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

Abstract

[Problem] The present invention relates to a method for producing a cellulose dispersion liquid and a cellulose molded body, in which an appropriate regenerated cellulose including a cellophane or the like that is difficult to recycle can be used as a dispersion liquid starting material. [Solution] The present invention includes: a grinding step (S1) in which regenerated cellulose is used as a dispersion liquid starting material and the dispersion liquid starting material is ground; a depolymerization step (S2) in which the polymerization degree of the ground starting material obtained in the grinding step is decreased to 350 or less; and a refining step (S3) in which the depolymerized cellulose obtained in the depolymerization step is refined so as to obtain a cellulose dispersion liquid. The present invention additionally includes a molding step (S4) in which the cellulose dispersion liquid obtained in the refining step is dried so as to obtain a molded body.

Description

Methods for producing cellulose dispersions derived from regenerated cellulose and cellulose molded articles derived from regenerated cellulose, as well as cellulose dispersions derived from regenerated cellulose, cellulose beads derived from regenerated cellulose, and cellulose molded articles derived from regenerated cellulose

[0001] The present invention relates to a cellulose dispersion derived from regenerated cellulose, a method for producing a cellulose product derived from regenerated cellulose, a cellulose dispersion derived from regenerated cellulose, cellulose beads derived from regenerated cellulose, and a cellulose product derived from regenerated cellulose.

[0002] Generally, regenerated cellulose is produced by a method such as the viscose method, in which cellulose fibers contained in raw material pulp or the like are derivatized with chemicals, dissolved in a solvent to produce viscose, and then coagulated. The regenerated cellulose obtained in this way is derived from natural materials and has properties such as biodegradability, so demand for it as a product is increasing, and it is molded into appropriate shapes such as fibers, films, and spheres, and processed into various products such as paper products, clothing, and sanitary goods.

[0003] In recent years, due to issues such as the environmental burden of treating waste liquids such as chemicals used in the viscose process and treating exhaust gases generated during the manufacturing process, a method has been proposed for producing regenerated cellulose by directly dissolving cellulose materials using ionic liquids without using the viscose process (see, for example, Patent Document 1). This method of producing regenerated cellulose has fewer steps than the viscose process, improving work efficiency, and does not require the exhaust gas treatment required in the viscose process, thereby reducing the environmental burden.

[0004] Meanwhile, with the promotion of the Sustainable Development Goals (SDGs), active efforts are being made in various fields to realize an environmentally friendly, recycling-oriented society. One well-known example of an environmentally friendly approach is recycling, which reuses discarded products as resources. Therefore, there is a demand for the use of regenerated cellulose as a recycled raw material in products.

[0005] However, regenerated cellulose is difficult to recycle because it does not have thermoplasticity and methods for dissolving it are limited. Furthermore, cellophane, a film product made from regenerated cellulose, may contain softeners such as glycerin as additives. Therefore, when cellophane is recycled as a raw material for regenerated cellulose, the softeners in the cellophane may remain in the ionic liquid, causing process abnormalities. Therefore, cellophane has been disposed of without being recycled.

[0006] Special Publication No. 2016-537461

[0007] The present invention has been made in consideration of the above points, and relates to a method for producing a cellulose dispersion that can use appropriate regenerated cellulose, including cellophane, which is difficult to recycle, as a raw material, and a method for producing a cellulose molded body using the cellulose dispersion.

[0008] That is, the first invention relates to a method for producing a cellulose dispersion derived from regenerated cellulose, which comprises a grinding step of grinding the dispersion raw material using regenerated cellulose as a dispersion raw material, a depolymerization step of reducing the degree of polymerization of the ground raw material obtained by the grinding step to 350 or less, and a micronization step of micronizing the depolymerized cellulose obtained by the depolymerization step to obtain a cellulose dispersion.

[0009] A second invention relates to a method for producing a cellulose dispersion derived from regenerated cellulose, in which the regenerated cellulose in the dispersion raw material has a degree of polymerization of 600 or less.

[0010] The third invention relates to a method for producing a cellulose dispersion derived from regenerated cellulose, in which, in the first or second invention, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite having an effective chlorine concentration of 0.13% or more in the depolymerization step.

[0011] The fourth invention relates to a method for producing a cellulose dispersion derived from regenerated cellulose, in which, in the first or second invention, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite having an effective chlorine concentration of 3% or more in the depolymerization step.

[0012] A fifth aspect of the present invention relates to a cellulose dispersion obtained by the production method of the first or second aspect of the present invention, wherein the cation demand of the cellulose dispersion per gram of cellulose is 4.0 μeq / gcell or more.

[0013] A sixth aspect of the present invention relates to a cellulose dispersion obtained by the production method of the third aspect of the present invention, wherein the cation demand of the cellulose dispersion is 4.0 μeq / gcell or more per gram of cellulose.

