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Bleikende tekstielbedryf

Bleikende tekstielbedryf


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Nadat die lap gemaak is, is dit gewoonlik gebleik. Tradisioneel is dit bereik deur die lap in suurmelk (melksuur) te week en dit op tenterhake in die oop velde te versprei sodat die son die bleikproses kan voltooi. Met hierdie metode kan dit tot agt maande neem voordat die lap gereed is om op die mark verkoop te word.

In 1746 het John Roebuck verdunde suur begin gebruik in plaas van suurmelk. Dit het die tyd wat nodig is vir die bleikproses gehalveer. Aan die einde van die eeu het Charles Tennant 'n bleikpoeier by sy chemiese werke in Glasgow ontwikkel. Dit het nie net die bleikproses versnel nie, maar ook 'n witter lap. Die toenemende gebruik van wielmasjiene in die 19de eeu verlaag ook die koste van bleik.


Die geskiedenis van weef en die tekstielbedryf

Het u al ooit opgehou om te wonder hoe die klere wat u tans dra, die gewilde t-hemp of nuwe jeans, gemaak is? Die meeste van ons beskou nie die ingewikkeldhede van die tekstielbedryf nie, maar die geskiedenis van klere- en lapproduksie is 'n ryk en kleurryke verhaal wat in almal se repertorium behoort te wees. Met dit in gedagte, neem ons dit terug na die basiese beginsels deur 'n bietjie lig te werp op die geskiedenis van weef en tekstiel - net om u iets te bedink wanneer u die Scrubba -wassak met u gunsteling uitrustings laai.

Antieke weefwerk:

Om die weefpraktyk en die rol daarvan in die florerende tekstielbedryf te verstaan, moet ons die drade van hierdie antieke kuns tot in die voorgeskiedenis volg.

Om 'n ongelooflike kort - en effens droë - opsomming te gee wat die revolusionêre proses op geen manier regverdig nie, behels die weefkuns om 'n stel vertikale drade, die 'wrap', met 'n stel horisontale drade, die 'inslag', te verbind. Dit lyk asof die praktyk byna in die menslike natuur ingeburger is, omdat die onderliggende beginsels nog voordat die weefproses geïmplementeer is, toegepas is by die skepping van alledaagse benodigdhede soos skuilings en mandjies. Hierdie kunsvlyt het staatgemaak op die ineenvleging van klein materiale, soos takkies en blare, om stabiele voorwerpe te vorm. Toe ou mense eers 20 of 30 duisend jaar gelede ontdek het hoe om plantvesels in 'n draad te maak, is hierdie basiese weefbeginsels uitgebreid gebruik en is uitgebreide en uiters praktiese items vervaardig deur die kuns van vingerweef, 'n vaardigheid wat vandag nog wyd beoefen word .

Weef self is een van die oudste oorlewende praktyke ter wêreld, met 'n geskiedenis wat gewortel is in die neolitiese tydperk (ongeveer 9000-4000 vC). Dit was in hierdie tyd dat die skepping van geweefde stowwe ontplof, terwyl elke huishouding lap vir persoonlike gebruik vervaardig. Weef het 'n onontbeerlike vaardigheid geword vir Neolitiese mense en was gevolglik nou verbonde aan die familie -eenheid, 'n tradisie wat duisende jare lank sou voortduur.

Draai en weef in die Middeleeue:

Die kuns van weef is oor duisende jare stadig geleidelik vervolmaak en verfyn, wat uiteindelik gelei het tot hoogs gespesialiseerde lap wat deur bekwame praktisyns vervaardig is. Dit is geen verrassing dat die vervaardiging van hierdie lap, wat hoër vaardigheidsvlakke vereis, saamval met die geleidelike beweging van weef weg van die huishouding en na die werkplek. Teen die Middeleeue is 'n goed ontwikkelde verskaffingsketting bestaande uit kleurers, spinners, wewers, vullers, draperers en kleermakers geïmplementeer om die bloeiende tekstiel- en weefbedryf te ondersteun wat vinnig een van die winsgewendste bedrywe in Europa was. Die stad Coventry was besonder ryk deur die plofbare weefhandel. Dit was die bekendheid van die stad dat die gesegde 'ware blou' na bewering afstam van die langer frase, 'so waar as Coventry blue', met verwysing na die stad se bekwaamheid om blou kleurstowwe te vervaardig wat nie geloop het nie en dus bly 'waar'.

Op hierdie tydstip het weef in Europa steeds plaasgevind by die weefstoel wat die weefproses vir millennia oorheers het, hoewel 'n aantal verbeterings, ingevoer uit China en ander wêreldryke, geleidelik ingestel is om die proses te bespoedig. Byvoorbeeld, in die 11de eeu het die bekendstelling van horisontale, voetbedrewe weefgewaaie 'n makliker, baie meer doeltreffende weefproses moontlik gemaak. Boonop het die draaiwiel, wat waarskynlik tussen 500 en 1000 nC in Indië ontstaan ​​het en uiteindelik uit die Midde -Ooste na Europa ingevoer is, die vorige metode vir handspin vervang. Die draaiwiel is veel meer as net 'n basiese uitgangspunt van die sprokie -tradisie, totdat dit die proses van veselomskakeling in die gare aansienlik kon bespoedig as voorbereiding op weefwerk. Die gevolglike tekort aan gare beklemtoon die noodsaaklikheid om die proses te meganiseer, wat die weg baan vir die plofbare vordering wat gedurende die Industriële Revolusie sou plaasvind.

Weef in die Industriële Revolusie:

In 1774 is 'n swaar belasting op katoendraad en lap wat in Brittanje vervaardig is, herroep, waarskynlik veroorsaak deur 'n aantal revolusionêre ontwikkelings in die handel. Die uitvindings wat hierdie ontwikkelings tot gevolg gehad het, was onder meer die Flying Shuttle (1733), wat toegelaat het dat wyer lap teen 'n vinniger spoed geweef kan word as wat voorheen moontlik was, die Spinning Jenny (1765), wat die aantal drade wat 'n enkele masjien kon draai, van ses tot meer toeneem tagtig, en die Water Frame (1769), wat water as 'n kragbron gebruik het, terwyl 'n beter draad as die Spinning Jenny vervaardig is. Crompton's Spinning Mule, ontwikkel in 1779, is gebaseer op hierdie idees deur die mees positiewe aspekte van die Spinning Jenny en die Water Frame te kombineer om die beste resultate van die eeu te lewer. Teen die 1790's word stoommasjiene wyd gebruik in katoenfabrieke om die tekstielproduksie verder te verbeter deur die afhanklikheid van water te verminder, wat die vorige kwessies van waterskaarste grootliks negeer.

Hierdie vordering het saamgeval met die verspreiding van chemiese bleikmiddels en kleurstowwe, waardeur bleek, kleur en druk op dieselfde plek kon plaasvind. Uiteindelik, met die uitvinding van Robert's Power Loom in 1812, is alle stadiums van die vervaardiging van katoen gekonsolideer en kan dit in die een fabriek plaasvind.

Die vooruitgang was so dat die rykdom van die tekstielbedryf gedurende die middel van die 1700's tot die middel van die 1800's vinnig toegeneem het. As gevolg hiervan het dit vinnig die hoofbedryf van die Industriële Revolusie geword met betrekking tot indiensneming en belê kapitaal, en was dit selfs die eerste wat moderne produksiemetodes gebruik het.

Weaving en die tekstielbedryf vandag:

Vandag is weef byna uitsluitlik gekommersialiseer, hoewel baie gemeenskappe en individue regoor die wêreld steeds met die hand weef, hetsy vir die pret, vir kulturele identifikasie of uit nood. Die outomatiese kragstelsels domineer nou die handel, wat hierdie belangrike aspek van die tekstielbedryf aansienlik verbeter en vaartbelyn.

