Method for the production of granules comprising surface-reacted calcium carbonate

Abstract

The present invention relates to a method for the production of granules comprising surface-reacted calcium carbonate by a) providing surface-reacted calcium carbonate, b) saturating the surface-reacted calcium carbonate with one or more liquids; c) providing one or more binder; d) combining the liquid saturated surface-reacted calcium carbonate with the one or more binder under agitation in an agitation device; e) removing the liquid from the mixture of step d); as well as to the granules comprising surface-reacted calcium carbonate obtained by this method.

Claims

1. A method for producing granules comprising surface-reacted calcium carbonate, the method comprising the steps of: a) providing surface-reacted calcium carbonate, wherein the surface-reacted calcium carbonate is a reaction product of natural ground or precipitated calcium carbonate with carbon dioxide and one or more acids, wherein the carbon dioxide is formed in situ by the acid treatment and/or is supplied from an external source; b) saturating the surface-reacted calcium carbonate of step a) with one or more liquids in order to obtain a liquid saturated surface-reacted calcium carbonate that is not oversaturated; c) providing one or more binders; d) combining the liquid saturated surface-reacted calcium carbonate of step b) with the one or more binders of step c) under agitation in an agitation device to form granules comprising surface-reacted calcium carbonate; and e) removing the liquid from the granules of step d).

2. The method according to claim 1, wherein the surface-reacted calcium carbonate in step a) is a reaction product of natural ground calcium carbonate with carbon dioxide and one or more acids, wherein the carbon dioxide is formed in situ by the acid treatment and/or is supplied from an external source, and wherein the natural ground calcium carbonate comprises marble, chalk, dolomite, limestone or any mixture thereof.

3. The method according to claim 1, wherein the surface-reacted calcium carbonate in step a) is a reaction product of precipitated calcium carbonate with carbon dioxide and one or more acids, wherein the carbon dioxide is formed in situ by the acid treatment and/or is supplied from an external source, and wherein the precipitated calcium carbonate comprises one or more aragonitic, vateritic and calcitic mineralogical crystal forms.

4. The method according to claim 1, wherein the surface-reacted calcium carbonate has a specific surface area of from 1 m.sup.2/g to 200 m.sup.2/g, measured using nitrogen and the BET method according to ISO 9277.

5. The method according to claim 1, wherein the surface-reacted calcium carbonate has a specific surface area of from 20 m.sup.2/g to 80 m.sup.2/g, measured using nitrogen and the BET method according to ISO 9277.

6. The method according to claim 1, wherein the surface-reacted calcium carbonate has a volume median grain diameter d.sub.50 of from 0.5 to 50 m.

7. The method according to claim 1, wherein the surface-reacted calcium carbonate has a volume median grain diameter d.sub.50 of from 1 to 10 m.

8. The method according to claim 1, wherein the surface-reacted calcium carbonate has an intra-particle porosity within the range of from 5 vol. % (v/v) to 50 vol. % (v/v), calculated from a mercury porosimetry measurement.

9. The method according to claim 1, wherein the surface-reacted calcium carbonate has an intra-particle porosity within the range of from 20 vol. % (v/v) to 50 vol. % (v/v), calculated from a mercury porosimetry measurement.

10. The method according to claim 1, wherein the surface-reacted calcium carbonate has an intra-particle intruded specific pore volume within the range of 0.150 to 1.300 cm.sup.3/g, calculated from mercury porosimetry measurement.

11. The method according to claim 1, wherein the surface-reacted calcium carbonate has an intra-particle intruded specific pore volume within the range of 0.178 to 1.244 cm.sup.3/g, calculated from mercury porosimetry measurement.

12. The method according to claim 1, wherein in step b), the liquid is selected from the group consisting of water, methanol, ethanol, n-butanol, isopropanol, n-propanol, and any mixture thereof.

