Alcohol-ester soluble polyurethane ink is the second generation of environmentally friendly, benzene-free and ketone-free ink promoted after alcohol-soluble polyamide ink. It mainly uses isopropanol, ethyl acetate, and acetone as solvents. Practice has proved that alcohol-ester soluble polyurethane ink has many advantages, such as easy operation, low price, stable performance indicators, bright gloss, good adhesion, and excellent heat resistance. It is currently the main ink variety in plastic flexible packaging printing.

The core technology of alcohol-soluble polyurethane ink is to introduce more urea groups and hydrogen bonds in the synthesis of polyurethane resin to ensure the compatibility of resin with alcohol solvents. The polyurethane molecular chain contains more amino esters, urea esters, hydrogen bonds, ether bonds, etc., which form joints with strong connection strength with the polar groups on the surface of plastic products such as PET and PA, and then form ideal adhesion. In the formulation system of alcohol-soluble polyurethane ink, the solvents used are mainly ethanol and a small amount of ethyl acetate. Alcohol-soluble polyurethane ink can present excellent printing adaptability, excellent substrate adhesion, freeze resistance, and heat resistance in the printing process, which can be compared with benzene-soluble chlorinated polypropylene ink.

Waterborne polyurethane ink is another major product newly launched in the polyurethane ink family. Compared with waterborne acrylic resin ink and epoxy resin ink, waterborne polyurethane ink has better wear resistance, water resistance, chemical resistance, impact resistance, flexibility, and hardness of the ink layer. It is mainly used in the rotogravure printing machine for food packaging printing of PET, PP, PE, and PVC films treated by electric spark.

The reason why the polyurethane series inks can be widely used in the soft packaging ink printing market in China mainly depends on some characteristics of polyurethane resin itself:

1. Compatibility of polyurethane resin: Polyurethane resin can be used as the core to match different auxiliary resins, such as polyketone resin, phenolic resin, chloroacetic acid ester, etc., to adjust the polyurethane ink system to show different characteristics to meet various operating needs.

2. Plasticity of polyurethane resin itself: In the synthesis process of polyurethane resin, it can be modified according to different raw materials to effectively guide the final product to have the functions we need.

The diversification of the functions of the polyurethane series inks is very consistent with the current situation and development of domestic soft packaging printing, so polyurethane ink is highly favored in the soft packaging printing industry.