Abstract: Organic Diazocompounds that can be employed in the manufacturing of PVC/Polyisocyanates based, foamed articles, and a process for the production of objects made of rigid, expanded polymer materials mainly based on PVC and Polyisocyanates include the use as cell nucleation agents, of alternative organic, free N2 gas releasing Diazocompounds, displaying, either as such and as far as their decomposition products is concerned, much lower hazards for humans and environment respect to currently used Diazocompounds. A method for obtaining the optimum dispersion of the gas releasing compounds to get the desired microsize “embryos” in the early stages of foam development is based on the capability of used Polyisocyanates and of some liquid, acid organic Anhydrides to dissolve Diazocompounds in the amounts demanded by the subject process. There is also new employment as cell nucleation agent in the subject process of the chemical compound named 2,2?-Azobis(2-methylbutanenitrile) (AMBN).

Abstract: Process for preparing shaped bodies with integrated polyurethane skin, which process comprises:(a) charging to a closed mould for rotational moulding a first premixed reactive polyurethane system;(b) causing the mould to rotate, according to rotational moulding technology, for a long enough time to form a thin layer of partially polymerised material on the inner surface of said mould; and(c) discontinuing the rotation and charging to the mould a reactive material which will fill the inner mould hollow.

Abstract: Stable dispersions of polyols having a viscosity lower than 10,000 mPa.times.sec and containing dispersed particles of polyvinylchloride, having a size within the range of from 1 to 10 micrometers and impregnated by the said polyols.

Abstract: Modified polyisocyanates with biuret structure containing terminal urethane groups and having general formula: ##STR1## in which R.sub.1 is an aliphatic, cycloaliphatic or aliphatic-cycloaliphatic radical, simple or substituted, and R.sub.2 can have the same meanings as R.sub.1 or can be the radical R.sub.3 (OC.sub.n H.sub.2n).sub.x --.Process for the preparation of modified polyisocyanates having biuret structure containing terminal urethane groups having general formula (I) consisting in reacting an organic diisocyanate with water or with a compound which splits off water, in the presence of a compatibilizing agent having a hydrogen atom reactive towards the isocyanate group, as it can be determined by Zerewitinoff's method.