The invention relates to the field of the preparation of aqueous dispersions of organic particles, organo-metallic or inorganic. In particular, the invention relates to the preparation of aqueous suspensions comprising organic particles, organo-metallic or mineral and at least one specific copolymer obtained by polymerization of at least one acid and at least one compound or of at least one ester derived from a particular acid in the presence of water, at least one initiator compound and at least one activator compound, followed by the total or partial neutralization by means of at least one compound selected from hydroxides of alkali metal, metal hydroxides, alkaline earth metal dihydroxides alkaline earth metal and mixtures thereof. Thep ) and molecular weight (Mw), its preparation method and its use, especially for preparing an aqueous paint composition.

Discloses water-soluble copolymers useful as dispersing agents in the preparation of particle suspensions. In particular, known dispersing agents for the preparation of gloss paint compositions comprising dispersed titanium dioxide particles.

For such compositions of paint, generally are sought coating gloss qualities obtained after application. Wanted also very good optical properties and very good mechanical properties.

Discloses the preparation of copolymers of acrylic acid and methods of ester implementing sodium thiosulfate; e.g. CN 101884888 discloses such grinding agents. JP 1986-53627 discloses the anti-corrosion properties of a copolymer comprising sulfonic groups. EP 2657261 discloses a homopolymer of acrylic acid.

Copolymers prepared by known sulfites need to be prepared in a manner highly diluted, for example a solids content of 7 to 12% by weight, to avoid formation of an insoluble precipitate upon neutralization with sodium hydroxide or potash.

Neutralization with ammonia then the only alternative despite the inconveniences that result.

Generally, the dispersants of the prior art are prepared by methods including neutralization step using ammonia thus improving the dispersing properties of the copolymer obtained. The choice of this particular neutralizing agent may also influence the optical properties of the paint coating carried out subsequently. It can also affect the mechanical properties of the coating.

For example, US 3859260 discloses a redox radical polymerization reaction which implements an initiator compound and a substantial amount of bisulfite as reducing agent. The polymer was neutralized with potassium hydroxide or with ammonia.

US 4102843 discloses an aqueous composition emulsion paint comprising a copolymer of alkyl acrylate and acrylic acid as a dispersing agent. This copolymer is obtained by polymerization in isopropanol and an initiator compound then it is neutralized using sodium hydroxide.

However, during the implementation of known methods, the residual presence of larger or smaller amounts of ammonia can lead to odor problems, health and industrial hygiene.

In addition, the presence of volatile organic compounds (VOCs), such as ammonia, in the paint compositions is also problematic.

Thus, besides the good dispersion properties of the particles and improved optical properties, dispersing agents should also prevent or reduce the presence of volatile organic compounds. In particular, such dispersants should not lead to the release of ammonia.

One solution to this problem could be to implement neutralizing agents, avoiding the presence of ammonia. However, the implementation of alkali metal cations generally degrades dispersant properties or optical properties.

In particular, some sulfonated polymers obtained by polymerization reaction catalyzed peroxide and bisulfite are difficult or impossible to neutralize by means of alkali metal compounds because of the risk of precipitation in the compositions prepared salts of these alkali metals, in particular alkali metal sulfates.

It is also necessary to have methods of preparation in which the concentration of the reaction mixture solids must be high while allowing to avoid the use of ammonia in the neutralization of the prepared polymers. Concentrations above 20 wt% or even above 30% or above 40 or 45% by weight are particularly preferred.

Moreover, the dispersants used in the preparation of suspensions of particles, including particle suspensions for the preparation of paint compositions, should help maintain or improve abrasion resistance or improved resistance to wet abrasion.

These dispersants must also maintain or improve the storage stability and the flow and leveling. The maintenance or improvement of the covering power must also be sought. pigment compatibility and resistance to blocking, ie the adhesion strength of the two coating layer brought into contact, are also the desired properties of the prepared coatings. For these coatings are also sought improved stain resistance.

An important property also lies in the stability of coating compositions during storage in containers.

The particles of dispersing agents must also have satisfactory or improved intrinsic properties, particularly a low viscosity. They must also be compatible with widely different types of particles or with different types of materials or additives. They must be very versatile.

