Method for preparing cellulose solution or cellulose material through normal-temperature hydrogen bond pre-reconstruction

Abstract

The invention discloses a method for preparing a cellulose solution or a cellulose material by hydrogen bond pre-reconstruction at normal temperature, which comprises the following steps: adding a cellulose raw material into a metal salt solvent, and quickly stirring and uniformly mixing at normal temperature to prepare a transparent cellulose solution; adding a water or alcohol or saline solution or solid salt for increasing hydrogen bonding between cellulose chains into the cellulose solution to obtain a transparent and flowable cellulose pre-gel solution; the cellulose pregel solution can be used for preparing a series of cellulose hydrogels, aerogels, films, fibers and the like with excellent performance. The metal salt in the cellulose solution and the subsequently added alcohol or salt can be recycled, the whole preparation process of the cellulose material is mild in reaction condition, simple and convenient to operate, low in energy consumption, short in time consumption and environment-friendly, the green process of preparing the high-strength cellulose material is realized, and the method has a good industrial application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of cellulose material preparation, and in particular relates to a method for preparing a cellulose solution or a cellulose material by hydrogen bond pre-reconstruction at room temperature. Background Art

[0002] Cellulose is the most abundant natural polymer in nature, with good mechanical properties, biodegradability, biocompatibility and biosafety. Cellulose dissolution is one of the important ways to achieve its high-value utilization, providing efficient means and methods for the processing and modification of cellulose raw materials and material construction. The cellulose solution obtained after dissolution can be used to prepare a series of cellulose-based materials, such as hydrogels, aerogels, films, fibers, etc., which have great application prospects in flexible electronic sensing, energy collection, food packaging, industrial filtration, ecological textiles and other fields. However, in the existing dissolution and regeneration process, the hydrogen bond recombination of the cellulose molecular chain is random, resulting in the formation of a disordered structure inside the material, causing stress concentration and crack propagation, which seriously restricts its application in the development of high-performance cellulose materials.

[0003] In recent years, regulating the network structure of cellulose after dissolution and regeneration has become a research hotspot. For example, patent CN119264331A uses a mixed aqueous solution of formic acid and zinc chloride as the cellulose solvent and a metal ion source solution as the coagulation bath to promote the self-assembly of cellulose formate molecules, resulting in the preparation of a high-strength cellulose-polyacrylamide bioplastic. Patent CN118085353A dissolves cellulose in a DMAC / LiCl solution and uses a vapor-induced phase separation method to prepare a cellulose organohydrogel. This hydrogel is then stretched, washed, and hot-pressed to produce an ultra-strong, ultra-tough, transparent cellulose film. However, these methods still rely on complex temperature control or organic solvent systems, resulting in complex processes, high costs, and environmental risks. Summary of the Invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] One of the objectives of this invention is to provide a method for preparing a cellulose solution by pre-reconstructing hydrogen bonds at room temperature. By introducing different ions / molecules during the deconstruction and reconstruction of cellulose hydrogen bonds, the pre-reconstructed hydrogen bond network is reconstructed, achieving directional pre-assembly of cellulose molecular chains. This process provides a structural foundation for subsequent material formation, overcoming the performance bottleneck caused by random hydrogen bond reorganization in traditional methods.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature, comprising:

[0008] Adding cellulose raw materials to a metal salt solvent, and rapidly stirring and mixing at room temperature to obtain a transparent cellulose solution;

[0009] Water, alcohol, salt water solution or solid salt which increases hydrogen bonding between cellulose chains is added to the cellulose solution to obtain a transparent and flowable cellulose pregel solution.

[0010] As a preferred embodiment of the method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature of the present invention, the metal salt solvent comprises a mixed solvent of one or two of aluminum chloride, zinc chloride, ferric chloride, manganese chloride, lithium chloride, and zinc bromide and water; and the molar ratio of the metal salt to water in the metal salt solvent is 1:3 to 1:6.

[0011] As a preferred embodiment of the method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature of the present invention, if the metal salt solvent contains two metal salts, the molar ratio of the two metal salts is 1:9 to 5:5.

[0012] As a preferred embodiment of the method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature of the present invention, the molar ratio of the amount of water, alcohol or saline solution added to the cellulose solution to the metal salt in the metal salt solvent is 0.5:1 to 5:1; the molar concentration of the saline solution is 0.01 to 5.66 mol / L at 20°C; and the molar ratio of the amount of solid salt added to the metal salt in the metal salt solvent is 0.01:1 to 0.1:1.

[0013] As a preferred embodiment of the method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature of the present invention, the salt in the brine solution or solid salt comprises a combination of one or more of carbonate, sulfate, chloride, nitrate, chlorate, phosphate, and organic acid salt;

[0014] The alcohol includes one or more of methanol, ethanol, 1-propanol, ethylene glycol, 2-propanol, and glycerol.

[0015] As a preferred embodiment of the method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature of the present invention, the solid content of the cellulose solution is 0.5 to 10.0 wt%.

[0016] As a preferred embodiment of the method for preparing cellulose solution by hydrogen bond pre-reconstruction at room temperature of the present invention, the degree of polymerization of the cellulose raw material is 200 to 4080.

[0017] Another object of the present application is to provide a method for preparing a cellulose material by room-temperature hydrogen-bonding pre-reconstitution, comprising,

[0018] A cellulose pre-gel solution obtained according to the method of any one of the above;

[0019] The cellulose pre-gel solution is prepared into a cellulose material by casting, coating or spinning.

[0020] As a preferred solution of the method for preparing a cellulose material by room-temperature hydrogen-bonding pre-reconstitution, the cellulose material comprises one or more of a hydrogel, an aerogel, a film, a fiber.

