INVESTIGATION OF THE PROCESS OF CHEMICAL CROSSLINKING OF NA-CMC POLYVALENT METAL IONS

Abstract

This article is devoted to the study of the Na-CMC structuring process under various conditions: structuring with polyvalent metal ions, structuring with polyvalent metal ions in the presence of polybasic acids. Structuring in a Na-CMC solution was investigated by adding polyvalent metal ions to it at various ratios Me+p / COO-, pH, which allowed us to characterize the structuring process as a reaction of macromolecules with low molecular weight compounds.It was found that the probability of intermacromolecular crosslinking, responsible for gelation, increases with an increase in the initial concentration of Na-CMC solution and with the additional presence of polybasic acids. When salts of polyvalent metals interact with solutions of polybasic acids in the presence of a 2N NaOH solution, their complex salts are formed.Titration calculations and IR spectra of dried salts confirmed the conclusion made about the formation of salts of structure I, II, III, IV. Crosslinking of Na-CMC has been shown to occur via compounds of the M2+ (3+) - OOS-R-type. It has been established that strong, transparent jellies are formed by trivalent metal ions, divalent metal ions also form brittle, cloudy jellies that stratify during a day.A suggestion has been made that the main reaction during gelation of the Na-CMC solution is the interaction of -COOH groups along the chain of the Na-CMC macromolecule with the Al+3 salt and citric acid of structure III. The role of citric acid is that it is a transverse bridge in the binding of Na-CMC macromolecules. During the process of chemical crosslinking, the system turns from a fluid state into a non-fluid one, and the dynamic viscosity of the system increases from 3.548 Pa·s to 1585 Pa·s.