Apparatus and method for controlled pelletization processing

Abstract

An apparatus and process to maintain control of the temperature of low-melting compounds, high melt flow polymers, and thermally sensitive materials for the pelletization of such materials. The addition of a cooling extruder, and a second melt cooler if desired, in advance of the die plate provides for regulation of the thermal, shear, and rheological characteristics of narrow melting-range materials and polymeric mixtures, formulations, dispersions or solutions. The apparatus and process can then be highly regulated to produce consistent, uniform pellets of low moisture content for these otherwise difficult materials to pelletize.

1 - 27 . (canceled) 
     
     
         28 . A method for pelletizing a melt having at least two different material components that remain mixed at a temperature of at least about 200° F. but are prone to phase separation upon cooling and therefore are difficult to pelletize in a pelletizer processing line in which it is desirable to have the melt at the die plate at a temperature of between about 75° F. to about 400° F. for pelletization while, at the same time, preventing the at least two different materials from undergoing phase separation but to remain mixed, the method comprising the steps of inputting a melt received from an upstream source at a temperature of between about 200° F. to about 600° F. into a melt cooler located upstream of a cooling extruder to cool the melt in advance of said cooling extruder, said melt cooler having static mixing elements for efficient cooling, said melt proceeding through the melt cooler to exit at a temperature of between about 100° F. to about 550° F. for entry into the cooling extruder, the cooling extruder having a dynamic mixing element and configured to receive the melt from the melt cooler at the temperature of between about 100° F. to about 550° F., said melt passing through said cooling extruder with said dynamic mixing element maintaining dispersive homogeneity of the melt while the melt is further cooled to an exit temperature from the cooling extruder of between about 75° F. to about 400° F. for extrusional pelletization, feeding the melt into an extrusion die of a pelletizer and pelletizing the melt into pellets. 
     
     
         29 . The method as claimed in  claim 28 , wherein the pelletizing step is carried out in an underwater, hot face, strand or water ring pelletizer. 
     
     
         30 . The method as claimed in  claim 28 , wherein the pelletizing step is carried out in an underwater pelletizer. 
     
     
         31 . The method as claimed in  claim 28 , wherein the pelletizing step is carried out in a hot face pelletizer. 
     
     
         32 . The method as claimed in  claim 28 , further comprising the step of passing the melt through a diverter valve in order to divert the melt from the pelletizer processing line before the melt reaches the extrusion die of the pelletizer. 
     
     
         33 . The method as claimed in  claim 32 , wherein said diverter valve is located downstream of the cooling extruder. 
     
     
         34 . The method as claimed in  claim 28 , wherein after said melt is passed through said cooling extruder, the melt is further pressurized and passed through a screen changer ( 345 ) before entering said extrusion die of the pelletizer. 
     
     
         35 . The method as claimed in  claim 28 , wherein the step of passing the melt through the cooling extruder includes the addition of thermally sensitive ingredients through one or more side feeders of said cooling extruder. 
     
     
         36 . The method as claimed in  claim 35 , wherein said sensitive ingredients may be solid or liquid and selected from the group consisting of rheological additives, miscibilizing agents, surfactants, expanding agents, catalysts, inhibitors, antioxidants, chain extenders, nucleation agents, flavors, fragrances, colorants, devolatilizing agents, chemical scavengers, or additives appropriate to the application for the materials being pelletized. 
     
     
         37 . The method as claimed in  claim 28 , wherein after passing said melt through said cooling extruder, the melt is passed through a second melt cooler located downstream of said cooling extruder for additional regulation of the temperature and final mixing of the melt before entering said extrusion die of the pelletizer. 
     
     
         38 . The method as claimed in  claim 28 , wherein after passing said melt through said melt cooler, the melt is passed through a first extruder for shear mixing and melting. 
     
     
         39 . The method as claimed in  claim 28 , wherein said dynamic mixing element is selected from a single, twin, multiple screw, or a ring extruder. 
     
     
         40 . An apparatus for pelletizing a melt that is a mixture of at least two materials prone to phase separation upon cooling and, as a result, is difficult to pelletize in a pelletizer processing line, the apparatus comprising a melt cooler, a cooling extruder with a dynamic mixing element and a pelletizer with an extrusion die, said melt cooler positioned to receive a melt at a temperature of between about 200° F. and about 600° F. from an upstream source, said melt cooler configured to reduce a temperature of the melt passing therethrough to between about 100° F. to about 550° F. for entry into the cooling extruder located downstream of said melt cooler, the cooling extruder configured to receive the melt from the melt cooler at the temperature of between about 100° F. to about 550° F., the dynamic mixing element of the cooling extruder increasing the dispersive homogeneity of the melt and the cooling extruder further cooling the melt to an exit temperature from the cooling extruder of between about 75° F. to about 400° F. for extrusional pelletization through the extrusion die of the pelletizer. 
     
     
         41 . The apparatus as claimed in  claim 40 , wherein the pelletizer is an underwater, hot face, strand or water ring pelletizer. 
     
     
         42 . The apparatus as claimed in  claim 40 , wherein the pelletizer is an underwater pelletizer. 
     
     
         43 . The apparatus as claimed in  claim 40 , wherein the pelletizer is a hot face pelletizer. 
     
     
         44 . The apparatus as claimed in  claim 40 , wherein said processing line includes one or more pumps sufficient to pressurize the melt to ensure its passage through the cooling extruder and through said extrusion die of said pelletizer. 
     
     
         45 . The apparatus as claimed in  claim 40 , wherein said processing line includes one or more pumps after said cooling extruder to further pressurize said melt before entering said extrusion die of the pelletizer. 
     
     
         46 . The apparatus as claimed in  claim 40 , wherein said processing line includes at least one diverter valve in advance of said extrusion die of the pelletizer to divert the melt from the processing line. 
     
     
         47 . The apparatus as claimed in  claim 40 , wherein said cooling extruder includes one or more side feeders for the addition of one or more thermally sensitive ingredients. 
     
     
         48 . The apparatus as claimed in  claim 47 , wherein said sensitive ingredients may be solid or liquid and selected from the group consisting of rheological additives, miscibilizing agents, surfactants, expanding agents, catalysts, inhibitors, antioxidants, chain extenders, nucleation agents, flavors, fragrances, colorants, devolatilizing agents, chemical scavengers, or additives appropriate to the application for the materials being pelletized. 
     
     
         49 . The apparatus as claimed in  claim 40 , wherein said processing line includes a second melt cooler after said cooling extruder for additional regulation of the material temperature and final mixing before entering said extrusion die of the pelletizer. 
     
     
         50 . The apparatus as claimed in  claim 40 , wherein said processing line includes a first extruder positioned upstream of said melt cooler, said melt passing through said first extruder for shear mixing and melting before passing into said melt cooler. 
     
     
         51 . The apparatus as claimed in  claim 40 , wherein said dynamic mixing element includes a single, twin, multiple screw, or a ring extruder. 
     
     
         52 . The apparatus as claimed in  claim 40 , wherein said melt cooler has only static mixing elements.