Patent ID: 12247128

EXAMPLES

A. Measurement Methods

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

pH Measurement

Any pH value was measured at 25° C. (+/−1° 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 was first made using commercially available buffer solutions having pH values of 4, 7 and 10 at 25° C. (from Aldrich). The reported pH values were the endpoint values detected by the instrument (signal differs by less than 0.1 mV from the average over the last 6 seconds).

Conductivity Measurement

Conductivity of a suspension was measured at 25° C. (+/−1° 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 was first calibrated in the relevant conductivity range using commercially available conductivity calibration solutions from Mettler Toledo. The influence of temperature on conductivity was automatically corrected by the linear correction mode. Measured conductivities were reported for the reference temperature of 20° C. The reported conductivity values were 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).

Particle Size Distribution and Weight Median Grain Diameter

Particle size distribution (mass % particles with a diameter <X) and weight median grain diameter (d50) of particulate materials were determined via the sedimentation method, i.e. an analysis of sedimentation behaviour in a gravimetric field. The measurement was made with a Sedigraph™ 5100 at 25° C. (+/−1° 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 was carried out in an aqueous solution of 0.1% by weight of Na4P2O7. The samples were dispersed using a high speed stirrer and ultrasonic.

Viscosity Measurement

Brookfield viscosity was measured after 1 minute (if no other indication) of stirring by the use of a RVT model Brookfield™ viscometer at a rotation speed of 100 rpm (revolutions per minute) with the appropriate disc spindle 2, 3 or 4. Without further indication the viscosity was measured at 25° C. (+/−1° C.).

Weight Solids (% by Weight) of a Material in Suspension

Weight solids was determined by dividing the weight of the solid material by the total weight of the aqueous suspension. The weight of the solid material was determined by weighing the solid material obtained by evaporating the aqueous phase of suspension and drying the obtained material to a constant weight.

Average Molecular Weight (Mw) and Polydispersity Index (PI)

A test portion of the polymer solution corresponding to 90 mg of dry matter was introduced into a 10 ml flask. Mobile phase, with an additional 0.04 wt. % of dimethylformamide, was added, until a total mass of 10 g was reached. The composition of this mobile phase at pH 9 was as follows: NaHCO3: 0.05 mol/l, NaNO3: 0.1 mol/l, triethanolamine: 0.02 mol/l, 0.03 wt. % of NaN3.

The gel permeation chromatography (GPC) equipment was equipped with an isocratic pump of the Waters™ 515 type, the flow rate was set to 0.8 ml/min., a Waters™ 717+ sample changer, a kiln containing a precolumn of the “Guard Column Ultrahydrogel Waters™” type which was 6 cm in length and had an internal diameter of 40 mm, followed by a linear column of the “Ultrahydrogel Waters™” type which was 30 cm in length and had an internal diameter of 7.8 mm.

Detection was accomplished by means of a Waters™ 410 type differential refractometer. The kiln was heated to a temperature of 60° C. and the refractometer was heated to a temperature of 45° C. The GPC equipment was calibrated with a series of powders of sodium polyacrylate standards supplied and certified by Polymer Standard Service or American Polymers Standards Corporation. (maximum (MP) molecular weight of between 900 and 2.25·106g/mol and a polydispersity index of between 1.4 and 1.8).

The calibration graph was of the linear type and took account of the correction obtained using the flow rate marker (dimethylformamide).

Acquisition and processing of the chromatogram were accomplished through use of the PSS WinGPC Scientific v. 4.02 application. The chromatogram obtained was incorporated in the area corresponding to molecular weights higher than 200 g/mol.

B. Materials Used

Calcium Carbonate-Comprising Material A

Natural CaCO3marble from Italy, Avenza, having a d50value of 50 μm, a d50value of 10 μm, and a d20value of 2 m.

Grinding Aid Agents

The at least one grinding aid polymer used as grinding aid agents are set out in the following table 1.

