Composition and method for controlling the wettability of surfaces

Abstract

The present invention relates to a composition comprising hedgehog shaped particles, at least one binder, and at least one hydrophobizing agent and/or at least one hydrophilizing agent, a method for controlling the wettability of substrate surfaces using these compositions, as well as a material comprising these compositions.

Claims

1. A method for controlling the wettability of a substrate surface comprising: a) coating the substrate surface with a coating formulation comprising a mixture of i) at least one binder, ii) hydrophilized hedgehog shaped particles pre-treated and coated with at least one hydrophilizing agent but not a hydrophobizing agent and hydrophobized hedgehog shaped particles pre-treated and coated with at least one hydrophobizing agent but not a hydrophilizing agent, and iii) optionally at least one hydrophobizing agent or at least one hydrophilizing agent, to form a coating layer; and b) applying one or more post-layers of at least one hydrophobizing agent and/or at least one hydrophilizing agent on top of the coating layer, wherein the at least one hydrophilizing agent is chosen independently in each instance of ii), iii), and b); and wherein the at least one hydrophobizing agent is chosen independently in each instance of ii), iii), and b).

2. The method of claim 1, wherein the substrate is selected from the group consisting of paper, board, wall-paper, wood, a wood composite, flake board, a plastic, foil, concrete, a coated rendering, an uncoated rendering, plaster, a metal, a ceramic, stone, a brickstone and glass.

3. The method according to claim 1, wherein the coating formulation does not include the at least one hydrophobizing agent or the at least one hydrophilizing agent in iii).

4. The method according to claim 1, wherein the coating formulation in iii) comprises the at least one hydrophobizing agent.

5. The method according to claim 1, wherein the coating formulation in iii) comprises the at least one hydrophilizing agent.

6. The method according to claim 1, wherein the at least one hydrophobizing agent is applied as the one or more post-layers in b).

7. The method according to claim 1, wherein the at least one hydrophilizing agent is applied as the one or more post-layers in b).

8. The method according to claim 1, wherein the coating formulation in iii) does not include the at least one hydrophobizing agent or the at least one hydrophilizing agent, and the at least one hydrophobizing agent is applied as the one or more post-layers in b).

9. The method according to claim 1, wherein the hedgehog shaped particles are composed of aragonitic precipitated calcium carbonate in a form of clusters of needle like crystals.

10. The method according to claim 1, wherein the hedgehog shaped particles are clusters and/or aggregates of scalenohedral precipitated calcium carbonate.

11. The method according to claim 1, wherein the at least one binder is a styrene-acrylic latex, an acrylonitrile, a polyvinyl alcohol or linseed oil.

12. The method according to claim 1, wherein the at least one hydrophobizing agent is chosen independently in each instance of ii), iii), and b) from the group consisting of fatty acids, stearic acid, palmitic acid, and their salts; alkylketene dimer; polyacrylamide resins; silicone resins, polysiloxanes, polysiloxane modified with a functional silicone resin, and any mixture thereof.

13. The method according to claim 1, wherein the at least one hydrophilizing agent is chosen independently in each instance of ii), iii), and b) from the group consisting of polyacrylic acids, salts of 1-hydroxyethane-1, 1-diphosphonic acid, alkali metal salts thereof, potassium salts thereof chelates of 1-hydroxyethane-1, 1-diphosphonic acid, aluminium hydroxide chelates thereof, aluminium hydroxide/1-hydroxyethane-1,1-diphosphonic acid chelates having a weight ratio of 1:5, and any mixture thereof.

14. The method according to claim 1, wherein the at least one binder is present in the coating formulation in an amount of up to 250 wt % based on the weight of the hedgehog shaped particles.

15. The method according to claim 1, wherein the at least one binder is present in the coating formulation in an amount of 3 to 25 wt %, based on the weight of the hedgehog shaped particles.

16. The method according to claim 1, wherein the coating formulation further comprises one or more additives selected from the group consisting of dispersing agents, siliconizing agents, thickeners, rheology modifiers, anti-settling agents, defoamers, antioxidants, bluing agents, surfactants, crosslinkers, flame retardants, catalysts, pH buffers, fillers, dyes, pigments, optical brighteners, waxes, coalescence agents, and biocides.

17. The method according to claim 1, wherein the coating formulation is in the form of a solution or dispersion in a liquid medium.

18. The method according to claim 1, wherein the coating formulation is in the form of a medium comprising one or more of water, an alcohol ether, an alcohol, an aliphatic hydrocarbon, and an ester.

Description

DESCRIPTION OF THE FIGURES

(1) FIGS. 1a and 1b show SEM images of hedgehog shaped PCC particles to be used in the invention.

(2) FIGS. 2a and 2b show SEM images of hedgehog shaped PCC particles to be used in the invention.

(3) FIGS. 3a and 3b show SEM images of hedgehog shaped PCC particles to be used in the invention.

(4) FIG. 4 shows contact angles of substrates coated with different samples of pre-hydrophobized and/or pre-hydrophilized hedgehog shaped particles according to the invention.

