Process for the formation of a porous film assembly

Abstract

A process for the formation of an assembly comprising a structured or compacted porous film (c) comprising a) application of a porous film (d) onto an elastic substrate (a) in a stretched state such that a reversible adhesion of the film on the stretched substrate (a) occurs, and b) relaxing the substrate (a) with the applied film thereon to obtain a structured or compacted porous film (c), c) applying a support material (e) to a part of the structured or compacted film (c) so that the structured or compacted film to which no support material (e) is attached is releasable.

Claims

1. A process for the formation of an assembly comprising a structured porous film the process, compromising: a) applying a porous film onto an elastic substrate in a stretched state such that a reversible adhesion of the film on the stretched substrate occurs; b) relaxing the substrate with the applied film thereon to obtain a structured porous film; and c) applying a support material to at least a part of the structured film so that the structured porous film to which no support material is attached is releasable.

2. The process according to claim 1, wherein the support material is a stabilizing support material or an elastomeric support material.

3. The process according to claim 1, further comprising: d) releasing the structured film.

4. The process according to claim 1, wherein the porous film comprises a member selected from a fluoropolymer, a polyvinylalcohol, and a polyurethane.

5. The process according to claim 1, wherein the substrate comprises a member selected from polysiloxane, fluorosilicone, and a rubber.

6. The process according to claim 1, wherein the substrate in step a) is stretched by at least 110% in at least one direction.

7. The process according to claim 1, wherein the elastic substrate is stretched at most 1100% in at least one direction.

8. The process according to claim 1, wherein the substrate is uniaxially or biaxially stretched.

9. The process according to claim 1, further comprising removing the structured film from the elastic substrate.

10. A process for the formation of a compacted porous film comprising: a) application of a porous film onto an elastic substrate in a stretched state such that a reversible adhesion of the film on the stretched substrate occurs; and b) relaxing the substrate with the applied film thereon to obtain a compacted porous film.

11. The process according to claim 10, further comprising applying a stabilizing support material or an elastomeric support material to the compacted film.

12. The process according to claim 10, wherein the film comprises a member selected from a fluoropolymer, a polyvinylalcohol, and a polyurethane.

13. The process according to claim 10, wherein the substrate comprises a member selected from a polysiloxane, fluorosilicone, and a rubber.

14. The process according to claim 10, wherein the substrate in step a) is stretched by at least 110% in at least one direction.

15. The process according to claim 10, wherein the elastic substrate is stretched by at most 1100% in at least one direction.

16. The process according to claim 10, wherein the substrate is uniaxially or biaxially stretched.

17. The process according to claim 10, further comprising removing the compacted film from the elastic substrate.

Description

(1) The present invention will be further illustrated by the examples described below, and by reference to the following figures:

(2) FIG. 1 show a schematic drawing of an exemplary device for performing the process of structuring a porous film involving biaxial stretching in a non-continuous manner.

(3) FIG. 2 shows a schematic drawing of a further exemplary device for performing the process of structuring or compacting a porous film involving uniaxial transverse stretching in a continuous manner.

(4) FIG. 3 shows a schematic drawing of a further exemplary device for performing the process of structuring or compacting a porous film involving uni- or biaxial stretching in a continuous manner.

(5) FIG. 4 shows a schematic drawing of a further exemplary device for performing the process of structuring or compacting a porous film involving biaxial stretching in a continuous manner.

(6) FIG. 5 shows a schematic drawing of a further exemplary device for performing the process of structuring or compacting a porous film involving uniaxial stretching in a continuous manner.

(7) FIG. 6 shows a schematic drawing of a further exemplary device for performing the process of structuring or compacting a porous film involving uniaxial stretching in a continuous manner.

(8) FIG. 7 shows a SEM image of a top view of the compacted film of Example 1A.

(9) FIG. 8 shows a SEM image (top view) of the initial, untreated film used in Example 1A.

(10) FIG. 9 shows an image of a molded film assembly being stabilized on a polypropylene knit of Example 1B.

(11) FIG. 10 is a SEM image (top view) of a released part with “straightened” fibrils on top of the molded shape shown in FIG. 9.

(12) FIG. 11 is a SEM image (top view) of the compacted, non-released part of the film of FIG. 9.

(13) FIG. 12 is a SEM image showing a top view of the compacted film of Example 1C with a PE nonwoven on top.

(14) FIG. 13 is a graph showing the airflow values measured with an ATEQ device at different pressures (Reference Example and Example 1C).

(15) FIG. 14 shows released parts of the structured film occurring between the elastomeric grid lines after the first stretch cycle (Example 2B1).

