KR20010080481A - calcium carbonates and their preparation methods - Google Patents

Abstract

Primary particle average short diameter of 0.1-0.5 micrometer with good dispersibility, 0.1-1.5 micrometer of primary particle average longitude, and 1.5-3.0 aspect ratio, and ideal particle shape, shape, or columnar cylindrical calcium carbonate, and Provided is a method for producing calcium carbonate, which can easily and inexpensively obtain such calcium carbonate. In the method for producing calcium carbonate by the reaction of calcium hydroxide and carbonic acid gas, an organic compound having a hydroxyl group is added at a ratio of 20 to 200 parts by weight based on 100 parts by weight of calcium oxide in terms of a calcium source as a raw material, and a carbonation reaction Do it.

Description

Calcium carbonates and their preparation methods

As a method of producing synthetic calcium carbonate, a "liquid-gas" method of blowing and reacting carbon dioxide gas into a calcium hydroxide slurry (suspension: a mixture of cement, clay, lime, and water) is typical, and the concentration, reaction temperature, and reaction of the calcium hydroxide slurry are typical. It is known that calcium carbonates having various particle diameters and shapes can be obtained by controlling the reaction conditions such as the method, the presence or absence of additives and the type thereof.

However, according to the liquid-gas method which is currently widely used industrially, the short-diameter primary particle average short diameter of 0.1-0.5 micrometer with favorable dispersibility, 0.15-1.5 micrometer of primary particle average long diameter, and 1.5-3.0 aspect ratio The production technology of calcium phosphate is not established. Such calcium carbonate improves various performances in coating pigments for papermaking, internal additives, and anti-fragment fillers for magnetic tape, which need to be highly controlled in particle size, shape and particle size distribution. There is a need for a method that is suitable for this purpose and that can be manufactured at low cost. In order to solve this problem, a method of adding a seed seed as a nucleus to a calcium hydroxide slurry or a partially carbonated calcium hydroxide slurry as a growth parent is disclosed in JP-A-7-5303 and JP-A-5. Although it is described in each publication of 3-19165, since preparation of a seed is a separate process and involves control of a gas flow rate, there exists a problem that it becomes complicated as a whole process.

In addition, Japanese Patent Application Laid-Open No. 3-3605 discloses a method in which some carbonation occurs to produce plate-like basic calcium carbonate under the condition that the pH value is not lowered by 0.2 or more, and then carbonization until the reaction is completed. However, it is necessary to switch the gas flow rate by the pH value while lowering and suppressing the flow rate of the carbon dioxide gas, which takes time during manufacture and makes the process complicated.

Furthermore, a method of completing the carbonation by wet grinding some carbonated calcium hydroxide slurry and then adding a second calcium hydroxide slurry is disclosed in Japanese Patent Application Laid-Open No. 5-2216345, but after some carbonation, As a result, the whole process is complicated.

In the above compounding method, since the produced calcium carbonate is a cube or rhombus, the particles tend to overlap, and when used in a coating pigment for papermaking, it is difficult to improve the smoothness and gloss of the coated paper surface.

On the other hand, the method of obtaining indulgence calcium carbonate is described in each of Unexamined-Japanese-Patent No. 54-28399, Unexamined-Japanese-Patent No. 6-56422, and Unexamined-Japanese-Patent No. 8-18827, This process is also complicated by preparing and adding seed crystals or wet grinding calcium hydroxide slurry as a raw material.

Insulating phase calcium carbonate is easy to break | shape the angle of particle | grains in the shape. This may reduce the standard strength of the coated paper, for example, when used in paper-based coating pigments, etc., and when used in the anti-fragment filler for magnetic tape, there is a possibility that powder may be generated and drop out. .

Accordingly, an object of the present invention is to easily disperse calcium carbonate and such calcium carbonate having a primary particle average shorter diameter of 0.1 to 0.5 µm, a primary particle average long diameter of 0.15 to 1.5 µm, and an aspect ratio of 1.5 to 3.0. To provide a method for producing calcium carbonate that can be obtained at a low cost.

