JP3469286B2 - Method for producing cubic 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 process for producing cubic calcium carbonate having almost no secondary aggregation, good dispersibility, uniform individual particles, and excellent stability at high temperature and stability with time. More specifically, a method for producing chemically stable calcium carbonate in which the particle shape is cubic and the side length of the particle can be arbitrarily selected in the range of 0.10 to 20.0 μm, and each particle size is uniform. Regarding

[0002]

2. Description of the Related Art Calcium carbonate is a rubber and a plastic because it is inexpensive, has a high degree of whiteness, is harmless, and can produce products of various particle sizes, because limestone, which is its raw material, is abundantly produced in Japan. It is used in various fields as a filler for paints, a paint, an extender pigment for inks, a filler for paper shavings, a pigment for paper coating, an additive for medicines, cosmetics, foods, agriculture and the like.

This calcium carbonate generally reacts with ground calcium carbonate, which is adjusted to various grades by mechanically crushing limestone and classifying the crushed product, with quick lime obtained by firing limestone at high temperature, and water. After adjusting the lime milk,
Chemicals such as carbon dioxide compounding process that synthesizes calcium carbonate by passing carbon dioxide gas generated in lime milk during firing of limestone, lime soda process that reacts sodium carbonate with lime milk, soda process that reacts sodium carbonate with calcium chloride, etc. It is roughly classified into two types: precipitated calcium carbonate (synthetic calcium carbonate) prepared by the method.

The above-mentioned heavy calcium carbonate has a broad particle size distribution due to its production method, and has a drawback that calcium carbonate having a fineness of a certain level or more cannot be produced by the present pulverization and classification techniques. It cannot be used for advanced industrial applications. On the other hand, precipitated calcium carbonate is generally produced using a carbon dioxide gas combination process from an economical point of view. Synthetic calcium carbonate produced using the carbon dioxide gas compounding process is different in primary particle shape. Although the target particles are uniform, usually the primary particles aggregate or aggregate to easily form secondary particles (aggregate particles of primary particles), so post-processing such as wet pulverization with a wet pulverizer etc. Producing precipitated calcium carbonate containing no secondary particles under non-conducting conditions has the drawback that it is not possible with the prior art, and it cannot be used for particularly high-level industrial applications.

Regarding the soda process for reacting a soluble calcium salt such as sodium carbonate with a soluble calcium salt such as calcium chloride, for example, as shown in Japanese Patent Laid-Open No. 3-50116, spherical calcium carbonate of vaterite type crystals is used. Mixed calcium carbonate is easily obtained, and this vaterite-type calcium carbonate has the instability of being transferred to calcite-type calcium carbonate or aragonite-type calcium carbonate by physical treatment such as heating and grinding. It has a drawback that it is easily transformed into calcite-type calcium carbonate when left in water at room temperature for a long time. In addition, cubic calcium carbonate obtained by the conventional soda process not only has a large number of secondary particles due to aggregation of primary particles, but also the size of individual primary particles is not uniform, and it is suitable for advanced industrial applications. Was not available.

At present, calcium carbonate is being studied for use not only in the above-mentioned applications but also in various advanced industrial applications such as anti-blocking agents for films and fibers. The dispersibility of calcium carbonate particles, the uniformity of particles, and the particle size distribution. It is eagerly desired to improve the physical properties such as sharpness and arbitrary setting of particle diameter, high temperature stability and long term stability over time.

For example, magnetic tapes such as audio tapes and video tapes, capacitors, photographs, packaging, OH
In the polyester film used for P etc.,
The slipperiness is a major factor that determines the workability of the film manufacturing process and the processing process in each application, and further the quality of the product. When this slipperiness is insufficient, for example, when a magnetic layer is applied to the surface of a polyester film and used as a magnetic tape, the friction between the coating roll and the film surface during application of the magnetic layer is severe, and the film surface Wear is severe,
In an extreme case, wrinkles, scratches, etc. occur on the film surface. In addition, even after slitting the film after coating the magnetic layer and processing it into audio, video, computer tape, etc., when pulling out from the reel or cassette, winding up and other operations, many guide parts, playback heads, etc. Abrasion occurs remarkably, and scratches and distortions occur, and as a result of depositing a white powder substance due to abrasion of the polyester film surface, etc., it often becomes a major cause of loss of magnetic recording signal, that is, dropout. .

Conventionally, as a method for decreasing the friction coefficient of polyester, many methods have been proposed in which fine particles are contained in the polyester to give fine and appropriate irregularities to the surface of the molded article to improve the surface smoothness of the molded article. Has been done. The particles forming the irregularities on the surface of these polyester films generally have a greater effect of improving the slipperiness as the size thereof increases, but for precision applications such as magnetic tape, particularly for video, Since large particles themselves may cause defects such as dropouts, the unevenness of the film surface needs to be as uniform and fine as possible, and there is a demand to satisfy these contradictory properties at the same time. is the current situation. However, calcium carbonate prepared by a conventional method has high physical properties such as high dispersibility of individual particles, particle uniformity, sharpness of particle size distribution and arbitrary setting of particle size, high temperature stability, long-term stability, etc. Such as polyester base films used in 8 mm video tapes used in 8 mm video decks, and films for capacitors with a film thickness of about 2.5 μm. It cannot be used as an anti-blocking agent for polyester films, the dispersibility of calcium carbonate particles, the uniformity of particles, the sharpness of the particle size distribution, and the particle size can be arbitrarily set
High-level stability such as high-temperature stability and long-term stability has been eagerly desired from all directions.

