Solution polymerization
Process features: (1) using high boiling point straight chain hydrocarbon as solvent, operating at a temperature higher than the melting point of polypropylene, all the polymers obtained are dissolved in the solvent and distributed uniformly; (2) high temperature gas extraction method is used to evaporate and remove the solvent to obtain molten polypropylene, and then extrude and granulate to obtain granular products; (3) only Kodak company in the United States is the manufacturer.
Liquid phase bulk method
The liquid-phase bulk polypropylene process is a new process developed in the middle and later stage of polypropylene production. The process came out seven years after the industrial production of polypropylene began in 1957.
To produce polypropylene by liquid phase bulk polymerization, the catalyst is directly dispersed in liquid phase propylene without any other solvent in the reaction system. The polymer is separated from liquid propylene and suspended in liquid propylene as fine particles. With the increase of reaction time, the concentration of polymer particles in liquid phase propylene increases. When the conversion of propylene reaches a certain degree, the unpolymerized propylene monomer can be recovered by flash evaporation, and the powder polypropylene product can be obtained. This is a relatively simple and advanced industrial production method of polypropylene. Liquid phase bulk process represents the new technology and level of polypropylene production in the 1980s.
