A method of regulating the crystallinity of regenerated cellulose

Abstract

The application discloses a method for regulating the crystallinity of regenerated cellulose, which comprises using low-molecular-weight cellulose and common cellulose as raw materials, and preparing the regenerated cellulose through a dissolution regeneration method. Based on the excellent characteristics of the low-molecular-weight cellulose, i.e. easy crystallization and small crystal size, the crystallinity and crystal size of the regenerated cellulose can be simply and accurately regulated by adding the low-molecular-weight cellulose into the common cellulose solution and regulating the polymerization degree and proportion of the low-molecular-weight cellulose. The crystallinity of the regenerated cellulose prepared by compounding the low-molecular-weight cellulose in the common cellulose solution is obviously increased, and the crystal size is small. The crystallinity and crystal size of the regenerated cellulose are simply and accurately regulated, which is of great significance for improving the strength and toughness of the regenerated cellulose material, and has a wide application prospect in the application market of the regenerated cellulose material.

Description

Technical Field

[0001] This invention belongs to the field of regenerated cellulose structure regulation technology, specifically relating to a method for regulating the crystallinity of regenerated cellulose. Background Technology

[0002] With the depletion of petroleum-based resources and the emergence of the concept of sustainable development, cellulose, as the most abundant, renewable, and biodegradable natural material on Earth, has become a research hotspot. Based on the structural characteristics and excellent properties of cellulose, various high-performance materials such as high-strength, biocompatible regenerated cellulose membranes and regenerated cellulose filaments have been prepared through dissolution and regeneration processes. Among these, the crystallinity and crystal size of regenerated cellulose have a significant impact on the mechanical properties of regenerated cellulose materials.

[0003] Currently, numerous researchers have studied methods for controlling the crystallinity of regenerated cellulose, which can be broadly categorized into three types: The first type involves partial dissolution, where the dissolution time is controlled to obtain partially dissolved cellulose, resulting in a composite of cellulose I and II crystals. However, the proportion of cellulose I crystals in the composite obtained through this method is difficult to control, hindering industrial-scale production of cellulose. The second type involves preparing nanocrystalline cellulose composites by incorporating cellulose nanocrystals (CNCs) into regenerated cellulose materials. However, due to the large size of the CNC crystal regions and their uneven dispersion within the regenerated cellulose material, the resulting composite material exhibits low toughness. The third type involves incorporating high-polymerization-degree cellulose into low-quality cellulose, which can construct entangled networks. However, this method struggles to control the aggregation state of regenerated cellulose. Therefore, finding a simple method that can accurately control the crystallinity and crystal size of regenerated cellulose has become an urgent technical problem to be solved. Summary of the Invention

[0004] To improve the above-mentioned technical problems, the present invention provides a method for regulating the crystallinity of regenerated cellulose, comprising the following steps: adding low molecular weight cellulose to a common cellulose raw material system, thereby regulating the crystallinity of regenerated cellulose.

[0005] According to an embodiment of the present invention, the degree of polymerization of the low molecular weight cellulose is 15 to 60, for example 20, 25, 30, 40, 50, 52.

[0006] According to an embodiment of the present invention, the molecular weight distribution of the low molecular weight cellulose is 1.2 to 2.3, for example 1.4, 1.5, 1.7, 2.1.

[0007] According to an embodiment of the present invention, the mass percentage of the low molecular weight cellulose to the cellulose raw material is 0.5% to 20%, preferably 1% to 20%, for example 3%, 5%, 7%, or 10%; the mass of the cellulose raw material is the sum of the masses of ordinary cellulose and low molecular weight cellulose.

[0008] According to an embodiment of the present invention, the low molecular weight cellulose is prepared from ordinary cellulose by at least one of acid degradation or solid acid catalyst preparation methods.

[0009] According to an embodiment of the present invention, the acid used in the acid degradation method is selected from at least one of hydrochloric acid, sulfuric acid, phosphoric acid, etc., preferably phosphoric acid.

[0010] According to an embodiment of the present invention, the low molecular weight cellulose is obtained by dissolving ordinary cellulose in an acidic solution and then degrading it by heating.

[0011] Preferably, the acid solution is prepared by mixing acid and water in a volume ratio of (100-400):(5-20).

