USE OF ADDITIVES CONTAINING PRIMARY ALKANOLAMINES IN AQUEOUS MINERAL SUSPENSIONS

Abstract

The present invention relates to the technical domain of additives for aqueous high solids suspensions of mineral materials. The inventive additive comprises specific primary amines and is used for increasing the pH-value of the suspension and/or for increasing the wettability of the mineral materials.

Claims

1. An aqueous suspension including an additive comprising a primary alkanolamine, the aqueous suspension containing 48 to 84 wt-%, based on the total weight of the suspension, of at least one mineral material for increasing the suspension pH by at least 0.3 pH units and/or for increasing the wettability of the at least one mineral material in the suspension, wherein the at least one mineral material has a density of 2.0 to 3.0 g/cm.sup.3; wherein the primary alkanolamine has at most 4 carbon atoms, has a surface tension of 30 to 40 mN/m at 23° C., has, a melting point of less than 5° C. and a boiling, point of less than 163° C., wherein the suspension contains at least one polycarboxylate dispersant in an amount of 0.1 to 1.5 wt.-%, based on the dry mineral material and wherein the primary alkanolamine is added in an amount of from 200 to 10 000 mg per kg of the aqueous phase of said suspension and wherein the weight ratio of primary alkanolamine to polycarboxylate dispersant is from 1:2 to 1:25, yielding a suspension pH of 8.0 to 11.5.

2. The aqueous suspension according to claim characterised in that the primary alkanolamine is 1-amino-2-propanal.

3. The aqueous suspension according to claim 1, characterised in that the at least one mineral material is selected from the group consisting of calcium carbonate, kaolin, clay, mica, talc, natural calcium carbonate (GCC), synthetic calcium carbonate (PCC) and mixtures of natural calcium carbonate and synthetic calcium carbonate.

4. The aqueous suspension according to claim 1, characterised in that the suspension conductivity change caused by the addition of the additive is less than 100 μS/cm/pH unit.

5. The aqueous suspension according to claim 1, characterised in that said suspension has a conductivity of between 100 and 3000 μS/cm.

6. The aqueous suspension according to claim 1, characterised in that the suspension viscosity after addition of the additive is in the range of 50 to 1500 mPas at 25° C.

7. The aqueous suspension according to claim 1, characterised in that said primary alkanolamine is added to said suspension in an amount to increase the pH of the suspension by at least 0.4 pH units.

8. The aqueous suspension according to according to claim 1, characterised in that the additive consists of 1-amino-2-propanol and water, and wherein the additive preferably contains at least 90 wt.-%, based on the weight of the additive of 1-amino-2-propanol.

9. The aqueous suspension according to claim 1, characterised in that the aqueous suspension contains 50 to 82 wt.-%, based on the total weight of the suspension, of at least one mineral material.

10. The aqueous suspension according to claim 1, characterised in that said additive is added prior to, during or after, a step of grinding said at least one mineral material.

11. The aqueous suspension according to claim 1, characterised in that the aqueous phase of the suspension has a surface tension of 55 to 65 mN/m at 23° C.

12. A method for increasing the pH of an aqueous suspension containing 48 to 84 wt.-%, based on the total weight of the suspension, of at least one mineral material characterised in that the method involves the step of adding a liquid additive comprising a primary alkanolamine to the suspension in an amount of from 200 to 10 000 mg, per kg of the aqueous phase of said suspension, so that the pH of the suspension is increased by at least 0.3 pH units yielding a suspension pH of 8.0 to 11.5, wherein the at least one mineral material has a density of 2.0 to 3.0 g/cm.sup.3 and wherein the primary alkanolamine has at most 4 carbon atoms, has a surface tension of 30 to 40 mN/m at 23° C., has a melting point of less than 5° C. and a boiling point of less than 163° C. and wherein the suspension contains at least one polycarboxylate dispersant in an amount of 0.1 to 1.5 wt.-%, based on the thy mineral material.

