Process for manufacturing aqueous suspensions of mineral materials or dried mineral materials, the obtained products, as well as uses thereof

Abstract

The invention relates to a process for manufacturing aqueous mineral material suspensions or dried mineral materials using at least one lithium ion neutralised water-soluble organic polymer, the ground mineral materials obtained by this process, the use of the mineral materials in paper, paints and plastics, as well as the use of the lithium ion neutralised water-soluble organic polymer in the manufacturing process as a dispersing and/or grinding enhancer.

Claims

1. An aqueous mineral material obtained by the process comprising the steps of: (a) providing at least one mineral material comprising calcium carbonate in the form of an aqueous suspension or in dry form, (b) providing at least one partially or totally lithium-neutralized water-soluble polyacrylic acid, wherein the molar rate of lithium neutralized acid groups is 50% to 100% and the molar rate of non-lithium neutralized acid groups is 50% to 0%, so that 100% of the acid groups of the water-soluble polyacrylic acid are neutralized; and (c) grinding and/or dispersing and/or upconcentrating the at least one mineral matter of step (a) in the presence of from 0.05 wt % to 1 wt %, relative to the total dry mineral material, of the at least one partially or totally lithium-neutralized water-soluble organic polyacrylic acid of step (b) in water to obtain an aqueous mineral material comprising calcium carbonate and the at least one partially or totally lithium-neutralized water-soluble polyacrylic acid, wherein the aqueous mineral material so obtained has a final solids content of 60 to 81 wt. % and a Brookfield viscosity of less than 200 mPa.Math.S after 1 minute of stirring at a rotation speed of 100 rpm at room temperature, when measured one hour after production of the aqueous mineral material and after eight days of unstirred storage of the aqueous mineral material.

2. The aqueous mineral material according to claim 1, wherein the calcium carbonate is marble, chalk, limestone, or any mixture thereof.

3. The aqueous mineral material according to claim 1, wherein the at least one partially or totally lithium neutralized water-soluble polyacrylic acid is totally or partially neutralized by a lithium ion containing base or by a combination of a lithium ion containing base with one or more neutralization agents having a monovalent neutralizing function or a polyvalent neutralizing function, or any mixture thereof.

4. The aqueous mineral material according to claim 3, wherein the monovalent function is selected from the group consisting of an alkaline cation, sodium, potassium, ammonium, a primary, secondary or tertiary aliphatic and/or cyclic amine, stearylamine, monoethanolamine, diethanolamine, triethanolamine, cyclohexylamine, methylcyclohexylamine, aminomethylpropanol, morpholine, an alkaline earth divalent cation, magnesium, calcium, zinc, strontium, a trivalent cation, aluminium, or a cation of higher valency.

5. The aqueous mineral material according to claim 1, wherein the at least one partially or totally lithium-neutralized water-soluble polyacrylic acid is a lithium neutralized polyacrylic acid.

6. The aqueous mineral material according to claim 1, wherein the at least one partially or totally lithium-neutralized water-soluble polyacrylic acid is a lithium/sodium neutralized polyacrylic acid.

7. The aqueous mineral material according to claim 1, wherein the water-soluble polyacrylic acid has a weight average molecular weight of 3000 to 12,000 g/mol.

8. The aqueous mineral material according to claim 1, wherein aqueous mineral material obtained in step (c) has a solids content of 65 to 80 wt. %, or is adjusted to have a solids content of 65 to 80 wt. %.

9. The aqueous mineral material according to claim 1, wherein the water-soluble polyacrylic acid has a polydispersity of more than 2.

10. The aqueous mineral material according to claim 1, wherein the water-soluble polyacrylic acid has a polydispersity of from 2.5 to 4.0.

11. The aqueous mineral material according to claim 1, having a d50 of from 0.2 to 2 m, determined using a Sedigraph 5100.

12. The aqueous mineral material according to claim 1, having a fraction of particles finer than 2 m of more than 80 wt %, and/or fraction of particles finer than 1 m of more than 75 wt % based on the total weight of dry mineral material, using a Sedigraph 5100.

13. The aqueous mineral material according to claim 1, which is dried.

14. A paper coating color comprising the aqueous mineral material according to claim 1 or dried mineral material thereof.

15. A paper comprising the aqueous mineral material according to claim 1 or dried mineral material thereof.

16. A plastic comprising the aqueous mineral material according to claim 1 or dried mineral material thereof.

17. A paint comprising the aqueous mineral material according to claim 1 or dried mineral material thereof.

Description

EXAMPLES

Example 1

(1) This example relates to the preparation of the material to be processed according to the present invention.

(2) All particle sizes and median diameters are measured using Sedigraph 5100, Micromeritics.

(3) All weight molecular weights (Mw), number molecular weights (Mn) and corresponding polydispersity of the different polymers are measured as 100 mol % sodium salt at pH 8 according to an aqueous Gel Permeation Chromatography (GPC) method calibrated with a series of five sodium polyacrylate standards supplied by Polymer Standard Service with references PSS-PAA 18 K, PSS-PAA 8K, PSS-PAA 5K, PSS-PAA 4K and PSS-PAA 3K.

(4) The BET specific surface area in m.sup.2/g is measured according to the standard ISO 4652 method.

(5) Tests 1a and 1b:

(6) This test concerns the preparation of a rhombohedral (R-) PCC of a d.sub.50 of 0.3 m.

(7) In view of such, 200 kg of calcium oxide (Tagger Kalk, Golling A) are added to 1700 litres of 40 C.-tap water in a stirred reactor; the reactor contents are mixed under continuous stirring for 30 minutes and the resulting slurry of calcium hydroxide (milk of lime) at 13.1% w/w solids is then screened on a 100 m screen.

(8) The calcium carbonate precipitation is conducted in a 1800 litre cylindrical stainless steel reactor equipped with an agitator and probes for monitoring the pH and conductivity of the suspension.

(9) 1700 litres of the calcium hydroxide suspension obtained in the slaking step as stated above are added to the carbonating reactor and the temperature of the reaction mixture is adjusted to the desired starting temperature of 16 C.

(10) A gas of 20-30% by volume of CO.sub.2 in air is then bubbled upwards through the suspension at a rate of 200 m.sup.3/h under a suspension agitation between 200 and 300 rpm. Overpressure in gas feed is 150-200 mbar, corresponding to hydrostatic pressure of Ca(OH).sub.2 suspension in the reactor.

