High viscosity cyanoacrylate adhesive compositions, and process for their preparation
AssigneeLoctite (Ireland) Limited
InventorsDenis J. O'Sullivan, Bernard J. Bolger
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Abstract
Stable cyanoacrylate adhesive compositions having viscosities greater than about 200 centipoise are prepared by incorporating therein, as a thickening agent, a soluble acrylic polymer having a reduced viscosity of about 5 or greater, and a content of free radical polymerization initiator less than 1% by weight. These properties are obtained by subjecting the thickening agent to temperatures of about 140.degree.-180.degree. C. for about 30-180 minutes prior to incorporating it in the cyanoacrylate.
Claims10
The process for preparing an improved cyanoacrylate adhesive composition which comprises heating an acrylate polymer which has a reduced viscosity of substantially less than 5 and a content of free radical polymerization initiator of at least about 1% by weight, at a temperature of about 140.degree. to about 180.degree. centigrade and for about 30 to about 180 minutes and thereby increasing the reduced viscosity to at least about 5 and reducing the content of free radical polymerization initiator to less than about 0.5% by weight, said acrylate polymer having the repeating unit ##STR5## wherein R.sup.1 is hydrogen, ethyl or methyl and R.sup.2 is a C.sub.1 to C.sub.4 alkyl or alkenyl group;
- and dissolving a quantity of the polymer so treated into a mixture of a monomeric ester of 2-cyanoacrylic acid and about 0.0005% to about 10% by weight of an inhibitor of anionic polymerization, the quantity of polymer being sufficient to produce a cyanoacrylate adhesive composition with a viscosity between about 500 and about 20,000 centipoise.
The process for preparing a cyanoacrylate adhesive composition which comprises at least one monomeric ester of 2-cyanoacrylic acid, about 0.0005 to about 10% by weight of an inhibitor of anionic polymerization and about 1 to about 15% by weight of a polyacrylate thickener having the repeating unit ##STR7## wherein R.sup.1 is hydrogen, ethyl or methyl and R.sup.2 is a C.sub.1 to C.sub.4 alkyl or alkenyl group, the improvement comprising heating the polyacrylate thickener at a temperature of about 140.degree. to about 180.degree. centigrade and for about 30 to about 180 minutes and thereby increasing its reduced viscosity to greater than about 5 and reducing its content of free radical polymerization initiator to less than about 1% by weight, and thereafter adding said polyacrylate thickener to the adhesive composition thereby increasing the viscosity of said composition to at least about 500 centipoise.
Dependencies are inferred from the claim text.