Carboxymethyl cellulose lithium fiber as well as preparation method and application thereof

Abstract

The invention discloses a carboxymethyl cellulose lithium fiber as well as a preparation method and application thereof, and belongs to the technical field of fiber modification preparation, the carboxymethyl cellulose lithium fiber is mainly obtained by carrying out substitution reaction on sodium carboxymethyl cellulose fiber subjected to acid pickling and lithium salt, the substitution degree of the carboxymethyl cellulose lithium fiber is 0.2-0.55, and the fineness of the carboxymethyl cellulose lithium fiber is 0.3-3.5 dtex. According to the method, the problem that conventional lithium carboxymethyl cellulose is difficult to form filaments is solved, the fiber-form lithium carboxymethyl cellulose is successfully prepared, the excellent conductivity of the lithium carboxymethyl cellulose can be effectively exerted, the high mechanical strength is achieved, and the good application prospect is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of fibers, and more specifically, it relates to a lithium carboxymethyl cellulose fiber, a preparation method thereof, and an application thereof. Background Art

[0002] The fields of flexible energy devices, intelligent textiles, functional textiles, etc. are changing with each passing day. Similarly, the requirements for the functional fibers that make up these products are also getting higher and higher. Among them, lithium carboxymethyl cellulose has gradually been widely used in energy devices due to its advantages of natural degradability, renewable nature, and excellent electrical conductivity.

[0003] The patent number CN112724266A with the name "A preparation method of lithium carboxymethyl cellulose for lithium batteries" provides a preparation method of lithium carboxymethyl cellulose, but the final product is powdery lithium carboxymethyl cellulose. The patent number CN102206286A with the name "A preparation method of lithium carboxymethyl cellulose for lithium batteries" also prepares lithium carboxymethyl cellulose powders with different degrees of substitution.

[0004] The lithium carboxymethyl cellulose in the prior art mainly exists in the form of powder and is usually used as a key material for the production of gels and solid electrolytes. When in use, it needs to rely on a solvent as a carrier, so it is difficult to effectively exert the excellent properties of lithium carboxymethyl cellulose. Most of the lithium carboxymethyl cellulose in the prior art exists in the form of powder, and this powdery lithium carboxymethyl cellulose needs to rely on other materials as a carrier when in use, which also limits the application of lithium carboxymethyl cellulose. Summary of the Invention

[0005] In view of the shortcomings and deficiencies in the prior art, the present invention provides a lithium carboxymethyl cellulose fiber that can effectively exert the excellent properties of lithium carboxymethyl cellulose, overcomes the problem that conventional lithium carboxymethyl cellulose is difficult to form filaments, successfully prepares lithium carboxymethyl cellulose in fiber form, not only can effectively exert the excellent electrical conductivity of carboxymethyl cellulose lithium, but also has high mechanical strength, and has a good application prospect, as well as a preparation method and an application thereof.

[0006] To achieve the above object, the present invention is realized through the following technical solutions: The lithium carboxymethyl cellulose fiber provided by the present invention is obtained by a substitution reaction of a hydrogenated carboxymethyl cellulose fiber with a lithium salt solution, and a lithium carboxymethyl cellulose fiber with a degree of substitution of 0.2 - 0.55 and a fineness of 0.3 - 3.5 dtex is obtained.

[0007] The lithium carboxymethyl cellulose fiber of the present invention has different properties from traditional powders. This is because in addition to the chemical composition, the longitudinal and transverse characteristics of the fiber will have a great impact on the fiber properties. 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.

[0008] Through experimental research, the inventors found that when the degree of substitution of the lithium carboxymethyl cellulose fiber is too low, although fibers can be obtained, the lithium content on the fibers is too low, and the obtained fibers are still difficult to effectively exert the role of "lithium" and cannot achieve a synergistic effect; when the degree of substitution of the lithium carboxymethyl cellulose fiber is too high, it is difficult to maintain the fiber structure. Therefore, in the present invention, sodium carboxymethyl cellulose fibers are first used to maintain a good fiber morphology in the initial stage, and then by strictly controlling the degree of substitution of the fiber to be 0.2 - 0.55, the prepared lithium carboxymethyl cellulose fiber product not only has a fibrous structure but also maintains a certain mechanical strength, realizes plasticity without a carrier, is environmentally friendly, 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 physical and chemical properties of lithium carboxymethyl cellulose to be effectively exerted.

[0009] On this basis, by further controlling the fineness of the fiber, when the fineness is finally in the range of 0.3 - 3.5 dtex, the prepared lithium carboxymethyl cellulose fiber has better mechanical strength and more excellent spinnability.

[0010] Preferably, the degree of orientation of the lithium carboxymethyl cellulose fiber measured by the optical birefringence method is 0.45 - 0.98. By adopting the above technical solution, the degree of alignment of the molecular chain segments in the polymer is called the degree of orientation, which can reflect that the cellulose macromolecular chain has a certain degree of orientation along the fiber axis. In the fiber of the present invention, since lithium ions are fixed on the carboxyl groups of carboxymethyl cellulose and will occupy a certain space, further limiting the degree of orientation of the fiber can ensure the orderly arrangement of lithium ions in a specific direction, making the corresponding lithium carboxymethyl cellulose fiber have more excellent mechanical properties and electrical conductivity.

[0011] Preferably, it specifically includes the following steps:

[0012] S1. React the hydrogenated carboxymethyl cellulose fiber with a lithium salt solution at room temperature for 1 - 48 h under the condition of pH ≥ 9 to obtain crude lithium carboxymethyl cellulose fibers;

[0013] The Li + dissociated from the lithium salt in the solution reacts with the hydrogen ion (-CH 2 COOH) on the carboxymethyl group of the hydrogenated carboxymethyl cellulose fiber. Among them, the lithium-containing material concentration of the lithium salt solution is 2 wt% - 5 wt%, and Li+ The molar ratio of the addition amount to the molar amount of -CH in the hydrogenated carboxymethyl cellulose fiber 2 to the addition amount of -COOH is 1 - 1.2:1;

[0014] S2. The lithium carboxymethyl cellulose thick fiber prepared in S1 is drawn to obtain lithium carboxymethyl cellulose fiber.

[0015] However, in the lithium salt solution, the negatively charged carboxymethyl cellulose fiber (H-CMC) combines with Li + to form lithium carboxymethyl cellulose. During the combination process, 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 originally irregularly distributed drawn fiber gradually deflects uniformly in the direction of the acting force after being stretched, the degree of orientation increases, and the lithium ions attached to the fiber also become directional, forming a long chain of lithium ions.

