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
EMULSION OF AN ASSOCIATIVE ACRYLIC POLYMER POLYMERIZED IN THE PRESENCE OF POLYGLYCEROLS AND USE OF SAME AS A THICKENING AGENT
IN AN AQUEOUS COMPOSITION
2. APPLICANT(S)
a) Name : COATEX
b) Nationality : FRENCH Company
c) Address : 35, RUE AMPÈRE,
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 new emulsions containing acrylic associative thickening agents which, when polymerised in the presence of particular polyglycerols, have a thickening power which is remarkably stable over time. The viscosimetric variance caused by this type of thickening agent, which appears very rapidly after several days' storage, is notably reduced by this means, in particular in paints with low VOC (Volatile Organic Compound) rates, or paints without VOCs. The user is thus guaranteed identical application properties for their paint, i.e. an unvarying rheological profile for the paint they formulate, and which they apply, independently of the storage time of the said paint, over a period which can be as long as several months.
Controlling the rheology of a paint both in the stage of its manufacture, and during its transport, storage or use, remains a priority at the current time. The wide variety of constraints observed in each of these steps relates to a multiplicity of different rheological properties. Nevertheless, it is possible to summarise the requirement of the skilled man in the art in obtaining an effect of the thickening of the said paint, both for reasons of stability over time, and for a possible application to a vertical surface, lack of spattering during use, or of sagging after application, etc. As a consequence, the products which contribute to this regulation of the rheological properties have been designated by the term "thickening agents".
Historically, since the 1950s cellulose-based gums and products have been used, one of the essential characteristics of which is their high molecular weight.
However, these compounds have a number of disadvantages, such as their instability over time (see document US 4 673 518), the need to use a large quantity of them (see document EP 0 250 943 A1), and their production costs, notably in terms of waste treatment (see document US 4 384 096).
Thickening agents called "associative" thickening agents were then created: these are water-soluble polymers having insoluble hydrophobic groups. Such macromolecules have an associating character: when introduced into water, the hydrophobic groups tend to assemble in the form of micellar aggregates. These aggregates are linked together by the hydrophilic parts of the polymers: a three-dimensional network is then formed which causes the viscosity of the medium to be increased. The operating mechanism and their characteristics are now 3
well known and described, for example in the documents “Rheology modifiers for water-borne paints” (Surface Coatings Australia, 1985, pp. 6-10) and "Rheological modifiers for water-based paints: the most flexible tools for your formulations” (Eurocoat 97, UATCM, vol. 1, pp 423-442).
Among these associative thickening agents, a technological platform is known which contains particular emulsions known as "HASE" (Hydrophobically modified Alkali-Soluble Emulsions). These contain polymers of (meth) acrylic acid, of an ester of these acids and of an associative monomer consisting of an oxyalkylated chain terminated by a hydrophobic group.
In the case of these associative monomers, the choice of hydrophobic group determines the varied rheological properties. The following patent applications filed by Coatex™ may be cited with this regard: EP 0 577 526 A1, which describes a fatty chain with linear or branched units of the alkyl and/or aryl type, having 26 to 30 carbon atoms, to develop high viscosities under a low shearing gradient, and EP 1 778 797 A1, which describes a branched terminal chain comprising 10 to 24 carbon atoms, to improve the pigmentary compatibility, and increase the viscosity generally.
However, associative thickening agents - and notably HASE - have a tendency to cause viscosities which may increase over the storage time, from the time when they are introduced into a paint. It is, indeed, well known that the thickening power which they develop tends to increase over time, when they are associated in the paint with binders which require no or little in the way of coalescence aid agents: this trend can generally be observed 8 days after formulation. Such variance is not desirable, since it is synonymous with a loss of control of the paint's rheological profile.
The Applicant has developed a new method for manufacturing aqueous emulsions containing HASE-type thickening agents, involving the use of particular polyglycerols. The resulting products develop viscosities which are completely stable within the paint formulations in which they are incorporated: a simple and effective solution is therefore found to the problem of rheological variance as mentioned above.
