Process for preparing emulsions that are polymerizable to absorbent foam materials

A continuous process for the preparation of a high internal phase emulsion which is suitable for subsequent polymerization and dewatering to form an absorbent foam material, which process comprises:

• A) providing a liquid feed stream of an oil phase comprising
• i) from about 7% to 40% by weight of a styrene monomer component;
• ii) from about 27% to 66% by weight of a comonomer component selected from butylacrylate, 2-ethylhexylacrylate, isoprene, and combinations of these comonomers;
• iii) from about 10% to 25% by weight of a divinylbenzene cross-linking agent component, and
• iv) from about 4% to 25% by weight of an emulsifier component selected from sorbitan monooleate and a mixture of sorbitan monooleate and sorbitan trioleate in a monooleate to trioleate weight ratio of from about 2:1 to 5:1;
• B) providing a liquid feed stream of a water phase comprising an aqueous solution containing from about 0.5% to 20% by weight of calcium chloride and from about 0.1% to 0.2% 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 that 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 shear agitation of from about 1500 to 3000 sec..sup.-1 for a period of time sufficient 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.degree. C. to 65.degree. C., and while subjecting the emulsified contents of said zone to continued shear agitation of from about 1500 to 3000 sec..sup.-1 for a period of time which is sufficient to 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;
• and
• G) continuously withdrawing said stable high internal phase emulsion from said static mixing zone such that said stable high internal phase emulsion can be thereafter polymerized and dewatered to form a solid absorbent foam.