MXPA00007365A - Aqueous dispersions. - Google Patents

Abstract

The present invention relates to a dispersion of particulate solid in a medium containing water and at least one dispersing agent. In particular, the dispersing agent comprises a water soluble polymer wherein X is H, Na, K, Ca, Mg, NH4<+> or A; and A is a polymer, copolymer or water soluble salt thereof, comprising one or more of the following monomers in polymerised form:- wherein R1 is H, OH, C1 to C9 alkyl or alkoxy or acetoxy or acetate R2 is H, C1 to C3 alkyl or alkxy, COOR3 R3 is H, Na, K, or C1 to C10 alkyl; hydroxylpropyl acrylate, propyl methacrylate, 2-acrylamido-2-propane sulphonic acid, sodium styrene sulphonate, sodium allylsulphonate, sodium methyl sulphonate, vinyl sulphonic acid, and salts thereof; acrylamide, methacrylamide, tert-butylacrylamide, (meth)acrylonitrile, styrene, vinyl acetate allyloxy-2-hydroxypropyl sulphonate and dialkylacrylamide; and further wherein A contains at least 10 monomers in polymerised form.

Description

AQUEOUS DISPERSIONS The present invention relates to aqueous dispersions or pastes of particulate solids; in particular, dispersions of mineral solids, which normally tend to aggregate, settle or separate in phases, and a method to inhibit these phenomena in aqueous pastes containing such mineral particles, in order to improve the viscosity of these aqueous pastes, making them more easy to work The present invention is suitable in producing aqueous pastes of various particulate solids, for example calcium carbonate for the paper and clays industry for use in the ceramic industry, but, in fact, the invention can be used in producing a dispersion or aqueous paste that can work from any particle of solids in high concentration. Previous attempts to produce these aqueous dispersions are described in, for example, EP-B-0129329. This document discloses aqueous pigment pastes containing water-soluble polymers of a molecular weight of 1,500 to 6,000, formed from one or more ethylenically unsaturated monomers, and containing acid groups, selected from the carboxylic and sulphonic groups. The present invention shows an improved performance on this prior art. US-A-4, S68, 228 discloses milling agents in aqueous suspensions of mineral materials and, in particular, the use of these milling agents to produce aqueous, low viscosity suspensions of mineral solids. These grinding agents are described as polymers and / or copolymers of acrylic acid, which are completely neutralized by at least one neutralizing agent, having a monovalent function and at least one neutralizing agent having a polyvalent function. EP-A2-0705892 discloses aqueous dispersions or pastes of solid particles in water, which also comprise a phosphonocarboxylic acid or its water-soluble salt, of the following formula, as a dispersing agent: H [CHRCHR] n - P03M2 / v where at least one group T in each unit is a group of C00M1 / v, and the other group R is hydrogen or a group COOM1 / v -hydroxyl, phosphono, sulphono, sulfato, Cx_7 alkyl or a carboxylate, phosphono, sulphono, sulfate and / or C1_1 alkyl substituted with hydroxy, or a C1_7 alkenyl group, and each M is a cation, so that the phosphonated carboxylate is soluble in water, and n (the number of monomer units in polymerized form in the polymer chain ) is from 1 to 6 and preferably less than 5, for example from 1 to 3. The solid particles dispersed in this prior art preferably have a size of less than 1 mm, for example less than 0.5 mm, preferably from 0.5 to 100 μm, especially from 1 to 50 μm. The present invention is directed to the supply of improved dispersions or pastes of solids particles in water. It is well known, for example, see patent PCT / US 91/94539, that it is especially difficult to achieve stable dispersions of fine materials; thus, it is of particular interest to produce stable dispersions of fine solid particles, such as those having a significant proportion with a particle size of less than 2 μm. This invention, therefore, provides a dispersion of a particulate solid within a medium containing water, and at least one dispersion agent, characterized in that this dispersion agent includes a water soluble polymer, comprising: O A- P OX OX where X is H, Na, K, Ca, Mg, NH4 +, or A; and A is a polymer, copolymer or a soluble salt thereof, which comprises one or more of the following monomers, in polymerized form: OR wherein R is H, OH, alkyl or C- to C9 alkoxy or acetoxy or acetate; R 2 is H, alkyl or C alkoxy? to C3, or COOR3; R, is H, Na, K, or C1 to C10 alkyl; hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propane acid, sodium styrene sulfonate, sodium allyl sulfonate, sodium methyl sulfonate, vinylsulfonic acid, and their salts; acrylamide, methacrylamide, tertiary butyl acrylamide, (meth) acrylonitrile, styrene, allyloxy-2-hydroxypropyl-sulphonate, vinyl acetate and dialkylacrylamide; and further, where A contains at least 10 monomers in polymerized form. The number of monomers, in the polymerized form,15 may be from 10 to more than 100, but preferably is from 15 to 85 and more preferably from 25 to 60. The dispersing agents may have a weight average molecular weight of from 1,000 to 10,000, and dispersing agents having a weight Weighted average molecular weight from 2000 to 6000 are 20 especially preferred. Although stable dispersions with low viscosity can be obtained with higher molecular weight dispersion agents, there is a tendency ll_l _ ^ _ ^ _ ^ _ taUÍ_íi _? _ tei_i _ «_ H? .............. - - - - - - - - - - - - - - - - for the formation of gel with polymers of molecular weight above 6000, which can be disadvantageous in some applications The invention is particularly suitable in the formation of dispersions of very fine particles, for example, those in which 70% or more of the particles are below 2 μm, and preferably those in which 70% or more are below 1 μm The invention works particularly well with dispersions of particles 10 fine particles in which 95% or more of the particles are below 1 μm. The dispersing agent, soluble in water, is preferably a homo- or co-polymer, finished in phosphono, of acrylic acid. The other monomer, when the The dispersing agent is a copolymer, it can be maleic acid or maleic anhydride, methacrylic acid, unsaturated sulphonic monomers or any unsaturated polymerizable monomer having a group of COOH. Such polymers can be obtained, for example, according to the? Or US Patents 4,046,707, US 5,376,731, US 5,077,361 and US 5,294,686.

