High-viscosity carboxymethyl cellulose and application thereof

Abstract

The invention discloses high-viscosity carboxymethyl cellulose and application thereof, and belongs to the technical field of modified carboxymethyl cellulos.Through precise molecular design, an alkenyl compound synthesized by an azido formate compound and p-aminophenyl propiolate is designed and introduced into a side chain of carboxymethyl cellulose, and the high-viscosity carboxymethyl cellulose is prepared. A rigid-flexible functionalized topological structure is constructed, a molecular weight gradient increase-dynamic crosslinking-conformation regulation three-stage synergistic tackifying mechanism is creatively realized, and the high-viscosity carboxymethyl cellulose and the application thereof are provided.

Description

Technical Field

[0001] This invention belongs to the field of modified carboxymethyl cellulose technology, specifically relating to a high-viscosity carboxymethyl cellulose and its applications. Background Art

[0002] Carboxymethyl cellulose (CMC), as an important water-soluble cellulose derivative, is widely used in food, pharmaceuticals, and oilfield extraction due to its excellent thickening properties, biocompatibility, and environmental friendliness. However, with the upgrading of material performance requirements in high-end applications such as biomedical materials and intelligent fluid systems, the inherent defects of traditional CMC are becoming increasingly prominent. Its core bottleneck lies in the difficulty of synergistically optimizing "high viscosity" and "functional controllability," specifically manifested in the following technical challenges: 1. Limitations of Traditional Thickening Methods: Existing technologies primarily rely on two strategies to increase the viscosity of carboxymethyl cellulose: molecular weight enhancement and physical / chemical crosslinking. While introducing calcium ion crosslinks or covalent crosslinks can improve viscosity in the short term, the crosslinking network is irreversible. Easily dissociated and covalently cross-linked, leading to deterioration in processability, and high-concentration solutions are prone to phase separation, making it difficult to meet long-term stability requirements.

[0003] 2. Conflict between functionalization modification and viscosity properties: To expand the functionality of carboxymethyl cellulose, existing technologies typically involve chemical modification with carboxymethyl or hydroxyl groups, such as grafting thermosensitive poly(N-isopropylacrylamide). However, such modifications often disrupt the regularity of the carboxymethyl cellulose backbone, leading to increased chain folding, flexible side chains inducing backbone conformation shrinkage, and a decrease in hydration radius, resulting in a conflict with viscosity properties.

[0004] 3. The contradiction between high viscosity and processability: Industrial processing requirements for carboxymethyl cellulose demand materials that possess both high viscosity and shear-thinning properties. However, traditional high-viscosity carboxymethyl cellulose exhibits a strong shear-thickening tendency due to excessive molecular chain entanglement, severely limiting its application in 3D printing, microfluidic devices, and other scenarios. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention constructs a functionalized topology with rigid-flexible properties on the side chain of carboxymethyl cellulose through precise molecular design. This achieves a balance between hydrophilic and hydrophobic regions and creatively realizes a three-level synergistic thickening mechanism of molecular weight gradient growth, dynamic crosslinking, and conformational regulation. This achieves compatibility between viscosity enhancement and processability, providing a high-viscosity carboxymethyl cellulose and its applications.

[0006] The technical solution for achieving the objective of this invention is as follows: A high-viscosity carboxymethyl cellulose having the general formula shown in Formula 1: Equation 1.

[0007] Preferably, the method for preparing the high-viscosity carboxymethyl cellulose includes the following steps: S1. Decarboxylation and grafting: Carboxymethyl cellulose was dissolved in an acetonitrile aqueous solution, stirred in a water bath at 50-70°C, and then silver nitrate was added and stirred in the dark; degassing was performed, and the initiator was added in batches, and the reaction was maintained at a temperature for 30-40 min; the alkenyl compound was dissolved in acetonitrile, and the alkenyl compound solution was slowly added dropwise to the above mixture, and the reaction was carried out under anaerobic conditions; after the reaction was completed, the mixture was cooled in an ice bath, and then sodium hydroxide was added to neutralize it, and the CMC-Na graft copolymer was obtained after purification; the structural formula of the alkenyl compound is shown in Formula 2: Formula 2; S2. Hydrolysis: The CMC-Na graft copolymer was dissolved in a 50% (w / w) aqueous ethanol solution. After stirring in an ice bath for 5-10 min, a 1% (w / w) trifluoroacetic acid solution was added. After stirring for 20-30 min, a cold saturated sodium bicarbonate solution was slowly added dropwise while stirring in an ice bath to neutralize the solution, thus obtaining crude carboxymethyl cellulose. S3. Purification: The crude carboxymethyl cellulose obtained in S2 is filtered, first washed with 50%~70% ethanol to remove salt, and then washed with 90% or more ethanol to dehydrate. After drying and pulverizing at 40℃~50℃, high-viscosity carboxymethyl cellulose is obtained.

[0008] Preferably, the initiator in step S1 is potassium persulfate, and the amount added is 0.5-1.5% of the mass fraction of carboxymethyl cellulose; the amount of silver nitrate added is 0.05-0.1% of the mass fraction of carboxymethyl cellulose; and the mass ratio of the alkenyl compound to carboxymethyl cellulose is 1:(1-5).

