Fouling control device

Abstract

A fouling control light-emitting device having a source of light, an optical medium that can transmit light, and a light-emitting surface, in which at least part or all of the light-emitting surface comprises a fouling control coating, wherein the fouling control coating comprises a non-curable liquid fluorinated polymer or oligomer.

Description

[0001] FOULING CONTROL DEVICE

[0002] Technical Field

[0003] The invention relates to control of aquatic biofouling on structures that are immersed permanently or temporarily in water.

[0004] Background Art

[0005] Fouling of ship hulls and other water-borne objects by aquatic organisms is a continuing problem. Fouling can increase frictional resistance of boats in the water, increasing fuel costs and greenhouse gas emissions. On static structures, for example on drilling rigs, it can alter the water flow around the supporting legs, risking unpredictable and increased stresses. Fouling can also make inspections more difficult by obscuring defects and cracks. It can further reduce the cross-sectional area of pipework such as cooling water or ballast tank intakes, leading to reduced flow rates.

[0006] Coatings can be used to reduce fouling. Such coatings can contain a biocide to control the growth of aquatic organisms on the surface. These fall typically into two broad categories, namely “hard” antifouling coatings, where biocide gradually leaches from the coating over time, and “eroding” antifouling coatings (sometimes called self-polishing coatings), where the coating gradually erodes to release the biocide. However, biocides can carry environmental risks, particularly in areas with heavy shipping activity. They are therefore the subject of increasingly stringent environmental legislation.

[0007] Biocide-free coatings are available, often termed “fouling control” or “fouling release” coatings, which result in a “low surface energy” surface that not only inhibits adherence of fouling organisms, but also causes them to be more easily washed from the surface. Examples of foul release coatings are described in GB1470465, W02002 / 074870, WO2013 / 000478, WO2014 / 131695 and WO2023 / 036923.

[0008] An alternative way of controlling fouling is to use ultraviolet light-emitting devices. Such devices are described for example by WO2013 / 132599 where UV light is propagated through a protected surface via an optical medium such as optical fibres or an optical coating or layer disposed proximate to the protected surface which allows portions of the UV light to escape the surface of the optical medium. Alternatively, for example Salters and Piola in Marine Technology Society Journal, 2017, 51(2), pp59-70, and WO2014 / 188347, WO2018 / 002205 and WO2019 / 016291 describe the use of a lighting module for the distribution of UV light (e.g. from a UV-LED) through an optical medium and its emission in a direction away from the protected surface, where the lighting modulke may, for example, be in the form of a tile, strip or foil made from a UV- transparent medium such as polysiloxane, which can be attached to the surface to be protected.

[0009] However, there remains a need for improved fouling control devices for submerged surfaces.

[0010] Summary of Invention

[0011] The invention relates to a fouling control light-emitting device having a source of light, an optical medium that can transmit light, and a light-emitting surface, in which at least part of the light-emitting surface comprises a fouling control coating, wherein the fouling control coating comprises a non-curable liquid fluorinated polymer or oligomer.

[0012] Terminology

[0013] Reference to alkyl groups in the text below includes linear, branched and cyclic alkyl groups. Cyclic alkyl groups include alkyl groups having cyclic and non-cyclic portions.

[0014] A haloalkyl group means an alkyl group having at least one halogen substituent.

[0015] Reference to the amount of any component in a coating composition, unless otherwise specified, relates to its content in the entire coating composition, i.e. based on the total of all component parts (including binder components and curing components).

[0016] Reference to curable components means components that react under the curing conditions to form part of a cured polymeric matrix. This will include, for example, binder resin and curing / crosslinking agents, but will exclude components such as non-curable fluids or polymers, solvents, inorganic pigments or catalysts.

[0017] Reference to fluorinated polymers or fluoropolymers means a polymer that is partially or fully fluorinated, i.e. in which one or more CH bonds are replaced with CF bonds.

[0018] Description of Embodiments

[0019] [Fouling control light-emitting device]

[0020] The fouling control light emitting device comprises a source of light and an optical medium that can transmit the light. The device also comprises at least one surface through which the light is emitted.

[0021] The light-emitting surface (or at least one light-emitting surface) comprises a fouling control coating. Optionally, all the light emitting surfaces comprise a fouling control coating. The fouling control coating can be directly in contact with the light emitting surface of the device, or there can be one or more intermediate coating layers (e.g. one or more undercoat or tie-coat layers).

[0022] [Source of light]

[0023] The source of light emits light which can directly or indirectly prevent or reduce biofouling, i.e. settlement or growth of bio-organisms. Typically, the emitted light will be or will comprise one or more wavelengths in the ultraviolet region, for example in the wavelength range of 100-400 nm. In embodiments, the wavelength range is 300 nm or below, for example in the range of from 100-300 nm or 200-300 nm. In further embodiments, the wavelength range will be in the IIV-C region, for example in the range of 220-280 nm or 240-280 nm.