[0021] As a preferred solution of the method for preparing a cellulose material by room-temperature hydrogen-bonding pre-reconstitution, the cellulose hydrogel prepared has a tensile strength of 212-1893 kPa and a tensile strain of 66%-140%.

[0022] The cellulose aerogel prepared has a compressive strength of 202-1539 kPa.

[0023] The cellulose film prepared has a tensile stress of 43-179 MPa, a tensile strain of 4%-15% and a water swelling rate of 23.9%-45.2%.

[0024] The cellulose fiber prepared has a strength of 129-852 MPa.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] The present application provides a method for preparing a high-strength cellulose material by room-temperature hydrogen-bonding pre-reconstitution. The metal salt in the cellulose solvent and the subsequently added alcohol or salt can be recycled and used, and the whole process of preparing the cellulose material has mild reaction conditions, simple operation, low energy consumption, short time consumption and environmental friendliness, realizing a green process for preparing the cellulose material. The whole cellulose material prepared according to the present application has excellent mechanical properties and can be applied in the fields of flexible electronic sensing, energy collection, food packaging, industrial filtration, ecological textile and the like, and has good prospects for industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. Among them:

[0028] Figure 11 are scanning electron micrographs of cellulose hydrogels prepared in Example 1 and Comparative Example 1 of the present invention; wherein, a1 is a scanning electron micrograph of Comparative Example 1 magnified 500 times, and a2 is a scanning electron micrograph of Comparative Example 1 magnified 3000 times; c1 is a scanning electron micrograph of Example 1 magnified 500 times, and c2 is a scanning electron micrograph of Example 1 magnified 3000 times;

[0029] Figure 2 1 is the X-ray diffraction pattern of the cellulose hydrogel prepared in Example 1 of the present invention and Comparative Example 1;

[0030] Figure 3 This is a physical picture of the cellulose hydrogel prepared in Example 1 of the present invention and a physical picture of its conductive properties;

[0031] Figure 4 This is a physical picture of the cellulose aerogel prepared in Example 1 of the present invention;

[0032] Figure 5 This is a physical picture of the cellulose film prepared in Example 1 of the present invention;

[0033] Figure 6 This is a physical picture of the cellulose fiber prepared in Example 1 of the present invention;

[0034] Figure 7 is a stress-strain curve of the cellulose film prepared in Example 1 of the present invention;

[0035] Figure 8 is a scanning electron micrograph of cellulose hydrogels prepared from different chloride solutions in Example 12 of the present invention;

[0036] Figure 9 1 is a scanning electron micrograph of cellulose hydrogels prepared with different sodium salts in Example 12 of the present invention. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0038] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0039] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0040] Unless otherwise specified, the raw materials used in the examples were purchased commercially.

[0041] Sources of raw materials used in the embodiments of the present invention:

[0042] Bleached broadleaf pulp with a degree of polymerization of 500: purchased from Nantong Acetate Cellulose Co., Ltd.; absorbent cotton with a degree of polymerization of 4080: purchased from Xuzhou Sanitary Materials Factory Co., Ltd.; microcrystalline cellulose with a degree of polymerization of 200: purchased from Sinopharm Chemical Reagent Co., Ltd.; bleached broadleaf pulp with a degree of polymerization of 700: purchased from Nantong Acetate Cellulose Co., Ltd.; cotton linters with a degree of polymerization of 2000: purchased from Hangzhou Wohua Filter Paper Co., Ltd.

[0043] Example 1

[0044] Aluminum chloride, zinc chloride, and water were evenly mixed in a ratio of 0.1:0.9:3.2 to form a metal salt solvent. 1 wt% of bleached hardwood pulp with a degree of polymerization of 500 was then added and dissolved at room temperature to prepare a transparent cellulose solution. Water with a molar ratio of 1.8 to the metal salt in the metal salt solvent was then added, and the mixture was rapidly stirred for 1 hour to obtain a cellulose pregel solution.

[0045] Comparative Example 1

[0046] The same metal salt solvent as in Example 1 was used to dissolve 1 wt % of bleached hardwood pulp with a degree of polymerization of 500 to obtain a transparent cellulose solution.

[0047] The cellulose pregel solution in Example 1 was cast into a polytetrafluoroethylene mold using 75% ethanol solution as a regeneration liquid and immersed in ethanol to regenerate a cellulose gel. The gel was washed and freeze-dried to obtain a cellulose aerogel. The gel was washed and dried at room temperature to obtain a cellulose film.

[0048] The transparent cellulose solution in Comparative Example 1 that has not been treated by the hydrogen bond pre-reconstruction process is subjected to the same regeneration to obtain a cellulose gel. The gel is washed and freeze-dried to obtain a cellulose aerogel. The gel is washed and dried at room temperature to obtain a cellulose film.

[0049] like Figure 1The scanning electron microscope images of the cellulose gels show that the cellulose gels are all three-dimensional porous structures with dense pore diameters. The cellulose hydrogel without the hydrogen bond pre-reconstruction process has a relatively uniform pore distribution, and the fibers are short. The cellulose hydrogel prepared by the hydrogen bond pre-reconstruction process still has a three-dimensional network structure, and the regenerated cellulose of the two gels is nanoscale and fine and uniform in length. In this experiment, the water added in the hydrogen bond pre-reconstruction process enters the cellulose structure and intertwines with each other to realize crosslinking. After the hydrogen bond pre-reconstruction process, the pore diameter of the cellulose gel gradually decreases, forming a more dense pore structure and more abundant cellulose clusters (hydrogen bond aggregates). This is because the addition of water in the hydrogen bond pre-reconstruction process plays a certain supporting network structure role, reducing the pore diameter and network density of the sample. Figure 2 The x-ray diffraction patterns of the cellulose hydrogels show that the cellulose crystal forms of the two cellulose hydrogels are both cellulose type II. The crystallinity index of the cellulose gel without the hydrogen bond pre-reconstruction process is 23.76%, and the crystallinity index of the cellulose gel prepared by the hydrogen bond pre-reconstruction process is 42.84%. The increase in the crystallinity index of the cellulose gel prepared by the hydrogen bond pre-reconstruction process further indicates that the hydrogen bond network of cellulose can be orderly regulated by treating the cellulose solution with the hydrogen bond pre-reconstruction process.