[0012] Preferably, the ratio of ordinary cellulose to acid is (10-40) g:(100-400) mL.

[0013] Preferably, the heating temperature is 10–50°C, and the degradation time is 2–14 days.

[0014] Preferably, the method for preparing the low molecular weight cellulose further includes pouring the heated degradation mixture into water, adding sodium bicarbonate to neutralize excess acid, and then washing and drying to obtain a powder. Preferably, the volume ratio of the mixture to water is 1:(1-10), exemplarily 1:6. Further, the sodium bicarbonate is added in the form of a sodium bicarbonate solution. For example, the concentration of the sodium bicarbonate solution is 6-10 wt%.

[0015] Preferably, the method for preparing the low molecular weight cellulose further includes dissolving the powder in dimethyl sulfoxide, and then washing and drying to obtain the low molecular weight cellulose.

[0016] According to an embodiment of the present invention, the solid acid catalyst is selected from one, two or more of the following substances: cation exchange resin type, immobilized liquid acid and metal salt.

[0017] For example, the cation exchange resin type is selected from sulfonic acid type cation exchange resin, sulfuric acid type cation exchange resin, and phosphoric acid type cation exchange resin; the immobilized liquid acid is selected from HF / Al2O3 and BF3 / Al2O3; and the metal salt is selected from sulfate or phosphate.

[0018] According to an embodiment of the present invention, the method for preparing the low molecular weight cellulose includes the following steps: mixing ordinary cellulose, ionic liquid, water and solid acid catalyst, heating and degrading to obtain the low molecular weight cellulose.

[0019] According to embodiments of the present invention, the ordinary cellulose may be selected from at least one of natural cellulose and degradation products of natural cellulose. For example, the natural cellulose may be selected from at least one of cotton pulp, wood pulp, seaweed cellulose, bacterial cellulose, etc. For example, the degradation products of natural cellulose may be at least one of microcrystalline cellulose (MCC), degradation products of frozen ball-milled cotton pulp, cellulose in plant straw, etc. Preferably, the degree of polymerization of the degradation products of natural cellulose is greater than that of the low molecular weight cellulose.

[0020] According to embodiments of the present invention, the dissolution and regeneration system used in the dissolution and regeneration method includes at least one of the following: an ionic liquid system, an alkaline system (adhesive method), a 4-methylmorpholine-N-oxide (NMMO) system, a dimethylacetamide / lithium chloride (DMAc / LiCl) system, and an alkaline / urea / water system; preferably, an ionic liquid system. Exemplarily, the ionic liquid includes, but is not limited to, one, two, or more of the following substances: 1-allyl-3-methylimidazolium chloride (AmimCl), 1-butyl-3-methylimidazolium chloride (BmimCl), 1-butyl-3-methylimidazolium acetate (BmimAc), dialkylimidazolium acetate (RmimAc), and 1-methyl-3-allylimidazolium carboxylic acid type ([Amim][HCOO]).

[0021] According to an embodiment of the present invention, both the low molecular weight cellulose and the ordinary cellulose are added to the reaction system in solution form. For example, the low molecular weight cellulose and the ordinary cellulose are first dissolved in the above-mentioned dissolution and regeneration system to obtain solutions, and then the two solutions are mixed to obtain a mixed solution.

[0022] According to an embodiment of the present invention, the concentration of the low molecular weight cellulose solution is 10-30%.

[0023] According to an embodiment of the present invention, the low molecular weight cellulose solution is prepared by heating to ensure complete dissolution of the raw materials. For example, the heating temperature is 70–90°C, and the heating time is 0.5–4 hours.

[0024] According to an embodiment of the present invention, the concentration of the ordinary cellulose solution is 2-15%.

[0025] According to an embodiment of the present invention, the ordinary cellulose solution is prepared by heating to completely dissolve the raw materials. For example, the heating temperature is 60–100°C (preferably 70–90°C), and the heating time is 2–5 hours.

[0026] According to an embodiment of the present invention, the method for regulating the crystallinity of regenerated cellulose further includes a step of stirring the mixture.

[0027] According to an embodiment of the present invention, the dissolution and regeneration method can be achieved by spinning or film laying.

