Use of an amphiphilic block copolymer as adhesion promoters of film-forming aqueous compositions on a low-energy surface

Translation of description of equivalent WO 02068550 A2

Use of amphiphilic block copolymers as adhesion promoters for film-forming aqueous compositions on a low energy surface

The present invention relates to the use of an amphiphilic block copolymer, comprising at least one hydrophilic block and at least one hydrophobic block, as additives for aqueous film-forming compositions, especially of the paint, latex or possibly putty type. silicone to ensure or promote adhesion of these compositions on a low energy surface such as a surface based on a plastic or thermoplastic polymer.

The invention also relates to aqueous film-forming compositions comprising these amphiphilic block copolymers.

For low energy surface in the sense of the invention means materials having a low affinity for water, which results in low wettability or zero.

This wettability is evaluated by measuring the contact angle of a drop of water deposited on the surface of the material. This contact angle, generally called angle alpha, corresponds to the angle existing between the surface and the tangent to the droplet at the interface surface / water / air and can be measured in particular with the aid of a measuring device. usual contact angle, such as for example the SDT-200 marketed by the IT Concept company, used in static mode. The plates must be perfectly clean, ie rubbed beforehand with ethanol. In addition, they are reconditioned, that is to say, maintained for 24 hours under conditions of temperature and humidity in an air-conditioned room (22 ° C, 55% relative humidity). This angle can be between 0 and 180 °. - If the angle is zero, then the wetting is total. The liquid spreads completely on the surface and so there are strong interactions between the support and the liquid. - If the angle is 180 ° then the wetting is zero. The liquid forms a ball. There is only one point of contact between the liquid and the support and especially no affinity.

- For intermediate angles, the wetting is partial. Thus, it is considered that when this contact angle is greater than 45 °, then the material has a low energy surface.

In general, low energy materials have a hydrophobic character. By surface of "hydrophobic" nature is meant, in the sense of the invention, a surface characterized by a contact angle of a drop of water greater than or equal to 45 ° and generally greater than 70 °. The term "hydrophilic" is used to designate a surface characterized by a contact angle of a drop of water less than 45 °, preferably less than or equal to 30 °.

By way of example of materials having a low energy surface, mention may be made of plastic or thermoplastic polymers such as polyamides, polycarbonates, polyethylene terephthalate, polymethyl methacrylate, polypropylenes, polyethylenes, polystyrenes and polyesters. , acrylonitrile butadiene styrene (ABS) or polyvinyl chlorides. Table I of Example 4 includes for illustrative purposes the measured values ​​of the angle alpha for these materials.

Thus, when a film-forming aqueous composition is applied directly to the surface of one of these materials, it is observed that the aqueous composition is wetted very badly by the aqueous composition, which makes it impossible to apply this composition, or leads, in the best cases, to obtaining a coating of poor quality.

In addition, the adhesion properties of the coatings thus obtained are degraded in the presence of moisture or contact with the water of these surfaces, in particular due to diffusion phenomena of the water at the interface. For all of these reasons, the deposition of an aqueous film-forming composition of the type of paint or putty, optionally silicone, on a support of low surface energy, of the plastic or thermoplastic polymer type, is generally not conceivable at the industrial level.

However, the Applicant has discovered that certain amphiphilic block copolymers can be used as additives in an aqueous film-forming composition to ensure or promote the adhesion of these compositions on low energy surfaces.

The changes in adhesion properties of the film-forming aqueous compositions induced by the presence of these block copolymers make it possible to overcome the problems encountered until now, and it is possible to obtain an improvement in the effectiveness of the application of a composition. aqueous film-forming type paint or putty, but also an improvement in the adhesion to the support of this effective and durable film-forming aqueous composition, even in the presence of water.

This improvement in the adhesion of the coating results in a prolonged decorative, protective or functional effect, advantageously throughout the life of the product, without the effect induced by the coating produced being liable to be challenged by washing with an aqueous solution (S) of pH of between 1 and 12, optionally comprising sodium chloride, at a concentration of at most 10M, peeling or disintegration of said coating, in particular under the effect of mechanical stresses .

More generally, the presence of these block copolymers of the invention within the film-forming aqueous compositions provides these compositions with such affinity with respect to the low energy surface that the bonding of this deposit to the treated surface remains ensured. for relative humidities ranging from 0 to 100%. Advantageously, this bonding remains assured in the presence of water, or even under water immersion, and this even on surfaces of very low energy and / or highly hydrophobic, such as for example surfaces based on polypropylene or polyethylene . By modifying the surface properties they induce, and taking into account their resistance to water, the coatings based on film-forming aqueous compositions comprising block copolymers produced according to US Pat.

Thus, according to a first aspect, the subject of the present invention is the use of an amphiphilic block copolymer comprising at least one block of hydrophobic nature (H) and at least one block of hydrophilic nature (h), the block of hydrophobic nature having hydrophilic units in an amount of between 0% and 95% by weight and preferably between 0.1 and 90% by weight relative to the total weight of the units of the hydrophobic block, said copolymer being optionally dissolved in a solvent such as an organic solvent, water or a water-alcohol mixture, as an additive in an aqueous film-forming composition, to ensure or promote the adhesion of said composition on a low energy surface.

The present invention also relates to an aqueous film-forming composition comprising said amphiphilic block copolymer.

The application of this aqueous film-forming composition according to the invention to the surface of energy can be carried out by applying this composition to the low-energy surface, or by immersing the surface to be treated in the composition, and then eliminating the less partially, and preferably substantially, the solvent initially contained in this composition, for example by drying.