Alhoewel die weefpraktyk byna heeltemal uit die openbare oog beweeg het, bly dit 'n belangrike stap in die lang voorsieningsketting in die wêreldwye modebedryf. Met 'n geskiedenis van ongeveer 30 000 jaar, is weef werklik een van die oudste bestaande vaardighede wat mense op wêreldwye vlak beoefen het, en dit is hierdie indrukwekkende geloofsbrief wat dit so verdien om 'n bietjie erkenning te gee die volgende keer as u na u gunsteling uitrusting!


Metode om tekstielmateriaal te bleik (opsies)

Die uitvinding het betrekking op chemiese tegnologie vir die bereiding van tekstielmateriaal, veral 'n metode om 'n tekstielmateriaal te bleik. Beskryf 'n metode om 'n tekstielmateriaal van natuurlike vesel te bleik, of 'n mengsel daarvan met chemiese of sintetiese vesels wat met 20-30 geïmpregneer is. , bytsoda, nie-ioniese benattingsmiddel gebaseer op geëthoxileerde vetalkoholen en optiese bleikmiddel is 'n afgeleide van stilbeen, met daaropvolgende spin-siklus, wat die materiaal binne 18-48 uur in 'n verseëlde volume hou, was en droog. Met hierdie metode kan u die verbruik van elektriese energie en stoom verminder. 2 S. bl. f-kristalle, 2 oortjies.

Die uitvinding het betrekking op chemiese tegnologie vir die bereiding van tekstielmateriaal, en meer in besonder op 'n metode om 'n gespesifiseerde materiaal wat natuurlike sellulose en/of chemiese vesels bevat, te bleik, vir vrystelling in die wit vorm van en vir die daaropvolgende kleur.

Tans is daar 'n manier om peroksied te bleek van materiaal wat katoen bevat. 153 tot 155, C. 233-230), naamlik dat die gespesifiseerde materiaal by verhoogde temperatuur geïmpregneer word met 'n waterige oplossing van die volgende samestelling: waterstofperoksied, bytsoda, Basilicata -stabilisator - Prestige IB, nie -ioniese benatting - Taralon OL, suurdeeg M, optiese bleikmiddel -telenovela -reeks, draai uit en hou dan ten minste 1 uur in 'n lugdigte volume, was met warm en koue water en droog.

Metode vir die bleek van tekstielmateriaal wat sintetiese (chemiese) vesel bevat, gebruik dieselfde samestelling by 50-100 o C, gevolg deur pers, hou 'n verseëlde volume binne 45-60 min, was en droog (Safonov eeue die afwerking van tekstielmateriaal.- M .: Legprombytizdat, 1991, S. 228).

Die nadeel van hierdie metodes is die hoë energieverbruik wat nodig is om stoom te produseer en die hoë temperatuurverwerking te handhaaf.

Die doel van die voorgestelde tegniese oplossing is om die nadeel uit die weg te ruim: die vermindering van die verbruik van elektrisiteit en stoom wat nodig is om die gewenste temperatuur van die behandeling van tekstielmateriaal te skep en te behou, terwyl die verbruikers se eienskappe behoue ​​bly.

Waterstofperoksied (100%) - 2-4
Samestelling Diurin op die basis van oksietilidendifosfonovaya suur - 0,2-0,5,
Metasilikaat of natriumsilikaat - 1,0-2,0,
Bytsoda (100%) - 1,5 tot 2,5,
Nie-ioniese benattingsmiddel gebaseer op geëthoksileerde vetalkoholen-0,2-0,7,
Die optiese Brightener is 'n afgeleide van stilbene - 0,1 tot 0,3,
Water - die res
die bevrugting word uitgevoer op 20-30 o en binne 18-48 uur in 'n verseëlde volume gehou.

In 'n variant van die metode om tekstielmateriaal van sintetiese vesels te bleik, word 'n waterige bleikoplossing wat waterstofperoksied bevat, nat bytsoda, natgemaak met natgemaakte materiaal in 'n verseëlde volume, intensiewe spoeling van warm en koue water en droog in die stabilisator gebruik as metasilikaat of natriumsilikaat as benattingsmiddel is 'n nie -ioniese benattingsmiddel gebaseer op geëthoksileerde vetalkoholen en word in die bleikoplossing 'n samestelling van dagboek verder toegedien op die basis van oksietilidendifosfonovaya -suur in die volgende verhouding, gew.%:
Waterstofperoksied (100%) - 0,3-0,7,
Samestelling Diurin op die basis van oksietilidendifosfonovaya suur van 0,2-0,3,
Metasilikaat of natriumsilikaat - 0,1-0,2
Bytsoda (100%) - 0,08-0,1,
Nie-ioniese benattingsmiddel gebaseer op geëthoksileerde vetalkoholen-0,2-0,3,
Die optiese Brightener is 'n afgeleide van stilbene - 0,005-0,1,
Water - die res
die bevrugting word uitgevoer op 20-30 o Met, en binne 18-48 uur gehou.

Onder natuurlike sellulose vesels word in hierdie geval verstaan ​​as katoen, linne of mengsels daarvan, en chemies - sinteties (poliëster, poliëtileen, poliamied - PA, polipropileen - PP) en sinteties (rayon, viskose modulus).

Samestelling Diurin gebaseerde oksietilidendifosfonovaya suur bekend onder THE 2638-023-17965829-98.

Soos nie -ionies met die manie).

As optiese Brightener telenovela reeks gebruik verkieslik Belfor OOR, IB.

Verduidelik vervolgens die essensie van die voorgestelde tegniese oplossings, spesifieke voorbeelde van die metode word in die tabel gegee. 1.

Elkeen van die gespesifiseerde tabel. 1 variante word in die volgende volgorde uitgevoer: tekstielmateriaal word eers geïmpregneer by 'n plusvokale masjien wat die toepaslike voorbeeldkomponente van die samestelling bevat by die ooreenstemmende temperatuur van die oplossing, uitgedraai verkieslik 70-100%, verpak in 'n verseëlde volume (bv. poliëtileenfilm), vir die gepaste tyd geïnkubeer, en daarna intensief met warm (70-90 o C) en koue water na die wasmasjien gewas en droog kontak of konveksie deur.

In die tabel. 2 toon die resultate van die behandeling van tekstielmateriaal en die verbruik van elektrisiteit en stoom.

Die datatabel. 2 toon aan dat die tekstielmateriaal wat volgens die voorgestelde metode behandel word, kwalitatiewe aanwysers hoër is as wat deur die prototipe verwerk word. Dit verminder die energiekoste met 60%en 'n paar met 70%.

1. Metode van bleek van tekstiel materalisim -oplossing bevat waterstofperoksied, bytsoda, stabilisator, benatting en optiese bleikmiddel - stilbene -afgeleide, gevolg deur pers, hou gehidreerde materiaal in 'n verseëlde volume, intense spoel warm en koue water en droog, met die kenmerk dat die stabilisator word gebruik as metasilikaat of natriumsilikaat, aangesien die benattingsmiddel 'n nie -ioniese benattingsmiddel is wat gebaseer is op geëthoxileerde vetterige alkohole, en in die bleikoplossing word 'n samestelling van die dagboek verder toegedien op die basis van oksietilidendifosfonovaya -suur in die volgende verhouding, gew.%:
Waterstofperoksied 100% - 2-4
Samestelling Diurien -gebaseerde oksoetieliedendifosfonzuur - 0,2-0,5
Metasilikaat of natriumsilikaat - 1,0-2,0
Bytsoda 100% en 1,5 - 2,5
Nie-ioniese benattingsmiddel gebaseer op geëthoksileerde vetalkoholen-0,2-0,7
Die optiese Brightener is 'n afgeleide van stilbene - 0,1-0,3
Water - die res
die bevrugting word uitgevoer op 20-30 o en binne 18-48 uur in 'n verseëlde volume gehou

