Metal surface treatment

Abstract

The invention relates to the use of at least one polymer P, obtained by free-radical copolymerization of a mixture of (i) acrylic acid; (ii) optionally, methacrylic acid; and (iii) at least one ethylenically unsaturated monomer carrying an unsaturated heterocycle with at least two nitrogen atoms, said monomer preferably being an ethylenically unsaturated imidazole, for treating a metal surface intended to be coated with a coating, varnish or adhesive, for example a metal surface intended to be bonded to another surface with an adhesive, in order to impart adhesion failure resistance to the resulting bond.

Description

[0001] This application claims priority to Nr 202021044019, filed in India on 9 October 2020, and Nr 20306448.0, filed in Europe on 26 November 2020, the entire contents of which are incorporated herein by reference for all purposes.

[0002] This invention relates to the field of treating metal-based surfaces, and more specifically to metal surfaces intended to be coated with film-forming compositions (such as coatings, varnishes, or adhesive compositions). The invention particularly relates to the treatment of said metal surfaces with the aim of providing enhanced adhesion of film-forming compositions to metal surfaces, which is especially effective for adhesive compositions.

[0003] Several methods have been proposed to provide enhanced adhesion of film-forming organic compositions (such as coatings, varnishes, or adhesives) to metal surfaces (especially aluminum or steel), including depositing inorganic coatings, particularly so-called "conversion coatings," on metal surfaces.

[0004] The term "conversion coating" is well known in the art and refers to a layer formed on a metal surface that is a favorable substitute for the natural oxides on the surface (especially on aluminum), and is obtained by controlled chemical formation of a film on the metal surface through a reaction with chemical elements of the metal surface, such that at least some of the cations dissolved from the metal material are deposited in the conversion coating.

[0005] Typically, coatings (such as conversion coatings) are obtained by reacting a metal surface with a solution containing metal cations and fluorides. Chromium-containing coatings have been proposed in the past (typically obtained by reacting the surface with a solution containing H₂CrF₆), and more recently, coatings based on less toxic metals such as zirconium, titanium, or others (e.g., obtained by reacting the surface with a solution containing H₂TiF₆, H₂ZrF₆, H₂HfF₆, H₂AlF₆, H₂SiF₆, H₂GeF₆, H₂SNF₄, or HBF₄) have been proposed. Conversion coatings may include other compounds, such as silane precursors.

[0006] To improve adhesion on coatings (such as conversion coatings), it is known to add additives, especially organic polymers. In this regard, the use of polyacrylic acid has been described, for example. A typical additive particularly suitable for coating compositions is ACUMER, available from Dow Chemical Company (and previously from Rohm & Haas). TM1510 has been extensively described for this application. For more details on this, see in particular WO 20109411, WO 20109413, WO 97 / 13588, US 4,191,596, or US 4921552.

[0007] One object of the present invention is to provide a novel method for treating metal surfaces, which imparts good adhesion to organic compositions, and in particular adhesive compositions, applied to the metal surface (the adhesive can be applied by coating an adhesive composition, which is typically an organic film-forming composition, usually available in the form of a paste, more or less a fluid; or by pre-formed adhesive films, such as L-F610 epoxy adhesive film (commercialized by L&L)).

[0008] To this end, the present invention proposes the use of a specific polymer, optionally (but not necessarily) in conjunction with the formation of a conversion coating (i.e., before, during, or after), resulting in a treated metal surface exhibiting the following highly significant characteristics: good adhesion is achieved between the surface and the coated composition when coated with a film-forming composition (such as a paint, varnish, or adhesive composition). Furthermore, the surface receives excellent protection, particularly against corrosion. When a metal surface is coated with an adhesive layer, the coated surface can typically be used to ensure a so-called "adhesive bond" between the coated metal surface and another surface (typically a similar metal surface treated with the same polymer) that is in contact with all or part of the adhesive coating. In this application, the specific polymer used according to the invention reduces the occurrence of adhesive failure (in other words, it imparts an "anti-adhesive failure property"). Within the scope of the invention, the inventors have now observed that the strength of the adhesion between the adhesive and the metal surface is particularly high, to the extent that when sufficiently high mechanical stress is applied to separate the adhesive-bonded surfaces, especially after exposure to corrosive conditions, cohesive failure occurs rather than (or at least more preferably) adhesive failure.

[0009] Cohesion loss effect is understood to mean that the failure between two surfaces bonded by an adhesive occurs within the adhesive itself, thus the adhesive remains on both surfaces.

[0010] Adhesive failure is understood as the failure between two surfaces bonded by an adhesive occurring on one surface, while the adhesive remains on the other.

[0011] The improved adhesion between two surfaces, treated with the polymer of the present invention and then assembled with an adhesive, is reflected in resistance to adhesive failure, which means that cohesive failure will instead occur, especially after aging, compared to other existing treatments.

[0012] More specifically, the present invention uses at least one polymer P, which is a polymer obtained by free radical copolymerization of a mixture of the following:

[0013] (i) acrylic acid; and

[0014] (ii) optionally, methacrylic acid; and

[0015] (iii) At least one monomer M, which is an olefinically unsaturated monomer carrying an unsaturated heterocycle having at least two nitrogen atoms, wherein the monomer M is preferably an olefinically unsaturated imidazole having the following formula (I):

[0016]

[0017] in:

[0018] R 1 It is H or methyl-CH3, and preferably H; and

[0019] A is a connection key selected from the following groups:

[0020] Covalent single bond; and

[0021] Spacer groups, such as the groups -CO-NH-(CH2). n -or -CO-O-(CH2) n -

[0022] Where n is an integer from 1 to 5, typically equal to 3 or 4.

[0023] All or some of the imidazole functional groups present in polymer P may optionally be quaternized. In this case, each quaternized imidazole functional group is associated with a suitable counter anion (e.g., Br-, TFSI, or any other suitable monoanion or polyanion), typically represented by the following formula:

[0024]

[0025] Where R 2 Typically H or alkyl, typically carrying 1 to 12 (preferably 1 to 6) carbon atoms.

[0026] Quaternization of all or part of the imidazole functional groups can be achieved by quaternization of all or part of the monomer and / or by post-quaternization of the imidazole functional groups of the polymer.

[0027] Monomer M can be, for example:

[0028] - Vinylimidazole having formula (Ia):

[0029]

[0030] - Quaternized vinylimidazoles of formula (Ib):

[0031]

[0032] Where R 2 It is as defined above;

[0033] - Monomers with formula (Ic)

[0034]

[0035] Where n and R 1 It is as defined above.

[0036] n is typically equal to 3;

[0037] - Quaternized monomers with formula (Id)

[0038]

[0039] Where n and R 1 and R 2 It is as defined above.

[0040] n is typically equal to 3;

[0041] - Its mixtures (e.g., a mixture of monomer (Ia) and monomer (Ib); or a mixture of monomer (Ic) and monomer (Id); or a mixture of four monomers).