13. A method for increasing the wettability of at least one mineral material in an aqueous suspension containing 48 to 84 wt.-%, based on the total weight of the suspension, of the at least one mineral material characterised in that the method involves the step of adding a liquid additive comprising a primary alkanolamine to the suspension in an amount of from 200 to 10 000 mg, per kg of the aqueous phase of said suspension, wherein the at least one mineral material has a density of 2.0 to 3.0 g/cm.sup.3 and wherein the primary alkanolamine has at most 4 carbon atoms, has a surface tension of 30 to 40 mN/m at 23° C., has a melting point of less than 5″C and a boiling point of less than 163° C. and wherein the suspension contains at least one polycarboxylate dispersant in an amount of 0.1 to 1.5 wt.-%, based on the dry mineral material.

14. Method according to claim 12, characterised in that the pH of the suspension is increased by at least 0.3 pH units yielding a suspension pH of 8.0 to 11.5 and the wettability of the at least one mineral material in the aqueous suspension is increased.

15. Method according to claim 12, characterised in that the at least one mineral material is selected from the group consisting of calcium carbonate, kaolin, clay, mica, talc, natural calcium carbonate, synthetic calcium carbonate and mixtures of natural calcium carbonate and synthetic calcium carbonate.

16. Method according to claim 12, characterised in that the primary alkanolamine is 1-amino-2-propanol.

17. Method according to claim 12, characterised in that the suspension conductivity change caused by the addition of the additive is less than 100 μS/cm/pH unit.

18. Method according to claim 12, characterised in that the obtained suspension is added to a paint composition, a paper coating composition or a paper composition.

19. Aqueous suspension obtainable by the method according to claim 12.

20. Aqueous suspension according to claim 19, wherein the aqueous phase of the obtained suspension has a surface tension of 53 to 65 mN/m at 23° C. and/or the solids in the mineral, suspension have an anionic charge density, wherein the charge of the solids in the mineral material suspension is −20 to −200 μVal/g.

Description

EXAMPLES

[0081] 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.

[0082] The following measurement methods were used for the provision of the following data and are contemplated to be used according to the present invention:

[0083] pH Measurement

[0084] Any pH value is measured at 25° C. using a Mettler-Toledo Seven Easy pH meter and a Mettler-Toledo InLab Expert Pro pH electrode. A three point calibration (according to the segment method) of the instrument is first made using commercially available buffer solutions having pH values of 4, 7 and 10 at 25° C. (from Aldrich). The reported pH values are the endpoint values detected by the instrument (signal differs by less than 0.1 mV from the average over the last 6 seconds).

[0085] Conductivity Measurement

[0086] Conductivity of a suspension is measured at 25° C. using Mettler Toledo Seven Multi instrumentation equipped with the corresponding Mettler Toledo conductivity expansion unit and a Mettler Toledo InLab 731 conductivity probe, directly following stirring the suspension at 1500 rpm using a Pendraulik tooth disc stirrer. The instrument is first calibrated in the relevant conductivity range using commercially available conductivity calibration solutions from Mettler Toledo. The influence of temperature on conductivity is automatically corrected by the linear correction mode. Measured conductivities are reported for the reference temperature of 20° C. The reported conductivity values are the endpoint values detected by the instrument (the endpoint is when the measured conductivity differs by less than 0.4% from the average over the last 6 seconds).

[0087] Particle size distribution (mass % particles with a diameter<X) and weight median grain diameter (d.sub.50) of particulate material are determined via the sedimentation method, i.e. an analysis of sedimentation behavior in a gravimetric field. The measurement is made with a Sedigraph™ 5100 at 25° C. The method and the instrument are known to the skilled person and are commonly used to determine grain size of fillers and minerals. The measurement is carried out in an aqueous solution of 0.1% by weight of Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and ultrasonic.

