Method for producing cellulose beads derived from regenerated cellulose and cellulose beads derived from regenerated cellulose

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

[Technical Field]

[0001] The present invention relates to cellulose derived from regenerated cellulose. beads Manufacturing method of regenerated cellulose and cellulose derived from regenerated cellulose beads Regarding. [Background technology]

[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, circular society. A well-known example of an environmentally friendly initiative 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. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2016-537461 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[0008] That is, the first invention is: a pulverization step of pulverizing cellophane having a degree of polymerization of 600 or less as a dispersion liquid raw material; a depolymerization step of reducing the degree of polymerization of the pulverized material obtained by the pulverization step to 350 or less with sodium hypochlorite having an effective chlorine concentration of 0.13% or more; and a micronization step of micronizing the depolymerized cellulose obtained by the depolymerization step to obtain a cellulose dispersion having a cation demand of 4.0 μeq / g-cell or more per gram of cellulose. The cellulose dispersion is dried and molded. Cellulose beads derived from regenerated cellulose with an average particle size (D50) of 50 μm or less and a molding step for obtaining a cellulose derived from regenerated cellulose. beads This relates to a manufacturing method of the above.

[0009] No. 2 The invention is 1 In the invention, in the depolymerization step, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite having an effective chlorine concentration of 3% or more. The cation demand of the cellulose dispersion obtained by the micronization step is 50.0 μeq / g-cell or more per 1 g of cellulose, and the average particle size (D50) of the cellulose beads derived from regenerated cellulose obtained by the molding step is 10 μm or less. The present invention relates to a method for producing a cellulose molded article derived from regenerated cellulose.

[0010] No. 3 The invention is 1 Cellulose obtained by the manufacturing method of the present invention beads The cellulose beads Cellulose derived from regenerated cellulose, having a molecular weight distribution index (Mw / Mn) of 3.5 or less, obtained by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn) of beads relates to.

[0011] No. 4 The invention is 2 Cellulose obtained by the manufacturing method of the present invention beads The cellulose beads Cellulose derived from regenerated cellulose, having a molecular weight distribution index (Mw / Mn) of 3.5 or less, obtained by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn) of beads relates to. [Effects of the Invention]

[0012] Cellulose derived from regenerated cellulose according to the first invention beads According to the manufacturing method of a pulverization step of pulverizing cellophane having a degree of polymerization of 600 or less as a dispersion liquid raw material; a depolymerization step of reducing the degree of polymerization of the pulverized material obtained by the pulverization step to 350 or less with sodium hypochlorite having an effective chlorine concentration of 0.13% or more; and a micronization step of micronizing the depolymerized cellulose obtained by the depolymerization step to obtain a cellulose dispersion having a cation demand of 4.0 μeq / g-cell or more per gram of cellulose. The cellulose dispersion is dried and molded. Cellulose beads derived from regenerated cellulose with an average particle size (D50) of 50 μm or less This involves a molding process to obtain cellophane, which is difficult to recycle. of Effectively used as a dispersion material The degree of polymerization of cellophane, which is the raw material for the dispersion, is reduced to a certain level in advance, which shortens the time required for each process. It is possible to improve production efficiency, efficiently cellulose beads can be manufactured At the same time, the cellulose beads have good slipperiness and a good texture with little roughness or squeaking. .

[0013] No. 2 Cellulose derived from regenerated cellulose according to the present invention beads According to the manufacturing method, 1 In the invention, in the depolymerization step, the degree of polymerization of the pulverized raw material is reduced by sodium hypochlorite having an effective chlorine concentration of 3% or more. The cation demand of the cellulose dispersion obtained by the micronization step is 50.0 μeq / g-cell or more per 1 g of cellulose, and the average particle size (D50) of the cellulose beads derived from regenerated cellulose obtained by the molding step is 10 μm or less. Therefore, the degree of polymerization of regenerated cellulose can be reduced more efficiently. This reduces the degree of polymerization of the regenerated cellulose, which is the raw material for the dispersion, to a certain degree in advance, shortening the time required for each process and improving production efficiency.In addition, the cellulose beads have good slipperiness and are less rough and squeaky, resulting in a better texture.

