Composite material

FIELD OF THE INVENTION

0001This invention relates to composite materials such as venting materials and vents containing said venting materials. More particularly, the present invention relates to air- or more generally gas-permeable venting composites that are oleophobic and liquid repellent.

BACKGROUND OF THE INVENTION

0002There are many types of vents on the market that allow containers to vent by allowing a small amount of air flow through the vent. Packaging vents are commonly used in providing venting solutions for consumer and industrial liquid cleaners. These liquid cleaners normally contain organic additives and surfactants which lower the surface tension of the liquid thereby promoting wetting and adherence to surfaces.

0003A further difficulty is that many types of newly developed liquid cleaners additionally have a higher viscosity than previously used. Higher viscosity liquids are preferred as this allows the liquid cleaner to function much better by increasing the adherence and contact time of the liquid to the surface to be cleaned. As a result of both the higher viscosity and the low surface tension, the viscous liquids also have the ability to stick much better to the vents themselves. The vents can therefore easily become clogged by liquid left on the surface of the vent. A further problem arises if the viscous liquid dries on the surface of the vent leaving an impermeable film made up of solid components dissolved in the liquid. The vent may therefore be rendered permanently inoperable with highly viscous liquids.

0004There is also the issue that many types of liquid cleaners emit small amounts of gaseous substances such as oxygen or chlorine which can lead to containers becoming over-inflated if a vent becomes clogged by a viscous liquid.

0005Viscous oils are a further type of liquid causing problems in automotive related venting applications. Motor oils, for example, have the ability to stick onto vents for electronic housings thereby preventing air flow and pressure exchange through the vent.

0006<patcit id="pcit0001" dnum="US5462586A"><text>US 5,462,586</text></patcit> relates to an oil- and water-repellent gas-permeable filter which contains a porous filter material that has its internal and external surfaces coated with a compound comprising a first fluoropolymer having a fluorine-containing aliphatic cyclic structure in the main chain and a second fluoropolymer containing polyfluoroalkyl groups. The coating in <patcit id="pcit0002" dnum="US5462586A"><text>US 5,462,586</text></patcit> is intended to have substantially no effect on the porosity of the porous filter material. <patcit id="pcit0003" dnum="US5462586A"><text>US 5,462,586</text></patcit> is incorporated herein by reference.

0007It is an object of at least one aspect of the present invention to obviate or mitigate at least one or more of the aforementioned problems.

0008It is a further object of at least one aspect of the present invention to provide a venting composite that is capable of providing sufficient residual gas flow (e.g. air flow) even after coming into contact with a liquid having both a high viscosity and low surface tension.

SUMMARY OF THE INVENTION

0009The present invention provides a venting apparatus according to claim 1 and a method of venting gas according to claim 22.

0010According to a first aspect there is provided a gas-permeable composite comprising: <ol id="ol0001" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and second component;</li><li>(d) said first component comprising oleophobic and hydrophobic fluorinated material; and</li><li>(e) said second component comprising a perfluoropolyether (PFPE), said PFPE comprising end-groups selected from the following:         -(O)_n - (CR₁R₂)_m - CR₃R₄R₅</li></ol> wherein: <ul id="ul0001" list-style="none" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H, F, Cl, Br or I;</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or 1; and</li><li>m = 0 - 10.</li></ul>

0011The R₅ group may be an alkyl- or aryl-group.

0012Typically, the PFPE may comprise two end-groups at opposite ends of the PFPE structure.

0013Typically, the PFPE may comprise two perfluorinated end-groups at opposite ends of the PFPE structure, such as, -OCF₃, -OC₂F₅, and -OC₃F₇,

0014However, there may also be non-perfluorinated end groups such as those containing H. Cl, Br or I radicals. Examples of non-perfluorinated end groups of PFPEs (e.g. neutral PFPEs) may comprise structures such as:         -CF₂R₆    R₆= H, Cl, Br, or I; or         -CFR₇-CF₃    R₇ = H, Cl, Br or I.

0015The end-groups according to the formula of -(O)_n - (CR₁R₂)_m - CR₃R₄R₅ may be selected from any combination of the following: <ul id="ul0002" list-style="none" compact="compact"><li>-OCF₃; -OC₂F₅; -OC₃F₇; -OC₄F₉; -OC₅F₁₁; -OC₆F₁₃; -OC₇F₁₅; -OC₈F₁₇;-OC₉F₁₉; -OC₁₀F₂₁;</li><li>-OCF₂H: -OC₂F₄H; -OC₃F₆H, -OC₄F₈H; -OC₅F₁₀H; -OC₆F₁₂H; -OC₇F₁₄H;-OC₈F₁₆H; -OC₉F₁₈H; -OC₁₀F₂₀H;</li><li>-OCF₂Cl; -OC₂F₄Cl; -OC₃F₆Cl; -OC₄F₈Cl; -OC₅F₁₀Cl; -OC₆F₁₂Cl; -OC₇F₁₄Cl; -OC₈F₁₆Cl; -OC₉F₁₈Cl; -OC₁₀F₂₀Cl;</li><li>-OCF₂Br; -OC₂F₄Br; -OC₃F₆Br; -OC₄F₈Br; -OC₅F₁₀Br; -OC₆F₁₂Br;-OC₇F₁₄Br; -OC₈F₁₆Br; -OC₉F₁₈Br; -OC₁₀F₂₀Br;</li><li>-OCF₂I; -OC₂F₄I; -OC₃F₆I; -OC₄F₈I; -OC₅F₁₀I; -OC₆F₁₂I; -OC₇F₁₄I; -OC₈F₁₆I; -OC₉F₁₈I; -OC₁₀F₂₀I;</li><li>-OCF₁H₂; -OC₂F₃H₂; -OC₃F₅H₂; -OC₄F₇H₂; -OC₅F₉H₂; -OC₆F₁₁H₂;-OC₇F₁₃H₂; -OC₈F₁₅H₂; -OC₉F₁₇H₂; -OC₁₀F₁₉H₂;</li><li>-OCFCl₂; -OC₂F₃Cl₂; -OC₃F₅Cl₂; -OC₄F₇Cl₂; -OC₅F₉Cl₂; -OC₆F₁₁Cl₂;-OC₇F₁₃Cl₂; -OC₈F₁₅Cl₂; -OC₉F₁₇Cl₂; -OC₁₀F₁₉Cl₂;</li><li>-OCF₁Br₂; -OC₂F₃Br₂; -OC₃F₅Br₂: -OC₄F₇Br₂; -OC₅F₉Br₂; -OC₆F₁₁Br₂;-OC₇F₁₃Br₂; -OC₈F₁₅Br₂; -OC₉F₁₇Br₂; -OC₁₀F₁₉Br₂;</li><li>-OCF₁I₂; -OC₂F₃I₂; -OC₃F₅I₂; -OC₄F₇I₂; -OC₅F₉I₂; -CC₆F₁₁I₂; -OC₇F₁₃I₂;-OC₈F₁₅I₂; -OC₉F₁₇I₂; -OC₁₀F₁₉I₂;</li><li>-CF₃; -C₂F₅; -C₃F₇; -C₄F₉; -C₅F₁₁; -C₆F₁₃; -C₇F₁₅; -C₈F₁₇; -C₉F₁₉; -C₁₀F₂₁;</li><li>-CF₂H; -C₂F₄H; -C₃F₆H; -C₄F₈H; -C₅F₁₀H; -C₆F₁₂H; -C₇F₁₄H; -C₈F₁₆H;-C₉F₁₈H; -C₁₀F₂₀H;</li><li>-CF₂Cl; -C₂F₄Cl; -C₃F₆Cl; -C₄F₈Cl; -C₅F₁₀Cl; -C₆F₁₂Cl; -C₇F₁₄Cl; -C₈F₁₆Cl;-C₉F₁₈Cl; -C₁₀F₂₀Cl;</li><li>-CF₂Br; -C₂F₄Br; -C₃F₆Br; -C₄F₈Br; -C₅F₁₀Br; -C₆F₁₂Br; -C₇F₁₄Br; -C₈F₁₆Br;-C₉F₁₈Br; -C₁₀F₂₀Br;</li><li>-CF₂I; -C₂F₄I; -C₃F₆I; -C₄F₈I; -C₅F₁₀I; -C₆F₁₂I; -C₇F₁₄I; -C₈F₁₆I; -C₉F₁₈I;-C₁₀F₂₀I;</li><li>-CF₁H₂; -C₂F₃H₂; -C₃F₅H₂; -C₄F₇H₂; -C₅F₉H₂; -C₆F₁₁H₂; -C₇F₁₃H₂; -C₈F₁₅H₂;-C₉F₁₇H₂; -C₁₀F₁₉H₂;</li><li>-CFCl₂; -C₂F₃Cl₂; -C₃F₅Cl₂; -C₄F₇Cl₂; -C₅F₉Cl₂; -C₆F₁₁Cl₂; -C₇F₁₃Cl₂;-C₁₈F₁₅Cl₂; -C₉F₁₇Cl₂; -C₁₀F₁₉Cl₂;</li><li>-CF₁Br₂, -C₂F₃Br₂; -C₃F₅Br₂; -C₄F₇Br₂; -C₅F₉Br₂; -C₆F₁₁Br₂; -C₇F₁₃Br₂;-C₈F₁₅Br₂; -C₉F₁₇Br₂; -C₁₀F₁₉Br₂; and</li><li>-CF₁I₂; -C₂F₃I₂; -C₃F₅I₂; -C₄F₇I₂; -C₅F₉I₂; -C₆F₁₁I₂; -C₇F₁₃I₂; -C₈F₁₅I₂; -C₉F₁₇I₂; -C₁₀F₁₉I₂.</li></ul>

0016The gas-permeable composite repells oils, water and/or water-based liquids. The gas-permeable composite may be used where a surface of the composite may come into contact with high viscosity, low surface tension liquids. The gas-permeable composite may therefore be used as a vent for receptacles (e.g. bottles) containing high viscosity liquids thereby preventing the receptacle becoming under- or over-pressurised. The vent may be located in a lid or cap of the receptacle.

0017The gas-permeable composite has the ability to repel high viscosity liquids such as industrial cleaners, detergent solutions and oils. The gas-permeable composite may be used to repel any form of hydrocarbon based liquids such as oils, lubrication oils, fuel oils, hydraulic fluids, gasoline, diesel and the like. The composite may therefore have uses in automotive applications where lubricating oil is used in vehicle engines and in gearbox transmissions or axles. The oleophobic and liquid repellent properties of the composite may also be used as a gas filter (e.g. an air filter) to prevent or least minimise air particle contamination. For example, the gas-permeable composite may be used to protect electronic components in mobile telephones, computers (such as disk drives) or automotive applications (such as sensors, motors, head lamps) or may be used in venting applications for medical equipment.

0018The gas-permeable composite may be substantially liquid-water resistant and may have a water entry pressure (WEP) higher than about 0.05 bar, 0.1 bar, 0.5 bar, 1.0 bar or 2.0 bar.

0019The gas-permeable composite may have an oil rating of greater than about 1, 2, 3, 4, 5, 6 or 7 according to AATCC Test Method 118-1989. The gas-permeable composite is therefore oleophobic.

0020The gas-permeable composite may have an air-permeability prior to any form of contact with a viscous liquid of less than about 1000 Gurley seconds, 200 Gurley seconds, 100 Gurley seconds, 50 Gurley seconds, or 30 Gurley seconds.

0021Typically, the gas-permeable composite may have a gas flow (e.g. air flow) recovery greater than about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90% as compared with the initial gas flow after exposure to a liquid for a set period of time such as about 5 seconds, 10 seconds, 30 seconds or 60 seconds. The gas flow recovery may be measured after a pre-determined waiting time such as about 1 minute, 5 minutes or 10 minutes, In particular embodiments, the gas-permeable composite may have a gas flow (e.g. air flow) recovery greater than about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90% as compared with the initial gas flow after exposure to a certain challenging test liquid such as described in an "air flow recovery test", which is described hereinafter in more detail. By exposure is meant any form of contact between the liquid (e.g. the test liquid) and a surface of the gas-permeable composite which includes inverting a liquid in a container onto a surface of the gas-permeable composite or dipping the gas-permeable composite into a liquid for a set period of time.

0022In the following, the removal of liquid from a surface is commonly designated as liquid repellency. By liquid repellency is meant the removal of liquid from a contact surface. So a vent with the ability to efficiently remove liquid from at least one of its surfaces is in the following designated as a vent with good liquid repellency properties.

0023The thickness of the gas-permeable composite may be in the region of a few micrometers to several hundreds of micrometers. For example, the composite may have a thickness of about 0.1 µm - 5000 µm, about 0.5 µm - 1000 µm, about 1 µm - 800 µm, about 5 µm - 800 µm, about 5 µm - 500 µm, about 10 µm - 800 µm, about 10 µm - 500 µm, about 50 µm - 500 µm, about 100 µm - 500 µm, about 10 µm - 100 µm, or about 10 µm - 50 µm.

0024The composite may also be attached to another or a plurality of other layers such as any appropriate backing layer to increase the mechanical integrity of the gas-permeable composite. The gas-permeable composite may therefore be formed into, for example, a laminate.

0025The coating is comprised of a combination of the first and second components forming a synergistical partnership. The first component may provide a certain degree of oleophobicity to prevent lower surface tension liquids from entering/wetting pores of the porous polymeric structure. The second component may support the liquid repellency properties of coated surfaces. The liquid repellency properties may be improved by increasing the total coating laydown thereby closing/clogging surface pores and/or smoothing an outer surface of the polymeric structure (typically the second component is a liquid, and a liquid inherently forms extremely "smooth" surfaces).

0026The ratio and amount of the first and second components may be chosen and adapted to provide an optimum combination of liquid entry pressure and liquid repellency. The liquid entry pressure is important to keep liquids out of the pores, i.e. to prevent wetting of the pores with low surface tension liquids. The liquid repellency is necessary for removal of liquid puddles/droplets or liquid films from the substrate surface. Both properties are important for air flow recovery of the vent after contact with challenging liquids.

0027It is found that although the first and second components can be chosen to give excellent liquid repellency properties, this can have a detrimental effect on the liquid entry pressure. There is therefore a balance and trade-off in selecting the first and second components to obtain acceptable values for both liquid repellency and liquid entry pressures.

