Txoj cai ntawm Twin Screw Extruder Degassing
● Ua haujlwm ntawm kev khwv nyiaj txiag
● Khaws max. yaj kub kom tsawg li tsawg tau (degradation, xim)
● Txo cov seem seem
● Ua tau zoo kho qhov muag thiab cov khoom siv kho qhov muag
● Tsis txhob gels thiab "dub pob".
Cov txheej txheem degassing.
Polymer | Cov khoom yuav tsum degassed | ||
Hom | Cov ntsiab lus pib | Cov ntsiab lus kawg | |
LDPE | Ethylene | 2, 000 ppm | < 100 ppm |
LLDPE | Hexane, cyclohexane | 10 - 15 % | < 500 ppm |
3% | < 250 ppm | ||
EVA | Vinylacetate | 5, 000 ppm | < 50 ppm |
PS | Styrene | 3, 000 - 5, 000 ppm | < 300ppm |
ABS | Acrylnitril (AN) | 20 ppm | <4 ppm |
PC | Methylene chloride | 20% | < 50 ppm |
PA | Caprolactame | 8% | < 0,8 % |
SIB, SBS | Hexane, cyclohexane | 15 - 70 % | < 1,000 ppm |
Kev sib cais ntawm cov pa los ntawm cov polymer yaj los ntawm diffusion. Cov roj, uas yog incorporated nyob rau hauv lub yaj yuav tsum tuaj rau ntawm lub melt txheej.
Lub diffusion yog cuam tshuam los ntawm:
● residence time --->ntev degassing tsam
● viscosity of the melt--->tsawg viscosity (= kub)
● thickness of the melt layer --->Tsawg sau qhov tseem ceeb ntawm cov ntsia hlau (40%)
● renewal of the melt surface --->intensive sib tov
● pressure difference --->lub tshuab nqus tsev
Daim ntawv A
• Up tig ntsia hlau yog npog
• thaj tsam intermeshing raug them
• Down tig ntsia hlau yog ib nrab npog
Polymer yaj, uas tsis lo rau screws (polyolefins)
Daim ntawv B
• Up tig ntsia hlau yog npog
• thaj tsam intermeshing raug them
Polymer yaj, uas zoo li lo rau screws (PA, PET)
Daim ntawv C
• Up tig ntsia hlau ib nrab npog
Tsawg viscous polymer yaj (degassing ntawm cov kuab tshuaj)
● Feed temperature too low -->Efficiency rau rear / back vent low
● Foaming in vent ports -->Kev txwv hauv lub tshuab nqus tsev
-->Nce ntawm cov ntsia hlau ceev
 | => |  | => |  |
● Gas velocities -->throughput, ntsia hlau ceev, ntsia hlau tsim
● max. melt temperature -->Screw ceev / ntsia hlau configuration
Degassing.
Daim ntawv qhia kab rau polymer degassing.
● Cov polymer yuav tsum tau molten tag.
● Cov fillers thiab cov khoom txhawb nqa yuav tsum tau wetted tag nrog yaj.
● Lub melting kub yuav tsum siab npaum li sai tau.
● Lub cheeb tsam degassing yuav tsum tau ntev li ntev tau.
● Lub tshuab nqus tsev yuav tsum qis dua qhov siab ntawm ib nrab ntawm cov khoom kom degassed.
● Cov khoom sau yuav tsum qis dua 40%.
● Lub qhov chaw nres nkoj yuav tsum tau xaiv raws li cov yam ntxwv ntawm polymer