Alkali cellulose material, viscose, and a 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

Description

TITLE OF THE INVENTION: ALKALI CELLULOSE MATERIAL, VISCOSE, AND METHOD FOR PRODUCING VISCOSE TECHNICAL FIELD

[0001] The present invention relates to an alkali cellulose material that is an intermediate material for producing viscose, and particularly to an alkali cellulose material using regenerated cellulose as a raw material. BACKGROUND ART

[0002] When producing cellulose products such as cellophane, rayon, and beads, by-products such as end materials and nonstandard products are generated. On the other hand, cellulose does not have thermoplasticity and is not dissolved in a conventional solvent, and thus a complicated operation process and high cost are required to prepare a cellulose solution such as viscose, by using a cellulose product as a raw material, in order to reuse the cellulose product.

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

[0004] Non-Patent Document 1 describes a method for producing viscose by uniformly spraying a small amount of a thick caustic soda solution using wood pulp as a raw material in order to omit squeezing for the purpose of reducing the amount of an aqueous alkali solution used (non-squeezing method).

[0005] Patent Document 1 describes that alkali cellulose to be sulfurized and dissolved is prepared by a step of immersing a recycled artificial cellulose-based raw material as a raw material in an aqueous alkali solution, followed by squeezing. PRIOR ART DOCUMENTS PATENT DOCUMENT

[0006] Patent Document 1: JP-A-2018-505973 NON-PATENT DOCUMENT

[0007] Non-patent Document 1: Tadashi Yurugi, “Report 1: Experimental Production of Non-Squeezed Viscose,” Sen'i Gakkaishi, Vol. 2, No. 2, pp. 79-81,1946. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

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

[0009] In addition, when the alkali cellulose of Patent Document 1 is sulfurized and dissolved, the solubility of cellulose is low, and thus viscose including a large amount of undissolved components is generated. Such viscose is problematic in that the filterability is deteriorated, and only a shaped product having a physical property of low strength is obtained, resulting in poor practicability.

[0010] The present invention solves the above problems, and an object of the present invention is to provide an alkali cellulose material capable of obtaining viscose having physical properties suitable for produce various cellulose shaped products, using regenerated cellulose as a raw material. SOLUTIONS TO THE PROBLEMS

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

[0012] [Aspect 2] The alkali cellulose material according to aspect 1, wherein a cellulose component is free of natural cellulose.

[0013] [Aspect 3] The alkali cellulose material according to aspect 1 or 2, wherein a cellulose component consists of regenerated cellulose.

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

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

[0016] [Aspect 6] A mixed alkali cellulose material comprising the alkali cellulose material according to any one of aspects 1 to 5 and an alkali cellulose material for a same use produced from a cellulose material other than regenerated cellulose.

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

[0018] [Aspect 8] A mixed sulfide of an alkali cellulose material with carbon disulfide, the mixed sulfide comprising a sulfide of the alkali cellulose material according to aspect 7 with carbon disulfide and a sulfide of an alkali cellulose material with carbon disulfide for a same use produced from a cellulose material other than regenerated cellulose.

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

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

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

[0022] [Aspect 12] The viscose according to aspect 9, having a filter clogging value of 6,000 or less, preferably 4,000 or less, more preferably 2,000 or less.

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

[0024] [Aspect 14] The viscose according to aspect 9,12 or 13, having an alkali concentration of 2 mass% or more, preferably 4 to 12 mass%, more preferably 5 to 10 mass%.

[0025] [Aspect 15] The mixed viscose according to aspect 10, having a content of regenerated cellulose of 1 to 99 mass%, preferably 2 to 50 mass%, more preferably 3 to 20 mass%, based on a cellulose component. EFFECTS OF THE INVENTION

[0026] The present invention provides an alkali cellulose material capable of providing viscose having physical properties suitable for produce various cellulose shaped products, using regenerated cellulose as a raw material. The present invention provides viscose having physical properties suitable for produce various cellulose shaped products, using the alkali cellulose material as an intermediate material. In addition, the present invention provides a method for producing viscose having physical properties suitable for produce various cellulose shaped products, using regenerated cellulose as a raw material. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] [Fig- 1] Fig. 1 is a schematic diagram of a graph in which characteristic values of the viscose for calculating the filter clogging value are plotted. DETAILED DESCRIPTION

[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 gist of the present invention. In addition, when a plurality of upper limit values and lower limit values are described for a specific parameter, an arbitrary upper limit value and an arbitrary lower limit value among these upper limit values and lower limit values can be combined to obtain a suitable numerical range.

