WO2002060997A1 - Method for preparing a coating limiting micro-organism adherence - Google Patents

Abstract

The invention concerns a method for a preparing a surface coating limiting micro-organism adherence, which consists in depositing on the surface to be treated, at least a polymer providing said surface, with a value gamma p, polar component of the surface energy, not less than 5 mN/m.

Description

 PROCESS FOR THE PREPARATION OF A COATING FOR LIMITING THE ADHESION OF MICROORGANISMS

The present invention relates to a process for preparing a coating of surfaces limiting the adhesion of microorganisms.

Limiting the proliferation of microorganisms is an important issue in many applications. In fact, in the phytosanitary field, fungi are pathogenic agents which, in particular, reduce the production of attacked plants, such as, for example, cereal plants. In the field of detergency, and more particularly household or industrial cleaning, efforts are made to limit the proliferation of molds or bacteria. One of the means conventionally used to combat microorganisms is the use of biocidal agents. These products are in most cases effective, but they very often pose a problem of toxicity for the user, or even of ecotoxicity. In addition, they promote in the more or less long term, the development of strains resistant to the biocide used.

The subject of the present invention is a solution different from that implemented previously. It consists in modifying the surface likely to be contaminated, so as to limit the affinity of microorganisms with the latter. In this way, the adhesion of microorganisms to the surface is considerably reduced and the microorganisms can be eliminated from the surface by rinsing under a stream of water, or even by leaching with rain water, for example. Thus, a first object of the present invention consists of a process for preparing a coating limiting the adhesion of microorganisms in which is deposited on the surface to be treated, at least one polymer conferring on said surface a value of γp, component polar surface energy, greater than or equal to

5 mN / m. In what follows, the term "microorganism" covers both bacteria and fungi, in particular at their various stages of germination (for example the spore, the germ tube, the appressorium ...). The term "microorganism" also covers yeasts, especially at their various stages of germination.

The surfaces treated according to the present invention are more particularly of the hydrophobic type.

Thus, surfaces having a polar component of the surface energy, γp, of less than 5 mN / m, preferably less than or equal to 3 mN / m, can be treated in accordance with the method according to the invention. The treated surfaces can be of any kind.

For example, the method according to the invention can advantageously be implemented for the treatment of the aerial surface of plants (leaves, stem, etc.).

The surfaces capable of being treated in accordance with the invention can also be plastics, such as polyvinyl chloride, polypropylene, polyethylene, polystyrene, polyurethanes, etc.

One can also treat surfaces like wood, metal, covered with varnish or paints.

Silicone-based surfaces, such as silicone seals, can also be treated according to the invention.

As indicated above, the method consists in preparing a coating based on at least one polymer, in order to give the surface to be treated a value of γp of at least 5 mN / m.

It is recalled that this value of γp, polar component of the surface energy, is measured by contact angle.

The method used is as follows:

The polymer in solution or in dispersion is deposited on the surface to be treated. The quantity of polymer present in the solution or dispersion is such that it makes it possible to obtain a deposit of 200 μg of polymer per square centimeter of surface. The polymer is then air dried.

A drop of a microliter of water is then deposited on a part of the surface thus covered, and the contact angle is measured (at 20 ° C).

On another part of the surface, drop a drop of a microliter of diiodomethane and measure the contact angle (at 20 ° C). The values obtained make it possible to calculate the surface energy and to find the value of the polar (γp) and dispersing (γd) components of the surface energy

(see "Physical Chemistry of Surfaces", 4 ^th Edition, AW Adamson, John Wiley & Sons, 1982).

According to an advantageous embodiment of the invention, the quantity of polymer deposited is at least 10 μg / cm ² . The upper limit can be very high.

However, no significant improvement in the anti-adhesion efficiency of the coating has been observed when the quantity of polymer deposited exceeds

200 μg / cm ² .

It should be noted that it is preferable that the entire surface to be treated is covered.

In addition, and for rather economic reasons, it is desirable that the thickness of said coating is uniform. The coating is obtained from at least one polymer which is more particularly chosen from polyhydroxylated, polyoxyalkylenated and / or polycarboxylated polymers and / or from polymers comprising at least one hydrophilic segment and at least one anchoring segment. Note that the term polymer designates both homopolymers and copolymers.

In addition, it is specified that by polymer is meant a compound having an average degree of polymerization of at least 3. Advantageously, the average degree of polymerization is at least 6. Preferably, the polymer is present in a soluble or dispersible form in aqueous or hydroalcoholic media. A polymer is said to be soluble in an aqueous or hydroalcoholic medium when it is in the form of a clear solution at a temperature between 20 and 30 ° C., at a concentration of 0.5 g / l. By dispersible is meant polymers which do not precipitate or sediment after one hour when they are dispersed in aqueous or aqueous-alcoholic media, at a temperature between 20 and 30 ° C, at a concentration of 0 , 5 g / l.