(16) FIG. 15 shows a vent in its flat state upon applying a low air pressure (Example 2B1).

(17) FIG. 16 shows the vent of FIG. 15 upon applying medium air pressure.

(18) FIG. 17 shows the vent of FIG. 15 upon applying high air pressure.

(19) FIG. 18 is an image of the film assembly of Example 2B2 having an elastomeric support material in the form of a grid coating. In the centre of the film assembly an additional circular elastomeric coating as sealing member is seen.

(20) FIG. 19 is a schematic drawing of a check valve (Example 2B3).

(21) FIG. 20 is an image of a check valve in its closed state (Example 2B3).

(22) FIG. 21 is an image of a check valve in its open state (Example 2B3).

(23) FIG. 22 is a diagram indicating the differential pressure at which the check valve of Example 2B3 is in its open or closed state.

(24) FIG. 23 is a SEM image (top view) of the compacted film of Example 2D1.

(25) FIG. 24 is an image showing the surface of Example 2D1 with elastomeric line coating before (right hand side) and after the first stretch cycle with periodic wrinkling (left hand side).

(26) FIG. 25 is a side view image (side view) of the obtained patterned film assembly (Example 3B1).

(27) FIG. 26 is a SEM image showing a top view of the reference film of Example 4A.

(28) FIG. 27 is a SEM image (top view) of the compacted film of Example 4B.

(29) FIG. 28 is a SEM image (top view) of the compacted film of Example 4C.

(30) In FIG. 29, the determination of the structure density of the structured film of Example 5 is shown (left hand image). In the right hand image, a surface topography of the film is shown.

(31) FIG. 30 is a SEM image (top view) of the reference film of Example 2A1.

(32) FIG. 31 is a SEM image (top view) of the structured film of Example 4D.

(33) FIG. 32 is a schematic drawing showing the principle of compacting a porous film.

(34) FIG. 33 is a schematic drawing showing the principle of structuring a porous film.

(35) FIG. 34A is a schematic drawing of the bonding area of a switchable valve (Example 2B4). FIG. 34B is a schematic drawing of a switchable valve in its closed state. FIG. 34C is a schematic drawing of a switchable valve in its opened state.

(36) FIG. 35A is a schematic drawing of the bonding area of another switchable valve (Example 2B5). FIG. 35B is a schematic drawing of a switchable valve in its closed state. FIG. 35C is a schematic drawing of a switchable valve in its opened state.

(37) FIG. 36 is a schematic drawing of a three dimensional representation of an external view of the switchable valve of Example 2B5 in its open state.

MEASUREMENT METHODS

(38) a) Rigidity Measurements

(39) Rigidity of the porous films may be measured according to ASTM D-2923-08, procedure B. Although this method is indicated to be suitable for polyolefin film, it may also be used for films made of other materials.

(40) For measuring the rigidity, a Handle-O-Meter test device (Thwing-Albert Instrument Company) may be used.

(41) b) ATEQ Airflow

(42) Airflow is measured using an ATEQ airflow meter at a pressure of 70 mbar.

(43) c) Gurley Number

(44) Gurley numbers [s] were determined using a Gurley Densometer according ASTM D 726-58.

(45) The results are reported in terms of Gurley Number which is the time in seconds for 100 cubic centimeters of air to pass through 6.54 cm.sup.2 of a test sample at a pressure drop of 1.215 kN/m.sup.2 of water.

(46) d) Structure Height

(47) Topography images were created with an areal confocal 3d measurement system “μsurf explorer” (Nanofocus AG). Such topographic images are e.g. given on the right hand side of FIG. 29.

(48) The height of the structures is the maximum distance between a height peak and a height dip(valley) of a representative sample evaluated via image analysis.

(49) e) Structure Density

(50) To determine the structure density in x (e.g. transverse) direction and y (e.g. longitudinal or machine) direction, 3D topography or SEM images were analysed. Multiple measurements per axis are made and averaged out to determine structure density in perpendicular directions x and y.

(51) Lines in x and y directions were applied on the images. All structure edges crossing a line were marked. Multiple measurements were taken and averaged. This procedure is depicted for the structured film of Example 5 in the left hand side pictures of FIG. 29.

(52) The structure density where evaluated using following formula: (As 2 edges define one structure, the average edge number is divided by 2)
Structure density in direction x=(average number of edges x/2)/evaluated sample width x
Structure density in direction y=(average number of edges y/2)/evaluated sample width y

(53) For example, this procedure yields for the structured film of Example 5 as shown in FIG. 29, left hand side, the following structure densities:
Direction x: (18+13+13)/3/2/4.29 mm=1.5/mm
Direction y: (10+12+16)/3/2/4.28 mm=1.5/mm
f) Further Properties

(54) Further properties, such as bubble point, water entry pressure, pore size, and porosity, were measured as indicated in US 2007/0012624, unless otherwise indicated.

