Application of Chitosan in Printing and Dyeing Industry
Information source: Textile and Apparel Weekly
As a natural and renewable resource, chitosan has attracted the attention of scholars because of its good biological activity, biodegradability, biocompatibility, and non-toxicity. Research shows that chitosan has broad prospects for application in the textile printing and dyeing industry.
The use of chitosan in printing and dyeing auxiliaries
Improve the dyeing rate
Since chitosan has a similar structure to cellulose, it is easily adsorbed onto the fabric surface, and in dilute acid solutions, chitosan has a positive charge that can increase the dyeing rate of anionic dyes. Research has found that after wool fabrics are treated with chitosan acidic solution, the charge on the wool fibers is reduced, thereby reducing the Coulomb repulsion of the negative charges on the fibers to the dye anions during the dyeing process, thereby increasing the dye uptake rate. The dye uptake rate increases; chitosan is evenly distributed on the fabric, which increases the concentration of amino cations (-NH+3) on the surface of the wool fiber, greatly increases the number of polar groups on the surface, and greatly improves the hydrophilicity. , the adsorption of dye anions by the amino groups on chitosan also increases, and the dye quickly adsorbs to the adsorption layer of chitosan, which significantly increases the dye concentration gradient between the wool surface and the interior, making it easier for the dye to diffuse into the interior of the fiber, and the diffusion speed and dye uptake rates were improved.
Color fixation
The chitosan molecule contains a large amount of -NH2 or -OH, which has good affinity with the fiber and can be dissolved into the fiber and combined with the active groups -OH and -NH2 of the fiber through hydrogen bonds or covalent bonds. And because it is a nitrogen-containing cationic polymer that can react with anionic dyes, it is considered an ideal fixing agent for anionic dyes.
As a natural printing paste
Chitosan is soluble in acetic acid, and its aqueous solution can form a viscous colloidal solution, which has good compatibility with acid dyes and direct dyes. The chitosan acetic acid solution is printed on the fabric as a printing paste. When drying and steaming, the acetic acid evaporates to form an insoluble film layer, which has good coating properties.
Application of Chitosan in Printing and Dyeing Wastewater Treatment
Wastewater produced by the textile industry usually contains salts, organic surfactants and dyes, which is extremely harmful to human health and the environment. Chitosan contains amino and hydroxyl groups, which have a strong adsorption effect on dyes. This adsorption includes: physical adsorption, chemical adsorption and ion exchange adsorption, mainly through hydrogen bonding, electrostatic attraction, ion exchange, van der Waals forces, etc. At the same time, because the molecular structure of chitosan contains a large number of primary amino groups, which are combined through coordination bonds to form an excellent polymer chelating agent, it can agglomerate dyes in wastewater, is non-toxic, and does not produce secondary pollution. It is used in printing and dyeing. It has broad application prospects in industrial environmental protection.
Application of chitosan in finishing
Another very important aspect of the use of chitosan in textile printing and dyeing is to use chitosan as a finishing agent for high-end and high-value-added processing of textiles, so that the physical and chemical properties of the fabric can be improved. According to current reports, chitosan can be used for the following types of finishing.
Anti-wrinkle finishing
The anti-wrinkle finishing of chitosan is mainly used in cotton fabrics, silk fabrics, linen fabrics, etc. that have poor wrinkle resistance. Because chitosan has strong film-forming properties and is similar in chemical structure to cellulose, it has good adsorption and compatibility with cotton fibers. In the study of the anti-wrinkle properties of chitosan-finished cotton fabrics and polyester-cotton blended fabrics, it was found that the elastic recovery angle of the fabrics increased, and the higher the concentration of the chitosan treatment solution, the larger the elastic recovery angle, which improved the wrinkle resistance. . Chitosan can also effectively improve the resilience and recovery ability of dye-rich linen fabrics printed and dyed, and its resilience recovery rate can be stabilized between 60% and 70%. When tartaric acid, citric acid solution and chitosan were used together for anti-wrinkle finishing of silk, it was found that the anti-printing and dyeing wrinkle recovery angle of silk increased, and at the same time, the amount of tartaric acid in the finishing solution increased, and the whiteness of the fabric also increased.
Antibacterial finishing of printing and dyeing dyes
Fabrics treated with chitosan have antibacterial capabilities. Cotton fabrics treated with glutaraldehyde as a cross-linking agent have an antibacterial rate of 100% against Escherichia coli, Pneumoniae, and Candida albicans, and an antibacterial rate of more than 75% against Bacillus subtilis. The antibacterial rate after soaping 50 times is still over 50%. Antibacterial and bacteriostatic tests on cotton fabrics treated with a mixture of chitosan and citric acid showed that the product had an obvious broad-spectrum antibacterial effect.
Antistatic finishing
Chitosan is used for antistatic finishing of polyester fabrics. The usual method is to first subject the polyester fabric to an alkali reduction treatment. On the one hand, cracks and reactive hydroxyl groups are produced on the fiber surface, which is beneficial to chitosan coating. On the other hand, it aims to hydrolyze the ester groups in the surface polyester fiber molecules to a certain extent and produce a certain number of carboxyl negative ions, which facilitates the combination of positively charged chitosan molecules and polyester fibers. Then the chitosan acetic acid solution is attached to the polyester fabric through the rolling-baking-baking process, so the chitosan film will be combined with the polyester fiber through physical adhesion, ionic bonds and intermolecular forces. Tests show that the moisture regain of fabrics after finishing can be increased several times.�Improved tensile strength; has certain antistatic durability. In addition, after the fabric is treated with chitosan, it can also improve the fabric’s shortcomings such as non-hygroscopicity and static electricity, and it also has antibacterial and
Anti-mildew and other functions.
At present, the annual production of chitin on the earth is very large, but its utilization is very small. The main reason is that the substance must be extracted from animal shells or bones, which is costly. However, under the requirements of the era of vigorously developing green resources and with the rapid advancement of science and technology, people’s research on the application of chitosan and its derivatives will become more and more in-depth and extensive. Our country is not only a big textile country, but also has many rivers and lakes and rich chitin resources. Therefore, in order to recycle waste, increase the added value of textiles and create environmentally friendly products, it is not only urgent but also of far-reaching significance to actively develop the application of chitosan in the printing and dyeing industry. .
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