METAL SURFACE TREATMENT

Abstract

The instant invention concerns the use of at least one polymer P obtained by radical copolymerization of a mixture of (i) acrylic acid; (ii) methacrylic acid; and (iii) at least one monomer of formula: for treating a metallic surface intended to be coated by a paint, a varnish or an adhesive, for example intended to be adhesive-bonded to another surface, in order to impart a resistance to the adhesive failure to the resulting bonding.

##STR00001##

Claims

1. A method for treating a metal surface intended to be coated by a paint, a varnish or an adhesive, the method comprising: applying onto the metal surface at least one polymer P obtained by radical copolymerization of a mixture of (i) acrylic acid; and (ii) methacrylic acid; and (iii) at least one monomer M having the Formula (I) below: ##STR00006## wherein: R.sup.1 is H or a methyl group —CH.sub.3; and A is a linkage selected from the group consisting of: a single covalent bond; and a spacer group.

2. The method according to claim 1, wherein the metal surface is a first metal surface (S1) intended to be bonded to a second surface (S2) by adhesive bonding, wherein polymer P imparts a resistance to the adhesive failure to the bonding.

3. The method according to claim 2, wherein polymer P further imparts to the bonding a resistance to corrosive atmospheres and to wet atmospheres.

4. The method according to claim 1, wherein polymer P further comprises below 20% mol of one or more further monomers M′ selected from the group consisting of hydrophobic monomers and amphiphilic monomers selected from the group consisting of: i) monoethyl maleic anhydride ester, diethyl maleic anhydride ester, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate ii) monohydroxyethyl maleic anhydride ester, dihydroxyethyl maleic anhydride ester, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate iii) poly(propylene oxide)-b-poly(ethylene oxide) maleic acid half ester iv) poly(propylene oxide)-b-poly(ethylene oxide)-ethyl (meth)acrylate v) poly(propylene oxide)-b-poly(ethylene oxide) (meth)acrylate, alkyl-poly(ethylene oxide) (meth)acrylate vi) vinyl acetate, vinyl propionate.

5. The method according to claim 4, wherein the proportion in mol of monomers M′ is below 15% mol.

6. (canceled)

7. The method according to claim 1, wherein the polymer P is obtained by radical copolymerization of a mixture having the following molar ratio, based on the total quantity of acrylic acid, methacrylic acid and monomer M of formula (I): acrylic acid: from 5 to 50%, methacrylic acid: from 30 to 90%, monomer M: from 1 to 50%.

8. The method according to claim 1, wherein the polymer P has a number average molecular weight of at least 7,500 Da.

9. The method according to claim 2, wherein the first metal surface (S1) is a surface comprising a metal selected from aluminum, steel, zinc, magnesium titanium, copper and their alloys, or cobalt-nickel alloys.

10. The method according to claim 9, wherein the first metal surface (S1) is a surface of aluminum or aluminum alloy.

11. The method according to claim 2, wherein the second surface (S2) is a metal surface.

12. The method according to claim 2, wherein the second surface (S2) is a non-metal surface.

13. The method according to claim 2, wherein the polymer P is used for treating both surfaces first metal surface (S1) and second surface (S2) before the adhesive bonding of the first metal surface (S1) and second surface (S2).

14. The method of claim 1, wherein the method further comprises coating the metal surface with a paint, a varnish or an adhesive.

15. A composition including a polymer P obtained by radical copolymerization of a mixture of (i) acrylic acid; and (ii) methacrylic acid; and (iii) at least one monomer M having the Formula (I) below: ##STR00007## wherein: R.sup.1 is H or a methyl group —CH.sub.3; and A is a linkage selected from the group consisting of: a single covalent bond; and a spacer group selected from —CO—NH—(CH.sub.2).sub.n— or —CO—O—(CH.sub.2).sub.n wherein n is an integer from 1 to 5.

16. A method for bonding a first metal surface (S1) with a second surface (S2), including: treating said first metal surface (S1) with at least one composition including at least one polymer P as defined in claim 15; and optionally treating the second surface (S2) with at least one composition including at least one polymer P in claim 15; and bonding the first metal surface (S1) and second surface (S2) via an adhesive composition applied between the first metal surface (S1) and second surface (S2).

17. The method according to claim 16, wherein the composition comprising the polymer P further comprises: a conversion composition including a polymer P; a solution or a dispersion of the polymer P, applied on a surface to be treated after having applied a conversion coating on the surface to be treated; a solution or a dispersion of the polymer P, applied on the surface to be treated without conversion coating; and the adhesive composition, that comprises a polymer P.