[0009] The preparation method of the alkenyl compound is as follows: (1) Under a nitrogen atmosphere, 1 eq of azide carbamate compound and 1 eq of p-aminophenyl propynate were mixed in a mixed solution of dimethyl sulfoxide and water in a volume ratio of 5:1. 0.1 eq of anhydrous copper sulfate and 0.2 eq of sodium ascorbate were added, and the mixture was stirred until homogeneous. The temperature was raised to 70 °C and reacted for 6 h. The aminotriazole intermediate was obtained by silica gel column chromatography, and its structure is shown in Formula 3. Formula 3; (2) Preparation of isocyanate intermediate: Under a nitrogen atmosphere, 1 eq of the aminotriazole intermediate obtained in step (1) was mixed with 6-8 eq of diisocyanate, and the mixture was heated to 90℃ and reacted for 12-14 h. After the reaction was completed, excess diisocyanate was removed by washing with hexane, and the mixture was dried under vacuum at 40℃ for 12 h to obtain the isocyanate intermediate, the structure of which is shown in Formula 4. Equation 4; (3) Under a nitrogen atmosphere, 1 eq of the isocyanate intermediate of step (2) and 2 eq of the chain enol were stirred in anhydrous dichloromethane for 5 min, 1 drop of dibutyltin dilaurate solution was added, the temperature was raised to 60℃ and stirred for 24 h, and after the reaction was completed, the purified alkenyl compound was obtained by silica gel column chromatography, and the structure is shown in Formula 2.

[0010] Preferably, the diisocyanate is selected from one or more of 1,6-hexamethylene diisocyanate, 1,5-pentanediisocyanate, and 1,4-butyl diisocyanate; the chain enol is selected from one or more of 9-decaeno-1-ol, 8-nonen-1-ol, 7-octen-1-ol, 6-hepten-1-ol, 5-hexen-1-ol, 4-penten-1-ol, and 3-buten-1-ol.

[0011] Preferably, the method for preparing the azidoformate compound includes the following steps: (1) Synthesis of isopropylidene-2,2-bis(methoxy)propionic acid: Under a nitrogen atmosphere, 1.0 eq of 2,2-dihydroxymethylpropionic acid and 0.03 eq of p-toluenesulfonic acid were dissolved in dry acetone and stirred at room temperature for 30 min. Then, 1.5 eq of 2,2-dimethoxypropane was added and stirred at room temperature for 2 h. The reaction was terminated by adding 0.1 eq of potassium carbonate. The solvent was removed under reduced pressure. The residue was dissolved in dichloromethane and washed three times with distilled water to obtain the white solid product isopropylidene-2,2-bis(methoxy)propionic acid, which was set aside. The structure of isopropylidene-2,2-bis(methoxy)propionic acid is shown in the following formula: ; (2) Synthesis of (2,2,5-trimethyl-1,3-dioxane-5-yl)methanol: Under a nitrogen atmosphere, 1 eq of trimethylolethane and p-toluenesulfonic acid were dissolved in dry acetone. After stirring at room temperature for 1 h, 2,2-dimethoxypropane was added, and the mixture was stirred at room temperature for 4 h. The reaction was terminated by adding potassium carbonate. The solvent was removed under reduced pressure, and the residue was dissolved in dichloromethane and washed three times with distilled water to obtain a transparent oily product (2,2,5-trimethyl-1,3-dioxane-5-yl)methanol, with the structure shown in the following formula: ; (3) Synthesis of p-toluenesulfonate compound: Under a nitrogen atmosphere, 1 eq of the product from step (2) was mixed with pyridine, and then a 45% p-toluenesulfonyl chloride pyridine solution was slowly added. The mixture was stirred and heated to 100°C for 2 h. After the reaction was completed, the reaction solution was poured into ice water, extracted with diethyl ether, the organic phases were combined, dried with anhydrous sodium sulfate, the solvent was removed by vacuum distillation, and the waxy white solid product p-toluenesulfonate compound was obtained by silica gel column chromatography. The structure is shown in the following formula: ; (4) Synthesis of azide compounds: Under a nitrogen atmosphere, 1 eq of the product obtained in step (3) was dissolved in a mixed solution of DMF:water in a volume ratio of 8:1, and 1.0~1.1 eq of sodium azide was added. The mixture was stirred at 100~110℃ for 16 h. After the reaction was completed, the reaction solution was poured into water, extracted with diethyl ether, the organic phases were combined, the solvent was removed by vacuum distillation, and the product was obtained by silica gel column chromatography as a transparent oily azide compound with the structure shown in the following formula: ; (5) Synthesis of azide carbamate compounds: Under a nitrogen atmosphere, 1 eq of the product from step (4) was dissolved in methanol, and 0.1 g to 0.5 g of DOWEX ion exchange resin was added. The mixture was heated to 40°C and stirred for 40 to 45 min. The mixture was filtered through a glass frit funnel, and the solvent was removed by vacuum distillation to obtain a diol intermediate for later use. The obtained diol intermediate was dissolved in dry dichloromethane, and 2 eq of the product from step (1), 0.6 to 0.8 eq of 4-dimethylaminopyridine p-toluenesulfonate, and 0.2 eq of 4-dimethylaminopyridine were added sequentially. After mixing, the mixture was stirred at 0°C for 40 to 50 min. Then, a dichloromethane solution of 2.1 to 2.2 eq of dicyclohexylcarbodiimide was slowly added dropwise. The mixture was heated to room temperature and stirred for 48 min. h; After the reaction was completed, the white precipitate was removed by filtration, the solvent was removed by vacuum distillation, the residue was dissolved in hot ethyl acetate, and the excess 4-dimethylaminopyridine p-toluenesulfonate was removed by crystallization. This process was repeated 2-3 times, and the transparent oily product, an azide carbamate compound, was obtained by silica gel column chromatography. The structure is shown in Formula 5. Formula 5.

