Overgrowth ghosting technology in cotton fabric printing

With domestic and foreign competition, fabric printing companies have become more cost-conscious than ever before. In order to ensure that the budget does not overrun, companies are constantly looking for lower-cost supplies and materials. A low price does not mean that the quality is poor. As an operator, it is necessary to know the constant changes in the composition and materials of the fabric. To maintain quality to a certain level, the quality of the materials to be printed must be tested and monitored on a regular basis. This is the only way to ensure that the printed products delivered can meet the needs of customers.

First, texture dye

It is usually printed on two major fabric materials: 100% cotton and 50% cotton/50% polyester. The following is the interaction between the cotton fabric dyes and the sol inks used in printing.

Pure cotton dyes are aqueous, and the dyeing process is accomplished by soaking hydrophilic (water-absorbing) cotton fibers in a water-repellent dye. The reason why 100% cotton is so commonly used in textile screen printing companies is because the fabric dye does not have the problem of ink overflow on the printed ink film. Because the dyestuffs used on cotton materials are water-soluble, the sol inks we use are often oil-based, and the dyes and inks do not melt, so they do not usually overflow.

However, it is worth our attention: In the textile industry, from printing companies to soft products suppliers, are constantly looking for ways to reduce costs in order to maintain competitiveness. Compared to the blank fabrics we buy, these cost reduction methods often bring accessories.

In order to prove this point, you can explain it through an example. The dyed 100% cotton fabric overflowed during the printing process. A company had previously printed and dyed a large amount of dark red 100% cotton fabrics, which were then printed on a cotton cloth using standard non-repellent white ink. Based on experience, printing operators believe that fabric dyes will not transfer to sol ink. However, this does not happen long after printing. The final reason for this was the use of very inexpensive water-dispersible dyes in the dyeing of fabric materials. Therefore, these dyes and sol ink films can be mixed, changing the appearance of the printed image. From a chemical point of view, water-based dyes and oil-based inks are completely immiscible, and dye transfer cannot occur. However, after some investigations and studies have found that the traditional dye transfer is not the culprit. In contrast, the printing staff finally concluded that the dye used in the fabric is heat-sensitive. In fact, the dye is sublimated from the fabric surface during drying and then mixed into the printing ink film.

In some cases, the problem is so severe that when the fabric comes out of the drying device, the printed area on the fabric is immediately detected. In the

The portion of the fabric where the effect does not appear immediately, the dye has typically partially penetrated into the printed area and subsequently spreads over the surface.

Second, prevent ghosting

Although this situation is caused by the material used. But it has triggered some very interesting issues, these related and more common printing problems - ghosting and its causes. When the spill-resistant ink film is in contact with the cotton fabric, the middle anti-spill media will push the dye out of the fabric adjacent to it, which will cause ghosting. This problem usually occurs when fabrics are placed on top of one another.

For overlapping fabrics, the elimination of gases from the fabric and the occurrence of ghosting problems occur mainly in two ways: first, when the fabrics with higher temperatures are stacked together, the spill-over medium (usually organic peroxide) The material will be released from the thermal ink film in the form of a gas, thereby discoloring the topmost thermal fabric. The second is when the surface of the cotton fabric is printed with a spill-resistant ink that has not completely dried and cured. At this time, the anti-spill components cannot completely dissolve into the ink film, so they will sublimate from the ink film and enter or exist on the surface of any other fabrics in contact therewith. As a result, the dye of the second fabric is bleached. Once the anti-spilling component produces the above ghosting problem, the fabric loses its original effect.

Another basic solution to avoid ghosting problems when using spill-resistant inks is to carefully control the printing process to minimize the thickness of the printed ink film. Thicker ink films require more heat and time to dry and cure. This is likely to be dry and hard to penetrate.

In order to obtain a thinner, more easily cured ink film, we must use a high-strength wire mesh, a minimum off-plate gap, and a minimum squeegee pressure. These parameters help to accumulate less ink and ensure that the ink is only in contact with the surface of the fabric. In this way, the contact area between the ink and the fabric is minimized and the possibility of ghosting is greatly reduced.

In general, dyes used in high-quality 100% cotton fabrics are safe and reliable, eliminating the need to print with spill-resistant inks. However, some companies have become accustomed to using anti-overflow inks on all fabrics. This is simply for ease of operation and standardization. This principle is not wrong, but if the ink film is not completely dry and solidified, ghosting may occur.

According to the many years of practice of the Edong printing factory, there is a very effective solution that uses inks that do not contain spill-resistant ingredients when printing 100% cotton fabrics, and use inks that resist spillage when printing 50/50 fabrics. If there is a problem with spillage on the cotton fabric, it can also be considered using an ink that resists spillage. The method of avoiding the use of such inferior 100% cotton fabrics is to further understand fabric manufacturers, and the fabrics are tested according to conventional methods. An effective way to detect dye quality is to print a thin layer of white sol ink that does not contain spill-resistant ingredients on the surface of the problematic 100% cotton fabric and then heat the sample. As long as the dye on the fabric is vaporized onto the ink film, transparency will immediately appear, warning you of the possibility of this problem. Then you can decide whether to use anti-spill inks or change fabric suppliers.

In short, although few 100% cotton fabric dyes will overflow, there may be a printing problem that may result in the loss of an important customer and waste. Controlling the printing process, printing with the smallest ink film thickness, conducting proper tests, and using the right products for the job all help to avoid these problems.

Source: Guangdong Printing Wang Nengyou

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