Cellulose derivatives inogadzirwa ne esterification kana etherification ye hydroxyl mapoka mu cellulose polymers ane makemikari reagents.Zvinoenderana nehunhu hwemagadzirirwo ezvigadzirwa, zvinobuda mu cellulose zvinogona kupatsanurwa muzvikamu zvitatu: cellulose ethers, cellulose esters, uye cellulose ether esters.Ma cellulose esters anonyanya kushandiswa pakutengeserana ndeaya: cellulose nitrate, cellulose acetate, cellulose acetate butyrate uye cellulose xanthate.Cellulose ethers zvinosanganisira: methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, cyanoethyl cellulose, hydroxypropyl cellulose uye hydroxypropyl methyl cellulose.Mukuwedzera, kune ester ether yakasanganiswa yakabva.
Zvivakwa uye mashandisirwo Kuburikidza nesarudzo yekutsiva reagents uye dhizaini dhizaini, chigadzirwa chinogona kunyungudutswa mumvura, dilute alkali solution kana organic solvent, kana kuve ne thermoplastic properties, uye inogona kushandiswa kugadzira kemikari fiber, mafirimu, mabhesi emafirimu, mapurasitiki, insulating. zvinhu, machira, slurry, polymeric dispersant, zvokudya zvinowedzera uye zuva nezuva zvigadzirwa zvemakemikari.Izvo zvinhu zve cellulose zvinobva kune zvinoenderana nehunhu hwezvinotsiva, dhigirii DS yemapoka matatu ehydroxyl paboka reglucose inotsiviwa, uye kugoverwa kwezvinotsiva pamwe neketani ye macromolecular.Nekuda kwekusarongeka kwekuita, kunze kwechigadzirwa chakatsiviwa chakafanana kana mapoka matatu ehydroxyl akatsiviwa (DS iri 3), mune dzimwe nguva (homogeneous reaction kana heterogeneous reaction), zvinotevera zvinzvimbo zvitatu zvakasiyana zvinowanikwa: Zvigadzirwa zvakasanganiswa ne asina kutsiva glucosyl mapoka: ① monosubstituted (DS is 1, C, C kana C chinzvimbo chinotsiviwa, structural formula ona cellulose);② yakabviswa (DS iri 2, C, C, C, C Kana C, C nzvimbo dzinotsiviwa);③ kutsiva kuzere (DS iri 3).Naizvozvo, zvimiro zveiyo yakafanana cellulose derivative ine imwechete yekutsiva kukosha inogona zvakare kuve yakasiyana.Semuenzaniso, cellulose diacetate yakananga esterified kuDS ye2 haina kunyungudika muacetone, asi cellulose diacetate inowanikwa ne saponification ye esterified yakazara cellulose triacetate inogona kunyungudika zvachose muacetone.Iyi heterogeneity yekutsiva ine chekuita nemirairo yekutanga ye cellulose ester uye etherification maitiro.
Mutemo wekutanga we cellulose esterification uye etherification reaction mu cellulose molecule, zvinzvimbo zvemapoka matatu ehydroxyl muboka reglucose zvakasiyana, uye pesvedzero yezvitsigiro zviri pedyo uye steric hindrance zvakasiyanawo.Huwandu hweasidhi uye dhigirii rekuparadzaniswa kwemapoka matatu ehydroxyl ndeiyi: C>C>C.Kana iyo etherification reaction ikaitwa mune alkaline svikiro, boka reC hydroxyl rinotanga kuita, kozoti C hydroxyl boka, uye pakupedzisira reC primary hydroxyl boka.Kana iyo esterification reaction ikaitwa mune acidic medium, kuoma kwekuita kweboka rega rega rehydroxyl kunopesana nehurongwa hwe etherification reaction.Paunenge uchiita ne bulky substitution reagent, steric hindrance effect ine simba rinokosha, uye boka reC hydroxyl rine diki steric hindrance effect iri nyore kuita kupfuura mapoka eC neC hydroxyl.
