Cationic dyeable (CD) polyester dyeing process: cationic dyes at 110°C

CD polyester is modified so it takes cationic dyes, which give very bright shades at a lower temperature than normal polyester. Here is the process we run, from the acid pre-wash to the reduction clear.

Cationic dyeable (CD) polyester is polyester modified with anionic groups, so it can be dyed with cationic (basic) dyes. Cationic dyes give very bright, clear shades, and CD polyester dyes at about 110°C instead of the 130°C that normal polyester needs with disperse dye. It is used on its own and in blends, including two-tone effects with normal polyester or cotton.

The route

1. Acid pre-wash at 70°C for 10 minutes with a demineralising agent and oxalic acid to remove oil and other residues, then rinse.
2. Cationic dyeing at pH 4, heated to 110°C and held 45 minutes.
3. Reduction clearing at 80°C for 20 minutes with a reducing agent and caustic.
4. Acetic acid to neutralise, softener, unload.

The dyeing curve

Step by step

1. Acid pre-wash: demineralising agent 2 g/L and oxalic acid 1 g/L at 70°C for 10 minutes, then rinse.
2. At 40°C, check the pH: 4.0 (acid buffer about 2 g/L).
3. Dose the levelling agent (retarder) over 5 minutes and run 5 minutes.
4. Dose the cationic dyes linearly over 20 minutes.
5. Dose Glauber’s salt (about 5 g/L) progressively over 10 minutes and run 10 minutes.
6. Steam up to 110°C at 1.5°C per minute and hold 45 minutes.
7. Cool to 70°C and check the shade.
8. Drain. Reduction clear at 80°C for 20 minutes when the fabric needs it, then acetic acid, softener, unload.

CD polyester in blends

Supplier recommendations for auxiliaries vary, so follow your dye supplier’s instructions for any extra additions.

Kamrul Islam

Textile engineer with 14+ years in dyeing and fabric development. He writes every guide on Dyeing Solution from real production work. Full profile