Multiple Modification On Starch And Application In Sizing

With the enhancements of people's environmental protection consciousness, substituting the chemical synthetic PVA with green size is the requirement of "Cleaning production" in textile industry. The modified starch will be the main kind of size in the future. Along with popularization of the "two-high-one-low"(high pressure, high concentration and low viscosity) sizing technics, the low viscosity size will represent the coming tendency. Low viscosity carboxymethyl starch possesses the advantages of low viscosity at high concentration, stable viscosity, good film-forming ability and good adhesivity to cotton fibre, which is considered as a perfect textile size. For example, the famous ASP size made by AVEBE Corp. is just low viscosity carboxymethyl potato starch, which has attracted much attention in markets. Following that, the low viscosity carboxymethyl starch was prepared in this paper by the combination of gamma irradiation and carboxymethylation on cornstarch and by the combination of acidolysis and carboxymethylation on cannaedulisker starch.Cornstarch was carboxymethylated after gamma irradiation to prepare carboxymethyl irradiated starch (CMIS) and cannaedulisker starch was carboxymethylated after acidolysis to prepare carboxymethyl acidolysis starch (ZY-CMS) in this paper for the first time. By studying on the property index of the low viscosity CMS and the relations between the property index and size performances, it was proved that the CMIS and ZY-CMS had a perfect sizing property. The ZY-CMS has been used as a green size with a wide developing foreground to replace the PVA.The effects of ⁶⁰Co-gamma radiation on cornstarch were studied in the paper. It was found that the viscosity of irradiated starches would decrease with the irradiation dose increasing, whereas the carboxyl and carbonyl groups contents in irradiated starch increased with the irradiation doses increasing. With the same irradiation dose, the higher the dose rate was, the higher the apparent viscosity was. The results also showed that the irradiated starch had a stable thermal viscosity and there was slightly increase on its acidity and whiteness degree. It also had good storage stability after irradiated. For irradiated cornstarch as a size, the best irradiation dose ranged from 5 to 10kGy. The decrease of relative crystallinity of irradiated starch was confirmed by X-ray diffraction analysis and DSC analysis, and the decrease of gelation temperature of gamma irradiated starch was confirmed by Brabendar viscosity analysis. Little change was found on the granules form of gamma irradiated starch by polarizing microscope, SEM analysis.Effects of reaction temperature, reaction time, ratio of ethyl alcohol and water, ratio of liquid and solid etc. on the degree of substitute (DS), viscosity, transparency and rheology of the carboxymethyl starch in ethyl alcohol reaction media were studied. It was found that DS, viscosity, and transparency of solution of CMS prepared at lower reaction temperature for a longer time were higher than those prepared at a higher temperature; and that to a certain extent along with the ratio of ethyl alcohol and water increasing or water content decreasing, the DS and viscosity of CMS increased. At the same time the transparency and PVI value decreased and the rheology approach non-Newton fluid. It was the carboxymethylation uniformity that was, to some extent, a decisive factor to affect the transparency. The best ratio range of ethyl alcohol and water was 80: 20～85: 15. The DS and viscosity decreased as the ratio of liquid and solid increased. The purity of CMS affected the viscosity seriously. The transparency of solution of CMS decreased sharply as the crosslink occurred. Apart from the effects of the ratio of ethyl alcohol and water on DS, viscosity, transparency and rheology etc, it was one of the most important factors that decided whether the reaction could be processed. More attention must be paid to it.Reaction kinetics of carboxymethylation of cornstarch was also studied in the paper. The equation of reaction rate corresponded with reaction of second-order. The main and side reaction rate constants at different temperature were obtained respectively, and the relationships between them correspond with the Arrhenius equation. The main reaction activation energy was E₁=64.77 kJ/mol, and the side reaction activation energy was E₂=87.72 kJ/mol. It was further proved that it is favor of the main reaction at lower temperature with high etherification efficiencyEffects of gamma radiation on the carboxymethylation of irradiated Cornstarch were studied carefully. It was found that irradiation dose influenced the viscosity of CMIS remarkably. The CMIS had the character of low viscosity at high concentration, and the more the irradiation dose, the lower the viscosity and the closer of the rheological behavior to a Newtonian liquid. The viscosity increased with the increasing of the dose rate and the degree of substitution. Because of the decrease of relative crystallinity of gamma irradiated starch, gamma irradiation could activate the starch to react with monochlo acetic acid. The more the irradiation dose was, the higher the degree of substitution and the reaction efficiency was. The CMIS had a stable thermal viscosity. Breaking tenacity and Extension at break of CMIS decreased as the viscosity decreased. The film property was sensitive to air humidity. It became hard and fragile, and had a higher breaking tenacity and lower extension at break in lower humidity. It became flexible and had a lower breaking tenacity and higher extension at break in higher humidity. The viscosity stability increased with the increasing of DS. The highest breaking tenacity was in the range of DS 0.2～0.3 and pH 7～9. The film property became better and better as the purity of CMIS increased.Using the multiple modified processes of acidolysis and etherification to prepare low viscosity carboxylmethyl starch with the cannaedulisker starch, which is the unique agriculture resource in west Guizhou, China. The viscosity of acidified starch decreased xremarkably, the relative crystallinity increased, and the gelation temperature decreased slightly. Etherification efficiency and DS of acidified starch were lower than the natural starch because the relative crystallinity of acidolysis starch increased. ZY-CMS had a granule shape, soluble in cold water and with high clarity of aqua solution. The results indicated ZY-CMS was a size with low viscosity at high concentration, which had a good viscosity thermal-stability. It possessed better adhesivity to the cotton fibers and had better film-forming property. 50% PVA could be replaced by ZY-CMS and reached excellent effect in the sizing test. It had good sizing properties such as wear-resistance and hairiness reducing percentage. ZY-CMS was trial-produced in a large scale for many times. The trial-production was operated successfully. The quality of trial-product corresponded with that of the sample from lab and the Standard Q/ZBG02-2004. The trial-production was confirmed to be a green size to replace PVA used in Wujiang C&D Corp and other factories. ZY-CMS supplied a gap in China and had a wide market foreground. The achievement appraisal organized by Guizhou Science and Technology Bureau was carried in 2004. ZY-CMS is very important to help the poor peasants and for the western development.