In the process of using plastisol inks, many printing manufacturers often suffer from ink discoloration, color migration, and discoloration of fabrics, causing quality problems and affecting the production and sales of products. How to avoid and solve these problems is of great significance to printing manufacturers.
First, the phenomenon of dye migration
When printing polyester and polyester/cotton fabrics, dye migration or bleeding may occur because the heating temperature of the fabrics exceeds 130 degrees Celsius, the dyes will sublimate, causing pigment dispersion. (Dye gradually changes from solid to gas). When the temperature exceeds 130 degrees Celsius (Note: Most thermosetting inks cure at around 160 degrees Celsius), the dye gradually enters the ink, causing the ink to discolor.
For example: In a red shirt (50% cotton/50% polyester) printed white ink (non-bleeding / high hiding power), the curing temperature is 160 degrees Celsius. After 12 hours, white began to turn purple.
Note: According to the adhesion of the ink and the difference in the dye, sometimes the dye migration phenomenon does not necessarily occur in 24 to 48 hours.
For directly printed and transferred inks, testing before printing the dyed fabric and sanding the fabric is very important. Due to the dyes used by certain fabrics themselves, the fabrics are easily discolored, especially when printed on cotton fabrics, and the fabrics are prevented from stacking with heat. The following tests will determine if fabric dyes will migrate:
1. Print the ink directly on fabrics that are thought to change color.
2. Use another piece of the same fabric to cover the top of the print (like sandwiches), and then spray the water mist thinly.
3, then, into the heat transfer machine, the heat press machine transferred to 95 Â°C, 5PSI pressure state.
4. Press the fabric for 4 hours. If the material is easily discolored, you will see the pattern you have printed on the upper fabric (also called Ghosting).
When printing polyester and polyester/cotton colored clothing, it is best to use high-quality, low-bleed color inks for bottoming. When printing polyester clothes, we recommend using chemical fiber white ink, but for new batches or new fabrics, it is best to try and print first. (Polyester fabrics generally bleed, and some cloths are quite bleed.)
When printing polyester fabrics (bleeding is usually quite severe), you must use chemical fiber white pulp.
Pure cotton fabrics are not easy to bleed, so when printing pure cotton fabrics, you can not use anti-bleeding ink, you can choose soft white pulp, good quality, strong hiding power and the price is relatively cheap.
Second, pigment bleeding
When some pigments are used in thermosetting inks, bleeding can occur. One of the colors will penetrate into another color, or it will penetrate into the color that covers the surface. Many of the red, orange, and yellow colors will have this condition.
Therefore, proper testing before production is a necessary condition to avoid this situation.
The following test methods can determine whether the pigment will bleed:
1. Ink layer (1): Ink that you think might be bleeding is printed on a cotton cloth and 110 mesh (43 mesh) is used.
2. The ink was cured for 30 seconds at a temperature of 110Â°C.
3. Ink layer (II): White, transparent or other color ink is covered with 110 gauze (43 mesh) on the first layer.
4. Heat treatment at 160Â°C for 2 minutes.
5. Visually measure the printed surface, if the ink color of the first layer penetrates into the second layer, causing discoloration, which indicates the problem of bleeding, and the use of non-bleed ink is selected.
The use of low-bleed color pigments to replace easily bleeding pigments is a better way to solve this problem.
Source: Guangzhou Geisha
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