CN108070109B - Method for improving processability and/or mechanical property of low-polymerization-degree cellulose material - Google Patents
Method for improving processability and/or mechanical property of low-polymerization-degree cellulose material Download PDFInfo
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Abstract
The invention discloses a method for improving the processability and/or mechanical property of a low-polymerization-degree cellulose material. The method for improving the processability and/or mechanical property of the low-polymerization-degree cellulose material is to use the blend of the high-polymerization-degree cellulose raw material and the low-polymerization-degree cellulose raw material as the raw material. The invention can simultaneously improve the processing performance and the mechanical property of the low-polymerization-degree cellulose material, and has the advantages of simple process, no pollution, low energy consumption and the like. Under the condition of using the ionic liquid as the cellulose solvent, the used ionic liquid solvent has simple synthesis method, low price, no toxicity and harm, easy solvent recovery and high safety. By adding a small amount of cellulose components with high polymerization degree, the processing performance (film forming property and fiber forming property) of the cellulose solution is obviously superior to that of the cellulose solution with low polymerization degree, and the strength of the obtained regenerated cellulose fiber or film is obviously superior to that of the regenerated cellulose fiber or film prepared from the cellulose raw material with low polymerization degree.
Description
Technical Field
The invention relates to a method for improving the processability and/or mechanical property of a low-polymerization-degree cellulose material, and relates to the field of natural polymer processing.
Background
With the increasing global environmental pollution problem and the rapid depletion of petroleum energy, the research on polymer materials using natural renewable resources as raw materials is rapidly developed. Cellulose is the most abundant natural polymer on the earth, is easy to obtain and regenerate, and has the advantages of low price, degradability, no pollution to the ecological environment and the like. At present, cellulose-based materials are widely applied to traditional industries such as plastics, textile, papermaking and the like, and are importantly applied to the fields of food, chemical industry, daily necessities, medicine, construction, oilfield chemistry and biochemistry. It is expected that, in the future, cellulose materials will play an important role in many aspects such as improvement of ecological environment, improvement of human quality of life, development of new materials, and the like.
In the production process, in order to ensure the performance of the regenerated cellulose material, the cellulose product is prepared by using high-purity and high-polymerization-degree cellulose as a raw material, and the cellulose product comprises cellulose raw materials with the polymerization degree of 600-800, such as wood pulp, cotton pulp and the like. In order to obtain regenerated cellulose products having more excellent performance, cellulose raw materials having a higher degree of polymerization, including high-quality wood pulp, cotton linter, and the like, having a degree of polymerization of 1000 or more are also used. These cellulose raw materials with high polymerization degree have the disadvantages of high production cost, long growth period of raw materials and the like. However, in the production and life of people, a large amount of cheap low-polymerization-degree cellulose exists, including microcrystalline cellulose (polymerization degree 220), cellulose in plant straws (polymerization degree 280), cellulose in waste cotton-containing textiles (polymerization degree 260), and the like. Since the degree of polymerization of these celluloses is low, the properties of regenerated cellulose materials prepared from them are low, which severely limits the use of low-polymerization cellulose. The effective method for utilizing the low-polymerization-degree cellulose raw material has important practical significance and economic value.
Disclosure of Invention
The object of the present invention is to provide a method for improving the processability and/or mechanical properties of a cellulose material having a low degree of polymerization, i.e., the present invention can remarkably improve the processability (film-forming property and fiber-forming property) of the resulting cellulose solution and the mechanical properties of regenerated cellulose fibers or regenerated cellulose films by using a small amount of a cellulose raw material having a high degree of polymerization (the degree of polymerization is usually more than 1300) together with a cellulose raw material having a low degree of polymerization, and thus a high-performance regenerated cellulose material can be simply and efficiently produced from a cellulose raw material having a low degree of polymerization by the present invention. .
The method for improving the processing performance and/or the mechanical property of the low-polymerization-degree cellulose material provided by the invention is to prepare the low-polymerization-degree cellulose material by taking the blend of the high-polymerization-degree cellulose raw material and the low-polymerization-degree cellulose raw material as raw materials.
In the method, the polymerization degree (measured by a copper ethylenediamine method) of the high-polymerization-degree cellulose raw material can be 1300-4000, and specifically can be 1500-3500, 1500, 2400 or 3500;
the high polymerization degree cellulose raw material can be at least one of wood pulp, cotton pulp, bamboo pulp, cotton linter and bacterial cellulose raw materials.