[0014] A seventh aspect of the present invention relates to a cellulose dispersion obtained by the production method of the fourth aspect of the present invention, wherein the cation demand of the cellulose dispersion per gram of cellulose is 50.0 μeq / gcell or more.

[0015] The eighth invention relates to a method for producing a cellulose molded body derived from regenerated cellulose, which includes a molding step of drying and molding the cellulose dispersion obtained by the manufacturing method of the first invention to obtain a cellulose molded body derived from regenerated cellulose.

[0016] A ninth invention relates to the method for producing a cellulose molded article derived from regenerated cellulose according to the eighth invention, wherein the degree of polymerization of the regenerated cellulose in the dispersion liquid raw material is 600 or less.

[0017] The tenth invention relates to a method for producing a cellulose molded body derived from regenerated cellulose, in which, in the eighth or ninth invention, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite having an effective chlorine concentration of 0.13% or more in the depolymerization process.

[0018] The eleventh invention relates to a method for producing a cellulose molded body derived from regenerated cellulose, in which, in the eighth or ninth invention, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite having an effective chlorine concentration of 3% or more in the depolymerization step.

[0019] The twelfth invention relates to a cellulose shaped body obtained by the manufacturing method of the tenth invention, wherein the cellulose shaped body is cellulose beads derived from regenerated cellulose and has an average particle diameter (D50) of 50 μm or less.

[0020] The thirteenth invention relates to a cellulose shaped body obtained by the manufacturing method of the eleventh invention, wherein the cellulose shaped body is cellulose beads derived from regenerated cellulose and has an average particle diameter (D50) of 10 μm or less.

[0021] The fourteenth invention relates to a cellulose molded body obtained by the manufacturing method of the tenth invention, which is a cellulose molded body derived from regenerated cellulose, and has a molecular weight distribution index (Mw / Mn) of 3.5 or less, obtained by dividing the weight average molecular weight (Mw) of the cellulose molded body by the number average molecular weight (Mn).

[0022] The fifteenth invention relates to a cellulose molded body obtained by the manufacturing method of the eleventh invention, which is a cellulose molded body derived from regenerated cellulose, and which has a 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) of 1.6 or less.

[0023] According to the method for producing a cellulose dispersion derived from regenerated cellulose of the first invention, regenerated cellulose is used as a dispersion raw material, and the method includes a grinding process for grinding the dispersion raw material, a depolymerization process for reducing the degree of polymerization of the ground raw material obtained by the grinding process to 350 or less, and a micronization process for micronizing the depolymerized cellulose obtained by the depolymerization process to obtain a cellulose dispersion.Therefore, it is possible to effectively use appropriate regenerated cellulose, including cellophane and the like, which are difficult to recycle, as a dispersion raw material to produce a cellulose dispersion.

[0024] According to the method for producing a cellulose dispersion derived from regenerated cellulose of the second invention, in the first invention, since the degree of polymerization of the regenerated cellulose of the dispersion raw material is 600 or less, the degree of polymerization of the regenerated cellulose, which is the dispersion raw material, is reduced to a certain level in advance, the time required for each process can be shortened, and production efficiency can be improved.

[0025] According to the method for producing a cellulose dispersion derived from regenerated cellulose of the third invention, in the first or second invention, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite with an effective chlorine concentration of 0.13% or more in the depolymerization process, thereby efficiently reducing the degree of polymerization of the regenerated cellulose.

[0026] According to the method for producing a cellulose dispersion derived from regenerated cellulose of the fourth invention, in the first or second invention, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite with an effective chlorine concentration of 3% or more in the depolymerization process, thereby making it possible to more efficiently reduce the degree of polymerization of the regenerated cellulose.

[0027] According to the regenerated cellulose-derived cellulose dispersion of the fifth invention, the cation demand of the cellulose dispersion obtained by the manufacturing method of the first or second invention is 4.0 μeq / gcell or more per 1 g of cellulose, so that a highly dispersible cellulose dispersion can be obtained.

[0028] According to the cellulose dispersion derived from regenerated cellulose of the sixth invention, the cation demand of the cellulose dispersion obtained by the manufacturing method of the third invention is 4.0 μeq / gcell or more per 1 g of cellulose, so that a highly dispersible cellulose dispersion can be obtained.

[0029] According to the cellulose dispersion derived from regenerated cellulose of the seventh invention, the cation demand of the cellulose dispersion obtained by the manufacturing method of the fourth invention is 50.0 μeq / gcell or more per 1 g of cellulose, so that a cellulose dispersion with higher dispersibility can be obtained.

[0030] The method for producing a cellulose molded body derived from regenerated cellulose according to the eighth invention includes a molding step in which the cellulose dispersion obtained by the manufacturing method of the first invention is dried and molded to obtain a cellulose molded body derived from regenerated cellulose, and therefore it is possible to effectively use appropriate regenerated cellulose, including cellophane and other materials that are difficult to recycle, as a raw material to produce a cellulose molded body.

