A method for shrink-proofing cashmere fibers

Abstract

The present application provides a shrink-proof treatment method of cashmere fibers, and relates to the field of textile fiber treatment technology, which comprises the following steps: step 1, plasma pretreatment; step 2, composite enzymatic hydrolysis treatment; step 3, high molecular grafting treatment; step 4, cross-linking and curing treatment; and step 5, finishing treatment. The composite enzyme solution comprises papain, laccase, alkaline pectinase and sodium bisulfite. The present application provides a shrink-proof treatment method of cashmere fibers. Through the four-step composite process of plasma activation, composite enzymatic hydrolysis, biological high molecular grafting and cross-linking and curing, the directional friction effect of the scales of the cashmere fibers is weakened, a stable biocompatible protective layer is formed, the shrink-proof effect and the natural performance of the fibers are synergistically optimized, the preparation method of the core material, the equipment parameters and the process details are clearly defined, and the technical scheme is repeatable and controllable in industrial safety.

Description

Technical Field

[0001] This invention relates to the field of textile fiber treatment technology, and in particular to a method for preventing shrinkage of cashmere fibers. Background Technology

[0002] Cashmere fibers are known as "soft gold" because of their excellent warmth and soft feel due to their surface scale structure and hollow characteristics. However, their scale layer is prone to directional friction under humid and hot environments and mechanical forces, which causes the fiber aggregate to move in a directional manner, shrink and become tight, resulting in felting (the standard washing felting rate of untreated cashmere fibers reaches 12%-15%).

[0003] Current anti-shrinkage treatment methods have the following drawbacks: Single enzyme treatment: It can only mildly hydrolyze the scale protein, and the anti-shrinkage effect is not lasting. After multiple washes, the felting shrinkage rate rises back to more than 5%, and the fiber breaking strength loss exceeds 15%; Chemical oxidation method (such as potassium permanganate treatment): Although it can destroy the scale structure, the chemical reagent residue can easily cause the fiber to yellow (yellowing value ≥3.0) and feel rough (subjective evaluation ≤3.0 points), and the wastewater COD value is as high as 300-500mg / L, causing serious pollution; Polymer coating method: Traditional resin coatings are easy to fall off and will significantly reduce the moisture absorption and breathability of cashmere fibers (breathability ≤80mm / s), resulting in decreased wearing comfort; Existing composite processes lack precise control over fiber surface activation, the binding force between polymer and fiber is insufficient, the anti-shrinkage durability is poor, and the felting shrinkage rate is ≥5% after 10 washes. Summary of the Invention

[0004] Based on the technical problems existing in the background art, the present invention proposes a method for preventing shrinkage of cashmere fibers.

[0005] The present invention proposes a method for preventing shrinkage of cashmere fibers, comprising the following steps: Step 1, Plasma pretreatment: Place cashmere fibers in a low-temperature radio frequency plasma generator, and introduce a mixed gas with an ammonia gas fraction of 30%-45%, the remainder being nitrogen gas with a purity of ≥99.99% and ammonia gas with a purity of ≥99.9%. Control the vacuum degree to 5-10 Pa, the processing power to 120-150 W, and the processing time to 8-12 min. The discharge frequency of the plasma generator is 13.56 MHz, the electrode structure is a roller-type double electrode, the electrode spacing is 50 mm, and the fiber laying thickness is 2-5 mm. Step 2, Compound Enzymatic Hydrolysis Treatment: Immerse the pretreated cashmere fibers in a compound enzyme solution at a bath ratio of 1:15 and a loading amount of 50 g / L (fiber oven-dry weight / solution volume). Adjust the pH value to 7.2-7.8, and treat at a constant temperature of 42-48℃ with shaking at 120-150 r / min for 40-60 min. Then inactivate at 75-80℃ for 8-12 min. After inactivation, wash twice with deionized water at 45℃ for 8 min each time. Step 3, Polymer Grafting Treatment: Immerse the enzymatically hydrolyzed cashmere fibers in the grafting solution at a bath ratio of 1:12, adjust the pH value to 6.2-6.8, raise the temperature to 43-47℃ at 2℃ / min, and keep it at that temperature for 2.5-3.5h. Step 4, cross-linking and curing treatment: Immerse the grafted cashmere fibers in the cross-linking solution at a bath ratio of 1:10, heat to 55-65℃ at 2℃ / min, let stand for 30-40min, and wash twice with 35℃ deionized water for 10min each time. Step 5, finishing treatment: Use deionized water at 30-35℃, with a water flow rate of 0.5-1.0m / s in the washing tank, wash 3 times, centrifuge and dehydrate, and dry at 0.09MPa vacuum and 60-65℃ for 2-3 hours to obtain shrink-resistant cashmere fiber. The complex enzyme solution contains papain, laccase, alkaline pectinase, sodium bisulfite, and phosphate buffer; the grafting solution contains chitosan-sericin complex macromolecules, transglutaminase, and acetic acid; and the cross-linking solution is an aqueous solution of 1,2-ethylene glycol diglycidyl ether.

