Method for injection molding at low, substantially constant pressure

• Main Authors: BERG JR., CHARLES JOHN, SCHILLER, GARY FRANCIS, SCHARRENBERG, RAINER, NEUFARTH, RALPH EDWARD, ALTONEN, GENE MICHAEL, LAYMAN, JOHN MONCRIEF
• Format: Patent
• Language: English
• Published: 03.03.2016
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; PERFORMING OPERATIONS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

Injection molding methods at low, substantially constant melt pressures in particular a method comprising: (a) filling with a shot comprising a molten thermoplastic material an unpressurized mold cavity of a molding apparatus, the shot comprising the molten material having a melt pressure that, upon injection into the mold cavity, exceeds a pre-injection pressure of the shot comprising the molten material; and, (b) while filling substantially the entire mold cavity with the shot comprising the molten material, maintaining the melt pressure substantially constant at less than 6000 psi, wherein: an internal portion of the mold cavity spaced at least 2 mm from a most immediate surface of the mold cavity contacting the shot comprising the molten material is maintained at a temperature of less than about 100[deg.]C, and the thermoplastic material has a melt flow index of 0.1 g/10 min to about 500 g/10 min.