Method and Apparatus for Forming an Expandable Foam Pellet Having a Hard Outer Shell by Underwater Pelletizing, and Expandable Foam Pellets Formed Thereby
AssigneeGala Industries, Inc.
InventorMark Anthony Lythgoe
Life of this patent
Estimating the term…
Abstract
A pre-expanded hard shell thermoplastic foam pellet is made by controlling the temperature of the melt exiting a die plate in an underfluid pelletizer, and by controlling the temperature and pressures of the cooling fluid as the pellet flows from the cutting chamber through the slurry line toward a centrifugal dryer. The process and apparatus used for controlling the above parameters is described in conjunction with making the pellets. The pellets thus formed may have a generally spherical shape, or they may have odd, irregular shapes with foam hemorrhages protruding therefrom, depending on the conditions during pre-expansion.
Claims24
An extrusion process for producing pre-expanded foam pellets having a hard outer shell, the process comprising:
- metering a blowing agent into a polymer melt;
- forcing the polymer melt through an extrusion die and into a cutting chamber comprising a fluid inlet and a pellet slurry outlet and enclosing a cutter hub assembly comprising a plurality of cutter blades;
- cutting the extruded melt by rotating the plurality of cutter blades at a programmed rotation speed to produce one or more pellets;
- directing a flow of fluid in the fluid inlet, through the cutting chamber, and out the pellet slurry outlet to pull the one or more pellets away from the cutting chamber in a pellet slurry;
- and
- cooling the one or more pellets in the pellet slurry at a temperature and pressure effective to produce one or more foam pellets having a hard outer shell.
An extrusion process for producing pre-expanded foam pellets having a hard outer shell, the process comprising:
- feeding a polymer material into a material blending system to form a blended material;
- feeding the blended material into a throat of an extruder to form a polymer melt;
- metering a blowing agent into the melt;
- extruding the melt through an extrusion die and into a cutting chamber comprising a fluid inlet and a pellet slurry outlet and enclosing a cutter hub assembly comprising a plurality of cutter blades;
- cutting the extruded melt by rotating the plurality of cutter blades at a programmed rotation speed to produce one or more pellets;
- directing a flow of fluid in the fluid inlet, through the cutting chamber, and out the pellet slurry outlet to pull the one or more pellets away from the cutting chamber in a pellet slurry;
- and
- cooling the one or more pellets in the pellet slurry effective to produce one or more foam pellets having a hard outer shell.
A system for forming foam pellets from a thermoplastic melt, comprising:
- a material blending section for receiving a polymer material and forming a blended material;
- an extruder configured to mix and melt the blended material to form a thermoplastic melt;
- a metering system for metering a blowing agent into the thermoplastic melt within the extruder;
- a die plate in fluid communication with the extruder;
- a cutter hub assembly having a plurality of cutter blades arranged on a cutter hub, the plurality of cutter blades being configured to cut the melt into one or more pellets;
- and
- a cutting chamber enclosing the cutter hub assembly and comprising a fluid inlet and a pellet slurry outlet, the cutting chamber being configured to receive a flow of fluid via the fluid inlet and discharge the flow of fluid via the pellet slurry outlet;
- a pump in fluid communication with the cutting chamber, the pump being configured to maintain a fluid pressure within the cutting chamber;
- a slurry line in fluid communication with the pellet slurry outlet of the cutting chamber;
- and
- a throttle valve positioned within the slurry line downstream of the cutting chamber, the throttle valve being configured to selectively manipulate pressure in the slurry line.
Dependencies are inferred from the claim text.