Two component polyurethane system for casting expanded polytetrafluoroethylene
US4814412A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 17, 1987 |
| Grant date | Mar 21, 1989 |
| Priority date | — |
| Expiry date | Dec 17, 2007 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/249958
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
The present invention provides a two component polyurethane system with excellent wetting properties for casting a supported or unsupported, expanded polytetrafluoroethylene structure. It consists essentially of a polyisocyanate component having an isocyanate functionality of 2.2 or less and a polyol blend having an overall hydroxyl functionality of 2.2 or less and a viscosity of less than 500 cps., preferably 200 cps. or less. The polyol blend consists essentially of (i) a linear polyether or polyester (about 200-2500 molecular weight), (ii) a diol or triol (less than 200 molecular weight), and (iii) a catalyst in an amount sufficient to provide gelling at greater than 2 minutes and less than 10 minutes. The isocyanate to hydroxyl ratio is between 0.95:1 and 1.10:1. In some cases, it is desirable to include selected siloxane surfactants when polyol blends with the higher viscosities, i.e., about 200-500 cps., are used. The casting system is useful for making membrane filters.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.