Gelled aqueous composition comprising a block copolymer containing at least one water-soluble block and one hydrophobic block

Abstract

The invention relates to a gelling aqueous composition comprising block copolymers containing at least one water-soluble block and at least one block predominantly hydrophobic in nature, and forming a viscoelastic gel.

1 . A block copolymer comprising at least one block water-soluble in nature and containing hydrophobic units and at least one block predominantly hydrophobic in nature, and, in solution in water, forming a viscoelastic gel.  
     
     
         2 . A block copolymer according to  claim 1 , wherein the predominantly hydrophobic block has hydrophilic units in an amount of between 0 and less than 33% by weight, with respect to the total weight of the units of the hydrophobic block.  
     
     
         3 . A block copolymer according to  claim 1 , wherein the predominantly hydrophobic block has hydrophilic units in an amount of between 1 and less than 33% by weight, with respect to the total weight of the units of the hydrophobic block.  
     
     
         4 . A block copolymer according to  claim 2 , wherein the predominantly hydrophobic block has hydrophilic units in an amount of between 2 and 15%, with respect to the total weight of the units of the hydrophobic block.  
     
     
         5 . A block copolymer according to  claim 1 , wherein the block water-soluble in nature has hydrophobic units in an amount of less than 70% by weight, with respect to the total weight of the units of the water-soluble block.  
     
     
         6 . A block copolymer according to  claim 1 , wherein the block water-soluble in nature has hydrophobic units in an amount of between 50 and 25%, with respect to the total weight of the units of the water-soluble block.  
     
     
         7 . A block copolymer according to  claim 5 , wherein the block water-soluble in nature has hydrophobic units in an amount of at least 1% by weight.  
     
     
         8 . A block copolymer according to  claim 1 , wherein the block predominantly hydrophobic in nature is a completely hydrophobic block.  
     
     
         9 . A block copolymer according to  claim 1 , wherein the mass ratio of the blocks predominantly hydrophilic in nature to the blocks predominantly hydrophobic in nature is between 95/5 and 20/80, preferably between 90/10 and 40/60.  
     
     
         10 . A block copolymer according to  claim 1 , wherein the copolymer is at a concentration of between 0.1% and 10% by weight.  
     
     
         11 . A block copolymer according to  claim 1 , wherein at least one of the said blocks is a copolymer coming from the copolymerization of hydrophilic and hydrophobic monomers.  
     
     
         12 . A block copolymer according to  claim 11 , wherein the amounts of hydrophilic and hydrophobic units in each of the said blocks are controlled by the respective contents of hydrophilic monomers and of hydrophobic monomers upon polymerization of the blocks.  
     
     
         13 . A block copolymer according to  claim 1 , wherein at least one of the said blocks is a copolymer prepared: 
 from the polymerization of monomers that may be rendered hydrophilic by hydrolysis, and optionally of non-hydrolysable hydrophobic monomers and of hydrophilic monomers, and then    from the hydrolysis of the polymer obtained.    
     
     
         14 . A block copolymer according to  claim 13 , wherein the amounts of hydrophilic and hydrophobic units in each of the said blocks are controlled by the amount of monomers that can be rendered hydrophilic by hydrolysis and by the degree of hydrolysis.  
     
     
         15 . A block copolymer according to  claim 13 , wherein the hydrophobic monomers are: 
 vinylaromatic monomers;    diolefins; or    alkyl acrylates and methacrylates, the alkyl group of which contains from 1 to 10 carbon atoms.    
     
     
         16 . A block copolymer according to  claim 13 , wherein the hydrophilic monomers are: 
 ethylenically unsaturated carboxylic acids;    acrylamide,(N-methylacrylamide, N-isopropylacrylamide), methacrylamide, polyethylene glycol methacrylate, polyethylene glycol acrylate;    sodium 2-acrylamido-2-methylpropanesulphonate (SAMPS), sodium styrenesulphonate or sodium vinylsulphonate.    
     
     
         17 . A block copolymer according to  claim 13 , wherein the monomers that can be rendered hydrophilic by hydrolysis are: 
 methyl acrylate, ethyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, tert-butyl acrylate;    vinyl acetate;    quaternized 2-dimethylaminoethyl methacrylate and acrylate;    acrylamide or methacrylamide.    
     
     
         18 . A block copolymer according to  claim 1 , being a diblock copolymer or a triblock copolymer having a block water-soluble in nature flanked by two blocks predominantly hydrophobic in nature.  
     