The present invention relates to calcium carbonate produced by the reaction of calcium hydroxide with carbonic acid gas, and a method for producing the same. Particularly, the average particle diameter of primary particles having good dispersibility is 0.1 to 0.5 µm and the average particle diameter of primary particles is 0.15 to The present invention relates to a calcium carbonate having a thickness of 1.5 µm and an aspect ratio of 1.5 to 3.0, and a method for producing the same.

1 is an electron micrograph (10,00 times) of the calcium carbonate obtained in Example 2. FIG.

2 is an electron micrograph (10,00 times) of the calcium carbonate obtained in Example 5. FIG.

In order to achieve the above object, the present invention has been described above to coexist with calcium ions, organic compounds having carbonates and hydroxyl groups in order to produce calcium carbonate having excellent dispersibility by reaction between calcium hydroxide and carbonic acid gas. The organic compound was added and the manufacturing method of calcium carbonate was comprised.

According to this invention, it is preferable that the organic compound which has a hydroxyl group is added before or after the start of carbonation, and the whole amount of predetermined amount is added until the carbonation rate becomes about 20% after the start of carbonation reaction. The organic compound is kneaded with the raw material of quicklime or slaked lime before the start of the carbonation reaction or is added dropwise to the digested water. In addition, it is added to a powder raw material in a mixer by spraying it, or adding it dropwise to calcium hydroxide slurry.

An organic compound adds 10-200 weight part with respect to 100 weight part of calcium oxide (CaO) conversion of the calcium source used as a raw material. At 10 parts by weight or less, the particle shape is close to a cubic shape, and rice grains, shapes (scattered) or angled columnar calcium carbonate particles of a desired shape are not obtained, and when the amount is 200 parts by weight or more, the effect reaches a limit point. It is not effective in terms of cost. Ideally, 50 to 180 parts by weight is added. In this range, since the aspect ratio of the primary particles is 2 or more, particles of excellent shape that tend to improve smoothness and the like when a pigment for papermaking or the like is obtained are obtained.

As the addition method, the quicklime or slaked lime powder is kneaded by a kneader, or added dropwise to water used for preparing digested water or slurry. It may be applied by spraying in a mixer, or may be added dropwise to calcium hydroxide slurry before the carbonation reaction starts or until the carbonation rate reaches about 20% after the start of the carbonation reaction. However, the addition method is not particularly limited as long as a state in which a calcium ion and an organic compound having a carbonate ion and a hydroxyl group coexist in the reaction is obtained.

Here, the organic compound which has a hydroxyl group is ideally molecular weight 600 or less, Glycols, such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, and butylene glycol; Ethanolamines such as monoethanolamine, diethanolamine and triethanolamine; Glycerin and mixtures thereof, such as glycerin and polyglycerine, are exemplified, with propylene glycol and ethylene glycol being ideal.

Before the reaction, calcium hydroxide slurry is ideally prepared at a concentration of 3 to 20% by weight and a temperature of 10 to 20 ° C. By blowing carbon dioxide gas or mixed gas containing a carbon dioxide gas into this calcium hydroxide slurry, it is made to react until carbonation rate becomes substantially 100%. When the concentration of calcium hydroxide is less than 3% by weight, industrial productivity is lowered, and when the concentration of calcium hydroxide is more than 20% by weight, the slurry viscosity becomes high and it is difficult to handle, which is not suitable for the conventional method of producing calcium hydroxide. When the temperature before the start of the reaction is less than 10 ° C, colloidal carsite is easily formed and becomes agglomerates, while when it exceeds 20 ° C, it becomes agglomerates of indulgent particles and colloidal carsites, and it is difficult to obtain uniform and good dispersibility. It is well known.

Under the above conditions, when calcium ions, carbonate ions, and an organic compound having a hydroxyl group are coexisted and carbonized, the dispersibility of the primary particles has a short average particle diameter of 0.1 to 0.5 µm, the primary particle average length of 0.5 to 1.5 µm, And a columnar calcium carbonate having an aspect ratio of 1.5 to 3.0 and a shape of rice grains, shapes or angles. However, it is preferable to add the organic compound which has a hydroxyl group until the carbonation rate of calcium hydroxide becomes 20% at the latest. If the carbonization rate exceeds 20%, the organic particles are added when the amount of carbon dioxide gas is large, and the produced particles are gelatinized when the carbonic acid content is large. .

