I-cellulose derivatives iveliswa yi-esterification okanye i-etherification yamaqela e-hydroxyl kwiipolymers ze-cellulose ezine-reagents zamakhemikhali.Ngokweempawu zolwakhiwo lweemveliso zokusabela, izinto eziphuma kwi-cellulose zinokwahlulwa zibe ngamacandelo amathathu: ii-cellulose ethers, ii-cellulose esters, kunye ne-cellulose ether esters.I-cellulose esters esetyenziswa ngokwenene kurhwebo zezi: i-cellulose nitrate, i-cellulose acetate, i-cellulose acetate butyrate kunye ne-cellulose xanthate.I-cellulose ethers iquka: i-methyl cellulose, i-carboxymethyl cellulose, i-ethyl cellulose, i-hydroxyethyl cellulose, i-cyanoethyl cellulose, i-hydroxypropyl cellulose kunye ne-hydroxypropyl methyl cellulose.Ukongeza, kukho i-ester ether exutywe izinto eziphuma kuzo.
Iipropati kunye nokusetyenziswa Ngokukhetha ukutshintshwa kwe-reagents kunye noyilo lwenkqubo, imveliso inokunyibilika emanzini, i-alkali isisombululo okanye i-solvent ye-organic, okanye ibe neempawu ze-thermoplastic, kwaye ingasetyenziselwa ukuvelisa imicu yeekhemikhali, iifilimu, iziseko zefilimu, iiplastiki, i-insulating. izinto eziphathekayo, iingubo, i-slurry, i-polymeric dispersant, izongezo zokutya kunye neemveliso zemichiza yemihla ngemihla.Iipropati ze-cellulose derivatives zihambelana nobume bama-substituents, i-DS degree yamaqela amathathu e-hydroxyl kwiqela le-glucose eguqulwayo, kunye nokuhanjiswa kwezinto ezithatha indawo kunye ne-macromolecular chain.Ngenxa yokungakhethi kwempendulo, ngaphandle kwemveliso efakwe endaweni efanayo xa onke amaqela amathathu e-hydroxyl efakwe endaweni (i-DS yi-3), kwezinye iimeko (impendulo ehambelanayo okanye i-heterogeneous reaction), ezi zikhundla zintathu zilandelayo ezahlukeneyo zifunyenwe: Iimveliso ezixutywe kunye amaqela eglucosyl angafakwanga endaweni yawo: ① i-monosubstituted (i-DS yi-1, i-C, i-C okanye indawo ye-C ifakwe endaweni, ifomyula yesakhiwo bona i-cellulose);② i-distituted (i-DS yi-2, i-C, i-C, i-C, i-C okanye i-C, i-C izikhundla zitshintshwa);③ endaweni epheleleyo (DS yi-3).Ke ngoko, iipropathi zeselulosi enye enexabiso elifanayo lokubuyisela zisenokwahluka kakhulu.Ngokomzekelo, i-cellulose diacetate esterified esterified ngqo kwi-DS ye-2 ayinyibiliki kwi-acetone, kodwa i-cellulose diacetate efunyenwe nge-saponification ye-cellulose esterified ngokupheleleyo i-triacetate inokuchithwa ngokupheleleyo kwi-acetone.Le heterogeneity yokutshintshwa inxulumene nemithetho esisiseko ye-cellulose ester kunye neempendulo ze-etherification.
Umthetho osisiseko we-cellulose esterification kunye ne-etherification reaction kwi-molecule ye-cellulose, izikhundla zamaqela amathathu e-hydroxyl kwiqela le-glucose ziyahluka, kunye neempembelelo ze-substituents ezikufutshane kunye nesithintelo se-steric nazo zahlukile.Ubumuncu obunxulumeneyo kunye neqondo lokuqhawulwa kwamaqela amathathu e-hydroxyl ngala: C>C>C.Xa i-etherification reaction isenziwa kwi-alkaline medium, iqela le-C hydroxyl lisabela kuqala, emva koko iqela le-C hydroxyl, kwaye ekugqibeleni iqela le-C primary hydroxyl.Xa i-esterification reaction iqhutyelwa kwi-acidic medium, ubunzima bokusabela kweqela ngalinye le-hydroxyl lichasene nomyalelo we-etherification reaction.Xa usabela nge-reagent substitution bulky, i-steric hindrance effect inefuthe elibalulekileyo, kunye neqela le-C hydroxyl elinempembelelo encinci yokuthintela i-steric kulula ukusabela kune-C kunye ne-C hydroxyl amaqela.
