Search

CN-121428685-B - Preparation method of high-strength Lyocell regenerated cellulose fiber

CN121428685BCN 121428685 BCN121428685 BCN 121428685BCN-121428685-B

Abstract

The invention discloses a preparation method of high-strength Lyocell regenerated cellulose fibers, and aims to solve the problem that the existing regenerated cellulose fibers have insufficient mechanical strength due to too wide pulp molecular weight distribution. The method protects the long molecular chain of cellulose to the maximum extent while efficiently removing lignin and hemicellulose through the synergistic effect of a mild pre-hydrolysis sulfate (PHK) cooking process and an optimized multi-section non-Element Chlorine (ECF) bleaching sequence (D 0 -E-D 1 ), and selectively dissolves short-chain cellulose by precisely controlling alkali concentration and low-temperature conditions through multistage gradient cold alkali extraction and purification treatment, thereby realizing active regulation and control and narrowing of the molecular weight distribution of cellulose and obtaining dissolving pulp with high polymerization degree and concentrated molecular weight distribution. Finally, the high-quality dissolving pulp is used for preparing the Lyocell fiber with obviously enhanced mechanical properties through NMMO solvent system dry-spray wet spinning.

Inventors

  • YANG SHUO
  • ZHAO JIAWEI
  • CHENG BOWEN
  • WU ZETIAN

Assignees

  • 天津科技大学

Dates

Publication Date
20260508
Application Date
20251222

Claims (9)

  1. 1. A method for preparing high-strength Lyocell regenerated cellulose fibers, which is characterized by comprising the following steps: (1) Pre-treating, namely screening raw materials and performing pre-hydrolysis treatment to obtain a pre-treated raw material with low hemicellulose content; (2) Cooking, namely cooking the pre-hydrolyzed raw materials by a sulfate method, and washing and screening to obtain pre-hydrolyzed sulfate pulp; (3) Multi-section chlorine-free bleaching ECF and chelation treatment, namely carrying out multi-section chlorine-free bleaching ECF on prehydrolysis sulfate pulp, wherein the multi-section chlorine-free bleaching ECF sequentially comprises a first section of chlorine dioxide bleaching D 0 , alkali treatment E and a second section of chlorine dioxide bleaching D 1 , and adding a chelant into the bleached pulp for chelation treatment; (4) Multistage gradient cold alkali extraction and purification, namely carrying out multistage gradient cold alkali extraction and purification treatment on the pulp after the chelation treatment, wherein the multistage gradient cold alkali extraction and purification treatment comprises a first stage cold alkali extraction treatment and a second stage cold alkali extraction treatment, so as to obtain dissolving pulp with high polymerization degree and concentrated molecular weight distribution, wherein the dosage of NaOH in the first stage cold alkali extraction treatment is 3-6% of the dosage of absolute dry pulp, the temperature is 15-20 ℃, and the dosage of NaOH in the second stage cold alkali extraction treatment is 10-15% of the dosage of absolute dry pulp, and the temperature is 20-25 ℃; (5) Wet spinning, namely placing the obtained high-polymerization-degree dissolving pulp into a reaction kettle, mixing with NMMO solution and antioxidant to obtain spinning solution, and adopting dry-jet wet spinning to obtain the high-strength Lyocell fiber.
  2. 2. The method for preparing high-strength Lyocell regenerated cellulose fiber according to claim 1, wherein the raw material is one or more of softwood, hardwood, bamboo, wheat straw and hemp.
  3. 3. The preparation method of the high-strength Lyocell regenerated cellulose fiber according to claim 1, wherein the specific conditions of the pre-hydrolysis treatment in the step (1) are that the temperature is 150-165 ℃, the heating time is 30-60 min, the heat preservation time is 30-60 min, the liquid ratio is 1:5, and the P factor is 100-250.
  4. 4. The preparation method of the high-strength Lyocell regenerated cellulose fiber according to claim 1, wherein the process conditions of the sulfate cooking in the step (2) are specifically that the temperature is 150-165 ℃, the heating time is 30-60 min, the heat preservation time is 30-120 min, the liquid ratio is 1:4, the cooking H factor is 300-800, the alkali consumption is 10-20% relative to the absolute dry raw material, and the vulcanizing degree is 20-30% relative to the absolute dry raw material.
  5. 5. The preparation method of the high-strength Lyocell regenerated cellulose fiber according to claim 1, wherein the specific process conditions of the first stage of chlorine dioxide bleaching D 0 in the step (3) are that ClO 2 is 3% -5% of absolute dry pulp, the temperature is 60% -75 ℃, the time is 15% -45 min, the pulp concentration is 5% -15%, the alkali treatment E is that NaOH is 0.5% -2% of absolute dry pulp, the temperature is 60% -75 ℃, the time is 30% -90 min, the pulp concentration is 5% -15%, the second stage of chlorine dioxide bleaching D 1 is that ClO 2 is 1% -3% of absolute dry pulp, the temperature is 60% -75 ℃, the time is 30% -90 min, the pulp concentration is 5% -15%, the chelating agent used in the chelating treatment is disodium ethylenediamine tetraacetate, the dosage is 0.5% -2% of absolute dry pulp, the temperature is 60% -75 ℃, the time is 30% -90 min, and the pulp concentration is 5% -15%.
  6. 6. The method for preparing the high-strength Lyocell regenerated cellulose fiber according to claim 1, wherein the specific conditions of the first stage of cold alkali extraction treatment in the step (4) are that the time is 30-60min and the pulp concentration is 5-15%.
  7. 7. The method for preparing the high-strength Lyocell regenerated cellulose fiber according to claim 1, wherein the specific conditions of the second-stage cold alkali extraction treatment in the step (4) are that the time is 60-90min, and the pulp concentration is 5-15%.
  8. 8. The method for producing a high-strength Lyocell regenerated cellulose fiber according to claim 1, wherein the antioxidant in the step (5) is propyl gallate, the amount of the antioxidant is 0.05 to 0.1% of the total mass of the high-polymerization-degree dissolving pulp and the NMMO solution, the mass fraction of the NMMO solution is 70 to 75%, and the mass ratio of the high-polymerization-degree dissolving pulp to the NMMO solution is 1 (15 to 40).
  9. 9. The preparation method of the high-strength Lyocell regenerated cellulose fiber according to claim 1, wherein the specific conditions of wet spinning are that the spinning solution is extruded from micropores of a spinneret plate after being metered by a metering pump under the pressure of 0.2-0.5 MPa, enters a coagulating bath with the concentration of 5-20% through an air section of 10-40 mm, is coagulated and formed in the coagulating bath at the temperature of 10-30 ℃, has the draft ratio of 3-10, and is washed with water and dried to obtain the high-strength Lyocell regenerated cellulose fiber.

