Method for producing regenerated cellulose-derived cellulose dispersion liquid and regenerated cellulose-derived cellulose molded article, regenerated cellulose-derived cellulose dispersion liquid, regenerated cellulose-derived cellulose beads, and regenerated cellulose-derived cellulose molded article

Abstract

[Problem] The present invention relates to a cellulose dispersion liquid and a method for producing a cellulose molded body, said cellulose dispersion liquid being capable of using, as a dispersion liquid raw material, an appropriate regenerated cellulose including glass paper that is difficult to recover. [Technical means] The method for producing a regenerated cellulose dispersion liquid comprises: a pulverization step (S1) in which a dispersion liquid raw material is pulverized; a depolymerization step (S2) in which the degree of polymerization of the pulverized raw material obtained in the pulverizing step is reduced to 350 or less; and a micronization step (S3) for obtaining a cellulose dispersion by micronizing the depolymerized cellulose obtained in the depolymerization step, and further comprising a molding step (S4) for obtaining a molded article by drying the cellulose dispersion obtained in the micronization step.

Description

Technical Field

[0001] This invention relates to a method for manufacturing cellulose dispersions from regenerated cellulose and cellulose molded articles from regenerated cellulose, as well as cellulose dispersions from regenerated cellulose, cellulose beads from regenerated cellulose, and cellulose molded articles from regenerated cellulose. Background Technology

[0002] Regenerated cellulose is typically manufactured through processes such as viscose processing, where cellulose fibers in raw pulp are derivatized using chemicals, dissolved in a solvent to form a viscose, and then solidified. Regenerated cellulose obtained in this way originates from natural materials and possesses properties such as biodegradability. Therefore, the demand for its products has increased, and it is molded into appropriate shapes such as fibers, films, and spheres, and processed into various products including paper products, clothing, and hygiene products.

[0003] In recent years, due to environmental concerns such as wastewater treatment from chemicals used in the viscose process and waste gas treatment generated during manufacturing, methods have been proposed to manufacture regenerated cellulose by directly dissolving cellulose materials with ionic liquids instead of using the viscose process (see, for example, Patent Document 1). This method of manufacturing regenerated cellulose has fewer steps and higher efficiency compared to the viscose process, and it eliminates the need for waste gas treatment as in the viscose process, thus reducing the environmental impact.

[0004] However, through the advancement of the Sustainable Development Goals (SDGs), initiatives are actively underway across various sectors toward achieving an environmentally conscious, circular society. As an environmentally conscious measure, the recycling of used waste products as resources is widely recognized. Therefore, it is also required that products made from regenerated cellulose be utilized as recycled raw materials.

[0005] However, regenerated cellulose lacks thermoplasticity and has limited solubility, making it difficult to recycle. Furthermore, cellophane, particularly in film products made from regenerated cellulose, sometimes contains softeners such as glycerin as additives. Therefore, when cellophane is recycled as a raw material for regenerated cellulose, the softeners remain in the ionic liquid, causing process abnormalities, which also becomes a problem. Consequently, cellophane is not recycled but disposed of as waste.

[0006] Existing technical documents Patent documents Patent Document 1: Japanese Patent Publication No. 2016-537461. Summary of the Invention

[0007] The problem that the invention aims to solve The present invention is made in view of the aforementioned problems and relates to a method for manufacturing a cellulose dispersion that can use suitable regenerated cellulose, including cellophane that is difficult to recycle, as a raw material, and a method for manufacturing a cellulose molded article using the cellulose dispersion.

[0008] Methods for solving problems That is, Invention 1 relates to a method for manufacturing a cellulose dispersion from regenerated cellulose, characterized in that: regenerated cellulose is used as the dispersion raw material, and the method includes the following steps: a pulverizing step, pulverizing the dispersion raw material; a depolymerization step, reducing the degree of polymerization of the pulverized raw material obtained by the pulverizing step to below 350; and a micronization step, micronizing the depolymerized cellulose obtained by the depolymerization step to obtain a cellulose dispersion.

[0009] Invention 2 relates to a method for manufacturing a cellulose dispersion from regenerated cellulose as described in Invention 1, wherein the degree of polymerization of the regenerated cellulose in the dispersion raw material is 600 or less.

[0010] Invention 3 relates to a method for manufacturing a cellulose dispersion from regenerated cellulose as described in Invention 1 or 2, wherein, in the depolymerization step, sodium hypochlorite with an effective chlorine concentration of 0.13% or higher is used to reduce the degree of polymerization of the pulverized raw material.

[0011] Invention 4 relates to a method for manufacturing a cellulose dispersion from regenerated cellulose as described in Invention 1 or 2, wherein, in the depolymerization step, sodium hypochlorite with an effective chlorine concentration of 3% or more is used to reduce the degree of polymerization of the pulverized raw material.

[0012] Invention 5 relates to a cellulose dispersion wherein the cellulose dispersion obtained by the manufacturing method of invention 1 or 2 has a cation requirement of 4.0 μeq / gcell or more per 1g of cellulose.

[0013] Invention 6 relates to a cellulose dispersion wherein the cellulose dispersion obtained by the manufacturing method of invention 3 has a cation requirement of 4.0 μeq / gcell or more per 1g of cellulose.