One of the characteristics of the polyglycerols in question, in addition to their chemical nature, is based on the fact that they are used during the synthesis of HASE-type thickening agents: in this sense, these are "polymerisation surfactants". Conversely, "formulation surfactants" are used after the polymerisation of the thickening agents, notably in order to use the finished product obtained after polymerisation in water.
The Applicant states that the use of surfactants during polymerisation of an acrylic associative thickening agent is already known: it is notably described in document WO 2009 019225 A1. Furthermore, it is already known to use glycerol during the same type of synthesis, as disclosed in document WO 98 06757 A1. Nevertheless, nothing described or suggested that the use of polyglycerols, as polymerisation surfactants, was likely to lead to new aqueous emulsions containing HASE-type associative thickening agents, giving the paints into which they are introduced particularly stable viscosities.
A first object of the invention therefore consists of an aqueous emulsion of an associative thickening agent obtained by polymerisation:
of at least one monomer which is (meth)acrylic acid, and preferentially methacrylic acid,
of at least one monomer which is an ester of (meth)acrylic acid, and preferentially ethyl acrylate,
of at least one monomer having at least one hydrophobic group,

characterised in that d) at least one polyglycerol of formula (I) is used during the said polymerisation
ROHOOH()n
(I)
where R designates hydrogen, an ester group functionalised by an alkyl group, having 8 to 22 carbon atoms, or an alkyl group having 8 to 22 carbon atoms, and preferentially an alkyl group having 8 to 22 carbon atoms.
4
This emulsion is also characterised in that, for the said associative thickening agent obtained by polymerisation, the said polymerisation consists in accomplishing a first step of introducing into water compounds d) and the said surfactants other than the compounds d), followed by a second step of increasing the temperature of the medium, followed by a third step of introducing polymerisation initiators, and then monomers, possibly added in combination with water and surfactants other than compounds d).
This emulsion is also characterised in that, for the said associative thickening agent obtained by polymerisation, in the said polymerisation the surfactants other than compounds d) are chosen from among the anionic surfactants, and preferentially from among sodium dodecyl sulphate, dioctyl sodium sulfosuccinate, sodium dodecylbenzenesulfonate, the non-ionic surfactants, and preferentially the ethers of fatty alcohols and of polyoxyethylene glycol, the esters of polyoxyethylene glycol and the blends of these surfactants.
This emulsion is also characterised in that, for the said associative thickening agent obtained by polymerisation, the mass % of surfactants other than d)/polymer is between 1% and 5% in the said polymerisation.
This emulsion is also characterised in that, for the said associative thickening agent obtained by polymerisation, the said polymerisation uses, as a % by weight, relative to the total weight of the said associative thickening agent:
from 20% to 60% by weight of at least one monomer which is (meth)acrylic acid, and preferentially methacrylic acid,
from 40% to 80% of at least one monomer which is an ester of (meth)acrylic acid, and preferentially ethyl acrylate,
from 0.5% to 25% of at least one monomer having at least one hydrophobic group,
from 0.1% to 10% by weight of at least one polyglycerol of formula (I),

ROHOOH()n
(I)
5 6
where R designates hydrogen, an ester group functionalised by an alkyl group, having 8 to 22 carbon atoms, or an alkyl group having 8 to 22 carbon atoms, and preferentially an alkyl group having 8 to 22 carbon atoms,
where the sum of the percentages a), b), c) and d) is equal to 100%.
This emulsion is also characterised in that, for the said associative thickening agent obtained by polymerisation, the monomer containing at least one hydrophobic group has the general formula R – (OE)p – (OP)q – R’, where:
- p and q designate integers of less than or equal to 150, at least one of which is non-zero, with preferentially q = 0 and 0 < p < 80,
- OE and OP designate respectively ethylene oxide and propylene oxide, positioned in a random or regular manner,
- R designates a polymerisable group, and preferentially the methacrylate or methacrylurethane group,
- R’ designates a hydrophobic group having at least 6 and at most 36 carbon atoms.
