Continuous process for the removal of residual monomer from aqueous dispersions of homo- and copolymers of vinyl chloride

Claim 1

In a process for the removal of residual monomer from aqueous dispersions of homo- and copolymers of vinyl chloride having a surface tension of below 60 dyn/cm. by a steam treatment in which foaming is avoided by rapid lowering of pressure at high flow velocity and which comprises the steps of (a) mixing a stream of the monomer-containing dispersion with steam in an elongate mixing zone maintained at a pressure of 150-600 torr at a rate such that the flow velocity of the mixture in the mixing zone is 1-20 m./sec., (b) withdrawing a stream of the mixture from the mixing zone at a velocity of 30-100 m./sec. from the mixing zone, (c) feeding the stream of the mixture withdrawn from the mixing zone to a degasification zone maintained at a pressure 30-200 torr lower than the pressure in the mixing zone, and (d) withdrawing a stream of the degasified dispersion from the degasification zone, (e) the improvement which comprises repeating the above steps, employing as starting material the degasified dispersion withdrawn from the degasification zone, in a second mixing zone maintained at a pressure of 150-600 torr and fitted internally with fluid flow diverting means, and in a second degasification zone maintained at a pressure 30-200 torr lower than the pressure in the second mixing zone.