U.S. patent application number 11/167170 was filed with the patent office on 2005-10-20 for grinding and/or dispersing aid of mineral materials in aqueous suspension, resulting aqueous suspensions and uses thereof.
This patent application is currently assigned to COATEX S.A.S.. Invention is credited to Jacquemet, Christian, Mongoin, Jacques, Suau, Jean-Marc.
Application Number | 20050234176 11/167170 |
Document ID | / |
Family ID | 8857939 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050234176 |
Kind Code |
A1 |
Mongoin, Jacques ; et
al. |
October 20, 2005 |
Grinding and/or dispersing aid of mineral materials in aqueous
suspension, resulting aqueous suspensions and uses thereof
Abstract
The invention relates to the use of water-soluble homopolymers
and/or copolymers of acrylic and/or methacrylic acid with one or
more acrylic, vinyl or allyl monomers as a dispersion and/or
grinding-aid agent for mineral particles in aqueous suspension. The
invention also concerns the said aqueous suspensions as well as
their uses in the fields of paper, paint and plastics
materials.
Inventors: |
Mongoin, Jacques;
(Quincieux, FR) ; Jacquemet, Christian; (Lyon,
FR) ; Suau, Jean-Marc; (Lucenay, FR) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
COATEX S.A.S.
GENAY
FR
|
Family ID: |
8857939 |
Appl. No.: |
11/167170 |
Filed: |
June 28, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11167170 |
Jun 28, 2005 |
|
|
|
10450454 |
Jun 19, 2003 |
|
|
|
10450454 |
Jun 19, 2003 |
|
|
|
PCT/FR01/04027 |
Dec 18, 2001 |
|
|
|
Current U.S.
Class: |
524/430 |
Current CPC
Class: |
B02C 23/06 20130101;
C09C 3/041 20130101; D21H 19/385 20130101; D21H 19/58 20130101;
D21H 17/675 20130101; B01F 17/0028 20130101; C09C 1/021 20130101;
B01F 17/005 20130101; C01P 2004/61 20130101; D21H 17/37 20130101;
C09D 17/004 20130101; D21H 17/69 20130101; B01F 17/0057 20130101;
C09C 3/10 20130101 |
Class at
Publication: |
524/430 |
International
Class: |
C08K 003/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2000 |
FR |
00/16683 |
Claims
1. A dispersion and/or grinding-aid agent for mineral fillers in
aqueous suspension, the agent comprising homopolymers and/or
copolymers of acrylic and/or methacrylic acid with one or more
acrylic, vinyl or allyl monomers, characterised in that the said
homopolymers and/or copolymers of acrylic and/or methacrylic acid
with one or more acrylic, vinyl or allyl monomers are neutralised
so that the molar percentage of the active acid sites of the
non-neutralised polymer is between 10% and 60% and that of the
active acid sites neutralised by at least one at least bifunctional
neutralisation agent is between 10% and 80%, the remainder to 100%
of the active acid sites of the polymer being neutralised by
monofunctional neutralisation agents.
2. (canceled)
3. The agent according to claim 1, characterised in that the at
least bifinctional neutralisation agents are selected from the
group consisting of hydroxides of alkaline-earth cations,
hydroxides of metallic cations, oxides of alkaline-earth cations,
oxides of metallic cations, bifunctional amines, and mixtures
thereof.
4. The agent according to claim 1, characterised in that the
monofunctional neutralisation agents are selected from the group
consisting of hydroxides of alkaline cations and ammonium
hydroxide, aliphatic primary amines, cyclic primary amines,
aliphatic secondary amines, and cyclic secondary amines.
5. The agent according to claim 1, characterised in that the said
homopolymers and/or copolymers of acrylic and/or methacrylic acid
with one or more acrylic, vinyl or allyl monomers have a mean
molecular weight in terms of Mw weight of between 1000 and 50,000,
as determined by aqueous gel permeation chromatography (GPC).
6. The agent according to claim 1, characterised in that the said
agent is a homopolymer of acrylic or methacrylic acid.
7. The agent according to claim 1, characterised in that the said
agent is a water-soluble copolymer of acrylic or methacrylic acid
with one or more acrylic, vinyl or allyl monomers selected from the
group consisting of acrylic acid, methacrylic acid, itaconic acid,
crotonic acid, fumaric acid, maleic anhydride,
2-acrylamido-2-methyl-1-propanesulphonic acid in acidic or
partially neutralised form, 2-methacrylamido-2-methyl-1-propane-
sulphonic acid in acidic or partially neutralised form,
3-methacrylamido-2-hydroxy-1-propanesulphonic acid in acidic or
partially neutralised form, allylsulphonic acid, methallylsulphonic
acid, allyloxybenzene sulphonic acid, methallyloxybenzene sulphonic
acid, 2-hydroxy-3-(2-propenyloxy)propanesulphonic acid,
2-methyl-2-propene-1-su- lphonic acid, ethylene sulphonic acid,
propene sulphonic acid, 2-methyl sulphonic acid, styrene sulphonic
acid and/or its salts, vinyl sulphonic acid, sodium
methallylsulphonate, sulphopropyl acrylate or methacrylate,
sulphomethylacrylamide, sulphomethylmethacrylamide, acrylamide,
methacrylamide, esters of acrylic and methacrylic acids,
vinylpyrrolidone, vinylcaprolactam, isobutylene, diisobutylene,
vinyl acetate, styrene, alphamethylstyrene, vinylmethylether, the
allyls, and derivatives thereof.
8. The agent according to claim 1, characterised in that the said
agent may, optionally before or after the neutralisation reaction,
be treated and separated into several phases by means of one or
more polar solvents selected from the group consisting of water,
methanol, ethanol, propanol, isopropanol, the butanols, acetone,
tetrahydrofuran and mixtures thereof.
9. The agent according to claim 1, characterised in that the said
agent is in powder form.
10. The agent according to claim 1, characterised in that the said
agent is introduced at the rate of 0.05% to 5% by dry weight with
respect to the dry weight of mineral material.