13. The method according to claim 1, wherein in step b), the liquid is water.

14. The method according to claim 1, wherein the one or more binders of step c) is selected from the group consisting of a synthetic polymer, methylcellulose, ethylcellulose, sodium carboxymethylcellulose, hydroxypropyl methylcellulose (HPMC), hydroxypropylcellulose (HPC), ethylhydroxyethylcellulose (EHEC), polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), a polyvinyl alcohol, apolymethacrylate, a natural binder, a plant gum, acacia, tragacanth, sandarac, ghatti, karaya, locust bean, guar, a protein, gelatin, casein, collagen, a saccharide, a polysaccharide, starch, a starch derivatives, inulin, cellulose, a pectin, a carrageenan, a sugar, an animal exudate, shellac, alginic acid, and any mixture thereof.

15. The method according to claim 1, wherein the one or more binders of step c) is selected from the group consisting of sodium carboxymethylcellulose, hydroxypropyl methylcellulose (HPMC), polyvinyl pyrrolidone (PVP), pectin, and locus beam gum.

16. The method according to claim 1, wherein the one or more binders of step c) is added in an amount of from 0.5 to 50 wt %, based on the weight of surface-reacted calcium carbonate of step a).

17. The method according to claim 1, wherein the one or more binders of step c) is added in an amount of from 2.5 to 15 wt %, based on the weight of surface-reacted calcium carbonate of step a).

18. The method according to claim 1, wherein the one or more binders of step c) is added in an amount of from 5 to 10 wt %, based on the weight of surface-reacted calcium carbonate of step a).

19. The method according to claim 1, wherein in step d), the agitation device is selected from the group consisting of an Eirich mixer, a fluidized bed dryer/granulator, a plate granulator, a table granulator, a drum granulator, a disc granulator, a dish granulator, a plowshare mixer, a high speed blender, and a rapid mixer granulator.

20. The method according to claim 1, wherein in step d), the one or more binders is added to the agitation device simultaneously with or after the liquid saturated surface-reacted calcium carbonate.

21. The method according to claim 1, wherein after the combination of the liquid saturated surface-reacted calcium carbonate and the one or more binders in step d), further surface-reacted calcium carbonate or liquid saturated surface-reacted calcium carbonate or a mixture thereof, and/or liquid is added until an agglomeration of the particles is observed.

22. The method according to claim 21, wherein the further surface-reacted calcium carbonate or liquid saturated surface-reacted calcium carbonate or mixture thereof is added in an amount of from 1 to 30 wt %, based on the weight of the surface-reacted calcium carbonate provided in step a).

23. The method according to claim 21, wherein the further surface-reacted calcium carbonate or liquid saturated surface-reacted calcium carbonate or mixture thereof is added in an amount of from 5 to 15 wt %, based on the weight of the surface-reacted calcium carbonate provided in step a).

24. The method according to claim 1, wherein in step e), the liquid is removed by separating the liquid from the granules.

25. The method according to claim 1, wherein in step e), the liquid is removed by drying in a rotational oven, jet-drying, fluidized bed drying, freeze drying or flash drying.

26. The method according to claim 1, wherein the granules obtained after step e) have a volume median particle size of from 0.1 to 6 mm, determined by sieve fractioning.

27. The method according to claim 1, wherein the granules obtained after step e) have a volume median particle size of from 0.2 to 2 mm, determined by sieve fractioning.

28. The method according to claim 1, wherein the granules obtained after step e) have a specific surface area of from 1 to 150 m.sup.2/g, measured using nitrogen and the BET method according to ISO 9277.

29. The method according to claim 1, wherein the granules obtained after step e) have a specific surface area of from 20 to 70 m.sup.2/g, measured using nitrogen and the BET method according to ISO 9277.

30. Granules comprising surface reacted calcium carbonate obtained by the method according to claim 1.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows SEM images of granules obtained according to comparative example 1 at 100 times (FIG. 1a) and 1000 times (FIG. 1b) magnification.

(2) FIGS. 2-5 are light microscope pictures of different sieve fractions of examples 9 to 12, namely: top-left=0 to 0.3 mm, top-right=0.3 mm to 0.6 mm, bottom-left=0.6 mm to 1 mm and bottom-right=1 mm to 2 mm.

