OXIDATIVE CLEARING OF POLYESTER AS AN ALTERNATIVE TO REDUCTION CLEAR: A COMPARATIVE STUDY J.I.N....

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



CottonCotton NYLON NYLON 6666

PEPE AcrylicAcrylic WoolWool


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


Sec Sec acetateacetate

CottoCottonn

NYLONYLON 66N 66

PEPE AcryliAcrylicc

WoolWool


4-5 5 4-5 5 5 5


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



CottoCottonn

NYLON NYLON 6666



4 5 4 5 5 5


3-4 5 4 5 5 5

III - HIII - H22OO22 4 5 4 4-5 5 5


4 5 4 5 5 5

Values of staining after ISO 105 C06 C2 for dyebath formula C on 100%

PE



CottoCottonn

NYLON NYLON 6666



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


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



CottoCottonn

NYLON NYLON 6666



3-4 4-5 3-4 4-5 5 5


4 5 4 4-5 5 5

III - HIII - H22OO22 3-4 4-5 3-4 4-5 5 5


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

OXIDATIVE CLEARING OF POLYESTER AS AN ALTERNATIVE TO REDUCTION CLEAR: A COMPARATIVE STUDY J.I.N....

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