11. An aqueous suspension of mineral particles obtained by
grinding, characterised in that it contains the grinding-aid agent
of claim 1 and in that its aqueous phase contains less than 10% of
the quantity of grinding-aid agent initially introduced into the
suspension before the grinding operation, determined by the total
organic carbon measurement method known as the TOC method.
12. An aqueous suspension of mineral particles according to claim
11, characterised in that it contains 0.05% to 5% by dry weight,
with respect to the dry weight of mineral material, of the
grinding-aid agent, and in that its aqueous phase contains less
than 10% of the quantity of grinding-aid agent initially introduced
into the suspension before the grinding operation, determined by
the total organic carbon measurement method known as the TOC
method.
13. An aqueous suspension of mineral particles obtained by
dispersion, characterised in that it contains the dispersion agent
of claim 1 and in that its aqueous phase contains less than 60% of
the quantity of dispersion agent introduced into the suspension,
determined by the total organic carbon measurement method known as
the TOC method.
14. An aqueous suspension of mineral particles according to claim
13, characterised in that it contains 0.05% to 5% by dry weight,
with respect to the dry weight of mineral material, of the
dispersion agent, and in that its aqueous phase contains less than
60% of the quantity of dispersion agent introduced into the
suspension, determined by the total organic carbon measurement
method known as the TOC method.
15. An aqueous suspension of mineral particles according to claim
11, characterised in that the mineral particles are selected from
the group consisting of natural calcium carbonate synthetic calcium
carbonate, dolomites, magnesium hydroxide, gypsum, aluminium
hydroxide, and mixtures thereof.
16. A method of using an aqueous suspension, the method comprising
manufacturing a sheet of paper using the aqueous suspension of
claim 11.
17. Paper manufactured and/or coated by the use of the aqueous
suspension of claim 11.
18. Paper coated according to claim 17, characterised in that it
has increased printability.
19. (canceled)
20. An aqueous suspension of mineral particles according to claim
13, characterised in that the mineral particles are selected from
the group consisting of natural calcium carbonate, synthetic
calcium carbonate, dolomites, magnesium hydroxide, gypsum,
aluminium hydroxide, and mixtures thereof.
21. A method of using an aqueous suspension, the method comprising
manufacturing a sheet of paper using the aqueous suspension of
claim 13.
22. Paper manufactured and/or coated by the use of the aqueous
suspension of claim 13.
23. Paper coated according to claim 22, characterized in that it
has increased printability.
24. The agent according to claim 1, characterized in that the said
homopolymers and/or copolymers of acrylic and/or methacrylic acid
with one or more acrylic, vinyl or allyl monomers are neutralised
so that the molar percentage of the active acid sites of the
non-neutralised polymer is between 10% and 50%.
Description
[0001] The present invention relates to the technical sector of
mineral fillers, notably for papermaking applications, and
appropriate treatments thereof in order to improve either the
method of manufacturing the sheet of paper or its properties, as
well as other applications such as notably paint or plastics
materials.
[0002] The invention relates to the use of homopolymers and/or
copolymers of acrylic and/or methacrylic acid with one or more
acrylic, vinyl, or allyl monomers as a grinding-aid agent and/or
dispersion agent for pigments and/or mineral fillers in aqueous
suspension.
[0003] The invention also relates to the said aqueous suspensions
of pigments and/or mineral fillers and uses thereof notably in the
fields of paper, such as amongst other things the manufacturing or
coating of paper, with the obtaining of improved properties of
printability of the paper, as well as in the fields of paint or
plastics materials.
[0004] Finally, the invention relates to the papers manufactured
and/or coated by the use of the said aqueous suspensions of
pigments and/or mineral fillers as well as the paints and/or
plastics materials using the said suspensions.
[0005] For a long time already skilled man in the art has known
about the use of grinding and/or dispersion agents of mineral
particles in aqueous suspension consisting of acrylic polymers
and/or copolymers, of low molecular weight, completely or partially
neutralised by various neutralisation agents (FR 2 603 042, EP 0
100 947, EP 0 127 388, EP 0 129 329, EP 0 278 880, EP 0 542 644, EP
0 850 282).
[0006] Skilled man in the art also knows of the use of grinding
and/or dispersion agents consisting of the fraction of the acrylic
polymers and/or copolymers whose specific viscosity is between 0.3
and 0.8 (patents FR 2 488 814, EP 0 100 948, EP 0 542 643).
[0007] However, these various types of grinding and/or dispersion
agents of low molecular weight, which make it possible to obtain
aqueous suspensions of mineral particles which are refined, fluid
and stable over time, do not result in aqueous suspensions of
pigments and/or mineral fillers, notably calcium carbonate, having
a small quantity of grinding-aid agent which is not adsorbed on the
surfaces of the mineral material and is present in the aqueous
phase of the suspension.
[0008] This quantity of grinding agent not adsorbed on the surfaces
of the mineral particles and present in the aqueous phase of the
suspension is, in the remainder of the present application,
referred to as the free quantity of grinding agent.
[0009] Likewise, when free quantity of dispersant is spoken of in
the remainder of the present application, it will be a case of a
quantity of dispersant which is not adsorbed on the surfaces of the
mineral particles and is present in the aqueous phase of the
suspension.
[0010] This is because the aqueous phase of these aqueous
suspensions of the prior art has high quantities of free dispersant
and/or grinding-aid agent then having the drawback of impairing the
properties of printability of the coated paper obtained by the use
of the said aqueous suspensions of mineral particles as well as the
drawback of requiring the use of high quantities of cationic agent
used as a retention agent for the mineral filler on the cellulose
fibre of the paper when the suspensions are used for the
manufacture of sheets of paper.
[0011] Confronted with this problem of improving the properties of
printability of the coated paper or reduction in the quantity of
filler retention agent during the manufacture of the sheet of
paper, related to the reduction in the quantity of free dispersant
and/or grinding-aid agent in the aqueous phase of the aqueous
suspensions of mineral particles used in the manufacture or coating
of the paper, the Applicant then found, surprisingly, that the
simultaneous selection of the molar rate of the active acid sites
which have remained acidic and of the molar rate of the
neutralisation of these active acid sites, by ions which are at
least bifunctional, water-soluble homopolymers and/or copolymers of
acrylic and/or methacrylic acid with one or more acrylic, vinyl or
allyl monomers makes it possible to obtain aqueous suspensions of
pigments and/or mineral fillers, notably calcium carbonate, having
a small quantity of free dispersant and/or grinding-aid agent
present in the aqueous phase of the suspension giving papermaking
formulations such as notably papermaking coating colors or the mass
filling of the paper with the properties described below.
