PROCESS FOR IMPROVING PARTICLE SIZE DISTRIBUTION OF CALCIUM CARBONATE-COMPRISING MATERIAL

Abstract

The present invention relates to a process for the preparation of an aqueous suspension comprising at least one calcium carbonate-comprising material, the calcium carbonate-comprising material having a ratio of particles having an average particle size d.sub.80 value to particles having an average particle size d.sub.20 value [d.sub.80/d.sub.20] in the range from 1.5 to 4 and the use of the calcium carbonate-comprising material in paper and board applications, in cosmetics, in caulks and sealants, in adhesives, in paints and coatings, in fibre applications, in plastics applications or for the replacement of PCC in general.

Claims

1. Process for the preparation of an aqueous suspension comprising at least one calcium carbonate-comprising material, the process comprising the following steps: a) providing a substantially dispersant-free aqueous suspension of at least one calcium carbonate-comprising material, and b) pre-heating the suspension of step a) to a temperature of from 40 to 95° C. at ambient pressure, and c) wet-grinding the pre-heated suspension in at least one grinding step for obtaining an aqueous suspension of at least one wet ground calcium carbonate-comprising material, and d) contacting the aqueous suspension before and/or during and/or after wet-grinding step c) and/or before and/or during and/or after removal step e) with at least one base for obtaining an aqueous suspension having a pH measured at 25° C. of ≧9.0, and e) removal of at least a part of the particles with a diameter >20 μm in the aqueous suspension of the at least one wet ground calcium carbonate comprising material, and f) storing the aqueous suspension obtained after removal step e) at a temperature of from 70 to 140° C. for a period of time of 0.25 to 8 hours, for obtaining an aqueous suspension of at least one calcium carbonate-comprising material having a ratio of particles having an average particle size d.sub.80 value to particles having an average particle size d.sub.20 value [d.sub.80/d.sub.20] in the range from 1.5 to 4.0.

2. The process according to claim 1, wherein the content of particles with a particle diameter <1 μm of the at least one calcium carbonate-comprising material provided in the aqueous suspension of step a) is between 30 to 90 wt.-%, preferably between 35 and 65 wt.-% and most preferably between 40 and 60 wt.-%.

3. The process according to claim 1, wherein the at least one calcium carbonate-comprising material provided in the aqueous suspension of step a) is dolomite and/or a natural ground calcium carbonate (NGCC), such as one or more of marble, limestone and/or chalk.

4. The process according to claim 1, wherein the aqueous suspension provided in step a) has a solids content of from 5.0 wt.-% to 60.0 wt.-%, preferably from 10.0 wt.-% to 55.0 wt.-% and most preferably from 15.0 wt.-% to 50.0 wt.-%, based on the total weight of the aqueous suspension.

5. The process according to claim 1, wherein the aqueous suspension of step a) is adjusted in pre-heating step b) to a temperature of from 50 to 95° C. at ambient pressure, preferably from 60 to 90° C. at ambient pressure and more preferably from 75 to 85° C. at ambient pressure.

6. The process according to claim 1, wherein contacting step d) is carried out after removal step e).

7. The process according to claim 1, wherein contacting step d) is carried out such that the obtained aqueous suspension has a pH measured at 25° C. of from 10.0 to 13.5 and preferably from 11.0 to 13.0.

8. The process according to claim 1, wherein the at least one base in contacting step d) is a) added in an amount of ≧0.05 wt.-%, preferably of ≧0.1 wt.-%, more preferably of ≧0.2 wt.-% and most preferably of from 0.2 to 1.0 wt.-%, based on the total dry weight of the calcium carbonate-comprising material, and/or b) at least one alkali metal hydroxide selected from the group comprising lithium hydroxide, sodium hydroxide, potassium hydroxide and mixtures thereof and/or at least one earth alkali metal hydroxide selected from the group comprising magnesium hydroxide, calcium hydroxide and mixtures thereof.

9. The process according to claim 1, wherein wet-grinding step c) is carried out at a starting temperature of from 40 to 95° C., preferably from 60 to 80° C., more preferably from 65 to 75° C.

10. The process according to claim 1, wherein the removal step e) is carried out by using a centrifuge, at least one sieve or a disc separator or mixtures thereof for removing >90 wt.-% of particles with a diameter >100 μm and >70 wt.-% of particles with a diameter >20 μm, preferably for removing essentially all particles with a diameter >100 μm and >90 wt.-% of particles with a diameter >20 μm, based on the weight of the at least one wet ground calcium carbonate comprising material.

11. The process according to claim 1, wherein the step 0 of storing the aqueous suspension is carried out at a temperature of from 75 to 130° C. and most preferably from 80 to 95° C., and/or for a period of time of 0.1 to 7 hours, preferably 0.5 to 3.5 hours, more preferably 0.75 to 2.5 hours and most preferably 1 to 2 hours.

