Crystallization Elution Fractionation. A New Separation Process for Polyolefin Resins

Abstract

Summary: New crystallization procedures have been developed for the analysis of the chemical composition distribution in polyolefins by pumping a small flow of solvent during the crystallization cycle. One of the new techniques, crystallization elution fractionation (CEF) combines the separation power of TREF and CRYSTAF and has been shown to provide very fast analysis of the composition distribution.

Separation of polyolefins based on comonomer content using high‐temperature gradient adsorption liquid chromatography with a graphitic carbon column

“…An ATREF experiment conducted in an optimal manner can take several hours -nonideal when throughput is concerned. However, the recently developed crystallization elution fractionation (CEF) technique, 7 combining some of the attributes of ATREF and CRYSTAF, has drastically reduced run times down to under an hour while obtaining the same chemical composition distribution information. CEF does not overcome the need for a crystallization step to take place, however, as it is still a crystallization-based technique.…”

Effect of Operating Conditions on Dynamic Crystallization of Ethylene/1‐Octene Copolymers

“…The characterization techniques for measuring the CCD of semicrystalline copolymers have been continuously developed, especially crystallization-based techniques that fractionate polymers according to chain crystallizabilities in a dilute solution, such as temp erature-rising elution fractionation (TREF), crystallization analysis fractionation (CRYSTAF), and crystallization elution fractionation (CEF). [ 1,[3][4][5][6][7][8] Dynamic crystallization (DC) was recently introduced as a new CCD analysis tool using fractionation concepts similar to TREF and CRYSTAF, but with the fractionation step occurring under a constant solvent fl ow to enhance the physical separation of the polymer chains during the crystallization step. [ 7,8 ] DC consists of two consecutive steps: crystallization and elution steps.…”

“…[ 1,[3][4][5][6][7][8] Dynamic crystallization (DC) was recently introduced as a new CCD analysis tool using fractionation concepts similar to TREF and CRYSTAF, but with the fractionation step occurring under a constant solvent fl ow to enhance the physical separation of the polymer chains during the crystallization step. [ 7,8 ] DC consists of two consecutive steps: crystallization and elution steps. In the crystallization step, the dilute polymer solution is loaded into a column packed with inert particles.…”

Recent Advances in High-Temperature Fractionation of Polyolefins

“…Monrabal et al [76] proposed this new approach which combines separation power of CRYSTAF and TREF and provides very fast analysis in comparison to long analysis times of other crystallization based techniques. CEF can be performed in a typical column based TREF instrument and can easily adapt viscometry, light scattering, composition or other molar mass sensitive detectors.…”

“…This allows the physical separation of the fractions according to crystallizability within the column in the crystallization cycle. The flow rate during the crystallization cycle is a very important factor to [76] with permission of Wiley-VCH) achieve better separation. Once the crystallization cycle is completed, the flow through the column is stopped and the column is heated to higher temperatures for a few minutes where all the components dissolve again.…”