JPS6090819A - Production of chain calcium carbonate from ultrafine cubic calcium carbonate - Google Patents

Abstract

PURPOSE:To produce chain CaCO3 having weak intercohesiveness among particles by introducing a CO2-contg. gas into an aq. Ca(OH)2 suspension contg. water soluble magnesium salt to carbonate said soln then adding polyphosphoric acid, etc. thereto. CONSTITUTION:Water soluble magnesium salt is added to an aq. Ca(OH)2 suspension having 1-20wt% concn. at 0.05-2.0% by weight of Ca(OH)2 and a CO- contg. gas adjusted to 15-30vol% concn. by an inert gas or air is introduced thereto to 7-9pH and to carbonate the suspension. Polyphosphoric acid or >=1 kind among the metallic salts thereof are added to an aq. ultrafine cubic CaCO3 suspension of <0.1mum average particle size formed by such carbonation at 0.002-2wt% by the weight of said CaCO3 to obtain chain CaCO3 having about 0.1-1mum average particle size. MgCl2, MgSO4, Mg(NO3)2, etc. are used as the above-mentioned water soluble magnesium salt and hexamethaphosphoric acid, pyrophosphoric acid, etc. or the salt of Na, K, etc. thereof are used as the metallic salt thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing chain calcium carbonate from the produced ultrafine cubic calcium carbonate having an average particle size of less than o, + p m.

Regarding the manufacturing method of chain calcium carbonate, currently;
The following manufacturing methods are also known.

1) A production method in which a water-based calcium hydroxide suspension is carbonated halfway and a water-soluble zinc salt is added to the sticky emulsion to complete the carbonation (Japanese Patent Publication No. 37-519) .

2) A manufacturing method in which a water-soluble magnesium salt is added to a sticky emulsion obtained by partially carbonating a suspension of calcium hydroxide in water to complete the carbonation (Japanese Patent Publication No. 47-229-44).

3> Production in which sulfuric acid or water-soluble sulfates (excluding zinc and magnesium) are added to a viscous colloid emulsion obtained by partially carbonating an aqueous calcium hydroxide suspension to complete carbonation. Method (Special Publication Sho 5O-3 3995).

4) A production method in which sulfuric acid is added to an aqueous suspension of calcium hydroxide and then carbonation is completed (Japanese Patent Publication No. 56-40118). 5) A chelating agent is added to an aqueous suspension of calcium hydroxide,
Water-soluble metal salts, sulfates, and phosphates that form insoluble precipitates in an aqueous suspension of calcium hydroxide are added to a partially carbonated, viscous, glue-like emulsion to complete carbonation. However, the present inventor has discovered that sodium hexametaphosphate, which has been used as a dispersant for calcium carbonate aqueous suspensions, under special conditions. It was discovered that when sodium hexametaphosphate was added to the resulting calcium carbonate aqueous suspension, it acted not as a dispersant, but on the contrary, as a flocculant.

As a result of intensive research, by adding and reacting an aqueous solution of condensed phosphoric acid or its metal salt to an aqueous suspension of extremely fine cubic calcium carbonate with an average particle diameter of less than 0.1 pm, it was found that the average particle diameter of o, + p The present inventors have discovered that ultrafine cubic calcium carbonate smaller than rnm are linked together to form chain calcium carbonate, and have arrived at the present invention.

To explain the present invention in more detail, the concentration of the calcium hydroxide aqueous suspension is 1 to 20% by weight, preferably 3 to 10% by weight, and the water-soluble magnesium salt is 0.05 to 2% of the calcium hydroxide. By weight, preferably from 0.1 to +1% by weight, the concentration of carbon dioxide-containing gas obtained by diluting the carbon dioxide carbon cage with an inert gas or air is increased to 15 to 35% by volume, preferably from to (up to) % by volume, Introduced under conditions that produce ultrafine cubic calcium carbonate with an average particle size o of less than 1 pm, and pH 7.
The introduction of the carbon dioxide-containing gas is stopped at 9 to 9, and the resulting ultra-fine cubic calcium carbonate aqueous suspension with an average particle size of less than 0.1 pm is condensed into the aqueous suspension or its metal. Salt in O,0C102~2M amount% relative to calcium carbonate
Preferably, by adding 0.02 to 1% by weight and reacting, ultrafine cubic calcium carbonate with an average particle size of less than 0.1 μm is chained, and a chain form with an average particle size of 0.1 to IPm is formed. becomes calcium carbonate. In addition, the amount of added phosphoric acid island or its metal salt is 0.0 with respect to calcium carbonate.
If it is less than 002 weight%, chain calcium carbonate will not be produced and it will be ultrafine cubic calcium carbonate as it is, or if it exceeds 2% by weight, chain calcium carbonate will not be produced and it will be r1 amorphous. Serves as a pseudopharyngeal body.

In this production method, in the calcium hydroxide aqueous suspension,
Water-soluble MAG, no nesium field added, 7, average particle size produced 0. + p less than + o', l: + j1 fine I1
1'[lfL Rectangular calcium carbonate aqueous suspension] Even when reacted with condensed phosphoric acid or its metal salt, ultrafine cubic calcium carbonate with an average particle size of less than 0.1 μm does not form into a chain. There is even a chi. Or the average particle! 0 fleas,
Even if a water-soluble magnesium salt and a condensed phosphoric acid or a metal salt thereof are reacted with a suspension of extremely fine cubic kanotosium carbonate, a chain carbonic acid)3,
,'l/l/ seam.

