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 2-hydroxyethyl methacrylate phosphate for treating a metallic surface intended to be adhesive-bonded to another surface, in order to impart a resistance to the adhesive failure to the resulting bonding.

Claims

1. A method of treating a first metallic surface (S1) intended to be bonded to a second surface (S2) by adhesive bonding, and for imparting a resistance to the adhesive failure to the bonding, comprising treating a metallic surface (S1) with at least one polymer P obtained by radical copolymerization of a mixture of (i) acrylic acid; (ii) methacrylic acid; and (iii) at least one 2-hydroxyethyl methacrylate phosphate of Formula (a) below: ##STR00003## wherein n is 1 or 2.

2. The method of claim 1, wherein the at least one polymer P imparts to the bonding a resistance to corrosive atmospheres and to wet atmospheres.

3. The method of 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 2-hydroxyethyl methacrylate phosphates of formula (a): acrylic acid: from 65 to 90%, methacrylic acid: 5 to 30%, 2-hydroxyethyl methacrylate phosphates: 2 to 12%.

4. The method of claim 1, wherein the polymer P has a molecular weight of at least 7,500 Da.

5. The method of claim 1, wherein the metal surface (S1) is a surface comprising a metal selected from aluminum, steel, zinc, magnesium titanium, copper and their alloys, or cobalt-nickel alloys.

6. The method according to claim 4, wherein the metal surface (S1) is a surface of aluminum or aluminum alloy.

7. The method of claim 1, wherein the second surface (S2) is a metallic surface.

8. The method of claim 1, wherein the second surface (S2) is a non-metallic surface.

9. The method of claim 1, wherein the polymer P is used for treating both surfaces (S1) and (S2) before the adhesive bonding of the two surfaces.

10. A process for bonding a first metallic surface (S1) with a second surface (S2) including: treating said first surface (S1) with at least one composition including at least one polymer P as defined in claim 1; and optionally treating the second surface (S2) with at least one composition including the at least one polymer P; and bonding the surfaces (S1) and (S2) via an adhesive composition applied between the two surfaces.

11. The process according to claim 10, wherein the composition comprising the polymer P is: a conversion composition including the polymer P; and/or a solution or a dispersion of the polymer P; and/or the adhesive composition, that comprises the polymer P.

12. A material comprising two adhesive-bonded surfaces including a first metal surface comprising a metal surface (S1) which is in all or part (i) treated with a polymer P as defined in claim 1 and (ii) bonded to a second surface (S2), via an adhesive, said material being a material having a metal surface (S1) in all or part covered by: at least one coating comprising the at least one polymer P; and/or a layer comprising a reaction product of the polymer P with a metal of the treated surface or another compound present in said layer, or the polymer P strongly linked with said other compound.

13. The process according to claim 10, wherein the metallic surface (S1) is a surface comprising a metal selected from aluminum, steel, zinc, magnesium titanium, copper and their alloys, or cobalt-nickel alloys.

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

15. The process according to claim 10, wherein the second surface (S2) is a metallic surface.

16. The process according to claim 10, wherein the second surface (S2) is a non-metallic surface.

17. The process according to claim 10, wherein the polymer P is used for treating both surfaces (S1) and (S2) before the adhesive bonding of the two surfaces.

18. The process according to claim 11, wherein the solution or dispersion of the polymer P is applied on the surface after having applied a conversion coating on the surface to be treated.

19. The method of 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 2-hydroxyethyl methacrylate phosphates of formula (a): acrylic acid: from 80 to 90% methacrylic acid: 5 to 15% 2-hydroxyethyl methacrylate phosphates: 2 to 10%.

20. The method of claim 1, wherein the polymer P has a molecular weight of at least 10 kDa to 1500 kDa.

Description

EXAMPLE

Example 1

[0059] A polymer according to the invention, obtained by a copolymerization of a mixture of acrylic acid, methacrylic acid, and 2-hydroxyethyl methacrylate phosphates of Formula (a), has been tested in this example. The process used to produce this polymer is based on conventional Free Radical polymerization, which is well known in the art.

[0060] This polymer (Polymer P1) presents the following characteristics: [0061] Weight average molecular weight Mw=24 000 g/mol, Number average molecular weight Mn=12 000 g/mol. Theses parameters 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-MALLS 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 NaH.sub.2PO.sub.4, 25 Mm Na.sub.2HPO.sub.4-15% 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. [0062] Molar ratio AA/MAA/2-hydroxyethyl methacrylate phosphates of Formula (a): 83/13/4

[0063] 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 SLS assemblies as described in D1002-10.

