Drying process

Abstract

The present invention refers to a process for making a calcium carbonate containing material, wherein the process includes a specific drying procedure and allows for the provision of calcium carbonate materials with reduced moisture pick-up and low porosity.

Claims

1. A process for making a calcium carbonate containing material comprising the following steps: a) providing a particulate moist calcium carbonate containing material, said material: i) having a moisture content of more than 65 wt.-%, based on the weight of the moist calcium carbonate containing material, and ii) containing no dispersant or containing a sub-effective amount of dispersant; b) reducing the moisture content of the moist calcium carbonate containing material of step a) by at least 10% by mechanical means at a temperature in the range of more than 0 C. to 65 C. in one or more steps, to remove a part of water soluble matter present in the particulate moist calcium carbonate and to obtain a moist calcium carbonate containing material having a reduced moisture content of less than 65 wt.-%, based on the weight of the moist calcium carbonate containing material; and c) thermally concentrating the moist calcium carbonate containing material with the reduced moisture content of step b) at a temperature in the range of 100 C. to 100 C. to obtain a final moisture content of not more than 1.0 wt.-%, based on the weight of the calcium carbonate containing material, wherein the calcium carbonate containing material obtained in step c) has a total specific pore volume of less than 0.83cm.sup.3 /g.

2. The process according to claim 1, wherein the moist calcium carbonate containing material of step a) has a moisture content of more than 70 wt.-%, based on the weight of the moist calcium carbonate containing material.

3. The process according to claim 1, wherein the moist calcium carbonate containing material of step a) has a moisture content of more than 75 wt.-%, based on the weight of the moist calcium carbonate containing material.

4. The process according to claim 1, wherein the moist calcium carbonate containing material of step a) has a moisture content of more than 80 wt.-%, based on the weight of the moist calcium carbonate containing material.

5. The process according to claim 1, wherein the moisture content of the moist calcium carbonate containing material in step b) is lowered to a reduced moisture content of less than 60 wt.-%, based on the weight of the moist calcium carbonate containing material.

6. The process according to claim 1, wherein the moisture content of the moist calcium carbonate containing material in step b) is lowered to a reduced moisture content of less than 50 wt.-%, based on the weight of the moist calcium carbonate containing material.

7. The process according to claim 1, wherein the moisture content of the moist calcium carbonate containing material in step b) is lowered to a reduced moisture content of less than 40 wt.-%, based on the weight of the moist calcium carbonate containing material.

8. The process according to claim 1, wherein the moisture content of the moist calcium carbonate containing material in step b) is lowered to a reduced moisture content of less than 30 wt.-%, based on the weight of the moist calcium carbonate containing material.

9. The process according to claim 1, wherein the moist calcium carbonate containing material is thermally concentrated in step c) to obtain a final moisture content of not more than 0.5 wt.-%, based on the weight of the moist calcium carbonate containing material.

10. The process according to claim 1, wherein the moist calcium carbonate containing material is thermally concentrated in step c) to obtain a final moisture content of not more than 0.2 wt.-%, based on the weight of the moist calcium carbonate containing material.

11. The process according to claim 1, wherein the moist calcium carbonate containing material is thermally concentrated in step c) to obtain a final moisture content of not more than 0.1 wt.-%, based on the weight of the moist calcium carbonate containing material.

12. The process according to claim 1, wherein the moist calcium carbonate containing material is thermally concentrated in step c) to obtain a final moisture content of not more than 0.07 wt.-%, based on the weight of the moist calcium carbonate containing material.

13. The process according to claim 1, wherein the moisture content of the moist calcium carbonate containing material in step b) is lowered in one or more steps by at least 30%, preferably by at least 50%, more preferably by at least 60% and most preferably by at least 70%.

14. The process according to claim 1, wherein the moisture content of the moist calcium carbonate containing material in step b) is lowered in one or more steps by at least 30%.

15. The process according to claim 1, wherein the moisture content of the moist calcium carbonate containing material in step b) is lowered in one or more steps by at least 50%.

16. The process according to claim 1, wherein the moisture content of the moist calcium carbonate containing material in step b) is lowered in one or more steps by at least 60%.

