Modified carboxymethyl cellulose fiber having high degree of substitution, and preparation method therefor and use thereof

Abstract

The present invention belongs to the technical field of the modification and preparation of fibers. Disclosed are a modified carboxymethyl cellulose fiber having a high degree of substitution, and a preparation method therefor and the use thereof. The present invention solves the technical problem in the prior art of conventional carboxymethyl cellulose products having a high degree of substitution being difficult to form into filaments. The modified carboxymethyl cellulose fiber having a high degree of substitution in the present invention is obtained by subjecting regenerated cellulose fibers to two or more cycles of "alkalization to etherification to washing", followed by neutralization, acid washing, and a substitution reaction with a lithium salt. The degree of substitution Ds of the lithium carboxymethyl cellulose fiber is greater than 0.55. By means of the preparation of lithium carboxymethyl cellulose having a fibrous morphology and a high degree of substitution, not only can good electrical conductivity of lithium carboxymethyl cellulose be effectively exerted, but the prepared fiber also exhibits high mechanical strength and has good application prospects.

Description

A modified high-substitution degree carboxymethyl cellulose fiber, its preparation method and application Technical Field

[0001] This invention relates to the field of fiber modification technology, specifically to a modified high-substitution degree carboxymethyl cellulose fiber, its preparation method, and its applications. Background Technology

[0002] Cellulose is a long-chain natural polymer formed by the dehydration of D-glucose monomers linked by β-1,4-glucosidic bonds. Each glucose ring in the cellulose macromolecule contains three hydroxyl groups: a primary hydroxyl group on the sixth carbon atom and secondary hydroxyl groups on the second and third carbon atoms. Hydrogen atoms in the hydroxyl groups are replaced by hydrocarbon groups to form cellulose ether derivatives.

[0003] In existing technologies, it is difficult to prepare commercially available carboxymethyl cellulose with a high degree of substitution. For example, with a ratio of m(cotton linters):m(NaOH):m(ClCH2COOH) = 1.0:1.1:1.2, using 95% ethanol as the dispersion medium and an etherification time of 1.5 min, the degree of substitution of the resulting product is only 0.7384. However, some commercially available carboxymethyl cellulose products have strict requirements for high substitution degrees. To improve the degree of substitution, methods such as increasing the amount of alkalizing and etherifying agents, extending the reaction time, and increasing the reaction temperature are commonly employed. However, prolonged high-temperature reaction conditions and large amounts of alkalizing and etherifying agents can cause cellulose degradation, resulting in a sharp decline in the physical properties of the product.

[0004] Lithium carboxymethyl cellulose (LCC) is increasingly being used in energy devices due to its natural biodegradability, renewability, and excellent conductivity. LCC offers significant advantages in battery applications such as film formation, electrolyte dispersion, and textile molding. To further improve its electrical performance per unit volume and energy storage capacity, LCC requires a higher degree of substitution.

[0005] Existing invention patents, such as CN112724266A and CN102206286A, disclose methods for preparing lithium carboxymethyl cellulose, which can produce lithium carboxymethyl cellulose with relatively high substitution degrees. However, the aforementioned methods for preparing lithium carboxymethyl cellulose with high substitution degrees are difficult to apply to the production of lithium carboxymethyl cellulose fibers. It mainly exists in powder form and requires a solvent as a carrier for subsequent use. This hinders the effective utilization of the excellent properties of lithium carboxymethyl cellulose. Summary of the Invention

[0006] This invention addresses the shortcomings and deficiencies of existing technologies by providing a modified high-substituted carboxymethyl cellulose fiber that overcomes the difficulty of forming conventional high-substituted carboxymethyl cellulose into fibers. This modified fiber not only effectively utilizes the excellent electrical conductivity of carboxymethyl cellulose but also possesses high mechanical strength and promising application prospects. The invention also includes its preparation method and applications.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: The modified high-substitution degree carboxymethyl cellulose fiber provided by the present invention is obtained by neutralizing regenerated cellulose fiber after two or more "alkalization-etherification-elution" processes under the condition that the cellulose is always kept in the cellulose state, obtaining sodium carboxymethyl cellulose fiber, obtaining hydrogenated carboxymethyl cellulose fiber by acid washing, and then undergoing a substitution reaction with lithium salt solution to obtain lithium high-substitution degree carboxymethyl cellulose fiber.

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

[0009] Due to the large difference between the fiber and powder states, the high-substituted carboxymethyl cellulose lithium fiber of the present invention, compared with the carboxymethyl cellulose lithium powder prepared in the prior art, except for having the same chemical composition elements, has longitudinal and transverse characteristics of the fiber state itself, which ultimately achieves synergistic effect between structure and composition, significantly improving the electrical and mechanical properties of the fiber.

[0010] The dispersion properties of fibers in water or other liquid media are a major factor affecting the quality of fiber dispersions or other wet-spun fiber materials. The inventors have found that if the substitution is too low, although fibers can be produced, the lithium content in the fibers is too low, and the resulting fibers still cannot effectively exert the role of "lithium"; if the substitution is too high, it is difficult to maintain the fiber structure.

[0011] To further address the challenge of maintaining the fiber structure with high substitution degrees, this invention, through extensive experimental research, reveals that the preparation mechanism of lithium carboxymethyl cellulose fiber primarily involves the exchange of sodium and hydrogen ions from sodium and hydrogen carboxymethyl cellulose with lithium ions. This ion exchange does not involve a change in the degree of substitution. Therefore, the necessary condition for the degree of substitution of lithium carboxymethyl cellulose fiber is determined by the process products sodium or hydrogen carboxymethyl cellulose. That is, the degree of substitution of lithium carboxymethyl cellulose cannot exceed the degree of substitution of sodium or hydrogen carboxymethyl cellulose. Clearly, to increase the degree of substitution of lithium carboxymethyl cellulose fiber, the degree of substitution of sodium or hydrogen carboxymethyl cellulose must be increased.

[0012] The aforementioned modified highly substituted sodium carboxymethyl cellulose or hydrogen carboxymethyl cellulose also suffer from the problem of difficulty in maintaining the fiber structure. To address this, the present invention uses regenerated cellulose fibers that undergo two or more "alkalization-etherification-elution" processes followed by neutralization to obtain sodium carboxymethyl cellulose fibers with a high degree of substitution. Subsequently, acidification is used to obtain hydrogenated carboxymethyl cellulose fibers with a high degree of substitution. Finally, lithium carboxymethyl cellulose fibers with a degree of substitution Ds > 0.55 are prepared through a substitution reaction. These fibers not only have a fibrous structure but also maintain a certain mechanical strength. They do not require a carrier and have a certain degree of plasticity. They are environmentally friendly, easy to process, and can be better applied to the production of flexible energy devices, smart textiles, functional textiles, and other products, allowing the excellent properties of lithium carboxymethyl cellulose to be effectively utilized.

[0013] Preferably, the degree of substitution of the carboxymethyl cellulose lithium fiber is 0.55 < Ds ≤ 3.0; the degree of orientation, measured by optical birefringence, is ≥ 0.45. By adopting the above technical solution, the present invention further limits the degree of substitution, fineness, and orientation, thereby producing fibers with better mechanical strength and superior spinnability. Specifically, the degree of orientation reflects the orientation of the cellulose polymer chains along the fiber axis. In the fibers of the present invention, since lithium ions occupy a certain space after being fixed on the carboxyl groups of carboxymethyl cellulose, further limiting the fiber orientation ensures that the lithium ions are arranged in an orderly manner in a specific direction, resulting in fibers with superior mechanical and electrical properties.

