Method for producing foamed plastic hollow bodies

US6162380A · kind A · utility

Assignee

• Wella GmbH · DE

Inventors

• Udo Kohn · Darmstadt, DE
• Franz Steigerwald · Griesheim, DE

Key dates

• Filing date: May 6, 1999
• Grant date: Dec 19, 2000
• Expiry date: May 6, 2019

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B29K2105/04
• WIPO field: Other special machines
• WIPO sector: Mechanical engineering

Abstract

In the method of producing a hollow foamed plastic body from polyethylene or polypropylene by means of an extrusion blow-molding process using a single-screw extruder and a blow-molding tool, the plastic material is foamed by means of a chemical blowing agent, and a pre-molded tube blank formed from the foamed plastic material is blow-molded in the blow-molding tool. The blow-molding tool has a tool surface temperature of at least 35.degree. C. over at least one portion of the surface. A blowing agent that decomposes endothermically and provides a nucleation effect is included in a blowing-agent master batch based on high density polyethylene. The master batch has an average grain size of about 1 mm and the pre-molded tube blank is blow molded at a pressure of from 0.5 to 2.0 bar, or the pre-molded tube blank is blow-molded in an interval blow-molding process with a blow-molding pressure of from 3 to 10 bar, preferably 8 to 10 bar, in a first time slot and a blow-molding pressure of from 0.5 to 1.0 bar in a second time slot.