GB2154514A

GB2154514A - Marine antifouling

Info

Publication number: GB2154514A
Application number: GB08427371A
Authority: GB
Inventors: Andrew Muir Bews
Original assignee: United Wire Group Ltd
Current assignee: United Wire Group Ltd
Priority date: 1983-10-31
Filing date: 1984-10-30
Publication date: 1985-09-11
Also published as: GB8328999D0; GB8427371D0

Abstract

An antifouling material which is transparent comprises a synthetic polymeric plastics material and metallic copper (or copper alloy), the copper being arranged so as not to provide copper ions at at least one surface of the material, but not totally to obscure the material. The copper can be in the form, for example, of a copper mesh or of small pieces, or of wire, normally embedded in, or on the surface of, the material.

Description

SPECIFICATION Marine antifouling This invention is concerned with marine antifouling materials.

It is well known that structures which are in contact with sea water are subject to marine fouling, i.e. to the growth thereon of marine organisms such as slimes, barnacles, molluscs, etc. Such fouling is generally undesirable and, in many instances, gives rise to problems. One example concerns the windows or visors of sub-sea equipment which, when the equipment is submerged for a period of time, become covered in marine growth. German patent specification no. 2617027 describes this problem and proposes to overcome it by subjecting the windows to ultrasonic vibrations, thus preventing or dislodging any marine growth thereon. This is a complex and expensive solution to the problem.

German patent specification no. 2411619 describes reducing or eliminating marine growth on glass inspection windows or instrument apertures (e.g. on nephelometers used in oceanography) by providing a special net-like structure of metal layers on the glass surface. The net is formed by applying a first layer of a metal such as titanium or chrome nickel by centrifuging or evaporating it onto the previously roughened glass surface (in the desired pattern) and then applying two or more layers of copper. In the uncoated areas, the glass is transparent and the presence of the copper on the titanium causes release of copper ions. Copper is toxic to many marine fouling organisms and hence the glass surface is kept clear of fouling. However, the manufacture of such glass windows is complex and expensive.

We have now devised another construction of window or visor for sub-sea use which is of simpler and cheaper construction than the glass of the German specification, and which is antifouling.

Furthermore, the material of the present invention is more versatile and has a wide range of uses in addition to its use as a window or the like.

According to the present invention, there is provided an antifouling material which comprises a layer of synthetic transparent carrier material including metallic copper or copper alloy, the said copper or copper alloy being accessible to sea water to provide copper ions at at least one surface of the said layer to prevent marine fouling thereon, the quantity and disposition of the copper or copper alloy being such that marine fouling of said one surface of the layer is prevented whilst the layer as a whole remains transparent.

As will be appreciated, the expression "synthetic transparent carrier materials" as used herein excludes glass but covers principally synthetic plastics material which are transparent.

The preferred carrier materials are polymers such as polypropylene and acrylics, but other synthetic materials may be used.

The copper (which term hereinafter includes cupronickel and other copper alloys) may be provided in a variety of ways. For example, a copper mesh may be embedded in the carrier material as is fully described in our U.K. patent specification no. 1604062 to which reference should be made for full details.

In one such arrangement, a mesh of copper or copper alloy embeded in said material with the knuckles of the mesh on one side being exposed at said surface, the area of exposure being at least 13% of the area of said surface.

Alternatively, the antifouling materials of the present invention may be as described in our U.K.

patent application no. 8324439 (specification no.

2126959A) except that a transparent carrier material is used. In such an arrangement, the antifouling surface comprises a continuum of said inert substance interspersed with a multiplicity of generally evenly sized discrete copper areas, there being at least 9 said copper areas per square inch (1.4 per square cm.) of surface, said areas being spaced by no more that 7 mm and in total constituting at least 13% of the area of said surface, and wherein said material has been made by mixing uniformly sized discrete copper pieces with said transparent carrier material by applying metallic copper to a non-apertured sheet of said carrier material.

Also, certain of the materials described in our copending U.K. patent application no. 8328998 may be used provided that a transparent carrier material is used and the amount and disposition of the copper is not such as to significantly obscure the transparency of the carrier material. Thus, in such an arrangement, the layer of carrier material has partially embedded in a surface thereof, at least one group of elongate copper or copper alloy members each extending substantially parallel in said group and being spaced by no more than about 7 mm, at least 13% of the area of said surface being said copper or copper alloy.

Reference should be made to these documents for full details.