(3) FIGS. 6a and 6b show granules produced according to the inventive production method and the conventional production method in dishes (FIG. 6a), as well as remaining dust after removing these samples from the dishes (FIG. 6b).

(4) FIG. 7 shows the particle size distributions of scalenohedral PCC and further comparative calcium carbonates combined with trisodium citrate and a cationic binder

(5) FIGS. 8a and b show SEM pictures of scalenohedral PCC (FIG. 8a) and further comparative calcium carbonate combined with trisodium citrate (FIG. 8b)

(6) FIG. 9 shows of scalenohedral PCC (FIG. 9a) and further comparative calcium carbonates combined with trisodium citrate and a cationic binder (FIG. 9b)

(7) FIG. 10 shows comparative calcium carbonate combined with trisodium citrate and a cationic binder

EXAMPLES

(8) 1. Measurement Methods

(9) The following measurement methods were used to evaluate the parameters given in the examples and claims.

(10) BET Specific Surface Area (SSA) of a Material

(11) The BET specific surface area was measured via the BET process according to ISO 9277 using nitrogen, following conditioning of the sample by heating at 250 C. for a period of 30 minutes. Prior to such measurements, the sample was filtered, rinsed and dried at 110 C. in an oven for at least 12 hours.

(12) Particle Size Distribution (Volume % Particles with a Diameter <X), d.sub.50 Value (Volume Median Grain Diameter) and d.sub.98 Value of a Particulate Material:

(13) Volume median grain diameter d.sub.50 was evaluated using a Malvern Mastersizer 2000 Laser Diffraction System (Malvern Instruments Plc., Great Britain) using the Fraunhofer light scattering approximation. The method and instrument are known to the skilled person are commonly used to determine particle sizes of fillers and other particulate materials.

(14) The d.sub.50 or d.sub.98 value, measured using a Malvern Mastersizer 2000 Laser Diffraction System, indicates a diameter value such that 50% or 98% by volume, respectively, of the particles have a diameter of less than this value. The raw data obtained by the measurement is analyzed using the Mie theory, with a particle refractive index of 1.57 and an absorption index of 0.005.

(15) The weight median grain diameter is determined by the sedimentation method, which is an analysis of sedimentation behaviour in a gravimetric field. The measurement is made with a Sedigraph 5100 of Micromeritics Instrument Corporation. The method and the instrument are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurement is carried out in an aqueous solution of 0.1 wt % Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and supersonicated.

(16) The processes and instruments are known to the skilled person and are commonly used to determine grain size of fillers and pigments.

(17) Porosity/Pore Volume

(18) The porosity or pore volume is measured using a Micromeritics Autopore IV 9500 mercury porosimeter having a maximum applied pressure of mercury 414 MPa (60 000 psi), equivalent to a Laplace throat diameter of 0.004 m ( nm). The equilibration time used at each pressure step is 20 seconds. The sample material is sealed in a 5 cm.sup.3 chamber powder penetrometer for analysis. The data are corrected for mercury compression, penetrometer expansion and sample material compression using the software Pore-Comp (Gane, P. A. C., Kettle, J. P., Matthews, G. P. and Ridgway, C. J., Void Space Structure of Compressible Polymer Spheres and Consolidated Calcium Carbonate Paper-Coating Formulations, Industrial and Engineering Chemistry Research, 35(5), 1996, p 1753-1764.).

(19) Scanning Electron Microscopy (SEM) Pictures

(20) Samples for SEM investigation were prepared by filtering the suspensions and letting them dry in a drying oven at 110 C. The samples were sputtered with 20 nm gold before taking the pictures.

