Anti-adhesive coatings based on condensed tannins

Abstract

The invention relates to a composition for coatings which includes at least one condensed tannin and water and which has a pH of more than 7. The invention also relates to an anti-adhesive coating composition including said type of composition for coatings.

Claims

1. A coating composition comprising at least one condensed tannin and water, having a pH greater than 7, wherein the coating composition further comprises a polymerization agent selected from the group consisting of phosphate derivatives, furfuryl alcohol, glyoxal, and mixtures thereof.

2. The coating composition according to claim 1, wherein the mass percent of water is between 50% and 95% relative to the total mass of water and condensed tannin.

3. The coating composition according to claim 1, wherein the condensed tannin has, as a base structure, one or more flavan-3-ol monomer and/or flavan-3,4-diol monomer units and/or phlorotannins.

4. The coating composition according to claim 1, wherein the condensed tannin has, as a base structure, one or more monomer units corresponding to the following formula: ##STR00003## in which the carbons in position 6, 8, 2 and 6 are substituted by a hydrogen, the carbons in position 4, 5, 3 and 5 are independently substituted by a hydroxyl group or by a hydrogen.

5. The coating composition according to claim 1, wherein the condensed tannin is biosourced or synthetic.

6. The coating composition according to claim 1, wherein the pH is between 8 and 13.

7. An anti-adhesive coating composition comprising a coating composition and at least one fluorocarbon resin, wherein the coating composition comprises at least one condensed tannin, a polymerization agent, and water and has a pH greater than 7, and wherein the polymerization agent is selected from the group consisting of phosphate derivatives, furfuryl alcohol, glyoxal, and mixtures thereof.

8. The anti-adhesive coating composition according to claim 7, wherein the fluorocarbon resin is selected from polytetrafluoroethylene (PTFE), tetrafluoroethylene/perfluoropropylvinylether copolymers (PFA), tetrafluoroethylene/hexafluoropropylene copolymers (FEP), polyvinylidene fluoride (PVDF), tetrafluoroethylene/polymethylvinylether copolymers (MVA), terpolymers of tetrafluoroethylene, polymethylvinylether and fluoroalkylvinylether (TFE/PMVE/FAVE), ethylene tetrafluoroethylene (ETFE), and mixtures thereof.

9. The anti-adhesive coating composition according to claim 7, wherein the fluorocarbon resin represents 10% to 99% by weight of the total dry weight of the anti-adhesive coating composition.

10. The anti-adhesive coating composition according to claim 7, wherein the condensed tannin has, as a base structure, one or more flavan-3-ol monomer and/or flavan-3,4-diol monomer units and/or phlorotannins.

11. The anti-adhesive coating composition according to claim 7, wherein the condensed tannin has, as a base structure, one or more monomer units corresponding to the following formula: ##STR00004## in which the carbons in position 6, 8, 2, and 6 are substituted by a hydrogen, the carbons in position 4, 5, 3, and 5 are independently substituted by a hydroxyl group or by a hydrogen.

12. The anti-adhesive coating composition according to claim 7, wherein the condensed tannin is biosourced or synthetic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a depicts a photograph of an item, prior to curing, achieved according to a first embodiment of the present invention described in Example 7;

(2) FIG. 1b depicts a photograph of the item illustrated in FIG. 1a after curing;

(3) FIG. 2a depicts a photograph of an item, prior to curing, achieved according to a second embodiment of the present invention described in Example 8;

(4) FIG. 2b depicts a photograph of the item depicted in FIG. 2a after curing;

(5) FIG. 3a depicts a photograph of an item, prior to curing, achieved according to a third embodiment of the present invention described in Example 9;

(6) FIG. 3b depicts a photograph of the item depicted in FIG. 3a after curing; and

(7) FIG. 4 depicts a photograph of an item, after curing, achieved according to a fourth embodiment of the present invention described in Example 10.

(8) The various embodiments depicted in FIGS. 1a through 4 are described in the examples below.