[0024] In alternative embodiments, longer wavelength light can be used, e.g. light in the region of greater than 300 nm, for example from 300 to 800 nm or from 400 to 800 nm, which can be converted to shorter wavelength (higher frequency) radiation (e.g. in the 100-300 nm, 200-300 nm, 220-280 nm or 240-280 nm wavelength range) by including suitable wavelength conversion materials in the optical medium. The wavelength conversion materials (sometimes called up-conversion materials) can be selected, for example, from phosphors, quantum dots, and non-linear media such as one or more photonic crystal fibres.

[0025] The source of light can be any suitable source of light such as a light emitting diode (LED), laser or mercury vapour lamp. In embodiments, the source of light is an LED, such as an LED that the emits light in the UV region, in particular the UV-C region.

[0026] In embodiments, the source can be embedded within the optical medium to avoid contact with the aqueous environment to which the device will be exposed. In further embodiments, the source can be partially or completely external to the optical medium, such that the light is coupled with or otherwise directed into and transmitted through the optical medium.

[0027] In embodiments, the source of light is controllable, for example it can be switched on and off, and in further embodiments the emitted light intensity can also be controlled.

[0028] In embodiments, the source of light is controllable via a control system that is configured to control the intensity of the light as a function of an external parameter. Examples of fouling control light-emitting devices comprising a source of light that is controllable via a control system that is configured to control the intensity of light as a function of one or more of a feedback signal related to biofouling risk or a timer for time-based varying the intensity of the lights are described in W02016 / 001227.

[0029] [Optical Medium]

[0030] The optical medium can be a glass medium or polymeric medium or a combination thereof. Examples of suitable glass media include quartz, silica and borosilicate glasses. The polymeric medium can be inorganic (e.g. being selected from polysiloxanes or formed from sols or gels). In other embodiments, the polymer can be based on organic or organometallic polymers, for example being selected from fluoropolymers. The optical medium is at least partially transparent to the emitted light from the lightemitting device. In embodiments it is a polymeric medium. The polymeric medium can be or comprise a polysiloxane. The polysiloxane is preferably free of strongly UV- absorbing groups such as aromatic groups. In embodiments they can be selected from polydialkylsiloxanes or polydifluoroalkylsiloxanes, such as polydimethylsiloxane (PDMS). In other embodiments, the optical medium can be or comprise a fluoropolymer. As with the polysiloxanes, they are preferably free of strongly UV-absorbing groups such as aromatic groups. Examples include fluorinated polyolefins such as fluorinated ethylene propylene copolymer (FEP) or polyvinylidene fluoride (PVDF). In further embodiments the polymeric medium can comprise both polysiloxane and fluoropolymer. In embodiments, the optical medium is predominantly comprised or polysiloxane and / or fluoropolymer such that greater than 50 wt% of the optical medium is made up of polysiloxane and / or fluoropolymer. In embodiments the amount is at least 60 wt% for example at least 75 wt% or at least 85 wt%. In embodiments, the entire optical medium is polysiloxane and / or fluoropolymer. Polysiloxanes are particularly attractive as they are compatible with many polysiloxane-based fouling release coatings, hence in embodiments the weight ratio of polysiloxane to fluoropolymer in the optical medium is greater than 1 : 1 , for example 2 : 1 or more, 4 : 1 or more or 9 : 1 or more. In embodiments, there is no fluoropolymer. Polysiloxane polymers tend to have improved UV transmission properties than other types of polymers or glasses.

[0031] In embodiments, the transparency of the optical medium is such that the transmittance of light with a wavelength of 270 nm of a planar sample of the optical medium with a thickness of 0.2 mm is 50% or more, for example 70% or more, 80% or more, or 90% or more.

[0032] The optical medium may be a cured (crosslinked) or a thermoplastic polymer medium. In embodiments, the optical medium comprises a cured polysiloxane, for example an addition-cured polysiloxane or a condensation cured polysiloxane.

[0033] In embodiments, the optical medium comprises an addition-cured polysiloxane, for example hydrosilylation-cured polysiloxane. The device can conveniently be in the form of a tile, a film, a foil or a laminar strip having a planar surface that can be adhered to the substrate, and an opposing planar surface with the fouling control coating which would be exposed to an aqueous environment. More than one light-emitting device can be used to cover the substrate.

[0034] The device can conveniently be manufactured using any suitable conventional manufacturing method or combination of methods, such as moulding, casting, extruding, vacuum infusion, potting, dipping, spraying, brushing, and bar, blade or roller application of component layers.

[0035] Suitable devices are described in WO2013 / 032599, WO2014 / 188347, W02018 / 002205 and WO2019 / 016291.

[0036] [Fouling control coating]

[0037] At least one optically transmitting surface of the fouling control light-emitting device comprises a fouling control coating. The fouling control coating is typically applied to a surface that would be in contact with an aqueous environment, for example a marine, saltwater, brackish or freshwater aqueous environment.

[0038] The fouling control coating is also at least partially transparent to the emitted light. Therefore, in preferred embodiments, the fouling control coating is based on polysiloxane resins or fluoropolymer resins or a mixture thereof.

