One bath dyeing cum bleaching agent for polyester/cotton blend

In textile industry, Polyester / Cotton (P/C) blends have dominant market share of about 60% in the knit sector. These blends are popular due to their aesthetic value and user friendly performance. 100% cotton knit fabric exhibits lower shape retention but higher moisture absorbency whereas 100% polyester fabric shows lower absorbency with higher strength and shape retention. Limitations of both fibres are offset by their blending which shows good strength and shape retention with an acceptable absorbency. However processing of P/C blends poses some challenges as cotton is non-absorbent in grey stage and needs to be scoured/bleached similar to 100% cotton before dyeing. In the exhaust dyeing of P/C blends, general practice is to first run the fabric through a preparatory process of scouring/bleaching and then dye each component separately under its optimum conditions, i.e. in a two-bath process. In high temperature (HT) dyeing method, polyester portion is dyed at 130oC and cotton part is dyed at 60–80oC however the dye bath is to be drained. This normally is a long process of over 8 hours of production time to dye both components with satisfactory fastness property.

To address the issue of productivity, economy and rising environmental concerns, several attempts have been made in the past to shorten this process.

SAREX has developed a product Dyebleach-BL which aids the dyeing of P/C blends without the bleaching process and thereby reducing the consumption of steam, water and power.

Unique Features:

· Polyester and cotton dyeing without pre bleaching — Shorter processing time.

· Only jet dyeing machine complete combined bleaching and dyeing step.

· No need to use jiggers for cotton bleaching thus makes jigger available for dyeing. Improves productivity of the plant.

· No need of reduction clearing.

· It bleaches cotton portion, hence most suitable for light and medium shades retaining their brightness.

· Avoids at least two drains in entire processing, thus reduce water consumption, steam for heating, process time, effluent load.

Dyebleach-BL process

For Polyester/Cotton or Polyester/Viscose woven, knit & yarn (67:37 & 48:52 blend)

Results:

Absorbency of fabric after polyester dyeing using Dyebleach BL.

Without Dyebleach-BL

Absorbency , sec — 20–21 sec 

Treatment—1.5% Caustic soda +2% H2O2

With Dyebleach-BL

Absorbency , sec — 1–2 sec

Treatment —2% Dyebleach-BL+1.5% Caustic soda + 2% H2O2 

Wash fastness test showing no need of reduction clearing: ISO 105 C10