JP2001070778A - Dispersion of granular solid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent slurry containing mineral particles from becoming flocculated by using a dispersant containing a specific water-soluble polymer, in a dispersion of granular solids in a medium containing water or at least one dispersant. SOLUTION: When a dispersion or slurry of mineral solids which tend to flocculate or precipitate or to be phased out, for example, slurry of calcium carbonate for paper manufacturing industry, is produced, a medium containing water and at least one dispersant is used. In this case, a dispersant containing a water-soluble polymer represented by formula I is used. In formula I, X is H, Na, K, Ca, Mg, NH4+ or A. A is a polymer, a copolymer or a water-soluble salt thereof in a polymerized state and including those represented by formula II (wherein, R1 is H, OH, an alkyl and the like; R2 is H, and alkyl, an alkoxy and the like and R3 is H, Na, K, an alkyl and the like).

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to dispersions or slurries of particulate solids in water, and in particular to dispersions of mineral solids, which usually tend to agglomerate, settle, or phase out, and to process them more. A method for suppressing these phenomena in slurries containing such mineral particles to improve the viscosity of the slurry to facilitate its operation.

The present invention is suitable for producing slurries of various particulate solids, such as calcium carbonate for the paper industry and clay for use in the ceramic industry. It can also be used to produce processable aqueous dispersions or slurries of high concentrations of any solid particles.

Prior attempts to produce such aqueous dispersions have been described, for example, in EP-B-012.
No. 9329. It has a molecular weight of 1,5
Disclosed is a pigment slurry comprising a water-soluble polymer having an acid group selected from carboxyl groups and sulfonic acid groups, wherein the slurry is from 00 to 6,000 formed from one or more ethylenically unsaturated monomers. The present invention shows higher performance than this prior art.

[0004] US Patent No. A-4,868,228 discloses that
Grinding aids (gri) in aqueous suspensions of mineral substances
and the use of such grinding aids in producing low-viscosity aqueous suspensions of mineral solids. The grinding aid is a polymer and / or copolymer of acrylic acid that is completely neutralized by at least one neutralizing agent having a monovalent functional group and at least one neutralizing agent having a polyvalent functional group. It is stated that there is.

EP-A2-0705892 teaches a dispersion or slurry of solid particles in water containing, as dispersant, phosphonocarboxylic acids or their water-soluble salts of the formula I have. H [CHRCHR] _n -PO ₃ M _{2 / v} wherein in each unit at least one R group is CO
OM _{1 / v} group and the other R groups are hydrogen or COO
M _{1 / v} , hydroxyl, phosphono, sulfono (sul
phono), sulphate, C
_1-7 alkyl groups; or a carboxylate, phosphono, sulphono, be a sulfate and / or C _1-7 alkyl group substituted by hydroxy or C _1-7 alkenyl groups; each M is a water phosphinothricin bone over gated carboxylate N (the number of monomer units in polymerized form in the polymer chain) is from 1 to 6, preferably less than 5, for example from 1 to 3.
The solid particles dispersed according to this prior art are 1 mm
Smaller, for example smaller than 0.5 mm, preferably 0.5 to 100 μm, particularly preferably 1 to 50 μm
It is preferable to have a particle size of

[0006] The present invention seeks to provide an improved dispersion or slurry of solid particles in water. It is well known that it is very difficult to obtain a stable dispersion of fine minerals, as described for example in PCT / US 91/94539;
Therefore, there is a particular interest in producing stable dispersions of fine solid particles, where a significant portion of the particle size is less than 2 μm.

[0007] The present invention therefore provides a dispersion of a particulate solid in a medium comprising water and at least one dispersant, wherein the dispersant comprises a water-soluble polymer comprising:

Embedded image Wherein X is H, Na, K, Ca, Mg, NH ₄ ⁺ or A; A is in polymerized form,

Embedded image Wherein R ₁ is H, OH, C ₁ -C ₉ alkyl or alkoxy, or acetoxy, or acetate; R ₂ is H, C ₁ -C ₃ alkyl or alkoxy, COOR ₃ ; ₃ is H, Na, K,
Or _{C 10} alkyl from _{C 1,} provided that when _{R 2} is COOR _3, said compound may be an acid anhydride, hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propanesulfonic acid , Sodium styrene sulfonate, sodium allyl sulfonate, sodium methyl sulfonate,
Vinyl sulfonic acid and salts thereof; acrylamide, methacrylamide, t-butylacrylamide,
Including (meth) acrylonitrile, styrene, vinyl acetate, allyloxy-2-hydroxypropylsulfonate, and one or more dialkylacrylamides;
A polymer, copolymer, or a water-soluble salt thereof, wherein A is at least one of the polymerized forms
Contains 0 monomers.

