Sodium carboxymethyl cellulose (CMC) is a common water-soluble cellulose ether that plays a variety of important roles in the textile printing and dyeing process. The following is an introduction to its specific roles and key indicators:
1. Role in the textile printing and dyeing process
Thickening effect: Sodium carboxymethyl cellulose can increase the viscosity of dye liquor and printing paste, so that the dye liquor or printing paste has good fluidity and stability, and prevents the occurrence of infiltration during the printing or dyeing process, thereby ensuring clear pattern outlines and uniform color, and improving the quality of printing and dyeing products. For example, in paint printing, a printing paste with a suitable viscosity can make the paint evenly distributed on the surface of the fabric to obtain a clear and bright pattern.
Dispersion effect: It can effectively disperse particles such as dyes and pigments, prevent them from aggregating and precipitating in the dye liquor or color paste, and make the dye particles evenly distributed in the solution, thereby improving the uniformity and coloring rate of dyeing. For example, when dyeing with reactive dyes, CMC helps the reactive dyes to maintain a good dispersion state in water, so that the dyes can react better with the fibers.
Slow dyeing effect: It can interact with dye molecules to slow down the speed of dye dyeing fibers, so that dye molecules can penetrate into the fiber more evenly, thereby achieving uniform dyeing effect and reducing the occurrence of problems such as uneven dyeing and color spots.
Washing effect: In the washing process after printing and dyeing, sodium carboxymethyl cellulose can prevent the dye from being contaminated again. It can adsorb on the fiber surface to form a protective film to prevent the dye washed off the fiber from reattaching to the fabric, improving the washing effect and the color fastness of the fabric.
Protective colloid effect: As a protective colloid, sodium carboxymethyl cellulose can stabilize the colloid system in the dye solution and printing paste, prevent the colloid particles from agglomerating, maintain the stability of the system, and facilitate the smooth progress of printing and dyeing processing.
2. Key indicators
Degree of substitution (DS): refers to the average number of hydroxyl groups on each glucose unit replaced by carboxymethyl groups. The higher the degree of substitution, the better the solubility and stability of sodium carboxymethyl cellulose in water, and its thickening, dispersing and other properties are also enhanced accordingly. Generally speaking, the degree of substitution of CMC used in textile printing and dyeing is more suitable between 0.6-1.2, and products with a degree of substitution within this range can better meet the performance requirements of the printing and dyeing process.
Viscosity: It reflects the thickness of the sodium carboxymethyl cellulose solution. Different printing and dyeing processes have different viscosity requirements for CMC solutions. For example, in the printing process, a higher viscosity CMC is usually required to ensure the clarity of the printed pattern; while in the dyeing process, the viscosity can be relatively low to facilitate the penetration of the dye. The viscosity of CMC generally used in textile printing and dyeing is in the range of 50-2000mPa·s (2% aqueous solution, 25℃).
Purity: Sodium carboxymethyl cellulose with high purity has fewer impurities and will not have an adverse effect on the quality of printing and dyeing products. Impurities such as unreacted cellulose, salts, etc. may affect the performance of CMC, such as reducing its thickening effect and affecting the dispersibility of dyes, so a higher purity is essential to ensure the quality of printing and dyeing.
Degree of polymerization (DP): refers to the number of glucose units in the cellulose molecule. The degree of polymerization is closely related to the viscosity, strength and other properties of CMC. Generally speaking, the higher the degree of polymerization, the greater the viscosity of CMC, the higher the strength of the formed film, but the solubility may become worse. In textile printing and dyeing, it is necessary to select CMC with a suitable degree of polymerization according to specific process requirements to balance its various properties.
