JPS6090820A - Production of chain calcium carbonate - Google Patents

Abstract

PURPOSE:To produce easily chain CaCO3 having weak intercohesiveness among particles by adding polyphosphoric acid or metallic salt thereof to an aq. Ca (OH)2 suspension and further introducing a CO2-contg. gas therein to carbonate the suspension. CONSTITUTION:Polyphosphoric acid or the metallic salt thereof is added to an aq. Ca(OH)2 suspension having 1-20wt% concn. at 0.5-10% by the weight of the Ca(OH)2. The aq. suspension is kept at 0-35 deg.C soln. temp. and a CO2-contg. gas diluted to 15-35vol% by an inert gas or air is introduced into said suspension to carbonate the same, by which chain CaCO3 having about 0.1-1mum average particle size is obtd. The introduction of the above-mentioned CO2-contg. gas is stopped at 7-9pH. Hexmethaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, ultraphosphoric acid, etc. are adequate as the polyphosphoric acid and alkali metal salts of Na, K, etc. are adequate as the metallic salt thereof. The CO2-contg. gas is preferably controlled to 10- 30mol/m<3>.min rate of carbonization (mol; molar number of Ca(OH)2, m<3>; amt. of the aq. suspension).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing chain calcium carbonate. It's fJ's.

The precipitated calcium carbonate currently produced industrially includes ultrafine cubic calcium carbonate with an average particle size of less than 0.1 μm, and spindle-shaped or needle-shaped calcium carbonate with an average particle size of 171111 or more. Chain-like calcium carbonate has been produced by a manufacturing method.

This method for producing chain-like calcium carbonate involves carbonating a calcium hydroxide aqueous suspension by introducing carbon dioxide-containing gas into it, and when it becomes a viscous thick emulsion, it can be used as an additive. Water-soluble zinc salt (Japanese Patent Publication No. 37-519), water-soluble magnesium salt (Japanese Patent Publication No. 47-2.29 Gel), water-soluble sulfate (Japanese Patent Publication No. 5o-33,995) (However, zinc and magnesium are excluded. ), or sulfuric acid (Special Publication Act 5.6-
170//8) to produce chain calcium carbonate, or carbonation is performed by introducing a carbon dioxide-containing gas into an aqueous suspension of calcium hydroxide containing a chelating agent,
A method of producing chain calcium carbonate by adding a water-soluble metal salt when it becomes a viscous glue-like emulsion (Tokukosho, 5
6-6266/3) is known.

However, the manufacturing method of these chain calcium carbonate is
There is a complication in that additives must be added in the form of a viscous glue-like emulsion during carbonation.

In order to eliminate this complication, the inventor of the present invention, as a result of intensive research, added condensed phosphoric triacid or its metal salt to an aqueous suspension of calcium hydroxide, and then introduced a carbon dioxide-containing gas to carbonate the calcium hydroxide aqueous suspension. The present invention was achieved based on the idea that chain-like calcium carbonate is produced when chemical reaction is carried out.

To explain the present invention in detail, the concentration of the calcium hydroxide aqueous suspension is 1 to 20% by weight, preferably 3 to IO% by weight,
Condensed phosphoric acid or its metal salts include hexametaphosphoric acid, pyrophosphoric acid, tri-, polyphosphoric acid, polyphosphoric acid, ultraphosphoric acid, or its alkali metal salts such as sodium and potassium, and the amount added is 0 relative to calcium hydroxide. The temperature of the calcium hydroxide aqueous suspension containing condensed phosphoric acid or its metal salt at 0 to +07% by weight, preferably from 1 to 5% by weight, from 0 to as@c, preferably from 15 to 25'
C. Diluting carbon dioxide with an inert gas or air,
Carbon dioxide concentration 15-35% by volume, preferably 20-35% by volume
b The introduction rate of the carbon dioxide-containing gas was changed to a carbonation rate of 10'
-30 m o l / m'am in (m o, 1
: Number of moles of calcium hydroxide, rnj: Volume of water suspension in 1 cubic meter, m11: Time (minutes) 1, good 4.
L<ha 15~25m ol/m'-min,
The introduction of carbon dioxide-containing gas is stopped at pH 7-9.

