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) methacrylic acid; and (iii) at least one monomer having the following formula, 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 European application filed on 9 October 2020 under number 20315432.3, 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 or crystals 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). TM 1510 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 coatings, applied to the metal surface. According to this specification, the term "adhesive coating" encompasses (i) films obtained by coating adhesive compositions, typically organic film-forming compositions, mostly in the form of pastes or more or less liquids, and (ii) pre-formed adhesive films, such as the L-F610 epoxy adhesive film commercialized by L&L Corporation.

[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 so-called "adhesive bonding" between the coated metal surface and another surface (typically a similar metal surface treated with the same polymer) 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 a "resistance to adhesive failure"). 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 obtainable by free radical copolymerization of a mixture of the following:

[0013] (i) acrylic acid; and

[0014] (ii) methacrylic acid; and

[0015] (iii) and at least one monomer M, which is an olefinic unsaturated urea group 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 2 or 3.

[0023] A suitable monomer M, which can be advantageously used to prepare the polymer P according to the invention, has the following formula (Ia):

[0024]

[0025] Where n is an integer from 1 to 5, typically equal to 2 or 3 (typically 2).

[0026] According to an example of interest, monomer M is methacrylamide ethyl ethylene urea (MAEEU), which is contained in a commercially available monomer, for example, commercialized by Solvay. WAM II.

[0027] More typically, the divalent spacer group A in formula (I) can be a group typically -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):

[0028]

[0029] It is produced by reacting with compounds having the formula (IY):

[0030]

[0031] X and Y are two groups that react together to form a covalent bond.

[0032] 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, epoxy resin or (terminated) isocyanate.

[0033] 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, acyl bromide, acid anhydride or ester.

[0034] Polymer P is a polymer obtained through comonomers (i), (ii), and (iii), i.e., it has the structure obtained through 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).

[0035] 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 advantageously be selected from: additional acrylic acid or methacrylic acid, or esters thereof; maleic anhydride; vinyl benzyl chloride; vinyl benzyl bromide; glycidyl methacrylate; epoxy styrene; and (terminated) ethyl isocyanate methacrylate. Preferred are additional acrylic acid or methacrylic acid, or esters thereof; maleic anhydride; glycidyl methacrylate; and epoxy styrene.

[0036] 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) can advantageously be selected from: additional acrylic acid, methacrylic acid, maleic anhydride or their esters, and (terminated) ethyl isocyanate methacrylate. Preferably, additional acrylic acid, methacrylic acid, maleic anhydride or their esters are preferred.

[0037] At least one polymer P, which is obtained by free radical copolymerization of a mixture of the following:

[0038] (i) Acrylic acid (AA); and

[0039] (ii) Methacrylic acid (MAA); and

[0040] (iii) At least one monomer M, which is an olefinic unsaturated urea group having formula (I).

[0041] It can be further included

[0042] (iv) less than 20% mol of one or more additional monomers M', which are selected from the group consisting of hydrophobic monomers and / or amphiphilic monomers.

[0043] 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:

[0044] 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.

[0045] 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.

[0046] 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,

[0047] 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.

[0048] 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.

[0049] 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

[0050] vii) Allyl ethers, such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, and 2-ethylhexyl vinyl ether.

[0051] viii) Vinyl esters, such as vinyl acetate or vinyl propionate.

[0052] (ix) Alkyl-substituted acrylamides, such as N-tert-butylacrylamide or N-methyl(meth)acrylamide.

[0053] Preferably, the additional monomer M' present in polymer P is selected from the group consisting of:

[0054] i) Monoethyl maleic anhydride, diethyl maleic anhydride, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate

[0055] ii) Maleic anhydride monohydroxyethyl ester, maleic anhydride dihydroxyethyl ester, (meth)acrylate hydroxyethyl ester, (meth)acrylate hydroxypropyl ester, (meth)acrylate hydroxybutyl ester

[0056] iii) Poly(propylene oxide)-b-poly(ethylene oxide) maleate half ester

[0057] iv) Poly(propylene oxide)-b-poly(ethylene oxide)-(meth)acrylate ethyl ester

[0058] v) Poly(propylene oxide)-b-poly(ethylene oxide)(meth)acrylate, alkyl-poly(ethylene oxide)(meth)acrylate

[0059] vi) Vinyl acetate and vinyl propionate.

[0060] Preferably, the list does not contain vinyl aromatic monomers, and in particular, it does not contain styrene.