[0012] Preferably, the method for preparing the p-aminophenyl propyne ester includes the following steps: (1) 1 eq of p-aminobenzoic acid, 1.1 eq of di-tert-butyl dicarbonate and 0.4-0.6 eq of triethylamine were dissolved in a mixed solution of 1,4-dioxane:water in a volume ratio of 5:1. The mixture was stirred at room temperature for 24 h. After the reaction was completed, the solvent was removed under reduced pressure. The amino-terminated carboxylic acid intermediate was obtained by silica gel column chromatography. The structure is shown in the following formula: ; (2) Dissolve 1 eq of the product from step (1) in anhydrous DMF, add 1.1 eq of sodium hydride in an ice bath, stir for 30 min, then slowly add 1.3~1.5 eq of 3-bromopropyne, raise the temperature to room temperature and stir for 16~20 h. After the reaction is complete, remove the solvent under reduced pressure, and obtain the alkynylated terminal amino-protected intermediate by silica gel column chromatography. The structure is shown in the following formula: ; (3) Dissolve 1 eq of the product from step (2) in dichloromethane, add 10-15 eq of trifluoroacetic acid in an ice bath, raise the temperature to room temperature and stir for 24 h. After the reaction is complete, remove the solvent and excess acid under reduced pressure, extract with cold saturated sodium bicarbonate solution and ethyl acetate, and separate by silica gel column chromatography to obtain p-aminophenyl propynate, the structure of which is shown in Formula 6: Formula 6; Another object of the present invention is to provide an application of high-viscosity carboxymethyl cellulose in lithium-ion battery anode slurry, wherein the lithium-ion battery anode slurry is prepared by the following steps, by weight percentage: 1) Dry mixing of negative electrode powder: 85%~98% graphite, 1%~5% high viscosity carboxymethyl cellulose, and 1%~10% conductive agent are placed in a double planetary mixer and dry mixed. The dry mixing time is set to 30~120 min, the revolution speed is set to 20~60 rpm, and the rotation speed is set to 0~500 rpm to obtain a powder mixture. 2) Slurry mixing: Add 30% to 60% of the solvent relative to the weight of the powder to the powder mixture. Set the slurry mixing time to 30 to 240 min, the revolution speed to 20 to 60 rpm, and the rotation speed to 0 to 500 rpm to obtain a slurry mixture. 3) High viscosity stirring: Add 10% to 30% solvent relative to the weight of powder to the mud mixture, set the mud stirring time to 30 to 240 min, set the revolution speed to 20 to 60 rpm, set the rotation speed to 0 to 1000 rpm, and carry out high viscosity stirring at 50,000 mpa.s or higher to obtain a high viscosity slurry; 4) Viscosity adjustment and stirring: Add 10% to 50% solvent relative to the weight of the powder to the high viscosity slurry, set the stirring time to 30 to 120 min, set the revolution speed to 20 to 60 rpm, and set the rotation speed to 0 to 1500 rpm to obtain a slurry that meets the viscosity requirements; 5) Vacuuming and degassing: Seal the inside of the double planetary mixer, turn on the vacuum device until the vacuum degree inside the mixer reaches below -90 KPa, turn on the double planetary mixer, set the revolution speed to 10~30 rpm, set the rotation speed to 0~200 rpm, reverse the stirring rod, and set the time to 20~60 min to obtain the negative electrode slurry.

[0013] Preferably, the graphite is at least one of natural graphite and artificial graphite.

[0014] Preferably, the conductive agent is at least one of carbon black and conductive graphite.

[0015] Preferably, the solvent is at least one of N-methylpyrrolidone and deionized water.