[0031] According to the ninth invention, in the method for producing a cellulose molded body derived from regenerated cellulose, in the eighth invention, the degree of polymerization of the regenerated cellulose in the dispersion liquid raw material is 600 or less, so that the degree of polymerization of the regenerated cellulose, which is the dispersion liquid raw material, is reduced to a certain level in advance, thereby shortening the time required for each process and improving production efficiency.

[0032] According to the tenth invention, the method for producing a cellulose molded body derived from regenerated cellulose, in the eighth or ninth invention, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite with an effective chlorine concentration of 0.13% or more in the depolymerization process, thereby efficiently reducing the degree of polymerization of the regenerated cellulose.

[0033] According to the method for producing a cellulose molded body derived from regenerated cellulose of the 11th invention, in the 8th or 9th invention, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite with an effective chlorine concentration of 3% or more in the depolymerization process, so that the degree of polymerization of the regenerated cellulose can be efficiently reduced.

[0034] According to the 12th invention, the cellulose beads derived from regenerated cellulose are a cellulose molded body obtained by the manufacturing method of the 10th invention, and the cellulose molded body is a cellulose bead, and since the average particle diameter (D50) is 50 μm or less, the cellulose beads have good slip properties and a good texture with little roughness or squeaking.

[0035] According to the 13th invention, there is provided a cellulose-based cellulose bead, which is a cellulose molded body obtained by the manufacturing method of the 11th invention, and the cellulose molded body is a cellulose bead, and since the average particle diameter (D50) is 10 μm or less, the cellulose beads have good slipperiness and are less rough and squeaky, resulting in a better texture.

[0036] According to the cellulose molded body derived from regenerated cellulose of the 14th invention, which is a cellulose molded body obtained by the manufacturing method of the 10th invention, 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, so that the molecular weight distribution index (Mw / Mn) is sharp and uniform, resulting in finely divided cellulose, which has better processability, and therefore it is possible to provide a cellulose molded body derived from regenerated cellulose with a small particle size.

[0037] According to the 15th invention, the cellulose molded body derived from regenerated cellulose is a cellulose molded body obtained by the manufacturing method of the 11th invention, and has a 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) of 1.6 or less, so that the molecular weight distribution index (Mw / Mn) becomes sharper and more uniform in the finely divided cellulose, and it has better processability, so that a cellulose molded body derived from regenerated cellulose with a small particle size can be provided.

[0038] FIG. 1 is a schematic process diagram of a method for producing a cellulose dispersion derived from regenerated cellulose and a cellulose molded body according to one embodiment of the present invention.

[0039] A method 10 for producing a cellulose dispersion derived from regenerated cellulose according to one embodiment of the present invention, shown in the schematic process diagram of Figure 1, is a method for producing a cellulose dispersion 11 using regenerated cellulose as a raw material. The method for producing this cellulose dispersion 10 includes a grinding step (S1), a depolymerization step (S2), and a micronization step (S3). A method 20 for producing a cellulose molded body derived 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) of the cellulose dispersion produced by the production method of the present invention. The lower the degree of polymerization of regenerated cellulose, the easier it is to defibrate and process the cellulose, thereby improving production efficiency. If the degree of polymerization of regenerated cellulose is too high, the cellulose may become difficult to defibrate, making it difficult to produce a cellulose dispersion or a cellulose molded body. For this reason, the degree of polymerization of the regenerated cellulose used as the dispersion raw material is desirably 600 or less. Generally, the degree of polymerization of regenerated cellulose produced by the viscose method is approximately 200 to 300, making it suitable for use as a raw material in the production method of the present invention. Furthermore, the degree of polymerization of regenerated cellulose obtained by a production method of regenerated cellulose using a cellulose solvent such as an ionic liquid is approximately 600, making it suitable as a raw material in the production method of the present invention.

[0041] The regenerated cellulose used as the dispersion raw material can be a material produced by a known method and having an appropriate form such as fiber, film, or sphere, or a regenerated cellulose product obtained by processing the produced regenerated cellulose. These regenerated celluloses are type II celluloses having a type II crystalline structure.

[0042] Examples of methods for producing regenerated cellulose include a method such as the viscose method in which cellulose fibers are chemically derivatized and then dissolved in a solvent, and a method in which cellulose fibers are dissolved in an ionic liquid. Examples of regenerated cellulose products include paper products, clothing, and hygiene products made from molded articles such as rayon, cellophane, and cellulose beads.

[0043] When regenerated cellulose is used as a dispersion liquid raw material, it is preferable to use regenerated cellulose products, etc. as recycled raw materials from the viewpoint of reducing the environmental burden. Regenerated cellulose recycled raw materials also include scraps, etc. generated during the manufacturing process of regenerated cellulose molded bodies, products, etc. Since regenerated cellulose products and scraps, etc. have traditionally been discarded as materials that are difficult to recycle, using them as recycled raw materials can greatly contribute to reducing the environmental burden.