[0012] This is because the use, according to the invention, of the
said aqueous suspensions in the manufacture of the paper as a mass
filling makes it possible to reduce the quantity of cationic agent
used as a retention agent for the mineral filler on the cellulose
fibre of the paper.
[0013] In parallel to these properties of the paper, the use
according to the invention of the said aqueous suspensions during
the coating of the paper makes it possible to obtain a coated paper
with improved properties of printability.
[0014] Thus one of the aims of the invention is the use of
water-soluble homopolymers and/or copolymers of acrylic and/or
methacrylic acid with one or more acrylic, vinyl or allyl monomers
specifically neutralised, as a grinding-aid and/or dispersion agent
for pigments and/or mineral fillers in aqueous suspension making it
possible to obtain aqueous suspensions of pigments and/or mineral
fillers, notably calcium carbonate, having a small quantity of free
dispersant and/or grinding-aid agent present in the aqueous phase
of the suspension giving papermaking formulations such as notably
papermaking coating slips or the mass filling for the paper, having
the aforementioned properties.
[0015] Another aim of the invention, apart from those already
mentioned, is to provide aqueous suspensions of mineral materials
obtained by dispersion and characterised in that they have a small
quantity of free dispersant present in the aqueous phase and in
that they contain 0.05% to 5% by dry weight, and preferentially
0.2% to 1.0% by dry weight with respect to the dry weight of
mineral material, of dispersion agent for mineral particles in
aqueous suspension used according to the invention.
[0016] Likewise, another aim of the invention, apart from those
already mentioned, is to provide aqueous suspensions of refined
mineral materials obtained by grinding and characterised in that
they have a small quantity of free grinding-aid agent present in
the aqueous phase and in that they contain 0.05% to 5% by dry
weight, and preferably 0.2% to 1.0% by dry weight, with respect to
the dry weight of mineral material, of grinding-aid agent in
aqueous suspension used according to the invention.
[0017] Finally, an additional aim of the invention concerns the use
of these mineral aqueous suspensions in the field of plastics,
paint, paper coating and mass filling during the manufacture of the
paper sheet.
[0018] Contrary to the teachings of the prior art, the Applicant
found surprisingly that the selection of the molar percentage of
the non-neutralised active acidic sites of the polymer must be
between 10% and 60% and the molar percentage of the neutralisation
by at least one neutralisation agent which is at least bifunctional
must be between 10% and 80% in order to obtain the aforementioned
properties. The remainder to 100% of the active acidic sites of the
polymer is neutralised by monofunctional neutralisation agents.
[0019] The at least bifunctional neutralisation agents are chosen
from amongst the hydroxides and/or oxides of alkaline-earth or
metallic cations, in particular the hydroxides and/or oxides of
magnesium, calcium, barium, zinc or aluminium, or from amongst the
bifunctional amines or mixtures thereof, and are preferably chosen
from amongst the calcium or magnesium hydroxides and/or oxides, and
mixtures thereof.
[0020] The monofunctional neutralisation agents are chosen from
amongst the hydroxides of alkaline cations, in particular sodium
and potassium, or lithium or ammonia, or from amongst the aliphatic
and/or cyclic primary or secondary amines such as for example the
ethanolamines, mono- and diethylamine or cyclohexylamine, or
mixtures thereof, and are very particularly chosen from amongst the
compounds containing the sodium ion.
[0021] These homopolymers and/or copolymers result from the various
known methods of radical polymerisation using the polymerisation
initiators well known to skilled man in the art such as for example
compounds based on hydroxylamine or using the polymerisation
initiators such as peroxides such as notably hydrogen peroxide,
tert-butyl hydroperoxide or persalts such as notably sodium
persulphate, ammonium persulphate, potassium persulphate or the
like, or sodium hypophosphite, hypophosphorous acid or phosphorous
acid and/or the salts thereof in the possible presence of metallic
salts, for example iron or copper, in a polymerisation medium which
may be water, methanol, ethanol, propanol, isopropanol, butanols or
mixtures thereof or dimethyl formamide, dimethylsulphoxide,
tetrahydrofuran, acetone, methylethylketone, ethyl acetate, butyl
acetate, hexane, heptane, benzene, toluene or xylene, and in the
presence possibly of molecular weight regulators, also referred to
as transfer agents, such as notably mercaptoethanol, thioglycolic
acid and esters thereof, n-dodecylmercaptan, acetic, tartric,
lactic, citric, gluconic or glucoheptonic acids,
2-mercaptopropionic acid, thiodiethanol, halogenated solvents such
as carbon tetrachloride, chloroform, methylene chloride, the
monopropylene glycol ethers, or mixtures thereof and the like.
[0022] These homopolymers used as a grinding-aid and/or dispersion
agent according to the invention result from the various methods of
radical polymerisation of acrylic or methacrylic acid.
[0023] These copolymers used as a grinding-aid and/or dispersion
agent according to the invention result from the various
aforementioned methods of radical copolymerisation of acrylic or
methacrylic acid with at least one of the monomers chosen from
amongst acrylic acid, methacrylic acid, itaconic acid, crotonic
acid, fumaric acid, maleic anhydride and/or
2-acrylamido-2-methyl-1-propanesulphonic acid in acidic or
partially neutralised form,
2-methacrylamido-2-methyl-1-propanesulphonic acid in acidic or
partially neutralised form, 3-methacrylamido-2-hydroxy-1-propan-
esulphonic acid in acidic or partially neutralised form,
allylsulphonic acid, methallylsulphonic acid, allyloxybenzene
sulphonic acid, methallyloxybenzene sulphonic acid,
2-hydroxy-3-(2-propenyloxy)propanesul- phonic acid,
2-methyl-2-propene-1-sulphonic acid, ethylene sulphonic acid,
propene sulphonic acid, 2-methyl sulphonic acid, styrene sulphonic
acid and/or its salts, vinyl sulphonic acid, sodium
methallylsulphonate, sulphopropyl acrylate or methacrylate,
sulphomethylacrylamide or sulphomethylmethacrylamide or from
amongst acrylamide, methacrylamide, esters of acrylic or
methacrylic acids such as notably ethyl acrylate, butyl acrylate,
methyl methacrylate, ethylene or propylene glycol acrylate or
methacrylate phosphate or from amongst vinylpyrrolidone,
vinylcaprolactam, isobutylene, diisobutylene, vinyl acetate,
styrene, alphamethylstyrene, vinylmethylether, the allyls such as
notably allyl amine and derivatives thereof.