[0006] Preferably, the mass composition of the complex enzyme solution in step 2 is as follows: papain 1.2%-1.5%, laccase 1.0%-1.2%, alkaline pectinase 1.5%-1.8%, sodium bisulfite 1.0%, phosphate buffer (0.2mol / L, pH 7.0) 5%, and deionized water as the balance. The papain activity is 500,000 u / g, the laccase activity is 600,000 u / g, and the alkaline pectinase activity is 600,000 u / g.

[0007] Preferably, the preparation method of the chitosan-serice protein composite macromolecule is as follows: chitosan and sericin are taken at a mass ratio of 1:1.8-2.2, deionized water and 0.3%-0.5% acetic acid are added, and the mixture is activated at 60°C with an ultrasonic power of 300W and a frequency of 40kHz for 30 minutes, with a stirring speed of 200r / min. The degree of deacetylation of the chitosan is ≥85%, the molecular weight is 50-150kDa, and the molecular weight of the sericin is 30-80kDa.

[0008] Preferably, the grafting solution in step 3 has the following composition by mass: 2.5%-3.5% chitosan-serin complex macromolecules, 0.8%-1.2% transglutaminase, 0.3%-0.5% acetic acid, and the balance being deionized water, wherein the transglutaminase activity is 100,000 u / g.

[0009] Preferably, the pH adjustment in steps 2 and 3 uses a 2 mol / L sodium hydroxide solution and a 2 mol / L acetic acid solution, respectively.

[0010] Preferably, the tail gas from the plasma pretreatment in step 1 is treated by a 5% dilute sulfuric acid absorption tower. After absorption, the acidic waste liquid is adjusted to pH 6-9 in a neutralization tank before being discharged. The equipment is made of 316L stainless steel.

[0011] Preferably, in step 4, the mass concentration of the crosslinking liquid is 1.8%-2.5%, the pH value is adjusted to 8.0-8.5, and the crosslinking waste liquid is discharged after being inoculated with Pseudomonas putida and biodegraded at 30°C for 4 hours, with epoxy residue ≤0.5mg / L.

[0012] Preferably, the centrifugal dehydration parameters in step 5 are 3000 r / min and the dehydration time is 5 min.

[0013] Preferably, the cashmere fiber has an initial fineness of 12-18 μm, an initial length of 30-55 mm, and an initial breaking strength ≥1.95 cN / dtex.

[0014] Preferably, the cashmere fiber obtained by this method has a felting shrinkage rate of ≤3.2%, a breaking strength retention rate of ≥88%, an air permeability of ≥120mm / s, a whiteness of ≥85%, a clo value of 0.85-0.95clo, and a thermal conductivity of 0.035-0.040W / (m・K) after being washed 20 times according to GB / T8878-2014 standard.

