Zur Fraktionierung von Polymeren mit entmischenden Flüssigkeiten

Abstract

Herrn Professor S. Petersen zum 65. Geburtstag gewidmet (Eingangsdatum: 4. August 1975) ZUSAMMENFASSUNG: Man kann chemisch verschiedene Polymere aus homogener Losung in einem geeigneten Mischlosungsmittel quantitativ voneinander trennen, wenn die Losungsmittel bei hohen Temperaturen mischbar sind, aber durch Temperaturerniedrigung entmischen. Die neuartige Fraktioniermethode wird mit Hilfe der Loslichkeitsparameter von Polymeren und Losungsmittelgemischen und an einigen Beispielen mit Hilfe der zweiten Virialkoeffzienten beschrieben. Die Nutzlichkeit der Fraktionierung wird gezeigt anhand der in einem einzigen Fraktionierschritt durchgefuhrten Trennung von ca. 30 verschiedenen Mischungen von Polymeren und Copolymeren inklusjve Pfropfcopolymeren nach ihrer chemischen Zusammensetzung. Die Fraktionierung mit entmischenden Fliissigkeiten 1st besonders in solchen Fallen nutzlich, bei denen andere Fraktioniermethoden, z. B. die Fallungsfraktionierung, keine befriedigenden Ergebnisse liefern.Mit der beschriebenen Fraktioniermethode ist es in speziellen Fallen moglich, drei chemisch verschiedene Polymere oder Oligomere quantitativ voneinander zu trennen. SUMMARY:It is possible to separate chemically different polymers dissolved in a suitable homogeneous solvent mixture quantitatively, if the solvents are miscible at high temperatures, but show phase separation at a lower temperature.The new method of fractionation is described in terms of the solubility parameters of polymers and of mixed solvents and in some cases by using the second virial coefficients.The usefulness of this fractionation method is demonstrated by the fact that about thirty different blends of polymers and copolymers, inclusively graft-copolymers can be separated in one fractionation step with respect to their chemical nature. The fractionation using demixing solvents is especially useful in cases where other fractionation methods, e.g. fractional precipitation, do not give satisfactory results. *) Vorgetragen auf dem IUPAC-Symposium, Bratislava, Juli 1975 und beim Makromolekularen Kolloquium in Freiburg i. Brsg., Marz 1976. 1525 R. KuhnIn special cases the new fractionation method allows quantitative separations of three chemically different polymers or oligomers.

Chemical composition distribution of a graft copolymer prepared from macromonomer: fractionation in demixing solvents

“…It is worth noticing that even a relatively small concentration of the copolymer in the solvent system substantially affects the phase-separation behavior. In the case under discussion (Figure 3), the presence of 0.5 wt % for the graft copolymer investigated lowers the demixing temperature by [10][11][12][13][14][15][16][17][18][19][20] °C, compared to the copolymer-free solvent system.…”

Phase Behaviour of Colloidal Crude Oil Systems

“…Ð The higher the solubility parameter of the petroleum fraction, the higher the solubility parameter of the solventprecipitant mixture at the flocculation point. Considering the behaviour of polymer solutions the following relations can be used for the interpretation: the solubility of polymers is determined by a critical value of the Flory-Huggins interaction parameter that can be calculated according to equation (2) As a criterion for metastability we can express: c ² c crit (4) In colloid disperse petroleum systems the limiting value of metastability should be determined by the particle volume of petroleum colloids. In equation (3) the solubility parameter at the surface of the colloid particle towards the dispersion medium d part has to be used.…”

Preparation of EPDM/SAN Dry Blends by Reactive Processing

“…This method allows the fractionation of a polymer blend according to the chemical composition of the different blend fractions, such as unreacted EPDM, unreacted SAN, gel and graft copolymer. So far, FDMS has been used for the fractionation of ABS12 and to the best of our knowledge has not yet been applied to the fractionation of EPDM/SAN blends prepared by reactive processing. FDMS should be an effective means for optimization of the reactive processing conditions towards balancing the ratio of EPDM crosslinking to the EPDM/SAN graft copolymer formation.…”