Since the calcium carbonate obtained by the present invention has a considerably good dispersibility, it is not necessary to disintegrate with a media mill or the like, but rather to prevent particle breakage, when a high concentration slurry is used, a short time by adding a dispersant It is desirable to remain only by the slurrying treatment.

According to the production method of the rice grain-shaped calcium carbonate according to the present invention, the uniform and excellent dispersibility of the primary particle average diameter is 0.1 to 0.5 탆, the primary particle average length is 0.15 to 1.5 탆 and the aspect ratio is 1.5 to 3.0. On the other hand, it is possible to obtain a columnar calcium carbonate in the shape of rice grains, shapes or angles. The manufacturing method of the rice grain-shaped calcium carbonate according to the present invention is only an apparatus for adding raw material powder, digestive water or calcium hydroxide slurry having a carbonation rate of about 20% by mixing or dissolving an organic compound having a hydroxyl group, It can be implemented by adding to existing equipment, and can be realized simply and inexpensively. In addition, since the added organic compound is not absorbed into the crystal of calcium carbonate, the separated water by dehydration is in a state in which the organic compound is dissolved, and can be circulated and used as water for preparing digested water or calcium hydroxide slurry, and thus, it is cheaper. It is possible to prepare a grained calcium carbonate in the form of rice grains, shells or angles.

Calcium carbonate prepared by the method for preparing calcium carbonate according to the present invention is excellent in dispersibility and easy to be slurry in high concentration, and especially when used as a coating pigment or additive for papermaking, it improves various performances such as whiteness, smoothness, and opacity. Even when used for magnetic tape, it can be used in the form of ethylene glycol dispersion or the like as a highly controlled anti-fragment filler and is expected to bring good performance. Moreover, since the uniformity of particle | grains is good, glossiness improves when it is used as a coating pigment for papermaking, and when it is used as a filler for a crack prevention, the shatterproof ability improves. Moreover, it has the shape of a rice grain, a symbol or an angled columnar shape, and since the particles do not overlap well, it is possible to prevent the dropout due to the reduction of the surface strength of the coated paper or the occurrence of powder when used as a filler for preventing cracking.

According to the method for producing calcium carbonate according to the present invention, the dispersibility of the primary particle average shorter diameter is 0.1 to 0.5 µm, the primary particle average long diameter is 0.15 to 1.5 µm, the aspect ratio is 1.5 to 3.0, and ideally the shape is Calcium carbonate can be obtained which is particulate, shaped or angled cylindrical.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the examples described below, but needless to say that modifications can be made within the scope of the gist of the present invention.

(Example 1)

The company's crushing lime mass (JIS industrial lime crushing lime special) is pulverized to less than 1mm in particle size as calcium oxide raw material. 30 parts by weight of ethylene glycol is added and mixed with 100 parts by weight of this calcium oxide powder, and 1.5 times (48 parts by weight) of water of about 20 ° C. of theoretical amount required for the oxidation of calcium oxide to calcium hydroxide is stirred and mixed (stirred). The mixture was digested and aged to obtain calcium hydroxide powder. The calcium hydroxide powder was used to adjust the slurry concentration to 7% and the temperature of 15 ° C., so that carbon dioxide gas was introduced at a flow rate of 4 L / min · kg-Ca (OH) 2 until the carbonation rate was substantially 100%. The reaction was completed to give calcium carbonate.

Electron microscopy of the obtained calcium carbonate showed that the primary particle average short diameter was 0.4 µm, the primary particle average long diameter was 0.6 µm, and the median diameter by the laser diffraction method was 1.0 µm. It confirmed that it was a particulate form, particle shape, or a columnar particle shape with an angle. That is, as shown in the electron micrograph of FIG. 1, in an alternative form, the central portion is columnar and both ends are hemispherical particles. Of course, the circumference and hemisphere may be distorted to some extent. The diameter in the axial direction of the columnar shape becomes the long diameter, and the diameter in the radial direction becomes the short diameter.

