EP1383843A1

EP1383843A1 - Liquid concentrate of mineral fillers containing grafted polymers and their use for preparing paints in aqueous and/or organic medium

Info

Publication number: EP1383843A1
Application number: EP02759807A
Authority: EP
Inventors: Pierre Legrand; Daniel Lefevre
Original assignee: Peintures Jefco Francis et Jean Dufour Les
Current assignee: Peintures Jefco Francis et Jean Dufour Les
Priority date: 2001-04-05
Filing date: 2002-03-29
Publication date: 2004-01-28
Also published as: EA200300959A1; US20040106715A1; WO2002081581A1; US7193008B2; FR2823213A1; EA005272B1; FR2823213B1

Abstract

The invention concerns a liquid concentrate of mineral fillers comprising an aqueous or organic solvent, mineral fillers useful for making paints, with a dry extract of mineral fillers not less than 65 %, and a grafted copolymer consisting of 1) 5 to 40 wt. %, preferably 15 to 35 wt. %, more preferably still 20 to 30 wt. % of said anchoring sequence(s) consisting of a linear copolymer formed from at least two different monomer units including: a first ethylene monomer unit comprising at least a basic nitrogenous group, a second unsaturated ethylene monomer unit comprising an aromatic group, preferably a phenyl, the weight content in said first monomer units relative to said second monomer units being from 40 to 60 wt. %, preferably about 50 wt. %; 2) 25 to 90 wt. %, preferably 40 to 80 wt. %, more preferably still 50 to 70 wt. % of said organo-soluble hydrophobic sequence(s) to disperse the particles in apolar medium; and 3) 5 to 70 wt. %, preferably 15 to 30 wt. %, more preferably still 10 to 20 wt. % of hydrophilic sequences comprising a water-soluble polymer.

Description

Liquid concentrate of mineral fillers containing grafted copolymers and their use for the preparation of paints in an aggressive and / or organic medium

The invention relates to concentrates of mineral fillers comprising graft copolymers comprising at least three sequences of distinct chemical natures, among which at least one sequence for anchoring on solid particles consisting of mineral fillers, at least one sequence of hydrophobic nature and at least one sequence of hydrophilic nature.

The term “sequence of hydrophilic nature” or “sequence of hydrophobic character” is understood here to mean that said sequence is more hydrophilic or respectively more hydrophobic than the other two said sequences.

The invention also relates to a method for preparing paint using said liquid concentrates of mineral fillers.

In said liquid concentrates of mineral fillers, said copolymers are used as a dispersing agent, stabilizer of solid particles and / or emulsifier in an aqueous and / or organic medium, as well as their use for the preparation of paints in an aqueous medium and / or organic.

At the end of their manufacturing process, the mineral fillers used in paints are in the form of aggregates or agglomerates. Their incorporation into a liquid, in order to obtain a stable suspension, therefore requires a dispersion step beforehand, a step during which these assemblies are dissociated into elementary particles under the effect of significant mechanical stresses.

The action of these mechanical forces cannot however be effective in the absence of a dispersing agent.

WO 97/28200 describes copolymers which are said to be

"Universal", that is to say mixtures or compatible with other compositions of binders, solvents and additives or pigment compositions, in order to prepare paints which can either be paints in an aqueous medium or a solvent medium. These graft copolymers are therefore used as dispersing and / or stabilizing agents for solid particles and / or emulsifier in an aqueous and / or organic medium, and / or compatibilizing in an aqueous and / or organic medium.

As a dispersing agent for solid particles in an aqueous and / or organic medium, the copolymers facilitate and complete the mechanical dispersion by good wetting of the particles by the continuous phase, and by eliminating the air film which surrounds them.

These copolymers are involved at each stage of the dispersion. First, they ensure good wetting of the particle by the continuous phase, replacing the air film surrounding the surface of the solid with liquid molecules.

Then, they significantly improve the efficiency of the dissolver / crusher during the deagglomeration phase of the associations.

To be effective, a copolymer which can be used as a dispersant must therefore comprise an anchoring sequence, having a good affinity for the surface of the particles, as well as one or more sequence (s) compatible with the continuous phase in which these solids are incorporated. In the absence of one of these constituents, or in the event of desorption of the dispersant, one attends the flocculation of the system, phenomenon which is manifested by the re-agglomeration of the particles, and an increase in viscosity of the dispersion. In the particular case of a paint, poor dispersion of the mineral fillers within the binder results in rapid sedimentation of the charge agglomerates in the paint with an increase in its viscosity. In addition, there is a drop in opacity and hiding power of the paint and a decrease in surface gloss and durability over time of the paint film.

As a stabilizing agent for solid particles in an aqueous and / or organic medium, the copolymers adsorb on the surface of the solid and coat the particles and constitute a layer of solvated copolymers which cause steric repulsion forces, as well that, in the case of polyelectrolytes in an aqueous medium, electrostatic repulsion forces, which oppose the attractive Van der Waals forces, thus ensuring the stability of the dispersion. It is therefore necessary that the anchoring sequence is strongly adsorbed on the surface of the solid particle for example by Van der Waals bonds and that one of the two other sequences respectively hydrophilic and hydrophobic, develops to create forces of steric repulsion and / or electrostatic repulsion depending on the environment of use.

