Dasteck ChemicalsYantai Dasteck Chemicals Co., Ltd.
Direct answer
Thiourea dioxide carries an anionic charge; our technical data sheet states anionic. It is therefore compatible with anionic and non-ionic auxiliaries and incompatible with cationic ones, which tend to adsorb onto it, form precipitates or simply cancel its effect. On addition order the rule is: dissolve in cold water, add the alkali last, and never in the same bath as an oxidant.
1. Compatibility at a glance
| Auxiliary type | Compatibility | Note |
|---|---|---|
| Anionic surfactants | Good | Standard scouring, wetting and detergent agents |
| Non-ionic surfactants | Good | Common reduction-clearing auxiliaries |
| Cationic auxiliaries | Poor | Cationic softeners and fixing agents can complex with the anionic reducer and precipitate |
| Chelating and dispersing agents | Good, and helpful | They bind iron and copper ions that would otherwise catalyse decomposition |
| Strong oxidants | Never in the same bath | Hydrogen peroxide, sodium perborate and similar agents consume the reducer directly |
| Strong acids | Never | Under acidic conditions thiourea dioxide is readily oxidised and loses its reducing power |
2. Correct addition order
1. Cold water first, dissolve the required amount of thiourea dioxide; hot water accelerates decomposition
2. Add anionic or non-ionic scouring agents and chelating or dispersing agents and stir well
3. Add the caustic soda shortly before use; an alkaline solution is unstable, so it must be made up and used immediately
4. Raise to process temperature, then load the fabric
3. Four combinations to avoid
4. Three practical points
1. Cationic softener goes last: rinse after reduction clearing, then soften, never in the same bath
2. Make up with demineralised or soft water: metal ions in hard water accelerate decomposition
3. Never keep the alkaline stock overnight: alkaline solutions must be used immediately; without alkali a solution is stable at room temperature for about 6 hours
Sources
Ionic charge, solution stability and temperature conditions come from our technical data sheet. Auxiliary compatibility must be verified on a bench sample using the actual products and recipe.