Moreover, the copolymers useful as dispersing agents such as acrylic dispersants for aqueous paint composition should be prepared in high concentrations and which are interesting commercially, in particular of 35% higher concentrations by weight of neutralized copolymer the solution.

There is therefore a need for the expert to have dispersant particles having improved properties.

The invention provides a solution to any or all of the problems with dispersing agents of the state of the art.

Thus, the invention provides a copolymer obtainable by a process comprising:

• at least a polymerization reaction:

(A) at least one acid selected from acrylic acid, methacrylic acid and mixtures thereof; and

(B) at least one compound or of at least one ester of a compound derived from an acid selected from acrylic acid, methacrylic acid, itaconic acid and maleic acid;

in the presence of water, at least one initiator compound selected from hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate and mixtures thereof and at least one activator compound selected from hypophosphites of alkali metals including sodium hypophosphite, potassium hypophosphite, and mixtures thereof, and preferably in the absence of sodium thiosulfate;

· The total or partial neutralization by means of at least one compound selected from

MgO, CaO, hydroxides of alkali metal, metal hydroxides, alkaline earth metal dihydroxides alkaline earth metal and mixtures thereof.

Advantageously, the invention provides a copolymer whose intrinsic characteristics can be controlled. Most preferably according to the invention, the copolymer obtained has a molecular weight (M w ) of from 1 000 to 6 000 g / mol, preferably from 1 500 to 4 000 g / mol. Also preferably according to the invention, the copolymer obtained has a polydispersity index (I p ) ranging from 1.5 to 3, preferably 1.8 to 2.3.

According to the invention, the neutralization is performed after the polymerization reaction. The invention therefore also provides an alkali metal salt or a metal salt alkaline earth of a copolymer obtained according to the invention or a mixture of such a salt and a copolymer obtained according to the invention.

Preferably according to the invention, the polymerization reaction implements an acid (a) selected from acrylic acid, methacrylic acid and mixtures thereof. Acrylic acid is preferred.

In addition to acrylic acid and methacrylic acid, the polymerization reaction can implement at least one other acid (a). Preferably, the polymerization reaction starts while also implementing another acid (a) selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid. Advantageously, the polymerization reaction can implement of acrylic acid with itaconic acid or maleic acid or of methacrylic acid with itaconic acid or maleic acid .

Also preferably according to the invention, the polymerization reaction implements 10 to 90, preferably 30 to 60 by weight of compound (a) with respect to the total quantity by weight of compounds (a) and ( b).

Most preferably according to the invention, the polymerization reaction uses at least one compound (b) which is a compound of formula (A):

(A)

in which :

• X, identical or different, independently represents a linear Ci-ClO alkylene group or branched;

• n is an integer or decimal number from 1 to 5;

• Q represents a group selected from C (O), CH 2 , CH 2 -0 and (CH 2 ) 4 -0;

• L represents a direct bond or a CH 2 ;

• R 1 represents H, CH 3 or C (0) OH;

• R 2 represents H or C (0) OH.

Also preferably according to the invention, the polymerization reaction uses at least one compound (b) of formulas (I), (II), III) or (IV):

P.)

(III) (IV)

in which :

• X, identical or different, independently represents a linear Ci-ClO alkylene group or branched;

• n is an integer or decimal number from 1 to 5;

• L represents a direct bond or a CH 2 ;

• R 1 represents H, CH 3 or C (0) OH;

• R 2 represents H or C (0) OH.

More preferably, the compound (b) is a compound of formulas (A), (I), (II), (III) or (IV) wherein X, identical or different, independently represents a group C 2 -C 4 alkylene linear or branched, in particular an ethylene group, a propylene group or a butylene group.

Even more preferably, the compound (b) is a compound of formulas (A), (I), (II), (III) or (IV) in which:

• L represents a direct bond, R 1 is H and R 2 is H; or

• L represents a direct bond CH 2 , R 1 represents CH 3 and R 2 is H; or

• L represents a direct bond, R 1 is H and R 2 is C (0) OH; or

• L represents a group CH 2 , R 1 is C (0) OH and R 2 is H.

