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Calcium is important for skeletal structure, blood coagulation and nerve functioning. Calcium deficiencies can lead to osteoporosis.
The best sources of calcium are dairy products, but for those who cannot consume these, additional calcium is needed. Calcium
carbonate is the most widely used and least expensive calcium dietary supplement. As calcium is such an important supplement,
it is important to manufacture calcium carbonate tablets as effectively as possible.
Manufacturing calcium carbonate tablets, as with many other tablets, involves processing steps where powder particles adhere
to each other into larger particles or granules (granulation) before being formed into the final tablet. The granulation step
has many advantages, such as reducing dust, improving the flow properties of the powder mix and preventing the constituents
of the mixture separating.1
There are two granulation methods: wet and dry. Wet granulation involves agitating the powder, and adding a polymeric binder
and liquid to bind the particles together. As the liquid is either water or a mixture of water and alcohol, a drying step
is required after granulation.2 Dry granulation involves pressing the powder between a tabletting press or the rollers of a compaction or briquetting machine.
Since no solvent is added to the powder, a drying step is not required, which is good for moisture- or heat-sensitive drugs,1 as well as being more environmentally friendly and economical than wet granulation. Powders with temperatures up to 1000
°C can also be compacted. However, dry granulation often produces tablets with low compactability, meaning they have low mechanical
strength.3
MethodsGranule preparation. An experiment was conducted to determine whether dry granulation is suitable for producing calcium carbonate tablets. This
study used precipitated calcium carbonate and four commonly used excipients: microcrystalline cellulose (Avicel PH101) (MCC),
hydroxypropyl cellulose (Klucel) (HPC), maltodextrin (MD) and polyethylene glycol (PEG). All these excipients are widely known
and used because of their good binding properties. Two main types of granules were used: granules of calcium carbonate prepared
by roller compaction and milling, and granules containing calcium carbonate and maltodextrin prepared by wet granulation and
milling.
A Miniroll (Riva SA, Argentina) system was used to compact the powder. The applied force of the rollers was 0–3000 kg, and
the diameter and width of the rollers was 135 mm and 26 mm, respectively. The pressure, roll and feeder speed could be varied
and stored for further experiments.
Table 1 Varying parameters during compaction of the different batches.
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The experiment used two combinations of Miniroll, pressure and roll and feeder speeds, which gave the greatest difference
in tablet properties. These were picked by compacting 12 samples of calcium carbonate with no excipients added using different
combinations of Miniroll settings. After being formed into tablets, their tensile strength and porosity were measured (Table
1). The pressures used ranged from 30 to 75 kg/cm2 , the feeder speeds from 18 to 40 rpm and the roll speeds from 6 to 2 rpm. The settings that gave the greatest difference
in properties are highlighted in Table 1.