[0009]

The present invention is useful for high-level industrial applications, has good dispersibility, does not contain unnecessary fine particles and coarse primary particles, and has an extremely uniform particle size. The present invention provides calcium carbonate that has a sharp distribution, a wide range of particle sizes that can be obtained, and an arbitrary particle size that can be set, and that has excellent high-temperature stability and long-term stability over time, at a simple and low cost.

[0010]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a carbonate solution of a specific concentration and a specific ratio is obtained under the condition of containing a specific amount of a reaction buffer. A calcium salt solution is mixed at a specific temperature and within a specific time, a specific additive is added at a specific ratio after a specific mixing time, and by imparting specific physical properties after washing with water, dispersibility of the obtained calcium carbonate particles, Improved particle uniformity, sharp particle size distribution, wide range of possible particle size,
In addition, it is possible to inexpensively and easily obtain cubic calcium carbonate particles composed of a substantially calcite-type crystal form, which can arbitrarily set the particle size, and has excellent high-temperature stability and long-term stability over time. Found and completed the present invention.

That is, according to the present invention, either 0.001 to 2.
A carbonate solution having a carbonate ion concentration of 0.1 to 3.0 mol / l and a calcium ion concentration of 0.1 to 3.0 mol / l prepared by adding a reaction buffer of 0 mol / l and a carbonate When a calcium salt solution having a calcium ion concentration ratio to ions of 0.5 to 2.0 is mixed to produce calcium carbonate, the carbonate solution is added to the calcium salt solution, or the calcium salt solution is added to the carbonate solution. The mixture is added dropwise within 1200 seconds, the carbonization reaction is carried out while maintaining the temperature in the mixing system at 5 to 40 ° C., and 90 seconds or more after the completion of the mixing of the carbonate solution and the calcium salt solution, the mixed solution is formed. A water-soluble salt or a water-soluble acid that reacts with calcium to produce a water-insoluble or sparingly soluble salt is added in an amount of 0.01 to 5% by weight with respect to the calcium carbonate present in the mixed system, and the resulting water suspension of calcium carbonate is added. Wash the suspension with water , The following (A), is prepared so as to satisfy the requirements of (b), and stable over time particle size with good dispersibility and the contents of the manufacturing method of the cubic shaped calcium carbonate 0.1 to 20 [mu] m. (A) The total amount of ammonium ions and alkali metal ions present in a water suspension having a calcium carbonate concentration of 3% by weight is 500 ppm or less. (A) The electrical conductivity of a water suspension having a calcium carbonate concentration of 3% by weight is 1000 μS / cm or less.

The characteristics of the calcium carbonate prepared by the method of the present invention are listed below. Cubic calcium carbonate having extremely high temperature stability and long-term stability. Although the essential shape is cubic, compared to cubic calcium carbonate prepared by conventional methods, the corners and edges of the vertices have roundness and the sharp knife-like edges Very few. Although the reason for this is not clear, although the primary particles of the calcium carbonate of the present invention are essentially composed of a calcite-type crystal type,
It is speculated that this may be because part of the surface of the primary particles and part of the inside of the primary particles are composed of amorphous calcium carbonate and / or calcium carbonate of vaterite type crystals. The following physical properties (a) to (h) are satisfied. (A) 0.1 ≦ DS1 ≦ 20.0 (b) DS2 = (π / 6) ^1/3 × DS1 (c) 1.15 ≦ DP3 / DS1 ≦ 1.40 (d) 0.90 ≦ DP3 / DS2 ≦ 1.15 (e) 1.0 ≦ DP2 / DP4 ≦ 2.0 (f) 1.0 ≦ DP1 / DP5 ≦ 2.5 (g) (DP2-DP4 / DP3) ≦ 0.5 (h) S ≦ 0.5 DS1: Volume averaged from the average side length (μm) of cubic calcium carbonate particles examined by scanning electron micrograph DS2: Average side length (μm) of cubic calcium carbonate particles examined by scanning electron microscope Diameter of the obtained sphere (μm) DP1: Centrifugal sedimentation type particle size distribution analyzer (Shimadzu SA-CP
In the particle size distribution measured using 3), the particle size when the cumulative weight is 10% calculated from the large particle size side (μm) DP2: Centrifugal sedimentation type particle size distribution analyzer (SA-CP manufactured by Shimadzu Corporation)
In the particle size distribution measured using 3), the particle size (μm) when the cumulative weight is 25% calculated from the large particle size side DP3: Centrifugal sedimentation type particle size distribution analyzer (Shimadzu SA-CP
In the particle size distribution measured using 3), the particle size at the time of cumulative 50% calculated from the large particle size side (μm) DP4: Centrifugal sedimentation type particle size distribution analyzer (SA-CP manufactured by Shimadzu Corporation)
In the particle size distribution measured using 3), the particle size when the cumulative total weight is 75% calculated from the large particle size side (μm) DP5: Centrifugal sedimentation type particle size distribution measurement device (Shimadzu SA-CP
In the particle size distribution measured using 3), the particle size at the time of cumulative weight of 90% calculated from the large particle size side (μm) Di: cubic side length of individual cubic calcium carbonate particles examined by scanning electron micrograph (Μm) S: Relative standard deviation