[0014] Preferably, it includes the following steps:

[0015] S1. Using regenerated cellulose fiber as raw material, after two or more "alkalization-etherification-elution" processes, neutralization is performed. During the "alkalization-etherification-elution" process, the cellulose is 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 preferred fineness of the regenerated cellulose fiber is 0.3-3.5 dtex.

[0016] S2. The sodium carboxymethyl cellulose fiber prepared in S1 is acid-washed and eluted to obtain hydrogenated carboxymethyl cellulose fiber.

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

[0018] By adopting the above technical solution, regenerated cellulose fiber refers to fiber made from natural cellulose substances, such as viscose fiber, cupro fiber, Tencel fiber, and Modal fiber. This invention uses regenerated cellulose fiber as raw material, which, compared to natural fibers, has the advantage of fiber orientation, making the solid electrolyte effect more controllable. Furthermore, regenerated fibers are widely available, low in cost, and can improve resource utilization to a certain extent, making them more suitable for industrial-scale sustainable development.

[0019] The regenerated cellulose fiber of the present invention can undergo a gradual substitution reaction by undergoing two or more "alkalization-etherification-elution" processes under alkaline conditions. This avoids high concentrations of alkalizing agents and etherifying agents, as well as excessively high reaction temperatures, thereby reducing the generation of by-products and the impact of the etherification reaction on fiber properties. As a result, sodium carboxymethyl cellulose fiber with a high degree of substitution and good fiber morphology can be prepared.

[0020] Based on this, sodium ions are removed from sodium carboxymethyl cellulose fibers by acid washing. Utilizing the reaction between lithium ions and carboxylic acids to form lithium carboxylate salts, the carboxyl groups on the carboxymethyl cellulose fibers, while maintaining the fiber structure, can react with lithium ions to form fibrous lithium carboxymethyl cellulose. It is important to note that the degree of substitution of sodium carboxymethyl cellulose obtained through alkalization and etherification refers to the carboxymethyl substitution of the hydroxyl hydrogen in the basic unit of cellulose. The resulting carboxymethyl cellulose, sodium carboxymethyl cellulose, and the carboxymethyl cellulose and lithium carboxymethyl cellulose produced by further acid washing and lithium salt reaction all have the same degree of substitution.

[0021] The above preparation method has simple steps and controllable conditions. It can not only harvest fibrous lithium carboxymethyl cellulose, but the prepared lithium carboxymethyl cellulose fibers also have good mechanical strength.

[0022] By adopting the above technical solution, the fineness of the fiber determines its specific surface area. 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 reactivity. If the regenerated cellulose fiber is too coarse, the subsequent alkalization, etherification, acid washing, and carboxylic acid binding with lithium ions will not be complete, and the fiber will lack carboxyl groups that can react with lithium ions. If the regenerated cellulose fiber is too fine, the fiber strength will weaken as the degree of substitution of carboxylic acid increases during the reaction, and the fiber will be prone to breakage. Since the raw materials need to maintain their fiber form throughout the entire preparation process, this invention requires strict control of the fineness of the raw material fiber when selecting regenerated cellulose fiber, preferably 0.3-3.5 dtex, which can indirectly control the fineness of the final 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, this 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 alkaline etherification reaction of this invention, and obtain lithium carboxymethyl cellulose fiber with both high mechanical strength and high electrical conductivity.

[0024] Preferably, the process also includes step S4, where, in step S1, when the regenerated cellulose fiber adopts a long fiber structure, the hydrogenated carboxymethyl cellulose fiber and the carboxymethyl cellulose lithium coarse fiber after the reaction of lithium salt in step S3 are stretched to obtain carboxymethyl cellulose lithium fiber.

[0025] Preferably, in step S4, the elongation ratio of the drawn fibers is 1:1.05-1.55. The regenerated cellulose fiber is prepared using a long-fiber structure. Since this fiber is obtained through fibrous morphology processing, the lithium carboxymethyl cellulose crude fiber obtained in step S3 can be directly cut, oiled, dried, crimped, and packaged to harvest the final lithium carboxymethyl cellulose fiber. The cut length of this fiber should preferably be ≥1 mm, and the length of the cut short fibers can be adjusted as needed.

[0026] However, in lithium salt solutions, negatively charged carboxymethyl cellulose fibers (H-CMC) react with lithium ions (Li... + The lithium ions combine to form lithium carboxymethyl cellulose. During this process, the lithium ions diffuse randomly and penetrate into the carboxymethyl cellulose fibers, which are covered with carboxyl groups, forming lithium carboxymethyl cellulose fibers. The lithium ions are extremely unevenly and randomly dispersed in the fibers. Therefore, in order to fix the lithium ions, the hydrogenated carboxymethyl cellulose fibers are immersed in a lithium salt solution and then stretched. The fibers, which are originally randomly distributed, gradually deflect uniformly in the direction of the force after being stretched, increasing the orientation. The lithium ions attached to the fibers also become directional, forming long chains of lithium ions.

[0027] Since the structure of a material determines its electrical conductivity, conductivity increases and resistivity decreases with increasing material orientation. Therefore, when fibers are stretched, their axial elongation and transverse dimension shorten, resulting in a reduction in lithium-ion spacing, which in turn increases the fiber's conductivity and decreases its resistivity.

[0028] The design draw force range is 1.5-3.7 (cN / dtex) of the monofilament. Within this range of fiber physical properties, excessive draw force can easily lead to fiber breakage, while insufficient force will not achieve the desired effect of increasing fiber orientation. Under draw conditions, the fiber will elongate to a certain extent, with an elongation ratio preferably between 1:1.05 and 1.55. If the elongation ratio is too small, the fiber is prone to springback, and the orientation will revert to its pre-elongation state; if the elongation ratio is too large, the fiber will break, making processing difficult.

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

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

[0031] The regenerated cellulose fibers are first pre-alkalized in a 25-30 wt% sodium hydroxide solution for 0.4-1.5 h, with the reaction temperature controlled at 55-70℃. Then, they are first pre-etherified in an etherification solution for 0.2-0.8 h, with the reaction temperature controlled at 55-70℃. The reaction byproducts are then removed by elution with an alcohol solution.

[0032] Subsequently, it is immersed in 25-30 wt% sodium hydroxide solution for alkalization again for 0.4-1.5 h, with the reaction temperature controlled at 55-70℃. Then, it is immersed in etherification solution for etherification again for 0.2-0.8 h, with the reaction temperature controlled at 55-70℃. The reaction byproducts are eluted with alcohol solution and then neutralized by immersion in neutralization solution, or the "alkalization-etherification-elution" steps are repeated before immersion in neutralization solution for neutralization to obtain sodium carboxymethyl cellulose fiber.

[0033] By adopting the above technical solution, based on the characteristics of cellulose's good alkali resistance and poor acid resistance, alkalization and etherification under the above conditions can maintain the pH of the system at an alkaline level. Neutralization is then performed after all alkalization and etherification are completed, thereby effectively reducing cellulose hydrolysis. Furthermore, the use of sodium hydroxide for alkalization in this invention reduces the entry of other impurities into the system. Eluenting with an alcohol solution promptly after preliminary alkalization and etherification not only effectively removes reaction byproducts but also gradually reduces the alkalinity of the system, allowing the fiber to maintain its morphology better.

[0034] This invention, by strictly controlling the amounts of components in the etherification solution, elution solution, and neutralization solution, can minimize the interference of water in the reagents on fiber morphology.