[0015] The shrinkage prevention treatment method for cashmere fibers proposed in this invention has the following beneficial effects: significantly improved shrinkage prevention performance: after being washed 5 times according to GB / T8878-2014 standard, the felting shrinkage rate of cashmere fibers is ≤2.5%; after 10 washes, the felting shrinkage rate is ≤2.8%; after 20 washes, the felting shrinkage rate is ≤3.2% (the felting shrinkage rate of untreated fibers is ≥10% after 10 washes), reaching the machine washable standard (machine washing conditions: 40℃, washing time 30min, rotation speed 800r / min).

[0016] The fiber properties are well preserved: Mechanical properties: breaking strength ≥1.7cN / dtex, breaking strength retention rate ≥88%, breaking elongation ≥35%; Moisture absorption and breathability: moisture regain maintained at 14%-16%, air permeability ≥120mm / s (GB / T5453-1997); Appearance properties: whiteness ≥85% (GB / T8424.2-2014), yellowing value ≤1.5 (GB / T29778-2013), subjective hand feel rating ≥4. 0.5 points (GB / T22700-2008, blind test on a 5-point scale, smooth and without roughness); Warmth retention: Clo value 0.85-0.95clo, thermal conductivity 0.035-0.040W / (m・K), the perceived temperature at -10℃ is 4-6℃ higher than that of untreated fibers, fully retaining natural warmth retention properties; Antibacterial properties: relying on the natural antibacterial properties of chitosan, the antibacterial rate against Staphylococcus aureus is ≥90% (GB / T20944.3-2008).

[0017] Excellent environmental performance: Wastewater indicators: COD≤80mg / L, BOD5≤20mg / L, ammonia nitrogen≤10mg / L, meeting the Class I standard of GB8978-2002 "Integrated Wastewater Discharge Standard"; Reagent residue: No heavy metals or chlorine-containing reagent residues, epoxy residue ≤0.5mg / L, biodegradation rate ≥90%.

[0018] Durability and stability: Wash resistance: After 20 standard washes, the protective film did not peel off, and the felting shrinkage rate remained ≤3.2%, which is far superior to existing enzyme treatment (felting shrinkage rate ≥5% after 10 washes) and Basol anti-shrinkage process (felting shrinkage rate ≥4% after 10 washes); Storage stability: After 12 months of storage in a dry environment at room temperature, the treated fibers showed no significant change in performance (felting shrinkage rate change ≤0.3%); Industrial stability: After three batches of scale-up experiments (100kg level), the enzyme activity fluctuation of the compound enzyme system was ≤5%, and the CV value of the treated fiber performance was ≤3%.

[0019] Economic advantages: Although the initial process cost is 10%-15% higher than that of the traditional chlorination process, the overall wastewater treatment cost is reduced by 60% and the product lifespan is extended by 30%, resulting in a 15%-20% reduction in the overall cost per unit product, which has significant industrial application value. Attached Figure Description

[0020] Figure 1 This is a flowchart of a shrink-proof treatment method for cashmere fibers proposed in this invention. Detailed Implementation

[0021] Reference Figure 1 This invention proposes a method for preventing shrinkage of cashmere fibers, comprising the following steps: 1. Plasma pretreatment: Equipment parameters: It adopts a low-temperature radio frequency plasma generator, the discharge type is capacitively coupled radio frequency discharge, the frequency is 13.56MHz, the electrode structure is a roller-type double electrode (electrode spacing 50mm), and the processing chamber is made of quartz material; Process parameters: Cashmere fibers are evenly laid in the processing chamber (laying thickness 2-5mm), and a mixed gas with an ammonia integral of 30%-45% (the remainder is nitrogen, purity ≥99.99%) is introduced. The vacuum degree is controlled at 5-10Pa, the processing power at 120-150W, and the processing time at 8-12min to activate the hydroxyl and amino groups on the fiber surface. Safety measures: The exhaust gas is treated by a dilute sulfuric acid absorption tower (5% mass concentration) before being discharged. The acidic waste liquid after absorption is neutralized in a neutralization tank to adjust the pH to 6-9. The equipment is made of 316L stainless steel for corrosion protection.

