WO2024257575A1 - Alkali cellulose material, viscose, and method for producing viscose - Google Patents

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

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.

The production of cellulose products such as cellophane, rayon, and beads generates by-products such as scraps and non-standard products. However, since cellulose does not have thermoplasticity and does not dissolve in general-purpose solvents, using cellulose products as a raw material to prepare a cellulose solution such as viscose for reuse requires complicated work processes and high costs.

Typically, viscose is prepared by first coarsely crushing the raw material dissolving pulp sheet and immersing it in a large amount of alkaline aqueous solution to turn it into alkaline cellulose (mercerization), squeezing it to remove excess alkaline aqueous solution, crushing it, reacting it with carbon disulfide to convert it into cellulose xanthate (sulfurization), and dissolving this in an alkaline aqueous solution.

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

Patent Document 1 describes the preparation of alkali cellulose, which is made from recycled artificial cellulose-based raw materials, by immersing the raw materials in an alkaline aqueous solution and then squeezing the raw materials, which undergoes sulfurization and dissolution.

Special Publication No. 2018-505973

Tadashi Maki, "First Report: Experiments on the Production of Viscose without Pressure," Journal of Sen'i Gakkaishi, Vol. 2, No. 2, pp. 79-81, 1946

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

In addition, when the alkali cellulose of Patent Document 1 is sulfurized and dissolved, cellulose has low solubility, so viscose containing a large amount of undissolved matter is produced. Such viscose has problems such as poor filterability and only molded bodies with low strength properties can be obtained, making it less practical.

The present invention aims to solve the above problems, and its purpose is to provide an alkali cellulose material that uses regenerated cellulose as a raw material to obtain viscose with physical properties suitable for use as a raw material for forming various cellulose molded products.

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.

[Aspect 2] An alkali cellulose material according to aspect 1, in which the cellulose component does not contain natural cellulose.

[Aspect 3] An alkali cellulose material according to aspect 1 or 2, wherein the cellulose component is made of regenerated cellulose.

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

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

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

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

[Aspect 8] A mixed sulfide of alkali cellulose material with carbon disulfide, comprising the sulfide of alkali cellulose material of aspect 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.

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

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

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

[Aspect 12] The viscose of aspect 9, having a clogging degree of 6,000 or less, preferably 4,000 or less, more preferably 2,000 or less.

[Aspect 13] Viscose according to aspect 9 or 12, having a cellulose concentration of 5% by mass or more, preferably 6 to 12% by mass, and more preferably 8 to 10% by mass.

[Aspect 14] Viscose according to aspect 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.

[Aspect 15] A mixed viscose according to aspect 10, having a regenerated cellulose content of 1 to 99% by mass, preferably 2 to 50% by mass, and more preferably 3 to 20% by mass, based on the cellulose component.

The present invention provides an alkali cellulose material that uses regenerated cellulose as a raw material to obtain viscose with physical properties suitable for use as a raw material for molding various cellulose molded products. The present invention provides viscose with physical properties suitable for use as a raw material for molding 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 molding various cellulose molded products, using regenerated cellulose as a raw material.

FIG. 1 is a schematic diagram of a graph in which characteristic values of viscose for calculating the degree of clogging are plotted.

The following describes in detail an embodiment of the present invention, but the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention. Furthermore, when multiple upper and lower limit values are listed for a particular parameter, any of these upper and lower limit values can be combined to create a suitable numerical range.

<Regenerated cellulose>
The regenerated cellulose used as a raw material is mainly cellulose obtained by liquefying natural cellulose by the conventionally known viscose method or cuprammonium method, and then solidifying and molding it into a predetermined shape. Regenerated cellulose includes cellulose molded products, cellulose products produced by cutting cellulose molded products, and by-products produced when manufacturing cellulose molded products. They may be pulverized to improve reaction efficiency. Specific examples of regenerated cellulose include scraps, non-standard products, defective products, and waste cellulose products generated when manufacturing cellulose molded products such as cellophane, rayon, and beads. Furthermore, regenerated cellulose can be reused as a raw material instead of natural cellulose.

<Natural cellulose>
The natural cellulose used as the 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 manufacturing method is also not particularly limited, and may be a mechanical method, a chemical method, or a method that combines the two. In terms of pulp quality, highly refined dissolving pulp, which is the main raw material for paper pulp, artificial fiber, cellophane, etc., is preferred.