[0028] This invention does not impose particular limitations on the conditions and parameters during the spinning or film-laying process; those skilled in the art can select them according to actual needs. For example, in the spinning method, the spinneret diameter is 0.2-2 mm, the air gap height is 3-8 cm, the spinning temperature is 70-100℃, and the pressure is 0.2-2 MPa. As another example, in the film-laying method, the film-laying device used can be an SZQ fabrication apparatus, and the film thickness is 250-1000 μm.

[0029] According to an embodiment of the present invention, the regenerated cellulose prepared by the dissolution and regeneration method can be regenerated cellulose fiber, regenerated cellulose microspheres, or regenerated cellulose membrane.

[0030] According to an embodiment of the present invention, the method for controlling the crystallinity of regenerated cellulose further includes a step of washing the regenerated cellulose. For example, the reaction product is washed with a solvent capable of dissolving the dissolution-regeneration system. Preferably, the dissolution-regeneration system is washed away in an aqueous coagulation bath to obtain regenerated cellulose gel fibers.

[0031] According to an embodiment of the present invention, the method for controlling the crystallinity of regenerated cellulose further includes drying the regenerated cellulose gel fibers. For example, the drying temperature is 50-90°C. Further, the drying time is 0.5-4 hours.

[0032] According to an embodiment of the present invention, the method for regulating the crystallinity of regenerated cellulose includes the following steps:

[0033] Step 1: Preparation of low molecular weight cellulose: Mix 100-400 mL of concentrated phosphoric acid and 5-20 mL of water, add 10-40 g of dried ordinary cellulose to the mixture, heat to 10-50℃, and degrade for 2-14 days. Pour the mixture into water, add 6-10 wt% sodium bicarbonate solution to neutralize excess acid, wash with water and dry into powder. Put the powder into 300-500 mL of dimethyl sulfoxide and stir at 60-100℃ for 2-6 h. After washing with water and drying, low molecular weight cellulose with a degree of polymerization (DP) of 10-60 is obtained.

[0034] Step 2: Preparation of ordinary cellulose solution: Take 10-15g of ordinary cellulose and mix it with 100-500mL of ionic liquid, then vacuum the mixture and dissolve it at 70-90℃ for 2-5h to obtain a 2-15% ordinary cellulose solution.

[0035] Step 3: Mix 2-3g of low molecular weight cellulose with 10-20mL of ionic liquid and dissolve at 70-90℃ for 0.5-2h to obtain a 10-30% low molecular weight cellulose solution.

[0036] Step 4: Stir and mix the low molecular weight cellulose solution and the ordinary cellulose solution until they are homogeneous, controlling the low molecular weight cellulose to account for 0.5 to 20 wt% of the total mass of cellulose in the mixed solution (the sum of the masses of low molecular weight cellulose and ordinary cellulose).

[0037] Step 5: The obtained composite cellulose solution is deposited on a glass plate (the depositor used is an SZQ depositor, and the deposit thickness is controlled between 250-1000 μm). Then, the ionic liquid is washed away in a water coagulation bath to obtain a regenerated cellulose gel membrane. The gel membrane is then dried into a dry membrane.

[0038] According to an embodiment of the present invention, the method for regulating the crystallinity of regenerated cellulose includes the following steps:

[0039] Step 1: Preparation of low molecular weight cellulose: Mix 100-300 mL of ionic liquid, 3-20 g of water, 3-15 g of ordinary cellulose, and 3-15 g of solid acid catalyst, and degrade at 50-120 °C for 0.5-2 h. Stop stirring and let stand to precipitate the solid acid catalyst. Then, pour the supernatant into water to wash, filter and dry to obtain powder. Put the powder into 300-500 mL of dimethyl sulfoxide and stir at 60-100 °C for 2-6 h. Then wash with water and dry to obtain low molecular weight cellulose with a degree of polymerization (DP) of 15-50.

[0040] Step 2: Preparation of ordinary cellulose solution: Take 10-15g of ordinary cellulose into 100-500mL of ionic liquid, stir evenly, then vacuum, and dissolve at 60-100℃ for 2-5h to obtain a 2-15% ordinary cellulose solution.