[0088] Viscosity Measurement

[0089] Brookfield viscosity is measured after 1 minute (if no other indication) of stirring by the use of a RVT model Brookfield™ viscometer at room temperature and a rotation speed of 100 rpm (revolutions per minute) with the appropriate disc spindle 2, 3 or 4 at 25° C.

[0090] Weight Solids (% by Weight) of a Material in Suspension

[0091] Weight solids is determined by dividing the weight of the solid material by the total weight of the aqueous suspension. The weight of the solid material is determined by weighing the solid material obtained by evaporating the aqueous phase of suspension and drying the obtained material to a constant weight. The additive is added an amount being defined by mg per kg of aqueous phase of the suspension. In order to evaluate the amount of additive per kg of the aqueous phase of a suspension, the weight in kg of the aqueous phase is first determined by subtracting the weight of the solid from the total weight of the suspension.

[0092] Density of Liquid Additive

[0093] The densities as indicated herein were determined by use of a pycnometer. A pycnometer is a glass flask of a known weight. To determine its exact volume it is filled with a calibration liquid (in the present case water) of a known density. By weighing the contained water, one can calculate the exact volume with the known density of water. In a third step, a simple calculation provides information about the exact volume (volume=weight/density). When determining the unknown density of the additive afterwards, the same formula is just used in a different way (density=weight/volume).

[0094] Densities at 5° C. were determined by first conditioning the additive and pycnometer at 3 to 5° C. for 24 hours in a refrigerator.

[0095] Foaming of Aqueous Phase of Suspension

[0096] The foaming tendency was measured by adding 10 ml of the aqueous phase of the suspension in a 15 ml (1 to 1 ml calibrated) polystyrene tube, closing it with a PE cap and shaking it strongly (by hand) for 30 sec. The height of foam after 10 sec. after 1 min and after 10 min can be read from the scaling of the tube.

[0097] Surface Tension

[0098] The surface tension was measured in triplicate at 23° C. (+1° C.) on a Kruss “Force Tensiometer-K100” (Serial Nr. 30001438) with the plate method (Wilhelmy-Method) (Plate PLOT/38371). The surface tension of the primary alkanolamine was measured at a concentration of at least 99 wt.-% (less than 1 wt.-% moisture).

[0099] Specific Surface Area

[0100] The specific surface area (in m.sup.2/g) is determined using the BET method (using nitrogen as adsorbing gas), which is well known to the skilled man (ISO 9277:2010). The total surface area (in m.sup.2) of the mineral material is then obtained by multiplication of the specific surface area and the mass (in g) of the corresponding sample.

[0101] The “Weight molecular weight Mw” means the average by weight of molecular weights determined using the size exclusion chromatography (SEC) method described below:

[0102] A test portion of the polymer solution corresponding to 90 mg of dry matter is introduced into a 10 ml flask. Mobile phase, with an additional 0.04 wt.-% of dimethylformamide, is added, until a total mass of 10 g is reached. The composition of this mobile phase at pH 9 is as follows: NaHCO.sub.3: 0.05 mol/1, NaNO.sub.3: 0.1 mol/1, triethanolamine: 0.02 mol/1, 0.03 wt.-% of NaN.sub.3.

[0103] The SEC equipment is consisting of an isocratic pump of the Waters™ 515 type, the flow rate of which is set at 0.8 ml/min., a Waters™ 717+ sample changer, a kiln containing a precolumn of the “Guard Column Ultrahydrogel Waters™” type, which is 6 cm in length and has an internal diameter of 40 mm, followed by a linear column of the “Ultrahydrogel Waters™” type which is 30 cm in length and has an internal diameter of 7.8 mm. Detection is accomplished by means of a Waters™ 410 type differential refractometer. The kiln is heated to a temperature of 60° C. and the refractometer is heated to a temperature of 45° C. The SEC is calibrated with a series of sodium polyacrylate standards supplied by Polymer Standard Service having maximum molecular weight of between 2000 and 1*10.sup.6 g/mol and a polydispersity index of between 1.4 and 1.7 and also with a sodium polyacrylate of average weight molecular weight of 5600 g/mol and polydispersity index equal to 2.4.

