Study On Chemical Modification Of Guar Gum By Dry Method And Its Application In Reactive Dye Printing

At present, sodium alginate (SA) is most widely used as a thickener in reactive printing for its easy colored, high quality of color, bright in color and soft handle of fabric after printing. In recent years, with the continuous development of printing technology, it raises high request about printing paste especially printing paste thickener. It doesn't meet the requirements of high quality printing that only use the sodium alginate as printing paste thickener. Moreover, the fluctuation in price and quality, as well as the limited supply of alginates, has increased the printing cost and affected the manufacturer's economic benefit directly. Therefore, it is very important to look for the alternatives of sodium alginate, which will not only improve the printing performance but also reduce the production cost. The aim of this thesis was to prepare oxidized guar gum and carboxymethyl guar gum with a simple dry method with guar gum as raw material, study the compatible behavior of modified product and the other natural polysaccharides and study the printing proprieties of all kinds of mixed paste. The main contents were summarized as follows:(1) The aim of this part of the work was to prepare oxidized guar gum (OGG) with a simple dry method and use hydrogen peroxide as oxidant. To obtain a product with suitable viscosity for reactive dye printing, the effects of various factors such as the amount of oxidant and solvent, reaction temperature and time were studied with respect to the viscosity of reaction products. The optimized reaction conditions in the oxidation reaction are:usage of H2O2,7%; percentage of solvent,30%; reaction temperature,65℃; and reaction time,1h. The product was characterized by FTIR, GPC, SEM and DSC. The hydrated rate of guar gum and oxidized guar gum was estimated. The rheological properties of OGG pastes were studied using a rotational viscometer. The effects of the salt concentration and pH on viscosity of the resultant product were studied. In addition, the applied effect of OGG paste in reactive dye printing was examined by assessing the fabric stiffness, color yield and sharp edge to the printed image in comparison with sodium alginate. And the results indicated that the OGG paste could use as thickener in reactive dye printing.(2) Carboxymethyl guar gum (CMGG) was synthesized with a simple dry method. The influences of a variety of reaction parameters for degree of substitution were evaluated. All these are with a view to optimizing the synthesis conditions for high degree of substitution. The optimized reaction conditions in the reaction are: nMCA/nNaOH,0.55; the volume of95%ethanol,15mL; the reaction temperature of the first and second step,30and60℃; and reaction time of the first and second step,40min and10h. The product was characterized by FTIR, SEM, XRD and DSC. The rheological properties of product pastes were studied using a rotational viscometer. The viscosity of products'solution decreased with increasing temperature and increased with increasing concentration. With the increase of storage time, the viscosity increased at first, and then decreased. In addition, a shear thinning pseudoplastic behavior was observed at all concentrations, temperatures and storage times. In addition, the applied effect of CMGG paste in reactive dye printing was examined by assessing the fabric stiffness, color yield and sharp edge to the printed image in comparison with sodium alginate. And the results indicated that the CMGG paste had a good performance as thickener in reactive dye printing.(3) The mixed paste among OGG, CMGG, SA, CMS, CMC and XG was prepared and their viscosities were determined by the viscometer. It can be seen from the viscosity of mixed paste that there existed strong synergistic interactions among the different polysaccharides. The rheological property of the mixed paste was appraised by the printing viscosity index (PVI). From the value of PVI, it can be seen that SA and CMC had a high PVI, but CMS and XG had a low PVI. In addition, the applied effect of mixed paste in reactive dye printing was examined by assessing the fabric stiffness, color yield and sharp edge to the printed image in comparison with sodium alginate. And the results indicated that CMGG had a better applied effect compared with OGG. The mixed paste of CMGG and CMS could partially replace sodium alginate as thickener in reactive dye printing in some situations. In addition, CMC could use as thickener in reactive dye printing but XG couldn't because of its worse flowability in the process of printing.