| 摘要 |
1. A process for preparing polyoles having at least one oxacyclopentane ring of the generic formula see diagramm : EP0052295,P5,F1 wherein R**1 is a hydroxyl group or the ether oxygen atom of a second oxacyclopentane ring, and R**2 being a hydrogen atom, a hydroxymethyl group or a bivalent radical of the formula -CH2 -CHOH- whereby in the latter case R**1 is a ether oxygen atom and R**1 and R**2 together with the carbon atoms with which they are attached form a second oxacyclopentane ring, by cleavage of water from sugar alcohols having 4 to 6 carbon atoms at elevated temperature in presence of a strongly acidic heterogeneous catalyst and in absence of organic solvents, outside water being introduced with the starting materials and during the reaction formed reaction water being at least partly distilled from the reaction mixture during the reaction, characterized in that the reaction is carried out in a melt liquid reaction system - preferably under reduced pressure - at temperature of no more than 160 degrees C, with the proviso that the temperature is selected in dependency of the pressure in such a way that prior to the completion of the reaction and the separation of the catalyst, respectively, essentially no distillation preparation of polyole reaction product(s) from the reaction mixture takes place. |
