Combined degumming method of deep eutectic solvent-biological complex enzyme for hemp fibers

Abstract

This invention discloses a combined degumming method for hemp fibers using a low-melting-point solvent and bio-enzyme complex. The method employs a two-stage coupled process: pretreatment with an aqueous low-melting-point solvent, material selection, and deep degumming with multiple enzymes. Taking advantage of the high lignin content and dense gum structure of hemp, a high-temperature aqueous low-melting-point solvent (choline chloride-urea / lactic acid) is used to break the hydrogen bonds in the gum, loosening the fibers and establishing enzyme penetration channels. A multi-indicator screening process is added, including weight loss rate, residual gum rate, and breaking strength, to standardize feed quality and improve batch-to-batch stability. This invention utilizes a quaternary enzyme complex of pectinase, xylanase, hemicellulase, and laccase to target and degrade various gums in a layered manner, effectively shortening the degumming cycle and increasing the gum removal rate. The entire process is free of strong acids and alkalis, and the solvent is recyclable, making it low-consumption and environmentally friendly. After treatment, the residual gum rate of hemp roving is ≤18.5%, and the fiber breaking strength is ≥3.56 cN·dtex, achieving both high degumming rate and low fiber damage, making it suitable for large-scale, green, and high-end production of hemp fibers.

Description

Technical Field

[0001] This invention belongs to the field of biotechnology and green processing technology of hemp fiber, and particularly relates to a method for degumming hemp fiber using a low eutectic solvent-biocompound enzyme combination. Background Technology

[0002] my country is the world's largest producer and exporter of textiles. Cotton, as a core textile raw material, has long faced a significant supply-demand gap and a high degree of dependence on imports. Developing high-yield, low-carbon, and renewable cotton alternative fibers is of strategic importance for ensuring the security of my country's textile industry chain and optimizing its raw material structure. Hemp is a natural negative carbon fiber, requiring far less water, fertilizer, and pesticides than cotton, while boasting high yields and a short growth cycle. It also possesses comprehensive properties such as antibacterial and breathable properties, softness and comfort, high-temperature resistance, UV resistance, and excellent insulation, making it a green textile raw material with great industrialization potential.

[0003] Hemp fibers are coated with a large amount of non-cellulose gums such as pectin, hemicellulose, and lignin, resulting in severe cross-linking and adhesion between fibers. Therefore, a degumming process is necessary to remove these gums and separate the individual fibers to meet the requirements of subsequent spinning and weaving. Currently, the main industrial process is traditional chemical degumming, which commonly employs strong acids, strong alkalis, and high-temperature, high-pressure boiling methods. This process suffers from problems such as high water consumption, high energy consumption, high production costs, high COD concentration in wastewater, and difficulty in pollutant treatment, leading to significant ecological pollution and severely hindering the green and sustainable development of the hemp industry.

[0004] To overcome the high pollution associated with chemical degumming, the industry has gradually promoted biological degumming technology, mainly including natural microbial degumming, single-strain degumming, and bioenzyme degumming. However, each type of biological degumming process has significant shortcomings. Traditional natural microbial degumming relies on natural microbial communities, which have complex compositions and poor controllability. These communities are prone to contamination by contaminating bacteria such as *Trichoderma*, which secrete cellulase. While decomposing the gum, these bacteria also erode the main cellulose skeleton of hemp fibers, causing a significant decrease in fiber strength and quality deterioration. Industrial-scale single-strain degumming, on the other hand, requires stringent production environments, including sterile equipment, LB-specific culture media, and strain propagation systems. The equipment investment and maintenance costs are high, and the production process is susceptible to contamination by other microorganisms, resulting in poor process stability. Furthermore, the activity of functional microbial communities is highly sensitive to environmental parameters. For example, efficient enzyme production degumming of *Bacillus subtilis* requires precisely maintaining a constant temperature of 37°C, a neutral pH of 7.0, and continuous oxygen supply, conditions that are difficult for conventional production lines to consistently meet, leading to low degumming efficiency and significant batch-to-batch variations. While conventional biological compound enzyme degumming can target and degrade gums with minimal fiber damage and is environmentally friendly, the penetration capacity of pure enzyme solutions is limited, making it difficult to quickly destroy the dense cross-linked network of gums. It generally suffers from long degumming cycles and low overall enzymatic hydrolysis efficiency, making it difficult to meet the needs of large-scale, high-efficiency production.

[0005] Eutectic solvents (DES) are a class of eutectic mixtures formed by combining hydrogen bond acceptors and hydrogen bond donors. They possess advantages such as low volatility, high thermal stability, non-toxicity, biodegradability, and ease of preparation. They can effectively disrupt the hydrogen bond network of biomass gums and have been gradually applied in the pretreatment of hemp and cellulose fibers. Currently, several published patents focus on the use of eutectic solvents for degumming cellulose and hemp fibers; however, existing technologies all have technical defects, which are analyzed in detail below:

[0006] In existing patent CN104178527B, Xing Yanjun et al. disclosed a method for processing cellulose raw materials through eutectic solvent pyrolysis. This method uses a highly polar polyol as a base, adds alkali metal carbonates in a molar ratio of 5:1 to 10:1, and heats and stirs at 80–100°C for 0.5–2 hours to prepare a uniform and transparent eutectic solvent system. Then, the cellulose raw material, which has undergone mechanical shearing or physicochemical pretreatment, is placed in this system and continuously heat-treated at 130–180°C for 1–6 hours to achieve cellulose pyrolysis and prepare a glucose-polyol solution. This process is simple, highly adaptable to industrial applications, and can achieve large-scale biomass decomposition. However, the core application of this technology is for sugar production from cellulose raw materials, not for degumming hemp fiber textiles. This process involves high processing temperatures and high overall energy consumption. The single eutectic solvent pyrolysis can only crack some of the shallow gums and cannot completely degrade the stubborn lignin and cross-linked hemicellulose in hemp. The gum degradation is incomplete, and the degumming cleanliness is difficult to meet the spinning standards. Furthermore, long-term high-temperature treatment can easily cause fiber brittleness and a decrease in strength.

[0007] CN113373527A discloses a method for degumming flax roving using a low-melt solvent and microorganisms. This process abandons traditional acid-alkali pretreatment and has the advantages of being environmentally friendly and improving degumming efficiency. However, it suffers from several inherent technical defects and cannot meet the industrial demands for high-quality, high-efficiency degumming of hemp fibers. The substrate it treats is flax roving with loose gum and low lignin content, which differs significantly from hemp fibers with dense gum cross-linking and higher lignin content. Therefore, the process parameters cannot be directly adapted to hemp processing. Furthermore, the downstream process uses single-strain microbial fermentation for degumming instead of a purified compound enzyme system, resulting in harsh production conditions, high costs, poor stability, and a degumming cycle of 14–20 hours, leading to extremely low production efficiency. In addition, this system lacks laccase specifically for lignin degradation, resulting in weak removal of stubborn lignin from hemp, incomplete gum removal, and easy fiber adhesion, making it difficult to meet the quality requirements of high-end spinning.

[0008] Publication No. CN113322525A discloses a one-step method for degumming ramie and extracting refined ramie fibers based on a eutectic solvent. The entire process relies solely on anhydrous high-concentration eutectic solvent for high-temperature boiling to achieve degumming, without the need for additional biological enzymes, resulting in a streamlined operation. However, this technology has two major drawbacks: First, the use of anhydrous eutectic solvent throughout the process leads to huge reagent consumption, high raw material production costs, and the high-temperature pure solvent directly damages the cellulose skeleton, causing significant loss of fiber breaking strength. Second, relying solely on the solvothermal effect only dissociates shallow pectin and hemicellulose, making it difficult to fully degrade large-molecule lignin, resulting in incomplete degumming, prominent fiber adhesion, and subsequent spinning issues such as filament bundling and increased breakage rates.

