Supercritical fluid processes

Abstract

A process for the preparation of toner additive wax particles which comprises the micronization of said particles from a supercritical solution.

What is claimed is: 
     
       1. A process for the preparation of toner additive wax particles which comprises the micronization of said particles from a supercritical solution. 
     
     
       2. A process in accordance with claim 1 wherein said particles are from about 0.001 to about 4 microns in volume average diameter. 
     
     
       3. A process in accordance with claim 1 wherein the wax particles are inserted into and sealed in a pressure vessel at a loading of from about 0.001 to about 50 weight/volume percent, or from about 0.001 to about 50 grams per 100 milliliters of vessel volume; the vessel is subsequently heated to from about 30°C. to about 400° C. and filled with said supercritical solution; the vessel is then agitated; the resulting solution is subsequently expanded across an orifice of from 5 to 100 microns in diameter that has been heated to a temperature higher than the critical temperature of the solution and which temperature is from about 50° C. to about 450° C.; and thereafter the resulting precipitating wax is separated from the expanding gas stream. 
     
     
       4. A process in a accordance with claim 3 wherein the supercritical fluid is carbon dioxide. 
     
     
       5. A process in accordance with claim 1 wherein the supercritical solution, or solvent is carbon dioxide, ethane, propane, butane, isobutane, pentane, chlorodifluoromethane or trifluoromethane. 
     
     
       6. A process in accordance with claim 1 wherein the wax is polypropylene, or polyethylene. 
     
     
       7. A process in accordance with claim 1 wherein the wax is polypropylene, or polyethylene, each with an M w  of from about 500 to about 20,000 Dalton and an M n  of from about 250 to about 10,000 Dalton. 
     
     
       8. A process in accordance with claim 1 wherein said micronization is accomplished by rapid expansion of said supercritical solution, thereby generating said wax particles from said supercritical solution. 
     
     
       9. A process in accordance with claim 1 wherein, subsequent to said micronization, the particles are isolated and are of a size of from about 0.001 to about 4.0 microns in volume average diameter. 
     
     
       10. A process in accordance with claim 1 wherein the process is accomplished at a pressure of from about 40 bar to about 850 bar, and at a temperature of from about 30° C. to about 500° C. 
     
     
       11. A process in accordance with claim 1 wherein the supercritical solution is comprised of a carbon dioxide fluid, and which carbon dioxide is at a temperature of above about 31° C. and a pressure of about 71 bar to about 232 bar. 
     
     
       12. A process in accordance with claim 11 wherein there is formed a supercritical phase at above the critical temperature of about 31° C. and above the critical pressure of about 71 bar to about 232 bar. 
     
     
       13. A process in accordance with claim 6 wherein said polypropylene is of a low molecular weight with an M w  of from about 1,000 to about 25,000, and an Mn of from about 500 to about 12,000. 
     
     
       14. A process in accordance with claim 6 wherein said polyethylene is of a low molecular weight with an M w  of from about 1,000 to about 25,000, and an M n  of from about 500 to about 12,000. 
     
     
       15. A process in accordance with claim 6 wherein said polypropylene is of a low molecular weight of from about 500 to about 10,000 number average; and wherein said polyethylene is of a low molecular weight of from about 700 to about 2,000 number average. 
     
     
       16. A process for the preparation of wax, which process comprises inserting and sealing the wax in a pressure vessel at a loading of from about 0.001 to about 50 weight/volume percent, or from about 0.001 to about 50 grams per 100 milliliters of vessel volume, the vessel being subsequently heated to from about 30° C. to about 400° C., and which vessel contains a solvent of carbon dioxide, ethane, propane, butane, isobutane, pentane, chlorodifluoromethane or trifluoromethane sufficient to yield an average density of from about 0.7 to about 1.5 grams/cc in the vessel; the vessel is then agitated for from about 1 to about 60 minutes to dissolve the wax; the solution from the lower or liquid phase of the vessel is then expanded across an orifice in the expansion chamber of from 5 to 100 microns in diameter and which chamber is retained at a temperature above the critical temperature of the solution, which temperature is from about 40° C. to about 510° C., thereby ensuring that the expansion is from said supercritical solution; and separating the resulting precipitating wax from the expanding gas stream. 
     
     
       17. A process in accordance with claim 16 wherein said wax is of a diameter of from about 0.001 to about 4 microns. 
     
     
       18. A process in accordance with claim 16 wherein said wax is of a diameter of is submicron in size. 
     
     
       19. A process in accordance with claim 18 wherein submicron is from about 0.001 to about 1 micron. 
     
     
       20. A process in accordance with claim 3 wherein said supercritical solution or solvent is carbon dioxide, ethane, propane, butane, isobutane, pentane, chlorodifluoromethane or trifluoromethane, wherein said vessel agitation is for from about 1 to about 60 minutes thereby dissolving the wax, and wherein said separating from said expanding gas is by filtration. 
     
     
       21. A process which comprises the micronization of wax particles from a supercritical solution.