Precipitated calcium carbonate (PCC) with defined grain size and grain size distribution

Abstract

Precipitated calcium carbonate (PCC) with a particle size distribution in which D 4.3 D 90 times 100 ≥ 59 and with an average grain size D 4.3 for (i) scalenohedral precipitated calcium carbonate (s-PCC) in the range of 1.5 to 5.0 µm; or (ii) rhombohedral precipitated calcium carbonate (r-PCC) in the range of 0.5 to 2.5 µm; or (iii) aragonitic precipitated calcium carbonate (a-PCC) in the range of 1 to 30 µm.

Description

[0001] The invention relates to precipitated calcium carbonate (PCC) with a defined grain size and defined grain size distribution. Technological background

[0002] A variety of processes are known in the art in which PCC is formed in an aqueous suspension of Ca(OH)2 (so-called lime milk) with the addition of CO2. The CO2 can be introduced into the lime milk in liquid form or as a gas via a suitable aeration system. With the aid of additives or seed crystals and with appropriately adapted process control, the desired PCC morphologies can be produced. On a large scale, the process is usually carried out in batch mode.

[0003] Modifications of PCC are sufficiently described in the literature. The term "modification" here refers to the family of industrially produced crystals of defined morphology, of which aragonites and calcites are particularly important, and vaterites and ikaites are far less important. Furthermore, special transitional forms exist, such as basic calcium carbonates or amorphous carbonates, which can also be isolated. Experts in the industry are generally familiar with the sometimes quite complex boundary conditions of their PCC plant, which can influence the modification, from numerous trials and failed attempts. Fundamental controlling parameters, such as the starting temperature at the beginning of a typical batch cycle in conjunction with the concentration of the lime milk introduced and the CO2 concentration, are determined in advance.Influences from the raw material are eliminated in long series of tests and, if necessary, controlled with various additives. It is also possible to adjust the degree of agglomeration of the PCC crystals by influencing the reaction conditions.

[0004] In recent years, there has been an increasing demand for technical properties of PCC, which relate to both an exact mean grain size (D4.3 value) and a defined grain size distribution for a specific PCC modification.

[0005] For example, in standard processes for scalenohedral precipitated calcium carbonate (s-PCC), a mean grain size D4.3 of approximately 2.1 to 2.2 µm is achieved. However, for formulations used to produce thermal paper, an s-PCC with a mean grain size D4.3 of 1.3 to 1.5 µm would be advantageous. An inappropriate mean grain size D4.3 can cause adverse consequences in the formulation used to produce thermal paper, such as thread breakage, altered viscosity behavior, and incomplete sizing.

[0006] Furthermore, s-PCC is used in the production of copy paper. Here, an s-PCC with an average grain size D4.3 of 2.8 to 3 µm would be particularly advantageous, as it allows for an increase in the filler content of the paper. This would reduce the proportion of the much more expensive pulp. However, more detailed preliminary studies have shown that as the D4.3 value increases, the grain size distribution also increases, which has a detrimental effect on some paper properties, such as tensile strength.

[0007] Rhombohedral precipitated calcium carbonate (r-PCC) is used as a filler for highly opaque thin-film papers. In this application, an average grain size D4.3 of 1.4 to 1.7 µm is desirable. Deviating grain sizes lead to a deterioration in opacity.

[0008] Another example is the use of small-particle PCC in the plastics industry, specifically as an additive for polycarbonates and polyamides. Here, there is a continuing need to use PCCs with a strictly limited particle size distribution between 0.2 µm and 1 µm. So-called oversized particles disrupt the manufacturing process, while undersized particles lead to an increased need for stabilizers. To date, no PCC has been found that can meet these requirements; commercially available PCCs in the appropriate range of a D4.3 value always contain disruptive particles of larger and smaller sizes.

[0009] In the applications described, it would therefore always be advantageous if the grain size distribution was very narrow.