12. The process according to claim 1, wherein the aqueous suspension stored in step 0 has solids content of from 5.0 wt.-% to 60.0 wt.-%, preferably from 10.0 wt.-% to 55.0 wt.-%, more preferably from 15.0 wt.-% to 50.0 wt.-% and most preferably from 20.0 wt.-% to 50.0 wt.-%, based on the total weight of the aqueous suspension.

13. The process according to claim 1, wherein the ratio of particles having an average particle size d.sub.80 value to particles having an average particle size d.sub.20 value [d.sub.80/d.sub.20] of the at least one calcium carbonate-comprising material obtained after storing step f) is in the range from 1.7 to 3.5, preferably from 2.2 to 3.4.

14. The process according to claim 1, wherein the process further comprises step g) of dewatering, preferably mechanically, and optionally drying the aqueous suspension obtained in step e) or f) to remove at least a portion of water to obtain a partially dewatered calcium carbonate-comprising material or to obtain a dried calcium carbonate-comprising material.

15. The process according to claim 14, wherein water, preferably deionised water, is added to the partially dewatered calcium carbonate-comprising material obtained after step g) or to the dried calcium carbonate-comprising material to obtain an aqueous suspension and the obtained aqueous suspension is dewatered, preferably mechanically, again, preferably the procedure of adding water and dewatering is repeated two times.

16. The process according to claim 14, wherein the material obtained after step f) or step g) is deagglomerated, preferably in a pin-mill.

17. The process according to claim 14, wherein the obtained material is heated to a temperature in the range from 60 to 150° C., preferably 70 to 130° C. and most preferably 80 to 110° C. to obtain a material with a total moisture content in the range from 0.05 to 0.2 wt.-%, preferably 0.01 to 0.1 wt.-% based on the total weight of the calcium carbonate-comprising material.

18. The process according to claim 15, wherein a) the partially dewatered calcium carbonate-comprising material is treated after dewatering step g) with at least one dispersing agent and re-diluted to obtain an aqueous suspension comprising a dispersed calcium carbonate-comprising material, and/or b) the partially dewatered calcium carbonate-comprising material and/or the dried calcium carbonate-comprising material is treated before or after dewatering or drying step g) with at least one saturated aliphatic linear or branched carboxylic acid and/or with at least one mono-substituted succinic anhydride and/or at least one mono-substituted succinic acid and/or salty reaction product(s) and/or with at least one phosphoric acid ester blend of one or more phosphoric acid mono-ester and/or reaction products thereof and one or more phosphoric acid di-ester and/or reaction products thereof to obtain a hydrophobized calcium carbonate-comprising material.

19. The process according to claim 1, wherein the at least one calcium carbonate-comprising material obtained in step 0 has a) a BET specific surface area of ≦15.0 m.sup.2/g, preferably in the range from 1.0 to 15.0 m.sup.2/g, more preferably from 2.0 to 14.0 m.sup.2/g, and most preferably from 2.5 to 13.0 m.sup.2/g, and/or b) a lower ratio of particles having an average particle size d.sub.80 value to particles having an average particle size d.sub.20 value [d.sub.80/d.sub.20] than a calcium carbonate-comprising material that is obtained in an identical manner but without pre-heating step b) and contacting step d) and/or storing step f).

20. The process according to claim 14, wherein the at least one calcium carbonate-comprising material obtained in step g) has a) a BET specific surface area of ≦15.0 m.sup.2/g, preferably in the range from 1.0 to 15.0 m.sup.2/g, more preferably from 2.0 to 14.0 m.sup.2/g, and most preferably from 2.5 to 13.0 m.sup.2/g, and/or b) a lower ratio of particles having an average particle size d.sub.80 value to particles having an average particle size d.sub.20 value [d.sub.80/d.sub.20] than a calcium carbonate-comprising material that is obtained in an identical manner but without pre-heating step b) and contacting step d) and/or storing step f).

21. A product comprising the calcium carbonate-comprising material obtainable by the process according to claim 1.

22. The product of claim 21, which is paper, paper board, a caulk, a sealant, an adhesive, a paint a coating, a fibre, or a non-woven.