The dispersed or suspended solid can be any particulate solid that is sufficiently chemically inert or dispersed or suspended in an aqueous medium. The particles are preferably inorganic and substantially insoluble in water. Examples include calcium carbonate, clays, kaolin, talc and metal oxides. The liquid medium can be water or a solution containing water. This medium can also contain alcohols, glycols, surfactants or wetting agents. The composition of the present invention provides at least two important advantages, i.e., a reduction in the viscosity of the dispersion and a reduction in the tendency of the dispersion to form a gel, particularly in dispersions of fine particles. In addition, these benefits are obtained for systems in which the weight percentage of the solid particles in the dispersion is high, for example, greater than 60% and preferably greater than 75%. Finally, the invention also provides a method for reducing the viscosity of a dispersion of particulate solid material in an aqueous medium, comprising contacting the aqueous medium, or before or after forming the dispersion of the particulate solid material, with an effective amount of at least one dispersing agent, wherein said dispersing agent comprises a polymer soluble in water, which includes: OR A- P OX I OX where X is H, Na, K, Ca, Mg, NH, +, or A; and A is a polymer, copolymer or a soluble salt thereof, which comprises one or more of the following monomers, in polymerized form: R, H > \ OR wherein R is H, OH, alkyl or C1 to C9 alkoxy or acetoxy or acetate; R2 is H, alkyl or C1 to C3 alkoxy, or COOR3; R3 is H, Na, K, or C1 to C10 alkyl; hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propane acid, sodium styrene sulfonate, sodium allyl sulfonate, sodium methyl sulfonate, vinylsulfonic acid, and their salts; acrylamide, methacrylamide, tert-butyl-acrylamide butyl, (meth) acrylonitrile, styrene, allyloxy-2-hydroxypropyl sulphonate, vinyl acetate and dialkyl acrylamide; and in addition, where A contains at least 10 monomers in polymerized form. fifteen • - < ajÉ "Íte * 'i.Jl.????????????????? J? Jty & **. ... _.-....» -.... _ ..... «- t - »-» ^ .- ^, - ^^., ^, > ^ «- ^ -. ... A, a * ^^ There are three general methods for obtaining a dispersion of fine particles of calcium carbonate. : 1) combine the natural calcium carbonate (which includes marble powder) water and the agent of 5 dispersing each other and mixing them to form an aqueous paste; 2) Precipitate the calcium carbonate from an aqueous solution of lime soda (calcium hydroxide) and carbon dioxide, collect the material The precipitate and mix it with water and a dispersing agent to form an aqueous paste; and 3) grinding the calcium carbonate to a desired particle size, and mixing with water and a dispersing agent to form an aqueous paste. The invention will now be described with reference to the following Examples.