[0050] The cellulose pre-gel solutions of Example 1 and Comparative Example 1 were cast in dumbbell-shaped molds, and dumbbell-shaped hydrogels were obtained after regeneration. The TRAPPEZIUM X tensile tester was used for mechanical property characterization. The tensile strength and strain of the cellulose gel prepared by the hydrogen bond pre-reconstruction process were 478 kPa and 70%, respectively, which were 2 times and 1.5 times those of the cellulose gel without the hydrogen bond pre-reconstruction process. Figure 3 The cellulose hydrogel is a physical photograph. The hydrogel has good conductivity at room temperature and low temperature.

[0051] The cellulose pre-gel solutions of Example 1 and Comparative Example 1 were cast in cylindrical molds, and cylindrical hydrogels were obtained after regeneration. The cellulose aerogel was obtained by freeze-drying the washed hydrogel. The TRAPPEZIUM X tensile tester was used for mechanical property characterization. The compressive strength of the cellulose gel prepared by the hydrogen bond pre-reconstruction process was 892 kPa, which was 1.8 times that of the cellulose gel without the hydrogen bond pre-reconstruction process. Figure 4 The aerogel is a physical photograph. The aerogel can support a weight 10,000 times its own weight.

[0052] As Figure 5As shown, the films prepared through the hydrogen bonding pre-reconstruction process exhibit high transparency. The cellulose films obtained in Example 1 and Comparative Example 1 were cut into specimens 5 mm wide and 15 mm long. Mechanical properties were characterized using a TRAPPEZIUM X-type tensile tester. The stress and strain of the cellulose films prepared through the hydrogen bonding pre-reconstruction process were 86 MPa and 8%, respectively. These tensile stress and strain were 1.5 times and 2 times higher than those of the cellulose films not treated with the hydrogen bonding pre-reconstruction process.

[0053] The water resistance of the cellulose film treated with hydrogen bond pre-reconstruction obtained in Example 1 and Comparative Example 1 and the cellulose film not treated with hydrogen bond pre-reconstruction were tested. The films were uniformly cut into specimens of 15mm×30mm in size, placed in an oven to dry until the weight was constant, and the weight M0 of the film at this time was recorded. After soaking the film in deionized water for 24 hours, take it out, and use dust-free paper to absorb the residual moisture on the surface of the film. The weight M of the film at this time was recorded, and then the water absorption rate of the film can be calculated according to the formula [(M-M0) / M0]×100. Compared with the cellulose film that has not been treated with hydrogen bond pre-reconstruction, the swelling of the cellulose film prepared by the hydrogen bond pre-reconstruction process is reduced from 43.0% to 22.1% after soaking for 24 hours, and the swelling is reduced from 52.2% to 27.2% after soaking for 15 days. This shows that the cellulose film prepared by the hydrogen bond pre-reconstruction process has better water resistance and weaker water absorption and swelling.

[0054] The cellulose pregel solution in Example 1 was squeezed into water through a syringe to directly regenerate a cellulose gel strip, which was then taken out and dried at room temperature to form cellulose fibers. The fiber photo is shown in FIG. Figure 6 As shown, at this time the fiber diameter is 0.227 mm and the tensile strength is 273 MPa, which is 3.8 times that of cellulose fibers without hydrogen bond pre-reconstruction treatment.

[0055] Example 2

[0056] Aluminum chloride, zinc chloride, and water were evenly mixed in a ratio of 0.1:0.9:3.5 to form a metal salt solvent, and then 1 wt% of bleached hardwood pulp with a degree of polymerization of 500 was added and dissolved at room temperature to prepare a transparent cellulose solution. Subsequently, a lithium chloride aqueous solution (0.01 mol / L) with a molar ratio of 1.5 to the metal salt in the metal salt solvent was added, and the mixture was rapidly stirred for 1 hour to obtain a cellulose pregel solution.

[0057] Comparative Example 2

[0058] The same metal salt solvent as in Example 2 was used to dissolve 1 wt % of bleached hardwood pulp with a degree of polymerization of 500 to obtain a transparent cellulose solution.

[0059] The cellulose pregel solution in Example 2 and the cellulose solution in Comparative Example 2 were cast into a polytetrafluoroethylene mold using a 75% ethanol solution as a regeneration liquid, and then immersed in ethanol for regeneration. A cellulose gel was obtained after washing with deionized water. The gel was freeze-dried to obtain a cellulose aerogel, and the gel was dried at room temperature to obtain a cellulose film.

[0060] The mechanical properties of the cellulose gels obtained in Example 2 and Comparative Example 2 were characterized. The tensile strength and strain of the cellulose hydrogel prepared through the hydrogen bonding pre-reconstruction process were 678 kPa and 90%, respectively, three times and two times that of the cellulose hydrogel without hydrogen bonding pre-reconstruction. The compressive strength of the cellulose aerogel prepared through the hydrogen bonding pre-reconstruction process was 854 kPa, 2.3 times that of the cellulose aerogel without hydrogen bonding pre-reconstruction.

