1. Use of a comb copolymer in the preparation of an aqueous slurry with reduced temperature sensitivity, said slurry comprising a calcium carbonate, the viscosity of said aqueous slurry as measured by a HAAKE Rheostress rheometer at 20 s-1 ranging from 25 and 1 000 mPa.s measured at 20°C and at 90°C, - wherein the specific viscosity of said polymer measured at 20°C and at a polymer concentration of 45 g/l differs from the specific viscosity of said polymer measured at 70°C by a specific viscosity difference Δηsp, wherein the absolute value of Δηsp is less than or equal to 0.5, - wherein said polymer does not have a cloud point between 20°C and 95°C measured in water, and - wherein said polymer has a specific charge from - 10 C/g to - 600 C/g at pH 8.

2. Use according to claim 1, wherein said copolymer has a specific charge from - 10 C/g to - 550 C/g at pH 8.

3. Use according to any one of the previous claims, wherein said copolymer has: - a negatively-charged skeleton consisting in randomly polymerized monomers of acrylic acid and methacrylic acid, and wherein the percentage by weight of monomers of methacrylic acid is more than the percentage by weight of monomers of acrylic acid, and - non-charged side chains consisting in polymerized epoxide-containing compounds.

4. Use according to any one of the previous claims, wherein said comb copolymer consists in: a) acrylic acid monomers and methacrylic acid monomers, wherein the percentage by weight of monomers of methacrylic acid is more than the percentage by weight of monomers of acrylic acid, and b) at least one macromonomer of formula (I): 29 R – X – R' (I) according to which : - X represents m units of propylene oxide (PO) and n units of ethylene oxide (EO), said units of PO and EO being disposed either randomly or regularly, wherein m and n are integers less than or equal to 150, with at least one of them being a nonzero, - R designates a polymerizable unsaturated function, - R' represents hydrogen or an alkyl group containing from 1 to 4 carbon atoms.

5. Use according to claim 4, wherein R in the macromonomer with formula (I) designates the methacrylate function, the methacrylurethane function, the acrylate function, the vinyl function or the allyl function.

6. Use according to claim 4 or 5, wherein said comb copolymer consists in, expressed as a percentage by weight of each of its components: a) from 5 to 60% of acrylic acid monomers and methacrylic acid monomers, wherein the percentage by weight of monomers of methacrylic acid is more than the percentage by weight of monomers of acrylic acid, and b) from 40 to 95% of one macromonomer of formula (I).

7. Use according to any one of claims 4 to 6, wherein said comb copolymer consists in, expressed as a percentage by weight of each of its components: A1) from 1 to 10% of acrylic acid monomers, A2) from 10 to 50% of methacrylic acid monomers, and B) from 40 to 90%, of macromonomers with formula (I).

8. Use according to any one of claims 4 to 7, wherein said comb copolymer consists in, expressed as a percentage by weight of each of its components: 30 A1) from 3 to 6% of acrylic acid monomers, A2) from 20 to 25% of methacrylic acid monomers, and B) from 70 to 77%, of macromonomers with formula (I).

9. Use according to any one of claims 4 to 8, wherein m in the macromonomer with formula (I) ranges from 0 to 10.

10. Use according to any one of claims 4 to 9, wherein n in the macromonomer with formula (I) ranges from 10 to 150.

11. Use according to any one of claims 4 to 10, wherein n and m in the macromonomer with formula (I) are such that he sum n+m is more than or equal to 17.

12. Use according to any one of the previous claims, wherein said copolymer is present in a quantity from 0.01 to 10 wt. %, based on the total weight of the solids in the slurry.

13. Use according to any of the previous claims, according to the preparation of a slurry having a particule size distribution such that about 60% by weight of the particles have an equivalent diameter of less than or equal to 2 μm.

14. Use according to any one of the previous claims, wherein said copolymer has a molecular weight below 100 000 g/mol.

15. Use according to any one of the previous claims, wherein the preparation of said slurry comprises a calcium carbonate grinding stage.

16. Use according to any of the previous claims, wherein said copolymer is partially or totally neutralized.

17. Comb copolymer for use in the preparation of an aqueous slurry with reduced temperature sensitivity, said slurry comprising a calcium carbonate, the viscosity of said aqueous slurry as measured by a HAAKE Rheostress rheometer ranging from 25 and 1 000 mPa.s measured at 20°C and at 90°C, 31 - wherein the specific viscosity of said copolymer measured at 20°C and at a copolymer concentration of 45 g/l differs from the specific viscosity of said copolymer measured at 70°C by a specific viscosity difference Δηsp, wherein the absolute value of Δηsp is less than or equal to 0.5, - wherein said copolymer does not have a cloud point between 20°C and 95°C measured in water, and - wherein said copolymer has a specific charge from -10 C/g to -600 C/g at pH 8, said comb copolymer having : - a negatively-charged skeleton consisting in randomly polymerized monomers of acrylic acid and methacrylic acid and wherein the percentage by weight of monomers of methacrylic acid is more than the percentage by weight of monomers of acrylic acid, and - non-charged side chains consisting in polymerized epoxide-containing compounds.

FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See Section 10, and rule 13)
1. TITLE OF INVENTION
USE OF A COMB POLYMER FOR PREPARING A SUSPENSION CONTAINING CALCIUM CARBONATE AND HAVING REDUCED TEMPERATURE SENSITIVITY
2. APPLICANT(S)
a) Name : COATEX
b) Nationality : FRENCH Company
c) Address : 35, RUE AMPÈRE,
Z.I. LYON NORD,
F-69730 GENAY,
FRANCE
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention
and the manner in which it is to be performed : -
2
The present invention relates to the use of a comb copolymer in the preparation of an aqueous
slurry comprising calcium carbonate, said slurry showing a reduced temperature sensitivity.
Nowadays, the industry is required to provide slurries of calcium carbonate for wide variety
of applications. Slurries of calcium carbonate are suspensions of insoluble solids in a liquid
medium which is generally a mix of water with at least one additive. The precise composition
of the slurry, e.g. the particle size of the calcium carbonate product or the nature of the
additive in the slurry, depends on its intended use. Slurries of calcium carbonate are indeed
used in a wide variety of applications including paper, paint, plastic and concrete.
The preparation of slurries of calcium carbonate generally involves milling and/or dispersing
processes. Reducing the particle size of the calcium carbonate product generally requires the
use of intensive energy mixing means. The slurry can thus get very hot due to energy induced
by shear grinders and dispersers. For example the temperatures can get up to 65°C and far
above, e.g. between 70°C and 105°C.
At such temperatures, the viscosity of the slurries can increase dramatically, then leading to
slurries no longer processable. Additives must be used to avoid this problem.
However, if the additives used to control the viscosity deteriorate at these high temperatures,
the particles of calcium carbonate flocculate and the machines get blocked. There is then a
high risk of damaging production units, such as grinding units. To avoid such a situation, it is
necessary to continuously cool the equipment. This can be nevertheless very costly.
Therefore, there is a need for improved additives that control, reduce, or prevent the viscosity
increase of slurries comprising calcium carbonate at elevated temperatures, e.g. at
temperatures above 65°C that is to say additives useful to reduce temperature sensitivity of
slurries containing calcium carbonate.
Furthermore, it would be desirable to provide additives that stabilize aqueous slurries
containing high solids calcium carbonate at elevated temperatures.
Another object of the present invention is to provide additives that will be compatible in
paper, paint, plastic and concrete formulations.
3
It has been found that the above-mentioned objects are solved by the use of a comb
copolymer in the preparation of an aqueous slurry with reduced temperature sensitivity, said
slurry comprising a calcium carbonate, the viscosity of said aqueous slurry as measured at 20
s-1 by a HAAKE Rheostress rheometer ranging from 25 and
1 000 mPa.s measured at 20°C and at 90°C,
- wherein the specific viscosity of said polymer measured at 20°C and at a polymer
concentration of 45 g/l differs from the specific viscosity of said polymer measured at
70°C by a specific viscosity difference __sp, wherein the absolute value of __sp is less than
or equal to 0.5,
- wherein said polymer does not have a cloud point between 20°C and 95°C measured in
water, and
- wherein said polymer has a specific charge from -10 C/g to - 600 C/g at pH 8.
The inventors have indeed surprisingly found that the use of a comb polymer having a
combination of the above-mentioned three characteristics (a specific viscosity difference __sp,
no cloud point in a defined temperature range and a specific charge in a defined range) is
especially advantageous to provide aqueous slurries containing calcium carbonate with
reduced temperature sensitivity. The comb polymers with the aforementioned characteristics
can reduce the heat sensitivity of such a slurry and prevent an unwanted viscosity increase of
the slurry.
For example, according to the invention, comb polymers prevent the aqueous slurry from
reaching to a viscosity above 1 000 mPa.s (HAAKE Rheostress rheometer at
20 s-1) at elevated temperatures, e.g. at temperatures above 65°C, for example at 90°C.
Weakly anionic and water-soluble copolymers are described in WO 01/96007. These
polymers are presented as enabling to obtain aqueous suspensions of mineral pigments
and/or fillers with a moderate to high mineral matter content, stable over time, without
sedimentation, weakly sensitive to pH and ionic strength of the media used in the
papermaking or petroleum formulations, and having a low Zeta potential. These polymers are
not described as useful in the preparation of a calcium carbonate aqueous slurry with reduced
temperature sensitivity, more precisely with a viscosity between 25 and 1 000 mPa.s as
measured at 20°C and 90°C. We can note that no slurry viscosity measurement is made at a
4
high temperature, i.e. 90°C, and that no specific viscosity measurement of the copolymer is
made at a high temperature, i.e. 70°C, thus that no calculation of specific viscosity difference
is made in this document. In addition, the copolymers described in this document may result
from the polymerization of an anionic monomer with a phosphoric function, which is
regarded as non desirable in terms of environmental pollution. Also, some of the copolymers
described in this application include cross-linking monomers, which are also not desirable in
the context of the present invention for rheology reasons. Still others copolymers of this
application include acrylamide compounds which are today regarded as potentially toxic for
human beings and animals.
For the purpose of the present invention, the term “calcium carbonate” refers to a substance
that comprises at least 80 wt. % calcium carbonate. The term “calcium carbonate” comprises
ground calcium carbonate (GCC), that-is-to-say a calcium carbonate obtained from natural
sources, such as limestone, marble, calcite or chalk, as well as precipitated calcium carbonate
(PCC), that-is-to-say a synthesized substance, generally obtained by precipitation following a
reaction of carbon dioxide and calcium hydroxide (hydrated lime) in an aqueous environment
or by precipitation of a calcium- and a carbonate source in water. Additionally, precipitated
calcium carbonate can also be the product of calcium and carbonate salts introduction, of
calcium chloride and sodium carbonate for example, in an aqueous environment.
PCC may be vaterite, calcite or aragonite.
The calcium carbonate component may be a ground calcium carbonate which has been
obtained by wet grinding of a calcium carbonate.
According to the present invention, the term “slurry” means a water suspension that
comprises insoluble solids and optionally at least one additive.
According to the present invention, the term “reduced temperature sensitivity” means that the
viscosity of the slurry is maintained between 25 and 1 000 mPa.s, when measured by a
HAAKE Rheostress rheometer at 20 s-1 at 20°C and at 90°C, that is to say when the slurry is
exposed to high temperatures.
“High temperature” means temperature above 60°C and more preferably temperature
between 65 and 105°C, for example 90°C.
