FR2820059A1 - PROCESS FOR PREPARING A COATING LIMITING THE ADHESION OF MICROORGANISMS - 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

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PROCESS FOR PREPARING A LIMITING COATING
THE ADHERENCE OF MICROORGANISMS
The present invention relates to a process for preparing a surface coating limiting the adhesion of microorganisms.

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

 The subject of the present invention is a solution different from that used previously. It consists in modifying the surface likely to be contaminated, so as to limit the affinity of the microorganisms with the latter. In this way, the adhesion of the microorganisms on the surface is considerably reduced and the microorganisms can be removed from the surface by rinsing under a stream of water, or by leaching with rainwater, for example.

 Thus, a first object of the present invention is constituted by 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 yp, component polar surface energy, greater than or equal to 5 mN / m.

 In what follows, the term "microorganism" covers both bacteria, fungi, especially at their various stages of germination (eg spore, germ tube, 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, yp, less than 5 mN / m, preferably less than or equal to 3 mN / m, can be treated according to the process according to the invention.

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The treated surfaces can be of any kind.

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

 The surfaces which can be treated according to the invention can also be plastics, such as polyvinyl chloride, polypropylene, polyethylene, polystyrene, polyurethanes, etc.

 We can also treat surfaces such as wood, metal, covered with varnish or paints.

 Silicone surfaces, such as silicone gaskets, can also be treated according to the invention.

 As has been indicated previously, the process consists in preparing a coating based on at least one polymer, in order to give the surface to be treated a value of yp of at least 5 mN / m.

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

The method used is as follows:
The polymer is deposited on the surface to be treated in solution or in dispersion. The amount of polymer present in the solution or the dispersion is such that it makes it possible to obtain a deposit of 200 n. g per square centimeter of surface.

 The polymer is then dried in air.

 Then deposited on a portion of the surface thus covered, a micro-drop of water and the contact angle is measured (at 20oC).

 On another part of the surface, a micro-drop of diiodomethane is deposited and the contact angle (at 20 ° C.) is measured.

 The values obtained make it possible to calculate the surface energy and to recover the value of the polar (yp) and dispersant (yd) components of the surface energy.

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

However, there has been no significant improvement in the anti-adhesion effectiveness of the coating when the amount of polymer deposited exceeds 200 g / cm 2.

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

 In addition, and for reasons of an economic nature, it is desirable for the thickness of said coating to be homogeneous.

 The coating is obtained from at least one polymer which is more particularly chosen from polyhydroxylated polymers and / or polycarboxylated polymers and / or polyoxyalkylenated polymers.

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 Note that the term polymer refers to both homopolymers and copolymers.

 Preferably, the polymer is in a form that is soluble or dispersible in aqueous or aqueous-alcoholic media. The term "dispersible" denotes the polymers of which at least 50% remain in suspension in the medium in question, in aqueous or aqueous-alcoholic media.

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

 The polysaccharides may 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.

gomme de Tara, la gomme de cassia, la gomme de Karaya, les carraghénanes, les dérivés de la chitine comme le chitosan, les amidons, les glucomannanes, le dextran, la gomme arabique, l'amidon soluble et ses dérivés non ioniques (cationique). As examples of polysaccharides, mention may be made without intending to be limited to alginates, galactomannans such as guar gum, carob 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. derived from these alkylated compounds.

méthylcellulose, l'hydroxybutylméthylcellulose, la carboxyméthylcellulose, l'éthylméthylcellulose, l'éthylcellulose, l'hydroxyéthylcellulose, l'hydroxypropylcellulose, ainsi que, d'une manière générale, les autres dérivés hydroxyalkylés de la cellulose, ainsi que les esters de cellulose tels que l'acétate de cellulose, le propionate de cellulose, le butyrate de cellulose, etc. As cellulose derivatives, there may be mentioned in particular hydroxyethers of cellulose, methylcellulose and its derivatives, hydroxypropyl-

methylcellulose, 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 other functionalized celluloses, such as celluloses comprising carbonate functional groups, as polyhydroxylated polymers.

 Suitable guar derivatives include compounds derived from etherification and / or esterification reactions, such as hydroxyalkyl guars (with the linear or branched alkyl radical containing 2 to 4 carbon atoms), such as hydroxypropyl guar, hydroxybutyl guar; like carboxymethyl guars; as carboxymethyl hydroxyalkyl guars (with the alkyl radical comprising 2 to 4 carbon atoms, linear or branched).

 The cationic compounds of guar bearing quaternary amine groups are likewise suitable. Finally, the alkyl compounds of the guar and derivatives mentioned above can be used in the invention.

