초록 ▼

An inorganic particulate material suitable for use as a pigment material in a paper coating composition has a particle size distribution which when represented as a graph of percentage of weight of particles having an equivalent spherical diameter (esd) of given size versus particle esd expressed in

An inorganic particulate material suitable for use as a pigment material in a paper coating composition has a particle size distribution which when represented as a graph of percentage of weight of particles having an equivalent spherical diameter (esd) of given size versus particle esd expressed in microns and plotted on a logarithmic base 10 scale has the following features: (a) a first peak at the coarse particle size and a second peak at a finer particle size and a dip or trough between the first and second peaks; (b) the mean particle size x.sub.1 of the particles making up the first peak being 2 to 4 microns; (c) the relationship between the first and second peaks being such that the value of the mean particle size x.sub.2 of the particles making up the second peak is separated in the particle size distribution graph from the value of x.sub.1 by at least 0.5; and (d) the minimum of the dip or trough is at a given particle esd dimension of between 0.5 and 5 microns. The material may be obtained by mixing in suitable amounts a coarse pigment material and a fine pigment material having individually the appropriate particle size distributions. The coarse and fine pigments may be calcium carbonate. The fine material may also contain kaolin.

대표청구항 ▼

[ I claim:] [1.] An inorganic particulate material suitable for use as a pigment composition in a paper coating composition which particulate material comprises material selected from one or more of kaolin, calcined kaolin, dolomite, ground natural calcium carbonate, precipitated calcium carbonate,

[ I claim:] [1.] An inorganic particulate material suitable for use as a pigment composition in a paper coating composition which particulate material comprises material selected from one or more of kaolin, calcined kaolin, dolomite, ground natural calcium carbonate, precipitated calcium carbonate, calcium sulphate or talc and has a particulate size distribution which when represented as a graph of percentage of weight of particles having an equivalent spherical diameter (esd) defined herein of given size versus particle esd expressed in microns and plotted on a logarithmic base 10 scale has the following features:(a) a first peak at a coarse particle size and a second peak at a finer particle size and a dip or trough between the first and second peaks; (b) the mean particle size x.sub.1 of the particles making up the first peak being in the range of from about 2 microns to about 4 microns; (c) the relationship between the said first and second peaks being such that the value of the mean particle size x.sub.2 of the particles making up the second peak is separated in the said particle size distribution graph from the value of x.sub.1 by at least 0.5; and (d) the minimum of the dip or trough is at a given particle esd dimension of between 0.5 microns and 1.5 microns.