NL2012036C2

NL2012036C2 - Antifouling foil.

Info

Publication number: NL2012036C2
Application number: NL2012036A
Authority: NL
Inventors: Carlos Martinez
Original assignee: Nautical Foil Solutions B V
Priority date: 2013-12-30
Filing date: 2013-12-30
Publication date: 2015-07-01

Description

Antifouling foil

FIELD OF THE INVENTION

The invention relates to an anti-fouling foil, which protects marine underwater structures that are immersed in water, especially sea water, from unwanted fouling by marine organisms which otherwise attach and grow there. The invention also pertains to underwater structures with an anti-fouling foil coat on at least part of its underwater surfaces, to processes for applying such a foil to these surfaces, and to a sticker comprising such a foil and an adhesive layer.

BACKGROUND OF THE INVENTION

Fouling is a major problem for (partly) underwater structures, such as platforms, oil rigs, mooring posts, floating devices such as buoys, watercrafts (e.g. ships, boats, submarines) and any other surface that is regularly immersed in water. Fouling is defined as the accumulation (or deposit) of unwanted material on solid surfaces which is detrimental to its function. The fouling material (i.e. the unwanted deposit) can consist of either living organisms (biofouling) or non-living (inorganic or organic) substances. Fouling of underwater structures is referred to as “marine fouling”. Marine fouling on underwater structures is the cause of severe economic losses, e.g. due to decreased possible operation time and subsequent increased wastage. For watercraft, marine fouling poses even a bigger problem, due to increased friction and therefore increased consumption of fuel, increased drag, increased resistance to waves and reduced maximum speed. Marine fouling involves the attachment and growth of marine organisms (microorganisms, plants, algae, animals) to surfaces which are exposed to sea and/or fresh water, but may also include the sedimentation of mineral or salt material (scaling).

Antifouling refers to the reduction or prevention of fouling, in particular marine fouling. Traditionally, antifouling involves painting of underwater structures such as boat hulls with antifouling paint. The presence of biocides reduces the attachment of organisms to the underwater structure, but also renders these paints highly toxic. Common antifouling paints may be divided in two main classes: (1) ablative bottom paints and (2) hard bottom paints or non-sloughing bottom paints. Ablative bottom paints provide antifouling properties when applied to an underwater surface such as a boat’s hull, by wearing away (sloughing) by water movement across the hull. As such, a fresh layer of coating is created repeatedly. Some ablative paints contain biocides that release during sloughing of the paint and the biocidic environment that is created prevents adherence of marine life. An antifouling coating of ablative paint may last as short as 4 months or up to about 12 months, before reapplying is required, and such coating thus needs to be reapplied seasonally. Hard bottom paints provide an antifouling coating with constant layer thickness, as their antifouling properties originate from slow release of biocides from the coating, while its macrostructure remains intact. A coating of hard bottom paint usually lasts one to maximally three years. US 5,354,603 describes a composite antifouling coating for underwater surfaces, which comprises a entrapped particulates comprising biocides. JP 61126002 describes the use of a polymeric laminate comprising biocidic trialkyltin moieties as antifouling coating for marine structures. WO 2004/111149 describes an antifouling tape, which contains an adhesive and an antifouling layer comprising a biocidic antifouling agent.

The major drawback of these common antifouling paints is the use of biocides such as copper or tin compounds. These toxic substances leach into the water, thereby providing a serious threat for marine life. Over the years several types of biocide-free antifouling paints and other alternatives have entered the market to meet the growing needs for environmentally acceptable alternatives, which render the underwater surface either too rough or too slippery for extensive marine fouling to occur. However, the currently available biocide free antifouling alternatives require elaborate and expensive processes to be applied on underwater surfaces. A typical process of coating an underwater surface such as the hull of a boat involves: (i) cleaning and chafing the surface, (ii) applying at least two layers of primer, (iii) applying a filler layer, (iv) applying at least three further layers of primer, (v) applying at least two layers of undercoat, (vi) applying 2-3 layers of antifouling paint. For polyester boats, only steps (i), (iii), (v) and (vi) are traditionally carried out, but even this already requires the application of at least six layers. For aluminium, steel and wooden boats, up to eleven layers may be required to render the appropriate coat. Irrespective of the time it takes to apply each layer, which may depend on the size of the boat and the skill of the practitioner, each layer needs to be dried before the next one can be applied thereon. The drying time between the application of two layers may amount up to at least 24 hours, which renders the coating of boat hulls with antifouling paint an elaborate and lengthy task. Moreover, this process usually needs to be repeated every year or every other year, as the antifouling properties of the paint deteriorate quickly.