2. Metode vir die bleek van tekstielmateriaal van sintetiese vesels, geïmpregneerde waterige bleikoplossing wat waterstofperoksied, natriumoksied bevat, is die gebruik van klam materiaal in 'n verseëlde volume, intensiewe spoel van warm en koue water en droog, met die kenmerk dat die stabilisator as metasilikaat gebruik word of natriumsilikaat as benattingsmiddel is 'n nie -ioniese benattingsmiddel gebaseer op geëthoksileerde vetalkoholen, en in die bleikoplossing word verder 'n samestelling van Dagboek toegedien op die basis van oksietilidendifosfonovaya -suur in die volgende verhouding, gew.%:
Waterstofperoksied 100% - 0,3-0,7
Samestelling Diurin op die basis van oksietilidendifosfonovaya suur - 0,2-0,3
Metasilikaat of natriumsilikaat - 0,1-0,2
Bytsoda 100% - 0,08-0,1
Nie-ioniese benattingsmiddel gebaseer op geëthoksileerde vetalkoholen-0,2-0,3
Die optiese Brightener is 'n afgeleide van stilbene - 0,005-0,1
Water - die res
die bevrugting word uitgevoer op 20-30 o Met, en binne 18-48 uur gehou


Siviele ingenieurswese

Vir groot siviele ingenieurswerke was die swaar werk van die aarde steeds gedurende hierdie tydperk afhanklik van menslike arbeid wat deur boukontrakteurs gereël is. Maar die gebruik van kruit-, dinamiet- en stoomgravers het gehelp om hierdie afhanklikheid teen die einde van die 19de eeu te verminder, en die bekendstelling van saamgeperste lug en hidrouliese gereedskap het ook bygedra tot die verligting van die druk. Laasgenoemde twee uitvindings was in ander opsigte belangrik, soos in mynbou -ingenieurswese en in die werking van hysbakke, sluithekke en hyskrane. Die gebruik van 'n tonnelskerm om 'n tonnel deur sagte of onseker rotslae te laat ry, is die pionier van die Franse emigrantingenieur Marc Brunel in die bou van die eerste tonnel onder die Teemsrivier in Londen (1825–42), en die tegniek is elders aangeneem. Die ysterklok of kasteel is ingebring om onder die watervlak te werk om fondamente vir brûe of ander strukture te lê, en brugbou het groot vordering gemaak met die vervolmaking van die hangbrug - deur die Britse ingenieurs Thomas Telford en Isambard Kingdom Brunel en die Duitser Amerikaanse ingenieur John Roebling - en die ontwikkeling van die stutbrug, eers in hout, dan in yster. Smeedijzer het geleidelik yster as 'n brugboumateriaal vervang, hoewel daar verskeie vooraanstaande gietysterbrue oorleef, soos dié wat tussen 1777 en 1779 op Ironbridge in Shropshire opgerig is, wat gepas beskryf is as die 'Stonehenge of the Industrial Revolution'. Die dele is gegiet by die Coalbrookdale -oond daar naby en aanmekaargesit deur die model van 'n houtkonstruksie vas te maak en vas te maak, sonder die gebruik van boute of klinknaels. Die ontwerp is vinnig vervang in ander gietysterbrue, maar die brug staan ​​steeds as die eerste belangrike strukturele gebruik van gietyster. Gietyster het baie belangrik geword in die opstel van groot geboue, en die elegante Crystal Palace van 1851 was 'n uitstekende voorbeeld. Dit is ontwerp deur die vindingryke argitek wat deur tuinier sir Joseph Paxton gemaak is op die model van 'n kweekhuis wat hy op die landgoed Chatsworth van die hertog van Devonshire gebou het. Die gietysterbalke is deur drie verskillende ondernemings vervaardig en getoets op grootte en sterkte op die terrein. Teen die einde van die 19de eeu het staal egter begin om gietyster sowel as smeedyster te vervang, en gewapende beton is ingestel. By watervoorsiening en rioolverwyderingswerke het siviele ingenieurswese 'n paar monumentale suksesse behaal, veral in die ontwerp van damme, wat aansienlik verbeter het in die tydperk, en in langpypleidings en -pompe.


Die vervaardiging van natriumhypochlorietbleikmiddel verg verskeie stappe. Al die stappe kan by een groot vervaardigingsfasiliteit uitgevoer word, of die chloor en bytsoda kan van verskillende aanlegte na die reaktorplek gestuur word. Beide chloor en bytsoda is gevaarlike chemikalieë en word volgens streng regulasies vervoer.

Die voorbereiding van die komponente

  • 1 Bytsoda word gewoonlik geproduseer en gestuur as 'n gekonsentreerde oplossing van 50%. Op sy bestemming word hierdie gekonsentreerde oplossing met water verdun om 'n nuwe 25% oplossing te vorm.
  • 2 Hitte word gevorm wanneer die water die sterk bytsoda -oplossing verdun. Die verdunde bytsoda word afgekoel voordat dit gereageer word.

Die chemiese reaksie

  • 3 Chloor en die bytsoda -oplossing word gereageer om natriumhypochlorietbleikmiddel te vorm. Hierdie reaksie kan plaasvind in 'n bondel van ongeveer 14.000 liter of in 'n deurlopende reaktor. Om natriumhypochloriet te skep, word vloeibare of gasvormige chloor deur die bytsoda -oplossing gesirkuleer. Die reaksie van chloor en bytsoda is in wese onmiddellik.

Verkoel en suiwer

  • 4 Die bleikoplossing word dan afgekoel om ontbinding te voorkom.
  • 5 Hierdie afgekoelde bleikmiddel word gereeld gevestig of gefiltreer om onsuiwerhede te verwyder wat die bleikmiddel kan verkleur of die ontbinding daarvan kan kataliseer.

Gestuur

  • 6 Die afgewerkte natriumhypochloriet bleikmiddel word na 'n bottelingsaanleg gestuur of ter plaatse gebottel. Huishoudelike sterkte bleikmiddel is tipies 5,25% natriumhypochloriet in 'n waterige oplossing.

Droog in die tekstielbedryf


Droog is nodig om die waterinhoud van die vesels, garings en weefsels na nat prosesse uit te skakel of te verminder. Droging, veral deur verdamping van water, is 'n hoë-energieverbruikende stap (alhoewel die algehele verbruik verminder kan word as hergebruik/herwinningsopsies gebruik word) (BAT vir die tekstielbedryf, Julie 2003).

2. TOEPASSINGSGEBIED


Droog kan toegepas word op die volgende tekstielmateriaal (BAT vir die tekstielbedryf, Julie 2003):

3. BESKRYWING VAN TEGNIEKE, METODES EN TOERUSTING

Droogtegnieke kan as meganies of termies geklassifiseer word. Meganiese prosesse word algemeen gebruik om die water wat meganies aan die vesel gebind is, te verwyder. Dit is daarop gemik om die doeltreffendheid van die volgende stap te verbeter. Termiese prosesse bestaan ​​uit die verhitting van die water en die omskakeling daarvan in stoom. Hitte kan oorgedra word deur middel van:

Oor die algemeen word droog nooit in 'n enkele masjien uitgevoer nie, wat gewoonlik ten minste twee verskillende tegnieke insluit.

Die waterinhoud van die vesel word aanvanklik verminder deur óf sentrifugale ekstraksie óf deur vermenging voordat dit verdamp.

  • Hanks droog: (BAT vir die tekstielbedryf, Julie 2003)
  • Sentrifugale ekstraksie:
  • Verdampende droog:

Die vog van gekleurde verpakkings word aanvanklik verminder deur middel van sentrifugale ekstraksie. Spesiaal ontwerpte sentrifuges, verenigbaar met die ontwerp van die kleurskep en garingdraers, word gebruik.

Tradisioneel was die pakkies in die oond gedroog, en baie lang verblyftye is nodig om die gare aan die binnekant van die verpakking te droog. Twee metodes word tans gebruik, vinnig (gedwonge) lugdroging en radiofrekwensiedroging, en laasgenoemde word soms saamgevoeg met die aanvanklike vakuum -ekstraksie. Gedwonge lugdroërs werk gewoonlik deur warm lug uit die binnekant van die vakuumontginning te sirkuleer. Gedwonge lugdrogers werk gewoonlik deur warm lug van binne aan die binnekant van die verpakking na buite te sirkuleer by 'n temperatuur van 100 ° C. gevolg deur kondisionering, waarin die oorblywende vog in 'n lugstroom van buite na die binnekant van die verpakking herverdeel word. Radiofrekwensie -drogers werk volgens die vervoerbandbeginsel en is miskien buigbaarder as die tipes hierbo genoem. Laer temperature kan gebruik word en die energie -doeltreffendheid word hoog geag (kommentaar gelewer op verdampende droging van los vesel geld ook in hierdie geval).