(21) 2. Material and Equipment

(22) 2.1. Equipment Fluidized Bed Mixer (Strea-1 laboratory fluid bed mixer by Aeromatic-Fielder using a 21 transparent cell) Ldige (Model L5, 5 l Mixer)

(23) 2.2. Material

(24) Surface-Reacted Calcium Carbonate Surface-reacted calcium carbonate (SRCC) 1 (d.sub.50=7.0 m, d.sub.98=16.1 m, SSA=55.4 m.sup.2 g.sup.1) The intra-particle intruded specific pore volume is 0.871 cm.sup.3/g (for the pore diameter range of 0.004 to 0.4 m).

(25) SRCC 1 was obtained by preparing 300 liters of an aqueous suspension of ground calcium carbonate in a mixing vessel by adjusting the solids content of a ground limestone calcium carbonate from Omya SAS, Orgon having a mass based median particle size of 1.3 m, as determined by sedimentation, such that a solids content of 10 wt %, based on the total weight of the aqueous suspension, is obtained.

(26) Whilst mixing the slurry at a speed of 12.7 m/s, 9.6 kg phosphoric acid was added in form of an aqueous solution containing 30 wt % phosphoric acid to said suspension over a period of 12 minutes at a temperature of 70 C. After the addition of the acid, the slurry was stirred for additional 5 minutes, before removing it from the vessel and drying. Surface-reacted calcium carbonate (SRCC) 2 (d.sub.50=6.6 m, d.sub.98=13.7 m, SSA=59.9 m.sup.2 g.sup.1) The intra-particle intruded specific pore volume is 0.939 cm.sup.3/g (for the pore diameter range of 0.004 to 0.51 m).

(27) SRCC 2 was obtained by preparing 350 liters of an aqueous suspension of ground calcium carbonate in a mixing vessel by adjusting the solids content of a ground limestone calcium carbonate from Omya SAS, Orgon having a mass based median particle size of 1.3 m, as determined by sedimentation, such that a solids content of 10 wt %, based on the total weight of the aqueous suspension, is obtained.

(28) Whilst mixing the slurry at a speed of 6.2 m/s, 11.2 kg phosphoric acid was added in form of an aqueous solution containing 30 wt % phosphoric acid to said suspension over a period of 20 minutes at a temperature of 70 C. After the addition of the acid, the slurry was stirred for additional 5 minutes, before removing it from the vessel and drying using a j et-dryer.

(29) Binder Sodium carboxymethylcellulose from Sigma Aldrich (average molar mass 90000 g/mol; CAS No. 9004-32-4) Hydroxypropylmethylcellulose (HPMC): Pharmacoat 603 (Harke Group, Mllheim an der Ruhr, Germany) Polyvinylpyrrolidone (PVP): Kollidon K30 (BASF) Pectin Citrus, Powder, from Alfa Aesar (Poly-D-galacturonic acid methyl ester; J61021; CAS number 9000-69-5; EC number 232-553-0) Locust beam gum from Ceratorin siliqua seeds from Sigma-Aldrich (Galactomannan polysaccharide; G0753; CAS number 9000-40-2; EC number 232-541-5)

(30) 3. Granulation Experiments

(31) 3.1. Fluid Bed Mixer Granulation

Example 1 (Comparative)

(32) 200 g surface-reacted calcium carbonate SRCC 1 was added to the fluid bed mixer. Additionally, a 10% (w/w) solution of Kollidon K30 (polyvinylpyrrolidone, PVP) in water was prepared. While running the fluid-bed system under varying air flows ranging from 0.5-2 m.sup.3 min.sup.1, the PVP solution was added to the system at a rate of about 30 g/min. After the addition of a total of 500 g PVP solution, granules were attained. At this point the liquid spray was turned off, while the air was allowed to continue until a dry product was attaing. The sample was then taken by pouring it out of the top of the 2 l vessel.

(33) The resulting granules were sieved on a Retsch sieve and had particle sizes of less than 600 m, mostly between 0.2-0.4 mm.

(34) The resulting granules are illustrated in FIG. 1.

(35) In Example 1, 25 wt % binder (50 g) had to be added in order to obtain granules of surface reacted calcium carbonate having particle sizes of less than 600 m, wherein the resulting granules were undesirably fragile and dusting.

