Digital Printing Process for Wool Fabrics

With the sustained development of China's economy, China has become the world's largest wool textile producer. In recent years, the amount of imported wool is more than 300,000 tons per year, which cost more than 1 billion US dollars, including 200,000 tons of Australian wool, accounting for 30% of the country's total wool production. The finished products of these wools have only a very small amount of exports, and the amount of woollen imports has been larger than the export volume for many years. This shows that China has become a major consumer of wool products. However, in addition to some printed sweaters on the domestic market, consumers rarely see other printed wool textile products. In fact, according to a survey conducted by the former International Wool Bureau and the Australian Federal Institute for Scientific and Industrial Research CSIRO, the output of printed wool fabrics accounted for about 1% of the total wool product output, which obviously cannot be compared with that of other textiles. The reasons for this situation are complex, but nothing more than the following: (1) Small batch size: As high-end apparel fabrics, printed wool fabrics are mainly produced in accordance with the needs of fashion apparel, and pattern patterns change more. To reflect the personalized requirements of small-lot production fashion. At present, the most advanced screen printing machine is suitable for high-speed production of high-speed production. For smaller batches of wool fabric printing, it must be designed. Drawings, making nets and other processes, not only processing time, but also the cost is not low. At the same time, general printing companies do not have the conditions for finishing wool fabrics. This limits the production of printed wool fabrics. (2) Fabric expensive: As the object of the printing process, the wool fabric is obviously much more expensive than other fabrics. In the screen printing process, to achieve the accuracy of the multi-color pattern of the flowers, it may cause fabric waste up to 5 meters, this situation is very obvious in the high-speed screen printing machine. In more complex printing technology, such as discharge printing process. Therefore, the waste in processing coupled with the small batch size makes it difficult to increase the output of printed wool fabrics.

However, after all, the market demand for printed wool fabrics has existed, especially with the rapid development of the domestic economy and the booming of the high-end fashion industry, which has brought great opportunities for wool printing. A best solution to the above problem is to use digital jet printing technology.

First, wool fabric digital jet printing fabric preparation

Chlorination has a very important role in the quality of jet printing before fabric printing. Chlorination can not only increase the depth of the printing color, improve the uniformity of the printing and the vividness of the printing pattern, but also increase the sharpness of the pattern due to the shrinkage prevention effect brought by chlorination and prevent the deformation of the pattern in the subsequent processing.

The chlorination of wool can be continuously processed by a top or continuously processed by a cloth, such as Kroy Unshrinkable Wool Ltd. The continuous production, but the printing company and even the majority of wool textile dyeing and finishing enterprises do not have such conditions. In addition, chlorine dioxide is used as the interstitial processing of sodium dichloroisocyanurate (DCCA). Regardless of the method, chlorination destroys the flake structure on the wool surface, increases the hydrophilicity of the wool surface, improves the spreading uniformity of the colorant or jet ink on the surface of the wool, and improves the dye on the wool during the steaming process. The dyeing rate and the amount of dyeing. Chlorination is generally performed under acidic conditions, and complex chemical reactions such as the oxidation of proline, the formation of N-chloramine, the cleavage of peptide bonds, and the like have occurred. These chemical reactions produce a number of strong anionic groups, such as R-SO-3, R-SHJ-3, R-COO- and polar groups R-SH, R-NHZ, accompanied by disulfide bonds and peptides. Broken key. The chlorination treatment needs to be well controlled; otherwise, the wool fabric will be seriously yellowed. Style destruction, strong damage. The fabrics that require a particularly bright or white color may be bleached and may be treated with oxidation or reduction.

After the chlorination of the wool fabric, the apparent color depth is significantly improved because the scaly layer of the wool is removed under the chlorination action, so that the polarity and the accessibility of the wool are increased, so that the wool is more easily wetted. And puffing, greatly improve the absorption capacity of the dye, making the printing color depth increased, the apparent color depth after chlorination plus bleaching has increased, because after bleaching, the fabric whiteness increases, is conducive to light reflection, This will increase the K/S value. From the above test results, it can be seen that the wool fabric can effectively increase the apparent color depth after the chlorination bleaching of the fabric before the pretreatment.

Second, wool fabric digital inkjet printing ink

The ink used for digital jet printing on wool fabrics is not currently available to manufacturers. It is mainly the acid inks or active inks produced by some large foreign companies. The basis for selecting inks is mainly the color depth, color light, color fastness, and adaptability to the nozzles.

Third, the development of digital jet printing pretreatment process for wool fabrics

Pre-treatment process: Modulation slurry one padding one drying one roll

(1) Selection of paste

In the pre-treatment component, in order to prevent bleeding of the dye sprayed on the fabric, maintain the sharpness of the print pattern, and obtain a certain apparent color yield, the general method is to pad or apply a certain amount of paste material on the fabric. .

(2) The choice of acid releasing agent

After adding different acid releasing agents, the sharpness did not change significantly, and the apparent color depth increased slightly.

(3) The effect of moisture absorbent on the printing effect

Adding urea and other moisture absorbers to the pretreatment agent can play a role in moisturizing the printed fabric during steaming and promoting the expansion of the fiber, which is conducive to the diffusion of the dye from the slurry into the fiber. It can be seen from Figure 1 that for the wool fabric The change of the concentration of the moisture absorber has a significant effect on the apparent color depths of the four color printings of C (cyan), M (magenta), Y (yellow), and K (black), thereby increasing the color depth and vividness when the urea concentration is reached. When it is increased to a certain degree, the print definition is reduced.

(4) Impact of rolling excess rate

From the above test results, we can see that the change of the rolling allowance rate within a certain range has no obvious effect on the depth of color of the printing table.

Fourth, the digital jet printing process of wool fabrics

Wool fabrics with printing processing requirements, in addition to wool sweaters and a small amount of woollen Nerong, most of the lightweight high-grade worsted fabrics, such as vain, women's clothing, pipa and so on. The design of the pattern on the computer and the jet printing by the computer are required to complete the process of processing the entire printed wool fabric. The general process flow is as follows: raw repair a singeing a (single tank cook it) (light shrinking velvet) a wash it a cook it chlorination a bleaching a water absorption a drying a spray printing a steaming a wash it a water absorption Dry one in the inspection of a repair hair brushing a hair and a steaming it is a finished product.

V. Conclusion

(l) Digital jet printing is suitable for high-grade wool fabric printing products in small quantities. Exquisite patterns. A strong and sexy request is an important direction for the development of digital printing technology in the future.

(2) As a fabric for digital jet printing of wool fabrics, chlorination can significantly increase the color depth, vividness and sharpness of the print pattern.

(3) Paste and hygroscopic agent in the pretreatment process. Factors such as acid release agents have a significant impact on the effect of jet printing. The processing of jet printing products for wool fabrics should also be considered in conjunction with the entire dyeing and finishing process to obtain good printing results without affecting the high grades of wool fabrics. style.

Source: Lianhua embroidery network