[0044] The pulverization step (S1) is a step in which regenerated cellulose, a dispersion liquid raw material, is pulverized to obtain a pulverized raw material. This pulverization step aims to improve the reactivity of the regenerated cellulose (pulverized raw material) in the depolymerization step (S2) described below by pulverizing the regenerated cellulose, a dispersion liquid raw material, to a finer particle size. The pulverized raw material obtained in the pulverization step is preferably pulverized to a size of 500 μm or less. The size of the regenerated cellulose is measured using a laser diffraction / scattering particle size distribution analyzer in accordance with JIS Z 8825 (2013). If the pulverized regenerated cellulose is too large, it may not be reactive enough in the depolymerization step (S2) described below, resulting in reduced productivity. In this pulverization step, known pulverization methods such as dry pulverization and wet pulverization can be used as appropriate.

[0045] The depolymerization step (S2) is a step in which the pulverized raw material obtained in the pulverization step is depolymerized to obtain depolymerized cellulose with a degree of polymerization reduced to 350 or less. This depolymerization step weakens the structure of the pulverized regenerated cellulose by depolymerizing the pulverized raw material, thereby making the cellulose more easily defibrated (depolymerized cellulose). The depolymerized cellulose obtained in the depolymerization step is adjusted to a degree of polymerization of 350 or less using chemicals such as sodium hypochlorite, enzymes, or the like. If the degree of polymerization of the depolymerized cellulose is too high, there is a risk that the defibration ability in the micronization step (S3) described below will be insufficient, resulting in reduced productivity.

[0046] In the depolymerization step, sodium hypochlorite is preferably used to depolymerize the pulverized raw material. Sodium hypochlorite oxidizes the hydroxyl groups at the 2- and 3-positions of cellulose, depolymerizing the cellulose through a β-alkoxy elimination reaction caused by the carbonyl groups. Sodium hypochlorite is preferably used because it is easy to handle and can efficiently reduce the degree of polymerization of regenerated cellulose by controlling the pH and temperature. Furthermore, the higher the concentration of sodium hypochlorite, the more easily it reduces the degree of polymerization of regenerated cellulose. In particular, when the effective chlorine concentration is 0.13% or higher, more preferably 3% or higher, the degree of polymerization of regenerated cellulose can be more efficiently reduced.

[0047] The micronization step (S3) is a step in which the depolymerized cellulose obtained in the depolymerization step is defibrated and micronized to form micronized cellulose, thereby obtaining a cellulose dispersion 11. The depolymerized cellulose is defibrated by mechanical (physical) defibration. The mechanical (physical) defibration is performed by a known method using a homogenizer, a water jet, or the like. The micronized cellulose obtained in this manner is in the form of a dispersion of chemically unmodified (unmodified) cellulose fine particles, since it has not been subjected to defibration using chemicals (chemical defibration).

[0048] Here, the regenerated cellulose, which is the raw material for the dispersion, has a reduced degree of polymerization due to the depolymerization process, and can be easily defibrated and pulverized without the application of high pressure. This ease of pulverizing depolymerized cellulose is advantageous in terms of equipment for the pulverization process.

[0049] The micronization of depolymerized cellulose may be performed in multiple steps. For example, by pre-defibrating using a mixer and then performing main defibration using a homogenizer, uniform micronized cellulose with a small particle size can be obtained. Furthermore, pre-defibrating reduces problems such as clogging of the defibration device, which is beneficial from the perspective of equipment protection. Pre-defibration is performed using a mixer, refiner, or the like, and is carried out by known methods. Micronization of depolymerized cellulose is sufficient as long as the average particle size is reduced to nanometers or several hundred nanometers. Setting the average particle size to approximately 2 to 800 nm, preferably 500 nm or less, improves the transparency of the micronized cellulose dispersion (cellulose dispersion). Cellulose dispersions can be used as coating agents by being applied to films, paper, and other three-dimensional objects, and highly transparent dispersions are suitable for such purposes. Furthermore, the high transparency of cellulose dispersions also enhances processability when formed into cellulose molded bodies.

[0050] The molding step (S4) is a step in which the cellulose dispersion (micronized cellulose) obtained in the micronization step is dried to obtain a cellulose molded body 21. The micronized cellulose in the form of a dispersion is dried and coagulated by spray drying, and molded into a granular (beaded) molded body. This molded body is derived from regenerated cellulose, since it is molded using regenerated cellulose as the dispersion raw material. In the molding step, the viscosity of the cellulose dispersion, measured using a Brookfield viscometer at a shear rate of 4.0 / sec in accordance with JIS Z 8803 (2011), is preferably 15,000 mPa·s or less. If the viscosity of the cellulose dispersion is higher than 15,000 mPa·s, the fluidity of the solution decreases, and there is a risk of clogging the liquid supply pipe to the spray drying apparatus or the spray drying nozzle.

