Aromaattisia ryhmiä sisältävien norborneenien endo- ja ekso- isomeerien rikastaminen

摘要

The invention relates to a method for enriching endo- and exo-isomers of aromatic substituent-containing norbornene which can be used in copolymerizing ethene and other olefins by the fractional crystallization of mixtures which contain the abovementioned isomers from organic solvents at low temperatures. The separation of the endo and exo-isomers of indenylnorbornene (1,4-methano 1,4,4a,9a-tetrahydrofluorene) provides an example of this invention. Converting the endo-isomer to the exo-isomer by means of chemical isomerization methods requires long reaction times and large quantities of an isomerization catalyst, such as silica-alumina. According to the invention example, it has now been possible to separate a pure endo-isomer of indenylnorbornene from n-hexane by fractional crystallization at a temperature of -75 degree C. The exo-isomer can be separated from the filtrate in a sufficiently pure state for polymerization when the endo isomer crystals have been removed.