According to a first variant, the polyhydroxylated polymer is chosen from polysaccharides of animal, vegetable or bacterial origin, cellulose derivatives, or also polyvinyl alcohol, polyphenolic polymers, or their derivatives.

The polysaccharides can be used in native form or chemically modified so as to give them an ionic, nonionic and / or hydrophobic character different from the native form.

As examples of polysaccharides, there may be mentioned without intending to be limited, alginates, galactomannans such as guar gum, locust bean gum, Tara gum, cassia gum, Karaya gum, carrageenans, chitin derivatives such as chitosan, starches, glucomannans, dextran, gum arabic, soluble starch and its nonionic derivatives (cationic). Also suitable are the alkyl derivatives of these compounds. As cellulose derivatives, mention may in particular be made of cellulose hydroxyethers, methylcellulose and its derivatives, hydroxypropylmethylcellulose, hydroxybutylmethylcellulose, carboxymethylcellulose, ethylmethylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, as well as, in general, the other hydroxyalkylated derivatives of cellulose, as well as cellulose esters such as cellulose acetate, cellulose propionate, cellulose butyrate, etc. It would not be departing from the scope of the present invention to use, as polyhydroxylated polymer, other functionalized celluloses such as celluloses comprising carbonate functions.

As suitable guar derivatives, mention may be made of compounds resulting from an etherification and / or esterification reaction, such as hydroxyalkyl guars (with the alkyl radical comprising 2 to 4 carbon atoms, linear or branched) such as l 'hydroxypropyl guar, hydroxybutyl guar; such as carboxymethyl guars; such as carboxymethyl hydroxyalkyl guars (with the alkyl radical comprising 2 to 4 carbon atoms, linear or branched). The cationic guar compounds, bearing quaternary amino groups, are likewise suitable. Finally, the alkylated compounds of guar and of the derivatives mentioned above can be used in the invention.

As polysaccharides of animal origin capable of being used, there may be mentioned in particular those obtained by fermentation under the action of bacteria or fungi belonging for example to Xanthomonas, in the genus Arthrobacter, in the genus

Azobacter, in the genus Agrobacter, in the genus Alkaligènes, in the genus Rhizobium, in the genus

Sclerotium, in the genus Corticium, in the genus Sclerotinia.

By way of example of such polysaccharides, mention may be made more particularly of xanthan gum, scleroglucans, succinoglycans. As polyhydroxylated polymers, and as indicated above, polyvinyl alcohol, polyphenolic alcohols or their derivatives are also suitable.

Among the possible derivatives, let us note the polyetherified polymers, such as those of which the ether part is a C1-C18 alkyl radical, or Cβ-Ciβ aryl, alkylaryl or even arylalkyl radical; the alkyl and aryl parts being defined above. As possible derivatives, and in particular polyvinyl alcohol, mention may be made of polymers having a variable acetylation rate so that the polymer is soluble or dispersible in the sense indicated above.

Polymers bearing at least one ionic radical (anionic, cationic, zwitterionic, amphoteric) may also be suitable as derivatives. As anionic radical, there may be mentioned without intending to be limited, the radicals of the sulfonate, sulfate, carboxylate, phosphate, phosphonate type; by way of example of a cationic radical, mention may be made of radicals of the quaternary ammonium type such as N (R4) + with R, identical or different, representing a hydrogen atom, a C1-C6 alkyl radical; the zwitterionic and amphoteric radicals corresponding to the combination of the two types of radicals mentioned above.

It is pointed out that polymers of polyphenolic type are natural substances, which can, in particular, be extracted from certain plants such as coffee trees, tea plants. As regards polymers of polyoxyalkylenated type, the latter correspond more particularly to the polyoxyalkylenated derivatives of glycol, the alkylene oxide part corresponding to ethylene oxide, propylene oxide or their mixtures. In the case where ethylene oxide and propylene oxide are present, their distribution can be random or block. Preferably, a polyoxyethylenated glycol derivative is used.

As regards polycarboxylated polymers, those obtained from: ^π at least one saturated or unsaturated monomer comprising 3 to 10 carbon atoms and comprising one or more carboxylic groups present in the form of acids or salts are suitable , as well as the corresponding esters or amides, ^D optionally combined with at least one monomer of alkylene oxide type, or ^D optionally combined with at least one hydrocarbon monomer carrying one or more ethylenic unsaturations. As saturated or unsaturated monomers comprising one or more carboxylic groups and comprising 3 to 10 carbon atoms, mention may be made of mono- or diacids, as well as their derivatives in the form of alkali, alkaline-earth metal, ammonium salts (type N (R) 4+, with R representing hydrogen or a C1-C4 alkyl radical). For example, mention may be made of acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, acrylamide, methacrylamide.

