DYEING OF POLYESTER BLENDS

1
DYEING OF POLYESTER BLENDS

• Limited manufacture in India
• Most popular blend 55/45 PET/Wool
• Other blend ratios 70/30 , 20/80
  
  
  
• 5545 blend warp and weft blended yarn
• Polyester Rich Blend 70/30 (textured 100 PET
  warp 5545 blended weft)
• Wool Rich Blend 20/80 (with 5545 blended weft
  and 100 wool weft)

2
PRETREATMENT

• Typical process sequence
• Grey inspection
• Scouring
• Dry
• Dye
• Singeing
• 11) Decatising and Pressing

• Stain removal
• Wool presetting(crabbing)
• Heat set
• Brushing, Cropping
• Steam or Damp
• Other sequences page 239

3
SCOURING

• Remove spin finish, lubricating agent, natural
  waxes, size, other contaminants
• Fabric relaxation
• Anionic or non-ionic detergents are used
• Use of alkali like soda ash should be avoided

• Rope form e.g. Dolly washing machine for wool
  rich or 5545 blends
• Open width e.g. for
• polyester rich blends

4
Non-ionic Detergent scouring

• Brief scouring at 100C above cloud point of
  detergent helps to form detergent-oil complex.
• Drain to remove surface impurities
• Scour 30 45 min. at 50C below the cloud point
  of detergent.

5
Crabbing

• For setting wool component
• Basically hot water treatment carried out in open
  width.
• Temp. boil, for 30 45 min.
• Does not have lasting effect due to heat setting
  on PET may be necessary to repeat crabbing to
  smoothout creases
• Second crabbing at 600C
• Dried on stenter at 1000C.

6
Heat setting

• Normally done before dyeing
• Important variables Time , Temperature,
• Distinct phases
• fabric setting up phase
• heat penetration phase
• molecular orientation phase
• cooling phase

7
Fabric heating up phase

• To raise the fabric surface temperature to the
  required value say 180/-100C.
• Time required depends on
• fabric structure
• rate of heating
• thermal conductivity of the fabric (15 sec.
  for low conductivity fabric)

8

• Heat Penetration and Molecular Orientation
  Phase quickest 5 sec.
• Cooling Phase stabilization of relaxed polymer
  structure - 10 sec.
• Total heat setting time - 30 sec.

9
Heat setting stage

• Grey heat setting
• After scouring

10
Grey heat setting

• Merits
• Stiffness imparted is removed during subsequent
  scouring
• Less chance of tendering due to absence of
  alkali left during scouring
• Easy to handle

• Demerits
• Oil stains and size are fixed -skittery
  appearance of dyed fabric

11
Heat setting after scouring

• Merits
• Clean operation
• Fabric appearance is bright
• Oils and other materials are not fixed faultless
  dyeing

• Demerits
• Stiff handle may be light fabric is needed
• If alkali is left in fabric damage of wool ,
  yellowing.

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DyeingGeneral considerations

• HTHP at 1300C-damage to wool component
• Heavy staining of wool with disperse dyes poor
  fastness properties should be avoided
• High temperature and prolonged dyeing time
  less staining , wool damage
• Lower temperature and shorter dyeing time are
  preferred.

13
Dyeing conditions

• At boil with carrier
• At 103 - 1060C with addition of smaller amount of
  carrier compared to at boil
• 110 -1150C with the addition of formaldehyde as
  wool protecting agent , a small amount of
  carrier if necessary

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Dyeing methods

• One bath method
• simultaneous dyeing of PET and wool with
  disperse and wool dyes
• common method for pale and medium depths of
  shade
• economical, minimum tendering of wool
• Two bath method
• mainly for navy and black shades
• no particular advantage over one-bath method
  

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Staining of wool

• Less in prolonged dyeing but chance of wool
  tendering
• More rapid exhaustion of disperse dye on PET
  less staining of wool
• Fine wool fibres are stained more severely than
  coarse wool fibres

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Dyebath Auxiliaries

• Dispersing agent
• Antifoam agent
• Carrier
• Crease inhibitor
• Levelling agent for wool dyeing
• Wool protecting agent