The number of monomers in the polymerized form is 10
To 100, preferably 15 to 85, most preferably 25 to 60. The dispersant is 10
Dispersants which can have a weight average molecular weight of from 00 to 10,000, with a weight average molecular weight of from 2000 to 6000, are particularly preferred. Stable dispersions with lower viscosity can be obtained with higher molecular weight dispersants, but polymers with molecular weights higher than 6000 may be disadvantageous in certain applications due to the increased tendency to gel formation.

The present invention is particularly suitable for producing dispersions of very fine particles, for example, those in which more than 70% of the particles are less than 2 μm, preferably more than 70% are less than 1 μm. . The present invention
Particularly, it is effective for dispersion of fine particles in which 95% or more of the particles are smaller than 1 μm.

The water-soluble dispersant is preferably a homopolymer or a copolymer of acrylic acid having a phosphono group as a terminal group. When the dispersant is a copolymer, the other monomer may be maleic acid, or maleic anhydride, methacrylic acid, a sulfonic unsaturated monomer, or an unsaturated polymerizable monomer having any COOH groups. it can. Such polymers are:
For example, US Pat. No. 4,046,707, US Pat. No. 5,376,731, US Pat. No. 5,077,361.
And US Patent No. 5,294,686.

The solid to be dispersed or suspended can be any particulate solid that is sufficiently chemically inert to be dispersed or suspended in an aqueous medium. The particles are
Preferably, they are inorganic and essentially do not dissolve in water. Examples include calcium carbonate, clay, kaolin, talc, and metal oxides.

The liquid medium can be water or a solution containing water. This medium contains alcohol, glycol,
Surfactants or wetting agents can also be included.

The compositions of the present invention have at least two important advantages: reducing the viscosity of the dispersion and reducing the tendency of the dispersion to form a gel, which are particularly fine. Obtained in the dispersion of particles. In addition, these advantages are due to the high weight percent of solid particles in the dispersion,
For example, it is obtained in a system higher than 60%, preferably higher than 75%.

Finally, the present invention comprises contacting the aqueous medium with an effective amount of at least one dispersant before or after forming the solid particulate dispersion.
A method for reducing the viscosity of a dispersion of a solid particulate material in an aqueous medium, wherein the dispersant comprises a water-soluble polymer comprising:

Embedded image Wherein X is H, Na, K, Ca, Mg, NH ₄ ⁺ or A; A is in polymerized form,

Embedded image Wherein R ₁ is H, OH, C ₁ -C ₉ alkyl or alkoxy, or acetoxy, or acetate; R ₂ is H, C ₁ -C ₃ alkyl or alkoxy, COOR ₃ ; ₃ is H, Na, K,
Or _{C 10} alkyl from _{C 1,} provided that when _{R 2} is COOR _3, said compound may be an acid anhydride, hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propanesulfonic acid , Sodium styrene sulfonate, sodium allyl sulfonate, sodium methyl sulfonate,
Vinyl sulfonic acid and salts thereof; acrylamide, methacrylamide, t-butylacrylamide,
Including (meth) acrylonitrile, styrene, vinyl acetate, allyloxy-2-hydroxypropylsulfonate, and one or more dialkylacrylamides;
A polymer, copolymer, or water-soluble salt thereof, wherein A comprises at least 10 monomers in polymerized form.

There are three general methods for producing fine calcium carbonate dispersions. 1) A method of combining, mixing and forming a slurry of natural calcium carbonate (including marble dust), water and a dispersant; 2) Carbonation from an aqueous solution of soda lime (calcium hydroxide) and carbon dioxide A method of sedimenting the calcium, collecting the sedimented mineral matter, mixing with water and a dispersing agent to form a slurry; and 3) grinding the calcium carbonate to a desired particle size, water and dispersing agent. A method of mixing and producing a slurry. The present invention is further described based on the following examples.

The coarse or fine precipitated calcium carbonate
General method (A) for preparing dispersions
A ) dissolving the dispersant in water in a beaker to form an aqueous solution; b) then stirring the aqueous solution and adding the mineral solids to be dispersed to it (adding slowly to prevent aggregation) C) after the addition of the mineral solids, stirring is carried out for about 10 minutes, d) Finally, the viscosity is immediately measured after 1 hour, 24 hours, 48 hours, Brookfield, Ford Cup, etc. Is measured using a known viscometer.