[0042] Instead of an imidazole group, monomer M may have another unsaturated heterocycle having at least two nitrogen atoms. For example, M may have a pyrazole group, an indazole group, or a triazole group.

[0043] The divalent spacer group A in formula (I) can typically be the group -CO-NH-(CH2). n -or -CO-O-(CH2) n However, any other covalently linked groups can be considered, for example, from compounds having formula (IX):

[0044]

[0045] - Produced by reaction with compounds having the formula (IY):

[0046]

[0047] - Where X and Y are two groups that react together to form a covalent bond.

[0048] For example, Y could be -(CH2). m -NH2 group, wherein m is from 1 to 4, preferably 2 or 3. In this case, X can be, for example, a carboxylic acid, acyl chloride, acid anhydride or epoxy.

[0049] According to another variant, Y can be -(CH2). m -OH group, wherein m is from 1 to 4, preferably 2 or 3. In this case, X can be, for example, a carboxylic acid, acyl chloride, acid anhydride or ester.

[0050] Polymer P is a polymer obtained through comonomers (i), (ii), and (iii), i.e., it has the structure obtained by such polymerization, but polymer P is not necessarily obtained by this method. Alternatively, polymer P can be obtained, for example, by: a first step (E1) copolymerizing acrylic acid, methacrylic acid, and a compound having formula (IX) to produce polymer P0, and then a second step (E2) post-grafting polymer P0 by reacting it with compound (IY).

[0051] -When the Y in the compound (IY) used in step (E2) is -(CH2). m When the -NH2 group is present, the compound (IX) used in step (E1) may be advantageously selected from: additional acrylic acid or methacrylic acid, or esters thereof; maleic anhydride; vinyl benzyl chloride; glycidyl methacrylate; and (block) ethyl isocyanate methacrylate.

[0052] -When the Y in the compound (IY) used in step (E2) is -(CH2). m When the -OH group is present, the compound (IX) used in step (E1) may be advantageously selected from additional acrylic acid, methacrylic acid, maleic anhydride or their esters.

[0053] - In addition, quaternization of all or part of the imidazole functional groups of polymer P can occur, which is produced by quaternization of all or part of the monomer and / or by post-quaternization of all or part of the imidazole functional groups of the polymer.

[0054] At least one polymer P, which is obtained by free radical copolymerization of a mixture of the following:

[0055] (i) Acrylic acid (AA); and

[0056] (ii) Optionally, methacrylic acid (MAA); and

[0057] (iii) At least one monomer M, which is an olefinically unsaturated monomer carrying an unsaturated heterocycle having at least two nitrogen atoms, wherein the monomer M is preferably an olefinically unsaturated imidazole having formula (I).

[0058] It can be further included

[0059] (iv) less than 10% mol of one or more additional monomers M', the additional monomers being selected from the group consisting of hydrophobic monomers and amphiphilic monomers, provided that the amount of AA and optionally MAA is at least 60% mol.

[0060] In this embodiment, when an additional monomer M' is present in polymer P, the hydrophobic and / or amphiphilic monomer is selected from the group consisting of the following monoolefinic unsaturated monomers:

[0061] i) Alkyl esters of maleic anhydride and (meth)acrylic acid, such as monomethyl maleic anhydride, dimethyl maleic anhydride, monoethyl maleic anhydride, diethyl maleic anhydride, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate.

[0062] ii) Hydroxyalkyl esters of maleic anhydride and (meth)acrylic acid, such as monohydroxyethyl maleic anhydride, dihydroxyethyl maleic anhydride, hydroxyethyl (meth)acrylic acid, hydroxypropyl (meth)acrylic acid, and hydroxybutyl (meth)acrylic acid.

[0063] iii) Ethoxylated and propoxylated derivatives of maleic anhydride, such as poly(propylene oxide)-b-poly(ethylene oxide) maleic acid half-ester or diester, alkyl-poly(ethylene oxide) maleic acid half-ester or diester,

[0064] iv) Ethoxylated and / or propoxylated ethoxylated and / or propoxylated derivatives of hydroxyalkyl (meth)acrylic acid, such as poly(propylene oxide)-b-poly(ethylene oxide)-(meth)acrylate ethyl ester.

[0065] v) Ethoxylated and / or propoxylated derivatives of (transesterified) esterified (meth)acrylic acid and esters, such as poly(propylene oxide)-b-poly(ethylene oxide)(meth)acrylate and alkyl-poly(ethylene oxide)(meth)acrylate.

[0066] vi) Vinyl ethers, such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, 2-ethylhexyl vinyl ether, vinyl cyclohexyl ether, dodecyl vinyl ether, 2-(diethylamino)ethyl vinyl ether, 2-(di-n-butylamino)ethyl vinyl ether

[0067] vii) Allyl ethers, such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, and 2-ethylhexyl vinyl ether.

[0068] viii) Vinyl esters, such as vinyl acetate or vinyl propionate.

[0069] (ix) Alkyl-substituted acrylamides, such as N-tert-butylacrylamide or N-methyl(meth)acrylamide.

[0070] Preferably, the additional monomer M' present in polymer P is selected from the group consisting of:

[0071] i) Monoethyl maleic anhydride, diethyl maleic anhydride, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate

[0072] ii) Maleic anhydride monohydroxyethyl ester, maleic anhydride dihydroxyethyl ester, (meth)acrylate hydroxyethyl ester, (meth)acrylate hydroxypropyl ester, (meth)acrylate hydroxybutyl ester

[0073] iii) Poly(propylene oxide)-b-poly(ethylene oxide) maleate half ester

[0074] iv) Poly(propylene oxide)-b-poly(ethylene oxide)-(meth)acrylate ethyl ester

[0075] v) Poly(propylene oxide)-b-poly(ethylene oxide)(meth)acrylate, alkyl-poly(ethylene oxide)(meth)acrylate

[0076] vi) Vinyl acetate and vinyl propionate.

[0077] Preferably, the list does not contain vinyl aromatic monomers, and in particular, it does not contain styrene.

[0078] The molar proportion of monomer M' must not exceed 10% mol of the total molar proportion of monomers (acrylic acid + methacrylic acid + M + M') present in polymer P; otherwise, polymerization in water will occur in the dispersion medium because the polymer will no longer be soluble in water, requiring the use of an undesirable surfactant in the final application. Advantageously, the molar proportion of monomer M' is less than 5% mol.

[0079] The minimum molar ratio of AA and optionally MAA is 60%, otherwise the performance in the application will be unsatisfactory.

[0080] In fact, the presence of hydrophobic and / or amphiphilic monomers M' is due to the need to polymerize the polymer P of the present invention in aqueous solution without the use of surfactants, and not in an emulsion as in the case of latex. The monomers used must be water-soluble or highly dispersible and should not affect the solubility of the resulting polymer P.

