Anti-corrosive paintings and coatings containing nanoparticles

[0001] The present invention relates to a nanoplide comprising paints and anti-corrosive coatings.

In particular, the present invention relates to anticorrosive paints and coatings comprising nanoparticles consisting of inorganic aluminosilicates having a plate-like shape in the following description referred to as nanoclays.

[0003] It is known that coating, paint and primer formulations are based on polymers comprising solid particles, pigments, plasticizing agents and other technological auxiliaries dissolved in organic solvents (coatings based on the organic phase) or water (water-based coatings) .

[0004] It is also known that among the currently available anti-corrosive paints and coatings, epoxy, acrylic and acrylic paints and coatings exhibit excellent adhesion and durability properties, and, in particular, are widely used for coating steel structures to delay corrosion effects, resulting from the combination of oxygen and moisture.

[0005] However, as a result of their inherent composition, these paints and coatings absorb moisture and are not an optimal barrier to oxygen. Moisture absorption and oxygen passage are the cause of the corrosion process of coated metals, leading to the formation of oxide at the metal-interfacial interface. After such a phenomenon the shell is peeled off (separation) and the distribution of the metallic substrate increases.

[0006] In order to overcome these limitations of previously known paints and coatings, a paint formulation having reduced permeability, comprising a film-forming agent, a pigment and a plurality of chemically treated nanoparticles having a plate shape, which are predominantly two-dimensional, is disclosed in US Pat. No. 6,878,776. developed, with transverse dimensions of a few hundred nanometers and a thickness of about one nanometer. According to said patent, the percentage of tiles (preferably aluminosilicate, in each case consisting of a water-impermeable material) dispersed in the formulation is from 1 to 10% by volume, and the plates are chemically treated with organic compounds (such as, for example, an amino or epoxy terminated silane) or inorganic compounds (such as, for example, aliphatic acid) to facilitate orientation in a direction parallel to the substrate, the paint being on not applied, thus increasing intermolecular forces between the plates. By arranging in a direction parallel to the surface of the substrate, the plates reduce the possible spaces to pass through the liquid and gas corrosive molecules and increase the distance to be overcome to reach the interface between the coating layer and the substrate, thereby reducing the possibility of oxide formation on the substrate. the interface and the resulting separation of the coating.

[0007] On the other hand, it has been demonstrated that formulations according to the document US 6 878 767 do not allow optimum orientation of the plates and therefore reduce the water resistance effect for which tiles are added. Through microscopic analysis, in particular Transmission Electron Microscopy (TEM) and transmission measurements, it was possible to check that the ordering and alignment of nanoclays at the nanometer level is disturbed due to the excess viscosity of the preparation, resulting in a weaker barrier effect to moisture and oxygen, and in as a result of increased corrosion. This is due to the fact that because of their shape with a particularly developed surface in terms of thickness (high aspect ratio), tiles added to paints based on polymeric resins are easily immobilized by polymer molecules.

[0008] In light of the above, it is apparent that there is a need to provide a preparation for anticorrosive paints and coatings comprising nanometer size tiles that overcome the limitations of formulations according to the document US 6 878 767.

[0009] In this context, it has been proposed to solve a problem in accordance with the present invention that aims to provide a formulation for anti-corrosive paints and coatings comprising nanoclays, wherein said nanoclays are chemically treated and the viscosity is controlled in such a way as to favor the deployment of nanoclays in parallel to the substrate on which the preparation is applied.

The object of the present invention is therefore to provide a formulation for anticorrosive paints and coatings comprising nanoclays and a process for its production, which allows to eliminate the limitations of solutions compatible with known technology and to achieve the previously described technical results.

[0011] A further object of the invention is that said formulation and process can be carried out at substantially reduced costs, both manufacturing and operation.

[0012] It is not the last object of the invention to offer a substantially simple, safe and reliable formulation and process.