A crushed natural calcium carbonate disc
General method (B) for preparing a version and its viscosity
A ) introducing water, a dispersant and a mineral source of natural calcium to be milled into a vessel containing milling aids (balls); b) adding the solution until the desired particle size is obtained; Shake or agitate, c) Measure the viscosity of the solution immediately after 1 hour, 24 hours, 48 hours. The viscosity can be measured using a known viscometer such as a Brookfield or Ford cup. Gel Tendency The gel tendency is the gel phase (gel ph ) of a polymer solid.
ase). Method 1 for measuring gel phase
One is gel permeation chromatography (GPC). The dispersants used in the above tests are shown in Table 1 below.

[0018]

[Table 1]

Key: DISPEX N40,
DISPEX DP6 and DISPEX 2695
Is a commercially available dispersant available from Allied Colloids Limited. DISPEX is
It is a registered trademark owned by Allied Colloids Limited. AA = acrylic acid MALAC = maleic acid AMPS = 2-acrylamide 2-methylpropanesulfonic acid EA = ethyl acrylate HEA = hydroxyethyl acrylate HPA = hydroxypropyl acrylate Dispersants 1, 10 and 11 are isopropyl alcohol as a chain transfer agent (IPA) using a known method,
Was prepared. Dispersants 2, 6 and 9 were prepared using sodium hypophosphite (NaHP) as the chain transfer agent. Dispersants 7 and 8 were prepared using sodium metabisulfite (SMBS), and dispersant AI was a polymer of the present invention containing a phosphonate, and phosphoric acid (H ₃ PO ₃ ) was used as a chain transfer agent. ).

Example 1: 70% of the precipitated calcium carbonate
Dispersion with particle size less than 2 microns
Measurement of viscosity and gelation tendency An aqueous dispersion having a particle size of 70% of the precipitated calcium carbonate of less than 2 microns was prepared using the general method (A) described above. The results for viscosity and gelation tendency are shown in Table 2 below.

[0021]

[Table 2]

The above results indicate that the dispersants used in the present invention, ie, C, D, and G, were dispersants 1 and 2
It has been shown to provide a much less viscous dispersion. Also, the gelling tendency, especially when using dispersants C and D, is significantly lower than the gelling tendency of similar dispersions using polymers without phosphonate groups as dispersants.

Example 2: Ground natural calcium carbonate
79-83% of the particle size is less than 1 micron
An aqueous dispersion of 79-83% of ground natural calcium carbonate having a particle size of less than 1 micron was prepared using the general method (B) described above. The results for viscosity and gelation tendency are shown in Table 3 below.

[0024]

[Table 3]

The above results show that Dispersant A containing phosphonate groups and prepared according to the present invention provides better viscosity and gelling tendency compared to Comparative Dispersants 3, 4, 5, and 6. It indicates that you want to.

Example 3: 95% of the precipitated calcium carbonate
Viscosity and gelation when particle size is less than 1 micron
An aqueous dispersion in which 95% of the precipitated calcium carbonate had a particle size of less than 1 micron was prepared using the general method (A) described above. The results for viscosity and gelation tendency are shown in Table 4 below.

[0027]

[Table 4]

The results in Table 4 show that phosphonopolycarboxylic acids can significantly improve the viscosity and gelling tendency of dispersed calcium carbonate having a particle size of less than 1 micron of 95%.

Example 4: Dispersant 12 (European publication no.
Prepared according to Example 1 of A-0569731,
Preferred phosphones of EP-A-705892
And the viscosity of the dispersant C
A 75% aqueous dispersion in which 90% of the precipitated calcium carbonate had a particle size of less than 1 micron was prepared using the general method (A) described above. 0.8% of the dispersant was used. Viscosity was measured using a Brookfield viscometer RV model (Spindle 4) at 10, 20, 50, and 100 rpm. The results are shown in Table 5 below.

[0030]

[Table 5]

Example 5: Dispersant 12 (European publication No.
Prepared according to Example 1 of A-0569731,
Preferred phosphones of EP-A-705892
% Of Oligomerized Oleate) and Dispersant C
A 75% aqueous dispersion of 90% of the precipitated calcium carbonate with a particle size of less than 1 micron was prepared using the general method (A) described above. 0.8% of the dispersant was used. The torque% is calculated as follows: time = 0, and 1, 2, 7
After a day, measurements were taken using a Brookfield viscometer RV III model and a helipath spindle (1 rpm / 25 s-spindle C). The results are shown in Table 6 below. The torque is determined by the gelation behavior of the calcium carbonate slurry.
aviour).

