WO2001042139A1 - Method for producing calcium carbonate in cubic form - Google Patents

Abstract

A method for producing calcium carbonate in a cubic form, which comprises providing a carbonate solution and a calcium solution, at least one of which contains a buffering agent dissolved therein, adding dropwise the carbonate solution into the calcium solution or the calcium solution into the carbonate solution, with mixing, to effect a calcium carbonate forming reaction, allowing to stand or agitating the resultant calcium carbonate suspension or a diluted solution thereof for a period of one hour or more, optionally with worming or the like, to thereby remove an ammonium, an alkali metal and a halide ion, and adding a water-soluble salt or acid capable of reacting with calcium and forming a salt being not soluble or hard to soluble in water in a step after calcium carbonate formation. The method enables the production of a calcium carbonate in a cubic form which is almost free from secondary agglomeration, is excellent in the dispersibility of respective particles, uniformity, the stability at a high temperature and the stability after the elapse of a long period of time, and further has a reduced content of impurities.

Description

 Description Method for producing cubic calcium carbonate

Technical field

 The present invention relates to a method for producing cubic calcium carbonate having almost no secondary agglomeration, excellent dispersibility, uniformity, high-temperature stability, and long-term stability of individual particles, and reduced impurities contained therein. The particle shape is cubic, the particle size can be arbitrarily selected over a wide range, the individual particle sizes are uniform, the dispersibility is good, the chemical stability is high, and the ammonium ions are alkali metal ions. · Related to a method for producing calcium carbonate having a low content of halide ions. Background art

 Calcium carbonate has many advantages, such as the abundant production of limestone as a raw material in Japan, and it is inexpensive, has high whiteness, is harmless, and can be obtained in various particle sizes. It is used in a variety of fields as additives for paints, paints, extenders for inks, pigments for paper rubbing, pigments for paper coating, pharmaceuticals, cosmetics, foods, agriculture, etc.

In general, calcium carbonate is produced by mechanically pulverizing limestone, classifying the pulverized material to adjust it to various grades, and reacting with quick lime obtained by calcining limestone at a high temperature and water to react with lime milk. The lime milk is made to pass through the carbon dioxide gas generated during limestone firing to synthesize calcium carbonate.The lime soda process reacts lime milk with sodium carbonate.The lime soda is added to calcium chloride. Precipitated carbonated calcium carbonate (synthetic carbonic acid calcium) prepared by a chemical method such as a soda process (Pum) is roughly divided into two types.

 For heavy calcium carbonate, limestone, which is a raw material, contains impurities composed of various elements other than calcium carbonate for the reason of its manufacturing method, so a highly pure carbonated calcium that dislikes such impurities is desired. Cannot be used for advanced industrial applications. Calcium carbonate, which has a broad particle size distribution and a fineness of a certain level or more, cannot be produced by current pulverization and classification techniques, and cannot be used for advanced industrial applications.

Precipitated calcium carbonate is generally produced using a carbon dioxide compounding process from an economic point of view. Synthetic calcium carbonate produced using the carbon dioxide compounding process has relatively uniform primary particle shapes, but usually the primary particles aggregate or aggregate to form secondary particles (aggregate particles of primary particles). It has properties that make it easy to do. Therefore, it is impossible to produce precipitated calcium carbonate completely free of secondary particles without performing post-processing such as wet pulverization by conventional techniques, and it cannot be used particularly in advanced industrial applications. The da process is a method in which a soluble calcium salt such as calcium chloride is reacted with a soluble carbonate such as sodium carbonate. For example, as disclosed in Japanese Patent Application Laid-Open No. 3-501116, Spherical carbonic acid of type crystal Calcium carbonate mixed with calcium is easily obtained. This vaterite-type calcium carbonate is unstable, and is transformed into calcium calcite carbonate or aragonite-type calcium carbonate by physical treatment such as heating or grinding, and is easy to stand in water at room temperature for a long time. However, there is a drawback in that it transfers to calcium carbonate. Furthermore, the cubic calcium carbonate obtained by the conventional Houda process not only has a large number of secondary particles due to the aggregation of the primary particles, but also the individual primary particles are not uniform in size, which further increases the reaction efficiency. Incomplete removal of sodium chloride, a by-product of Cannot be used for industrial purposes.

 However, as a result of various researches and improvements made to calcium carbonate, not only the above-mentioned applications, but also advanced industrial uses such as lighting covers, light diffusing plates for transmissive displays, and light diffusing materials for lighting signs etc. Used to Describing the light diffusing material, it is necessary that the lighting cover and the light diffusing plate used for the lighting equipment and the transmission type display have both high transparency and light diffusing property with respect to the light rays emitted from the light source.

 For the purpose of providing these properties, it has been conventionally proposed to mix inorganic particles as a light diffusing material in a resin base material. For example, Japanese Patent Publication No. 3-21888 discloses an acrylic resin. In addition, there has been proposed a method of blending inorganic particles such as barium sulfate, calcium carbonate, silicon dioxide, talc, titanium dioxide, and aluminum hydroxide. In each of these cases, light diffusing property is imparted to a lighting cover or the like by utilizing the difference in refractive index between the resin base material and the inorganic particles, and at the same time, the light transmitting property is designed by designing the average particle diameter and the filling amount of the inorganic particles. It is intended to control

 However, light diffusivity and light transmissivity are contradictory physical properties, and no inorganic particles that have been used conventionally can satisfy both physical properties. That is, some of the above-mentioned inorganic particles have an adverse effect on the light diffusion of the lighting cover due to insufficient dispersibility and uniformity of the shape of the individual particles. Due to the insufficient sharpness of the particle size distribution, it is necessary to incorporate more inorganic particles than necessary to satisfy the light diffusivity, which adversely affects the light transmittance of the illumination cover.

 Therefore, inorganic particles having a uniform particle shape, good dispersibility, and a sharp particle size distribution are required.In addition, inorganic particles capable of freely selecting the average particle size while maintaining the particle size distribution and particle shape are desired. ing.

In response to the above request, Japanese Patent Application Laid-Open No. 7-1966316 discloses that The formation of calcium carbonate in a sodab mouth process with a strictly defined reaction method results in almost no secondary agglomeration, excellent dispersibility and uniformity of individual particles, high-temperature stability, and stability over time. A method for producing cubic calcium carbonate in which an arbitrary average particle size can be selected within a range has been proposed. With such a technique, when calcium carbonate is used as a light diffusing material, it has become possible to obtain an optimum light transmissivity by selecting a high light diffusing property and a particle size and a filling amount.

 However, when calcium carbonate particles obtained in the above-mentioned Japanese Patent Application Laid-Open No. 7-1963616 are mixed with acryl resin or polycarbonate resin to form a lighting cover, the reflected light will have the color tone of ordinary calcium carbonate. It was found that the transmitted light was yellowish or reddish. As disclosed in Japanese Patent Application Laid-Open No. 9-71685, use of such a light-diffusing material as an illumination cover has been proposed. Taste · There is great expectation for a light diffusion material for lighting covers that has no reddish taste.

 Since the method for producing calcium carbonate proposed in the above-mentioned Japanese Patent Application Laid-Open No. 7-1966316 is a soda process, ammonium ion is contained in a carbonate solution, a calcium salt solution and a reaction buffer as raw materials. Contains metal ions, halide ions, and halide ions. These ions are present as impurities inside or on the surface of the carbonated calcium particles obtained by the reaction, which change the refractive index of a light beam of a certain wavelength, thereby causing yellow light to pass through the illumination cover and the like. It is considered to have a taste or reddish taste, and its removal is desired.

 Calcium carbonate has also been used in advanced industrial applications such as anti-blocking agents for films and fibers through various studies and improvements.

As an example, film applications are described as follows: for capacitors, for magnetic recording media such as audio tape and video tape, for photography, and packaging. And polyester films used for HP and the like.

 The purpose of using calcium carbonate in these applications is to form irregularities on the film surface by adding calcium carbonate to polyester, as shown in, for example, Japanese Patent Application Laid-Open No. 9-111101, This is to give the film or processed product slipperiness も し く は abrasion resistance.

 In terms of the need for slipperiness and abrasion resistance, taking a film for a capacitor as an example, when manufacturing a capacitor using a polyester film as an insulator, in general, a method of superposing and winding an insulating film and a metal thin film, There is a method in which a metal is vapor-deposited on the surface of an insulating film and the film is wound. In each case, the film is wound up in the form of a film roll. No moderate slippage when winding the roll! Not only is it difficult to form a film roll, but also when the film is taken out of the roll, the films adhere to each other, making it impossible to take out the film smoothly and causing problems such as breakage of the film. Therefore, it is necessary to form moderate irregularities on the film surface, and many methods for incorporating fine particles into polyester have been proposed in response to this requirement.

 In general, for particles that form irregularities on the film surface, the larger the particles, the larger the convexities and the improved slipperiness. Must be increased. However, in applications where electrical characteristics are required, such as capacitors, if the projections on the film surface are too large, insulation defects may occur, which is not preferable. Voltage characteristics and insulation resistance characteristics deteriorate, which is not preferable.

Therefore, the irregularities on the film surface must be within a specific range and must be minimized, and the particles that form the irregularities must have a high degree of dispersibility, uniformity, Optional sharpness of particle size distribution and particle size High physical properties such as stability at high temperature against heat applied during polyester resin synthesis and long-term stability are considered indispensable.

 In recent years, the demand for smaller, lighter, and larger capacity electric and electronic circuits has never stopped, and it is increasingly desirable to reduce the thickness of capacitor films.Particularly, capacitor films with a film thickness of 2.5 ιη or less are used. It came to be. When the film thickness of the condenser film becomes less than 2.5 m, the particles added for the purpose of imparting smoothness to the film are the above-mentioned individual particles with high dispersibility, uniformity of the particles and sharpness of the particle size distribution. In addition, physical properties such as arbitrary setting of particle size, high-temperature stability against heat applied during polyester resin synthesis, and long-term stability over time are required. Although the reason is not clear, it is known that ammonium ions, alkali metal ions, etc., decrease the electrical characteristics and charging ability of the final product capacitor. Ammonium ions, alkali metal ions, and chloride ions contained as impurities have become problematic.

 As the particles for imparting smoothness, for example, the particles described in the above-mentioned Japanese Patent Application Laid-Open No. 7-196316 are sufficient even if they are added to a film having a thickness of 2.5 m or less. However, since it is a production method of obtaining particles by the soda process, removal of ammonium ions, alkali metal ions, chloride ions, etc., which are by-produced during particle generation, cannot be said to be complete. The ion has the disadvantage that the insulating property and the charging ability are reduced.

As described above, each particle has a high degree of dispersibility, and excellent properties such as uniformity of particles, sharpness of particle size distribution and arbitrary setting of particle size, high-temperature stability, and long-term stability over time. In addition, ammonium ions, alkali metal ions, halo, etc., which hinder the final products such as lighting covers, light diffusion plates for transmissive displays, lighting signboards, film for condensers, etc. There is an aspiring need for particles that have had genoide ions removed.