[0013] Therefore, a first specific object of the present invention is a formulation for anticorrosive paints and coatings based on epoxide, polyurethane, acrylic acid, alkyd, polyester and mixtures thereof, dissolved in organic or inorganic solvents, and containing a plurality of nanoparticles, most of which are two-dimensional, with transverse dimensions of a few hundred nanometers and a thickness of about one nanometer, wherein the rotational viscosity of the formulation at 10 rpm, measured in accordance with ASTM D4212, is less than 55,000 mPa and preferably less than 40,000 mPa.s.

In particular, according to the invention, the amount of said nanoparticles is less than 2% by weight, based on the total weight of the formulation, preferably less than 1% by weight, based on the total weight of the preparation and most preferably equal to 0.5% by weight, based on the total weight of the preparation.

[0015] In particular, according to the invention, said nanoparticles consist of ion-exchangeable materials available for ion exchange reactions previously subjected to an ion-exchange reaction with long-chain molecules, preferably at least 16 carbons, to achieve both: good introduction of Na + nanoparticles and physical compatibility with the matrix of the bisphenol A diglycidal ether.

[0016] According to the invention, said nanoparticles preferably always consist of aluminosilicate-based materials, even more preferably montmorillonite.

[0017] Moreover, again in accordance with the present invention, said long-chain molecule ions are obtained by protonating amines and other compounds compatible with the other ingredients of the formulation.

[0018] The invention will now be described in an illustrative but non-limiting manner, in particular with reference to preferred embodiments and certain illustrative examples.

[0019] According to the present invention, the plates from which the formulation is prepared are chemically treated to make it easier to orientate in a direction parallel to the substrate to which the paint is applied, thereby increasing the intermolecular forces between the plates. Furthermore, the viscosity is controlled so that it does not reach values ​​that would prevent easy movement of the plates within the matrix consisting of a polymeric paint, i.e. to position them parallel to the metallic substrate (and thus to offer as much corrosion protection as possible) as a result of the mechanical action carried out by the devices used to apply the paint layer to the substrate. In addition, in order to obtain sufficiently low viscosities,

Example 1. Pre-treatment of nanoclays [0020] 50g clays from Cloisite Na (NC-Na), CAS N. 1318-93-0; 95Meq / 100g, from Southern Clay Products, were dispersed in 1500ml of water at room temperature for 30 minutes, and the resulting dispersion was then heated at 85 ° C and held in a standing position for 2 hours.

[0021] A second solution was prepared separately by dissolving in 1300ml of water at 85 ° C, 19g octadecylamine (ODA), C18H39N, CAS N. 124-30-1, FW = 269.51, from Fluka, cat. No. 74752. Subsequently, 37% hydrochloric acid (HCl) was added until the pH was 4.5, FW = 36.5, and the solution was stirred for 0.3 hours.

[0022] This solution was then added to the aqueous dispersion of the nanoclay by stirring at 85 ° C for 1 hour and then allowed to cool.

Under these conditions a white colored precipitate was formed which was then separated from the clear liquid and then washed first with ethanol and then three times with water.

[0024] The solid precipitate was then collected and dried by heating at 80 ° C for 15 hours and then at 110 ° C for 2 hours.

[0025] A dried sludge consisting of platelet clay with attached functional groups from the Cloisite Na material is ready for addition to paints.

[0026] The basis of the nanoclay treatment is to allow the exchange of Na ion⁺ (or another ion present in the nanoclays to be treated) with a long chain containing an ion. In this way, the distance between the plates forming the structure of ceramic nanoclays is increased, thus facilitating the delamination of nanoclays, obtaining individual nanoclays (1 nm thick).

As a long chain containing an ion, an amine can be used, protonated with such an amount of acid to allow protonization, i.e. with an ammonium ion which is exchanged with an Na + ion (specifically for Example 1, octadecylamine is protonated with hydrochloric acid).