[0029] <Regenerated cellulose> Regenerated cellulose used as a raw material mainly refers to cellulose obtained by dissolving natural cellulose by a conventional viscose method or copper ammonia method, and then coagulating into a predetermined shape. Regenerated cellulose includes a cellulose shaped product, a cellulose product produced by cutting the cellulose shaped product, a by-product in producing the cellulose shaped product, and the like. These may be comminuted to improve reaction efficiency. Specific examples of the regenerated cellulose include end materials, nonconforming products, defective products and waste products of cellulose products generated when a cellulose shaped product such as cellophane, rayon, or beads is produced. Further, regenerated cellulose can be reused as a raw material instead of natural cellulose.

[0030] <Natural cellulose> The natural cellulose used as a raw material of the viscose is not particularly limited, and examples thereof include pulp made from biomass such as wood, cotton, straw, bamboo, hemp, jute and kenaf. In addition, the production method thereof is not particularly limited, and may be a mechanical method, a chemical method or a hybrid approach combining the two. As the quality of pulp, in addition to pulp for papermaking, dissolving pulp that is a main raw material for artificial fibers, cellophane, and the like and has a high degree of purification is preferable.

[0031] <Alkali cellulose material> Regenerated cellulose is reacted by being brought into contact with an aqueous alkali solution, and cellulose included therein is converted into alkali cellulose. This step is generally called mercerization. A mercerized mixture including regenerated cellulose, alkali and water is referred to as an alkali cellulose material. The property of the alkali cellulose material may be a solution, a dispersion including an insoluble matter or a solid. Mercerization causes cellulose to swell, improving reaction efficiency when alkali cellulose is sulfurized. As the alkali, a strong alkali compound such as sodium hydroxide, lithium hydroxide or potassium hydroxide can be used.

[0032] The mercerization step is generally performed by immersing the cellulose material in a large amount of aqueous alkali solution, and the mixture is subsequently squeezed to remove the excessive aqueous alkali solution. In contrast, in the present invention, a minimum amount of a concentrated aqueous alkali solution necessary for sulfurization and dissolution of regenerated cellulose is previously added to regenerated cellulose to perform mercerization. Depending on the state of regenerated cellulose, means such as spraying may be used for uniform addition. The aqueous alkali solution is not excessively added, and thus a dehydration step such as squeezing is unnecessary and is not performed.

[0033] When the regenerated cellulose is immersed in an aqueous alkali solution, the regenerated cellulose adsorbs a large amount of moisture and swells strongly. Therefore, it is difficult to increase the cellulose concentration to an appropriate level by a typically performed dehydrating means such as squeezing.

[0034] The amount of the aqueous alkali solution added is adjusted depending on the moisture content of the regenerated cellulose used as a raw material, and is adjusted such that the alkali concentration in the mixture of the regenerated cellulose and the aqueous alkali solution is 8 to 20 mass%, preferably 9 to 18 mass%, and more preferably 10 to 16 mass%. In addition, the cellulose concentration in the mixture is adjusted to 27 to 40 mass%, preferably 29 to 38 mass%, and more preferably 30 to 36 mass%. Adjusting the alkali concentration and the cellulose concentration in the mixture to the above ranges causes the physical properties of the obtained viscose to become suitable for produce a cellulose shaped product.

[0035] Subsequently, the aqueous alkali solution and regenerated cellulose are mixed and stirred to progress mercerization. For the mixing and stirring in this case, a stirring apparatus suitable for mixing a small amount of an aqueous alkali solution with solid regenerated cellulose is selected. It is desirable that the stirring apparatus has a stirring tank and has a temperature control jacket capable of regulating the temperature around the stirring tank. In order to accurately adjust the reaction temperature, it is preferable to use, in mercerization, a mixing apparatus including a low-speed blade that makes the temperature of the mixture uniform by stirring the entire inside of the stirring tank during the reaction. Examples of the shape of the low-speed blade include an anchor blade, a ribbon anchor blade, a helical ribbon blade, a gate blade and a paddle blade, and among these, the anchor blade and the ribbon anchor blade are more preferable. Further, in order to improve stirring efficiency, a baffle plate may be provided in the stirring tank or the stirring tank itself may be rotated in addition to making the stirring shaft oblique, horizontal or eccentric.