[0041] Step 3: Mix 2-3g of low molecular weight cellulose with 10-20mL of ionic liquid and dissolve at 70-90℃ for 0.5-2h to obtain a 10-30% low molecular weight cellulose solution.

[0042] Step 4: Stir and mix the low molecular weight cellulose solution and the ordinary cellulose solution until they are homogeneous, controlling the low molecular weight cellulose to account for 0.5 to 20 wt% of the total mass of cellulose in the mixed solution (the sum of the masses of low molecular weight cellulose and ordinary cellulose).

[0043] Step 5: The obtained composite cellulose solution is spun in a pneumatic spinning machine at a temperature of 70-100℃ and a pressure of 0.2-2MPa, with a spinneret diameter of 0.2-2mm and an air gap height of 3-8cm to obtain regenerated cellulose fibers. Then, the ionic liquid is washed away in a water coagulation bath to obtain regenerated cellulose gel fibers, which are then dried into dry filaments.

[0044] The present invention also provides regenerated cellulose prepared by the above method.

[0045] According to an embodiment of the present invention, the raw materials for preparing the regenerated cellulose include low molecular weight cellulose and ordinary cellulose.

[0046] According to an embodiment of the present invention, the crystallinity of the regenerated cellulose is 10-50%, for example 19.5%, 20%, 24.2%, 26%, 27.9%, 30%, and 40%.

[0047] According to an embodiment of the present invention, the percentage of low molecular weight cellulose in the total mass of low molecular weight cellulose and ordinary cellulose is 0.5-20%, preferably 1-20%.

[0048] According to an embodiment of the present invention, the regenerated cellulose may be regenerated cellulose fiber, regenerated cellulose microspheres, or regenerated cellulose membrane.

[0049] The beneficial effects of this invention:

[0050] (1) Based on the excellent characteristics of low molecular weight cellulose (LMW) being easy to crystallize and having small crystal size, this invention allows for simple and accurate control of the crystallinity and crystal size of regenerated cellulose by adding LMW to a regular cellulose solution and adjusting its degree of polymerization and proportion. For example, adding LMW with a degree of polymerization (DP) of 25 to a cotton pulp cellulose solution obtained by dissolving it in AmimCl, and controlling the LMW content to 5% of the total cellulose, results in a significant difference in the crystallinity and crystal size of the regenerated cellulose material. The crystallinity of pure cotton pulp regenerated cellulose is 13%, with a crystal size of 1.9 nm in the 1-10 crystal plane direction. However, after adding 5% LMW with a DP of 25, the crystallinity increases to 26%, with a corresponding crystal size of 4.1 nm. This invention provides a simple and accurate control of the crystallinity and crystal size of regenerated cellulose, which is of great significance for improving the strength and toughness of regenerated cellulose materials and has broad prospects in the market for regenerated cellulose materials.

[0051] (2) The present invention significantly increases the crystallinity of regenerated cellulose by compounding low molecular weight cellulose in ordinary cellulose solution, which is of great significance for improving the modulus and strength of regenerated cellulose materials.

[0052] (3) The present invention obtains regenerated cellulose with smaller crystal size by compounding low molecular weight cellulose in ordinary cellulose solution, which is of great significance for improving the toughness of regenerated cellulose materials. Attached Figure Description

[0053] Figure 1 This is a gel permeation chromatogram of low molecular weight cellulose formed after the degradation of microcrystalline cellulose in Example 1.

[0054] Figure 2 The image shows the X-ray diffraction pattern of the regenerated cellulose dry film prepared in Example 1.

[0055] Figure 3 The regenerated cellulose gel fibers prepared in Example 2 13 C CP / MAS solid-state NMR spectrum.

[0056] Figure 4 The dried filaments prepared in Example 2 13 C CP / MAS solid-state NMR spectrum. Detailed Implementation

[0057] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0058] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0059] Example 1

[0060] The method for regulating the crystallinity of regenerated cellulose includes the following steps:

[0061] Step 1: Preparation of low molecular weight cellulose: Take 250 mL of concentrated phosphoric acid and 10 mL of water into a three-necked flask, slowly add 25 g of vacuum-dried microcrystalline cellulose (MCC) into the three-necked flask, place the three-necked flask in a 30 °C oil bath, and slowly degrade for 9 days. Pour the mixture into water, add 8 wt% sodium bicarbonate solution to neutralize excess acid, wash repeatedly with deionized water 6 times, and then air dry into powder. Put the powder into 400 mL of dimethyl sulfoxide and stir at 90 °C for 3 h. Wash repeatedly with deionized water 3-6 times, and dry in a vacuum oven at 60 °C for 12 h to obtain low molecular weight cellulose with a degree of polymerization (DP) of 25 and a molecular weight distribution of 1.5.