[0014] Invention 7 relates to a cellulose dispersion wherein the cellulose dispersion obtained by the manufacturing method of invention 4 has a cation requirement of 50.0 μeq / gcell or more per 1g of cellulose.

[0015] Invention 8 relates to a method for manufacturing a cellulose molded body from regenerated cellulose, comprising the following molding steps: drying and molding the cellulose dispersion obtained by the manufacturing method of Invention 1 to obtain a cellulose molded body from regenerated cellulose.

[0016] Invention 9 relates to a method for manufacturing a cellulose molded body from regenerated cellulose as described in Invention 8, wherein the degree of polymerization of the regenerated cellulose in the dispersion raw material is 600 or less.

[0017] Invention 10 relates to a method for manufacturing a cellulose molded body from regenerated cellulose as described in Invention 8 or 9, wherein, in the depolymerization step, sodium hypochlorite with an effective chlorine concentration of 0.13% or higher is used to reduce the degree of polymerization of the pulverized raw material.

[0018] Invention 11 relates to a method for manufacturing a cellulose molded body from regenerated cellulose as described in Invention 8 or 9, wherein, in the depolymerization step, sodium hypochlorite with an effective chlorine concentration of 3% or more is used to reduce the degree of polymerization of the pulverized raw material.

[0019] Invention 12 relates to a cellulose bead derived from regenerated cellulose, which is a cellulose molded body obtained by the manufacturing method of invention 10, wherein the cellulose molded body is a cellulose bead and the average particle size (D50) is less than 50 μm.

[0020] Invention 13 relates to a cellulose bead derived from regenerated cellulose, which is a cellulose molded body obtained by the manufacturing method of invention 11, wherein the cellulose molded body is a cellulose bead and the average particle size (D50) is less than 10 μm.

[0021] Invention 14 relates to a cellulose molded body derived from regenerated cellulose, which is a cellulose molded body obtained by the manufacturing method of invention 10, wherein the molecular weight distribution index (Mw / Mn) obtained by dividing the weight-average molecular weight (Mw) of the cellulose molded body by the number-average molecular weight (Mn) is 3.5 or less.

[0022] Invention 15 relates to a cellulose molded body derived from regenerated cellulose, which is a cellulose molded body obtained by the manufacturing method of invention 11, wherein the molecular weight distribution index (Mw / Mn) obtained by dividing the weight-average molecular weight (Mw) of the cellulose molded body by the number-average molecular weight (Mn) is 1.6 or less.

[0023] Invention Effects According to the method for manufacturing a cellulose dispersion from regenerated cellulose as disclosed in Invention 1, using regenerated cellulose as the dispersion raw material, the method includes the following steps: a pulverizing step, pulverizing the dispersion raw material; a depolymerization step, reducing the degree of polymerization of the pulverized raw material obtained by the pulverizing step to below 350; and a micronization step, micronizing the depolymerized cellulose obtained by the depolymerization step to obtain a cellulose dispersion. Therefore, suitable regenerated cellulose, including cellophane that is difficult to recycle, can be effectively used as the dispersion raw material to manufacture a cellulose dispersion.

[0024] According to the method for manufacturing a cellulose dispersion from regenerated cellulose involved in Invention 2, the degree of polymerization of the regenerated cellulose in the dispersion raw material of Invention 1 is 600 or less. Therefore, by reducing the degree of polymerization of the regenerated cellulose as the dispersion raw material to a certain extent in advance, the time required for each process can be shortened, and production efficiency can be improved.

[0025] According to the method for manufacturing a cellulose dispersion from regenerated cellulose according to Invention 3, in Invention 1 or 2, sodium hypochlorite with an effective chlorine concentration of 0.13% or higher is used in the depolymerization step to reduce the degree of polymerization of the pulverized raw material, thereby efficiently reducing the degree of polymerization of regenerated cellulose.

[0026] According to the method for manufacturing a cellulose dispersion from regenerated cellulose involved in Invention 4, in Invention 1 or 2, sodium hypochlorite with an effective chlorine concentration of 3% or more is used in the depolymerization process to reduce the degree of polymerization of the pulverized raw material, thereby reducing the degree of polymerization of regenerated cellulose more efficiently.

[0027] According to the cellulose dispersion from regenerated cellulose involved in Invention 5, since the cation requirement of the cellulose dispersion obtained by the manufacturing method of Invention 1 or 2 reaches 4.0 μeq / gcell or more per 1g of cellulose, a cellulose dispersion with high dispersibility can be produced.

[0028] According to the cellulose dispersion from regenerated cellulose involved in Invention 6, since the cation requirement of the cellulose dispersion obtained by the manufacturing method of Invention 3 reaches 4.0 μeq / gcell or more per 1g of cellulose, a cellulose dispersion with high dispersibility can be produced.

[0029] According to the cellulose dispersion from regenerated cellulose involved in Invention 7, since the cation requirement of the cellulose dispersion obtained by the manufacturing method of Invention 4 reaches more than 50.0 μeq / gcell per 1g of cellulose, a cellulose dispersion with higher dispersibility can be produced.

[0030] According to the manufacturing method of cellulose molded articles from regenerated cellulose according to Invention 8, since it includes a molding step of drying and molding the cellulose dispersion obtained by the manufacturing method of Invention 1 to obtain cellulose molded articles from regenerated cellulose, it is possible to effectively use appropriate regenerated cellulose, including cellophane that is difficult to recycle, as raw material to manufacture cellulose molded articles.

