Modified high-substitution-degree carboxymethyl cellulose fiber as well as preparation method and application thereof

Abstract

The invention discloses a modified high-substitution-degree carboxymethyl cellulose fiber as well as a preparation method and application thereof, and belongs to the technical field of fiber modification preparation. The technical problem that a conventional high-substitution-degree carboxymethyl cellulose product is difficult to form filaments in the prior art is solved. The modified high-substitution-degree carboxymethyl cellulose fiber is obtained by carrying out alkalization-etherification-elution on regenerated cellulose fiber twice or more than twice, then carrying out neutralization and acid pickling, and then carrying out substitution reaction with lithium salt, the substitution degree Ds of the carboxymethyl cellulose lithium fiber is greater than 0.55, and fiber-form high-substitution-degree carboxymethyl cellulose lithium is prepared. The excellent conductivity of the carboxymethyl fiber lithium can be effectively exerted, and the carboxymethyl fiber lithium battery has relatively high mechanical strength and a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber modification, and specifically to a modified high-substitution-degree carboxymethyl cellulose fiber, a preparation method thereof, and an application thereof. Background Art

[0002] Cellulose is a long-chain natural polymer formed by dehydration between D-glucose monomers and connected in the form of β-1,4-glucoside bonds. Each glucose ring in the cellulose macromolecule contains three hydroxyl groups, namely the primary hydroxyl group on the sixth carbon atom and the secondary hydroxyl groups on the second and third carbon atoms. The hydrogen in the hydroxyl group is replaced by a hydrocarbon group to form a cellulose ether derivative.

[0003] In the prior art, it is difficult to obtain a high-substitution-degree carboxymethyl cellulose product. For example, when m(cotton linter):m(NaOH):m(ClCH 2 COOH) = 1.0:1.1:1.2, using 95% ethanol as the dispersion medium and an etherification time of 1.5 min, the substitution degree of the obtained product is only 0.7384. However, some products have strict requirements for the high substitution degree of carboxymethyl cellulose. In order to increase the substitution degree of carboxymethyl cellulose, a scheme of increasing the dosage of alkalization and etherifying agent, prolonging the reaction time, and increasing the reaction temperature is usually adopted. However, long-time high-temperature reaction conditions and a large amount of alkalization and etherifying agent will cause the degradation of cellulose, and the physical properties of the product will drop sharply.

[0004] Lithium carboxymethyl cellulose is gradually widely used in energy devices due to its advantages of natural degradability, renewability, and excellent electrical conductivity. Lithium carboxymethyl cellulose has absolute advantages in battery application directions such as film formation, electrolyte dispersion, and textile forming. In order to further improve the electrical performance per unit volume and the electricity storage performance, lithium carboxymethyl cellulose has higher requirements for the substitution degree.

[0005] Existing invention publication numbers such as CN112724266A and CN102206286A disclose preparation methods of lithium carboxymethyl cellulose, which can prepare some lithium carboxymethyl cellulose with relatively high substitution degrees. However, the above preparation methods of high-substitution-degree lithium carboxymethyl cellulose are difficult to correspondingly form lithium carboxymethyl cellulose fibers in fiber form, and they mainly exist in powder form. Subsequently, when used, they need to rely on a solvent as a carrier, which makes it difficult to effectively exert the excellent properties of lithium carboxymethyl cellulose. Summary of the Invention

[0006] Aiming at the disadvantages and deficiencies existing in the prior art, the present invention provides a modified high-substitution-degree carboxymethyl cellulose fiber and its preparation method and application, which overcome the problem that conventional high-substitution-degree lithium carboxymethyl cellulose is difficult to form filaments, successfully prepare high-substitution-degree lithium carboxymethyl cellulose in fiber form, not only can effectively exert the excellent electrical conductivity of lithium carboxymethyl cellulose, but also has high mechanical strength and good application prospects.

[0007] To achieve the above object, the present invention is realized through the following technical solutions: The modified high-substitution-degree carboxymethyl cellulose fiber provided by the present invention is prepared by subjecting regenerated cellulose fiber to two or more "alkalization-etherification-elution" processes while always maintaining the condition of cellulose in fiber state, then neutralizing to obtain sodium carboxymethyl cellulose fiber, pickling to obtain hydrogenated carboxymethyl cellulose fiber, and then performing a substitution reaction with a lithium salt solution to obtain high-substitution-degree lithium carboxymethyl cellulose fiber;

[0008] The fineness of the regenerated cellulose fiber is 0.3-3.5 dtex, and the substitution degree Ds of the lithium carboxymethyl cellulose fiber is >0.55.

[0009] Due to the large difference between the fiber state and the powder state, compared with the lithium carboxymethyl cellulose powder prepared in the prior art, except that the chemical composition elements are the same, the longitudinal and transverse characteristics of the fiber state itself of the present invention finally realize the synergistic effect between the structure and the composition, significantly improving the electrical and mechanical properties of the fiber.

[0010] The dispersion performance of the fiber in water or other liquid media is the main factor affecting the quality of the fiber dispersion or other wet-spun fiber materials. The inventors have found that if the substitution degree is too low, although fibers can be prepared, the lithium content on the fibers is too low, and the obtained fibers are still difficult to effectively exert the role of "lithium"; if the substitution degree is too high, it is difficult to maintain the fiber structure.

[0011] In order to further solve the difficulty of maintaining the fiber structure at a high substitution degree, through a large number of experimental studies, the preparation reaction mechanism of the lithium carboxymethyl cellulose fiber of the present invention is mainly obtained by exchanging sodium and hydrogen in sodium carboxymethyl cellulose and hydrogenated carboxymethyl cellulose with lithium ions, and the ion exchange does not involve the change of the substitution degree. Therefore, the necessary condition for the substitution degree of the lithium carboxymethyl cellulose fiber is determined by the process products sodium carboxymethyl cellulose or hydrogenated carboxymethyl cellulose. That is, the substitution degree of lithium carboxymethyl cellulose cannot be greater than the substitution degree of the process products sodium carboxymethyl cellulose or hydrogenated carboxymethyl cellulose. Obviously, to increase the substitution degree of the lithium carboxymethyl cellulose fiber, it is necessary to increase the substitution degree of sodium carboxymethyl cellulose or hydrogenated carboxymethyl cellulose.

[0012] The above-mentioned modified high-substituted sodium carboxymethyl cellulose or carboxymethyl cellulose hydrogen also has the problem of being difficult to maintain the fiber structure. Therefore, in the present invention, regenerated cellulose fibers are neutralized after being subjected to "alkalization-etherification-elution" twice or more times, whereby sodium carboxymethyl cellulose fibers with a high degree of substitution can be obtained. Subsequently, high-substituted hydrogenated carboxymethyl cellulose fibers are correspondingly obtained by acidification. Finally, lithium carboxymethyl cellulose fibers with a degree of substitution Ds > 0.55 are prepared by a substitution reaction. This fiber not only has a fibrous structure but also maintains a certain mechanical strength, does not require a carrier, has a certain plasticity, is environmentally friendly, is easy to process, and can be better applied to the production of flexible energy devices, smart textiles, functional textiles and other products, enabling the excellent properties of lithium carboxymethyl cellulose to be effectively exerted.

[0013] Preferably, the degree of substitution of the lithium carboxymethyl cellulose fiber is 0.55 < Ds ≤ 3.0; the degree of orientation measured by the optical birefringence method is ≥ 0.45. By adopting the above technical solution, the present invention further limits the degree of substitution, fineness and degree of orientation, and the fibers prepared thereby have better mechanical strength and more excellent spinnability. Among them, the degree of orientation can reflect that the cellulose macromolecular chains are oriented to a certain extent along the fiber axis. In the fiber of the present invention, since lithium ions are fixed on the carboxyl groups of carboxymethyl cellulose, they will occupy a certain space. At this time, further limiting the degree of orientation of the fiber can ensure the orderly arrangement of lithium ions in a specific direction, and the corresponding fiber has more excellent mechanical properties and electrical conductivity.

[0014] Preferably, it includes the following steps:

[0015] S1. Using regenerated cellulose fibers as raw materials, after being subjected to "alkalization-etherification-elution" twice or more times, neutralization is carried out. During the "alkalization-etherification-elution" process, the cellulose is always maintained in a fibrous state, and the pH of the reaction system is maintained > 7 throughout the process to obtain sodium carboxymethyl cellulose fibers; the fineness of the regenerated cellulose fibers is preferably 0.3-3.5 dtex.

