A. Special Dyeing Processes
Achieving optimal wet rubbing fastness in dyed
fabrics requires a combination of pre-treatment, dyeing technique, and fabric
quality. Key considerations include:
1.
Singeing and Dyeing
Combination
A singeing process before dyeing helps remove protruding fibers, resulting in a
smoother fabric surface. This allows better dye penetration and adhesion,
significantly improving wet rubbing fastness.
2.
Enzymatic Treatment
Impact
While enzymatic treatments help in bio-polishing and surface cleaning,
over-treatment may reduce wet rubbing fastness by loosening surface fibers.
Therefore, it should be carefully controlled when used in combination with
reactive or direct dyeing.
3.
Compact Yarn
Quality (Combed & Compact Yarn)
Using high-quality compact yarns reduces hairiness, which directly correlates
to better wet rubbing fastness. Fabrics made with combed and compact yarns
exhibit improved surface smoothness and dye fixation.
4.
Effective Washing
Process
A thorough and clear post-dyeing wash removes unfixed dyes and auxiliaries,
thereby enhancing the wet rubbing grade. Poor washing leads to dye migration
and low rubbing results.
B.
Special Finishing Treatments
The final finish plays a critical role in
ensuring acceptable wet rubbing fastness, especially for export-grade fabrics.
·
China
Export Standards
China-bound fabrics often require wet rubbing fastness grades of 3–4, which can be challenging to achieve
consistently. While grades 2–3
are commonly attainable, special wet rubbing agents are necessary to push the
performance to grade 3 or above.
·
Finishing
Process Parameters
Finishing involves the application of wet rubbing fastness enhancers under
controlled conditions:
o Stentering Temperature: 150–170°C
o Wet Rubbing Agent Dosage: 30–100 g/L
o Pick-Up Rate: ~80%
o pH Control: Maintain at 5–6
For CVC (Chief Value Cotton) fabrics,
slightly lower stentering temperatures of 130–140°C are recommended to prevent thermal damage and
ensure chemical fixation.
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