NED System

Pigment dyeing by exhaustion

Cotton dyeing

  • Cotton fibres currently represent 40% of worldwide fibre consumption.
    In sectors like knitted goods (garments), this represents up to 80% of global consumption
  • The dyes used for dyeing cotton fibres are classed in five basic dye families
    • Reactive dyes
    • Vat dyes
    • Direct dyes
    • Sulphur dyes
    • Naphtol dyes
  • The latter 2 dye families are only used in specific processes and applications

Reactive dyes / CO

Advantages

  • All sorts of hues such as brilliant hues, clean hues  etc.
  • Relatively cheap

Disadvantages

  • Relatively complex dyeing process
  • Wastewater with high concentration of electrolytes
  • Medium light fastnesses
  • Essential and laborious soaping (hydrolysis)

Without question the most used dye family.

Non optimum light fastness limits the universality of its use.

Vat dyes / CO

Advantages

  • Optimum light fastness
  • Low dyeing temperatures

Disadvantages

  • Difficulty in lavelling (color variation from quinine to leuco)
  • Complex dyeing process with few specialists on the matter
  • Look ok clean hues
  • High prices

Vat dyes are used in continuous process (Pad-Steam) and
rarely used in discontinuous one.

Direct dyes / CO

Advantages

  • From good to optimum light fastness
  • Very clean and bright hues
  • Simple dyeing process

Disadvantages

  • Low washing fastness.  Fixing agents after dyeing are required
  • Dyeing at boiling (pilling)
  • Expensive

Direct dyes cover the sector left void by reactive dyes

Alternative

  • All dye families offer positive and negative aspects
  • None of them offer an optimum solution

Does any alternative exist?

  • Possibilities of pigment dispersion have been studied for years
  • This family is a pillar of textile printing and is used on a small scale in simultaneous dyeing and finishing systems

Pigmentary dispersions offer very clear advantages

–     Optimum light fastness
–    Very bright and clean hues
–    Low price

but their dry and wet rubbing fastness are low

NED System ~ I

  • The new dyeing system with pigmentary dispersions is based on previous ideas but uses two basic products :
    • Adrafix CM (P-722)
    • Adracril CP-F (P-724)
  • Adrafix CM is a synergetic blend of surfactant agents with an ecologic solvent and a cotton mordent agent
  • Fixation of the mordent agent is delayed by retarding agents (leveling agents) that assure regular surface fixation.  Likewise, surfactant agents and the presence of solvents provide the perfect disaggregation of the pigmentary dispersion and the beginning of its slow fixation on the fibre when added to liquor.
  • Adracril CP-F is added in this phase
  • Adracril CP-F is a combination of cationic resins fixed on the fibre by exhaustion, following a temperature fixation process, they polymerize and react with the cotton fibre
  • On one hand, these form a polymeric structure on pigments forming macropolymers to improve dry and wet rubbing fastness and discolouring from washing
  • On the other hand, they become nice and soft to handle while keeping good hidrophility

NED System ~ II

  • The amount of Adrafix CM  is practically constant as the fibre catonization action is independent from the amount of pigment used
  • Adracril CP-F will be used according to:
    • Necessary amount of pigment
    • Required fastness on textile goods
    • Handling requirements

Pigment application by exhaustion

  • The fibre is previously mordented with a product to attract and fix the disperse pigment on the fibre to exhaust the pigments
  • With the pigment on the fibre, its position is fixed with a suitable binder
  • A well known system that has very important drawbacks
    • Irregular distribution on fibre
    • Low exhaustion (Wastewater)
    • Low dry and wet rubbing fastness
    • Rough and stiff to handle
  • Not applied in industry

Process by “jet”

Following pretreatment and rinsing of the goods, the jet is filled
with soft water at 20 – 30ºC

  1. Add Adrafix CM, circulate for 15 minutes
  2. Add pigment, circulate for 5 minutes
  3. Add Adracril  CP-F. Simultaneously, slowly increase  temperature to 55ºC
  4. Maintain for 20 minutes
  5. The liquor is hereby completely exhausted. All the pigment is fixed on the fibre

During final drying, to achieve good rubbing and washing
fastness, polymerize the resin for 1’ at 160ºC

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