[0022] 2. Compound enzymatic hydrolysis treatment: Preparation of the complex enzyme solution: The solution is composed of the following components in the following mass ratios: papain (activity 500,000 u / g) 1.2%-1.5%, laccase (activity 600,000 u / g) 1.0%-1.2%, alkaline pectinase (activity 600,000 u / g) 1.5%-1.8%, sodium bisulfite 1.0%, phosphate buffer (0.2 mol / L, pH 7.0) 5%, and deionized water as the balance. Stir until homogeneous (magnetic stirring, 200 r / min, 10 min). Process parameters: The pretreated cashmere fibers were immersed in a compound enzyme solution at a bath ratio of 1:15 and a loading of 50 g / L (fiber dry weight / solution volume). The pH value was adjusted to 7.2-7.8 with 2 mol / L sodium hydroxide. The solution was subjected to constant temperature shaking at 42-48℃ (shaking frequency 120-150 r / min, amplitude 20 mm) for 40-60 min. Then, the enzyme was inactivated by hot water treatment at 75-80℃ for 8-12 min. After inactivation, the solution was washed twice with deionized water at 45℃ for 8 min each time. Enzyme activity stability control: The compound enzyme solution should be refrigerated at 4°C before use and has a shelf life of 7 days. It should be prepared and used immediately.

[0023] 3. Polymer grafting treatment: Preparation of core materials (chitosan-serice protein composite macromolecules): Raw material selection: chitosan (degree of deacetylation ≥85%, molecular weight 50-150kDa, viscosity 100-300mPa・s), sericin (molecular weight 30-80kDa, purity ≥95%). Composite process: Chitosan and sericin were added to deionized water at a mass ratio of 1:1.8-2.2, and 0.3%-0.5% acetic acid was added to adjust the dissolution. The mixture was activated by ultrasonic power of 300W and frequency of 40kHz at 60℃ for 30min, and magnetic stirring was performed at a speed of 200r / min. After cooling to room temperature, the mixture was filtered (using a 100-mesh filter) to obtain a chitosan-sericein composite macromolecular solution. Grafting solution preparation: Composed of the following components in the following mass ratios: chitosan-serin complex macromolecules 2.5%-3.5%, transglutaminase (activity 100,000 u / g) 0.8%-1.2%, acetic acid 0.3%-0.5%, and deionized water balance; Process parameters: The enzymatically hydrolyzed cashmere fibers are immersed in the grafting solution at a bath ratio of 1:12. The pH value is adjusted to 6.2-6.8 with 2 mol / L acetic acid. The temperature is increased to 43-47℃ at 2℃ / min and kept at this temperature for 2.5-3.5h (with magnetic stirring throughout at 100r / min) to achieve covalent grafting of biomacromolecules on the fiber surface. Storage stability: Grafting solution should be stored in a sealed container at 4°C for 5 days. Avoid direct sunlight.

[0024] 4. Cross-linking and curing treatment: Preparation of crosslinking solution: 1.8%-2.5% (w / w) aqueous solution of 1,2-ethylene glycol diglycidyl ether (EGDGE), with pH adjusted to 8.0-8.5 using 2 mol / L sodium hydroxide; Process parameters: Immerse the grafted cashmere fibers in the crosslinking solution at a bath ratio of 1:10, heat to 55-65℃ at 2℃ / min, and gently stir at low speed (30-50r / min) for 30-40min to avoid fiber accumulation and uneven crosslinking, so that the surface macromolecules form a crosslinking network. Environmental treatment: The cross-linked waste liquid needs to be introduced into a biodegradation tank and inoculated with Pseudomonas putida for degradation at 30°C for 4 hours to ensure that the epoxy residue is ≤0.5mg / L.