[0039] The transparency of the of the fouling control coating may be less than the transparency of the optical medium provided that the intensity of light emitted by the fouling control emitting device is sufficiently high to inhibit fouling on some or all of the light-emitting surface. In embodiments, the transmittance of light with a wavelength of 270 nm of a planar sample of the fouling control coating with a thickness of 0.2 mm is 4% or more, for example 5% or more, or 6% or more. In embodiments, the transmittance of the fouling control coating is in the range of from 4 to 40% or from 5 to 30 %, for example in the range of from 6 to 20%. The fouling control coating is formed from a fouling control coating composition. This is typically applied as a liquid phase fouling control coating composition which then hardens by drying or curing to form the fouling control coating.

[0040] In embodiments, the fouling control coating is formed by a curing process from a fouling control coating composition. In embodiments, the curing process is an addition-cure process, a condensation-cure process, or a combination thereof. The fouling control coating composition comprises one or more binder resins and one or more curing agents or crosslinking agents. Before application, the binder resin(s) and the curing agent(s) / crosslinking agent(s) are usually provided in separate components or parts, namely a binder component (or Part A component) for the binder resin(s), and a curing component (or Part B) for the curing agent(s) and / or crosslinking agent(s). In embodiments, a curing catalyst or crosslinking catalyst can also be provided in order to accelerate the curing / crosslinking process. This can be included as a separate component from the binder component and curing component (i.e. as a Part C component).

[0041] In embodiments, it is possible to formulate a single-component (1-pack) composition. These often have a moisture activated curing agent or crosslinking agent, for example which is in a chemically protected form until it contacts moisture. If a catalyst is provided, it can sometimes be part of a two-component (2-pack) composition, for example where the curable binder resins and (protected) curing / crosslinking agent are present in a first component, and the catalyst is provided in a second component.

[0042] In embodiments, curing is initiated by simply mixing the component parts of the coating composition. In embodiments, curing can be effected by alternative means, e.g. using radiation such as UV radiation. In further embodiments, curing is initiated by contact with atmosphere, e.g. atmospheric moisture. In still further embodiments, heat can be used to initiate or accelerate curing.

[0043] In embodiments, to ensure sufficient UV-transparency, the fouling control coating is polysiloxane-based and / or fluoropolymer-based. This means that more than 50 wt% in total of the curable components of the coating composition are comprised of curable polysiloxane and / or curable fluoropolymer, where curable components are those that, after curing, form part of the cured polymeric matrix such as the binder resins, the curing or crosslinking agents, and reactive diluents. This total excludes non-curable components, for example any non-curable oils or fluids such as non-curable oligomers or polymers, any solvents, any catalysts or any inorganic pigments.

[0044] The curable polysiloxane and / or curable fluoropolymer of the fouling control composition may be a curable hydrophilically-modified polysiloxane and / or fluoropolymer, such as a curable polysiloxane and / or fluoropolymer comprising block or pendant polyether segments. Examples of fouling control coatings that comprise a curable polysiloxane comprising block or pendant polyether segments are described in WO2013 / 000478.

[0045] In embodiments, the fouling control coating composition used to produce the fouling control coating comprises greater than 50 wt% curable polysiloxane and / or curable fluoropolymer resins amongst the curable components (e.g. curable resins, crosslinking / curing agents, and reactive diluents).

[0046] In embodiments, at least 70wt% of the curable components in the coating composition are made up of polysiloxane and / or fluoropolymer, and in further embodiments at least 80 wt% are made up of polysiloxane and / or fluoropolymer. In embodiments, polysiloxane forms a greater proportion of the coating composition compared to fluoropolymer, i.e. in embodiments the weight ratio of polysiloxane to fluoropolymer is 60:40 or more, for example 70:30 or more, 80:20 or more or 90:10 or more. In embodiments, there is no curable fluoropolymer component in the fouling control coating, or in the fouling control coating composition.

[0047] In embodiments, the fouling control coating composition comprises a curable polysiloxane, optionally a crosslinking agent, and optionally a crosslinking catalyst.

[0048] Examples of curable polysiloxanes include curable polysiloxanes such as curable polydimethylsiloxane. The reactive groups on the polysiloxanes can be on pendant or terminal positions or both. In embodiments, the reactive groups are at terminal positions.

[0049] Examples of reactive groups on the polysiloxanes include hydride-, hydroxy-, alkoxy-, acetoxy-, oxime, vinyl-, (meth)acrylic-, amine-, thiol-, carboxylic acid-, epoxy- and isocyanate- groups. In embodiments they are selected from condensation-curable hydroxy and alkoxy groups such as C1-4 alkoxy groups.

[0050] Examples of condensation-curable crosslinking agents include Si(OR1)nR24-n where n is at least 2, R1is C1-6 alkyl or a -N=C(R3R4) group, R2is C1-6 alkyl optionally substituted with one or more groups selected from C1-6 alkoxy, C2-6 epoxy, C1-6 alkylamino and hydroxy groups, R3is selected from C1-6 alkyl, and R4is selected from H and C1-6 alkyl. Specific examples include tetraethoxy silane, glycidoxypropyl trimethoxy silane, glycidoxypropyl triethoxy silane, aminopropyl trimethoxy silane, aminopropyl triethoxysilane, and methyl tris(methylethylketoxime) silane.