EXAMPLES

A) Device

Example D1

(55) FIG. 1 shows a typical and simple device for forming a structured film in a non-continuous manner, wherein an elastic carrier (a) is inflated to stretch the elastic carrier (a) and a film (d) is applied at a stretched state. The inner pressure is reduced by opening a valve and so that the substrate is relaxed and, thereby, the structured film (c) is formed on the elastic carrier (a).

Example D2

(56) FIG. 2 shows a schematic illustration of an embodiment of a continuous processing method and device for forming a structured or compacted film, wherein a rotatable elastic carrier belt (a) is fixed to two rotating elements that induce and release transverse stretch to the silicone substrate along a circular motion. A film (d) is applied via pressure roll (h) on the stretched elastic carrier belt (a). The film moves on the stretched elastic carrier belt (a) and a structured or compacted film (c) is formed during relaxation of the elastic carrier belt (a). Optionally, a support material (e) is preheated with e.g. an IR heater (g) and applied via pressure roll (b) on the structured or compacted film (c) to form a composite (f) comprising a structured or compacted film (c) and a support material (e).

Example D3

(57) FIG. 3 shows a schematic illustration of a further embodiment of a continuous processing method and device for forming a structured or compacted film, wherein a rotatable elastic carrier belt (a) rotates between two rolls with a surface velocity ratio.

(58) To induce stretch in the elastic carrier (a) the surface velocity of roll 2 is lower than surface velocity of roll 1. This ratio causes the elastic carrier belt (a) to change its stretch state from relaxed to stretched during rotation. The elastic carrier (a) is fixed on the sides with clamps (i) that run in a rail (g) so that they can change their distance depending on the stretch ratio in the elastic carrier (a) where they are fixed to while keeping the elastic carrier (a) at a constant width.

(59) In another version of this process the rails (g) form an angle so that the elastic carrier belt (a) is in addition to the longitudinal stretch, stretched in the transverse direction with changing its width repeatable during rotation.

(60) A film (d) is applied on the stretched elastic carrier via pressure roll (b).

(61) A structured or compacted film (c) is formed on the elastic carrier (a). A support material (e) is provided and laminated to the structured or compacted film (c) on the elastic carrier (a) via pressure roll (h) to form a composite material (f) comprising the structured or compacted film (c).

Example D4

(62) FIG. 4 shows a schematic illustration of a further embodiment of a continuous processing method and device for forming a structured or compacted film, wherein a rotatable elastic carrier belt (a) rotates between two rolls with a surface velocity ratio.

(63) To induce stretch in the elastic carrier (a) the surface velocity of roll 2 is lower than surface velocity of roll 1. This ratio causes the elastic carrier belt (a) to change its stretch state from relaxed to stretched during rotation.

(64) A film (d) is applied on the stretched elastic carrier via pressure roll (b).

(65) A structured or compacted film (c) is formed on the elastic carrier (a). A support material (e) is provided and preheated with an IR heater (f) to melt an adhesive component and laminated to the structured or compacted film (c) on the elastic carrier (a) via pressure roll (h) to form a composite material (g) comprising the structured or compacted film (c).

(66) The elastic carrier (a) and consequently the film (d) in this process are contracted in the machine direction while an expansive force acts in the transverse direction depending on the Poisson's ratio of the elastic carrier material.

Example D5

(67) FIG. 5 shows a schematic illustration of a further embodiment of a continuous processing method and device for forming a structured or compacted film, wherein a roll of elastic carrier material (a) is provided. The roll is at least stretched in one direction, before the film (d) is applied with a pressure roll (b). In this case the elastic carrier is hold by clamps (e) on the sides and the clamps increase their distance in the machine direction to stretch the elastic carrier. After applying the film the stretch is released. A structured or compacted film (c) is formed on the elastic carrier. The clamps release the elastic carrier at the end of the process.

(68) As shown in the image the elastic carrier with the structured or compacted film is spooled on a roll. This roll can then be used for further processes, e.g. a coating step, after which the elastic carrier is removed from the coated structured or coated compacted film. Another method would be to remove the structured or compacted film from the elastic carrier before the elastic carrier is spooled on a roll.