18. A composition comprising two adhesive-bonded surfaces including a metal surface comprising a first metal surface (S1) which is in all or part (i) treated with a polymer P as defined in claim 15 and (ii) bonded to a second surface (S2), via an adhesive, wherein the first metal surface (S1) is in all or part covered by: at least one coating comprising at least one polymer P as defined in claim 15; and/or a layer comprising a reaction product of the polymer P as defined in claim 15 with a metal of the first metal surface (S1) or another compound present in said layer, or a polymer P strongly linked with said other compound.

19. The method of claim 1, wherein the spacer group is —CO—NH—(CH.sub.2).sub.n— or —CO—O—(CH.sub.2).sub.n, wherein n is an integer from 1 to 5

Description

EXAMPLE

[0127] Polymers according to the invention, obtained by a copolymerization of a mixture of acrylic acid, methacrylic acid, and methacrylamidoethyl ethylene urea (MAEEU), were tested in these examples.

Example 1.1

[0128] The polymer P1 (AA/MAA/MAEUU 27/70/03 mol/mol/mol) has been prepared as follows: 71 g of a 2,2′-Azobis(2-methylpropionamidine)dihydrochloride (V50) solution at 10% active content in water, 2.28 g of AA at 70% active content in water, 2.58 g of sodium hydroxide at 35% active content in water and 110 g of deionized water are charged at room temperature into a 700 ml reactor fitted with adequate stirring, inlets, feeding and temperature control devices.

[0129] The reactor temperature is then heated to 60° C. within 1 h, with nitrogen degassing.

[0130] When temperature has reached 60° C., 2 feeds are started, under nitrogen blanket: [0131] 43.9 g of AA at 70% active in water, over 4 h [0132] 23.9 g of SIPOMER® WAM 11 containing 10.3 g of MAEEU and 6.8 g of MAA, plus 156.2 g of MAA at 60% in water, plus 108.3 g of sodium hydroxide at 35% in water, over 5 h

[0133] Once the longest feed is over, the reaction mixture is maintained for 2 additional hours at 60° C., before it is cooled down to room temperature and diluted with 119 g of deionized water to get the solids content at about 31%.

[0134] The smooth incorporation of monomers was monitored by 1H NMR spectroscopy over the polymerization and the final product was analyzed by both 1H NMR spectroscopy and size exclusion chromatography.

[0135] A Brucker 300 MHz spectrometer was used to record proton nuclear magnetic resonance (.sup.1H NMR) spectra. To measure AA, MAA and MAEEU conversions, four drops of the reaction mixture were diluted in around 1 g of deuterated water (D.sub.2O). AA conversion >99%; MAA conversion >99.9%; MAEEU conversion >99.9%.

[0136] Average molecular weights were measured by Size Exclusion Chromatography (SEC) equipped with a MultiAngle Laser Light Scattering (MALLS) Mini Dawn TREOS detector and an Agilent concentration detector (RI detector). The SEC system is running on three columns Varian Aquagel OH mixed H, 8 μm, 3*30 cm at a flow rate of 1 mL/min and with the following mobile phase: 85% water, 100 mM NaCl, 25 mM NaH2PO4, 25 Mm Na2HPO4—15% methanol. Polymer samples were diluted down to 0.5 active wt % in the mobile phase for at least 4 hours then filtrated in a Millipore filter 0.45 μm and 100 microliters were injected in the mobile phase flow. Absolute molar masses were obtained with the dn/dC of the poly(acrylic acid) equal to 0.1875 mL/g. M.sub.n=44 kg/mol; M.sub.w=134 kg/mol; Ð=3.

Example 1.2 the Same Process was Used to Prepare the Polymer P2 (AA/MAA/MAEUU 22/70/08 mol/mol/mol)

[0137] Total weight of V50 at 10% active in water: 73.3 g [0138] Total weight of AA at 70% in water: 37.1 g [0139] Total weight of MAA at 60% in water: 136.2 g [0140] Total weight of SIPOMER® WAM II solution: 62.3 g [0141] AA conversion >99%; MAA conversion >99.9%; MAEEU conversion >99.9%. [0142] M.sub.n=70 kg/mol; M.sub.w=400 kg/mol; Ð=6.

[0143] Performances were assessed through Single Lap Shear (SLS) tests, before and after ageing in corrosive conditions. Coupons were prepared according to the protocol below and assembled to form Single Lap assemblies as described in D1002-10.

[0144] Step 1—20 coupons (aluminum alloy coupons: AA5754 H111, from FBCG; 100 mm long, 25 mm wide, 3 mm thick) are cleaned and etched all together in one single step, combining cleaning and etching, in a 4 L bath at 50° C. contained in a stainless steel tank, typically made by diluting a commercially available formulation, DBT ALU 200, available from Chemtec Aertec (5 g of DBT ALU 200 into 995 g of water) for 3 min. under light stirring. The coupons were then rinsed twice during 1 min. with deionized water.