[0051] In embodiments the crosslinking agent is selected from those where n=3 or 4, R1is C1-6 alkoxy, and R2is C2-6 epoxy-substituted C1-6 alkoxy.

[0052] Other examples of crosslinking agents include alkyl silicate polymers, for example C1-4 alkyl silicate polymers (e.g. an ethyl silicate polymer) derived from tetraethoxy silane by partial hydrolysis of the ethoxy groups to hydroxyl groups and subsequent condensation with formation of siloxane bonds. In embodiments the silicon dioxide (silica) content of the alkyl silicate polymer is 30 to 50% upon complete hydrolysis.

[0053] Further examples of crosslinking catalysts include carboxylic acid salts of various metals, such as tin, zinc, iron, lead, barium, and zirconium. The salts can be salts of long-chain carboxylic acids, for example dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate, iron stearate, tin (II) octoate, and lead octoate. Further examples include organobismuth compounds, organotitanium compounds and organo-phosphates such as bis(2-ethyl- hexyl)hydrogen phosphate. Other examples include chelates such as dibutyltin acetoacetonate. In further embodiments, the catalyst may comprise a halogenated organic acid which has at least one halogen substituent on a carbon atom which is in the a-position relative to the acid group and / or at least one halogen substituent on a carbon atom which is in the alpha-position relative to the acid group, or a derivative which is hydrolysable to form such an acid under the conditions of the condensation reaction.

[0054] Examples of catalysts that can be used include transition metal compounds, metal salts and organometallic complexes of various metals, such as tin, iron, lead, barium, cobalt, zinc, antimony, cadmium, manganese, chromium, nickel, aluminium, gallium, germanium, titanium and zirconium.

[0055] The salts preferably are salts of long-chain carboxylic acids and / or chelates or organometal salts, triflates, triethyl tin tartrate, stannous octoate, carbomethoxyphenyl tin trisuberate, isobutyl tin triceroate.

[0056] Further examples of suitable catalysts include organobismuth compounds, such as bismuth 2-ethylhexanoate, bismuth octanoate and bismuth neodecanoate.

[0057] Further examples of suitable catalysts include organotitanium, organzirconium and organohafnium compounds and titanates and zirconate esters. Specific examples include titanium naphthenate, zirconium naphthenate, tetrabutyl titanate, tetrakis(2- ethylhexyl)titanate, triethanolamine titanate, tetra(isopropenyloxy)-titanate, titanium tetrabutanolate, titanium tetrapropanolate, titanium tetraisopropanolate, tetrabutyl zirconate, tetrakis(2-ethylhexyl) zirconate, triethanolamine zirconate, tetra(isopropenyloxy)-zirconate, zirconium tetrabutanolate, zirconium tetrapropanolate, zirconium tetraisopropanolate and chelated titanates such as diisopropyl bis(acetylacetonyl)titanate, di isopropyl bis(ethylacetoacetonyl)titanate and diisopropoxytitanium bis(ethylacetoacetate), and the like.

[0058] Further examples of suitable catalysts include amines such as laurylamine, tertiary amines such as triethylamine, tetrametylethylenediamine, pentamethyl diethylenetriamine and 1 ,4-ethylenepiperazine or quaternary ammonium compounds such as tetramethylammonium hydroxide.

[0059] Further examples of suitable catalysts include guanidine based catalysts such as 1 butyl- 2, 3-dicyclohexyl-1 -methyl guanidine.

[0060] Further examples of suitable catalysts include organo-phosphates such as bis(2-ethyl- hexyl) hydrogen phosphate, (trimethylsilyl)octylphosphonic acid, octylphosphonic acid, bis(trimethylsilyl)octylphosphate and (2-ethyl-hexyl) hydrogen phosphonic acid. The catalyst can alternatively be a Lewis acid catalyst for example BF3, B(C6Fs)3, FeCh, AICI3, ZnCh, ZnBr2 or boron, aluminium, gallium, indium or thallium compounds with a monovalent aromatic moiety preferably having at least one electron-withdrawing element or group such as -CF3, -NO2 or -CN, or substituted with at least two halogen atoms.

[0061] Further, the catalyst may comprise a halogenated organic acid which has at least one halogen substituent on a carbon atom which is in the alpha-position relative to the acid group and / or at least one halogen substituent on a carbon atom which is in the betaposition relative to the acid group, or a derivative which is hydrolysable to form such an acid under the conditions of the condensation reaction.

[0062] In embodiments, the catalyst comprises tin.

[0063] In embodiments, addition-curable polysiloxanes that can be crosslinked by a hydrosilylation reaction can also be used. Such polymers are known as "hydride silicones" and are disclosed, for instance, in EP0874032A2 on page 3, viz. a polydiorganosiloxane of the formula R'-(SiOR'2)m-SiR'3, wherein each R' independently is a hydrocarbon or fluorinated hydrocarbon radical, at least two R' radicals per molecule being unsaturated, or hydrogen, at least two R' radicals per molecule being hydrogen, and m has an average value in the range of about 10 to 1 ,500. Cyclic polydiorganosiloxanes analogous to those of the formula above may also be employed. The hydride silicone preferably is a hydrogen polydimethylsiloxane.