In the above method, the degree of polymerization (measured by copper ethylenediamine method) of the low-polymerization-degree cellulose raw material may be 150 to 300, specifically 220 to 280, 220, 260, or 280;
the low-polymerization-degree cellulose raw material can be at least one of microcrystalline cellulose, cellulose prepared from plant straws and cellulose raw material prepared from waste cotton-containing textiles.
In the above method, the mass ratio of the high-polymerization-degree cellulose raw material to the low-polymerization-degree cellulose raw material may be 1: 4-8, specifically 1: 4. 1: 5. 1: 7 or 1: 8.
in the above method, the cellulose raw material having a high degree of polymerization and the cellulose raw material having a low degree of polymerization are pulverized and used, and the effect is more excellent.
In the above method, the method comprises the steps of: dissolving the blend in a solvent to obtain a cellulose solution;
the processability (film-forming property and fiber forming property) of the cellulose solution is obviously better than that of the cellulose solution with low degree of polymerization;
the solvent can be N-methylmorpholine oxide aqueous solution (NMMO), ionic liquid or mixed solution of the ionic liquid and at least one of N, N-dimethyl sulfoxide and N, N-dimethylformamide;
the ionic liquid can be at least one of 1-ethyl-3-methylimidazolium chloride (EMIMCl), 1-propyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride (PMIMCl), 1-allyl-3-methylimidazolium chloride (BMIMCl), 1-methallyl-3-methylimidazolium chloride (mMIMCl), 1-ethyl-3-methylimidazolium acetate (EMIMAc), 1-propyl-3-methylimidazolium acetate (PMIMAc), 1-butyl-3-methylimidazolium acetate (BMIMAc), 1-allyl-3-methylimidazolium acetate (AMIMAc) and 1-methallyl-3-methylimidazolium acetate (mMIMAc).
In the above method, the cellulose solution may have a mass percentage concentration of 5 to 20%, specifically 5 to 18%, 5 to 16%, 5 to 10%, 5 to 9%, 5%, 6%, 9%, 10%, 16%, 18%, or 20%.
In the above method, the dissolving temperature may be 25 to 100 ℃, specifically 80 to 90 ℃, 80 ℃ or 90 ℃.
In the above method, the method further comprises a step of preparing the cellulose solution into regenerated cellulose fibers or regenerated cellulose films;
the strength of the regenerated cellulose fiber or the regenerated cellulose film is remarkably superior to that of the regenerated cellulose fiber or film prepared from the cellulose raw material with low polymerization degree and even close to that of the regenerated cellulose fiber or film prepared from the cellulose raw material with high polymerization degree.
In the method, the regenerated cellulose fiber is obtained by sequentially carrying out spinning and coagulating bath forming on the cellulose solution;
the cellulose solution is sequentially subjected to film spraying and coagulating bath forming to obtain the regenerated cellulose film;
the coagulating bath used for the coagulating bath forming can be water and/or ethanol, and when a mixture of water and ethanol is used, the weight ratio of water to ethanol is 95: 5-50: 50, specifically 80: 20.
the temperature of the coagulating bath forming is 25-90 ℃, and specifically can be 25-40 ℃, 25 ℃, 35 ℃ or 40 ℃.
In the method, the solvent can be recycled and reused, and can be recycled by multiple-effect evaporation, membrane separation or salting-out.
The method can simultaneously improve the processing performance and the mechanical property of the low-polymerization-degree cellulose material, and has the advantages of simple process, no pollution, low energy consumption and the like. Under the condition of using the ionic liquid as the cellulose solvent, the used ionic liquid solvent has simple synthesis method, low price, no toxicity and harm, easy solvent recovery and high safety. By adding a small amount of cellulose components with high polymerization degree, the processing performance (film forming property and fiber forming property) of the cellulose solution is obviously superior to that of the cellulose solution with low polymerization degree; the strength of the regenerated cellulose fiber or film obtained by spinning or film spraying treatment, coagulating bath forming, washing, drying and other treatments is obviously superior to that of the regenerated cellulose fiber or film prepared by the low-polymerization-degree cellulose raw material, even close to that of the regenerated cellulose fiber or film prepared by the high-polymerization-degree cellulose raw material. Thereby greatly expanding the application range of the low-polymerization-degree cellulose and improving the utilization rate of the low-polymerization-degree cellulose.
