Focus on Cellulose ethers

Zeziphi imathiriyeli ekrwada ye-hydroxypropyl methylcellulose (HPMC)

I-Hydroxypropyl methylcellulose (HPMC) yinto ebalulekileyo ye-semi-synthetic cellulose ether compound, esetyenziswa kakhulu kumayeza, izinto zokwakha, ukutya, iingubo kunye namanye amashishini. I-HPMC inokuqina okulungileyo, i-emulsification, ifilimu-ukwenza, ukuthambisa, ukuzinzisa kunye nezinye iipropati, ngoko inexabiso elibalulekileyo lesicelo kwiinkalo ezininzi. Izinto eziphambili ekrwada zokuvelisa i-HPMC ziquka i-cellulose, i-sodium hydroxide, i-propylene oxide, i-methyl chloride kunye namanzi.

1. Iselulosi

I-Cellulose yeyona nto ingundoqo ekrwada ye-HPMC, edla ngokuthathwa kwimicu yezityalo yendalo efana nomqhaphu kunye neenkuni. I-cellulose yeyona polymer yendalo ininzi emhlabeni. Isakhiwo sayo se-molecular is a long-chain polysaccharide eyenziwe ngamayunithi e-glucose adityaniswe ngamabhondi e-β-1,4-glycosidic. I-cellulose ngokwayo ayinyibiliki emanzini kwaye ayinayo i-chemical reactivity elungileyo. Ke ngoko, uthotho lweenkqubo zokuguqulwa kweekhemikhali ziyafuneka ukunyusa ukunyibilika kwayo kunye nokusebenza kwayo ukulungiselela iimveliso ezahlukeneyo ze-cellulose ether.

2. I-sodium hydroxide (NaOH)

I-sodium hydroxide, eyaziwa ngokuba yi-caustic soda, yikhompawundi yealkaline eyomeleleyo edlala indima ebalulekileyo njenge-alkalizer kwinkqubo yokuvelisa i-HPMC. Kwinqanaba lokuqala lemveliso, i-cellulose iphendula kunye nesisombululo se-sodium hydroxide ukwenza amaqela e-hydroxyl asebenze kwitsheyini ye-cellulose yemolekyuli, ngaloo ndlela ibonelela ngeesayithi zokusabela kwimpendulo elandelayo ye-etherification. Eli nyathelo likwabizwa ngokuba yi "alkalization reaction". I-alkalized cellulose ifumana utshintsho oluthile lwesakhiwo, okwenza kube lula ukusabela kwiikhemikhali ze-reagents ezilandelayo (ezifana nepropylene oxide kunye ne-methyl chloride).

3. Ipropylene oxide (C3H6O)

I-Propylene oxide yenye yezinto eziphambili ze-etherifying kwimveliso ye-HPMC, isetyenziselwa ukuguqula amaqela e-hydroxyl kwi-cellulose ibe ngamaqela e-hydroxypropyl. Ngokukodwa, i-alkalized cellulose isabela kunye nepropylene oxide phantsi kweemeko ezithile zobushushu kunye noxinzelelo, kwaye amaqela epoxy asebenzayo kwipropylene oxide adityaniswe kwitsheyini yemolekyuli yeselulosi ngokuphendula kwindandatho yokuvula ukwenza i-hydroxypropyl substituent. Le nkqubo inika HPMC elungileyo ukunyibilika kwamanzi kunye nokutyeba isakhono.

4. I-Methyl chloride (CH3Cl)

I-Methyl chloride yenye i-agent etherifying ebalulekileyo esetyenziselwa ukuguqula amaqela e-hydroxyl ye-cellulose ibe ngamaqela e-methoxyl. I-Methyl chloride isabela kunye namaqela e-hydroxyl kwitsheyini ye-cellulose yemolekyuli ngokusebenzisa i-nucleophilic substitution reaction ukuvelisa i-methyl cellulose. Ngale mpendulo ye-methylation, i-HPMC ifumana i-hydrophobicity elungileyo, ngakumbi ibonisa ukunyibilika okugqwesileyo kwezinye izinyibilikisi zendalo. Ukongezelela, ukuqaliswa kwamaqela e-methoxy kuphucula ngakumbi ipropati yokwenza ifilimu kunye nokuzinza kweekhemikhali ze-HPMC.

