Alkali cellulose material, viscose, and method for producing viscose

Abstract

The present invention addresses the problem of using a recycled cellulose as a starting material to provide an alkali cellulose material capable of yielding viscose having physical properties suitable for use as a starting material for the molding of a variety of cellulose molded objects. The means for solving this problem is an alkali cellulose material which is used as an intermediate material for producing viscose through sulfidization with carbon disulfide, said material containing recycled cellulose, an alkali, and water, and having a cellulose concentration of 27-40 mass% and an alkali concentration of 8-20 mass%.

Description

Alkali cellulose material, viscose, and method for producing viscose

[0001] The present invention relates to an alkali cellulose material that is an intermediate material for producing viscose, and in particular to an alkali cellulose material that uses regenerated cellulose as a raw material.

[0002] The production of cellulose products such as cellophane, rayon, and beads generates by-products such as scraps and off-spec products. However, because cellulose is not thermoplastic and does not dissolve in common solvents, using cellulose products as raw materials to prepare a cellulose solution such as viscose for reuse requires complicated work processes and high costs.

[0003] Viscose is usually prepared by first coarsely crushing a dissolving pulp sheet as the raw material and immersing it in a large amount of aqueous alkali solution to form alkali cellulose (mercerization), squeezing it to remove excess aqueous alkali, crushing it, reacting it with carbon disulfide to convert it into cellulose xanthate (sulfurization), and dissolving it in an aqueous alkali solution.

[0004] Non-Patent Document 1 describes a method for producing viscose from wood pulp as a raw material by uniformly spraying a small amount of concentrated caustic soda solution onto the pulp to omit pressing in order to reduce the amount of alkaline aqueous solution used (non-pressure method).

[0005] Patent Document 1 describes the preparation of alkali cellulose by using recycled artificial cellulose-based raw materials as raw materials, immersing them in an alkaline aqueous solution, and then squeezing them, thereby sulfurizing and dissolving them.

[0006] Special table 2018-505973 publication

[0007] Tadashi Manki, "Part 1: Experiments on the Production of Viscose without Pressure," Seni Gakkaishi Journal, Vol. 2, No. 2, pp. 79-81, 1946

[0008] However, the viscose produced by the method of Non-Patent Document 1 has a problem in that a large amount of unreacted fibers remain, and the state of dispersion and dissolution is poor.

[0009] Furthermore, when the alkali cellulose of Patent Document 1 is sulfurized and dissolved, the cellulose has low solubility, so that viscose containing a large amount of undissolved matter is produced, which has problems of poor filterability and poor practicality, since only molded articles with low strength can be obtained.

[0010] The present invention solves the above-mentioned problems, and its purpose is to provide an alkali cellulose material that can be used to obtain viscose using regenerated cellulose as a raw material, and that has physical properties suitable for use as a raw material for molding various cellulose molded products.

[0011] The present invention provides the following aspects: [Aspect 1] An alkali cellulose material containing regenerated cellulose, an alkali, and water, which is used to produce viscose by sulfurization with carbon disulfide, the alkali cellulose material having a cellulose concentration of 27 to 40% by mass, preferably 29 to 38% by mass, and more preferably 30 to 36% by mass, and an alkali concentration of 8 to 20% by mass, preferably 9 to 18% by mass, and more preferably 10 to 16% by mass.

[0012] [Embodiment 2] The alkali cellulose material of embodiment 1, wherein the cellulose component does not include native cellulose.

[0013] [Embodiment 3] The alkali cellulose material of embodiment 1 or 2, wherein the cellulose component comprises regenerated cellulose.

[0014] [Aspect 4] The alkali cellulose material of any one of Aspects 1 to 3, wherein the viscose has a cellulose concentration of 5% by weight or more, preferably 6 to 12% by weight, and more preferably 8 to 10% by weight.

[0015] [Aspect 5] The alkali cellulose material of any one of aspects 1 to 4, wherein the viscose has a clogging factor of 6,000 or less, preferably 4,000 or less, and more preferably 2,000 or less.