Detailed Description
The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
Examples 1,
The selected low-polymerization-degree cellulose raw material is microcrystalline cellulose, the polymerization degree of the selected low-polymerization-degree cellulose raw material is 220 measured by a copper ethylenediamine method, and the selected high-polymerization-degree cellulose raw material is wood pulp, and the polymerization degree of the selected high-polymerization-degree cellulose raw material is 1500 measured by the copper ethylenediamine method. 18.8g of dried EMIMCl ionic liquid, 1.0g of dried microcrystalline cellulose and 0.2g of dried wood pulp were weighed out and mixed with stirring at 90 ℃. After about 60 minutes, a clear, transparent, brownish yellow solution was formed, which was black in the field of observation with a polarizing microscope, indicating complete dissolution of the cellulose, and a cellulose solution having a concentration of 6.0% by weight was thus obtained, the weight ratio of the cellulose having a high degree of polymerization to a low degree of polymerization being 1: 5. and (3) defoaming the mixed cellulose solution for 120 minutes, and then carrying out a tensile rheology test on the mixed cellulose solution, wherein the breaking time of a liquid bridge of the mixed cellulose solution is 10 s. The mixed cellulose solution is evenly spread on the surface of a glass plate and is put into a coagulating basin with water as coagulating bath, and the temperature is 25 ℃. After washing and drying, the regenerated cellulose film containing a small amount of cellulose with high polymerization degree is obtained, the tensile strength of the regenerated cellulose film is 80MPa, and the elongation at break of the regenerated cellulose film is 15%. The water in the coagulation bath was evaporated to yield the recovered emimccl solvent.
Comparative examples 1,
The selected low-polymerization-degree cellulose raw material is microcrystalline cellulose, the polymerization degree of the microcrystalline cellulose is 220 measured by a copper ethylenediamine method, 18.8g of dry EMIMCl ionic liquid and 1.2g of dry microcrystalline cellulose are weighed and stirred and mixed at 90 ℃. After about 60 minutes, a clear, transparent, brownish yellow solution formed, which was black in the field of view when observed with a polarizing microscope, indicating complete dissolution of the cellulose, and a cellulose solution having a concentration of 6.0% by weight was thus obtained. And (3) defoaming the microcrystalline cellulose solution for 120 minutes, and then carrying out a tensile rheology test on the microcrystalline cellulose solution, wherein the breaking time of a liquid bridge of the cellulose solution is 0.4 s. The microcrystalline cellulose solution is evenly spread on the surface of a glass plate and is put into a coagulating basin with water as coagulating bath, and the temperature is 25 ℃. The regenerated cellulose film is obtained by washing and drying, and the microcrystalline cellulose film is subjected to tensile test, wherein the microcrystalline cellulose film is easy to break in the test process, the tensile strength of the microcrystalline cellulose film is 40MPa, and the elongation at break of the microcrystalline cellulose film is 5%. The water in the coagulation bath was evaporated to yield the recovered emimccl solvent.
Examples 2,
The selected low-polymerization-degree cellulose raw material is cellulose prepared from wheat straws, the polymerization degree of the cellulose is 280 measured by a copper ethylenediamine method, the selected high-polymerization-degree cellulose raw material is cotton linters, the polymerization degree of the cellulose is 3500 measured by the copper ethylenediamine method, 18.0g of dry PMIMCl ionic liquid, 1.6g of cellulose prepared from the dry wheat straws and 0.4g of dry cotton linters are weighed and stirred and mixed at the temperature of 80 ℃. After about 60 minutes, a clear, transparent, brownish yellow solution was formed, which was black in the field of observation with a polarizing microscope, indicating complete dissolution of the cellulose, and a cellulose solution having a concentration of 10.0% by weight was thus obtained, the weight ratio of the cellulose having a high degree of polymerization to a low degree of polymerization being 1: 4. and (3) defoaming the mixed cellulose solution for 120 minutes, and then carrying out a tensile rheology test on the mixed cellulose solution, wherein the breaking time of a liquid bridge of the mixed cellulose solution is 41 s. And spinning the mixed cellulose solution on a small spinning device in a wet spinning mode. The diameter of the spinneret orifice was 100 μm, and water was used as a coagulation bath at a temperature of 40 ℃. And (3) drawing, washing, drawing and drying to obtain the regenerated cellulose fiber containing a small amount of cellulose with high polymerization degree, wherein the fiber strength is 5.2 cN/tex. The water in the coagulation bath was evaporated to give a recovered PMIMCl solvent.
