Abstract:
Process of microencapsulation employing acid precursor (type A) gelatin as the encapsulating macrocolloid, particularly applicable to the formation of liquid center microcapsules containing a basic (cationic) nitrogen compound. For example, an aqueous solution of acid-precursor gelatin is mixed at an alkaline pH with a water-immiscible organic solvent solution of the nitrogen compound, such as an amine or quaternary. The pH of the mixture and the gelatin phase is reduced to at least 4.0 and preferably 3.0 or below, the liquid phases being intermixed to disperse and emulsify the organic solvent phase in the aqueous phase, thereby providing minute droplets of the basic nitrogen containing organic solvent surrounded by the aqueous solution of the acid-precursor gelatin. On the completion of the pH reduction, the gelatin will have formed a coating around the individual droplets to provide encapsulating skins therefor. While the encapsulated droplets can be recovered with some success at the lowest acid pH, it is much preferred to raise the pH to a pH at least above 5.5 and preferably to an alkaline pH before recovering the microcapsules. An auxiliary coating can be applied to the recovered microcapsules by contacting them with an aqueous solution of alkali-precursor gelatin.
Abstract:
PROCESS OF MICROENCAPSULATION EMPLOYING ALKALI-PRECURSOR (TYPE B) GELATIN AS THE ENCAPSULATING MACROCOLLOID, PARTICULARLY APPLICABLE TO THE FORMATION OF LIQUID CENTER MICROCAPSULES CONTAINING A BASIC (CATIONIC) NITROGEN COMPOUND. FOR EXAMPLE, AN AQUEOUS SOLUTION OF ALKALI-PRECURSOR GELATIN IS MIXED AT AN ALKALINE PH WITH A WATER-IMMISCIBLE ORGANIC SOLVENT SOLUTION OF A NITROGEN COMPOUND, SUCH AS AN AMINE OR A QUATERNARY. THE PH OF THE MIXTURE (VIZ, THE GELATIN PHASE) IS THEN REDUCED TO AT LEAST 4.5 AND PREFERABLY 3.8 OR BELOW, THE LIQUID PHASES BEING INTERMIXED TO DISPERSE AND EMULSIFY THE ORGANIC SOLVENT PHASE IN THE AQUEOUS PHASE, THEREBY PROVIDING MINUTE DROPLETS OF THE BASIC NITROGEN CONTAINING ORGANIC SOLVENT SURROUNDED BY THE AQUEOUS SOLUTION OF THE ALKALI-PRECURSOR GELATIN. AT THE LOW ACID PH, THE GELATIN FORMS A COATING ON THE DROPLETS AND PROVIDES ENCAPSULATING SKINS THEREFOR. WHILE THE ENCAPSULATED DROPLETS CAN BE RECOVERED AT THE LOW ACID PH, IT IS PREFERRED TO RAISE THE PH TO A PH ABOVE 5.5 (PREFERABLY 7.5-11), AND THEN RECOVER THE MICROCAPSULES. AN AUXILIARY COATING CAN BE APPLIED TO THE RECOVERED MICROCAPSULAR MATERIAL THUS PRODUCED BY CONTACTING THE MICROCAPSULES WITH AN AQUEOUS SOLUTION OF ACID-PRECURSOR GELATIN.
Abstract:
A process for production of weighted liquid center microcapsules by coacervation of a macro-colloid from an emulsion having minute droplets of a substantially water-immiscible organic solvent containing a chemical treating agent as the dispersed phase of an aqueous solution of macro-colloid as the continuous phase wherein a powdered metal compound is mixed into the aqueous phase prior to encapsulation resulting in weighted microcapsules having a specific gravity of 1.3 to 2.6. The powdered metal compound functions as an auxiliary wetting agent as well as a weighting agent.