0028The weight ratio between the first and second components in the formed coating may be selected from any of the following ranges: about 1 weight part of the first component to about 0.01 - 100 weight parts of the second component; from about 1 weight part of the first component to about 0.1 - 30 weight parts of the second component; from about 1 weight part of the first component to about 0.5 - 20 weight parts of the second component, from about 1 weight part of the first component to about 2 - 20 weight parts of the second component; from about 1 weight part of the first component to about 1 - 10 weight parts of the second component; from about 1 weight part of the first component to about 3 - 7 weight parts of the second component; or from about 1 weight part of the first component to about 3 - 5 weight parts of the second component.

0029The molar ratio between the first and second components in the coating may be selected from any of the following ranges: from about 1 mol part of the first component to about 0.05 - 15000 mol parts of the second component; from about 1 mol part of the first component to about 0.5 - 10000 mol parts of the second component; or from about 1 mol part of the first component to about 1 - 5000 mol parts of the second component.

0030The coating covers/encloses at least some of the structural features of the outer and inner surface of the porous polymeric structure by a thin layer thus modifying the chemical nature of the surface and by that modifying the surface energy of the porous polymeric structure to prevent ingression of liquids (e.g. organic liquids) or oils.

0031The coating may also form at least one or more or a plurality of closed and/or occluded surface portions by, for example, a thin closed and/or gas-impermeable coating layer on parts of the outer surface of the porous polymeric structure. For example, in the case of expanded PTFE the coating layer may cover the nodes and fibrils on the outer surface of the porous structure and may block and/or occlude some of the pores on the outer surface of the porous polymeric structure. By outer surface is meant the outermost surface extending around a perimeter of the porous polymeric structure which can be physically touched and which first comes into contact with a liquid to be repelled. lt is this outer surface that is important for liquid repe11el1cy. The term "outer surface" is not intended to Include the inner structure within the main body of the porous polymeric structure.

0032It was found that in case of the gas-permeable membrane with the best liquid repellency behaviour, a portion of the surface pores may be covered/occluded by the coating, thus forming bridging elements between the solid, non-porous surface regions of the membrane. Without wishing to be bound by theory, it is thought that these bridging elements are at least one reason for the improved liquid repellency behaviour and that the second component in, for example, a liquid form has a smoothing effect on the surface of the porous polymeric structure.

0033The smallest occluded surface portion may be in a size substantially equivalent to that of a pore/opening of the porous substrate. The closed and/or occluded surface portions occurring on the outer surface of the porous polymeric structure may have a size from several µm² (square-micrometers) to several hundreds of µm², and in total may comprise greater than about 1%, 2%, 5%, 7%, 10%, 20%, 30%, 50% of the outer surface.

0034The coating may also soak through the whole porous polymeric structure so that the other (uncoated) side is also rendered oleophobic.

0035The coating may penetrate (e.g. soak and/or impregnate) into the main body of the porous polymeric structure, however, it is intended that a portion of the coating remains on the outer surface of the porous polymeric structure, thus allowing the formation of closed and/or occluded surface portions.

0036The coating may both efficiently promote liquid repellency and may prevent or substantially prevent ingression of low surface tension liquids into pores of the porous polymeric structure and therefore maintain the ability to have a gas flow through the composite after contact with a viscous liquid. The coating may therefore be used to provide a vent with significantly improved liquid repellency performance and significantly improved air flow recovery.

0037The coating layer both covering the structural features and covering/occluding the surface pores may have a typical thickness in the range of about 0.001 µm to 5 µm, about 0.01 µm to 1 µm, or about 0.1 µm to 0.5 µm

0038The coating does not fully block and/or occlude the porous structure, thus the composite remains gas-permeable. The coating may be found to block and/or occlude about 0.1 - 80 %, about 0.1 - 50 %, about 0.1 - 30 %, about 0.5 - 10 %, or about 1 - 5 % of the surface pores. In particular embodiments, at least about 0.1 %, 1 %, 5 %, 10 %, 20%, 30 %, 50 % or 70 % of the surface pores may be blocked and/or occluded. The total coating weight relative to the porous polymeric structure weight range may range from about 0.1 - 1000 wt. %, about 0.1 <i>-</i> 500 wt. %, about 0.1 <i>-</i> 300 wt%, about 1 - 500 wt.%, about 1 - 200 wt%, about 1 - 100 wt.%, about 1 - 50 wt.%, about 5 - 100 wt%, about 1 - 30 wt.%, about 5 - 30 wt% or about 2 - 15 wt.%.

0039The ratio of total coating weight relative to the weight of the porous polymeric structure may be at least about 3%, 5%, 10% or 20%.

0040Typically, the coating may be deposited in a range of about 0.01 - 1000 g/m², about 0.05 - 300 g/m², about 0.1 - 800 g/m², 0.5 - 500 g/m², 0.5 - 300 g/m², about 1 - 300 g/m², about 5 - 200 g/m², about 10 - 100 g/m², about 0.1 - 100 g/m², about I - 50 g/m² or about 20 - 50 g/m². Alternatively, the coating may be deposited in a range of at least about 0.05 g/m², 0.1 g/m², 1 g/m², 10 g/m², 20 g/m², 30 g/m², 40 g/m², 80 g/m², 100 g/m², 500 g/m² or 1000 g/m².

0041Typically, the first component may have a molecular weight ranging from about 500 a.m.u. to about 10,000,000 a.m.u. or about 5000 a.m.u. to about 1,000,000 a.m.u.. Preferably, the molecular weight of the first component may range from about 10,000 a.m.u. to about 1,000,000 a.m.u..

0042The fluorine content of the first component may be at least about 1 wt. %, 5 wt.%, 10 wt.%. 20 wt.% or 40 wt.% of the molecular structure of the first component.

0043The first component comprises any fluorinated material which is both oleophobic and hydrophobic, i. e. both oil- and water-repellent. Applied as a coating on a porous substrate, the first component prevents ingression of oils and low surface tension liquids into the pores of the substrate.

0044The first component may comprise a fluorinated or perfluorinated form of an ester such as an acrylate or methacrylate. Homo- or copolymers of fluorinated acrylate or methacrylate compounds are well-known in the art. Examples for those polymers are described in "<nplcit id="ncit0001" npl-type="b"><text>Modern Fluoropolymers", edited by John Scheirs, Wiley Series in Polymer Science, John Wiley &amp;. Sons (Chichester, New York, Weinheim, Brisbane, Singapore, Toronto), 1997, Chapter 26</text></nplcit>: Fluorinated Acrylic Ester Polymers, which is incorporated herein by reference. Copolymers of fluorinated acrylates or methacrylates may comprise a range of other vinyl-monomers and are selected to adjust the required performance.

0045An example for a structural element of a fluorinated acrylic ester polymer may be as follows:         R_f-(CH₂)_m-CO₂-(CR₁₀-CH₂)_n- R₁₀ = -H, -CH₃; m = 1,2; and R_f = perfluoroalkyl.

0046The first component may also be in the form of a co- or ter-polymer of tetrafluoroethytene (TFE) with, optionally, other fluorinated or non-fluorinated monomers.

0047In particular embodiments, the first component may comprise at least one amorphous fluoropolymer, amorphous perfluoropolymer, or a combination thereof, which can be dissolved in fluorinated solvents or mixtures thereof. Commercially available amorphous perfluoropolymers are known as Teflon® AF (DuPont), Hyflon® AD (Solvay Solexis) and Cytop® (Asahi Glass).

0048Teflon AF® is a family of amorphous fluoropolymers made by DuPont and are made by the copolymerisation of 2,2-bis-trifluoromethyl-4,5-difluoro-1,3,-dioxole (PDD) with other fluorine-containing monomers. At present the commercial Teflon® AF grades are copolymers of PDD and tetrafluoroethylene (TFE) and are known as Teflon® AF1600 and Teflon® AF2400 (DuPont).

0049The chemical structure of Teflon® AF1600 and Teflon® AF2400 is as follows: <chemistry id="chem0001" num="0001"><img file="EP1985355B1_D0001.tif" /></chemistry> x/y = about 36/64 for Teflon® AF1600 (64 mol% PDD) x/y = about 17/83 for Teflon® AF2400 (83 mol% PDD)

0050Hyflon® AD (from Solvay Solexis) is a family of amorphous perfluoropolymers made by copolymerization of 2,2,4-Trifluoro-5-trifluoromethoxy-1,3-dioxole (TTD) and tetrafluoroethylene (TFE). The chemical structure of Hyflon AD®60X and Hyflon AD®80X is as follows: <chemistry id="chem0002" num="0002"><img file="EP1985355B1_D0002.tif" /></chemistry> x/y = about 40/60 for Hyflon AD®60X (about 60 mol% TTD) x/y = about 15/85 for Hyflon AD®80X (about 85 mol% TTD)

0051Cytop® is a PBVE polymer manufactured by Asahi Glass (PBVE = poly(heptafluoro-1-burene-trifluoro-vinylether)).

0052Besides the already mentioned commercially available fluoropolymers there are many others known in the art. <patcit id="pcit0004" dnum="US6248823B1"><text>US 6,248,823 B1</text></patcit> for example describes solvents for amorphous fluoropolymers such as poly(HFP/TFE), poly(TFE/PMVE) or poly(TFE/PMVE/PEVE) [HFP=hexafluoropropene; TFE=tetrafluoroethylene; PMVE=perfluoro(methyl vinyl ether); PEVE=perfluoro(ethyl vinyl ether)]. <patcit id="pcit0005" dnum="EP0633257A"><text>EP 0 633 257</text></patcit> describes amorphous homo- and co-polymers of perfluorodioxoles. <patcit id="pcit0006" dnum="US5883177A"><text>US 5,883,177</text></patcit> describes amorphous perfluoropolymers based on TTD which are dissolved in fluoro-containing solvents to obtain solutions for coatings. <patcit id="pcit0007" dnum="US5663255A"><text>US 5,663,255</text></patcit> describes novel amorphous TFE-HFP copolymers. <patcit id="pcit0008" dnum="US5919878A"><text>US 5,919,878</text></patcit> describes amorphous fluoropolymers containing PEVE. <patcit id="pcit0009" dnum="US6248823B1"><text>US 6,248,823 B1</text></patcit>, <patcit id="pcit0010" dnum="EP0633257A"><text>EP 0 633 257</text></patcit>, <patcit id="pcit0011" dnum="US5883177A"><text>US 5,883,177</text></patcit>, <patcit id="pcit0012" dnum="US5663255A"><text>US 5,663,255</text></patcit> and <patcit id="pcit0013" dnum="US5919878A"><text>US 5,919,878</text></patcit> are incorporated herein by reference.

0053The first component may also comprise hydro- and oleophobic polymers containing PFPE blocks or units respectively obtained by chemical reactions of functionalized PFPEs compounds. For example, <patcit id="pcit0014" dnum="EP1270631A1"><text>EP 1 270 631 A1</text></patcit> describes the preparation of PFPEs terminated with isocyanate groups which are reacted with hydrogenated diols to yield urethane polymers with PFPE units. <patcit id="pcit0015" dnum="EP1270631A1"><text>EP 1 270 631 A1</text></patcit> is incorporated herein by reference.

0054The above given examples for the first component should only serve as examples. In general the first component is not particularly limited as long as it comprises a fluorinated material which is both oleophobic and hydrophobic, i. e. both oil- and water-repellent.

0055Typically, the first component may be deposited in a range of about 0.01 - 1.000 g/m², about 0.05 - 500 g/m², about 0.1 - 400 g/m², about 0.5 - 300 g/m², about 1 - 200 g/m², about 5 - 100 g/m², about 10 - 500 g/m², about 5- 100 g/m², or about 20 - 40 g/m². Alternatively, the first coating may be deposited in a range of at least about 0.01 g/m², 0.1 g/m², 1 g/m², 10 g/m², 20 g/m², 40 g/m², 100 g/m², 500 g/m² or 1000 g/m².

0056The second component may comprise any form or combination of a neutral PFPE. In general PFPEs differ by the type of end groups in the molecular chain. There are PFPEs which have neutral, non-reactive end groups. These types of PFPEs are called neutral PFPEs and those are included in the present invention. They are also sometimes referred to as unpolar or non-polar PFPEs. Common terminal end groups of neutral PFPEs are -OCF₃, -OC₂F₅, and -OC₃F₇. However, neutral PFPEs may comprise also other types of non-perfluorinated end groups such as those containing H-, Cl-, Br- or I-radicals.

0057Moreover, PFPEs containing radicals such as H-, Cl-, Br-, I- or even other radicals within their backbone (i. e. not just as end groups) may still be regarded as neutral PFPEs according to the present invention, as long as they are hydrophobic. An example for a repeating unit with H-, Cl, Br, and/or I- within the backbone may be CR₁R₂CF₂CF₂O wherein R₁ and R₂ independently have the meaning of H, Cl, Br, I, or C₁-C₄ perfluoroalkyl.

0058Neutral PFPEs differ from functionalised PFPEs which may have been modified by end groups of a polar and reactive nature. These are commercially available, for example, under the trade name Fluorolink® (Solvay Solexis).

0059This invention refers to neutral PFPEs. Neutral PFPEs are thermally stable, substantially insoluble in water and most common solvents, and cannot be leached out after a coating application.

0060Commercially available PFPEs suitable for the present invention are, for example, known under the trade names Fomblin®, Galden® (both from Solvay Solexis), Krytox® (DuPont) and Demnum® (Daikin). These compounds are available in a substantially pure form, and are also sometimes supplied as a microemulsion in water, such as Fomblin FE 20C or Fomblin FE 20 EG.

0061A general description of PFPEs is found in the book "<nplcit id="ncit0002" npl-type="b"><text>Modern Fluoropolymers", edited by John Scheirs, Wiley Series in Polymer Science, John Wiley &amp; Sons (Chichester, New York, Wienheim, Brisbane, Singapore, Toronto), 1997, Chapter 24</text></nplcit>: Perfluoropolyethers (Synthesis, Characterization and Applications), which is incorporated herein by reference.

0062A description of some newer types of neutral PFPEs as received by direct fluorination are given in the book "<nplcit id="ncit0003" npl-type="b"><text>Fluoropolymers 1, Synthesis", edited by G. Hougham, P. E. Cassidy, K. Johns, T. Davidson, Kluwer Academic/Plenum Publishers (New York, Boston, Dordrecht, London, Moscow), Chapter 14.3: Perfluoropolyethers, 1999</text></nplcit>, which is incorporated herein by reference.

