420. What are the alkaline agents commonly used in vat printing pastes?
A: The alkaline agent commonly used in vat dye printing paste is caustic soda. Sodium carbonate, potassium carbonate. Baking soda, etc., of which potassium carbonate is more common, its hygroscopicity, soft alkaline. Different alkaline agents have different reduction potentials. For example, the potential of caustic soda is the largest one among common alkaline agents. When it is used as an alkali agent, the stability of Rong white powder is reduced, so it is only used for the partial reduction of dyes. Especially for dyes that are easily hydrolyzed individually, when caustic soda is used, baking soda should be added to reduce the pH and prevent hydrolysis.
421. What are the vat dye printing processes?
A: The vat dye printing process is divided into the leuco dye printing method and the vat dye printing method. The reduction dye leuco body printing method is further divided into two methods: pre-reduction method and non-reduction method.
422. How does the vat dye leuco pre-reduced printing paste be modulated?
A: Add the dye, glycerin and appropriate amount of water (if necessary, add alcohol to promote wetting) into the grinding machine. After a while, adjust the consistency with water and continue grinding for 8 hours. The grinded dye was slowly added to the previously weighed slurry, uniformly stirred, and the lye was added. When the alkali is added, the speed is slow, and it is usually not less than two minutes per kilogram. Then heat the container together with water in a water bath. After reaching the limit temperature, add the infusible powder slowly, preferably at a speed of not less than 10 minutes per kilogram. Then stir well, cooled to room temperature before adding Rong white powder, adjust the total to 70 kg. For direct printing, as long as the additional slurry or water, transferred to 100 kg standby. For printing and dyeing printing, according to the requirements of the printing, additional white powder or water must be added to make 100 kg of spares. A layer of fire oil should be added to the paste surface to prevent crusting.
423. Under what circumstances should be used repoxide dye leucotrope pre-reduction method and pre-reduction method?
A: Some repoxide leucolutides have large negative potentials and are difficult to reduce. We often use strong alkali and pre-reduction of insurance powder. However, some of the vat dye leucosomes have low solubility in strong bases and insurance powder reducing agents. For example, bromoindole blue 4B is prone to precipitation, and the leuco form formed in the distillation is less soluble in weak base media. Such dyes should be prepared without pre-reduction method. This paste can be added only by reduction of white powder.
424. What are the characteristics of the vat dye suspension printing method and the formula of the reducing liquid?
A: The vat dye suspension printing method does not contain any alkali agent and reducing agent in the printing paste, and after printing, it is immersed in the alkaline reducing solution. The reducing solution is as follows:
A B
Insurance powder 15g 40-80g
Caustic Soda (36°Be) 30ml 80-100ml
Starch Paste (15%) 100g 100g
The above-mentioned Party A applies to the dye concentration below 1%, and when the dye concentration is between 2% and 3%, Party B is used.
425. What are the advantages of reactive dye printing paste?
Answer: Reactive dyes have complete chromatograms and bright colors. Good washing fastness and low price, and the printing and dyeing process is simple and easy to grasp. At the same time, the paste used for the printing paste is sodium alginate prepared from brown algae of the genus Algae, which is abundant in resources and can save a large amount of food. Now it has become the main dye for printing.
426. What is the direct printing mechanism of reactive dyes?
A: Reactive dyes are composed of two parts, a chromophore and a reactive group (reactive group). Such as reactive brilliant red X-3B (also known as active pink), its structural formula contains water-soluble sulfonic acid groups, making it water-soluble. There are two active chlorine atoms on the active group, which can be dyed and fixed in an alkaline medium at 20-40°C, and the fixation rate is 60%. Used for the dyeing and printing of cotton, hemp, silk, wool, viscose and cotton spinning fibers.
427. What is the role of urea, a reactive dye printing additive?
Answer: The name of urea is diammonium carbonate, and its role is reflected in the following aspects.
(1) Solubilization in reactive dye printing improves the dissolution ratio of dissolved dyes.