(11) During carbonation, the temperature of the suspension is not controlled and allowed to rise due to the heat generated in the exothermic precipitation reaction. After conductivity reached a minimum gassing is continued for another 4 minutes and then stopped.

(12) The 16.7% w/w solids aqueous slurry of precipitated calcium carbonate obtained by this carbonation step is subsequently screened on a 45 m screen and fed to a centrifuge for mechanical dewatering. The filter cake discharged by the centrifuge is redispersed in water and made-down into a 47.2% w/w slurry. During slurry make-down of the produced rhombohedral (R-) PCC, 1.0% w/w (calculated as dry matter on dry calcium carbonate) of a sodium polyacrylate-based anionic dispersing aid having an Mw of 12500 and a polydispersity of 2.8 is added to the mixture.

(13) The slurry is then forced to pass through a vertical attritor mill (1.4 litre Dynomill), containing 0.6-1.2 mm ZrO beads as media, to de-agglomerate the primarily clustered precipitated calcium carbonate into discrete particles in order to obtain an average particle size d.sub.50 of about 0.3 m (Micromeritics Sedigraph 5100) after milling.

(14) The resulting slurry of discrete ultrafine precipitated calcium carbonate is then further upconcentrated in a vacuum evaporator to obtain final slurry solids of 66.7% w/w solids.

(15) Physical properties of the final product are given in Table 1a below.

(16) TABLE-US-00001 TABLE 1a PCC PCC suspension viscosity suspension (mPa .Math. s) SSA solid content (Brookfield DV II, PCC d50 BET (%) 100 rpm, Spindle 3) polymorph (m) (m.sup.2/g) 66.7 850 rhombohedral 0.27 16.5 calcite (R-PCC)

(17) The mineral slurry so obtained is then spray-dried to a solid content>99.5 weight % (w %) and is named Mineral 1a according to the prior art.

(18) With the same procedure as described above an equivalent R-PCC, but in presence of 2000 ppm by weight of LiOH added prior to the step regarding carbonation process to the slaked lime. During slurry make-down of the produced R-PCC 1.0% w/w (calculated as dry matter on dry calcium carbonate) of a lithium polyacrylate-based anionic dispersing aid having an Mw of 12500 and a polydispersity of 2.8 is added to the mixture.

(19) The slurry is then forced to pass through a vertical attritor mill (1.4 litre Dynomill), containing 0.6-1.2 mm ZrO beads as media, to de-agglomerate the primarily clustered precipitated calcium carbonate into discrete particles in order to obtain an average particle size d.sub.50 of about 0.3 m (Micromeritics Sedigraph 5100) after milling.

(20) The resulting slurry of discrete ultrafine precipitated calcium carbonate is then further upconcentrated in a vacuum evaporator to obtain a final slurry solids of 67.7% w/w solids.

(21) Physical properties of the final product are given in Table 1b below.

(22) TABLE-US-00002 TABLE 1b PCC PCC suspension viscosity suspension (mPa .Math. s) SSA solid content (Brookfield DV II, PCC d50 BET (%) 100 rpm, Spindle 3) polymorph (m) (m.sup.2/g) 67.7 230 rhombohedral 0.29 15.8 calcite (R-PCC)

(23) The slurry precipitated in presence of Li.sup.+ ions has lower viscosity at even higher solids compared to the prior art slurry using 0.063 mg/m.sup.2 of dispersant.

(24) The slurry is then spray-dried>99.5 weight % solids and is named Mineral 1b according to the invention.

(25) Test 2

(26) This test concerns the preparation of a natural, ground calcium carbonate of Norwegian origin having a d.sub.50 of 45 m.

(27) Norwegian marble rocks of the region of Molde having a diameter of 10-300 mm are autogenously dry ground to a fineness of a d.sub.50 in the range of 42-48 m. The mineral so obtained is named Mineral 2.

(28) Test 3

(29) This test concerns the preparation of a natural, ground calcium carbonate of Norwegian origin having a d.sub.50 of 0.8 m.

(30) Mineral 2 is wet ground at 20 weight % solids in tap water in a vertical attritor mill (Dynomill) in a recirculation mode without adding additives, such as dispersing and/or grinding aids to a fineness till 60 weight % of the particle having a diameter of <1 m. After grinding the product has a median diameter d.sub.50 of 0.8 m and a specific surface of 6.7 m.sup.2/g.

(31) After grinding the slurry is concentrated by a tube press to form crumbles of 80-83 weight % solids.

(32) The mineral so obtained is named Mineral 3.

(33) Tests 4a and 4b

(34) These tests concern the preparation of two natural, ground calcium carbonate of Norwegian origin having a d.sub.50 of 0.6 m.

(35) Mineral 2 is wet ground at 15-25 weight % solids in tap water in a vertical attritor mill (Dynomill) in a recirculation mode without adding additives, such as dispersing and/or grinding aids to a fineness until 75 weight % of the particle having a diameter<1 m. After grinding the product has a median diameter d.sub.50 of 0.6 m and a specific surface of 9.8 m.sup.2/g. The mineral so obtained is named Mineral 4a.

(36) After grinding the slurry is concentrated by a filter press to form a filter-cake of 69.5 weight % solids.

(37) The mineral so obtained is named Mineral 4b.

(38) Test 5

(39) This test concerns the preparation of a natural, ground calcium carbonate of Norwegian origin having a d.sub.50 of 0.4 m.

(40) Mineral 2 is wet ground at 20 weight % solids in tap water in a vertical attritor mill (Dynomill) in a recirculation mode without adding additives, such as dispersing and/or grinding aids to a fineness until 85 weight % of the particle having a diameter<1 m. After grinding the product has a median diameter of 0.4 m.

(41) After grinding the slurry is concentrated by a tube-press to form a filter-cake of 78 to 80 weight % solids.

(42) The mineral so obtained is named Mineral 5.

(43) Test 6

(44) These tests concern the preparation of a natural, ground calcium carbonate of Norwegian origin having a d.sub.50 of 0.6 m.

(45) Mineral 2 is wet ground at 78 weight % solids in tap water in a vertical attritor mill (Dynomill) in a recirculation mode using additives according to the invention and according to the prior art to a fineness until 65 weight % of the particles having a diameter<1 m.

(46) The mineral so obtained is named Mineral 6.

(47) Tests 7a and 7b:

(48) This test concerns the preparation of a scalenohedral PCC of a d.sub.50 of 2.3 m.

