Improve the strong loss in wool fabric protease anti-shrinking finishing

Wool fabrics are popular among consumers because of their unique properties such as good elasticity, good warmth and soft handfeel. Especially the woollen fabrics, which are the main clothing fabrics in winter, are rich in texture, full-feeling and warm. It is very popular among consumers, but wool is a textile fiber with a typical scale structure. This particularity makes it uniquely fluffy. People have been working on wool anti-felting for a century. So far, the most widely used industrial production is chlorination/polymer technology. However, due to the large amount of Absorbable Organic Halogen (AOX) substances in the chlorination process, the problem of environmental pollution has become more and more important. The anti-felting finishing of wool fabrics with enzyme treatment has become the focus of research. In this paper, the effect of Savinase on the anti-felting finishing process of wool fabrics was studied. The main problem of the reduction of wool fabrics caused by protease reduction was analyzed.
1 experiment
1.1 Experimental principle Protease anti-shrinking finishing of wool is to use the hydrolysis of the wool peptide bond by protease to partially dissolve the scales and cell membrane complex of the wool, remove the scales or remove the scales and corners to achieve the anti-shrinking purpose. However, the treatment of wool with enzyme alone has little effect. The reason is that when the protease reacts with the wool, it is affected by the structure of the wool scale layer. It is not easy to enter the fiber interior, and it is difficult to digest and decompose the surface layer and the high sulfur protein. Therefore, the enzyme treatment method must first modify the scale structure.
1.2 Materials and instruments
14x 14 3/1↗ Pure white fabric, Novozymes Savinase 4.0 T, chitosan (300M molecular weight, 80% deacetylation), 30 hydrogen peroxide, catalase, glacial acetic acid , penetrant JFC, sodium silicate, etc.
Y(B)O89 automatic shrinkage washing machine (Wenzhou Darong Textile Standard Instrument Factory), HDO26N Electronic Fabric Strength Instrument (Wenzhou Darong Textile Standard Instrument Factory), YG(B)022D Automatic Fabric Stiffness Tester (Wenzhou Darong Textile Instrument Co., Ltd.), SBD-1 Digital Whiteness Meter (Wenzhou Instrument Factory), YG(B)541D-I Automatic Digital Fabric Wrinkle Elasticity Instrument (Wenzhou Darong Textile Instrument Co., Ltd.), 722s visible spectrophotometry JSM-6700 field emission scanning electron microscope (Japan Electronics Co., Ltd.), Nexus 870 type Fourier transform infrared spectrometer (American Thermo Fisher Company).
1.3 Performance test
1.3.1 Shrinkage rate test Y(B)089 automatic shrinkage washing machine, synthetic washing powder 4g/L, neutral soap sheet 0.5g/L, bath ratio 40:1, washing fabric lkg, washing temperature 40 °C, continuous washing for 3h, dehydration and drying, after the moisture absorption balance, calculate the area shrinkage according to formula (1).
Felt rate (%) one (1 after washing fabric area / fabric area before washing) X 100 % (1)
1.3.2 Reduction rate test Before and after the fabric treatment, the fabric was baked to constant weight at 105 °C in the oven and accurately weighed. The reduction rate was calculated by equation (2).
Reduction rate (%) one (1 sample weight after treatment / sample weight before treatment) X100 % (2)
1.3.3 The dye uptake rate is measured by the 722s visible spectrophotometer, and the absorbance of the dye solution and the dye residue is measured respectively. The percentage of dyeing is calculated according to formula (3).
The dye uptake rate F(%) of the sample = (1 - At / A.) × 100 % (3)
Where F is the dye uptake rate and At is the absorbance of the dye liquor residue (taking into account the dilution factor), A. The absorbance for the standard dye solution.
1.3.4 Determination of the breaking strength The tensile breaking strength of the wool fabric was tested by the method of the strip yarn method, and the wool fabric with the size of 5 cm×20 cm was cut and carried out on the HD026N electronic fabric strength meter.
1.3.5 The fabric is tested for flexibility. The YG (B) type automatic fabric stiffness tester is used. The pattern is about 2 cm wide and 15 cm long.
1.3.6 Wrinkle resistance test is carried out on YG (B) 541D-I automatic digital fabric crease elastic instrument, each group is tested 10 and averaged.