23. The product according to claim 22, wherein the plastic is selected from the group consisting of film applications, preferably blown film applications breathable film applications, biaxially oriented films, preferably polyethyleneterephthalate-, polyamide-, polyethylene- or polypropylene-comprising biaxially oriented films; granulates; pipes; technical profiles; wall panels; ceiling panels cladding panels; wire or cable insulations; sheets; fibres; flexible packaging for industrial and consumer applications, preferably roll stocks, bags, pouches, labels, wraps, liddings, shrink sleeves and stretch films; rigid packaging for industrial and consumer applications preferably plastic bottles, cups and containers; building and construction materials, preferably pipes and conduits, cladding and profiles, insulations, seals and gaskets; geotextiles; agriculture and horticulture materials preferably greenhouse materials, mulch films, tunnel, silage, bale wraps, boxes and crates; transportation and automotive applications preferably interior parts such as instrument and door panels, consoles, pillars and seating, exterior parts such as bumper fascia, fenders, tailgates, under the hood applications preferably air ducts, air intake manifolds, radiators and cooling hoses; electrical and electronic applications preferably CD players, DVD systems, personal computers and TV sets, notebooks, tablets, smartphones, cookers, refrigerators and freezers, washing machines, dishwashers, tools and office equipment; medical and health applications preferably disposable caps, gowns, masks, scrub suits and shoe covers, drapes, wraps and packs, sponges, dressings and wipes, bed linen, contamination control gowns, examination gowns, lab coats, isolation gowns, diagnostic medical machinery and medical devices; personal care products preferably absorbent hygiene products, baby diapers, feminine hygiene products and adult incontinence products, wipes, skin care products, depilatory strips; household and furniture products, preferably wood composites, decorative foils, floor coverings, flooring, kitchen ware, cleaners, pet care, lawn and garden articles; toys, sports and leisure articles preferably playhouses, building kits, play vehicles, sports and fitness devices, shoes, clothing and sportswear, safety equipment like helmets and kneepads, sports equipment and suit cases.

24. The product according to claim 22, wherein the plastic is PVC for window profiles, pipes, technical profiles such as cable- or wire conducts, wall-, ceiling-, or cladding panels or wire insulations.

Description

EXAMPLES

[0378] Measurement Methods

[0379] The following measurement methods are used to evaluate the parameters given in the examples and claims.

[0380] Brookfield Viscosity

[0381] The Brookfield-viscosity of a slurry was determined with a Brookfield Viscometer type RVT equipped with a LV-3 spindle at a speed of 100 rpm and room temperature (20±3° C.).

[0382] BET Specific Surface Area of a Material

[0383] The BET specific surface area is measured via the BET method according to ISO 4652 using nitrogen, following conditioning of the sample by heating at 250° C. for a period of 30 minutes. Prior to such measurements, the sample is filtered, rinsed and dried at 110° C. in an oven for at least 12 hours.

[0384] Particle Size Distribution (Mass % Particles with a Size <X) and Weight Median Particle Size (d.sub.50) of a Particulate Material

[0385] Throughout the present invention, d.sub.50 is the weight median particle diameter by weight, i.e. representing the particle size so that 50 wt.-% of the particles are coarser or finer.

[0386] The average weight median particle diameter of the final products was measured using the sedimentation method. Particle mass was measured directly via X-ray absorption. The sedimentation method measures the gravity-induced settling rates of different size particles in a liquid with known properties. The measurement is made with a Sedigraph™ III Plus 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 was carried out in an aqueous solution of 0.1 wt.-% sodium pyrophosphate-solution (Na.sub.4P.sub.2O.sub.7). The samples were dispersed using a high speed stirrer and supersonic.

[0387] The average volume defined particle size and the average particle size volume distribution of the starting materials are determined via laser diffraction, i.e. the light from a laser passes though a suspension and the particle size distribution is calculated from the resulting diffraction pattern. For samples wherein all particles have the same density, then the volume and mass particle size distributions are the same. The measurement is made with a CILAS 920 particle-size-analyzer of CILAS, Orleans, France.

[0388] pH of an Aqueous Suspension

[0389] The pH of the aqueous suspension is measured using a standard pH-meter at approximately 25° C.

[0390] Solids Content of an Aqueous Suspension

[0391] The suspension solids content (also known as “dry weight”) is determined using a Moisture Analyser HR73 commercialized by Mettler-Toledo HB43 with the following settings: temperature of 160° C., automatic switch off 3, standard drying, 5-20 g of suspension.

[0392] d/d

[0393] The term “d/d” refers to the dry amount based on the dry amount of the solid material.

[0394] Ash Content

[0395] The ash content test was performed by burning 5 to 30 g of the corresponding polymer composition at 570° C. for 120 minutes.

[0396] Filter Pressure Value (FPV)

[0397] 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 μm 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.).

[0398] Yield Stress

[0399] Yield stress determination was performed according to ISO 527-3. The film specimen width was 15 mm and the testing length 5 cm.

[0400] Yield Elongation

[0401] Yield stress determination was performed according to ISO 527-3. The film specimen width was 15 mm and the testing length 5 cm.

[0402] Tensile E-Modulus

[0403] Yield stress determination was performed according to ISO 527-3. The film specimen width was 15 mm and the testing length 5 cm. The E-modulus corresponded to the inclination of the tensile test curve between the points at 0.02% and 2% of elongation.

