Ma cellulose amapangidwa ndi esterification kapena etherification yamagulu a hydroxyl mu ma polima a cellulose okhala ndi mankhwala opangira mankhwala.Malinga ndi mawonekedwe a zinthu zomwe zimapangidwira, zotumphukira za cellulose zitha kugawidwa m'magulu atatu: ma cellulose ethers, cellulose esters, ndi cellulose ether esters.Ma cellulose esters omwe amagwiritsidwa ntchito pamalonda ndi awa: cellulose nitrate, cellulose acetate, cellulose acetate butyrate ndi cellulose xanthate.Ma cellulose ethers akuphatikizapo: methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, cyanoethyl cellulose, hydroxypropyl cellulose ndi hydroxypropyl methyl cellulose.Kuphatikiza apo, palinso ester ether yosakanikirana yochokera.
Katundu ndi ntchito Kudzera posankha ma reagents olowa m'malo ndi kapangidwe kazinthu, mankhwalawa amatha kusungunuka m'madzi, kusungunula alkali solution kapena organic solvent, kapena kukhala ndi thermoplastic properties, ndipo atha kugwiritsidwa ntchito popanga ulusi wamankhwala, mafilimu, zoyambira zamafilimu, mapulasitiki, zotetezera. zipangizo, zokutira, slurry, polymeric dispersant, zowonjezera chakudya ndi tsiku mankhwala mankhwala.Makhalidwe a zotumphukira za cellulose zimagwirizana ndi chikhalidwe cha zolowa m'malo, digiri ya DS yamagulu atatu a hydroxyl pagulu la glucose omwe amalowetsedwa m'malo, ndi kugawa kwa zolowa m'malo motsatira unyolo wa macromolecular.Chifukwa cha kusakhazikika kwa zomwe zimachitika, kupatula zomwe zidalowetsedwa m'malo mofananirako pomwe magulu atatu a hydroxyl alowe m'malo (DS ndi 3), nthawi zina (machitidwe osakanikirana kapena osakanikirana), magawo atatu otsatirawa amapezedwa: magulu osalowa m'malo a glucosyl: ① monosubstituted (DS ndi 1, C, C kapena C malo amalowetsedwa m'malo, mawonekedwe opangidwa ndi cellulose);② zosinthidwa (DS ndi 2, C, C, C, C kapena C, C malo amalowetsedwa);③ kulowetsa kwathunthu (DS ndi 3).Choncho, katundu wa cellulose yemweyo wotengedwa ndi mtengo wolowa m'malo womwewo angakhalenso wosiyana kwambiri.Mwachitsanzo, cellulose diacetate yopangidwa mwachindunji ku DS ya 2 sisungunuka mu acetone, koma cellulose diacetate yopezedwa ndi saponification ya cellulose triacetate yokhazikika imatha kusungunuka kwathunthu mu acetone.Kusiyanasiyana kwa kusintha kumeneku kumakhudzana ndi malamulo oyambirira a cellulose ester ndi etherification reactions.
Lamulo lofunikira la cellulose esterification ndi etherification reaction mu cellulose molecule, malo a magulu atatu a hydroxyl mu gulu la shuga ndi osiyana, komanso chikoka cha olowa m'malo oyandikana nawo ndi cholepheretsa steric ndizosiyana.Kuchuluka kwa acidity ndi kuchuluka kwa kutha kwa magulu atatu a hydroxyl ndi: C>C>C.Pamene etherification reaction ikuchitika mu alkaline sing'anga, gulu C hydroxyl amachita poyamba, kenako C hydroxyl gulu, ndipo potsiriza C primary hydroxyl gulu.Pamene anachita esterification ikuchitika mu sing'anga acidic, vuto la zimene gulu lililonse hydroxyl ndi zosiyana ndi dongosolo la anachita etherification.Pochita ndi bulky substitution reagent, steric chotchinga mphamvu imakhala ndi chikoka chofunikira, ndipo gulu la C hydroxyl lomwe lili ndi cholepheretsa chaching'ono cholepheretsa ndilosavuta kuchitapo kuposa magulu a C ndi C hydroxyl.
