POLYMERS FOR METAL SURFACE TREATMENT

Abstract

The instant invention concerns the use of polymers obtained by radical copolymerization of a mixture of (1) acrylic acid; (2) methacrylic acid; and (3) at least one allylcatechol selected from 4-allylbenzene-1,2-diol, 3-allylbenzene-1,2-diol; methylated forms thereof (eugenols); and mixtures thereof, 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 first metallic surface (S1) with at least one polymer P obtained by radical copolymerization of a mixture of: acrylic acid; methacrylic acid; and at least one methylated or not methylated allylcatechol which is selected from 4-allylbenzene-1,2-diol; 3-allylbezene-1,2-diol; corresponding eugenols; and mixtures thereof.

2. The method according to claim 1, for further imparting to the bonding a resistance to corrosive atmospheres and to wet atmospheres.

3. The method according to claim 1, wherein the polymer P contains a mixture of two isomers 4-allylbenzene-1,2-diol and 3-allylbenzene-1,2-diol as the allylcatechol.

4. The method according to claim 1, wherein the polymer P has a molecular weight between 10 and 150 kDa.

5. The method according to claim 1, wherein the polymer P contains acrylic acid (AA) at a content of 10 to 90% in mol; methacrylic acid (MAA) at a content of 1 to 90% in mol, and allylcatechol at a content of 1 to 20% in mol, each molar ratio being calculated on the basis of a total quantity of AA, MAA and allylcatechol, with a ratio MAA/AA of more than 1/1.

6. The method according to claim 1, wherein the metal surface is a surface comprising a metal selected from aluminum, steel, zinc, magnesium and their alloys.

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

8. The method according to claim 1, wherein the second surface (S2) is a non-metallic surface or a composite surface.

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

10. The method according to claim 1, wherein the treatment of the surface (S1) and if any of the surface (S2) are followed by a rinsing step.

11. A process for bonding a first metallic surface (S1) with a second surface (S2) including: treating the 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 in claim 1; and bonding the surfaces (S1) and (S2) via an adhesive composition applied between the two surfaces.

12. The process according to claim 11, wherein a composition comprising the polymer P is: a conversion composition including a polymer P; and/or a solution or a dispersion of the polymer P, applied on the surface after having applied a conversion coating on the surface to be treated; and/or an adhesive composition, that comprise a polymer P.

13. 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, the material being a material having a metal surface in all or part covered by: at least one coating comprising the at least one polymer P as defined in claim 1; and/or a layer comprising a reaction product of the polymer P as defined in claim 1 with a metal of the treated surface or another compound present in the layer, or the polymer P strongly linked with the other compound.

14. The method according to claim 3, wherein a molar ratio of 4-allylbenzene-1,2-diol to 3-allylbenzene-1,2-diol between 30/70 and 70/30.

Description

EXAMPLE 1

Synthesis of Polymers Useful According to the Invention

Poly(AA-stat-MAA-stat-allylcatechol)

EXAMPLE 1.1

[0071] A polymer P1 (AA/MAA/allyl catechol=26/70/04 mol/mol/mol) was prepared as follows: 4-allylpyrocatechol (5.50 g, 36.6 mmol) having a molar ratio 4-allylbenzene-1,2-diol and 3-allylbenzene-1,2-diol of 60/40, acrylic acid (AA) at 58.4% in water (1.47 g, 11.9 mmol) and 2,2′-Azobis(2-methylpropionamidine)dihydrochloride (V-50) at 5% in water (74.49 g, 13.7 mmol) were added in a 500 mL three-neck round-bottom flask. After stirring for 20 minutes under nitrogen, the round-bottom flask was placed into a 66° C. oil bath. After 10 minutes, two aqueous solutions of AA at 58.4% (13.96 g, 113.1 mmol) and methacrylic acid (MAA) at 58.4% (37.79 g, 256.4 mmol) were added dropwise over 2 hours. After completion, two aqueous solutions of AA at 58.4% (13.96 g, 113.1 mmol) and MAA at 58.4% (56.68 g, 384.5 mmol) were again added dropwise over 4 hours and 6 hours respectively. After a final 2 hours cooking, the round-bottom flask was removed from the oil bath.

[0072] The reaction mixture was analysed by 1H NMR spectroscopy and size exclusion chromatography.