[0061] The mechanical properties and waterproof properties of the cellulose films obtained in Example 2 and Comparative Example 2 were characterized. The stress and strain of the cellulose films prepared by the hydrogen bond pre-reconstruction process were as follows: Figure 7 As shown, they are 157 MPa and 14% respectively. After soaking in water for 24 hours, the swelling degree is 24.1%. The tensile stress and strain are 2.4 times and 2.2 times of the cellulose film without hydrogen bond pre-reconstruction process, respectively, and the swelling degree is reduced by about 15%.

[0062] The cellulose pregel in Example 2 was squeezed into water through a needle, and after regeneration, it was taken out and dried to form cellulose fibers. At this time, the fiber diameter was 0.311 mm and the tensile strength was 472 MPa, which was 5.4 times that of the cellulose fibers that had not been treated by the hydrogen bond pre-reconstruction process.

[0063] Example 3

[0064] Aluminum chloride, zinc chloride, and water were uniformly mixed in a ratio of 0.1:0.9:4 to form a metal salt solvent, and then 0.5 wt% of absorbent cotton with a degree of polymerization of 4080 was added and dissolved at room temperature to prepare a transparent cellulose solution. Subsequently, a saturated sodium acetate solution (5.66 mol / L, 20°C) with a molar ratio of 1 to the metal salt in the metal salt solvent was added, and the mixture was rapidly stirred for 1 hour to obtain a cellulose pregel solution.

[0065] Comparative Example 3

[0066] The same metal salt solvent as in Example 3 was used to dissolve 0.5 wt % of absorbent cotton having a degree of polymerization of 4080 to obtain a transparent cellulose solution.

[0067] The cellulose pregel solution in Example 3 and the cellulose solution in Comparative Example 3 were cast into a polytetrafluoroethylene mold using a 75% ethanol solution as a regeneration liquid, and then immersed in ethanol for regeneration. A cellulose gel was obtained after washing with deionized water. The gel was freeze-dried to obtain a cellulose aerogel, and the gel was dried at room temperature to obtain a cellulose film.

[0068] The mechanical properties of the cellulose gels obtained in Example 3 and Comparative Example 3 were characterized. The tensile strength and strain of the cellulose gel prepared through the hydrogen bonding pre-reconstruction process were 859 kPa and 124%, respectively, three times and 1.6 times those of the cellulose gel not treated through the hydrogen bonding pre-reconstruction process. The compressive strength of the cellulose aerogel prepared through the hydrogen bonding pre-reconstruction process was 1025 kPa, three times that of the cellulose aerogel not treated through the hydrogen bonding pre-reconstruction process.

[0069] The mechanical properties and waterproof properties of the cellulose films obtained in Example 3 and Comparative Example 3 were characterized. The stress and strain of the cellulose film prepared by the hydrogen bond pre-reconstruction process were 153 MPa and 15%, respectively. The swelling degree was 23.7% after immersion in water for 24 hours. The tensile stress and strain were 3.2 times and 3.9 times that of the cellulose film not treated by the hydrogen bond pre-reconstruction process, respectively, and the swelling degree was reduced by about 17%.

[0070] The cellulose pregel in Example 2 was squeezed into water through a needle, and after regeneration, it was taken out and dried to form cellulose fibers. At this time, the fiber diameter was 0.253 mm and the tensile strength was 604 MPa, which was 5.9 times that of the cellulose fibers that had not been treated by the hydrogen bond pre-reconstruction process.

[0071] Example 4

[0072] Zinc chloride and water are evenly mixed in a ratio of 1:3.2 to form a metal salt solvent, and then 1.5 wt% of bleached hardwood pulp with a degree of polymerization of 500 is added and dissolved at room temperature to prepare a transparent cellulose solution. Subsequently, ethanol with a molar ratio of 1.8 to the metal salt in the metal salt solvent is added, and the mixture is rapidly stirred for 1 hour to obtain a cellulose pregel solution.

[0073] Comparative Example 4

[0074] The same metal salt solvent as in Example 4 was used to directly dissolve 1.5 wt% of bleached hardwood pulp with a degree of polymerization of 500 to obtain a transparent cellulose solution.

[0075] The cellulose pregel solution in Example 4 and the cellulose solution in Comparative Example 4 were cast into a polytetrafluoroethylene mold using a 75% ethanol solution as a regeneration liquid, and then immersed in ethanol for regeneration. A cellulose gel was obtained after washing with deionized water. The gel was freeze-dried to obtain a cellulose aerogel, and the gel was dried at room temperature to obtain a cellulose film.

[0076] The mechanical properties of the cellulose gels obtained in Example 4 and Comparative Example 4 were characterized. The tensile strength and strain of the cellulose gel prepared through the hydrogen bonding pre-reconstruction process were 1633 kPa and 124%, respectively, which were 4.2 times and 3.9 times higher than those of the cellulose gel without hydrogen bonding pre-reconstruction. The compressive strength of the cellulose aerogel prepared through the hydrogen bonding pre-reconstruction process was 1561 kPa, which was 1.9 times higher than that of the cellulose aerogel without hydrogen bonding pre-reconstruction.

[0077] The mechanical properties and waterproof properties of the cellulose films obtained in Example 4 and Comparative Example 4 were characterized. The stress and strain of the cellulose film prepared by the hydrogen bond pre-reconstruction process were 146 MPa and 8%, respectively. The swelling degree was 22.9% after immersion in water for 24 hours. The tensile stress and strain were 2.6 times and 2 times of the cellulose film that was not treated by the hydrogen bond pre-reconstruction process, respectively, and the swelling degree was reduced by about 9.3%.