[0010] However, there is currently no systematic approach to producing PCC with a defined grain size and defined (narrow) grain size distribution. This may be due to the complex interplay of numerous parameters. These include, for example, gassing parameters in conjunction with the CO2 concentration, the geodetic effective height of a reactor, and the dissipative energy input. Furthermore, in a typical batch reaction, which is the dominant industrial process, important process parameters change at every moment of the reaction with different characteristics, such as the pH value of the suspension to be gassed, the conductivity, the temperature, the ratio of free calcium ions to bicarbonate ions, the density of the suspension, and the viscosity of the suspension.Furthermore, the dynamics of these changes are not consistently constant; some parameters, such as pH and conductivity, only change noticeably towards the end of the batch cycle, but then change dramatically. Other parameters, however, show a quasi-linear change characteristic, such as the temperature increase, the change in density, and the viscosity. In addition, there are clearly two main phases during the reaction: a phase of preferential nucleation right at the beginning of the reaction, followed by a phase of preferential nucleation growth. As described in recent literature, nucleation does not proceed in a straight line, but rather involves a whole series of intermediate stages of widely varying morphologies.

[0011] For these reasons, knowledge about which of the numerous phenomena are decisive, controllable, and adjustable for the characteristic expression of the mean grain size (D4.3 value) and the width of the grain size distribution is very limited at best. Accordingly, there is hardly any indication of what measures a specialist should take in an existing PCC plant to achieve a product with a defined grain size and grain size distribution. Therefore, the goal has so far only been achieved erratically.

[0012] US 6,251,356 B1 proposes influencing the average grain size in a pressure reactor by varying the operating pressure. The grain size ratio is supposed to be narrower than in conventional processes. The process itself is technically very complex.

[0013] EP 1 222 146 B1 relates to a two-stage continuous process. In the first stage, a specific concentration of nuclei is generated. To achieve this, the volumetric flow rate of the lime milk is varied while maintaining a constant gas flow rate. In addition, the desired grain size is assumed to be influenced by introducing a fine lime milk with increased reactivity.

[0014] According to Gernot Krammer et al. (Part. Part. Syst. Charact. 19 (2002) 348-353), increasing CO2 concentration leads to a reduction in the mean grain size. An opposite effect of CO2 concentration on the mean grain size is described by Bo Feng et al., Materials Science and Engineering A 445-446 (2007) 170-179 "Effect of various factors on the particle size of calcium carbonate formed in a precipitation process."

[0015] The concentration of the milk of lime is another parameter that influences the mean particle size (Kralj et Brecivic from Croatica Chimica Acta, 80 (3-4) 467-484 (2007) "On Calcium Carbonates from fundamental research to application"). Higher solids contents in the milk of lime generally lead to coarser particles, while lower solids contents are said to lead to finer particles.

[0016] It is also known that during continuous operation of a PCC plant, aragonitic crystals gradually increase in size.

[0017] Pust (from dissertation “The production of precipitated calcium carbonate - PCC” RWTH Aachen, 1992) describes the influence of the slaking parameters in the production of quicklime on the size of the crystals later formed during the reaction.

[0018] EP 1 712 597 A1 describes the influence of the addition of various additives, such as Zn salts, Mg salts, and cationic and anionic dispersants on the particle size distribution.

[0019] There is therefore a continuing need for systematic solutions that enable the production of precipitated calcium carbonate of a defined grain size and defined grain size distribution using a given PCC plant. Summary of the invention

[0020] The limitations of the state of the art described above can be eliminated or at least reduced by the process for producing precipitated calcium carbonate (PCC) by introducing carbon dioxide into lime milk in a PCC plant. The PCC has a particle size distribution in which D 4.3D 90 times 100≥59, preferably ≥ 60, particularly preferably ≥ 62 and most preferably ≥ 65. Depending on the process, the average grain size D4.3 for (i) scalenohedral precipitated calcium carbonate (s-PCC) in the range of 1.5 to 5.0 µm, particularly preferably 2.0 to 4.0 µm, in particular 2.9 to 3.1 µm; or (ii) rhombohedral precipitated calcium carbonate (r-PCC) in the range of 0.5 to 2.5 µm, particularly preferably 0.8 to 2.2 µm, in particular 0.9 to 2 µm; or (iii) aragonitic precipitated calcium carbonate (a-PCC) in the range of 1 to 30 µm, more preferably 2 to 20 µm, in particular 2.5 to 15 µm.

