USE OF POLYETHERS FOR PIGMENT DISPERSIONS

Abstract

The present invention relates to the use of a polymer containing acid groups as a dispersant for stabilising an aqueous inorganic pigment slurry, wherein the polymer containing acid groups comprises polyether groups of the structural unit (I) *UX-(AlkO).sub.nW (I) where * indicates the bonding site to the polymer containing acid groups. U represents a chemical bond or an alkylene group having 1 to 8 carbon atoms. X is oxygen or an NR.sup.1 group, n is an integer with a mean, based on the polymer containing acid groups, in the range from 3 to 300, Alk is C.sub.2-C.sub.4-alkylene, where Alk may be the same or different within the (Alk-O).sub.n group, W is a hydrogen, C.sub.1-C.sub.6-alkyl or aryl radical or is the YF group where Y is a linear or branched alkylene group which has 2 to 8 carbon atoms and may bear a phenyl ring, F is a nitrogen-bonded 5- to 10-membered nitrogen heterocycle which may have, as ring members, as well as the nitrogen atom and as well as carbon atoms, 1, 2 or 3 additional heteroatoms selected from oxygen, nitrogen and sulphur, where the nitrogen ring members may have an R.sup.2 group, and where 1 or 2 carbon ring members may be in the form of carbonyl groups, R.sup.1 is hydrogen, C.sub.1-C.sub.4-alkyl or benzyl, and R.sup.2 is hydrogen, C.sub.1-C.sub.4-alkyl or benzyl, wherein the inorganic pigment slurry is selected from the group consisting of titanium dioxide slurry, calcium hydroxide slurry, ultrafine precipitated calcium carbonate (PCC) slurry and ground calcium carbonate (GCC) slurry. The invention provides pigment slurries having improved viscosity characteristics together with improved stability over time.

Claims

1. A polymer containing acid groups as a dispersant for stabilising an aqueous inorganic pigment slurry, wherein the polymer containing acid groups comprises polyether groups of the structural unit (I) ##STR00012## where * indicates a bonding site to the polymer containing acid groups, U represents a chemical bond or an alkylene group having 1 to 8 carbon atoms, X is oxygen or an NR.sup.1 group, n is an integer with a mean, based on the polymer containing acid groups, in a range from 3 to 300, Alk is C.sub.2-C.sub.4-alkylene, where Alk may be the same or different within the (Alk-O).sub.n group, W is a hydrogen, C.sub.1-C.sub.6-alkyl, or aryl radical or is the YF group where Y is a linear or branched alkylene group which has 2 to 8 carbon atoms and may bear a phenyl ring, F is a nitrogen-bonded 5- to 10-membered nitrogen heterocycle which may have, as ring members, as well as the nitrogen atom and as well as carbon atoms, 1, 2, or 3 additional heteroatoms selected from oxygen, nitrogen, and sulphur, where the nitrogen ring members may have an R.sup.2 group, and where 1 or 2 carbon ring members may be in the form of carbonyl groups, R.sup.1 is hydrogen, C.sub.1-C.sub.4-alkyl, or benzyl, and R.sup.2 is hydrogen, C.sub.1-C.sub.4-alkyl, or benzyl, wherein the inorganic pigment slurry is selected from the group consisting of a titanium dioxide slurry, a calcium hydroxide slurry, an ultrafine precipitated calcium carbonate (PCC) slurry, and a ground calcium carbonate (GCC) slurry.

2. The polymer according to claim 1, wherein the acid group of the polymer is at least one from the group of carboxyl, aromatic acids, carbolic acids, phosphono, sulphino, sulpho, sulphamido, sulphoxy, sulphoalkyloxy, sulphinoalkyloxy, and phosphonooxy group.

3. The polymer according to claim 1, wherein the polymer containing acid groups is a polycondensation product comprising (II) a structural unit having an aromatic or heteroaromatic system and a polyether group of the formula (I), and (III) a phosphated structural unit having an aromatic or heteroaromatic system.

4. The polymer according to claim 3, wherein the structural units (II) and (III) are represented by the following general formulae ##STR00013## where A is the same or different and is represented by a substituted or unsubstituted, aromatic or heteroaromatic compound having 5 to 10 carbon atoms in the aromatic system, where the further radicals are as defined for structural unit (I); ##STR00014## where D is the same or different and is represented by a substituted or unsubstituted, aromatic or heteroaromatic compound having 5 to 10 carbon atoms in the aromatic system where E is the same or different and is represented by N, NH, or O where m=2 if E=N and m=1 if E=NH or O where R.sup.3 and R.sup.4 are the same or different and are each independently represented by a branched or unbranched C.sub.1- to C.sub.10-alkyl radical, C.sub.5- to C.sub.8-cycloalkyl radical, aryl radical, heteroaryl radical, or H where b is the same or different and is represented by an integer from 0 to 300 where M is independently of one another alkali metal ion, alkaline earth metal ion, ammonium ion, organic ammonium ion, and/or H, a is 1 or in the case of alkaline earth metal ions 1/2.

5. The polymer according to claim 3, wherein the polycondensation product contains a further structural unit (IV) which is represented by the following formula ##STR00015## where Y is the same or different and is independently represented by (II), (III) or further constituents of the polycondensation product, where R.sup.5 and R.sup.6 are preferably the same or different and are represented by H, CH.sub.3, COOH, or a substituted or unsubstituted, aromatic or heteroaromatic compound having 5 to 10 carbon atoms.

6. The polymer according to claim 4, wherein the structural units (II) and (III) are represented by the following general formulae ##STR00016## where A is the same or different and is represented by a substituted or unsubstituted, phenyl group, where the further radicals are as defined for structural unit (I); ##STR00017## where D is the same or different and is represented by a substituted or unsubstituted, phenyl group where E is the same or different and is represented by O where m=1.

