Continuous process for expanding thermoplastic minipellets

Abstract From the Canadian patent

The subject invention pertains to a continuous process for expanding thermoplastic minipellets particularly, polypropylene. The minipellets are continuously expanded by continuously charging and mixing water and minipellets in a slurry tank to form a slurry which is subsequently pressurized. A blowing agent such as butane is entrained into the pressurized slurry flow, which said slurry is then heated by a heating means such as a shell and tube heat exchanger to the softening point, of the minipellets. The heated minipellets are given the time necessary for impregnation by permitting them to flow through one or more impregnation vessels. The impregnated minipellets are released through an …