Time-efficient process for making expanded polymeric products with multipass expansion of polystyrene bead

US5114640A · kind A · utility

Assignee

• BASF SE

Inventors

• William H. Harclerode · Ewing, US
• John C. Knutsen · Highland Park, US
• Barry J. Pekich · Bridgeton, US
• John V. Wiman · Morristown, US
• John Charles Voss · Redwood City, US

Key dates

• Filing date: Oct 15, 1991
• Grant date: May 19, 1992
• Expiry date: Oct 15, 2011

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S264/15
• WIPO field: Other special machines
• WIPO sector: Mechanical engineering

Abstract

A method for making low density (0.8-1.1 lb./cu.ft.) expanded polymeric products uses blowing agent in an amount of any from 2 to 4.4 weight percent and aging periods of from 1 to 80 hours after each expansion step. The process uses 2 to 5 expansion steps and a polymer having a particular polydispersity, weight average molecular weight and M.sub.z :M.sub.n, this polymer having a greater expandability than conventional polymers. The process requires only about half of the amount of blowing currently being used in commercially viable processes for making expanded polystyrene products. The process can be used with or without a molding step.