[0021] The procedure includes the following steps: (a) recording all parameters of the PCC plant which make a significant contribution to the specific molar energy input during operation of the PCC plant, whereby the specific molar energy input corresponds to the energy input of the entire system required to introduce one mole of CO2 from the start of the reaction up to a conversion degree of 90% of the batchwise reaction; b) Determination of the mean grain size D4.3 as a function of the specific molar energy input; c) Determining the D 4.3D 90−ratio depending on at least one of the following parameters: CO2 concentration during the reaction, temperature of the milk of lime, fill level in the reactor of the PCC plant, and speed of a gassing stirrer of the PCC plant; and d) introducing carbon dioxide into the milk of lime in accordance with the specifications determined in steps b) and c).

[0022] There are different ways to describe the width or narrowness of the particle size distribution. In this case, the characterization is carried out using the ratio of D4.3D90. D90 means that 90% of the particles are volume-weighted smaller than the assigned value.

[0023] The mean particle size D4.3 is the arithmetic mean of a distribution across all particles. A very narrow particle size distribution is, for example, given when the D4.3 is 3.1 and the corresponding D90 is 5.0 µm. D 4,3D 90 times 100 ratio The resulting numerical value is 62. These figures apply to the formation of the so-called primary particles of the PCC process. Agglomerations at a later time are not taken into account.

[0024] Size determination can be performed using a laser diffraction particle sizer. All values ​​refer to a dispersed product to minimize agglomeration. In this case, all measurements were performed using either a Malvern particle size analyzer (Malvern 3000) or a Quantachrome particle size analyzer (Cilas 1064 L). Both instruments are widely used in the paper industry and consistently delivered very similar values.

[0025] The invention is based, among other things, on the finding that the specific molar energy input is the decisive controlling parameter for grain size. This value describes the sum of the specific energy input of the entire system required to introduce one mole of CO2 in the decisive part of the reaction, from approximately zero to 90% of the batchwise reaction. The energy input must be recorded regardless of its source. In a conventional PCC plant, contributions from the existing CO2 concentration of the gas, the volumetric specific gas throughput, the reactor fill level, the rotational speed of the frequency-controlled gasification turbine or agitator, and the power output of an upstream blower, if present, must be taken into account when determining the specific energy input.

[0026] In step a) of the process, the individual influencing factors of a PCC plant that make a significant contribution to the specific molar energy input are recorded. It has been shown that the cumulative contribution of all these influencing factors to the specific molar energy input is directly related to the desired grain size.

[0027] In step b), this relationship is therefore determined for the PCC plant in question. It has generally been determined that the grain size decreases with increasing specific molar energy input. Preferably, a linear relationship between the average grain size D4.3 and the specific molar energy input of the overall system is determined in step b). To specifically determine the relationship between the specific molar energy input and the grain size in a PCC plant, in practice, for example, a number of test settings are run with a predetermined specific molar energy input and the grain sizes are then determined. Both values ​​are plotted against each other, and a corresponding linear function is determined using a graphical evaluation method. The necessary energy input for a desired grain size can then be determined using this function.The influencing variables are then adjusted accordingly to represent this energy input.

[0028] Surprisingly, it was discovered that the specific energy input of the feed system is the decisive parameter for the grain size of the resulting crystals. It can be adjusted from any combination of the gassing parameters and the applied CO2 concentration to create the target value for the desired grain size. Thus, for the first time, it is possible to set specific specifications for the grain size of the PCC crystals based on basic knowledge of the gassing system's characteristics.

[0029] The relationship D 4.3D 90 by 100 For conventionally produced particle sizes in the range of approximately 2.8 µm and larger, the maximum value is 55 and is generally significantly smaller. This is due to spinodal demixing processes during the reaction, which lead to the continuous formation of smaller zones with higher or lower supersaturation than the average value. As a result, new, smaller nuclei form, while existing crystals continue to grow into larger crystals.

[0030] Only within the scope of the present invention has it been experimentally determined which influencing factors from the abundance of almost infinite possibilities are actually significant for the grain size distribution and are used in determining the respective desired ratio of D 4.3D 90 by 100 The following parameters were determined: CO2 concentration during the reaction, temperature of the lime milk, fill level in the reactor of the PCC plant, and speed of a gassing stirrer in the PCC plant (step c) of the process). The four measures can be applied individually or in any combination and, if properly considered, result in a reduction in the particle size distribution.