Also, 7N oxidizing power! Addition of water and soluble 2gnesium salt 1: to the renium and N suspension causes condensation, and even if the acid or its metal mass is added at 7 or 71 OL, chain noflucium carbonate will not be obtained.

The characteristics of the present invention are as follows: 11 particles with a particle diameter of 9.1 '40. Ipr
It is possible to produce chain-like lesium carbonate with an average particle size of 0.1 to 1 um from extremely fine cubic calcium carbonate.

Until now, the production of ultrafine cubic calcium carbonate with flat particle diameters of less than o, +, p m, to the production of chain calcium carbonate, or from the production of chain calcium carbonate to the production of average particles. Reacted to switching production of ultrafine cubic calcium carbonate with F diameter of 0゜J and less than 1m! 4. There was a lot of trouble involved in cleaning the Touge scale, paddle, etc., and changing reaction conditions.
Pa, this trouble! There is the convenience of being able to arbitrarily produce ultrafine cubic calcium carbonate with a diameter of 1":1 and an angle of 3.I p w0.

Manufactured by the present invention, investigation warrant for calcium carbonate 1.
Average tear size: 0. ．． l ) l Compared to ultrafine cubic calcium carbonate of 1 m size, the mutual cohesiveness between particles is weaker, and the dispersibility of rubber, plus one, etc.
It has a tx, continuous, tll-like structure, and the dispersion of rubber, plastic, etc., and the rest is 1. Three-dimensional/,
The ζ structure is made of rubber, plastic, etc. to increase the reinforcing properties.

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

Example 1 2.5g of magnesium sulfate and 500g of calcium hydroxide
After adding water to make a homogeneous water suspension, a carbon dioxide-containing gas diluted with air at a concentration of 25% by volume was introduced at a rate of 40 J2/min, and the pH was adjusted to 8.
The introduction of carbon dioxide-containing gas was stopped at . The produced calcium carbonate was ultrafine cubic calcium carbonate with an average particle diameter of 0.04 JIm and a specific surface area of 3:1 m2/g (B'ET method). To this calcium carbonate aqueous suspension, 1.5 g of sodium hexametaphosphate dissolved in 1001!1 of water was added, and after 1 hour of mixing reaction, dehydration,
After drying and pulverizing, the average particle size is 0.4 m, and the specific surface area is 42.
11,127 g of 50'g of chain calcium carbonate were obtained.

Example 2 In the same manner as in Example 1, using pyrophosphoric acid instead of sodium hexametaphosphate, the average particle size was 0.
640 g of chain calcium carbonate with a specific surface area of 45 l1127 g were obtained.

Example 3 Using potassium tripolyphosphate instead of sodium hexametaphosphate and using the same method as in Example 1, the average particle size was 0.3 pm and the specific surface area was 44 I! 640 g of chain calcium carbonate of 12/g were obtained.

Comparative Example 1 630 g of ultrafine cubic calcium carbonate having an average particle diameter of 0.0°4 pm and a specific surface area of 32 rn/g was prepared in exactly the same manner as in Example 1 using monobasic sodium phosphate instead of sodium hexametaphosphate. I want to get it.

Comparative example 2.

Water was added to 500 g of calcium hydroxide to make it 101, and a water suspension with a liquid temperature of 2)'(+ was diluted with air; a concentration of 25% by volume of carbon oxide-containing gas was introduced at a rate of 100 g/min.
The introduction of carbon dioxide-containing gas was stopped at P'H8. The produced fx R acid calcium has an average particle size of 0.04) 1 m
It was ultrafine cubic calcium carbonate with a specific surface area of 30 m''/'g.Into this calcium carbonate aqueous suspension, 2.5 g of magnesium sulfate dissolved in water SO+R+F, and 1+5 g of sodium hexametaphosphate dissolved in water+OO.
, mJ was added, and after 1 hour of mixing reaction,
After dehydration, drying and pulverization, 630 g of ultrafine cubic calcium carbonate having an average particle size of 0.04 pm and a specific surface area of 28 m''/g was obtained.

[Brief explanation of the drawing]

Claims (1)

[Claims] Adding a water-soluble magnesium salt to a calcium hydroxide aqueous suspension and introducing a carbon dioxide-containing gas produces ultrafine cubic carbonic acid particles with an average particle diameter of less than o, + p'm. A method for producing chain calcium carbonate by adding condensed phosphoric acid or its metal salt to a calcium carbonate suspension. The manufacturing method according to claim 1, wherein the concentration of the calcium dihydroxide aqueous suspension is 1 to 20% by weight. 3 Water-soluble magnesium salts include magnesium chloride,
The manufacturing method according to claim 1, wherein water-soluble salts such as magnesium sulfate and magnesium nitrate are used. 4 One or more types of water-soluble magnesium salts described in claim 3 are added in an amount of 0.0 based on the weight of calcium hydroxide.
5 to 2.0% by weight of added condensed phosphoric acid or 11 its metal salts include hexametaphosphoric acid, pyrophosphoric 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. 6. One or more of the condensed phosphoric acids or metal salts thereof as described in claim 5 is added in an amount of 0.0000000000% based on the weight of ultrafine cubic calcium carbonate having an average particle diameter of less than o, + pm.
The manufacturing method according to claim 1, wherein 0.002 to 2% by weight is added. 7- The manufacturing method according to claim 1, in which carbon dioxide is diluted with an inert gas or air to give a carbon dioxide concentration of 15 to 35% by volume. 8. The manufacturing method according to claim 1, wherein the introduction of the carbon dioxide-containing gas is stopped at pH 7 to 9.