Therefore, there still exists a need in the art for antifouling solutions that are environmentally friendly (i.e. do not contain biocides) but at the same time are easily applicable.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a foil as coating for marine applications, having improved anti-fouling properties. The inventors surprisingly found that using a fluoropolymer-containing foil coating greatly facilitates the application of the antifouling coating compared to the multiple layers of paints traditionally applied. Hence the present invention provides a foil as coating for marine applications, wherein the foil comprises a fluoropolymer. The fluoropolymer- containing foil provides a fast and economical improvement over time-consuming and cumbersome paint coatings. Moreover, the fluoropolymer-containing foil provides improved antifouling properties and at the same time reduces the friction forces between boat hulls and the water, thereby increasing the energy efficiency of the watercraft. In order to optimize adhesion between the fluoropolymer-containing layer and the surface of the underwater structure to be protected the top layer is preferably provided with an inner textured layer to which a water-resistant adhesive layer is adhered.

PREFERRED EMBODIMENTS 1. Use of a foil for coating an underwater structure, wherein the foil comprises a fluoropolymer. 2. Use according to embodiment 1, wherein the underwater structure is a watercraft, preferably a boat. 3. Use according to embodiment 2, which is for increasing the energy efficiency of the watercraft. 4. Use according to any of embodiments 1 to 3, which is for antifouling. 5. Use according to any of embodiments 1 to 4, wherein the fluoropolymer is polyvinyl fluoride. 6. Use according to any of embodiments 1 to 5, wherein the foil is provided with a water-resistant adhesive layer on one side. 7. Use according to embodiment 6, wherein the one side of the foil is textured. 8. Underwater structure, comprising an underwater surface which is at least partly coated with a foil comprising a fluoropolymer. 9. Process for coating at least part of an underwater structure, comprising: (a) providing a foil comprising a fluoropolymer; (b) applying the foil to at least part of an underwater structure, wherein said part is an underwater surface. 10. Process according to embodiment 9, wherein the foil is applied to the entire underwater surface of the underwater structure. 11. Process according to embodiment 9 or 10, wherein the underwater structure is a watercraft, preferably a boat. 12. Process according to embodiment 11, wherein the underwater surface includes a hull. 13. Process according to any one of embodiments 9 to 12, wherein one side of the foil is provided with an adhesive layer and that one side is attached to at least part of the underwater structure. 14. Sticker, comprising: (a) a foil comprising a fluoropolymer, wherein the foil has a textured side; (b) a water-resistant adhesive layer provided on the textured side of the foil. 15. Sticker according to embodiment 14, wherein the adhesive layer is provided with a protective layer.

DETAILED DESCRIPTION

The present invention concerns the use of a foil comprising a fluoropolymer for coating underwater structures, in particular as antifouling coating. The invention also concerns the use of a foil comprising a fluoropolymer for increasing the energy efficiency of watercrafts. In a further aspect, the invention pertains to a process for coating underwater structures and coated underwater structures obtainable by said process.

In the context of the present invention, an “underwater structure” is a structure that -when in use - is (partly) immersed in water. Underwater structures include platforms, oil rigs, mooring posts, floating devices such as buoys, watercrafts (e g. ships, boats, submarines) and any other surface that is regularly immersed in water. Underwater structures comprise one or more underwater surfaces, which represent the (outer) surface of the structure which is in direct contact with water. Typically, the underwater surfaces are located below the waterline. The preferred underwater structures for the present invention are watercrafts, more preferably boats. In the context of the invention, the term “boat” is intended to cover all buoyant vehicles, irrespective of size and means of propelling.

In a first aspect, the present invention concerns the use of a foil comprising a fluoropolymer for coating an underwater structure, preferably a watercraft, more preferably a boat. This use according to the invention is preferably for increasing the energy efficiency of the watercraft and/or for antifouling. This aspect of the invention can also be worded as a method for increasing the energy efficiency of the watercraft, preferably a boat, and/or for preventing fouling of an underwater surface of an underwater structure, preferably a watercraft, more preferably a boat, comprising the step of applying the foil to at least part of an underwater structure, wherein said part is an underwater surface.

