JP3055334B2 - Method for producing colloidal calcium carbonate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing colloidal calcium carbonate, and more particularly, to an average particle size by electron microscopy (hereinafter referred to as "electron microscope particle size") of more than 0.02 .mu.m.
The present invention relates to a method for producing cubic colloidal calcium carbonate sized to have a uniform particle size within a range of less than 8 μm.

[0002]

2. Description of the Related Art Calcium carbonate having a particle diameter of 0.1 μm or less, so-called colloidal calcium carbonate, is mainly used as a functional filler for rubber, plastics, paints, sealants or inks. Limestone, which is a raw material of this colloidal calcium carbonate, is also one of the few mineral resources in Japan, has high whiteness and purity, and colloidal calcium carbonate is one of the first effective uses thereof.

Among such colloidal calcium carbonates having an electron microscopic particle size of 0.1 μm or less, the finer the particle size, the higher the effect of imparting functions such as strength and flow characteristics is.
Conversely, the finer the particle, the stronger the cohesive force and the wider the particle size distribution. In particular, the higher the mixing ratio of ultrafine particles having an electron microscopic particle size of 0.04 μm or less, the stronger the cohesive force.

However, when such colloidal calcium carbonate particles having a strong cohesive force are used after being kneaded with a matrix or a vehicle for each application, if the shearing force at the time of the kneading treatment is weak, the aggregated secondary particles remain. Will be mixed
In many cases, the original effect of the secondary particles cannot be exhibited.

Hereinafter, this point will be described in more detail. Colloidal calcium carbonate obtained by a gas compounding method of introducing carbon dioxide into lime milk is calcium chloride (CaCl 2).
₂ ) Unlike the so-called liquid phase reaction method in which sodium carbonate (NaCO ₃ ) is reacted with sodium carbonate (NaCO ₃ ), the particle size of the electron microscope is usually 0.03
~ 0.04 μm colloidal calcium carbonate. If the colloidal calcium carbonate particles having a particle diameter of 0.03 to 0.04 μm remain too cohesive, they are conventionally transferred to a tank by means of aging, that is, for example, by heating to 70 ° C. Let stand for 3 to 4 days without stirring and adjust the pH to 1
When stabilized at around 1.5, colloidal calcium carbonate having an electron microscopic particle size of 0.08 μm was obtained.

[0006] Such an electron microscopic particle size of 0.03 to 0.04 µm
The particle size of the colloidal calcium carbonate having a particle diameter of 0.08 μm obtained by maturation or the maturation of colloidal calcium carbonate is referred to as a primary particle size. In addition, in order to prevent the particles having such a primary particle size from agglomerating during drying and to improve the compatibility with a matrix or a vehicle to be mixed, the particles are subjected to a surface treatment with a fatty acid or a resin acid, followed by dehydration, drying, What was classified and powdered is called a secondary particle size.

[0007] These colloidal calcium carbonate powders are coated with a paint,
When mixed into a sealant or the like, it is difficult to disperse the particles to the primary particle size, and they are almost mixed in a state of the secondary particle size.

On the other hand, paints, sealants, and the like are required to have thixotropic functionality, called sagging, in addition to dispersibility, called the degree of roughness, and it is said that the finer the secondary particle size, the better the powder.

However, even when the particle diameter is determined by the electron microscope or the BET method, the average particle diameter is expressed to the last. The content of irregularly shaped particles that have not been sized to an appropriate particle size is a little. That is, irregularities in the particle diameter and the particle shape cause aggregation, which causes the formation of a large aggregate during drying.

[0010] From these facts, the electron microscope particle size is 0.02
It is desired to use colloidal calcium carbonate which has been sized to an arbitrary uniform particle size exceeding μm and less than 0.08 μm, and which has been aged and formed into a cubic shape.

[0011]

In the conventional aging method, after the colloidal calcium carbonate having a particle size of 0.03 to 0.04 μm obtained by the reaction is put in a tank, it is statically moved without any movement and stirring. If you have not placed
The phenomenon of so-called ripening does not occur, so that no particle growth is observed and the particle size remains at 0.03 to 0.04 μm.

The ripening is a phenomenon that occurs when the neutral pH immediately after the reaction becomes weakly alkaline due to release of carbon dioxide gas by heating or standing for a long period of time. The phenomenon of elution into the suspension due to its high solubility, recrystallization on lattice defects of other relatively large particles, lowering its surface activity, reducing cohesion, and growing particles larger It is believed that.

