Anionic thermoviscosifying water-soluble polymers, preparation method and application thereof

A method for preparing an anionic thermoviscosifying water-soluble polymer, comprising the following steps:

• (1) preparing an aqueous phase with an acrylamide monomer, an anionic monomer, a temperature-sensitive polyether, an inorganic salt, and deionized water, with pH values in between 6.5 and 7.5;
• preparing an oil phase by adding an emulsifier to an oil;
• wherein a percentage of the aqueous phase ranges from 10% to 90% based on a total mass of both the aqueous phase and the oil phase;
• obtaining an emulsion by uniformly mixing the aqueous phase and the oil phase under stirring or gradually adding the aqueous phase to the oil phase to be emulsified;
• adding an initiator in the emulsion under an inert gas atmosphere to form an emulsion system;
• increasing a temperature of the emulsion system to 40-60° C. to initiate a polymerization, or performing a photo-initiated polymerization on the emulsion by heating the emulsion to 40-60° C. without adding the initiator;
• and
• after completing the polymerization or the photo-initiated polymerization, keeping the temperature for 2-6 hours to obtain an inverse emulsion of the anionic thermoviscosifying water-soluble polymer;
• wherein, mass percentages of various components in the aqueous phase are as follows:
• 20%-50% of the acrylamide monomer, 5%-15% of the anionic monomer, 1%-20% of the temperature-sensitive polyether, and 1%-10% of the inorganic salt;
• in the oil phase, a mass percentage of the emulsifier is 1%-20%;
• and
• the emulsifier is a triblock polymeric emulsifier of long-chain fatty acid-polyoxyethylene-long-chain fatty acid, the initiator is at least one selected from the group consisting of a hydrogen peroxide-based initiator, an azo-based initiator, and a benzoin-series initiator;
• the hydrogen peroxide-based initiator is ammonium peroxide or potassium peroxide, the azo-based initiator is 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride or azobisisobutyronitrile, and the benzoin-series initiator is benzoin dimethyl ether;
• and an amount of the initiator is 0.006% to 0.3% based on a total mass of the acrylamide monomer, the anionic monomer, and the temperature-sensitive polyether, the anionic monomer is a salt obtained by a neutralization of acrylic acid, methacrylic acid, or 2-acrylamide-2-methylpropanesulfonic acid, and a base used for the neutralization is at least one selected from the group consisting of ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate;
• and
• (2) precipitating, washing, centrifuging, and drying the inverse emulsion to obtain a dry powder of the anionic thermoviscosifying water-soluble polymer;
• or adding a reverse demulsifier to the inverse emulsion to obtain an emulsion of the anionic thermoviscosifying water-soluble polymer, followed by dissolution in water and dilution to obtain desired diluted solutions,
• wherein the temperature-sensitive polyether is a triblock polymer of polyoxyethylene-polyoxypropylene-polyoxyethylene with a structural formula of:
• wherein a structure and a property of the temperature-sensitive polyether vary with values of m and n.