Manufacturing method for inverse emulsion polymer

A method to prepare a water-soluble polymer by batch inverse emulsion polymerization comprising:

• (i) preparing an aqueous monomer solution, and if necessary, adjusting pH value of the aqueous monomer solution,
• (ii) preparing an organic solution consisting of a water-immiscible organic liquid that does not interfere with the radical polymerization reaction in step (iv) and (v), said organic solution containing one or more surfactants,
• (iii) adding the aqueous phase of step (i) to the organic phase of step (ii) to prepare a water-in-oil emulsion,
• (iv) removing oxygen and initiating the polymerization reaction by addition of an initiator system,
• (v) adjusting the reaction temperature by external cooling and/or external heating to allow complete polymerization of the monomers into a polymer,
• (vi) optionally adding an inverter surfactant for facilitated inversion or further additives, and
• wherein the initiator system of step (iv) is a
• redox initiator system, said redox initiator system consisting of at least one oxidizing agent and at least one reducing agent, and wherein the oxidizing agent is first added to the reaction mixture followed by all-at-once addition of the reducing agent that optionally also removes residual oxygen;
• and
• wherein the water-soluble polymer comprises a synthetic polymer consisting essentially of:
• (I) 10 to 90% by weight of structural formula (I)
• wherein
• R1, R2 and R3 independently are hydrogen or C1-C6-alkyl,
• (II) 1 to 95% by weight structural units of formula (II)
• wherein
• R4 is hydrogen or C1-C6-alkyl,
• R5 is hydrogen, a cation of an alkaline metal, of an earth alkaline metal, of ammonia and/or of an organic amine,
• A is a covalent C—S bond or a two-valent organic bridging group,
• (III) from 0 to 30% by weight structural units of formula (III)
• wherein
• B is a covalent C—C bond or a two-valent organic bridging group
• R6 and R7 are independently of one another hydrogen, C1-C6-alkyl, —COOR9 or —CH2—COOR9, with R9 being hydrogen, a cation of an alkaline metal, of an earth alkaline metal, of ammonia and/or of an organic amine,
• R8 is hydrogen, a cation of an alkaline metal, of an earth alkaline metal, of ammonia and/or of an organic amine, or is C1-C6-alkyl, a group —CnH2n—OH with n being an integer between 2 and 6, or is a group —CoH2o—NR10R11, with o being an integer between 2 and 6, and
• R10 and R11 are independently of one another hydrogen or C1-C6-alkyl,
• (IV) from 0 to 50% by weight structural units of formula (IV)
• wherein
• R12 and R13 are independently of one another hydrogen, C1-C6-alkyl, —COOR16 or —CH2—COOR16, with
• R16 being hydrogen, a cation of an alkaline metal, of an earth alkaline metal, of ammonia and/or of an organic amine,
• R14 is hydrogen or, C1-C6-alkyl, and
• R15 is —COH, —CO—C1-C6-alkyl or
• R14 and R15 together with the nitrogen atom to which they are attached form a heterocyclic group with 4 to 6 ring atoms,
• (V) from 0 to 20% by weight structural units of formula (V)
• wherein
• D is a covalent C—P bond or a two-valent organic bridging group
• R17 is hydrogen or, C1-C6-alkyl, and
• R18 and R19 are independently of one another hydrogen, a cation of an alkaline metal, of an earth alkaline metal, of ammonia and/or of an organic amine,
• B is a covalent C—P bond or a two-valent organic bridging group;
• wherein the percentage of the structural units of formulae (I) to (V) refer to the total mass of the copolymer and the percentage of the structural units of formulae (I) to (V) amounts to 100%.