How to understand the important role of polyurethane resin in printing inks?

The Role of Adhesive in Ink Composition 

In the world of ink composition, the liquid component is referred to as the adhesive, while solids are known as pigments or dyes, along with various additives. The adhesive, a gel-like fluid with a certain viscosity, serves multiple purposes. Its primary role is to act as a carrier for pigments, facilitating the dispersion of pigments and making fine grinding easier. Secondly, it functions as a binding agent, fixing the pigment to the substrate's surface to display characters, images, symbols, and decorations. Lastly, the adhesive also serves as a protective film on printed matter, providing necessary shine and even safeguarding the base.

Impact of Adhesive Quality on Ink Performance 

The quality of the adhesive directly influences the performance of the ink, as it largely determines the ink's viscosity, dryness, and fluidity. To achieve high-quality ink, a high-quality adhesive is a must. The properties of ink adhesives dictate the various uses of ink, making it suitable for its properties. Resins used for plastic gravure printing inks usually include Chlorinated polypropylene (CPP resin), Polyamide resin, Polyurethane resin, etc.

Polyurethane (PU) resin: A Preferred Choice for Ink Adhesive 

For a long time, chlorinated polypropylene has dominated the gravure composite ink resin market due to its low cost and good adhesion to OPP. However, its major drawback is its reliance on toluene as the main solvent, which is not environmentally friendly. On the other hand, solvent-based polyurethane ink resin boasts of easy usage, stable performance, strong adhesion, good gloss, and excellent heat resistance. It is suitable for various printing methods, especially screen printing, plastic packaging, and laminated film.

The Rise of Polyurethane Ink adhesives

Polyurethane ink adhesives, which saw industrialization in foreign countries in the 1970s, are usually imported and used in processing in China. The demand has reached 30,000 tons. In recent years, many domestic production and research institutions have engaged in the research of polyurethane ink adhesives, achieving good results. However, the overall performance of the products still lags behind imported products. The focus of domestic research on polyurethane ink connection is to improve the overall performance of the product and develop multifunctional products.

The Composition of Polyurethane Resins Used in Inks 

The polyurethane resins used in inks are typically made of polyester/polyether polyols and isocyanates, with molecular forces of about 20,000 to 40,000. Its solvent is mainly benzene, ketone, ester, and other solvents. In the process of research and development, according to the environmental requirements of the ink factory and printing plant, ketone ester solvent or alcohol ester solvent can be used to prepare the corresponding benzene-free ink resin.