7. The polymer according to claim 4, wherein the structural unit (II) is represented by the following general formula ##STR00018## where A is the same or different and is represented by a substituted or unsubstituted phenyl group, where U is a single bond where X=O where AlkO is an ethyleneoxy and/or propyleneoxy unit, where n is in a range of from 10 to 150, where W=H.

8. The polymer according to claim 4, wherein the condensation product also comprises structural unit (VII) which is represented by the following general formula ##STR00019## wherein D, E, R.sup.3, R.sup.4, b, and m have the same meanings as defined in regard to formula (II).

9. The polymer according to claim 3 where a ratio of structural unit (II): structural unit (III) is from 10:1 to 1.

10. The polymer according to claim 5 where a ratio of structural unit (II): is from 10:1 to 1:10.

11. The polymer according to claim 3, wherein the polycondensation product is obtainable from a reaction mixture comprising at least (IIa) a monomer capable of yielding the structural unit (II), (IIIa) a monomer capable of yielding the structural unit (III), (IVa) a monomer having an aldehyde group and a phosphating agent.

12. The polymer according to claim 11, wherein the monomer (IIIa) is first reacted with a phosphating agent and the monomer (IIa) thus obtained is subjected to polycondensation with the monomers (IIIa) and (IVa).

13. The polymer according to claim 11, wherein the monomers (IIa), (IIIa), and (IVa) are subjected to polycondensation and the polycondensate obtained is then reacted with a phosphating agent.

14. The polymer according to claim 11, wherein the monomers (IIa), (IIIa), and (IVa) and the phosphating agent are reacted simultaneously.

15. The polymer according to claim 3, wherein the polycondensate is obtainable by a process comprising carrying out the polycondensation and the phosphation in a reaction mixture.

16. The polymer according to claim 1, wherein the polymer containing acid groups is at least one copolymer obtainable by polymerizing a mixture of monomers comprising (V) at least one ethylenically unsaturated monomer comprising at least one radical from the group of carboxylic acid, carboxylic salt, carboxylic ester, carboxamide, carboxylic anhydride, and carboximide and (VI) at least one ethylenically unsaturated monomer with a polyether group of structural unit (I).

17. The polymer according to claim 16, wherein the ethylenically unsaturated monomer (V) is represented by at least one of the following general formulae from groups (Va), (Vb), and (Vc) ##STR00020## where R.sup.7 and R.sup.8 are each independently hydrogen or an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, B is H, COOM.sub.a, COO(C.sub.qH.sub.2qO).sub.rR.sup.9, CONH(C.sub.qH.sub.2qO)R.sup.9 M is hydrogen, a mono- or divalent metal cation, an ammonium ion, or an organic amine radical, a is ? or 1 R.sup.9 is hydrogen, an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, a cycloaliphatic hydrocarbyl radical having 5 to 8 carbon atoms, an optionally substituted aryl radical having 6 to 14 carbon atoms, q for each (C.sub.qH.sub.2qO) unit is the same or different and is independently 2, 3, or 4 and r is 0 to 200 Z is O, NR.sup.3, ##STR00021## where R.sup.10 and R.sup.11 are each independently hydrogen or an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, a cycloaliphatic hydrocarbyl radical having 5 to 8 carbon atoms, an optionally substituted aryl radical having 6 to 14 carbon atoms, R.sup.12 is the same or different and is represented by (C.sub.nH.sub.2n)SO.sub.3H where n=0, 1, 2, 3, or 4, (C.sub.nH.sub.2n)OH where n=0, 1, 2, 3, or 4; (C.sub.nH.sub.2n)PO.sub.3H.sub.2 where n=0, 1, 2, 3, or 4, (C.sub.nH.sub.2n)OPO.sub.3H.sub.2 where n=0, 1, 2, 3, or 4, (C.sub.6H.sub.4)SO.sub.3H, (C.sub.6H.sub.4)PO.sub.3H.sub.2, (C.sub.6H.sub.4)OPO.sub.3H.sub.2 and (C.sub.nH.sub.2n)NR.sup.14.sub.b, where n=0, 1, 2, 3, or 4 and b=2 or 3, R.sup.13 is H, COOM.sub.a, COO(C.sub.qH.sub.2qO).sub.rR.sup.9, CONH(C.sub.qH.sub.2qO).sub.rR.sup.9, where M.sub.a, R.sup.9, q and r are each as defined above, R.sup.14 is hydrogen, an aliphatic hydrocarbyl radical having 1 to 10 carbon atoms, a cycloaliphatic hydrocarbyl radical having 5 to 8 carbon atoms, an optionally substituted aryl radical having 6 to 14 carbon atoms, Q is the same or different and is represented by NH, NR.sup.15 or O; where R.sup.15 is an aliphatic hydrocarbyl radical having 1 to 10 carbon atoms, a cycloaliphatic hydrocarbyl radical having 5 to 8 carbon atoms or an optionally substituted aryl radical having 6 to 14 carbon atoms.

18. The polymer according to claim 16, wherein the ethylenically unsaturated monomer (VI) is represented by the following general formula ##STR00022## in which each radical is as defined above.

19. The polymer according to claim 16, in which the structural unit (VI) is a vinyloxybutyl polyethylene glycol, preferably comprising a polyethylene glycol having a mean molecular weight Mw from 800 to 4,000, more preferably from 2,000 to 4,000.

20. The polymer according to claim 1, wherein the inorganic pigment is calcium hydroxide and is present in the slurry in an amount of at least 45% solids.

21. The polymer according to claim 1, wherein the inorganic pigment is ultrafine precipitated calcium carbonate (PCC) and is present in the slurry in an amount of at least 50% solids.

22. The polymer according to claim 1, wherein the inorganic pigment is a ground calcium carbonate (GCC) and is present in the slurry in an amount of at least 50% solids.

23. A method of stabilizing an aqueous inorganic pigment slurry comprising adding a polymer of claim 1 to the inorganic pigment slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0037] It has been found, unexpectedly, that aqueous inorganic pigment slurries produced by the inventive use have for a given high solids exhibit reduced viscosity characteristics.

