Preparation of low-salt and low-viscosity polyacrylamide water-in-water dispersion by seed swelling method

Abstract

The invention belongs to the technical field of synthesis of water-soluble polymer dispersion, and particularly relates to a method for polymerizing anionic polyacrylamide water-in-water dispersion liquid. Preparation of low-salinity and low-viscosity polyacrylamide water-in-water dispersion liquid by employing a seed swelling method comprises the following steps: firstly, preparing a seed polymer (SP) by a copolymerization reaction, and then preparing the polyacrylamide water-in-water dispersion liquid by taking the prepared seed polymer (SP) as a raw material, wherein the molecular weight of the seed polymer (SP) is controlled at 1*10<6> to 3*10<6>. By adopting the method, low viscosity and stability of the system in the process of preparing the polyacrylamide water-in-water dispersion liquid can be effectively ensured; meanwhile, the dosage of inorganic salt is reduced. Thus, the condition that the prepared product has high molecular weight, high mobility and high storage stability is ensured.

Description

technical field [0001] The invention belongs to the technical field of water-soluble polymer dispersion synthesis, and in particular relates to a method for polymerizing an anionic polyacrylamide water-in-water dispersion. Background technique [0002] The existing industrial production methods of polyacrylamide include solution polymerization, inverse suspension polymerization and inverse emulsion polymerization. The product obtained by the solution polymerization production method is a powder. Except for the high viscosity problem in the production process, it is similar to the reverse phase suspension polymerization. Since drying and granulation is required in the end, it is inevitable to introduce dry granulation equipment, which increases production costs. At the same time Dust is generated during production, and the final product still has problems such as difficulty in dissolving. However, inverse suspension polymerization and inverse emulsion polymerization use a la...

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Problems solved by technology

[0007] (3) The polyacrylamide copolymer water-in-water dispersion prepared by the "self-polymerization nucleation" method has high viscosity, poor fluidity and poor storage performance

As mentioned above, in the process of "self-polymerization nucleation", phase separation is promoted by the addition of a large amount of inorganic salts. In a high-concentration inorganic salt solution, the repulsion of the electric double layer of the latex particle surface charge is weakened, and the particle stability is greatly reduced. , a steric stabilizer must be added to prevent the agglomeration between particles. Most of the existing patent documents focus on the use of various macromolecular dispersants and composite dispersants to improve the stability of latex particles. Stable due to steric hindrance, in order to improve the adsorption effect and stabilization performance, the molecular weight is often very large, usually as high as 500,000 to 1,500,000, which results in poor fluidity of the final product dispersion, which is not conducive to practical application

This is the shortcoming that the traditional "self-polymerization nucleation" method cannot overcome

[0008] (4) In the "self-polymerization nucleation" method, the system in the early stage of the reaction is mainly monomer and water, and a large amount of monomer is dissolved in water, which makes it difficult to separate the formed polymer in time and increases the viscosity of the system. The system is phase-separated in time, and a high inorganic salt concentration must be maintained; but in the late stage of the reaction, the system is mainly composed of polymer and water, and the polymer can promote the phase separation. As the concentration increases in disguise, the dispersant chains that provide steric hindrance curl up, the stabilization efficiency decreases, and the polymer particles are easy to aggregate

It can be seen that the concentration of inorganic salts plays an important role in the polymerization process. There are different requirements for the concentration of inorganic salts in the early and late stages of the reaction, and it is difficult to adopt different reaction conditions for different periods of the reaction by using the "self-polymerization nucleation" method.

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