Pre-foamed particles of polypropylene resin and process for production thereof
US4379859A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 19, 1981 |
| Grant date | Apr 12, 1983 |
| Priority date | — |
| Expiry date | Nov 19, 2001 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC08J2423/00
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
Substantially non-crosslinked pre-foamed particles of a polypropylene resin, characterized by the fact that they are composed of an ethylene/propylene random copolymer or a mixture of an ethylene/propylene random copolymer with low density polyethylene and/or an ethylene/vinyl acetate copolymer as a base resin; and a process for producing pre-foamed particles of a polypropylene resin, which comprises dispersing substantially non-crosslinked particles of the polypropylene resin composed of an ethylene/propylene random copolymer or a mixture of an ethylene/propylene random copolymer with low-density polyethylene and/or an ethylene/vinyl acetate copolymer and a volatile blowing agent in water in the presence of a dispersing agent within a closed vessel; heating the dispersion to a temperature above a temperature at which the resin particles soften, thereby to impregnated the blowing agent in the resin particles; and while maintaining the pressure of the inside of the vessel higher than the vapor pressure of the blowing agent, opening one end of the vessel to release the resin particles and water simultaneously into an atmosphere kept at a lower pressure than the inside of the vessel.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.