The amino acids or their salts can likewise be suitable for carrying out the invention, like aspartic acid, as are the esters of such amino acids. The esters are preferably C 1 -C ₂ alkyl esters.

As regards the monomer of alkylene oxide type, mention may be made of ethylene oxide, propylene oxide or their mixtures.

As regards the hydrocarbon-based monomer, mention may be made, without intending to be limited, of C ₂ -C ₁₂ hydrocarbon-based monomers, which may or may not include an aryl radical, and which also have at least one ethylenic unsaturation.

Butadiene, isobutylene, diisobutylene, styrene, alphamethylstyrene, vinyltoluene are suitable, among others.

Another variant of the invention consists in using a polymer comprising at least one hydrophilic segment and at least one anchoring segment. The term anchoring segment means that said segment has an affinity with the surface to be treated. As indicated above, the surface to be treated is hydrophobic and the latter may or may not carry anionic charges in the presence of an aqueous medium. Consequently, according to a first possibility, the anchoring segment can itself be hydrophobic without ionic charge under the conditions of use of the polymer. In such a case, the interactions between the surface and the anchoring segment will be of the hydrophobic - hydrophobic type. The anchoring segment can carry cationic charges under the conditions of use of the polymer. In this case, the interactions between the surface and the anchoring segment will be of the electrostatic type.

The anchoring segment can finally carry positive and negative ionic charges so that the proportion of negative charges relative to positive charges is close to 1 (1 ± 0.2). According to this possibility, the interactions between the anchoring segment and the surface will be of the electrostatic type and / or will be the result of a limited solubility of the polymer in the medium, which promotes its deposition on the surface.

Whatever the option chosen, the anchoring segment consists of at least one repeating pattern. Furthermore, it is preferable that the average molar mass by total weight of the anchoring segment or segments represents at most the average molar mass by total weight of the hydrophilic segment or segments. The report is evaluated by measuring the molar mass by weight of the polymer by the MALLS technique (Multi-Angle Laser Light Scattering) coupled with gel permeation chromatography (absolute mass) and then by proton NMR analyzes. and / or carbon.

It should be noted that the polymers used can be linear polymers, of comb structure, or of star structure, the first two structures being preferred.

The segments of the polymer can therefore constitute the various fragments (blocks) of a linear polymer. In the case of polymers of comb structure, said segments can be found in the main chain of the polymer, or in the side chains

(grafts) or even, in the case of star-shaped polymers, in the branches.

It is recalled that the segments of the polymer are such that there are at least two segments whose chemical composition is different. By different chemical composition is meant more particularly that the chemical nature of at least one of the monomers is different from one segment to another, and / or that the respective proportions of the monomers from one segment to another are different.

Finally, it should be noted that each segment can have a distribution of monomers of a statistical type, or have a concentration gradient.

Linear polymers include at least two segments. The polymers with comb structure preferably have an anchoring skeleton onto which hydrophilic segments are grafted. With regard to polymers with a star structure, several possibilities are possible. According to a particular embodiment, if we consider each branch of the star, it can comprise either a polymer of which at least one of the segments is an anchoring segment, the other segment or segments of the hydrophilic segments . According to this possibility, it is preferable that the star includes a reduced number of branches. According to another, more advantageous embodiment, still considering each branch of the star, the latter can be constituted by a polymer of the same nature (hydrophilic or anchoring).

The polymers can be obtained from hydrophobic monomers, neutral cationic, anionic or hydrophilic monomers.

As regards the hydrophobic monomers, the latter can be chosen from the following monomers:

- esters of mono- or polycarboxylic acids, linear, branched, cyclic or aromatic, comprising at least one ethylenic unsaturation, - αβ-ethylenically unsaturated nitriles, vinyl ethers, vinyl esters, vinylaromatic monomers, halides of vinyl or vinylidene,

- hydrocarbon monomers, linear or branched, aromatic or not, comprising at least one ethylenic unsaturation, optionally substituted by a halogen atom, more particularly comprising 2 to 12 carbon atoms, - propylene oxide, butylene; alone or in mixtures, as well as the macromonomers derived from such monomers. The term macromonomer designates a macromolecule carrying one or more functions which can be polymerized by the chosen polymerization method.

As specific examples of monomers which can be used in the preparation of the hydrophobic segment (s), mention may be made of:

- esters of (meth) acrylic acid with an alcohol comprising 1 to 12 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (meth) n-butyl acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl acrylate; - vinyl acetate, vinyl Versatate®, vinyl propionate, vinyltoluene, styrene, α-methylstyrene, vinyl chloride, vinylidene chloride, methyl vinyl ether, ethyl vinyl ether;

- vinyl nitriles more particularly include those having 3 to 12 carbon atoms, such as in particular acrylonitrile and methacrylonitrile; - butadiene, isobutylene, diisobutylene, chloroprene, isoprene;

- propylene oxide, butylene oxide; alone or in mixtures, as well as the macromonomers derived from such monomers. The preferred monomers are the acrylic acid esters with linear or branched C1-C4 alcohols such as methyl, ethyl, propyl and butyl acrylate, vinyl esters such as vinyl acetate, styrene, α-methylstyrene.