(36) 3.2. Ldige Mixer Granulation

Example 2 (Comparative)

(37) A 7.5 wt % sodium carboxymethylcellulose solution was prepared using tap water. 600 g SRCC 2 was then saturated with 300 g of this binder containing solution, such that 22.5 g of sodium carboxymethylcellulose was added. This product was then added to the Ldige mixer and, using a spray bottle, 100 g of this solution was added over time, while mixing the powder with both the blending element (speed varied between 500 rpm and the maximum speed (999 rpm), mainly between 700-999 rpm) and the cutter. After this was finished and a total of 5 wt % sodium carboxymethylcellulose based on the weight of surface-reacted calcium carbonate was added to the SRCC 2, tap water was sprayed in until the material passed the clumpy pre-granule state and the sample turned to a paste. This was again rectified via the addition of 150 g dry surface-reacted calcium carbonate SRCC 2. The sample was mixed a few more minutes until individual granules were formed. The final solids of this sample was 60 wt %. Subsequently, the sample was removed and dried at 90 C. for 12 hours.

(38) The dried sample was sieved on a Retsch sieve into separate size fractions, namely <0.3 mm, between 0.3 and 0.6 mm, between 0.6 and 1 mm, and between 1 and 2 mm.

Example 3 (Inventive)

(39) 530 g surface-reacted calcium carbonate SRCC 2 was saturated with water providing a solids content of 61 wt % and added to the Ldige mixer. Subsequently, 51 g sodium carboxymethylcellulose was added, dry, and the combination was mixed for several minutes to ensure proper blending. Subsequently, using a spray bottle, tap water was added over time, while mixing the powder with both the blending element (speed varied between 500 rpm and the maximum speed (999 rpm), mainly between 700-999 rpm) and the cutter until the material started to look a little clumpy. At this point, a little more water was then added and the sample turned to a paste. This was again rectified via the addition of 100 g dry surface-reacted calcium carbonate SRCC 2. The sample was mixed a few more minutes until individual granules were formed. The final solids of this sample was 61 wt %. Subsequently, the sample was removed and dried at 90 C. for 12 hours.

(40) The dried sample was sieved on a Retsch sieve into separate size fractions, namely <0.3 mm, between 0.3 and 0.6 mm, between 0.6 and 1 mm, and between 1 and 2 mm. The results can be taken from table 3.

Examples 4-12 (Inventive)

(41) Using the method established in Example 3, Examples 4 to 12 were run with varying amounts of surface-reacted calcium carbonate SRCC 2, sodium carboxymethylcellulose binder and water, as well as varying blending speeds.

(42) The respective variables and values can be taken from table 2. The respective granule size distributions can be taken from table 3.

(43) FIGS. 2-5 are light microscope pictures of the different sieve sizes of Examples 9 to 12, namely: top-left=0 to 0.3 mm, top-right=0.3 mm to 0.6 mm, bottom-left=0.6 mm to 1 mm and bottom-right=1 mm to 2 mm.

(44) TABLE-US-00001 TABLE 2 Solids after Binder Extra Blending SRCC water Binder wt % on SRCC speed Example [g] [wt %] [g] SRCC [g] [rpm] 3 530 61% 51 9.6% 100 500-999 4 512 63% 51 10.0% 100 500-999 5 521 64% 51 9.8% 100 999 6 523 67% 52 9.9% 100 900-999 7 521 65% 51 9.8% 100 900-999 8 517 63% 51 9.9% 100 900-999 9 521 63% 51 9.8% 0 900-999 10 515 66% 51 9.9% 30 900-999 11 522 65% 26 5.0% 100 900-999 12 524 65% 39 7.4% 100 900-999

(45) TABLE-US-00002 TABLE 3 wt % of Particle size x [mm] Example x < 0.3 0.3 < x < 0.6 0.6 < x < 1 1 < x < 2 3 16 15 19 49 4 11 13 21 55 5 13 18 26 44 6 13 16 21 50 7 12 18 27 43 8 18 20 26 36 9 49 23 13 15 10 2 20 33 45 11 8 11 19 62 12 13 21 26 40