Description

Preparation method of high-strength Lyocell regenerated cellulose fiber Technical Field The invention relates to a preparation method of high-strength Lyocell regenerated cellulose fibers, and belongs to the technical field of bio-based fiber materials. Background Lyocell fiber is a green regenerated cellulose fiber using N-methylmorpholine-N-oxide (NMMO) as a solvent, and is favored because of its environmental protection in the production process and excellent fabric properties. The overall properties, in particular the mechanical strength, depend to a large extent on the quality of the dissolving pulp used. However, the strength of existing Lyocell fibers is still difficult to fully meet the increasing demands in the field of high-end textiles and industrial textiles. It is currently widely accepted in the industry that increasing the average degree of polymerization of dissolving pulp is one of the key pathways to enhance Lyocell fiber strength. For this reason, researchers have made many searches. For example, although hemicellulose and lignin can be effectively removed by the eutectic solvent pretreatment technology (patent CN 112482069B) proposed by the group Shen Kuizhong of the national institute of forestry science in 2020, the polymerization degree of cellulose is not controlled with emphasis, and the polymerization degree of the obtained pulp is at a conventional level (about 500-700). In 2022, a method for refining dissolving pulp by using gamma valerolactone (patent CN 112144308B) developed by the group Wang Jiang of Shandong Qilu industrial university has improved the purity of alpha cellulose, but the polymerization degree of the finished dissolving pulp is difficult to break through 800 because the treated object is degraded chemical pulp. However, the average degree of polymerization is not the only critical factor determining the strength of the fibers, and the molecular weight distribution of the cellulose is also critical. Too broad a molecular weight distribution means that both long and too many short molecular chains are present in the pulp (which may affect the dissolution and spinning process). These short chain celluloses are not able to effectively bear stresses during the fiber forming process, but rather can be weak points in the structure, thereby limiting the ultimate strength improvement of the fibers. Thus, the prior art is faced with the following outstanding problems and limitations: (1) The technical target is single, and most dissolving pulp preparation processes are still focused on removing lignin and hemicellulose to improve purity and whiteness, and lack consciousness and means for effectively regulating and controlling cellulose molecular weight distribution. (2) The strength bottleneck is not solved, and the molecular weight distribution of the pulp prepared by the existing method is often wider, so that the mechanical strength of the Lyocell fiber produced by the method is insufficient. (3) The process has insufficient consistency, but the potential function of cold caustic extraction in the selective removal of short chain cellulose and narrowing of molecular weight distribution is not fully recognized and exploited. In order to solve the technical problems, the invention aims to provide a method capable of preparing dissolving pulp with high polymerization degree and concentrated molecular weight distribution, thereby realizing stable preparation of high-quality raw materials of high-performance Lyocell fibers. Disclosure of Invention The invention aims to provide a preparation method of high-strength Lyocell regenerated cellulose fibers, which is used for solving the problem of insufficient mechanical strength of the existing regenerated cellulose fibers caused by too wide molecular weight distribution of pulp. In order to achieve the above purpose, the present invention adopts the following technical scheme: a method for preparing high-strength Lyocell regenerated cellulose fibers, which comprises the following steps: (1) Pre-treating, namely screening raw materials and performing pre-hydrolysis treatment to obtain a pre-treated raw material with low hemicellulose content; (2) Cooking, namely cooking the pre-hydrolyzed raw materials by a sulfate method, and washing and screening to obtain pre-hydrolyzed sulfate pulp; (3) Multi-section chlorine-free bleaching ECF and chelation treatment, namely carrying out multi-section chlorine-free bleaching ECF on prehydrolysis sulfate pulp, wherein the multi-section chlorine-free bleaching ECF sequentially comprises a first section of chlorine dioxide bleaching D 0, alkali treatment E and a second section of chlorine dioxide bleaching D 1, and adding a chelant into the bleached pulp for chelation treatment; (4) Multistage gradient cold alkali extraction and purification, namely performing multistage gradient cold alkali extraction and purification treatment on the chelated pulp, wherein the multistage gradient cold alkali