I-Cellulose yi-crystalline ye-polymer yendalo.Uninzi lwe-esterification kunye ne-etherification reactions ziimpendulo ezingafaniyo xa i-cellulose ihlala yomelele.Imeko yokusasazwa kweereagents zokusabela kwifiber yeselulosi ibizwa ngokuba kukufikeleleka.Ilungiselelo le-intermolecular yengingqi ye-crystalline icwangciswe ngokuqinileyo, kwaye i-reagent inokusasaza kuphela kwindawo ye-crystalline.Ilungiselelo le-intermolecular kwingingqi ye-amorphous ikhululekile, kwaye kukho amaqela akhululekileyo e-hydroxyl alula ukunxibelelana nama-reagents, kunye nokufikeleleka okuphezulu kunye nokuphendula okulula.Ngokuqhelekileyo, izinto eziluhlaza ezinekristallini ephezulu kunye nobukhulu obukhulu bekristale akulula ukusabela njengezinto eziluhlaza kunye ne-crystallinity ephantsi kunye nobukhulu obuncinci bekristal.Kodwa oku akuyonyani ngokupheleleyo, umzekelo, izinga le-acetylation lemicu ye-viscose eyomileyo ene-crystallinity ephantsi kunye ne-crystallinity encinci iphantsi kakhulu kune-cotton fiber ene-crystallinity ephezulu kunye ne-crystallinity enkulu.Oku kungenxa yokuba ezinye iindawo zokudibanisa i-hydrogen ziveliswa phakathi kweepolima ezikufutshane ngexesha lenkqubo yokomisa, ethintela ukusasazwa kwee-reagents.Ukuba ukufuma kwi-cellulose emanzi kuthatyathelwa indawo sisinyibilikisi esikhulu se-organic (esifana ne-acetic acid, benzene, pyridine) emva koko yomiswe, ukusebenza kwayo kwakhona kuya kuphuculwa kakhulu, kuba ukomisa akukwazi ukukhupha ngokupheleleyo isinyibilikisi, kwaye ezinye zinkulu. Iimolekyuli zibanjelwe “kwimingxuma” ye-cellulose ekrwada, zenza into ebizwa ngokuba yi-cellulose.Umgama oye wandiswa ngokudumba akukho lula ukubuyisela, nto leyo enceda ukusasazwa kwee-reagents, kwaye ikhuthaza izinga lokuphendula kunye nokufana kwempendulo.Ngenxa yesi sizathu, kwinkqubo yokuvelisa iintlobo ezahlukeneyo ze-cellulose, kufuneka kubekho unyango oluhambelanayo lokudumba.Ngokuqhelekileyo amanzi, i-asidi okanye i-concentration ethile yesisombululo se-alkali isetyenziswa njenge-ejenti yokuvuvukala.Ukongeza, ubunzima bokusabela kweekhemikhali kwi-pulp yokunyibilika kunye nezikhombisi ezifanayo zomzimba kunye neekhemikhali zihlala zihluke kakhulu, ezibangelwa yimiba ye-morphological yeentlobo ezahlukeneyo zezityalo okanye iiseli ezinemisebenzi eyahlukeneyo ye-biochemical kunye nesakhiwo kwisityalo esinye.ye.Udonga oluphambili lomaleko wangaphandle wefayibha yezityalo luthintela ukungena kwe-reagents kwaye lubambezele ukusabela kweekhemikhali, ngoko ngokuqhelekileyo kuyimfuneko ukusebenzisa iimeko ezihambelanayo kwinkqubo yokukhupha udonga oluphambili ukuze kufumaneke i-pulp yokunyibilika ngokusebenza ngcono.Ngokomzekelo, i-bagasse pulp yinto eluhlaza kunye ne-reactivity embi ekuveliseni i-viscose pulp.Xa ulungiselela i-viscose (i-cellulose xanthate isisombululo se-alkali), i-carbon disulfide eninzi idliwe kune-cotton linter pulp kunye ne-pulp yokhuni.Izinga lokuhluza liphantsi kunelo le-viscose elilungiselelwe kunye nezinye iipulps.Oku kungenxa yokuba udonga oluphambili lweeseli zefayibha zommoba alonakaliswanga ngokufanelekileyo ngexesha lokucofa kunye nokulungiswa kwe-alkali cellulose ngeendlela eziqhelekileyo, okukhokelela kubunzima ekuphenduleni ukuba tyheli.
Imicu ye-alkaline ye-alkaline ye-pulp yangaphambi kwe-hydrolyzed] kunye ne-Figure 2 [i-bagasse pulp fibers emva kokufakwa kwe-alkali] yimifanekiso ye-electron microscope yokuskena umphezulu we-bagasse pulp fibers emva kwenkqubo yealkaline yangaphambi kwe-hydrolyzed kunye nokufakwa kwe-alkaline eqhelekileyo ngokulandelelanayo, eyokuqala isengabonwa imingxuma ecacileyo;ekugqibeleni, nangona imingxuma inyamalala ngenxa yokudumba kwesisombululo sealkali, udonga oluphambili lusagubungela yonke ifayibha.Ukuba "ukufakelwa kwesibini" (ukufakelwa okuqhelekileyo okulandelwa kukufakelwa kwesibini kunye nesisombululo se-alkali esixubileyo kunye nesiphumo esikhulu sokudumba) okanye ukudipha ukugaya (i-impregnation eqhelekileyo edityaniswe nokusila ngomatshini), ukusabela kwe-yellowing kunokuqhubeka kakuhle, izinga lokuhluza i-viscose. iphuculwe kakhulu.Oku kungenxa yokuba zombini ezi ndlela zimbini zingentla ziyakwazi ukuxobula udonga oluphambili, ukuveza umaleko wangaphakathi wokuphendula ngokulula, okulungele ukungena kwi-reagents kunye nokuphucula ukusebenza kokusabela (Umfanekiso wesi-3 [ukufakwa kwesibini kwe-bagasse pulp fiber ], Umzobo wokugaya iBagasse Pulp Fibers]).
Kwiminyaka yakutshanje, iinkqubo ze-solvent ezingenamanzi ezinokuthi zichithe ngokuthe ngqo i-cellulose ziye zavela.Njenge-dimethylformamide kunye ne-NO, i-dimethyl sulfoxide kunye ne-paraformaldehyde, kunye nezinye i-solvents ezixubileyo, njl., yenza ukuba i-cellulose ikwazi ukusabela ngendlela efanayo.Nangona kunjalo, eminye yale mithetho ikhankanywe ngasentla yokusabela ngaphandle kwesigaba ayisasebenzi.Ngokomzekelo, xa ulungiselela i-cellulose diacetate e-soluble kwi-acetone, akuyimfuneko ukuba uqhube i-hydrolysis ye-cellulose triacetate, kodwa i-esterified ngokuthe ngqo de i-DS ibe yi-2.
Ixesha lokuposa: Feb-27-2023