[0009] Bio-based compound enzyme degumming is a significant innovative technology for green processing of hemp. By employing the synergistic and targeted action of multiple enzyme components, it precisely degrades pectin, effectively avoiding many drawbacks of microbial degumming. A compound enzyme system centered on pectinase, xylanase, and hemicellulase can achieve highly efficient degradation of 83.3% of pectin and 79.2% of hemicellulose, retaining over 90% of fiber breaking strength, improving fiber surface smoothness by 40%, and significantly reducing fiber damage. This technology boasts advantages such as precision and controllability, green and low-carbon operation, and economic efficiency: targeted enzyme catalysis avoids fiber breakage caused by uncontrollable microbial metabolism, significantly improving fiber splitting uniformity; the combined process reduces production water consumption by 70%, with wastewater COD values ​​as low as 1050–1500 mg / L, only one-third of traditional chemical processes, and the entire process is free of sulfur and chlorine chemicals; combined with an enzyme preparation recycling and wastewater recovery system, it can achieve a 45% reduction in unit energy consumption and a 60% reduction in water treatment costs. However, single-enzyme degumming is limited by the enzyme solution penetration rate and catalytic efficiency, resulting in long degumming cycles and low overall production efficiency. Eutectic solvents can effectively break down the dense cross-linked structure of the adhesive, compensating for the technical shortcomings of single-enzyme degumming. The combination of the two can achieve complementary advantages.

[0010] In summary, existing hemp degumming technologies have significant technical shortcomings: traditional chemical degumming is highly polluting, energy-intensive, and causes significant fiber damage; microbial degumming suffers from poor controllability, weak batch stability, and severe fiber strength loss; single-bio-enzyme degumming is inefficient and time-consuming; and single eutectic solvent degumming is energy-intensive and incomplete. Existing patents combining eutectic solvents with biological treatment are either only suitable for heterogeneous bast fibers such as flax and ramie, or employ inefficient microbial systems, lack key enzyme components for lignin degradation, and rely on high-temperature, high-energy-consumption conditions, failing to meet the demands of efficient, low-damage, low-carbon, and stable industrial degumming production of hemp fibers. Therefore, developing a novel eutectic solvent-bio-enzyme combined degumming process that is suitable for hemp fibers, operates under mild conditions, degummes thoroughly, and minimizes fiber damage is a pressing technical problem to be solved in this field. Summary of the Invention

[0011] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a low-eutectic solvent-bio-compound enzyme combined degumming method for hemp fibers that can shorten degumming time, improve the overall removal rate of adhesives, reduce fiber mechanical damage, and is low-consumption, green, and pollution-free.

[0012] The core of this invention is a two-stage synergistic coupling process of pretreatment screening with aqueous eutectic solvent and low-temperature deep degumming using a compound of pectinase / xylanase / hemicellulase / laccase. Through three core innovations—solvent pretreatment of loose gums, multi-enzyme targeted stratified degradation of gums, and the addition of pretreatment sample screening quality control—this invention solves multiple technical defects of traditional chemical degumming, such as heavy pollution, poor penetration and low efficiency of single biological enzymes, insufficient lignin removal by pure eutectic solvents, fiber damage from microbial degumming, and interference of process variables with degumming evaluation.

[0013] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination, comprising the following steps:

[0014] (1) Pretreatment preparation: The strips of hemp roving are soaked in room temperature water, dehydrated and then dried to constant weight to obtain dried hemp roving to be treated;

[0015] (2) High-temperature eutectic solvent pretreatment: Prepare an aqueous solution of eutectic solvent, wherein the eutectic solvent uses choline chloride as the hydrogen bond acceptor and the hydrogen bond donor is selected from at least one of urea and lactic acid; the mass fraction of water in the aqueous solution of eutectic solvent is 10% to 40%; mix the dried hemp roving with the aqueous solution of eutectic solvent at a bath ratio of 1:(20 to 50), place it in a closed heating system, and keep it at 130℃ to 160℃ for 60 min to 240 min; after the treatment, take out the material and wash it thoroughly with water to remove the residual eutectic solvent on the surface of the roving;

[0016] (3) Pre-treatment material classification and screening: The hemp roving treated in step (2) was subjected to offline performance testing, and the roving was selected that simultaneously met the following requirements: weight loss rate ≥11.25%, residual glue rate ≤22.78%, and fiber breaking strength ≥2.81cN·dtex. -1 Hemp roving was used as the raw material for compound enzymatic hydrolysis; hemp roving that failed the test was returned to step (2) for high temperature and low eutectic solvent pretreatment again;

[0017] (4) Targeted deep degumming with compound enzymes: Prepare a compound enzyme aqueous solution, wherein the compound enzymes include pectin degrading enzyme, lignin oxidation degrading enzyme, and hemicellulose degrading enzyme. The cellulase activity in the enzyme system is extremely low and there is no fiber damage activity. The pH value of the enzyme solution is adjusted to 4.0-5.0 using a buffer system. The qualified hemp roving is added to the enzyme solution system and enzymatically hydrolyzed by shaking at a constant temperature of 48-52℃ for 5-7 hours.

[0018] (5) Post-processing: After enzymatic hydrolysis, take out the hemp roving, wash it with water and dry it to constant weight to obtain refined hemp roving.

[0019] In the above-mentioned degumming method for hemp fiber using a eutectic solvent-biocomposite enzyme combination, in step (2), the molar ratio of choline chloride to urea is 1:2, and the molar ratio of choline chloride to lactic acid is 1:5.

[0020] The preferred process parameters in step (2) of the above-mentioned degumming method for hemp fiber using a low eutectic solvent-biocomposite enzyme combination are: bath ratio 1:50, treatment temperature 150℃, and treatment time 240min.

[0021] The above-mentioned degumming method using a eutectic solvent-bio-compound enzyme combination for hemp fiber, in step (3), yields a set of critical indicators for qualified hemp roving: weight loss 14.59%, residual glue rate 22.78%, and breaking strength 2.81 cN·dtex. -1 .

[0022] The above-described degumming method using a eutectic solvent-bio-enzyme combination for hemp fibers yields refined hemp roving that meets the following requirements: residual gum content ≤ 18.5%, and fiber breaking strength ≥ 3.56 cN·dtex. -1 .

[0023] In the above-mentioned degumming method for hemp fiber using a low eutectic solvent-biocompound enzyme combination, in step (1), the soaking time in room temperature water is 5-7 hours, and the drying temperature is controlled at 100-110℃.

[0024] In the above-mentioned degumming method for hemp fibers using a eutectic solvent-biocomposite enzyme combination, the mass ratio of hemp roving to the aqueous solution of the enzymatic hydrolysis system in step (4) is 1:8 to 1:12, preferably 1:10.

[0025] In the above-mentioned method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination, in step (4), the pectin-degrading enzyme is pectinase, the hemicellulose-degrading enzymes are xylanase and hemicellulase, and the lignin-oxidizing degrading enzyme is laccase; pectinase is the core degrading enzyme, xylanase and hemicellulase are the synergistic degrading enzymes, and laccase is the auxiliary enzyme; the pH of the enzyme solution is adjusted to 4.0-5.0 using 0.05mol / L acetate-sodium acetate buffer; based on the percentage of fabric weight owf, the amount of pectinase added is 3%-5% owf, the amount of xylanase added is 1%-2% owf, the amount of hemicellulase added is 1%-2% owf, and the amount of laccase added is 0.8%-1.2% owf.

[0026] The above-mentioned degumming method for hemp fiber using a eutectic solvent-bio-compound enzyme combination has a cellulase relative activity in the compound enzyme system that is no higher than 5% of the total pectinase activity; when tested with standard cotton cellulose substrate, the cellulose degradation rate is less than 3% within a 7-hour enzymatic hydrolysis cycle.