[0064] In embodiments, the hydrosilylation reaction is catalysed by a suitable catalysts that promotes addition-curing, such as Group VIII metals or derivatives thereof. Examples of such catalysts in a metallic state are platinum, ruthenium, rhodium, palladium, and iridium. Also useful are compounds or complexes of these metals, such as PtCL, PtCle.SFLO, Na2PtCl4.4H20, platinum-olefin complexes, platinum-alcohol complexes, platinum-ether complexes, platinum-aldehyde complexes, platinum-ketone complexes (e.g., the reaction product of PtCle.SFLO and cyclohexanone), platinum-vinylsiloxane complexes (e.g., platinum-divinyl-tetramethyldisiloxane complex), palladium triphenylphosphine, and rhodium triphenylphosphonium chloride. The fouling control coating comprises a non-curable liquid fluorinated polymer or oligomer, and is typically a foul release coating.

[0065] [Non-curable fluorinated polymer or oligomer]

[0066] The fouling control coating comprises one or more non-curable fluorinated polymers or oligomers which is a liquid according to the definition of ASTM D4359-90 (2019), for example being liquids or oils at room temperature (20 °C) and atmospheric pressure. In embodiments they have a viscosity in the range of from 50 to 100 000 mPa.s at 25 °C, measured for example using method ASTM D4287-00 (2019).

[0067] They are also substantially non-volatile species, in embodiments having a boiling point in excess of 150 °C at atmospheric pressure, for example greater than 200 °C. In some cases, the non-curable fluorinated polymers can decompose before boiling, in which case the decomposition temperature can be in excess of 150 °C, for example greater than 200 °C.

[0068] The non-curable fluorinated polymer can, in embodiments, be selected from fluorinated alkyl- or alkoxy-containing polymers and oligomers. Examples are described in W02002 / 074870, W02013 / 000478 and WO2014 / 131695. In embodiments, the weight average molecular weight, Mw, is in the range of from 400 to 40 000, for example in the range of from 500 to 10 000 or from 750 to 10 000.

[0069] Specific examples of suitable non-curable fluorinated polymers and oligomers include linear and branched trifluoromethyl or fluorine end-capped perfluoropolyethers (e.g. Fomblin™ Y, Krytox™ K fluids, or Demnum™ S oils); linear di-organo (OH) end- capped perfluoropolyethers (e.g. Fomblin™ Z DOL, Fluorolink™ E); low molecular weight polychlorotrifluoroethylenes (e.g. Daifloil™ CTFE fluids), and fluoroethylene / vinyl ether copolymers (or polyfluorovinylethers).

[0070] In embodiments, the fouling control coating is formed by a curing process from a fouling control coating composition. The fouling control coating composition comprises one or more binder resins and one or more curing agents or crosslinking agents. Before application, the binder resin(s) and the curing agent(s) / crosslinking agent(s) are usually provided in separate components or parts, namely a binder component (or Part A component) for the binder resin(s), and a curing component (or Part B) for the curing agent(s) and / or crosslinking agent(s). In embodiments, a curing catalyst or crosslinking catalyst can also be provided in order to accelerate the curing / crosslinking process. This can be in a further separate component (e.g. as a Part C component).

[0071] The non-curable fluorinated polymer can be included in the fouling control coating composition in any part, although in embodiments it is included with the binder component.

[0072] Optionally other ingredients can be included in the fouling control coating composition that is used to form the fouling control coating. In embodiments, these can be selected from other curable resins, reactive diluents, adhesion promoters, solvents, dyes, pigments, gloss additives, waxes, rosins, fillers and extenders, thixotropic agents, plasticizers, inorganic and organic dehydrators (stabilizers), UV stabilizers, marine biocides, defoamers, chain transfer agents, other non-curable polymers, oligomers and oils, and any combinations thereof.

[0073] In embodiments, the curable resins in total constitute in the range of from 50 to 80 wt% of the fouling control coating composition.

[0074] In embodiments, the curing / crosslinking agents constitute from 0.5 to 20 wt% of the fouling control coating composition, for example from 1 to 10 wt% of the coating composition.

[0075] In embodiments, the curing / crosslinking catalyst constitutes from 0 to 5 wt% of the fouling control coating composition, for example from 0.1 to 2 wt% of the fouling control coating composition.

[0076] In embodiments, the total amount of non-curable fluorinated polymer and oligomer in the fouling control coating or the fouling control coating composition is in the range of from 1 to 30 wt%, for example in the range of from 2 to 20 wt% or from 3 to 15 wt%. In embodiments, organic solvent can be present in the fouling control coating composition in amounts of from 0 to 40 wt%, for example from 10 to 40 wt%. Organic solvents are typically those that have a boiling point of less than 250 °C at 20 °C and atmospheric pressure.

[0077] In embodiments, there is little or no pigment or filler in the coating composition, since these are typically opaque and have poor transparency. Amounts used are, in embodiments, no more than 10 wt%, for example no more than 5 wt% or no more than 2 wt%. In further embodiments, there is no more than 1 wt% in total of pigments and fillers.