General Method (A) for Preparing Scattered Calcium Carbonate Dispersions of Thick or Fine Size and Measurement of 20 Viscosity a) An aqueous solution was formed by dissolving a dispersing agent in water in a laboratory cuvette; b) the aqueous solution was then stirred and the mineral solid to be dispersed was added; a slow addition rate is necessary to avoid agglomeration; c) stirring was maintained for about 10 minutes, after the addition of the mineral solid; 10 d) finally, the viscosity was measured, immediately and after 1 hour, 24 hours and 48 hours, using conventional viscometers, such as the Brookfield, Ford cup, etc. 15 General Method (B) for Preparing Natural Calcium Carbonate Dispersions Ground and Viscosity Measurement a) The water, dispersing agent and natural calcium carbonate, to be ground, were introduced into a container containing an agent of 20 grinding (balls); b) the solution is then shaken or stirred until the desired particle size is obtained; c) the viscosity of the solution was then measured immediately and after 1 hour, 24 hours and 48 hours. The viscosity can be measured using conventional viscometers, such as the Brookfield, Ford cup, etc. The dispersing agents used in the above tests are described in the following Table 1.

Table 1: Compositions of Scattering Agents Composition Agent Dispersion 1 (Comp.)? OOAA (IPA) Mw 5010 solids 43.5 - pH 7.5 (DISPEX DP6) 2 (Comp.? OOAA (ANP) - Mw 3500 -% solids 42.5 - pH 8.0 3 (Comp.95AA / 5HEA - Mw 4560 -% of solids 42.4 - pH of 8.1 4 (Comp.95AA / 5HPA - Mw 4570 -% solids 41.8 - pH 7.4 5 (Comp 95AA / 5HEA - Mw 4520 -% solids 42.6 - pH 7.5 6 (Com.? OOAA (A P) Mw 4830 -% solids 47.7 - pH 7.0 7 (Comp.)? OOAA (SMBS) - Mw 2000 -% solids 43.0 - pH 7.2 8 (Comp.? OOAA (SMBS) - Mw 4500 -% solids 45.0 - pH 7.0 9 (Comp.) 100AA (ANP - Mw 3500 -% solids 42.5 - pH 5.5 U_ ^ t «_? _« _ MÉ_É_i_M_M_Í_l_HtfÍM_tt_Í_ _- .. ---- < Table 1 (Continued) Composition Agent Dispersion A (Exp.) 100AA / (H3PO3) - Mw 5110 -% solids 45.8 - pH 6.6 B íExp. ) 100AA / (H3PO3) - Mw 4880 -% rg solids 48.7 - pH of 7.1 C (Exp.) 100AA / (H3PO3) - Mw 3600 -% solids 40.0 - pH 7.0 D (Exp.) 90AA / 10MALAC (H3PO3) - Mw 2000 -% solids 50.0 - pH 7.5 E (Exp.) 100AA / (H3PO3) - Mw 2000 -% solids 50.0 - pH 7.5 F (Exp.) 100AA / (H3PO3) - Mw 5170 -% solids 42.0 - pH 5.5 G (Exp.) 100AA / (H3PO3) - Mw 5170 -% solids 42.0 - pH 7.0 H (Exp.) 100AA / (H3P03) - Mw 5800 -% solids 42.0 - pH 5.5 T (Exp) 100AA / (H3P03) - Mw 5800 -% solids 42.0 - pH 5.5 Key : .-.- ^ -t - »-» - ^, -----...-. ..- * - .. > .,. .. ~ * - ..,. ^^ g & amp; DISPEX N40, DISPEX DP6 and DISPEX 2695 are commercial dispersion agents, available from Allied Colloids Limited. DISPEX is a trademark owned by Allied Colloids Limits. 5 AA = acrylic acid MALAC = maleic acid AMPS = 2-acrylamido-2-methyl-propan-sulfonic acid EA = ethyl acrylate HEA hydroxyethyl acrylate 10 HPA = hydroxypropyl acrylate Dispersing agents 1, 10 and 11 were prepared using a method well known to those skilled in the art, using isopropyl alcohol (IPA) as the chain transfer agent. The dispersing agents 2, 6 and 15 9 were prepared using sodium hypophosphite (ANP) as the chain transfer agent. Dispersing agents 7 and 8 were prepared using sodium raetabisulfite (SMBS) and dispersing agents A-I are phosphonate-containing polymers of the present invention and all were prepared 20 using the phosphorous acid (H3P03) as the chain transfer agent.