5
“Stabilizing” or “stabilization” means that the viscosity of the slurry is maintained between
25 and 1 000 mPa.s, when the slurry is exposed to a temperature above 60°C and more
preferably to a temperature between 65 and 105°C.
According to the present invention, the aqueous slurry with reduced temperature sensitivity
comprising a calcium carbonate and at least one comb copolymer according to the present
invention, has a viscosity as measured by a HAAKE Rheostress rheometer at 20 s-1 which is
between 25 and 1 000 mPa.s measured at 20°C and at 90°C. It is to be noted that at viscosity
values over 1 000 mPa.s, there is a risk of blocking and damaging production units, such as
grinding units. It is thus an object of the present invention to keep viscosities of the slurry
below 1 000 mPa.s not only at room temperature, but also at higher temperatures.
For the purpose of the present invention, the term “comb copolymer” refers to a copolymer
composed of a main chain, also referred to as skeleton, and of comb branched
macromonomers.
According to a first aspect of the invention, the specific viscosity of the comb copolymer
measured at 20°C at a polymer concentration of 45 g/l differs from the specific viscosity of
said polymer measured at 70°C by a specific viscosity difference __sp, such that the absolute
value of __sp is less than or equal to 0.5.
The term “specific viscosity difference” in the meaning of the present invention is defined as
the difference of the specific viscosities measured at 70°C and at 20°C.
sp sp °C sp °C Δ = − 70 20 η η η
The term “specific viscosity” in the context of the present invention is defined as the
difference of the relative viscosity as measured at a determined temperature (e.g. 20°C and
70°C) minus 1.
= −1 sp rel η η
The relative viscosity as used herein is the quotient of the solution viscosity η and the
solvent viscosity 0
η
0 η
η
η = rel
6
wherein the solvent viscosity 0
η is defined as the viscosity of the pure solvent at a
determined temperature (e.g. 20°C or 70°C) and the solution viscosity η is defined as the
viscosity of the comb copolymer dissolved in the pure solvent at a determined temperature
(e.g. 20°C or 70°C) and at a determined polymer concentration (e.g. 45 g/l).
However, to determine the relative viscosity it is sufficient to measure the flow time t (of the
solution) and t0 (of the solvent) at a given temperature (e.g. 20°C or 70°C) if the boundary
conditions are constant. Therefore, the relative viscosity may be defined as:
0 t
t
ηrel =
and thus, the specific viscosity may be defined as:
1
0
= −
t
t
sp η
The term “specific viscosity difference” in the context of the present invention is defined as
the difference of the specific viscosities measured at 70°C and at 20°C.
sp sp °C sp °C Δ = − 70 20 η η η
The specific viscosity of the polymer is obtained from an aqueous polymer solution with a
polymer concentration of 45 g/l in water. The flow times t and t0 were measured at 20°C and
at 70°C and sp η and sp Δη are calculated according to the above mentioned formulas.
According to a second aspect of the present invention, the comb copolymer does not have a
cloud point between 20°C and 95°C measured in water.
The “cloud point of the polymer” is the temperature at which polymers dissolved in water are
no longer completely soluble at atmospheric pressure, but precipitate, giving the water a
cloudy appearance.
According to a third aspect of the invention, the comb copolymer has a specific charge from -
10 C/g to - 600 C/g at pH 8.
This means that the comb copolymer according to the present invention is an anionically
charged comb copolymer, that-is-to-say that the total or net charge (i.e. the sum of all positive
and negative charges) of the copolymer is negative.
7
According to one embodiment of the invention, said copolymer has a specific charge from -
10 C/g to - 550 C/g at pH 8.
According to another embodiment of the invention, said copolymer has a specific charge
from - 100 C/g to - 550 C/g at pH 8.
According to still another embodiment of the invention, said copolymer has a specific charge
from - 200 C/g to - 550 C/g at pH 8.
According to one embodiment of the present invention, the comb copolymer is a synthetic
polymer with anionic charge on the skeleton and non-charged side chains.
According to this aspect, the side chains of the anionically charged comb polymer may
comprise polymerized epoxide-containing compounds, such as, for example, ethylene oxide,
propylene oxide, 1-butylene oxide. It is preferred that the polyether side chains comprise
polyethylene oxide or polypropylene oxide or a mixed copolymer comprising ethylene oxide
and propylene oxide and have at their free end a hydroxyl group or an alkyl group having
between 1 and 4 carbon atoms, being a straight or branched chain.
According to one another embodiment of the invention, the comb copolymer consists in:
a) at least one monomer which is acrylic acid and/or methacrylic acid, and
b) at least one macromonomer of formula (I):
R – X – R' (I)
according to which :
- X represents m units of propylene oxide (PO) and n units of ethylene oxide (EO), said
units of PO and EO being disposed either randomly or regularly, wherein m and n are
integers less than or equal to 150, with at least one of them being a non-zero,
- R designates a polymerizable unsaturated function,
- R' represents hydrogen or an alkyl group from 1 to 4 carbon atoms.
According to one embodiment of the present invention, the comb copolymer is such that R in
the macromonomer of formula (I) designates the methacrylate function, the
methacrylurethane function, the acrylate function, the vinyl function or the allyl function.
8
According to one another embodiment of the present invention, the comb copolymer consists
in, expressed as a percentage by weight of each of its components:
a) from 5 to 60% of at least one monomer which is acrylic acid and/or methacrylic acid,
and
b) from 40 to 95% of one macromonomer of formula (I).
According to still one another embodiment of the present invention, the comb copolymer
consists in:
a) monomers of acrylic acid,
b) monomers of methacrylic acid, and
c) macromonomers with the formula (I),
wherein the percentage by weight of monomers of acrylic acid is less than the
percentage by weight of monomers of methacrylic acid.
According to this embodiment of the present invention, the inventors have indeed realized
that to solve the above-mentioned problem of providing aqueous slurries containing calcium
carbonate with reduced temperature sensitivity, it is advantageous to use a comb copolymer
having:
- a negatively-charged skeleton consisting in randomly polymerized monomers of
acrylic acid and methacrylic acid and wherein the percentage by weight of monomers
of methacrylic acid is higher than the percentage by weight of monomers of acrylic
acid and
- non-charged side chains consisting in polymerized epoxide-containing compounds.
It is known that homopolymers of acrylic acid are more efficient to disperse pigments than
homopolymers of methacrylic acids. Surprisingly, according to this embodiment of the
invention, the comb copolymers having a negatively-charged skeleton consisting in randomly
polymerized monomers of acrylic acid and methacrylic acid and wherein the percentage by
weight of monomers of methacrylic acid is higher than the percentage by weight of