(5) FIG. 5 shows a photograph of a droplet on a substrate being coated with a coating formulation according to the invention having a high contact angle.

(6) FIG. 6 shows contact angles of substrates coated with different samples of highly coated pre-hydrophobized and/or pre-hydrophilized hedgehog shaped particles according to the invention, as well as additional hydrophilizing agents.

(7) FIG. 7 shows contact angles of substrates coated with different samples of slightly coated pre-hydrophobized and/or pre-hydrophilized hedgehog shaped particles according to the invention, as well as additional hydrophilizing agents.

(8) FIG. 8 shows contact angles of substrates coated with different samples of pre-hydrophilized hedgehog shaped particles and different binders.

(9) FIG. 9 shows a photograph of a droplet on a substrate having been coated with a coating formulation according to the invention having a low contact angle.

(10) FIG. 10 shows contact angles of substrates coated with different samples of pre-hydrophobized and pre-hydrophilized hedgehog shaped particles according to the invention, as well as additional hydrophilizing agents and binders.

(11) FIG. 11 shows contact angles of substrates coated with different samples of pre-hydrophobized hedgehog shaped particles in combination with silicone post-layers.

(12) FIG. 12 shows a photograph illustrating the wetting behaviour of substrates coated with pre-hydrophilized hedgehog shaped particles.

(13) FIG. 13 shows a photograph illustrating the wetting behaviour of substrates coated with pre-hydrophobized hedgehog shaped particles.

(14) FIG. 14 shows a photograph illustrating the wetting behaviour of substrates coated with pre-hydrophobized hedgehog shaped particles and two silicone post-layers.

(15) FIG. 15 shows a photograph illustrating the wetting behaviour of substrates coated with pre-hydrophobized hedgehog shaped particles and three silicone post-layers.

(16) FIG. 16 shows contact angles of substrates coated with different samples of pre-hydrophobized hedgehog shaped particles using different hydrophobizing agents, and post-layers of hydrophobizing agents.

(17) FIG. 17 shows contact angles of substrates coated with different coating formulations and post-layers according to the invention.

EXAMPLES

(18) The following experiments were carried out for determining the properties of compositions according to the invention on the wetting of substrates. This is achieved by preparing coating formulations, applying the same on substrates, wetting the substrate surface, and subsequent measurement of the contact angles of the water droplets present on the substrate surface, wherein the contact angle is an indicator for hydrophobicity/hydrophilicity of a surface.

(19) For this purpose, coating formulations of pre-hydrophobized, pre-hydrophilized and untreated hedgehog shaped PCCs as well as mixtures thereof were prepared, optionally comprising further components.

(20) These coating formulations were applied to Synteape® foils and raw paper, and, after drying, and, in some cases, application of post-layers of hydrophobizing agent and other agents, the contact angle and/or wetting behaviour was determined.

Example 1

Pre-Treated Hedgehog Shaped Particles

(21) 1. Material

(22) 1.1. Laboratory Equipment and Methods of Measurement

(23) For Coating the Substrates:

(24) Erichsen Bar Coater K-Control-Coater K202, Model 624/Fabr. No. 57097-4/wire-wound rod No. 1//Belt dryer 7.0 mmin.sup.−1/150 ° C.

(25) Viscosity Measurement

(26) All Brookfield-viscosities are measured with a Brookfield DV-II Viscometer equipped with a LV-3 spindle at a speed of 100 rpm and room temperature (20±3° C.).

(27) Solids Content of an Aqueous Slurry

(28) All mineral preparation solids content (also known as “dry weight”) was measured using a Mettler Toledo HB 43-S Moisture Analyser.

(29) For SEM Images:

(30) RDS-ARM-MIC Lims: 220017

(31) Scanning electron micrographs (SEM) were carried out by adjusting the solids content to a concentration of 20 wt % in water using an ultraturax (rotor-stator-mixer). A few drops (approximately 100 mg) were diluted in 250 ml distilled water and filtered through 0.2 μm pore membrane filter. Preparations obtained on the membrane filter in this way were sputtered with gold and evaluated in the SEM at various enlargements.

(32) Regarding the SEM images of coatings, a sample of the coated substrate was sputtered with gold and evaluated in the SEM at various enlargements.

(33) For Contact Angle Measurements:

(34) For measuring the contact angle, 4 water drops of 5 μl each were applied on 4 Synteape® foils, a photograph was taken 120 s after application. The determination of the contact angle was carried out visually with the aid of the measuring module of the Image Access database Version 8 based on the photos made of the droplets, and an average value was calculated.

