1.Isakhiwo kanye nomgomo wokulungiselela we-cellulose ether
Umfanekiso 1 ubonisa ukwakheka okujwayelekile kwama-cellulose ethers. Iyunithi ngayinye ye-bD-anhydroglucose (iyunithi ephindaphindayo ye-cellulose) ingena esikhundleni seqembu elilodwa endaweni ethi C (2), C (3) kanye no-C (6), okungukuthi, kungaba namaqembu e-ether amathathu. Ngenxa ye-intra-chain kanye ne-inter-chain hydrogen bond yei-cellulose macromolecules, kunzima ukuncibilika emanzini futhi cishe zonke izincibilikisi eziphilayo. Ukwethulwa kwamaqembu e-ether ngokusebenzisa i-etherification kubhubhisa izibopho ze-hydrogen ze-intramolecular kanye ne-intermolecular, kuthuthukisa i-hydrophilicity yayo, futhi kuthuthukisa kakhulu ukuncibilika kwayo emithonjeni yamanzi.
Ama-etherified ajwayelekile amaqembu amaqembu e-alkoxy enesisindo esiphansi (1 kuya ku-4 ama-athomu ekhabhoni) noma amaqembu e-hydroxyalkyl, angase athathelwe indawo amanye amaqembu asebenzayo njenge-carboxyl, i-hydroxyl noma amaqembu e-amino. Okushintshwayo kungase kube uhlobo olulodwa, ezimbili noma ngaphezulu ezihlukene. Eceleni kochungechunge lwe-cellulose macromolecular, amaqembu e-hydroxyl ku-C(2), C(3) kanye no-C(6) weyunithi ngayinye ye-glucose ashintshwa ngezilinganiso ezihlukene. Uma sikhuluma ngokuqinile, i-cellulose ether ngokuvamile ayinaso ukwakheka kwamakhemikhali okuqondile, ngaphandle kwaleyo mikhiqizo eshintshwa ngokuphelele uhlobo olulodwa lweqembu (wonke amaqembu amathathu e-hydroxyl ayashintshwa). Le mikhiqizo ingasetshenziswa kuphela ekuhlaziyeni nasekucwaningeni ilabhorethri, futhi ayinalo inani lezohwebo.
(a) Isakhiwo esijwayelekile samayunithi amabili e-anhydroglucose eketango lengqamuzana le-cellulose ether, R1~R6=H, noma into ephilayo;
(b) Ucezu lweketango lamangqamuzana e-carboxymethyli-hydroxyethyl cellulose, izinga lokushintshwa kwe-carboxymethyl ngu-0.5, izinga lokushintshwa kwe-hydroxyethyl ngu-2.0, futhi izinga lokushintshwa kwe-molar ngu-3.0. Lesi sakhiwo simelela izinga lokushintshwa elimaphakathi lamaqembu e-etherified, kodwa ama-substitute empeleni awahleliwe.
Kokushintshwayo ngakunye, inani eliphelele le-etherification livezwa ngezinga lokushintsha inani le-DS. Ububanzi be-DS bungu-0~3, okulingana nenani elimaphakathi lamaqembu e-hydroxyl esikhundleni samaqembu e-etherification kuyunithi ngayinye ye-anhydroglucose.
Kuma-hydroxyalkyl cellulose ether, ukusabela kokushintsha kuzoqala ukufakwa kwe-etherification kusuka kumaqembu amasha e-hydroxyl yamahhala, futhi izinga lokushintsha lingalinganiswa ivelu ye-MS, okungukuthi, i-molar degree of substitution. Imele inombolo emaphakathi yama-moles we-etherifying reactant engezwe kuyunithi ngayinye ye-anhydroglucose. I-reactant evamile i-ethylene oxide futhi umkhiqizo une-hydroxyethyl esikhundleni. Emfanekisweni 1, inani le-MS lomkhiqizo ngu-3.0.
Ngokombono, awukho umkhawulo ophezulu wevelu ye-MS. Uma inani le-DS lezinga lokushintshanisa eqenjini ngalinye leringi ye-glucose laziwa, ubude beketango elimaphakathi leketango le-ether Abanye abakhiqizi futhi bavame ukusebenzisa ingxenyenamba enkulu (wt%) yamaqembu e-etherification ahlukene (njenge -OCH3 noma -OC2H4OH) ukuze amele izinga lokushintsha kanye neziqu esikhundleni samanani e-DS ne-MS. Ingxenye enkulu yeqembu ngalinye kanye nenani lalo le-DS noma le-MS lingaguqulwa ngokubala okulula.