By partial elimination is meant an elimination of at least 70% by weight of the solvent initially present, preferably at least 80% by weight, and still more preferably at least 90% by weight.

A removal of the solvent "essentially" corresponds to an elimination of at least 95% by weight of the solvent initially present, preferably at least 97% by weight, and even more preferably at least 99% by weight. % by mass. The concentration of block copolymer in the aqueous film-forming composition is, in the most general case, between 0.001 and 10% by weight relative to the total mass of the dry extract of said composition.

In order to obtain optimum wetting of the support and to prevent the appearance of heterogeneities within the deposit produced, it is preferred to use a block copolymer concentration of between 0.005 and 4% and even more preferably between 0.01 and and 1% by weight relative to the total mass of the dry extract of said composition.

Such contents give the aqueous composition a viscosity suitable for application to the low energy surface. Moreover, these contents lead to the production of a continuous film (without the appearance of dewetting zones) when they are applied with a filmstrip on flat surfaces, or, more generally, when the surface to be treated is immersed in said solution.

In addition, these concentrations are particularly well suited to achieve, by simple drying, a partial or total removal of an aqueous solvent.

The drying is carried out for example at a temperature of between 15 ° C. and 50 ° C. (preferably between 19 ° and 25 ° C.) and under humidity conditions of between 10% and 70%, and preferably between 50%. and 60%. In the case where the deposition of the aqueous film-forming composition on the low-energy surface is carried out using a film-puller, the film obtained has a thickness of between 10 and 100 microns, and advantageously between 40 and 60 microns. Thus, the thickness of the deposited film may even more advantageously be of the order of 50 microns. After drying, a deposit of the aqueous film-forming composition with a thickness of between 10 nm and 1 μm, advantageously between 40 and 600 nm, and preferably between 50 and 500 nm, is obtained.

For the purposes of the invention, the term "aqueous film-forming composition" means any aqueous composition in the form of a dispersion or a solution, generally in the form of a dispersion in which the dispersed phase advantageously has a size between 10 to 100 μm, and comprising:

- As a continuous phase or solvent, water, optionally in combination with other water-soluble compounds such as alcohols, including ethanol; and

compounds of the polymer or precursor type of polymers, of acrylic resin or of silicones, which are capable of leading to the formation of a polymer film, an acrylic film or a silicone film following the application of the composition on a surface and at least partial evaporation of water, and optionally other water-soluble compounds such as ethanol.

Thus, in a nonlimiting manner, the film-forming aqueous compositions of the invention may for example be compositions comprising an aqueous or hydro-alcoholic dispersion of carbonaceous polymers in the form of a latex or of an adhesive-type formulation, putty or paint for example, comprising such a latex, or silicone precursors and in particular a mastic composition of the type of those described in EP 665 862, WO 98/13410 or WO 99/65973.

The block copolymers used in carrying out the deposition of the invention are preferably such that their hydrophilic block (h) consists, at least in part, of monomeric units chosen from:

ethylenically unsaturated mono- and dicarboxylic acids, such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, or fumaric acid,

the mono-alkyl esters of the above-mentioned ethylenic unsaturated dicarboxylic acids, preferably with Cι-C alcohols₄as well as their N-substituted derivatives, such as for example 2-hydroxyethyl acrylate or methacrylate, - amides of unsaturated carboxylic acids, such as acrylamide, methacrylamide, or - ethylenic monomers comprising a ureido group such as that ethylene urea ethyl methacrylamide, or ethylene urea ethyl methacrylate, or

the ethylenic monomers comprising at least one acidic phosphate or phosphonate group, such as vinylphosphonic acid or vinylidenephosphonic acid, or

phosphated polyethylene glycol acrylates or methacrylates, or phosphatized polypropylene glycol acrylates or methacrylates, or

ethylenic monomers comprising a sulphonic acid group or an alkali or ammonium salt thereof, for example vinylsulfonic acid, vinylbenzene sulphonic acid, alpha-acrylamidomethylpropanesulphonic acid, or 2-sulphoethylene methacrylate; , or

