Mixing apparatus for continuous production of monomer emulsion
Mixing apparatus and methods for the continuous production of monomer emulsions that may be used in the production of polymer dispersions by radical aqueous emulsion polymerization. The mixing apparatus can include a pipe-in-pipe injector ( 100 ) and a suitable rotor-stator mixer ( 102 ). Liquids are delivered to the rotor-stator mixer via an inner ( 110 ) and an outer ( 108 ) pipe in such a way as to substantially prevent feed inconsistencies in a feed ratio of the liquids prior to entering a mixing zone of the rotor-stator mixer for emulsion formation.
1. A method of forming a monomer emulsion for a continuous polymerization process, comprising:
supplying a first liquid at a first mass flow rate to a rotor-stator mixer that has a leading surface through an inner pipe of a pipe-in-pipe injector;
supplying a second liquid to the rotor-stator mixer through an outer pipe of the pipe-in-pipe injector at a second mass flow rate that is about fifty percent a final mass flow rate for the second liquid, where the second liquid is immiscible with the first liquid and at least one of the first liquid and the second liquid contains monomers;
increasing the second mass flow rate of the second liquid from about fifty percent the final mass flow rate to the final mass flow rate over a predetermined time interval;
keeping the first liquid separate from the second liquid until a predetermined distance of about 1.5 to about 0.5 times an inner diameter of the inner pipe away from the leading surface of the rotor; and
providing a residence time sufficient for the first liquid and the second liquid in the rotor-stator mixer to form the monomer emulsion from the first liquid and the second liquid.
2. The method of claim 1 , where the first liquid has a first density, and the second liquid has a second density lesser than the first density of the first liquid.
3. The method of claim 1 , where the predetermined time interval is about five minutes.
4. The method of claims 1 , including substantially preventing pre-mixing of the first liquid and the second liquid prior to entering a mixing zone of the rotor-stator mixer.
5. The method of claim 1 , where providing a residence time sufficient for the first liquid and the second liquid in the rotor-stator mixer to form the monomer emulsion includes adjusting a liquid back-pressure exerted by the monomer emulsion from the rotor-stator mixer.
6. The method of claim 1 , where supplying the second liquid to the rotor-stator mixer includes surrounding a continuous stream of the first liquid with a continuous stream of the second liquid.
7. The method of claim 1 , where the first liquid is an aqueous solution and the second liquid is an organic solution having ethylenically unsaturated monomers.