 In view of such circumstances, the present invention is useful for advanced industrial applications, has good dispersibility, does not contain unnecessary fine or coarse particles, has a very uniform particle size, and has a sharp particle size distribution. Calcium carbonate with a wide range of particle sizes that can be obtained, and with a particle size that can be set arbitrarily, has extremely good high-temperature stability and long-term stability over time, and has a low content of ammonium ions, alkali metal ions, and halide ions. It is provided simply and inexpensively. Disclosure of the invention

 The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, after including a specific amount of a reaction buffer and performing a carbonation reaction under specific conditions, washing, diluting and leaving Removal of calcium ions, alkali metal ions, and halide ions in calcium carbonate obtained by standing, etc. to improve dispersibility and particle uniformity, sharp particle size distribution, and possible particle size range The particle size is wide and the particle size can be set arbitrarily. It has excellent high temperature stability and long-term stability, low content of ammonium ion, alkali metal ion and halide ion, extremely good physical properties, and It has been found that cubic carbonated calcium particles composed of a substantially calcite-type crystal form having good handling properties can be obtained inexpensively and easily. Invention has been completed.

 That is, the present invention includes a method for producing cubic calcium carbonate, comprising the following steps.

The carbonate ion concentration and the calcium ion concentration are each 0.1 to 3.0 mol / s, and the concentration ratio of calcium ions to carbonate ions is 0.5 to 2.0. A reaction buffer solution with a reaction buffer concentration of 0.001 to 2. Under stirring, the carbonate solution is placed in the calcium salt solution, or the calcium salt solution is placed in the carbonate solution, while maintaining the temperature in the reaction system at 5 to 40 ° C within a period of 70 to 1200 seconds. The mixture is dropped and mixed to form calcium carbonate,

 The obtained calcium carbonate suspension is subjected to at least one removal method selected from the following (a) to (: f) to remove at least one of ammonium ion, alkali metal ion, and halide ion. Remove the seeds,

 A water-soluble salt or a water-soluble acid which reacts with calcium to form a water-insoluble or sparingly soluble salt, 0.01 to 5% by weight based on calcium carbonate in the carbonated calcium suspension, a step after the calcium carbonate formation reaction And adjust so as to satisfy the following requirements (I) to (V).

 (a) The obtained calcium carbonate suspension or a diluent thereof is left for at least 1 hour or stirred, and then washed.

 (b) The obtained calcium carbonate suspension or its diluted solution is left or stirred for 1 hour or more, then adjusted to 40 ° C. or more, left for 1 hour or more, and washed.

 (c) Leave the resulting calcium carbonate suspension or diluent for at least 1 hour, wash after leaving or stirring, and then adjust to 40 ° C or more and leave for at least 1 hour or stirring, and then wash. .

 (d) After washing the obtained calcium carbonate suspension, any one of the above methods (a) to (c) is used.

 (e) In each of the above methods (a) to (d), a water-soluble calcium salt solution is added when leaving or stirring for 1 hour or more.

 (f) In each of the above methods (a) to (d), the pH of the calcium carbonate suspension or its diluent is lowered by 1 or more when left or stirred for 1 hour or more.

(I) When the calcium carbonate concentration is 3% by weight, The sum of ammonium ion and alkali metal ion is 300ppm or less

(II) When the calcium carbonate concentration is 3% by weight, the halide ion in the aqueous suspension is 100 ppm or less.

 (I I I) The electric conductivity of the aqueous suspension is not more than 500 S / cm when the concentration of carbonic acid is 3 wt%. -

(IV) The sum of the ammonium ions and metal ions contained in the cubic calcium carbonate obtained by drying is 10, OOOppm or less.

 (V) Cubic calcium carbonate obtained by drying contains less than 1, OOOppm of halide ions.

 In a preferred embodiment, the total amount of ammonium ions and alkali metal ions contained in the cubic calcium carbonate obtained by drying is 5, OOOppm or less, and halide ion is 500 ppm or less.

 In a more preferred embodiment, the total of the ammonium ion and the aluminum metal ion contained in the cubic calcium carbonate obtained by drying is 2,000 ppm or less, and the halide ion is 200 ρππι or less. BRIEF DESCRIPTION OF THE FIGURES

 Figure 1 is a schematic diagram showing the equipment used to evaluate the wear characteristics of the film. BEST MODE FOR CARRYING OUT THE INVENTION

Examples of the carbonate used in the present invention include sodium, potassium, ammonium and the like. These can be used alone or in combination of two or more, but it is preferable to use sodium carbonate alone from the viewpoint of economy. Carbonate solution is prepared by dissolving the above carbonate in water As long as it is available as a carbonate solution and it is economically advantageous, the present invention may be used even if the carbonate solution is used by adjusting its concentration by operations such as concentration and dilution. The concentration of the carbonate solution varies depending on the desired particle diameter / set temperature, reaction buffer amount, ratio with calcium salt, reaction time, etc., but usually 0.1 to 3.0 m01 ZL is appropriate.

 When the below-described relative standard deviation S, which is an index indicating the uniformity of the individual particle diameters of the primary particles of calcium carbonate obtained by the present invention, is set to 0.4 or less, 0.3 to 2.5 mol ZL is obtained. When the relative standard deviation S is set to 0.3 or less, 0.5 to 2. Omol / L is preferable.

 When the concentration of the carbonate solution is less than 0.1 mo1 / L, not only is it economically disadvantageous, but also the carbonated calcium carbonate of the present invention having the following characteristics cannot be obtained, which is preferable. Absent. If the concentration of the carbonate solution exceeds 3.Omo 1 / L, calcium carbonate having the following characteristics cannot be obtained, which is not preferable.

 Examples of the calcium salt used in the present invention include water-soluble calcium salts such as calcium chloride, calcium nitrate, calcium nitrite, calcium bromide and calcium iodide. These can be used alone or in combination of two or more, but calcium chloride is preferably used alone from the viewpoint of economy.

The calcium ion solution is prepared by dissolving the above calcium salt in water, but it is available as a calcium salt solution, and if it is economically advantageous, adjust the concentration by concentrating and diluting the calcium salt solution. The present invention can be used without any problem. The concentration of the calcium salt solution varies depending on the particle size to be obtained, the set temperature, the amount of the reaction buffer, the ratio to the carbonate, the reaction time, and the like, but usually 0.1 to 3.0 mo 1 ZL is appropriate. It is an index representing the uniformity of the particle size of each primary particle of the calcium carbonate obtained by the present invention. When the relative standard deviation S described below is set to 0.4 or less, 0.3 to 2.5mo 1 ZL is preferable, and when the relative standard deviation S is set to 0.3 or less, 0.5 to 2.0 mo 1 ZL is preferred.

 When the concentration of the calcium salt solution is less than 0.1 mol 1 ZL, it is not only economically disadvantageous but also unfavorable because the carbonated calcium carbonate of the present invention having the following characteristics cannot be obtained. On the other hand, when the concentration of the calcium salt solution exceeds 3.times.mo1 / L, calcium carbonate having the following characteristics is not obtained, which is not preferable.

 The concentration ratio of the calcium ion in the calcium salt solution to the carbonate in the carbonate solution is 0.5 to 2.0, preferably 0.75 to 1.33, and more preferably 0.8. 9 to 1.13. If the concentration ratio exceeds 2.0 or is less than 0.5, carbonate ions or calcium ions that do not contribute to the reaction are not preferable because they adversely affect the reaction.

 The reaction buffer solution used in the present invention is mixed with a carbonate solution or a calcium salt solution or both, but from the viewpoint of reducing the complexity of the concentration adjustment and increasing the accuracy of the concentration adjustment in the reaction, a carbonic acid solution is used. It is preferable to mix only the salt solution or only the calcium salt solution.

 The reaction buffer may be an electrolyte, and examples thereof include alkali metal or ammonium hydroxides, nitrates, sulfates, and chlorides. These may be used alone or in combination of two or more. From the viewpoint of economy, sodium, potassium hydroxide and sulfate are preferred. In addition, since most of the above-mentioned electrolytes react with calcium ions to generate calcium salts, in the present invention, it is preferable to mix only the carbonate solution.

The amount of the reaction buffer is such that the solution concentration after the addition is in the range of 0.001 to 2.Omo1 / L, preferably 0.05 to 1.5 mol / L, and 1. Omo 1 ZL is more preferred. Also, the carbonate concentration in the carbonate solution It is desirable not to exceed the calcium salt concentration in the calcium salt solution.

 When the amount of the reaction buffer is less than 0.001 m0.1 / L, unstable amorphous calcium carbonate or paterite-type calcium carbonate is present in a large amount, which is the object of the present invention. Calcium carbonate cannot be obtained. On the other hand, when the amount of the reaction buffer exceeds 2.0 OmolZL, not only the carbonation reaction becomes difficult to occur, but also the characteristic carbonic acid calcium which is the object of the present invention cannot be obtained. Further, if the concentration of the carbonate in the carbonate solution or the concentration of potassium salt in the calcium salt solution is exceeded, the reaction is adversely affected, and the calcium carbonate, which is the object of the present invention, cannot be obtained.

 The carbonate solution and the calcium salt solution to which the reaction buffer has been added, prepared by the above method, are mixed under stirring to carry out a carbonation reaction. As for the mixing method, the carbonate solution may be added dropwise to the calcium salt solution, or the calcium salt solution may be added dropwise to the carbonate solution. The latter method is preferred.

 The temperature in the carbonation reaction system is preferably maintained at 5 to 40 ° C, more preferably 15 to 20 ° C, from the viewpoint of homogenizing the primary particles. If the temperature in the carbonation reaction system is lower than 5 ° C., the obtained particles are likely to become unstable amorphous calcium carbonate, and the calcium carbonate intended in the present invention cannot be obtained. Further, when the temperature in the carbonation reaction system exceeds 40 ° C., it becomes aragonite-type calcium carbonate, and crystal grows in a needle-like manner from the primary crystal particles of calcium carbonate in all directions, so that calcium carbonate, which is the object of the present invention, is obtained. I can't get it. The temperature of each of the carbonate solution and the calcium salt solution to which the reaction buffer is added is not particularly limited, but the temperature difference between the solutions is 2 (preferably TC or less, and 10 ° C or less. More preferred.

The dripping mixing time begins when one salt solution is dropped and mixed with the other salt solution. From 70 to 1200 seconds. When the relative standard deviation described below, which is an index representing the uniformity of each primary particle of the calcium carbonate obtained by the present invention, is set to 0.4 or less, it is preferably 180 to 900 seconds, and the relative standard deviation Is set to 0.3 or less, 240 to 600 seconds is more preferable. When the mixing time is less than 70 seconds, a large amount of vaterite-type spherical calcium carbonate is mixed, which is not preferable.When the mixing time exceeds 1200 seconds, a sharp edge is formed. It is unfavorable because it becomes calcium carbonate of cubic calcite crystal with a standard deviation exceeding 0.5.

 Next, the aqueous suspension containing calcium carbonate prepared by the above method is subjected to at least one removal method selected from the following (a) to (f) to remove the ammonium carbonate containing calcium carbonate particles. Remove at least one of the impurities selected from ions, alkali metal ions, and halide ions.