<Alkaline 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 after mercerization, which contains regenerated cellulose, alkali, and water, 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 causes the cellulose to swell, improving the reaction efficiency when sulfurizing the alkali cellulose. As the alkali, strong alkaline compounds such as sodium hydroxide, lithium hydroxide, and potassium hydroxide can be used.

　The mercerization process is generally carried out by immersing the cellulose material in a large amount of an aqueous alkaline solution, followed by squeezing to remove the 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 add it uniformly. Because an excessive amount of aqueous alkaline solution is not added, a dehydration process such as squeezing is unnecessary and is not carried out.

When regenerated cellulose is immersed in an alkaline aqueous solution, it absorbs a large amount of water and swells significantly. For this reason, it is difficult to increase the cellulose concentration to an appropriate level using the usual dehydration methods such as squeezing.

The amount of alkaline aqueous solution added is adjusted according to 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 mass%, preferably 9 to 18 mass%, and more preferably 10 to 16 mass%. 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%. By adjusting the alkali concentration and cellulose concentration in the mixture to within the above ranges, the physical properties of the resulting viscose become suitable as a raw material for molding cellulose products.

Then, the alkaline aqueous solution and the regenerated cellulose are mixed and stirred to proceed with mercerization. For mixing and stirring at this time, a stirring device suitable for mixing a small amount of alkaline aqueous solution with solid regenerated cellulose is selected. The stirring device has a stirring tank and preferably has a temperature control jacket around the stirring tank that can control the temperature. In order to precisely control the reaction temperature, it is preferable to use a device equipped with low-speed blades that homogenize the temperature of the mixture by stirring the entire inside of the stirring tank during the reaction in mercerization. The shape of the low-speed blades includes anchor blades, ribbon anchor blades, helical ribbon blades, gate blades, paddle blades, etc., and among these, anchor blades and ribbon anchor blades are more preferable. Furthermore, in order to improve the stirring efficiency, the stirring shaft may be made oblique, horizontal, or eccentric, and a baffle plate may be provided in the stirring tank or the stirring tank itself may be rotated.

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 temperature during mercerization is less than -20°C, labor and energy are required to maintain the liquid temperature at a low temperature, and if it exceeds 50°C, labor and time are required to cool it to a temperature suitable for sulfurization. The reaction time for mercerization is usually in the range of 0.5 to 120 hours, preferably 1 to 72 hours, and more preferably 2 to 48 hours. If the reaction time for mercerization is too short, penetration will be insufficient and the reaction will not progress to the center, resulting in an increase in undissolved matter, but if the reaction time is too long, the degree of polymerization will decrease. In addition, since this decrease in the degree of polymerization occurs due to oxidation with oxygen in the air, mercerization may be carried out under reduced pressure or by replacing the air with nitrogen gas, hydrogen gas, etc.

The alkali cellulose material of the present invention can be used by mixing 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 cellulose materials other than regenerated cellulose include natural cellulose such as dissolving pulp.

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 the regenerated cellulose as much as possible, the recycling rate of the regenerated cellulose can be improved, and the effect of reducing the environmental load can be enhanced.

The alkali cellulose material of the present invention is reacted with carbon disulfide and converted into cellulose xanthate. This process is generally called sulfurization. Sulfurization can be carried out by adding carbon disulfide to the alkali cellulose material after mercerization, and mixing and stirring the mixture. It is also possible to mix cellulose, an aqueous alkali solution, and carbon disulfide at once to carry out mercerization and sulfurization simultaneously.

　For a mixture containing regenerated cellulose, an aqueous alkali solution, and carbon disulfide, the cellulose concentration and the concentration of the alkali compound are diluted with carbon disulfide added after mercerization unless further adjustment is required. The amount of carbon disulfide added to the mixture is adjusted to 5-60% by mass, preferably 10-50% by mass, and more preferably 15-40% 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, and if it exceeds 60% by mass, side reactions of carbon disulfide will increase or unreacted carbon disulfide will remain, which may reduce safety.