Example 1: - Measurement of Viscosity and the Trend to Form Gel for Scattered Calcium Carbonate Dispersions, with Particle Size of 70% < 2 Mies Calcium carbonate dispersions were prepared 5 precipitate with 70% particle size < 2 microns, using the General Method < ?), described above. The results of gel viscosity and tendency are presented in the following Table 2. ] 0 Table 2 Viscosity and Gel Tendency Results for Precipitated Calcium Carbonate Dispersions with a Particle Size of 70% < 2 microns The above results demonstrate that the dispersing agents used in the present invention, ie, C, D and G, provide dispersions with a significantly lower viscosity as compared to the dispersing agents 1 and 2. Likewise, with the dispersing agents C and D, in particular, the tendency to form gel is much less than that obtained for similar dispersions, which use polymers that do not contain phosphonate, as the dispersing agent. Example 2: - Measurement of Viscosity and Gel Tendency for Ground Natural Calcium Carbonate, with Particle Size of 79-83% < 1 Miera Aqueous dispersions of carbonate were prepared L5 natural ground calcium, with a particle size of 79-83% < 1 miera, using the General Method (B), described above. The results of Viscosity and tendency to form gel are presented in the following Table 3. 20 Table 3: - Results of Viscosity and Tendency to Form Gel for Natural Calcium Carbonate Ground with Particle Size of 79-83% < 1 Miera As shown by the above results, the dispersing agent A, which contains phosphonate groups and is in accordance with the present invention, provides a favorable viscosity and gel tendency, in comparison with the comparative dispersing agents 3, 4, 5 and 6 Example 3: - Measurement of Viscosity and Trend to Form Gel for Precipitated Calcium Carbonate Dispersions with a 95% Particle Size < 1 Miera Aqueous dispersions of precipitated calcium carbonate, with a particle size of 95% < 1 miera, m? ^ Mm ¿t ?? were prepared using the General Method (A), described above. The results of the viscosity and tendency to form gel are presented in the following Table.

Table 4; - Measurement of Viscosity and Results of the Trend to Form Gel, Obtained for Scattered Calcium Carbonate Dispersions of 95% Particle Size < 1 Miera.

From the results in Table 4 it will be noted that the phosphonopolycarboxylic acids provide a significant improvement in viscosity and the tendency to form a gel. 5 the dispersions of calcium carbonate with 95% of particles being less than 1 miera in size.

Example 4: Comparison of the Viscosity of the Dispersion Agent C Against the Viscosity of the Scattering Agent LO 12 (the preferred phosphonate oligonmaleate of EP-A-705892, which was prepared according to Example 1 of the EP patent) A-0569731). Aqueous dispersions were prepared at 75% precipitated calcium carbonate, with a particle size 15 of 90% < 1 miera, using the General Method (A), described above. 0.8% dispersion agents were used. Viscosity was measured using a Brookfield viscometer model RV (axis 4) at 10, 20, 50 and 100 rpm. The results are presented in Table 5. 20 Table 5: - Viscosity of the Dispersion Agent C against the Scattering Agent 12 Example 5: Comparison of the Torsion% of the Dispersion Agent C versus the Torsion% of the Dispersion Agent 12 (the preferred phosphonated oligonmaleate of EP-A-705892, which was prepared according to Example 1 of the 10 patent EP-A-0569731). Aqueous dispersions were prepared at 75% precipitated calcium carbonate, with a particle size of 90% < 1 miera, using the General Method (A), described above. 0.8% dispersion polymers were used. In this At that time, the twist% was measured at time zero and after 1, 2 and 7 days, using a Brookfield viscometer What is it? ? m? iif? - r m ._-- in? i.? i ?? h. ».. •.«. - • - ** - - * - - * - model RV III and a Helipath axis (1 rpm / 25 s - C axis). The results are presented in Table 6 below. The torsion is related to the behavior of the gel formation of the aqueous calcium carbonate pastes.