[0031] It is particularly preferred if, in step c), at the start of the reaction, the CO2 concentration corresponds to 0.5 to 0.8 times, in particular 0.6 to 0.7 times, the CO2 concentration at the end of the reaction and the CO2 concentration is increased continuously or stepwise. Therefore, if, as is almost always the case, a fixed value for the CO2 concentration of the source is known (e.g., for power plants between 10 and 11%, for kilns for the production of quicklime approximately 22 to 26%, for biogas plants between approximately 35 and 55%, or for synthetic gases approximately 98%), the starting concentration is reduced to a value that is 20 to 50%, in particular 30 to 40%, lower than the CO2 concentration of the source, and is increased continuously or stepwise to the maximum possible concentration until the end of the reaction. This can be achieved very simply by diluting with air. It was surprisingly found that this measure increased the value for D 4.3D 90 by 100 increased, especially to 59 or more.

[0032] Furthermore, it is preferred if, in step c), a temperature is specified at the start of the reaction at which the PCC is obtained in the respectively desired morphology, and this temperature is kept constant throughout the reaction or is reduced continuously or stepwise by up to 15°C, in particular by up to 10°C, until the end of the reaction. The starting temperature is therefore specified as the temperature at which the desired morphology can significantly form. In the case of s-PCC, the starting temperature is in the range from 25 to 45°C, in the case of r-PCC in the range from 8 to 25°C, and in the case of a-PCC in the range between 45 and 75°C. Although a specific starting temperature is also conventionally specified, the temperature is subsequently not regulated, and due to the exothermic nature of the reaction, a temperature increase is the result. In contrast, according to the invention, the temperature is kept constant or reduced stepwise or continuously by up to 15°C.It was surprisingly found that this measure increased the value for. D 4.3D 90 by 100 increased, in particular to 59 or more. Furthermore, it is preferred if, in step c), at the start of the reaction, the lime milk fill level is 50% to 80% of the working volume of the reactor and, after a nucleation phase, lime milk is added continuously or stepwise until the end of the reaction. At the start of the reaction, the reactor is therefore only filled to 50% to 80% of its working volume with lime milk of the required strength. At the earliest after the end of the so-called nucleation phase, which in practical operation for all morphologies is the case after about 20 minutes, lime milk is further added stepwise or continuously, distributed as evenly as possible over the entire T90 running time until the reactor has reached its nominal working volume. After the T90 time, i.e. the relevant reaction time in which 90% of the total conversion has been completed, no further refilling takes place.It was surprisingly found that this measure increased the value for. D 4.3D 90 by 100 increased, especially to 59 or more.

[0033] Finally, it is preferred if, in step c), at the beginning of the reaction, the speed of the gassing stirrer corresponds to 0.5 to 0.9 times, in particular 0.8 to 0.9 times the speed at the end of the reaction and the speed is increased continuously or stepwise to the final value when more than 90% conversion of the reaction is achieved. The reactor is therefore started at the pre-calculated speed, which was selected so that an increase potential of about 10 to 50% is still possible. After the nucleation phase has ended, but at the latest after the T 90 time has elapsed, the speed of the gassing stirrer is increased continuously or stepwise by the missing 10 to 50% until the end of the reaction. It was surprisingly found that this measure D 4.3D 90 by 100 100, especially to 59 or more.

[0034] The invention relates to precipitated calcium carbonate (PCC) which can be produced or is produced by the process described above. The PCC obtainable by the process has a special combination of grain size D4.3 and the ratio D 4.3D 90 on.

[0035] These properties cannot be achieved with previously known PCC processes. The invention thus further relates to precipitated calcium carbonate with a particle size distribution in which D 4.3D 90 times 100≥59, and with an average grain size D 4.3 for (i) scalenohedral precipitated calcium carbonate (s-PCC) in the range of 1.5 to 5.0 µm, particularly preferably 2.0 to 4.0 µm, in particular 2.9 to 3.1 µm; or (ii) rhombohedral precipitated calcium carbonate (r-PCC) in the range of 0.5 to 2.5 µm, particularly preferably 0.8 to 2.2 µm, in particular 0.9 to 2 µm; or (iii) aragonitic precipitated calcium carbonate (a-PCC) in the range of 1 to 30 µm, more preferably 2 to 20 µm, in particular 2.5 to 15 µm.