[0016] S2. After pickling and eluting the sodium carboxymethyl cellulose fibers prepared in S1, hydrogenated carboxymethyl cellulose fibers are obtained.

[0017] S3. Reacting the hydrogenated carboxymethyl cellulose fibers prepared in S2 with a lithium salt solution to obtain crude lithium carboxymethyl cellulose fibers; the degree of substitution of the hydrogenated carboxymethyl cellulose fibers is 0.55 < Ds ≤ 3.0.

[0018] By adopting the above technical solution, regenerated cellulose fiber refers to fibers made from natural cellulose materials, such as viscose fiber, cuprammonium fiber, Tencel fiber, modal fiber, etc. The present invention uses regenerated cellulose fiber as the raw material, which has the advantage of fiber orientation degree compared with natural fiber, making the effect of solid electrolyte more controllable; in addition, regenerated fiber has a wide source, low cost, and can also improve the resource utilization rate to a certain extent, and is more suitable for industrial batch sustainable development.

[0019] The regenerated cellulose fiber of the present invention can make the substitution reaction proceed step by step through two or more "alkalization - etherification - elution" under alkaline conditions, avoiding high concentrations of alkalizing agents, etherifying agents, and too high reaction temperatures, reducing the generation of by-products, reducing the impact of the etherification reaction on fiber properties, and thus preparing sodium carboxymethyl cellulose fiber with a high degree of substitution and capable of maintaining the fiber morphology well in the system.

[0020] On this basis, the sodium ions on the sodium carboxymethyl cellulose fiber are removed by pickling. Based on the reaction that lithium ions react with carboxylic acid to form lithium carboxylate salt, the carboxyl groups on the carboxymethyl cellulose fiber maintaining the fiber structure can react with lithium ions to form fibrous carboxymethyl cellulose lithium. It should be particularly pointed out that the degree of substitution of sodium carboxymethyl cellulose obtained by alkalization and etherification refers to the carboxymethyl substitution of the hydroxyl hydrogen of the cellulose basic unit. Thus, the carboxymethyl cellulose, sodium carboxymethyl cellulose obtained, and the carboxymethyl cellulose and carboxymethyl cellulose lithium generated by pickling and lithium salt reaction have the same degree of substitution.

[0021] The steps of the above preparation method are simple and the conditions are controllable. Not only can fibrous carboxymethyl cellulose lithium be obtained well, but the prepared carboxymethyl cellulose lithium fiber also has good mechanical strength.

[0022] By adopting the above technical solution, the fineness of the fiber determines the specific surface area of the fiber. The finer the fiber, the larger the specific surface area. A larger specific surface area can effectively improve the specific capacity of the material, and a high specific surface area is also one of the decisive factors for chemical reaction activity; if the regenerated cellulose fiber is too thick, the subsequent alkalization, etherification, pickling, and combination of carboxylic acid and lithium ions of the fiber will not react completely, and there is a lack of carboxyl groups in the fiber interior to react with lithium ions; if the regenerated cellulose fiber is too fine, during the reaction process, as the degree of substitution of the carboxylic acid increases, the fiber strength weakens and the fiber is prone to breakage. Since the raw material needs to maintain the fiber morphology throughout the preparation process, therefore, when selecting the regenerated cellulose fiber in the present invention, the fineness of the raw material fiber needs to be strictly controlled and preferably is 0.3 - 3.5 dtex, thereby indirectly controlling the fineness of the finally formed carboxymethyl cellulose lithium fiber.

[0023] The degree of substitution of sodium carboxymethyl cellulose fiber plays a decisive role in the degree of substitution of lithium carboxymethyl cellulose fiber. Through experimental research, the present invention has found that when the degree of substitution of sodium carboxymethyl cellulose fiber is 0.55 < Ds ≤ 3.0, it can better maintain the fiber morphology in the corresponding alkalization and etherification reaction of the present invention, and obtain lithium carboxymethyl cellulose fiber with both high mechanical strength and high electrical conductivity.

[0024] Preferably, it further includes S4. When the regenerated cellulose fiber adopts a long fiber structure in step S1, the lithium carboxymethyl cellulose thick fiber after the reaction of the hydrogenated carboxymethyl cellulose fiber with the lithium salt in step S3 is drawn to produce lithium carboxymethyl cellulose fiber.

[0025] Preferably, in step S4, the draw ratio is 1:1.05 - 1.55. Prepared from regenerated cellulose fiber with a long fiber structure, since this fiber is obtained by treating the fiber morphology, the lithium carboxymethyl cellulose thick fiber obtained in step S3 of the present invention can be directly cut, then oiled, dried, crimped, and packed to harvest the final lithium carboxymethyl cellulose fiber. The length of the cut fiber is preferably ≥ 1 mm, and the length of the cut short fiber can be adjusted according to needs at this time.

[0026] However, in the lithium salt solution, the negatively charged carboxymethyl cellulose fiber (H-CMC) combines with lithium ions (Li + ) to form lithium carboxymethyl cellulose. During the combination process, the lithium ions diffuse disorderly and penetrate into the carboxymethyl cellulose fiber covered with carboxyl groups to form lithium carboxymethyl cellulose fiber. The lithium ions are extremely unevenly dispersed and disorderly in the fiber. Therefore, in order to fix the lithium ions, the hydrogenated carboxymethyl cellulose fiber is immersed in the lithium salt solution and then drawn. The drawn fiber was originally randomly distributed. After being stretched by force, it gradually deflects uniformly in the direction of the acting force, the degree of orientation increases, and the lithium ions attached to the fiber also become directional, forming a long chain of lithium ions.

[0027] Since the structure of the material determines the electrical conductivity of the material, with the increase of the degree of orientation of the material, the electrical conductivity increases and the resistivity decreases. Therefore, after the fiber is drawn, the axial length increases and the transverse dimension shortens. The shortening of the lithium ion spacing makes the electrical conductivity of the fiber increase and the resistivity decrease.

[0028] The designed draw force range is 1.5 - 3.7 (cN / dtex) for a single filament, within the range of the fiber physical index. Too strong a draw force is likely to cause fiber breakage, and too small a draw force cannot achieve the effect of increasing the degree of orientation of the fiber. Under the drawing conditions, the fiber will have a certain elongation. The draw ratio is preferably 1:1.05 - 1.55. If the draw ratio is too small, the fiber is likely to rebound and the degree of orientation returns to the state before elongation; if the draw ratio is too large, the fiber breaks and the processing is difficult.

[0029] Preferably, in step S1, the etherification solution comprises the following components: 40-48 wt% of sodium chloroacetate, 27-40 wt% of alcohol, and the balance being distilled water; the eluate after etherification comprises the following components: alcohol ≥ 60 wt%, and the balance being distilled water; the neutralization solution comprises the following components: 1-4 wt% of acid, alcohol ≥ 60 wt%, and the balance being distilled water.

[0030] Preferably, in step S1, the specific preparation method of the sodium carboxymethyl cellulose fiber comprises the following steps:

[0031] Immerse the regenerated cellulose fiber in a 25-30 wt% sodium hydroxide solution for preliminary alkalization for 0.4-1.5 h, control the reaction temperature at 55-70 °C, then immerse it in the etherification solution for preliminary etherification for 0.2-0.8 h, and then control the reaction temperature at 55-70 °C to elute and remove the reaction by-products with an alcohol solution;

[0032] Subsequently, immerse it in a 25-30 wt% sodium hydroxide solution for re-alkalization for 0.4-1.5 h, control the reaction temperature at 55-70 °C, then immerse it in the etherification solution for re-etherification for 0.2-0.8 h, and then control the reaction temperature at 55-70 °C to elute and remove the reaction by-products with an alcohol solution, immerse it in the neutralization solution for neutralization, or repeat the steps of "alkalization-etherification-elution" and then immerse it in the neutralization solution for neutralization to obtain the sodium carboxymethyl cellulose fiber.

[0033] By adopting the above technical solution, based on the characteristics that cellulose has good alkali resistance and poor acid resistance, alkalization and etherification under the above conditions can keep the pH of the system well in the alkaline range, and neutralization treatment is carried out after all alkalization and etherification are completed, thereby effectively reducing the hydrolysis of cellulose. On this basis, the present invention uses sodium hydroxide for alkalization to reduce the entry of other impurities into the system, and elutes with an alcohol solution in time after preliminary alkalization and etherification. This alcohol solution can not only effectively elute and remove the reaction by-products, but also gradually reduce the alkalinity of the system, so that the fiber can maintain its shape well.