(a) The obtained calcium carbonate suspension or a diluent thereof is left for at least 1 hour or stirred, and then washed.

 (b) The obtained calcium carbonate suspension or its diluted solution is left or stirred for 1 hour or more, then adjusted to 40 ° C. or more, left for 1 hour or more, and washed.

 (c) The obtained calcium carbonate suspension or its diluent is left or stirred for 1 hour or more, washed, and then adjusted to 40 ° C or more, left for 1 hour or more, and washed. .

 (d) After washing the obtained calcium carbonate suspension, any one of the above methods (a) to (c) is used.

 (e) In each of the above methods (a) to (d), a water-soluble calcium salt solution is added when leaving or stirring for 1 hour or more.

(f) In each of the above methods (a) to (d), leave for at least 1 hour or disturb When stirring, lower the pH of the calcium carbonate suspension or its diluent by one or more.

 For (a) to (d), if the standing time is less than 1 hour, wash the carbonated calcium suspension and then dry the calcium carbonate to obtain the total of ammonium ion and alkaline metal ion in calcium carbonate. It cannot be less than lOOOOppm and halide ion cannot be less than lOOOOppm. For (b) and (c), by leaving or stirring at a temperature of 40 ° C. or more, ammonium ions, alkali metal ions, and halides can be more effectively treated than at a temperature lower than 40 ° C. Ions can be removed. The dilution of the suspension is preferably higher as the dilution ratio is higher, but is preferably 10 times or less in view of economy. Further, the stirring is not particularly limited, but is preferably about 10 to 1000 rpm.

 Regarding (a) to (f), at least one method selected from the following (a1) to (: f1) is more preferable.

 (a 1> Wash the obtained calcium carbonate suspension or its diluted solution after standing or stirring for preferably at least 8 hours, more preferably at least 16 hours. The standing or stirring time is infinite. Even if it is prolonged, ions are not removed according to the time and hardly removed in a fixed time. Therefore, in consideration of economic efficiency and the amount of removed ions, 100 hours or less is preferable.

 (b1) After leaving the obtained calcium carbonate suspension or a diluted solution thereof for 1 hour or more, stirring or stirring, the temperature is preferably adjusted to 55 to 100, more preferably 70 to 100 ° C, and preferably 8 to 100 ° C. Washing is performed after standing or stirring for at least 16 hours, more preferably at least 16 hours. The upper limit of the standing or stirring time is preferably 100 hours or less for the same reason as described above.

(c1) The suspension obtained in (a) or a diluent thereof is adjusted to preferably 55 to 100 ° C, more preferably 70 to 100 ° C, and more preferably for 8 hours or more. More preferably, it is washed after being left or stirred for 16 hours or more. Also, the upper limit of the standing or stirring time is preferably 100 hours or less for the same reason as described above.

(d1) After washing the obtained calcium carbonate suspension, any one of the above methods (a1) to (c1) is used.

 (el) In the methods (a) to (d), the mole number of calcium is preferably 0.5 times or more, more preferably 1 time, with respect to the mole number of calcium carbonate in the suspension at the time of standing or stirring. More preferably, a water-soluble calcium salt solution having twice or more moles is added.

 Examples of the water-soluble calcium salt include calcium chloride, calcium acetate, calcium nitrate, calcium nitrite, calcium bromide, calcium iodide, and the like. These may be used alone or in combination of two or more. Calcium chloride and calcium acetate are preferably used from the viewpoint of economy. In addition, when the number of moles of calcium in the water-soluble calcium salt solution is less than 0.5 times the number of moles of calcium carbonate in the suspension, the effect is higher than when no water-soluble calcium salt solution is added. If there is no big difference, and if it exceeds 20 times, it is not preferable in terms of economy.

(F 1) in the above methods (a) ~ (d), left or at the time of stirring, dissolved in equilibrium constant K (or Ka) is a solution of ^{1 X 10_ 4 ~ 1 X 10-} 7 , or water, the One or more of solids and gases exhibiting an equilibrium constant are selected and added to a calcium carbonate suspension or a diluent thereof, and the pH of the suspension or diluent is preferably 5 or more, more preferably 2 or more. More preferably, it is reduced by 2.5 or more. As the above acid, it is preferable to blow carbon dioxide gas into the liquid for economic reasons. In addition, when the decrease in pH of the calcium carbonate suspension or diluent was less than 1, the effect was not much different from the case where the pH was not reduced, and when the decrease in pH was greater than 6, it was generated. Carbonic acid It is not preferable because it dissolves calcium.

 The water-soluble salt and the water-soluble acid which react with calcium to form an insoluble or hardly soluble salt used in the present invention include: fatty acids or salts thereof, resin acids or salts thereof, phosphoric acid, phosphate esters, phosphates, and 6 Monoethylenically unsaturated polycarboxylic acids or salts thereof or (co) polymers thereof can be exemplified.

 These are used singly or in combination of two or more. Among them, alkali metal salts of phosphoric acid, ammonium salts, and alkali metal salts of monoethylenically unsaturated monocarboxylic acids and ammonium salts are preferred. It is preferable to use an alkali metal salt or an ammonium salt of condensed phosphoric acid such as hexametaphosphoric acid and tripolyphosphoric acid. The water-soluble salt or water-soluble acid should be added after the step in which the carbonate solution is added to the calcium salt solution, or the calcium salt solution is added dropwise to the carbonate solution to carry out the carbonation reaction. Although it is good, it is preferable to add it after performing the above operations (a) to (f). When it is added before or during the above-mentioned steps (a) to (: f), it is preferable to make the amount as small as possible. After adding the water-soluble salt or the water-soluble acid, if there is a possibility that by-produced salts, ions, alkalis, etc. may adhere to the surface of the calcium carbonate particles obtained in the present invention, they are removed by washing. Need to ο

The washing of the calcium carbonate suspension may be carried out according to a conventional method.For example, the operations such as concentration and dilution may be repeated using a centrifuge, a dehydrator, or the like, or may be performed using a rotary filter, a filter press, or the like. Is also good. The reason why the content of ammonium ion, alkali metal ion or halide ion in the calcium carbonate obtained by drying the suspension can be reduced by the method of the present invention is not clear, but it is estimated as follows. . Ammonia ions, alkali metals, which are free in the suspension liquid Ions and halide ions can be removed by washing, but those that are chemically or physically adsorbed on the particle surface or present inside the particle cannot be removed simply by washing . By leaving the suspension or its diluted solution for at least 1 hour or warming it by the method of the present invention, it is possible to release those ions in the solution and remove them by washing. it is conceivable that. -The above method is adjusted so as to satisfy the following conditions (I) to (V), and preferably adjusted so as to satisfy the following conditions (Ia) to (IIIa).

 (I) When the calcium carbonate concentration is 3% by weight, the sum of the ammonium ion and the metal ion in the aqueous suspension is 300 ppm or less.

(II) When the calcium carbonate concentration is 3% by weight, the halide ion in the aqueous suspension is less than 100 ppm.

 (Ii) The electrical conductivity of the water suspension is 500 uS / cm or less when the calcium carbonate concentration is 3% by weight.

 (IV) The sum of the ammonium ion and the aluminum metal ion contained in the cubic calcium carbonate obtained by drying is not more than 10, OOOppm.

 (V) Cubic calcium carbonate obtained by drying contains less than 1, OOOppm of halide ions.

 (la) When the calcium carbonate concentration is 3% by weight, the total amount of ammonium ions and alkali metal ions in the aqueous suspension is preferably 200 ppm or less, more preferably 100 ppm or less.

With regard to (I) and (la), when the total amount of ammonium ion and alkali metal ion in a water suspension having a calcium carbonate concentration of 3% by weight exceeds 300 ppm, not only is the dispersibility of the particles poor, but also The suspension The total amount of ammonium ions and metal ions contained in the dried powder obtained by drying exceeds 10, OOOppm, and it is not preferable because desired particles cannot be obtained.

 In the present invention, ammonium ion and alkali metal ion of a 3% by weight calcium carbonate suspension were measured using an ion concentration meter "Ionme-Ichiichi IM-40S" manufactured by Toa Denpa Kogyo Co., Ltd. 115B), potassium ion (K-135), and ammonium ion (AE-235).

 (Ila) When the calcium carbonate concentration is 3% by weight, the halide ion concentration in the aqueous suspension is preferably 50 ppm or less, more preferably 20 ppm or less.

 In the case of (II) and (Ila), when the calcium ion concentration in the aqueous suspension containing 3% by weight of calcium carbonate exceeds 100 ppm, the dry powder obtained by drying the suspension contains Halide ion exceeds 1, OOOppm. · Undesirable particles cannot be obtained.

 In the present invention, the measurement of the halide ion of a 3% by weight calcium carbonate suspension was carried out by using an ion concentration meter “Ionmeter IM-4OS” manufactured by Toa Denpa Kogyo Co., Ltd. using chlorine ion (CI-125B) and iodine. The ion (1-125) and fluoride ion (F-125) electrodes are used.

 (Ilia) The electric conductivity of the aqueous suspension when the concentration of calcium carbonate is 3% by weight is preferably 300 S / cm or less, more preferably 100 S / cm or less.

With regard to (ΠΙ) and (Ilia), when the electrical conductivity of the aqueous suspension having a calcium carbonate concentration of 3% by weight exceeds 500 S / cm, not only the dispersibility of the particles is poor, but also The total amount of ammonium ion and alkali metal ion contained in the dry powder obtained by drying the liquid exceeds ^), OOOppm, and It is not preferable because the gender ion exceeds 1,000 ppm and the desired particles cannot be obtained.

 In the present invention, the measurement of the electric conductivity of the 3% by weight calcium carbonate suspension is performed using an electric conductivity meter “model SC-82” manufactured by Yokogawa Electric Corporation.

 Calcium carbonate obtained by the above method has a number of characteristics as described below. -

(1) It is a cubic calcium carbonate with extremely good high-temperature stability and long-term stability.

 (2) The essential shape is cubic, but the corners and edges of the vertices are rounded, and there are very few sharp knife-shaped edges of cubic carbonic acid rubbish prepared by conventional methods. .

 (3) The resulting cubic calcium carbonate has extremely low contents of ammonium ion, alkali metal ion and halide ion.

 カ ル シ ウ ム Calcium carbonate satisfying the following physical properties (a) to (h) can be obtained as a factor indicating the dispersibility, particle size range and sharpness of the particle size distribution of the calcium carbonate particles.

 (a) 0.1 ≤DS 1 ≤2 0.0

(b) DS 2 = (6 / ττ) ^1/3 xDS 1

 (c) 1.15≤DP 3 / D S I ≤I .40

 (d) 0.9 0 ≤DP 3 / DS 2≤ 1.15

 (e) 1.0 ≤ D P 2 / D P 4 ≤ 2.0

 (f) 1.0 ≤ DP 1 / DP 5 ≤ 2.5

 (g) (DP 2 -DP 4 / DP 3) ≤ 0.5

 (h) S≤ 0.5

However, n

S = [∑ (D i -DS 1) V (n-1)] ^1/2 / DS 1 i = 1

 DS 1: Average of one side length of cubic calcium carbonate particles examined by scanning electron microscope (im)

 DS 2: Diameter (m) of a sphere obtained by volume conversion from the average (im) of one side length of cubic calcium carbonate particles examined by a scanning electron microscope

DP1: Particle size (zm) at a cumulative weight of 10% calculated from the large particle size in the particle size distribution measured using a scattering type laser analysis type particle size distribution analyzer (Microcrac-FRA manufactured by Northrop).

