High-strength and high-toughness regenerated cellulose membrane and preparation method thereof

Abstract

The invention discloses a high-strength and high-toughness regenerated cellulose membrane and a preparation method thereof, and the high-strength and high-toughness regenerated cellulose membrane is prepared by controlling coagulating bath conditions and adjusting drying conditions based on a green solvent system. The hydrogel is replaced by the organic solvent (such as ethanol), and then is blow-dried by the wet hot air (dried by the drying oven), so that the elongation at break of the obtained regenerated cellulose membrane is remarkably improved, and the regenerated cellulose membrane has better strength and modulus.

Description

Technical Field

[0001] The invention belongs to the field of material preparation, and specifically relates to a high-strength and high-toughness regenerated cellulose film and a preparation method thereof. Background Art

[0002] Cellulose, as the world's most abundant natural polymer material, has received extensive attention. However, cellulose does not melt and is difficult to dissolve in common solvents, and its processing performance is poor. In recent years, a variety of green solvent systems for cellulose have been developed, such as ionic liquids, NMMO, and alkaline urea systems. These green solvents directly dissolve cellulose to form solutions, which are converted into cellulose gels in a coagulation bath. The gels are further dried to prepare different regenerated cellulose materials such as films and fibers.

[0003] With the development of green solvent systems, regulating the mechanical properties of cellulose materials has become an important research direction. For example, for cellulose films, improving their elongation at break is an important basis for their wide application. Currently, the main strategy to improve the elongation at break of cellulose films is to increase the content of plasticizers. Although this strategy can significantly increase the elongation at break, the tensile strength and modulus of the film will decrease significantly. Therefore, it is a challenge to develop high-strength and high-toughness cellulose films. Summary of the invention

[0004] In order to improve the above technical problems, the present invention provides a high-strength and high-toughness regenerated cellulose film and a preparation method thereof. Based on a green solvent system, a high-strength and high-toughness cellulose film is prepared by controlling the coagulation bath conditions and adjusting the drying conditions.

[0005] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0006] A method for preparing a regenerated cellulose film comprises laying a cellulose solution into a film, and drying the film after a coagulation bath reaction to obtain the regenerated cellulose film.

[0007] According to an embodiment of the present invention, the solvent system of the cellulose solution includes at least one of an ionic liquid system, an alkali system (viscose method), a 4-methylmorpholine-N-oxide (NMMO) system, a dimethylacetamide / lithium chloride (DMAc / LiCl) system, an alkali / urea / water system, etc.; 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, dialkyl imidazole acetate (RmimAc), 1-methyl-3-allylimidazole formic acid type ([Amim][HCOO]).

[0008] According to an embodiment of the present invention, the solvent used in the coagulation bath reaction may be alcohol or water.

[0009] According to an embodiment of the present invention, when the solvent used in the coagulation bath reaction is water, it is necessary to further use an alcohol solvent for replacement.

[0010] Preferably, the alcohol includes at least one of methanol, ethanol, propanol, etc.;

[0011] According to an embodiment of the present invention, the drying temperature is room temperature to 80°C, for example 30 to 75°C, 40 to 70°C; exemplary are 25°C, 30°C, 40°C, 60°C, 70°C, 75°C, 80°C.

[0012] According to an embodiment of the present invention, the drying humidity is 5-80%, such as 10-60%; exemplary are 5%, 10%, 20%, 30%, 40%, 60%, 80%.

[0013] According to an embodiment of the present invention, the cellulose raw material includes at least one of microcrystalline cellulose (MCC), cotton pulp, wood pulp, and the like.

[0014] According to an embodiment of the present invention, the concentration of the cellulose solution is 2-20%, such as 3-15%, 4-16%.

[0015] According to an embodiment of the present invention, the method for preparing the regenerated cellulose film comprises the following steps:

[0016] Scenario 1:

[0017] Step 1: preparing a cellulose solution: taking 3-30 g of cotton pulp and dissolving it in 100-200 g of 1-allyl-3-methylimidazolium chloride (AmimCl), stirring it evenly and then evacuating it, setting the dissolving temperature to 70-90° C., dissolving it for 1-4 hours and then taking it out to obtain a 3-15% (w / w) cellulose solution;

[0018] Step 2: preparing cellulose ethanol gel membrane: spreading the obtained cellulose solution into a membrane, washing away the ionic liquid in an ethanol coagulation bath, and obtaining a regenerated cellulose ethanol gel membrane;

[0019] Step 3: Preparation of regenerated cellulose film with high mechanical properties: Dry the cellulose ethanol gel film at 30-80° C. and 10-60% humidity to obtain a cellulose film material with high mechanical properties.