17. The process according to claim 1, wherein the moisture content of the moist calcium carbonate containing material in step b) is lowered in one or more steps by at least 70%.

18. The process according to claim 1, wherein the calcium carbonate containing material obtained in step b) is washed one or more times with deionised water prior to the thermal drying step c).

19. The process according to claim 1, wherein the calcium carbonate containing material obtained in step c) is treated with a hydrophobizing agent.

20. The process according to claim 19, wherein hydrophobizing agent is selected from the group consisting of monocarboxylic acids having from 6 to 24 chain carbon atoms, dicarboxylic acids having from 6 to 24 chain carbon atoms, and mixtures thereof.

21. The process according to claim 19, wherein hydrophobizing agent is selected from the group consisting of stearic acid, behenic acid, palmitic acid, isostearic acid, montanic acid, capric acid, lauric acid, myristic acid, and any mixture thereof.

22. The process according to claim 19, wherein hydrophobizing agent is selected from the group consisting of caprylic acid, salts thereof, and mixtures thereof.

23. The process according to claim 19, wherein the treatment with the hydrophobizing agent is carried out at elevated temperature such that the hydrophobizing agent is in the liquid or molten state.

24. The process according to claim 19, wherein the treatment with the hydrophobizing agent is carried out at a temperature of at least 50 C.

25. The process according to claim 19, wherein the treatment with the hydrophobizing agent is carried out at a temperature of at least 75 C.

26. The process according to claim 19, wherein the treatment with the hydrophobizing agent is carried out at a temperature of between 50 C. and 200 C.

27. The process according to claim 19, wherein the treatment with the hydrophobizing agent is carried out at a temperature of between 70 C. and 110 C.

28. The process according to claim 19, wherein the treatment with the hydrophobizing agent is carried out at elevated temperature in a heatable treatment device, and wherein the treated calcium carbonate containing material is removed from the device after cooling down.

29. The process according to claim 28, wherein the heatable treatment device is a heatable mixing device.

30. The process according to claim 28, wherein the treated calcium carbonate containing material is removed from the device after cooling down to 50 C.

31. The process according to claim 28, wherein the treated calcium carbonate containing material is removed from the device after cooling down to room temperature (20 C. ) or lower.

32. A process for making a calcium carbonate containing material comprising the following steps: a) providing a particulate moist calcium carbonate containing material, said material: i) having a moisture content of more than 65 wt.-%, based on the weight of the moist calcium carbonate containing material, and (ii) containing no dispersant or containing a sub-effective amount of dispersant; b) reducing the moisture content of the moist calcium carbonate containing material of step a) by at least 10% by mechanical means at a temperature in the range of more than 0 C. to 65 C. in one or more steps, to remove a part of water soluble matter present in the particulate moist calcium carbonate and to obtain a moist calcium carbonate containing material having a reduced moisture content of less than 65 wt.-%, based on the weight of the moist calcium carbonate containing material; and c) thermally concentrating the moist calcium carbonate containing material with the reduced moisture content of step b) at a temperature in the range of 100 C. to 100 C. to obtain a final moisture content of not more than 1.0 wt.-%, based on the weight of the calcium carbonate containing material, wherein the calcium carbonate containing material obtained in step c) has a lower porosity than a product obtained in step c) on the same particulate moist calcium carbonate containing material of step a) in which process step b) is omitted.

Description

EXAMPLES

(1) The scope and interest of the invention may be better understood on basis of the following examples which are intended to illustrate embodiments of the present invention. However, they are not to be construed to limit the scope of the claims in any manner whatsoever.

(2) Particle Size Distribution

(3) The weight median particle size d.sub.50 as used herein is determined based on measurements made by using a Sedigraph 5100 instrument of Micromeritics Instrument Corporation. The method and the instrument are known to the skilled person and are commonly used to determine the particle 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 are dispersed using a high speed stirrer and supersonics. Hydrophobized samples have to be heated first at 400 C. for 5 hours in an oven to remove the hydrophobic coating.

(4) BET Specific Surface Area of a Material

(5) According to the present invention, the specific surface area (expressed in m.sup.2/g) of a mineral filler is determined using the BET method (using nitrogen as adsorbing gas), which is well known to the skilled person (ISO 9277:1995). The total surface area (in m.sup.2) of the mineral filler can be obtained by multiplication of the specific surface area (in m.sup.2/g) and the mass (in g) of the mineral filler.

