Printing and dyeing auxiliaries
Introduction
In the textile industry, in the various processing procedures from spinning, spinning, weaving, printing and dyeing to finished products, different auxiliary chemicals are required according to the performance of various fibers to improve the quality of textiles, improve processing effects, increase production efficiency, and simplify Process, reduce production costs and give textiles a variety of excellent application properties. This auxiliary chemical is commonly known as textile dyeing and finishing auxiliaries.
Dyeing and finishing auxiliaries are often divided into three categories: printing and dyeing pretreatment agents, printing and dyeing auxiliaries, and finishing agents according to the steps and uses of dyeing and finishing.
03
Pretreatment agent for printing and dyeing
The pre-treatment process of printing and dyeing includes fiber singeing, desizing, scouring, bleaching, mercerizing and other processing processes. It is necessary to add penetrants, emulsifiers, cleaning agents and other surfactants, such as organic sulfates, sulfonates and polyoxyethylene. Mainly ether.
Penetrants, wetting agents, penetrants commonly used in the textile industry include ricinoleic acid butyl sulfate, butyl naphthalene sulfonic acid sodium salt and so on. In neutral solution, dioctyl sodium succinate sulfonate has a particularly strong penetrating ability; in acid solution, in addition to the above varieties, fatty alcohol polyoxyethylene ether or alkylphenol polyoxyethylene ether is commonly used; and in strong alkaline In the solution, for example, the mercerizing process requires the use of shorter carbon chain sulfates such as octanol sulfate.
Emulsifiers are often oiled to improve the lubricating properties of silk and yarn in the weaving process. However, the oil should be removed before printing and dyeing, so as not to affect the dyeing. Therefore, it is necessary to add an emulsifier in these textile oils, or add an emulsifier in the cleaning bath to ensure the removal of oil spots, generally non-ionic surfactants are used.
Cleaning agents, namely detergents and detergents, remove oily stains on textiles. In the past, soap was the mainstay, but now a variety of synthetic detergents and non-ionic surfactants are used, including slightly more expensive oleic acid amide derivatives. . In addition, there are enzymes used to promote starch hydrolysis during desizing; activators and anti-corrosion agents added during bleaching speed up the bleaching process and increase the whiteness without corroding the equipment. At present, it has been developed to complete desizing, scouring and bleaching in one bath, and a new compound powerful cleaning aid is used.
02
Printing and dyeing auxiliaries
There are many types of textile dyes, and the dyeing process is different, and the corresponding supporting auxiliaries are needed. Therefore, there are many kinds of such auxiliaries, mainly as follows:
2.1 Water softener: metal ion chelating agent
Heavy metal ions in water often affect the color or solubility of dyes. We can use water softeners to remedy them. Commonly used water softeners include sodium hexametaphosphate, sodium nitrilotriacetate and sodium ethylenediaminetetraacetate.
2.2 Solvents and co-solvents
When using or preparing liquid dyes for certain dyes, a filling solvent is needed to help dissolve them, such as ethylene glycol, diethylene glycol, glycol ethers, formamide, thiodiethanol, etc. As the dye solvent; when dyeing with phthalocyanine blue, use the auxiliary solvent and copper salt, and use the auxiliary solvent sodium benzylaminobenzene sulfonate for the vat dye.
2.3 Reducing agent and oxidizing agent
When using vat dyes, you must first use a reducing agent to dissolve the vat dyes. Commonly used are sodium hydrosulfite (sodium dithionite), hanging white block (sodium formaldehyde sulfoxylate), and thiourea dioxide. When vat dyes are used for anti-dyeing, mild oxidizing agent sodium m-nitrobenzene sulfonate can be used. This product can also be used in printing pastes to protect the dyes from possible reducing components in the pastes.
2.4 Fixing agent and color-developing auxiliary
When dyeing with direct dyes, acid dyes and reactive dyes, fixation agents are used before and after dyeing to increase the amount of color and fastness. Fixing agent mainly uses amine salt and polymer quaternary ammonium salt. Dyes for printing sometimes use color development aids, such as diethylethanolamine when steaming and color development of fastamine.
2.5 Dispersant, also known as diffuser
When printing and dyeing with disperse dyes and vat dyes, dispersants and protective colloids should be added to ensure uniform dyeing and prevent stains. Commonly used dispersants are sulfonated oil (Taikoo oil, Turkish oil), sodium alkyl or long-chain amidobenzene sulfonate, alkyl polyoxyethylene ether, sodium lignin sulfonate, naphthalenesulfonic acid formaldehyde condensate, oleoyl Polyamino carboxylates and the like.
2.6 Leveling agent, that is, leveling agent
Polyoxyethylene ether surfactants are commonly used as levelling agents for dyes, cationic surfactants should be used for cationic dyes, and anionic surfactants should be used for acid dyes.
2.7 Matting agent
Compared with natural fibers, the surface of synthetic fibers is too smooth and the reflectivity is too high, so titanium dioxide, zinc sulfide, etc. must be added to improve it.
2.8 Defoamer
Used to remove foam caused by surfactants in the printing and dyeing process. In the past, tributyl phosphate, octanol, etc. were generally used, but now they have all used organic stone compounds.
2.9 Printing paste and thickener
In the past, natural slurries were used, but now they have tended to use semi-synthetic or synthetic slurries, such as starch ether, sodium alginate, etherified locust bean powder, cellulose esters, polyvinyl alcohol, and polyacrylates. The synthetic slurry has high consistency and low dosage, which can make the color of printing deep. The chemical structure of the thickener is macromolecular polyethylene glycol bisether or diester, or polyacrylate copolymerized with acrylate.
