1. Kapangidwe ndi kukonzekera mfundo ya efa ya cellulose
Chithunzi 1 chikuwonetsa kapangidwe kabwino ka ma ether a cellulose. Gawo lililonse la bD-anhydroglucose (gawo lobwerezabwereza la cellulose) limalowa m'malo mwa gulu limodzi pamalo a C (2), C (3) ndi C (6), ndiko kuti, pakhoza kukhala magulu atatu a ether. Chifukwa cha ma bond a hydrogen a intra-chain ndi inter-chain amacromolecule a cellulose, n'kovuta kusungunuka m'madzi ndi pafupifupi zinthu zonse zachilengedwe zosungunulira. Kulowetsedwa kwa magulu a ether kudzera mu etherification kumawononga ma hydrogen bond amkati mwa mamolekyulu ndi pakati pa mamolekyulu, kumawonjezera hydrophilicity yake, komanso kumawonjezera kwambiri kusungunuka kwake m'madzi.
Zinthu zosinthidwa ndi ether ndi magulu a alkoxy otsika kulemera kwa molekyulu (maatomu a kaboni 1 mpaka 4) kapena magulu a hydroxyalkyl, omwe amatha kusinthidwa ndi magulu ena ogwira ntchito monga carboxyl, hydroxyl kapena amino. Zinthu zosinthidwa zitha kukhala zamtundu umodzi, ziwiri kapena zingapo zosiyana. Pamodzi ndi unyolo wa macromolecular wa cellulose, magulu a hydroxyl omwe ali pa C(2), C(3) ndi C(6) pa unit iliyonse ya glucose amasinthidwa mosiyanasiyana. Kunena zoona, cellulose ether nthawi zambiri imakhala ndi kapangidwe kake ka mankhwala, kupatulapo zinthu zomwe zimasinthidwa kwathunthu ndi mtundu umodzi wa gulu (magulu onse atatu a hydroxyl amasinthidwa). Zinthuzi zitha kugwiritsidwa ntchito kokha pa kusanthula kwa labotale ndi kafukufuku, ndipo sizili ndi phindu lamalonda.
(a) Kapangidwe ka mayunitsi awiri a anhydroglucose a cellulose ether molecular chain, R1~R6=H, kapena organic substituent;
(b) Chidutswa cha molekyulu cha carboxymethylhydroxyethyl cellulose, mlingo wa kusintha kwa carboxymethyl ndi 0.5, mlingo wa kusintha kwa hydroxyethyl ndi 2.0, ndipo mlingo wa kusintha kwa molar ndi 3.0. Kapangidwe kameneka kakuyimira kuchuluka kwapakati kwa magulu osinthika a ether, koma zolowa m'malo mwake zimakhala zosasinthika.
Pa chosinthira chilichonse, kuchuluka konse kwa etherification kumawonetsedwa ndi kuchuluka kwa DS yosinthira. Mtundu wa DS ndi 0 ~ 3, womwe ndi wofanana ndi kuchuluka kwa magulu a hydroxyl omwe amasinthidwa ndi magulu a etherification pa unit iliyonse ya anhydroglucose.
Pa ma ether a hydroxyalkyl cellulose, kusintha kwa zinthu kudzayamba kusinthika kuchokera ku magulu atsopano a hydroxyl, ndipo kuchuluka kwa kusinthaku kungayesedwe ndi MS value, ndiko kuti, molar degree of substitution. Kumayimira chiwerengero chapakati cha ma moles a etherifying agent reactant omwe amawonjezeredwa ku anhydroglucose unit iliyonse. Reactant wamba ndi ethylene oxide ndipo chinthucho chili ndi hydroxyethyl substituent. Mu Chithunzi 1, MS value ya chinthucho ndi 3.0.
Mwachidziwitso, palibe malire apamwamba a mtengo wa MS. Ngati mtengo wa DS wa digiri ya kusintha pa gulu lililonse la mphete ya shuga umadziwika, kutalika kwa unyolo wapakati wa unyolo wa mbali ya ether. Opanga ena nthawi zambiri amagwiritsa ntchito gawo la kulemera (wt%) la magulu osiyanasiyana a etherification (monga -OCH3 kapena -OC2H4OH) kuyimira mulingo ndi digiri ya kusintha m'malo mwa DS ndi MS. Gawo la kulemera kwa gulu lililonse ndi mtengo wake wa DS kapena MS lingasinthidwe mwa kuwerengera kosavuta.
