Process for manufacturing polyurethane prepolymers for use as adhesive, and especially as a binder for natural cork

摘要

Process for manufacturing polyurethane prepolymers for use as adhesive, and especially as a binder for natural cork. Includes: the placing of a polyol of a multifunctional polyether or polyester with terminal hydroxyl groups in a reactor with an organic or Lewis acid; heating the reactor to a temperature of 40 to 60 degree C, adding a toluene diisocyanate to the reactor and carrying out the reaction between 70 and 90 degree C for 4 to 6 hours until a percentage of NCO groups of between 3.6 and 6% is obtained, and adding a diphenylmethane diisocyanate to the reactor; before the reaction mixture is cooled, a moisture prevention additive is added; all so that the prepolymer obtained has a percentage of toxic diisocyanate below 1% and is therefore regarded as being harmful but not toxic.