In addition, a primary particle average short diameter is an electron measuring apparatus (measures the thickness of an object and the inner diameter and the outer diameter of an empty tube of two diagonal grains in an electron micrograph of 30,000 times magnification taken at random). ), The shortest chord of the particle (that is, the length of the diameter in the radial direction of the circumference of the particle) was measured, which was taken as the short diameter of the particle, and the average value thereof was determined to be the primary particle average short diameter. In the same way, the longest chord (i.e., the length of the axial diameter of the circumferential shape of the particle) of the two diagonal particles in the electron micrograph is measured, which is taken as the long diameter of the particle, and the average value is determined to determine the primary particle average. I made a long view. In addition, the median glasses by a laser diffraction method are the numerical values measured by the laser diffraction method particle size distribution measuring apparatus LA-500 by a chief manufacturing company, and the particle diameter of a secondary aggregation state is measured. The median glasses are numerical values indicating that dispersibility is better as the value is smaller than the primary particle size.

(Example 2)

Calcium carbonate was obtained by the same procedure as in Example 1 except that 80 parts by weight of ethylene glycol was added and mixed with 100 parts by weight of calcium oxide powder. Electron microscopic observation confirmed that the obtained calcium carbonate was a grain-shaped grain having good uniform dispersibility with a primary particle average diameter of 0.4 µm, primary particle average major diameter of 0.8 µm, and a median diameter of 1.2 µm by laser diffraction. . Electron micrographs (10,000 times) are shown in FIG. 1.

(Example 3)

Calcium carbonate was obtained by the same procedure as in Example 1 except that 150 parts by weight of ethylene glycol was added to and mixed with 100 parts by weight of calcium oxide powder. Electron microscopic observation confirmed that the obtained calcium carbonate was uniform and dispersible rice grains having a primary particle average short diameter of 0.4 m, primary particle average long diameter of 1.0 m, and a laser diffraction method having a median diameter of 1.3 m.

Example 4

Calcium carbonate was obtained as a result of the carbonation reaction in the same manner except that the flow rate of carbon dioxide gas in Examples 1 to 3 was 10 l / min · kg-Ca (OH) 2. The results observed with an electron microscope will be shown below. That is, the same figure as FIG. 1 in Example 5 is shown in FIG.

Example 4 Rice grains having good uniformity and dispersibility of 0.2 µm of primary particle average diameter, 0.3 µm of primary particle average diameter and 0.6 µm median diameter by laser diffraction.

Example 5 Rice grains having good uniformity and good dispersibility of 0.2 µm of primary particle average diameter, 0.4 µm of primary particle average diameter and 0.6 µm median diameter by laser diffraction.

Example 6: Rice grains having uniform and good dispersibility of 0.2 µm of primary particle average diameter, 0.5 µm of primary particle average diameter and 0.8 µm median diameter by the laser diffraction method.

(Example 7)

30 parts by weight of propylene glycol is added and mixed with 100 parts by weight of calcium carbonate equivalent (132 parts by weight of slaked ash) of calcium hydrated lime powder (JIS Industrial Slaked lime lime special), and water is added so as to have a concentration of 7% by weight. The calcium hydroxide slurry was obtained by adjusting to 15 degreeC. Next, as a result of the carbonation reaction in the same manner as in Example 1, calcium carbonate was obtained. Electron microscopic observation confirmed that the obtained calcium carbonate was uniform and dispersible rice grain-shaped particles having a primary particle average diameter of 0.4 μm, primary particle average major diameter of 0.6 μm, and median diameter by laser diffraction method of 1.0 μm. .

(Example 8)

80 parts by weight of propylene glycol was dissolved in use water in advance with respect to 100 parts by weight of calcium oxide equivalent of the slaked lime used in Example 7, and the slaked ash was added thereto so that the concentration was 7% by weight. It was adjusted so that calcium hydroxide slurry was obtained. Electron microscopic observation confirmed that the obtained calcium carbonate was uniform and dispersible rice grain-shaped particles having a primary particle average short diameter of 0.4 µm, a primary particle average long diameter of 0.8 µm, and a median diameter of 1.3 µm by laser diffraction. .

(Examples 9 to 10)

Calcium carbonate was obtained as a result of the carbonation reaction in the same procedure except that the flow rate of the carbon dioxide gas was set to 10 l / min · kg-Ca (OH) 2 in Examples 7 to 8. The results of observation with an electron microscope are described below.