[0104] The calibration graph is of the linear type and takes account of the correction obtained using the flow rate marker (dimethylformamide).

[0105] Acquisition and processing of the chromatogram are accomplished through use of the PSS WinGPC Scientific v. 4.02 application. The chromatogram obtained is incorporated in the area corresponding to molecular weights higher than 65 g/mol.

[0106] Charge Measurement of the Suspension

[0107] Principle:

[0108] A sample of the suspension is treated under strong agitation with an excess of cationic polymer (poly-DADMAC) using automatic titrator (Mettler T.X serie, for example T7), is filtered, is buffered at pH 4.65 (Acetate/Acetic acid) and the excess of poly-DADMAC is then back titrated using an anionic polymer (KPVS). The endpoint is detected by an optical electrode, which measures/detects the turbidity/cloudiness of the poly-DADMAC/KPVS precipitate.

[0109] Reagents:

[0110] 0.01 M aqueous solution of poly Di-allyl-dimethyl-ammonium chloride (poly-DADMAC), medium molecular weight 200,000-350,000, (Sigma-Aldrich Art. 409022-1L);

[0111] 0.01 M aqueous solution of potassium polyvinylsulfat (KPVS), (SERVA Feinbiochemica Heidelberg.

[0112] Pre-Titration of the Samples with Poly-DADMAC (Slow Dosing of 10 mL)

[0113] 1.0 g of suspension sample are weighed in and suspended into an end volume of approx. 30 mL with demineralized water. 10 ml of 0.01 M aqueous poly-DADMAC solution is dosed. To ensure that the reaction of the cationic groups of the poly-DADMAC with the anionic dispersant of the sample as complete as possible, it is dosed quite slowly (0.1 mL per 10 s) under stirring. The whole pre-titration thus takes about 17 min.

[0114] Filtration of the Pre-Titrated Samples

[0115] Prior to the filtration the poly-DADMAC has to react as complete as possible and the solids content should sediment sufficiently, so that filtration is possible. This takes about 30-60 min before the filtration is made. The filtration is made over 0.8 μm membrane filters. If the filtrate is turbid, 0.45 μm or 0.2 μm membrane filters have to be used.

[0116] (Back-)Titration of the Samples

[0117] To obtain reproducible values, approx. 5 mL titration solution should be consumed during the back titration. If the consumption is <2 mL or >8 mL, the determination has to be repeated with corrected weight-in quantity. The clear filtrated samples having a pH value of approx. 8 are adjusted to a pH value of 4.65 using 0.1 molar acidic acid/acetate buffer. With a titrator the amount of excess poly-DADMAC is determined using 0.01 M of the reagent KPVS and the Phototrode DP5 from Mettler to detect the equivalence point. The Phototrode is adjusted to approx. 1200-1800 mV using clear water. A factor of the poly-DADMAC solution versus KPVS (KPVS f=1.00) is determined

[0118] Calculation

[00001]$Q_{\mathrm{atro}}=\frac{\left(\left(V_{\mathrm{PDADMAC}}*t_{\mathrm{PDADMAC}}\right)-V_{\mathrm{KPVS}}\right)*\left(-1000\right)}{m_{\mathrm{sample}}*\mathrm{FS}}\left[\mathrm{\mu Val}\text{/}g\right]$

wherein:
m sample=Weight-in quantity of sample [g]
FS=solids content [%]
V.sub.PDADMAC=Volume poly-DADMAC [ml]
V.sub.KPVS=Volume KPVS [mL]

[0119] t.sub.PDADMAC=Titer poly-DADMAC (Factor against KPVS)

Q.sub.atro=Charge [μVal/g] of the solids in the mineral material suspension

[0120] Melting point (m.p.)/boiling point (b.p.)