As an emulsifying agent in an aqueous and / or organic medium, when the continuous phase of a dispersion of solid particles is not miscible with the continuous phase of the paint which receives it, the copolymers facilitate and complete the mechanical emulsification of the phase continues from the first into the second. The emulsifying effect of the copolymer develops as soon as the copolymer has hydrophilic and hydrophobic sequences long enough and numerous to deploy each in its respective affinity medium, water / organic solvent. The anchoring sequence plays little role in the emulsifying effect.

As a compatibilizing agent for preparing the dispersion of solid particles in an aqueous and / or organic medium with respect to the other constituents of the paint. The compatibilizing effect of the copolymer is optimized if the conditions of the stabilizing effect and of the emulsifying effect are met.

The plurality of chemical functions within the same copolymer, as well as the possibility of formulating dispersions of solid particles without elongation resin and / or without surfactants, improve compatibility with the resins, thus allowing the formulation of paints from a wide range of binders in aqueous and / or organic phase.

These copolymers contain a block allowing their anchoring on the solid particles, as well as at least 2 blocks of hydrophilic / water-soluble and hydrophobic / organosoluble character respectively, authorizing their use in compositions in aqueous and / or organic medium. The presence of an insoluble sequence in a selective medium surprisingly increases the amount of dispersant adsorbed on the surface of the particles, thus avoiding the flocculation phenomenon when mixing different pigments.

In WO97 / 28200, a graft copolymer consists of:

1/1 to 80% by mass, preferably 5 to 40% by mass, of one or more anchoring sequence (s) on the solid particles, consisting of a hydrocarbon chain, linear or branched, cycloalkyl or aromatic, comprising basic nitrogen groups of type: heterocyclic, -NH2, -NH-, -NHR, -NR2, - CONH2, -CONHR, -CONR2 (where R is an (C1-C6) alkyl radical, optionally substituted by one or more group (s) -OH, -COO-, -CO-, -O-, -SO3H), and whose molecular mass is between 150 and 10,000, preferably between 300 and 3000, the mass content of basic nitrogen monomers in the anchoring chain being at least 5%, and preferably 30%, and

2/10 to 90% by mass, preferably 25 to 80% by mass, of one or more sequence (s) of hydrophobic nature, consisting of a hydrocarbon chain, linear or branched, cycloalkyl or aromatic, which may contain groups - COO-, -S-, -F, -Si (OR ') n (R ") 2-n- (where R' and R" represent alkyl or aryl radicals, similar or different, in C1-C10, and n = 0 to 2), formed from monomer units whose solubility parameter is less than or equal to 21.5 J1 / 2 / cm3 / 2, preferably less than 19 J1 / 2 / cm3 / 2, and whose molecular mass is between 250 and 10,000, preferably between 500 and 3,500, and

3/10 to 90% by mass, preferably 15 to 70% by mass, of one or more sequence (s) of hydrophilic nature, constituted by a hydrocarbon chain, linear or branched, comprising groups -O-, - OH, -NCO-, -COO-, -COOH, - CONH2, -CONHR '"(where R'" is a (C1-C3) alkyl radical), -NH-, -S-, -SO3H, formed (s ) of monomer units whose solubility parameter is greater than 22 J1 / 2 / cm3 / 2, preferably greater than 22.5 J1 / 2 / cm3 / 2, and whose molecular mass is between 250 and 10,000, preferably between 300 and 3000.

The anchoring sequences are preferably produced by radical copolymerization of monomers comprising ethylenic monomers carrying basic nitrogen groups, these nitrogen monomers being arranged statistically along the chain.

In WO97 / 28200, it has been proposed as an anchoring sequence to copolymerize the nitrogenous monomers mentioned above with one or more ethylenic unsaturated monomer (s). When trying to modify certain properties, such as the glass transition temperature, stability or even mechanical properties. However, in the preferred embodiments, the anchoring sequences only include ethylenic monomers comprising nitrogen groups, to the exclusion of any other monomer. In WO97 / 28200, the preferred graft copolymers have been specially developed for producing liquid concentrates of pigment dyes and include:

a main anchoring chain on the solid particles comprising dialkylaminoethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine groups,

N, N-dimethylacrylamide, alone or as a mixture,

one or more hydrophilic poly (ethylene oxide) grafts, and

- one or more hydrophobic grafts based on alkyl (meth) acrylates, on vinyl esters alone or copolymerized with styrenic and alkylstyrenic derivatives, fluorinated monomers (trifluoroethyl methacrylate), or 3- (trimethoxysilyl) propyl methacrylate .

These liquid concentrates of pigment dyes contain a dry extract of coloring pigments, less than 60% by weight.

These copolymers do not make it possible to obtain liquid concentrates of colorless mineral fillers of the carbonate, silicate, sulphate and silica type used in paints, in particular those listed in Table 2 of Example 2, which are suitable for the modular manufacture of paint. , that is to say with dry extracts of said colorless mineral fillers representing a weight content greater than or equal to 65% by weight of the liquid concentrate.

Said colorless mineral fillers in a paint are the main constituent with the binder; they provide a thick microporous and opaque structure, and give the paint a specific mat, satin or shiny surface finish. And, a paint should preferably contain at least 45 to 50% of dry extract of these colorless mineral fillers.

The qualifier "colorless" and the generic expression "colorless mineral filler" are used here to better distinguish these thickening and opacifying mineral fillers from paints of the carbonate, silicate, sulphate and silica type, compared with the mineral coloring pigments used for coloring the paintings.