[0036] Mercerization of regenerated cellulose is performed at a temperature of -20 to 50°C, preferably 0 to 40°C, more preferably 10 to 30°C. When the temperature during mercerization is lower than -20°C, labor and energy are required to maintain the liquid temperature at a low temperature, and when the temperature exceeds 50°C, labor and time are required to cool the liquid to a temperature suitable for sulfurization. The reaction time for mercerization is typically in the range of 0.5 to 120 hours, preferably 1 to 72 hours, and more preferably 2 to 48 hours. When the reaction time for mercerization is too short, the penetration becomes insufficient and the reaction does not proceed to the central portion, and the undissolved fraction increases, but when the reaction time is too long, the degree of polymerization decreases. In addition, this decrease in degree of polymerization occurs by oxidation with oxygen in the air, and thus mercerization may be performed under reduced pressure or by replacing air with nitrogen gas, hydrogen gas, or the like.

[0037] The alkali cellulose material of the present invention can be used by being mixed with an alkali cellulose material prepared by a conventional method from a cellulose material other than regenerated cellulose. The alkali cellulose material to be mixed with the alkali cellulose material of the present invention is preferably used for the purpose of producing viscose by sulfurization with carbon disulfide. Examples of the cellulose material other than regenerated cellulose include natural cellulose such as dissolving pulp.

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

[0039] The alkali cellulose material of the present invention is brought into contact with carbon disulfide and reacted to be converted into cellulose xanthate. This step is generally called sulfurization. Sulfurization can be performed by adding carbon disulfide to the alkali cellulose material after mercerization and mixing and stirring the mixture. In addition, it is also possible to simultaneously perform mercerization and sulfurization by mixing cellulose, an aqueous alkali solution and carbon disulfide at once.

[0040] For a mixture including regenerated cellulose, an aqueous alkali solution and carbon disulfide, the cellulose concentration and the concentration of the alkali compound are values diluted with carbon disulfide added after mercerization unless it is necessary to newly adjust the concentration. The addition amount of carbon disulfide in the mixture is adjusted to 5 to 60 mass%, preferably 10 to 50 mass%, and more preferably 15 to 40 mass% relative to the mass of cellulose. When the amount of carbon disulfide added is less than 5 mass%, the reaction with the alkali cellulose becomes insufficient, and when the amount of carbon disulfide added is more than 60 mass%, the side reaction of carbon disulfide increases, unreacted carbon disulfide remains, and the safety may be lowered.

[0041] During the sulfurization, the temperature of the mixture is made uniform by stirring the entire inside of the stirring tank. In sulfurization, while alkali cellulose is solid, carbon disulfide is present as a liquid or a gas, and thus it is preferable to use, as a stirring apparatus, an apparatus including a low-speed blade that rotates along a wall surface of a stirring tank to make a mixture uniform and having a temperature control jacket, similarly to mercerization.

[0042] Sulfurization of the alkali cellulose is performed at a temperature of 0 to 50°C, preferably 5 to 40°C, and more preferably 10 to 30°C. When the temperature during sulfurization is lower than 0°C, labor and energy are required to maintain the liquid temperature at a low temperature, and when the temperature exceeds 50°C, the degree of polymerization of cellulose easily decreases, and the risk of ignition or the like also increases. The reaction time of sulfurization is set such that carbon disulfide sufficiently permeates the entire alkali cellulose, and is typically in the range of 30 minutes to 12 hours, preferably 1 to 9 hours, and more preferably 2 to 6 hours.

[0043] In addition, the obtained sulfide is dissolved at a temperature of 0 to 40°C, preferably 5 to 35°C, more preferably 10 to 30°C. When the temperature during dissolution is less than 0°C, labor and energy are required to maintain the liquid temperature at a low temperature, and when the temperature exceeds 40°C, the solubility of cellulose easily decreases. The time for dissolution is set such that the filter clogging value reaches a desired value and is completed, and is typically in the range of 2 minutes to 48 hours, preferably 4 minutes to 36 hours, and more preferably 5 minutes to 24 hours, depending on conditions such as stirring. In this case, particularly when a high-speed blade is used in combination, dissolution can be performed in a short time. Examples of the shape of the high-speed blade include a disper blade, a turbine blade, a propeller blade, a paddle blade, and a rotor stator, and among these, a disper blade is preferable.