[0020] Scenario 2:

[0021] Step 1: preparing a cellulose solution: taking 3-30 g of cotton pulp and dissolving it in 100-200 g of 1-allyl-3-methylimidazolium chloride (AmimCl), stirring it evenly and then evacuating it, setting the dissolving temperature to 70-90° C., dissolving it for 1-4 hours and then taking it out to obtain a 3-15% (w / w) cellulose solution;

[0022] Step 2: preparing a cellulose hydrogel membrane: laying a membrane with the obtained cellulose solution, washing away the ionic liquid in a water coagulation bath, and obtaining a regenerated cellulose hydrogel membrane;

[0023] Step 3: preparing cellulose ethanol gel membrane: replacing the cellulose hydrogel membrane with anhydrous ethanol to obtain a regenerated cellulose ethanol gel membrane;

[0024] Step 4: Preparation of regenerated cellulose film with high mechanical properties: Dry the cellulose ethanol gel film at 30-80° C. and 10-60% humidity to obtain a cellulose film material with high mechanical properties.

[0025] Solution 3:

[0026] Step 1: preparing a cellulose solution: taking 3-30 g of cotton pulp and dissolving it in 100-200 g of 1-allyl-3-methylimidazolium chloride (AmimCl), stirring it evenly and then evacuating it, setting the dissolving temperature to 70-90° C., dissolving it for 1-4 hours and then taking it out to obtain a 3-15% (w / w) cellulose solution;

[0027] Step 2: preparing a cellulose hydrogel membrane: laying a membrane with the obtained cellulose solution, washing away the ionic liquid in a water coagulation bath, and obtaining a regenerated cellulose hydrogel membrane;

[0028] Step 3: Preparation of regenerated cellulose membrane with high mechanical properties: Drying the cellulose hydrogel membrane at 30-80° C. and 10-60% humidity to obtain a cellulose membrane material with high mechanical properties.

[0029] The present invention also provides a regenerated cellulose film prepared by the method.

[0030] According to an embodiment of the present invention, the thickness of the regenerated cellulose film is 20-40 μm, exemplified by 20 μm, 30 μm, and 40 μm.

[0031] According to an embodiment of the present invention, the elongation at break of the regenerated cellulose film is 20-45%, exemplified by 20.5%, 26%, 30%, 35%, 40%, and 45%.

[0032] According to an embodiment of the present invention, the strength of the regenerated cellulose film is 120-145 MPa, exemplified by 120 MPa, 130 MPa, 132 MPa, 135 MPa, 140 MPa, and 143 MPa.

[0033] According to an embodiment of the present invention, the elastic modulus of the regenerated cellulose film is 3000-5500 MPa, exemplified by 3000 MPa, 3500 MPa, 4000 MPa, 4500 MPa, 4700 MPa, 5000 MPa, 5200 MPa, and 5500 MPa.

[0034] Beneficial effects of the present invention:

[0035] (1) The present invention can obtain a high-strength and high-toughness regenerated cellulose film by drying cellulose gel (including hydrogel, alcohol gel, etc.) with moist hot air. The elongation at break of the regenerated cellulose film of the present invention is significantly improved, and the film has good strength and modulus.

[0036] (2) The present invention adjusts the coagulation conditions of the cellulose solution in the coagulation bath, and obtains a relatively dense hydrogel skeleton at a relatively low temperature (eg, room temperature) in the membrane solution and the coagulation bath, and has better mechanical properties after drying.

[0037] (3) The present invention replaces the hydrogel with an organic solvent (such as ethanol) and then blows it dry with moist hot air, which can further significantly improve the elongation at break of the cellulose dry film (the elongation at break of the water bath film is 20.5%, the elongation at break of the water bath ethanol replacement film is 45%, and the elongation at break of the ethanol bath film is 26%), while maintaining a relatively high strength (the strength of the water bath film is 143 MPa, the strength of the water bath ethanol replacement film is 132 MPa, and the strength of the ethanol bath film is 130 MPa) and elastic modulus (the elastic modulus of the water bath film is 4700 MPa, the elastic modulus of the water bath ethanol replacement film is 3500 MPa, and the elastic modulus of the ethanol bath film is 5200 MPa). BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a test diagram of the mechanical properties of regenerated cellulose film. DETAILED DESCRIPTION

[0039] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations 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 included in the scope that the present invention is intended to protect.

