Enzymes are called "biocatalysts" and they have a close relationship with human life. Whether it is in animals and plants or in microorganisms, it can be found everywhere. The use of enzymes can be traced back to 4000a, when the working people of our country were able to make maltose, wine and vinegar. With the development of science and technology, biotechnology is changing with each passing day, and the variety of enzymes is increasing and the use is becoming more and more extensive. Biological enzymes are not only used in light industry such as food fermentation, textile, tanning, medicine, papermaking, but also in energy development and environmental management. In the dyeing and finishing industry, enzymes were mainly used in the de-slurry of cotton fabrics and the degumming of silk. Nowadays, it has been found that the treatment of textiles with bio-enzymes can not only improve and improve the taking performance, but also contribute to the protection of the ecological environment. The process of applying biological enzymes to treat textiles belongs to the green production process and has great development prospects.

1. Structure and characteristics of biological enzymes

Biological enzymes are proteins with catalytic functions. Enzyme molecules like other proteins consist of long chains of amino acids. A part of the chain is spiraled, and a part is a folded sheet structure, and the two parts are connected by an unfolded amino acid chain, so that the entire enzyme molecule becomes a specific three-dimensional structure.

Biological enzymes are produced from organisms and have a special catalytic function. Compared with the general catalyst, it has the following characteristics [1]: 1) high catalytic efficiency. The catalytic efficiency of the enzyme is 103 to 106 times that of the general inorganic catalyst. 2) Strong specificity. Generally, the catalyst has poor specificity for the substrate, and the enzyme has strict selectivity to the substrate (an enzyme can often only catalyze a certain type of substance). 3) The reaction conditions are mild. The enzyme-catalyzed reaction does not require high temperature, high pressure, strong acid, strong alkali and other severe conditions as the general catalyst, but can be carried out under milder normal temperature and normal pressure. 4) has the ability to adjust. The catalytic activity of many enzymes can be flexibly regulated by a variety of regulatory mechanisms.

There are many types of enzymes, and the conditions under which different enzymes are most suitable are also different. There are many factors affecting the catalytic activity of the enzyme, such as enzyme concentration, substrate concentration, reaction temperature, pH value, time, and the like. In order to make biological enzymes better applied in the dyeing and finishing industry, it requires constant research and development and practice.

2. Development and application of biological enzymes in dyeing and finishing industry

2.1, enzyme desizing

2.1.1, amylase desizing

Desizing of cotton fabrics containing starch with amylase is the first process in which biological enzymes are applied to pre-treatment of dyeing and finishing. Cotton fabrics use alkali desizing to reduce the starch pulp. The use of oxidizing agents or acid desizing can cause serious damage to the fabric if the process conditions are not properly controlled. The amylase which can decompose the starch slurry converts the starch into a dissolved state under mild temperature and pH conditions, not only has a high desizing rate, but also has no damage to the cotton fabric, and the product feels soft. Therefore, the use of enzyme desizing in cotton fabrics has been recognized as an ideal desizing process. In the past, the cost of amylase was much higher than that of alkali, and it did not remove other slurries, limiting its application. With the development of biotechnology, the price of amylase has been continuously reduced, so the process has once again attracted people's attention.

2.1.2, lipase assisted desizing,

The use of lipase-assisted desizing process has also been reported abroad [2]. In traditional sizing processes, starch and animal and plant based lubricants (triglycerides) are often used as sizing components. This is mainly because they are natural raw materials that can be continuously supplied, are easy to buy, and are quite cheap. With the traditional desizing/refining process, only less than 10% of the plants and animals are saponified. The triglyceride-based lubricant can be almost completely hydrolyzed by lipase. Therefore, for a fabric sized with a starch/plant blend, a desizing agent of amylase and lipase may be used for desizing.

The desizing method adopts the rolling method. The process conditions are lipase concentration 5000 LU/kg cotton, amylase concentration 25NAU/kg cotton pH value 7, temperature 75 ° C, 2 h, bath ratio 1:1, desizing rate 98%.

Desizing using high temperature short steaming method: lipase concentration 100LU/kg cotton, amylase concentration 50NAU/kg cotton, pH 7, temperature above 90 °C, time 5min, bath ratio 1:20, desizing rate of more than 90%.

The above process has good desizing uniformity, and the fabric feels soft, which can reduce environmental pollution and refining burden. If the steaming treatment is more than 90 °C, the desizing time can be shortened.

2.2, enzyme refining

Cotton fabrics have a long history of using caustic soda scouring, and so far almost all cotton fabrics have been refined with alkali. However, with the demand of human beings to protect the ecological environment, research using enzyme scouring is on the rise. According to the relevant information, the use of pectinase and cellulase synergistically to treat cotton fabrics can significantly improve the wettability of the fabric, and the fabric damage is small.

The specific process of enzyme scouring is as follows: pectinase 2.2% (owf), cellulase 4.4% (owf), pH 5 (HAcNaAc buffer), temperature 50 ° C, time 60 min, bath ratio 1:12.

