Fiber-based microwave bowls with selective spray coating
Methods and apparatus for vacuum forming and subsequently applying topical coatings fiber-based food containers. The slurry includes one or more of an embedded moisture barrier, vapor barrier, and oil barrier, and the topical coating comprises one or more of a vapor barrier, a moisture barrier, an oil barrier, and an oxygen barrier. For food containers having deep sidewalls, a spray coating system includes a first nozzle for applying a full cone spray pattern to the bottom surface of the container, and a second nozzle for applying a hollow cone spray pattern to the inside surfaces of the side walls.
1. A coated microwaveable bowl of the type characterized by a substantially flat, circular, bottom region bounded by a circumferential sidewall obtained by:
providing a wire mesh mold substantially the same as a desired shape of the coated microwaveable bowl;
preparing an aqueous fiber based slurry comprising at least one of hardwood virgin fiber particles and softwood virgin fiber particles;
adding an embedded moisture barrier to the aqueous fiber based slurry, where some of the embedded moisture barrier is bonded to the fiber particles;
immersing the mold in the aqueous fiber based slurry;
drawing a vacuum across the mold within the aqueous fiber based slurry until a desired thickness of fiber particles accumulates at a surface of the mold;
removing the accumulated fiber particles from the mold;
drying and pressing the accumulated fiber particles in a press to thereby form the microwaveable bowl;
where the microwaveable bowl comprises a substantially flat, circular, bottom region bounded by a circumferential sidewall;
transferring the microwaveable bowl from the press to a coating station; and
applying, at the coating station, a topical oil barrier layer to at least a portion of the microwaveable bowl to form the coated microwaveable bowl, wherein the topical oil barrier layer comprises solids in a water solution, the solids including at one of acrylate, rice bran wax, pectin, pea protein, and liquid ammonium.
2. The coated microwaveable bowl of claim 1 , wherein the embedded moisture barrier comprises 2%-5% alkyl ketene dimer (AKD).
3. The coated microwaveable bowl of claim 1 , further comprising: adding a dry strength additive to the slurry.
4. The coated microwaveable bowl of claim 3 , wherein the dry strength additive comprises 0.5%-4.5% starch.
5. The coated microwaveable bowl of claim 1 , wherein the topical oil barrier layer comprises about 27.5% solids in a water solution.
6. The coated microwaveable bowl of claim 5 , wherein the solids comprise a tackiness component and an emulsifier.