[0016] Since the structure of the material determines the conductive performance of the material, with the increase of the degree of orientation of the material, the 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 conductivity of the fiber increase and the resistivity decrease.

[0017] Preferably, in step S2, after the hydrogenated carboxymethyl cellulose fiber reacts with the lithium salt, it is drawn, and the draw elongation ratio is 1:1.05 - 1.55. The designed draw force range is 1.5 - 3.7 (cN / dtex) for single filaments, within the range of the fiber physical indexes. 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, and the elongation ratio is preferably 1:1.05 - 1.55. If the elongation ratio is too small, the fiber is likely to rebound and the degree of orientation returns to the state before elongation; if the elongation ratio is too large, the fiber breaks and the processing is difficult.

[0018] Preferably, in step S1, the hydrogenated carboxymethyl cellulose fiber is immersed in the lithium salt solution for reaction, and the lithium salt solution includes the following components: 2 - 5 wt% lithium-containing material, 55 - 79 wt% alcohol inhibitor, and the balance is distilled water.

[0019] Preferably, in step S1, 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, and lithium hexafluoroarsenate.

[0020] By adopting the above technical solution, the lithium salt can be well dispersed in the fibers in the form of a solution in the present invention to carry out the reaction. The hydrogenated carboxymethyl cellulose fiber can better maintain its fibrous morphology in the lithium salt solution under this formulation, promoting the better binding of lithium to the fiber, and thus obtaining fibrous lithium carboxyhydroxycellulose fibers with excellent mechanical strength and orientation performance. The alcohol therein can be one or more of ethanol, methanol, and isopropanol. Keeping the alcohols in the above alcohol category consistent with those in the acidifying solution has a better dispersion effect to promote the effective progress of the reaction.

[0021] 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 hydride, oxide, nitride, sulfide, chloride, hypochlorite, silicate, and other substances. After lithium hydride, oxide, sulfide, etc. are dissolved in the aqueous alcohol solution, reactions will occur and corresponding lithium ions will be formed, while lithium chloride, hypochlorite, silicate, etc. will hydrolyze to produce lithium ions after being dissolved 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, and lithium hexafluoroarsenate 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.

[0022] Preferably, step S3 further includes a post-treatment step: After stretching the lithium carboxymethyl cellulose fiber, it is oiled, dried at a temperature less than or equal to 110 °C until the moisture content < 18%, and then packed to obtain high-purity lithium carboxymethyl cellulose fiber.

[0023] Preferably, in step S1, the preparation method of the hydrogenated carboxymethyl cellulose fiber includes the following steps:

[0024] S11: Using regenerated cellulose fiber as the raw material, it is alkalized and etherified to generate sodium carboxymethyl cellulose fiber;

[0025] S12: After the sodium carboxymethyl cellulose fiber prepared in step S11 is pickled and eluted at room temperature, hydrogenated carboxymethyl cellulose fiber is generated.

[0026] Preferably, in step S1, the regenerated cellulose fiber refers to a fiber made of natural cellulose materials, and the fineness of the regenerated cellulose fiber is 0.5-3.5 dtex; the degree of substitution of the sodium carboxymethyl cellulose fiber is 0.2-0.55. The regenerated cellulose fiber is specifically any one of viscose fiber, cuprammonium fiber, tencel fiber, and modal fiber. Taking the regenerated cellulose fiber as the raw material, compared with natural fibers, the present invention has the advantage of fiber orientation degree, making the solid electrolyte effect more controllable; in addition, the 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.

[0027] The regenerated cellulose fiber of the present invention can be alkalized and etherified to form sodium carboxymethyl cellulose fiber. Thus, the degree of substitution in sodium carboxymethyl cellulose can be controlled according to actual use needs. Then, the sodium ions on the 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 that maintains the fiber structure combine 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 degree of substitution of the obtained carboxymethyl cellulose, sodium carboxymethyl cellulose, and the carboxymethyl cellulose and carboxymethyl cellulose lithium generated by pickling and lithium salt reaction is the same.

[0028] 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 increase 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 carboxylic acid combining with lithium ions of the fiber are all incomplete reactions, and there are few carboxyl groups in the fiber that react with lithium ions inside; if the regenerated cellulose fiber is too thin, 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 always maintain the fiber form 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 thus the fineness of the finally formed carboxymethyl cellulose lithium fiber can be indirectly controlled.

[0029] By adopting the above technical solution, when preparing carboxymethyl cellulose lithium fiber in the present invention, a large amount of sodium ions need to be completely removed. Therefore, the degree of substitution of the carboxymethyl cellulose fiber is the key directly affecting the subsequent lithium array. In addition, the present invention also needs to consider the state of the sodium carboxymethyl cellulose fiber during pickling, elution, and lithium salt substitution. When the degree of substitution of the carboxymethyl cellulose fiber is 0.2-0.55, the fiber can not only be uniformly dispersed during pickling, elution, and lithium salt substitution, but also can better maintain the fiber form, thereby making the substitution reaction of lithium for sodium more complete.

[0030] When preparing sodium carboxymethyl cellulose fibers, the components of the alkalization solution, the alkalization time, the components of the etherification solution, and the etherification time will all directly affect the degree of substitution of the regenerated cellulose fibers. Therefore, the inventor obtained the above reaction parameters through a large number of experiments, and then prepared sodium carboxymethyl cellulose fibers with a specific degree of substitution (0.2 - 0.55) by strictly controlling the reaction parameters, laying a raw material foundation for the preparation of lithium carboxymethyl cellulose fibers.

[0031] Preferably, in step S11, the preparation method of the sodium carboxymethyl cellulose fiber specifically includes the following steps: Immerse the regenerated cellulose fiber in a 25 - 30 wt% sodium hydroxide solution for alkalization for 0.8 - 1.5 h. After the alkalization is completed, immerse it in an etherification solution containing 40 - 48 wt% sodium chloroacetate for etherification for 0.8 - 1.5 h. After the etherification is completed, filter off the etherification solution to obtain the sodium carboxymethyl cellulose fiber.

[0032] During the alkalization reaction, the mass ratio of sodium hydroxide to regenerated cellulose fiber added is 1:3 - 5; during the etherification reaction, the mass ratio of sodium chloroacetate to regenerated cellulose fiber added is 1:3 - 4.

[0033] Preferably, in step S11, the etherification solution includes the following components: 40 - 48 wt% sodium chloroacetate, 27 - 40 wt% alcohol, and the balance is distilled water.

