Bayer Aktiengesellschaft

Heinrich Grave

Hanns P Muller

Herbert Stutz

Martin Matner

Werner Clarenz

Eckart Waldau

Hans-Georg Frosch

Dietrich Tegtmeyer

Peter Fuhrmann

Hans-Gunter Vogt

Hermann-Josef Bross

Anno Borkowsky

Bernd Von Der Linden

Henning Bachem

Latices based on conjugated dienes are produced using emulsion polymerization by introducing the monomers to be polymerized into the initially introduced seed latex in the presence of a free-radical forming activator and an emulsifier in such a manner that the ratio of the monomer polymerization rate to the monomer feed rate is less than 0.7:1 and by performing polymerization up to a monomer conversion of .gtoreq.95% at temperatures of 10 to 85.degree. C., wherein the addition of the emulsifier is controlled in such a manner that the final particle size (TG.sub.L) of the latex to be produced is governed by the following equation:

Process for the production of latices based on conjugated dienes by

Latex dispersions are concentrated by a process in which, in a two-stage crossflow filtration, the latex dispersion is first concentrated under pressures of 2 to 7 bar and at temperatures of 20.degree. to 70.degree. C. under turbulent flow conditions, the permeate accumulating together with the emulsifier present therein is then also concentrated at 10 to 40 bar and at temperatures of 20.degree. to 50.degree. C. and the concentrate obtained is returned with the emulsifier to the first stage of the crossflow filtration process while the permeate of the second stage is returned to the production process.

Process for concentrating latex dispersions

The present invention relates to a process for the preparation of diisocyanates corresponding to the formula

Process for the preparation of (cyclo)aliphatic diisocyanates

The present invention relates to a process for the production of aliphatic and/or cycloaliphatic diisocyanates which are color stable to heat, which is characterized in that a diisocyanate with aliphatically-and/or cycloaliphatically-bound isocyanate groups is heated in the presence of about 0.1 to 3% by weight, based on the diisocyanate, of at least one compound which is soluble in the diisocyanate and contains at least 3% by weight of structural units corresponding to the formula: ##STR1## for up to about 5 hours at a temperature of about 100.degree. to 220.degree. C. and the diisocyanate which has been treated in this way is subsequently purified by distillation. The present invention also relates to the use of the products of the present process for the production of modified polyisocyanates having improved coloration.

Process for the production of thermally color stable aliphatic and/or

Growing community of inventors

Bergisch Gladbach, Germany

Heinrich Grave