The Synthesis Of Guar Gum Derivatives

Guar gum, a water-soluble natural polymer, is composed mostly of ploygalactomannans which is essentially a straight chain mannan with single membered galactose branches. The mannose units are linked in a l-4-.beta.-glycosidic linkage and the galactose branching takes place by means of a 1-6 linkage on alternate mannose units. The ratio of galactose to mannose in the guar polymer is, therefore, one to two. Guar gum is often chemically modified to improve its physical and chemical properties, so that it can be used as thickeners for foods, paints, oil well fluids, personal care products, and many other functional applications.Hydroxypropyl guar gum (HPG) is prepared by the reaction of guar gum with propylene oxide. NMR and IR are used to characterize the structure of HPG; spectrometry is also used to determine molar substitution. The synthetic procedure was studied as the base of the content of insoluble residue and the viscosity, them the best technical conditions were determined. Comparing with original guar gum, HPG remains its viscosity and cross linking ability, and considerably decrease its content of insoluble residue. The cost of production has been decreased greatly.In order to prepare cationic guar gum, the cationic etherifying agent 3-chloro-2-hydroxypropyl-trimethyl ammonium chloride (CHPTMA) was synthesized firstly. The structure of CHPTMA was confirmed by IR, MS, NMR and DSC, and the optimum conditions were determined. Then, cationic guar gum was synthesized with the cationic etherifying agent CHPTMA and guar gum by organic solvent process. All kinds of influence factors are studied in detail, and the optimum conditions were determined. The modified cationic guar gum remains its viscosity, and has low burn residue and high content of nitrogen.In this paper, amphoteric guar gum was also studied, there are two synthetic routes. First phosphate anionic guar gum was prepared; afterwards amphoteric guar gum was synthesized with the cationic etherifying agent CHPTMA and phosphate anionic guar gum, in this product, maybe the anionic and cationic substituents are at the same chain link or at the different chain link, its isoelectric zone is 6.3~6.6. In order to get the amphoteric guar gum that the anionic and cationic substituents are at the same chain link, 3-chloro-2- hydroxypropyl phosphate and phosphobetaine were synthesized. The structure of these two compounds was confirmed by MS, IR, and NMR, and then amphoteric guar gum was synthesized with the amphoteric intermediate phosphobetaine and guar gum, and the optimum technological conditions were determined. Its isoelectric zone is 7.4~8.6, and has good salt tolerance.