Calcium carbonate in paper

Calcium carbonate - The use of calcium carbonate in paper coatings had been restricted to specialty applications prior to the advent of alkaline papermaking. A large amount of the furnish for the coated paper s base stock is composed of coated broke. The calcium carbonate in the coating was incompatable with the acid pH in the wet end. 

The use of calcium carbonate in paint, paper, and plastics make up the principal part of the market. In the paper industry calcium carbonate products find two uses as a filler in the papermaking process and as a part of the coating on paper. 

One major paper attacking the problem of the relationship between the preservation of calcium carbonate in shallow anoxic marine sediments and their chemistry was by Aller (1982). The study was conducted at sites in Long Island Sound. The calcium carbonate content of the sediments decreased with increasing water depth. At the shallow FOAM (Friends of Anaerobic Muds) site shell layers associated with storms resulted in irregular variations in the carbonate content of the sediment. Ca2+ loss from the pore waters, indicative of calcium carbonate precipitation, was found only at the FOAM site below -20 cm depth. During the winter, elevated Ca2+ to CL ratios were observed near the sediment-water interface... 

Figure 4. Presence of alum and calcium carbonate in book papers, 1500-...

The principal components of ash are calcium carbonate— in the form of precipitated calcium carbonate (PCC) or ground calcium carbonate (GCC)—that typically constitutes 20% and up to 75% of dry sludge content, and clay. These two minerals are typically loaded into paper as a coating and filler to improve the mechanical characteristics as well as the appearance of paper. The resulting papermaking sludge, particularly mixed office paper sludge, consists primarily of two major components, that is, fiber and minerals finely mixed with each other. 

Uses Optical brightener for stock applic. in sized and unsized papers, esp. neutrally sized and calcium carbonate-filled papers and for use in coatings which contain casein as a sec. binder Features H igh ly su bstantive exhibits very good buildup even at low cones. very good stability to hard and soft water and alkaline conditions for use continuously or batchwise compat. with most anionic and nonionic prods. Properties Yel.-brn. clear liq. readily dilutable with water dens. 1.211 kg/ I vise. < 150 mPa s (20 C), < 600 mPa s (0 C) solid, pt. -18 C pH 8.5 anionic... 

Calcium carbonate or whiting is commonly also used in paints, coatings, adhesives, plastics, glazing, ceramics, and blackboard chalk. More calcium carbonate is being used in place of clay in paper manufacture because calcium carbonate has a neutralizing effect on acid components in paper. Europe has been using calcium carbonate in place of clay in paper manufacture for many years. 

Air floated and water-washed grades of kaolin are widely used in paper, packaging and construction adhesives based on starch, emulsion and latex based waterborne systems. They are also used in fabric adhesives, mastics and caulking compoimds. Calcined kaolin is used as a low moisture reinforcing agent in one or two part construction and automotive sealants based on butyl, methane and silicone elastomers. Calcined kaolin is less acidic and so can be used with precipitated calcium carbonate in polysulfide sealants. Typical loading of kaolin fillers are 5 to 25% in adhesives, 5 to 20 % in sealants, and 25 to 50 % in mastics. 

Rotary kilns and, to a lesser extent, Fluo-SoHds kilns are used to calcine a wet precipitated calcium carbonate filter cake in the kraft or sulfate paper-pulp process (15). Lime is regenerated for use as a causticization reagent in recovering caustic soda for pulp digestion. Losses in lime recovery are replaced by purchased lime (see Paper Pulp). 

Though functionally and chemically similar, fillers and pigments ate distinguished from one another in that fillers are added at the wet end of the paper machine, and serve to fill the sheet pigments are added at the size press and serve to alter the surface of the sheet. The most common fillers are mineral pigments, eg, clay, titanium dioxide [13463-67-7] calcium carbonate, siUca [7631-86-9], hydrated alumina [21645-51 -2], and talc [14807-96-6]. 

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