POLYMERS FOR METAL SURFACE TREATMENT

Abstract

The instant invention concerns 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 and mixtures thereof. The polymers are especially useful for treating a metallic surface intended to be coated by a paint, a varnish or an adhesive. The invention also concerns methods of coatings making use of this polymer P, compositions comprising the polymer P and useful for these methods, and the obtained coated materials.

Claims

1. A polymer P obtained by radical copolymerization of a mixture of acrylic acid; methacrylic acid; and at least one allylcatechol selected from the group consisting of 4-allylbenzene-1,2-diol; 3-allylbezene-1,2-diol, having the formulae below, and mixtures thereof. ##STR00002##

2. The polymer P of claim 1, wherein the at least one allylcatechol is a mixture of 4-allylbenzene-1,2-diol and 3-allylbenzene-1,2-diol.

3. The polymer P of claim 1 that have wherein the polymer has a molecular weight between 10 and 150 kDa.

4. The polymer P of claim 1, wherein the polymer contains acrylic acid (AA) at a content of 10 to 90% in mol; methacrylic acid (MAA) at a content of 1 to 70% in mol, and allylcatechol at a content of 1 to 20% in mol, each of the molar ratio being calculated on the basis of the total quantity of AA, MAA and allylcatechol.

5. A method, comprising treating a metallic surface intended to be coated by a paint, a varnish or an adhesive with at least one polymer P as defined in claim 1.

6. The method of claim 5, wherein the metal surface is a surface comprising a metal selected from the group consisting of aluminum, steel, zinc, magnesium and their alloys.

7. The method of claim 5, wherein a conversion composition a is applied on the metallic surface for forming a conversion coating thereon, and wherein: said conversion composition include all or part of the polymer P as an additive; and/or the conversion coating is applied on the metallic surface, and then all or part of the polymer P is applied on the conversion coating.

8. The method according to claim 5, wherein all or part of the polymer P is present in a paint, a varnish or a coating applied on the surface.

9. A process for coating a metallic surface with a paint, a varnish or an adhesive, comprising a step of treating said surface with at least one composition including at least one polymer P as defined in claim 1.

10. The process of claim 9, wherein the process is for coating a metallic surface with a paint.

11. The process of claim 9, wherein the composition comprising the polymer P is: a conversion composition including a polymer P; and/or a solution or a dispersion of the polymer P; and/or the paint, varnish or adhesive, that comprise a polymer P.

12. A conversion composition comprising at least one polymer P as defined in claim 1.

13. A paint, varnish or adhesive composition containing at least one polymer P as defined in claim 1.

14. A material comprising a metal surface which is in all or part (i) treated with at least one polymer P as defined in claim 1 and (ii) covered by a paint, a varnish or an adhesive.

15. The polymer P of claim 2, wherein the mixture has a molar ratio of 4-allylbenzene-1,2-diol to 3-allylbezene-1,2-diol between 30/70 and 70/30.

16. The method of claim 6, wherein the metal surface is a surface of aluminum or aluminum alloy.

17. The method according to claim 8, wherein all or part of the polymer P is present in a paint, a varnish or a coating applied on the surface after application of a conversion coating on the metal surface.

18. The process of claim 11, wherein the composition comprising the polymer P is 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.

19. The material of claim 14, wherein said material is a material having a metal surface 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 at least one polymer P with a metal of the treated surface or another compound present in the layer.

Description

EXAMPLE

Example 1

Synthesis of a Polymer P1 According to the Invention

Poly(AA-stat-MAA-stat-allylcatechol) 26/70/4 mol %

[0054] A polymer P1 was prepared as follows:

[0055] 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 and the reaction mixture was analysed by .sup.1H NMR spectroscopy (AA conversion=99%; MAA conversion=97%; 4-allylpyrocatechol conversion =91%) and by size exclusion chromatography (M.sub.w=57 kg/mol; M.sub.n=21 kg/mol; D=2.1).