Comparative examples 2,
The cellulose raw material with low polymerization degree is cellulose prepared from wheat straws, the polymerization degree of the cellulose is 280 measured by a copper ethylene diamine method, 18.0g of dry PMIMCl ionic liquid and 2g of cellulose prepared from the dry wheat straws are weighed and stirred and mixed at the temperature of 80 ℃. After about 60 minutes, a clear, transparent, brownish yellow solution was formed, which was black in the field of view when observed with a polarizing microscope, indicating that the cellulose was completely dissolved, thereby producing a cellulose solution having a concentration of 10.0% by weight. And (3) defoaming the cellulose solution for 120 minutes, and then carrying out a tensile rheology test on the cellulose solution prepared from the wheat straws, wherein the breaking time of a liquid bridge of the cellulose solution is 1.2 s. And spinning the cellulose solution prepared from the wheat straws on small-sized spinning equipment in a wet spinning mode. The diameter of the spinneret orifice was 100 μm, and water was used as a coagulation bath at a temperature of 40 ℃. Since continuous regenerated cellulose fibers were not available, the fiber strength was not measured. The water in the coagulation bath was evaporated to give a recovered PMIMCl solvent.
Examples 3,
Selecting cellulose with low polymerization degree as cellulose prepared from waste cotton-containing textile fabric, measuring the polymerization degree of the cellulose with low polymerization degree as 260 by a copper ethylenediamine method, selecting cellulose with high polymerization degree as bamboo pulp, measuring the polymerization degree of the cellulose with high polymerization degree as 2400 by the copper ethylenediamine method, and weighing 16.8g of NMMO/H2O solvent, 2.8g of cellulose prepared from dried waste cotton-containing textile and 0.4g of dried bamboo pulp are stirred and mixed at 90 ℃. After about 60 minutes, a cellulose solution having a concentration of 16% by weight was thus obtained, the weight ratio of cellulose having a high degree of polymerization to cellulose having a low degree of polymerization being 1: 7. and (3) defoaming the mixed cellulose solution for 120 minutes, and then carrying out a tensile rheological test on the mixed cellulose solution, wherein the breaking time of a liquid bridge of the mixed cellulose solution is increased from 1.5 to 48s compared with the cellulose solution prepared from pure waste cotton-containing textile fabrics with the same concentration. And uniformly spreading the mixed cellulose solution in a polytetrafluoroethylene mold, and adding water as a solidification solution at the temperature of 35 ℃. Compared with the regenerated cellulose fiber film prepared by taking cellulose prepared from pure waste cotton-containing textiles as a raw material, the tensile strength of the regenerated cellulose film containing a small amount of cellulose with high polymerization degree is improved from 50MPa to 97MPa, and the elongation at break is improved from 7% to 19%. Evaporating off the most of the coagulation bathMost of the water, to obtain recovered NMMO/H2And (4) O solvent.
Examples 4,
The selected low-polymerization-degree cellulose raw material is microcrystalline cellulose, the polymerization degree of the selected low-polymerization-degree cellulose raw material is 220 measured by a copper ethylenediamine method, the selected high-polymerization-degree cellulose raw material is cotton linter, the polymerization degree of the selected high-polymerization-degree cellulose raw material is 3500 measured by the copper ethylenediamine method, 18.0g of dry BMIMAc ionic liquid, 0.8g of dry microcrystalline cellulose and 0.2g of dry cotton linter are weighed and stirred and mixed at 90 ℃. After about 60 minutes, a clear, transparent, brownish yellow solution was formed, which was black in the field of observation with a polarizing microscope, indicating complete dissolution of the cellulose, and a cellulose solution having a concentration of 5.0% by weight was thus obtained, the weight ratio of the cellulose having a high degree of polymerization to a low degree of polymerization being 1: 4. and (3) after the mixed cellulose solution is defoamed for 120 minutes, performing a tensile rheological test on the mixed cellulose solution, and increasing the breaking time of a liquid bridge of the mixed cellulose solution from 0.3s to 22s compared with the microcrystalline cellulose solution with the same concentration. The mixed solution is evenly spread on the surface of a glass plate and is put into a coagulating basin with ethanol as a coagulating bath, and the temperature is 25 ℃. Compared with the regenerated cellulose fiber film prepared by taking pure microcrystalline cellulose as a raw material, the regenerated cellulose film containing a small amount of high-polymerization cellulose has the advantages that the tensile strength is improved from 42MPa to 120MPa, and the elongation at break is improved from 5% to 18%. The water in the coagulation bath was evaporated to yield recovered BMIMAc solvent.