1.4 Oxidation pretreatment hydrogen peroxide concentration 35mL / L, sodium silicate 3.5g / L, penetrant lg / L, temperature 50 ° C, bath ratio 1:50, treatment time 1h. Then remove excess hydrogen peroxide on the surface of the fabric and stop continuing oxidation.
The deoxygenation process is: catalase 0.1g / L, pH 6.5 (acetate adjustment), treatment at 45 ° C for 15min.
1.5 Chitosan treatment Chitosan was dissolved in 1 acetic acid solution at a concentration of 2g / L, bath ratio of 1:20. The wool fabric was immersed in the chitosan solution, taken out after 10 minutes, baked in an oven at 120 °C for 5 min, washed away with residual acetic acid, and dried at low temperature.
1.6 Protease treatment
Savinase protease 3% (owf), with sodium carbonate to adjust the pH to 8, temperature 50 ° C, bath ratio 1:30, 40min treatment. Then the enzyme was inactivated, the pH was adjusted to about 4 with acetic acid, and the hot water was inactivated at 80 °C for 10 min.
2 Results and discussion
2.1 Protease treatment process The best experimental scheme for enzymatic treatment by orthogonal experiment: at the concentration of 3 (owf), pH=8, temperature 50 °C, bath ratio 1:30, 40min treatment, the shrinkage rate is the smallest, the strength loss is small. The process is: hydrogen peroxide treatment - deoxygenation - a protease treatment - an enzyme inactivation. The results are shown in Table 1.
2.2 Protease and transglutaminase (TG) co-finishing treatment process: after hydrogen peroxide pretreatment, take TGO. Treatment with 5% (owf) and different concentrations of protease (0.5%, 1.0%, 2.0%, 3.0%), temperature T=50°C, time t=40min, bath ratio 1:30. Then adjust the pH to about 4 with acetic acid and inactivate the water at 80 °C for 10 min. The results are shown in Table 2.
It can be seen from Tables 1 and 2 that after the addition of transglutaminase (TG), the protease can greatly improve the felting of the wool fabric at a low concentration, because the weight of glutamine and glutamic acid in the wool is 14 .9%, lysine residues account for 3.1%, and transglutaminase (TG) is a transferase that catalyzes the cross-linking between proteins to modify proteins. In the catalytic reaction, the 7-amido group of the glutamine residue on the peptide chain is an acyl donor, and ε-(r-glutamyl)lysine is formed with a primary amine on lysine or a residue thereof. At the same time, the strong loss is also lower than that of the protease alone, indicating that the protease and the transglutaminase (TG) have synergistic complementarity, but still do not achieve the desired effect, so the finishing process needs further study.

2.3 Protease chitosan composite finishing After the hydrogen peroxide pretreatment, the wool fabric was treated with different concentrations of chitosan, and then the protein was concentrated with a concentration of 3% protease. The process is: hydrogen peroxide pretreatment, chitosan treatment, a protease treatment, the experimental results are shown in Table 3.
It can be seen from Table 1 that the oxidative pretreatment + protease treatment significantly improved the felting problem of the wool fabric, but the strong loss was severe, indicating that the protease not only attacked the scale layer but also damaged the cortical layer. It can be seen from Table 3 that the first treatment with chitosan and protease can not only improve the strong loss caused by protease treatment, but also reduce the felting rate of wool fabric to meet the requirements of machine washability, indicating chitosan. It has a certain protective effect on wool. With the increase of chitosan concentration, the shrinkage rate and strength are linearly decreasing. When the concentration is 0.2%, it is ideal, and the concentration of 0.3% and 0.2% is not much different. Considering the cost factor, the chitosan concentration is determined to be 0.2%. This will make the fabric shrinkage rate of 6.87%, while the strength loss is only 5.78%.

2.4 Surface morphology after wool fabric treatment Electron microscopy was performed on the wool fabric before and after treatment with JSM-6700 field emission scanning electron microscope. The results are shown in Fig. 1.
It can be seen from Fig. 1(a) that the scales on the surface of the original fabric are regularly arranged and the sharp corners are prominent. After treatment with hydrogen peroxide + protease, the surface is smooth, most of the scales fall off, the edges of the scales are passivated, the sharp corners disappear, and the damage to the wool is relatively serious. After treatment with chitosan and then treated with protease, the surface of the fiber is also very smooth, the scales are loosely arranged, the sharp corners are lifted, the opening angle becomes smaller, and the degree of edge passivation is lower than that of the protease directly after the treatment with hydrogen peroxide, as shown in Fig. 1. (c) and (d). This is because chitosan fills the gap between the scale and the scale, forming a protective mold on the surface of the fiber, thereby preventing the protease from over-attacking the scale layer and the cortex layer, so that the protease only occurs in the sharp corner portion of the scale layer. The effect, as shown in Figure 1 (b), so the strength of the fabric after the addition of chitosan is improved.

