A modification process for improving the ductility and flexibility of regenerated cellulose materials

Abstract

The application discloses a modification method for improving the ductility and flexibility of regenerated cellulose material, which comprises the following steps: treating the regenerated cellulose material with a composite solution containing hygroscopic salt and plasticizer to obtain modified regenerated cellulose material. The ductility of the regenerated cellulose material can be significantly improved in a simple and fast way by treating the regenerated cellulose material with the composite solution containing hygroscopic salt and plasticizer under specific conditions (i.e. the regenerated cellulose material is in a gel state) and drying. For example, the elongation rate of the regenerated cellulose material is increased from 18% to 45% after the modification treatment. The application has important significance for improving the ductility and flexibility of the regenerated cellulose material and has a broad prospect in the application field of the regenerated cellulose material.

Description

Technical Field

[0001] This invention belongs to the field of cellulose membrane modification technology, specifically relating to a modification method for improving the extensibility and flexibility of regenerated cellulose materials. Background Technology

[0002] Cellulose materials, such as commonly used fibers and membranes, have inherently low ductility and flexibility, which greatly limits their applications. Significantly improving the ductility of cellulose materials has always been a key focus and challenge in the cellulose field. Furthermore, dry air is a frequent problem in social production and daily life, and cellulose is a material that is quite sensitive to humidity. Low air humidity further reduces the ductility and flexibility of cellulose materials, which also greatly affects their normal use.

[0003] A common industrial method to improve the ductility of cellulose materials is to add plasticizers, such as glycerin. However, this method typically increases the elongation of the cellulose membrane to nearly 30%, without significantly improving the material's flexibility. Therefore, finding a simple process to improve the ductility and flexibility of regenerated cellulose materials is of great significance to the field of cellulose materials. Simultaneously enhancing the resistance of cellulose materials to dry environments could further expand their application range. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a modification method for improving the ductility and flexibility of regenerated cellulose materials, the modification method comprising:

[0005] Modified regenerated cellulose material is obtained by treating regenerated cellulose material with a composite solution containing hygroscopic salt and plasticizer.

[0006] According to an embodiment of the present invention, the composite solution comprises a hygroscopic salt, a plasticizer, and a solvent.

[0007] According to an embodiment of the present invention, the concentration of the hygroscopic salt in the composite solution is 0.1 to 50 wt%, preferably 1 to 20 wt% or 0.1 to 10 wt%, for example 1 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, or 20 wt%.

[0008] According to an embodiment of the present invention, the concentration of plasticizer in the composite solution is 0.1 to 99.9 wt%, preferably 0.1 to 50 wt% or 0.1 to 15 wt%, and even more preferably 1 to 20 wt%, for example 1 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 40 wt%.

[0009] According to embodiments of the present invention, the hygroscopic salt includes, but is not limited to, one, two or more of lithium chloride, calcium chloride, potassium chloride, magnesium chloride, zinc chloride, copper chloride, calcium sulfate, zinc sulfate, magnesium sulfate, lithium sulfate, zinc acetate, etc., preferably lithium chloride and / or calcium chloride.

[0010] According to embodiments of the present invention, the plasticizer includes, but is not limited to, one, two, or more of glycerol, ethylene glycol, propylene glycol, castor oil, polyethylene glycol, silicone oil, diethyl phthalate, dibutyl phthalate, fatty acid esters (e.g., epoxidized soybean oil butyl ester), benzoic acid esters (e.g., dipropylene glycol dibenzoate), and alkyl sulfonates (e.g., alkyl sulfonates), with glycerol being preferred.

[0011] According to embodiments of the present invention, the solvent includes, but is not limited to, one, two, or more of water (e.g., deionized water), ethanol, diethyl ether, glycerol, etc., with water being preferred.

[0012] According to embodiments of the present invention, the regenerated cellulose material can be prepared using techniques known in the art. For example, the regenerated cellulose material refers to a gel material obtained by gelling a cellulose solution in a coagulation bath, or a gel material modified by other treatments. Preferably, the morphology of the regenerated cellulose material includes at least one of gel fibers, gel membranes, aerogels, gel microspheres, etc., and is preferably gel fibers or gel membranes.

[0013] According to an embodiment of the present invention, the cellulose solution comprises a cellulose material and a solvent.

[0014] According to an embodiment of the present invention, the concentration of cellulose material in the cellulose solution is 1 to 40 wt%, preferably 2 to 20 wt%, for example 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%.