[0016] [Embodiment 6] A mixed alkali cellulose material comprising the alkali cellulose material of any one of embodiments 1 to 5 and an alkali cellulose material for the same purpose that is produced from a cellulose material other than regenerated cellulose.

[0017] [Embodiment 7] A sulfide of an alkali cellulose material with carbon disulfide, comprising regenerated cellulose, alkali, and water, and having a cellulose concentration of 27 to 40% by mass, preferably 29 to 38% by mass, and more preferably 30 to 36% by mass, and an alkali concentration of 8 to 20% by mass, preferably 9 to 18% by mass, and more preferably 10 to 16% by mass.

[0018] [Embodiment 8] A mixed sulfide of alkali cellulose material with carbon disulfide, comprising the sulfide of alkali cellulose material of embodiment 7 with carbon disulfide and the sulfide of alkali cellulose material for the same purpose produced from a cellulose material other than regenerated cellulose with carbon disulfide.

[0019] [Aspect 9] Viscose comprising regenerated cellulose, alkali, and water, and containing a sulfide, with carbon disulfide, of an alkali cellulose material having a cellulose concentration of 27 to 40% by weight, preferably 29 to 38% by weight, and more preferably 30 to 36% by weight, and an alkali concentration of 8 to 20% by weight, preferably 9 to 18% by weight, and more preferably 10 to 16% by weight.

[0020] [Aspect 10] A mixed viscose comprising the viscose of aspect 9 and a viscose produced from a cellulose material other than regenerated cellulose.

[0021] [Aspect 11] A method for producing viscose, comprising sulfurizing with carbon disulfide an alkali cellulose material containing regenerated cellulose, alkali, and water, the alkali cellulose material having a cellulose concentration of 27 to 40% by weight, preferably 29 to 38% by weight, and more preferably 30 to 36% by weight, and an alkali concentration of 8 to 20% by weight, preferably 9 to 18% by weight, and more preferably 10 to 16% by weight.

[0022] [Embodiment 12] The viscose of embodiment 9, having a clogging degree of 6,000 or less, preferably 4,000 or less, and more preferably 2,000 or less.

[0023] [Embodiment 13] The viscose of embodiment 9 or 12, having a cellulose concentration of 5% by mass or more, preferably 6 to 12% by mass, more preferably 8 to 10% by mass.

[0024] [Embodiment 14] The viscose of embodiment 9, 12, or 13, having an alkali concentration of 2% by mass or more, preferably 4 to 12% by mass, and more preferably 5 to 10% by mass.

[0025] [Embodiment 15] The mixed viscose of embodiment 10, having a regenerated cellulose content of 1 to 99% by mass, preferably 2 to 50% by mass, more preferably 3 to 20% by mass, based on the cellulose component.

[0026] The present invention provides an alkali cellulose material that uses regenerated cellulose as a raw material to produce viscose with physical properties suitable for use as a raw material for forming various cellulose molded products.The present invention also provides viscose with physical properties suitable for use as a raw material for forming various cellulose molded products, using this alkali cellulose material as an intermediate material.The present invention also provides a method for producing viscose with physical properties suitable for use as a raw material for forming various cellulose molded products, using regenerated cellulose as a raw material.

[0027] FIG. 1 is a schematic diagram of a graph plotting characteristic values ​​of viscose for calculating the degree of clogging.

[0028] Hereinafter, embodiments of the present invention will be described in detail, but the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the spirit of the present invention. Furthermore, when multiple upper and lower limit values ​​are specified for a specific parameter, any upper and lower limit values ​​can be combined to form a suitable numerical range.

[0029] <Regenerated Cellulose> The regenerated cellulose used as a raw material is primarily cellulose obtained by liquefying natural cellulose using the conventional viscose method or cuprammonium method, followed by solidification and molding into a predetermined shape. Regenerated cellulose includes cellulose molded products, cellulose products produced by cutting cellulose molded products, and by-products produced during the production of cellulose molded products. These may be pulverized to improve reaction efficiency. Specific examples of regenerated cellulose include offcuts, non-standard products, defective products, and waste cellulose products generated during the commercialization of cellulose molded products such as cellophane, rayon, and beads. Furthermore, regenerated cellulose can also be reused as a raw material instead of natural cellulose.