[0028] When the protonized amine solution is added to the aqueous dispersion of ceramic nanoclays, ion exchange occurs. The obtained precipitate consists of nanoclays treated with ODA (which is hydrophobic).

Example 2. Preparation of a primer (primer) containing clay with attached functional groups [0029] Nanoclays obtained in accordance with example 1 were added to the epoxy primer (primer) in accordance with the various sets of ingredients as reported in Table 1, and mixed until homogeneous dispersion.

[0030] The different sets of primer components obtained were separately applied to identical metallic substrates, then analyzed, and the results were recorded in Table 1.

Table 1

<td>% NG</td><td>Viscosity mPa ^ s</td><td>Thickness um</td><td>Number of bubbles</td><td>resistivity Ω · ^²</td>

<td>0</td><td>27000</td><td>150</td><td>4</td><td>9x10⁷</td>

<td>0.5</td><td>32000</td><td>140</td><td>0</td><td>8x10⁹</td>

<td>1.0</td><td>37100</td><td>140</td><td>2</td><td>5x10⁹</td>

<td>2.0</td><td>52400</td><td>142</td><td>2</td><td>1x10⁹</td>

[0031] In particular, in table 1,% NG shows the percentage of nanoclays in relation to the whole formulation, the viscosity is the rotational viscosity at 10 rpm, measured according to ASTM D4212, the number of bubbles measured after 700 hours of exposure to salt sprayers (salt spray test: ASTM

B117), and the resistivity was measured after 700 hours exposure to and at a thickness of 80 μm according to the Electrochemical Impedance Spectroscopy: ISO 16773-3: 2009.

Example 3. Preparation of a paint formulation containing attached functional groups. The nanoclays obtained according to Example 1 were added to the epoxy paint formulation according to the various component kits as noted in Table 2 and mixed until homogeneous dispersion.

[0033] The various paint component kits obtained were separately applied to identical metal substrates, then analyzed, and the results were recorded in Table 1.

Table 2

<td>% NG</td><td>Viscosity mPa ^ s</td><td>Thickness um</td><td>Number of bubbles</td><td>resistivity Ω · ^²</td>

<td>0</td><td>26600</td><td>160</td><td>20</td><td>2x10¹⁰</td>

<td>0.5</td><td>39000</td><td>130</td><td>0</td><td>11x10¹²</td>

<td>1.0</td><td>51400</td><td>135</td><td>3</td><td>8x10¹¹</td>

<td>2.0</td><td>85700</td><td>130</td><td>5</td><td>1x10¹¹</td>

In particular in Table 2,% NG shows the percentage of the nanoclays in relation to the whole formulation, the viscosity is the rotational viscosity at 10 rpm, measured according to ASTM D4212, the number of bubbles measured after 700 hours of exposure to salt sprayers ( salt spray test: ASTM

B117), and the resistivity was measured after 700 hours of exposure and an equal thickness

150 μm according to Electrophemic Impedance Spectroscopy: ISO 16773-3: 2009.

Example 4. Comparative Evaluation of Peel Strength of Paint Formulations Containing Along Affected Creatives [0035] Nanoclays obtained in accordance with Example 1 and other Cloning nanoclays (30 B Closite) not subjected to the same treatment were added to the epoxy paint formulation according to different sets ingredients, as noted in Table 3 (the first row of the table refers to the preparation without the addition of a nanoclay); separately applied to identical metallic substrates (in order to create a coating of low thickness), and subsequently subjected to adhesion tests, by means of a break method, and the results are recorded in Table 3.

The adhesion test is a direct method, according to EN ISO 4624, which is aimed at checking the quality of the coating, and which is carried out by a destructive test to evaluate the peel strength of the paint film layer. Two adhesion tests were carried out for each preparation in dry conditions and one in wet tests.