[0078] The cellulose pregel solution in Example 4 was squeezed into water through a syringe, and after regeneration, it was taken out and dried to form cellulose fibers. At this time, the fiber diameter was 0.354 mm and the tensile strength was 521 MPa, which was 3.5 times that of the cellulose fibers that had not been treated by the hydrogen bond pre-reconstruction process.

[0079] Example 5

[0080] Manganese chloride, zinc chloride, and water were uniformly mixed in a ratio of 0.1:0.9:3.5 to form a metal salt solvent, and then 0.5 wt% of bleached hardwood pulp with a degree of polymerization of 500 was added and dissolved at room temperature to prepare a transparent cellulose solution. Subsequently, a sodium carbonate aqueous solution (0.01 mol / L) with a molar ratio of 0.5 to the metal salt in the metal salt solvent was added, and the mixture was rapidly stirred for 1 hour to obtain a cellulose pregel solution.

[0081] Comparative Example 5

[0082] The same metal salt solvent as in Example 5 was used to directly dissolve 0.5 wt % of bleached hardwood pulp with a degree of polymerization of 500 to obtain a transparent cellulose solution.

[0083] The cellulose pregel solution in Example 5 and the cellulose solution in Comparative Example 5 were cast into a polytetrafluoroethylene mold using a 75% ethanol solution as a regeneration liquid, and then immersed in ethanol for regeneration. A cellulose gel was obtained after washing with deionized water. The gel was freeze-dried to obtain a cellulose aerogel, and the gel was dried at room temperature to obtain a cellulose film.

[0084] The mechanical properties of the cellulose gels obtained in Example 5 and Comparative Example 5 were characterized. The tensile strength and strain of the cellulose gel prepared through the hydrogen bonding pre-reconstruction process were 557 kPa and 76%, respectively, 2.5 times and 1.8 times that of the cellulose gel without hydrogen bonding pre-reconstruction. The compressive strength of the cellulose aerogel prepared through the hydrogen bonding pre-reconstruction process was 422 kPa, 1.3 times that of the cellulose aerogel without hydrogen bonding pre-reconstruction.

[0085] The mechanical properties and waterproof properties of the cellulose films obtained in Example 5 and Comparative Example 5 were characterized. The stress and strain of the cellulose film prepared by the hydrogen bond pre-reconstruction process were 108 MPa and 9%, respectively. The swelling degree was 45.2% after immersion in water for 24 hours. The tensile stress and strain were 2.6 times and 2.3 times that of the cellulose film that had not been treated by the hydrogen bond pre-reconstruction process, respectively, and the swelling degree was reduced by about 5.7%.

[0086] The cellulose pregel solution in Example 5 was squeezed into water through a syringe, and after regeneration, it was taken out and dried to form cellulose fibers. At this time, the fiber diameter was 0.428 mm and the tensile strength was 311 MPa, which was 2.5 times that of the cellulose fibers that had not been treated by the hydrogen bond pre-reconstruction process.

[0087] Example 6

[0088] Zinc bromide and water were mixed uniformly in a ratio of 1:3.8 to form a metal salt solvent, and then 1 wt% of bleached hardwood pulp with a degree of polymerization of 500 was added and dissolved at room temperature to prepare a transparent cellulose solution. Subsequently, a sodium carbonate solution (0.5 mol / L) with a molar ratio of 3 to the metal salt in the metal salt solvent was added, and the mixture was rapidly stirred for 1 hour to obtain a cellulose pregel solution.

[0089] Comparative Example 6

[0090] The same metal salt solvent as in Example 6 was used to directly dissolve 1 wt % of bleached hardwood pulp with a degree of polymerization of 500 to obtain a transparent cellulose solution.

[0091] The cellulose pregel solution in Example 6 and the cellulose solution in Comparative Example 6 were cast into a polytetrafluoroethylene mold using a 75% ethanol solution as a regeneration liquid, and then immersed in ethanol for regeneration. A cellulose gel was obtained after washing with deionized water. The gel was freeze-dried to obtain a cellulose aerogel, and the gel was dried at room temperature to obtain a cellulose film.

[0092] The mechanical properties of the cellulose gels obtained in Example 6 and Comparative Example 6 were characterized. The tensile strength and strain of the cellulose gel prepared through hydrogen bonding pre-reconstruction were 378 kPa and 92%, respectively, 2.4 times and 1.7 times those of the cellulose gel without hydrogen bonding pre-reconstruction. The compressive strength of the cellulose aerogel prepared through hydrogen bonding pre-reconstruction was 291 kPa, 1.5 times that of the cellulose aerogel without hydrogen bonding pre-reconstruction.

[0093] The mechanical properties and waterproof properties of the cellulose films obtained in Example 6 and Comparative Example 6 were characterized. The stress and strain of the cellulose film prepared by the hydrogen bond pre-reconstruction process were 114 MPa and 10%, respectively. The swelling degree was 42.9% after immersion in water for 24 hours. The tensile stress and strain were 2.5 times and 3.4 times that of the cellulose film not treated by the hydrogen bond pre-reconstruction process, respectively, and the swelling degree was reduced by about 9.9%.

[0094] The cellulose pregel solution in Example 6 was squeezed into water through a syringe, and after regeneration, it was taken out and dried to form cellulose fibers. At this time, the fiber diameter was 0.377 mm and the tensile strength was 426 MPa, which was 3.6 times that of the cellulose fibers that had not been treated by the hydrogen bond pre-reconstruction process.

[0095] Example 7

[0096] Lithium chloride, zinc chloride, and water were uniformly mixed in a ratio of 0.1:0.9:3 to form a metal salt solvent, and then 10 wt% of microcrystalline cellulose (MCC) with a degree of polymerization of 200 was added and dissolved at room temperature to prepare a transparent cellulose solution. Subsequently, a sodium sulfate solution (0.2 mol / L) with a molar ratio of 5 to the metal salt in the metal salt solvent was added, and the mixture was rapidly stirred for 1 hour to obtain a cellulose pregel solution.

