A method for reducing the degree of polymerization of cellulose by enzymatic method in a dry process for producing lyocell fibers using papermaking pulp
By combining alkali-resistant complex enzymes with NMMO solvent in the dry process, the problem of reduced cellulose polymerization degree in dry papermaking pulp was solved, achieving low-cost and high-efficiency cellulose degradation. This method is suitable for producing lyocell fiber from papermaking pulp, simplifying the process and reducing environmental pollution.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TAIAN XINDELI BIOTECHNOLOGY CO LTD
- Filing Date
- 2026-04-30
- Publication Date
- 2026-07-21
AI Technical Summary
Existing technologies struggle to effectively reduce the degree of cellulose polymerization in paper pulp under dry conditions, and traditional enzyme preparations are prone to inactivation in alkaline environments, resulting in high difficulty, high cost, and poor environmental performance in pulp preparation.
An alkali-resistant compound enzyme is combined with NMMO solvent to directly reduce the degree of cellulose polymerization in paper pulp through a dry process, including dry pulp pretreatment, enzymatic hydrolysis, enzyme inactivation and vacuum dehydration steps, avoiding the addition of additional water, and using an alkali-resistant compound enzyme to maintain enzyme activity in a high pH environment.
This technology enables low-cost and efficient reduction of cellulose polymerization in the dry production of lyocell fibers, thereby reducing raw material costs, simplifying the process, reducing wastewater discharge, and meeting environmental protection requirements.
Smart Images
Figure CN122428533A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of regenerated cellulose fiber production technology, specifically to a method for reducing the degree of polymerization of cellulose using an enzymatic method in the dry process of producing lyocell fiber from paper pulp. Background Technology
[0002] Lyocell fiber is produced by dissolving high-quality wood pulp fiber in NMMO as a solvent to form a pulp porridge, which is then drawn into fibers. It is a mainstream variety of high-performance regenerated cellulose, characterized by its green and environmentally friendly nature and high solvent recovery rate. In its production process, the degree of polymerization (DP) of cellulose directly determines the difficulty of pulp preparation, dissolution efficiency, spinning solution stability, and fiber mechanical properties.
[0003] Currently, the methods for reducing the degree of polymerization of pulp are mainly divided into two categories: 1) Wet enzymatic process: Water is added to dilute and pulverize the pulp, and after heating, a compound enzyme is used to reduce the degree of polymerization. This process is mature, but it follows the viscose fiber approach and has a long process: impregnation → enzymatic hydrolysis → neutralization / high-temperature enzyme inactivation → vacuum dehydration to make pulp → filtration and defoaming → spinning. This method has problems such as high water consumption, high wastewater, many pieces of equipment, and high energy consumption.
[0004] 2) Traditional dry process: Dry pulp is directly mixed with NMMO to swell, and the solubility is gradually improved through vacuum dehydration. The advantage is that the process is short, but it has high requirements for pulp. When using paper pulp, the DP is high, the pulp porridge is difficult to make, the pulp porridge is not viscous, the dissolution is insufficient, and the fiber quality fluctuates greatly.
[0005] In summary, the existing technologies have the following technical defects: wet enzymatic methods require the addition of water and cannot be adapted to dry systems; dry porridge making cannot add water; conventional enzyme preparations are not tolerant to alkaline environments with pH > 10 and are easily deactivated below 70℃. High-DP paper pulp is difficult to polymerize under dry process conditions, making it challenging to achieve stable industrialization. Furthermore, existing processes all require high-quality wood fiber pulp, while this invention uses only paper pulp. The price of paper pulp is lower than that of high-quality wood pulp because its degree of polymerization is nearly 300 times higher than that of high-quality wood pulp cellulose. Summary of the Invention
[0006] To address the problems existing in the prior art, this invention provides a method for reducing the degree of polymerization of cellulose in the dry process of producing lyocell fiber using paper pulp instead of high-quality wood pulp. This method eliminates the need for additional water and employs a synergistic combination of alkali-resistant compound enzymes and NMMO to reduce the degree of polymerization of paper pulp, thus achieving dry production of lyocell from paper pulp. While paper pulp is cheaper than high-quality wood pulp, reducing the degree of polymerization of cellulose is difficult due to its complex composition. Relying solely on NMMO solvent is insufficient to reduce the degree of polymerization to the ideal value for pulping. Using a compound enzyme preparation in conjunction with NMMO solvent significantly reduces the degree of polymerization of cellulose in paper pulp.