(46) The above examples clearly show that granules can be produced from surface-rected calcium carbonate with standard binding agents. However, it can be seen that excessive binder does not have to necessarily lead to a better product. Due to the porosity of the material large amounts of binder gets lost, when the liquid is absorbed into the pores. This is the reason why, e.g. in Example 1, although 25 wt % PVP binder (considered one of the best binders) was used, the sample did not show any better qualities. In fact, it was rather fragile. The binder solution had a higher concentration, and it is believed that this solution filled the pores, thus wasting the binder.

(47) Subsequent trials using the Ldige mixer showed that saturating the surface-reacted calcium carbonate with the solvent prior to binder and binding solvent, resultated in a decreased amount of binder needed for producing stable granules of different sizes (cf. especially Examples 11 and 12 using 5 and 7.4 wt % binder instead of 10 wt % at comparable results).

(48) This applies for different equipments, wherein using a fluidized bed mixer for granulation appear to provide a more uniform granule size distribution than the Ldige mixer, whereas the Ldige mixer gives a wider size distribution. Thus, also multiple size ranges may be provided.

(49) Furthermore, the products according to the invention are much more stable and provide significantly less dusting.

(50) This is illustrated in FIGS. 6a and 6b. On the left hand side of FIG. 6a, granules of Example 11 (using 5 wt % sodium carboxymethylcellulose binder) are shown. On the right hand side a sample of Example 2 is shown, which was produced without previous liquid saturation. From FIG. 6b it can be taken that, after removing both of the samples, no visible dust is left from inventive Example 11, whereas a considerable amount of dust remains in the dish of Example 2 produced according to the conventional production method without initial liquid saturation of surface-reacted calcium carbonate.

(51) This clearly shows the advantage of the method for producing granules comprising surface-reacted calcium carbonate according to the invention.

Examples 13-21 (Inventive)

(52) Using the method established in Example 3, Examples 13 to 21 were run with surface-reacted calcium carbonate SRCC 1, varying amounts of Locust beam gum (Example 13 to 17) and Pectin Citrus (Example 18 to 21) binders and water.

(53) The respective variables and values can be taken from table 4. The respective granule size distributions can be taken from table 5.

(54) TABLE-US-00003 TABLE 4 Solids after Binder Extra Blending SRCC water Binder wt % on SRCC speed Example [g] [wt %] [g] SRCC [g] [rpm] 13 550 65% 55 10% 100 500-999 14 550 64% 27.5 .sup.5% 100 500-999 15 550 64% 13.75 2.5% 100 999 16 550 64% 5.5 .sup.1% 100 900-999 17 550 63% 2.75 0.5% 100 900-999 18 550 65% 27.5 .sup.5% 100 900-999 19 550 65% 13.75 2.5% 100 900-999 20 550 63% 5.5 .sup.1% 100 900-999 21 550 67% 2.7 0.5% 100 900-999

(55) TABLE-US-00004 TABLE 5 Exam- wt % of Particle size x [mm] Yield ple x < 0.3 0.3 < x < 0.6 0.6 < x < 1 1 < x < 2 x > 2 [%] 13 1 1 1 2 64 69 14 1 3 11 22 31 68 15 1 3 12 29 53 98 16 6 15 16 15 41 93 17 11 19 18 19 26 93 18 2 4 7 22 59 94 19 11 24 13 10 27 85 20 13 19 16 17 28 93 21 6 15 24 24 24 93

(56) The above examples clearly show that granules can be produced from surface-reacted calcium carbonate with standard binding agents.

(57) 4. Comparative Experiments

(58) The following examples serve to demonstrate the importance of a) the use of a surface-reacted calcium carbonate according to the present invention as well as b) the saturation of the surface-reacted calcium carbonate as defined in the present invention. These Examples, e.g., reflect compositions such as those described in EP 2 662 416 A1.