monomers of acrylic acid, show better efficiency to reduce temperature sensitivity of calcium
carbonate slurries, the viscosity of said slurry as measured by a HAAKE Rheostress
rheometer at 20 s-1 being between 25 and 1 000 mPa.s measured at 20°C and at 90°C.
9
According to one embodiment of the present invention, the comb copolymer used in the
preparation of an aqueous slurry with reduced temperature sensitivity, said slurry comprising
a calcium carbonate, the viscosity of said slurry as measured by a HAAKE Rheostress
rheometer at 20 s-1 ranging from 25 and 1 000 mPa.s measured at 20°C and at 90°C,
- wherein the specific viscosity of said polymer measured at 20°C and at a polymer
concentration of 45 g/l differs from the specific viscosity of said polymer measured at
70°C by a specific viscosity difference Δηsp, such that the absolute value of Δηsp is
less than or equal to 0.5,
- wherein said polymer does not have a cloud point between 20°C and 95°C measured
in water, and
- wherein said polymer has a specific charge from - 10 C/g to - 600 C/g at pH 8,
said comb copolymer consisting in:
A1) monomers of acrylic acid,
A2) monomers of methacrylic acid, and
B) macromonomers of formula (I):
R – X – R' (I)
in which :
- X represents m units of propylene oxide (PO) and n units of ethylene oxide (EO), said
units of PO and EO being disposed either randomly or regularly, wherein m and n are
integers less than or equal to 150, with at least one of them being a non-zero,
- R designates a polymerizable unsaturated function,
- R' represents hydrogen or an alkyl group from 1 to 4 carbon atoms,
said copolymer is such that the percentage by weight of monomers of acrylic acid is less than
the percentage by weight of monomers of methacrylic acid.
According to one embodiment of the present invention, the comb copolymer consists in,
expressed as a percentage by weight of each of its components:
A1) from 1 to 10% of monomers of acrylic acid,
A2) from 10 to 50% of monomers of methacrylic acid, and
B) from 40 to 90% of macromonomers of formula (I).
10
According to one embodiment of the present invention, the comb copolymer consists in,
expressed as a percentage by weight of each of its components:
A1) from 1 to 8% of monomers of acrylic acid,
A2) from 30 to 50% of monomers of methacrylic acid, and
B) from 40 to 70% of macromonomers of formula (I).
According to one embodiment of the present invention, the comb copolymer consists in,
expressed as a percentage by weight of each of its components:
A1) from 3 to 6% of monomers of acrylic acid,
A2) from 20 to 25% of monomers of methacrylic acid, and
B) from 70 to 77% of macromonomers of formula (I).
According to one another embodiment of the present invention, the comb copolymer consists
in, expressed as a percentage by weight of each of its components:
A1) from 3 to 6% of monomers of acrylic acid,
A2) from 30 to 35% of monomers of methacrylic acid, and
B) from 60 to 67% of macromonomers of formula (I).
According to one embodiment of the present invention, the comb copolymer is such that m in
the macromonomer with formula (I) ranges between 0 and 10.
According to one embodiment of the present invention, the comb copolymer is such that n in
the macromonomer with formula (I) ranges between 10 and 150.
According to one embodiment of the present invention, the comb copolymer is such that n
and m in the macromonomer with formula (I) are such that the sum n+m is more than or
equal to 17.
According to one embodiment of the present invention, the comb copolymer has a molecular
weight below 100 000 g/mol, for example between 10 000 and
100 000 g/mol, for example between 10 000 and 40 000 g/mol, for example between 10 000
and 20 000 g/mol.
11
Said copolymer is obtained by the known methods of conventional radical copolymerization
in solution, in bulk, in direct or inverse emulsion, in suspension or by precipitation in suitable
solvents, in the presence of known catalytic systems and transfer agents, or again, by
processes of controlled radical polymerization such as the method known as Reversible
Addition Fragmentation Transfer (RAFT), the method known as Atom Transfer Radical
Polymerization (ATRP), the method known as Nitroxide Mediated Polymerization (NMP), or
again, the method referred to as Cobaloxime Mediated Radical Polymerization.
It is obtained in the acid and possibly distilled form. It can also be partially or totally
neutralized by one or more neutralization agents selected from the hydroxides of sodium,
calcium, magnesium and potassium and their mixtures or selected from the amines.
According to one embodiment of the present invention, said comb copolymer is partially or
totally neutralized.
According to one another embodiment of the present invention, said copolymer is 100%
neutralized with sodium hydroxide.
In the context of the present invention, it is to be noted that the different embodiments may be
combined with each other.
According to one embodiment, the comb polymer is present in an amount from 0.01 to 10 wt.
%, based on the total weight of the solids in the slurry, for example from 0.05 to 5 wt. %, or
for example from 0.1 to 3.0 wt. %, or for example from 0.2 to 2.0 wt. %, or for example from
0.25 to 1.5 wt. % or for example from 0.5 to 1.25 wt. %.
According to another embodiment, the aqueous slurry according to the present invention
consists in water, a calcium carbonate as defined above and a comb copolymer according to
the present invention. According to this embodiment, the aqueous slurry does not contain any
other additive than the comb copolymer described in the present application, thus it does not
comprise for example another polymer or dispersant.
The calcium carbonate aqueous slurry may be obtained by a method comprising 1/ a step of
dispersion and 2/ a step of grinding. Alternatively, the calcium carbonate aqueous slurry may
12
be obtained by a method comprising 1/ a step of grinding and 2/ a step of dispersing.
According to another method, the calcium carbonate aqueous slurry may be obtained by a
method comprising 1/ a step of grinding until a determined solids content SC1 and a
determined particle size distribution PSD1, 2/ a step of dispersing and 3/ a step of grinding
until a determined solids content SC2 and a determined particle size distribution PSD2.
According to another method, the step of dispersing and the step of mixing may be carried
out at the same time.
The step of dispersion consists in preparing, under agitation, a suspension of calcium
carbonate. More precisely, it may notably consist in introducing all or part of the comb
copolymer according to the invention into the aqueous phase (i.e. water), and then the
calcium carbonate, so as to obtain an aqueous suspension with a determined calcium
carbonate content. In other words, the step of dispersion may consist in mixing the at least
one comb copolymer with water, then mixing the calcium carbonate component with the
comb copolymer solution. Alternatively, it may consist in introducing all or part of the
calcium carbonate into the aqueous phase (i.e. water), and then the comb copolymer
according to the invention. In this case, the step of dispersion consist in mixing the calcium
carbonate component with water, then mixing the at least one comb copolymer with the
calcium carbonate suspension.
The step of dispersion may be carried out into a mixer or into any other equipment which has
