Method of injection molding PVC products

• US 4,792,424 A
• Filed: 09/10/1985
• Issued: 12/20/1988
• Est. Priority Date: 01/10/1984
• Status: Expired due to Fees

• Current Assignee: Wavin BV (Orbia Advance Corporation, S.A.B. de C.V.)
• Original Assignee: Wavin BV (Orbia Advance Corporation, S.A.B. de C.V.)
• Inventors: Loman, Henricus G. M.
• Primary Examiner(s): Thurlow, Jeffery
• Assistant Examiner(s): Tentoni, Leo B.
• Application Number:
  US06/776,114
• Time in Patent Office: 1,197 Days
• Field of Search: 264/40.4, 264/328.14, 264/328.2, 264/101, 264/102, 264/174, 264/232, 264/328.17, 425/147, 425/203, 425/204, 425/205, 425/587
• US Class Current: 264/102
• CPC Class Codes: B29C 45/48 Plasticising screw and injection screw comprising two separate screws
• CPC Class Codes: B29C 45/63 Venting or degassing means

Abstract

The present disclosure is directed to a method of injection molding PVC products from powdered raw material, while employing an injection molding machine having a plasticizing unit having a rotary screw and a rotary screw and an injection unit having a screw which both rotates and reciprocates. The powdered raw material is subjected firstly to a prejellifying treatment during forced transportation through the plasticizing unit in which it is heated and brought to agglomerate in a relatively short time and the agglomerate is subjected to a vacuum after the prejellifying treatment and its introduction into the injection unit at an absolute pressure of less than 50 kPa.

Claims

1. The method of injection molding PVC products from powdered raw material while employing an injection molding machine of a two stage cascade type having an upper plasticizing double screw extruder and a lower injection apparatus having one injection screw, wherein the raw material is subjected to a prejellifying treatment during forced transportation of the powdered raw material through the upper plasticizing screw extruder unit in which it is heated and brought to an agglomerated state in a relatively short time, subjecting the plasticized material to a vacuum while passing through the lower injection unit.

2. The method of claim 1 wherein during the prejellifying the material is heated to about 140°

C.

3. The method of claim 2 wherein the vacuum is applied at the location between the end of the prejellifying treatment and the filling opening of the injection unit down to an absolute pressure of less than 50 kPa.