 DP 2: Particle size (m) at 25% cumulative weight calculated from the large particle size in the particle size distribution measured using a scattering type laser analysis type particle size distribution analyzer (Microcrac-FRA manufactured by Northrop).

 DP 3: In the particle size distribution measured using a scattering type laser analysis type particle size distribution analyzer (Microtrac-FRA manufactured by Northrop Co.), the particle size (m )

 DP 4: In the particle size distribution measured using a scattering type laser analysis type particle size distribution analyzer (Microcrac-FRA manufactured by North Pip Co., Ltd.), the particle size at a cumulative weight of 75% calculated from the large particle size ( / m)

 DP 5: Scattering laser—In the particle size distribution measured using an analytical particle size distribution analyzer (Microtrac-FRA manufactured by Northrop Co., Ltd.), the particle size (/ im )

 D i: one side length of each particle of cubic calcium carbonate examined by scanning electron microscope (/ m)

 S: Relative standard deviation

As described above, the calcium carbonate obtained by the present invention has an average The particle size can be freely selected by adjusting the above conditions over a wide range, specifically, for example, between 0.1 and 20 m. For example, when the calcium carbonate obtained in the present invention is used as a light diffusing material for a lighting cover or the like, the average particle diameter is 0.1 to 10 in terms of slipperiness, abrasion resistance, light diffusing property, light transmitting property and the like. m is preferable, and 0.1 to 5 μm is more preferable. If the average particle diameter is less than 0.1 m, the sliding property, abrasion resistance, light diffusion and light transmittance are poor, and if it exceeds 20 m, the abrasion resistance and light transmittance tend to be poor.

 The calcium carbonate obtained by the present invention has excellent dispersibility and uniformity

In the present invention, the dispersibility and uniformity of calcium carbonate are indicated by the relative standard deviation of the particle size.However, the calcium carbonate obtained by the present invention has its relative standard deviation adjusted by adjusting the above conditions. Can be freely selected

. For example, when the calcium carbonate obtained in the present invention is used as a light diffusing material for a lighting cover or the like, the relative standard deviation is preferably 0.5 or less from the viewpoint of slipperiness, abrasion resistance, light diffusing property, light transmitting property and the like. , 0.3 or less, more preferably 0.2 or less. If the relative standard deviation exceeds 0.5, the slipperiness and light transmittance tend to be poor.

By adjusting the above conditions, the calcium carbonate obtained by the present invention can reduce the total amount of ammonium ion and aluminum metal contained in the dry powder to 10, OOOppm or less. When the calcium carbonate obtained by the present invention is used especially as a light diffusing material for a lighting cover, the total amount of the contained ammonium ions and metal ions is preferably 10, from the viewpoint of yellowing and reddish coloring of transmitted light. OOOppm or less is preferred, 5, OOOppm or less is more preferred, 3, OOOppm or less is more preferred, and l. OOOppm or less is most preferred. When the total amount of ammonium ions and metal ions exceeds 10,000 OOp pm, the transmitted light of the obtained lighting cover becomes yellowish / reddish. Color is not preferred. In addition, the measurement of the ammonium ion contained in the dry powder of calcium carbonate is carried out using the phenol blue absorption spectrophotometry in accordance with JI SK 0102-4.2.1. The measurement of alkali metal ions is performed by flame atomic absorption spectroscopy in accordance with JI SK 0102—47.2 (Natrium), 48.2 (Liuium) and the like.

 By adjusting the above conditions, the calcium carbonate obtained by the present invention can reduce the total amount of halide ions contained in the dry powder to 1, OOOppm or less. For example, when the calcium carbonate obtained in the present invention is used as a light diffusing material for lighting covers, the total amount of halide ions contained is preferably 1, OOO ppm or less, more preferably 500 ppm or less, from the viewpoint of coloring transmitted light. , 300 ppm or less, most preferably 100 ppm or less. When the halide ion exceeds lOOOOppm, the transmitted light of the lighting cover is undesirably colored yellowish to reddish. The above-mentioned measurement of the halide ion contained in the calcium carbonate dry powder was carried out according to the method described in JI SK 0101 — 311 (fluorinated) lanthanum-aryzalyline complexone spectrophotometry, 32.1 (chloride). Product) Mercury thiocyanate (Π) Spectrophotometric method, 33.1 (iodine) Spectrophotometric method for iodine extraction, 34.2 (bromide) Perform ion chromatography according to each method.

 As described above, calcium carbonate prepared by the method of the present invention has almost no secondary agglomeration, good dispersibility, uniform individual particles, excellent high-temperature stability, excellent stability over time, ammonium ion, It is a cubic calcium carbonate having a low content of alkali metal ions and halide ions.

The calcium carbonate prepared by the method of the present invention may be used in order to further enhance its dispersibility and stability, or depending on the intended use, organic acids such as fatty acids, resin acids, acrylic acid, methacrylic acid, oxalic acid, citric acid, etc. Organic acids, tartaric acid, phosphoric acid, condensed phosphoric acid, inorganic acids such as hydrofluoric acid, their polymers, Surface treatment with alkali metal salt, ammonium salt, alkaline earth metal salt or their surface treatment agent such as ester, coupling agent such as silane, titanium etc., dispersant such as surfactant, etc. Preferably

. The surface treatment amount is generally used in an amount of 5% by weight or less based on calcium carbonate.

 The calcium carbonate prepared by the method of the present invention is dehydrated and concentrated, then dried and pulverized, and is used as a powder in various applications, as well as an aqueous suspension or a suspension of another solvent depending on the application. Also used as Calcium carbonate prepared by the method of the present invention may contain other particles used as a light-diffusing material, such as kaolin, talc, black carbon, molybdenum sulfide, gypsum, aluminum oxide, aluminum hydroxide, and sulfuric acid. It can be used in combination with barium, lithium fluoride, calcium fluoride, zeolite, calcium phosphate, silicon dioxide, titanium dioxide, heat-resistant polymers, and the like.

 In addition, calcium carbonate prepared by the method of the present invention includes oxazole-based and coumarin-based fluorescent whitening agents used as colorants for lighting covers and the like, bluing agents such as ultramarine blue, various stabilizers, antioxidants, Even if various additives such as a processing aid and an antistatic agent are added together, the light diffusion property and light transmittance of the calcium carbonate of the present invention are not impaired.

The calcium carbonate obtained by the present invention can be used not only for the light diffusing material described so far but also as an additive for other synthetic resins for advanced industrial applications because of its characteristics. There are no particular restrictions on the type of synthetic resin to which the particles obtained in the present invention can be applied, and the type of synthetic resin molded product. Examples of thermoplastic resins include polyolefins such as polyethylene and polypropylene, polystyrene, polyvinyl acetate, and polyacrylic acid. Ester, Polyacrylamide, Polyester, Polyacrylonitrile, Polyamide, Polyvinyl chloride, Polyester Examples include vinylidene chloride and the like, and examples of the thermosetting resin include a phenol resin, an epoxy resin, an unsaturated polyester resin, an alkyd resin, a urea resin, a melamine resin, a urethane resin, and a silicon resin.

 Among them, it is useful as an antiblocking agent for films and fibers made of polyolefin resin represented by polyethylene, and is especially used as a raw material for resins such as polyethylene terephthalate, polyethylene naphtholate, polypropylene, and polyphenylene sulfide. As an anti-booking agent for various industrial films and textiles.

• In addition, it can be used as a composition of semiconductor encapsulant and liquid encapsulant using epoxy resin and phenolic resin, and as a molding material for various printed circuit boards.

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

 The abbreviations used in Tables 1 and 3 below each refer to the following.

 Q 1: The ratio of the volume of the solution after washing and dilution to the volume of the suspension immediately after the reaction. θ 1: Leaving time [hr]

 R 1: magnification of the calcium ion amount of the calcium salt solution added to the number of moles of calcium carbonate in the suspension.

 Q 2: The ratio of the amount of the liquid after washing and dilution to the amount of the suspension immediately after the reaction when left standing while heating.

 Θ 2: Leaving time during heating [hr]

 T 1: Heating temperature [te]

 R 2: Magnification of the amount of potassium salt of the calcium salt solution to be added to the number of moles of calcium carbonate in the suspension when left standing.

N 1: Ammonium contained in calcium carbonate dry powder Total amount [ppm]

 N 2: The amount of chloride ions contained in the dry powder of calcium carbonate.

 * Equivalent: Equivalent to the suspension immediately after the reaction.

Example 1

 Sodium carbonate solution (carbonate solution) with a concentration of 0.6 mo1 / L, calcium chloride solution (calcium salt solution) with a concentration of 0.6 m01 ZL, hydroxylation of a concentration of 0.6-0.25 mo1 ZL 100 L of each sodium solution (reaction buffer) was prepared, and the sodium carbonate solution and the sodium hydroxide solution were mixed. The mixed solution and the calcium chloride solution were each adjusted to 17.0 ° C., and 100 L of the calcium chloride solution was added to 200 L of a mixed solution of sodium carbonate and sodium hydroxide under stirring (50%). rpm, the same applies hereinafter) for 27 seconds, followed by carbonation reaction.

 The obtained calcium carbonate suspension was left under stirring for 1 hour, and sodium hexame phosphate equivalent to 0.4% by weight based on the calcium carbonate in the suspension was added to the suspension. Then, the mixture was stirred for 20 minutes. Thereafter, the suspension was repeatedly concentrated and diluted using a centrifugal dehydrator, and the total of the ammonium ion concentration and the alkali metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight was 5 ppm, and the electric conductivity was 5%. Was washed to 20 SZ cm.

