CS257648B1 - A method for producing an activated coating pigment for a color developing layer of direct copy paper - Google Patents

Abstract

A method of producing an active material for the receiving layer of direct-copy papers, in which alkaline triphosphate is used to increase the final whiteness and reduce viscosity. The iron ions released in the acid activation process are bound to colorless complexes by the addition of triphosphate. This increases the whiteness of the final product and at the same time improves its rheological properties.

Description

The present invention relates to the production of an active pigment for a color developing layer of direct copy paper in which a color forming reaction is applied to the surface of the active pigment.

In the papermaking industry, pigment production is used in the production of self-copy paper, which allows color transcription to be induced. As a pigment, it is used specifically, mostly by acid activation of treated natural or synthetic aluminosilicates or mixtures thereof. Pigment, due to papermaking technology, must have certain properties, in particular it should be as whitish as possible and its viscosity must be low.

The active pigment is obtained either by the acid activation of sorted clay raw materials or synthetically in various forms of alumosilicates. Acid activation is usually accomplished by heating the feedstock with acids. The activated clay feedstock is further washed with water, filtered, dried, optionally annealed, ground and graded. The finely sorted acid-activated feedstock is then used as a basic component to prepare the coating paste for the uptake layer of the carbonless paper.

These methods of preparing active pigments are described in the following foreign patents: NSR Pat. No. 2303825, 2512448, 2213130,

US Pat. No. 3963852,

United Kingdom pat. No. 1307319.

The active pigment obtained as described above exhibits some drawbacks, such as low whiteness and a higher viscosity of the supplements prepared therefrom, when applied to the uptake layer of the carbon black paper.

Said drawbacks are overcome by the coating pigment prepared according to the invention, where an alkaline triphosphate is added to the acid activated clay feed suspension as an agent to increase the whiteness of the final product and reduce its viscosity.

The following examples illustrate the invention in greater detail:

Example 1

The extracted bentonite raw material is disconnected in the chain breaker with water, the sand fraction is separated to 0.3 mm sieves and the undersized bentonite mash is acidified by the addition of 8% wt.

100% HCl (based on raw material) as a concentrated acid. Activated at boiling for 4 hours. The suspension contains 200-400 g / l solid phase. After activation, the alkaline triphosphate solution is added to the hot slurry in a 4% wt. Solution. The whiteness of the final activation product will increase by 2% when using alkaline triphosphate compared to the product where the triphosphate is not used.The suspension of the pigment thus produced shows a lower viscosity value compared to the pigment where the triphosphate has not been used.

Example 2

For activation according to Example 1, bentonite in admixture with kaolin is used as starting material. Kaolin is mixed with the bentonite feedstock prior to acid activation.

Example 3

For activation according to Example 1, instead of concentrated hydrochloric acid, an eluate from the production of citric acid is used. The eluate contains 6 to 8 wt. % HCl. The eluate is added to the suspension prior to activation in an amount of 8 wt. % HCl (based on the weight of the solid phase of the suspension). Upon completion of activation, an alkali triphosphate in an amount of 4 wt. % (based on raw material again). The procedure is the same as in Example 1.

Claims (1)

SUBJECT OF THE INVENTION A process for the production of an activated coating pigment for a color-forming layer of direct copy paper, wherein the bentonite, optionally in admixture with kaolin, is activated by heating with acid, filtered, washed with water, dried, ground and graded. the suspension is mixed with 1 to 20 wt. alkali triphosphate, based on dry weight.