TABLE 1Grinding aid polymers usedGrinding aidMwPINeutralizationpolymerComposition[g/mol](Mw/Mn)[mol %]A (comparative)Homopolymer of6 0002.670% Na+,acrylic acid30% Ca2+B (inventive)Homopolymer of3 6002.0100% Na+acrylic acidC (inventive)Homopolymer of3 7702.090% Na+;acrylic acid10% carboxylic acidfunctionsD (comparative)Homopolymer of6 0002.6100% NH4+acrylic acidE (inventive)Acrylic acid/14 1103.8100% Na+hydroxypropylacrylate copolymer(74/26 molar)F (inventive)Acrylic acid/ ethyl4 9252.2100% Na+acrylate copolymer(88/12 molar)G (comparative)Acrylic acid/2 0007.5100% NH4+hydroxypropylacrylate copolymer(74/26 molar)
C. Test Results
2. Trials 1 to 8
Preparation of Pigment Particles Suspension

An aqueous suspension having solids content of 71 wt.-% (+/−1 wt.-%), based on the total weight of the suspension, was prepared by mixing tap water with 1 500 ppm of the respective grinding aid polymer as set out in tables 2 and 3 and the calcium carbonate-comprising material A using a Ystral mixer (Dispermix, Ystral GmbH, Germany). Subsequently, the obtained mixture was wet ground in a 200-litre vertical attritor mill using zircon silicate beads of 0.6 to 1.0 mm diameter. The slurry temperature at the mill inlet was 20° C. and at the outlet between 50 and 70° C. The mill parameters where adjusted in order to reach a particle size distribution of at least 45%<2 μm.

The results are summarized in tables 2 and 3 below.

TABLE 2Wet grinding of a calcium carbonate-comprising material suspension with varioushomopolymers (P1) as grinding aid polymersGrindingaidPSDGrindingpolymerSlurrySlurry%%aidquantitysolidsViscosity<2<1d50Trialpolymer[ppm][wt.-%][mPa · s]μmμm[μm]pH1 (comparative)A1 50071.723746.727.02.29.02 (inventive)B1 50071.712346.226.52.29.53 (inventive)C1 50071.88846.027.02.39.34 (comparative)D1 50071.0ViscosityN/AN/AN/AN/Atoo high,not ableto grind

TABLE 3Wet grinding of a calcium carbonate-comprising material suspension with various copolymers(P2) as grinding aid polymersGrindingaidGrindingpolymerSlurrySlurryPSDaidquantitysolidsViscosity%%d50Trialpolymer[ppm][wt.-%][mPa · s]<2 μm<1 μm[μm]pH5 (inventive)E1 50071.531045.627.12.39.36 (inventive)F1 50071.410247.128.32.29.47 (comparative)A1 50071.523746.727.02.29.08 (comparative)G1 50071.5>1 000N/AN/AN/AN/A(notpossible togrind)

In a subsequent stage, the suspensions set out in tables 2 and 3 were up-concentrated using a thermal pilot evaporator from EPCON™ brand. The evaporator was operated at a suspension temperature of 95° C. Samples were taken at different solids concentration and the viscosity was measured after cooling down of the suspension to 25° C. The target was to identify the solids content corresponding to a viscosity (at 25° C.) of approximately 500 mPa·s. The results are shown in tables 4 and 5 below.

TABLE 4thermal up-concentration - viscosityat different solids concentrationsTrialSolids [wt.-%]Viscosity [mPa · s] at 25° C.2A (inventive)74.632076.87803A (inventive)74.914377.224578.8510

TABLE 5thermal up-concentration - viscosityat different solids concentrationsTrialSolids [wt.-%]Viscosity [mPa · s] at 25° C.5A (inventive)74.9537771 17077.81 4166A (inventive)76.332477.75587A (comparative)76.93 112

From tables 4 and 5, it can be gathered that the viscosity of the aqueous suspensions comprising a ground calcium carbonate-comprising material in a solids content of at least 70 wt.-%, based on the total weight of the suspension, prepared by the inventive process, i.e. by using the at least one grinding aid polymer, is lower compared to a comparative aqueous suspension prepared by a process using the same amount of a grinding aid agent of the prior art. In addition, the grinding aid polymers used according to the invention allow such result where a comparative polymer (see trials 4 and 8; comparatives in tables 2 and 3) even did not allow grinding the mineral material.