liter round bottomed flask impurities such as water and alchools were removed via azeotropic distillation thereafter 1 0 g of trimethylhexamethylene diisocyanate and about 100 mg of zinc cyclohexane butyrate catalyst dissolved in 10 ml of triethylamine were added thereto the flask was equipped with a reflux condenser and a cacl 2 drying tube and the reaction mixture was refluxed overnight at 142 u00b0 c while open to the atmosphere the product was filtered washed and suspended again in 400 ml of xylene next 1 98 g of trimethylhexamethylenediamine was added all at once followed by the dropwise addition of 3 00 g ddi 1410 diisocyanate dissolved in 150 ml of xylene the mixture was refluxed again overnight at 142 u00b0 c while open to the atmosphere and the final product filtered washed dried crushed sieved and silylated as in example 1 10 g of silica were thermally treated overnight at 500 u00b0 c in a high temperature furnace the silica was then transferred into a 1 liter round bottomed flask equiped with a reflux condenser and a cacl 2 drying tube 500 ml of zylene and 5 grams of n betaamino ethyl gammaaminopropyltrimethoxysilane a product from dow corning were added and the mixture refluxed overnight at 142 u00b0 c with the system open to the.