Example D6

(69) FIG. 6 shows a schematic illustration of a further embodiment of a continuous processing method and device of the invention wherein a roll of elastic carrier material (a) is provided. The roll is stretched in machine direction, before the film is applied. A ratio between the surface velocity of roll 1 and roll 2 stretches the elastic carrier (a). A film (d) is applied on the stretched elastic carrier via pressure roll (b). The stretch is released, with roll 3 having a lower surface velocity than roll 2, to form a structured or compacted film (c). Usually surface velocity of roll 1 equals approximately the surface velocity of roll 1. The elastic carrier (a) and consequently the film (d) in this process are contracted in the machine direction while an expansive force acts in the transverse direction depending on the Poisson's ratio of the elastic carrier material.

B) Process/Structured and Compacted Porous Film

(70) The principle of compacting or structuring a film is described first.

(71) The principle of compacting a porous film according to the invention is shown in FIG. 32. A porous film (2a) having straight fibrils connecting the nodes is applied to a stretched elastic substrate (1a) so that reversible adhesion of the film on the stretched substrate occurs, see upper part of FIG. 32. Upon uniaxially relaxing the substrate with the applied film thereon, the fibrils of the film bend and the density of the porous film increases. The lower part of FIG. 32 shows the so obtained compacted film (2b) on the elastic substrate (1b) in its relaxed state.

(72) The principle of structuring a porous film according to the invention is shown in FIG. 33. A porous film (2a) is applied to a stretched elastic substrate (1a) so that reversible adhesion of the film on the stretched substrate occurs, see upper part of FIG. 33. Upon uniaxially relaxing the substrate with the applied film thereon, the film partially delaminates from the substrate and out-of-plane structures occur. The lower part of FIG. 33 shows the so obtained structured film (2b) on the elastic substrate (1b) in its relaxed state. The structured film (2b) shows wrinkles and foldings.

Example 1

Example 1A

(73) An ePTFE membrane was made by processes known in the art for example U.S. Pat. No. 3,953,566. The membrane had an average ATEQ airflow of 120 l/hr (at 70 mbar test pressure), a WEP (Water Entry Pressure) of 1.75 bar, a thickness of 80 μm, a mass/area of 25 g/m.sup.2.

(74) In Example 1A, a PDMS(polydimethylsiloxane) sheet (Elastosil RT620, Wacker silicones) was used as elastic substrate. The membrane was adhered to the prestretched PDMS sheet with slight pressure. The PDMS sheet was biaxially relaxed at a processing ratio of 200% (2:1 biaxially; 4:1 areal change) with the adhered film thereon, thereby obtaining a compacted film.

(75) The microstructure or intra-film structure changed as can be seen in FIG. 7. For comparison, the initial, untreated membrane having nodes and “straight” fibrils is shown in FIG. 8.

(76) This film has a low density and is very soft so that it will not delaminate from the elastic substrate upon relaxation up to about 250% in biaxial relaxation.

Example 1B

(77) Example 1B is an example of a film assembly. The film composite of Example 1A was bonded to a polypropylene extruded knit material acting as stabilising support material in a heat press at a temperature of 185° C., 4 bar pressure using a SEFA mini heat press with 160 mm×160 mm press area for 10 s. The heated side of the press was faced to the polypropylene knit side. After cooling the elastic substrate was removed from this composite material.

(78) For releasing a part of the compacted film, the composite material was clamped in a 10 mm diameter circular molding tool. A hot air gun set to 200° C. and low fan speed was used to melt the polypropylene support structure. A vacuum was applied from the lower side to mold the composite material to form a spherical shape.

(79) FIG. 9 shows a molded film assembly being stabilized on the polypropylene knit. FIG. 10 shows a released part on top of this molded shape with “straightened” fibrils, whereas FIG. 11 shows an unmolded area, i.e. the still compacted, non-released part of the film.

Example 1C

(80) Example 1C is an example of a molded vent comprising the film assembly of the invention. A Polyethylene Nonwoven material was applied in a heatpress at 130° C. for 2 s at 2 bar to the membrane.

(81) The membrane with the PE nonwoven was adhered to a prestretched PDMS sheet (Elastosil RT620, Wacker silicones) with slight pressure, the Nonwoven side facing outside. The elastic substrate and adhered film were heated to about 130° C. with an IR heater arranged about 15 cm above the elastic substrate. The PDMS sheet was biaxially relaxed at a processing ratio of 200% (2:1 biaxially, 4:1 areal change) with the adhered film there on. The microstructure or intra-film structure of the obtained compacted film changed. The nonwoven material did flow on the film and after cooling the nonwoven stabilized the compacted film, so that it could be removed from the elastic substrate. FIG. 12 shows the compacted film with the PE nonwoven on top.