[0034] Preferably, in step S12, the sodium carboxymethyl cellulose fiber is immersed in an acidifying solution for acid washing and sodium removal, and the soaking time is 0.5 - 28 h; the acidifying solution includes the following components: 1 - 4 wt% acid, 60 - 70 wt% alcohol, and the balance is distilled water. By adopting the above technical solution, 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, and it is 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. Among them, 1 - 4 wt% acid combined with 60 - 70 wt% alcohol can obtain an acidifying solution that can not only effectively remove "sodium", but also better maintain the fibrous structure. Alcohol is used as an inhibitor to prevent CMC - H from being water - soluble after binding lithium, resulting in the inability to maintain the fibrous state. Therefore, the present invention further preferably uses it.

[0035] Preferably, the acid in the acidifying solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, citric acid, acetic acid, and tartaric acid.

[0036] Preferably, the alcohol in the acidifying solution is one or more of ethanol, methanol, and isopropyl alcohol. The above alcohols can not only better maintain the fibrous form 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 drying of the fiber.

[0037] Preferably, in step S12, the pickling of the sodium carboxymethyl cellulose fiber is carried out in two times. After the first pickling and elution, the second pickling is carried out. For the first pickling, according to the mass ratio, the amount of the eluent 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%; for the second pickling, according to the mass ratio, the amount of the eluent 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%. By adopting the above technical solution, in the lithium salt substitution reaction, the sodium ions eluted by pickling will combine with the anions in the pickling to form sodium salts. The sodium salts are easy to adhere to the fibers, which will not only affect the purity of the fibers, but also affect the substitution effect to a certain extent. Therefore, in the present invention, pickling is carried out in two times. The first pickling mainly removes the sodium on the sodium carboxymethyl cellulose fiber, and then the eluted sodium ions and the residual acid are removed after elution, reducing the generation of sodium salts in the follow-up; the second pickling is mainly to keep the system acidic. In an acidic environment, the sodium-free carboxymethyl cellulose fiber can better maintain its fibrous form, and then better carry out the subsequent unidirectional substitution reaction, reducing the re-separation of lithium ions from lithium carboxymethyl cellulose.

[0038] Preferably, in step S12, the eluent after pickling the sodium carboxymethyl cellulose fiber is a mixture of alcohol and distilled water, and the proportion of distilled water in the eluent is ≤40 wt%. Preferably, the alcohol in the eluent is one or more of ethanol, methanol and isopropanol. Keeping the same alcohols as those in the acidifying solution has a better elution effect. By adopting the above technical solution, the fiber forms a negatively charged carboxymethyl cellulose fiber (H-CMC) after pickling. The alcohol in the eluent can undergo a reversible esterification reaction with the carboxyl groups 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, the above eluent can be effectively miscible with the acidifying solution under the action of alcohol, and thus has a good elution effect, eluting the excess acid and other impurities such as sodium salts in the system after the original reaction, reducing the interference of impurities on the fiber.

[0039] By adopting the above technical solution, the raw material used in the present invention is regenerated cellulose fiber. Whether it is a short fiber structure or a long fiber structure, it already has a certain degree of orientation. Therefore, the fiber of the present invention can directly use regenerated cellulose fiber with a short fiber structure, or can use regenerated cellulose fiber with a long fiber structure, which is alkalized and etherified and then cut into short fibers, or can directly use the long fiber structure to prepare filaments. Among the above three cases, the degree of orientation increases in turn, and the performance of the obtained lithium carboxymethyl cellulose fiber 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 easy to entangle, which is not convenient for subsequent weaving or non-woven operations.

[0040] If it is prepared from regenerated cellulose fibers with a long fiber structure, since the fibers are obtained by fiber morphology treatment, the lithium carboxymethyl cellulose coarse fibers 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.

[0041] The application of the lithium carboxymethyl cellulose fibers of the present invention can be preferably used in flexible energy devices, smart textiles, functional textiles, flexible electrodes, smart home appliances and other fields.

[0042] For example, due to the fiber morphology, the lithium carboxymethyl cellulose fibers have good weavability and non-woven properties, and when used as a separator material for lithium-ion batteries, they have good ion conductivity and mechanical stability. The lithium carboxymethyl cellulose fibers can be made into a separator with a certain void density through a non-woven process. Its rich lithium-ion binding and detachment characteristics can improve the efficiency of lithium-ion conduction, thereby improving the charge and discharge efficiency of the battery.

[0043] The present invention provides a lithium carboxymethyl cellulose fiber, a preparation method and an application thereof, having the following beneficial effects:

[0044] (1) The lithium carboxymethyl cellulose fibers of the present invention have good mechanical strength and conductivity, meeting the processing requirements. The dry breaking strength is 1.60 - 6.13 cN / dtex, the wet breaking strength is 1.26 - 4.20 cN / dtex, the coefficient of variation Cv is 8.5 - 9, the degree of substitution is 0.2 - 0.55, the fineness is 0.3 - 3.5 dtex, the orientation degree is ≥0.45, and the resistivity is 100 - 5000 Ω·m.

[0045] (2) The steps of the preparation method of the lithium carboxymethyl cellulose fibers of the present invention are simple and the conditions are controllable. Not only can the fibrous lithium carboxymethyl cellulose be harvested well, but the prepared lithium carboxymethyl cellulose fibers also have good mechanical strength.

[0046] (3) Since the fibers of the lithium carboxymethyl cellulose fibers of the present invention have a certain spatial structure. Therefore, after the hydrogenated carboxymethyl cellulose fibers react with the lithium salt, stretching is carried out, so that 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 have directionality, forming a long chain of lithium ions; the regularly arranged lithium ions increase the conductivity of the lithium carboxymethyl cellulose fibers and better play the conductive effect of lithium ions.