More particularly, a "colorless mineral filler" is defined as a powdered mineral substance, practically insoluble in aqueous or organic suspension media, having a refractive index of less than 1.7. As soon as it is introduced into an aqueous or organic medium, it becomes colorless thanks to the refraction phenomenon linked to the difference in refractive index between the medium and the powdered material. This refractive index is due to the crystallographic structure and the chemical nature of the mineral compound concerned.

The object of the present invention is to provide a liquid concentrate of colorless mineral fillers, also called a “mineral fill module”, comprising universal copolymers having the properties listed above in a solvent or aqueous medium, and having an extract content. dry of high loads, in particular a weight content of dry extract of load greater than or equal to 65%, while being stable and compatible with the other constituents of paints, so as to be able to directly prepare the paints with these load modules.

It is in fact advantageous to be able to prepare paints with liquid charge modules, therefore storable in tanks, pumpable, dosable automatically and easily mixable to make the manufacture of a paint.

fast and economical. This reduces the manufacturing times of paints, as well as the costs of stocking raw materials in number and quantity, as well as the costs of manufacturing and formulating paints. And, this also increases the diversification of paints, as well as the flexibility of production and automation of paint production.

Insofar as the load modules are the majority constituent of paints, and that the paints must have a dry extract with a weight content of at least 45% and have good application qualities, it is necessary to have mineral charge modules with the highest possible dry solids content, in particular at least 65%.

These load modules must be liquid in order to be storable, pumpable and dosable using traditional equipment available in the paint industry. The term “liquid” is understood here to mean a fluid whose rheological characteristics measured at 20 ° C. are as follows:

- flow threshold less than 15 N / m ² , and

- viscosity at 500 s ^"1 , less than 40 Pa.s. These load modules must be stable to remain homogeneous during their transport and storage: neither decantation nor syneresis should be noted when they are held without temporary agitation. And, no flocculation of the solid particles should be noted on contact with the other constituents of the paint during the incorporation into the paint formula.

The problem posed by the present invention is therefore to develop specific copolymers corresponding to these additional properties allowing the preparation of a concentrate of mineral fillers with a high dry extract content, liquid and stable, in combination with the preceding properties sought for copolymers ( dispersion, stabilization, emulsification).

Another problem underlying the present invention is to be able to provide effective copolymers for the various types of mineral fillers used in paints, in particular fillers constituted by aluminum oxide and hydroxide, in particular silica, such as quartz, silicate, such as talc, kaolin and mica, barium sulfate, or calcium carbonate, such as chalk, calcite, dolomite and marble.

Another object of the present invention is to provide modules of said colorless mineral fillers which allow paints to be easily prepared by a simple mixture of liquid concentrates without the addition of external solid matter.

It appears from the tests carried out by the inventors that it is difficult to obtain a copolymer which meets all of the properties sought according to the objectives of the present invention.

In particular, an antagonism between the dispersing power and the stabilizing power of a copolymer has been found. A copolymer endowed with good dispersing functions, will tend to provide liquid concentrates of colorless mineral fillers of high dry extracts, but not very stable and not very compatible. Conversely, a copolymer having high stabilizing properties will tend to provide a liquid concentrate of colorless mineral fillers of reduced dry extracts, but with higher stability and compatibility.

In addition, it is likely that the ionic environment of the mineral charges will interfere with the chemical affinity and absorption between the anchoring sequence. polymers and said solid particles. Thus, mineral fillers of the silica type have many hydroxyl groups on the surface, while fillers of the carbonate type have carboxylic groups on the surface.

The various objectives of the present invention are achieved with a liquid concentrate of colorless mineral fillers useful for the manufacture of paint, comprising an aqueous or organic solvent, said mineral fillers and a graft copolymer comprising at least three sequences of distinct chemical natures, among which at least one anchoring sequence capable of being absorbed on solid particles consisting of said mineral fillers, at least one sequence of hydrophobic character and at least one sequence of hydrophilic character, characterized in that it comprises a dry extract of said mineral fillers greater than or equal to 65% by weight of said liquid concentrate, and said copolymer consists of:

1/5 to 40%, preferably 15 to 35%, more preferably 20 to 30% by mass content of said anchoring sequence (s) constituted (s) by a linear copolymer constituted from at at least two separate monomer units comprising:

a first ethylenic monomer unit comprising at least one basic nitrogen group preferably chosen from -NH2, -NH-, -NHR, -NR ₂ , - CONH, -CONHR, R representing a C1-C6 alkyl radical, and the groups heterocyclic, pyridine type,

a second unsaturated ethylenic monomer unit comprising an aromatic group, preferably a phenyl,

the mass content of said first monomer units with respect to said second monomer units being from 40 to 60%, preferably about 50%.

2/25 to 90%, preferably 40 to 80%, more preferably 50 to 70% by mass content of said hydrophobic sequence (s) comprising an organosoluble polymer, and

3 / from 5 to 70%, preferably 15 to 30%, more preferably 10 to 20% of mass content (s) of hydrophilic block (s), comprising a water-soluble polymer. The anchoring sequences as defined above make it possible to obtain liquid concentrates of mineral charges with high dry extracts while being stable and compatible with the other constituents of the paints, both in a solvent medium and an aqueous medium, and this for the different fillers of mineral type used in paints.

