Aromatic poly(fluorocarbinol)s: Soluble, hydrophobic binders for inkjet formulations

Abstract

Aromatic poly(fluorocarbinol)s with molecular weights (Mn) in the range 11,000–115,000 g mol−1 have been synthesised and their potential as polymeric binders in ink formulations for deposition by continuous inkjet (CIJ) printers investigated. A small scale, proof of concept study, using a drop-on-demand inkjet printer, suggested that the three lowest molecular weight polymers (Mn = 11,500–25,200 g mol−1) could behave as very good binders in this type of application. Two of these poly(fluorocarbinol)s (Mn = 11,500 and 25,200 g mol−1) were analysed as MEK solutions, pre-deposition, using shear-flow rheology. The lower-MW material exhibited Newtonian fluid characteristics whereas the higher-MW polymer behaved as a non-Newtonian fluid. For CIJ printing, both polymers were formulated in MEK using Orasol Orange®, an ionic cobalt dye-complex, to visualise the prints and provide a charge for deflection of ink droplets. The resulting solutions were deposited successfully on a variety of different packaging substrates using a CIJ printhead, resulting in high-resolution printed code. Magnified views of the jetstream during printing showed well-defined droplet formation without any evident satellite drops. These polymeric binders showed limited adhesion to low density poly(ethylene) (LDPE) and polypropylene (PP) surfaces, but moderately good adhesion to steel and excellent adhesion to poly(ethylene terephthalate) (PET), nylon-6,6 and glass. Contact angle measurements on drawn-down films of these poly(fluorocarbinol)s showed that, despite their ready solubility in high-polarity solvents such as alcohols and ketones, poly(fluorocarbinol)s afford coatings with relatively hydrophobic surfaces (water contact angles ca. 90°). Such polymers thus appear to be excellent candidates for binders in inkjet formulations, with materials having Mn in the range 10,000 to 25,000 g mol−1 displaying properties that are very well suited to use in continuous inkjet deposition for coding and marking on an industrial scale.