1. Isimiso sokwakheka nokulungiselela se-cellulose ether
Isithombe 1 sibonisa isakhiwo esijwayelekile sama-cellulose ethers. Iyunithi ngayinye ye-bD-anhydroglucose (iyunithi ephindaphindayo ye-cellulose) ithatha indawo yeqembu elilodwa ezikhundleni ze-C (2), C (3) kanye ne-C (6), okungukuthi, kungaba namaqembu e-ether amathathu. Ngenxa yezibopho ze-hydrogen zangaphakathi kwe-chain kanye ne-inter-chain ze-ama-macromolecule e-cellulose, kunzima ukuncibilika emanzini kanye cishe kuzo zonke izinyibilikisi eziphilayo. Ukungeniswa kwamaqembu e-ether ngokusebenzisa i-etherification kubhubhisa izibopho ze-hydrogen zangaphakathi kwama-molecule kanye naphakathi kwama-molecule, kuthuthukisa ukunamathela kwayo emanzini, futhi kuthuthukisa kakhulu ukuncibilika kwayo emanzini.
Izinto ezivamile ezifakwa esikhundleni se-ether ngamaqembu e-alkoxy anesisindo esiphansi sama-molecule (ama-athomu e-carbon angu-1 kuya kwangu-4) noma amaqembu e-hydroxyalkyl, angase afakwe esikhundleni ngamanye amaqembu asebenzayo njenge-carboxyl, i-hydroxyl noma amaqembu e-amino. Izinto ezifakwa esikhundleni zingaba uhlobo olulodwa, ezimbili noma ngaphezulu ezihlukene. Eceleni kwe-cellulose macromolecular chain, amaqembu e-hydroxyl ezindaweni ze-C(2), C(3) kanye ne-C(6) zeyunithi ngayinye ye-glucose afakwa esikhundleni ngezilinganiso ezahlukene. Empeleni, i-cellulose ether ngokuvamile ayinaso isakhiwo samakhemikhali esiqondile, ngaphandle kwaleyo mikhiqizo efakwe esikhundleni ngokuphelele uhlobo olulodwa lweqembu (wonke amaqembu amathathu e-hydroxyl afakwa esikhundleni). Le mikhiqizo ingasetshenziswa kuphela ekuhlaziyweni kwelabhorethri kanye nocwaningo, futhi ayinalo inani lezentengiselwano.
(a) Isakhiwo esijwayelekile samayunithi amabili e-anhydroglucose ochungechungeni lwama-molecule e-cellulose ether, i-R1~R6=H, noma into ethatha indawo yezinto eziphilayo;
(b) Ingcezu yeketanga lama-molecule ye-carboxymethyli-hydroxyethyl cellulose, izinga lokushintshaniswa kwe-carboxymethyl lingu-0.5, izinga lokushintshaniswa kwe-hydroxyethyl lingu-2.0, kanti izinga lokushintshaniswa kwe-molar lingu-3.0. Lesi sakhiwo simelela izinga lokushintshaniswa elimaphakathi lamaqembu afakwe i-ether, kodwa empeleni izinto ezithatha indawo azihleliwe.
Kumuntu ngamunye othatha indawo, inani eliphelele le-etherification livezwa yizinga lenani le-DS lokufaka esikhundleni. Ububanzi be-DS bungu-0~3, okulingana nenani elimaphakathi lamaqembu e-hydroxyl athathelwe indawo amaqembu e-etherification kuyunithi ngayinye ye-anhydroglucose.
Kuma-ether e-hydroxyalkyl cellulose, ukusabela kokushintsha kuzoqala ukwenziwa kwe-ether kusuka kumaqembu amasha e-hydroxyl yamahhala, futhi izinga lokushintsha lingalinganiswa ngenani le-MS, okungukuthi, izinga le-molar lokushintsha. Limelela inani elimaphakathi lama-moles e-etherifying agent reactant engeziwe kuyunithi ngayinye ye-anhydroglucose. I-reactant ejwayelekile yi-ethylene oxide futhi umkhiqizo une-hydroxyethyl substituent. KuMfanekiso 1, inani le-MS lomkhiqizo lingu-3.0.
Ngokwethiyori, akukho mkhawulo ophezulu wenani le-MS. Uma inani le-DS lezinga lokushintshana eqenjini ngalinye lendandatho ye-glucose laziwa, ubude beketanga elimaphakathi lochungechunge lwe-ether. Abanye abakhiqizi bavame ukusebenzisa ingxenye enkulu (wt%) yamaqembu ahlukene e-etherification (njenge--OCH3 noma i--OC2H4OH) ukumela izinga lokushintshana kanye nezinga esikhundleni samanani e-DS kanye ne-MS. Ingxenye enkulu yeqembu ngalinye kanye nenani layo le-DS noma le-MS ingaguqulwa ngokubala okulula.