In the context of the present invention, a “foil” is a layer of plastic material. In the art, such a foil may also be referred to as a film, or a plastic film. Foils have two sides, which in the context of the present invention are referred to as “inner side”, i.e. the side which is or is intended to be applied to or in contact with the underwater surface of the underwater structure, and as “outer side”, i.e. the side which is not in direct contact, or at least not intended to be, in direct contact with the underwater surface, but instead is or is intended to be in direct contact with the water. When the foil according to the invention is applied to an underwater surface, the outer side of the foil is visible.

The foil according to the invention comprises, preferably is made of, a fluoropolymer. A “fluoropolymer” is a polymer comprising multiple fluorine atoms, typically attached to carbon as the C-F bond is particularly strong, preferably wherein at least one of the one or more distinct monomeris units comprises at least one fluorine atom. Preferred fluoropolymers to be used in the present invention include polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), ethylene tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE) and polyethylenechlorotrifluoroethylene (ECTFE). The foil according to the invention may comprise one type of fluoropolymer or a combination of two or more distinct fluoropolymers, preferably the foil contains one type of fluoropolymer. In an especially preferred embodiment, the fluoropolymer is selected from PTFE, PVF and PVDF, more preferably from PFTE and PVF, most preferably the fluoropolymer is PVF. PVF is also known under the trade name Tedlar. PTFE is also known under the trade name Teflon. The foil preferably comprises at least 50 wt% fluoropolymer, more preferably at least 90 wt%, more preferably at least 95 wt% fluoropolymer. In a preferred embodiment, the foil according to the invention is made of PTFE, PVF, PFA, FEP, ETFE, PVDF, PCTFE, ECTFE or combinations thereof, more preferably of PTFE, PVF, PVDF or combinations thereof, even more preferably of PTFE or PVF, most preferably of PVF.

The foil preferably has a thickness of 5.0 - 250 μηι, more preferably 10 - 100 μιη, most preferably 15 - 40 μιη, The foil preferably has an area factor of 5.0 - 100 m2/kg, more preferably 10-50 m2/kg. Further preferred properties of the foil according to the invention are listed here. The test method which is to be applied to determine these properties are given in parentheses. The foil preferably has a coefficient of friction (foil on metal) of 0.03 - 0.50, more preferably 0.05 - 0.25 (ASTM D-1894). The foil preferably has a tensile modulus of 50 MPa - 10 GPa, more preferably 250 MPa - 5.0 GPa, most preferably 1.0- 3.0 GPa (ASTM D-882). The foil preferably has a bursting strength of 1.0 - 100 GPa/m, more preferably 5.0 - 20 GPa/m (Mullen ASTM D-774). The foil preferably has a moisture vapour transmission of 1.0 - 100 g/m2d, more preferably 10-40 g/m2d (ASTM E-96).

Typically, at one side, preferably the inner side, the foil according to the invention is provided with an adhesive layer, to facilitate the application of the foil onto a surface. The resulting product comprised of the foil according to the invention and the adhesive layer may be referred to as a sticker. The present invention also concerns such a sticker. The sticker according to the invention comprises the fluoropolymer-comprising foil according to the invention and a water-resistant adhesive layer connected to one side of the foil, typically to the inner side. Preferably, the adhesive layer of the sticker is provided with a protective layer which can readily be removed before use. Any type of water-resistant adhesive known in the art may be used. The adhesive layer may comprise any solution or compound with adhesive properties, provided that the adhesive is water-resistant, such as rubber-based adhesives, resin adhesives, wax-based adhesives, inorganic adhesives, or any other suitable adhesive compound. Preferably, the adhesive layer comprises a pressure-sensitive adhesive such as adhesives based on acrylics, polyesters, epoxies, rubbers and pressure-sensitive mastics. In a preferred embodiment, the adhesive layer comprises a solvent-based adhesive. The fluoropolymer-containing foil is preferably textured at the same side as the to the adhesive layer is applied, preferably the adhesive layer is textured at the inner side, in order to facilitate adherability. Texturing is preferably selected from corona treatment, atmospheric plasma treatment, flame plasma treatment and chemical plasma treatment, preferably corona treatment. The adhesive can be pre-applied to foil or can be applied to a surface before the foil is to be applied thereto.