Iningi lama-cellulose ether angama-polymers ancibilika emanzini, kanti amanye ancibilika kancane kuzincibilikisi zemvelo. I-Cellulose ether inezici zokusebenza kahle okuphezulu, intengo ephansi, ukucubungula kalula, ubuthi obuphansi kanye nezinhlobonhlobo ezibanzi, kanye nezinkambu zesidingo nezisetshenziswa zisakhula. Njengomenzeli osizayo, i-cellulose ether inamandla amakhulu okusebenza emikhakheni eyahlukene yezimboni. ingatholwa nge-MS/DS.
Ama-cellulose ether ahlukaniswa ngokuya ngesakhiwo samakhemikhali sezinto ezibambele ku-anionic, cationic kanye nama-nonionic ether. Ama-ether angama-nonionic angahlukaniswa abe yimikhiqizo encibilikayo emanzini nencibilika uwoyela.
Imikhiqizo eyenziwe ngezimboni ibalwe engxenyeni engenhla yeThebula 1. Ingxenye engezansi yeThebula 1 ibala amanye amaqembu e-etherification aziwayo, angakabi yimikhiqizo ebalulekile yohwebo.
I-oda lesifinyezo se-ether exutshwe esikhundleni singaqanjwa ngokulandelana kwezinhlamvu noma izinga le-DS (MS), isibonelo, ku-2-hydroxyethyl methylcellulose, isifinyezo sithi HEMC, futhi singabhalwa njenge-MHEC ukuze kugqanyiswe i-methyl ebambele.
Amaqembu e-hydroxyl ku-cellulose awafinyeleleki kalula ngama-etherification agents, futhi inqubo ye-etherification ngokuvamile yenziwa ngaphansi kwezimo ze-alkaline, ngokuvamile kusetshenziswa ukuhlangana okuthile kwesisombululo samanzi se-NaOH. I-cellulose iqala ukwakheka ibe i-alkali cellulose evuvukele enesisombululo samanzi se-NaOH, bese ithola ukusabela kwe-etherification nge-ejenti ye-etherification. Ngesikhathi sokukhiqizwa nokulungiswa kwama-ether axubile, izinhlobo ezahlukene zama-etherification kufanele zisetshenziswe ngesikhathi esisodwa, noma ukufakwa kwe-etherification kufanele kwenziwe isinyathelo ngesinyathelo ngokuphakela ngezikhathi ezithile (uma kunesidingo). 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-ester ye-asidi engaphili, futhi 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 ekuphenduleni okunjalo. Imikhiqizo ye-cellulose ether ethuthukisiwe i-methyl cellulose, i-ethyl cellulose ne-carboxymethyl cellulose yimikhiqizo ye-Williamson etherification reaction.
Ifomula yokusabela (2) iwukusabela okungeziwe kwe-base-catalyzed epoxides (njenge-R=H, CH3, noma i-C2H5) kanye namaqembu e-hydroxyl kuma-molecule we-cellulose ngaphandle kokusebenzisa isisekelo. Lokhu kusabela kungase kuqhubeke njengoba amaqembu amasha e-hydroxyl ekhiqizwa ngesikhathi sokuphendula, okuholela ekwakhekeni kwamaketanga e-oligoalkylethylene oxide ohlangothini: 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 imikhiqizo ye-base-catalyzed epoxidation.
Ifomula yokusabela (3) iwukusabela phakathi kwe-Cell-OH nezinhlanganisela eziphilayo eziqukethe amabhondi amabili asebenzayo endaweni ye-alkaline, u-Y iqembu elihoxisa i-electron, njenge-CN, CONH2, noma i-SO3-Na+. Namuhla lolu hlobo lokusabela aluvamile ukusetshenziswa ezimbonini.
Ifomula yokusabela (4), i-etherification nge-diazoalkane ayikasungulwa kuze kube manje.
- Izinhlobo ze-cellulose ethers
I-cellulose ether ingaba i-monoether noma i-ether exutshwe, futhi izakhiwo zayo zihlukile. Kunamaqembu e-hydrophilic afakwe endaweni ephansi ku-cellulose macromolecule, njengamaqembu e-hydroxyethyl, anganikeza umkhiqizo ngezinga elithile lokuncibilika kwamanzi, kuyilapho amaqembu e-hydrophobic, njenge-methyl, i-ethyl, njll., ukufaka esikhundleni okusesilinganisweni kuphela Izinga eliphakeme linganikeza umkhiqizo ukuncibilika okuthile kwamanzi, futhi isixazululo esincibilikisiwe esincibilikisiwe emanzini singancibilika kuphela. Ngocwaningo olujulile mayelana nezakhiwo zama-cellulose ethers, ama-cellulose ether amasha kanye nezinkambu zokusetshenziswa kwawo kuzothuthukiswa futhi kukhiqizwe ngokuqhubekayo, futhi amandla amakhulu okushayela imakethe yezicelo ebanzi futhi ecwengisisiwe ngokuqhubekayo.