[0014] No. 3 Cellulose derived from regenerated cellulose according to the present invention beads According to the1 Cellulose obtained by the manufacturing method of the present invention beads The cellulose beads The molecular weight distribution index (Mw / Mn) obtained by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn) is 3.5 or less, so the molecular weight distribution index (Mw / Mn) is sharp and uniform, resulting in finely divided cellulose, which has excellent processability and is therefore a regenerated cellulose-derived cellulose with a fine particle size. beads can be provided.

[0015] No. 4 Cellulose derived from regenerated cellulose according to the present invention beads According to the 2 Cellulose obtained by the manufacturing method of the present invention beads The cellulose beads The molecular weight distribution index (Mw / Mn) obtained by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn) is 1.6 or less, so the molecular weight distribution index (Mw / Mn) is sharper and more uniform, resulting in finely divided cellulose with better processability, making it a regenerated cellulose-derived cellulose with a fine particle size. beads can be provided. [Brief explanation of the drawings]

[0016] [Figure 1] 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. DETAILED DESCRIPTION OF THE INVENTION

[0017] 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. 11 The method for producing a cellulose molded article (20) from regenerated cellulose includes a pulverization step (S1), a depolymerization step (S2), and a micronization step (S3). The method for producing a cellulose molded article (20) from regenerated cellulose further includes a molding step (S4) to obtain a cellulose molded article (21).

[0018] 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.

[0019] 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, etc. These regenerated celluloses are type II celluloses having a type II crystalline structure.

[0020] 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.

[0021] 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.

[0022] The pulverization step (S1) is a step in which regenerated cellulose, a raw material for the dispersion, 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 raw material for the dispersion, 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 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.

[0023] 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, 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 or enzymes. If the polymerization degree 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.

[0024] 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, an effective chlorine concentration of 0.13% or higher, more preferably an effective chlorine concentration of 3% or higher, can more efficiently reduce the degree of polymerization of regenerated cellulose.

[0025] 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 is not defibrated using chemicals (chemical defibration).

[0026] 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.

[0027] 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 can prevent 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 hundreds of 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 applying them to films, paper, and other three-dimensional objects, and highly transparent dispersions are suitable for coating agents. Furthermore, the high transparency of cellulose dispersions also improves processability when they are made into cellulose molded bodies.

[0028] 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 B-type 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 device and the spray drying nozzle.

[0029] 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.

[0030] Furthermore, in the method for producing a cellulose shaped body derived from regenerated cellulose according to the present invention, a collection step (S5) is carried out after the molding step (S4) as needed. 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 possible to recover suitable particles, and collection can be carried out by known collection means such as a bag filter or a cyclone dust collector.

[0031] 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). A cellulose molded body is then obtained through the molding step (S4). This allows for the production of a cellulose dispersion or a cellulose molded body using regenerated cellulose as the dispersion raw material. In particular, cellophane, which has traditionally been difficult to recycle, can be recycled as a dispersion raw material, significantly contributing 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.

[0032] 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.

[0033] 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 agent 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 index of the dispersibility of cellulose fine particles in the cellulose dispersion. The larger the cationic demand, the better the dispersibility, and the more uniform the cellulose dispersion. The cationic demand of a cellulose dispersion is 4.0 per 1 g of cellulose. μeq / g-cell More preferably, 50.0 μeq / g-cell It is best to consider this as the above.

[0034] 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.

[0035] Furthermore, as the effective chlorine concentration of sodium hypochlorite increases, the molecular weight distribution index (Mw / Mn) of the cellulose molded body, calculated by dividing the weight-average molecular weight (Mw) 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 preferably 3.5 or less, and more preferably 1.6 or less.

[0036] 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% of the 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. [Example]

[0037] [Preparation of regenerated cellulose-derived cellulose dispersion and molded body] The cellulose dispersions derived from regenerated cellulose and the molded articles of the following prototype examples and comparative examples were produced under the following conditions according to the process diagram of FIG.

[0038] The following raw materials were used for the regenerated cellulose. Cellophane film produced by the viscose method (Futamura Chemical Co., Ltd., "PUT") was designated as regenerated cellulose 1 (C1). Ground dissolving pulp was added to a TBAA / DMSO mixed solvent to a concentration of 10%. The contents were heated to 50°C or higher and dissolved in a kneader (Seiwa Giken Co., Ltd.). The resulting cellulose solution was extruded into a film form from a T-die (Plastic 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.