[0044] The sulfide of the alkali cellulose material of the present invention by carbon disulfide can be used for producing viscose by being dissolved in an aqueous alkali solution, or can be used by being mixed with a sulfide of an alkali cellulose material prepared by a conventional method from a cellulose material other than regenerated cellulose by carbon disulfide. Examples of the cellulose material other than regenerated cellulose include natural cellulose, and in addition to pulp using biomass such as wood, cotton, straw, bamboo, hemp, jute, and kenaf as a raw material, waste paper, paper dust, and the like can be used, and among these, pulp produced from wood is preferable.

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

[0046] <Viscose> The viscose of the present invention obtained after completion of sulfurization and dissolution has physical properties equivalent to those of the viscose such as the viscose that is a raw material of various cellulose shaped products. The viscose of the present invention exhibits a filter clogging value of 6,000 or less, preferably 4,000 or less, more preferably 2,000 or less. The filter clogging value is smaller, indicating that the solubility of cellulose xanthate in the sulfide is more excellent. A method for calculating the filter clogging value is described below.

[0047] (Filter clogging value) The viscose is subjected to pressure filtration by applying a pressure of 0.04 MPa at 23 °C using a filter cloth made of 5 layers of cotton cloth, and the mass V (g) of the filtrate is measured over time. After a lapse of a certain time, the filtration time t (min) and the reciprocal t / V of the filtration speed are plotted, and the filter clogging value is calculated from the slope (k / 2) of the obtained straight line on the basis of the following formula. Fig. 1 is a schematic view of a graph in which measured characteristic values of viscose are plotted. Filter clogging value = 100,000 x k

[0048] The viscose of the invention has a cellulose concentration of 5 mass% or more, preferably of 6 to 12 mass%, more preferably of 8 to 10 mass%. The cellulose concentration is at the same level as the viscose such as the viscose that is a raw material of various cellulose shaped products. When the cellulose concentration of the viscose is high, the viscosity becomes too high, and when the cellulose concentration is low, the strength of the cellulose shaped product becomes insufficient, and the amount of chemicals such as acids used also increases, and thus the economic efficiency also decreases. A method for measuring the cellulose concentration is shown below.

[0049] (Cellulose concentration) The viscose is spread thinly on a pre-weighed glass plate using a Baker applicator (SA-201 manufactured by TESTER SANGYO CO., LTD.) and then the mass is measured and the mass of the viscose is calculated. Thereafter, the glass plate is allowed to stand in a constant temperature dryer at 70°C for 40 minutes, and each of the glass plate is immersed in a 10 mass% ammonium chloride aqueous solution for 30 minutes to peel off the coagulated viscose from the glass plate. This viscose is washed with distilled water and then dried in a hot air dryer at 105°C to measure the mass, and the cellulose concentration of the viscose is calculated from the following formula. Cellulose concentration = {mass after drying / (mass of viscose)} x 100

[0050] The viscose of the invention has an alkali concentration of 2 mass% or more, preferably of 4 to 12 mass%, more preferably of 5 to 10 mass%. The alkali concentration is at the same level as the viscose such as the viscose that is a raw material of various cellulose shaped products. When the alkali concentration of the viscose is high, the amount of acid required for neutralization increases, and when the alkali concentration is low, solubility decreases.

[0051] The viscose of the present invention is easily coagulated when added to a salt solution, a dilute acid such as sulfuric acid or hydrochloric acid, and an organic solvent, or heated, and can be regenerated with an acid to obtain a shaped product such as cellophane, rayon, or beads. In addition, when a dilute acid is used for coagulation, coagulation and regeneration proceed simultaneously.

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

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

[0054] The present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto. The unit "part" in 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 crashed, passed through a round net with hole of a diameter of ImmO, and washed with water to prepare a wet product (cellulose content: 43 mass%) from which a softener (glycerin) adhered thereto was removed.

[0056] 100 parts of the regenerated cellulose sample and 36 parts of a 40 mass% aqueous sodium hydroxide solution were charged into a stirring tank of a stirring device, and were mixed using a low-speed stirrer (three-one motor BL-600 manufactured by Shinto Scientific Co., Ltd.) equipped with a paddle impeller. While the mixture was stirred, mercerization was performed at room temperature of approximately 20°C to obtain alkali cellulose. The obtained alkali cellulose includes 32 mass% of cellulose and 11 mass% of sodium hydroxide.