[0047] (4) When preparing lithium carboxymethyl cellulose fibers in the present invention, the method of "two - step pickling" is adopted, so that the harvested hydrogenated carboxymethyl cellulose fibers have few impurities and good stability. Combined with the component limitations of the pickling solution and the eluent, the hydrogenated carboxymethyl cellulose fibers can fully react with the lithium salt, further improving the mechanical strength and conductivity of the lithium carboxymethyl cellulose fibers. Brief Description of the Drawings

[0048] Figure 1 It is an electron micrograph of the drawn lithium hydrogenated carboxymethyl cellulose fiber in Example 1;

[0049] Figure 2 It is an electron micrograph of the cross - section of the cut drawn lithium hydrogenated carboxymethyl cellulose fiber in Example 1;

[0050] Figure 3 It is an electron micrograph of the undrawn lithium hydrogenated carboxymethyl cellulose fiber in Example 15;

[0051] Figure 4 It is an electron micrograph of the cross - section of the cut undrawn lithium hydrogenated carboxymethyl cellulose fiber in Example 15. Detailed Description of the Embodiments

[0052] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0053] The lithium carboxymethyl cellulose fibers provided by the present invention use existing fibers as materials and can be obtained by subjecting sodium carboxymethyl cellulose fibers to pickling and then carrying out a substitution reaction with a lithium salt. The present invention mainly uses regenerated fibers as the initial raw materials. After alkalization and etherification treatment, sodium carboxymethyl cellulose fibers can be harvested. After pickling treatment, hydrogenated carboxymethyl cellulose fibers can be harvested. Then, the prepared hydrogenated carboxymethyl cellulose fibers are reacted with a lithium salt to harvest crude lithium carboxymethyl cellulose fibers. Finally, they are oiled, dried, and packed according to needs and then harvested.

[0054] The above - mentioned regenerated fibers can be one or more of viscose fibers, cuprammonium fibers, tencel fibers, and modal fibers. They have a wide source and low cost and can be directly purchased on the market, but the orientation degree index of the commercially available regenerated cellulose fibers is 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, and will not be further elaborated here.

[0055] Among them, the degree of substitution and fineness of the fibers have a greater impact on the mechanical strength. The specific detection methods are as follows:

[0056] ①Degree of substitution

[0057] Detection of the degree of substitution of sodium carboxymethyl cellulose fiber: Refer to the test for the degree of substitution of sodium carboxymethyl cellulose in the Pharmacopoeia of the People's Republic of China (2020 Edition).

[0058] The method for detecting the degree of substitution of lithium carboxymethyl cellulose fiber is as follows:

[0059] (1) Take lithium carboxymethyl cellulose fiber. 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 digest it completely by heating with an electric furnace;

[0060] (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.

[0061] (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:

[0062] Table 1 Recommended measurement conditions

[0063] Inspection wavelength nm 670 Flame type Air-acetylene Ratio Ratio Air:acetylene = 3 - 5:1 Air:acetylene = 3 - 5:1

[0064] When carrying out the measurement, proceed as follows: First, measure the absorbance of a series of standard solutions, draw a standard curve, then directly measure the absorbance of the sample solution and the blank solution, calculate the lithium element content in the sample solution and the blank solution, and then subtract the lithium element content in the blank solution from the lithium element content in the sample solution to obtain the mass percentage concentration of lithium ions, that is, the lithium content in the lithium carboxymethyl cellulose fiber.

[0065] After measuring the mass percentage concentration of lithium ions in the lithium carboxymethyl cellulose fiber sample by using the above method for measuring the lithium content in the lithium carboxymethyl cellulose fiber, substitute it into the following calculation equation for calculating the degree of substitution of the sample:

[0066]

[0067] 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 (%).

[0068] ②Fineness: It is measured by a fineness tester.

[0069] The present invention will be further described in detail below with reference to the accompanying drawings, examples and comparative examples.

[0070] Example 1

[0071] The preparation method of lithium carboxymethyl cellulose fiber of the present invention comprises the following steps:

[0072] S1. Select 400,000 denier regenerated cellulose fiber - viscose filament bundle, fiber with a single fiber fineness of 1.33 dtex as raw materials, immerse them in a sodium hydroxide solution with a concentration of 28 wt% for alkalization, raise the temperature to 65 °C, and the alkalization time is 1 h. After the alkalization is completed, filter off the sodium hydroxide solution; immerse them in an etherification solution, which is composed of 45 wt% sodium chloroacetate, 35 wt% ethanol, and 20 wt% distilled water, raise the temperature to 60 °C, and the etherification time is 1 h. After the etherification is completed, filter off the etherification solution to obtain sodium carboxymethyl cellulose fiber, and its degree of substitution is detected to be 0.40.

[0073] S2. At room temperature, immerse the sodium carboxymethyl cellulose fiber 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 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; when the acidification solution of primary acidification is completely eluted, stop passing the elution solution, and perform the first pickling. According to the mass ratio, the amount of the elution solution is 10 - 20 times that of the fiber, and elute until the dry fiber is tested by atomic absorption spectrometry and the sodium ion content < 2%; immerse the sodium carboxymethyl cellulose fiber again in the acidification solution with the same components as the primary acidification for secondary acidification. At room temperature, after soaking in the acidification solution for 12 h, pass the elution solution, and perform the second pickling. According to the mass ratio, the amount of the elution solution is 10 - 20 times that of the fiber, and elute until the dry fiber is tested by atomic absorption spectrometry and the sodium ion content < 0.2%. When the elution solution completely elutes the acidification solution, hydrogenated carboxymethyl cellulose fiber is obtained.

[0074] 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 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 to obtain crude lithium carboxymethyl cellulose fiber.

[0075] S4. Oil, dry, and crimp the crude lithium carboxymethyl cellulose fiber prepared in S3, and then cut it into short fibers with a length of 3.8 cm. After packing, collect lithium carboxymethyl cellulose fiber with a degree of substitution of 0.40 and a fineness of 1.25 dtex. The electron micrograph of its product is shown in Figure 1 and Figure 2 from Figure 1 and Figure 2In the electron microscope photograph, it can be clearly seen that the overall external morphology of the lithium carboxymethyl cellulose fiber prepared by the preparation method of the present invention is straight, and the cut cross-sectional view can further show that the product fiber always maintains a consistent cutting surface direction, and the cutting operation will not change its overall structural properties.

[0076] Example 2

[0077] The preparation method of the lithium carboxymethyl cellulose fiber of the present invention comprises the following steps:

[0078] S1. Select 400,000 denier regenerated cellulose fiber - cuprammonium fiber filament bundle with a single fiber fineness of 0.5 dtex as the raw material, immerse it in a sodium hydroxide solution with a concentration of 25 wt% for alkalization, raise the temperature to 65°C, and the alkalization time is 0.8 h. After the alkalization is completed, filter off the sodium hydroxide solution; immerse it in an etherification solution, which consists of 42 wt% sodium chloroacetate, 40 wt% ethanol, and 18 wt% distilled water, raise the temperature to 60°C, and the etherification time is 0.8 h. After the etherification is completed, filter off the etherification solution to obtain sodium carboxymethyl cellulose fiber, and the degree of substitution is detected to be 0.30;

[0079] 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. Under room temperature conditions, soak for 12 h; pass an elution solution into 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 of the primary acidification is completely eluted, perform the first pickling. According to the mass ratio, the amount of the elution solution is 10 - 20 times that of the fiber, and elute until the sodium ion content of the dry fiber tested by atomic absorption spectrometry is < 2%; stop passing the elution solution, immerse the sodium carboxymethyl cellulose fiber again in the same acidification solution as the primary acidification for secondary acidification. Under room temperature conditions, after soaking in the acidification solution for 12 h, pass the elution solution. After the elution solution completely elutes the acidification solution, perform the second pickling. According to the mass ratio, the amount of the elution solution is 10 - 20 times that of the fiber, and elute until the sodium ion content of the dry fiber tested by atomic absorption spectrometry is < 0.2%. After the elution solution is completely replaced, hydrogenated carboxymethyl cellulose fiber is obtained.

