Polytetrafluoroethylene micor powders, their preparation and use

US5641571A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Ludwig Mayer · San Jose, US
• Kai-Uwe Tonnes · Gerolzhofen, DE
• Hermann Bladel · Emmerting, DE

Key dates

• Filing date: Oct 5, 1995
• Grant date: Jun 24, 1997
• Expiry date: Oct 5, 2015

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/2982
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

Polytetrafluoroethylene micropowders, which can contain up to about 3% by weight of comonomers, are obtained with a narrow molecular weight distribution, a narrow range of specific surface area and a primary particle size of from 150 to 250 nm by polymerization in aqueous medium using hydrogen, methane or ethane as chain transfer agent and at an availability of free radicals remaining essentially constant over the polymerization time. These micropowders are particularly suitable for preparations of polyacetals which give only small deposits in the molds during melt processing and have increased color stability.