MXPA99010702A - Seeding of aragonite calcium carbonate and the product thereof - Google Patents

Abstract

Fine-grained aragonite precipitated calcium carbonate is produced on a commercial scale by seeding with a coarse-grained aragonite precipitated calcium carbonate. The coarse-grained seeding material is produced by interrupting, after the production of 0.1 to 0.6 g/L min. of calcium carbonate, the supply of carbon dioxide to the quicklime slurry early in the reaction to allow subsequent nucleation of the crystals and then continuing the supply of carbon dioxide at reaction rates of 0.1 g/L min. to 0.6 g/L min. This coarse-grained seeding material has a Blaine surface area which may be less than 30,000 cm2/g, the solids of which are 35 to 70 weight percent aragonite, and isadded to subsequent batches as a slurry at about 1 weight percent, based on the total weight of the slurry of the material to be seeded. For the seeded batches, carbonation is carried out at reaction rates of up to 1.8 g/L min. at the commercial scale resulting in fine-grained aragonite product. This final seeded product need not be ground, has solids in which the weight percent of aragonite is greater than 90, has a median particle size between 0.30 to about 0.5 microns, a particle size distribution where about 60 to 70 weight percent are less than 0.5 micron equivalent spherical diameter, and a Blaine surface area which may be greater than 35,000 cm2/g.

Description

SEEDING OF ARAGONITE CALCIUM CARBONATE AND PRODUCT OF THE SAME DESCRIPTION OF THE INVENTION The present invention relates to precipitated calcium carbonate, and more particularly, to a method for commercial scale production of precipitated calcium carbonate of fine-grained aragonite. and the product developed by this method. Aragonite is a form of calcium carbonate that has crystals in the form of needles and physical properties that depend to a greater extent on the length of the needles. Some manufactured aragonite consists of dense glomeruli of needles in which the length of the individual needle is so small that it can not be seen even under the optical microscope. This product finds application in pharmaceuticals, in dentifrices, as a filler and as a pigment. It is distinguishable from calcite, the stable form of precipitated calcium carbonate, by analytical tests such as X-ray diffraction measurements or by the Mohr salt test. Now some aragonite can be manufactured in crystal sizes up to lengths of needles over 50 microns. This larger-sized aragonite can be used as a filter aid, in cosmetics, as a filler, and as a replacement for mineral powders. The length of the aragonite needle can be varied to some degree to suit any particular application. For example, as a filter aid for premium sugar liquors, needle lengths in the range of 10-25 microns are preferred, whereas in filling agents and other applications, a small particle size may be required. In papermaking, calcium carbonate can be used in both coating applications and as a filler that is applied to paper to increase gloss and flexibility and to improve printing. If used as a filler, the main advantages of gloss, opacity and fiber replacement are improved. If used in the coating application, the precipitated calcium carbonate pigments are applied to the paper by coating the paper with an aqueous suspension containing the precipitated calcium carbonates and an adhesive. The calcium carbonate used as a filler pigment or in the coating application in papermaking may be in the form of aragonite or calcite and calcium carbonate may be precipitated, wherein the calcium carbonate pigment is manufactured by reactions controlled chemicals. This manufacturing process for precipitated calcium carbonate may involve a quenching step wherein the lime and water are mixed together to form a suspension followed by a carbonation step where the suspension is transferred to a carbonate apparatus and gas is applied carbon dioxide to precipitate the calcium carbonate from the suspension. The suspension is then subjected to a sieving process to remove impurities, and then transferred to a storage or paper mill for final processing for the desired application. In the application of the precipitated calcium carbonate in the paper coating, calcium carbonate is usually prepared in a fine particle size where the average particle size is between 0.3 and 0.5 μ, then the water is removed, and it is already transported. either as a dry product or as a suspension concentrated in solids to a paper manufacturer that either suspends the dry product by mixing it with a suitable amount of an adhesive in enough water to give the desired consistency, or uses this concentrated suspension in solids "as is". Examples of the prior art pertaining to the precipitation of calcium carbonate to obtain an aragonite form thereof or to the precipitation of a calcium carbonate composition are described in US Patent Nos. 3,627,480; 3,669,620; 3,869,299; 4,244,933; 4,824,654; 5,230,734; and 5,232,678; and in Japanese Patent No. 09181286; 91210498; 7894920; 63256514; 8889705; and 2302317. These methods do not involve a planting material.