The present invention will be described in detail below. Examples of the carbonate used in the present invention include sodium, potassium and ammonium carbonates, which may be used alone or in combination of two kinds. Among them, sodium carbonate can be preferably used from the viewpoint of economy. The carbonate is dissolved in water to prepare a carbonate ion solution. The concentration of the carbonate solution varies depending on the desired particle size, set temperature, reaction buffer amount, ratio with calcium salt, reaction time, etc.
It may be 3.0 mol / l. When the above-mentioned relative standard deviation, which is an index showing the uniformity of the particle diameter of each primary particle of calcium carbonate obtained by the present invention, is 0.4 or less,
0.30 to 2.5 mol / l is preferable, and 0.50 to 2.0 mol / l is particularly preferable when the relative standard deviation is 0.3 or less. When the concentration of the carbonate is less than 0.10 mol / l, not only is it economically disadvantageous, but the calcium carbonate of the present invention having the above-mentioned characteristics cannot be obtained.

The calcium salt used in the present invention includes:
Calcium chloride, calcium nitrate, calcium nitrite,
Water-soluble calcium salts such as calcium bromide and calcium iodide can be exemplified, and these can be used alone or in combination of two or more kinds. Among them, calcium chloride can be preferably used from the viewpoint of economy. The calcium salt is dissolved in water to prepare a calcium ion solution. The concentration of the calcium salt solution varies depending on the desired particle size, set temperature, reaction buffer amount, ratio with carbonate, reaction time, etc.
It may be 10 to 3.0 mol / l. When the above-mentioned relative standard deviation, which is an index showing the uniformity of the particle size of each primary particle of calcium carbonate obtained by the present invention, is 0.4 or less, 0.30 to 2.5 mol / l is preferable, and the relative standard When the deviation is 0.3 or less, 0.50 to 2.0 mol / l is particularly preferable. When the concentration of the calcium salt is less than 0.10 mol / l, not only is it economically disadvantageous, but the calcium carbonate of the present invention having the above-mentioned characteristics cannot be obtained.

The calcium ion concentration ratio in the calcium salt solution to the carbonate ion in the carbonate solution is 0.5 to 2.
It may be 0, preferably 0.75 to 1.33, and more preferably 0.89 to 1.13. Concentration ratio is 2.0
When it is more than 0.5 and less than 0.5, carbonate ions or calcium ions which do not contribute to the reaction adversely affect the reaction, which is not preferable.

Next, a reaction buffer is added to the carbonate solution, the calcium salt solution, or both prepared by the above method. The reaction buffer used in the present invention may be any electrolyte, but one or more selected from alkali metal or ammonium nitrates, sulfates, and chlorides can be preferably used. Among them, sodium is economically preferable. , Potassium hydroxide and sulfate are particularly preferable.
The total amount of the reaction buffers added is 0.001
It may be 2.0 mol / l, but it is desirable that the concentration of carbonate and calcium salt is not exceeded. The reaction buffer is preferably added only to the carbonate solution. If the amount of the reaction buffer is less than 0.001 mol / l, unstable amorphous calcium carbonate or vaterite-type calcium carbonate is mixed in a large amount, which is not preferable, and 2.0 m
When it exceeds ol / l, a large number of calcium carbonate of calcite crystals in which individual primary particles are non-uniform are mixed, and the calcium carbonate having the characteristic feature of the present invention cannot be obtained.

Next, the carbonate solution added with the reaction buffer prepared by the above method and the calcium salt solution are mixed to carry out a carbonation reaction. The mixing method is as follows: the carbonate solution is dropped into the calcium salt solution. The calcium salt solution may be mixed, or the calcium salt solution may be added dropwise to the carbonate solution, but the latter method is preferable from the viewpoint of stability of the prepared calcium carbonate. The dropping and mixing time may be 70 seconds or more and 1200 seconds or less after the start of dropping and mixing of one salt solution to the other salt solution, and the dropping and mixing time may be completed. When the above-mentioned relative standard deviation, which is an index showing the uniformity of particle diameter, is 0.4 or less,
It is preferably 180 seconds or more and 900 seconds or less, and particularly preferably 240 seconds or more and 600 seconds or less when the relative standard deviation is 0.3 or less. When the drop mixing is performed in a short time of less than 70 seconds, a large amount of vaterite-type spherical calcium carbonate is mixed, and when the drop mixing is performed for more than 1200 seconds, the relative standard deviation having a sharp edge is 0. Cubic calcite crystals of calcium carbonate in excess of 5 have been prepared and are not preferred. The temperature in the carbonation reaction system is 5 to
The temperature may be maintained at 40 ° C, but from the viewpoint of homogenizing the primary particles, it is preferably maintained at 10 to 30 ° C.
20 ° C. is more preferable. There is no particular limitation on the temperature of each salt solution before mixing, but the temperature difference between the salt solutions is 2
It is preferably 0 ° C. or lower, more preferably 10 ° C. or lower.