[0030] <Natural Cellulose> The natural cellulose used as a raw material for viscose is not particularly limited, and examples thereof include pulp made from biomass such as wood, cotton, straw, bamboo, hemp, jute, and kenaf. The method for producing the natural cellulose is also not particularly limited, and may be a mechanical method, a chemical method, or a method combining the two. In terms of pulp quality, highly refined dissolving pulp, which is used as a main raw material for papermaking pulp, artificial fibers, cellophane, and the like, is preferred.

[0031] <Alkali Cellulose Material> Regenerated cellulose is reacted with an aqueous alkali solution to convert the cellulose contained therein into alkali cellulose. This process is generally called mercerization. The mixture containing regenerated cellulose, alkali, and water after mercerization is called alkali cellulose material. The alkali cellulose material may be in the form of a solution, a dispersion containing insoluble matter, or a solid. Mercerization swells the cellulose, improving the reaction efficiency when sulfurizing the alkali cellulose. Strong alkaline compounds such as sodium hydroxide, lithium hydroxide, and potassium hydroxide can be used as the alkali.

[0032] The mercerization process is generally carried out by immersing the cellulose material in a large amount of aqueous alkaline solution, followed by squeezing to remove excess aqueous alkaline solution. In contrast, in the present invention, mercerization is carried out by adding to the regenerated cellulose in advance the minimum amount of concentrated aqueous alkaline solution necessary for sulfurizing and dissolving the regenerated cellulose. Depending on the state of the regenerated cellulose, spraying or other means may be used to ensure uniform addition. Because an excessive amount of aqueous alkaline solution is not added, a dehydration step such as squeezing is unnecessary and is not carried out.

[0033] When regenerated cellulose is immersed in an alkaline solution, it absorbs a large amount of water and swells significantly, making it difficult to increase the cellulose concentration to an appropriate level by conventional dehydration methods such as squeezing.

[0034] The amount of alkaline aqueous solution added is adjusted depending on the moisture content of the regenerated cellulose used as a raw material, but is adjusted so that the alkali concentration in the mixture of regenerated cellulose and alkaline aqueous solution is 8 to 20% by mass, preferably 9 to 18% by mass, and more preferably 10 to 16% by mass. The cellulose concentration in the mixture is also adjusted to 27 to 40% by mass, preferably 29 to 38% by mass, and more preferably 30 to 36% by mass. By adjusting the alkali concentration and cellulose concentration in the mixture to fall within the above ranges, the physical properties of the resulting viscose become suitable for use as a raw material for forming cellulose molded products.

[0035] Next, the aqueous alkaline solution and the regenerated cellulose are mixed and stirred to proceed with mercerization. A stirring device suitable for mixing a small amount of aqueous alkaline solution with solid regenerated cellulose is selected for this mixing and stirring. The stirring device preferably has a stirring tank and a temperature-control jacket surrounding the stirring tank that can adjust the temperature. To precisely control the reaction temperature, it is preferable to use a device equipped with low-speed impellers that stir the entire stirring tank during the reaction, thereby homogenizing the temperature of the mixture. Examples of low-speed impeller shapes include anchor impellers, ribbon anchor impellers, helical ribbon impellers, gate impellers, and paddle impellers, with anchor impellers and ribbon anchor impellers being more preferred. Furthermore, to improve stirring efficiency, the stirring shaft may be tilted, horizontal, or eccentric, or a baffle may be installed in the stirring tank or the stirring tank itself may be rotated.