[0121] The melting points and boiling points are determined in accordance with “Basics: Laborpraxis, Band 2: Messmethoden, Kapitel 6.1.1 ff and 8.2.2 ff; 6. Auflage, Springer Verlag 2017”. The equipment which was used is Büchi Melting point B-540 for melting and boiling points.

[0122] In the following the tests are described:

[0123] The additives which were used and compared are listed below. It is indicated which additives are inventive and which additives represent comparative examples. The melting points (m.p.) and boiling points (b.p.) were taken out of the literature (Rompps Chemie-Lexikon, 8. Ausgabe, 1979 and CRC Handbook of Chemistry and Physics, 82nd edition, 2001-2002 or were measured with the method described above. It is indicated for each additive where the data are derived from (“Rompp” or “measured”).

[0124] Surface tension of MEA was taken out of CRC Handbook of Chemistry and Physics, 82nd edition, 2001-2002. Surface tension of MIPA and AMP were measured with the method described above.

[0125] Comparative:

2-aminoethanol—MEA, CAS 141-43-5 (<1 wt.-% moisture)

m.p. 10° C., (Römpp) b.p. 171° C. (Römpp)

[0126] Surface tension: 48.3 mN/m; CRC Handbook of Chemistry and Physics, 82nd edition, 2001-2002

[0127] Comparative:

2-amino-2-methyl-1-propanol—AMP, CAS 124-68-5 (<1 wt.-% moisture)
m.p. 29-30° C. (measured)
b.p. 167° C. (measured)
Surface tension: solid at 23° C. (cannot be measured) [0128] measured at 40° C.: <30 mN/m (30.0/29.4/29.7)

[0129] Inventive:

1-amino-2-propanol—MIPA, CAS 78-96-6 (<1 wt.-% moisture)

m.p. 1° C., (Römpp)

[0130] b.p. 158-159° C. (measured)
Surface tension: 36 mN/m (36.5/36.4/36.4) at 23° C.

Example 1

[0131] This example relates to the measurement of the density and viscosity of the respective additives at a temperature of +5° C. (simulating cold outdoor conditions) using a Pycnometer.

[0132] Density of the additive at +5° C.

MEA: solid
AMP: solid
MIPA: the density at +5° C. is 0.957 g/ml

[0133] Brookfield viscosity of the additive at +5° C.

MEA: solid, not possible to measure at +5° C./Brookfield visc.>>1000 mPas
AMP: solid, not possible to measure at +5° C./Brookfield visc.>>1000 mPas
MIPA: Brookfield visc.<500 mPas at +5° C., easy to pump

Example 2

[0134] This example implements a natural calcium carbonate of Limestone (Avignon, France origin), which was obtained by first dry grinding to a d.sub.50 of between 40 to 50 μm, and subsequently wet grinding this dry-ground product in water, wherein 1.05 wt.-% of a sodium and magnesium-neutralized polyacrylate (Mw=6 000 g/mol, Mn=2 300 g/mol) “PAANaMg” in respect to dry calcium carbonate were added. The wet grinding took place in a 1.4-litre vertical attritor mill at a weight solids content of 76.1% by weight under recirculation until:

98% by weight of the particles have a diameter<2 μm,
85% by weight of the particle have a diameter<1 μm
27% by weight of the particle have a diameter<0.2 μm.

[0135] The specific surface (BET) was 14.1 g/m.sup.2.

0.75 mg polycarboxylate dispersant per m.sup.2 of the dry mineral were contained. The anionic charge of the solids in the mineral material suspension was −111 μVal./g.

[0136] 0.4 kg of this suspension are introduced in a 1-litre beaker having a diameter of 8 cm. A Pendraulik tooth disc stirrer is introduced in the beaker such that the stirrer disk is located approximately 1 cm above the bottom of the beaker. The initial suspension conductivity and pH values are reported in table 1 below. Under stirring at 5000 rpm,

[0137] MIPA is added in the indicated amount to the suspension over a period of one minute. After completed addition, the suspension is stirred for additional 5 minutes. The suspension pH, the conductivity and the viscosity were determined after 1 hour of storage. The pH and conductivity of the 6000 ppm sample was again measured after 24 h.