Compared with alkali scouring, enzyme scouring has mild reaction conditions, low energy consumption, simple equipment requirements, and no wastewater treatment problems. The fabric after the enzyme refining is fluffy and soft. The dyed fabric after the enzyme training has bright color and bright luster, and the appearance effect is obviously better than alkali refining. It can be seen that the enzyme scouring process is the most promising process for replacing alkali scouring.

2.3, enzyme degumming

Protease degumming is the traditional degumming process of silk fabrics in China. Due to the increase in the price of enzymes in recent years, the cost of this process is relatively high, so with the promotion and application of rapid scouring agents, the enzyme training process is gradually eliminated. However, the obvious feature of the protease scouring process is that it is irreplaceable with a fast scouring agent. If the product feels full and soft, the gloss is soft. Especially for the processing of silk crepe fabrics, the enamel effect is good, the process flow is relatively simple, and the operation is easy to control, so the process is re-recognized by people.

After several years of experiments and discussions, some manufacturers found that the protease and the rapid scouring agent can be combined reasonably, that is, the 2709 protease is applied in the scouring pretreatment stage and then re-repaired by the scouring agent, and the effect is very satisfactory. The specific process conditions are as follows:

Pretreatment: 2709 protease 0.9 g/L, WA dispersant 2.7 g/L, temperature 42-45 ° C, time 80 min. Rehabilitation process conditions: soda ash 0.9g / L, water glass 1g / L, scouring agent 2g / L, temperature 60 ° C, time 100min.

The use of the above process to produce silk crepe fabric not only shortens the scouring time (20 minutes shorter than the conventional process), reduces the scouring temperature, saves production energy consumption, and the appearance and internal quality of the product are ideal. Therefore, the process is very popular.

2.4, enzyme low temperature dyeing

The traditional wool dyeing process is boiling at 100 °C. This dyeing process not only consumes a lot of energy but also damages the wool fiber, resulting in a rough hand dyeing product. The use of suitable proteases for wool dyeing and destruction of the phosphine structure on the surface of wool fibers promotes the diffusion of dyes into the fibers, increasing the dyeing rate and percentage of dyeing, so that wool dyeing can be carried out at lower temperatures. According to the data [3]: SEP or Alcalase 2.0T protease was selected, and the dyeing effect was obtained by dyeing wool at a pH of 5.5 and a dyeing temperature of 85 °C.

Compared with the traditional boiling dyeing process, protease low-temperature dyeing has the following advantages: 1) the dyeing temperature is reduced, which is conducive to saving production energy and reducing fiber damage; 2) saving dye dosage and reducing environmental pollution; 3) improving The feel of the dyed product improves the quality of the product. This process is worth promoting.

2.5, enzyme wash

2.5.1, enzyme washing of denim,

The thick cotton twill denim is washed with stone, and the color becomes blue and white, and the hand feels soft and comfortable. This kind of clothing is popular nowadays because it is suitable for some people to pursue the requirements of novel appearance and comfortable wearing.

Conventional denim processing is a "stone grinding" of fabrics with pumice impregnated with sodium hypochlorite or potassium permanganate. The fly in the ointment is that the denim is too strong. The use of cellulase for denim water washing has the following advantages compared with pumice water washing: excellent quality of processed garments; less wear on equipment; environmental protection, and reduced fabric strength.

Denim enzyme washing is divided into three stages: first, pre-washing and desizing. Followed by cellulase washing, and finally detergent washing and water washing and drying. Since cellulase itself can impart a soft hand to the fabric, in the final cleaning stage, in addition to requiring ultra-softness, it is generally unnecessary to add a softener. In addition, since the enzyme washing is carried out at a pH near neutral, the contamination of the denim by the indigo dye is improved. It can be seen that neutral cellulase is more suitable for water washing of denim.

2.5.2, enzyme washing of high-grade cellulose fabric

Cellulase has not only been successfully used in stonewashing of denim, but also in delicate fabrics or fabrics that are easily hydrolyzed by cellulase. It has been found [4] that a concentrated acid cellulase is the best choice for fabrics such as linen and viscose rayon that require mild surface lightening and abrasion.

The optimum process conditions for enzyme washing: pH value 5.0-5.5, temperature 50-55 ° C, time 30 min. After enzyme washing, the temperature was raised to above 70 ° C, the pH was raised to 7.5 or higher, and treated for 10 min to rapidly deactivate the enzyme.

The above process can improve the hand feeling of the linen fabric, and the viscose rayon fabric can be obtained in the style of the artificial silk fabric.

3. Application prospects of biological enzymes

The biological enzyme has mild conditions, specific catalytic performance and high catalytic efficiency, which is unmatched by any other chemical additives. The bio-enzyme-treated textiles are soft to the touch, comfortable to wear, bright in color, bright in gloss, and high in product quality. The use of biological enzymes for dyeing and finishing can save dyeing and chemical materials, save energy and have no environmental pollution. Therefore, with the demand for “green” textiles, with the deepening of research on biological enzyme technology, it is believed that in the near future, biological enzymes will be applied to various processes of dyeing and finishing.

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