JPS5969425A - Manufacture of calcitic calcium carbonate - Google Patents

Abstract

PURPOSE:To improve the dispersibility of the resulting particles and to manufacture fine calcitic calcium caronbate by reacting an aqueous suspension of calcium hydroxide with a gas contg. CO2, adding Sr or Ba, and completing carbonation. CONSTITUTION:When an aqueous suspension of calcium hydroxide prepared from natural limestone is reacted with a gas contg. CO2 to manufactured precipitated calcitic calcium carbonate, Sr and/or Ba is added before the rate of carbonation reaches about 90%, preferably about 50% in said carbonation reaction, and the reaction is completed. The amount of Sr and/or Ba to be added is >=0.005% of the amount of the resulting calcium carbonate. The total amount of Sr to be added and Sr contained in the limestone used as a starting material is >=0.05%, and that of Ba to be added and Ba contained in the limestone is >=0.01%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called sedimentation product obtained by reacting an aqueous suspension of calcium hydroxide (hereinafter abbreviated as milk of lime) with a carbon dioxide-containing gas (hereinafter abbreviated as carbon dioxide gas). The present invention relates to a method for producing calcium carbonate.

Currently, as an industrial method for producing precipitated calcium carbonate, the carbon dioxide method, in which carbon dioxide gas is passed through milk of lime, is widely adopted. Rubber, plastic, H paper depending on the needs.

It is widely used in large quantities as a filler or pigment in paints, etc. In addition, in order to further improve the physical properties of precipitated calcium carbonate used for these purposes, the particle surface is generally treated with various inorganic or organic treatment agents depending on the purpose of use. It is used.

However, precipitated calcium carbonate produced by this carbon dioxide gas method originally has a very strong cohesive force between secondary particles, and a large number of seventh particles aggregate to form large secondary particles (7
It is said that it is difficult to disperse this slurry of secondary particles into approximately 7th-order particles even if vigorous stirring is continued for a long time.

When precipitated calcium carbonate containing a large number of aggregates of such seventh-order particles is used as a filler or pigment for rubber, plastic, paper, paint, etc., the secondary particles appear to be seven-dimensional.
It behaves like secondary particles, and the blending effect due to the particle size of 1 particle, etc., which would normally be obtained if seventh particles were blended, cannot be obtained. Similarly, even if precipitated calcium carbonate containing a large number of aggregates is treated with an inorganic or organic surface treatment agent, only the surface of the secondary particles will be treated; It is not effective enough.

To date, research on dispersing these/secondary particle aggregates has been
Although many reports have been made, the following methods are generally adopted.

α) Add a dispersant such as phosphate, polyacrylate, etc. to precipitated calcium carbonate and stir vigorously.

(2) Strongly agitate and destroy using a ball mill, sand grinder mill, etc.

However, in the method (1), aggregates with relatively weak bonding force between particles can be dispersed, but it is completely powerless to disperse aggregates with strong bonding, and whether it is preferable or not. Regardless, the dispersant used for dispersion gets mixed in between the precipitated calcium carbonate particles, and the dispersant is absorbed onto the surface of the particles, so that the uses of precipitated calcium carbonate are greatly reduced. In addition, in case ①, the dispersion method is pulverization using strong sand grinding, so the seventh particles are destroyed at the same time as the aggregates are dispersed, and as a result, the surface condition is extremely It is difficult to say that this is a preferable method because particles that are unstable and even smaller than the desired secondary particle size, incompletely dispersed 7Z particles, and secondary agglomerated particles coexist, resulting in a wide particle size distribution.

The present invention is directed to the production of calcite-based calcium carbonate, in which calcite-based calcium carbonate is produced by reacting carbon dioxide-containing gas with an aqueous suspension containing calcium hydroxide as a main component created using naturally occurring limestone. To provide a method for producing calcite-based calcium carbonate, characterized in that the carbonation reaction is completed under conditions in which S or Ba or both are added during the carbonation reaction. The objective is to achieve improved dispersibility in water.