[0038] Furthermore, it has been shown that the use according to the present invention enables aqueous inorganic pigment slurries to be produced with improved stability for longer periods of time. These significantly improved viscosity properties lead to better flow characteristics, for example when pumping or feeding the slurries, dispersing or applying the slurries. The improvements in stability over periods of time are important for storage enabling the slurries produced according to the invention to be used effectively even after longer storage periods.

[0039] An important aspect of the polymer employed in the inventive use is the presence of acid groups. The term acid group in the present invention is understood to mean both free acid and the salts thereof.

[0040] The acid may preferably be at least one from the group of carboxyl, phosphono, aromatic acids, carbolic acids, sulphino, sulpho, sulphamido, sulphoxy, sulphoalkyloxy, sulphinoalkyloxy and phosphonooxy group. Particular preference is given to carboxyl and phosphonooxy groups.

[0041] The polymer of the inventive use may be a polycondensation product or it may be a vinyl addition polymer.

[0042] In one preferred embodiment, the polymer is a polycondensation product containing acid groups. The polycondensation product preferably comprises structural unit having an aromatic or heteroaromatic system, and a polyether group. More preferably still, the polycondensation product comprises a phosphated structural unit having an aromatic or heteroaromatic system.

[0043] In a particularly preferred embodiment, the polymer containing acid groups is a polycondensation product comprising

[0044] (II) a structural unit having an aromatic or heteroaromatic system and a polyether group of the formula (I) and

[0045] (III) a phosphated structural unit having an aromatic or heteroaromatic system.

[0046] The structural units (II) and (III) are preferably represented by the following general formulae

##STR00002##

[0047] where

[0048] A is the same or different and is represented by a substituted or unsubstituted, aromatic or heteroaromatic compound having 5 to 10 carbon atoms in the aromatic system, where the further radicals are as defined for structural unit (1);

[0049] U, X, Alk, n and W all have the same definitions as those given for general formula (I).

[0050] Preferably, X is O.

[0051] Preferably, Alk is ethylene or propylene and more preferably ethylene.

[0052] Preferably, W is H

##STR00003##

[0053] where

[0054] M is independently of one another an alkali metal ion, alkaline earth metal ion, ammonium ion, organic ammonium ion and/or H, a is 1 or in the case of alkaline earth metal ions 1/2.

[0055] D is the same or different and is represented by a substituted or unsubstituted, aromatic or heteroaromatic compound having 5 to 10 carbon atoms in the aromatic system.

[0056] In addition, E is the same or different and is represented by N, NH or O, m=2 if E=N and m=1 if E=NH or O.

[0057] R.sup.3 and R.sup.4 are the same or different and are each independently represented by a branched or unbranched C.sub.1- to C.sub.10-alkyl radical, C.sub.5- to C.sub.8-cycloalkyl radical, aryl radical, heteroaryl radical or H, preferably by H, methyl, ethyl or phenyl, more preferably by H or methyl and especially preferably by H. In addition, b is the same or different and is represented by an integer from 0 to 300. If b=0, E=O.

[0058] The polycondensation product preferably contains a further structural unit (IV) which is represented by the following formula

##STR00004##

[0059] where

[0060] Y is the same or different and is independently represented by (II), (III) or further constituents of the polycondensation product.

[0061] R.sup.5 and R.sup.6 are preferably the same or different and are represented by H, CH.sub.3, COOH or a substituted or unsubstituted, aromatic or heteroaromatic compound having 5 to 10 carbon atoms. In this context, R.sup.5 and R.sup.6 in structural unit (IV) are preferably each independently represented by H, COOH and/or methyl.

[0062] In a particularly preferred embodiment, R.sup.5 and R.sup.6 are each represented by H.

[0063] More preferably, the structural units (II) and (III) are represented by the following general formulae

##STR00005##

[0064] where

[0065] A is the same or different and is represented by a substituted or unsubstituted, phenyl group, where the further radicals are as defined for structural unit (I);

##STR00006##

[0066] where

[0067] D is the same or different and is represented by a substituted or unsubstituted, phenyl group

[0068] where

[0069] E is the same or different and is represented by O where

[0070] m=1.

[0071] More preferably still, the structural unit (II) is represented by the following general formula

##STR00007##

[0072] where

[0073] A is the same or different and is represented by a substituted or unsubstituted, phenyl group,

[0074] where

[0075] U is a single bond

[0076] where

[0077] X=O

[0078] where

[0079] AlkO is an ethyleneoxy and/or propyleneoxy unit,

[0080] where

[0081] n is in the range of from 10 to 150,

[0082] where

[0083] W=H.

[0084] In a more preferred embodiment, the condensation product also comprises structural unit (VII) an is represented by the following general formula

##STR00008##

[0085] wherein D, E, R.sup.3, R.sup.4, b and m have the same meanings as defined above in regard to formula (II).

[0086] The molar ratio of the structural units (II), (III) and (IV) of the inventive phosphated polycondensation product can be varied within wide ranges. It has been found to be appropriate that the molar ratio of the structural units [(II)+(III)]:(IV) is 1:0.8 to 3, preferably 1:0.9 to 2 and in one more preferred embodiment 1:0.95 to 1.

[0087] The molar ratio of the structural units (II):(III) is normally 1:10 to 10:1, often 1:7 to 5:1, preferably 1.5:1 to 1:5, more preferably 3:1.2 to 1:5, more preferably 1:1 to 1:3.

[0088] The A and D groups in the structural units (II) and (III) of the polycondensation product are usually represented by phenyl, 2-hydroxyphenyl, 3-hydroxyphenyl, 4-hydroxyphenyl, 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, naphthyl, 2-hydroxynaphthyl, 4-hydroxynaphthyl, 2-methoxynaphthyl, 4-methoxynaphthyl, preferably phenyl, where A and D may be selected independently of one another and may also each consist of a mixture of the compounds mentioned. The X and E groups are preferably each independently represented by O.

