A preparation method of regenerated cellulose fiber and regenerated cellulose fiber

Abstract

The present invention belongs to the field of regenerated cellulose fibers and discloses a method for preparing regenerated cellulose fibers and regenerated cellulose fibers. The preparation method comprises the following steps: 1) pretreatment: partially substituting hydroxyl groups in cellulose pulp to prepare modified cellulose pulp with a degree of substitution of 0.001 to 2.0; 2) mixing unmodified cellulose pulp with modified cellulose pulp, and then mixing and swelling with an NMMO solution; 3) dissolving, spinning, and post-processing under vacuum conditions to produce a regenerated cellulose fiber product. The present invention pretreats cellulose to obtain a modified cellulose pulp with partially substituted hydroxyl groups; then physically blending different fiber pulps to prepare a spinning solution, thereby improving fibrillation while ensuring the mechanical properties of the fibers. Compared to traditional crosslinking methods, the method eliminates the need for toxic chemicals, water washing, or acid washing, thereby reducing the discharge of harmful substances and wastewater, and also reducing energy consumption caused by crosslinking agent reactions.

Description

Technical Field

[0001] The present invention belongs to the field of regenerated cellulose fibers, and specifically relates to a preparation method of regenerated cellulose fibers and regenerated cellulose fibers; more specifically, it relates to a pretreatment method of cellulose pulp raw materials and a method for preparing cellulose fibers by mixing different cellulose raw materials. Background Art

[0002] Regenerated cellulose fiber is a man-made fiber made from natural cellulose or other cellulose-containing raw materials through chemical treatment. The raw materials of regenerated cellulose fiber can come from waste paper, wood pulp, crop straw, sugarcane bagasse, etc., and are transformed into spinnable fibers through multiple chemical treatment processes. Regenerated cellulose fiber has the characteristics of biodegradability, hygroscopicity and breathability. At the same time, it also has good dyeability and washability, is not easy to deform, has good elasticity, and has been widely used. However, regenerated cellulose fiber will cause poor fiber fibrillation under wet friction conditions, seriously affecting the quality of yarn and fabric. At present, the main way to solve the problem of easy fibrillation of Lyocell cellulose fiber is to perform cross-linking post-treatment on the fiber or fiber fabric, for example:

[0003] Patent publication number CN104005225A reports that fibers are immersed in a solution containing a cross-linking agent, a catalyst, and a penetrant. After preliminary rolling and drying, the fibers are pre-treated and cured by baking and cross-linking, and then washed with warm soft water and cold soft water to produce anti-fibrillation Lyocell fibers. This method is simple and can be used in Lyocell fiber industrial production lines. However, steps such as preheating and baking time in this method not only cause the mechanical properties of the fibers to decline, but also substances such as catalysts and surfactants introduced to improve cross-linking efficiency increase wastewater discharge and processing difficulty.

[0004] Patent publication number CN113718350A discloses a method for adding a crosslinking agent to an oil. To prevent the crosslinker from reacting with water, the crosslinker is first end-capped. Subsequently, the fiber drying temperature is adjusted to de-end the crosslinker, allowing the crosslinker to continue reacting with the hydroxyl groups in the cellulose. This method effectively reduces fiber fibrillation and allows Lyocell fibers to be processed using conventional preparation processes, eliminating steaming and other steps, significantly reducing costs. However, the de-end capping of the crosslinker can easily activate some functional groups, making it difficult to control.

[0005] Patent publication number CN114457591A discloses a fibrillation-resistant cellulose fiber and its preparation method. By adding an aldehyde-free crosslinking agent, a glycidyl ether epoxy resin, to the cellulose fibers during spinning or post-processing, and allowing the glycidyl ether epoxy resin to crosslink the cellulose fibers under appropriate content, ratio, and reaction conditions, the fibrillation-resistant cellulose fibers are prepared, addressing the problem of cellulose fibers being prone to fibrillation. However, this method still requires the addition of a glycidyl ether epoxy resin as a crosslinking agent, which is costly and requires subsequent processing.

[0006] In addition, the chemical cross-linking methods mentioned above generally have problems such as toxicity and insufficient process stability, which have changed the green and environmentally friendly properties of the new solvent-based cellulose fiber.

