Patent GB-1000672-A (GB)
Title: Calcium carbonate dispersions
Inventor: VOORHEES VANDERVEER
IPC: C10M159/20
Filed: 1963-08-09
Abstract: A transparent colloidal dispersion of calcium carbonate in oil is obtained in a two-stage reaction in which, in the first stage, CO2 is passed into a suspension of finely-divided calcium oxide (derived by burning CaCO3 above 2000 DEG  F.) in methanol of <1% by volume water content in an amount 5-50% of that required to convert CaO to CaCO3 and, in the second stage, the oil and an oil-soluble dispersant are added and further CO2 is passed in to complete absorption, the dispersion then being distilled to remove methanol, treated with water and dehydrated.  A thinner such as a "naphtha," particularly Stoddard solvent, kerosene, or preferably varnish maker's and painter's naphtha or alternatively an aromatic solvent such as benzene, toluene or xylene or a chlorinated solvent such as carbon tetrachloride or trichlorethylene may be included in the oil dispersion. Suitable oils are the petroleum lubricating oils, low-viscosity hydraulic oils, synthetic polyolefinic hydrocarbons such as polypropylene and polybutylene, the non-hydrocarbon polyethers and polyesters e.g. the esters of di-basic acids such as dinonyl, dilauryl and dioctyl adipate, azelate, sebacate and phthalate, the fatty acid glycerides and glycol esters and the esters of polyfunctional alcohols such as trimethylol propane. Sulphonic, phosphonic and carboxylic acids of at least 12, usually 20-60, carbon atoms may be used as dispersing agents.  The oil-soluble sulphonates, particularly the petroleum or "mahogany" sulphonates are preferred; C20+ alkyl salicylic acids, the higher fatty acids, oleic, stearic, arachidic and erucic acid, naphthenic acids and the resin acids, characterized by abietic acids, are also suitable. The dispersant may be used as the free acid but is preferably in the form of its salt with calcium (preferred) barium, magnesium, lithium, sodium or potassium.ALSO:A transparent colloidal dispersion of calcium carbonate in oil is obtained in a two-stage reaction in which, in the first stage, CO2 is passed into a suspension of finely-divided calcium oxide (derived by burning calcium carbonate above 2000 DEG F.) in anhydrous methanol, i.e. methanol of <1% by volume water content, in an amount 5-50% of that required to convert CaO to CaCO3, and, in the second stage, the oil and an oil-soluble dispersant are added and further CO2 is passed in to complete absorption, the dispersion then being distilled to remove methanol, treated with hot water or wet steam and dehydrated.  The finely-divided calcium oxide is preferably ground to pass a 100 mesh sieve (U.S. Standard) and may be mixed with methanol in a ratio 10-30: 100 parts by weight, treated with CO2 to a 25% oxide to carbonate conversion, mixed with a solution of the dispersing agent in the oil in weight ratio calcium oxide: oil-sulphonate 1: 5 to 1: 3, and treated with further CO2, the temperature throughout being maintained above 70 DEG  F. and below 150 DEG  F., or below the boiling point of methanol at the pressure employed; the quantity of water used in the subsequent treatment may be 1-20%.  A solvent or thinner such as a naphtha, benzene, toluene or xylene, carbon tetrachloride or trichloroethylene may be included in the dispersion, usually 1/2 to 2 volumes of solvent per volume of oil being used.  The dispersing agent and solvent are most conveniently blended with the oil before mixing with the methanol and the calcium oxide but may be added to the methanol if desired. Suitable dispersing agents are the sulphonic, phosphonic and carboxylic acids which have at least 12, usually 20-60, carbon atoms; oil-soluble sulphonates, particularly "mahogany sulphonates" are preferred, particularly in the form of their soaps with calcium, which is preferred, barium, magnesium, lithium, sodium or potassium. The oil employed is generally a petroleum lubricating oil, but low viscosity hydraulic oils, synthetic hydrocarbon oils, nonhydrocarbon oils such as polyethers and polyesters, and fatty oils may also be used.  The oil dispersion is desirably filtered, either before removing solvent or as the final step in the process, for example using a diatomaceous earth. Solvent stripping may be effected at 400 DEG  F.