Core-shell flow improver

Abstract

A flow improver comprising a plurality of core-shell particles that can be formed by emulsion polymerization. The core of the core-shell particles can include a drag reducing polymer, while the shell of the particles can include repeat units of a hydrophobic compound and an amphiphilic compound. The flow improver can demonstrate increased pumping stability over conventionally prepared latex flow improvers.

1 . A flow improver comprising: solid particles having a polymeric core and a polymeric shell at least partly surrounding said core, wherein said core comprises a drag reducing polymer, wherein said shell comprises a shell copolymer having repeat units of a hydrophobic compound and repeat units of a first amphiphilic compound. 
   
   
       2 . The flow improver of  claim 1 , wherein said core and said shell are formed by emulsion polymerization. 
   
   
       3 . The flow improver of  claim 1 , wherein said hydrophobic compound is selected from the group consisting of: 
     
       
         
         
             
             
         
       
     
     wherein R 1  is H or a C 1 -C 10  alkyl radical, and R 2  is H, a C 1 -C 30  alkyl radical, a C 5 -C 30  substituted or unsubstituted cycloalkyl radical, a C 6 -C 20  substituted or unsubstituted aryl radical, an aryl-substituted C 1 -C 10  alkyl radical, a —(CH 2 CH 2 O) x —R A  or —(CH 2 CH(CH 3 )O) x —R A  radical wherein x is in the range of from 1 to 50 and R A  is H, a C 1 -C 30  alkyl radical, or a C 6 -C 30  alkylaryl radical;
   R 3 -arene-R 4   (B) 
 
     wherein arene is a phenyl, naphthyl, anthracenyl, or phenanthrenyl, R 3  is CH═CH 2  or CH 3 —C═CH 2 , and R 4  is H, a C 1 -C 30  alkyl radical, a C 5 -C 30  substituted or unsubstituted cycloalkyl radical, Cl, SO 3 , OR B , or COOR C , wherein R B  is H, a C 1 -C 30  alkyl radical, a C 5 -C 30  substituted or unsubstituted cycloalkyl radical, a C 6 -C 20  substituted or unsubstituted aryl radical, or an aryl-substituted C 1 -C 10  alkyl radical, and wherein R C  is H, a C 1 -C 30  alkyl radical, a C 3 -C 30  substituted or unsubstituted cycloalkyl radical, a C 6 -C 70  substituted or unsubstituted aryl radical, or an aryl-substituted C 1 -C 10  alkyl radical; 
     
       
         
         
             
             
         
       
     
     wherein R 5  is H, a C 1 -C 30  alkyl radical, or a C 6 -C 20  substituted or unsubstituted aryl radical; 
     
       
         
         
             
             
         
       
     
     wherein R 6  is H, a C 1 -C 30  alkyl radical, or a C 6 -C 20  substituted or unsubstituted aryl radical; 
     
       
         
         
             
             
         
       
     
     wherein R 7  is H or a C 1 -C 18  alkyl radical, and R 8  is H, a C 1 -C 18  alkyl radical, or Cl; 
     
       
         
         
             
             
         
       
     
     wherein R 9  and R 10  are independently H, a C 1 -C 30  alkyl radical, a C 6 -C 10  substituted or unsubstituted aryl radical, a C 5 -C 30  substituted or unsubstituted cycloalkyl radical, or heterocyclic radicals; 
     
       
         
         
             
             
         
       
     
     wherein R 11  and R 12  are independently H, a C 1 -C 30  alkyl radical, a C 6 -C 20  substituted or unsubstituted aryl radical, a C 5 -C 30  substituted or unsubstituted cycloalkyl radical, or heterocyclic radicals: 
     
       
         
         
             
             
         
       
     
     wherein R 13  and R 14  are independently H, a C 1 -C 30  alkyl radical, a C 6 -C 20  substituted or unsubstituted aryl radical, a C 5 -C 30  substituted or unsubstituted cycloalkyl radical, or heterocyclic radicals: 
     
       
         
         
             
             
         
       
     
     wherein R 15  is H, a C 1 -C 30  alkyl radical, a C 6 -C 20  substituted or unsubstituted aryl radical, a C 5 -C 30  substituted or unsubstituted cycloalkyl radical, or heterocyclic radicals; 
     
       
         
         
             
             
         
       
     
     wherein R 16  is H, a C 1 -C 30  alkyl radical, or a C 6 -C 20  aryl radical; 
     
       
         
         
             
             
         
       
     
     wherein R 17  and R 18  are independently H, a C 1 -C 30  alkyl radical, a C 6 -C 10  substituted or unsubstituted aryl radical, a C 5 -C 30  substituted or unsubstituted cycloalkyl radical, or heterocyclic radicals; and 
     
       
         
         
             
             
         
       
     
     wherein R 19  and R 20  are independently H, a C 1 -C 30  alkyl radical, a C 6 -C 20  substituted or unsubstituted aryl radical, a C 5 -C 30  substituted or unsubstituted cycloalkyl radical, or heterocyclic radicals. 
   
   
       4 . The flow improver of  claim 1 , wherein said first amphiphilic compound is a polymerizable surfactant, wherein the weight ratio of repeat units of said hydrophobic compound to repeat units of said first amphiphilic compound in said shell copolymer is in the range of from about 0.5:1 to about 40:1. 
   
   
       5 . The flow improver of  claim 4 , wherein said hydrophobic compound comprises an acrylate and/or methacrylate. 
   
   
       6 . The flow improver of  claim 1 , wherein said first amphiphilic compound is polyethylene glycol methacrylate and/or said hydrophobic compound is 2-ethylhexyl methacrylate. 
   