[0015] According to an embodiment of the present invention, in the cellulose solution, the mass ratio of cellulose material to solvent is 10-20:100-500, for example, 14g:186g.

[0016] According to an embodiment of the present invention, the method for preparing the cellulose solution includes: mixing cellulose material with a solvent (e.g., stirring and dissolving for 1-5 hours) to obtain the cellulose solution. Preferably, the specific dissolution temperature and vacuum conditions during the stirring and mixing of the cellulose material and the solvent can be selected by those skilled in the art based on the different solvents, and the present invention does not impose specific limitations.

[0017] According to an embodiment of the present invention, the solvent in the cellulose solution includes at least one of an alkaline system (viscose method), an ionic liquid, 4-methylmorpholine-N-oxide (NMMO), a dimethylacetamide / lithium chloride (DMAc / LiCl) system, an alkaline / urea / water system, etc., preferably an ionic liquid.

[0018] According to embodiments of the present invention, 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]).

[0019] According to an embodiment of the present invention, the cellulose material used in the cellulose solution includes at least one of natural cellulose, natural cellulose degradation products, etc.

[0020] Preferably, the natural cellulose can be selected from at least one of wood pulp cellulose, cotton pulp cellulose, seaweed cellulose, bacterial cellulose, etc., with cotton pulp cellulose or wood pulp cellulose being more preferred.

[0021] Preferably, the natural cellulose degradation product can be at least one of microcrystalline cellulose (MCC), degradation products of frozen ball-milled cotton pulp cellulose, and cellulose from plant straw.

[0022] According to an embodiment of the present invention, the coagulation bath includes, but is not limited to, one, two, or more solvent systems such as water, ethanol, methanol, acetone, DMSO, DMF, and water / ionic liquid, with water being preferred.

[0023] According to an embodiment of the present invention, the processing steps in the method specifically include: contacting and / or soaking the regenerated cellulose material with a composite solution including hygroscopic salts and plasticizers, followed by washing.

[0024] Preferably, the temperature of the treatment is -50 to 80°C, for example -20°C, 0°C, 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, etc.

[0025] Preferably, the processing time is 1 to 30 minutes, for example, 5 minutes, 10 minutes, or 20 minutes.

[0026] According to an embodiment of the present invention, the modification method further includes drying the product. Specifically, the drying is carried out at a temperature of 30–200°C.

[0027] According to an embodiment of the present invention, the modification method specifically includes the following steps:

[0028] 1) Prepare a composite solution including hygroscopic salt and plasticizer;

[0029] 2) Treatment of regenerated cellulose material: Immerse the regenerated cellulose material in the composite solution at 10-50℃ for 1-30 minutes, then wash it;

[0030] 3) Post-processing: The regenerated cellulose material treated with the modified solution in step 2) is dried to obtain the modified regenerated cellulose material.

[0031] According to an exemplary embodiment of the present invention, the modification method for improving the ductility and flexibility of regenerated cellulose materials specifically includes the following steps:

[0032] 1') Preparation of a composite solution including hygroscopic salt and plasticizer: Take 0.1-100g of calcium chloride and 0.1-200g of glycerol in 100-200g of deionized water, stir evenly at 0-40℃, and after dissolution, obtain a composite solution of calcium chloride and glycerol with mass fractions of 0.1-10wt% and 0.1-15wt%, respectively;

[0033] 2') Modification treatment of hydrogel fibers: Immerse hydrogel fibers in the composite solution in step 1') for 1-30 min at 10-50℃.

[0034] 3') Drying treatment: The modified hydrogel fiber in step 2') is dried at 30-200℃ to obtain the modified hydrogel fiber.

[0035] Preferably, in step 2'), the hydrogel fiber refers to a cellulose solution obtained by dissolving cotton pulp cellulose with BmimCl ionic liquid, the concentration of the cellulose solution being 1-30%, and then spinning it using water as a coagulation bath through a dry-jet wet spinning process.

[0036] According to an exemplary embodiment of the present invention, the modification method for improving the ductility and flexibility of regenerated cellulose materials specifically includes the following steps:

[0037] 1”) Preparation of a composite solution of hygroscopic salt and plasticizer: Take 0.1-100g of lithium chloride and 0.1-200g of glycerol in 100-200g of deionized water, stir evenly at 0-40℃, and after dissolution, obtain a composite solution of lithium chloride and glycerol with mass fractions of 0.1-10wt% and 0.1-15wt%, respectively.

[0038] 2”) Modification treatment of cellulose hydrogel membrane: Immerse the cellulose hydrogel membrane in the composite solution in step 1”) for 1-30 min at 5-80℃.