(35) TABLE-US-00001 Camera: Canon EOS 5D Mark II Objective: Canon EF 100 mm f/2 8L Macro IS USMDDDD Difference adjustment: 0.3 m Distance rings: Kenko distance rings 12 + 24 + 36 mm Tripod and illumination Kaiser microdrive tripod + 2x Repro illumination equipment RB5055 HF Release: Canon remote control/Timer TC-80N3 Data of recording: Brightness balance: automatically Lens opening: lens opening adjustment 32 Illumination time: automatically Release delay: 120 s after drop application Drop size: 5 μl

(36) 1.2. Raw Material

(37) PCC 1: precipitated calcium carbonate; solids content 18 wt %; BET specific surface area: 2 m.sup.2/g, d.sub.50: 8 μm; calcite content>99%, the crystals having a clustered scalenohedral morphology (cf. FIGS. 1a and b)

(38) PCC 2: precipitated calcium carbonate; solids content 14 wt %; BET specific surface area: 11.7 m.sup.2/g (cf. FIGS. 2a and 2b)

(39) PCC 2 was prepared as follows:

(40) a) Stage 1: Seed Preparation

(41) 160 kg of quicklime CaO (e.g., the quicklime supplied by Mississippi Lime Co., Ste. Geneviéve, Mo.) was slaked by adding the compound to 1.300 litres of 50° C. tap water in a stirred reactor. The quicklime was slaked for 30 minutes under continuous stirring and the resulting slurry of calcium hydroxide (“milk of lime”) was adjusted to 13% solids content via dilution with 60° C. water and was then screened on a 100 μm screen. Prior to the carbonation, 5.0 wt % percent of Sr(OH).sub.2.8H.sub.2O (based on the dry weight of calcium hydroxide) was added to the milk of lime.

(42) The aragonitic PCC seed precipitation was conducted in a 1 000 litre baffled cylindrical stainless steel reactor equipped with an gassing agitator, a stainless steel carbonation tube to direct a carbon dioxide/air gas stream to the impeller and probes for monitoring the pH and conductivity of the suspension. 800 litres of the calcium hydroxide suspension obtained in the slaking step above, adjusted to a temperature of 60° C., were added to the carbonating reactor. A gas of 6% by volume of CO.sub.2 in air was then bubbled upwards through the slurry at a rate of 100 m.sup.3/h for 15 minutes (calculated from start of introduction of the CO.sub.2 gas) under a slurry agitation of 1 480 rpm. Thereafter, the CO.sub.2 volume fraction in the gas was augmented to 24% and the gas flow rate was augmented to 200 m.sup.3/h. The CO.sub.2 volume fraction and gas flow rate were maintained at this rate until the end of the reaction. During the carbonation, the temperature of the reaction mix was not controlled and was allowed to rise due to the heat generated in the exothermic precipitation reaction. After conductivity reached a minimum corresponding to the total conversion of Ca(OH).sub.2 into PCC, the gassing was continued for another 8 minutes before the introduction of gas was stopped. Carbonation time, calculated from start of gas introduction to the time of minimum conductivity, was 84 minutes. The aragonitic PCC seed slurry was then screened on a 45 μm screen and the screened product was recovered as an aqueous slurry of the aragonitic PCC seed. The aragonitic seed carbonation with the addition of 5.0 wt % Sr(OH).sub.2.8H.sub.2O yielded an aragonitic PCC seed slurry having 96.1% aragonite.

(43) The aragonitic PCC seed slurry was submitted to post processing by dewatering and grinding it to yield particles having an SSA of 20.6 m.sup.2/g and a weight median diameter of 0.22 μm.

(44) b) Stage 2: Manufacturing of Final Aragonitic PCC2

(45) Slaking and carbonation were performed in the same manner as described above in Stage 1, except that no Sr(OH).sub.2.8H.sub.2O was added and 2.5% weight percent (calculated as dry calcium carbonate based on dry weight of calcium hydroxide) of the ground aragonitic PCC seeds formed in Stage 1 was added to the milk of lime prior to carbonation. Testing conducted on the final aragonitic PCC product indicated that 77.6 wt % of the product was of the aragonitic crystal form. In addition, post processing was conducted, as described in Stage 1 above, to yield particles having an SSA of 11.7 m.sup.2/g and a median diameter of 0.41 μm. Subsequently, an aqueous slurry was prepared having a solids content of 14 wt %. The hedgehog particle form of PCC2 can be perfectly seen in FIGS. 2a and 2b.

(46) Hydrophobizing Agents:

(47) Blend of palmitic acid and stearic acid (weight ratio: 1:1) (30 wt % in 95% ethanol): 0.4 g/100 g (0.4 pph) (slightly coated) and 1.9 g/100 g (1.9 pph) (highly coated) based on the weight of PCC

(48) Hydrophilizing agents:

(49) Polymer solution of 0.33 wt % partially neutralized polyacrylic acid with a mass weight of 12 000 g/mol and a polydispersity D (Mw/Mn) of about 3, wherein about 50 mole % of the carboxylic groups are neutralized with Na.sup.+ ions; and 0.17 wt % NaH.sub.2PO.sub.4; 0.5 g/100 g (0.5 pph) based on the weight of PCC
K4-HEDP (potassium salt of hydroxy ethane-1,1-diphosphonic acid); solids content 55 wt %; prepared under stirring by adding potassium hydroxide to HEDP until a pH of 12 is reached:
Potassium hyroxide (SIGMA-Aldrich Art.No.: 60370)
HEDP (hydroxy ethane-1,1-diphosphonic acid; solids content 60 wt %, CF Budenheim; trade name Budex 5120)
Al(OH).sub.3-HEDP (aluminium hydroxide / hydroxy ethane-1,1-diphosphonic acid chelate; weight ratio 1:5); solids content 53 wt %; prepared under stirring by adding aluminium hydroxide to HEDP in a weight ratio of 1:5 at room temperature until a homogeneous mixture is obtained; subsequently heating to up to 90° C. for 1 h until chelate solution is obtained)
Al(OH).sub.3, Martinswerk (ALBEMARLE corporation), MARTIFIN OL-107
HEDP (hydroxy ethane-1,1-diphosphonic acid; solids content 60 wt %, CF Budenheim; trade name Budex 5120)

