Practice of reactive dye pressing and fixing process

At present, the proportion of printed products in the entire printing and dyeing products is about 25%, and new printing processes and new equipment are emerging. Special printing a little glue (drop plastic), heat transfer (thermal transfer), bronzing, hot silver, gold and silver powder, luminous, three-dimensional printing, sticky beads, etc., the equipment used in printing has screen printing machine, transfer printing machine , electrostatic flocking printing machine, digital jet printing machine, pressing machine, etc. The press machine was developed with the development of the transfer printing process and the T-shirt industry.

With the people-oriented, the concept of sustainable development is deeply rooted in the hearts of the people, and the demand for eco-textiles is increasing. It is required that printing and dyeing enterprises should adopt environmentally-friendly reactive dye printing in the production process. The reactive dyes are bright in color, easy to use, complete in chromatography, excellent in fastness and soft to the touch. When printing and fixing, most of them adopt steaming and fixing process, which will limit the application of the process to enterprises lacking steaming equipment. Therefore, it is of great significance to study and improve the reactive dye printing method and printing process. Taking the printing of T-shirts as an example, a new process of fixing the reactive dyes by pressing is used.

Process flow

Pattern design → photosensitive plate making / modulation color paste → printing → drying → pressing and fixing color → cold water washing → soaping → hot water washing → cold water washing → drying → ironing and finishing.

Equipment requirements

The manual press is currently mainly used for heat transfer printing and heat transfer, and is widely used in the design of T-shirts, bags, handbags, shoes and hats, socks, gloves, etc. The size of the press is 40×60cm, the maximum temperature can reach 399°C, and the maximum adjustable time is 60s. Since the maximum adjustable time of the device is only 60s, the dye must be quickly fixed in a short time.

Dye selection

Reactive dyes are reactive dyes. The types of dyes are X type, ME type, KN type, K type, etc., which have been widely recognized both at home and abroad, and new reactive dyes are continuously developed and applied to production, making solid The color rate is greatly improved. The reactive dye has complete chromatogram, strong applicability, good soaping fastness and good rubbing fastness. It is consistent with the requirement that the T-shirt should be washed frequently during use and needs good soaping fastness. As a reactive dye for printing, it should have high solubility, high fixation rate, low directness, good stability, good light fastness and washing fastness, good compatibility and reproducibility. In the experiment, ME, KN and K reactive dyes with good stability were selected for the process experiment. Due to the high requirements of the printing process, dyes with high fixing rate should be selected.

Color paste composition

The reactive dye printing paste is usually composed of dye, anti-staining salt S, urea, sodium alginate paste, small soda (or soda ash), water, and is steam-fixed. Due to the use of pressing and fixing, the time is short. In the selection of the alkali agent, it is considered to improve the alkalinity, shorten the fixing time, and improve the fixing rate. To this end, the experiment uses ME type, KN type reactive dye paste to select soda ash, K type reactive dye paste selects soda ash, caustic soda, the color paste is composed of dye, sodium alginate, soda ash (or caustic soda) and water.

The process prescription uses reactive dyes: 1% to 10%; sodium alginate paste (6%): 60%; soda ash: 2%; or caustic soda (36 Baume): 4ml/100g.

Process prescription and process conditions selection

Determination of pressing temperature

The pure cotton KBR, the reactive black KNB and the reactive brilliant red M-3BE were selected by the cotton twill weave bleaching fabric. The comparison experiment with time of 60s showed that the solid color rate increased and the color became deeper with the increase of temperature; When the temperature is above 190 ° C and above, the fabric begins to turn yellow. Therefore, it is recommended that the pressing temperature be controlled up to 180 °C.

Determination of pressing time

1) The active black KBR dye was selected and the experiment was carried out with caustic soda as the alkali agent at a temperature of 180 ° C. It was proved that when the time was less than 40 s, the color increased significantly with the increase of the experiment, over 40 s, with the increase of time, color Significantly shallower.

2) Select active black KNB dye, use soda ash as alkali agent, and experiment at temperature of 180 °C. When the time is less than 40 seconds, the color will be deepened with the increase of the experiment, over 40 seconds, with the increase of time. The color light is obviously reddish.

Selection of alkaline agent

The active black KBR dye was used, the temperature was 180 ° C, and the experiment was carried out for 40 s, which proved that the alkali was enhanced and the color was obviously deepened. However, in the application of caustic soda, when the dye concentration is high, the pH of the color paste exceeds 11, which makes the colorant unstable and forms a gel. It is recommended to use soda ash in the alkaline agent.

experiment analysis

It can be seen from the above comparison test that the pressing method has a fixing effect on the reactive dye, and the fixing fastness is very good, the white background is not stained, and the pattern is not attached to the surface of the fabric like the coating, and the dye penetrates into the surface. In the fiber, it feels good when touched, washable and wear-resistant. However, in the pressing process, attention should be paid to the control of temperature and time, the temperature is increased, the fixing rate is increased, and the color is deepened as the temperature is raised. However, after the temperature exceeds 180 ° C, the fabric begins to turn yellow, which is unsuitable. The fixing rate increases with time and the color will deepen. During the experiment, we found that the dye pressing method requires fast fixing in a short time, and the longest time is 40 seconds, which greatly reduces the time and energy than the steaming method. The reactive dye pressing method has its advantages and of course, and the reactive dye has poor coverage of the dark base fabric and does not achieve the effect of color saturation. This method is only suitable for light-bottomed fabrics, if the color of the dark fabric is not obvious. The reactive dye pressing method has been proved to be feasible by experiments, and it fills a new process for the use of reactive dyes in hand-made screen printing on garments and cut pieces.

Process effect analysis

Reactive dye pressing method ensures that the reactive dye printing avoids water stains caused by the dripping of condensed water when steaming and fixing, and the reactive dye pressing and fixing method is simple and requires no large-scale machine equipment, only manual pressing machine is required. It has simple operation, strong flexibility, short process, high fixing rate, bright color, no need to add anti-dye salt urea, reduce the consumption of dyeing chemicals and additives, reduce printing cost, save energy and save water. At the same time, the reactive dyes rarely contain harmful aromatic amine structures, making them the dyes of choice for the production of cellulosic fiber eco-textiles. The fabric feels good, the color fastness to washing, the color fastness to rubbing is good, and the fabric is printed. The tension in the process is small, and the pressing and fixing method is particularly suitable for the reactive dye printing process of garments such as T-shirts and cut-off printing products of small printing enterprises, and also for the use of reactive dyes in cellulose fiber fabrics. .

With the improvement of people's consumption level, the small home textile and T-shirt industry is booming. The reactive dye pressing method is simple and easy to operate, and is suitable for small batch and multi-variety production. Being able to satisfy people's individual pursuits will surely be widely used.

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