[0081] Therefore, in a preferred embodiment of the invention, polymer P contains no additional monomer M', meaning that polymer P is obtained by free radical copolymerization of a mixture consisting essentially of, and notably, of, the following:

[0082] (i) acrylic acid; and

[0083] (ii) optionally, methacrylic acid; and

[0084] (iii) At least one monomer M, which is an olefinic unsaturated monomer carrying an unsaturated heterocycle having at least two nitrogen atoms, wherein the monomer M is preferably an olefinic unsaturated imidazole having formula (I).

[0085] According to this embodiment, apart from (i), (ii), and (iii), no other monomers exist in polymer P, and polymer P has high solubility in water. This solubility in water is assessed by measuring the transparency of 1% of the active ingredient in water: the transmittance measured in a glass trough with a light path length of 1 cm must be higher than 95%.

[0086] This requirement for the water solubility of polymer P makes it easy to use in applications because it can be sprayed or deposited in any manner without foaming or requiring the use of surfactants (defoamers) to control foam. This is not the case for polymers obtained by polymerization in emulsions, such as latex, where foaming is a limiting factor for its sprayability and instability under high shear.

[0087] Typically, polymer P is obtained by free radical copolymerization of a mixture of acrylic acid (preferably methacrylic acid) and at least one monomer M. Preferably, polymer P is obtained by free radical copolymerization of a mixture having the following molar ratio based on the total amount of acrylic acid, methacrylic acid, and monomer M having formula (I):

[0088] - Acrylic acid (AA): from 5% to 95%, notably from 5% to 50%, preferably from 20% to 40% (e.g., about 25% to 30%),

[0089] - Methacrylic acid (MAA): from 0% to 90%, preferably from 25% to 90%, more preferably from 60% to 80% (e.g., about 65% to 75%).

[0090] - Monomer M: from 1% to 50%, for example from 1% to 30%, notably from 1% to 20%, and even 2% to 15% (for example, about 3% to 10%).

[0091] Compared to polymers outside the above ranges, the above molar ratios of monomers in polymer P show particularly good results in terms of resistance to adhesive failure. For example, when the amount of AA+MAA in polymer P is too low (below 60% mol), the performance is unsatisfactory. The same situation occurs when monomer M is absent. When the amount of M is too high (above 50%), there is a risk of product discoloration, and the resulting polymer is economically unfeasible.

[0092] Furthermore, the polymer P used according to the present invention preferably has the following number-average molecular weight (M). n ): At least 7,500 Da, for example 10 kDa to 1500 kDa, for example 10 kDa to 150 kDa, notably between 10 kDa and 100 kDa. Typically, the polymer P used according to the invention has a number average molecular weight (M) from 20 to 100 kDa, for example 20 to 50 kDa. n ).

[0093] The polymer P, particularly suitable for use in this invention, is a statistical (random) copolymer having a weight-average molecular weight of about 20 to 50 kDa, which is a copolymer of acrylic acid, optionally methacrylic acid, and monomer M (preferably in a molar ratio of about 26 / 70 / 04 to 20 / 70 / 10).

[0094] Number-average and weight-average molecular weights were measured using size exclusion chromatography (SEC). Notably, the SEC was equipped with a multi-angle laser scattering (MALLS) Mini Dawn TREOS detector and an Agilent concentration detector (RI detector). The SEC-MALLS system was run on a three-column Varian Aquagel OH mixed H, 8 μm, 3 × 30 cm, at a flow rate of 1 mL / min, with the following mobile phase: 85% water, 100 mM NaCl, 25 mM NaH₂PO₄, 25 mM Na₂HPO₄-15% methanol. Polymer samples were diluted to 0.5 wt% activity in the mobile phase for at least 4 hours, then filtered through a 0.45 μm microporous filter, and 100 μL were injected into the mobile phase stream. Absolute molar masses were obtained, where the dn / dC of poly(acrylic acid) was equal to 0.1875 mL / g.

[0095] Polymer P can be prepared by conventional free radical polymerization as well as by reversible deactivation (controlled) free radical polymerization. The reversible deactivation (controlled) free radical polymerization technique will be selected according to the composition of the target polymer. For example, for polymers containing up to 30 mol% of methacryloyl-based monomers (examples of AA / MAA / vinylimidazole = 50 / 30 / 20 mol / mol / mol), it can be prepared by MADIX with xanthate (such as Rhodixan A1 from Solvay), or for polymers containing more than 30 mol% of methacryloyl-based monomers (examples of AA / MAA / vinylimidazole = 20 / 70 / 10 mol / mol / mol), it can be prepared by RAFT with trithiocarbonate (such as 4-((((2-carboxyethyl)thio)thiocarbonyl)thio)-4-cyanopentanoic acid (BM1433, from Boron Molecular).

[0096] According to a specific aspect, a particular object of the present invention is the use of at least one polymer P as defined above for treating metal surfaces intended to be coated with paint, varnish, or adhesive (preferably adhesive). The metal surface to be treated is preferably a surface of a metal selected from aluminum, steel, zinc, magnesium, and alloys thereof. The present invention is of particular interest for metal surfaces of aluminum or aluminum alloys.

[0097] According to a possible (but not mandatory) embodiment, a conversion coating is applied to the metal surface to be treated (in other words, the conversion composition is applied to the metal surface to form a conversion coating thereon) through a reaction between the surface and the conversion composition. In this case, typically:

[0098] - The conversion composition contains all or part of polymer P as an additive; and / or

[0099] - Apply a conversion coating to the metal surface and then apply all or part of the polymer P onto the conversion coating.

[0100] According to another possible embodiment compatible with the previous embodiments, all or part of the polymer P is present in the coating, varnish or adhesive coating applied to the surface, optionally after the conversion coating is applied to the metal surface.

[0101] According to another aspect, a specific object of the present invention is a method for coating a metal surface with a paint, varnish, or adhesive, the method comprising the step of treating said surface with at least one composition comprising at least one polymer P as defined above. Within this scope, compositions comprising polymer P can typically be:

[0102] - A conversion composition comprising polymer P; and / or

[0103] - A solution or dispersion of the polymer P, preferably applied to the surface after the conversion coating is applied to the surface to be treated; and / or

[0104] - Coatings, varnishes, or adhesives that may contain all or part of the polymer P.

[0105] The specific objects of the invention also include the useful polymer P and compositions containing polymer P (especially conversion compositions containing polymer P; coating, varnish or adhesive compositions containing polymer P; and solutions or dispersions containing polymer P for surface treatment).

[0106] Typically, polymer P is present in the conversion composition and / or in a solution or dispersion applied to the surface to be treated. In this case, a coating, varnish, or adhesive is usually applied to the surface previously treated with the polymer. According to some specific embodiments, an additional layer may be applied between the treated surface and the coating, varnish, or adhesive.

