Method for manufacturing cellophane and method for manufacturing a composite cellulose molded article

Abstract

This invention provides a method for producing cellophane that can be made biodegradable by adding a cellulose molded material as an alternative raw material to PMMA. [Solution] The method includes a type I depolymerization step (S11) in which sodium hypochlorite is added to a cellulose raw material to reduce the degree of polymerization of the cellulose raw material; a mechanical defibration step (S12) in which the depolymerized cellulose obtained in the type I depolymerization step (S11) is defibrated by mechanical defibration; a type I molding step (S13) in which the type I unmodified cellulose fine fibers obtained in the mechanical defibration step (S12) are dried to form the cellulose molded body; and a film formation step in which the cellulose molded body is added to a cellophane raw material as a lubricant and / or an antiblocking agent to form a film.

Description

Technical Field

[0001] The present invention relates to a method for producing cellophane by adding a cellulose molded body as a lubricant or / and an antiblocking agent, and a method for producing a composite cellulose molded body.

Background Art

[0002] Cellophane produced by processing cellulose obtained from plant-derived raw materials such as pulp is generally produced by the viscose method. In the viscose method, for example, pulp is immersed in an alkaline solution such as sodium hydroxide, and then carbon disulfide is added and sulfided to prepare viscose by alkali dissolution. After aging the viscose, it is discharged into an acid solution such as sulfuric acid in a film shape and coagulated to obtain cellophane. This type of cellophane is suitably used, for example, as packaging materials for foods and pharmaceuticals, and as adhesive sheets.

[0003] In recent years, due to the promotion of sustainable development goals (SDGs), efforts have been actively made to realize a circular society that takes environmental considerations into account in various fields. Recycling, which reuses products and the like discarded after use as resources, is well known as an environmentally friendly effort, and it is desired to utilize cellophane products as recycled products. However, since cellophane is not thermoplastic, it is difficult to recycle, and for example, waste materials such as trimming parts and off-spec products discharged during the manufacturing process have generally been disposed of. Therefore, in recent years, studies on technologies for making cellophane appropriately recyclable have been continued.

[0004] On the other hand, when cellophane is commercialized, various additives such as antiblocking agents, lubricants, antistatic agents, emulsifiers, and pigments are added. Among them, in cellophane products, fine particles such as PMMA (polymethyl methacrylate) are preferably used as antiblocking agents and lubricants (see Patent Document 1). PMMA, which is preferably used as an additive for cellophane products, is plastic fine particles and is so-called microplastics.

[0005] Microplastics are materials that accumulate in marine organisms and soil, and have been identified as one of the factors contributing to the worsening of environmental pollution. As part of the Sustainable Development Goals (SDGs), reducing plastic use is required, and considering the recycling and reuse of cellophane products, there is a need for additives that have a lower environmental impact than PMMA as additives for cellophane products. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2001-96670 [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, the inventors focused on cellulose, a natural material that is biodegradable. With cellulose, for example, it is possible to process cellulose fine fibers such as cellulose nanofibers and cellulose microfibers into various molded bodies. These types of cellulose molded bodies can also be processed into forms such as beads (granules), and are expected to be a substitute raw material for microplastics. Moreover, cellulose molded bodies are compatible with cellophane, which is manufactured from cellulose, and can be made into a 100% biodegradable film. Furthermore, since they do not hinder the recycling of cellophane products, they are considered promising as an additive for cellophane products.

[0008] The present invention has been made in view of the above points, and provides a method for producing cellophane that can be made biodegradable by adding a cellulose molded article as a substitute raw material for PMMA as a lubricant or antiblocking agent.

[0009] Furthermore, in the manufacture of cellulose molded articles, it is more preferable to use recycled cellulose materials from the viewpoint of reducing environmental impact. Therefore, the present invention provides a method for manufacturing a composite cellulose molded article using regenerated cellulose derived from cellophane as an additive suitable for cellophane, as an alternative raw material to PMMA as an antiblocking agent or lubricant. [Means for solving the problem]

[0010] In other words, the first invention relates to a method for producing cellophane, characterized by comprising: a type I depolymerization step of adding sodium hypochlorite to a cellulose raw material to reduce the degree of polymerization of the cellulose raw material; a mechanical defibration step of mechanically defibrating the depolymerized cellulose obtained in the type I depolymerization step; a type I molding step of drying the type I unmodified cellulose fine fibers obtained in the mechanical defibration step to form a cellulose molded body; and a film formation step of adding the cellulose molded body to a cellophane raw material as a lubricant and / or antiblocking agent to form a film.

[0011] The second invention relates to a method for producing cellophane, comprising: a mercerization step of mercerizing a cellulose raw material; a type II depolymerization step of reducing the degree of polymerization of the mercerized cellulose obtained by the mercerization step; an alkali defibration step of adding an alkali metal hydroxide to the mercerized depolymerized cellulose obtained by the type II depolymerization step to defibrate the mercerized depolymerized cellulose; a neutralization step of neutralizing the cellulose fine fibers obtained by the alkali defibration step with an acid; a type II molding step of drying the type II unmodified cellulose fine fibers obtained by the neutralization step to form a cellulose molded body; and a film formation step of adding the cellulose molded body to a cellophane raw material as a lubricant and / or antiblocking agent to form a film.

[0012] The third invention relates to a method for producing cellophane, comprising: a cellulose dissolution step of dissolving a cellulose raw material in a cellulose solvent; a low-crystallinity molding step of producing a wet molded body by discharging the cellulose solution obtained in the cellulose dissolution step into a molding aqueous solution containing the cellulose solvent, washing the wet molded body, and drying it to form the cellulose molded body; and a film formation step of adding the cellulose molded body to a cellophane raw material as a lubricant and / or antiblocking agent to form a film.

[0013] The fourth invention relates to a method for producing a composite cellulose molded article, characterized by comprising a mixing step of mixing unmodified cellulose fine fibers in a ratio of 1 to 80% by weight into a cellulose dispersion derived from regenerated cellulose, and a composite molding step of drying the cellulose composite liquid obtained in the mixing step to form a cellulose molded article.

[0014] The fifth invention relates to a method for producing a composite cellulose molded article, wherein the cellulose dispersion derived from regenerated cellulose is obtained by a process comprising: a grinding step of using regenerated cellulose as a dispersion raw material and grinding the dispersion raw material; a regenerative depolymerization step of reducing the degree of polymerization of the grinding raw material obtained in the grinding step; and a micronization step of micronizing the depolymerized cellulose obtained in the regenerative depolymerization step.

[0015] The sixth invention relates to a method for producing a composite cellulose molded article in which the unmodified cellulose microfibers are obtained through a type I depolymerization step of adding sodium hypochlorite to a cellulose raw material to reduce the degree of polymerization of the cellulose raw material, and a mechanical defibration step of mechanically defibrating the depolymerized cellulose obtained in the type I depolymerization step.

[0016] The seventh invention relates to a method for producing a composite cellulose molded article, wherein the unmodified cellulose microfibers are obtained by a mercerization step of mercerizing a cellulose raw material, a type II depolymerization step of reducing the degree of polymerization of the mercerized cellulose obtained by the mercerization step, an alkali defibration step of adding an alkali metal hydroxide to the mercerized depolymerized cellulose obtained by the mercerization step to defibrate it, and a neutralization step of neutralizing the cellulose microfibers obtained by the alkali defibration step with an acid.

[0017] The eighth invention relates to a cellulose molded article using regenerated cellulose, characterized in that the cellulose molded article consists of 99 to 20% by weight of cellulose derived from regenerated cellulose and 1 to 80% by weight of unmodified cellulose fine fibers.

[0018] The ninth invention relates to a composite cellulose molded article in which, in the eighth invention, the cellulose molded article has a surface coated with a surface treatment agent.

[0019] The tenth invention relates to a composite cellulose molded article in which the surface treatment agent comprises at least one of the following: a wax-based treatment agent, a synthetic resin-based treatment agent, a chromium complex salt-based treatment agent, a fluorine-based treatment agent, a metal soap-based treatment agent, a cationic surfactant, a silicone-based treatment agent, and an amino acid-based treatment agent, in accordance with the ninth invention.

[0020] The eleventh invention relates to cellulose beads made of a composite cellulose molded body described in any of the eighth to tenth inventions, characterized in that the cellulose beads have a swelling rate of 500% or less when immersed in a 3% by weight sodium hydroxide aqueous solution for 24 hours.

[0021] The twelfth invention relates to composite cellulose beads in the eleventh invention, wherein the swelling rate is 200% or less.

[0022] The 13th invention relates to cellophane, characterized in that it is a film to which the composite cellulose beads described in the 11th invention are added.

[0023] The 14th invention relates to cellophane, characterized in that it is a film to which the composite cellulose beads described in the 12th invention are added.

Advantages of the Invention

[0024] According to the method for producing cellophane according to the 1st invention, a type I depolymerization step of adding sodium hypochlorite to a cellulose raw material to lower the degree of polymerization of the cellulose raw material, a mechanical fibrillation step of fibrillation the depolymerized cellulose obtained by the type I depolymerization step by mechanical fibrillation, a type I forming step of drying the type I unmodified cellulose microfibers obtained by the mechanical fibrillation step to form a cellulose molded body, and a film-forming step of adding the cellulose molded body as a lubricant or / and an antiblocking agent to a cellophane raw material to form a film are included. Therefore, a cellulose molded body that can be efficiently obtained by a simple process can be suitably used as an alternative raw material for PMMA as an antiblocking agent or a lubricant, and cellophane with enhanced biodegradability can be provided.

[0025] The method for producing cellophane according to the second invention includes a mercerization step of mercerizing a cellulose raw material, a type II depolymerization step of reducing the degree of polymerization of the mercerized cellulose obtained in the mercerization step, an alkali defibration step of adding an alkali metal hydroxide to the mercerized depolymerized cellulose obtained in the type II depolymerization step to defibrate the mercerized depolymerized cellulose, a neutralization step of neutralizing the cellulose fine fibers obtained in the alkali defibration step with an acid, a type II molding step of drying the type II unmodified cellulose fine fibers obtained in the neutralization step to form a cellulose molded body, and a film formation step of adding the cellulose molded body to the cellophane raw material as a lubricant and / or antiblocking agent to form a film. As such, a cellulose molded body that can be efficiently obtained in a simple process can be suitably used as a substitute raw material for PMMA as an antiblocking agent or lubricant, and cellophane with enhanced biodegradability can be provided.

[0026] The method for manufacturing cellophane according to the third invention includes a cellulose dissolution step of dissolving a cellulose raw material in a cellulose solvent, a low-crystallinity molding step of producing a wet molded body by discharging the cellulose solution obtained in the cellulose dissolution step into a molding aqueous solution containing the cellulose solvent, washing and drying the wet molded body to form the cellulose molded body, and a film formation step of adding the cellulose molded body to the cellophane raw material as a lubricant and / or antiblocking agent to form a film. As such, a cellulose molded body that can be efficiently obtained through a simple process can be suitably used as a substitute raw material for PMMA as an antiblocking agent or lubricant, and a cellophane with enhanced biodegradability can be provided.

[0027] The method for producing a composite cellulose molded article according to the fourth invention includes a mixing step of mixing unmodified cellulose fine fibers in a ratio of 1 to 80% by weight into a cellulose dispersion derived from regenerated cellulose, and a composite molding step of drying the cellulose composite liquid obtained in the mixing step to form a cellulose molded article. Therefore, a composite cellulose molded article that is suitable as a substitute raw material for PMMA as a lubricant or antiblocking agent and is easily recyclable can be efficiently obtained in a simple process.

[0028] According to the method for producing a composite cellulose molded article of the fifth invention, in the fourth invention, the cellulose dispersion derived from regenerated cellulose is obtained by a process that includes a grinding step of grinding the dispersion raw material using regenerated cellulose as the dispersion raw material, a regenerative depolymerization step of reducing the degree of polymerization of the grinding raw material obtained in the grinding step, and a micronization step of micronizing the depolymerized cellulose obtained in the regenerative depolymerization step. Therefore, a cellulose dispersion can be efficiently obtained by effectively using appropriate regenerated cellulose, including cellophane and the like, which is difficult to recycle.