[0040] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0041] Example 1

[0042] The method for preparing a regenerated cellulose film comprises the following steps:

[0043] Step 1: preparing a cellulose solution: taking 14 g of wood pulp cellulose with a DP value of 817 and 186 g of pure AmimCl ionic liquid under vacuum conditions at 80° C., dissolving them with a kneader to obtain a cellulose solution with a concentration of 7%;

[0044] Step 2: Preparation of cellulose gel membrane: At 105°C, a solution without bubbles is spread into a 500 μm film using a film spreader, water is used as a coagulation bath and repeatedly washed to obtain a hydrogel membrane, and then replaced and washed with anhydrous ethanol for multiple times to obtain a water-free ethanol gel membrane;

[0045] Step 3: Preparation of regenerated cellulose membrane with high mechanical properties: To prevent shrinkage, fix the four sides of the ethanol gel membrane on the glass plate with tape and put it into a constant temperature and humidity forced air oven at 60°C and 40% humidity. The obtained dry film (water bath ethanol replacement membrane) is balanced at 25°C and 50% for 24 hours before testing.

[0046] Example 2

[0047] The method for preparing a regenerated cellulose film comprises the following steps:

[0048] Step 1: preparing a cellulose solution: taking 14 g of wood pulp cellulose with a DP value of 817 and 186 g of pure AmimCl ionic liquid under vacuum conditions at 80° C., dissolving them with a kneader to obtain a cellulose solution with a concentration of 7%;

[0049] Step 2: Preparation of cellulose gel film: At 105°C, a solution without bubbles is spread into a 500 μm film using a film spreader, and water is used as a coagulation bath and repeatedly washed to obtain a hydrogel film;

[0050] Step 3: Preparation of regenerated cellulose membrane with high mechanical properties: To prevent shrinkage, fix the four sides of the hydrogel membrane on the glass plate with tape and directly put it into a constant temperature and humidity forced air oven at 60°C and 40% humidity. The obtained dry film (water bath membrane) was balanced at 25°C and 50% for 24 hours before testing.

[0051] Example 3

[0052] Step 1: preparing a cellulose solution: taking 14 g of wood pulp cellulose with a DP value of 817 and 186 g of pure AmimCl ionic liquid under vacuum conditions at 80° C., dissolving them with a kneader to obtain a cellulose solution with a concentration of 7%;

[0053] Step 2: Preparation of cellulose gel film: At 105°C, a solution without bubbles is spread into a 500 μm film using a film spreader, and ethanol is used as a coagulation bath and repeatedly washed to obtain an ethanol gel film;

[0054] Step 3: Preparation of high mechanical properties regenerated cellulose membrane: To prevent shrinkage, fix the four sides of the ethanol gel membrane on the glass plate with tape and put it into a constant temperature and humidity forced air oven at 60°C and 40% humidity. The obtained dry film (ethanol bath membrane) is balanced at 25°C and 50% for 24 hours before testing.

[0055] The mechanical properties of the regenerated cellulose films prepared in Examples 1-3 were tested. Figure 1 As shown. It can be seen from the figure: the elongation at break of the regenerated cellulose film (water bath ethanol replacement film) prepared in Example 1 of the present invention is 45%, the strength is 132MPa, and the elastic modulus is 3500MPa; the elongation at break of the regenerated cellulose film (water bath film) prepared in Example 2 is 20.5%, the strength is 143MPa, and the elastic modulus is 4700MPa; the elongation at break of the regenerated cellulose film (ethanol bath film) prepared in Example 3 is 26%, the strength is 130MPa, and the elastic modulus is 5200MPa. This shows that the present invention can further significantly improve the elongation at break of the regenerated cellulose dry film by replacing the hydrogel with an organic solvent (such as ethanol) and then drying it with humid hot air, while maintaining a relatively high strength and elastic modulus.