Example 9: The uniform particle | grains of the grain shape of a primary particle average short diameter 0.2 micrometer, the primary particle average long diameter 0.3 micrometer, and the median diameter by a laser diffraction method of 0.6 micrometer are favorable.

Example 10 Primary particle average short diameter 0.2 탆, Primary particle average long diameter 0. A grain-shaped grain having good uniformity and dispersibility of 4 µm and median diameter of 0.6 µm by laser diffraction.

(Comparative Examples 1 to 4)

In Examples 1, 4, 7, and 9, the result of observing with a microscope the obtained calcium carbonate by the carbonation reaction by the same process except having made the addition amount of ethylene glycol or propylene glycol into 5 weight% follows.

Comparative Example 1: Uniform and excellent dispersible cubic particles having a primary particle average particle diameter of 0.5 μm and a median diameter of 1.1 μm by laser diffraction.

That is, the primary particle average particle diameter means that one side of a particle is measured by an electronic measuring instrument with respect to two diagonal particles in an electron microscope photograph with a magnification of 30,000 times taken by randomness, and this is determined as a particle size, and the average value is 1 It was set as the primary particle average particle diameter.

Comparative example 2: 1st average particle size 0.2 micrometer and the particle | grains of the uniform and good dispersibility of median diameter of 0.7 micrometer by a laser diffraction method with favorable dispersibility.

Comparative Example 3: Uniform and good dispersibility cubic particles having a first average particle diameter of 0.4 mu m and a median diameter of 0.8 mu m by the laser diffraction method.

Comparative Example 4: Uniform and good dispersibility cubic particles having a first average particle diameter of 0.2 mu m and a median diameter of 0.6 mu m by the laser diffraction method.

(Comparative Examples 5-8)

In Example 1, 4, 7, 9, except for not adding ethylene glycol or propylene glycol, the result of having observed the calcium carbonate obtained by the carbonation reaction by the same process by the electron microscope was described below.

Comparative Example 5: Polyhedral particles having a primary mean particle size of more than 1 µm and median shock by laser diffraction method of 3. 4 µm

Comparative Example 6: Aggregates of gelled particles having a primary particle average particle diameter of less than 0.01 µm and a median diameter of 4. 3 µm by the laser diffraction method

Comparative Example 7: Polyhedral particles having a primary particle average particle diameter of more than 1 µm and a median diameter of 3.1 µm by the laser diffraction method

Comparative Example 8: Aggregate of Gelled Particles with Primary Particle Average Particle Size Over 0.01 µm and Median Diameter by Laser Diffraction Method of 4.0 µm

Table 1 summarizes the synthesis conditions and results of the Examples and Comparative Examples.

Table 1

additive How to add Amount Carbon dioxide flow rate [ℓ / min · kg-Ca (OH) ₂] Primary particle size (electron microscope observation) Median diameter [㎛] shape Example 1 Comparative Example 1 Comparative Example 5 Example 2 Example 3 Ethylene Glycol Ethylene Glycol Mixed with quicklime Mixed with quicklime — Mixed with quicklime Mixed with quicklime 305-80150 44444 Short diameter: 0.4 m Long diameter: 0.6 m Particle diameter: 0.5 m Particle diameter:> 1 m Short diameter: 0.4 m Long diameter: 0.8 m Short diameter: 0.4 m Long diameter: 1.0 m 1.01.13.41.21.3 Particle TypeCubular Polyhedron Particle Type Particle Type Example 4 Comparative Example 2 Comparative Example 6 Example 5 Example 6 Ethylene Glycol Ethylene Glycol Mixed with quicklime Mixed with quicklime — Mixed with quicklime Mixed with quicklime 305-80150 1010101010 Short diameter: 0.2 m Long diameter: 0.3 m Particle diameter: 0.2 m Particle diameter: <0.1 m Short diameter: 0.2 m Long diameter: 0.4 m Short diameter: 0.2 m Long diameter: 0.5 m 0.60.74.30.60.8 Particulate cuboid colloid aggregate particulate type Example 7 Comparative Example 3 Comparative Example 7 Example 8 Propylene Glycol Propylene Glycol Mixed Into Lime Mixed Into Lime-Mixed In Detergent 305-80 4444 Short diameter: 0.4 m Long diameter: 0.6 m Particle diameter: 0.4 m Particle diameter:> 1 m Short diameter: 0.4 m Long diameter: 0.8 m 1.00.83.71.2 Particulate Cube Polyhedron Example 9 Comparative Example 4 Comparative Example 8 Example 10 Propylene Glycol Propylene Glycol Mixed with hydrated lime Mixed with lime-mixed with assistant 305-80 10101010 Short diameter: 0.2 m Long diameter: 0.3 m Particle diameter: 0.2 m Particle diameter: <0.1 m Short diameter: 0.2 m Long diameter: 0.4 m 0.60.64.00.6 Particulate cuboid colloid aggregate

