JPS5933625B2 - Method for producing calcium carbonate-mica-containing clay mixture pigment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a calcium carbonate-mica-containing clay mixture powder pigment having a low tendency to secondary agglomeration.

Calcium carbonate pigments, especially heavy calcium carbonate.

Powdered pigment products have a relatively large tendency to secondary agglomeration, and for this reason, in the paper manufacturing field, dispersions in water have often been purchased and used instead of powdered products. However, dispersions in water are inconvenient to store and transport, and there has therefore been a strong desire to develop powder products with a low tendency to secondary agglomeration. The present inventor conducted various studies to solve the above problems, and as a result, by adding mica-containing clay powder to calcium carbonate pigment,
It has been found that the tendency to agglomerate is significantly reduced, and
It was also discovered that the secondary aggregation tendency of mica-containing clay powder pigments is reduced by the addition of calcium carbonate, and the present invention was completed based on these findings.

Therefore, in the present invention, (a) a 50-75% by weight dispersion of finely divided calcium carbonate powder with a particle size of 325 mesh or less in water is prepared; - A 30% by weight dispersion in water is made, provided that the mica-containing clay powder consists essentially of 30-60% by weight of mica, 40-70% by weight of kaolin mineral and 0-5% by weight of silica, ←→ The mixture ratio (weight ratio) of calcium carbonate and mica-containing clay is 97:3 to 10:90. The present invention relates to a method for producing a calcium carbonate-mica-containing clay mixture pigment.

There are no particular restrictions on the type of calcium carbonate used in the present invention; for example, natural and synthetic heavy products, light products and mixtures thereof can be used.

In addition to pure calcium carbonate, calcium carbonate containing some impurities can of course be used. The mica-containing clay used in the present invention consists essentially of 30-60% by weight mica, 40-70% by weight kaolin mineral and 0-5% by weight silica.

There are no particular restrictions on the type of mica; any type of mica group mineral, natural or synthetic, may be used, examples of which include muscovite, sericite, but in some cases black Colored micas such as mica could also be used. Further, phlogopite, scad mica, chinwaldite, pearl mica, etc. can also be used. There is no particular restriction on the type of kaolin mineral in the mica-containing clay in view of ease of crushing and color, and kaolinite, nacrite, dateskite, halloysite, etc. can be used. It is preferable that the amount of contaminant silica in the mica-containing clay is small, and the amount is O-5 as described above.
% by weight (preferably O-3% by weight) (
based on the weight of mica-containing clay).

Mica-containing clays that meet the above conditions are naturally occurring, and examples include sericite-containing kaolin clays.

Although it is convenient to use such naturally produced mica-containing clay in the present invention, it is of course possible to prepare a mica-containing clay by mixing kaolin mineral clay with mica powder.
In the method of the present invention, a dispersion of calcium carbonate powder in water is first prepared.

Good results cannot be obtained unless this powder is a fine powder of 325 mesh or less. The solid content (calcium carbonate) concentration of this water dispersion is 5075% by weight, preferably 60-68% by weight.
It is. Separately, a dispersion of fine mica-containing clay powder (325 mesh or less) in water is prepared. The solid content (mica-containing clay) concentration of this dispersion is 15-30% by weight, preferably 17% by weight.
-25% by weight. The calcium carbonate dispersion in water is then mixed with the mica-containing clay dispersion in water.

The mixing ratio (in weight units) of these two dispersions corresponds to the ratio of calcium carbonate to mica-containing clay in the desired product, the calcium carbonate monomica-containing clay mixture pigment. Of course, it will be clear to those skilled in the art. This mixing operation can be carried out according to a conventional method. The dispersion mixture thus obtained is dried in a conventional manner to obtain the desired pigment powder.

The ratio (weight ratio) of calcium carbonate to mica-containing clay in the calcium carbonate monomica-containing clay mixture pigment obtained by the method of the present invention is 97:3 to 10:90.
1 should preferably be between 95:5 and 20:80.