Die droogproses vir stof bestaan ​​gewoonlik uit twee stappe: die eerste is daarop gemik om water wat meganies aan vesels gebind is, te verwyder, terwyl die tweede een nodig is om die stof heeltemal te droog.

  • Hidro-ekstraksie deur te druk:
  • Hidro-ekstraksie deur suiging:
  • Sentrifugale hidro-ekstraktor:
  • Stenter:

Die stof word ondersteun en beweeg deur twee parallelle eindelose kettings. Die stof is golwend gehaak en nie gespanne om te laat krimp tydens droog nie.

  • Warmrookdroër:
  • Kontakdroër (verhitte silinder):
  • Transportband stof droër

Hierdie masjien kan gebruik word vir was, versag en droog op geweefde en gebreide materiaal in touvorm. Tydens die droogfase word die weefsel in touvorm in die masjien hersirkuleer deur middel van 'n hoogs onstuimige lugvloei. Water word dus deels meganies onttrek en deels verdamp. Danksy die besondere ontwerp van hierdie masjien is dit moontlik om in dieselfde masjien natbehandelings soos wasgoed uit te voer. In hierdie geval word die onderkant van die masjien gevul met water en die benodigde chemikalieë, en die stof word deurlopend geweek en ingedruk. Die kapasiteit van hierdie masjien word bepaal deur die aantal kanale (van 2 tot 4).

Stenters speel 'n belangrike rol in die verf- en afwerkingswerk. Benewens droog, hitteverhitting en verharding van materiaal, het dit ook 'n uitwerking op die voltooide lengte, breedte en eienskappe van die stof. Stof kan met 'n snelheid van 10 - 100 meter/ minuut en by temperature tot en met 200 ° C verwerk word. Gesofistikeerde voer- en vervoermeganismes beteken dat die stof op 'n manier in die oond geplaas word om te verseker dat die finale produk aan die vereistes van die kliënt voldoen. Stenters kan op verskillende maniere verhit word. Die mees algemene manier om te verhit is deesdae deur direkte gasvuur, met die verbranding van gasdampe in die oond. 'N Paar eenhede word indirek met gas aangevuur, maar die doeltreffendheid daarvan is swak in vergelyking met stelsels wat direk gevuur word. Gasvuurstenters is hoogs beheerbaar oor 'n wye reeks prosestemperature. Verwarming van termiese olie is 'n ander metode. Maar dit verg 'n klein ketel met termiese olie (gewoonlik met gas) en al die gepaardgaande verspreidingspypleidings. Minder doeltreffend as direkte gasvuur met hoër kapitaal en bedryfskoste. Weereens kan dit gebruik word oor 'n wye reeks prosestemperature. Olie self kan gebruik word om stenters te verhit. Vanweë die probleme met onvolledige verbranding kan dit slegs indirek via 'n warmtewisselaar gedoen word. Dit, soos met indirekte gasvuur, is relatief ondoeltreffend. Baie min stenters gebruik deesdae hierdie manier van verhitting. Laastens is daar 'n aantal stoomverhitte stenters. Maar as gevolg van temperatuurbeperkings (gewoonlik 'n maksimum van tot 160 ° C), kan dit slegs gebruik word om droog te word en nie vir hitte -instelling of termofiksering nie. Die lug word verhit, teen die stof gedwing en dan hersirkuleer. 'N Fraksie van hierdie lug word uitgeput en bestaan ​​uit vars lug. Om beter beheer te bied, word stenters verdeel in 'n aantal kompartemente, gewoonlik tussen 2 en 8 meter van drie meter elk met 'n temperatuursonde, brander/hitteruiler, waaiers, uitlaat en demper. Vir 'n tipiese warm lug droog werk op 'n stenter, sal die energie -uiteensetting die volgende komponente insluit:



Die energie -uiteensetting met warm lug droogprosesse word oorheers deur verdamping en lugverhitting. Dit is dus noodsaaklik om die voginhoud op die stof te verminder en die uitlaatluchtvloei te verminder. Baie stenters word steeds swak beheer deurdat hulle staatmaak op die handmatige verstelling van uitlaatgasse en op sommige, die skatting van die droogte van die stof.

Die belangrikste geleenthede vir energiebesparing op hierdie tipe masjien kan dus soos volg geklassifiseer word:

