Single Screw Extruder Of Polymers
A process is provided for single screw extruder of a composition or masterbatch comprising a polymer and an antistatic agent wherein the feed zone temperature is maintained below 385° F. in order to allow processability of the composition.
This twins screw extruder is concerned with compositions and masterbatches of selected antistatic agents in polymers, preferably certain copolyesters based on terephthalic acid, naphthalenedicarboxylic acid, and/or 1,4-cyclohexanedicarboxylic acid and on the blending of these masterbatches with the same or other homo- or copolyesters to provide films, sheeting, and thermoformed articles having antistatic properties.
Examples
In the examples, the following is to be noted.
Larostat HTS 905A antistat is a quaternary ammonium sulfonate salt, sold under the registered trademark of BASF Corporation.
Eastar PETG 6763 is a copolyester based on terephthalic acid, ethylene glycol, and 1,4-cyclohexanedimethanol, produced and sold by Eastman Chemical Company.
The copolyester is PETG containing 12 mole % CHDM, 88 mole % ethylene glycol, and 100 mole % terephthalic acid.
Example 1
A masterbatch consisting of 3.5 weight percent Larostat HTS 905A antistat and a polyethylene terephthalate copolyester containing 12 mole percent CHDM was prepared using a 30-mm Werner & Pfleiderer twin extruder. A 50/50 pellet blend consisting of the masterbatch and PETG 6763 was extruded into 20-mil sheet using a 1.5-inch Killion screw extruder. In order to generate a sheet sample for subsequent of antistatic properties, if feeding problems developed, then the extruder was force fed. Consequently, the extruder amps did not provide a good indication of the extrusion performance. Alternatively, the performance was indicated by higher transition zone pressure and melt pressure at the end of the sheet production extruder.
Example 2
A masterbatch consisting of 5.3 weight percent Larostat HTS 905A antistat and a polyethylene terephthalate copolyester containing 12 mole percent CHDM was prepared using a 30-mm Werner & Pfleiderer twin screw extruder. The masterbatch was then mixed via pellet-pellet blending with Eastar PETG 6763 and subsequently extruded into 20-mil sheet using a 1.5-inch Killion single screw extruder. The level of masterbatch, the extrusion conditions, and the resulting extrusion performance as indicated by the extruder amps, output, and exit melt pressure are given in Table 2.1. The data shows that consistently the amps, output, and melt pressure are higher indicating better feeding during extrusion when the feed zone temperature is 300° F. and 365° F. while there is a dramatic decrease in amps, output, and melt pressure when the feed zone temperature is 430° F. Thus, feeding during single screw extruder is improved by using feed zone temperatures of 300° F. and 365° F.