Precipitated calcium carbonate is generally preferred over calcium carbonate in the production of paper as a filler or coating pigments since the morphology, size, and size distribution of the particles can be controlled. These characteristics are important when used in the papermaking industry. The demand for precipitated calcium carbonate has increased. Ideally, the speed of production to produce the precipitated calcium carbonate should be increased to meet this demand. One of the problems with the current precipitation processing of aragonite is thought to be related to the nucleation phenomenon since it is difficult to control the nucleation behavior. If the nucleation rate is very low, the batches of product may be inconsistent with respect to the percentage of aragonite in the precipitated product, and very few cores are produced resulting in large elongated crystals that require a grinding process in order to obtain the desired size and particle size distribution for papermaking applications. The inherent, elongated form of the aragonite already causes a problem with respect to at least the viscosity, and the elongated crystals, large as a result of a "very low" nucleation rate, compose the problems of viscosity and pH associated with The precipitation processing of today's form of calcium carbonate aragonite. Also, if the nucleation rates are very low, the subsequent growth of the crystals will produce a coarse particle. It is known that seeding is an effective method and commonly used to control nucleation. This technique is well known in the technique of crystal growth, in general, and is also known in the preparation of precipitated calcium carbonate. US Pat. No. 3,197,322 describes such a seeding process for the precipitation of calcium carbonate. This process involves (a) the formation of an aqueous suspension by mixing several parts of calcium carbonate (CaC03) crystals from a previously prepared batch; calcium chloride (CaCl2); and calcined deactivated dolomite which is a mixture of magnesium oxide (Mg (OH) 2) and calcium oxide (Ca (OH 2)); (b) carbonating the aqueous suspension; and (c) filtering, washing, and pulping the product. The seed mixture which is a pre-carbonated mixture containing CaC03 crystals is made according to the same procedure as the seeded mixture. The final suspension consists of between 15 to 80 weight percent of aragonite having an average size between 0.8 and 1.2 microns, between about 25 and 40 percent smaller than 0.6 microns, at least 13 weight percent more than 2 microns and has a viscosity of about 4.0 poises at room temperature when diluted to approximately 65 percent total solids. These properties and / or characteristics may be desirable for paper coating, however, in some applications that require "high gloss", this product is not suitable since only about 50 weight percent of the aragonite solids is less than 0.5 microns. The mass fraction of the crystals needs to be > 50% less than 0.5 microns for high gloss applications. Additional prior art methods that relate to the precipitation of aragonite through seeding are U.S. Patent 5,164,172 and Japanese Patent No. 04321515; 89167267; 04224110; and 81135220. Most of the descriptions of this prior art relate to methods for producing long aragonite needles for non-paper applications, and most involve the use of phosphoric acid prior to carbonation. The prior art methods for precipitating calcium carbonate in the form of aragonite with seed material have proved to be unsatisfactory, especially when used on the commercial scale since the product behavior of the different lots tends to be inconsistent; and the nucleation rates are generally very low, resulting in larger crystals since few nuclei are produced, which means that the final product has to be crushed. Since there are problems in the processes of the prior art, production and capital costs have increased to non-economic levels. Additionally, some types of limes used in the precipitation process fail to easily form aragonite nuclei. It is taught in the present that these various problems can be rectified by increasing the nucleation rate. If enough aragonite cores are generated early in the reaction, the reaction rates can be increased so that production and capital costs are reduced. An increase in the nucleation rate may result in a decrease in the size of the aragonite needles since the size is a function of the nucleation rate. The decrease in the size of the needles can mean that the aragonite does not need to be crushed, which, in turn, means that the suspension form of the product has a lower viscosity and a better controlled pH since it is known that the process of crushed tends to release lime which increases the viscosity and pH values of the suspension. Eliminating the crushing stage eliminates the need to recarbonate the product to counteract these negative effects carried out by the crushing. In this way, the precipitated calcium carbonate processing process can be shortened, which helps reduce production costs. It has been found that satisfactory results are obtained first in preparing a seed material through a precipitated calcium carbonate process involving carbonation, and using this seed material in a precursor process for the commercial scale production of an aragonite form. for use in a papermaking process. The present invention is directed to a method for the production on a commercial scale of calcium carbonate precipitated from fine-grained aragonite (CCP) when seeding with coarse-grained aragonite. For purposes of the present invention related to the invention, fine grain aragonite can be defined as having particles of mass fraction less than 0.5 μ greater than or equal to 50%, preferably 60 to 80 weight percent solids, and an average particle size between 0.3 and 0.5 μm, and preferably between 0.3 and 0.4 μm. Coarse-grained aragonite can be defined as having mass fraction particles less than 0.5 μ that are less than 50% and an average particle size greater than 0.5 μ. The method of the invention first involves the production of coarse-grained seed material having a Blaine surface area of less than 30,000 cm 2 / g. This coarse-grained seeding material is produced by interrupting the supply of carbon dioxide to the lime slurry early in the reaction, after production of about 0.1 to about 0.6 g / L min. of calcium carbonate for a short period of time (1 to 5 minutes) and then continue the carbonation step at a reaction rate of from about 0.1 to about 0.6 g / L min. This coarse-grained seed material has a Blaine surface area of less than 30,000 cm 2 / g, the solids of which are 40 to 70 weight percent of aragonite. This sowing material is then added to the subsequent batches of slaked lime suspensions at about 1 weight percent based on the weight of the suspension. These subsequent batches later become the seeded material. The carbonation of the seeded lots is carried out at significantly higher reaction rates of up to approximately 1.8 g / L min. on the commercial scale that results in a fine-grained aragonite product. The concentration of the calcium oxide lime (CaO) in the suspension may be approximately 120 g / L, but concentrations as high as approximately 200 g / L are possible. The quench temperature can be about 38 ° C to about 90 ° C or about 120 ° C to about 210 ° F (99 ° C); and the carbonation temperature throughout the carbonation step can be about 50 ° C or 120 ° F. The final fine-grained aragonite product has a weight percent of aragonite greater than about 90, an average particle size between about 0.30 to about 0.5 microns, a particle size distribution where about 70 weight percent is less than 0.5 microns (esd), and a surface area of Blaine greater than 35,000 cm2 / g. There are several advantages obtained by the method of the invention. These are: (1) a high percentage of aragonite is produced in the final seeded product, that is, more than 90% of the solids in the suspension is aragonite. 2) Higher reaction rates are achieved, which results in an increase in production speeds, which, in turn, lowers capital and operating costs. 3) shorter aragonite needles are produced. The shorter needles reduce the viscosity of the suspension making post-crystallization processing easier, such as sieving, pumping, water removal. More importantly, shorter needles eliminate the need to grind the final product to achieve the desired particle size characteristic for paper applications. Eliminating the grinding step also minimizes the problems that may be encountered in the non-sown production of aragonite of the prior art.

