Starch-based packaging material, apparatus and method for making same
Starch-based packaging material and methods for making the material are described. The starch-based packaging material can comprise layers of expanded starch with a cellulosic web disposed between the layers. The expanded starch can be formed by extruding starch with water which acts as an expanding agent and causes the starch to expand resulting in an extrudate having a density of no more than about 5 lbs/ft 3 . An apparatus and methods for post-processing the expanded starch are described wherein the expanded starch is extruded as a tube that enters a funnel and is advanced forward by forced air. The tube passes over a blade where the tube is slit and subsequently opened up into a sheet by a second supply of forced air. The sheet then exits the funnel and can be calendered as well as stacked with subsequent lamination.
1 . A packaging material comprising
a plurality of sheets of expanded starch and a cellulosic web laminated directly between two of the sheets, with starch presenting surfaces on the outside of the packaging material, wherein the cellulosic web has a thickness of no more than about 2 mm.
2 . The packaging material of claim 1 wherein the cellulosic web comprises paper towel material.
3 . The packaging material of claim 1 wherein the expanded starch has a density of no more than about 5 lbs/ft 3 .
4 . The packaging material of claim 1 wherein each of the sheets of expanded starch comprises at least about 50 wt % starch.
5 . The packaging material of claim 1 wherein the sheets of expanded starch are fluted.
6 . The packaging material of claim 1 wherein the packaging material comprises a stack of a plurality of alternating cellulosic webs between sheets of expanded starch.
7 . The packaging material of claim 1 wherein each of the sheets of expanded starch comprises at least about 50 wt % starch and from about 2 wt % to about 30 wt % polyvinyl alcohol or copolymers thereof.
8 . The packaging material of claim 1 wherein each of the sheets of expanded starch further comprises up to about 10 wt % of an elastomeric or lower melting thermoplastic polymer.
9 . The packaging material of claim 1 wherein the sheets of expanded starch include fluted and nonfluted sheets.
10 . The packaging material of claim 1 wherein the packaging material is biodegradable.
11 . The packaging material of claim 1 wherein the expanded starch is formed from melted starch.
12 . The packaging material of claim 1 wherein the sheets of expanded starch are formed by extrusion.
13 . The packaging material of claim 1 wherein the expanded starch has a density of no more than about 10 lbs/ft 3 .
14 . The packaging material of claim 1 wherein the cellulosic web has a thickness no more than about 0.8 mm.
15 . The packaging material of claim 1 wherein each of the sheets of expanded starch has a thickness from about ¼ inch to about 6 inches.
16 . The packaging material of claim 15 wherein each of the sheets of expanded starch has a width of up to about 6 feet.
17 . The packaging material of claim 2 wherein the paper towel material is embossed.
18 . A packaging material comprising
a plurality of sheets of expanded starch and a cellulosic web laminated directly between two of the sheets, with starch presenting surfaces on the outside of the packaging material, wherein the cellulosic web has a thickness of no more than about 2 mm wherein the cellulosic web comprises from about 60 wt % to about 100 wt % of cellulose fibers.
19 . The packaging material of claim 18 wherein each of the sheets of expanded starch has a thickness from about ¼ inch to about 6 inches.
20 . A packaging material comprising
a plurality of sheets of expanded starch and a cellulosic web laminated directly between two of the sheets, wherein the plurality of sheets of expanded starch comprise fluted sheets.
21 . The packaging material of claim 20 wherein outer surfaces of the packaging material comprise starch presenting surfaces.
22 . The packaging material of claim 20 wherein the plurality of sheets of expanded starch comprise fluted and nonfluted sheets.
23 . The packaging material of claim 20 wherein each sheet of the plurality of sheets of expanded starch has a thickness from about ¼ inch to about 6 inches.
24 . The packaging material of claim 20 comprising a plurality of cellulosic webs, and the plurality of sheets of expanded starch and the plurality of cellulosic webs comprise a stack of alternating cellulosic webs between sheets of expanded starch.