The reasons why these anchoring sequences, and more generally the copolymers as defined according to the present invention, are particularly suitable for the application sought after according to the present invention, are not fully understood by the inventors. It seems that the two types of monomers of the anchoring sequence make it possible to establish both hydrogen bonds between the nitrogen groups and the hydroxyl groups of the charges in solvent medium or the carboxyl groups of the charges in aqueous medium, as well as polar bonds. between the aromatic groups and said hydroxyl and carboxyl groups.

The inventors also hypothesize that, in a solvent medium, the basic nitrogen groups tend to exert a repulsive effect with respect to the solvent, which propels the aromatic groups towards the mineral charge and accentuates the polar bonds. And, conversely, the aromatic groups exert a repellent effect on aqueous media, propelling the nitrogen groups towards the mineral charges and accentuating the hydrogen bonds with their hydroxyl and carboxyl environment.

The synthesis of these graft copolymers is based on the use of the "macromonomer" technique and / or the grafting of functionalized telomeres on a preformed linear or grafted chain. Thus, they can be prepared by radical copolymerization of one or more hydrophilic macromonomer (s) and of one or more hydrophobic macromonomer (s) with one or more nitrogenous comonomer (s).

These syntheses are carried out under an inert atmosphere in the presence of a suitable solvent or mixture of solvents, that is to say in which the reagents, macromonmers, comonomers are completely soluble and the final products are totally or at least partially soluble. These solvents will in particular be chosen from aromatic hydrocarbons such as toluene or xylene; ethers such as dioxane or tetrahydrofuran; ketones such as acetone or methyl ethyl ketone; esters such as ethyl acetate or butyl acetate. We preferably use dioxane or tetrahydrofuran when preparing the graft copolymers.

The synthesis begins with the preparation of the macromonomers, by telomerization then fixation of a double bond at the end of the chain, step followed by the copolymerization of said macromonomers with the comonomers.

One can also prepare the grafted copolymers according to the invention by fixing one or more functionalized molecule (s), one of the two types of hydrophilic or hydrophobic grafts, or even the two types of grafts, on a polymer preformed with the using reactive monomers, this chain may already contain one or more hydrophilic or hydrophobic graft (s) incorporated by radical route. In this case, the course of the reaction requires the use of at least two separate reactors, the first serving for the preparation of the main chain, the second intended for the preparation of the telomer.

The grafting of these side chains on the preformed polymer can then be carried out by adding the content of the reactor (s) containing the telomeres to the first.

The graft copolymers according to the invention have, distributed along their anchoring sequence, monomeric units comprising basic nitrogen groups, arranged in a statistical fashion.

Said basic groups can be defined by their pKa, between 2 and 14, preferably between 5 and 14, in particular between 5 and 12. The measurements of pKa are carried out at 25 ° C. in water at a concentration of 0, 01 molar.

The invention therefore relates to a liquid concentrate of colorless mineral fillers comprising a graft copolymer as defined above in which the anchoring sequence (s) more particularly comprises:

1. - said first monomers with basic nitrogen groups introduced from one or more compound (s) chosen from vinylpyridine and preferably aminoalky! (Meth) acrylate of formula I below:

where H is a hydrogen atom or a (C1-C4) alkyl radical; R ₂ and R _{3, which are} identical or different, each represent a hydrogen or a (C1-C4) alkyl radical, n = 0 to 6, and

2. - Said second monomer of the anchoring sequence consists of a monomer of formula II below:

R 5, R_ \ /

C = = c

/ \

R ₆ R7 (il)

in which

- R ₄ , R ₅ , R ₆ are identical or different and each represents a hydrogen or a C1-C4 alkyl radical, preferably hydrogen,

- R ₇ represents an aromatic group, in particular a phenyl group optionally substituted, in particular by a C1-C4 alkyl radical.

Said first monomer can in particular be an aminoalkyl methacrylate or else a vinylpyridine.

Said second monomer can in particular be a styrene or alkylstyrene such as and methylstyrene or tert-butylstyrene.

More particularly, in said anchoring sequence, said first monomer is the monomer of 2-dymetylaminoethyl methacrylate (MADAME) and said second monomer is styrene.

The sequence (s) with hydrophobic character is (or) are chosen (s) so that their solubility properties are complementary to those of the sequence (s) with hydrophilic character mentioned below, in order to give the bigreffe copolymer its character as a universal dispersant with respect to solvents and binders. Advantageously, said hydrophobic sequence consists of a hydrocarbon chain comprising -COOR ₁₀ - groups, in which R ₁₀ is a C1-C10 alkyl radical and, preferably, a C4-C8 alkyl radical.

Preferably, said hydrophobic sequence is obtained from a macromonomer of formula (III) below:

^R 5, ^R 4

\ /

C = C 6 (III) in which:

- R ₄ , R ₅ , R ₆ are identical or different and each represents a hydrogen or a C1-C4 alkyl radical, preferably a hydrogen,

- R ₈ consists of a polymer, the monomer units of which contain groups - COOR ₁₀ -, in which R _i0 is a C1-C10, and preferably C4-C8, alkyl radical.

The organosoluble polymers formed from monomer units whose solubility parameter less than or equal to 21.5 J1 / 2 / cm3 / 2, preferably less than 19 J1 / 2 / cm3 / 2, constitute these sequences of hydrophobic nature and make it possible to disperse the particles in an apolar medium.