This emulsion is also characterised in that, for the said associative polymer obtained by polymerisation, it has an average molecular mass by weight of between 20,000 g/mol and 1,000,000 g/mol, as measured by GPC.
Another object of the present invention consists in the use of such an emulsion, as a thickening agent of an aqueous formulation or an adhesive, where the said aqueous formulation is preferentially a water-based paint, a thick film coating, or a filler.
Another object of the present invention lies in the fact that in the aqueous formulation or adhesive containing said emulsion, the said aqueous formulation is preferentially a water-based paint, a thick film coating, or a filler.
A final object of the present invention concerns the use of the polyglycerol of formula (I) as a monomer to prepare by polymerisation an associative thickening agent in the form of an aqueous emulsion. 7
The following examples will enable the present invention to be better apprehended, without however limiting its scope.
EXAMPLES
In each of the following examples, the molecular masses of the associative thickening agents are determined by GPC.
Synthesis of the said thickening agents is well known to the skilled man in the art, and reference may be made in particular to the various documents cited in the Application as background concerning HASE technology.
The paints are formulated using the methods well known to the skilled man in the art. All the Brookfield™ viscosities of the paint formulations are determined at 25°C.
Example 1
This example illustrates the synthesis and use of the various associative thickening agents according to the invention (presence of polyglycerol during the synthesis), or outside the invention (without additives, with glycerol used during the synthesis or as a formulation agent, with polyglycerol added as a formulation surfactant).
The use in question occurs in a water-based paint formulation, the constitution of which is given in table 1; the figures indicate the mass in grams of each constituent. Water 294.0
Ammonia 31% 2.0
Ecodis 40 (Coatex™) 3.0
Acticide MBS (Thor™) 2.0
Byk™ 34 (Byk™) 1.0
TiONA™ 568 (Cristal™) 41.0
Durcal 5 (Omya™) 328.0
Omyacoat™ 850 OG (Omya™) 215.0
Axilat™ DS 910 (Hexion™) 82.0
Butyl diglycol 20.0
Thickening agent subject to testing 12.0 *
Table 1
* the value of 12 grams is equal the mass of an emulsion containing 30% by dry weight of polymer (except for test n° 4 which uses 3.0 grams by dry weight of a commercial thickening agent in powder form)
Test n° 1:
This test illustrates a HASE thickening agent outside the invention, polymerised with a conventional surfactant.
This thickening agent results from the synthesis, expressed as a % by weight of the monomers, of:
a) 37.4% of methacrylic acid,
b) 54.3% of ethyl acrylate,
c) 8.3% of a monomer of formula (I), in which:
where R designates the methacrylate group,
q = 0, p = 25,
where R’ designates the hydrophobic group resulting from oxo alcohol having 16 carbon atoms.
In a 1-litre reactor, 485.4 grams of bipermuted water and 6.66 grams of sodium dodecyl sulphate and 11.5 g of non-ionic surfactant, which is isotridecyl alcohol condensed with 3 molecules of ethylene oxide, are weighed. The base of the tank is then heated to 72°C ± 2°C.
During this time, a pre-emulsion is prepared by weighing the following in a beaker:
149 grams of bipermuted water,
2.33 grams of sodium dodecyl sulphate,
111.33 grams of methacrylic acid,
161.45 grams of ethyl acrylate,
24.6 grams of macromonomer of formula (I).

The mass of non-ionic surfactant therefore accounts in this case for 3.8% of the total mass of the manufactured polymer.
obtained in this manner is filtered.
Test n° 2:
This test illustrates a HASE thickening agent outside the invention, polymerised with a conventional surfactant.
This is the same thickening agent as that of test n° 1, in which the non-ionic surfactant has been replaced, in mass terms, by nonylphenol condensed with 4 molecules of ethylene oxide.
Test n° 3:
This test illustrates a HASE thickening agent outside the invention, polymerised with a conventional surfactant.