[0404] Visual Evaluation of the Blown Film

[0405] Film samples have been put under a light microscope. Calcium carbonate agglomerates appear black upon illumination from below and white upon illumination from above. The evaluation “good” means that no pinholes can be observed in the film.

[0406] Visual Evaluation of the Breathable Film

[0407] 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.

[0408] Tear Propagation Resistance

[0409] Determination was performed according to ISO 6383.

[0410] Dart Drop Test

[0411] Measurement was performed according to ASTMD 1709A.

[0412] Water Vapour Transmission Rate (WVTR)

[0413] 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.

[0414] Hydrostatic Pressure Test

[0415] 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 centimetres 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.

[0416] Charpy Impact Strength

[0417] Charpy notched impact strength was measured according to ISO 179-1:2000 according to conditions 1eA on V-notched extruded samples which were cut out of the extrudate in machine direction. Measuring conditions: 23° C.±2° C. and 50%±10% relative humidity. The test specimens were prepared by extrusion as described in ISO 3167 Typ A.

[0418] Surface Gloss

[0419] The surface gloss was measured with a Byk Spectro Guide Sphere Gloss at an angle of 60° from the plane surface according to ISO 2813:1994. The gloss value is determined by calculating the average value of n measurement. In the present set up n=10.

[0420] L*a*b*

[0421] Determination was performed according to DIN 6174.

[0422] Moisture Pick-Up Susceptibility

[0423] The moisture pick up susceptibility has been determined in mg moisture/g after exposure to an atmosphere of 10 and 85% relative humidity, respectively, for each 2.5 h at a temperature of +23° C. (±2° C.). For this purpose, the sample has been first kept at an atmosphere of 10% relative humidity for 2.5 h, then the atmosphere has been 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 has been used to calculate the moisture pick-up in mg moisture/g of sample.

[0424] Tackfreetime

[0425] The tack free time has been determined according to ASTM C679-03(2009)e1. The sealant/adhesive is applied out of a cartridge (3 mm opening) as a 20 cm long string on a plastic film. Every 5 minutes a piece of plastic film (3 cm times 3 cm) is placed on the string of adhesives with soft pressure for 10 seconds. Then the piece of plastic film is removed. If there is no sealant/adhesive residue left on the plastic film, the tack free time is reached. The test is repeated every 5 minutes until tack free time is reached.

[0426] Bond Strength and Maximum Force

[0427] The lap shear test for determining the bond strength has been carried out according to ISO 6237 (2003): standard and is using wood substrates to produce lap shear test pieces. The adhesive is applied with a thickness of 1 mm on an area of 25 mm times 25 mm.

[0428] The maximum force is the force that was applied by the measurement device to destroy the lap shear test piece.

[0429] Tensile Strength at Break

[0430] The tensile strength at break is the force per square mm that is needed to destroy Dumbel test pieces (ISO 37).

[0431] Elongation at Break

[0432] The elongation at break is the maximum elongation which was achieved with the Dumbell test pieces (ISO 37) at the point when the test piece broke.

[0433] Rotational Viscosity

[0434] The viscosity has been measured with a Paar Physica MCR 301 with a plate-plate set up (1 mm gap) with a rotation measurement set up. The viscosity has been measured at different shear rates between 0.1 and 50 Pa s.

[0435] Sodium Content

[0436] The sodium content has been determined by ion chromatography on a Metrohm Compact IC 882 plus.

[0437] Sodium Hydroxide Content

[0438] After the filter cakes were dried and de-agglomerated, they were analysed via XRD for detection of cristallized NaOH. No Na-bearing phase was found in the dried samples so that NaOH does not crystallize during filter cake drying, but is rather present as an amorphous phase. In the trials the remaining NaOH was calculated after determination of the sodium content.

[0439] Preparation of Calcium Carbonate-Comprising Material

Example A (Comparative Example)

[0440] A slurry of dispersant-free wet-ground natural calcium carbonate (obtained by processing of marble from Omya's quarry in Gummern, Austria) featuring an average particle size of about 19 μm (measured on CILAS 920 from Cilas S.A.) was adjusted to a solids content of 45.8 wt.-% and adjusted to a temperature of 40° C.

[0441] The resulting suspension was then further wet-ground in a vertical agitated bead mill with 1.96 m.sup.3 net volume (empty grinding chamber) that was filled with 1 500 kg ZrO.sub.2/Al.sub.2O.sub.3-based grinding beads having a diameter in the range from 1.8 to 2.0 mm and a bulk density of 2 400 kg/m.sup.3. Volumetric feed rate and rotational speed of the mixing shaft were adjusted to obtain a target average particle size after the mill of about 1.8 μm (measured on Sedigraph III Plus from Micromeritics). Shaft rotational speed at these operating conditions was 220 min.sup.−1. Power uptake was 158 kW at 5.0 m.sup.3/h feed rate, corresponding to a specific grinding energy of 49 kWh/dry metric ton.