cationic monomers chosen from aminoalkyl (meth) acrylates and aminoalkyl (meth) acrylamides; monomers comprising at least one secondary, tertiary or quaternary amine functional group, or a heterocyclic group containing a nitrogen atom, vinylamine, ethylene imine; diallyldialkyl ammonium salts; these monomers being taken alone or in mixtures, as well as in the form of salts, the salts being preferably chosen such that the counterion is a halide such as, for example, a chloride, or a sulphate, a hydrosulphate, an alkyl sulphate (for example example comprising 1 to 6 carbon atoms), a phosphate, a citrate, a formate, an acetate, such as dimethyl amino ethyl (meth) acrylate, dimethyl amino propyl (meth) acrylate, ditertiobutyl aminoethyl (meth) acrylate, dimethylamino methyl (meth) acrylamide, dimethylamino propyl (meth) acrylamide; ethylene imine, vinylamine, 2-vinylpyridine, 4-vinylpyridine; trimethylammonium ethyl (meth) acrylate chloride, trimethylammonium ethyl acrylate methyl sulfate, benzyl dimethylammonium chloride ethyl (meth) acrylate, 4-benzoylbenzyl dimethyl ammonium chloride ethyl acrylate, trimethyl ammonium chloride ethyl (meth) acrylamido vinylbenzyl trimethylammonium chloride; diallyldimethyl ammonium chloride alone or in mixtures, or their corresponding salts, or polyvinyl alcohol resulting from the hydrolysis of a polyvinyl acetate, for example, or 4-vinylpyridine; trimethylammonium ethyl (meth) acrylate chloride, trimethylammonium ethyl acrylate methyl sulfate, benzyl dimethylammonium chloride ethyl (meth) acrylate, 4-benzoylbenzyl dimethyl ammonium chloride ethyl acrylate, trimethyl ammonium chloride ethyl (meth) acrylamido vinylbenzyl trimethylammonium chloride; diallyldimethyl ammonium chloride alone or in mixtures, or their corresponding salts, or polyvinyl alcohol resulting from the hydrolysis of a polyvinyl acetate, for example, or 4-vinylpyridine; trimethylammonium ethyl (meth) acrylate chloride, trimethylammonium ethyl acrylate methyl sulfate, benzyl dimethylammonium chloride ethyl (meth) acrylate, 4-benzoylbenzyl dimethyl ammonium chloride ethyl acrylate, trimethyl ammonium chloride ethyl (meth) acrylamido vinylbenzyl trimethylammonium chloride; diallyldimethyl ammonium chloride alone or in mixtures, or their corresponding salts, or polyvinyl alcohol resulting from the hydrolysis of a polyvinyl acetate, for example, or trimethylammonium ethyl (meth) acrylamido chloride, vinylbenzyl trimethylammonium chloride; diallyldimethyl ammonium chloride alone or in mixtures, or their corresponding salts, or polyvinyl alcohol resulting from the hydrolysis of a polyvinyl acetate, for example, or trimethylammonium ethyl (meth) acrylamido chloride, vinylbenzyl trimethylammonium chloride; diallyldimethyl ammonium chloride alone or in mixtures, or their corresponding salts, or polyvinyl alcohol resulting from the hydrolysis of a polyvinyl acetate, for example, or

cyclic amides of vinylamine, such as n-vinylpyrrolidone, or

a hydrophilic monomer originating from a chemical modification of a hydrophobic block, for example by hydrolysis of an alkyl polyacrylate to polyacrylic acid.

Preferably, the monomer units present within the hydrophilic block (h) are chosen from acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and styrene sulphonate (SS). monomers comprising ureido groups, monomers comprising phosphate groups or phosphonates or mixtures thereof.

Even more preferably, acrylic acid units (AA) or ethylenic monomers comprising ureido groups are used.

The hydrophobic block (H) of the block copolymers used in carrying out the deposition of the invention preferably consists, at least in part, of monomeric units chosen from:

styrenic derived monomers such as styrene, alphamethylstyrene, paramethylstyrene or paratertiobutylstyrene, or

esters of acrylic acid or methacrylic acid with C1-C12, preferably C1-C8, and optionally fluorinated alcohols, such as, for example, methyl acrylate or ethyl acrylate; , propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, t-butyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, vinyl nitriles containing from 3 to 12 carbon atoms, and in particular acrylonitrile or methacrylonitrile,

vinyl esters of carboxylic acids, such as vinyl acetate, vinyl versatate, or vinyl propionate, and

vinyl halides, for example vinyl chloride; and - diene monomers, for example butadiene or isoprene.

Preferably, the monomer units present within the hydrophobic block (H) of the block copolymer used in carrying out the deposition of the invention are esters of acrylic acid with linear or branched C 1 -C 8 alcohols, and especially C 1 -C 4, such as, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate or 2-ethylhexyl acrylate, or styrenic derivatives such as styrene.

This hydrophobic block (H) may contain, in addition, between 0 and 95% of hydrophilic monomers chosen from the list mentioned above of hydrophilic monomers (h).

The block copolymers according to the invention may advantageously be diblock copolymers consisting essentially of the combination of the two blocks (h) and (H).

The block copolymers of the invention may also be triblock copolymers of formula (h) (H) (h ') or (H) (h) (H'), where (h ') represents a hydrophilic block similar or not at (h), and wherein (H ') represents a hydrophobic group, similar or not to (H).

As particularly advantageous block copolymers in the context of the invention, there may be mentioned diblock copolymers based on a hydrophilic block poly (acrylic acid) and a hydrophobic block poly (butyl acrylate), and poly (acrylic acid) - poly (butyl acrylate), so-called PAA-PbuA diblock copolymers.

These PAA-PbuA copolymers are characterized by a mass ratio (acrylic acid) / (butyl acrylate) which can be between 10: 90 and 90:10, and preferably this ratio is between 10: 90 and 50:50.

Other block copolymers which are particularly advantageous in the context of the invention are, for example, block copolymers in which the hydrophilic block (h) is a poly (acrylic acid) and the hydrophobic block (H) is a statistical copolymer based on styrene and acrylic acid containing at least 25%, preferably 50%, and even more preferably 75% by weight of acrylic acid relative to the total weight of the mixture. These copolymers are characterized by a mass ratio (acrylic acid block) / (styrene block) which may be between 95: 5 and 60:40, and preferably this ratio is between 85:15 and 95: 5.

In general, the amphiphilic block copolymers used in the invention have a number-average molecular weight of between 1,000 and 100,000. Most often, their number-average molecular mass is between 2,000 and 60,000.

Whatever its exact chemical composition, the block copolymer used in carrying out the deposition of the invention may advantageously be prepared according to a controlled radical polymerization process, carried out in the presence of a control agent.

