초록 ▼

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

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.

대표청구항 ▼

[ What is claimed is:] [1.] A method of making a hollow foamed plastic body from polyethylene in an extrusion blow-molding process, said method comprising the steps of:a) providing a blowing-agent master batch that disintegrates endothermically and provides a nucleation effect during the blow-moldin

[ What is claimed is:] [1.] A method of making a hollow foamed plastic body from polyethylene in an extrusion blow-molding process, said method comprising the steps of:a) providing a blowing-agent master batch that disintegrates endothermically and provides a nucleation effect during the blow-molding process, said blowing-agent master batch having an average grain size of about 1 mm;b) making a mixture comprising a polyethylene granulate and a portion of the blowing-agent master batch, said polyethylene granulate comprising high density polyethylene;c) extruding the mixture formed in step b) with a single-screw extruder to form a pre-molded tube blank; andd) blow molding the pre-formed tube blank at a blow-molding pressure of between 0.5 and 2.0 bar with a blow-molding tool having at least one portion of a tool surface at a tool surface temperature of at least 35.degree. C. to form the hollow foamed plastic body.