[0035] Preferably, in step S2, the acid washing of the sodium carboxymethyl cellulose fiber is performed in two stages. After the first acid washing, the fiber is eluted before the second acid washing.

[0036] For the first acid wash, the eluent volume should be 10-20 times the fiber volume by mass. Eluent is continued until the dry fiber content, as determined by atomic absorption spectrometry, is <2%.

[0037] For the second acid wash, the eluent volume is 10 to 20 times the fiber volume, and the fibers are eluted until the sodium ion content is <0.2% when tested by atomic absorption spectrometry.

[0038] Preferably, in step S2, the sodium carboxymethyl cellulose fiber is immersed in an acidification solution for acid elution to remove sodium, and the immersion time is 0.5-28 h; the acidification solution includes the following components: 1-4 wt% acid, 60-70 wt% alcohol, and the balance being distilled water.

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

[0040] Preferably, in step S2, the eluent after acid washing of the sodium carboxymethyl cellulose fiber is a mixture of alcohol and distilled water, with the water content in the eluent ≤40wt%. After acid washing, the fiber forms negatively charged carboxymethyl cellulose fiber (H-CMC). The alcohol in the eluent can undergo a reversible esterification reaction with the carboxyl groups on the carboxymethyl cellulose fiber, which to a certain extent maintains the stability of the molecular structure of the carboxymethyl cellulose fiber. At the same time, the eluent can also be effectively miscible with the acidification solution under the action of alcohol, thus having a good elution effect, washing away excess acid and other impurities such as sodium salts that participated in the reaction, 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 acid washing combine with the anions in the acid washing process to form sodium salts. Sodium salts easily adhere to the fibers, affecting not only the fiber purity but also the substitution effect to some extent. Especially for sodium carboxymethyl cellulose fibers that have undergone multiple alkalization and etherification processes, the degree of sodium substitution is high. This invention performs acid washing in two stages. The first acid washing primarily removes sodium from the sodium carboxymethyl cellulose fibers. After further elution, the removed sodium ions and residual acid are removed, reducing the likelihood of subsequent sodium salt formation. The second acid washing not only further removes the sodium ions not removed in the first acid washing but also maintains the system in an acidic state, reducing the reverse recombination of sodium ions with the fibers, thus facilitating subsequent unidirectional substitution reactions and minimizing the re-separation of lithium ions from the lithium carboxymethyl cellulose.

[0042] In actual operation, if the acid content in the acidification solution is too high, it will easily cause excessive hydrolysis of the fiber, making it difficult to maintain the fibrous structure. If the acid content is too low, it will be difficult to effectively remove the sodium from the fiber. The acidification solution obtained by combining 1-4 wt% acid with 60-70 wt% alcohol can not only effectively remove the sodium, but also maintain the fibrous structure well. Therefore, this invention regards it as a further preferred option.

[0043] Preferably, in step S3, the hydrogenated carboxymethyl cellulose fiber is immersed in a lithium salt solution for reaction, the lithium salt solution comprising the following components: 2-5 wt% lithium-containing material, 55-79 wt% 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, lithium salt can be well dispersed in the fiber in solution for reaction in this invention. Hydrogenated carboxymethyl cellulose fibers can maintain their fibrous morphology well in the lithium salt solution under this formulation, promoting better binding of lithium to the fiber, thereby obtaining fibrous carboxymethyl cellulose lithium fibers with excellent mechanical strength and guiding properties. The alcohol can be one or more of ethanol, methanol, and isopropanol. Maintaining consistency with the alcohols in the acidification solution provides better dispersion and promotes effective reaction.

[0046] 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, etc. Lithium hydrides, oxides, and sulfides react to form lithium ions when dissolved in an alcohol-water solution, while lithium chlorides, hypochlorites, and silicates hydrolyze to release lithium ions when dissolved in water. Therefore, the above-mentioned lithium-containing materials can effectively separate lithium ions to participate in the fiber substitution reaction. Further preferred lithium chloride, lithium hydroxide, lithium oxide, lithium nitride, lithium carbide, lithium sulfide, lithium sulfate, lithium nitride, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, and lithium iron phosphate all have good water solubility and can reduce impurity generation compared to other lithium-containing materials, thereby obtaining carboxymethyl cellulose lithium fibers with superior mechanical strength.

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

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

[0049] By adopting the above technical solution, the raw material used in this invention is regenerated cellulose fiber. Whether it's a short fiber structure or a long fiber structure, it already possesses a certain degree of orientation. Therefore, the fiber of this invention can be directly made from regenerated cellulose fiber with a short fiber structure, or it can be made from regenerated cellulose fiber with a long fiber structure after alkalization and etherification treatment followed by cutting into short fibers, or it can be directly made into filaments using a long fiber structure. The degree of orientation increases sequentially in these three cases, and the performance of the resulting carboxymethyl cellulose lithium fiber also gradually improves. In this invention, the fiber length of the short fiber structure is further preferably 1mm-15cm. If the fiber length is too short, it is difficult to maintain its fiber effect; if the fiber is too long, it is prone to entanglement, which is inconvenient for subsequent weaving or non-woven operations or other processes or uses.

[0050] Preferably, step S5 further includes oiling, drying, and packaging the carboxymethyl cellulose lithium crude fiber prepared in step S3 to obtain the finished carboxymethyl cellulose lithium fiber.

[0051] The aforementioned high-substitution degree carboxymethyl cellulose lithium fiber can be well applied in flexible energy devices, battery construction devices for various applications and scenarios, smart textiles, functional textiles, flexible electrodes, smart home appliances and other fields.

[0052] Modified high-substitution degree carboxymethyl cellulose fiber is prepared by neutralizing regenerated cellulose fiber after undergoing two or more "alkalization-etherification-elution" processes while maintaining the cellulose in a fibrous state. The regenerated cellulose fiber has a fineness of 0.3-3.5 dtex and the carboxymethyl cellulose sodium fiber has a substitution degree Ds > 0.55.

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

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

[0055] The regenerated cellulose fibers are first pre-alkalized in a 25-30 wt% sodium hydroxide solution for 0.4-1.5 h, with the reaction temperature controlled at 55-70℃. Then, they are first pre-etherified in an etherification solution for 0.2-0.8 h, with the reaction temperature controlled at 55-70℃. The reaction byproducts are then removed by elution with an alcohol solution.

[0056] Subsequently, it is immersed in 25-30 wt% sodium hydroxide solution for alkalization again for 0.4-1.5 h, with the reaction temperature controlled at 55-70℃. Then, it is immersed in etherification solution for etherification again for 0.2-0.8 h, with the reaction temperature controlled at 55-70℃. The reaction byproducts are eluted with alcohol solution and then neutralized by immersion in neutralization solution, or the "alkalization-etherification-elution" steps are repeated before immersion in neutralization solution for neutralization to obtain sodium carboxymethyl cellulose fiber.

[0057] Modified high-substitution degree carboxymethyl cellulose fiber is prepared by neutralizing regenerated cellulose fiber after undergoing two or more "alkalization-etherification-elution" processes while maintaining the cellulose fiber state, and then acid washing to obtain hydrogenated carboxymethyl cellulose fiber; the fineness of the regenerated cellulose fiber is 0.3-3.5 dtex, and the degree of substitution Ds of the hydrogenated carboxymethyl cellulose fiber is >0.55.

[0058] Preferably, the degree of substitution of hydrogenated carboxymethyl cellulose fiber is 0.55 < Ds ≤ 3.0; and the degree of orientation measured by optical birefringence is ≥ 0.45.