By "controlled radical polymerization" is meant a specific radical polymerization process, also referred to as "living polymerization", in which control agents are used such that the polymer chains in formation are functionalized by terminal groups. which can be reactivated as free radicals by reversible termination and / or transfer reactions.

By way of example of such polymerization processes, mention may be made in particular of:

the processes of the applications WO 98/58974, WO 00/75207 and WO 01/42312 which implement controlled radical polymerization by xanthate control agents,

the radical polymerization process controlled by dithioester type control agents of the application WO 97/01478

the process of the application WO 99/03894 which implements a polymerization in the presence of nitroxide precursors; the radical polymerization process controlled by dithiocarbamate type control agents of the application WO 99/31144;

the radical polymerization process controlled by dithiophosphoroester type control agents of application PCT / FR 01/02374. the process of the application WO 96/30421 which uses a radical polymerization by atom transfer (ATRP),

the radical polymerization process controlled by iniferters type control agents according to the teaching of Otu et al., Makromol. Chem. Rapid. Commun., 3, 127 (1982), the method of controlled radical polymerization controlled by degenerative transfer of iodine according to the teaching of Tatemoto et al., Jap. 50, 127, 991 (1975), Daikin Kogyo Co. Itd Japan and Matyjaszewski et al., Macromolecules, 28, 2093 (1995),

the method of radical polymerization controlled by tetraphenylethane derivatives, disclosed by D. Braun et al. In Macromol. Symp.

111, 63 (1996), or

the radical polymerization process controlled by organocobalt complexes described by Wayland et al. In J.Am. Chem. Soc. 116, 793 (1994). In general, it is preferred that the block copolymers used according to the invention come from a controlled radical polymerization process using, as control agent, one or more compounds chosen from dithioesters, thioethers-thiones, dithiocarbamates, and xanthates. In a particularly advantageous manner, the block copolymers used according to the invention are derived from a controlled radical polymerization carried out in the presence of control agents of the xanthate type.

According to a preferred embodiment, the block copolymer used can be obtained according to one of the methods of applications WO 98/58974, WO 00/75207 or WO 01/42312 which implement controlled radical polymerization by control agents. xanthates type, said polymerization can be carried out especially in bulk, in solvent, or, preferably in aqueous emulsion, so as to obtain directly the copolymer in the form of an aqueous or hydro-alcoholic solution, or easily applicable to a content between 0.001 and 10% by weight. A solution of the copolymer with a content of between 0.001 and 10% by weight obtained directly by a polymerization process in the same organic solvent is also usable.

Thus, it is possible to implement a method comprising the following steps:

a controlled radical polymerization is carried out leading to the production of a functionalized polymer useful as a control agent in a controlled radical polymerization reaction, said step being carried out by bringing into contact:

ethylenically unsaturated monomeric molecules,

a source of free radicals, and at least one control agent of formula (I):

S

\\

C - S - R1 (I)

/ GOLD

in which :

- R represents:

- H or Cl; an alkyl, aryl, alkenyl or alkynyl group;

a saturated or unsaturated carbon cycle, optionally aromatic;

a heterocycle, saturated or unsaturated, optionally aromatic;

an alkylthio group,

an alkoxycarbonyl, aryloxycarbonyl, carboxy, acyloxy or carbamoyl group;

a cyano, dialkyl- or diarylphosphonato, dialkyl- or diarylphosphinato group; a polymer chain,

a group (R2) O-, (R2) (R'2) N-, in which the radicals R2 and R'2, which are identical or different, each represent:

an alkyl, acyl, aryl, alkenyl or alkynyl group; a saturated or unsaturated carbon cycle, optionally aromatic; or

a heterocycle, saturated or unsaturated, optionally aromatic; and

R1 represents:

an alkyl, acyl, aryl, alkenyl or alkynyl group; a saturated or unsaturated, optionally aromatic carbon ring;

a heterocycle, saturated or unsaturated, optionally aromatic; or

a polymer chain,

(b) following step (a), a controlled radical polymerization step is carried out, or several successive controlled radical polymerization steps, said step (s) each consisting in performing a controlled radical polymerization leading to the obtaining a functionalized block copolymer useful as a control agent in a controlled radical polymerization reaction, said step or steps being carried out by bringing into contact: ethylenically unsaturated monomeric molecules different from those used in the previous step,

- a source of free radicals, and

the functionalized polymer resulting from the preceding step.

It is understood that one of the polymerization steps (a) and (b) defined above leads to the formation of the hydrophilic block (h), and that another of the polymerization stages of steps (a) and (b) ) leads to the formation of the hydrophobic block (H). In particular, it should be noted that the ethylenically unsaturated monomers used in steps (a) and (b) are chosen from suitable monomers to obtain an amphiphilic block copolymer having blocks (h) and (H) as defined previously.

Thus, in the context of the formation of the hydrophobic block (H), the monomers used may, for example, advantageously be esters of acrylic acid with linear or branched C 1 -C 4 alcohols, such as, for example, acrylate. methyl, ethyl, propyl or butyl, alone or mixed with other monomers, or styrene mixed with at least 25% by weight of acrylic acid relative to the total weight of the hydrophobic block (H ).

In general, the polymerization steps (a) and (b) are carried out in a solvent medium consisting of water and / or an organic solvent such as tetrahydrofuran or a linear C 1 -C 8 aliphatic alcohol, cyclic or branched such as methanol, ethanol, or cyclohexanol, or a diol such as ethylene glycol.