While the nature of the problems of the prior art is not fully understood, it is theorized that the grinding step with sand can liberate the free lime that is present in all the precipitated calcium carbonates at levels of tenths of percent by weight that it leads to the pH of the suspension to 10 to 12 by the release of hydroxide ions, and the free lime tends to increase the viscosity of the suspension at a Brookfield viscosity of about 1000 cps by bridging the molecules of the dispersing agent in suspension with the calcium ions. The pH values of 10 to 12 for the suspension may be unacceptable for most paper applications that generally require a pH of 9 to 10, and the high viscosity value may render the suspension pumpable for storage and / or storage. transportation purposes. The present invention is directed to a process for producing calcium carbonate precipitated from coarse-grained aragonite, for use as a seeding material, the steps comprising: quenching the calcium oxide lime in a continuous quenching process to produce a suspension of slaked lime; Carbonate the suspension for a relatively short period of time to initiate the reaction, discontinue the supply of carbon dioxide gas to the suspension for a period of time to allow the nucleation of the aragonite crystals, and continue the carbonation of the suspension until the calcium carbonate is again precipitated at a predetermined reaction rate and until the pH of the suspension is less than about 8.5. the invention further relates to a coarse grain product having about 30 to about 70 weight percent aragonite solids and a Blaine surface area of less than about 30,000 cm 2 / g to be used as seed material. The invention is still further directed to a process for producing a fine-grained aragonite product wherein the steps comprise introducing a coarse-grained product into a suspension of calcium carbonate material to be seeded, and carbonating the suspension until the precipitate is precipitated. calcium carbonate at a reaction rate approximately equal to or greater than the reaction rate produced by the coarse-grained aragonite product. The invention is still further directed to a fine-grained aragonite product having an average particle size of less than 0.50 microns, a particle size distribution where about 70 weight percent is less than 0.5 microns of equivalent spherical diameter, a percent by weight of aragonite solids greater than 90, and a surface area of Blaine greater than 35,000 cm 2 / g. These and other objects of the present invention will be better appreciated and understood by those skilled in the art from the following description of the invention and the claims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic flow chart of the process for producing seed material used in the seeded lots. Figure 2 is a schematic flow diagram of the process for producing batches seeded using the planting material. Figure 3 is a SEM photo of product No. CN7049 of seeded lot. The present invention is directed to the production of aragonite through a precipitated calcium carbonate process by using a seeding technique. The total process is divided into two parts: 1) the production of seeded material (ie, precipitated calcium carbonate used to plant subsequent batches); and 2) batches of seeded product (lots that receive the planting material before the carbonation stage). In the examples herein, "concentrated calcium quicklime" is used. This "concentrated calcium quicklime" has available calcium oxide greater than 92%, that is, more than 92% of the calcium oxide is in the reactive form. In the description of the invention, the precipitated calcium carbonate may be in abbreviated form and appear as "CCP". In the examples, the addition of sowing is based on the total volume or weight of the seeded batch, and sufficient sowing is added to the material to be sown to achieve 1 weight percent of the material to be sown. For example, if the lot to be planted is 16,000 gallons with 20% solids, then 160 gallons of planting material with 20% solids have been added to the lot to be planted. Therefore, the amount of the planting material and the percentage of solids used in the lots to be planted is approximately 1 weight percent of the total volume or weight of the suspension of the batch to be seeded in the same percentage of solids. If the percentage of solids from the planting lot and lot to be planted are different, then the proportion of the percentage of solids can be used to adjust the volume of the sowing added to the lot to be planted. Production of the planting material General procedure The general procedure for making the planting material in Figur 1 is shown, and is as follows: (1) turning off about 145 to about 200 grams / liter, preferably 180 grams / liter, (expressed as Calcium carbonate equivalents where CaC03 = Ca (OH) 2) of quicklime calcium oxide (CaO) at approximately 120 ° F (49 ° C) to 0.74 about 210 ° F (99 ° C), preferably 180 ° F (82 ° C), in a continuous shutdown process, which is known in the art as being a continuous flow during the hydration reaction process opposite to a batch process. (2) Screen the slaked lime suspension (Ca (OH) 2) in a mesh of about 60 to about 120, preferably a mesh of about 120. (This is equivalent to an aperture size of about 250 to about 125 microns. ) This resulting suspension can have a content of "low solids" in the range of 12 to 20%. (3) Transfer this sifted suspension to a lime tank, and during this transfer heat the suspension to about 95 ° F (35 ° C) to about 140 ° F (60 ° C), preferably 120 ° F (149 ° C), when passing the suspension through a heat exchanger in such a way that the temperature of the suspension equals approximately the desired temperature of the carbonation stage, in which the desired temperature is determined by the type and size desired product (4) Carbonate the suspension in a reactor that is equipped with a stirrer when mixing the suspension and in which the agitator is equipped with a device that disperses the gas entering the bottom of the reactor. In the carbonation stage, the reaction is exothermic, which may tend to increase the temperature of the suspension slightly. The gas stream contains about 5 to 6.5% carbon dioxide in air, preferably 6.0%. the carbon dioxide gas is introduced into the lower part of the reactor for approximately 15 seconds at 6 minutes in order to initiate the nucleation of the aragonite and in sufficient quantities to produce a low reaction rate of from about 0.1 to about 0.7 g / L min., Preferably 0.45 g / L min. of calcium carbonate (CaCO3). This reaction rate can be measured by periodically measuring the concentration of calcium hydroxide by endpoint titration of phenoftalein with hydrochloric acid, where a pH of 8.3 indicates the end point of the reaction. The gas is discontinued for about 1 to 15 minutes, and then introduced back into the reactor in sufficient quantities to again produce a low reaction rate of from about 0.1 to about 0.7 g / L min., Preferably 0.45 g / L min. . of calcium carbonate (CaCO3). Prior to the carbonation step, the pH of the suspension may be about 11.5 to about 12.0, and this remains in this range until all solid Ca (OH) 2 is consumed. The pH then decreases rapidly to about 8.5 or about 8.3, as long as Ca (OH) 2 is consumed in solution. After the end point is reached, the carbon dioxide gas is still supplied in the reactor for an additional 10 to 60 minutes (over carbonation) in order to minimize the residual lime which may have from about 0.2 to about 0.7 percent in volume. weight of solids. The "over carbonation" is defined herein as that period of time in which a mixture of carbon dioxide gas / air is still supplied in the suspension after the pH of the suspension reaches at least 8.3, indicating that the end point of the CCP reaction has been reached. (5) Transfer the precipitated calcium carbonate suspension to a batch storage tank. (6) Sieve the suspension through a 325 mesh screen (approximately 45 micron size). (7) Transfer the sifted suspension to a storage tank for subsequent use in the commercial scale production of aragonite. This resulting seed material in suspension form contains between about 15 to 20 weight percent dry solids, based on the weight of the suspension.

These solids are between 35 and 70 weight percent of aragonite, as determined by X-ray diffraction analysis (XRD), with the rest of the solids being up to calcite of coarse crystallites. Knowing the percentage of aragonite in this planting material is important to determine the amount of sowing necessary to be added to the subsequent batches of product to be planted in order to achieve the desired final product characteristics. It is believed herein that the consistency of the characteristics of the final product, such as percent by weight of aragonite, particle size, and particle size distribution of the final aragonite, depends to a greater extent on the size, the amount of the percentage by weight, the reaction rate, and the percentage by weight of the solids in this planting material. Lots of commercial-scale planting material The above procedure is performed by examples 1-5. 'Example 1 Calcium oxide (CaO) is turned off at 180 grams / liter at 180 ° F (82 ° C) in a continuous shutdown process. The resulting suspension is screened in a 60 mesh, and transferred to the lime tank while adjusting the temperature of the suspension to the initial carbonation temperature of 120 ° F (49 ° C) when passing the suspension through a heat exchanger. The suspension is then carbonated at 120 ° F (49 ° C) for 300 seconds using a gas stream containing 6.5% carbon dioxide in air or using an amount of C02 to produce 0.46 g / L min. of CaCO3, then cut for 15 minutes. The carbonation is resumed using a sufficient amount of gas to produce another 0.46 g / L min. of CaCO3, and continue until the pH of the suspension decreases below 8.5, indicating that the end point of the reaction has been reached. At this time, over-carbonation of the suspension is performed for 60 minutes. The CCP batch is transferred to the batch storage tank, sifted through the 325 mesh screen, and then transferred to the storage tank. The seed material produced in this way has a Blaine surface area of 33,000 cm 2 / g and has 16.2 weight percent solids, based on the weight of the suspension, with 65 weight percent of the solids that are aragonite with the rest that is calcite. This product is identified as CN6359 in Table 1.