The foil of the invention as well as the sticker according to the invention, is impervious to a wide range of temperatures, ranging from -40 to 100 °C and all salinities occurring on earth (i.e. 0-40 g/L), without any deterioration in properties. Hence, the present foil may be applied to all underwater structures, irrespective of the location or type of application. Thus, the foil according to the invention is highly suitable for coating boats, preferably for coating hulls of boats, which usually are exposed to very variable conditions, such as significant changes in water temperature and/or salinity, in a relatively short period of time.

Using the foil according to the invention as coating, in particular as outer layer of underwater structures, in particular watercrafts, has several unexpected benefits. First of all, the roughness of the underwater structure is dramatically reduced, which gives rise to a greatly reduced extent of fouling, as the foil has improved anti-fouling properties. Also, using the foil according to the invention increases the energy efficiency of the watercraft. Without being bound to a theory, it is expected that the foil reduces the resistance that occurs when a boat cleaves through the water in view of the low coefficient of friction of fluoropolymers, in particular PTFE. It should be noted that for fuel operated watercrafts, the increased energy efficiency refers to increased fuel efficiency, i.e. the fuel consumption per unit distance. A further advantage of using the foil according to the invention as coating of underwater structures, in particular watercrafts, is that once applied, the foil provides antifouling properties and the other advantages described herein for at least five years without the need of changing the underwater water structure and/or reapplying the antifouling coating.

The process for coating underwater structures is also facilitated with the use of the foil according to the invention. Thus, in a second aspect the invention also concerns a process for coating at least part of an underwater structure, comprising: (e) providing a foil according to the invention; (f) applying the foil to at least part of an underwater structure, wherein said part is located beneath the waterline when the underwater structure is in regular use.

Preferably, the foil according to the invention is applied on a primer layer, which has previously been applied to the underwater surface. Suitable primers for use on underwater surfaces of e.g. boats are known in the art and include epoxy primers. Preferably, the foil according to the invention is not applied directly on the bare surface of the underwater structure, as that would impart insufficient protection of the underwater surface, in particular for the hull of a watercraft. Preferably, the foil according to the invention is not applied on a different antifouling coating, such as an old antifouling paint which needs to be renewed.

In a preferred embodiment, the process according to the invention comprises a step (a) of cleaning and chafing at least part of the underwater structure, wherein said part is located beneath the waterline when the underwater structure is in regular use, to obtain a bare surface. Step (a) is especially useful when the underwater structure that is to be coated is not new but has been in use, or part of it gas been in use, under water for a certain period of time, such as for a year or more. In case the underwater structure is newly manufactured, step (a) is not required.

In a preferred embodiment, the process according to the invention comprises a step (b) of applying at least one, preferably at least two layers of primer on said part, to obtained a primed surface. These first layers of primer may impart protective properties to the underwater structure, such as an anti-corrosive layer to protect a steel hull.

In a preferred embodiment, the process according to the invention comprises a step (c) of applying a filler layer, to obtain a smoothened surface. Applying a filler layer is preferably included in the process if the underwater surface is insufficiently smooth. Usually, it is beneficial to apply up to three further layers of primer to the primed or the smoothened surface, to obtain a pretreated surface, which imparts further protection on the underwater surface.

Thus, in a preferred embodiment, the process according to the invention comprises: (a) cleaning and chafing at least part of the underwater structure, wherein said part is located beneath the waterline when the underwater structure is in regular use, to obtain a bare surface. (b) applying at least one, preferably at least two layers of primer on said part, to obtained a primed surface; (c) preferably applying a filler layer, to obtain a smoothened surface (d) applying 0 to 3 further layers of primer, to obtain a pretreated surface; (e) providing a foil according to the invention; (f) applying the foil to said primed or said smoothened or said pretreated surface.

In the process according to the invention, the foil according to the invention comprises a fluoropolymer, as is described in detail above. Preferably, one side of the foil is provided with an adhesive layer, which is referred to as the inner side, and that inner side of the foil is attached to at least part of the underwater structure, or to the primed or smoothened surface. Preferably, the foil is applied to at least 50 area% of the underwater surface, more preferably at least 80 area% of the underwater surface, even more preferably at least 95 area% of the underwater surface, more preferably at least 99 area% of the underwater surface, most preferably the entire underwater surface of the underwater structure, i.e. the entire surface of the structure that is located beneath the waterline when the underwater structure is in regular use. Preferably, the underwater structure that is coated in the process according to the invention is a watercraft, more preferably a boat, and the underwater surface includes its hull.

