Process for producing longer fibers in injection molded solid parts by dissolving of gas during plasticizing

A polymeric part made by the process 1 comprising:

• introducing a long glass fiber filled polymeric material to a hopper of an injection molding machine, wherein the glass fibers have a pre-molding length;
• controlling delivery of the long glass fiber filled polymeric material through an airlock and maintaining a pressure within the plasticizing unit by selectively operating a plurality of valves arranged in the airlock;
• sealing the plasticizing unit with a seal and the airlock mounted between a barrel of the injection molding machine and the hopper, wherein the seal is located between a screw and a cylinder of the plasticizing unit to prevent the loss of blowing agent at the end of the screw;
• melting the glass fiber filled polymeric material to form a melt in a plasticizing unit;
• pressurizing the plasticizing unit of the injection molding machine with a blowing agent, and applying a back pressure during plasticizing of at least 5 bar greater than the pressurizing pressure and below the critical point of the blowing agent;
• dissolving the gaseous blowing agent into the melt during plasticizing;
• injecting the melt into a mold cavity up to 100% of volume;
• and
• forming the solid part by applying a packing pressure to the mold cavity after injecting the melt into the mold cavity and allowing gas to escape, wherein a post-molding length of the glass fibers in the solid part is greater than a post-molding length of glass fibers in a similarly dimensioned solid part made without pressurizing a plasticizing unit, without making the blowing agent supercritical, and without dissolving the gaseous blowing agent into the melt resulting in greater fiber breakage due to harsh mixing conditions.

An injection molding device configured to produce a solid part, comprising:

• a hopper configured to introduce a long glass fiber filled polymeric material, wherein the glass fibers have a pre-molding length;
• a plasticizing unit configured to melt the glass fiber filled polymeric material to form a melt;
• an airlock arranged between a barrel of the injection molding device and the hopper, wherein the airlock comprises a plurality of valves configured to control delivery of the long glass fiber filled polymeric material and maintain a pressure within the plasticizing unit;
• a seal configured to seal the plasticizing unit, wherein the seal is arranged between a screw and a cylinder of the plasticizing unit;
• a gas source configured to pressurize the plasticizing unit of the injection molding device with a gaseous blowing agent to dissolve the blowing agent into the melt and to maintain the gaseous blowing agent below its critical point;
• and
• the plasticizing unit further configured to deliver the melt into a mold cavity up to 100% of volume to form the solid part, wherein the mold cavity is configured to apply packing pressure while allowing gas to escape;
• wherein the plasticizing unit is further configured to operate in conjunction with a gas dissolvent such that a post-molding length of the glass fibers in the solid part is greater than a post-molding length of glass fibers in a similarly dimensioned solid part made without a pressurized plasticizing unit and without the gas dissolvent resulting in greater fiber breakage due to harsh mixing conditions, and
• wherein the plasticizing unit is further configured for application of a back pressure during plasticizing of at least 5 bar greater than a pressurizing pressure.