Much more preferably, the compound (b) is a compound of formulas (A), (I), (II), (III) or (IV) wherein n represents 1 and:

• L represents a direct bond, R 1 is H and R 2 is H; or

• L represents a direct bond CH 2 , R 1 represents CH 3 and R 2 is H; or

• L represents a direct bond, R 1 is H and R 2 is C (0) OH; or

• L represents a group CH 2 , R 1 is C (0) OH and R 2 is H; including a compound of formulas (A), (I), (II), (III) or (IV) wherein n represents

In a :

• L represents a direct bond, R 1 is H and R 2 is H; or

• L represents a direct bond CH 2 , R 1 represents CH 3 and R 2 is H.

Particularly preferred according to the invention, the reaction of polymerization implements a compound (b) selected from acrylate hydroxyéthylèneoxy the hydroxypropylèneoxy acrylate, hydroxyéthylèneoxy methacrylate, hydroxypropylèneoxy methacrylate. The hydroxypropylèneoxy acrylate or 2-hydroxypropyl acrylate (CAS 999-61-1) is preferred.

Also preferably according to the invention, the polymerization reaction implements 10 to 90, preferably 40 to 70 by weight of compound (b) relative to the total quantity by weight of compounds (a) and ( b).

According to the invention, the polymerization reaction is conducted in the presence of water, at least one initiator compound and at least one activator compound. The preferred initiator compound is hydrogen peroxide (H 2 0 2 ) which can be associated with metal salts, in particular iron salts, copper salts or mixtures thereof. The preferred promoter compound is sodium hypophosphite (NaP0 2 H 2 ). Preferably according to the invention, the polymerization reaction implements from 5 to 15% by weight, preferably 7 to

II% by weight, hypophosphites of alkali metal relative to the total quantity by weight of monomers.

De manière préférée selon l'invention, la neutralisation totale ou partielle est réalisée au moyen d'au moins un composé choisi parmi NaOH, KOH, MgO, CaO, Mg(OH)2, Ca(OH)2 et leurs mélanges. De manière avantageuse, la neutralisation partielle est réalisée au moyen de NaOH, KOH, MgO, CaO, Mg(OH)2, Ca(OH)2 et leurs mélanges et la neutralisation totale est réalisée au moyen de NaOH, KOH et leurs mélanges. De manière particulièrement préférée selon l'invention, la neutralisation totale ou partielle est réalisée au moyen de potasse ou de soude et en particulier au moyen de potasse.

De manière avantageuse selon l'invention, le composé initiateur peut être choisi parmi le peroxyde d'hydrogène, le persulfate de sodium, le persulfate de potassium, le persulfate d'ammonium et leurs mélanges et la neutralisation peut être réalisée au moyen de potasse.

Outre un copolymère particulier, l'invention concerne également un procédé de préparation de ce copolymère. Le procédé selon l'invention comprend :

« au moins une réaction de polymérisation

(a) d'au moins un acide choisi parmi l'acide acrylique, l'acide méthacrylique et leurs mélanges ; et

(b) d'au moins un composé ou d'au moins un ester d'un composé dérivés d'un acide choisi parmi l'acide acrylique, l'acide méthacrylique, l'acide itaconique et l'acide maléique ;

in the presence of water, at least one initiator compound selected from hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate and mixtures thereof and at least one activator compound selected from hypophosphites of alkali metals including sodium hypophosphite, potassium hypophosphite, and mixtures thereof, and preferably in the absence of sodium thio sulfate;

• the total or partial neutralization by means of at least one compound selected from MgO, CaO, hydroxides of alkali metal, metal hydroxides, alkaline earth metal dihydroxides alkaline earth metal and mixtures thereof.

For the process according to the invention, the polymerization reaction may be repeated. Neutralization is then carried out after the polymerization reaction. The invention therefore also provides a process for preparing an alkali metal salt or of a metal of alkaline earth salt of a copolymer obtained according to the method of the invention or a mixture of such a salt and a copolymer obtained by the process of the invention.

A preferred method of the invention implements an acid (a) selected from acrylic acid, methacrylic acid and mixtures thereof. Acrylic acid is preferred. In addition to acrylic acid and methacrylic acid, the polymerization reaction can to

work at least one other acid (a). Preferably, the polymerization reaction starts while also implementing another acid (a) selected from acrylic acid, methacrylic acid, itaconic acid and maleic acid. Advantageously, the polymerization reaction can implement of acrylic acid with itaconic acid or maleic acid or of methacrylic acid with itaconic acid or maleic acid .