[0089] Preferably, n in structural unit (II) is represented by an integer from 5 to 280, more preferably from 10 to 160, even more preferably from 12 to 150. Suitably, b in structural unit (III) by an integer from 0 to 10, preferably 1 to 7 and more preferably 1 to 5. The respective radicals, the length of which is defined by n and b, may consist here of uniform component groups, but it may also be appropriate that they are a mixture of different component groups. In addition, the radicals of the structural units (II) and (III) may each independently have the same chain length, in which case n and b are each represented by a number. However, it will generally be appropriate that mixtures with different chain lengths are involved in each case, such that the radicals of the structural units in the polycondensation product have different numerical values for n and, independently, from b.

[0090] In a particular embodiment, the present invention further envisages that a sodium, potassium, ammonium and/or calcium salt and preferably a sodium and calcium salt of the phosphated polycondensation product is involved.

[0091] Frequently, the inventive phosphated polycondensation product has a weight-average molecular weight from 4,000 g/mol to 150,000 g/mol, preferably from 10,000 to 100,000 g/mol and more preferably from 20,000 to 75,000 g/mol.

[0092] With regard to the phosphated polycondensation products for use with preference in accordance with the present invention, and the preparation thereof, reference is also made to patent applications WO 2006/042709 and WO 2010/040612, the contents of which are hereby incorporated into the application.

[0093] Suitably, the polycondensation product is obtainable from a reaction mixture comprising at least [0094] (IIa) a monomer capable of yielding the structural unit (II), [0095] (IIIa) a monomer capable of yielding the structural unit (III), [0096] (IVa) a monomer having an aldehyde group and a phosphating agent.

[0097] Desirably the monomer (IIIa) can be reacted with a phosphating agent and the monomer (IIa) so obtained can then be subjected to polycondensation with the monomers (IIIa) and (IVa).

[0098] Alternatively, the monomers (IIa), (IIIa) and (IVa) are subjected to polycondensation and the polycondensate obtained is then reacted with a phosphating agent.

[0099] In a further alternative form, the monomers (IIa), (IIIa) and (IVa) and the phosphating agent are reacted simultaneously.

[0100] Suitably, the polycondensate can be obtainable by a process comprising carrying out the polycondensation and the phosphating in a reaction mixture.

[0101] In a further preferred embodiment, the polymer containing acid groups is a vinyl addition polymer. Preferably, * represents the bonding site to the carbon backbone of the polymer containing acid groups. The acid groups would suitably be bonded to said carbon backbone of the polymer.

[0102] Preferably, the polymer containing acid groups is at least one copolymer obtainable by polymerizing a mixture of monomers comprising

[0103] (V) at least one ethylenically unsaturated monomer comprising at least one radical from the group of carboxylic acid, carboxylic salt, carboxylic ester, carboxamide, carboxylic anhydride and carboximide

[0104] and

[0105] (VI) at least one ethylenically unsaturated monomer with a polyether group of structural unit (I).

[0106] The copolymers according to the present invention contain at least two monomer units. However, it may also be advantageous to use copolymers with three or more monomer units.

[0107] In a preferred embodiment, the ethylenically unsaturated monomer (V) is represented by at least one of the following general formulae from groups (Va), (Vb) and (Vc):

##STR00009##

[0108] In the mono- or dicarboxylic acid derivative (Va) and the monomer (Vb) in cyclic form, where Z?O (acid anhydride) or NR.sup.7 (acid imide), R.sup.7 and R.sup.8 are each independently hydrogen or an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, preferably a methyl group. B is H, COOM.sub.a, COO(C.sub.qH.sub.2qO).sub.rR.sup.9, CONH(C.sub.qH.sub.2qO).sub.rR.sup.9.

[0109] M is hydrogen, a mono- or divalent metal cation, preferably a sodium, potassium, calcium or magnesium ion, or else ammonium or an organic amine radical, and a=? or 1, according to whether M is a mono- or divalent cation. The organic amine radicals used are preferably substituted ammonium groups which derive from primary, secondary or tertiary C.sub.1-20-alkylamines, C.sub.1-20-alkanolamines, C.sub.5-8-cycloalkylamines and C.sub.6-14-arylamines. Examples of the corresponding amines are methylamine, dimethylamine, trimethylamine, ethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, cyclohexylamine, dicyclohexylamine, phenylamine, diphenylamine in the protonated (ammonium) form.

[0110] R.sup.9 is hydrogen, an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, a cycloaliphatic hydrocarbyl radical having 5 to 8 carbon atoms, an aryl radical having 6 to 14 carbon atoms which may optionally also be substituted, q=2, 3 or 4 and r=0 to 200, preferably 1 to 150. The aliphatic hydrocarbons here may be linear or branched and saturated or unsaturated. Preferred cycloalkyl radicals are considered to be cyclopentyl or cyclohexyl radicals, and preferred aryl radicals to be phenyl or naphthyl radicals, which may especially also be substituted by hydroxyl, carboxyl or sulpho groups.

[0111] The following formula represents the monomer (Vc):

##STR00010##

[0112] R.sup.10 and R.sup.11 here can each independently the hydrogen or an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, a cycloaliphatic hydrocarbyl radical having 5 to 8 carbon atoms, an optionally substituted aryl radical having 6 to 14 carbon atoms. Q may be the same or different and is represented by NH, NR.sup.9 or O, where R.sup.9 is as defined above.