[0059] The preparation method of the above-mentioned modified high-substitution degree carboxymethyl cellulose fiber includes the following steps:

[0060] S1. Using regenerated cellulose fiber as raw material, after two or more "alkalization-etherification-elution" processes, neutralization is performed. During the "alkalization-etherification-elution" process, the cellulose is 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 preferred fineness of the regenerated cellulose fiber is 0.3-3.5 dtex.

[0061] S2. The sodium carboxymethyl cellulose fiber prepared in S1 is acid-washed and eluted to obtain hydrogenated carboxymethyl cellulose fiber.

[0062] This invention provides a modified, highly substituted carboxymethyl cellulose fiber, its preparation method, and its applications. It offers the following advantages:

[0063] (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 carboxymethyl cellulose lithium is difficult to prepare into fibers. Through two or more "alkalization-etherification-elution" operations, high-substitution degree carboxymethyl cellulose lithium in fiber form is prepared, which has good mechanical strength and conductivity to meet processing requirements. 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 degree of substitution 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.

[0064] (2) The high-substitution degree carboxymethyl cellulose lithium fiber of the present invention has a certain spatial structure. Therefore, after the hydrogenated carboxymethyl cellulose fiber reacts with lithium salt, it is then stretched, so that the originally irregularly distributed fiber gradually deflects uniformly in the direction of the force after being stretched, the orientation degree increases, and the lithium ions attached to the fiber also become directional, forming long chains of lithium ions; the regularly arranged lithium ions increase the conductivity of the carboxymethyl cellulose lithium fiber, and better exert the conductive effect of lithium ions.

[0065] (3) In the preparation of lithium carboxymethyl cellulose fiber, the present invention adopts the method of "two acid washing", which makes the harvested hydrogenated carboxymethyl cellulose fiber with fewer impurities and better stability. In addition, the composition of the acidification liquid and the elution liquid is limited, so that the hydrogenated carboxymethyl cellulose fiber reacts fully with the lithium salt, further improving the mechanical strength and conductivity of the lithium carboxymethyl cellulose fiber. Attached Figure Description

[0066] Figure 1 is an electron microscope image of the drawn carboxymethyl cellulose lithium fibers;

[0067] Figure 2 is an electron microscope image of unstretched carboxymethyl cellulose lithium fibers. Detailed Implementation

[0068] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0069] The high-substitution degree carboxymethyl cellulose lithium fiber provided by this invention uses existing fibers as materials. In order to better control the performance parameters of the fibers, this invention mainly uses regenerated fibers as initial raw materials. Sodium carboxymethyl cellulose fibers can be obtained through alkalization and etherification treatment, and hydrogenated carboxymethyl cellulose fibers can be obtained through acid washing treatment. Then, the obtained hydrogenated carboxymethyl cellulose fibers are reacted with lithium salts to obtain crude carboxymethyl cellulose lithium fibers. Finally, oiling, drying and packaging are carried out as needed to obtain the final product.

[0070] The aforementioned regenerated fibers can be one or more of viscose fiber, cupro fiber, Tencel fiber, and modal fiber. They are widely available and inexpensive, and can be purchased directly from the market; however, the orientation index of commercially available regenerated cellulose fibers is strictly controlled. All other raw materials used in this invention are of industrial production specifications, and the equipment and tools used are also common equipment in the spinning industry, and will not be further described here.

[0071] The degree of fiber substitution and fineness have a significant impact on mechanical strength. The specific testing methods are as follows: ① Degree of substitution

[0072] Degree of substitution of sodium carboxymethyl cellulose fiber: See the Degree of substitution test of sodium carboxymethyl cellulose in the Pharmacopoeia of the People's Republic of China (2020 edition).

[0073] Degree of substitution of lithium carboxymethyl cellulose fiber: (1) Take lithium carboxymethyl cellulose fiber, wash and dry it with a hot ethanol solution of 60℃ and 90% (v / v) when washing the lithium carboxymethyl cellulose sample, add an acid aqueous solution (nitric acid: distilled water = 1:2), and use an electric furnace to heat and digest completely;

[0074] (2) Transfer the homogeneous solution obtained after digestion into a 50 mL volumetric flask, dilute to volume with high-purity water, and then take 0.5 mL of the solution and dilute to volume in the 50 mL volumetric flask for later use; during this step, a blank test can be performed at the same time to obtain a blank solution.

[0075] (3) The mass percentage concentration C of lithium ions in the solution was determined using an atomic absorption spectrometer; the instrument measurement conditions were as recommended in Table 1 below:

[0076] Table 1 Recommended Measurement Conditions

[0077] The inspection wavelength is 670 nm. The flame type is air-acetylene. The air-acetylene ratio is 3-5:1.

[0078] When performing the determination, follow these steps: First, measure the absorbance of a series of standard solutions and plot a standard curve. Then, directly measure the absorbance of the sample solution and the blank solution, calculate the lithium content of the sample solution and the blank solution, and then subtract the lithium content of the blank solution from the lithium content of the sample solution to obtain the mass percentage concentration of lithium ions, i.e., the lithium content of carboxymethyl cellulose lithium.

[0079] After determining the lithium ion mass percentage concentration of the lithium carboxymethyl cellulose sample using the method described above, the values ​​are substituted into the following equation for calculating the degree of substitution of the sample:

[0080] ,

[0081] 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 (%).

[0082] ② Fineness: Measured using a fineness tester.

[0083] The present invention will be further described in detail below with reference to the accompanying drawings, embodiments and comparative examples.

[0084] Example 1

[0085] The method for preparing highly substituted carboxymethyl cellulose lithium fibers of the present invention includes the following steps:

[0086] S1. Using 400,000 denier regenerated cellulose fiber—viscose fiber filament bundles with a single filament fineness of 1.33 dtex—as raw material, the fibers were initially alkalized for 0.5 h by immersing them in a 28 wt% sodium hydroxide solution at 65°C. Then, they were immersed in an etherification solution composed of 45 wt% sodium chloroacetate, 35 wt% ethanol, and 20 wt% distilled water for 0.5 h at 60°C. After etherification, the reaction products were washed away with an alcohol solution composed of 70 wt% ethanol and 30 wt% distilled water. Subsequently, the fibers were again alkalized for 0.5 h by immersing them in a 28 wt% sodium hydroxide solution at 65°C, followed by etherification again at 60°C for 0.5 h by immersing them in the same etherification solution. After washing away the reaction products with the same alcohol solution, the fibers were then neutralized by immersion in a neutralization solution composed of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water. The composition is as follows: wt%; the pH of the reaction system is maintained above 7 during the "alkalization-etherification-elution" process to harvest sodium carboxymethyl cellulose fibers, and the degree of substitution is measured to be 0.80.

[0087] S2. Immerse the sodium carboxymethyl cellulose fibers prepared in S1 into an elution container containing 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 hours. Elute the primary acidified sodium carboxymethyl cellulose fibers by passing an eluent composed of 65 wt% ethanol and 35 wt% distilled water through the eluent. After complete elution with the primary acidifying solution, stop passing the eluent. Use an eluent volume 15 times the fiber mass. Elute until the sodium ion content of the dry fibers is <2% as determined by atomic absorption spectrometry.

[0088] Sodium carboxymethyl cellulose fibers were immersed again in the same acidifying solution as the first acidification for a second acidification. After soaking in the acidifying solution for 12 hours, an eluent was introduced. The amount of eluent used was 15 times the mass of the fiber. The fibers were eluted until the sodium ion content was <0.2% when tested by atomic absorption spectrometry. After the eluent was completely replaced, hydrogenated carboxymethyl cellulose fibers were obtained.

