Study on ethanol resistance stability and adhesion properties of polyacrylate latex for PE or BOPP film inks

Waterborne inks based on the polyacrylate latex typically suffer from poor ethanol resistance and low adhesion on the PE or BOPP films. In this contribution, self-crosslinkable polyacrylate latex binders with core-shell structure and diacetone acrylamide (DAAM)/adipic acid dihydrazide (ADH) crosslinking agent for the application in the PE (polyethylene) or BOPP (Biaxially oriented polypropylene) film inks were synthesized. The effect of DAAM distribution in latex particles on ethanol resistance stability and the adhesion on the PE and BOPP thin films of the latexes and the corresponding inks was studied. Also, two functional monomers, isobornyl acrylate (IBOA) and acrylamide (AM) were introduced into the polyacrylate, respectively, to investigate their effect on the adhesion of the latexes and the inks on the PE and BOPP films. The results demonstrated that the more DAAM distributed in the core layer of the latex particles, the better the ethanol resistance, but the weaker the initial adhesion on the BOPP and PE thin films and the lower crosslinking degree of the latexes and the relative inks. However, the difference in cross-linking degree and adhesion between the latex film with DAAM located within the shell part and that of DAAM located in the shell part keeps reducing with the prolongation of film-forming time. Thus, when half of the DAAM is in the shell layer of latex particles, the latexes and the corresponding inks possess a balanced comprehensive property. The introduction of IBOA into polyacrylate is beneficial for improving the adhesion on both the BOPP and PE films of the inks due to the reduced surface tension of the latex. However, AM is only effective on the PE film, which may be due to the structural similarity of AM to erucate amide and oleate amide contained in the PE film, improving interaction between ink and the PE film.