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 As polysaccharides of animal origin that may be used, mention may be made in particular of those obtained by fermentation under the action of bacteria or fungi belonging, for example, to Xanthomonas, to the genus Arthrobacter, to the genus Azobacter, to the genus Agrobacter, to the genus Alcaligenes, Rhizobium genus, Sclerotium genus, Corticium genus, Sclerotinia genus.

 By way of example of such polysaccharides, mention may be made more particularly of xanthan gum, scleroglucans and succinoglycans.

 As polyhydroxylated polymers, and as indicated previously, polyvinyl alcohol, polyphenol alcohols or their derivatives are also suitable.

 Among the possible derivatives include polyetherified polymers, such as those whose ether portion is a C1-C18 alkyl radical, or C6-C18 aryl, alkylaryl or arylalkyl; the alkyl and aryl parts being defined above.

 As possible derivatives, and especially polyvinyl alcohol, there may be mentioned polymers having a variable rate of acetylation.

 Polymers bearing at least one ionic radical (anionic, cationic, zwitterionic, amphoteric) may also be suitable as derivatives. By way of anionic radical, mention may be made without intention of being limited to sulphonate, sulphate, carboxylate, phosphate or phosphonate radicals; by way of example of a cationic radical, mention may be made of quaternary ammonium radicals such as N (R 4) + with R 2, which may be identical or different, representing a hydrogen atom or a C 1 -C 6 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 the polyoxyalkylene-type polymers, the latter more particularly correspond to polyoxyalkylene derivatives of glycol, the alkylene oxide part corresponding to ethylene oxide, propylene oxide or mixtures thereof. In the case where ethylene oxide and propylene oxide are present, their distribution can be statistical or block. Preferably, a polyoxyethylene glycol derivative is used.

 With regard to the polycarboxylated polymers, those obtained from: a of at least one saturated or unsaturated monomer comprising 3 to 10 carbon atoms and comprising one or more carboxylic groups in the form of an acid, of salts or alkali metal, ester, acrylamide, optionally combined with at least one alkylene oxide monomer, or

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 optionally combined with at least one hydrocarbon monomer carrying one or more ethylenic unsaturations.

 As saturated or unsaturated monomer comprising one or more carboxylic groups and comprising 3 to 10 carbon atoms, mention may be made of mono- or diacids, and their derivatives in the form of alkali metal, alkaline-earth metal or ammonium salts. (N (R) 4+ type, with R representing hydrogen or a C1-C4 alkyl radical).

 For example, there may be mentioned acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid.

 The amino acids or their salts may likewise be suitable for carrying out the invention, such as aspartic acid, as well as the esters of such amino acids.

More particularly, the esters are C1-C22 alkyl esters.

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

intention de s'y limiter des monomères hydrocarbonés en C2-C12, comprenant ou non un radical aryle, et présentant en outre au moins une insaturation éthylénique. Conviennent entre autres le butadiène, l'isobutylène, le diisobutylène, le styrène, le vinylstyrène, l'alphaméthylstyrène, le vinyltoluène. With regard to the hydrocarbon monomer, mention may be made without

intended to be limited to C2-C12 hydrocarbon monomers, including or not an aryl radical, and further having at least one ethylenic unsaturation. Among others, butadiene, isobutylene, diisobutylene, styrene, vinylstyrene, alphamethylstyrene and vinyltoluene are suitable.

The coating can be obtained from one or more of the previously described polymers.

 In addition, the polymer used more particularly has a weight-average molecular weight of between 10 and 10 g / mol. Preferably, the molecular weight is between 5.105 and 5. 106 g / mol, and according to a more particular variant, between 106 and 5. 106 g / mol.

 These masses are measured either by steric exclusion chromatography, or by quasi-elastic light scattering.

 According to a particularly advantageous embodiment of the present invention, the polymer is used in the presence of at least one metal compound comprising at least one metal chosen from columns IVA, IB and IIIB of the periodic table of elements. Preferably, the metal is selected 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 carboxylic, aliphatic and saturated carboxylic acid salts.

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 or not, linear or branched, comprising 2 to 18 carbon atoms, and optionally comprising one or more hydroxyl groups.

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

 Another variant consists in using the metal compound in the form of chelates of ss-diketones or aliphatic s-ketoesters comprising 5 to 10 carbon atoms, or comprising at least one aromatic radical.

 Suitable compounds of this type include acetylacetone, methyl acetylacetonate, ethyl acetylacetonate, benzoylacetone, dibenzoylmethane, octanoylbenzoylmethane, stearoyl benzoylmethane chelates.

 According to a second possibility, the metal compound is used in the form of mineral derivatives chosen from oxides, hydroxides or their mixtures.

 It should be noted that the metal compound can be used in a form which is poor or not soluble in an aqueous or aqueous-alcoholic 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 employed in a finely divided form. More particularly, the average particle size is less than one micron and preferably less than 200 nm. Note that the term particles includes not only solid and / or liquid particles.

