Transcript dyg of polyester blend

DYEING OF POLYESTER
BLENDS
•
•
•
•
•
Limited manufacture in India
Most popular blend :55/45 PET/Wool
Other blend ratios : 70/30 , 20/80
55:45 blend –warp and weft blended yarn
Polyester Rich Blend: 70/30 (textured
100% PET warp & 55:45 blended weft)
• Wool Rich Blend : 20/80 (with 55:45
blended weft and 100% wool weft)
PRETREATMENT:
Typical process sequence:
1)
3)
Grey inspection
Scouring
5)
7)
9)
11)
Dry
Dye
Singeing
Decatising and Pressing
2) Stain removal
4) Wool
presetting(crabbing)
6) Heat set
8) Brushing, Cropping
10) Steam or Damp
Other sequences page 239
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 55:45
blends
• Open width e.g. for
polyester rich blends
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.
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.
Heat setting
• Normally done before dyeing
• Important variables: Time , Temperature,
• Distinct phases:
* fabric setting up phase
* heat penetration phase
* molecular orientation phase
* cooling phase
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)
• Heat Penetration and Molecular
Orientation Phase: quickest – 5 sec.
• Cooling Phase : stabilization of
relaxed polymer structure - ~ 10 sec.
• Total heat setting time - ~30 sec.
Heat setting stage:
• Grey heat setting
• After scouring
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
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.
Dyeing
General 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.
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
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
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
Dyebath Auxiliaries:
•
•
•
•
•
•
Dispersing agent
Antifoam agent
Carrier
Crease inhibitor
Levelling agent for wool dyeing
Wool protecting agent
Carrier
The choice depends on the machinery used:
Closed machinery
• Fully flooded
• Partly flooded
• Covered machines
• Open machines
Carrier
-Very volatile carriers- 70100% 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)
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.
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 : 1:2 metal complex
preferred
• Dyeing pH: 4.5 –5.5
Mixture dyes:
• Disperse/wool dye mixture- available since 1985,
suitable for 55:45 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
• Developed dyes show poor light fastness,
• not commercially suitable
dyes
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
• 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
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 >40 min), carrier optional,
formaldehyde necessary
• High temperature dyeing is recommended for deep
shades –yellowing is not so critical
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
Dyeing methods:
• One bath dyeing method with disperse and
acid or metal complex dyes
• Dye selection:
– Disperse dye –low energy ->minimum
staining of wool –easily removed by after
wash
– Acid or metal complex –not so critical
General dyeing recipe
•
•
•
•
•
•
X% disperse dye
Y% acid/metal complex dye
Z% carrier
1 –2% dispersing agent
5 -10% glauber’s salt
pH :4.5 –5.5 with acetic acid
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
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’
•
•
•
•
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
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
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
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
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
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