(2) It has good hygroscopicity. When steaming, it will make the fiber fully expanded. The expanded fiber is good for the dye to enter the fiber and improve the permeability. At the same time, the dyestuff after printing is in a dry state. When the fabric enters the steamer, the chemical reaction continues to proceed depending on the hygroscopicity of urea, and the dye is further dissolved and diffused, thereby increasing the amount of color imparted to the dark K-type. Reactive dyes have the most significant effect.
(3) Has the effect of buffering pH. When some reactive dyes are bonded to fibers at high temperatures, acids are released, and urea can neutralize them, thereby acting as a buffer.
(4) During the high-temperature baking process, the water content of the colorant rapidly evaporates, which affects the fixation reaction of reactive dyes, and adding an appropriate amount of urea is beneficial to the fixation of the dye.
428. What is the role of reactive dyestuffs printing additive in dye-staining salt S?
A: The anti-staining salt has a scientific name of sodium meta-nitrobenzene sulfonate, and it is a weak oxidant. The yellow powder has high solubility and can promote the dissolution of the dye. In reactive dye applications, it is mainly used to counteract the reduction of substances at high temperatures. If 5-10 g/l of anti-staining salt is added to the color paste, the fiber can be prevented from reducing at high temperature, and the reversible gas in the white pulp can be prevented from affecting the color of the dye. However, for reactive dyes susceptible to reduction, the amount of anti-staining salt S should be increased to 15 g/l, such as brilliant red K2G and violet K-3R. For oxidation-sensitive reactive dyes, anti-staining salts S such as Brilliant Blue X-BR may not be added.
429. What is the role of reactive dye printing aid hexametaphosphate?
A: Sodium hexametaphosphate, also known as sodium hexapolyphosphate, is a colorless transparent flake or white powder that is hygroscopic and soluble in water. Sodium alginate is considered to be a good slurry of reactive dyes because it loses its ability to bond to cellulose because it does not covalently bond to reactive dyes. In addition, due to its negative charge, it is repelled by reactive dyes, which facilitates dye uptake. However, if you use hard water to color, the slurry and the water of calcium, magnesium and other metal ions will precipitate, forming a gel phenomenon, will make sodium alginate lose negative charge, lose the repulsive effect of reactive dyes, especially more active dye, easy Form color stains. Sodium hexametaphosphate (5-10 g/l) is added to the slurry to protect it from hard water.
430. What is the main role of baking soda in reactive dye printing?
A: The name of baking soda is sodium bicarbonate, which is decomposed into soda ash by heat and has strong alkalinity. It plays two roles in reactive dye printing.
(1) As an alkali releasing agent, the dye and cellulose are bonded under the conditions of heat and alkali.
(2) Acidic substances are released when reactive dyes and fibers are bonded. Baking soda as a neutralizing agent does not cause the fabrics to become brittle.
431. Reactive dye printing methods are divided into several types?
Answer: The printing method of reactive dyes is divided into one phase method (conventional method). Two-phase method and three kinds of sodium trichloroacetate printing method.
432. What is the reactive dye-one-phase printing process?
A: The reactive dyestuff printing process is as follows.
(1) Steaming method
Fabric Preparation -> Printing -> Drying -> Steaming -> Washing -> Soaping -> Washing -> Dehydration -> Drying -> Inspection -> Storage.
(2) Curing method
Fabric preparation->printing->baking->washing->cooking->washing->dehydration->scaling->inspection->packaging->storage.
433. How to formulate reactive dyestuff printing paste formula?
Answer: The formula of reactive dyestuff printing paste is as follows.
4% Sodium Alginate Paste 300-500ml
Urea 50-1OOg
Hot water 100-200ml
Reactive dyes 10-70g
Sodium Dihydrogen Phosphate (1:1) 5-10ml
Baking soda (1:1) 20-25ml
Total: 1000ml
434. What are the main features of the two-phase printing paste?
A: The two-phase printing paste does not contain any alkali agent and the color paste has high stability. The reactive dye KN type (ethylene vinyl type) is suitable for this method.
435. What is the two-phase printing paste recipe?
A: The two-phase printing paste formula is as follows.
KN type (ethylene vinyl type) reactive dye xg
Urea 50g
Hot water xg
Starch-sodium alginate paste (1:1) 400-500g
Anti-stain salt S 15g
Acetic acid (15%) 10ml
Total: 1000g