In addition, the implementation of this method preferably begins with any warm water [
It is even more preferable to prepare milk of lime with any calcium hydroxide concentration and pass carbon dioxide gas therein before its carbonation rate reaches 2θ! Before heating the finished calcium carbonate to 8L or 500 liters, add more than 8L or more of Sr to the finished calcium carbonate, and adjust the amount of Sr contained in the raw limestone to 8L or more. The total amount of Sr or Ba is 0.0l% or more and a is Oθ/
It is characterized by being more than .

The size of the 7th particle of calcite-based precipitated calcium carbonate (hereinafter referred to as "calcite-based"), which is generally produced by the carbon dioxide method, is determined by the concentration of milk of lime at the start of the carbonation reaction (hydroxylation in milk of lime). It is determined by the interaction between the temperature and the concentration and flow rate of carbon dioxide gas flowing into the milk of lime.In the present invention, the temperature of the precipitated calcium carbonate obtained at the end of the carbonation reaction is determined by the The above manufacturing conditions are arbitrarily selected so that the particle size becomes the desired particle size,
Just start the carbonation reaction.

Sr and Ba are contained in raw limestone in trace amounts (see Table-j), but Sr, Ba, which is used in the present invention,
Ba,! : U, ri(!: L f'j 5l-Cos
t5rc4! Whether it is easily soluble or poorly soluble in water, such as lBaSO4, it can be used without any problem.

In addition, the content of these products is 0.00% as the total amount of Sr or B8 or both relative to calcium carbonate.
05% or more, preferably O0j%
~/%. When the amount of these additives is less than 0.005%, no significant effect of addition is observed compared to when no additive is added, and it is difficult to obtain calcium carbonate that is easily dispersible in water. On the other hand, even if the amount added is large, it will only become more expensive as an additive.
It is economically disadvantageous, and it is difficult to confirm the significant effect of excessive addition due to excessive addition. Furthermore, even if the raw limestone contains a large amount of S, Ba, calcium carbonate that is easily dispersible in water cannot be obtained unless additives are added; Bad, in that case, OO as Sr in calcium carbonate after production.
So that it contains more than the punchline or more than 007% as Ba,
It is necessary to add it during the carbonation reaction process. The timing of adding these additives is determined when the carbonation rate of the reaction solution is 0 to 90 during the carbonation reaction process in which carbon dioxide gas is introduced into the milk of lime.
It should be added preferably at a rate of 0 to 20%, and even if added after the carbonation rate exceeds 90%, no significant addition effect will be observed.

12. Here, carbonation rate is when the weight of calcium hydroxide in the reaction solution is W, and the weight of calcium carbonate is °,
Defined by the following formula Next, the present invention will be explained in more detail with reference to Examples.

[Example-/]

Lime milk adjusted to 3θ0C (carbonation rate θ%) containing calcium hydroxide with a concentrated IK of A/RimuA (carbonation rate θ%) 5rCo8 to 3o1 (07 as Sr to finished calcium carbonate)
%) and after stirring and mixing with the milk of lime, carbon dioxide gas having a carbon dioxide concentration of θ t M % was introduced into the milk of lime at a speed history of 300−1−/re, and at a stirring speed of 3 θ rprn. The carbonation reaction was carried out while stirring the reaction solution, and 72 hours after the start of the reaction, P
The carbonic acid reaction was stopped at H72 temperature g, toc.

As a result of X-ray diffraction, the calcium carbonate obtained in this way has a calcite structure with a particle size of υ to θg/l (the particle diameter according to an electron microscope field of view, hereinafter abbreviated as an electron microscope field). ), and its dispersibility in water was good. The particle size distribution of this calcium carbonate is shown in the table.