[0062] Step 2: Preparation of cellulose solution: Take 10g of cotton pulp into 190mL of 1-allyl-3-methylimidazolium chloride (AmimCl), stir evenly, put it into a two-way kneader, vacuum, set the dissolution temperature to 80℃, and take it out after dissolving for 4 hours to obtain a cellulose solution of about 5%.

[0063] Step 3: Place 2.37g of the low molecular weight cellulose (DP25) obtained in Step 1 into a three-necked flask and mix well. Dissolve at 80℃ for 2h to obtain a 19% low molecular weight cellulose solution.

[0064] Step 4: Stir and mix the low molecular weight cellulose solution and the cotton pulp cellulose solution evenly, controlling the low molecular weight cellulose to account for 3wt% and 5wt% of the total mass of cellulose in the mixed solution (the sum of the mass of low molecular weight cellulose and cotton pulp cellulose), respectively.

[0065] Step 5: The two composite cellulose solutions obtained in Step 4 are respectively laid on glass plates. The film laying device used is an SZQ preparation device. The film thickness is controlled at 750μm. The ionic liquid is washed away in a water coagulation bath to obtain a regenerated cellulose gel membrane. The gel filaments are then naturally dried into a dry film.

[0066] Figure 1 This is a gel permeation chromatogram of low molecular weight cellulose (LMC) formed after the degradation of microcrystalline cellulose. It was used to measure the molecular weight and molecular weight distribution of LMC. Calculations show that the degree of polymerization (DP) of LMC is 25, and its molecular weight distribution is 1.5.

[0067] The dry films prepared in this embodiment were subjected to X-ray diffraction tests to calculate the crystallinity and crystal size of the regenerated cellulose filaments. The results are as follows: Figure 2 As shown, the crystallinity was calculated using the peak area fitting method. The crystallinity of regenerated cellulose made from pure cotton pulp was 13%, and the crystal size in the 1-10 crystal plane direction was 1.9 nm. The crystallinity of regenerated cellulose made from cotton pulp and 3 wt% low molecular weight cellulose (DP25) was 20%, and the crystal size in the 1-10 crystal plane direction was 3.2 nm. The crystallinity of regenerated cellulose made from cotton pulp and 5 wt% low molecular weight cellulose (DP25) was 26%, and the crystal size in the 1-10 crystal plane direction was 4.1 nm.

[0068] Example 2

[0069] The method for regulating the crystallinity of regenerated cellulose includes the following steps:

[0070] Step 1: Preparation of low molecular weight cellulose: Take 200 mL of 1-butyl-3-methylimidazolium chloride (BmimCl), 4 g of water, 10 g of microcrystalline cellulose (MCC), and 4 g of Amberlyst 15 solid acid catalyst in a three-necked flask. Set the oil bath temperature to 80 °C and degrade for 60 min. Stop stirring and let stand for 10 min to allow the Amberlyst 15 solid acid catalyst to precipitate to the bottom of the flask. Then wash the supernatant repeatedly with deionized water 6 times, filter and air dry to obtain powder. Put the powder into 400 mL of dimethyl sulfoxide and stir at 90 °C for 3 h. After washing with water and drying, a low molecular weight cellulose with a degree of polymerization (DP) of 15 and a molecular weight distribution of 1.4 is obtained.

[0071] Step 2: Preparation of cellulose solution: Take 10g of wood pulp into 190mL of BmimCl, stir evenly, put it into a two-way kneader, vacuum, set the dissolution temperature to 80℃, dissolve for 4 hours, and then take it out to obtain a cellulose solution of about 5%.

[0072] Step 3: Mix 2.37g of the low molecular weight cellulose obtained in Step 1 with 10mL of BmimCl in a three-necked flask and dissolve at 80℃ for 2h to obtain a 19% low molecular weight cellulose solution.