Cellulose ndi crystalline chilengedwe polima.Zambiri mwa esterification ndi etherification zimachitikira mosiyanasiyana pamene mapadi amakhalabe olimba.Kufalikira kwa ma reagents mu cellulose fiber amatchedwa kufikirako.Makonzedwe a intermolecular a dera la crystalline amakonzedwa mwamphamvu, ndipo reagent imatha kufalikira pamtunda wa crystalline.Makonzedwe a intermolecular m'dera la amorphous ndi otayirira, ndipo pali magulu ambiri aulere a hydroxyl omwe ndi osavuta kukhudzana ndi ma reagents, opezeka kwambiri komanso osavuta kuchita.Nthawi zambiri, zida zokhala ndi crystallinity yayikulu komanso kukula kwakukulu kwa kristalo ndizosavuta kuchita ngati zida zokhala ndi kristalo wochepa komanso kukula kwa kristalo kakang'ono.Koma izi sizowona kwathunthu, mwachitsanzo, kuchuluka kwa acetylation kwa ulusi wowuma wa viscose wokhala ndi crystallinity yochepa ndi crystallinity yaying'ono ndi yotsika kwambiri kuposa ya thonje ya thonje yokhala ndi crystallinity yapamwamba ndi crystallinity yaikulu.Izi ndichifukwa choti malo ena omangirira ma haidrojeni amapangidwa pakati pa ma polima oyandikana nawo panthawi yowumitsa, zomwe zimalepheretsa kufalikira kwa ma reagents.Ngati chinyezi mu chonyowa mapadi zopangira m`malo ndi lalikulu organic zosungunulira (monga acetic acid, benzene, pyridine) ndiyeno zouma, reactivity ake adzakhala bwino kwambiri, chifukwa kuyanika sangathe kwathunthu kuthamangitsa zosungunulira, ndi zina zazikulu. mamolekyu amatsekeredwa mu "mabowo" a cellulose yaiwisi, kupanga zomwe zimatchedwa cellulose.Mtunda womwe wakulitsidwa ndi kutupa siwosavuta kuchira, womwe umathandizira kufalikira kwa ma reagents, ndipo umalimbikitsa kuchuluka kwa zomwe zimachitika komanso kufanana kwa zomwe zimachitika.Pachifukwa ichi, popanga zotumphukira zosiyanasiyana za cellulose, payenera kukhala chithandizo chofanana cha kutupa.Nthawi zambiri madzi, asidi kapena ndende ya alkali solution amagwiritsidwa ntchito ngati chotupa.Komanso, vuto la zochita mankhwala a Kutha zamkati ndi yemweyo thupi ndi mankhwala zizindikiro nthawi zambiri zosiyana kwambiri, amene amayamba chifukwa cha morphological zinthu za mitundu yosiyanasiyana ya zomera kapena maselo osiyana biochemical ndi structural ntchito mu chomera chomwecho.za.Khoma lalikulu lakunja kosanjikiza kwa ulusi wa chomera limalepheretsa kulowa kwa ma reagents ndikulepheretsa kusintha kwamankhwala, chifukwa chake ndikofunikira kugwiritsa ntchito mikhalidwe yofananira mu pulping kuwononga khoma loyambirira kuti mupeze zamkati zosungunuka ndi reactivity yabwino.Mwachitsanzo, bagasse zamkati ndi zopangira ndi osauka reactivity kupanga viscose zamkati.Pokonzekera viscose (cellulose xanthate alkali solution), carbon disulfide imadyedwa kuposa zamkati za thonje ndi zamkati zamatabwa.Mlingo wa kusefera ndi wotsika kuposa wa viscose wokonzedwa ndi zamkati zina.Izi zili choncho chifukwa khoma loyambirira la ma cell a nzimbe silinawonongeke bwino panthawi yopukutira komanso kupanga alkali cellulose pogwiritsa ntchito njira zachizoloŵezi, zomwe zimapangitsa kuti chikasu chikhale chovuta.
Ulusi wa alkaline wa pre-hydrolyzed alkaline bagasse zamkati] ndi Chithunzi 2 [zingwe zamkati zamkati pambuyo pa kulowetsedwa kwa alkali] ndi zithunzi za ma electron maikulosikopu zowunikira pamwamba pa ulusi wa zamkati wa bagasse pambuyo pa ndondomeko ya alkaline isanayambe ndi hydrolyzed ndi kuyamwitsa kwamchere motsatana motsatana, zoyambazo zimatha kuwonedwabe. maenje owoneka bwino;potsirizira pake, ngakhale kuti maenje amatha chifukwa cha kutupa kwa njira ya alkali, khoma loyambirira limaphimbabe ulusi wonse.Ngati "kulowetsedwa kwachiwiri" (kulowetsedwa wamba ndikutsatiridwa ndi kulowetsedwa kwachiwiri ndi njira yothetsera alkali ndi kutupa kwakukulu) kapena kuviika-kupera (kulowetsedwa wamba pamodzi ndi makina akupera) ndondomeko, chikasu cha chikasu chikhoza kupitilira bwino, kusefera kwa viscose. ndi bwino kwambiri.Izi ndichifukwa chakuti njira ziwiri zomwe zili pamwambazi zimatha kupukuta khoma loyambirira, ndikuwulula zamkati mwazochita zosavuta, zomwe zimathandizira kulowa kwa ma reagents ndikuwongolera magwiridwe antchito (mkuyu 3 [kuphatikiza kwachiwiri kwa bagasse zamkati CHIKWANGWANI). ], Mkuyu. Kugaya Bagasse Pulp Fibers]).
M'zaka zaposachedwa, zida zosungunulira zopanda madzi zomwe zimatha kusungunula mwachindunji mapadi apezeka.Monga dimethylformamide ndi NO, dimethyl sulfoxide ndi paraformaldehyde, ndi zosungunulira zina zosakanikirana, ndi zina zotero, zimathandiza kuti cellulose igwirizane ndi homogeneous reaction.Komabe, ena mwa malamulo omwe tawatchulawa onena za zochitika zakunja sakugwiranso ntchito.Mwachitsanzo, pokonzekera cellulose diacetate sungunuka mu acetone, sikoyenera kukumana ndi hydrolysis ya cellulose triacetate, koma akhoza esterified mwachindunji mpaka DS ndi 2.
Nthawi yotumiza: Feb-27-2023