EXAMPLES

(9) Tests

(10) Evaluating the Adhesion of a Coating on a Surface

(11) A cross-cut test was conducted in accordance with the standard NF T 30-038 (standard NF EN ISO 2049), followed by the immersion of the coated surface in three environments, consisting of three alternating cycles of: three hours in boiling water followed by three hours in oil at 200 C., followed by a two hour and forty minute dishwasher cycle with detergent. Then, after scoring the surface into a grid of 1010=100 squares over 1 cm.sup.2 using a fine razor blade, the anti-adhesive coating of each square was evaluated for the appearance of scratching or peeling. The rating is determined as detailed in the table below.

(12) TABLE-US-00001 Rat- ing Description 0 The edges of the cuts are completely smooth: none of the squares of the cross-cut area are detached. 1 Detachment of small flakes of the coating at the intersections of the cuts, affecting approximately 5% of the cross-cut area. 2 The coating has flaked along the edges or at the intersections of the cuts, and the detached surface represents significantly more than 5%, and up to approximately 15% of the cross-cut area. 3 The coating has flaked along the edges of the cuts either partially or fully in large ribbons, or has flaked partially or fully in various parts of the cross-cut areas. The detached surface represents significantly more than 15%, and up to approximately 35% of the cross-cut area. 4 The coating has flaked along the edges of the cuts in large ribbons or some squares have detached partially or fully. The detached surface represents significantly more than 35%, and up to 65% of the cross-cut area. 5 Any degree of flaking beyond the classification criteria set forth for rating 4.

(13) Test of the Hydrophobicity of a Coating

(14) The hydrophobic characteristics of a coating are evaluated by measuring the contact angle of a drop of water on the coating using a GBX Digidrop goniometer.

(15) Measurement of the Thickness of a Coating

(16) Coating thickness is measured using a coating thickness measurement device, such as the device sold by the company Fischer Instruments under the name PERMASCOPE.

(17) Three measurements were made in nine different areas of the coating and the average was calculated.

Examples Produced

Example 1Preparation of a Coating Composition SF1

(18) A coating composition based on condensed tannins derived from mimosa, SF1, is prepared, the composition of which is detailed in the following table.

(19) TABLE-US-00002 SF1 (mass in g) % wet % dry Condensed tannin 30.0 12.41 65.7 derived from mimosa, powdered form NH.sub.4OH 180.0 74.44 (at 10.25% in water) Glycerol 1.8 0.74 Triethyl phosphate 30.0 12.41 34.3 (TEP) (at 52.2% dry extract) TOTAL 241.8 100.0 100.0

(20) The coating composition SF1 is prepared at ambient temperature by: obtaining a homogenous mixture comprising ammonia and additives (glycerol and TEP) by mixing with a shear disperser; adding tannin powder, while mixing, to obtain a homogenous mixture.

(21) The characteristics of the resulting SF1 composition are measured: viscosity: 33 s in the 2.5 mm AFNOR viscosity flow cup. (CA 2.5) pH: 11.3

Example 2Preparation of a Coating Composition SF2

(22) A coating composition based on condensed tannins derived from quebracho, SF2, is prepared, the composition of which is detailed in the following table.

(23) TABLE-US-00003 SF2 (mass in g) % wet % dry Condensed tannin 10.0 5.89 50.25 derived from quebracho, powdered form NH.sub.4OH 40.0 23.54 (at 10.25% in water) Glycerol 7.0 4.12 Furfuryl alcohol (FA) 9.9 5.83 49.75 Demineralized water 103.0 60.62 TOTAL 170.0 100.00 100.00

(24) The coating composition SF2 is prepared at ambient temperature by: obtaining a homogenous mixture comprising ammonia and glycerol by mixing with a shearing blade disperser; adding tannin powder, while continuing to mix; adding FA, while continuing to mix; and finally homogenization of the coating composition via extended mixing.

(25) The characteristics of the resulting SF2 composition are measured: viscosity: 33 s in the 2.5 mm AFNOR viscosity flow cup. (CA 2.5) pH: 6.4

Example 3Preparation of an Anti-Adhesive Primer Layer Coating Composition P1

(26) An anti-adhesive coating composition P1 based on the coating composition SF1 from Example 1 is prepared, the composition of which is detailed in the following table.