[0064] Step 1—20 coupons (aluminum alloy coupons: AA5754, 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 mn under light stirring. The coupons were then rinsed twice during 1 mn with deionized water.

[0065] Step 2—the coupons are then pre-treated by dipping for 2 mn 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 mn and dried for 30 mn at 60° C.

[0066] 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 T 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 mn at 180° C. Finally, paper clips are removed.

[0067] Step 4—tensile strength test I on assemblies as obtained in step 3

[0068] Used material: Zwick/Roell—Z50, with jaws grasping assembly tips over 50 mm and a pulling speed of 10 mm/mn (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 jaws are then moved for pulling each of the coupon horizontally in the direction starting from the bonding zone towards the grasping zone)

[0069] Step 5—tensile strength test II performed on assemblies as obtained in step 3 after ageing

[0070] 5.1. Ageing Cyclic Test [0071] A cyclic ageing test is performed according to ASTM G85— Annex 3 (SWAAT, 2011) [0072] in a corrosion chamber Q-FOG CRH 600 L, from Q-FOG [0073] in the following conditions: [0074] a 30-minute acidified salt fog spray followed by [0075] a 90-minute soak at >98% relative humidity [0076] under the following conditions: [0077] Chamber temperature—constant 49° C. [0078] Air saturator temperature—constant 57° C. [0079] Relative humidity—>98% [0080] pH of fall out solution 2.8-3.0 [0081] Volume of fall out solution—1.0-2.0 ml/80 cm.sup.2/hour [0082] Exposure period—1000 hours [0083] After the exposure period is completed, the assemblies are washed down with luke-warm water to remove and neutralise excess acid and any remaining salt residues. All assemblies were then air dried using forced ambient temperature before being for submitted to lap-shear tensile testing.

[0084] 5.2. Tensile Strength Test

[0085] In the conditions of the tensile strength test I of step 4

[0086] The obtained results are reported in Tables 2-5 below (the values are average values: the tests were performed on 3 assemblies before ageing and on 5 assemblies after ageing), with the following variations in step 2:

TABLE-US-00001 TABLE 1 conditions of step 2 Test Concentration of polymer no. in the treating bath pH 1 NONE (control) 2 1000 ppm 2.13 3 1000 ppm 8.97 4 5000 ppm 2.56 5 5000 ppm 6.15 6 5000 ppm 8.39

[0087] 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 STRAIN Maximum STRAIN Before ageing (test I) After ageing (test II) maximum STD maximum STD Retention Test no. strain (MPa) (MPa) strain (MPa) (MPa) (%) 1 (control) 34.7 0.7 12.4 13.7 36 2 37.0 0.6 23.4  0.6 80 3 36.2 1.4 24.7  9.1 68 4 33.8 1.1 24.3  5.1 72 5 34.4 2.4 28.1  1.9 82 6 35.3 1.2 27.3  1.1 77

TABLE-US-00003 TABLE 3 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) 10837.9 217.7 3862.4 4292.6 36 2 11558.0 179.9 9202.5  176.3 80 3 11306.5 434.4 7729.8 2837.3 68 4 10555.7 352.2 7597.1 1607.9 72 5 10761.5 764.6 8795.5  590.5 82 6 11043.1 385.5 8533.4  333.6 77

TABLE-US-00004 TABLE 4 Maximum ENERGY Maximum ENERGY 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 2.8 4.0 24 2 14.3 0.7 8.7 0.4 61 3 13.7 1.6 6.8 3.6 50 4 11.1 1.0 5.7 2.3 51 5 11.7 2.2 7.6 1.2 65 6 12.8 1.3 7.7 1.0 60

TABLE-US-00005 TABLE 6 FACIES after bond failure FACIES after failure Test no. Before ageing (test I) After ageing (test II) 1 (control) c  a 2 c ~c 3 c ~c 4 c ~c 5 c ~c 6 c ~c (c): cohesive fracture (a): adhesive fracture (~c): rather cohesive fracture

Example 2

[0088] Other polymers according to the invention, obtained by a copolymerization of a mixture of acrylic acid, methacrylic acid, and 2-hydroxyethyl methacrylate phosphates of Formula (a), have been tested in this example. The process used to produce polymers P2 and P3 is based on conventional Free Radical polymerization, which is well known in the art. The process used to produce P4 is based on controlled radical polymerization.