(49) In view of such, 200 kg of calcium oxide (Tagger Kalk, Golling A) are added to 1700 litres of 40 C.-tap water in a stirred reactor; the reactor contents are mixed under continuous stirring for 30 minutes and the resulting slurry of calcium hydroxide (milk of lime) at 13.3% w/w solids is then screened on a 100 m screen.

(50) The calcium carbonate precipitation is conducted in a 1800 litre cylindrical stainless steel reactor equipped with an agitator and probes for monitoring the pH and conductivity of the suspension.

(51) 1700 litres of the calcium hydroxide suspension obtained in the slaking step as stated above are added to the carbonating reactor and the temperature of the reaction mixture is adjusted to the desired starting temperature of 50 C.

(52) A gas of 20-30% by volume of CO.sub.2 in air is then bubbled upwards through the suspension at a rate of 200 m.sup.3/h under a suspension agitation of between 200 and 300 rpm. Overpressure in gas feed is 150-200 mbar, corresponding to hydrostatic pressure of Ca(OH).sub.2 suspension in the reactor.

(53) During carbonation, the temperature of the suspension is not controlled and allowed to rise due to the heat generated in the exothermic precipitation reaction.

(54) After conductivity reached a minimum gassing is continued for another 4 minutes and then stopped.

(55) The product obtained by this carbonation step is subsequently screened on a 45 m screen and recovered as a 17.4% w/w solids aqueous slurry of precipitated calcium carbonate.

(56) Physical properties of the precipitated calcium carbonate product after carbonation are given in Table 2a below.

(57) TABLE-US-00003 TABLE 2a PCC PCC suspension viscosity suspension (mPa .Math. s) SSA solid content (Brookfield DV II, PCC d50 BET (%) 100 rpm, Spindle 2) polymorph (m) (m.sup.2/g) 17.4 15 scalenohedral 2.3 6.3 calcite (S-PCC)

(58) The mineral slurry so obtained is then spray-dried at a solid content of >99.5 weight % (w %) and is named Mineral 7a according to the prior art.

(59) With the same procedure as described above an equivalent S-PCC but in presence of 500 ppm by weight of LiOH added prior do the step regarding carbonation process to the slaked lime. The slurry is then spray-dried to >99.5 weight % solids and is named Mineral 7b according to the invention.

(60) Physical properties of the precipitated calcium carbonate product after carbonation are given in Table 2b below.

(61) TABLE-US-00004 TABLE 2b PCC PCC suspension viscosity suspension (mPa .Math. s) SSA solid content (Brookfield DV II, PCC d50 BET (%) 100 rpm, Spindle 2) polymorph (m) (m.sup.2/g) 17.7 15 scalenohedral 2.4 6.1 calcite (S-PCC)

(62) As can be seen in Table 2a versus Table 2b the presence of LiOH during precipitation had no influence on measured physical properties of the S-PCC.

(63) Test 8:

(64) This test concerns the preparation of a mixture of natural, ground chalk of French origin, and natural, ground dolomite of Norwegian origin.

(65) 1 kg of Norwegian dolomite rocks from the region of Bergen are dry ground in a ball mill to a fineness of a d.sub.50 in the range of 10.9 m. The obtained mineral is wetted with approximately 188 g of water, and then screening on a 63 m sieve. 323 g of material is retained on the sieve, while the remaining 672.5 g of material passes through the sieve with water to form a suspension having a dry weight of 78.2%.

(66) In parallel, 1 tonne of natural, ground chalk of French origin having a d.sub.50 of 2.5 m and an approximate humidity of 20% is dried in a rotating drier to approximately 0.2% humidity, reaching a d.sub.50 of 1.95 m, due to autogeneous grinding in the drier, on exiting the drier.

(67) Then 134.5 g of the so-dried chalk is added to the dolomite suspension described above, and diluted with water to form a 73.5% solids suspension.

(68) The mineral in this final suspension is named Mineral 8.

Example 2

(69) This example relates to the introduction of the polyacrylate in view of dispersing spray dried PCC named Mineral 7a.

(70) Test 9

(71) This test illustrates the prior art.

(72) In order to perform it, the Mineral 7a is dispersed at a solid content of 60.1 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 1.50 weight % on dry mineral of a conventional (50 mol %/50 mol %) sodium/magnesium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(73) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(74) Test 10

(75) This test illustrates the invention.

(76) In order to perform it, the Mineral 7a is dispersed at a solid content of 59.7 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.74 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(77) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(78) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(79) The results are gathered in the following table 3.

(80) TABLE-US-00005 TABLE 3 Dispersant on Initial. Brookfield 8 days Brookfield Test Solid Content dry mineral Viscosity 100 rpm. Viscosity 100 rpm. number (weight %) (weight %) Spindle 3 Spindle 3 Prior art 9 60.1% 1.50% >4000 mPa .Math. s >4000 mPa .Math. s Invention 10 59.7% 0.74% 117 mPa .Math. s <200 mPa .Math. s

(81) The results demonstrate clearly the efficiency of the process using lithium-neutralised polyacrylate in order to disperse PCC, and notably demonstrate that it is impossible to obtain a PCC slurry with a solid content of about 60.0 weight % and a Brookfield viscosity less than 150 mPa.Math.s using conventional polyacrylate.

Example 3

(82) This example relates to the introduction of lithium neutralised polyacrylate after wet grinding in view of dispersing wet ground marble of median diameter d.sub.50 of 0.6 m.

(83) Test 11

(84) This test illustrates the prior art.

(85) In order to perform it, 0.48 weight % on dry mineral of a conventional (50 mol %/50 mol %) sodium/magnesium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 are put in the Mineral 4a at 20 w % solids before upconcentrated in the lab in an open loop before wishing to be upconcentrated in the lab at a solid content of 68.5 weight %. Nevertheless, the trial is stopped then it is too viscous due to the high increase of Brookfield viscosity above 8000 mPa.Math.s.

(86) Test 12

(87) This test illustrates the invention.

(88) In order to perform it, 0.32 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 are put in the Mineral 4a suspension at 20 w % solids before upconcentrated in the lab in an open loop at a solid content of 68.5 weight %.

(89) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(90) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(91) Test 13

(92) This test illustrates the invention.

(93) In order to perform it, 0.32 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 are put in the Mineral 4a suspension at 20 w % solids before upconcentrated in the lab in an open loop at a solid content of 70.0 weight %.

(94) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(95) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(96) Test 14

(97) This test illustrates the invention.