[0007] In summary, there is a need for a green and simple method to improve the fibrillation problem of lyocell fiber while ensuring the mechanical properties of the fiber. This method can not only eliminate the toxicity problems caused by the current cross-linking agents, but also reduce the wastewater discharge and NMMO recovery problems caused by the introduction of cross-linking agent catalysts, water washing and acid washing.

[0008] In view of this, the present invention is proposed. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing regenerated cellulose fiber and regenerated cellulose fiber. The present invention pretreats cellulose to obtain a modified cellulose pulp in which hydroxyl groups are partially substituted. Unmodified cellulose pulp is then premixed with an NMMO solution and then mixed with the modified cellulose pulp. This ensures that the unmodified cellulose pulp is fully swollen in the NMMO solution and the modified pulp is uniformly dispersed in the mixed system. Hydrogen bonding between hydroxyl groups increases the lateral bonding between molecular chains, affecting changes in the fiber aggregation structure and improving the fiber's resistance to fibrillation. Furthermore, the mixing method between the pretreated pulp and the untreated pulp of the present invention is a purely physical method, requiring no addition of any reaction reagents, thereby reducing energy consumption for subsequent fiber washing.

[0010] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is:

[0011] The present invention provides a method for preparing solvent-processed regenerated cellulose fiber, comprising the following steps:

[0012] 1) Pretreatment: Substituting some hydroxyl groups of cellulose pulp to prepare modified cellulose pulp with a degree of substitution of 0.001 to 2.0;

[0013] 2) Mixing unmodified cellulose pulp with modified cellulose pulp, and then mixing with NMMO solution to swell,

[0014] 3) dissolving, spinning and post-processing under vacuum conditions to obtain regenerated cellulose fiber products.

[0015] The present invention provides a method for preparing regenerated cellulose fibers using a new solvent method, wherein cellulose pulp is pretreated and heterochains / heterogroups are introduced to obtain a modified cellulose pulp in which hydroxyl groups are partially substituted; unmodified cellulose pulp is then mixed with modified cellulose pulp, and then mixed and swelled with an NMMO solution, followed by dehydration and dissolution under certain vacuum conditions to obtain a uniformly dissolved cellulose solution. The pretreatment method provided by the present invention is simple and easy to control, does not affect the green fiber preparation process, and can improve fibrillation by physically blending different pulps. At the same time, it can also maintain the mechanical properties of the fibers, ensure the quality of the fibers, and do not change the existing fiber industrialization process. Compared with traditional crosslinking methods, toxic chemicals, water washing, acid washing, etc. are not introduced, which reduces the discharge of harmful substances and wastewater, and also reduces the energy consumption caused by crosslinking agent reactions.

[0016] In the present invention, the modified pulp selectively replaces some hydroxyl groups in the cellulose molecular chain by introducing hybrid groups (carboxymethyl, methyl, hydroxyethyl or acetyl, etc.) into the original cellulose chain. When the cellulose chain crystallizes, the hybrid groups can only be dispersed in the amorphous region due to the difficulty in entering the crystalline region. The arrangement of the cellulose chain where the hybrid groups are located is hindered, resulting in a decrease in the overall orderliness of the fiber arrangement, which is not conducive to fiber crystallization. At the same time, the molecular chains with reduced orderliness increase the lateral bonding through the action of hydroxyl groups. Therefore, after the modified pulp is mixed with the unmodified pulp, the hybrid groups also play a role in disrupting the molecular arrangement and strengthening the lateral bonding in the blending system. The fibrillation of Lyocell fibers is mainly caused by the highly ordered arrangement and orientation of the molecular chains, which leads to weak lateral connections between the molecular chains. Therefore, the present invention can achieve the purpose of improving fiber fibrillation mainly by mixing modified pulp and unmodified pulp (physical mixing). The mixing of modified cellulose pulp and unmodified cellulose pulp is purely physical mixing, which mainly relies on the hydrogen bonding effect of hydroxyl groups to increase the lateral bonding between molecular chains, affecting the changes in the fiber aggregation structure. Compared with cross-linked fibers, it shortens the process flow and greatly reduces equipment investment and the complexity of the preparation process.

