Nippon Aerogel Co., Ltd. under the trade names Aerogel (registered trademark) RY50, RY-51, NY-50, NY-50L, RA200H, and RA200HS.

[0050] In the binder C10, the mass of the inorganic oxide particles C3 relative to the mass of the binder particles C2 is preferably 0.3 mass% or more and 8.0 mass% or less, more preferably 0.5 mass% or more and 5.0 mass% or less, and even more preferably 0.7 mass% or more and 4.0 mass% or more.

[0051] This improves the dispersion stability of the composite particles C1. That is, by setting the mass ratio of the inorganic oxide particles C3 to the binding material particles C2 within the above range, the composite particles C1 are prevented from agglomerating to form coarse particles, and the dispersion stability of the composite particles C1 is improved.

[0052] 1.1.3.Other Configurations The binder C10 may contain the composite particles C1 described above and may further contain other components. For example, the binder C10 may contain, in addition to the composite particles C1 described above, binder material particles C2 to which inorganic oxide particles C3 are not attached, or may contain inorganic oxide particles C3 to which binding material particles C2 are not attached.

[0053] However, the content of the composite particles C1 in the binder C10 is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, so that the above-mentioned effects are more significantly exhibited.

[0054] 1.1.4. Other conditions The binder C10 preferably satisfies the following conditions.

[0055] For example, the content of the binder particles C2 in the binder C10 is preferably 90.0 mass% or more and 99.9 mass% or less, more preferably 95.0 mass% or more and 99.7 mass% or less, and even more preferably 97.0 mass% or more and 99.4 mass% or less. This makes the above-mentioned effects more pronounced.

[0056] The content of inorganic oxide particles C3 in binder C10 is preferably 0.1 mass % or more and 10.0 mass % or less, more preferably 0.3 mass % or more and 5.0 mass % or less, and even more preferably 0.6 mass % or more and 3.0 mass % or less.

[0057] This more significantly enhances the effect obtained by integrating the binding material particles C2 and the inorganic oxide particles C3, i.e., a repulsive force acts between the inorganic oxide particles C3, suppressing aggregation of the binding material particles C2, and improving the dispersibility of the composite particles C1.

[0058] 2. Manufacturing method of binder The binder C10 can be produced by mixing the binder particles C2 and the inorganic oxide particles C3 by a method known to those skilled in the art.

[0059] When starch particles are used as the binding material particles C2, the weight-average molecular weight of the starch is adjusted by the above-mentioned method, and the average particle size of the starch particles is adjusted by classification using a known method, and then the resulting starch can be used to produce the binding material C10. Furthermore, inorganic oxide particles C3 are prepared by preparing the above-mentioned inorganic oxide particle C3 material and introducing carbon into the material using a surface treatment agent containing hydrocarbon. The method for introducing carbon into inorganic oxide particles C3 can be any known method for introducing a hydrophobic substance onto the surface, without any particular limitation.

[0060] The inorganic oxide particles C3 containing a predetermined amount of carbon prepared as described above and the binder particles C2 are mixed and stirred using a mixer such as a super mixer, Henschel mixer, or turbulizer. By stirring the binder particles C2 and the inorganic oxide particles C3 under a certain shear force, frictional heat is generated on the particle surfaces, promoting integration of the binder particles C2 and the inorganic oxide particles C3. After mixing, the mixture is sieved using a sieve with openings of 20 μm to 100 μm to obtain the binder C10.

[0061] 3. Manufacturing method of molded body Hereinafter, a method for manufacturing a molded body will be described, in which fibers are bonded together using the binder C10 to manufacture a molded body. The method for manufacturing a molded body includes a depositing step of depositing a mixture containing fibers and the binder C10, a humidifying step of adding moisture to the deposited mixture, and a molding step of heating and pressurizing the moistened mixture to obtain a molded body.

[0062] 3.1. Deposition process In the deposition step, a mixture containing the fibers and binder C10 is deposited in air.

[0063] The mixing ratio of the fibers and binder C10 in this step is not particularly limited, but the content of binder C10 in the mixture obtained in this step is preferably 1% by mass or more and 50% by mass or less, more preferably 2% by mass or more and 45% by mass or less, and even more preferably 3% by mass or more and 40% by mass or less.

[0064] This allows the final molded body to have a sufficiently high fiber content and excellent strength, and also allows the binder C10 to be transported more smoothly during the manufacturing process of the molded body.

[0065] The fibers mixed with the binder C10 in this step may be moistened in advance, for example, prior to the moistening step described below, i.e., the step of moistening the mixture. Alternatively, the fibers may be moistened between mixing with the binder C10 and depositing the mixture obtained by this mixing.

