Does Thiourea Dioxide Work Particularly Well for Polyester Reduction Clearing?

Direct Answer

Direct Answer This is one of its strongest applications and the first one listed in our technical data sheet.

Why it suits the job

• The purpose of polyester reduction clearing is to remove unfixed disperse dye and lift fastness, which calls for gentle but complete reduction rather than aggressive stripping
• Release is controlled, so dye already on the fibre is less likely to be over-reduced and the shade drifts less than with hydrosulfite
• The full reducing effect is only developed above 70 C and in the presence of alkali

Recommended recipes

The application covers disperse dyeing and printing on polyester or polyester/cotton, as a final or intermediate reduction clear.

Three points to watch

• Release is slow below 70 C, and carrying over a low-temperature recipe leads to the false conclusion that performance is poor
• Insufficient alkali clearly reduces cleaning performance
• For very deep shades, keep a small hydrosulfite addition in the blend to control cost

How to judge the result

In bench trials compare wet and dry rub fastness, wash fastness, shade shift as delta E, and whiteness or brightness. Judge by fastness ratings rather than by eye.

Bottom line

Cross winder or overflow: 0.5 to 1.0 g/L at 70 to 95 C for 20 to 30 minutes. Continuous washing line: 2.0 to 3.0 g/L at 80 to 95 C for 15 to 80 seconds.

Sources

1. 我司产品技术数据表《THIOUREA DIOXIDE Technical Data Sheet》（TDO-TDS，签发日期 2024-05-08）
2. Effective reduction clearing parameters involving alternative reducing agent（2021），DOI 10.54693/piche.04916