2.5 Infrared spectroscopy
2.5 Infrared spectroscopy was performed using the Nexus 870 Fourier transform infrared spectrometer from Thermo Fisher, USA, as shown in Figure 2. Fig. 2(a) and (b) are the spectrum diagrams of the chitosan and protease of the reagent, respectively, and the curves 1 and 2 in Fig. 3 are the spectrum diagrams of the grey fabric and the knitted fabric of hydrogen peroxide + chitosan + protease. It can be seen from Fig. 3 that the bands with large changes are mainly distributed in three regions of 3 500~3 000 cm-1, 3 000 2 700 cm-1 and 1 675-900 cm-1, and these bands have strong absorption peaks. , different from the infrared spectrum of unfinished wool fabric. 3 500 to 3 000 cm-1 of curve 2 in Fig. 3 are characteristic absorption peaks of 0-H and N-H; -CH3, -CH2.
(3 000~2 700cm-1) showed obvious absorption peak; in addition, the characteristic absorption peak of carbonyl C=O appeared around 1 650cm-1, and these peaks can be seen in Fig. 2(a), (b) chitosan Similar traits were found on the spectrogram of the protease, indicating that chitosan and protease reacted chemically with wool. The vibration zone belonging to S-O at 1 200~1 O00 cm-1 can provide information on the oxidation products and oxidation intermediates of cystine on the wool surface, which is the result of oxidative pretreatment.

2.6 Properties of wool fabric after chitosan/protease treatment
2.6.1 Shrinkage, strength, rigidity and wrinkle resistance are passed through H202. After the pretreatment, the wool fabric treated with chitosan and chitosan was tested for strength, shrinkage, rigidity and wrinkle resistance. The results are shown in Table 4. After treatment, the shrinkage of the fabric decreased from 18.1% to 5.87%, the strength decreased by 5.78%, the shrinkage rate reached the machine washable standard, and the strength loss was not large. At the same time, the softness and elasticity of the fabric are improved, which improves the hand and anti-crease ability of the fabric.
2.6.2 Dyeing properties The weakly dyed dyes were used to dye the wool fabric before and after treatment. 5O °C human dyeing, heating to 90 °C at a rate of l ° C / min, constant temperature dyeing 60min at each time of dyeing to take out 2mL of stock solution and dye solution, respectively, test the absorbance, calculate the percentage of dyeing. The result is shown in Figure 4. It can be seen from Fig. 4 that after the preparation of chitosan-protease by hydrogen peroxide pretreatment, the percentage of wool dyeing is significantly increased, especially the initial dyeing rate is very different, but the final equilibrium dyeing rate is not much different.
According to the theoretical analysis, the normal wool fiber should have good dyeing performance. The difficulty mainly comes from the dense structure of the scale layer and the diffusion resistance of the dye macromolecule to the fiber. At low temperatures, this resistance is very large, so the normal wool fiber is at a low temperature in the initial dyeing period, and the dyeing rate is small. After the enzyme treatment, the scale layer is damaged or even detached, which is beneficial to the diffusion of the dye. . At the same time, the oxidative pretreatment also destroys the disulfide bond in the keratinocyte macromolecule, transforming it into a sulfonic acid group, improving the hygroscopic swelling property of the wool fiber and contributing to the diffusion of the dye in the wool fiber. At high temperatures, the kinetic energy of the dye molecules increases, the chance of contact between the dye and the fiber increases, and at the same time, the wet expansion of the fiber is intensified, the scales are opened, the diffusion resistance of the dye molecules to the fibers is reduced, and the degree of polymerization of the dye molecules is lowered, thereby making the scales The barrier effect of the layer is reduced, so the dyeing rate of the untreated fabric is significantly increased after the temperature rises to 90 °C, so that the final equilibrium dyeing rate of the two is not much different.

3 Conclusion
(1) The use of chitosan and protease to finish the fabric to make up for the serious loss of strength caused by the use of protease alone, and to obtain a more ideal anti-felting effect, so that it can reach the machine washable standard.
(2) After treatment with a solution of chitosan and hydrogen peroxide, the percentage of dyeing of wool fabrics, especially the initial dyeing rate, is significantly improved, which can shorten the dyeing time of wool fabrics.
(3) After the wool chitosan-protease anti-felt finishing, the original wearing performance of the wool fabric can be retained, and the hand feeling and anti-crease ability of the fabric can be improved.
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