[0016] Beneficial effects

[0017] The present invention has the following beneficial effects: This invention, through precise molecular design, constructs a functionalized topology on the side chain of carboxymethyl cellulose, creatively achieving three-dimensional synergistic enhancement of viscosity properties. The specific enhancement mechanism is as follows: 1. Enhanced molecular chain structure: The grafted macromolecular side chain groups directly increase the effective molecular weight of carboxymethyl cellulose, strengthen the molecular chain entanglement network, and increase the solution viscosity; the side chains contain hydrophobic groups, forming dynamic physical cross-linking points. At low concentrations, the hydrophobic microregions induce intermolecular association to form a supramolecular network, while at high concentrations, the interchain entanglement density is enhanced, significantly improving viscoelasticity. 2. Chain conformation optimization: A rigid side chain structure is designed to generate steric repulsion through steric hindrance, which inhibits the folding of carboxymethyl cellulose molecular chains, promotes chain extension, increases the hydration radius, and improves the apparent viscosity. 3. By specifically designing a ketal structure in the molecule, multiple hydroxyl groups are released upon hydrolysis, which helps to: (1) Hydrogen bond network reinforcement and inter-chain interaction: Increase hydrogen bond density, form intramolecular and intermolecular hydrogen bonds with adjacent hydroxyl groups on the carboxymethyl cellulose backbone, and enhance the inter-chain crosslinking density; Dense hydrogen bond network restricts the free movement of molecular chains and significantly increases solution viscosity; (2) Enhanced hydration and chain extension: Hydroxyl groups bind more water molecules through hydrogen bonds, forming an extended hydration shell, increasing the effective mechanical volume of the molecule, improving zero-shear viscosity, and at the same time, strong hydration capacity reduces the tendency of phase separation, which helps to stabilize high-concentration solutions; the electrostatic repulsion of hydroxyl groups promotes the extension of carboxymethyl cellulose molecular chains, reduces chain folding, increases the radius of rotation, and thus increases viscosity.

[0018] (3) Environmental responsiveness and functional expansion: The pKa of hydroxyl groups is usually between 9 and 11. The ionization state can be changed by adjusting the pH of the solution to achieve reversible viscosity control. Hydroxyl groups can also be used as chemical modification sites. Functional groups can be introduced through esterification, etherification or click chemistry to further form a covalent cross-linked network and further improve viscosity.

[0019] In summary, this invention utilizes a triple mechanism of hydrogen bond network strengthening and interchain interaction, enhanced hydration and chain extension and functional expansion to synergistically enhance the solution viscosity and viscoelasticity of carboxymethyl cellulose, providing a novel carboxymethyl cellulose-based solution with both ultra-high performance and customizable functionality for high-end fields such as intelligent fluid systems. Attached Figure Description

[0020] Figure 1 This refers to the synthesis process of high-viscosity carboxymethyl cellulose. Figure 2Infrared spectra of sodium carboxymethyl cellulose, alkenyl compound 1, and modified carboxymethyl cellulose 1. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0023] The raw materials and equipment used in the embodiments and comparative examples are described below: p-Aminophenylpropynate: Prepared in-house, as follows: (1) 1 eq of p-aminobenzoic acid, 1.1 eq of di-tert-butyl dicarbonate and 0.4-0.6 eq of triethylamine were dissolved in a mixed solution of 1,4-dioxane:water in a volume ratio of 5:1. The mixture was stirred at room temperature for 24 h. After the reaction was completed, the solvent was removed under reduced pressure. The amino-terminated carboxylic acid intermediate was obtained by silica gel column chromatography. The structure is shown in the following formula: ; (2) Dissolve 1 eq of the product from step (1) in anhydrous DMF, add 1.1 eq of sodium hydride in an ice bath, stir for 30 min, then slowly add 1.3~1.5 eq of 3-bromopropyne, raise the temperature to room temperature and stir for 16~20 h. After the reaction is complete, remove the solvent under reduced pressure, and obtain the alkynylated terminal amino-protected intermediate by silica gel column chromatography. The structure is shown in the following formula: ; (3) Dissolve 1 eq of the product from step (2) in dichloromethane, add 10-15 eq of trifluoroacetic acid in an ice bath, raise the temperature to room temperature and stir for 24 h. After the reaction is complete, remove the solvent and excess acid under reduced pressure, extract with cold saturated sodium bicarbonate solution and ethyl acetate, and separate by silica gel column chromatography to obtain p-aminophenyl propynyl ester, the structure of which is shown in the following formula: ; Azide carbamate compound 1: prepared in-house, as follows: (1) Synthesis of isopropylidene-2,2-bis(methoxy)propionic acid: Under a nitrogen atmosphere, 1.0 eq of 2,2-dihydroxymethylpropionic acid and 0.03 eq of p-toluenesulfonic acid were dissolved in dry acetone and stirred at room temperature for 30 min. Then, 1.5 eq of 2,2-dimethoxypropane was added and stirred at room temperature for 2 h. The reaction was terminated by adding 0.1 eq of potassium carbonate. The solvent was removed under reduced pressure. The residue was dissolved in dichloromethane and washed three times with distilled water to obtain the white solid product isopropylidene-2,2-bis(methoxy)propionic acid, which was set aside. The structure of isopropylidene-2,2-bis(methoxy)propionic acid is shown in the following formula: ; (2) Synthesis of (2,2,5-trimethyl-1,3-dioxane-5-yl)methanol: Under a nitrogen atmosphere, 1 eq of trimethylolethane and p-toluenesulfonic acid were dissolved in dry acetone. After stirring at room temperature for 1 h, 2,2-dimethoxypropane was added, and the mixture was stirred at room temperature for 4 h. The reaction was terminated by adding potassium carbonate. The solvent was removed under reduced pressure, and the residue was dissolved in dichloromethane and washed three times with distilled water to obtain a transparent oily product (2,2,5-trimethyl-1,3-dioxane-5-yl)methanol, with the structure shown in the following formula: ; (3) Synthesis of p-toluenesulfonate compound: Under a nitrogen atmosphere, 1 eq of the product from step (2) was mixed with pyridine, and then a 45% p-toluenesulfonyl chloride pyridine solution was slowly added. The mixture was stirred and heated to 100°C for 2 h. After the reaction was completed, the reaction solution was poured into ice water, extracted with diethyl ether, the organic phases were combined, dried with anhydrous sodium sulfate, the solvent was removed by vacuum distillation, and the waxy white solid product p-toluenesulfonate compound was obtained by silica gel column chromatography. The structure is shown in the following formula: ; (4) Synthesis of azide compounds: Under a nitrogen atmosphere, 1 eq of the product obtained in step (3) was dissolved in a mixed solution of DMF:water in a volume ratio of 8:1, and 1.0~1.1 eq of sodium azide was added. The mixture was stirred at 100~110℃ for 16 h. After the reaction was completed, the reaction solution was poured into water, extracted with diethyl ether, the organic phases were combined, the solvent was removed by vacuum distillation, and the product was obtained by silica gel column chromatography as a transparent oily azide compound with the structure shown in the following formula: ; (5) Synthesis of azide carbamate compounds: Under a nitrogen atmosphere, 1 eq of the product from step (4) was dissolved in methanol, and 0.1 g to 0.5 g of DOWEX ion exchange resin was added. The mixture was heated to 40°C and stirred for 40 to 45 min. The mixture was filtered through a glass frit funnel, and the solvent was removed by vacuum distillation to obtain a diol intermediate for later use. The obtained diol intermediate was dissolved in dry dichloromethane, and 2 eq of the product from step (1), 0.6 to 0.8 eq of 4-dimethylaminopyridine p-toluenesulfonate, and 0.2 eq of 4-dimethylaminopyridine were added sequentially. After mixing, the mixture was stirred at 0°C for 40 to 50 min. Then, a dichloromethane solution of 2.1 to 2.2 eq of dicyclohexylcarbodiimide was slowly added dropwise. The mixture was heated to room temperature and stirred for 48 min. h; After the reaction was completed, the white precipitate was removed by filtration, the solvent was removed by vacuum distillation, the residue was dissolved in hot ethyl acetate, and the excess 4-dimethylaminopyridine p-toluenesulfonate was removed by crystallization. This process was repeated 2-3 times, and the transparent oily product azidoformate compound 1 was obtained by silica gel column chromatography. The structure is shown in the following formula: .