the ability to homogeneously mix or homogenize the components of the slurry. The Person
skilled in the art will adapt to these mixing and/or homogenizing conditions such as the
mixing speed and temperature, and according to the available process equipment.
The term “grinding” means that the mineral particles are divided into smaller particles.
The step of grinding may take place into a mill or into any other equipment which has the
ability to divide particles of calcium carbonate into smaller particles.
The step of dispersing and the step of mixing may be carried out at room temperature, i.e. at
20°C or at other temperatures, for example at temperatures varying between 5 and 140°C.
Heat may be introduced by internal shear or by an external source or a combination thereof.
13
The method of preparation of a calcium carbonate aqueous slurry may also comprise a step of
concentration. The term “concentration” means lowering the water content of the slurry, so as
to adjust the solids content of the aqueous slurry. The step of concentration may be
performed by the methods known by the Person skilled in the art. It may notably be
performed by thermal means, for example by means of an evaporator or any other adapted
evaporation equipment.
The calcium carbonate aqueous slurry may be dried with any suitable method known in the
art. It may notably be thermally dried, for example by means of a hair dryer, or it may
mechanically dried, for example by means of filters.
According to one embodiment, the aqueous slurry is an aqueous slurry containing a high
content in solids, for example a slurry having a content in solids of at least
45 wt. %, based on the total weight of the aqueous slurry.
According to a preferred embodiment, the aqueous slurry according to the present invention
has a solids content from 45 to 82 wt. %, preferably from 60 to 78 wt. %, and more
preferably from 70 to 78 wt. %, based on the total weight of the aqueous slurry.
According to one embodiment of the invention, the comb polymers is used in the preparation
of a slurry having a particule size distribution such that about 60% by weight of the particles
have an equivalent diameter of less than or equal to 2 μm.
According to one embodiment of the present invention, the aqueous slurry has a pH ranging
from 7 to 12.
According to one embodiment of the present invention, the amount of said comb copolymer
is calculated such that the aqueous slurry containing calcium carbonate has a viscosity as
measured by an HAAKE Rheostress rheometer at 20 s-1 between 25 and
800 mPa.s measured at 20°C and at 90°C, for example between 30 to 500 mPa.s at 20°C and
at 90°C, or for example between 35 to 300 mPa.s measured at 20°C and at 90°C.
14
According to one embodiment, no additive, e.g. no dispersant, having a specific charge of
more than -500 C/g at pH 8 is added to the aqueous slurry.
The aqueous slurry of the present invention thus obtained can be used in numerous
applications such as in paper, plastics, paint, and/or concrete applications.
Another object of the present invention is a comb copolymer for use in the preparation of an
aqueous slurry with reduced temperature sensitivity, said slurry comprising a calcium
carbonate, the viscosity of said aqueous slurry as measured by a HAAKE Rheostress
rheometer at 20 s-1 being between 25 and 1 000 mPa.s measured at 20°C and at 90°C,
- wherein the specific viscosity of said copolymer measured at 20°C and at a copolymer
concentration of 45 g/l differs from the specific viscosity of said copolymer measured
at 70°C by a specific viscosity difference Δηsp, wherein the absolute value of Δηsp is
less than or equal to 0.5,
- wherein said copolymer does not have a cloud point between 20°C and 95°C
measured in water, and
- wherein said copolymer has a specific charge from -10 C/g to -600 C/g at pH 8.
Another object of the present invention is a comb copolymer comprising:
a) at least one monomer which is acrylic acid and/or methacrylic acid, and
b) at least one macromonomer with the formula (I):
R – X – R' (I)
- X represents m units of propylene oxide (PO) and n units of ethylene oxide (EO), said
units of PO and EO being disposed either randomly or regularly, wherein m and n are
integers less than or equal to 150, with at least one of them being a non-zero,
- R designates a polymerizable unsaturated function,
- R' represents hydrogen or an alkyl group with from 1 to 4 carbon atoms.
15
Another object of the present invention is a comb copolymer consisting in:
A1) at least one monomer which is acrylic acid,
A2) at least one monomer which is methacrylic acid, and
B) at least one macromonomer with the formula (I):
R – X – R' (I)
- X represents m units of propylene oxide (PO) and n units of ethylene oxide (EO), said
units of PO and EO being disposed either randomly or regularly, wherein m and n are
integers less than or equal to 150, with at least one of them being a non-zero,
- R designates a polymerizable unsaturated function,
- R' represents hydrogen or an alkyl group with from 1 to 4 carbon atoms,
wherein the percentage by weight of monomers of acrylic acid is less than the
percentage by weight of monomers of methacrylic acid.
The following examples enable a better understanding of the present invention without
limiting its scope.
Examples
The specific charge of the exemplified polymers is measured by the cationic polymer demand
that is necessary to achieve a charge value of zero, as detected through polyelectrolyte
titration until the charge neutral point 0mV. The equipment necessary to achieve the
measurement consists in the MüteK PCD-02 and the MüteK PCD-03 detector. If necessary,
the sample is adjusted to pH 8.0 ± 0.1 with NaOH (0.1M) prior to measurement. This method
is designed for the charge detection (result in ml) of an aqueous sample and the calculation to
the specific charge quantity (unit: C/g). The cationic reactant used to perform the
measurement is poly-diallyl-dimethyl-ammonium-choride (Poly-DADMAC) (0.001 N).
The cloud point of the exemplified polymers is measured by a turbidity test, in an aqueous
0.2 mol/l NaCl solution adjusted to pH 10 with NaOH (polymer concentration 45 g/l). The
test tube is immerged in an oil bath the temperature of which is adjusted. Once the targeted
16
temperature is reached, the temperature is maintained at a constant level for at least 15
minutes. Then the test tube is removed from the bath and the turbidity is immediately
evaluated visually.
The specific viscosity difference is determined by a Lauda PVS system, on aqueous polymer
solutions (polymer concentration 45 g/l). Measurements are performed with a capillary
Hubbelohde DIN (Schott) of type I (K= 0.010).
The molecular mass of the copolymers according to the invention is determined by steric
exclusion chromatography (SEC).
Copolymers, according to the invention, are prepared according to recognized methods of
radical copolymerization.
A preparation method example is described below in example 1.
EXAMPLE 1
This example illustrates the use of different polymers (tests 1 to 7) in the preparation of a
ground calcium carbonate aqueous slurry (GCC) at 71% solids content with a particle size
distribution such that about 60 ± 1% by weight of the particles have an equivalent spherical
diameter less than 2 μm.
Test 1 illustrates the use of a homopolymer of acrylic acid with a specific charge which is not