[0089] S3. After removing the hydrogenated carboxymethyl cellulose fiber prepared in S2, 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. Under 90°C, the immersion reaction is carried out for 5 min. After immersion, the fiber is stretched using a stretching roller with an elongation ratio of 1:1.55 to harvest the carboxymethyl cellulose lithium crude fiber.

[0090] S4. The crude carboxymethyl cellulose lithium fiber prepared in S3 was oiled, dried, and crimped before being cut into short fibers of 3.8 cm in length. After packaging, carboxymethyl cellulose lithium fiber with a degree of substitution of 0.80 and a fineness of 1.15 dtex was harvested. See Figure 1 for its electron micrograph.

[0091] Example 2

[0092] The method for preparing highly substituted carboxymethyl cellulose lithium fibers of the present invention includes the following steps:

[0093] S1. Using 400,000 denier regenerated cellulose fiber (cupramolecular fiber) filament bundles with a single filament fineness of 0.5 dtex as raw material, the fibers were initially alkalized for 0.4 h by immersing them in a 25 wt% sodium hydroxide solution at 65°C, followed by immersion in an etherification solution composed of 40 wt% sodium chloroacetate, 40 wt% ethanol, and 20 wt% distilled water. The etherification time was 0.2 h at 60°C. After etherification, the reaction products were washed away with an alcohol solution composed of 60 wt% ethanol and 40 wt% distilled water. Subsequently, the fibers were alkalized again for 0.4 h by immersion in a 25 wt% sodium hydroxide solution at 65°C, followed by etherification again for 0.2 h at 60°C by immersion in the same etherification solution. After washing away the reaction products with the same alcohol solution, the fibers were neutralized by immersion in a neutralization solution composed of 1 wt% hydrochloric acid, 70 wt% ethanol, and 29 wt% distilled water. The composition is wt%, in which the pH of the reaction system is maintained at >7 during the "alkalization-etherification-elution" process, and sodium carboxymethyl cellulose fibers are harvested, with a degree of substitution of 0.56 as detected.

[0094] S2. Immerse the sodium carboxymethyl cellulose fibers prepared in S1 into an elution container containing 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 hours. Elute the primary acidified sodium carboxymethyl cellulose fibers by passing an eluent composed of 65 wt% ethanol and 35 wt% distilled water through the eluent. After complete elution with the primary acidifying solution, stop passing the eluent. Use an eluent volume 10 times the fiber mass and elute until the sodium ion content of the dry fibers is <2% as determined by atomic absorption spectrometry.

[0095] Sodium carboxymethyl cellulose fibers were immersed again in the same acidifying solution as the first acidification for a second acidification. After soaking in the acidifying solution for 12 hours, an eluent was introduced. The amount of eluent used was 10 times the mass of the fiber. The fibers were eluted until the sodium ion content was <0.2% when tested by atomic absorption spectrometry. After the eluent was completely replaced, hydrogenated carboxymethyl cellulose fibers were obtained.

[0096] S3. After removing the hydrogenated carboxymethyl cellulose fiber prepared in S2, 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. Under 90°C, the immersion reaction is carried out for 5 min. After immersion, the fiber is stretched using a stretching roller with an elongation ratio of 1:1.55 to harvest the carboxymethyl cellulose lithium crude fiber.

[0097] S4. The carboxymethyl cellulose lithium coarse fiber prepared in S3 is cut into short fibers of 3.8 cm in length after oiling, drying, and crimping. After packaging, carboxymethyl cellulose lithium fiber with a degree of substitution of 0.56 and a fineness of 0.42 dtex is harvested. Example 3

[0098] The method for preparing highly substituted carboxymethyl cellulose lithium fibers of the present invention includes the following steps:

[0099] S1. Using 400,000 denier regenerated cellulose fiber (Tencel fiber) filament bundles with a single filament fineness of 3.0 dtex as raw material, the fibers were initially alkalized for 1.0 h by immersing them in a 30 wt% sodium hydroxide solution at 65°C, followed by immersion in an etherification solution composed of 48 wt% sodium chloroacetate, 27 wt% ethanol, and 25 wt% distilled water. The etherification time was 0.6 h at 60°C. After etherification, the reaction products were washed away with an alcohol solution composed of 80 wt% ethanol and 20 wt% distilled water. Subsequently, the fibers were alkalized again for 1.0 h by immersion in a 30 wt% sodium hydroxide solution at 65°C, followed by etherification again for 0.6 h at 60°C by immersion in the same etherification solution. After washing away the reaction products with the same alcohol solution, the fibers were neutralized by immersion in a neutralization solution composed of 3 wt% hydrochloric acid, 70 wt% ethanol, and 27 wt% distilled water. The composition was determined by maintaining the pH of the reaction system > 7 during the "alkalization-etherification-elution" process, and sodium carboxymethyl cellulose fibers were harvested, with a degree of substitution of 2.8.

[0100] S2. Immerse the sodium carboxymethyl cellulose fibers prepared in S1 into an elution container containing 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 hours. Elute the primary acidified sodium carboxymethyl cellulose fibers by passing an eluent composed of 65 wt% ethanol and 35 wt% distilled water through the eluent. After complete elution with the primary acidifying solution, stop passing the eluent. Use an eluent volume 20 times the fiber mass and elute until the sodium ion content of the dry fibers is <2% as determined by atomic absorption spectrometry.

[0101] Sodium carboxymethyl cellulose fibers were immersed again in the same acidifying solution as the first acidification for a second acidification. After soaking in the acidifying solution for 12 hours, an eluent was introduced. The amount of eluent used was 10 times the mass of the fiber. The fibers were eluted until the sodium ion content was <0.2% when tested by atomic absorption spectrometry. After the eluent was completely replaced, hydrogenated carboxymethyl cellulose fibers were obtained.

[0102] S3. After removing the hydrogenated carboxymethyl cellulose fiber prepared in S2, immerse it in a lithium salt solution. The lithium salt solution consists of 4 wt% lithium chloride, 60 wt% ethanol and 36 wt% distilled water. Under 90℃ conditions, the immersion reaction is carried out for 5 min. After immersion, the fiber is stretched using a stretching roller with an elongation ratio of 1:1.55 to harvest the carboxymethyl cellulose lithium crude fiber.

[0103] S4. The carboxymethyl cellulose lithium coarse fiber prepared in S3 is cut into short fibers of 3.8 cm in length after oiling, drying, and crimping. After packaging, carboxymethyl cellulose lithium fiber with a degree of substitution of 2.8 and a fineness of 2.5 dtex is harvested. Examples 4-6

[0104] Examples 4-6 are based on the method of Example 1, with adjustments made to the alkalization, etherification, and elution parameters of the regenerated cellulose fibers in step S1. Specific adjustments are shown in Table 2 below.

[0105] Table 2. Processing parameters for regenerated cellulose fibers in Examples 1, 4-6.

[0106]

[0107] Examples 7-13

[0108] Examples 7-13 are based on the method of Example 1, but the composition of the lithium salt solution in step S3 is adjusted. For details of the adjustment, please refer to Table 3 below.