[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A method for reducing the degree of polymerization of cellulose using an enzymatic method in the dry process of producing lyocell fiber from paper pulp includes the following steps: (1) Pretreatment of dry pulp The cellulose pulp is pulverized to obtain dry pulverized pulp for later use. (2) Preparation of alkali-resistant complex enzyme and NMMO mixture Take NMMO solvent, add formic acid to adjust the pH to 10.5–11.0, add alkali-resistant complex enzyme, stir and mix well to obtain a mixture.
[0008] The alkali-resistant complex enzyme consists of 90%-100% cellulase and 0-10% xylanase.
[0009] (3) Dry mixing Add the mixture directly to the dry, pulverized pulp and stir to combine. (4) Enzymatic hydrolysis reduces the degree of polymerization The reaction is carried out at 55–70℃ for 40 minutes to achieve simultaneous swelling and reduction of the degree of polymerization to 500–680. (5) Enzyme inactivation After the reaction is complete, heat to 85–95℃ and incubate to inactivate the enzyme. (6) Vacuum dehydration and porridge making After enzyme inactivation, vacuum dehydration is performed, and the temperature is controlled (after enzyme inactivation, the product is transferred to a vacuum bottle, and the vacuum dehydration temperature is 75–85℃, the time is ≥1.5h, and the product is cooled to obtain a pulp porridge). The pulp porridge preparation is completed and then proceeds to the subsequent production of Lyocell fiber.
[0010] In step (4), the enzymatic hydrolysis environment is pH=11 and the temperature is 70℃. The inactivation rate of the composite enzyme is low (60% enzyme activity is still present), thus achieving dry depolymerization.
[0011] Furthermore, in step (5), the enzyme inactivation time is 10 min; the heat preservation method in the process is a water bath.
[0012] This process allows for the control of the degree of polymerization from raw material DP 850–1150 to product DP 500–680.
[0013] The beneficial effects of this invention are as follows: The process of this invention can solve the industry difficulty that cannot be solved by adding water and enzymes in dry porridge making. It is compatible with existing dry processes, does not require the addition of new equipment, and has low cost. Paper pulp can be used as a substitute for high-quality wood pulp. Currently, the price of paper pulp is 4,000 yuan / ton, high-quality wood pulp is 6,700 yuan / ton, and high-quality cotton pulp is 8,100 yuan / ton (prices may fluctuate at different times).
[0014] Green and environmentally friendly: No neutralized wastewater, no pressure filtration process. Attached Figure Description
[0015] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation
[0016] The technical solution will now be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0017] Example 1 The total experimental volume is calculated as 100g: 1) Take 7.5g of crushed paper pulp (initial degree of polymerization DP=1020); 2) Take 66g of NMMO solvent; 3) Adjust the pH of NMMO to 10.5 using 0.5g of formic acid; 4) Add 26g of alkali-resistant complex enzymes, including 100% cellulase and 0% xylitolase, and mix well to obtain a mixture. 5) Add the mixture to the pulp and stir well; 6) Keep warm in a water bath at 55℃ for 40 minutes, stirring once every 5 minutes; 7) Heat to 90℃ and hold for 10 minutes to inactivate the enzyme; 8) After enzyme inactivation, transfer to a vacuum bottle, dehydrate under vacuum at 80°C for 1 hour, and then cool to obtain a porridge.
[0018] Test results: The degree of polymerization of cellulose in the pulp is DP=550. The pulp has good uniformity and can be directly used for dissolving, defoaming, and dry-jet wet spinning.
[0019] Example 2 The process steps are the same as in Example 1, except that in step (3), formic acid is used to adjust the pH of NMMO to 11. In step (6), the water bath is kept at 70°C; the alkali-resistant complex enzymes are: 95% cellulase and 5% xylanase.
[0020] Test result: DP=680.
[0021] Example 3 Same as in Example 1, except that in step (3), formic acid is used to adjust the pH of NMMO to 10.7; In step (6), the water bath is kept at 60°C; the alkali-resistant complex enzymes are: 90% cellulase and 10% xylitolase.
[0022] Test result: DP=590.
