Preparation of acrylic resins modified with epoxy resins and their behaviors as binders of waterborne printing ink on plastic film

Polymers have low-energy surfaces and are difficult to be adhered by waterborne inks due to the higher surface tension of the waterborne inks. An approach to prepare acrylic resin used as a binder of waterborne printing ink on plastic film with excellent adhesion and water resistance is described. The epoxy resin is incorporated into the acrylic resin to enhance the molecular interactions between binder molecules in ink and surface molecules of plastic film. The binder resin is obtained by esterifying epoxy resin with methyl acrylic acid and then co-polymerizing the esterification product with several acrylic monomers via a free radical polymerization. The acrylic resin modified by bisphenol A epoxy resins (EP-MA-AR) shows significant enhancement over the acrylic resin without modification (AR) in adhesion between ink and polyethylene terephthalate (PET) film surface and as well water resistance performance. N-Hydroxymethyl acrylamide (NHMA) is introduced into the synthesis recipe to further enhance the interactions between the polymer chains in ink and the polar groups on the surface of non-polar polypropylene(PP) film caused by the corona discharge treatment and improves the adhesion between ink on and surface of PP film dramatically, whatever using AR or EP-MA-AR as binder. The adhesion between ink and PET film surface is also further improved by this method. The water resistance of AR and EPMA-AR is also greatly improved under the appropriate content of NHMA. Two Tgs appear on the DSC curve of EP-MA-AR, suggesting the separated status of the epoxy modified acrylic chains and the acrylic chains without modification in EP-MA-AR. The experimental data of waterborne ink on PET and PP indicate the EP-MA-AR resin prepared in this way is an applicable binder of waterborne ink on plastic film.