As regards the cationic monomers, the following may in particular be suitable: - aminoalkyl (meth) acrylates, aminoalkyl (meth) acrylamides;

- the monomers comprising at least one secondary, tertiary or quaternary amine function, or a heterocyclic group containing a nitrogen atom, vinylamine, ethylene imine;

- diallyldialkyl ammonium salts; alone or in mixtures, or the corresponding salts; as well as the macromonomers derived from such monomers.

As more specific examples of such monomers, we can retain those from the following list:

- dimethyl amino ethyl (meth) acrylate, dimethyl amino propyl (meth) acrylate ditertiobutyl aminoethyl (meth) acrylate, dimethyl amino methyl (meth) acrylamide, dimethyl amino propyl (meth) acrylamide;

- ethylene imine, vinylamine, 2-vinylpyridine, 4-vinylpyridine;

- trimethylammonium ethyl (meth) acrylate chloride, trimethylammonium ethyl acrylate methyl sulfate, benzyl dimethylammonium ethyl (meth) acrylate chloride, 4-benzoylbenzyl dimethyl ammonium ethyl acrylate chloride, trimethyl ammonium ethyl (meth) chloride acrylamido, trimethyl ammonium chloride, vinylbenzyl;

- diallyldimethyl ammonium chloride; alone or as mixtures, or their corresponding salts, as well as the macromonomers derived from such monomers.

The salts of these monomers (more particularly with quaternized amino functions) are preferably of ammonium NR4 + type with R, identical or not, representing a hydrogen atom, an alkyl radical comprising 1 to 10 carbon atoms, preferably 1 to 4, optionally carrying a hydroxyl radical, the counterion can be chosen from halides such as, for example, chlorine, sulphates, hydrosulphates, alkyl sulphates (for example comprising 1 to 6 carbon atoms), phosphates, citrates, formates, acetates.

Preferably, under the conditions of use of the polymer, the units carrying ionizable functions are in an at least partially ionized, or even fully ionized, form.

The anionic monomers can in particular be chosen from the monomers below: - linear, branched, cyclic or aromatic mono- or polycarboxylic acids, comprising at least one ethylenic unsaturation, and at least 3 to 10 carbon atoms; N-substituted derivatives of such acids; monoesters of polycarboxylic acids, comprising at least one ethylenic unsaturation; - linear, branched, cyclic or aromatic vinyl carboxylic acids;

- amino acids comprising one or more ethylenic unsaturations; alone or as mixtures, their precursors, their sulfonic or phosphonic, phosphoric counterparts as well as the macromonomers derived from such monomers; the monomers or macromonomers which may be in the form of salts. As examples of anionic monomers, there may be mentioned without intending to be limited thereto: acrylic acid, methacrylic acid, fumaric acid, itaconic acid, citraconic acid, maleic acid, acrylamido glycolic acid, 2-propene 1- sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, α-acrylamido methylpropane sulfonic acid, 2-sulfoethylene methacylate, sulfopropyl acrylic acid, l bis-sulfopropyl acrylic acid, bis-sulfopropyl methacrylic acid, sulfatoethyl methacrylic acid, hydroxyethyl methacrylic acid phosphate ester, as well as alkali metal salts, such as sodium, potassium, or ammonium; - vinyl sulfonic acid, vinylbenzene sulfonic acid, vinyl phosphonic acid, vinylidene phosphoric acid, vinyl benzoic acid, as well as alkali metal salts, such as sodium, potassium, or ammonium ; N-methacryloyl alanine, N-acryloyl-hydroxy-glycine; alone or in mixtures, as well as the macromonomers derived from such monomers. It should be noted, as indicated above, that it would not be departing from the scope of the present invention to use precursor monomers of those which have just been mentioned. In other words, these monomers have units which, once incorporated in the polymer chain, can be transformed, in particular by a chemical treatment such as hydrolysis, to restore the aforementioned anionic species. For example, the fully or partially esterified monomers of the aforementioned monomers can be used to be, subsequently, completely or partially hydrolyzed.

Preferably, under the conditions of use of the polymer, the units carrying ionizable functions are in an at least partially ionized, or even fully ionized, form.

The nonionic hydrophilic monomers can be chosen from:

- ethylene oxide; - amides of mono- or polycarboxylic acids, linear, branched, cyclic or aromatic, comprising at least one ethylenic unsaturation or derivatives;

- hydrophilic esters derived from (meth) acrylic acid;

- vinyl esters making it possible to obtain polyvinyl alcohol blocks after hydrolysis, vinyipyrrolidone;

- sugars and their vinyl esters; alone or in mixtures as well as the macromonomers derived from such monomers.