[0034] By strictly controlling the component dosages of the etherification solution, eluate and neutralization solution in the present invention, the interference of water in the reagent to the fiber morphology can be minimized.

[0035] Preferably, in step S2, the acid washing of the sodium carboxymethyl cellulose fiber is carried out in two times. After the first acid washing, it is eluted and then the second acid washing is carried out.

[0036] For the first acid washing, according to the mass ratio, the amount of the eluate is 10-20 times that of the fiber, and it is eluted until the sodium ion content of the dry fiber tested by atomic absorption spectrometry is < 2%.

[0037] For the second acid washing, according to the mass ratio, the amount of the eluate is 10-20 times that of the fiber, and it is eluted until the sodium ion content of the dry fiber tested by atomic absorption spectrometry is < 0.2%.

[0038] Preferably, in step S2, the sodium carboxymethyl cellulose fiber is immersed in an acidifying solution for pickling and sodium removal, and the soaking time is 0.5 - 28 h; the acidifying solution comprises the following components: 1 - 4 wt% of acid, 60 - 70 wt% of alcohol, and the balance is distilled water.

[0039] Preferably, in step S2, the acid in the acidifying solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, citric acid, acetic acid, and tartaric acid; the alcohol in the acidifying solution is one or more of ethanol, methanol, and isopropanol. The above alcohols can not only better maintain the fiber morphology of the carboxymethyl cellulose fiber, but also have the characteristics of low boiling point and good volatility, which is convenient for subsequent operations such as fiber drying.

[0040] Preferably, in step S2, the eluent after pickling of the sodium carboxymethyl cellulose fiber is a mixture of alcohol and distilled water, and the proportion of water in the eluent is ≤ 40 wt%. After pickling, the fiber forms negatively charged carboxymethyl cellulose fiber (H - CMC). The alcohol in the eluent can undergo a reversible esterification reaction with the carboxyl group on the carboxymethyl cellulose fiber, maintaining the molecular structure of the carboxymethyl cellulose fiber in a stable state to a certain extent. At the same time, under the action of the alcohol, the above eluent can also be effectively miscible with the acidifying solution, thereby having a good elution effect, eluting the excess acid and other impurities such as sodium salts in the system after the original reaction, and reducing the interference of impurities on the fiber.

[0041] By adopting the above technical solution, in the lithium salt substitution reaction, the sodium ions removed by pickling will combine with the anions in the pickling to form sodium salts. The sodium salts are easy to adhere to the fiber, which will not only affect the purity of the fiber, but also affect the substitution effect to a certain extent. Especially for the sodium carboxymethyl cellulose fiber after multiple alkalization and etherification, the substitution degree of sodium is relatively high. In the present invention, pickling is carried out in two steps. The first pickling mainly removes the sodium on the sodium carboxymethyl cellulose fiber, and then after elution, the removed sodium ions and the residual acid are removed, reducing the generation of sodium salts in the subsequent process; the second pickling can not only further elute the sodium ions that were not eluted in the first pickling, but also keep the system acidic, reducing the reverse combination of sodium ions with the fiber, and thus better carrying out the subsequent one - way substitution reaction and reducing the re - separation of lithium ions from lithium carboxymethyl cellulose.

[0042] In the actual operation process, if the acid content in the acidifying solution is too high, it is easy to cause excessive hydrolysis of the fiber, making it difficult to ensure the fibrous structure of the fiber. If the acid content is too low, it is difficult to effectively remove the "sodium" on the fiber. The acidifying solution obtained by combining 1 - 4 wt% of acid with 60 - 70 wt% of alcohol can not only effectively remove the "sodium", but also better maintain the fibrous structure, so the present invention further optimizes it.

[0043] Preferably, in step S3, the hydrogenated carboxymethyl cellulose fiber is immersed in a lithium salt solution for reaction, and the lithium salt solution comprises the following components: 2-5 wt% of a lithium-containing material, 55-79 wt% of an alcohol, and the balance being distilled water.

[0044] Preferably, in step S3, the lithium-containing material is selected from at least one of lithium chloride, lithium hydroxide, lithium oxide, lithium nitride, lithium carbide, lithium sulfide, lithium sulfate, lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, and lithium iron phosphate.

[0045] By adopting the above technical solution, the lithium salt can be better dispersed in the fiber in the form of a solution for reaction in the present invention. The hydrogenated carboxymethyl cellulose fiber can better maintain its fibrous form in the lithium salt solution under this formulation, promoting better binding of lithium to the fiber, and thus obtaining fibrous lithium carboxyhydroxycellulose fibers with excellent mechanical strength and orientation performance. The alcohol can be one or more of ethanol, methanol, and isopropanol. Keeping the alcohols in the above alcohol solution consistent with those in the acidifying solution has a better dispersion effect to promote the effective progress of the reaction.

[0046] Among them, the lithium-containing material in the lithium salt solution can be a water-soluble or alcohol-soluble lithium-containing substance, including but not limited to compounds, complexes, or mixtures composed of lithium hydrides, oxides, nitrides, sulfides, chlorides, hypochlorites, silicates, and other substances. After lithium hydrides, oxides, sulfides, etc. dissolve in the alcohol aqueous solution, they will react to form corresponding lithium ions, while lithium chlorides, hypochlorites, silicates, etc. will hydrolyze to produce lithium ions after dissolving in water. Therefore, the above lithium-containing materials can all effectively separate lithium ions and then participate in the substitution reaction of the fiber. Further preferably, lithium chloride, lithium hydroxide, lithium oxide, lithium nitride, lithium carbide, lithium sulfide, lithium sulfate, lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, and lithium iron phosphate all have good water solubility, and can reduce the generation of impurities compared with other lithium-containing materials, thereby obtaining lithium carboxymethyl cellulose fibers with more excellent mechanical strength.

[0047] Preferably, in step S1, the regenerated cellulose fiber is directly alkalized and etherified in a short fiber structure.

[0048] Preferably, in step S1, the regenerated cellulose fiber has a long fiber structure, and the sodium carboxymethyl cellulose fiber after alkalization and etherification is cut into a short fiber structure.

[0049] By adopting the above technical solution, the raw material used in the present invention is regenerated cellulose fiber, which already has a certain degree of orientation whether it is in the short fiber structure or the long fiber structure. Therefore, the fiber of the present invention can directly use regenerated cellulose fiber in the short fiber structure, or use regenerated cellulose fiber in the long fiber structure, which is alkalized and etherified and then cut into short fibers, or can be directly prepared into filaments in the long fiber structure. Among them, the degree of orientation in the above three cases increases in turn, and the performance of the lithium carboxymethyl cellulose fiber obtained thereby also gradually increases. In the present invention, the fiber length of the short fiber structure is further preferably 1 mm - 15 cm. If the fiber length is too small, it is difficult to maintain its fiber effect. If the fiber is too long, it is prone to entanglement, which is not convenient for subsequent weaving or non-woven operations and other processes or use.

[0050] Preferably, it further includes S5. After the lithium carboxymethyl cellulose rough fiber prepared in step S3 is oiled, dried, and packed, the finished lithium carboxymethyl cellulose fiber is obtained.

[0051] The application of the above high-substitution-degree lithium carboxymethyl cellulose fiber, which can be preferably applied to flexible energy devices, battery construction devices in various application occasions and scenarios, intelligent textiles, functional textiles, flexible electrodes, intelligent home appliances and other fields.

[0052] The modified high-substitution-degree carboxymethyl cellulose fiber is prepared by neutralizing the carboxymethyl cellulose sodium fiber obtained by subjecting the regenerated cellulose fiber to two or more "alkalization-etherification-elution" under the condition of always maintaining the cellulose in the fiber state. The fineness of the regenerated cellulose fiber is 0.3 - 3.5 dtex, and the substitution degree Ds of the carboxymethyl cellulose sodium fiber is > 0.55.

[0053] Preferably, the substitution degree of the carboxymethyl cellulose sodium fiber is 0.55 < Ds ≤ 3.0; the degree of orientation measured by the optical birefringence method is ≥ 0.45.

