MARINE COATING FORMULATIONS

Abstract

A formulation for a coating for applications on maritime infrastructure or vessels to inhibit fouling and corrosion that comprises: (a) a nano-active material; and (b) a polymer binder; and (c) additives which include pigments, booster antifoulants, booster anticorrosion materials, solvents, polymerisation activators, viscosity modifiers and fillers, where the nano-active material, the binder and additives provide the coating with the desired most desirable properties of antifoul, anticorrosion, adhesion, and strength, required for the coating application.

Claims

1. A formulation comprising: (a) a nano-active material comprising a powder material with an average particle size in the range of 1-300 microns, with a volumetric pore surface area greater than 100 m.sup.2/cm.sup.3; and (b) a polymer binder; and (c) additives comprising pigments, booster antifoulants, booster anticorrosion materials, solvents, polymerisation activators, viscosity modifiers and fillers; wherein the booster anticorrosion materials comprise lanthanide material; wherein the mixture of the nano-active material, the binder and the additives provides an antifouling and anticorrosion coating to maritime infrastructure or vessels, when applied.

2. The formulation of claim 1, wherein the nano-active material is at least 10 wt %, and 30-75% of the set coating weight depending on the coating application.

3. The formulation of claim 1, wherein the nano-active material is a powder material with an average particle size typically in the range of 1-300 microns, which is sufficiently porous with a volumetric pore surface area greater than 100 m.sup.2/cm.sup.3.

4. The formulation of claim 3, wherein the nano-active material is a powder material with an average particle size typically in the range of 4-10 microns.

5. The formulation of claim 3, wherein the nano-active materials include nano-active powders with a chemical composition of AgO, ZnO, CuO, Cu.sub.2O, MgO, SiO.sub.2, Al.sub.2O.sub.3, Mn.sub.3O.sub.4 and combinations thereof.

6. The formulation of claim 5, wherein the chemical purity of these materials is 80% or more.

7. The formulation of claim 6, wherein the chemical purity of these materials is greater than 95%.

8. The formulation of claim 1, wherein the polymer binder is drawn from a wide range of polymer materials, including acrylic, saturated or unsaturated polyester, alkyd, polyurethane or polyether, polyvinyl, cellulosic, silicon-based polymers, co-polymers thereof, and contain reactive groups such as epoxy, carboxylic acid, hydroxyl, isocyanate, amide, carbamate, amine and carboxylate groups, among others, including mixtures thereof, wherein combinations of film-forming polymers are used, and wherein the materials include thermosetting polymers, polymers that require initiators, accelerants, or polymers that set through volatilisation of solvents, wherein the selection of the binder and additives are determined to provide a coating which is adhesive to the substrate, hard, ablative, hydrophobic or superhydrophobic as required for the application when combined the with nano-active material.

9. The formulation of claim 8, wherein the applications include an inner coating or primer for coating on appropriately prepared steels of various compositions, aluminium, aluminium alloys, zinc-aluminium alloys, clad aluminium, and aluminium plated steel, wherein the substrates comprise more than one metal or metal alloy, in that the substrate is a combination of two or more metal substrates assembled together, such as hot dipped galvanized steel assembled with aluminium substrates; wherein the adhesion of the coating is an important consideration for the selection of the binder and additives, and the corrosion inhibition is an important consideration for selection of the nano-active material, while maintaining the fouling inhibition.

10. The formulation of claim 9, wherein in the application, the corrosion properties are enhanced by the addition of booster anticorrosion material such as lanthanide materials, where the materials, including the binding of the booster anticorrosion material to the nano-active material and the binder, are determined to release the anticorrosion materials at a rate to inhibit and repair any corrosion of the substrate.

11. The formulation of claim 1, wherein the applications include an outer coating where the fouling inhibition is an important consideration, a selection of the nano-active material with biofoulant properties, and the booster antifoulants which are selected to inhibit the growth of primary, secondary and tertiary foulants.