[0027] The above-mentioned degumming method for hemp fiber using a low eutectic solvent-bio-compound enzyme combination involves step (3) using an offline batch detection method to determine the weight loss rate, residual glue rate, and fiber breaking strength of the pretreated hemp roving. Only materials that simultaneously meet the three specified ranges are allowed to enter the degumming process of the compound enzyme in step (4), while roving that does not meet the standards is returned to step (2) for re-pretreatment.

[0028] The present invention provides a method for degumming hemp fibers using a eutectic solvent-bio-compound enzyme combination, which has the following technical advantages and beneficial effects compared to existing technologies:

[0029] First, this invention achieves synergistic optimization of process performance through the coupling of two processes, rather than simply adding up a single step. The pretreatment stage employs an aqueous eutectic solvent system of choline chloride-urea and choline chloride-lactic acid. Under high-temperature conditions, this competitively disrupts the hydrogen bond structure between pectin and hemicellulose molecules, effectively loosening the dense gum cross-linking network of the fibers, dispersing aggregated fiber bundles, and pre-removing some of the surface and middle layers of the fibers. This creates channels within the fibers for enzyme penetration, which to some extent improves the limited penetration capacity of single biological enzyme systems, insufficient degradation of deep gums, and low degumming efficiency. Simultaneously, the introduction of water into the solvent system effectively mitigates the corrosive effect of the high-temperature pure eutectic solvent on the cellulose skeleton, achieving selective loosening of the gums and ensuring that the fiber breaking strength after pretreatment remains stably maintained at 2.81 cN·dtex. -1 The above points are important. Pretreatment with a single eutectic solvent typically only effectively removes superficial pectin and hemicellulose, with limited effect on lignin removal, resulting in relatively high residual gum content in the finished product. Single bio-enzyme systems, due to insufficient permeation channels, struggle to fully degrade deeply cross-linked gums. This invention, by coupling two processes, achieves stepwise, layered removal of pectin, hemicellulose, and persistent lignin, reducing the residual gum content from 22.78% to 18.46%. Simultaneously, the gentle pretreatment with an aqueous eutectic solvent combined with a low-damage enzyme system effectively degummes while better protecting the fiber structure, increasing the breaking strength of the finished fiber to 3.56 cN·dtex. -1 Compared to single-process treatment, it shows a good synergistic optimization effect.

[0030] Secondly, this invention employs a three-component compound enzyme system, which is well-suited to the degumming requirements of hemp fibers with high lignin content. It enables the stratified and targeted degradation of multiple gum components, reducing fiber damage during the degumming process. Pectinase is the core degrading enzyme, primarily breaking down the pectin filling the fiber gaps; xylanase and hemicellulase are synergistic degrading enzymes, effectively degrading the hemicellulose component; and laccase is an auxiliary enzyme, assisting in the decomposition of stubborn lignin that is difficult to remove with eutectic solvents, compensating for the insufficient lignin degradation capacity of single-solvent systems. Simultaneously, this invention strictly limits the cellulase activity in the compound system, controlling the relative cellulase activity to no more than 5% of the total pectinase activity. Within a 7-hour enzymatic hydrolysis cycle, the cellulose degradation rate can be controlled below 3%, ensuring the enzyme system primarily acts on the gum components. This significantly reduces the erosion and damage to the cellulose backbone, better preserving the original mechanical and wear properties of hemp fibers, and improving the surface smoothness and uniformity of single fiber splitting in the finished fiber.

[0031] Third, the invention adds a pretreatment index selection process, which helps improve the overall stability and repeatability of the process. After the eutectic solvent pretreatment is completed, the invention uses offline detection of sample weight loss rate, residual glue rate, and fiber breaking strength to screen homogeneous samples that meet the process thresholds for subsequent enzymatic hydrolysis. Rovings that do not meet the pretreatment standards can be reworked, effectively unifying the subsequent enzymatic hydrolysis feed state and alleviating the problem of uneven degumming effect caused by initial raw material differences and pretreatment process fluctuations. This makes the overall process more controllable, helps improve batch production consistency, and better adapts to the needs of stable industrial production.

[0032] Fourth, the overall process of this invention is green and mild, with relatively low energy and water consumption, and possesses good potential for clean production and industrial application. The entire degumming process does not require the use of highly polluting chemical agents such as strong acids, strong alkalis, sulfur-containing, or chlorine-containing chemicals. It mainly relies on the hydrogen bonding loosening effect of the eutectic solvent and the mild catalytic effect of biological enzymes to achieve gumming removal, resulting in mild process conditions. Compared with traditional chemical and microbial degumming processes, this invention can effectively reduce production water and energy consumption, lower wastewater COD load, and reduce the pressure and cost of subsequent wastewater treatment. Simultaneously, the eutectic solvent can be recycled, resulting in high raw material utilization. The overall process aligns with the development trend of green, low-carbon, and clean production in the hemp textile industry.

[0033] Fifth, the process of this invention is specifically adapted to hemp fiber raw materials with dense cross-linking and high lignin content, representing an improvement in raw material compatibility and process system. Compared to existing low eutectic solvent combined with biological treatment technologies, which are mostly suitable for low-lignin bast fibers such as flax and ramie, and conventional microbial combined processes which suffer from long fermentation cycles and weak controllability, this invention uses a targeted compound enzyme system to replace traditional strain fermentation, shortening the treatment cycle and improving process controllability. It can better meet the production requirements of efficient, low-loss, and stable degumming of hemp fiber, and has a wider range of process adaptability and industrial application potential. Attached Figure Description

[0034] Figure 1 Scanning electron microscope image of undegummed raw hemp roving fibers;

[0035] Figure 2 A scanning electron microscope image of hemp roving fibers that have only undergone degumming treatment with bio-compound enzymes;

[0036] Figure 3 Scanning electron microscope image of hemp roving fibers pretreated only with an aqueous solution of choline chloride-urea eutectic solvent;

[0037] Figure 4 Scanning electron microscope image of hemp roving fibers pretreated only with an aqueous solution of choline chloride-lactic acid eutectic solvent;

[0038] Figure 5 Scanning electron microscope image of hemp roving fibers after pretreatment with choline chloride-urea eutectic solvent coupled with bio-compound enzyme degumming;

[0039] Figure 6 A polarized light microscope image of raw hemp roving fibers without any degumming treatment;

[0040] Figure 7 Polarized light microscope image of hemp roving fibers after pretreatment with an aqueous solution of choline chloride-urea eutectic solvent;

[0041] Figure 8 Polarized light microscope image of hemp roving fibers after pretreatment with choline chloride-urea eutectic solvent aqueous solution combined with degumming by biological compound enzyme. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] In this invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or working state, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish an order. The term "multiple" means "two or more". It should be noted that the following embodiments are merely preferred embodiments of this application and are not intended to limit the scope of protection of this application. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of this invention are all within the scope of protection of this invention.

[0044] This invention provides a combined degumming method for hemp fibers using a eutectic solvent and bio-enzyme combination. The overall process employs a segmented, coupled system: pretreatment purification—high-temperature loosening pretreatment with an aqueous eutectic solvent—pretreatment sample selection—low-damage, targeted, deep degumming with a bio-enzyme combination—post-treatment shaping. Based on the synergistic effect of the hydrogen bond dissociation loosening mechanism of the eutectic solvent and the targeted, precise degradation mechanism of multiple enzymes, this invention overcomes the technical shortcomings of traditional chemical degumming, such as severe pollution, poor penetration and low efficiency of single bio-degumming, incomplete removal of gum by pure eutectic solvents, and uncontrollable fiber damage. Under green process conditions without the involvement of strong acids, strong alkalis, or highly polluting sulfur and chlorine agents, it achieves high-efficiency, low-damage, and high-stability degumming of hemp roving, meeting the needs of large-scale green production.

