Application of sodium acetate in printing and dyeing process

Sodium acetate can be weathered and combustible in air. Soluble in water, slightly soluble in ethanol, insoluble in ether. It is used as an esterifying agent in organic synthesis, as well as photographic medicine, medicine, printing and dyeing mordant, buffer agent, chemical reagent, meat preservative, pigment, tanning leather and many other aspects.

Sodium acetate should be the acid that most commonly used in printing and dyeing process: acid neutralization of alkaline pretreatment, pH regulation of dyeing with disperse dyes, acid dyes, cationic dyes, pH regulation of acid cellulase polishing, etc. So why is acetic acid used in large quantities?

Effect of acid on cotton fiber

1.Acid can cause cotton fiber to decrease

The hydrolysis of cotton cellulose occurs when it encounters acids. The principle is that the glucose residues of cellulose macromolecules are linked by 1,4-glycoside bonds, which are sensitive to acids. The hydrolysis of cotton cellulose by acid results in the formation of glucose when all the glycoside bonds in the cellulose macromolecule are broken. Cellulose hydrolyzed to form cellulose hydrolysate, the degree of polymerization decreased and the strength decreased. Therefore, acid can cause the strength of cotton fibers to decrease.

2.Effect of different acids on the strength of cotton fibers

Hydrochloric acid and nitric acid had the most severe reduction of cotton fiber, followed by sulphuric acid and sodium bisulfate and phosphoric acid. Formic acid is much weaker than acetic acid, but now many dyeing plants are still neutralizing it with formic acid because the cost of formic acid is lower than that of sodium acetate. Comprehensive consideration, sodium acetate is the most suitable acid for cotton fiber processing.

Acetic acid sodium acetate PH buffer system

Buffer solution: A mixed solution consisting of weak acid and its salts, weak base and its salts can counteract and alleviate to a certain extent the influence of external strengthened acid or strong base on the acidity and basicity of the solution, thus maintaining a relatively stable pH value of the solution.

In the dyeing of disperse dyes, acid dyes, cationic dyes and other dyes, PH is generally acidic. In order to achieve stable PH control, some factories will use acetic acid-sodium acetate buffer system for accurate control of PH, in order to improve the reproducibility and success rate of dyeing.

Preparation of acetic acid sodium acetate buffer solution commonly used in PH.

Acetic acid sodium acetate buffer (pH3.6)

Take acetic acid sodium 5.1g, add glacial acetic acid 20ml, add water to dilute to 250ml.    

Acetic acid sodium acetate buffer (pH3.7)

Take anhydrous sodium acetate 20 g, add water 300 ml to dissolve, add bromophenol blue indicator solution 1 ml and glacial acetic acid 60 ~ 80 ml, to the solution from blue to pure green, and then dilute water to 1000 ml.

Acetic acid sodium acetate buffer (pH3.8)

Take 2 mol/L sodium acetate solution 13 ml and 2 mol/L acetic acid solution 87 ml, add 1 mg copper sulfate solution 0.5 ml per ml, then dilute to 1000 ml with water.

Acetic acid sodium acetate buffer (pH4.5)

Take acetic acid sodium 18G, add glacial acetic acid 9.8ml, add water to dilute to 1000ml, that is.

Acetic acid sodium acetate buffer (pH4.6)

Take sodium acetate 5.4 g, add water 50 ml to dissolve, with glacial acetic acid to adjust the pH value to 4.6, and then dilute water to 100 ml, then get.

Acetic acid sodium acetate buffer (pH6.0)

Remove the sodium acetate 54.6g, add 1mol/L acetic acid solution 20ml, and add water to 500ml.

Advantages of acetic acid when cellulase is polished

Cotton fabric polishing is now widely used. Cellulase can remove hairiness and fine hairiness balls on the surface of cotton fiber. Sodium acetate is used to polish cotton fabric because acetic acid will produce sodium acetate when it encounters alkaline substances. Sodium acetate is formed when alkali occurs, and the PH value inside the fiber is on the high side. Therefore, it is helpful to protect the strength of the fiber and achieve the effect of surface polishing.