a) Gebruik eers minder energie -intensiewe metodes: Net soos met kontakdroging, is dit belangrik om eers minder energie -intensiewe metodes te gebruik, soos die mangel, sentrifuge, suiggleuf, lugmes of droogsilinders. Alhoewel droogsilinders ongeveer vyf keer meer energie -intensief is as 'n suiggleuf, is hulle steeds ongeveer 1½ tot 2 keer minder energie -intensief as 'n stenter. Deur die stof tot ongeveer 25-30% terug te droog voordat dit deur die stenter beweeg, is dit steeds moontlik om die stofwydte aan te pas by die behoeftes van die klante. Ander tegnieke wat gebruik word om droogkoste te verminder, sluit in infrarooi en radiofrekwensie droog. Gasvuur-infrarooi is gebruik om tekstiele voor te droog voordat dit ingekap word. Dit kan tot gevolg hê dat die droogsnelheid met tot 50%verhoog word, en sodoende produksieknelpunte wat gewoonlik rondom stenters is, verlig. Normaalweg kan u verwag dat die infra -rooi droogenergiebehoefte met 50 - 70% sal afneem in vergelyking met konvensionele stenter -droog. As 'n doeltreffende manier om die stof na die breedte te trek, vir 'n kort warm soneslengte bedink kan word, kan infrarooi gebruik word om al die droging te doen. Radiofrekwensie -droog word wyd gebruik vir die droog en kleur van los materiaal, verpakkings, toppe en hante van wol en katoen. Die energiebehoefte vir radiofrekwensie -droog in vergelyking met konvensionele droging in 'n stoomverhitte droër kan tot 70%wees. Dit is egter beperk tot los voorraad en verpakkings en kan tot dusver nie aangepas word om gebreide of geweefde materiaal te akkommodeer nie, aangesien die tradisionele stentertransportmeganisme, penne en klemme die RF -droogveld kan veroorsaak wat ontlading veroorsaak. b) Moenie uitdroog nie: Net soos met kontakdroog van tekstiele, is dit belangrik om nie te veel droog te word nie. Meer nog oor stenters, aangesien dit 'n meer energie -intensiewe droogtegniek is. Daar is outomatiese infrarooi, radioaktiewe (* bron) of geleidingsgebaseerde stelsels wat gekoppel kan word aan die spoedbeheer om die stof so na as moontlik te herwin. c) Skakel uitlaatpype uit tydens ledig: Kleure en afwerkers van kommissies is geneig om met relatief klein groepgroottes te werk, en in sommige uiterste gevalle kan dit nodig wees dat die werkers elke uur oorskakel na verskillende weefselkwaliteite. Dit is algemeen om die uitlaatpype aan te hou tydens hierdie omskakelings, wat 10 - 15 minute of langer kan duur. Met die groot behoefte aan lugverhitting, is dit belangrik om die uitlaatgange te isoleer, of ten minste gedeeltelik toe te maak, waar moontlik tydens periodes van stilstand. d) Droog by hoër temperature: As die stof dit toelaat, beteken droging teen 'n hoër temperatuur dat bestralings- en konveksieverliese relatief kleiner word in vergelyking met verdampingsenergie. e) Maak panele toe en verseël: Op ouer masjiene kan die sypanele beskadig word, wat die delikate lugbalans in die masjien kan versteur. Alle foutiewe panele moet herstel of vervang word om 'n effektiewe seël rondom die oond te verseker. f) Verbetering van isolasie is gewoonlik nie prakties moontlik nie. Alhoewel dit op sommige ouer masjiene koste -effektief kan wees om die dakpanele te isoleer. f) Isolasie g) Optimaliseer uitlaatvochtigheid: By droging is daar 'n optimale uitlaatgassnelheid waaraan voldoen moet word. Aangesien 'n aansienlike aantal stenters steeds staatmaak op die handmatige beheer van uitlaatgasse, wat basies 'heeltyd heeltemal oop' beteken, is die potensiaal vir energiebesparing aansienlik. en die wat in die praktyk voorkom, verskil aansienlik. Vandaar die neiging om hulle heeltemal oop te laat. Optimalisering van uitlaatgasse kan verkry word deur die humiditeit van die uitlaatpyp te beperk tot tussen 0,1 en 0,15 kg water/ kg droë lug. Dit word die Wadsworth -maatstaf genoem. Dit is nie ongewoon om stenters teëkom waar die uitlaatvochtigheid 0,05 kg water/ kg droë lug is nie. Dit beteken 'n aansienlike vermorsing van energie. Daar is instrumente beskikbaar wat die dempers outomaties beheer om die humiditeit van die uitlaat binne hierdie gespesifiseerde reeks te handhaaf, waardeur lugverliese verminder word sonder om die stofdeurvoer aansienlik te beïnvloed. Dit wissel van nat/droë bol temperatuurstelsels tot vloeibare ossillators wat die variasie in klank deur 'n spesiale filterkop meet. As droging van oplosmiddel gebaseerde werk nodig is, is die hoë lugverliese om veiligheidsredes moontlik nie te vermy nie. Alhoewel baie oplosmiddels gebaseerde stelsels nou deur waterige stelsels vervang is weens die Wet op Omgewingsbeskerming. h) Hitteherwinning: Uitlaatwarmterugwinning kan verkry word met behulp van lug tot lug stelsels soos die plaatwarmtewisselaar, glaswarmtewisselaar of hittewiel. Die doeltreffendheid is oor die algemeen ongeveer 50-60%, maar daar kan probleme met lugomleiding, besoedeling en korrosie wees. As daar eers ander maatreëls toegepas word, soos stofvogbeheer en humiditeitsbeheer, is daar gewoonlik geen of min ekonomiese rede vir sulke stelsels nie. Lug -tot -water -stelsels, soos 'n spuitherwinnaar, vermy besoedeling en maak die uitlaat skoon, maar daar kan probleme met korrosie wees. Daar is ook 'n behoefte aan sekondêre water/water -hitte -uitruil en natuurlik die probleem van saamval. As stenters onbeperkte hoeveelhede vlugtige organiese of formaldehied uitput, is dit moontlik dat 'n vorm van skrop, elektrostatiese neerslag of selfs 'n verbrandingsoond nodig is om te voldoen aan die statutêre perke wat in die EPA -prosesaanwysings gestel word. In hierdie gevalle is dit sinvol om hitteherwinning op te neem sodat ten minste die installeringskoste verhaal kan word. i) Direkte gasvuur: In vergelyking met ander stenterverhittingstelsels is direkte gasvuur skoon en goedkoop. Toe dit die eerste keer bekendgestel is, was daar die vrees dat stikstofoksiede, wat tot 'n mate gevorm word deur blootstelling aan lug aan die verbrandingskamer -temperature, stof of 'n gedeeltelike bleek van kleurstowwe kan veroorsaak. Dit is sedertdien bewys dat dit onregverdig is. In teenstelling met stoom- en termiese oliestelsels, is daar geen verspreidingsverliese waaroor u u hoef te bekommer nie. Die opwarmingstye is korter en die termiese kapasiteit minder, wat alles tot laer ledigverliese lei.

4. KOMPETERENDE TEGNOLOGIEë EN ENERGIEBESPARENDE POTENSIALE

  • "Hoe om tekstiel te droog sonder om te droog te word", Kaisa Bengtsson, Kathrine Segel, Henrietta Havsteen-Mikkelsen (pdf-lêer)
  • “Energy saving in textile processing“, Nandish Mehta (Technical Director)

b) Changes in the energy distribution system No information is available.


Bleaching Textile Industry - History

A BRIEF HISTORY OF DYESTUFFS & DYEING

by Lady Siobhan nicDhuinnshleibhe

Presented at Runestone Collegium, 19 February 2000

Ever since primitive people could create, they have been endeavoring to add color to the world around them. They used natural matter to stain hides, decorate shells and feathers, and paint their story on the walls of ancient caves. Scientists have been able to date the black, white, yellow and reddish pigments made from ochre used by primitive man in cave paintings to over 15,000 BCE. With the development of fixed settlements and agriculture around 7,000-2,000 BCE man began to produce and use textiles, and would therefore add color to them as well. Although scientists have not yet been able to pinpoint an exact time where adding color to fibers first came into practice, dye analysis on textile fragments excavated from archaeological sites in Denmark have placed the use of the blue dye woad along with an as yet unidentified red dye in the first century CE (Grierson, 5).

In order to understand the art and history of dyeing, we must first understand the process of dyeing itself. According to Webster s dictionary, dyeing is the process of coloring fibers, yarns or fabrics by using a liquid containing coloring matter for imparting a particular hue to a substance. There are three basic methods of imparting a particular hue to a substance. The first is by staining an item, a temporary means of coloration where the color is rubbed or soaked into an item without the benefit of some sort of chemical fixative to preserve the color. The next is the use of pigmentation, wherein the color is fixed to the surface of an object by another adhesive medium. A true dye is when the color of a substance is deposited on another substance in an insoluble form from a solution containing the colorant.

Natural dyes can be broken down into two categories: substantive and adjective. Substantive, or direct dyes, become chemically fixed to the fiber without the aid of any other chemicals or additives, such as indigo or certain lichens. Adjective dyes, or mordant dyes, require some sort of substance, (usually a metal salt) to prevent the color from washing or light-bleaching out. Most natural dyes are adjective dyes, and do require the application of a mordant (the metal salt) solution to the fibers at some point in the dyeing process. Aluminum and iron salts were the most common traditional mordants, with copper, tin and chrome coming into use much later. In rural areas where these metals were not widely available, plants were also used as mordants, especially those that have a natural ability to extract such minerals from the earth, such as club moss. Most ancient and medieval dyers mordanted their yarns and fabrics before dyeing them. Alum and Iron were used as mordants in Egypt, India and Assyria from early times, as there are many alum deposits in the Mediterranean region. Medieval dyers used alum, copper and iron as mordants, and cream of tartar and common salt were used as to assist in the dyeing process.

Different fibers also have different tendencies to absorb natural and synthetic dyes. Protein and cellulose fibers (the two main divisions for fibers used historically in spinning and dyeing) need to be mordanted differently because of their structural and chemical composition. Mordants to cellulose fibers such as cotton and linen usually involve the use of washing soda or tannins to create an alkaline dyebath. Tannins (plantstuffs, such as oak galls containing tannic acid) are widely used in dyeing cellulose fibers as they attach well to the plant fibers, thus allowing the dyes to attach themselves to the tannins, whereas they might not be able to adhere to the fibers themselves (Tannins are sometimes classified as mordants in and of themselves, but are usually considered a chemical to assist in the dyeing process.) Mordants for protein fibers, like wool and silk, are usually applied in acidic dyebaths. Alum with the assistance of cream or tartar, is the most common mordant used to assist the dyes in taking to the fibers.

