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Abstract

There is described a multi step mini-emulsion process for preparing a hybrid acrylic/polyurethane pressure sensitive adhesive (PSA) of very high shear strength, good peel strength and/or also high moisture vapor transmission rate, the process comprising the steps of: a) forming a first aqueous mixture comprising a hydrophilic stabilizer; b) forming separately a second oil mixture comprising: i) at least one vinyl functional polyurethane (optionally prepared from an isocyanate functional monomer; at least one monol and/or at least one α,β-ethylenically unsaturated monomer ii) optionally at least one hydrocarbon polymer (such as polystyrene); and iii) at least one α,β-ethylenically unsaturated monomer (such as (meth)acrylate or acids thereof; and/or iv) option-=ally at least one hydrophobic stabilizer; where components (ii), (iii) and/or (iv) may optionally be the same; c) mixing the aqueous and oil mixtures together to form a pre-(macro) emulsion; d) generating a stable mini-emulsion there-from optionally by applying high shear to form an aqueous continuous phase and stabilized oil droplets of average diameter from about 10 to about 1000 nm, and e) polymerizing the polymer precursor(s) within the droplets, optionally in the presence of a free radical initiator; to obtain a polymer latex.

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