[0025] 5. Post-processing: Washing: Use deionized water at 30-35℃, with a linear velocity of 0.5-1.0m / s and a water flow rate of 0.5-1.0m / s in the washing tank, and wash 3 times (10min each time) to remove unreacted reagents; Dehydration: Centrifuge (3000 r / min, 5 min) to avoid mechanical compression that could damage the fibers; Drying: Dry at 0.09 MPa vacuum and 60-65℃ for 2-3 hours to obtain shrink-resistant cashmere fibers.

[0026] The specific working principle is as follows: Ammonia plasma pretreatment (13.56MHz radio frequency discharge): High-energy particles bombard the surface of cashmere fibers, breaking some peptide bonds in the scaly layer proteins and introducing a large number of hydroxyl (-OH) and amino (-NH2) groups, increasing the number of surface active groups by 40%-60%, providing sufficient reaction sites for subsequent enzymatic hydrolysis and polymer grafting; Compared with microwave discharge (local overheating) and dielectric barrier discharge (DBD, uneven activation), radio frequency discharge can achieve uniform activation of the fiber surface and avoid strength loss caused by local over-etching.

[0027] Synergistic effect of complex enzymes: Papain specifically hydrolyzes keratin on the surface of scales (hydrolysis rate 25%-30%), laccase oxidizes tyrosine residues on the scale surface to form active sites, and alkaline pectinase removes residual plant impurities on the fiber surface (removal rate ≥90%). The synergistic effect of the three can weaken the directional friction effect of scales under mild conditions, and the enzymatic hydrolysis depth is controllable (scale removal rate ≤30%), reducing the loss of fiber strength; sodium bisulfite, as a mild keratin disulfide bond cleavage agent and enzyme activity stabilizer, can reduce enzyme activity loss during enzymatic hydrolysis (≤10%), and phosphate buffer stabilizes the pH of the enzymatic hydrolysis system to avoid a sudden drop in enzyme activity.

[0028] Biopolymer covalent grafting: Transglutaminase acts as a bridging agent, catalyzing the formation of amide bonds (bond energy 305kJ / mol) between amino groups on the fiber surface and carboxyl groups of chitosan-serin complex macromolecules, achieving a firm grafting of polymers onto the fiber surface and forming a continuous protective film with a thickness of 80-120nm. This protective film can block direct friction and directional movement between fibers, while retaining the moisture absorption and breathability channels of the fibers.

[0029] Cross-linking and curing reinforcement: 1,2-ethylene glycol diglycidyl ether undergoes a cross-linking reaction with the hydroxyl groups of the grafted macromolecules through epoxy groups to form a three-dimensional network structure (cross-linking degree ≥75%), which significantly improves the wash resistance and mechanical stability of the protective film and prevents the grafted layer from falling off during washing. Example

[0030] 1. Plasma pretreatment: Cashmere fibers (fineness 12-18μm, length 30-55mm, initial breaking strength 1.98cN / dtex) are placed in a radio frequency plasma generator (13.56MHz, roller-type double electrode), and a nitrogen-ammonia mixed gas with an ammonia gas integral of 35% is introduced. The vacuum degree is 7Pa, the processing power is 135W, the processing time is 10min, and the fiber laying thickness is 3mm. 2. Compound enzymatic hydrolysis treatment: Prepare a compound enzyme solution containing 1.3% papain, 1.1% laccase, 1.6% alkaline pectinase, 1.0% sodium bisulfite, 5% phosphate buffer, and 94.0% deionized water. Mix with magnetic stirring at 200 rpm for 10 min. The fiber oven-dry loading is 50 g / L. The bath ratio is 1:15. Adjust the pH to 7.5 with 2 mol / L sodium hydroxide. Shake at 45℃ (130 rpm) for 50 min. Inactivate with hot water at 78℃ for 10 min. Wash twice with deionized water at 45℃ for 8 min each time. 3. Polymer Grafting Treatment: Chitosan (88% deacetylation, 100kDa) and sericin (50kDa) were compounded at a mass ratio of 1:2, dissolved in 0.4% acetic acid, and activated by ultrasonication at 300W / 40kHz for 30 min at 60℃ with stirring speed of 200r / min to obtain chitosan-serialin composite macromolecules. The grafting solution consisted of 3.0% composite macromolecules, 1.0% transglutaminase, 0.4% acetic acid, and 95.6% deionized water. The pH was adjusted to 6.5 with 2mol / L acetic acid, and the temperature was increased to 45℃ at 2℃ / min and kept at this temperature for 3 h with stirring at 100r / min. 4. Crosslinking and curing treatment: Prepare a 2.2% EGDGE aqueous solution, adjust the pH value to 8.2 with 2 mol / L sodium hydroxide, bath ratio 1:10, heat to 60℃ at 2℃ / min, gently stir at 40r / min for 35min, wash twice with 35℃ deionized water for 10min each time; 5. Post-processing: Wash 3 times with 32℃ deionized water (linear velocity in the washing tank is 0.8m / s), centrifuge at 3000r / min for 5min, and vacuum dry at 0.09MPa and 62℃ for 2.5h.

