Extrusion method and apparatus

Abstract

Improvements in the extrusion of thermohardenable materials are achieved by cooling the material in the initial zone ( 2 ) of the extruder ( 1 ) and reducing residence time by use of a prescribed length to diameter ratio and screw speed, particularly useful for intermittent application during robotically controlled mass production.

1 . A process for the provision of thermally activatable materials on a substrate comprising extruding the material onto the substrate at a temperature below the activation temperature wherein the material is fed to an extruder, the material is coded within the initial zone of the barrel of the extruder, heating the material to a temperature above the melting point and below the activation temperature of the material in a subsequent zone of the barrel of the extruder and extruding the molten material onto the substrate where it bonds to the substrate and cools to provide thermally activatable material on the substrate. 
     
     
         2 . A process according to  claim 1 , wherein the initial zone of the barrel of the extruder is cooled by passing a cooling fluid around the initial zone of the barrel of the extruder and the temperature of the fluid is controlled so that as it leaves the initial zone of the barrel of the extruder zone its temperature is no greater than 15° C. 
     
     
         3 . A process according to  claim 1 , wherein the extrusion is intermittent. 
     
     
         4 . A process according to  claim 1 , wherein the thermally activatable material is a thermohardenable material. 
     
     
         5 . A process according to  claim 1 , wherein the thermally activatable material is a thermally foamable material. 
     
     
         6 . A process according to  claim 1  wherein the material that is fed to the extruder is dry to touch. 
     
     
         7 . A process according to Claim  6 , wherein the material is in pellet form. 
     
     
         8 . A process according to  claim 1  wherein the compression ratio of the extruder is from 1.5 to 2. 
     
     
         9 . A process according to  claim 1 , wherein the length to diameter ratio of the extruder is 24 or lower, preferably between 24 and 16, more preferably between 20 and 16. 
     
     
         10 . A process according to  claim 1 , wherein the extruder operates at between 10 and 50 revolutions of the extruder screw per minute. 
     
     
         11 . A process according to  claim 1 , wherein the length of the initial zone of the barrel of the extruder is from two times to five times the diameter of the extruder barrel. 
     
     
         12 . A process according to  claim 1 , wherein the material is extruded at a temperature In the range of 60° C. to 120° C. 
     
     
         13 . A process according to  claim 3 , wherein the direction of rotation of the screw of the extruder is reversible and it is reversed when if is desired to stop extrusion. 
     
     
         14 . A process according to Claim  13  wherein the screw is reversed and reactivated one or more times during the extrusion of material onto a single component. 
     
     
         15 . A process according to  claim 1 , wherein the extruder is moved in a predetermined manner relative to the surface of the substrate. 
     
     
         16 . A process according to  claim 1 , wherein the substrate is moved relative to the die of the extruder. 
     
     
         17 . A process according to  claim 15 , wherein the process is robotically controlled and the robot supports and moves the extruder while the substrate is static or the robot moves the substrate while the extruder is static. 
     
     
         18 . A process according to  claim 1 , wherein the extruder is programmed to stop and start extruding several times on a single substrate. 
     
     
         19 . A process according to  claim 1 , wherein the residence time of the material in the extruder is less than 10 minutes. 
     
     
         20 . A process according to  claim 1  comprising sequential operations wherein a substrate is placed on a table beneath the extruder die extrusion commenced and the substrate and/or the die are moved relative to each other to provide the desired pattern or array of the extrudate on the substrate which may be continuous or discontinuous; once the pattern or array is complete the extruder screw is automatically reversed to stop extrusion; the substrate carrying the extrudate is removed and replaced with the next substrate and extrusion recommenced to form a deposit of the thermoactivatable material on the new substrate. 
     
     
         21 - 34 . (canceled)