[0066] In the above case, the moisture content in the fibers subjected to this step is preferably 0.1% by mass or more and 12.0% by mass or less, more preferably 0.2% by mass or more and 10.0% by mass or less, and even more preferably 0.3% by mass or more and 9.0% by mass or less.

[0067] This makes it possible to effectively prevent the fibers from being adversely affected by static electricity before this process, for example, preventing the fibers from sticking to the wall surfaces of the molding manufacturing equipment due to static electricity, and also makes it possible to mix the fibers and the binder C10 more uniformly.

[0068] Fibers are the main component of the molded body produced using the molded body production method, and are a component that contributes greatly to maintaining the shape of the molded body and also has a significant effect on the properties of the molded body, such as strength.

[0069] The fibers may be made of any material, but it is preferable that the material be one that can maintain its fibrous state even when heated during the molding process.

[0070] The fibers may be synthetic fibers made of synthetic resins such as polypropylene, polyester, polyurethane, etc., but are more preferably naturally occurring fibers, particularly cellulose fibers.

[0071] Cellulose fibers are recyclable fibers. Reusing cellulose fibers that have been used more than once, such as waste paper and old cloth, as raw materials for fibers contributes to the protection of forest resources. Furthermore, among various fibers, cellulose fibers have particularly high theoretical strength, making them advantageous from the perspective of further improving the strength of molded articles.

[0072] Cellulose fibers are generally composed mainly of cellulose, but may contain components other than cellulose, such as hemicellulose and lignin.

[0073] In particular, the fibers are preferably made of a substance containing at least one chemical structure selected from the group consisting of a hydroxyl group, a carbonyl group, and an amino group.

[0074] This makes it easier to form hydrogen bonds between the fibers and the binder, for example, when starch is used as the binder, thereby improving the bonding strength between the fibers and binder C10 and improving the strength of the molded body as a whole, for example, the breaking strength of a sheet-shaped molded body.

[0075] Furthermore, the cellulose fibers used may be those that have been subjected to a treatment such as bleaching.

[0076] The fibers may also be treated with ultraviolet light, ozone, plasma, or other processes, which can increase the hydrophilicity of the fibers and enhance their affinity with the binding material. More specifically, these treatments can introduce functional groups, such as hydroxyl groups, onto the fiber surface, allowing for more efficient hydrogen bonding with the binding material.

[0077] The average length of the fibers is not particularly limited, but is preferably 0.1 mm or more and 50.0 mm or less, more preferably 0.2 mm or more and 5.0 mm or less, and even more preferably 0.3 mm or more and 3.0 mm or less.

[0078] This allows the molded article to be produced with improved stability of shape, strength, etc.

[0079] The average thickness of the fibers is not particularly limited, but is preferably 0.005 mm or more and 0.500 mm or less, and more preferably 0.010 mm or more and 0.050 mm or less.

[0080] This makes it possible to improve the stability of the shape, strength, etc. of the produced molded article, and also makes it possible to more effectively prevent the occurrence of undesired irregularities on the surface of the molded article.

[0081] The average aspect ratio of the fibers, that is, the average length to the average thickness, is not particularly limited, but is preferably 10 or more and 1,000 or less, and more preferably 15 or more and 500 or less.

[0082] This makes it possible to improve the stability of the shape, strength, etc. of the produced molded article, and also makes it possible to more effectively prevent the occurrence of undesired irregularities on the surface of the produced molded article.

[0083] 3.2. Humidification process In the moistening step, moisture is added to the mixture deposited in the depositing step, that is, the mixture containing the fibers and the binder C10, to moisten it.

[0084] This allows the bonding strength between the fibers and the binder material and between the fibers via the binder material to be excellent in the molding step described below, and the strength of the final molded body to be sufficiently excellent. Furthermore, molding in the molding step can be preferably carried out under relatively mild conditions.

[0085] The method for humidifying the mixture is not particularly limited, but is preferably carried out without contact with the mixture. Examples include placing the mixture in a high-humidity atmosphere, passing the mixture through a high-humidity space, spraying a mist of a water-containing liquid onto the mixture, and passing the mixture through a space in which a mist of a water-containing liquid is suspended. One or more methods selected from these can be combined. More specifically, the mixture can be humidified using, for example, various humidifiers such as evaporative and ultrasonic humidifiers. The mixture may be humidified at multiple stages, for example, during the process of producing a molded product. The water-containing liquid may contain, for example, an antiseptic, an antifungal agent, an insecticide, etc.

[0086] The amount of water added to the mixture in the humidification step is not particularly limited, but it is preferable to add 1 to 50 parts by mass of water per 100 parts by mass of the mixture subjected to the humidification step, more preferably 5 to 40 parts by mass of water, and even more preferably 10 to 30 parts by mass of water.