Therefore, aging requires a certain period of time. For example, when the particles are allowed to stand for 4 days to grow the particles from 0.03 to 0.04 μm to 0.08 μm in size, an intermediate time is required. On the 1st to 3rd days, large differences were observed in the pH and electron microscope particle diameters of the samples at the center and the periphery of the tank, or the top, middle and bottom parts, and almost the same values were obtained by the 4th day. It is a reality.

As described above, in the conventional aging method, in the aging tank, all the particles have a particle size of 0.03 to 0.04 with time.
Instead of changing from μm to particles having a particle size of 0.08 μm, some particles have a particle size of 0.08 μm, and the remaining particles have a particle size of 0.03 to 0.04 μm. The ripening is completed when the ratio of the particles having a diameter of 0.08 μm increases. For this reason, the particle size distribution of the obtained particles is broad.

Therefore, in the conventional method, the particle size is 0.08 μm
It is composed of finer and more functional particles than
Particle sizes of 0.08 μm and 0.0
It has been difficult to obtain a colloidal calcium carbonate having an arbitrary particle size in the middle of 2 μm and sized and shaped into a uniform particle size and a uniform particle shape.

The present invention has been made in view of the above-mentioned conventional circumstances, and has an average particle diameter of more than 0.02 μm and 0.02 μm.
Easily and efficiently produce colloidal calcium carbonate, which is composed of cubic sized particles having a uniform particle size of less than 8 μm and has a high functionality, has almost no cohesiveness and is excellent in dispersibility, and has an excellent function-imparting effect. It is an object of the present invention to provide a method for producing colloidal calcium carbonate which can be produced.

[0017]

According to a first aspect of the present invention, there is provided a method for producing colloidal calcium carbonate, wherein carbon dioxide gas is introduced into a lime milk suspension to which sugars and alcohols are added, so that the average particle diameter is 0.02 μm or less. PH of colloidal calcium carbonate
A suspension of 6.8 ± 0.2 was obtained, to which calcium or sodium hydroxide was added to adjust the pH to 7.6 ± 0.2.
After adjusting to 0.2, the temperature was raised to a temperature of 45 to 95 ° C,
Stirring and aging are performed until the suspension pH rises to a predetermined pH, and the suspension containing cubic calcium carbonate carbonate sized to an arbitrary particle diameter of more than 0.02 μm and less than 0.08 μm. It is characterized by obtaining a suspension.

The method for producing colloidal calcium carbonate according to claim 2 is the method according to claim 1, wherein the saccharide has a weight of 50 to 200 wt.
pm and 2 to 10% by volume of alcohols.
Introducing carbon dioxide gas having a concentration of 20 to 40% by volume into a suspension of lime milk having a concentration of 3 to 7% by weight and a temperature of 14 to 17 ° C. at a rate of 40 to 100 L / min · kg-Ca (OH) _2. It is characterized by.

The method for producing colloidal calcium carbonate according to claim 3 is characterized in that, in the method according to claim 1 or 2, stirring and aging are performed by stirring in a tank or turbulent stirring in a pipeline. And

According to a fourth aspect of the present invention, in the method of the first to third aspects, the pH of the suspension is 9.
Aging is performed until the temperature rises to 5 to 12.0. After completion of the aging, carbon dioxide gas is introduced into the suspension to adjust the pH to 6.8 ± 0.2.
To obtain a colloidal calcium carbonate having an average particle diameter of more than 0.02 μm and less than 0.08 μm.

The method for producing colloidal calcium carbonate according to claim 5 is the method according to claims 1 to 4, wherein the average particle diameter is 0.02.
The method is characterized in that a suspension containing colloidal calcium carbonate having a size of more than μm and less than 0.08 μm is concentrated to a concentration of 14 ± 1% by weight, and then sent to a surface treatment step.

Hereinafter, the present invention will be described in detail.

In the present invention, first, carbon dioxide gas is introduced into a lime milk suspension to which sugars and alcohols have been added in a conventional manner, so that the average particle diameter, preferably the electron microscope particle diameter is 0.02 μm or less. Preferably 0.01 to 0.02
pH containing ultra-fine particle size colloidal calcium carbonate
A suspension of 6.8 ± 0.2 is obtained.

Specifically, a saccharide is used in an amount of 50 to 200 parts by weight pp.
m (hereinafter simply referred to as "ppm"), alcohols are added at 2 to 10% by volume, mixed at a concentration of 3 to 7% by weight, and in a lime milk suspension at a temperature of 14 to 17 ° C, 20 to 40 volumes are added. % Carbon dioxide gas at 40-100 liters / min.kg-Ca (O
H) Introduced at a speed of ₂ to give an electron microscope particle size of 0.02 μm or less,
Preferably, a suspension having a pH of 6.8 ± 0.2 containing 0.01 to 0.02 μm of colloidal calcium carbonate is obtained.