[0051] The spray-drying conditions are an air pressure of 0.025 to 0.6 MPa. If the air pressure during spray drying is insufficient, the cellulose microparticles will not be refined and the particle size will increase, resulting in poor physical properties and texture. Furthermore, if the air pressure is higher than 0.6 MPa, the air generator will be too large and this is not practical.

[0052] Furthermore, in the method for producing a cellulose shaped body derived from regenerated cellulose according to the present invention, a collection step (S5) is optionally carried out after the molding step (S4). The collection step is a step of removing unnecessary particles from the granular cellulose shaped body (cellulose beads) formed in the molding step to recover a cellulose shaped body of suitable particles. The collection means is not particularly limited as long as it is capable of recovering suitable particles, and collection can be carried out by known collection means such as a bag filter or a cyclone dust collector.

[0053] Thus, in the manufacturing method of the present invention, the regenerated cellulose dispersion raw material is pulverized to 500 μm or less in the pulverization step (S1) to obtain the pulverized raw material, the degree of polymerization of the pulverized raw material is adjusted to 350 or less in the depolymerization step (S2), a cellulose dispersion is obtained in the micronization step (S3), and a cellulose molded body is obtained through the molding step (S4). Therefore, a cellulose dispersion or a cellulose molded body can be obtained using regenerated cellulose as the dispersion raw material. In particular, cellophane, which has traditionally been difficult to recycle, can be used as a recycled raw material for the dispersion raw material, which significantly contributes to reducing the environmental impact. Furthermore, because this regenerated cellulose-derived cellulose molded body is a molded body of unmodified cellulose that has not undergone chemical defibration, the amount of environmentally harmful chemicals used can be reduced compared to conventional cellulose molded bodies.

[0054] In the cellulose dispersion or molded article derived from regenerated cellulose obtained by the production method of the present invention, sodium hypochlorite having an effective chlorine concentration of 0.13% or more, preferably 3% or more, is preferably used in the depolymerization step.

[0055] As the available chlorine concentration of sodium hypochlorite increases, the cationic demand of the cellulose dispersion increases. The cationic demand refers to the amount of cationic chemical required to neutralize negatively charged particles in the colloid and fine particle dispersion region (particle diameter 1 nm to several hundred μm) to an equal charge, and is an indicator of the dispersibility of cellulose fine particles in the cellulose dispersion. The greater the cationic demand, the better the dispersibility, and the more uniform the cellulose dispersion. The cationic demand of the cellulose dispersion is preferably 4.0 μeq / gcell or more per gram of cellulose, and more preferably 50.0 μeq / gcell or more.

[0056] Cellulose dispersions can be used as coating agents for films, sheets, resin molded products, etc., and can impart various functions such as improved strength, gas barrier properties, hydrophilicity, etc. Therefore, if the cellulose dispersion has good dispersibility, when it is used as a coating agent, it is advantageous because the coating layer tends to be uniform, the functionality is imparted well, and handling is improved.

[0057] Furthermore, as the effective chlorine concentration of sodium hypochlorite increases, the molecular weight distribution index (Mw / Mn), calculated 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 index of the sharpness of the molecular weight distribution, and the sharper the molecular weight distribution, the better the processability and the smaller the particle size of the cellulose molded body can be. The molecular weight distribution index (Mw / Mn) of the cellulose molded body is set to 3.5 or less, and more preferably, the molecular weight distribution index (Mw / Mn) is set to 1.6 or less.

[0058] In particular, for cellulose molded bodies that are cellulose beads, when the available chlorine concentration of sodium hypochlorite in the depolymerization process is 0.13% or higher, the average particle diameter (D50) at 50% cumulative value in the particle size distribution is 50 μm or less, and more preferably, when the available chlorine concentration of sodium hypochlorite is 3% or higher, the average particle diameter (D50) is 10 μm or less. The average particle diameter (D50) is the median diameter, and when this average particle diameter (D50) is 50 μm or less, the cellulose beads have good slipperiness and a good texture with little roughness or squeaking, and when the average particle diameter (D50) is 10 μm or less, an even better texture is obtained.

[0059] [Preparation of regenerated cellulose-derived cellulose dispersion and shaped article] The regenerated cellulose-derived cellulose dispersion and shaped article of each of the following prototype examples and comparative examples were prepared under the following conditions according to the process diagram of FIG.