This is because it has been confirmed through experiments that the present mixture pigment having a mixing ratio within this range has a very low tendency to secondary aggregation (see Examples below).
. One important embodiment of the present invention is to mix mica-containing clay with ground calcium carbonate, which has a high tendency to secondary condensation, to reduce the tendency to condensate. When making paper pigments, it is preferable to use sericite as the mica component.
In practice, it may be convenient to use commercially available sericite-containing clays. As described in the Examples below, the secondary agglomeration tendency of heavy calcium carbonate can be significantly reduced by adding a small amount (for example, about 5 to 20% by weight) of sericite-containing clay. On the other hand, mica powders, especially sericite-containing clays themselves also have a tendency to secondary agglomeration, but in this case the addition of heavy or light calcium carbonate (for example about 10-40%) can effectively reduce the agglomeration tendency. (See Examples below).

In the present invention, no chemicals that may have an adverse effect on the properties of the pigment are used, so the resulting mixture-based pigment has excellent pigment properties and has a low tendency to secondary aggregation, so it can be used in various fields. It can be used very advantageously.

Next, examples of the present invention will be shown.

EXAMPLE A dispersion of finely divided (325 mesh) heavy calcium carbonate in water was prepared by wet-pulverizing and classifying naturally produced white limestone in accordance with a conventional method.

The solid content concentration of this dispersion was 65%. Separately, a dispersion of fine particulate kaolinite-sericite clay in water was prepared by wet-pulverizing and classifying white clay produced in Itaya, Yonezawa City, Yamagata Prefecture according to a conventional method.

The solid content concentration of this dispersion was about 20%, and the particle size was 325 mesh. This fine-grained clay consisted of about 49% kaolinite, about 49% sericite, and about 2% other minerals (silica minerals, etc.).

The above dispersion of fine particulate heavy calcium carbonate in water and the above dispersion of fine particulate clay in water were mixed in various ratios, filtered and dried according to a conventional method to prepare a powdery mixed pigment. The samples were stored for 30 days, and the degree of secondary aggregation that occurred during storage was examined.

The degree of secondary aggregation was measured by the following method.

A powdered pigment sample was dispersed in water according to a conventional method to prepare a 10% dispersion in water, this dispersion was passed through a standard sieve of 325 mesh, and the residue on the sieve was dried and weighed. The results of this test are shown in Table 1 and the graphs in the accompanying drawings. As is clear from Table 1 and the graphs in the attached drawings, approximately 5 to 15% by weight of sericite-containing clay is added to heavy calcium carbonate.
By adding it, the tendency of secondary aggregation of calcium carbonate can be extremely reduced.

More specifically, by adding about 5% clay, the amount of secondary aggregates is reduced to less than about 1, and about 10-15%.
It was confirmed that the amount of aggregates was reduced to a very small amount, almost zero, by adding . Furthermore, it was also confirmed that the secondary agglomeration tendency of the clay itself can be further reduced by adding calcium carbonate.

As is clear from the above description, according to the present invention, a calcium carbonate monomica mixture powder pigment with a low tendency for secondary aggregation can be obtained, and the tendency for secondary aggregation of the calcium carbonate pigment is significantly reduced by adding a small amount of mica. Moreover, the present invention can
It also has the advantage of being easy to implement without using expensive materials or equipment.

As described above, the present invention has remarkable effects and is of high practical value. Although certain embodiments of the invention are described in detail herein, it will be apparent to those skilled in the art that the invention can be practiced in various ways.

[Brief explanation of the drawing]

The graphs in the accompanying drawings are graphs illustrating the experimental results described in the above examples.

Claims (1)

[Scope of Claims] 1. (a) Prepare a 50-75% by weight dispersion in water of finely divided calcium carbonate powder with a particle size of 325 mesh or less, and (b) Separately prepare 15% by weight dispersion of finely divided mica-containing clay powder with a particle size of 325 mesh or less in water. - A 30% by weight dispersion in water is made, provided that the mica-containing clay powder consists essentially of 30-60% by weight mica, 40-70% by weight kaolin mineral and 0-5% silica.
% by weight, and (c) mixing the above two dispersions with each other, and (d) drying after mixing to obtain a powder pigment. A method for producing a calcium carbonate-mica-containing clay mixture pigment having a ratio (weight ratio) of 97:3 to 10:90.