Apparatus for producing a foamed polystyrene sheet having a density gradient decreasing from the external surfaces inwardly
US4009976A · kind A · utility
15Cited by
7References
2Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Nov 21, 1974 |
| Grant date | Mar 1, 1977 |
| Priority date | — |
| Expiry date | Nov 21, 1994 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29L2023/00
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
Polystyrene foam is extruded upwardly as a tube into a cooling media of boiling water, both the interior and exterior surfaces of the cylindrically shaped extrudate passing through a bath of boiling water of variable depth. The polystyrene foam extrudate produced by such a method has a high density at the interior and exterior surfaces, with the density progressively decreasing from these surfaces toward the center core of the extrudate.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.