[0109] Table 3. Composition of lithium salt solutions in Examples 1, 7-13

[0110] Components Example 1 Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Lithium chloride / wt% 325 / / 363 Lithium hydroxide / wt% / / / 3 / / / / Lithium iron phosphate / wt% / / / / 3 / / / Ethanol / wt% 60 / / 60 60 50 60 / Methanol / wt% / 55 / / / / / 60 Isopropanol / wt% / / 79 / / / / / Distilled water / wt% 3743163737473437 Degree of substitution of lithium cellulose carboxymethyl cellulose 0.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80

[0111] Example 14

[0112] This embodiment, based on the method of Example 1, replaces the long-fiber regenerated cellulose fibers in step S1 with short-fiber regenerated cellulose fibers of 3.8 cm in length, and omits the stretching operation in step S3, obtaining 1.15 dtex lithium carboxymethyl cellulose fibers. Figure 2 shows an electron microscope image of the unstretched lithium carboxymethyl cellulose fibers. Comparing this image with the stretched lithium carboxymethyl cellulose fibers obtained in Example 1, it is clear that the stretched lithium carboxymethyl cellulose fibers have a straighter overall morphology and are more regular and orderly, providing a more favorable morphology for subsequent improvement of electrochemical performance.

[0113] Comparative Example 1 Commercially available lithium carboxymethyl cellulose powder was used, with a lithium content of 3 wt% and a wet viscosity of 26 mPa*S at 1%. Because this lithium carboxymethyl cellulose powder does not possess a fibrous morphology, it cannot be directly subjected to fiber-related mechanical property testing.

[0114] Comparative Example 2 This comparative example discloses a method for preparing carboxymethyl cellulose lithium fiber, including the following steps:

[0115] S1. Using 400,000 denier regenerated cellulose fiber (viscose fiber) filament bundles with a single filament fineness of 1.33 dtex as raw material, the fibers were immersed in a 35 wt% sodium hydroxide solution for alkalization at 65°C for 1 hour. After alkalization, the sodium hydroxide solution was filtered off. The fibers were then immersed in an etherification solution composed of 50 wt% sodium chloroacetate, 30 wt% ethanol, and 20 wt% distilled water at 60°C for 1 hour. After etherification, the etherification solution was filtered off, and sodium carboxymethyl cellulose fibers were harvested. The degree of substitution was measured to be 0.90.

[0116] S2. Immerse the sodium carboxymethyl cellulose fibers prepared in S1 into an elution vessel containing an acidifying solution (2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water) for a first acidification process, soaking for 24 hours. Then, pass an eluent (65 wt% ethanol and 35 wt% distilled water) into the acidified sodium carboxymethyl cellulose fibers for elution. After complete elution with the acidifying solution, stop passing the eluent. Use an eluent volume 15 times the fiber mass. Elute until the sodium ion content of the dry fibers, as determined by atomic absorption spectrometry, is <2%.

[0117] Sodium carboxymethyl cellulose fibers were immersed again in the same acidifying solution as the first acidification for a second acidification. After soaking in the acidifying solution for 12 hours, an eluent was introduced. The amount of eluent used was 15 times the weight of the fiber. The fibers were eluted until the sodium ion content was <0.2% when tested by atomic absorption spectrometry. After the eluent completely washed away the acidifying solution, hydrogenated carboxymethyl cellulose fibers were obtained.

[0118] S3. After removing the hydrogenated carboxymethyl cellulose fiber prepared in S2, 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. Under 90°C, the immersion reaction is carried out for 5 min. After immersion, the fiber is stretched using a stretching roller with an elongation ratio of 1:1.55 to harvest the carboxymethyl cellulose lithium crude fiber.

[0119] S4. The carboxymethyl cellulose lithium coarse fiber prepared in S3 is cut into short fibers of 3.8 cm in length after oiling, drying, and crimping. After packaging, carboxymethyl cellulose lithium fiber with a degree of substitution of 0.40 and a fineness of 1.25 dtex is harvested.

[0120] Comparative Example 3

[0121] Based on Example 1, the difference lies in that, in step S1, the sample is immersed in a 45 wt% sodium hydroxide solution at 65°C for initial alkalization for 0.5 h, followed by immersion in an etherification solution composed of 45 wt% sodium chloroacetate, 35 wt% ethanol, and 20 wt% distilled water at 60°C for 0.5 h. After etherification, the reaction product is eluted with an alcohol solution composed of 70 wt% ethanol and 30 wt% distilled water. Subsequently, the sample is immersed in a 45 wt% sodium hydroxide solution at 65°C for another alkalization for 0.5 h, and then immersed in the same etherification solution at 60°C for another etherification for 0.5 h. After eluting the reaction product with the same alcohol solution, the sample is then immersed in a neutralization solution composed of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water for neutralization. The composition was determined by maintaining the pH of the reaction system > 7 during the "alkalization-etherification-elution" process, and sodium carboxymethyl cellulose fibers were harvested, with a degree of substitution of 1.0. Lithium carboxymethyl cellulose was then obtained by acid washing in step S2 and immersion in a lithium salt solution in step S3.

[0122] Comparative Example 4

[0123] Based on Example 1, the difference lies in that, in step S1, the product is immersed in an etherification solution composed of 55 wt% sodium chloroacetate, 25 wt% ethanol, and 20 wt% distilled water. The etherification time is 0.5 h at 60°C. After etherification, the reaction product is eluted with an alcohol solution composed of 70 wt% ethanol and 30 wt% distilled water. Subsequently, the product is immersed in a 28 wt% sodium hydroxide solution for alkalization again for 0.5 h. At 60°C, the product is immersed in the same etherification solution again for 0.5 h. After eluting the reaction product with the same alcohol solution, the product is then immersed in a neutralization solution for neutralization. The neutralization solution is composed of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water. During the "alkalization-etherification-elution" process, the pH of the reaction system is maintained >7. Sodium carboxymethyl cellulose fibers are harvested, and the degree of substitution is measured to be 1.2. After acid washing in step S2 and immersion in lithium salt solution in step S3, lithium carboxymethyl cellulose is obtained.

[0124] Comparative Example 5

[0125] Based on Example 1, the difference lies in that the acidification solution in step S2 consists of 25 wt% hydrochloric acid, 53 wt% ethanol, and 22 wt% distilled water, and is soaked for 12 hours. An eluent, consisting of 65 wt% ethanol and 35 wt% distilled water, is then passed through the acidified sodium carboxymethyl cellulose fiber for elution. After complete elution with the acidification solution from the first acidification, the flow of the eluent is stopped, and the sodium carboxymethyl cellulose fiber is immersed again in the same acidification solution for a second acidification. After soaking in the acidification solution for 12 hours, the eluent is passed through until it is completely replaced, yielding hydrogenated carboxymethyl cellulose fiber. This is then further processed in step S3 by immersion in a lithium salt solution to obtain lithium carboxymethyl cellulose.

[0126] Performance testing 1. The performance of the products from the above examples and comparative examples was tested, and the results are shown in Table 4 below. The test methods are as follows:

[0127] Fiber orientation was determined using the optical birefringence method;

[0128] The test methods for fiber tensile properties and coefficient of variation shall refer to GB / T 14337-2022;

[0129] The degree of fiber substitution was determined using the above-described testing method;

[0130] The lithium ion content is determined by flame photometry. After the fiber is ashed, lithium ions are sprayed into the flame, and the lithium ion content is determined by detecting the intensity of the emitted light. The lithium ion content in the fiber is then determined by comparison.