[0089] Those polymers present the following characteristics:

[0090] Polymer P2 [0091] Weight Average molecular weight Mw=22 000 g/mol, Mn=13 000 g/mol. [0092] Molar ratio AA/MAA/2-hydroxyethyl methacrylate phosphates of Formula (a): 77/11/12

[0093] Polymer P3 [0094] Weight Average molecular weight Mw=68 000 g/mol, Mn=26 000 g/mol. [0095] Molar ratio AA/MAA/2-hydroxyethyl methacrylate phosphates of Formula (a): 77/11/12

[0096] Polymer P4 [0097] Weight Average molecular weight Mw=19 000 g/mol, Mn=10 000 g/mol. [0098] Molar ratio AA/MAA/2-hydroxyethyl methacrylate phosphates of Formula (a): 79/12/9

COMPARATIVE EXAMPLES

[0099] Comparative Polymer C0:

[0100] A polymer was prepared according to the same process as described for example 1 but with the following molar ratios: AA/MAA/2-hydroxyethyl methacrylate phosphate of formula (a) molar ratios=26/70/4

[0101] This polymer was not soluble in the acidic treatment bath and thus could not be tested.

[0102] Comparative Polymer C1: AA 100

[0103] A polyacrylic acid (100% AA) was prepared has been tested.

[0104] This polymer has a Mw=26 000 g/mol and a Mn=19 000 g/mol (same method of measure as described previously).

[0105] Comparative Polymers C2, C3:

[0106] Two comparative polymers were prepared with benzotriazole ethyl methacrylate instead of hydroxyethyl methacrylate phosphates. Details are given below:

[0107] General Formula:

##STR00002##

[0108] Comparative Polymer C2: 4 Mol % of Benzotriazole Ethyl Methacrylate (BztMA)

[0109] MAA/AA/BztMA=76/20/4 mol %

[0110] Mw=30 000 g/mol, Mn=15 000 g/mol (same method of measure as described previously).

[0111] Comparative Polymer C3: 10 Mol % of Benzotriazole Ethyl Methacrylate (BztMA)

[0112] MAA/AA/BztMA=67/23/10 mol %

[0113] Mw=30 000 g/mol, Mn=15 000 g/mol (same method of measure as described previously).

[0114] Performance Tests

[0115] Performances were assessed through Single Lap Shear (SLS) tests, before and after ageing in corrosive conditions. Coupons were prepared according to the protocol described for example 1 and assembled to form SLS assemblies as described in D1002-10.

[0116] Two waves of tests have been done.

[0117] Wave 1 Conditions:

[0118] Step 1: the bath is prepared with Chemtec DBT ALU 200 at 5% and heated to at 50° C. Coupons are immersed in it for 3 mn, and are then rinsed for 1 mn in hot water and then de-ionized water.

[0119] Step 2: the bath is heated to 50° C.; the pH is adjusted with sulfuric acid; coupons are immersed for 2 mn and are then rinsed for 1 mn with de-ionized water.

[0120] Wave 2 Conditions:

[0121] Step 1: the bath is prepared with Chemtec DBT ALU 200 at 5% and heated to at 50° C. Coupons are immersed in it for 1 mn, and are then rinsed for 1 mn in hot water and then de-ionized water.

[0122] Step 2: the bath is heated to 50° C.; the pH is adjusted with sulfuric acid; coupons are immersed for 2 mn and are then rinsed for 1 mn with de-ionized water.