Next, after 90 seconds or more have passed from the end of mixing, the mixture of the carbonate solution and the calcium salt solution was mixed, preferably within 120 to 600 seconds, more preferably 150 to 360 seconds. A water-soluble salt or a water-soluble acid which reacts with calcium to form a water-insoluble or sparingly soluble salt is added to 0.01 to the calcium carbonate present in the mixed system.
Add ~ 5% by weight. When a water-soluble salt or a water-soluble acid that reacts with calcium to produce a water-insoluble or sparingly soluble salt is added within 90 seconds after mixing the carbonate solution and the calcium salt solution, the amorphous particles are obtained in the obtained calcium carbonate. Are not preferable because they are mixed. When the amount of the water-soluble salt or water-soluble acid that reacts with calcium to produce a water-insoluble or sparingly soluble salt is less than 0.01% by weight, calcium carbonate whose particle surface is disintegrated is easily obtained. If it exceeds, the calcium carbonate itself does not have any defects, but when the obtained calcium carbonate is used for a wide variety of industrial purposes, the use may be restricted, which is not preferable. In the method of the present invention, water-soluble which forms a water-insoluble or sparingly soluble salt by reacting with calcium, and water-soluble which forms a water-insoluble or sparingly soluble salt by reacting with calcium within a time period of adding a water-soluble salt or a water-soluble acid Before adding a salt or a water-soluble acid, an electrolyte such as an alkali metal or ammonium nitrate, sulfate or chloride for the purpose of completely completing the carbonation reaction is used in an amount not more than 3 times the reaction buffer used in the present invention. It may be added in the range of, but in this case, these electrolytes are finally removed.

The water-soluble salt or water-soluble acid which reacts with calcium to produce a water-insoluble or sparingly soluble salt used in the present invention is not particularly limited, but it is a fatty acid or its salt, a resin acid or its salt, phosphoric acid, phosphoric acid. Examples thereof include esters, phosphates, α, β monoethylenically unsaturated polycarboxylic acids or copolymers obtained by copolymerizing salts thereof, and these may be used alone or in combination of two or more. Salts, ammonium salts, alkali metal salts and ammonium salts of α, β monoethylenically unsaturated polycarboxylic acid can be preferably used, and use of alkali metal salts and ammonium salts of condensed phosphoric acid such as hexametaphosphoric acid and tripolyphosphoric acid is particularly preferable. preferable.

Next, the aqueous suspension containing calcium carbonate prepared by the above method is washed with water to obtain ammonium ions in the aqueous suspension having a calcium carbonate concentration of 3% by weight.
The present invention can be achieved by adjusting the total amount of alkali metal ions present to 500 ppm or less and the electric conductivity of the aqueous suspension to 1000 μS / cm or less. In order to further improve the dispersion of calcium carbonate obtained by the present invention, ammonium ions in an aqueous suspension,
The total amount of alkali metal ions present is preferably 100 ppm or less, and the electric conductivity of the water suspension is preferably adjusted to 300 μS / cm or less, and industrial use is a field requiring particularly high dispersibility such as a capacitor film. In the above, it is more preferable to adjust to 20 ppm or less and 100 μS / cm or less, and 10 ppm or less and 50 μS / c.
Most preferably, it is adjusted to m or less. There is no particular limitation on the method of washing with water, and normally, concentration and dilution with water may be repeated using a centrifuge, a dehydrator, a rotary filter or the like. If the total amount of ammonium ions and alkali metal ions present exceeds 500 ppm, or if the electric conductivity of the aqueous suspension exceeds 1000 μS / cm, the above characteristics (c) to (g) cannot be satisfied. However, calcium carbonate having poor dispersibility is prepared, which is not preferable.

The calcium carbonate prepared by the method of the present invention as described above has substantially no secondary agglomeration, good dispersibility, uniform individual particles, and cubic shape excellent in high temperature stability and stability over time. Since it is calcium carbonate, it can be applied to advanced industrial fields such as synthetic fibers such as polyester, synthetic resin films such as polyester and polyolefin, and blocking inhibitors for synthetic resin films, not to mention industrial applications where calcium carbonate has been conventionally used. The calcium carbonate prepared by the method of the present invention is an organic acid such as a fatty acid, a resin acid, acrylic acid, methacrylic acid, or oxalic acid for further improving the dispersibility, stability, etc. of the calcium carbonate particles, or depending on the intended use. , Organic acids such as citric acid, tartaric acid,
Inorganic acids such as phosphoric acid, condensed phosphoric acid, hydrofluoric acid, polymers thereof, surface treatment agents such as alkali metal salts, ammonium salts, alkaline earth metal salts thereof, or esters thereof, coupling agents such as silane and titanium, A dispersant such as a surfactant is preferably surface-treated according to a conventional method and used, and generally an amount of 5% by weight or less based on calcium carbonate is used. The calcium carbonate prepared by the method of the present invention can be dehydrated and concentrated, then dried and pulverized to be used as a powder for various purposes. It is also useful as a suspension. For example, when calcium carbonate according to the method of the present invention is used as an anti-blocking agent for advanced polyester films, it can be used as an ethylene glycol suspension. Calcium carbonate prepared by the method of the present invention is also used in the field of other particles used in industrial applications such as polyester film, kaolin, talc, carbon black, molybdenum sulfide, gypsum, aluminum oxide, barium sulfate, fluorinated. Lithium, calcium fluoride, zeolite, calcium phosphate, silicon dioxide,
It can be used in combination with titanium dioxide or heat-resistant polymer particles.