[0031] According to the manufacturing method of cellulose molded body from regenerated cellulose involved in Invention 9, in Invention 8, the degree of polymerization of the regenerated cellulose in the dispersion raw material is 600 or less. Therefore, by reducing the degree of polymerization of the regenerated cellulose as the dispersion raw material to a certain extent in advance, the time required for each process can be shortened, and production efficiency can be improved.

[0032] According to the method for manufacturing cellulose molded articles from regenerated cellulose involved in Invention 10, in Invention 8 or 9, sodium hypochlorite with an effective chlorine concentration of 0.13% or more is used in the depolymerization process to reduce the degree of polymerization of the pulverized raw material, thereby efficiently reducing the degree of polymerization of regenerated cellulose.

[0033] According to the method for manufacturing cellulose molded articles from regenerated cellulose as described in Invention 11, in Invention 8 or 9, sodium hypochlorite with an effective chlorine concentration of 3% or more is used in the depolymerization process to reduce the degree of polymerization of the pulverized raw material, thereby efficiently reducing the degree of polymerization of regenerated cellulose.

[0034] According to the invention 12, the cellulose beads derived from regenerated cellulose are cellulose molded bodies obtained by the manufacturing method of the invention 10. The cellulose molded bodies are cellulose beads with an average particle size (D50) of less than 50 μm. Therefore, the cellulose beads have good sliding properties and can obtain a good texture with less roughness or friction.

[0035] According to the invention 13, the cellulose beads derived from regenerated cellulose are cellulose molded bodies obtained by the manufacturing method of the invention 11, wherein the cellulose molded bodies are cellulose beads with an average particle size (D50) of less than 10 μm. Therefore, the cellulose beads have good sliding properties and can obtain a better texture with less roughness or friction.

[0036] The cellulose molded article derived from regenerated cellulose according to invention 14 is a cellulose molded article obtained by the manufacturing method of invention 10, wherein the molecular weight distribution index (Mw / Mn) obtained by dividing the weight average molecular weight (Mw) of the cellulose molded article by the number average molecular weight (Mn) is 3.5 or less, thus becoming a fine cellulose with a narrow and homogeneous molecular weight distribution index (Mw / Mn), with better processability, and thus providing a cellulose molded article derived from regenerated cellulose with a small particle size.

[0037] The cellulose molded article from regenerated cellulose according to invention 15 is a cellulose molded article obtained by the manufacturing method of invention 11, wherein the molecular weight distribution index (Mw / Mn) obtained by dividing the weight average molecular weight (Mw) of the cellulose molded article by the number average molecular weight (Mn) is 1.6 or less, thus becoming a fine cellulose with a narrower and more homogeneous molecular weight distribution index (Mw / Mn), and having better processability, thus providing a cellulose molded article from regenerated cellulose with a small particle size. Attached Figure Description

[0038] [ Figure 1 [This is a schematic process diagram of a method for manufacturing a cellulose dispersion and a cellulose molded article derived from regenerated cellulose according to one embodiment of the present invention.] Detailed Implementation

[0039] Figure 1 The schematic process diagram shows a method 10 for manufacturing a cellulose dispersion from regenerated cellulose according to one embodiment of the present invention. This method uses regenerated cellulose as a raw material to manufacture a cellulose dispersion 11. The method for manufacturing the cellulose dispersion 10 includes a pulverizing step (S1), a depolymerization step (S2), and a micronization step (S3). Furthermore, the method 20 for manufacturing a cellulose molded body from regenerated cellulose further includes a molding step (S4) to obtain a cellulose molded body 21.

[0040] Regenerated cellulose is the main raw material (dispersion raw material) for the cellulose dispersion produced in the manufacturing method of the present invention. The lower the degree of polymerization of the regenerated cellulose, the easier it is to depolymerize and process, thus improving production efficiency. If the degree of polymerization of the regenerated cellulose is too high, it becomes difficult to depolymerize, potentially making it difficult to manufacture cellulose dispersions or cellulose moldings. Therefore, the degree of polymerization of the regenerated cellulose in the dispersion raw material is preferably 600 or less. Typically, the degree of polymerization of regenerated cellulose produced by the viscose method is around 200 to 300, making it suitable as a raw material for the manufacturing method of the present invention. Furthermore, the degree of polymerization of regenerated cellulose obtained by methods using cellulose solvents such as ionic liquids is around 600, making it suitable as a raw material for the manufacturing method of the present invention.

[0041] Regenerated cellulose used as a dispersion feedstock can be materials of suitable forms, including fibrous, film-like, and spherical shapes, manufactured by known methods, or regenerated cellulose products obtained by processing the manufactured regenerated cellulose. These regenerated celluloses are type II celluloses with a type II crystal structure.

[0042] Examples of methods for manufacturing regenerated cellulose include: methods such as the viscose process, which chemically derivatizes cellulose fibers and then dissolves them in solvents; and methods that use ionic liquids to dissolve cellulose fibers. Examples of regenerated cellulose products include: paper products, clothing, and hygiene products made from molded materials such as rayon, cellophane, and cellulose beads.

