1. A method of reducing slippage of the melt at the die wall during the extrusion of polymers comprising:
- (a) heating the polymer in a vacuum oven until the polymer reaches a molten state; and
- (b) evacuating the space in the oven over the polymer.
2. The method of claim 1, wherein:
- the gas that diffuses from the polymer after said evacuation of the space over the polymer is also evacuated.
3. The method of claim 1, wherein:
- said evacuation of the space over the polymer is continued while gas diffuses from the polymer.
4. The method of claim 1, wherein:
- said polymer is maintained at a temperature of at least 190.degree. C.
5. The method of claim 1, wherein:
- said polymer is maintained under vacuum for at least 24 hours prior to extrusion.
6. A method of reducing slippage of the melt at the die wall during the extrusion of polymers using extrusion equipment including at least a hopper, a feed region, and a die including an entrance and an exit region comprising:
- (a) sealing the hopper containing the molten polymer resin; and
- (b) evacuating the space external to and surrounding at least a portion of the extrusion equipment.
7. The method of claim 6, wherein:
- said space surrounds the feed region of the extrusion system.
8. The method of claim 6, wherein:
- said space surrounds the exit region of the die.
9. A method of reducing slippage of the melt at the die wall during the extrusion of polymers using extrusion equipment including at least a hopper, a feed region, and a die including an entrance and an exit region comprising:
- (a) sealing the hopper containing the molten polymer resin; and
- (b) evacuating the vapor from the hopper after said sealing.
10. A method of reducing slippage of the melt at the die wall during the extrusion of polymers using extrusion equipment including at least a hopper, a feed region, and a die including an entrance and an exit region comprising:
- (a) sealing the space around the exit region of the die; and
- (b) evacuating said space around the exit region of said die.
11. A method of reducing slippage of the melt at the die wall during the extrusion of polymers using extrusion equipment including at least a hopper, a feed region, and a die including an entrance and an exit region comprising:
- (a) heating the polymer to obtain and maintain said polymer in a molten state;
- (b) evacuating the space over the molten polymer;
- (c) sealing the hopper containing the polymer; and
- (d) evacuating the space surrounding the extrusion equipment.
12. A method of extruding polymers using extrusion equipment including at least a hopper, a feed region, and a die including an entrance and an exit region comprising:
- (a) heating the polymer to obtain and maintain a said polymer in a molten state;
- (b) evacuating the space over the molten polymer;
- (c) extruding said molten polymer.
13. A method of extruding polymers using extrusion equipment including at least a hopper, a feed region, and a die including an entrance and an exit region comprising:
- (a) heating the polymer to obtain and maintain a said polymer in a molten state;
- (b) evacuating the space over the molten polymer;
- (c) transferring the molten polymer to the hopper in an extrusion device;
- (d) sealing the hopper containing the polymer;
- (e) evacuating the air from the hopper after the hopper is sealed; and
- (f) extruding the polymer.
14. The method of claim 13, further comprising:
- drawing a vacuum over the feed region of the extrusion system.
15. The method of claim 13, further comprising:
- drawing a vacuum over the exit region of the die.
16. The method of claim 13, further comprising:
- drawing a vacuum over the extrusion system.
17. A method of reducing slippage of the melt at the die wall during the extrusion of polymers using extrusion equipment including at least a hopper, a feed region, and a die including an entrance and an exit region comprising:
- (a) reducing the concentration of air in the molten polymer; and
- (b) minimizing the potential for air to be introduced into the extrusion system.
18. The method of claim 17, wherein:
- the potential for air to be introduced into the extrusion system is reduced by drawing a vacuum over the feed region of the extrusion system.
19. The method of claim 17, wherein:
- the potential for air to be introduced into the extrusion system is reduced by drawing a vacuum over the exit region of the die.
20. The method of claim 17, wherein: the potential for air to be introduced into the extrusion system is reduced by drawing a vacuum over the extrusion system.