[0131] The resistivity test method employed a Seebeck coefficient measuring instrument. The fibers were tested under vacuum conditions at room temperature with a moisture regain of 22%. The prepared carboxymethyl cellulose lithium fibers were twisted at a twist rate of 150 r / m. The twisted sample was fixed in the testing vacuum device, ensuring close contact between the two electrodes and both ends of the sample, with the effective test length precisely controlled at 25 mm ± 1 mm. The frequency and measurement voltage of the resistivity meter were adjusted. After the frequency range and all measurement parameters were adjusted, the resistance value was read.

[0132] Table 4 Performance Test Data Table

[0133] Example Orientation Degree Dry Fracture Strength / CN / dtex Wet Fracture Strength / CN / dtex Coefficient of Variation Cv Degree of Substitution Lithium Ion Content (%) Resistivity / Ω.m Example 1 0.87 1.9 1.3 10% 0.8 9.13 50 Example 2 0.88 2.6 1.95% 0.56 8.27 70 Example 3 0.81 3.4 2.77% 2.81 6.21 80 Example 4 0.83 1.9 1.3 10% 1.91 11 .0270 Example 5 0.78 1.8 1.15% 2.50 20.51 90 Example 6 0.81 1.9 1.27% 1.44 9.43 20 Example 7 0.88 1.9 1.410% 0.8 7.85 50 Example 8 0.73 1.9 1.210% 0.81 4.52 70 Example 9 0.87 1.9 1.310% 0.8 9.13 50 Example 10 0.87 1.7 0.910% 0.8 8.6440 Example 11 0.87 1.9 1.3 10% 0.8 9.1350 Example 12 0.87 1.8 1.3 10% 0.8 9.1350 Example 13 0.87 1.8 1.3 10% 0.8 9.7270 Example 14 0.70 2.0 1.4 10% 0.8 6.22750 Comparative Example 1 No data No data No data No data 0.5 1.9 No data Comparative Example 2 Fracture No data Fracture No data Countless fractures According to the fracture data, there was no data. 0.91 1.5 fracture data. Comparative Example 3: 0.57 0.9 0.52 8 1.0 9.5 fracture data. Comparative Example 4: 0.55 0.8 fracture data. Fracture data 1.21 0.5 fracture data. Comparative Example 5: No fracture data detected. Fracture data 0.8 9.1 fracture data. Blank Group – Raw material of Example 1: Ordinary viscose fiber 0.70 2.1 1.4 10% unsubstituted, ashed, lithium ion >100000

[0134] Examples 1-3 used different regenerated cellulose fibers as raw materials. The test results show that different regenerated cellulose fibers can all be used to obtain the corresponding carboxymethyl cellulose lithium fibers using the preparation method of the present invention.

[0135] Based on the test results of Examples 5-7, it can be concluded that the neutralization operation after two or more "alkalization-etherification-elution" cycles, as well as the composition and alkalization time of the alkalization solution and the composition and etherification time of the etherification solution, all have a certain impact on the degree of substitution of carboxymethyl cellulose. Preferredly, regenerated cellulose fibers are initially alkalized by immersing them in a 25-30 wt% sodium hydroxide solution for 0.4-1.5 h at a reaction temperature controlled at 55-70°C. Then, they are initially etherified by immersing them in an etherification solution for 0.2-0.8 h at a reaction temperature controlled at 55-70°C, and the reaction byproducts are removed by elution with an alcohol solution. Subsequently, they are alkalized again by immersing them in a 25-30 wt% sodium hydroxide solution for 0.4-1.5 h at a reaction temperature controlled at 55-70°C, and then etherified again by immersing them in an etherification solution for 0.2-0.8 h at a reaction temperature controlled at 55-70°C, and the reaction byproducts are removed by elution with an alcohol solution. Finally, they are neutralized by immersion in a neutralizing solution, or the "alkalization-etherification-elution" steps are repeated before immersion in a neutralizing solution for neutralization, to obtain sodium carboxymethyl cellulose fibers.

[0136] Referring to the test results of Examples 1 and 8-13, it can be seen that the present invention immerses hydrogenated carboxymethyl cellulose fibers in a lithium salt solution for reaction, and further specifies that the lithium salt solution includes the following components: 2-5 wt% lithium-containing material, 55-79 wt% alcohol, and the balance being distilled water. This can further reduce the carboxylic acid of carboxymethyl cellulose fibers to lithium carboxylate, while better maintaining the integrity of the fibers, so that the resulting carboxymethyl cellulose lithium fibers have better mechanical strength.

[0137] Comparative Example 1: Commercially available lithium carboxymethyl cellulose powder, being in powder form, could not pass the sample test for fibrous form.

[0138] Comparative Example 2, which was produced through a single alkalization and etherification process, also had a high degree of substitution. However, due to the use of high concentrations of alkalizing and etherifying agents, the fibers were severely degraded and could not maintain their morphology.

[0139] Comparative Examples 3, 4, and 5 show that excessive alkalizing agents, etherifying agents, and acidifying solutions caused severe fiber degradation and prevented the fiber from maintaining its shape.

[0140] Referring to the test results of Example 14, it can be seen that the length and shape of the regenerated cellulose fibers of the present invention, as well as whether or not the fibers are subsequently drawn, will affect the orientation and electrical properties of the fibers to a certain extent. The fibers of the present invention can be directly made from regenerated cellulose fibers with a short fiber structure.

[0141] When the elongation ratio of the stretching in step S4 is 1:1.05-1.55, the regenerated cellulose fiber with a long fiber structure is prepared. Since the fiber is obtained by fiber morphology treatment, the resulting high-substituted carboxymethyl cellulose lithium fiber has excellent mechanical and electrical properties, which significantly improves its application range.

[0142] In particular, comparing the data from Example 14 with that from Example 1, the electrical properties of the high-substituted carboxymethyl cellulose lithium fibers in step S4 were as follows: the resistivity of the fibers after stretching in Example 1 was 350 Ω·m, while the resistivity of the fibers without stretching in Example 14 was 2750 Ω·m. This fully demonstrates that before stretching, the negatively charged carboxymethyl cellulose fibers (H-CMC) and lithium ions (Li) in the lithium salt solution... + The lithium ions combine to form lithium carboxymethyl cellulose. During the combination process, the lithium ions diffuse randomly and penetrate into the carboxymethyl cellulose fibers full of carboxyl groups to form lithium carboxymethyl cellulose fibers. The lithium ions are extremely unevenly and randomly dispersed in the fibers.

[0143] Hydrogenated carboxymethyl cellulose fibers are immersed in a lithium salt solution and then stretched. Initially randomly distributed, the fibers gradually align themselves uniformly with the direction of the applied force after stretching, increasing their orientation. The lithium ions attached to the fibers also follow this orientation, forming long chains and achieving orderly fixation of the lithium ions. Furthermore, since the material's structure determines its conductivity, conductivity increases and resistivity decreases with increasing orientation. Therefore, the axial elongation and lateral shortening of the fibers after stretching, along with the reduced spacing between lithium ions, improves conductivity and decreases resistivity.

[0144] The design draw force range is 1.5-3.7 (cN / dtex) of the monofilament. Within this range of fiber physical properties, excessive draw force can easily lead to fiber breakage, while insufficient force will not achieve the desired effect of increasing fiber orientation. Under draw conditions, the fiber will elongate to a certain extent, with an elongation ratio preferably between 1:1.05 and 1.55. If the elongation ratio is too small, the fiber is prone to springback, and the orientation will revert to its pre-elongation state; if the elongation ratio is too large, the fiber will break, making processing difficult.