[0078] In embodiments, the fouling control coating composition is non-aqueous, i.e. comprises in the range of from 0 to 5 wt% water, for example in the range of from 0 to 2 wt% water.

[0079] In embodiments, other components constitute no more than 25 wt% of the fouling control coating composition, for example no more than 20 wt% or no more than 15 wt% of the fouling control coating composition.

[0080] Examples of suitable fouling control coatings and fouling control coating compositions are described in W02002 / 074870, WO2013 / 000478, and WO2014 / 131695.

[0081] [Application of the fouling control coating composition]

[0082] The fouling control coating composition can be applied to the fouling control light-emitting device by conventional means, for example by brush, roller, air-spray, airless spray or dip-coating. The coating composition can be applied to the fouling control light-emitting device before it is attached to the substrate. Alternatively, the fouling control lightemitting device can be attached to the substrate first and subsequently coated.

[0083] In embodiments, the fouling control coating composition is applied to provide a dry film thickness of 25-1000 pm, for example 25-750 pm, or 50 to 250 pm. In embodiments the fouling control light-emitting device is made using a mould, and the fouling control coating composition can be applied to the light-emitting surface while inmould.

[0084] An advantage of applying the fouling control coating composition before attachment of the fouling control light-emitting device to the substrate is that it is much easier to apply riblets or patterns to the coated surface. This can be advantageous where such riblets or patterns reduce drag. Applying such adaptions to the surface is substantially more difficult and time-consuming after application to a large substrate such as a ship’s hull.

[0085] [Advantages of the invention]

[0086] The use of non-curable fluorinated polymer or oligomer is advantageous compared to other fluids that can be used in fouling control coatings (e.g. foul release coatings) because the stability of the optical transparency is maintained even after immersion in water. It also provides a secondary means of fouling control in addition to the light emitting device alone. This can be advantageous in that it can provide continued fouling control activity in the event of failure of the light emitting source, or inconsistent emission of light through the light-emitting surface. It also allows less intense light to achieve an equivalent level of fouling control performance compared to a device without such a fouling control coating.

[0087] [Substrate]

[0088] The fouling control light-emitting device is typically used on substrates that will be fully or partially immersed permanently or temporarily in water. Examples include ship or boat hulls, offshore structures such as drilling rigs, FPSO (floating production storage and offloading) structures, pipes and pipelines, offshore wind turbines, tidal and wave energy devices, and cooling water intakes for power plants.

[0089] The surface to which they are attached can be metallic surfaces, such as steel or aluminium, wood, surfaces of composite materials such as carbon-fibre or glass-fibre boat hulls, or concrete such as foundation piles for offshore or shore-side static structures. The fouling control light-emitting device can be attached to the substrate surface by various means, e.g. via mechanical interlocking adaptions on the substrate surface and on the fouling control light-emitting device, via mechanical fastenings such as clamps, screws or bolts, or via chemical adhesives, e.g. epoxy, polyurethane, silicone, silane- terminated polyether or acrylic adhesives.

[0090] Examples

[0091] The invention will now be described with reference to the following, non-limiting examples.

[0092] [Synthesis of fouling control coating compositions]

[0093] Fouling control coating compositions were prepared by mixing the components shown in

[0094] Table 1.

[0095] Example Coating Compositions 1 and 2 comprise a non-curable fluorinated polymer or oligomer fluid. Comparative Coating Compositions 3 to 8 comprise a hydrophilically- modified polysiloxane fluid. Comparative Coating Composition 9 comprises a hydrophobic phenylmethylsiloxane fluid. Comparative Coating Composition 10 comprises no non-curable fluid.

[0096] Table 1 - Fouling Control Coating Compositions [1] Polydimethylsiloxane polymer with terminated, curable silanol functionality, viscosity = 4,000 ePoise (Dow Corning, 3-0213 polymer)

[0097] [2] Ethyl silicate polymer (Wacker, Wacker Silicate TES 40 WN)

[0098] [3] Diooctyltin dilaurate

[0099] [4] 2,4-pentanedione

[0100] [5] Xylene

[0101] [6] Solvay Fluorolink™ D10-H

[0102] [7] Solvay Fluorolink™ E10-6

[0103] [8] (Hydroxy)polypropyleneglycol-modified polydimethylsiloxane, 20-25% non-siloxane

[0104] [9] (Methoxy)polyethyleneglycol-modified polydimethylsiloxane, 25-30% non-siloxane

[0105]

[0010] (Methoxy)polyethyleneglycol-modified polydimethylsiloxane, 50-55% non-siloxane

[0106]

[0011] (Methoxy)polyethyleneglycol-modified polydimethylsiloxane, 80-85% non-siloxane

[0107]

[0012] (Hydroxy)polyethyleneglycol-terminated polydimethylsiloxane, 60% non-siloxane

[0108]

[0013] Polysiloxane glycol copolymer

[0109]

[0014] Phenylmethylpolysiloxane

[0110] In the discussion below, the Example and Comparative Coating Compositions, after being applied and cured, will be referred to as corresponding Example and Comparative Coatings.

