1. Cov qauv thiab kev npaj ntawm cellulose ether
Daim Duab 1 qhia txog cov qauv ib txwm muaj ntawm cellulose ethers. Txhua chav bD-anhydroglucose (chav rov ua dua ntawm cellulose) hloov ib pawg ntawm C (2), C (3) thiab C (6) txoj haujlwm, uas yog, tuaj yeem muaj txog peb pawg ether. Vim yog cov hydrogen bonds hauv thiab inter-chain ntawmcov cellulose macromolecules, nws nyuaj rau yaj hauv dej thiab yuav luag txhua cov kuab tshuaj organic. Kev qhia txog cov pab pawg ether los ntawm etherification rhuav tshem cov hydrogen bonds intramolecular thiab intermolecular, txhim kho nws cov hydrophilicity, thiab txhim kho nws cov solubility hauv dej media.
Cov tshuaj hloov pauv etherified feem ntau yog cov pab pawg alkoxy qis molecular (1 txog 4 carbon atoms) lossis hydroxyalkyl pab pawg, uas tom qab ntawd tuaj yeem hloov los ntawm lwm cov pab pawg ua haujlwm xws li carboxyl, hydroxyl lossis amino pab pawg. Cov tshuaj hloov pauv yuav yog ib, ob lossis ntau hom sib txawv. Raws li cov saw hlau cellulose macromolecular, cov pab pawg hydroxyl ntawm C (2), C (3) thiab C (6) txoj haujlwm ntawm txhua chav glucose raug hloov pauv hauv cov feem sib txawv. Hais lus nruj, cellulose ether feem ntau tsis muaj cov qauv tshuaj lom neeg meej, tsuas yog cov khoom lag luam uas tau hloov pauv tag nrho los ntawm ib hom pab pawg (tag nrho peb pawg hydroxyl raug hloov pauv). Cov khoom no tsuas yog siv tau rau kev tshuaj ntsuam thiab kev tshawb fawb hauv chaw kuaj mob, thiab tsis muaj txiaj ntsig lag luam.
(a) Cov qauv dav dav ntawm ob lub anhydroglucose units ntawm cov cellulose ether molecular saw, R1 ~ R6 = H, lossis ib qho organic substituent;
(b) Ib daim molecular saw ntawm carboxymethylhydroxyethyl cellulose, qib ntawm kev hloov pauv ntawm carboxymethyl yog 0.5, qib ntawm kev hloov pauv ntawm hydroxyethyl yog 2.0, thiab qib ntawm kev hloov pauv ntawm molar yog 3.0. Cov qauv no sawv cev rau qib nruab nrab ntawm kev hloov pauv ntawm cov pab pawg etherified, tab sis cov substituents yog qhov tseeb random.
Rau txhua tus neeg hloov pauv, tag nrho cov nyiaj ntawm etherification yog qhia los ntawm qib ntawm kev hloov pauv DS tus nqi. Qhov ntau ntawm DS yog 0 ~ 3, uas yog sib npaug rau tus lej nruab nrab ntawm cov pab pawg hydroxyl hloov los ntawm cov pab pawg etherification ntawm txhua chav tsev anhydroglucose.
Rau hydroxyalkyl cellulose ethers, qhov kev hloov pauv yuav pib etherification los ntawm cov pab pawg hydroxyl dawb tshiab, thiab qib ntawm kev hloov pauv tuaj yeem ntsuas los ntawm MS tus nqi, uas yog, molar degree ntawm kev hloov pauv. Nws sawv cev rau tus lej nruab nrab ntawm moles ntawm etherifying agent reactant ntxiv rau txhua chav tsev anhydroglucose. Ib qho reactant ib txwm yog ethylene oxide thiab cov khoom muaj hydroxyethyl substituent. Hauv Daim Duab 1, MS tus nqi ntawm cov khoom yog 3.0.
Hauv kev xav, tsis muaj qhov txwv siab tshaj plaws rau tus nqi MS. Yog tias tus nqi DS ntawm qib kev hloov pauv ntawm txhua pawg glucose ring paub, qhov nruab nrab ntawm cov saw hlau ntawm ether sab saw hlau. Qee cov chaw tsim khoom kuj feem ntau siv cov feem pua ntawm cov pawg etherification sib txawv (xws li -OCH3 lossis -OC2H4OH) los sawv cev rau qib kev hloov pauv thiab qib es tsis txhob siv DS thiab MS tus nqi. Cov feem pua ntawm txhua pawg thiab nws tus nqi DS lossis MS tuaj yeem hloov pauv los ntawm kev suav yooj yim.
Feem ntau cov cellulose ethers yog cov polymers uas yaj tau hauv dej, thiab qee qhov kuj yaj tau ib nrab hauv cov organic solvents. Cellulose ether muaj cov yam ntxwv ntawm kev ua haujlwm siab, tus nqi qis, kev ua haujlwm yooj yim, kev lom tsawg thiab ntau yam, thiab qhov kev thov thiab daim ntawv thov tseem nthuav dav. Ua tus neeg sawv cev pabcuam, cellulose ether muaj peev xwm siv tau zoo hauv ntau qhov chaw ntawm kev lag luam. tuaj yeem tau txais los ntawm MS / DS.