(50) Binders

(51) Acronal® S360D (styrene-acrylic latex); solids content 50 wt %, BASF Art.: 50005 562

(52) Hycar 1562X117 Emulsion (medium acrylonitril; polar latex); solids content 41.4 wt %, Emerald Performance Materials

(53) PVA BF 05 (Polyvinylalcohol) Chang Chun Petrochemicals Taiwan diluted in cooking water and cooled down, solids content 18 wt %

(54) Linseed oil, Aldrich Art. Nr. 430021-250 ML

(55) Post-Layer Treating Agents

(56) GE Bayer Release Agent M: (siliconizing agent)

(57) Stearic acid solution (saturated in 95% ethanol at room temperature (20±3° C.).

(58) Substrate:

(59) YUPO (Synteape®)/Art.: 675227, white half-matt PP 18×26 (468 cm.sup.2); 62 g/m.sup.2

(60) Raw paper: Sappi Magno matt classic 18×26 (468 cm.sup.2) 82 g/m.sup.2

(61) 2. Methods

(62) 2.1. Sample Preparation

(63) 2.1.1 Pre-Treated Hydrophobized Particles

(64) 4 000 g of the repective PCC slurries were heated up to 80° C. and a blend of palmitic acid and stearic acid (weight ratio: 1:1) diluted in warm 95% ethanol (about 50° C.) was added during 10 minutes. The mixture was stirred for 1 h at 80° C. in a 5 litre double wall steel vessel fitted with viscojet stirrer and thermostat for temperature control. After cooling down, the slurries were dried in an oven for 15 h at 120° C.

(65) 2.1.2. Pre-Treated Hydrophilized Particles

(66) To 8 000 g of the respective PCC slurries 0.5 pph of the afore-mentioned polymer solution of partially neutralized polyacrylic acid were added during 10 minutes. The mixture was stirred for 1 h at room temperature in a 10 litre plastic bucket. The slurries were dried in an oven for 15 h at 120° C.

(67) 2.1.3. Coating Formulations

(68) The coating formulations were produced by adding the pre-hydrophobized and/or pre-hydrophilized PCC particles in portions, as well as optionally further components such as further hydrophilizing agents (as indicated below) to a mixture (ideally a solution) of the respective binder in tap water under stirring in a VMA Dispermat® (VMA-Getzmann GmbH, Reichshof, Germany) with a 70 mm dispersing disk, and subsequently stirring the mixture for 1 hour. The coating formulations were screened over a small tea-sieve having a screen size of 500 nm, and viscosity and solids content were determined (cf. tables 1 to 5)

(69) All coating formulations showed thixotropic and settling properties. All coating formulations containing hydrophobic particles showed anti-wetting properties.

(70) The coating formulations were coated on an impermeable plastic substrate (Synteape®) (two papers per colour) and raw paper for samples 20 (raw) and 21 (raw). On the Synteape° foils, the formulations were applied, pre-dried 3 times under a 150° C. heater via a rolling conveyor belt and post dried 24 h at room temperature. The resulting film thickness was from 0.1 to 0.3 mg/cm.sup.2.

(71) 2.1.4. Post-Layer

(72) For verifying the impact of post-layering, sample 1 was post-treated by applying silicone post-layer on top of the PCC coating after drying. This was carried out by means of a commercial spray agent by applying for 3 seconds the spray mist onto the coated composition surface. Thus, 1 (sample 22S1), 2 (sample 22S2), and 3 (sample 22S3) silicone post-layers, respectively, were formed on top of the PCC coating.

(73) TABLE-US-00002 TABLE 1 Mixtures of pre-hydrophobized and pre-hydrophilized PCC 1 Sample 1 Sample 2 Sample 3 Sample 4 Hydrophobized PCC 1 190.5 g 133.3 g  57.1 g — (dry) (0.4 pph) Hydrophilized PCC 1 —  57.1 g 133.2 g 190.5 g (dry) Acronal S 360 D  19.0 g  19.0 g  19.0 g  19.0 g Tap water 290.5 g 290.5 g 290.5 g 290.5 g Total 500.0 g 500.0 g 500.0 g 500.0 g Viscosity 130   102   160   152   mPa .Math. s/ 100 rpm Final solids content, 38.9 37.9 39.6 39.8 wt %