[0097] Comparative Example 7

[0098] The same metal salt solvent as in Example 7 was used to directly dissolve 10 wt % of microcrystalline cellulose (MCC) having a degree of polymerization of 200 to obtain a transparent cellulose solution.

[0099] The cellulose pregel solution in Example 7 and the cellulose solution in Comparative Example 7 were cast into a polytetrafluoroethylene mold using a 75% ethanol solution as a regeneration liquid, and then immersed in ethanol for regeneration. A cellulose gel was obtained after washing with deionized water. The gel was freeze-dried to obtain a cellulose aerogel, and the gel was dried at room temperature to obtain a cellulose film.

[0100] The mechanical properties of the cellulose gels obtained in Example 7 and Comparative Example 7 were characterized. The tensile strength and strain of the cellulose gel prepared through the hydrogen bonding pre-reconstruction process were 456 kPa and 113%, respectively, which were 2 times and 2.1 times those of the cellulose gel without hydrogen bonding pre-reconstruction. The compressive strength of the cellulose aerogel prepared through the hydrogen bonding pre-reconstruction process was 328 kPa, which was 2.1 times that of the cellulose aerogel without hydrogen bonding pre-reconstruction.

[0101] The mechanical properties and waterproof properties of the cellulose films obtained in Example 7 and Comparative Example 7 were characterized. The stress and strain of the cellulose film prepared by the hydrogen bond pre-reconstruction process were 231 MPa and 12%, respectively. The swelling degree after immersion in water for 24 hours was 42.3%. The tensile stress and strain were 2.2 times and 2.4 times that of the cellulose film that had not been treated by the hydrogen bond pre-reconstruction process, respectively, and the swelling degree was reduced by about 8.5%.

[0102] The cellulose pregel solution in Example 7 was squeezed into water through a syringe, and after regeneration, it was taken out and dried to form cellulose fibers. At this time, the fiber diameter was 0.261 mm and the tensile strength was 581 MPa, which was 5.7 times that of the cellulose fibers that had not been treated by the hydrogen bond pre-reconstruction process.

[0103] Example 8

[0104] Ferric chloride, zinc chloride, and water were mixed in a ratio of 0.3:0.7:6 to form a metal salt solvent. 1 wt% of bleached hardwood pulp with a degree of polymerization of 700 was then added and dissolved at room temperature to prepare a transparent cellulose solution. Subsequently, a sodium phosphate aqueous solution (0.08 mol / L) was added at a molar ratio of 1 to the metal salt in the metal salt solvent, and the mixture was rapidly stirred for one hour to obtain a cellulose pregel solution.

[0105] Comparative Example 8

[0106] The same metal salt solvent as in Example 8 was used to directly dissolve 1 wt % of bleached hardwood pulp with a degree of polymerization of 700 to obtain a transparent cellulose solution.

[0107] The cellulose pregel solution in Example 8 and the cellulose solution in Comparative Example 8 were cast into a polytetrafluoroethylene mold using a 75% ethanol solution as a regeneration liquid, and then immersed in ethanol for regeneration. A cellulose gel was obtained after washing with deionized water. The gel was freeze-dried to obtain a cellulose aerogel, and the gel was dried at room temperature to obtain a cellulose film.

[0108] The cellulose gel obtained from Example 8 and Comparative Example 8 was subjected to mechanical property characterization. The tensile strength and strain of the cellulose gel prepared by the hydrogen bond pre-reconstitution process were 254 kPa and 78%, respectively, which were 1.3 times and 1.7 times that of the cellulose gel without the hydrogen bond pre-reconstitution process. The compressive strength of the cellulose aerogel prepared by the hydrogen bond pre-reconstitution process was 202 kPa, which was 1.2 times that of the cellulose aerogel without the hydrogen bond pre-reconstitution process.

[0109] The cellulose film obtained from Example 8 and Comparative Example 8 was subjected to mechanical property and waterproof property characterization. The stress and strain of the cellulose film prepared by the hydrogen bond pre-reconstitution process were 98 MPa and 7%, respectively, and the swelling degree after 24 h of immersion in water was 39.5%. The tensile stress and strain were 1.7 times and 1.3 times that of the cellulose film without the hydrogen bond pre-reconstitution process, and the swelling degree was reduced by about 5.8%.

[0110] The cellulose pre-gel solution in Example 8 was extruded into water through a needle tube, and after regeneration, cellulose fibers were obtained by drying. At this time, the fiber diameter was 0.305 mm, and the tensile strength was 264 MPa, which was 2.7 times that of the cellulose fibers without the hydrogen bond pre-reconstitution process.

[0111] Example 9

[0112] Iron chloride, zinc chloride, and water were mixed in a ratio of 0.5:0.5:4 to form a metal salt solvent, and then 1 wt% cotton linters with a degree of polymerization of 2000 were dissolved at room temperature to prepare a cellulose transparent solution. Subsequently, a calcium chloride aqueous solution (2 mol / L) with a molar ratio of 2 to the metal salt in the metal salt solvent was added, and rapid stirring was performed for 10 minutes to obtain a cellulose pre-gel solution.

[0113] Comparative Example 9

[0114] The same metal salt solvent as in Example 9 was used to directly dissolve 1 wt% cotton linters with a degree of polymerization of 2000 to obtain a cellulose transparent solution.