[0045] This invention improves batch stability and experimental repeatability by adding a pretreatment sample selection process to unify the subsequent enzymatic hydrolysis feed state, eliminating the interference of process variables caused by initial differences in raw materials and uneven pretreatment. At the same time, it adopts a four-component compound enzyme system with extremely low cellulase activity, which can efficiently remove pectin, hemicellulose and lignin complex gums while maximally protecting the main cellulose skeleton of hemp fiber, taking into account both high degumming rate and excellent fiber mechanical properties.

[0046] The present invention specifically includes the following steps:

[0047] (1) Pretreatment preparation: Soak the strips of hemp roving in room temperature water for 5-7 hours to fully wet and dissolve surface impurities and soluble components. After soaking, dehydrate and dry at 100-110℃ to constant weight to obtain dry and uniform hemp roving to be treated.

[0048] (2) High-temperature eutectic solvent pretreatment: Prepare an aqueous eutectic solvent solution containing water, wherein choline chloride is used as the hydrogen bond acceptor and urea or lactic acid is selected as the hydrogen bond donor; the molar ratio of choline chloride to urea is 1:2, and the molar ratio of choline chloride to lactic acid is 1:5; the mass fraction of water in the prepared eutectic solvent solution is 10% to 40%. Mix the dried hemp roving with the eutectic solvent solution at a bath ratio of 1:(20 to 50), place it in a closed heating system, and keep it at 130℃ to 160℃ for 60 min to 240 min; after the treatment, take out the material and wash it thoroughly with water to remove the residual eutectic solvent on the surface of the roving. The preferred process parameters are: bath ratio 1:50, treatment temperature 150℃, and treatment time 240 min.

[0049] The eutectic solvent pretreatment system of this invention is used in conjunction with the subsequent biological enzyme system to strictly control enzyme activity: the relative activity of cellulase in the compound enzyme system is no more than 5% of the total activity of pectinase. When tested with standard cotton cellulose substrate, the cellulose degradation rate is less than 3% within a 7-hour enzymatic hydrolysis cycle, thus preventing the degradation and destruction of the main fiber structure from the source.

[0050] (3) Pre-treatment material grading and screening: The hemp roving treated in step (2) was tested in batches using offline performance testing method to detect the weight loss rate, residual glue rate and fiber breaking strength. The screening was carried out to meet the following conditions: weight loss rate ≥11.25%, residual glue rate ≤22.78%, and fiber breaking strength ≥2.81cN·dtex. -1 Qualified samples were used as raw materials for subsequent enzymatic hydrolysis. The optimal pretreated sample parameters were: weight loss 14.59%, residual gum 22.78%, and tensile strength 2.81 cN·dtex. -1 . The roving that does not meet the pretreatment standard is returned to step (2) for high-temperature pretreatment with eutectic solvent to ensure that the pretreatment effect of the material entering the enzymatic hydrolysis section is uniform and consistent.

[0051] (4) Targeted Deep Degumming with Compound Enzymes: A solution of compound enzymes was prepared. The compound enzymes used consisted of pectinase, xylanase, hemicellulase, and laccase. Pectinase was the core degrading enzyme, xylanase and hemicellulase were the synergistic degrading enzymes, and laccase was the auxiliary enzyme. These enzymes respectively achieved targeted degradation of pectin, hemicellulose, and lignin. The overall cellulase activity of the enzyme system was extremely low, with no fiber damage. The pH of the enzyme solution was adjusted to 4.0–5.0 using 0.05 mol / L acetate-sodium acetate buffer to create a mild reaction environment suitable for the synergistic catalysis of the four enzymes. Based on the percentage of owf (owf) of fabric mass, the amount of pectinase added was 3%–5% owf, the amount of xylanase added was 1%–2% owf, the amount of hemicellulase added was 1%–2% owf, and the amount of laccase added was 0.8%–1.2% owf. Selected hemp roving and enzymatic hydrolysis water are added to the enzyme solution system at a mass ratio of 1:8 to 1:12, with a preferred bath ratio of 1:10. The enzyme is then hydrolyzed by shaking at a constant temperature of 48 to 52°C for 5 to 7 hours to achieve deep, stratified, and precise degradation of residual gum.

[0052] (5) Post-processing and shaping: After the enzymatic hydrolysis is completed, the hemp roving is taken out, thoroughly washed with water to remove the residual enzyme solution and gum degradation products on the surface, and dried to constant weight to finally obtain refined hemp roving.

[0053] The refined hemp roving processed by the combined process of this invention can have a residual glue content controlled within 18.5% and a fiber breaking strength ≥3.56 cN·dtex. -1 The fiber adhesive is thoroughly removed, has a high degree of splitting, a smooth surface, and excellent mechanical properties, fully meeting the requirements of high-end textile spinning and processing.

[0054] In this invention, the waste eutectic solvent system after degumming is filtered to remove impurities such as adhesive residue and fiber debris. After the moisture content is detected, pure water and a small amount of solvent components are added to reconstitute the parameters and then it can be reused in the pretreatment process. The solvent recovery rate is high, and the energy consumption and material costs are low, which fully improves the green and low-carbon process system.

[0055] This invention utilizes the hydrogen bond disruption effect of high-temperature pretreatment with an aqueous eutectic solvent to loosen the dense pectin cross-linking network of hemp fibers, disperse fiber bundles, and pre-remove surface pectin, overcoming the technical bottlenecks of poor permeability of single biological enzyme solutions, difficulty in degrading deep cross-linked pectin, and long degumming cycles. A pretreatment selection mechanism standardizes feed quality, improving process repeatability and batch stability. The subsequent quaternary compound enzyme system can specifically degrade residual pectin, hemicellulose, and stubborn lignin, compensating for the insufficient lignin degradation capacity of a single eutectic solvent. The two processes are synergistically coupled and complementary, resulting in a green, low-consumption process with no high-polluting reagent emissions. While improving degumming efficiency and quality, it maximizes the preservation of fiber mechanical properties, making it suitable for continuous, large-scale, and green industrial degumming of hemp roving.

[0056] The hemp roving used in this invention is a conventional raw material in the industry. It is produced by harvesting and retting hemp plants to obtain hemp fibers, which are then processed through combing, sliver forming, and binding. It is a mature and commonly used raw material in this field. The pectinase, xylanase, hemicellulase, and laccase used in this invention are all industrial-grade compound enzyme preparations specifically for degumming hemp fibers.

[0057] The present application will be specifically described below through specific embodiments. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0058] Example 1

[0059] This embodiment represents the optimal implementation process of the present invention, providing a method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination, specifically including the following steps:

[0060] (1) Pretreatment preparation: Weigh 20g of strip hemp roving and soak it in deionized water at room temperature for 6 hours to fully wet the fiber and dissolve the surface dust and soluble impurities; after soaking, dehydrate and dry it in an oven at 105℃ until constant weight, and set aside for later use.

[0061] (2) Preparation of eutectic solvent and high-temperature pretreatment: Choline chloride was selected as the hydrogen bond acceptor and urea as the hydrogen bond donor. They were mixed and melted at a molar ratio of 1:2 to prepare a homogeneous and transparent eutectic solvent. Deionized water was added to the solvent to prepare an aqueous solution of eutectic solvent with a water mass fraction of 25%. The dried hemp roving was mixed with the aqueous solution of solvent at a preferred bath ratio of 1:50 and placed in a closed heating system. It was kept at 150°C for 240 min. After the pretreatment, the roving was taken out and rinsed thoroughly with sufficient flowing deionized water to completely remove residual solvent from the fiber surface and pores, so as to avoid residual components interfering with the subsequent enzymatic hydrolysis reaction.