[0022]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 A sodium carbonate solution (carbonate ion solution) having a concentration of 1.0 mol / 1 liter, a calcium chloride solution (calcium ion solution) having a concentration of 1.0 mol / 1 liter, and 0.03 mol / 1 liter of sodium hydroxide solution (reaction buffer) was prepared to 100 liters each. The sodium hydroxide solution and the sodium carbonate solution are mixed to prepare a mixed solution, and the liquid temperature of the mixed solution and the sodium chloride solution are both 1
The temperature was adjusted to 7.0 ° C. Next, 100 liters of the sodium chloride solution was added dropwise to 200 liters of a mixed solution of a sodium hydroxide solution and a sodium carbonate solution, a carbonation reaction was carried out under stirring conditions, and 270 seconds after the start of the addition, the dropwise addition was terminated. 180 seconds after the completion of the dropping, sodium hexametaphosphate was added in an amount corresponding to 0.4% by weight of the theoretical amount of calcium carbonate existing in the reaction system, and the mixture was stirred for another 5 minutes. The aqueous suspension of calcium carbonate prepared as described above was concentrated using a centrifugal dehydrator, water was added to the concentrate to dilute it, and after stirring, the diluted solution was concentrated again using the centrifugal dehydrator. The total amount of ammonium ions and alkali metal ions in the obtained 3% by weight aqueous solution of calcium carbonate was measured to be 8 ppm.
And its electric conductivity was measured to be 30 μS / c
It was m. As a result of observing the obtained calcium carbonate with an electron microscope, the shape was cubic calcium carbonate having roundness at the vertices and edge portions. As a result of observation by X-ray diffraction, it was confirmed that the crystal form of the obtained calcium carbonate was almost calcite. Table 1 shows the production conditions of this example, Table 8 shows the physical properties of the obtained calcium carbonate, and FIG. 1 shows an electron micrograph.

Examples 2-11, 15-29 Sodium carbonate solution (carbonate ion solution) with a concentration of x mol / 1 liter, calcium chloride solution (calcium ion solution) with a concentration of y mol / 1 liter, and z mol / 1 liter each of sodium hydroxide solution (reaction buffer)
00 liters were prepared. The sodium hydroxide solution and the sodium carbonate solution were mixed to prepare a mixed solution, and the liquid temperature of the mixed solution and the sodium chloride solution were both adjusted to T ° C. Next, 100 liters of the sodium chloride solution was added dropwise to 200 liters of a mixed solution of a sodium hydroxide solution and a sodium carbonate solution, a carbonation reaction was carried out under stirring conditions, and the dropping supply was finished 1 second after the start of dropping θ 1. Two seconds after the completion of dropping θ, sodium hexametaphosphate in an amount corresponding to M weight% of the theoretical amount of calcium carbonate existing in the reaction system was added, and the mixture was further stirred for 5 minutes. The aqueous suspension of calcium carbonate prepared as described above was concentrated using a centrifugal dehydrator, water was added to the concentrate to dilute it, and after stirring, the diluted solution was concentrated again using the centrifugal dehydrator. The total amount of ammonium ions and alkali metal ions in the obtained 3% by weight aqueous solution of calcium carbonate was measured to be Hppm, and the electric conductivity thereof was measured to be L μS / cm. As a result of observing the obtained calcium carbonate with an electron microscope, the shape was found to be cubic calcium carbonate having roundness at the apex and the edge. Further, as a result of observation by X-ray diffraction, it was confirmed that the crystal forms of the obtained calcium carbonate were both almost calcite. Manufacturing conditions of this example are shown in Tables 1 and 2,
3, 4, and 5 show the physical properties of the obtained calcium carbonate in Table 9,
10, 11, 12, 13, and 14 are shown. Example 2
2 and 3 are electron micrographs of the calcium carbonate obtained in Steps 1 and 3.