[0087] This allows a molded article of sufficient strength to be produced with significantly less water than in conventional papermaking methods, allowing the effects of the present invention to be more pronounced.

[0088] 3.3. Molding process In the molding step, the mixture moistened in the moistening step is pressurized and heated to obtain a molded body. The moistening step and the molding step may be carried out simultaneously.

[0089] The pressure applied to the mixture in the molding step is not particularly limited, but is preferably 0.1 MPa or more and 100.0 MPa or less, and more preferably 0.3 MPa or more and 80.0 MPa or less.

[0090] This allows the binder C10 to be more suitably applied to the surface of the fibers, resulting in a molded article with improved strength.

[0091] The heating temperature in the molding step is not particularly limited, but is preferably 50°C or higher and 200°C or lower, more preferably 60°C or higher and 150°C or lower, and even more preferably 70°C or higher and 120°C or lower.

[0092] This allows the binder C10 to be more suitably blended on the surface of the fibers while effectively preventing undesired deterioration, denaturation, etc. of the components of the fibers and binder C10. As a result, the strength and reliability of the produced molded body can be improved. This is also preferable from the viewpoint of energy saving. In particular, when the binder particles C2 are composed of a material containing starch as a binder, it is possible to suitably promote the gelatinization of the water-absorbed starch and effectively prevent undesired deterioration, etc. of the constituent materials of the molded body.

[0093] The molding step can be performed using, for example, a heat press, a heat roller, etc. This allows the binder C10 to be more suitably blended on the surface of the fibers while effectively preventing undesired deterioration, denaturation, etc. of the components of the fibers and binder C10. As a result, the strength and reliability of the produced molded body can be improved.

[0094] In the binder C10, the inorganic oxide particles C3 contain carbon in an amount of 2% by mass or more relative to the mass of the inorganic oxide particles C3, so that the angle of repose of the binder C10 can be reduced. As a result, when the binder C10 is used as the binder C10 to bond fibers together in a method for producing a molded body, the composite particles C1 can be uniformly mixed with the fibers. Therefore, a molded body in which the binder C10 is uniformly distributed can be obtained, and a molded body having sufficient strength can be produced.

[0095] The above-described method for producing a molded body can be suitably carried out, for example, by using a molded body production apparatus described below.

[0096] 4. Molded body manufacturing equipment Next, a manufacturing apparatus for the molded body will be described.

[0097] Fig. 2 is a schematic explanatory diagram showing the configuration of a manufacturing apparatus suitable for carrying out the method for manufacturing a molded body. Note that, for convenience of explanation, the upper side in Fig. 2 may be referred to as "upper" or "upper side," the lower side as "lower" or "lower side," the left side as "left" or "upstream side," and the right side as "right" or "downstream side."

[0098] In the following description, a sheet manufacturing apparatus 100 that manufactures a sheet S as a molded body will be taken as an example of an apparatus for manufacturing a molded body.

[0099] 2, the sheet manufacturing apparatus 100, which is an apparatus for manufacturing a formed body, includes a raw material supply section 11, a coarse crushing section 12, a defibrating section 13, a sorting section 14, a first web forming section 15, a fine dividing section 16, a mixing section 17, a refining section 18, a second web forming section 19, a sheet forming section 20, a cutting section 21, and a stocking section 22. The sheet manufacturing apparatus 100 also includes a humidifying section 231, a humidifying section 232, a humidifying section 233, and a humidifying section 234.

[0100] The operation of each unit included in the sheet manufacturing apparatus 100 is controlled by a control unit (not shown).

[0101] The method for manufacturing the sheet S, which is a formed body, includes a raw material supplying process, a crushing process, a defibrating process, a sorting process, a first web forming process, a dividing process, a mixing process, a loosening process, a second web forming process, a moistening process, a sheet forming process, and a cutting process. The sheet manufacturing apparatus 100 can execute these processes in order.

[0102] The configuration of each part of the sheet manufacturing apparatus 100 will be described below.

[0103] The raw material supply unit 11 is a unit that performs a raw material supply step of supplying a sheet material M1 to the crushing unit 12. This sheet material M1 is a sheet material that contains fibers such as cellulose fibers.

[0104] The crushing unit 12 is a part that performs a crushing step in which the sheet material M1 supplied from the raw material supply unit 11 is crushed in air or the like. The crushing unit 12 has a pair of crushing blades 121 and a hopper 122.

[0105] The pair of crushing blades 121 rotate in opposite directions to each other, and can crush, i.e., cut, the sheet material M1 between them into crushed pieces M2. The shape and size of the crushed pieces M2 are preferably suitable for defibration processing in the defibrating unit 13, and are preferably small pieces with a side length of 100 mm or less, and more preferably 10 mm to 70 mm.

