Li-derivatives tsa cellulose li hlahisoa ke esterification kapa etherification ea lihlopha tsa hydroxyl ka li-polymer tsa cellulose tse nang le lik'hemik'hale tsa lik'hemik'hale.Ho ea ka litšoaneleho tsa sebopeho sa lihlahisoa tsa karabelo, li-derivatives tsa cellulose li ka aroloa ka mekhahlelo e meraro: cellulose ethers, cellulose esters, le cellulose ether ester.Li-cellulose ester tse hlileng li sebelisoang khoebong ke: cellulose nitrate, cellulose acetate, cellulose acetate butyrate le cellulose xanthate.Li-cellulose ethers li kenyelletsa: methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, cyanoethyl cellulose, hydroxypropyl cellulose le hydroxypropyl methyl cellulose.Ho phaella moo, ho na le lihlahisoa tse tsoakiloeng tsa ester ether.
Thepa le ts'ebeliso Ka khetho ea li-reagents le moralo oa ts'ebetso, sehlahisoa se ka qhibiliha ka metsing, sa hlapolla alkali solution kapa organic solvent, kapa se na le thepa ea thermoplastic, 'me se ka sebelisoa ho etsa likhoele tsa lik'hemik'hale, lifilimi, metheo ea lifilimi, polasetiki, insulating. lisebelisoa, liaparo, slurry, polymeric dispersant, li-additives tsa lijo le lihlahisoa tsa letsatsi le letsatsi tsa lik'hemik'hale.Thepa ea lintho tse nkiloeng ho cellulose e amana le sebopeho sa li-substitute, tekanyo ea DS ea lihlopha tse tharo tsa hydroxyl sehlopheng sa tsoekere e nkeloang sebaka, le ho ajoa ha lintho tse ling ho latela ketane ea macromolecular.Ka lebaka la karabelo e sa fetoheng, ntle le sehlahisoa se fetotsoeng ka mokhoa o ts'oanang ha lihlopha tse tharo tsa hydroxyl li nkeloa sebaka (DS ke 3), maemong a mang (homogeneous reaction kapa heterogeneous reaction), ho fumanoa maemo a mararo a fapaneng a fapaneng: lihlopha tsa glucosyl tse sa nkeloang sebaka: ① monosubstituted (DS ke 1, C, C kapa C boemo bo nkeloa sebaka, foromo ea sebopeho bona selulose);② disubstituted (DS ke 2, C, C, C, C Kapa C, C maemo a nkeloa sebaka);③ Phapang e felletseng (DS ke 3).Ka hona, thepa ea mofuta o tšoanang oa selulose e nang le boleng bo tšoanang ba phapanyetso e kanna ea fapana haholo.Ka mohlala, cellulose diacetate e entsoeng ka ho toba ho DS ea 2 ha e qhibilihe ka har'a acetone, empa cellulose diacetate e fumanoang ka saponification ea cellulose triacetate e feletseng e ka qhibiliha ka ho feletseng ka acetone.Ena heterogeneity of substitution e amana le melao ea motheo ea cellulose ester le etherification reactions.
Molao oa motheo oa cellulose esterification le etherification reaction ka molek'hule ea cellulose, maemo a lihlopha tse tharo tsa hydroxyl sehlopheng sa tsoekere a fapane, le tšusumetso ea li-substituent tse haufi le tšitiso ea steric le tsona li fapane.Asiti e lekanyelitsoeng le tekanyo ea ho arohana ha lihlopha tse tharo tsa hydroxyl ke: C>C>C.Ha karabelo ea etherification e etsoa ka mokhoa oa alkaline, sehlopha sa C hydroxyl se arabela pele, ebe sehlopha sa C hydroxyl, 'me qetellong sehlopha sa C primary hydroxyl.Ha karabelo ea esterification e etsoa ka mokhoa o nang le asiti, bothata ba karabelo ea sehlopha ka seng sa hydroxyl bo fapane le taelo ea karabelo ea etherification.Ha o sebetsana le "bulky substitution reagent", "steric block" e na le ts'usumetso ea bohlokoa, 'me sehlopha sa C hydroxyl se nang le tšitiso e nyane ea steric ho bonolo ho arabela ho feta lihlopha tsa C le C hydroxyl.
