oxidative clearing of polyester as an alternative to reduction clear: a comparative study j.i.n....
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OXIDATIVE CLEARING OF POLYESTER AS OXIDATIVE CLEARING OF POLYESTER AS AN ALTERNATIVE TO REDUCTION CLEAR: AN ALTERNATIVE TO REDUCTION CLEAR:
A COMPARATIVE STUDYA COMPARATIVE STUDY
J.I.N. Rocha Gomes, C.J.E. Lima and J.I.N. Rocha Gomes, C.J.E. Lima and J.R.AlmeidaJ.R.Almeida
Textile Department, University of Textile Department, University of MinhoMinho
4810 Guimarães, Portugal4810 Guimarães, Portugal
IntroductionIntroduction Four main factors must be considered for any new
process in the dyehouse: water , due the scarce resources available energy, due to its cost. pollution due to the limits imposed and the
ecological awareness of today’s society. time, or duration of the process, which must be in
line with the requirements for high productivity
– The process of dyeing Cotton/Polyester blends with reactive/disperse dyes is an example of a typical process that is highly polluting, wastes water, energy and time
Reduction Clearing Process
Necessary for destroying and removing the disperse dye deposited on polyester fibre
Cause of large wastage of water, energy and time due to the rinses necessary to remove reducing agent
Highly polluting due to the high conductivity and COD values produced
Oxidative Clearing
An oxidative clearing process with peroxide can be applied as an alternative for destroying and removing the deposited disperse dye
It can be applied after the process of dyeing Cotton/Polyester blends with reactive/disperse dyes unlike the reduction clearing
It is less polluting since the process uses an oxidising agent
It saves on water and time since there’s no need to rinse the peroxide
Bleaching
Dyeing PES
Reduction clear Dyeing CO
Washing –off Oxidative Clearing
20
40
60
80
100
120
140 ºC
Classic process
Eliminated with oxidative clearing
Added with oxidative clearing
Oxidative clearing vs. Reduction clear
Post-Bleaching
Bleaching after dyeing (post-bleaching) saves even more time since it avoids rinsing after bleaching
Post-bleaching conditions for cotton dyed with reactive dyes (alkaline hydrogen peroxide) when applied to cotton/polyester, clear disperse dye
For polyester/cotton blends dyed with reactive dyes, need to protect the reactive dye. Free radical quenchers have been used with success. However, even with protection some dyes are not resistant to the peroxide in alkaline conditions.
Effect of different conditions of oxidative clearing process on reactive
dye C.I. Black 5
Process E
I- Untreated --
II- Oxidative treatment with 1.5 g/l H2O2 + soda ash
3.09
III-Oxidative treatment with 1,5 g/l sodium perborate
2.87
IV- Oxidative treatment with 1.5 g/l of sodium perborate and 2% Quencher
0.96
Post-Bleaching vs Reduction Clear
Bleaching
Dyeing PES
Reduction clear
Dyeing CO
Washing –off +
Post-Bleaching
20
40
60
80
100
120
140 ºC
Classic process
Eliminated with post-bleaching
Added with post-bleaching
Oxidative clearing:Process conditions
Different process conditions were tested with and without alkali
Sodium perborate was tested as an alternative to alkaline hydrogen peroxide
Process was carried out in a laboratory machine with fabric movement so as to resemble the industrial reduction clearing process (Linitest of Heraeus)
Washfastness
Samples of fabric were taken after after dyeing and washing off and submitted to ISO 105 C06-C2 standard test (60ºC., 30 minutes, 4g/l sodium carbonate)
Samples of fabric were also stentered so as to evaluate the influence of the thermomigration on the washfastness
Values of staining for dyebath formula A on PE/CO
after ISO 105 C06 C2 (60ºC, 30 min, ECE detergent, 4g/l sodium carbonate)
ProcessProcessS.D.C. Multifiber Test FabricS.D.C. Multifiber Test Fabric
Sec Sec acetatacetatee
CottoCottonn
NYLONYLON 66N 66
PEPE AcryliAcrylicc
WoolWool
I -I -Reduction Reduction clearingclearing
1-2 4 2 3 4-5 4-5
II - HII - H22OO22 + + sodium sodium carbonatecarbonate
2-3 4 3 3-4 4-5 4-5
III - HIII - H22OO22 2 4 2-3 3 4-5 4-5
IV – IV – sodium sodium perborateperborate
2-3 4 3 3-4 4-5 4-5
Values of staining after ISO 105 C06 C2 for dyebath formula A on PE/CO -
after stentering
ProcessProcessS.D.C. Multifiber Test FabricS.D.C. Multifiber Test Fabric
Sec Sec acetatacetatee
CottonCotton NYLON NYLON 6666
PEPE AcrylicAcrylic WoolWool