[0029] According to the method for producing a composite cellulose molded article of the sixth invention, in the fourth or fifth invention, the unmodified cellulose microfibers are type I unmodified cellulose microfibers obtained through a depolymerization step in which sodium hypochlorite is added to a cellulose raw material to reduce the degree of polymerization of the cellulose raw material, and a mechanical defibration step in which the depolymerized cellulose obtained in the depolymerization step is defibrated by mechanical defibration. Since they are not chemically modified, they are highly safe and possess water resistance as well as organic solvent resistance derived from cellulose.

[0030] According to the method for producing a composite cellulose molded article of the seventh invention, in the fourth or fifth invention, the unmodified cellulose microfibers are type II unmodified cellulose microfibers obtained by adding an alkali metal hydroxide to mercerized depolymerized cellulose obtained through a mercerization step of mercerizing a cellulose raw material, a depolymerization step of reducing the degree of polymerization of the mercerized cellulose obtained through the mercerization step, an alkali metal hydroxide step of defibration, and a neutralization step of neutralizing the cellulose microfibers obtained through the alkali defibration step with an acid. Since they are not chemically modified, they are highly safe and possess water resistance as well as organic solvent resistance derived from cellulose.

[0031] According to the composite cellulose molded article of the eighth invention, the cellulose molded article uses regenerated cellulose, and the cellulose molded article consists of 99-20% by weight of cellulose derived from regenerated cellulose and 1-80% by weight of unmodified cellulose fine fibers. Therefore, swelling in alkaline solutions is suppressed, making it suitable as a substitute raw material for PMMA as a lubricant or antiblocking agent, and it is easily recyclable.

[0032] According to the composite cellulose molded article of the ninth invention, in the eighth invention, the cellulose molded article can be given appropriate functionality because its surface is coated with a surface treatment agent.

[0033] According to the composite cellulose molded article of the 10th invention, in the 9th invention, the surface treatment agent consists of at least one of the following: a wax-based treatment agent, a synthetic resin-based treatment agent, a chromium complex salt-based treatment agent, a fluorine-based treatment agent, a metal soap-based treatment agent, a cationic surfactant, a silicone-based treatment agent, and an amino acid-based treatment agent, so that the desired functionality can be appropriately imparted.

[0034] According to the composite cellulose beads of the 11th invention, the cellulose beads are made of a composite cellulose molded body as described in any of the 8th to 10th inventions, and since the swelling rate of the cellulose beads when immersed in a 3% by weight sodium hydroxide aqueous solution for 24 hours is 500% or less, they are less likely to disintegrate in alkaline solutions and can be suitably used as a substitute raw material for PMMA as a lubricant or antiblocking agent.

[0035] According to the composite cellulose beads of the 12th invention, the stability in alkaline solutions is further improved because the swelling rate is 200% or less compared to the 11th invention.

[0036] According to the cellophane of the 13th invention, since it is a film to which the composite cellulose beads described in the 11th invention are added, it is possible to reduce the amount of plastic used and it is also recyclable, thus contributing to reducing the environmental burden.

[0037] According to the cellophane of the 14th invention, since it is a film to which the composite cellulose beads described in the 12th invention are added, it is possible to reduce the amount of plastic used and it is also recyclable, thus contributing to reducing the environmental burden. [Brief explanation of the drawing]

[0038] [Figure 1] This is a schematic process diagram of a method for manufacturing cellophane according to the first embodiment of the present invention. [Figure 2] This is a schematic process diagram of a method for manufacturing cellophane according to a second embodiment of the present invention. [Figure 3] This is a schematic process diagram of a method for manufacturing cellophane according to a third embodiment of the present invention. [Figure 4] This is a schematic process diagram of a method for manufacturing a composite cellulose molded article according to one embodiment of the present invention. [Figure 5] This is a schematic process diagram of the method for producing a cellulose dispersion derived from regenerated cellulose. [Modes for carrying out the invention]

[0039] The present invention relates to a method for producing cellophane to which additives such as lubricants and antiblocking agents are added, and more particularly to a method for producing cellophane using a cellulose molded article as a substitute for fine particles such as PMMA (polymethyl methacrylate) used as such additives.

[0040] Cellulose molded articles are plant-derived molded articles formed using cellulose as a raw material. Pulp is preferred as the starting material for cellulose. Pulp is a raw material obtained by crushing wood and removing impurities such as lignin to increase the purity of the cellulose component. Cotton linter pulp, obtained by removing impurities from cotton to increase the purity of the cellulose component, may also be used. In addition, pulp is fibrous and therefore highly reactive with chemicals, making it a preferred cellulose raw material. Besides pulp, animal-derived celluloses such as bacterial cellulose produced by microorganisms can also be used. Furthermore, purified cellulose obtained by refining these raw materials can be used.

[0041] Furthermore, while cellulose raw materials are usually preferably those from which impurities such as lignin have been removed to increase the purity of the cellulose component, pulp mainly composed of cellulose containing 25% by weight or less, more preferably 0.1 to 20% by weight, of xylose as a constituent sugar may also be used as a raw material. Since hemicellulose, which was conventionally an impurity component, is not removed from such pulp, the raw material can be effectively utilized, and depending on the application, physical properties derived from hemicellulose can be arbitrarily imbued into the cellulose molded product.

[0042] Cellulose molded articles are intended for use as additives in cellophane, such as lubricants and antiblocking agents, and therefore are in granular (bead-like) form. Suitable cellulose molded articles for the above-mentioned additives include molded articles of type I unmodified cellulose microfibers, molded articles of type II unmodified cellulose microfibers, and low-crystallinity cellulose molded articles. The following describes a method for manufacturing cellophane to which each of the above-mentioned cellulose molded articles is added.

[0043] The cellophane manufacturing method (S10) according to the first embodiment of the present invention shown in Figure 1 is a method for manufacturing cellophane to which a molded body of type I unmodified cellulose fine fibers obtained by a step of mechanically defibrating a cellulose raw material is added, and includes a type I depolymerization step (S11), a mechanical defibration step (S12), a type I molding step (S13), and a film formation step (S15).

[0044] The Type I depolymerization step S11 is a step in which sodium hypochlorite is added to the cellulose raw material to reduce the degree of polymerization of the cellulose raw material and obtain depolymerized cellulose. In this Type I depolymerization step S11, by reducing the degree of polymerization of the cellulose raw material, the structure of the cellulose raw material is weakened and made easier to defibrillate. In the Type I depolymerization step S11, the degree of polymerization can be appropriately reduced by depolymerizing the raw material cellulose with sodium hypochlorite. In the Type I depolymerization step S11, it is preferable to reduce the degree of polymerization of the cellulose raw material to 1200 or less, more preferably to 600 or less. If the degree of polymerization of the cellulose raw material is too high, it will become difficult to defibrillate, which may interfere with the mechanical defibrillation step described later.

[0045] In the Type I depolymerization step S11, it is preferable to use a low concentration of sodium hypochlorite so that the hydroxyl groups of cellulose are not oxidized to carboxyl groups. Sodium hypochlorite is a highly safe chemical, and by using a low concentration, for example, an effective chlorine concentration of about 0.04 to 3.0%, more preferably 0.3 to 2.5%, the degree of polymerization of cellulose can be reduced while the cellulose remains unmodified and unchemically modified. Furthermore, since the efficiency of depolymerization improves when the reaction in the Type I depolymerization step S11 is carried out at a temperature higher than room temperature, it is preferable to carry it out in the temperature range of 40 to 70°C. The reaction time in this case depends on the effective chlorine concentration of sodium hypochlorite, but is generally about 1 to 5 hours.

[0046] In the Type I depolymerization step S11, if the effective chlorine concentration of sodium hypochlorite is too low, the reaction time will be prolonged, reducing efficiency and potentially preventing sufficient depolymerization. If the effective chlorine concentration is too high, the hydroxyl groups of cellulose may be oxidized to carboxyl groups, or the low molecular weight cellulose raw material may dissolve in the solvent, leading to concerns about reduced yield and corrosion of the equipment. By appropriately adjusting the effective chlorine concentration of sodium hypochlorite, an efficient depolymerization reaction can be expected.

[0047] The mechanical defibration step S12 is a step in which the depolymerized cellulose obtained in the type I depolymerization step S11 is mechanically defibrated to obtain type I unmodified cellulose fine fibers. The depolymerized cellulose to be mechanically defibrated is washed with ion-exchanged water or the like as needed, and then ion-exchanged water is added to form a dispersion.

[0048] Mechanical defibration is a method of defibration performed by known physical (mechanical) techniques such as homogenizers and water jets. In this mechanical defibration, the depolymerized cellulose, whose degree of polymerization has been reduced while remaining unmodified in the Type I depolymerization step S11, is mechanically defibrated without the use of chemicals (chemical defibration). As a result, the resulting cellulose fine fibers are in an unmodified form, offering superior safety. In particular, it is preferable to perform defibration using a high-pressure homogenizer in the mechanical defibration step S12. A high-pressure homogenizer performs shear treatment under high-pressure conditions, allowing for efficient and finer defibration of the depolymerized cellulose.

[0049] Furthermore, in the mechanical defibration process S12, defibration may be performed in multiple stages as needed. Examples of multiple defibration stages include performing preliminary defibration on the depolymerized cellulose (dispersion) followed by main defibration. Preliminary defibration is performed by known methods, such as using a mixer or refiner. Preliminary defibration helps to suppress malfunctions such as clogging of the defibration equipment, which is significant from the viewpoint of equipment protection. By performing main defibration using a homogenizer or the like after preliminary defibration using a mixer or the like, cellulose microfibers with a uniform and small fiber diameter close to single nanoscale can be obtained. In cellulose microfibers, a small average fiber diameter is preferred because it results in good transparency of the dispersion.

[0050] In this mechanical defibration process S12, since the depolymerized cellulose is in a state that is easily defibrated by the type I depolymerization process S11, it becomes possible to defibrate nano-level cellulose by mechanical defibration without chemical defibration. In particular, by setting the effective chlorine concentration of sodium hypochlorite to about 0.04-3.0% in the type I depolymerization process S11, the degree of polymerization of the cellulose raw material is reduced to 1200 or less, so the cellulose raw material can be easily defibrated to the single nanometer level, resulting in a small fiber diameter and good design properties. The cellulose microfibers obtained in this process are type I unmodified cellulose microfibers with a high-strength type I crystalline structure. Furthermore, in the mechanical defibration process S12, since the degree of polymerization of cellulose is reduced, defibration is possible even without applying high pressure, which is advantageous from an equipment perspective.

[0051] The Type I molding step S13 is a step in which the Type I unmodified cellulose microfibers obtained in the mechanical defibration step S12 are dried to form a granular (bead-shaped) cellulose molded body. As for the method of molding the cellulose molded body, it is preferable to use a known granular molding method, such as spray drying, with the obtained dispersion of Type I unmodified cellulose microfibers. In the spray drying method, the dispersion of cellulose microfibers aggregates as it dries, allowing it to be easily molded into a granular (bead) shape. The molding conditions are set appropriately according to the desired size of the molded body, but for example, it is preferable to set the spray drying air pressure to about 0.025 to 0.6 MPa. If the spray drying air pressure is insufficient, the particle size may become too large, potentially degrading the physical properties and texture. Increasing the air pressure would require an excessively large air generator, so it is not practical to increase it unnecessarily.

[0052] Following the I-formation process S13, a collection process S14 is performed as needed. The collection process S14 is a process of removing unwanted particles from the granular cellulose molded body (cellulose beads) formed in the I-formation process S13 and recovering a cellulose molded body with suitable particles. The collection means is not particularly limited as long as it is possible to recover the appropriate particles, but collection can be done using known collection methods such as bag filters or cyclone dust collectors.

[0053] The molded cellulose material has the advantage of being highly safe because it is not chemically modified. Furthermore, since the constituent material of this cellulose material is type I unmodified cellulose microfiber, it does not redissolve in water, unlike cellulose microfibers with functional groups such as oxidized cellulose, and therefore possesses both water resistance and organic solvent resistance derived from cellulose. For this reason, since this cellulose material does not dissolve when added to various solutions, it is suitable as a constituent material for additives with functional properties such as lubricants and antiblocking agents, and is a promising alternative raw material to PMMA for use as a lubricant or antiblocking agent. In addition, since this cellulose material is plant-derived, it can be recycled even when used as an additive.

[0054] Film formation step S15 is a process in which a cellulose molded body of molded type I unmodified cellulose fine fibers is added to the cellophane raw material as an additive such as a lubricant or antiblocking agent to form a film. The cellophane raw material is a material that has been treated with a predetermined process to prepare it for molding into a film. In addition to pulp, cotton linter pulp, animal cellulose such as bacterial cellulose, and purified cellulose can preferably be used as the cellophane raw material.