An alcoholic solvent is more particularly recommended in the context of the use of hydrophilic monomers of the acrylic acid (AA), acrylamide (AM) or 2-acrylamido-2-methylpropanesulfonic acid type. (AMPS), and styrene sulfonate (SS) and / or in the context of the implementation of hydrophobic monomers such as n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate or t-butyl acrylate.

In general, the coatings obtained by applying the film-forming aqueous composition of the invention to a low energy surface are such that they have a strong cohesion between the surface and the coating produced.

As a general rule, the affinity of the coating for the low energy surface is such that the force peels at 90 ° from this deposit at a peel rate of 300 mm / min, which can be measured, for example, using a dynamometer of the type Adamel-Lhomagry DY-30 is generally greater than or equal to 0.5 N / mm, advantageously greater than 1 N / mm or even 2 N / mm. In some cases the peel force may even be greater than 3 N / mm.

This strong affinity of the coating for the support naturally results in a very good stability of the coating on the surface.

In addition, the adhesion of the coating on the surface is not questioned in the presence of water. Thus, even when the material is maintained for a period of 72 hours under 100% relative humidity conditions, the 90 ° peel strength of the deposit generally remains greater than 0.5 N / mm, and it is not rare that it remains greater than 1 N / mm, or even 2 N / mm at a peel rate of 300 mm / min.

In the case of painted surfaces, the stability of the deposit can also be demonstrated by a wet abrasion resistance test, according to the DYN 53778 standard, of rubbing the coating obtained with a brush of hardness and standardized weights. a surfactant-additive water droplet which maintains the wetting of the surface, and measuring the number of brushing cycles required to remove the coating throughout its thickness so as to discover the support.

The advantage of using the copolymers of the invention is clear from the implementation of such tests, where it is found that the holding of an adhesive coating is greatly increased in the presence of these block copolymers.

The object and advantages of the present invention will appear even more clearly in view of the various implementation examples described below.

EXAMPLE 1 Preparation of a poly (butyl acrylate) -polv (acrylic acid) diblock copolymer according to the invention, characterized by a ratio (butyl acrylate) / poly (acrylic acid) of 50:50 by weight.

The following mixture is introduced into a reactor equipped with a magnetic stirrer and a reflux column, and comprising 160 g of acetone:

3.04 g of O-ethyl dithiocarbonate (more simply designated by the term "xanthate" hereinafter) -21.24 g of isopropanol, and

0.82 g of azobis-isobutyronitrile (AIBN). The mixture is then stirred and maintained at reflux at 70 ° C.

66 g of acrylic acid (AA) and 15 g of water were added gradually for 3 hours. Then 0.41 g of azobis-isobutyronitrile was added after one hour of addition, then another 0.41 g of azobis-isobutyronitrile was added after a second hour of addition.

After the addition of acrylic acid is complete, the polymerization is allowed to continue for another hour. An amount of 0.20 g of reaction mixture is taken as a sample of PAA homopolymer.

The temperature is then lowered to 65 ° C., by adding 560 g of acetone. While maintaining the temperature at 65 ° C., 140 g of butyl acrylate (BA) are added gradually over a period of 3 hours. 0.40 g of AIBN is added at the beginning of the BA addition. The reaction is allowed to continue for another 3 hours. The reaction mixture is cooled and the solvents are almost completely removed using a rotavapor (rotary evaporator). The residue obtained is dispersed in water and freeze-dried. The polymer obtained is analyzed by carbon 13 nuclear magnetic resonance and by a measurement of its acid content.

The number-average molecular weight of the copolymer is 15,000.

The glass transition temperature of the hydrophobic block is -54 ° C. The surface tension is 55 mN / m at 10^"4 mol / l.

EXAMPLE 2 Preparation of a diblock poly (butyl acrylate) -poly (acrylic acid) copolymer according to the invention characterized by a ratio (butyl acrylate) / poly (acrylic acid) of 70: 30 by weight.

The following mixture is introduced under a nitrogen atmosphere into a reactor equipped with a magnetic stirrer and a reflux column, and comprising 160 g of acetone:

- 0.61 g of xanthate - 4.25 g of isopropanol,

0.16 g of azobis-isobutyronitrile The mixture thus obtained is put under and maintained at reflux at 70.degree. 13.2 g of acrylic acid (AA) and 30.3 g of water are added gradually over 3 hours. Then 0.08 g of azo-bis-isobutyronitrile are added after one hour of addition and then another 0.08 g of azobis-isobutyronitrile are added after a second hour of addition. After the addition of acrylic acid is complete, the polymerization is allowed to continue for another hour. A quantity of 4.1 g of reaction mixture is taken as a sample of PAA homopolymer.

The temperature is then lowered to 65 ° C. by the addition of 112 g of acetone. While maintaining the temperature at 65 ° C., 28 g of butyl acrylate (BA) are added gradually over 3 hours. 0.08 g of AIBN is added at the beginning of the BA addition. The nitrogen purge is stopped and the reaction is allowed to continue for a further 12 hours. The reaction mixture is cooled and the solvents are almost completely removed using a rotavapor (rotary evaporator). The residue obtained is dispersed in water and freeze-dried. The polymer obtained is analyzed by carbon 13 nuclear magnetic resonance and by measuring the acid content.

The number-average molecular weight is 15,000.

The glass transition temperature of the hydrophobic block is: -54 ° C.