[0442] The slurry discharged from the mill was then transferred to a decanter centrifuge (SC3043, supplied by Bird-Humboldt) for degritting and to remove coarse particles contained in the slurry. Drum diameter of the centrifuge was 465 mm, pool depth 320 mm and cone angle 10°. Feed rate to the centrifuge was 5.0 m.sup.3/h. Rotational speed was 1 600 min.sup.−1 and differential speed set to 50 min.sup.−1, resulting in a torque of 12%.

[0443] The product discharged from the degritting centrifuge was recovered as an aqueous slurry of ground calcium carbonate. Physical data are given in Table 1a, column A. PSD Sedigraph is given in FIG. 1.

Example B (Invention)

[0444] A slurry of dispersant-free wet-ground natural calcium carbonate (obtained by processing of marble from Omya's quarry in Gummern, Austria) featuring an average particle size of about 17 μm (measured on CILAS 920 from Cilas S.A.) was adjusted to a solids content of 44.5 wt.-% and adjusted to a temperature of 40° C.

[0445] The resulting suspension was then further wet-ground in a vertical agitated bead mill with 1.96 m.sup.3 net volume (empty grinding chamber) that was filled with 3 000 kg ZrO.sub.2/SiO.sub.2-based grinding beads having a diameter in the range from 0.7 to 1.4 mm and a bulk density of 2 300 kg/m.sup.3. Volumetric feed rate and rotational speed of the mixing shaft were adjusted to obtain a target average particle size after the mill of about 1.0 μm (measured on Sedigraph III Plus from Micromeritics). Shaft rotational speed at these operating conditions was 190 min.sup.−1. Power uptake was 268 kW at 4.0 m.sup.3/h feed rate, corresponding to a specific grinding energy of 109 kWh/dry metric ton. To the bottom of the bead mill 5.2 m.sup.3/h of 20° C. tap water was added for dilution.

[0446] The slurry discharged from the mill was then transferred to a decanter centrifuge (SC3043, supplied by Bird-Humboldt) for degritting and to remove coarse particles contained in the slurry. Drum diameter of the centrifuge was 465 mm, pool depth 320 mm and cone angle 10°. Feed rate to the centrifuge was 9.2 m.sup.3/h. Rotational speed was 1800 min.sup.−1 and differential speed set to 60 min.sup.−1, resulting in a torque of 13%.

[0447] The product discharged from the degritting centrifuge was transferred to an agitated autoclave vessel and 0.5% (calculated as active on dry matter CaCO.sub.3) of a 48 wt-% NaOH solution was added. The reaction mixture was then heated and stored at a temperature of 115° C. under agitation for 120 minutes. After 120 min, the slurry was cooled to 25° C. and recovered as an aqueous slurry of ground calcium carbonate. Physical data are given in Table 1a, column B. PSD Sedigraph is given in FIG. 1.

Example C (Comparative Example)

[0448] A slurry of dispersant-free wet-ground natural calcium carbonate (obtained by processing of marble from Omya's quarry in Gummern, Austria) featuring an average particle size of about 31 μm (measured on CILAS 920 from Cilas S.A.) was adjusted to a solids content of 45.2 wt.-% and adjusted to a temperature of 40° C.

[0449] The resulting suspension was then further wet-ground in a vertical agitated bead mill with 1.96 m.sup.3 net volume of the empty grinding chamber and that was filled with 4 000 kg ZrO.sub.2-based grinding beads with a diameter in the range from 0.9 to 1.1 mm and a bulk density of 3800 kg/m.sup.3. Volumetric feed rate and rotational speed of the mixing shaft were adjusted to obtain a target average particle size after the mill of about 60%<1 μm (measured on Sedigraph III Plus from Micromeritics). Shaft rotational speed at these operating conditions was 320 min.sup.−1. Power uptake was 843 kW at 5.6 m.sup.3/h feed rate, corresponding to a specific grinding energy of 241 kWh/dry metric ton. To the bottom of the bead mill 6.4 m.sup.3/h of 20° C. tap water was added for dilution.

[0450] The slurry discharged from the mill was then transferred to a decanter centrifuge (SC3043, supplied by Bird-Humboldt) for degritting and to remove coarse particles contained in the slurry. Drum diameter of the centrifuge was 465 mm, pool depth 320 mm and cone angle 10°. Feed rate to the centrifuge was 12.0 m.sup.3/h. Rotational speed was 1 800 min.sup.−1 and differential speed set to 60 min.sup.−1, resulting in a torque of 15%.

