JPH0134540B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved easily dispersible calcium carbonate-based composite pigment, and more specifically to a highly dispersible calcium carbonate composite pigment.
The present invention relates to an improved easily dispersible calcium carbonate-based composite pigment obtained by surface-improving a calcium carbonate-silicate pigment having a BET specific surface area and oil absorption.

In the past, there have been many publications on improving the surface of ordinary calcium carbonate powder by coating in order to obtain easily dispersible calcium carbonate pigments. No research has yet been conducted on the possibility of further coating a calcium carbonate-based composite pigment, which is a colloidal product, to impart new functions without impairing the desirable physical properties of the original pigment.

Various calcium carbonate fillers are used in rubber, plastics, paints, inks, sealants, etc., but the finer the filler particles, the stronger the cohesive force between the particles, resulting in secondary agglomeration. In this method, it is extremely difficult to disperse particles close to primary particles in the medium. In order to promote the dispersion of such fillers with strong cohesive force and improve their compatibility with organic substances, fillers coated with fatty acid-based or resin-acid-based substances have been mainly produced and used.

However, in the case of fillers that are prone to secondary agglomeration, there is a limit to their dispersion even with this coating, so it is better to use a coating with a material that has good dispersibility rather than using a material that originally has poor dispersibility as a raw material. It is clear that it is more advantageous to do so. In general, fine particles with a primary particle diameter of about 0.02 μm have particularly remarkable secondary agglomeration, and it is difficult to use those obtained by conventionally known methods for producing calcium carbonate pigments unless they are coated with an organic substance. . On the other hand, since the calcium carbonate composite pigment used in the present invention is produced under unique reaction conditions, it can easily be dispersed into primary particles without coating.
This easily dispersible filler or pigment exhibits sufficiently excellent functions when added to rubber or the like as is. For example, when added to rubber, it increases strength and improves abrasion resistance, and when added to paints, inks, and sealants, it increases viscosity and imparts properties. When coated, an easily dispersible conductive filler can be obtained. When mixed with rubber, this filler can be used to improve wear resistance and be applied to antistatic safety shoes, etc. When mixed with fibers, antistatic fibers can be obtained. It will be done.

Conventional fillers with conductive functions have relatively large particle sizes, and when added to rubber, for example, they usually do not have reinforcing properties themselves, but the fillers or pigments of the present invention have a conductive function. Products coated with this material have electrical conductivity, as well as reinforcing properties and wear resistance.

The method for producing the improved easily dispersible pigment according to the present invention is as follows.

First, the easily dispersible calcium carbonate-based composite filler used in the present invention is obtained by the method described in "Easily dispersible pigment and method for producing the same (Japanese Patent Publication No. ^59-164370 )" which is already pending. BET specific surface area of
This calcium carbonate pigment is a composite of supercolloidal silicic acid and zinc, which has an oil absorption of 70ml/100g or more. The metal sulfate or acetate that can be produced is blown into the calcium hydroxide suspension together with carbon dioxide gas until the carbonation rate reaches 3%, and then carbon dioxide is blown alone until the carbonation rate reaches 80%. It is then produced by adding an alkali silicate or silicate sol and further blowing carbon dioxide gas to complete carbonation. The pigment thus obtained is dispersed in water, stirred in a slurry state, metathesized, and then dried to add a water-soluble metal salt solution that imparts conductivity, and further reacts with this metal salt to form a precipitate on the pigment surface. Add a reagent that can coat the metal compound, react, and filtrate.
The pigment is dried (for example, at 90° C. for 3 hours) and pulverized to obtain a supercolloidal, easily dispersible pigment having the desired function.

The water-soluble metal salts used in the above reaction that impart electrical conductivity upon drying after metathesis are deposited on the surface of the calcium carbonate composite filler particles to impart electrical conductivity, such as tin, zinc, antimony or titanium salts. , for example, halides of these metals, especially stannic chloride, antimony chloride, titanium tetrachloride, and salts of oxides and basic oxides of these metals, especially sodium stannate, potassium antimonate, sodium titanate. etc., and one or more of these compounds may be used in combination.

The calcium carbonate-based composite pigment used as a raw material in the present invention has a very large specific surface area, and even if the amount of coating material is small, each particle will be coated uniformly, and even if the amount is large, it will not be coated. The particles will not aggregate secondary to form a floc.

The present invention will be explained in more detail with reference to the following examples.

Example 1 Obtained by the manufacturing method described in Japanese Patent Application No. 58-38173
BET specific surface area 80m ² /g, oil absorption 90ml / 100g 10
Kg dissolved in water, add with stirring and disperse thoroughly. Add No. 3 water glass (SiO ₂ 29% liquid) to this liquid.
Add 312.5g. While continuing to stir, a solution prepared by dissolving 100 g of stannic chloride in 2 kg of water is gradually added to this dispersion. After the addition was completed and the mixture was stirred a little, it was depressurized using a Nutsuchie filter, the cake remaining on the paper was pressed well and the water was thoroughly drained, and then the cake was washed several times with water from above, and then it was heated to 90℃ for 3 Dry for an hour. The electrical resistance was measured when this dried product was filled with finely ground sand into a cell with 1 cm ² electrodes set at 1 cm intervals at a pressure of 10 Kg/cm ² and was 2×10 ⁴ Ω.
It was hot.

In contrast, commercially available colloidal calcium carbonate (BET specific surface area 26m ² /g, oil absorption 30ml/100g)
The electrical resistance of the similarly coated
It was ¹⁰⁸ Ω.

Example 2 In the manufacturing method described in Example 1, 10 kg of slurry with a solid content concentration of 10% at the end of carbonation was taken (BET specific surface area when drying was 90 m ² /g, oil absorption amount was 95 ml / 100 g),
Add a solution prepared by dissolving 150 g of No. 3 water glass in 2 kg of water and stir well to disperse. On the other hand, a solution prepared by dissolving 470 g of antimony chloride in 1 kg of acetone is poured into the dispersion obtained earlier with thorough stirring. The resulting coated product was filtered through a Nutsuie filter, the filter cake was thoroughly pressed to drain water, and further washed with water and dried. The conductivity of the dry powder was 10 ⁶ Ωcm.

Claims (1)

[Claims] 1 BET specific surface area of 60m ² /g or more and 70ml /
An improved easily dispersible calcium carbonate composite pigment obtained by treating a calcium carbonate-silicate pigment having an oil absorption of 100 g or more with a water-soluble metal salt by drying or dehydrating it after metathesis, and then by neutralizing it.