12. The formulation of claim 1, wherein the booster antifoulant is a biocide, and its impact is directed towards the inhibition of primary and secondary foulants through release of the antifoulant into the water at a release rate determined by the dissolution of the antifoulants and the other constituents of the coating, or the ablation of the coating, and the nano-active materials are directed towards inhibition of the tertiary foulants within the coating.

13. The formulation of claim 12, wherein the booster antifoulant is bound within the nano-active material.

14. The formulation of claim 12, wherein the booster antifoulant is a second nano-active material.

15. The formulation of claim 1 for a hydrophobic or superhydrophobic coating for coating a vessel in which the nano-active material, or other additives, spontaneously produces indentations, or the indentations are printed during or after application, where such indentations reduce the hydrodynamic drag of the vessel and the antifouling nano-active material and the booster material inhibit fouling when the vessel is stationary.

16. The formulation of claim 15, in which the indentations regenerates as the coating is worn down by friction.

Description

DESCRIPTION OF THE INVENTION

[0048] Preferred embodiments of the invention will now be described by reference to the non-limiting examples.

[0049] The embodiments described herein are marine coating formulations incorporating at least one nano-active oxide material as described by Sceats and Hodgson. Preferably, the formulation for a coating comprises (a) a nano-active material; and (b) a polymer binder; and (c) additives which include pigments, booster antifoulants, booster anticorrosion materials, solvents, polymerisation activators, viscosity modifiers and fillers. It may be appreciated that any type of pigments, booster antifoulants, booster anticorrosion materials, solvents, polymerisation activators, viscosity modifiers or fillers may be used. It has been found by experiment that the nano-active magnesium oxide powder behaves in a formulation similar to a filler, and or a conventional antifoulant, material, so that the established arts of marine coating formulations may be applied by substituting these materials with only minimal changes required to optimise the performance.

[0050] The nano-active material, the binder and additives provide the coating with the desired most desirable properties of antifoul, anticorrosion, adhesion, and strength, required for the coating application. The specific examples described use nano-active MgO as the material which describes the material which has the primary impact against tertiary colonisers so that the material may replace in whole or part, of the copper materials that are conventionally used. Preferably, the nano-active material is at least 10 wt %, and 30-75% of the set coating weight depending on the coating application. The nano-active material is a powder material with an average particle size typically in the range of 1-300 microns, which is sufficiently porous with a high volumetric surface area comparable to, or exceeding, that of nanoparticles with a dimension less than 100 nm. It is most preferable that the nano-active material is a powder material with an average particle size typically in the range of 4-10 microns. Other nano-active materials, such as AgO, ZnO, CuO, MgO, SiO.sub.2, Al.sub.2O.sub.3, Mn.sub.3O.sub.4 described by Sceats and Hodgson. The Sceats Hodgson patent disclosed the use of nano-active AgO, ZnO, CuO, MgO, SiO.sub.2, Al.sub.2O.sub.3, Mn.sub.3O.sub.4 in marine coatings. In the context of marine coatings, the use of nano-active Cu.sub.2O is relevant. Embodiments with mixtures of such nano-active materials may be used to optimise the performance of the formulation. The chemical purity of these materials may be 80% or more. Most preferably, the chemical purity of these materials are greater than 95%.

[0051] The polymer binder may be drawn from a wide range of polymer materials, including acrylic, saturated or unsaturated polyester, alkyd, polyurethane or polyether, polyvinyl, cellulosic, silicon-based polymers, co-polymers thereof, and contain reactive groups such as epoxy, carboxylic acid, hydroxyl, isocyanate, amide, carbamate, amine and carboxylate groups, among others, including mixtures thereof, wherein combinations of film-forming polymers are used, and wherein the materials include thermosetting polymers, polymers that require initiators, accelerants, or polymers that set through volatilisation of solvents, wherein the selection of the binder and additives are determined to provide a coating which is adhesive to the substrate, hard, ablative, hydrophobic or superhydrophobic as required for the application when combined the with nano-active material.

