Polyacrylamide (PAM) preparation method-inverse microemulsion polymerization

(3) Reverse microemulsion polymerization

In recent years, inverse microemulsion polymerization has appeared on the basis of inverse emulsion polymerization
.

Using surfactants to stabilize the microemulsion to polymerize acrylamide can produce thermodynamically stable and optically transparent water-soluble PAM emulsions with a particle size of 0.

The process is as follows
.

Add the acrylamide monomer and the desalinated water into the batching kettle, and configure the acrylamide monomer aqueous solution with a fixed mass concentration

Table 3-9 Process parameters of PAM microemulsion prepared by inverse microemulsion polymerization

(4) Precipitation polymerization

The key to precipitation polymerization is to use an appropriate solvent to dissolve the monomers, while the resulting polymer does not dissolve in it and precipitates, and a powdery product can be directly obtained
.

In the process of preparing PAM by precipitation polymerization, the main attention is paid to the choice of solvent and dispersant
.

The solvent includes a polar solvent selected, the polarity of a mixed solvent of water or a polar solvent mixture (see Table 3-10), aqueous inorganic salt solution and an aqueous solution of an inorganic salt added to the dispersion and the like

Table 3-10 Effective solvents for precipitation polymerization

① When the monomer concentration is 27% to 32%, the relative molecular weight of the product is as high as 9×10 ⁵
.

②Adjust the mass ratio of the mixed solvent and the monomer concentration to obtain the relative molecular mass of PAM (2.

0-24)×10 ⁴ , and the AM conversion rate can reach 97%

③When the isopropanol content is lower than 36%, it is normal solution adjustment polymerization, when 36%～75% is incomplete precipitation polymerization, when it is higher than 75%, it is precipitation polymerization, and the relative molecular weight of PAM obtained is 10 ⁴～10 ⁶
.

④AM is 20%, the dosage of K ₂ S ₂ O ₈ and NaHSO ₃ are 0.
2% respectively.
When the isopropanol content is lower than 45%, the molecular weight decreases with the increase of temperature; while the isopropanol content is higher than 45% , The molecular weight increases with the increase of temperature, and precipitation polymerization is obvious at this time
.

⑤Under the same reaction conditions, the molecular weight of the precipitation polymerization product is higher than that of the solution polymerization product
.

(5) Disperse polymerization

A new PAM product, namely water-in-water PAM emulsion, can be prepared by the dispersion polymerization method
.

The so-called water-in-water emulsion refers to a polymer emulsion prepared by dispersing a water-soluble polymer into an aqueous medium under the action of a dispersant.

Preparation of water-in-water PAM emulsion: add the dispersion stabilizer and acrylamide monomer to the reaction medium and stir at room temperature, and pass nitrogen into the reaction system to drive oxygen.
After the dispersion stabilizer and AM are all dissolved in the dispersion medium, When a homogeneous system is formed, adjust the temperature of the system to 20-80°C, add an initiator, and stir for 4-10h under a nitrogen atmosphere
.

After the reaction is completed, it is cooled to room temperature to obtain a water-in-water PAM emulsion product

Related Links: Polyacrylamide (PAM) Preparation Method-Inverse Emulsion Polymerization (3)