Pressure-sensitive label laminates with improved convertability and broad temperature adhesion performance
This invention is directed to an improvement of the label convertibility of all temperature pressure sensitive adhesives based on acrylic emulsion. It maintains clarity in the final finished product after drying. It offers good broad and low temperature adhesion performance on wide range of substrates. The base polymer in the all temperature pressure sensitive adhesives is an acrylic emulsion polymer. The converting improvement resides in adding a vinyl acetate homopolymer and/or copolymers that will not increase the glass transition temperature of overall PSA that do not adversely impact to low temperature adhesion. The combination of unique features of this invention offers advantages for high-speed production in pressure sensitive label and tape industries.
1 . In an all temperature acrylic emulsion based polymer pressure sensitive adhesive, the improvement which comprises:
a vinyl acetate polymer present in an amount from about 1 to 10% by weight of said pressure sensitive adhesive on a dry basis.
2 . The pressure sensitive adhesive of claim 1 wherein the acrylic emulsion based polymer is a 2-ethyl hexyl acrylate (2-EHA) homopolymer or copolymer.
3 . The pressure sensitive adhesive of claim 1 wherein the acrylic emulsion based polymer has a Tg in the range of −50° C. to −80° C.
4 . The pressure sensitive adhesive of claim 3 wherein the acrylic emulsion based polymer has polymerized units of 2-ethyl hexyl acrylate from 70% to 100%.
5 . The pressure sensitive adhesive of claim 2 wherein the acrylic emulsion based polymer has the number average particle size from 100 nm to 1000 nm.
6 . The pressure sensitive adhesive of claim 1 wherein the Tg of the vinyl acetate copolymer is from 30° C. to 70° C.
7 . The pressure sensitive adhesive of claim 6 wherein the vinyl acetate polymer is a homopolymer or copolymer containing from 50% to 100% vinyl acetate.
8 . The pressure sensitive adhesive of claim 6 wherein the vinyl acetate polymer has a number average particle size from 100 nm to 300 nm.
9 . The pressure sensitive adhesive of claim 6 wherein said vinyl acetate polymer is added in an amount from about 4% to 8% by weight of said pressure sensitive adhesive on a dry basis of polymer.
10 . The pressure sensitive adhesive of claim 1 wherein the pressure sensitive adhesive includes a tackifier dispersion from 0% to 30% by weight of said pressure sensitive adhesive on a dry basis of polymer.
11 . The pressure sensitive adhesive of claim 10 wherein the pressure sensitive adhesive includes a tackifier dispersion having a the Ring & Ball softening point from 25° C. to 90° C.
12 . The pressure sensitive adhesive of claim 10 wherein the pressure sensitive adhesive includes a tackifier dispersion based on rosin acid, rosin ester, hydrocarbon resin, terpene phenolic resin or their hybrids/blends.
13 . The pressure sensitive adhesive of claim 1 wherein the pressure sensitive adhesive includes optionally a silicone polymer from 0% to 5% by weight of said pressure sensitive adhesive on a wet basis of polymer.
14 . The pressure sensitive adhesive of claim 13 wherein the pressure sensitive adhesive includes a silicone polymer.
15 . The pressure sensitive adhesive of claim 1 wherein the insoluble fraction in THF is from 40% to 80%.