Ana samar da abubuwan da suka samo asali na cellulose ta hanyar esterification ko etherification na ƙungiyoyin hydroxyl a cikin polymers cellulose tare da sinadaran reagents. Dangane da sifofi na samfurin amsawa, ana iya raba abubuwan da suka samo asali na cellulose zuwa kashi uku: ethers cellulose, esters cellulose, da esters cellulose. Esters cellulose da ake amfani da su a zahiri na kasuwanci sune: cellulose nitrate, cellulose acetate, cellulose acetate butyrate da cellulose xanthate. Cellulose ethers sun hada da: methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, cyanoethyl cellulose, hydroxypropyl cellulose da hydroxypropyl methyl cellulose. Bugu da ƙari, akwai nau'ikan ester ether gauraye.
Kayayyaki da amfani Ta hanyar zaɓin masu maye gurbin reagents da ƙirar tsari, ana iya narkar da samfurin a cikin ruwa, maganin alkali mai narkewa ko sauran kaushi, ko kuma suna da kaddarorin thermoplastic, kuma ana iya amfani da su don kera sinadarai na zaruruwa, fina-finai, sansanonin fim, robobi, insulating. kayan, rufi, slurry, polymeric dispersant, abinci Additives da kullum sinadaran kayayyakin. Abubuwan da aka samo asali na cellulose suna da alaƙa da yanayin masu maye gurbin, matakin DS na ƙungiyoyin hydroxyl guda uku a kan rukunin glucose ana maye gurbinsu, da rarraba abubuwan maye tare da sarkar macromolecular. Saboda bazuwar amsawar, ban da samfurin da aka musanya daidai lokacin da aka maye gurbin duk ƙungiyoyin hydroxyl guda uku (DS shine 3), a wasu lokuta (haɗin kai ko haɓakawa daban-daban), ana samun waɗannan wurare daban-daban na musanya guda uku: samfuran gauraye tare da Ƙungiyoyin glucosyl da ba a maye gurbinsu ba: ① monosubstituted (DS shine 1, C, C ko matsayi C an maye gurbinsa, tsarin tsarin duba cellulose); ② an canza (DS shine 2, C, C, C, C Ko C, an maye gurbin matsayi na C); ③ cikakken maye (DS shine 3). Saboda haka, kaddarorin na asali na cellulose iri ɗaya tare da ƙimar canji iri ɗaya na iya bambanta sosai. Alal misali, cellulose diacetate kai tsaye esterified zuwa DS na 2 ne insoluble a acetone, amma cellulose diacetate samu ta saponification na cikakken esterified cellulose triacetate za a iya gaba daya narkar da a acetone. Wannan nau'in maye gurbin yana da alaƙa da ainihin ka'idodin ester cellulose da halayen etherification.
Asalin ka'idar esterification cellulose da amsawar etherification a cikin kwayoyin cellulose, matsayi na ƙungiyoyin hydroxyl guda uku a cikin rukunin glucose sun bambanta, kuma tasirin abubuwan da ke kusa da su da kuma hanawa mai ƙarfi suma sun bambanta. Dangantakar acidity da matakin rabuwar ƙungiyoyin hydroxyl uku sune: C>C>C. Lokacin da etherification dauki da aka za'ayi a cikin wani alkaline matsakaici, da C hydroxyl kungiyar reacts farko, sa'an nan C hydroxyl kungiyar, kuma a karshe C primary hydroxyl kungiyar. Lokacin da esterification dauki da za'ayi a cikin wani acidic matsakaici, da wuya na dauki kowane hydroxyl kungiyar ne akasin da oda na etherification dauki. Lokacin da ake amsawa tare da reagent mai ƙaƙƙarfan maye gurbin, tasirin hanawa mai ƙarfi yana da tasiri mai mahimmanci, kuma ƙungiyar C hydroxyl tare da ƙaramin tasirin hanawa ya fi sauƙi don amsawa fiye da ƙungiyoyin C da C hydroxyl.