Since the difference in mordanting different fibers has been mentioned, it would be remiss not to spend a moment on the historic nature of the fibers themselves. Wool, a protein-based fiber, has been found in Europe dating back to 2000 BCE. It was a common medieval fabric in both dyed and natural colors, and was processed by both professional manufacturers and housewives. Silk, another protein-based fiber, was imported from China to Persia as early as 400-600 BCE. It became quite popular in the Late Middle Ages, and major silk manufacturing centers were set up in France, Spain and Italy. These silk production centers also became centers of dye technology, as most silk was dyed and required the highest quality dyes available. Cotton was considered a luxury fabric, as it was imported all the way from India and usually dyed or painted before it was shipped. Cotton was also valued because of the brightness and colorfastness of the dyes used to color it, and also for its use in making candle wicks. Samples of cotton fabrics have been found in India and Pakistan dating to 3000 BCE, but it did not appear in Europe until the 4th century. Cotton waving establishments were formed in Italy in the 13th & 14th centuries but they did not make a significant economic impact on the industry as they produced a coarser quality of fabric than the imported fabric, and therefore had difficulty in obtaining a good supply of cotton fiber.

Scientists are almost certain that dyeing was practiced throughout the world, but it is difficult to obtain proof on this for two reasons. First, not all cultures left written records of their practices. Second, because of the wide variance of environmental conditions and degree of geological disturbance, it is not easy to find well-preserved evidence of dyed textiles in many archaeological sites. A Chinese text from 3,000 BCE lists dye recipes to obtain red, black and yellow on silks. Ancient Indian texts describe several different yellow dyestuffs, how to obtain reds from the wood and bark of certain trees, and also notes the use of indigo to create blues on cotton. In Central and South America they dyed bast fibers (plant fibers) in shades of red and purple with the bodies of the cochineal insects (Dactylopius coccus). (Grierson, 6)

A Greek artifact known as the Stockholm Papyrus details dyestuffs and techniques in almost a recipe fashion as it was practiced Egypt in the third and fourth centuries CE. The great detail in which the preparation of the fibers and the dyeing materials and the dyeing process itself are recorded has led scholars to believe that it had to have been practiced for thousands of years previously in order to raise the process to such a science and art. It discusses mordanting the fibers using alum, copper and iron oxides to darken or sadden the red, blue, green and purple dyes, as well as the occasional use of tin and zinc. It describes over ten different recipes for using alkanet (Anchusa tinctoria) root as a dye employing camel and sheep urine, lentils, vinegar, wild cucumber and barley malt among others as aids to producing color. It also gave recipes on obtaining purple hues by overdyeing the alkanet with woad (Isatis tinctoria), madder (Rubia tinctorum), kermes (made from the dried bodies of the female shield louse or scale insect (Kermes ilicis)) and the heliotrope plant (Heliotropium arborescens). Excavated coptic textiles dating from the fourth to the sixth century CE show use of weld (Reseda luteola) to produce yellow, madder and woad for dark purple, and blue from indigo (Indigofera tinctoria). Scientists have been able to date a red obtained from Egyptian madder root from the fourteenth century BCE. (Grierson, 6)

In the Mediterranean before the advent of Christianity, a whole dyeing industry arose around Tyrian purple. Tyrian purple is produced from the mucous gland adjacent to the respiratory cavity within some species of Purpura and Murex species of shellfish (Schetky, 4). The shells were crushed to extract this fluid, which only turns purple once it has been applied to the fiber and exposed to light and oxidation with the air. The Phoenicians, skillful shipbuilders and sailors that they were, scoured the coastlines for sight of these whelk shells, and established a dyeworks and trading station wherever they found a plentiful population of these shellfish. Coastal Indians of Mexico were also using shellfish, but their delicate method involved blowing and tickling the shellfish to get them to spit out the dye precursor directly onto the cotton fibers. Even Ireland can produce archaeological evidence of dyeing with the native dog-whelk shells in the seventh century CE. (Grierson, 6 & 7) Both Discorides, the Greek physician and Pliny the Elder, the Roman naturalist, mention in their first century works the preparation and dyeing of wool with various shellfish to produce colors of red, blue, purple and violet after first being mordanted with soapwort (Saponaria officinalis), oxgall or alum. (Schetky, 4) Both authors also mention the use of Indigo from the Orient to obtain blues, and Herodotus describes its use in a 450 BCE text. Dioscorides also mentions other dye plants of the ancient world, including madder, saffron (Crocus sativus) and weld for yellow, and woad for blue. Walnut shells (Juglans nigra), oak bark (Quercus sp.), pomegranate flowers (Punica granatum) and broom (Genista tinctoria) were also used in conjunction with various mordants but galls formed on trees could mordant themselves, being high in tannic acid (Schetky, 5).

In Europe the art of dyeing rose to new heights with the diversity of climate, culture and migration/invasion waves. This was further influenced by the direct impact of trade instigated by the Crusades and furthered by the growing cultural awareness of the Renaissance period - everyone in Europe wanted the exotic, colorful dyestuffs from the Orient, and later from the Americas. Caravans of camels would cross the Gobi desert for centuries bringing goods from China to the Mediterranean. By the 12th century the two main trade routes for imported dyestuffs headed through Damascus: the first led from Baghdad to Damascus to Jerusalem and Cairo, the other went to Damascus to Mosul to the Black Sea to Byzantium (Istanbul).

Venice was one of the major early centers for imported dyestuffs, supplying Brazilwood (Caesalpinia sappan) from the East, lac (another insect dye) and indigo from India from the fifteenth century CE onward. Dyers of Italy soon became adept in their use, in 1429 the Venetian dyer s guild wrote a book for its members containing a number of different dye recipes, including Brazilwood and lac. The Plictho de Larti de Tentori by Venetian author Giovanni Ventur Rosetti (sp - also listed as Giovanventura Rosetti) in the 1540s lists instructions for using both lac and indigo, as well as 217 other recipes for dyeing cloth, linen, cotton and silk with many varieties of dyestuffs. It would remain the best source for dyeing instruction for the next 200 years (Schetky, 6).

From Venice the dyestuffs were traded by ship around the coast of France to Flanders, Southampton and London in the Mediterranean at Florence, Pisa and Genoa and northward on the continent to the distribution centers of Basle and Frankfurt (Schetky, 6). Basle was a noted center of trade for saffron, the expensive yellow obtained from certain species of crocus. In later years crocus were grown in that area directly, and the crop became such a vital part of the local economy that they crocus was featured on the city s coat of arms. Frankfurt housed trade fairs from the twelfth to fourteenth centuries that dominated the trade of many dyestuffs, but mainly that of locally grown woad, the only blue dyestuff available to European dyers before the coming of indigo. Many regions in Germany specialized in growing and processing the woad through its complex fermentation process, and strict legislation was placed on every aspect of the trade. (Grierson, 8)

The government of Spain controlled the trade of cochineal, the red dye from the bodies of the Cochineal bugs of Central America. In 1587 approximately 65 tons were shipped to Spain, and from there northward throughout Europe (Grierson, 10). Italian dyers shunned cochineal in favor of the already established dye kermes, made from the dried bodies of the female shield louse or scale insect (Kermes ilicis) (Schetky, 4). It s use was first recorded in 1727 BCE and it was long the standard red dye for silk, wool and leather, but the intense colorific value and relative cheapness of cochineal soon eliminated most of the kermes use in England, so Spain hung on to control of their lucrative monopoly. (Grierson, 10)

European dyers reached their height of skill in the thirteenth century, mainly due to the guild systems who vigilantly maintained a high standard of quality. In many countries dyers were graded by the guild system, the master dyers being allowed to use the major fast dyes while their lesser colleagues were restricted to the slower, fugitive dyes. In some places it was forbidden to possess, let alone use, major dyestuffs unless you were a member of a guild. In Germany, the dyers and woad workers were regulated by the guilds, each grower having to present his crop to a sworn dyer to determine its quality, weight and condition before it could be sold. (Grierson, 8-9) English producers of woad had fewer restrictions, mainly that of a proclamation in 1587 to restrict growers to certain field size and ensure that no woad mills were sited within three miles of a royal residence, market town or city because of the highly offensive odor they emit. Even the local doctors in Venice in 1413 city fathers to prohibit dyeing with either woad or ox-blood after March first because of the unhealthy smell. (Grierson, 9) France had developed an extensive and efficient textile industry by the 13th century and also increased the dyers craft by developing varied techniques to achieve additional colors from the basic dyestuffs. At the end of the 16th century, there were over 220 master dyers listed in Paris alone. (Schetky, 8)

While the powerful guild system had numerous dyestuffs with which to blend their color palates of fiber for the bluebloods and wealthy merchants, dyeing in the lower classes was a bit more restrictive. Without the money (or connetions) to buy indigo, cochineal and turmeric, clothing in the country tended to natural colors whites, blacks, browns, grays, and tans of the natural colors of the fibers themselves, with the reds, greens and yellows of local plants used for both food, medicine and dyes. In short, home dyers used any plants they could lay their hands on that would give a good color. Some colors were even derived accidentally. Washing bee hives in preparation for making mead could yield yellows and golds. Blackberries and Bilberries that stained the fingers of pickers could also be used to achieve pale blues and purples, although these were not often color or lightfast. In England, the multitudinous variety of lichens and mosses produced greens, grays and browns.

