MARINE ANTI-FOULING CLADDING

Abstract: Marine anti-fouling cladding comprises a foil of anti-fouling copper alloy such as copper/nickel/iron alloy (4) adhered to a bituminous adhesive layer which is preferably a polymer-modified bitumen layer (8) having a reinforcing scrim (10) therethrough.

Description: - 1 - MARINE ANTI-FOULING CLADDING The present invention relates to anti-fouling cladding for surfaces such as boat hulls, dock walls, and the underwater surfaces of off-shore and deep water drilling and production rigs,etc. The invention is concerned mainly with such marine surfaces but is applicable also to protect non-marine surfaces similarly liable to aquatic biological fouling, e.g. those of septic tanks. U.S. Patent No. 3761334 issued in 1973 and since twice re-issued, proposes protecting boat hulls against fouling by cladding the hull with a foil of marine anti-fouling copper alloy, the foil being adhesively secured to the hull. The foil ought to give excellent; protection against fouling, but heretofore serious attempts over "he several years since publication of No. 3761334 to put the described procedure into commercial practice, using what were considered to be the best available adhesives, have given disappointing results; difficulties were experienced in applying the foil to the hull, and the foil too readily delaminated from the clad hull when subjected to normal operating environment, the proposed anti-fouling treatment thus having appeared to be ineffective in practice. The present invention resides in the use of bituminous adhesive to secure the anti-fculing foil to the surface to be protected. Surprisingly, with use of bituminous adhesive, the foil is readily applied to give a high integrity protective skin with a greater resis¬ tance to delamir,ation from the substrate surface than has previously been attainable. The bituminous adhesive will usually be supplied and used according to the invention as preformed sheets. Metal (usually copper or aluminium) foil coated with bituminous composition has previously been used for decorative roofing- and like purposes, but u m, :ι - 2 - bituminous material has never been considered as an adhesive for the cladding purposes with which the present -invention is concerned, and the strength and operational durability of adhesion obtainable in marine and like anti-fouling cladding according to the invention is unexpected - particularly in comp-arison with the poor performance of conventional types of ad esives previously proposed and used for the purpose- The bituminous adhesive employed according to the invention will generally incorporate one or more modifiers (e.g. synthetic polymer) to render it flexible or workable at -ambient temperature. Bituminous adhesives are heat sensitive, and accordingly one nay employ such an adhesive which is non-tacky at ambient tempera¬ ture but which becomes tacky on heating, the foil being adhered to the substrate surface by way of such adhesive under heat -and pressure. On the other hand, it is currently preferred to employ a bituminous adhesive which adheres on contact at ambient -temperature; in this case the rapidity and permanence of adhesion can sometimes be improved by first applying to the substrate surface an appropriate primer; the latter may for example be a bituminous emulsion or a solution of polymer in an * organic solvent. It is presently preferred, however, to employ a bituminous adhesive layer which adheres cn contact without a primer; such a bituminous layer which adheres on contact at summer temperatures may need the application of heat under colder conditions. The bituminous material incorporated in or constituting the adhesive used according to the invention may be derived from petroleum and/or coal etc. sources e.g. may comprise one or more of bitumen, asphalt, and coal tar pitch; natural or synthetic bituminous - - material derived from petroleum sources is preferred. For heat- bonding, at least part of the bituminous component of the adhesive is preferably refined (e.g. air blown) so that it does not generate volatiles on heating. The presence of elastomer in the bituminous adhesive can improve its flexibility at the temperatures to which the applied cladding is subject, preventing failure in the integrity of the cladding due to cracking of the adhesive. The thickness of the bituminous adhesive layer will vary according to the circumstances, and may for example be from 1/2 mm. to 2 mm. or more. Thin adhesive layers will be appropriate where the cladding is to be applied to relatively smooth surfaces, e.g. the new or cleaned hulls of boats. Thicker adhesive layers will be appropriate where the cladding is to be applied to rougher surfaces, e.g. to pitted boat hulls or to the concrete surfaces of dry docks or septic tanks; the thickness of the bituminous adhesive layer is then able