0063In most cases, neutral PFPEs have basic repeating units selected from any one of or combination of the following: CF₂O; CF₂CF₂O; CF(CF₃)O; CF₂CF₂CF₂O; CF₂CF(CF₃)O; and CF(CF₃) CF₂O. Some newer types of neutral PFPEs may also contain other repeating units (e. g. C(CF₃)₂O) or such with more than three carbon atoms: e. g. C₄F₈O; or C₆F₁₂O.

0064Some suitable neutral PFPE structures which are commercially available are as follows: <ul id="ul0003" list-style="none"><li>Fomblin® Y:         CF₃-[(OCF(CF₃)CF₂)_m -(OCF₂)_n-]OCF₃ where m+n = 8 to 45 and m/n = 20 to 1000</li><li>Fomblin® Z:         CF₃-[(OCF₂CF₂)_m-(OCF₂)_n-]OCF₃ where m+n = 40 to 180 and m/n = 0.5 to 2</li><li>Krytox®:         CF₃CF₂CF₂O-(CF(CF₃)CF₂O)_n-CF₂CF₃ where n = 10 to 60</li><li>Demnum®:         CF₃CF₂CF₂O-(CF₂CF₂CF₂O)_n-CF₂CF₃</li></ul>

0065A common characteristic of PFPEs is the presence of perfluoroalkyl ether moieties. PFPE is synonymous to perfluoropolyalkylether. Other synonymous terms frequently used include" "PFPE", "PFPE oil", "PFPE fluid" and "PFPAE.

0066The second component may comprise any suitable neutral PFPE available as a liquid, oil or grease which may be non-water or substantially non-water soluble.

0067The second component comprising a neutral PFPE may be a viscous liquid with viscosities ranging from about 10 mPa.s to about 1,000,000 mPa.s, about 10 mPa.s to about 10,000 mPa.s or preferably about 100 mPa.s to about 3000 mPa.s. The second component may have a viscosity greater than about 50 mPa.s, 100 mPa.s, 150 mPa.s, 200 mPa.s, 250 mPa.s or 300 mPa.s. Typically, the second component may be a viscous liquid with a viscosity greater than about 100 mPa.s.

0068The second component may have a surface tension lower than about 40 mN/m, 30 mN/m, 25 mN/m. 20 mN/m. 15 mN/m or 10 mN/m. Typically, the second component may have a surface tension lower than about 28 mN/m.

0069The second component may have a boiling point or decomposition point respectively of greater than about 150°C, 200°C, 250°C or 300°C. Typically, the second component may have a boiling point or decomposition point of greater than about 200°C.

0070The second component may have a vapour pressure at about 20°C lower than about 10^-1 mm Hg, 10^-2 mm Hg, 10^-3 mm Hg, 10^-4 mm Hg, 10^-5 mm Hg, 10^-6 mm Hg, or preferably lower than 10^-2 mm Hg.

0071Typically, the second component may have a molecular weight ranging from about 500 a.m.u. to about 500,000 a.m.u or about 1000 a.m.u. to about 100,000 a.m.u.. Preferably, the molecular weight of the second component may range from about 2,000 a.m.u to about 20,000 a.m.u.

0072The second component may have an average molecular weight of at least about 1,000 a.m.u., 10,000 a.m.u., 50,000 a.m.u. or 100,000 a.m.u.. Preferably, the second component may have an average molecular weight of at least 1,000 a.m.u..

0073Typically, the second component may be deposited in the range of about 0.01 - 1000 g/m², about 0.05 - 500 g/m², about 0.1 - 400 g/m², about 0.5 - 300 g/m², about 1 - 200 g/m², about 5 - 100 g/m², about 1.0 - 500 about 5 - 100 g/m², or about 20 - 40 g/m². Alternatively, the second component may be deposited in the range of at least about 0.01 g/m², 0.1. g/m², 1 g/m², 10 g/m², 20 g/m², 40 g/m², 100 g/m², 500 g/m² or 1000 g/m².

0074The fluorine content of the second component may be at least about 1 wt.%, 10 wt.%, 20 wt.% or 40 wt.% of the molecular structure of the second component

0075It is preferred that the second component may be substantially chemically inert, have high thermal stability, have a boiling point or decomposition point respectively greater than about 150°C or 200°C, have a low vapour pressure, have low surface tension, have oleophobic properties and have low solubility in common solvents.

0076Typically, the porous polymer structure may have passageways or continuous pores through the material. The passageways may open on both sides of the porous polymer structure allowing the structure to function as a vent.

0077The porous polymeric structure may be selected from any suitable porous structure and may be in the form of a layer with a thickness ranging from about 0.1 µm to about 5000 µm, about 1 µm to about 500 µm, or about 10 µm to about 400 µm. In particular embodiments, the porous polymeric structure may have a thickness of about 100 µm, about 200 µm or about 300 µm. In alternative embodiments where the porous polymeric structure is in the form of, for example, a tape, the thickness of the tape may range from about 10 µm to about 500 µm.

0078Typically, the porous polymeric structure may comprise one fluoropolymer or a combination of fluoropolymers. The porous polymeric structure may comprise polytetrafuoroethylene (PTFE). The porous polymeric structure may comprise one of or a combination of suitable fluoropolymers such as PTFE or polyvinylidene fluoride. Alternatively, the porous polymeric structure may also comprise non-fluorinated polymers, such as any one of or a combination of polyolefins (e.g. polyethylene, polypropylene), polyamides, polyester, polysulfone, poly(ethersulfone), polycarbonate, polyurethane and combinations thereof.

0079In particular embodiments, the porous polymeric structure may be in the form of a membrane.

0080The porous polymeric structure may be expanded in at least one direction and may therefore be uni-axial or multi-axial expanded. In a particular embodiment the porous structure may be expanded in two directions, such as in two substantially perpendicular directions, providing a bi-axial structure. The porous polymeric structure may therefore be either mono- or bi-axially expanded such as mono- or bi-axially expanded polytetrafluoroethylene.

0081The porous polymeric structure may be at least partially composed of fibrils and/or nodes.

0082In one embodiment the porous polymeric structure may be exemplified by a porous ePTFE film. The layer thickness, densities and pore-size of the ePTFE layer used can vary, depending on the application.

0083Typically, an ePTFE vent may have a thickness in the range of about 5 µm to about 500 µm, a density in the range of about 0.4 to about 1.5 g/cm³ and an average pore size in the range of about 0.05 to about 10 µm. Preferred embodiments may have a thickness of about 30 µm to about 350 µm, a density in the range of about 0.5 to about 1.5 g/cm³, and an average pore size of about 0.1 µm to about 5 µm.

0084A particular preferred substrate is a porous PTFE made by stretching PTFE tape or film as described in <patcit id="pcit0016" dnum="US3953566A"><text>US 3,953,566</text></patcit>, which is incorporated herein by reference. In this procedure, the structure comprises an interconnected network of nodes and fibrils interconnecting the nodes, the nodes and fibrils comprising the internal structure that defines the pores.

0085The porous polymeric layer may be an ePTFE membrane such as described in <patcit id="pcit0017" dnum="US3953566A"><text>US 3,953,566</text></patcit>, which is incorporated herein by reference.

0086In particular embodiments, the gas-permeable composite may comprise an ePTFE layer coated with a solution of, for example, about 0.5 wt.% - 2 wt.% Teflon® AF (e.g. Teflon® AF 1600) and about 1 wt.% - 20 wt.% PFPE in an appropriate solvent such as an organic fluorinated solvent. In further embodiments, the gas-permeable composite may comprise an already oleophobic treated membrane, which has an additional PFPE coating deposited thereon in a second coating step with, for example, a coating solution concentration of the PFPE in the range of about 1 wt.% - 10 wt.%.

0087According to a second aspect, there is provided a gas-permeable composite comprising: <ol id="ol0002" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and second component;</li><li>(d) said first component comprising oleophobic and hydrophobic fluorinated material; and</li><li>(e) said second component comprising a block copolymer, said block-copolymer comprising a PFPE backbone.</li></ol>

0088The block copolymer may be in the form of an A-B or an A-B-A block copolymer wherein either of the A or B units may be PFPE based such as non-polar PFPE or neutral PFPE. The PFPE may comprise repeating units such as any one of or combination of the following: CF₂O; CF₂CF₂O; CF(CF₃)O; CF₂CF₂CF₂O; CF₂CF(CF₃)O; CF(CF₃)CF₂O; -(C(CF₃) ₂O)-; -CF₂CF₂CF₂CF₂O-; -(C₄F₈O)- or-(C₆F₁₂O)-.

0089The PFPE forming the backbone of the copolymer is covalently linked to a non-PFPE block such as any suitable hydrocarbon based block. The hydrocarbon based block may be selected from any polyolefin (such as polyethylene, polypropylene), polyester, polyurethane, polyamide or any other suitable polymeric forming components.

0090An example with a block-copolymer comprising PFPE- and poly(έ-caprolactone)-blocks is described in <nplcit id="ncit0004" npl-type="s"><text>Polymer 42 (2001) 1771-1779 (M. Toselli</text></nplcit>, et al.) which is incorporated herein by reference.

0091According to a third aspect, there is provided a gas-permeable composite comprising: <ol id="ol0003" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and second component;</li><li>(d) said first component comprising oleophobic and hydrophobic fluorinated material; and</li><li>(e) said second component comprising a neutral perfluoropolyether (PFPE).</li></ol>

0092In most cases, neutral PFPEs have basic repeating units selected from any one of or combination of the following: CF₂O; CF₂CF₂O; CF(CF₃)O; CF₂CF₂CF₂O; CF₂CF(CF₃)O; and CF(CF₃) CF₂O. Some newer types of neutral PFPEs may also contain other repeating units (e. g. C(CF₃)₂O) or such with more than three carbon atoms: e. g. C₄F₈O; or C₆F₁₂O,

0093According to a fourth aspect, there is provided a gas-permeable composite comprising: <ol id="ol0004" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and second component;</li><li>(d) said first component comprising oleophobic and hydrophobic fluorinated material; and</li><li>(e) said second component comprising a hydrophobic fluorinated liquid.</li></ol>

0094According to a fifth aspect, there is a provided a method of forming a gas-permeable composite, said method comprising: <ol id="ol0005" compact="compact"><li>(a) providing a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface</li><li>(b) providing a coating on at least a portion of said outer surface of said porous polymeric structure, wherein said coating comprises at least a first and second component, wherein said first material comprises an oleophobic and hydrophobic fluorinated material and said second component comprises a perfluoropolyether (PFPE), said PFPE comprising end-groups selected from the following:         -(O)_n - (CR₁R₂)_m - CR₃R₄R₅</li></ol> wherein: <ul id="ul0004" list-style="none" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H, F, Cl Br or I;</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or 1; and</li><li>m = 0 - 10.</li></ul>

0095According to a sixth aspect, there is a provided a method of forming a gas-permeable composite, said method comprising; <ul id="ul0005" list-style="none" compact="compact"><li>(a) providing a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(e) providing a coating on at least a portion of said outer surface of said porous polymeric structure, wherein said coating comprises at least a first and second component, wherein said first material comprises an oleophobic and hydrophobic fluorinated material and said second component comprises a block copolymer, said block-copolymer comprising a PFPE backbone.</li></ul>

0096The method comprises forming a coating which may be obtained by dissolving together both the first and second components in an appropriate solvent to form a coating solution and then depositing this coating solution onto at least part of the outer surface of the porous polymeric structure using any suitable technique. The first and second components may form a coating solution in any appropriate concentration such as about 0.1 - 50 wt.%, about 0.5 - 30 wt.%, or about 1 - 10 wt.%.

0097Typically, an organic solvent such as a fluorinated or perfluorinated organic solvent may be used to dissolve the first and second components. The solvent may be a low molecular weight C₁ - C₂₀ or C₂ - C₁₀ fluorinated or perfluorinated solvent. Suitable solvents are available under the tradename 3M^™ Fluorinert^™ Liquids, 3M^™ Performance Fluids or 3M^™ Novec^™ Fluids. The solvent is intended to evaporate off leaving behind the first and second components to form the coating. The boiling point of the solvent may be below about 150°C, 100°C or 70°C.

0098Any suitable form of deposition technique may be used to form the coating such as a roller coating process, dipping, spray coating, brush coating, print coating, spin coating, depositing with a dropper such as a pipette, and the like. In alternative embodiments, either the first or second component may initially be deposited in a first step at least onto the outer surface of the porous polymeric structure and thereafter in a second step the remaining of either the first or second component deposited.

0099In particular embodiments, the porous polymeric structure may have an initial oleophobic and hydrophobic coating formed from the first component. The second component dissolved in solvent may then be added on top of the oleophobic and hydrophobic coating. Depending on the compatibility of both components, the components may then either at least partially dissolve into each other, or may stay separated. For each of the two separate coating steps, any suitable form of deposition technique may be used such as a roller coating process, dipping, spray coating, brush coating, print coating, spin coating, depositing with a dropper such as a pipette, and the like. The first component comprising oleophobic and hydrophobic fluorinated material may further be deposited by a plasma deposition coating step or another coating step out of the gas phase.

0100The first component may at least partially dissolve in the second component. It should also be noted that there may also be more than a two-component system, other than the solvent. The first component may at least partially dissolve in the second component, especially when a high weight ratio of the first to the second component such as about 1 : 10 (i.e. in excess of the second component) is used. This can, for example, be the case for the aforementioned amorphous perfluoropolymers (as first component) and neutral PFPEs as second component.

0101On addition of the first component to the second component, the first and second components may simply mix with each other to form an admixture whereupon there is no chemical reaction or substantially no chemical reaction between the two components.

0102In certain embodiments, the first component may also be regarded as swollen by the second component rather than dissolved.

0103It is also found that by coating with a mixture of said first and second components prevents total clogging of the pores. Total clogging of the pores of a porous structure can be an issue when a high concentration of a high molecular weight polymer such as Teflon® AF in a coating solution is used. Surprisingly, in the present invention it was found that although using a high overall concentration of said first and second components in the coating solution, total clogging of the pores does not happen. Although not wishing to be bound by theory, it is thought total clogging of the pores is avoided because of the low molecular weight range of the oils (e.g. a molecular weight of a few thousand grams/mol, more oligomers than polymers) used as the second component. This surprising finding has significant advantages in that some previously known oleophobic materials are extremely expensive (e.g. Teflon® AF1600) and these expensive materials can now be mixed with much less expensive materials such as fluorinated PFPE oils to provide significant technical advantages such as improved liquid repellency and avoidance of total clogging of the pores.