[0054] The preparation method of the above modified high-substitution-degree carboxymethyl cellulose fiber includes the following steps:

[0055] The regenerated cellulose fiber is immersed in a 25 - 30 wt% sodium hydroxide solution for preliminary alkalization for 0.4 - 1.5 h, the reaction temperature is controlled at 55 - 70 °C, then immersed in an etherification solution for preliminary etherification for 0.2 - 0.8 h, and the reaction temperature is controlled at 55 - 70 °C, and the reaction by-products are eluted and removed with an alcohol solution;

[0056] Subsequently, it is immersed in a 25-30 wt% sodium hydroxide solution for re-alkalization for 0.4-1.5 h, the reaction temperature is controlled at 55-70 °C, then immersed in an etherification solution for re-etherification for 0.2-0.8 h, and after that, the reaction temperature is controlled at 55-70 °C, and the reaction by-products are eluted and removed with an alcohol solution. It is immersed in a neutralization solution for neutralization, or after repeating the steps of "alkalization-etherification-elution", it is immersed in the neutralization solution for neutralization to obtain sodium carboxymethyl cellulose fiber.

[0057] The modified high-substitution-degree carboxymethyl cellulose fiber is prepared by neutralizing the sodium carboxymethyl cellulose fiber obtained by subjecting the regenerated cellulose fiber to two or more "alkalization-etherification-elution" processes that always maintain the cellulose in a fibrous state, and pickling to obtain hydrogenated carboxymethyl cellulose fiber;

[0058] The fineness of the regenerated cellulose fiber is 0.3-3.5 dtex, and the substitution degree Ds of the hydrogenated carboxymethyl cellulose fiber is >0.55.

[0059] Preferably, the substitution degree of the hydrogenated carboxymethyl cellulose fiber is 0.55 < Ds ≤ 3.0; the orientation degree measured by the optical birefringence method is ≥0.45.

[0060] The preparation method of the above-mentioned modified high-substitution-degree carboxymethyl cellulose fiber comprises the following steps:

[0061] S1. Using the regenerated cellulose fiber as the raw material, after two or more "alkalization-etherification-elution" processes and then neutralization, during the "alkalization-etherification-elution" process, the cellulose is always maintained in a fibrous state, and the pH of the reaction system is maintained >7 throughout the process to obtain sodium carboxymethyl cellulose fiber; the fineness of the regenerated cellulose fiber is preferably 0.3-3.5 dtex,

[0062] S2. After pickling and eluting the sodium carboxymethyl cellulose fiber prepared in S1, hydrogenated carboxymethyl cellulose fiber is obtained.

[0063] The present invention provides a modified high-substitution-degree carboxymethyl cellulose fiber, its preparation method and application. It has the following beneficial effects:

[0064] (1) The modified high-substitution-degree carboxymethyl cellulose fiber of the present invention, its preparation method and application overcome the problem that conventional high-substitution-degree lithium carboxymethyl cellulose is difficult to be prepared into fibers. Through two or more "alkalization-etherification-elution" operations, lithium carboxymethyl cellulose with a fiber form is prepared, making it have good mechanical strength and electrical conductivity to meet the processing requirements. Among them, the dry breaking strength is 1.46 - 4.02 cN / dtex, the wet breaking strength is 1.28 - 3.15 cN / dtex, the coefficient of variation Cv is 7.9 - 10.7, the substitution degree is Ds > 0.55, the fineness is 0.3 - 3.5 dtex, the orientation degree is ≥0.45, and the resistivity is 50 - 3000 Ω·m.

[0065] (2) Due to the certain spatial structure of the fiber, in the lithium salt fiber of high-substitution-degree carboxymethyl cellulose of the present invention, after the hydrogenated carboxymethyl cellulose fiber reacts with the lithium salt and then is drawn, the fibers originally distributed irregularly are gradually deflected uniformly in the direction of the acting force after being stressed and stretched, the orientation degree increases, and the lithium ions attached to the fibers also become directional, forming a long chain of lithium ions; the regularly arranged lithium ions increase the electrical conductivity of the lithium carboxymethyl cellulose fiber and better exert the conductive effect of lithium ions.

[0066] (3) When preparing the lithium carboxymethyl cellulose fiber of the present invention, the method of "two acid washes" is adopted, so that the harvested hydrogenated carboxymethyl cellulose fiber has less impurities and good stability. Combined with the component limitation of the acidifying solution and the eluting solution, the hydrogenated carboxymethyl cellulose fiber reacts fully with the lithium salt, further improving the mechanical strength and electrical conductivity of the lithium carboxymethyl cellulose fiber. Description of the Drawings

[0067] Figure 1 is the electron microscope image of the drawn lithium carboxymethyl cellulose fiber;

[0068] Figure 2 is the electron microscope image of the undrawn lithium carboxymethyl cellulose fiber. Detailed Embodiments

[0069] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0070] The high-substitution-degree lithium carboxymethyl cellulose fiber provided by the present invention uses existing fibers as materials. In order to better control the performance parameters of the fibers, the present invention mainly uses regenerated fibers as the initial raw materials. Through alkalization and etherification treatments, sodium carboxymethyl cellulose fibers can be obtained, and through pickling treatment, hydrogenated carboxymethyl cellulose fibers can be obtained. Then, the prepared hydrogenated carboxymethyl cellulose fibers are reacted with lithium salts to obtain crude lithium carboxymethyl cellulose fibers, and finally, oiling, drying, and packing are carried out according to needs to obtain the final product.

[0071] The above-mentioned regenerated fibers can be one or more of viscose fibers, cuprammonium fibers, tencel fibers, and modal fibers. They are widely sourced and low in cost, and can be directly purchased on the market, but the orientation degree index of commercially available regenerated cellulose fibers needs to be strictly controlled. Other raw materials of the present invention all adopt industrial production specifications, and the equipment and tools used are also general equipment in the spinning industry, which will not be further elaborated here.

[0072] Among them, the substitution degree and fineness of the fibers have a greater impact on the mechanical strength. The specific detection methods are as follows: ① Substitution degree

[0073] Detection of the substitution degree of sodium carboxymethyl cellulose fibers: Refer to the substitution degree test of sodium carboxymethyl cellulose in the Pharmacopoeia of the People's Republic of China (2020 Edition).

[0074] Detection of the substitution degree of lithium carboxymethyl cellulose fibers:

[0075] (1) Take lithium carboxymethyl cellulose fibers. When washing the lithium carboxymethyl cellulose sample, wash it with a hot ethanol solution at 60 °C and 90% (v / v) and dry it. Add an acid aqueous solution (nitric acid: distilled water = 1:2), and use an electric furnace to heat and digest completely;

[0076] (2) Transfer the uniform solution obtained after digestion into a 50 mL volumetric flask, make up the volume with high-purity water, and then take 0.5 mL of the solution and dilute and make up the volume in a 50 mL volumetric flask for use; in this step, a blank test can be carried out simultaneously to obtain a blank solution.

[0077] (3) Use an atomic absorption spectrometer to measure the mass percentage concentration C of lithium ions in the solution; the instrument measurement conditions are carried out according to the recommended conditions in Table 1 below:

[0078] Table 1 Recommended measurement conditions

[0079] Inspection wavelength nm 670 Flame type Air-acetylene Ratio Ratio Air:acetylene = 3 - 5:1 Air:acetylene = 3 - 5:1

[0080] When conducting the determination, the following steps are carried out: First, measure the absorbance of a series of standard solutions, plot the standard curve, then directly measure the absorbance of the sample solution and the blank solution, calculate the lithium element content of the sample solution and the blank solution, and then subtract the lithium element content of the blank solution from the lithium element content of the sample solution to obtain the mass percentage concentration of lithium ions, that is, the lithium content of lithium carboxymethyl cellulose.

[0081] After measuring the mass percentage concentration of lithium ions in the lithium carboxymethyl cellulose sample by using the above method for measuring the lithium content of lithium carboxymethyl cellulose, substitute it into the following equation for calculating the degree of substitution of the sample:

[0082]

[0083] In the formula: DS represents the degree of substitution of the sample; C represents the mass percentage concentration of lithium ions in the sample, expressed as a percentage (%).

[0084] ②Fineness: It is measured by a fineness tester.

[0085] The present invention will be further described in detail below in conjunction with the accompanying drawings, examples and comparative examples.

