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| Buckle joint |
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| Flexible sheet molding compound and method of making the same |
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| Low pressure sheet molding compounds |
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Apparatus and method for extruding ethylene polymers
| Details |
Inventors: Miller, John C.; Burnett, Archibald L.;
Assignee: Union Carbide Corporation (Danbury, CT)
Primary Examiner: Thurlow; Jeffery R.
Assistant Examiner:
Attorney, Agent or Firm: Vicari; Clement J.
A novel extruder screw having at least three segments wherein the pitch remains constant in each segment and changes abruptly from one segment to the following segment and wherein the pitch ratio divided by the depth ratio is greater than 2/3. |
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the drawing only illustrates extruder screws and mixers for purposes of practicing the method of the present invention, it will be understood that these screws are utilized in their normal environment, i.
e.
, in cooperative association with conventional frame means, a horizontally extending barrel, feed and hopper means and a drive means all of which are not shown since, as mentioned previously, they constitute well-known apparatus commercially available to the art.
Merely as illustrative, the extruder screws can be mounted in the apparatus disclosed in U.
S.
Pat.
Nos.
4,155,655 and 4,053,143.
The screw 10, as shown in FIG.
1, is a single stage screw, having a helical flight 12 of constant outside diameter and includes a screw root 14.
According to the method of the instant invention, the designated ethylene polymer is introduced into the apparatus for plastication and extrusion and enters the inlet end 16 of the extruder screw 10.
Reference numberal P.
sub.
F designates the pitch in the inlet end 16 and as will be seen from FIG.
1, the pitch decreases uniformly along the length of the extruder screw 10.
Situated adjacent to the mixing head 18 is the discharge end 20 of the extruder screw.
Reference numeral P.
sub.
D designates the pitch in the discharge end of the extruder screw 10.
Thus, and with reference to FIG.
1 of the drawing, the pitch decreases, preferably linearly, from the inlet end of the screw to the discharge end of the screw, and the decreasing pitch is substantially uniform as it proceeds from P.
sub.
F to P.
sub.
D.
On the other hand the depth D of the screw remains substantially constant throughout the length of the screw.
The specific dimensions of the screw utilized in the process of the present invention can be determined empirically, calculated using conventional equations.
Merely for purposes of illustration, the pitch P.
sub.
F can be approximately 2.
5 inches and all succeeding pitches can be linearly uniformly decreased terminating with pitch P
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Nonmetallic Processes 
