JPS60103025A - Manufacture of calcium carbonate - Google Patents

Abstract

PURPOSE:To manufacture easily hyperfine chain CaCO3 having a specified specific surface area or above by carbonating an aqueous suspension of Ca(OH)2 in the presence of properly added chemicals under properly selected reaction conditions. CONSTITUTION:A crystal nuclei forming agent such as acetic acid or Al2(SO4)3 is added to an aqueous suspension of Ca(OH)2, and gaseous CO2 having >=15vol% concn. is blown into the suspension at >=40l/min/kg Ca(OH)2 flow rate. Before the rate of carbonation attains to 40%, a chain particle formation accelerator such as sodium citrate is added, and carbonation is continued to manufacture hyperfine chain CaCO3 having >=60m<2>/g BET specific surface area. When the CaCO3 is blended as a filler for rubber for plastics, it is easily dispersed and provides high tensile strength and rigidity. When the CaCO3 is kneaded as an extender for paint, it is well dispersed in the early stage and gives a smooth paint film with high luster.

Description

Detailed Description of the Invention The present invention relates to a method for producing extremely fine calcium carbonate having a B 14 'P specific surface area (hereinafter referred to as specific surface area) of 6Of71''/g or more. No. 17 relates to a method for producing extremely fine calcium carbonate.

Calcium carbonate used as a filler for plastics, paints, and pigments for in-A includes heavy calcium carbonate obtained by mechanically crushing limestone, and precipitated calcium carbonate obtained from a chemical reaction. Precipitated carbonate is divided into light calcium carbonate with a specific surface area of less than 10g/g and ultrafine calcium carbonate with a specific surface area of 10'n''/9 or more.

Precipitated calcium carbonate is generally produced by a method in which a carbonation reaction is carried out by blowing carbon dioxide gas into an aqueous suspension of calcium hydroxide, by appropriately adjusting conditions such as concentration, temperature, and amount of carbon dioxide gas blown into a calcium hydroxide aqueous suspension. (In"Light calcium carbonate with large crystal particles of less than 7 g and ultrafine calcium carbonate with small crystal particles with a specific surface area of 10 m"/ji or more are manufactured and commercially available. Among these, calcium carbonate with a specific surface area of 10 m"/, 9 or more Ultrafine calcium carbonate is produced in the carbonation process under conditions where a relatively large amount of carbon dioxide gas is blown.

The fineness has so far been about 50 or more in terms of specific surface area. In addition, even if obtained experimentally, so-called aggregates in which crystal particles are tightly aggregated in the shape of a bunch of grapes may be produced.
e) Only calcium carbonate particles can be obtained. Even when these powders are mixed and applied directly to organic polymers and solvents such as rubber, plastics, paints, and inks, their dispersibility is extremely poor, so they have never been commercialized to date.

Therefore, in order to improve the dispersibility of ultrafine calcium carbonate, a chain-shaped calcium carbonate with crystal particles similar to Mitarashi dango was polished and investigated. These methods include carbonation reaction of an aqueous suspension of calcium hydroxide, which is hydrolyzed into zinc hydroxide at the point where it denatures into a viscous colloid emulsion during carbonation. The method of adding salt (Japanese Patent Publication No. 57-519), the method of adding aqueous agnesium salt (Japanese Patent Publication No. 47-2294F), and the method of adding all sulfuric acid or water-soluble sulfates (excluding zinc and magnesium) (Special Publication No. 57-519), Publication No. 5o-36995), a method of carrying out a carbonation reaction by adding sulfuric acid to a calcium hydroxide water suspension (
Comparing to the method of simply adjusting the reaction conditions when carbonating a turbid liquid, namely the concentrated 10-1 temperature and the amount of carbon dioxide gas blown in. The particles have become somewhat finer, and some particles that have grown in a chain due to f′ can be seen in a small part, but the large sword is a large block of calcium carbonate aggregates that has been secondary condensed in the shape of a grape cluster. Even if these are mixed into organic polymers and solvents, very satisfactory dispersion cannot be obtained.

Yet again.

First, carbon dioxide gas is blown into a calcium hydroxide suspension containing a chelating agent to start the carbonation reaction.

Method of adding water-soluble metal salts during carbonation (Special Publication 1986-
No. 26613) has been proposed.

Even with this method, the crystal particles are made finer and chain particles are also observed, but rather the chain particles form secondary aggregates in the form of chain bundles with several to tens of water bundles. Rubber, plastic fillers, and paints have insufficient dispersibility in polymers and solvents.

Calcium carbonate is used as a pigment for ink, and it is strongly desired to improve the physical properties of its compounds, and for this reason, it is used in rubber and plastics.

