초록 ▼

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 comp

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.

대표청구항 ▼

1. 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 effe

1. 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, the 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., anda 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,aaa) a stable aciueous 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, andeee) optionally, the latex obtained in stage ddd) is heated at a temperature of between 40 and 90° C., andb) recovery of the latex thus obtained. 2. 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., anda surface tension of less than 50 millinewtons per metre. 3. The process according to claim 1, wherein the transfer agent is selected from the group consisting of dithioesters, thioethers-thiones, dithiocarbamates and xanthates. 4. The process according to claim 1, 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, andat least one transfer agent of formula (I):wherein:R represents an R2O-, R2R′2N- or R3- group with:R2 and R′2, which are identical or different, representing: (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,R3 representing H, Cl, an alkyl, aryl, alkene or alkyne group, an optionally substituted, saturated or unsaturated (hetero)cycle, an alkylthio, alkoxycarbonyl, aryloxycarbonyl, carboxyl, acyloxy, carbamoyl, cyano, dialkyl- or diarylphosphonato, dialkyl- or diarylphosphinato group, or a polymer chain,R1 represents(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,bb) repeating, at least once, the above operation of bringing into contact using:different monomers from the preceding implementation, andinstead of the precursor compound of formula (I), the polymer resulting from the preceding implementation, andcc) rendering the transfer agent inert at the end of the polymerization. 5. Th e process according to claim 4, 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. 6. The process according to claim 4, 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, andethylenic monomers comprising a sulphonic acid group and its alkali metal or ammonium salts. 7. The process according to claim 4, 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, andunsaturated ethylenic monomers comprising a secondary, tertiary or quaternary amino group, or a heterocyclic group comprising nitrogen. 8. The process according to claim 7, 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. 9. The process according to claim 8, wherein the polymerization of the copolymer is carried out in tetrahydrofuran or in a linear, cyclic or branched C 1 -C 8 aliphatic alcohol. 10. The process according to claim 9, 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). 11. The process according to claim 1, 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., andin optional step ccc), the temperature is of between 60 and 80° C. 12. The process according to claim 1, wherein the ethylenically unsaturated monomer or monomers are selected from the group consisting of styrene, styrene derivatives, butadiene, chloroprene, (meth)acrylic esters and vinyl nitriles. 13. The process according to claim 1, 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 eight of the monomers is employed during the polymerization of the latex. 14. The process according to claim 13, 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 is employed during the polymerization of the latex. 15. The process according to claim 1, 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 is employed during the polymerization of the latex. 16. The process according to claim 15, wherein 1 to 4% by weight of the surface-active block co polymer with respect to the total weight of water is employed during the polymerization of the latex, and of 2 to 5% by weight of the surface-active block copolymer with respect to the total weight of the monomers is employed during the polymerization of the latex.