For the synthesis of polycarboxylic acid water-reducing agent, the design of molecular structure is very important, including the main chain group, side chain density and side chain length in the molecule. The synthesis methods mainly include in-situ polymerization grafting method, polymerization first and then functionalization method and monomer direct copolymerization method.
1. In-situ polymerization grafting method
Polyether is used as the polymerization medium of unsaturated monomers to make the main chain polymerization and the introduction of side chains proceed at the same time.
The process is simple, and the molecular weight of the synthesized water reducing agent can be controlled to a certain extent, but the ester involved in this method The chemical reaction is a reversible reaction, which is carried out in an aqueous solution, resulting in a relatively low grafting rate, which has been gradually eliminated.
2. First polymerization and then functionalization method
This method is mainly to synthesize the main chain of the water reducer first, and then introduce the side chain into functionalization by other methods. This method is difficult to operate, the molecular structure of the water reducer is not flexible and the compatibility between monomers is not good, making The use of this method has been greatly restricted.
3. Direct monomer copolymerization method
In this method, the reactive macromonomer is prepared first, and then the small monomer and the macromonomer are copolymerized under the initiation of an initiator in an aqueous solution. With the increasing maturity of the synthesis process of macromonomers and the increasing variety, this synthesis method has become the most commonly used method for the synthesis of polyanthoic acid water reducers at this stage.