(27) TABLE-US-00004 P1 (wet mass in g) % wet % dry Dispersion of PTFE 26.0 17 39.5 (at 60% in water) SF1 (at 18.9% dry 126.5 83 60.5 extract) TOTAL 152.5 100 100.0

(28) The anti-adhesive coating composition P1 is prepared at ambient temperature by: mixing the dispersion of PTFE with SF1 with a (non-shearing) blade disperser to obtain a homogenous mixture.

(29) The characteristics of the resulting P1 composition are measured: viscosity: 43 s in the 2.5 mm AFNOR viscosity flow cup. (CA 2.5) pH: 10-11

Example 4Preparation of an Anti-Adhesive Primer Layer Coating Composition P2

(30) An anti-adhesive coating composition P2 based on the coating composition SF1 from Example 1 is prepared, the composition of which is detailed in the following table.

(31) TABLE-US-00005 P1 (mass in g) % wet % dry Dispersion of PTFE 58.07 11.8 27.6 (at 60% in water) Dispersion of PFA 30.32 6.2 12.0 (at 50% in water) SF1 (at 18.9% dry 403.23 82.0 60.4 extract) TOTAL 491.62 100.0 100.0

(32) The anti-adhesive coating composition P2 is prepared at ambient temperature by: mixing the dispersion of PTFE and the dispersion of PFA with SF1 with a (non-shearing) blade disperser to obtain a homogenous mixture.

(33) The characteristics of the resulting P2 composition are measured: viscosity: 43 s in the 2.5 mm AFNOR viscosity flow cup. (CA 2.5) pH: 10-11

Example 5Preparation of an Anti-Adhesive Intermediate Layer Coating Composition M1

(34) An anti-adhesive coating composition M1 based on the coating composition SF1 from Example 1 is prepared, the composition of which is detailed in the following table.

(35) TABLE-US-00006 M1 (mass in g) % wet % dry Dispersion of PTFE 232.28 52.4 64.23 (at 60% in water) Dispersion of PFA 121.20 27.3 27.93 (at 50% in water) SF1 (at 18.9% dry 90.00 20.3 7.84 extract) TOTAL 443.48 100.0 100.00

(36) The anti-adhesive coating composition M1 is prepared at ambient temperature by: mixing the dispersion of PTFE and the dispersion of PFA with SF1 with a (non-shearing) blade disperser to obtain a homogenous mixture.

(37) The characteristics of the resulting M1 composition are measured: viscosity: 53 s in the 2.5 mm AFNOR viscosity flow cup. (CA 2.5) pH: 10-11

Example 6Preparation of an Anti-Adhesive Finish Layer Coating Composition F1

(38) An anti-adhesive coating composition F1 based on the coating composition SF2 from Example 2 is prepared, the composition of which is detailed in the following table.

(39) TABLE-US-00007 F1 (wet F1 mass in g) % wet % dry (dry mass in g) Dispersion of PTFE 84.94 88.78 97.6 50.96 (at 60% in water) Propylene glycol (PG) 1.52 1.59 SF2 (at 11.7% dry 9.00 9.41 2.0 1.05 extract) Mica flakes 0.21 0.22 0.4 0.21 TOTAL 95.67 100.00 100.0 52.22

(40) The anti-adhesive coating composition F1 is prepared at ambient temperature by: mixing the dispersion of PTFE with the PG and SF2 with a (non-shearing) blade disperser to obtain a homogenous mixture; and then adding mica flakes, while continuing to mix, to obtain a homogenous mixture.

(41) The characteristics of the resulting F1 composition are measured: viscosity: 45 s in the 2.5 mm AFNOR viscosity flow cup. (CA 2.5) pH: 9-11

Example 7Preparation of an Anti-Adhesive Finish Layer Coating Composition F2

(42) An anti-adhesive coating composition F2 based on the coating composition SF1 from Example 1 is prepared, the composition of which is detailed in the following table.

(43) TABLE-US-00008 F2 F2 (wet mass in g) % wet % dry (dry mass in g) Dispersion of PTFE 84.94 91.71 98.1 50.96 (at 60% in water) SF1 (at 18.9% dry 4.00 4.32 1.5 0.76 extract) Mica flakes 0.21 0.23 0.4 0.21 Water 3.46 3.74 TOTAL 92.61 100.00 100.00 51.93

(44) The anti-adhesive coating composition F2 is prepared at ambient temperature by: mixing the dispersion of PTFE with SF1 with a (non-shearing) blade disperser to obtain a homogenous mixture; adding mica flakes, while continuing to mix, to obtain a homogenous mixture; and finally adding water, while continuing to mix, to obtain a homogenous mixture.