[0052] The applications include an inner coating or primer for coating on appropriately prepared steels of various compositions, aluminium, aluminium alloys, zinc-aluminium alloys, clad aluminium, and aluminium plated steel, wherein the substrates comprise more than one metal or metal alloy, in that the substrate is a combination of two or more metal substrates assembled together, such as hot dipped galvanized steel assembled with aluminium substrates; wherein the adhesion of the coating is an important consideration for the selection of the binder and additives, and the corrosion inhibition is an important consideration for selection of the nano-active material, while maintaining the fouling inhibition. For the primary purpose of corrosion and adhesion, the substrates include, for example, steels of various compositions, aluminium, aluminium alloys, zinc-aluminium alloys, clad aluminium, and aluminium plated steel. Substrates may also comprise more than one metal or metal alloy, in that the substrate may be a combination of two or more metal substrates assembled together, such as hot dipped galvanized steel assembled with aluminium substrates. Surfaces generally have to be prepared before application. Where corrosion inhibition described herein is not used, the substrate may be coated with a conventional anti-corrosion material. Formulations may be described herein that describe a primer for corrosion protection based on nano-active materials. In the application, the corrosion properties are enhanced by the addition of booster anticorrosion material such as lanthanide materials, where the materials, including the binding of the booster anticorrosion material to the nano-active material and the binder, are determined to release the anticorrosion materials at a rate to inhibit and repair any corrosion of the substrate.

[0053] A coating may be applied in a number of applications in which the formulation is varied layer by layer, with the binder being chosen to give the desired adhesion. In the example embodiments, the binder may be drawn from a wide range of polymer materials, including acrylic, saturated or unsaturated polyester, alkyd, polyurethane or polyether, polyvinyl, cellulosic, silicon-based polymers, co-polymers thereof, and may contain reactive groups such as epoxy, carboxylic acid, hydroxyl, isocyanate, amide, carbamate, amine and carboxylate groups, among others, including mixtures thereof. Combinations of film-forming polymers can be used. The materials include thermosetting polymers, polymers that require initiators, accelerants, or polymers that set through volatilisation of solvents. Importantly, formulations include common polymers that are used to make hard and ablative coatings through additives. Other additives include pigments, fillers, diluents and viscosity modifiers.

[0054] The coating compositions of the present invention may be applied by known application techniques, such as dipping or immersion, spraying, intermittent spraying, dipping followed by spraying, spraying followed by dipping, brushing, or by roll-coating. Usual spray techniques and equipment for air spraying and electrostatic spraying, either manual or automatic methods, may be used. Many of these techniques are not used in the maritime industry, and the formulations described herein can be applied using conventional techniques used for marine coatings.

[0055] The first example embodiment of the present invention is a formulation which comprises as the bioactive material nano-active MgO powder and an aluminium compatible biocide and booster biocide in an ablative formulation. The desirable amounts of nano-active MgO powder are 5-50 wt %, and preferably 25-50% including the biocide and booster biocide. The role of the biocide and booster biocide is to inhibit the growth of primary and secondary colonisers that lay down the biofilms to which the larvae of the tertiary colonisers grow. The biocide inhibit the growth of the tertiary colonisers. The role of the nano-active MgO powder is to firstly further inhibit the growth of the tertiary colonisers by deterring the invasion of the tendrils from the larvae into the bulk of the coating through the release of ROS, and secondly to provide corrosion protection of the substrate, and thirdly to inhibit the of primary and secondary colonisers. The biocide and booster biocide may be materials that are incorporated into the nano-active MgO material by adsorption onto the surface wherein the release rate of the biocide and booster biocide is controlled by the strength of the biding and the dissolution of the nano-active MgO near the surface. It would be recognised by a person skilled in the art that the release of ROS, the release of the biocide and booster biocide, and the ablation rate are factors pertinent to the performance of the coating to minimise fouling, both in selection of the booster biocide, polymer and additive. Other examples of this embodiment include the substitution of the nano-active MgO, in whole or in part, by other nano-active materials where the role of the materials is to inhibit fouling. Given that both the biocide and booster-biocide are toxic, it would be most desirable that the formulation would minimise the use of the biocide and booster biocide, and most desirable that the formulation it would the need for biocide and booster biocide are not required.