Ama-ether amaningi e-cellulose angama-polymer ancibilika emanzini, kanti amanye ancibilika kancane ezinyibilikisini eziphilayo. I-ether ye-cellulose inezici zokusebenza kahle kakhulu, intengo ephansi, ukucubungula okulula, ubuthi obuphansi kanye nokuhlukahluka okubanzi, kanti izinkambu zesidingo kanye nezicelo zisakhula. Njenge-ejenti yokusiza, i-ether ye-cellulose inamandla amakhulu okusebenzisa emikhakheni eyahlukene yemboni. ingatholakala nge-MS/DS.
Ama-ether e-cellulose ahlukaniswa ngokwesakhiwo samakhemikhali sezinto ezithathelwa indawo zibe ama-ether e-anionic, cationic kanye nama-ether angewona ama-ionic. Ama-ether angewona ama-ionic angahlukaniswa abe imikhiqizo encibilika emanzini kanye nemikhiqizo encibilika ku-oyela.
Imikhiqizo eye yathuthukiswa ibhalwe engxenyeni engenhla yeThebula 1. Ingxenye engezansi yeThebula 1 ibala amanye amaqembu aziwayo e-etherification, angakabi yimikhiqizo ebalulekile yezentengiselwano.
Ukuhlelwa kwesifinyezo sezinto ezithathelwe indawo ze-ether ezixubile kungaqanjwa ngokwe-alfabhethi noma izinga le-DS (MS) efanele, isibonelo, i-2-hydroxyethyl methylcellulose, isifinyezo yi-HEMC, futhi singabhalwa njenge-MHEC ukuze kugqanyiswe indawo ethathelwe indawo ye-methyl.
Amaqembu e-hydroxyl ku-cellulose awatholakali kalula ngama-etherification agents, futhi inqubo ye-etherification ivame ukwenziwa ngaphansi kwezimo ze-alkaline, ngokuvamile kusetshenziswa ukuhlushwa okuthile kwesisombululo samanzi se-NaOH. I-cellulose yakhiwa kuqala ibe yi-alkaline cellulose evuvukele ngesisombululo samanzi se-NaOH, bese ibhekana nokusabela kwe-etherification nge-etherification agent. Ngesikhathi sokukhiqizwa nokulungiswa kwama-ethers axubile, izinhlobo ezahlukene zama-etherification agents kufanele zisetshenziswe ngesikhathi esisodwa, noma i-etherification kufanele yenziwe isinyathelo ngesinyathelo ngokudla ngezikhathi ezithile (uma kudingeka). Kunezinhlobo ezine zokusabela ku-etherification ye-cellulose, ezifingqiwe ngefomula yokusabela (i-cellulosic ithathelwa indawo yi-Cell-OH) kanje:
I-equation (1) ichaza ukusabela kwe-Williamson etherification. I-RX iyi-inorganic acid ester, kanti i-X iyi-halogen Br, Cl noma i-sulfuric acid ester. I-Chloride R-Cl ivame ukusetshenziswa embonini, isibonelo, i-methyl chloride, i-ethyl chloride noma i-chloroacetic acid. Inani lesisekelo se-stoichiometric liyasetshenziswa kulezi zindlela zokusabela. Imikhiqizo ye-cellulose ether eyenziwe ngezimboni i-methyl cellulose, i-ethyl cellulose kanye ne-carboxymethyl cellulose yimikhiqizo yokusabela kwe-Williamson etherification.
Ifomula yokusabela (2) yindlela yokwengeza ama-epoxide asekelwe ku-base-catalyzed (njenge-R=H, CH3, noma i-C2H5) kanye namaqembu e-hydroxyl kuma-molecule e-cellulose ngaphandle kokudla isisekelo. Lokhu kusabela kungenzeka kuqhubeke njengoba amaqembu amasha e-hydroxyl ekhiqizwa ngesikhathi sokusabela, okuholela ekwakhekeni kwamaketanga aseceleni e-oligoalkylethylene oxide: Ukusabela okufanayo ne-1-aziridine (aziridine) kuzokwakha i-aminoethyl ether: I-Cell-O-CH2-CH2-NH2. Imikhiqizo efana ne-hydroxyethyl cellulose, i-hydroxypropyl cellulose kanye ne-hydroxybutyl cellulose yonke iyimikhiqizo ye-base-catalyzed epoxidation.
Ifomula yokusabela (3) yindlela yokusabela phakathi kwe-Cell-OH kanye namakhemikhali e-organic aqukethe ama-bond asebenzayo kabili ku-alkaline medium, i-Y iyiqembu elikhipha ama-electron, njenge-CN, i-CONH2, noma i-SO3-Na+. Namuhla lolu hlobo lokusabela aluvamile ukusetshenziswa embonini.
Ifomula yokusabela (4), i-etherification nge-diazoalkane ayikathuthukiswa okwamanje.