to cater for irregularities in the surface to be treated. Where a thicker (e.g. 2 mm. gauge) bituminous adhesive layer is employed, it may be advantageous for the latter to be ' reinforced, e.g. by one or more embodied layers of plastics sheet material or of scrim (preferably glass or polypropylene scrim) . Such -reinforcement, preferably of glass or plastics scrim, may also be provided for thin a-dhesive layers. The reinforcement extends through the adhesive layer, rather than only over a surface thereof. A particularly preferred bituminous adhesive layer for use in the invention is a preformed reinforced sheet of the latter type of about 1 mm. thick¬ ness; where a thicker depth of adhesive is required, two or more such layers may then be applied face to face - this provides more accurate and uniform positioning of the reinforcement within the bituminous - A - material than is possible with a single layer of equivalent overall thickness. The preferred copper alloys for the foil are copper- nickel alloys, preferably containing about 90 wt.% copper .and 10 wt.% nickel and most preferably containing also a small amount of iron. An especially preferred alloy is the known marine anti-fouling alloy "706 Mariner" which contains 88.2 wt.% copper, 10 wt.% nickel and 1.4 wt.% iron. It is important that the foil from the mill should be thoroughly cleaned before adhesion to the bituminous adhesive layer; to improve adhesion of the foil and bituminous layers, it can be of advantage to provide the relevant face of the foil with a matt or patterned finish, e.g. by use of a correspondingly matt or patterned final roll in the foil production mill or by subsequent scouring. According to the inventio , a number of ways are available for forming the anti-fouling cladding on a substrate surface. For example it is possible to employ a preformed laminate of the foil with a coating layer of the bituminous adhesive, the exposed face of this adhesive coating layer preferably being covered by a release sheet and the laminate normally, being supplied in the roll. In this "case, when the bituminous adhesive re-quires heat activation, the • bituminous adhesive is coated over a prepared surface of the foil with the application of heat, and a rεlεasable protective layer of paper or like can be applied to the exposed face of the bituminous layer in conventional manner; for application of such a laminate,the protective layer is progressively stripped away from the adhesive, heat being supplied as the exposed face of the adhesive layer is applied to the substrate surface to be clad under pressure applied (e,g. by roller or squeegee or the like) to the exposed foil surface. - 5 - Where the bituminous adhesive is one which adheres on contact, it is also possible to employ it as a preformed laminate with the foil and with a release sheet on its face away from the foil, such a laminate again preferably being supplied in the roll. In this case, the adhesive/foil laminate may be produced by applying an appropriate primer to the relevant face of the foil (if necessary after cleaning and/or roughening of this foil surface) , and then applying the bituminous adhesive layer over the primed surface", followed if desired by application of a release layer over the exposed surface of the adhesive layer; in use of such a laminate, the substrate surface is preferably cleaned and if necessary primed, and the cladding laminate is progressively applied thereto as the release layer is peeled therefrom; as with heat bonding, pressure may ¬ be applied by roller or squeegee or the like to the exposed foil surface to improve bonding of the foil to the surface. In a particularly preferred procedure for preparing a bituminous adhesive/foil laminate, the foil is lead continuously through cleaning apparatus and then combined between a pair of nip rollers with a preformed sheet of bituminous ' adhesive (preferably scrim-reinforced as described above) supplied concurrently and ■ continuously from a separata source. In the cleaning appa atus, the surface of the foil to be adhered is scoured by passage under a scouring -roller which preferably oscillates across the path of the foil as well as rotating about its axis, water being sprayed onto the foil surface both before and after the roller; most of the water from the scouring is removed by a doctor blade immediately following the roller, and the treated surface is then thoroughly dried by powerful air jet. To minimise surface oxidation, the cleaned sheet passes over as short a - 6 - ■ -_.