Process for the preparation of latices using block copolymers as surfactants

Abstract

A subject-matter of the present invention is a process for the preparation of a latex by radical aqueous emulsion polymerization in the presence of at least one ethylenically unsaturated monomer, of at least one radical polymerization initiator and of at least one surface-active block copolymer comprising at least one hydrophilic block and at least one hydrophobic block which is prepared by a “living” or “controlled” preparation process, the said copolymer exhibiting a number-average molecular mass of between 2 000 and 20 000, preferably between 4 000 and 16 000, a glass transition temperature of the hydrophobic block of less than 30° C., preferably of less than 25° C., and greater than −100° C., and a surface tension of less than 60 millinewtons per metre (mN/m), preferably of less than 50 mN/m, measured at a concentration in demineralized water of less than or equal to 10 −4 mol/l at 20° C. and under one atmosphere, and the transfer agent having been rendered inert with respect to the said radical polymerization. The latices obtained can be used in particular in paints, adhesives and building materials.

1 - 20 . (Canceled)  
     
     
         21 . A process for the preparation of a latex comprising the steps of: 
 a) radical aqueous emulsion polymerization of a reaction mixture, to obtain a latex, said reaction mixture comprising at least one ethylenically unsaturated monomer, at least one radical polymerization initiator and at least an effective amount of a surface-active block copolymer comprising at least one hydrophilic block and at least one hydrophobic block which is prepared by a “living” preparation process using a transfer agent being a dithiocarbonate selected from the group consisting of the compounds of following formulae (IA), (IB) and (IC):                          wherein:    R2 and R2′ represent    (i) an alkyl, acyl, aryl, alkene or alkyne group,    (ii) an optionally aromatic, saturated or unsaturated carbonaceous ring, or    (iii) a saturated or unsaturated heterocycle,    groups and rings (i), (ii) and (iii) being optionally substituted,    R1 and R1′ represent    (i) an optionally substituted alkyl, acyl, aryl, alkene or alkyne group,    (ii) a carbonaceous ring which is saturated or unsaturated and which is optionally substituted or aromatic, or    (iii) an optionally substituted, saturated or unsaturated heterocycle or a polymer chain, and    p is between 2 and 10; and    said copolymer exhibiting:    a number-average molecular mass of between 2 000 and 20 000 g/mol,    a glass transition temperature of the hydrophobic block of less than 30° C., and greater than −100° C., and    a surface tension of less than 60 millinewtons per metre (mN/m), measured at a concentration in demineralized water of less than or equal to 10 −4  mol/l at 20° C. and under one atmosphere,    the transfer agent having been rendered inert with respect to the said radical polymerization, and    b) recovery of the latex thus obtained.    
     
     
         22 . The process according to claim  1 , wherein the copolymer exhibits: 
 a number-average molecular mass of between 4 000 and 16 000 g/mol,    a glass transition temperature of the hydrophobic block of less than 25° C., and    a surface tension of less than 50 millinewtons per metre.    
     
     
         23 . The process according to  claim 21 , wherein the block copolymer is prepared by a process comprising the following steps: 
 aa) as a first implementation, bringing into contact to obtain a polymer:    at least one ethylenically unsaturated monomer,    at least one source of free radicals, and    at least one transfer agent of formulae (IA), (IB) or (IC):    bb) repeating, at least once, the above operation of bringing into contact using:    different monomers from the preceding implementation, and    instead of the precursor compound of formula (I), the polymer resulting from the preceding implementation, and    cc) rendering the transfer agent inert at the end of the polymerization.    
     
     
         24 . The process according to  claim 23 , wherein step cc) comprises masking of active chemical functional groups of the transfer agent by means of a masking agent or destruction of the transfer agent by a hydrolysis or oxidation reaction by metal catalysis or by use of primary radicals.  
     
     
         25 . The process according to  claim 23 , wherein the hydrophilic block derives from hydrophilic monomers selected from the group consisting of: 
 unsaturated ethylenic mono- and dicarboxylic acids,    monoalkyl esters of the dicarboxylic acids of the type mentioned with alkanols preferably having 1 to 4 carbon atoms and their N-substituted derivatives,    amides of unsaturated carboxylic acids, and    ethylenic monomers comprising a sulphonic acid group and its alkali metal or ammonium salts.    
     