[0024] These homopolymers and/or copolymers used as a grinding-aid
and/or dispersion agent according to the invention resulting from
the various aforementioned radical polymerisation methods can also
be treated by any known means in order to isolate it in the form of
a powder and to use it in this form.
[0025] According to another variant, the homopolymer or copolymer
resulting from the polymerisation reaction may, optionally before
or after the neutralisation reaction, be treated and separated into
several phases, according to static or dynamic methods known to
skilled man in the art, by one or more polar solvents belonging
notably to the group consisting of water, methanol, ethanol,
propanol, isopropanol, butanols, acetone, tetrahydrofuran or
mixtures thereof.
[0026] One of the phases then corresponds to the polymer used
according to the invention as a grinding-aid and/or dispersion
agent for mineral materials in aqueous suspension.
[0027] These homopolymers and/or copolymers used as a dispersion
and/or grinding-aid agent according to the invention are
selectively neutralised so that the molar percentage of active acid
sites of the non-neutralised polymer is between 10% and 60% and
that of the active acid sites neutralised by at least one at least
bifunctional neutralisation agent is between 10% and 80%, the
remainder to 100% of the active acid sites of the polymer being
neutralised by monofunctional neutralisation agents.
[0028] Preferentially, these homopolymers and/or copolymers used as
dispersion and/or grinding-aid agents according to the invention
are selectively neutralised so that the molar percentage of the
active acid sites of the non-neutralised polymer is between 15% and
30% and that of the active acid sites neutralised by at least one
at least bifunctional neutralisation agent is between 15% and 60%,
the remainder to 100% of the active acid sites of the polymer being
neutralised by monofunctional neutralisation agents.
[0029] Thus, according to the invention, the use of homopolymers
and/or copolymers of acrylic and/or methacrylic acid with one or
more acrylic, vinyl or allyl monomers as a dispersion and/or
grinding-aid agent for pigments and/or mineral fillers in aqueous
suspension is characterised in that the said homopolymers and/or
copolymers of acrylic and/or methacrylic acid with one or more
acrylic, vinyl or allyl monomers are neutralised so that the molar
percentage of the active acid sites of the non-neutralised polymer
is between 10% and 60% and that of the active acid sites
neutralised by at least one at least bifunctional neutralisation
agent is between 10% and 80%, the remainder to 100% of the active
acid sites of the polymer being neutralised by monofunctional
neutralisation agents.
[0030] Preferentially, the use according to the invention of
homopolymers and/or copolymers of acrylic and/or methacrylic acid
with one or more acrylic, vinyl or allyl monomers as a grinding-aid
and/or dispersion agent for pigments and/or mineral fillers in
aqueous suspension is characterised in that the said homopolymers
and/or copolymers of acrylic and/or methacrylic acid with one or
more acrylic, vinyl or allyl monomers are neutralised so that the
molar percentage of the active acid sites of the non-neutralised
polymer is between 15% and 30% and that of the active acid sites
neutralised by at least one at least bifunctional neutralisation
agent is between 15% and 60%, the remainder to 100% of the active
acid sites of the polymer being neutralised by monofunctional
neutralisation agents.
[0031] The homopolymers and/or copolymers intended to be used
according to the invention as a grinding-aid and/or dispersion
agent in water for mineral particles are selected from amongst the
homopolymers or copolymers having a mean molecular weight in terms
of M.sub.w weight of between 1000 and 50,000, preferentially
between 3500 and 25,000, determined by aqueous gel permeation
chromatography (GPC), the standards for which, used as references,
belong to a series of sodium polyacrylates sold by the company
Polymer Standards Service under the names PSS-PAA varying from 18K
to 2K.
[0032] Moreover, the use according to the invention of a selection
of water-soluble homopolymers and/or copolymers of acrylic and/or
methacrylic acid with one or more acrylic, vinyl or allyl monomers
allows the grinding of mineral substances, notably calcium
carbonate, resulting in the obtaining of aqueous suspensions of
mineral materials which are refined, fluid and stable over time,
having a small quantity of free dispersant present in the aqueous
phase of the solution making it possible to achieve papermaking
formulations such as notably papermaking coating slips or the mass
filling for the paper, having the aforementioned properties.
[0033] Thus, according to the invention, the aqueous suspensions of
pigments and/or mineral fillers obtained by grinding are
characterised in that they contain the said grinding-aid agent and
in that their aqueous phase contains less than 10% of the quantity
of grinding-aid agent initially introduced into the suspension
before the grinding operation.
[0034] Likewise according to the invention the aqueous suspensions
of pigments and/or mineral fillers obtained by dispersion are
characterised in that they contain the said dispersion agent and in
that their aqueous phase contains less than 60%, preferentially
less than 55% of the quantity of dispersion agent initially
introduced into the suspension.
[0035] These quantities of grinding-aid and/or dispersion agent
contained in the aqueous phase of the suspensions of pigments
and/or mineral fillers according to the invention, also referred to
as quantities of free dispersant and/or grinding-aid agent, are
measured by the measuring method described below, referred to in
the present application as the TOC method.
[0036] The principle of this measurement is as follows:
[0037] The quantity of polymer (grinding-aid agent and/or
dispersion agent used according to the invention) present in the
solution before the grinding or suspension is determined, using a
TOC meter. The value TOC 1 is obtained.
[0038] The quantity of polymer (the grinding-aid and/or dispersion
agent used according to the invention) present in the solution
after the grinding or dispersion is measured after filtration of
the suspension using the same TOC meter and gives the value TOC
2.