[0115] A 75% ethanol solution was used as a regeneration liquid, and the cellulose pre-gel solution in Example 9 and the cellulose solution in Comparative Example 9 were cast in a polytetrafluoroethylene mold and soaked in ethanol for regeneration. After washing with deionized water, a cellulose gel was obtained. After freeze-drying of the gel, a cellulose aerogel was obtained. After drying the gel at room temperature, a cellulose film was obtained.

[0116] The mechanical properties of the cellulose gels obtained in Example 9 and Comparative Example 9 were characterized. The tensile strength and strain of the cellulose gel prepared through the hydrogen bonding pre-reconstruction process were 1893 kPa and 122%, respectively, 4.5 times and 3.1 times those of the cellulose gel without hydrogen bonding pre-reconstruction. The compressive strength of the cellulose aerogel prepared through the hydrogen bonding pre-reconstruction process was 1539 kPa, 2.6 times that of the cellulose aerogel without hydrogen bonding pre-reconstruction.

[0117] The mechanical properties and waterproof properties of the cellulose films obtained in Example 9 and Comparative Example 9 were characterized. The stress and strain of the cellulose film prepared by the hydrogen bond pre-reconstruction process were 179 MPa and 9%, respectively. The swelling degree after immersion in water for 24 hours was 32.5%. The tensile stress and strain were 4.1 times and 2.3 times that of the cellulose film that had not been treated by the hydrogen bond pre-reconstruction process, respectively, and the swelling degree was reduced by about 7.4%.

[0118] The cellulose pregel solution in Example 9 was squeezed into water through a syringe, and after regeneration, it was taken out and dried to form cellulose fibers. At this time, the fiber diameter was 0.355 mm and the tensile strength was 652 MPa, which was 7.7 times that of the cellulose fibers that had not been treated by the hydrogen bond pre-reconstruction process.

[0119] Example 10

[0120] Aluminum chloride, zinc chloride, and water were uniformly mixed in a ratio of 0.1:0.9:3.5 to form a metal salt solvent, and then 1 wt% of bleached hardwood pulp with a degree of polymerization of 500 was added and dissolved at room temperature to prepare a transparent cellulose solution. Subsequently, sodium citrate solid was added at a molar ratio of 0.1 to the metal salt in the metal salt solvent, and the mixture was rapidly stirred for 60 minutes to obtain a cellulose pregel solution.

[0121] Comparative Example 10

[0122] The same metal salt solvent as in Example 10 was used to dissolve 1 wt % of bleached hardwood pulp with a degree of polymerization of 500 to obtain a transparent cellulose solution.

[0123] The cellulose pregel solution in Example 10 and the cellulose solution in Comparative Example 10 were cast into a polytetrafluoroethylene mold using a 75% ethanol solution as a regeneration liquid, and then immersed in ethanol for regeneration. A cellulose gel was obtained after washing with deionized water. The gel was freeze-dried to obtain a cellulose aerogel, and the gel was dried at room temperature to obtain a cellulose film.

[0124] The mechanical properties of the cellulose gels obtained in Example 10 and Comparative Example 10 were characterized. The tensile strength and strain of the cellulose gel prepared through the hydrogen bonding pre-reconstruction process were 658 kPa and 140%, respectively, 3.1 times and 3.3 times that of the cellulose gel without hydrogen bonding pre-reconstruction. The compressive strength of the cellulose aerogel prepared through the hydrogen bonding pre-reconstruction process was 508 kPa, 2.3 times that of the cellulose aerogel without hydrogen bonding pre-reconstruction.

[0125] The mechanical properties and waterproof properties of the cellulose films obtained in Example 10 and Comparative Example 10 were characterized. The stress and strain of the cellulose film prepared by the hydrogen bond pre-reconstruction process were 127 MPa and 8%, respectively. The swelling degree after immersion in water for 24 hours was 35.6%. The tensile stress and strain were 3.1 times and 2 times that of the cellulose film not treated by the hydrogen bond pre-reconstruction process, respectively, and the swelling degree was reduced by about 12%.

[0126] The cellulose pregel in Example 10 was squeezed into water through a syringe, and after regeneration, it was taken out and dried to form cellulose fibers. At this time, the fiber diameter was 0.251 mm and the tensile strength was 344 MPa, which was 3.4 times that of the cellulose fibers that had not been treated by the hydrogen bond pre-reconstruction process.

[0127] Example 11

[0128] Aluminum chloride, zinc chloride, and water were uniformly mixed in a ratio of 0.1:0.9:4 to form a metal salt solvent, and then 1 wt% of bleached hardwood pulp with a degree of polymerization of 500 was added and dissolved at room temperature to prepare a transparent cellulose solution. Subsequently, sodium acetate solid was added at a molar ratio of 0.01 to the metal salt in the metal salt solvent, and the mixture was rapidly stirred for 60 minutes to obtain a cellulose pregel solution.

[0129] Comparative Example 11

[0130] The same metal salt solvent as in Example 11 was used to dissolve 1 wt % of bleached hardwood pulp with a degree of polymerization of 500 to obtain a transparent cellulose solution.

[0131] The cellulose pregel solution in Example 11 and the cellulose solution in Comparative Example 11 were cast into a polytetrafluoroethylene mold using a 75% ethanol solution as a regeneration liquid, and then immersed in ethanol for regeneration. A cellulose gel was obtained after washing with deionized water. The gel was freeze-dried to obtain a cellulose aerogel, and the gel was dried at room temperature to obtain a cellulose film.

[0132] The mechanical properties of the cellulose gels obtained in Example 11 and Comparative Example 11 were characterized. The tensile strength and strain of the cellulose gel prepared through the hydrogen bonding pre-reconstruction process were 314 kPa and 85%, respectively, 1.48 times and 2 times that of the cellulose gel without hydrogen bonding pre-reconstruction. The compressive strength of the cellulose aerogel prepared through the hydrogen bonding pre-reconstruction process was 366 kPa, 1.66 times that of the cellulose aerogel without hydrogen bonding pre-reconstruction.