Examples 12 to 14 Sodium carbonate solution (carbonate ion solution) with a concentration of x mol / 1 liter, calcium chloride solution (calcium ion solution) with a concentration of y mol / 1 liter, and sulfuric acid with z mol / 1 liter. Sodium solution (reaction buffer) 10 each
0 liter was prepared. The sodium hydroxide solution and the sodium carbonate solution were mixed to prepare a mixed solution, and the liquid temperature of the mixed solution and the sodium chloride solution were both adjusted to T ° C. Next, 100 liters of the sodium chloride solution was added dropwise to 200 liters of a mixed solution of a sodium hydroxide solution and a sodium carbonate solution, a carbonation reaction was carried out under stirring conditions, and the dropping supply was finished 1 second after the start of dropping θ 1. Two seconds after the completion of dropping θ, sodium hexametaphosphate in an amount corresponding to M weight% of the theoretical amount of calcium carbonate existing in the reaction system was added, and the mixture was further stirred for 5 minutes. The aqueous suspension of calcium carbonate prepared as described above was concentrated using a centrifugal dehydrator, water was added to the concentrate to dilute it, and after stirring, the diluted solution was concentrated again using the centrifugal dehydrator. The total amount of ammonium ions and alkali metal ions in the obtained 3% by weight aqueous solution of calcium carbonate was measured to be Hppm, and the electric conductivity thereof was measured to be L μS / cm. As a result of observing the obtained calcium carbonate with an electron microscope, the shape was found to be cubic calcium carbonate having roundness at the apex and the edge. Further, as a result of observation by X-ray diffraction, it was confirmed that the crystal forms of the obtained calcium carbonate were both almost calcite. The manufacturing conditions of this example are shown in Tables 2 and 3.
Table 11 shows the physical properties of the obtained calcium carbonate.

Comparative Examples 1 to 13 Calcium carbonate was prepared in the same manner as in Example 2 except that the production conditions were changed to those shown in Tables 6, 7, and 8. The physical properties of the obtained calcium carbonate are shown in Tables 15, 16, and 1.
7 shows. The obtained calcium carbonate was examined with an electron microscope and X
The results of observation by line diffraction are listed below. Further, electron microscope photographs of calcium carbonate obtained in Comparative Examples 1 and 9 are shown in FIGS. Comparative Example 1: Calcite-shaped cubic calcium carbonate having knife-edge-shaped sharp vertices and sides, and primary particles of various sizes are present. Comparative Example 2: A large number of calcite-shaped cubic calcium carbonate aggregates, and primary particles of various sizes are present. Comparative Example 3: A large number of calcite-shaped cubic calcium carbonate aggregates, and primary particles of various sizes are present. Comparative Example 4: A large number of spherical calcium carbonate of vaterite crystals are mixed. Comparative Example 5: Many calcite-shaped cubic calcium carbonates are aggregated, and primary particles of various sizes are present. Comparative Example 6: A large number of calcite-shaped cubic calcium carbonate aggregates, and primary particles of various sizes are present. Comparative Example 7: A large number of spherical calcium carbonate of vaterite crystals are mixed. Comparative Example 8: Calcite-shaped cubic calcium carbonate having knife-edge-shaped sharp vertices and sides is aggregated. Comparative Example 9: Calcite-type calcium carbonate in which the particle surface is disintegrated and a large number of knife-edge-shaped sharp vertices and sides are present on the particle surface and a large number of holes are present. Comparative Example 10: Indefinite calcium carbonate mixed with vaterite crystal calcium carbonate. Comparative Example 11: Fine calcium carbonate aggregates of calcite crystals of less than 0.1 μm. Comparative Example 12: Petal-like aggregate of calcium carbonate in vaterite and aragonite crystals. Comparative Example 13: Calcite-type cubic calcium carbonate aggregates.

Application Example A Calcium carbonate powder prepared by treating the calcium carbonate prepared in the above Examples 13, 19 and 22 and Comparative Examples 9 and 13 with 0.5% by weight of sodium stearate, and as an anti-blocking agent for comparison. Using commercially available A-type zeolite, kaolin clay, and synthetic silica, a polypropylene composition was prepared in the following manner to obtain a biaxially oriented polypropylene film, and its quality was evaluated. The results are shown in Table 18. Production of film 100 parts by weight of polypropylene resin having a melt flow rate of 1.9 g / 10 minutes, 0.10 parts by weight of 2,6-di-t-butyl-p-cresol as an antioxidant, 0.02 parts by weight of Irganox 1010, 0.05 parts by weight of calcium stearate as a hydrochloric acid catching agent and the anti-blocking agent according to the present invention were added, mixed with a super mixer and pelletized with an extruder. This pellet is made into a sheet film using an extruder and stretched 5 times in the longitudinal direction and 10 times in the transverse direction to finally obtain a thickness of 30 μm.
To obtain a stretched film. One surface of the stretched film was subjected to corona discharge treatment. The transparency, blocking property and foaming property of these biaxially stretched films were measured. The film transparency was measured according to ASTM-D-1003 by stacking four films. The blocking property of the film is that after stacking so that the contact area of the ^two films is 10 cm ² and placing it between the two glass plates, and applying a load of 50 g / cm ² and leaving it in an atmosphere of 40 ° C. for 7 days. Using a Shopper type tester, peeling was performed at a pulling speed of 500 mm / min, and the maximum load was read and evaluated. The foamability of the film was measured by adding 170 parts of the mixed composition of 1 part of sample to 100 parts by weight of resin [polyethylene (SMA-110)].
The mixture is kneaded with a roll at 5 ° C for 5 minutes, and then press-molded at 170 ° C for 4 minutes to a thickness of 1 mm to obtain a sample plate. The sample plate was sandwiched between glass plates like a sandwich layer, and left in a heating oven at 230 ° C. for 1 hour to observe the foaming state. As for the evaluation of foaming property, one that does not foam at all as in the case of the blank and one that remarkably foamed were evaluated as 4 and evaluated in four stages.