(6) Moisture Pick Up Susceptibility

(7) The moisture pick up susceptibility of a material according to the present invention may be determined in mg moisture/g after exposure to an atmosphere of 10 and 85% relative humidity, respectively, for 2.5 hours at a temperature of +23 C. (2 C.). For this purpose, the sample is first kept at an atmosphere of 10% relative humidity for 2.5 hours, then the atmosphere is changed to 85% relative humidity at which the sample is kept for another 2.5 hours. The weight increase between 10 and 85% relative humidity is then used to calculate the moisture pick-up in mg moisture/g of sample. The moisture pick up susceptibility in mg/g divided by the specific surface area in m.sup.2 (BET method) corresponds to the normalized moisture pick up susceptibility expressed in mg/m.sup.2 of sample.

(8) Total Moisture Content

(9) The total moisture content of the filler is measured according to the Karl Fischer Coulometric titration method, desorbing the moisture in an oven at 220 C. for 10 min and passing it continuously into a KF coulometer (Mettler Toledo Coulometric KF Titrator C30, combined with Mettler oven DO 0337) using dry nitrogen at 100 ml/min for 10 min. A calibration curve using water has to be recorded and a blank of 10 min nitrogen flow without a sample has to be taken into account.

(10) Porosimetry Testing

(11) 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). The equilibration time used at each pressure is 60 seconds. Approximately 0.3 g of sample material is sealed in a 5 cm.sup.3 chamber powder penetrometer for analysis. The maximum applied pressure of mercury was 414 MPa, equivalent to a Laplace throat diameter of 0.004 m. The data is corrected for mercury compression penetrometer expansion and sample material compression using a 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.). The porosity of the samples is measured in powder form, wherein the sample has a moisture content of not more than 1.0 wt.-%, based on the weight of the sample to be measured.

(12) By taking the first derivative of the cumulative intrusion curves the pore size distributions based on equivalent Laplace diameter, inevitably including pore-shielding, was revealed. The FWHM is calculated from the pore size distribution curve.

(13) Ash Content

(14) The ash content test was performed by burning 5 to 30 g of the corresponding polymer composition at 570 C. for 120 minutes.

(15) Filter Pressure Value (FPV)

(16) The filter pressure test was performed on a commercially available Collin Pressure Filter Test Teach-Line FT-E20T-IS. The test method was performed in agreement with European Standard EN 13900-5 with each of the corresponding polymer compositions (16 g effective calcium carbonate per 200 g of final sample, diluent: LLDPE ExxonMobil LL 1001 VX) using a 14 m type 30 filter (GKD Gebr. Kufferath AG, Duren, Germany), wherein no melt pump was used, the extruder speed was kept at 100 rpm, and wherein the melt temperature was 225 to 230 C. (temperature setting: 190 C./210 C./230 C./230 C./230 C.).

(17) Extrusion Simulation

(18) The extrusion simulation was developed to evaluate the mineral dispersion in a polymer composition. The test equipment and conditions are the same as for the filter pressure value test. Each of the corresponding polymer composition (215 g effective calcium carbonate per 400 g of final sample, diluent: LLDPE ExxonMobil LL 1001 VX) was measured using a 25 m type 30 filter (GKD Gebr. Kufferath AG, Duren, Germany). The results are expressed in bar and can be calculated by subtracting the final melt pressure (determined after 5 min of purging with pure polymer material) from the initial pressure of the polymer composition.

(19) Visual Evaluation of the Breathable Film

(20) The evaluation is done visually during the processing of the visual film without any auxiliary means for enlargement, ok means that no holes, no pineholes, and no stripes are observed.

(21) Water Vapour Transmission Rate (WVTR)

(22) The WVTR value of the breathable films was measured with a Lyssy L80-5000 (PBI-Dansensor A/S, Denmark) measuring device according to ASTM E398.