[0145] Step 2—the coupons are then pre-treated by dipping for 2 min. in the treatment bath, containing the polymer at 50° C. and at several concentration indicated in the Table 1 below. They are then rinsed altogether with a flow of deionized water for 1 min. and dried for 30 min. at 60° C.

[0146] Step 3—the coupons are then assembled in pairs, each pair forming a so called single lap shear “assembly”: two coupons are placed horizontally, parallel, one above the other forming an overlap of 12.5 mm long and 25 mm wide (“overlap zone”, including one of terminal zone of each of the two coupons of 25 mm wide, namely the last 12.5 mm of the 100 mm length of the coupon). A structural high temperature curing epoxy adhesive bead (Betamate 1496, from Dow) is applied with a gun under 7 bars on the overlap zone of the lower coupon. The upper coupon is then pressed, thus forming a bonding zone of 12.5 mm long, and 25 mm wide. Paper clips are used to maintain the assembly integrity before and during curing. The adhesive is then cured according to adhesive producer guidelines, typically for 40 min. at 180° C. Finally, paper clips are removed.

[0147] Step 4—tensile strength test I on assemblies as obtained in step 3

[0148] Used material: Zwick/Roell—Z50, with jaws grasping assembly tips over 50 mm and a pulling speed of 10 mm/min. (each jaw holds one of the bonded coupon of the pair, on a grasping zone of 50 mm of said coupon located at the end zone of each coupon opposite to the overlap zone. The upper jaw is then moved upwards for pulling each of the coupon horizontally in the direction starting from the bonding zone towards the grasping zone)

[0149] Step 5—tensile strength test II performed on assemblies as obtained in step 3 after ageing

[0150] 5.1. Ageing Cyclic Test [0151] A cyclic ageing test is performed according to ASTM G85—Annex 3 (SWAAT, 2011) [0152] in a corrosion chamber Q-FOG CRH 600 L, from Q-FOG [0153] in the following conditions: [0154] a 30 min. acidified salt fog spray followed by [0155] a 90 min. soak at >98% relative humidity [0156] under the following conditions: [0157] Chamber temperature—constant 49° C. [0158] Air saturator temperature—constant 57° C. [0159] Relative humidity—>98% [0160] pH of fall out solution—2.8-3.0 [0161] Volume of fall out solution—1.0-2.0 ml/80 cm.sup.2/hour [0162] Exposure period—1000 hours [0163] After the exposure period is completed, the assemblies are washed down with lukewarm water to remove and neutralize excess acid and any remaining salt residues. [0164] All assemblies were then air dried using forced ambient temperature before being for submitted to lap-shear tensile testing.

[0165] 5.2. Tensile Strength Test [0166] In the conditions of the tensile strength test I of step 4

[0167] The tests were performed on three assemblies before ageing and on five assemblies after ageing, with the following variations in step 2.

[0168] Polymers were diluted with de-ionized water and the resulting treatment bath was tested as such (no pH adjustment, “native pH”).

TABLE-US-00001 TABLE 1 conditions of step 2 Concentration of Test polymer in the pH of the no. Polymer treatment bath treatment bath 1 NONE (control) — — The coupons were only degreased and etched. 2 P1 1000 ppm 7.7 (native pH) 3 P2 1000 ppm 8.1 (native pH)

[0169] The obtained results are reported in Tables 2 to 5 below (the values are average values). Below are reported performances before ageing, after ageing, and the ratio between values after ageing and values before ageing, called “retention”:

TABLE-US-00002 TABLE 2 Maximum LOAD Maximum LOAD Before ageing (test I) After ageing (test II) maximum STD maximum STD Retention Test no. load (N) (N) load (N) (N) (%) 1 (control) 10838 218 3862 4293 36 2 9242 363 6784 1139 73 3 9407 451 6881 151 73

TABLE-US-00003 TABLE 3 STRAIN measured at the maximum load STRAIN measured at the maximum load Before ageing (test I) After ageing (test II) Strain STD Strain STD Retention Test no. (MPa) (MPa) (MPa) (MPa) (%) 1 (control) 35 0.7 12 14 36 2 30 1.2 22 3.6 73 3 30 1.4 22 0.5 73

TABLE-US-00004 TABLE 4 ENERGY measured at the maximum load ENERGY measured at the maximum load Before ageing (test I) After ageing (test II) maximum STD maximum STD Retention Test no. Energy (J) (MPa) Energy (J) (MPa) (%) 1 (control) 12 0.8 3 4.0 24 2 22 3.5 8 3.9 38 3 24 4.4 8 0.5 35

TABLE-US-00005 TABLE 5 FACIES after bond failure FACIES after failure*** Test no. Before ageing (test I) After ageing (test II) 1 (control) c a 2 c a/c 3 c ~c *** (c): cohesive fracture (a): adhesive fracture (a/c): adhesive and cohesive fracture (~c): rather cohesive fracture