[0055] In the film formation process S15, which involves forming a film from cellophane raw materials, known manufacturing methods such as the viscose method and the ionic liquid method can be suitably used. For example, in the viscose method, raw materials such as pulp are prepared into viscose using alkali and carbon disulfide, a cellulose molded body is added to this viscose, and then the viscose is extruded in a film-like manner into an acid solution such as sulfuric acid, and solidified into a film to obtain cellophane. In the ionic liquid method, raw materials such as pulp are prepared into a cellulose solution by dissolving them in a solvent containing an ionic liquid, and then the cellulose solution is extruded in a film-like manner into water, and solidified into a film to obtain cellophane.

[0056] As described above, in the cellophane manufacturing method of the first embodiment, a cellulose molded body of type I unmodified cellulose fine fibers, which can be efficiently obtained through a simple process, can be suitably used as a substitute raw material for PMMA as a lubricant or antiblocking agent. Furthermore, by adding the obtained cellulose molded body to the cellophane raw material as an antiblocking agent or lubricant, 100% biodegradable cellophane derived from cellulose can be obtained, thereby reducing the environmental burden.

[0057] The cellophane production method (S20) according to the second embodiment of the present invention shown in Figure 2 is a method for producing cellophane to which a molded body of type II unmodified cellulose fine fibers obtained through a step of mercing a cellulose raw material is added, and includes a mercing step (S21), a type II depolymerization step (S22), an alkali defibration step (S23), a neutralization step (S24), a type II molding step (S25), and a film formation step (S27).

[0058] The mercerization process S21 is a process in which cellulose raw material is mercerized to obtain mercerized cellulose. In the mercerization process S21, the cellulose raw material is added to an alkali metal hydroxide such as caustic soda (NaOH), and stirred while being heated as needed, causing the cellulose fibers to swell (mercerization). In the mercerized cellulose obtained in this way, the cellulose fibers become negatively charged when immersed in the alkali metal hydroxide, generating Coulomb forces, which cause each fiber to repel and become easily defibrillated.

[0059] Alkali metal hydroxides used in the mercerization process include caustic soda (NaOH), lithium hydroxide, and potassium hydroxide. Caustic soda is preferred from the standpoint of cost, safety, and environmental impact.

[0060] The Type II depolymerization step S22 is a step in which the degree of polymerization of the mercerized cellulose obtained in the mercerization step S21 is reduced to obtain mercerized depolymerized cellulose. In this Type II depolymerization step S22, the mercerized cellulose whose degree of polymerization is reduced has excess alkali metal hydroxide removed as needed, and the solid content concentration is adjusted as appropriate.

[0061] In the Type II depolymerization step S22, the mercerized cellulose, whose solid content has been adjusted, is appropriately pulverized and oxidatively decomposed by oxygen in the air to age, thereby reducing the degree of polymerization. Ageing of the mercerized cellulose is carried out at room temperature or under heated conditions. To accelerate the depolymerization rate, heated conditions that do not cause the raw materials to dry out are preferably used. In addition, an ageing accelerator such as manganese(II) sulfate may be added to promote the ageing reaction.

[0062] The degree of polymerization of mercerized cellulose, which is reduced by the type II depolymerization step S22, becomes easier to defibrate as the degree of polymerization decreases. Therefore, a preferred degree of polymerization for mercerized cellulose is 760 or less, more preferably 310 or less. When the degree of polymerization of mercerized cellulose is 760 or less, the defibration of cellulose fibers is easy, and the transparency of the resulting dispersion of cellulose fine fibers is ensured. Mercerized cellulose with a reduced degree of polymerization in this way becomes mercerized depolymerized cellulose that can be defibrated into fine fibers. Mercerized depolymerized cellulose is type II cellulose having a type II crystalline structure.

[0063] The alkali defibration step S23 is a step in which an alkali metal hydroxide is added to the mercerized depolymerized cellulose obtained in the type II depolymerization step S22, and then the mercerized depolymerized cellulose is defibrated to obtain cellulose fine fibers.

[0064] In this alkali defibration process S23, alkali metal hydroxide is added to the depolymerized cellulose, which has been made more easily defibrated by mercerization, to make the cellulose fibers even more easily defibrated. At this time, it is preferable to add alkali metal hydroxide and a solvent (ion-exchanged water) to the mercerized depolymerized cellulose and adjust the total concentration to about 2.5 to 17.5%. If the total concentration of alkali metal hydroxide is too low, the swelling of the cellulose may be insufficient, making defibration difficult. If the total concentration is too high, the salt concentration will be high, making the cellulose fibers more prone to aggregation, which may actually make defibration more difficult. In addition, if defibration is insufficient because the alkali metal hydroxide is not adjusted to an appropriate total concentration, the transparency of the resulting dispersion of cellulose fine fibers may be low, which may reduce the aesthetic appeal.

[0065] Examples of alkali metal hydroxides used here include caustic soda (NaOH), lithium hydroxide, and potassium hydroxide. Caustic soda is preferred from the standpoint of cost, safety, and environmental impact.

[0066] Mercerized depolymerized cellulose, with its total alkali metal hydroxide concentration adjusted, is defibrated by mechanical defibration. Mechanical defibration is performed using known physical (mechanical) methods such as homogenizers or water jets. In this process, the mercerized depolymerized cellulose being defibrated is in a state that is easily defibrated by mercerization, thus reducing the energy required for defibration. In this mechanical defibration, since defibration is performed mechanically without the use of chemicals (chemical defibration), the resulting cellulose fine fibers are in an unmodified form, resulting in superior safety. In particular, in the alkali defibration step S23, it is preferable to defibrate using a high-pressure homogenizer. A high-pressure homogenizer performs shear treatment under high-pressure conditions, allowing for efficient and finer defibration of the depolymerized cellulose.

[0067] Furthermore, in the alkaline defibration process S23, defibration may be performed in multiple stages as needed. Examples of multiple defibration stages include performing preliminary defibration on the depolymerized cellulose (dispersion) followed by main defibration. Preliminary defibration is performed by known methods, such as using a mixer or refiner. Preliminary defibration helps to suppress malfunctions such as clogging of the defibration equipment, which is significant from the standpoint of protecting the equipment. By performing main defibration using a homogenizer or the like after preliminary defibration using a mixer or the like, cellulose microfibers with a uniform and small fiber diameter close to single nanoscale can be obtained. In cellulose microfibers, a small average fiber diameter is preferred because it results in good transparency of the dispersion.

[0068] The cellulose microfibers obtained in this way are defibrated to have an average fiber diameter ranging from nanoscale to several hundred nanoscale. In particular, since the type II cellulose, which has a type II crystalline structure, is defibrated without chemical modification after the type II depolymerization step S22, it becomes unmodified type II cellulose microfibers. These cellulose microfibers are strongly alkaline because they have been treated with alkali metal hydroxides.

[0069] The neutralization step S24 is a process in which the strongly alkaline cellulose microfibers obtained in the alkaline defibration step S23 are neutralized with an acid. Examples of acids used in the neutralization step S24 include sulfuric acid, hydrochloric acid, lactic acid, and other suitable acids. In the neutralization step S24, after neutralization with acid, the material is washed and re-defibrated as appropriate to obtain neutralized type II unmodified cellulose microfibers. These type II unmodified cellulose microfibers are easy to handle and have excellent moldability.

[0070] The Type II molding step S25 is a step in which the Type II unmodified cellulose microfibers obtained in the neutralization step S24 are dried to form a granular (bead-shaped) cellulose molded body. The cellulose molded body is preferably formed using a known granular molding method such as spray drying with the obtained dispersion of Type II unmodified cellulose microfibers. In the spray drying method, the dispersion of cellulose microfibers aggregates as it dries, and can be easily formed into a granular (bead) shape. The molding conditions are set appropriately according to the desired size of the molded body, but for example, it is preferable to set the air pressure for spray drying to about 0.025 to 0.6 MPa. If the air pressure for spray drying is insufficient, the particle size may become too large, which may worsen the physical properties and texture. If the air pressure is increased, the air generator will become excessive, so it is not practical to increase it more than necessary.

[0071] Following the Type II molding process S25, a collection process S26 is performed as needed. The collection process S26 is a process of removing unwanted particles from the granular cellulose molded body (cellulose beads) molded in the Type II molding process S25 and recovering a cellulose molded body with suitable particles. The collection method is not particularly limited as long as it is possible to recover the appropriate particles, but collection can be done using known collection methods such as bag filters or cyclone dust collectors.

[0072] The molded cellulose material has the advantage of being highly safe because it is not chemically modified. Furthermore, since the constituent material of this cellulose material is type II unmodified cellulose microfiber, it does not redissolve in water, unlike cellulose microfibers with functional groups such as oxidized cellulose, and therefore possesses both water resistance and organic solvent resistance derived from cellulose. For this reason, since this cellulose material does not dissolve when added to various solutions, it is suitable as a constituent material for additives with functional properties such as lubricants and antiblocking agents, and is a promising alternative raw material to PMMA for use as a lubricant or antiblocking agent. In addition, since this cellulose material is plant-derived, it can be recycled even when used as an additive.

[0073] The film formation process S27 is a process in which a molded cellulose molded body of type I unmodified cellulose fine fibers is added to the cellophane raw material as an additive such as a lubricant or antiblocking agent to form a film. In the film formation process S27, known manufacturing methods such as the viscose method and the ionic liquid method can be suitably used. For example, in the viscose method, raw materials such as pulp are prepared into viscose using alkali and carbon disulfide as the cellophane raw material, and after the cellulose molded body is added to this viscose, the viscose is discharged in a film-like manner into an acid solution such as sulfuric acid, and the film is allowed to solidify to obtain cellophane. In the ionic liquid method, raw materials such as pulp are prepared into a cellulose solution by dissolving them in a solvent containing an ionic liquid as the cellophane raw material, and the cellulose solution is discharged in a film-like manner into water, and the film is allowed to solidify to obtain cellophane.

[0074] As described above, in the cellophane manufacturing method of the second embodiment, a cellulose molded body of type II unmodified cellulose fine fibers, which can be efficiently obtained through a simple process, can be suitably used as a substitute raw material for PMMA as a lubricant or antiblocking agent. Furthermore, by adding the obtained cellulose molded body to the cellophane raw material as an antiblocking agent or lubricant, 100% biodegradable cellophane derived from cellulose can be obtained, thereby reducing the environmental burden.

[0075] The method for producing cellophane according to the third embodiment of the present invention shown in Figure 3 (S30) is a method for producing cellophane to which a low-crystallinity cellulose molded body obtained regardless of the xylose concentration in the constituent sugars of the cellulose raw material is added, and includes a cellulose dissolution step (S31), a low-crystallinity molding step (S32), and a film formation step (S34).

[0076] The cellulose dissolution step S31 is a step in which a cellulose raw material is dissolved in a cellulose solvent to obtain a cellulose solution. Generally, the cellulose raw material used for low-crystalline cellulose molded articles is pulp containing high concentrations of cellulose and xylose as a constituent sugar, obtained by removing impurities such as lignin. In this step, pulp mainly composed of cellulose containing 25% by weight or less, more preferably 0.1 to 20% by weight, of xylose as a constituent sugar can be used as the raw material. In other words, in the production of low-crystalline cellulose molded articles, it becomes possible to use pulp with high cellulose purity in addition to the pulp with low cellulose purity that is normally used. Therefore, not only is the range of raw material selection broadened, but the range of applications for the resulting molded articles can also be expanded.

[0077] Furthermore, xylose, as a constituent sugar, inhibits the crystallization of cellulose when the cellulose solution solidifies, as described later, and can therefore be added to arbitrarily control the crystallinity of cellulose. A cellulose molded body with a high degree of crystallinity has increased rigidity and decreased transparency, while one with a low degree of crystallinity is more flexible and has improved transparency. Therefore, the content can be adjusted as appropriate depending on the physical properties required for the desired cellulose molded body. In the third embodiment, the cellulose raw material will be described as pulp.

[0078] A cellulose solvent is a solvent for dissolving cellulose raw materials such as pulp, and in particular, a solvent that can uniformly dissolve the pulp in a short time without pretreatment steps, regardless of the crystalline form of the pulp, is used. From the viewpoint of reducing environmental impact, it is preferable that this cellulose solvent does not contain halogens as anions. As the cellulose solvent, a solvent containing tetraalkylammonium acetate represented by the following formula (Fi) and an aprotic polar solvent is preferably used.