(23) Hydrostatic Pressure Test

(24) The hydrostatic pressure test has been carried out according to a procedure which is equivalent to AATCC Test Method 127-2013, WSP 80.6 and ISO 811. A film sample (test area=10 cm.sup.2) was mounted to form a cover on the test head reservoir. This film sample was subjected to a standardized water pressure, increased at a constant rate until leakage appears on the outer surface of the film, or water burst occurs as a result of film failure (pressure rate gradient=100 mbar/min.). Water pressure was measured as the hydrostatic head height reached at the first sign of leakage in three separate areas of the film sample or when burst occurs. The head height results were recorded in centimeters or millibars of water pressure on the specimen. A higher value indicated greater resistance to water penetration. The TEXTEST FX-3000, Hydrostatic Head Tester (Textest AG, Switzerland), was used for the hydrostatic pressure measurements.

(25) Tests No 1, No 2 and No 3

(26) Materials

(27) Marble Used as Starting Material (Marble)

(28) Marble of the region of Carrara, Italy, comprising 99.6 wt.-% CaCO.sub.3, 0.35 wt.-% silicates and 0.05 wt.-% of pyrite was used as starting material. The weight median particle size d.sub.50 was about 45 m (measured by screens). The BET surface was less than 1.0 m.sup.2/g.

(29) Marble Obtained after Grinding (Marble Slurry)

(30) The marble slurry as used for the tests described hereinafter was produced by wet grinding the above-specified marble at a moisture content of 80 wt.-% solids, based on the weight of moist calcium carbonate, in tap water (20 dH) in the absence of any dispersant in a stirred pearl mill (1-3 mm pearls composed of zircon dioxide) with a grinding volume of 4.5 m.sup.3. The obtained marble slurry contained calcium carbonate material having a weight median diameter d.sub.50 of 1.7 m (d.sub.98 of 8.5 m, d.sub.80 2.6 m, d.sub.20 0.5 m). The BET surface was measured to be 3.8 m.sup.2/g. The temperature during grinding raised from 22 C.2 C. at the inlet of the grinder to 56 C.5 C. at the outlet of the grinder. The final moisture content of the marble slurry obtained after grinding was 79.6 wt.-%.

(31) Test No 4

(32) Starting Material

(33) The starting material as used for this test described hereinafter was produced by wet grinding Carrara marble having a weight median diameter d.sub.50 of 8.63 m at a moisture content of 80 wt.-% solids, based on the weight of moist calcium carbonate, in tap water (20 dH) in the absence of any dispersant in a dynomill (0.6-1.0 mm Verac beads). The obtained starting material contained calcium carbonate material having a weight median diameter d.sub.50 of 0.7 m, a d.sub.75 diameter value of less than and a BET specific surface of 7.0 m.sup.2/g.

(34) Test No 5

(35) Starting Material

(36) The starting material as used for this test described hereinafter was produced by wet grinding Omey limestone at a moisture content of 80 wt.-% solids, based on the weight of moist calcium carbonate, in tap water (20 dH). The obtained starting material contained calcium carbonate material having a weight median diameter d.sub.50 of 1.8 m, and a BET specific surface of 3.1 m.sup.2/g.

(37) Tests

(38) Test No 1 (Invention)

(39) The marble slurry having a moisture content of 79.6 wt.-%, based on the weight of the moist calcium carbonate material, was first mechanically concentrated to 50 wt.-% moisture by using a centrifuge. In a second step, the mechanically concentrated moist calcium carbonate material content was thermally concentrated to 0.11 wt.-% residual moisture content using a Niro spray drier. By the corresponding process a powder (test no 1) was obtained.

(40) In order to produce a hydrophobically treated product, 500 g of the spray dried powder (test no 1) were added to an MTI Mixer and the sample was heated for 5 minutes at 120 C. and 3000 rpm. Thereafter, 0.85 wt.-%, based on the weight of the spray dried powder (test no 1), of a blend of palmitic acid and stearic acid (molar 2:1) was introduced to the mixer (treatment A) or 0.5 wt.-%, based on the weight of the spray dried powder (test no 1), of caprylic acid, (octanoic acid (product number 00040, commercially available from TCI Europe N.V, Belgium) was introduced to the mixer (treatment B) or 0.7 wt.-%, based on the weight of the spray dried powder (test no 1), of alkenyl succinic anhydride (CAS [68784-12-3], concentration >93%) was introduced to the mixer (treatment C). The contents of the mixer were mixed at 120 C. under a stirring speed of 3000 rpm for a period of 5 minutes.