[0061] The molar proportion of monomer M' must not exceed 20% 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 surfactants undesirable in the final application. Advantageously, the molar proportion of monomer M' is less than 15% mol, preferably less than 10% mol, and more preferably less than 5% mol.

[0062] In fact, the presence of hydrophobic and / or amphiphilic monomers M' is limited because the polymerization of the polymer P of the present invention needs to be carried out in an 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.

[0063] 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:

[0064] (i) acrylic acid; and

[0065] (ii) methacrylic acid; and

[0066] (iii) At least one monomer M, which is an olefinic unsaturated urea group having formula (I). 。

[0067] 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%.

[0068] 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 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.

[0069] Typically, polymer P is obtained by free radical copolymerization of a mixture of acrylic acid, 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):

[0070] - Acrylic acid (AA): from 5% to 50%, preferably from 20% to 40% (e.g., about 25% to 30%),

[0071] - Methacrylic acid (MAA): from 30% to 90%, preferably from 60% to 80% (e.g., about 65% to 75%)

[0072] - Monomer M: from 1% to 50%, for example from 1% to 30%, notably from 2% to 20% (e.g., about 3% to 10%).

[0073] Compared to polymers outside the above range, the above molar ratios of monomers in polymer P show particularly good results in terms of resistance to adhesive failure. For example, when MAA is absent in polymer P, polymer P does not possess suitable mechanical and structural properties (strength, Tg, crystallinity, hygroscopicity, etc.). When monomer M is absent, the adhesive properties are unsatisfactory. When the amount of M is too high (above 50%), there is a risk of product discoloration, and the resulting polymer is economically unfeasible.

[0074] Furthermore, the polymer P used according to the invention preferably has the following number-average molecular weight (Mn): at least 7,500 Da, for example 10 kDa to 1500 kDa, for example 10 kDa to 150 kDa, notably between 10 and 100 kDa. Typically, the polymer P used according to the invention has a number-average molecular weight (Mn) from 20 to 100 kDa, for example 30 to 100 kDa.

[0075] The polymer P, particularly suitable for use in this invention, is a statistical (random) copolymer having a number-average molecular weight of about 30 to 100 kDa, which is a copolymer of acrylic acid, methacrylic acid, and monomer M (preferably in a molar ratio of about 28 / 70 / 02 to 20 / 70 / 10).

[0076] 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 was injected into the mobile phase stream. Absolute molar masses were obtained, with dn / dC of poly(acrylic acid) equal to 0.1875 mL / g.

[0077] 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 / acrylamidoethyl ethylene urea = 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 / MAEEU = 22 / 70 / 08 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).

[0078] 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.

[0079] The metal surface is preferably treated with polymer P at a pH of at least 5, more preferably at least 7, for example between 7 and 10.

[0080] 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:

[0081] - The conversion composition contains all or part of polymer P as an additive; and / or

[0082] - Apply a conversion coating to the metal surface and then apply all or part of the polymer P onto the conversion coating.

[0083] 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.

[0084] 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:

[0085] - A conversion composition comprising polymer P; and / or

[0086] - 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

[0087] - Coatings, varnishes, or adhesives that may contain all or part of the polymer P.

[0088] The useful polymer P according to the invention and compositions containing polymer P (especially conversion compositions containing polymer P; coating, varnish or adhesive compositions containing it; and solutions or dispersions containing polymer P that can be used to treat surfaces) also constitute a particular object of the invention.

[0089] 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.

[0090] 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).

[0091] 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.

[0092] 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).

[0093] 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.

[0094] 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.

[0095] The second surface (S2) can be a metallic or non-metallic surface.

[0096] 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.

[0097] 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).

[0098] 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:

[0099] - The conversion composition contains all or part of polymer P as an additive; and / or

[0100] - Apply a conversion coating to the surface (S1), and then apply all or part of the polymer P to the conversion coating.

[0101] 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).

[0102] 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:

[0103] - 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

[0104] - 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

[0105] - The two surfaces are bonded together by applying an adhesive composition between the surface (S1) and the surface (S2).

[0106] Within this scope, compositions containing polymer P can typically be:

[0107] - A conversion composition comprising polymer P; and / or

[0108] - 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

[0109] - An adhesive composition which may contain all or part of polymer P.

[0110] 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.

[0111] 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.).

[0112] 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.

[0113] These materials include, in particular, materials having a metallic surface (S1) that is wholly or partially covered by the following:

[0114] - At least one coating (typically a conversion coating and / or paint, varnish, or adhesive layer) comprising at least one polymer P; and / or

[0115] - 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).

