The expansion of kaolin materials leads to an increase of the division stage of the clay, not by a grinding process but by a process of de-lamellation. The initial microcrystal consisting of parallel, adjacent two dimensional layers having the general composition Al.sub.2 O.sub.3 --2SiO.sub.2 --2H.sub.2 O is transformed into a microcrystal which has approximately the same composition and morphology, but between the layers of which certain molecules have been introduced.
In this manner, the accessible surface area increases from about 20 to about 800 m2/g, which would correspond for spherical particles to decrease their cross section by a factor of 40 (for instance by grinding).
Intercalation complexes of montmorillonite with quaternary amines (Bentones) having specific areas of about 800 m2/g are known. These bentones are used as a loading for paintings and varnishes, as thickeners in greases, etc.
As the natural deposits of montmorillonite minerals are rather limited, and as the demand for bentones goes ever increasing, there has been considerable investigation for finding substitute products for this type of products.
The scientific literature thus discloses a kaolinite complex with potassium acetate. This kaolinite complex was prepared by grinding the clay with potassium acetate.
There is also known a hydrazine-kaolinite complex obtained by dispersing the clay in hydrazine.
There is further described an ammonium acetate complex of kaolinite which is prepared by contacting the kaolinite with a saturated ammonium acetate solution. The reaction is very sensitive to pH and temperature and is reported to be rather troublesome.
A number of specific intercalation complexes of kaolinite in the series consisting of kaolinite complexes with alkaline metal (Na, K, Rb, Cs) salts of lower aliphatic acids (acetic, propionic, butyric, isovaleric acids) have also been described. Some of these may be obtained by direct contact of the kaolinite with a saturated solution of the salt to be intercalated; others are very slow or impossible to form according to this method; another disclosed method for obtaining this specific type of intercalation complexes of kaolinite comprises using hydrazine as a "hauling agent" (German: "Schlepper") to introduce the salt into the kaolinite lattice.