[0057] Carbon disulfide of 35 mass% per mass of cellulose was added to the alkali cellulose, and sulfurization was performed for 4 hours while stirring was performed at 30rpm using the low-speed stirrer. An aqueous sodium hydroxide solution was added to the obtained sulfide, and the sulfide was dissolved at room temperature for 19 hours with stirring at 600 rpm to obtain viscose. The obtained viscose included 9.8 mass% of cellulose and 6.0 mass% of sodium hydroxide.

[0058] The viscose obtained after completion of sulfurization and dissolution was measured for viscosity and the filter clogging value. The solubility of cellulose was evaluated based on the filter clogging value. 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 B-type viscometer (No. 5 Rotor x 20 rpm).

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

[0061] A (excellent): filter clogging value of 2,000 or less B (favorable): filter clogging value of 6,000 or less C (poor): filter clogging value of more than 6,000

[0062] <Example 2> Viscose was obtained in the same manner as in Example 1 except that sulfide obtained by adding 25 mass% of carbon disulfide per mass of cellulose to the alkali cellulose prepared in Example 1 was dissolved for 10 minutes while being stirred at 5,000 rpm at room temperature using a high-speed stirrer equipped with a disper blade (“LABOLUTION” (trade name) manufactured by PRIMIX Corporation). The obtained viscose included 9.6 mass% of cellulose and 6.1 mass% of sodium hydroxide.

[0063] <Comparative Example 1> Mercerization was performed by immersing 100 parts of the regenerated cellulose sample prepared in Example 1 in 1000 parts of a 18 mass% aqueous sodium hydroxide solution at 50°C for 1.5 hours, and dehydration was performed at 3,000 rpm using a centrifuge HF type 110 F (Trade name, manufactured by KOKUSAN Co., Ltd) until discharge of the solution was stopped to obtain alkali cellulose. The obtained alkali cellulose included 22 mass% of cellulose and 16 mass% of sodium hydroxide.

[0064] Viscose was obtained in the same manner as in Example 1 except that this alkali cellulose was used. The obtained viscose included 8.2 mass% of cellulose and 6.1 mass% of sodium hydroxide.

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

[0066] [Table 1] Viscosity (mPa ■ s) Solubility Filter clogging value Remarks Example 1 1,380 B 4,400 Less undissolved fraction Example 2 1,560 B 4,800 Same as above Comparative Example 1 250 C Unmeasurable Immediately clogging A large amount of undissolved components remained. The alkali cellulose concentration is low, and thus side reactions during sulfurization increase, and solubility deteriorates.

[0067] As in Comparative Example 1, when an attempt is made to dissolve cellophane, which is regenerated cellulose, according to a general method for producing viscose, solubility decreases. The cause is that cellophane is significantly swollen in an aqueous alkali solution, and is not sufficiently dehydrated, and the cellulose concentration of the alkali cellulose is lowered (25 mass% or less). That is, it is considered that when the dehydration of the alkali cellulose was insufficient, the side reaction increased at the time of sulfurization, the conversion rate to cellulose xanthate decreased, and the solubility decreased.

[0068] In Examples 1 and 2, although there was a difference in the addition amount of carbon disulfide and the stirring condition during dissolution, alkali cellulose having a high cellulose concentration of 32 mass% could be prepared by adding a minimal amount of the concentrated aqueous alkali solution for essential purposes to regenerated cellulose and uniformly mixing them instead of immersing and dehydrating the regenerated cellulose in a large amount of an aqueous alkali solution. As a result, the viscose having excellent cellulose solubility could be obtained.

[0069] In Non-Patent Document 1 in which pulp is used as a raw material, it is considered that it is difficult to filter viscose (the filtration time of 300 g of the viscose is 177.4 seconds in the conventional method and 320 seconds in its method) as compared with a conventional method, and the mixing of hemicellulose and the like in the raw material pulp and the non-uniformity of alkali cellulose are the causes. However, when the raw material was replaced with regenerated cellulose, filtration could not be performed by a conventional method, but filtration could be performed in the present application, which is considered to be due to the low content of hemicellulose in the raw material.