[0106] The hopper 122 is disposed below the pair of crushing blades 121 and is, for example, funnel-shaped, so that the hopper 122 can receive the coarsely crushed pieces M2 that have been crushed by the crushing blades 121 and dropped.

[0107] Moreover, above the hopper 122, a humidifying section 231 is disposed adjacent to the pair of coarse crushing blades 121. The humidifying section 231 humidifies the coarsely crushed pieces M2 in the hopper 122. This humidifying section 231 is configured as an evaporative humidifier that has a filter (not shown) that contains moisture and supplies humidified air with increased humidity to the coarsely crushed pieces M2 by passing air through the filter. By supplying humidified air to the coarsely crushed pieces M2, it is possible to prevent the coarsely crushed pieces M2 from adhering to the hopper 122, etc. due to static electricity.

[0108] The hopper 122 is connected to the defibrating unit 13 via a pipe 241, which is a flow path. The coarse fragments M2 collected in the hopper 122 pass through the pipe 241 and are transported to the defibrating unit 13.

[0109] The defibrating unit 13 is a part that performs a defibrating process in which the coarsely crushed pieces M2 are defibrated in air, such as in the atmosphere, i.e., in a dry manner. By the defibrating process in this defibrating unit 13, defibrated material M3 can be generated from the coarsely crushed pieces M2. Here, "defibrating" refers to untangling the coarsely crushed pieces M2, which are made up of multiple fibers bonded together, into individual fibers. This untangled material becomes the defibrated material M3. The shape of the defibrated material M3 is linear or strip-like. Furthermore, the defibrated material M3 may exist in a state where it is entangled with other pieces and forms a mass, that is, in a state where it forms so-called "lumps."

[0110] In this embodiment, for example, the defibrating unit 13 is configured with an impeller mill having a rotor that rotates at high speed and a liner positioned on the outer periphery of the rotor. The coarse fragments M2 that flow into the defibrating unit 13 are sandwiched between the rotor and the liner and defibrated.

[0111] Furthermore, the defibrating unit 13 can generate an air flow from the crushing unit 12 to the sorting unit 14 by rotating the rotor, i.e., an airflow. This allows the coarsely crushed pieces M2 to be sucked into the defibrating unit 13 from the pipe 241. Furthermore, after the defibrating process, the defibrated material M3 can be sent to the sorting unit 14 via the pipe 242.

[0112] A blower 261 is installed midway through the pipe 242. The blower 261 is an airflow generating device that generates an airflow heading toward the screening unit 14. This promotes the sending out of the defibrated material M3 to the screening unit 14.

[0113] The sorting unit 14 is a section that performs a sorting process to sort the defibrated material M3 according to the length of the fibers. In the sorting unit 14, the defibrated material M3 is sorted into a first sorted material M4-1 and a second sorted material M4-2 that is larger than the first sorted material M4-1. The first sorted material M4-1 has a size suitable for the subsequent production of the sheet S. The second sorted material M4-2 includes, for example, material that is insufficiently defibrated and material in which defibrated fibers have excessively aggregated together.

[0114] The sorting unit 14 has a drum unit 141 and a housing unit 142 that houses the drum unit 141.

[0115] The drum part 141 is a sieve made up of a cylindrical mesh body that rotates around its central axis. The defibrated material M3 flows into this drum part 141. As the drum part 141 rotates, defibrated material M3 that is smaller than the mesh openings is sorted as first sorted material M4-1, and defibrated material M3 that is larger than the mesh openings is sorted as second sorted material M4-2.

[0116] The first sorted item M4-1 falls from the drum section 141.

[0117] The second sorted material M4-2 is sent out to pipe 243, which is a flow path connected to drum section 141. Pipe 243 is connected to pipe 241 on the side opposite to drum section 141. The second sorted material M4-2 that passes through pipe 243 merges with the coarsely crushed fragments M2 in pipe 241 and flows into the defibrating section 13 together with the coarsely crushed fragments M2. As a result, the second sorted material M4-2 is returned to the defibrating section 13 and is defibrated together with the coarsely crushed fragments M2.

[0118] The first sorted material M4-1 from the drum unit 141 falls while dispersing in the air and heads toward the first web forming unit 15, which is a separation unit located below the drum unit 141. The first web forming unit 15 is a unit that performs the first web forming process, which forms the first web M5 from the first sorted material M4-1. The first web forming unit 15 has a mesh belt 151, which is a separation belt, three tension rollers 152, and a suction unit 153.

