Water-Based Inks Based on a New Class of Polyester Resins, 1991 Polymers, Laminations & Coatings Conference Proceedings

A new class of water-dispersible polyester resins is finding application in waterborne gravure and flexographic printing inks. Unlike other aqueous ink systems that rely on relatively high-acid-number resins for water dispersibility, the new polyesters require no neutralizing agents, such as ammonia or amines, to maintain water dispersibility. The need to balance ink pH on the press is thus unnecessary; and odor problems associated with volatile amines, both in the pressroom and in the surrounding community, are avoided. Actual press experience has shown that these polyester systems dry faster on the substrate than many common types of waterborne inks and overprint lacquers, permitting faster press speeds or lower oven temperatures. At the same time, they exhibit rewettability on the press (cylinders, plates, anilox rolls). This unusual combination of properties is made possible by the unique chemical nature of the new resins, which can be described as linear aromatic polyesters containing sodiosulfo groups (-SO3 Na + ). Several examples of the successful use of sulfo polyesters in commercial-scale printing are described.