[0113] In addition, R.sup.12 can be the same or different and is represented by (C.sub.nH.sub.2n)SO.sub.3H where n=0, 1, 2, 3 or 4, (C.sub.nH.sub.2n)OH where n=0, 1, 2, 3 or 4; (C.sub.nH.sub.2n)PO.sub.3H.sub.2 where n=0, 1, 2, 3 or 4, (C.sub.nH.sub.2n)OPO.sub.3H.sub.2 where n=0, 1, 2, 3 or 4, (C.sub.6H.sub.4)SO.sub.3H, (C.sub.6H.sub.4)PO.sub.3H.sub.2, (C.sub.6H.sub.4)OPO.sub.3H.sub.2 and (C.sub.nH.sub.2n)NR.sup.14.sub.2 where n=0, 1, 2, 3 or 4.)

[0114] R.sup.13 can be H, COOM.sub.a, COO(C.sub.qH.sub.2qO).sub.rR.sup.9, CONH(C.sub.qH.sub.2qO).sub.rR.sup.9, where M.sub.a, R.sup.9, q and r are each as defined above.

[0115] R.sup.14 can be hydrogen, an aliphatic hydrocarbyl radical having 1 to 10 carbon atoms, a cycloaliphatic hydrocarbyl radical having 5 to 8 carbon atoms, an optionally substituted aryl radical having 6 to 14 carbon atoms.

[0116] R.sup.15 can be an aliphatic hydrocarbyl radical having 1 to 10 carbon atoms, a cycloaliphatic hydrocarbyl radical having 5 to 8 carbon atoms or an optionally substituted aryl radical having 6 to 14 carbon atoms.

[0117] Preferably, the ethylenically unsaturated monomer (V) is any of acrylic acid, or salts thereof, methacrylic acid, or salts thereof, maleic acid, or salts thereof, or maleic anhydride. More preferably, the ethylenically unsaturated monomer (V) is any of acrylic acid, or salts thereof, maleic acid, or salts thereof, or maleic anhydride. More preferably still, the ethylenically unsaturated monomer (V) is acrylic acid or salts thereof.

[0118] In a particularly preferred embodiment the ethylenically unsaturated monomer (VI) is represented by the following general formula

##STR00011##

[0119] in which each radical is as defined above.

[0120] Preferably, in the ethylenically unsaturated monomer (VI) R.sup.7 and R.sup.8 are each independently selected from hydrogen, methyl or ethyl. More preferably, R.sup.7 and R.sup.8 are both hydrogen.

[0121] Preferably, U in the ethylenically unsaturated monomer (VI) represents a chemical bond or an alkylene group having from 1 to 2 carbon atoms, more preferably a chemical bond or a methylene group, more preferably still a chemical bond.

[0122] Preferably, X is oxygen.

[0123] Preferably, Alk is same or different C.sub.2-C.sub.4 alkylene, preferably containing entirely or predominantly ethylene groups, in which the (AlkO).sub.n has a mean molecular weight Mw from 800 to 8,000, preferably from 1,500 to 5,000, preferably from 2,000 to 4,000, more preferably still from 2,000 to 3,500, in particular from 2,500 to 3,500.

[0124] Preferably, Alk is different C.sub.2-C.sub.4 alkylene containing predominantly ethylene groups. More preferably, (AlkO).sub.n is a single butylene oxide unit bonded to a chain of ethylene oxide units, preferably, 1,4-butanediol mono vinyl ether with a polyethylene oxide, in which the polyethylene oxide component contains from 3 to 250 repeating ethylene oxide units, more preferably from 5 to 200 repeating ethylene oxide units, more preferably still from 12 to 150 repeating ethylene oxide units, in particular from 15 to 100 repeating units.

[0125] In a further preferred embodiment, Alk is different C.sub.2-C.sub.4 alkylene containing predominantly ethylene groups. More preferably, (AlkO).sub.n is a single butylene oxide unit bonded to a chain of ethylene oxide units, preferably, 1,4-butanediol mono vinyl ether with a polyethylene oxide, in which the polyethylene oxide component contains from 30 to 250 repeating ethylene oxide units, more preferably from 35 to 200 repeating ethylene oxide units, more preferably still from 42 to 150 repeating ethylene oxide units, in particular from 45 to 100 repeating units.

[0126] Preferably, the structural unit (VI) is a vinyloxybutyl polyethylene glycol, more preferably comprising a polyethylene glycol having a mean molecular weight Mw from 800 to 8,000, suitably from 800 to 5,000, desirably from 800 to 4,000, more desirably from 1,500 to 4,000, more desirably still from 2,000 to 4,000, more preferably still from 2,000 to 3,500, in particular from 2,500 to 3,500.

[0127] The molar ratio of the structural units (V):(VI) is preferably from 1:4 to 15:1, preferably from 1:1 to 10:1.

[0128] The preparation of the copolymers is carried out in a conventional way, for example by free-radical polymerization. It is, for example, described in EP0894811, EP1851256, EP2463314, EP0753488.

[0129] The inorganic pigment slurry is selected from the group consisting of titanium dioxide slurry, calcium hydroxide slurry, ultrafine precipitated calcium carbonate (PCC) slurry and ground calcium carbonate (GCC) slurry. The invention is particularly suitable for these inorganic pigment slurries which tend to have especially fine particle sizes, especially as these inorganic pigment slurries suitably have a pH of greater the 7. The invention addresses the problem that when producing these specific inorganic pigment slurries it can be difficult to obtain the balance of properties. The invention can be suitable for forming stable and effective aqueous slurries of such inorganic pigments.

[0130] In the inventive use, the polymer may be used in doses of up to 3% by weight, based on the total weight of the aqueous inorganic pigment slurry. Generally, though, the optimum dose of the polymer is often below this level. The exact dose may vary according to the particular inorganic pigment, the average particle size of the pigment and the required solids content of the slurry thereof. Typically, the dose may be from 0.05% to 2.5% by weight, for instance from 0.1% to 1% by weight, typically from 0.2% to 0.7% by weight.

[0131] Typically, the aqueous inorganic pigment slurry according to the present invention has a pH greater than 7. The pH of the slurry may be at least 8, often at least at least 8.5, for instance at least 9. The pH of the aqueous inorganic pigment slurry may lie in the range from 8 to 12.5 or above.

