Calcium carbonate is a white powder commonly found in
rocks and in shells of marine and land organism, pearls, and egg shell. The
main applications of calcium carbonate are in paper, construction industry,
paints, plastics, ceramics and food. It is also found in agricultural
lime which adjusts soil properties and acts as a fertilizer. It is
commonly used as a calcium supplement or antacid.
Calcium carbonate is processed into different types; grounded or
GCC, precipitated or PCC and coated precipitated or CPCC. The particle sizes in
PCC are smaller than GCC and thus it is more effective as filler in products
such as paper for better brightness, opacity and printability. PCC also offers
better retention than other fillers and reduces fiber consumption as it fills
the paper effectively. It is less abrasive than GCC due to the smaller size and
thus the paper machine lasts longer and has greater speed, productivity and
readability. However, paper containing PCC has poorer formed than those
GCC is cheaper and provides relatively high brightness. GCC also
creates a porous surface due to the large particle size and as it is
hydrophobic, it liberates water readily. PCC is coated with small amount of
fatty acids such as stearic acid or other organic materials to be used in
non-aqueous systems to obtain a coated precipitated calcium carbonate or CPCC.
The coatings allow greater compatibility and easier dispersal of PCC in polymer
or solvent. Overall, the coating enhances the performance and efficiency of the
PCC. The enhanced performance in the CPCC differentiates itself from GCC and it
is commonly used in polymers such as PVC.
Most industrial calcium carbonate is extracted by mining or
quarrying. The pure form can be produced from pure quarried sources such as
marble. Pure calcium carbonate minerals include calcite, aragonite and
vaterite. Industrial sources of calcium carbonate include rocks such as
limestone, chalk, marble and travertine, and shells such as eggshells and
seashells. Ground calcium carbonate (GCC) is made from crushing limestone to
create a powder like form which is graded by size and other properties for
It can be prepared from calcium oxide. Water is added to calcium
oxide to give calcium hydroxide, and carbon dioxide is passed through
calcium hydroxide to precipitate calcium carbonate. Precipitated calcium carbonate
(PCC) is derived from this method, which has very fine and controlled particle
size on the order of 2 microns in diameter. Coated calcium carbonate is made
from precipitating calcium carbonate by coating it with stearic acid.
Typically, GCC is used in the construction industry, as building
material by itself, such as marble, or as an aggregate of limestone for road
building. It is also a raw component of cement or as a starting material for
lime which is important for materials such as glass by burning in a kiln. It is
also used to make mortar for bonding, building materials such as bricks,
concrete blocks, stones and tiles.
PCC and GCC is used as a filler in paper during the alkaline
paper making process to make the paper bright and smooth. It can also be used
to coat the paper white. Calcium carbonate results in paper having a high
degree of whiteness, opacity, gloss and brightness and good printability yet
the paper can be sold at attractive prices. The use of PCC, especially ensures
paper machines last longer and operate faster.
Typically, PCC is used as an extender in paints, particularly in
the matte emulsion paint which has chalked or marble typically 30% by weight in
the paint. PCC is used by itself as it can be used as a white pigment or with
additives as white paint or in whitewashing.
Typically, CPCC is used as filler in plastics to improve
mechanical properties such as tensile strength and elongation and electrical
properties such as volume resistivity. Polypropylene compounds are filled with
calcium carbonate to increase rigidity, especially to withstand high
temperatures. It is used as filler in thermosetting resins, and is mixed with
other ingredients to form compression molded poker chips.
Calcium carbonate is known as whiting, and it is commonly used
for many glazes in its white powdered form. The whiting acts as a flux material
in the glaze when the glaze is fired in a kiln. Ground calcium carbonate will
not scratch most materials such as glass and ceramics, and have a moderate
effect on softer metals such as copper.
Usually, PCC is used as a food preservative. Regulating acidity,
it prevents caking and acts as a stabilizer and maintains color of food. Soy
milk and almond milk products such as dietary calcium sources also apply
Calcium Carbonate in the production. It serves as a firming agent in many
canned or bottled vegetable products, and functions as raw material in sugar
refining from sugar beet.