[0086] Example 1

[0087] The method for preparing lithium carboxymethyl cellulose fibers with a high degree of substitution of the present invention includes the following steps:

[0088] S1. Select 400,000 denier regenerated cellulose fibers - viscose fiber filaments with a single filament fineness of 1.33 dtex as raw materials. Immerse them in a sodium hydroxide solution with a concentration of 28 wt% at 65 °C for preliminary alkalization for 0.5 h, and then immerse them in an etherification solution. The etherification solution consists of 45 wt% sodium chloroacetate, 35 wt% ethanol, and 20 wt% distilled water. Etherify at 60 °C for 0.5 h. After the etherification is completed, elute and remove the reaction product with an alcohol solution. The alcohol solution consists of 70 wt% ethanol and 30 wt% distilled water; Subsequently, immerse them in a sodium hydroxide solution with a concentration of 28 wt% at 65 °C for re-alkalization for 0.5 h, and then immerse them in the same etherification solution at 60 °C for re-etherification for 0.5 h. After eluting and removing the reaction product with the same alcohol solution, immerse them in a neutralization solution for neutralization. The neutralization solution consists of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water; During the process of "alkalization - etherification - elution", maintain the pH of the reaction system > 7, harvest sodium carboxymethyl cellulose fibers, and the measured degree of substitution is 0.80;

[0089] S2. Immerse the sodium carboxymethyl cellulose fibers prepared in S1 into an elution container filled with an acidifying solution for primary acidification. The acidifying solution consists of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water, and soak for 12 h. Then, pass an eluent through the sodium carboxymethyl cellulose fibers after primary acidification for elution. The eluent consists of 65 wt% ethanol and 35 wt% distilled water. After the elution of the acidifying solution for primary acidification is complete, stop passing the eluent. The amount of eluent used is 15 times the mass of the fibers, and elute until the sodium ion content of the dry fibers tested by atomic absorption spectrometry is < 2%.

[0090] Immerse the sodium carboxymethyl cellulose fibers again into the same acidifying solution as for primary acidification for secondary acidification. After soaking in the acidifying solution for 12 h, pass the eluent through. The amount of eluent used is 15 times the mass of the fibers, and elute until the sodium ion content of the dry fibers tested by atomic absorption spectrometry is < 0.2%. After the eluent is completely replaced, the hydrogenated sodium carboxymethyl cellulose fibers are obtained.

[0091] S3. Take out the hydrogenated sodium carboxymethyl cellulose fibers prepared in S2 and immerse them into a lithium salt solution. The lithium salt solution consists of 3 wt% lithium chloride, 60 wt% ethanol, and 37 wt% distilled water. Under the condition of 90 °C, soak and react for 5 min. After soaking, perform drawing using a drawing roll, and the elongation ratio is 1:1.55 to obtain crude lithium carboxymethyl cellulose fibers.

[0092] S4. Oil, dry, and crimp the crude lithium carboxymethyl cellulose fibers prepared in S3, and then cut them into short fibers with a length of 3.8 cm. After packing, lithium carboxymethyl cellulose fibers with a substitution degree of 0.80 and a fineness of 1.15 dtex are obtained. The electron micrograph is shown in Figure 1 .

[0093] Example 2

[0094] The method for preparing high-substitution-degree lithium carboxymethyl cellulose fibers of the present invention includes the following steps:

[0095] S1. Select 400,000 denier regenerated cellulose fiber (cuprammonium fiber) filament bundles and fibers with a single fiber fineness of 0.5 dtex as raw materials. At 65 °C, immerse them in a sodium hydroxide solution with a concentration of 25 wt% for preliminary alkalization for 0.4 h, and then immerse them in an etherification solution. The etherification solution consists of 40 wt% sodium chloroacetate, 40 wt% ethanol, and 20 wt% distilled water. At 60 °C, the etherification time is 0.2 h. After the etherification is completed, elute and remove the reaction product with an alcohol solution. The alcohol solution consists of 60 wt% ethanol and 40 wt% distilled water. Subsequently, at 65 °C, immerse it in a sodium hydroxide solution with a concentration of 25 wt% for re-alkalization for 0.4 h. At 60 °C, immerse it in the same etherification solution again for etherification for 0.2 h. After eluting and removing the reaction product with the same alcohol solution, immerse it in a neutralization solution for neutralization. The neutralization solution consists of 1 wt% hydrochloric acid, 70 wt% ethanol, and 29 wt% distilled water. During the process of "alkalization - etherification - elution", maintain the pH of the reaction system > 7, and harvest sodium carboxymethyl cellulose fiber. After testing, the degree of substitution is 0.56.

[0096] S2. Immerse the sodium carboxymethyl cellulose fiber prepared in S1 in an elution container filled with an acidification solution for primary acidification. The acidification solution consists of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water, and soak for 12 h. Pass an elution solution through the sodium carboxymethyl cellulose fiber after primary acidification for elution. The elution solution consists of 65 wt% ethanol and 35 wt% distilled water. After the acidification solution for primary acidification is completely eluted, stop passing the elution solution. The amount of elution solution used is 10 times the mass of the fiber, and elute until the sodium ion content of the dry fiber tested by atomic absorption spectrometry < 2%.

[0097] Immerse the sodium carboxymethyl cellulose fiber again in the same acidification solution as the primary acidification for secondary acidification. After soaking in the acidification solution for 12 h, pass the elution solution through. The amount of elution solution used is 10 times the mass of the fiber, and elute until the sodium ion content of the dry fiber tested by atomic absorption spectrometry < 0.2%. After the elution solution is completely replaced, hydrogenated sodium carboxymethyl cellulose fiber is obtained.

[0098] S3. Take out the hydrogenated sodium carboxymethyl cellulose fiber prepared in S2 and immerse it in a lithium salt solution. The lithium salt solution consists of 3 wt% lithium chloride, 60 wt% ethanol, and 37 wt% distilled water. At 90 °C, soak and react for 5 min. After soaking, perform stretching with a stretching roller, and the elongation ratio is 1:1.55, and harvest thick lithium carboxymethyl cellulose fiber.

[0099] S4. Cut the thick lithium carboxymethyl cellulose fiber prepared in S3 into short fibers with a length of 3.8 cm after oiling, drying, and crimping, and pack and harvest lithium carboxymethyl cellulose fiber with a degree of substitution of 0.56 and a fineness of 0.42 dtex.

[0100] Example 3

[0101] The preparation method of lithium carboxymethyl cellulose fiber with high degree of substitution of the present invention comprises the following steps:

[0102] S1. Select a 400,000 denier regenerated cellulose fiber (tencel fiber) filament bundle with a single fiber fineness of 3.0 dtex as the raw material. Immerse it in a sodium hydroxide solution with a concentration of 30 wt% at 65 °C for preliminary alkalization for 1.0 h, and then immerse it in an etherification solution. The etherification solution is composed of 48 wt% sodium chloroacetate, 27 wt% ethanol, and 25 wt% distilled water. At 60 °C, the etherification time is 0.6 h. After the etherification is completed, elute and remove the reaction product with an alcohol solution. The alcohol solution is composed of 80 wt% ethanol and 20 wt% distilled water. Subsequently, immerse it in a sodium hydroxide solution with a concentration of 30 wt% at 65 °C for re-alkalization for 1.0 h. At 60 °C, immerse it in the same etherification solution again for etherification for 0.6 h. After eluting and removing the reaction product with the same alcohol solution, immerse it in a neutralization solution for neutralization. The neutralization solution is composed of 3 wt% hydrochloric acid, 70 wt% ethanol, and 27 wt% distilled water. During the process of "alkalization - etherification - elution", maintain the pH of the reaction system > 7, and harvest sodium carboxymethyl cellulose fiber. After detection, the degree of substitution is 2.8;

[0103] S2. Immerse the sodium carboxymethyl cellulose fiber prepared in S1 in an elution container filled with an acidifying solution for primary acidification. The acidifying solution is composed of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water, and soak for 12 h. Pass an elution solution into the sodium carboxymethyl cellulose fiber after primary acidification for elution. The elution solution is composed of 65 wt% ethanol and 35 wt% distilled water. After the acidifying solution of primary acidification is completely eluted, stop passing the elution solution. The amount of elution solution used is 20 times the mass of the fiber, and elute until the sodium ion content of the dry fiber tested by atomic absorption spectrometry < 2%;

[0104] Immerse the sodium carboxymethyl cellulose fiber in the same acidifying solution as the primary acidification for secondary acidification. After soaking in the acidifying solution for 12 h, pass an elution solution. The amount of elution solution used is 10 times the mass of the fiber, and elute until the sodium ion content of the dry fiber tested by atomic absorption spectrometry < 0.2%; After the elution solution is completely replaced, hydrogenated carboxymethyl cellulose fiber is obtained;

[0105] S3. Take out the hydrogenated carboxymethyl cellulose fiber prepared in S2 and immerse it in a lithium salt solution. The lithium salt solution is composed of 4 wt% lithium chloride, 60 wt% ethanol, and 36 wt% distilled water. At 90 °C, soak and react for 5 min. After soaking, perform stretching with a stretching roller, and the elongation ratio is 1:1.55, and harvest lithium carboxymethyl cellulose coarse fiber;

[0106] S4. Cut the lithium carboxymethyl cellulose thick fibers prepared in S3 into short fibers with a length of 3.8 cm after oiling, drying, and crimping, and pack and collect the lithium carboxymethyl cellulose fibers with a substitution degree of 2.8 and a fineness of 2.5 dtex.