0104The first component prior to forming the coating may be in a solid and/or amorphous form and may comprise any suitable fluorinated or per-fluorinated oleophobic and hydrophobic oligomer and/or polymer, or combination thereof. The first component may exist as a solid at, for example, about 20 °C and about 1 bar.

0105The second component prior to forming the coating is typically in a liquid form and may comprise any neutral PFPE.

0106According to a seventh aspect, there is provided a venting apparatus having an opening for venting gas from an enclosure or receptacle, said venting apparatus comprising: <ul id="ul0006" list-style="none" compact="compact"><li>a porous gas-permeable composite venting element located within, outside or on said venting apparatus and forming a liquid-tight seal for said opening, said porous gas-permeable composite venting element comprising: <ol id="ol0006" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and a second component</li><li>(d) said first component comprising an oleophobic and hydrophobic fluorinated material; and</li><li>(e) said second component comprising a perfluoropolyether (PFPE), said PFPE comprising end-groups selected from the following:         -(O)_n - (CR₁R₂)_m - CR₃R₄R₅</li></ol></li></ul> wherein: <ol id="ol0007" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H, F, Cl, Br or I;</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or 1; and</li><li>m = 0 - 10.</li></ol>

0107According to an eighth aspect there is provided a venting apparatus having an opening for venting gas from an enclosure or receptacle, said venting apparatus comprising: <ul id="ul0007" list-style="none" compact="compact"><li>a porous gas-permeable composite venting element located within, outside or on said venting apparatus and forming a liquid-tight seal for said opening, said porous gas-permeable composite venting element comprising: <ol id="ol0008" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and a second component</li><li>(d) said first component comprising an oleophobic and hydrophobic fluorinated material; and</li><li>(e) said second component comprising a block copolymer, said block-copolymer comprising a PFPE backbone.</li></ol></li></ul>

0108The venting apparatus may be used as a vent for receptacles (e.g. bottles) containing liquids. The vent may be located in a lid or cap of the receptacle.

0109Additionally, the venting apparatus may be used in automotive applications where lubricating oil is used in vehicle engines and in gearbox transmissions or axles.

0110In further applications, the venting apparatus may be used to protect electronic components in mobile telephones, computers (such as disk drives) or automotive applications (such as sensors, motors, head lamps), or may be used in venting applications for medical equipment.

0111According to a ninth aspect, there is provided a method of venting gas from an enclosure or receptacle, said method comprising: <ul id="ul0008" list-style="none" compact="compact"><li>providing a porous gas-permeable composite element within, outside or on a venting apparatus and forming a liquid-tight seal for an opening on said venting apparatus, said porous gas-permeable composite venting element comprising: <ol id="ol0009" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and a second component</li><li>(d) said first component comprising an oleophobic and hydrophobic Fluorinated material; and</li><li>(e) said second component comprising a perfluoropolyether (PFPE), said PFPE comprising end-groups selected from the following:         -(O)_n - (CR₁R₂)_m - CR₃R₄R₅</li></ol></li></ul> wherein: <ul id="ul0009" list-style="none" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H, F, Cl, Br or I;</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or 1; and</li><li>m = 0 - 10.</li></ul>

0112According to a tenth aspect, there is provided a method of venting gas from an enclosure or receptacle, said method comprising: <ul id="ul0010" list-style="none" compact="compact"><li>providing a porous gas-permeable composite element within, outside or on a venting apparatus and forming a liquid-tight seal for an opening on said venting apparatus, said porous gas-permeable composite venting element comprising: <ol id="ol0010" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and a second component</li><li>(d) said first component comprising an oleophobic and hydrophobic fluorinated material; and</li><li>(e) said second component comprising a block copolymer, said block-copolymer comprising a PFPE backbone.</li></ol></li></ul>

0113The method includes venting or filtering gas from any of the following: receptacles (e.g. bottles) containing high viscosity liquids; in automotive applications where lubricating oil is used in vehicle engines and in gearbox transmissions or axles; protecting electronic components in mobile telephones, computers (such as disk drives) or automotive applications (such as sensors, motors, head lamps); and in medical equipment applications.

0114According to a eleventh aspect, there is provided a gas-permeable composite comprising: <ol id="ol0011" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and second component;</li><li>(d) said first component comprising an oleophobic and hydrophobic fluorinated material;</li><li>(e) said second component comprising a perfluoropolyether (PFPE), said PFPE comprising end-groups selected from the following:         -(O)_n - (CR₁R₂)_m - CR₃R₄R₅</li></ol> wherein: <ul id="ul0011" list-style="none" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H, F, Cl, Br or I;</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or I; and</li><li>m = 0- 10;</li></ul> wherein the gas-permeable composite has a gas flow recovery (compared with the initial/original gas flow) greater than about 5% after exposure to a viscous liquid having a viscosity greater than about 10 mPa.s and a surface tension lower than about 35 mN/m at about 25°C.

0115According to a twelfth aspect, there is provided a gas-permeable composite comprising: <ol id="ol0012" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and second component;</li><li>(d) said first component comprising an oleophobic and hydrophobic fluorinated material;</li><li>(e) said second component comprising a block copolymer, said block-copolymer comprising a PFPE backbone;</li></ol> wherein the gas-permeable composite has a gas flow recovery (compared with the initial/original gas flow) greater than about 5% after exposure to a viscous liquid having a viscosity greater than about 10 mPa.s and a surface tension lower than about 35 mN/m at about 25°C.

0116Typically, the gas-permeable composite may have a gas flow recovery greater than about 5% after exposure to a viscous liquid having a viscosity in the range 10 mPa.s - 50 m.Pa.s and a surface tension higher than about 27 mN/m at about 25°C.

0117According to a thirteenth aspect, there is provided a gas-permeable composite comprising: <ol id="ol0013" compact="compact"><li>(a) a layer of a porous PTFE structure with an inner and outer surface and having passageways through the structure;</li><li>(b) the porous structure comprising a coating on at least a portion of said outer surface:</li><li>(c) said coating comprising at least a first and second component:</li><li>(d) said first component comprising at least one oleophobic and hydrophobic fluoropolymer that imparts to the composite an oil rating of at least 3;</li><li>(e) said second component comprising a perfluoropolyether (PFPE), said PFPE comprising end-groups selected from the following:         -(O)_n-(CR₁R₂)_m-CR₃R₄R₅</li></ol> wherein: <ul id="ul0012" list-style="none" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H, F, Cl, Br or I;</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or 1; and</li><li>m = 0 - 10;</li></ul> wherein the gas-permeable composite has a gas flow recovery greater than about 5% after exposure to a viscous liquid having a viscosity at about 25 °C greater than about 10 mPa.s and a surface tension at about 25 °C lower than about 35 mN/m.

0118According to a fourteenth aspect, there is provided a gas-permeable composite comprising: <ol id="ol0014" compact="compact"><li>(a) a layer of a porous PTFE structure with an inner and outer surface and having passageways through the structure;</li><li>(b) the porous structure comprising a coating on at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and second component;</li><li>(d) said first component comprising at least one oleophobic and hydrophobic fluoropolymer that imparts to the composite an oil rating of at least 3;</li><li>(e) said second component comprising a block copolymer, said block-copolymer comprising a PFPE backbone;</li></ol> wherein the gas-permeable composite has a gas flow recovery (compared with the initial/original gas flow) greater than about 5% after exposure to a viscous liquid having a viscosity greater than about 10 mPa.s and a surface tension lower than about 35 mN/m at about 25°C.

0119According to a fifteenth aspect, there is provided a gas-permeable composite obtainable by: <ol id="ol0015" compact="compact"><li>(a) providing a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) coating at least a portion of said outer surface of the porous polymeric structure with a first and second component;</li><li>(c) said first component comprising an oleophobic and hydrophobic fluorinated material; and</li><li>(d) said second component comprising a perfluoropolyether (PFPE), said PFPE comprising end-groups selected from the following:         -(O)_n-(CR₁R₂)_m-CR₃R₄R₅</li></ol> wherein: <ul id="ul0013" list-style="none" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H, F, Cl, Br or I;</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or 1: and</li><li>m = 0-10.</li></ul>

0120According to a sixteenth aspect, there is provided a gas-permeable composite obtainable by: <ol id="ol0016" compact="compact"><li>(a) providing a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) coating at least a portion of said outer surface of the porous polymeric structure with a first and second component;</li><li>(c) said first component comprising an oleophobic and hydrophobic fluorinated material; and</li><li>(d) said second component comprising a block copolymer, said block-copolymer comprising a PFPE backbone.</li></ol>

0121According to a seventeenth aspect, there is provided use of a gas-permeable composite in a vent or gas filter, said gas-permeable composite comprising: <ol id="ol0017" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and second component;</li><li>(d) said first component comprising an oleophobic and hydrophobic fluorinated material; and</li><li>(e) said second component comprising a perfluoropolyether (PFPE), said PFPE comprising end-groups selected from the following:         -(O)_n - (CR₁R₂)_m - CR₃R₄R₅</li></ol> wherein: <ul id="ul0014" list-style="none" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H, F, Cl, Br or I;</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or 1; and</li><li>m=0-10.</li></ul>

0122According to an eighteenth aspect, there is provided use of a gas-permeable composite in a vent or gas filter, said gas-permeable composite comprising: <ol id="ol0018" compact="compact"><li>(a) a porous polymeric structure having a structure defining a plurality of pores extending therethrough and with at least one outer surface;</li><li>(b) a coating covering at least a portion of said outer surface;</li><li>(c) said coating comprising at least a first and second component;</li><li>(d) said first component comprising an oleophobic and hydrophobic fluorinated material; and</li><li>(e) said second component comprising a block copolymer, said block-copolymer comprising a PFPE backbone.</li></ol>

0123According to a ninteenth aspect, there is provided a gas-permeable composite comprising: <ol id="ol0019" compact="compact"><li>(a) a layer of a porous expanded PTFE structure with an inner and outer surface and having passageways through the structure;</li><li>(b) the microporous structure comprising a coating on at least a portion of said outer surface:</li><li>(c) said coating comprising at least a first and second component;</li><li>(d) said first component comprising at least one of or a combination of oleophobic and hydrophobic amorphous fluoropolymers/perfluorpolymers; and</li><li>(e) said second component comprising a perfluoropolyether (PFPE), said PFPE comprising end-groups selected from the following:         -(O)_n - (CR₁R₂)_m - CR₃R₄R₅</li></ol> wherein: <ul id="ul0015" list-style="none" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H. F, Cl, Br or I:</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or 1; and</li><li>m=0-10.</li></ul>

0124According to a twentieth aspect, there is provided a gas-permeable composite comprising: <ol id="ol0020" compact="compact"><li>(a) a layer of a porous expanded PTFE structure with an inner and outer surface and having passageways through the structure;</li><li>(b) the microporous structure comprising a coating on at least a portion of said outer surface;</li><li>(c) said coating having at least a first and second component;</li><li>(d) said first component comprising at least one of or a combination of oleophobic and hydrophobic amorphous fluoropolymers/perfluoropolymers; and</li><li>(e) said second component comprising a block copolymer, said block-copolymer comprising a PFPE backbone.</li></ol>

BRIEF DESCRIPTION OF THE DRAWINGS

0125Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: <ul id="ul0016" list-style="none" compact="compact"><li><figref idref="f0001">Figure 1</figref> is a representation of venting apparatus according to an embodiment of the present invention;</li><li><figref idref="f0002">Figure 2</figref> is a schematic top view of a coated porous PTFE structure;</li><li><figref idref="f0003">Figures 3A - 3C</figref> are representations of apparatus and a procedure used for conducting an air flow recovery test;</li><li><figref idref="f0003">Figure 4</figref> is an expanded view of part of the apparatus shown in <figref idref="f0003">Figure 3A</figref>;</li><li><figref idref="f0004">Figure 5</figref> is a representation of apparatus and a procedure used for conducting a vertical immersion test referred to as a "liquid repellency test";</li><li><figref idref="f0005">Figures 6A and 6B</figref> are representations of test liquid residing on four different test samples 1 - 4 at t = 0 sec and t = 15 sec, respectively;</li><li><figref idref="f0006">Figures 7A and 7B</figref> are expanded views of sample 3 as shown in <figref idref="f0005">Figures 6A and 6B</figref> at t = 0 sec and t = 15 sec, respectively;</li><li><figref idref="f0007">Figure 8</figref> is a representation of coating apparatus used to form a gas-permeable composite;</li><li><figref idref="f0008 f0009">Figures 9 - 10</figref> are SEM surface images at different scales of magnification of a gas-permeable composite which was coated by a solution of 1 wt.% Teflon® AF1600 in a fluorinated solvent;</li><li><figref idref="f0010 f0011 f0012">Figures 11 - 13</figref> are SEM images at different scales of magnification of an air-permeable composite which was coated by a solution of 1 wt.% Teflon® AF1600 and 10 wt.% PFPE in a fluorinated solvent;</li><li><figref idref="f0013">Figure 14</figref> is a graph showing the percentage of area covered by test liquid vs. time for gas-permeable composites;</li><li><figref idref="f0014">Figure 15</figref> is a graph showing the percentage of air flow recovery and liquid entry pressure vs. wt.% PFPE in a coating solution for gas-permeable composites;</li><li><figref idref="f0015">Figure 16</figref> is a graph showing the percentage of air flow recovery vs. wt.% PFPE in a coating solution for gas-permeable composites;</li><li><figref idref="f0016">Figure 17</figref> is a graph showing the percentage of area covered with a test liquid vs. time for gas-permeable composites;</li><li><figref idref="f0017">Figure 18</figref> is a graph showing the percentage of air flow recovery and liquid entry pressure vs. wt.% PFPE in a coating solution for gas-permeable composites;</li><li><figref idref="f0018">Figure 19</figref> is a graph showing the percentage of area covered by a liquid vs. time for gas-permeable composites;</li><li><figref idref="f0019">Figure 20</figref> compares SEM images of two samples, the first coated with a solution of 1 wt.% Teflon® AF1600 in a fluorinated solvent (left image), and the second coated with a mixture of 1 wt.% Teflon® AF1600 and 10 wt.% PFPE in a fluorinated solvent (right image); and</li><li><figref idref="f0020 f0021">Figures 21- 22</figref> are SEM images at different scales of magnification of an air-permeable composite which was coated by a solution of 1 wt.% Teflon® AF1600 in a fluorinated solvent; and</li><li><figref idref="f0022 f0023">Figures 23 - 24</figref> are SEM images at different scales of magnification of an air-permeable compositewhich was coated by a solution of 1 wt.% Teflon® AP1600 and 4 wt.% PFPE in a fluorinated solvent.</li></ul>

DETAILED DESCRIPTION OF THE INVENTION

0126<figref idref="f0001">Figure 1</figref> is one possible representation of apparatus according to the present invention, generally designated 100. The apparatus 100 comprises a lid 102 containing a gas-permeable vent 104 (e.g. an air-permeable vent). The gas-permeable vent 104 is centrally located in the lid 102 and permits gas flow 110 through the vent 104. Although not shown, it is not necessary for the gas-permeable vent 104 to be centrally located on the lid 102. The lid 102 is secured to a container 106 via a screwthread. The container 106 contains a viscous, low surface tension liquid 108. The container 106 may be used as a receptacle for any type of liquid. As shown in <figref idref="f0001">Figure 1</figref>, any viscous liquid 109 contacting the gas-permeable vent 104 is repelled. The lid 102 and gas permeable vent 104 contained therein, form a liquid-tight, gas permeable seal for the container 106.

