Process for injection molding foam synthetic resin materials involving introduction of the expansion agent into the metering zone between injection molding steps

Abstract

Abstract THE PRESENT DISCLOSURE IS DIRECTED TO A METHOD FOR THE PRODUCTION OF FOAMED MOLDED ARTICLES BY INJECTION MOLDING A HEAT-PLASTICATED MIXTURE OF A THERMOPLASTIC SYNTHETIC MATERIAL WITH A LOW-BOILING LIQUID OR GASEOUS EXPANDING AGENT IN AN INJECTION DEVICE CONTAINING A FEED ZONE, A ZONE OF INCREASING PRESSURE AND A METERING ZONE, WHEREIN A FLUID PREMIX OF A THERMOPLASTIC SYNTHETIC MATERIAL IS INTRODUCED INTO THE FEED ZONE OF THE SCREW BARREL CHAMBER OF AN INJECTION MOLDING DEVICE WHERE IT IS SUBJECTED TO THE EFFECTS OF HEAT AND PRESSURE AND SUBSEQUENTLY MIXED WITH AN EXPANDING AGENT INTRODUCED INTO THE METERING ZONE OF THE SCREW BARREL CHAMBER OF THE INJECTION MOLDING DEVICE, SAID MIXTURE BEING EJECTED UNDER HIGH PRESSURE INTO AN INJECTION MOLD WHERE THE MIXTURE EXPANDS AND FOAMS UP IN A PRESSURE-EXPANDED FASHION FORMING SAID FOAMED MOLDED ARTICLES. IN THIS METHOD THE EXPANDING AGENT IS INTRODUCED AFTER THE COMPRESSION ZONE OF INCREASING PRESSURE INTO THE METERING ZONE OF ESSENTIALLY UNIFORM-REMAINING PRESSURE OF THE SCREW BARREL CHAMBER IN SUCH A MANNER THAT THE EXPANDING AGENT IS FED INTO THE SCREW BARRED CHAMBER ONLY DURING THE TIME INTERVAL OF PLASTICATING BETWEEN TWO SUCCESSIVE INJECTION MOLDING STEPS.

Inventors

• 👤 H Finkmann
• 👤 H Felger
• 👤 P Zingsheim

Bibliographic Details