Also preferred according to the invention implements 10 to 90, preferably 30 to 60 by weight of compound (a) with respect to the total quantity by weight of compounds

(A) and (b).

A preferred method according to the invention uses at least one compound (b) which is a compound of formula (A):

(A)

in which :

• X, identical or different, independently represents a linear Ci-ClO alkylene group or branched;

• n is an integer or decimal number from 1 to 5;

• Q represents a group selected from C (O), CH 2 , CH 2 -0 and (CH 2 ) 4 -0;

• L represents a direct bond or a CH 2 ;

• R 1 represents H, CH 3 or C (0) OH;

• R 2 represents H or C (0) OH.

Also preferred according to the invention uses at least one compound (b) which is a compound of formulas (I), (II) or (III:

P.)

(III) (IV)

in which :

• X, identical or different, independently represents a C1-C10 linear or branched alkylene group;

• n is an integer or decimal number from 1 to 5;

• L represents a direct bond or a CH 2 ;

• R 1 represents H, CH 3 or C (0) OH;

• R 2 represents H or C (0) OH.

More preferably for the method according to the invention, the compound (b) is a compound of formulas (A), (I), (II), (III) or (IV) wherein X, identical or different, represents independently a group C 2 -C 4 linear or branched alkylene, in particular an ethylene group, a propylene group or a butylene group. Even more preferably, the compound (b) is a compound of formulas (A), (I), (II), (III) or (IV) in which:

• L represents a direct bond, R 1 is H and R 2 is H; or

• L represents a direct bond, R 1 is CH 3 and R 2 is H; or

• L represents a direct bond, R 1 is H and R 2 is C (0) OH; or

• L represents a group CH 2 , R 1 is C (0) OH and R 2 is H.

Much more preferably, the compound (b) is a compound of formulas (A), (I), (II), (III) or (IV) wherein n represents 1 and:

• L represents a direct bond, R 1 is H and R 2 is H; or

• L represents a direct bond, R 1 is CH 3 and R 2 is H; or

• L represents a direct bond, R 1 is H and R 2 is C (0) OH; or

• L represents a group CH 2 , R 1 is C (0) OH and R 2 is H; including a compound of formulas (A), (I), (II), (III) or (IV) wherein n represents 1 and:

• L represents a direct bond, R 1 is H and R 2 is H; or

• L represents a direct bond, R 1 is CH 3 and R 2 is H.

Particularly preferred according to the invention, the reaction of polymerization implements a compound (b) selected from acrylate hydroxyéthylèneoxy the hydroxypropylèneoxy acrylate, hydroxyéthylèneoxy methacrylate, hydroxypropylèneoxy methacrylate. The hydroxypropylèneoxy acrylate is preferred.

Also preferred according to the invention implements 10 to 90, preferably 40 to 70 by weight of compound (b) relative to the total quantity by weight of compounds (a) and (b).

For the process according to the invention, the polymerization reaction is conducted in the presence of water, at least one initiator compound and at least one activator compound. The preferred initiator compound is hydrogen peroxide (H2O2) which can be combined with metal salts, particularly iron salts, copper salts or mixtures thereof. The preferred promoter compound is sodium hypophosphite (NaP0 2 H 2 ). Preferably according to the invention, the polymerization reaction implements from 5 to 15% by weight, preferably 7 to 11% by weight, hypophosphites of alkali metal relative to the total quantity by weight of monomers.

Furthermore a particular copolymer and a copolymer of this preparation process, the invention also relates to the use of this copolymer.

Preferably, the invention relates to the use of at least one copolymer according to the invention for the preparation of an aqueous dispersion, in particular for the preparation of an aqueous dispersion of organic particles, organo-metallic or inorganic.

The invention therefore provides a particular aqueous dispersion comprising at least one copolymer according to the invention and organic particles, organometallic or inorganic dispersed in an aqueous medium, preferably dispersed in water.

Preferably, the particles employed in the invention are particles of at least one pigment. Also preferably, the particles implemented according to the invention are mineral particles. More preferably, it is Ti0 particles 2 .