[0132] In one preferred embodiment of the inventive use, the inorganic pigment is calcium hydroxide (d90 below 120 ?m, preferably 80 ?m and more preferably below 60 ?m). Often the calcium hydroxide would have a range of particle sizes. For instance, the d50 can be below 40 ?m and usually in the range from 20 ?m to 35 ?m, for instance from 25 ?m to 30 ?m. The distribution of particle sizes would normally include very small particles of below 2 ?m. Frequently, the volume of calcium hydroxide particles below 2 ?m may be as much as 15% or more but usually can be in the range from 2% to 10%, for example from 3% to 8%. The d10 may range from 1 ?m to 10 ?m, for instance from 2 ?m to 10 ?m. The d90 may be in the range from 40 ?m to 90 ?m, for instance from 50 ?m to 80 ?m, such as from 60 ?m to 75 ?m. Typically, the aqueous slurry of calcium hydroxide may have a solids content of at least 35% by weight based on the total weight of the slurry, often at least 40% by weight, for instance at least 45% by weight. Suitable calcium hydroxide slurries may have a solids content in the range from 40% to 50% by weight, often from 42% to 48% by weight, for instance from 43% to 47% particularly from 44 to 46%, usually around 45%. Aqueous calcium hydroxide slurries tend to have much higher pH, often above 10.5, for instance from 11 to 12.5. These highly alkaline suspensions are often difficult to achieve effective high solids and low suspensions with conventional dispersants. The polymer employed in accordance with the inventive use have been found to be particularly effective at dispersing calcium hydroxide slurries of high solids and achieving effective low viscosities. Furthermore, the polymer used according to the present invention can achieve stability over prolonged periods of time without any significant loss of viscosity over time by comparison to some conventional dispersants. This is especially so for conventional dispersants which contain an ester link. The dose of the polymer may typically lie in the range from 0.05% to 1.4% by weight, based on the total weight of the slurry. Often the dose may be from 0.1% to 1% by weight, typically from 0.1% to 0.8% by weight, frequently from 0.1% to 0.6% by weight, for instance from 0.2% to 0.4% by weight.

[0133] In another preferred embodiment of the invention the inorganic pigment is ultrafine precipitated calcium carbonate (ultrafine PCC). Typically, the aqueous slurry of ultrafine precipitated calcium carbonate may have a solids content of at least 40% by weight based on the total weight of the slurry, often at least 45% by weight, for instance at least 50% by weight. Suitable ultrafine precipitated calcium carbonate (ultrafine PCC) may have a solids content in the range from 40% to 55% by weight, often from 45% to 53% by weight, for instance from 47% to 52% by weight, desirably from 48% to 51% by weight, such as from 48% to 50% by weight, often around 50% by weight. Aqueous precipitated calcium carbonate slurries may have a pH in the range from 8 to 12, often from 8.5 to 11.5, usually from 9 to 11, for instance from 9 to 10.5, typically from 9 to 10. Normally ultrafine precipitated calcium carbonate (ultrafine PCC) may have particles in the range from 0.02 ?m to 0.1 ?m (from 20 nm to 100 nm). Suitably the mean particle size distribution by weight may range from 0.05 ?m to 0.1 ?m, for instance from 0.06 ?m to 0.1 ?m, often from 0.07 ?m to 0.09 ?m. Some grades of ultrafine calcium carbonate may have a d50 in the range from 80 to 160 nm, for instance from 90 to 150 nm, often from 100 to 140 nm. Such grades may have d90 in the range from 250 nm to 350 nm, for instance from 260 nm to 340 nm, often from 270 nm to 330 nm. Other grades of ultrafine calcium carbonate may have a granule size d50 much larger, for instance from 15 ?m to 40 ?m, for instance from 20 ?m to 35 ?m, such as from 20 ?m to 30 ?m. Typically, such grades may have an average particle size from 20 nm to 100 nm, for instance from 30 nm to 80 nm, such as from 40 nm to 60 nm. The polymer employed in accordance with the inventive use have been found to be particularly effective at dispersing ultrafine precipitated calcium carbonate (ultrafine PCC) slurries of high solids and achieving effective low viscosities. Furthermore, the polymer used according to the present invention can achieve stability over prolonged periods of time without any significant loss of viscosity over time by comparison to some conventional dispersants. The dose of the polymer may typically lie in the range from 0.4% to 3% by weight, based on the total weight of the slurry. Often the dose may be from 0.6 to 2.5% by weight, typically from 0.8% to 2.5% by weight, frequently from 1.0% to 2.0% by weight.

[0134] In a further preferred embodiment of the invention the inorganic pigment is ultrafine ground calcium carbonate (ultrafine GCC). Typically, the aqueous slurry of ultrafine ground calcium carbonate may have a solids content of at least 70% by weight based on the total weight of the slurry, often at least 72% by weight, for instance at least 75% by weight, particularly at least 77% by weight. Suitable ultrafine ground calcium carbonate (ultrafine GCC) may have a solids content in the range from 70% to 85% by weight, often from 72% to 80% by weight, for instance from 75% to 79% by weight, desirably from 75% to 78% by weight, such as from 76% to 77% by weight, often around 77% by weight. Aqueous ground calcium carbonate slurries may have a pH in the range from 8 to 11.5, often from 8.5 to 11, usually from 8.5 to 10.5, for instance from 9 to 10. Normally ultrafine ground calcium carbonate (ultrafine GCC) may have a mean particle size (d50) below 5 ?m and preferably below 2 ?m. The particle size may for instance be between 60% and 99% below 2 ?m. It is possible for the ultrafine ground calcium carbonate (ultrafine GCC) to have coatings on the surface of the particles which may provide the ultrafine ground calcium carbonate (ultrafine GCC) with desirable properties, for instance rendering the particles more hydrophobic. However, such coatings can render the product more difficult to produce stable high solids and low viscosity dispersions.

