Abstract: 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:TG.sub.L =TG.sub.S .times.(m.sub.L /D.sub.L).sup.1/3 (m.sub.S /D.sub.S).sup.1/3,in whichD.sub.L =density of the latex particles in the latex to be producedD.sub.S =density of the particles of the seed usedm.sub.L =mass of the latex particles in the latex to be producedm.sub.S =mass of the particles of the seed usedTG.sub.L =particle size of the latex to be producedTG.sub.

Abstract: 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.

Abstract: The present invention relates to a process for the preparation of diisocyanates corresponding to the formulaOCN--R--NCOwhereinR denotes a (cyclo)aliphatic hydrocarbon group with up to 15 carbon atomsby phosgenation of the corresponding diamines represented by the formulaH.sub.2 N--R--NH.sub.2in the gas phase, characterized in that(a) the diamines in vapor form, optionally diluted with an inert gas or with the vapors of an inert solvent, and phosgene are separately heated to temperatures of about 200.degree. to 600.degree. C. and continuously reacted together in a cylindrical reaction chamber which is free from moving parts and heated to about 200.degree. to 600.degree. C., while a turbulent flow is maintained in the reaction chamber.

Abstract: 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.