[0031] Results of performance testing of treated cashmere fibers: Example

[0032] 1. Plasma pretreatment: ammonia gas integral 40%, vacuum degree 8Pa, processing power 140W, processing time 11min, fiber laying thickness 4mm; 2. Compound enzymatic hydrolysis treatment: Papain 1.4%, laccase 1.2%, alkaline pectinase 1.7%, sodium bisulfite 1.0%, phosphate buffer 5%, pH 7.6, 46℃ shaking treatment (140r / min) for 55min; 3. Polymer grafting treatment: Chitosan (degree of deacetylation 86%, molecular weight 80kDa) and sericin (molecular weight 40kDa) were compounded at a mass ratio of 1:1.8. The grafting solution contained 3.2% polymer and 1.1% transglutaminase. The pH value was 6.6. The mixture was kept at 46℃ for 3.2h. 4. Crosslinking and curing treatment: 2.4% EGDGE aqueous solution, pH 8.3, 62℃, 40r / min stirring treatment for 38min, crosslinking and then washing with water; 5. Post-processing: Wash with deionized water at 34℃ (linear velocity 0.9m / s), centrifuge at 3000r / min for 5min to dehydrate, and vacuum dry at 63℃ for 2.8h.

[0033] Results of performance testing of treated cashmere fibers:

[0034] Comparative experiment (with existing technology)

[0035] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preventing shrinkage of cashmere fibers, characterized in that, Includes the following steps: Step 1, Plasma pretreatment: Place cashmere fibers in a low-temperature radio frequency plasma generator, and introduce a mixed gas with 30%-45% ammonia and the remainder nitrogen. Control the vacuum degree to 5-10 Pa, the processing power to 120-150 W, and the processing time to 8-12 min. The discharge frequency of the plasma generator is 13.56 MHz, the electrode structure is a roller-type double electrode, the electrode spacing is 50 mm, and the fiber laying thickness is 2-5 mm. Step 2, Compound Enzymatic Hydrolysis Treatment: Immerse the pretreated cashmere fibers in a compound enzyme solution at a bath ratio of 1:15 and a loading of 50g / L. Adjust the pH value to 7.2-7.8, and treat with constant temperature shaking at 120-150r / min at 42-48℃ for 40-60min. Then inactivate at 75-80℃ for 8-12min. After inactivation, wash twice with deionized water at 45℃ for 8min each time to remove residual enzyme solution. Step 3, Polymer Grafting Treatment: Immerse the enzymatically hydrolyzed cashmere fibers in the grafting solution at a bath ratio of 1:12, adjust the pH value to 6.2-6.8, raise the temperature to 43-47℃ at 2℃ / min, and keep it at that temperature for 2.5-3.5h. Step 4, cross-linking and curing treatment: Immerse the grafted cashmere fibers in the cross-linking solution at a bath ratio of 1:10, heat to 55-65℃ at 2℃ / min, let stand for 30-40min, stir gently at low speed for 30-50r / min for 30-40min, and wash twice with 35℃ deionized water for 10min each time to remove unreacted cross-linking agent. Step 5, finishing treatment: Use deionized water at 30-35℃, with a water flow rate of 0.5-1.0m / s in the washing tank, wash 3 times, centrifuge and dehydrate, and dry at 0.09MPa vacuum and 60-65℃ for 2-3 hours to obtain shrink-resistant cashmere fiber. The complex enzyme solution contains papain, laccase, alkaline pectinase, sodium bisulfite, and phosphate buffer; the grafting solution contains chitosan-sericin complex macromolecules, transglutaminase, and acetic acid; and the cross-linking solution is an aqueous solution of 1,2-ethylene glycol diglycidyl ether.