The incorporation of this sequence (s) or graft (s) into the copolymer can be carried out by radical copolymerizing one or more organosoluble macromonomer (s) with one or more ethylenic comonomer (s) ) unsaturated (s) mentioned above in the description of the anchoring sequence, namely one or more ethylene nitrogenous monomer (s), optionally one or more ethylenic monomer (s) ) unsaturated neutral (s) and at least one hydrophilic macromonomer described below (from the initiators usually used, for example organic peroxides, redox systems, or preferably azo compounds), and will lead to the formation of a bigreffe copolymer.

These hydrophobic grafts can also be fixed by radical copolymerization or by grafting on a linear or branched copolymer consisting of one or more ethylenic nitrogenous or unsaturated monomer (s) mentioned above in the description of the anchoring sequence, and / or one or more macromonomer (s) to hydrophilic character described below.

Preferably, said hydrophobic sequences according to the invention have a hydrophobicity such that the solubility parameter of the monomers of the hydrophobic sequence is less than 22.5 J ^1/2 / cm ^3/2 .

The solubility parameters expressed in J ^1/2 / cm ^3/2 , were calculated by the increment method of Hoftyzer-Van Krevelen or measured experimentally (case of polydimethylsiloxane). The molar volumes required when calculating the solubility parameters are calculated from the data of Feedor. These calculation methods and experimental values are exposed in the work: DW VAN KREVELEN, "Properties of polymers. Their correlation w / t chemical structure; their numerical estimation and prediction from additive group contributions", Third edition, Elsevier, 1990, p . 189-225.

More particularly, according to the invention, the monomer units constituting the macromonomers used to prepare the sequence (s) of hydrophobic nature are preferably compounds of formula IV below:

in which :

- R ' _s represents COOR ₁₀ , with R ₁₀ which is a C1-C10 alkyl, preferably substituted by a C4-C8 alkyl radical.

More particularly, in said formula IV above, R'8 is an ethylhexyl methacrylate (EHMA).

The hydrophilic sequence (s), distributed statistically along the main chain of the copolymer, are at the origin of the solubility of the copolymers in water. It is these sequences which stabilize the dispersions of particles in an aqueous medium. The solubility parameter of the monomer units constituting these hydrophilic grafts is greater than or equal to 22 J ^{1 2} / cm ^3/2 , preferably greater than 22.5 J ^{1 2} / cm ³² .

Advantageously, said hydrophilic sequence consists of a hydrocarbon chain comprising groups chosen from -O-, -OH, and -COOH.

The introduction of these side chains into the copolymer can be carried out using one or more macromonomer (s) of hydrophilic nature. A macromonomer of this type consists of a water-soluble polymer terminated at one of its ends by a group which can be polymerized in a radical manner.

Preferably, said hydrophilic sequence is obtained from a macromonomer of formula (V) below:

R ₅ R ₄ \ /

C = C

^//

R, ^

(V)

- R, R ₅ , Rβ are identical or different and each represents a hydrogen or a C1-C4 alkyl radical, preferably a hydrogen,

- R ₉ is a hydrophilic block consisting of a polymer, the monomer units of which comprise groups chosen from -O-, -OH, - COOH.

The copolymerization of one or more of these hydrophilic macromonomer (s) with one or more ethylenic unsaturated comonomer (s) mentioned above in the description of the anchoring sequence, namely one or more several compound (s) a) one or more ethylenic unsaturated monomer (s) neutral (s), and at least one macromonomer of hydrophobic character described above (from the initiators usually used, for example the organic peroxides, redox systems, or preferably azo compounds) will lead to the formation of a bigreffe copolymer according to the invention. These hydrophilic grafts can also be fixed by radical copolymerization or grafting on a linear or branched copolymer consisting of one or more ethylene nitrogenous or unsaturated monomer (s) mentioned above in the description of the anchoring sequence.

As mentioned previously, in a graft copolymer according to the invention, the hydrophilic block is of a chemical nature distinct from said hydrophobic block, as well as from said anchoring block on the one hand, and on the other hand, the hydrophilicity of the hydrophilic sequence is greater than that of said hydrophobic and anchoring sequences.

Preferably, said hydrophilic blocks have a hydrophilicity such that the solubility parameter of the monomers of the hydrophilic block is greater than 22.5 J ^1/2 / cm ³ ' ² , more preferably still greater than 24 J ^1/2 / cm ³² .

According to the invention, the monomer units constituting the macromonomers, used to prepare the sequence (s) of hydrophilic nature will preferably be chosen from:

- ethylene oxide,

- (meth) acrylic acids, maleic acid, fumaric acid, itaconic acid,

More preferably, in formula (V) above, R ₉ is polyethylene glycol.

More particularly, the graft copolymers according to the invention are prepared by the radical route ("macromonomer" technique), from macromonomers such as:

(meth) acrylates of poly (ethyleneglycol) preferably of molecular mass greater than or equal to 500, such as HEMA-10, sold by Bimax Chemicals Ltd.

Advantageously, the molecular weight of the graft copolymer is between 5,000 and 25,000, preferably between 10,000 and 20,000. Said copolymers can be prepared by radical copolymerization from macromonomers and / or by grafting of functionalized polymers on a preformed chain, and therefore have a well-controlled structure.