[0119] The mesh belt 151 is an endless belt on which the first sorted material M4-1 accumulates. The mesh belt 151 is looped around three tension rollers 152. As the tension rollers 152 rotate, the first sorted material M4-1 on the mesh belt 151 is transported downstream.

[0120] The size of the first sorted material M4-1 is equal to or larger than the mesh openings of the mesh belt 151. This restricts the first sorted material M4-1 from passing through the mesh belt 151, and therefore the first sorted material M4-1 can be accumulated on the mesh belt 151. Furthermore, the first sorted material M4-1 is accumulated on the mesh belt 151 and transported downstream together with the mesh belt 151, and is formed as a layered first web M5.

[0121] Furthermore, the first sorted material M4-1 may contain, for example, dust and dirt. For example, dust and dirt may be mixed in with the sheet material M1 when the sheet material M1 is supplied from the raw material supply unit 11 to the crushing unit 12. This dust and dirt is smaller than the mesh size of the mesh belt 151. As a result, the dust and dirt passes through the mesh belt 151 and falls further downward.

[0122] The suction section 153 can suck air from below the mesh belt 151. This allows dust and dirt that has passed through the mesh belt 151 to be sucked in together with the air.

[0123] The suction unit 153 is connected to the collection unit 27 via a pipe 244, which is a flow path. The dust and dirt sucked by the suction unit 153 is collected in the collection unit 27.

[0124] A pipe 245, which is a flow path, is further connected to the collection unit 27. A blower 262 is installed midway through the pipe 245. By operating the blower 262, a suction force can be generated in the suction unit 153. This promotes the formation of the first web M5 on the mesh belt 151. Dust and dirt are removed from this first web M5. By operating the blower 262, the dust and dirt pass through the pipe 244 and reach the collection unit 27.

[0125] The housing 142 is connected to the humidifying section 232. The humidifying section 232 is configured as an evaporative humidifier similar to the humidifying section 231. This allows humidified air to be supplied into the housing 142. This humidified air can humidify the first sorted item M4-1, thereby preventing the first sorted item M4-1 from adhering to the inner wall of the housing 142 due to electrostatic force.

[0126] A humidifying unit 235 is disposed downstream of the sorting unit 14. The humidifying unit 235 is configured with an ultrasonic humidifier that sprays water. This allows moisture to be supplied to the first web M5, thereby adjusting the moisture content of the first web M5. This moisture adjustment makes it possible to suppress adhesion of the first web M5 to the mesh belt 151 due to electrostatic force. This allows the first web M5 to be easily peeled off from the mesh belt 151 at the position where the mesh belt 151 is folded back by the tension roller 152.

[0127] The dividing unit 16 is disposed downstream of the humidifying unit 235. The dividing unit 16 is a section that performs a dividing step of dividing the first web M5 peeled off from the mesh belt 151. The dividing unit 16 has a rotatably supported propeller 161 and a housing unit 162 that houses the propeller 161. The first web M5 is divided by being caught in the rotating propeller 161. The divided first web M5 becomes divided bodies M6. The divided bodies M6 descend within the housing unit 162.

[0128] The housing 162 is connected to the humidifying section 233. The humidifying section 233 is configured as an evaporative humidifier similar to the humidifying section 231. This allows humidified air to be supplied into the housing 162. This humidified air can also prevent the fragmented bodies M6 from adhering to the propeller 161 or the inner wall of the housing 162 due to electrostatic force.

[0129] A mixing section 17 is disposed downstream of the subdivision section 16. The mixing section 17 is a section where a mixing step of mixing the fragmented bodies M6 with the aforementioned binder C10 is carried out. The mixing section 17 has a binder supply section 171, a pipe 172 which is a flow path, and a blower 173.

[0130] The pipe 172 connects the housing portion 162 of the refining unit 16 and the housing portion 182 of the refining unit 18, and is a flow path through which the mixture M7 of the refining bodies M6 and the binder C10 passes.

[0131] A binder supply unit 171 is connected to the middle of the pipe 172. The binder supply unit 171 has a screw feeder 174. When this screw feeder 174 is driven to rotate, it is possible to supply the binder C10 to the pipe 172. The binder C10 supplied to the pipe 172 is mixed with the fragmented bodies M6 to form a mixture M7.

[0132] In addition, the binder supply unit 171 may contain, in addition to the binder C10, for example, a colorant for coloring the fibers, an aggregation inhibitor for suppressing aggregation of the fibers or aggregation of the binder C10, a flame retardant for making the fibers, etc. less flammable, etc.

[0133] Furthermore, a blower 173 is installed in the pipe 172 downstream of the binder supply unit 171. The blower 173 can generate an air current directed toward the refining unit 18. This air current can agitate the fragmented bodies M6 and the binder C10 within the pipe 172. This allows the mixture M7 to flow into the refining unit 18 with the fragmented bodies M6 and the binder C10 uniformly dispersed. Furthermore, the fragmented bodies M6 in the mixture M7 are refinished as they pass through the pipe 172, becoming finer fibrous.