This is the same thickening agent as that of test n° 1, in which the non-ionic surfactant has been replaced, in mass terms, by a surfactant sold by the company Clariant™ under the name Polyglykol™ B11/150.
Test n° 4:
This test illustrates a thickening agent outside the invention, formulated in water with the introduction of glycerol after polymerisation.
The thickening agent is that of test n° 1, polymerised according to the technique described in test n° 1.
In the final solution with 30% by dry weight of active matter, 3% by dry weight of glycerol from the company Oleon™ relative to the dry weight of polymer is introduced.
Test n° 5:
This test illustrates a thickening agent outside the invention, formulated in water with the introduction of polyglycerol after polymerisation
The thickening agent is that of test n° 1, polymerised according to the technique described in test n° 1.
In the final solution with 30% by dry weight of active matter, 3% by dry weight, relative to the dry weight of polymer, of polyglycerol-3 of formula (I), with R = H, and n = 3 sold by the company Solvay™, is introduced.
Test n° 6:
This test illustrates a thickening agent outside the invention, formulated in water with the introduction of polyglycerol after polymerisation.
The thickening agent is that of test n° 1, polymerised according to the technique described in test n° 1.
In the final solution with 30% by dry weight of active matter, 3% by dry weight, relative to the dry weight of polymer, of hydrophobic polyglycerol, which is Chimexane™ NB of formula (I) with R = C18H35 and n = 2 sold by the company Chimex™, is introduced.
Test n° 7:
This test illustrates a thickening agent outside the invention, polymerised in the presence of glycerol.
The thickening agent is that of test n° 1, polymerised according to the technique described in test n° 1, except that the non-ionic polymerisation surfactant has been substituted, in mass terms, by glycerol from the company Oleon™.
Test n° 8:
This test illustrates a thickening agent according to the invention, polymerised in the presence of polyglycerol-3, which is the one used in test n° 6.
The thickening agent is that of test n° 1, polymerised according to the technique described in test n° 1, except that the non-ionic polymerisation surfactant has been substituted, in mass terms, by the polyglycerol-3 of test n° 5.
Test n° 9:
This test illustrates a thickening agent according to the invention, polymerised in the presence of Chimexane™ NB, which is the one used in test n° 6.
The thickening agent is that of test n° 1, polymerised according to the technique described in test n° 1, except that the non-ionic polymerisation surfactant has been substituted, in mass terms, by the Chimexane™ NB of test n° 6.
For each of these tests the Brookfield™ viscosities were determined at 25°C, at 10 and 100 revolutions per minute, at instants t = 1 day (μ10 1D, μ100 1D) and t = 7 days (μ10 7D, μ100 7D), where instant t = 0 is the time of manufacture of the paint.
The results are shown in table 2.
Test n° 1 2 3 4 5
Outside Invention
Invention OI OI OI OI OI
μ10 1D (mPa.s) 6,600 6,500 6,800 5,600 6,200
μ100 1D (mPa.s) 2,600 2,700 2,800 2,200 2,700
μ10 7D (mPa.s) 7,500 7,700 7,850 5,900 6,400
μ100 7D (mPa.s) 3,300 3,450 3,600 2,650 3,100
Δμ10 (%) 12 16 13 5 3
Δμ100 (%) 21 22 22 10 13

Test n° 6 7 8 9
Outside Invention
INvention OI OI IN IN
μ10 1D (mPa.s) 6,400 9,100 10,500 5,000
μ100 1D (mPa.s) 2,800 3,600 3,800 2,100
μ10 7D (mPa.s) 6,750 10,600 10,800 5,050
μ100 7D (mPa.s) 3,150 4,900 3,900 2,100
Δμ10 (%) 5 14 3 1
Δμ100 (%) 13 27 3 0
12 These results demonstrate that only the thickening agents polymerised in the presence of polyglycerols according to the invention enable the changes of viscosity of the paint after 7 days to be limited.
With test n° 9, which represents the preferential variant of the invention, it is even possible to stabilise the paint's viscosity almost perfectly one week after its manufacture.