[0039] The quantities of grinding-aid and/or dispersion agent
contained in the aqueous phase of the suspensions of pigments
and/or mineral fillers according to the invention, also referred to
as quantities of free dispersant and/or grinding-aid agent, are
then expressed by the equation: 1 % of free dispersant and / or
grinding - aid agent = TOC 2 TOC 1 .times. 100
[0040] In practical terms, the suspension of mineral particles to
be studied is first of all filtered on an "API Fluid Loss
Measurement" filter press from Barod equipped with a 90 mm diameter
filter paper (Whatman N.sup.o 50) and a metallic sieve.
[0041] The filtration is carried out at a pressure of 100 psi (7
bar). The filtrate obtained is then filtered once again on a
Millipore.TM. filter with a 0.2 micrometre porosity.
[0042] The waters then obtained are analysed using a TOC meter of
the Lab TOC.TM. make sold by Spectrafrance making it possible to
determine the total organic carbon (TOC) present in the solution by
measuring the release of carbon dioxide obtained after a complete
oxidation of the organic material catalysed by means of ultraviolet
radiation in the presence of sodium persulphate and phosphoric acid
at respective contents of 2.5% and 6.8% and under oxygen
bubbling.
[0043] The aqueous suspensions of pigment and/or mineral filler are
also characterised in that the filler and/or pigment is chosen from
amongst natural calcium carbonate such as notably calcite, chalk or
marble, synthetic calcium carbonate, also known as precipitated
calcium carbonate, dolomites, magnesium hydroxide, gypsum or
aluminium hydroxide or mixtures thereof or any other filler and/or
pigment normally used in the field of papermaking, paint and/or
plastics materials.
[0044] The aqueous suspensions of fillers and/or pigments obtained
by grinding according to the invention are more particularly
characterised in that they contain 0.05% to 5% by dry weight of the
said agent with respect to the total dry weight of the fillers
and/or pigments, and also more particularly 0.2% to 1.0% by dry
weight of the said agent with respect to the total dry weight of
the fillers and/or pigments and in that their aqueous phase
contains less than 10%, determined according to the aforementioned
method, of the quantity of grinding aid agent initially introduced
into the suspension before the grinding operation.
[0045] In practice, the operation of grinding the mineral substance
to be refined consists of grinding the mineral substance with a
grinding body consisting of very fine particles in an aqueous
medium containing initially all or part of the quantity of the
grinding-aid agent with grinding conditions adjusted so that the
final pH of the ground suspension is between 8 and 10,
preferentially between 8.5 and 9.5.
[0046] An aqueous suspension of the mineral substance to be ground
is formed.
[0047] While initially using part of the quantity of the
grinding-aid agent, the remainder is added in parallel during the
mechanical grinding operation.
[0048] To the suspension of the mineral substance to be ground,
there is added the grinding body with a granulometry advantageously
between 0.20 and 4 millimetres. The grinding body is generally in
the form of particles of materials as diverse as silicon oxide,
aluminium oxide, zirconium oxide or mixtures thereof, as well as
high-hardness synthetic resins, steels, or others. An example of
the composition of such grinding bodies is given by the patent FR 2
303 681, which describes grinding elements formed by 30 to 70% by
weight zirconium oxide, 0.1 to 5% aluminium oxide, and 5 to 20%
silicon oxide. The grinding body is preferably added to the
suspension in a quantity such that the ratio by weight between this
grinding material and the mineral substance to be ground is at
least 2/1, this ratio preferably being between the limits 3/1 and
5/1.
[0049] The mixture of the suspension and grinding body is then
subjected to the mechanical stirring action such as that which
occurs in a conventional grinder with microelements.
[0050] The grinding-aid agent according to the invention is also
introduced, on one or more occasions, into the mixture formed by
the aqueous suspension of mineral substances and the grinding body
at the rate of 0.05% to 5% by weight, and preferentially 0.2% to
1.0% by weight, of the dried fraction of the said polymers with
respect to the dry weight of the mineral substance to be
refined.
[0051] The time necessary for achieving excellent fineness of the
mineral substance after grinding varies according to the nature and
quantity of the mineral substances to be ground, and according to
the stirring mode used and the temperature of the medium during the
grinding operation.
[0052] The aqueous suspensions of fillers and/or pigments obtained
by dispersion according to the invention are characterised more
particularly in that they contain 0.05% to 5% by dry weight of the
said agent with respect to the total dry weight of the fillers
and/or pigments, and also more particularly 0.2% to 1.0% by dry
weight of the said agent with respect to the total dry weight of
the fillers and/or pigments and in that their aqueous phase
contains less than 60%, preferably less than 55%, determined
according to the aforementioned method, of the quantity of
dispersion agent initially introduced into the suspension.
[0053] In practice, the dispersion operation consists of
introducing the mineral filler into an aqueous solution containing
all or some of the dispersing agent, the remainder of which is
possibly added in parallel to the addition of the mineral
filler.
[0054] The aqueous suspensions thus obtained can be used in the
field of papermaking for mass filling or coating.
[0055] The papers manufactured and/or coated are characterised in
that they contain the said aqueous suspensions of fillers and/or
pigments according to the invention.
[0056] The papers manufactured by the use of the mass filling
composition according to the invention are characterised in that
they contain less retention agent for mineral filler on the
cellulose fibres than the papers of the prior art.
[0057] The papers coated by the use of the coating color according
to the invention are characterised in that they have increased
printability, that is to say printability greater than the
printability of the coated papers of the prior art.
[0058] The scope and advantage of the invention will be perceived
more clearly by means of the following examples, which are not
limitative.
EXAMPLE 1
[0059] This example relates to the selection of the proportion of
active acid sites which have remained non-neutralised and the
proportion of one or more at least bifunctional agents
characteristic of the homopolymer and/or copolymer intended
according to the invention to be used as a grinding-aid agent for
obtaining an aqueous suspension of refined natural calcium
carbonate with a low quantity of free grinding-aid agent present in
the aqueous phase.
