AI DISCHARGE VAT DYE
Reducing agent for direct printing with vat dyes. Discharging agent for printing white and colored discharges.
PROPERTIES
- Nature: Sulfinic acid derivative
- Physical form: White powder
- Decomposition temperature: From 125.8C
- pH: 9-11 (10% aqueous solution)
- Solubility: Readily soluble in water (to approx. 600 g/l at 20 8C), with an endothermic reaction.
- Stability: AI DISCHARGE VAT DYE has good stability to alkalis, but is decomposed by acids. Its decomposition by acids, and oxidation, are exothermic processes. The product is stable over an extended period in neutral and alkaline print thickenings.
The above values characterize the physical range of properties. Details of the tolerances are provided in the product specification.
APPLICATION
AI DISCHARGE VAT DYE is used mainly in the printing of woven and knitted cellulosic fiber materials.
SHELF LIFE
When stored correctly, in sealed containers, AI DISCHARGE VAT DYE has a shelf life of 24 months.
STORAGE
Since the product is hygroscopic, the containers should be stored under dry, but not-too-warm conditions, away from acids. Only dry scoops should be used to remove product, after which the drum should be closed tightly again.
1. Direct printing with vat dyes
For direct printing with vat dyes, it is customary to prepare a stock thickening that contains 130-140 g/kg AI DISCHARGE VAT DYE and about the same to 1.1 times this amount of potash. The potash may, however, be substituted partly or entirely by soda. In this case, 100 parts by weight potash can be replaced by 75 parts by weight soda.
Guideline recipe for a stock thickening:
- 550 g thickening
- 30-50 g glycerin
- 130 g potash
- or 100 g soda
- 130 g AI DISCHARGE VAT DYE
- … g water or thickening
- 1000 g
Owing to its good solubility, AI DISCHARGE VAT DYE can be stirred into the thickening direct. The thickening should be adjusted either neutral or alkaline.
The above quantities apply for rotary screen printing. For flat screen printing, the amounts of reducing agent and alkali can be decreased by 20%.
The actual print paste is formulated as follows:
- … g Indanthren dye (printing quality)
- 650 g stock thickening
- … g water or thickening
- 1000 g
After printing and drying, the prints are steamed for 8-12 min. with saturated steam.
2. Printing colored discharges with vat dyes on cellulosic fiber grounds dyed with dischargeable dyes
The stock thickening described in Section 1 is also very suitable for printing colored discharges on cellulosic fiber materials dyed with dischargeable dyes. However, depending on the dischargeability and depth of shade of the dyed ground, it may be necessary to increase the amount of AI DISCHARGE VAT DYE used, and possibly also the amount of potash and/or soda.
3. Printing white discharges on dyed cellulosic fiber grounds that are dischargeable to white
AI DISCHARGE has also proved very satisfactory as a discharging and reducing agent for printing white discharges.
| A | B |
|---|---|
| 510 | 510g thickening and |
| 150 | 200g AI DISCHARGE VAT DYE |
| are mixed together, after which | |
| - | 40g caustic soda 38 8BÈ and |
| - | 40g soda |
| are added and the paste made up with | |
| 340 | 210g water or thickening to |
| 1000 g |
The white discharge print paste A is used mainly for discharge printing on readily dischargeable grounds dyed with direct or reactive dyes. Print paste B is used for producing white discharge prints on grounds dyed with less readily dischargeable reactive dyes and naphthol combinations.
If necessary, the caustic soda can be replaced partly or entirely by soda. The discharge effect can be improved by adding 10 g/kg anthraquinone powder.
However, to prevent the subsequent development of a pink coloration in the white discharged areas, the prints should then be given a hot, alkaline wash after they have been steamed, followed by a good rinse and acidification.
After drying, the prints are steamed for 8-10 min with saturated steam.