[0073] A Brucker 300 MHz spectrometer was used to record proton nuclear magnetic resonance (1H NMR) spectra. To measure AA, MAA and 4-allylpyrocatechol conversions, four drops of the reaction mixture was diluted in around 1 g of deuterated water (D2O). AA conversion=99%; MAA conversion=97%; 4-allylpyrocatechol conversion=91%

[0074] Molar masses 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 Agilent Aquagel OH mixed H, 8 μm, 3*30 cm at a flow rate of 1 mL/min and with the following mobile phase: H.sub.2O 100% vol. 0.1 M NaCl, 25 mM NaH2PO4, 25 mM Na2HPO4 buffer solution pH 7. Polymer samples have been dissolved at 0.5 wt % in the mobile phase for at least 4 hours then filtrated in a Millipore filter 0.45 μm. Absolute molar masses were obtained with the dn/dC of the poly(acrylic acid) equal to 0.1875 mL/g. Mw=33 kg/mol; Mn=16.5 kg/mol; Ð=1.9

EXAMPLE 1.2

[0075] A polymer P2 (AA/MAA/allyl catechol=80/12/08 mol/mol/mol), was prepared with the same protocol as in example 1.1, with the differences identified in the Table 1 below, with the following results: AA conversion=96%; MAA conversion=99.9%; 4-allylpyrocatechol conversion=81%−Mw=29 kg/mol; Mn=14 kg/mol; Ð=2

TABLE-US-00001 TABLE 1 preparation of polymers P1 and P2 Monomers used and how they are added (initial/feeds#1 and/or feeds#2) Global Initial quantity fraction Feeds #1 * Feeds #2 ** Poly- mass in the fraction dura- fraction dura- mer (g) mmol reactor added tion added tion P1 allyl 5.50 36.6 100% — — catechol AA 17.16 238.1  5% 47.5%   2 h 47.5%   4 h MAA 55.17 640.9 — 40% 2 h 60% 6 h P2 allyl 11.00 73.2 100% — — catechol AA 52.73 732.0  10% 40% 1 h 50% 3 h MAA 9.45 109.8 — 40% 1 h 60% 3 h * both feeds start 10 mn after heating ** both feeds start when feeds #1 are over

EXAMPLE 2

Use of the Polymers of Example 1

[0076] Performances of the polymers P1 and P2 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.

[0077] 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.

[0078] 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 (except for one test identified in Table 2) with a flow of deionized water for 1 mn and dried for 30 mn at 60° C.

[0079] 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, typical for 40 mn at 180° C. Finally, paper clips are removed.

[0080] Step 4—tensile strength test I on assemblies as obtained in step 3

[0081] 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)

[0082] Step 5—tensile strength test II performed on assemblies as obtained in step 3 after ageing

[0083] 5.1. Ageing Cyclic Test [0084] A cyclic ageing test is performed according to ASTM G85—Annex 3 (SWAAT, 2011) in a corrosion chamber Q-FOG CRH 600L, from Q-FOG [0085] in the following conditions: [0086] a 30-minute acidified salt fog spray followed by [0087] a 90-minute soak at >98% relative humidity [0088] under the following conditions: [0089] Chamber temperature—constant 49° C. [0090] Air saturator temperature—constant 57° C. [0091] Relative humidity—>98% [0092] pH of fall out solution—2.8-3.0 [0093] Volume of fall out solution—1.0-2.0 ml/80 cm.sup.2/hour [0094] Exposure period—1000 hours [0095] 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.

[0096] 5.2. Tensile Strength Test [0097] In the conditions of the tensile strength test I of step 4

[0098] The obtained results are reported in Tables 2-4 below (the values are average values: 3-4 assemblies were tested before ageing, 5 assemblies were tested after ageing), with the following variations in step 2:

TABLE-US-00002 TABLE 2 conditions of step 2 Concentration of Test polymer in the Rinsing step no. Polymer treating bath pH after treatment 1 NONE (control) — — — 2 P1 1000 ppm 2.47 yes 3 P2 1000 ppm 2.54 yes 4 P2 1000 ppm 2.54 no

TABLE-US-00003 TABLE 3 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 35.7 0.9 28.0 1.8 78 3 27.1 1.0 21.2 8.2 78 4 27.1 1.3 14.1 11.9 52