[0451] The product discharged from the degritting centrifuge was recovered as an aqueous slurry of ground calcium carbonate. Physical data are given in Table 1a, column C, PSD Sedigraph is given in FIG. 2.

Example D (Invention)

[0452] The aqueous slurry obtained under example C was transferred to an agitated autoclave vessel and 0.5% (calculated as active on dry matter CaCO.sub.3) of a 48 wt.-% NaOH solution was added. The reaction mixture was then heated and stored at a temperature of 115° C. under agitation for 120 minutes. After 120 minutes, the slurry was cooled to 25° C. and recovered as an aqueous slurry of ground calcium carbonate. Physical data are given in Table 1a, column D. PSD Sedigraph is given in FIG. 2.

TABLE-US-00001 TABLE 1a Example A B C D Unit CE IE CE IE NaOH (% active/ 0 0.5 0 0.5 dry CaCO.sub.3) pH before storage 8.3 12.4 8.3 12.9 Storage temp. ° C. — 115 — 115 Storage after mill min — 120 — 120 SSA m.sup.2/g 5.1 3.0 7.3 4.6 PSD   <5 μm wt.-% 91 97 98 98   <2 μm wt.-% 58 58 84 78   <1 μm wt.-% 32 11 57 33 <0.5 μm wt.-% 15 1 23 5 <0.2 μm wt.-% 6 6 d.sub.50 μm 1.66 1.82 0.87 1.26 d.sub.98 μm 8.20 5.70 5.00 5.20 d.sub.p μm 0.44 0.72 0.30 0.48 Δd.sub.50d.sub.p % 280 146 190 163 Steepness factor 5.5 2.3 4.2 3.3 [d.sub.80/d.sub.20] Normalized SSA 10.sup.6 m/g 3.1 1.7 8.4 3.7 (SSA/d.sub.50) CE: Comparative Example IE: Inventive Example.

[0453] Further Process Steps

[0454] The aqueous slurry obtained in Example D was divided into three parts (Samples D1 to D3) and submitted to further process steps.

[0455] Sample D1 started with a CaCO.sub.3 slurry of 10 000 g of 25 wt.-% solids content. The slurry was not mechanically dewatered but spray dried at an inlet temperature of 200° C.

[0456] Sample D2 started with a CaCO.sub.3 slurry of 10 000 g of 25 wt.-% solids content. The slurry was mechanically dewatered to a solids content of 50 wt.-% by using a press filter equipment at a pressure of 2 to 2.5 bar and the obtained cake was dried in an oven at 110° C. During mechanical dewatering, 7 500 g of tap water was removed.

[0457] Sample D3 started with a CaCO.sub.3 slurry of 10 000 g of 25 wt.-% solids content. The slurry was dewatered by using a press filter equipment at a pressure of 2 to 2.5 bar and the cake was washed out with deionised water. During the first mechanical dewatering step, 2 783 g of tap water were removed in order to obtain a solids content of 47.1 wt.-%. The filter cake was then diluted back with deionised water to a solid content of 26.1 wt.-%. Therefore, 2 679.7 g deionised water were added. Again, the slurry was mechanically dewatered by using the same filter press equipment at a pressure of 2 to 2.5 bar to a solids content of 53.7 wt.-%. Therefore 2760.5 g water were removed. The filter cake was then diluted back with deionised water to a solid content of 26.5 wt.-%. Therefore, 2720.6 g of deionised water were added. And finally the slurry was mechanically dewatered again to a solids content of 54.8 wt.-% by removing 2830 g water. This procedure was repeated two times and the obtained cake after the third dewatering step was dried in an oven at 110° C.

TABLE-US-00002 TABLE 1b D1 D2 D3 Moisture pick-up [mg/g] 10.11 1.73 0.50 NaOH content [wt.-%].sup.a n.d. 0.40 0.06 Sodium content [ppm] n.d. 1291 193 .sup.a)wt.-% based on dry weight of calcium carbonate; n.d. = not determined.

[0458] As can be gathered from Table 1b the washing out of residual base is a very efficient measure for lowering the moisture pick-up of the product obtained after the storing step. The moisture pick-up susceptibility correlates directly with the sodium content and NaOH content in the product.

[0459] Applications in Polymers

Example 1: Preparation of Masterbatches in Polyethylene for Blown Films

[0460] Masterbatches containing 30 wt.-% LLDPE LL 6101 Series (Exxon Mobil), and 70 wt.-% CC1 (comparative example, ground calcium carbonate, commercially available from Omya International AG, Switzerland, d.sub.50: 1.7 μm; d.sub.98: 6 μm, surface-treated with 1 wt.-% stearic acid, commercially available from Sigma-Aldrich, Croda, based on the total weight of the ground calcium carbonate) or CC2 (inventive example, calcium carbonate according to example D and surface-treated with 1 wt.-% stearic acid, based on the total weight of the ground calcium carbonate, commercially available from Sigma-Aldrich, Croda), respectively, 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 2 below. The precise filler content was determined by the ash content. Furthermore, a filter pressure test was carried out in order to determine the dispersion quality of the filler material product.

