Investigation of Dye-Fiber Reactions in SC-CO2

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Investigation of Dye-Fiber Reactions in SC-CO2

• NSF Green Processing Summer Research Experience
  for Undergraduates
• Faculty Mentors Dr. David Hinks and Dr. Gerardo
  Montero
• Graduate Student Mentor Mr. Ahmed El-Shafei
• North Carolina State University, College of
  Textiles
• Undergraduate Student Nneka C. Ubaka-Adams
• Bennett College and North Carolina Agricultural
  and Technical State University

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Abstract

• This project is one phase of the push to use
  carbon dioxide as an environmentally safe solvent
  as opposed to the traditional solvent of choice,
  water. The piece under investigation is the
  reaction between a specific functional group and
  nylon and wool fibers at varying temperatures.
  The bond strength was measured indirectly by
  measuring the color fastness. After the dyed
  fiber was measured for color depth (by way of
  reflectance curve) it was rinsed with acetone and
  measured again. Extreme loss in color implied
  weak or incomplete bonding minor loss in color
  indicated complete or very near complete covalent
  bonding. It is expected that temperature will
  have a direct effect on the degree of complete
  covalent bonding.

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Objectives

• To demonstrate and quantify dye-fiber covalent
  bond formation between selected dyes and nylon,
  wool and cotton fibers in a supercritical carbon
  dioxide medium
• To optimize reaction conditions (temperature,
  pressure and time)
• To conduct a literature review

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Who and What does this Research Affect?

• Economy
• The dyeing industry
• The entire textile industry
• Health
• Factory Workers
• water systems
• Quality of Products
• Textile consumers

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Background

• Conventional dye-fiber reactions use water as a
  transport medium, and result in
• Low reaction efficiency due to the competing
  hydrolysis reaction with hydroxyl ions in water
  (hydrolyzed dye cannot react w/fiber)
• Environmental problems due to residual,
  unreacted/hydrolyzed dye present in effluent
• Replacing water with supercritical fluids (SCF)
  as a transport medium can result in
• Eliminating toxic waste (no hydrolyzed
  by-product)
• Lower costs for the entire dyeing process

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Hypothesis

• Color fastness of fibers dyed in supercritical
  fluid will be similar to fibers dyed in water
• Color fastness of fibers dyed with disperse
  (non-reactive) dye will be extremely low
• Dye-fiber Reaction (color fastness) will be
  directly proportional to the temperature increase

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Chemistry of Dyes

• Reactive dyes for cotton, rayon, silk, and wool
  form stable chemical links with textile materials
  to produce colored fabrics with excellent overall
  fastness, other dyestuffs only form loose bonds
  with fibers (VS-dye)
• Acetate, nylon, and polyester fibers colored with
  dispersed dyes retain their color even after
  repeated exposure to sunlight and washing (ES-dye)

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Conventional aqueous-based dye-fiber reaction
Polyamide (nylon 6.6.)
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Dye-Fiber Reaction in SC CO2
Polyamide (nylon 6.6.)
no hydrolyzed by-products
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Sulfonyl-azo-dyes
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Dyeing Procedure

• Add fiber and dye to vessel
• Pressurize system (with CO2) up to 800 psi and
  stir at approximately 850 rpm
• Heat to required temperature (100 -180 ºC)
• Pressurize to 3500 psi hold for 2 hours
• Release pressure, remove fabric

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(1) Gas cylinder of CO2, (2) High pressure pump,
(3) Autoclave reactor vessel with stirrer, V
1000 ml, (4) Circulation pump- acquisition in
future (5) Electrical heating jacket
CO2 Dyeing System
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High Pressure Batch Reactor
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Testing Dye-Fiber Reaction

• Measure color strength (K/S) of each dyed fiber
• Wash fiber with acetone (remove surface dye)
• Conduct soxhlet extraction using ethyl acetate
  (to remove unreacted dye)
• Compare effect of vinylsulfone reactive group on
  dye fixation

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Results
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Results
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Comparison of Dyed Fabrics
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Initial Conclusions

• Color depth improved with increasing temperature
• Strong evidence for dye-fiber bond formation
  using vinylsulfone-based dye on nylon and wool
• ES-dyeing on wool fibers showed extremely low
  color yields after extraction (no reaction)
• 94 fixation at 180 oC/ 3500 psi on wool

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Future Work

• Test time as a factor- 60-90 min
• Test with cotton fiber
• Test with commercial dye
• Test with different amount of dye- i.e. 0.5
  o.w.f, 1.5 o.w.f.
• Extract nylon fibers with a better solvent

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Acknowledgements

• NSF Green Processing REU
• North Carolina State University, College of
  Textiles
• Dr. Christine Grant
• Dr. Steve Peretti
• Dr. David Hinks
• Dr. Gerardo Montero
• Mr. Ahmed El-Shafei
• Mrs. Kirsten Reberg-Horton
• Mr. Lynell Williamson
• Jacob Hooker
• Mr. Jeff Krauss
• Mr. Chris Cazzola

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Acknowledgements

• This research was conducted with the support of
  the NSF
• Green Processing Undergraduate Research Program
  with a
• grant from the National Science Foundation, Award
  
• Number, EEC-9912339.