(45) The characteristics of the resulting F2 composition are measured: viscosity: 45 s in the 2.5 mm AFNOR viscosity flow cup. (CA 2.5) pH: 9-11

Example 8Preparation of a Support Comprising a Layer of Composition SF1

(46) The coating composition SF1 from Example 1 is sprayed onto an aluminum support surface previously subjected to a surface treatment to ensure a clean surface conducive to the proper anchoring of the composition.

(47) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition on the surface.

(48) The resulting film, which is a glossy yellow ochre color, demonstrates the good coverage of the composition SF1, as depicted in FIG. 1a.

(49) After curing at 430 C. for 11 minutes, the resulting uniform film appears smooth and has a glossy dark brown color as depicted in FIG. 1b.

(50) The average thickness of the measured cured film is 6.4 m.

(51) The cured film exhibits very strong adhesion to the support: the adhesion test carried out on the surface coated with the cured film resulted in a rating of 0.

Example 9Preparation of a Support Comprising a Layer of Composition P1

(52) The anti-adhesive coating composition P1 is sprayed onto an aluminum support surface previously subjected to a surface treatment to ensure a clean surface conducive to the proper anchoring of the primer.

(53) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition on the surface.

(54) The resulting film, which is a glossy yellow ochre color, demonstrates the good coverage of the composition SF1, as depicted in FIG. 2a.

(55) After curing at 430 C. for 11 minutes, the resulting uniform film has a matte dark brown color as depicted in FIG. 2b.

(56) The average thickness of the measured cured film is 6 m.

(57) The cured film exhibits very strong adhesion to the support: the adhesion test carried out on the surface coated with the cured film resulted in a rating of 0.

(58) The cured film also exhibits very hydrophobic characteristics: the contact angle with a drop of water is greater than 100.

Example 10Preparation of a Support Comprising a Layer of Composition P1 and a Layer of Composition P2

(59) The anti-adhesive coating composition P1 is sprayed onto an aluminum support surface previously subjected to a surface treatment to ensure a clean surface conducive to the proper anchoring of the primer.

(60) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition P1 on the surface. The support is then cooled to ambient temperature.

(61) The anti-adhesive coating composition P2 is then sprayed onto the surface coated with the dried P1 composition.

(62) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition P2 on the film of composition P1.

(63) The resulting composite of films P1+P2, which is a glossy brown ochre color, demonstrates the good spreadability and coverage of compositions P1 and P2, as depicted in FIG. 3a.

(64) After curing at 430 C. for 11 minutes, a uniform coating P1+P2 is obtained and has a matte dark brown color as depicted in FIG. 3b.

(65) The average thickness of the measured coating is 10 m.

(66) The coating exhibits very strong adhesion to the support: the adhesion test carried out on the surface of the coating resulted in a rating of 0.

(67) The coating also exhibits hydrophobic characteristics: the contact angle between the surface of the coating and a drop of water is greater than 120.

Example 11Preparation of a Support Comprising a Layer of Composition P1 and a Layer of Composition M1

(68) The anti-adhesive coating composition P1 is sprayed onto an aluminum support surface previously subjected to a surface treatment to ensure a clean surface conducive to the proper anchoring of the primer.

(69) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition P1 on the surface. The support is then cooled to ambient temperature.

(70) The anti-adhesive coating composition M1 is then sprayed onto the surface coated with the dried P1 composition.

(71) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition M1 on the film of composition P1.

(72) The resulting composite of films P1+M1, which is a glossy brown ochre color, demonstrates the good spreadability and coverage of compositions P1 and M1.

(73) After curing at 430 C. for 11 minutes, a uniform coating P1+M1 is obtained that is matte black in color.

(74) The average thickness of the measured coating is 14 m.

(75) The coating exhibits very strong adhesion to the support: the adhesion test carried out on the surface coated with the coating resulted in a rating of 0.