(41) Test No 2 (Comparative)

(42) The marble slurry having a moisture content of 79.6 wt.-%, based on the weight of the moist calcium carbonate material, was first mechanically adjusted to 65 wt.-% moisture by using a centrifuge. In a second step, the mechanically concentrated moist calcium carbonate material content was thermally concentrated to 0.09 wt.-% residual moisture content using a Niro spray drier. By the corresponding process a powder (test no 2) was obtained.

(43) In order to produce a hydrophobically treated product, 500 g of the spray dried powder (test no 2) were added to an MTI Mixer and the sample was heated for 5 minutes at 120 C. and 3000 rpm. Thereafter, 0.85 wt.-%, based on the weight of the spray dried powder (test no 2), of a blend of palmitic acid and stearic acid (molar 2:1) was introduced to the mixer (treatment A) or 0.5 wt.-%, based on the weight of the spray dried powder (test no 2), of caprylic acid, (octanoic acid (product number 00040, commercially available from TCI Europe N.V, Belgium) was introduced to the mixer (treatment B) or 0.7 wt.-%, based on the weight of the spray dried powder (test no 2), of alkenyl succinic anhydride (CAS [68784-12-3], concentration >93%) was introduced to the mixer (treatment C). The contents of the mixer were mixed at 120 C. under a stirring speed of 3000 rpm for a period of 5 minutes.

(44) Test No 3 (Comparative)

(45) The marble slurry having a moisture content of 79.6 wt.-%, based on the weight of the moist calcium carbonate material, was thermally concentrated to 0.09 wt.-% residual moisture content using a Niro spray drier. By the corresponding process a powder (test no 3) was obtained.

(46) In order to produce a hydrophobically treated product, 500 g of the spray dried powder (test no 3) were added to an MTI Mixer and the sample was heated for 5 minutes at 120 C. and 3000 rpm. Thereafter, 0.85 wt.-%, based on the weight of the spray dried powder (test no 3), of a blend of palmitic acid and stearic acid (molar 2:1) was introduced to the mixer (treatment A) or 0.5 wt.-%, based on the weight of the spray dried powder (test no 3), of caprylic acid, (octanoic acid (product number 00040, commercially available from TCI Europe N.V, Belgium) was introduced to the mixer (treatment B) or 0.7 wt.-%, based on the weight of the spray dried powder (test no 3), of alkenyl succinic anhydride (CAS [68784-12-3], concentration >93%) was introduced to the mixer (treatment C). The contents of the mixer were mixed at 120 C. under a stirring speed of 3000 rpm for a period of 5 minutes.

(47) Results

(48) The total specific pore volume as well as the volume defined pore size polydispersity expressed as full width at half maximum (FWHM) of the respective products resulting from test no 1, test no 2 and test no 3 prior to the treatment with the hydrophobizing agent was determined and is shown in table 1 below.

(49) TABLE-US-00001 TABLE 1 comparison of total pore volume and the volume defined pore size polydispersity expressed as full width at half maximum (FWHM) for Treatment A Test no 3 Test no 2 Test no 1 Moisture content 80 65 50 before thermal treatment [wt.-%] *Total specific 0.918 0.844 0.794 pore volume of untreated powder [cm.sup.3/g] **Total specific 0.496 0.473 0.458 pore volume of untreated powder [cm.sup.3/g] Volume defined 0.79 0.90 1.16 pore size polydispersity expressed as full width at half maximum (FWHM) [m] *Total specific pore volume of untreated powder for the pore diameter range of 0.004 to 400.0 m **Total specific pore volume of untreated powder for the pore diameter range of 0.004 to 2.4 m

(50) The moisture pick-up susceptibility of the respective products resulting from test no 1, test no 2 and test no 3 after the treatment with the hydrophobizing agent was determined and is shown in table 2 below.

