Synthesis Of Modified Starch And Its Application In The Printing Paste

Paste is generally used as thickener to adjust the rheological properties ofcolorants in reactive dye printing. Alginate is the first choice of reactive dyes printingpaste because it does not react with the reactive dyes, high color yield, completelychromatography, easy to wash away from the fabric, printed fabric soft, etc. but it ismore expensive, the cost of printing is high. With the printing technology continues toimprove, alginate has been unable to meet the demand of high quality textiles. So lookfor a low-cost, good-performance paste has became a top priority.In the subject, corn starch and chloroacetic acid is main raw material, ethanol isorganic solvents, synthesis of carboxymethyl starch (CMS) by mix in alkaline step bystep. Take the viscosity and substitution degree of the CMS as indicator,comprehensive study of the ration of materials, water consumption, reaction time,reaction temperature and other process conditions to determine the optimum processparameters and experimental program. Through the physical and chemical propertiestest and the printing effects test such as viscosity, rheology, printing color yield andde-paste rate, We find that CMS as reactive printing have the advantage of strongpseudoplastic、high stability and drawback of poor water absorbability、low de-pasterate. Chosen alginate and LD plant paste which have strong water absorbability andhigh de-paste rate mixed with CMS to make up the shortfall and meet the printingrequirements. Aimed at replace the paste of alginate, improve the printingperformance and reduce the production costs.Single factor analysis and orthogonal experiment method have been used in theprocess of preparation CMS, determined the factors affecting the degree ofsubstitution primary to the secondary: ethanol concentration> dosage of ethanol>etherification temperature> dosage of sodium hydroxide> etherification time>alkalization temperature> dosage of chloroacetic acid> alkalization time. Optimalexperimental conditions are as follows: chloroacetic acid and starch molar ratio is1.25, sodium hydroxide and starch molar ratio is2.8, alkalization temperature is37℃,alkalization time is70min, alkalization temperature is65℃, alkalization time is4.3h,ethanol concentration is97%and dosage of ethanol is4.25ml/g. Prepared under optimum conditions the substitution degree of carboxymethyl starch is0.88, pastewhose mass fraction is4%viscosity is6650mPa.s. The modified starch used incotton fabric with reactive dyes printing, we found those rheological properties andstorage stability is better than alginate, the color yield, pattern clarity, color fastnessand other aspects is also equal to alginate, but its paste removal rate low will affectthe fabric handle. CMS should be improved if it used as printing paste separately.This topic mixed alginate and LD plant paste with CMS, mixed thickenersappeared some changes in properties. According to the viscosity, rheologicalproperties and PVI value, six appropriate proportion mixed paste have been selected,such as CMS:SA=1:4、 CMS:SA=2:3、 CMS:LD=2:3、 CMS:LD=2.5:2.5、CMS:SA:LD=2:3:1and CMS:SA:LD=3:2:1. Based on the properties and printingeffect of compound paste, complex system paste removal rate can be increased tosome extent can be found, all more than85%. As a whole, color yield andpermeability of the CMS-LD is superior to the CMS-SA complex system, but its pasteremoval rate and softness are worse. Three mixed system compound paste isequivalent to two mixed system on printing effect. Paste type and mixed ratio have noinfluence on chemical stability of mixed thickeners and color uniformity and fastnessof printing fabric.In a word, the compound paste mixed alginate and LD plant paste with CMSregulated the rheological properties of the paste, improved the printing effect of thefabric, reduced the production cost of the enterprises. We can select suitable types andproportion mixed paste according to the printing equipment and flower pattern in theactual production.