TABLE-US-00001 TABLE 1 Amount MIPA of MIPA Weight of (0.96 (based Suspension/ g/ml Brookfield on water water at Viscosity 100 rpm Conduc- phase) phase 25° C.) Spindle 3 tivity ppm g μl 5 sec 1 min 2 min pH μS/cm 0 400 g/ 0 220 221 222 10.4 1002 95.6 g 500 400 g/  50 μl 219 219 221 10.6 1009 95.6 g 1000 400 g/ 100 μl 222 222 223 10.7 1021 95.6 g 2000 400 g/ 200 μl 221 221 221 10.8 1036 95.6 g 3000 400 g/ 300 μl 221 220 220 10.9 1046 95.6 g 4000 400 g/ 400 μl 218 218 218 11.0 1041 95.6 g 6000 400 g/ 600 μl 215 216 217 11.1 1050 95.6 g after 24 hours: 11.1 1046

[0138] The weight ratio of MIPA to PAA dispersant ranges from 1:20 (500 ppm MIPA) to 1:2.5 (6000 ppm MIPA).

[0139] The corresponding results are reflected by FIGS. 1, 2 and 3.

Example 3

[0140] A 0.4 kg of HYDRAGLOSS 90 SENK Kaolin clay slurry (OMYA/KaMin, Macon, Ga. 31217, USA) at 72-73 wt.-% solids having the following physical properties was used:

TABLE-US-00002 TABLE 2   <5 μm wt.-% 99.2   <2 μm % 98.6   <1 μm % 97.3 <0.5 μm % 89.3 <0.2 μm % 53.8 Median (D.sub.50) μm 0.206 Specific Surface m.sup.2/g 21.20

[0141] The suspension contains approx. 0.5 wt.-% of sodium polyacrylate dispersant on dry Kaolin clay, resulting in 0.23 mg polycarboxylate dispersant per m.sup.2 of the dry mineral. 0.4 kg of this suspension are introduced in a 1-litre beaker having a diameter of 8 cm. A Pendraulik tooth disc stirrer is introduced in the beaker such that the stirrer disk is located approximately 1 cm above the bottom of the beaker. The initial suspension conductivity and pH values are reported in table 3 below. Under stirring at 5000 rpm, MIPA is added in the indicated amount to the suspension over a period of one minute. After completed addition, the suspension is stirred for additional 5 minutes. The suspension pH, the conductivity and the viscosity were determined after 1 hour of storage.

TABLE-US-00003 TABLE 3 Amount of MIPA MIPA (based Weight of (0.96 Brookfield on water Suspension/ g/ml at Viscosity 100 rpm Conduc- phase) water phase 25° C.) Spindle 3 tivity ppm g μl 5 sec 1 min 2 min pH μS/cm 0 400/ 0 560 565 580  8.1 2570 110 water 6000 400/ 680 μl 470 478 485 10.3 2490 110 water

Example 4

[0142] This example implements a natural calcium carbonate of Dolomitic Marble (Kärnten, Austria origin) obtained by first dry grinding to a d.sub.50 of between 40 to 50 μm, and subsequently wet grinding this dry-ground product in water, wherein 0.75% by weight, based on dry weight of the mineral material, of a sodium and magnesium-neutralized polyacrylate (Mw=6 000 g/mol, Mn=2 300 g/mol) were added. The wet grinding took place in 1.4-litre vertical attritor mill at a weight solids content of 78% by weight under recirculation within the mill until approximately 95% by weight of the particles have a diameter <2 μm. The resulting physical properties are as follows:

Solids content after grinding: 78.1 wt.-%
97% by weight of the particles have a diameter <2 μm,
80% by weight of the particle have a diameter <1 μm
24% by weight of the particle have a diameter <0.2 μm.

[0143] The specific surface (BET) was 15.7 g/m.sup.2 resulting in 0.48 mg polycarboxylate dispersant per m.sup.2 of the mineral material.

