DISPERSION AND/OR GRINDING AID AGENTS OF KAOLIN IN AQUEOUS SUSPENSION, AQUEOUS SUSPENSIONS OBTAINED AND USES THEREOF

Abstract

The present invention relates to a ternary mixture consisting of at least one homopolymer or copolymer of (meth)acrylic acid, partially or completely neutralized with sodium, with potassium, with lithium and/or with an amine, at least one solution of silicate or metasilicate chosen from the group consisting of a sodium silicate of formula Na.sub.2O.nSiO.sub.2 (with n varying between 1 and 4), sodium metasilicate Na.sub.2SiO.sub.3, a potassium silicate K.sub.2O.nSiO.sub.2 (with n varying between 1 and 4), potassium metasilicate K.sub.2SiO.sub.3 and a mixture of these compounds, and at least one base, as dispersion and/or grinding aid agents of kaolin in aqueous suspension.

Claims

1. A dispersion and/or grinding aid agent of kaolin in aqueous suspension, consisting of a ternary mixture of a) at least one homopolymer or copolymer of (meth)acrylic acid, partially or completely neutralized with sodium, potassium, lithium and/or an amine, b) at least one solution of silicate or metasilicate selected from the group consisting of sodium silicate of formula Na.sub.2O.nSi0.sub.2 with n varying between 1 and 4, sodium metasilicate Na.sub.2SiO.sub.3, potassium silicate K.sub.2O.nSiO.sub.2 with n varying between 1 and 4, potassium metasilicate K.sub.2SiO.sub.3 and a mixture thereof, and c) at least one base, in an amount such that the at least one base is in excess of at least 2 mol % with respect to a theoretical amount of the base necessary for a complete neutralization of said homopolymer or copolymer of (meth)acrylic acid, in which wherein the homopolymer/copolymer:silicate/metasilicate ratio by dry weight is between 20:80 and 80:20.

2. The agent according to claim 1, wherein said homopolymer or copolymer of (meth)acrylic acid has a molecular weight of less than or equal to 7 000 g/mol, as measured by SEC.

3. The agent according to claim 1, wherein said homopolymer or copolymer of (meth)acrylic acid has a molecular weight of less than or equal to 6 000 g/mol, as measured by SEC.

4. The agent according to claim 1, wherein said homopolymer or copolymer of (meth)acrylic acid has a PI index of between 1.5 and 3.

5. The agent according to claim 1, wherein the amount of the at least one base is such that the at least one base is in excess of at least 5 mol % with respect to the theoretical amount of the base necessary for the complete neutralization of said homopolymer or copolymer of (meth)acrylic acid.

6. The agent according to claim 1, wherein b) is a solution of silicate, which is a sodium silicate of formula Na.sub.2O.2Si0.sub.2.

7. The agent according to claim 1, consisting of a ternary mixture of: a) from 20% to 80% by weight of said at least one homopolymer or copolymer of (meth)acrylic acid, b) from 20% to 80% by weight of said at least one solution of silicate or metasilicate, and c) from 1% to 10% by weight of said at least one base.

8. A method for preparing the agent according to claim 1, the method comprising: adding the at least one base to the at least one solution of silicate or metasilicate, thereby obtaining a mixture; and introducing into the mixture the at least one homopolymer or copolymer of (meth)acrylic acid, wherein the at least one base is added in an amount such that the at least one base is in excess of at least 2 mol % with respect to a total number of moles of the at least one homopolymer or copolymer of (meth)acrylic acid.

9. The method according to claim 8, which is carried out with stirring at a temperature of between 5° C. and 50° C.

Description

EXAMPLES

[0112] In all of the examples which follow, use is made, as polymer of (meth)acrylic acid, of a polymer having the following characteristics and obtained by the method described below.

[0113] Characteristics of the Acrylic Acid Polymer

[0114] Molecular weight Mw (determined by SEC as indicated above): 2 900 g/mol

[0115] Molecular weight Mn (determined by SEC as indicated above): 1 320 g/mol

[0116] PI Index: 2.2

[0117] SC (Solids Content): 42%

[0118] pH=8 (polymer completely neutralized NaOH)

Example 1

[0119] This example illustrates the preparation of an agent according to the method described in the patent U.S. Pat. No. 4,742,105 (test 1-1, prior art) and also the preparation of an agent according to the method of the present invention (test 1-2).

[0120] Test 1-1

[0121] 354.9 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, and 98.4 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Vasil® 0112; SC: 50.5%) are mixed together with addition of 20 g of water.

[0122] Test 1-2

[0123] 12.3 g of NaOH (20%) are added to 98.4 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Vasil® 0112; SC: 50.5%).

[0124] 354.9 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are subsequently added to the preceding mixture with addition of 20 g of water.