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

[0061] <Prototype Example 1> Regenerated cellulose 1 (C1) was crushed to 500 μm using a hammer crusher (manufactured by Sansho Industry Co., Ltd.) (crushing step). 200 ml of sodium hypochlorite (1% solution, effective chlorine concentration 0.13%) was added to 8 g of the crushed raw material obtained by crushing and reacted in a water bath at 55 °C for 30 minutes to obtain depolymerized cellulose with a degree of polymerization reduced to 196 (depolymerization step). The depolymerized cellulose obtained by depolymerization was washed with ion-exchanged water, and 400 ml of ion-exchanged water was added to form a dispersion. This dispersion was then pre-defibrated using a mixer (manufactured by Primix Corporation). The mixture was then pulverized using a homogenizer (manufactured by SMT Co., Ltd.) at a pressure of 70 MPa to obtain a cellulose dispersion derived from regenerated cellulose (Prototype Example 1). The cellulose dispersion was spray-dried using a spray dryer (manufactured by Tokyo Rikakikai Co., Ltd.) at an air pressure of 0.2 MPa (throughput 300 ml / hr) (molding step). The particles were collected using a cyclone dust collector (manufactured by Tokyo Rikakikai Co., Ltd.) (collection step), and a cellulose molded article derived from regenerated cellulose of Prototype Example 1 was obtained.

[0062] <Prototype Example 2> The procedure was the same as that of prototype example 1, except that the depolymerized cellulose used in the depolymerization step was a 10% solution of sodium hypochlorite, an effective chlorine concentration of 1.30%, and a degree of polymerization reduced to 74. A cellulose dispersion derived from regenerated cellulose and a cellulose molded body derived from regenerated cellulose for prototype example 2 were obtained.

[0063] <Prototype Example 3> The procedure was the same as that of prototype example 1, except that the depolymerized cellulose in the depolymerization step was a 20% solution of sodium hypochlorite, an effective chlorine concentration of 3.00%, and a degree of polymerization was reduced to 62, to obtain a cellulose dispersion derived from regenerated cellulose and a cellulose molded body derived from regenerated cellulose for prototype example 3.

[0064] <Prototype Example 4> A cellulose dispersion derived from regenerated cellulose and a cellulose molded article derived from regenerated cellulose were obtained in the same manner as in Example 1, except that the sodium hypochlorite used in the depolymerization step was a 100% solution, the effective chlorine concentration was 12.00%, and the depolymerized cellulose had a degree of polymerization reduced to 38. The viscosity was measured using a B-type viscometer (manufactured by Eiko Seiki Co., Ltd.) at a shear rate of 4.0 / sec, a measurement temperature of 25°C, and a measurement time of 1 minute, and was 13,607 mPa s.

[0065] <Prototype Example 5> A cellulose dispersion derived from regenerated cellulose and a cellulose molded article derived from regenerated cellulose were obtained in the same manner as in Example 1, except that the dispersion raw material used was regenerated cellulose 2 (C2). The degree of polymerization of the depolymerized cellulose obtained in the depolymerization step was 326.

[0066] <Prototype Example 6> A cellulose dispersion derived from regenerated cellulose and a cellulose molded article derived from regenerated cellulose were obtained in the same manner as in Type 4, except that the dispersion raw material used was regenerated cellulose 2 (C2). The degree of polymerization of the depolymerized cellulose obtained in the depolymerization step was 47.

[0067] Comparative Example 1 Comparative Example 1 was prepared in the same manner as Prototype Example 1, except that the depolymerization step was not carried out.

[0068] Comparative Example 2 Comparative Example 2 was the same as Prototype Example 1 except that the depolymerization step, the micronization step, and the molding step were not carried out.

[0069] Comparative Example 3 Comparative Example 3 was prepared in the same manner as Prototype Example 5, except that the depolymerization step, the micronization step, and the molding step were not carried out.

[0070] To evaluate the performance of Prototype Examples 1 to 6 and Comparative Examples 1 to 3, the average particle size (D50) and molecular weight distribution index were measured.

[0071] [Cation Demand] A particle charge meter (PCD-06 Premium, manufactured by Voith Turbo K.K.) was used to measure the cation demand. The regenerated cellulose-derived cellulose dispersions of the prototypes and comparative examples were diluted to an arbitrary concentration, and 10 mL of each was added to the apparatus. A 1 / 400 N DADMAC (diallyldimethylammonium chloride) solution was added dropwise to measure the amount of titrant consumed until the charge was neutralized. The dilution rate of each sample was adjusted so that the amount of titrant consumed was 1 to 5 mL. The cation demand (μeq / L) was calculated using the following formula (i), and converted to the cation demand per gram of cellulose (μeq / g-cell) using the following formula (ii):

[0072]

[0073]

[0074] [Average Particle Diameter (D50)] The average particle diameter (D50) was measured in accordance with JIS Z 8825 (2013). A laser diffraction / scattering particle size distribution analyzer ("MT3200II" manufactured by Microtrac-Bell Corporation) was used for the measurement. First, a slurry prepared by mixing the cellulose samples of the prototype and comparative examples with ion-exchanged water was filled into a sample circulator. The slurry was stirred immediately before supply to a level where no unevenness was visible to the naked eye. The slurry was then supplied to the measuring device, and the particle diameter (D50) corresponding to 50% of the cumulative particle size distribution (volume basis) was measured using the following measurement parameters: a refractive index of 1.33 for ion-exchanged water, light transmittance of the particles to be measured, and a measurement time of 10 seconds.