[0024] Azide carbamate compound 2: prepared in-house, the preparation method is the same as that of azide carbamate compound 1, except that step (5) is omitted, and all other conditions remain unchanged, to obtain azide carbamate compound 2, the structure of which is shown in the following formula: .

[0025] Sodium carboxymethyl cellulose: available in-house or commercially, MW 250000 (DS=0.9), 1500-3100 mPa·s; Silver nitrate: purchased from Sinopharm Reagent. Peroxide: Potassium persulfate, purchased from Sinopharm Reagent; 2,2-Dimethylolpropionic acid: Product number B802228, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; 2,2-Dimethoxypropane: Product No. D806894, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; p-Toluenesulfonyl chloride: Product number T485782, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Sodium azide: 0.05% sodium azide solution, product number RTC000068, purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd. DOWEX ion exchange resin: 50-100 mesh, product number R035355, purchased from Shanghai Yi'en Chemical Technology Co., Ltd. 4-Dimethylaminopyridine p-toluenesulfonate: Product No. BD240521, purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.; 4-Dimethylaminopyridine: Product No. D109207, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Dicyclohexylcarbodiimide: Product No. D106074, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Di-tert-butyl dicarbonate: Product No. D806925, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Triethylamine: Product number D806925T818772, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Sodium hydride: Product number S110860, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Trifluoroacetic acid: Product number T818778, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Sodium ascorbate: Product number S817635, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Dibutyltin dilaurate: Product No. 5204, purchased from Shandong Xiya Chemical Co., Ltd.; Trimethylolethane: Product number T818900, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; p-Aminobenzoic acid: Product number A108862, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; 3-Bromopropyne: Product number P815876, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Preparation Example Preparation Example 1 Alkenyl compound 1: Prepared in-house, the preparation method is as follows: (1) Under a nitrogen atmosphere, 1 eq of azide carbamate compound 1 and 1 eq of p-aminophenyl propynate were mixed in a mixed solution of dimethyl sulfoxide and water in a volume ratio of 5:1. 0.1 eq of anhydrous copper sulfate and 0.2 eq of sodium ascorbate were added, and the mixture was stirred until homogeneous. The temperature was raised to 70°C and the reaction was carried out for 6 h. The aminotriazole intermediate was obtained by silica gel column chromatography, and its structure is shown in the following formula: ; (2) Preparation of isocyanate intermediate: Under a nitrogen atmosphere, 1 eq of the aminotriazole intermediate obtained in step (1) was mixed with 6 eq of 1,6-hexanediisocyanate, and the mixture was heated to 90℃ and reacted for 12-14 h. After the reaction was completed, excess 1,6-hexanediisocyanate was removed by washing with hexane. After vacuum drying at 40℃ for 12 h, the 1,6-hexanediisocyanate intermediate was obtained, with the structure shown in the following formula: ; (3) Under a nitrogen atmosphere, 1 eq of the product 1,6-hexanediisocyanate intermediate from step (2) and 2 eq of 9-decaen-1-ol were stirred in anhydrous dichloromethane for 5 min. One drop of dibutyltin dilaurate solution was added, and the mixture was heated to 60℃ and stirred for 24 h. After the reaction was completed, the purified product alkenyl compound 1 was obtained by silica gel column chromatography. The structure is shown in the following formula: .