[0036] Mercerization of regenerated cellulose is carried out at temperatures between -20 and 50°C, preferably between 0 and 40°C, and more preferably between 10 and 30°C. If the mercerization temperature is below -20°C, labor and energy are required to maintain the liquid temperature at a low level, while if it exceeds 50°C, labor and time are required to cool the liquid to a temperature suitable for sulfurization. The mercerization reaction time is typically between 0.5 and 120 hours, preferably between 1 and 72 hours, and more preferably between 2 and 48 hours. If the mercerization reaction time is too short, penetration is insufficient, preventing the reaction from reaching the center and increasing the amount of undissolved material; if the reaction time is too long, the degree of polymerization decreases. Furthermore, since this decrease in degree of polymerization occurs due to oxidation by oxygen in the air, mercerization may be carried out under reduced pressure or by replacing the air with nitrogen gas, hydrogen gas, or the like.

[0037] The alkali cellulose material of the present invention can be used in combination with alkali cellulose materials prepared by conventional methods from cellulose materials other than regenerated cellulose. The alkali cellulose materials to be mixed with the alkali cellulose material of the present invention are preferably used for the purpose of producing viscose by sulfurization with carbon disulfide. Examples of cellulose materials other than regenerated cellulose include natural celluloses such as dissolving pulp.

[0038] In this case, the content of regenerated cellulose in the mixed alkali cellulose material is 1 to 99% by mass, preferably 2 to 50% by mass, and more preferably 3 to 20% by mass, based on the cellulose component. By increasing the content of regenerated cellulose as much as possible, the recycling rate of regenerated cellulose can be improved, and the effect of reducing environmental load can be enhanced.

[0039] The alkali cellulose material of the present invention is converted into cellulose xanthate by contacting it with carbon disulfide and reacting it. This process is commonly called sulfurization. Sulfurization can be carried out by adding carbon disulfide to the alkali cellulose material after mercerization, mixing, and stirring. Alternatively, cellulose, an aqueous alkali solution, and carbon disulfide can be mixed at the same time to carry out mercerization and sulfurization simultaneously.

[0040] In a mixture containing regenerated cellulose, an aqueous alkali solution, and carbon disulfide, the cellulose concentration and the alkali compound concentration are determined by diluting the mixture with carbon disulfide added after mercerization, unless further adjustments are required. The amount of carbon disulfide added to the mixture is adjusted to 5 to 60% by mass, preferably 10 to 50% by mass, and more preferably 15 to 40% by mass, based on the mass of cellulose. If the amount of carbon disulfide added is less than 5% by mass, the reaction with the alkali cellulose will be insufficient. If the amount of carbon disulfide added is more than 60% by mass, side reactions of carbon disulfide will increase or unreacted carbon disulfide will remain, potentially reducing safety.

[0041] During sulfurization, the temperature of the mixture is uniformed by stirring the entire contents of the stirring vessel. Since the alkali cellulose is a solid during sulfurization, while carbon disulfide exists as a liquid or gas, it is preferable to use a stirring device equipped with a low-speed blade that rotates along the wall of the stirring vessel to uniformize the mixture, and equipped with a temperature-regulating jacket, as in the case of mercerization.

[0042] The sulfurization of alkali cellulose is carried out at a temperature of 0 to 50°C, preferably 5 to 40°C, and more preferably 10 to 30°C. If the temperature during sulfurization is below 0°C, labor and energy are required to maintain the liquid temperature at a low temperature, while if it exceeds 50°C, the degree of polymerization of cellulose is likely to decrease and the risk of fire increases. The sulfurization reaction time is set so that carbon disulfide is sufficiently permeated throughout the alkali cellulose, and is usually in the range of 30 minutes to 12 hours, preferably 1 to 9 hours, and more preferably 2 to 6 hours.

[0043] The resulting sulfide is dissolved at a temperature of 0 to 40°C, preferably 5 to 35°C, and more preferably 10 to 30°C. If the dissolution temperature is below 0°C, labor and energy are required to maintain the liquid temperature at a low temperature, and if it exceeds 40°C, the cellulose solubility is likely to decrease. The dissolution time is set so that the clogging degree reaches the desired value and is complete, and although it depends on stirring and other conditions, it is usually in the range of 2 minutes to 48 hours, preferably 4 minutes to 36 hours, and more preferably 5 minutes to 24 hours. In this case, dissolution can be achieved in a short time, particularly when high-speed impellers are used in combination. Examples of the shape of the high-speed impeller include disperser impellers, turbine impellers, propeller impellers, paddle impellers, rotor-stators, etc., with disperser impellers being preferred.