[0060] For each test, the different grinding-aid agents are tested
by the introduction, in the quantities indicated in the table
below, expressed as a percentage by dry weight with respect to the
weight of dry calcium carbonate to be ground, of the grinding-aid
agent in a suspension of calcium carbonate to be ground.
[0061] For all the tests of the example, the calcium carbonate to
be ground is a calcite with a granulometry such that 19.0% of
particles have a diameter of less than 2 micrometers.
[0062] The suspension circulates in a grinder of the Dyno-Mill.TM.
type with fixed cylinder and rotating impeller, the grinding body
of which consists of corundum balls with a diameter lying in the
range 0.6 millimetres to 1.0 millimetre.
[0063] The total volume occupied by the grinding body is 1150 cubic
centimetres whilst its weight is 2900 g.
[0064] The grinding chamber has a volume of 1400 cubic
centimetres.
[0065] The circumferential speed of the grinder is 10 metres per
second.
[0066] The calcium carbonate suspension is recycled at the rate of
18 litres per hour.
[0067] The discharge from the Dyno-Mill.TM. grinder is provided
with a separator with a 200 micron mesh for separating the
suspension resulting from the grinding and the grinding body.
[0068] The temperature during each grinding test is maintained at
approximately 60.degree. C.
[0069] At the end of the grinding (To), a sample of the pigmentary
suspension is recovered in a flask. The granulometry of this
suspension is measured by means of a Sedigraph.TM. 5100
granulometer from Micromeritics.
[0070] Test N.sup.o 1:
[0071] This test, which illustrates the prior art, uses a
suspension, obtained by grinding calcite with 76.0% by dry matter
and 1.00% by dry weight, with respect to the dry weight of calcite,
of a completely neutralised sodium polyacrylate with a mean
molecular weight, in terms of M.sub.w weight, of 7000, determined
by aqueous GPC, the standards for which, used as references, belong
to a series of sodium polyacrylates sold by the company Polymer
Standards Service under the names PSS-PAA varying from 18K to
2K.
[0072] The aqueous suspension of calcite obtained has a
granulometry such that 95.0% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 48.0%.
[0073] Test N.sup.o 2:
[0074] This test, which illustrates the prior art, uses a
suspension, obtained by grinding calcite with 75.0% by dry matter
and 0.35% by dry weight, with respect to the dry weight of calcite,
of a mixed calcium and sodium polyacrylate (30% calcium-70% sodium
molar) with a mean molecular weight, in terms of M.sub.w weight, of
5500, determined by aqueous GPC, the standards for which, used as
references, belong to a series of sodium polyacrylates sold by the
company Polymer Standards Service under the names PSS-PAA varying
from 18K to 2K.
[0075] The aqueous suspension of calcite obtained has a
granulometry such that 60.2% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 15.0%.
[0076] Test N.sup.o 3:
[0077] This test, which illustrates the prior art, uses a
suspension, obtained by grinding marble with 74.9% by dry matter
and 0.63% by dry weight, with respect to the dry weight of marble,
of a mixed sodium and calcium polyacrylate (70% sodium-30% calcium
molar) with a mean molecular weight, in terms of M.sub.w weight, of
4500, determined by aqueous GPC, the standards for which, used as
references, belong to a series of sodium polyacrylates sold by the
company Polymer Standards Service under the names PSS-PAA varying
from 18K to 2K.
[0078] The aqueous suspension of marble obtained has a granulometry
such that 89.1% of particles have a diameter of less than 2
micrometres and a proportion of free grinding-aid agent present in
the aqueous phase of the suspension, measured according to the
method described above, equal to 21.6%.
[0079] Test N.sup.o 4:
[0080] This test, which illustrates a field outside the invention,
uses a suspension, obtained by grinding calcite at 76.0% by dry
matter and 1.00% by dry weight, with respect to the dry weight of
calcite, of a sodium polyacrylate (5% free carboxylic-95% sodium
molar) with a mean molecular weight in terms of M.sub.w weight of
5500, determined by aqueous GPC, the standards for which, used as
references, belong to a series of sodium polyacrylates sold by the
company Polymer Standards Service under the names PSS-PAA varying
from 18K to 2K.
[0081] The aqueous suspension of calcite obtained has a
granulometry such that 95.0% of particles have a diameter of less
than 1 micrometre and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 40.0%.
[0082] Test N.sup.o 5:
[0083] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 75.0% by dry matter and
0.60% by dry weight, with respect to the dry weight of calcite, of
a mixed sodium-calcium polyacrylate (10% free carboxylic-70%
sodium-20% calcium molar) with a mean molecular weight in terms of
M.sub.w weight of 5500, determined by aqueous GPC, the standards
for which, used as references, belong to a series of sodium
polyacrylates sold by the company Polymer Standards Service under
the names PSS-PAA varying from 18K to 2K.
[0084] The aqueous suspension of calcite obtained has a
granulometry such that 90.2% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 8.4%.
[0085] Test N.sup.o 6:
[0086] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 75.0% by dry matter and
0.30% by dry weight, with respect to the dry weight of calcite, of
a mixed sodium-calcium polyacrylate (20% free carboxylic-70%
sodium-10% calcium molar) with a mean molecular weight in terms of
M.sub.w weight of 5500, determined by aqueous GPC, the standards
for which, used as references, belong to a series of sodium
polyacrylates sold by the company Polymer Standards Service under
the names PSS-PAA varying from 18K to 2K.
[0087] The aqueous suspension of calcite obtained has a
granulometry such that 59.7% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 9.5%.
[0088] Test N.sup.o 7:
[0089] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 75.3% by dry matter and
0.38% by dry weight, with respect to the dry weight of calcite, of
a mixed sodium-calcium polyacrylate (25% free carboxylic-40%
sodium-35% calcium molar) with a mean molecular weight in terms of
M.sub.w weight of 5500, determined by aqueous GPC, the standards
for which, used as references, belong to a series of sodium
polyacrylates sold by the company Polymer Standards Service under
the names PSS-PAA varying from 18K to 2K.
[0090] The aqueous suspension of calcite obtained has a
granulometry such that 88.1% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 9.6%.