Application Example B Aqueous suspensions of calcium carbonate prepared according to Examples 1, 2, 3 and Comparative Examples 6, 9, 10, 11 above the surface corresponding to 1.5% by weight with respect to calcium carbonate. Treatment agent (the weight ratio of each of acrylic acid and butyl methacrylate is 70:
30 copolymers in which 20% of all carboxyl groups in the acrylic acid moiety are ammonium salts) are surface-treated under stirring conditions, ethylene glycol is then added, and further flushing is performed using a rotary evaporator. Then, water was removed to prepare an ethylene glycol slurry of calcium carbonate. The solid content concentration of calcium carbonate in the ethylene glycol is 20.0% by weight.
Met. These ethylene glycol slurries are added before the polyesterification reaction to carry out the polyesterification reaction,
A polyethylene terephthalate having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.62 dl / g containing 0.3% by weight of a blocking agent was prepared. The polyethylene terephthalate was dried at 160 ° C., melt-extruded at 290 ° C., then rapidly cooled and solidified on a casting drum kept at 40 ° C. to obtain an unstretched film. Then, after preheating the unstretched film to 70 ° C. with a heating roller,
It was stretched in the machine direction while being heated by an infrared heater. Subsequently, it was stretched in the transverse direction at a temperature of 90 ° C. and then heat-treated at 200 ° C. to obtain a biaxially oriented film having a thickness of 10 μm.

The quality of the film thus obtained was evaluated by the method described below, and the results are shown in Tables 19 and 20.
Shown in. Wearability evaluation-I A 1/2 width film surface was brought into contact with a stainless steel fixed pin (surface roughness 0.58) with a diameter of 5 mm at an angle of 150 °, and reciprocated about 15 cm at a speed of 2 m per minute and rubbed. Let (At this time, the entrance side tension T _{1 is set} to 70 g).
This operation is repeated and the degree of scratches generated on the friction surface is visually determined after the measurement is repeated 50 times. At this time, there are 4 levels of ∘: scratches are not generated, ∘: Scratches are slightly generated, ∘: Many scratches are generated on the entire surface, ×: Scratches are intermediate between the former two. judge. Evaluation of Friction Property-II The abrasion property of the running surface of the film is evaluated using a 5-stage mini super calender. The calender is a five-stage calender consisting of a nylon roll and a steel roll. The processing temperature is 80 ° C., the linear pressure applied to the film is 200 kg / cm, and the film speed is 70 m / min. The running film is evaluated for the sharpness of the film by the dirt attached to the top roller of the calender when the running film is run for 3000 m. <Four-level judgment> ◎: Nylon roll is not soiled at all ○: Nylon roll is barely soiled ×: Nylon roll is soiled × ×: Nylon roll is very soiled The number of large protrusions on the film surface Aluminum was thinly deposited on the film surface. After that, the number of coarse projections of four or more rings (number per 1 mm ^{2 of} measurement area) was counted using a two-beam interference microscope, and the number of coarse projections was used to express the following ranking. 1st grade: 16 or more 2nd grade: 10
15 pieces 3rd grade: 6 to 9 pieces 4th grade: 2 to 5
5th grade: 0 to 1

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

[Table 6]

[0036]

[Table 7]

[0037]

[Table 8]

[0038]

[Table 9]

[0039]

[Table 10]

[0040]

[Table 11]

[0041]

[Table 12]

[0042]

[Table 13]

[0043]

[Table 14]

[0044]

[Table 15]

[0045]

[Table 16]

[0046]

[Table 17]

[0047]

[Table 18]

[0048]

[Table 19]

[0049]

[Table 20]

[0050]

As described above, the calcium carbonate produced by the method of the present invention has good dispersibility, does not contain unnecessary fine particles and coarse primary particles, and has an extremely uniform particle size. Since the particle size distribution is sharp, the range of possible particle sizes is wide, the particle size can be arbitrarily set, and the stability at high temperature and the long-term stability are extremely good, it can be used for various advanced industrial applications. For example, when it is used for a synthetic resin film, it exhibits good blocking resistance, and above all, a film having no foaming property and good transparency can be prepared as a blocking agent for a polyolefin film. In the case of a polyester film, a good film having excellent slipperiness and abrasion resistance and having few coarse projections can be obtained.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing the particle structure of calcium carbonate obtained in Example 1.

FIG. 2 is an electron micrograph showing the particle structure of calcium carbonate obtained in Example 2.

FIG. 3 is an electron micrograph showing the particle structure of calcium carbonate obtained in Example 3.

FIG. 4 is an electron micrograph showing the particle structure of calcium carbonate obtained in Comparative Example 1.