[0039] <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 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 of 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.

[0040] <Prototype example 2> The procedure was the same as in prototype 1, except that the depolymerization step used a 10% solution of sodium hypochlorite, an effective chlorine concentration of 1.30%, and depolymerized cellulose whose degree of polymerization had been reduced to 74. A cellulose dispersion derived from regenerated cellulose and a cellulose molded body derived from regenerated cellulose were obtained in prototype 2.

[0041] <Prototype example 3> The procedure was the same as in prototype 1, except that the depolymerization step used a 20% solution of sodium hypochlorite, an effective chlorine concentration of 3.00%, and depolymerized cellulose whose degree of polymerization had been reduced to 62. A cellulose dispersion derived from regenerated cellulose and a cellulose molded body derived from regenerated cellulose were obtained in prototype 3.

[0042] <Prototype example 4> The procedure was the same as in Prototype 1, except that the sodium hypochlorite used in the depolymerization step was a 100% solution, the available chlorine concentration was 12.00%, and the depolymerized cellulose had a degree of polymerization reduced to 38. The regenerated cellulose-derived cellulose dispersion and regenerated cellulose-derived cellulose molded product of Prototype 4 were obtained. 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.

[0043] <Prototype example 5> The procedure was the same as in Example 1, except that the dispersion raw material used was regenerated cellulose 2 (C2), and a cellulose dispersion derived from regenerated cellulose and a cellulose molded article derived from regenerated cellulose were obtained as Example 5. The degree of polymerization of the depolymerized cellulose obtained in the depolymerization step was 326.

[0044] <Prototype Example 6> The procedure was the same as in Example 4, except that the dispersion raw material used was regenerated cellulose 2 (C2), and a cellulose dispersion derived from regenerated cellulose and a cellulose molded article derived from regenerated cellulose were obtained as Example 6. The degree of polymerization of the depolymerized cellulose obtained in the depolymerization step was 47.

[0045] <Comparative Example 1> This was treated as Comparative Example 1 in the same manner as Prototype 1 except that the depolymerization step was not carried out.

[0046] <Comparative Example 2> Comparative Example 2 was prepared in the same manner as Prototype Example 1, except that the depolymerization step, the pulverization step, and the molding step were not carried out.

[0047] <Comparative Example 3> This was treated as Comparative Example 3 in the same manner as Prototype Example 5, except that the depolymerization step, the pulverization step, and the molding step were not carried out.

[0048] 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.

[0049] [Cation demand] A particle charge meter (PCD-06 Premium, manufactured by Voith Turbo Co., Ltd.) was used to measure the cation demand. The regenerated cellulose-derived cellulose dispersions of the prototypes and comparative examples were diluted to the desired concentration, and 10 mL of each was placed in the device. A 1 / 400 N DADMAC (diallyldimethylammonium chloride) solution was added dropwise, and the amount of titrant consumed until the charge was neutralized was measured. 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).

[0050]

number

[0051]

number

[0052] [Average particle diameter (D50)] The average particle size (D50) was measured in accordance with JIS Z 8825 (2013). A laser diffraction / scattering particle size analyzer (Microtrac-Bell Corporation, "MT3200II") was used for the measurement. The cellulose samples of the prototype and comparative examples were mixed with ion-exchanged water to prepare a slurry, which was then filled into a sample circulator. The slurry was stirred immediately before feeding until no irregularities were visible. The sample was then fed into the measuring device, and the particle size (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.

[0053] [Molecular weight distribution index (Mw / Mn)] The cellulose samples of 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 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.

[0054] [Degree of polymerization] The degree of polymerization was measured by the viscosity method using a copper ethylenediamine solution as follows: The dried cellulose sample was dissolved in a 0.5 M copper ethylenediamine solution (solution 1) to make solution 2. The viscosities of solutions 1 and 2 were measured using a capillary viscometer. The viscosity of viscosity 1 was designated η1 and the viscosity of solution 2 was designated η2, and the intrinsic viscosity [η] of the cellulose sample was calculated using the following formula, from which the degree of polymerization (DP) was calculated. c is the concentration (g / L) of the cellulose sample. Limiting concentration [η]={(η2 / η1)-1} / c Degree of polymerization DP=Ultimate concentration [η] / (8.8×10 -4 )

[0055] [Table 1]

[0056] [Table 2]

[0057] [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. 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 significantly superior results in terms of the dispersibility of the cellulose microparticles.