The calcium carbonate suspension was dried, and the amount of ammonium 'Natrium' potassium in the dry powder was determined. The total amount was 9400 ppm, and the amount of chloride ion was 900 ppm. Was. As a result of observing the obtained calcium carbonate with an electron microscope, it was found to be a cubic calcium carbonate having a layered aggregate, rounded apexes and edges, and having irregularities on the particle surface. Further, 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, and Table 2 shows the physical properties of the obtained calcium carbonate. Examples 2 and 3

 A calcium carbonate suspension was prepared under the same conditions as in Example 1 except that the standing time under stirring was changed to 11 hour. The carbonated calcium suspension was dried in the same manner as in Example 1, and the total amount of the ammonium powder and sodium hydroxide in the dry powder was N 1 pm, and the amount of chloride ion was N 2 pm. The obtained calcium carbonate was observed with an electron microscope. As a result, it was found to be a cubic calcium carbonate having a layered aggregate with rounded apexes and edges, and having irregularities or pores on the particle surface. . Table 1 shows the production conditions of this example, and Table 2 shows the physical properties of the obtained calcium carbonate. Example 4

The calcium carbonate suspension prepared under the reaction conditions of Example 1 was allowed to stand for 1 hour with stirring, then the temperature of the suspension was adjusted to 45 ° C, and the suspension was left for 1 hour with stirring. Next, sodium hexaphosphate was added to the suspension in an amount equivalent to 0.4% by weight based on the calcium carbonate in the suspension, and the mixture was stirred for 20 minutes. The suspension was repeatedly concentrated and diluted by a centrifugal dehydrator, and the total of the ammonium ion concentration and the metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight was 5 ppm, and the electric conductivity was 2%. Washed until 0 // SZ cm. The calcium carbonate suspension was dried, and the amount of ammonium, sodium and potassium in the dried powder was determined. The total amount was 780 ppm and the amount of chloride ions was 76 O ppm. As a result of observing the obtained calcium carbonate with an electron microscope, it was found to be a cubic calcium carbonate having a layered aggregate, rounded vertices and edges, and having irregularities or pores on the particle surface. Was. Further, 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, and Table 2 shows the physical properties of the obtained calcium carbonate. Examples 5 to 9

 After leaving for 1 hour under stirring, adjust the temperature of the suspension to T1, and change to leave it for 02 hours under stirring, under the same conditions as in Example 4, except for the calcium carbonate suspension. A liquid was made. The suspension of calcium carbonate was dried in the same manner as in Example 1, and the total amount of ammonium 'sodium' potassium in the dry powder was N lppm and the amount of chloride ion was N2ppm. -As a result of observing the obtained calcium carbonate with an electron microscope, it was found to be a cubic calcium carbonate having a layered aggregate, rounded apexes and edges, and having irregularities or pores on the particle surface. . Table 1 shows the production conditions of this example, and Table 2 shows the physical properties of the obtained calcium carbonate.

Example 10

After the calcium carbonate suspension prepared under the reaction conditions of Example i was left under stirring for 16 hours, the suspension was repeatedly concentrated and diluted with a centrifugal dehydrator to obtain a suspension having a calcium carbonate concentration of 3% by weight. The suspension was washed until the total of the ammonium ion concentration and the metal ion concentration of the aluminum hydroxide became 5 ppm and the electric conductivity became 20 Scm. The suspension after washing was diluted with water to a volume 4 times that of the original reaction solution, the temperature of the suspension was adjusted to 85 ° C, and the suspension was left under stirring for 16 hours. Further, sodium hexamethaphosphate was added to the suspension in an amount equivalent to 0.4% by weight based on the calcium carbonate in the suspension, and the mixture was stirred for 20 minutes. The suspension was repeatedly concentrated and diluted by a centrifugal dehydrator, and the total of the ammonium ion concentration and the metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight was 5 ppm, and the electric conductivity was 20%. Washed to S / cm. The carbonated calcium suspension was dried, and the amount of ammonium sodium-potassium in the dry powder was determined. The total amount was 350 ppm, and the chlorine amount was 8 ppm. . Observation of the obtained calcium carbonate with an electron microscope revealed that the shape consisted of a layered aggregate and was rounded at the top and edges. Cubic carbon dioxide with irregularities and pores on the particle surface

. In addition, 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, and Table 2 shows the physical properties of the obtained calcium carbonate.

Example 1 1

 The calcium carbonate suspension prepared under the reaction conditions of Example 1 was repeatedly concentrated and diluted with a centrifugal dehydrator, and the ammonium ion concentration and the metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight were repeated. The sample was washed until the total was 5 ppm and the electrical conductivity was 20 ^ SZ cm. The suspension after washing was diluted with water to an equal volume of the original reaction solution, and left for 1 hour with stirring. Further, sodium hexametaphosphate equivalent to 0.4% by weight based on the calcium carbonate in the suspension was added to the suspension, and the mixture was stirred for 20 minutes. Concentration and dilution were repeated with a centrifugal dehydrator again, and the ammonium ion concentration and alkaline metal ion concentration of a suspension having a calcium carbonate concentration of 3% by weight were measured. Washed to 20 SZ cm. The calcium carbonate suspension was dried, and the amount of ammonium potassium in the dried powder was determined. The total amount was 580 ppm, and the amount of chloride ion was 550 ppm. As a result of observing the obtained calcium carbonate with an electron microscope, it was found that the shape was cubic calcium carbonate having a rounded shape composed of a layered aggregate at the vertices and edges, and having irregularities on the particle surface. Further, 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, and Table 2 shows the physical properties of the obtained calcium carbonate. Example 1 2

The calcium carbonate suspension prepared under the reaction conditions of Example 1 was repeatedly concentrated and diluted with a centrifugal dehydrator to obtain a suspension having a calcium carbonate concentration of 3% by weight. The concentration of ammonium ions and the concentration of metal ions were measured, and the samples were washed until the total was 5 pm and the electric conductivity was 20 SZcm. The suspension after washing was diluted with water to a volume 4 times that of the original reaction solution, and left under stirring for 16 hours. The suspension was again concentrated and diluted by a centrifugal dehydrator, and the ammonium ion concentration and the alkali metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight were measured. Washing was performed until the electric conductivity reached 2 l / S / cm. The washed suspension was diluted with water to a volume 4 times that of the original reaction solution, and left under stirring for 01 hour. Further, the suspension after washing was diluted with water to a volume four times that of the original reaction solution, adjusted to 85 ° C., and left under stirring for 16 hours. The suspension was concentrated and diluted three times with a centrifugal dehydrator, and the ammonium ion concentration and alkali metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight were measured. Washing was performed until the electric conductivity reached 20 〃 SZcm at pm. Thereafter, sodium hexahexaphosphate was added to the suspension in an amount equivalent to 0.4% by weight based on the calcium carbonate in the suspension, and the mixture was stirred for 20 minutes. The suspension was concentrated and diluted with a centrifugal dehydrator four times, and the ammonium ion concentration and the metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight were measured. Washing was performed until the electric conductivity reached 20 S / cm. The calcium carbonate suspension was dried, and the amounts of ammonium, sodium, and potassium in the dry powder were determined. The total was 180 ppm and the amount of chloride ions was 4 ppm. As a result of observing the obtained calcium carbonate with an electron microscope, it was found to be a cubic carbonated calcium carbonate having a rounded shape composed of a layered aggregate at the vertices and edges, and having irregularities or pores on the particle surface. Further, 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, and Table 2 shows the physical properties of the obtained calcium carbonate. Example 13

 To the calcium carbonate suspension prepared under the reaction conditions of Example 1, a calcium chloride solution corresponding to 0.5 times the number of moles of calcium ion relative to the number of moles of calcium carbonate in the suspension was added, The mixture was allowed to stand for 16 hours under stirring, and then 0.4% by weight of sodium hexametaphosphate based on calcium carbonate in the suspension was added to the suspension and stirred for 20 minutes. The suspension was repeatedly concentrated and diluted with a centrifugal dehydrator. The total of the ammonium and aluminum metal concentrations of the suspension having a calcium carbonate concentration of 3% by weight was 5 ppm, and the electrical conductivity was 2 ppm. Washed to 0 SZ cm. The carbonated calcium suspension was dried, and the amount of ammonium, sodium and potassium in the dried powder was determined. The total amount was 250 ppm. The chlorine content was determined to be 220 ppm. As a result of observing the obtained calcium carbonate with an electron microscope, it was found to be a cubic calcium carbonate having a layered aggregate and rounded apexes and edge portions. In addition, as a result of observation by X-ray diffraction, it was confirmed that the crystal form of the obtained calcium carbonate was almost potassium hydroxide. Table 1 shows the production conditions of this example, and Table 2 shows the physical properties of the obtained calcium carbonate.

Examples 14 and 15

To the calcium carbonate suspension prepared under the reaction conditions of Example 1, a calcium chloride solution corresponding to calcium ions in an amount R times the number of moles of calcium carbonate in the suspension was added, and stirred. For 0.1 hour, and then an amount of 0.4% by weight, based on the calcium carbonate in the suspension, of sodium hexamephosphate was added to the suspension and stirred for 20 minutes. The suspension was repeatedly concentrated and diluted by a centrifugal dehydrator. The total of the ammonium ion concentration and the metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight was 5 ppm, and the electric conductivity was 20%. Washed to / SZ cm. The carbonated calsi The aluminum suspension was dried, and the amount of ammonium, sodium, and potassium in the dried powder was determined. The total amount was N 1 ppm. When the amount of chlorine ions was determined, it was N 2 ppm. Observation of the obtained calcium carbonate with an electron microscope revealed that the shape was a cubic calcium carbonate composed of a layered aggregate and having rounded vertices and edges. Further, 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, and Table 2 shows the physical properties of the obtained calcium carbonate.

Example 16

The calcium carbonate suspension prepared under the reaction conditions of Example 1 was repeatedly concentrated and diluted with a centrifugal dehydrator to reduce the ammonium ion concentration and alkaline metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight. It was washed until the total was 5 ppm and the electrical conductivity was 20 S / cm. The suspension after washing is diluted with water to an equivalent volume of the original reaction solution, and acetic acid corresponding to 0.5 times the number of moles of calcium ions with respect to the number of moles of calcium carbonate in the suspension. The calcium solution was added and left under stirring for 16 hours. The suspension was again concentrated and diluted by a centrifugal dehydrator, and the ammonium ion concentration and the metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight were measured. Washing was performed until the electric conductivity reached 20 pm / SZcm. Dilute the suspension after washing with water to make the same volume as the original reaction solution, adjust to 85 ° C, and use 0.5 times the number of moles of calcium carbonate in the suspension. A calcium acetate solution corresponding to the calcium ions was added and left under stirring for 16 hours. Thereafter, sodium hexametaphosphate equivalent to 0.4% by weight based on the calcium carbonate in the suspension was added to the suspension, and concentration and dilution were repeated with a centrifugal dehydrator to reduce the calcium carbonate concentration to 3%. Determine the ammonium ion concentration and the metal ion concentration of the suspension by weight. Then, washing was performed until the total sum was 5 ppm and the electric conductivity was 20 S / cm. The calcium carbonate suspension was dried, and the amount of ammonium 'sodium' potassium in the dry powder was determined. The total amount was 800 pm, and the amount of chloride ions was 20 ppm. Observation of the obtained calcium carbonate with an electron microscope revealed that the shape was a rounded cubic calcium carbonate composed of a layered aggregate at the apex and edge portions. In addition, as a result of observation by X-ray diffraction, it was confirmed that the crystal form of the obtained calcium carbonate was almost potassium hydroxide. Table 1 shows the production conditions of this example, and Table 2 shows the physical properties of the obtained calcium carbonate.