[0017] Cellulose has the best water retention when no substitution reaction occurs. The higher the degree of substitution, the worse the water retention. The present invention controls the degree of substitution of modified cellulose pulp within the range of 0.001 to 2.0.

[0018] The degree of substitution range is primarily determined by the solubility of the modified pulp in NMMO. Modified pulp exhibits reduced hydrophilicity due to the presence of hybrid groups. The higher the degree of substitution and the lower the hydrophilicity, the greater the likelihood that the cellulose chains will be insoluble in NMMO. For example, carboxymethyl cellulose, methyl cellulose, and hydroxyethyl cellulose mentioned in the invention have a degree of substitution range of 0.001 to 0.5, and cellulose acetate has a degree of substitution range of 0.5 to 2.0 to better dissolve in NMMO solutions and be mixed with unmodified pulp.

[0019] In the present invention, different means can be used to pretreat the cellulose pulp to obtain modified cellulose pulp with different degrees of substitution.

[0020] In a further embodiment, in step 1), the substitution treatment comprises esterification, carboxymethylation, methylation, oxidation or hydroxyethylation of the cellulose pulp.

[0021] In the present invention, the manner or means of esterification, carboxymethylation, methylation, oxidation or hydroxyethylation of cellulose pulp is not limited, and any existing technology can be used. The substitution treatment can be completed in one step or multiple steps, as long as the degree of substitution is controlled within the range of 0.001 to 2.0.

[0022] As a solution, in step 1), the cellulose pulp is first alkalized and then subjected to an etherification reaction to produce carboxymethyl cellulose, methyl cellulose or hydroxyethyl cellulose with a degree of substitution of 0.001 to 0.5.

[0023] In a further embodiment, the reagents used in the etherification reaction include but are not limited to chloroacetic acid, chloroformic acid, dimethyl sulfate, etc., and the types of modified pulp prepared are different due to different etherification reagents.

[0024] In the present invention, the modified cellulose meeting the degree of substitution requirement can be directly prepared, or the cellulose with a high degree of substitution can be first prepared and then hydrolyzed to make the modified cellulose meet the degree of substitution requirement.

[0025] As another embodiment, in step 1), cellulose acetate is obtained by esterification of cellulose pulp, and then subjected to secondary hydrolysis to obtain a degree of substitution of 0.5 to 2.0;

[0026] Preferably, the cellulose acetate is physically crushed to a particle size of less than 1000 μm, preferably less than 500 μm, before being hydrolyzed.

[0027] The purpose of pulverization is to better mix the two pulps. Since cellulose acetate is a solid, pulverization allows for more complete mixing with unmodified pulp. Modified pulps such as methyl cellulose are essentially water-soluble and can be fully mixed with unmodified pulp after dissolving in NMMO, so pulverization is not necessary.

[0028] In a further embodiment, the solution used for the secondary hydrolysis is selected from the group consisting of aqueous NaOH solution, NaOH and ethanol solution, acetic acid solution, and aqueous solution;

[0029] Preferably, the temperature of the solution used in the secondary hydrolysis is 10-125°C, the concentration is 0-1.0 mol / L, the secondary hydrolysis time is 0.1-15h, and the polymerization degree of the pulp after hydrolysis is 200-800; after the secondary hydrolysis, the modified pulp is washed to neutrality for subsequent use.

[0030] Furthermore, after the preparation of the modified cellulose pulp is completed, it needs to be washed with water, and the pH range of the washing liquid is 7-12.

[0031] In a further embodiment, in step 2), the unmodified cellulose pulp is pre-mixed with the NMMO solution and then mixed with the modified cellulose pulp.

[0032] Preferably, the modified cellulose pulp accounts for 1%-10% by weight of the total weight of all raw pulps, preferably 1%-5%.

[0033] Furthermore, the degree of polymerization of the unmodified cellulose pulp is 500-1500.

[0034] In a further embodiment, unmodified cellulose pulp is pre-mixed with a NMMO solution having a mass concentration of 70%-84%, at a mixing temperature of 70-100°C for ≥5 minutes, preferably 5-30 minutes;

[0035] Then, the mixture is quickly mixed with modified cellulose pulp at a mixing temperature of 80-110° C. for a time of ≥2 minutes, preferably 2-10 minutes.