Among aqueous dispersions, the invention preferably provides an aqueous suspension (or slurry) comprising organic particles, organo-metallic or mineral and at least one copolymer according to the invention in an aqueous medium, preferably in water .

Le copolymère selon l'invention, la dispersion aqueuse selon l'invention ou la suspension aqueuse selon l'invention peuvent être utilisés pour la préparation de nombreuses compositions. De manière préférée, le copolymère selon l'invention, la dispersion aqueuse selon l'invention ou la suspension aqueuse selon l'invention sont utilisés pour la préparation d'une composition adhésive aqueuse ou d'une composition aqueuse de revêtement, notamment d'un revêtement de couche épaisse ou d'un revêtement de couche mince.

De manière particulièrement préférée selon l'invention, la composition aqueuse de revêtement est une composition aqueuse de vernis ou une composition aqueuse de peinture, par exemple de peinture décorative ou de peinture industrielle.

Ainsi, de manière préférée, l'invention fournit également une composition aqueuse de peinture comprenant, dans un support aqueux, de préférence dans de l'eau,

« au moins un latex de copolymère filmogène ;

• au moins un pigment organique ou minéral ;

• au moins un copolymère selon l'invention.

Les caractéristiques particulières, avantageuses ou préférées du copolymère selon l'invention permettent de définir des dispersions aqueuses particulières, avantageuses ou préférées selon l'invention, des suspensions aqueuses particulières, avantageuses ou préférées selon l'invention et des compositions particulières, avantageuses ou préférées selon l'invention.

Les exemples qui suivent permettent d'illustrer les différents aspects de l'invention.

Example 1: method (1) the preparation of copolymers according to the invention:

In a glass reactor of 1000 ml equipped with a mechanical stirring system and a heating system type of system oil bath, weighed:

310 grams of water,

0.134 g sulfate do heptahydraté,

0.02 g of copper sulphate pentahydrate.

The assembly is then heated to 95 ° C ± 2 ° C and then added with périlstatiques three pumps by continuous additions for two hours at 95 ° C the following reagents:

Pump 1: the monomers:

o acrylic acid: 284.04 g

o acrylate de 2-hydroxypropylèneoxy : 180 g

o water: 31.6 g

Pump 2: the initiator compound:

o hydrogen peroxide 130 volumes: 37 g

o water: 45 g

Pump 3: Reduction activator compound:

o solution à 50 % d'hypophosphite de sodium : 96 g.

After rinsing the pumps, the assembly is then baked for 45 min at 95 ° C. A polymer is obtained which is then analyzed:

Residual monomers: acrylic acid = 30 ppm and acrylate, 2-hydroxy propyl <60 ppm,

- Mw = 2 795 g/mol,

- Ip = 2.

This polymer is then neutralized to pH 8 ± 0.5 in two forms and a solids content of 45% + 0.5%:

neutralization with sodium hydroxide to obtain the copolymer 1-1,

neutralization with potassium hydroxide to obtain the copolymer 1-2.

Example 2: Method (2) Preparation of comparative copolymers:

In a glass reactor of 1000 ml equipped with a mechanical stirring system and a heating system type of system oil bath, weighed:

310 grams of water,

0.134 g sulfate do heptahydraté,

0.02 g of copper sulphate pentahydrate.

The assembly is then heated to 95 ° C ± 2 ° C and then added with périlstatiques three pumps by continuous additions for two hours at 95 ° C the following reagents:

Pump 1: the monomers:

o acrylic acid: 284.04 g

o acrylate de 2-hydroxypropylèneoxy : 180 g

o water: 31.6 g

Pump 2: the initiator compound:

o hydrogen peroxide 130 volumes: 37 g

o water: 45 g

Pump 3: Reduction activator compound:

o solution à 50 % d'hypophosphite de sodium : 96 g.

After rinsing the pumps, the assembly is then baked for 45 min at 95 ° C. A polymer is obtained which is then analyzed:

Residual monomers: acrylic acid = 30 ppm and acrylate, 2-hydroxy propyl <60 ppm,

- Mw = 2 755 g/mol,

- Ip = 3.

this polymer is then neutralized to pH 8 ± 0.5 and a solids content of 45% ± 0.5% by neutralization with ammonia to obtain the copolymer 2-1.