   
       7 . The flow improver of  claim 1 , wherein said shell copolymer further comprises repeat units of a second amphiphilic compound, wherein said first amphiphilic compound is a non-ionic polymerizable surfactant and said second amphiphilic compound is an ionic polymerizable surfactant, wherein the weight ratio of repeat units of said first amphiphilic compound to repeat units of said second amphiphilic compound in said shell copolymer is in the range of from about 0.25:1 to about 30:1. 
   
   
       8 . The flow improver of  claim 1 , wherein at least 90 weight percent of said solid particles have a particle size greater than 25 nanometers and at least 90 weight percent of said solid particles have a particle size less than 500 nanometers, wherein the average thickness of said shell is in the range of from about 0.1 to about 20 percent of the average particle diameter of said solid particles. 
   
   
       9 . The flow improver of  claim 1 , wherein said flow improver is in the form of a latex comprising said solid particles dispersed in a liquid continuous phase, wherein said latex comprises said solid particles in an amount in the range of from about 10 to about 60 weight percent. 
   
   
       10 . A latex flow improver comprising: an aqueous continuous phase and a plurality of polymeric particles dispersed in said continuous phase, wherein said polymeric particles comprise a core and a shell at least partly surrounding said core, wherein said core comprises a drag reducing polymer formed by emulsion polymerization, wherein said shell is formed around said core by emulsion polymerizing at least one hydrophobic monomer and at least one polymerizable surfactant in the presence of said core. 
   
   
       11 . The flow improver of  claim 10 , wherein said shell comprises repeat units of said hydrophobic monomer in an amount in the range of from about 25 to about 98 weight percent. 
   
   
       12 . The flow improver of  claim 11 , wherein said hydrophobic monomer is a methacrylate or acrylate monomer. 
   
   
       13 . The flow improver of  claim 11 , wherein the emulsion polymerization carried out to form said shell includes the use of a first non-ionic polymerizable surfactant and a second ionic polymerizable surfactant, wherein said shell comprises repeat units of said first polymerizable surfactant in an amount in the range of from about 2 to about 50 weight percent and repeat units of said second polymerizable surfactant in an amount in the range of from about 0.05 to about 30 weight percent. 
   
   
       14 . The flow improver of  claim 10 , wherein said polymeric particles have an average particle size less than about 1 micron, wherein the average thickness of said shell is in the range of from about 0.5 to about 30 nanometers. 
   
   
       15 . A process for making a flow improver comprising:
 (a) forming a plurality of core particles of a drag reducing polymer by emulsion polymerization; and   (b) forming shells around at least a portion of said core particles by emulsion polymerization to thereby produce a plurality of core-shell particles.   
   
   
       16 . The process of  claim 15 , wherein said emulsion polymerization of step (a) is carried out in a first reaction mixture comprising a first liquid continuous phase, wherein said emulsion polymerization of step (b) is carried out in a second reaction mixture comprising a second liquid continuous phase and at least a portion of said core particles, wherein said second liquid continuous phase comprises at least a portion of said first liquid continuous phase. 
   
   
       17 . The process of  claim 16 , wherein said second liquid continuous phase comprises substantially all of said first liquid continuous phase. 
   
   
       18 . The process of  claim 15 , wherein said forming of step (b) includes polymerizing one or more shell-forming monomers and at least one polymerizable surfactant so that said shell comprises repeat units of said shell-forming monomer and repeat units of said at least one polymerizable surfactant. 
   
   
       19 . The process of  claim 18 , wherein said shell-forming monomers comprise an acrylate and/or methacrylate monomer. 
   
   
       20 . The process of  claim 18 , wherein said shell-forming monomers and said polymerizable surfactant do not chemically react with said core particles during said forming of step (b). 
   
   
       21 . The process of  claim 15 , wherein said shells comprise repeat units of a hydrophobic monomer, a non-ionic polymerizable surfactant, and an ionic polymerizable surfactant, wherein the weight ratio of repeat units of said hydrophobic monomer to repeat units of said non-ionic polymerizable surfactant in said shells is in the range of from about 0.5:1 to about 40:1, wherein the weight ratio of repeat units of said non-ionic polymerizable surfactant to repeat units of said ionic polymerizable surfactant in said shells is in the range of from about 0.25:1 to about 30:1. 
   
   
       27 . A process for reducing pressure loss associated with the turbulent flow of a fluid through a conduit, said process comprising: using a pump to inject a latex flow improver into said fluid flowing through said conduit, wherein said flow improver comprises solid particles having a polymeric core and a polymeric shell at least partly surrounding said core, wherein said core comprises a drag reducing polymer, wherein said shell comprises a shell copolymer having repeat units of a hydrophobic compound and repeat units of a first amphiphilic compound. 
   
   
       23 . The process of claim  22 , wherein said solid particles have a mean particle size of less than 1 micron, wherein said shell has a thickness in the range of from about 0.5 to about 30 nanometers. 
   
   
       24 . The process of claim  22 , wherein said shell further comprises repeat units of a second amphiphilic compound, wherein said first amphiphilic compound is a non-ionic polymerizable surfactant and said second amphiphilic compound is an ionic polymerizable surfactant, wherein the weight ratio of repeat units of said first polymerizable surfactant to repeat units of said second polymerizable surfactant in said shell is in the range of from about 0.25:1 to about 30:1. 
   
   
       25 . The process of claim  42 , wherein said pump injects said flow improver at a pressure of at least 500 psig, wherein said flow improver is injected into said fluid at a rate sufficient to provide in the range of from about 0.1 to about 200 ppmw of said drag reducing polymer in said fluid, wherein said fluid is a hydrocarbon-containing fluid.