Examples 17 and 18

The calcium carbonate suspension prepared under the reaction conditions of Example 1 was repeatedly concentrated and diluted with a centrifugal dehydrator, and the ammonium ion concentration and the metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight were repeated. The sample was washed until the total was 5 ppm and the electric conductivity was 20 SZ cm. Dilute the suspension after washing with water to the same volume as the original reaction solution.Calcium acetate solution corresponding to 1 times the number of moles of calcium ions relative to the number of moles of calcium carbonate in the suspension Was added and left under stirring for 01 hour. The suspension was again concentrated and diluted by a centrifugal dehydrator, and the concentration of ammonium carbonate and the concentration of metal ion in a suspension having a calcium carbonate concentration of 3% by weight were measured. Washing was performed until the conductivity reached 20 SZcm at ppm. Dilute the suspension after washing with water to make the same volume as the original reaction solution, adjust to T 1 ° C, and R 2 times the number of moles of calcium carbonate in the suspension. A calcium acetate solution corresponding to the calcium ion was added, and the mixture was left under stirring for 02 hours. Thereafter, 0.4 wt% of sodium hexamune phosphate based on the calcium carbonate in the suspension was added to the suspension, and concentration and dilution were repeated with a centrifugal dehydrator to reduce the calcium carbonate concentration to 3%. weight% The suspension was measured for ammonium ion concentration and alkaline metal ion concentration, and washed until the total was 5 ppm and the electric conductivity was 20 SZ cm. The calcium carbonate suspension was dried, and the amount of ammonium sodium in the dried powder was determined. The total amount was N 1 ppm and the amount of chloride ion was N 2 pm. Observation of the obtained calcium carbonate with an electron microscope revealed that the shape was a rounded cubic calcium carbonate composed of a layered aggregate at the apex and edge portions. Further, 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, and Table 2 shows the physical properties of the obtained calcium carbonate.

Example 19

 Carbon dioxide gas was blown into the calcium carbonate suspension prepared under the reaction conditions of Example 1 until the pH of the suspension dropped to 3.0, and the suspension was left under stirring for 1 hour. After standing, the suspension was repeatedly concentrated and diluted by a centrifugal dehydrator, and the concentration of ammonium carbonate and the concentration of metal ions in the suspension having a calcium carbonate concentration of 3% by weight were measured. Was 5 ppm and the electric conductivity was 20〃S / cm.

The calcium carbonate suspension was dried, and the amount of ammonium, sodium, and potassium in the dried powder was determined. The total amount was 320 ppm, and the amount of chloride ions was 300 ppm. Observation of the obtained calcium carbonate with an electron microscope revealed that the shape was a rounded cubic calcium carbonate composed of a layered aggregate at the vertices and edges. Further, 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, and Table 2 shows the physical properties of the obtained calcium carbonate.

Table 1 continued 1

 ,, removal method (d) (e) (0 Example 11 12 13 14 15 16 17 18 19 Washing at the end of the reaction (before leaving) Yes Yes, No suspension Yes Yes Yes No

Q1: Suspension dilution ratio * Equivalent 4---* Equivalent * Equivalent * Equivalent 1

^: Leaving time !: ^] 1 16 16 16 16 16 16 16 1 Water-soluble calcium salt ― Calcium chloride Calcium chloride Calcium chloride Calcium sulfate Calcium peroxylate Calcium sulfate pH pH adjustment ― ― ― ― ― ― ― ― 3.0 Decline

R1: Calcium salt addition ratio ― ― 0.5 1 2 0.5 1 2

Other--After washing, finished After washing, finished After washing, finished--After washing-finished Whether or not to wash before standing for warming-Yes---Yes Yes Yes

Q2: Suspension dilution ratio-4 1-1-1 1 1-

02: Idle time [hr] — 16 one one one 16 16 16

 T1: Heating temperature [° C] 85 85 85 85

Water-soluble calcium salt

 R2: Calcium salt addition ratio 0.5 1 2

Other After cleaning, finished After cleaning, finished After cleaning, finished After cleaning, finished After cleaning, finished

 N1: Ammonia 'alkali amount (ppm) 5800 180 2500 2400 2200 800 780 760 3200

N2: halide ion amount (ppm) 550 4 220 210 200 20 18 16 300

Table 2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10

DS 1 3.00 2.96 2.90 3.02 3.04 3.16 3.02 3.08 3.16 3.16

DS2 3J2 3.67 3.60 3J5 3J7 3.92 3J5 3.82 3.92 3.92

DP 1 4.50 4.46 4.42 4.52 4.52 4.52 4.54 4.57 4.62 4.65

DP2 4.29 4.25 4.19 4.34 4.31 4.31 4.33 4.41 4.41 4.42

DP3 3J5 3J5 3J1 3.81 3.72 3J2 3.83 3.87 3.91 3.95

DP4 3.09 3.07 3.03 3.13 3.1 1 3.1 1 3.12 3.15 3.19 3.24

DP5 2.22 2.20 2.18 2.22 2.24 2.23 2.24 2.28 2.32 2.33

DP3 / DS 1 1.25 1.27 1.28 1.26 1.22 1.18 1.27 1.26 1.24 1.25

DP3 / DS2 1.01 1.02 1.03 1.02 0.99 0.95 1.02 1.01 1.00 1.01

DP2 / DP4 1.39 1.38 1.38 1.39 1.39 1.39 1.39 1.40 1.38 1.36

DP1 / DP5 2.03 2.03 2.03 2.04 2.02 2.03 2.03 2.00 1.99 2.00

(DP2-DP4VDP3 0.32 0.31 0.31 0.32 0.32 0.32 0.32 0.33 0.31 0.30

S 0.24 0.25 0.26 0.25 0.26 0.26 0.25 0.25 0.28 0.29

Table 2 continued 1 Example 1 1 Example 12 Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Example 1 9

DS 1 3.00 3.20 2.96 3.00 3.00 2.98 3.00 3.02 3.00

DS2 3J2 3.97 3.67 3.12 3J2 3J0 3J2 3.75 3.72

DP1 4.50 4.54 4.46 4.50 4.52 4.50 4.52 4.50 4.50

DP2 4.29 4.29 4.25 4.29 4.29 4.29 4.29 4.29 4.29

DP3 3J4 3.83 3J5 3.75 3.77 3.75 3Jf 3J7 3J5

DP4 3.09 3.1 1 3.07 3.09 3.1 1 3.09 3.09 3.09 3.07

DP5 2.21 2.24 2.20 2.22 2.24 2.22 2.27 2.22 2.22

DP3ZDS 1 1.25 1.20 1.27 1.25 1.26 1.22 1.26 1.25 1.25

DP3 / DS2 1.00 0.96 1.02 1.01 1.01 1.01 1.01 1.01 1.01

DP2ZDP4 1.39 1.38 1.38 1.39 1.38 1.39 '1.39 1.39 1.40

DP1 / DP5 2.04 2.03 2.03 2.03 2.02 2.03 1.99 2.03 2.03

(DP2-DP4VDP3 0.32 0.31 0.31 0.32 0.31 0.32 0.32 0.32 0.33

S 0.25 0.29 0.28 0.28 0.28 0.29 0.29 0.29 0.25

Comparative Example 1

 Immediately after the reaction of the calcium carbonate suspension prepared under the reaction conditions of Example 1, 0.4% by weight of sodium hexametaphosphate corresponding to the calcium carbonate in the suspension was added to the suspension. Stirred for 20 minutes.

 Thereafter, the suspension was repeatedly concentrated and diluted by a centrifugal dehydrator to obtain a total of 400 ppm of the ammonium ion concentration and the aluminum ion concentration of the suspension having a calcium carbonate concentration of 3% by weight. Washing was performed until the total halide ion content reached 200 ppm and the electrical conductivity reached 600 SZ cm. The calcium carbonate suspension was dried, and the amount of ammonium, sodium and potassium in the dried powder was determined, and the total amount was 5800 ppm. Further, the amount of chloride ions was 600,000 ppm. As a result of observing the obtained calcium carbonate with an electron microscope, the shape was a rounded cubic carbonic acid luminum having layered aggregates at the vertices and edges. In addition, 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 3 shows the production conditions of this comparative example, and Table 4 shows the physical properties of the obtained carbonated calcium carbonate.

Comparative Example 2

 Immediately after the reaction of the calcium carbonate suspension prepared under the reaction conditions of Example 1, 0.4% by weight of sodium hexahexaphosphate corresponding to the calcium carbonate in the suspension was added to the suspension. And stirred for 20 minutes.

After that, the suspension was repeatedly concentrated and diluted by a centrifugal dehydrator, and the total of the ammonium ion concentration and the metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight was 5 ppm. Washing was performed until the conductivity reached 20 // SZ cm. The calcium carbonate suspension was dried, and the amount of ammonium and sodium potassium in the dried powder was determined. The total amount was 360,000 ppm and the amount of chloride ion was 290 ppm. Was. The resulting carbonic acid As a result of observing the calcium with an electron microscope, it was found to be a rounded cubic calcium carbonate composed of layered aggregates at the vertices and edges.

 In addition, 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 3 shows the production conditions of this comparative example, and Table 4 shows the physical properties of the obtained calcium carbonate. -Comparative example 3

 The calcium carbonate suspension obtained by adding sodium hexaphosphate and obtained in Comparative Example 1 and washed was further concentrated and diluted by a centrifugal dehydrator to repeat the ammonium carbonate suspension having a calcium carbonate concentration of 3% by weight. Washing was performed until the sum of the metal ion concentration and the alkali metal ion concentration became 1 ppm and the gas conductivity reached 5 S / cm.

 The calcium carbonate suspension was dried, and the amount of ammonium, sodium, and potassium in the dry powder was determined. The total amount was 1,800 ppm. Further, the amount of chloride ions was 190,000 ppm. Observation of the obtained calcium carbonate with an electron microscope revealed that the shape was rounded cubic calcium carbonate composed of a layered aggregate at the vertices and edges. Further, 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 3 shows the production conditions of this comparative example, and Table 4 shows the physical properties of the obtained calcium carbonate.

Comparative Example 4

 The calcium carbonate suspension prepared under the reaction conditions of Example 1 was allowed to stand for 45 minutes under stirring, and then suspended with 0.4% by weight of sodium hexametaphosphate equivalent to calcium carbonate in the suspension. Added to the suspension and stirred for 20 minutes

. After that, the suspension was repeatedly concentrated and diluted with a centrifugal dehydrator to repeat calcium carbonate. Washing was carried out until the total of the ammonium ion concentration and the metal ion concentration of the suspension having a rubber concentration of 3 weight and the concentration of metal ions became 5 ppm and the electric conductivity became 20 SZ cm. The calcium carbonate suspension was dried, and the amount of ammonium 'sodium' potassium in the dry powder was determined. The total amount was 1200 ppm. The chloride ion content was 11 ppm. Observation of the obtained calcium carbonate with an electron microscope revealed that the shape was rounded cubic calcium carbonate composed of a layered aggregate at the vertices and edges. Further, 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 3 shows the production conditions of this comparative example, and Table 4 shows the physical properties of the obtained calcium carbonate.