[0036] The ratio is preferably D 4.3D 90 times 100≥60, particularly preferably ≥ 62, most preferably ≥ 65.

[0037] A further aspect of the invention lies in the use of the PCC according to the invention as a filler in paper or plastic.

[0038] Further preferred embodiments of the invention can be found in the claims and the following description. Short description of the characters

[0039] The invention is explained in more detail below using exemplary embodiments and accompanying drawings. The figures show: Fig. 1 a schematic representation of a PCC plant; Fig. 2 shows the results of batch reactions in the pilot reactor for r-PCC, where D4,3 is plotted as a function of the specific energy input; Fig. 3 shows the results of batch reactions in the pilot plant reactor for r-PCC, where D4,3 is plotted as a function of the specific energy input. Fig. 4 shows the results of batch reactions in the pilot reactor for s-PCC, where D4,3 is plotted as a function of the specific energy input; and Fig. Figure 5 shows the results of batch reactions in the pilot plant reactor for s-PCC, where D4,3 is plotted as a function of the specific energy input. Detailed description of the invention

[0040] Fig. Figure 1 illustrates—highly schematically—the basic structure of a PCC plant 10 that can be used to carry out the process according to the invention. The PCC plant 10 comprises a batch reactor 20, into which an aqueous suspension of Ca(OH)2 (so-called lime milk) is initially introduced, and in which PCC is subsequently formed with the introduction of CO2. The lime milk is fed via a receiver 30. The CO2 is introduced into the lime milk as a gas via a suitable aeration system 40, which in this example comprises a gasification stirrer 42. An additional stirrer 50 can be provided. The reactor 20 is temperature-controlled. The PCC plant 10 includes sensor means (not shown in detail here) for monitoring the fill level of the reactor 20 and detecting the temperature of the lime milk. Furthermore, sensor means can be provided with which a CO2 concentration in the lime milk can be determined directly or indirectly.

[0041] The invention is based, among other things, on the finding that the specific molar energy input is the decisive controlling parameter for grain size. Accordingly, all parameters of the PCC plant 10 that make a significant contribution to the specific molar energy input during its operation must be recorded. The specific molar energy input corresponds to the energy input of the entire system required to introduce one mole of CO2 from the start of the reaction up to a conversion rate of 90% in the batchwise reaction.

[0042] As is generally known, the formation of calcium carbonate from calcium hydroxide and CO2 proceeds approximately linearly during the majority of the reaction. Starting at approximately 90 to 95% of the total reaction time, the pH and conductivity drop sharply, and the CO2 yield also decreases sharply. Therefore, the average CO2 yield in the first 90% of the total reaction time is used as the relevant reaction time.

[0043] The so-called vvm value is commonly used to determine the specific gassing rate, which means the volume unit of gas per volume unit of reactor content per unit of time. In industrial practice and with a typical reactor content of 10 m 3 For example, gassing rates of about 0.25 vvm to 5 vvm are common, which means that the rector can expect gassing rates of 150 Nm 3 per hour up to about 3000 Nm 3per hour. Smaller values ​​are considered uneconomical, and larger values ​​are technically impossible due to the increasing risk of breakthrough of the gassing air in the reactor. Breakthrough means that the gas bubbles suddenly coalesce when the permissible gassing rate is exceeded, thus preventing any significant mass transfer.

[0044] PCC plants usually have complex reactor gassing arrangements that allow for the most uniform CO2 input across the reactor's height and cross-section while minimizing energy consumption. The total hourly energy consumption of the entire system is essentially the sum of the energy consumption of the motor-driven agitators or gassing turbines located in the reactor and the blower station that may provide the pre-pressure. Typically, energy consumption figures based on the mass of PCC produced range from approximately 60 kWh to 250 kWh per ton of PCC produced, depending on the characteristics of the gassing system and the specified CO2 concentration. The plant operator generally knows this energy consumption very precisely.For simplification, the total energy consumed can be assumed to be proportional to the energy actually input.