(74) TABLE-US-00003 TABLE 2 Mixtures of highly coated pre-hydrophobized and pre- hydrophilized PCC 2, and additional hydrophilizing agents Sample 5 Sample 6 Sample 7 Sample 8 Hydrophobized PCC 2  94.1 g  85.8 g  36.8 g — (dry) (1.9 pph) Hydrophilized PCC 2 —  36.8 g  85.8 g 122.5 g (dry) Acronal S 360 D  9.4 g  12.3 g  12.3 g  12.3 g Tap water 294.3 g 362.8 g 362.7 g 362.8 g K4-HEDP, 55%  2.0 g  2.2 g  2.2 g  2.2 g Al(OH).sub.3-HEDP, 53%  0.2 g  0.2 g  0.2 g  0.2 g Total 400.0 g 500.0 g 500.0 g 500.0 g Viscosity 340   170   130   121   mPa .Math. s/100 rpm Final solids content, 24.9 24.9 24.8 25.3 wt %

(75) TABLE-US-00004 TABLE 3 Mixtures of slightly coated pre-hydrophobized and pre- hydrophilized PCC 2, and additional hydrophilizing agents Sample 9 Sample 10 Sample 11 Sample 12 Hydrophobized PCC 2 151.9 g  86.0 g  36.9 g — (dry) (0.4 pph) Hydrophilized PCC 2 —  36.9 g  86.0 g 122.9 g (dry) Acronal S 360 D  15.2 g  12.3 g  12.3 g  12.3 g Tap water 561.1 g 363.0 g 363.0 g 363.0 g K4-HEDP, 55%  1.6 g  1.6 g  1.6 g  1.6 g Al(OH).sub.3-HEDP, 53%  0.2 g  0.2 g  0.2 g  0.2 g Total 730.0 g 500.0 g 500.0 g 500.0 g Viscosity 110   130   130   127   mPa .Math. s/100 rpm Final solids content, 21.9 26.0 26.0 26.0 wt %

(76) TABLE-US-00005 TABLE 4 Different binders used with pre-hydrophilized PCC1 Sample 13 Sample 14 Sample 15 Sample 16 Hydrophilized 152.0 g 145.5 g 142.9 g 136.5 g PCC 1 (dry) Hycar,  18.4 g  35.1 g — — 41.4 wt % PVA, 15 wt % — —  49.3 g  94.1 g Tap water 249.6 g 319.4 g 182.9 g 164.4 g Total 420.0 g 500.0 g 275.0 g 395.0 g Viscosity 177   177   719   388   mPa .Math. s/100 rpm Final solids 37.4 31.4 39.5 38.1 content, wt %

(77) TABLE-US-00006 TABLE 5 Different PCCs in the presence of further hydrophilizing agents Sample Sample Sample Sample Sample 17 18 19 20 21 Hydrophilized  73.5 g — — — — PCC 1 (dry) Hydrophobized — — — — 10.0 g PCC 1 (dry) Hydrophobized —  10.4 g  10.4 g 10.0 g — PCC 2 (dry) (1.9 pph) Acronal S — — — — — 360 D Linseed oil — — — 20.0 g 20.0 g K4-HEDP  1.3 g — — — — Al(OH).sub.3-HEDP  0.1 g — — — — PVA, 18 wt %  20.1 g  69.6 g  69.6 g — — Tap water 205.0 g — 120.0 g — — Total 300.0 g  80.0 g 200.0 g 30.0 g 30.0 g Viscosity 102   mPa .Math. s/100 rpm Final solids 25.2 24.1 10.6 content, wt %

(78) 2.2. Determination of the Contact Angle

(79) For determining the contact angle, water drops of 5 μl each were applied on the coated Synteape® foils. The drops thus formed were photographed and the contact angle was determined with the aid of the measuring module of the Image Access database Image Access Version 8. The below listed contact angles are an average of several measurements of the same setup.

(80) TABLE-US-00007 TABLE 6 Coated sheets and wetting contact angles Coating/ Coating/ Coating/ Coating/ Weight ratio Average sheet sheet sheet sheet Hydro-phob./ contact Std. (sheet 1) (sheet 1) (sheet 2) (sheet 2) Hydro-phil. angle deviation Sample [mg] [mg/cm.sup.2] [mg] [mg/cm.sup.2] PCC [°] [°]  1 148.8 0.3 115.6 0.3 100:0 139 9  2 129.8 0.3 110.7 0.3  70:30 112 4  3 133.4 0.3 163.2 0.3  30:70 107 10  4 140.2 0.3 86.8 0.2   0:100 102 2  5 59.8 0.2 49.2 0.2 100:0 100 4  6 45.9 0.2 37.5 0.2  70:30 67 3  7 50.3 0.2 51.3 0.2  30:70 61 9  8 56.8 0.2 51.4 0.2   0:100 44 8  9 38.6 0.1 42.7 0.2 100:0 102 2 10 50.7 0.1 55.7 0.2  70:30 58 9 11 62.5 0.2 60.0 0.2  30:70 44 9 12 66.0 0.2 54.3 0.2   0:100 29 7 13 70.5 0.3 84.6 0.3   0:100 86 2 14 85.5 0.3 72.8 0.3   0:100 81 4 15 115.8 0.3 105.1 0.3   0:100 48 11 16 134.2 0.3 113.4 0.3   0:100 30 8 17 205.3 0.7 197.0 0.7   0:100 7 1 18 300.5 0.8 332.5 0.8 100:0 46 3 19 158.2 0.5 157.6 0.5 100:0 34 3 20 472.5 1.5 405.5 1.3 100:0 88 2 20 raw — — — — 100:0 110 3 21 — — — — 100:0 85 2 21 raw — — — — 100:0 103 3 22S1 — — — — 100:0 132 2 22S2 — — — — 100:0 133 5 22S3 — — — — 100:0 130 4