[0044] The carbon disulfide sulfide of the alkali cellulose material of the present invention can be dissolved in an alkaline aqueous solution and used to produce viscose, or it can be mixed with a carbon disulfide sulfide of an alkali cellulose material prepared by a conventional method from a cellulose material other than regenerated cellulose. Examples of cellulose materials other than regenerated cellulose include natural cellulose, and in addition to pulp made from biomass such as wood, cotton, straw, bamboo, hemp, jute, and kenaf, waste paper, paper powder, etc. can also be used, but pulp made from wood is particularly preferred.

[0045] In this case, the content of regenerated cellulose in the sulfide of the mixed alkali cellulose material with carbon disulfide is 1 to 99% by mass, preferably 2 to 50% by mass, and more preferably 3 to 20% by mass, based on the cellulose component. By increasing the content of regenerated cellulose as much as possible, the recycling rate of regenerated cellulose can be improved, and the effect of reducing environmental load can be enhanced.

[0046] <Viscose> The viscose of the present invention obtained after sulfurization and dissolution has the same physical properties as viscose, such as viscose, which is a raw material for forming various cellulose molded products. The viscose of the present invention has a clogging degree of 6,000 or less, preferably 4,000 or less, more preferably 2,000 or less. The smaller the clogging degree, the more excellent the solubility of cellulose xanthate in the sulfide. The method for calculating the clogging degree is shown below.

[0047] (Clogging Degree) Viscose is subjected to pressure filtration at 23°C under a pressure of 0.04 MPa using a filter cloth made of five layers of cotton cloth, and the mass V (g) of the filtrate is measured over time. After a certain time has passed, the filtration time t (minutes) and the reciprocal of the filtration rate t / V are plotted, and the clogging degree is calculated from the slope (k / 2) of the obtained line based on the following formula. Figure 1 is a schematic diagram of a graph on which the measured characteristic values ​​of viscose are plotted. Clogging degree = 100,000 x k

[0048] The viscose of the present invention has a cellulose concentration of 5% by mass or more, preferably 6 to 12% by mass, and more preferably 8 to 10% by mass. This cellulose concentration is at the same level as that of viscose, which is a raw material for forming various cellulose molded products. If the cellulose concentration of the viscose is too high, the viscosity will be too high, while if it is too low, the strength of the cellulose molded product will be insufficient and the amount of chemicals such as acid used will increase, reducing economic viability. The method for measuring the cellulose concentration is described below.

[0049] (Cellulose Concentration) Viscose is thinly spread on a pre-weighed glass plate using a Baker applicator (SA-201, manufactured by Tester Sangyo Co., Ltd.), and the mass is measured to calculate the mass of the viscose. The glass plate is then left to stand in a constant temperature dryer at 70°C for 40 minutes, and each glass plate is immersed in a 10% by mass aqueous ammonium chloride solution for 30 minutes to peel the solidified viscose from the glass plate. The viscose is then washed with distilled water, dried in a hot air dryer at 105°C, and the mass is measured, and the cellulose concentration of the viscose is calculated using the following formula: Cellulose concentration = {mass after drying / (mass of viscose)} x 100

[0050] The viscose of the present invention has an alkali concentration of 2% by mass or more, preferably 4 to 12% by mass, and more preferably 5 to 10% by mass. This alkali concentration is at the same level as that of viscose, which is a raw material for forming various cellulose molded products. If the alkali concentration of the viscose is high, the amount of acid required for neutralization increases, while if the alkali concentration is low, the solubility decreases.

[0051] The viscose of the present invention easily coagulates when placed in a salt solution, a dilute acid such as sulfuric acid or hydrochloric acid, an organic solvent, or when heated, and can be regenerated with an acid to give molded products such as cellophane, rayon, beads, etc. When a dilute acid is used for coagulation, coagulation and regeneration proceed simultaneously.