(76) The coating also exhibits hydrophobic characteristics: the contact angle between the surface of the coating and a drop of water is greater than 100.

Example 12Preparation of a Support Comprising a Layer of Composition P1 and a Layer of Composition P2 and a Layer of Composition F2

(77) The anti-adhesive coating composition P1 is sprayed onto an aluminum support surface previously subjected to a surface treatment to ensure a clean surface conducive to the proper anchoring of the primer.

(78) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition P1 on the surface. The support is then cooled to ambient temperature.

(79) The anti-adhesive coating composition P2 is then sprayed onto the surface coated with the dried P1 composition.

(80) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition P2 on the film of composition P1. The support is then cooled to ambient temperature.

(81) The anti-adhesive coating composition F2 is then sprayed onto the surface coated with the dried composite of films P1+P2.

(82) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition F2 on the composite of films P1+P2.

(83) After curing at 430 C. for 11 minutes, a uniform coating P1+P2+F2 is obtained that is a glossy, speckled dark brown as depicted in FIG. 4.

(84) The average thickness of the measured coating is 23 m.

(85) The coating exhibits very strong adhesion to the support: the adhesion test carried out on the surface of the coating resulted in a rating of 0.

(86) The coating also exhibits hydrophobic characteristics: the contact angle between the surface of the coating and a drop of water is greater than 100.

(87) The coating also exhibits anti-adhesive characteristics verified by multiple cycles of cooking a volume of 30 ml of milk on the surface of the coating until carbonization of the liquid occurs. The milk that carbonized on the surface is easily detached from the coating with no more than the pressure of a jet of cold water from the faucet.

Example 13Preparation of a Support Comprising a Layer of Composition P1, a Layer of Composition M1 and a Layer of Composition F2

(88) The anti-adhesive coating composition P1 is sprayed onto an aluminum support surface previously subjected to a surface treatment to ensure a clean surface conducive to the proper anchoring of the primer.

(89) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition P1 on the surface. The support is then cooled to ambient temperature.

(90) The anti-adhesive coating composition M1 is then sprayed onto the surface coated with the dried P1 composition.

(91) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition M1 on the film of composition P1. The support is then cooled to ambient temperature.

(92) The anti-adhesive coating composition F2 is then sprayed onto the surface coated with the dried composite of films P1+M1.

(93) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition F2 on the composite of films P1+M1.

(94) After curing at 430 C. for 11 minutes, a uniform coating P1+M1+F2 is obtained that is a glossy, speckled dark brown as depicted in FIG. 4.

(95) The average thickness of the measured coating is 27 m.

(96) The coating exhibits very strong adhesion to the support: the adhesion test carried out on the surface of the coating resulted in a rating of 0.

(97) The coating also exhibits hydrophobic characteristics: the contact angle between the surface of the coating and a drop of water is greater than 100.

(98) The coating also exhibits anti-adhesive characteristics verified by multiple cycles of cooking a volume of 30 ml of milk on the surface of the coating until carbonization of the liquid occurs. The milk that carbonized on the surface is easily detached from the coating with no more than the pressure of a jet of cold water from the faucet.

Example 14Preparation of a Support Comprising a Layer of Composition P1 and a Layer of Composition F1

(99) The anti-adhesive coating composition P1 is sprayed onto an aluminum support surface previously subjected to a surface treatment to ensure a clean surface conducive to the proper anchoring of the primer.

(100) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition P1 on the surface. The support is then cooled to ambient temperature.

(101) The anti-adhesive coating composition F1 is then sprayed onto the surface coated with the dried P1 composition.

(102) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition F1 on the film of composition P1.

(103) After curing at 430 C. for 11 minutes, a uniform coating P1+F1 is obtained that is a matte dark brown color.

(104) The average thickness of the measured coating is 18 m.

(105) The coating exhibits very strong adhesion to the support: the adhesion test carried out on the surface of the coating resulted in a rating of 0.

(106) The coating also exhibits hydrophobic characteristics: the contact angle between the surface of the coating and a drop of water is greater than 100.