5. Amanzi

Amanzi, njengesixhobo sokunyibilikisa kunye nokusabela, ahamba kuyo yonke inkqubo yemveliso ye-HPMC. Kwi-alkalization kunye ne-etherification reactions, amanzi awancedi kuphela ukunyibilikisa i-sodium hydroxide kunye nokulungelelanisa imeko ye-hydration ye-cellulose, kodwa ithatha inxaxheba kulawulo lobushushu bokusabela ukuqinisekisa ulawulo lobushushu kuyo yonke inkqubo yokusabela. Ukucoceka kwamanzi kunempembelelo ebalulekileyo kumgangatho we-HPMC, kwaye amanzi ahlambulukileyo aphezulu okanye amanzi adibeneyo ahlala efunekayo.

6. Izinyibilikisi zendalo

Kwinkqubo yemveliso ye-HPMC, amanye amanyathelo enkqubo anokufuna ukusetyenziswa kwezinye izinyibilikisi eziphilayo, ezifana ne-methanol okanye i-ethanol. Ezi zinyibilikisi ngamanye amaxesha zisetyenziselwa ukulungelelanisa i-viscosity yenkqubo yokusabela, ukunciphisa ukubunjwa kwe-reaction by-products, okanye ukukhuthaza ukuphendulwa kweekhemikhali ezithile. Ukukhethwa kwe-solvent ye-organic kufuneka kumiselwe ngokweemfuno zenkqubo yokuvelisa kunye nokusetyenziswa kwemveliso yokugqibela.

7. Ezinye izinto ezincedisayo

Ukongeza kwezi zinto ziphambili zingasentla, kwinkqubo yokuvelisa, ezinye izinto ezincedisayo kunye nezongezo, ezinje nge-catalysts, stabilizers, njl. yemveliso yokugqibela.

8. Amanyathelo aphambili enkqubo yokuvelisa

Amanyathelo enkqubo ephambili yokuvelisa i-HPMC inokwahlulwa ibe ngamacandelo amathathu: i-alkalization, i-etherification kunye ne-neutralization unyango. Okokuqala, i-cellulose iphendula kunye ne-sodium hydroxide ukuze i-alkalize yenze i-alkali cellulose. Emva koko, i-etherification yenzeke ekuphenduleni kwe-alkali cellulose kunye ne-propylene oxide kunye ne-methyl chloride ukwenza i-hydroxypropyl kunye ne-methoxy endaweni ye-cellulose ethers. Ekugqibeleni, ngonyango lwe-neutralization, ukuhlamba, ukomisa kunye nezinye iinkqubo, iimveliso ze-HPMC ezine-solubility ethile, i-viscosity kunye nezinye iimpawu zifunyenwe.

9. Isiphumo somgangatho wempahla ekrwada ekusebenzeni kweemveliso zeHPMC

Imithombo eyahlukeneyo yezinto ezikrwada kunye nokucoceka kunempembelelo ebalulekileyo kumgangatho kunye nokusebenza kwe-HPMC yokugqibela. Ngokomzekelo, ukucoceka kunye nokusabalalisa ubunzima be-molecular of cellulose eluhlaza kuya kuchaphazela i-viscosity kunye ne-solubility ye-HPMC; idosi kunye neemeko zokusabela kwepropylene oxide kunye nemethyl chloride iya kugqiba iqondo le-hydroxypropyl kunye ne-methoxy substitution, ngaloo ndlela ichaphazela umphumo wokuqina kunye neepropati zokwenza ifilimu yemveliso. Ke ngoko, ukukhethwa kunye nokulawulwa komgangatho wemathiriyeli ekrwada kubalulekile ngexesha lenkqubo yokuvelisa.

Izinto eziphambili ze-hydroxypropyl methylcellulose (HPMC) ziquka i-cellulose, i-sodium hydroxide, i-propylene oxide, i-methyl chloride kunye namanzi. Ngokusebenzisa uthotho lweekhemikhali ezintsonkothileyo, ezi zixhobo ziguqulwa zibe yimathiriyeli esebenzayo enexabiso elibanzi losetyenziso. Uluhlu lwezicelo lwe-HPMC lubandakanya iindawo ezininzi ezinje ngamayeza, izixhobo zokwakha, kunye nokutya. Iimpawu zayo ezintle zomzimba kunye neekhemikhali ziyenza ibaluleke kakhulu kumashishini amaninzi.


Ixesha lokuposa: Sep-30-2024
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