DE60023072T2 - Aqueous dispersions - Google Patents

Description

The The present invention relates to dispersions or slurries of particulate solids in water, especially dispersions of mineral solids that normally tend to aggregate, sediment or form a separate phase, and a method for suppressing such phenomena in slurries, which contain such mineral particles, thereby reducing the viscosity of such slurries to improve what makes them more workable.

The The present invention is for making slurries of different particulate Suitable for solids, e.g. Calcium carbonate for the paper industry and clays for use in the ceramics industry, but in fact the Invention for making a workable aqueous dispersion or slurry of any solid particles can be used in high concentrations.

Earlier experiments for preparing such aqueous dispersions are described for example in EP-B-0129329. This document discloses pigment slurries, which water-soluble polymers containing a molecular weight of 1,500 to 6,000, which formed from one or more ethylenically unsaturated monomers are and acid groups, selected from carboxyl and sulfone groups. The present invention shows improved performance over this prior art.

US-A-4,868,228 discloses milling media in aqueous suspensions of mineral materials and in particular the use of such Milling agent for preparing aqueous suspensions of mineral solids with low viscosity. It is described that the Milling agent acrylic acid polymers and / or copolymers which are replaced by at least one neutralizing reagent with a monovalent function and at least one neutralizing reagent are completely neutralized with a multi-valued function.

EP-A2-0705892 shows dispersions or slurries of solid particles in water which also contain a phosphonocarboxylic acid or a water-soluble salt thereof having the following formula as a dispersion: H [CHRCHR] n -PO 3 M 2 / v wherein at least one group R in each unit is a COOM _{1 / v} group and the other group R is hydrogen or a COOM _{1 / v} , hydroxyl, phosphono, sulfono, sulfato, C _1-7 alkyl group or a carboxylate -, phosphono, sulfono, sulfato and / or hydroxy substituted C _1-7 alkyl or C _1-7 alkenyl group, and each M is a cation such that the phosphonated carboxylate is water soluble and n (the number the monomer units in polymerized form in the polymer chain) is from 1 to 6, and preferably less than 5, eg 1 to 3. The dispersed solid particles in this prior art preferably have a particle size of less than 1 mm, for example less than 0.5 mm, preferably 0.5 to 100 μm, especially 1 to 50 μm.

The The present invention seeks to improve dispersions or slurries of solid particles in water. It is well known see. e.g. WO-A-92/00347, that it especially difficult is stable dispersions of fine materials to reach; therefore, it is of particular interest to use stable dispersions of fine solid particles, such as those which produce a have significant fraction with a particle size of less than 2 microns.

worin X H, Na, K, Ca, Mg, NH₄ ⁺ oder A ist und
A ein Polymer, Copolymer oder wasserlösliches Salz davon ist, umfassend ein oder mehrere der folgenden Monomere in polymerisierter Form:

worin R₁ H, OH, C₁ bis C₉-Alkyl oder -Alkoxy oder Acetoxy oder Acetat ist, R₂ H, C₁ bis C₃-Alkyl oder -Alkoxy, COOR₃ ist, R₃ H, Na, K oder C₁ bis C₁₀-Alkyl ist;
Hydroxypropylacrylat, Propylmethacrylat, 2-Acrylamido-2-propansulfonsäure, Natriumstyrolsulfonat, Natriumallylsulfonat, Vinylsulfonsäure und Salze davon, Acrylamid, Methacrylamid, tert.-Butylacrylamid, (Meth)acrylnitril, Styrol, Vinylacetat, Allyloxy-2-hydroxypropylsulfonat und Dialkylacrylamid,
und weiter worin A mindestens 10 Monomere in polymerisierter Form enthält.The present invention therefore provides a 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:

wherein X is H, Na, K, Ca, Mg, NH ₄ ⁺ or A and
A is a polymer, copolymer or water-soluble salt thereof comprising one or more of the following monomers in polymerized form:

wherein R _{1 is} H, OH, C ₁ to C ₉ alkyl or alkoxy or acetoxy or acetate, R _{2 is} H, C ₁ to C ₃ alkyl or alkoxy, COOR ₃ , R _{3 is} H, Na, K or C ₁ to C ₁₀ alkyl;
Hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propanesulfonic acid, sodium styrenesulfonate, sodium allylsulfonate, vinylsulfonic acid and salts thereof, acrylamide, methacrylamide, tert-butylacrylamide, (meth) acrylonitrile, styrene, vinyl acetate, allyloxy-2-hydroxypropylsulfonate and dialkylacrylamide,
and further wherein A contains at least 10 monomers in polymerized form.