[0043] When using regenerated cellulose as a dispersion feedstock, from the viewpoint of reducing environmental impact, it is preferable to use regenerated cellulose products as recycled feedstock. Recycled feedstocks of regenerated cellulose also include scraps generated during the manufacturing process of regenerated cellulose molds or products. Since regenerated cellulose products or scraps were previously difficult to recycle and were often discarded, using them as recycled feedstock can significantly contribute to reducing environmental impact.

[0044] The pulverization step (S1) is a process of pulverizing the regenerated cellulose, which serves as the raw material for the dispersion, to obtain pulverized raw material. This pulverization step aims to improve the reactivity of the regenerated cellulose (pulverized raw material) in the subsequent depolymerization step (S2) by finely pulverizing the regenerated cellulose. Preferably, the pulverized raw material obtained in the pulverization step is regenerated cellulose pulverized to a size of 500 μm or less. The size of the regenerated cellulose is determined using a laser diffraction / scattering particle size distribution measuring device according to JIS Z8825 (2013). If the pulverized regenerated cellulose is too large, its reactivity in the subsequent depolymerization step (S2) will be insufficient, potentially reducing production capacity. Known pulverization methods such as dry pulverization or wet pulverization can be appropriately employed in this pulverization step.

[0045] The depolymerization process (S2) depolymerizes the pulverized raw material obtained in the pulverization process to obtain depolymerized cellulose with a degree of polymerization reduced to below 350. This depolymerization process weakens the structure of the pulverized regenerated cellulose by depolymerizing the raw material, making the cellulose easier to depolymerize (depolymerized cellulose). Chemicals such as sodium hypochlorite or enzymes are used to adjust the degree of polymerization of the depolymerized cellulose obtained in the depolymerization process to below 350. If the degree of polymerization of the depolymerized cellulose is too high, insufficient depolymerization will occur in the subsequent micronization process (S3), potentially reducing production capacity.

[0046] In the depolymerization process, sodium hypochlorite is preferably used when depolymerizing the pulverized raw materials. Sodium hypochlorite oxidizes the hydroxyl groups at the 2 and 3 positions of cellulose, depolymerizing cellulose through a β-alkoxy elimination reaction caused by the carbonyl group. Sodium hypochlorite is easy to handle, and by controlling pH or temperature, it can efficiently reduce the degree of polymerization of regenerated cellulose, making it suitable for use. Furthermore, the higher the concentration of sodium hypochlorite, the easier it is to reduce the degree of polymerization of regenerated cellulose, especially when the available chlorine concentration is 0.13% or higher, more preferably 3% or higher, which can more efficiently reduce the degree of polymerization of regenerated cellulose.

[0047] The micronization process (S3) involves defibrillating the depolymerized cellulose obtained through the depolymerization process to produce micronized cellulose and obtain a cellulose dispersion 11. The defibrillation of the depolymerized cellulose is performed mechanically (physically). Mechanical (physical) defibrillation is carried out using known methods such as homogenizers or water jets. The micronized cellulose obtained in this way, because it has not undergone defibrillation using chemicals (chemical defibrillation), is in the form of a dispersion of unmodified cellulose microparticles.

[0048] Here, since the degree of polymerization of regenerated cellulose, which is used as a dispersion feedstock, is reduced through a depolymerization process, it can be easily depolymerized and micronized even without applying high pressure. This ease of micronization of depolymerized cellulose is therefore significant in terms of equipment for the micronization process.

[0049] The micronization of depolymerized cellulose can be performed in multiple stages. For example, after pre-depolymerization using a mixer, primary depolymerization can be performed using a homogenizer, thereby producing micronized cellulose with uniform particle size. Furthermore, pre-depolymerization helps prevent blockages and other adverse effects of depolymerized cellulose in the depolymerization equipment, which is beneficial from an equipment protection perspective. Pre-depolymerization is performed using known methods such as mixers or refining machines. Micronization of depolymerized cellulose only requires reducing the average particle size to the nanometer to several hundred nanometer scale; if it reaches approximately 2 to 800 nanometers, more preferably below 500 nanometers, the transparency of the micronized cellulose dispersion (cellulose dispersion) is improved. The cellulose dispersion can be used as a coating agent by coating films, paper, or other three-dimensional materials; dispersions with high transparency are suitable for coating. In addition, due to the high transparency of the cellulose dispersion, it also exhibits excellent processability when forming cellulose molded articles.

[0050] The molding process (S4) involves drying the cellulose dispersion (micronized cellulose) obtained through the micronization process to obtain cellulose molded body 21. The micronized cellulose, in dispersion form, aggregates and is molded into granular (bead-like) molded bodies during spray drying. This molded body is formed using regenerated cellulose as the dispersion raw material, and is therefore a cellulose molded body derived from regenerated cellulose. In the molding process, the viscosity of the cellulose dispersion, measured using a type B viscometer according to JIS Z8803 (2011) at a shear rate of 4.0 / s, is preferably 15000 mPa·s or less. If the viscosity of the cellulose dispersion exceeds 15000 mPa·s, the fluidity of the solution decreases, potentially causing blockage in the pipeline supplying the liquid to the spray drying apparatus or in the spray drying nozzle.

