Plastic and nonmetallic article shaping or treating: processes – Encapsulating normally liquid material – Liquid encapsulation utilizing an emulsion or dispersion to...
Patent
1983-04-06
1985-06-04
Lovering, Richard D.
Plastic and nonmetallic article shaping or treating: processes
Encapsulating normally liquid material
Liquid encapsulation utilizing an emulsion or dispersion to...
264 47, 424 32, 424 36, 426805, 42840221, B01J 1302
Patent
active
045213526
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to microencapsulation processes and more especially to processes for encapsulating fine droplets of a hydrophilic liquid in a hydrophobic continuous phase.
It has been proposed in the prior art to produce microcapsules containing aqueous amine solutions by emulsifying the aqueous solution in an organic liquid with the aid of a suitable surfactant and forming a polymer membrane around the droplets by interfacial polymerisation. For example, it has been proposed to add sebacoyl, succinoyl, adipoyl, phthaloyl, terephthaloyl or citroyl chloride or succinic anhydride to the continuous phase to produce a polyamide membrane. Once the microcapsules have been produced it is frequently desirable to change the continuous phase from a hydrophobic liquid to a hydrophilic liquid, especially water. This is normally effected by decanting or centrifuging off the majority of the hydrophobic liquid, and washing and redispersing the microcapsules several times in a hydrophilic liquid containing large amounts of surfactant.
In the processes proposed in the prior art, certain precautions have to be taken to avoid aggregation of microcapsules, especially at the phase-change stage of the process where the capsules are close together and, for instance, free acid chloride groups in the polymer membrane of one capsule may condense with, for instance, residual free amino groups in the polymer membrane of a second capsule thereby forming chemical bonds between the capsules, or for example, residual acid chloride or anhydride in the reaction medium may condense with residual free amino groups on two or more adjacent capsules.
For many applications of the capsules aggregation or clumping of the capsules is highly undesirable and efforts have been made to ensure that the polymerisation reaction goes to completion thereby avoiding any possibility of aggregation of the capsules.
U.K. Application No. 2040863 discloses a process for the production of microcapsules containing an aqueous solution of a hydrophilic protein containing a plurality of free amine groups, which comprises forming an emulsion of the aqueous protein solution as disperse phase in a substantially non-polar solvent as the continuous phase and adding to the emulsion a solution of a compound containing a plurality of groups capable of reacting with amine groups to form a polymer, especially to form a polyamide.
It is possible when operating in accordance with the instructions of patent specification No. 2040863 to obtain batches of microcapsules in which little or no aggregation has occurred but great care has to be taken in carrying out the process and attempts have therefore been made to find a satisfactory and consistent way of preventing or controlling aggregations of the capsules.
This invention provides a process for microencapsulation of an aqueous amine solution by emulsifying the aqueous solution in an organic liquid and forming a polymer membrane around the droplets by interfacial polymerisation by reaction with a poly basic acid chloride or anhydride, wherein, when the reaction has proceeded to the desired extent the reaction is terminated by introducing water into the reaction medium to react with and destroy residual acid chloride or anhydride.
Water can be introduced into the reaction medium by any method that ensures intimate contact of the water with the acid chloride or anhydride dissolved in the hydrophobic phase of the emulsion or with acid chloride or anhydride groups remaining in the polymer membrane of the capsules.
The water is preferably introduced into the reaction medium by adding to the reaction medium a solution of water in an organic liquid, which solution is substantially miscible with the hydrophobic phase of the emulsion.
The organic liquid serves as a carrier vehicle to introduce water into the hydrophobic phase of the emulsion where it substantially immediately reacts with the acid chloride or anhydride thereby rendering it incapable of taking part in further reaction. Accordingly, when the capsules are brought
REFERENCES:
patent: 3575882 (1971-04-01), Vandegaer et al.
patent: 4322311 (1982-03-01), Lim et al.
patent: 4376059 (1983-03-01), Davis et al.
Handbook of Chemistry and Physics, edited by Hodgman et al., 35th edition, publ. by Chemical Rubber Publ. Co., Cleveland, Ohio, (1953), pp. 912 and 913.
Lovering Richard D.
Mars Incorporated
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