(51) TABLE-US-00002 TABLE 2 comparison of moisture pick up susceptibility Test no 3 Test no 2 Test no 1 Moisture content 80 65 50 before thermal treatment [wt.-%] Moisture pick up 0.9753 0.4853 0.3796 susceptibility of hydrophobically treated powder [mg/g CaCO.sub.3] Treatment A Moisture pick up 0.7011 0.6248 0.5051 susceptibility of hydrophobically treated powder [mg/g CaCO3] - Treatment B Moisture pick up 0.7592 0.6300 0.5323 susceptibility of hydrophobically treated powder [mg/g CaCO3] - Treatment C

(52) In order to demonstrate the correlation between concentration of water soluble matter or ions in the aqueous phase and the moisture sorption properties of the dried product, several experiments were carried out. During these experiments the moisture susceptibility of a calcium carbonate containing material being obtained by thermally drying a low solids slurry (comparative) and being obtained by the inventive two-step process were compared. The results obtained by the corresponding tests appear to clearly support the surprising finding of the inventors, namely that the specific two-step process as claimed herein leads to different products having improved properties, especially a reduced total pore volume and a reduced moisture pick-susceptibility. The obtained results are also reflected by FIGS. 1 and 2 showing the total pore volume of test no 1, test no 2 and test no 3 (FIG. 1) as well as the pore volume distribution of said tests (FIG. 2).

(53) Test No 4 (Invention)

(54) The starting material having a moisture content of 80 wt.-%, based on the weight of the moist calcium carbonate material, was first mechanically concentrated to 37 wt.-% moisture by using a press filter equipment (at 2 to 2.5 bar). In a second step, the mechanically concentrated moist calcium carbonate material content was thermally dried to 0.1 wt.-% residual moisture content using a drying oven at a temperature of 160 C. The resulting dried product was then de-agglomerated in a centrifugal mill ZM200 (sieve 0.2 mm trapezoid holes).

(55) In order to produce a hydrophobically treated product, 1 136 g of the dried and pre-heated product (overnight in an oven at 160 C.) was added to a Ldige Mixer L5, that was pre-heated to 150 C. The sample was mixed for 5 minutes at a temperature of 108 C. and a speed of 980 rpm. Thereafter, 1.66 wt.-%, based on the weight of the dried product, of a blend of palmitic acid and stearic acid (molar 2:1) was introduced to the mixer. The contents of the mixer were mixed at 108 C. at a stirring speed of 980 rpm for a period of 30 minutes. After that, the product was allowed to cool down in the mixer before removing it. After another de-agglomeration step in a centrifugal mill ZM200 (sieve 0.2 mm trapezoid holes), a moisture pick up susceptibility of the hydrophobically treated powder of 0.2228 mg/g calcium carbonate was measured.

(56) Test No 5 (Invention)

(57) The starting material having a moisture content of 80 wt.-%, based on the weight of the moist calcium carbonate material, was first mechanically concentrated to 50 wt.-% moisture by using a centrifuge. In a second step, the mechanically concentrated moist calcium carbonate material content was thermally dried to 0.1 wt.-% residual moisture content using a spray drier.

(58) In order to produce a hydrophobically treated product, 1 670 g of the dried product was pre-heated overnight in an oven at 160 C. Then the dried and pre-heated was added to a Ldige Mixer L5, that was pre-heated to a temperature of 160 C. The sample was mixed for 5 minutes at a temperature of 160 C. and a speed of 980 rpm. Thereafter, 0.73 wt.-%, based on the weight of the dried product, of a blend of palmitic acid and stearic acid (molar 2:1) was introduced to the mixer. The contents of the mixer were mixed at 160 C. at a stirring speed of 980 rpm for a period of 30 minutes. After that, the product was allowed to cool down in the mixer to the temperatures given in below Table 3 before removing it. Table 3 also lists the moisture pick up susceptibility of the hydrophobically treated powders.