[0107] A more specific object of the present invention is the use of at least one polymer P, as defined above, for treating a first metal surface (S1) intended to be bonded to a second surface (S2) by an adhesive and for imparting resistance to adhesive failure (in other words, for providing resistance to adhesive failure for the connection between surfaces S1 and S2). An additional advantage of the adhesive bond obtained according to the invention is its high resistance to corrosive and humid atmospheres, which results in a durable adhesive bond. In most cases, the polymer is also used to obtain this additional effect (i.e., to further impart resistance to corrosive and humid atmospheres to the bond; in other words, to obtain both highly effective and durable adhesion).

[0108] In other words, at least one polymer P as defined above is used to treat a first metal surface (S1) intended to be bonded to a second surface (S2) by adhesive bonding and to impart resistance to adhesive failure to the bond, while also providing very good resistance to aging of the adhesive bond. This property can be measured by tensile testing of so-called “single lap-shear” (SLS) components, as defined in ASTM D-1002 10, on newly bonded SLS components, and on SLS components aged in a corrosive atmosphere, a humid atmosphere, or a corrosive atmosphere followed by a humid atmosphere, as in ASTM G85-Annex 3. Other tests combine corrosive stress and mechanical stress (e.g., compressive load), such as BV 101-07, known as the Ford Durability Stress Test for Adhesive Lap-shear Bonds, or the Arizona Proven Ground Exposure (APGE). Notably, adhesive bonding between the two surfaces S1 and S2 using the polymer P according to the invention has been shown to provide a failure phase that retains greater cohesion after aging.

[0109] Typically (but not necessarily), the second surface (S2) is also a metallic surface, having or not having the same properties as the first surface (S1). According to an advantageous embodiment, the second surface (S2) is a metallic surface also treated with a polymer P having formula (a), typically but not necessarily the same polymer P as the first surface (S1).

[0110] More generally, the polymer P used according to the invention is preferably used to treat the two surfaces (S1) and (S2) before the adhesive bonds the two surfaces, especially when (S2) is a metallic surface.

[0111] The first metal surface (S1) is preferably a surface comprising a metal selected from aluminum, steel, zinc, magnesium, titanium, copper and their alloys, or cobalt-nickel alloys. The present invention is particularly interested in metal surfaces of aluminum or aluminum alloys. The present invention is particularly interested in the case where the surface (S1) is an aluminum or aluminum alloy metal surface.

[0112] The second surface (S2) can be a metallic or non-metallic surface.

[0113] According to an embodiment of interest, the second surface (S2) is a surface comprising a metal, advantageously selected from aluminum, steel, zinc, magnesium, titanium, copper and alloys thereof, or cobalt-nickel alloys. According to one embodiment, surfaces (S1) and (S2) are identical in nature, but they may also be different according to other possible embodiments of the invention. According to a variant of interest, both surfaces (S1) and (S2) are metallic surfaces of aluminum or aluminum alloys.

[0114] According to another possible embodiment, the second surface (S2) is a non-metallic surface, such as a plastic surface (e.g., a plastic surface based on polyamide, PEEK, or ABS); or a composite surface (based on, for example, CFRP or glass fiber reinforced plastic).

[0115] Regardless of the exact properties of surfaces (S1) and (S2), according to possible embodiments, a conversion coating can be applied to the metal surface (S1) through a reaction between the surface and the conversion composition (in other words, the conversion composition is applied to the metal surface to form a conversion coating thereon). However, according to the invention, the use of a conversion coating is not mandatory, and according to specific embodiments, a conversion coating is not applied to surface (S1). When using the conversion composition, typically:

[0116] - The conversion composition contains all or part of polymer P as an additive; and / or

[0117] - Apply a conversion coating to the surface (S1), and then apply all or part of the polymer P to the conversion coating.

[0118] The second surface (S2) can also be treated with a similar conversion coating under the same conditions, especially when the second surface (S2) is a metallic surface. However, according to the invention, the use of a conversion coating is not mandatory, and in certain embodiments, a conversion coating may not be applied to the surface (S2).

[0119] According to another possible embodiment compatible with the previous embodiments, all or part of the polymer P is included in the adhesive composition applied to surfaces (S1) and (S2). According to this embodiment, the polymer can typically be introduced into the adhesive composition as a solid powder, the powder containing only the polymer or the polymer contained on the surface of the mineral filler (the powder is typically obtained by spray drying a solution or suspension of the polymer, typically in the presence of the mineral filler). According to another aspect, another specific object of the invention is a method for bonding a first metal surface (S1) to a second surface (S2) (preferably as defined above), the method comprising:

[0120] - Treat the first surface (S1) with at least one composition containing at least one polymer P as defined above (preferably the surface (S1) is cleaned and / or activated prior to treatment with the polymer P); and

[0121] - Optionally, the second surface (S2) is treated with at least one composition comprising at least one polymer P as defined above (and preferably, the surface (S2) is cleaned and / or activated prior to treatment with the polymer P); and

[0122] - The two surfaces are bonded together by applying an adhesive composition between the surface (S1) and the surface (S2).

[0123] Within this scope, compositions containing polymer P can typically be:

[0124] - A conversion composition comprising polymer P; and / or

[0125] - A solution or dispersion of the polymer P, preferably applied to the surface after the conversion coating is applied to the surface to be treated; and / or

[0126] - An adhesive composition which may contain all or part of polymer P.

[0127] Typically, polymer P is present in the conversion composition and / or in a solution or dispersion applied to the conversion coating. In this case, the binder is applied to the surface previously treated with the polymer.

[0128] According to some specific embodiments, an additional layer is applied between the treated surface (S1) and the adhesive (this is, for example, for a metal coil or part that is treated at a first location and then bonded to a second location): in this case, a lubricant can be applied to the treated coil or part to protect it during transport and storage and to facilitate downstream operations (coil cutting, punching, stamping, forming, etc.).

[0129] According to yet another aspect, a specific object of the invention is to include materials comprising two surfaces bonded together by an adhesive, the first metal surface comprising a metal surface (S1) which is wholly or partially (i) treated with a polymer P as defined above and (ii) bonded by an adhesive to a second surface (S2) preferably defined above.

[0130] These materials include, in particular, materials having a metallic surface (S1) that is wholly or partially covered by the following:

[0131] - At least one coating (typically a conversion coating and / or paint, varnish, or adhesive layer) comprising at least one polymer P; and / or

[0132] - A layer (typically a conversion coating) containing the following: a reaction product of polymer P as defined above with a metal having a treated surface or another compound present in the layer, or polymer P tightly bonded to the other compound (e.g., through complexation, ionic bonding or hydrogen bonding).

[0133] The specific features and possible embodiments will now be described in more detail.

