Abstract: The invention concerns a branched or crosslinked linear polymer obtainable by polymerising N-alkyl acrylamide, wherein the alkyl radical is linear or branched and comprises 1 to 6 carbon atoms, with one or several monomers selected among the cationic monomers or monomers comprising at least a strong acid function partly salified or completely salified. The invention also concerns a method for preparing same and microlatex or positive latex containing same and their use as heat-thickening agent.

Abstract: Linear, branched or crosslinked polymer, capable of being obtained by polymerization of N-alkylacrylamide, in which the alkyl radical is linear or branched and comprises from 1 to 6 carbon atoms, with one or more monomers chosen from cationic monomers, monomers comprising at least one partially salified or completely salified strong acid functional group or monomers comprising at least one partially salified or completely salified weak acid functional group. A method of preparing the polymer is also disclosed.

Abstract: Linear, branched or crosslinked polymer, capable of being obtained by polymerization of N-alkylacrylamide, in which the alkyl radical is linear or branched and comprises from 1 to 6 carbon atoms, with one or more monomers chosen from cationic monomers, monomers comprising at least one partially salified or completely salified strong acid functional group or monomers comprising at least one partially salified or completely salified weak acid functional group. A method of preparing the polymer is also disclosed.

Abstract: Novel associative acrylic polymers prepared by radical inverse emulsion polymerization. It is a methacrylic ester in which the radical is composed of a hydrophilic segment and of a hydrophobic segment. The associative polymers of the invention can be used as thickeners, flocculating agents or filler-retaining agents.

Abstract: An invert microlatex of at least one cationic water-soluble vinyl monomer, if necessary copolymerized with at least one anionic or non-anionic water-soluble vinyl monomer, is prepared by a process consisting in a first stage (a) of preparation of an invert microemulsion (of the water-in-oil type) and a second stage (b) in which the invert microemulsion obtained in stage (a) is subjected to conditions of polymerization, stage (a) consisting in mixing: (A) an aqueous solution of at least one cationic water-soluble vinyl monomer, if necessary mixed with at least one anionic or non-ionic water-soluble vinyl monomer, (B) an oil phase containing at least one liquid hydrocarbon, and (C) at least one non-ionic surface active agent, in a proportion sufficient to obtain an invert microemulsion, and having an HLB, either between 11 and 15 when the cationic water-soluble vinyl monomer is alone or mixed with an anionic water-soluble vinyl monomer, or between 7.

Abstract: Process for the purifiying water using an effective proportion of a flocculating agent consisting of a reverse microlatex comprising a polymer of at least one water-soluble cationic vinyl monomer, which may be copolymerized with at least one water-soluble anionic or non-ionic vinyl monomer, possessing a molecular weight at least equal to 2.times.10.sup.6.The said microlatex is in the form of particles of a microlatex having a diameter of between 30 and 160 nm and its polydispersity index is between 1.05 and 1.2.

Abstract: By a new process, inverse microlatices of watersoluble copolymers are prepared by copolymerization within an inverse microemulsion obtained by admixing an aqueous phase containing the hydrosoluble monomers to be copolymerized, an organic phase and a non-ionic surfactant or a mixture of non-ionic surfactants, whose H L B ranges from 8 to 11.The resultant microlatices can be diluted in water so as to form thickened solutions, which can be used to improve the production of hydrocarbons from oil formations, particularly in enhanced recovery methods or methods for preventing water inflows in producing wells.

Abstract: A transparent and stable microlatex is dispersed into water and the resultant solution is used for treating an oil or gas well to achieve enhanced oil recovery. The microlatex is prepared by polymerization of a water-soluble monomer in a microemulsion of the water-in-oil type.