[0134] The disentangling unit 18 is a unit that performs a disentangling step of disentangling entangled fibers in the mixture M7. The disentangling unit 18 has a drum unit 181 and a housing unit 182 that houses the drum unit 181.

[0135] The drum section 181 is a sieve formed of a cylindrical mesh body that rotates around its central axis. The mixture M7 flows into the drum section 181. As the drum section 181 rotates, fibers and the like of the mixture M7 that are smaller than the mesh openings can pass through the drum section 181. At that time, the mixture M7 is loosened.

[0136] Housing 182 is connected to humidifier 234. Humidifier 234 is configured as an evaporative humidifier similar to humidifier 231. This allows humidified air to be supplied into housing 182. This humidified air can humidify the inside of housing 182, and therefore can also prevent mixture M7 from adhering to the inner wall of housing 182 due to electrostatic force.

[0137] The mixture M7 loosened by the drum unit 181 falls while being dispersed in the air, and heads toward the second web forming unit 19 located below the drum unit 181. The second web forming unit 19 is a section where a second web forming step is performed to form a second web M8 from the mixture M7. In this embodiment, the second web forming step is a deposition step in which the mixture M7 containing fibers and a binder C10 is deposited in the air. The second web forming unit 19 has a mesh belt 191 which is a separation belt, a tension roller 192, and a suction unit 193.

[0138] The mesh belt 191 is an endless belt on which the mixture M7 is deposited. The mesh belt 191 is looped around four tension rollers 192. As the tension rollers 192 are rotated, the mixture M7 on the mesh belt 191 is transported downstream.

[0139] Furthermore, most of the mixture M7 on the mesh belt 191 has a size equal to or larger than the mesh openings of the mesh belt 191. This prevents the mixture M7 from passing through the mesh belt 191, and therefore allows the mixture M7 to accumulate on the mesh belt 191. Furthermore, the mixture M7 accumulates on the mesh belt 191 and is transported downstream together with the mesh belt 191, and is formed as a layered second web M8.

[0140] The suction unit 193 can suck air from below the mesh belt 191. This allows the mixture M7 to be sucked onto the mesh belt 191, thereby facilitating the deposition of the mixture M7 on the mesh belt 191.

[0141] A pipe 246, which is a flow path, is connected to the suction unit 193. A blower 263 is installed midway through the pipe 246. By operating the blower 263, a suction force can be generated in the suction unit 193.

[0142] A humidifying section 236 is disposed downstream of the refining section 18. The humidifying section 236 is a section where the humidifying step described above is performed. The humidifying section 236 is configured with an ultrasonic humidifier similar to the humidifying section 235. This allows moisture to be supplied to the second web M8, thereby adjusting the moisture content of the second web M8. This moisture adjustment allows the bonding strength between the fibers and the bonding material in the sheet S as the final formed body to be optimized.

[0143] Furthermore, humidification can suppress electrostatic attraction of the second web M8 to the mesh belt 191. This allows the second web M8 to be easily peeled off from the mesh belt 191 at the position where the mesh belt 191 is folded back by the tension roller 192.

[0144] A sheet forming unit 20 is disposed downstream of the second web forming unit 19. The sheet forming unit 20 is a section that performs a sheet forming process, which is a molding process for forming a sheet S from the second web M8. The sheet forming unit 20 has a pressurizing unit 201 and a heating unit 202.

[0145] The pressure applying unit 201 has a pair of calender rollers 203, and is capable of applying pressure to the second web M8 between them. This increases the density of the second web M8. The second web M8 is then transported toward the heating unit 202. One of the pair of calender rollers 203 is a driven roller driven by the operation of a motor (not shown), and the other is a driven roller.

[0146] The heating section 202 has a pair of heating rollers 204, and can heat and pressurize the second web M8 between them. This heating and pressurization melts the binder C10 in the second web M8, and the fibers are bonded together via the molten binder C10. This forms a sheet S as a shaped body. The sheet S is then transported toward the cutting section 21. One of the pair of heating rollers 204 is a drive roller driven by the operation of a motor (not shown), and the other is a driven roller.

[0147] The cutting unit 21 is disposed downstream of the sheet forming unit 20. The cutting unit 21 is a section that performs a cutting step of cutting the sheet S. The cutting unit 21 has a first cutter 211 and a second cutter 212.

[0148] The first cutter 211 cuts the sheet S in a direction intersecting the conveying direction of the sheet S.

