Coated polymeric films and coating solutions for use with polymeric films
View Patent ↗Polymeric film structures incorporating at least one coating comprising a cross-linked EVOH copolymer and coating solutions suitable for use on polymeric films comprising at least one EVOH copolymer and at least one cross-linker are provided. The coated films may be single or multi-layered film structures. The films may also be metallized. The coated films exhibit beneficial water vapor and oxygen transmission rates. The coated films may also exhibit the beneficial barrier characteristics under conditions of high humidity. The coated films are suitable for packaging applications. The coating solutions exhibit beneficial stability characteristics over extended time periods.
1. A method of coating a polymeric film substrate comprising: (i) coating at least one surface of the film substrate with a coating solution comprising at least one solvent which comprises water, 100 phr by weight of at least one ethylene vinyl alcohol copolymer and from about 0.1 phr to about 25 phr by weight of at least one cross-linking agent and (ii) drying the coating solution coated on the at least one surface of the substrate to remove at least a portion of the at least one solvent to provide a cross-linked coating layer on the at least one surface of the film substrate at a concentration of about 0.2 g/m 2 to about 3 g/m 2 , wherein prior to being cross-linked the at least one ethylene vinyl alcohol copolymer has: (a) a solubility in the solvent; (b) from about 80 mol % to about 95 mol % of vinyl alcohol units and from about 5 mol % to about 20 mol % of the ethylene derived units; (c) a degree of hydrolysis of about 75% to about 100%; (d) a degree of polymerization of about 300 to about 4,000 and a number average molecular weight of about 13,300 to about 400,000; (e) a viscosity of between about 3 cps and about 40 cps at 4% solids and 20° C. and a pH of 4 to 7.5; and (f) repeating units derived from ethylene and vinyl alcohol.
2. The method of claim 1 , wherein the coating solution is 100% aqueous.
3. The method of claim 1 , wherein the coating solution further comprises a cross-linking catalyst.
4. The method of claim 1 , wherein the barrier coating is present on at least one of the first and second surfaces at a concentration of from about 2 g/m 2 to about 3 g/m 2 and the barrier coating is cross-linked from about 90% to about 100%.
5. The method of claim 1 , wherein the film substrate is comprised of a material selected from the group consisting of polypropylene, copolymers of propylene, polyethylene, copolymers of ethylene, polybutene, copolymers of butene, polystyrene, polyvinyl chloride, polyesters, amorphous polyester, polyethylene terephtalate glycol, polyethylene naphthalate, and oriented nylon.
6. The method of claim 1 , wherein the film substrate is comprised of a material selected from the group consisting of oriented polyolefin film, biaxially oriented polyolefin film, cast polyolefin film, and biaxially oriented polypropylene film.
7. The method of claim 1 , wherein the film substrate is opaque.
8. The method of claim 1 , wherein the film substrate is transparent.
9. The method of claim 1 , wherein the film substrate is pigmented.
10. The method of claim 1 , wherein the film substrate of the film is comprised of at least three layers.
11. The method of claim 1 , wherein at least one layer of the film substrate is voided.
12. The method of claim 1 , wherein said film further comprises a metallized layer adjacent to the barrier coating.
13. The method of claim 12 , wherein the film has a water vapor transmission rate of about 0.03 g/m 2 /d to about 0.8 g/m 2 /d at 90% relative humidity.
14. The method of claim 1 , wherein the film has an oxygen transmission rate of about 0.02 cc/m 2 /d to about 0.8 cc/m 2 /d at 0% relative humidity.
15. The method of claim 12 , wherein the film has a water vapor transmission rate of about 0.03 g/m 2 /d to about 0.4 g/m 2 /d at 90% relative humidity and wherein the film has an oxygen transmission rate of 0.02 cc/m 2 /d to 0.2 cc/m 2 /d at 0% relative humidity.
16. The method of claim 1 , wherein the baffler coating is on the first surface of the film substrate and the second surface of the substrate comprises a functional film layer.