[0051] Furthermore, spray drying requires an air pressure of 0.025~0.6 MPa. If the air pressure during spray drying is insufficient, the cellulose microparticles cannot be finely processed, resulting in larger particle sizes and deterioration of physical properties or texture. Additionally, maintaining an air pressure higher than 0.6 MPa would require an excessively large and impractical air generator.

[0052] Furthermore, in the method for manufacturing cellulose molded articles from regenerated cellulose according to the present invention, a collection step (S5) is performed after the molding step (S4) as needed. The collection step is a step of removing unwanted particles from the granular cellulose molded articles (cellulose beads) formed by the molding step to recover suitable particles from the cellulose molded articles. As for the collection device, it is not particularly limited as long as it can recover suitable particles, and for example, it can be carried out by using known collection devices such as bag filters or cyclone dust collectors.

[0053] Thus, the manufacturing method of the present invention involves pulverizing regenerated cellulose from the dispersion raw material to below 500 μm in a pulverizing step (S1) to obtain pulverized raw material; adjusting the degree of polymerization of the pulverized raw material to below 350 in a depolymerization step (S2); obtaining a cellulose dispersion in a micronization step (S3); and further obtaining a cellulose molded body through a molding step (S4). Therefore, regenerated cellulose can be used as a dispersion raw material to obtain a cellulose dispersion or a cellulose molded body. In particular, materials such as cellophane, which were previously considered difficult to recycle, can be used as recycled raw materials for the dispersion raw material, thus greatly contributing to reducing environmental impact. Furthermore, the cellulose molded body derived from regenerated cellulose is a molded body of unmodified cellulose that has not undergone chemical defibrillation, thus reducing the amount of environmentally burdensome pharmaceuticals used compared to conventional cellulose molded bodies.

[0054] In the cellulose dispersion or molded body obtained by the manufacturing method of the present invention from regenerated cellulose, sodium hypochlorite with an effective chlorine concentration of 0.13% or more, preferably 3% or more, can be used in the depolymerization process.

[0055] If the effective chlorine concentration of sodium hypochlorite increases, the cation requirement of the cellulose dispersion increases. The cation requirement refers to the amount of cationic agent needed to neutralize negatively charged particles in the colloidal or particulate dispersion region (particle size 1 nm to several hundred μm) to an equal charge; it is an indicator of the dispersibility of cellulose particles in the cellulose dispersion. A higher cation requirement indicates better dispersibility, resulting in a more uniform cellulose dispersion. Preferably, the cation requirement of the cellulose dispersion is 4.0 μeq / gcell or higher per 1 g of cellulose, more preferably 50.0 μeq / gcell or higher.

[0056] Cellulose dispersions can be used as coating agents for films, sheets, resin molded articles, etc., imparting various functions such as increased strength, gas barrier properties, and hydrophilicity. Therefore, if the cellulose dispersion has good dispersibility, it is significant when used as a coating agent, as the coating is easy to form evenly, the functional properties are well imparted, and the processing is also improved.

[0057] Furthermore, if the effective chlorine concentration of sodium hypochlorite increases, the molecular weight distribution index (Mw / Mn), obtained by dividing the weight-average molecular weight (Mw) of the cellulose molded body by the number-average molecular weight (Mn), decreases. The molecular weight distribution index (Mw / Mn) is an indicator of the narrowness of the molecular weight distribution; the narrower the molecular weight distribution, the better the processability, and the more finely sized cellulose molded bodies can be produced. The molecular weight distribution index (Mw / Mn) of the cellulose molded body is set to 3.5 or less, and more preferably 1.6 or less.

[0058] In particular, for cellulose beads, in the depolymerization process, when the effective chlorine concentration of sodium hypochlorite is 0.13% or higher, the average particle size (D50) of the cumulative 50% of the particle size distribution is set to 50 μm or less; more preferably, when the effective chlorine concentration of sodium hypochlorite is 3% or higher, the average particle size (D50) is set to 10 μm or less. The average particle size (D50) is the median diameter. If the average particle size (D50) is 50 μm or less, the cellulose beads have good sliding properties, resulting in a good texture with low roughness or friction; if the average particle size (D50) is 10 μm or less, an even better texture can be obtained. Example

[0059] [Preparation of cellulose dispersions and molded articles from regenerated cellulose] Regarding the cellulose dispersions and molded articles derived from regenerated cellulose in the following trial examples and comparative examples, according to Figure 1 The process diagram is to be produced under the following conditions.

[0060] The following raw materials were used as regenerated cellulose. Cellophane film manufactured using the viscose method (manufactured by Futamura Chemical Co., Ltd., "PUT") was used as regenerated cellulose 1 (C1). Crushed dissolving slurry was added to a TBAA / DMSO mixed solvent to a concentration of 10%, and while heating the contents to above 50°C, it was dissolved using a mixer (manufactured by Seiwa Giken Co., Ltd.). The resulting cellulose solution was extruded through a T-die (manufactured by Plastics Engineering Research Institute Co., Ltd.) into a water bath to form a film, which then solidified. The cellulose film obtained from the cellophane production line was used as regenerated cellulose 2 (C2). The degree of polymerization of regenerated cellulose 1 (C1) was 239, and the degree of polymerization of regenerated cellulose 2 (C2) was 559.