[0039] 3”) Drying treatment: The modified cellulose hydrogel membrane in step 2”) is dried at 20-100℃ to obtain the modified cellulose hydrogel membrane;

[0040] Preferably, in step 2), the cellulose hydrogel membrane refers to a cellulose solution obtained by dissolving wood pulp cellulose with AmimCl ionic liquid, the concentration of the cellulose solution being 2-40 wt%, and the cellulose solution being prepared using a solution film-forming process and water as a coagulation bath.

[0041] According to an exemplary embodiment of the present invention, the method for improving the ductility and flexibility of regenerated cellulose materials includes the following steps:

[0042] 1”') Preparation of a composite solution of hygroscopic salt and plasticizer: Take 1-80g of calcium chloride and 1-100g of glycerol in 100-200g of deionized water, stir evenly at 10-60℃, dissolve and take out to obtain a composite solution with calcium chloride concentration of 1-40wt% and glycerol concentration of 1-50wt%.

[0043] 2”') Modification treatment of cellulose hydrogel membrane: Under the conditions of 5-80℃, the cellulose hydrogel membrane is immersed in the composite solution in step 1”') for 1-30 min to obtain the modified cellulose hydrogel membrane;

[0044] 3”') Drying treatment: The modified cellulose hydrogel membrane in step 2”') is dried at 30-200℃ to obtain the modified cellulose hydrogel membrane.

[0045] Preferably, in step 2”’), the cellulose hydrogel membrane refers to a cellulose solution with a concentration of 1-30% obtained by dissolving wood pulp cellulose in an NMMO / water system, gelling it using a film-laying process and water as a coagulation bath, and then washing it clean.

[0046] The present invention also provides a modified regenerated cellulose material, which is obtained by the above-described modification method; the elongation of the modified regenerated cellulose material is 1-200%.

[0047] According to an embodiment of the present invention, the elongation is preferably 20-200%, for example 20%, 40%, 60%, 80%, 100%, 120%, 160%, or 200%.

[0048] According to an embodiment of the present invention, the elongation of the modified regenerated cellulose material is increased by at least 80%, for example, at least 100%, or at least 150%, or even up to 310%, compared to the elongation of the regenerated cellulose material.

[0049] According to an embodiment of the present invention, the softness value of the modified regenerated cellulose material is reduced by more than 20% compared with that of the regenerated cellulose material.

[0050] The beneficial effects of this invention are:

[0051] (1) This invention significantly and quickly improves the ductility of regenerated cellulose materials by treating them with a composite solution containing hygroscopic salts and plasticizers under specific conditions (referring to the gel state of the regenerated cellulose material) and then drying them. For example, after the modification treatment of this invention, the elongation of the regenerated cellulose material increases from the initial 18% to 45%. This invention is of great significance for improving the ductility and flexibility of regenerated cellulose materials and has broad prospects in the application field of regenerated cellulose materials.

[0052] (2) The present invention can significantly improve the flexibility of regenerated cellulose materials in a very simple and quick manner, and the softness value can be reduced by more than 20%. Moreover, the present invention cannot significantly improve the flexibility of cellulose materials by adding only hygroscopic salt or plasticizer. Only the combined effect of both can achieve this effect.

[0053] (3) This invention is applicable to gel materials prepared by direct dissolution processing of cellulose. The processing method is convenient and fast, can be well integrated into industrial production processes, and is easy to promote.

[0054] (4) The present invention can also improve the water absorption of cellulose materials and enhance their tolerance and performance in dry environments. Attached Figure Description

[0055] Figure 1 The mechanical spectra of the regenerated cellulose fibers before and after modification (i.e., Preparation Example 3 and Example 3, respectively);

[0056] Figure 2 The mechanical spectra of the regenerated cellulose membrane before and after modification (i.e., preparation example 3, example 2 and example 3, respectively);

[0057] Figure 3 The images show the water content spectra of the regenerated cellulose membrane before and after modification (i.e., Preparation Example 3, Example 2, and Example 3, respectively). Detailed Implementation

[0058] 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.

[0059] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0060] In the following examples, the ionic liquids AmimCl and BmimCl were both purchased from Qingdao Aolike New Material Technology Co., Ltd.

[0061] The cellulose gel membranes used in the following examples are from Shandong Henglian Group (Shandong Henglian Transparent Roll Cellophane - Gel Membrane Material Taken Out During Production Process), which uses AmimCl ionic liquid as the dissolution system in its cellophane production line.