Examples 5,
The selected low-polymerization-degree cellulose raw material is cellulose prepared from wheat straws, the polymerization degree of the cellulose is 280 measured by a copper ethylenediamine method, the selected high-polymerization-degree cellulose raw material is bamboo pulp, the polymerization degree of the cellulose is 2400 measured by the copper ethylenediamine method, 16.4g of dry BMIMAc/DMF mixed solvent, 3.0g of cellulose prepared from the dry wheat straws and 0.6g of dry bamboo pulp are weighed and stirred and mixed at 90 ℃. After about 60 minutes, a clear, transparent, brownish yellow solution was formed, which was black in the field of observation with a polarizing microscope, indicating complete dissolution of the cellulose, and a cellulose solution having a concentration of 18.0% by weight was thus obtained, the weight ratio of the cellulose having a high degree of polymerization to a low degree of polymerization being 1: 5. and (3) defoaming the mixed cellulose solution for 120 minutes, and then carrying out a tensile rheology test on the mixed cellulose solution, wherein the breaking time of a liquid bridge of the mixed cellulose solution is increased from 2.1s to 55s compared with the cellulose solution prepared from the wheat straws with the same concentration. The mixed solution is evenly spread on the surface of a glass plate and is put into a coagulating basin with the mixed solution of water and ethanol as coagulating bath, the weight ratio of the water to the ethanol is 80:20, and the temperature is 25 ℃. And compared with the regenerated cellulose fiber film prepared by taking cellulose prepared from pure wheat straws as a raw material, the tensile strength of the regenerated cellulose film containing a small amount of cellulose with high polymerization degree is improved from 53MPa to 105MPa, and ethanol and DMF are used for obtaining the recovered BMIMAc solvent.
Examples 6,
The selected low-polymerization-degree cellulose raw material is microcrystalline cellulose, the polymerization degree of the selected low-polymerization-degree cellulose raw material is 220 measured by a copper ethylenediamine method, the selected high-polymerization-degree cellulose raw material is wood pulp, the polymerization degree of the selected high-polymerization-degree cellulose raw material is 1500 measured by the copper ethylenediamine method, 18.2g of dry AMIMCl ionic liquid, 1.6g of dry microcrystalline cellulose and 0.2g of dry wood pulp are weighed, and stirring and mixing are carried out at 90 ℃. After about 60 minutes, a clear, transparent, brownish yellow solution was formed, which was black in the field of observation with a polarizing microscope, indicating complete dissolution of the cellulose, and a cellulose solution having a concentration of 9.0% by weight was thus obtained, the weight ratio of the cellulose having a high degree of polymerization to a low degree of polymerization being 1: 8. and (3) after the mixed cellulose solution is defoamed for 120 minutes, performing a tensile rheological test on the mixed cellulose solution, and increasing the breaking time of a liquid bridge of the mixed cellulose solution from 1.3s to 40s compared with the microcrystalline cellulose solution with the same concentration. The mixed cellulose solution is spun by means of wet spinning on a small spinning device. The diameter of the spinneret orifice was 100 μm, and water was used as a coagulation bath at a temperature of 40 ℃. The regenerated cellulose fiber containing a small amount of cellulose with high polymerization degree is obtained by drawing, washing, drawing and drying, while the continuous regenerated cellulose fiber cannot be obtained by using pure microcrystalline cellulose as a raw material, and the fiber strength of the regenerated cellulose fiber containing a small amount of cellulose with high polymerization degree is 4.5 cN/tex. The water in the coagulation bath was evaporated to yield the recovered amimccl solvent.