Cellulose ke polymer ea tlhaho ea crystalline.Bongata ba karabelo ea esterification le etherification ke karabelo e fapaneng ha selulose e lula e tiile.Boemo ba ho hasana ha li-reagents tsa karabelo ka har'a fiber ea cellulose bo bitsoa ho fihlella.Tokisetso ea li-intermolecular ea sebaka sa crystalline e hlophisitsoe ka thata, 'me reagent e ka hasana feela holim'a kristale.Tokisetso ea li-intermolecular sebakeng sa amorphous e hlephile, 'me ho na le lihlopha tsa mahala tsa hydroxyl tse bonolo ho kopana le li-reagents, tse nang le phihlello e phahameng le karabelo e bonolo.Ka kakaretso, lisebelisoa tse tala tse nang le crystallinity e phahameng le boholo bo boholo ba kristale ha li bonolo ho itšoara joaloka lisebelisoa tse tala tse nang le kristale e tlaase le boholo bo bonyenyane ba kristale.Empa sena ha se 'nete ka ho feletseng, ka mohlala, tekanyo ea acetylation ea likhoele tse omeletseng tsa viscose tse nang le crystallinity e tlaase le crystallinity e nyenyane e tlaase haholo ho feta ea fiber ea k'hothone e nang le crystallinity e phahameng le crystallinity e khōloanyane.Lebaka ke hore lintlha tse ling tsa hydrogen bonding li hlahisoa lipakeng tsa li-polymers tse haufi nakong ea ts'ebetso ea ho omisa, e thibelang ho ata ha li-reagents.Haeba mongobo o ka har'a selulose se metsi se tala se nkeloa sebaka ke motsoako o moholo oa organic (joalo ka acetic acid, benzene, pyridine) ebe o omisitsoe, ts'ebetso ea ona e tla ntlafala haholo, hobane ho omisa ho ke ke ha leleka solvent ka botlalo, 'me tse ling. limolek'hule li qabeletsoe ka har'a "likoti" tsa thepa e tala ea cellulose, ho etsa seo ho thoeng ke selulose.Sebaka se ekelitsoeng ke ho ruruha ha se bonolo ho hlaphoheloa, e leng se loketseng ho hasana ha li-reagents, 'me se khothalletsa sekhahla sa karabelo le ho tšoana ha karabelo.Ka lebaka lena, ts'ebetsong ea tlhahiso ea li-derivatives tse fapaneng tsa cellulose, ho tlameha ho ba le phekolo e lumellanang ea ho ruruha.Hangata metsi, asiti kapa motsoako o itseng oa tharollo ea alkali e sebelisoa e le moemeli oa ho ruruha.Ho phaella moo, bothata ba ho itšoara ha lik'hemik'hale tsa makhasi a qhibilihang ka lipontšo tse tšoanang tsa 'mele le tsa lik'hemik'hale hangata li fapane haholo, tse bakoang ke lintlha tsa morphological tsa mefuta e sa tšoaneng ea limela kapa lisele tse nang le mesebetsi e fapaneng ea lik'hemik'hale le ea sebopeho semeleng se le seng.ea.Lerako le ka sehloohong la lera le ka ntle la fiber ea limela le sitisa ho kenella ha li-reagents le ho thibela lik'hemik'hale tsa lik'hemik'hale, kahoo hangata hoa hlokahala ho sebelisa maemo a lumellanang le ts'ebetso ea pulping ho senya lerako le ka sehloohong e le hore u fumane pulp e qhibilihisang ka ho sebetsa hantle.Mohlala, makhasi a bagasse ke thepa e tala e nang le ts'ebetso e mpe ea tlhahiso ea viscose pulp.Ha u lokisetsa viscose (selulose xanthate alkali tharollo), carbon disulfide e ngata e jeoa ho feta makhasi a k'hothone le makhasi a lehong.Sekhahla sa ho sefa se tlase ho feta sa viscose se lokiselitsoeng ka li-pulps tse ling.Sena se bakoa ke hore lerako le ka sehloohong la lisele tsa 'moba ha lea senyeha hantle nakong ea ho phunya le ho lokisoa ha selulose ea alkali ka mekhoa e tloaelehileng, e leng se bakang bothata ba ho arabela ha mosehla.
Pele ho hydrolyzed alkaline bagasse pulp fibers] le Figure 2 [bagasse pulp fibers after alkali impregnation] ke electron microscope scanning images of the surface of bagasse pulp fibers after pre-hydrolyzed alkaline process and common alkaline impregnation ka tatellano, ea pele e ntse e ka bonoa likoti tse hlakileng;qetellong, le hoja likoti li nyamela ka lebaka la ho ruruha ha tharollo ea alkali, lerako le ka sehloohong le ntse le koahela fiber eohle.Haeba "imregnation ea bobeli" (ho kenngoe ka tloaelo ho lateloa ke ho kenngoa ha bobeli ka tharollo ea alkali e hlapollang e nang le phello e kholo ea ho ruruha) kapa ho sila (ho kenngoa ka mokhoa o tloaelehileng ho kopantsoe le ho sila ka mechine), ts'ebetso ea yellowing e ka tsoela pele hantle, tekanyo ea filtration ea viscose. e ntlafalitsoe haholo.Lebaka ke hore mekhoa e 'meli e ka holimo e ka senya lerako le ka sehloohong, e pepesa lera le ka hare la karabelo e batlang e le bonolo, e leng se loketseng ho kenella ha li-reagents le ho ntlafatsa ts'ebetso ea ts'ebetso (setšoan. ], Fig. Ho sila Bagasse Pulp Fibers]).
Lilemong tsa morao tjena, ho hlahile lisebelisoa tse se nang metsi tse ka qhalang selulose ka ho toba.Tse kang dimethylformamide le NO, dimethyl sulfoxide le paraformaldehyde, le li-solvents tse ling tse tsoakiloeng, joalo-joalo, li nolofalletsa cellulose hore e be le karabelo e tšoanang.Leha ho le joalo, e meng ea melao e boletsoeng ka holimo ea maikutlo a ka ntle ho mokhahlelo ha e sa sebetsa.Mohlala, ha ho etsoa selulose diacetate e qhibilihang ka har'a acetone, ha ho hlokahale hore ho etsoe hydrolysis ea cellulose triacetate, empa e ka esterified ka kotloloho ho fihlela DS e le 2.
Nako ea poso: Feb-27-2023