[0116] The specific features and possible embodiments will now be described in more detail.

[0117] Metal surface (S1)

[0118] 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:

[0119] - Aluminum or aluminum-based alloys; or

[0120] - Steel, such as galvanized steel (hot-dip galvanized HDG or electro-galvanized EG); or cold-rolled steel (CRS); or

[0121] - Magnesium or magnesium-based alloys; or

[0122] - Zinc or zinc-based alloys; or

[0123] - Titanium or titanium-based alloys.

[0124] 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 AA1050, 2024, 3003, 5005, 5182, 5754, 6111, 6016, 6060, 6063, 6182, 7075)).

[0125] Optional conversion coating

[0126] 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.

[0127] 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.

[0128] 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.

[0129] The conversion composition may also contain other compounds, such as silane precursors, and / or cerium salts, and / or terbium molybdate.

[0130] 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.

[0131] 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).

[0132] 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.

[0133] 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.

[0134] The following examples illustrate the present invention.

[0135] Example

[0136] In these examples, polymers according to the invention were tested, which were obtained by copolymerization of a mixture of acrylic acid, methacrylic acid and methacrylamide ethyl ethylene urea (MAEEU).

[0137] Example 1.1

[0138] Polymer P1 (AA / MAA / MAEUU 27 / 70 / 03mol / mol / mol) was prepared as follows:

[0139] At room temperature, 71g of a 10% active ingredient solution of 2,2'-azobis(2-methylpropanediamine) dihydrochloride (V50), 2.28g of AA with 70% active ingredient content in water, 2.58g of sodium hydroxide with 35% active ingredient content in water, and 110g of deionized water were added to a 700ml reactor equipped with adequate stirring, inlet, feed, and temperature control devices.

[0140] Then, under nitrogen degassing conditions, the reactor temperature is heated to 60°C within 1 hour.

[0141] When the temperature has reached 60℃, two feeding operations begin under the nitrogen layer:

[0142] - Within 4 hours, 43.9g of AA in water had an activity level of 70%.

[0143] - Within 5 hours, 23.9g contains 10.3g of MAEEU and 6.8g of MAA. WAM II, plus 156.2g of 60% MAA in water, plus 108.3g of 35% sodium hydroxide in water.

[0144] After the longest feed is completed, the reaction mixture is kept at 60°C for another 2 hours, then cooled to room temperature and diluted with 119g of deionized water to achieve a solids content of approximately 31%.

[0145] 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.

[0146] Proton nuclear magnetic resonance was recorded using a 300 MHz spectrometer from Bruker. 1 ¹H NMR spectra. To measure the conversion rates of AA, MAA, and MAEEU, four drops of the reaction mixture were diluted in approximately 1 g of deuterated water (D₂O). The conversion rates of AA were >99%; MAA >99.9%; and MAEEU >99.9%.

[0147] 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: 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. n =44kg / mol; M w =134 kg / mol;

[0148] Example 1.2 uses the same method to prepare polymer P2 (AA / MAA / MAEUU 22 / 70 / 08mol / mol / mol):

[0149] The total weight of V50 with 10% active ingredient in water is 73.3g.

[0150] Total weight of 70% AA in water: 37.1g

[0151] Total weight of 60% MAA in water: 136.2g

[0152] Total weight of WAM II solution: 62.3g

[0153] AA's conversion rate is >99%; MAA's conversion rate is >99.9%; MAEEU's conversion rate is >99.9%.

[0154] M n =70kg / mol; M w =400kg / mol;

[0155] Performance was evaluated by single lap shear (SLS) tests before and after aging under corrosive conditions. Specimens were prepared according to the following protocol and assembled to form a single lap assembly as described in D1002-10.

[0156] Step 1 - Twenty specimens (aluminum alloy specimens: AA5754 H111, from FBCG; 100 mm long, 25 mm wide, 3 mm thick) were all cleaned and etched together in a single combined cleaning and etching step in a 4 L bath at 50°C in a stainless steel tank for 3 min with gentle agitation. This bath was typically prepared by diluting a commercially available formulation, DBT ALU 200 (available from Chemtec Aertec), (5 g of DBT ALU 200 in 995 g of water). The specimens were then rinsed twice with deionized water over 1 min.

[0157] Step 2 - The samples were then pretreated by immersion in a treatment bath containing polymers at 50°C and at the concentrations shown in Table 1 below for 2 minutes. They were then rinsed together with a stream of deionized water for 1 minute and dried at 60°C for 30 minutes.