Umthetho ojwayelekile wethonya lamaqembu kuma-ether axubile ezimpahleni zokuncibilika uthi:
1) Khulisa okuqukethwe kwamaqembu e-hydrophobic kumkhiqizo ukwandisa i-hydrophobicity ye-ether futhi wehlise iphuzu le-gel;
2) Khulisa okuqukethwe kwamaqembu e-hydrophilic (njengamaqembu e-hydroxyethyl) ukwandisa iphuzu layo lejeli;
I-3) Iqembu le-hydroxypropyl likhethekile, futhi i-hydroxypropylation efanele inganciphisa izinga lokushisa le-gel lomkhiqizo, futhi izinga lokushisa le-gel lomkhiqizo ophakathi kwe-hydroxypropylated lizophinde livuke, kodwa izinga eliphezulu lokufaka esikhundleni lizonciphisa iphuzu layo le-gel; Isizathu singenxa yesakhiwo esikhethekile sobude be-carbon chain yeqembu le-hydroxypropyl, i-hydroxypropylation esezingeni eliphansi, izibopho ze-hydrogen ezibuthakathaka phakathi naphakathi kwama-molecule ku-cellulose macromolecule, namaqembu e-hydrophilic hydroxyl emaketangeni egatsha. Amanzi abusayo. Ngakolunye uhlangothi, uma ukufakwa esikhundleni kuphezulu, kuzoba ne-polymerization eqenjini elihlangothini, okuqukethwe okuhlobene kweqembu le-hydroxyl kuzokwehla, i-hydrophobicity izokwanda, futhi i-solubility izoncishiswa esikhundleni.
Ukukhiqizwa kanye nocwaningo lwei-cellulose etherinomlando omude. Ngo-1905, i-Suida yabika okokuqala nge-etherification ye-cellulose, eyayine-methylated ne-dimethyl sulfate. Ama-alkyl ether angama-nonionic anikezwe ilungelo lobunikazi ngu-Lilienfeld (1912), Dreyfus (1914) kanye no-Leuchs (1920) wama-cellulose ethers ancibilika emanzini noma ancibilika uwoyela, ngokulandelana. U-Buchler noGomberg bakhiqiza i-benzyl cellulose ngo-1921, i-carboxymethyl cellulose yaqala ukukhiqizwa ngu-Jansen ngo-1918, futhi u-Hubert wakhiqiza i-hydroxyethyl cellulose ngo-1920. Ekuqaleni kwawo-1920, i-carboxymethylcellulose yayithengiswa eJalimane. Kusukela ngo-1937 kuya ku-1938, ukukhiqizwa kwezimboni ze-MC kanye ne-HEC kwenziwa e-United States. ISweden yaqala ukukhiqizwa kwe-EHEC encibilikayo emanzini ngo-1945. Ngemva kuka-1945, ukukhiqizwa kwe-cellulose ether kwanda ngokushesha eNtshonalanga Yurophu, e-United States naseJapane. Ekupheleni kuka-1957, i-China CMC yaqala ukufakwa ekukhiqizeni e-Shanghai Celluloid Factory. Ngo-2004, amandla okukhiqiza ezwe lami azoba amathani angu-30,000 e-ionic ether kanye namathani angu-10,000 e-ether engeyona i-ionic. Ngo-2007, izofinyelela amathani angu-100,000 e-ionic ether kanye namathani angu-40,000 e-Nonionic ether. Izinkampani zobuchwepheshe ezihlanganyelwe ekhaya nakwamanye amazwe nazo zihlale zivela, futhi umthamo wokukhiqiza we-cellulose ether waseChina kanye nezinga lobuchwepheshe lithuthuka njalo.
Eminyakeni yamuva nje, ama-cellulose monoether amaningi kanye nama-ether axubile anamanani ahlukene e-DS, ama-viscosity, ubumsulwa kanye nezakhiwo ze-rheological ziye zathuthukiswa ngokuqhubekayo. Njengamanje, ukugxila kwentuthuko emkhakheni we-cellulose ethers ukwamukela ubuchwepheshe bokukhiqiza obuphambili, ubuchwepheshe obusha bokulungiselela, imishini emisha, imikhiqizo emisha, imikhiqizo esezingeni eliphezulu, kanye nemikhiqizo ehlelekile kufanele kucwaningwe ngobuchwepheshe.
Isikhathi sokuthumela: Apr-28-2024