[Example--Implementation ffU group]

The carbonation reaction was carried out in the same manner as in Example-/, except that the additive 5rco8 used in Example-/ was changed to the additive and amount shown in Table-/.

The calcium carbonate thus obtained was a calcium carbonate having a calcite structure and a particle size (electron microscopic field) of 02 to 011μ, as in Example 1, and its dispersibility in water was good.

The particle size distribution of these calcium carbonates is shown in 'tff-,2.

[Comparative example-/]

The carbonation reaction was carried out in the same manner as in Example-/, except that the additive 5rCOs used in Example-/ was not added. The calcium carbonate thus obtained had a calcite structure and a particle size (electron microscopic field) of 02 to 0 gμ, as in Example 1, but the dispersibility in water was different from Example 2. It was extremely poor compared to the previous version. The particle size distribution of this calcium carbonate is shown in Table-2.

[Execution [Tari-3-] The same additive S rCOs used in Example-/ was carbonated as in Example-/, except that it was added only when the carbonation rate reached 20 or more. The reaction was carried out. The calcium carbonate thus obtained had a calcite structure and a particle size of 02 to 0 gμ (electron microscopic field) as in Example-/, and its dispersibility in water was good. The particle size distribution of this calcium carbonate is shown in Table-2.

[Comparative example - λ]

The timing of addition of the additive 5rCOs used in the implementation i+u-t was set at a carbonation rate of 9! of the carbonation reaction solution. The carbonation reaction was carried out as in Example-j, except for changing to H. The calcium carbonate thus obtained had a calcite structure and a particle size (electron microscopic field) of Q to 0 gμ, as in Example-j, but its dispersibility in water was poor. The particle size distribution of this calcium carbonate is shown in Table 1.

[Comparative Example-3] The amount of additive 5rco3 used in Example-/ was changed to o2♂
t (003% as sr based on finished calcium carbonate)
) The carbonation reaction was carried out in the same manner as in Example -/, except that The calcium carbonate thus obtained has a calcite structure and o2~
Although it had a particle size (electron microscopic field) of Ot The IC was ugly. The particle size distribution of this calcium carbonate is shown in Table-2.

[Example-6] 5rCo8 in lime milk (carbonation rate 0chi) 7θ1 adjusted to 20°C containing calcium hydroxide total // θtA concentration
'r: /&, 2y (0/h as Sr based on the finished calcium carbonate) is added to the milk of lime and stirred by mixing waves. Carbon dioxide gas having a carbon dioxide concentration of 20 volume/h is added to the above milk of lime.
The carbonation reaction was carried out while stirring the reaction solution at a stirring speed of 300 rpm, and the carbonation reaction was stopped at a pH of 7.0C and a temperature of 7θ0C.

The calcium carbonate thus obtained had a particle size of 0/3μ of a calcite structure (electron microscopic field), and its dispersibility in water was extremely good. The particle size distribution of this calcium carbonate is shown in Table-2.

[Comparative example-G]

The carbonation reaction was carried out in the same manner as in Example 6, except that the additive 5rCO++ used in Example 6 was not added. The calcium carbonate thus obtained has a calcite structure similar to Example B and has a θ/! Although it has a particle size (electron microscopic field) of μ, its dispersibility is extremely poor.

[Example-7] Milk of lime was prepared using limestone containing 003% as Sr and θoo3'% as Ba, and this product was heated at a temperature of 3%.
00C, adjust concentration/4t to 4 and glaze milk EtO
5rcos as additive in L9. /f (θ/th as Sr to the finished calcium carbonate) was added, and a carbonation reaction was carried out as in Example/. The calcium carbonate thus obtained had a calcite structure, a particle size of 02 to 0 μg (electron microscopic field), and had good dispersibility. This particle size distribution is shown in the table.

- [Comparative Example-j] The milk of lime used in Example-2 was subjected to a carbonation reaction as in Example-7 without using any additive. The calcium carbonate obtained in this way has a calcite structure with θ
Although it has a particle size of ~θgμ (electron microscopy field)
However, its dispersibility was extremely poor. This particle size distribution is shown in Table-λ.