Table 6; - A Compassion of the Results of the Trend to Form Gel, Obtained for the Dispersion Agent C, Compared to the Dispersion Agent 12.

As demonstrated by the results of Tables 5 and 6 above, the phosphonated dispersing agents of the present invention provide significantly improved performance over the L5 dispersing agents of the prior art, EP-A-0705892, which ^ mm? É »? * í ?? á? i ?? ? M B? ? ^ ÉIÉ i M? ? táiutM? iá t i provides stable dispersions with lower viscosity, even after resting for several days.

Claims (9)

1. Dispersion of a particulate solid in a medium containing water and at least one dispersing agent, characterized in that the dispersing agent comprises: a water-soluble polymer, which includes: O A- P • OX OX THE where X is H, Na, K, Ca, Mg, NH4 +, or A; and A is a polymer, copolymer or a soluble salt thereof, which comprises one or more of the following monomers, in polymerized form: pjilHiMiiriÉi 1 1? i? ? 1 rt? I rrili? R? - - »--- - - > ~ »- - * - = - J- - • - O wherein R is H, OH, alkyl or Cx to C9 alkoxy or acetoxy or acetate; R, is H, alkyl or C1 to C3 alkoxy, or COOR3; R3 is H, Na, K, or Cx to C10 alkyl; hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propane acid, sodium styrene sulfonate, sodium allyl sulfonate, sodium methyl sulfonate, vinylsulfonic acid, and their salts; acrylamide: methacrylamide, tertiary butyl acrylamide, (meth) acrylonitrile, styrene, allyloxy-2-hydroxypropyl sulphonate, vinyl acetate and dialkyl acrylamide; and further, where A contains at least 10 monomers in polymerized form.

2. Dispersion, according to claim 1, comprising at least 60% by weight of the dispersion of the particulate solid.

3. Dispersion, according to claim 1, in which the weight average molecular weight of the dispersing agent is from 1000 to 10,000.

4. Dispersion, according to claim 1, in which the weight average molecular weight of the dispersing agent is 2000 to 6000.

5. Dispersion, according to claim 1, wherein 70% or more of the particulate solid has a particle size of less than 2 μm.

6. Dispersion, according to claim 1, wherein the dispersing agent is selected from the group consisting of a phosphonate-terminated homopolymer of acrylic acid, with a weight-average molecular weight of 2000 to 5800, and a phosphonate-terminated copolymer of the acid acrylic and maleic anhydride, with a weight average molecular weight of 2000 to 5800.

7. Dispersion, according to claim 1, wherein the particulate solid is selected from the group consisting of one or more of the calcium carbonate, kaolin, clay, talc and metal oxides.

8. Method for reducing the viscosity of a dispersion of a solid particulate material in an aqueous medium, which comprises contacting the aqueous medium, before or after formation of the dispersion of the solid particulate material, with an effective amount of at least one dispersing agent, in which this dispersing agent comprises: 10 a water soluble polymer, which includes: O A- P OX I ox where X is H, Na, K, Ca, Mg, NH4 +, or A; and A is a polymer, copolymer or a soluble salt thereof, which comprises one or more of the following monomers, in polymerized form: wherein Rx is H, OH, alkyl or C to C9 alkoxy or acetoxy or acetate; R2 is H, alkyl or C1 to C3 alkoxy, or COOR3; R3 is H, Na, K, or Cx to C10 alkyl; hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propane acid, sodium styrene sulfonate, sodium allyl sulfonate, sodium methyl sulfonate, vinylsulfonic acid, and their salts; acrylamide, methacrylamide, tertiary-butyl acrylamide butyl, (meth) acrylonitrile, styrene, allyloxy-2-hydroxypropyl sulphonate, vinyl acetate and dialkylacrylamide; and further, where A contains at least 10 monomers in polymerized form. iiitnt iiiílltnrtl i t r r? if frrWfitrf titin i innriliii],. ^ - J .. * ----- ^. > -a - ^ - * - «» .- > .

9. Method, according to claim 7, wherein the dispersion comprises at least 60% by weight of the particulate solid. n - * * * - - *? Ili? Iíüf-? I urttll m iturná "'" ~ * ~ L, t l "" *