[0045] The following example illustrates the calculation of the specific molar energy demand. Calculation example

[0046] The following data set of an implementation is given, where the goal is the extraction of s-PCC: Production of a reactive lime milk with 11% dry weight of calcium hydroxide and a density of 1.065 kg per m 3 , thus containing 15.8 kmol calcium hydroxide in 10 m 3 The viscosity of lime milk is about 50 mps.

[0047] The reactor is equipped with 10 m 3 filled with this milk of lime.

[0048] The constant gassing rate is 2,000 Nm 3 / h, which corresponds to a vvm value of 3.33.

[0049] The CO2 concentration is 26%.

[0050] The average CO2 utilization rate is 90%. The relevant 90% conversion time (T90 time) is 46 minutes.

[0051] The measured power requirement of a turbine is 130 kW.

[0052] The power consumption of an upstream fan contributes 40 kW.

[0053] The gas inlet temperature is set to 40°C by cooling.

[0054] The starting temperature in the reactor (lime milk) is 38°C. After 90% of the conversion, the temperature in the reactor is 72°C.

[0055] In the 41 minutes of reaction time, 90% of the initial lime milk was converted to s-PCC. This corresponds to the formation of 14.3 kmol or 1,430 kg of s-PCC. A longer reaction time is required for the remaining 10% of unconverted lime milk, as the specific conversion rate is known to drop at the end of the batch cycle.

[0056] The total energy consumption for the T90 time is 117 kWh.

[0057] During this period, 14.3 kmol of CO2 were introduced. The specific energy input (ε) per mole of CO2 is 117 kWh14.3 mol CO2=8.2 Wh / mol CO2

[0058] The influence of individual variables on the specific molar energy input is generally known or can be easily determined by a specialist for a given PCC plant. For example, for a plant, the reactor fill level can be plotted against the total power input (sum of blower, gassing unit, stirrer, etc.). Likewise, the dependence of gas utilization on the applied CO2 concentration, the speed of the gassing stirrer, the relative gas input, etc. can be recorded and evaluated.

[0059] The Fig. Figures 2 to 5 show the results from test series conducted with a pilot reactor and a commercial reactor, respectively. In each case, the characteristic mean particle size D4.3 is plotted against the specific energy input per mole of CO2 introduced in the relevant part of the batch reaction (0 to 90%). The characteristic particle size D4.3 was determined using a Mastersizer laser diffraction particle sizer from Malvern.

[0060] In a first series of experiments, rhombohedral crystals (r-PCC) with a grain size D4.3 in the range of approximately 0.8 µm to 2.0 µm were grown in the pilot reactor ( Fig. 2) and technical reactor ( Fig. 3). In a further experimental series, scalenohedral crystals (s-PCC) with a grain size D4.3 in the range of approximately 1.1 µm to 3.0 µm were produced in the pilot reactor ( Fig. 4) and technical reactor ( Fig.5). To adjust the energy input, the CO2 concentration, the fill level, the gas quantity, as well as the speed and the inlet pressure of the gas turbine were varied individually or in combination in the individual experiments.

[0061] Two data sets for the pilot reactor are given below as examples: Example 1 - Production of r-PCC in a pilot reactor

[0062] The following data set was used as a basis: Milk of lime 11.6% by weight Reactor level: 9 l Gas turbine speed: 55 Hz vvm : 1.1 (0.594 Nm 3 / h) CO2 concentration: 30% Reaction time T 90: 117 min Gas utilization rate: 90.0% CO2 input in time T 90 : 13.1 mol Total energy input during time T 90: 1244 Wh Specific energy input per mole of CO2: 95 Wh per mole of CO2 r-PCC was produced with a D4.3 of 1.4 µm. Example 2 - Production of s-PCC in a pilot reactor

[0063] The following data set was used as a basis: Lime milk 11.3% by weight Reactor level: 9 l Gas turbine speed: 35 Hz vvm : 0.5 (0.27 Nm 3 / h) CO2 concentration: 30% Reaction time T 90: 281 min Gas utilization rate: 81% CO2 input in time T 90 : 12.8 mol Total energy input during time T 90: 536 Wh Specific energy input per mole of CO2: 42 Wh per mole of CO2

[0064] s-PCC was generated with a D4.3 of 2.83 µm.