(59) TABLE-US-00003 TABLE 3 Cooling down temperatures and moisture pick up susceptibility of the respective products Cooling down temperature moisture pick up of sample after treatment susceptibility at 160 C. in [mg/g] 100 C. 0.4423 80 C. 0.3901 50 C. 0.3481 20 C. 0.1715
Polymer Products
Materials
Dried Calcium Carbonate (CC) Materials

(60) CC1 (comparative): Natural ground calcium carbonate, commercially available from Omya International AG, Switzerland (d.sub.50: 1.7 m; d.sub.98: 6 m), surface-treated with 1 wt.-% stearic acid (commercially available from Sigma-Aldrich, Croda, USA) based on the total weight of the ground calcium carbonate. CC2 (inventive): Natural ground calcium carbonate, produced according to Test no 1, surface-treated with Treatment B CC3 (comparative): Natural ground calcium carbonate, produced according to Test no 3, surface-treated with Treatment B CC4 (inventive): Natural ground calcium carbonate, produced according to Test no 1, wherein the surface-treatment was carried out with 1 wt.-%, based on the weight of the spray dried powder (test no 1) of 1 wt.-% stearic acid (commercially available from Sigma-Aldrich, Croda, USA) based on the total weight of the ground calcium carbonate CC5 (inventive): Natural ground calcium carbonate, produced according to Test no 1, surface-treated with Treatment C CC6 (comparative): Natural ground calcium carbonate, produced according to Test no 2, surface-treated with Treatment C
Thermoplastic Polymers P1: LLDPE LL 6101XR (MFR: 20 g/10 min (190 C., 2.16 kg), density: 0.924 g/cm.sup.3 according to technical data sheet), commercially available from ExxonMobil Chemical, USA. P2: LLDPE Dowlex 2035 (MFR: 6 g/10 min (190 C., 2.16 kg), density: 0.919 g/cm.sup.3 according to technical data sheet), commercially available from The Dow Chemical Company, USA. P3: LDPE Dow SC 7641 (MFR: 2 g/10 min (190 C., 2.16 kg), density: 0.923 g/cm.sup.3 according to technical data sheet), commercially available from The Dow Chemical Company, USA.
Application in Polymers

Example 1

Preparation of Masterbatches in Polyethylene for Blown Films

(61) Masterbatches containing 25 wt.-% LLDPE LL 6101XR (Exxon Mobil), and 75 wt.-% CC2 or CC3 were prepared on a Buss kneader (PR 46 from Buss AG, Switzerland). The compositions and filler contents of the prepared masterbatches are compiled in Table 4 below. The precise filler content was determined by the ash content. Furthermore, a filter pressure test and the extrusion simulation test were carried out in order to determine the dispersion quality of the filler material product.

(62) TABLE-US-00004 TABLE 4 Compositions and properties of prepared masterbatches. Extrusion Ash content FPV at 14 m simulation Masterbatch Filler [wt.-%] [bar/g] [bar] MB2 (inventive) CC2 71.0 0.58 11.1 MB4 (comparative) CC3 73.3 0.58 17.1

(63) The results shown in Table 4 confirm that masterbatches with good quality were produced.

Example 2

Preparation of Polyolefin Compounds for Breathable Films

(64) Compounds containing 45 wt.-% P2, 5 wt.-% P3, and 50 wt.-% CC4 or CC5 or CC6, respectively, were continuously prepared on Buss kneader (PR46 from Buss AG, Switzerland). The compositions and filler contents of the prepared compounds are compiled in Table 5 below. The precise filler content was determined by the ash content.

(65) TABLE-US-00005 TABLE 5 Compounds for breathable film Ash content Compound Filler [wt.-%] CO1 (inventive) CC4 49.8 CO2 (inventive) CC5 49.8 CO3 (comparative) CC6 50.2

Example 3

Preparation of Breathable Films

(66) Breathable films were produced by a pilot-extrusion cast-film line with integrated MDO-II unit (Dr. Collin GmbH, Germany) the extruder temperature settings were 195 C.-210 C.-230 C.-230 C., and the rotation speed of the extruder was approximately 35 rpm using the compounds of Example 3. The roller speed of the stretching unit was 130/130%.

(67) The film quality of the obtained breathable films was inspected visually and the films were tested regarding their water vapour transmission rate (WVTR) and their hydrostatic pressure. The results are shown in Table 6 below.

(68) TABLE-US-00006 TABLE 6 Compositions and properties of prepared breathable films. Hydrostatic WVTR pressure Sample Compound Film quality [g/m.sup.2 day] [mbar] 2 (inventive) CO1 ok 3750 393 3 (inventive) CO2 ok 3812 388 5 (comparative) CO3 ok 3650 343

(69) The results shown in Table 6 confirm that the inventive breathable films provide excellent quality and breathability.