Extruder screw for use in foam plastic extruder
US5297948A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 24, 1992 |
| Grant date | Mar 29, 1994 |
| Priority date | — |
| Expiry date | Sep 24, 2012 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29K2105/16
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
In the production of foamed plastic articles using a screw extruder, it is known to introduce a gaseous foaming agent into the plastic while the latter is passing through the extruder. It has been found that a foamed thermoplastic with pores or cells of uniform size and distribution can be produced by passing a gaseous foaming agent, e.g. nitrogen gas through a central passage extending substantially the entire length of the extruder screw, discharging the agent into the thermoplastic proximate the discharge end of the extruder, and mixing the foaming agent with the plastic immediately prior to discharge of the mixture into a mold.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.