Aqueous polymer dispersion obtainable by free-radical initiated emulsion polymerisation in the presence of a molecular weight regulator composition

摘要

Molecular weight regulators are typically used in very high purity in respect of sulphur-containing compounds in order that unforeseeable and undesired effects of the sulphur-containing compounds on the course of the emulsion polymerisation and on the quality and product properties of the chain growth addition polymer formed may be minimised. Molecular weight regulators based on mercaptoalkyl carboxylic esters such as, mercaptoethyl propionate have the disadvantage that purification is very cosdy and inconvenient. The reason is that, owing to the nature of the synthesis, not only low-boiling constituents, ethylene sulphide and middle boilers mercapto-ethanol, but also high-boiling constituents (eg, oligomeric and polymeric polyethylene sulphides and esters thereof) are generated in the synthesis.