[0036] The mass ratio of NMMO to the total raw pulp is determined based on the desired cellulose concentration. Modified cellulose pulp accounts for 1%-10% of the total raw pulp, with the remainder being unmodified cellulose pulp. Modified cellulose pulp is comminuted and mixes more efficiently with solvents. Therefore, premixing unmodified cellulose pulp with NMMO solvent before blending it with modified cellulose pulp effectively reduces solubility differences between pulps, promotes uniform dissolution of the cellulose system, and improves the quality of the stock solution.

[0037] In a further embodiment, in step 3), the vacuum degree of the dissolution process is controlled to be 0-10 KPa absolute pressure and the temperature is 90-130° C.;

[0038] Preferably, the absolute vacuum pressure during the dissolution process is controlled to be 3-8 KPa and the temperature to be 105-120°C.

[0039] In a further embodiment, in step 3), during spinning, the temperature of the spinning solution is controlled to be 90-130°C, the aperture of the spinneret is 0.05-0.3 mm, and the air gap cooling height is 5-200 mm. Simultaneously, the process conditions of the post-processing system are adjusted so that the cellulose fibers are subjected to appropriate tension for each preparation stage. The filaments are continuously spun at a spinning speed of 20-500 m / min to obtain the finished product. The fiber spinning process includes washing, oiling, drying, packaging, and winding.

[0040] In addition, the method of the present invention has a wider range of dissolution and spinning conditions than conventional ones. Generally, the spinning speed of Lyocell fiber is about 38 m / min, while the spinning solution prepared by the present invention can be spun at a high spinning speed.

[0041] The present invention also provides a regenerated cellulose fiber prepared by the above-mentioned preparation method, wherein the regenerated cellulose fiber has a wet friction time greater than 10s, a dry tensile strength of 3.4 to 3.9 cN / dtex, and a dry elongation of 9% to 10%;

[0042] Preferably, the wet friction time of the regenerated cellulose fiber is 11.9s to 18.4s.

[0043] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0044] 1) The method for preparing cellulose fibers provided by the present invention first pre-treats and modifies cellulose pulp, i.e., esterifies, carboxylates, methylates, oxidizes, or hydroxyethylates some of the hydroxyl groups. This process introduces only a small amount of heterochains, which are still cellulose derivatives without introducing new substances. This method has good compatibility with the Lyocell system, and the pre-treatment reaction steps are simple and easy to obtain.

[0045] 2) In the method for preparing cellulose fibers provided by the present invention, no chemical reaction occurs during the fiber preparation process. The mixing of modified cellulose pulp and unmodified cellulose pulp is purely physical mixing, which mainly relies on the hydrogen bonding effect of hydroxyl groups to increase the lateral bonding between molecular chains, affecting the changes in the fiber aggregation structure. Compared with cross-linked fibers, the process flow is shortened, and the equipment investment and the complexity of the preparation process are greatly reduced.

[0046] 3) The cellulose fiber preparation method provided by the present invention does not require the introduction of new equipment in the mixing process of different cellulose pulps. The purpose is achieved mainly by controlling the pre-mixing and re-mixing temperature and time. The operation is simple and can be directly operated on the existing production line without adding additional costs.

[0047] 4) The preparation method of cellulose fibers provided by the present invention uses a relatively small amount of modified pulp. Although the pretreatment process involves chemical reactions and water washing procedures, it significantly reduces production costs compared to the water washing and drying energy consumption of cross-linked fibers.

[0048] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an undue limitation of the present invention. Obviously, the drawings described below are only some embodiments. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without inventive effort. In the accompanying drawings:

[0050] Figure 1 Schematic diagram of the pulp pretreatment method of the present invention;

[0051] Figure 2 is a flow chart of the preparation of the fiber of the present invention;

[0052] Figure 3 is a morphology diagram of the regenerated cellulose fiber prepared in Example 2 of the present invention;

[0053] Figure 4 is a morphology diagram of the regenerated cellulose fiber prepared in Comparative Example 1 of the present invention;

[0054] The specific reference numerals are:

[0055] 1: Mixing kettle, 2: Discharge pump, 3: Vacuum pump, 4: Dissolving kettle, 5: Spinneret, 6: Coagulation bath, 7: Water washing device.