Comparative Example 5

The calcium carbonate suspension prepared under the reaction conditions of Example 1 was adjusted to 85 and allowed to stand under stirring for 1 hour. Then, an amount equivalent to 0.4% by weight based on the calcium carbonate in the suspension was obtained. Sodium hexaphosphate was added to the suspension and stirred for 20 minutes. After that, the suspension was repeatedly concentrated and diluted by a centrifugal dehydrator, and the total of the ammonium ion concentration and the alkali metal ion concentration of the suspension having a calcium carbonate concentration of 3% by weight was 5 ppm. Was washed to 20 S / cm. The calcium carbonate suspension was dried, and the amount of ammonium “sodium” potassium in the dry powder was determined. The total amount was 1150 ppm. Further, the amount of chloride ions was 130 ppm. As a result of observing the obtained calcium carbonate with an electron microscope, it was found to be a cubic calcium carbonate having a rounded shape composed of a layered aggregate at the vertices and edges, and having irregularities or pores on the particle surface. Further, 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 3 shows the production conditions of this comparative example, and Table 4 shows the physical properties of the obtained calcium carbonate. Comparative Examples 6, 7

As Comparative Example 6, a calcium carbonate reagent special grade (manufactured by Wako Pure Chemical Industries, Ltd.) was prepared. As Comparative Example 7, heavy calcium carbonate “R heavy coal” (manufactured by Maruo Calcium) was prepared.

Table 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Presence or absence of cleaning at the end of the reaction (before standing) Performing only cleaning Performing only cleaning Performing only cleaning None 1-

Q1: Suspension dilution factor ― ― one ― ― one ―

01: Leaving time [hr] ― ― 1 0J5 1 1 ― Water-soluble calcium salt 1 1 ― ― ― ― ― pH adjustment ― 1 1 ― ― ― ―

R1: Calcium salt addition rate ― 1 ― ― ― ― ― Other ― 1 ― Finish after washing ― 1 ― Washing before heating and standing ― 1 ― 1 No ― ―

Q2: Suspension dilution factor ― ― ―

S 2: Leaving time [hr] ― 1 1 1 1 ―

T1: Heating temperature [° C] 85

Water soluble calcium salt

 PH adjustment

 R2: Calcium salt addition magnification

Others Finish after cleaning

 N1: Ammonia 'alkali content (ppm) 58000 36000 18000 12000 11500 <5 250

N2: halide ion amount (ppm) 6000 2900 1900 1100 1300 <1 21

Table 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example

DS1 3.00 3.00 2.98 3.00 3.82 8.50 3.00

DS2 3.72 3.72 3.70 3.72 4.74--

DP1 4.90 4.52 4.48 4.50 5.46 14.76 5.78

DP2 4.49 4.29 4.27 4.29 5.15 13.04 4.62

DP3 4.04 3.77 3.75 3.75 4.62 8.27 3.24

DP4 3.35 3.11 3.07 3.03 3.22 4.70 1.64

DP5 3.10 2.24 2.22 2.22 2.25 2.07 0.78

DP3 / DS1 1.35 1.26 1.26 1.25 1.21 0.97 1.08

DP3ZDS2 1.09 1.01 1.01 1.01 0.97

 DP2 / DP4 1.34 1.38 1.39 1.42 1.60 2.11 2.82

DP1 / DP5 1.58 2.02 2.02 2.03 2.43 7.13 7.41

(DP2-DP4) / DP3 0.28 0.31 0.32 0.34 0.42 1.01 0.92

S 0.25 0.25 0.26 0.26 0.51 0.71 0.58

Application Examples 1 to 5, Comparative Application Examples 1 to 7

 After drying the calcium carbonate obtained in Examples 1, 3, 10, 15, 18, and 18 and Comparative Examples 1 to 5, or after adding calcium carbonate to Comparative Examples 6, 7 The stearic acid equivalent to 1.5% by weight of the surface was subjected to a surface treatment using a Hensile mixer under operating conditions of 115 ° C for 45 minutes. 2 parts by weight of the obtained surface-treated calcium carbonate was added to 100 parts by weight of methacrylic resin beads (SUMIPEX EXA; manufactured by Sumitomo Chemical Co., Ltd.), mixed with a Henschel mixer for 1 minute, and then mixed with a 40 mm single screw extruder. The molten resin was extruded from a T-die at a resin temperature of 265 ° C using (Tanabe Plastics Machinery Co., Ltd.), and passed through three polishing rolls to obtain a sheet having a width of 23 cm and a thickness of 2 mm.

 The physical properties of the obtained sheet were evaluated by the following methods. Tables 5 and 6 show the evaluation results.

 1) Particle dispersibility in sheet

 The obtained sheet was observed with a transmission microscope and judged according to the following criteria. A: No aggregated particles or coarse particles are observed.

 〇: Aggregated particles or coarse particles are slightly observed.

 Δ: Aggregated particles or coarse particles are considerably observed.

 : Many agglomerated particles or coarse particles are observed.

 2) Smoothness of sheet surface

 The obtained sheet was visually determined and evaluated according to the following criteria.

 A: Smooth without surface irregularities.

 〇: Irregularities are visible on a part of the surface.

 Δ: Irregularities occupy half of the surface.

 X: The entire surface has irregularities.

3) Total light transmittance (T t) According to ASTM D1003-61T, it was measured with a Poick's integrating sphere haze meter (SEP-HS-30D manufactured by Nippon Seimitsu Kogaku).

4) Light diffusion

 The following transmitted light intensity was measured using an automatic goniophotometer GR-1R (manufactured by Murakami Color Research Laboratory). / Is light diffusing. .

 Transmitted light intensity at a transmission angle of 0 ° by vertically incident light (1.)

Transmitted light intensity at a transmission angle of ₇₀ ° due to normal incident light (I ₇₀ ) 5) Yellowness (Yellow Index)

 The yellowness of reflected light and transmitted light was determined using SM-2 manufactured by Suga Test Instruments. The higher the number, the more yellow.

 6) Comprehensive evaluation

 Excellent sheets were comprehensively evaluated according to the following criteria.

 ：: optimal as a light diffusion sheet.

 〇: More preferable than the conventional light diffusion sheet.

 Δ: equivalent to a conventional light diffusion sheet.

X: Not suitable as a light diffusion sheet.

Table 5

J Γ '? ", Ffl field ^ Wl l 1 I ri- m ^ Ell rt- m iEll r field A rt- m J-a \ c

Ixffl-shi 7 gray s / U Renomu Incapacitating case Ί Femoral case o 夹 iEliiJI U Fuminoru no tp (Hine ϋ Juto X1 King vQ) ©) Total light transmittance (Tt) 55.4 56.1 56.4 55.3 54.9 Light Diffusivity 56.2 55.5 55.2 54.8 54.9 Yellowness (reflected light)-6-7 -8-7 -7 Yellowness (transmitted light) 8 7 5 7 6 Overall evaluation 〇 〇〜 ◎ ◎ 〇〜 ◎ ◎

Table 6 Comparative Application Example 1 Comparative Application Example 2 Comparative Application Example 3 Comparative Application Example 4 Comparative Application Example 5 Comparative Application Example 6 Comparative Application Example 7 Calcium Carbonate Used Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Particle dispersibility in sheet X ◎ ◎ ◎ mm 〇 平滑 Smoothness of sheet surface 〇 ◎ ◎ ◎ Δ XX Total light transmittance (Tt) 60.3 55.8 55.6 54.8 60.3 65.2 62.3 Light diffusivity 42.2 56.3 54.4 55J 39.4 38.2 43.4 Yellowness (reflected light) -2 -3-3 -4-5 -10 0 Yellowness (transmitted light) 20 17 15 1 1 8 4 17 Overall evaluation X Δ Δ mm XXX

Application Examples 6 to 10, Comparative Application Examples 8 to 1 2

 The suspensions of calcium carbonate obtained in Examples 1, 3, 10, 15 and 18 and Comparative Examples 1 to 5 were added with a surface treatment agent (acrylic) equivalent to 5% by weight based on calcium carbonate. The surface treatment of a copolymer of acid and butyl methacrylate in which the weight ratio of each is 70:30, in which 20% of the total carboxyl groups in the acrylic acid portion are in the form of an ammonium salt) is carried out with stirring. After that, ethylene glycol slurry was added, and further, the water was removed by flushing using an evaporator to prepare ethylene glycol slurry of calcium carbonate. The solid concentration of calcium carbonate in ethylene glycol was 20.0 weight.

 These ethylenic glycol slurries were added prior to the polyesterification reaction to carry out the polyesterification reaction, and the limiting viscosity number (orthochlorophenol, 35 ° C) containing 0.3% by weight of the blocking agent was 0.62 dl. / g of polyethylene terephthalate was prepared. The polyethylene terephthalate was dried at 160 ° C., melted and extruded at 29 ° C., and quenched and solidified on a casting drum maintained at 40 ° C. to obtain an unstretched film. Subsequently, the unstretched film was preheated to 70 ° C. with a heating nozzle, and then stretched in a vertical direction while being heated by an infrared heater. Subsequently, the film was stretched in the transverse direction at a temperature of 90 ° C. and then heat-treated at 200 to obtain a biaxially oriented film having a thickness of 10 / m. The quality of the film thus obtained was evaluated by the following method. Tables 7 and 8 show the results.

 1) Particle dispersibility of polyester composition

 The polyester composition was observed with a transmission microscope and judged according to the following criteria.

 A: No aggregated particles or coarse particles are observed.

〇: Aggregated particles or coarse particles are slightly observed. Δ: Aggregated particles or coarse particles are considerably observed.

 X: Many agglomerated particles or coarse particles are observed.

 2) The specific resistance of the polyester composition during melting (p)

 Melt the film at a temperature of 285 ° C and measure its specific resistance. In this measurement, it is known to reduce the amount of a catalyst metal added during the production of the polyester or to add phosphoric acid or a phosphoric acid compound such as a phosphoric ester for the purpose of reducing the activity of the metal. In the present invention, the measurement was performed by adding lithium acetate as a catalyst metal to the polyester at 1 O O pm and further adding the same amount of phosphoric acid.

 3) Evaluation of film wear characteristics I

 Use the device shown in Fig. 1 to measure as follows. In Fig. 1, 1 is the take-out reel, 2 is the tension controller, 3, 5, 6, 8, 9, and

1 1 is a free roller, 4 is a tension detector (entrance), 7 is a stainless steel net SUS304 fixed pin (outer diameter 5 mm), and 10 is a tension detector

(Exit), 1 2 indicates the guide opening, 1 3 indicates the take-up reel

A slit of film with a width of 1.27 cm (1Z2 inch) was placed on a stainless steel fixing pin 7 (surface roughness 0.58) at an angle of 150 ° using the above device. Contact and reciprocate about 15 cm at a speed of 2 m / min. In this case, the entry side tension T] is 70 g.

 After repeating this operation 50 times, scratches generated on the contact surface with the fixing pin were visually observed, and the abrasion resistance was determined based on the following criteria.

 A: Scratch hardly occurs.

 〇: Scratch generation is slight.

 Δ: Scratches account for half of the film surface.

X: Scratch occurs over the entire film. 4) Evaluation of wear characteristics of film II

 The sharpness of the film running surface is evaluated using a five-stage mini super calendar.