[0145] The carboxymethyl cellulose lithium coarse fibers obtained in step S3 of this invention can be directly cut, oiled, dried, crimped, and packaged to harvest the final carboxymethyl cellulose lithium fibers. The cut fiber length should preferably be ≥1 mm; the length of the cut short fibers can be adjusted as needed. Example 1: Raw material (ordinary viscose fiber), according to the above tests and substitution degree test, showed no substitution, no lithium ions after ashing, and a resistivity value reaching 10. 9 Therefore, it does not possess the excellent electrical properties of lithium carboxymethyl cellulose fiber.

[0146] Application examples

[0147] The carboxymethyl cellulose lithium fibers prepared in Examples 1-14 of this invention can be applied to, but are not limited to, the following fields: flexible energy devices, battery construction devices for various applications and scenarios, smart textiles, functional textiles, flexible electrodes, and smart home appliances. Specifically, they can be made into flexible conductive films, fabrics, negative electrode sheets, etc., as needed.

[0148] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0149] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A modified, highly substituted carboxymethyl cellulose fiber, characterized in that, Sodium carboxymethyl cellulose fiber is prepared by neutralization after two or more "alkalization-etherification-elution" processes under conditions that always maintain the cellulose fiber state, followed by acid washing to obtain hydrogenated carboxymethyl cellulose fiber, and then a substitution reaction is carried out with lithium salt solution to obtain lithium carboxymethyl cellulose fiber with a high degree of substitution. The regenerated cellulose fiber has a fineness of 0.3-3.5 dtex, and the degree of substitution of the carboxymethyl cellulose lithium fiber is Ds > 0.

55.

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

45.

3. The method for preparing modified high-substituted carboxymethyl cellulose fiber according to claim 1 or 2, characterized in that, Includes the following steps: S1. Using regenerated cellulose fiber as raw material, the cellulose is neutralized after two or more "alkalization-etherification-elution" processes, wherein the cellulose is kept in a fibrous state throughout the "alkalization-etherification-elution" process, 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. S2. The sodium carboxymethyl cellulose fiber prepared in S1 is acid-washed and eluted to obtain hydrogenated carboxymethyl cellulose fiber. S3. The hydrogenated carboxymethyl cellulose fiber obtained in S2 is reacted with a lithium salt solution to obtain crude carboxymethyl cellulose lithium fiber; 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. The lithium salt solution comprises the following components: 2-5 wt% lithium-containing material, 55-79 wt% alcohol, and the balance being 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 alkalized and etherified using a short fiber structure; or the regenerated cellulose fiber can be alkalized and etherified using a long fiber structure. When the regenerated cellulose fiber in step S1 uses a long fiber structure, step S4 is also included, in which the hydrogenated carboxymethyl cellulose fiber in step S3 is drawn with the carboxymethyl cellulose lithium coarse fiber after reacting with lithium salt to obtain carboxymethyl cellulose lithium fiber; the elongation ratio of the drawn fiber is 1:1.05-1.

55.

5. The method for preparing modified high-substitution degree carboxymethyl cellulose fiber according to claim 4, characterized in that, In step S1, the etherification solution comprises the following components: sodium chloroacetate 40-48 wt%, alcohol 27-40 wt%, and the balance being distilled water; the eluent after etherification comprises the following components: The neutralizing solution comprises: 1-4 wt% acid, ≥60 wt% alcohol, and the balance being distilled water; In step S1, the specific preparation method of the sodium carboxymethyl cellulose fiber... The process includes the following steps: immersing regenerated cellulose fibers in a 25-30 wt% sodium hydroxide solution for initial alkalization for 0.4-1.5 h, then immersing them in an etherification solution for initial etherification for 0.2-0.8 h, followed by elution of reaction byproducts with an alcohol solution; subsequently immersing them in a 25-30 wt% sodium hydroxide solution for further alkalization for 0.4-1.5 h, then immersing them in an etherification solution for further etherification for 0.2-0.8 h, followed by elution of reaction byproducts with an alcohol solution, and then immersing them in a neutralization solution for neutralization, or repeating the "alkalization-etherification-elution" steps before immersing them in a neutralization solution for neutralization, to obtain sodium carboxymethyl cellulose fibers.

6. The method for preparing modified high-substitution degree 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 in two stages. After the first acid washing is completed, the fiber is eluted and then subjected to a second acid washing. For the first acid wash, the eluent volume should be 10-20 times the fiber volume by mass. Eluent is continued until the dry fiber content, as determined by atomic absorption spectrometry, is <2%. For the second acid wash, the eluent volume should be 10-20 times the fiber volume by mass. Eluting continues until the sodium ion content of the dry fiber, as determined by atomic absorption spectrometry, is <0.2%. In step S2, the sodium carboxymethyl cellulose fiber is immersed in an acidification solution for acid elution to remove sodium, and the immersion time is 0.5-28 h; the acidification solution includes the following components: 1-4 wt% acid, 60-70 wt% alcohol, and the balance being distilled water; In step S2, the acid in the acidification solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, citric acid, acetic acid, and tartaric acid; the alcohol in the acidification solution is one or more of ethanol, methanol, and isopropanol; in step S2, the eluent after acid washing of the sodium carboxymethyl cellulose fiber is a mixture of alcohol and distilled water, and the water content in the eluent is ≤40wt%.

7. A modified, highly substituted carboxymethyl cellulose fiber, characterized in that, Sodium carboxymethyl cellulose fiber is prepared by neutralization after two or more "alkalization-etherification-elution" processes in which the cellulose is always maintained in a fibrous 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 optical birefringence is ≥0.

45.

8. The method for preparing modified high-substitution degree carboxymethyl cellulose fiber according to claim 7, characterized in that, Includes the following steps: Regenerated cellulose fibers are initially alkalized by immersing them in a 25-30 wt% sodium hydroxide solution for 0.4-1.5 h, then initially etherified by immersing them in an etherification solution for 0.2-0.8 h, and finally eluted with an alcohol solution to remove the reaction byproducts. Subsequently, they are alkalized again by immersing them in a 25-30 wt% sodium hydroxide solution for 0.4-1.5 h, then etherified again by immersing them in an etherification solution for 0.2-0.8 h, and finally eluted with an alcohol solution to remove the reaction byproducts. The fibers are then neutralized by immersing them in a neutralizing solution, or the "alkalization-etherification-elution" steps are repeated before immersing them in a neutralizing solution for neutralization, to obtain sodium carboxymethyl cellulose fibers.

9. A modified, highly substituted carboxymethyl cellulose fiber, characterized in that, Sodium carboxymethyl cellulose fiber is obtained by neutralizing regenerated cellulose fiber after two or more "alkalization-etherification-elution" processes that maintain the cellulose fiber state; hydrogenated carboxymethyl cellulose fiber is obtained by acid washing. The regenerated cellulose fiber has a fineness of 0.3-3.5 dtex, and 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 optical birefringence is ≥ 0.

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10. The method for preparing modified high-substituted carboxymethyl cellulose fiber according to claim 9, characterized in that, Includes the following steps: S1. Using regenerated cellulose fiber as raw material, neutralize it after two or more "alkalization-etherification-elution" processes, ensuring that the cellulose remains in a fibrous state throughout the "alkalization-etherification-elution" process, and maintaining the pH of the reaction system > 7 throughout the process, to obtain sodium carboxymethyl cellulose fiber; the fineness of the regenerated cellulose fiber is preferably 0.3-3.5 dtex. S2. After acid washing and elution, hydrogenated carboxymethyl cellulose fiber is obtained from the sodium carboxymethyl cellulose fiber prepared in S1.

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