Multi-functional barrier coating for molded fiber containers
Coating compositions are disclosed that can be applied to at least a food-facing surface of a molded fiber container to make the coated container suitable for applications involving long term storage of a dry or frozen food item combined with short term contact with the food item in a liquid or moist state. The coating compositions include carboxylated polyvinyl alcohol copolymer and a crosslinking resin that is epichlorohydrin-based and/or azetidinium-functionalized. The compositions can also include clay particles or other suitable fillers. After crosslinking and drying, the compositions form a thermoset barrier coating in which the polyvinyl alcohol is bonded to the crosslinker by a plurality of function groups including ester functional groups.
1. A liquid coating composition, comprising:
a carboxylated polyvinyl alcohol (PVOH) copolymer;
an epichlorohydrin-based crosslinking resin; and
clay particles dispersed throughout the coating composition;
wherein the carboxylated PVOH copolymer, the crosslinking resin, and the clay particles together account for at least 90% of a dry solids content of the composition, and
wherein the composition consists essentially of the carboxylated PVOH copolymer, the crosslinking resin, and the clay particles.
2. The composition of claim 1 , wherein the carboxylated PVOH copolymer, the crosslinking resin, and the clay particles together account for at least 95% of the dry solids content of the composition.
3. The composition of claim 1 , wherein the composition consists of the carboxylated PVOH copolymer, the crosslinking resin, and the clay particles.
4. The composition of claim 1 , wherein a solids ratio of the carboxylated PVOH copolymer to the crosslinking resin is in a range from 4:1 to 9:1.
5. The composition of claim 4 , wherein the solids ratio is substantially 6:1.
6. A method, comprising:
providing a molded fiber container adapted for holding food, the container having a container wall having a first surface for facing the food;
applying the liquid coating composition of claim 1 to the container to provide a coating on a first surface area; and
drying the coating.
7. A liquid coating composition, comprising:
a carboxylated polyvinyl alcohol (PVOH) copolymer;
an azetidinium-functionalized crosslinking resin; and
clay particles dispersed throughout the coating composition;
wherein the carboxylated PVOH copolymer, the crosslinking resin, and the clay particles together account for at least 90% of a dry solids content of the composition, and
wherein the composition consists essentially of the carboxylated PVOH copolymer, the crosslinking resin, and the clay particles.
8. The composition of claim 7 , wherein the carboxylated PVOH copolymer, the crosslinking resin, and the clay particles together account for at least 95% of the dry solids content of the composition.
9. The composition of claim 7 , wherein the composition consists of the carboxylated PVOH copolymer, the crosslinking resin, and the clay particles.
10. The composition of claim 7 , wherein a solids ratio of the carboxylated PVOH copolymer to the crosslinking resin is in a range from 4:1 to 9:1.
11. The composition of claim 10 , wherein the solids ratio is substantially 6:1.
12. A method, comprising:
providing a molded fiber container adapted for holding food, the container having a container wall having a first surface for facing the food; and
applying the liquid coating of claim 7 to the container to provide a coating on the first surface; and
drying the coating.