Modified overprint varnish
View Patent ↗In an embodiment, the invention comprises a thermoformable sheet which comprises a polymer layer, and a barrier layer disposed adjacent the polymer layer. The barrier layer comprises a plurality of particles coated in an adhesion promotor. The plurality of coated particles are dispersed in a barrier solution of polyvinyl alcohol.
1 . A method of forming a modified over print varnish, the method comprising:
coating a moisture resistant agent selected from talc, wax, or silicon dioxide with a fatty acid;
dispersing the coated moisture resistant agent in an over print varnish comprising a water-based emulsion of polymeric droplets;
mixing the coated moisture resistant agent and the over print varnish to form a mixture, wherein the fatty acid coating prevents a disruption of the water-based emulsion of polymeric droplets during mixing; and
drying the mixture to evaporate at least some of the water from the over print varnish to form a continuous film with the coated moisture resistant agent entrapped therein, wherein the modified over print varnish provides resistance to both oil and water transfer.
2 . The method of claim 1 , wherein the mixing step creates a heterogenous system.
3 . The method of claim 1 , wherein during the drying step, the polymer droplets coalesce into a film.
4 . The method of claim 1 , wherein the over print varnish is selected from the group consisting of an acrylic emulsion, acrylic emulsion with a thickener, and a polyvinyl acetate-polyethylene copolymer.
5 . The method of claim 1 , wherein the polymeric droplets provide a solids content between about 40% and about 60% of the total over print varnish.
6 . The method of claim 1 , wherein the polymeric droplets are liquid droplets with a size of between about 20 nm and about 200 nm.
7 . The method of claim 1 , wherein the moisture resistant agent is a plurality of particles.
8 . The method of claim 7 , wherein the plurality of particles have a flat plane.
9 . The method of claim 7 , wherein the plurality of particles are spherical particles.
10 . The method of claim 7 , wherein the plurality of particles are talc particles having a size between about 1 um and 7 um.
11 . The method of claim 1 , wherein the fatty acid coating prevents the moisture resistant agent from binding to the polymeric droplets.
12 . The method of claim 1 , wherein the moisture resistant agent is wax.
13 . The method of claim 1 , wherein the fatty acid comprises stearic acid.
14 . The method of claim 1 , further comprising drying the fatty acid coating before dispersing the coated moisture resistant agent.