[0123] Results

[0124] Wave 1

TABLE-US-00006 TABLE 7 conditions of step 2—Wave 1 Polymer concentration Test in the Treatment nº Polymer Details treatment bath bath pH Comment 1.1 None NONE (control) NONE (control) — Control 1.2 P1 AA/MAA/formula a: 83/12/4  50 ppm 2.36 Mw 24 000 g/mol—Mn 12 000 g/mol 1.3 P1 AA/MAA/formula a: 83/12/4  200 ppm 2.26 Mw 24 000 g/mol—Mn 12 000 g/mol 1.4 P1 AA/MAA/formula a: 83/12/4  500 ppm 2.32 Mw 24 000 g/mol—Mn 12 000 g/mol 1.5 P1 AA/MAA/formula a: 83/12/4 1000 ppm 2.38 Mw 24 000 g/mol—Mn 12 000 g/mol 1.6 P2 AA/MAA/formula a: 77/11/12 1000 ppm 5.06 Mw 22 000 g/mol—Mn 13 000 g/mol 1.7 P2 AA/MAA/formula a: 77/11/12 1000 ppm 2.35 Mw 22 000 g/mol—Mn 13 000 g/mol 1.8 P3 AA/MAA/formula a: 77/11/12 1000 ppm 4.91 Mw 68 000 g/mol—Mn 26 000 g/mol 1.9 P3 AA/MAA/formula a: 77/11/12 1000 ppm 2.35 Mw 68 000 g/mol—Mn 26 000 g/mol 1.10 C0 AA/MAA/formula a: 29/70/4 Not soluble 2.35 Not tested 1.11 C2 MAA/AA/BztMA: 76/20/4  200 ppm 2.34 Mw 30 000 g/mol—Mn 26 000 g/mol 1.12 C2 MAA/AA/BztMA: 76/20/4 1000 ppm 2.36 Mw 30 000 g/mol—Mn 26 000 g/mol 1.13 C3 MAA/AA/BztMA: 67/23/10  200 ppm 2.32 Mw 30 000 g/mol—Mn 26 000 g/mol 1.14 C3 MAA/AA/BztMA: 67/23/10 1000 ppm 2.40 Mw 30 000 g/mol—Mn 26 000 g/mol

TABLE-US-00007 TABLE 8 STRAIN at maximum Load—Wave 1 STRAIN at Maximum Load Before ageing (test I) After ageing (test II) Av. Av. Test strain STD strain STD Retention no. (MPa) (MPa) (MPa) (MPa) (%) 1.1 28.2 1.4 21.9 1.5 78 1.2 29.8 0.9 25.8 0.7 87 1.3 30.6 0.7 25.8 0.7 84 1.4 29.3 0.9 25.8 0.3 88 1.5 29.1 0.5 25.1 0.9 86 1.6 29.3 0.6 25.2 1.6 86 1.7 29.5 0.8 26.4 0.8 89 1.8 29.5 1.2 25.3 1.2 86 1.9 29.8 1.7 26.2 0.6 88 1.11 29.6 0.5 25.7 0.5 87 1.12 28.7 0.4 22.4 1.7 78 1.13 27.7 0.8 22.9 1.0 83 1.14 27.7 0.2 17.8 0.4 64

TABLE-US-00008 TABLE 9 MAXIMUM LOAD—Wave 1 Maximum Load Before ageing After ageing (test I) (test II) Test Av. Max. STD Av. Max. STD Retention no. Load (N) (N) Load (N) (N) (%) 1.1 9056 356 7410 663 82 1.2 9571 313 8304 96 87 1.3 9709 135 8032 233 83 1.4 9340 323 8178 101 88 1.5 9355 215 8042 159 86 1.6 9320 279 7841 399 84 1.7 9289 245 8406 181 90 1.8 9709 119 7940 332 82 1.9 9419 423 8206 137 87 1.11 9435 66 7948 177 84 1.12 9225 114 7154 422 78 1.13 8862 177 7260 306 82 1.14 8822 85 5513 85 62

TABLE-US-00009 TABLE 10 Energy at maximum Load —Wave 1 Energy at Maximum Load Before ageing (test I) After ageing (test II) Av. Energy SD Av. Energy SD Test at max Energy at max Energy Retention no. load (J) (J) load (J) (J) (%) 1.1 13.8 3.9 6.0 1.1 44 1.2 18.6 2.4 7.4 0.4 40 1.3 19.5 2.2 6.9 1.0 36 1.4 16.6 2.5 7.8 0.4 47 1.5 16.8 1.8 7.6 0.7 45 1.6 15.5 1.3 6.5 0.7 42 1.7 16.4 1.9 9.0 1.2 55 1.8 20.0 0.5 7.0 1.2 35 1.9 16.2 3.1 7.9 0.6 49 1.11 16.6 0.7 6.8 0.3 41 1.12 15.5 2.1 5.1 0.9 33 1.13 12.9 2.2 5.6 0.5 43 1.14 12.4 0.3 2.2 0.3 18