[0144] The anionic charge of the solids in the mineral material suspension was −80 μVal./g.

[0145] 2100 mg of different alkanolamine additives per kg of aqueous phase of the suspension were added to 510 ml of aqueous phase of suspension (corresponding to ˜835 g of the suspension). For one sample no additive was used. The suspensions were placed in a filtering unit of an API Low Pressure, Low Temperature (LPLT) Filter Press of the Series 300 LPLT Filter Press (Basic LPLT Filter Press Assembly Part No. 207127) using compressed air. At the bottom of the cup, a paper filter (Ø9 cm) for use with LPLT filter press (part No. 206051) was used. The cup was closed and the suspension was filtered under a pressure of 45 psi till 35 to 40 ml of filtrate were obtained.

[0146] The obtained filtrates were used in the foaming test described below as well as for determining the surface tension in Example 5.

[0147] Foaming Test

[0148] The foaming tendency of the respective suspensions is an important parameter for high turbulence applications and was investigated with the filtrates obtained as describes above. Foaming was evaluated by adding 10 ml of the respective aqueous phase/filtrate in a 20 ml graduated tube (1 ml scale), closing the tube and shaking it vigorously by hand for 1 min. The height of the generated foam was determined after 10 s and after 1 min and after 10 min (by taking a reading of the scaling of the tube). The results are shown in table 3 below.

TABLE-US-00004 TABLE 4 Additive 10 sec/ml foam 1 min/ml foam 10 min/ml foam Filtrate without <1 ml <1 ml <1 ml additive Filtrate with 3.0 ml 2.5 ml 1.5 ml 2100 mg/kg MEA Filtrate with 0.2 ml 0.2 ml <0.1 ml 2100 mg/kg AMP Filtrate with 0.5 ml 0.2 ml <0.1 ml 2100 mg/kg MIPA

[0149] As can be gathered from table 4, the inventive additive MIPA has an unexpected low foaming tendency, whereas e.g. MEA shows significant foaming properties.

Example 5

[0150] In order to investigate the wetting properties of the additive, the surface tension of the aqueous phase of the respective suspensions containing different additives was measured. A lower surface tension is indicative for a better wettability of the mineral material surface. For the measurement of the surface tension the filtrates/aqueous phase of the respective samples of Example 4 were used. The surface tension was measured in triplicate at 23° C.±1° C. on a Kriiss “Force Tensiometer K100” (Serial Nr. 30001438) with the plate method (Wilhelmy-Method) (Plate PLOT/38371).

[0151] Procedure Control:

Detection speed: 10 mm/min
Detection sensitivity: 0.005 g
Immersion depth: 2.00 mm

Acquisition: Linear

[0152] Max. Meas. Time: 60 s.

[0153] For each measurement, the measuring process is repeated until a stable (deviation of less than 0.1 mN/m within 5 subsequent measurements) value is obtained (requires usually 5 to 20 repetitions).

Values for mean: 3
Standard deviation: 0.1 mN/m

[0154] A quality test (QTI) was performed with deionized water prior to the measurements. The results are shown in table 5 below.

TABLE-US-00005 TABLE 5 Surface tension measured at room temperature (23° C., mN/m) Measure- Measure- Measure- standard Sample ment 1 ment 2 ment 3 average deviation QTI 72.16 72.08 72.32 72.19 0.12 (water) Filtrate with- 68.93 68.93 68.78 68.88 0.09 out additive Filtrate with 50.94 50.96 50.76 50.89 0.11 2100 mg/kg MEA Filtrate with 62.19 61.62 61.46 61.76 0.38 2100 mg/kg AMP Filtrate with 59.18 58.45 58.16 58.60 0.55 2100 mg/kg MIPA

[0155] The inventive MIPA-additive significantly lowers the surface tension of the aqueous phase of the suspension and, thus, provides improved wettability to the surface of the mineral material.