Applying thermal insulation to pipes - by spray application of polyurethane foam compsn.

摘要

In a process for applying thermal insulation to pipes, the pipe is sprayed whilst undergoing rotational and translational movement, with a compsn. comprising a polyol, a diisocyanate, a catalyst and a blowing agent, the mixt. having a cream time of between 7 and 10 seconds. Spraying is carried out to give a layer of polyurethane foam 30-50 mm thick and with a density of 80-120 kg/m3 on the tube. Catalyst used is pref. 2.5-3.5% (w.r.t. of polyol) of an amine such as dimethylethylamine. Process is suitable for applying polyurethane foam insulation to large dia. pipes. Adjustment of the cream time to 7-10 sec. as opposed to 2-3 sec. for prior art compsns., gives improved foam layers which are free from cavities and surface pitting.