WO1996021697A1 - Process for preparing pigments - Google Patents

Abstract

The present invention relates to the preparation of coated pigments and may be used in chemical industry, construction materials industry as a substitute for traditional pigments in the preparation of paints, enamels, colored cements, concretes, ceramics, polymeric and other materials. A filler is ground in a vibrating centrifugal mill, thereupon the ground filler is mixed with a dye for not less than 4 minutes, wherein co-treating of the mixture so obtained is also carried out in the vibrating centrifugal mill. The present process affords reduction of power consumption and simplification of the manufacturing process.

Description

PROCESS FOR PREPARING PIGMENTS

TECHNICAL FIELD

The present invention relates to the preparation of coated Pigments and may be used in chemical industrt, construction materials industry as a substitute for traditional pigments in the preparation of paints, enamels, colored cements, concretes, ceramics, polymeric and other materials.

BACKGROUND ART

There has been known a process for preparing pigments bv co-grinding a filler (talo) and a dye (titanium dioxide) in a jet mill, in a gaseous medium, at a supersonic speed, a pressure of 7.5 - 17.0 bar and a temperature of 160 - 550ºC (see FR application No. 2575170, 1969).

Of the major drawbacks of said process are relatively high power consumption, complexity of maintaining parameters of the manufacturing process and its apparatuses.

SUMMARY OF THE PRESENT INVENTION

The present invention is made in order to solve the above problems included in the prior arts, and an object of this invention is to produce coated pigments while considerably reducing power consumption. simplifying the manufacturing process and its apparatuses.

The above object is solved in accordance with the present process for preparing pigments, in which a filler is preground in a vibrating centrifugal mill, thereupon the ground filler is mixed with a dye for not less than 4 minutes, wherein co-treating of the mixture so obtained is also carried out in the vibrating centrifugal mill under the action of a sum of centrifugal and Coriolis forces for 1 - 2 minutes.

Barite, calcite, talc, kaolin and other natural minerals are used in the present process as a base-filler. Inorganic, organic pigments and other dyes may be used as color carriers.

BEST MODE FOR CARRYING OUT THE INVENTION

Example

A natural mineral barite which has been ground to a particle size of 2 - 30gm is fed to a vibrating centrifugal mill - a mechanical activator. The supply of the milled bodies amounts to 50 % of a grinding chamber capacity, vibration frequency is 75 s^-1, vibration amplitude is 50 mm, acceleration is 40 g, wherein the milled bodies are steel bails of a 12 - 17 mm diameter. Residence time of the material in said grinding chamber is 1 - 2 minutes.

A treated filler is loaded into a mixer. At the same time, a dye is loaded into the same mixer and mixed for not less than four minutes. The mixture so obtained is fed to another vibrating centrifugal mill and treated for 1 - 2 minutes under the same parameters which were used for treating the filler.

A total action on the milled bodies, the filler and a mixture of centrifugal and Coriolis forces for 1 - 2 minutes provides for the most intense and complex type of power- loading of particles of a treated material which. in turn. results in a maximal activation ox the filler particles surface and the most complete encapsulation of the filler with the dye. Action time of less than one minute does not provide for the achievement of optimal characteristics ( whiteness, covering power, etc.) and that of more than two minutes - does not lead to a further improvement thereof.

Mixing of the treated filler with the dye for not less than four minutes provides for a good mixture homogenisation before encapsulation, that is the most uniform distribution of the dye particles between the filler particles in the bulk of the mixture. Thus, optimal conditions for applying a dye coat onto the filler particles are created and time for treating the mixture in the vibrating centrifugal mill is reduced, wherein the mill power is only spent for encapsulating, rather than for mixing and encapsulating as the case may be when separately supplying or loading the constituents used. Mixing time is stipulated by the fact that when mixing for less than

four minutes a sufficient degree of the mixture homogenization is not achieved.

Barite. talc, kaolin. calcite and other minerals may be used as the filler, whereas anorganic or organic pigments may be used as the dye.

The properties of pigments produced are summarized in the following Table.

A process for manufacturing pigments is as follows.

A filler (a base) is fed to a vibrating centrifugal mill, where its extra milling and mechanical activation takes place, then to a mixer, where a dye is loaded simultaneously. In the mixer. the treated filler and the dye are mixed for nor less than four minutes, thereupon the mixture is fed to the vibrating centrifugal mill, where encapsulation of the base particles with the dye occurs. Residence rime of the filler and the mixture in vibrating centrifugal mills equals to 1 - 2 minutes depending on the constituents used.

The present process is ecologically safe, since there are no production waste, sewages and effluents when realizing thereof.

Claims

WHAT IS CLAIMED IS:

A process for the preparation of pigments, comprising the step of co-treating a filler and a dye. wherein the filler is preground in a vibrating centrifugal mill, thereupon the ground filler is mixed with the dye for not less than 4 minutes, and co-treating of the mixture obtained is also carried out in the vibrating centrifugal mill.