[0134] Metal surface (S1)

[0135] Any metal surface can be treated with the polymer P of the present invention, but the present invention is particularly suitable for treating the following metal surfaces:

[0136] - Aluminum or aluminum-based alloys; or

[0137] - Steel, such as galvanized steel (hot-dip galvanized HDG or electro-galvanized EG); or cold-rolled steel (CRS); or

[0138] - Magnesium or magnesium-based alloys; or

[0139] - Zinc or zinc-based alloys; or

[0140] - Titanium or titanium-based alloys.

[0141] The present invention is of particular interest for the metallic surfaces of aluminum and aluminum alloys (such as aluminum alloy AA 5754 tested in the appended examples or other alloys such as the 1xxx, 2xxx, 3xxx, 4xxx, 5xxxx, 6xxx, 7xxx series (such as AA 1050, 2024, 3003, 5182, 5005, 6111, 6016, 6060, 6063, 6182, 7075)).

[0142] Optional conversion coating

[0143] When a conversion coating is applied to one or both of surfaces (S1) and / or (S2), the conversion coating can be obtained by bringing the surface into contact with any conversion composition known from the prior art.

[0144] Contact between the metal surface and the conversion composition can be made by any means known per se, such as dip coating in a conversion bath or spray coating, as an illustrative example.

[0145] The conversion compositions used according to the invention typically contain fluoride anions and cationic metals, such as compounds like H2CrF6, or more preferably chromium-free compounds such as H2TiF6, H2ZrF6, H2HfF6, H2AlF6, H2SiF6, H2GeF6, H2SNF4, or HBF4.

[0146] The conversion composition may also contain other compounds, such as silane precursors, and / or cerium salts, and / or terbium molybdate.

[0147] Furthermore, according to specific embodiments, the conversion composition may contain all or part of the polymer P used in the invention for surface treatment. In this case, the application of the conversion layer itself results in the surface treatment according to the invention.

[0148] In other respects, this treatment is typically obtained after the formation of the conversion layer by bringing the metal surface with the conversion layer into contact with polymer P (which can typically be applied to the conversion layer in the form of a solution or suspension of polymer P, or within a paint, varnish, or adhesive composition applied to the conversion layer).

[0149] According to specific embodiments, it is possible to use polymer P both in the conversion composition and in the adhesive composition applied to the conversion layer.

[0150] If any patent, patent application, or disclosure incorporated herein by reference conflicts with the description of this application to the extent that it may lead to ambiguity in terminology, then this description shall take precedence.

[0151] The following examples illustrate the present invention.

[0152] Example

[0153] Example 1.

[0154] In these examples, polymers according to the invention were tested, which were obtained by copolymerization of a mixture of acrylic acid, methacrylic acid and N-vinylimidazole (VIm).

[0155] Example 1.1

[0156] Polymer P1 (AA / MAA / VIm 26 / 70 / 04mol / mol / mol) was prepared as follows:

[0157] Solution 1: Dissolve 7.8 g of 97% 2,2'-azobis(2-methylpropanediamine) dihydrochloride (V50) in 68.3 g of water.

[0158] Solution 2a (AA / VIm = 26 / 04 mol / mol): 35.4 g of AA and 7 g of VIM were diluted in 17.6 g of water.

[0159] Solution 2b: 35% caustic alkali solution in water (113 mL).

[0160] Solution 3: Dilute 114g of MAA in 74g of water.

[0161] Solution 1, along with 5% solution 2a and 114 g of deionized water, was placed together in a 700 ml reactor at room temperature. The reactor was equipped with appropriate stirring, inlet, feed, and temperature control devices.

[0162] Then, under nitrogen degassing conditions, the reactor temperature is heated to 60°C within 1 hour.

[0163] When the temperature has reached 60°C, two feeding operations begin under the nitrogen layer:

[0164] - Within 4 hours, feed the remaining 95% of solution 2a and solution 2b.

[0165] - Feed solution 3 within 5 hours

[0166] Once the longest feed is finished, keep the reaction mixture at 60°C for another two hours, then cool it to room temperature.

[0167] During the aggregation process, through 1 The successful introduction of monomers was monitored by 1H NMR spectroscopy, and by... 1 Both ¹H NMR spectroscopy and size exclusion chromatography were used to analyze the final product.

[0168] Proton nuclear magnetic resonance was recorded using a 300 MHz spectrometer from Bruker. 1 ¹H NMR spectrum. To measure the conversion rates of AA, MAA, and VIM, four drops of the reaction mixture were diluted in approximately 1 g of deuterated water (D₂O). The conversion rates of AA were >99.6%; MAA >99.9%; and VIM >99.9%.

[0169] The average molecular weight was measured using size exclusion chromatography (SEC) equipped with a multi-angle laser scattering (MALLS) Mini Dawn TREOS detector and an Agilent Technologies concentration detector (RI detector). The SEC system was run on a three-column Varian Aquagel OH mixed H, 8 μm, 3 × 30 cm column at a flow rate of 1 mL / min, with the following mobile phase: 100% water, 100 mM NaCl, 25 mM NaH₂PO₄, 25 mM Na₂HPO₄, buffer pH = 7. Polymer samples were diluted to 0.5 wt% activity in the mobile phase for at least 4 hours, then filtered through a 0.45 μm microporous filter, and 100 μL were injected into the mobile phase stream. Absolute molar masses were obtained, where the dn / dC of poly(acrylic acid) was equal to 0.1875 mL / g. n =29.5 kg / mol; M w =76 kg / mol; polydispersity index

[0170] Example 1.2

[0171] Polymer P2 (AA / MAA / VIm 20 / 70 / 10mol / mol / mol) was prepared using the same method:

[0172] Solution 1: Dissolve 7.0 g of 97% 2,2'-azobis(2-methylpropanediamine) dihydrochloride (V50) in 60.7 g of water.

[0173] Solution 2a (AA / VIm = 20 / 10 mol / mol): 24.2 g of AA and 15.8 g of VIM were diluted in 16.6 g of water.

[0174] Solution 2b: 35% caustic alkali solution (129 mL) in water.

[0175] Solution 3: Dilute 101g of MAA in 66g of water.

[0176] AA's conversion rate is 99%; MAA's conversion rate is >99.9%; VIM's conversion rate is >99.9%.

[0177] M n =41kg / mol; M w =107 kg / mol; polydispersity index

[0178] The properties of polymers P1 and P2 were evaluated using H111 aluminum alloy specimens (100 mm long, 25 mm wide, 3 mm thick) of type AA 5754 from FBCG, by single lap shear (SLS) tests before and after aging under corrosive conditions. The specimens were prepared according to the following protocol and assembled to form a single lap assembly as described in D1002-10.

[0179] Step 1 - All 20 samples were cleaned and etched together in a single combined cleaning and etching step in a 4L bath at 50°C in a stainless steel tank for 3 minutes with gentle agitation. This bath was typically prepared by diluting a commercially available formulation, Chemtec DBT ALU 200 (available from Chemtec Aertec) (5g DBT ALU 200 in 995g of water). The samples were then rinsed twice with deionized water over 1 minute.