0127<figref idref="f0002">Figure 2</figref> is a schematic top view of a uni-axially expanded PTFE structure generally designated 200 which may form an outer surface of a porous composite. The PTFE structure 200 is made up of nodes 210 and fibrils 212, with pores 214 located between the fibrils 212. There is a coating layer 216 (represented by shading) on the surface of the fibrils 212, between some of the fibrils 212, and on top of the nodes 210. The coating layer 216 is a combination of a first component comprising oleophobic and hydrophobic fluorinated material and a second component. The second comprises PFPE, said PFPE comprising end-groups selected from the following:         -(O)_n - (CR₁R₂)_m - CR₃R₄R₅ wherein: <ul id="ul0017" list-style="none" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H, F, Cl, Br or I;</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or I; and</li><li>m = 0- 10.</li></ul> Alternatively, the second component is a block copolymer comprising a PFPE backbone.

0128The coating layer 216 covers/fills at least partially some of the pores 214 made up by the space between the fibrils 212. The coating layer 216 may cover/fill at least part of the pores 214 on the outermost surface of the PTFE structure 200 but may also partially penetrate/impregnate into the main body of the PTFE structure 200. The coating layer 216 therefore covers/coats the nodes 210 and fibrils 212 on the outer surface of the PTFE structure 200 and may block and/or occlude some of the surface pores 214 of the PTFE structure 200.

DEFINITION OF TERMS

0129By "gals-permeable composite" is meant a porous material that permits bulk flow of air or other gases through it. This is in contrast to non-porous materials in which gas permeation is controlled by diffusion mechanisms.

0130By "oleophobic (coating) component/material" is meant a material which repells oils. Typically these materials are fluorinated and exhibit surface energies lower than about 26 mN/m, preferred lower than about 24 mN/m, most preferred lower than about 20 mN/m.

0131By "oleophobic substrate/composite/membrane" is meant a porous article with an AATCC Test Method 118-1989 oil rating of at least 1. This means that the gas-permeable substrate/composite/membrane has a degree of repellency towards oils and/or low surface tension liquids.

0132By "hydrophobic (coating) component" is meant a material which repells water. Typically these materials are substantially insoluble in water and exhibit contact angles with water greater than about 60°, preferred greater than about 90°.

0133By "solid" is meant a state of matter which can support loads, has a definite shape and volume, and whose constituent elements have a substantially fixed position in space relative to each other which accounts for a degree of rigidity.

0134By "liquid" is meant a state of matter that has the ability to flow under the action of extremely small shear stresses and to conform to the shape of a confining vessel. The term "liquid" also includes all forms of oils and greases.

0135By "liquid tight seal" is meant a seal which can withstand a water entry pressure of at least about 0.03 bar without leakage.

0136By "outer surface" is meant the outermost surface extending around an outer external perimeter of the porous polymeric structure which can be physically touched and which first comes into contact with a liquid to be repelled. It is this outer surface that is important for liquid repellency. The "outer surface" is not intended to include the inner structure within the main body of the porous polymeric structure.

0137By "coating" is meant a material covering surfaces on the "outer surface" of the porous polymeric structure and the inner structure within the main body of the porous polymeric structure. The coating may form at least one or more or a plurality of closed and/or occluded surface portions by, for example, regions of a closed and/or gas-impermeable coating layer.

0138By "fluorinated material" is meant a material with a fluorine content of at least 1 wt.%.

0139By "neutral PFPE" is meant a perfluoropolyether with neutral or non-reactive end groups. These are also sometimes referred to as unpolar or non-polar PFPEs. Neutral PFPEs differ from the functionalized PFPEs which contain reactive end groups. Common terminal end groups of neutral PFPEs are -OCF₃, -OC₂F₅, and-OC₃F₇. However, there may be also other types of non-perfluorinated end groups such as those containing H- ,Cl- Br- or I-radicals. Examples for non-pertluorinated end groups of neutral PFPEs comprise structures such as -CF₂R (R= H, Cl, Br or I) or -CFR-CF₃ (R= H, Cl, Br or I). Also PFPEs containing radicals such as H-, Cl-, I- or Br- or even other radicals within their backbone (i. e. not just as end groups) may still be regarded as neutral PFPEs according to the present invention, as long as they are hydrophobic.

0140By "porous" is meant material that allow passage of gases, especially air. These include materials that comprise pores and voids that form passageways extending through the thickness of a material. Such materials may have very small, microscopic voids throughout an internal structure which form an interconnected continuous air path (passageway) from one surface to another. The passageways open on sides of the material and may be interconnected internally by, for example, fibrils and nodes.

0141By "polymer structure" is meant any form of dimer, trimer, other forms of higher adducts, co-polymers, block co-polymers, ter-polymers, branched polymers, cross-linked polymers, low molecular weight polymers or high molecular weight polymers. A "polymer structure" may be formed by a polymerisation reaction such as a radical polymerisation, a condensation or addition type reaction and may have repeat structural units and/or monomers connected by covalent bonds.

0142By "oligomer" is meant a relatively small number of monomer units such as less than about 100 monomer units or less than about 30 monomer units.

0143By "component" is meant a chemical molecule, compound and/or composition which is used as one of the ingredients to form the coating.

Definition of the Term "Liquid Repellency"

0144The term "liquid repellency" is used as a generic term for the ability of a surface to repel or remove liquids from a surface when forces such as gravity or surface tension work. The term is used irrespective of the exact mechanism how the liquid is repelled or leaves the surface. It implies the contraction of liquids on a surface to droplets, but also formation of a liquid film on the surface which contracts and/or slides down, or any other suitable mechanism.

0145There was the need to come up with a test method which quantifies the liquid repellency property of a porous substrate. The test method used is described below.

TEST DESCRIPTIONS

Oil Rating

0146The oil rating was determined using the AATCC Test Method 118-1989. The higher the rating, the better the oil repellency/resistance. A value of greater than 1, more preferably 4, or higher is preferred. The oil rating was determined on the side where the coating solution was applied or on the side that was directed towards the coating solution bath, respectively.

Water Entry Pressure

0147Water entry pressure (WEP) provides a test method for water intrusion through membranes. A test sample is clamped between a pair of testing plates. The lower plate has the ability to pressurise a section of the sample with water. A piece of pH paper is placed on top of the sample between the plate on the non-pressurized side as an indicator of evidence for water entry. The sample is then pressurized with a rate of 1 bar/100 seconds until the pH paper gets wet which is the first sign of water entry. The water pressure at breakthrough is recorded as the WEP.

Liquid Entry Pressure

0148The same test method as described for the measurement of the water entry pressure was used, only water replaced by another liquid. In all measurements, a liquid composed of 68 wt.% water, 30 wt.% of 2-Propanol (Isopropanol, 99%) and 2 wt.% sodium dodecylsulfate (SDS) was used as test liquid. A surface tension of 26.5 mN/m and a viscosity of 2.5 mPa.s (at a shear rate of 50 sec^-1) were measured at a temperature of 25°C for this test liquid. (This test liquid was used as an approximation to standard liquid cleaners).

Gurley Air Flow Data

0149The Gurley air flow test measures the time in seconds for 100 cc of air to flow through a one square inch sample at 4.88 inches of water pressure. A sample is measured in a Gurley Densometer Model 4110 (ASTM 0726-58). The sample is placed between the clamp plates. The cylinder is then dropped gently. The automatic timer (or stopwatch) is used to record the time (seconds) required for a specific volume recited above to be displaced by the cylinder. This time is the Gurley number.

Pore size

0150Pore size is determined using a standard PMI Porometer, Model CFP-1500 AEXL. A silicone fluid is used for wetting of the pores (Silicones for personal care, 200 10 cst, from Dow Corning). The determined mean flow pore size is given as the pore size of the substrates used in the description of the examples.

Surface Tension Measurement

0151Surface tension of the challenge fluid was measured with a Krüss K-12 tensiometer, using a Krüss K12 hardware using the Wilhelmy plate method. Wilhelmy plate immersions were conducted with flamed Krüss standard platinum plate and the software default parameters. All given surface tensions refer to a temperature of 25°C.

Viscosity Measurements

0152The viscosity of the reference liquids is determined by a Haake rheometer, model RheoStress 1. A plate /cone arrangement (cone designation C35/2 Ti) was used for all the measurements. All given viscosity data refer to a temperature of 25°C and a shear rate of 50 sec.^-1.

Determination of Coating Laydown

0153The total coating laydown was determined by hot solvent extraction. For these measurements, 25 mm diameter discs of all samples were weighted before and after hot solvent extraction. From the weight difference of those samples the coating laydown was determined.

0154The samples were extracted for several days first with hot perfluorinated solvent FC-77 (from 3M company), afterwards with hot fluorinated solvent HFE-7500 (from 3M company) until no more weight loss of the samples was detected.

Air Flow Recovery Test

0155<figref idref="f0003">Figures 3A - 3C</figref> represent the air flow recovery test. <figref idref="f0003">Figure 3A</figref> is a schematic representation of the air-flow recovery test apparatus, generally designated 300. The air-flow recovery test apparatus 300 comprises a cylindrical container 302 with a diameter of 80 mm which may be used to retain a volume of 100 ml of test liquid 304. As test liquid, a water based liquid composed of 3 wt.% Polyvinylpyrrolidone (from Aldrich Company, Art. No. 437190, mean molecular weight of 1300000 as determined by LS (Light Scattering)), 3 wt.% of the silicone surfactant Tegoprene® 5847 (wetting agent from Goldschmidt AG), and 94 wt.% deionised water was used. A surface tension of 23 mN/m and a viscosity of 13.7 mPa.s (measured at a shear rate of 50 sec^-1) were determined for the test liquid at a temperature of 25°C. The test liquid must always be freshly prepared on the day of the measurement. This test liquid was used for the characterisation of all samples and in the following, all air flow data after performing air-flow recovery test always refer to this test liquid unless otherwise stated.

0156A second test liquid, a viscous oil was used for three samples only (Examples 1 , 4 and 5) to demonstrate the ability of surfaces to repel oils. The designation of this oil was "Castrol Transmax Z" (automatic transmission fluid from Deutsche Castrol VertriebsgeseHschaft mbH. Hamburg). A surface tension of 29.5 mN/m and a viscosity of 59.7 mPa.s (measured at a shear rate of 50 sec^-1) was determined at 25°C.

0157As shown in <figref idref="f0003">Figure 3A</figref>, there is an adapter 306 through which air may enter into the container 302 for measurement of the initial air flow and residual air flow after liquid contact. Both air flows are measured at a pressure of 1.2 mbar (i.e. at an overpressure of 12 mbar compared with the surrounding pressure) yielding the air flow in the units norm/standard-liters/hour/cm². All air now data regarding air flow recovery test hereinafter referred to are therefore in the units of standard liters/hour/cm² measured at a pressure of 12 mbar.

0158The membrane being tested is located at the top end 308 of the container 302. <figref idref="f0003">Figure 4</figref> is an expanded view of the top end 308 of the container 302 which shows a microporous test sample 310 extending across a neck 302a of the container 302. The material the container 302 and the neck 302a were constructed of was polycarbonate (Makrolon®).

0159The radius of the neck 302a rounding was 1 mm. The microporous test sample 310 is secured in place using a seating ring 312 and a counter-pressure plate 314. A substantially circular 20mm diameter section of the microporous test sample is exposed to the test liquid 304. In the event that a sample to be tested has a smaller diameter, then an adaptor plate may be used to seal and locate the test sample or vent construction, respectively, within the perimeter of the neck 302a. A simple calculation can then be used to scale the obtained results for these smaller types of microporous test samples. Smaller samples may therefore be measured with this apparatus.

0160To perform the air flow recovery test, the container 302 as shown in <figref idref="f0003">Figure 3B</figref> is inverted so that the test liquid 304 contacts the microporous test sample 310 for 5 seconds. The height of the liquid column over the test sample is 2 cm. As shown in <figref idref="f0003">Figure 3C</figref>, the container 302 is then returned to its original position whereupon the residual air flow was measured after a waiting time of exactly 5 minutes. The air flow recovery test is performed at room temperature.

0161The percent air flow recovery of a porous test sample was determined by the following formula: (residual air flow / initial air flow)*100. Both air flows were determined as described in the air flow recovery test.

Liquid Repellency Test

0162<figref idref="f0004">Figure 5</figref> is a representation of apparatus 400 used to perform a liquid repellency test.

0163One side of a glass slide 402 (3.4 cm x 8 cm) is provided with a double-sided adhesive tape 404 onto which a sample of the microporous substrate 406 to be tested is fixed.

0164To perform the liquid repellency test, the glass slide 402 with the fixed porous substrate 406 is vertically immersed into a bath 408 containing test liquid 410 for about 1 - 2 seconds and then pulled out. The test liquid was coloured with a few drops (5 drops per 100 g of liquid) of the following blue dyestuff solution: Duasyn Cyan FRL 10 liq. (Clariant. Produkte (Deutschland) GmbH, Frankfurt am Main). The test was practically done by vertically fixing the glass slide 402 with a sample holder (not shown), and lifting the bath 408 with the test liquid 410 from below until about 80% of the length of the fixed porous substrate 406 is immersed. After an immersion time of about 1 - 2 seconds, the bath 408 was quickly pulled away from the bottom so that a thin film of the test liquid 410 was left on outer surface 406a of the porous substrate 406. The sliding down and contraction behaviour of the liquid film of 410 on the outer surface 406a during time may be recorded with a video camera 412 for subsequent evaluation.

