This document discusses methods for high temperature dyeing of wool-polyester blends to minimize damage to the wool. It recommends using formaldehyde or similar agents to protect the wool at temperatures up to 120°C. Specific dyeing times and temperatures are provided for different levels of wool protection. One-bath and two-bath dyeing methods are described that allow deep shades while reducing staining of the wool component. Post-treatment and troubleshooting steps are also outlined.

1. Minimisation of damage to wool The advantages of high temperature dyeing above 110 0 C are Fast deep shades Shorter leveling time Better levelling Less staining of wool Disadvantages Wool degradation –reduction in strength, elongation, abrasion resistance, yellowing

2. Therefore, to protect the wool component during high temperature dyeing, Most common agent HCHO (5% owf) allows dyeing at 105 0 C for 4 hrs 110 0 C for 3 hrs 115 0 C for2 hrs 120 0 C for 1 hr pH: 3.5-4.5

3. Recommended dyeing times 100 0 C for 120-150 min with carrier, no formaldehyde 106 0 C ,90 –120 min with carrier and without formaldahyde 110 -115 0 C, 60 –90 min, reduced amount of carrier, formaldehyde necessary 120 0 C, 20-30 min (not >40 min), carrier optional, formaldehyde necessary High temperature dyeing is recommended for deep shades –yellowing is not so critical

4. Precautions for formaldehyde use Shades of some dyes are affected -careful dye selection HCHO vapours are potentially hazardous -restricted use by health and safety considerations Therefore, agents which will release HCHO during dyeing (in-situ release) are preferred. E.g DMEU -HCHO release above 0 0 C

5. Dyeing methods: One bath dyeing method with disperse and acid or metal complex dyes Dye selection: Disperse dye –low energy ->minimum staining of wool –easily removed by after wash Acid or metal complex –not so critical

6. General dyeing recipe X% disperse dye Y% acid/metal complex dye Z% carrier 1 –2% dispersing agent 5 -10% glauber’s salt pH :4.5 –5.5 with acetic acid

7. Dyeing procedure Set bath with auxuliaries Preheat 10 –20 min at 50 -70 0 C Add disperse and dissolved acid dye Treat for 10 min Raise temperature to boil or 103-106 0 C 30-45 min Dye for 1½-2hrs depending on depth of shade Cool, cold and hot rinse –shading 80 -100 0 C

8. One-bath dyeing Improve dye exhaustion Minimise wool staining Wool protecting agent is necessary Recipe: X% disperse dye Y% acid / metal complex dye 3-5% HCHO (30%) 1-2% dispersing agent , pH : 5 -6 with HAC’

9. Pretreat with auxiliary at 50-60 0 C Add disperse and acid dyes Treat for 10 min Raise temperature to 110 0 C/120 0 C in 45 min Dye for 30 –60 min

10. After treatment Staining of wool with disperse dyes cannot be avoided even if the process is carried out with most siutable dyes under the most favourable conditions Disperse staining on wool –poor fastness –must be removed completely One-bath method –reduction clear is not possible After wash: 1-2 gpl non-ionic detergent, pH 5-6 with HAC’, 20-30 min at 60 0 C, good rinse With deep shades, repeat the above process

11. Two bath process Used for deep shades -particularly navy and black Dye polyester component with X % disperse dye Y% carrier 1 –2% dispersing agent pH 5-6 with HAC’ Maximum temperature :103 -106 0 C or boil Cold rinse

12. Reduction clearing: 3 gpl hydrose 0.5- 1 ml/l ammonia(25%) 0.5-1 gpl non-ionic emulsifying agent For 30 min at 45 -50 0 C Good rinse, acidify with HAC’ Dyeing of wool component

13. Thermosol dyeing Not common Can be used for coloration of PET component only Wool component is dyed seperately ( detail sin page 256-257) Dry heat treatment: 190 -200 0 C for 45 –60 secs Not harmful to wool except slight yellowing Less wool staining

14. Correction of faulty dyeings Faulty shades can be levelled or partially stripped with X gpl carrier 2-4% levelling agent for wool 1 –2% emulsifying agent pH 5-6% with HAC’ Treatment at boil for 1 –2 hrs or 103 -106 0 C for 1 –1 ½ hrs If only shade on wool is to be corrected, carrier is not necessary