Abstract: A process for retanning leather has been found, which is characterized in that a) a tanned leather is treated in aqueous liquor in the presence of hollow microspheres filled with blowing agent, b) the leather obtained according to a) is dried after further optional retanning steps and c1) treated with steam at 80 to 120° C., in particular at 80 to 100° C., or c2) with infrared radiation having a wavelength of 0.7 to 100 ?m, it also being possible for a finishing step b1) and/or a milling step b2) to follow at a time after the drying step b).

Abstract: A process for the retanning of iron-tanned leather, comprising applying to iron-tanned leather condensates based on:

Abstract: The novel process for working up solutions or suspensions of organic synthesis products having a pH value of <3, preferably <1, is carried out with the aid of an asymmetrical, semipermeable membrane composed of cyclic polyureas with repeating structural units of the formula (I) ##STR1## wherein the substituents R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, X and Y and the index n are each as defined in the description.

Abstract: The process for the working-up of effluents and disposal of the loads, present therein, by a combination of concentration by membrane filtration, evaporation and gas phase oxidation, is particularly viable economically because the concentrates to be incinerated have a very low salt content.

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: By adding boric acid or salts of boric acid before or during the pressure permeation of anionic dyestuff solutions, the filtration flux is substantially increased, resulting in a low-cost process, due to the shorter plant time required.

Abstract: Stable aqueous solutions of anionic dyestuffs, preferably reactive dyestuffs, are obtained at very low costs by pressure permeation, if the feed solution for the pressure permeation is prepared by stirring the optionally dried presscake or the suspension of the crude dyestuff in an electrolyte solution.