Table 3

<td></td><td colspan="3">Dry adhesion (MPa)</td><td>Wet adhesion (MPa)</td>

<td></td><td>Value 1</td><td>Value 2</td><td>Average</td><td></td>

<td>No nanoglins</td><td>17.0</td><td>17.0</td><td>17.0</td><td>12.0</td>

<td>1% Example 1</td><td>13.4</td><td>15.0</td><td>14.2</td><td>16.4</td>

<td>1% Closite 30 B</td><td>5.2</td><td>6.0</td><td>5.6</td><td>3.6</td>

<td>2% Example 1</td><td>15.0</td><td>17.0</td><td>16.0</td><td>19.0</td>

<td></td><td colspan="3">Dry adhesion (MPa)</td><td>Wet adhesion (MPa)</td>

<td></td><td>Value 1</td><td>Value 2</td><td>Average</td><td></td>

<td>2% Closite 30 B</td><td>5.0</td><td>5.0</td><td>5.0</td><td>4.8</td>

[0037] The examples allow to check that a new preparation, such as described in the present invention, inhibits the passage of moisture and oxygen through protective coatings on the metal surface, so as to minimize the effects of corrosion. This inhibition occurs as a result of the orderly and parallel arrangement of the expanded surface of the inorganic nanoclays obtained by treatment according to example 1.

[0038] Moreover, the examples demonstrate the greater effectiveness of anticorrosive formulations according to the present invention, with the addition of nanoclays with attached functional groups than preparations with the addition of nanoclays without attached functional groups.

[0039] With reference to the amount of nanoclays added to the anti-corrosive paint and coating formulation according to the present invention, the amount of nanoclays to be used must be such that it does not lead to an undesirable increase in viscosity. In order to achieve viscosity targets, the paint formulation can usually be diluted with non-reactive reagents (organic or water-based) that reduce viscosity and evaporate after curing the coating.

The adhesion test is a direct method according to the EN ISO 4624 standard, which purpose is to check the quality of the coating, and which is carried out by a destructive test to evaluate the peel strength of the paint film layer. Two adhesion tests were carried out for each preparation in dry conditions and one in wet tests.

Table 3

<td></td><td colspan="3">Dry adhesion (MPa)</td><td>Wet adhesion (MPa)</td>

<td></td><td>Value 1</td><td>Value 2</td><td>Average</td><td></td>

<td>No nanoglins</td><td>17.0</td><td>17.0</td><td>17.0</td><td>12.0</td>

<td>1% Example 1</td><td>13.4</td><td>15.0</td><td>14.2</td><td>16.4</td>

<td>1% Closite 30 B</td><td>5.2</td><td>6.0</td><td>5.6</td><td>3.6</td>

<td>2% Example 1</td><td>15.0</td><td>17.0</td><td>16.0</td><td>19.0</td>

<td>2% Closite 30 B</td><td>5.0</td><td>5.0</td><td>5.0</td><td>4.8</td>

[0041] The examples allow to check that a new preparation, such as described in the present invention, inhibits the passage of moisture and oxygen through protective coatings on the metal surface, so as to minimize the effects of corrosion. This inhibition occurs as a result of the orderly and parallel arrangement of the expanded surface of the inorganic nanoclays obtained by treatment according to example 1.

[0042] Moreover, the examples demonstrate the greater effectiveness of anticorrosive formulations according to the present invention with the addition of nanoclays with attached functional groups than formulations with the addition of nanoclays without attached functional groups.

[0043] With reference to the amount of nanoclays added to the anti-corrosive paint and coating formulation according to the present invention, the amount of nanoclays to be used must be such that it does not lead to an undesirable increase in viscosity. In order to achieve viscosity targets, the paint formulation can usually be diluted with non-reactive reagents (organic or water-based) that reduce viscosity and evaporate after curing the coating.

The present invention has been described in an illustrative but non-limiting manner in accordance with its preferred embodiments, but it should be understood that variations and / or modifications may be made by those skilled in the art without departing from its scope, as defined in the appended claims. .

Nanto SRL Agent:

PL-PAT-2012-958

EP 2 352 789 B1