Cov txheej txheem tsim tawm ntawm hydroxypropyl starch ethers (HPS) feem ntau muaj cov kauj ruam tseem ceeb suav nrog kev npaj cov khoom siv raw, alkalization, etherification cov tshuaj tiv thaiv, nruab nrab thiab purification, thiab ziab. Tag nrho cov txheej txheem yog ua raws li kev tswj hwm nruj ntawm pH, kub, thiab kev tiv thaiv roj inert kom ntseeg tau tias muaj kev hloov pauv siab thiab kev ua haujlwm ruaj khov ntawm cov khoom.
Cov txheej txheem ntau lawm ntawm Hydroxypropyl Starch Ethers (Kev Siv Cov Txheej Txheem Ua Piv Txwv)
1. Kev npaj cov khoom nyoos
Cov khoom siv tseem ceeb: cov hmoov txhuv nplej siab ntuj (xws li pob kws, qos yaj ywm, los yog cov hmoov txhuv nplej siab), propylene oxide (etherifying agent), sodium hydroxide (catalyst), ethanol lossis isopropanol (organic hnyav).
Cov hmoov txhuv nplej siab yuav tsum tau ua ntej- qhuav kom qhuav rau cov dej noo tsawg dua 15% thiab sieved kom tshem tawm cov impurities kom ntseeg tau tias cov tshuaj tiv thaiv zoo ib yam.
2. Dispersion thiab Alkalization
Ntxiv cov hmoov txhuv nplej siab rau hauv ethanol- dej sib tov hnyav los npaj qhov kev ncua ntawm kwv yees li 30% -40%. Maj mam ntxiv cov tshuaj sodium hydroxide thaum nplawm.
Tswj lub cev pH ntawm 9.0-10.5 thiab qhov kub ntawm 40-50℃rau 1 teev kom tag nrho cov hmoov txhuv nplej siab granules thiab tsim sodium starch (Starch-O⁻Na⁺), npaj rau tom ntej etherification.
3. Etherification Reaction
Nyob rau hauv kev tiv thaiv nitrogen, maj mam ntxiv propylene oxide nyob rau hauv batch, tsis txhob ua phem exothermic tshua.
Khaws cov tshuaj tiv thaiv kub ntawm 40-50℃thiab tsis tu ncua do rau 18-24 teev kom propylene oxide kom tag nrho lub nplhaib- qhib etherification nrog cov hmoov txhuv nplej siab hydroxyl pawg, tsim cov hydroxypropyl substituents (-OCH₂CHOHCH₃).
Qhov℃ntawm kev hloov pauv (DS) tuaj yeem tswj tau qhov tseeb los ntawm kev kho tus nqi ntawm propylene oxide thiab lub sijhawm tshuaj tiv thaiv, feem ntau yog lub hom phiaj 0.1-0.3.
4. Neutralization thiab kev txiav txim siab ntawm qhov kev tshwm sim
Tom qab cov tshuaj tiv thaiv, kho lub cev pH rau 5.0-5.5 nrog dilute hydrochloric acid kom tshem tawm cov seem alkali thiab tshem tawm cov tshuaj tiv thaiv.
5. Ntxuav thiab lim
Cov khoom yog ntxuav ntau zaus nrog ethanol lossis dej kom tshem tawm cov khoom tsis zoo propylene oxide, cov khoom siv (xws li propylene glycol), thiab cov ntsev inorganic, yog li txhim kho cov khoom purity.
6. Qhuav thiab sib tsoo
Tom qab ntxuav, cov khoom ntub dej yog centrifuged kom tshem tawm cov dej, tom qab ntawd tsuag tsuag - qhuav los yog nqus tsev vacuum - qhuav kom tswj cov dej noo zaum kawg kom tsawg dua lossis sib npaug li 15%.
Cov hmoov qhuav yog tom qab ntawd hauv av rau qhov yuav tsum tau ua kom zoo (feem ntau 80-120 mesh) siv lub tshuab cua tshuab, sieved, thiab ntim kom tau cov khoom dawb, zoo hmoov.