Steps (a) to (d) are known in the art and also part of the conventional process for coating an underwater structure. Step (c) is preferably included in the process if the underwater surface is insufficiently smooth. The use of the foil according to the invention avoids steps (v) and (vi) of the conventional process for coating an underwater structure.

Carrying out the process according to the invention avoids the necessity of applying undercoating and paint coating to the underwater structure for proper antifouling properties, but instead applies an efficient antifouling coating in a single step. In effect, steps (v) and (vi) of the conventional process of coating an underwater structure are avoided. Moreover, the need for extensive waiting for the paint to dry inbetween the application of two layers is circumvented, as applying a foil does not require a drying time.

In a third aspect, the invention concerns a sticker comprising a foil comprising a fluoropolymer, preferably as decribed above, and a water-resistant adhesive layer, preferably as described above. The water-resistant adhesive layer is connected to one side of the foil, which is referred to as the inner side. Preferably, the adhesive layer of the sticker is provided with a protective layer which can be readily removed before use. Thus, in the sticker of the invention, an adhesive layer is applied onto a foil comprising a fluoropolymer and onto the adhesive layer a protective layer is present.

In a fourth aspect, the invention concerns a coated underwater structure, which is coated with a film comprising a fluoropolymer. The underwater structure according to the invention preferably comprises an underwater surface which is at least partly coated with the foil according to the invention, preferably at least 50 area% of the underwater surface, more preferably at least 80 area% of the underwater surface, even more preferably at least 95 area% of the underwater surface, most preferably the entire (i.e. at least 99 area%) underwater surface is coated with the foil according to the invention. The greater the area% of the underwater surface of the underwater structure that is coated with the foil according to the invention, the greater the effect in terms of improved antifouling properties and increased energy efficiency. The underwater structure according to the invention is preferably a watercraft, more preferably a boat. preferably, the coated underwater structure according to the invention is obtained by the process according to the invention.

EXAMPLE

Foils used: TUT20BG3 and TUT10AG3 (Tedlar, DuPont).

Foil characteristics: 100 wt% PVF; thickness: 25 pm (TUT20BG3) or 50 pm (TUT10AG3). TUT20BG3 has two textured sides to increase adherability, while TUT10AG3 has one textured and one smooth side.

Each of the foils was applied to the hull of a metal boat, which was pretreated with a layer of epoxy primer. Control experiments are performed on a glass surface. The roughness of the epoxy primer layer was tested, as well as this layer further applied with a TUT20BG3 foil, and with two layers of conventional undercoat and two layers of conventional chloro rubber antifouling paint. Roughnesses were determined with a Surface Roughness Meter type HRT-6200 RA/RZ. It was found that the roughness of the hull was markedly decreased when the above foils are used, see table 1. Lower Rz values indicate smoother surfaces.

Table 1: Roughness values

These results are indicative of outstanding antifouling properties of a fluoropolymer-containing foil.

Claims

Use of a film for coating an underwater structure, wherein the film contains a fluoropolymer.

Use according to claim 1, wherein the underwater structure is a vessel, preferably a boat.

Use according to claim 2, which increases the energy efficiency of the vessel.

Use according to any of claims 1 to 3, which is for antifouling.

The use according to any of claims 1 to 4, wherein the fluoropolymer is polyvinyl fluoride.

Use according to any one of claims 1 to 5, wherein the film is provided on one side with a water-resistant adhesive layer.

The use according to claim 6, wherein one side of the film is pretreated.

An underwater structure comprising an underwater surface that is at least partially coated with a film containing a fluoropolymer.

A method for coating at least a portion of an underwater structure, comprising: (a) providing a film containing a fluoropolymer; (b) applying the film to at least a portion of the underwater structure, the portion being an underwater surface.

The method of claim 9, wherein the film is applied to the entire underwater surface of the underwater structure.

A method according to claim 9 or 10, wherein the underwater structure is a vessel, preferably a boat.

The method of claim 11, wherein the underwater surface comprises the hull.

A method according to any of claims 9 to 12, wherein one of the foil is provided with an adhesive layer and one side is adhered to at least a part of the underwater structure.

A sticker comprising: (a) a film containing a fluoropolymer, the film having a pretreated side; (b) a water-resistant adhesive layer provided on the pre-treated side of the film.

15. A sticker according to claim 14, wherein the adhesive layer is provided with a protective layer.