Txoj kev tsim cov hydroxypropyl methylcellulose

Feem ntau, hauv kev sib xyaw ua ke ntawmhydroxypropyl methylcellulose, cov paj rwb cellulose uas tau ua kom zoo raug kho nrog cov kua alkali ntawm 35-40 ° C rau ib nrab teev, nias, cov cellulose raug pulverized, thiab laus kom haum ntawm 35 ° C, yog li ntawd cov alkali fibers tau txais yog qhov nruab nrab polymerized degree yog nyob rau hauv qhov xav tau. Muab cov alkali fiber rau hauv lub lauj kaub etherification, ntxiv propylene oxide thiab methyl chloride ua ke, thiab etherify ntawm 50-80 ℃ rau 5 teev rau qhov siab siab ntawm kwv yees li 1.8 MPa. Tom qab ntawd ntxiv cov hydrochloric acid thiab oxalic acid rau hauv dej kub ntawm 90 ° C kom ntxuav cov khoom kom nthuav qhov ntim. Dehydrate nrog lub centrifuge. Ntxuav kom txog thaum nruab nrab, thaum cov dej hauv cov khoom tsawg dua 60%, ziab nws nrog cua kub ntws ntawm 130 ° C kom tsawg dua 5%.

Alkalization: Cov paj rwb uas tau ua kom zoo tom qab qhib lawm ces muab ntxiv rau hauv cov tshuaj inert solvent, thiab ua kom nrog alkali thiab dej mos kom o ua rau cov crystal lattice ntawm cov paj rwb uas tau ua kom zoo, uas ua rau cov molecule etherifying agent nkag mus tau zoo thiab ua kom cov tshuaj etherification uniformity zoo dua. Cov alkali siv rau hauv alkalization yog cov hlau hydroxide lossis cov organic base. Cov alkali ntxiv (los ntawm qhov hnyav, tib yam hauv qab no) yog 0.1-0.6 npaug ntawm cov paj rwb uas tau ua kom zoo, thiab cov dej mos yog 0.3-1.0 npaug ntawm cov paj rwb uas tau ua kom zoo; cov tshuaj inert yog cov cawv thiab hydrocarbon sib xyaw, thiab cov tshuaj inert ntxiv yog paj rwb uas tau ua kom zoo. 7-15 npaug: cov tshuaj inert kuj tuaj yeem yog cawv nrog 3-5 carbon atoms (xws li cawv, propanol), acetone. Nws kuj tuaj yeem yog aliphatic hydrocarbons thiab aromatic hydrocarbons; qhov kub yuav tsum tau tswj hwm hauv 0-35 ° C thaum lub sijhawm alkalization; lub sijhawm alkalization yog li 1 teev. Qhov kev hloov kho ntawm qhov kub thiab lub sijhawm tuaj yeem txiav txim siab raws li qhov yuav tsum tau ua ntawm cov khoom siv thiab cov khoom.

Etherification: Tom qab kev kho alkalization, nyob rau hauv lub tshuab nqus tsev, etherification yog ua tiav los ntawm kev ntxiv tus neeg sawv cev etherifying, thiab tus neeg sawv cev etherifying yog propylene oxide. Txhawm rau kom txo qhov kev siv ntawm tus neeg sawv cev etherifying, tus neeg sawv cev etherifying tau ntxiv ob zaug thaum lub sijhawm etherification.