Example 22

(59) Preparation

(60) A water based scalenohedral PCC (S-PCC) in the form of a suspension having a solids content of 14 wt % (available from Omya Switzerland) and having a d.sub.50 of 4.2 m and a d.sub.95 of 9 m measured using the Malvern Mastersizer 20000 Laser Difraction System (corresponding to a d.sub.50 of 2.5 m and a d.sub.95 of 5 m measured using a Sedigraph instrument) was provided. Then, a 35 wt % solution of trisodium citrate (prepared from tridosium citrate dihydrate, commercially available from Sigma Aldrich) was added under stirring to the S-PCC suspension to have 0.09 wt % ratio of trisodium citrate to S-PCC based on dry amounts. After ten minutes of further stirring, 0.2 wt % (based on dry amounts on S-PCC) Niklacell T10G (carboxymethylcellulose (CMC) having a molecular weight of 60 000 g/mol; commercially available from Mare Austria GmbH) and 0.28 wt % (based on dry amounts on S-PCC) Niklacell CH90F (carboxymethylcellulose (CMC) having a molecular weight of 200 000 g/mol; commercially available from Mare Austria GmbH) were added as 6 wt % suspensions under continued stirring.

(61) The particle size distribution of the resulting intermediary product (PHCH 0) was measured and SEM pictures were taken.

(62) Subsequently, 2 wt % (based on dry amounts on S-PCC) of cationic starch (C*Bond HR 35845, commercially available from Cargill Deutschland GmbH) was added as cationic polymer in the form of a powder to the above product under stirring. Then, the suspension was heated to 100 C. and stirred for 1 hour. The suspension then was cooled down to room temperature under ambient conditions (no active cooling).

(63) The particle size distribution of the final product (PHCH 1) was measured and SEM pictures were taken.

(64) In order to show that the eventually formed soft aggregates due to the cationic starch addition are not stable, additionally also a sample of the final product was subjected to 1 min of ultra-sonication in the Malvern Mastersizer 2000 before performing the PSD measurement (PHCH 1 US).

(65) Results:

(66) As can be seen in FIG. 7, there is a very small shift of the PSD from the starting material (S-PCC) to the intermediate product (PHCH 0), however, the change in d.sub.50 is negligible (table 6).

(67) TABLE-US-00005 TABLE 6 d.sub.50 (m) S-PCC 4.2 PHCH0 4.3 PHCH 1 11.3 PHCH 1 US 9.7

(68) FIG. 8 also shows that the obtained product from PHCH0 (FIG. 8b) does not differ visually from the starting material S-PCC (FIG. 8a). So the treatment that is applied in the PHCH0 example is not leading to a (surface) modification of the starting material (S-PCC) into a surface reacted calcium carbonate according to the present invention, which, in the case of PCC, would have required an excess of solubilised calcium ions as described in WO 2009/074492 A1 and mentioned above.

(69) Furthermore, it can be seen that the addition of cationic starch leads to a small shift of the PSD to increased particle sizes, also reflected by the d.sub.50 (table 1). It also can be seen that a small amount of agglomerates (around 1 vol %) is formed around 100 m (apparent as shoulder around 100 m).

(70) However, as the ultrasonic treatment in PHCH1 US treatment is able to reduce the amount of agglomerates and generally shift the PSD curve to finer values (FIG. 7, table 6), it is also shown that the formed agglomerates are only weakly held together and cannot be considered as granules according to the present invention.

(71) Furthermore, as the amount of agglomerates is very small, the d.sub.50 of the PHCH 1 sample is still well below the typical size range that is obtained by granulation according to the present invention.

(72) In FIG. 9 it also can be seen visually that the addition of cationic starch to PHCH0 (FIG. 9b) did not lead to the formation of granules as the PCC particles still appear as individual particle as in the case of S-PCC ((FIG. 9a).

(73) FIG. 10 also shows visually that no agglomerates can be found in the described size range.