[0149] The second cutter 212 is located downstream of the first cutter 211 and cuts the sheet S in a direction parallel to the conveying direction of the sheet S.

[0150] The sheet S is obtained as a compact of a desired size by cutting with the first cutter 211 and the second cutter 212. The sheet S is then conveyed further downstream and accumulated in the stock section 22.

[0151] 5. Working Example Next, an embodiment of the present invention will be described.

[0152] 5.1. Preparation of binder 5.1.1. Preparation of raw starch Starch with a weight-average molecular weight of 1,300,000 (G-800, manufactured by Nippon Starch Chemical Co., Ltd.) was suspended in water, and then treated with sulfuric acid under conditions that did not gelatinize the starch. The mixture was thoroughly mixed and stirred for 12 hours. The mixture was dried at 50°C for 24 hours to reduce the moisture content to 10% by mass or less, and then heated at 120 to 180°C to obtain a starch paste. The starch paste was then washed with water, freeze-dried, and coarsely pulverized to obtain raw starch 1 with a weight-average molecular weight of 100,000. Furthermore, starch with a weight-average molecular weight of 1,300,000 (G-800, manufactured by Nippon Starch Chemical Co., Ltd.) was treated in the same manner as in the production of Raw Starch 1, except that the treatment conditions (sulfuric acid concentration, stirring time) were changed, to obtain Raw Starch 2 (weight-average molecular weight 20,000), Raw Starch 3 (weight-average molecular weight 55,000), Raw Starch 4 (weight-average molecular weight 380,000), and Raw Starch 5 (weight-average molecular weight 470,000), which have weight-average molecular weights different from Raw Starch 1.

[0153] 5.1.2. Preparation of starch granules Raw starch 1 was pulverized using a fluidized bed opposed jet mill (Counter Jet Mill AFG-R, manufactured by Hosokawa Micron Corporation) at a processing pressure of 4.0 bar to obtain starch granules 1-1 having an average particle size of 10 μm as binding material particles C2. Raw starches 2 to 5 were also treated in the same manner as raw starch 1 to obtain starch granules 2-1, 3-1, 4-1, and 5-1, respectively. Raw starch 1 was also treated in the same manner as starch granule 1, except that the processing pressure during pulverization was changed, to obtain starch granules 1-2 having an average particle size of 2 μm (processing pressure 8.0 bar), starch granules 1-3 having an average particle size of 40 μm (processing pressure 1.5 bar), and starch granules 1-4 having an average particle size of 55 μm (processing pressure 1.0 bar).

[0154] 5.1.3. Preparation of binder 99 parts by mass of starch particles 1-1 as binding material particles C2 and 1 part by mass of fumed silica (manufactured by Tokuyama Corporation, product name: Reolosil (registered trademark), product number: DM-30S) as inorganic oxide particles C3 were loaded into a Henschel mixer (FM Mixer FM 20C / I manufactured by Nippon Coke & Engineering Co., Ltd.) and mixed at a frequency of 60 Hz for 10 minutes. The mixture was then sieved through a sieve with 30 μm openings to prepare a binding material C10 containing the composite particles C1 of Example 1, in which the starch particles 1-1 as binding material particles C2 and the fumed silica as inorganic oxide particles C3 were integrated.

[0155] The binder C10 of Examples 2 to 16 and Comparative Example 1 was prepared in the same manner as in Example 1, except that the binder particles C2, inorganic oxide particles C3, and the compounding ratio of the binder particles C2 and inorganic oxide particles C3 were set to the compositions shown in Table 1. The inorganic oxide particles C3 in Table 1 are as follows. DM-30S Tokuyama Corporation, Reolosil, Part Number: DM-30S, Fumed Silica HM-20L Tokuyama Corporation, Reolosil, product number: HM-20L, fumed silica HM-30S Tokuyama Corporation, Reolosil, Part Number: HM-30S, Fumed Silica ZD-30ST Tokuyama Corporation, Reolosil, Part Number: ZD-30ST, Fumed Silica DM-30 Tokuyama Corporation, Reolosil, product number: DM-30, fumed silica NY-50 Nippon Aerogel Co., Ltd., Aerosil (registered trademark), product number: NY-50, fumed silica

[0156] [Table 1]

[0157] 5.1.4. Production of Sheets as Molded Bodies Using the binder of Example 1, a sheet was produced as a molded body.

[0158] A sheet manufacturing apparatus 100 (Seiko Epson Corporation's PaperLab (registered trademark) A-8000) was prepared by modifying it so that the sheet could be humidified after forming and before being pressed. In addition, commercially available copy paper (Fuji Xerox Co., Ltd.'s GR70-W) on which business documents were printed using an inkjet printer was used as the fiber source, and this was used as the sheet material M1.