[0075] [Molecular weight distribution index (Mw / Mn)] The cellulose samples according to the prototypes and comparative examples were added to a sample bottle with a TBAA / DMSO mixed solvent so that the cellulose concentration was 0.1% by weight, and the mixture was dissolved by mixing overnight at room temperature. The prepared samples were subjected to HPLC analysis (detector: RID (Shimadzu Corporation, "RID-10A"), column temperature 50°C, eluent 0.6 ml / min) using an organic solvent SEC (GPC) column (Resonac Corporation, "KD-804" and "KD-805" connected). The TBAA / DMSO mixed solvent was used as the eluent.

[0076] [Degree of Polymerization] The degree of polymerization was measured by the viscosity method using a copper ethylenediamine solution as follows. A dried cellulose sample was dissolved in a 0.5 M copper ethylenediamine solution (solution 1) to prepare solution 2. The viscosities of solution 1 and solution 2 were measured using a capillary viscometer. The viscosity of viscosity 1 was calculated as η １ , the viscosity of solution 2 is η ２ The intrinsic viscosity [η] of the cellulose sample was calculated using the following formula, and the degree of polymerization (DP) was calculated. c is the concentration (g / L) of the cellulose sample. Intrinsic concentration [η] = {(η ２ / η １ )-1} / c Degree of polymerization DP=Ultimate concentration [η] / (8.8×10 －４ )

[0077]

[0078]

[0079] [Results and Discussion] The cellulose dispersions of Prototype Examples 1 to 6 all had a higher cationic demand than the cellulose dispersions of Comparative Examples 1 to 3, indicating that the cellulose microparticles were well dispersed in the cellulose dispersions due to the micronization process. In comparing the cellulose dispersions of Prototype Examples 1 to 4 with the cellulose dispersions of Comparative Examples 1 and 2, the cellulose dispersion of Prototype Example 1 had a cationic demand that was about twice that of the cellulose dispersion of Comparative Example 1, which had not undergone the depolymerization process, and about four times that of the cellulose dispersion of Comparative Example 2, which had not undergone the depolymerization process, micronization process, and molding process, demonstrating extremely superior results in terms of the dispersibility of the cellulose microparticles.

[0080] Furthermore, compared with the cellulose dispersions of Prototype Examples 1 to 4, it was shown that increasing the sodium hypochlorite concentration further increased the cationic demand, leading to easier and more satisfactory defibration of cellulose. When the available chlorine concentration of sodium hypochlorite is particularly 0.13% or higher, the cationic demand is 4.0 μeq / gcell or higher per 1 g of cellulose, and more preferably, when the available chlorine concentration is 3% or higher, the cationic demand is 50.0 μeq / gcell or higher per 1 g of cellulose, making it suitable for use as a coating agent for molded articles such as films.

[0081] When the cellulose dispersions of prototypes 5 and 6, which used regenerated cellulose prepared using a cellulose solvent such as an ionic liquid as the dispersion raw material, were compared with the cellulose dispersion of comparative example 3, the trends were similar to those of the cellulose dispersions of prototypes 1 to 4 and the cellulose dispersions of comparative examples 1 and 2, demonstrating that high-quality cellulose dispersions can be obtained by the manufacturing method of the present invention even when different regenerated celluloses are used as the dispersion raw material.

[0082] The cellulose molded bodies of Prototype Examples 1 to 6 all had smaller average particle diameters (D50) than the cellulose molded bodies of Comparative Examples 1 to 3, indicating that the cellulose was well defibrated by the refining process. Comparing the cellulose molded bodies of Prototype Examples 1 to 4 with the cellulose molded bodies of Comparative Examples 1 and 2, the cellulose molded body of Prototype Example 1 had an average particle diameter (D50) that was less than half that of the cellulose molded body of Comparative Example 1, which had not undergone the depolymerization process, refining process, and molding process, and was about one-fifth that of the cellulose molded body of Comparative Example 2, which had not undergone the depolymerization process, refining process, and molding process.

[0083] It was also shown that by increasing the sodium hypochlorite concentration, the average particle size (D50) becomes smaller, making cellulose defibration easier and better. When the effective chlorine concentration of sodium hypochlorite is particularly 0.13% or more, the average particle size (D50) becomes 50 μm or less, and more preferably, when the effective chlorine concentration is 3% or more, the average particle size (D50) becomes 10 μm or less, so that the cellulose beads can be of good quality for use in cosmetics, etc.

[0084] Furthermore, in the cellulose molded bodies of prototypes 5 and 6 and the cellulose molded body of comparison example 3, which used regenerated cellulose produced using a cellulose solvent such as ionic liquid as the dispersion liquid raw material, the cellulose molded bodies of prototypes 5 and 6, which also underwent the depolymerization and micronization processes, showed good results, with the average particle size (D50) of the cellulose molded body of prototype 5 being less than 1 / 10 and the cellulose molded body of prototype 6 being less than 1 / 100, compared to the cellulose molded body of comparison example 3.Therefore, it is believed that there are no restrictions on the manufacturing method of the regenerated cellulose used as the raw material, and that there are no restrictions on the regenerated cellulose used as the raw material.

