Method for preparing amphoteric chitosan water reducing agents

The invention relates to a method for preparing amphoteric chitosan water reducing agents. The amphoteric chitosan water reducing agents are prepared from chitosan, methoxy polyethylene glycol, acetic anhydride and chlorosulfonic acid through reaction. The method has the innovation point that the natural chitosan is used as raw materials, methoxy polyethylene glycol (MPEG) and hydrophilic sulfo groups are introduced, and the novel amphoteric chitosan water reducing agents are prepared. The prepared amphoteric chitosan water reducing agents have the advantages that the product performance is stable, the cement adaptability is high, the compatibility is good, the cement initial net pulp flowability can reach a value higher than 250mm (W/C=0.29), the concrete water reducing rate can reach about 25 percent, the one-hour collapsbillity can reach 140mm, and in addition, no pollution is caused on the environment. The preparation method has the advantages that the preparation process is noveland unique, the industrial production is convenient, and the like.