[0180] Step 2 - The samples were then pretreated by immersion in a treatment bath for 2 minutes containing polymers at 50°C and at the concentrations shown in Table 1 below. They were then rinsed together with a stream of deionized water for 1 minute and dried at 60°C for 30 minutes.

[0181] Step 3 – Then assemble the specimens in pairs, each pair forming a so-called single-overlap shear “assembly”: Place two specimens horizontally parallel, one on top of the other, forming a 12.5 mm long and 25 mm wide overlap (“overlap area”, including one of the end areas of each of the two 25 mm wide specimens, i.e., the last 12.5 mm of the specimen’s 100 mm length). Apply structural high-temperature curing epoxy adhesive beads (Betamate 1496, from Dow Chemical Company) to the overlap area of ​​the lower specimen using a gun at 7 bar. Then press the upper specimen down, thus forming a 12.5 mm long and 25 mm wide bond area. Use paperclips before and during curing to maintain the integrity of the assembly. Then cure the adhesive according to the adhesive manufacturer’s guidelines, typically at 180°C for 40 min. Finally, remove the paperclips.

[0182] Step 4 - Perform a tensile strength test on the component obtained in Step 3.

[0183] Materials used Zwick / Roell-Z50 features jaws with a gripping component tip exceeding 50 mm and a traction speed of 10 mm / min. (Each jaw clamps one of a pair of bonded specimens in a 50 mm gripping area located at the end of each specimen opposite the overlapping area. The jaws are then moved to traction each specimen horizontally in the direction from the initial self-bonding area toward the gripping area.)

[0184] Step 5 - Perform tensile strength testing on the components obtained in Step 3 after aging.

[0185] 5.1. Aging Cycle Test

[0186] The aging test was conducted according to ASTM G85-Annex 3 (SWAAT, 2011) in a Q-FOG CRH 600L corrosion chamber from Q-FOG.

[0187] Under the following conditions:

[0188] • 30 minutes of acidified salt spray, followed by

[0189] • Soak for 90 minutes at a relative humidity >98%.

[0190] Under the following conditions:

[0191] • Room temperature - constant 49℃

[0192] • Air saturator temperature - constant 57℃

[0193] Relative humidity -> 98%

[0194] • The pH of the falling solution is between -2.8 and 3.0.

[0195] • Volume of the falling solution: -1.0 to 2.0 ml / 80 cm³ 2 / Hour

[0196] • Exposure period - 1000 hours

[0197] After the exposure period is complete, the components are washed with lukewarm water to remove and neutralize any excess acid and any remaining salt residue.

[0198] Then, all components are air-dried using forced ambient temperature, followed by an overlap shear tensile test.

[0199] 5.2 Tensile Strength Test

[0200] Under the conditions of tensile strength test I in step 4

[0201] The results are reported in Tables 2 through 5 below (values ​​are averages: these tests were performed on 3 pre-aging components and 5 post-aging components), with the following changes in step 2. The polymer was diluted with deionized water, and the resulting treatment bath was tested either as is (without pH adjustment, "initial pH") or after acidification (pH adjusted with sulfuric acid):

[0202]

[0203] Table 1: Conditions for steps 1 and 2

[0204] The following are the reported performance before and after aging, and the ratio between the post-aging value and the pre-aging value (referred to as the "retention rate"):

[0205]

[0206] Table 2: Maximum Load

[0207]

[0208] Table 3: Strain measured under maximum load

[0209]

[0210] Table 4: Energy measured under maximum load

[0211]

[0212]

[0213] Table 5: Phase after adhesive failure

[0214] ***:

[0215] (c): Cohesive fracture

[0216] (a): Adhesive fracture

[0217] (a / c): Adhesion and cohesive fracture

[0218] (~c): Slightly cohesive fracture

[0219] *Actual performance

[0220] Example 2 describes a polymer according to the invention, which has an amide propyl spacer between the polymer backbone and the imidazole group:

[0221] Example 2: The following preparation of polymer P3 (AA / methacrylamide propylimidazolium 92 / 0.8 mol / mol):

[0222] Synthesis of poly(acrylic acid) via reversible deactivated (controlled) free radical polymerization:

[0223] 219 ml of DI water and 69 ml of methanol were placed in a round-bottom flask. 30 g of acrylic acid was added to the flask, and the reaction mixture was stirred until homogeneous. Then, 0.32 g of Rhodixan A1 was added as a control agent. The solution was then purged with N2 for 1 hour. 0.4048 g of VA-044 initiator (2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, TCI) was added to the reaction mixture, and purging was continued for 15 min. Polymerization was carried out at 60 °C under N2 atmosphere for 5 hours. The reaction mixture was then exposed to air, and aliquots were taken in D2O for proton NMR spectra recording using a Bruker 400 MHz instrument. 1 (H NMR). This confirmed the complete conversion of the acrylic acid monomer. The polymer was precipitated in acetone, dissolved in water, and precipitated again in acetone. The precipitated polymer was dried under vacuum at 60°C for 12 hours.

[0224] Mean molecular weight was measured by gel permeation chromatography (GPC) using a Waters 515 instrument equipped with a column oven, licensed software (GPC module), and a Shodex RI-71 detector. The SEC system was run at a flow rate of 1 mL / min on a polymerLab Aquagel-OH-50 column with a guard column (linear MW operating range: 500 to 600,000 g / mol, PS equivalent) with the following mobile phase: 0.25 M NaNO3 + 0.03 M Na2HPO4 + 0.003 M NaN3-pH-9. A diluted solution of the polymer sample at 10 mg / mL was prepared in the mobile phase and then filtered through a 0.2 μm microporous filter before injection into the system. 100 μL of this solution was injected into the mobile phase, and the run time was 30 min. Measurements were performed at 40 °C. Poly(acrylate-Na salt) (Polymer Lab-PL2140-0100) was used as the calibration standard. Results: M n =26,000 g / mol, M w =57,000 g / mol, polydispersity index =2.17.

[0225] The aminopropyl imidazole-functionalized poly(acrylic acid) (polymer P3) was synthesized in an organic NMP solvent via a conventional DCC (dicyclohexylcarbodiimide) coupling reaction.

[0226] In a 500 ml round-bottom flask equipped with a water condenser and mechanical stirrer, 25 g of poly(acrylic acid) (PAA; synthesized as described above) and 100 ml of NMP were introduced at room temperature (22 °C). The mixture was degassed by bubbling nitrogen at room temperature for 30 min. The reaction mixture was then heated to 60 °C with continuous stirring and incubated overnight under a nitrogen atmosphere. After the PAA was completely dissolved, 7 g of DCC (Sigma-Aldrich) was slowly added at 60 °C with stirring for 30 min, followed by the addition of 4.34 ml of aminopropylimidazolium (Sigma-Aldrich) over 20 min; the reaction mixture was then maintained at 70 °C for 48 h.