0165<figref idref="f0005">Figures 6A and 6B</figref> show a typical evaluation of four test SarTlples 1, 2, 3, 4 in parallel. Sample 1 was coated with a solution of 1 wt.% Teflon® AF1600 in a fluorinated solvent, Sample 2 was coated with a solution of 1 wt.% Teflon® A.F1600 and 1 wt.% PFPE in a fluorinated solvent, Sample 3 was coated with a solution of 1 wt.% Teflon® AF1600 and 5 wt.% PFPE, and Sample 4 was coated with a solution of 1 wt.% Teflon® AF1600 and 10 wt.% PFPE in a fluorinated solvent. The PFPE used was Fomblin® Y LVAC 25/6 (Solvay Solexis; average molecular weight: 3300 a.m.u.). <figref idref="f0005">Figure 6A</figref> shows a first snapshot immediately after removal of the bath (t = 0 seconds) and <figref idref="f0005">Figure 6B</figref> shows a second snapshot after a waiting time of 15 seconds, respectively. The test liquid used was a mixture of water, polyvinylpyrrolidone and a silicone surfactant (Tegoprene® 5847) as described before. This test liquid had a surface tension of 23 mN/m and a viscosity of 13.7 mPa.s (at a shear rate of 50 sec^-1), both measured at a temperature of 25°C.

0166<figref idref="f0005">Figure 6B</figref> shows that Sample 1 is ineffective at repelling the test liquid as the percentage of area covered remains almost unchanged after 15 seconds. However, Samples 3 - 4 which were coated with increasing amounts of PFPE exhibit much improved liquid repellency properties. Sample 4 has the best liquid repellency properties as virtually all of test liquid has been repelled from the contact surface after 15 seconds.

0167<figref idref="f0006">Figures 7A and 7B</figref> are magnified views of the images taken of Sample 3 at t = 0 seconds and t = 15 seconds, respectively. The liquid repellency test requires the fraction of the area within the evaluated area which is still covered by the test liquid to be determined after a certain time t. For Sample 3, after a waiting time of 1.5 seconds about 50% of the evaluated area is still covered by the test liquid. The evaluated area was 2.5 cm (width of the sample) x 4.0 cm (distance from the liquid borderline at t = 0 seconds to the lower edge).

0168Whilst specific embodiments of the present invention have been described above, it will be appreciated that departure from the described embodiments may still fall within the scope of the present invention. For example, any suitable oleophobic and hydrophobic fluorinated material may be used to form the first component and any suitable second component comprising a PFPE with end-groups as follows may be used:         -(O)_n - (CR₁R₂)_m - CR₃R₄R₅ wherein: <ul id="ul0018" list-style="none" compact="compact"><li>R₁ = H, F, Cl, Br or I;</li><li>R₂ = H, F, Cl, Br or I;</li><li>R₃ = H, F, Cl, Br or I;</li><li>R₄ = H, F, Cl, Br or I;</li><li>R₅ = H, F, Cl, Br, I, alkyl or aryl;</li><li>n = 0 or 1; and</li><li>m=0- 10.</li></ul>

0169Alternatively, the second component may comprise a block copolymer comprising a PFPE backbone.

EXAMPLES

0170In the following examples, four different expanded polytetrafluoroethylene (cPTFE) membranes were used as a porous polymer substrate.

Substrate 1

0171An uncoated porous monoaxial expanded polytetrafluoroethylene membrane having a thickness of 308 µm, an area weight of 275 g/m², a porosity of 59.3 %, a mean pore size of 0.32 µm, an air flow of 24 Gurley seconds, a water entry pressure of 0.93 bar, and an oil rating of 2 was used. The polytetrafluoroethylene membrane was manufactured as defined in <patcit id="pcit0018" dnum="US3953566A"><text>US 3,953,566</text></patcit>, which is incorporated herein by reference.

Substrate 2

0172An uncoated porous expanded polytetrafluoroethylene membrane commercially available under the article number #13883na from W.L.Gore &amp; Associates was used. The polytetrafluoroethylene membrane has a porosity of 53% and was oleophobically treated with a fluoromethacrylate.

0173This oleophobically treated ePTFE membrane had a thickness of 1.91 µm, an area weight of 205 g/m², a porosity of 51 %, a mean pore size of 0.72 µm, an air flow of 25 Gurley seconds, a water entry pressure of 1.19 bar, and an oil rating of 8.

Substrate 3

0174A commercially available biaxial expanded ePTFE membrane (available from W. L. Gore &amp; Associates GmbH, Germany, Article No. GMP 20233). This ePTFE membrane had a thickness of 25 µm, an area weight of 16 g/m², a porosity of 71%, a mean pore size of 0.19 µm, an air flow of 13.4 Gurley seconds, a water entry pressure of 4.38 bar, and an oil rating of 1.

Substrate 4

0175An uncoated porous monoaxial expanded polytetrafluoroethylene membrane having a thickness of 106 µm, a width of 12.0 cm, an area weight of 83 g/m², a porosity of 64 %, a mean pore size of 0,32 µm, an air flow of 22 Gurley seconds, a water entry pressure of 1.40 bar, and an oil rating of 1 was used. The polytetrafluoroethylene membrane was manufactured as defined in <patcit id="pcit0019" dnum="US3953566A"><text>US 3,953,566</text></patcit>, which is incorporated herein by reference.

0176The parameters and properties of Substrates 1, 2, 3 and 4 are shown in Table 1 below. <tables id="tabl0001" num="0001"><table frame="all"><title><u>Table 1</u></title><tgroup cols="9"><colspec colnum="1" colname="col1" colwidth="19mm" /><colspec colnum="2" colname="col2" colwidth="20mm" /><colspec colnum="3" colname="col3" colwidth="19mm" /><colspec colnum="4" colname="col4" colwidth="18mm" /><colspec colnum="5" colname="col5" colwidth="19mm" /><colspec colnum="6" colname="col6" colwidth="18mm" /><colspec colnum="7" colname="col7" colwidth="20mm" /><colspec colnum="8" colname="col8" colwidth="20mm" /><colspec colnum="9" colname="col9" colwidth="19mm" /><thead><row><entry>Substrate No,</entry><entry>Thickness (µm)</entry><entry>Area Weight (g/m²)</entry><entry>Density (g/cm³)</entry><entry>Porosity (%)</entry><entry>Pore Size PMI MFP AVG (µm)</entry><entry>Air flow in Gurley sec.</entry><entry>WEP (bar)</entry><entry>Oil rating</entry></row></thead><tbody><row><entry>Substrate 1</entry><entry align="center">308</entry><entry align="center">275</entry><entry align="char" char=".">0.892</entry><entry align="char" char=".">59.3</entry><entry align="char" char=".">0.32</entry><entry align="center">24.2</entry><entry align="char" char="." charoff="10">0.93</entry><entry align="center">2</entry></row><row><entry>Substrate 2</entry><entry align="center">191</entry><entry align="center">205</entry><entry align="char" char=".">1.074</entry><entry align="char" char=".">51.0</entry><entry align="char" char=".">0.72</entry><entry align="center">25.4</entry><entry align="char" char="." charoff="10">1.19</entry><entry align="center">8</entry></row><row><entry>Substrate 3</entry><entry align="center">25</entry><entry align="center">16</entry><entry align="char" char=".">0.636</entry><entry align="char" char=".">71.0</entry><entry align="char" char=".">0.19</entry><entry align="center">13.4</entry><entry align="char" char="." charoff="10">4.38</entry><entry align="center">1</entry></row><row><entry>Substrate 4</entry><entry align="center">106</entry><entry align="center">83</entry><entry align="char" char=".">0.789</entry><entry align="char" char=".">64.0</entry><entry align="char" char=".">0.32</entry><entry align="center">22</entry><entry align="char" char="." charoff="10">1.40</entry><entry align="center">1</entry></row></tbody></tgroup></table></tables>

0177The Substrates 1., 2, 3 and 4 were treated to form composites. Two different coating processes were used for the treatment.

Coating Process A - continuous immersion/dipping process

0178<figref idref="f0007">Figure 8</figref> is a representation of apparatus generally designated 500 used in coating process A. As shown in <figref idref="f0007">Figure 8</figref>, a microporous substrate 502 is passed over a first roller 504 and then using an immersion roller 506 is passed through a bath 508 containing coating solution 510. The speed of the substrate 502 through the bath 508 is adjusted (typically around 1 m/min) so that the opaque microporous substrate 502 is substantially transparent when pulled out of the bath 508 (as an indication for filling of the pores with the coating solution). Afterwards, the coated substrate is fixed on a tenter frame (not shown) and passed through an oven (not shown) for a dwell time of about 2 minutes to completely remove the solvent. The oven temperature may be varied depending on the solvent to be evaporated and may, for example, range from about 25°C - 150°C. Regarding the described Examples 1 - 15. the oven temperature was in the range of about 80 - 100°C.

Discontinuous Coating Process B - hand sample process

0179One side of a glass slide (2.5 cm x 7.5 cm) is provided with a double-sided adhesive tape onto which a sample of the substrate is fixed.

0180The supported substrate is then held at about a 60° angle over a catch pan and saturated with the coating solution using a pipette. The coating solution almost immediately wetted out the pores of the substrate (i.e. the pores were filled with the coating solution as evidenced by the normally opaque PTFE membrane becoming transparent), and excess solution dripped off into the pan.

0181Afterwards, the coated substrate is dried for 10 minutes at room temperature in a fume hood and an additional 5 minutes at 100°C in a ventilated oven.

0182The following Examples were tested for air permeability (reported in Gurley seconds), water entry pressure (WEP), liquid entry pressure (LEP), resistance to wetting with oil (Oil Rating), the initial air flow and the residual air flow after exposure to a testing liquid.

Comparative Example 1

0183Substrate 1 was only coated with a 1 wt.% Teflon® AF1600 coating solution using the continuous coating process A. The Teflon® AF1600 renders the substrate oleaphobic. The coating laydown of Teflon® AF1600 was about 3.7 g/m².

0184The coating solution was obtained by placing 1 g of a copolymer of tetrafluoroethylene (TFE) and 2,2-bis-trifluoromethyl-4,5-difluoro-1,3,-dioxol (PDD), Teflon® AF1600 amorphous fluoropolymer (64 mole% PDD) supplied by DuPont company, in 99 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.% solution of Teflon® AF1600. The mixture was stirred for around 6 hours at room temperature until the Teflon® AF1600 was completely dissolved.

0185The resultant coated substrate 1 had an oil rating of 6 and therefore is oleophobic. Furthermore, the coated substrate 1 showed all air flow of about 17 Gurley seconds, a WEP of about 0.93 bar and a LEP of about 0.27 bar. The initial air flow of coated substrate 1 was 3.32 1/h/cm² (measured at a pressure of 12 mbar).

0186The residual air flow after the air flow recovery test was 0.0 l/h/cm² (measured at a pressure of 12 mbar). There was therefore no air flow recovery after exposure to the test liquid as described in air-flow recovery test.

0187<figref idref="f0008">Figures 9</figref> and <figref idref="f0009">10</figref> show two surface SEM images at different magnification of Example 1.

0188All measured data are shown in Table 2 below.

Comparative Example 2

0189The substrate 1 was coated with a 10 wt.% PFPE coating solution using the continuous coating process A. The coating laydown of the PFPE was of about 38.2 g/m².

0190The coating solution was obtained by placing 10 g of PFPE (Fomblin® Y LVAC 25/6 from Solvay Solexis company) in 90 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 10 wt.% coating solution of PFPE. The solution was shaken until the PFPE was completely dissolved.

0191This coated substrate showed only a very low oil-rating of 2, a Gurley number of about 12.1. seconds, a WEP of about 0.71 bar and a very low LEP of only about 0.07 bar. The initial air flow of the coated substrate 1 was 4.20 l/h/cm² (measured at a pressure of 1.2 mbar).

0192The residual air flow after air flow recovery test was about 3.04 l/h/cm² measured at a pressure of 12mbar). Therefore, this example showed an air flow recovery after exposure to the low surface tension test liquid of air flow recovery test, but only a poor oil rating and very low liquid entry pressure. Therefore this sample will get wetted after longer exposure to low surface tension liquids, or if some hydrostatic pressure is applied.

0193All measured data are shown in Table 2 below.

Example 3

0194The substrate 1 was coated with a coating solution comprising 1 wt.% Teflon® AF1600 and 1 wt.% PFPE using the continuous coating process A. The total coating laydown was about 7.5 g/m².

0195The coating solution was obtained by placing 1 g of Teflon® AF1600 and 1 g of PFPE (Fomblin® Y LVAC 25/6) in 98 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.% Teflon® AF1600 / 1 wt.% PFPE coating solution. The mixture was stirred around 6 hours at room temperature until the Teflon® AF1600 was completely dissolved.

0196The resultant coated Example 3 showed an oil-rating of 7, an air now of 15.3 Gurley seconds, a WEP of about 0.86 bar and a LEP of about 0.26 bar.

0197The residual air flow after air flow recovery test was 0.0 l/h/cm² (at a pressure of 12mbar). Therefore this sample showed no air flow recovery after exposure to the test liquid as described in air now recovery test.

0198All measured data are shown in Table 2 below.

Example 4

0199The substrate was coated with a coating solution comprising 1 wt.% Teflon® AF1600 and 5 wt.% PFPE (Fomblin® Y LVAC 25/6) using the continuous coating process A. The total coating laydown was about 23.5 g/m².

0200The coating solution was obtained by placing 1 g of Teflon® AF1600 and 5 g of PFPE (Fomblin® Y LVAC 25/6) in 94 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.% Teflon® AF1600 / 5 wt.% PFPE coating solution. The mixture was stirred around 6 hours at room temperature until the Teflon® AF1600 was completely dissolved.

0201The resultant coated substrate 1 had an on-rating of 6, a Gurley number of about 12.5 seconds, a WEP of about 0.79 bar and a LEP of about 0.19 bar. The initial air flow of coated substrate 1 was about 3.87 l/h/cm² (measured at a pressure of 12 mbar).

0202This sample showed a residual air flow of about 2.79 l/h/cm² (measured at 12mbar) after air flow recovery test. This corresponded to an air flow recovery of 72%.

0203Therefore this sample showed both a high liquid entry pressure which is important for practical venting applications and a good liquid repellency performance with a challenging liquid as demonstrated by the high air flow recovery after exposure to air-flow recovery test.

0204All measured data are shown in Table 2 below.