[0080] S3. Take out the hydrogenated carboxymethyl cellulose fiber prepared in S2 and immerse it in a lithium salt solution, which consists of 3 wt% lithium chloride, 60 wt% ethanol, and 37 wt% distilled water. Under room temperature conditions, after soaking, perform stretching with a stretching roller, and the elongation ratio is 1:1.34 to obtain lithium carboxymethyl cellulose rough fiber;

[0081] S4. Oil, dry, and crimp the lithium carboxymethyl cellulose rough fiber prepared in S3, then cut it into short fibers with a length of 3.8 cm, and after packing, obtain lithium carboxymethyl cellulose fiber with a degree of substitution of 0.30 and a fineness of 0.49 dtex.

[0082] Example 3

[0083] This example discloses a lithium carboxymethyl cellulose fiber, and its preparation method includes the following steps:

[0084] S1. Select 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% for alkalization, raise the temperature to 65 °C, and the alkalization time is 1.2 h. After the alkalization is completed, filter out the sodium hydroxide solution; immerse it in the etherification solution, which consists of 48 wt% sodium chloroacetate, 27 wt% ethanol, and 25 wt% distilled water, raise the temperature to 60 °C, and the etherification time is 1.2 h. After the etherification is completed, filter out the etherification solution to obtain sodium carboxymethyl cellulose fiber. After testing, the degree of substitution is 0.44;

[0085] S2. Immerse the sodium carboxymethyl cellulose fiber prepared in S1 into 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. Under room temperature conditions, soak for 12 h; pass the elution solution into 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 of primary acidification is completely eluted, perform the first pickling. According to the mass ratio, the amount of the elution solution is 10 - 20 times that of the fiber, and elute until the dry fiber is tested by atomic absorption spectrometry and the sodium ion content < 2%. Stop passing the elution solution, and immerse the sodium carboxymethyl cellulose fiber into the same acidification solution as the primary acidification for secondary acidification. Under room temperature conditions, after soaking in the acidification solution for 12 h, pass the elution solution. After the elution solution completely elutes the acidification solution, perform the second pickling. According to the mass ratio, the amount of the elution solution is 10 - 20 times that of the fiber, and elute until the dry fiber is tested by atomic absorption spectrometry and the sodium ion content < 0.2%; after the elution solution is completely replaced, the hydrogenated carboxymethyl cellulose fiber is obtained.

[0086] S3. Take out the hydrogenated 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. Under the condition of 90 °C, soak and react for 5 min. After soaking, use a drawing roller for drawing, and the elongation ratio is 1:1.55 to obtain the lithium carboxymethyl cellulose coarse fiber;

[0087] S4. Oil, dry, and crimp the lithium carboxymethyl cellulose coarse fiber prepared in S3, and then cut it into short fibers with a length of 3.8 cm. After packing, obtain the lithium carboxymethyl cellulose fiber with a degree of substitution of 0.44 and a fineness of 2.8 dtex.

[0088] Example 4

[0089] This embodiment discloses a lithium carboxymethyl cellulose fiber, and its preparation method includes the following steps:

[0090] S1. Select a 400,000 denier regenerated cellulose fiber (modal fiber) filament bundle with a single filament fineness of 3.5 dtex as the raw material, immerse it in a sodium hydroxide solution with a concentration of 28 wt% for alkalization, raise the temperature to 65 °C, and the alkalization time is 1.5 h. After the alkalization is completed, filter off the sodium hydroxide solution; immerse it in an etherification solution, which is composed of 45 wt% sodium chloroacetate, 35 wt% ethanol, and 20 wt% distilled water. Raise the temperature to 60 °C, and the etherification time is 1.5 h. After the etherification is completed, filter off the etherification solution to obtain sodium carboxymethyl cellulose fiber. After testing, the degree of substitution is 0.52.

[0091] 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 is composed of 2 wt% hydrochloric acid, 70 wt% ethanol, and 28 wt% distilled water. Under room temperature conditions, 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 acidification solution of the primary acidification is completely eluted, perform the first pickling. According to the mass ratio, the amount of the elution solution is 10 - 20 times that of the fiber, and elute until the dry fiber is tested by atomic absorption spectrometry and the sodium ion content < 2%. Stop passing the elution solution, and immerse the sodium carboxymethyl cellulose fiber again in the same acidification solution as the primary acidification for secondary acidification. Under room temperature conditions, after soaking in the acidification solution for 12 h, pass the elution solution, and perform the second pickling. According to the mass ratio, the amount of the elution solution is 10 - 20 times that of the fiber, and elute until the dry fiber is tested by atomic absorption spectrometry and the sodium ion content < 0.2%. After the acidification solution is completely eluted by the elution solution and the elution solution is completely replaced, the hydrogenated carboxymethyl cellulose fiber is obtained.

[0092] S3. Take out the hydrogenated carboxymethyl cellulose fiber prepared in S2 and immerse it 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 drafting roller for drafting, and the elongation ratio is 1:1.4 to obtain the lithium carboxymethyl cellulose coarse fiber;

[0093] S4. Oil, dry, and crimp the lithium carboxymethyl cellulose coarse fiber prepared in S3, and then cut it into short fibers with a length of 3.8 cm. After packing, the lithium carboxymethyl cellulose fiber with a degree of substitution of 0.52 and a fineness of 3.3 dtex is obtained.

[0094] Examples 5 - 6

[0095] Examples 5 - 6 are based on the method of Example 1, and the processing parameters of the regenerated cellulose fiber in step S1 are adjusted. For specific adjustments, see Table 2 below.

[0096] Table 2 Processing parameter table of regenerated cellulose fibers in Examples 1, 5 - 6

[0097]

[0098] Examples 7 - Example 14

[0099] Based on the method of Example 1, in Examples 7 - Example 14, the components of the lithium salt solution in step S3 are adjusted. For specific adjustments, refer to Table 3 below.