For the latter test, the Brookfield™ viscosities measurements at 10 and 100 revolutions per minute were repeated after 2 months: a variation of the viscosities of less than 3% of the initially measured values was observed, denoting excellent stability over time.
Example 2
This example illustrates the synthesis and use of different associative thickening agents, according to the invention (presence of polyglycerol during the synthesis), or outside the invention (without addition of polyglycerol during the synthesis).
The use in question occurs in a water-based paint formulation, the constitution of which is given in table 3; the figures indicate the mass in grams of each constituent.
Water 281.0
Ammonia 31% 2.0
Ecodis 40 (Coatex™) 3.0
Acticide MBS (Thor™) 2.0
Byk™ 34 (Byk™) 1.0
TiONA™ 568 (Cristal™) 41.0
Durcal 5 (Omya™) 328.0
Omyacoat™ 850 OG (Omya™) 215.0
Axilat™ DS 910 (Hexion™) 82.0
Butyl diglycol 20.0
Thickening agent subject to testing 24.0 *
Table 3
* the 24 grams are the mass of an emulsion containing 30% by dry weight of polymer
Test n° 10:
This test illustrates a HASE thickening agent outside the invention, polymerised with a conventional surfactant.
This thickening agent results from the synthesis, expressed as a % by weight of the monomers, of:
a) 33.7% of methacrylic acid,
b) 59.4% of ethyl acrylate,
c) 6.9% of a monomer of formula (I), in which:
R designates the methacrylate group
q = 0, p = 25,
R’ designates the branched hydrophobic group with 16 carbon atoms.
In a 1-litre reactor, 288 grams of bipermuted water, 3.5 grams of sodium dodecyl sulphate and 11.5 g of non-ionic surfactant, which is isotridecyl alcohol condensed with 3 molecules of ethylene oxide, are weighed. The base of the tank is then heated to 72°C ± 2°C.
During this time, a pre-emulsion is prepared by weighing the following in a beaker:
285 grams of bipermuted water,
3.5 grams of sodium dodecyl sulphate,
102.06 grams of methacrylic acid,
180 grams of ethyl acrylate,
21 grams of macromonomer of formula (I),
0.64 g of dodecylmercaptan.

The mass of non-ionic surfactant therefore accounts in this case for 3.6% of the total mass of the manufactured polymer.
0.95 gram of ammonium persulphate is then weighed, diluted in 10 grams of bipermuted water for the first catalyst, and 0.095 gram of sodium metabisulphite diluted in 10 grams of
bipermuted water for the second catalyst. When the base of the tank is at the required temperature both catalysts are added and polymerisation is effected for 2 hours at 76°C ± 2°C, with simultaneous addition of the pre-emulsion. The pump is rinsed with 20 grams of bipermuted water, and is fired for 1 hour at 76°C ± 2°C. Finally it is cooled to ambient temperature, and the dispersion obtained in this manner is filtered.
Test n° 11:
This test illustrates a thickening agent according to the invention, polymerised in the presence of polyglycerol-3 sold by the company Solvay™.
The thickening agent is that of test n° 10, polymerised according to the technique described in test n° 10, except that the non-ionic polymerisation surfactant has been substituted, in mass terms, by the polyglycerol-3 of test n° 5.
Test n° 12:
This test illustrates a thickening agent according to the invention, polymerised in the presence of Chimexane™ NB.
The thickening agent is that of test n° 10, polymerised according to the technique described in test n° 10, except that the polymerisation surfactant has been substituted, in mass terms, by the Chimexane™ NB.
Test n° 13:
This test illustrates a HASE thickening agent outside the invention, polymerised with a conventional surfactant.
This thickening agent results from the synthesis, expressed as a % by weight of the monomers, of:
a) 35.57% of methacrylic acid,
b) 52.43% of ethyl acrylate,
c) 12% of a monomer of formula (I), in which:
R designates the methacrylate group,
q = 0, p = 30,
R’ designates the hydrophobic group consisting of 12 carbon atoms and derived from ethoxylation of an oxo alcohol consisting of 12 carbon atoms.
