Synthesis of Self-Crosslinkable Water-Borne Pressure Sensitive Adhesives

• Published in: Macromolecular reaction engineering 2013-10, Vol.7 (10), p.484-492
• Main Authors: Trevino, María Esther, Dube, Marc Arnold
• Format: Article
• Language: English
• Subjects: acrylic latex; Adhesives; crosslink; emulsion polymerization; pressure sensitive adhesives; Shear strength
• ISSN: 1862-832X; 1862-8338
• DOI: 10.1002/mren.201300100

Self‐crosslinkable acrylic pressure‐sensitive adhesives (PSAs) functionalized with 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (TMI) are prepared by starved, seeded semi‐batch emulsion polymerization. n‐Dodecanethiol is used as a chain transfer agent (CTA) and EF‐800 as an anionic surfactant. A three‐level factorial design (32) is performed by varying the TMI and CTA concentrations. Increasing the TMI decreases the rate of polymerization. Nonetheless, high monomer conversions and zero coagulum are observed at the end of all reactions. The latexes are used to prepare PSA films for the evaluation of tack, peel strength, and shear strength. Crosslinking reactions caused by the isocyanate groups of TMI lead to films with very high gel content, even in cases where the CTA concentration is high. As a result, shear strength is greatly improved. The same films preserve sufficient tack but display low peel strength. Empirical models of the tack and peel strength data indicate that TMI has a significant effect on these properties. Self‐crosslinking pressure sensitive adhesives films can be produced using acrylic monomers and 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (TMI) via emulsion polymerization. The isocyanate groups in the TMI are protected from water within the polymer particles and react at room temperature during film formation to provide a continuous gel structure conducive to improved cohesive properties.