ANTI-CORROSIVE PAINTINGS AND COATINGS CONTAINING NANOPARTICLES

Abstract

The present invention refers to a formulation for anticorrosion paints and coatings, based on epoxy, polyurethane, acrylic, alkylic, polyester resins and mixtures thereof, dissolved in organic or inorganic solvent and comprising a multitude of mostly bi-dimensionally developed nanoparticles, with a few hundred and about one nanometer, respectively, as to lateral dimensions and thickness, wherein the viscosity of the formulation is lower than 55000 mPa.Math.s.

Claims

1. An anticorrosion paint or coating formulation comprising an epoxy, polyurethane, acrylic, alkydic or polyester resin or a mixture thereof and comprising a multitude of mostly bi-dimensionally developed nanoparticles, with a few hundred and about one nanometer, respectively, as to lateral dimensions and thickness, wherein said nanoparticles consist of materials containing ions available for ion exchange reactions, previously treated by ion exchange reaction with ions of long chain molecules having at least 16 carbon atoms, the rotational viscosity of the formulation at 10 rpm being lower than 55000 mPa.Math.s

2. The anticorrosion paint or coating formulation of claim 1, wherein the viscosity of the formulation is lower than 40000 mPa.Math.s.

3. The anticorrosion paint or coating formulation of claim 2, wherein the amount of said nanoparticles is lower than 2% by weight, based on the total weight of the formulation.

4. The anticorrosion paint or coating formulation of claim 3, wherein the amount of said nanoparticles is lower than 1% by weight, based on the total weight of the formulation.

5. The anticorrosion paint or coating formulation of claim 4, wherein the amount of said nanoparticles is equal to 0.5% by weight, based on the total weight of the formulation.

6. The anticorrosion paint or coating formulation of claim 4 wherein said nanoparticles consist of silico-aluminate based materials.

7. The anticorrosion paint or coating formulation of claim 6, wherein said nanoparticles consist of montmorillonite.

8. The anticorrosion paint or coating formulation of claim 5, wherein said long chain molecule ions are obtained by protonising amines or other compounds compatible with other formulation components.

9. Formulation for anticorrosion paints and coatings, based on epoxy, polyurethane, acrylic, alkylic, polyester resins and mixtures thereof comprising a multitude of mostly bi-dimensionally developed nanoparticles, with a few hundred and about one nanometer, respectively, as to lateral dimensions and thickness, wherein said nanoparticles consist of materials containing ions available for ion exchange reactions, previously treated by ion exchange reaction with ions of long chain molecules having at least 16 carbon atoms.

10. The anticorrosion paint or coating formulation according to claim 1, wherein said nanoparticles consist of bentonite.

11. A method for preparing an anticorrosion paint or coating formulation comprising: a) treating nanoparticles by ion exchange reaction to obtain nanoparticles comprising at least 16 carbon atom hydrophobic chains attached to a surface of said nanoparticles; and b) adding less than 1% by weight of said obtained nanoparticles to the paint or coating formulation, based on the total weight of the formulation, thereby obtaining an anticorrosion paint or coating formulation having a viscosity lower than 55000 mPa.Math.s at 10 rpm.

12. The method of claim 11, wherein the 16 carbon atom hydrophobic chains are octadecylamine chains.

13. The method of claim 11 wherein said nanoparticles consist of silicoaluminate based materials.

14. The method of claim 11, wherein said nanoparticles consist of montmorillonite.

15. The method of claim 11, wherein said nanoparticles consist of bentonite.

Description

DETAILED DESCRIPTION

[0019] The invention now will be described by an illustrative, but not limitative way, particularly with reference to preferred embodiments and some illustrative examples.

[0020] According to the present invention, the platelets the formulation is made of are chemically treated in order to facilitate their orientation according to parallel direction of substrate the paint is applied on, thus increasing the platelets intermolecular forces. Moreover, the viscosity is controlled in order not to reach values preventing the platelets to move easily within the matrix consisting of polymeric paint, that is to align parallel to the metallic substrate (and therefore to offer as high as possible corrosion protection) as a result of the mechanical action carried out by devices used to spread the paint layer on the substrate. Further, in order to obtain low enough viscosities it is possible to add solvents to the paint (that are evaporated during drying) or reduce the solid content of the epoxy (like: calcium carbonate, metal oxides and other solids that are used in conventional paints).

EXAMPLE 1

Nanoclay Preliminary Treatment

[0021] 50g of Cloisite Na nanoclays (NC-Na), CAS N. 1318-93-0; 95Meq/100 g, from Southern Clay Products, have been dispersed in 1500 ml of water at room temp. for 30 minutes and the resulting dispersion then has been heated at 85 C. and hold standing for 2 hours.

[0022] Apart a second solution, obtained by dissolving in 1300 ml of water, at temperature of 85 C., 19 g of octadecylamine (ODA), C.sub.18H.sub.39N, CAS N. 124-30-1, FW=269,51, from Fluka, cat N. 74752, has been prepared. Then hydrochloric acid (HCl) at 37% has been added up to pH 4.5. FW=36.5. and the solution stirred for 0.3 hours.

[0023] Then this solution has been added to the water nanoclay dispersion by mixing at 85 C. for 1 hour, subsequently allowing to cool.

[0024] In these conditions, a white colour precipitate has been formed, then separated from clarified liquid and successively washed, firstly with ethanol and then, for three times, with water.

[0025] Solid precipitate then has been collected and dried by heating at 80 C. for 15 hours and successively at 110 C. for 2 hours.

