Multi-color printing technology

Any kind of technology has both advantages and disadvantages. Every practical need has the most suitable technology for itself. This is actually a dialectical relationship. In the process of textile printing, there is also a dialectical relationship. If the pigment or dye thickener, binder and various additives are not selected properly, the dye can not be fully dissolved, there is still insoluble matter; or the printing paste is placed For a long time, there will also be some attraction between the dye ions or between the dye ions and the slurry molecules, causing the dyes to re-aggregate to form a print pattern, causing color spots or uneven dyeing. This is an undesirable flaw in the printing process. It is also a cause of defective printing.

This kind of defect is something people don't want to see. In the printing process, we must try our best to overcome it. Some people think that since color dots are shortcomings in printing, whether they can turn shortcomings into favorable ones suits their technical needs. If the irregular color dots are arranged in a novel style or pattern, then how good is the printing, so that the printing will produce another visual effect, resulting in a novel printing product called multi-color multi-point printing. Multi-color micro-printing methods have emerged. How to generate a lot of color points? Using micro-encapsulation technology can be achieved. Microcapsule technology is a technique that uses a film-forming material to coat solid or liquid dyes to form tiny particles. The tiny particles obtained are called microcapsules, and the dyes encapsulated inside the microcapsules are called capsule cores, and the external coating film is called wall material. The encapsulated dye is called microencapsulated dye. With it, multi-color multi-point printing can be realized.

Multi-color multi-point printing is generally the same as conventional printing in process and equipment, but is different. One of the differences is the use of micro-capsule dyes. In the printing paste, different color micro-capsule dyes are encapsulated by the envelope film. Cover, so do not mix with each other into a color, only after printing, through the fixing conditions such as steaming the capsule rupture, the dyes of various colors are released, the fibers are colored separately, so the formation of a variety of color style unique Micro dot pattern. The shape of the micro-dots differs depending on the shapes of the microcapsule dyes, and may be spherical, elliptical, droplet-shaped, scale-like, fiber-shaped, or the like.

If the conventional yellow dye and blue dye are mixed in the same color paste with a conventional printing process, it will become a green slurry, still a monochromatic printing. If the yellow and blue dyes are made into microcapsule dyes, they can also be in the same colorant. Due to the barrier enveloped by the capsules, the two dyes do not come into contact with each other, ie they do not mix. Only after printing is steamed, the dyes are released from the capsule and the fibers are colored separately. This forms microscopic dots of different colors. For visual reasons, the green pattern is seen from afar and the yellow and blue are visible when viewed from a near distance. The composition of the micro dots. Therefore, it gives people the impression of “look at the colors from afar.” Some people claim that multi-color multi-point printing is a unique style of printing that is different from the general “snow” effect.

The second difference is that because the capsular film of the microcapsule dye is of a release type and has a certain degree of sturdiness, the slurry mixing and the temperature should be strictly controlled. It is better to first sample the sample to find out the specific operation process conditions, especially the capsule Conditions should be explored in advance to get a satisfactory printing effect. Due to the different preparation methods of microcapsules, the properties of the capsules will also be different, and the composition of the printing pastes will also need to be adjusted accordingly. For example, MCP-HP microcapsule dyes produced by the Japan Forest Chemical Company may be added with urea to facilitate penetration. However, microcapsule dyes prepared by the spinning cutting method cannot be added with urea; some cannot be prepared with water.

After multi-color multi-point printing and drying on one side of the fabric, the same multi-color multi-point printing can be performed on the opposite side of the fabric to produce double-sided multi-color multi-point printing products. A multi-color multi-point pattern consisting of printed micro-dots and printed micro-dots transmitted from the other side can be seen on each side, and the main colors of the two sides can be different. In addition, the use of padding can also get double-sided multi-color printing effect. Ordinary dyes may also be added to the enamel or color paste in the padding liquor so that a ground color can be obtained. For example, a polyester-cotton fabric can be used to add a separate reactive dye, so that the surface of the fabric can have a multi-colored multi-pattern and a whitening effect. The garments and interior decoration products made from double-sided multi-color printing products are very popular with customers.

The microcapsule dye particles are small, and the dyes per kilogram of microcapsules can reach 100 to 10 million particles. The microcapsule dye consists of an inner core, a dye, and an outer film. Due to limitations of the manufacturing method, the inner core dyes are currently limited to non-concentrated dyes. Water soluble reducing, dispersing, acidic and cationic dyes. It is more difficult and complicated to form microcapsules with water-soluble dyes. The most suitable dye microcapsule is a disperse dye, because it is insoluble in water, and the commercial dye itself contains a dispersant, which is easily dispersed in water and coated with a water-soluble wall material such as methyl cellulose, and thus is a water-insoluble dye. The microcapsules can be formed using a phase separation single coagulation method, a complex agglomeration method, and a physical method. However, it needs to be further explained that since NNO, a dispersing agent contained in gelatin and disperse dyes, easily aggregates directly into a lump, some synthetic dragon gum may be added as a protective colloid to prevent agglomeration in order to obtain a particulate state. In order to obtain an increase in the strength of the microcapsule wall film so that it can withstand the requirements of various printing methods, such as the pressure of a rubber roll, a copper blade or a magnet bar, a certain amount of dye microcapsules may be hardened. 39% formaldehyde, when cooled to 10°C, treated with sodium hydroxide to adjust the PH = 8 ~ 9 conditions, with the control of temperature, reaction time and the amount of formaldehyde added to adjust the degree of hardening, if the hardened excessive treatment, the wall film is too hard, It may be that the microcapsules cannot be broken due to excessive hardness during gasification treatment, no dye is released, and the fabric is difficult to dye. If you want to get smaller dye microcapsules, you can reduce the amount of synthetic agglomerate, and accelerate the speed of adding acids and slow the stirring speed. If you want to get larger particles, you can add some gelatin or diffusion agent NNO to form the dye micro After the capsule, the dispersion can be divided into two layers after being placed, and the supernatant liquid is filtered. The lower layer is the dye microcapsule particles.

The printing process is: slurry preparation → printing → pre-baking → 140°C high-pressure steaming → washing → reduction cleaning → washing → drying → finished products.

The composition (%) of disperse dye microcapsule printing paste is introduced as follows:

Microcapsule Disperse Dyes 20~40

Sodium alginate pulp 50~85

Urea 5

Anti-stain salt 2

Tartaric acid (adjusting PH value) moderate

Water amount

Total 100

The application of microencapsulated dyes in the textile printing industry is still in its infancy. In the long run, it is a dye printing method with promising applications. For example, the vat dye suspension padding, reducing agent can not coexist with the dye, you must first padding vat dye suspension, drying and then padding reducing liquid, and then gas steam reduction, if the reducing agent after microencapsulation can be Dye co-dissolution applications. The color phenol rendering of the ice dye and the color development of the chromophore are performed twice. The polyester/polyacrylonitrile and polyester/hair blends are dyed with two dyes. When the two dyes meet each other, precipitation occurs, affecting the The use of a dissolving method, such as the microencapsulation of one of the dyes, can achieve a one-time application dyeing, simplifying the printing and dyeing process. In addition, some dyeing auxiliaries with special properties can also be coated and dyed simultaneously with dyes.

People expect that microcapsule dyes will continue to open up many new uses in the textile printing and dyeing industry.

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