[0061] <Trial Production Example 1> Regenerated cellulose 1 (C1) was pulverized to 500 μm using a hammer mill (manufactured by Sansho Kogyo Co., Ltd.) (pulverization process). 200 ml of sodium hypochlorite (1% solution, effective chlorine concentration 0.13%) was added to 8 g of the pulverized raw material, and the mixture was reacted in a hot water bath at 55°C for 30 minutes to reduce the degree of polymerization to 196, yielding depolymerized cellulose (depolymerization process). The depolymerized cellulose was washed with ion-exchange water, and 400 ml of ion-exchange water was added to prepare a dispersion. Pre-depolymerization was performed using a mixer (manufactured by PRIMIX Co., Ltd.). Then, the dispersion was micronized using a homogenizer (manufactured by SMT Co., Ltd.) under a pressure of 70 MPa to obtain the cellulose dispersion from regenerated cellulose in Prototype Example 1. The cellulose dispersion was spray-dried using a spray dryer (manufactured by Tokyo Rika Kiki Co., Ltd.) at an air pressure of 0.2 MPa (processing capacity 300 ml / hour) (forming process). The particles were collected using a cyclone dust collector (manufactured by Tokyo Rika Kiki Co., Ltd.) to collect dust (collection process), resulting in the cellulose molded body from regenerated cellulose of Prototype Example 1.

[0062] <Trial Production Example 2> Except for preparing a 10% sodium hypochlorite solution with an effective chlorine concentration of 1.30% in the depolymerization process to produce depolymerized cellulose with a degree of polymerization reduced to 74, the same procedure as in Experimental Example 1 was followed to obtain the cellulose dispersion and cellulose molded body from regenerated cellulose in Experimental Example 2.

[0063] <Trial Production Example 3> Except for preparing a 20% sodium hypochlorite solution with an effective chlorine concentration of 3.00% to produce depolymerized cellulose with a degree of polymerization reduced to 62, the same procedure as in Experimental Example 1 was followed to obtain the cellulose dispersion and cellulose molded body from regenerated cellulose in Experimental Example 3.

[0064] <Trial Production Example 4> Except for preparing a 100% solution of sodium hypochlorite and an effective chlorine concentration of 12.00% to produce depolymerized cellulose with a degree of polymerization reduced to 38, the same procedure as in Experimental Example 1 was followed to obtain the cellulose dispersion and cellulose molded body from regenerated cellulose in Experimental Example 4. It should be noted that the viscosity measured using a Type B viscometer (manufactured by Eiko Seiki Co., Ltd.) at a shear rate of 4.0 / second, a measurement temperature of 25°C, and a measurement time of 1 minute was 13607 mPa·s.

[0065] <Trial Production Example 5> Except that the dispersion raw material used was regenerated cellulose 2 (C2), the same procedure as in Experimental Example 1 was followed to obtain the cellulose dispersion and cellulose molded body from regenerated cellulose in Experimental Example 5. It should be noted that the degree of polymerization of the depolymerized cellulose obtained in the depolymerization process was 326.

[0066] <Trial Production Example 6> Except that the dispersion raw material used was regenerated cellulose 2 (C2), the same procedure as in Experimental Example 4 was followed to obtain the cellulose dispersion and cellulose molded body from regenerated cellulose in Experimental Example 6. It should be noted that the degree of polymerization of the depolymerized cellulose obtained in the depolymerization process was 47.

[0067] <Comparative Example 1> Except for not undergoing the depolymerization process, the same procedure as in Prototype Example 1 was followed, serving as Comparative Example 1.

[0068] <Comparative Example 2> Except for not undergoing the depolymerization, micronization, and molding processes, the operation was the same as that of Prototype Example 1, serving as Comparative Example 2.

[0069] <Comparative Example 3> Except for not undergoing the depolymerization, micronization, and molding processes, the process was the same as that of Prototype Example 5, and this was used as Comparative Example 3.

[0070] As a performance evaluation of test examples 1-6 and comparative examples 1-3, the average particle size (D50) and molecular weight distribution index were measured.

[0071] [Cation Demand] The cation requirement was determined using a particle charge meter (manufactured by Voith Turbo Co., Ltd., "PCD-06 Premium"). Cellulose dispersions from regenerated cellulose in the test and comparative examples were diluted to arbitrary concentrations, and 10 mL was added to the apparatus. A 1 / 400N DADMAC (diallyldimethylammonium chloride) solution was added dropwise, and the amount of titrant consumed until the charge was neutralized was measured. It should be noted that the dilution ratio for each sample was adjusted so that the amount of titrant consumed was 1–5 mL. The cation requirement (μeq / L) was calculated using the following formula (i), and converted to the cation requirement per gram of cellulose (μeq / g-cell) using the following formula (ii).

[0072] [Mathematical Expression 1] [Mathematical Expression 2] [Average Particle Size (D50)] The average particle size (D50) was determined according to JIS Z 8825 (2013). A laser diffraction / scattering particle size distribution measuring device (MicrotracBEL Co., Ltd., "MT3200II") was used for the determination. During the determination, the cellulose samples involved in the test examples and comparative examples were first mixed with ion-exchanged water to prepare slurries, which were then filled into sample circulators. The slurries were stirred until no visually observable inhomogeneities were observed just before feeding. Then, the slurries were fed into the measuring device, and the following measurement parameters were set: the refractive index of the ion-exchanged water was set to 1.33, the light transmittance of the target particles was set to transmittance, the measurement time was set to 10 seconds, and the particle size (D50) corresponding to 50% of the cumulative particle size distribution (volume basis) was measured.