Example 2 The same procedure is performed for this example. CaO is turned off at 158 g / liter at 180 ° F (82 ° C) in a continuous shutdown process, and then screened in a 100 mesh. The temperature of the suspension is brought to 120 ° F (49 ° C). In the reactor, the suspension is carbonated at 120 ° F (49 ° C) for 15 seconds using a stream of gas containing 5.0% carbon dioxide in air or using a sufficient amount of CO2 to produce 0.52 g / L min. of CaC03. After 15 seconds, the C02 is cut off for one minute, after which it is restarted again in an amount sufficient to produce 0.52 g / Liter min. of CaC03. This carbonation step continues until the pH of the suspension decreases below 8.5 indicating that the end point of the reaction has been reached. Overloading of the suspension is performed for 60 minutes. The seed material produced in this way has a Blaine surface area of 30,300 cm 2 / g, and has approximately 14.4 weight percent solids, based on the weight of the suspension, with 67 weight percent of the solids that It's aragonite. This product is identified as CN7047 in Table 1. Example 3 This example follows the same procedure as Example 1. The CaO is turned off at 150 g / liter at 180 ° F (82 ° C) in a continuous shutdown process, and then sieve in a 100 mesh. The temperature of the suspension is increased to 122 ° F (50 ° C). In the reactor, the suspension is carbonated at 122 ° F (50 ° C) for 15 seconds using a stream of gas containing 5.0% carbon dioxide in air or using an amount of CO 2 sufficient to yield 0.53 g / liter min. of CaC03. The carbonation is cut off for 3 minutes, and then resumed using a sufficient amount of gas to produce 0.53 g / L min. of CaCO3, and continues until the pH of the suspension reaches below 8.5. The over carbonation of the suspension is carried out for another 60 minutes. The seed material produced in this way has a Blaine surface area of 24,600 cm 2 / g and has 13.7 percent solids, based on the weight of the suspension, with 48 percent by weight of the solids that are aragonite. This product is identified as CN7196 in Table 1. Example 4 This example follows the same procedure as Example 1. The CaO is turned off at 146 g / liter at 120 ° F (49 ° C) in a continuous shutdown process, and then sieved in a 100 mesh. The temperature of the suspension is brought to 124 ° F (51 ° C). The suspension is carbonated at 124 ° F (51 ° C) for 40 seconds using a gas stream containing 4.0% C02 in air or using an amount of C02 to produce 0.56 g / liter min. of CaC03. The carbonation is cut for 10 minutes, and then resumed until 0.56 g / L min is produced. of CaC03.

Carbonation is continued until the pH decreases below 8.5. The over carbonation of the suspension is carried out for 60 minutes. The seed material produced in this way has a Blaine surface area of 24,400 cm 2 / g and has 13.4 percent solids, based on the weight of the suspension, with 44 percent by weight of the solids that are aragonite. This product is identified as CN7816 in Table 1. Example 5 This example follows the same procedure as the Example 1. The CaO is turned off at 150 g / liter at 180 ° F (82 ° C) in a continuous shutdown process, and then screened in a 60 mesh. The temperature of the suspension is brought to 118 ° F. The suspension is carbonated at 118 ° F for 1 minute using a stream of gas containing 5.0% C02 in air or using an amount of C02 to produce 0.54 g / liter min. of CaCQ3. The carbonation is cut off for 5 minutes, and then resumed until 0.54 g / L min. of CaC03. Carbonation is continued until the pH of the suspension reaches below 8.5. The over carbonation is carried out for 60 minutes. The seeding material produced has a Blaine surface area of 20,300 cm 2 / g and has approximately 13.7 weight percent solids, based on the weight of the suspension, with 34 weight percent of the solids being aragonite. This product is identified as CN7629 in Table 1.

The properties of these five seed lots are summarized in Table 1. All batches are made using variations of the same method in which C02 is cut shortly after the reaction is initiated, and then the reaction is restarted after about how many minutes. Table 1 - Data from the aragonite seed lot (commercial scale) Lot No. Percent in Concentration Method Area Speed weight of (g /) reaction (g / L aragonite surface min.) Blaine (XRD) (cm2 / g) CN6359 65 180 0.46 3, 000 300 S, 6.5%, 15 m.

CN7047 67 158 0.52 30,300 15 S, 5.0% 1 m.

CN7196 48 150 0.53 24,600 15 S, 5.0%, 3 m.

CN7816 44 146 0.56 24,400 40 S, 4.0%, X0 m.