set between -10 C/g and -600 C/g at pH 8.
We use a homopolymer of acrylic acid 100% neutralized with sodium hydroxide (molecular
weight : 5 600 g/mol), commercially available under the name of Rheosperse® 3030 (Coatex
Company France).
Test 2 to 5 illustrate the use of a comb copolymer according to the invention having the
combination of the three claimed features (specific viscosity difference, no cloud point
between 20°C and 95°C, a specific charge from -10 to -600 C/g à pH 8) and having :
- a negatively-charged skeleton consisting in randomly polymerized monomers of
acrylic acid and methacrylic acid and wherein the percentage by weight of monomers
of methacrylic acid is higher than the percentage by weight of monomers of acrylic
acid and
17
- non-charged side chains consisting in polymerized epoxide-containing compounds.
More precisely:
Test 2:
Comb copolymer 100% neutralized with sodium hydroxide (molecular weight:
12 900 g/mol).
The polymer has the following composition (in % by weight):
- 7.3% of monomers of acrylic acid,
- 47.3% of monomers of methacrylic acid, and
- 45.4% of macromonomers which are a methacrylic ester of poly(ethylene oxide) with
an average molecular weight of 750 g/mol and having a methyl group at the stage of
the end chain.
The process for preparing this copolymer is the following one:
In a 1 L reactor equipped with mechanical stirring and a heating oil bath,
243 g of water is weighted.
In a first beaker, are weighted: 15.18 g of acrylic acid, 98.38 g of methacrylic acid, 94.43 g of
methacylate of poly(ethylene oxide) having an average molecular weight of 750 g/mol and
having a methyle group at the end of the terminal chain and 147.69 g of water.
In a second beaker, 5.7 g of dimercapto-1,8-dioxa-3,6-octane is weighted.
In a third beaker, are weighted 5.886 g of ammonium persulfate and 50 g of water.
The reactor is heated to 86°C and the various reactants of the three beakers are continuously
added using pumps in three hours. The mixture is then cooked for 1 hour and then neutralized
with 50 % NaOH until pH 8.
The others copolymers exemplified hereafter are prepared according to a similar process.
Test 3:
Comb copolymer 100% neutralized with sodium hydroxide (molecular weight:
17 900 g/mol).
The polymer has the following composition (in % by weight):
18
- 4.7% of monomers of acrylic acid,
- 31.7% of monomers of methacrylic acid, and
- 63.6% of macromonomers which are a methacrylic ester of poly(ethylene oxide) with an
average molecular weight of 2 000 g/mol and having a methyl group at the end chain.
Test 4:
Comb copolymer 100% neutralized with sodium hydroxide (molecular weight:
35 000 g/mol).
The polymer has the following composition (in % by weight):
- 2.1% of monomers of acrylic acid,
- 21.9% of monomers of methacrylic acid, and
- 76% of macromonomers which are a methacrylic ester of poly(ethylene oxide) with an
average molecular weight of 5 000 g/mol and having a methyl group at the end chain.
Test 5:
Comb copolymer 100% neutralized with sodium hydroxide (molecular weight:
18 500 g/mol).
The polymer has the following composition (in % by weight):
- 4.0% of monomers of acrylic acid,
- 26.7% of monomers of methacrylic acid, and
- 69.3% of macromonomers which are a methacrylic ester of poly (ethylene oxide and
propylene oxyde) with about 2 units of PO and 43 units of EO with an average molecular
weight of 2 000 g/mol and having an hydrogen atom at the end chain.
Test 6 and 7 illustrate the use of comb polymers marketed under the brand name of Melpers®
(BASF company) having a specific charge of more than -200 C/g
(i.e. - 169 C/g and - 170 C/g), respectively MelPers® 2450 and MelPers® 4343 to be more
precise.
Ground calcium carbonate (GCC) aqueous slurries, at 71 ± 1% solids content, are prepared in
this example. 0.6% by dry weight of a polymer (tests 1 to 7), based on the total weight of the
solids in the slurry, is introduced into a vessel containing two litres of water. Then 5 kg of
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ground calcium carbonate, marble of Italian origin, are introduced under agitation into the
vessel.
The suspensions are then introduced into a 1.4-liter horizontal grinder (Dynomill®) so as to
grind the carbonate.
The grinding is stopped when an end product having a particle size distribution such that
about 60 ± 1% by weight of the particles have an equivalent spherical diameter less than
2 μm is obtained.
Particle size distribution, and more generally granulometric characteristics of calcium
carbonate particles are determined via a sedimentation method determined from a
Sedigraph™ 5100 device, sold by MICROMERITICS™ Company, i.e. an analysis of the
sedimentation behaviour in a gravimetric field.
The method and the instrument are known to the Person skilled in the art and are commonly
used to determine grain size of fillers and pigments.
The polymers used in example 1 have the following characteristics:
Test number Cloud point (°C) Specific Charge
(C/g of dry polymer) Δη sp
1 > 100 - 925 0,04
2 > 100 - 494 0,18
3 > 100 - 337 0,28
4 > 95 - 279 0,43
5 > 100 - 330 0,43
6 > 100 - 169 0,27
7 > 100 - 170 0,34
Table 1
Viscosity at different temperatures
The viscosity of each slurry is measured at 20°C and 90°C with a HAAKE RheoStress 600
rheometer (Thermo Electro Corporation) equipped with a DC 60/2° Ti (222 – 1229) and
MP/DC 60 L (222 – 1546) measuring system.
20
The reported viscosity values are measured at 20 s-1 shearing speed.
The temperature automatically varies between 20°C and 90°C with an Universal Temperature
Controller.
To avoid evaporation at the surface of the slurry, the system is sealed with a silicone grease
and is covered with a thin layer of mineral oil (Aldrich article number: 33,077-9).
Test number
Viscosity aqueous slurry 20s-1 (mPa.s)
20°C 90°C
1 70 150
2 30 30
3 30 20
4 30 90
5 30 90
6 30 90
7 50 540
Table 2
The results from Table 2 show that all the polymers of tests 1 to 7 allow to control the
viscosity of the CaCO3 (GCC) ground calcium carbonate slurries heated at 20°C and 90°C.
The polymer of test 1 has a highly negative specific charge, which has a great influence on
the surfacial charge of CaCO3 particles. This can constitute a major problem within certain
scopes of applications, for example while preparing paper or for paper coating (bad
interaction between paper cellulose, charge retention problem when coating paper). It is then
necessary to neutralize these particles by adding cationic additives.
The polymers of tests 2 to 7 have a specific charge comprised between -10 and
-600 C/g at pH 8. Such polymers solve the above-mentioned problems while allowing to
21
prepare aqueous CaCO3 slurries having a reduced temperature sensitivity. Such slurries can
then be used in various applications, notably for preparing paper and for paper coating.
EXAMPLE 2
This example illustrates the use of different polymers (test 8 to 11) in the preparation of a
GCC aqueous slurry at 75% solids content with a particle size distribution such that about 90
± 1% by weight of the particles have an equivalent spherical diameter less than 2 μm.
Test 8/8a:
This test illustrates the use of a comb polymer outside the scope of the present invention in
the preparation of a GCC aqueous slurry. This comb polymer is 100% neutralized with
sodium hydroxide (molecular weight: 37 500 g/mol).