Example 3: method (3) Preparation of comparative copolymers:

In a glass reactor of 1000 ml equipped with a mechanical stirring system and a heating system type of system oil bath, weighed:

180 grams of water,

0.003 g sulfate heptahydraté do.

The assembly is then heated to 73 ° C ± 2 ° C and then added with périlstatiques three pumps by continuous additions for two hours at 73 ° C the following reagents:

Pump 1: the monomers:

o acrylic acid: 245 g

o acrylate de 2-hydroxypropylèneoxy : 159,89 g

o water: 60 g

Pump 2: the initiator compound:

o persulfate d'ammonium : 5,88 g

o water: 60 g

Pompe 3 : le composé activateur réducteur :

o solution à 40 % de bisulfite de sodium : 142 g.

Les monomères et le composé réducteur sont ajoutés durant 3 h 30 min, le composé initiateur est ajouté durant 3 h 35 min. Après rinçage des pompes, l'ensemble est ensuite cuit durant 60 min à 73°C. On obtient un polymère qui est alors analysé :

monomères résiduels : acide acrylique = 60 ppm et acrylate de 2-hydroxypropyle < 60 ppm,

- Mw = 3 115 g/mol,

- Ip = 2,4.

On neutralise ensuite ce polymère à pH = 8 + 0,5 sous deux formes et pour un extrait sec de 45 % + 0,5 % :

neutralisation à la soude pour obtenir le copolymère 3-1,

neutralisation à la potasse pour obtenir le copolymère 3-2.

Exemple 4 : procédé (4) de préparation de copolymères comparatifs :

In a glass reactor of 1000 ml equipped with a mechanical stirring system and a heating system type of system oil bath, weighed:

180 grams of water,

0.003 g sulfate heptahydraté do.

The assembly is then heated to 73 ° C ± 2 ° C and then added with périlstatiques three pumps by continuous additions for two hours at 73 ° C the following reagents:

Pump 1: the monomers:

o acrylic acid: 245 g

o acrylate de 2-hydroxypropylèneoxy : 159,89 g

o water: 60 g

Pump 2: the initiator compound:

o persulfate d'ammonium : 5,88 g

o water: 60 g

Pump 3: Reduction activator compound:

or a 40% solution of sodium bisulfite of: 142 g.

The monomers and the reducing compound are added during 3 h 30 min, the initiator compound is added during 3 h 35 min. After rinsing the pumps, the assembly is then baked for 60 min at 73 ° C. A polymer is obtained which is then analyzed:

Residual monomers: acrylic acid = 60 ppm and acrylate, 2-hydroxy propyl <60 ppm,

- Mw = 2 640 g/mol,

- Ip = 2,l.

this polymer is then neutralized to pH 8 ± 0.5 and a solids content of 45% ± 0.5% by neutralization with ammonia to obtain the copolymer 4-1.

The molecular weight of the copolymers is determined by steric exclusion chromatography (CES) or English "Gel Permeation Chromatography" (GPC). This technique uses a Waters brand liquid chromatograph equipped with a detector. This detector is a refractive concentration detector Waters brand. This liquid chromatography apparatus has a size exclusion column to separate the different molecular weights of the copolymers studied. The elution liquid phase is an aqueous phase adjusted to pH 9.00 using sodium hydroxide IN containing 0.05M NaHCO, NaN0 0.1M, 0.02M triétanolamine and 0.03% NaN 3 .

In a first step, 0.9% dry diluted copolymer solution in the ESC of the solubilization solvent, which corresponds to the elution liquid phase of the ESC to which is added 0.04% of dimethylformamide playing the role of flow marker or internal standard. Then, filtered to 0.2 μιη. 100 μΐ ^ are then injected into the chromatograph (eluent: an aqueous phase adjusted to pH 9.00 by N sodium hydroxide containing 0.05 M NaHC0, NaN0 0.1M, 0.02M triétanolamine and 0, 03% of NaN 3 ).