2. The method for preventing shrinkage of cashmere fibers according to claim 1, characterized in that, The mass composition of the complex enzyme solution in step 2 is as follows: papain 1.2%-1.5%, laccase 1.0%-1.2%, alkaline pectinase 1.5%-1.8%, sodium bisulfite 1.0%, phosphate buffer (0.2mol / L, pH 7.0) 5%, and deionized water as the balance. The papain activity is 500,000 u / g, the laccase activity is 600,000 u / g, and the alkaline pectinase activity is 600,000 u / g.

3. The method for preventing shrinkage of cashmere fibers according to claim 2, characterized in that, The preparation method of the chitosan-serice protein composite macromolecule is as follows: chitosan and sericin are taken at a mass ratio of 1:1.8-2.2, deionized water and 0.3%-0.5% acetic acid are added, and the mixture is activated by ultrasonic power of 300W and frequency of 40kHz at 60℃ for 30min, with a stirring speed of 200r / min. The degree of deacetylation of the chitosan is ≥85%, the molecular weight is 50-150kDa, and the molecular weight of the sericin is 30-80kDa.

4. The method for preventing shrinkage of cashmere fibers according to claim 3, characterized in that, The grafting solution in step 3 has the following composition by mass: 2.5%-3.5% chitosan-serin complex macromolecules, 0.8%-1.2% transglutaminase, 0.3%-0.5% acetic acid, and the balance being deionized water, wherein the transglutaminase activity is 100,000 u / g.

5. The method for preventing shrinkage of cashmere fibers according to claim 4, characterized in that, In steps 2 and 3, the pH value is adjusted using 2 mol / L sodium hydroxide solution and 2 mol / L acetic acid solution, respectively.

6. The method for preventing shrinkage of cashmere fibers according to claim 5, characterized in that, The tail gas from the plasma pretreatment in step 1 is treated by a 5% dilute sulfuric acid absorption tower. After absorption, the acidic waste liquid is neutralized in a neutralization tank to adjust the pH to 6-9 before being discharged. The equipment is made of 316L stainless steel.

7. The method for preventing shrinkage of cashmere fibers according to claim 6, characterized in that, In step 4, the mass concentration of the crosslinking solution is 1.8%-2.5%, the pH value is adjusted to 8.0-8.5, and the crosslinking waste liquid is discharged after being inoculated with Pseudomonas malodorans and biodegraded at 30°C for 4 hours.

8. The method for preventing shrinkage of cashmere fibers according to claim 7, characterized in that, In step 5, the centrifugal dehydration parameters are 3000 r / min and the dehydration time is 5 min.

9. The method for preventing shrinkage of cashmere fibers according to claim 8, characterized in that, The cashmere fiber has an initial fineness of 12-18 μm, an initial length of 30-55 mm, and an initial breaking strength ≥1.95 cN / dtex.

10. A method for preventing shrinkage of cashmere fibers according to claim 9, characterized in that, The cashmere fibers obtained by this method have a felting shrinkage rate of ≤3.2%, a breaking strength retention rate of ≥88%, an air permeability of ≥120mm / s, a whiteness of ≥85%, a clo value of 0.85-0.95clo, and a thermal conductivity of 0.035-0.040W / (m・K) after 20 standard washes.

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