Continuously variable transmission fluid and method of making same

Abstract

A continuously variable transmission fluid comprises a hydrogenated cyclic dimer of α-alkyl styrene and a low temperature viscosity control agent. The fluid does not contain more than 20 wt. % of a linear dimer of the α-alkyl styrene, and the fluid has a kinematic viscosity of greater than about 2.5×10 −6 m 2 /s at 100° C., as measured according to ASTM D-445. The dimerized α-alkyl styrene can be made by (a) contacting an α-alkyl styrene with a supported acid catalyst to effect oligomerization of the α-alkyl styrene to a cyclic dimer; and (b) hydrogenating the cyclic dimer in the presence of a hydrogenation catalyst to produce a fully hydrogenated cyclic dimer, wherein the α-alkyl styrene is contacted with the supported acid catalyst in the absence of a solvent for the α-alkyl styrene and a free acid.

What is claimed is:  
     
         1 . A continuously variable transmission (CVT) fluid, comprising or obtained by mixing: 
 a hydrogenated cyclic dimer of α-alkyl styrene; and    a low temperature viscosity control agent,    wherein the fluid comprises less than about 20 wt % of a linear dimer of the α-alkyl styrene, and the fluid has a kinematic viscosity of greater than about 2.5×10 −6  m 2 /s at 100° C., as measured according to ASTM D-445.    
     
     
         2 . The CVT fluid of  claim 1 , wherein the kinematic viscosity of the fluid is greater than about 3.0×10 −6  m 2 /s at 100° C.  
     
     
         3 . The CVT fluid of  claim 1 , wherein the kinematic viscosity of the fluid is from about 3.0×10 −6  m 2 /s at 100° C. to about 8.0×10 −6  m 2 /s at 100° C.  
     
     
         4 . The CVT fluid of  claim 1 , wherein the kinematic viscosity of the fluid is greater than about 8.0×10 −6  m 2 /s at 100° C.  
     
     
         5 . The CVT fluid of  claim 1 , wherein the fluid has a traction coefficient (100° C.) of at least about 0.08.  
     
     
         6 . The CVT fluid of  claim 1 , wherein the fluid has a traction coefficient (100° C.) form about 0.08 to about 0.109.  
     
     
         7 . The CVT fluid of  claim 1 , wherein the fluid has a traction coefficient (100° C.) of at least about 0.109.  
     
     
         8 . The CVT fluid of  claim 1 , wherein the fluid has a Brookfield viscosity (−30° C.) of less than about 100 Pa·s.  
     
     
         9 . The CVT fluid of  claim 1 , wherein the fluid has a Brookfield viscosity (−30° C.) of from about 100 Pa·s to about 5 Pa·s.  
     
     
         10 . The CVT fluid of  claim 1 , wherein the fluid has a Brookfield viscosity (−30° C.) of less than about 5 Pa·s.  
     
     
         11 . The CVT fluid of  claim 1 , wherein the hydrogenated cyclic dimer of α-alkyl styrene is present in greater than about 80 wt %.  
     
     
         12 . The CVT fluid of  claim 1 , wherein the hydrogenated cyclic dimer of α-alkyl styrene is present in greater than about 85 wt %.  
     
     
         13 . The CVT fluid of  claim 1 , wherein the hydrogenated cyclic dimer of α-alkyl styrene is present in greater than about 90 wt %.  
     
     
         14 . The CVT fluid of  claim 1 , wherein the low temperature viscosity control agent has a viscosity of greater than 2.5×10 −6  m 2 /s at 100° C.  
     
     
         15 . The CVT fluid of  claim 1 , further comprising an additive selected from dispersants, detergents, viscosity index improvers, friction modifiers, anti-wear agents, or mixtures thereof.  
     
     
         16 . The CVT fluid of  claim 1 , wherein the low temperature viscosity control agent is selected from oligomers or polymers of linear alpha olefins of at least 12 carbon atoms, naphthenic oils, synthetic ester oils, polyether oils, or mixtures thereof  
     
     
         17 . The CVT fluid of  claim 1 , wherein the low temperature viscosity control agent has a viscosity of less than 2.5×10 −6  m 2 /s at 100 ° C.  
     
     
         18 . The CVT fluid of  claim 1 , wherein the low temperature viscosity control agent comprises an oligomer or polymer of linear alpha olefins having 12 to about 20 carbon atoms, said oligomer or polymer having a molecular weight of about 250 to about 600.  
     
     
         19 . The CVT fluid of  claim 1 , wherein the low temperature viscosity control agent comprises a naphthenic oil.  
     
     
         20 . The CVT fluid of  claim 1 , wherein the α-alkyl styrene is α-methyl styrene.  
     
     
         21 . A method of making dimerized α-alkyl styrene and products thereof, comprising: 
 contacting an α-alkyl styrene with a supported acid catalyst under a temperature and pressure condition to effect oligomerization of the α-alkyl styrene to produce an oligomerization product, the oligomerization product comprising a cyclic dimer of the α-alkyl styrene; and  
 hydrogenating the cyclic dimer of the α-alkyl styrene in the presence of a hydrogenation catalyst to produce a fully hydrogenated cyclic dimer of the α-alkyl styrene,  
 wherein the α-alkyl styrene is contacted with the supported acid catalyst in the absence of a solvent for the α-alkyl styrene and a free acid.  
 
     
     
         22 . The method of  claim 21 , further comprising mixing the fully hydrogenated cyclic dimer with an additive to form a continuously variable transmission fluid, wherein the continuously variable transmission fluid comprises less than about 20 wt. % of a linear dimer of the α-alkyl styrene.  
     
     
         23 . The method of  claim 22 , wherein the transmission fluid comprises less than about 5 wt. % of a trimer or higher oligomer of the α-alkyl styrene.  
     
     
         24 . The method of  claim 22 , wherein the α-alkyl styrene is α-methyl styrene.  
     
     
         25 . The method of  claim 24 , wherein the fully-hydrogenated dimer is 1-cyclohexyl-1,1,3-trimethylhydrindane.  
     
     
         26 . The method of  claim 25 , wherein the 1-cyclohexyl-1,1,3-trimethylhydrindane is mixed with an oil additive to form a continuously variable transmission fluid.  
     
     
         27 . The method of  claim 26 , wherein the transmission fluid comprises less than about 20 wt. % of a linear dimer of α-methyl styrene.  
     
     
         28 . The method of  claim 26 , wherein the transmission fluid comprises less than about 5 wt. % of a trimer or higher oligomer of α-methyl styrene.  
     
     
         29 . The method of  claim 22 , wherein the supported acid catalyst is a column of an acidic ion exchange resin.  
     
     
         30 . The method of  claim 29 , wherein the acidic ion exchange resin is a strongly acidic ion exchange resin.  
     
     
         31 . The method of  claim 29 , wherein the α-alkyl styrene is passed through the acidic resin exchange resin column at a temperature from about 25° C. to about 250° C.  
     
     
         32 . The method of  claim 31 , wherein the α-alkyl styrene has a residence time in the acidic ion exchange column in the range of about 1 second to about 250 minutes.  
     
     
         33 . The method of  claim 29 , wherein the acidic ion exchange resin column has a column pressure in the range from about 15 psig (103 kPa) to about 44 psig (303 kPa).  
     
     
         34 . The method of  claim 21 , further comprising separating the cyclic dimer of the α-alkyl styrene from other oligomers of the α-alkyl styrene prior to the hydrogenation of the cyclic dimer.