- Izinhlobo ze-cellulose ethers
I-cellulose ether ingaba yi-monoether noma i-ether exubile, futhi izakhiwo zayo zihlukile. Kunezinhlobo eziphansi ze-hydrophilic ezifakwe esikhundleni se-cellulose macromolecule, njengezinhlobo ze-hydroxyethyl, ezinganikeza umkhiqizo izinga elithile lokuncibilika kwamanzi, kuyilapho emaqenjini angenawo amanzi, njenge-methyl, i-ethyl, njll., kuphela ukushintshwa okumaphakathi Izinga eliphezulu linganikeza umkhiqizo ukuncibilika kwamanzi okuthile, kanti umkhiqizo ophansi uvuvukala emanzini kuphela noma ungancibilika kusisombululo se-alkali esincibilikisiwe. Ngocwaningo olujulile ngezakhiwo ze-cellulose ethers, ama-cellulose ethers amasha kanye nezinkambu zawo zokusetshenziswa zizothuthukiswa futhi zikhiqizwe njalo, futhi amandla amakhulu okushayela yimakethe yokusetshenziswa ebanzi neqhubekayo ehlanjululwe.
Umthetho ojwayelekile wethonya lamaqembu kuma-ether axubile ezimpahleni zokuncibilika uthi:
1) Khulisa okuqukethwe kwamaqembu angenawo umoya kumkhiqizo ukuze kwandiswe ukungabi namanzi kwe-ether futhi kwehliswe iphuzu lejeli;
2) Khulisa okuqukethwe kwamaqembu athanda amanzi (njengamaqembu e-hydroxyethyl) ukuze kwandiswe iphuzu lawo lejeli;
3) Iqembu le-hydroxypropyl likhethekile, futhi i-hydroxypropylation efanele inganciphisa izinga lokushisa le-gel lomkhiqizo, futhi izinga lokushisa le-gel lomkhiqizo ophakathi we-hydroxypropyl lizokhuphuka futhi, kodwa izinga eliphezulu lokushintsha lizonciphisa iphuzu layo le-gel; Isizathu singenxa yesakhiwo esikhethekile sobude be-carbon chain seqembu le-hydroxypropyl, i-hydroxypropylation esezingeni eliphansi, izibopho ze-hydrogen ezibuthakathaka phakathi kwama-molecule kuma-cellulose macromolecule, kanye namaqembu e-hydroxyl aphilic emaketangeni amagatsha. Amanzi ayabusa. Ngakolunye uhlangothi, uma ukushintsha kuphezulu, kuzoba ne-polymerization eqenjini eliseceleni, okuqukethwe okuhlobene kweqembu le-hydroxyl kuzoncipha, i-hydrophobicity izokwanda, futhi ukuncibilika kuzoncipha esikhundleni salokho.
Ukukhiqizwa kanye nocwaningo lwe-i-cellulose etherinomlando omude. Ngo-1905, uSuida wabika okokuqala ngokwenziwa kwe-cellulose ibe yi-ether, eyayine-methylated nge-dimethyl sulfate. Ama-alkyl ethers angewona ama-ionic anelungelo lobunikazi nguLilienfeld (1912), uDreyfus (1914) noLeuchs (1920) ngama-cellulose ethers ancibilika emanzini noma ancibilika ku-oyela, ngokulandelana. UBuchler noGomberg bakhiqiza i-benzyl cellulose ngo-1921, i-carboxymethyl cellulose yakhiqizwa okokuqala nguJansen ngo-1918, kwathi uHubert wakhiqiza i-hydroxyethyl cellulose ngo-1920. Ekuqaleni kwawo-1920, i-carboxymethylcellulose yathengiswa eJalimane. Kusukela ngo-1937 kuya ku-1938, ukukhiqizwa kwezimboni kwe-MC ne-HEC kwatholakala e-United States. ISweden yaqala ukukhiqizwa kwe-EHEC encibilika emanzini ngo-1945. Ngemuva kuka-1945, ukukhiqizwa kwe-cellulose ether kwanda ngokushesha eNtshonalanga Yurophu, e-United States naseJapane. Ekupheleni kuka-1957, i-China CMC yaqala ukukhiqizwa eShanghai Celluloid Factory. Ngo-2004, amandla okukhiqiza ezweni lami azoba amathani angu-30,000 e-ionic ether kanye namathani angu-10,000 e-non-ionic ether. Ngo-2007, izofinyelela amathani angu-100,000 e-ionic ether kanye namathani angu-40,000 e-Nonionic ether. Izinkampani zobuchwepheshe ezihlangene ekhaya nakwamanye amazwe nazo ziyavela njalo, futhi amandla okukhiqiza i-cellulose ether yaseShayina kanye nezinga lobuchwepheshe lihlala lithuthuka.
Eminyakeni yamuva nje, ama-monoether amaningi e-cellulose kanye nama-ether axubile anamanani ahlukene e-DS, ubumsulwa, ubumsulwa kanye nezakhiwo ze-rheological kuye kwathuthukiswa ngokuqhubekayo. Njengamanje, ukugxila kwentuthuko emkhakheni wama-ether e-cellulose ukusebenzisa ubuchwepheshe bokukhiqiza obuthuthukisiwe, ubuchwepheshe obusha bokulungiselela, imishini emisha, Imikhiqizo emisha, imikhiqizo esezingeni eliphezulu, kanye nemikhiqizo ehlelekile kufanele kucwaningwe ngobuchwepheshe.
Isikhathi sokuthunyelwe: Ephreli-28-2024