Glycol-based magnetorheological fluids containing inorganic clays, and their method of manufacture

Abstract

A magnetorheological (MR) fluid comprising a glycol-based carrier fluid, a magnetizeable particle, and an inorganic clay. The MR fluid is particularly suitable for use in devices that have materials incompatible with typical hydrocarbon-based MR fluids, for example in devices where natural rubber is in contact with the fluids as in automotive engine mounts. The fluid is substantially non-foaming, and an improvement over glycol fluids thickened with organoclays.

1 . A magnetorheological fluid comprising a glycol-based carrier fluid, a magnetizeable particle, and an inorganic clay. 
   
   
       2 . The fluid of  claim 1 , wherein the carrier fluid comprises at least one of ethylene glycol and propylene glycol. 
   
   
       3 . The fluid of  claim 1 , wherein the glycol portion of the carrier fluid comprises at least 60 percent ethylene glycol and at least 20 percent propylene glycol. 
   
   
       4 . The fluid of  claim 1 , wherein the glycol portion of the carrier fluid comprises about 70 percent ethylene glycol and about 30 percent propylene glycol. 
   
   
       5 . The fluid of  claim 1 , wherein the carrier fluid comprises at least 3 weight percent water, based on the total weight of the magnetorheological fluid. 
   
   
       6 . The fluid of  claim 1 , wherein the carrier fluid comprises less than 15 weight percent water based on the total weight of the magnetorheological fluid. 
   
   
       7 . The fluid of  claim 1  comprising substantially no organic thickeners. 
   
   
       8 . The fluid of  claim 1 , wherein the inorganic clay comprises at least one of bentonite or hectorite. 
   
   
       9 . The fluid of  claim 1 , wherein the inorganic clay comprises between about 0.1 and about 10 weight percent based on the total weight of the magnetorheological composition. 
   
   
       10 . The fluid of  claim 1 , wherein the inorganic claim comprises between about 0.1 and about 6 weight percent based on the total weight of the composition. 
   
   
       11 . The fluid of  claim 1 , wherein the magnetizeable particle comprises from about 50 to about 90 weight percent, based on the total weight of the composition. 
   
   
       12 . The fluid of  claim 1 , wherein the fluid comprises about 80 percent by weight magnetizable particle. 
   
   
       13 . The fluid of  claim 1 , wherein the fluid comprises about 19 percent by weight carrier fluid. 
   
   
       14 . A method of manufacturing a magnetically responsive fluid comprising the steps of:
 a) preparing a grease comprising an inorganic clay and water;   b) delaminating the inorganic clay in the grease;   c) dispersing the grease in a glycol fluid; and,   d) mixing magnetically responsive particles into the dispersed grease to form a magnetically responsive fluid.   
   
   
       15 . The method of  claim 14 , wherein the grease of step a) further comprises glycol. 
   
   
       16 . The method of  claim 15 , wherein the grease is prepared by mixing an inorganic clay into glycol and water in about a 1:3:3 ratio. 
   
   
       17 . The method of  claim 14 , wherein the grease is allowed to stand for sufficient time to thicken prior to step b). 
   
   
       18 . The method of  claim 14 , wherein step a) is performed in a mixer rotating at approximately 2500 revolutions per minute. 
   
   
       19 . The method of  claim 14 , wherein step b) is performed under high shear stress. 
   
   
       20 . The method of  claim 14 , wherein step b) is performed in a 3-roll mill. 
   
   
       21 . The method of  claim 14 , wherein step c) is performed by dispersing one part of the grease in three parts of the glycol fluid.