With the continuous development of my country’s economy, my country has become a major wool textile producer in the world. In recent years, the annual import of wool has been over 300,000 tons, costing more than US$1 billion, of which 200,000 tons of Australian wool, accounting for about 30% of the country’s total wool production. These wool products are exported in a very small amount, while the amount of wool fabrics imported has been greater than the export volume for many years. It can be seen from this that my country has become a major consumer of wool products. However, in the domestic market, consumers can hardly see other printed wool textile products except for some printed sweaters. In fact, according to the survey by the former International Wool Bureau and CSIRO, the Australian Federal Scientific and Industrial Research Organization, the output of printed wool fabrics accounts for about % of the total wool product output, which is obviously incomparable to the printing processing volume of other textiles.
The reasons for this situation are complex, but they are nothing more than the following aspects:
(1) Small batch size: As high-end clothing fabrics, printed wool fabrics are mainly produced in response to the needs of fashion clothing. The pattern changes a lot to reflect the personalized requirements of small-scale production fashion. Currently, advanced screen printing machines are suitable for high-speed operation with high output production. For small batches of wool fabric printing, they must be patterned. The process of tracing, network making and other processes not only have a long processing time, but also has also a low cost. At the same time, general printing companies do not have the conditions for post-organization and processing of wool fabrics. This limits the production of printed wool fabrics.
(2) Fabric expensive: As the object of printing processing, wool fabrics are obviously much more expensive than other fabrics. In screen printing processing, achieving multi-color patterns of flower accuracy may cause waste of fabrics as large as 5 meters. This situation is very obvious in high-speed screen printing machines. It is even more serious in complex printing techniques, such as in drawing and dyeing printing processing. Therefore, the waste in processing and the small batch volume 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 rise of the high-end fashion industry, which has brought good opportunities for wool printing. A good solution to the above problems is to use digital jet printing technology.
1. Fabric preparation for digital jet printing of wool fabric
In fabric preparation before printing, chlorination plays a very important role in the quality of the printing. Chlorination not only increases the depth of the printing color, improves the uniformity of the printing print and brightness of the printing print pattern, but also improves the clarity of the pattern and prevents the deformation of the pattern during subsequent processing due to the anti-shrinkage effect of chlorination.
The chlorination of wool can be continuously processed by wool strips or continuous processed by mattresses, such as Kroy Unshrinkable Wool Ltd. but printing companies and even most wool textile dyeing and finishing companies do not meet such conditions. In addition, the method is to use the chlorine release agent sodium dichloroisocyanurate (DCCA) to interstitial processing. Regardless of the method, chlorination destroys the wool surfaceThe scale structure increases the hydrophilicity of the wool surface, improves the spread uniformity of color paste or jet ink on the wool surface, and improves the dyeing rate and amount of dyeing on the wool during the evaporation process. The chlorination treatment is generally carried out under acidic conditions, and complex chemical reactions occur, such as the oxidation reaction of crosinine, the formation reaction of N-chloramine, the peptide bond rupture reaction, etc. These chemical reactions produce many 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 Breakage of bonds. The chlorination treatment needs to be well controlled, otherwise it will cause severe yellowing of the wool fabric. Destruction of style and damage to strength. Fabrics that require particularly bright colors or white color requirements can be bleached and can be treated with oxidation or combined with reduction methods.
After chlorination of wool fabrics, the apparent color depth is significantly increased. The reason is that under chlorination, the scale layer on the surface of the wool can be removed, increasing the polarity and accessibility of the wool, thereby making the Wool is more likely to soak and puff, greatly improving the absorption capacity of dye, increasing the printing color depth, and increasing the apparent color depth after chlorination and bleaching. This is because after bleaching, the whiteness of the fabric base color increases, and It is conducive to light reflection, thereby increasing the K/S value. From the above test results, it can be seen that wool fabrics can effectively increase the apparent color depth of the printed fabrics after chlorination and bleaching before pretreatment.
2. Ink for digital jet printing of wool fabrics
There are not many manufacturers currently used for digital jet printing of wool fabrics. It is mainly acidic inks or reactive inks produced by some large foreign companies. The basis for choosing inks is mainly color depth, color light, color fastness and its adaptability to the nozzle.
I. Preparation of pretreatment process for digital jet printing of wool fabric
Pretreatment process: preparation of slurry, dipping, drying, and rolling
(1) Selection of paste
In the pretreatment component, in order to prevent the infiltration of dye sprayed onto the fabric, maintain the clarity of the printing pattern and obtain a certain apparent color, the general method is to dip or scrape a certain amount of paste on the fabric. substance.
(2) Selection of acid release agents
After adding different acid release agents, the clarity did not change significantly, and the apparent color depth increased slightly.
(3) Effect of moisture absorbent on printing effect
Add hygroscopic agent such as human urea to the pretreatment agent can moisturize the printed fabric during steaming and promote the expansion of fibers, which is beneficial to the The dye diffuses from the slurry to the fibers. As can be seen from Figure 1, for wool fabrics, the changes in the concentration of hygroscopic agents are used to four-color printing tables. The effect of color depth is significant, thereby increasing the color depth and brightness. When the urea concentration increases to a certain level, the printing clarity is reduced.
(4) Effect of rolling ratio
From the above test results, it can be seen that the change in rolling ratio within a certain range of the printing appearance color depth can be seen.Not obvious.
IV. Process flow of digital jet printing of wool fabrics
Wool fabrics with printing processing needs, except for wool sweaters and a small amount of coarse wool wool wool, are mostly light and thin high-end worsted fabrics, such as Fanli Is there any women’s clothes, and so on. In addition to completing the pattern design on the computer and controlling the spray printing, the wool worsted dyeing factory needs to cooperate to complete the entire process of printed wool fabrics. The general process flow is as follows: Raw repair, burning hair (boiled in a single tank) (shrinking velvet) Wash, boiling, chlorination, bleaching, absorbing water, drying, spray printing, steaming, washing, absorbing water, and baking One middle school inspection, one cooked and one brushed, one cut and one steamed, one finished product.
5. Conclusion
(l) Digital jet printing is suitable for high-end wool fabric printing products with small batch sizes. The pattern is exquisite. The requirement of strong personality is an important direction for the development of digital printing technology in the future.
(2) As a fabric preparation for digital jet printing of wool fabrics, chlorination treatment can significantly improve the color depth, brightness and clarity of the printing pattern.
(3) Paste and hygroscopic agent during pretreatment. Factors such as acid release agents have a significant impact on the printing effect. The spray printing product processing of wool fabrics should also be combined with the entire dyeing and finishing process to achieve good printing effect without affecting the high-end wool fabrics. style.
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