 The force renderer is a five-stage force renderer consisting of a nip roll and a steel roll. The processing temperature is 80 ° C, the linear pressure on the film is 200 kg cm, and the film speed is 7 OmZ. When the running film has traveled a total length of 300 m, the dirt adhering to the top roller of the force renderer is used to evaluate the scalability of the film based on the following criteria.

 ◎: There is no dirt on the nylon roll.

 〇: There is almost no dirt on the nylon roll.

 Δ: Nail roll is very dirty.

 X: The nylon roll is very dirty.

 5) Number of coarse protrusions on the film surface

 After thinly depositing aluminum on the film surface, the number of coarse projections (number per 1 mm 2 measurement area) of quadruple ring or more was counted using a two-beam interference microscope. Expressed by criteria ranking

Grade 1: 16 or more

 Second grade: 10-15

 3rd grade: 6-9

 Level 4: 2-5

 5th grade: 0-1

 6) Film breakdown voltage

The measurement was performed using an AC withstand voltage tester in accordance with JIS-C2318. That is, using a 10 kV DC withstanding voltage tester, the voltage was increased at a rate of 100 / ^ 6 in an atmosphere of 23 ° C and 50% RH, and the film was broken and the The voltage at the time of shutdown was measured.

 7) Insulation resistance characteristics

The resulting films using a resistive heating type metal depositing apparatus to the surface, 1 3 3. The pressure in the vacuum chamber ^{3 2 2 X 1 0 - 4} P a (1 0 "4 T orr) set below Arumuniu厶Was vapor-deposited to a thickness of 35 OA in the form of a stripe having a margin in the longitudinal direction of the polyester film (deposition of a vapor deposition portion of 8 mm and a margin portion of 1 mm).

 The obtained aluminum-deposited polyester film was slit into a 4.5 mm wide tape having a left or right margin of 1 mm. Further, one roll of each of the left margin and right margin vapor deposition films was wound in the width direction such that the vapor deposition portion protruded by 0.5 mm to obtain a roll.

The wound body was pressed for 5 minutes at a temperature 1 4 0 ° C · pressure ^{4 9. 0 3 5 1 0 5} P a (5 0 K g · cm 2), Metariko on both end surfaces of the wound body after pressing After melting the lead into a lead wire, impregnating it with a liquid epoxy resin, then heating and melting the powdered epoxy resin to provide a 0.5 mm thick outer casing with a capacitance of 0.1 〃F A film capacitor was obtained. The capacitance [C] of the obtained film capacitor was measured using a Yokogawa Hewlett Packard LCR meter 4284 A under an atmosphere of 23 ° C and 50% RH.

¾

 The obtained film capacitor was applied with a DC voltage of 100 V between the electrodes of the capacitor at 23 ° C using a high resistance meter 4329 A made by Yokogawa Hyurette Packard Co., Ltd. The resistance value R was measured. Note that the resistance value R showed the maximum value immediately after the voltage was applied, and then decreased.

The evaluation of the insulation resistance of the capacitor was performed by the product of the above-mentioned capacitance and resistance value [C x R]. ) Comprehensive evaluation

The resulting film was comprehensively evaluated according to the following criteria.

A: Optimum as a film capacitor. 〇: More preferable than the conventional film capacitor, Δ: Equivalent to the conventional film capacitor, X: Unsuitable as the film capacitor.

Table 7 Application example 6 Application example 7 Application example 8 Application example 9 Application example 10 Calcium carbonate used Example 1 Example 3 Example 10 Example 15 Example 18 Particle dispersibility in polyester composition ◎ ◎ ◎ ◎ ◎ ◎ specific resistance when melted polyester composition _{(Ρ [Ω 'cm])} 1 X 10 one ^{7 7x 10- 7 4x10- 8 7x 10-} 7 3.5X 1 (Γ 8 wear properties of film evaluation I ◎ O O O評 価 Evaluation of film wear characteristics Π ◎ ◎ 〇 〇 ◎ ◎ Number of coarse protrusions on the film surface Class 5 Class 5 Class 5 Class 5 Dielectric breakdown voltage of film [V'jUm] 730 650 530 530 680 700 Insulation resistance characteristics of film '[CX R [Ω-F ]] 2.8 X 10- 4 3.1 X 10- 4 4.0 X 10- 4 3.1 10- 4 3.5 X 10- 4 overall evaluation O 〇_～ ◎ ◎ 〇_～ ◎ ◎

Table 8 Comparative application examples 8 Comparative application examples 9 Comparative application examples 10 Comparative application examples 11 Comparative application examples 12 Calcium carbonate used Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Particle dispersibility in polyester composition厶◎ ◎ ◎ resistivity at melting of Δ polyester composition (p [Ω 'cm]) 1 10 "5 1.2X1CT 6 6 10" 6 9X 10- 6 3x10-7 wear properties of the film rating I 〇 ◎ 〇 © Evaluation of wear characteristics of X film Π X 〇 Δ 数 Δ Number of coarse protrusions on film surface Grade 3 Grade 5 Grade 5 Grade 3 Grade Film dielectric breakdown voltage [V'jUm] 450 680 530 720 720 480 Insulation resistance characteristics of film '[CXR [Q'F]] 2.3 X 10 1 ² 2.5X 1CT ³ 3.4 X 10— ³ 2.4 X 10 ” ⁴ 3.8 X 10— ⁴ Overall rating XXX Δ X

Industrial applicability

 As described above, according to the present invention, the dispersibility is good, the unnecessary fine particles and the coarse particles are not contained, the particle size is extremely uniform, and the particle size distribution can be obtained in a sharp particle size range. Cubic calcium carbonate with a wide range of sizes, arbitrarily set particle size, high-temperature stability, extremely long-term stability, and a low content of ammonium ions, alkali metal ions, and halide ions. In addition, it can be suitably used in applications where the presence of ammonium ions, alkali metal ions, and chloride ions interferes, and its usefulness is extremely large.

Claims

The scope of the claims 1. A method for producing cubic calcium carbonate, comprising the following steps:  The carbonate buffer concentration and the calcium ion concentration are each 0.1 to 3.0 mol / s, and the concentration ratio of the calcium ion to the carbonate ion is 0.5 to 2.0. Dissolve the reaction buffer solution with a degree of 0.001 to 2.0 mol / L,  Under stirring, the carbonate solution is dropped into the calcium salt solution, or the calcium salt solution is dropped into the carbonate solution, and the temperature in the reaction system is maintained at 5 to 40 ° C, and the solution is dropped within a time of 70 to 1200 seconds. Mix to perform the calcium carbonate generation reaction,  The obtained calcium carbonate suspension is subjected to at least one of a removal method selected from the following (a) to (; f) to remove at least ammonium ion, alkali metal ion, and halide ion. Remove one species,  Water-soluble salts or water-soluble acids that react with calcium to form water-insoluble or sparingly soluble salts, 0.01 to 5% by weight based on the calcium carbonate in the calcium carbonate suspension, And adjust so as to satisfy the following requirements (I) to (V).  (a) The obtained calcium carbonate suspension or a diluent thereof is left for at least 1 hour or stirred, and then washed.  (b) The obtained calcium carbonate suspension or its diluted solution is left or stirred for 1 hour or more, then adjusted to 40 ° C. or more, left for 1 hour or more, and washed. (c) Leave the resulting calcium carbonate suspension or diluent for at least 1 hour, wash it after leaving or stirring, then adjust it to 40 or more and leave it for 1 hour or more, then wash it. . (d) After washing the obtained calcium carbonate suspension, any one of the above-mentioned (a) to (c) is used.  (e) In each of the above-mentioned methods (a) to (d), a water-soluble potassium salt solution is added when leaving or stirring for at least one hour.  (ii) In each of the above methods (a) to (d), the pH of the calcium carbonate suspension or its diluent is lowered by 1 or more when left standing or stirring for 1 hour or more.  (I) When the calcium carbonate concentration is 3% by weight, the total amount of ammonium ions and metal ions in the aqueous suspension is 300 ppm or less. (II) When the calcium carbonate concentration is 3% by weight, the halide ion in the aqueous suspension is less than 100 ppm.  (Iii) The electrical conductivity of the water suspension is 500 S / cm or less when the calcium carbonate concentration is 3% by weight.  (IV) The total power of the ammonium ions and metal ions contained in the cubic calcium carbonate obtained by drying is 0, OOOppm or less.  (V) Cubic calcium carbonate obtained by drying contains less than 1, OOOppm of halide ions.  2. The calcium carbonate according to claim 1, wherein the total amount of ammonium ions and metal ions contained in the cubic calcium carbonate obtained by drying is 5, OOOppm or less, and halide ions are 500 ppm or less. Production method. 3. The calcium carbonate according to claim 1, wherein the total amount of ammonium ions and metal ions contained in the cubic calcium carbonate obtained by drying is 2, OOO ppm or less, and halide ion is 200 ppm or less. Manufacturing method. 4. The method for producing calcium carbonate according to claim 1, 2 or 3, wherein the cubic calcium carbonate satisfies the following physical properties (a) to (h).  (a) 0.1 ≤DS 1 ≤2 0.0 (b) DS 2 = (Q / π) ^1/3 xDS 1  (c) 1.15 ≤ DP 3 / DS I ≤ I. 40  (d) 0.90 ≤DP 3 / DS 2≤ 1.15  (e) 1.0 ≤ D P 2 / DP A ≤ 2.0  (f) 1.0 ≤ DP 1 / DP 5 ≤ 2.5  (g) (D P 2-DP 4 / DP 3) ≤ 0.5  (h) S≤ 0.5  However,  n S = [∑ (D i -DS 1) V (n-1)] ^{] / 2} / DS 1 i = 1  DS 1: Average of one side length of cubic calcium carbonate particles measured by scanning electron microscope (m)  DS 2: Diameter (m) of sphere obtained by volume conversion from average (xzm) of one side length of cubic calcium carbonate particles examined by scanning electron microscope  DP1: Particle size at a cumulative weight of 10% calculated from the large particle size (m) in the particle size distribution measured using a scattering type laser analysis type particle size distribution analyzer (Microcrac-FRA manufactured by Northrop).  DP 2: Particle size at 25% cumulative weight (m) calculated from the large particle size in the particle size distribution measured using a scattering type laser analysis type particle size distribution analyzer (Microtrac-FRA manufactured by Northrop). DP 3: In the particle size distribution measured using a scattering type laser analysis type particle size distribution analyzer (Microcrac-FRA manufactured by Northrop Co.) Particle size at 50% of the cumulative weight calculated (/ im)  DP4: Particle size at 75% of the cumulative weight calculated from the large particle size in the particle size distribution measured using a scattering type laser analysis type particle size distribution analyzer (Microtrac-FRA manufactured by Northrop).  DP 5: Particle size (zm) at 90% of the cumulative weight calculated from the large particle size in the particle size distribution measured using a scattering type laser analysis type particle size distribution analyzer (Crotrac-FRA manufactured by Northrop)  D i: One side length of each particle of cubic calcium carbonate examined by scanning electron microscope (m)  S: Relative standard deviation.