![]() A typical example is the use of aqueous calcium carbonate slurries in the production of graphic papers. It is desirable for the latter to be raised as high as possible, owing to the high energy and transportation costs. To ensure wide industrial use these dispersions, also known as slurries, need to show both good pumpability and stability in storage (low deterioration in pumpability) coupled with a high solids content. The invention relates to a process for producing aqueous solutions of acrylic acid polymers.ĭispersants, in particular polyacrylic acids, are widely used in industrial processes where a solid is converted into a pumpable dispersion. The process according to claim 1, wherein the polymerization is carried out under an inert gas atmosphere. The process according to claim 1, wherein up to 30 wt % of comonomers selected from the group consisting of methacrylic acid, maleic acid, maleic anhydride, vinylsulfonic acid, allylsulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid are copolymerized.ħ. The process according to claim 1, wherein all feeds commence simultaneously.Ħ. The process according to claims 1, wherein the total feed time for the hypophosphite solution t 3-t 3. ![]() The process according to claim 1, wherein the molar ratio x of acrylic acid to phosphorus-bound hydrogen / over a time period in which at least 75% of the acrylic acid is converted is 1.5☐.5.Ĥ. ![]() 0 determines commencement of the polymerization.ģ. 0 determine the start of the respective feeds and t 4. ![]() 0) and the polymerization takes place in the time period (t 4-t 4. 0) and the total amount m 3 of aqueous hypophosphite solution over a time period (t 3-t 3. 0), the total amount m 2 of free-radical starter solution over a time period (t 2-t 2. The process according to claim 1, wherein said process comprises adding continuously at a constant or varying dosing rate or discontinuously the total amount m 1 of acrylic acid over a time period (t 1-t 1. 0), and that the time-averaged dosing time point for the hypophosphite solution is 0.3 to 0.45 times the total feed time for the hypophosphite solution.Ģ. A process for producing aqueous solutions of acrylic acid polymers by polymerization of acrylic acid in feed operation with a free-radical starter in the presence of hypophosphite in water as solvent, which comprises (i) initially charging water and optionally acrylic acid in acidic, unneutralized form, optionally one or more ethylenicaliy unsaturated comonomers, optionally aqueous hypophosphite solution, and optionally initiator, (ii) adding acrylic acid in acidic, unneutralized form, optionally one or more ethylenicaliy unsaturated comonomers, aqueous free-radical starter solution, and aqueous hypophosphite solution, (iii) adding a base to the aqueous solution after termination of the acrylic acid feed, wherein the comonomer content does not exceed 30 wt % based on the total monomer content, wherein the acrylic acid, the aqueous free-radical starter solution and the aqueous hypophosphite solution are added such that the molar ratio x of acrylic acid to phosphorus-bound hydrogen / over a time period in which at least 75% of the acrylic acid is converted has a value x which is constant to within ☐.5 and is in the range from 0.8 to 2, that the time-averaged dosing time point for the hypophosphite solution t _ dosing = 1 m 3 ∫ t 3.0 t 3 ( d ( t ) * t ) dt is 0.3 to 0.47 times the total feed time for the acrylic acid (t 1-t 1. Wherein the comonomer content does not exceed 30 wt % based on the total monomer content, wherein the acrylic acid, the aqueous free-radical starter solution and the aqueous hypophosphite solution are added such that the molar ratio x of acrylic acid to phosphorus-bound hydrogen / over a time period in which at least 75% of the acrylic acid is converted has a value x which is constant to within ☐.5 and is in the range from 0.8 to 2.ġ. (iii) adding a base to the aqueous solution after termination of the acrylic acid feed,.(ii) adding acrylic acid in acidic, unneutralized form, optionally one or more ethylenicaliy unsaturated comonomers, aqueous free-radical starter solution and aqueous hypophosphite solution,.(i) initially charging water and optionally acrylic acid in acidic, unneutralized form, optionally one or more ethylenicaliy unsaturated comonomers, optionally aqueous hypophosphite solution and optionally initiator,.A process for producing aqueous solutions of acrylic acid polymers by polymerization of acrylic acid in feed operation with a free-radical starter in the presence of hypophosphite in water as solvent, which comprises
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