TABLE-US-00004 TABLE 4 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 11159.0 269.3 8735.5 556.9 78 3 8482.0 309.8 6637.4 2549.6 78 4 8461.4 395.1 4398.0 3714.1 52

TABLE-US-00005 TABLE 5 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 13.1 1.1 8.3 1.1 63 3 16.1 2.7 7.1 4.7 44 4 6.3 1.0 3.0 2.7 47

TABLE-US-00006 TABLE 6 FACIES after failure FACIES after failure Test no. Before ageing (test I) After ageing (test II) 1 (control) c a 2 c ~c 3 c a/c 4 ~a ~a (c): cohesive fracture (~c): rather cohesive fracture (a): adhesive fracture (~a): rather adhesive fracture (a/c): 50% adhesive 50% cohesive

EXAMPLE 3

Comparative Polymers C2, C3:

[0099] Two comparative polymers were prepared with benzotriazole ethyl methacrylate instead of allyl cathecol. Details are given below:

General formula:

##STR00003##

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

[0100] MAA/AA/BztMA=76/20/4 mol %

[0101] Mw=30 000 g/mol, Mn=15 000 g/mol (same method of measure as described previously).

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

[0102] MAA/AA/BztMA=67/23/10 mol %

[0103] Mw=30 000 g/mol, Mn=15 000 g/mol (same method of measure as described previously).

EXAMPLE 4

Use of Comparative Polymers C2, C3

[0104] 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 2 and assembled to form SLS assemblies as described in D1002-10.

Conditions

[0105] 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.

[0106] 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.

TABLE-US-00007 TABLE 7 conditions of step 2 Polymer concentration Treat- in the ment Test Poly- treatment bath no mer Details bath pH 4.1 None NONE (control) NONE (control) — 4.2 C2 MAA/AA/BztMA: 76/20/4  200 ppm 2.34 Mw 30 000 g/mol - Mn 26 000 g/mol 4.3 C2 MAA/AA/BztMA: 76/20/4 1000 ppm 2.36 Mw 30 000 g/mol - Mn 26 000 g/mol 4.4 C3 MAA/AA/BztMA: 67/23/10  200 ppm 2.32 Mw 30 000 g/mol - Mn 26 000 g/mol 4.5 C3 MAA/AA/BztMA: 67/23/10 1000 ppm 2.40 Mw 30 000 g/mol - Mn 26 000 g/mol

TABLE-US-00008 TABLE 8 STRAIN at maximum Load STRAIN at Maximum Load Before ageing (test I) After ageing (test II) Av. strain STD Av. strain STD Test no. (MPa) (MPa) (MPa) (MPa) Retention (%) 4.1 28.2 1.4 21.9 1.5 78 4.2 29.6 0.5 25.7 0.5 87 4.3 28.7 0.4 22.4 1.7 78 4.4 27.7 0.8 22.9 1.0 83 4.5 27.7 0.2 17.8 0.4 64

TABLE-US-00009 TABLE 9 MAXIMUM LOAD Maximum Load Before ageing (test I) After ageing (test II) Av. Max. Av. Max. Test no. Load (N) STD (N) Load (N) STD (N) Retention (%) 4.1 9056 356 7410 663 82 4.2 9435 66 7948 177 84 4.3 9225 114 7154 422 78 4.4 8862 177 7260 306 82 4.5 8822 85 5513 85 62

TABLE-US-00010 TABLE 10 Energy at maximum Load Energy at Maximum Load Before ageing (test I) After ageing (test II) Av. Energy SD Av. Energy SD at max load Energy at max load Energy Test no. (J) (J) (J) (J) Retention (%) 4.1 13.8 3.9 6.0 1.1 44 4.2 16.6 0.7 6.8 0.3 41 4.3 15.5 2.1 5.1 0.9 33 4.4 12.9 2.2 5.6 0.5 43 4.5 12.4 0.3 2.2 0.3 18

TABLE-US-00011 TABLE 11 FACIES after bond failure Test Facies after failure no Before ageing (test I) After ageing (test II) 4.1 c a 4.2 ~c a 4.3 c/a a 4.4 ~a a 4.5 ~a a c: cohesive fracture; ~c: rather cohesive fracture; c/a: fracture both cohesive and adhesive; ~a: rather adhesive fracture; a: adhesive fracture