[Example-1]

Milk of lime is created using limestone containing 0/M'lr as Sr and Qooj as Ba, and this material is heated to a temperature of 3.
θQC1 concentration/g! Lime milk adjusted to 2/1 and garnished 30
1, add S and SO2 as additives (00j'1y as Sr to finished calcium carbonate),
The carbonation reaction was carried out as in Example-/.

The calcium carbonate thus obtained had a calcite structure, a particle size of 02 to 0 μg (electron microscopic field), and had good dispersibility. This particle size distribution is shown in the complete table.

[Comparison 1] - B] No additives were used in the milk of lime used in Example -.
The carbonation reaction was carried out as in Example. Although the thus obtained carbonic acid lucicum had a particle size of θ, 2 to 0 μ (electron microscopic field), its dispersibility was extremely poor. Shown in 2.

The measurement of the particle size distribution was carried out using a SA-CP type particle size distribution d+lJ device manufactured by Takasugi Seisakusho under the following conditions.

Solvent (NaPO*) e O-, 2% solution rotation speed /, 20 θrpm liquid lo (1 high 3) In addition, the upper 6-carbon average Masako diameter was calculated from each particle size distribution using the following formula.

8 w w; Direct placement in each section [Application example] A paper coating test was conducted using the calcium carbonate produced in Implementation U-/ and Comparative Example-/. First, calcium carbonate so, 7. ．． tt%, starch 3.1% by weight, latex S, O heavy shield 1, dispersant 0. and weight% and water content 0
A coating liquid consisting of Kosaichi was prepared, and this was coated on one side of coated paper made of U.S. tsubogi cypress using a coating rod at /3y/i at a temperature of to″c and a pressure of 2g!θ/l. Me!
After passing the paper three times, the coated paper was subjected to a super calender and the following test results were obtained.

In addition, evaluation of each test is performed using the following method.

White paper gloss; measured with gloss meter 730-7jt0 Print gloss; Gloss Make-730-7! ; Measured at 0 Opacity; Measured with Hunter set white 17I meter Surface strong gray, I
As is clear from the above coating test results measured using a GT printability tester, the calcium carbonate obtained according to the present invention has good dispersibility in water and is therefore superior in various physical properties. You can check it.

[Application example-1]

Using the calcium carbonate obtained in Example B and Comparative Example G treated with 3.0% by weight of sodium stearate, it was used as a filler for thermoplastic resin polypropylene in accordance with JIS K, j'lOθ. An impact resistance test was conducted.

(Composition) Polypropylene resin (Jinmin Chemical H-30/)? 0 parts Calcium carbonate 20 parts The above blended product was kneaded for 70 minutes with an electric roll (surface temperature 230°C),
Molded with an injection molding machine (molding temperature 24tθ'C), /θ
A sheet of Gm

The impact strength is determined by jθ, breaking energy (anti-flour), and falling dart size (inch diameter): measured at z3cc. Based on the above results, 1) Lucium carbonate obtained by the present invention has a good dispersibility when filled in polypropylene. It can be seen that the impact resistance is extremely excellent.

Claims (1)

[Claims] α) Calcite-based calcium carbonate is produced by reacting a carbon dioxide-containing gas with an aqueous suspension containing calcium hydroxide as a main component prepared using naturally occurring limestone. A method for producing calcite-based calcium carbonate, characterized in that the carbonation reaction is completed under conditions in which Sr or Ba or both are added during the carbonation reaction. (2) Sr or B for finished calcium carbonate
Before adding a or both, 0.0 (81 or more,
And, the total amount of the added amount and the Sr content or 4 minutes contained in the raw limestone is such that Sr is 005 or more or B8 is θO
The manufacturing method according to claim 1, which is equal to or more than 0.