CN7629 34 150 0.54 20,300 1 S, 5.0%, 5 ra. The notation in the "Method" column in Table 1, for example, "300 s., 6.5%, 15 m" for lot No. 6359, means that at the beginning of the carbonation stage the C02 is at the 30 seconds at a concentration of 6.5%, and then cut for 15 minutes, and then restart at a concentration of 6.5%. It is observed that the weight percent of the aragonite used for the sowing of the batches of product in both laboratory experiments and on the commercial scale has a marked effect on the percent of aragonite in the final seeded product. Therefore, it is believed that it is important to have some method to estimate the percentage of aragonite in the material to be planted at least when it is produced commercially. The standard quality assurance test for aragonite at the plant level is the Mohr salt test where ammonium sulfate is added to the final product and the change in color from white to green is used to indicate the presence of aragonite. . As it is currently used, this is a qualitative technique. A semiquantitative method taught to be already useful in the plant comes from the observation that there is a relatively good correlation between the percentage of aragonite in the planting material and its surface area. These values can be plotted in Table 1, that is, the percent by weight of aragonite (Column 2) and the surface area of Blaine (Column 5) to produce a linear relationship. This linear relationship, based on the weight percent of aragonite and the Blaine surface area of the siemhra material, can then be used to determine the percent of aragonite needed to sow subsequent batches. It is taught that this correlation is suitable for production purposes, particularly in view of the fact that both the weight percent of the CaO solids and the reaction rates in the previous examples for the batches of planting material are not fixed. This linear relationship allows the percent of aragonite in the planting material to be estimated to be within 5% to 6% in order to better control the actual amount of planting material added to the subsequent seeded lots. Until this correlation of the surface area of Blaine and the percent of aragonite obtained in the seed material of Examples 1-5 above is understood, the amount of the seed material used to produce the seeded product is set at 1 percent by weight. weight of the total weight of the suspension of the material to be sown, as explained hereinabove. Examples 6-12 below employ a seeding material whose amount is 1 weight percent of the total weight of the suspension of the batch to be seeded. Production of seeded product General procedure The general procedure for making the product seeded from the seed material of Examples 1-5 is shown in Figure 2, and is as follows: (1) Shut off about 110 to about 4-80 grams / liter , preferably 160 grams / liter, (expressed as calcium carbonate equivalents) of calcium oxide lime (CaO) at about 120 ° F (49 ° C) to about 180 ° F (82 ° C), preferably 120 ° F (49 ° C), in a continuous shutdown process. (2) sieving the slaked lime suspension (Ca (OH) 2) in about 60 mesh to about 120 (250 to 125 microns open size), preferably a mesh of about 120. (3) Transfer this sifted suspension to a lime storage tank, while heating the suspension to about 95 ° F (35 ° C) to about 140 ° F (60 ° C), preferably 120 ° F (49 ° C) ). This heating step is achieved by passing the suspension through a heat exchanger during its transfer to the lime storage tank. (4) transferring the suspension to a reactor, and simultaneously introducing the seed material in amounts of from about 0.1 to about 5.0 percent by weight, preferably about 1 percent by weight, based on the total weight of the suspension of the material to be planted. It is known that the higher the percentage of aragonite in the sowing material, the smaller the particle size and the higher the percentage of aragonite in the final sown product. (5) Carbonate the suspension in the reactor equipped with an agitator to mix the suspension and equip the agitator with a device that disperses the gas entering the bottom of the reactor. The concentration of the carbon dioxide gas in the air in the gas stream is about 10 to 20%, and preferably 18%. The amount of the gas mixture introduced is sufficient to produce about 0.1 to about 2.0 g / L min., Preferably 1.5 g / L min. of CaCO3 and is pumped into the lower part of the reactor according to well-known practice. The carbonation continues until the pH of the suspension decreases from 11.5 - 12.0 to less than 8.5, indicating that the end point of the reaction has been reached. The suspension is then carbonated for approximately 60 minutes, to minimize the amount of residual lime in the suspension. (6) Transfer the CCP suspension to a batch storage tank. (7) Sieve the CCP suspension through a 325 mesh screen (45 microns open size). (8) Transfer the suspension to a storage tank for future use in the purpose of papermaking. The commercial-scale batches of the sown aragonite suspension can contain 10.3-14.5 weight percent solids, based on the total weight of the axle suspension which is more than 85 weight%, and preferably more than 90 weight percent It's aragonite. This can be determined by X-ray diffraction analysis (XRD). The rest of the solids are made of thick glass calcite. Aragonite has an average particle size of less than 0.5 microns, preferably about 0.3 to 0.4 microns, and has a mass fraction where more than 50%, preferably more than 70%, is less than 0.5 microns. Lots planted on a commercial scale The above general procedure is carried out for Example 6-12. The process data are shown in Table 2, and the mineralogical data of the aragonite batch are shown in Table 3. In the following Examples 6-12, the amount of seeded material introduced into the material to be seeded is 1 percent. by weight of the total weight of the suspension to be sown since the linear relationship of the percentage of aragonite and the surface area of Blaine of the sowing material has not been realized at the time of the experimentation. Example CaO is turned off at 156 g / L at 180 ° F (82 ° C) in a continuous shutdown process. The resulting suspension is screened in a 100 mesh, and while it is transferred to the lime storage tank its temperature is adjusted to the initial carbonation temperature of 122 ° F (50 ° C) by passing it through the heat exchanger. The suspension is transferred to the reactor. The seed material is introduced in an amount of 1 weight percent of the total weight of the suspension of the material to be sown in the upper part of the reactor at the same time as the suspension to be sown in the reactor is introduced. The sowing material is that of Lot No. CN7047 of Table 1 which contains 14.4% solids of which 67 weight percent is aragonite. Carbonation is carried out at an initial temperature of 122 ° F (50 ° C), increasing to approximately 130 ° F (54 ° C) during the course of the reaction. The concentration of carbon dioxide gas is approximately 13%, and in an amount which is sufficient to produce 0.43 g / L min. of CaC03. Carbonation is continued until the pH decreases from about 11.5 -12.0 to less than 8.5 indicating that the end point of the reaction is reached, which takes 360 minutes. The carbonation of the suspension is continued for an additional 60 minutes. The CCP lot is transferred to the batch tank, sifted through a 325 mesh screen and transferred to a storage tank. The final seeded product produced in this way has a Blaine surface area of 46,700 cm 2 / g. The suspension has 14.5 weight percent solids, of which 93 weight percent is aragonite. The average non-crushed particle size is 0.33 microns e.s.d., and the mass fraction is less than 0.5 microns e.s.d. as measured by Sedigraph it is 77%. This is identified as Lot No. CN7048 in Tables 2 and 3. Example 7 This example is carried out with the same procedure as Example 6. The CaO is turned off at 150 g / L at 180 ° F (82 ° C). ) and sieved in a 100 mesh. The temperature of the lime suspension is adjusted to 123 ° F (50.5 ° C). The seed material is introduced in an amount of 1 weight percent of the total weight of the suspension to be seeded in the reactor. The planting material of batch No. CN7047 of Table 1 containing 14.4% solids of which 67 percent by weight is aragonite. Carbonation is carried out at an initial temperature of 123 ° F (50.5 ° C), increasing to that of 130 ° F (54 ° C), and using a C02 concentration of 13% in an amount sufficient to produce 1.6 g / L min. of CaC03. Carbonation continues until the pH of the seeded suspension is less than 8.5 which takes 141 minutes. Over carbonation is carried out for an additional 60 minutes after the pH of the suspension is less than 8.5. The final seeded product has a Blaine surface area of 45,800 cm2 / g. The suspension of the final product is 15 weight percent solids, based on the total weight of the suspension of the product, of the solids, 97 weight percent is aragonite. 