TABLE-US-00010 TABLE 11 FACIES after bond failure—Wave 1 Test Facies after failure nº Before ageing (test I) After ageing (test II) 1.1 c a 1.2 c ~c  1.3 c ~c  1.4 c ~c  1.5 c ~c  1.6 c ~c  1.7 c ~c  1.8 c ~c  1.9 c c/a 1.11 ~c  a 1.12 c/a a 1.13 ~a  a 1.14 ~a  a c: cohesive fracture; ~c: rather cohesive fracture; c/a: fracture both cohesive and adhesive; ~a: rather adhesive fracture; a: adhesive fracture

[0125] Wave 2

TABLE-US-00011 TABLE 12 conditions of step 2—Wave 2 Polymer concentration Treat- Test in the ment nº Polymer Details treatment bath bath pH 2.1 None Control 2.2 P1 AA/MAA/formula a: 83/12/4  50 ppm 2.30 Mw 24 000 g/mol—Mn 12 000 g/mol 2.3 P2 AA/MAA/formula a: 77/11/12  50 ppm 2.35 Mw 22 000 g/mol—Mn 13 000 g/mol 2.4 P2 AA/MAA/formula a: 77/11/12 1000 ppm 2.35 Mw 22 000 g/mol—Mn 13 000 g/mol 2.5 P4 AA/MAA/formula (a): 79/12/9  50 ppm 2.35 Mw = 19 000 g/mol—Mn = 10 000 g/mol 2.6 P4 AA/MAA/formula (a): 79/12/9 1000 ppm 2.35 Mw = 19 000 g/mol—Mn = 10 000 g/mol 2.7 C1 AA: 100  50 ppm 2.29 Mw = 26 000 g/mol—Mn = 19 000 g/mol 2.8 C1 AA: 100 1000 ppm 2.29 Mw = 26 000 g/mol—Mn = 19 000 g/mol

TABLE-US-00012 TABLE 13 STRAIN at maximum Load—Wave 2 Strain at Maximum Load Before ageing (test I) After ageing (test II) Test Av. Strain SD Strain Av. Strain SD Strain Retention nº (Mpa) (MPa) (Mpa) (MPa) (%) 2.1 30.3 0.3 18.9 11.1 62% 2.2 30.3 2.5 26.7 0.5 88% 2.3 31.2 0.5 27.7 0.7 89% 2.4 30.9 0.4 27.4 0.5 88% 2.5 29.4 0.8 26.3 0.3 90% 2.6 29.1 0.6 26.1 0.4 90% 2.7 31.4 0.4 27.2 0.5 87% 2.8 31.0 0.3 26.2 0.3 84%

TABLE-US-00013 TABLE 14 MAXIMUM LOAD—Wave 2 Maximum Load Before ageing (test I) After ageing (test II) Test Av. Max. SD Max. Av. Max. SD Max. Retention nº Load (N) Load (N) Load (N) Load (N) (%) 2.1 9457  53 5974 3485  63% 2.2 9589 550 8369 116 87% 2.3 9833  16 8909 234 91% 2.4 9709 200 8660 106 89% 2.5 9510  34 8398  62 88% 2.6 9241 217 8267 163 89% 2.7 9676 157 8363 170 86% 2.8 9843 135 8247 148 84%

TABLE-US-00014 TABLE 15 ENERGY at maximum Load—Wave 2 Energy at Maximum Load Before ageing (test I) After ageing (test II) Test Av. Energy SD Energy Av. Energy SD Energy Retention nº (J) (J) (J) (J) (%) 2.1 8.74 0.42 3.80 2.46 44% 2.2 9.05 2.36 6.16 0.17 68% 2.3 9.82 0.20 6.88 0.66 70% 2.4 9.28 0.60 6.51 0.26 70% 2.5 10.52 0.40 6.24 0.06 59% 2.6 10.47 2.19 6.76 0.50 65% 2.7 10.48 1.10 6.27 0.44 60% 2.8 11.04 0.71 6.15 0.46 56%

TABLE-US-00015 TABLE 16 FACIES after bond failure—Wave 2 Test FACIES after failure nº Before ageing (test I) After ageing (test II) 2.1 c/a a 2.2 c ~c  2.3 ~c  ~c  2.4 ~c  ~c  2.5 c ~c  2.6 c ~c  2.7 c c/a 2.8 c c/a c: cohesive fracture; ~c: rather cohesive fracture; c/a: fracture both cohesive and adhesive; ~a: rather adhesive fracture; a: adhesive fracture