Calcium carbonate, which is used as a filler or pigment in paints, inks, etc., makes the particles finer, and if these particles do not solidify during the carbonation process, dehydration, or drying process, and can be broken down to primary particles by ordinary mechanical grinding, It can be added to rubber, rubber/lasty, etc. to not only improve dispersibility but also to further improve physical properties such as reinforcing properties.

The present inventors have discovered that ultrafine chain particles with a specific surface area of 60 yd/. As a result of conducting various experiments on calcium carbonate, we found that when carbonating an aqueous suspension of calcium hydroxide, by appropriately selecting the additive chemicals and reaction conditions, extremely fine chains with a specific surface area of 6o#/g or more can be created. The fact that highly developed calcium carbonate can be easily produced led to the completion of the present invention.

The carbonation rate referred to herein is defined by the following formula VC, where the weight of calcium carbonate in the reaction solution is 31 (-w) and the weight of calcium hydroxide is Wl.

Carbonation rate=w+7□×100 BET specific surface area is a low temperature nitrogen adsorption method. The particle shape is determined by electron microscopy observation.

In the present invention, when producing calcium carbonate with a specific surface of -R60d/11 or more, a crystal nucleating agent is added to a calcium hydroxide aqueous suspension, and then carbon dioxide gas with a concentration of 15V% or more is flowed at a flow rate of 11/min/ Very fine carbonic acid with a highly developed chain structure, characterized by the fact that the carbonation reaction is carried out by adding a chain particle formation accelerator until the carbonation rate reaches 4096. A method for producing calcium is provided.

When adding the additive chemicals used in the present invention, ultrafine particles with a large specific surface area can be obtained by adding the crystal nucleating agent to the aqueous suspension of calcium hydroxide before the carbonation reaction. Even if this crystal nucleating agent is added during the carbonation reaction, a product with a larger υ specific surface area cannot be obtained than when added before the carbonation reaction. When the chain particle formation promoter is added up to a carbonation rate of 40%, the effect of forming chains becomes large.

Furthermore, there is little aggregation of the formed chain particles.

Addition of the chain particle formation promoter before the crystal nucleation agent has little effect, and the dehydrated and dried product becomes hard after the carbonation reaction is completed.

The crystal nucleating agents used in the present invention are hydrochloric acid and sulfuric acid.

Mineral acids such as nitric acid, lower carboxylic acids such as formic acid, acetic acid, propionic acid, and/or ammonium salts and alkali metal salts thereof1. aluminum.

Examples include water-soluble metal salts such as zinc, red sea bream, and sium; polyhydric alcohols such as turpinto and pentaerythritol; and sucrose. Chain particle formation promoters used in the present invention include citric acid, malic acid, etc. Hydroxycarboxylic acid.

Gluconic acid, polyhydroxycarboxylic acids such as ~11 tartaric acid, aminocarboxylic acids such as enalediaminetetraacetic acid, 2F lilotriacetic acid, and sodium tripolyphosphate. Boririn rRJ, such as sodium hegisametaphosphate, A
I Any chelating agent and alkali metal salts and ammonium salts of polymeric polycarphonic acids such as isobutylene-maleic acid copolymer, styrene-maleic acid copolymer, acrylic acid-maleic acid copolymer, polyacrylic acid, etc. Examples include polymeric compounds.

The amount of the crystal nucleating agent used in the present invention is 0.5 to 15 parts by weight, preferably 1 to 12 parts by weight per 100 parts by weight of calcium hydroxide.

When the amount added is less than 0.5 parts by weight, the specific surface area of the particles produced becomes small. If the amount added exceeds 15 parts by weight, irregularly shaped particles will be produced.

The amount of the chain particle formation promoter used in the present invention is [105 to 8 parts by weight,
Preferably it is 0.1 to 7 parts by weight. If the amount added is less than α05 parts by weight, fewer particles will form a chain. If the amount added exceeds 8 parts by weight, aggregates of chain particles will be formed and the specific surface area will decrease.

The carbon dioxide concentration used in the present invention needs to be 15V% or more. When the carbon dioxide concentration is less than 15V%, coarse particles are generated.

The carbon dioxide gas injection rate used in the present invention is 401/min/
Hp Oa (OH)2 or more, preferably 50-15°1/min/KPOa (OH)2. When the carbon dioxide gas flow rate is 40 II / min / b Ca (O
H) If it is less than 2, aggregates of chain particles will be produced, and the shape of the aqueous calcium hydroxide suspension used in the present invention and the particles produced will be non-uniform, and the specific surface area will also be small.

The temperature of the calcium hydroxide aqueous suspension used in the present invention is 0.
-25°C9, preferably 3-20°C. temperature is 2
When the temperature exceeds 5°C, coarse particles are generated.

The calcium carbonate of the present invention is obtained after the carbonation reaction is completed.

Press dehydration was carried out, and this was dried and ground to obtain a powdered product.