The liquid chromatography apparatus contains an isocratic pump (Waters 515) whose flow rate is set at 0.8 mL / min. The chromatography apparatus further comprises an oven which itself comprises in series the following column system: a type precolumn Guard Column Ultrahydrogel Waters 6 cm in length and 40 mm internal diameter, and a linear type column Waters Ultrahydrogel 30 cm length and 7.8 mm internal diameter. The detection system consists of a refractometric detector type RI Waters 410 The furnace is heated to a temperature of 60 ° C and the refractometer is heated to a temperature of 45 ° C.

The chromatograph is calibrated using standards powdered sodium polyacrylate of molecular weights different certified by the supplier: Polymer Standard Service or Polymers American Standards Corporation.

Table 1 shows the characteristics of the prepared copolymers.

Table 1

When carrying out the process (1) is obtained limpid and stable solutions on storage. When carrying out the process (2), only the polymer neutralized with aqueous ammonia is clear.

Thus, the polymerization according to the invention, which implements an initiator consisting of sodium hypophosphite type allows to obtain acrylic copolymers useful as dispersing agents with high, commercially attractive concentrations (> 35% or even 40% or to 43% for example) and with alkali cations from neutralization.

It is not possible to obtain such results when the gear initiator compound is sodium bisulfite, unless using ammonia in the neutralization of the copolymer thus resulting in the presence of a release of volatile organic compounds in use of these polymers.

Example 5: use of the copolymers for the preparation of coating compositions and evaluation of paint properties:

three paint formulations were prepared by mixing the components shown in Table 2.

Amount

Composition

(kg) phase d'empâtage

water 37.78

potassium tripolyphosphate sequestering agent (KTPP) 0.45 dispersant copolymer 1-1,

according to the invention or comparative 2.09 1-2 or 2-1

surfactant Triton CF-10 1.36

defoamer Rhodaline 640 0.45

Fungicide Karhon LX (1.5%) 0.68

carbonate de sodium Aldrich 1,91

Ti02 rutile (76.5% one Kronos 2310 / Tronox CR 828 / TI-PURE

Weight 112,49) R 902

Kaolin Polygloss 90 9,07

water 38.28

complement

Arkema latex Encor 300 158,76

Arkema latex Encor 626 68.04

defoamer Rhodaline 640 0.91

thickener Coatex Rheotech 2800 9.84

thickener Coatex Rheotech 4800 0.18

water 44.45

TOTAL 486,75

Table 2

The Stormer viscosity (KU) (ASTM D 562), the ICI viscosity (ASTM D 4287) and the Brookfield viscosity (ASTM D 2196) at 10 revolutions / min and 100 rev / min at 25 ° C was measured for three formulations paint. The results are presented in Table 3.

Table 3

The dispersing properties of copolymers used were evaluated by performing deflocculation curves for different grades of T1O2 particles. Thus demonstrating the effectiveness of the dispersing agent in the suspension in water of titanium dioxide at a particular concentration.

A Ti0 aqueous slurry was prepared 2 by introducing 190 g of water in a beaker and then adding 612 g of Ti0 2 rutile (Kronos 2310, Tronox CR 828 and Du Pont TI-PURE R 902) and mixing slowly by means of a mechanical mixer until complete homogenization. Forming a slurry which is checked solids content by means of a dry balance. The solids content should be 76.5 ± 0.5%.

Measuring the Brookfield viscosity (ASTM D 2196) of the initial slurry to 100 t / min. Then was added a first amount of dispersing agent and mixed for 5 minutes to obtain a dispersion of particles of Ti0 2 .

Measuring the Brookfield viscosity (ASTM D 2196) of the slurry comprising the dispersing agent to 100 t / min.

claims

1. Copolymer obtainable by a process comprising:

• at least a polymerization reaction:

(A) at least one acid selected from acrylic acid, methacrylic acid and mixtures thereof; and

(B) at least one compound or of at least one ester of a compound derived from an acid selected from acrylic acid, methacrylic acid, itaconic acid and maleic acid;

in the presence of water, at least one initiator compound selected from hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate and mixtures thereof and at least one activator compound selected from hypophosphites of alkali metals including sodium hypophosphite, potassium hypophosphite, and mixtures thereof, and preferably in the absence of sodium thio sulfate;

• the total or partial neutralization by means of at least one compound selected from MgO, CaO, hydroxides of alkali metal, metal hydroxides, alkaline earth metal dihydroxides alkaline earth metal and mixtures thereof.

