| 摘要 |
<p>1,168,140. Extruding polypropylene pipes. AVISUN CORP. 23 June, 1967 [28 June, 1966], No. 29017/67. Heading B5A. A method of making polypropylene piping of uniform wall thickness and with a smooth internal surface comprises extruding molten polypropylene at a constant rate through an annular die 21 having a width "W" at least 13% less than that of the desired wall thickness "T" of the finished pipe, then passing the extruded pipe through a cooled sizer 19 in contact with the die and drawing off the pipe on take-off rolls (not shown) at a constant speed. Air enters the interior of the pipe through a bore 29 in a mandrel 15 and ensures contact of the pipe exterior with the sizer interior surface. The width "W" of the die is preferably not less than 22% the desired wall thickness of the pipe and the molten polypropylene is delivered to the orifice at about 410‹ F., the sizer being maintained at about 80‹ F.</p> |
