Agglomerated microcapsules

The commonly used complex coacervation processes of microencapsulation have several drawbacks, including a need for constant attention and the adjustment of stirring conditions, solution viscosity, pH, and temperature. The process also often produces significant amounts of agglomerated microcapsules. A European... 

One of the major problems related to the capsule formation is capsule agglomeration. It involves the irreversible or largely irreversible sticking together of microcapsules that can occur during the encapsulation process and/or during the isolation step. 

It was determined that the ideal stilt material should have a size 1.5-2.5 times the diameter of the microcapsules or microcapsule clusters. Since the microcapsules are often agglomerated into clusters of a maximum size of 10 pm, the optimal stilt diameter should vary from 15 to 25 pm, with an average of 20 pm.204 In addition, a round stilt material is more efficient than a polygonal material which can fracture the microcapsules by contact. It also should possess a certain rigidity to provide protection to the microcapsules during normal manipulation of the carbonless paper, but not be so... 

Suspensions of liposomes, microspheres and microcapsules, and nanospheres and nanocapsules formed from a variety of polymers or proteins, as discussed in section 8.6.3 form a new class of pharmaceutical suspension in which physical stability is paramount. It is important that on injection these carrier systems do not aggregate, as this will change the effective size and the fate of the particles. The exception to this is the deliberate flocculation of latex particles administered to the eye, where aggregation leads to agglomerated... 

The so-called multinucleus-type capsules/ microcapsules are essentially agglomerated particles with prescribed released characteristics, which can be controlled by the concentration and solubility of the binder. In agglomeration, the amount of binder is kept to a minimum, as long as the agglomerates are... 

This unique process introduced a reaction period at elevated temperature between emulsification and polyamine addition, and allows microcapsules of 10 pm or less average diameter to be made at greater than 40% by weight solids without agglomeration or resultant excess viscosity. 

The microcapsules can be seen under the microscope as individual spherical particles or as small agglomerates. 

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