[0052] The viscose of the present invention can be used in combination with viscose prepared by a conventional method from a cellulose material other than regenerated cellulose, such as natural cellulose such as dissolving pulp.

[0053] In this case, the content of regenerated cellulose in the mixed viscose is 1 to 99% by mass, preferably 2 to 50% by mass, and more preferably 3 to 20% by mass, based on the cellulose component. By increasing the content of regenerated cellulose as much as possible, the recycling rate of regenerated cellulose can be improved, and the effect of reducing the environmental load can be enhanced.

[0054] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. The unit "parts" in the examples is a unit based on mass.

[0055] Example 1 As a regenerated cellulose sample, cellophane ("PT #300" (trade name) manufactured by Rengo Co., Ltd.) was mechanically crushed, passed through a round net with a diameter of 1 mm, and washed with water to remove any adhering softener (glycerin) to prepare a wet product (cellulose content: 43% by mass).

[0056] 100 parts of a regenerated cellulose sample and 36 parts of a 40% by weight aqueous sodium hydroxide solution were placed in a stirring vessel of a stirring device and mixed using a low-speed stirrer equipped with paddle blades (Three-One Motor BL-600, manufactured by Shinto Scientific Co., Ltd.). While stirring, this mixture was mercerized at room temperature of about 20°C to obtain alkali cellulose. The obtained alkali cellulose contained 32% by weight of cellulose and 11% by weight of sodium hydroxide.

[0057] To this alkali cellulose, 35% by mass of carbon disulfide was added per cellulose mass, and sulfurization was carried out for 4 hours while stirring at 30 rpm using the low-speed stirrer. Aqueous sodium hydroxide solution was added to the resulting sulfide, and the mixture was dissolved at room temperature for 19 hours while stirring at 600 rpm to obtain viscose. The resulting viscose contained 9.8% by mass of cellulose and 6.0% by mass of sodium hydroxide.

[0058] After completion of the sulfurization and dissolution, the viscosity and clogging degree of the obtained viscose were measured. The solubility of cellulose was evaluated based on the clogging degree. The results are shown in Table 1.

[0059] (Viscosity) The temperature of the viscose was adjusted to 20°C, and the viscosity was measured using a Brookfield viscometer (No. 5 rotor x 20 rpm).

[0060] (Solubility) The evaluation criteria for solubility were as follows.

[0061] A (Excellent) Clogging level: 2,000 or less B (Good) Clogging level: 6,000 or less C (Poor) Clogging level: Over 6,000

[0062] Example 2 Viscose was obtained in the same manner as in Example 1, except that the sulfide obtained by adding 25% by mass of carbon disulfide per mass of cellulose to the alkali cellulose prepared in Example 1 was dissolved in water for 10 minutes while stirring at 5,000 rpm at room temperature using a high-speed mixer equipped with a dispersing blade ("Labo-Lution" (trade name) manufactured by Primix Corporation). The obtained viscose contained 9.6% by mass of cellulose and 6.1% by mass of sodium hydroxide.

[0063] Comparative Example 1: One hundred parts of the regenerated cellulose sample prepared in Example 1 was immersed in 1,000 parts of an 18% by weight aqueous sodium hydroxide solution at 50°C for 1.5 hours to perform mercerization, and the solution was dehydrated at 3,000 rpm using a centrifuge, Model HF110F (trade name, manufactured by Kokusan Co., Ltd.), until the solution stopped discharging, to obtain alkali cellulose. The obtained alkali cellulose contained 22% by weight of cellulose and 16% by weight of sodium hydroxide.

[0064] Except for using this alkali cellulose, viscose was obtained in the same manner as in Example 1. The obtained viscose contained 8.2% by mass of cellulose and 6.1% by mass of sodium hydroxide.

[0065] The viscosity and clogging degree of the obtained viscose were measured in the same manner as in Example 1. The solubility of cellulose was evaluated based on the clogging degree. The results are shown in Table 1.