The polymer has the following composition (wt. %):
- 13.7% of monomers of acrylic acid,
- 6.6% of monomers of methacrylic acid and
- 79.7% of macromonomers which are methacrylic ester of poly(ethylene oxide) having an
average molecular weight of 2 000 g/mol and having a methyl group at the end chain.
Test 9:
This test illustrates the use of a comb polymer as defined by the present invention in the
preparation of a GCC aqueous slurry. This comb polymer is 100% neutralized with sodium
hydroxide (molecular weight: 17 900 g/mol).
The polymer has the following composition (wt. %):
- 4.7% of monomers of acrylic acid,
- 31.7% of monomers of methacrylic acid and
- 63.6% of macromonomers which are methacrylic ester of poly(ethylene oxide) having an
average molecular weight of 2 000 g/mol and having a methyl group at the end chain.
Test 10/10a and 11:
These tests illustrate the use of comb polymers marketed under the brand name of Melpers®
(BASF company) having a specific charge of more than -200 C/g
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(i.e. - 169 C/g and - 170 C/g), respectively MelPers® 2450 and MelPers® 4343 to be more
precise.
Various aqueous slurries of ground calcium carbonate (GCC), each having 75 ± 1% of solids
content, are prepared in this example. 1% by dry weight of a polymer according to test 8, 9,
10 or 11, or 1,2% by dry weight of a polymer according to test 8a, 10a or 11a based on the
total weight of the solids in the slurry, is introduced into a vessel containing two litres of
water. Then, 5 kg of ground calcium carbonate, marble of Italian origin, are introduced under
agitation into the vessel.
The specific charge, the cloud point and the specific viscosity, as well as the molecular
weight of the polymers are measured as the methods indicated in Example 1.
The suspensions are then introduced into a 1.4-liter horizontal grinder (Dynomill®) so as to
grind the carbonate.
The grinding is stopped when an end product having a particle size distribution such that
about 90 ± 1 % by weight of the particles have an equivalent spherical diameter of less than 2
μm is obtained.
The polymers used in example 2 have the following characteristics:
Test number Cloud point
(°C)
Specific Charge
(C/g of dry polymer) Δη sp
8 and 8a nd - 198 0,83
9 > 100 - 337 0,28
10 and 10a > 100 - 169 0,26
11 and 11a > 100 - 170 0,35
Table 3
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Viscosity at different temperatures
The viscosity of each slurry is measured at 20°C and 90°C with a HAAKE RheoStress 600
rheometer (Thermo Electro Corporation) equipped with a DC 60/2° Ti (222 – 1229) and
MP/DC 60 L (222 – 1546) measuring system.
The reported viscosity values are measured at 20 s-1 shear rate.
The temperature automatically varies between 20°C and 90°C with an Universal Temperature
Controller.
To avoid evaporation at the surface of the slurry, the system is sealed with a silicone grease
and is covered with a thin layer of mineral oil (Aldrich article number: 33,077-9).
Test number
Viscosity aqueous slurry 20s-1 (mPa.s)
20°C 90°C
8 370 11 540
8a 300 8 750
9 160 180
10 380 550
10a 200 500
11 570 1 730
11a 1200 2300
Table 4
The polymer of test 8 (1 wt. % of polymer (dry %), on the basis of the total quantity of solids
in the slurry), outside of scope of the invention since the specific viscosity of said polymer
measured at 20°C and at a polymer concentration of 45 g/l differs from the specific viscosity
of said polymer measured at 70°C by a specific viscosity difference Δηsp, by an absolute
value of Δηsp higher than 0.5, does not allow to have a slurry viscosity at 90°C comprised
between 25 and 1 000 mPa.s.
Adjusting the content to 1.2 wt. % (dry %) (test 8a) does not reduce the viscosity at 90°C
below 1 000 mPa.s.
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EXEMPLE 3
This example illustrates the use of different polymers (test 12 to 16) in the preparation of a
GCC aqueous slurry at 75% solids content with a particle size distribution such that about 90
± 1% by weight of the particles have an equivalent spherical diameter less than 2 μm.
Test 12:
This test illustrates the use of a comb copolymer as defined by the present invention in the
preparation of a GCC aqueous slurry. This comb copolymer is 100% neutralized with sodium
hydroxide (molecular weight: 22 250 g/mol, pH : 7,1).
The polymer has the following composition (wt. %):
- 4.25% of monomers of acrylic acid,
- 24.0% of monomers of methacrylic acid and
- 71.75% of macromonomers which are methacrylic ester of poly(ethylene oxide) with an
average molecular weight of 2 000 g/mol and having a methyl group at the end chain.
Test 13:
This test illustrates the use of a comb polymer outside the scope of the present invention in
the preparation of a GCC aqueous slurry. This comb polymer is 100% neutralized with
sodium hydroxide (molecular weight: 37 500 g/mol).
The polymer has the following composition (wt. %):
- 13.7% of monomers of acrylic acid,
- 6.6% of monomers of methacrylic acid and
- 79,7% of macromonomers which are a methacrylic ester having an average molecular
weight of 3 000 g/mol and consisting of 70% by weight of poly(ethylene oxide) and 30%
by weight of poly(propylene oxide).
Test 14:
This test illustrates the use of a comb polymer outside the scope of the present invention in
the preparation of a GCC aqueous slurry. This comb polymer is 100% neutralized with
sodium hydroxide (molecular weight: > 100 000 g/mol).
The polymer has the following composition (wt. %):
25
- 13.7% of monomers of acrylic acid,
- 6.6% of monomers of methacrylic acid and
- 79,7% of macromonomers which are a methacrylic ester having an average molecular
weight of 3 000 g/mol and consisting of 70% by weight of poly(ethylene oxide) and 30%
by weight of poly(propylene oxide).
Test 15:
This test illustrates the use of a comb copolymer outside the scope of the present invention in
the preparation of a GCC aqueous slurry. This comb copolymer is 100% neutralized with
sodium hydroxide (molecular weight: 15 600 g/mol, pH: 8.5).
The polymer has the following composition (wt. %):
- 28.25% of monomers of acrylic acid,
- 71.75% of macromonomers which are a methacrylic ester of poly(ethylene oxide) with an
average molecular weight of 2 000 g/mol and having a methyl group at the end chain.
Test 16:
This test illustrates the use of a comb copolymer in the preparation of a GCC aqueous slurry.
This comb copolymer is 100% acid (molecular weight: 22 250 g/mol, pH: 2.3).
The polymer has the following composition (wt. %):
- 4.25% of monomers of acrylic acid,
- 24.0% of monomers of methacrylic acid and
- 71.75% of macromonomers which are methacrylic ester of poly(ethylene oxide) with an
average molecular weight of 2 000 g/mol and having a methyl group at the end chain.
Various ground calcium carbonate (GCC) aqueous slurries, each at 75 ± 1% solids content,
are prepared in this example. 1% by dry weight of a polymer according to test 12, based on
the total weight of the solids in the slurry, is introduced into a vessel containing two litres of
water. Then, 5 kg of ground calcium carbonate, marble of Italian origin, are introduced under
agitation into the vessel.
The specific charge, the cloud point and the specific viscosity, as well as the molecular
weight of the polymers are measured as the methods indicated in Example 1.