As more specific examples, there may be mentioned inter alia ethylene oxide; amides of mono- or polycarboxylic acids, linear, branched, cyclic or aromatic, comprising at least one ethylenic unsaturation or derivatives, such as (meth) acrylamide, N-methyloI (meth) acrylamide; hydrophilic esters derived from (meth) acrylic acid such as for example 2-hydroxyethyl (meth) acrylate; vinyl esters making it possible to obtain polyvinyl alcohol blocks after hydrolysis, such as vinyl acetate, vinyl Versatate®, vinyl propionate; vinyipyrrolidone; sugar type monomers such as osides, highly depolymerized polyholosides as well as vinyl esters of such compounds. By strongly depolymerized is meant compounds whose molecular weight by weight is more particularly less than 20,000 g / mole.

Osides are compounds which result from the condensation, with elimination of water, of daring molecules between them or even of daring molecules with non-carbohydrate molecules. Among the osides, the holosides which are formed by the combination of exclusively carbohydrate units are preferred, and more particularly the oligoholosides (or oligosaccharides) which contain only a limited number of these units, that is to say a number generally lower. or equal to 10. As examples of oligoholosides, mention may be made of sucrose, lactose, cellobiose, maltose. The highly depolymerized polyholosides (or polysaccharides) suitable are described for example in the work of P. ARNAUD entitled "organic chemistry course", GAUTHIER-VILLARS editors, 1987. As a non-limiting example of highly depolymerized polyholosides, it is possible to cite dextran, starch. Such monomers can be used alone or in mixtures, as well as in the form of macromonomers.

The composition of the anchor segment may vary depending on the options chosen. Thus, in the case of a hydrophobic anchoring segment, the monomers from which said segment is obtained are preferably chosen from hydrophobic monomers. However, it is not excluded that said segment comprises ionic or hydrophilic nonionic monomers, as soon as the weight proportion of these monomers represents less than 20 mol% of the monomers hydrophobic. If present, these monomers are preferably statistically within the hydrophobic segment.

If the anchoring segment is of the cationic type, the monomers from which it is obtained are cationic, possibly hydrophobic. It can likewise include nonionic hydrophilic monomers as well as anionic monomers. Preferably, if such monomers are present, the weight proportion of these monomers represents less than 20 mol% of the cationic monomers.

Finally, if the anchoring segment comprises anionic and cationic monomers such that the weight proportion of anionic charges relative to the cationic charges is close to 1, the monomers from which it is prepared are anionic, cationic and optionally hydrophobic. Said segment can also comprise hydrophilic monomers but their proportion preferably does not represent more than 20 mol% of the cationic and anionic monomers. As for the hydrophilic segment, it can be obtained from hydrophilic, anionic neutral monomers. If it comprises hydrophobic monomers, the latter do not represent more than 20 mol% of the hydrophilic monomers.

The polymers which have just been detailed are compounds well known to those skilled in the art. Thus, the polymers can be prepared by implementing polymerizations by the anionic route, by the cationic route, by the so-called living or controlled radical route. It is likewise possible to carry out, depending on the monomers used, a group transfer polymerization (called "group transfer") or else a cycle opening polymerization (in particular case of polymerization from the N-carboxy anhydride cycle) , or also by a polymerization involving a transesterification of terminal groups.

Preferably, said polymers are obtained by implementing at least one step of living radical polymerization.

By way of example of so-called living or controlled polymerization processes, reference may in particular be made to:

- radical polymerization controlled by xanthates according to the teaching of application WO 98/58974,

the radical polymerization controlled by the dithioesters according to the teaching of the application WO 98/01478, the polymerization using nitroxide precursors according to the teaching of the request WO 99/03894,

the radical polymerization controlled by the dithiocarbamates according to the teaching of the application WO 99/31144, - radical polymerization by atom transfer (ATRP) according to the teaching of application WO 96/30421.

In the case of polymers carrying grafts (comb polymers), they can in particular be obtained by various methods, such as for example a copolymerization of a monomer with a macromonomer. More particularly, this method firstly implements the grafting at the end of the segment of a radical polymerizable function. This grafting can be carried out by usual methods of organic chemistry. Then, in a second step, the macromonomer thus obtained is polymerized with the monomer chosen to form the skeleton and a so-called "comb" polymer is obtained.

Comb polymers can also be obtained by polymerization of a monomer followed by grafting onto the skeleton thus obtained. The grafting of the lateral polymer segments onto a skeleton polymer segment can be carried out according to conventional techniques familiar to those skilled in the art (European Polymer Journal 4, 343 (1968) for example). Among these conventional techniques, mention may be made in particular of those known as direct grafting.