Ma ether ambiri a cellulose ndi ma polima osungunuka m'madzi, ndipo ena amasungunuka pang'ono mu zosungunulira zachilengedwe. Cellulose ether ili ndi mawonekedwe a kugwira ntchito bwino, mtengo wotsika, kukonzedwa kosavuta, poizoni wotsika komanso mitundu yosiyanasiyana, ndipo malo ofunikira ndi ogwiritsidwa ntchito akukulirakulirabe. Monga wothandizira wothandizira, cellulose ether ili ndi kuthekera kwakukulu kogwiritsidwa ntchito m'magawo osiyanasiyana amakampani. Itha kupezeka ndi MS/DS.
Ma ether a cellulose amagawidwa m'magulu malinga ndi kapangidwe ka mankhwala a zinthu zomwe zimalowa m'malo mwake kukhala ma ether a anionic, cationic ndi nonionic. Ma ether a nonionic amatha kugawidwa m'magulu osungunuka m'madzi ndi osungunuka ndi mafuta.
Zinthu zomwe zakhala zikugwiritsidwa ntchito m'mafakitale zalembedwa pamwamba pa Table 1. Gawo la pansi pa Table 1 likulemba magulu ena odziwika bwino a etherification, omwe sanakhale zinthu zofunika kwambiri zamalonda.
Ndondomeko yachidule ya zinthu zosakanikirana za ether ikhoza kutchulidwa malinga ndi dongosolo la zilembo kapena mulingo wa DS (MS) womwe uli nawo, mwachitsanzo, pa 2-hydroxyethyl methylcellulose, chidule chake ndi HEMC, ndipo chingalembedwenso kuti MHEC kuti iwonetse cholowa cha methyl.
Magulu a hydroxyl pa cellulose sapezeka mosavuta ndi zinthu zoyeretsera, ndipo njira yoyeretsera nthawi zambiri imachitika pansi pa mikhalidwe ya alkaline, nthawi zambiri pogwiritsa ntchito kuchuluka kwa NaOH aqueous solution. Cellulose imapangidwa koyamba kukhala alkali cellulose yotupa ndi NaOH aqueous solution, kenako imadutsa mu etherification reaction ndi zinthu zoyeretsera. Pakupanga ndi kukonzekera ma ether osakanikirana, mitundu yosiyanasiyana ya zinthu zoyeretsera ziyenera kugwiritsidwa ntchito nthawi imodzi, kapena etherification iyenera kuchitika pang'onopang'ono podyetsa pang'onopang'ono (ngati pakufunika). Pali mitundu inayi ya reaction mu etherification ya cellulose, yomwe imafotokozedwa mwachidule ndi njira yoyeretsera (cellulosic imalowetsedwa m'malo ndi Cell-OH) motere:
Equation (1) ikufotokoza za Williamson etherification reaction. RX ndi inorganic acid ester, ndipo X ndi halogen Br, Cl kapena sulfuric acid ester. Chloride R-Cl nthawi zambiri imagwiritsidwa ntchito m'mafakitale, mwachitsanzo, methyl chloride, ethyl chloride kapena chloroacetic acid. Kuchuluka kwa stoichiometric kwa base kumagwiritsidwa ntchito muzochita zotere. Zinthu zopangidwa ndi ether za cellulose zopangidwa ndi mafakitale monga methyl cellulose, ethyl cellulose ndi carboxymethyl cellulose ndi zinthu zopangidwa ndi Williamson etherification reaction.
Fomula ya reaction (2) ndi njira yowonjezera ya ma epoxides opangidwa ndi base-catalyzed (monga R=H, CH3, kapena C2H5) ndi magulu a hydroxyl pa mamolekyulu a cellulose popanda kugwiritsa ntchito base. Njirayi ikuyembekezeka kupitilira pamene magulu atsopano a hydroxyl amapangidwa panthawi ya reaction, zomwe zimapangitsa kuti pakhale ma chain a oligoalkylethylene oxide: Njira yofanana ndi 1-aziridine (aziridine) ipanga aminoethyl ether: Cell-O-CH2-CH2-NH2. Zinthu monga hydroxyethyl cellulose, hydroxypropyl cellulose ndi hydroxybutyl cellulose zonse ndi zopangidwa ndi base-catalyzed epoxidation.
Fomula ya reaction (3) ndi reaction pakati pa Cell-OH ndi organic compounds zomwe zili ndi active double bonds mu alkaline medium, Y ndi gulu lochotsa ma electron, monga CN, CONH2, kapena SO3-Na+. Masiku ano mtundu uwu wa reaction sugwiritsidwa ntchito kawirikawiri m'mafakitale.
Fomula ya reaction (4), etherification ndi diazoalkane sizinachitikebe m'mafakitale.