[0107] Examples 4 - 6

[0108] Based on the method of Example 1, in Examples 4 - 6, the alkalization, etherification, and elution treatment parameters of the regenerated cellulose fibers in step S1 were adjusted respectively. For specific adjustments, refer to Table 2 below.

[0109] Table 2 Treatment parameter table of regenerated cellulose fibers in Example 1, Examples 4 - 6

[0110]

[0111] Examples 7 - 13

[0112] Based on the method of Example 1, in Examples 7 - 13, the components of the lithium salt solution in step S3 were adjusted. For specific adjustments, refer to Table 3 below.

[0113] Table 3 Composition table of lithium salt solutions in Example 1, Examples 7 - 13

[0114]

[0115] Example 14

[0116] Based on the method of Example 1, in this example, the regenerated cellulose fibers with a long fiber structure in step S1 were replaced with regenerated cellulose fibers with a short fiber structure of 3.8 cm in length, and the stretching operation in step S3 was omitted subsequently, obtaining lithium carboxymethyl cellulose fibers with a fineness of 1.15 dtex. The electron microscope photograph of the obtained lithium carboxymethyl cellulose fibers is as Figure 2 shown in the electron microscope image of the non - stretched lithium carboxymethyl cellulose fibers. Compared with the electron microscope image of the stretched lithium carboxymethyl cellulose fibers obtained in Example 1, it can be clearly seen that the overall external morphology of the stretched lithium carboxymethyl cellulose fibers is straightened and more regular and orderly, providing a more favorable morphology for improving the subsequent electrochemical performance.

[0117] Comparative Example 1

[0118] Commercially available lithium carboxymethyl cellulose powder was used, with a lithium content of 3 wt% and 1% wet viscosity: 26 mPa*S. Since this lithium carboxymethyl cellulose powder does not have a fiber morphology, it is impossible to directly conduct mechanical property detection tests related to fibers.

[0119] Comparative Example 2

[0120] This comparative example discloses a method for preparing lithium carboxymethyl cellulose fibers, which includes the following steps:

[0121] S1. Select a 400,000-denier regenerated cellulose fiber (viscose fiber) filament bundle with a single-filament fineness of 1.33 dtex as the raw material, immerse it in a sodium hydroxide solution with a concentration of 35 wt% for alkalization. Under the condition of 65 °C, the alkalization time is 1 h. After the alkalization is completed, filter out the sodium hydroxide solution; immerse it in an etherification solution, which is composed of 50 wt% sodium chloroacetate, 30 wt% ethanol, and 20 wt% distilled water. Under the condition of 60 °C, the etherification time is 1 h. After the etherification is completed, filter out the etherification solution to obtain sodium carboxymethyl cellulose fibers. After detection, the degree of substitution is 0.90;

[0122] S2. Immerse the sodium carboxymethyl cellulose fibers prepared in S1 in an elution container filled with an acidification solution for primary acidification. The acidification solution is composed of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water, and soak for 24 h; pass an elution solution into the sodium carboxymethyl cellulose fibers after primary acidification for elution. The elution solution is composed of 65 wt% ethanol and 35 wt% distilled water; when the acidification solution of the primary acidification is completely eluted, stop passing the elution solution. The amount of the elution solution used is 15 times the mass of the fibers, and elute until the sodium ion content of the dry fibers tested by atomic absorption spectrometry is < 2%;

[0123] Immerse the sodium carboxymethyl cellulose fibers again in the same acidification solution as the primary acidification for secondary acidification. After soaking in the acidification solution for 12 h, pass an elution solution. The amount of the elution solution used is 15 times the mass of the fibers, and elute until the sodium ion content of the dry fibers tested by atomic absorption spectrometry is < 0.2%; when the elution solution completely elutes the acidification solution, hydrogenated carboxymethyl cellulose fibers are obtained;

[0124] S3. Take out the hydrogenated carboxymethyl cellulose fibers prepared in S2 and immerse them in a lithium salt solution, which is composed of 3 wt% lithium chloride, 60 wt% ethanol, and 37 wt% distilled water. Under the condition of 90 °C, soak and react for 5 min. After soaking, use a draw roll for drawing, and the elongation ratio is 1:1.55 to obtain thick lithium carboxymethyl cellulose fibers;

[0125] S4. Oil, dry, and crimp the thick lithium carboxymethyl cellulose fibers prepared in S3, and then cut them into short fibers with a length of 3.8 cm. After packing, lithium carboxymethyl cellulose fibers with a degree of substitution of 0.40 and a fineness of 1.25 dtex are obtained.

[0126] Comparative Example 3

[0127] On the basis of Example 1, the difference lies in that in step S1, it is immersed in a sodium hydroxide solution with a concentration of 45 wt%, at 65 °C, initially alkalized for 0.5 h, and then immersed in an etherification solution. The etherification solution consists of 45 wt% sodium chloroacetate, 35 wt% ethanol, and 20 wt% distilled water. At 60 °C, the etherification time is 0.5 h. After the etherification is completed, the reaction product is eluted and removed with an alcohol solution. The alcohol solution consists of 70 wt% ethanol and 30 wt% distilled water; subsequently, at 65 °C, it is immersed in a sodium hydroxide solution with a concentration of 45 wt% and alkalized again for 0.5 h. At 60 °C, it is immersed in the same etherification solution as above and etherified again for 0.5 h. After the reaction product is eluted and removed with the same alcohol solution as above, it is immersed in a neutralization solution for neutralization. The neutralization solution consists of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water. During the process of "alkalization - etherification - elution", the pH of the reaction system is maintained > 7, and sodium carboxymethyl cellulose fibers are harvested. After detection, the degree of substitution is 1.0. Then, through the pickling in step S2 and immersion in a lithium salt solution in step S3, lithium carboxymethyl cellulose is prepared.

[0128] Comparative Example 4

[0129] On the basis of Example 1, the difference lies in that in step S1, it is immersed in an etherification solution. The etherification solution consists of 55 wt% sodium chloroacetate, 25 wt% ethanol, and 20 wt% distilled water. At 60 °C, the etherification time is 0.5 h. After the etherification is completed, the reaction product is eluted and removed with an alcohol solution. The alcohol solution consists of 70 wt% ethanol and 30 wt% distilled water; subsequently, it is immersed in a sodium hydroxide solution with a concentration of 28 wt% and alkalized again for 0.5 h. At 60 °C, it is immersed in the same etherification solution as above and etherified again for 0.5 h. After the reaction product is eluted and removed with the same alcohol solution as above, it is immersed in a neutralization solution for neutralization. The neutralization solution consists of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water. During the process of "alkalization - etherification - elution", the pH of the reaction system is maintained > 7, and sodium carboxymethyl cellulose fibers are harvested. After detection, the degree of substitution is 1.2. Then, through the pickling in step S2 and immersion in a lithium salt solution in step S3, lithium carboxymethyl cellulose is prepared.