The suspensions are then introduced into a 1.4-liter horizontal grinder (Dynomill®) so as to
grind the carbonate.
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The grinding is stopped when an end product having a particle size distribution such that
about 90 ± 1% by weight of the particles have an equivalent spherical diameter of less than 2
μm is obtained.
The polymers used in example 3 have the following characteristics:
Test Cloud point (°C)
Specific charge
(C/g of dry polymer)
__ sp
12 >95 - 315 0.48
13 22 - 223 0.5
14 22 - 207 0.83
15 >95 - 328 0.37
16 >95 - 315 0.48
Table 5
Viscosity at different temperatures
The viscosity of each slurry is measured at 20°C and 90°C with a HAAKE RheoStress 600
rheometer (Thermo Electro Corporation) equipped with a DC 60/2° Ti (222 - 1229) and
MP/DC 60 L (222 - 1546) measuring system. The reported viscosity values are measured at
20 s-1 shearing speed. The temperature automatically varies between 20°C and 90°C with an
Universal Temperature Controller. To avoid evaporation at the surface of the slurry, the
system is sealed with a silicone grease and is covered with a thin layer of mineral oil (Aldrich
article number: 33,077-9).
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Test
Viscosity of the aqueous slurry at 20s-1 (mPa.s)
Observations
20°C 90°C
12 255 255 -
13 nd nd
Grinding not finished,
pressure rising in the grinder
14 nd nd Suspension impossible
15 466 738
Grinding not finished,
pressure rising in the grinder
16 675 1220 -
Table 6
The polymers of tests 13 to 15, outside of the invention, do not allow obtaining a
concentrated suspension of grinded CaCO3. The polymer of test 16, in non neutralized form,
does not allow to obtain a CaCO3 suspension according to the invention, that is to say having
a viscosity at 90°C below 1 000 mPa.s.
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WE CLAIM:
1. Use of a comb copolymer in the preparation of an aqueous slurry with reduced
temperature sensitivity, said slurry comprising a calcium carbonate, the viscosity of
said aqueous slurry as measured by a HAAKE Rheostress rheometer at 20 s-1 ranging
from 25 and 1 000 mPa.s measured at 20°C and at 90°C,
- wherein the specific viscosity of said polymer measured at 20°C and at a polymer
concentration of 45 g/l differs from the specific viscosity of said polymer
measured at 70°C by a specific viscosity difference Δηsp, wherein the absolute
value of Δηsp is less than or equal to 0.5,
- wherein said polymer does not have a cloud point between 20°C and 95°C
measured in water, and
- wherein said polymer has a specific charge from - 10 C/g to - 600 C/g at pH 8.
2. Use according to claim 1, wherein said copolymer has a specific charge from
- 10 C/g to - 550 C/g at pH 8.
3. Use according to any one of the previous claims, wherein said copolymer has:
- a negatively-charged skeleton consisting in randomly polymerized monomers of
acrylic acid and methacrylic acid, and wherein the percentage by weight of
monomers of methacrylic acid is more than the percentage by weight of
monomers of acrylic acid, and
- non-charged side chains consisting in polymerized epoxide-containing
compounds.
4. Use according to any one of the previous claims, wherein said comb copolymer
consists in:
a) acrylic acid monomers and methacrylic acid monomers, wherein the percentage
by weight of monomers of methacrylic acid is more than the percentage by weight
of monomers of acrylic acid, and
b) at least one macromonomer of formula (I):
29
R – X – R' (I)
according to which :
- X represents m units of propylene oxide (PO) and n units of ethylene oxide (EO),
said units of PO and EO being disposed either randomly or regularly, wherein m
and n are integers less than or equal to 150, with at least one of them being a nonzero,
- R designates a polymerizable unsaturated function,
- R' represents hydrogen or an alkyl group containing from 1 to 4 carbon atoms.
5. Use according to claim 4, wherein R in the macromonomer with formula (I)
designates the methacrylate function, the methacrylurethane function, the acrylate
function, the vinyl function or the allyl function.
6. Use according to claim 4 or 5, wherein said comb copolymer consists in, expressed as
a percentage by weight of each of its components:
a) from 5 to 60% of acrylic acid monomers and methacrylic acid monomers, wherein
the percentage by weight of monomers of methacrylic acid is more than the
percentage by weight of monomers of acrylic acid, and
b) from 40 to 95% of one macromonomer of formula (I).
7. Use according to any one of claims 4 to 6, wherein said comb copolymer consists in,
expressed as a percentage by weight of each of its components:
A1) from 1 to 10% of acrylic acid monomers,
A2) from 10 to 50% of methacrylic acid monomers, and
B) from 40 to 90%, of macromonomers with formula (I).
8. Use according to any one of claims 4 to 7, wherein said comb copolymer consists in,
expressed as a percentage by weight of each of its components:
30
A1) from 3 to 6% of acrylic acid monomers,
A2) from 20 to 25% of methacrylic acid monomers, and
B) from 70 to 77%, of macromonomers with formula (I).
9. Use according to any one of claims 4 to 8, wherein m in the macromonomer with
formula (I) ranges from 0 to 10.
10. Use according to any one of claims 4 to 9, wherein n in the macromonomer with
formula (I) ranges from 10 to 150.
11. Use according to any one of claims 4 to 10, wherein n and m in the macromonomer
with formula (I) are such that he sum n+m is more than or equal to 17.
12. Use according to any one of the previous claims, wherein said copolymer is present in
a quantity from 0.01 to 10 wt. %, based on the total weight of the solids in the slurry.
13. Use according to any of the previous claims, according to the preparation of a slurry
having a particule size distribution such that about 60% by weight of the particles
have an equivalent diameter of less than or equal to 2 μm.
14. Use according to any one of the previous claims, wherein said copolymer has a
molecular weight below 100 000 g/mol.
15. Use according to any one of the previous claims, wherein the preparation of said
slurry comprises a calcium carbonate grinding stage.
16. Use according to any of the previous claims, wherein said copolymer is partially or
totally neutralized.
17. Comb copolymer for use in the preparation of an aqueous slurry with reduced
temperature sensitivity, said slurry comprising a calcium carbonate, the viscosity of
said aqueous slurry as measured by a HAAKE Rheostress rheometer ranging from 25
and 1 000 mPa.s measured at 20°C and at 90°C,
31
- wherein the specific viscosity of said copolymer measured at 20°C and at a
copolymer concentration of 45 g/l differs from the specific viscosity of said
copolymer measured at 70°C by a specific viscosity difference Δηsp, wherein the
absolute value of Δηsp is less than or equal to 0.5,
- wherein said copolymer does not have a cloud point between 20°C and 95°C
measured in water, and
- wherein said copolymer has a specific charge from -10 C/g to -600 C/g at pH 8,
said comb copolymer having :
- a negatively-charged skeleton consisting in randomly polymerized monomers of
acrylic acid and methacrylic acid and wherein the percentage by weight of
monomers of methacrylic acid is more than the percentage by weight of
monomers of acrylic acid, and
- non-charged side chains consisting in polymerized epoxide-containing
compounds.