[0111] [Effect of immersion on LIV-C transmittance of fouling control coatings]

[0112] The effect of immersion in water on the LIV-C transmittance of foul release coating films comprising different fluid components was determined by applying the coating compositions to degreased glass panels (15 x 10 cm) using a drawdown bar with a gap size of 200 pm. After curing under ambient conditions for a minimum of 48 hours, the resulting cured coating films were carefully peeled from the glass panel for subsequent testing.

[0113] The transmittance of the coating films was determined in the LIV-C range at 270 nm using a Cary 60 UV-Vis spectrophotometer (Agilent Technologies).

[0114] The films were then immersed in water and the transmittance at 270 nm was remeasured after an immersion period of 3 months. The results are shown in Table 2, with the results expressed as the relative loss of transmittance of the film upon immersion expressed as a percentage (RLT%), where RLT% = 100 x (To - Tjmm) / To and To is the transmittance prior to immersion and Tjmm is the transmittance after immersion. Results were rated as Excellent, Good or Poor depending on the determined relative loss of transmittance following immersion, where Excellent = RLT% < 25.0; Good = 25.0

[0115] < RLT% < 50.0; Poor = RLT% > 50.0.

[0116] Table 2 - RLT% at 270 nm upon immersion in water

[0117] The results show that the relative loss of transmittance at 270 nm after immersion was less than 50% for the coating films that comprise a non-curable fluorinated polymer fluid.

[0118] In contrast, the loss of transmittance for the coating films that comprise a polyether- modified polysiloxane fluid was more than 50%. Such coatings were categorized as Poor. In the case of Comparative Coating 9, the transmittance of this film before and after immersion was substantially zero, and hence it was not possible to effectively measure the relative loss of transmission.

[0119] The relative loss of transmittance of the control film without any fluid component in the composition (Comparative Coating 10) was also less than 50% and was categorised as Excellent. However, this sample had poor foul release performance.

[0120] [Biofilm growth and release testing]

[0121] The general procedure described in H. O. G. Benschop, A. J. Guerin, A. Brinkmann, M. L. Dale, A. A. Finnie, W.-P. Breugem, A. S. Clare, D. Stubing, C. Price and K. J. Reynolds, “Drag-reducing riblets with foul-release properties: development and testing”, Biofouling, 2018, 34(5), pages 532-544, was followed. In summary, test coatings were applied onto glass microscope slides, 5-7 replicate slides for each coating, and after curing at room temperature the coated slides were immersed in seawater for 32 days and then aged in a multispecies biofilm culturing reactor for 21 days. The slides were removed and tested for biofilm release in a variable-speed hydrodynamic flow-cell where the surfaces of the slides were exposed to fully turbulent seawater flow, with the water velocity being increased incrementally from zero to 4.1 m s-1. The slides were photographed and the amount of biofilm present on the surface was assessed using image analysis software (Imaged, version 1.53t). The results were expressed as the average percentage of the total area (% cover) of biofilm present after testing for each set of replicate slides.

[0122] Two commercial coatings, Lumisil™ 903 and Intersleek™ 1100SR, were also coated onto further sets of replicate microscope slides and cured and tested in the same way, except that the Lumisil™ 913 was cured at 95 °C for 24 hours, in line with the manufacturer’s guidance. Results are shown in Table 3 below.

[0123] Lumisil™ 903 (Wacker Chemie) is an addition-curing, low viscosity, two-part curable polysiloxane composition that is UV-transparent at room temperature. It is intended for transparent potting in the lighting and electronics industry, and is not used as a fouling control coating.

[0124] Intersleek™ 1100SR (AkzoNobel) is an opaque, pigmented, commercial advanced fluoropolymer-containing foul-release coating.

[0125] [Pseudobarnacle adhesion tests]

[0126] The general procedure for pseudobarnacle adhesion tests was based on a modification to the method described by J. Stein et al., “Structure-Property Relationships of Silicone Biofouling-Release Coatings: Effect of Silicone Network Architecture on Pseudobarnacle Attachment Strengths”, Biofouling, 2003, 19:2, 87-94, whereby aluminium studs (psesudobarnacles) of known diameter were glued to the coated glass microscope slides after completion of the biofilm growth and release test. A PVA glue (Evo-Stick™) was used as the adhesive. The adhesive was allowed to harden for 7 days under ambient conditions and the mean pseudobarnacle adhesion strength (N cm-2) for each coating was measured using a force gauge (CFG-50, Mecmesin) mounted parallel to the coating surface. Results are shown in Table 3 below. Table 3 - Foul release performance tests

[0127] As can be seen from Table 3, all of the tested coatings that comprise a fluid additive show % biofilm coverage after exposure to seawater at 4.1 ms-1of 7% or less, approaching or matching the performance of Intersleek™ 1100SR. The biofilm coverage is less than the values of 9% and 30% observed, respectively, for the non-curable fluid- free polysiloxane controls of Comparative Coating 10 and Lumisil™ 903.

