Process for producing pre-foamed particles of polypropylene resin
US4504601A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 29, 1983 |
| Grant date | Mar 12, 1985 |
| Priority date | — |
| Expiry date | Sep 29, 2003 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S264/09
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A process for producing pre-foamed particles of a polypropylene resin which comprises expanding original pre-foamed particles of a polypropylene resin, said original pre-foamed particles having the following relation EQU 2<E.sup.1/3 .times.n.sup.1/2 <45 PA1 wherein E is the expansion ratio of the original pre-foamed particles, and n is the number of cells per mm.sup.2 of the cross section of the original pre-foamed particles, by (1) imparting expanding ability to the original pre-foamed particles and then heating them with a heated gas to the heat distortion temperature of the base resin of the pre-foamed particles or a higher temperature or (2) heating the original pre-foamed particles with steam to the heat distortion temperature of the base resin of the particles or a higher temperature with or without imparting expanding ability thereto, whereby pre-foamed particles having an expansion ratio higher than the original expansion ratio E are obtained.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.