[0026] Dried precipitate consisting of platelet shaped Cloisite Na functionalised nanoclays is ready to be added to paints.

[0027] The principle of nanoclays treatment is to allow Na.sup.+ion exchange (or other ion occurring within the nanoclays to be treated) with a long chain containing ion to be carried out. In this way the distance among the platelets forming the structure of ceramic nanoclays is increased, thus facilitating the de-lamination of the nanoclays resulting in single nanoclays (1 nm thick).

[0028] As a long chain containing ion can be used an amine, protonised with a such acid amount to allow the protonization to be carried out, that is, an ammonium ion which is exchanged with Na+ ion (specifically for example 1 octadecylamine is protonised with hydrochloric acid).

[0029] When the protonised amine solution is added to the water dispersion of ceramic nanoclays the ion exchange occurs. Resulting precipitate consist of ODA (which is hydrophobic) treated nanoclays.

EXAMPLE 2

Preparation of a Priming Formulation (Primer) Containing Functionalised Nanoclays

[0030] Nanoclays obtained according to example 1 have been added to an epoxy priming formulation (primer), depending on various compositions as reported in table 1 and mixed until an uniform dispersion has been obtained.

[0031] Various primer obtained compositions have been individually applied to identical metallic substrates, then analysed, with the results reported in table 1.

TABLE-US-00001 TABLE 1 Viscosity Thickness No. of Resistance % NC mPaS m bubbles cm.sup.2 0 27000 150 4 9 10.sup.7 0.5 32000 140 0 8 10.sup.9 1.0 37100 140 2 5 10.sup.9 2.0 52400 142 2 1 10.sup.9

[0032] Particularly, in table 1,% NC shows the nanoclay percentage on the total of the formulation, viscosity is rotational viscosity at 10 rpm, measured according to ASTM D2196, bubble number has been measured after 700 hours of exposure to saline sprays (salt spray test : ASTM B117) and resistance has been measured after 700 hours of exposure and thickness of 80 m according to Electrochemical Impedence Sprectoscopy: ISO 16773-3:2009.

Example 3

Preparation of a Painting Formulation Containing Functionalised Nanoclays

[0033] Nanoclays obtained according to example 1 have been added to an epoxy painting formulation, depending on the various compositions as reported in table 2, and mixed until an uniform dispersion has been obtained.

[0034] Various paint obtained compositions have been individually applied to identical metallic substrates, then analysed, with the results reported in table 1.

TABLE-US-00002 TABLE 2 Viscosity Thickness No. of Resistance % NC mPaS m bubbles cm.sup.2 0 26600 160 20 2 10.sup.10 0.5 39000 130 0 1 10.sup.12 1.0 51400 135 3 8 10.sup.11 2.0 85700 130 5 1 10.sup.11

[0035] Particularly, in table 2,% NC shows the nanoclay percentage on the total of the formulation, the viscosity is rotational viscosity at 10 rpm, measured according to ASTM D2196, the bubble number has been measured after 700 hours of exposure to saline sprays (salt spray test: ASTM B117) and resistance has been measured after 700 hours of exposure and thickness of 150 m according to Electrochemical Impedence Sprectoscopy: ISO 16773-3:2009.

Example 4

Comparative Evaluation of Detachment Strength of Painting Formulation Containing Functionalised Nanoclays

[0036] Nanoclays obtained according to example 1, and other closite nanoclays (30 B closite) not subjected to the same treatment, have been added to an epoxy painting formulation, according to various compositions as reported in table 3 (the first line of the table referring to a not nanoclay added formulation); individually applied to identical metallic substrates (to form a low thickness coating), and successively subjected to adhesion tests, by means of pull-off analysis, with results as reported in table 3.

[0037] Pull-Off test is a direct method, according to EN ISO 4624, aiming to check the quality of a coating and it is carried out by a destructive test allowing the detachment strength of the paint coating layer to be evaluated. For each formulation two adhesion tests in dry and one in wet conditions have been carried out.

TABLE-US-00003 TABLE 3 Dry adhesion (MPa) Wet adhesion Value 1 Value 2 Average (MPa) Without nanoclays 17.0 17.0 17.0 12.0 1% Example 1 13.4 15.0 14.2 16.4 1% Closite 30 B 5.2 6.0 5.6 3.6 2% Example 1 15.0 17.0 16.0 19.0 2% Closite 30 B 5.0 5.0 5.0 4.8

[0038] The examples allow to verify that the new formulation as described in the present invention inhibits the humidity and oxygen permeation through the protective coatings on the metallic surface, so as to minimize the corrosion effects. Such inhibition occurs as a result from the ordered and parallel orientation of surface extended inorganic nanoclays obtained by means of the treatment according to example 1.

[0039] Moreover, the examples show higher effectiveness of functionalised nanoclays added anticorrosion formulations according to the present invention than not functionalised nanoclays added formulations.

[0040] With reference to the amount of nanoclays added to the formulation for anticorrosion paints and coatings according to the present invention, the amount of nanoclays to be used must be such not to result in an undesired viscosity increase. In order the viscosity objectives to be reached, the paint formulation can conveniently be diluted with not reacting reagents (organic or water based) reducing the viscosity level and evaporating after the coating curing.

[0041] The present invention has been described by an illustrative, but not limitative way, according to preferred embodiments thereof, but it is to be understood that variations and/or modifications could be carried out by those skilled in the art without departing from the scope thereof, as defined in enclosed claims.