Patent ID: 7758688

Claim:
A composition comprising calcined kaolin, the calcined kaolin having a particle size distribution wherein: ( particle ⁢ ⁢ size ⁢ ⁢ at ⁢ ⁢ a ⁢ ⁢ cumulative ⁢ ⁢ mass ⁢ ⁢ of ⁢ ⁢ < ⁢ 80 ⁢ % ) ( particle ⁢ ⁢ size ⁢ ⁢ at ⁢ ⁢ a ⁢ ⁢ cumulative ⁢ ⁢ mass ⁢ ⁢ of ⁢ ⁢ < ⁢ 20 ⁢ % ) ≤ 3 ; further wherein the calcined kaolin has a median particle size ranging from at least about 1 μm to about 3 μm; and the total of alkali and alkaline earth metals present in the composition is less than or equal to about 0.6% by weight, relative to the total weight of the composition.