[0056] A Brucker 300 MHz spectrometer was used to record proton nuclear magnetic resonance (.sup.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 (D.sub.2O).

[0057] 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 NaH.sub.2PO.sub.4, 25 mM Na.sub.2HPO.sub.4 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.

Example 2

Use of the Polymer of Example 1

[0058] Tests have been performed on aluminum alloy panels (AA5005, from Q-Panel), with usual lab equipment (beakers, oven, . . . ), a powder coating installation (GEMA 2C from Industrie Systemes) and a corrosion chamber (Q-FOG CRH 600L, from QFOG).

[0059] In each test, the following protocol has been applied:

[0060] Cleaning and etching [0061] It was made by dipping each pannel to be tested in a combined cleaning-etching bath, which was a 1 L bath is 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). The pannel was dipped in the cleaning-etching bath for 3min under light stirring (200rpm) at 50° C. The pannel was then rinsed with 1 L of de-ionized water.

[0062] Treatment [0063] It was performed by dipping the panel obtained after the cleaning/etching of the previous step in a treatment bath, which was a 1 L bath made by diluting in water: [0064] zirconium hexafluoride H.sub.2ZrF.sub.6 at a concentration of 200 ppm active (0.02wt %); and [0065] the additive to be tested (Polymer P1 of example 1 according to the invention, vs ACUMER™ 1510 in the comparative examples), at concentrations from 50 ppm active (0.005wt %) up to 1,000 ppm (0.1wt %)given in the tables below:

[0066] The panel was immerged for 2min in the treatment bath at 25° C. It was not rinsed.

[0067] The excess of bath solution was flushed away from the surface with compressed air.

[0068] The panel was then dried for 30min in an oven at 60° C.

[0069] Painting: [0070] Each panel was then painted with a polyester white powder paint from RIPOL (BIANCO RAL 9010).

[0071] Tests

[0072] Each Panel was then tested according to protocols similar to those described in the following standards listed below: [0073] Acetic acid salt spray: T=35 (+/−2)° C., [NaCl]=50 (+/−5)g/L, pH=3.1-3.3 (ISO 9227) [0074] Scribing protocol: as described in ISO 17872 [0075] Degree of rusting quoted as described in ISO 4628-3 [0076] Degree of blistering quoted as described in ISO 4628-2

[0077] Rusting Results

[0078] assessed according to ISO 4628-3

TABLE-US-00001 Polymer ACUMER ™ 1510 Comparative P1 Exposure time 308 h 564 h 758 h 1000 h 308 h 564 h 758 h 1000 h 0.005 wt % R1 R3 R3 R0 R0 R2 0.010 wt % R1 R2 R3 R0 R0 R2 0.020 wt % R1 R3 R3 R0 R0 R1 0.100 wt % R1 R2 R2 R0 R0 R2

[0079] Whatever the polymer concentration, rusting appears faster with the comparative example than with the polymer of the invention.

[0080] Blistering Results assessed according to ISO 4628-2

TABLE-US-00002 Polymer ACUMER ™ 1510 Comparative P1 Exposure time 308 h 564 h 758 h 1000 h 308 h 564 h 758 h 1000 h 0.005 wt % 1S1 1S1 1S1 5S1 0 0 0 2S1 2S1 4S1 0 1S1 2S1 4S1 0 1S1 0.010 wt % 1S1 1S1 2S1 3S1 0 5 little 0 2S1 2S1 2S1 blisters 1S1 1S1 2S1 2S1 1S1 1S1 0.020 wt % 1S1 2S1 3S1 4S1 0 0 0 1 little 3S1 3S1 0 blister 3S1 3S1 0 1S1 0 0.100 wt % 0 1 little 2S1 2S1 0 0 0 0 blister 2S1 2S1 0 0 2S1 2S1 0 0

[0081] Here again, the polymer of the invention is clearly better than the comparative, even after 1000 h.