High Temperature Crosslinked Polysulfones Used for Downhole Devices

Abstract

Thermally crosslinked polysulfone may be made from linear polysulfone, such as polyethersulfone, in powder form blended with a powdered inorganic peroxide such as magnesium peroxide or another oxygen source, to form a mixture followed by compression inside a mold. The mixture is cured at a an elevated temperature, for instance above 325° C., for an effective period of time to form a dense object. The object is then boiled in water, optionally under pressure, to remove the salt to give a structure that is open and porous which may be used as a filtration device on a downhole tool for hydrocarbon recovery. If a powdered salt is not used, a thermally crosslinked, solid, void-free polysulfone is made which may be strong and rigid at ambient, surface temperatures, but is an elastomer at elevated downhole temperatures, and is thus suitable for use as a packer or an O-ring.

1 . Thermally crosslinked polysulfone made by a process comprising:
 mixing a polysulfone powder, where the polysulfone powder is selected from the group consisting of polyethersulfone, polyphenylsulfone, polysulfone and mixtures thereof, with oxygen from a source selected from the group consisting of air, oxygen and a powdered inorganic peroxide; and   heating the mixture at a temperature above about 325° C. for a time period effective to crosslink the polysulfone with oxygen to give a thermally crosslinked polysulfone.   
     
     
         2 . The thermally crosslinked polysulfone of  claim 1  where the time period is at least eight hours. 
     
     
         3 . The thermally crosslinked polysulfone of  claim 1  where the inorganic peroxide is magnesium peroxide. 
     
     
         4 . The thermally crosslinked polysulfone of  claim 1  where heating the mixture is at a temperature above about 350° C. 
     
     
         5 . The thermally crosslinked polysulfone of  claim 1  where the process further comprises compressing the mixture into a mold after mixing and prior to heating. 
     
     
         6 . The thermally crosslinked polysulfone of  claim 1  where the process further comprises mixing the polysulfone powder and the powdered inorganic peroxide with a powdered salt selected from the group consisting of NaCl, KCl, and combinations thereof, and after heating to give the thermally crosslinked polysulfone, boiling the cured crosslinked polysulfone in water and removing the salt therefrom to recover a porous crosslinked polysulfone. 
     
     
         7 . The thermally crosslinked polysulfone of  claim 6  where the boiling is conducted at a temperature in the range of from about 100 to about 121° C. and the pressure ranges from about 0 to about 0.1 MPa. 
     
     
         8 . The thermally crosslinked polysulfone of  claim 6  where the porous crosslinked polysulfone can pass fluids therethrough at a differential pressure of 0.1 psi or less. 
     
     
         9 . The thermally crosslinked polysulfone of  claim 6  where the weight ratio of powdered salt to polysulfone powder ranges from about 80:20 to about 50:50. 
     
     
         10 . The thermally crosslinked polysulfone of  claim 1  where in the mixing of the polysulfone powder with a salt powder, a liquid polyurethane adhesive is included in the mixing in an amount ranging from about 1 to about 10 wt % based on the total polysulfone powder weight. 
     
     
         11 . A process for making thermally crosslinked polysulfone comprising:
 mixing a polysulfone powder, where the polysulfone powder is selected from the group consisting of polyethersulfone, polyphenylsulfone, polysulfone and mixtures thereof, with oxygen from a source selected from the group consisting of air, oxygen and a powdered inorganic peroxide; and   heating the mixture at a temperature above about 325° C. to crosslink the polysulfone with oxygen to give a thermally crosslinked polysulfone.   
     
     
         12 . The process of  claim 11  where the time period is at least eight hours. 
     
     
         13 . The process of  claim 11  where the inorganic peroxide is magnesium peroxide. 
     
     
         14 . The process of  claim 11  where heating the mixture is at a temperature above about 350° C. 
     
     
         15 . The process of  claim 11  further comprising compressing the mixture into a mold after mixing and prior to heating. 
     
     
         16 . The process of  claim 11  further comprising mixing the polysulfone powder and the powdered inorganic peroxide with a powdered salt selected from the group consisting of NaCl, KCl, and combinations thereof, and after heating to give the thermally crosslinked polysulfone, boiling the cured crosslinked polysulfone in water and removing the salt therefrom to recover a porous crosslinked polysulfone. 
     
     
         17 . The process of  claim 16  where the boiling is conducted at a temperature in the range of from about 100 to about 121° C. and the pressure ranges from about 0 to about 0.1 MPa. 
     
     
         18 . The process of  claim 11  where in the mixing of the polysulfone powder with a salt powder, a liquid polyurethane adhesive is included in the mixing in an amount ranging from about 1 to about 10 wt % based on the total polysulfone powder weight. 
     
     
         19 . The process of  claim 16  where the weight ratio of powdered salt to polysulfone powder ranges from about 80:20 to about 50:50. 
     
     
         20 . A wellbore seal comprising:
 a substrate; and   a thermally crosslinked polysulfone on the substrate, where the thermally crosslinked polysulfone is made by the process comprising:
 mixing a polysulfone powder, where the polysulfone powder is selected from the group consisting of polyethersulfone, polyphenylsulfone, polysulfone and mixtures thereof, with oxygen from a source selected from the group consisting of air, oxygen and a powdered inorganic peroxide; and 
 heating the mixture at a temperature above about 325° C. to crosslink the polysulfone with oxygen to give a thermally crosslinked polysulfone; 
   
       where the thermally crosslinked polysulfone may not be an elastomer at surface ambient temperature, but is an elastomer at an elevated temperature in the wellbore. 
     
     
         21 . The wellbore seal of  claim 20  where the elevated temperature in the wellbore is in the range of about 220 to about 350° C. 
     
     
         22 . A wellbore filtration device comprising: a shape-memory porous polysulfone material, the shape-memory porous polysulfone material having a compressed position and an expanded position, where the shape-memory porous polysulfone material is maintained in the compressed position at a temperature below its glass transition temperature, where the shape-memory porous polysulfone material expands from its compressed position to its expanded position when it is heated to a temperature above its glass transition temperature, where the shape-memory porous polysulfone material is a thermally crosslinked polysulfone made by the process comprising:
 mixing a polysulfone powder, where the polysulfone powder is selected from the group consisting of polyethersulfone, polyphenylsulfone, polysulfone and mixtures thereof, with oxygen from a source selected from the group consisting of air, oxygen and a powdered inorganic peroxide and a powdered salt selected from the group consisting of NaCl, KCl, and combinations thereof,   compressing the mixture into a mold;   heating the mixture at a temperature above about 325° C. for a period of time effective to crosslink the polysulfone to give a crosslinked polysulfone; and   boiling the cured crosslinked polysulfone in water and removing the salt therefrom to recover the shape-memory porous polysulfone material.   
     
     
         23 . The wellbore filtration device of  claim 22  where in the process of making the thermally crosslinked polysulfone, the boiling is conducted at a temperature in the range of from about 100 to about 121° C. and the pressure ranges from about 0 to about 0.1 MPa.