Agglomerate particle form

The initial process to achieve success was developed by Miyata of Kyowa in the mid 1970s [101].This process is based on the hydrothermal conversion in an autoclave of the fine agglomerated particles formed by addition of ammonia or lime to a magnesium salt solution. This hydrothermal conversion results in the formation of particles of about 1 micron in size and with a fairly low aspect ratio. This original process appears to be expensive to operate because of the low value of the ammonium or calcium chloride co-product which has to be disposed of and because the reported reaction conditions give a low yield and a relatively slow reaction. 

Using a highly simplified agglomerate particle shape, the relation between the number of agglomerated particles formed by a combination of primary particle of diameter, dp, is given by... 

In order to obtain a homogenous and stable latex compound, it is necessary that insoluble additives be reduced in particle size to an optimum of ca 5 )Tm and dispersed or emulsified in water. Larger-size chemical particles form a nucleus for agglomeration of smaller particles and cause localized dispersion instabiHty particles <3 fim tend to cluster with similar effect, and over-milled zinc oxide dispersions are particularly prone to this. Water-soluble ingredients, including some accelerators, can be added directly to the latex but should be made at dilute strength and at similar pH value to that of the latex concentrate. 

In drying solutions or slurries of solutions, the location of the feed-injection nozzle (spray nozzle) has a great effecl on the size of particle formed in the bed. Also of importance are the operating temperature, relative humidity of the off gas, and gas velocity. Particle growth can occur as agglomeration or as an onion sldnuing. ... 

The polymer particles are not stabilized and tend to agglomerate to form a polymer paste or slurry. In addition, the polymerization rate is independent of the number of particles ( ). ... 

There is an upper limit of about 23 microns in size. This may be due to the fact that the precipitation was accomplished at 90 C., or from the fact that rare earth oxalates tend to form very small particles during precipitation which then grow via Ostwald ripening and agglomeration to form larger ones. Nevertheless, it is clearly evident that when the oxalate is heated at elevated temperature ( 900 °C), the oxide produced retains the same PSD characteristics of the original precipitate. 

Venturi and orifice scrubbers are simple forms of wet scrubbers. The turbulence created by the venturi or orifice is used to atomise water sprays and promote contact between the liquid droplets and dust particles. The agglomerated particles of dust and liquid are then collected in a centrifugal separator, usually a cyclone. 

Pharmaceutical scientists have developed improved suspension dosage forms to overcome problems of poor physical stability and patient-perceived discomfort attributed to some active ingredients. An important development aspect of any suspension is the ability to resuspend easily any settled particles prior to instillation in the eye and ensure that a uniform dose is delivered. It would be ideal to formulate a suspension that does not settle since the patient may not always follow the labeled instructions to shake well before using. However, this is usually not feasible or desirable since the viscosity required to retard settling of the insoluble particles completely would likely be excessive for a liquid eyedrop. The opposite extreme, of allowing complete settling between doses, usually leads to a dense layer of agglomerated particles that are difficult to resuspend. 

Using sands of narrow and wide size distributions suspended in various organic liquids, Capes and Sutherland (C7) have shown that large, compact agglomerates are formed if the amount of the bridging liquid is sufficient to occupy about 44-88% of the pore space in a densely compacted bed of sand particles. The final size distribution attained represents a balance between... 

For surface energy reasons, the tendency of these small particles to agglomerate and form crystallites increases with decreasing particle size. This is particularly true for the final phase of pigment manufacture, the drying and milling processes. 

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