Surface tension is 52 mN / m at 10^"4 mol / l.

Example 3 Preparation of a diblock copolymer poly (styrene-co-acrylic acid) -poly (acrylic acid) according to the invention, characterized by a hydrophobic block of 2K and a hydrophilic block of 14K with a variable rate of acrylic acid in the hydrophobic block (in particular 73%).

- Synthesis of a random copolymer of styrene, methacrylic acid and ethyl acrylate with mass ratios: St / AMA / Aet = 25/2/73. The polymerization is carried out in emulsion, in a jacketed reactor equipped with a tri-pale stainless steel stirrer. 875 g of water, 13.9 g of dodecyl sulphate, sodium salt (Aldrich) and 0.31 g of sodium carbonate Na 2 CO 3 are introduced at room temperature. The resulting mixture is stirred for 30 minutes (190 rpm) under nitrogen. The stirring is continued for a further 55 minutes during which the temperature is raised to 75 ° C., and then a mixture comprising 2.16 g of styrene and 9.01 g of alpha- (o-ethylxanthyl) propionate is incorporated. methyl (CH3CHCO2Me) SCSOEt, 0.17 g of methacrylic acid and 6.32 g of ethyl acrylate. The temperature is then raised to 85 ° C. and 1. 58 g of ammonium persulfate (NH 4) 2 S 2 O 5 are added. After five minutes, 19.49 g of styrene, 1. 56 g of methacrylic acid and 56.91 g of ethyl acrylate are added for one hour. After complete addition, an emulsion polymer (latex) is obtained, which is maintained at 85 ° C for one hour.

197.29 g of the previously obtained emulsion copolymer are obtained. 0.79 g of ammonium persulfate (NH4) 2S2θ5 and 3.5 g of water are added to it at 85 ° C. After five minutes, the addition of a mixture consisting of: 661.27 g of ethyl acrylate (Aet) is begun,

-13.49 g of methacrylic acid (AMA), and simultaneously another compound of: -420 g of water -0.75 g of Na2CO3 The addition lasts 1 hour. The system is maintained at this temperature for an additional three hours. 2) Hydrolysis of the diblock copolymer:

The hydrolysis is also carried out in a jacketed reactor equipped with a tri-pale stainless steel stirrer. It introduces: - 54 g of the above copolymer (35.09% dry extract), - 250.8 g of water (to adjust the dry extract to 4%).

The temperature is raised to 85 ° C and yet the emulsion is stirred vigorously. Then 182 g of 2N sodium hydroxide (corresponding to two molar equivalents of sodium hydroxide with respect to the ethyl acrylate) are added for two hours. After complete addition of the soda, the temperature is brought to

95 ° C and the reaction is maintained under these conditions for 48 hours. Example 4 Use of polybutyl acrylate-polv (acrylic acid) diblock copolymers according to the invention as additives in aqueous film-forming compositions in the form of latices

The poly (butyl acrylate) -poly (acrylic acid) diblock copolymers obtained in Examples 1 and 3 are used to produce film-forming aqueous compositions according to the invention.

The latex used in this example is an industrial acrylic latex used in particular in decorative paint, marketed by Rhodia under the reference DS 1003. It is an aqueous dispersion of styrene-acrylate copolymer particles whose average diameter is 150 nm and characterized by a polymer content of 50% by weight based on the total weight of the aqueous composition.

In the various tests, one adds in this latex one of the poly (butyl acrylate) -poly (acrylic acid) diblock copolymers obtained in Examples 1 and 3 in variable amounts: 0.07%, 0.1% or 0.35% in dry weight relative to the dry weight of latex.

Coatings are then produced from the compositions thus obtained, on different supports having flat surfaces of low energy. In each of the tests, the surface of the support is first cleaned with a cloth soaked in ethanol, so as to carry out its degreasing. After cleaning, each of the supports is placed for 4 hours in a room conditioned at 22 ° C (+/- 3 ° C) and under conditions of relative humidity of 55% (+/- 5%). The characteristics of the supports are summarized in Table I below: TABLE I

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A film of uniform thickness equal to 50 microns is applied to the surface of the support thus conditioned using a film of uniform thickness, starting from the tested composition, which is immediately covered with a strip of film. fabric 25 mm wide, intended to allow a subsequent 90 ° peel test of the resulting coating.

The film thus formed is then allowed to dry for 12 hours, in a room conditioned at 22 ° C. (+/- 3 ° C.) and under conditions of relative humidity of 55% (+/- 5%), so that achieve an adherent coating.

Accelerated aging of the coated support thus obtained is then carried out, placing it for 12 hours in an oven at 40 ° C. and at 30% relative humidity. The samples are then placed for 12 hours in a room conditioned at 22 ° C (+/- 3 ° C) and at 55% relative humidity (+/- 5%).