0.30 microns e.s.d. and the mass fraction is less than 0.5 microns e.s.d. As measured by Sedigraph it is 85%. This product is identified as CN7049 in Tables 2 and 3. Example 8 The CaO is turned off at 150 g / L at 180 ° F (82 ° C) and sieved in a 100 mesh. The temperature of the lime suspension is adjusted at 122 ° F (50 ° C), and transferred to the reactor. The nucleation of the aragonite in the suspension is initiated by the sowing material of batch No. CN7196 of Table 1 in the suspension of lime to be sown. This seed lot has 13.7 weight percent solids, of which 48 weight percent is aragonite and is introduced in an amount of 1 weight percent of the total weight of the suspension to be sown. Carbonation is carried out at an initial temperature of 122 ° F (50 ° C), increasing to 130 ° F (54 ° C), and using a C02 concentration of 13% in an amount to produce 0.82 g / L min . of CaC03. The pH is decreased to less than 8.5, which takes 183 minutes, and over carbonation is performed for an additional 60 minutes. The final seeded product has a Blaine surface area of 37,600 cm2 / g. The final seeded suspension contains 13.7 weight percent solids, based on the total weight of the sown suspension, of which 97 weight percent is aragonite. The average non-crushed particle size is 0.36 microns e.s.d. and the mass fraction is less than 0.5 microns e.s.d. As measured by Sedigraph it is 74%. This product is identified as CN7197 in Table 2. Example 9 The CaO is turned off at 116 g / L at 120 ° F (49 ° C) and sieved in a 100 mesh. The temperature of the suspension is adjusted to 122 ° F. (50 ° C), and transferred to the reactor. The nucleation of the aragonite is initiated by introducing the sowing material of batch No. CN7196 of Table 1 into the suspension of the lime to be sown. The amount of the planting material is 1 weight percent of the total weight of the suspension to be sown. This planting material has 13.7 weight percent solids, of which 48 percent by weight is aragonite. Carbonation is carried out at an initial temperature of 123 ° F (50.5 ° C), increasing to 130 ° F (54 ° C) °, and using a C02 concentration of 13% in an amount to produce 0.94 g / L min. of CaC03. The pH is decreased to less than 8.5, which takes 123 minutes, and over carbonation is performed for an additional 60 minutes. The final seeded product has a Blaine surface area of 41,000 cm / g. The final seeded suspension contains about 10.8 weight percent solids, based on the total weight of the suspension sown, of which 95 weight percent is aragonite. The average non-crushed particle size is 0.34 microns e.s.d. and the mass fraction is less than 0.5 microns e.s.d. As measured by Sedigraph it is 73%. This product is identified as CN7198 in Tables 2 and 3. Example 10 The CaO is turned off at 113 g / L at 120 ° F (49 ° C) and sieved in a 60 mesh. The temperature of the lime suspension is adjusted at 125 ° F (52 ° C), and then transferred to the reactor. The nucleation of the aragonite is initiated by introducing the planting material of batch No. CN7629 of Table 1 into the suspension of the lime to be sown. The amount of the planting material is 1 weight percent of the total weight of the suspension to be sown. This suspension of planting material has 13.7 weight percent solids, of which 34 weight percent is aragonite. Carbonation is carried out at an initial temperature of 125 ° F (52 ° C), increasing to 130 ° F (54 ° C), during the reaction, and at a C02 concentration of 13% in an amount to produce 0.99 g / L min. of CaC03. When the seeded suspension reaches a pH of less than 8.5, which takes 114 minutes, over carbonation is performed for an additional 60 minutes. The final seeded product has a Blaine surface area of 37,400 cm2 / g. The final seeded suspension contains 10.6 weight percent solids, the solids of which 93 weight percent is aragonite. The average non-crushed particle size is 0.41 microns e.s.d. and the mass fraction is less than 0.5 microns e.s.d. As measured by Sedigraph it is 65%. This product is identified as lot No. CN7630 in Tables 2 and 3. Example, .11. The CaO is turned off at 126 g / L at 120 ° F (49 ° C) and sieved in a 60 mesh. The temperature of the lime slurry is adjusted to 118 ° F (48 ° C), and transferred to the reactor . The nucleation of the aragonite is initiated by introducing the planting material of lot No. CN7629 into the suspension of the lime to be planted. The amount of the planting material is 1 weight percent of the total weight of the suspension to be sown. This suspension of planting material has 13.7 weight percent solids, of which 34 weight percent is aragsnite. Carbonation is carried out at an initial temperature of 118 ° F (48 ° C), increasing to approximately 130 ° F (54 ° C) during the reaction, and using a C02 concentration of 18% in an amount to produce 1.78 g / L min. of CaC03. When the pH is reduced to less than 8.5, which takes 71 minutes, over-carbonation of the sowed suspension is performed for an additional 60 minutes. The final seeded product has a Blaine surface area of 44,700 cm / g. The final seeded suspension contains 11.7 weight percent solids, based on the total weight of the suspension sown, the solids of which 89 weight percent is aragonite. 0.32 micron e.s.d. average non-crushed particle size. and the mass fraction is less than 0.5 microns e.s.d. As measured by Sedigraph it is 70%. This product is identified as CN7631 batch No. in Tables 2 and 3. Example 12 The CaO is turned off at 150 g / L at 120 ° F (49 ° C) and screened in a 60 mesh. The temperature of the lime suspension at 124 ° F (51 ° C) and transferred to the reactor. The nucleation of the aragonite is initiated by introducing the planting material of batch No. CN7816 of Table 1 into the suspension of the lime to be sown. The amount of the planting material is 1 weight percent of the total weight of the suspension to be sown. This suspension of planting material has approximately 13.7 weight percent solids, of which 44 percent by weight is aragonite. Carbonation is carried out at an initial temperature of 120 ° F (49QC), increasing to 130 ° F (54 ° C), during the reaction, and at a C0 concentration of 13% in an amount to produce 0.89 g / L min. of CaC03. When the pH of the sown suspension is reduced to less than 8.5, which takes 169 minutes, over carbonation is performed for an additional 60 minutes. The final seeded product has a Blaine surface area of 45,500 cm2 / g. The final seeded suspension contains 13.7 weight percent solids, based on the total weight of the suspension sown, the solids of which 93 weight percent is aragonium. The average non-crushed particle size is 0.4 microns e.s.d. and the mass fraction is less than 0.5 microns e.s.d. As measured by Sedigraph it is 69%. This is identified in Tables 2 and 3 as Lot No. CN7817.