[0023] In the above Examples 1-3, the cellulase can be either Xindeli alkaline cellulase XDL-ZX400 or commercially available alkaline cellulase model GFY-3311, and the xylanase can be commercially available alkaline xylanase for papermaking.
[0024] The degree of polymerization of the product is determined using a viscosity method. The principle is that cellulose dissolves in copper ethylenediamine (CED) or copper ammonia solution, and the degree of polymerization is calculated using the intrinsic viscosity. Applicable to: pulp, cellulose powder, lyocell fiber, and porridge samples.
[0025] step: (1) Prepare copper ethylenediamine solution (CED) or copper ammonia solution.
[0026] (2) Accurately weigh 0.1–0.2 g of the completely dry sample.
[0027] (3) Add copper ethylenediamine solution, dissolve completely, and prepare a solution of a certain concentration.
[0028] (4) Use an Ubbelohde viscometer to measure the outflow time.
[0029] (5) Calculate the intrinsic viscosity [η], and then calculate DP according to the formula: DP calculation formula: DP = 0.78 × [η]^1.13 Or DP = 1.16 × [η] (commonly used simplified form) In summary, during the dry preparation of slurry, the synergistic effect of adding an alkali-resistant complex enzyme and NMMO without adding water can achieve excellent reduction of the degree of polymerization, meeting the requirements for lyocell spinning. The results are shown in Tables 1 and 2.
[0030] Table 1 Comparison of Degree of Polymerization and Depolymerization Effect Table 2 Comparison of Process Economy and Environmental Protection The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention without creative effort.
Claims
1. A method for reducing the degree of polymerization of cellulose using an enzymatic method in a dry process for producing lyocell fiber from paper pulp, characterized in that: Includes the following steps: (1) Pretreatment of dry pulp The cellulose pulp is pulverized to obtain dry pulverized pulp for later use. (2) Preparation of alkali-resistant complex enzyme and NMMO mixture Take NMMO solvent, add formic acid to adjust the pH to 10.5–11.0, add alkali-resistant complex enzyme, stir and mix well to obtain a mixture; (3) Dry mixing Add the mixture directly to the dry, pulverized pulp and stir to combine. (4) Enzymatic hydrolysis reduces the degree of polymerization The reaction is carried out at 55–70℃ for 40 minutes to achieve simultaneous swelling and reduce the degree of polymerization to 500–680.
2. The method for reducing the degree of polymerization of cellulose using an enzymatic method in the dry process for producing lyocell fiber from paper pulp according to claim 1, characterized in that: It also includes steps (5) Enzyme inactivation After step (4) is completed, heat to 85–95℃ and incubate to inactivate the enzyme; (6) Vacuum dehydration to make porridge.
3. The method for reducing the degree of polymerization of cellulose using an enzymatic method in the dry process for producing lyocell fiber from paper pulp according to claim 1, characterized in that: The alkali-resistant complex enzyme consists of 90%-100% cellulase and 0-10% xylanase.
4. The method for reducing the degree of polymerization of cellulose using an enzymatic method in the dry process for producing lyocell fiber from paper pulp according to claim 3, characterized in that: The alkali-resistant complex enzyme is composed of 100% cellulase and 0% xylanase.
5. The method for reducing the degree of polymerization of cellulose using an enzymatic method in the dry process for producing lyocell fiber from paper pulp according to claim 3, characterized in that: The alkali-resistant complex enzyme consists of 90% cellulase and 10% xylanase.
6. The method for reducing the degree of polymerization of cellulose using an enzymatic method in the dry process for producing lyocell fiber from paper pulp according to claim 2, characterized in that: Step (6): After enzyme inactivation, vacuum dehydration is performed at a temperature of 75–85℃ for ≥1.5h, followed by cooling to obtain porridge.
7. The method for reducing the degree of polymerization of cellulose using an enzymatic method in the dry process for producing lyocell fiber from paper pulp according to claim 2, characterized in that: In step (4), the enzymatic hydrolysis environment is pH=11 and the temperature is 70℃.
8. The method for reducing the degree of polymerization of cellulose using an enzymatic method in the dry process for producing lyocell fiber from paper pulp according to claim 2, characterized in that: Furthermore, in step (5), the enzyme inactivation time is 10 min; the heat preservation method in the process is a water bath.