(A) as a reactive dye printing paste

Theoretically speaking, the hydroxyl OH in the starch molecule is easily bonded to the reactive group in the reactive dye, resulting in disadvantages such as poor fastness, light color, easy formation of bleed in the case of water droplets, and wash-off and drop-out. Therefore, any carbohydrate containing a large number of hydroxyl groups, such as starch, agglomerates, yellow dextrin, and arbitic gum, etc., should not be used as a printing paste for reactive dyes. The ideal slurry for reactive dye printing is when sodium alginate is pushed because it not only has good properties but also does not have functional groups that react chemically with reactive dyes.

Note: 1. Although the structure of sodium alginate also contains hydroxyl groups, it exists in the form of secondary hydroxyl:choh, the reaction is less active, and the affinity for reactive dyes is very low.

2. Others think that there is no primary hydroxyl in sodium alginate. Ch2oh, only carboxyl. Coona, carboxyl ion. The coo- is negatively charged, so the sodium alginate itself is anion-charged, and the reactive dyes also have an anionic charge (the reactive dyes have a hydrophilic, water-soluble group in their precursors, such as carboxyl, sulfonic acid, sulfonamides. Bases, etc., are ionized in water and have a negative charge), so that electrostatic repulsion occurs, thereby preventing the binding of reactive dyes and pastes and promoting dye uptake.

3. It must be noted that when sodium alginate encounters calcium ions in hard water, Ca++ and other metal ions form calcium alginate or other heavy metals that precipitate. This precipitate causes the carboxyl ion to lose its charge. Therefore, the secondary hydroxyl group in the alginate paste = choh may work with the dye, which not only damages the performance of the color paste, but also easily causes color instability and causes color difference, and also affects the color fastness, especially the active green. Blue kn5g. Therefore, in the preparation of the raw paste, sodium hexametaphosphate must be added in order to complex heavy metal ions, which can improve the good permeability of the printing paste and ensure the proper color fastness. The complexing power of softener b is too strong, and it has an effect on some reactive dyes containing complex metal ions, so it is generally not used.
4. Sodium alginate paste preparation prescription warm water (50 ~ 60 °C) 80 kg Sodium hexametaphosphate 0.6 ~ 0.8 kg Soda 0.2 ~ 0.6 kg Sodium alginate 5 ~ 8 kg Formaldehyde (37.5%) 1 ~ 2 liters Add water to synthesize 100 kg

Operation: Put the warm water into the barrel first, add the sodium hexametaphosphate, continue stirring, slowly pour sodium alginate into the warm water, stir until it is uniform and no granular paste, add water to the total amount, and then use soda ash. adjust
PH value to 7 ~ 8, then add formaldehyde, spare.

The paste does not need boiling, generally should not exceed 60 °C, otherwise it will make the viscosity drop, sodium alginate paste by the role of light hydrolysis will occur, the viscosity dropped sharply, so storage must be placed in a dark place. It is relatively stable at ph values ​​from 6 to 11 and gels in the presence of strong acids and alkalis. Heavy metal ions can also cause gelation, which can be prevented with sodium hexametaphosphate. The general concentration of white powder, insurance powder, sodium chlorate, etc. does not affect it at room temperature.

(B) for India dye printing paste Yindi dye for India, printing paste with starch paste, due to the poor permeability of starch paste, often produce color uneven phenomenon. The use of sodium alginate paste to modulate the printing and the use of a net pattern to engrave a full-faced barrel print can increase the color uniformity of the dye. Bleached sodium alginate should be dechlorinated with appropriate amount of sodium thiosulfate during the paste making, because most of the reactive dyes and some of the Indian dyes such as blue o4b, black ib, etc. are not resistant to chlorine, otherwise printing Paste will affect their hair color.

(3) When Lapiamole black printing paste Lapyrazol Black (commonly known as black or pull element) is printed, wheat starch paste can be used for the general pattern, but fine lines are printed to ensure good permeability. Color uniformity, smooth lines, usually using sodium alginate paste, and add some triethanolamine, increase color stability and prevent sodium alginate condensation.
The sodium alginate paste used for printing is extremely susceptible to deterioration on hot days, or it may contain a small amount of preservatives such as formaldehyde. However, it should be noted that sodium alginate to which formaldehyde has been added should not be used for lapamoxol black.

(D) For polycondensation Cui blue printing paste Condensation Cui Lan i5g printing, no special requirements for the paste, starch, sodium alginate, synthetic Longjiao can be used. The type of paste used is based on the properties of the dyestuff with the dyestuff: When the colorant is mixed with the reactive dye, the sodium alginate paste can be used, and when not mixed with the reactive dye, the starch paste or the synthetic agglomerate can be used.