How to choose ink for plastic packaging bags and how to improve printing effects?

Printing on plastic packaging bags differs from printing on paper. Besides the pre-treatment mentioned earlier, another issue is the smooth surface of the film, which prevents ink penetration. While paper appears smooth, its surface is actually rough, allowing ink to penetrate, facilitating quick drying and adhesion to the paper. So, how should ink for plastic packaging bag printing be selected, and how can printing quality be improved? Shunxingyuan Packaging, a professional flexible packaging manufacturer, will explain.

I. Factors to Consider When Choosing Ink

1. Heat Distortion Temperature and Heat Resistance

When choosing drying inks, consider whether the maximum drying temperature of the ink is compatible with the temperature the plastic can withstand.

2. Solvent Resistance

Solvents with some solubility in plastic films help the ink adhere to the film, but strong action may reduce the film's mechanical properties.

3. Plasticizers and Other Additives

Some plastic films contain plasticizers and other additives that can migrate to the surface and soften or damage the ink bond.

4. Other Factors

The rigidity, brittleness, dimensional stability, and coefficient of expansion of the plastic film all affect the durability of the ink bond.

II. How to Improve the Printing Effect of Plastic Films

Printing ink is a pasty colloid made by uniformly mixing pigments, binders, and fillers. As a viscous fluid, inks vary in properties depending on their type, including consistency, viscosity, and drying speed. Therefore, accurately understanding the composition and function of ink components is crucial for adjusting ink properties and improving film printing quality.

1. Pigments

Pigments include pigments and dyes. The colored materials used in printing inks are usually pigments, although some dyes are also used. They are extremely fine colored substances. Pigments are insoluble in water and binders, mostly suspended in solution; dyes are generally soluble in binders. The relative density, transparency, heat resistance, light resistance, and chemical resistance of the ink are all related to the pigment. Its color determines the hue of the ink; its quantity determines the concentration of the ink; its use affects the drying properties of the ink, especially for inks that primarily dry through oxidation polymerization.

2. Binders

A binder is a fluid with a certain viscosity and adhesiveness. It has multiple functions. As a pigment carrier, it mixes and binds powdery pigments and other solid particles, allowing the adhered pigments to adhere to the printed matter. The quality of the binder directly affects its gloss, abrasion resistance, and viscosity and flow.

3. Additives

Additives make printing more efficient. Commonly used additives include diluents, additives, detackifiers, anti-tack agents, and ink adjusters. The good printability and strong adhesion and dispersion of printing inks are inseparable from additives.