TABLE 2 - Process data of the aragonite batch Lot No. Temp Concentration, Temp. From Vel. Time (g / L) off CF) carbonation elapsed reaction (pin) (° C) total initial (g / L CF) (° C). min) CN7048 156 180 (82) 122 (50) 0.43 360 CN7049 150 180 (82) 123 (50.5) 1.06 141 CN7197 180 (82) 122 (50) CN7198 116 120 (49) 122 (50) 0.94 123 CN7630 113 120 (49) 125 (52) 0.99 114 CN7631 126 120 (49) 11848) 1.78 71 CN7817 150 120 (49) 12451.5) 0.89 169 * excluding carbonation TABLE 3- Mineralogical data of the aragonite lot Lot number Percent of Size d? part. % < 0.5 μ (no aragonite surface area (XRD) Average μ (unground) ground e.s.d. of Blaine (cm2 / g) (XRD) e.s.d. CN7048 93 0.33 77 46,, 700 CN7049 97 0.30 81 45, 800 CN7197 0.36 37,, 600 CN7198 0.36 73 41,, 000 CN7630 93 0.41 65 37,, 400 CN7631 89 0.32 70 44,, 700 CN7817 93 0.40 69 45,, 500 These seven lots seeded with CCP containing aragonite are produced at the CCP plant of the transferee in Canton, North Carolina. The concentration is nominally fixed at 150 g / L of target for the first three batches and a shutdown temperature of 180 ° F (82 ° C). The initial carbonation temperature is nominally objective at 122 ° F (50 ° C). The following three batches are run at low solids and a low quench temperature in order to lower the viscosity at levels which may allow the product to be sieved better on a 325 mesh, and thereby improve the brightness. The production ratio and recovery / rejection of the suspension is better at lower viscosity values. Attempts are made to set the total reaction rate in batches CN7049, 7197 and 7198, however, considerable variation occurs in the reaction rates for these three samples. This is due, in part, to variations in the C02 concentration of the source, the source which is the flow gas of the lime kiln of the host paper mill where the C02 gas is impure, and also, in part, to increases in the viscosity of the suspension that reduces the efficiency of the reaction. The reason for this increase in the viscosity of the suspension for these three batches is complicated. Factors include temperature, surface area, particle size and conformation. The final aragonite product produced by the seeding method of the invention is typically observed to be present as "bundles" of 1 to 2 microns of agglomerated needles. The beams are easily separated during the removal of the water in the shorter needles (<1.0 microns) from which they are made, producing a product with an average particle size in the range of size 0.3 to 0.4 microns e.s.d. An example of these "beams" is shown in Figure 3 for lot No. CN7049. Arrow No. 2 indicates one of these "beams", and arrow No. 1 indicates a single needle which measures less than 0.5 microns on the 1.8 micron scale in the SEM photo of Figure 3. The first batch is run (CN7048) at a reaction rate similar to that used in the unseeded batches of Examples 1-5 for comparison purposes. These unseeded lots of the aragonite of Examples 1-5 produce a product in which the solids are 67% aragonite, the remainder being made of coarse-grained calcite (> 2.0 μ). The sown lots of Examples 6-12, in contrast, produce solids on an average that are approximately 95% aragonite as measured by XRD (Table 3). The comparison of the aragonite percentages in Tables 1 £. 3 seems to indicate that a consistent product can not be produced without sowing. The part of . Process precipitation for the seven seeded lots is under control, which is considered here as a necessary condition to produce a consistent product. The samples taken at 15 minute intervals are measured throughout the CN7028 reaction (aragchnite) using both XRD and Ca (0H) 2 titration. This provides a set of known CaC03 / Ca (OH) 2 ratio standards that indicate that XRD analyzes are accurate within 5% of most cases. Based on this discovery, it is decided that the use of X-ray diffraction, which is standard practice for determining the percentage of solids in mixtures, is a practical way to determine the percent by weight of aragonite in the products of the invention. In contrast to the case for the planting material, it seems that the surface area of the sown lot does not correlate with the% of aragonite in the product. Therefore, knowing the surface area of Blaine 'does not appear to be an' adequate quality control measure for 'production purposes. Therefore, a useful minimum target of a Blaine surface area of 30,000 cm 2 / g for the planting material, and a Blaine surface area of 38,000 cm 2 / g for the sown product can be assumed. The percentage of aragonite in the solids seems to be associated more closely with either the quench temperature or the reaction rate. The limited dependence of the reaction rate on other product characteristics indicates that there is little or no harmful effect with the increase in the reaction rate in seeded lots, a matter of considerable importance for capital costs and production speed. That is, higher reaction rates do not degrade product characteristics and, therefore, behavior. Faster reaction speeds equal to higher production where two as many tons can be produced. With reference again to the material sown in the Table 2, the variation of% of aragonite with quench temperature may be of importance since the latter seems to correlate with the parameters of particle size. Two of the batches that are turned off at 180 ° F (82 ° C) produce a product that has 97% aragonite, which is considered co or that is considerably "pure". Those turned off at 120 ° F (49 ° C) produce a less pure product, although only marginally. This change in the shutdown temperature to 120 ° F (49 ° C) is made in an attempt to see if the shutdown temperature affects the brightness of the product. It is shown that the shutdown temperature above 180 ° F (82 ° C) does not increase the brightness of the product by approximately 0.7 gloss units (TAPPI). Different quenching conditions can also have an effect on the nucleation rates of aragonite, since the surface area of the slaked lime particles is changed. A positive correlation between the percent by weight of aragonite and% < 0.5 μ, seems to reflect the fact that a higher surface area of slaked lime results in higher nucleation rates, producing a purer product with a finer particle size. Since the difference in% aragonite of the seeded material of Tables 2 and 3 is minimal, it is believed that the quench temperature can be manipulated to adjust the particle size within a narrow range. The concentration of solids of Examples 6-12 appears to have an effect on the characteristics of the product, although not as pronounced as the quench temperature. It seems that the combination of low shutdown temperatures, low solids, and low percentages of planting material to be added to the material to be planted could be more effective in swelling the seeded product, concentrated solids, and high percentages of the added planting material It can be more effective to make the product finer. - The% by weight of the sowing material added to the seeded lots also seems to correlate with the particle size, and is a variable that can be easily manipulated to control the size of the control product. The thing to be noticed is that the variables can be changed in the process of the intention to produce the desired characteristics of the final seeded suspension and, in this way, the final sown product. The above examples are illustrative of the invention, and are not considered to be limited to the precise embodiments described and shown. While the present invention has been particularly indicated in terms of specific embodiments thereof, it will be understood in view of the present disclosure that numerous variations on the invention are now allowed by those skilled in the art, variations that reside within the scope of the invention. of the invention. Accordingly, the invention is broadly construed, and is limited only by the scope and spirit of the claims now appended hereto.