TABLE-US-00003 TABLE 2 Compositions and properties of prepared masterbatches. Ash FPV at content MFI (190° C., 5 kg) 14 μm Masterbatch Filler [wt.-%] ISO 1133 [g/10 min] [bar/g] MB1 (comparative) CC1 69.1 23.4 0.6 MB2 (inventive) CC2 69.4 23.1 1.4

[0461] The results shown in Table 2 confirm that masterbatches with good quality were produced.

Example 2: Manufacture of Blown Film Samples

[0462] A blown film having a filler content of 20 wt.-% was produced using 71.4 wt.-% of LLDPE LL 6101 Series (Exxon Mobil) and 28.6 wt.-% of a masterbatch according to the above examples (BF1=Comparative Example, BF2=Inventive Example). Films were produced on a Dr. Collin blown film extrusion line (60 mm circular die, 1.2 mm die gap, 30 mm screw diameter, L/D ratio=30, screw with mixing element). The films were processed with a BUR (blow up ratio) of 2.2 and the frost line high was kept at 16 cm high (distance from die).

[0463] The extruder had the following configuration:

TABLE-US-00004 TABLE 3 Extruder configuration. Zone 1 2 3 4 5 T [° C.] 175 195 215 215 215

[0464] Extruder speed was kept constantly at 60 rpm and the average film grammage was set to 35 g/m.sup.2 by appropriate adjustment of the line speed. Also the cooling air flow was adjusted accordingly to keep the frost line at the same position.

[0465] Material and Mechanical Properties of Blown Film Samples:

TABLE-US-00005 TABLE 4 Material and mechanical properties of blown film samples BF1 and BF2. Blown film sample Direction.sup.a BF1 BF2 Yield stress [N .Math. mm.sup.−2] MD 10.1 11.3 CD 10.8 11.8 Yield elongation [%] MD 10.9 10.4 CD 7.6 6.7 Tensile modulus [N .Math. mm.sup.−2] MD 301 315 CD 349 361 Tear propagation resistance [cN] MD 650 720 CD 779 798 Σ 1429 1518 Dart drop fall weight [g] — 657 675 Visual evaluation of film — good good Ash content [wt.-%] — 19.0 18.2 Film thickness [μm] — 34 32 MD = machine direction, CD = cross direction.

[0466] As can be gathered from Table 4 the films comprising the filler according to present invention show improved mechanical properties.

Example 3—Preparation of Polyolefin Masterbatches for Breathable Films

[0467] The following polyolefins have been used for the preparation of masterbatches.

[0468] P1: 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.

[0469] P2: 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.

[0470] Masterbatches containing 45 wt.-% P1, 5 wt.-% P2, and 50 wt.-% CC1 (comparative example, ground calcium carbonate, commercially available from Omya International AG, Switzerland, d.sub.50: 1.7 μm; d.sub.98: 6 μm, surface-treated with 1 wt.-% stearic acid, commercially available from Sigma-Aldrich, Croda, based on the total weight of the ground calcium carbonate) or CC2 (inventive, according to example D and coated with 1 wt.-% stearic acid, based on the total weight of the calcium carbonate, commercially available from Sigma-Aldrich, Croda), respectively, were continuously prepared on Buss kneader (PR46 from Buss AG, Switzerland). The compositions and filler contents of the prepared masterbatches are compiled in Table 5 below. The precise filler content was determined by the ash content.

TABLE-US-00006 TABLE 5 Compositions and properties of prepared masterbatches. Ash content Masterbatch Filler [wt.-%] MB1 (comparative) CC1 48.9 MB2 (inventive) CC2 49.4

Example 4—Preparation of Breathable Films

[0471] 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 masterbatches of Example 3. The roller speed of the stretching unit was 135/135%.

[0472] 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.

TABLE-US-00007 TABLE 6 Compositions and properties of prepared breathable films. Hydro- Film static Sample Masterbatch quality WVTR pressure 1 (comparative) MB1 ok 3850 g//m.sup.2 × day) 330 mbar 2 (inventive) MB2 ok 4700 g/(m.sup.2 × day) 275 mbar

[0473] The results shown in Table 6 confirm that the inventive breathable film has a good quality and breathability, which is superior to the comparative breathable film.

Example 5: Preparation and Testing of PVC-Samples

[0474] The components for comparative examples PVC1, as well as inventive examples PVC2 were previously mixed using the usual hot/cold mixing process known to the skilled person, and extruded on a Krauss-Maffei KMD 2-90 profile extrusion line, L/D=22, with counter rotating parallel twin screws, the screws having a diameter of 90 mm each.