- Mitundu ya ethers ya cellulose
Cellulose ether ikhoza kukhala monoether kapena mixed ether, ndipo makhalidwe ake ndi osiyana. Pali magulu otsika-substituted hydrophilic pa cellulose macromolecule, monga magulu a hydroxyethyl, omwe amatha kupatsa mankhwalawa kuchuluka kwa madzi osungunuka, pomwe magulu osagwirizana ndi hydrophobic, monga methyl, ethyl, ndi zina zotero, kusintha pang'ono kokha. Kuchuluka kwapamwamba kumatha kupatsa mankhwalawa kusungunuka kwa madzi, ndipo mankhwala otsika-substituted amangodzaza m'madzi kapena amatha kusungunuka mu dilute alkali solution. Ndi kafukufuku wozama pa makhalidwe a cellulose ethers, ma cellulose ethers atsopano ndi minda yawo yogwiritsira ntchito idzapangidwa ndikupangidwa mosalekeza, ndipo mphamvu yayikulu yoyendetsera ntchito ndi msika waukulu komanso wokonzedwa mosalekeza.
Lamulo lalikulu la mphamvu ya magulu mu ma ether osakanikirana pa zinthu zosungunuka ndi:
1) Wonjezerani kuchuluka kwa magulu odana ndi madzi mu chinthucho kuti muwonjezere kusowa kwa madzi kwa ether ndikuchepetsa mfundo ya gel;
2) Wonjezerani kuchuluka kwa magulu okonda madzi (monga magulu a hydroxyethyl) kuti muwonjezere mfundo yake ya gel;
3) Gulu la hydroxypropyl ndi lapadera, ndipo hydroxypropylation yoyenera imatha kuchepetsa kutentha kwa gel kwa chinthucho, ndipo kutentha kwa gel kwa chinthu chapakati cha hydroxypropyl kudzakweranso, koma kusintha kwakukulu kudzachepetsa mfundo yake ya gel; Chifukwa chake ndi chifukwa cha kapangidwe kake ka unyolo wapadera wa carbon wa gulu la hydroxypropyl, hydroxypropylation yotsika, zomangira za hydrogen zofooka mkati ndi pakati pa mamolekyu mu cellulose macromolecule, ndi magulu a hydroxyl ophilic pa unyolo wa nthambi. Madzi ndi ochulukirapo. Kumbali ina, ngati kusinthako kuli kwakukulu, padzakhala polymerization pa gulu la mbali, kuchuluka kwa hydroxyl kudzachepa, hydrophobicity idzawonjezeka, ndipo kusungunuka kudzachepa m'malo mwake.
Kupanga ndi kufufuza zaether ya celluloseili ndi mbiri yakale. Mu 1905, Suida adalemba koyamba za etherification ya cellulose, yomwe idapangidwa ndi methylated ndi dimethyl sulfate. Ma nonionic alkyl ethers adapatsidwa patent ndi Lilienfeld (1912), Dreyfus (1914) ndi Leuchs (1920) ya ma cellulose ethers osungunuka m'madzi kapena osungunuka ndi mafuta, motsatana. Buchler ndi Gomberg adapanga benzyl cellulose mu 1921, carboxymethyl cellulose idapangidwa koyamba ndi Jansen mu 1918, ndipo Hubert adapanga hydroxyethyl cellulose mu 1920. Kumayambiriro kwa zaka za m'ma 1920, carboxymethylcellulose idagulitsidwa ku Germany. Kuyambira 1937 mpaka 1938, kupanga mafakitale kwa MC ndi HEC kunachitika ku United States. Sweden idayamba kupanga EHEC yosungunuka m'madzi mu 1945. Pambuyo pa 1945, kupanga cellulose ether kudakula mwachangu ku Western Europe, United States ndi Japan. Kumapeto kwa chaka cha 1957, China CMC idayamba kupangidwa ku Shanghai Celluloid Factory. Pofika mu 2004, mphamvu yopangira dziko langa idzakhala matani 30,000 a ionic ether ndi matani 10,000 a non-ionic ether. Pofika mu 2007, idzafika matani 100,000 a ionic ether ndi matani 40,000 a Nonionic ether. Makampani ogwirizana aukadaulo kunyumba ndi kunja akutukuka nthawi zonse, ndipo mphamvu yopangira cellulose ether ku China komanso mulingo waukadaulo zikukula nthawi zonse.
M'zaka zaposachedwapa, ma cellulose monoether ambiri ndi ma ether osakanikirana okhala ndi ma DS values osiyanasiyana, viscosities, chiyero ndi rheological properties akhala akupangidwa mosalekeza. Pakadali pano, cholinga chachikulu cha chitukuko m'munda wa ma cellulose ethers ndikugwiritsa ntchito ukadaulo wapamwamba wopanga, ukadaulo watsopano wokonzekera, zida zatsopano, Zinthu zatsopano, zinthu zapamwamba, ndi zinthu zokonzedwa bwino ziyenera kufufuzidwa mwaukadaulo.
Nthawi yotumizira: Epulo-28-2024