Comparative Example 1Preparation of a Coating Composition SFC

(107) TABLE-US-00009 SFC SFC (wet mass in g) % wet (dry mass in g) PAI resin 325.0 32.50 97.5 (30% in NEP) NMP 78.3 7.83 NEP 76.8 7.68 Triethylamine 23.6 2.36 Diethylethanolamine 8.9 0.89 Demineralized water 487.4 48.74 Total 1000.0 100.00 97.5

(108) The coating composition SFC is prepared at ambient temperature by: obtaining a homogenous mixture comprising PAI resin, solvents and amines by mixing with a shearing blade disperser; adding demineralized water, while continuing to mix to obtain a homogenous mixture; and finally grinding the mixture for one hour and thirty minutes.

(109) The viscosity of the resulting composition SFC is measured: viscosity: 10-15 s in the 4 mm AFNOR viscosity flow cup. (C.A. 4)

Comparative Example 2Preparation of an Anti-Adhesive Primer Layer Coating Composition PC1

(110) An anti-adhesive coating composition PC1 based on the coating composition SFC1 from Comparative Example 1 is prepared, the composition of which is detailed in the following table.

(111) TABLE-US-00010 PC1 PC1 (wet mass in g) (dry mass in g) % wet SFC (at 9.75% dry 145.9 14.22 50 extract) Dispersion of PTFE 23.7 14.22 50 (at 60% in water) Total 169.6 28.44 100

(112) The anti-adhesive coating composition PC1 is prepared at ambient temperature by: mixing the PTFE dispersion with SFC using a (non-shearing) blade disperser to obtain a homogenous mixture.

(113) The viscosity of the resulting composition PC1 is measured: viscosity: 50-60 s in the 2.5 mm AFNOR viscosity flow cup. (C.A. 2.5)

Comparative Example 3Preparation of an Anti-Adhesive Primer Layer Coating Composition PC2

(114) An anti-adhesive coating composition PC2 based on the coating composition SFC1 from Comparative Example 1 is prepared, the composition of which is detailed in the following table.

(115) TABLE-US-00011 PC2 PC2 (wet mass in g) (dry mass in g) % wet SFC (at 9.75% dry 328.0 32.0 50 extract) Dispersion of PTFE 37.5 22.5 35.2 (at 60% in water) Dispersion of PFA 19.0 9.5 14.8 (at 50% in water) Total 384.5 64.0 100.0

(116) The anti-adhesive coating composition PC2 is prepared at ambient temperature by: mixing the dispersions of PTFE and PFA with SFC using a (non-shearing) blade disperser to obtain a homogenous mixture.

(117) The viscosity of the resulting composition PC2 is measured: viscosity: 40-50 s in the 2.5 mm AFNOR viscosity flow cup. (C.A. 2.5)

Comparative Example 4Preparation of Support Comprising a Layer of Composition PC1

(118) The anti-adhesive coating composition PC1 is sprayed onto an aluminum support surface previously subjected to a surface treatment to ensure a clean surface conducive to the proper anchoring of the primer.

(119) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition on the surface.

(120) After curing at 430 C. for 11 minutes, a uniform coating is obtained of an average measured thickness of 5 m.

(121) The cured film exhibits very strong adhesion to the support: the adhesion test carried out on the surface coated with the cured film resulted in a rating of 0.

(122) The cured film also exhibits hydrophobic characteristics: the contact angle with a drop of water is greater than 100

Comparative Example 5Preparation of Support Comprising a Layer of Composition PC1 and a Layer of Composition PC2

(123) The anti-adhesive coating composition PC1 is sprayed onto an aluminum support surface previously subjected to a surface treatment to ensure a clean surface conducive to the proper anchoring of the primer.

(124) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition PC1 on the surface. The support is then cooled to ambient temperature.

(125) The anti-adhesive coating composition PC2 is then sprayed onto the surface coated with the dried PC1 composition.

(126) The drying of the film is carried out following this coating process at approximately 70-80 C. to set the composition PC2 on the film of composition PC1.

(127) After curing at 430 C. for 11 minutes, a uniform coating P1+P2 is obtained of an average measured thickness of 11 m.

(128) The coating exhibits very strong adhesion to the support: the adhesion test carried out on the surface of the coating resulted in a rating of 0.

(129) The coating also exhibits sufficiently hydrophobic characteristics: the contact angle between the surface of the coating and a drop of water is greater than 90.