[0066]

[0067] As in Comparative Example 1, when trying to dissolve cellophane, which is regenerated cellulose, according to a general viscose manufacturing method, the solubility is low. The reason is that cellophane swells significantly in an alkaline aqueous solution, is not sufficiently dehydrated, and the cellulose concentration of the alkali cellulose is low (25% by mass or less). In other words, when the alkali cellulose is not sufficiently dehydrated, side reactions increase during sulfurization, the conversion rate to cellulose xanthate decreases, and the solubility is reduced.

[0068] In Examples 1 and 2, although there were differences in the amount of carbon disulfide added and the stirring conditions during dissolution, alkali cellulose with a high cellulose concentration of 32% by mass could be prepared by adding a small amount of concentrated alkaline aqueous solution to the regenerated cellulose and uniformly mixing it, instead of soaking the regenerated cellulose in a large amount of alkaline aqueous solution and dehydrating it. As a result, a viscose with excellent cellulose solubility was obtained.

[0069] In Non-Patent Document 1, which uses pulp as the raw material, filtration of viscose is more difficult than with conventional methods (the filtration time for 300 g of viscose is 177.4 seconds with the conventional method, but 320 seconds with this method), which is thought to be due to the presence of hemicellulose and other contaminants in the raw pulp and the non-uniformity of the alkali cellulose. However, when the raw material was replaced with regenerated cellulose, filtration was possible with this application, whereas filtration was not possible with the conventional method, and this is thought to be due to the low hemicellulose content in the raw material.

[0070] Example 3: Viscose produced from cellophane of Example 1 was mixed with industrial viscose. Ten parts of the viscose of Example 1 were mixed with 90 parts of viscose manufactured by Rengo Co., Ltd. (prepared from dissolving pulp by a conventional method) to prepare a mixed viscose (cellulose: 9.7% by mass, sodium hydroxide: 6.2% by mass).

[0071] The viscosity and clogging degree of the obtained viscose were measured in the same manner as in Example 1. The solubility of cellulose was evaluated based on the clogging degree. The results are shown in Table 2.

[0072] Example 4: Mixing the sulfurized cellophane of Example 1 with sulfurized pulp The sulfurized regenerated cellulose sample of Example 1 was mixed with a sulfide prepared from dissolving pulp by a conventional method so that the mass ratio of regenerated cellulose to native cellulose was 1:9, and the mixture was dissolved in an alkaline aqueous solution to prepare viscose (cellulose: 9.8 mass%, sodium hydroxide: 6.1 mass%).

[0073] The viscosity and clogging degree of the obtained viscose were measured in the same manner as in Example 1. The solubility of cellulose was evaluated based on the clogging degree. The results are shown in Table 2.

[0074] Example 5: Mercerized cellophane from Example 1 mixed with mercerized pulp The mercerized regenerated cellulose sample from Example 1 was mixed with mercerized pulp prepared from dissolving pulp by a conventional method so that the mass ratio of regenerated cellulose to native cellulose was 1:9. 35% by mass of carbon disulfide per cellulose mass was added, and the mixture was sulfurized for 4 hours. The mixture was then dissolved in an alkaline aqueous solution to prepare viscose (cellulose: 9.8% by mass, sodium hydroxide: 6.1% by mass).

[0075] The viscosity and clogging degree of the obtained viscose were measured in the same manner as in Example 1. The solubility of cellulose was evaluated based on the clogging degree. The results are shown in Table 2.

[0076] Comparative Example 2: Mixing crushed cellophane with pulp. A regenerated cellulose sample and dissolving pulp were mixed so that the mass ratio of regenerated cellulose to native cellulose was 1:9. This mixture was immersed in an 18% by mass aqueous sodium hydroxide solution at 50°C for 1.5 hours to perform mercerization, and then pressed to obtain alkali cellulose (cellulose: 26% by mass, sodium hydroxide: 16% by mass). Carbon disulfide was added to the alkali cellulose to a concentration of 35% by mass per cellulose mass, and sulfurization was carried out for 4 hours. Aqueous sodium hydroxide solution was added to the obtained sulfide, and the mixture was dissolved with stirring at 20°C for 19 hours to prepare viscose (cellulose: 9.6% by mass, sodium hydroxide: 6.0% by mass).