 According to one particular embodiment of the invention, the metal compound, if it is not or only slightly soluble in an aqueous or aqueous-alcoholic medium, can be used with a suitable amphiphilic compound (dispersant, surfactant) improving the homogeneous distribution. of said metal compound at the time of preparation of the coating.

 Among the metal compounds that are very advantageously suitable are zirconium lactate, zirconium citrate, zirconium acetylacetonate, zirconium acetate, titanium oxide and aluminum oxide.

 The coating is obtained by applying to the surface to be treated an aqueous or aqueous-alcoholic solution or dispersion comprising the polymer and optionally the metal compound, and the polymer solution or dispersion 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 solution of polymer free of metal compound, having the same concentration.

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 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 by the preparation of the coating, the solution or suspension may comprise additives and / or active ingredients that 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 appropriate means, whether spraying, brushing, etc.

 Once the solution or suspension has been deposited, it is allowed to dry or the latter is dried.

 Drying is generally carried out under air.

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

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

 The coating obtained according to the invention may be useful for limiting the adhesion of bacteria such as staphylococcus (aureus, etc.), streptochocci, etc.

 The coating makes it possible, during simple leaching, to increase by at least 20%, the removal of the 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, especially in the phytosanitary field, in the treatment of hydrophobic surfaces, whether or not these are exposed to the outside.

 A concrete example will now be presented.

EXAMPLE
This example aims to show the spore removal rate of the fungus Magnaporthe Grisea.

 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 gram, and zirconium acetate at 0.2 g / l.

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 The comparative test 1 consists of an untreated surface.

 Test 2 is carried out in accordance with the invention with a polymer deposition of 20 g / cm 2.

 Test 3 is carried out according to the invention with a polymer deposition of 200 g / cm 2.

 The polymer solution is deposited by means of a pipette and 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 to an image acquisition and analysis software. The observed area is 1 mm2.

 Each surface (comparative tests 1, 2 and 3) is brought into contact with fungal spores 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 adhered to the surface (measurement by transmission and reflection).

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

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

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

<Tb>
<tb> Assay <SEP> 1 <SEP> Assay <SEP> 2 <SEP> Assay <SEP> 3
<tb> 15% <SEP> 70% <SEP> 95%
<Tb>

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

Claims (14)

 1. 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 giving said surface a value of yp, polar component of the surface energy, greater or equal to 5 mN / m. 2. Method according to the preceding claim, characterized in that is deposited at least one polymer selected from polyhydroxylated polymers and / or polycarboxylated and / or polyoxyalkylenated. 3. Method according to one of the preceding claims, characterized in that the polyhydroxylated polymer is selected from polysaccharides of animal, plant or bacterial origin, or polyvinyl alcohol, or their derivatives. 4. Process 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 polyhydroxy polymer is selected from guar, alkyl 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 comprises 2 to 4 carbon atoms, linear or branched. 6. Process according to any one of the preceding claims, characterized in that the polyoxyalkylenated polymer is chosen from polyoxyalkylenated derivatives of glycol, the alkylene oxide part corresponding to ethylene oxide, propylene oxide, or their mixtures. 7. Process 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 more carboxylic groups in the form of acid, alkali metal salts, optionally combined with at least one alkylene oxide monomer, or <Desc / Clms Page number 10>  cl optionally combined with at least one hydrocarbon monomer carrying one or more ethylenic unsaturations. 8. Process 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 elements, preferably from zirconium, titanium, copper and aluminum. 9. Process according to the preceding claim, characterized in that the crosslinking agent is a water-soluble, water-dispersible or emulsifiable compound in the form of: organic derivatives chosen from: carboxylic acid salts, aliphatic, saturated or non-linear, linear or branched, comprising 2 to 18 carbon atoms, and optionally comprising one or more hydroxyl groups; chelates of ss-diketones or aliphatic s-ketoesters comprising 5 to 10 carbon atoms and / or comprising at least one aromatic radical; of mineral derivatives selected from oxides, hydroxides, or mixtures thereof. 10. Method according to any one of the preceding claims, characterized in that the amount of polymer deposited on the surface to be treated is at least 10 μg / cm, preferably at least 20 μg / cm. 11. Process according to any one of the preceding claims, characterized in that an aqueous or aqueous-alcoholic 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 dried. dispersion. 12. 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 a polymer-free aqueous solution. crosslinking agent, having the same concentration. 13. Method according to one of claims 11 or 12, 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. <Desc / Clms Page number 11> 14. Use of the coating obtained by the process according to any one of claims 1 to 13, for the treatment of hydrophobic surfaces having a value of yp internal to 5, preferably less than or equal to 3, in order to limit the adhesion of microorganisms.