Incidentally, sucrose, glucose and the like can be used as saccharides to be added. Further, as the alcohols, methanol, ethanol and the like can be used.

Next, in order to neutralize free carbon dioxide in the obtained suspension, calcium hydroxide (Ca (OH)
₂ ) Or add sodium hydroxide (NaOH) to the suspension to adjust the pH of the suspension to 7.6 ± 0.2.

Thereafter, the suspension is heated to an arbitrary temperature within the range of 45 to 95 ° C. by using an in-line heater or the like, and is then transferred to, for example, a tank, where stirring is continued while maintaining the temperature. In this case, the temperature is raised to 45 to 75 ° C., transferred to another tank, and stirred at the temperature for about 3 to 12 hours. Or transfer with turbulent stirring in the pipeline. In this case, the temperature is raised to 76 to 95 ° C., and the mixture is turbulently stirred in a pipe for 1 to 3 hours. By this means (the above or the method and conditions are appropriately determined depending on the equipment scale, the number of workers, operating conditions, etc.), stirring is performed until the suspension pH rises to a predetermined pH,
Perform aging.

When the pH of the suspension reaches a predetermined value, carbon dioxide gas is introduced into the suspension, and p
By neutralizing H with carbon dioxide gas to lower the pH to 6.8 ± 0.2, the ripening growth is stopped, and a suspension containing colloidal calcium carbonate having a desired particle diameter by electron microscopy is obtained. Here, as the carbon dioxide gas, the same as described above can be used. By introducing equipment for automatically introducing carbon dioxide gas when the pH of the suspension reaches the set pH, labor saving can be achieved.

In this case, by appropriately setting the pH to be increased by aging, a colloidal calcium carbonate having a desired particle size under an electron microscope can be obtained. That is, the pH is adjusted to 9.5 to 12.
By stopping the ripening by raising the pH to an arbitrary pH of 0, it is possible to obtain a cubic colloidal calcium carbonate sized to an arbitrary particle diameter of more than 0.02 μm and less than 0.08 μm. . Note that, by further aging, a product having a larger particle size can be obtained.

After obtaining a suspension containing colloidal calcium carbonate having a desired particle size under an electron microscope, the suspension is concentrated to a concentration of 14%.
It is concentrated to about ± 1% by weight and transferred to a subsequent surface treatment step to obtain cubic calcium carbonate having a very small expected cohesiveness and a uniform particle size.

Here, the concentration of the suspension may be performed, for example, with a thickener while adding a precipitant such as polyacrylamide or PAC to the suspension.

In addition, the surface treatment is performed on the concentrated suspension,
According to a conventional method, the reaction is performed by adding a fatty acid or a resin acid. By the surface treatment, drying, prevention of aggregation and improvement in affinity with a matrix, a vehicle or the like to be kneaded can be achieved.

After the surface treatment, if necessary, after a dehydration by a filter press, a finishing treatment such as drying, pulverization, classification, etc. is performed to obtain a surface-treated colloidal calcium carbonate powder.

[0034]

According to the present invention, a suspension of colloidal calcium carbonate having an ultrafine particle diameter of not more than 0.02 μm obtained by introducing carbon dioxide into a lime milk suspension to which sugars and alcohols are added is used. By aging, the average particle size is 0.0
In addition to growing colloidal calcium carbonate particles of 2 μm or less, the surface of the particles can be stabilized, and the cohesive force can be significantly reduced. In addition, since this aging is performed while stirring, cubic calcium carbonate carbonate having a uniform particle size according to the degree of aging can be obtained.

Moreover, depending on the pH at the end of ripening, it is possible to easily, reliably and inexpensively obtain a calcium carbonate carbonate having a desired average particle diameter of more than 0.02 μm and not more than 0.08 μm.

Such colloidal calcium carbonate is excellent in functionality, low in cohesion, and extremely excellent in function-imparting ability.

According to the method of claims 2 and 3, the reaction can be performed more efficiently.

According to the method of the fourth aspect, the average particle diameter is 0.1.
When it is more than 02 µm and less than 0.08 µm, it is possible to reliably obtain cubic colloidal calcium carbonate sized to an arbitrary uniform particle size.

According to the method for producing colloidal calcium carbonate according to the fifth aspect, a surface-treated colloidal calcium carbonate having even lower cohesiveness and excellent dispersibility can be obtained.

[0040]

The following examples, comparative examples and use examples are given below.
The present invention will be described more specifically.