[0073] Step 4: Stir and mix the low molecular weight cellulose solution and the wood pulp cellulose solution evenly, controlling the low molecular weight cellulose to account for 1 wt% and 3 wt% of the total mass of cellulose in the mixed solution (the sum of the mass of low molecular weight cellulose and cotton pulp cellulose), respectively.

[0074] Step 5: Spin the two composite cellulose solutions obtained in Step 4 into small pneumatic spinning machines at a temperature of 90℃ and a pressure of 2MPa. The spinneret diameter is 0.2mm and the air gap height is 5cm. Wash away the ionic liquid in a water coagulation bath to obtain regenerated cellulose gel filaments. Dry the gel filaments into dry filaments.

[0075] The regenerated cellulose gel fibers prepared in this embodiment were subjected to solid-state NMR spectroscopy to calculate the crystallinity and crystal size of the regenerated cellulose fibers. 13 CCP / MAS solid-state NMR spectrum as shown Figure 3 As shown, the crystallinity was calculated using the peak area fitting method. The crystallinity of regenerated cellulose made from pure cotton pulp was 19.5%, the crystallinity of regenerated cellulose made from cotton pulp and 1 wt% low molecular weight cellulose (DP15) was 24.2%, and the crystallinity of regenerated cellulose made from cotton pulp and 3 wt% low molecular weight cellulose (DP15) was 27.9%.

[0076] The dried filaments prepared in this embodiment were subjected to solid-state NMR testing, and the results are as follows: Figure 4As shown, compared to regenerated cellulose gel filaments, the peaks in the spectrum of dry filaments are blunted, which is due to the reduced mobility of molecular chains in the dried state.

[0077] Example 3

[0078] The method for regulating the crystallinity of regenerated cellulose includes the following steps:

[0079] Step 1: Preparation of low molecular weight cellulose: Take 200 mL of 1-butyl-3-methylimidazolium chloride (BmimCl), 4 g of water, 10 g of microcrystalline cellulose (MCC), and 4 g of Amberlyst 15 solid acid catalyst in a three-necked flask, set the oil bath temperature to 80℃, degrade for 30 min, wash with water and dry to obtain low molecular weight cellulose with a degree of polymerization (DP) of 40 and a molecular weight distribution of 1.7;

[0080] Step 2: Preparation of cellulose solution: Take 10g of cotton pulp into 190mL of BmimCl, stir evenly, put it into a two-way kneader, vacuum, set the dissolution temperature to 80℃, dissolve for 4 hours, and then take it out to obtain a 5% cellulose solution.

[0081] Step 3: Mix 2.37g of low molecular weight cellulose with 10mL of BmimCl in a three-necked flask and dissolve at 80℃ for 2h to obtain a 19% low molecular weight cellulose solution.

[0082] Step 4: Stir and mix the low molecular weight cellulose solution and the wood pulp cellulose solution evenly, controlling the low molecular weight cellulose to account for no more than 5 wt% of the total mass of cellulose in the mixed solution (the sum of the mass of low molecular weight cellulose and cotton pulp cellulose).

[0083] Step 5: Spin the obtained composite cellulose solution in a small pneumatic spinning machine at a temperature of 90℃ and a pressure of 2MPa. The spinneret diameter is 0.2mm and the air gap height is 5cm. Wash away the ionic liquid in a water coagulation bath to obtain regenerated cellulose gel filaments. Dry the gel filaments into dry filaments.

[0084] Example 4

[0085] The method for regulating the crystallinity of regenerated cellulose includes the following steps:

[0086] Step 1: Preparation of low molecular weight cellulose: Take 250 mL of concentrated phosphoric acid and 10 mL of water into a three-necked flask, slowly add 25 g of vacuum-dried microcrystalline cellulose (MCC) into the three-necked flask, place the three-necked flask in a 30 °C oil bath, and slowly degrade for 48 h. Pour the mixture into water, add 8 wt% sodium bicarbonate solution to neutralize excess acid, wash repeatedly with deionized water 6 times, and then air dry into powder. Put the powder into 400 mL of dimethyl sulfoxide and stir at 90 °C for 3 h. Wash repeatedly with deionized water 3-6 times, and dry in a 60 °C vacuum oven for 12 h to obtain low molecular weight cellulose with a degree of polymerization (DP) of about 52 and a molecular weight distribution of 2.1.