[0091] Test N.sup.o 8:
[0092] This test, which illustrates the prior art, uses a
suspension, obtained by grinding calcite at 72.0% by dry matter and
0.65% by dry weight, with respect to the dry weight of calcite, of
a mixed polyacrylate of magnesium and sodium (50% magnesium-50%
sodium molar) with a mean molecular weight in terms of M.sub.w
weight of 5500, determined by aqueous GPC, the standards for which,
used as references, belong to a series of sodium polyacrylates sold
by the company Polymer Standards Service under the names PSS-PAA
varying from 18K to 2K.
[0093] The aqueous suspension of calcite obtained has a
granulometry such that 90.4% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 13.0%.
[0094] Test N.sup.o 9:
[0095] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 72.0% by dry matter and
0.65% by dry weight, with respect to the dry weight of calcite, of
a mixed polyacrylate of sodium and magnesium (25% free
carboxylic-25% sodium-50% magnesium molar) with a mean molecular
weight in terms of M.sub.w weight of 5500, determined by aqueous
GPC, the standards for which, used as references, belong to a
series of sodium polyacrylates sold by the company Polymer
Standards Service under the names PSS-PAA varying from 18K to
2K.
[0096] The aqueous suspension of calcite obtained has a
granulometry such that 89.7% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension measured, according
to the method described above, equal to 5.4%.
[0097] Test N.sup.o 10:
[0098] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 72.0% by dry matter and
0.65% by dry weight, with respect to the dry weight of calcite, of
a mixed polyacrylate of sodium and magnesium (25% free
carboxylic-45% sodium-30% magnesium molar) with a mean molecular
weight in terms of M.sub.w weight of 5500, determined by aqueous
GPC, the standards for which, used as references, belong to a
series of sodium polyacrylates sold by the company Polymer
Standards Service under the names PSS-PAA varying from 18K to
2K.
[0099] The aqueous suspension of calcite obtained has a
granulometry such that 90.3% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 8.2%.
[0100] Test N.sup.o 11:
[0101] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 75.0% by dry matter and
0.60% by dry weight, with respect to the dry weight of calcite, of
a mixed polyacrylate of sodium and magnesium (10% free
carboxylic-30% sodium-60% magnesium molar) with a mean molecular
weight in terms of M.sub.w weight of 3500, determined by aqueous
GPC, the standards for which, used as references, belong to a
series of sodium polyacrylates sold by the company Polymer
Standards Service under the names PSS-PAA varying from 18K to
2K.
[0102] The aqueous suspension of calcite obtained has a
granulometry such that 90.5% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 9.9%.
[0103] Test N.sup.o 12:
[0104] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 75.0% by dry matter and
0.60% by dry weight, with respect to the dry weight of calcite, of
a copolymer acrylic acid-ethylene glycol phosphate
methacrylate-methyl methacrylate (respectively 54.6%-34.6%-10.8%
weight) and neutralised with sodium and magnesium (20% free
carboxylic-40% sodium-40% magnesium molar) with a mean molecular
weight in terms of M.sub.w weight of 15 000, determined by aqueous
GPC, the standards for which, used as references, belong to a
series of sodium polyacrylates sold by the company Polymer
Standards Service under the names PSS-PAA varying from 18K to
2K.
[0105] The aqueous suspension of calcite obtained has a
granulometry such that 80.4% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 9.3%.
[0106] Test N.sup.o 13:
[0107] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 75.0% by dry matter and
0.60% by dry weight, with respect to the dry weight of calcite, of
a mixed polyacrylate of sodium and zinc (20% free carboxylic-70%
sodium-10% zinc molar) with a mean molecular weight in terms of
M.sub.w weight of 12 000, determined by aqueous GPC, the standards
for which, used as references, belong to a series of sodium
polyacrylates sold by the company Polymer Standards Service under
the names PSS-PAA varying from 18K to 2K.
[0108] The aqueous suspension of calcite obtained has a
granulometry such that 60.1% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 9.6%.
[0109] Test N.sup.o 14:
[0110] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 75.0% by dry matter and
0.60% by dry weight, with respect to the dry weight of calcite, of
a mixed polyacrylate of magnesium and sodium (50% free
carboxylic-10% magnesium-40% sodium molar) with a mean molecular
weight in terms of M.sub.w weight of 5 500, determined by aqueous
GPC, the standards for which, used as references, belong to a
series of sodium polyacrylates sold by the company Polymer
Standards Service under the names PSS-PAA varying from 18K to
2K.
[0111] The aqueous suspension of calcite obtained has a
granulometry such that 82% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 9.0%.
[0112] Test N.sup.o 15:
[0113] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 75.0% by dry matter and
0.60% by dry weight, with respect to the dry weight of calcite, of
a copolymer acrylic acid-maleic anhydride (respectively 70%-30%
weight) and neutralised with sodium and magnesium (35% free
carboxylic-50% sodium-15% magnesium molar) with a mean molecular
weight in terms of M.sub.w weight of 25 000, determined by aqueous
GPC, the standards for which, used as references, belong to a
series of sodium polyacrylates sold by the company Polymer
Standards Service under the names PSS-PAA varying from 18K to
2K.
[0114] The aqueous suspension of calcite obtained has a
granulometry such that 57.9% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 9.7%.
[0115] Test N.sup.o 16:
[0116] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 75.0% by dry matter and
0.60% by dry weight, with respect to the dry weight of calcite, of
a copolymer acrylic acid-acrylamido methyl propane sulfonic acid
(respectively 60%-40% weight) and neutralised with sodium and
calcium (25% free carboxylic-45% sodium-30% calcium molar) with a
mean molecular weight in terms of M.sub.w weight of 20 000,
determined by aqueous GPC, the standards for which, used as
references, belong to a series of sodium polyacrylates sold by the
company Polymer Standards Service under the names PSS-PAA varying
from 18K to 2K.
[0117] The aqueous suspension of calcite obtained has a
granulometry such that 81.3% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 8.7%.
[0118] Test N.sup.o 17:
[0119] This test, which illustrates the invention, uses a
suspension, obtained by grinding calcite at 75.0% by dry matter and
0.60% by dry weight, with respect to the dry weight of calcite, of
a copolymer acrylic acid-acrylamide (respectively 70%-30% weight)
and neutralised with sodium and magnesium (30% free carboxylic-55%
sodium-15% magnesium molar) with a mean molecular weight in terms
of M.sub.w weight of 5 500, determined by aqueous GPC, the
standards for which, used as references, belong to a series of
sodium polyacrylates sold by the company Polymer Standards Service
under the names PSS-PAA varying from 18K to 2K.