[0026] Preparation Example 2 Alkenyl compound 2: prepared in-house. The preparation method is the same as that of alkenyl compound 1, except that 1,6-hexanediisocyanate in step (2) is replaced with 1,4-butyl diisocyanate, and 9-decaen-1-ol in step (3) is replaced with 3-buten-1-ol. All other conditions remain unchanged. Alkenyl compound 2 is obtained, and its structure is shown in the following formula: .

[0027] Preparation Example 3 Alkenyl compound 3: prepared in-house. The preparation method is the same as that of alkenyl compound 1, except that in step (1), azidoformate compound 1 is replaced with azidoformate compound 2, while all other conditions remain unchanged. Alkenyl compound 3 is obtained with the following structure: .

[0028] Preparation Example 4 Alkenyl compound 4: Acrylic acid, product number A980638, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0029] Example Example 1

[0030] Modified carboxymethyl cellulose 1: Self-made, preparation method as follows: S1. Decarboxylation and grafting: 20 g of carboxymethyl cellulose was dissolved in a mixed solvent of acetonitrile and water in a volume ratio of 1:3. After stirring in a water bath at 60°C for 30 min, 0.02 g of silver nitrate was added and stirred in the dark for 15 min. High-purity nitrogen was introduced for degassing, and 0.2 g of potassium persulfate was added in two portions. The temperature was controlled below 65°C and the reaction was maintained for 30 min. 6.5 g of alkenyl compound was dissolved in acetonitrile and added dropwise to the above mixture at a rate of 1 mL / L. The mixture was heated to 60°C under anaerobic conditions and reacted for 2.5 h. After the reaction was completed, the mixture was cooled in an ice bath and then neutralized with sodium hydroxide. The CMC-Na graft copolymer was purified. S2. Hydrolysis: The CMC-Na graft copolymer was dissolved in a 50% ethanol solution, stirred in an ice bath for 5-10 min, and then a 3% trifluoroacetic acid solution was added. After stirring for 30 min, a cold saturated sodium bicarbonate solution was slowly added dropwise while stirring in an ice bath to neutralize the mixture, thus obtaining crude carboxymethyl cellulose. S3. Purification: The crude carboxymethyl cellulose obtained in S2 was filtered, washed with a 60% ethanol solution to remove salt, and then washed with a 90% ethanol solution to dehydrate. After drying and pulverizing at 40°C, high-viscosity carboxymethyl cellulose 1 was obtained.

[0031] Example 2

[0032] Modified carboxymethyl cellulose 2: prepared in-house. The preparation method is the same as that of modified carboxymethyl cellulose 1, except that the amount of alkenyl compound 1 added in step S2 is replaced with 1 g, while other conditions remain unchanged, to obtain modified carboxymethyl cellulose 2.

[0033] Example 3

[0034] Modified carboxymethyl cellulose 3: prepared in-house. The preparation method is the same as that of modified carboxymethyl cellulose 1, except that the amount of alkenyl compound 1 added in step S2 is replaced with 20 g, while other conditions remain unchanged, to obtain modified carboxymethyl cellulose 3.

[0035] Example 4

[0036] Modified carboxymethyl cellulose 4: prepared in-house. The preparation method is the same as that of modified carboxymethyl cellulose 1, except that the alkenyl compound 1 added in step S2 is replaced with alkenyl compound 2, while other conditions remain unchanged, thus obtaining modified carboxymethyl cellulose 4.

[0037] Example 5

[0038] Modified carboxymethyl cellulose 5: prepared in-house. The preparation method is the same as that of modified carboxymethyl cellulose 1, except that the alkenyl compound 1 added in step S2 is replaced with alkenyl compound 3, while other conditions remain unchanged, thus obtaining modified carboxymethyl cellulose 5.

[0039] Comparative Example 1 Modified carboxymethyl cellulose 6: prepared in-house. The preparation method is the same as that of modified carboxymethyl cellulose 1, except that the alkenyl compound 1 added in step S2 is replaced with alkenyl compound 4, while other conditions remain unchanged, thus obtaining modified carboxymethyl cellulose 6.

[0040] Comparative Example 2 Modified carboxymethyl cellulose 7: Sodium carboxymethyl cellulose is used.