During sulfurization, the temperature of the mixture is made uniform by stirring the entire inside of the mixing vessel. In sulfurization, the alkali cellulose is a solid, whereas carbon disulfide exists as a liquid or gas. Therefore, as in mercerization, it is preferable to use a mixing device equipped with a low-speed blade that rotates along the wall of the mixing vessel to homogenize the mixture and that has a temperature-regulating jacket.

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, it takes time and energy to maintain the liquid temperature low, and if it exceeds 50°C, the degree of polymerization of the 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.

The obtained 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 temperature during dissolution is less than 0°C, labor and energy are required to maintain the liquid temperature at a low temperature, and if it exceeds 40°C, the solubility of the cellulose is likely to decrease. The dissolution time is set so that the clogging degree reaches the desired value and is completed, and although it depends on the stirring 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, especially when high-speed impellers are used in combination. The shape of the high-speed impeller can be a dispersion impeller, a turbine impeller, a propeller impeller, a paddle impeller, a rotor/stator, etc., and among these, a dispersion impeller is preferable.

The carbon disulfide sulfide of the alkali cellulose material of the present invention can be used to produce viscose by dissolving it in an alkaline aqueous solution, or it can be mixed with the carbon disulfide sulfide of the 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, with pulp made from wood being particularly preferred.

In this case, the content of regenerated cellulose in the sulfide of the mixed alkali cellulose material produced by 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 the regenerated cellulose as much as possible, the recycling rate of the regenerated cellulose can be improved, and the effect of reducing the environmental load can be enhanced.

<Viscose>
The viscose of the present invention obtained after completion of 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 the cellulose xanthate in the sulfide. The method for calculating the clogging degree is shown below.

(Clogging degree)
Viscose is filtered at 23°C under a pressure of 0.04 MPa using a filter cloth made of five layers of cotton, and the mass V (g) of the filtrate is measured over time. After a certain time has passed, the filtration time t (min) and the reciprocal of the filtration rate t/V are plotted, and the degree of clogging is calculated from the slope (k/2) of the resulting 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

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. Such a 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 high, the viscosity will be too high, and if it is low, the strength of the cellulose molded product will be insufficient and the amount of chemicals such as acid used will increase, reducing economic efficiency. The method for measuring the cellulose concentration is shown below.

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

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. Such an 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, and if it is low, the solubility decreases.

The viscose of the present invention easily solidifies 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 acid to obtain molded products such as cellophane, rayon, and beads. Furthermore, when a dilute acid is used for coagulation, coagulation and regeneration proceed simultaneously.

The viscose of the present invention can be used in combination with viscose prepared by conventional methods from cellulose materials other than regenerated cellulose. Examples of cellulose materials other than regenerated cellulose include natural cellulose such as dissolving pulp.

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 the regenerated cellulose as much as possible, the recycling rate of the regenerated cellulose can be improved, and the effect of reducing the environmental load can be enhanced.

The present invention will be explained 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.

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

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

To this alkali cellulose, 35% by mass of carbon disulfide per mass of cellulose was added, 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 obtained sulfide, and it was dissolved while stirring at 600 rpm at room temperature for 19 hours to obtain viscose. The obtained viscose contains 9.8% by mass of cellulose and 6.0% by mass of sodium hydroxide.

The viscosity and clogging degree of the viscose obtained after sulfurization and dissolution were measured. The solubility of cellulose was evaluated based on the clogging degree. The results are shown in Table 1.

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

(Solubility)
The evaluation criteria for solubility were as follows:

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

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

<Comparative Example 1>
100 parts of the regenerated cellulose sample prepared in Example 1 was immersed in 1000 parts of 18% by weight aqueous sodium hydroxide solution at 50°C for 1.5 hours to perform mercerization, and the sample was dehydrated at 3,000 rpm using a centrifuge HF110F (trade name, manufactured by Kokusan Co., Ltd.) until the discharge of the solution stopped, to obtain an alkali cellulose. The obtained alkali cellulose contained 22% by weight of cellulose and 16% by weight of sodium hydroxide.

Viscose was obtained in the same manner as in Example 1, except that this alkali cellulose was used. The obtained viscose contained 8.2% by mass of cellulose and 6.1% by mass of sodium hydroxide.

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.