[0073] [Molecular weight distribution index (Mw / Mn)] The cellulose samples involved in the test and comparative examples were added to the sample vials along with a TBAA / DMSO mixed solvent to achieve a cellulose concentration of 0.1% by weight. The mixture was stirred overnight at room temperature to allow dissolution. The prepared samples were analyzed by HPLC using an organic solvent-based SEC (GPC) column (manufactured by Resonac Co., Ltd., coupled with "KD-804" and "KD-805") (detector: RID (manufactured by Shimadzu Corporation, "RID-10A"), column temperature 50°C, flow rate 0.6 ml / min). A TBAA / DMSO mixed solvent was used as the eluent.

[0074] [Degree of Aggregation] The degree of polymerization was determined using the viscosity method with copper ethylenediamine solution, as follows: A dried cellulose sample was dissolved in 0.5 M copper ethylenediamine solution (solution 1) to prepare solution 2. The viscosities of solutions 1 and 2 were measured using a capillary viscometer. The viscosity of solution 1 was denoted as η1, and the viscosity of solution 2 as η2. The limiting viscosity [η] of the cellulose sample was calculated using the following formula, and the degree of polymerization DP was then determined. c is the concentration of the cellulose sample (g / L).

[0075] Limiting concentration [η] = {(η2 / η1)-1} / c Degree of polymerization DP = limiting concentration [η] / (8.8 × 10⁻⁶) -4 ) [Table 1] [Table 2] [Results and Investigations] Compared to the cellulose dispersions of Comparative Examples 1-3, the cation requirements of the cellulose dispersions of Test Examples 1-6 were all increased, which can be understood as the micronization process enabling good dispersion of cellulose microparticles in the cellulose dispersion. In the comparison between the cellulose dispersions of Test Examples 1-4 and the cellulose dispersions of Comparative Examples 1 and 2, the cation requirement of the cellulose dispersion of Test Example 1 was approximately twice that of the cellulose dispersion of Comparative Example 1 without the depolymerization process, and approximately four times that of the cellulose dispersion of Comparative Example 2 without the depolymerization, micronization, and molding processes, demonstrating excellent dispersibility of the cellulose microparticles.

[0076] Furthermore, in the comparison of the cellulose dispersions in Examples 1-4, increasing the sodium hypochlorite concentration further increased the cation demand, indicating that cellulose defibrillation was easier and better performed. In particular, if the effective chlorine concentration of sodium hypochlorite reaches 0.13% or more, the cation demand reaches 4.0 μeq / gcell or more per gram of cellulose; more preferably, if the effective chlorine concentration is 3% or more, the cation demand reaches 50.0 μeq / gcell or more per gram of cellulose. Therefore, it is suitable for use as a coating agent for molded materials such as films.

[0077] Even when comparing the cellulose dispersions of Test Examples 5 and 6, which use regenerated cellulose prepared using cellulose solvents such as ionic liquids as dispersion raw materials, with the cellulose dispersion of Comparative Example 3, the trends of the cellulose dispersions of Test Examples 1 to 4 and the cellulose dispersions of Comparative Examples 1 and 2 are the same. This shows that even when different regenerated celluloses are used as dispersion raw materials, high-quality cellulose dispersions can be obtained by the manufacturing method of the present invention.

[0078] Compared to the cellulose molded bodies of Comparative Examples 1-3, the average particle size (D50) of the cellulose molded bodies of Test Examples 1-6 was reduced, which can be understood as the cellulose being effectively depolymerized through a micronization process. In the comparison between the cellulose molded bodies of Test Examples 1-4 and the cellulose molded bodies of Comparative Examples 1 and 2, the average particle size (D50) of the cellulose molded body of Test Example 1 was less than 1 / 2 of that of the cellulose molded body of Comparative Example 1 without the depolymerization process, and about 1 / 5 of that of the cellulose molded body of Comparative Example 2 without the depolymerization, micronization, and molding processes.

[0079] Furthermore, by increasing the sodium hypochlorite concentration, the average particle size (D50) is further reduced, indicating that cellulose defibrillation is easier and better. In particular, if the effective chlorine concentration of sodium hypochlorite reaches 0.13% or more, the average particle size (D50) is 50 μm or less; more preferably, if the effective chlorine concentration reaches 3% or more, the average particle size (D50) is 10 μm or less, thus achieving good quality cellulose beads for use in cosmetics and the like.

[0080] Furthermore, regarding the cellulose molded bodies of Test Examples 5 and 6, which use regenerated cellulose prepared using cellulose solvents such as ionic liquids as dispersion raw materials, and the cellulose molded body of Comparative Example 3, similarly, compared with the cellulose molded body of Comparative Example 3, the average particle size (D50) of the cellulose molded body of Test Examples 5 and 6, which underwent depolymerization and micronization processes, was less than 1 / 10 and less than 1 / 100 in the cellulose molded body of Test Example 6, showing good results. Therefore, it is concluded that there is no limitation on the manufacturing method of regenerated cellulose as raw material, and there is no limitation on the regenerated cellulose used as raw material.