The Number of monomers in polymerized form may be from 10 to more being 100, but preferably 15 to 85 and more preferable from 25 to 60. The dispersants may be a weight average of Molecular weight of 1,000 to 10,000, and dispersant having a weight average molecular weight of 2,000 to 6,000 are particularly preferred. Although stable dispersions with lower viscosity obtained with dispersants having a higher molecular weight can be there is an increased Tendency to gel with polymers of molecular weight over 6,000, which can be disadvantageous in some applications.

The This invention is particularly useful for forming dispersions fine particles, e.g. those in which 70% or more the particles below 2 microns and preferably those in which 70% or more are below 1 μm. The Invention works particularly well with dispersions of fine Particles in which 95% or more of the particles are below 1 μm.

The water-soluble Dispersing agent is preferably a phosphono-terminated homo- or copolymer of acrylic acid. If the dispersant is a copolymer, the other monomer may be maleic acid or maleic anhydride, methacrylic acid, sulfonic unsaturated Monomers or any unsaturated polymerizable Be monomers with a COOH group. Such polymers may be, for example according to US 4,046,707, US 5,376,731, US 5,077,361 and US 5,294,686.

Of the dispersed or suspended solid may be any particulate solid which is chemically sufficiently inert to be in an aqueous medium to be dispersed or suspended. The particles are preferably inorganic and essentially insoluble in water. Examples include calcium carbonate, Clays, kaolin, talc and metallic oxides.

The liquid Medium may be water or a solution containing water. This medium may also contain alcohols, glycols, surfactants Contain agent or wetting agent.

The Composition of the present invention provides at least two important benefits, namely a reduction in viscosity the dispersion and a reduction in the tendency of the dispersion, a Gel, especially with fine particle dispersions. In addition will be these benefits for Get systems in which the weight percentage of solid Particles in the dispersion is high, e.g. greater than 60% and preferably greater than 75%.

worin X H, Na, K, Ca, Mg, NH₄ ⁺ oder A ist und
A ein Polymer, Copolymer oder wasserlösliches Salz davon ist, umfassend ein oder mehrere der folgenden Monomere in polymerisierter Form:

worin R₁ H, OH, C₁ bis C₉-Alkyl oder -Alkoxy oder Acetoxy oder Acetat ist, R₂ H, C₁ bis C₃-Alkyl oder -Alkoxy, COOR₃ ist, R₃ H, Na, K oder C₁ bis C₁₀-Alkyl ist;
Hydroxypropylacrylat, Propylmethacrylat, 2-Acrylamido-2-propansulfonsäure, Natriumstyrolsulfonat, Natriumallylsulfonat, Vinylsulfonsäure und Salze davon, Acrylamid, Methacrylamid, tert.-Butylacrylamid, (Meth)acrylnitril, Styrol, Vinylacetat, Allyloxy-2-hydroxypropylsulfonat und Dialkylacrylamid,
und weiter worin A mindestens 10 Monomere in polymerisierter Form enthält.Finally, the invention also provides a method for reducing the viscosity of a dispersion of solid particulate material in an aqueous medium, comprising contacting the aqueous medium, either before or after forming the dispersion of solid particulate material, with an effective amount of at least one dispersant this dispersant comprises a water-soluble polymer comprising:

wherein X is H, Na, K, Ca, Mg, NH ₄ ⁺ or A and
A is a polymer, copolymer or water-soluble salt thereof comprising one or more of the following monomers in polymerized form:

wherein R _{1 is} H, OH, C ₁ to C ₉ alkyl or alkoxy or acetoxy or acetate, R _{2 is} H, C ₁ to C ₃ alkyl or alkoxy, COOR ₃ , R _{3 is} H, Na, K or C ₁ to C ₁₀ alkyl;
Hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propanesulfonic acid, sodium styrenesulfonate, sodium allylsulfonate, vinylsulfonic acid and salts thereof, acrylamide, methacrylamide, tert-butylacrylamide, (meth) acrylonitrile, styrene, vinyl acetate, allyloxy-2-hydroxypropylsulfonate and dialkylacrylamide,
and further wherein A contains at least 10 monomers in polymerized form.

• 1) Kombinieren von natürlichem Calciumcarbonat (einschließlich Marmorstaub), Wasser und Dispersionsmittel miteinander und Mischen unter Bildung einer Aufschlämmung;
• 2) Ausfällen von Calciumcarbonat aus einer wäßrigen Lösung von Natronkalk (Calciumhydroxid) und Kohlendioxid, Sammeln des ausgefallenen Materials und Mischen mit Wasser und einem Dispersionsmittel unter Bildung einer Aufschlämmung; und
• 3) Zerkleinern von Calciumcarbonat zur gewünschten Teilchengröße und Mischen mit Wasser und Dispersionsmittel unter Bildung einer Aufschlämmung.