(98) In order to perform it, 0.32 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 are put in the Mineral 4a suspension at 20 w % solids before upconcentrated in the lab in an open loop at a solid content of 70.7 weight %.

(99) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(100) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(101) Test 15

(102) This test illustrates the invention.

(103) In order to perform it, 0.32 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 are put in the Mineral 4a suspension at 20 w % solids before upconcentrated in the lab in an open loop at a solid content of 70.7 weight %. Then an additional quantity of 0.05% of the same 100 mol % lithium neutralised polyacrylic acid is added to continue the upconcentration until a solid content of 72.0%.

(104) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(105) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(106) Test 16

(107) This test illustrates the invention.

(108) In order to perform it, 0.32 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 are put in the Mineral 4a suspension at 20 w % solids before upconcentrated in the lab in an open loop at a solid content of 70.7 weight %. Then an additional quantity of 0.05% of the same 100 mol % lithium neutralised polyacrylic acid is added to continue the upconcentration until a solid content of 72.6%.

(109) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(110) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(111) Test 17

(112) This test illustrates the invention.

(113) In order to perform it, 0.32 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 are put in the Mineral 4a suspension at 20 w % solids before upconcentrated in the lab in an open loop at a solid content of 70.7 weight %. Then an additional quantity of 0.05% of the same 100 mol % lithium neutralised polyacrylic acid is added to continue the upconcentration until a solid content of 73.6%.

(114) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(115) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(116) The results are gathered in the following table 4

(117) TABLE-US-00006 TABLE 4 Dispersant on Initial. Brookfield 8 days Brookfield Test Solid Content dry mineral Viscosity 100 rpm. Viscosity 100 rpm. number (weight %) (weight %) Spindle 3 Spindle 3 Prior art 11 68.5% 0.48% Too viscous Too viscous to pump to pump >4000 mPa .Math. s >4000 mPa .Math. s Invention 12 68.5% 0.32% 75 mPa .Math. s <200 mPa .Math. s Invention 13 70.0% 0.32% 81 mPa .Math. s <200 mPa .Math. s Invention 14 70.7% 0.32% 98 mPa .Math. s <200 mPa .Math. s Invention 15 72.0% 0.37% 101 mPa .Math. s <200 mPa .Math. s Invention 16 72.6% 0.37% 104 mPa .Math. s <200 mPa .Math. s Invention 17 73.6% 0.37% 108 mPa .Math. s <200 mPa .Math. s

(118) The table shows clearly the efficiency of the process using lithium-neutralised polyacrylate in order to disperse wet ground marble of median diameter d.sub.50 of 0.6 m.

Example 4

(119) This example relates to the introduction of a lithium neutralised polymer after the upconcentration step in view of dispersing a filter-cake issued from an upconcentrated wet ground marble of median diameter d.sub.50 of 0.6 m.

(120) Test 18

(121) This test illustrates the prior art.

(122) In order to perform it, the Mineral 4b is dispersed at a solid content of 55.4 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 1.05 weight % on dry mineral of a conventional (50 mol %/50 mol %) sodium/magnesium neutralised polyacrylic acid of Mw=1000 and having a polydispersity of 3.3.

(123) The Brookfield viscosity is then measured at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(124) Test 19

(125) This test illustrates the prior art.

(126) In order to perform it, the Mineral 4b is dispersed at a solid content of 67.8 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.88 weight % on dry mineral of a conventional 100 mol % potassium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(127) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(128) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(129) Test 20

(130) This test illustrates the prior art.

(131) In order to perform it, the Mineral 4b is dispersed at a solid content of 66.8 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.73 weight % on dry mineral of a conventional 100 mol % sodium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(132) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(133) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(134) Test 21

(135) This test illustrates the prior art.

(136) In order to perform it, the Mineral 4b is dispersed at a solid content of 67.5 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.50 weight % on dry mineral of a conventional 100 mol % sodium neutralised polyacrylic acid of Mw=10000 and having a polydispersity of 3.4.

(137) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(138) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(139) Test 22

(140) This test illustrates the prior art.

(141) In order to perform it, the Mineral 4b is dispersed at a solid content of 67.5 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.89 weight % on dry mineral of a conventional 100 mol % sodium neutralised polyacrylic acid of Mw=10000 and having a polydispersity of 3.4.

(142) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(143) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(144) Test 23

(145) This test illustrates the prior art.

(146) In order to perform it, the Mineral 4b is dispersed at a solid content of 67.5 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 1.77 weight % on dry mineral of a conventional 100 mol % sodium neutralised polyacrylic acid of Mw=10000 and having a polydispersity of 3.4.

(147) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(148) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(149) Test 24

(150) This test illustrates the prior art.

(151) In order to perform it, the Mineral 4b is dispersed at a solid content of 67.2 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.49 weight % on dry mineral of a conventional 100 mol % sodium neutralised copolymer of acrylic acid-maleic anhydride (50 weight %/50 weight %) of Mw=12000 and having a polydispersity of 3.0.

(152) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(153) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(154) Test 25

(155) This test illustrates the invention.

(156) In order to perform it, the Mineral 4b is dispersed at a solid content of 61.6 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.40 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=1000 and having a polydispersity of 3.3.

(157) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(158) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(159) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(160) Test 26

(161) This test illustrates the invention.

(162) In order to perform it, the Mineral 4b is dispersed at a solid content of 66.2 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.14 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(163) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(164) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(165) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(166) Test 27

(167) This test illustrates the invention.

(168) In order to perform it, the Mineral 4b is dispersed at a solid content of 66.2 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.16 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(169) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(170) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(171) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(172) Test 28

(173) This test illustrates the invention.

(174) In order to perform it, the Mineral 4b is dispersed at a solid content of 66.2 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.29 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(175) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(176) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(177) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(178) Test 29

(179) This test illustrates the invention.

(180) In order to perform it, the Mineral 4b is dispersed at a solid content of 69.5 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.17 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(181) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(182) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(183) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(184) Test 30

(185) This test illustrates the invention.

(186) In order to perform it, the Mineral 4b is dispersed at a solid content of 64.0 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.23 weight % on dry mineral of a partially (85 mol %) lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(187) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(188) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(189) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(190) Test 31

(191) This test illustrates the invention.

(192) In order to perform it, the Mineral 4b is dispersed at a solid content of 68.1 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.25 weight % on dry mineral of a (50 mol %/50 mol %) lithium/potassium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(193) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(194) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(195) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(196) Test 32

(197) This test illustrates the invention.