Example 5

0205The substrate 1 was coated with a coating solution comprising 1 wt.% Teflon® AF1600 and 10 wt.% PFPE using the continuous coating process A. The total coating laydown was about 42.1 g/m².

0206The coating solution was obtained by placing 1g of Teflon® AF1600 and 10g of PFPE (Fomblin® Y LVAC 25/6) in 89g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.% Teflon® AF1600 / 10 wt.% PFPE coating solution. The mixture was stirred around 6 hours at room temperature until the Teflon® AF1600 was completely dissolved.

0207The resultant coated substrate had an oil-rating of 5, a Gurley number of about 11 seconds, a WEP of about 0.73 bar and a LEP of about 0.12 bar. The initial air flow of coated substrate 1 was 4.76 1/h/cm² (measured at a pressure of 12 mbar).

0208This sample showed a residual air flow of about 3.58 l/h/cm² (measured at a pressure of 12mbar) after air flow recovery test. This corresponded to an air flow recovery of 75.2 %.

0209Therefore, this sample showed both a higher liquid entry pressure and also an air flow recovery after exposure to air flow recovery test.

0210All measured data are shown in Table 2.

0211<figref idref="f0010">Figure 11</figref> and <figref idref="f0011">12</figref> show two surface SEM images of Example 5 coated with the addition of 10 wt.% PFPE to 1 wt.% Teflon® AF 1600 solution. The surface of Example 5 shows both a significantly improved liquid repellency performance and also a marked difference in visual appearance compared with Example 1. Example 5 exhibits bridging elements between nodal island-like regions of the surface. These bridging elements consist of pores (made up by the space between two fibrils) which are (at least partially) filled or covered with the coating components. Clusters of fined/covered pores are also visible.

0212<figref idref="f0012">Figure 13</figref> is a further magnified view of Example 5.

0213Without wishing to be bound by theory, it is thought that these bridging elements are a reason for the significant improved liquid repellency performance. Another point noteworthy is the fact that although several pores were closed or covered, respectively, the air flow of the coated composite did not deteriorate but still showed high air flow performance.

Table 2: Summary of the measurements of the Examples 1 to 5 (substrate 1 was used for preparation of all samples).

0214<tables id="tabl0002" num="0002"><table frame="all"><title><u>Table 2</u></title><tgroup cols="10"><colspec colnum="1" colname="col1" colwidth="18mm" /><colspec colnum="2" colname="col2" colwidth="26mm" /><colspec colnum="3" colname="col3" colwidth="27mm" /><colspec colnum="4" colname="col4" colwidth="19mm" /><colspec colnum="5" colname="col5" colwidth="26mm" /><colspec colnum="6" colname="col6" colwidth="27mm" /><colspec colnum="7" colname="col7" colwidth="27mm" /><colspec colnum="8" colname="col8" colwidth="26mm" /><colspec colnum="9" colname="col9" colwidth="26mm" /><colspec colnum="10" colname="col10" colwidth="26mm" /><thead><row><entry align="center" valign="top" /><entry align="center" valign="top" /><entry align="center" valign="top" /><entry align="center" valign="top" /><entry align="center" valign="top" /><entry align="center" valign="top" /><entry align="center" valign="top" /><entry namest="col8" nameend="col10" align="center" valign="top">Air-flow recovery test</entry></row><row><entry align="center">Example</entry><entry align="center">Coating Solution Composition</entry><entry align="center" valign="middle">Total Coating Laydown (g/m²)</entry><entry align="center">Oil rating</entry><entry align="center" valign="middle">Air permeability (Gurley) (sec.)</entry><entry align="center" valign="top">Water entry pressure (WEP) (bar)</entry><entry align="center" valign="top">Liquid entry pressure (LEP) (bar)</entry><entry align="center" valign="top">Initial air flow (1/h/cm²) @ 12mbar</entry><entry align="center" valign="top">Residual air flow (1/h/cm²) @ 12mbar</entry><entry align="center">% air flow recovery</entry></row></thead><tbody><row><entry align="center">1</entry><entry align="center">1% AF1600</entry><entry align="center">3.7</entry><entry align="center">6</entry><entry align="center">17</entry><entry align="char" char=".">0.93</entry><entry align="char" char=".">0.27</entry><entry align="char" char=".">3.32</entry><entry align="center">0</entry><entry align="center">0</entry></row><row><entry align="center">2</entry><entry align="center">10% PFPE</entry><entry align="center">38.2</entry><entry align="center">2</entry><entry align="center">12.1</entry><entry align="char" char=".">0.71</entry><entry align="char" char=".">0.07</entry><entry align="char" char=".">4.2</entry><entry align="center">3.04</entry><entry align="center">72.3</entry></row><row><entry align="center">3</entry><entry align="center">1% AF1600/ 1% PFPE</entry><entry align="center">7.5</entry><entry align="center">7</entry><entry align="center">1.5.3</entry><entry align="char" char=".">0.86</entry><entry align="char" char=".">0.26</entry><entry align="char" char=".">3.6</entry><entry align="center">0</entry><entry align="center">0</entry></row><row><entry align="center">4</entry><entry align="center">1% AF1600/ 5% PFPE</entry><entry align="center">23.5</entry><entry align="center">6</entry><entry align="center">12.5</entry><entry align="char" char=".">0.79</entry><entry align="char" char=".">0.19</entry><entry align="char" char=".">3.87</entry><entry align="center">2.79</entry><entry align="center">72.0</entry></row><row><entry align="center">5</entry><entry align="center">1% AF1600/ 10% PFPE</entry><entry align="center">42.1</entry><entry align="center">5</entry><entry align="center">11.2</entry><entry align="char" char=".">0.73</entry><entry align="char" char=".">0.12</entry><entry align="char" char=".">4.76</entry><entry align="center">3.58</entry><entry align="center">75.2</entry></row></tbody></tgroup></table></tables>

0215<figref idref="f0013">Figure 14</figref> is a graph showing the % of area covered by test liquid vs. time using the liquid repellency test for Examples 1, 3, 4 and 5. As test liquid the already described mixture of water, Polyvinylpyrrolidone and Tegoprene® 5847 was used. A surface tension of 23 mN/m and a viscosity of 13.7 mPa.s (measured at a shear rate of 50 sec^-1) were determined for this test liquid at a temperature of 25° C. The graph clearly shows that Examples 4 and 5 which have the coating of both Teflon® AF1600 and PFPE have much improved repellency towards the test mixture than Example 1 which only has a coating of Teflon® AF1600.

0216<figref idref="f0014">Figure 15</figref> shows the % air flow recovery versus the % PFPE oil in the coating solution referring to the Examples 1, 3, 4, 5. Additionally the liquid entry pressure (LEP) of the samples is plotted. <figref idref="f0014">Figure 15</figref> additionally shows the corresponding sample as described in Example 2 which was only coated with the PFPE oil. The test liquid for measuring the liquid entry pressure was the already described mixture of water, 2-Propanol and sodium dodecylsulfate (surface tension: 26.5 mN/m; viscosity: 2.8 mPa.s). <figref idref="f0014">Figure 15</figref> clearly demonstrates that with the two component coating both a significantly improved air flow recovery and a high liquid entry pressure can be achieved.

0217<figref idref="f0015">Figure 16</figref> shows the % air flow recovery versus the % PFPE in the coating solution for Examples 1, 4 and 5. As test liquid this time a viscous oil was used (Castrol Transmax Z, automatic transmission fluid from Deutsche Castrol Vertriebsgesellschaft mbH, Hamburg). Again a significant improvement in air flow recovery by addition of the PFPE to the coating formulation was recorded. The measured data are summarized in Table 3. <tables id="tabl0003" num="0003"><table frame="all"><title>Table 3: Results from the air flow recovery test with transmission oil Castrol Transmax Z for Examples 1, 4, 5 (substrate 1).</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="32mm" /><colspec colnum="2" colname="col2" colwidth="33mm" /><colspec colnum="3" colname="col3" colwidth="34mm" /><colspec colnum="4" colname="col4" colwidth="35mm" /><colspec colnum="5" colname="col5" colwidth="33mm" /><thead><row><entry valign="top" /><entry valign="top" /><entry namest="col3" nameend="col5" align="center" valign="top">air flow recovery test</entry></row><row><entry align="center">Example</entry><entry>Coating Solution Composition</entry><entry>Initial air flow (1/h/cm²)@ 12mbar</entry><entry valign="middle">Residual air flow (1/h/cm²)@ 12mbar</entry><entry>% air flow Recovery</entry></row></thead><tbody><row><entry align="center">1</entry><entry align="center">1% AF1600</entry><entry align="char" char=".">3.17</entry><entry align="char" char=".">1.56</entry><entry align="char" char="." charoff="11">49.3</entry></row><row><entry align="center">4</entry><entry align="center">1% AF1600/ 5% PFPE</entry><entry align="char" char=".">4.11</entry><entry align="char" char=".">3.85</entry><entry align="char" char="." charoff="11">93.7</entry></row><row><entry align="center">5</entry><entry align="center">1% AF1600/ 10% PFPE</entry><entry align="char" char=".">4.76</entry><entry align="char" char=".">4.58</entry><entry align="char" char="." charoff="11">96.2</entry></row></tbody></tgroup></table></tables>

0218The following Examples (Examples 6 - 9) were conducted to demonstrate that an improvement in liquid repellency performance can be also achieved by applying one of the two components first, and the second component in a second coating step. Further a fluoromethacrylate was used as the oleophobic and hydrophobic first component. The Examples start with the already oleophobic treated Substrate 2 (Example 6), where gradually more and more of a PFPE oil is added (Examples 7 - 9).

Comparative Example 6

0219The oleophobic substrate 2 was tested without any addition of PFPE. The substrate 2 had an oil-rating of 8, a Gurley number of about 25.5 seconds, a WEP of about 1.11 bar and a LEP of about 0.33 bar. The initial air flow of oleophobic substrate 2 was 2.20 l/h/cm² (measured at a pressure of 12 mbar).

0220The residual air flow was 0.0 l/h/cm² (measured at 12 mbar). Therefore, there was no air flow recovery after exposure to air flow recovery test. All measured data are shown in Table 4 below.

Example 7

0221The oleophobic substrate 2 was coated with a 1 wt.% PFPE coating solution using the continuous coating process A. The total coating laydown was about 6.4 g/m².

0222The coating solution was obtained by placing 1 g of PFPE (Fomblin® Y LVAC 25/6 from Solvay Solexis company) in 99 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.% coating solution of PFPE. The solution was shaken until the PFPE was completely dissolved. The resultant coated substrate had an oil-rating of 8, a Gurley number of about 26 seconds, a WEP of about 1.02 bar and a LEP of about 0.32 bar. The initial air flow of coated oleophobic substrate 2 was 2.15 l/h/cm² (measured at a pressure of 12 mbar).

0223The residual air flow after was 0.0 l/h/cm² (measured at a pressure of 12 mbar). Therefore, there was no air flow recovery after exposure to air flow recovery test. All measured data are shown in Table 4 below.

Example 8

0224The oleophobic substrate 2 was coated with a 5 wt.% PFPE coating solution using the continuous coating process A. The total coating laydown was of about 14.5 g/m².

0225The coating solution was obtained by placing 5 g of PFPE (Fomblin® Y LVAC 25/6 from Solvay Solexis company) in 95 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 5 wt.% coating solution of PFPE. The solution was shaken until the PFPE was completely dissolved. The resultant coated substrate had an oil-rating of 6, a Gurley number of about 25.4 seconds, a WEP of about 1.09 bar and a LEP of about 0.28 bar. The initial air flow of coated oleophobic substrate 2 was 2.13 l/h/cm² (measured at a pressure of 12 mbar).

0226The residual air flow was 1.02 l/h/cm² (measured at 12 mbar). Therefore, this example showed both a high liquid entry pressure and an air flow recovery of around 48% after exposure to the low surface tension test liquid of air flow recovery test.

0227All measured data are shown in Table 4 below.

Example 9

0228The oleophobic substrate 2 was coated with a 10 wt. % PFPE coating solution using the continuous coating process A. The total coating laydown was of about 25.8 g/m².

0229The coating solution was obtained by placing 10 g of PFPE (Fomblin® Y LVAC 25/6 from Solvay Solexis company) in 90 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 10 wt.% coating solution. The solution was shaken until the PFPE was completely dissolved. The resultant coated substrate had an oil-rating of 5, a Gurley number of about 24.4 seconds, a WEP of about 1.01 bar and a LEP of about 0.21 bar. The initial air flow of coated oleophobic substrate 2 was 2.36 1/h/cm² (measured at a pressure of 12 mbar).

0230The residual air flow was 1.20 l/h/cm² (measured at 1.2 mbar). Therefore, this example showed both a moderate high liquid entry pressure and a high air flow recovery of 51% after exposure to the low surface tension test liquid of air flow recovery test.

0231All measured data are shown in Table 4 below.