Example 1 To a suspension of lime milk of 5% by weight and 17 ° C. to which 80 ppm of saccharose and 2% by volume of methanol were added, 30% by volume
50 l / min · kg-Ca (OH) ₂
And when the pH reaches 6.8, the electron microscopic particle size is 0.0
A suspension containing colloidal calcium carbonate having an ultrafine particle diameter of 2 μm was obtained.

A 1% by weight concentration of Ca (OH) was added to this suspension.
_After adding ₂ aqueous solutions to raise the pH to 7.6 ± 0.2, the temperature was raised to 85 ° C. by steam using an inline heater. This was transferred to a tank, and aged at 85 ° C. for 1.5 hours to raise the pH of the suspension to 11.0. Then, the pH of the suspension was lowered to 6.8 through carbon dioxide gas. 14% by weight with thickener while adding 30ppm of Alonflock (Toagosei precipitant) in a box
Concentrated.

The concentrated solution was transferred to a blender, and 30% by weight of a fatty acid soda (manufactured by NOF Corporation) at 90 ° C. was 3.0 parts by weight / Ca.
Surface treatment was performed by adding -100 parts by weight of CO ₃ . Then
After dehydrating and concentrating to a solid content of 55% by weight with a filter press, drying at 80 ° C., pulverizing and classifying the particles to give a particle size of 0.
A colloidal calcium carbonate powder of 07 μm was obtained.

Example 2 The same procedure as in Example 1 was carried out except that 180 ppm of saccharose and 10% by volume of methanol were added and mixed, and the suspension containing colloidal calcium carbonate having an ultrafine particle diameter of 0.01 μm was similarly obtained. I got And the aging condition is 65
C. for 5 hours, and a colloidal calcium carbonate powder having an electron microscopic particle size of 0.05 [mu] m was obtained in the same manner except that the final pH during aging was changed to 10.5.

Example 3 The procedure of Example 1 was repeated, except that the Ca (OH) ₂ aqueous solution was replaced with 5
% Colloidal calcium carbonate powder having an electron microscopic particle size of 0.03 μm was obtained in the same manner except that the aging condition was set at 55 ° C. for 7 hours using an aqueous solution of NaOH and the final pH during aging was changed to 10.0. .

Comparative Example 1 In the same manner as in Example 1, except that Ca (OH) ₂ was not added, the aging conditions were changed to 65 ° C. and 5 hours, and the final pH during aging was changed to 7.2. Electron microscope particle size 0.02μm
A colloidal calcium carbonate powder not completely aged was obtained.

Comparative Example 2 In Example 1, pH after adding Ca (OH) ₂ aqueous solution
Was adjusted to 11.5, the aging conditions were 65 ° C., 5 hours, and the final pH during aging was 11.5, to obtain irregularly-sized colloidal calcium carbonate powder having an electron microscopic particle size of 0.04 μm. Was.

FIG. 1, FIG. 2, FIG. 3, FIG.
The figure shows electron micrographs of the colloidal calcium carbonate obtained in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2, respectively.

1 to 3, according to the method of the present invention, the electron microscopic particle diameters are 0.07 μm, 0.05 μm, and 0.03 μm.
It is clear that cubic colloidal calcium carbonate sized to a uniform particle size of m can be obtained. On the other hand, from FIGS. 4 and 5, it can be seen that the colloidal calcium carbonate obtained in Comparative Examples 1 and 2 is irregular particles.

Use Example 1 Using the colloidal calcium carbonate powders obtained in Examples 1 to 3 and Comparative Examples 1 and 2, a vinyl chloride sealant was prepared according to the following formulation, stirred for 10 minutes in an automatic mortar, and dried to a thickness of 5 mm. (JIS K6830) and the degree of roughness by a grind gauge were measured. Table 1 shows the results. In Table 1, it can be said that the smaller the numerical value of the sagging and the degree of rubbing, the better the quality.

Formulation Geon 121 (vinyl chloride, paste resin): 50 g DOP (di, optyl, phthalate): 60 g Colloidal calcium carbonate powder: 30 g Use Example 2 Colloidal carbonate obtained in Examples 1 to 3 and Comparative Examples 1 and 2 Using a calcium powder, a silicone-based sealing agent having the following formulation was prepared, and the number of revolutions was 2 min ^-1 (V
₂ ) and 10 min ^-1 (V ₁₀ ) after 60 seconds. Table 1 shows the results. It should be noted that the higher the numerical value of the viscosity, the better the quality.

Formulation (main ingredient) Kaneka MS polymer: 100 g DOP: 30 g Colloidal calcium carbonate powder: 110 g Nocrack NS-6: 1 g (hardening agent) Tin ocamelate: 3 g Taurylamine: 1 g DOP: 5 g Titanium oxide: 15 g

[0053]

[Table 1]

From Table 1, it is clear that the colloidal calcium carbonate obtained by the method of the present invention is of remarkably high quality.