5 is an electron micrograph showing the particle structure of calcium carbonate obtained in Comparative Example 9. FIG.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI // C08J 5/18 C08J 5/18 (56) References JP-A-1-108117 (JP, A) JP-A-59-203728 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C01F 11/18

Claims (17)

(57) [Claims] 1. A carbonate ion concentration of 0.1 to 2.0 mol / l prepared by adding a reaction buffer to either or both of a carbonate solution and a calcium salt solution.
A 1 to 3.0 mol / l carbonate solution and a calcium salt solution having a calcium ion concentration of 0.1 to 3.0 mol / l and a calcium ion concentration ratio to carbonate ion of 0.5 to 2.0 are mixed. When producing calcium carbonate, the carbonate solution was added dropwise to the calcium salt solution or the calcium salt solution within the carbonate solution within 70 to 1200 seconds, and the temperature in the mixing system was maintained at 5 to 40 ° C. Then, the carbonation reaction is carried out, and after the completion of mixing the carbonate solution and the calcium salt solution, 9
After 0 seconds or more, a water-soluble salt or water-soluble acid that reacts with calcium in the mixed solution to form a water-insoluble or sparingly soluble salt is added to the mixed solution in an amount of 0.01
Particles having good dispersibility and stable with time, prepared by adding 5% by weight to 5% by weight, washing the resulting aqueous suspension of calcium carbonate with water, and satisfying the following requirements (a) and (a): A method for producing cubic calcium carbonate having a diameter of 0.1 to 20 μm. (A) The total amount of ammonium ions and alkali metal ions present in a water suspension having a calcium carbonate concentration of 3% by weight is 500 ppm or less. (A) The electrical conductivity of a water suspension having a calcium carbonate concentration of 3% by weight is 1000 μS / cm or less. 2. The carbonate ion concentration in the carbonate solution is 0.3.
The method for producing calcium carbonate according to claim 1, wherein the calcium salt solution has a calcium ion concentration of 0.3 to 2.5 mol / l. 3. The carbonate ion concentration in the carbonate solution is 0.5.
The method for producing calcium carbonate according to claim 1, wherein the calcium salt solution has a calcium ion concentration of 0.5 to 2.0 mol / l. 4. The ratio of calcium ions in the calcium salt solution to carbonate ions in the carbonate solution is 0.75.
It is 1.33, The manufacturing method of the calcium carbonate of Claim 1. 5. The ratio of calcium ions in the calcium salt solution to carbonate ions in the carbonate solution is 0.89 to.
It is 1.13, The manufacturing method of the calcium carbonate of Claim 1. 6. The method for producing calcium carbonate according to claim 1, wherein the dropping and mixing time of the carbonate solution and the calcium salt solution is 180 to 900 seconds. 7. The method for producing calcium carbonate according to claim 1, wherein the dropping and mixing time of the carbonate solution and the calcium salt solution is 240 to 600 seconds. 8. A water-soluble salt or a water-soluble acid which reacts with calcium to form a water-insoluble or sparingly soluble salt is added to the mixed solution within 120 to 600 seconds after the completion of the mixing of the carbonate solution and the calcium salt solution. The method for producing calcium carbonate according to claim 1. 9. A water-soluble salt or a water-soluble acid which reacts with calcium to form a water-insoluble or sparingly soluble salt is added to the mixed solution within 150 to 360 seconds after the completion of mixing the carbonate solution and the calcium salt solution. The method for producing calcium carbonate according to claim 1. 10. The method for producing calcium carbonate according to claim 1, wherein the carbonation reaction is carried out while maintaining the temperature in the mixing system at 10 to 30 ° C. 11. The method for producing calcium carbonate according to claim 1, wherein the carbonation reaction is carried out while maintaining the temperature in the mixing system at 15 to 20 ° C. 12. The total amount of ammonium ions, sodium ions, and potassium ions present in an aqueous suspension having a calcium carbonate concentration of 3% by weight is 100 ppm or less, and the electric conductivity is 300 μS / cm or less.
A method for producing the described calcium carbonate. 13. The total amount of ammonium ions, sodium ions, and potassium ions present in an aqueous suspension having a calcium carbonate concentration of 3% by weight is 20 ppm or less,
The method for producing calcium carbonate according to claim 1, which has an electric conductivity of 100 μS / cm or less. 14. The total amount of ammonium ions, sodium ions, and potassium ions present in a water suspension having a calcium carbonate concentration of 3% by weight is 10 ppm or less,
The method for producing calcium carbonate according to claim 1, which has an electric conductivity of 50 μS / cm or less. 15. The method for producing calcium carbonate according to claim 1, wherein the reaction buffer is one or more selected from the group consisting of alkali metal or ammonium nitrates, sulfates and chlorides. 16. The water-soluble salt or water-soluble acid which reacts with calcium to form a water-insoluble or sparingly soluble salt is one or more selected from the group consisting of phosphoric acid, phosphoric acid ester and phosphate. Method for producing calcium carbonate. 17. The water-soluble salt or water-soluble acid which reacts with calcium to produce a water-insoluble or sparingly soluble salt is one or more selected from the group consisting of alkali metal salts and ammonium salts of condensed phosphoric acid. A method for producing the described calcium carbonate.