[0158] 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.

[0159] Step 4 - Perform a tensile strength test on the component obtained in Step 3.

[0160] 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 upper jaw is then moved upward to traction each specimen horizontally in the direction from the initial self-bonding area toward the gripping area.)

[0161] Step 5 - After aging Perform tensile strength test II on the components obtained in step 3.

[0162] 5.1. Aging Cycle Test

[0163] The aging test was conducted according to ASTM G85-Annex 3 (SWAAT, 2011) in a Q-FOG CRH 600L corrosion chamber from Q-FOG.

[0164] Under the following conditions:

[0165] • 30 minutes of acidified salt spray, followed by

[0166] • Soak for 90 minutes at a relative humidity >98%.

[0167] Under the following conditions:

[0168] • Room temperature - constant 49℃

[0169] • Air saturator temperature - constant 57℃

[0170] Relative humidity -> 98%

[0171] • The pH of the falling solution is between -2.8 and 3.0.

[0172] • Volume of the falling solution: -1.0 to 2.0 ml / 80 cm³ 2 / Hour

[0173] • Exposure duration - 1000 hours

[0174] 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.

[0175] Then, all components are air-dried using forced ambient temperature, followed by an overlap shear tensile test.

[0176] 5.2 Tensile Strength Test

[0177] Under the conditions of tensile strength test I in step 4

[0178] Tests were conducted on three pre-aging components and five post-aging components, with the following changes made in step 2.

[0179] The polymer was diluted with deionized water, and the resulting treatment bath was tested as is (without pH adjustment, "initial pH").

[0180]

[0181] Table 1: Conditions for Step 2

[0182] The results are reported in Tables 2 to 5 below (values ​​are averages).

[0183] 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"):

[0184]

[0185] Table 2: Maximum Load

[0186]

[0187]

[0188] Table 3: Strain measured under maximum load

[0189]

[0190] Table 4: Energy measured under maximum load

[0191]

[0192] Table 5: Phase after adhesive failure

[0193] ***:

[0194] (c): Cohesive fracture

[0195] (a): Adhesive fracture

[0196] (a / c): Adhesion and cohesive fracture

[0197] (~c): Slightly cohesive fracture

Claims

1. Use of at least one polymer P for treating a metal surface intended to be coated with an adhesive, said at least one polymer P being obtained by free radical copolymerization of a mixture of: (i) acrylic acid; and (ii) methacrylic acid; and (iii) at least one monomer M having the following formula (I): Equation (I) in: R 1 It is H or methyl-CH3; and A is a covalent single bond or a spacer group. The polymer P is used to treat the first metal surface (S1) intended to be bonded to the second surface (S2) by an adhesive and to impart resistance to adhesive failure to the bond. The polymer P further comprises less than 20 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 (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate 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 ethyl ester v) Poly(propylene oxide)-b-poly(ethylene oxide)(meth)acrylate, alkyl-poly(ethylene oxide)(meth)acrylate vi) Vinyl acetate, vinyl propionate In addition to acrylic acid, methacrylic acid, M and M', no other monomers are present in polymer P, and cohesive failure is more preferred than adhesive failure when sufficiently high mechanical stress is applied to separate the adhesive-bonded surfaces. Cohesive failure means that the failure between the two surfaces bonded by the adhesive occurs within the adhesive, so the adhesive is retained on both surfaces, while adhesive failure means that the failure between the two surfaces bonded by the adhesive occurs on one surface, and the adhesive is retained on the other surface.

2. The use according to claim 1, wherein R 1 It's H.

3. The use according to claim 1, wherein the spacer group is: -CO-NH-(CH2) n -or -CO-O-(CH2) n , where n is an integer from 1 to 5.

4. The use according to claim 3, wherein n is 2 or 3.

5. The use according to claim 1, for further imparting the adhesive with resistance to corrosive atmospheres and resistance to humid atmospheres.

6. The use according to claim 1, wherein, The molar percentage of monomer M' is less than 15 mol%.

7. The use according to claim 1, wherein, The molar percentage of monomer M' is less than 10 mol%.

8. The use according to claim 1, wherein, The molar percentage of monomer M' is less than 5 mol%.

9. The use according to any one of claims 1-8, wherein, The polymer P was obtained by free radical copolymerization of a mixture consisting of the following: (i) acrylic acid; and (ii) methacrylic acid; and (iii) At least one monomer M having formula (I).