In the case of star-type polymers, the syntheses can be essentially classified into two groups. The first corresponds to the formation of the polymer arms from a multifunctional compound constituting the center ("core-first" technique) (Kennedy, JP and coll. Macromolecules, 29, 8631 (1996), Deffieux, A. and coll Ibid, 25, 6744, (1992), Gnanou, Y. and coll. Ibid, 31, 6748 (1998)) and the second corresponds to a method where the polymer molecules which will constitute the arms are first synthesized and then bonded together on a heart to form a star-shaped polymer ("arm-first" technique). Among the methods which can be used to link the arms, mention may in particular be made of the method comprising the reaction of these arms with a compound having a plurality of functional groups capable of reacting with terminal antagonistic functional groups of said arms (Fetters, LJ and coll. Macromolecules, 19, 215 (1986), Hadjichristidis, N. and coll. Macromolecules, 26, 2479 (1993), Roovers, J. and coll. Macromolecules, 26, 4324 (1993)). Let us also cite the method comprising the addition of a compound having a plurality of polymerizable groups, followed by the polymerization of said arms (Rempp, P. and coll., Polym. Sci. Part C, 22, 145 (1968), Fetters, LJ and coll. Macromolecules, 8, 90 (1975), Higashimura and coll. Ibid, 24, 2309 (1991)).

In order to obtain the polymer chains subsequently constituting the arms of the stars, methods are generally used to control the polymerization reaction. Thus, living anionic and cationic polymerizations are the most widely used methods today. In addition, the polymer used has more particularly a molecular weight by weight of between 3000 and 5.106 g / mol.

In the case of polyhydroxylated, polyoxyalkylenated, polycarboxylated polymers, the molecular mass is advantageously between 10 ⁴ and 5.106 g / mol, preferably between 5.105 and 5.106, and according to a more particular variant, between 106 and 5.106 g / mol.

In the case of polymers having at least one hydrophilic segment and at least one anchoring segment, the molecular weight by weight is preferably between 5000 and 5.105 g / mol. These molecular weights by weight are absolute weights, measured by the MALLS technique (Multi-Angle Laser Light Scattering) coupled with gel permeation chromatography.

The coating can therefore be obtained from one or more of the polymers described above. The solution or dispersion applied has a polymer content such that it is less than the solubility or sedimentation limit of said polymer or mixture of polymers. Illustratively, the concentration of polymer (s) in the solution or dispersion is between 0.1 and 250 g / l.

According to a particularly advantageous embodiment of the present invention, and in the case where it has at least one free hydroxyl group, the polymer is used in the presence of at least one metallic compound comprising at least one metal chosen from columns IVA, IB and IIIB of the periodic table. Preferably, the metal is chosen from zirconium, titanium, copper and aluminum. These metals can be used alone or in combination. The metal compound is more particularly in the form of a water-soluble, water-dispersible or emulsifiable compound.

According to a first possibility, the metal compound is in the form of organic derivatives chosen from the salts of carboxylic acids, aliphatic, saturated or not, linear or branched, comprising 2 to 18 carbon atoms, and optionally comprising one or more groups hydroxyls.

For example, the salts of acetic, citric, lactic, oleic, stearic, myristoleic acid are suitable.

Another variant consists in using the metallic compound in the form of β-diketone chelates or aliphatic β-ketoesters comprising 5 to 10 carbon atoms, or comprising at least one aromatic radical.

Among suitable compounds of this type, mention may in particular be made of acetylacetone chelates, methyl acetylacetonate, ethyl acetylacetonate, benzoylacetone, dibenzoylmethane, octanoylbenzoylmethane, stearoyl benzoylmethane.

According to a second possibility, the metal compound is used in the form of mineral derivatives chosen from oxides, hydroxides or their mixtures. Note that the metal compound can be used in a form which is sparingly or not soluble in an aqueous or hydroalcoholic medium. In this case, it will then be present, during the preparation of the coating, in the form of a dispersion, an emulsion or a microemulsion.

In such a case, and to best promote its dispersion, the metal compound is preferably used in a finely divided form. More particularly, the average particle size is less than a micron and preferably less than

200 nm. Note that the term particles includes not only solid and / or liquid particles.

According to a particular embodiment of the invention, the metallic compound, if it is not or only slightly soluble in aqueous or hydroalcoholic medium, can be used with an appropriate amphiphilic compound (dispersant, surfactant) improving the homogeneous distribution of said metal compound when preparing the coating.

Among the metal compounds which are very advantageously suitable, mention may be made of zirconium lactate, zirconium citrate, zirconium acetylacetonate, zirconium acetate, titanium oxide, aluminum oxide.