[0062] (3) Pre-treatment material grading and screening: The hemp roving treated in step (2) was subjected to offline performance testing. The weight loss rate, residual glue rate and fiber breaking strength were measured in batches. The screening was carried out with the following conditions: weight loss rate ≥11.25%, residual glue rate ≤22.78%, and breaking strength ≥2.81cN·dtex. -1 Qualified samples and non-compliant rovings are returned to step (2) for re-pretreatment to ensure that the quality of materials entering the enzymatic hydrolysis section is uniform.

[0063] Batch testing verified that pretreated samples meeting the above-mentioned threshold values ​​exhibited excellent fiber loosening, no damage to the cellulose skeleton, and complete preservation of mechanical properties. These samples provide the optimal pretreated substrate for the two-stage synergistic degumming process of this invention, fully leveraging the synergistic effect of eutectic solvent loosening and bioenzymatic degradation. The performance indicators of the optimal pretreated samples selected in this embodiment are shown in Table 1.

[0064] Table 1. Fiber properties of hemp roving after treatment with the optimal eutectic solvent.

[0065] 2.81 14.59 22.78

[0066] 10g of the optimal pretreated hemp roving sample was selected as the raw material for subsequent enzymatic hydrolysis and deep bio-enzymatic degumming treatment.

[0067] (4) Targeted deep degumming with compound enzymes: A quaternary low-damage biological compound enzyme aqueous solution was prepared. The compound enzyme system consisted of pectinase, xylanase, hemicellulase, and laccase, with pectinase as the core degrading enzyme, xylanase and hemicellulase as synergistic degrading enzymes, and laccase as an auxiliary enzyme. The relative enzyme activity of cellulase in the enzyme system was strictly controlled to be no more than 5% of the total activity of pectinase. Using standard cotton cellulose substrate as a test, the cellulose degradation rate was less than 3% within a 7-hour enzymatic hydrolysis cycle, ensuring that the enzyme system only targeted the degradation of the gum component and did not erode the cellulose skeleton. Based on the percentage of owf by fabric weight, the amount of pectinase added was 4% owf, the amount of xylanase added was 1.5% owf, the amount of hemicellulase added was 1.5% owf, and the amount of laccase added was 1.0% owf. The pH of the enzyme solution was adjusted to 4.0-5.0 using 0.05 mol / L acetate-sodium acetate buffer to adapt to the optimal reaction environment for the synergistic catalysis of the four enzymes. The screened hemp roving was fed with enzymatically hydrolyzed deionized water at a mass ratio of 1:10 and placed under constant temperature shaking at 50℃ for 6 hours to achieve stratified, precise and deep degradation of residual pectin, hemicellulose and stubborn lignin.

[0068] (5) Post-processing: After enzymatic hydrolysis, take out the hemp roving and rinse it repeatedly with sufficient deionized water to thoroughly remove residual enzyme solution and gum degradation products on the fiber surface. Then dry it to constant weight to obtain refined hemp roving finished product.

[0069] The key performance indicators of the finished hemp roving after the combined degumming process in this embodiment are shown in Table 2.

[0070] Table 2 Performance indicators of refined hemp roving fibers after combined degumming treatment

[0071] 3.56 15.5 18.46

[0072] All the above performance indicators were tested in accordance with the current national textile standards: the residual glue rate of hemp fiber was determined according to GB / T20392-2006, the fiber breaking strength was determined according to GB / T16256-2008, and the weight loss rate was performed in accordance with the general test method for fiber mass loss in textiles in GB / T29862.

[0073] To further verify the low-damage advantage of the compound enzyme system of the present invention, a comparative test was conducted on the cellulose degradation effect of different processes, and the results are shown in Table 3.

[0074] Table 3 Comparison of cellulose degradation effects of different degumming processes

[0075] Process Group 7h enzymatic cellulose degradation rate relative enzyme activity of cellulase Fiber surface morphology characteristics This invention combines processes 2.12% ≤5% total pectinase activity Smooth and free from etching and fiber splitting Degumming of wild fungi (Comparative Example 3) 12.75% Without control, miscellaneous bacteria produce large amounts of cellulase. Deep etching of fiber surface leads to a significant decrease in strength. Common commercial compound enzymes (uncontrolled cellulase activity) 8.63% 18% Localized fiber damage and decreased tensile strength

[0076] Test data shows that, compared to a single eutectic solvent pretreatment process, the two-stage coupled synergistic degumming process of this invention can further remove stubborn composite adhesives at a deeper level, reducing the residual adhesive rate of the finished product from 22.78% to 18.46%, resulting in more thorough and uniform adhesive removal. Simultaneously, the fiber breaking strength increases from 2.81 cN·dtex to 3.56 cN·dtex, which can alleviate to some extent the contradiction commonly found in traditional degumming processes: "thorough degumming leads to severe fiber damage, while maintaining strength results in incomplete degumming." (See attached microstructure diagram.) Figure 5 , Figure 7 , Figure 8 As can be seen, the hemp fiber surface after treatment in this embodiment has no obvious glue residue or etching defects. The fiber bundles are fully stretched and dissociated, the single fiber splitting degree is high, the surface is smooth and uniform, the degumming consistency and the overall quality of the finished product are excellent, which can fully meet the quality requirements of high-end hemp spinning processing.

[0077] Example 2

[0078] This embodiment is basically the same as the process steps in Embodiment 1, except that: the eutectic solvent used is a choline chloride-lactic acid system, with a choline chloride to lactic acid molar ratio of 1:5, and a eutectic solvent aqueous solution with a water mass fraction of 30% is prepared; the pretreatment bath ratio is 1:30, the treatment temperature is 140℃, and the holding time is 180 min; the amount of compound enzymes added is: pectinase 3% owf, xylanase 1% owf, hemicellulase 1% owf, laccase 0.8% owf, the enzymatic hydrolysis temperature is 48℃, the enzymatic hydrolysis time is 5 h, and the roving to water mass ratio is 1:8. All other process parameters, sample screening criteria, and enzyme activity limiting conditions are consistent with those in Embodiment 1.

[0079] Test results show that this embodiment can loosen the hemp fiber gum network, remove most of the surface and middle layers of gum, and the fibers show no obvious brittleness or strength reduction. The degumming effect is better than that of single biological enzyme degumming and single eutectic solvent pretreatment processes. (See attached...) Figure 4 Microscopic morphology shows that, compared with the choline chloride-urea system, the choline chloride-lactic acid system in this embodiment has a relatively weaker ability to remove adhesive residue. There are still trace amounts of adhesive residue on the fiber surface. The overall degumming uniformity and fiber splitting degree are slightly lower than those in Example 1. It can be adapted to the degumming production of conventional civilian textiles.

[0080] Example 3

[0081] This embodiment is basically the same as the process steps in Example 1, except that: the water mass fraction of the eutectic solvent aqueous solution is 10%; the pretreatment bath ratio is 1:20; the treatment temperature is 130℃; and the treatment time is 60 min. The amount of compound enzymes added is: pectinase 5% owf, xylanase 2% owf, hemicellulase 2% owf, and laccase 1.2% owf; the enzymatic hydrolysis temperature is 52℃; the enzymatic hydrolysis time is 7 h; and the roving to water mass ratio is 1:12. The remaining processes, screening criteria, and enzyme activity limiting conditions are the same as in Example 1.

[0082] The pretreatment process in this embodiment is gentler and has lower overall energy consumption. It can effectively remove the surface layer and most of the middle layer of adhesive from the fiber, meet the basic degumming requirements of conventional textile processing, and has wider process adaptability, making it suitable for large-scale, low-cost production applications.

[0083] Comparative Example 1 (Degumming process using a single biological compound enzyme)

[0084] This comparative example uses the same four-component compound enzyme system, enzymatic hydrolysis temperature, time, pH, and bath ratio as Example 1 to directly enzymatically degumme the raw, untreated hemp roving, omitting the eutectic solvent high-temperature pretreatment and sample selection process.