[0128] Additionally, the results in Table 3 show that all of the tested coatings that comprise a fluid additive have a mean pseudobarnacle adhesion strength of 2.1 N cm-2or less, approaching or surpassing the performance of the commercial foul release coating, Intersleek™ 1100SR. As with the biofilm coverage results, the measured pseudobarnacle pull-off strengths are less than the those of the fluid-free crosslinked polysiloxane control (2.1 N cm-2) and significantly less than the results for the UV- transparent polysiloxane control (6.2 N cm-2).

[0129] [Fouling control light-emitting device]

[0130] Following the general procedure described by Salter and Piola, “UVC Light for Antifouling”, Marine Technology Society Journal, 2017, 51(2), pages 59-70, circular UV- C emitting devices, 9 cm diameter, 1 cm thick, were prepared from a cured UV- transparent polysiloxane rubber (Lumisil™ 903, Wacker Chemie) with an embedded UV- C emitting LED (ILR-LP01_S270-LEDIL-SC201 , Intelligent ED Solutions) and associated electrical wiring. The LED was configured to emit UV-C light from the surface of the lightemitting device. [Coated light-emitting device]

[0131] Coated light-emitting devices were prepared by applying the selected coating to the top surface of a device using a drawdown bar with a gap size of 500 micrometres and allowed to cure under ambient conditions for a minimum of 48 hours.

[0132] The device was turned on with a 12 V d.c. forward voltage and a 10 mA forward current. The intensity of the emitted IIV-C light was measured 20 mm from the surface of the coated lighting unit at 441 points across a 40 mm x 40 mm array centred on the LED with a spatial resolution between measurement points of 2 mm in the x and y directions. Measurements were made with a silicon carbide UV photodetector with integrated amplifier converting UV light intensity into an output voltage. The output voltage was measured with a voltmeter and the measured UV light intensity at each measurement point was recorded and expressed as pW / cm2.

[0133] The average and minimum intensity of emitted UV-C light over the measurement area is shown in Table 4, along with the average intensity expressed as a percentage relative to the uncoated lighting unit control. An uncoated lighting unit was used as a control.

[0134] Table 4 - Intensity of emitted UV-C from coated and uncoated lighting units

[0135] To prevent marine biofouling, a threshold emission value of about 1 x 10'9W / mm2or 0.1 pW / cm2is typically required. This is easily exceeded by the coated devices shown above

[0136] In contrast the average intensity of UV-C light emitted from the surface of a lighting unit coated with a foul release coating that comprises a phenylmethylpolysiloxane fluid is less than 5% of the average intensity emitted from the surface of an uncoated control lighting unit. The minimum intensity of IIV-C light emitted from this coated lighting unit is below the threshold value at some measurement points.

Claims

Claims1 . A fouling control light-emitting device having a source of light, an optical medium that can transmit light, and a light-emitting surface, in which at least part or all of the lightemitting surface comprises a fouling control coating, wherein the fouling control coating comprises a non-curable fluorinated polymer or oligomer that is liquid according to ASTM D4359-90 (2019).

2. The fouling control light-emitting device as claimed in claim 1 , in which the lightemitting device emits one or more wavelengths in the range of from 100-300 nm.

3. The fouling control light-emitting device as claimed in claim 1 or claim 2, in which the source of light is a controllable LIV-LED or UVC-LED.

4. The fouling control light-emitting device as claimed in any one of claims 1 to 3, in which greater than 50wt% of the optical medium is polysiloxane and / or fluoropolymer.

5. The fouling control light-emitting device as claimed in any one of claims 1 to 4, in which the fouling control coating composition used to form the fouling control coating comprises more than 50 wt% curable polysiloxane and / or curable fluoropolymer.

6. The fouling control light-emitting device as claimed in any one of claims 1 to 5, in which the non-curable fluorinated polymer or oligomer is selected from:- linear and branched trifluoromethyl or fluorine end-capped perfluoropolyethers;- linear di-organo (OH) end- capped perfluoropolyethers;- low molecular weight polychlorotrifluoroethylenes; and- fluoroethylene / vinyl ether copolymers.

7. The fouling control light-emitting device as claimed in any one of claims 1 to 6, which is in the form of a tile, a film, a foil or a laminar strip.

8. The fouling control light-emitting device as claimed in any one of claims 1 to 7, in which the total amount of pigments and fillers in the fouling control coating is no more than 10 wt%.

9. A substrate that comprises on its surface a fouling control light-emitting device as claimed in any one of claims 1 to 8.

10. The substrate as claimed in claim 9, which is intended to be permanently or intermittently immersed in water.

11. The substrate as claimed in claim 10, selected from ship and boat hulls, offshore structures such as drilling rigs, FPSO (floating production storage and offloading) structures, pipes and pipelines, offshore wind turbines, tidal and wave energy devices, and cooling water intakes for power plants.

12. A method for controlling aqueous biofouling comprising exposing the biofouling to light that can reduce or prevent the biofouling, the light being emitted from a fouling control light-emitting device as claimed in any one of claims 1 to 8.

13. The method of claim 12, in which the light is one or more wavelengths in the ultraviolet region.

14. The method of claim 13, in which the light is one or more wavelengths in the range of from 100 to 300 nm.

15. Use of a fouling control light-emitting device as claimed in any one of claims 1 to 8 for controlling aqueous biofouling on a substrate.

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