By the seventeenth century a world-wide shipping and trading network was in place, allowing dyestuffs from all parts of the world to be brought to Europe. Legislation from earlier centuries to protect the growers and users of specific dyestuffs was overturned in favor of new demands and standards set by the growing consumer-focused society who wanted more colors and better quality. In the eighteenth and nineteenth centuries the practice of colonialism insured that there would always be a supply of foreign dyestuffs, and the Industrial Revolution met the demands of large-scale productions while finding new ways to make the colors brighter and longer-lasting to wear and washing.

As textile weaving technology advanced with the advent of machines to spin, design and weave fabric, dyers were forced to be able to produce dyes with exact shades, matching color lots and most importantly, ones that would stand fast to the new mechanical and chemical processing. In addition, exporters wanted colors that would stand up to tropical sunlight and still be exotic enough for foreign tastes. Dyers in turn demanded from their suppliers purer chemicals and dyestuffs of consistent quality. Hand in hand, dyers, manufacturers, chemists, and dyestuff producers worked hand in hand to keep up with the progress of technology. (Grierson, 15) Chemists in many countries had found a means of extracting highly concentrated powders or pastes from traditional dyestuffs that made stronger colors, such as cochineal carmine and madder garancine. Other procedures were used to extract indigo that gave us sulphonated indigo and Saxon blue. A few novel dyes (precursors of future chemical dyes) such as the yellow obtained from picric acid also made an appearance. With the tremendous rise in the interest of Chemistry in the mid nineteenth century, several important innovations in dyeing came about. W.H. Perkin, a student of celebrated European scientist Wilhelm von Hoffman, accidentally discovered the first synthetic dye in an attempt to synthesize quinine. The 18-year old student s purple precipitate, later called mauviene, was quickly put into industrial application, allowing the young Perkin to start his own factory in London to commercially produce his dyestuff. Two years letter a synthetic red dye called magenta or fuchsine was patented in France, and hardly a year passed until the end of the century without a new synthetic dye being patented.

Eventually, the old natural dyes lost popularity in favor of the newer synthetic ones. By the end of the nineteenth century a few Scottish tweed producers were the only ones still using natural dyes, and now the use of natural dyes on a commercial scale barely exists, mainly in remote areas where people have either little access to synthetic dyes or a vested interest in retaining their ancient dyeing customs. Use of natural dyes is gaining popularity again with the renaissance in hand crafting, most notably in the fields of spinning and weaving, basketry, papermaking and leathercraft. There is also renewed scientific and historic interest in natural dyeing, both to help identify dyestuffs in recently discovered archaeological finds and to preserve the dyed textiles housed in museums and private collections. As Su Grierson says in her book Dyeing and Dyestuffs, Whilst the dyeing industry of today keeps pace with modern science, the future use of natural dyes will also follow a new path, but one firmly rooted in tradition. (21)

Cochineal Insect. Microsoft Encarta Online Encyclopedia 2000 . http://encarta.msn.com/ 1997-2000 Microsoft Corporation.

Grierson, Su. Dyeing and Dyestuffs . Aylesbury, Bucks: Shire Album 229, Shire Publications Ltd. 1989.

Hartley, Dorothy. Lost Country Life . New York: Pantheon Books. 1979.

Heliotrope. University of Washington Medicinal Herb Garden Online . http://www.nnlm.nlm.nih.gov/pnr/uwmhg/species.html

Schetky, Ethel Jane McD. The Ageless Art of Dyeing. Handbook on Dye Plants & Dyeing . Brooklyn: Brooklyn Botanic Garden Record. 1986. (Special reprint of Plants & Gardens Vol. 20, No. 3)

Smith, Jodi. Medieval Dyes . Loveland: Spinning Madly. 1993. (7th printing, June 1999).


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Tzanko Tzanov, University of Minito, Artur Cavaco-Paulo University of Minito

Abstract

A bleaching agent is a material that lightens or whitens a substrate through chemical reaction. The bleaching reactions usually involve oxidative or reductive processes that degrade color systems. These processes may involve the destruction or modification of chromophoric groups in the substrate as well as the degradation of color bodies into smaller, more soluble units that are more easily removed in the bleaching process. The most common bleaching agents generally fall into two categories: chlorine and its related compounds (such as sodium hypochlorite) and the peroxygen bleaching agents, such as hydrogen peroxide and sodium perborate. Reducing bleaches represent another category. Enzymes are a new category of bleaching agents. They are used for textile, paper, and pulp bleaching as well as for home laundering. Chlorine-containing bleaching agents are the most cost-effective bleaching agents known. They are also effective disinfectants, and water disinfection is often the largest use of many chlorine-containing bleaching agents. They may be divided into four classes: chlorine, hypochlorites, N.-chloro compounds, and chlorine dioxide. Except to bleach wood pulp and flour, chlorine itself is rarely used as a bleaching agent. The principal form of hypochlorite produced is sodium hypochlorite. Other hypochlorites include calcium hypochlorite and bleach liquor, bleaching powder and tropical bleach. The principal solid chlorine bleaching agents are the chlorinated isocyanurates, eg, sodium dichloroisocyanurate dihydrate. Ander N.-chloro compounds include halogenated hydantoins, and sodium N.-chlorobenzenesulfonamide (chloramine B). Chlorine dioxide is a gas that is more hazardous than chlorine. Large amounts for pulp bleaching are made by several processes in which sodium chlorate is reduced with chloride, methanol, or sulfur dioxide in highly acidic solutions by complex reactions. Hydrogen peroxide is one of the most common bleaching agents. It is the primary bleaching agent in the textile industry, and is also used in pulp, paper, and home laundry applications. Hydrogen peroxide reacts with many compounds, such as borates, carbonates, pyrophosphates, sulfates, etc, to give peroxy compounds or peroxyhydrates. Peracids have superior cold water bleaching capability versus hydrogen peroxide because of the greater electrophilicity of the peracid peroxygen moiety. Lower wash temperatures and phosphate reductions or bans in detergent systems account for the recent utilization and vast literature of peracids in textile bleaching. The reducing agents generally used in bleaching include sulfur dioxide, sulfurous acid, bisulfites, sulfites, hydrosulfite (dithionites), sodium sulfoxylate formaldehyde, and sodium borohydride. These materials are used mainly in pulp and textile bleaching.