[0085] Experimental results show that single-component biological enzyme solutions have limited penetrating power and cannot effectively penetrate the dense cross-linked network of hemp fibers, making it difficult to degrade deep cross-linked gums in the fibers. This results in problems such as low degumming efficiency, long degumming cycle, and uneven degumming. (Combined with...) Figure 2 Microscopic morphology shows that the fiber surface is still covered with a large amount of glue after degumming with only a single biological enzyme. The adhesion and aggregation between fibers are significant, the splitting degree of individual fibers is poor, and the residual glue rate of the finished product is much higher than that of the combined degumming process of this invention. It is impossible to achieve deep degumming and it is difficult to meet the requirements of high-end spinning processing.

[0086] Comparative Example 2 (Separate Eutectic Solvent Pretreatment Process)

[0087] This comparative example only uses the choline chloride-urea aqueous eutectic solvent system with the optimal parameters of Example 1 to pretreat hemp roving at high temperature. After pretreatment, it is directly washed and dried with water, omitting the subsequent biological compound enzyme deep degumming process. The rest of the operation is the same as in Example 1.

[0088] Experimental results show that a single eutectic solvent can effectively disrupt the hydrogen bonds between pectin and hemicellulose molecules, loosen the fiber bundle structure, and remove most of the surface gum, but its ability to degrade structurally stable and stubborn lignin is insufficient. (Combined with...) Figure 3 Microscopic morphology reveals that a small amount of stubborn adhesive remains on the fiber surface, indicating incomplete adhesive removal and a high residual adhesive rate in the finished product. This fails to meet the quality requirements of high-end spinning for low residual adhesive and high fiber splitting, highlighting the significant technical deficiencies of the single pretreatment process.

[0089] Comparative Example 3 (Conventional Wild Microbial Degumming Process)

[0090] This comparative example uses the traditional hemp wild fungus natural degumming process, selects hemp roving from the same batch, and relies on the metabolism of natural environmental microbial communities to achieve gum degradation. There is no artificial bacterial control or precise enzyme ratio throughout the process, and it is a conventional room temperature natural degumming treatment.

[0091] Experimental results show that wild-type microbial communities are complex and poorly controllable, easily contaminating with other bacteria that secrete cellulase. While degrading the gum, these microbial communities severely erode the main structure of hemp cellulose, leading to a significant deterioration in fiber mechanical properties, with fiber strength losses reaching 30%–50%. Furthermore, the activity of these microbial communities is highly sensitive to environmental temperature and humidity, as well as interference from other bacteria. They exhibit poor batch stability, lengthy degumming cycles, and require large amounts of additives, resulting in high COD wastewater and expensive environmental treatment costs. Therefore, their overall industrialization value is far lower than that of the green combined degumming process of this invention.

[0092] Comparative Example 4 (Traditional Industrial Strong Alkali Chemical Degumming)

[0093] Hemp roving from the same batch was processed using a standard high-temperature, strong-alkali calcination process: caustic soda concentration 12 g / L, liquor ratio 1:50, calcination at 160℃ for 4 hours, followed by washing, neutralization, and drying. Test results showed a residual glue rate of 19.21% and a fiber breaking strength of only 2.42 cN·dtex. -1 The process results in significant loss of fiber strength; the entire process is characterized by high alkali and high water consumption, with wastewater COD reaching 4500-6000 mg / L, leading to high water treatment costs and significant environmental pollution; the degummed fiber surface has numerous etching and splitting defects, resulting in a significantly higher yarn breakage rate than the process described in this invention.

[0094] As can be seen from the comparison, the combined process of this invention has lower residual glue, higher fiber strength, and no strong alkali pollution. Its comprehensive performance is superior to the mainstream chemical degumming process in industrialization, and it has outstanding industrialization advantages.

[0095] Two-stage synergistic degumming mechanism

[0096] This invention employs a two-stage synergistic process mechanism: high-temperature pretreatment with an aqueous eutectic solvent coupled with deep degumming using a quaternary low-damage bio-compound enzyme. Through complementary functions and mutual elimination of weaknesses in the two processes, it achieves efficient removal of sizing from hemp roving with minimal fiber damage. The specific mechanism is as follows:

[0097] The first stage involves high-temperature pretreatment with an aqueous eutectic solvent. This invention uses choline chloride as a hydrogen bond acceptor and urea or lactic acid as a hydrogen bond donor to prepare an eutectic solvent, which is then mixed with 10%–40% deionized water to form an aqueous solvent system. Under high-temperature conditions of 130℃–160℃, the eutectic solvent generates a large number of free hydrogen bond sites, competitively disrupting the hydrogen bond cross-linking structure within pectin and hemicellulose, as well as between the gum and cellulose layers. This breaks down the dense gum network of the fiber, expands the aggregated fiber bundles, and constructs interconnected permeable channels within the fiber, effectively solving the problem of single biological enzymes being unable to penetrate deep into the fiber and incomplete degumming. The moisture in the system weakens the corrosive effect of the solvent on cellulose, achieving selective gum removal, preferentially removing pectin and hemicellulose from the surface and middle layers of the fiber. Furthermore, the gum removal effect of the choline chloride-urea system is superior to that of the choline chloride-lactic acid system. This pretreatment process only loosens the gum structure, completely preserving the main cellulose skeleton, ensuring that the fiber breaking strength after pretreatment remains stably above 2.81 cN·dtex. Meanwhile, qualified samples are selected based on three indicators: weight loss rate, residual glue rate, and fracture strength, which unifies the subsequent enzymatic hydrolysis feeding state and greatly improves the stability and repeatability of the process.

[0098] The second stage involves the targeted deep degradation by a quaternary low-damage bio-enzyme complex. After solvent pretreatment to loosen the channels, the complex enzyme system can fully contact the deep residual gum in the fiber. Each enzyme component works synergistically to target and degrade the fiber: pectinase is the core degrading enzyme, breaking pectin ester and glycosidic bonds and eliminating pectin filling the fiber gaps; xylanase and hemicellulase are synergistic degrading enzymes, degrading the hemicellulose xylan backbone and peeling off the thin gum layer on the fiber surface; laccase is the auxiliary enzyme, oxidizing and breaking stubborn lignin macromolecules and specifically degrading aromatic lignin components that are difficult to remove with eutectic solvents, thus compensating for the insufficient lignin degradation capacity of single solvents. Simultaneously, this invention strictly controls the relative enzyme activity of cellulase to no more than 5% of the total activity of pectinase, and the cellulose degradation rate is less than 3% within a 7-hour enzymatic hydrolysis cycle. The enzyme system targets only the gum and lignin, hardly eroding the cellulose skeleton, thus alleviating the deterioration of fiber mechanical properties from the root, unlike the defects of traditional wild microbial degumming bacteria that damage fibers.

[0099] The synergistic coupling of the two processes achieves significant efficiency gains: Eutectic solvent pretreatment loosens macroscopic gum and removes most shallow gum, opening up enzyme penetration channels and shortening the degumming cycle; the compound enzyme system precisely degrades deep-crosslinked gum and stubborn lignin, achieving deep-refining degumming. Neither single process can simultaneously achieve fiber loosening and complete gum removal. The combined two-stage process improves degumming performance, reducing residual gum content from 22.78% to 18.46%, increasing total weight loss to 15.5%, and raising fiber breaking strength to 3.56 cN·dtex. -1The accompanying microscopic morphology confirms that the original fiber adhesive is highly aggregated and that single-process degumming has obvious defects. However, the two-stage coupled process of this invention can achieve complete degradation of the adhesive and full expansion and dissociation of individual fibers, with a reliable mechanism and stable effect.