[0041] The following are the test methods for performance parameters involved in this invention: (1) Viscosity test: Weigh 5 g of modified carboxymethyl cellulose 1~7 dried at 105℃ for 2 h, accurate to 0.001 g, and prepare a 1% solution for later use; measure 495 mL of water (prepare a 1% CMC-Na solution) into a wide-mouth bottle; place the wide-mouth bottle under a stirrer, turn on the stirrer power, adjust the speed very slowly to 300 rpm, slowly add the sample, and make sure to add all the sample into the solution. After the sample is completely added, slowly adjust the stirring speed to 900 rpm and stir for about 2 h (3-4 h for high viscosity products) until the sample is completely dissolved and uniform; place the wide-mouth bottle containing the prepared sample solution in a constant temperature water bath at 25℃, keep it at a constant temperature for at least 1 h, check the temperature of the sample solution, and if the value is within the range of 25±0.2℃, use a DV2T viscometer to perform the test.

[0042] (2) Peel test: Adhesion performance is typically evaluated using a peel strength test. In this test, a pre-prepared electrode sheet is first adhered to an aluminum substrate, and then firmly bonded to the electrode-coated surface using 3M tape. Specifically, a 120×25 mm electrode sample is placed on 3M transparent tape, which is then applied to the coating and pulled at a 180° angle. The force required to pull the tape at a fixed speed of 100 mm / min is recorded.

[0043] The electrode sheet was prepared as follows: A silicon-oxygen anode, conductive carbon black, single-walled carbon nanotubes, and modified carboxymethyl cellulose 1-7 were weighed in a mass ratio of 95:1:0.05:3.95. The modified carboxymethyl cellulose 1-7 were dissolved in a solvent, and appropriate amounts of solvent were added according to the viscosity of the solution. The weighed silicon-oxygen anode, conductive carbon black, and single-walled carbon nanotubes were added to an agate mortar and ground until uniformly mixed. The dissolved modified carboxymethyl cellulose 1-7 was then added, and appropriate amounts of solvent were added again according to the viscosity of the slurry. A small beaker was sealed with plastic wrap and stirred on a stirrer for 12 hours. The stirred electrode slurry was coated onto copper foil that had been wiped and dried with anhydrous ethanol to obtain the electrode sheet. The electrode sheet was then dried in a 50°C oven for 12 hours to obtain the electrode sheet.

[0044] (3) Cyclic capacity retention: The positive electrode material (active material is NCM811) and the negative electrode material (silicon-oxygen negative electrode, conductive carbon black, single-walled carbon nanotubes and modified carboxymethyl cellulose 1-7 in a mass ratio of 95:1:0.05:3.95) were stirred, coated, rolled and die-cut to obtain positive electrode sheets and negative electrode sheets respectively. The obtained positive electrode sheets, negative electrode sheets and separator (12+4 ceramic coated separator) were stacked, spot-welded, packaged and baked. After injecting electrolyte (solute is LiPF6, solvent is EC and DMC in a mass ratio of 4:1), the electrolyte was injected, stood, formed, aged and capacity tested in sequence to obtain lithium-ion batteries. The obtained lithium-ion batteries were cycled at 1C / 1C for 500 cycles between 2.75 and 4.2 V to test their capacity retention.

[0045] (4) Fourier Transform Infrared Spectroscopy (FT-IR): FT-IR analysis was performed using a Thermo Nicolet IS10 Fourier Transform Infrared Spectrometer. From the blue line alkenyl compound 1, it can be seen that at 3065 cm⁻¹... -1 The presence of a weak peak at this point represents the =CH stretching vibration of the terminal olefin, indicating the presence of a CH2=CH- structure; while the red line shows a peak at 3065 cm⁻¹ for modified carboxymethyl cellulose. -1 The disappearance of the weak peak indicates that the CH2=CH- structure does not exist, proving that the terminal alkenyl group of alkenyl compound 1 has reacted.

[0046] Table 1 Performance Tests of Examples and Comparative Examples

[0047] As shown in the table above, the viscosity first increases and then decreases with the increase of alkenyl compound 1. Example 2 has the lowest viscosity, presumably due to the low grafting amount and low degree of modification. Example 3 has the highest viscosity, presumably because the alkenyl compound may increase molecular chain entanglement through hydrophobic interaction and chemical crosslinking, but excessive amounts may lead to local aggregation, which is not conducive to uniform dissolution. Example 1 has a moderate viscosity, balancing hydrophobic modification and solubility. The viscosities of Examples 4 and 5 are lower than that of Example 1, presumably because the performance of alkenyl compound 1 is better than that of alkenyl compound 2 and alkenyl compound 3. Comparative Example 1 grafts acrylic acid, introducing strongly polar carboxylic acid groups, which disrupts the original hydrophilic-hydrophobic balance of carboxymethyl cellulose, resulting in molecular chain shrinkage and decreased viscosity. Comparative Example 2, the unmodified carboxymethyl cellulose, lacks hydrophobic modification, has no molecular crosslinking effect, and has low viscosity.

