Method for preventing uncontrolled polymer flow in preform neck finish during packing and cooling stage
US6063325A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 22, 1996 |
| Grant date | May 16, 2000 |
| Priority date | — |
| Expiry date | Aug 22, 2016 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C2949/3038
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A method of reducing uncontrolled flow of a molten polymer during the packing and cooling stage of an injection molding cycle. A plurality of polymers are injected between a mold cavity and core for making a multilayer plastic article such as a preform, having an exterior layer of a first polymer and an interior layer of a second polymer. In a tapered region of the mold, a minimum width of the tapered region is selected to prevent the second polymer from developing an enhanced leading/trailing edge effect which causes the second polymer to reverse flow during the packing and cooling stage. The method is particularly useful for making preforms for blow molded containers, such as a ketchup container, having a relatively long and thin neck profile. In addition, the method maintains the interior (barrier) layer a minimum distance from the top sealing surface of the preform, in order to prevent defective heat-bonded seals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.