(198) In order to perform it, the Mineral 4b is dispersed at a solid content of 63.2 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.21 weight % on dry mineral of a (85 mol %/15 mol %) lithium/sodium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(199) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(200) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(201) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(202) Test 33

(203) This test illustrates the invention.

(204) In order to perform it, the Mineral 4b is dispersed at a solid content of 64.6 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.16 weight % on dry mineral of a (93 mol %/7 mol %) lithium/sodium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(205) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(206) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(207) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(208) Test 34

(209) This test illustrates the invention.

(210) In order to perform it, the Mineral 4b is dispersed at a solid content of 64.6 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.26 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=50000 and having a polydispersity of 6.25.

(211) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(212) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(213) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(214) Test 35

(215) This test illustrates the invention.

(216) In order to perform it, the Mineral 4b is dispersed at a solid content of 67.2 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.25 weight % on dry mineral of a (50 mol %/50 mol %) lithium/sodium neutralised copolymer of acrylic acid-maleic anhydride (50 weight %/50 weight %) of Mw=12000 and having a polydispersity of 3.0.

(217) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(218) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(219) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage. The results are gathered in the following table 5.

(220) TABLE-US-00007 TABLE 5 Solid dispersant Initial 8 days Con- on dry Brookfield Brookfield Test tent mineral Viscosity Viscosity pH num- (wt (weight 100 rpm. 100 rpm. 1 hour/8 ber %) %) Spindle 3 Spindle 3 days Prior 18 55.4% 1.05% 1130 >2000 art mPa .Math. s mPa .Math. s Prior 19 67.8% 0.88% >4000 >4000 art mPa .Math. s mPa .Math. s Prior 20 66.8% 0.73% >4000 >4000 art mPa .Math. s mPa .Math. s Prior 21 67.5% 0.50% >4000 >4000 art mPa .Math. s mPa .Math. s Prior 22 67.5% 0.89% >4000 >4000 art mPa .Math. s mPa .Math. s Prior 23 67.5% 1.77% >4000 >4000 art mPa .Math. s mPa .Math. s Prior 24 67.2% 0.49% 121 >500 9.9/9.6 art mPa .Math. s mPa .Math. s Inven- 25 61.6% 0.40% 64 <200 9.8/9.7 tion mPa .Math. s mPa .Math. s Inven- 26 66.2% 0.14% 85 <200 10.1/10.1 tion mPa .Math. s mPa .Math. s Inven- 27 66.2% 0.16% 56 <200 9.8/9.8 tion mPa .Math. s mPa .Math. s Inven- 28 66.2% 0.29% 64 <200 9.8/9.8 tion mPa .Math. s mPa .Math. s Inven- 29 69.5% 0.17% 69 <200 10.1/10.1 tion mPa .Math. s mPa .Math. s Inven- 30 64.0% 0.23% 74 <200 10.0/10.0 tion mPa .Math. s mPa .Math. s Inven- 31 68.1% 0.25% 71 <200 9.7/9.6 tion mPa .Math. s mPa .Math. s Inven- 32 63.2% 0.21% 52 <200 10.0/10.2 tion mPa .Math. s mPa .Math. s Inven- 33 64.6% 0.16% 60 <200 9.6/9.4 tion mPa .Math. s Inven- 34 64.6% 0.26% 84 <200 10.2/10.2 tion mPa .Math. s mPa .Math. s Inven- 35 67.2% 0.25% 70 <200 10.1/10.1 tion mPa .Math. s mPa .Math. s

(221) The table shows clearly, by comparison of a lithium-neutralised polymer with the same conventionally neutralised polymer and the corresponding solid content of the slurry, the efficiency of the process using lithium-neutralised polyacrylate in order to disperse a filter-cake issued from an upconcentrated wet ground marble of median diameter d.sub.50 of 0.6 m.

Example 5

(222) This example relates to the introduction of a lithium neutralised polymer after the upconcentration step in view of dispersing hard filter crumbles of >75 w % solids issued from an upconcentrated wet ground marble of median diameter d.sub.50 of 0.8 m.

(223) Test 36

(224) This test illustrates the prior art.

(225) In order to perform it, the Mineral 3 is dispersed at a solid content of 72.1 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 2.00 weight % on dry mineral of a conventional 100 mol % sodium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(226) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(227) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(228) Test 37

(229) This test illustrates the invention.

(230) In order to perform it, the Mineral 3 is dispersed at a solid content of 72.1 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.24 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(231) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(232) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(233) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(234) The results are gathered in the following table 6.

(235) TABLE-US-00008 TABLE 6 Solid dispersant Initial 8 days Con- on dry Brookfield Brookfield pH Test tent mineral Viscosity Viscosity 1 num- (weight (weight 100 rpm. 100 rpm. hour/8 ber %) %) Spindle 3 Spindle 3 days Prior 36 72.1% 2.00% >4000 >4000 art mPa .Math. s mPa .Math. s Inven- 37 72.1% 0.24% 81 <200 10.1/ tion mPa .Math. s mPa .Math. s 9.9

(236) The table shows clearly the efficiency of the process using lithium-neutralised polyacrylate in order to disperse wet ground marble of median diameter d.sub.50 of 0.8 m.

Example 6

(237) This example relates to the introduction of lithium neutralised polyacrylate after wet grinding in view of dispersing a filter-cake issued from an upconcentrated wet ground marble of median diameter d.sub.50 of 0.4 m.

(238) Test 38

(239) This test illustrates the prior art.

(240) In order to perform it, the Mineral 5 is dispersed at a solid content of 65.0 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 2.00 weight % on dry mineral of a conventional 100 mol % sodium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(241) Then, it is not possible to measure the Brookfield viscosity because the calcium carbonate suspension is nearly solid.

(242) Test 39

(243) This test illustrates the prior art.

(244) In order to perform it, the Mineral 5 is dispersed at a solid content of 72.1 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.78 weight % on dry mineral of a conventional 100 mol % sodium neutralised copolymer of acrylic acid-maleic anhydride (50 weight %/50 weight %) of Mw=12000 and having a polydispersity of 3.0.

(245) The Brookfield viscosity is then measured at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(246) Test 40

(247) This test illustrates the invention.

(248) In order to perform it, the Mineral 5 is dispersed at a solid content of 72.1 weight % using a Pendraulik toothed disc stirrer (speed of 3500 to 5000 rpm during 5 to 10 minutes) and 0.24 weight % on dry mineral of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(249) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(250) The Brookfield viscosity after 8 days of storage at room temperature without stirring is measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(251) Two values of pH are measured: the initial pH after one hour of production and the 8 days pH after 8 days of storage.