     
         26 . The process according to  claim 25 , wherein the hydrophilic block derives from hydrophilic monomers selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, 2-hydroxyethyl acrylate or methacrylate, acrylamide, methacrylamide, vinylsulphonic acid, vinylbenzenesulphonic acid, alpha-acrylamidomethylpropanesulphonic acid, 2-sulphoethyl methacrylate, 2-acrylamido-2-methylpropanesulphonic acid and styrenesulphonate.  
     
     
         27 . The process according to  claim 23 , wherein the hydrophobic block derives hydrophobic monomers selected from the group consisting of: 
 esters of acrylic acid and of methacrylic acid with hydrogenated or fluorinated C 1 -C 12  alcohols,    vinyl nitriles having from 3 to 12 carbon atoms,    carboxylic acid vinyl esters,    vinyl halides,    vinylamine amides, and    unsaturated ethylenic monomers comprising a secondary, tertiary or quaternary amino group, or a heterocyclic group comprising nitrogen.    
     
     
         28 . The process according to  claim 27 , wherein the hydrophobic block derives hydrophobic monomers selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, t-butyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl versatate, vinyl propionate, vinylformamide, vinylacetamide, vinylpyridines, vinylimidazole, dimethylaminoethyl acrylate or methacrylate, di-tert-butylaminoethyl acrylate or methacrylate, and dimethylaminomethylacrylamide or -methacrylamide.  
     
     
         29 . The process according to  claim 28 , wherein the polymerization of the copolymer is carried out in tetrahydrofuran or in a linear, cyclic or branched C 1 -C 8  aliphatic alcohol.  
     
     
         30 . The process according to  claim 29 , wherein the alcohol is methanol, ethanol, cyclohexanol or ethylene glycol, and wherein the hydrophilic monomer is acrylic acid (AA), acrylamide (AM), 2-acrylamido-2-methylpropanesulphonic acid (AMPS) or styrenesulphonate (SS).  
     
     
         31 . The process according to  claim 21 , wherein said process comprises the following steps: 
 aaa) a stable aqueous preemulsion comprising starting ethylenically unsaturated monomers and the surface-active block copolymer is prepared,    bbb) a reaction mixture comprising a conventional surfactant, an initiator and water is introduced into a radical polymerization reactor comprising two openings and from 1 to 10% by weight of preemulsion prepared in step aaa) is added to the said mixture,    ccc) the reaction mixture obtained at the end of stage bbb) is heated to a temperature of between 40 and 90° C., for the purpose of generating a seed formed of latex particles in dispersion in the water,    ddd) the preemulsion obtained in stage aaa) is added with an additional amount of initiator via the two separate openings of the reactor to produce the latex, and    eee) optionally, the latex obtained in stage ddd) is heated at a temperature of between 40 and 90° C.    
     
     
         32 . The process according to  claim 31 , wherein: 
 in step bbb) of preemulsion prepared is of between 3 and 7%,    in step ccc), the temperature is of between 60 and 80° C., and    in optional step eee), the temperature is of between 60 and 80° C.    
     
     
         33 . The process according to  claim 21 , wherein the ethylenically unsaturated monomer or monomers are selected from the group consisting of styrene, styrene derivatives, butadiene, chloroprene, (meth)acrylic esters and vinyl nitrites.  
     
     
         34 . The process according to  claim 21 , wherein 0.5 to 5% by weight of the surface-active block copolymer with respect to the total weight of water is employed during the polymerization of the latex, or of 1 to 8% by weight of the surface-active block copolymer copolymer with respect to the total weight of the monomers employed during the polymerization of the latex.  
     
     
         35 . The process according to  claim 34 , wherein 1 to 4% by weight of the surface-active block copolymer with respect to the total weight of water is employed during the polymerization of the latex, and 2 to 5% by weight of the surface-active block copolymer with respect to the total weight of the monomers employed during the polymerization of the latex.  
     
     
         36 . The process according to  claim 31 , wherein 0.5 to 5% by weight of the surface-active block copolymer with respect to the total weight of water is employed during the polymerization of the latex, or 1 to 8% by weight of the surface-active block copolymer copolymer with respect to the total weight of the monomers employed during the polymerization of the latex.  
     
     
         37 . The process according to  claim 36 , wherein 1 to 4% by weight of the surface-active block copolymer with respect to the total weight of water is employed during the polymerization of the latex, and 2 to 5% by weight of the surface-active block copolymer with respect to the total weight of the monomers employed during the polymerization of the latex.