I -I -Reduction Reduction clearingclearing
2 5 2 3 4-5 4-5
II - HII - H22OO22+ + sodium sodium carbonatecarbonate
2-3 5 2-3 3 4-5 4-5
III - HIII - H22OO22 2 5 2 3 4-5 4-5
IV – sodium IV – sodium perborateperborate
2-3 5 2-3 3 4-5 4-5
Values of staining after ISO 105 C06 C2 for dyebath formula B on PE/CO
ProcessProcessS.D.C. Multifiber Test FabricS.D.C. Multifiber Test Fabric
Sec Sec acetateacetate
CottoCottonn
NYLONYLON 66N 66
PEPE AcryliAcrylicc
WoolWool
I -I -Reduction Reduction clearingclearing
4-5 5 4-5 5 5 5
II - HII - H22OO22 + + sodium sodium carbonatecarbonate
5 5 4 5 5 5
III - HIII - H22OO22 3-4 5 4 5 5 5
IV – IV – sodium sodium perborateperborate
4-5 5 4-5 5 5 5
Values of staining after ISO 105 C06 C2 for dyebath formula B on PE/CO -
after stentering
ProcessProcessS.D.C. Multifiber Test FabricS.D.C. Multifiber Test Fabric
Sec Sec acetatacetatee
CottoCottonn
NYLON NYLON 6666
PEPE AcrylicAcrylic WoolWool
I -I -Reduction Reduction clearingclearing
4 5 4 5 5 5
II - HII - H22OO22 + + sodium sodium carbonatecarbonate
3-4 5 4 5 5 5
III - HIII - H22OO22 4 5 4 4-5 5 5
IV – sodium IV – sodium perborateperborate
4 5 4 5 5 5
Values of staining after ISO 105 C06 C2 for dyebath formula C on 100%
PE
ProcessProcessS.D.C. Multifiber Test FabricS.D.C. Multifiber Test Fabric
Sec Sec acetatacetatee
CottoCottonn
NYLON NYLON 6666
PEPE AcrylicAcrylic WoolWool
I -I -Reduction Reduction clearingclearing
4 5 4 4-5 5 5
II - HII - H22OO22+ + sodium sodium carbonatecarbonate
4 5 4 5 5 5
III - HIII - H22OO22 3 4-5 3 4 5 5
IV – sodium IV – sodium perborateperborate
4-5 5 4-5 5 5 5
Values of staining after ISO 105 C06 C2 for dyebath formula C on 100%
PE - after stentering
ProcessProcessS.D.C. Multifiber Test FabricS.D.C. Multifiber Test Fabric
Sec Sec acetatacetatee
CottoCottonn
NYLON NYLON 6666
PEPE AcrylicAcrylic WoolWool
I -I -Reduction Reduction clearingclearing
3-4 4-5 3-4 4-5 5 5
II - HII - H22OO22 + + sodium sodium carbonatecarbonate
4 5 4 4-5 5 5
III - HIII - H22OO22 3-4 4-5 3-4 4-5 5 5
IV – sodium IV – sodium perborateperborate
4 5 4 5 5 5
Discussion of results
For PE/CO, for dyes of low fastness (A) reduction clearing gave worse results than any of the oxidative clearing processes, both before and after stentering(tables 1 and 2)
For PE/CO, for dyes of higher fastness (B) processes II and IV, with alkaline peroxide and with sodium perborate respectively, gave the best results before stentering, and equivalent to reduction clearing after stentering (table 3 and 4)
For 100% PE, for dyebath formula C, the results are again better for processes II and IV, both before and after stentering
18
pH Conductivity
S/cm
COD mg/l
POST-BLEACH 1st wash after post-bleach 10,4 1011 290
REDUCTION CLEAR Sample 1 (red)
1st wash after Reduction clearing
12,3 6200 -
Sample 2 (navy) 1st wash after Reduction
clearing 11,7 2650 313
2nd wash 11,0 844 110 3rd wash 10,2 441 59
Sample 3 (navy) 1st wash after Reduction
clearing 12,0 4650 650
2nd wash 11,8 2760 390 SOAPING AND WASHING
OFF
Sample 1 (red) 2nd wash after soaping 7,74 483 51 3rd wash 7,49 410 49
Sample 2 (brown) 1st wash after soaping 7,64 309 37 2nd wash 8,00 304 34 3rd wash 7,75 288 34 4th wash 7,69 280 17
Pollution parameters
DIFFERENCE IN TIMEDIFFERENCE IN TIME(PE/CO)(PE/CO)
Time Standard Oxid Clearmin 945 783
min
Oxid Clear
Standard
0
200
400
600
800
1000
min
Time of the total process
Costs Standard Oxid ClearWater 1,97 1,39steam 0,22 0,34Electricity 21,00 20,25Recipe 56,28 45,25
Stand
ard
Oxid C
lear
Water
steam
Electricity
Recipe
0,00
10,00
20,00
30,00
40,00
50,00
60,00p
ort
ug
ue
se e
scu
do
s (P
TE
)
Costs in PTE per kg of dyed knitwear
Comparison of costs Comparison of costs
Recipe costsRecipe costs
Standard Oxid ClearRecipe costs 100,0 80,4
0,0
20,0
40,0
60,0
80,0
100,0
%
Recipe costs
Standard
Oxid Clear
ConclusionsConclusions
11. Ecological advantages. Ecological advantages
Besides the considerable savings on the water consumed, there is the ecological advantage of not using reduction clearing for polyester.
This factor alone lowers the COD values.
ConclusionsConclusions
22. Productivity. Productivity
17% less time for PE/CO At 75% application: 12,5% average more
productivity Example:
– 500 000 Kg PE/CO production /year: 62 000Kg more of PE/CO
ConclusionsWashfastness
Oxidative Clearing is as efficient in providing good washfastness or even more efficient with some dyes than Reduction Clearing