Cellulose shine polymer na halitta crystalline. Yawancin esterification da etherification halayen halayen iri-iri ne lokacin da cellulose ya kasance mai ƙarfi. Yanayin yaduwa na reagents a cikin fiber cellulose ana kiransa isarwa. Tsarin intermolecular na yankin crystalline an tsara shi sosai, kuma reagent na iya yaduwa kawai zuwa saman crystalline. Tsarin intermolecular a cikin yankin amorphous yana kwance, kuma akwai ƙarin ƙungiyoyin hydroxyl kyauta waɗanda ke da sauƙin tuntuɓar masu reagents, tare da samun dama da sauƙi. Gabaɗaya, albarkatun ƙasa tare da babban kristal da babban girman kristal ba su da sauƙin amsawa azaman albarkatun ƙasa tare da ƙarancin crystallinity da ƙananan girman crystal. Amma wannan ba gaskiya bane gaba ɗaya, alal misali, ƙimar acetylation na busassun filaye na viscose tare da ƙananan crystallinity da ƙaramin crystallinity yana da ƙasa da ƙasa fiye da na fiber na auduga tare da crystallinity mafi girma da kristal mafi girma. Wannan shi ne saboda wasu wuraren haɗin gwiwar hydrogen suna haifar da su tsakanin polymers masu kusa yayin aikin bushewa, wanda ke hana yaduwar reagents. Idan danshi a cikin rigar cellulose ya maye gurbinsa da wani kaushi mai girma (irin su acetic acid, benzene, pyridine) sannan kuma ya bushe, za a inganta aikin sa sosai, saboda bushewa ba zai iya fitar da sauran ƙarfi gaba ɗaya ba, wasu kuma mafi girma. kwayoyin sun makale a cikin "ramukan" na albarkatun cellulose, suna samar da abin da ake kira cellulose. Nisa da aka haɓaka ta hanyar kumburi ba shi da sauƙi a dawo da shi, wanda ke ba da gudummawa ga watsawar reagents, kuma yana haɓaka ƙimar amsawa da daidaituwar halayen. Saboda wannan dalili, a cikin tsarin samar da nau'o'in cellulose daban-daban, dole ne a sami maganin kumburi daidai. Yawancin lokaci ana amfani da ruwa, acid ko wani yanki na maganin alkali azaman wakili mai kumburi. Bugu da kari, wahalar da sinadaran da ke narkar da ɓangaren litattafan almara tare da alamomi iri ɗaya na zahiri da sinadarai sau da yawa yakan bambanta sosai, wanda ke haifar da yanayin yanayin halittar nau'ikan tsire-tsire ko sel daban-daban waɗanda ke da ayyuka daban-daban na biochemical da tsarin tsarin a cikin shuka iri ɗaya. na. Babban bangon bangon waje na fiber na shuka yana hana shigar da reagents kuma yana hana halayen sinadarai, don haka yawanci ya zama dole a yi amfani da yanayin da ya dace a cikin tsarin pulping don lalata bangon farko don samun narkewar ɓangaren litattafan almara tare da mafi kyawun amsawa. Misali, ɓangaren litattafan almara na bagasse wani ɗanyen abu ne tare da ƙarancin amsawa a cikin samar da ɓangaren litattafan almara. Lokacin shirya viscose (cellulose xanthate alkali bayani), ƙarin carbon disulfide yana cinyewa fiye da ɓangaren litattafan almara na auduga da ɓangaren litattafan almara. Adadin tacewa yayi ƙasa da na viscose da aka shirya tare da sauran ɓangarorin. Wannan shi ne saboda bangon farko na ƙwayoyin fiber na sukari ba a lalacewa yadda ya kamata a lokacin ɗigon ruwa da kuma shirye-shiryen alkali cellulose ta hanyoyin al'ada, yana haifar da wahala a cikin halayen rawaya.
Pre-hydrolyzed alkaline bagasse ɓangaren litattafan almara fibers] da Hoto 2 [bagasse ɓangaren litattafan almara zaruruwa bayan alkali impregnation] su ne electron microscope scanning images na saman bagasse ɓangaren litattafan almara zaruruwa bayan pre-hydrolyzed alkaline tsari da na al'ada alkaline impregnation bi da bi, tsohon za a iya gani zuwa ga. bayyanannun ramuka; a karshen, duk da cewa ramukan bace saboda kumburin maganin alkali, bangon farko yana rufe dukkan fiber. Idan "na biyu impregnation" ( talakawa impregnation bi ta biyu impregnation tare da tsarma alkali bayani tare da babban kumburi sakamako ) ko tsoma-nika (na kowa impregnation hade da inji nika) tsari, da yellowing dauki iya ci gaba smoothly, da viscose tace kudi an inganta sosai. Wannan shi ne saboda duka hanyoyin biyu na sama na iya kwasfa bangon farko, suna fallasa sashin ciki na yanayin sauƙi mai sauƙi, wanda ke ba da gudummawa ga shigar da reagents kuma yana haɓaka aikin amsawa (Fig. 3 [na biyu impregnation na bagasse ɓangaren litattafan almara fiber fiber bagasse. ], Hoton Niƙa Bagasse Pulp Fibers]).
A cikin 'yan shekarun nan, tsarin narkewa mara ruwa wanda zai iya narkar da cellulose kai tsaye ya bayyana. Irin su dimethylformamide da NO, dimethyl sulfoxide da paraformaldehyde, da sauran gauraye kaushi, da dai sauransu, taimaka cellulose sha wani iri-iri dauki. Duk da haka, wasu daga cikin dokokin da aka ambata a sama na halayen da ba su yi aiki ba sun daina aiki. Alal misali, lokacin shirya cellulose diacetate mai narkewa a cikin acetone, ba lallai ba ne a sha hydrolysis na cellulose triacetate, amma za a iya kai tsaye esterified har DS ne 2.
Lokacin aikawa: Fabrairu-27-2023