[0079] [ka]

[0080] In formula (Fi), R1, R2, R3, and R4 are alkyl groups having 3 to 6 carbon atoms. R1 to R4 may be the same alkyl group or different alkyl groups. If the alkyl group has 2 or fewer carbon atoms, or 7 or more carbon atoms, the solubility of the solvent in the pulp may decrease.

[0081] Kamlet-Taft parameters are used as evaluation indicators for the solvent properties of cellulose solvents. Kamlet-Taft parameters consist of three parameters: hydrogen bond acidity (α), hydrogen bond basicity (β), and bipolarity / polarity (π), with hydrogen bond basicity (β) being related to cellulose solubility. In the present invention, the desired cellulose solubility is preferably such that the hydrogen bond accepting ability (β value) of the Kamlet-Taft parameters is 0.8 to 1.3. By setting the hydrogen bond accepting ability (β value) of the Kamlet-Taft parameters of the cellulose solvent to 0.8 to 1.3, the cellulose material can be uniformly dissolved in a short time without pretreatment steps, regardless of the crystalline form of the cellulose material, and the fluidity of the cellulose solution obtained by dissolving the cellulose material can be increased.

[0082] Tetraalkylammonium acetate is a material used to efficiently dissolve cellulose materials such as pulp. This tetraalkylammonium acetate is used in combination of one or more of the following: tetrabutylammonium acetate, tetrapropylammonium acetate, tetrapentylammonium acetate, and tetrahexylammonium acetate.

[0083] Among the tetraalkylammonium acetates mentioned above, tetrabutylammonium acetate is preferred due to its excellent polysaccharide dissolution efficiency. Tetrabutylammonium acetate is an ionic ammonium acetate salt with a C4 alkyl group, possessing a good balance of affinity for hydrogen bonds and hydrophobicity as an organic substance. Due to these properties, it is thought that it penetrates between crystalline cellulose in pulp, breaking intermolecular and intramolecular hydrogen bonds, while re-aggregation is suppressed by the action of hydrophobic groups in the molecule. Therefore, it can efficiently dissolve the cellulose crystals, which are the main component of pulp.

[0084] Aprotic polar solvents are used to dissolve tetraalkylammonium acetates, such as tetrabutylammonium acetate, which are solids at room temperature. Furthermore, aprotic polar solvents enable homogeneous dissolution of tetraalkylammonium acetate in a short time, and can also lower the viscosity of the cellulose solution obtained by dissolving the pulp, thereby appropriately adjusting its fluidity.

[0085] Furthermore, since tetraalkylammonium acetate, which constitutes the cellulose solvent, has a strong electric charge, it readily forms electrostatic bonds with pulp, which has a large number of hydroxyl groups in its molecule, through hydrogen bonding and other means. Therefore, if a protic solvent is used, interactions (hydrogen bonding) with tetraalkylammonium acetate occur, inhibiting the cleavage of hydrogen bonds in cellulose by tetraalkylammonium acetate; for this reason, an aprotic catalyst is preferred. Moreover, since it is difficult to dissolve tetraalkylammonium acetate if a nonpolar solvent is used, a polar solvent is preferred. Accordingly, an aprotic polar solvent is preferably used as the solvent for cellulose.

[0086] The proportion of tetraalkylammonium acetate used is 1% to 45% by weight, preferably 5% to 40% by weight, and more preferably 10% to 35% by weight, from the viewpoint of solubility and dissolution rate in pulp. If the proportion of tetraalkylammonium acetate is too low, the pulp may not dissolve sufficiently, and if the proportion is too high, the solubility and dissolution rate of the pulp may decrease.

[0087] Aprotic polar solvents are preferably characterized by strong hydrogen bond acceptor properties and solubility parameters similar to those of tetraalkylammonium acetate. Therefore, aprotic polar solvents are preferably characterized by a donor number of 20 to 50, more preferably 25 to 40, and even more preferably 25 to 35. The donor number is one indicator of the basicity of a solvent, and is the value expressed as -ΔH (kcal / mol) of the heat of reaction (enthalpy) when solvent molecules react with 3 to 10 mol / L of Lewis acid (SbCl5) in a 1,2-dichloroethane solution. If the donor number is too small, the hydrogen bond acceptor properties of the aprotic polar solvent may decrease, potentially reducing the solubility of the pulp. If it is too large, the compatibility between the aprotic polar solvent and tetraalkylammonium acetate may decrease.

[0088] Furthermore, in the case of aprotic polar solvents, at least one selected from amide solvents, sulfoxide solvents, and pyridine solvents is preferably used from the viewpoint of solubility of tetraalkylammonium acetate and pulp. Specifically, at least one selected from the group consisting of N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, N,N'-dimethylpropylene urea, 1,3-dimethyl-2-imidazolidinone (N,N'-dimethylethylene urea), tetramethylurea, tetraethylurea, pyridine, and 4-methylpyridine, and their derivatives. These are preferred from the viewpoint of economy and mass production because they are relatively inexpensive and easy to procure.

[0089] For the aprotic polar solvents listed above, the number of donors measured by the Gutmann method was 26.6 for N,N-dimethylformamide, 30.9 for N,N-diethylformamide, 27.8 for N,N-dimethylacetamide, 32.2 for N,N-diethylacetamide, 29.8 for dimethyl sulfoxide, 27.3 for N-methyl-2-pyrrolidone, 29.3 for N,N'-dimethylpropyleneurea, 27.8 for 1,3-dimethyl-2-imidazolidinone, 31.0 for tetramethylurea, 28.0 for tetraethylurea, 33.1 for pyridine, and 31.5 for 4-methylpyridine.

[0090] These aprotic polar solvents can be used individually or in combination of two or more. For example, when using two or more in combination, at least one of them should be an aprotic polar solvent with a donor number of 20 to 50, and the other aprotic polar solvents used in combination may be outside this range.

[0091] The content of the aprotic polar solvent is preferably 55% by weight or more, from the viewpoint of obtaining high fluidity in the cellulose solution obtained by dissolving pulp by reducing the content of tetraalkylammonium acetate in the cellulose solvent. Increased fluidity of the cellulose solution improves the processability of the molded article. The upper limit of the aprotic polar solvent content is not particularly limited as long as even a trace amount of tetraalkylammonium acetate is included, and it is not limited to 100% by weight. For example, the upper limit of the aprotic polar solvent content is 90-99% by weight. If the content of the aprotic polar solvent is too low, the cellulose solvent may become slurry-like, reducing fluidity and potentially worsening the fluidity and homogeneity of the cellulose solution obtained by dissolving pulp. Conversely, if the content is too high, the solubility of the pulp may decrease.

[0092] In cellulose solvents, the solubility and dissolution rate of pulp, as well as the viscosity of the cellulose solution, can be adjusted depending on the combination of tetraalkylammonium acetate and aprotic polar solvent used.

[0093] Here, we will explain the mechanism of dissolution of pulp (cellulose) by cellulose solvents. In cellulose solvents, tetraalkylammonium acetate is dissolved by an aprotic polar solvent (dimethyl sulfoxide in this example: DMSO) into the cation shown in formula (Fi) (tetraalkylammonium ion: TAA + ) and anions (acetate ion: CH3COO - ) is broken down into dimethyl sulfoxide (DMSO) oxygen and tetraalkylammonium ion (TAA + ) interacts with a macrocation ([DMSO+TAA] + ) is formed.

[0094] In cellulose solvent, pulp (cellulose) contains acetate ions (CH3COO - The hydrogen bonds in cellulose are broken by the acetate ion (CH3COO). - ) forms hydrogen bonds with it. Also, oxygen in cellulose and macrocations ([DMSO+TAA] + A weak interaction is formed between the two. As a result, cellulose is thought to exist in the solvent in the form shown in formula (Fii) below. Therefore, it is thought that cellulose can be uniformly dissolved in a short time without pretreatment, regardless of its crystalline form.

[0095] [ka]

[0096] The cellulose solution is a solution obtained by dissolving a predetermined amount of pulp in the cellulose solvent described above. The amount of pulp dissolved in the cellulose solvent is set according to the degree of polymerization, crystallinity, etc., but from the viewpoint of production efficiency, such as being able to easily prepare the cellulose solution with little burden and easy solidification, it is preferable that the amount added is at a concentration of about 3 to 15% by weight relative to the weight of the cellulose solvent. If the concentration of pulp is too dilute, the time required for solidification in the molding process described later will increase, and handling during processing and treatment may become difficult. If the concentration is too high, the viscosity of the cellulose solution will increase, requiring a long time to dissolve the pulp, and a large amount of tetraalkylammonium acetate will be required, which may be economically and efficiently disadvantageous.

[0097] When dissolving pulp in a cellulose solvent, it is preferable to use relatively mild temperature conditions for dissolution. The lower limit of the dissolution temperature is set to be above the solidification temperature of the aprotic polar solvent used, for example, around 20°C, from the viewpoint of ensuring the fluidity of the cellulose solvent and the reactivity between the pulp and tetraalkylammonium acetate. On the other hand, the upper limit of the dissolution temperature is set to, for example, around 50°C, from the viewpoint of controlling the reaction by suppressing excessive reaction between the pulp and tetraalkylammonium acetate and reducing the equipment required for heating. By dissolving pulp in a cellulose solvent at a mild temperature range, work can be carried out at room temperature, or if heating is required, a simple heating device is sufficient, thus eliminating the need for special heating equipment and reducing the equipment costs required for production. In addition, evaporation of components of the cellulose solvent can be suppressed, resulting in a safer working environment. It is possible to shorten the reaction time by raising the dissolution temperature, but it is not desirable to raise the dissolution temperature more than necessary due to reasons such as the decomposition of the cellulose solvent and the generation of colored substances due to side reactions.

[0098] Furthermore, when dissolving pulp in a cellulose solution, additives such as antioxidants, plasticizers, fillers, UV absorbers, pigments, antistatic agents, and other polymer materials may be added as needed. The amount of additives added should be appropriately determined depending on the type and application of the additive.

[0099] The cellulose solution is prepared by adding pulp, cellulose solvent, and additives as needed in a predetermined ratio, and stirring appropriately. For stirring the materials, mechanical stirring or ultrasonic vibration is suitable when the pulp content is relatively low and the cellulose solution has high fluidity, while a twin-screw extruder or kneader is suitable when the pulp content is relatively high and the cellulose solution has high viscosity. The stirring time depends on the fluidity of the solution, but is preferably about 10 to 90 minutes. If the stirring time is too short, it will be difficult to sufficiently dissolve the pulp. Also, if the stirring time is extended unnecessarily, no improvement in physical properties will be observed, so it should be stopped at an appropriate time. Stirring the materials promotes the dissolution of pulp and improves the uniformity of the solution. The pulp may also be dissolved in an inert gas. This suppresses the decrease in the degree of polymerization of cellulose in the pulp.

[0100] The low-crystallinity molding step S32 is a process in which a cellulose solution obtained in the cellulose dissolution step is discharged into a molding aqueous solution containing a cellulose solvent to produce a wet molded body, and the wet molded body is washed and dried to form a granular (bead-shaped) cellulose molded body. The wet molded body is an intermediate product of the final cellulose molded body and is composed of granular (bead-shaped) material.

[0101] The cellulose solution is dispensed using an appropriate dispensing device capable of dispensing the cellulose solution in a fine form such as a mist. Preferably, known injection devices such as atomizers, pressurized nozzles, and two-fluid nozzles are used as the dispensing device.

[0102] The molding aqueous solution is an aqueous solution containing the same cellulose solvent as the cellulose dissolution step S31, and solidifies upon contact with the cellulose solution. The materials constituting the molding aqueous solution are cellulose solvent and ion-exchanged water. The amount of cellulose solvent in the molding aqueous solution is preferably around 20-50%. If the cellulose solvent content is too low, the solidification rate of the discharged cellulose solution will be too fast, and the crystallization of cellulose will proceed easily, which may result in an excessively high degree of crystallization. Conversely, if the content is too high, the solidification of the cellulose solution may be insufficient, which may make molding difficult.