[0056] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0058] It should be noted that the spinning process of the present invention can be carried out using conventional technical conditions in the art. As one embodiment, during spinning, the spinning solution temperature is controlled to be 90-130°C, the spinneret aperture is 0.05-0.3mm, and the air gap cooling height is 5-200mm. Simultaneously, the post-processing system process conditions are adjusted to ensure that the cellulose fibers are subjected to appropriate tension at each preparation stage, and the filaments are continuously spun at a spinning speed of 20-500m / min to produce the finished product. The Lyocell fiber spinning process includes, in sequence, washing, oiling, drying, and packaging or winding.

[0059] The esterification reaction and etherification reaction described in the present invention all adopt conventional technical conditions.

[0060] It should be noted that the specific spinning conditions in the following examples and comparative examples of the present invention are the same.

[0061] Index detection method:

[0062] The wet friction test adopts FZ / T 52019-2018 "Lyocell Staple Fiber". At a constant rotation speed, the wet friction time corresponds to the number of wet frictions. The longer the wet friction time or the more wet friction times, the stronger the anti-fibrillation ability.

[0063] The dry tensile strength / (cN / dtex) and dry elongation / (%) are measured according to GB / T 14337-2022 "Test method for tensile properties of chemical staple fibers".

[0064] Example 1

[0065] (1) Cellulose pulp is esterified to produce cellulose acetate, which is then crushed in a grinder to a particle size of approximately 500 μm for later use. An appropriate amount of cellulose acetate is then placed in a 0.5 mol / L alkaline alcohol solution (NaOH and ethanol) and reacted at 40°C for 60 min. After washing with water, modified cellulose pulp (DP = 1.75) is obtained.

[0066] (2) Unmodified cellulose pulp (DP = 700) and a 76% NMMO solution were premixed in a mixing apparatus at 85°C and stirred at 300 rpm for 20 minutes. After the unmodified cellulose pulp was thoroughly dispersed, cellulose acetate was added (the added cellulose acetate accounted for 3% of the total weight of the raw pulp). The temperature was raised to 90°C, the stirring rate was increased to 500 rpm, and mixing was continued for 5 minutes, until the cellulose concentration reached 12%.

[0067] (3) The mixture was then transferred to a dissolving apparatus at 110°C and dehydrated under vacuum at a degree of vacuum of 7 kPa until the cellulose was completely dissolved, thereby obtaining a uniform, transparent, amber-colored cellulose solution. The cellulose solution was then filtered, degassed, and spun to produce a regenerated cellulose fiber product. The properties of the resulting regenerated cellulose fiber are shown in Table 1.

[0068] Example 2

[0069] (1) Cellulose is esterified to produce cellulose acetate, which is then crushed in a grinder to a particle size of approximately 500 μm for later use. An appropriate amount of cellulose acetate is then placed in a 0.5 mol / L alkaline alcohol solution (NaOH and ethanol) and reacted at 60°C for 60 minutes. After washing, modified cellulose pulp (DP = 1.35) is obtained.

[0070] The methods of step (2) raw material mixing and step (3) fiber preparation are the same as those in Example 1.

[0071] Example 3

[0072] (1) Cellulose is esterified to produce cellulose acetate, which is then crushed in a grinder to a particle size of approximately 500 μm for later use. A small amount of cellulose acetate is then placed in a 0.5 mol / L alkaline alcohol solution (NaOH and ethanol) and reacted at 80°C for 60 minutes. After washing, a modified pulp (DP = 1.06) is obtained.

[0073] The methods of step (2) raw material mixing and step (3) fiber preparation are the same as those in Example 1.

[0074] Comparative Example 1

[0075] In this comparative example, the following method was used to prepare novel solvent-processed cellulose fibers:

[0076] Unmodified cellulose pulp (DP=700) and a 76% NMMO solution were placed in a mixing device at 85° C. and mixed for 20 minutes at a temperature of 85° C. and a stirring rate of 300 rpm, wherein the cellulose concentration was 12%.