This synthesis mode also offers the possibility of adjusting the molecular mass of the anchoring sequence, in order to increase the adsorption rate of the copolymers on the particles, both mineral and organic, as well as that of the side chains. , improving their compatibility with the continuous phase.

Thus, by using the graft copolymers according to the invention for the preparation of pigment concentrates, a dispersion state is obtained which is higher than that obtained from the dispersants of the prior art. In addition, the high molecular weight of the products according to the invention makes it possible to prepare pigment concentrates without elongation resin.

The radical copolymerization is preferably carried out at a temperature between 50 ° C and 140 ° C, and the grafting reaction at a temperature preferably between 20 ° C and 150 ° C.

Advantageously, the order of addition of the monomers during the radical copolymerization is as follows:

the macromonomers, of high molecular mass and therefore less reactive, are incorporated from the start in the reactor, with the solvent;

- The comonomer (s) constituting the main chain, which are more reactive, are introduced continuously over time, so that their concentration is always low compared to that of the macromonomers.

According to a first variant, a process for the preparation of a graft copolymer as defined above comprising at least three sequences of distinct chemical nature, among which an anchoring sequence on the solid particles, one or more sequence (s) with character hydrophobic and one or more sequence (s) of hydrophilic nature, in which the main chain is an anchoring sequence on the solid particles, characterized in that the radical copolymerization of: i) said first monomer (s) comprising at least one basic nitrogen group, in particular monomers of formula I above, and said second monomers comprising an aromatic group, in particular monomers of formula II above

ii) hydrophobic macromonomers represented by formula III:

^R 5 / ^R 4

\ / C = C

^R 6 ^R 8 (, „) where R, R ₅ , R ₆ , and R ₈ have the meanings given above.

iii) of said hydrophilic macromonomers represented by formula V:

where R4, R5, R6 and R9 are as defined above.

The invention also relates to said copolymer in the form of one of its salts, obtained by quaternization or neutralization of the basic functions.

The subject of the present invention is a liquid concentrate of mineral fillers comprising a solvent which may also be an aqueous or organic solvent, colorless mineral fillers useful for the manufacture of paints, preferably carbonate, silicate, silica and / or sulfate, and additives, characterized in that it comprises a graft copolymer as defined above.

It should be recalled here that by “liquid” is meant here a fluid whose rheological characteristics measured at 20 ° C. are as follows:

- flow threshold less than 15 N / m ² , and

- viscosity at 500 s ^"1 less than 40 Pa.s. The liquid mineral filler concentrate according to the invention comprises a dry extract of mineral filler, preferably greater than or equal to 70%.

More preferably, the liquid concentrate according to the present invention comprises a dry extract of said graft copolymer whose weight content represents from 10 to 15% of the weight of said liquid concentrate.

The formulation of load modules according to the invention makes it possible to reduce:

- paint manufacturing times to a few minutes,

- the cost of holding stocks of raw materials (number and quantity), and

- the costs of manufacturing and formulating paints and increasing the diversification of paints and creativity (new paints), as well as production flexibility and finally automating the production of paints.

The present invention also relates to a process for preparing paint using a liquid mineral filler concentrate according to the invention, which is mixed with the other constituents of the paint, such as dyes, binders in an organic or aqueous medium, and other additives, in particular drying agents or bactericidal agents, anti-foaming agents as explained in Example 3..

Other characteristics and advantages of the present invention match in light of the detailed embodiments which follow.

EXAMPLE 1: PREPARATION OF COPOLYMERS

1.1. - Protocol

The various components are added in a tank, in semi-batch, so as to avoid too great a drift in composition, due to a different reactivity of the various reagents. The copolymerization takes place at 80 ° C.

The conditions are described below:

Composition of the base

EHMA macromere: 200 g HEMA 10 macromer 44 g

STYRENE 40 g

MADAME 40 g

AIBN 4 g

THF 900 g

Total tank 1228 g

At the end of the addition for the base stock, the reactor is left at 80 ° C. for approximately 10 hours to obtain total conversion.

The solution obtained, once cooled, has a clear appearance without gel formation.

The phase change of the copolymer obtained is done by adding it to the aqueous phase and the exchange is done by azeotropic distillation.

The final suspension of copolymer in the aqueous phase is translucent after cooling.

2.2. - Example of copolymers

The characteristics of some of the copolymers prepared are collated in Table 1.

Copolymers Nos. 7, 8, 10, 12, 14, 17 and 20 comprise anchor sequences according to the invention. Copolymers Nos. 7, 8, 10, 12 and 20 include a preferred anchor sequence.

Among these, the copolymers No. 10, 12, and 17 comprise a preferred hydrophobic block according to the invention (EHMA), and the copolymers No. 7, 10, 14, 17 and 20 comprise a preferred hydrophilic block according to the invention (HEMA-10). TABLE 1

(1) MADAME: 2-dimethylaminoethyl metacrylate.

(2) PLMA: lauryl polymethacrylate Molar mass: 3000, Polydispersity index 1.40

(3) Molar mass: 2000, Polydispersity index: 1.26

(4) Molar mass: 2700, Polydispersity index: 1.80

10

EXAMPLE 2 PREPARATION OF LIQUID CONCENTRATE OF MINERAL LOADS

These liquid concentrates of mineral fillers are hereinafter called "load modules".

2.1. - Operating procedure

Two types of load modules have been prepared.

