Mizusawa Industrial Chemicals, Ltd.

Kazumitsu Enomoto

Masahide Ogawa

Masao Takahashi

Kiyoshi Abe

Toshio Kitsu

Yuuzi Washio

Teiji Sato

The amorphous silica has a large apparent specific gravity despite of its BET specific surface area of 200 to 500 m.sup.2 /g, has an oil absorption amount of as small as 50 to 120 ml/100 g, has an agglomeration degree (D1/D0=DA) defined by the ratio of silica elementary particle diameter D0 to primary particle diameter D1 of from 10 to 50, and has nearly a spherical particulate structure which is quite different from that of the conventional gelation method silica (DA=OO). The amorphous silica-type filler exhibits excellent properties in regard to handling, processability, dispersion property and abrasion-resistant property and, when added as, for example, an anti-blocking agent, makes it possible to obtain resin films having transparency and scratch-resistant property without fisheyes or voids. Owing to the above properties, the amorphous silica that is used as a filler for the heat-sensitive recording papers suppresses ground fogging, improves the image concentration, makes it possible to apply a highly viscous coating solution since the filler dispersed in an aqueous solution creates very small viscosity, and imparts excellent abrasion resistance to the apparatus during the step of coating.

Amorphous silica filler

The amorphous silica has a large apparent specific gravity despite of its BET specific surface area of 200 to 500 m.sup.2 /g, has an oil-absorption amount of as small as 50 to 120 ml/100 g, has an agglomeration degree (D1/D0=DA) defined by the ratio of silica elementary particle diameter D0 to primary particle diameter D1 of from 10 to 50, and has nearly a spherical particulate structure which is quite different from that of the conventional gelation method silica (DA=.infin.). The amorphous silica-type filler exhibits excellent properties in regard to handling, processability, dispersion property and abrasion-resistant property and, when added as, for example, an anti-blocking agent, makes it possible to obtain resin films having transparency and scratch-resistant property without fisheyes or voids. Owing to the above properties, the amorphous silica that is used as a filler for the heat-sensitive recording papers suppresses ground fogging, improves the image concentration, makes it possible to apply a highly viscous coating solution since the filler dispersed in an aqueous solution creates very small viscosity, and imparts excellent abrasion resistance to the apparatus during the step of coating.

The amorphous silica has a large apparent specific gravity despite of its BET specific surface area of 20 to 500 m.sup.2 /g, has an oil absorption amount of as small as 50 to 120 ml/100 g, has an agglomeration degree (D1/D0=DA) defined by the ratio of silica elementary particle diameter D0 to primary particle diameter D1 of from 10 to 50, and has nearly a spherical particulate structure which is quite different from that of the conventional gelation method silica (DA=.infin.). The amorphous silica-type filler exhibits excellent properties in regard to handling, processability, dispersion property and abrasion-resistant property and, when added as, for example, an anti-blocking agent, makes it possible to obtain resin films having transparency and scratch-resistant property without fisheyes or voids. Owing to the above properties, the amorphous silica that is used as a filler for the heat-sensitive recording papers suppresses ground fogging, improves the image concentration, makes it possible to apply a highly viscous coating solution since the filler dispersed in an aqueous solution creates very small viscosity, and imparts excellent abrasion resistance to the apparatus during the step of coating.

Amorphous silica-type filler

Disclosed is a filler for ink jet recording paper, said filler being composed of amorphous silica particles having a median diameter, measured by the coulter counter method, of 2 to 15 .mu.m, an oil absorption of at least 180 ml/100 g, a refractive index, measured by the solvent method, of at least 1.450, and a moisture absorption, measured when it is caused to absorb moisture for 200 hours at a relative humidity of 90% and a temperature of 25.degree. C., of at least 35%, and a coating of a compound of a metal of Group II of the periodic table on the surface of the silica particles in an amount of 0.5 to 20% by weight.

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Niigata, Japan

Kazumitsu Enomoto