[0227] The polymer was precipitated in a mixture of ethyl acetate and THF (1:1), dissolved in MeOH, and then reprecipitated in ethyl acetate. The polymer was then dried in a vacuum oven at 70-75°C for 24 hours. The polymer yield was approximately 90%.

[0228] Proton NMR spectra were recorded using NMR (Bruker 400MHz). 1The percentage of propylimidazolium groups introduced into the polymer was calculated using ¹H NMR. Approximately 20 mg of the polymer was dissolved in deuterated water (D₂O) to record the spectrum. The results showed that the ratio of acrylic units to imidazolium propylacrylamide units was 92 / 8 mol / mol.

[0229] Examples 3 and 4 describe polymers according to the invention having imidazoline groups:

[0230] Example 3: Preparation of polymer P4 by complete quaternization of polymer P3 with hexane

[0231] In a 250 ml round-bottom flask equipped with a water condenser and mechanical stirrer, 7 g of aminoimidazole (8 mol%) functionalized PAA (polymer P3, from Example 2) and 70 ml of NMP were introduced at room temperature (22 °C). The mixture was degassed by vigorously bubbling nitrogen at room temperature for 30 min. After the polymer was completely dissolved, 11.88 g of hexane (Sigma-Aldrich) was added, and the mixture was stirred at 90 °C under a nitrogen atmosphere for 24 h.

[0232] The polymer was precipitated in a mixture of ethyl acetate and THF (1:1), then dissolved in methanol, and precipitated again in ethyl acetate. The polymer was then dried in a vacuum oven at 70-75°C for 24 hours. The yield of the functionalized polymer was approximately 50%.

[0233] Proton NMR spectra were recorded using NMR (Bruker 400MHz). 1 The percentage of quaternization of imidazole groups on the polymer backbone was calculated using ¹H NMR. Approximately 20 mg of the polymer was dissolved in deuterated methanol for spectral recording. Complete quaternization of the polymer was observed (acrylate units / imidazolium hexyl bromide units = 92 / 0.8 mol / mol).

[0234] The bromide content of the polymer was also calculated using argentometric titration. Details of the instrument used for the measurement are as follows: a Metrohm 905 automatic titrator equipped with an Ag / AgCl electrode (Metrohm part number: 6.0450.100) and Tiamo software (version 2.5), and an analytical balance capable of weighing up to 0.0001 mg.

[0235] Use the following reagents (obtained from Sigma-Aldrich).

[0236] 1. Methanol

[0237] 2.0.01N silver nitrate solution (AgNO3) - standardized in water using anhydrous potassium chloride (KCl) before the experiment.

[0238] 3. Potassium chloride (KCl)

[0239] 4.50% v / v nitric acid aqueous solution (HNO3)

[0240] 5. Milli Q Water (Deionized Water)

[0241] Sample preparation and titration: Weigh 0.0050 to 0.0060 g of the quaternized polymer and dissolve it in 30 mL of methanol, stirring until the sample is completely dissolved. Add 3-4 drops of 50% v / v HNO3 aqueous solution to acidify the sample solution. Titrate the solution with 0.01 N AgNO3 solution using an Ag / AgCl electrode. Record the endpoint as EP1.

[0242] Ionic bromide in μeq / g = (EP1 * 1000 * actual equivalent concentration of AgNO3) / weight of sample in g

[0243] ppm of ionic bromide = μeq / g of ionic bromide * 79.9 (molar mass of bromide)

[0244] % of ionic bromide = ppm of ionic bromide / 10000

[0245] The polymer contains 5% bromide by weight.

[0246] Example 4: Preparation of polymer P5 by copolymerization of acrylic acid, methacrylic acid, and monomers generated by hexyl bromide quaternization of vinylimidazolium:

[0247] The synthetic copolymer poly(methacrylic acid-co-acrylic acid-co-(3-hexyl-1-vinyl-1H-imidazolium-3-bromide)), VIMBr, was synthesized according to the method described in Separation and Purification Technology 224(2019)388-396, in which it was synthesized by a conventional free radical polymerization initiator: α,α′-azobisisobutylamidine dihydrochloride (AAPH or V50, Sigma-Aldrich).

[0248] Monomers: MAA (Sigma-Aldrich) = 75 mol%, AA (Sigma-Aldrich) = 20 mol%, VIMBr = 5 mol%.

[0249] Stock solution:

[0250] 70 wt% AA in H2O, 60 wt% MAA in H2O, 70 wt% VimBr in H2O, 10 wt% V50 in H2O

[0251] Molar ratio: I / (VImBr+AA+MAA)=1.5mol%

[0252] Final solids content 35 wt%

[0253] In a 100 mL three-necked round-bottom flask equipped with a magnetic stirrer, 0.22 g (5 wt% stock solution) of acrylic acid, 0.36 g (5 wt% stock solution) of 3-hexyl-1-vinyl-1H-imidazolium-3-bromide (VImBr), 42 g of water, and 0.87 g of V50 (10 wt% aqueous solution) were introduced at room temperature (22 °C). The mixture was degassed by purge with nitrogen for 60 min while the temperature of the solution was raised to 60 °C. The remaining 95% of the AA and VImBr stock solutions were mixed together, and a total of 11.08 g of the mixture of the two monomers was introduced into the reaction mixture over 3 h. Simultaneously, the MAA solution was started and carried out over 4 h (flow rate = 0.0723 mL / min). During the monomer addition, the solution became gelled, and the reaction was stopped after the complete addition of MAA.

[0254] The reaction mixture was precipitated in diethyl ether. The polymer was redissolved in methanol and then reprecipitated in ethyl acetate. Unreacted monomers were removed by Soxhlet extraction in THF. The polymer was filtered, dried under vacuum at 60 °C for 6 h, and characterized by 1H NMR in D₂O. The polymer contained no residual unreacted monomers. The polymer yield was approximately 50%.

[0255] Mean molecular weight was measured by gel permeation chromatography (GPC) using a Waters 515 equipped with a column oven, Clarity software (GPC module), and a Shodex RI-71 detector. The SEC system was run on two columns with guard columns—Polymer Lab Aquagel-OH-40 and Polymer Lab Aquagel-OH-30 in series—at a flow rate of 1 mL / min with the following mobile phase: 0.4 M NaCl + 0.05 M Na₂HPO₄ + 0.003 M NaN₃-pH-9 (pH adjusted with a few drops of 0.05 M NaH₂PO₄). A diluted solution of the polymer sample at 10 mg / mL was prepared in the mobile phase and then filtered through a 0.2 μm microporous filter before injection into the system. 100 μL of this solution was injected into the mobile phase, and the run time was 30 min. Measurements were performed at 40 °C. A Ready Cal-Kit PEO / PEG (PSS-PEOkitr1) was used as the calibration standard. Results: M n =81kDa, M w =162kDa, multidispersion index =2.