[0085] Next, the molecular weight distribution index (Mw / Mn) of the cellulose molded bodies of Prototype Examples 1 to 6 was smaller than that of Comparative Examples 1 to 3, which indicates that the cellulose molded bodies obtained by the manufacturing method of the present invention have a sharp and homogeneous molecular weight distribution. In the depolymerization step, when the available chlorine concentration of sodium hypochlorite is greater than 1.30%, the molecular weight distribution index (Mw / Mn) becomes particularly good.

[0086] According to the method for producing a cellulose dispersion derived from regenerated cellulose and a cellulose molded body of the present invention, a cellulose dispersion or a cellulose molded body can be produced using regenerated cellulose containing difficult-to-recycle cellophane as a raw material, thereby significantly contributing to reducing the environmental burden. Furthermore, the resulting cellulose dispersion has high dispersibility of cellulose microparticles, resulting in homogeneous and high-quality results when used in coating agents, etc. Furthermore, because the cellulose molded body obtained by the production method of the present invention has fine and homogeneous particles, it is a promising alternative to microplastics and chemically modified cellulose beads used in conventional cosmetics.

[0087] REFERENCE SIGNS LIST 10: METHOD FOR PRODUCING A cellulose dispersion derived from regenerated cellulose 11: CELLULOSE DISPERSION 20: METHOD FOR PRODUCING A cellulose-formed body derived from regenerated cellulose 21: CELLULOSE FORMED BOD S1: CRACKING PROCESS S2: DEPOLYMERIZATION PROCESS S3: MICROFIBER PROCESS S4: FORMING PROCESS S5: CAPTURE PROCESS

Claims

1. A method for producing a cellulose dispersion derived from regenerated cellulose, comprising the steps of: using regenerated cellulose as a dispersion raw material; grinding the dispersion raw material; depolymerizing the ground raw material obtained by the grinding process to reduce the degree of polymerization to 350 or less; and micronizing the depolymerized cellulose obtained by the depolymerization process to obtain a cellulose dispersion.

2. A method for producing a cellulose dispersion derived from regenerated cellulose as described in claim 1, wherein the degree of polymerization of the regenerated cellulose in the dispersion raw material is 600 or less.

3. A method for producing a cellulose dispersion derived from regenerated cellulose as described in claim 1 or 2, wherein in the depolymerization step, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite having an effective chlorine concentration of 0.13% or more.

4. A method for producing a cellulose dispersion derived from regenerated cellulose as described in claim 1 or 2, wherein in the depolymerization step, the degree of polymerization of the ground raw material is reduced by sodium hypochlorite having an effective chlorine concentration of 3% or more.

5. A cellulose dispersion obtained by the process according to claim 1 or 2, having a cationic demand of 4.0 μeq / gcell or more per gram of cellulose.

6. A cellulose dispersion obtained by the process according to claim 3, having a cationic demand of 4.0 μeq / gcell or more per gram of cellulose.

7. A cellulose dispersion obtained by the method according to claim 4, having a cationic demand of 50.0 μeq / gcell or more per gram of cellulose.

8. A method for producing a cellulose molded body derived from regenerated cellulose, comprising the steps of drying and molding the cellulose dispersion obtained by the method according to claim 1 to obtain a cellulose molded body derived from regenerated cellulose.

9. The method for producing a cellulose molded article derived from regenerated cellulose according to claim 8, wherein the degree of polymerization of the regenerated cellulose in the dispersion liquid raw material is 600 or less.

10. A method for producing a cellulose molded body derived from regenerated cellulose as described in claim 8 or 9, wherein the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite having an effective chlorine concentration of 0.13% or more in the depolymerization process.

11. A method for producing a cellulose molded body derived from regenerated cellulose as described in claim 8 or 9, wherein the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite having an effective chlorine concentration of 3% or more in the depolymerization step.

12. A cellulose molded body obtained by the manufacturing method described in claim 10, the cellulose molded body being cellulose beads derived from regenerated cellulose, the average particle diameter (D50) being 50 μm or less.

13. A cellulose molded body obtained by the manufacturing method described in claim 11, said cellulose molded body being cellulose beads derived from regenerated cellulose, the average particle size (D50) of which is 10 μm or less.

14. A cellulose molded body obtained by the manufacturing method described in claim 10, which is derived from regenerated cellulose and has a molecular weight distribution index (Mw / Mn) of 3.5 or less, calculated by dividing the weight average molecular weight (Mw) of the cellulose molded body by the number average molecular weight (Mn).

15. A cellulose molded body derived from regenerated cellulose obtained by the manufacturing method described in 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 1.6 or less.

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