__t.a_CB as possible to the nip rolls for combination with the preformed adhesive layer. The latter will normally be supplied with a release "r.eet- on each face, tfie " sheet on the f ce towards the foil being removed tiring travel tow-ards the nip rolls, and the exposed face of the -ituminous adhesive preferably being heated before combination with the foil (even if the adhesive is one which will adhere on contact) to -ϊr,sure optimum contact and bonding with the foil between the nip rolls. ~ latter preferably do no more than ensure contact between adhesive • ϊ.d foil, having substantially perfect operating surfaces and fixed " pacing so as to avoid pressure variations so far as possible during -ami-nation; undue pressure and pressure variation can lead to lateral extrusion of the adhesive and to gauge variation in the resulting 1-minatε. In the cleaning apparatus, both sides of the foil can be cleaned simultaneously as described if desired. Where the bituminous adhesive employed is one which adheres on contact, it is also possible for adhesive and foil to be ap lied separately. In this case, preformed sheets or strips of the adhesive (supplied with a protective release layer on one or both faces) are first applied to the substrate surface to be protected after the latter has been prepared by cleaning and optionally then priming, and the anti-fouling copper alloy foil is then applied over the adhesive. The surface of the foil to contact the insitu adhesive will preferably have been prepared (e.g. by cleaning and mechanical scouring) d optionally provided with a primer coating to enhance rapid and permanent bonding to the adhesive, this surface of the foil normally •being protected by a release layer which is removed as the foil is applied. The separate application of bituminous adhesive and protective foil can be especially useful for achieving an effective integral r x—r r_ _ - 7 - protective skin around sharp edges and other awkward locations. Separate application of bituminous adhesive and protective foil, is also possible where the adhesive requires heat activation,ϋ2vϊt is best suited to the case where the contact type of adhesive is employed. As previously indicated, the bituminous adhesive layer, whether provided as a separate item or as a prelaminate with the protective foil, is preferably reinforced by a reinforcing net or scrim or material such as glass or polypropylene. In the practice of the present invention, a foil/ bituminous adhesive combination may be applied in strips with lapped joints to. ensure complete sealing of the surface covered; in this case it is important for the exposed foil face to be clean and prepared to ensure sound adhesion at the lapped joint(s) with the adjacεnt strip(s). The anti-fouling foil (preferably the Mariner 706 previously referred to) currently preferred for use according to the invention has a thickness of about 5 or 6 thousandths of an inch (i.e. about 0.12 or 0.16 mm.) , and is generally used in strips of about 3 inches (i.e. about 200 mm.) in width. Other gauges of the foil are - however available, and it can be used in other widths. The foil- as received is normally greased on both faces, and degreasing may be necessary before the cleaning (e.g. scouring) procedures mentioned above. Scouring has been found to be a particularly effective- method of preparing the foil surface for combination with the bituminous adhesive; a preferred scouring material is the "Scotch Brite" range available from the Minnesota Mining and 2-ianufacturing Company Limited, a suitable grade for present purposes being 7A medium, though other grades may be employed according to the depth of scouring required in each case; the "Scotch Brite" material may be obtained as pads for ' hand use, or as a cover for ■ ... - - the roller or rollers of cleaning apparatus of the type described above. For the application of the bituminous adhesive (or the bituminous adhesive/foil prelaminate) to the surface to be protected, . it is important that the latter should be in a thoroughly clean condition and roughened (e.g. by sanding, scouring, or grit blasting) condition; a wooden surface, particularly an old wooden surface which has had to be cleaned back to the bare wood, is advantageously treated prior to application of the bituminous adhesive with -an epoxy primer, e.g. Group 58 epoxy compound obtainable from R.I.W. Protection Products Limited. Skin fittings through surfaces protected by according to the invention are preferably of the same copper alloy as that of the foil of the cladding; if there is any danger of electrolytic action in operation between the foil of cladding according to the invention and a skin fitting or the like, a small gap (e.g. about 3/3 inch) is preferably left between the fitting and the cladding. The invention resides in laminates of anti-fouling copper alloy foil with bituminous adhesive and their formation, in the use of the bituminous adhesive and foil either prεlaminated or sequentially applied to form an anti-fouling cladding, and in surfaces provided with such anti- fouling cladding. The invention and its practice are illustrated by the following description to be taken