[0087] Step 2: Preparation of cellulose solution: Take 10g of wood pulp into 190mL of BmimCl, stir evenly, put it into a two-way kneader, vacuum, set the dissolution temperature to 80℃, dissolve for 4 hours, and then take it out to obtain a 5% cellulose solution.

[0088] Step 3: Mix 2.37g of low molecular weight cellulose with 10mL of BmimCl in a three-necked flask and dissolve at 80℃ for 2h to obtain a 19% low molecular weight cellulose solution.

[0089] Step 4: Stir and mix the low molecular weight cellulose solution and the wood pulp cellulose solution evenly, controlling the low molecular weight cellulose to account for no more than 5 wt% of the total mass of cellulose in the mixed solution (the sum of the mass of low molecular weight cellulose and cotton pulp cellulose).

[0090] Step 5: Spin the obtained composite cellulose solution in a small pneumatic spinning machine at a temperature of 90℃ and a pressure of 2MPa. The spinneret diameter is 0.2mm and the air gap height is 5cm. Wash away the ionic liquid in a water coagulation bath to obtain regenerated cellulose gel filaments. Dry the gel filaments into dry filaments.

[0091] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for regulating the crystallinity of regenerated cellulose, comprising the following steps: adding low molecular weight cellulose to a common cellulose raw material system, and preparing regenerated cellulose by a dissolution and regeneration method, thereby regulating the crystallinity of the regenerated cellulose; The ordinary cellulose is selected from at least one of natural cellulose and degradation products of natural cellulose; The degree of polymerization of the degradation product of the natural cellulose is greater than that of the low molecular weight cellulose; The low molecular weight cellulose has a degree of polymerization of 15-60 and a molecular weight distribution of 1.2-2.

3. The low molecular weight cellulose accounts for 0.5 to 20 wt% of the sum of the mass of low molecular weight cellulose and ordinary cellulose.

2. The method according to claim 1, characterized in that, The low molecular weight cellulose is prepared from ordinary cellulose by at least one of acid degradation or solid acid catalyst preparation methods.

3. The method according to claim 2, characterized in that, The acid used in the acid degradation method is selected from at least one of hydrochloric acid, sulfuric acid, and phosphoric acid.

4. The method according to claim 2, characterized in that, The low molecular weight cellulose is obtained by dissolving ordinary cellulose in an acidic solution and then degrading it by heating. The acid solution is prepared by mixing acid and water in a volume ratio of (100~400):(5~20); The ratio of ordinary cellulose to acid is (10~40) g:(100~400) mL; The heating temperature is 10~50℃, and the degradation time is 2~14 days.

5. The method according to claim 2, characterized in that, The solid acid catalyst is selected from one, two or more of the following substances: cation exchange resin type, immobilized liquid acid and metal salt; The cation exchange resin type is selected from sulfonic acid type cation exchange resin, sulfuric acid type cation exchange resin, and phosphoric acid type cation exchange resin; The supported liquid acid is selected from HF / Al2O3 and BF3 / Al2O3; The metal salt is selected from sulfates or phosphates.

6. The method according to any one of claims 1-5, characterized in that, The method for preparing the low molecular weight cellulose includes the following steps: mixing ordinary cellulose, ionic liquid, water and solid acid catalyst, heating and degrading to obtain the low molecular weight cellulose.

7. The method according to any one of claims 1-5, characterized in that, The natural cellulose is selected from at least one of cotton pulp, wood pulp, seaweed cellulose, and bacterial cellulose; And / or, the degradation products of the natural cellulose are at least one of microcrystalline cellulose (MCC) and degradation products of frozen ball milled cotton pulp.

