A process of preparing a liquid reaction product in a column reactor, which reactor comprises a space between coaxial tubular interior surfaces comprising an inner interior surface and an outer interior surface, comprising the steps, a) feeding the liquid precursor reactant material through an inlet port in the outer interior surface, b) flowing the liquid precursor material through the space between the outer interior surface and the inner interior surface, c) subjecting the liquid precursor material in step (b) to reaction conditions to form the liquid reaction product, d) passing the liquid polymer composition through an outlet port in the outer interior surface, characterised in that the distance of the inner internal surface and the outer interior surface is less than 20 mm and the ratio of the cross-sectional diameter (D′) of the inner interior surface to the cross-sectional diameter (D″) of the outer interior surface is at least 0.8:1. Also claimed is an apparatus suitable for carrying out chemical reactions. Derisably the apparatus and process can be used to make liquid polymer compositions.