[0100] Comparative analysis of microscopic morphology diagrams

[0101] The microstructure of the samples from various processes was visually characterized using scanning electron microscopy and polarizing microscopy.

[0102] Depend on Figure 1 It is evident that the surface of the original hemp roving fibers is completely covered by a large amount of gum, which tightly binds and clumps the individual fibers together, making it difficult to separate the fiber bundles. The original degumming state is extremely poor, making it unsuitable for direct use in spinning.

[0103] Figure 2 The image shows the SEM morphology of hemp roving fibers after degumming with a single biological compound enzyme. Only a small amount of surface gum was peeled off, and the surface of the fibers in some areas tended to be smooth. However, there were still large areas of gum adhesion between the fibers, indicating that the overall degree of degumming was limited, the removal of deep gum was insufficient, and the degumming uniformity was poor.

[0104] Figure 3 The image shows the SEM morphology of the fibers after pretreatment with a choline chloride-urea eutectic solvent. Most of the adhesive on the fiber surface was effectively dissolved and removed, leaving only trace amounts of adhesive fragments. The fiber bundle looseness was significantly improved, but some local adhesive adhesion defects still existed, making complete degumming impossible.

[0105] Figure 4 The image shows the SEM morphology of the fibers after pretreatment with choline chloride-lactic acid eutectic solvent alone. The pretreatment process can only remove part of the surface gum, and a large amount of blocky residual gum remains on the fiber surface. The overall gum removal effect is significantly weaker than that of the choline chloride-urea system.

[0106] Figure 5 This image shows the SEM morphology of fibers after pretreatment with a choline chloride-urea eutectic solvent coupled with deep degumming by a bio-compound enzyme. After the two-stage synergistic process, the composite adhesive coating on the fiber surface was almost completely degraded and removed, with no obvious adhesive residue. Individual fibers were fully extended, fiber bundles were thoroughly dissociated, and the fiber surface achieved optimal smoothness, demonstrating the most outstanding degumming effect.

[0107] Figure 6 This is a polarized light micrograph of untreated raw hemp roving. A large amount of brownish-red gum fills the gaps between individual fibers, causing multiple fibers to be tightly bound and aggregated, resulting in poor fiber splitting.

[0108] Figure 7 The polarized light microstructure of the sample pretreated with choline chloride-urea eutectic solvent was optimal. Figure 8The images show the polarized light microstructure of the sample after degumming treatment with a eutectic solvent and a bio-enzyme combination. Comparison of the two sets of micrographs reveals that the degree of fiber dissociation in the sample treated with the coupled degumming process is further enhanced, the amount of residual gum between fibers is further reduced, and the dispersed distribution of individual fibers is clearly discernible.

[0109] Analysis of Key Performance Test Results

[0110] This invention sets up four core tests: weight loss rate, residual glue rate, fiber breaking strength, and cellulose degradation rate, to quantitatively evaluate the degumming effect and the degree of fiber damage. The results are analyzed below with reference to the accompanying drawings:

[0111] (1) Analysis of weight loss rate test

[0112] Weight loss rate is used to quantitatively characterize the total mass ratio of pectin dissolution and removal during the eutectic solvent pretreatment stage. A higher weight loss rate indicates a higher total amount of pectin, hemicellulose, and other gums dissolved during the pretreatment stage, resulting in better fiber bundle loosening. This invention limits the weight loss rate of qualified pretreatment samples to ≥11.25%, with the optimal weight loss rate of the sample pretreated with a single choline chloride-urea eutectic solvent being 14.59%. After combined degumming process, the total weight loss rate of the finished product is further increased to 15.50%.

[0113] By comparing the attached diagrams, we can see that: Figure 1 , Figure 6 No colloidal leaching occurred in the original sample, and the weight loss rate was close to zero. Figure 3 , Figure 7 Samples pretreated with a single eutectic solvent achieved extensive surface gelation due to hydrogen bond disruption, resulting in a significant increase in weight loss and a marked improvement in fiber bundle looseness. Figure 5 , Figure 8 The combined process samples further degraded residual gum on the basis of pretreatment, resulting in a further increase in weight loss rate and complete dissociation of single fibers; Figure 2 The single-enzyme degummed sample had no pre-loosening process, and the amount of gum dissolved was extremely low. The weight loss rate was much lower than that of the pretreated sample of this invention, which fully demonstrates that the low eutectic solvent pretreatment can effectively solve the defects of poor penetration, low amount of gum removal, and insufficient degumming in pure biological enzyme degumming.

[0114] (2) Residual glue content test and analysis

[0115] Residual gum content is a core indicator for evaluating the degumming effect of hemp. It is used to quantify the relative content of residual pectin, hemicellulose, and lignin on the fiber surface and between fibers. The lower the residual gum content, the more thorough the degumming, and the better the fiber spinning performance and finished product quality. This invention limits the residual gum content of qualified pre-treated samples to ≤22.78%, with the optimal residual gum content for a single pre-treated sample being 22.78%. The residual gum content of the finished product from the combined process can be controlled within 18.5%, with the optimal measured residual gum content being 18.46%.

[0116] By comparing the morphology of the attached diagrams, we can see that: Figure 1 , Figure 6 The original sample had complete gel coating and the highest residual gel rate; Figure 2 Single-enzyme degelatinization cannot remove deep-seated gels from samples, resulting in a large amount of residual gel. Figure 4 The choline chloride-lactic acid pretreatment system resulted in poor gel removal and high residual gel content in the samples. Figure 3 , Figure 7 Pretreatment with a single urea system can significantly reduce the residual lignin rate, but stubborn lignin residues still exist. Figure 5 , Figure 8 The combined process thoroughly removes composite adhesives through the synergistic effect of solvent loosening and multi-enzyme targeted degradation, significantly reducing the residual adhesive rate and effectively overcoming the technical defects of single eutectic solvents in degrading lignin and incomplete degumming.

[0117] (3) Fiber breaking strength test and analysis

[0118] Fiber breaking strength is used to evaluate the degree of damage to the hemp cellulose backbone caused by the degumming process. Higher breaking strength indicates a more intact fiber structure, resulting in superior spinning stability and finished product mechanical properties. This invention limits the breaking strength of pretreated samples to ≥2.81 cN·dtex. -1 The fracture strength of the single optimal pretreated sample was 2.81 cN·dtex. -1 The fracture strength of the finished product from the combined process is ≥3.56 cN·dtex. -1 The optimal measured value is 3.56 cN·dtex. -1 Traditional wild microbial degumming processes can result in a 30% to 50% loss of fiber strength, causing severe fiber damage.

[0119] Based on the morphology in the attached diagram, it can be seen that: the original fiber skeleton is intact but cannot be spun; the surface of the fiber is etched and damaged by traditional microbial degumming, and its strength is greatly reduced; Figure 3 , Figure 7 Single solvent pretreatment acts only on the gums without damaging the cellulose skeleton, resulting in stable fiber strength; Figure 5 , Figure 8 The combined process uses a low-damage compound enzyme system that targets and degrades the gum without eroding the fiber body. After treatment, the fiber surface is smooth and the outline is intact, and the breaking strength is significantly improved, effectively solving the technical problems of severe damage and strong deterioration of traditional biological degummed fibers.

[0120] (4) Cellulose degradation rate test and analysis

[0121] Cellulose degradation rate is used to detect the ability of the compound enzyme system to erode the cellulose skeleton, and is the core basis for verifying the rationality of the low-damage degumming formulation of this invention. This invention strictly limits the relative enzyme activity of cellulase in the compound enzyme system to no more than 5% of the total activity of pectinase, and the cellulose degradation rate to less than 3% within a 7-hour enzymatic hydrolysis cycle, thus protecting the main fiber structure to the greatest extent from the formulation level.