[0062] Preparation Example 1

[0063] Preparation of BmimCl ionic liquid cellulose solution: Take 10g of wood pulp (i.e., wood pulp cellulose) into 190mL of BmimCl, stir evenly, put it into a two-dimensional kneader, vacuum, set the dissolution temperature to 80℃, dissolve for 4h, and then take it out to obtain a cellulose solution with a cellulose concentration of 5%.

[0064] Spinning was performed in a small pneumatic spinning machine at a temperature of 90℃ and a pressure of 2MPa. The spinneret diameter was 0.2mm and the air gap height was 5cm. The ionic liquid was washed away in a water coagulation bath to obtain high-stretch hydrogel fibers for later use.

[0065] Preparation Example 2

[0066] The high-stretch hydrogel fiber obtained in Preparation Example 1 was dried to obtain high-stretch dry fiber for later use.

[0067] Preparation Example 3

[0068] The cellulose gel membrane from Shandong Henglian Company was dried to obtain a dry cellulose membrane for later use.

[0069] Example 1

[0070] The method for treating regenerated cellulose materials with modified solutions specifically includes the following steps:

[0071] Step 1: Preparation of calcium chloride and glycerol composite aqueous solution: Take 2g of calcium chloride, 2g of glycerol and 96g of deionized water, mix them at 25℃ and stir with a magnetic stirrer to dissolve them, to obtain a composite aqueous solution with a mass fraction of 2wt% for both calcium chloride and glycerol;

[0072] Step 2: Cellulose material modification solution treatment: The high-stretch hydrogel fiber obtained in Preparation Example 1 was selected and soaked in the composite aqueous solution obtained in Step 1 for 10 min at 25°C to obtain the treated regenerated cellulose fiber.

[0073] Step 3: Drying the regenerated cellulose fibers: The treated regenerated cellulose fibers obtained in Step 2 are dried at 60°C to obtain modified regenerated cellulose fibers with an elongation of 12%, which is an improvement compared to the dry fibers of Preparation Example 2 (elongation of 9%). The extensibility of the regenerated cellulose fibers treated with the modified solution in this embodiment is improved.

[0074] Example 2

[0075] The method for treating regenerated cellulose materials with modified solutions specifically includes the following steps:

[0076] Step 1: Preparation of lithium chloride and glycerol composite aqueous solution: Take 2g of lithium chloride, 2g of glycerol and 96g of deionized water, mix them at 25℃ and stir with a magnetic stirrer to dissolve them, to obtain an aqueous solution with a mass fraction of 2wt% for both lithium chloride and glycerol;

[0077] Step 2: Cellulose material modification solution treatment: Select cellulose gel membrane from Shandong Henglian Company, and soak it in the modified aqueous solution from Step 1 for 30 minutes at 25℃ to obtain the treated regenerated cellulose gel membrane.

[0078] Step 3: Drying the regenerated cellulose gel membrane after drying: The regenerated cellulose gel membrane obtained in step 2 is dried at 60°C to obtain the modified regenerated cellulose dry membrane, whose elongation is increased from 18% in the unmodified regenerated cellulose dry membrane (preparation example 3) to 45%.

[0079] Example 3

[0080] The difference between Example 3 and Example 2 is as follows:

[0081] In step one, a composite aqueous solution with a mass fraction of 2% for both calcium chloride and glycerol is prepared.

[0082] The remaining steps and conditions are the same as in Example 2, and the modified cellulose membrane material (dry membrane) is prepared.

[0083] The mechanical properties of the modified cellulose membrane material (dry membrane) water bath gel membrane prepared after treatment with modified solutions of different hygroscopic salts are listed in Table 1.

[0084] Preparation of the cellulose dry film in Example 3 (i.e. Figure 1 The mechanical diagrams of the original cellulose membrane material (dry film) and the modified cellulose membrane material (dry film) in Example 3 are shown below. Figure 1 As shown.

[0085] Preparation of the cellulose dry film in Example 3 (i.e. Figure 2 The mechanical properties of the modified cellulose membrane materials (dry films) in Examples 1 and 2 and 3 are shown in Table 1 below.

[0086] In Table 1, the longitudinal or transverse softness was measured using the YN-RRY1000 microcomputer softness tester or the ZY-RRD1000 film softness tester.