In general (as is described in our earlier patent and applications referred to above), we have found that in order to provide effective antifouling, the amount of copper exposed at a surface of the carrier material should be such as to constitute at least 13%, and preferably at least 20%, of the area of that surface. In general, provided the above minimum requirement is met, the amount of copper will be kept low in order to achieve a high overall transparency for the antifouling material. It will be understood that the presence of metallic copper necessarily reduces the transparency of the carrier material, but we have found that enough copper can be included for antifouling purposes without reducing the overall transparency to unacceptably low levels.

If desired, both surfaces of the layer of carrier material can be antifouling (i.e. include exposed copper), but normally it will be necessary only for one surface to be antifouling.

The material of the invention has a wide variety of uses. It may be used as a window material, in the form of relatively rigid panels of a thickness necessary to provide adequate strength. Panels may also be used as covers for sub-sea structures, enabling the underlying surface to remain visible.

Thus, for example, important parts of a sub-sea structure can be provided with a covering of a material of the invention to enable them easily to be inspected for maintenance and safety purposes.

The materials of the invention can also be used as markers. Thus, if an identification mark is applied to the rear surface of a panel, it will remain visible through the panel. Alternatively, an identification mark on a sub-sea structure can be kept clear and visible by covering it with an antifouling material of the invention. Thus, the invention includes a marine identification marker for attachment to a submerged or submersible structure to provide an identification means thereon, which marker comprises an alphanumeric having a transparent antifouling material of the invention thereover to reduce or prevent obscuration of the marker by marine fouling.

In the case of tubular sub-sea components, such as the legs of oil rigs or the like, antifouling material of the invention can be applied thereto by winding an elongate strip of material helically around the components and securing it with a suitable adhesive. The component remains visible for periodic safety inspection.

It will be apparent that the materials of the invention, being essentially simple of construction in a variety of forms, have a large number of uses. In particular, they extend the utility of the materials described in our previous patent and applications and enable the excellent antifouling properties thereof to be used in further and different ways.

Claims

1. A marine antifouling material which com prises a layer of synthetic transparent carrier material including metallic copper or copper alloy, the said copper or copper alloy being accessible to sea water to provide copper ions at at least one surface of the said layer to prevent marine fouling thereon, the quantity and disposition of the copper alloy being such that marine fouling of said one surface of the layer is prevented whilst the layer as a whole remains transparent.

2. A material according to claim 1 which com prises a mesh of copper or copper alloy embedded in said material with the knuckles of the mesh on one side being exposed at said surface, the area of exposure being at least 13% of the area of said surface.

3. A material according to claim 1, wherein said surface comprises a continuum of said inert substance interspersed with a multiplicity of generally evenly sized discrete copper areas, there being at least 9 said copper areas per square inch (1.4 per square cm.) of surface, said areas being spaced by no more than 7 mm and in total constituting at least 13% of the area of said surface, and wherein said material has been made by mixing uniformly sized discrete copper pieces with said transparent carrier material or by applying metallic copper to a "non-apertured sheet of said carrier material.

4. A material according to claim 3, which has been made by: a) forming a mixture of discrete pieces of metallic copper and, as said carrier material, a curable plastics material; b) rolling the mixture to form a layer; and c) curing the plastics material.

5. A material according to claim 4, wherein the copper pieces are chopped wire.

6. A material according to claim 3, which has been made by spraying copper onto a surface of a non-apertured sheet of said carrier material, to form said multiplicity of discrete copper areas on said surface.

7. A material according to any preceding claim which further contains, in addition to the copper another toxin against marine fouling organisms.

8. A material according to claim 7, wherein said another toxin is present as a coating on the copper pieces.

9. A material according to claim 1, wherein the layer of carrier material has partially embedded in a surface thereof, at least one group of elongate copper or copper alloy members each extending substantially parallel in said group and being spaced by no more than about 7 mm, at least 13% of the area of said surface being said copper or copper alloy.

10. A material according to claim 9, wherein said elongate members are or include wires.

11. A material according to claim 10, wherein the wires are of a gauge of from 0.1 to 2.0 mm.

12. An antifouling material as claimed in any preceding claim, which is in the form of a panel.

13. An antifouling material as claimed in any of claims 1 to 11, which has been formed in situ on a marine structure.

14. A marine identification marker for attachment to a submerged or submersible structure to provide an identification means thereon, which marker comprises an alphanumeric having a transparent antifouling material as claimed in any of claims 1 to 11 thereover to reduce or prevent obscuration of the marker by marine fouling.