Process for converting coarse aqueous polymer emulsion to fine emulsion

Abstract

Abstract The preparation of stable aqueous latices from solvent dispersions of elastomers and other high polymer compositions has presented problems including excessive viscosity during processing and foaming, which have produced losses and increased costs. Herein combinations of steps are disclosed which reduce or eliminate various of these problems and enable the preparation of stable latices of high solids content. The process in common with that of related copending applications is characterized, inter alia, by the establishment of a flow of steam as a continuous phase into which an emulsion of a cement of the polymer is dispersed as an aerosol of latex droplets in a solvent-vapor continuum, followed by coalescence of the latex droplets and separation of the resulting coalesced liquid phase from the resulting solvent-vapor phase. In one embodiment of the present method an aqueous emulsion is prepared the dispersed phase of which principally comprises particles of precursor latex particle size and which may contain a lesser proportion of particles of greater than precursor latex particle size. This emulsion is converted to a stable latex by subjecting the same to special conditions which cause selective agglomeration of the particles of greater than precursor latex particle size, and removing the so agglomerated particles to yield a latex essentially free of particles of greater than colloidal size. In preferred embodiments provision is made for the continuous production of aqueous emulsion of polymer solvent cement essentially entirely of precursor latex particle size, which may be of narrow size distribution, or may have imparted thereto a wider size distribution, or an altered particle size or viscosity or both. As in the processes of my prior applications hereinafter referred to, the separation of the gaseous and liquid latex phases is effected by impinging the same on a liquid body, preferably a flow of partially concentrated liquid latex; and preferred arrangements for generating the aerosol, for effecting the said impingement, for effecting concentration of the latex under controlled conditions minimizing the formation of coagulum therefrom, and for recovering the latex from the gaseous phases, are also disclosed, which may be employed in lieu of or together with other features of said copending applications. In certain embodiments, in addition, special provisions are made for eliminating, from the latex, particles of greater than colloidal size by controlling the heating and stripping operations so that in combination, such larger particles are essentially avoided and/or agglomerated or coagulated and removed to yield latex essentially free of greater than colloidal sized particles. In other embodiments special provisions are made for altering the viscosity of the aqueous polymer/solvent emulsion and/or of the latex product, by special treatment of at least a part thereof before delivery from the system. Furthermore, special provisions are made for cOagulum removal and recovery, and to contribute to a more expeditious processing of the materials into stable latices and a reduction in coagulum losses and increase in efficiency.

Inventors

• 👤 Jr Oliver W Burke

Bibliographic Details