Biopolymer coated fiber food service items
A biodegradable food service item is disclosed, which includes a biodegradable substrate having at least one food contact surface. This substrate is made of cellulosic fibers. The food service item also includes a coating applied over the at least one food contact surface. This coating is made up of from about 25 to about 60 weight percent of at least one biodegradable polymer, such as polyhydroxyalkanoates. A method for making the biodegradable food service item is also disclosed.
1. A biodegradable food service item comprising:
a biodegradable substrate having at least one food contact surface, wherein the substrate comprises from about 75 weight percent to about 95 weight percent cellulosic fibers on a dry basis; and
a coating applied over the at least one food contact surface,
wherein the biodegradable substrate is formed from an aqueous slurry comprising cellulosic fibers and from about 10 to about 70 weight percent of a biodegradable aqueous dispersion,
wherein the biodegradable aqueous dispersion comprises from about 25 to about 60 weight percent of polyhydroxyalkanoates, and
wherein the coating also consists of the biodegradable aqueous dispersion.
2. The biodegradable food service item of claim 1 , wherein the polyhydroxyalkanoates have a weight average molecular weight from about 50,000 to about 2.5 million Daltons.
3. The biodegradable food service item of claim 1 , wherein the biodegradable substrate comprises a biodegradable plate, cup, bowl, takeout container, straw, or eating utensil.
4. The biodegradable food service item of claim 1 , wherein the biodegradable aqueous dispersion further comprises from about 0.1 to about 2.0 weight percent of a surfactant, from about 0.1 to about 2.0 weight percent of a rheology modifier, optionally from about 0.1 to about 1.0 weight percent defoamer, optionally from about 1 to about 20% of a filler, and from about 0.001 to about 2.0 weight percent of a biocide, wherein all weight percentages are on a wet basis.
5. The biodegradable food service item of claim 1 , wherein at least a portion of the cellulosic fibers are derived from sugarcane, bagasse, wheatgrass, or recycled wood pulp.
6. The biodegradable food service item of claim 1 , wherein the coating is applied over the at least one food contact surface at a coat weight, on a dry basis, from about 5 to about 50 grams per square meter.
7. The biodegradable food service item of claim 1 , wherein the coating exhibits a Cobb water absorption value, measured according to TAPPI Standard T441, of less than 25 grams per square meter.
8. The biodegradable food service item of claim 1 , wherein the coating exhibits Kit Test grease resistance value, measured according to TAPPI Standard T559 cm-12, of greater than Kit Value 5.
9. A method for making a biodegradable food service item, the method comprising the steps of:
providing a biodegradable aqueous dispersion which comprises water and from about 25 weight percent to about 60 weight percent of polyhydroxyalkanoates;
forming a layer of an aqueous slurry over a mold, wherein the aqueous slurry comprises cellulosic fibers and from about 10 to about 70 weight percent of a biodegradable aqueous dispersion;
molding the aqueous slurry, using a combination of heat and pressure, wherein the heat and pressure from the molding step at least partially dries the slurry to form a biodegradable substrate having at least one food contact surface which comprises from about 75 weight percent to about 95 weight percent cellulosic fibers on a dry basis;
applying an amount of the biodegradable aqueous dispersion over the substrate to form a layer of the dispersion over the at least one food contact surface of the substrate; and
curing the dispersion layer so as to form a coating which also consists of the biodegradable aqueous dispersion on the at least one food contact surface of the biodegradable substrate.
10. The method of claim 9 , wherein the aqueous dispersion is spray coated over at least one surface of the molded slurry layer.
11. The method of claim 9 , wherein the slurry is molded at a temperature from about 85° C. to about 170° C. and a pressure from about 1000 psi to about 100,000 psi.
12. The method of claim 9 , wherein the slurry has a solids content from about 10 to about 85 weight percent when initially formed over the mold.
13. The method of claim 9 , wherein the aqueous dispersion has a solids content from about 25 to about 60 weight percent when applied over the slurry layer.
14. The method of claim 9 , wherein the polyhydroxyalkanoates have a weight average molecular weight from about 50,000 to about 2.5 million Daltons.