[0100] Table 3 Composition table of lithium salt solutions in Examples 1, 7 - 14

[0101]

[0102] Example 15

[0103] Based on the method of Example 1, in this example, the lithium carboxymethyl cellulose fibers obtained in step S3 are directly cut into lithium carboxymethyl cellulose short fibers with a length of 3.8 cm. Subsequently, the stretching operation in step S3 is correspondingly omitted, and lithium carboxymethyl cellulose fibers with 1.34 dtex are obtained. The electron micrographs can be seen in Figure 3 and Figure 4 , and further compared with the electron micrograph of the product in Example 1, it can be clearly seen that the outer surface of the lithium carboxymethyl cellulose fibers without stretching treatment is rough, especially Figure 4 In the cross-sectional view in, it can be more clearly seen that the lithium carboxymethyl cellulose fibers without stretching treatment are slightly disordered and uneven.

[0104] Comparative Example 1

[0105] Commercially available lithium carboxymethyl cellulose powder is used, with a carboxymethyl cellulose content ≥ 99.5 wt%, 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 cannot be directly used for fiber-related mechanical property testing experiments.

[0106] Comparative Example 2

[0107] Based on Example 1, the difference is that after soaking in step S3, stretching is performed using a stretching roller, and the elongation ratio is 1:2.50, and broken lithium carboxymethyl cellulose fibers are obtained.

[0108] Comparative Example 3

[0109] Based on Example 3, take the filament bundle of tencel fiber and the fiber with a single filament fineness of 3.0 dtex as raw materials. The difference is that in step S1, it is immersed in a sodium hydroxide solution with a concentration of 50 wt% for alkalization, the temperature is raised to 65 °C, and the alkalization time is 1.2 h. After the alkalization is completed, the sodium hydroxide solution is filtered off; it is immersed in an etherification solution, which consists of 48 wt% sodium chloroacetate, 27 wt% ethanol, and 25 wt% distilled water. The temperature is raised to 60 °C, and the etherification time is 1.2 h. After the etherification is completed, the etherification solution is filtered off, and then sodium carboxymethyl cellulose fiber is obtained. After detection, the degree of substitution is 0.60. Then, through step S3, it is immersed in a lithium salt solution, and finally lithium carboxymethyl cellulose is prepared.

[0110] Comparative Example 4

[0111] Based on Example 3, take the filament bundle of tencel fiber and the fiber with a single filament fineness of 3.0 dtex as raw materials. After alkalization, it is immersed in an etherification solution. The difference is that in step S1, the etherification solution consists of 55 wt% sodium chloroacetate, 25 wt% ethanol, and 20 wt% distilled water. The temperature is raised to 60 °C, and the etherification time is 1.2 h. After the etherification is completed, the etherification solution is filtered off, and then sodium carboxymethyl cellulose fiber is obtained. After detection, the degree of substitution is 0.81. Then, through step S3, it is immersed in a lithium salt solution, and finally lithium carboxymethyl cellulose is prepared.

[0112] Comparative Example 5

[0113] Based on Example 1, in step S2, the sodium carboxymethyl cellulose fiber prepared in S1 is immersed in an elution container filled with an acidification solution for primary acidification. The difference is that the acidification solution consists of 25 wt% hydrochloric acid, 55 wt% ethanol, and 20 wt% distilled water. At room temperature, it is soaked for 12 h; an elution solution is passed 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 of the primary acidification is completely eluted, the first acid washing is carried out. According to the mass ratio, the amount of the elution solution 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%, then the passage of the elution solution is stopped. The sodium carboxymethyl cellulose fiber is immersed again in the acidification solution with the same components as the primary acidification for secondary acidification. After soaking in the acidification solution for 12 h, the elution solution is passed through. The second acid washing is carried out. According to the mass ratio, the amount of the elution solution 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%. When the elution solution completely elutes the acidification solution, hydrogenated sodium carboxymethyl cellulose fiber is obtained. Then, through step S3, it is immersed in a lithium salt solution, and finally lithium carboxymethyl cellulose is prepared.

[0114] Comparative Example 6

[0115] Based on Example 1, the difference lies in that in step S2, single acidification is adopted. The specific steps are as follows: Immerse the sodium carboxymethyl cellulose fiber prepared in step S1 into an elution container filled with acidifying solution for single acidification. The acidifying solution is composed of 30 wt% hydrochloric acid, 55 wt% ethanol, and 15 wt% distilled water. Under room temperature conditions, after the acidifying solution soaks for 12 h, eluent is introduced. According to the mass ratio, the amount of eluent is 10 - 20 times that of the fiber. Elute until the sodium ion content in the dry fiber tested by atomic absorption spectrometry is < 2%. After the eluent completely elutes the acidifying solution, the hydrogenated carboxymethyl cellulose fiber is obtained.

[0116] Performance detection test

[0117] Perform performance tests on the products of the above-mentioned examples and comparative examples. The inspection results are shown in Table 4 below. The test methods are as follows:

[0118] The fiber orientation degree is measured by the optical birefringence method;

[0119] The detection methods for the fiber tensile properties and coefficient of variation refer to GB / T 14337 - 2022;

[0120] The fiber substitution degree is measured according to the above detection method;

[0121] For the determination method of lithium ion content, the flame photometry method is adopted. After the fiber is ashed, the lithium ions are sprayed into the flame, and the content of lithium ions in the fiber is determined by detecting the intensity of the emitted light.

[0122] For the resistivity test method, a Seebeck coefficient measuring instrument is used. The fibers are all tested for resistance 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. Fix the twisted sample in the test vacuum device, make the two electrodes in close contact with both ends of the sample respectively to ensure good contact, and accurately control the effective test length of the sample at 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 measurement parameters are adjusted, read the resistance value.

[0123] Table 4 Performance test data table

[0124]

[0125] Combined with the above table, it can be seen that in Examples 1 - 4 of the present invention, different regenerated cellulose fibers are used as raw materials. From the detection results, it can be obtained that different regenerated cellulose fibers can all obtain the corresponding lithium carboxymethyl cellulose fibers by using the preparation method of the present invention.