[0056] Specific example embodiments are given for an ablative coating derived, for example from formulations made from toxic Cuprous Oxide, Cu.sub.2O are shown in Table 1.

TABLE-US-00001 TABLE 1 Reference Formulation Nano-Active Formulations Constituents wt % wet Example 1 wt % wet Example 2 wt % wet Example 3 wt % wet 1° biocide cuprous 40-50%  nano-active 50-60% nano-active 35-40% nano-active 50-60% oxide MgO MgO MgO 2° biocide thiram 1-10% — cuprous 15-20% nano-actove 10-20% oxide ZnO thinner n-butanol 1-20% n-butanol  1-20% n-butanol  1-20% n-butanol  1-20% thinner xylene 10-20%  xylene 10-20% xylene 10-20% xylene 10-20% binder rosin 1-10% rosin  1-10% rosin  1-10% rosin  1-10% pigment zinc oxide 10-20%  zinc oxide 10-20% zinc oxide 10-20% plasticisers various .sup. <5% various   <5% various   <5% various   <5% tints various  <15% various .sup. <15% various .sup. <15% various .sup. <15%

[0057] Similar formulations for ablative coatings may be made using copper isothionate as the reference toxic biocide, for example where the 2.sup.nd biocide may be copper isothianate or pyrithione zinc, and the thinners may be mixtures of ethylbenzene and xylene

[0058] A further embodiment is a formulation which comprises as the bioactive material nano-active MgO powder and an aluminium compatible biocide such as cuprous oxide and copper isothionate and booster biocide materials, both at reduced rates, in an ablative formulation. The amounts of nano-active MgO powder in the ablative polymer is a direct % w/w direct substitution of the biocide and booster biocide.

[0059] The second embodiment of the present invention is a hard coating in which the polymer and non-active additives for an ablative coating, is replaced by a polymer and additives for a hard coating. A further embodiment of this example is a formulation which comprises as the bioactive material nano-active MgO powder and a biocide and booster biocide materials, both at reduced rates. The porous MgO powder allows some penetration by water to activate the ROS.

[0060] Further enhancement of either the first and second embodiments with respect to corrosion is where the corrosion rate is inhibited by the addition of a lanthanum material to the composition, and most preferably where the lanthanum ions are bound into the nano-active material so that its release rate is optimised to repair the corrosion. Other “repair” materials may be also be used instead of lanthanum, including any of the lanthanide elements or mixtures thereof. It is noted that corrosion occurs on the substrate when the coating is punctured. Thus this formulation may be applicable to an embodiment for a primer in which the polymer is selected to form a hard coating.

[0061] A third embodiment of the present invention is similar to the first embodiment where a fraction of the nano-active powder material is converted to a form that enables the formulation that is superhydrophobic when used with selected polymer systems, which are most likely to be polymers which create hard coatings. The formation of such nano-active superhydrophobic particles may be formed by reaction of the nano-active particles with stearic acid and the like. It is preferable that such a reaction is limited to the surface of the nano-active particle so that the release of ROS for inhibition of fouling and corrosion is not impeded. It would be understood by a person skilled in the art that such desirable properties are established by the properties of the organic chains of the stearate-like materials. An extension of this embodiment is one in which the particle size of the nano-active material is selected to form and maintain an indented structure to minimise drag when applied to a vessel.

[0062] It would be appreciated by a person skilled in the art that the formulations disclosed above may be applied as separate coatings. For example, a hard formulation may include an inner coating doped with lanthanum to minimise corrosion, a mid-layer with a formulation to mitigate both corrosion and fouling, and an outer layer to minimise fouling and friction such as a superhydrophobic structure.

[0063] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms, in keeping with the broad principles and the spirit of the invention described herein.

[0064] The present invention and the described preferred embodiments specifically include at least one feature that is industrially applicable.