In the textile industry, auxiliaries (or textile auxiliaries) refer to chemicals that are used alongside dyes, pigments, or finishing agents to improve various processes or impart specific properties to the fabric. These substances don’t contribute directly to the coloring or final appearance of the textile but play crucial roles in optimizing processes such as dyeing, printing, finishing, and enhancing the performance of the fabric.
Key Functions of Textile Auxiliaries:
Facilitate Processes: Auxiliaries help to enhance or control textile processes like scouring, bleaching, dyeing, printing, and finishing by improving the efficiency of these processes.
Improve Product Quality: They improve properties such as softness, water repellency, flame retardancy, and fabric durability.
Modify Performance: Auxiliaries can modify the interaction between dyes and fibers, ensuring even coloration, improved dye fixation, and preventing issues like fading or fabric damage.
Types of Textile Auxiliaries:
1. Pre-treatment Auxiliaries
These are used during the preparation of the fabric before dyeing or printing:
Scouring Agents: Help remove natural impurities (waxes, oils, dirt) from natural fibers like cotton and wool.
Example: Sodium hydroxide (NaOH), surfactants, or enzyme-based agents.
Wetting Agents: Reduce the surface tension of water, improving the penetration of water into the textile fibers.
Example: Non-ionic surfactants, alcohol ethoxylates.
Bleaching Auxiliaries: Assist the bleaching process by stabilizing bleaching agents or controlling the reaction.
Example: Sodium silicate, hydrogen peroxide stabilizers.
Desizing Agents: Remove sizing agents (like starch) applied during weaving to strengthen the yarn.
Example: Amylase enzymes, oxidizing agents.
2. Dyeing Auxiliaries
These are essential to ensure smooth dyeing, better dye absorption, and even distribution of color:
Dispersing Agents: Ensure that dye particles remain suspended in water and do not agglomerate during dyeing.
Example: Lignosulfonates, polycarboxylates.
Levelling Agents: Control the rate of dye uptake, ensuring even coloration across the fabric.
Example: Polyethylene glycols, fatty alcohol ethoxylates.
Fixing Agents: Improve dye fixation on the fibers, reducing the likelihood of dye bleeding or fading during washing.
Example: Formaldehyde-free fixatives, cationic fixatives.
Sequestering Agents: Bind with metal ions in water to prevent their interference with the dyeing process.
Example: EDTA (Ethylenediaminetetraacetic acid), phosphonates.
3. Printing Auxiliaries
Used in textile printing to ensure proper dye adhesion and fabric performance:
Thickeners: Increase the viscosity of printing pastes to control dye application on the fabric.
Example: Sodium alginate, guar gum, acrylic thickeners.
Binders: Help pigments stick to the fabric surface in pigment printing.
Example: Acrylic binders, polyurethane binders.
Anti-foaming Agents: Reduce foam formation during the printing process.
Example: Silicone-based defoamers, non-silicone defoamers.
4. Finishing Auxiliaries
Used to give specific properties to the finished fabric, such as softness, water repellency, or flame retardancy:
Softening Agents: Improve the hand feel (softness) of the fabric.
Example: Silicone softeners, fatty acid condensates.
Flame Retardants: Impart flame resistance to fabrics.
Example: Phosphorus-based retardants, halogen-free retardants.
Waterproofing Agents: Provide water repellency to fabrics.
Example: Silicone-based agents, wax emulsions, fluorocarbon-based repellents.
Anti-pilling Agents: Reduce the formation of small fiber balls (pills) on the surface of fabrics.
Example: Synthetic resins, silicone emulsions.
Anti-static Agents: Reduce the buildup of static electricity in synthetic fabrics.
Example: Quaternary ammonium compounds, polyethylene glycols.
5. Specialty Auxiliaries
These include a wide range of chemicals used for specific technical or aesthetic effects on textiles:
Antimicrobial Agents: Used to inhibit bacterial growth in fabrics, especially in sportswear or medical textiles.
Example: Silver nanoparticles, triclosan, chitosan.
UV Absorbers: Provide protection against harmful ultraviolet (UV) rays.
Example: Titanium dioxide (TiO2), benzotriazole derivatives.
Optical Brightening Agents (OBAs): Enhance fabric whiteness by converting UV light to visible blue light.
Example: Fluorescent whitening agents.
Enzymes: Used in eco-friendly treatments, such as bio-polishing or desizing, to replace harsh chemicals.
Example: Cellulase, protease, amylase.