[0130] Comparative Example 5

[0131] On the basis of Example 1, the difference lies in that the acidifying solution in step S2 is composed of 25 wt% hydrochloric acid, 53 wt% ethanol, and 22 wt% distilled water, and the soaking time is 12 h; an eluting solution is passed through the sodium carboxymethyl cellulose fiber after the first acidification for elution, and the eluting solution is composed of 65 wt% ethanol and 35 wt% distilled water; after the elution of the acidifying solution in the first acidification is complete, the passage of the eluting solution is stopped, and the sodium carboxymethyl cellulose fiber is immersed again in the same acidifying solution as in the first acidification for secondary acidification. After the acidifying solution is soaked for 12 h, the eluting solution is passed through. After the eluting solution is completely replaced, the hydrogenated carboxymethyl cellulose fiber is obtained. Then, it is immersed in a lithium salt solution through step S3 to obtain lithium carboxymethyl cellulose.

[0132] Performance detection test

[0133] 1. The performance of the products in the above examples and comparative examples was tested, and the inspection results are shown in Table 4 below. The inspection results are shown in Table 4 below, and the test methods are as follows:

[0134] The fiber orientation degree was measured by the optical birefringence method;

[0135] The detection methods for the fiber tensile properties and coefficient of variation refer to GB / T 14337-2022;

[0136] The fiber substitution degree was measured according to the above detection method;

[0137] For the determination method of lithium ion content, the flame photometry method was used. After the fiber was ashed, the lithium ions were sprayed into the flame, and the content of lithium ions was determined by detecting the intensity of the emitted light. After comparison, the content of lithium ions in the fiber was determined.

[0138] For the resistivity test method, a Seebeck coefficient measuring instrument was used. The resistance of the fiber was tested under the conditions of a moisture regain of 22% and room temperature vacuum. Take the lithium carboxymethyl cellulose fiber prepared above and twist it at a twist of 150 r / m. The twisted sample was fixed in the test vacuum device, and the two electrodes were in close contact with both ends of the sample respectively to ensure good contact. The effective test length of the sample was accurately controlled within 25 mm ± 1 mm. Adjust the parameters such as the frequency of the resistance meter and the measuring voltage. After the frequency range and various measuring parameters were adjusted, the resistance value was read.

[0139] Table 4 Performance test data table

[0140]

[0141] Examples 1 to 3 used different regenerated cellulose fibers as raw materials. From the detection results, it can be obtained that corresponding lithium carboxymethyl cellulose fibers can be obtained by using the preparation method of the present invention for different regenerated cellulose fibers.

[0142] Combined with the test results of Examples 5-7, it can be obtained that the neutralization operation after "alkalization-etherification-elution" for two or more times, the composition and alkalization time of the alkalization solution, and the composition and etherification time of the etherification solution will all have a certain impact on the substitution degree of carboxymethyl cellulose. Preferably, the regenerated cellulose fiber is immersed in a 25-30 wt% sodium hydroxide solution for preliminary alkalization for 0.4-1.5 h, the reaction temperature is controlled at 55-70 °C, and then immersed in the etherification solution for preliminary etherification for 0.2-0.8 h, and the reaction temperature is controlled at 55-70 °C, and the reaction by-products are eluted and removed with an alcohol solution; then immersed in a 25-30 wt% sodium hydroxide solution for re-alkalization for 0.4-1.5 h, the reaction temperature is controlled at 55-70 °C, and then immersed in the etherification solution for re-etherification for 0.2-0.8 h, and the reaction temperature is controlled at 55-70 °C, and the reaction by-products are eluted and removed with an alcohol solution, and then immersed in the neutralization solution for neutralization or repeated "alkalization-etherification-elution" steps and then immersed in the neutralization solution for neutralization to obtain carboxymethyl cellulose sodium fiber.

[0143] Referring to the test results of Example 1 and Examples 8-13, it can be obtained that in the present invention, the hydrogenated carboxymethyl cellulose fiber is immersed in a lithium salt solution for reaction, and it is further defined that the lithium salt solution includes the following components: 2-5 wt% lithium-containing material, 55-79 wt% alcohol, and the balance is distilled water, which can further convert the carboxylic acid of the carboxymethyl cellulose fiber into lithium carboxylate, and at the same time better maintain the integrity of the fiber, so that the prepared lithium carboxymethyl cellulose fiber has more excellent mechanical strength.

[0144] Comparative Example 1, commercially available lithium carboxymethyl cellulose powder, because it is in powder form, cannot be tested by samples in fiber form.

[0145] Comparative Example 2, prepared by one-time alkalization and etherification, although it also has a high substitution degree, but due to the use of high-concentration alkalizing agent and etherifying agent, the fiber is severely degraded and the fiber form cannot be maintained.

[0146] Comparative Examples 3, 4, and 5, excessive alkalizing agent, etherifying agent, and acidifying solution cause severe degradation of the fiber and the fiber form cannot be maintained.

[0147] Referring to the test results of Example 14, it can be obtained that the length and shape of the regenerated cellulose fiber of the present invention and whether the subsequent fiber is drawn will all have a certain impact on the orientation degree and resistance performance of the fiber. The fiber of the present invention can directly adopt the regenerated cellulose fiber with a short fiber structure.

[0148] When in step S4, the draw elongation ratio is 1:1.05 - 1.55, it is prepared from regenerated cellulose fibers with a long fiber structure. Since the fibers are obtained by treating in fiber form, the prepared lithium carboxymethyl cellulose fibers with a high degree of substitution simultaneously have excellent mechanical properties and electrical properties, significantly expanding their application scope.

[0149] In particular, from the comparison data between Example 14 and Example 1, in step S4, for the electrical properties of lithium carboxymethyl cellulose fibers with and without drawing, the resistivity of the drawn fibers in Example 1 is 350 Ω·m, and the resistivity of the non-drawn fibers in Example 14 is 2750 Ω·m, fully demonstrating that before drawing, in the lithium salt solution, the negatively charged carboxymethyl cellulose fibers (H-CMC) combine with lithium ions (Li + ) to form lithium carboxymethyl cellulose. During the combination process, the lithium ions diffuse disorderly and penetrate into the carboxymethyl cellulose fibers covered with carboxyl groups to form lithium carboxymethyl cellulose fibers. The lithium ions are extremely unevenly dispersed and disorderly in the fibers.

[0150] After immersing the hydrogenated carboxymethyl cellulose fibers in the lithium salt solution and then drawing, the originally randomly distributed drawn fibers gradually deflect uniformly in the direction of the acting force after being stretched, the degree of orientation increases, and the lithium ions attached to the fibers also become directional, forming a long chain of lithium ions, realizing the orderly fixation of lithium ions. And since the structure of the material determines the electrical conductivity of the material, with the increase of the degree of orientation of the material, the conductivity increases and the resistivity decreases. Therefore, after the fibers are drawn, the axial length increases and the lateral dimension shortens, and the shortening of the lithium ion spacing makes the conductivity of the fibers increase and the resistivity decrease.

[0151] The designed draw force range is 1.5 - 3.7 (cN / dtex) for a single filament, within the range of the fiber physical index. Too strong a draw force is likely to cause fiber breakage, and too small a draw force cannot achieve the effect of increasing the degree of orientation of the fibers. Under the drawing conditions, the fibers will have a certain elongation, and the elongation ratio is preferably 1:1.05 - 1.55. If the elongation ratio is too small, the fibers are prone to spring back and the degree of orientation returns to the state before elongation; if the elongation ratio is too large, the fibers break and the processing is difficult.

[0152] The crude lithium carboxymethyl cellulose obtained in step S3 of the present invention can be directly cut, then oiled, dried, crimped, and packed to obtain the final lithium carboxymethyl cellulose fibers. The length of the cut fibers is preferably ≥1 mm, and the length of the cut short fibers can be adjusted according to needs at this time.

[0153] The raw material of Example 1 (ordinary viscose fiber), after the above tests, according to the degree of substitution test, has no substitution, no lithium ions after ashing, and the resistance value can reach 10 9 levels. Therefore, it does not have the excellent electrical properties of lithium carboxymethyl cellulose fibers.

[0154] Application Example

[0155] The lithium carboxymethyl cellulose fibers prepared in Examples 1-14 of the present invention can be applied to fields including but not limited to: flexible energy devices, battery construction devices for various applications and scenarios, smart textiles, functional textiles, flexible electrodes, smart home appliances. Specifically, they can be made into flexible conductive films, fabrics, negative electrode sheets, etc. according to needs.