In a 1-litre reactor 485.4 grams of bipermuted water and 6.66 grams of sodium dodecyl sulphate and 11.5 g of a surfactant sold by the company Clariant™ under the name Polyglykol™ B11/150 are weighed. The base of the tank is then heated to 72°C ± 2°C.
During this time, a pre-emulsion is prepared by weighing the following in a beaker:
149 grams of bipermuted water,
0.33 gram of sodium dodecyl sulphate,
105.8 grams of methacrylic acid,
155.9 grams of ethyl acrylate,
35.7 grams of macromonomer of formula (I).

The mass of surfactant therefore accounts in this case for 3.87% of the total mass of the manufactured polymer.
0.95 gram of ammonium persulphate is then weighed, diluted in 10 grams of bipermuted water for the first catalyst, and 0.095 gram of sodium metabisulphite diluted in 10 grams of bipermuted water for the second catalyst. When the base of the tank is at the required temperature both catalysts are added, and polymerisation is effected for 2 hours at 76°C ± 2°C, with simultaneous addition of the pre-emulsion. The pump is rinsed with 20 grams of bipermuted water, and is fired for 1 hour at 76°C ± 2°C. Finally it is cooled to ambient temperature, and the polymer obtained in this manner is filtered.
Test n° 14:
This test illustrates a thickening agent according to the invention, polymerised in the presence of polyglycerol-4 of the company Solvay™.
The thickening agent is that of test n° 13, polymerised according to the technique described in test n° 13, except that the non-ionic polymerisation surfactant has been substituted, in mass terms, by polyglycerol-4.
Test n° 15:
This test illustrates a thickening agent according to the invention, polymerised in the presence of Chimexane™ NB sold by the company Chimex™.
The thickening agent is that of test n° 13, polymerised according to the technique described in test n° 13, except that the non-ionic polymerisation surfactant has been substituted, in mass terms, by the Chimexane™ NB.
For each of these tests, the Brookfield™ viscosities were determined at 25°C, at 10 and 100 revolutions per minute, at instants t = 1 day (μ10 1D, μ100 1D) and t = 7 days (μ10 7D, μ100 7D), where instant t = 0 is the time of manufacture of the paint.
The results are shown in table 4.
Test n° 10 11 12
Outside Invention
INvention OI IN IN
μ10 1D (mPa.s) 7,700 8,500 8,200
μ100 1D (mPa.s) 2,700 2,900 3,000
μ10 7D (mPa.s) 8,100 8,600 8,300
μ100 7D (mPa.s) 3,100 3,000 3,000
Δμ10 (%) 5 1 1
Δμ100 (%) 15 3 0

Test n° 13 14 15
Outside Invention
INvention OI IN IN
μ10 1D (mPa.s) 7,300 7,000 7,100
μ100 1D (mPa.s) 3,000 2,400 2,500
μ10 7D (mPa.s) 8,700 7,500 7,600
μ100 7D (mPa.s) 3,300 2,500 2,600
Δμ10 (%) 19 7 7
Δμ100 (%) 10 4 4
Table 4
These results demonstrate that only the thickening agents polymerised in the presence of polyglycerols according to the invention enable the changes of viscosity of the paint after 7 days to be limited, and the best results are always obtained with the preferred variant of the invention.
The excellent result obtained with test n° 12 may be noted. For the latter test, the Brookfield™ viscosities measurements at 10 and 100 revolutions per minute were repeated after 1 month: a variation of viscosities of less than 5% of the initially measured values is observed.
WE CLAIM:
1 - An aqueous emulsion of an associative thickening agent obtained by polymerisation:
of at least one monomer which is (meth)acrylic acid, and preferentially methacrylic acid,
of at least one monomer which is an ester of (meth)acrylic acid, and preferentially ethyl acrylate,
of at least one monomer having at least one hydrophobic group,

characterised in that d) at least one polyglycerol of formula (I) is used during the said polymerisation :
ROHOOH()n
(I)
where R designates hydrogen, an ester group functionalised by an alkyl group, having 8 to 22 carbon atoms, or an alkyl group having 8 to 22 carbon atoms, and preferentially an alkyl group having 8 to 22 carbon atoms.