[0048] Regarding peel strength, it increased with the increase of grafting amount, indicating that the hydrophobic groups of alkenyl compound 1 enhanced the interfacial bonding force between carboxymethyl cellulose and electrode material through physical entanglement and chemical crosslinking; the use of short-chain alkenyl compound 2 in Example 4 presumably reduced the flexibility of the molecular chain and reduced the effective contact with the electrode material; the alkenyl compound 3 in Example 5 had fewer reactive sites and decreased viscosity; the peel strength of Comparative Example 1 and Comparative Example 2 was significantly reduced, among which the modified carboxymethyl cellulose lacked hydrophobic modification and relied only on hydrogen bonding, resulting in the lowest bonding strength.

[0049] Regarding the cycle capacity retention rate, Example 3 had the highest viscosity, but the cycle capacity retention rate decreased. It is speculated that excessive grafting led to excessive molecular chain entanglement. Although the viscosity increased, the ion mobility decreased, resulting in a decrease in the cycle capacity retention rate instead of an increase.

[0050] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A high-viscosity carboxymethyl cellulose, characterized in that, It has the general formula shown in Equation 1: Equation 1.

2. The high-viscosity carboxymethyl cellulose according to claim 1, characterized in that, The degree of carboxymethyl substitution of the carboxymethyl cellulose is 0.7 to 1.

4.

3. The high-viscosity carboxymethyl cellulose as described in claim 1, characterized in that, The method for preparing the high-viscosity carboxymethyl cellulose includes the following steps: S1. Decarboxylation and grafting: Carboxymethyl cellulose was dissolved in an acetonitrile aqueous solution, stirred in a water bath at 50-70°C, and then silver nitrate was added and stirred in the dark; degassing was performed, and the initiator was added in batches, and the reaction was maintained at a temperature for 30-40 min; the alkenyl compound was dissolved in acetonitrile, and the alkenyl compound solution was slowly added dropwise to the above mixture, and the reaction was carried out under anaerobic conditions; after the reaction was completed, the mixture was cooled in an ice bath, and then sodium hydroxide was added to neutralize it, and the CMC-Na graft copolymer was obtained after purification; the structural formula of the alkenyl compound is shown in Formula 2: Formula 2; S2. Hydrolysis: Dissolve the CMC-Na graft copolymer in an aqueous ethanol solution, stir in an ice bath for 5-10 min, add a 1%-5% trifluoroacetic acid solution, stir for 20-30 min, slowly add a cold saturated sodium bicarbonate solution and stir in an ice bath to neutralize, to obtain crude carboxymethyl cellulose. S3. Purification: The crude carboxymethyl cellulose obtained in S2 is filtered, first washed with 50%~70% ethanol to remove salt, and then washed with 90% or more ethanol to dehydrate. After drying and pulverizing at 40℃~50℃, high-viscosity carboxymethyl cellulose is obtained.

4. The high-viscosity carboxymethyl cellulose as described in claim 3, characterized in that, The initiator in step S1 is potassium persulfate, and the amount added is 0.5-1.5% of the mass fraction of carboxymethyl cellulose; the amount of silver nitrate added is 0.05-0.1% of the mass fraction of carboxymethyl cellulose; the mass ratio of the alkenyl compound to carboxymethyl cellulose is 1:(1-5).

5. The high-viscosity carboxymethyl cellulose as described in claim 3, characterized in that, The preparation method of the alkenyl compound includes the following steps: (1) Under a nitrogen atmosphere, the azide carbamate compound and p-aminophenyl propynate were mixed in a solution of dimethyl sulfoxide and water, anhydrous copper sulfate and sodium ascorbate were added, and the mixture was stirred until homogeneous. The temperature was then raised to 70°C. After the reaction was completed, an aminotriazole intermediate was obtained, the structure of which is shown in Formula 3: Formula 3; (2) Preparation of isocyanate intermediate: Under a nitrogen atmosphere, the aminotriazole intermediate obtained in step (1) was mixed with diisocyanate, heated to 90°C, and washed with hexane after the reaction was completed. After vacuum drying, the isocyanate intermediate was obtained, with the structure shown in Formula 4: Equation 4; (3) Under a nitrogen atmosphere, the isocyanate intermediate and the chain enol of step (2) were stirred in anhydrous dichloromethane, 1 drop of dibutyltin dilaurate solution was added, and the temperature was raised to 60°C. After the reaction was completed, the purified alkenyl compound was obtained.

6. The method for preparing the alkenyl compound according to claim 5, characterized in that, The diisocyanate is selected from one or more of 1,6-hexanediisocyanate, 1,5-pentanediisocyanate, and 1,4-butyl diisocyanate; the chain enol is selected from one or more of 9-decaen-1-ol, 8-nonen-1-ol, 7-octen-1-ol, 6-hepten-1-ol, 5-hexen-1-ol, 4-penten-1-ol, and 3-buten-1-ol.

7. The method for preparing the alkenyl compound according to claim 5, characterized in that, The structure of the azidoformate compound is shown in Formula 5; the structure of the p-aminophenylpropynate is shown in Formula 6. Equation 5; Formula 6.

8. The application of a high-viscosity carboxymethyl cellulose as described in any one of claims 1 to 7 in a lithium-ion battery negative electrode paste binder.

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