The coating is obtained by applying to the surface to be treated an aqueous or hydroalcoholic solution or dispersion comprising the polymer and optionally the metal compound, and the solution or dispersion of polymer is dried or allowed to dry. According to an advantageous embodiment, the polymer concentration in the solution or dispersion is such that the viscosity of said solution or dispersion is less than or equal to 10 times the viscosity of an aqueous polymer solution free of metallic compound, having the same concentration.

More particularly, the weight ratio of the metal compound to the polymer is between 0.005 and 2, preferably between 0.01 and 0.5.

Depending on the application concerned with the preparation of the coating, the solution or suspension may include additives and / or active ingredients which are conventional in the field.

More particularly, it is not excluded to introduce into said solutions or suspensions, fungicidal agents, biocides.

The application of the solution or suspension can be done by any suitable means, such as spraying, application with a brush, etc. Once the solution or suspension has been deposited, it is left to dry or it is dried.

Drying is generally carried out in air.

The drying temperature can vary within a wide range, depending on the application. Usually it is done at room temperature.

At the end of this drying step, a coating of the surface to be treated is therefore obtained; the whole is not linked by covalent bonds but rather by interactions of the hydrophobic type - hydrophobic, electrostatic, etc.

The coatings obtained by the process according to the invention are useful for limiting the adhesion of spores of fungi, for example phytopathogenic fungi, such as Magnaporthe Grisea, Colletotrichum fungi.

The coating obtained according to the invention can be useful for limiting the adhesion of bacteria such as staphilochoccus (aureus, ...), streptochoccus, ...

The coating allows, during a simple leaching, to increase by at least 20%, the removal of microorganisms preferably by at least 50%, or even up to 80% deposited on the surface thus coated.

The method according to the invention can find applications, in particular in the phytosanitary field, in that of the treatment of hydrophobic surfaces, whether the latter are exposed or not to the outside.

A concrete example will now be presented.

EXAMPLE

The purpose of this example is to show the rate of spore removal from the Magnaporthe Grisea fungus.

The treated surface is polished teflon.

The polymer solution used consists of an aqueous solution of

Jaguar® 8000 (marketed by Rhodia Chimie) at 0.5 g / l, and zirconium acetate at 0.2 g / l.

Comparative test 1 consists of an untreated surface. Test 2 is carried out in accordance with the invention, with a polymer deposit of 20 μg / cm ² .

Test 3 is carried out in accordance with the invention, with a polymer deposit of 200 μg / cm ² . The polymer solution is deposited using a pipette and then allowed to dry at room temperature to obtain the coating.

The surfaces to be tested are introduced into a Hele-Shaw type laminar flow cell placed under a microscope and coupled with image acquisition and analysis software. The surface observed is 1 mm ² .

Each surface (tests 1 comparison, 2 and 3) is brought into contact with spores of the fungi, from an aqueous suspension (with a phosphate buffer) which is injected into the cell. The spores are deposited on the surface by sedimentation (approximately 10 minutes) so as to obtain an average of 200 spores which have adhered to the surface (measurement by transmission and reflection).

The spores deposited on the surface are then subjected to a tearing force of around 10 nN, thanks to a flow of buffered water (phosphate).

Once the number of spores torn off has stabilized, the image is recorded and the number of spores remaining on the surface is measured.

The results, expressed as% of spores removed, are collated in the table below:

It is found that the spores on the surfaces treated according to the invention adhere less than on an untreated surface.