     
         19 . A block copolymer according to  claim 1 , wherein it is a diblock copolymer comprising a block water-soluble in nature and a block predominantly hydrophobic in nature, 
 the block water-soluble in nature containing acrylic acid (AA) units and ethyl acrylate (EtA) units and    the block predominantly hydrophobic in nature containing styrene (St) units and methacrylic acid (MAA) or hydroxyethyl methacrylate (HEMA) units.    
     
     
         20 . A block copolymer according to  claim 19 , wherein the block water-soluble in nature comes: 
 from the polymerization of methacrylic acid (MAA) and of ethyl acrylate (EtA) in an EtA/MAA weight ratio from 90/10 to 99/1, and then    from the hydrolysis of the polymer obtained to a degree of at least 50 mol % up to 95 mol %.    
     
     
         21 . A block copolymer according to  claim 20 , wherein the block predominantly hydrophobic in nature comes from the polymerization of a monomer mixture containing at least 80% by weight styrene.  
     
     
         22 . A block copolymer according to  claim 1 , having a molecular mass of at most 100,000 g/mol.  
     
     
         23 . A process for preparing a block copolymer as defined in  claim 1 , prepared from a so-called living or controlled polymerization process.  
     
     
         24 . A process for the preparation of a block copolymer as defined in  claim 1 , comprising the steps of: 
 a) bringing into contact with one another: 
 at least one ethylenically unsaturated monomer,  
 at least one source of free radicals and  
 at least one compound of formula (I):  
                     
  wherein: 
 R represents an R 2 O—, R 2 R′ 2 N— or R 3 — group, where: R 2  and R′ 2 , which are identical or different, represent (i) an alkyl, acyl, aryl, alkene or alkyne group or (ii) a saturated or unsaturated, possibly aromatic, carbocycle or (iii) a saturated or unsaturated heterocycle, these groups and rings (i), (ii) and (iii) possibly being substituted,  
 R 3  represents H, Cl, an alkyl, aryl, alkene or alkyne group, a saturated or unsaturated ring, a saturated or unsaturated heterocycle, an alkylthio, alkoxycarbonyl, aryloxycarbonyl, carboxy, acyloxy, carbamoyl, cyano, dialkylphosphonato, diarylphosphonato, dialkylphosphinato or diarylphosphinato group, or a polymer chain,  
 R 1  represents (i) an optionally substituted alkyl, acyl, aryl, alkene or alkyne group or (ii) an optionally substituted or aromatic, saturated or unsaturated, carbocycle or (iii) an optionally substituted, saturated or unsaturated, heterocycle, or a polymer chain; to obtain a polymer  
 
   b) repeating above step a) at least once, using: 
 monomers differing from those used in step a), and  
 in lieu of the precursor compound of formula (I), the polymer obtained in the previous step b);  
   c) optionally, hydrolysing the copolymer obtained in step b): and    d)recovering said copolymer.    
     
     
         25 . A process according to  claim 24 , wherein the compound of formula (I) is a dithiocarbonate chosen from compounds of the following formulae (IA), (IB) and (IC):  
       
         
           
           
               
               
           
         
       
       wherein: 
 R 2  and R 2  represent (i) an alkyl, acyl, aryl, alkene or alkyne group, or (ii) an optionally aromatic, saturated or unsaturated, carbocycle or (iii) a saturated or unsaturated heterocycle, these groups and rings (i), (ii) and (iii) possibly being substituted;  
 R 1  and R 1′  represent (i) an optionally substituted alkyl, acyl, aryl, alkene or alkyne group or (ii) an optionally substituted or aromatic, saturated or unsaturated, carbocycle or (iii) an optionally substituted, saturated or unsaturated, heterocycle, or a polymer chain;  
 p is between 2 and 10.  
 
     
     
         26 . A process for controlling the hydrophilic/hydrophobic balance of amphiphilic block copolymers having at least one block coming from the polymerization of hydrophilic monomers and at least one block coming from the polymerization of hydrophobic monomers, wherein: 
 hydrophilic units are introduced into the block coming from the polymerization of hydrophobic monomers, and/or    hydrophobic units are introduced into the block coming from the polymerization of hydrophilic monomers.    
     
     
         27 . a gelling agent or a thickener comprising a copolymer as defined in  claim 1.