Process for producing expandable thermoplastic resin beads using polypropylene as nucleus
AssigneeSekisui Kaseihin Kogyo Kabushiki Kaisha
InventorsMutsuhiko Kajimura, Hideaki Sasaki
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Abstract
A process for producing expandable thermoplastic resin beads which comprises suspending in an aqueous medium 20 to 70% by weight of polypropylene resin particles and 30 to 80% by weight of a vinyl aromatic monomer such as styrene, polymerizing the vinyl aromatic monomer in the presence of a polymerization catalyst to graft the vinyl aromatic monomer onto the backbone of polypropylene and, optionally, adding a cross-linking agent, to form graft-copolymerized thermoplastic resin beads, and introducing a blowing agent into the thermoplastic resin beads. The resulting resin beads have excellent foamability and molding fusability, and a foamed shaped article having superior thermal stability can be prepared from these beads.
Claims9
A process for producing expandable thermoplastic resin beads which comprises suspending in an aqueous medium from 20 to 70% by weight of polypropylene resin particles and from 30 to 80% by weight of a vinyl aromatic monomer, polymerizing the vinyl aromatic monomer in the presence of a polymerization catalyst to graft the vinyl aromatic monomer onto the backbone of the polypropylene to form graft-copolymerized thermoplastic resin beads, and thereafter introducing a blowing agent composed of an easily volatilizable hydrocarbon or halogenated hydrocarbon into the thermoplastic resin beads.
In a process for producing expandable thermoplastic resin beads which comprises suspending in an aqueous medium containing 0.01 to 5% by weight, based on water present in the aqueous medium, of a dispersing agent selected from the group consisting of polyvinyl alcohol, methyl cellulose, calcium phosphate, magnesium pyrophosphate and calcium carbonate, from 20 to 70% by weight of polypropylene resin particles and from 30 to 80% by weight of a vinyl aromatic monomer, polymerizing the vinyl aromatic monomer in the presence of a polymerization catalyst to graft the vinyl aromatic monomer onto the backbone of the polypropylene to form graft-copolymerized thermoplastic resin beads, and thereafter introducing a blowing agent composed of an easily volatilizable hydrocarbon or halogenated hydrocarbon into the thermoplastic resin beads, the improvement comprising heating the aqueous medium to a temperature at which the vinyl aromatic monomer can be polymerized before adding the vinyl aromatic monomer and the polymerization catalyst thereto, and adding said vinyl aromatic monomer and said polymerization catalyst to the heated aqueous medium.
Dependencies are inferred from the claim text.