Studies of Dimethyl Meta‐Isopropenylbenzyl Isocyanate (TMI) for Preparation of Ambient Cross‐linkable Latexes—Film Formation and Cross‐Linking

Single‐pack, ambient cross‐linkable acrylic latexes containing dimethyl meta‐isopropenylbenzyl isocyanate (TMI) repeat units were prepared by batch and semicontinuous emulsion polymerization processes at 40°C using methyl methacrylate (MMA) and n‐butyl acrylate (BA) as the principal comonomers and methacrylic acid (MAA) as a functional comonomer. Degree of cross‐linking and mechanical properties of films from batch latexes increased as the level of TMI increased from 0–5 wt%. Increasing latex pH (from 1–4) to 9 by adding dilute aqueous NaOH brings about an increase in degree of cross‐linking and mechanical properties of films. This effect is further enhanced by incorporation of MAA repeat units, which also give rise to physical cross‐linking through associations between MAA repeat units. Thus, by use of both TMI and MAA, a synergy is achieved in which the TMI repeat units provide for chemical cross‐linking that is accelerated by the effect of MAA repeat units, which also provide for physical cross‐linking...