[0056] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a regenerated cellulose film, characterized in that: The method comprises laying a film of cellulose solution, reacting the film in a coagulation bath and then drying the film to obtain a regenerated cellulose film.

2. The preparation method according to claim 1, characterized in that The solvent system of the cellulose solution includes at least one of an ionic liquid system, an alkali system (viscose method), a 4-methylmorpholine-N-oxide (NMMO) system, a dimethylacetamide / lithium chloride (DMAc / LiCl) system, an alkali / urea / water system, etc.; 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, dialkyl imidazole acetate (RmimAc), 1-methyl-3-allylimidazole carboxylic acid type ([Amim][HCOO]).

3. The preparation method according to claim 1, characterized in that: The solvent used in the coagulation bath reaction can be alcohol or water. Preferably, when the solvent used in the coagulation bath reaction is water, it needs to be further replaced with an alcohol solvent. Preferably, the alcohol includes at least one of methanol, ethanol, propanol and the like.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The drying temperature is room temperature to 80°C, for example, 30 to 75°C, 40 to 70°C.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The drying humidity is 5-80%, for example 10-60%.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The cellulose raw material includes at least one of microcrystalline cellulose (MCC), cotton pulp, wood pulp and the like.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The concentration of the cellulose solution is 2-20%, such as 3-15%, 4-16%.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The method for preparing the regenerated cellulose film comprises the following steps: Scenario 1: Step 1: preparing a cellulose solution: taking 3-30 g of cotton pulp and dissolving it in 100-200 g of 1-allyl-3-methylimidazolium chloride (AmimCl), stirring it evenly and then evacuating it, setting the dissolving temperature to 70-90° C., dissolving it for 1-4 hours and then taking it out to obtain a 3-15% (w / w) cellulose solution; Step 2: preparing cellulose ethanol gel membrane: spreading the obtained cellulose solution into a membrane, washing away the ionic liquid in an ethanol coagulation bath, and obtaining a regenerated cellulose ethanol gel membrane; Step 3: Preparation of regenerated cellulose film with high mechanical properties: Dry the cellulose ethanol gel film at 30-80° C. and 10-60% humidity to obtain a cellulose film material with high mechanical properties. Scenario 2: Step 1: preparing a cellulose solution: taking 3-30 g of cotton pulp and dissolving it in 100-200 g of 1-allyl-3-methylimidazolium chloride (AmimCl), stirring it evenly and then evacuating it, setting the dissolving temperature to 70-90° C., dissolving it for 1-4 hours and then taking it out to obtain a 3-15% (w / w) cellulose solution; Step 2: preparing a cellulose hydrogel membrane: laying a membrane with the obtained cellulose solution, washing away the ionic liquid in a water coagulation bath, and obtaining a regenerated cellulose hydrogel membrane; Step 3: preparing cellulose ethanol gel membrane: replacing the cellulose hydrogel membrane with anhydrous ethanol to obtain a regenerated cellulose ethanol gel membrane; Step 4: Preparation of regenerated cellulose film with high mechanical properties: Dry the cellulose ethanol gel film at 30-80° C. and 10-60% humidity to obtain a cellulose film material with high mechanical properties. Solution 3: Step 1: preparing a cellulose solution: taking 3-30 g of cotton pulp and dissolving it in 100-200 g of 1-allyl-3-methylimidazolium chloride (AmimCl), stirring it evenly and then evacuating it, setting the dissolving temperature to 70-90° C., dissolving it for 1-4 hours and then taking it out to obtain a 3-15% (w / w) cellulose solution; Step 2: preparing a cellulose hydrogel membrane: laying a membrane with the obtained cellulose solution, washing away the ionic liquid in a water coagulation bath, and obtaining a regenerated cellulose hydrogel membrane; Step 3: Preparation of regenerated cellulose membrane with high mechanical properties: Drying the cellulose hydrogel membrane at 30-80° C. and 10-60% humidity to obtain a cellulose membrane material with high mechanical properties.

9. The regenerated cellulose film prepared by the preparation method according to any one of claims 1 to 8.

10. The regenerated cellulose film according to claim 9, characterized in that The breaking elongation of the regenerated cellulose film is 20-45%. Preferably, the strength of the regenerated cellulose film is 120-145 MPa. Preferably, the elastic modulus of the regenerated cellulose film is 3000-5500 MPa.

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