[0156] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

[0157] As mentioned above, the above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A modified high-substituted carboxymethyl cellulose fiber, characterized in that: The regenerated cellulose fiber is subjected to "alkalization-etherification-elution" for two or more times under the condition that the cellulose is always in the fiber state, and then neutralized to obtain sodium carboxymethyl cellulose fiber, and the hydrogenated carboxymethyl cellulose fiber is obtained by acid washing, and then subjected to substitution reaction with a lithium salt solution to obtain high-substituted lithium carboxymethyl cellulose fiber; The fineness of the regenerated cellulose fiber is 0.3-3.5 dtex, and the degree of substitution Ds of the carboxymethyl cellulose lithium fiber is greater than 0.

55.

2. The modified high-substituted carboxymethyl cellulose fiber according to claim 1, characterized in that: The substitution degree of the carboxymethyl cellulose lithium fiber is 0.55<Ds≤3.0; the orientation degree measured by the optical birefringence method is ≥0.

45.

3. The method for preparing the modified high-substituted carboxymethyl cellulose fiber according to claim 1 or 2, characterized in that: The following steps are involved: S1. Regenerated cellulose fiber is used as raw material, and neutralized after two or more "alkalization-etherification-elution", wherein the cellulose is always kept in a fiber state during the "alkalization-etherification-elution" process, and the pH of the reaction system is maintained at > 7 during the whole process, to obtain sodium carboxymethyl cellulose fiber; the fineness of the regenerated cellulose fiber is preferably 0.3-3.5 dtex; S2, acid-washing and eluting the sodium carboxymethyl cellulose fiber prepared in S1 to obtain hydrogenated carboxymethyl cellulose fiber; S3, reacting the hydrogenated carboxymethyl cellulose fiber obtained in S2 with a lithium salt solution to obtain crude carboxymethyl cellulose lithium fibers; the degree of substitution of the hydrogenated carboxymethyl cellulose fiber is 0.55<Ds≤3.

0.

4. The method for preparing modified high-substituted carboxymethyl cellulose fiber according to claim 3, characterized in that: In step S3, the hydrogenated carboxymethyl cellulose fiber is immersed in a lithium salt solution for reaction, wherein the lithium salt solution comprises the following components: 2-5 wt% lithium-containing material, 55-79 wt% alcohol, and the remainder is distilled water; The lithium-containing material is selected from at least one of lithium chloride, lithium hydroxide, lithium oxide, lithium nitride, lithium carbide, lithium sulfide, lithium sulfate, lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, and lithium iron phosphate; In step S1, the regenerated cellulose fiber can be directly subjected to alkalization and etherification treatment using a short fiber structure; or the regenerated cellulose fiber can be subjected to alkalization and etherification treatment using a long fiber structure; When the regenerated cellulose fiber adopts a long fiber structure in step S1, the method further includes step S4, in which the crude carboxymethyl cellulose lithium fiber obtained by reacting the hydrogenated carboxymethyl cellulose fiber with the lithium salt in step S3 is stretched to obtain carboxymethyl cellulose lithium fiber; the stretching ratio is 1:1.05-1.

55.

5. The method for preparing modified high-substituted carboxymethyl cellulose fiber according to claim 4, characterized in that: In step S1, the etherification liquid comprises the following components: 40-48wt% sodium chloroacetate, 27-40wt% alcohol, and the remainder is distilled water; the etherified eluent comprises the following components: Alcohol ≥ 60wt%, the balance is distilled water; the neutralization solution comprises the following components: acid 1-4wt%, alcohol ≥ 60wt%, the balance is distilled water; In step S1, the specific preparation method of the sodium carboxymethyl cellulose fiber comprises the following steps: immersing the regenerated cellulose fiber in a 25-30wt% sodium hydroxide solution for preliminary alkalization for 0.4-1.5h, then immersing the regenerated cellulose fiber in an etherification solution for preliminary etherification for 0.2-0.8h, and then eluting the reaction by-products with an alcohol solution; then immersing the regenerated cellulose fiber in a 25-30wt% sodium hydroxide solution for alkalization again for 0.4-1.5h, then immersing the regenerated cellulose fiber in an etherification solution for etherification again for 0.2-0.8h, and then eluting the reaction by-products with an alcohol solution, immersing the regenerated cellulose fiber in a neutralization solution for neutralization, or repeating the "alkalization-etherification-elution" steps and then immersing the regenerated cellulose fiber in a neutralization solution for neutralization, to obtain the sodium carboxymethyl cellulose fiber.

6. The method for preparing modified high-substituted carboxymethyl cellulose fiber according to claim 3, characterized in that: In step S2, the acid washing of the sodium carboxymethyl cellulose fiber is carried out twice, and after the first acid washing, the fiber is eluted and then subjected to the second acid washing; For the first acid wash, the amount of eluent is 10 to 20 times that of the fiber according to the mass ratio, and the dry fiber is eluted until the sodium ion content is less than 2% when tested by atomic absorption spectrometry; The second acid wash, according to the mass ratio, the amount of eluent is 10 to 20 times that of the fiber, eluted until the dry fiber is tested by atomic absorption spectrometry, the sodium ion content is less than 0.2%; In step S2, the sodium carboxymethyl cellulose fiber is immersed in an acidifying solution for acid elution and sodium removal, and the immersion time is 0.5-28 hours; the acidifying solution comprises the following components: 1-4wt% acid, 60-70wt% alcohol, and the balance is distilled water; In step S2, the acid in the acidified solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, citric acid, acetic acid and tartaric acid; the alcohol in the acidified solution is one or more of ethanol, methanol and isopropanol; In step S2, the eluent of the sodium carboxymethyl cellulose fiber after acid washing is a mixture of alcohol and distilled water, and the proportion of water in the eluent is ≤40wt%.

7. A modified high-substituted carboxymethyl cellulose fiber, characterized in that: The sodium carboxymethyl cellulose fiber is prepared by neutralizing the regenerated cellulose fiber after the regeneration cellulose fiber is subjected to the "alkalization-etherification-elution" process for two or more times while the cellulose fiber is always kept in a fiber state. The fineness of the regenerated cellulose fiber is 0.3-3.5 dtex, the degree of substitution of the sodium carboxymethyl cellulose fiber is Ds>0.55; the degree of substitution of the sodium carboxymethyl cellulose fiber is 0.55<Ds≤3.0; and the degree of orientation measured by the optical birefringence method is ≥0.

45.

8. The method for preparing modified high-substituted carboxymethyl cellulose fiber according to claim 7, characterized in that: The steps include: The regenerated cellulose fiber is immersed in a 25-30wt% sodium hydroxide solution for preliminary alkalization for 0.4-1.5h, then immersed in an etherification solution for preliminary etherification for 0.2-0.8h, and then the reaction by-products are eluted and removed with an alcohol solution; then immersed in a 25-30wt% sodium hydroxide solution for alkalization again for 0.4-1.5h, then immersed in an etherification solution for etherification again for 0.2-0.8h, and then the reaction by-products are eluted and removed with an alcohol solution, immersed in a neutralization solution for neutralization or repeating the "alkalization-etherification-elution" steps and then immersed in a neutralization solution for neutralization to obtain sodium carboxymethyl cellulose fiber.

9. A modified high-substituted carboxymethyl cellulose fiber, characterized in that: The regenerated cellulose fiber is subjected to two or more "alkalization-etherification-elution" processes to keep the cellulose in a fibrous state, followed by neutralization to obtain sodium carboxymethyl cellulose fiber, and acid washing to obtain hydrogenated carboxymethyl cellulose fiber; The fineness of the regenerated cellulose fiber is 0.3-3.5 dtex, the degree of substitution of the hydrogenated carboxymethyl cellulose fiber is Ds>0.55; the degree of substitution of the hydrogenated carboxymethyl cellulose fiber is 0.55<Ds≤3.0; and the degree of orientation measured by an optical birefringence method is ≥0.

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10. The method for preparing modified high-substituted carboxymethyl cellulose fiber according to claim 9, characterized in that: The steps include: S1. Regenerated cellulose fiber is used as raw material, and after two or more "alkalization-etherification-elution" processes, the cellulose is neutralized, and the cellulose is always kept in a fiber state during the "alkalization-etherification-elution" process, and the pH of the reaction system is maintained at > 7 during the whole process, to obtain sodium carboxymethyl cellulose fiber; the fineness of the regenerated cellulose fiber is preferably 0.3-3.5 dtex, S2. The sodium carboxymethyl cellulose fiber prepared in S1 is acid-washed and eluted to obtain hydrogenated carboxymethyl cellulose fiber.

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