Method and system for forming low-density polymer foam article
US5985190A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 28, 1998 |
| Grant date | Nov 16, 1999 |
| Priority date | — |
| Expiry date | Apr 28, 2018 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29K2995/0041
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A crystalline polymer resin, such as poly(ethylene terephthalate), is heated to melting. One or more blowing agents is selected wherein at least one of the blowing agents has a boiling point greater than the glass transition temperature for the resin and less than the forming temperature, such as the temperature of the mold used to form the useful article. The blowing agent(s) and resin are combined to create a mixture with a blowing agent concentration sufficient to produce a theoretical sheet foam density of less than 0.4 g/cm.sup.3. The mixture is cooled to a temperature approaching the freezing point of the mixture, and then extruded into a substantially uniform closed cell polymer foam sheet of density less than 0.4 g/cm.sup.3. The extruded sheet is then cooled by direct contact with a cooling surface at a surface temperature below the glass transition temperature such that the blowing agent(s) condenses and the sheet has a density of greater than 0.4 g/cm.sup.3 and a sheet crystallinity of less than 15%. An article is then formed from the cooled sheet by applying heat such that the condensed blowing agent(s) vaporizes and the article crystallizes at a density of less than 0.4…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.