[0133] The mechanical properties and waterproof properties of the cellulose films obtained in Example 11 and Comparative Example 11 were characterized. The stress and strain of the cellulose film prepared by the hydrogen bond pre-reconstruction process were 77 MPa and 5%, respectively. The swelling degree after immersion in water for 24 hours was 37.3%. The tensile stress and strain were 1.9 times and 1.2 times that of the cellulose film not treated by the hydrogen bond pre-reconstruction process, respectively, and the swelling degree was reduced by about 9.2%.

[0134] The cellulose pregel in Example 11 was squeezed into water through a syringe, and after regeneration, it was taken out and dried to form cellulose fibers. At this time, the fiber diameter was 0.279 mm and the tensile strength was 257 MPa, which was 2.5 times that of the cellulose fibers that had not been treated by the hydrogen bond pre-reconstruction process.

[0135] Example 12

[0136] Based on Example 2, this Example 12 investigated the effects of different chloride solution types on the mechanical properties of cellulose gel prepared by the hydrogen bond pre-reconstruction process, the mechanical properties and waterproof properties of cellulose film, and the fiber strength properties. The specific performance test results are shown in Table 1. Figure 8 shown.

[0137] Table 1

[0138]

[0139] Example 13

[0140] Based on Example 4, this Example 13 investigated the effects of different alcohol types on the mechanical properties of cellulose gel prepared by hydrogen bond pre-reconstruction, the mechanical properties and waterproof properties of cellulose film, and the fiber strength properties. The specific performance test results are shown in Table 2.

[0141] Table 2

[0142]

[0143]

[0144] Example 14

[0145] Based on Example 10, this Example 14 investigated the effects of different sodium salt types on the mechanical properties of cellulose gel prepared by hydrogen bond pre-reconstruction, the mechanical properties and waterproof properties of cellulose film, and the fiber strength properties. The specific performance test results are shown in Table 3. Figure 9 shown.

[0146] Table 3

[0147]

[0148] The present invention provides a method for preparing high-strength cellulose materials through room-temperature hydrogen bond pre-reconstruction. The metal salts in the transparent cellulose solution and the alcohol or salt subsequently added can be recycled and reused. The entire cellulose material preparation process features mild reaction conditions, simple operation, low energy consumption, short processing time, and environmental friendliness, achieving an environmentally friendly cellulose material preparation process and promising prospects for industrial application.

[0149] The all-cellulose material produced according to the present invention has excellent mechanical properties and can be used in flexible electronic sensing, energy harvesting, food packaging, industrial filtration, ecological textiles and other fields. It provides broad application prospects for the high-value utilization of dissolved cellulose.

[0150] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature, characterized in that: include, Adding cellulose raw materials to a metal salt solvent, and rapidly stirring and mixing at room temperature to obtain a transparent cellulose solution; Water, alcohol, salt water solution or solid salt which increases hydrogen bonding between cellulose chains is added to the cellulose solution to obtain a transparent and flowable cellulose pregel solution.

2. The method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature according to claim 1, wherein: The metal salt solvent includes a mixed solvent of one or two of aluminum chloride, zinc chloride, ferric chloride, manganese chloride, lithium chloride, zinc bromide and water; the molar ratio of the metal salt to water in the metal salt solvent is 1:3 to 1:

6.

3. The method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature according to claim 2, wherein: If the metal salt solvent contains two metal salts, the molar ratio of the two metal salts is 1:9 to 5:

5.

4. The method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature according to claim 1, wherein: The molar ratio of the water, alcohol or salt solution added to the cellulose solution to the metal salt in the metal salt solvent is 0.5:1 to 5:1; the molar concentration of the salt solution is 0.01 to 5.66 mol / L at 20°C; and the molar ratio of the solid salt added to the metal salt in the metal salt solvent is 0.01:1 to 0.1:

1.

5. The method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature according to claim 4, characterized in that: The salt in the brine solution or solid salt includes one or more combinations of carbonates, sulfates, chlorides, nitrates, chlorates, phosphates, and organic acid salts; The alcohol includes one or more of methanol, ethanol, 1-propanol, ethylene glycol, 2-propanol, and glycerol.

6. The method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature according to any one of claims 1 to 5, characterized in that: The solid content of the cellulose solution is 0.5-10.0 wt%.

7. The method for preparing a cellulose solution by hydrogen bond pre-reconstruction at room temperature according to claim 6, characterized in that: The degree of polymerization of the cellulose raw material is 200-4080.

8. A method for preparing cellulose materials by hydrogen bond pre-reconstruction at room temperature, characterized in that: include, The cellulose pregel solution obtained according to the method according to any one of claims 1 to 7; The cellulose pregel solution is cast, coated or spun to prepare the cellulose material.

9. The method for preparing a cellulose material by hydrogen bond pre-reconstruction at room temperature according to claim 8, wherein: The cellulose material includes one or more of hydrogels, aerogels, films, and fibers.

10. The method for preparing a cellulose material by hydrogen bond pre-reconstruction at room temperature according to claim 9, characterized in that: The prepared cellulose hydrogel has a tensile strength of 212 to 1893 kPa and a tensile strain of 66% to 140%. The prepared cellulose aerogel has a compressive strength of 202-1539 kPa; The prepared cellulose film has a tensile stress of 43-179 MPa, a tensile strain of 4%-15%, and a water swelling ratio of 23.9%-45.2%. The strength of the prepared cellulose fibers is 129-852 MPa.

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