in conjunction with the accompanying drawing, in which :- Figure 1 is a schematic cross section through a cladding laminate according to the invention, and Figure 2 is a schematic representation of the formation of a cladding laminate according to the invention. The cladding 2 of Fig.l comprises a foil 4 of Mariner 706 copper/nickel/iron alloy of a thickness of 6 thousandths of an inch adhered to a layer 6 1 mm. thick of a polymer-modified bituminous composition 8 through which extends a reinforcing scrim 10 of polypropylene. The bituminous composition 8 is a synthetic o polymer/bitumen blend which at a temperature about 80 F. is adhesive on contact. The face 12 of layer 6 remote from foil 4 may be covered by a release sheet (not shown) or in adhesive contact with a surface (not shown) such as a boat hull which the cladding protects from fouling. Figure 2 illustrates a method and apparatus for form¬ ing a cladding such as that of Fig.l. The degrεased foil 4 is passed continuously through a cleaning apparatus 20 and via a conveyor roller 18 into adhesive combination with bituminous adhesive layer 6 between nip rolls 34 to form the cladding 36 for subsequent application to a surface to be protected from fouling. In apparatus 20 both faces of foil 4 are scoured by rotating rolls 22 facεd with scouring surfaces 24, the rolls 22 reciprocating transversely of foil as well as rotating. Water is sprayed onto the foil surfaces as at 26 both before and after the rolls 22. Debris is removed from the cleanεd foil surfaces by the water. Excess water is removed by flexible doctor blades 28, and the foil surfaces are then dried by air jets 30. The prepared foil is then passed via roll 13, over a distance of a few feet at the most, to the nip rolls 34. From a supply roil 16 a preformed layer 6 of bituminous adhesive as described with reference to Fig.l, but having a relεasε sheet on. each face, is fed towards nip rolls 34; the release sheet 14 towards foil 4 is removed and the - 10 - exposed face of the bituminous composition passes heater 32 before coming into contact with foil 4 between rolls 34. If a thicker adhesive application is required, a further layer or layers 6 may be fed simultaneously as indicated in broken lines in Fig.2, with appropriate release layers of course being removed prior to lamination between nip rolls 34. With the bituminous composition 8 mentioned in connection with Fig.l, heating at 32 is suitably to a temperature of o about 30 C. The heater 32 is suitably an infra-red heater, e.g. a Claudgen 4 x 1 kw infra-red lamp heater type No.HO:6610B/2lB. The nip rolls 34 have substantially perfect cylindrical surfaces and fixed axial spacing such as to exert pressure sufficient only to give bonding of adhesive layer(s) and foil without extrusion of the adhesive or variation in the finished laminate 36. The apparatus 2θ is suitably a GMP brush finishing machine with the addition of water sprays 26, blades 28 and air -jets 30. The scouring surface 24 of each roll 22 is suitably a "Scctchbrite" Grade 7A medium roll cover. In some cases, only the upper surface of foil 4 need be prepared as described, in which case the lowermost scouring surface, sprays, blade and air jet may be emitted; a suitable single roller is the Model 25V or 4831 single roller machine made by GMP Machines Limited. It -will be appreciated that the fouling against which the cladding according to the invention is designed to protect is of course biological fouling by algae, barnacles, tube worms, tunicatεs, encrusting bryozoans and like growths which tend to accumulate on the surfaces normally remaining under or subject to water for long periods. The invention is applicable to the protection of the whole range of materials normally subject to such fouling, including wood, metal plastics (particularly fibre-glass) , and concrete.

Claims: - 1 1 . C A I S : • 1. A method.,of protecting a surface against aquatic biological fouling which comprises cladding said surface with anti- fouling copper alloy foil by means of an adhesive bituminous layer. 2. A surface protected against aquatic biological fouling by means of copper alloy foil adhered to said surface by a layer of bituminous composition. 3. A cladding for protecting a surface against aquatic biological fouling, the cladding comprising anti-fouling copper alloy foil having an adherent bituminous adhesive layer.over one face thereof. 4. A method of forming an. anti-fouling cladding laminate . which comprises scouring a face of an anti-fouling copper alloy foil and immediately coating the scoured surface with a bituminous adhesive layer so as to bond the foil and bituminous layer together. Y ■ *-- • -/

Inventors: MITCHELL FREDERICK CHARLES
Applicants: MARINE BIO GUARD SYSTEMS INC, MITCHELL FREDERICK CHARLES
Application year: 1982
Main classification: B63B59
IPC codes: B63B59