(252) The results are gathered in the following table 7.

(253) TABLE-US-00009 TABLE 7 dispersant Initial 8 days on dry Brookfield Brookfield pH Test Solid mineral Viscosity Viscosity 1 Num- Content (weight 100 rpm. 100 rpm. hour/8 ber (wt %) %) Spindle 3 Spindle 3 days Prior 38 65.0% 2.00% Not Not art pumpable, pumpable nearly solid Prior 39 72.1% 0.78% 175 280 mPa .Math. s 9.8/9.5 art mPa .Math. s Inven- 40 72.1% 0.24% 81 <200 mPa .Math. s 10.2/ tion mPa .Math. s 10.3

(254) The table shows clearly the efficiency of the process using lithium-neutralised polyacrylate in order to disperse wet ground marble of median diameter d.sub.50 of 0.4 m.

Example 7

(255) This example relates to the addition of lithium neutralised polyacrylate in two different steps of the process. The first addition is performed during the wet grinding of the PCC and the second addition is made after the grinding step and during the thermal upconcentration step of the wet ground PCC of median diameter d.sub.50 of 0.3 m.

(256) Test 41

(257) This test illustrates the invention.

(258) In order to perform it, the Mineral 1b is wet ground at 62.5 weight % solids in tap water in presence of 0.67 weight % of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000, of polydispersity of 2.5 and of a pH=8.73, in a vertical attritor mill (Dynomill) in recirculation mode to a finesse till 50 weight % of the particles having a diameter<0.3 m.

(259) The Brookfield viscosity then measured at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3 is equal to 78 mPa.Math.s.

(260) Then, this slurry is further thermal concentrated adjusting the viscosity during concentrating by further addition of the same lithium neutralised polyacrylic acid as used during grinding.

(261) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(262) The Brookfield viscosity after 30 days of storage at 60 C. without stirring is measured after two minutes of stirring at room temperature at 1500 rpm using a conventional laboratory stirrer and the Brookfield viscosity is measured according to the same conditions and apparatus than the former tests.

(263) Two values of pH are measured: the initial pH after one hour of production and the 30 days pH after 30 days of storage.

(264) The obtained results are as follows in table 8:

(265) TABLE-US-00010 TABLE 8 Weight % Visc. Lithium Initial Visc. Brookfield polyacrylate Brookfield 100 rpm. pH added in the Solid Content 100 rpm. Spindle 3 1 hour/30 second step (weight %) Spindle 3 after 30 days days 0.80% 66.0% 128 mPa .Math. s <200 mPa .Math. s 0.80% 67.5% 128 mPa .Math. s <200 mPa .Math. s 0.80% 68.6% 160 mPa .Math. s <200 mPa .Math. s 9.6/9.7 0.89% 70.6% 317 mPa .Math. s 410 mPa .Math. s 0.89% 72.1% 607 mPa .Math. s 820 mPa .Math. s 9.8/9.8

(266) Test 42

(267) This test illustrates the prior art.

(268) For comparison the same procedure as in Test 41 is used to produce a slurry of the same Mineral 1a with a prior art 100 mol % sodium neutralised polyacrylate of the same batch of polyacrylic acid having a polydispersity of 2.5 as above.

(269) The obtained results are as follows in table 9:

(270) TABLE-US-00011 TABLE 9 Weight % Sodium polyacrylate added Solid Content Visc. Brookfield in the second step (weight %) 100 rpm. Spindle 3 0.80% 55.0% 2000-3000 mPa .Math. s 0.80% 62.5% Paste: >4000 mPa .Math. s

(271) It is then impossible to get a solid content of 67 weight % by using 0.80 weight % of the sodium polyacrylate because the viscosity increases above 5000 mPa.Math.s.

Example 8

(272) This example illustrates the use of lithium neutralised polymer in a high solid grinding process.

(273) Test 43

(274) This test illustrates the prior art.

(275) In order to perform it, the Mineral 2 is wet ground at 77-80 weight % solids in tap water in presence of a 100 mol % sodium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 in a vertical attritor mill (Dynomill) in recirculation mode to a fineness till 50 weight % of the particles having a diameter of <0.7 m.

(276) Test 44

(277) This test illustrates the invention.

(278) For comparison the same procedure is used to produce slurry with 100 mol % lithium neutralized polyacrylic acid of the same batch of polyacrylic acid having a polydispersity of 2.5 as above

(279) The obtained results are as follows in table 10:

(280) TABLE-US-00012 TABLE 10 Initial 8 days Size dis- Brook- Brook- distri- persant field field bution on dry Viscosity Viscosity Sedi- pH Slurry mineral 100 rpm. 100 rpm. graph 1 solids in Spindle Spindle 5100 hour/ Weight weight 3 3 Weight 8 Test % % mPa .Math. s mPa .Math. s % days Prior 43 78.0 0.7 very 9.3/ art sticky 9.5 im- possible to pump into the mill Inven- 44 78.1 0.58 149 <200 <2 9.6/ tion mPa .Math. s m 92 9.4 <1 m 64 <0.2 m 16

(281) The table shows clearly the efficiency of the process according to the invention.

Example 9

(282) This example illustrates that the lithium neutralisation allows to use polymer with high polydispersity by comparing results obtained on one side by neutralising polyacrylic acid with sodium according to the prior art and on the other side by neutralising polyacrylic acid with lithium according to the invention.

(283) Test 45

(284) This test illustrates the prior art.

(285) In order to perform it, the 100 mol % sodium neutralised polyacrylic acid is prepared by mixing three different 100 mol % sodium neutralised polyacrylic acids in a weight ratio of 1:1:1. It is clear for an expert that such a blend has to have a much higher polydispersity vs. each single polymer in the blend.

(286) The first 100 mol % sodium neutralised polyacrylic acid has a Mw=1000 and a polydispersity of 3.3, the second 100 mol % sodium neutralised polyacrylic acid has a Mw=3500 and a polydispersity of 2.9, and the third has a Mw=6000 and a polydispersity of 2.5. The corresponding blend had a Mw of 3300 and a polydispersity>3.

(287) After having prepared this 100 mol % sodium neutralised polyacrylic acid, the Mineral 4b is dispersed at a solid content of 66.9 weight % using a Pendraulik toothed disc stirrer (speed of 3000 rpm during 5 to 10 minutes) and 2.60 weight % on dry mineral of the prepared 100 mol % sodium neutralised polyacrylic acid.