2 - An emulsion according to claim 1, characterised in that, for the said associative thickening agent obtained by polymerisation, the said polymerisation consists in accomplishing a first step of introducing into water compounds d) and the said surfactants other than the compounds d), followed by a second step of increasing the temperature of the medium, followed by a third step of introducing polymerisation initiators, and then monomers, possibly added in combination with water and surfactants other than compounds d).
3 - An emulsion according to one of the claims 1 or 2, characterised in that, for the said associative thickening agent obtained by polymerisation, in the said polymerisation the surfactants other than compounds d) are chosen from among the anionic surfactants, and preferentially from among sodium dodecyl sulphate, dioctyl sodium sulfosuccinate, sodium dodecylbenzenesulfonate, the non-ionic surfactants, and 18
preferentially the ethers of fatty alcohols and of polyoxyethylene glycol, the esters of polyoxyethylene glycol and the blends of these surfactants.
4 - An emulsion according to one of the claims 1 to 3, characterised in that, for the said associative thickening agent obtained by polymerisation, the mass % of surfactants other than d)/polymer is between 1% and 5% in the said polymerisation.
5 - An emulsion according to one of the claims 1 to 4, characterised in that, for the said associative thickening agent obtained by polymerisation, the said polymerisation uses, as a % by weight, relative to the total weight of the said associative thickening agent:
from 20% to 60% by weight of at least one monomer which is (meth)acrylic acid, and preferentially methacrylic acid,
from 40% to 80% of at least one monomer which is an ester of (meth)acrylic acid, and preferentially ethyl acrylate,
from 0.5% to 25% of at least one monomer having at least one hydrophobic group,
from 0.1% to 10% by weight of at least one polyglycerol of formula (I),

ROHOOH()n
(I)
where R designates hydrogen, or an ester group functionalised by the alkyl group, having 8 to 22 carbon atoms, or an alkyl group having 8 to 22 carbon atoms, and preferentially an alkyl group having 8 to 22 carbon atoms,
where the sum of the percentages a), b), c) and d) is equal to 100%.
6 - An emulsion according to one of the claims 1 to 5, characterised in that, for the said associative thickening agent obtained by polymerisation, the hydrophobic group of the monomer containing at least one hydrophobic group has at least 6 and at most 36 carbon atoms. 19
7 - An emulsion according to one of the claims 1 to 6 characterised in that, for the said associative thickening agent obtained by polymerisation, the monomer containing at least one hydrophobic group has the general formula R – (OE)p – (OP)q – R’, where:
p and q designate integers of less than or equal to 150, at least one of which is non-zero, with preferentially q = 0 and 0 < p < 80,
OE and OP designate respectively ethylene oxide and propylene oxide,
R designates a polymerisable group, and preferentially the methacrylate or methacrylurethane group,
R’ designates a hydrophobic group having at least 6 and at most 36 carbon atoms.

8 - An emulsion according to one of the claims 1 to 7, characterised in that, for the said associative polymer obtained by polymerisation, it has an average molecular mass by weight of between 20,000 g/mol and 1,000,000 g/mol, as measured by GPC.
9 - Use of an emulsion according to one of the claims 1 to 8, as a thickening agent of an aqueous formulation or an adhesive.
10 - Use according to claim 9, according to which the said aqueous formulation is a water-based paint, a thick film coating or a filler.
11 - An aqueous formulation or adhesive containing an emulsion according to one of the claims 1 to 8.
12 - An aqueous formulation according to claim 11, according to which the said formulation is a water-based paint, a thick film coating, or a filler.
13 - Use of the polyglycerol of formula (I) as a monomer to prepare by polymerisation an associative thickening agent in the form of an aqueous emulsion.