As described above, the calcium carbonate of the present invention has a specific surface roughness of 60 depending on the order and timing of addition of the selected additive chemicals added to the calcium hydroxide aqueous suspension and the severe conditions during carbonation.
The calcium carbonate of the present invention has a high bulk, and is the first to obtain a product with ultrafine chain particles having a diameter of /y or more, in which the ultrafine chain particles are not aggregated but are dispersed in a single manner.

It was a powder that felt smooth to the touch with the tip of a finger.

The calcium carbonate of the present invention is easily dispersed when blended as a filler in rubber and plastics.

The formulation provides high tensile strength and high stiffness.

It goes without saying that when kneaded as an extender pigment in a paint, early dispersion is excellent, and physical properties such as monodispersibility and reinforcing properties can be further improved as a filler or pigment by applying known surface treatments.

Next, the manufacturing method of the present invention will be specifically explained using examples.

Example 1 A calcium hydroxide aqueous suspension 10001j prepared at a concentration of 6 Wt% and a temperature of 15°C was placed in a reaction vessel.

To this, 60 drops of aluminum sulfate water bath solution adjusted to a concentration of 10 Wi, % was added and mixed, and then carbon dioxide gas of Ia + 155 V% was added at a flow rate of 80 I! /min/I(70a(O
Blow in with i()Q and carbonate to a carbonation rate of 1596.

Then, citric acid l-I adjusted to a concentration of 10 Wt%
A carbonation reaction was carried out by adding 5.6 liters of Jum aqueous solution.

A chain-like extremely developed ultrafine carbonate Calcilla 5 was obtained. The mother liquor of 1 µl of this calcium carbonate was separated using a press dehydrator, and then dried and pulverized to give a final product of approximately 5oKP.

The results of testing the obtained preform of the present invention are shown in Table 1, and an electron micrograph of chain calcium carbonate is shown in FIG. In addition.

Table 1 also shows the results for the products obtained in Examples 2-4.

Example 2 A calcium hydroxide aqueous suspension 1000111 prepared at a concentration aWt, % and a temperature of 2o''C was placed in a reaction vessel.

After adding and mixing 28 glasses of acetic acid water adjusted to a concentration of 10Wt%, carbon dioxide gas with a concentration of 35V% was added at a flow rate of 5%.
0 d/min/Ky (E!1(OH)2) Carbonate at a carbonation rate of 25%. Then, the concentration is 1-O.
Wt.

% of an anionic polymer compound (trade name: Inpan, sodium salt of isobutylene-maleic anhydride copolymer manufactured by Shio Kuraray) was added to carry out a carbonation reaction to form a chain-like polymer. This calcium carbonate suspension was separated from the mother liquor using a press dehydrator, then dried and pulverized to give a powder of about 531J.
Finished.

Example 3 A 1000 KP calcium hydroxide aqueous suspension prepared at a concentration of 7 Wt% and a temperature of 18°C was placed in a reaction vessel.

To this was added and mixed sorbitol aqueous solution 10.5 KP prepared to a concentration of 10 Wt, %, and then carbon dioxide gas with a concentration of 35 V% was added at a flow rate of ID 071/min/40a (
Carbonate by blowing with OH)2 to a carbonation rate of 7%. Next, 7 ml of disodium ethylenediaminedetratetraacetate adjusted to a concentration of SWt% was added to carry out a carbonation reaction to obtain extremely fine calcium carbonate with a highly developed chain structure. The mother liquor of this calcium carbonate suspension is separated using a press dehydrator and then dried.

I crushed it and finished about 941 pieces.

Example 4 Concentration SWt, %, temperature 12°temperature 1 pear Put 1000 KP of lucium water suspension into the reaction vessel.

Add to this a 25K sucrose aqueous solution prepared to a concentration of 10Wt and %.
After adding and mixing P, carbon dioxide gas having a concentration of XSV% is blown in at a flow rate of 1201/min/Kp 0a(OH)2 to carbonate the mixture to a carbonation vehicle weight of 396. Then the concentration is 10W
t. Sodium tripolyphosphate aqueous solution prepared in %
5 1 (7%7) was added and a carbonation reaction was performed to obtain extremely fine calcium carbonate with a very developed chain. This calcium carbonate suspension was passed through a press dehydrator to completely separate the 1υ liquid, and then It was dried and ground to about 67 Fy.

The hardness of the dried lumps before pulverization starts from the hardest. It was rated as ``hard'', ``slightly hard'', and ``soft J''.

From the results shown in Table 1 and FIG. 1, it is clear that the product of the present invention is extremely fine calcium carbonate with a highly developed chain structure.