[0135] The polymer employed in accordance with the inventive use have been found to be particularly effective at dispersing ultrafine ground calcium carbonate (ultrafine PCC) slurries of high solids and achieving effective low viscosities. Furthermore, the polymer used according to the present invention can achieve stability over prolonged periods of time without any significant loss of viscosity over time by comparison to some conventional dispersants. The dose of the polymer may typically lie in the range from 0.05% to 1.4% by weight, based on the total weight of the slurry. Often the dose may be from 0.1% to 1% by weight, typically from 0.1% to 0.8% by weight, frequently from 0.1% to 0.6% by weight, for instance from 0.2% to 0.4% by weight.

[0136] The following examples are intended to illustrate the invention and are not in any way limiting.

EXAMPLES

[0137] The following polymers are used in the examples.

Product AInventive

[0138] Product A is prepared employing a heatable reactor equipped with a stirrer is charged with 17.8 parts of polyphosphoric acid and heated to 90? C. Within 15 min, 30.7 parts of phenoxyethanol are metered in while stirring. After 60 min, 445 parts of poly(ethylene oxide) monophenyl ether (mean molecular weight 5,000 g/mol), 34.8 parts of concentrated methanesulphonic acid, 14.16 parts of paraformaldehyde and 23.2 parts of water are added. The reaction mixture is heated to 105? C. while stirring for a further 6 hours. It is then allowed to cool and neutralized to pH 7 with 50% sodium hydroxide solution. The condensation product has a mean molecular weight Mw of approx. 22,000 g/mol (determined by GPC).

Product BCommercial Product Melflux? 6685Inventive

[0139] Commercially available polycarboxylate ether from BASF Constructions Additives GmbH. The polymer is based on the monomers acrylic acid and vinyloxybutyl polyethylene glycol3000.

Product CCommercial Product Melflux? PCE 1493Inventive

[0140] Commercially available polycarboxylate ether from BASF Constructions Additives GmbH. The polymer is based on the monomers acrylic acid and vinyloxybutyl polyethylene glycol3000.

Product DCommercial Product Melpers? 2450Inventive

[0141] Commercially available polycarboxylate ether from BASF Construction Additives GmbH. The polymer is based on the monomers maleic anhydride and vinyloxybutyl polyethylene glycol1100.

Product EInventive

[0142] Copolymer of 1.0 molar parts of vinyloxybutyl polyethylene glycol3000 and 2.7 molar parts of acrylic acid with a mean molecular weight (Mw) of approximately 36,200 g/mol (determined by GPC).

Product FComparative

[0143] Copolymer of 1.0 molar parts of methyl end capped polyethylene glycol1000 methacrylate; 3.7 molar parts of methacrylic acid; and 10.3 molar parts of acrylic acid with a mean molecular weight (Mw) of approximately 9,600 g/mol (determined by GPC).

Product GComparative

[0144] Polyacrylic acid, sodium salt prepared using ammonium sulfate starter and isopropanol chain transfer agent, polymer having a mean molecular weight (Mw) of approximately 7,800 g/mol.

Product HComparative

[0145] Polyacrylic acid, sodium salt prepared using ammonium persulphate starter and isopropanol chain transfer agent, polymer having a mean molecular weight (Mw) of approximately 3,500 g/mol.

Product IComparative

[0146] Polyacrylic acid, sodium salt prepared using ammonium persulphate starter and isopropanol chain transfer agent, polymer having a mean molecular weight (Mw) of approximately 7,800 g/mol.

Product JComparative

[0147] Polyacrylic acid, sodium salt prepared using sodium persulphate starter and sodium hypophosphite chain transfer agent, polymer having a mean molecular weight (Mw) of approximately 4,500 g/mol.

Description of Evaluation Test Work

Example 1Formation of Calcium Hydroxide Slurries

Test Conditions:

[0148] 45% solid Ca(OH).sub.2Company Honeywell Fluka, Standard Goods (Material Number: 31219-500G) [0149] 0.2-2.0% solid polymer (Products A-J) (based on mass of Ca(OH).sub.2 solid)

[0150] Particle size specification of the calcium hydroxide is presented in Table 1

TABLE-US-00001 TABLE 1 Particle size Ca(OH).sub.2 powder, Fluka d10 4.16 ?m d50 27.7 ?m d90 68.9 ?m Volume <2 ?m 5.6%

Test Procedure:

[0151] The calculated amount of polymer is solved in demineralized water in 100 ml glass beaker and powder Ca(OH).sub.2 is added into polymer solution while stirring in approx. 3 minutes. The slurry is stirred for 5 minutes and the viscosity is measured. The viscosity is determined by using Anton Pair MCR-102 with spindle LV 3 at 100 rpm at 23? C.

[0152] Devices: Heidolph RZR 2102 control, 32 mm dispersing disc, 100 mL glass beaker, Anton Paar Rheometer MCR 102

[0153] The test results are presented in Table 2.