Claims

1. Method for preparing a coating limiting the adhesion of microorganisms in which is deposited on the surface to be treated, at least one polymer conferring on said surface a value of γp, polar component of the surface energy, greater than or equal at 5 mN / m. 2. Method according to the preceding claim, characterized in that at least one polymer is chosen chosen from polyhydroxylated and / or polyoxyalkylenated and / or polycarboxylated polymers. 3. Method according to one of the preceding claims, characterized in that the polyhydroxylated polymer is chosen from polysaccharides of animal, vegetable or bacterial origin, or also polyvinyl alcohol, or their derivatives. 4. Method according to the preceding claim, characterized in that the polyhydroxylated polymer is chosen from guar gum, as well as its nonionic, anionic, cationic or amphoteric derivatives. 5. Method according to the preceding claim, characterized in that the polyhydroxylated polymer is chosen from guar, alkylated derivatives of guar; hydroxyalkyl guars for which the alkyl radical comprises 2 to 4 carbon atoms, linear or branched; carboxymethyl guar; carboxymethyl hydroxyalkyl guar, for which the alkyl radical contains 2 to 4 carbon atoms, linear or branched. 6. Method according to any one of the preceding claims, characterized in that the polyoxyalkylenated polymer is chosen from polyoxyalkylenated glycol derivatives, the alkylene oxide part corresponding to ethylene oxide, propylene oxide, or their mixtures. 7. Method according to any one of the preceding claims, characterized in that the polycarboxylated polymer is chosen from those obtained from: - at least one saturated or unsaturated monomer, comprising 3 to 10 carbon atoms and comprising one or several carboxylic groups in the form of an acid, of alkali metal salts, - optionally combined with at least one monomer of alkylene oxide type, or - Optionally combined with at least one hydrocarbon monomer carrying one or more ethylenic unsaturations. 8. Method according to any one of the preceding claims, characterized in that the polymer comprising at least one hydrophilic segment and at least one anchoring segment of hydrophobic, cationic nature, or carrying positive and negative ionic charges so that the proportion of negative charges compared to positive charges is close to 1 (1 ± 0.2). 9. Method according to the preceding claim, characterized in that the polymer is obtained from hydrophobic monomers chosen from the following monomers: - the esters of mono- or polycarboxylic acids, linear, branched, cyclic or aromatic, comprising at least one ethylenic unsaturation, - ccβ-ethylenically unsaturated nitriles, vinyl ethers, vinyl esters, vinyl aromatic monomers, vinyl or vinylidene halides, - hydrocarbon monomers, linear or branched, aromatic or not, comprising at least one ethylenic unsaturation, optionally substituted by a halogen atom, more particularly comprising 2 to 12 carbon atoms, - propylene oxide, butylene oxide; alone or in mixtures, as well as the macromonomers derived from such monomers. 10. Method according to claim 8, characterized in that the polymer is obtained from cationic monomers chosen from the following monomers: - aminoalkyl (meth) acrylates, aminoalkyl (meth) acrylamides; - the monomers comprising at least one secondary, tertiary or quaternary amine function, or a heterocyclic group containing a nitrogen atom, vinylamine, ethylene imine; - diallyldialkyl ammonium salts; alone or in mixtures, or the corresponding salts; as well as the macromonomers derived from such monomers. 11. Method according to claim 8, characterized in that the polymer is obtained from anionic monomers chosen from the following monomers: - linear, branched, cyclic or aromatic mono- or polycarboxylic acids, comprising at least one ethylenic unsaturation, and at least 3 to 10 carbon atoms; N-substituted derivatives of such acids; monoesters of polycarboxylic acids, comprising at least one ethylenic unsaturation; - linear, branched, cyclic or aromatic vinyl carboxylic acids; - amino acids comprising one or more ethylenic unsaturations; alone or as mixtures, their precursors, their sulfonic or phosphonic, phosphoric counterparts as well as the macromonomers derived from such monomers; the monomers or macromonomers which may be in the form of salts. 12. Method according to claim 8, characterized in that the polymer is obtained from non-ionic hydrophilic monomers chosen from the following monomers: - ethylene oxide; - amides of mono- or polycarboxylic acids, linear, branched, cyclic or aromatic, comprising at least one ethylenic unsaturation or derivatives; - hydrophilic esters derived from (meth) acrylic acid; - vinyl esters making it possible to obtain polyvinyl alcohol blocks after hydrolysis, vinyipyrrolidone; - sugars and their vinyl esters; alone or in mixtures as well as the macromonomers derived from such monomers. 13. Method according to any one of the preceding claims, characterized in that the polymer is used in the presence of at least one crosslinking agent comprising at least one metal chosen from columns IVA, IB and IIIB of the periodic table of the elements, preferably from zirconium, titanium, copper and aluminum. 14. Method according to the preceding claim, characterized in that the crosslinking agent is a water-soluble, water-dispersible or emulsifiable compound found in the form: * organic derivatives chosen from: ^π the salts of carboxylic, aliphatic acids, saturated or not, linear or branched, comprising 2 to 18 carbon atoms, and optionally comprising one or more hydroxyl groups; ^D the chelates of β-diketones or of aliphatic β-ketoesters comprising 5 to 10 carbon atoms and / or comprising at least one aromatic radical; * of mineral derivatives chosen from oxides, hydroxides, or mixtures thereof. 15. Method according to any one of the preceding claims, characterized in that the quantity of polymer deposited on the surface to be treated is at least 10 μg / cm ² , preferably at least 20 μg / cm ² . 16. Method according to any one of the preceding claims, characterized in that an aqueous or hydroalcoholic solution or dispersion comprising the polymer and optionally the crosslinking agent is applied to the surface to be treated, and the solution is dried or dispersion. 17. Method according to the preceding claim, characterized in that the polymer concentration in the solution or dispersion is such that the viscosity of said solution or dispersion is less than or equal to 10 times the viscosity of an aqueous polymer solution free of crosslinking agent, having the same concentration. 18. Method according to one of claims 16 or 17, characterized in that the weight ratio of the crosslinking agent and the polymer is between 0.005 and 2, preferably between 0.01 and 0.5. 19. Use of the coating obtained by the method according to any one of claims 1 to 18, for the treatment of hydrophobic surfaces having an internal γp value of 5, preferably less than or equal to 3, in order to limit the adhesion of microorganisms.