[0065] It can be seen that there is a direct relationship between the molar energy input per mole of CO2 introduced and the resulting characteristic grain size D4.3. The greater the amount of energy introduced per mole of CO2, the smaller the crystals become, and vice versa. Surprisingly, even at lower CO2 concentrations, smaller particles can be produced by combining appropriate parameters—for example, the gassing, the fill level, and the speed of the gassing device—provided the appropriate parameters are combined in such a way that the corresponding resulting specific energy input can be represented.

[0066] The following two examples 3 and 4 show exemplary s-PCC batches with a very high value for D 4.3D 90 by 100, which was achieved by deliberately varying the experimental conditions. Example 3 - Production of s-PCC

[0067] The following data set was used as a basis: Lime milk 11.3% by weight

[0068] Reactor filling level: at the beginning of the reaction: 220 l, after 20 min 280 l, after 40 min 240 l until the end of the reaction

[0069] Speed ​​of gas turbine: at the beginning of the reaction 38 Hz, after 20 min 40 Hz, after 40 min 45 Hz until the end of the reaction

[0070] Temperature: 45°C, constant (heat dissipation via internal cooler)

[0071] CO2 concentration: 45% (biogas), constant

[0072] vvm : 1.5 per min, constant

[0073] Specific energy input per mole of CO2 immediately at the start of the reaction: 7 Wh per mole of CO2

[0074] s-PCC was produced with a characteristic D4.3 of 3.0 µm and a value for D 4.3D 90 by 100 of 62. Example 4 - Production of s-PCC

[0075] The following data set was used as a basis: Lime milk 11.3% by weight Reactor filling level: at the beginning of the reaction: 220 l, after 20 min 280 l, after 40 min 240 l until the end of the reaction Speed ​​of gas turbine: at the beginning of the reaction 38 Hz, after 20 min 40 Hz, after 40 min 45 Hz until the end of the reaction Temperature: at the beginning of the reaction 45°C, after 20 min 43°C, after 40 min 41°C until the end of the reaction (heat dissipation via internal cooler) CO2 concentration: 35% at the beginning of the reaction, 45% after 40 min vvm : 1.5 per min, constant Specific energy input per mole of CO2 immediately at the start of the reaction: 8 Wh per mole of CO2

[0076] s-PCC was produced with a characteristic D4.3 of 2.9 µm and with a value for D 4.3D 90 by 100 of 61. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 6,251,356 B1

[0012] EP 1 222 146 B1

[0013] EP 1 712 597 A1

[0018] Cited non-patent literature

[0000] According to Gernot Krammer et al. (Part. Part. Syst. Charact. 19 (2002) 348- 353

[0014] Bo Feng et al., Materials Science and Engineering A 445-446 (2007) 170-179

[0014] Kralj et Brecivic from Croatica Chimica Acta, 80 (3-4) 467- 484 (2007) “On Calcium Carbonates from fundamental research to application

[0015] The production of precipitated calcium carbonate - PCC“ RWTH Aachen, 1992

[0017]

Claims

[1] Precipitated calcium carbonate (PCC) with a particle size distribution in which D 4.3D 90 times 100≥59 and with an average grain size D 4.3 for (i) scalenohedral precipitated calcium carbonate (s-PCC) in the range of 1.5 to 5.0 µm; or (ii) rhombohedral precipitated calcium carbonate (r-PCC) in the range of 0.5 to 2.5 µm; or (iii) aragonitic precipitated calcium carbonate (a-PCC) in the range of 1 to 30 µm. [2] PCC according to claim 1, wherein for the D 4.3D 90−ratio applies: D 4.3D 90 times 100≥60. [3] PCC according to claim 1, wherein the s-PPC has an average grain size D 4.3 in the range of 2.0 to 4.0 µm, in particular 2.9 to 3.1 µm. [4] PCC according to claim 1, wherein the r-PPC has an average grain size D 4.3 in the range of 0.8 to 2.2 µm. [5] PCC according to claim 1, wherein the a-PPC has an average grain size D 4.3 in the range of 2 to 20 µm. [6] Filler for paper or plastic containing precipitated calcium carbonate (PCC) according to claim 1.

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