Example 7
The selected low-polymerization-degree cellulose raw material is cellulose prepared from waste cotton-containing textile fabrics, the polymerization degree of the selected low-polymerization-degree cellulose raw material is 260 measured by a copper ethylenediamine method, the selected high-polymerization-degree cellulose raw material is cotton linters, the polymerization degree of the selected high-polymerization-degree cellulose raw material is 3500 measured by the copper ethylenediamine method, 14.0g of dry mAIMAC ionic liquid, 5.0g of cellulose prepared from the dry waste cotton-containing textile fabrics and 1.0g of dry cotton linters are weighed and stirred and mixed at the temperature of 90 ℃. After about 60 minutes, a clear, transparent, brownish yellow solution was formed, which was black in the field of observation with a polarizing microscope, indicating complete dissolution of the cellulose, and a cellulose solution having a concentration of 20.0% by weight was thus obtained, the weight ratio of the cellulose having a high degree of polymerization to a low degree of polymerization being 1: 5. and (3) defoaming the mixed cellulose solution for 120 minutes, and then carrying out a tensile rheology test on the mixed cellulose solution, wherein compared with the cellulose solution prepared from pure waste cotton-containing textile fabrics with the same concentration, the breaking time of a liquid bridge of the mixed cellulose solution is increased from 2.5s to 60 s. And uniformly spreading the mixed cellulose solution in a polytetrafluoroethylene mold, and adding water as a solidification solution at the temperature of 25 ℃. Compared with the regenerated cellulose fiber film prepared by taking cellulose prepared from pure waste cotton-containing textiles as a raw material, the tensile strength of the regenerated cellulose film containing a small amount of cellulose with high polymerization degree is improved from 52MPa to 101MPa, and the elongation at break is improved from 6% to 20%. Evaporating water from the coagulation bath to obtain the recovered mAmAc solvent.
Claims (7)
1. A method of improving the processability and/or mechanical properties of a low degree of polymerization cellulosic material, characterized in that: preparing the low-polymerization-degree cellulose material by using a blend of a high-polymerization-degree cellulose raw material and a low-polymerization-degree cellulose raw material as a raw material;
the polymerization degree of the high-polymerization-degree cellulose raw material is 1300-4000;
the polymerization degree of the low-polymerization-degree cellulose raw material is 150-300;
the mass ratio of the high-polymerization-degree cellulose raw material to the low-polymerization-degree cellulose raw material is 1: 4-8;
the high-polymerization-degree cellulose raw material is at least one of wood pulp, cotton pulp, bamboo pulp, cotton linter and bacterial cellulose raw materials;
the low-polymerization-degree cellulose raw material is at least one of microcrystalline cellulose, cellulose prepared from plant straws and cellulose raw material prepared from waste cotton-containing textiles;
the method comprises the following steps: dissolving the blend in a solvent to obtain a cellulose solution;
the solvent is N-methylmorpholine oxide aqueous solution, ionic liquid or mixed solution of the ionic liquid and at least one of N, N-dimethyl sulfoxide and N, N-dimethylformamide.
2. The method of claim 1, wherein: the ionic liquid is at least one of 1-ethyl-3-methylimidazole chloride salt, 1-propyl-3-methylimidazole chloride salt, 1-butyl-3-methylimidazole chloride salt, 1-allyl-3-methylimidazole chloride salt, 1-methallyl-3-methylimidazole chloride salt, 1-ethyl-3-methylimidazole acetate, 1-propyl-3-methylimidazole acetate, 1-butyl-3-methylimidazole acetate, 1-allyl-3-methylimidazole acetate and 1-methallyl-3-methylimidazole acetate.
3. The method of claim 2, wherein: the mass percentage concentration of the cellulose solution is 5-20%.
4. The method of claim 2, wherein: the dissolving temperature is 25-100 ℃.
5. The method of claim 2, wherein: the method further comprises the step of preparing the cellulose solution into regenerated cellulose fibers or a regenerated cellulose film.
6. The method of claim 5, wherein: the cellulose solution is sequentially subjected to spinning and coagulating bath forming to obtain the regenerated cellulose fiber;
and the cellulose solution is sequentially subjected to film spraying and coagulating bath forming to obtain the regenerated cellulose film.
7. A low-polymerization-degree cellulosic material produced by the method of any one of claims 1-6.
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