Liquid concentrates of charge materials are prepared, called charge modules of the following two types:

The procedure for manufacturing the load modules is as follows, which can be applied to the different types of load materials, comprises the following successive steps:

1 - introduction of water or solvent into a tank

2 - addition of the quantity of copolymers

3 - placing of the tank under a variable speed agitator with a dispersion disk adapted to the size of the tank

4 - gradual introduction of the charges with stirring at moderate speed (500-800 rpm).

This first phase is defined as the mashing phase which makes it possible to wet the surface of the filler with the copolymer; the charge is not yet in its state of maximum dispersion (complete separation of the particles forming charge agglomerates); a mashing time of approximately 20 minutes to 40 minutes according to the characteristics of the load. Some additives are also added during this mashing phase

5 - The "grinding" operation is carried out by increasing the dispersion speed around 1500 rpm with a significant peripheral speed around 15-20 m / second. In this designation of grinding, it is not a question of grinding the elementary particles of fillers but of dispersing these particles contained in the agglomerates (grinding of the agglomerates). The grinding time can vary from 20 minutes to 60 minutes depending on the nature of the load and especially its particle size, its specific surface. The second part of additives can be added at the end of grinding.

6 - The module characteristics are checked by measuring:

- Dry extract

- Rheological characteristics

- Stability, compatibility

2.2. Types of charges used

The characteristics of the mineral fillers used in the examples are explained in Table 2 below.

2.3. Examples of modules

The examples of modules have been brought together in table 3 below, with copolymers n ° 1 to n ° 20 of example 1.

1 - Stability test:

Scale used in the tables

3-good 2-satisfactory 1-poor

The stability test is carried out on the modules but also on the paints made from the mixture of modules. This test is carried out on a module sample which is placed for 3 weeks in an oven at 50 ° C. 3 boxes of 200 ml are prepared and checked before introduction into the oven.

At the end of each week we take out a box from the oven and after a night of waiting to stabilize its temperature (at room temperature) the following checks are performed to analyze whether the stability is good or not:

- verification of the module in the box: presence or not of a rise to the surface (syneresis), or decantation (presence of a deposit at the bottom of the box, hard, soft, important or not deposit)

- viscosity measurement and comparison with control before baking: analysis to check whether the product has become fluid, or has thickened, or hardened.

These observations and measurements are made after 1, 2, and 3 weeks; according to the different analyzes the module is classified on the scale above.

2 - Compatibility test:

Scale used in the tables

3-good 2-satisfactory 1-poor

The compatibility test must make it possible to check the physicochemical behavior of the module mixed with other modules or constituents of a modular paint: resin (binder), solvent, water, etc.

The module is mixed in predetermined proportions with several constituents in the 50/50 ratio:

- a binder in the aqueous phase - a binder in the solvent phase

After mixing with a disc stirrer, at a speed of around 600 rpm, the mixture is analyzed: - product observation: presence of agglomerate, phase separation, sedimentation, etc.

- viscosity measurement,

- application with an applicator calibrated at 100 microns on a support commonly used in painting, a contrast card, to check in wet the transparency of the deposited film and then dry after drying,

- verification of the characteristics of the dry film: opacity, gloss.

Based on this analysis, the module will be classified according to the above scale more or less compatible.

From these results, it appears that it is possible to obtain a dry extract concentrate with a charge greater than 65%, while having good or at least satisfactory compatibility and stability properties only for copolymers comprising two types of monomers in the anchoring sequence, in accordance with the present invention, namely copolymers no. 7, 8, 10, 12, 14, 17 and 20.

The highest dry extracts are obtained with the anchoring sequences composed of MADAME and styrene (copolymers 7, 8, 10, 12 and 20).

Furthermore, copolymers with hydrophobic blocks with moderate hydrophobicity obtained with macromers (EHMA) and hydrophilic blocks with high hydrophilicity obtained with HEMA-10 macromers (copolymers 7, 8, 10 and 17) have the best stability and compatibility.

TABLE 2 - Types of loads used

a

TABLE 3

(1): short chain polymer dispersant on the market

EXAMPLE 3 - PREPARATION OF MODULAR PAINTS

3.1. Operating procedure

Two types of paints are prepared with the load modules.

The modular components are all liquids, therefore storable in tanks, pumpable, dosable automatically and easily mixed.

The manufacture of a paint can therefore be quick and economical.

The procedure for manufacturing modular paints which can be applied to all mass or volume combinations between the various liquid constituents comprises the following successive steps:

1 - introduction of the various constituents into a tank

2 - placing of the tank under a variable speed agitator with a mixing propeller suitable for mixing liquids relative to the size of the tank with a mixing time of approximately 20 minutes at a speed of 700 rpm. The mixing can also be done with an agitator of the vibrational agitator type on packages of 1 to 20 liters in which the various liquid constituents have been dosed. The mixing takes place after closing the lid and shaking the packaging by the agitator for a time of approximately 5 minutes.

3 - The checks on the characteristics of the paints are carried out by measuring the following parameters:

• For liquid paint: - Density (g / cm ₃ )

- Dry extract

- Viscosities

- Stability

• For dry film:

- Color coordinates

- Opacity

- Surface gloss

The paint formulas prepared are explained in Table 5.

The best results are obtained with modules A and H comprising copolymers 10 and 7.