Claims (1)

1. CLAIMS 1. A process for producing calcium carbonate precipitated with coarse-grained aragonite, for use as a planting material, the stages characterized because they comprise: quenching calcium oxide lime (CaO) at approximately 120 ° F (49 ° C) ) at approximately 210 ° F (99 ° C) in a continuous shutdown process to produce a slaked lime slurry; sieving the slaked lime suspension in a mesh of about 60 to about 120; heat the sifted suspension at about 95 ° F (35 ° C) to about 140 ° F (60 ° C); Carbonate the suspension at a reaction rate of approximately 0.1 g / L mi. at about 0.6 g / L min; discontinuing the supply of the carbon dioxide gas to the suspension for a period of time to allow the subsequent nucleation of the aragonite crystals; and continue to carbonate the suspension until the calcium carbonate is again precipitated at a reaction rate of approximately 0.1 g / L min. Approximately 0. 6 g / L min. and also until the pH of the suspension is less than about 8.5 2. A process according to claim 1 characterized in that it further comprises: screening the resulting suspension through a 325 mesh to produce the coarse-grained aragonite. 3. A process in accordance with the claim 1 characterized in that it further comprises: when the suspension is carbonated, use carbon dioxide gas in a concentration of about 5.0% to about 7.0%. 4. A process in accordance with the claim 1, characterized in that it further comprises: in the quenching step, using about 145 to about 210 grams / liter of the quicklime of calcium oxide (expressed as CaC03 equivalents). A coarse grain product produced according to the process of claim 1, characterized in that it is about 30 weight percent to about 70 weight percent of aragonite solids and a surface area of less than about 30,000 cm 2 / g . 6. A process for producing a fine-grained aragonite product, characterized in that the steps comprise: introducing the coarse-grained product of claim 5 into a suspension of calcium carbonate material to be seeded, and carbonating the suspension until the calcium carbonate precipitates at a reaction rate approximately equal to or greater than the reaction rate for the coarse-grained aragonite product. 7. A fine-grained aragonite product produced according to the process of claim 6, characterized in that it has an average particle size of less than 0.50 microns, a particle size distribution where about 70% by weight are less than 0.5 microns equivalent spherical diameter, one percent by weight of aragonite solids greater than about 90, and a surface area of Blaine greater than 35,000 cm / g. 8. A process for producing a fine-grained aragonite product characterized in that the steps comprise: quenching the calcium oxide lime at about 100 ° F (38 ° C) to about 210 ° F (99 ° C) on a continuous shutdown process to produce a lime suspension off; sieving the slaked lime suspension in a mesh of about 60 to about 120; heating the sifted suspension between about 95 ° F (35 ° C) to about 140 ° F (60 ° C); transferring the suspension in a carbonator and at the same time introducing a coarse-grain seed aragonite material into the carbonator in an amount from about 0.1 to about 5.0 weight percent of the total weight of the suspension; and carbonating the suspension until the calcium carbonate is precipitated at a reaction rate of from about 0.1 to about 2.0 g / L min. and until the pH of the suspension is less than 8.5. 9. A process according to claim 8 characterized in that it further comprises: sieving the resulting suspension through a 325 mesh. 10. A process according to claim 8 characterized in that it also comprises, when the suspension is carbonated, use carbon dioxide gas at a concentration of about 10% to about 20%. 11. A process according to claim 8, characterized in that it further comprises: in quenching the calcium oxide lime, using approximately 110 to approximately 200 grams / liter of the quicklime calcium oxide (expressed as CaC03 equivalents) ). 12. A process according to claim 8 characterized in that it further comprises: introducing the sowing material of the coarse-grained aragonite into the suspension to be sown in an amount of about 1.0 weight percent of the total weight of the suspension to be planted. 13. A fine-grained aragonite product produced in accordance with the process of claim 8, characterized in that it has one percent by weight of aragonite solids greater than 90, an average particle size less than 0.5 microns, and a of particle size where approximately 70 percent by weight are less than 0.5 micron esd 14. A product according to claim 12 characterized in that the seeded material has a surface area of Blaine greater than 35,000 cm2 / g. 15. A process for producing coarse-grained aragonite precipitated calcium carbonate, for use as a seeding material, characterized in that the steps comprise: quenching the calcium oxide lime in a continuous quenching process to produce a lime slurry. off; Carbonate the suspension for a relatively short period of time to initiate the reaction; discontinuing the supply of carbon dioxide gas to the suspension for a period of time to allow nucleation of the aragonite crystals; and continuing to carbonate the suspension until the calcium carbonate is again precipitated at a predetermined reaction rate and until the pH of the suspension is less than about 8.5. 16. A process for producing a fine-grained aragonite product, characterized in that the steps comprise: introducing the coarse-grained product of claim 15 into a suspension of calcium carbonate material to be seeded; and carbonating the suspension until the calcium carbonate precipitates at a reaction rate equal to or greater than the reaction rate for the coarse-grained aragonite product. 17. A coarse grain product characterized in that it has about 30 to about 70 weight percent aragonite solids and a Blaine surface area of less than about 30,000 cm 2 / g. 18. A fine-grained aragonite product characterized in that it has an average particle size of less than 0.50 microns, a particle size distribution where about 70% by weight is less than 0.5 microns of equivalent spherical diameter, and one percent by weight of aragonite solids greater than 90. 19. A product according to claim 18 characterized in that the seeded material has a surface area of Blaine greater than 35,000 cm2 / g. SUMMARY OF THE INVENTION Precipitated calcium carbonate with fine-grained aragonite is produced on a commercial scale by seeding precipitated calcium carbonate with coarse-grained aragonite. After producing 0.1 g / L min. at 0.6 g / L min. of calcium carbonate, the coarse-grained seed material is produced by interrupting the supply of carbon dioxide to the lime slurry before the reaction to allow the subsequent nucleation of the crystals and then continue the supply of carbon dioxide at speeds of reaction of 0.1 g / L min. at 0.6 g / L min. This coarse-grained seed material has a surface area of Blaine that can be less than 30,000 cm2 / g. , the solids thereof have 35 to 70% by weight of aragonite and are added to subsequent batches as a suspension of approximately 1% by weight based on the total weight of the suspension of the material to be seeded. In the seeded lots, carbonation is carried out at reaction rates of up to 1.89 g / L min., On the commercial scale resulting in the fine-grained aragonite product. This final seeded product does not need to be ground, it has solids in which the weight percent of aragonite is greater than 90, it has an average particle size, between 0.30 to about 5.0 microns, a particle size distribution where about 60 to 70 % by weight is less than 0.5 microns in equivalent spherical diameter and a surface area of Blaine that can be greater than 35,000 cm2 / g.