The produced chain calcium carbonate has an average particle size of 0. iJ
Jm ungrooved particles are chained in one or two rows, resulting in an average particle diameter of 0.1 to IJJm. Furthermore, as the amount of condensed phosphoric acid or its metal salt added as an additive increases, the average particle diameter of chain calcium carbonate increases. The lower the carbonation rate, the larger the primary particle size forming the chain of calcium carbonate. However, the carbonation rate is 1
If it is less than 0 mol/m'-min, chain calcium carbonate will not be formed, but spindle-shaped calcium carbonate will be formed, and even if the avalency exceeds 35'O, spindle-shaped calcium carbonate will be formed.

Instead of condensed phosphoric acid or its metal salt as an additive, phosphoric acid, monophosphoric acid, diphosphoric acid or its alkali metal salts such as sodium and potassium, or alkaline earth metal salts such as calcium and magnesium are added. Then, the produced calcium carbonate does not become chain calcium carbonate and has an average particle size of 0. Pole less than l p m results in fine cubic calcium carbonate.

The chain calcium carbonate obtained by the present invention has a weaker cohesiveness between particles than ungrooved ultrafine cubic calcium carbonate with an average particle diameter of 0.1 μm, so it has poor dispersibility in rubber, plastics, etc. Because it has a secondary structure called a chain, it is thought that after being dispersed into rubber, plastic, etc., it will give three-dimensional structural properties and increase reinforcing properties for rubber, plastic, etc.

Examples will be shown below in order to make the features of the present invention more clear.

Example 1 Add 4.0 g of sodium hexametaphosphate dissolved in 00 g of calcium hydroxide to make an aqueous suspension of 10 g. , the liquid temperature was set to 20'O.

A concentration of 25% by volume of a carbon dioxide-containing gas diluted with air was introduced into this aqueous suspension at ao i' /III 1n. The introduction of carbon dioxide-containing gas was stopped at pH 8.5, and the mixture was filtered, dried, and pulverized to obtain chain calcium carbonate.

Table 1 shows the results of electron microscopic observation of the obtained chain calcium carbonate.

Examples 2 to 6 Example 1 except that 0.5 to 10% by weight of various condensed phosphoric acids or metal salts thereof listed in Table 1 were used based on the calcium hydroxide instead of sodium hexametaphosphate.
Chained calcium carbonate was synthesized in exactly the same manner. Table 1 shows the results of the obtained chain calcium carbonate.

Comparative Examples 1 to 3 Instead of sodium hexametaphosphate, phosphoric acid or alkali metal salts or alkaline earth metal salts of various phosphoric acids listed in Table 1 were added to calcium hydroxide at a concentration of 0.5 to 1
Calcium carbonate was synthesized in exactly the same manner as in Example 1 except that 0% by weight was used.

The results of the obtained calcium carbonate are shown in Table-1.

[Brief explanation of drawings]

No. 17 is an electron micrograph (40,000x magnification) of chain calcium carbonate obtained in Example 1, Figure 2! Electron micrograph of cubic calcium carbonate obtained in Comparative Example 3 (
Magnification table 1

Claims (1)

[Scope of Claim] A method for producing chain calcium carbonate obtained by adding condensed phosphoric acid or its metal salt to an aqueous suspension of calcium monohydroxide and introducing a carbon dioxide-containing gas. The manufacturing method according to claim 1, wherein the concentration of the calcium dihydroxide aqueous suspension is 1 to 20% by weight. Tricondensed phosphoric acids include hexametaphosphoric acid, birophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, and ultraphosphoric acid.
The manufacturing method according to claim 1, wherein the metal salt is an alkali metal salt such as sodium or potassium. 2. The manufacturing method according to claim 1, wherein 0.5 to 10% by weight of one or more types of 4-condensed phosphoric acid or its metal salt is added based on calcium hydroxide. The manufacturing method according to claim 1, wherein the aJA0-3511C is an aqueous suspension of calcium hydroxide containing 5-condensed phosphoric acid or a metal salt thereof. 6. The manufacturing method according to claim 1, in which carbon dioxide is diluted with an inert gas or air to 15 to 35% by volume as the carbon dioxide-containing gas'. 7. Carbonation rate IQ-3: 1 mol/m'-mi
The manufacturing method according to claim 1, wherein n (mol: number of moles of calcium hydroxide, m3: 1 cubic meter of liquid volume of the aqueous suspension, min: time (minutes)). 8. The manufacturing method according to claim 1, wherein the introduction of the carbon dioxide-containing gas according to claim 6 is stopped at pH 7 to 9.