[0087] Table 1

[0088]

[0089] Example 4

[0090] The method for treating regenerated cellulose materials with modified solutions specifically includes the following steps:

[0091] Step 1: Preparation of lithium chloride and glycerol composite ethanol solution: Take 3g of lithium chloride, 3g of glycerol and 94g of ethanol, mix and dissolve them with magnetic stirring at 25℃ to obtain an ethanol solution with a mass fraction of 3wt% for both lithium chloride and glycerol.

[0092] Step 2: Cellulose material modification solution treatment: Select cellulose gel membrane from Shandong Henglian Company. Under the condition of 25℃, first wash and soak it repeatedly with the modified ethanol solution in Step 1, and then soak it in a new composite modified ethanol solution for 30 minutes to obtain the treated regenerated cellulose gel membrane.

[0093] Step 3: Drying the regenerated cellulose gel membrane after drying: The regenerated cellulose gel membrane obtained in step 2 is dried at 60°C to obtain the modified regenerated cellulose dry membrane, whose elongation is increased from 18% in the unmodified regenerated cellulose dry membrane (preparation example 3) to 61%.

[0094] Example 5

[0095] The difference between Example 5 and Example 2 is that magnesium chloride is used instead of lithium chloride.

[0096] Comparative Example 1

[0097] The difference between Comparative Example 1 and Example 2 is that no hygroscopic salt was added.

[0098] Comparative Example 2

[0099] The difference between Comparative Example 2 and Example 2 is that glycerol was not added.

[0100] Comparative Example 3

[0101] The difference between Comparative Example 3 and Example 3 is that glycerol was not added.

[0102] Comparative Example 4

[0103] The difference between Comparative Example 4 and Example 5 is that glycerol was not added.

[0104] Table 2 Summary of the softness of regenerated cellulose membrane before and after modification

[0105]

[0106] Figure 2 The mechanical spectra of the regenerated cellulose membrane before and after modification are shown; Sample 1 represents Preparation Example 3, Sample 2 represents Example 3, and Sample 3 represents Example 2.

[0107] Figure 3 The images show the water content spectra of the regenerated cellulose membrane before and after modification. Sample 1 represents Preparation Example 3, Sample 2 represents Example 3, and Sample 3 represents Example 2.

[0108] Table 3 shows the method for testing moisture content:

[0109] At 25℃ and 50% humidity, nitrogen TGA is heated to 180℃ and kept constant for half an hour to completely evaporate the water. The water content after water loss is then observed.

[0110] Table 3

[0111] Moisture content Preparation Example 3 9.8％ Example 3 16.33％ Example 2 20.9％

[0112] The embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modification method for improving the ductility and flexibility of regenerated cellulose materials, characterized in that, The modification method includes: Modified regenerated cellulose material is obtained by treating regenerated cellulose material with a composite solution containing hygroscopic salt and plasticizer.

2. The method according to claim 1, characterized in that, The composite solution comprises a hygroscopic salt, a plasticizer, and a solvent, wherein the concentration of the hygroscopic salt is 0.1–50 wt%, and the concentration of the plasticizer is 0.1–99.9 wt%.

3. The method according to claim 1, characterized in that, The hygroscopic salts include, but are not limited to, one, two, or more of lithium chloride, calcium chloride, potassium chloride, magnesium chloride, zinc chloride, copper chloride, calcium sulfate, zinc sulfate, magnesium sulfate, lithium sulfate, and zinc acetate. Preferably, the plasticizer is selected from one, two or more of the following: glycerol, ethylene glycol, propylene glycol, castor oil, polyethylene glycol, silicone oil, diethyl phthalate, dibutyl phthalate, fatty acid esters, polyphenolic esters, alkyl sulfonates, etc.

4. The method according to claim 2, characterized in that, The solvent is selected from one, two or more of water, ethanol, diethyl ether, and glycerol.

5. The method according to claim 1, characterized in that, The regenerated cellulose material can be prepared using techniques known in the art. For example, the regenerated cellulose material refers to a gel material obtained by gelling a cellulose solution in a coagulation bath, or a gel material modified by other treatments.

6. The method according to claim 1, characterized in that, The regenerated cellulose material includes at least one of the following forms: gel fiber, gel membrane, aerogel, gel microsphere, etc.

7. The method according to claim 1, characterized in that, The processing temperature is -50 to 80°C.

8. The method according to claim 1, characterized in that, The processing time is 1 to 30 minutes.

9. A modified regenerated cellulose material, said modified regenerated cellulose material being prepared by the modification method according to any one of claims 1-8.

10. The material according to claim 9, characterized in that, The elongation of the modified regenerated cellulose material is 1-200%, preferably 20-200%.

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