[0125] All the results have been combined in Table 1 below.

TABLE-US-00001 TABLE 1 Test 1-1 Test 1-2 Nasil ® 0112 98.4 g 21.7% 98.4 g 21.1% NaOH   0 g   0% 12.3 g 2.6% Polymer 354.9 g  78.3% 354.9 g  76.3% Water .sup. 20 g — .sup. 20 g — Observations Instantaneous precipitation —

[0126] A problem of immediate precipitation is found when the method described in the patent U.S. Pat. No. 4,742,105 is followed.

[0127] No immediate precipitation is found in the case of test 1-2.

Example 2

[0128] This example illustrates the use of different amounts of sodium hydroxide NaOH.

[0129] Test 2-1

[0130] 26.4 g of sodium hydroxide NaOH (50%) are added to a solution of 274 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Vasil® 0112; SC: 50.5%).

[0131] 328 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are subsequently added to the preceding mixture with addition of 57.1 g of water.

[0132] This test corresponds to an excess of NaOH of 7.2 mol %.

[0133] Test 2-2

[0134] 19.8 g of sodium hydroxide NaOH (50%) are added to a solution of 274 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Nasil® 0112; SC: 50.5%).

[0135] 328 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are subsequently added to the preceding mixture with addition of 57.1 g of water.

[0136] This test corresponds to an excess of NaOH of 5.4 mol %.

[0137] Test 2-3

[0138] 13.2 g of sodium hydroxide NaOH (50%) are added to a solution of 274 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Vasil® 0112; SC: 50.5%).

[0139] 328 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are subsequently added to the preceding mixture with addition of 57.1 g of water.

[0140] This test corresponds to an excess of NaOH of 3.6 mol %.

[0141] All the results have been combined in Table 2 below.

TABLE-US-00002 TABLE 2 Test 2-1 Test 2-2 Test 2-3 Polymer 328 g 47.6%  328 g 48.2%  328 g 48.7% NaOH  26 g 4.6% 19.8 g 3.5% 13.2 g 2.3% Silicate 274 g 47.8%  274 g 48.3%  274 g 49.0% Water 57.1 g  — 57.1 g — 57.1 g — SC (%) 42.3% 42.2% 42.1% P/S ratio 50/50 50/50 50/50 Sedimentation >40 days 35 days 15 days limit ambient temperature P/S ratio = polymer/silicate ratio by weight (dry weight)

Example 3

[0142] This example illustrates the use of different polymer/silicate ratios.

[0143] Test 3-1

[0144] 26.4 g of sodium hydroxide NaOH (50%) are added to a solution of 137.2 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Vasil® 0112; SC: 50.5%).

[0145] 492.7 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are subsequently added to the preceding mixture with addition of 30.1 g of water.

[0146] Test 3-2

[0147] 19.8 g of sodium hydroxide NaOH (50%) are added to a solution of 274 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Vasil® 0112; SC: 50.5%).

[0148] 328 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are subsequently added to the preceding mixture with addition of 57.1 g of water.

[0149] Test 3-3

[0150] 26.4 g of sodium hydroxide NaOH (50%) are added to a solution of 411.7 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Nasil® 0112; SC: 50.5%).

[0151] 164.2 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are subsequently added to the preceding mixture with addition of 84.1 g of water.

[0152] All the results have been combined in Table 3 below.

TABLE-US-00003 TABLE 3 Test 3-1 Test 3-2 Test 3-3 Polymer 492.7 g 328 g 164.2 g NaOH 26.4 g 19.8 g 26.4 g Nasil ® 0112 137.2 g 274 g 411.7 g Water 30.1 g 57.1 g 84.1 g SC (%) 42.3% 42.2% 42.3% P/S ratio 75/25 50/50 25/75 Sedimentation 25 days 34 days >40 days limit ambient temperature P/S ratio = polymer/silicate ratio by weight (dry weight)

Example 4

[0153] This example illustrates the use of potassium hydroxide as base of the ternary mixture.

[0154] Test 4-1

[0155] 88.2 g of KOH (50%) are added to a solution of 623.7 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Nasil® 0112; SC: 50.5%).

[0156] 746.5 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are subsequently added to the preceding mixture with addition of 129.8 g of water.

[0157] All the results have been combined in Table 4 below.

TABLE-US-00004 TABLE 4 Test 4-1 Nasil ® 0112 623.7 g KOH 88.2 g Polymer 746.5 g Water 129.8 g SC (%) 41.6% P/S ratio 50/50 Sedimentation limit >40 days ambient temperature P/S ratio = polymer/silicate ratio by weight (dry weight)

Example 5

[0158] This example illustrates the use of a polymer of acrylic acid with a molecular weight equal to 4 500 g/mol to prepare a dispersing and/or grinding aid agent according to the invention. It also illustrates the use of a polymer of acrylic acid with a molecular weight equal to 7 300 g/mol to prepare a grinding aid agent.