[0070] <Example 3> Mixing viscose produced from the cellophane of Example 1 with an industrial viscose A mixed viscose (cellulose: 9.7 mass%, sodium hydroxide: 6.2 mass%) was prepared by mixing 10 parts of the viscose of Example 1 with 90 parts of the viscose manufactured by Rengo Co., Ltd. (prepared from dissolving pulp by a conventional method).

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

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

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

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

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

[0076] <Comparative Example 2> Mixing crashed cellophane with pulp The regenerated cellulose sample and the dissolving pulp were mixed such that the mass ratio of the regenerated cellulose to the natural cellulose was 1:9. This mixture was mercerized by immersing the mixture in a 18 mass% aqueous solution of sodium hydroxide at 50°C for 1.5 hours, and squeezed to obtain alkali cellulose (cellulose: 26 mass%, sodium hydroxide: 16 mass%). Carbon disulfide was added to alkali cellulose so as to be 35 mass% per mass of cellulose, and sulfurization was performed for 4 hours. An aqueous sodium hydroxide solution was added to the obtained sulfide, and the sulfide was dissolved at 20°C for 19 hours with stirring to prepare viscose (cellulose: 9.6 mass%, sodium hydroxide: 6.0 mass%).

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

[0078] <Comparative Example 3> Mixing mercerized cellophane of Comparative Example 1 with mercerized pulp The mercerized regenerated cellulose sample of Comparative Example 1 was mixed with mercerized pulp prepared from dissolving pulp by a conventional method such that the mass ratio of regenerated cellulose to natural cellulose was 1:9, and the mixture was sulfurized and then dissolved in an aqueous alkali solution to prepare viscose (cellulose: 9.6 mass%, sodium hydroxide: 6.0 mass%).

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

[0080] [Table 2] Viscosity (mPa • s) Solubility Filter clogging value Example 3 4,720 A 1,600 Example 4 5,280 A 900 Example 5 5,200 B 2,800 Comparative Example 2 5,050 C 13,000 Comparative Example 3 5,000 C 15,000

[0081] Examples 3,4, and 5 have favorable solubility. In contrast, in Comparative Examples 2 and 3 in which immersion and squeezing were performed by a conventional method, solubility deteriorated. In addition, Example 5 has lower solubility than Examples 3 and 4. The reason for this is considered to be that cellophane having a small surface area in the sulfurization reaction had lower reactivity than pulp, and sulfurization proceeded non-uniformly. It is expected that the cellophane and the pulp are sulfurized separately whereby the reaction becomes uniform and more preferable in terms of solubility.

[0082] In the present invention, the conditions for mercerizing regenerated cellulose to obtain alkali cellulose were optimized, and thus it has been found that viscose that is suitable for production of a shaped product is able to be obtained, even when the alkali cellulose, or in the form of sulfurized alkali cellulose, is mixed with an alkali cellulose material derived from wood pulp, or the alkali cellulose is mixed with industrial viscose in the form of viscose which has been sulfurized and dissolved in an aqueous alkali solution. As a result, it is less necessary to prepare dedicated manufacturing equipment, and existing equipment can be effectively used, and it is also advantageous in terms of energy cost.

Claims

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

2. The alkali cellulose material according to claim 1, wherein a cellulose component is free of natural cellulose.

3. The alkali cellulose material according to claim 1 or 2, wherein a cellulose component is composed of regenerated cellulose.

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

5. The alkali cellulose material according to any one of claims 1 to 4, wherein the viscose has a filter clogging value 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 use produced from a cellulose material other than regenerated cellulose.

7. A sulfide of an alkali cellulose material with carbon disulfide, the alkalicellulose material comprising regenerated cellulose, alkali and water, and having a cellulose concentration of 27 to 40 mass% and an alkali concentration of 8 to 20 mass%.

8. A mixed sulfide of an alkali cellulose material with carbon disulfide, the mixed sulfide comprising a sulfide of the alkali cellulose material according to claim 7 with carbon disulfide and a sulfide of an alkali cellulose material with carbon disulfide for the same use produced from a cellulose material other than regenerated cellulose.

9. Viscose comprising a sulfide of an alkali cellulose material with carbon disulfide, the alkali cellulose material including regenerated cellulose, alkali and water, and having a cellulose concentration of 27 to 40 mass% and an alkali concentration of 8 to 20 mass%.

