PREPARATION OF PRESSURE SENSITIVE ADHESIVE DISPERSIONS FROM MULTI-STAGE EMULSION POLYMERIZATION FOR APPLICATIONS OF PROTECTIVE FILMS

摘要

The invention describes a preparation process of pressure sensitive adhesives, wherein a multi-stage emulsifier-free emulsion polymerization and applications of the obtained dispersions for pressure sensitive protective films are included. At least one carboxylic acid group containing monomer is used in the first stage of emulsion polymerization. The theoretical glass transition temperatures are lower than 0° C. (for the first stage polymer), −20° C. (for the second stage polymer) and −15° C. (for the overall dispersion), respectively. The dispersion is preferably cross-linked with polyfunctional crosslinking agents, such as aziridine, isocyanate, carbodiimide and oxazoline. The adhesives obtained from the process thereof can be used for the application of protective films to reduce or eliminate ghost shadow on the protected surfaces.

主权项

1. A process for preparing a pressure sensitive adhesive dispersion, the process comprising:
1) performing a first emulsion polymerization comprising
i) forming a first-stage dispersion by polymerizing a first-stage monomer composition consisting of at least one ethylenically unsaturated monomer and at least one carboxylic acid group containing ethylenically unsaturated monomer, to form the first-stage dispersion comprising a first-stage polymer particle in an aqueous medium, such that a proportion of the carboxylic acid group containing ethylenically unsaturated monomer is at least 1.0 wt % of the first-stage monomer composition,ii) adding a chain transfer agent to the first-stage monomer composition, such that an addition amount of the chain transfer agent is 0.3-1.5 wt %, based on the weight of the first-stage monomer composition, andiii) neutralizing the first-stage dispersion with an aqueous base solution to a pH value of between 5.0 and 7.0 to form a neutralized first-stage dispersion; and 2) performing a second emulsion polymerization in the presence of the neutralized first-stage dispersion, by polymerizing a second-stage monomer composition consisting of at least one ethylenically unsaturated monomer and optionally at least one multi-ethylenically unsaturated monomer into the first-stage polymer particles to form second-stage polymer particles, and thereby obtaining a pressure sensitive adhesive dispersion,
wherein a weight ratio of the first-stage monomer composition to a total weight of the first-stage monomer composition and the second-stage monomer composition is in 5-50 wt %.