Cellulose ethers raug faib ua pawg raws li cov qauv tshuaj ntawm cov khoom hloov pauv mus rau hauv anionic, cationic thiab nonionic ethers. Nonionic ethers tuaj yeem faib ua cov khoom yaj hauv dej thiab cov khoom yaj hauv roj.
Cov khoom lag luam uas tau raug tsim kho tshiab tau teev nyob rau sab saud ntawm Rooj 1. Sab qis ntawm Rooj 1 teev qee pawg etherification paub, uas tseem tsis tau dhau los ua cov khoom lag luam tseem ceeb.
Qhov kev txiav txim luv ntawm cov sib xyaw ether substituents tuaj yeem raug hu ua raws li cov ntawv sau lossis qib ntawm DS (MS), piv txwv li, rau 2-hydroxyethyl methylcellulose, qhov kev txiav txim luv yog HEMC, thiab nws kuj tseem tuaj yeem sau ua MHEC los qhia txog methyl substituent.
Cov hydroxyl pawg ntawm cellulose tsis yooj yim nkag mus los ntawm cov neeg sawv cev etherification, thiab cov txheej txheem etherification feem ntau yog ua tiav hauv qab alkaline, feem ntau siv qee qhov concentration ntawm NaOH aqueous kua. Lub cellulose yog thawj tsim rau hauv alkali cellulose o nrog NaOH aqueous kua, thiab tom qab ntawd dhau los ntawm etherification tshuaj tiv thaiv nrog etherification tus neeg sawv cev. Thaum lub sijhawm tsim khoom thiab npaj cov ethers sib xyaw, ntau hom etherification tus neeg sawv cev yuav tsum tau siv tib lub sijhawm, lossis etherification yuav tsum tau ua tiav ib kauj ruam zuj zus los ntawm kev pub mis tsis tu ncua (yog tias tsim nyog). Muaj plaub hom tshuaj tiv thaiv hauv etherification ntawm cellulose, uas tau sau los ntawm cov mis tshuaj tiv thaiv (cellulosic hloov los ntawm Cell-OH) raws li hauv qab no:
Kab zauv (1) piav qhia txog Williamson etherification reaction. RX yog ib qho inorganic acid ester, thiab X yog halogen Br, Cl lossis sulfuric acid ester. Chloride R-Cl feem ntau yog siv hauv kev lag luam, piv txwv li, methyl chloride, ethyl chloride lossis chloroacetic acid. Ib qho stoichiometric ntawm lub hauv paus yog noj nyob rau hauv cov tshuaj tiv thaiv zoo li no. Cov khoom lag luam cellulose ether methyl cellulose, ethyl cellulose thiab carboxymethyl cellulose yog cov khoom ntawm Williamson etherification reaction.
Cov mis tshuaj tiv thaiv (2) yog qhov kev sib ntxiv ntawm cov epoxides uas ua rau lub hauv paus (xws li R = H, CH3, lossis C2H5) thiab cov pab pawg hydroxyl ntawm cov cellulose molecules yam tsis tau noj cov hauv paus. Qhov kev sib xyaw no yuav txuas ntxiv mus raws li cov pab pawg hydroxyl tshiab tau tsim thaum lub sijhawm sib xyaw, ua rau muaj cov saw hlau oligoalkylethylene oxide: Ib qho kev sib xyaw zoo sib xws nrog 1-aziridine (aziridine) yuav tsim cov aminoethyl ether: Cell-O-CH2-CH2-NH2. Cov khoom xws li hydroxyethyl cellulose, hydroxypropyl cellulose thiab hydroxybutyl cellulose yog txhua yam khoom ntawm cov epoxidation uas ua rau lub hauv paus.
Cov qauv tshuaj tiv thaiv (3) yog qhov tshuaj tiv thaiv ntawm Cell-OH thiab cov organic compounds uas muaj cov active ob chav bonds hauv alkaline medium, Y yog ib pawg electron-withdrawal, xws li CN, CONH2, lossis SO3-Na+. Niaj hnub no hom tshuaj tiv thaiv no tsis tshua siv hauv kev lag luam.
Cov mis tshuaj tiv thaiv (4), etherification nrog diazoalkane tseem tsis tau muaj kev lag luam.
- Hom cellulose ethers
Cellulose ether tuaj yeem yog monoether lossis sib xyaw ether, thiab nws cov khoom sib txawv. Muaj cov pab pawg hydrophilic qis-hloov pauv ntawm cellulose macromolecule, xws li hydroxyethyl pawg, uas tuaj yeem muab cov khoom nrog qee qib ntawm kev yaj dej, thaum rau cov pab pawg hydrophobic, xws li methyl, ethyl, thiab lwm yam, tsuas yog nruab nrab hloov pauv qib siab tuaj yeem muab cov khoom qee qhov kev yaj dej, thiab cov khoom qis-hloov pauv tsuas yog swells hauv dej lossis tuaj yeem yaj hauv cov kua alkali dilute. Nrog rau kev tshawb fawb tob txog cov khoom ntawm cellulose ethers, cov cellulose ethers tshiab thiab lawv cov teb thov yuav raug tsim kho thiab tsim tawm tas li, thiab lub zog tsav tsheb loj tshaj plaws yog kev lag luam dav thiab txuas ntxiv kho kom zoo.