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

11. A method for producing viscose, the method comprising sulfurizing an alkali cellulose material with carbon disulfide, the alkali cellulose material including regenerated cellulose, alkali and water, and having a cellulose concentration of 27 to 40 mass% and an alkali concentration of 8 to 20 mass%.INTERNATIONAL SEARCH REPORT International application No. PCT / JP2024 / 019027 A. CLASSIFICATION OF SUBJECT MATTER COSB 16 / 00(2006.01)1; COSB 1 / 08(2006.01)1; COSB 9 / 00(2006.01)1; D01F2 / 06(2006.01)1; D01F2 / 18(2006.01)1 FI: C08B16 / 00; C08B1 / 08; C08B9 / 00; D01F2 / 06 Z; D01F2 / 18 According to International Patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHEDMinimum documentation searched (classification system followed by classification symbols)C08B16 / 00: C08B1 / 08; C08B9 / 00; D01F2 / 06; D01F2 / 18Documentation searched other than minimum documentation to the extent that such documents are included in the fields searchedPublished examined utility model applications of Japan 1922-1996Published unexamined utility model applications of Japan 1971-2024Registered utility model specifications of Japan 1996-2024Published registered utility model applications of Japan 1994-2024Electronic data base consulted during the international search (name of data base and, where practicable, search terms used) JSTPlus / JST7580 / JSTChina (JDreamlll)DOCUMENTS CONSIDERED TO BE RELEVANTCategory* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. X JP 62-034053 B2 (HOECHST AKTIENGESELLSCHAFT) 24 July 1987 (1987-07-24) column 1, line 23 to column 2. line 2, column 7, lines 20-22. column 7, line 25 to column 8, line 2, column 8, line 29 to column 9, line 2 1,4-5,7, 9, 11 Y column 1, line 23 to column 2, line 2, column 7, lines 20-22, column 7, line 25 to column 1-11 8, line 2, column 8, line 29 to column 9, line 2 Y JP 2018-505973 A (LENZING AG) 01 March 2018 (2018-03-01) paragraphs [0011], [0017] 1-11 A JP 8-239504 A (HOECHST AKTIENGESELLSCHAFT) 17 September 19% (1996-09-17) entire text, all drawings 1-11 A JP 53-046234 B2 (OOMI KENSHIKK) 12 December 1978 (1978-12-12) entire text, all drawings 1-11| | Further documents are listed in the continuation of Box C. | / | See patent family annex. * Special categories of cited documents: “T” later document published after the international filing date or priority “A” document defining the general state of the art which is not considered date and not in conflict with the application but cited to understand the to be of particular relevance principle or theory underlying the invention “D” document cited by the applicant in die international application “X” document of particular relevance; the claimed invention cannot be “E" earlier application orpatent but published on or after the international considered novel or cannot be considered to involve an inventive step filing date when the document is taken alone •SL” document which may throw doubts on priority claim(s) or which is “Y” document of particular relevance; the claimed invention cannot be cited to establish the publication date of another citation or other considered to involve an inventive step when the document is special reason (as specified) combined with one or more other such documents, such combination “O” document referring to an oral disclosure, use, exhibition or other being obvious to a person skilled in the art means document member of the same patent family “P” document published prior to the international filing date but later than the priority date claimed Date of the actual completion of the international search 31 July 2024 Date of mailing of the international search report 13 August 2024 Name and mailing address of the ISA / JP Japan Patent Office (ISA / JP) 3-4-3 Kasumigaseki, Chiyoda-ku, Tokyo 100-8915 Japan Authorized officer Telephone No.Form PCT / ISA / 210 (second sheet) (July 2022)INTERNATIONAL SEARCH REPORT Information on patent family membersInternational application No.PCT / JP2024 / 019027Patent document cited in search report Publication date (day / month / year) Patent family member)s) Publication date (day / month / year) JP 62-034053 B2 24 July 1987 US 4340429 A column 1, lines 7-12, column 4, lines 25-27, column 4, lines 29-39, column 4, line 66 to column 5, line 22 EP 3135 A2 JP 2018-505973 A 01 March 2018 US 2018 / 0002836 Al paragraphs [0017], [0024] EP 3253912 Al CN 107208325 A JP 8-239504 A 17 September 19% US 5609676 A entire text, all drawings EP 717131 Al JP 53-046234 B2 12 December 1978 (Family: none)

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