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1.OXIDATIVE CLEARING OF POLYESTER ASAN ALTERNATIVE TO REDUCTION CLEAR:A COMPARATIVE STUDYJ.I.N. Rocha Gomes, C.J.E. Lima andJ.R.AlmeidaTextile Department, University ofMinho4810 Guimarães, Portugal
2.Introduction Four main factors must be considered for any newprocess in the dyehouse: water , due the scarce resources available energy, due to its cost. pollution due to the limits imposed and theecological awareness of today’s society. time, or duration of the process, which must be inline with the requirements for high productivity– The process of dyeing Cotton/Polyester blends withreactive/disperse dyes is an example of a typicalprocess that is highly polluting, wastes water, energyand time
3.Reduction ClearingProcess Necessary for destroying and removing the dispersedye deposited on polyester fibre Cause of large wastage of water, energy and time dueto the rinses necessary to remove reducing agent Highly polluting due to the high conductivity and CODvalues produced
4.Oxidative ClearingAn oxidative clearing process with peroxide can be appliedas an alternative for destroying and removing thedeposited disperse dyeIt can be applied after the process of dyeingCotton/Polyester blends with reactive/disperse dyesunlike the reduction clearingIt is less polluting since the process uses an oxidising agentIt saves on water and time since there’s no need to rinse theperoxide
5.Oxidative clearing vs. ReductionclearDyeingPESºC140120100Washing –offOxidative ClearingBleachingReductionclearDyeing CO80604020Classic processEliminated with oxidative clearingAdded with oxidative clearing
6.Post-Bleaching Bleaching after dyeing (post-bleaching) saves even moretime since it avoids rinsing after bleaching Post-bleaching conditions for cotton dyed with reactivedyes (alkaline hydrogen peroxide) when applied tocotton/polyester, clear disperse dye For polyester/cotton blends dyed with reactive dyes,need to protect the reactive dye. Free radical quenchershave been used with success. However, even withprotection some dyes are not resistant to the peroxide inalkaline conditions.
7.Effect of different conditions ofoxidative clearing process on reactivedye C.I. Black 5ProcessI- Untreated E-II- Oxidative treatment with 1.5 g/l 3.09H2O2 soda ashIII-Oxidative treatment with 1,5 g/l 2.87sodium perborateIV- Oxidative treatment with 1.5g/l of sodium perborate and 2%Quencher0.96
8.Post-Bleaching vs ReductionClearDyeingPESºC140120100Washing –off Post-BleachingBleachingReductionclear80Dyeing CO604020Classic processEliminated with post-bleachingAdded with post-bleaching
9.Oxidative clearing:Process conditions Different process conditions were tested with andwithout alkali Sodium perborate was tested as an alternative toalkaline hydrogen peroxide Process was carried out in a laboratory machinewith fabric movement so as to resemble theindustrial reduction clearing process (Linitest ofHeraeus)
10.Washfastness Samples of fabric were taken after after dyeingand washing off and submitted to ISO 105 C06C2 standard test (60ºC., 30 minutes, 4g/l sodiumcarbonate) Samples of fabric were also stentered so as toevaluate the influence of the thermomigration onthe washfastness
11.Values of staining for dyebath formula A onPE/COafter ISO 105 C06 C2 (60ºC, 30 min, ECE detergent, 4g/lsodium carbonate)S.D.C. Multifiber Test FabricProcessSecacetateCottonNYLON 66PEAcrylicWoolIReductionclearing1-24234-54-5II - H2O2 sodiumcarbonate2-3433-44-54-5III - H2O2242-334-54-5IV –sodium2-3433-44-54-5
12.Values of staining after ISO 105 C06C2 for dyebath formula A on PE/CO after stenteringS.D.C. Multifiber Test FabricProcessSecacetateCottonNYLON PE66AcrylicWoolIReductionclearing25234-54-5II - H2O2 sodiumcarbonate2-352-334-54-5III - H2O225234-54-552-334-54-5IV – sodium 2-3perborate
13.Values of staining after ISO 105 C06C2 for dyebath formula B on PE/COS.D.C. Multifiber Test FabricProcessSecCottoacetate nNYLON 66PEAcrylicWoolIReductionclearing4-554-5555II - H2O2 sodiumcarbonate554555III - H2O23-454555IV –sodiumperborate4-554-5555
14.Values of staining after ISO 105 C06C2 for dyebath formula B on PE/CO after stenteringS.D.C. Multifiber Test FabricProcessSecacetateCottonNYLON PE66AcrylicWoolIReductionclearing454555II - H2O2 sodiumcarbonate3-454555III - H2O24544-555IV – sodium 4perborate54555
15.Values of staining after ISO 105 C06C2 for dyebath formula C on 100%PES.D.C. Multifiber Test FabricProcessSecacetateCottonNYLON PE66Acrylic WoolIReductionclearing4544-555II - H2O2 sodiumcarbonate454555III - H2O234-5345554-5555IV – sodium 4-5perborate
16.Values of staining after ISO 105 C06C2 for dyebath formula C on 100%PE - after stenteringS.D.C. Multifiber Test FabricProcessSecacetateCottonNYLON PE66Acrylic WoolIReductionclearing3-44-53-44-555II - H2O2 sodiumcarbonate4544-555III - H2O23-44-53-44-55554555IV – sodium 4perborate
17.Discussion of results For PE/CO, for dyes of low fastness (A) reduction clearinggave worse results than any of the oxidative clearingprocesses, both before and after stentering(tables 1 and 2) For PE/CO, for dyes of higher fastness (B) processes II andIV, with alkaline peroxide and with sodium perboraterespectively, gave the best results before stentering, andequivalent to reduction clearing after stentering (table 3 and 4) For 100% PE, for dyebath formula C, the results are againbetter for processes II and IV, both before and afterstentering
18.Pollution parametersPOST-BLEACH1st wash after post-bleachREDUCTION CLEARSample 1 (red)1st wash after ReductionclearingSample 2 (navy)st1 wash after Reductionclearing2nd wash3rd washSample 3 (navy)st1 wash after Reductionclearing2nd washSOAPING AND WASHINGOFFSample 1 (red)2nd wash after soaping3rd washSample 2 (brown)st1 wash after soaping2nd wash3rd wash4th washpHConductivity S/cmCODmg/l10,4101129012,36200-11,7265031311,010,28444411105912,0465065011,827603907,747,4948341051497,648,007,757,693093042882803734341718
19.DIFFERENCE IN TIME(PE/CO)TimeminStandard Oxid Clear945783Time of the total process1000min800Standard600400200Oxid Clear0min
20.Comparison of costsStandard Oxid Clear1,971,390,220,3421,0020,2556,2845,25Costs in PTE per kg of dyed knitwear60,0050,0040,00Recipe30,00Electricity20,00steam10,00WaterCleardOxiandard0,00Stportuguese escudos(PTE)CostsWatersteamElectricityRecipe
21.Recipe costsStandardRecipe costs100,0Oxid Clear80,4100,080,0Standard40,0Oxid Clear%60,020,00,0Recipe costs
22.Conclusions1. Ecological advantagesBesides the considerable savings onthe water consumed, there is theecological advantage of not usingreduction clearing for polyester.This factor alone lowers the CODvalues.
23.Conclusions2. Productivity 17% less time for PE/COAt 75% application: 12,5% average moreproductivityExample:– 500 000 Kg PE/CO production /year:62 000Kg more of PE/CO
24.ConclusionsWashfastnessOxidative Clearing is as efficient inproviding good washfastness oreven more efficient with somedyes than Reduction Clearing
25.