1. This is a preparation method using a macromolecular reaction. The reaction of polyacrylamide with formaldehyde and dimethylamine is as follows:

The product is a tertiary amine type, which can be easily quaternized into quaternary ammonium salt type with CH, Cl, (CH, O) 2SO, etc. The raw materials for this product are readily available and easy to prepare. The relative molecular mass may vary with the parent polyacrylamide. Therefore, it is a cationic variety that is easy to use and has a large amount. The problems are: the residues of aldehydes and amines in the product should be reduced as much as possible.

Its product is unstable (formaldehyde cross-linking); because of the high viscosity of the polyacrylamide aqueous solution, the concentration used for preparation cannot be high (generally only 1% ~ 2%), and the product storage and transportation is very uneconomical. This product is not easy to make dry powder. Recently developed into latex, the polymer content can be increased.

2. Cationic polymer based on acrylamide copolymerization

At present, most cationic flocculants with high molecular weight come from copolymers of cationic monomers and acrylamide.

Cationic monomers are generally less than 10% due to their high price, which is sufficient for water treatment. Commonly used cationic monomers are:

(1) Ester type:

In the above formula, R is H or CH3; R, R, is CH, or CH, -CH2; X is CI- or (CH3) 2S02. .

Its preparation:

(2) Amide type:

Its preparation:

For the above two types of monomers, the ester bond contained in the ester type is easy to hydrolyze under neutral and alkaline conditions, and there is a risk of losing the cation property by removing the amino group, while the amide type is relatively stable.