[0159] Next, the sheet-like material M1 was supplied to the raw material supply section 11 of the sheet manufacturing apparatus 100, and the binder C10 produced in the binder preparation process was supplied to the binder supply section 171. The sheet manufacturing apparatus 100 was operated, and the process included a coarse crushing process, a defibrating process, a sorting process, a first web forming process, a dividing process, a mixing process, a loosening process, a second web forming process which is a stacking process, a humidifying process, a sheet forming process which is a shaping process, and a cutting process, to produce an A4-sized sheet S as a shaped product. The basis weight of the obtained sheet S was 90 g / m 2 It was.

[0160] At this time, the sheet S as the final molded product was adjusted to contain 90 parts by mass of fibers and 10 parts by mass of binder C10 as raw materials.

[0161] A4 size sheets S were produced as compacts in the same manner as in Example 1, except that the binders of the corresponding Examples 2 to 16 or Comparative Example 1 were used as binder C10.

[0162] Evaluation 5.2.1. Binder fluidity The angle of repose and compressibility of the binders of Examples 1 to 16 and Comparative Example 1 were measured using a powder property evaluation device (Powder Tester (registered trademark) PT-X, manufactured by Hosokawa Micron Corporation). From the measurement results, the fluidity value, which is the product of the angle of repose [°] and the compressibility [%], was calculated and evaluated according to the following criteria. It can be said that the smaller the fluidity value, the better the fluidity.

[0163] A: Liquidity value is less than 10. B: Liquidity value is 10 or more and less than 12. C: Liquidity value is 12 or more and less than 14. D: Liquidity value is 14 or more and less than 17. E: Liquidity value is 17 or more. The results are shown in Table 2.

[0164] 5.2.2. Strength of molded body Sheets as molded articles produced in Examples 1 to 16 and Comparative Example 1 S A 100 mm x 20 mm strip was cut out from each sample, and the breaking strength of the strip was measured in the longitudinal direction. The breaking strength was measured using an autograph AGS-1N manufactured by Shimadzu Corporation at a pulling speed of 20 mm / sec. The specific tensile strength was calculated from the measured values ​​and evaluated according to the following criteria. It can be said that the higher the specific tensile strength, the better the strength.

[0165] A: Specific tensile strength is 25 Nm / g or more. B: Specific tensile strength is 20 Nm / g or more and less than 25 Nm / g. C: Specific tensile strength is 15 Nm / g or more and less than 20 Nm / g. D: Specific tensile strength is 10 Nm / g or more and less than 15 Nm / g. E: Specific tensile strength is less than 10 Nm / g. The results are shown in Table 2.

[0166] [Table 2]

[0167] As is clear from Table 2, Examples 1 to 16 achieved good results in the strength test of the molded body, with a rating of C or higher. On the other hand, Comparative Example 1 achieved a rating of D for the strength of the molded body, which was not a satisfactory result. Also, in the powder fluidity test, the binders of Examples 1 to 16 achieved a rating of C or higher, while the binder of Comparative Example 1 achieved a rating of D, which supported the results of the strength test of the molded body. [Explanation of symbols]

[0168] C10...Binding material, C1...Composite particles, C2...Binding material particles, C3...Inorganic oxide particles.

Claims

1. The starch particles contain starch that binds cellulose fibers together when moisture is added, and and a binder comprising inorganic oxide particles, the binder contains composite particles in which the starch particles and the inorganic oxide particles are combined together, The inorganic oxide particles contain carbon, and the carbon content is determined by the mass of the inorganic oxide particles. The binder is 2% by weight or more.

2. The starch according to claim 1, wherein the weight average molecular weight of the starch is 50,000 or more and 400,000 or less. The binder used.

3. 2. The method according to claim 1, wherein the average particle size of the starch particles is 1.0 μm or more and 50.0 μm or less.

3. The binder according to claim 2.

4. 2. The inorganic oxide particles according to claim 1, wherein the average particle size is 1.0 nm or more and 20.0 nm or less.

4. A binder according to any one of claims 1 to 3.

5. In the binder, the ratio of the mass of the inorganic oxide particles to the mass of the starch particles is 0. The binder according to any one of claims 1 to 4, wherein the binder is 5% by mass or more and 5.0% by mass or less. 。

6. 6. The inorganic oxide particles according to claim 1, wherein the inorganic oxide particles are made of a material containing silica. The binder according to any one of claims 1 to 4.

7. A mixture comprising cellulose fibers and a binder according to any one of claims 1 to 6. a deposition step of depositing a humidifying step of adding moisture to the deposited mixture; a molding step of heating and pressurizing the mixture to which moisture has been added to obtain a molded body; A method for producing a molded body comprising the steps of:

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