2. The copolymer of claim 1 wherein the compound (a) is acrylic acid, methacrylic acid or mixtures thereof, or optionally combined with at least one other acid selected from acrylic acid, methacrylic acid, itaconic acid and maleic acid; preferably acrylic acid.

3. Copolymer according to one of claims 1 and 2 wherein the polymerization reaction implements 10 to 90, preferably 30 to 60 by weight of compound (a) with respect to the total quantity by weight of compounds (a) and (b).

4. Copolymer according to one of claims 1 to 3 wherein the compound (b) is a compound of formula (A):

(A)

in which :

• X, identical or different, independently represents a C1-C10 linear or branched alkylene group;

• n is an integer or decimal number from 1 to 5;

• Q represents a group selected from C (O), CH 2 , CH 2 -0 and (CH 2 ) 4-0;

• L represents a direct bond or a CH 2 ;

• R 1 represents H, CH 3 or C (0) OH;

• R 2 represents H or C (0) OH.

5. Copolymer according to one of claims 1 to 4 wherein compound (b) is a compound of formula I), (II), (III) or (IV):

(I) (Π)

(ΙΠ) (IV) wherein:

• X, identical or different, independently represents a linear Ci-ClO alkylene group or branched;

• n is an integer or decimal number from 1 to 5;

• L represents a direct bond or a CH 2 ;

• R 1 represents H, CH 3 or C (0) OH;

R 2 represents H or C (0) OH.

6. Copolymer according to one of Claims 4 or 5 wherein the compound (b) is a compound of formulas (A), (I), (II), (III) or (IV) in which:

• X, identical or different, independently represents a linear Ci-ClO alkylene group or branched, preferably a C 2 linear or branched C4-alkylene, especially an ethylene group, a propylene group or a butylene group;

• n represents a whole or decimal number from 1 to 5, preferably 1;

and wherein:

• L represents a direct bond, R 1 is H and R 2 is H; or

· L is a direct bond, R 1 represents C¾ and R 2 is H; or

• L represents a direct bond, R 1 is H and R 2 is C (0) OH; or

• L represents a group CH 2 , R 1 is C (0) OH and R 2 is H.

7. Copolymer according to one of claims 1 to 6 wherein the polymerization reaction implements 10 to 90, preferably 40 to 70 by weight of compound (b) relative to the total quantity by weight of compounds (a) and (b).

8. Copolymer according to one of claims 1 to 7, the molecular weight (M w ) is from 1 000 to 6 000 g / mol, preferably from 1 500 to 4 000 g / mol.

9. A process for preparing a copolymer comprising:

• at least a polymerization reaction:

(A) at least one acid selected from acrylic acid, methacrylic acid and mixtures thereof;

(B) at least one compound or of at least one ester derivative of an acid compound selected from acrylic acid, methacrylic acid, itaconic acid and maleic acid;

in the presence of water, at least one initiator compound selected from hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate and mixtures thereof and at least one activator compound selected from metal hypophosphites alkali, including sodium hypophosphite, potassium hypophosphite and mixtures thereof, and preferably in the absence of sodium thio sulfate;

• the total or partial neutralization by means of at least one compound selected from MgO, CaO, hydroxides of alkali metal, metal hydroxides, alkaline earth metal dihydroxides alkaline earth metal and mixtures thereof.

10. Use of at least one copolymer according to one of claims 1 to 9 for the preparation of an aqueous dispersion of organic particles, organo-metallic or inorganic.

11. An aqueous dispersion comprising particles of organic, organometallic or inorganic and at least one copolymer according to one of claims 1 to 9.

12. An aqueous suspension or slurry comprising organic particles, organo-metallic or mineral and at least one copolymer according to one of claims 1 to 9.

13. Use of at least one copolymer according to one of claims 1 to 9 for the preparation of an aqueous adhesive composition or an aqueous coating composition, in particular a varnish composition, a paint composition eg decorative painting and industrial painting.

14. An aqueous paint composition comprising:

• at least one film-forming copolymer latex;

• at least one organic or inorganic pigment;

· At least one copolymer according to one of claims 1 to 9.