17
Carrier The choice depends on the machinery
used

• Closed machinery
• Fully flooded
• Partly flooded
• Covered machines
• Open machines

• Carrier
• -Very volatile carriers- 70- 100 volatility
  e.g.dichloro trichloro benzene
• -Medium to low volatality (40 70) e.g.mixture
  of i)biphenyl /trichlorobenzene
• ii)biphenyl/orthophenylphenol
• -As above
• -Low volatile (orthophenyl phenol, benzyl phenol)

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Dyes for PET and Wool

• Disperse dyes (DD)
• High temperature not suitable
• Low energy DDs-low sublimation fastness
• Medium energy dyes pale shades or dyeing at
  1060C
• High energy dyes- not suitable but can be used
  for max. colour yield and fastness is required
  applied to 1300C prior to PET/wool blending
• pH 4.5 5.5.

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Wool Dyes

• Acid and premetallised dyes most suitable
• No staining on PET
• Build up 40 - 500C
• Complete exhaustion at boil in 30 min.
• Dye selection is not critical
• Wet fastness is important 12 metal complex
  preferred
• Dyeing pH 4.5 5.5

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Mixture dyes

• Disperse/wool dye mixture- available since 1985,
  suitable for 5545 PET/wool
• Advantages
• simplified selection, reduced weighing/handling
  of dyes
• good reproducibility (from batch to batch or
  lab.to bulk scale)
• tone and tone dyeings as a result of good
  compatibility of acid and disperse dyes within
  each mixture
• suitable for computer colour matching
• Single dye class e.g. reactive disperse
  dyes
• Developed dyes show poor light fastness,
• not commercially suitable

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Minimisation of damage to wool

• The advantages of high temperature dyeing above
  1100C are
• Fast deep shades
• Shorter leveling time
• Better levelling
• Less staining of wool
• Disadvantages
• Wool degradation reduction in strength,
  elongation, abrasion resistance, yellowing

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• Therefore, to protect the wool component during
  high temperature dyeing,
• Most common agent HCHO (5 owf) allows dyeing at
• 1050C for 4 hrs
• 1100C for 3 hrs
• 1150C for2 hrs
• 1200C for 1 hr
• pH 3.5-4.5

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Recommended dyeing times

• 1000C for 120-150 min with carrier, no
  formaldehyde
• 1060C ,90 120 min with carrier and without
  formaldahyde
• 110 -1150C, 60 90 min, reduced amount of
  carrier, formaldehyde necessary
• 1200C, 20-30 min (not gt40 min), carrier optional,
  formaldehyde necessary
• High temperature dyeing is recommended for deep
  shades yellowing is not so critical

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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 00C

25
Dyeing methods

• One bath dyeing method with disperse and acid or
  metal complex dyes
• Dye selection
• Disperse dye low energy -gtminimum staining of
  wool easily removed by after wash
• Acid or metal complex not so critical

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General dyeing recipe

• X disperse dye
• Y acid/metal complex dye
• Z carrier
• 1 2 dispersing agent
• 5 -10 glaubers salt
• pH 4.5 5.5 with acetic acid

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Dyeing procedure

• Set bath with auxuliaries
• Preheat 10 20 min at 50 -700C
• Add disperse and dissolved acid dye
• Treat for 10 min
• Raise temperature to boil or 103-1060C 30-45 min
• Dye for 1½-2hrs depending on depth of shade
• Cool, cold and hot rinse shading 80 -1000C

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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

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• Pretreat with auxiliary at 50-600C
• Add disperse and acid dyes
• Treat for 10 min
• Raise temperature to 1100C/1200C in 45 min
• Dye for 30 60 min

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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 600C, good rinse
• With deep shades, repeat the above process

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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 -1060C or boil
• Cold rinse

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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 -500C
• Good rinse, acidify with HAC
• Dyeing of wool component

33
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 -2000C for 45 60 secs
• Not harmful to wool except slight yellowing
• Less wool staining

34
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 -1060C for
  1 1 ½ hrs
• If only shade on wool is to be corrected,
  carrier is not necessary