[0103] The reaction conditions between the cellulose solution and the molding aqueous solution are such that the temperature is approximately 10 to 70°C, preferably 10 to 40°C. If the temperature of the molding aqueous solution is too high, it will solidify rapidly, which may reduce the density and strength of the cellulose molded product. In addition, the energy cost required to maintain the temperature of the molding aqueous solution will be high.

[0104] When a cellulose solution is discharged into a molding aqueous solution, the cellulose solution solidifies due to the molding aqueous solution, yielding a transparent, wet molded body consisting of cellulose components and residual cellulose solvent. In particular, when the cellulose solution is discharged in a mist form, it solidifies into granular (bead-like) particles. Meanwhile, the components of the cellulose solvent (tetraalkylammonium acetate, an aprotic polar solvent) separated from the cellulose and eluted into the molding aqueous solution are recovered by fractional distillation or other methods. After recovery, they are subjected to filtration, purification, or other processes to make them reusable as cellulose solvent.

[0105] The wet-molded body is washed and then dried to form a granular (bead-shaped) cellulose molded body. Washing the wet-molded body is performed by contacting it with a washing solution such as water at a room temperature of about 20-30°C, thereby replacing and separating the cellulose solvent in the wet-molded body with the washing water. As the washing water, a solvent with high affinity for cellulose and no solubility is preferred, and readily available water is particularly preferred. This washing is preferably performed multiple times (about twice) from the viewpoint of more reliably removing components other than cellulose from the wet-molded body.

[0106] A cellulose molded body (granular cellulose) can be obtained by appropriately drying the wet molded body after washing. The drying method is not particularly limited as long as the wet molded body after washing can be dried, and can be any method such as natural drying at room temperature or drying by a drying method such as hot air.

[0107] Following the low-crystallinity molding process S32, a collection process S33 is performed as needed. The collection process S33 is a process of removing unwanted particles from the granular cellulose molded body (cellulose beads) molded in the low-crystallinity molding process S32 and recovering a cellulose molded body with suitable particles. The collection means is not particularly limited as long as it is possible to recover the appropriate particles, but collection can be done using known collection methods such as bag filters or cyclone dust collectors.

[0108] The molded cellulose article has a cellulose type II crystalline structure because the cellulose crystalline structure changes to cellulose type II after the cellulose raw material is dissolved in a cellulose solvent and regenerated. Furthermore, the molded cellulose article is a low-crystallinity cellulose article. A low-crystallinity cellulose article preferably has a crystallinity of 60% or less. The crystallinity is the proportion of crystalline components in the cellulose article and affects physical properties such as transparency and strength. Generally, the lower the crystallinity, the more transparent the cellulose article tends to be.

[0109] The degree of crystallinity can be calculated by X-ray diffraction measurement using the following equation (i). In equation (i), Ic is the diffraction intensity of the cellulose type II crystal lattice plane ((1-10) plane, peak value around 2θ=13°), Ia1 is the diffraction intensity at the point where the line connecting the diffraction intensities at 2θ=8° and 15° intersects with the line drawn perpendicularly from 13°, and Ia2 is the diffraction intensity of the amorphous region (2θ=15°).

[0110]

number

[0111] The cellulose molded article of the third embodiment exhibits improved performance in various aspects, such as transparency, flexibility, dyeability, and chemical reactivity during post-processing, due to its low crystallinity. The transparency of the cellulose molded article contributes to its appearance. Highly transparent cellulose molded articles have good design and aesthetic appeal. Furthermore, this cellulose molded article possesses both water resistance and organic solvent resistance derived from cellulose. Therefore, since this cellulose molded article does not dissolve when added to various solutions, it is suitable as a constituent material for additives with functional properties such as lubricants and antiblocking agents, and is promising as a substitute raw material for PMMA. Moreover, since this cellulose molded article is plant-derived, it is recyclable even when used as an additive.

[0112] The film formation process S34 is a process in which a molded cellulose molded body of low-crystallinity cellulose fine fibers is added to the cellophane raw material as an additive such as a lubricant or antiblocking agent to form a film. In the film formation process S34, known manufacturing methods such as the viscose method and the ionic liquid method can be suitably used. For example, in the viscose method, raw materials such as pulp are prepared into viscose using alkali and carbon disulfide as the cellophane raw material, and after the cellulose molded body is added to this viscose, the viscose is discharged in a film-like manner into an acid solution such as sulfuric acid, and the film-like solidification is obtained to obtain cellophane. In the ionic liquid method, raw materials such as pulp are prepared into a cellulose solution by dissolving them in a solvent containing an ionic liquid as the cellophane raw material, and the cellulose solution is discharged in a film-like manner into water, and the film-like solidification is obtained to obtain cellophane.

[0113] As described above, in the cellophane manufacturing method of the third embodiment, a cellulose molded body of low-crystallinity cellulose fine fibers, which can be efficiently obtained through a simple process, can be suitably used as a substitute raw material for PMMA as a lubricant or antiblocking agent. Furthermore, by adding the obtained cellulose molded body to the cellophane raw material as an antiblocking agent or lubricant, 100% biodegradable cellophane derived from cellulose can be obtained, thereby reducing the environmental burden.

[0114] Incidentally, in cellulose molded articles used as a substitute raw material for PMMA as a lubricant or antiblocking agent, recycling is recommended as one of the recent efforts toward realizing an environmentally conscious circular society, so it is preferable to use recycled cellulose as a constituent material. Examples of recycled cellulose materials include regenerated cellulose obtained by generating viscose from cellulose raw materials such as pulp and solidifying it, or by directly dissolving cellulose raw materials with an ionic liquid. Furthermore, since cellophane is a product that is commonly distributed using regenerated cellulose, recycling cellophane and using it as a constituent material for cellulose molded articles makes it possible to provide cellulose molded articles that contribute to reducing environmental impact.

[0115] Generally, regenerated cellulose is known to be a difficult material to recycle because it does not have thermoplastic properties. Therefore, the inventors investigated the recycling of cellophane and found that it could be recycled by treating it to reduce the degree of polymerization of regenerated cellulose, and proceeded to manufacture granular cellulose molded products using cellophane (regenerated cellulose) as a recycled material. However, when the obtained cellulose molded product was used as an additive to cellophane in place of PMMA as a lubricant or antiblocking agent, it was found that the cellulose molded product swelled and collapsed in strongly alkaline viscose, making it difficult to use as an additive to cellophane.

[0116] The inventors conducted further intensive research to ensure that cellulose molded bodies using regenerated cellulose could be appropriately used as an additive for cellophane. As a result, they discovered that a composite cellulose molded body, obtained by mixing regenerated cellulose and cellulose fine fibers under predetermined conditions, can be suitably used as an additive for cellophane.

[0117] The above-mentioned composite cellulose molded article can be suitably produced by the composite cellulose molded article manufacturing method (S40) shown in Figure 4. This composite cellulose molded article manufacturing method (S40) includes a mixing step (S41) and a composite molding step (S42).

[0118] Mixing step S41 is a step in which unmodified cellulose fine fibers are mixed with a cellulose dispersion derived from regenerated cellulose to obtain a cellulose composite liquid. The cellulose dispersion derived from regenerated cellulose is a cellulose dispersion obtained using regenerated cellulose as a dispersion liquid raw material, and is obtained by a manufacturing method (S50) that includes a grinding step (S51), a regeneration depolymerization step (S52), and a micronization step (S53), as shown in Figure 5.

[0119] The regenerated cellulose used as the raw material for the dispersion is a material in an appropriate form such as fibrous, film-like, or spherical, manufactured by a known method, or a regenerated cellulose product obtained by processing the manufactured regenerated cellulose, or a regenerated material using these. These regenerated celluloses are type II cellulose having a type II crystalline structure.

[0120] Regenerated cellulose can be produced by methods such as chemically derivatizing cellulose raw materials using the viscose process and then dissolving them with a solvent, or by dissolving cellulose raw materials with an ionic liquid. Examples of regenerated cellulose products include paper products, clothing, and sanitary products processed from molded products such as rayon, cellophane, and cellulose beads.

[0121] Furthermore, recycled materials for regenerated cellulose include scraps and other materials generated during the manufacturing process of molded products and other items made from regenerated cellulose. Since regenerated cellulose products and scraps were previously discarded as difficult to recycle, using them as recycled raw materials can significantly contribute to reducing environmental impact.

[0122] When using regenerated cellulose as a dispersion raw material, the lower the degree of polymerization, the easier it is to defibrillate and process the cellulose, thereby improving production efficiency. On the other hand, if the degree of polymerization of the regenerated cellulose is too high, the cellulose may become difficult to defibrillate, potentially reducing its processability. Therefore, it is desirable that the degree of polymerization of the regenerated cellulose used be around 600 or less. Generally, the degree of polymerization of regenerated cellulose produced by the viscose method is around 200 to 300, and the degree of polymerization of regenerated cellulose obtained using cellulose solvents such as ionic liquids is around 600. Therefore, these regenerated celluloses can be suitably used as dispersion raw materials.

[0123] The grinding step S51 is a process of grinding the regenerated cellulose, which is the raw material for the dispersion, to obtain a grinding raw material. This grinding step aims to improve the reactivity of the grinding raw material (regenerated cellulose) in the regenerated depolymerization step (S52) described later by grinding the regenerated cellulose of the raw material for the dispersion into fine particles. It is preferable that the grinding raw material obtained in grinding step S51 is ground to a size of 500 μm or less. The size of the grinding raw material is measured in accordance with JIS Z 8825 (2013) using a laser diffraction / scattering particle size distribution analyzer. If the ground regenerated cellulose (grinding raw material) is too large, the reactivity in the regenerated depolymerization step (S52) described later may be insufficient, which may reduce productivity. In this grinding step, known grinding methods such as dry grinding and wet grinding can be used as appropriate.

[0124] The regeneration depolymerization step S52 is a step in which the degree of polymerization of the pulverized raw material obtained in the pulverization step S51 is reduced to obtain depolymerized cellulose. In this regeneration depolymerization step S52, the structure of the pulverized regeneration cellulose is weakened by the depolymerization of the pulverized raw material, making the cellulose more easily defibrillated (depolymerized cellulose). The degree of polymerization of the depolymerized cellulose obtained in the regeneration depolymerization step S52 is adjusted using chemicals such as sodium hypochlorite or enzymes. The degree of polymerization of the depolymerized cellulose is preferably around 350 or less. If the degree of polymerization of the depolymerized cellulose is too high, the defibrillability in the finer processing step (S53) described later may be insufficient, which may reduce productivity.

[0125] In the regeneration depolymerization step S52, it is preferable to use sodium hypochlorite when depolymerizing the pulverized raw material. Sodium hypochlorite oxidizes the hydroxyl groups at positions 2 and 3 of cellulose, causing a β-alkoxy elimination reaction due to the carbonyl group, which depolymerizes the cellulose. Sodium hypochlorite is suitable because it is easy to handle and the degree of polymerization of regenerated cellulose can be efficiently reduced by controlling the pH and temperature. Furthermore, the higher the concentration of sodium hypochlorite, the easier it is to reduce the degree of polymerization of regenerated cellulose, and in particular, when the effective chlorine concentration is 0.13% or higher, and more preferably 3% or higher, the degree of polymerization of regenerated cellulose can be reduced more efficiently.

[0126] The micronization process S53 is a process in which the depolymerized cellulose obtained in the regeneration depolymerization process S52 is micronized to obtain micronized cellulose. The micronization of the depolymerized cellulose is performed by mechanical (physical) defibrillation. Mechanical defibrillation is a defibrillation method that is carried out by known physical (mechanical) methods such as homogenizers and water jets. In this mechanical defibrillation, defibrillation is performed mechanically without using chemical substances (chemical defibrillation), so it takes the form of a dispersion of unmodified cellulose fine particles (cellulose dispersion), which is highly safe. Furthermore, since the degree of polymerization of the regeneration cellulose, which is the raw material for the dispersion, has been reduced in the regeneration depolymerization process S52, it can be easily defibrillated and micronized even without applying high pressure. Thus, because the micronization of depolymerized cellulose is easy, it is also advantageous in terms of equipment for the micronization process S53.

[0127] Furthermore, the micronization (mechanical defibration) of depolymerized cellulose may be carried out in multiple stages as needed. Examples of multiple defibration stages include performing preliminary defibration on the depolymerized cellulose (dispersion) followed by main defibration. Preliminary defibration is carried out by known methods, such as using a mixer or refiner. Preliminary defibration helps to suppress malfunctions such as clogging of the defibration equipment, which is significant from the standpoint of protecting the equipment. By performing preliminary defibration using a mixer, etc., followed by main defibration using a homogenizer, etc., uniform micronized cellulose with small particle sizes can be obtained.