(Application example)

The calcium carbonate obtained in Examples 1 and 4 and Comparative Examples 1 and 5 was dehydrated by a filter press to obtain a cake having a solid content concentration of 65.5% by weight. Subsequently, 0.6 weight% of dispersing agent was added to this dewatering cake in conversion of solid content, and it was made to disperse | distribute, and it was set as the high concentration calcium carbonate slurry of 65.0 weight of solid content concentration. Using this slurry as a coating pigment, 6 parts by weight of starch (Japanese Food Processing # 4600), 12 parts by weight of latex (Japanese Synthetic Rubber No. 102), and printability enhancing agent (Dong-A Chemical Wheatmaster) in 100 parts by weight of the lime calcium GT 360) 0.75 parts by weight, a water-resistant agent (Chuo Chemical Smirez 613), and 0.35 parts by weight of water are added to prepare a pigment composition having a solid concentration of 50.0% by weight, which is coated to 65 g / m 2 and subjected to ultra gloss treatment. After twice, the physical properties of the coated paper were evaluated.

Table 2 summarizes the coated paper physical properties in the application example.

TABLE 2

Item Example 1 Comparative Example 1 Comparative Example 5 Example 4 White paper glossiness (75 °) [%] Smoothness [㎛] Opacity [%] Hunter whiteness [%] 58.30.7186.197.1 50.30.8286.197.1 43.60.9883.295.6 65.70.6886.496.7

How to measure

Glossiness: Measured by JIS P8142, the higher the value, the higher the gloss

Smoothness: Perker print-surf roughness & porosity tester MODEL PPS78 DIGITAL H ₂ Measured at 0kg / ㎠, 10-point average, smaller value is better.

Opacity: measured according to JIS P8138, the larger the value, the better.

Hunter whiteness: measured by JIS P8123

It can be seen that the physical properties of the coated paper using the calcium carbonate slurries obtained in Examples 1 and 4 were superior to those obtained in Comparative Examples 1 and 5 as a whole.

Calcium carbonate prepared by the method for preparing calcium carbonate according to the present invention is excellent in dispersibility and easy to be slurry in high concentration, and especially when used as a coating pigment or additive for papermaking, it improves various performances such as whiteness, smoothness, and opacity. Even when used for magnetic tape, it can be used in the form of ethylene glycol dispersion or the like as a highly controlled anti-fragment filler and is expected to bring good performance. Moreover, since the uniformity of particle | grains is good, glossiness improves when it is used as a coating pigment for papermaking, and when it is used as a filler for a crack prevention, the shatterproof ability improves. Moreover, it has the shape of a rice grain, a symbol or an angled columnar shape, and since the particles do not overlap well, it is possible to prevent the dropout due to the reduction of the surface strength of the coated paper or the occurrence of powder when used as a filler for preventing cracking.

Claims (3)

Calcium carbonate whose primary particle average short diameter is 0.1-0.5 micrometer, primary particle average long diameter is 0.15-1.5 micrometer, and aspect ratio 1.5-3.0. 2. Calcium carbonate according to claim 1, wherein the shape is a particulate shape, a representation or an angled columnar shape. In the method for producing calcium carbonate by the reaction of calcium hydroxide and carbonic acid gas, an organic compound having a hydroxyl group is added at a ratio of 20 to 200 parts by weight based on 100 parts by weight of calcium oxide in terms of a calcium source as a raw material, and carbonation is carried out. Process for producing calcium carbonate, characterized in that the reaction.