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PCC is a purified, synthetic or refined Calcium Carbonate. It stands for Precipitated Calcium Carbonate. PCC has same chemical formula as other Calcium Carbonates like chalk, marble and limestone. The carbon, oxygen and calcium atoms can arrange themselves in three diverse ways in order to create three different calcium carbonate minerals. One of the most common arrangement is for both ground and precipitated calcium carboneates is the hexagonal form, which is acknowledged as Calcite. Various calcite crystal forms can be made: prismatic, scalenohedral and rhombohedra. Apart from the most common arrangement, there is also a less common arrangement that is called aragonite. It has a clustered or discrete needle orthorhombic crystal structure. Generally unstable and rare is the vaterite calcium carbonate mineral.
Calcium Carbonates that also include PCC, are non-toxic. The Food and Drug Administration of USA has affirmed Calcium Carbonate to be GRAS. It means that Calcium Carbonate is generally recognized as safe. If PCC meets the purity requirements then it can be used as a pharmaceutical, direct food additive and as an indirect additive in paper products, which come in contact with food. Similar approvals and acceptances exist all over the world where PCCs are used extensively in these applications. You can check out the Contact Us link to know specific regulations covering the usage of PCCs in these health-related uses. You can also check the MSDS link to download a Material Safety Data Sheet that covers a Specialty Minerals Inc.'s PCC Product.
Since 1841, PCCs have been made for commercial purposes. These were first manufactured by the English company, John E. Sturge Ltd. It treated the residuary calcium chloride from their potassium chlorate and manufactured it with carbon dioxide and soda ash to make precipitated chalk. Later in the year 1898, a new factory was established in Birmingham. Here, the milk of lime process is used to make the PCCs. This operation or process is now the part of the Performance Minerals Group of SMI.
In U.S., the production of PCC began in the year 1938. It began when the C.K. Williams Company in Massachusetts, started making PCC with the use of limestone from their adjoining mine. Later, this plant was acquired by Pfizer in the year 1962. It became part of the Performance Minerals Group of SMI on the creation of our parent, Minerals Technologies Inc., in 1992.
Almost every PCC is manufactured by direct carbontion of hydrated lime, which is recognized as the milk of lime process. This process is very simple in concept:
This process is effortless on a laboratory scale. But when it comes to making the precipitated calcium carboneates on a large scale for commercial purposes, then it is a great deal of process technology and process control to ensure the surface area, right size, shape, uniformity and surface chemistry. This body of PCC technology, which is developed by us, is what makes our PCCs excellent in consistency and quality.
PCC is mostly made by using high purity calcium carbonate rock, which is called limestone. We use premium quality limestone sources for our PCC products, including some of our mines. Limestone is a result of skeletons being laid down on the ocean floor and a very thick layer of prehistoric sea shells. These skeletons and shells were largely composed of calcium carbonate. Over the time of five hundred million years, this limestone deposit was under high pressure and high temperature and therefore it changed to a coarsely crystallized limestone. The organic matter that was present in the deposit was removed throuogh a oxidation process called diagenesis.
If this type of geological process continues for a long period of time, then the crystals become very small and form marble, which is a very hard form of calcium carbonate. If the time, pressure and temperature are not great, then the seabed only partly metamorphoses. Therefore, the result is soft chalk like the formation of Whilte Cliffs of Dover in England. When you pick up the chalk, you can still see the remnants of skeletons and shells.
There are two main reasons. First of all, there are various points in the PCC process where Calcium Carbonate is purified. Much of the rock is removed from the deposit, which is not calcium carbonate. You will always find some impurities in any limestone deposit. These comprise heavy metals, feldspar as well as other silicaceous minerals. Second, the PCC process allow us to grow crystals of various shapes. The particle formed is dictated by the temperature, control of reaction time, pressure, agitation, rate of carbon dioxide addition and post-crystallization processing. These shapes- cubes, clustered needles, rhombohedrons and prisms have various physical properties like powder density, oil absorption and surface area that give them excellent performance in many applications where ground calcium carbonate does not have good performance.
Not only this, the precipitation process also helps in the growing of very fine particles, down to hundredths of a micron or nanometers-much finer than which can be acquired by just crushing the limestone rock. These ultrafine nano PCCs have good applications where excellent performance is needed.
The various shapes enable PCC to act as a functional additive in adhesives, sealants, plastics, inks, rubber, paper, nutritional supplements, pharmaceuticals and many other demanding applications. A formulator can select a shape as well as the physical properties, which result from that shape that ensure the excellent performance in the end use.
In the process of PCC, products can be manufactured with very small sizes with high oil absorption, high surface areas, or/and with different powder bulk density-from super high powder to ultra low densities.
PCCs often have coating of a low percentage (1 to 3%) of a fatty acid like organic materials or stearic acid for use in non-aqueous systems. These coatings increase the dispersibility of the PCC in the solvent or polymer as well as its compatibility with the solvent or polymer that in turn maximizes the efficiency and performance of the PCC. The selection of coating depends on the type of polymer, which will be used in the PCC and also the performance desired. As polymers differ widely in solubility and polarity constants, different organics are selected to ensure the best balance of properties and the best compatibility.
How Does Precipitated Calcium Carbonate Differ From Ground Calcium Carbonate (GCC)?
When it comes to the chemical composition, they are the same. PCC is much purer than the limestone from which it is manufactured. It is lower in lead and silica. PCC's size and shape are different from that of ground calcium carbonate (GCC).
GCC becomes irregularly rhombohedral in shape under high magnification. The PCC crystal shape depends on the product. While the particles are regular and more uniform. The dispersion of particle sizes in a GCC is much broader as compared to the PCC of the same size- because there are several large and small particles than in a PCC.
As compared to the GCC, the lower top size of a PCC ensures excellent impact resistance in plastics. The smaller particle size distribution enables the generation of high oil absorption, which is useful in certain applications.
We are one of the most renowned manufacturer of PCCs, with an output of more than 4 million tons of PCC each year. We offer our PCC products for paper, paperboard filling and coating that include Velacarb®, Megafil® and Opacarb® precipitated calcium carbonates. For pharmaceutical products, food, nutritional supplements and personal care products, the series of five CalEssence® ultra low lead PCCs and eight ViCALity® USP/FCC precipitated calcium carbonates are made by us. Calopake EP PCC and Five SturcalTM healthcare grades are made by us.
A wide range of water-based and polymeric industrial products use Albaglos®, Super-Pflex®, Albacar® and Tuffgard® PCCs along with the Multifex-MM®, Ultra-Pflex®, nano PCCs and a series of Thixo-Carb® PCCs that come from U.S. The Calofort® nano PCCs and Calopake® PCC come from our production plant.