TABLE-US-00008 TABLE 7 Compositions and properties of prepared PVC compounds. Example PVC1 PVC2 PVC resin, K-value 66 100 (phr)  100 (phr)  (Evipol SH6630) Acrylic impact modifier 6 (phr) 6 (phr) (Paraloid KM370) Ca—Zn containing 4.65 (phr)   4.65 (phr)   stabilizer (Stabilox CZ 2913 GN) Titanium dioxide 3.5 (phr)   3.5 (phr)   (Kronos 2220) CaCO.sub.3 according to 8 (phr) 0 Example D CaCO.sub.3.sup.a) 0 8 (phr) Charpy impact strength 49.4 59.5 [kJ/m.sup.2] ISO179/1fC Gloss 60° [—] 50.5 52.0 L*-value 95.2 95.3 a*/b*-value −0.45/3.92 −0.58/3.54 .sup.a)Ground calcium carbonate, commercially available from Omya AG, Switzerland, particle size d.sub.50: 0.8 μm; top cut d.sub.98: 5.0 μm.

TABLE-US-00009 TABLE 8 Compositions and properties of prepared PVC compounds. Example PVC1 PVC2 PVC resin, K-value 66 100 (phr)  100 (phr)  (Evipol SH6630) Acrylic impact modifier  6 (phr)  6 (phr) (Paraloid KM370) Ca—Zn containing 4.65 (phr)   4.65 (phr)   stabilizer (Stabilox CZ 2913 GN) Titanium dioxide 3.5 (phr)  3.5 (phr)  (Kronos 2220) CaCO.sub.3.sup.a) 16 (phr) 0 CaCO.sub.3 according to 0 16 (phr) Example D Charpy impact resistance 55.2 56.9 [kJ/m.sup.2] ISO179/1fC Gloss 60° [—] 33.7 40.7 L*-value 95.5 95.3 a*/b*-value −0.22/4.18 −0.45/4.04 .sup.a)Ground calcium carbonate, commercially available from Omya AG, Switzerland, particle size d.sub.50: 0.8 μm; top cut d.sub.98: 5.0 μm.

[0475] As can be gathered from the results given in Tables 7 and 8 mechanical and optical properties improve when the inventive products are applied. Particularly noteworthy is the significant improvement of the gloss at higher filler contents (see Table 8).

Example 6: Preparation and Testing of Parquet Adhesives (PA)

[0476] For the preparation of the parquet adhesives PA1 and PA2 the base resin, softener and calcium carbonate were added in a planetary mixer and stirred for 30 minutes, at 400 rpm under full vacuum at 65° C. After allowing the resulting mixture to cool to room temperature the remaining components as given in Table 9 were added and stirring was continued for another 5 minutes at 200 rpm under vacuum (413 mbar). Afterwards the planetary mixer was purged with nitrogen and the obtained mixture was filled into a cartridge and was stored for 24 hours at 23° C. and 50% humidity.

TABLE-US-00010 TABLE 9 Compositions of prepared parquet adhesives. Example PA1 (comparison) PA2 (invention Base resin 246 (g) 246 (g) (Kaneka SAX260) Softener 123 (g) 123 (g) (DIUP, Jayflex by Exxon) Vinyl silane 1  6.0 (g)  6.0 (g) (Dynasylan VTMO) Aminosilane  7.5 (g)  7.5 (g) (Dynassylan AMMO) Hardening catalyst  2.5 (g)  2.5 (g) (Neostann S-1) UFPCC 103 g 103 g CaCO.sub.3.sup.a) 512 (g) — CaCO.sub.3 according to — 512 (g) Example D .sup.a)Ground calcium carbonate, commercially available from Omya AG, Switzerland, particle size d.sub.50: 0.9 μm; top cut d.sub.98: 5 μm, moisture pick-up: 0.35%.

TABLE-US-00011 TABLE 10 Results of application tests, mechanical properties and viscosity. Example PA1 (comparison) PA2 (invention Tackfreetime [min] 50 50 Extrusion rate [g/min] 220 280 Bond strength [N/mm.sup.2] 2.10 2.53 Maximum force [N] 1265 1515 Modulus 100% [%] 2.0 2.1 Tensile at break 1.8 2.2 Elongation at break 145 165 [N/mm.sup.2] η at 0.1 s.sup.−1 [Pa .Math. s] 2505 2640 η at 1 s.sup.−1 [Pa .Math. s] 380 400 η at 5 s.sup.−1 [Pa .Math. s] 100 105 η at 10 s.sup.−1 [Pa .Math. s] 65 65 η at 50 s.sup.−1 [Pa .Math. s] 20 25

[0477] As can be gathered from the results given in Tables 10 mechanical and rheological properties improve when the inventive products are applied.