2.10 Adhesives for printing and dyeing
Various synthetic latexes such as copolymers of butadiene, styrene, acrylonitrile, vinyl acetate, vinyl chloride and acrylic esters can be used. It is required to have strong adhesion, that is, good fastness to abrasion and rubbing, soft hand feeling, and not easy to yellow under high temperature and light. At present, high-quality general-purpose adhesives are polyacrylate copolymers with self-crosslinking groups and polyurethanes.
03
Cleaning agent for post-printing and dyeing treatment
After the printing and dyeing process is completed, the fabric is generally washed to remove the floating color to improve the color fastness. The synthetic cleaning agent used varies with the dye and the printing and dyeing process. For example, after the disperse dye dyes the polyester-cotton fabric, the floating color on the polyester must be removed , And to prevent the cotton fiber from being polluted, special non-ionic detergents must be used.
3.1 Finishing agent
Chemicals used to improve the appearance, feel, shrinkage rate of fabrics, stabilize appearance, extend life, waterproof, fireproof, antifouling, anti-mildew, etc. Resin finishing agent, the most important finishing agent, is a polymer compound that can bond with the hydroxyl group of cellulose to achieve a longer-lasting anti-wrinkle and non-ironing effect. When mixed with an appropriate softener, it can improve the feel of the fabric.
Commonly used resins include urea-formaldehyde resin, melamine-formaldehyde resin, dimethylol ethylene urea resin, dimethylol dihydroxy ethylene urea resin and bishydroxyethyl sulfone. Among them, dimethylol dihydroxy ethylene urea resin is the most widely used, which is formed by the condensation of glyoxal, urea and formaldehyde. Penetrants, catalysts (commonly used metal salts, ammonium salts or organic amine salts) and feel modifiers should be added to the resin finishing working fluid. The latter is usually a softener. The newly developed resin finishing agent, polyurethane, has a slightly higher price, but has high styling performance, no residual formaldehyde, and does not cause skin allergies.
3.2 Softener
It is mainly a cationic long-chain fat-based finishing agent. Because the cationic finishing agent has affinity for fibers, the dosage can be reduced, and its adhesion is strong, which can show longer-lasting softness. Its soft and lubricating performance mainly comes from its long-chain fat-based finishing agent. . Adding emulsified mineral oil and wax to this softener can increase lubricity.
Some softeners react with the hydroxyl or amine groups in the fiber to enhance the washing resistance of the fiber and have long-lasting softness. Recently, silicone oil dispersion softeners have appeared, and their ionic properties vary depending on the emulsifier used. After treatment, the fabric has a particularly soft and smooth feel, which is suitable for high-speed sewing. If adding a cross-linkable silicon compound, it can also enhance the elasticity of the fabric.
3.3 Waterproofing agent
Although the rubber paste coating is waterproof, it has poor air permeability when worn. Rainproof slurry is a mixture of aluminum salt and paraffin, but it is not durable. Long-chain aliphatic hydrocarbon compounds that react with fabrics are used for durable waterproofing agents with breathability.
The acrylate coating can also be waterproof after cross-linking. The newly developed water-repellent agent is hydrogen-containing silicone oil and its derivatives.
3.4 Flame retardants
Temporary ones include amine salt, sodium tungstate, borax, water glass, etc. The cotton cloth treated with diammonium hydrogen phosphate and urea can have a certain degree of durability. Organic matter is mainly compounds containing bromine, phosphorus, nitrogen, and chlorine, which can inhibit combustion. If it can be combined with fibers, it can have a lasting effect. The main varieties of flame retardants for cotton have the following structure: there is still a lack of effective durable flame retardants for synthetic fibers. Tris (2,3-bisbromopropyl) phosphate has been used in polyester, which is effective in flame retardancy. Because of its toxicity, it was banned in 1977. Currently, tetrahydroxyphosphorus chloride compounds, sulfides or hydroxy compounds and resins are used, which have better durability. There are also flame retardants added before the spinning of synthetic fibers, but they have a certain effect on fiber performance and strength. Currently, new polybrominated compounds are being developed as flame retardants for synthetic fibers.
3.5 Antistatic agent, namely antistatic agent
Mainly used for synthetic fibers, which can prevent static electricity and make the fabric easy to decontaminate. Mainly include polyacrylic acid, polyethylene glycol esters and polymer amphoteric compounds.
3.6 Anti-mold additives
Cotton fabrics are prone to mildew in the presence of microorganisms, especially in the presence of slurry and appropriate temperature and humidity conditions, they are more prone to mildew. The antifungal agents used include various copper salts and organic phenol derivatives, such as Copper pentachlorophenate, copper naphthenate, copper 8-hydroxyquinoline, dihydroxydichlorodiphenylmethane, salicylanilide, etc.
3.7 Anti-greasy agent
Mainly various derivatives of organic fluorine, its surface energy is particularly low, non-oily, and resin-like structure is combined with fibers.
3.8 Coating agent
It is a new type of finishing agent, including polyacrylate, polyurethane, etc., which give the fabric various additional properties, such as waterproof, flame retardant, light-proof, elasticity, and make inexpensive fabrics have properties like leather.
3.9 Functional finishing additives
There are also many finishing auxiliaries that give fibers special functions, such as far-infrared heat preservation and health care finishing agents, anti-ultraviolet emulsion treatment agents, antibacterial sanitary finishing agents, ceramic powder far-infrared finishing agents, aromatic finishing agents, etc.