Pre-expanded plastic beads based on poly-para-methylstyrene

US4459373A · kind A · utility

Assignee

• BASF SE

Inventors

• Klaus Hahn · Lampertheim, DE
• Isidoor De Grave · Monsheim, DE
• Rupert Schick · Schifferstadt, DE

Key dates

• Filing date: Sep 13, 1983
• Grant date: Jul 10, 1984
• Expiry date: Sep 13, 2003

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08J2325/00
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

The invention relates to pre-expanded plastic beads based on poly-para-methylstyrene with the following properties: PA0 (a) the bead size lies between 0.2 and 3 cm, PA0 (b) the thermal stability, measured in accordance with DIN 53,424 is above 110.degree. C., and PA0 (c) the bulk density is below 35 g/l. The corresponding expandable plastic beads are prepared through the polymerization of para-methylstyrene in an aqueous suspension with the addition of volatile organic blowing agents during or after polymerization, whereby polymerization occurs in the presence of molecular-weight-regulating substances. Typical molecular-weight-regulating substances are organic chain transfer agents with a transfer constant K between 0.1 and 50, said agents being added in amounts ranging from 0.1 percent by weight to 1 percent by weight when a yield ranging from 20 to 95 percent is reached. Oligomers of the styrene or para-methylstyrene in quantities from 0.1 percent by weight to 10 percent by weight may also be employed.