Cellulose icrystalline natural polymer.Mazhinji esterification uye etherification maitiro ane heterogeneous maitiro kana cellulose ikaramba yakasimba.Iyo yekupararira mamiriro ekuita reagents mu cellulose fiber inonzi kusvikika.Iyo intermolecular kurongeka kweiyo crystalline dunhu yakanyatso kurongeka, uye iyo reagent inogona kungopararira kune iyo crystalline pamusoro.Iyo intermolecular kurongeka munharaunda yeamorphous yakasununguka, uye kune akawanda emahara hydroxyl mapoka ari nyore kuonana nemareagents, ane yakakwirira kuwanikwa uye nyore kuita.Kazhinji, zvigadzirwa zvine crystallinity yakakura uye saizi hombe yekristaro haisi nyore kuita seyakagadzirwa zvinhu zvine yakaderera crystallinity uye saizi diki yekristaro.Asi izvi hazvisi zvechokwadi zvachose, semuenzaniso, iyo acetylation rate yeakaomeswa viscose fibers ine yakaderera crystallinity uye madiki crystallinity yakaderera zvakanyanya kupfuura iyo yekotoni fiber ine yakakwirira crystallinity uye yakakura crystallinity.Izvi zvinodaro nekuti mamwe ma hydrogen bonding point anogadzirwa pakati pemapolymer ari padyo panguva yekuomesa, izvo zvinotadzisa kupararira kwemareagents.Kana hunyoro huri mune wet cellulose raw material yakatsiviwa neyakakura organic solvent (yakadai seacetic acid, benzene, pyridine) yobva yaomeswa, reactivity yayo inovandudzwa zvakanyanya, nekuti kuomesa hakugone kudzinga zvachose solvent, uye zvimwe. mamorekuru akavharirwa mu "maburi" e cellulose mbishi zvinhu, achigadzira iyo inonzi ine cellulose.Kureba kwakawedzerwa nekuzvimba hakusi nyore kupora, izvo zvinoita kuti pave nekupararira kwemareagents, uye inosimudzira chiyero chekuita uye kufanana kwekuita.Nechikonzero ichi, mukugadzirwa kweakasiyana cellulose derivatives, panofanirwa kuve nekuenderana kuzvimba kurapwa.Kazhinji mvura, asidhi kana imwe fungidziro yealkali solution inoshandiswa seyakazvimba.Mukuwedzera, kuoma kwekuita kwemakemikari ekunyunguduka kwepulp ine zviratidzo zvakafanana zvemuviri uye kemikari zvinowanzosiyana zvakanyanya, izvo zvinokonzerwa nemaitiro emhando yemhando dzakasiyana dzemiti kana masero ane maitiro akasiyana-siyana ehupenyu uye maitiro mumiti imwe chete.ye.Rusvingo rwekutanga rwekunze kweiyo fiber fiber inotadzisa kupinda kwemareagents uye kudzoreredza kuita kwemakemikari, saka kazhinji zvinodikanwa kushandisa mamiriro anoenderana mukuita pulping kuti uparadze madziro ekutanga kuitira kuti uwane kunyungudika pulp nekuita zvirinani.Semuenzaniso, bagasse pulp chinhu chakasvibirira chine hurombo reactivity mukugadzira viscose pulp.Paunenge uchigadzira viscose (cellulose xanthate alkali solution), yakawanda kabhoni disulfide inopedzwa kupfuura donje linter pulp uye huni pulp.Iyo filtration rate yakaderera pane ye viscose yakagadzirirwa nemamwe mapulp.Izvi zvinodaro nekuti madziro ekutanga enzimbe fiber masero haana kukuvara zvakanaka panguva yekukweva uye kugadzirwa kwealkali cellulose nenzira dzakajairika, zvichikonzera kuomerwa kweyero.
Pre-hydrolyzed alkaline bagasse pulp fibers] uye Figure 2 [bagasse pulp fibers after alkali impregnation] maelectronic microscope scanning mifananidzo yepamusoro pebagasse pulp fibers mushure me pre-hydrolyzed alkaline process uye yakajairwa alkaline impregnation zvichiteerana, yekutanga inogona kuonekwa makomba akajeka;mune yekupedzisira, kunyangwe makomba anonyangarika nekuda kwekuzvimba kwealkali solution, madziro ekutanga achiri kuvhara iyo fiber yese.Kana iyo "yechipiri impregnation" (yakajairika impregnation inoteverwa neyechipiri impregnation ine dilute alkali solution ine yakakura kuzvimba maitiro) kana dip-grinding (yakajairika impregnation yakasanganiswa ne mechanical grinding) process, iyo yellowing reaction inogona kuenderera zvakanaka, iyo viscose filtration rate. inovandudzwa zvakanyanya.Izvi ndezvokuti nzira mbiri dziri pamusoro apa dzinogona kubvisa rusvingo rwekutanga, kuratidza mukati memukati wekuita nyore nyore, iyo inobatsira kupinda mukati me reagents uye inovandudza maitiro ekuita (Fig. 3 [secondary impregnation ye bagasse pulp fiber. ], Fig. Kukuya Bagasse Pulp Fibers]).
Mumakore achangopfuura, asiri-aqueous solvent masisitimu anogona kunyungudutsa cellulose akabuda.Zvakadai se dimethylformamide uye NO, dimethyl sulfoxide uye paraformaldehyde, uye zvimwe zvakasanganiswa zvinonyungudutsa, nezvimwewo, zvinoita kuti cellulose iite homogeneous reaction.Zvakadaro, mimwe yemitemo yataurwa pamusoro apa yekubuda kwechikamu hachichashandi.Semuenzaniso, kana uchigadzira cellulose diacetate soluble muacetone, hazvifanirwe kuita hydrolysis ye cellulose triacetate, asi inogona kuve yakananga esterified kusvika DS iri 2.
Nguva yekutumira: Feb-27-2023