[0077] The viscosity and clogging degree of the obtained viscose were measured in the same manner as in Example 1. The solubility of cellulose was evaluated based on the clogging degree. The results are shown in Table 2.

[0078] Comparative Example 3: Mercerized cellophane from Comparative Example 1 mixed with mercerized pulp The mercerized regenerated cellulose sample from Comparative Example 1 was mixed with mercerized pulp prepared from dissolving pulp by a conventional method in a mass ratio of regenerated cellulose to native cellulose of 1:9. After sulfurization, the mixture was dissolved in an alkaline aqueous solution to prepare viscose (cellulose: 9.6 mass%, sodium hydroxide: 6.0 mass%).

[0079] The viscosity and clogging degree of the obtained viscose were measured in the same manner as in Example 1. The solubility of cellulose was evaluated based on the clogging degree. The results are shown in Table 2.

[0080]

[0081] Examples 3, 4, and 5 exhibit good solubility. In contrast, Comparative Examples 2 and 3, which were subjected to conventional immersion and squeezing, exhibited poor solubility. Furthermore, Example 5 exhibited lower solubility than Examples 3 and 4. This is thought to be because cellophane, which has a small surface area, is less reactive than pulp in the sulfurization reaction, causing the sulfurization to proceed unevenly. Separate sulfurization of cellophane and pulp results in a more uniform reaction, which is expected to be more favorable in terms of solubility.

[0082] In the present invention, the conditions for obtaining alkali cellulose by mercerizing regenerated cellulose have been optimized, and it has been found that viscose suitable for producing molded articles can be obtained by mixing it with viscose from wood pulp at that stage or in a sulfurized state, or by mixing it with industrial viscose in the form of viscose sulfurized and dissolved in an alkaline aqueous solution. This reduces the need for dedicated production equipment, allows the effective use of existing equipment, and is advantageous in terms of energy costs.

Claims

1. An alkali cellulose material comprising regenerated cellulose, an alkali and water for use in producing viscose by sulfurization with carbon disulfide, the alkali cellulose material having a cellulose concentration of 27-40% by weight and an alkali concentration of 8-20% by weight.

2. The alkali cellulose material of claim 1, wherein the cellulose component does not include native cellulose.

3. The alkali cellulose material according to claim 1 or 2, wherein the cellulose component comprises regenerated cellulose.

4. An alkali cellulose material according to any one of claims 1 to 3, wherein the viscose has a cellulose concentration of 5% by mass or more.

5. The alkali cellulose material according to any one of claims 1 to 4, wherein the viscose has a clogging factor of 6,000 or less.

6. A mixed alkali cellulose material comprising the alkali cellulose material according to any one of claims 1 to 5 and an alkali cellulose material for the same purpose produced from a cellulose material other than regenerated cellulose.

7. A sulfide of an alkali cellulose material containing regenerated cellulose, alkali and water, having a cellulose concentration of 27-40% by mass and an alkali concentration of 8-20% by mass, with carbon disulfide.

8. A mixed sulfide of alkali cellulose material with carbon disulfide comprising the sulfide of alkali cellulose material as claimed in claim 7 with carbon disulfide and a sulfide of alkali cellulose material for the same use produced from a cellulose material other than regenerated cellulose with carbon disulfide.

9. Viscose comprising regenerated cellulose, alkali and water, and comprising the sulfidation with carbon disulfide of an alkali cellulose material having a cellulose concentration of 27-40% by weight and an alkali concentration of 8-20% by weight.

10. A mixed viscose comprising the viscose according to claim 9 and a viscose made from a cellulose material other than regenerated cellulose.

11. A method for producing viscose, comprising sulfurizing an alkali cellulose material containing regenerated cellulose, an alkali and water, the alkali cellulose material having a cellulose concentration of 27-40% by weight and an alkali concentration of 8-20% by weight with carbon disulfide.

Images