(81) As can be taken from the above contact angles, it is possible to control accurately the hydrophobicity/hydrophilicity of substrate surfaces by tailor-made coatings using hedge-hog shaped PCC according to the invention.

(82) As can be seen from samples 1 to 4, the contact angle, and thus the hydrophobicity of the substrate surface can be accurately adjusted by mixing hydrophobized and hydrophilized hedgehog shaped PCC (cf. FIG. 4).

(83) The high contact angle of sample 1 is illustrated by FIG. 5.

(84) The same applies to samples 5 to 8 using a slightly different particle form. Also, in these tests, the contact angle, and thus the hydrophobicity of the substrate surface can be accurately adjusted by mixing hydrophobized and hydrophilized hedgehog shaped PCC. Furthermore, as can be taken from these samples, by admixing further hydrophilizing agents, it is possible to lower the hydrophobicity as desired reflected by lower contact angles (cf. FIG. 6)

(85) As can be taken from the results of samples 9 to 12, being essentially identical with samples 5 to 8 apart from the fact that the hydrophobized PCC comprises less hydrophobizing agent, the effects can already be observed at a rather low amount of hydrophobizing agent (cf. FIG. 7)

(86) In samples 13 to 16, the influence of different binders was evaluated, and it was found that also by using different binders the hydrophilic properties can be further controlled. Thus, with the same kind of hydrophilized PCC, hydrophilicity can be increased by using Hycar instead of Acronal, and can be even more increased by using PVA (cf. FIG. 8)

(87) As can be taken from the results of sample 17, this effect can even be increased by adding further hydrophilizing agents leading to a nearly complete wetting of the substrate surface. The low contact angle of sample 17 is illustrated by FIG. 9.

(88) The influence of different binders on hydrophobized PCC can be taken from the results of samples 18 to 21. Thus, PVA decreases hydrophobicity compared with Acronal, wherein the effect is dependent on the amout of water in the coating formulation. In this respect, it was also shown that the control of hydrophobicity is not only possible with aqueous formulations, but also in oil-based formulations such as those based on linseed oil (cf. samples 20 and 21) providing comparable effects (cf. FIG. 10).

(89) Furthermore, looking at the contact angles of samples 20 and 21 on Synteape® foil and raw paper, it can be seen that a higher contact angle, i.e. increased hydrophobicity can be obtained on raw paper.

(90) In samples 22S1, 22S2, 22S3, the influence of a silicone post-layer was verified. For this purpose a coating of sample 1 was one to three times coated with silicone post-layers. The results show that the high hydrophobization degree of sample 1 is essentially equal with the siliconized samples (cf. FIG. 11)

(91) 2. 3. Wetting

(92) For investigating the wetting behaviour, especially the wetting behaviour with finely divided water droplets simulating mist or dew, sheets coated with samples 1, 12, 22S2 and 22S3 were mounted on a metal panel. Deionized water was applied by a micro diffuser. After each stroke a picture of the sheet was made and the weight of the applied deionized water was measured. From table 7, the amounts of applied deionized water can be taken.

(93) TABLE-US-00008 TABLE 7 Sample Sample Sample Sample Stroke 1 12 22S2 22S3 No. [g] [g] [g] [g] 0 0.000 0.000 0.000 0.000 1 0.327 0.375 0.256 0.483 2 0.756 0.807 0.668 0.889 3 1.253 1.143 1.185 1.240 4 1.783 1.467 1.643 1.759 5 2.277 1.758 2.022 2.152 6 2.753 2.110 2.520 2.623 7 3.546 2.480 3.064 3.090 8 3.528 2.796 3.599 3.555 9 3.970 3.120 4.359 4.005 10 4.411 3.421 4.941 4.516 11 4.797 3.685 5.491 4.956 12 5.271 3.950 6.022 5.468 13 5.767 4.209 6.556 5.983 14 6.178 4.607 7.044 6.492 15 6.677 5.039 7.577 6.959 16 7.129 5.461 8.006 7.393 17 7.639 5.944 8.422 7.920 18 7.992 6.355 8.859 8.363 19 8.366 6.799 9.325 8.879 20 8.740 7.200 9.828 9.323 21 9.129 7.701 10.253 9.874 22 9.466 8.149 10.731 10.366 23 9.870 8.636 11.185 10.970 24 10.143 9.275 11.609 11.529 25 10.542 9.776 12.090 11.987

(94) From the images shown in FIGS. 12 to 15 clearly the wetting (superwetting) behaviour of hydrophilized PCC sample 12 promoting a film wetting and disabling drop formation can be seen compared to samples 1, 22S2 and 22S3, showing repellent/superhydrophobic behaviour promoting drop formation and drop roll-off, wherein any one of these samples were sprayed with the same amount of water of about 5 g as can be taken from table 7 (bold amounts reflect the samples illustrated by FIGS. 12 to 15).

