Rotating extrusion die with spray nozzle

#This invention relates generally to the formation of shaped objects from expanded biodegradable materials, and, in particular, to an extrusion die for ultimately forming sheets of biodegradable material.

#Biodegradable materials are presently in high demand for applications in packaging materials. Commonly used polystyrene (“Styrofoam” (Trademark)), polypropylene, polyethylene, and other non-biodegradable plastic-containing packaging materials are considered detrimental to the environment and may present health hazards. The use of such non-biodegradable materials will decrease as government restrictions discourage their use in packaging applications. Indeed, in some countries in the world, the use of styrofoam (trademark) is already extremely limited by legislation. Biodegradable materials that are flexible, pliable and non-brittle are needed in a variety of packaging applications, particularly for the manufacture of shaped biodegradable containers for food packaging. For such applications, the biodegradable material must have mechanical properties that allow it to be formed into and hold the desired container shape, and be resistant to collapsing, tearing or breaking.

#Starch is an abundant, inexpensive biodegradable polymer. A variety of biodegradable based materials have been proposed for use in packaging applications. Conventional extrusion of these materials produces expanded products that are brittle, sensitive to water and unsuitable for preparation of packaging materials. Attempts to prepare biodegradable products with flexibility, pliability, resiliency, or other mechanical properties acceptable for various biodegradable packaging applications have generally focused on chemical or physio-chemical modification of starch, the use of expensive high amylose starch or mixing starch with synthetic polymers to achieve the desired properties while retaining a degree of biodegradability. A number of references relate to extrusion and to injection molding of starch-containing compositions.

#The present invention is better understood by reading the following description of non-limitative embodiments, with reference to the attached drawings wherein like parts in each of the several figures are identified by the same reference character, and which are briefly described as follows.

#FIG. 1 is a cross-sectional view of an embodiment of the invention fully assembled.

#FIG. 2 is a cross-sectional view of an embodiment of the die fully assembled with centering and flow control devices.

#It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of the inventions scope, as the invention may admit to other equally effective embodiments.

#Referring to FIG. 1, a cross-section view of an embodiment of the invention is shown. The die 1 is made up of several discrete annular members which share the same longitudinal central axis 3. A mounting plate 20 is located in the center of the die 1 and is the member to which most of the remaining parts are attached. At one end of the mounting plate 20, an extruder adapter 10 is attached for connecting the die 1 to an extruder (not shown). A backplate 11 is attached between the extruder adapter 30 and the mounting plate 20. At an end opposite to the extruder adapter 10, several spacers 100 are positioned in counter sunk holes in the mounting plate 20 at various locations equidistant from the longitudinal central axis 3. A mandrel 30 has counter sunk holes which correspond to those in the mounting plate 20. The mandrel 30 is fixed to the mounting plate 20 with the spacers 100 between, the spacers being inserted into the respective counter sunk holes. On the same side of the mounting plate 20 as the mandrel 30, a seal ring 40 is inserted into an annular spin channel 22 of the mounting plate 20. At the periphery of the mounting plate 20, the mounting plate 20 has a bearing portion 71 which extends around the seal ring 40. An end cap 80 is attached to the distal end of the bearing portion 71 of the mounting plate 20 to lock the seal ring 40 in the spin channel 22. An outer ring 50 is attached to the seal ring 40 around the outside of the mandrel 30 to form an extrusion orifice 5 between the outer ring 50 and the mandrel 30. Finally, a die wheel 90 is attached to the outer ring 50. As described more fully below, a motor and drive system drive the die wheel 90 to rotate the outer ring 50 about the mandrel 30.

#The die 1 has a port 7 which extends through a side of the extruder adapter 10 and into the flow bore 23. A hose 8 connects the port 7 to a supply vessel, not shown, which supplies a fibrous material. Inside the flow bore 23, an elbow pipe 9 is connected to the port 7. A pipe 12 extends along the longitudinal central axis 3 from the elbow pipe 9 in the flow bore 23 and through the mandrel 30. A nozzle 13 is connected to the distal end of the pipe 12 in the interior of the mandrel 30.