[0055]

As described above in detail, according to the method for producing colloidal calcium carbonate of the present invention, it is conventionally difficult to produce the same, and the average particle diameter exceeds 0.02 μm and 0.08 μm.
A cubic calcium carbonate having an arbitrary electron microscopic particle diameter in the range of less than and sized to a uniform particle diameter, which has a remarkably low cohesiveness and excellent dispersibility. . Since such colloidal calcium carbonate has low cohesiveness, it can be used in a state where the secondary particle size is close to the primary particle size, and is excellent in functionality and ability to impart functions.

According to the production method of the present invention, cubic calcium carbonate having a uniform particle size can be easily and easily prepared using various kinds of quicklime and slaked lime, which have conventionally been difficult to produce colloidal calcium carbonate. It can be obtained at low cost.

According to the method of claims 2 and 3, the reaction can be performed more efficiently.

According to the method of claim 4, the average particle diameter is 0.1.
It is possible to reliably obtain a cubic colloidal calcium carbonate having a particle size of more than 02 µm and 0.08 µm and having a uniform particle size.

According to the method for producing colloidal calcium carbonate of the fifth aspect, a surface-treated colloidal calcium carbonate having even lower cohesiveness and excellent dispersibility can be obtained.

[Brief description of the drawings]

FIG. 1 is an electron micrograph (magnification: 25,000 times) of cubic calcium carbonate carbonate obtained in Example 1 and sized to a particle size of 0.07 μm.

FIG. 2 is an electron micrograph (magnification: 25,000 times) of cubic colloidal calcium carbonate obtained in Example 2 and sized to a particle size of 0.05 μm.

FIG. 3 is an electron micrograph (magnification: 25,000 times) of the cubic calcium carbonate carbonate obtained in Example 3 and sized to a particle size of 0.03 μm.

FIG. 4 is an electron micrograph (magnification: 20,000 times) of irregularly-sized colloidal calcium carbonate obtained in Comparative Example 1.

FIG. 5 is an electron micrograph (magnification: 20,000 times) of irregularly shaped colloidal calcium carbonate obtained in Comparative Example 2.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaru Tamori 3-11-6 Otsuka, Bunkyo-ku, Tokyo Inside Ryoumitsu Lime Industry Co., Ltd. (72) Keiji Kokubo 3-11-6 Otsuka, Bunkyo-ku, Tokyo (56) References JP-A-5-208814 (JP, A) JP-A-3-126616 (JP, A) JP-A-50-147498 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C01F 11/18

Claims (5)

(57) [Claims] 1. Carbon dioxide is introduced into a lime milk suspension to which sugars and alcohols have been added, so that the pH of the suspension containing colloidal calcium carbonate having an average particle size of 0.02 μm or less is adjusted.
A suspension of 8 ± 0.2 was obtained, to which calcium or sodium hydroxide was added to adjust the pH to 7.6 ± 0.2.
After adjusting to 2, the mixture was heated to a temperature of 45 to 95 ° C., stirred and aged until the suspension pH increased to a predetermined pH, and the average particle diameter was more than 0.02 μm and less than 0.08 μm. A method for producing colloidal calcium carbonate, comprising obtaining a suspension containing cubic calcium carbonate which is sized to an arbitrary particle size. 2. A lime milk suspension having a concentration of 3 to 7% by weight and a temperature of 14 to 17 ° C. mixed with 50 to 200% by weight of saccharides and 2 to 10% by volume of alcohols at a concentration of 20 to 40% by volume. 40 to 100 liters / min.kg of carbon dioxide
The method for producing colloidal calcium carbonate according to claim 1, wherein the introduction is performed at a rate of -Ca (OH) ₂ . 3. The method for producing colloidal calcium carbonate according to claim 1, wherein the stirring and aging are performed by stirring in a tank or turbulent stirring in a pipeline. 4. Aging is performed until the pH of the suspension rises to 9.5 to 12.0, and after completion of the aging, carbon dioxide is introduced into the suspension to adjust the pH to 6.8 ± 0.2. By lowering,
The method for producing a calcium carbonate according to any one of claims 1 to 3, wherein a calcium carbonate having an average particle diameter of more than 0.02 µm and less than 0.08 µm is obtained. 5. An average particle size exceeding 0.02 μm and 0.08
A suspension containing sub-μm colloidal calcium carbonate at a concentration of 1
The method for producing a calcium carbonate according to any one of claims 1 to 4, wherein the concentrated calcium carbonate is fed to a surface treatment step after concentration to 4 ± 1% by weight.