Example 2

Untreated Hedgehog Shaped Particles

(95) In Example 2, instead of pre-hydrophobizing/pre-hydropilizing the hegdehog shaped particles, the untreated particles were combined with the corresponding hydrophilizing and/or hydrophobizing agents upon preparation of the coating formulation only, and/or by ways of one or several post-layers.

(96) 1. Material

(97) 1.1. Laboratory Equipment and Measurement Methods

(98) For Coating the Substrates:

(99) Erichsen Bar Coater K-Control-Coater K202, Model 624/Fabr. No. 57097-4/coating rods 1-5 (control of the liquid flow)//Belt dryer 7.0 mmin.sup.−1/150° C.

(100) Spraying

(101) Eco Spray Microdiffusor, Labo Chimie

(102) Solids Content of an Aqueous Slurry

(103) All mineral preparation solids contents (also known as “dry weight”) were measured using a Mettler Toledo HB 43-S Moisture Analyser.

(104) For SEM Images:

(105) RDS-ARM-MIC Lims: 220017

(106) Scanning electron micrographs (SEM) were carried out by adjusting the solids content to a concentration of 20 wt % in water using an ultraturax (rotor-stator-mixer). A few drops (approximately 100 mg) were diluted in 250 ml distilled water and filtered through 0.2 μm pore membrane filter. Preparations obtained on the membrane filter in this way were sputtered with gold and evaluated in the SEM at various enlargements.

(107) For Contact Angle Measurements:

(108) TABLE-US-00009 Camera: Canon EOS 5D Mark II Objective: Canon EF 100 mm f/2 8L Macro IS USMDDDD Difference adjustment: 0.3 m Distance rings: Kenko distance rings 12 + 24 + 36 mm Tripod and illumination Kaiser microdrive tripod + 2x Repro illumination equipment RB5055 HF Release: Canon remote control/Timer TC-80N3 Data of recording: Brightness balance: automatically Lens opening: lens opening adjustment 32 Illumination time: automatically Release delay: 120 s after drop application Drop size: 5 μl

(109) 1.2. Raw Material

(110) PCC 2: precipitated calcium carbonate; solids content 14 wt %; BET specific surface area: 11.7 m.sup.2/g; prepared as described above (cf. FIGS. 2a and 2b)

(111) PCC 3: precipitated calcium carbonate Omya Syncarb® (available from Omya AG, Switzerland); solids content: 14 wt %; BET specific surface area: 3.5-6.5 m.sup.2/g (cf. FIGS. 3a and 3b)

(112) Hydrophobizing Agents:

(113) ASA Nalsize 7541 (Alkyl succinic anhydride); solids content 22.29 wt %, Ondeo Nalco Co.

(114) AKD DR28XL (alkylketene dimer); solids content 23.9 wt %, Eka Chemicals

(115) Stearic acid, Sigma S4751-100G

(116) Wükoseal® 805; solids content 40 wt %; Süddeutsche Emulsions-Chemie GmbH (SEC), Mannheim-Neckarau, Germany

(117) Silres BS 1306 (polysiloxane modified with functional silicone resin), solids content 55 wt %; Wacker Chemie AG

(118) Binders

(119) Acronal® S360D (styrene-acrylic latex) solids content 50 wt %, BASF Art.: 50005 562 Substrate:

(120) YUPO (Synteape®)/Art.: 675227, white half-matt PP 18×26 (468 cm.sup.2); 62 g/m.sup.2

(121) 2. Methods

(122) 2.1. Sample Preparation

(123) With the below samples given in tables 8 and 9, several embodiments of the invention were verified:

(124) a) Samples 23 to 26 (PCC2) and 28 to 29 (PCC3): Combination of hedgehog shaped particles with the binder and the hydrophobizing agent in order to obtain a corresponding coating formulation

(125) b) Samples 26 SA1 (PCC2), 26 SA2 (PCC2), 28 SA (PCC3) and 29 SA (PCC3): Combination of sample 26 comprising hedgehog shaped particles, binder and hydrophobizing agent with additional hydrophobizing agent in the form of one to two post-layers of stearic acid after having coated it onto the substrate.

(126) c) Samples 27 SA (PCC3): Combination of hedgehog shaped particles and binder, whereas the hydrophobizing agent is combined with this mixture in the form of a post-layer of stearic acid after having coated it onto the substrate.