[0077] The cellulose was then transferred to a dissolution device at 110°C and dehydrated under vacuum at 7 kPa until the cellulose was completely dissolved, producing a uniform, transparent, amber-colored cellulose solution. The cellulose solution was then filtered, degassed, and spun to produce a regenerated cellulose fiber product. The properties of the resulting regenerated cellulose fiber are shown in Table 1.

[0078] Comparative Example 2

[0079] (1) Cellulose is esterified to produce cellulose acetate, which is then crushed in a grinder to a particle size of approximately 500 μm for later use. An appropriate amount of cellulose acetate is then placed in a 0.5 mol / L alkaline alcohol solution (NaOH and ethanol) and reacted at 20°C for 40 minutes. After washing, modified cellulose pulp (DP = 3) is obtained.

[0080] The methods of step (2) raw material mixing and step (3) fiber preparation are the same as those in Example 1.

[0081] Comparative Example 3

[0082] (1) Cellulose is esterified to produce cellulose acetate, which is then crushed in a grinder to a particle size of approximately 500 μm for later use. An appropriate amount of cellulose acetate is then placed in a 0.5 mol / L alkaline alcohol solution (NaOH and ethanol) and reacted at 20°C for 10 minutes. After washing with water, modified cellulose pulp (DP = 4) is obtained.

[0083] The methods of step (2) raw material mixing and step (3) fiber preparation are the same as those in Example 1.

[0084] The properties of the regenerated cellulose fibers obtained in Examples 1-3 and Comparative Example 1 were tested, and the results are shown in Table 1.

[0085] Table 1 Effect of different degrees of substitution (DS) modified pulp on fiber properties

[0086]

[0087]

[0088] Result analysis:

[0089] From the results in Table 1, it can be seen that compared with Comparative Example 1 in which no modified cellulose pulp was added, the mechanical properties of the regenerated cellulose fibers prepared by adding modified cellulose pulp with a certain degree of substitution in Examples 1-3 were slightly reduced, but they could still meet the subsequent use requirements, indicating that the acetyl group as a hybrid group does reduce the overall arrangement order of the cellulose molecular chain, and reduces the mechanical properties of the fiber to a certain extent by reducing the fiber crystallization; the orientation of the fiber molecular chain decreases, and the hydroxyl groups (not completely substituted) on the modified pulp molecular chain and the hydroxyl groups of the unmodified cellulose molecular chain or the hydroxyl groups between the unmodified molecular chains are combined with each other through hydrogen bonds, which increases the lateral bonding between the molecular chains, thereby improving the anti-fibrillation performance of the fiber to a certain extent, which is manifested in a significant increase in the wet friction time.

[0090] The morphology of the regenerated cellulose fiber prepared in Example 2 is as follows Figure 3 As shown, the morphology of the regenerated cellulose fiber prepared in Comparative Example 1 is as follows Figure 4 As shown in the figure, it can be seen intuitively that the fibrillation degree of the fiber prepared in Example 2 has been greatly improved.

[0091] In Comparative Examples 2 and 3, the substitution degree of the modified cellulose pulp is too high and the modified pulp is difficult to dissolve in the Lyocell system, which is equivalent to the modified pulp not being added successfully. Therefore, the fiber properties do not change significantly compared with Comparative Example 1.

[0092] When the degree of substitution exceeds 2, cellulose acetate cannot be dissolved in NMMO solvent. At this time, only unmodified pulp is dissolved in NMMO to make a spinning solution and spun into fibers, and cellulose acetate is not successfully added to the system. The fiber properties are similar to those of Comparative Example 1.

[0093] Example 4

[0094] The preparation of modified cellulose pulp (DP=1.35), raw material mixing and fiber preparation process are the same as in Example 2, with the only difference being that the cellulose acetate added in this example accounts for 1% of the total mass of all raw material pulps.

[0095] Example 5

[0096] The preparation of modified cellulose pulp (DP=1.35), raw material mixing and fiber preparation process are the same as in Example 2, with the only difference being that the cellulose acetate added in this example accounts for 5% of the total mass of all raw material pulps.