[0128] The micronization of depolymerized cellulose only requires that the average particle size be reduced from nanoscale to several hundred nanoscale, and the transparency of the dispersion of micronized cellulose improves when it is around 2 to 800 nm, more preferably 500 nm or less. The cellulose dispersion derived from regenerated cellulose obtained in this way is highly safe because the dispersed cellulose is not chemically modified, and it also has good aesthetic appeal due to its small particle size.

[0129] Thus, the method for producing a cellulose dispersion derived from regenerated cellulose, S50, can efficiently obtain a cellulose dispersion by effectively using appropriate regenerated cellulose, including cellophane and other materials that are difficult to recycle.

[0130] Unmodified cellulose microfibers are materials used to suppress the swelling of regenerated cellulose, which is the raw material for cellulose dispersions derived from regenerated cellulose, in alkaline solutions. As mentioned above, granular cellulose molded bodies made using regenerated cellulose swell and collapse in strongly alkaline viscose. This is thought to be because the molded body is an aggregate of fine particles, making it prone to swelling and collapse when immersed in an alkaline solution. On the other hand, unmodified cellulose microfibers are formed by the intertwining of fibers, so they hardly swell even in alkaline solutions. Therefore, it is thought that by mixing unmodified cellulose microfibers with cellulose dispersions derived from regenerated cellulose, the cellulose microfibers act as a binder for the regenerated cellulose particles (molded bodies) in the dispersion, thereby suppressing the swelling of the cellulose molded bodies in alkaline solutions.

[0131] It is preferable to mix unmodified cellulose microfibers with the regenerated cellulose-derived cellulose dispersion in a ratio of 1 to 80% by weight, more preferably 3 to 80% by weight, and even more preferably 5 to 80% by weight. Even a small amount of unmodified cellulose microfibers relative to the regenerated cellulose-derived cellulose dispersion suppresses swelling of the cellulose molded article. Furthermore, the effect of suppressing swelling of the cellulose molded article is enhanced by increasing the amount of unmodified cellulose microfibers mixed in, but if the amount is too high, the regenerated cellulose content decreases, which is undesirable from the viewpoint of reducing environmental impact. Therefore, by mixing an appropriate amount of unmodified cellulose microfibers with the regenerated cellulose-derived cellulose dispersion, with an upper limit of about 80% by weight, it is possible to appropriately suppress swelling of the cellulose molded article while contributing to reducing environmental impact.

[0132] The unmodified cellulose microfibers are preferably type I unmodified cellulose microfibers or type II unmodified cellulose microfibers. Type I unmodified cellulose microfibers can be obtained through the same process as the type I depolymerization step S11 and mechanical defibration step S12 of the cellophane manufacturing method S10 shown in Figure 1. Type II unmodified cellulose microfibers can be obtained through the same process as the mercerization step S21, type II depolymerization step S22, alkaline defibration step S23 and neutralization step S24 of the cellophane manufacturing method S20 shown in Figure 2.

[0133] Type I and Type II unmodified cellulose microfibers are highly safe because they are not chemically modified, and their small fiber diameter also gives them good design appeal. Furthermore, unlike cellulose microfibers with functional groups such as oxidized cellulose, Type I and Type II unmodified cellulose microfibers do not redissolve in water, thus possessing both water resistance and resistance to organic solvents derived from cellulose.

[0134] The composite molding process S42 is a process in which the cellulose composite liquid obtained in the mixing process S41 is dried to form a composite cellulose molded body. The finely ground cellulose, which is in the form of a dispersion, is dried by spray drying and aggregated to form a granular (bead-shaped) molded body. Since this molded body is formed using regenerated cellulose as the molded body raw material, it is a composite cellulose molded body derived from regenerated cellulose.

[0135] In the composite molding process S42, it is preferable that the viscosity of the finely milled cellulose dispersion, measured using a B-type viscometer under the condition of a shear rate of 4.0 / sec according to JIS Z 8803 (2011), be 15,000 mPa·s or less. If the viscosity of the finely milled cellulose dispersion is too high, the fluidity of the solution will decrease, which may cause blockage of the liquid supply piping to the spray drying apparatus and the spray drying nozzles. By having the finely milled cellulose dispersion with an appropriate viscosity, the fluidity of the solution will be good.

[0136] Furthermore, the conditions for spray drying are an air pressure of approximately 0.025 to 0.6 MPa. If the air pressure for spray drying is insufficient, the cellulose particles will not be properly atomized, resulting in larger particle sizes and a deterioration of physical properties and texture. In addition, increasing the air pressure above 0.6 MPa would require an oversized air generator, making it impractical.

[0137] In the manufacturing method S40 for composite cellulose molded articles, a collection step S43 is performed after the composite molding step S42 as needed. The collection step S43 is a step in which unwanted particles are removed from the granular composite cellulose molded article (composite cellulose beads) molded in the composite molding step S42, and composite cellulose molded articles with suitable particles are recovered. The collection means is not particularly limited as long as it is possible to recover the appropriate particles, but collection can be done using known collection means such as a bag filter or a cyclone dust collector.

[0138] The molded composite cellulose article is composed of 99-20% by weight of cellulose derived from regenerated cellulose and 1-80% by weight of unmodified cellulose microfibers. By mixing unmodified cellulose microfibers with the cellulose derived from regenerated cellulose, the swelling of the regenerated cellulose in alkaline solutions is suppressed, improving its stability. Furthermore, because the composite cellulose article contains unmodified cellulose microfibers that have not undergone chemical modification, it is highly safe and possesses water resistance as well as organic solvent resistance inherent to cellulose. Therefore, since this composite cellulose article does not dissolve when added to various solutions, it is suitable as a component material for additives with functional properties such as lubricants and antiblocking agents, and is promising as a substitute raw material for PMMA. Moreover, because this composite cellulose article is plant-derived, it is recyclable even when used as an additive.

[0139] Furthermore, it is preferable that the surface of the composite cellulose molded article is coated with a surface treatment agent in order to impart appropriate functionalities such as water repellency and fluidity. As the surface treatment agent, any suitable treatment agent capable of imparting the desired functionality can be used. For example, at least one of the following is preferably used: wax-based treatment agents, synthetic resin-based treatment agents, chromium complex salt-based treatment agents, fluorine-based treatment agents, metal soap-based treatment agents, cationic surfactants, silicone-based treatment agents, amino acid-based treatment agents, etc. By using these surface treatment agents appropriately, the desired functionalities such as water repellency and fluidity can be appropriately imparted.

[0140] As described above, the method for producing a composite cellulose molded article involves a simple process of mixing unmodified cellulose fine fibers with a regenerated cellulose dispersion and molding it, thereby efficiently obtaining a composite cellulose molded article with suppressed swelling in alkaline solutions. Furthermore, because this composite cellulose molded article exhibits suppressed swelling in alkaline solutions, as described above, it is suitable as a substitute raw material for PMMA as a lubricant or antiblocking agent, and since it is a plant-derived molded article, it is easily recyclable even when used as an additive.

[0141] The above-described composite cellulose molded body can be suitably used as cellulose beads (composite cellulose beads). Furthermore, since these cellulose beads are intended to be used as a substitute raw material for PMMA, an additive in cellophane, it is required that swelling in alkaline solutions be appropriately suppressed. Therefore, it is preferable that the swelling rate of the cellulose beads when immersed in a 3% by weight aqueous sodium hydroxide solution for 24 hours is 500% or less, more preferably 300% or less, and even more preferably 200% or less.

[0142] The swelling rate is a value that represents the ratio of the swelling of cellulose beads after immersion to the swelling of cellulose beads before immersion, assuming that the cellulose beads are used as an additive in cellophane and the alkaline solution conditions are set as described above. If the swelling rate is too high, the cellulose beads will be prone to disintegration, and there is a risk that they will not be usable as a substitute raw material for PMMA as a lubricant or antiblocking agent. Cellulose beads with an appropriately controlled swelling rate are less prone to disintegration in alkaline solutions and can be suitably used as a substitute raw material for PMMA, and the lower the swelling rate, the more stable they are in alkaline solutions.

[0143] By using the above-mentioned composite cellulose beads as an additive such as a lubricant or anti-blocking agent in a film, cellophane (regenerated cellulose film) can be obtained in which 100% biodegradable additives made from plant-derived materials are used instead of additives made from plastic materials such as PMMA. This cellophane can be manufactured by known methods such as the viscose process. For example, in the viscose process, cellophane raw material (pulp) is immersed in an alkaline solution such as sodium hydroxide, carbon disulfide is added to it to cause sulfurization, viscose is prepared by alkaline dissolution, then aged, and the viscose with the composite cellulose beads added is extruded in a film-like manner into an acidic solution such as sulfuric acid, and solidified into a film to obtain cellophane. In this way, since the regenerated cellulose film using composite cellulose beads is composed of plant-derived materials, it is possible to reduce the amount of plastic used, and furthermore, it can be recycled into regenerated cellulose, enabling a circular process and contributing to the reduction of environmental impact. [Examples]

[0144] [Making cellophane] Cellophane samples 1-3, to which granular cellulose molded bodies (cellulose beads) were added, were prepared as follows. Note that the cellulose molded body in sample 1 is made of type II unmodified cellulose microfibers, the cellulose molded body in sample 2 is made of type I unmodified cellulose microfibers, and the cellulose molded body in sample 3 is made of low-crystallinity cellulose.

[0145] [Prototype Example 1] The cellophane for prototype example 1 was prepared according to the process diagram in Figure 2. First, 18% by weight of caustic soda (manufactured by Kishida Chemical Co., Ltd.) was heated to 50°C, and 2% by weight of dissolved pulp ("LNDP" manufactured by Nippon Paper Industries Ltd.), the cellulose raw material, was added and stirred until it became a slurry to perform mercing (mercing process). After that, the excess caustic soda was removed and the solid content was adjusted to 33% by weight. Aging treatment was performed at 50°C to obtain raw cellulose with a degree of polymerization of 752 for the merced cellulose (Type II depolymerization process).

[0146] 10.6g of raw cellulose, 330.65g of deionized water, and 8.75g of caustic soda (total caustic soda concentration 2.5%) were placed in a 500mL container, and preliminary defibration was performed using a mixer (Primix Corporation, "Labo-Solution"). Subsequently, main defibration was performed using a homogenizer (SMT Corporation, "LAB1000") (alkaline defibration process).

[0147] 125 g of the prepared slurry was taken and neutralized by adding 20% ​​by weight sulfuric acid while stirring (neutralization step). The neutralized sample was filtered by suction and washed with 300 mL of deionized water. Deionized water was added to the washed sample to a total weight of 250 g, and preliminary defibration was performed using a mixer (Primix Corporation, "Labo-Solution"). Subsequently, the final defibration was performed using a homogenizer (SMT Corporation, "LAB1000") to obtain a dispersion of type II unmodified cellulose fine fibers.

[0148] The dispersion of the obtained type II unmodified cellulose microfibers was spray-dried using a spray dryer (manufactured by Tokyo Rikakikai Co., Ltd.) at an air pressure of 0.2 MPa (processing volume of 300 ml / hr) to form granules (type II molding process). The particles were collected using a cyclone dust collector (manufactured by Tokyo Rikakikai Co., Ltd.) (collection process) to obtain a cellulose molded body of granular type II unmodified cellulose microfibers.

[0149] As a raw material for cellophane, dissolved pulp was immersed in an aqueous sodium hydroxide solution, sulfurized by adding carbon disulfide, and then alkaline-dissolved in an aqueous sodium hydroxide solution to prepare viscose. The resulting granular cellulose molded body was diluted with water and added to the viscose at a concentration of 800 ppm relative to the cellulose content to prepare a homogeneous dispersion. This dispersion was supplied to a slit using a gear pump and discharged into a bath of sulfuric acid and sodium sulfate to coagulate and regenerate the cellulose. The formed film was washed by passing it through a water tank, and then purified by passing it through a desulfurization bath of sodium sulfide and caustic soda, and a bleaching bath of sodium hypochlorite. Finally, it was passed through a softening bath containing a softening agent such as glycerin, and moisture was removed in a drum-type hot air dryer to produce a cellophane film with a thickness of approximately 21 μm (film formation process).