[0126] Combined with the test results of Examples 5-6, it can be obtained that the components of the alkalization solution, the alkalization time, the components of the etherification solution, and the etherification time will have a certain impact on the substitution degree of carboxymethyl cellulose. And during the whole alkalization process, it is only necessary to keep all the fibers completely immersed in the alkalization solution to realize the preparation method of lithium carboxymethyl cellulose fiber of the present invention. The present invention further defines that "immersing the regenerated cellulose fiber in a 25-30 wt% sodium hydroxide solution for alkalization for 0.8-1.5 h, filtering off the sodium hydroxide solution after the alkalization is completed, immersing it in an etherification solution containing 40-48 wt% sodium chloroacetate for etherification for 0.8-1.5 h, and filtering off the etherification solution after the etherification is completed" and "the etherification solution includes the following components: 40-48 wt% sodium chloroacetate, 27-40 wt% alcohol, and the balance is distilled water" to prepare sodium carboxymethyl cellulose fiber. Thereby ensuring that the substitution degree of the prepared carboxymethyl cellulose fiber is within the range of 0.2-0.55, and further promoting that the sodium carboxymethyl cellulose fiber can not only be evenly dispersed during pickling, elution, and lithium salt substitution, but also can better maintain the fiber morphology, and further making the substitution reaction of lithium for sodium more complete.

[0127] Referring to the test results of Example 1 and Examples 7-14, it can be obtained that the present invention immerses the hydrogenated carboxymethyl cellulose fiber in a lithium salt solution for reaction, and further defines 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.

[0128] Referring to the test results of Example 1 and Example 15, it can be obtained that the length and morphology of the regenerated cellulose fiber of the present invention and whether the subsequent fiber is drawn will affect the orientation degree of the fiber to a certain extent. The fiber of the present invention can directly adopt the regenerated cellulose fiber with a short fiber structure.

[0129] Comparative Example 1, commercially available lithium carboxymethyl cellulose powder, without fiber structure, is obviously different from the content of this patent.

[0130] Comparative Example 2, excessive drawing leads to the inability to maintain the fiber morphology, and the subsequent spinnability and electrical properties are poor.

[0131] Comparative Examples 3, 4, and 5, the alkalization concentration, etherification concentration, and acidification concentration for the preparation of lithium carboxymethyl cellulose fiber are too high, and the physical properties of the fiber decline severely and lose spinnability.

[0132] Comparative Example 6, pickling once is bound to increase the acid concentration, and cellulose degrades under high acid concentration.

[0133] Meanwhile, compared with the carboxymethyl cellulose lithium fibers prepared by the preparation method of the comparative example, the carboxymethyl cellulose lithium fibers prepared by the present invention have good conductivity, and the resistivity can reach 450 Ω·m. Combining the above mechanical properties, the carboxymethyl cellulose lithium fibers prepared by the present invention can simultaneously have good mechanical strength and conductivity, meeting more application and processing requirements.

[0134] In particular, Example 15 is based on the method of Example 1. The carboxymethyl cellulose lithium fibers prepared in step S3 are cut into carboxymethyl cellulose lithium short fibers with a length of 3.8 cm, and the subsequent stretching operation in step S3 is correspondingly omitted to obtain carboxymethyl cellulose lithium fibers with a fineness of 1.34 dtex. The electron micrographs are shown in Figure 3 and Figure 4 , from Figure 1 - Figure 4 the electron micrographs, it can be clearly seen the appearance difference between the stretched and non-stretched carboxymethyl cellulose lithium fibers. The stretched carboxymethyl cellulose lithium fibers are in an oriented and ordered distribution state.

[0135] From the electrical property test results, it can be obtained that as the blank group of Example 1 - the raw material ordinary viscose fiber of Example 1, after the above tests, according to the degree of substitution test, there is no substitution, and there are no lithium ions after ashing, and the resistance value > 100000 Ω·m, which does not have the excellent electrical properties of the carboxymethyl cellulose lithium fibers prepared by the present invention; the resistivity of Example 15 is 4100 Ω·m. Compared with the resistivity of 950 Ω·m of the carboxymethyl cellulose lithium fibers prepared by the stretched examples, it can be further clearly obtained that for the preparation method of the present invention, in the lithium salt solution, the negatively charged H-CMC combines with Li + to form carboxymethyl cellulose lithium. During the combination process, lithium ions diffuse disorderly and penetrate into the carboxymethyl cellulose fibers covered with carboxyl groups to form carboxymethyl cellulose lithium fibers. The lithium ions are extremely unevenly dispersed and chaotic in the fibers.

[0136] After the hydrogenated carboxymethyl cellulose fibers are immersed in the lithium salt solution and then stretched, the stretched fibers were originally randomly distributed. After being stretched by force, they gradually deflect uniformly in the direction of the acting force, the degree of orientation increases, and the lithium ions attached to the fibers also become directional, forming a long chain of lithium ions, effectively fixing the lithium ions. Since the structure of the material determines the conductive performance of the material, as the degree of orientation of the material increases, the conductivity increases and the resistivity decreases. Therefore, when the fiber is stretched, the axial length increases and the transverse dimension shortens. The shortening of the lithium ion spacing makes the conductivity of the fiber increase and the resistivity decrease.

[0137] The hydrogenated carboxymethyl cellulose fiber is stretched after reacting with a lithium salt, and the elongation ratio of the stretching is 1:1.05 - 1.55. The designed stretching force range is 1.5 - 3.7 (cN / dtex) for a single filament, within the range of the fiber physical indexes. Too strong a stretching force is likely to cause the fiber to break, and too small a stretching force cannot achieve the effect of increasing the fiber orientation degree. Under the stretching conditions, the fiber will have a certain elongation, and the elongation ratio is preferably 1:1.05 - 1.55. If the elongation ratio is too small, the fiber is prone to rebound, and the orientation degree returns to the state before elongation; if the elongation ratio is too large, the fiber breaks and processing is difficult.

[0138] Application Example

[0139] In summary, the lithium carboxymethyl cellulose fibers prepared in Examples 1 - 14 of the present invention are flexible materials with good mechanical properties and electrical properties, and can be widely used in the following fields including but not limited to: flexible energy devices, smart textiles, functional textiles, flexible electrodes, and can be specifically made into flexible conductive films, fabrics, negative electrode sheets, etc. according to needs.