(127) TABLE-US-00010 TABLE 8 Sample 23 Sample 24 Sample 25 Sample 26 PCC 2 (dry) 238.5 g 242.1 g 249.6 g 236.0 g Acronal S360D  6.9 g  7.0 g  7.0 g  6.8 g AKD Eka DR 28  5.8 g — —  5.7 g XL Wükoseal 805 —  0.9 g —  0.9 g Silres BS 1306 — —  0.6 g  0.6 g Tap water 148.8 g 150.0 g 211.8 g 150.0 g Total weight 400.0 g 300.0 g 460.0 g 400.0 g Final solids 18.5 18..0 15.7 18.8 content, wt %

(128) TABLE-US-00011 TABLE 9 Material Sample 27 Sample 28 Sample 29 PCC 3 (dry)  82.8 g  82.2 g  44.3 g Acronal S360D  3.1 g  3.1 g  1.7 g AKD Eka DR 28 —  2.6 g — XL ASA Nalsize — —  1.5 g Tap water  14.1 g  12.1 g  2.5 g Total weight 100.0 g 100.0 g 100.0 g Final solids 33.2 wt % 33.6 wt % 36.2 wt % content, wt %

(129) The coating formulations were prepared by adding PCC2 or PCC3, respectively, as well as the hydrophobizing agents (if present), in portions, to a mixture (ideally a solution) of the respective binder in tap water under stirring in a VMA Dispermat® (VMA-Getzmann GmbH, Reichshof, Germany) with a 70 mm dispersing disk, and subsequently stirring the mixture for 1 hour. The coating formulations were screened over a small tea-sieve having a screen size of 500 μm, and the solids content was determined (cf. tables 8 and 9). Subsequently, the solids content was adjusted by adding further water.

(130) The resulting coating formulations were coated onto an impermeable plastic substrate (Synteape®) with coating rods 1-3. Two papers were coated per colour and coating rod.

(131) Drying circles were carried out in a belt dryer at 150° C. with a band speed of 6-7 until the colour is dry.

(132) The Synteape® papers coated with samples 26, 27, 28 and 29 were additionally sprayed with a solution of 2.8 g stearic acid in 46.0 g ethanol (6 wt % solution) into a small fume hood. The solution was prepared by heating the ethanol to 50° C. in a water bath. After the solvent had reached the temperature, the stearic acid was added manually, mixed by rotation in a round bottomed flask and then sprayed directly on the surface of the coated papers.

(133) In the case of samples 26SA1 and 26 SA2 one or two spray cycles, respectively, were carried out to obtain a good coating layer (cf. table 11). In the case of samples 27 to 29 the coated sheets were sprayed until the layer weight given in table 12 was obtained.

(134) 2.2. Determination of the Contact Angle

(135) For determining the contact angle, the coated sheets were wetted by dropping 5 μl deionized water during 120 s onto the sheet surface. The drop thus formed was photographed and the contact angle was determined with the aid of the measuring module of the Image Access database Image Access Version 8.

(136) TABLE-US-00012 TABLE 11 Coating weights Average Average Average coating/ coating/ Contact Std. sheet sheet angle deviation Trial [mg] [mg/cm.sup.2] [°] [°] Sample 23 265.0 0.1 128 5 Sample 24 321.0 0.1 132 2 Sample 25 200.5 0.1 124 3 Sample 26 313.5 0.1 144 5 Sample 26SA2 313.5 0.1 140 3 Sample 26SA2 313.5 0.1 131 6

(137) TABLE-US-00013 TABLE 12 Coating and Post-layer weights Average Average Average Average Average coating/ coating/ postlayer/ postlayer/ Contact Std. sheet sheet sheet sheet angle deviation Trial [mg] [mg/cm.sup.2] [mg] [mg/cm.sup.2] [°] [°] Sample 27SA 34.7 0.1 149.7 0.3 139.8 9.5 Sample 28 140.3 0.3 — — 130.9 3.0 Sample 28SA 140.3 0.3 149.2 0.3 144.9 8.1 Sample 29 105.6 0.2 — — 103.2 12.1 Sample 29SA 105.6 0.2 148.8 0.3 122.7 12.5

(138) From FIG. 16, the influence of untreated PCC 2 combined with different hydrophobizing agents and binder upon preparation of a coating formulation is illustrated by the contact angles of samples 23 to 26, wherein any one of the samples provide a good hydrophobicity reflected by contact angles of around 124 to 132°. The hydrophobization can even be increased by a combination of the hydrophobizing agents as reflected by sample 26 providing a contact angle of 144°.

(139) Furthermore, several tests were made with respect to a further hydrophobization of sample 26 by post-layering with stearic acid. As can be seen from FIG. 16, this treatment resulted in a decrease of the hydrophobization.

(140) The contact angle of sample 27 exemplifying hydrophobization by post-layering only, illustrates that a high hydrophobization degree can also be achieved by post-layering.

(141) Finally, the contact angles of samples 28 and 29 show the influence of different hydrophobizing agents combined with untreated PCC and binder upon preparation of a coating formulation, wherein the hydrophobization in both cases can be increased by post-layering as exemplified by samples 28SA and 29SA (cf. FIG. 17).