[0097] Comparative Example 4

[0098] The preparation of modified cellulose pulp (DP=1.35), raw material mixing and fiber preparation process are the same as in Example 2, with the only difference being that the cellulose acetate added in this example accounts for 12% of the total mass of all raw material pulps.

[0099] Comparative Example 5

[0100] The preparation of modified cellulose pulp (DP=1.35), raw material mixing and fiber preparation process are the same as in Example 2, with the only difference being that the cellulose acetate added in this example accounts for 0.5% of the total mass of all raw material pulps.

[0101] The properties of the regenerated cellulose fibers obtained in Examples 4-5 and Comparative Examples 4-5 were tested, and the results are shown in Table 2.

[0102] Table 2 Effects of different contents of modified pulp on fiber properties

[0103]

[0104] Result analysis:

[0105] From the results in Table 2, it can be seen that compared with Comparative Example 1 in which no modified cellulose pulp is added, the wet friction time of the regenerated cellulose fibers prepared by adding modified cellulose pulp in an appropriate proportion in Examples 2 and 4-5 is greatly improved, which gives the fibers anti-fibrillation properties, and although the dry tensile strength is slightly reduced, it still meets the requirements of subsequent applications (the principle is the same as the analysis of Examples 1-3 and Comparative Example 1).

[0106] In Comparative Examples 4 and 5, the addition amount of modified cellulose pulp is too low or too high. Due to the cellulose acetate preparation process, the degree of polymerization of cellulose acetate has been significantly reduced compared to unmodified pulp. Therefore, after mixing with unmodified pulp, the small molecular weight cellulose acetate has a certain plasticizing effect in the system. Therefore, although a high content is beneficial to weakening the fiber fibrillation ability, the mechanical properties of the fiber will be greatly reduced and cannot meet the subsequent use requirements; when the content is too low, the effect of cellulose acetate is not obvious, and therefore the purpose of reducing fibrillation cannot be achieved or the effect is not obvious.

[0107] Example 6

[0108] Take an appropriate amount of cellulose pulp and 20% sodium hydroxide and ethanol solution for alkalization at 35°C, then add the prepared chloroacetic acid ethanol solution and etherify at 70°C for 3 hours. The final carboxymethyl cellulose detection standard is a transparent substance soluble in water (DS=0.1), then wash and dry for use.

[0109] The method of step (2) raw material mixing and step (3) fiber preparation is the same as that of Example 1, wherein the proportion of carboxymethyl cellulose is 3%.

[0110] Example 7 (methylcellulose)

[0111] An appropriate amount of cellulose pulp is alkalized with a 20% sodium hydroxide and ethanol solution at 35°C, and then the prepared chloroform reagent is added and reacted at room temperature to obtain methyl cellulose.

[0112] The method of step (2) raw material mixing and step (3) fiber preparation is the same as that of Example 1, wherein the proportion of carboxymethyl cellulose is 3%.

[0113] Example 8 (Hydroxyethyl Cellulose)

[0114] An appropriate amount of cellulose pulp is reacted with a 35% sodium bicarbonate aqueous solution at room temperature. After 15 minutes, the pulp is taken out, squeezed and crushed, and then reacted with ethylene oxide at room temperature for 1 minute. The hydroxyethyl cellulose is then washed with alcohol to obtain the cellulose.

[0115] The method of step (2) raw material mixing and step (3) fiber preparation is the same as that of Example 1, wherein the proportion of carboxymethyl cellulose is 3%.

[0116] Table 3 Effects of different types of modified pulp on fiber properties

[0117]

[0118] Result analysis:

[0119] As can be seen from the results in Table 3, compared to Comparative Example 1, which did not include modified cellulose pulp, the wet friction time of the regenerated cellulose fibers prepared in Examples 2 and 6-8, which added different types of modified cellulose pulp, was improved, giving the fibers resistance to fibrillation. The dry tensile strength and dry elongation were similar, while also ensuring the mechanical properties of the fibers. This indicates that the fibers prepared by the present method have improved resistance to fibrillation. Although the fiber strength was slightly reduced, it did not affect the fiber's usability requirements. The principle is the same as that of the analysis in Examples 1-3 and Comparative Example 1.