(288) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 6.

(289) The Brookfield viscosity value is 6690 mPa.Math.s and the pH is 9.3.

(290) Test 46

(291) This test illustrates the invention.

(292) In order to perform it, the 100 mol % lithium neutralised polyacrylic acid is prepared by mixing three different 100 mol % lithium neutralised polyacrylic acids in a weight ratio of 1:1:1. It is clear for an expert that such a blend has to have a much higher polydispersity vs. each single polymer in the blend.

(293) The first 100 mol % lithium neutralised polyacrylic acid has a Mw=1000 and a polydispersity of 3.3, the second 100 mol % lithium neutralised polyacrylic acid has a Mw=3500 and a polydispersity of 2.9, and the third has a Mw=6000 and a polydispersity of 2.5. The corresponding blend had a Mw of 3300 and a polydispersity>3.

(294) After having prepared this 100 mol % lithium neutralised polyacrylic acid, the Mineral 4b is dispersed at a solid content of 68.8 weight % using a Pendraulik toothed disc stirrer (speed of 3000 rpm during 5 to 10 minutes) and 0.23 weight % on dry mineral of the prepared 100 mol % lithium neutralised polyacrylic acid.

(295) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 6.

(296) The Brookfield viscosity value is 70 mPa.Math.s and the pH is 10.0.

(297) The reading of the two results clearly shows that the use of the lithium neutralised polyacrylic acid allows to highly decrease the quantity of polymer used to obtain a well better fluid calcium carbonate suspension at a higher solid content.

Example 10

(298) This example illustrates the use of the mineral suspension according to the invention in the coating of paper and plastic.

(299) Test 47

(300) This test illustrates the invention in coating application.

(301) In order to perform it, the Mineral 4a is upconcentrated by lab-evaporation from 20 weight % to a solids content up to 75 weight %, by using a continuous addition of a 100 mol % lithium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5.

(302) Then, different samples were taken during upconcentration of Mineral 4a corresponding to different solid contents from 55.4 weight % to 75.5 weight % as well as to different quantities of polymer used from 0.203 weight % to 0.273 weight % on dry mineral are taken in view of preparing the corresponding paper coating colours prepared by using 12 parts (on dry basis) of Acronal S 360 D, BASF, a paper coating binder and 88 parts (on dry basis) and coated on a plastic support (Synteape, Argo Wiggins) at different coat weight.

(303) The scattering coefficient S greater than 100 m.sup.2/kg for a coating weight of 20 g/m.sup.2 reflecting the ability of a coating to scatter visible light is measured according to the method described in WO 02/49766 (p. 8 to 10). Accordingly, the ability to scatter light is expressed by the Kubelka-Munk light scattering coefficient, determined by the method, well-known to experts, described in the publications of Kubelka and Munk (Zeitschrift fr Technische Physik 12,539, (1931)), de Kubelka (J. Optical Soc. Am. 38(5), 448, (1948) et J. Optical Soc. Am. 44(4), 330, (1954)).

(304) The results are gathered in the following table 11.

(305) TABLE-US-00013 TABLE 11 Scattering Solid Solid coefficient Content Content (S) at (weight %) (weight %) 20 g/m.sup.2 Test W % of of pigment of coating coat weight number LiPolyacrylate slurry colour (m.sup.2/kg) Invention 47a 0.203 55.4 53.0 199.5 Invention 47b 0.234 65.2 60.0 194.5 Invention 47c 0.256 69.1 60.0 177.4 Invention 47d 0.264 71.0 60.0 151.8 Invention 47e 0.264 72.3 60.0 147.3 Invention 47f 0.264 73.8 60.0 140.5 Invention 47g 0.273 75.5 60.0 125.8

(306) The table shows clearly the efficiency of the process using lithium-neutralised polyacrylate in order to disperse wet ground marble of median diameter d.sub.50 of 0.6 m in a coating application.

(307) Test 48

(308) This test illustrates the invention.

(309) In order to perform it, Mineral 2 (which has a BET specific surface area of 1.4 m.sup.2/g) was wet ground at 77 wt % solids in tap water in presence of 0.33 wt %, relative to the dry weight of mineral, of a 93 mol % lithium/7 mol % sodium neutralized polyacrylic acid of Mw=6000, of Mn=2400 g/mol and having a polydispersity of 2.5, in a 1500-litre vertical pearl mill containing 0.6-1 mm zirconium silicate grinding beads, operating in continuous mode to reach a fineness such that 58 wt % of the particles have a diameter of <2 m.

(310) At the inlet of the mill, the slurry of Mineral 2 had a pH of 9.7. The maximum temperature at the outlet of the mill attained during grinding was 97 C. The obtained mineral was in the form of 80.5 wt % solids slurry and is named Mineral 9. This slurry had a Brookfield viscosity at 25 C. of 175 mPa.Math.s measured at 100 rpm.

(311) Thereafter, the suspension of Mineral 9 was formulated in a paper coating color consisting, in parts per hundred parts of dry Mineral 9, of the following: 8 parts of carboxylated styrene-butadiene synthetic binder having particles with a diameter of between 0.08 to 0.12 m; 0.1 parts carboxymethyl cellulose; 0.5 parts of an acrylate rheology modifier.

(312) The obtained coating color has a solids content of 77% by dry weight and a Brookfield viscosity at 25 C. of 510 mPa.Math.s measured at 100 rpm. The good viscosity, among other properties, translated in a good runnability during subsequent paper coating.

Example 11

(313) This example relates to the introduction of different quantities of lithium neutralised polyacrylate after wet grinding in view of dispersing wet ground marble of median diameter d.sub.50 of 0.6 m.

(314) Test 49

(315) This test illustrates the prior art.

(316) In order to perform it, different quantities of a conventional (100 mol %) 2-amino-2-methyl-1-propanol (AMP) neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 are put into the Mineral 4b at 66.1 w % solids.

(317) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(318) Test 50

(319) This test illustrates the invention.

(320) In order to perform it, different quantities of a (50 mol %/50 mol %) AMP/lithium hydroxide neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 are put into the Mineral 4b at 68.6 w % solids.

(321) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(322) The results are gathered in the following table 12.