TABLE 5

(1}: Aqueous dispersion of an acrylic thermoplastic - styrene copolymer at 50% dry

(2): Alkyd resin at 65% of oil length and 60% of dry extract dissolved in white spirit with less than 1% of aromatic solvent.

(3): Additives adjusted to control the independent characteristics of the charge modules: defoamers, bactericides, rheology agents, driers, ...

(4): 3 = good.

2 = satisfactory. 1 = weak.

Claims

1. Liquid concentrate of colorless mineral fillers useful for the manufacture of paints comprising an aqueous or organic solvent, said mineral fillers and a graft copolymer comprising at least three sequences of distinct chemical natures, among which at least one anchoring sequence suitable for s '' absorb on solid particles consisting of said mineral fillers, at least one sequence of hydrophobic nature and at least one sequence of hydrophilic nature, characterized in that it comprises a dry extract of said mineral fillers greater than or equal to 65% by weight of said liquid concentrate, and said copolymer consists of:

a first ethylenic monomer unit comprising at least one basic nitrogen group preferably chosen from -NH2, -NH-, -NHR, -NR ₂ , - CONH ₂ , -CONHR, R representing a C1-C6 alkyl radical, and the heterocyclic groups,

2/25 to 90%, preferably 40 to 80%, more preferably 50 to 70% of mass content of hydrophobic block (s) comprising organosoluble polymers, and

3 / from 5 to 70%, preferably 15 to 30%, more preferably 10 to 20% of mass content (s) of hydrophilic block (s), comprising water-soluble polymers.

2. Liquid concentrate according to claim 1, characterized in that said copolymer comprises a said anchoring sequence consists of a chain hydrocarbon comprising monomeric units constituted from vinyl pyridine, or preferably aminoalkyl (meth) acrylate of formula (I) below:

. n is an integer from 0 to 6,

Ri is hydrogen or a (C1-C4) alkyl radical,

. R ₂ and R ₃ are the same or different and each represents a hydrogen or a C1-C4 alkyl radical.

3. Liquid concentrate according to claim 1 or 2, characterized in that said second monomer of the anchoring sequence consists of a monomer of formula II below:

R ₅ c = = c Λ

/ \

R ₆ Ry Cl)

in which :

- R, R ₅ , R ₆ are identical or different and each represents a hydrogen or a C1-C4 alkyl radical, preferably a hydrogen,

- R ₇ represents an aromatic group, in particular an optionally substituted phenyl group.

4. Liquid concentrate according to claim 1 or 2, characterized in that in said anchoring sequence, said first monomer is the 2-dymetylaminoethyl methacrylate monomer and said second monomer is styrene.

5. Liquid concentrate according to one of claims 1 to 4, characterized in that said hydrophobic sequence consists of a hydrocarbon chain comprising -COOR ₁₀ - groups, in which R ₁₀ is a C1-C10 alkyl and, preferably also OH groups.

6. Liquid concentrate according to claim 5, characterized in that said hydrophobic sequence is obtained from a macromonomer of formula (III) below:

R ₅ R ₄

\ /

C = C

(III)

in which :

- R ₈ consists of a polymer, the monomer units of which contain groups - COOR ₀ in which R ₁₀ is a C1-C10- alkyl, and preferably a C4-C8 alkyl.

7. Liquid concentrate according to claim 6, characterized in that in said hydrophobic sequence of formula III, R8 consists of monomeric units of formula (IV) below:

R ₅ A

\ /

C = C

R ₆ ^R s _(IV)

in which :

- R's represents COOR ₁₀₎ with R which is a C1-C10 alkyl radical, preferably substituted by a C4-C8 alkyl radical.

8. Liquid concentrate according to claim 7, characterized in that in said formula 4, R ₉ is an ethylhexyl methacrylate.

9. Liquid concentrate according to one of claims 1 to 8, characterized in that said hydrophilic sequence consists of a hydrocarbon chain comprising groups chosen from -O-, -OH, -COOH.

10. Liquid concentrate according to one of claims 1 to 9, characterized in that said hydrophilic sequence is obtained from a macromonomer of formula

(V) following:

R R,

/

= C

/ \

R,, 6 (V)

- R ₉ is a hydrophilic block consisting of a polymer, the monomer units of which comprise groups chosen from -O-, -OH, -COOH.

11. Liquid concentrate according to claim 10, characterized in that in formula (V), R ₉ is polyethylene glycol.

12. Liquid concentrate according to claim 11, characterized in that the hydrophilic sequence consists of a macromonomer of polyethylene glycol methacrylate, of molecular mass greater than or equal to 500.

13. Liquid concentrate according to one of claims 1 to 12, characterized in that the molecular weight of the graft copolymer is between 5000 and 25000, preferably between 10000 and 20000.

14. Liquid concentrate according to one of claims 1 to 13, characterized in that said colorless mineral fillers useful for the manufacture of paints are chosen from fillers of the carbonate, silicate, silica and sulfate type.

15. Liquid concentrate of mineral fillers according to one of claims 1 to 14, characterized in that it comprises a dry extract of mineral fillers greater than or equal to 70%.

16. Liquid concentrate of mineral fillers according to one of claims 1 to 15, characterized in that the weight content of the dry extract of said graft copolymers is 10 to 15% by weight of said liquid concentrate.

17. Paint preparation process, characterized in that a liquid concentrate of mineral fillers is used according to one of claims 1 to 15, which is mixed with the other constituents of the paint.