[0120] Comparison of the above examples and comparative examples reveals that the modified cellulose pretreatment method and the method for preparing cellulose fibers by mixing different cellulose raw materials provided by the present invention exhibit good compatibility between the modified and unmodified cellulose systems, and the mixing process is purely physical. This not only improves fiber fibrillation but also maintains the mechanical properties of the fibers. Compared to traditional crosslinking methods, this method eliminates the need for toxic crosslinking agents and the complex crosslinking process, significantly reducing equipment investment and raw material consumption. It is simple to operate and can be directly applied to production lines.

[0121] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present invention can make slight changes or modifications to equivalent embodiments using the above-mentioned technical contents without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the solution of the present invention.

Claims

1. A method for preparing regenerated cellulose fiber, characterized in that: The following steps are involved: 1) Pretreatment: Substituting some hydroxyl groups of cellulose pulp to prepare modified cellulose pulp; 2) Unmodified cellulose pulp is premixed with NMMO solution and then mixed with modified cellulose pulp; 3) Dissolving, spinning and post-processing under vacuum conditions to produce regenerated cellulose fiber products; In step 1), cellulose pulp is first alkalized and then subjected to an etherification reaction to produce carboxymethyl cellulose, methyl cellulose or hydroxyethyl cellulose with a degree of substitution of 0.001 to 0.5; alternatively, cellulose pulp is subjected to an esterification reaction to produce cellulose acetate, which is then subjected to a secondary hydrolysis to obtain a degree of substitution of 0.5 to 2.0; The modified cellulose pulp accounts for 1%-10% of the total weight of all raw pulps.

2. The preparation method according to claim 1, characterized in that Before hydrolysis, cellulose acetate was pulverized to a particle size of <1000 μm.

3. The preparation method according to claim 1, characterized in that Before hydrolysis, cellulose acetate was pulverized to a particle size of <500 μm.

4. The preparation method according to claim 1, characterized in that The solution used for secondary hydrolysis is selected from NaOH aqueous solution, NaOH and ethanol solution, acetic acid solution, and aqueous solution.

5. The preparation method according to claim 4, characterized in that The temperature of the solution used in the secondary hydrolysis is 10-125° C., the concentration is 0-1.0 mol / L, the secondary hydrolysis time is 0.1-15 h, and the polymerization degree of the pulp after hydrolysis is 200-800; after the secondary hydrolysis, the modified pulp is washed to neutrality for subsequent use.

6. The preparation method according to any one of claims 1 to 5, characterized in that Unmodified cellulose pulp is premixed with NMMO solution with a mass concentration of 70%-84%, the mixing temperature is 70-100℃, and the mixing time is ≥5min; Then the mixture is quickly mixed with modified cellulose pulp at a mixing temperature of 80-110° C. for a time of ≥2 minutes.

7. The preparation method according to claim 6, characterized in that Unmodified cellulose pulp is premixed with NMMO solution having a mass concentration of 70%-84% for 5-30 minutes.

8. The preparation method according to claim 6, characterized in that The time for rapid mixing with the modified cellulose pulp is 2-10 minutes.

9. The preparation method according to any one of claims 1 to 5, characterized in that In step 3), the vacuum degree of the dissolution process is controlled to be 3-10 KPa absolute pressure and the temperature is controlled to be 90-130°C.

10. The preparation method according to any one of claims 1 to 5, characterized in that: In step 3), the absolute vacuum pressure during the dissolution process is controlled to be 3-8 KPa and the temperature to be 105-120°C.

11. The preparation method according to any one of claims 1 to 5, characterized in that: In step 3), during spinning, the temperature of the spinning solution is controlled to be 90-130° C., the aperture of the spinneret is 0.05-0.3 mm, the air gap cooling height is 5-200 mm, and the filament bundle is continuously spun at a spinning speed of 20-500 m / min to obtain a finished product.

12. A regenerated cellulose fiber prepared by the method according to any one of claims 1 to 11, characterized in that: The regenerated cellulose fiber has a wet friction time greater than 10 seconds, a dry tensile strength of 3.4 to 3.9 cN / dtex, and a dry elongation of 9% to 10%.

13. The regenerated cellulose fiber according to claim 12, characterized in that The wet friction time of the regenerated cellulose fiber is 11.9s~18.4s.

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