Process for preparing emulsions that are polymerizable to absorbent foam materials

Claim 1

A continuous process for the preparation of an absorbent foam material made from a polymerized high internal phase emulsion, process comprises: A) providing a liquid feed stream of an oil phase comprising i) from about 7% to 40% by weight of a substantially water-insoluble, monofunctional glassy monomer component selected from styrene-base-d-monomer types; ii) from about 27% to 66% by weight of a substantially water-insoluble, monofunctional rubbery comonomer component selected from butylacrylate, 2-ethylhexylacrylate, butadiene, isoprene, and combinations of these comonomers types; iii) from about 10% to 25% by weight of a substantially water-insoluble, cross-linking agent component comprising a difunctional monomer type selected from divinylbenzene, divinyltolulene, diallylphthalate, one or more diacrylic acid esters of a polyol and combinations of these difunctional monomer types; and iv) from about 4% to 25% by weight of an emulsifier component which is selected from sorbitan fatty acid esters, polyglycerol fatty acid esters, polyoxyethylene fatty acids and esters and combinations of such emulsifiers; B) providing a liquid feed stream of a water phase comprising an aqueous solution containing from about 0.2% to 40% by weight of water-soluble electrolyte selected from salts of alkali or alkaline earth metals, and from about 0.02% to 0.4% by weight of a water-soluble, free radical polymerization initiator; C) simultaneously introducing said liquid feed streams into a dynamic mixing zone at flow rates such the initial weight ratio of water phase to oil phase being introduced ranges from about 2.5:1 to 5:1; D) subjecting the combined feed streams in said dynamic mixing zone to sufficient shear agitation to at least partially form an emulsified mixture in said zone while maintaining steady, non-pulsating flow rates for the oil and water phase streams; E) steadily increasing the ratio of water to oil feed streams being introduced into said dynamic mixing zone to within the range of from about 20:1 to 70:1 at a rate of increase which does not destroy the emulsified nature of the contents of said dynamic mixing zone, while maintaining the emulsified contents of said dynamic mixing zone at a temperature of from 35° C. to 65° C., and while subjecting the emulsified contents of said zone to continued shear agitation which is sufficient to eventually form a high internal phase emulsion that, upon subsequent polymerization, provides a foam having an average cell size of from about 10 to 90 microns; F) continuously withdrawing the emulsified contents of said dynamic mixing zone and continuously introducing said emulsified contents into a static mixing zone wherein said emulsified contents are further subjected to sufficient shear mixing to thereby completely form a stable high internal phase emulsion having a water to oil phase weight ratio of from about 20:1 to 70:1; G) continuously withdrawing said stable high internal phase emulsion from said static mixing zone; and H) subjecting said stable high internal phase emulsion withdrawn from said static mixing zone to conditions suitable for effecting polymerization of the polymerizable monomers, comonomers and cross-linking agents in the oil phase of said stable high internal phase emulsion to thereby form upon subsequent dewatering a polymeric absorbent foam material.