[0140] The above are only examples of the present invention. For example, in step S1, 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, and lithium hexafluoroarsenate; the regenerated cellulose fiber is specifically any one of viscose fiber, cuprammonium fiber, tencel fiber, and modal fiber; the acid in the acidifying solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, citric acid, acetic acid, and tartaric acid, and the alcohol in the acidifying solution is one or more of ethanol, methanol, and isopropanol; in step S12, the eluent after pickling the sodium carboxymethyl cellulose fiber is a mixture of alcohol and distilled water, and the proportion of distilled water in the eluent is ≤40 wt%; in step S11, the regenerated cellulose fiber is directly alkalized and etherified using a short fiber structure, and the short fiber length is 1 - 15 cm; or the regenerated cellulose fiber uses a long fiber structure, and the sodium carboxymethyl cellulose fiber after alkalization and etherification is cut into a short fiber structure, and the length of the cut short fiber is ≥1 mm; the orientation degree of the lithium carboxymethyl cellulose fiber measured by the optical birefringence method is 0.45 - 0.98; in step S1, the hydrogenated carboxymethyl cellulose fiber and the lithium salt solution are subjected to a room temperature substitution reaction for 1 - 48 h under the condition of pH≥9 to obtain lithium carboxymethyl cellulose thick fiber; -CH 2 COO - of the hydrogenated carboxymethyl cellulose fiber reacts with Li + dissociated from the lithium salt in the solution, wherein the concentration of the lithium-containing material in the lithium salt solution is 2 wt% - 5 wt%, and the molar number of the added amount of Li + and -CH in the hydrogenated carboxymethyl cellulose fiber 2 COO -The molar ratio of the addition amount is 1 - 1.2:1; and by selecting the alkalization, etherification, and acidification temperatures that match according to the actual application situation, the lithium carboxymethyl cellulose fiber of the present invention, its preparation method, and application can all be realized.

[0141] The embodiments described above are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall all fall within the protection scope determined by the claims of the present invention.

Claims

1. A carboxymethyl cellulose lithium fiber, characterized in that The hydrogenated carboxymethyl cellulose (H-CMC) fiber is subjected to a substitution reaction with a lithium salt solution to obtain a carboxymethyl cellulose lithium fiber with a substitution degree of 0.2-0.55 and a fineness of 0.3-3.5 dtex.

2. The carboxymethyl cellulose lithium fiber according to claim 1, characterized in that The orientation degree of the carboxymethyl cellulose lithium fiber measured by optical birefringence method is 0.45-0.98; the length of the carboxymethyl cellulose lithium fiber is 1mm-15cm.

3. The method for preparing carboxymethyl cellulose lithium fiber according to claim 1 or 2, characterized in that: The specific steps include: S1. Carrying out a substitution reaction between hydrogenated carboxymethyl cellulose fiber and a lithium salt solution at room temperature for 1-48 hours under a pH ≥ 9 condition to obtain crude carboxymethyl cellulose lithium fiber; Lithium ions (Li + ) undergoes a substitution reaction with the hydrogen ions (-CH2COOH) on the carboxylmethyl groups of the hydrogenated carboxymethyl cellulose fibers, wherein the lithium salt solution contains a lithium material concentration of 2wt%-5wt%, and Li + The molar ratio of the added amount to the molar ratio of -CH2COOH added in the hydrogenated carboxymethyl cellulose fiber is 1-1.2:1; S2. Stretch the crude carboxymethyl cellulose lithium fiber prepared in S1 to obtain carboxymethyl cellulose lithium fiber, and keep the fiber unbroken during the stretching process.

4. The method for preparing carboxymethyl cellulose lithium fiber according to claim 3, characterized in that: In step S2, the hydrogenated carboxymethyl cellulose fiber is stretched after reacting with the lithium salt, and the stretching ratio is 1:1.05-1.

55.

5. The method for preparing carboxymethyl cellulose lithium fiber according to claim 3, characterized in that: In step S1, 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 inhibitor, 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, and lithium hexafluoroarsenate.

6. The method for preparing carboxymethyl cellulose lithium fiber according to claim 3, characterized in that: In step S1, the method for preparing hydrogenated carboxymethyl cellulose fiber comprises the following steps: S11, using regenerated cellulose fiber as raw material, generating sodium carboxymethyl cellulose fiber through alkalization and etherification; S12, acid-washing and eluting the sodium carboxymethyl cellulose fiber prepared in step S11 to generate hydrogenated carboxymethyl cellulose fiber; The regenerated cellulose fiber refers to a fiber made from natural cellulose material, and the fineness of the regenerated cellulose fiber is 0.5-3.5 dtex; the degree of substitution of the sodium carboxymethyl cellulose fiber is 0.2-0.55; The regenerated cellulose fiber is specifically any one of viscose fiber, cuprammonium fiber, tencel fiber, and modal fiber; In step S11, the preparation method of the sodium carboxymethyl cellulose fiber specifically comprises the following steps: immersing the regenerated cellulose fiber in a 25-30wt% sodium hydroxide solution at a reaction temperature of 60-70°C for alkalization for 0.8-1.5h, and then immersing the regenerated cellulose fiber in an etherification liquid containing 40-48wt% sodium chloroacetate at a reaction temperature of 60-70°C for etherification for 0.8-1.5h after the alkalization, and filtering off the etherification liquid after the etherification to obtain the sodium carboxymethyl cellulose fiber; During the alkalization reaction, the mass ratio of sodium hydroxide added to the regenerated cellulose fiber is 1:3-5; During the etherification reaction, the mass ratio of sodium chloroacetate to regenerated cellulose fiber is 1:3-4; The etherification liquid comprises the following components: 40-48 wt % of sodium chloroacetate, 27-40 wt % of alcohol, and the balance is distilled water.

7. The method for preparing carboxymethyl cellulose lithium fiber according to claim 6, characterized in that: In step S12, 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; 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 acidified liquid is one or more of ethanol, methanol and isopropanol.

8. The method for preparing carboxymethyl cellulose lithium fiber according to claim 7, characterized in that: In step S12, the acid washing of the sodium carboxymethyl cellulose fiber is performed twice, and after the first acid washing is completed and eluted, the second acid washing is performed; 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%; The eluent of the sodium carboxymethyl cellulose fiber after acid washing is a mixture of alcohol and distilled water, and the proportion of distilled water in the eluent is ≤40wt%.

9. The method for preparing carboxymethyl cellulose lithium fiber according to claim 3, characterized in that: In step S11, the regenerated cellulose fiber is directly alkalized and etherified with a short fiber structure, and the short fiber length is 1 mm-15 cm; or the regenerated cellulose fiber is a long fiber structure, and the sodium carboxymethyl cellulose fiber after the alkalization and etherification treatment is cut into a short fiber structure, and the short fiber length after cutting is ≥1 mm.

10. Application of the carboxymethyl cellulose lithium fiber according to any one of claims 1-2 or the carboxymethyl cellulose lithium fiber prepared by the preparation method according to any one of claims 3-9 in the field of flexible functional materials, specifically in flexible energy devices, smart textiles, functional textiles, flexible electrodes, and smart home appliances.

Images