For a long time, the dyeing fastness of polyester and its blended fabrics dyed with disperse dyes has been a difficult problem. Among them, reduction cleaning is a common and simple method. Because the disperse dyes attached to the fiber surface will be "reduced" to colorless, and more soluble in water. The traditional reduction cleaning method is to use sodium hydroxide and sodium hydroxide. At present, most domestic dyeing factories are still using this method.

1、 Why restore cleaning?

The main reason is that polyester fiber is dyed at high temperature and high pressure. Although the disperse dye molecules are small, it can not guarantee that all the dye molecules enter into the fiber during dyeing. Some disperse dyes will adhere to the fiber surface, resulting in poor fastness. At this time, the reduction cleaning method will not destroy the dye molecules entering into the fiber to improve the fastness and shade.

2、 Disadvantages of traditional reduction cleaning process

With the improvement of consumers' requirements for fabric fastness and shade, reduction cleaning in the dyeing process: complex process, occupying a lot of dyeing time; washing water for many times, adding neutralization, increasing sewage discharge.

The traditional method requires to be carried out under alkaline conditions, while disperse dyeing is under acidic conditions. Therefore, after dyeing, the dyeing solution must be discharged first, followed by reduction cleaning, then hot water washing and cold water washing, and finally acidification treatment. The whole process is complicated, which not only consumes a lot of energy, but also has a low long-term rate of process time.

In addition, sodium hydrosulfite is a sulfur-containing compound, the main component of which is Na2S2O4. The residual sulfide is also found in the sewage discharge, which increases the burden of sewage treatment.

Polyester fiber dyeing process belongs to the production mode of high energy consumption, high water consumption and high pollution discharge, especially when dyeing with disperse / reactive dyes and acid dyes in two bath, the influence is very significant. Under the condition of ensuring the dyeing quality, how to reduce energy consumption and pollution discharge is the concern of the dyeing factory. After dyeing with traditional disperse dyes, sodium sulfite is generally used as the raw material of reducing cleaning agent, and it is not easy to use Only the process cycle is long, the energy consumption is high, and the environmental pollution is large. The application of reducing cleaning agent alittm can directly add reducing cleaning without changing the acid condition of dyeing bath, which can achieve better cleaning effect (such as dry and wet rubbing fastness, soaping fastness, etc.) than the traditional sodium silicate process, and save time and improve production efficiency.

Common reduction cleaning methods:

Insurance powder;

Thiourea dioxide;

Reducing agent;

1、 Insurance powder

Sodium hydrosulfite is widely used in textile industry for reducing dyeing, reducing cleaning, printing and decolorization, as well as bleaching of silk, wool, nylon and other fabrics.

In fact, insurance powder is not "safe". Many accidents show that the spontaneous combustion, explosion, toxicity, water or acid flammability of insurance powder, as well as the instability of its aqueous solution determine its risk. Once an accident occurs, its fire risk is huge.

Reduction cleaning process of conventional sodium hydrosulfite

Conventional sodium hydrosulfite is reduced in alkaline condition, so it is necessary to drain water after dyeing, add water, alkali and sodium hydrosulfite, raise the temperature to 80 ° C, keep the temperature for 20 minutes to achieve the reduction effect, and then wash water and add glacial acetic acid for acid neutralization.

2、 Thiourea dioxide

Thiourea dioxide is a kind of compound without oxidation and reduction. The product is stable in acidic solution, but it is easy to decompose in alkaline condition, forming strong reductive sulfite, which makes the product have controllable reduction. Compared with sodium hydrosulfite, this product has higher reduction potential, better safety performance and no pollution in production and use. In the textile industry, it is mainly used in bleaching, dyeing, reduction cleaning, discharge printing, decolorization and other processes.

Due to the unique reducibility of thiourea dioxide, it is very effective for the reductive cleaning of blended fabrics dyed with disperse dyes. Moreover, it has high stability because it can be used in both acidic and alkaline reductive baths simultaneously. Thiourea dioxide can be directly applied to the acid or alkaline reduction cleaning process without damaging the fiber on the fabric fiber, which can save the process cost more than sodium hydrosulfite under the acid condition.

Usage and dosage of thiourea dioxide in reductive cleaning

After the dyestuff is OK, add 2% thiourea dioxide directly, raise the temperature to 80 ° c-85 ° C, keep the temperature for 20 minutes, wash and wash 80 ° C for 10 minutes. After washing and cooling, the next process can be operated.

In t / C, CVC and polyester / cotton blends, the washing fastness after reduction cleaning can reach grade 3. Compared with sodium sulfite, thiourea dioxide can improve the washing fastness by about 0.5.

3、 Telijie ™

Telijie ™ It is specially developed for acid dyeing with disperse dyes. It can replace thiourea dioxide and sodium hydrosulfite for reductive cleaning of polyester, polyester and cotton fabrics. It has the advantages of strong reductive ability, good color removal effect, high application safety, low dosage, simple liquid addition, etc. it can be directly used for reductive cleaning without alkali neutralization, light, medium and dark colors without liquid discharge, thus shortening the operation time, Reduce production costs. It is a new environment-friendly acid reducing agent, mainly used for t / C, CVC, t / R polyester and other polyester / cotton blended disperse dye reduction cleaning. It can completely replace thiourea dioxide and sodium hydrosulfite.

Usage and dosage:

When the dye content is less than 3.0, use special Li Jie ™ 2%, after the dyestuff and polyester samples are OK, add terlijie directly at 80 ° C ™ The next process can be operated after cold water cleaning. When the dye content is above 3.0-5.0, use terlijie ™ Under the condition of 80 ° C, add it directly, raise the temperature from 80 ° C to 85 ° C, keep the temperature for 20 minutes, and wash it with cold water.

Alite can be used for reducing cleaning of disperse dyes in the same bath after dyeing. Compared with the reduction cleaning with sodium hydrosulfite, alite can save two courses of water, save time and reduce power consumption.

conclusion

In the process of reductive cleaning after dyeing with disperse dyes, terlijie ™ It can save water twice, thus reducing the cost of sewage treatment, saving 40-60 minutes. Under the condition of the same addition, the fastness is higher than that of the conventional sodium hydrosulfite process and thiourea dioxide reduction cleaning process.