Thermally Conductive Filler Suspended by Thixotropic Agents in Lubricant Oil

Abstract

Lubricant fluid compositions which include a base oil fluid medium which contains thermally conductive filler particles and a thixotropic shear thinning viscosifier. The shear thinning viscosifier allows the particles to be suspended within the lubricant fluid composition when at rest.

What is claimed is: 
     
         1 . A lubricant fluid composition comprising:
 a base oil fluid medium;   a thermally conductive filler within the fluid medium; and   a thixotropic shear thinning viscosifier within the fluid medium.   
     
     
         2 . The lubricant fluid composition of  claim 1  wherein the base oil fluid medium comprises at least one of the group consisting of natural oil, synthetic oil or a combination comprising at least one of the foregoing. 
     
     
         3 . The lubricant fluid composition of  claim 1  wherein the thermally conductive filler comprises at least one of the group consisting of Al 2 O 3  (aluminum oxide), SiO 3  (silicate), BN (Boron nitride), AlN (Aluminum nitride), Si 3 N 4  (Silicon nitride) or a combination comprising at least one of the foregoing. 
     
     
         4 . The lubricant fluid composition of  claim 1  wherein the thixotropic shear thinning viscosifier comprises at least one of the group consisting of organophilic clays, and polymers, including substituted styrene acrylic copolymers, a polyamide, or a combination comprising at least one of the foregoing. 
     
     
         5 . The lubricant fluid composition of  claim 3  wherein there is a concentration of from about 1% to about 20% by volume of thermally conductive filler. 
     
     
         6 . The lubricant fluid composition of  claim 4  wherein there is a concentration of from about 0.1% to about 10% by volume of thixotropic shear thinning viscosifier. 
     
     
         7 . A method of making a lubricant fluid composition comprising the steps of:
 providing a base oil fluid medium;   adding a thermally conductive filler to the base oil fluid medium in an amount effective to increase the thermal conductivity of the base oil fluid medium; and   adding a thixotropic viscosifier agent to the base oil medium in an amount effective to suspend particles of the thermally conductive filler within the base oil fluid medium when the lubricant fluid composition is substantially at rest.   
     
     
         8 . The method of  claim 7  wherein the step of adding a thermally conductive filler further comprises adding the thermally conductive filler in a concentration of from about 1% to about 20% of the lubricant fluid composition by volume. 
     
     
         9 . The method of  claim 7  wherein the step of adding a thixotropic viscosifier agent further comprises adding the thixotropic viscosifier agent in a concentration of from about 0.1% to about 10% of the lubricant fluid composition by volume. 
     
     
         10 . The method of  claim 7  wherein the base oil fluid medium comprises at least one of the group consisting of natural oil, synthetic oil or a combination comprising at least one of the foregoing. 
     
     
         11 . The method of  claim 7  wherein the thermally conductive filler comprises at least one of the group consisting of Al 2 O 3  (aluminum oxide), SiO 3  (silicate), BN (Boron nitride), AlN (Aluminum nitride), Si 3 N 4  (Silicon nitride) or a combination comprising at least one of the foregoing. 
     
     
         12 . The method of  claim 7  wherein the thixotropic shear thinning viscosifier comprises at least one of the group consisting of organophilic clays and polymers, such as styrene acrylics or a combination comprising at least one of the foregoing. 
     
     
         13 . A submersible electric motor for downhole use, the motor comprising:
 a shaft;   at least one rotor and at least one bearing mounted on said shaft;   a stator positioned external to the at least one rotor;   a running clearance located between an internal diameter of the stator and an outside diameter of the rotor; and   a lubricant fluid composition disposed within the running clearance and other cavities of the motor;   wherein the lubricant fluid composition comprises a base oil fluid medium, a thermally conductive filler, and a thixotropic viscosifier.   
     
     
         14 . The submersible electric motor of  claim 13  wherein the fluid medium comprises at least one of the group consisting of natural oil, synthetic oil or a combination comprising at least one of the foregoing. 
     
     
         15 . The submersible electric motor of  claim 13  wherein the thermally conductive filler comprises at least one of the group consisting of Al 2 O 3  (aluminum oxide), SiO 3  (silicate), BN (Boron nitride), AlN (Aluminum nitride), Si 3 N 4  (Silicon nitride) or a combination comprising at least one of the foregoing. 
     
     
         16 . The submersible electric motor of  claim 13  wherein the thixotropic viscosifier comprises at least one of the group consisting of organophilic clays and polymers, such as styrene acrylics or a combination comprising at least one of the foregoing.