0232Table 4: Summary of the measurements of the Examples 6 to 9 (Example 6 refers to Substrate 2 which was already oleophobic treated. Examples 7 - 9 refer to Substrate 2 which was additionally coated with a PPPE oil). <tables id="tabl0004" num="0004"><table frame="all"><title><u>Table 4</u></title><tgroup cols="10"><colspec colnum="1" colname="col1" colwidth="18mm" /><colspec colnum="2" colname="col2" colwidth="25mm" /><colspec colnum="3" colname="col3" colwidth="26mm" /><colspec colnum="4" colname="col4" colwidth="20mm" /><colspec colnum="5" colname="col5" colwidth="26mm" /><colspec colnum="6" colname="col6" colwidth="27mm" /><colspec colnum="7" colname="col7" colwidth="27mm" /><colspec colnum="8" colname="col8" colwidth="26mm" /><colspec colnum="9" colname="col9" colwidth="25mm" /><colspec colnum="10" colname="col10" colwidth="26mm" /><thead><row><entry namest="col1" nameend="col7" align="left" valign="top" /><entry namest="col8" nameend="col10" align="center" valign="top">Air flow recovery test.</entry></row><row><entry align="center">Example</entry><entry align="center">Coating Solution Composition</entry><entry align="center">Total Coating Laydown (g/m²)</entry><entry align="center">Oil Rating</entry><entry align="center">Air permeability (Gurtey) (sec.)</entry><entry align="center">water entry pressure (WEP)(bar)</entry><entry align="center">Liquid entry pressure (LEP)(bar)</entry><entry align="center">initial air flow (I/h/cm²) @ 12mbar</entry><entry align="center">residual air flow after 5min (I/h/cm² @ 12Mbar</entry><entry align="center">% air flow recovery</entry></row></thead><tbody><row><entry align="center">6</entry><entry align="center">no PFPE</entry><entry align="center">4.3</entry><entry align="center">8</entry><entry align="center">25.5</entry><entry align="char" char=".">1.11</entry><entry align="char" char=".">0.33</entry><entry align="center">2.2</entry><entry align="center">0</entry><entry align="center">0</entry></row><row><entry align="center">7</entry><entry align="center">1% PFPE</entry><entry align="center">6.4</entry><entry align="center">8</entry><entry align="center">26</entry><entry align="char" char=".">1.02</entry><entry align="char" char=".">0.32</entry><entry align="center">2.15</entry><entry align="center">0</entry><entry align="center">0</entry></row><row><entry align="center">8</entry><entry align="center">5% PFPE</entry><entry align="center">14.5</entry><entry align="center">6</entry><entry align="center">25.4</entry><entry align="char" char=".">1.09</entry><entry align="char" char=".">0.28</entry><entry align="center">2.13</entry><entry align="center">1.02</entry><entry align="center">47.7</entry></row><row><entry align="center">9</entry><entry align="center">10% PFPE</entry><entry align="center">25.8</entry><entry align="center">5</entry><entry align="center">24.4</entry><entry align="char" char=".">1.10</entry><entry align="char" char=".">0.21</entry><entry align="center">2.36</entry><entry align="center">1.2</entry><entry align="center">51</entry></row></tbody></tgroup></table></tables>

0233<figref idref="f0016">Figure 17</figref> is a graph showing the % of area covered by the test liquid vs. time using liquid repellency test for Examples 6, 7, 8 and 9. As test liquid again the already described mixture of water, Polyvinylpyrrolidone and Tegoprene® 5847 was used (surface tension of 23 mN/m and a viscosity of 13.7 mPa.s at 25°C). The graph in <figref idref="f0016">Figure 17</figref> clearly shows that Examples 8 and 9 which have the coating of PFPE as well as the oleophobic coating on the ePTFE substrate 2 have much improved repellency towards the test mixture than Example 6 which has no additional PFPE coating.

0234<figref idref="f0017">Figure 18</figref> is a graph showing both the % air flow recovery-and also the liquid entry pressure (LEP) vs. wt.% of PFPE in the coating solution for Examples 6, 7, 8 and 9. The test liquid for measuring the % air flow recovery was again the already described mixture of water, Polyvinylpyrrolidone and Tegoprene® 5847. The test liquid for measuring the liquid entry pressure was the already described mixture of water, 2-Propanol and sodium dodecylsulfate (surface tension: 26.5 mN/m; viscosity: 2.8 mPa.s). The graph in <figref idref="f0017">Figure 18</figref> clearly shows that Examples 8 and 9 have a much improved repellency towards the test mixture than Example 6, but still exhibit a high LEP greater than 0.2 bar.

0235Examples 10 and 11 described below were prepared to prove a good liquid repellency performance using different types of PFPE oils. In these examples, Krytox® GPL107 (from DuPont Company) and Fomblin® Y LVAC25/6 from (Solvay Solexis Company) were tested and compared with each other. In both cases about the same good liquid repellency performance was achieved.

Example 10

0236The substrate 1 was coated with a coating solution comprising 1 wt.% Teflon® AF1600 and 10 wt.% PFPE-oil (Krytox® GPL107 from DuPont) using the discontinuous coating process B.

0237The coating solution was obtained by placing 1 g of Teflon® AF 1600 and 10g of PFPE (Krytox® GPL107 from DuPont) in 89g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.% Teflon® AF1600 / 10 wt.% PFPE coating solution. The mixture was stirred around 6 hours at room temperature until the Teflon® AF1600 was completely dissolved.

Example 11

0238The substrate 1 was coated with a coating solution comprising 1 wt.% Teflon® AF1600 and 10 wt.% PFPE-oil (Fomblin® Y LVAC 25/6 from Solvay Solexis company) using the discontinuous coating process B.

0239The coating solution was obtained by placing 1 g of Teflon® AF1600 and 10 g of PFPE (Fomblin® Y LVAC 25/6 from Solvay Solexis company) in 89 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.% Teflon® AF1600 / 10 wt.% PFPE coating solution. The mixture was stirred for around 6 hours at room temperature until the Teflon® AF 1600 was completely dissolved.

0240<figref idref="f0018">Figure 19</figref> is a graph showing the % of area covered by the test liquid vs. time using liquid repellency test for Examples 10 and 11. As test liquid again the already described mixture of water, Polyvinylpyrrolidone and Tegoprene® 5847 was used (surface tension of 23 mN/m and a viscosity of 13.7 mPa.s at 25°C). The graph shows that both types of PFPE oils are about same effective in improving the liquid repellency performance of the prepared substrates.

0241Examples 12 and 13 are examples with the biaxial expanded ePTFE membrane (Substrate 3). Also in this case an improvement in air flow recovery was achieved by combining a liquid PFPE oil with Teflon® AF.

Example 12

0242Substrate 3 was only coated with a 1 wt.% Teflon® AF1600 coating solution using the continuous coating process A.

0243The coating solution was obtained by placing 1 g Teflon® AF1600 in 99 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.% solution of Teflon® AF1600. The mixture was stirred for around 6 hours at room temperature until the Teflon® AF1600 was completely dissolved.

0244The resultant coated substrate 3 had an oil rating of 5. Furthermore, the coated substrate 12 showed an air flow of about 15.6 Gurley seconds, a WEP of about 3.7 bar and a LEP of about 0.69 bar. The initial air flow of coated substrate 3 was 4.85 1/h/cm² (measured at a pressure of 12 mbar).

0245The residual air flow was 0.0 1/h/cm² (measured at a pressure of 12 mbar). There was therefore no air flow recovery after exposure to the test liquid as described in air flow recovery test.

0246All measured data are shown in Table 5 below.

Example 13

0247The substrate 3 was coated with a coating solution comprising 1 wt.% Teflon® AF1600 and 10 wt.% PFPE oil (Fomblin® Y LVAC 25/6 from Solvay Solexis company) using the continuous coating process A.

0248The coating solution was obtained by placing 1 g of Teflon® AF1600 and 10 g of PFPE (Fomblin® Y LVAC 25/6 from Solvay Solexis company) in 89 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.%, Teflon® AF1600 / 10 wt.% PFPE coating solution. The mixture was stirred around 6 hours at room temperature until the Teflon® AF 1600 was completely dissolved.

0249The resultant coated substrate 3 had an oil rating of 4. Furthermore, the coated substrate 3 showed an air flow of about 40.6 Gurley seconds, a WEP of about 2.60 bar and a LEP of about 0.35 bar. The initial air flow of coated substrate 1 was 3.05 1/h/cm² (measured at a pressure of 12 mbar).

0250The residual air flow was 0.25 l/h/cm² (measured at a pressure of 12 mbar). This means an air flow recovery of 8 % after exposure to the test liquid as described in air flow recovery test.

0251All measured data are shown in Table 5 below.

0252Table 5: Summary of the measurements on the Examples 12 and 13 (substrate 3 was used for preparation of all samples). <tables id="tabl0005" num="0005"><table frame="all"><title><u>Table 5</u></title><tgroup cols="9"><colspec colnum="1" colname="col1" colwidth="18mm" /><colspec colnum="2" colname="col2" colwidth="23mm" /><colspec colnum="3" colname="col3" colwidth="16mm" /><colspec colnum="4" colname="col4" colwidth="23mm" /><colspec colnum="5" colname="col5" colwidth="18mm" /><colspec colnum="6" colname="col6" colwidth="18mm" /><colspec colnum="7" colname="col7" colwidth="18mm" /><colspec colnum="8" colname="col8" colwidth="18mm" /><colspec colnum="9" colname="col9" colwidth="18mm" /><thead><row><entry valign="top" /><entry valign="top" /><entry valign="top" /><entry valign="top" /><entry valign="top" /><entry valign="top" /><entry namest="col7" nameend="col9" align="center" valign="top">Air-flow recovery test</entry></row><row><entry valign="top">Example</entry><entry valign="top">Coating Solution Composition</entry><entry valign="top">Oil Rating</entry><entry valign="top">Air permeability (Gurley) (sec.)</entry><entry valign="top">Water entry pressure (WEP) (bar)</entry><entry valign="top">Liquid entry pressure (LEP) (bar)</entry><entry valign="top">Initial air flow (1/h/cm²) @ 12mbar</entry><entry valign="top">Residual air flow after 5 min (1/h/cm²) @ 12mbar</entry><entry valign="top">% air flow recovery</entry></row></thead><tbody><row><entry>12</entry><entry>1 % AF1600</entry><entry>5</entry><entry align="char" char=".">15.6</entry><entry align="char" char=".">3.7</entry><entry align="char" char=".">0.69</entry><entry align="char" char=".">4.85</entry><entry align="char" char=".">0</entry><entry align="char" char=".">0</entry></row><row><entry>13</entry><entry>1% AF1600/ 10% PFPE</entry><entry>4</entry><entry align="char" char=".">40.6</entry><entry align="char" char=".">2.6</entry><entry align="char" char=".">0.35</entry><entry align="char" char=".">3.05</entry><entry align="char" char=".">0.25</entry><entry align="char" char=".">8.0</entry></row></tbody></tgroup></table></tables>

0253<figref idref="f0019">Figure 20</figref> compares an SEM image of Example 12 with Example 13. As already pointed out for Example 5 in the earlier examples. Example 13 also shows that a significant amount of pores are filled or covered by the coating components.

0254Example 15 in the following is a further example showing both a high air flow recovery after liquid challenge and also a high liquid entry pressure (LEP). Example 14 is added as for comparison purposes.

Example 14

0255Substrate 4 was coated with a 1 wt.% Teflon® AF1600 coating solution using the continuous coating process A.

0256The coating solution was obtained by placing 1 g Tefllon® AF1600 in 99 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.% solution of Teflon® AF1600. The mixture was stirred for around 6 hours at room temperature until the Teflon® AF1600 was completely dissolved.

0257The resultant coated substrate 4 showed an oil rating of 6. Furthermore, the coated substrate 4 exhibited an air flow of about 13.5 Gurley seconds, a WEP of about 1.36 bar and a LEP of about 0.35 bar. The initial air flow of coated substrate 4 was 3.64 l/h/cm² (measured at a pressure of 12 mbar).

0258The residual air flow was 0.57 l/h/cm² (measured at a pressure of 12 mbar). This means an air flow recovery of 15.7 % after exposure to the test liquid as described in air flow recovery test.

0259<figref idref="f0020">Figures 21</figref> and <figref idref="f0021">22</figref> show SEM surface images of Example 14 which is only Teflon® AF coated.

0260All measured data are shown in Table 6 below.

Example 15

0261Substrate 4 was coated with a coating solution comprising 1 wt.% Teflon® AF1600 and 4 wt.% PFPE using the continuous coating process A.

0262The coating solution was obtained by placing 1 g of Teflon® AF1600 and 4 g of PFPE (Fomblin® Y LVAC 25/6) in 95 g of the perfluorinated solvent PF-5070 (from 3M company) to result in a 1 wt.% Teflon® AF1600 / 4 wt.% PFPE coating solution. The mixture was stirred around 6 hours at room temperature until the Teflon® AF1600 was completely dissolved.

0263The resultant coated substrate 4 had an oil-rating of 6, a Gurley number of about 13.1 seconds, a WEP of about 1.21 bar and a LEP of about 0.25 bar. The initial air flow of coated substrate 1 was 4.95 l/h/cm² (measured at a pressure of 12 mbar).

0264This sample showed a residual air flow of about 3.89 l/h/cm² (measured at 12mbar). This corresponded to an air flow recovery of 78.5%.

0265Therefore this sample showed both a superior air flow recovery with a challenging liquid as demonstrated by the high air flow recovery after exposure to air flow recovery test and also a higher liquid entry pressure which is important for practical venting applications.

0266<figref idref="f0022">Figures 23</figref> and <figref idref="f0023">24</figref> show SEM images of Example 15 with the combination of Teflon® AF and PFPE oil. Example 15 exhibits bridging elements between the nodal areas consisting of the coating components at least partially filling or covering pores.

0267All measured data are shown in Table 6 below.

0268Table 6: Summary of the measurements on the Examples 14 and 15 (substrate 4 was used for preparation of all samples). <tables id="tabl0006" num="0006"><table frame="all"><title><u>Table 6</u></title><tgroup cols="9"><colspec colnum="1" colname="col1" colwidth="18mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><colspec colnum="3" colname="col3" colwidth="16mm" /><colspec colnum="4" colname="col4" colwidth="23mm" /><colspec colnum="5" colname="col5" colwidth="18mm" /><colspec colnum="6" colname="col6" colwidth="18mm" /><colspec colnum="7" colname="col7" colwidth="18mm" /><colspec colnum="8" colname="col8" colwidth="19mm" /><colspec colnum="9" colname="col9" colwidth="18mm" /><thead><row><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry namest="col7" nameend="col9" align="center">Air flow recovery test</entry></row><row><entry align="center">Example</entry><entry align="center">Coating Solution composition</entry><entry align="center">Oil rating</entry><entry align="center">Air permeability (Gurley) (sec.)</entry><entry align="center">Water entry pressure (WEP) (bar)</entry><entry align="center">Liquid entry pressure (LEP) (bar)</entry><entry align="center">Initial air flow (1/h/cm²) @ 12mbar</entry><entry align="center">Residual air flow after 5min (1/h1cm²) @ 12mbar</entry><entry align="center">% air flow recovery</entry></row></thead><tbody><row><entry align="center">14</entry><entry align="center">1% AF1600</entry><entry align="center">6</entry><entry align="char" char=".">13.5</entry><entry align="char" char=".">1.36</entry><entry align="char" char=".">0.35</entry><entry align="char" char=".">3.64</entry><entry align="char" char=".">0.57</entry><entry align="char" char=".">15.7</entry></row><row><entry align="center">15</entry><entry align="center">1% AF1600/ 4% PFPE</entry><entry align="center">6</entry><entry align="char" char=".">13.1</entry><entry align="char" char=".">1.21</entry><entry align="char" char=".">0.25</entry><entry align="char" char=".">4.95</entry><entry align="char" char=".">3.89</entry><entry align="char" char=".">78.5</entry></row></tbody></tgroup></table></tables>