Analysis of Digital Printing Process of High-grade Wool Textile
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Small batch size: As a high-end apparel fabric, printed wool fabrics are mainly produced in response to the needs of fashionable apparel, and the pattern patterns vary widely to reflect the individual requirements of small-batch production of apparel. At present, the most advanced screen printing machine is suitable for the high-speed operation of high-volume production. For the printing of wool fabrics in small batches, it has to go through the process of pattern design, drafting, and screen making. Not only the processing time is long, but the cost is also high. Not low. At the same time, general printing companies do not have the conditions for finishing and processing wool fabrics. This limits the production of printed wool fabrics.
Fabric is expensive: As the object of printing process, wool fabric is obviously much more expensive than other fabrics. In the screen printing process, to achieve the accuracy of multi-color pattern registration, it is possible to waste up to 5 meters of fabric. This situation is very obvious on the high-speed screen printing machine. It is more serious in complex printing techniques, such as discharge printing. Therefore, the waste in processing and the small batch size make it difficult to increase the output of printed wool fabrics.
However, the market demand for printed wool fabrics exists after all, especially with the rapid development of the domestic economy and the booming high-end fashion industry, which brings good opportunities for wool printing. In view of the above problems, one of the best solutions is to use digital jet printing technology.
1. Fabric preparation for digital jet printing of wool fabric
In the fabric preparation before printing, chlorination plays a very important role in the quality of 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 improve the definition of the pattern due to the shrink-proof effect brought by the chlorination, and prevent the deformation of the pattern in the subsequent processing.
The chlorination of wool can be processed by continuous topping or continuous processing of piece cloth, such as the continuous production of Kroy Unshrinkable Wool Ltd., but printing companies and even most wool textile dyeing and finishing companies do not have such conditions. The other method is to use the chlorine releasing agent sodium dichloroisocyanurate for intermittent processing. Regardless of the method, chlorination destroys the scale structure of the wool surface, increases the hydrophilicity of the wool surface, improves the spreading uniformity of the color paste or jet ink on the wool surface, and improves the dye on the wool during the steaming process. The dye uptake rate and amount of dye uptake. Chlorination is generally carried out under acidic conditions, and complex chemical reactions have occurred, such as the oxidation of tyrosine, the formation of N-chloramine, the cleavage of peptide bonds, and so on. These chemical reactions produced many strong anionic groups, which were accompanied by the rupture of disulfide bonds and peptide bonds. The chlorination treatment needs to be well controlled, otherwise it will cause the wool fabric to become yellowish. Destroyed style and impaired strength. The fabrics that require particularly bright colors or white ground can be bleached, and can be treated by oxidation or a combination of reduction methods.
After chlorination of wool fabrics, the apparent color depth is significantly increased. The reason is: under the action of chlorination, the scale layer on the surface of the wool can be removed, and the polarity and accessibility of the wool can be increased, so that the wool can be wetted more easily. And puffing, which greatly improves the absorption capacity of dyes, which increases the depth of the printing color. After chlorination and bleaching, the apparent color depth increases again. This is because the whiteness of the fabric background color increases after bleaching, which is beneficial to light reflection. As a result, the K/S value increases.
It can be seen from the above test results that the chlorination and bleaching of wool fabrics before pretreatment can effectively increase the apparent color depth of the printing.
2. the ink for digital jet printing on wool fabrics
Currently, there are not many manufacturers of inks for digital jet printing on wool fabrics. They are mainly acid inks or reactive inks produced by some large foreign companies. The basis for selecting inks is color depth, shade, color fastness, and adaptability to the printhead.
3. Formulation of pre-treatment process for digital jet printing of wool fabrics Pre-treatment process:
The choice of paste
In the pre-treatment components, in order to prevent the bleeding of the dye sprayed on the fabric, maintain the clarity of the sprayed pattern and obtain a certain amount of apparent color, the general method is to pad or scrape a certain amount of paste material on the fabric .
Choice of acid release agent
After adding different acid release agents, the clarity did not change significantly, and the apparent color depth increased slightly.
The influence of moisture absorbent on the printing effect
The addition of moisture absorbents such as urea to the pretreatment agent can play the role of moisturizing the printed fabric and promoting the expansion of the fiber during steaming, which is conducive to the diffusion of the dye from the slurry to the fiber. It can be seen from Figure 1 that for wool fabrics , The change of moisture absorbent concentration has a significant impact on the apparent color depth of C, M, Y, K four-color printing, thereby increasing the color depth and vividness. When the urea concentration increases to a certain level, the printing clarity is reduced. .
The influence of the margin rate
From the above test results, it can be seen that the change in the reduction ratio within a certain range has no obvious effect on the apparent color depth of the print.
4.the process flow of digital jet printing on wool fabrics
Except for woolen sweaters and a small amount of woolen woolen fabrics, most of the wool fabrics that require printing processing are light and thin high-end worsted fabrics, such as Fanli, women's clothing, and whistle. In addition to completing the design of the pattern on the computer and completing the jet printing under the control of the computer, the wool worsted dyeing and finishing plant needs to cooperate to complete the processing process of the entire printed wool fabric. The general process flow is as follows: raw and repair-singeing--washing-cooking-chlorination-bleaching-water absorption-drying-printing-steaming-washing-water absorption ——Drying——Inspection——Mature repair——Brushing——Shearing——Steaming——Finished product.
Digital jet printing is suitable for small batches of high-end wool fabric printing products. The pattern is exquisite. This strong requirement is an important direction for the development of digital printing technology in the future.
As a fabric preparation for digital jet printing of wool fabrics, chlorination treatment can significantly improve the color depth, vividness and clarity of the jet printing patterns.
Paste and moisture absorbent in the pre-treatment process. Factors such as acid release agents have a significant impact on the spray printing effect. The spray printing product processing of wool fabrics should also be considered in conjunction with the entire dyeing and finishing process to obtain a good printing effect without affecting the high-end wool fabrics style.
Zhengzhou New Century Digital Technology Co., Ltd.,- (Fedar Printer:www.fedar.com.cn)is a high-tech enterprise specializing in research, manufacture, sale and service of sublimation printer，digital textile printer ,inkjet heat transfer printing machine and related consumables.
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