Printing ink plays an important role in packaging application by supporting printing not only for providing information regarding the product but also helps to promote the product among the consumers. So designing of printing ink formulation is very crucial particularly in terms of choice of raw materials. In this article I am particularly focusing on the innovation in the areas of polyurethane (PU) as a printing ink raw material in solvent-based flexible packaging ink formulations.

Generally, the solvent-based flexible packaging ink formulation contains grinding resins, binder resins, pigments, solvents, additives and fillers. For the last one decade, PU has been gaining importance both as binder and grinding resin because of its compatibility with various other types of resins & lamination adhesives, its excellent pigment grinding & adhesion promotion properties towards various substrates, and most importantly the chemistry of PU allows the preparation of various tailor-made products to suit different printing applications.

For preparation of this article, patent publications published during last five years have been extensively studied to understand the recent innovation trend those are taking place in the areas of PUs for ink and in particular solvent-borne ink formulations for flexible packaging application.

Based on the patent analysis data, the active players who are continuously engaged on conducting innovation in the areas of PU for above mentioned application are found to be Toyo Ink Co Ltd, Dainippon Ink & Chem Inc, Sakata Inks Co Ltd, Sanyo Chem Ind Ltd, Hitachi Chem Co Ltd, Suzhou Ink Color Co Ltd, Suzhou Zhongya Printing Ink Co Ltd, Arakawa Chem Ind Ltd, Shanxi Inst Applied Chem, Sunchemical Corp, and a joint venture between Dow corning and Kuraray. Ink composition containing PU resins have been the prime focus of majority of the above assignees, while Hitachi and Sanyo particularly focused on PU synthesis.

As patents are filed in different regions/countries based on the business protection interest, it is interesting to see that during the last five years most players find Japan as the most preferred filing country followed by China, United States, Europe and Korea. The other reason why Japan is the most preferred filing country could be due to the fact that majority of the active players are originated from Japan.

The key technological trends are found to be use of Carbodiimide, hydroxydialkyl amine, Branched polyol, Castor oil derived PU, Acrylic PU and use of polyamine with primary and secondary groups.

The key advantages that are frequently discussed are environmental friendly application, boil and retort application, solvent resistance particularly alcohols and esters, better lamination Strength, blocking resistance and printability.

The readers, who are actively involved in this type of business, should conduct similar prior-art searches regularly to understand the recent technological advancements in this area.