Txoj cai dav dav ntawm kev cuam tshuam ntawm cov pab pawg hauv cov ethers sib xyaw rau cov khoom solubility yog:
1) Ua kom cov ntsiab lus ntawm cov pab pawg hydrophobic hauv cov khoom kom nce qhov hydrophobicity ntawm ether thiab txo qhov gel point;
2) Ua kom cov ntsiab lus ntawm cov pab pawg hydrophilic (xws li cov pab pawg hydroxyethyl) nce nws cov gel point;
3) Pawg hydroxypropyl yog qhov tshwj xeeb, thiab hydroxypropylation kom raug tuaj yeem txo qhov kub ntawm cov khoom, thiab qhov kub ntawm cov khoom nruab nrab hydroxypropylated yuav nce dua, tab sis qib siab ntawm kev hloov pauv yuav txo nws cov ntsiab lus gel; Qhov laj thawj yog vim muaj cov qauv tshwj xeeb ntawm cov saw hlau carbon ntawm pawg hydroxypropyl, qib qis hydroxypropylation, cov hydrogen bonds tsis muaj zog hauv thiab ntawm cov molecules hauv cellulose macromolecule, thiab hydrophilic hydroxyl pawg ntawm cov saw ceg. Dej yog qhov tseem ceeb. Ntawm qhov tod tes, yog tias qhov kev hloov pauv siab, yuav muaj polymerization ntawm pawg sab, cov ntsiab lus sib piv ntawm pawg hydroxyl yuav txo qis, hydrophobicity yuav nce ntxiv, thiab solubility yuav txo qis.
Kev tsim khoom thiab kev tshawb fawb ntawmcellulose ethermuaj keeb kwm ntev. Xyoo 1905, Suida thawj zaug tshaj tawm txog kev sib xyaw ntawm cellulose, uas tau methylated nrog dimethyl sulfate. Cov cellulose ethers uas tsis yog ionic tau txais patent los ntawm Lilienfeld (1912), Dreyfus (1914) thiab Leuchs (1920) rau cov cellulose ethers uas yaj tau hauv dej lossis roj uas yaj tau hauv dej, raws li. Buchler thiab Gomberg tau tsim benzyl cellulose xyoo 1921, carboxymethyl cellulose tau tsim thawj zaug los ntawm Jansen xyoo 1918, thiab Hubert tau tsim hydroxyethyl cellulose xyoo 1920. Thaum ntxov xyoo 1920, carboxymethylcellulose tau muag hauv lub teb chaws Yelemees. Txij xyoo 1937 txog 1938, kev tsim khoom lag luam ntawm MC thiab HEC tau pom tseeb hauv Tebchaws Meskas. Sweden tau pib tsim cov dej-soluble EHEC xyoo 1945. Tom qab xyoo 1945, kev tsim cov cellulose ether tau nthuav dav sai hauv Western Europe, Tebchaws Meskas thiab Nyiv. Thaum kawg ntawm xyoo 1957, Tuam Tshoj CMC tau muab tso rau hauv kev tsim khoom thawj zaug hauv Shanghai Celluloid Factory. Los ntawm xyoo 2004, kuv lub teb chaws lub peev xwm tsim khoom yuav yog 30,000 tons ntawm ionic ether thiab 10,000 tons ntawm non-ionic ether. Los ntawm xyoo 2007, nws yuav ncav cuag 100,000 tons ntawm ionic ether thiab 40,000 tons ntawm Nonionic ether. Cov tuam txhab sib koom ua ke hauv tsev thiab txawv teb chaws kuj tseem niaj hnub tshwm sim, thiab Tuam Tshoj lub peev xwm tsim khoom cellulose ether thiab qib kev txawj ntse tau txhim kho tas li.
Nyob rau hauv xyoo tas los no, ntau cellulose monoethers thiab mixed ethers nrog cov nqi DS sib txawv, viscosities, purity thiab rheological zog tau tsim kho tas li. Tam sim no, qhov tseem ceeb ntawm kev txhim kho hauv thaj teb ntawm cellulose ethers yog los txais yuav cov thev naus laus zis tsim khoom siab heev, cov thev naus laus zis npaj tshiab, cov khoom siv tshiab, cov khoom tshiab, cov khoom lag luam tshiab, cov khoom lag luam zoo, thiab cov khoom lag luam systematic yuav tsum tau tshawb fawb txog kev siv tshuab.
Lub sijhawm tshaj tawm: Plaub Hlis-28-2024