[0120] The aqueous suspension of calcite obtained has a
granulometry such that 87.9% of particles have a diameter of less
than 2 micrometres and a proportion of free grinding-aid agent
present in the aqueous phase of the suspension, measured according
to the method described above, equal to 9.5%.
[0121] The results of the different tests are set out in Tables 1a.
and 1b. below.
1 TABLE 1a % free Test Quantity molar % neutralisation Granulometry
Dry matter grinding-aid N.sup.o of agent (%) COOH Ca Mg Na (% <
2 .mu.m) concentration agent Prior art 1 1.00 0 0 0 100 95.0 76.0
48.0 Prior art 2 0.35 0 30 0 70 60.2 75.0 15.0 Prior art 3 0.63 0
30 0 70 89.1 74.9 21.6 Outside the 4 1.00 5 0 0 95 95.0 76.0 40.0
invention Invention 5 0.60 10 20 0 70 90.2 75.0 8.4 Invention 6
0.30 20 10 0 70 59.7 75.0 9.5 Invention 7 0.38 25 35 0 40 88.1 75.3
9.6 Prior art 8 0.65 0 0 50 50 90.4 72.0 13.0 Invention 9 0.65 25 0
50 25 89.7 72.0 5.4 Invention 10 0.65 25 0 30 45 90.3 72.0 8.2
[0122]
2 TABLE 1b Quantity molar % neutralisation Granulometry Dry matter
% free grinding- Test N.sup.o of agent (%) COOH Ca Mg Na (% < 2
.mu.m) concentration aid agent Invention 11 0.60 10 0 60 30 90.5
75.0 9.9 Invention 12 0.60 20 0 40 40 80.4 75.0 9.3 Invention 13
0.60 20 10 Zn 0 70 60.1 75.0 9.6 Invention 14 0.60 50 0 10 40 82.0
75.0 9.0 Invention 15 0.60 35 0 15 50 57.9 75.0 9.7 Invention 16
0.60 25 30 0 45 81.3 75.0 8.7 Invention 17 0.60 30 0 15 55 87.9
75.0 9.5
[0123] A reading of the different results in Tables 1a. and 1b.
shows that, in order to obtain a percentage of free grinding-aid
agent present in the aqueous phase of the suspension, after
grinding measured according to the method described above, of less
than 10%, the selection of the molar percentage of the
non-neutralised active acid sites of the polymer must be between
10% and 60% and the molar percentage of the neutralisation by at
least one at least bifunctional neutralisation agent must be
between 10% and 80% in order to obtain the aforementioned
properties, the remainder to 100% of the active acid sites of the
polymer being neutralised by monofunctional neutralisation
agents.
EXAMPLE 2
[0124] This example relates to the selection of the proportion of
active acid sites which have remained non-neutralised and of the
proportion of one or more at least bifunctional agents
characteristic of the homopolymer and/or copolymer intended
according to the invention to be used as a dispersion agent, also
referred to as a dispersing agent for obtaining an aqueous
suspension of mineral filler and more particularly synthetic
calcium carbonate with a small quantity of free dispersing agent
present in the aqueous phase.
[0125] To do this, the test is carried out by introducing, into
water, 0.73 percent by dry weight with respect to the dry weight of
the mineral filler to be dispersed, of the dispersing agent to be
tested.
[0126] After homogenisation, a sample of the water with dispersant
added is taken in order to measure the TOC1 and then the mineral
filler to be dispersed is introduced and kept stirred for 30
minutes.
[0127] Once the stirring has stopped, a sample of the aqueous
suspension is taken in order to measure its TOC2.
[0128] The determination of the percentage of free dispersant
contained in the aqueous phase of the aqueous suspension of mineral
fillers is carried out in the same way as before.
[0129] Test N.sup.o 18:
[0130] This test, which illustrates the prior art, uses a
suspension of precipitated calcium carbonate (PCC) sold by Solvay
under the name Socal.TM. P3 with a dry matter concentration of 70%
and 0.73% by dry weight, with respect to the dry weight of PCC, of
a completely neutralised sodium polyacrylate with a mean molecular
weight, in terms of M.sub.w weight, of 5500, determined by aqueous
GPC, the standards for which, used as references, belong to a
series of sodium polyacrylates sold by the company Polymer
Standards Service under the names PSS-PAA varying from 18K to
2K.
[0131] The aqueous suspension of PCC obtained has a percentage of
free dispersion agent present in the aqueous phase of the
suspension, measured according to the method described previously,
of 67%.
[0132] Test N.sup.o 19:
[0133] This test, which illustrates the invention, uses a
suspension of PCC sold by Solvay under the name Socal.TM. P3 with a
dry matter concentration of 70% and 0.7% by dry weight, with
respect to the dry weight of PCC, of a mixed sodium and calcium
polyacrylate (25% free carboxylic-40% sodium-35% calcium molar)
with a mean molecular weight, in terms of M.sub.w weight, of 5500,
determined by aqueous GPC, the standards for which, used as
references, belong to a series of sodium polyacrylates sold by the
company Polymer Standards Service under the names PSS-PAA varying
from 18K to 2K.
[0134] The aqueous suspension of PCC obtained has a percentage of
free dispersion agent present in the aqueous phase of the
suspension, measured according to the method described previously,
of 51%.
[0135] A reading of these different results shows that, in order to
obtain a percentage of free dispersant present in the aqueous phase
of the suspension obtained by dispersion, measured according to the
method described previously, of less than 60%, preferentially less
than 55%, the selection of the molar percentage of the
non-neutralised active acid sites of the polymer must be between
10% and 60% and the molar percentage of the neutralisation by at
least one at least bifunctional neutralisation agent must be
between 10% and 80% in order to obtain the aforementioned
properties, the remainder to 100% of the active acid sites of the
polymer being neutralised by monofunctional neutralisation
agents.
* * * * *