The high water- chemicals-, and energy-consuming bleaching process in textile industry might be replaced with bioprocesses using appropriate enzymatic systems. Enzymes, in both free and immobilized form, can be used for generation of the oxidizing agent necessary for bleaching as well as for direct bleaching of the textile substrate or for recycling of peroxide containing bleaching effluents. Suitable novel enzymatic systems are the glucose oxidases, chloroperoxidases, laccases, and catalases. Bleaching is a decolorization or whitening process that can occur in solution or on a surface. The color-producing materials in solution or on fibers are typically organic compounds that possess extended conjugated chains of alternating single and double bonds and often include heteroatoms, carbonyl, and phenyl rings in the conjugated system. The portion of molecule that absorbs a photon of light is referred to as the chromophore. Bleaching and decolorization can occur by destroying one or more of the double bonds in the conjugated chain, by cleaving the conjugated chain, or by oxidation of one of the other moieties in the conjugated chain. The molecule then absorbs light in the ultraviolet region, and no color is produced. Chlorine bleaches react with more chromophores than oxygen bleaches. The mechanism of bleaching of hydrogen peroxide is not well understood. Reducing agents are thought to work by reduction of the chromophoric carbonyl groups in textiles or pulp. The most widely used bleach in the United States is liquid chlorine bleach, an alkaline aqueous solution of sodium hypochlorite. This bleach is highly effective at whitening fabrics and also provides germicidal activity at usage concentrations. Dry and liquid bleaches that deliver hydrogen peroxide to the wash are used to enhance cleaning on fabrics. They are less efficacious than chlorine bleaches but are safe to use on more fabrics. The dry bleaches typically contain sodium perborate in an alkaline base whereas the liquid peroxide bleaches contain hydrogen peroxide in an acidic solution. The worldwide decreasing wash temperatures, which decrease the effectiveness of hydrogen peroxide-based bleaches, have stimulated research to identify activators to improve bleaching effectiveness. Tetraacetylethylenediamine (TAED) is widely used in European detergents to compensate for the trend to use lower wash temperatures. TAED has not been utilized in the United States, where one activator nonanoyloxybenzene sulfonate (NOBS) has been commercialized and incorporated into several detergent products. NOBS is claimed to provide superior cleaning in contrast to perborate bleaches. In industrial and institutional bleaching, either liquid or dry chlorine bleaches are used because of their effectiveness, low cost, and germicidal properties. Bleaching agents are used in hard surface cleaners to remove stains caused by mildew, foods, etc, and to disinfect surfaces. Disinfection is especially important for many industrial uses. Alkaline solutions of 1–5% sodium hypochlorite that may contain surfactants and other auxiliaries are most often used for these purposes. In-tank toilet cleaners use calcium hypochlorite, dichloroisocyanurates, or N.-chloro compounds to release hypochlorite with each flush. The primary role of bleach in automatic dishwashing and warewashing is to reduce spotting and filming. Many textiles are bleached to remove any remaining soil and colored compounds before dyeing and finishing. Cotton is the principal fiber bleached today, and almost all cotton is bleached. Other textiles are described.


Simple and economic bleaching process for cotton fabric

Cotton fabric was bleached in a simple and economic process using a bleaching system composed of sodium chlorite and hexamethylenetetramine. Different bleaching trials were carried out keeping fixed sodium chlorite concentration and varying other reaction conditions. The obtained results reveal that bleached cotton fabric with satisfactory whiteness index and reasonable tensile strength can be obtained by treating the fabric at 95 °C in a bleaching bath containing 5 g/l sodium chlorite, 0.02 g/l hexamethylenetetramine and 1 g/l non-ionic wetting agent using a material to liquor ratio of 1:30. These optimum conditions lead to completion of the bleaching process in a reasonable duration of 2 h with minimum evolution of harmful chlorine dioxide gas. Lower concentrations of the activator hexamethylenetetramine were found to prolong the bleaching duration without getting satisfactory whiteness index. Higher concentrations of the activator were found to cause fast sodium chlorite decomposition without imparting bleaching effect to the fabric.

Hoogtepunte

► Cotton fabric was bleached in one-step simple and economic process. ► Bleached fabric with good whiteness index and tensile strength were obtained. ► The optimum conditions led to completion of the bleaching process in 2 h.


Gentle Bleaching

Switzerland-based Huntsman Textile Effects is constantly developing new platforms to improve
fabric performance and reduce energy and water consumption in the textile industry. Palo Alto,
Calif.-based Genencor, a division of Denmark-based Danisco A/S, focuses on discovering, developing
and delivering highly innovative, eco-friendly, efficient enzyme technologies. Both companies see
this new process as a contribution to a more sustainable textile industry.


Perfect Preparation

The new gentle bleaching process is truly innovative. Traditional bleaching requires a high
water temperature, while the new gentle bleaching takes place at a low temperature of 65°C and
almost neutral pH conditions, making it especially suitable for all delicate fibers that are
temperature- and pH-sensitive. Even after bleaching under these gentler conditions, cotton is
perfectly prepared for dyeing all shades.

By applying the latest enzyme technology as a core component of the solution, it is now
possible under these mild conditions to prepare cotton with very good results for dyeing. Aan
regenerated cellulosic fibers, excellent full white levels can be obtained as well. Een
recipe is enough for all fibers sensitive to temperature and pH. A multitude of fibers can be
treated, including regenerated cellulosic fibers such as viscose, MicroModal®, lyocell, bamboo and
blends with cotton, elastane, acetate, acrylic, silk and wool. Similar bleaching recipes for all
fibers and blends result in simple recipe management and reduced sources of errors.

Although the technology is completely new, the process flow remains similar to the current
Smart Prep pretreatment system. The process is applicable on all closed discontinuous equipment
such as jets, jiggers, overflow and cheese dyeing machines. A liquid system is offered that is
suitable for automatic dosing systems.


The Gentle Power Bleach&trade enzyme-based peroxide bleaching process requires a water
temperature of only 65°C for bleaching and fewer rinsing cycles than traditional bleaching
stelsels.


Soft Hand

In the case of cotton, fabrics pretreated with the new bleaching technology are said to have
a superior hand compared to that of conventionally bleached goods. The main characteristics are:

&bull very soft, bulky and natural hand

&bull fast and permanent effect

&bull excellent crease recovery properties

&bull improved needle resistance, or sewability, and stretch and

&bull very durable elastane properties.

The very mild process conditions also should ensure maximum strength of the textile material,
with the lowest degree of chemical damage on cotton compared to goods processed using traditional
bleaching methods.


Improved Color Yield

Optimal bleaching is a prerequisite for true colors. Compared with traditional bleaching
systems, the Gentle Power Bleach system brings the following advantages to the subsequent dyeing
process:

&bull better color yield with more vivid and intense shades that have excellent
fastness properties

&bull possible cost savings in the dyeing process and

&bull improved wash-, water- and rubbing-fastness properties.


Energy Savings …

Energy consumption savings by almost half are possible owing to the considerably lower
treatment and rinsing temperatures compared to conventional bleaching systems. No neutralization is
required, and at least one or two rinsing baths can be omitted, leading to a substantial reduction
in water usage.

When treating cotton, savings over traditional bleaching are attainable thanks to the fact
that the weight loss is reduced considerably. As the material remains naturally soft and bulky,
possible savings in softening may be obtained, and previously unattained softness levels may be
realized.

The new bleaching process further enables improvements in right-first-time production,
reducing costly re-works and second-quality products, and offering the following:

&bull improved reproducibility in reactive dyeing by avoiding the risk of
excessive residual alkalinity at the beginning of the dyeing cycle

&bull reduced swelling of the natural fiber and avoidance of a channeling
effect in yarn cheese/package dyeing machines, leading to more uniform results and

&bull reduced risk of crease marking in piece-goods and garment processing.


… And Water Savings

Primarily, the reduced use of water and energy makes this process environmentally friendly.
By lowering the treatment temperature from boiling down to 65°C, the new bleaching technology is
said to be unique in the field of energy reduction. Even rinsing is conducted below this
temperature. Additionally, the effluent salt load is reduced by eliminating harsh chemicals such as
caustic soda. All auxiliaries used exhibit excellent bio-elimination, and are free of alkylphenol
ethoxylates and adsorbable organic halogen. In the case of cotton, the reduced weight loss leads to
a considerable reduction of both biochemical oxygen and chemical oxygen demand in the wastewater
stream. The enzyme-based peroxide bleaching technology is a way forward. It can help the textile
industry make better use of scarce natural resources and contribute to a more sustainable
environment – also for future generations.


Kyk die video: Textiel recycling (Januarie 2023).

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