There are three general methods for preparing a dispersion of calcium carbonate fines:

• 1) combining natural calcium carbonate (including marble dust), water and dispersant together and mixing to form a slurry;
• 2) precipitating calcium carbonate from an aqueous solution of soda lime (calcium hydroxide) and carbon dioxide, collecting the precipitated material and mixing with water and a dispersant to form a slurry; and
• 3) Crush calcium carbonate to the desired particle size and mix with water and dispersant to form a slurry.

The Invention will now be described with reference to the following examples described.

General procedure (A) for preparing dispersions of either coarse or fine precipitated Calcium carbonate and measurement of the viscosity thereof.

• a) An aqueous solution is through dissolution a dispersant formed in water in a beaker.
• b) The aqueous solution is then stirred and the mineral solid to be dispersed added; around agglomeration To avoid this, a slow rate of addition is needed.
• c) stirring is for maintained about 10 minutes after addition of the mineral solid.
• d) Finally Immediately the viscosity measured and then after 1 hour, 24 hours and 48 hours under Use of conventional Viscometers, such as Bookfield, Ford cups, etc.

General procedure (B) for preparing dispersions of ground natural Calcium carbonate and measurement of the viscosity thereof.

• a) water, dispersants and to be ground natural Calcium are poured into a jar, which contains the grinding agent (balls).
• b) The solution is then shaken or stirred, until the desired Particle size obtained becomes.
• c) The viscosity of the solution is then measured immediately and then after 1 hour, 24 hours and 48 hours. The viscosity can be measured using conventional viscometers, such as Bookfield, Ford cup, etc. The dispersants used in the above tests are described in Ta belle 1 described:

Table 1: Dispersant Compositions

Key:

AA

= Acrylsäure

MALAC

= Maleinsäure

AMPS

= 2-Acrylamido-2-methylpropansulfonsäure

EA

= Ethylacrylat

HEA

= Hydroxyethylacrylat

HPA

= Hydroxypropylacrylat

DISPEX N40, DISPEX DP 6 and DISPEX 2695 are commercial dispersants available from Allied Colloids Limited. DISPEX is a trademark owned by Allied Colloids Limited.

AA

= Acrylic acid

MALAC

= Maleic acid

AMPS

= 2-acrylamido-2-methylpropanesulfonic acid

EA

= Ethyl acrylate

HEA

= Hydroxyethyl acrylate

HPA

= Hydroxypropyl acrylate

Dispersants 1, 10 and 11 were prepared using a method known to those skilled in the art using isopropyl alcohol (IPA) as the chain transfer agent. Dispersants 2, 6 and 9 were prepared using sodium hypophosphite (NaHP) as a chain transfer agent. The dispersants 7 and 8 were prepared using sodium metabisulfite (SMBS) and the dispersants A-I are phosphonate-containing polymers of the present invention and were all prepared using phosphonic acid (H ₃ PO ₃ ) as a chain transfer agent.

Example 1: Measurement of viscosity and validity for Dispersions of precipitated Calcium carbonate with particle size 70% <2 microns

Aqueous dispersions from precipitated Calcium carbonate with particle size 70% <2 microns were using the general method described above (A) produced. The viscosity and Applicable results are given in Table 2 below.

Table 2: Viscosity and Assay Results for Precipitated Calcium Carbonate Dispersions of 70% <2 microns particle size

The The above results show that in the present invention used dispersants, i. C, D and G, dispersions with significantly lower viscosity as the dispersants 1 and 2 provide. Likewise is with the dispersants C and D in particular the validity clear less than those for similar ones Dispersions obtained, the non-phosphonate-containing polymers as a dispersing agent.

Example 2: Measurement of viscosity and validity for ground natural Calcium carbonate of particle size 79-83% <1 micrometer

Aqueous dispersions of ground natural Calcium carbonate with particle size 79-83% <1 micrometer were using the general method described above (B) produced. The viscosity and actual results are shown in Table 3 below.

Table 3: Viscosity and Assay Results for Ground Natural Calcium Carbonate of particle size 79-83% <1 micron

As show the above results, provides the dispersant A, which contains phosphonate groups and according to the present invention is, cheap viscosity and validity in comparison to the comparative dispersants 3, 4, 5 and 6.

Example 3: Measurement of viscosity and validity for Dispersions of precipitated Calcium carbonate of particle size 95% <1 micrometer

Aqueous dispersions of like Calcium carbonate with particle size 95% <1 micrometer were accordingly of the general method (A) described above. The viscosity and valid results are shown in Table 4 below.

Table 4: Measurement of Viscosity and Applicability Results Obtained for Dispersions of Precipitated Calcium Carbonate of 95% <1 micron particle size.

outgoing From the results in Table 4 it should be mentioned that phosphonopolycarboxylic acids have a significant improvement in the viscosity and validity of dispersed Calcium carbonate, where 95% of the particles have a size of less than 1 micrometer have to deliver.