10. The use according to claim 9, wherein, The polymer P is obtained by free radical copolymerization of a mixture, and based on the total amount of acrylic acid, methacrylic acid and monomer M having formula (I) in the mixture, the acrylic acid, methacrylic acid and monomer M in the mixture have the following molar percentages: - Acrylic acid: from 5% to 50%, - Methacrylic acid: from 30% to 90%, - Monomer M: from 1% to 50%.

11. The use according to claim 9, wherein, The polymer P is obtained by free radical copolymerization of a mixture, and based on the total amount of acrylic acid, methacrylic acid and monomer M having formula (I) in the mixture, the acrylic acid, methacrylic acid and monomer M in the mixture have the following molar percentages: - Acrylic acid: from 20% to 40%, - Methacrylic acid: from 60% to 75%, - Monomer M: from 1% to 30%, The total molar percentage of acrylic acid, methacrylic acid, and monomer M is 100%.

12. The use according to claim 9, wherein, The polymer P is obtained by free radical copolymerization of a mixture, and based on the total amount of acrylic acid, methacrylic acid and monomer M having formula (I) in the mixture, the acrylic acid, methacrylic acid and monomer M in the mixture have the following molar percentages: - Acrylic acid: from 20% to 40%, - Methacrylic acid: from 60% to 75%, - Monomer M: from 1% to 20%, The total molar percentage of acrylic acid, methacrylic acid, and monomer M is 100%.

13. The use according to claim 9, wherein, The polymer P is obtained by free radical copolymerization of a mixture, and based on the total amount of acrylic acid, methacrylic acid and monomer M having formula (I) in the mixture, the acrylic acid, methacrylic acid and monomer M in the mixture have the following molar percentages: - Acrylic acid: from 20% to 40%, - Methacrylic acid: from 60% to 75%, - Monomer M: from 2% to 15%, The total molar percentage of acrylic acid, methacrylic acid, and monomer M is 100%.

14. The use according to any one of claims 1 to 8, wherein, The polymer P has a number-average molecular weight of at least 7,500 Da.

15. The use according to any one of claims 1 to 8, wherein, The polymer P has a number-average molecular weight ranging from 10 kDa to 1500 kDa.

16. The use according to any one of claims 1 to 8, 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.

17. The use according to claim 16, wherein, The first metal surface (S1) is an aluminum or aluminum alloy surface.

18. The use according to any one of claims 1 to 8, wherein, The second surface (S2) is a metallic surface.

19. The use according to any one of claims 1 to 8, wherein, The second surface (S2) is a non-metallic surface.

20. The use according to claim 19, wherein, The second surface (S2) is a plastic surface or a composite surface.

21. The use according to any one of claims 1 to 8, 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).

22. A method for coating a metal surface with a paint or adhesive, the method comprising the step of treating the surface with at least one composition comprising at least one polymer P according to any one of claims 1 to 8.

23. A method for coating a metal surface with a varnish, the method comprising the step of treating the surface with at least one composition comprising at least one polymer P according to any one of claims 1 to 8.

24. A composition for use in the method according to claim 22 or 23, the composition comprising polymer P according to any one of claims 1 to 8.

25. 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 according to any one of claims 1 to 8; as well as - Optional The second surface (S2) is treated with at least one composition comprising at least one polymer P according to any one of claims 1 to 8; and - The two surfaces are bonded together by applying an adhesive composition between the first metal surface (S1) and the second surface (S2).

26. The method of claim 25, wherein, The composition comprising polymer P is: - A conversion composition containing polymer P; or - A solution or dispersion of the polymer P, which is applied to the surface after the conversion coating is applied to the surface to be treated; or - A solution or dispersion of the polymer P, applied to the surface to be treated without a conversion coating; or - The adhesive composition contains polymer P.

27. A material comprising two adhesively bonded surfaces, the adhesively bonded surfaces including a first metal surface (S1), the first metal surface (S1) being wholly or partially (i) treated with polymer P according to any one of claims 1 to 8 and (ii) bonded by an adhesive to a second surface (S2) according to any one of claims 1 to 8, the material being a material having the first metal surface (S1) wholly or partially covered by: - At least one coating comprising at least one polymer P according to any one of claims 1 to 8; and / or - A layer comprising the following: a reaction product of polymer P according to any one of claims 1 to 8 with a metal on a treated surface or another compound present in the layer, or polymer P tightly bonded to the other compound.

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