[0150] [Prototype Example 2] The cellophane for prototype example 2 was prepared according to the process diagram in Figure 1. First, 8 g of kraft pulp (degree of polymerization 1750, xylose concentration in constituent sugars 8.2%), the cellulose raw material, was added to 191 g of deionized water as a solvent and mixed using a mixer (Primix Corporation, "Labo-Solution"). 1 g of sodium hypochlorite was added to the slurry after mixing to obtain a solution with a sodium hypochlorite concentration of 0.5% and an available chlorine concentration of 0.04%. This solution was reacted in a 55°C water bath for 3 hours to obtain depolymerized cellulose in which the degree of polymerization of the cellulose raw material was reduced to 1200 (Type I depolymerization process).

[0151] Depolymerized cellulose was washed with deionized water, and deionized water was added to obtain a dispersion of 1600 g in total volume. This dispersion was pre-defibrated using a mixer (Primix Corporation, "Labo-Solution"), and then fully defibrated using a homogenizer (SMT Corporation, "LAB1000") under a pressure of 70 MPa to obtain a dispersion of type I unmodified cellulose fine fibers (mechanical defibration process).

[0152] The resulting dispersion of unmodified type I cellulose microfibers was spray-dried using a spray dryer (manufactured by Tokyo Rikakikai Co., Ltd.) at an air pressure of 0.2 MPa (processing volume of 300 ml / hr) to form granules (Type I molding process). The particles were collected using a cyclone dust collector (manufactured by Tokyo Rikakikai Co., Ltd.) (collection process) to obtain a cellulose molded body of granular unmodified type I cellulose microfibers.

[0153] As a raw material for cellophane, dissolved pulp was immersed in an aqueous sodium hydroxide solution, sulfurized by adding carbon disulfide, and then alkaline-dissolved in an aqueous sodium hydroxide solution to prepare viscose. The resulting granular cellulose molded body was diluted with water and added to the viscose at a concentration of 800 ppm relative to the cellulose content to prepare a homogeneous dispersion. This dispersion was supplied to a slit using a gear pump and discharged into a bath of sulfuric acid and sodium sulfate to coagulate and regenerate the cellulose. The formed film was washed by passing it through a water tank, and then purified by passing it through a desulfurization bath of sodium sulfide and caustic soda, and a bleaching bath of sodium hypochlorite. Finally, it was passed through a softening bath containing a softening agent such as glycerin, and moisture was removed in a drum-type hot air dryer to produce a cellophane film with a thickness of approximately 21 μm (film formation process).

[0154] [Prototype Example 3] The cellophane for prototype example 3 was prepared according to the process diagram in Figure 3. First, 28% by weight of tetrabutylammonium acetate (manufactured by Tokyo Chemical Industry Co., Ltd.) was mixed with 72% by weight of dimethyl sulfoxide (manufactured by Kishida Chemical Co., Ltd.) as an aprotic polar solvent to obtain a cellulose solvent. 1410g of the cellulose solvent was placed in a 2L separable flask, and 90g of dissolved pulp (manufactured by Oji Paper Co., Ltd.; "LDKP", xylose concentration in constituent sugars 1.9%) as a cellulose raw material was added to the cellulose solvent. The mixture was then dissolved in a 55°C water bath while stirring with a stirrer (manufactured by Kobe Steel Environmental Solutions Co., Ltd.; "Logbone") to obtain a cellulose solution (cellulose dissolution process).

[0155] Using a cellulose solvent prepared identically to the one used to dissolve the cellulose material, a molding aqueous solution was prepared to a concentration of 20% and a temperature of 10°C. A gear pump (Barmag; "Oerlikon") was used to discharge the cellulose solution from a nozzle into the molding aqueous solution, causing it to solidify and obtaining a granular wet molded body. After washing the obtained wet molded body with running water, it was air-dried to obtain a granular low-crystallinity cellulose molded body (low-crystallinity molding process).

[0156] As a raw material for cellophane, dissolved pulp was immersed in an aqueous sodium hydroxide solution, sulfurized by adding carbon disulfide, and then alkaline-dissolved in an aqueous sodium hydroxide solution to prepare viscose. The resulting granular cellulose molded body was diluted with water and added to the viscose at a concentration of 800 ppm relative to the cellulose content to prepare a homogeneous dispersion. This dispersion was supplied to a slit using a gear pump and discharged into a bath of sulfuric acid and sodium sulfate to coagulate and regenerate the cellulose. The formed film was washed by passing it through a water tank, and then purified by passing it through a desulfurization bath of sodium sulfide and caustic soda, and a bleaching bath of sodium hypochlorite. Finally, it was passed through a softening bath containing a softening agent such as glycerin, and moisture was removed in a drum-type hot air dryer to produce a cellophane film with a thickness of approximately 21 μm (film formation process).

[0157] [Measurement of the coefficient of dynamic friction] As Comparative Example 1, a cellophane film was prepared by adding PMMA (manufactured by Nippon Shokubai Co., Ltd.; "Epostor") to cellophane. For the cellophane films of Prototype Example 1 and Comparative Example, the dynamic friction coefficient (μk) was measured using a Tensilon universal tester (manufactured by A&D Co., Ltd.; "RTG-1210") under the conditions of a load of 236g, a travel distance of 160mm, and a speed of 200mm / min, in accordance with ASTM-D-1894-95. The measurement results of the dynamic friction coefficient for Prototype Example 1 and Comparative Example are shown in Table 1. Note that Prototype Examples 2 and 3 were not measured, so they are indicated with "-".

[0158] [Table 1]

[0159] [Results and Discussion (1)] As shown in Table 1, the cellophane of Prototype Example 1 had a dynamic friction coefficient close to that of the comparative example cellophane with added PMMA, and possessed equivalent slipperiness. Therefore, it was demonstrated that the cellulose molded article of type II unmodified cellulose microfibers (Prototype Example 1) can be suitably used as a substitute material for PMMA. Furthermore, the cellophanes of Prototype Examples 1 to 3 could be wound onto and unwound from the rolls during the creation of the prototypes. Therefore, it was demonstrated that the cellulose molded article of type I unmodified cellulose microfibers (Prototype Example 2) and the low-crystallinity cellulose molded article (Prototype Example 3) can also be suitably used as a substitute material for PMMA. Since each of these cellulose molded articles is suitable as a substitute material for PMMA, by adding them, it is possible to obtain 100% biodegradable cellophane derived from cellulose, thereby reducing the environmental burden.

[0160] [Composite cellulose molded product] The composite cellulose molded articles of prototype examples 11 to 20 were manufactured as follows, according to the process diagram shown in Figure 4. Regenerated cellulose-derived cellulose dispersion and unmodified cellulose microfibers were used as constituent materials for the composite cellulose molded articles. Regenerated cellulose-derived cellulose dispersion A and regenerated cellulose-derived cellulose dispersion B were manufactured as follows, according to the process diagram shown in Figure 5. Unmodified cellulose microfibers, specifically Type I unmodified cellulose microfibers and Type II unmodified cellulose microfibers, were manufactured as follows.

[0161] [Preparation of Cellulose Dispersion A derived from regenerated cellulose] The raw material for the dispersion, regenerated cellulose (manufactured by Futamura Chemical Co., Ltd.; "NPU"), was crushed to 500 μm using a hammer crusher (manufactured by Sansho Industry Co., Ltd.) (crushing step). 2 kg of the resulting crushed raw material was mixed with 6 kg of sodium hypochlorite (15% solution, effective chlorine concentration 1.3%) and reacted in a 60°C water bath for 1 hour to obtain depolymerized cellulose (regenerated depolymerization step). This depolymerized cellulose was washed with deionized water, and then deionized water was added to make a dispersion of 40 kg in total volume. Preliminary defibration was performed using a mixer (manufactured by Primix Co., Ltd., "Labo-Solution"), and then the final defibration was performed using a homogenizer (manufactured by SMT Co., Ltd.) under a pressure of 70 MPa to finely pulverize it, obtaining a cellulose dispersion A derived from regenerated cellulose with a solid content of 4.6% by weight (fine pulverization step).

[0162] [Preparation of Cellulose Dispersion B derived from regenerated cellulose] The regenerated cellulose used as the dispersion raw material was prepared by adding crushed dissolved pulp to a TBAA / DMSO mixed solvent to a concentration of 10%, dissolving it in a kneader (manufactured by Seiwa Giken Co., Ltd.) while heating the contents to over 50°C, and then extruding the resulting cellulose solution in a film form into a water bath from a T-die (manufactured by Plastics Engineering Laboratory Co., Ltd.) to solidify, and then passing it through a cellophane production line. The obtained regenerated cellulose was crushed to 500 μm using a hammer crusher (manufactured by Sansho Industry Co., Ltd.) (crushing process), and 6 kg of sodium hypochlorite (15% solution, effective chlorine concentration 1.3%) was added to 2 kg of the obtained crushed raw material and reacted in a 60°C water bath for 1 hour to obtain depolymerized cellulose (regenerated depolymerization process). This depolymerized cellulose was washed with deionized water, and then deionized water was added to make a dispersion of 40 kg in total volume. After preliminary defibration in a mixer (Primix Corporation, "Labo-Solution"), the main defibration was performed in a homogenizer (SMT Corporation) under a pressure of 70 MPa to finely pulverize it, and a cellulose dispersion B derived from regenerated cellulose with a solid content of 3.9% by weight was obtained (fine pulverization process).

[0163] [Preparation of Type I unmodified cellulose microfibers] 4 g of kraft pulp, the raw material for cellulose, was mixed with 166 g of deionized water as a solvent using a mixer (Primix Corporation, "Labo-Solution"). 30 g of sodium hypochlorite was added to the resulting slurry to obtain a solution with a sodium hypochlorite concentration of 15% and an available chlorine concentration of 1.3%. This solution was reacted in a 60°C water bath for 1 hour to obtain depolymerized cellulose (Type I depolymerization step). The depolymerized cellulose was washed by displacement with deionized water, and deionized water was added to obtain a dispersion of 200 g in total volume. After preliminary defibration of this dispersion using a mixer (Primix Corporation, "Labo-Solution"), the final defibration was performed using a homogenizer (SMT Corporation) under a pressure of 70 MPa to obtain Type I unmodified cellulose fine fibers with a solid content of 1.6% by weight.

[0164] [Preparation of Type II unmodified cellulose microfibers] 18% by weight caustic soda (manufactured by Kishida Chemical Co., Ltd.) was heated to 50°C, and 2% by weight of dissolved pulp (manufactured by Nippon Paper Industries Ltd., "LNDP"), the cellulose raw material, was added and stirred until it became a slurry to perform merceleration (merceleration process). After that, excess caustic soda was removed and the solid content was adjusted to 33% by weight. Aging treatment was performed at 50°C to obtain raw cellulose with a degree of polymerization of 752 for the mercelerated cellulose (Type II depolymerization process). 10.6g of raw cellulose, 330.65g of deionized water, and 8.75g of caustic soda (total caustic soda concentration 2.5%) were placed in a 500mL container and pre-defibration was performed using a mixer (manufactured by Primix Corporation, "Labo-Solution"). After that, main defibration was performed using a homogenizer (manufactured by SMT Corporation, "LAB1000") (alkaline defibration process). 125 g of the prepared slurry was taken and neutralized by adding 20% ​​by weight sulfuric acid while stirring (neutralization step). The neutralized sample was filtered by suction and washed with 300 mL of deionized water. Deionized water was added to the washed sample to a total weight of 250 g, and preliminary defibration was performed using a mixer (Primix Corporation, "Labo-Solution"). Subsequently, final defibration was performed using a homogenizer (SMT Corporation, "LAB1000") to obtain a dispersion of type II unmodified cellulose fine fibers with a solid content of 4.2% by weight.

[0165] [Fabrication of composite cellulose molded bodies] The proportions of regenerated cellulose-derived cellulose dispersion and unmodified cellulose microfibers were changed and mixed in a mixer (Primix Corporation, "Labo-Solution") to adjust the mixing ratio of unmodified cellulose microfibers and obtain a cellulose composite liquid (mixing step). The obtained cellulose composite liquid was spray-dried in a spray dryer (Tokyo Rikakikai Co., Ltd.) at an air pressure of 0.2 MPa (processing volume of 300 ml / hr) (composite molding step). Particles were collected using a cyclone dust collector (Tokyo Rikakikai Co., Ltd.) to obtain composite cellulose molded articles of prototype examples 11 to 20.