[0256] The properties of polymers P3, P4, and P5 were evaluated using AA5754 H22 aluminum alloy specimens (100 mm long, 25 mm wide, and 3 mm thick) from FBCG by single lap shear (SLS) tests before and after aging under corrosive conditions. As described above for polymers P1 and P2, specimens were prepared and assembled to form single lap assemblies.

[0257] The properties of polymer P2 were also evaluated using AA5754 H22 aluminum alloy samples from the same batch.

[0258] Table 6 reports the method changes, and Tables 7-10 report the performance results.

[0259]

[0260] Wipe the sample with acetone.

[0261] Table 6: Conditions for Steps 1 and 2

[0262]

[0263] Table 7: Maximum Load

[0264]

[0265] Table 8: Strain under maximum load

[0266]

[0267]

[0268] Table 9: Energy under Maximum Load

[0269]

[0270] Table 10: Phase after adhesive failure

[0271] (c): Cohesive fracture

[0272] (a): Adhesive fracture

[0273] (a / c): Adhesion and cohesive fracture

Claims

1. Use of at least one polymer P for treating a metal surface intended to be coated with a paint, varnish, or adhesive, said at least one polymer being obtained by free radical copolymerization of a mixture of: (i) 5 mol% to 95 mol% acrylic acid; (ii) optionally, 0 mol% to 90 mol% methacrylic acid; and (iii) 2 mol% to 15 mol% of at least one monomer M, said monomer M being an olefinically unsaturated imidazole having the following formula (I): Formula (I) in: R 1 is H or methyl; and A is a connection key selected from the following groups: Covalent single bond; and a spacer group selected from the group consisting of -CO-NH-(CH2) n - or -CO-O-(CH2)n- Where n is an integer from 1 to 5; Based on the total amount of acrylic acid, methacrylic acid and monomer M having formula (I).

2. Use according to claim 1, wherein, n is an integer equal to 3 or 4.

3. Use according to claim 1, wherein, The polymer P is used to treat the first metal surface (S1) which is intended to be bonded to the second surface (S2) by an adhesive and to impart resistance to adhesive failure to the bond.

4. The use according to claim 3, for further imparting the adhesive with resistance to corrosive atmospheres and resistance to humid atmospheres.

5. Use according to any one of claims 1 to 4, wherein, Polymer P further comprises less than 10 mol% of one or more additional monomers M', wherein the additional monomers are selected from the group consisting of hydrophobic monomers and amphiphilic monomers, wherein the hydrophobic monomers and amphiphilic monomers are selected from the group consisting of: i) Monoethyl maleic anhydride, diethyl maleic anhydride, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate ii) Maleic anhydride monohydroxyethyl ester, maleic anhydride dihydroxyethyl ester, (meth)acrylate hydroxyethyl ester, (meth)acrylate hydroxypropyl ester, (meth)acrylate hydroxybutyl ester iii) Poly(propylene oxide)-b-poly(ethylene oxide) maleate half ester iv) Poly(propylene oxide)-b-poly(ethylene oxide)-(meth)acrylate v) Poly(propylene oxide)-b-poly(ethylene oxide)(meth)acrylate, alkyl-poly(ethylene oxide)(meth)acrylate vi) Vinyl acetate, vinyl propionate, The prerequisite is that (i) the total amount of acrylic acid and optionally (ii) methacrylic acid is at least 60% mol.

6. The use according to claim 5, wherein, The molar proportion of monomer M' is less than 5 mol.

7. The use according to claim 5, wherein, The polymer P was obtained by free radical copolymerization of a mixture of monomers (i), (ii) and (iii).

8. The use according to claim 7, wherein, The polymer P is obtained by free radical copolymerization of a mixture, based on the total amount of acrylic acid, methacrylic acid, and monomer M having formula (I), the mixture having the following molar ratio: - Acrylic acid: from 5% to 50% - Methacrylic acid: from 25% to 90% - Monomer M: from 2% to 15%.

9. The use according to claim 8, wherein the mixture has an acrylic acid molar ratio of 20% to 40%.

10. The use according to claim 8, wherein the mixture has a molar ratio of 60% to 80% methacrylic acid.

11. The use according to any one of claims 1 to 4, wherein, The polymer P has a number-average molecular weight of at least 7,500 Da.

12. The use according to claim 11, wherein, The polymer P has a number-average molecular weight ranging from 10 kDa to 1500 kDa.

13. The use according to any one of claims 2 to 4, wherein, The first metal surface (S1) is a surface containing a metal selected from aluminum, steel, zinc, magnesium, titanium, copper and their alloys, or cobalt-nickel alloys.

14. The use according to claim 13, wherein, The first metal surface (S1) is an aluminum or aluminum alloy surface.

15. The use according to claim 3, wherein, The second surface (S2) is a metallic surface.

16. The use according to claim 3, wherein, The second surface (S2) is a non-metallic surface.

17. The use according to claim 16, wherein, The non-metallic surface is either a plastic surface or a composite surface.

18. The use according to any one of claims 2 to 4, wherein, The polymer P is used to treat the two surfaces before the adhesive bonding of the first metal surface (S1) and the second surface (S2).

19. A method for coating a metal surface with a paint, varnish or adhesive, the method comprising the step of treating the surface with at least one composition comprising at least one polymer P as defined in any one of claims 1 to 12.

20. A composition that can be used in the method of claim 19, the composition comprising polymer P as defined in any one of claims 1 to 12.

21. A method for bonding a first metal surface (S1) to a second surface (S2), the method comprising: - Treat the first metal surface with at least one composition (S1), the composition comprising at least one polymer P as defined in any one of claims 1 to 12; and - Optional The second surface is treated with at least one composition (S2), the composition comprising at least one polymer P as described in any one of claims 1 to 12; and - The two surfaces are bonded together by applying an adhesive composition between the first metal surface (S1) and the second surface (S2).

22. The method according to claim 21, wherein, The composition containing polymer P is: - A conversion composition comprising polymer P; and / or - A solution or dispersion of the polymer P; and / or - The adhesive composition contains polymer P.

23. The method of claim 22, wherein the solution or dispersion of the polymer P is applied to the surface after the conversion coating is applied to the surface to be treated.

24. A material comprising two adhesively bonded surfaces, the adhesively bonded surfaces including a first metal surface, the first metal surface comprising a first metal surface (S1) wholly or partially (i) treated with a polymer P as defined in any one of claims 1 to 12 and (ii) bonded by an adhesive to a second surface (S2) as defined above, the material being a material having a first metal surface (S1) wholly or partially covered by: - At least one coating comprising at least one polymer P as defined in any one of claims 1 to 12; and / or - A layer comprising: a reaction product of polymer P as defined in any one of claims 1 to 12 with a metal having a treated surface or another compound present in the layer, or polymer P as defined in any one of claims 1 to 12 in close connection with other compounds.

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