Process for producing an aqueous polymer dispersion from a vinyl aromatic compound and a conjugated aliphatic diene

Abstract

The invention relates to a process for producing an aqueous polymer dispersion by means of radically initiated aqueous emulsion polymerisation by polymerising, in an aqueous medium, in accordance with a monomer feed process: (a) 40 to 75 parts by weight styrene; (b) 24.9 to 59.9 parts by weight butadiene; (c) 0.1 to 10 parts by weight of at least one ethylenically unsaturated carboxylic acid; and (d) 0 to 15 parts by weight other monomers, wherein the parts by weight of monomers (a) to (d) add up to 100 parts by weight, which process comprises the following steps: a) creating a template of a seed latex and 1 to 10 parts by weight monomers, based on the total monomer amount; b) starting the polymerisation at a temperature ≥80° C. in this template; and c) subsequently steadily metering monomers and emulsifier into this reaction mixture; c1) wherein at a time when 40 to 55% of the total metering time of the monomers has elapsed and 40 to 55 parts by weight of the monomer amounts to be metered in are metered in, the metering rate of the emulsifier for a period P2 that lasts at most for 30 minutes is increased to 10 to 100 times the average metering rate of the emulsifier during the period P1, wherein the period P1 is the preceding length of time beginning with the start of the emulsifier metering; c2) and at a time when 60 to 85% of the total metering time of the monomers has elapsed and 60 to 85 parts by weight of the monomer amount to be metered in are metered in, the metering rate of the emulsifier for a period P4 that lasts at most 30 minutes is increased to 10 to 120 times the average metering rate of the emulsifier of the period P1 and with the proviso that the aqueous polymer dispersion has a solids content of ≥58 wt. %. The invention also relates to the dispersion obtained according to the process, and to the use thereof as a binder, adhesive, sizing agent for fibres, for producing coatings or for producing a paper coating slip.

Dependencies are inferred from the claim text.