When trying to dissolve cellophane, a regenerated cellulose, according to a typical viscose manufacturing method, as in Comparative Example 1, the solubility is low. The reason for this is that cellophane swells significantly in the alkaline aqueous solution and is not sufficiently dehydrated, resulting in a low cellulose concentration in the alkali cellulose (25% by mass or less). In other words, it is believed that when the alkali cellulose is not sufficiently dehydrated, there are more side reactions during sulfurization, the conversion rate to cellulose xanthate decreases, and the solubility decreases.

In Examples 1 and 2, although there were differences in the amount of carbon disulfide added and the stirring conditions during dissolution, instead of soaking the regenerated cellulose in a large amount of alkaline aqueous solution and dehydrating it, a small amount of the minimum necessary concentrated alkaline aqueous solution was added to the regenerated cellulose and mixed uniformly, making it possible to prepare alkaline cellulose with a high cellulose concentration of 32% by mass. As a result, a viscose with excellent cellulose solubility was obtained.

In addition, in Non-Patent Document 1, which uses pulp as the raw material, filtering of viscose is more difficult than with the conventional method (the filtering time for 300 g of viscose is 177.4 seconds with the conventional method and 320 seconds with this method), which is considered 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, filtering was possible with this application, whereas filtering was not possible with the conventional method, and this is thought to be due to the low hemicellulose content in the raw material.

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

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.

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% by mass, sodium hydroxide: 6.1% by mass).

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.

Example 5
The mercerized cellophane of Example 1 was mixed with the mercerized pulp. The mercerized regenerated cellulose sample of 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 was added per mass of cellulose, 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).

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.

<Comparative Example 2>
Mixing crushed cellophane with pulp The regenerated cellulose sample and dissolving pulp were mixed so that the mass ratio of regenerated cellulose to native cellulose was 1:9. The 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 performed for 4 hours. Aqueous sodium hydroxide solution was added to the obtained sulfide, and the mixture was dissolved while stirring at 20°C for 19 hours to prepare viscose (cellulose: 9.6% by mass, sodium hydroxide: 6.0% by mass).

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.

<Comparative Example 3>
The mercerized cellophane of Comparative Example 1 was mixed with the mercerized pulp. The mercerized regenerated cellulose sample of 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%).

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.

Examples 3, 4 and 5 have good solubility. In contrast, Comparative Examples 2 and 3, which were subjected to conventional soaking and squeezing, have poor solubility. Also, Example 5 has lower solubility than Examples 3 and 4. This is thought to be because cellophane, which has a small surface area, is less reactive in the sulfurization reaction than pulp, and the sulfurization proceeds unevenly. By sulfurizing cellophane and pulp separately, the reaction becomes uniform, which is expected to be more favorable in terms of solubility.

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 bodies 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 that has been 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 also advantageous in terms of energy costs.

Claims (11)

An alkali cellulose material containing regenerated cellulose, an alkali, and water, used to produce viscose by sulfurization with carbon disulfide, the alkali cellulose material having a cellulose concentration of 27-40% by mass and an alkali concentration of 8-20% by mass. The alkali cellulose material of claim 1, wherein the cellulose component does not contain natural cellulose. The alkali cellulose material according to claim 1 or 2, wherein the cellulose component is made of regenerated cellulose. The 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. The alkali cellulose material according to any one of claims 1 to 4, wherein the viscose has a clogging degree of 6,000 or less. 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 application produced from a cellulose material other than regenerated cellulose. A sulfide produced by carbon disulfide of an alkali cellulose material containing regenerated cellulose, alkali, and water, and having a cellulose concentration of 27-40% by mass and an alkali concentration of 8-20% by mass. A mixed sulfide of alkali cellulose material with carbon disulfide comprising the sulfide of alkali cellulose material described in claim 7 with carbon disulfide of alkali cellulose material for the same use produced from a cellulose material other than regenerated cellulose. Viscose containing regenerated cellulose, alkali and water, and containing a sulfide of an alkali cellulose material having a cellulose concentration of 27-40% by mass and an alkali concentration of 8-20% by mass with carbon disulfide. A mixed viscose comprising the viscose according to claim 9 and a viscose produced from a cellulose material other than regenerated cellulose. A method for producing viscose, comprising sulfurizing an alkali cellulose material containing regenerated cellulose, an alkali, and water, and having a cellulose concentration of 27-40% by mass and an alkali concentration of 8-20% by mass, with carbon disulfide.

Images