[0032]

[Table 6]

As the results of Tables 5 and 6 above show, the phosphonate dispersants of the present invention show significantly improved performance over the dispersants of the prior art document EP-A-0 705 892. Provides a stable dispersion with low viscosity, even after standing for several days.

 ──────────────────────────────────────────────────の Continuation of the front page (72) Inventor Allen Dufour France, 06550 Pegomas, Shman de Tape 472, Les Peverel, Villa Number 27

Claims (9)

[Claims] 1. A dispersion of a particulate solid in a medium comprising water and at least one dispersant, wherein the dispersant comprises a water-soluble polymer comprising: Wherein X is H, Na, K, Ca, Mg, NH ₄ ⁺ or A; A is in polymerized form, Wherein R ₁ is H, OH, C ₁ -C ₉ alkyl or alkoxy, or acetoxy, or acetate; R ₂ is H, C ₁ -C ₃ alkyl or alkoxy, COOR ₃ ; ₃ is H, Na, K,
Or _{C 10} alkyl from _{C 1,} provided that when _{R 2} is COOR _3, said compound may be an acid anhydride, hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propanesulfonic acid , Sodium styrene sulfonate, sodium allyl sulfonate, sodium methyl sulfonate,
Vinyl sulfonic acid and salts thereof; acrylamide, methacrylamide, t-butylacrylamide,
Including (meth) acrylonitrile, styrene, vinyl acetate, allyloxy-2-hydroxypropylsulfonate, and one or more dialkylacrylamides;
A polymer, copolymer, or a water-soluble salt thereof, wherein A is at least one of the polymerized forms
Contains 0 monomers. 2. The method of claim 1, wherein the weight of the dispersion is at least 60.
2. The dispersion of claim 1, comprising at least one particulate solid. 3. The dispersant has a weight average molecular weight of 1,000 to 1.
The dispersion of claim 1, wherein the dispersion is 000. 4. The dispersant has a weight average molecular weight of 2,000 to 6,
2. The dispersion of claim 1, wherein the dispersion is 000. 5. The dispersion of claim 1, wherein at least 70% of the particulate solid has a particle size of less than 2 μm. 6. A dispersant having a weight average molecular weight of 2,000 to 5,800, a homopolymer of acrylic acid having a phosphonate group as a terminal group, and a weight average molecular weight of 2,000
2. The dispersion of claim 1, wherein the dispersion is selected from the group consisting of a copolymer of acrylic acid and maleic anhydride terminated with phosphonate groups. 7. The method of claim 1, wherein the particulate solid comprises one or more calcium carbonates,
The dispersion of claim 1, wherein the dispersion is selected from the group consisting of kaolin clay, talc, and metal oxide. 8. A method for reducing the viscosity of a dispersion of solid particulate matter in an aqueous medium comprising contacting the aqueous medium with an effective amount of at least one dispersant before or after forming the dispersion of solid particulate matter. Wherein the dispersant comprises a water-soluble polymer comprising: Wherein X is H, Na, K, Ca, Mg, NH ₄ ⁺ or A; A is in polymerized form: Wherein R ₁ is H, OH, C ₁ -C ₉ alkyl or alkoxy, or acetoxy, or acetate; R ₂ is H, C ₁ -C ₃ alkyl or alkoxy, COOR ₃ ; ₃ is H, Na, K,
Or _{C 10} alkyl from _{C 1,} provided that when _{R 2} is COOR _3, said compound may be an acid anhydride, hydroxypropyl acrylate, propyl methacrylate, 2-acrylamido-2-propanesulfonic acid , Sodium styrene sulfonate, sodium allyl sulfonate, sodium methyl sulfonate,
Vinyl sulfonic acid and salts thereof; acrylamide, methacrylamide, t-butylacrylamide,
Including (meth) acrylonitrile, styrene, vinyl acetate, allyloxy-2-hydroxypropylsulfonate, and one or more dialkylacrylamides;
A polymer, copolymer, or a water-soluble salt thereof, wherein A is at least one of the polymerized forms
Contains 0 monomers. 9. A dispersion comprising at least 60% by weight.
9. The dispersion of claim 8, comprising a particulate solid of