[0122] Based on the accompanying microscopic morphology verification: conventional high-cellulosic enzyme activity systems easily cause fiber wall grooves, micropores, and breakage; under the low-enzyme activity formulation of this invention, Figure 2 The single-enzyme degummed sample only had residual gum, and the fiber itself had no corrosion defects; Figure 5 The fiber surface of the combined process sample is smooth and uniform, without micropores, etching, or damage. The cellulose degradation rate is less than 3%, which fully demonstrates that the compound enzyme formula of this invention can achieve ultra-low fiber damage while ensuring efficient degumming, thus avoiding fiber skeleton erosion from the source of the formula.

[0123] Based on the comprehensive analysis of the four performance test data from various embodiments and three comparative examples, and the comparison with SEM and polarized light microstructure, compared with traditional chemical degumming, single biological compound enzyme degumming, single eutectic solvent pretreatment, and wild microbial community degumming processes, the two-stage coupled synergistic degumming process of this invention has five core advantages.

[0124] First, it achieves high degumming depth and excellent finished product quality. This invention relies on the solvent's loose hydrogen bonds and the targeted synergistic degradation mechanism of multiple enzyme components to remove stubborn composite adhesives in layers—the surface, middle, and deep layers. The finished product has low residual adhesive rate, high weight loss rate, and significantly improved fiber splitting degree and surface smoothness. It completely solves the problems of large residual adhesive and uneven degumming in single-process degumming, fully meeting the spinning and processing requirements of high-end hemp textiles.

[0125] Secondly, the degumming process results in minimal damage and excellent fiber mechanical properties. This invention, through a limited low-cellulose enzyme activity formula and a segmented, gentle process, fundamentally avoids the erosion and damage of the cellulose skeleton. This not only effectively preserves the original strength of the fiber but also optimizes its overall mechanical properties, completely overcoming the inherent defects of traditional biological degumming and microbial degumming methods, which cause significant fiber damage and substantial strength loss.

[0126] Furthermore, the process synergistically enhances efficiency and increases production productivity. Pre-treatment with a low-eutectic solvent at high temperature can rapidly loosen the dense adhesive network, build internal fiber penetration channels, and open up the enzyme solution action pathway. This solves the problems of poor penetration, slow reaction, and difficulty in deep degumming caused by single enzyme solutions, significantly shortening the degumming cycle and improving overall production efficiency.

[0127] Meanwhile, the process exhibits strong stability and repeatability. This invention adds a pre-treatment sample selection and rework quality control mechanism, standardizes the enzymatic hydrolysis feed substrate, eliminates effect deviations caused by fluctuations in raw material batches and process parameters, significantly improves batch production stability and experimental repeatability, and is suitable for industrial mass production.

[0128] Finally, the entire process is green and low-pollution, with a wide range of industrial applicability. The process does not use strong acids, strong alkalis, or chlorine-containing additives, resulting in lower water and energy consumption, and wastewater COD is far lower than that of traditional processes. The preferred choline chloride-urea solvent system provides better adhesive stripping effect, and the process is mild and controllable, making it suitable for large-scale continuous green production lines, thus supporting the sustainable industrialization of high-quality hemp textiles.

[0129] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should be protected by the present invention.

Claims

1. A method for degumming hemp fibers using a eutectic solvent-bio-compound enzyme combination, characterized in that, Includes the following steps: (1) Pretreatment preparation: The strips of hemp roving are soaked in room temperature water, dehydrated and then dried to constant weight to obtain dried hemp roving to be treated; (2) High-temperature eutectic solvent pretreatment: Prepare an aqueous solution of eutectic solvent, wherein the eutectic solvent uses choline chloride as the hydrogen bond acceptor and the hydrogen bond donor is selected from at least one of urea and lactic acid; the mass fraction of water in the aqueous solution of eutectic solvent is 10% to 40%; mix the dried hemp roving with the aqueous solution of eutectic solvent at a bath ratio of 1:(20 to 50), place it in a closed heating system, and keep it at 130℃ to 160℃ for 60 min to 240 min; after the treatment, take out the material and wash it thoroughly with water to remove the residual eutectic solvent on the surface of the roving; (3) Pre-treatment material classification and screening: The hemp roving treated in step (2) was subjected to offline performance testing, and the roving was selected that simultaneously met the following requirements: weight loss rate ≥11.25%, residual glue rate ≤22.78%, and fiber breaking strength ≥2.81cN·dtex. -1 Hemp roving was used as the raw material for compound enzymatic hydrolysis; hemp roving that failed the test was returned to step (2) for high temperature and low eutectic solvent pretreatment again; (4) Targeted deep degumming with compound enzymes: Prepare a compound enzyme aqueous solution, wherein the compound enzymes include pectin degrading enzyme, lignin oxidation degrading enzyme, and hemicellulose degrading enzyme. The cellulase activity in the enzyme system is extremely low and there is no fiber damage activity. The pH value of the enzyme solution is adjusted to 4.0-5.0 using a buffer system. The qualified hemp roving is added to the enzyme solution system and enzymatically hydrolyzed by shaking at a constant temperature of 48-52℃ for 5-7 hours. (5) Post-processing: After enzymatic hydrolysis, take out the hemp roving, wash it with water and dry it to constant weight to obtain refined hemp roving.

2. The method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination according to claim 1, characterized in that: In step (2), the molar ratio of choline chloride to urea is 1:2, and the molar ratio of choline chloride to lactic acid is 1:

5.

3. The method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination according to claim 1, characterized in that: The preferred process parameters in step (2) are: bath ratio 1:50, treatment temperature 150℃, and treatment time 240min.

4. The method for degumming hemp fibers using a eutectic solvent-bio-compound enzyme combination according to claim 1, characterized in that: The critical indicators for the qualified hemp roving obtained in step (3) are: weight loss rate 14.59%, residual glue rate 22.78%, and breaking strength 2.81 cN·dtex. -1 .

5. The method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination according to claim 1, characterized in that: The refined hemp roving obtained after treatment by the above method meets the following requirements: residual gum content ≤18.5%, fiber breaking strength ≥3.56 cN·dtex. -1 .

6. The method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination according to claim 1, characterized in that: In step (1), the soaking time in room temperature water is 5 to 7 hours, and the drying temperature is controlled at 100 to 110°C.

7. The method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination according to claim 1, characterized in that: In step (4), the mass ratio of hemp roving to the enzymatic hydrolysis system aqueous solution is 1:8 to 1:12, preferably 1:

10.

8. The method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination according to claim 1, characterized in that: In step (4), the pectin-degrading enzyme is pectinase, the hemicellulase is xylanase and hemicellulase, and the lignin oxidation-degrading enzyme is laccase; pectinase is the core degrading enzyme, xylanase and hemicellulase are the co-degrading enzymes, and laccase is the auxiliary enzyme; the pH of the enzyme solution is adjusted to 4.0-5.0 using 0.05mol / L acetate-sodium acetate buffer; based on the percentage of fabric weight owf, the amount of pectinase added is 3%-5% owf, the amount of xylanase added is 1%-2% owf, the amount of hemicellulase added is 1%-2% owf, and the amount of laccase added is 0.8%-1.2% owf.

9. The method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination according to claim 1, characterized in that: In the compound enzyme system, the relative enzyme activity of cellulase is no higher than 5% of the total activity of pectinase; when tested with standard cotton cellulose substrate, the cellulose degradation rate is less than 3% within a 7-hour enzymatic hydrolysis cycle.

10. The method for degumming hemp fibers using a eutectic solvent-biocompound enzyme combination according to claim 1, characterized in that: Step (3) uses offline batch testing to determine the weight loss rate, residual glue rate and fiber breaking strength of the pretreated hemp roving. Only materials that meet the three indicators simultaneously within the specified range enter the compound enzyme degumming process in step (4). The roving that does not meet the standards is returned to step (2) for re-pretreatment.

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