TABLE-US-00002 TABLE 2 Calcium Hydroxide Slurries - Viscosity (mPas) at 23? C. - 45% pigments solids by weight based on total weight of slurry Polymer Dose Product Product Product Product Product Product Product Product Product Product (%) A B C D E F G H I J 0.2 155 571 315 376 257 426 1342 1074 1555 Solid 0.3 Not Not Not Not Not 243 Not Not Not Solid tested tested tested tested tested tested tested tested 0.4 49 57 59 187 61 110 917 931 601 Solid 0.5 Not Not Not Not Not 68 Not Not Not Solid tested tested tested tested tested tested tested tested 0.6 17 34 20 94 20 27 596 760 980 Solid 0.7 Not Not Not Not Not 29 Not Not Not Solid tested tested tested tested tested tested tested tested 0.8 26 34 24 103 36 36 385 568 852 Solid 0.9 No Not Not Not Not 13 Not Not Not 269 tested tested tested tested tested tested tested tested 1.0 12 23 9 70 34 Not 249 398 701 176 tested 1.1 Not Not Not Not Not Not Not Not Not 86 tested tested tested tested tested tested tested tested tested 1.2 Not 10 31 66 14 29 144 442 679 66 tested 1.3 Not Not Not Not Not <0 Not Not Not Not tested tested tested tested tested tested tested tested tested 1.4 20 8 33 60 15 Not 72 215 598 47 tested 1.5 Not Not Not Not Not Not Not Not Not Not tested tested tested tested tested tested tested tested tested tested 1.6 Not 17 29 47 36 Not 50 89 441 27 tested tested 1.7 Not Not Not Not Not Not Not Not Not <0 tested tested tested tested tested tested tested tested tested 1.8 12 31 16 44 35 Not 31 36 362 Not tested tested 1.9 Not Not Not Not Not Not Not Not Not Not tested tested tested tested tested tested tested tested tested tested 2.0 31 7 33 53 35 Not 14 41 266 Not tested tested

[0154] The results in Table 2 illustrate that for the preparation of 45% solids calcium hydroxide slurries, Product A should the best performing dispersing agent, achieving the lowest viscosity value at 0.2% w/w polymer. By contrast comparative tests using standard polyacrylate products G-J required many times more polymer (more than 5 times the amount of polymer in the case of the best performing of these, Product G, to achieve the same viscosity as for Product A and more than 4 times the amount of polymer required for Product E. Comparative polyether polymer Product F required between 1.5 and twice as much polymer as required for inventive Product A.

Example 2Formation of Ultrafine Calcium Carbonate Slurries

Test Conditions:

[0155] 50% solid ultrafine calcium carbonate (in a filtered cake/paste form) [0156] 1.0-2.0% solid polymer (based on ultrafine calcium carbonate)

[0157] Specification of ultrafine calcium carbonate is presented in Table 3

TABLE-US-00003 TABLE 3 Technical specifications Unit Value Moisture % <1 Bulk density g/cm.sup.3 0.75 pH 7-9 Appearance (25? C.) white powder Granule size d50% ?m 25 Particle size d50% nm Approx 130 Particle size d90% nm Approx 300

Test Procedure:

[0158] Application: 80-90 g of the ultrafine calcium carbonate paste is weighed into a PE cup. As a dispersing agent, 0.5% polymer (based on solids) is weighed in. The mixture is then stirred manually until it is completely liquid dispersion. The base is then refilled into an 80 mL PE cup and re-stirred for 5 minutes more with a dispersing disc at 1500 rpm to obtain homogenous dispersion.

[0159] Sample is tested with Anton Paar Rheometer MCR 102 with Brookfield Adapter and Spindle LV 3 measured at 100 rpm at 23? C. The sample is stored and measured again after 5 h and 24 h.

[0160] Devices: Heidolph RZR 2102 control, 32 mm dispersing disc, 80 mL PE cup, Anton Paar Rheometer MCR 102

[0161] The results are presented in Table 4.

[0162] Conventional comparative polyacrylate Products G-J do not provide the effectiveness as the polymers according to the present invention. The best performing product is Product A at 1% w/w the dosage level. The closest 2nd best performance can be seen from Product D. Polycarboxylate Products G-J do not come close to Product A even when twice as much polymer is used.

Example 3Formation of Ground Calcium Carbonate Slurries

Test Conditions:

[0163] 77% solid CaCO3 OmyaCarb 2-GU (particle size distribution d50=3.8 microns; d90=9.6 microns); [0164] 0.2% solid polymer (based on CaCO3 solid)

[0165] Specification of ground calcium carbonate is presented in Table 5

TABLE-US-00004 TABLE 5 Particle size Ground Calcium Carbonate (GCC) d10 0.774 ?m d50 3.86 ?m d90 9.69 ?m Volume <2 ?m 26.57%

Test Procedure:

[0166] The calculated amount of polymer is solved in demineralized water in 100 ml glass beaker and powder CaCO.sub.3 is added into polymer solution while stirring in approx. 3 minutes. The slurry is stirred for 5 minutes and the viscosity is measured. The viscosity is determined by using Anton Pair MCR-102 with spindle LV 3 at 100 rpm at 23? C.

[0167] Devices: Heidolph RZR 2102 control, 32 mm dispersing disc, 100 mL glass beaker, Anton Paar Rheometer MCR 102.

[0168] The results are presented in Table 6.

[0169] Product A gave the best overall viscosity and stability over 24 hours. The other polymers of the invention, Products B-E also provided good viscosities and stability over 24 hours. The comparative polyacrylate Product J appeared to provide acceptable viscosities initially but sedimented after 24 hours. Comparative polyether Product F appeared to provide an initial acceptable viscosity but very quickly showed increase in viscosity with time such that at 24 hours the viscosity had increased quite significantly to 1,160 mPas which would be unsuitable for use and indicates declining stability.

TABLE-US-00005 TABLE 4 Ultrafine Calcium Carbonate Slurries - Viscosity (mPas) at 23? C. - 50% by weight pigment solids based on total weight of slurry Polymer Dose Product Product Product Product Product Product Product Product Product Product (%) A B C D E F G H I J 1.0 91 Solid Solid 691 Solid Solid Solid Solid Solid Solid 1.5 109 111 1228 165 402 301 Solid Solid Solid Solid 2.0 99 149 335 <0 387 358 2369 Solid 1618 Solid

TABLE-US-00006 TABLE 6 Ground Calcium Carbonate Slurries - Viscosity (mPas) at 23? C. - 77% by weight pigment solids based on total weight of slurry at a fixed dose of 0.2% w/w. Time Product Product Product Product Product Product Product (hours) A B C D E F J 0 287 340 333 333 380 265 317 1 340 428 324 378 517 520 399 5 343 417 369 445 560 644 371 24 404 467 424 558 681 1160 Sedimented