Example 4: Comparison the viscosity of dispersant C the viscosity of dispersant 12 (the preferred phosphonated oligomaleate of EP-A-705892, which according to example 1 of EP-A-0569731).

A 75% aqueous dispersion from precipitated Calcium carbonate with particle size 90% <1 micrometer was using the general method described above (A) produced. 0.8% dispersant was used. The viscosity was using a Brookfield viscometer RV model (spindle 4) measured at 10, 20, 50 and 100 rpm. The results are below in Table 5.

Table 5: Viscosity for Dispersant C versus Dispersant 12

Example 5: Comparison the% torque of dispersant C versus the% torque of dispersant 12 (the preferred phosphonated oligomaleate of EP-A-705892, which according to example 1 of EP-A-0569731).

A 75% aqueous dispersion from precipitated Calcium carbonate with particle size 90% <1 micrometer was using the general method described above (A) produced. 0.8% dispersion polymers were used. This Sometimes the% torque was measured at time = zero, and after 1, 2 and 7 days using a Brookfield viscometer RV III models and a helipath spindle (1 rpm / 25 s - spindle C). The results are shown below in Table 6. The Torque is related to the gelling behavior of calcium carbonate slurries connected.

Table 6: Comparison of the Applicability Results Obtained for Dispersant C versus Dispersant 12.

As show the results of Tables 5 and 6 above the phosphonated dispersants of the present invention a significantly improved performance compared to the Dispersants of document EP-A-0705892, which stable dispersions with a lower viscosity deliver even when left for several days.

Claims (9)

A dispersion of particulate solid in a medium containing water and at least one dispersing agent, characterized in that the dispersing agent comprises: a water-soluble polymer comprising:

wherein X is H, Na, K, Ca, Mg, NH ₄ ⁺ or A and A is a polymer, copolymer or water-soluble salt thereof comprising one or more of the following monomers in polymerized form:

wherein R _{1 is} H, OH, C ₁ to C ₉ alkyl or alkoxy or acetoxy or acetate, R _{2 is} H, C ₁ to C ₃ alkyl or alkoxy, COOR ₃ , R _{3 is} H, Na, K or C ₁ to C ₁₀ alkyl; Hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propanesulfonic acid, sodium styrenesulfonate, sodium allylsulfonate, vinylsulfonic acid and salts thereof, acrylamide, methacrylamide, tert-butylacrylamide, (meth) acrylonitrile, styrene, vinyl acetate, allyloxy-2-hydroxypropylsulfonate and dialkylacrylamide, and further wherein A contains at least 10 monomers in polymerized form. A dispersion according to claim 1, comprising at least 60% by weight of the particulate solid dispersion. A dispersion according to claim 1 wherein the weight average the molecular weight of the dispersing agent of 1,000 to 10,000 is. A dispersion according to claim 1 wherein the weight average the molecular weight of the dispersant from 2,000 to 6,000 is. A dispersion according to claim 1, wherein 70% or more of the particulate Solid a particle size of less than 2 μm exhibit. A dispersion according to claim 1, wherein the dispersing agent from the group consisting of a phosphonate-terminated homopolymer of acrylic acid having a weight average molecular weight of 2,000 to 5,800 and a phosphonate-terminated copolymer of acrylic acid and maleic anhydride having a weight average molecular weight of 2,000 to 5,800, selected is. The dispersion of claim 1, wherein the particulate solid from the group consisting of one or more of calcium carbonate, Kaolin, clay, talc and metal oxides. A process for reducing the viscosity of a dispersion of a particulate solid material in an aqueous medium, comprising contacting the aqueous medium either before or after forming the dispersion of the particulate solid material with an effective amount of at least one dispersant, the dispersant comprising: a water-soluble polymer, full:

wherein X is H, Na, K, Ca, Mg, NH ₄ ⁺ or A and A is a polymer, copolymer or water-soluble salt thereof comprising one or more of the following monomers in polymerized form:

wherein R _{1 is} H, OH, C ₁ to C ₉ alkyl or alkoxy or acetoxy or acetate, R _{2 is} H, C ₁ to C ₃ alkyl or alkoxy, COOR ₃ , R _{3 is} H, Na, K or C ₁ to C ₁₀ alkyl; Hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propanesulfonic acid, sodium styrenesulfonate, sodium allylsulfonate, vinylsulfonic acid and salts thereof, acrylamide, methacrylamide, tert-butylacrylamide, (meth) acrylonitrile, styrene, vinyl acetate, allyloxy-2-hydroxypropylsulfonate and dialkylacrylamide, and further wherein A contains at least 10 monomers in polymerized form. The method of claim 8, wherein the dispersion is at least 60% by weight of the particulate Solid includes.