8. The method according to any one of claims 1-5, characterized in that, The dissolution and regeneration method employs at least one of the following dissolution and regeneration systems: ionic liquid system, alkaline system, 4-methylmorpholine-N-oxide system, dimethylacetamide / lithium chloride system, and alkaline / urea / water system. The ionic liquid includes, but is not limited to, one, two or more of the following substances: 1-allyl-3-methylimidazolium chloride (AmimCl), 1-butyl-3-methylimidazolium chloride (BmimCl), 1-butyl-3-methylimidazolium acetate (BmimAc), dialkylimidazolium acetate (RmimAc), and 1-allyl-3-methylimidazolium carboxylate ([Amim][HCOO]). Both low molecular weight cellulose and ordinary cellulose are added to the reaction system in solution form. First, the low molecular weight cellulose and ordinary cellulose are dissolved in the dissolution and regeneration system to obtain solutions. Then, the low molecular weight cellulose solution and the ordinary cellulose solution are mixed to obtain a mixed solution.

9. The method according to claim 8, characterized in that, The concentration of the low molecular weight cellulose solution is 10-30%; The concentration of the ordinary cellulose solution is 2-15%.

10. The method according to any one of claims 1-5, characterized in that, The dissolution and regeneration method is achieved through spinning or film laying.

11. The method according to claim 10, characterized in that, The regenerated cellulose prepared by the dissolution and regeneration method is regenerated cellulose fiber, regenerated cellulose microspheres, or regenerated cellulose membrane.

12. The method according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Preparation of low molecular weight cellulose: Mix 100-400 mL of concentrated phosphoric acid and 5-20 mL of water, add 10-40 g of dried ordinary cellulose to the mixture, heat to 10-50℃, and degrade for 2-14 days. Pour the mixture into water, add 6-10 wt% sodium bicarbonate solution to neutralize excess acid, wash with water and dry into powder. Put the powder into 300-500 mL of dimethyl sulfoxide and stir at 60-100℃ for 2-6 hours. After washing with water and drying, low molecular weight cellulose with a degree of polymerization of 15-60 is obtained. Step 2: Preparation of ordinary cellulose solution: Take 10-15g of ordinary cellulose and 100-500mL of ionic liquid, stir and mix, then vacuum, and dissolve at 70-90℃ for 2-5h to obtain a 2-15% ordinary cellulose solution; Step 3: Mix 2-3g of low molecular weight cellulose with 10-20mL of ionic liquid and dissolve at 70-90℃ for 0.5-2h to obtain a 10-30% low molecular weight cellulose solution. Step 4: Mix the low molecular weight cellulose solution and the ordinary cellulose solution thoroughly, controlling the low molecular weight cellulose content to be 0.5~20 wt% of the sum of the low molecular weight cellulose and ordinary cellulose in the mixed solution. Step 5: Spread the obtained composite cellulose solution onto a glass plate, then wash away the ionic liquid in a water coagulation bath to obtain a regenerated cellulose gel membrane, and dry the gel membrane into a dry film.

13. The method according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Preparation of low molecular weight cellulose: Mix 100-300 mL of ionic liquid, 3-20 g of water, 3-15 g of ordinary cellulose, and 3-15 g of solid acid catalyst, and degrade at 50-120 °C for 0.5-2 h. Stop stirring and let stand to allow the solid acid catalyst to precipitate. Then, pour the supernatant into water to wash, filter and dry to obtain powder. Put the powder into 300-500 mL of dimethyl sulfoxide and stir at 60-100 °C for 2-6 h. Then wash with water and dry to obtain low molecular weight cellulose with a degree of polymerization of 15-50. Step 2: Preparation of ordinary cellulose solution: Take 10-15g of ordinary cellulose into 100-500mL of ionic liquid, stir evenly, then vacuum, and dissolve at 60-100℃ for 2-5h to obtain a 2-15% ordinary cellulose solution. Step 3: Mix 2-9g of low molecular weight cellulose with 20-30mL of ionic liquid and dissolve at 70-90℃ for 0.5-2h to obtain a 10-30% low molecular weight cellulose solution; Step 4: Mix the low molecular weight cellulose solution and the ordinary cellulose solution thoroughly, controlling the low molecular weight cellulose content to be 0.5~20 wt% of the sum of the low molecular weight cellulose and ordinary cellulose in the mixed solution; Step 5: The obtained composite cellulose solution is spun to obtain regenerated cellulose fibers, and then the ionic liquid is washed away in a water coagulation bath to obtain regenerated cellulose gel fibers. The gel fibers are then dried into dry fibers.

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