Following these different steps, a peel test is carried out at 90 ° of the coating obtained, consisting in pulling the strip of fabric fixed on the coating in a direction perpendicular to the surface of the support until a separation of the coating and the coating is obtained. surface, over a length of 100 mm, by measuring the forces involved using an Adamel-Lhomagry dynamometer type DY-30 with a sensor of 100 N maximum. At the end of this test, an average tractive force of 90 ° (T₉₀) expressed in N / mm, which reflects the affinity of the coating made vis-à-vis the support surface and the stability of this coating. The results obtained in the various tests carried out are collated in Tables II to VII below:

Table II

<img file="WO02068550A2_D0002.tif" />

Table III

<img file="WO02068550A2_D0003.tif" />

Table IV

<img file="WO02068550A2_D0004.tif" /> Table V

<img file="WO02068550A2_D0005.tif" />

Table VI

<img file="WO02068550A2_D0006.tif" />

Table VII

<img file="WO02068550A2_D0007.tif" />

Example 5: Use of the poly (butyl acrylate) -poly (acrylic acid) and poly (styrene-co-acrylic acid) - poly (acrylic acid) diblock copolymers of the invention to improve wet abrasion resistance of a coating of paint deposited on a thermoplastic polymer support: simplified formulation. The diblock copolymers of Examples 1 and 3 are used to add a latex entering a paint formulation whose deposition is carried out on a black PVC flat support, referred to as Lénéta paper.

The surface of the support used is previously cleaned with a cloth soaked in ethanol, so as to perform a degreasing. After cleaning, the support is placed for 4 hours in a room conditioned at 22 ° C (+/- 3 ° C) and under conditions of relative humidity of 55% (+/- 5%).

The latex DS1003 as defined in Example 4 is then added with variable amounts (x = 0.1% and 0.5% by weight relative to the solids content of the latex) added with sodium hydroxide until a pH of 8.5

Then deposited on the cleaned surface, using a film puller, a film of 1.5 mm thick of a paint formulation comprising:

- 100 parts by weight of calcium carbonate

10 parts by weight of additive DS 1003 latex of x% of the diblock-water copolymer, added so as to obtain a formulation having a solids content of 72% by weight.

The film obtained is then allowed to dry for 21 days, in a room conditioned at 22 ° C. (+/- 3 ° C.) and under conditions of relative humidity of 55% (+/- 5%). Following these different steps, the coated support obtained is subjected to a wet abrasion resistance test (RAH) as defined in the standard DYN 53778, which evaluates the resistance of the paint to washing and / or leaching.

It consists of the cyclic abrasion of a paint film by a brush standardized in mass and hardness under a drip of a soap solution. RAH is expressed as the number of wearable abrasion cycles by the film before the media appears: 100% of the paint has been removed.

The results of the RAH test are collated in Table VIII below: Table VIII

<img file="WO02068550A2_D0008.tif" />

The increase in the number of wet abrasion cycles required when adding diblock copolymer in a certain concentration range clearly demonstrates the improvement in the cohesion between the support and the coating induced by the implementation of the copolymer. Sequence of the invention as a latex additive in the composition of a simplified paint formulation.

Example 6: Use of the poly (butyl acrylate) -poly (acrylic acid) and poly (styrene-co-acrylic acid) - poly (acrylic acid) diblock copolymers of the invention to increase wet abrasion resistance of a layer of paint on a support of the thermoplastic polymer type: complete formulation.

The diblock copolymers of Examples 1 and 3 are used to add a latex used in the formulation of a paint, a deposit of which is made on a black PVC flat support, referred to as Lénéta paper.

The surface of the support used is previously cleaned with a cloth soaked in ethanol, so as to perform a degreasing. After cleaning, the support is placed for 4 hours in a room conditioned at 22 ° C (+/- 3 ° C) and under conditions of relative humidity of 55% (+/- 5%).

The latex DS1003 as defined in Example 4 is then added with variable amounts (x = 0.1% and 0.5% by weight relative to the solids content of the latex) added with sodium hydroxide until a pH of 8.5

Next, a 1.5 mm thick film of a paint formulation comprising: - 100 parts by weight of a pigment base described below is deposited on the cleaned surface using a film puller;

16 parts by weight of latex DS 1003, additive of x% of the diblock copolymer

water, added so as to obtain a formulation having a solids content of 63.4% by weight. The pigment base used is shown in Table IX below:

Table IX

<img file="WO02068550A2_D0009.tif" />

The resulting film is then allowed to dry for 21 days in a room conditioned at 22 ° C (+/- 3 ° C) and at 55% relative humidity (+/- 5 ° C).

Following these different steps, the coated support obtained is subjected to a wet abrasion resistance test (RAH) as defined in the standard DYN 53778, which evaluates the resistance of the paint to washing and / or leaching.

It consists of the cyclic abrasion of a paint film by a brush standardized in mass and hardness under a drip of a soap solution. RAH is expressed as the number of wearable abrasion cycles by the film before the media appears: 100% of the paint has been removed.

The results of the RAH test are summarized in Table X below: Table X

<img file="WO02068550A2_D0010.tif" />

It is noted that in the case of a full-form paint, the resistance to wet abrasion is lower than in the case of a simplified formulation (number of cycles necessary for a lower total abrasion). However, there is an increase in the number of cycles during the addition of diblock copolymer in a certain concentration range, which clearly demonstrates the improvement of the cohesion between the support and the coating induced by the implementation of the Sequence copolymer of the invention as a latex additive in the composition of a complete paint formulation.

EXAMPLE 7 Use of poly (butyl acrylate) -poly (acrylic acid) and poly (styrene-co-acrylic acid) - poly (acrylic acid) diblock copolymers according to the invention for improving the efficiency of the deposition of a paint on a thermoplastic polymer type support

The diblock copolymers obtained in Examples 1 and 3 are used to add a latex used in the formulation of a paint, a layer of which is deposited on a flat PVC support. For comparison, the deposition of the paint formulated with a nonadditive latex is also performed on PVC.

