Polybutylene terephthalate (PBT) yog ib qho kev ua haujlwm siab - thermoplastic polyester siv dav hauv cov haujlwm xws li hluav taws xob, khoom siv hluav taws xob, kev tsim tsheb, thiab tshuab. Cov txheej txheem tsim khoom rau polybutylene terephthalate yog cov ncauj lus hauv qab no.
Kev npaj raw khoom
Cov khoom siv tseem ceeb rau kev tsim cov polybutylene terephthalate yog terephthalic acid (PTA) thiab 1,4-butanediol (BDO). PTA yog dawb crystalline khoom los yog hmoov uas yuav tsum tau siab purity-feem ntau tshaj 99%. BDO yog xim tsis muaj xim, kua nplaum; nws qhov zoo thiab purity yuav tsum tau ua kom ntseeg tau los pab txhawb cov tshuaj tiv thaiv tom ntej. Ua ntej pib tsim khoom, cov khoom siv raw tau raug kuaj xyuas zoo thiab ua ntej kom tshem tawm impurities thiab ya raws.
Direct Esterification Txheej txheem ntau lawm
1. Esterification Reaction
PTA thiab BDO raug them rau hauv esterification reactor ntawm ib qho molar piv (feem ntau yog li ntawm 1: 1.1 txog 1: 1.5). Nyob rau hauv lub reactor, PTA thiab BDO undergo esterification nyob rau hauv lub xub ntiag ntawm ib tug catalyst los tsim bis (4-}hydroxybutyl) terephthalate (BHBT) thiab dej. Cov catalysts muaj xws li titanium-raws li thiab antimony- raws hom; titanium-based catalysts nyiam rau lawv cov haujlwm siab thiab cov tshuaj tiv thaiv sai. Cov tshuaj tiv thaiv kub yog feem ntau khaws cia ntawm 220℃thiab 250 degree, nrog lub siab khaws cia ntawm atmospheric lossis qib zoo me ntsis. Thoob plaws hauv cov tshuaj tiv thaiv, cov dej uas tsim tawm tsis tu ncua kom tsav cov tshuaj tiv thaiv rau pem hauv ntej.
2. Polycondensation Reaction
BHBT tau txais los ntawm theem esterification yog pauv mus rau polycondensation reactor. Nyob rau hauv cov xwm txheej ntawm qhov kub thiab txias (240-260 degree) thiab lub tshuab nqus tsev siab (qis dua 100 Pa), BHBT tau dhau los ua polycondensation los ua polybutylene terephthalate thiab 1,4-butanediol. Raws li cov tshuaj tiv thaiv tshwm sim, qhov hnyav molecular ntawm polymer maj mam nce. Ib qho me me ntawm stabilizers thiab antioxidants feem ntau yog ntxiv los txhim kho cov tshuaj tiv thaiv ceev thiab polymer zoo. Cov tshuaj tiv thaiv polycondensation yuav tsum tau siv sijhawm ntev, feem ntau ntawm 2 mus rau 4 teev.
3. Tshaj tawm - kev ua haujlwm
Tom qab ua tiav cov tshuaj tiv thaiv polycondensation, cov polymer yaj yog extruded los ntawm lub reactor thiab dhau mus tom qab- cov kauj ruam ua haujlwm - xws li cua txias thiab pelletizing - kom tawm los ntawm polybutylene terephthalate (PBT) pellets. Kev ua kom txias feem ntau yog ua tiav ntawm dej los yog cua kom ceev cov polymer yaj sai. Lub pelletizer txiav cov polymers txias rau hauv cov pellets zoo li qub, ua kom yooj yim khaws cia thiab thauj.
Transesterification txheej txheem ntau lawm
1. Transesterification Reaction
Cov txheej txheem transesterification siv dimethyl terephthalate (DMT) thiab 1,4-butanediol ua raw khoom. DMT thiab 1,4-butanediol raug them rau hauv lub tshuab hluav taws xob hloov pauv hauv cov kev faib ua feem, qhov twg cov tshuaj tiv thaiv tshwm sim nyob rau hauv lub xub ntiag ntawm ib tug catalyst (xws li acetate). Cov tshuaj tiv thaiv kub yog feem ntau tswj ntawm 180℃thiab 220 degree; methanol yog generated raws li ib tug byproduct. Nruam distillation ntawm methanol tsav cov tshuaj tiv thaiv rau kev tsim ntawm bis (4-hydroxybutyl) terephthalate.
2. Polycondensation thiab Post- ua
Cov tom ntej polycondensation thiab post- theem ua tiav rau bis (4-hydroxybutyl) terephthalate tau los ntawm transesterification yog qhov tseem ceeb tib yam li cov txheej txheem esterification ncaj qha. Polycondensation yog ua nyob rau hauv siab -kub thiab lub tshuab nqus tsev siab, ua raws li qhov txias thiab pelletizing kom tau txais cov khoom kawg.
Kev sib piv ntawm ob txoj kev tsim khoom
Cov txheej txheem esterification ncaj qha muaj qhov zoo ntawm cov nqi raw khoom tsawg (siv terephthalic acid), tsawg dua cov kauj ruam, thiab kev ua haujlwm siab. Txawm li cas los xij, nws xav tau cov khoom siv raw purity siab thiab cuam tshuam nrog cov tshuaj tiv thaiv nruj. Cov txheej txheem transesterification tau txais txiaj ntsig los ntawm cov tshuaj tiv thaiv me me thiab cov khoom siv purity qis dua. Hloov pauv, nws tso siab rau DMT kim dua thiab tsim cov tshuaj methanol ua cov khoom lag luam, tsim nyog rov qab thiab kho.