[0081] Next, let's look at the molecular weight distribution index (Mw / Mn). The cellulose molded bodies of Specimens 1-6 are all smaller than those of Comparative Examples 1-3. Therefore, it can be said that the molecular weight distribution of the cellulose molded bodies obtained by the manufacturing method of the present invention is narrower and more homogeneous. In the depolymerization process, if the effective chlorine concentration of sodium hypochlorite is greater than 1.30%, the molecular weight distribution index (Mw / Mn) becomes particularly good.

[0082] Industrial practicality According to the method for manufacturing cellulose dispersions and cellulose molded articles derived from regenerated cellulose of the present invention, regenerated cellulose, including materials such as cellophane that are difficult to recycle, can be used as raw materials to manufacture cellulose dispersions or cellulose molded articles, thus making a significant contribution to reducing environmental impact. Furthermore, the resulting cellulose dispersions exhibit high dispersibility of cellulose particles, resulting in homogeneous and high-quality products when used in coating agents, etc. Moreover, the cellulose molded articles obtained by the manufacturing method of the present invention have fine and homogeneous particles, thus showing promise as alternatives to conventional microplastics or chemically modified cellulose beads used in cosmetics.

[0083] Marker description 10: A method for manufacturing a cellulose dispersion from regenerated cellulose; 11: Cellulose dispersion; 20: A method for manufacturing cellulose molded articles derived from regenerated cellulose; 21: Cellulose molded body; S1: Crushing process; S2: Depolymerization process; S3: Minimization process; S4: Molding process; S5: Collection process.

Claims

1. A method for manufacturing a cellulose dispersion from regenerated cellulose, characterized in that: Using regenerated cellulose as the dispersion raw material, and including the following steps: The pulverizing process involves pulverizing the dispersion raw material. The depolymerization process reduces the degree of polymerization of the pulverized raw material obtained through the pulverization process to below 350. as well as The micronization process micronizes the depolymerized cellulose obtained through the depolymerization process to obtain a cellulose dispersion.

2. The method for manufacturing a cellulose dispersion from regenerated cellulose according to claim 1, wherein, The degree of polymerization of the regenerated cellulose in the dispersion raw material is below 600.

3. The method for producing a cellulose dispersion from regenerated cellulose according to claim 1 or 2, wherein, In the depolymerization process, sodium hypochlorite with an effective chlorine concentration of 0.13% or higher is used to reduce the degree of polymerization of the pulverized raw material.

4. The method for producing a cellulose dispersion from regenerated cellulose according to claim 1 or 2, wherein, In the depolymerization process, sodium hypochlorite with an effective chlorine concentration of 3% or higher is used to reduce the degree of polymerization of the pulverized raw material.

5. A cellulose dispersion, wherein, The cellulose dispersion obtained by the manufacturing method according to claim 1 or 2 has a cation requirement of 4.0 μeq / gcell or more per 1g of cellulose.

6. A cellulose dispersion, wherein, The cellulose dispersion obtained by the manufacturing method according to claim 3 has a cation requirement of 4.0 μeq / gcell or more per 1g of cellulose.

7. A cellulose dispersion, wherein, The cellulose dispersion obtained by the manufacturing method according to claim 4 has a cation requirement of 50.0 μeq / gcell or more per 1g of cellulose.

8. A method for manufacturing a cellulose molded body from regenerated cellulose, comprising the following molding step: drying and molding the cellulose dispersion obtained by the manufacturing method of claim 1 to obtain a cellulose molded body from regenerated cellulose.

9. The method for manufacturing a cellulose molded article from regenerated cellulose according to claim 8, wherein, The degree of polymerization of the regenerated cellulose in the dispersion raw material is below 600.

10. The method for manufacturing a cellulose molded article from regenerated cellulose according to claim 8 or 9, wherein, In the depolymerization process, sodium hypochlorite with an effective chlorine concentration of 0.13% or higher is used to reduce the degree of polymerization of the pulverized raw material.

11. The method for manufacturing a cellulose molded article from regenerated cellulose according to claim 8 or 9, wherein, In the depolymerization process, sodium hypochlorite with an effective chlorine concentration of 3% or higher is used to reduce the degree of polymerization of the pulverized raw material.

12. A cellulose bead derived from regenerated cellulose, which is a cellulose molded body obtained by the manufacturing method of claim 10, wherein, The cellulose molded body is cellulose beads with an average particle size (D50) of less than 50 μm.

13. A cellulose bead derived from regenerated cellulose, which is a cellulose molded body obtained by the manufacturing method of claim 11, wherein, The cellulose molded body is cellulose beads with an average particle size (D50) of less than 10 μm.

14. A cellulose molded article derived from regenerated cellulose, obtained by the manufacturing method of claim 10, wherein, The molecular weight distribution index (Mw / Mn) obtained by dividing the weight-average molecular weight (Mw) of the cellulose molded body by the number-average molecular weight (Mn) is less than 3.

5.

15. A cellulose molded article derived from regenerated cellulose, obtained by the manufacturing method of claim 11, wherein, The molecular weight distribution index (Mw / Mn) obtained by dividing the weight-average molecular weight (Mw) of the cellulose molded body by the number-average molecular weight (Mn) is less than 1.6.

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