The latex used in this example is an industrial acrylic latex used especially in decorative paint, marketed by Rhodia under the reference DS 1003. These characteristics are detailed in Example 4. In each of the tests carried out, the surface of the support used is previously cleaned with a cloth soaked in ethanol, so as to perform a degreasing. After cleaning, each of the supports is placed for 4 hours in a room conditioned at 22 ° C (+/- 3 ° C) and under conditions of relative humidity of 55% (+/- 5 ° C).

The latex DS1003 as defined in Example 4 is then added with variable amounts (x = 0.1% and 0.5% by weight relative to the solids content of the latex) added with sodium hydroxide until a pH of 8.5

Then deposited on the cleaned surface, using a film puller, a film of 1.5 mm thick of a paint formulation comprising:

100 parts by weight of a pigment base described in Example 6.

16 parts by weight of additive DS latex of x% of the diblock copolymer

water, added so as to obtain a formulation having a solids content of 63.4% by mass, which is immediately covered by a 25 mm wide strip of fabric, intended to allow a subsequent test to be carried out. 90 ° peel of the coating obtained.

This film is then allowed to dry for 12 hours, in a room conditioned at 22 ° C. (+/- 3 ° C.) and under conditions of relative humidity of 55% (+/- 5%).

Accelerated aging of the coated support thus obtained is then carried out, placing it for 12 hours in an oven at 40 ° C. and at 30% relative humidity.

The samples are then placed for 12 hours in a room conditioned at 22 ° C (+/- 3 ° C) and at 55% relative humidity (+/- 5%).

A 90 ° peel test is then carried out on the coating obtained, consisting in pulling the strip of fabric fixed on the coating in a direction perpendicular to the surface of the support at a speed of 300 mm / min until a separation of the coating is obtained. of the surface, over a length of 100 mm, by measuring the forces involved using a Dy-30 Adamel-Lhomagry dynamometer with a sensor of 100 N maximum. At the end of this test, an average tractive force of 90 ° (T₉₀) expressed in N / mm, which reflects the affinity of the coating made vis-à-vis the support surface and the stability of this coating.

The results obtained in the various tests carried out are collated in the following table XI:

Table XI

<img file="WO02068550A2_D0011.tif" />

This peel test makes it possible to show that the additive to latex of amphiphilic block copolymers makes it possible to improve the adhesion of a layer of paint formulated with this latex on a plastic support of PVC type.

Example 8 Use of diblock copolymers polv (butyl acrylate) -poly (acrylic acid) and poly (styrene-co-acrylic acid) -polyfacid acrylic) according to the invention to improve the efficiency of the deposition of a paint on a thermoplastic polymer-type support in the presence of water

The diblock copolymers obtained in Examples 1 and 3 are used to add a latex used in the formulation of a paint, a layer of which is deposited on a flat PVC support. For comparison, the deposition of the paint formulated with a nonadditive latex is also performed on PVC. The latex used in this example is an industrial acrylic latex used in particular in decorative paint, marketed by Rhodia under the reference DS 1003. These characteristics are detailed in Example 4.

In each of the tests carried out, the surface of the support used is first cleaned with a cloth soaked in ethanol, so as to perform a degreasing. After cleaning, each of the supports is placed for 4 hours in a room conditioned at 22 ° C (+/- 3 ° C) and under conditions of relative humidity of 55% (+/- 5%).

The latex DS1003 as defined in Example 4 is then added with variable amounts (x = 0.1% and 0.5% by weight relative to the solids content of the latex) added with sodium hydroxide until a pH of 8.5

Then deposited on the cleaned surface, using a film puller, a film of 1.5 mm thick of a paint formulation comprising:

100 parts by weight of a pigment base described in example 6. 16 parts by weight of latex DS 1003, additive of x% of the diblock copolymer

water, added so as to obtain a formulation having a solids content of 63.4% by mass, which is immediately covered by a 25 mm wide strip of fabric, intended to allow a subsequent test to be carried out. 90 ° peel of the coating obtained.

This film is then allowed to dry for 12 hours, in a room conditioned at 22 ° C. (+/- 3 ° C.) and under conditions of relative humidity of 55% (+/- 5%).

Accelerated aging of the coated support thus obtained is then carried out, placing it for 12 hours in an oven at 40 ° C. and at 30% relative humidity.

The samples are then placed for 12 hours in a room conditioned at 22 ° C (+/- 3 ° C) and at 55% relative humidity (+/- 5%). The coated supports are immersed for 2 hours in demineralized water and then dried for 24 hours in a room conditioned at 22 ° C (+/- 3 ° C) and under conditions of relative humidity of 55% ( +/- 5%).

At the end of this dipping / drying cycle, a peel test at 90 ° of the coating obtained is then performed, consisting in pulling the web of fabric fixed on the coating in a direction perpendicular to the surface of the support at a speed of 300 mm. / mn until the coating and the surface are separated over a length of 100 mm, by measuring the forces involved using a Dy-30 Adamel-Lhomagry dynamometer with a sensor of 100 N maximum. At the end of this test, a tensile force at 90 ° average (Tgn) expressed in N / mm, which reflects the affinity of the coating made with respect to the surface of the support and the stability of this surface, is determined. coating.

The results obtained in the various tests carried out are summarized in the following Table XII:

Table XII

<img file="WO02068550A2_D0012.tif" />

This recovery test makes it possible to show that the additivation to latex of amphiphilic block copolymers makes it possible to improve the adhesion of a layer of paint formulated with this latex on a plastic support of PVC type, even after a prolonged immersion in some water.