[0159] Test 5-1

[0160] 44.1 g of KOH (50%) are added to a solution of 213.9 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Nasil® 0112; SC: 50.5%).

[0161] 687.5 g of polymer of acrylic acid (Mw=4 500 g/mol, Mn=1 850 g/mol, SC=42%), completely neutralized with sodium hydroxide, are then added to the preceding mixture with addition of 54.5 g of water.

[0162] Test 5-2

[0163] 43.1 g of NaOH (50%) are added to 406.2 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Nasil® 0112; SC: 50.5%).

[0164] 540.5 g of polymer of acrylic acid (Mw=7 300 g/mol, Mn=2 700 g/mol, SC=38%), completely neutralized with sodium hydroxide, are then added to the preceding mixture with addition of 40.3 g of water.

[0165] All the results have been combined in Table 5 below.

TABLE-US-00005 TABLE 5 Test 5-1 Test 5-2 Nasil ® 0112 213.9 g 406.2 g KOH/NaOH 44.1 g 43.1 g Polymer 687.5 g 540.5 g Water 54.5 g 40.3 g SC (%) 42.2% 42.2% P/S ratio 73/27 53/47 Sedimentation limit >40 days <2 days ambient temperature P/S ratio = polymer/silicate ratio by weight (dry weight)

Example 6

[0166] This test illustrates the stability of a ternary mixture according to the invention under different conditions: after one week at a temperature of 50° C. and also after one or three freeze/thaw cycles.

[0167] More specifically, the freeze/thaw cycle consists in storing overnight in a freezer at a temperature of −18° C.

[0168] All the results are given in Table 6 below.

[0169] The viscosity (expressed in mPa.s) of each agent at 20° C. is measured with a viscometer of Brookfield DVIII type. The values of the viscosities shown are measured after stirring, at a speed of 100 rev/min.

[0170] The values of the viscosities under these extreme conditions are very particularly relevant for the purpose of evaluating the characteristics of the agent from the viewpoint of its storage and use in industrial methods.

[0171] Test 6

[0172] 60 g of NaOH (50%) are added to 405 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Vasil® 0112; SC: 50.5%).

[0173] 950 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are then added to the preceding mixture with addition of 87 g of water.

TABLE-US-00006 TABLE 6 Test 6 Stability at ambient temperature Viscosity 100 rev/min (mPa .Math. s) 118 Stability after one week at 50° C. Viscosity 100 rev/min (mPa .Math. s) 114 Stability after one freeze/thaw cycle Viscosity 100 rev/min (mPa .Math. s) 104 Stability after three freeze/thaw cycles Viscosity 100 rev/min (mPa .Math. s) 98

Example 7

[0174] This test illustrates the use of different ternary mixtures as dispersion aid agents of kaolin particles. Two kaolin suspensions are prepared from Capim® DG (Imerys) kaolin particles at a concentration of 70%, each containing a variable amount of the agent according to test 7-1 or according to test 7-2.

[0175] Test 7-1

[0176] 50 g of NaOH (50%) are added to 497 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Vasil® 0112; SC: 50.5%).

[0177] 630 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are then added to the preceding mixture with addition of 110 g of water.

[0178] Test 7-2

[0179] 60 g of NaOH (50%) are added to 405 g of sodium silicate of formula Na.sub.2O.2SiO.sub.2 (Vasil® 0112; SC: 50.5%).

[0180] 950 g of polymer of acrylic acid (Mw=2 900 g/mol, Mn=1 320 g/mol, SC=42% by weight), completely neutralized with sodium hydroxide, are then added to the preceding mixture with addition of 87 g of water.

[0181] The two mixtures of tests 7-1 and 7-2 are used in a method for the dispersion of kaolin, comprising a stage of dispersion of kaolin in aqueous suspension. The viscosity of the suspension/dispersion of kaolin is measured according to the protocol given in example 6.

[0182] The effective amount of agents is determined by means of a deflocculation curve according to the protocol which follows.

[0183] An aqueous solution is prepared by weighing out a predetermined amount of water and of agents according to test 7-1 or according to test 7-2, in order to obtain a suspension of kaolin with a solids content of 70% containing 0.07% dry/dry of said agent, and the pH of this solution is adjusted to 8.

[0184] A predetermined amount of kaolin powder is introduced with stirring into this aqueous solution. Stirring is maintained for 15 minutes.

[0185] The Brookfield viscosity is measured at 100 rev/min.

[0186] The measurement is repeated with increasing doses of agents, namely 0.1%, 0.13%, 0.18% and 0.28%.

[0187] The results are presented in FIG. 1.