[0166] [Prototype Example 11] Prototype Example 11 is a composite cellulose molded article consisting of 214.2 g of cellulose dispersion A derived from regenerated cellulose and 6.1 g of unmodified type I cellulose microfibers, with the unmodified cellulose microfibers being mixed at a ratio of 1% by weight.

[0167] [Prototype Example 12] Prototype Example 12 is a composite cellulose molded article consisting of 212.1 g of cellulose dispersion A derived from regenerated cellulose and 12.3 g of type I unmodified cellulose microfibers, with the unmodified cellulose microfibers being mixed at a ratio of 2% by weight.

[0168] [Prototype Example 13] Prototype Example 13 is a composite cellulose molded article consisting of 210.0 g of cellulose dispersion A derived from regenerated cellulose and 18.4 g of unmodified type I cellulose microfibers, with a mixing ratio of 3% by weight of unmodified cellulose microfibers.

[0169] [Prototype Example 14] Prototype Example 14 is a composite cellulose molded article consisting of 205.6 g of cellulose dispersion A derived from regenerated cellulose and 30.7 g of type I unmodified cellulose microfibers, with the unmodified cellulose microfibers being mixed at a ratio of 5% by weight.

[0170] [Prototype Example 15] Prototype Example 15 is a composite cellulose molded article consisting of 194.8 g of cellulose dispersion A derived from regenerated cellulose and 61.3 g of type I unmodified cellulose microfibers, with the unmodified cellulose microfibers being mixed at a ratio of 10% by weight.

[0171] [Prototype Example 16] Prototype example 16 is a composite cellulose molded article consisting of 173.2 g of cellulose dispersion A derived from regenerated cellulose and 122.7 g of type I unmodified cellulose microfibers, with the unmodified cellulose microfibers being mixed at a ratio of 20% by weight.

[0172] [Prototype Example 17] Prototype Example 17 is a composite cellulose molded article consisting of 204.6 g of cellulose dispersion B derived from regenerated cellulose and 122.7 g of type I unmodified cellulose microfibers, with the unmodified cellulose microfibers being mixed at a ratio of 20% by weight.

[0173] [Prototype Example 18] Prototype Example 18 is a composite cellulose molded article consisting of 129.9 g of cellulose dispersion A derived from regenerated cellulose and 95.9 g of unmodified type II cellulose microfibers, with a mixing ratio of 40% by weight of unmodified cellulose microfibers.

[0174] [Prototype Example 19] Prototype Example 19 is a composite cellulose molded article consisting of 86.6 g of cellulose dispersion A derived from regenerated cellulose and 143.9 g of unmodified type II cellulose microfibers, with a mixing ratio of 60% by weight of unmodified cellulose microfibers.

[0175] [Prototype Example 20] Prototype example 20 is a composite cellulose molded article consisting of 43.3 g of cellulose dispersion A derived from regenerated cellulose and 191.8 g of type II unmodified cellulose microfibers, with the unmodified cellulose microfibers being mixed at a ratio of 80% by weight.

[0176] [Comparative Example 2] As Comparative Example 2, a cellulose molded article was prepared using regenerated cellulose that did not contain unmodified cellulose microfibers as the molding material. The cellulose molded article of Comparative Example 2 was obtained by spray-drying a cellulose dispersion A derived from regenerated cellulose using a spray dryer (manufactured by Tokyo Rikakikai Co., Ltd.) at an air pressure of 0.2 MPa (processing volume of 300 ml / hr) to form granules.

[0177] [Measurement of swelling rate] 0.1 g of a composite cellulose molded body was added to 9.9 g of a 3 wt% sodium hydroxide aqueous solution and stirred for 3 minutes. After stirring, the mixture was allowed to stand for 24 hours, and the average particle size (D50) was measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac-Bell Co., Ltd., "MT3200II"). Similarly, the average particle size (D50) was measured for composite cellulose molded bodies dispersed in deionized water at arbitrary concentrations, and the swelling rate was calculated using the following formula. The average particle size (D50) after immersion in sodium hydroxide aqueous solution for 24 hours was defined as P1, and the average particle size (D50) in deionized water was defined as P0. Swelling rate (%) = (P1 / P0) × 100

[0178] [Table 2]

[0179] [Results and Discussion (2)] Comparative Example 2 is a cellulose molded article made from regenerated cellulose that does not contain unmodified cellulose microfibers, whereas Prototype Examples 11-20 are composite cellulose molded articles made from regenerated cellulose that contains unmodified cellulose microfibers. As shown in Table 2, the composite cellulose molded articles of Prototype Examples 11-20 all had lower swelling rates than the cellulose molded article of Comparative Example 2, and their stability in alkaline solutions was improved.

[0180] As can be seen from Table 2, the swelling rates of prototypes 11-20 tended to decrease as the mixing ratio of unmodified cellulose microfibers increased. In comparative example 2, which contained no unmodified cellulose microfibers (mixing ratio 0% by weight), the swelling rate exceeded 600%, whereas even with a small amount (mixing ratio 1% by weight), as in prototype example 11, the swelling rate remained below 500% (swelling rate 460.4%), demonstrating an excellent swelling suppression effect.

[0181] Furthermore, when the mixing ratio of unmodified cellulose microfibers was around 3-5% by weight (Prototype Examples 13 and 14), the swelling rate was around 300% (especially in Prototype Example 14 with a mixing ratio of 5% by weight, the swelling rate was 282.9%), demonstrating a significant improvement in the swelling suppression effect. Moreover, it was found that when the mixing ratio of unmodified cellulose microfibers was around 40% by weight (Prototype Example 18), the swelling rate fell below 200%, indicating an even better swelling suppression effect.

[0182] Thus, in granular cellulose molded articles using regenerated cellulose, even a small amount of unmodified cellulose microfibers mixed in suppresses swelling in alkaline solutions and improves stability. This is thought to be because, when fine-particle regenerated cellulose and fibrous unmodified cellulose microfibers are mixed, the unmodified cellulose microfibers, which do not swell easily in alkaline solutions, act as a binder for the regenerated cellulose particles, suppressing the swelling of the cellulose molded article.

[0183] Furthermore, when cellophane films were prepared using the composite cellulose molded bodies of prototypes 11-20 as additives, swelling was appropriately suppressed in all cases, and good slipperiness was obtained. Therefore, the composite cellulose molded bodies of prototypes 11-20 are suitable as alternative materials to PMMA. [Industrial applicability]

[0184] The present invention's method for producing cellulose molded articles allows for the efficient and simple acquisition of cellulose molded articles suitable as a substitute for PMMA, thereby significantly contributing to the reduction of environmental impact. Furthermore, the present invention's method for producing composite cellulose molded articles allows for the efficient and simple acquisition of composite cellulose molded articles suitable as a substitute for PMMA by mixing regenerated cellulose and unmodified cellulose fine fibers, thereby significantly contributing to the reduction of environmental impact. [Explanation of Symbols]

[0185] S10 Method for manufacturing a cellulose molded article (a molded article of type I unmodified cellulose fine fibers) S11 Type I depolymerization process S12 Mechanical defibration process S13 I-type molding process S14 Collection process S15 Film Formation Process S20 Method for manufacturing a cellulose molded body (a molded body of type II unmodified cellulose fine fibers) S21 Mercerization process S22 Type II depolymerization process S23 Alkali defibration process S24 Neutralization process S25 II molding process S26 Collection process S27 Film Formation Process S30 Method for manufacturing cellulose molded articles (low-crystallinity cellulose molded articles) S31 Cellulose dissolution process S32 Low crystal molding process S33 Collection process S34 Film Formation Process S40 Method for manufacturing a composite cellulose molded article S41 Mixing process S42 Composite molding process S43 Collection process S50 Method for producing a cellulose dispersion derived from regenerated cellulose S51 Grinding Process S52 Regeneration depolymerization process S53 Refinement process

Claims

1. The process includes: a type I depolymerization step in which sodium hypochlorite is added to a cellulose raw material to reduce the degree of polymerization of the cellulose raw material; a mechanical defibration step in which the depolymerized cellulose obtained in the type I depolymerization step is defibrated by mechanical defibration; a type I molding step in which the type I unmodified cellulose fine fibers obtained in the mechanical defibration step are dried to form a cellulose molded body; and a film formation step in which the cellulose molded body is added to a cellophane raw material as a lubricant and / or antiblocking agent to form a film. A method for manufacturing cellophane, characterized by the following features.

2. The process includes: a mercerization step of mercing a cellulose raw material; a type II depolymerization step of reducing the degree of polymerization of the mercerized cellulose obtained in the mercerization step; an alkali defibration step of adding an alkali metal hydroxide to the mercerized depolymerized cellulose obtained in the type II depolymerization step to defibrate the mercerized depolymerized cellulose; a neutralization step of neutralizing the cellulose microfibers obtained in the alkali defibration step with an acid; a type II molding step of drying the type II unmodified cellulose microfibers obtained in the neutralization step to form a cellulose molded body; and a film formation step of adding the cellulose molded body to a cellophane raw material as a lubricant and / or antiblocking agent to form a film. A method for manufacturing cellophane, characterized by the following features.

3. The process includes a cellulose dissolution step in which a cellulose raw material is dissolved in a cellulose solvent; a low-crystallinity molding step in which the cellulose solution obtained in the cellulose dissolution step is discharged into a molding aqueous solution containing the cellulose solvent to produce a wet molded body, and the wet molded body is washed and dried to form the cellulose molded body; and a film formation step in which the cellulose molded body is added to a cellophane raw material as a lubricant and / or antiblocking agent to form a film. A method for manufacturing cellophane, characterized by the following features.

4. A method for producing a composite cellulose molded article, comprising a mixing step of mixing unmodified cellulose fine fibers in a ratio of 1 to 80% by weight into a cellulose dispersion derived from regenerated cellulose, and a composite molding step of drying the cellulose composite liquid obtained in the mixing step to form a cellulose molded article.

5. The method for producing a composite cellulose molded article according to claim 4, wherein the cellulose dispersion derived from regenerated cellulose is a cellulose dispersion obtained by a process comprising: a grinding step of using regenerated cellulose as a dispersion raw material and grinding the dispersion raw material; a regenerative depolymerization step of reducing the degree of polymerization of the grinding raw material obtained in the grinding step; and a micronization step of micronizing the depolymerized cellulose obtained in the regenerative depolymerization step.

6. The method for producing a composite cellulose molded article according to claim 4 or 5, wherein the unmodified cellulose fine fibers are obtained by a type I depolymerization step of adding sodium hypochlorite to a cellulose raw material to reduce the degree of polymerization of the cellulose raw material, and a mechanical defibration step of mechanically defibrating the depolymerized cellulose obtained in the type I depolymerization step.

7. A method for producing a composite cellulose molded article according to claim 4 or 5, wherein the unmodified cellulose microfibers are obtained by a mercerization step of mercerizing a cellulose raw material, a type II depolymerization step of reducing the degree of polymerization of the mercerized cellulose obtained by the mercerization step, an alkali defibration step of adding an alkali metal hydroxide to the mercerized depolymerized cellulose obtained by the mercerization step to defibrate it, and a neutralization step of neutralizing the cellulose microfibers obtained by the alkali defibration step with an acid.

8. A cellulose molded article using regenerated cellulose, The cellulose molded article is characterized by comprising 99 to 20% by weight of cellulose derived from regenerated cellulose and 1 to 80% by weight of unmodified cellulose fine fibers.

9. The composite cellulose molded article according to claim 8, wherein the surface of the cellulose molded article is coated with a surface treatment agent.

10. The composite cellulose molded article according to claim 9, wherein the surface treatment agent comprises at least one of the following: a wax-based treatment agent, a synthetic resin-based treatment agent, a chromium complex salt-based treatment agent, a fluorine-based treatment agent, a metal soap-based treatment agent, a cationic surfactant, a silicone-based treatment agent, and an amino acid-based treatment agent.

11. A cellulose bead comprising a composite cellulose molded body according to any one of claims 8 to 10, characterized in that the cellulose bead has a swelling rate of 500% or less when immersed in a 3% by weight sodium hydroxide aqueous solution for 24 hours.

12. The composite cellulose beads according to claim 11, wherein the swelling rate is 200% or less.

13. A cellophane characterized by being a film to which the composite cellulose beads described in claim 11 are added.

14. A cellophane characterized by being a film to which the composite cellulose beads described in claim 12 are added.

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