(323) TABLE-US-00014 TABLE 12 Initial dispersant Brookfield Solid on dry Viscosity Test Content mineral 100 rpm. number (weight %) (weight %) Spindle 3 Prior art 49a 66.1% 0.50% >4000 mPa .Math. s Prior art 49b 66.1% 1.05% 3000 mPa .Math. s Prior art 49c 66.1% 1.28% 3000 mPa .Math. s Prior art 49d 66.1% 1.48% 3000 mPa .Math. s Prior art 49e 66.1% 1.98% 3250 mPa .Math. s Invention 50a 68.6% 0.28% 1450 mPa .Math. s Invention 50b 68.6% 0.40% 476 mPa .Math. s Invention 50c 68.6% 0.43% 252 mPa .Math. s Invention 50d 68.6% 0.48% 132 mPa .Math. s Invention 50e 68.6% 0.49% 123 mPa .Math. s Invention 50f 68.6% 0.52% 119 mPa .Math. s

(324) The table shows clearly the efficiency of the process using lithium-neutralised polyacrylate in order to disperse wet ground marble of median diameter d.sub.50 of 0.6 m

(325) Test 51

(326) This test illustrates the prior art.

(327) In order to perform it, 0.73 weight % on dry calcium carbonate of a conventional 100 mol % sodium neutralised polyacrylic acid of Mw=6000 and having a polydispersity of 2.5 are put into the Mineral 4b at 65.5 w % solids.

(328) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(329) Test 52

(330) This test illustrates the invention.

(331) In order to perform it, the carboxylic groups of the poly(ethylene-acrylic acid) were neutralized using lithium hydroxide. The molar ratio of monomer of the poly(ethylene-acrylic acid) was 80/20. Such neutralized EAA was put into the Mineral 4b at 65.5 w % solids.

(332) The initial Brookfield viscosity is then measured after one hour of production and after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(333) The results are gathered in the following table 13.

(334) TABLE-US-00015 TABLE 13 Initial Dispersant Brookfield Solid on dry Viscosity Test Content mineral 100 rpm. number (weight %) (weight %) Spindle 3 Prior art 51 65.5% 0.73% >3000 mPa .Math. s Invention 52a 65.5% 0.08% 1490 mPa .Math. s Invention 52b 65.5% 0.104% 228 mPa .Math. s Invention 52c 65.5% 0.116% 200 mPa .Math. s Invention 52d 65.5% 0.171% 165 mPa .Math. s Invention 52e 65.5% 0.284% 170 mPa .Math. s

(335) One part of the sample of the test 52e is then stored at rest during 1 day, 3 days 6 days and the Brookfield viscosity is then measured after one minute of stirring at room temperature and at 100 rpm by the use of a Brookfield viscosimeter type RVT equipped with the spindle 3.

(336) The results are 216 mPa.Math.s, 247 mPa.Math.s and 308 mPa.Math.s, respectively.

(337) Another part of the sample stored at room temperature under stirring during 7 days gives a Brookfield viscosity of 274 mPa.Math.s

(338) These results as well as the one gathered in table 13 show also the efficiency of the lithium neutralised polymer according to the invention.

Example 12

(339) This example relates to dispersing a mixture of screened natural, dry-ground dolomite and natural, dry-ground chalk, by introduction of lithium neutralised polyacrylate.

(340) Test 53

(341) This test illustrates the invention.

(342) 1082 g of the suspension of Mineral 8 obtained in Test 8 is dispersed by addition, under shearing in a beaker using a tooth disc stirrer (of 4 cm diameter), of 0.035%, based on the dry weight of the suspension, of polyacrylate in the form of a 35 wt-% solution, wherein 100% of the carboxyl groups are lithium neutralised, and the polyacrylate has a polydispersity of 2.5. The obtained suspension has a Brookfield viscosity (measured at 100 rpm using disc 3) of 160 mPa.Math.s.

(343) It is to remark that under these stirring conditions in the presence of dolomite, the chalk fraction of Mineral 8 is further divided.

(344) The resulting dispersion is thereafter screened on a 63 m sieve, recovering 12.2 g on the screen, while the remaining 783 g of solids passes through the sieve with water to form a diluted suspension having a dry weight of 72.3%.

Example 13

(345) This example illustrates the use of lithium neutralized polymer in a high solid two-step continuous grinding process at industrial scale (i.e. for the manufacturing of products in tons).

(346) Test 54

(347) This test illustrates the invention.

(348) In order to perform it, Mineral 2 (which has a BET specific surface area of 1.4 m.sup.2/g) was wet ground at 76.5 wt % solids in tap water in presence of 0.3% by weight, relative to the dry weight of mineral, of a 93 mol % lithium/7 mol % sodium neutralized polyacrylic acid of Mw=6000, of Mn=2400 g/mol and having a polydispersity of 2.5, in a 160-litre vertical pearl mill containing 300 kg of 0.6-1 mm zirconium silicate grinding beads, under a feed rate of Mineral 2 of 245 litres/hours, operating in continuous mode to reach a fineness such that 60 weight % of the particles have a diameter of <2 um. At the inlet of the mill, the slurry of Mineral 2 had a pH of 9.7. The maximum temperature at the outlet of the mill attained during grinding was 73 C. The obtained mineral was in the form of 80 weight % solids slurry and is named Mineral 10. This slurry had a Brookfield viscosity at 25 C. of 185 mPa.Math.s measured at 100 rpm. Mineral 10 had a BET specific surface area of 8.4 m.sup.2/g.

(349) Mineral 10 was then diluted to reach a solids content of 78% by weight, and further ground in the same mill as above under a feed rate of Mineral 10 of 235 litres/hours, dosing 0.3% by weight, relative to the dry weight of mineral, of a 93 mol % lithium/7 mol % sodium neutralized polyacrylic acid of Mw=6000, of Mn=2400 g/mol and a polydispersity of 2.5, at the inlet of the mill, and dosing 0.1% by weight, relative to the dry weight of mineral, of this same polymer at the outlet of the mill. The grinding was performed such that particles exiting the mill featured the following particle size distribution:

(350) 91% by weight<2 um

(351) 62.4% by weight<1 um

(352) At the inlet of the mill, the slurry of Mineral 10 had a pH of 10.1. The maximum temperature at the outlet of the mill attained during grinding was 90 C. The obtained mineral was in the form of an 80.3 weight % solids slurry and is named Mineral 10. This slurry had a Brookfield viscosity at 25 C. of 335 mPa.Math.s measured at 100 rpm, and a pH of 9.8. Mineral 10 had a BET specific surface area of 13.1 m.sup.2/g.