Comparative Examples 1 to 5 Aluminum sulfate and sodium citrate were added to the calcium hydroxide aqueous suspension at the same time (Comparative Example 1), aluminum sulfate was not added (Comparative Example 2), and sodium citrate was not added (Comparative Example 1). Example 3), sodium citrate was added instead of aluminum sulfate, and aluminum sulfate was added instead of thorium citrate (Comparative Example 4).
), or in the same manner as in Example 1 except that aluminum sulfate and sodium citrate were not added at all (Comparative Example 5),
The carbonation reaction was carried out, and the results of testing the obtained product of Comparative Example are shown in Table 2, together with the electrical results of the chain bundled calcium carbonate of Comparative Example 4.

Comparative Examples 6 to 8 Adding 6% of an aluminum sulfate aqueous solution with a concentration of 10Wt and % (Comparative Example 6), adding 0.2% of a sodium citrate aqueous rR solution with a concentration of 10Wt and % (Comparative Example 7), or adding citric acid A carbonation reaction was carried out in the same manner as in Example 1, except that the sodium solution was added at the point when the carbonation rate reached 50% (comparative example day).

Comparative Examples 9 to 12 The concentration of the calcium hydroxide aqueous suspension was set to 10 Wt, % (Comparative Example 9), and the temperature of the calcium hydroxide aqueous suspension was set to 3.
0°C (Comparative Example 10).

The carbon dioxide concentration was set to 10V% (Comparative Example 11), or the carbon dioxide gas blowing rate was set to 30 l/min/'y O
A carbonation reaction was carried out in the same manner as in Example 3 except that a(OH) 2 was used (Comparative Example 12).

Reference Example 1 100 parts by weight of the invention of Example 1, 5BR1502100
Parts by weight, 5 parts by weight of zinc white, 1 part by weight of stearic acid, 1.2 parts by weight of accelerator DM, 2 parts by weight of TTo, and 2 parts by weight of sulfur, and the results of measuring the physical properties of the vulcanized rubber are shown in Table 6. Shown below. Table 4 shows the comparison of the calcium carbonate of Comparative Examples 3 and 4, commercially available calcium carbonate, and commercial product A (surface-treated calcium carbonate, \X square, specific surface area s o d/P)
, the results of using the comparative Ichisaka product B (light calcium carbonate, spindle shape, specific surface area 5 n?/V-) in place of the present invention are also shown. : (Table 3 dispersibility evaluation; -r, lN11Il for cross section of vulcanized comb)
vC,,l:.

The product of the present invention is as shown in Table 3 as shown in Table 3.
.

Comparative example of calcium carbonate (comparison)
1 Dispersion 4 Raw-b compared to II 1 J Calcium Acid:
l! A '7-kai Shikoyo(, gives high modulus, high bow length, high (ie degree), and has a great reinforcing effect.

[Brief explanation of the drawing]

Figure 1 shows the fruit/l01 (J in Attachment 11) obtained by the method of the present invention.
Very finely developed eastern chain-like 1-deficient cut, 2/
＋＞Mu. Figure 2 shows the chain bundled carbonic acid-77A Si-Jino of Comparative Example 4;
An electron micrograph is shown. (Hereinafter) Patent Applicant: Shiraishi Chuosun Co., Ltd. [Kyupli Diagram 1 Procedural Amendment (Method) Date: February 1, 1982 Case Indication: 1982 Patent Application No. 207950 2
, Q Akeno name of calcium carbonate! lI9 Construction method 6 Part 1 No. J with the person making the amendment Patent applicant location 4-y Motohama-cho, Amagasaki-shi 81 Piece J [II5 Date of amendment discussion January 31, 1980 6, Subject of amendment
[Brief Description of Drawings] 1136, ・A1-' Amendment Contents Part t? ,+(i-th IM, l +++ i) The full text of the column "Brief explanation of i-th IM, l +++i" has been corrected as below. 1st shot, ultra-fine particles (obituary, Figure 2 is for comparison) Chain bundle-like particles of calcium carbonate (11 yen f51r each shown as an electron hirr imitation) It's probably true (below)

Claims (1)

[Claims] ■ In producing calcium carbonate having a BET specific surface area of 60♂/g or more, a crystal nucleating agent is added to an aqueous suspension of calcium hydroxide. Carbon dioxide gas with a concentration of 15V% or more at a flow rate of 40//min/
Ky Oa (OH) blown at 2 or more, carbonation rate 4
1. A method for producing ultrafine calcium carbonate with a highly developed chain, characterized by adding a chain particle formation promoter and carrying out a carbonation reaction until reaching 096. ■ The crystal nucleating agent is a mineral acid, a lower carboxylic acid and/or an ammonium salt of these acids. The method for producing calcium carbonate according to claim 1, which comprises an alkali metal salt, a water-soluble metal salt, a polyhydric alcohol, and sucrose. (2) The method for producing carbonate and calcium oxide as described in claim 1, wherein the chain particle formation promoter is a chelating agent or an anionic polymer compound.