[0058] Furthermore, in comparison with the cellulose dispersions of Prototype Examples 1 to 4, it was shown that by increasing the sodium hypochlorite concentration, the cationic demand further increased, and cellulose defibration proceeded more easily and satisfactorily. When the available chlorine concentration of sodium hypochlorite was 0.13% or more, the cationic demand increased to 4.0 per 1 g of cellulose. μeq / g-cell More preferably, when the available chlorine concentration is 3% or more, the cationic demand is 50.0 per gram of cellulose. μeq / g-cell For these reasons, the composition is suitable for use as a coating agent for molded products such as films.

[0059] When comparing 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, 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.

[0060] 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 successfully 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 did not undergo the depolymerization process, and was about one-fifth that of the cellulose molded body of Comparative Example 2, which did not undergo the depolymerization process, refining process, and molding process.

[0061] It was also shown that increasing the sodium hypochlorite concentration further reduces the average particle size (D50), making cellulose defibration easier and better. When the available chlorine concentration of sodium hypochlorite is particularly 0.13% or higher, the average particle size (D50) becomes 50 μm or less, and more preferably, when the available chlorine concentration is 3% or higher, the average particle size (D50) becomes 10 μm or less, which allows for good quality cellulose beads to be used in cosmetics, etc.

[0062] Furthermore, even 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 compared to the cellulose molded body of comparison example 3, with the average particle size (D50) being less than 1 / 10 for the cellulose molded body of prototype 5 and less than 1 / 100 for the cellulose molded body of prototype 6.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.

[0063] Next, the molecular weight distribution index (Mw / Mn) of the cellulose molded bodies of Prototype Examples 1 to 6 is smaller than that of the cellulose molded bodies 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. [Industrial Applicability]

[0064] 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. [Explanation of symbols]

[0065] 10. Method for producing cellulose dispersion derived from regenerated cellulose 11 Cellulose dispersion 20. Method for producing cellulose-based molded body derived from regenerated cellulose 21 Cellulose molding S1 Crushing process S2 depolymerization process S3 Refinement process S4 Molding process S5 Collection process

Claims

1. A dispersion liquid raw material is cellophane having a degree of polymerization of 600 or less, a pulverization step of pulverizing the dispersion raw material; a depolymerization step in which the pulverized raw material obtained by the pulverization step is subjected to sodium hypochlorite with an effective chlorine concentration of 0.13% or more to reduce the degree of polymerization to 350 or less; a micronization step of micronizing the depolymerized cellulose obtained in the depolymerization step to obtain a cellulose dispersion having a cation demand of 4.0 μeq / g-cell or more per gram of cellulose; and a molding step of drying and molding the cellulose dispersion to obtain cellulose beads derived from regenerated cellulose having an average particle diameter (D50) of 50 μm or less. A method for producing cellulose beads derived from regenerated cellulose, comprising:

2. 2. The method for producing cellulose beads derived from regenerated cellulose according to claim 1, 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 3% or more, the cation demand of the cellulose dispersion obtained in the micronization step is 50.0 μeq / g-cell or more per 1 g of cellulose, and the average particle size (D50) of the cellulose beads derived from regenerated cellulose obtained in the molding step is 10 μm or less.

3. Cellulose beads obtained by the manufacturing method described in claim 1, which are derived from regenerated cellulose and have a molecular weight distribution index (Mw / Mn) of 3.5 or less, calculated by dividing the weight average molecular weight (Mw) of the cellulose beads by the number average molecular weight (Mn).

4. Cellulose beads obtained by the manufacturing method described in claim 2, which are derived from regenerated cellulose and have a molecular weight distribution index (Mw / Mn) of 1.6 or less, calculated by dividing the weight average molecular weight (Mw) of the cellulose beads by the number average molecular weight (Mn).

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