In recent years, the application of protease in wool fibers has attracted much attention.
According to the “China Textile News” report, wool is generally processed by chlorination to prevent shrinkage, mercerization, anti-pilling, and increase wearability. After shrinkage treatment, anti-shrink wool can absorb halogenated compounds up to 5-6 ppm. , more than 10 times the limit value, such substances are also found in the discharge liquid, and there are serious problems such as organic halogenated compounds Aox and environmental hormones. Therefore, in the above-mentioned types of processing, wool protease reduction processing and finishing are becoming increasingly important.
Protease is a biological catalyst that can function under mild reaction conditions such as normal temperature, normal pressure, and nearly neutral pH. Wool is an ideal substrate for protease, and the catalytic efficiency of protease is 105-107 times higher than that of inorganic catalysts. The specificity of catalytic reactions is one of the important characteristics of enzymes. Different proteases have different specificities. In fact, a single protease has different activity effects on different substrates (wool). Based on the very complex ecological structure of wool, someone has developed an enzyme preparation consisting of at least three basic enzymes, namely protease, lipase and lipo-protease. Protease mainly acts in the stratum corneum, lipase mainly acts in the lipid and fat area, and lipo-protease mainly acts in the ester bond area.
Our country’s scientific and technological staff screened mainly Bacillus enzymes and Aspergillus niger enzymes, and selected protease preparations with stable or similar pH and multiple functions for preparation. They added stabilizers, activators and pH regulators to form a composite protease, and at the same temperature Treated in the same bath under certain conditions to give full play to the synergistic effect of multiple proteases. At present, compound protease has been promoted and applied in many areas with very good results.
Under normal circumstances, protease can have greater weight reduction activity on wool after wool has been pretreated. This weight reduction activity does not increase with the increase in enzyme concentration. The pretreatment of wool treated with composite protease usually refers to pre-treatment with chlorine, hydrogen peroxide and persulfate to improve the enzyme’s weight reduction activity on wool, efficiently catalyze the decomposition of cystine peptide bonds, and dissolve part of the protein in the surface structure of wool, reducing scales. Subject to certain damage, the purpose of reduction is achieved. Currently, two methods are used abroad: chlorination first and then enzyme treatment or oxidation first and then enzyme treatment.
The chlorine enzyme method is based on chlorination shrinkage prevention, which deeply chlorines the surface of wool fibers, and then uses complex protease for weight reduction treatment. However, the impact of weight reduction is different for different wool varieties. In actual production, process parameters should be adjusted accordingly according to different wool varieties. In general, some thicker wool yarns can become thinner, have silk-like luster and super soft feel, and can reach the “machine washable” level without shrinkage, and the anti-pilling level of wool can be improved from level 3. By level 4-5, the effect is very obvious.
Hydrogen peroxide pretreatment opens the disulfide bonds (also known as cystine bonds) in wool protein, making the protein molecules more susceptible to deformation, which is beneficial to the enzyme reduction of the complex protease, and is beneficial to the modification of the surface of wool fibers. The hydrophilicity is significantly increased, and the enzyme reduction can reach 5%-7%. It is generally believed that wool scales account for 10% of the total amount of wool. If the reduction reaches 6.5%-7%, it is equivalent to 2/3 of the wool scales being hydrolyzed. This is the golden ratio of scale reduction, and the anti-felting performance reaches “Machine washable” level. However, the concentration of hydrogen peroxide should not be too high, otherwise it will not only fail to increase the loss rate, but will cause oxidative damage to the wool fiber. The ecological environment after pretreatment with hydrogen peroxide is good and can be completely decomposed by catalase, so it is called a “double green product”, that is, green technology and green wool products.
The currently used composite proteases are mainly complexes of a variety of microbial proteases. Due to the high specificity of proteases, one enzyme can only catalyze one or a type of substrate with a similar structure. Among composite proteases,There is a synergistic effect. After treatment, the whiteness of the fabric increases, and it has multiple functions such as anti-pilling effect, super-soft feel, and significantly improved low-temperature dyeing of wool. The complex protease removes the attachments on the surface of wool scales, making the wool scales smoother and completely able to achieve the biological mercerizing effect. Some people measured the gloss after treatment and showed that the gloss of thick pile threads increased by 25%, while the gloss of fine pile threads could still be increased by 15% due to their better gloss.
Wool fabrics are treated with chlorenase or biological mercerization process, and then are softened. The quality and style of the softener will directly affect the feel of single wool fibers. At present, the most commonly used smoothing softener is mainly amino silicone emulsion with ultra-high molecular weight and high viscosity. This liquid has a milky white appearance, is weakly cationic, will not stratify, and has excellent water solubility. The wool fiber has been reduced to varying degrees, resulting in denudation of the scales or flat edges of the scales, making the hand feel rough and lacking elasticity. It is treated with the mercerized wool smoothing agent SWF to allow the ultra-high molecular weight amino silicone emulsion to quickly enter the wool scale layer, first smoothing out the unevenness. Fill the areas flat, and then lay a film on the surface of the fiber to concentrate and reflect the light. The mercerizing effect is very obvious, the hand feels particularly soft, and it has an extremely smooth feeling.
Compound protease has been gradually promoted and applied in wool fiber reduction process, mainly because it has obvious advantages in environmental protection, energy saving, increasing product added value and developing new raw materials. The application of microbial enzymes has been called the four major development directions of current textile technology applications along with supercritical carbon dioxide dyeing, low-temperature plasma processing and digital printing technology. It is entirely possible that compound protease will become a widely used technology method in the wool spinning industry.
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