(82) The composite material was cut out in circles and bonded to a plastic disc with a circular hole with 2 mm diameter. The disc was clamped in a molding tool. For releasing a part of the compacted film, a hot air gun set to 160° C. and low fan speed was used to melt the nonwoven material. A vacuum was applied from the lower side to mold the composite material to form a spherical shape.

(83) As a reference example, the membrane was used untreated and bonded to a plastic disc with a 2 mm circular hole.

(84) The water entry pressure was 1.75 bar for both samples, so it can be seen that the compacting and molding did not damage the film pore structure. The airflow was measured with an ATEQ device at different pressures as can be seen FIG. 13. The airflow was increased up to 5 times using a film assembly according to the invention (“3d”) in comparison to the reference example (“flat”).

Example 2

(85) An ePTFE membrane was made by processes known in the art for example U.S. Pat. No. 5,814,405 or DE 69617707. The membrane had an average ATEQ airflow of 54 l/hr (at 12 mbar test pressure), a WEP (Water Entry Pressure) of 28 psi (1.93 bar), a bubble point of 8.2 psi (0.57 bar), an average Gurley number of 2.8 Gurley seconds and a mass/area of 10 g/m.sup.2. The membrane had an average transverse direction rigidity of 29.7 g/m and average machine direction rigidity of 9.8 g/m, measured according to ASTM D2923-08 Method B, using a Handle-O-Meter test device (Thwing-Albert Instrument Company) at 20° C.

(86) Examples 2B and 2C are examples of a film assembly comprising a structured film. In examples 2A, 2B and 2C, a Bicomponent Copolyester Spunbond was used as support material. To adhere the support material to the membrane samples a polyurethane hot melt web adhesive (Article Number: D6C8F 10 g/m.sup.2; Company: Protechnic (France)) was used. The web adhesive was pre-applied to the support material in a heat press at 120° C. and 5 psi (0.34 bar) areal pressure at 15 seconds dwell time.

(87) In Examples 2B and 2C, different processing types as indicated have been used.

(88) Examples 2D and 2E are examples of a film assembly comprising a compacted film. In examples 2D and 2E, the membrane was adhered to the elastic substrate with slight pressure. The elastic substrate was relaxed in longitudinal direction at different ratios. No visible out-of-plane structures occurred as evidenced by a structure density of 0.0/mm in both x and y direction, but only the fibrils folded. No delaminating of the compacted membrane from the elastic substrate occurred upon relaxation in longitudinal direction.

(89) Process conditions and results are given in Table 1 below.

(90) TABLE-US-00001 TABLE 1 2A (ref- erence) 2B 2C 2D 2E Processing — Biaxial Transverse Longi- Longi- type tudinal tudinal Processing 100 200 200 350 200 ratio [%] Processing 20 20 20 20 20 temperature [° C.] Elastic — Elastosil ECOFLEX Elastosil Elastosil substrate RT 620 0010 RT 620 RT 620 Elastic — smooth smooth smooth smooth substrate surface Structure — 4.4/mm 7.5/mm 0.0/mm 0.0/mm density direction x Structure — 0.6/mm 0.0/mm 0.0/mm 0.0/mm density direction y

Example 2B1

(91) The structured film of example 2B was coated with an elastomeric support material to form a film assembly. A 100 micron paper was lasercut with slots of 100 micron width and about 1 mm distance. Wacker Elastosil RT 620 Silicones component A and B were mixed at a mass ratio of 9:1 and the material was pressed through the slots of the paper. The material was cured in an oven for 3 min at 80° C.

(92) A 2.sup.nd similar line coating with Elastosil RT 620 was applied rectangular to the first line coating to form a grid coating. After coating the structure was cured again at 80° C. for 3 min.

(93) FIG. 14 shows released sections of the structured film occurring between the elastomeric grid lines after the first stretch cycle (releasing). The released section of the structured film form periodic, released structures on the otherwise structured film.

(94) The film of Example 2B1 was assembled onto a circular air nozzle and used as a vent. FIG. 15 shows the vent in its flat state upon applying a low air pressure. Applying medium and high air pressure imparts a spherical shape to the film assembly as seen in FIGS. 16 and 17.

Example 2B2

(95) The structured film of example 2B was coated with an elastomeric support material to form a film assembly. A 100 micron paper was lasercut with slots of 100 micron width and about 1 mm distance. Wacker Elastosil RT 620 Silicones component A and B were mixed at a weight ratio of 9:1 and the material was pressed through the slots of the paper. The material was cured in an oven for 3 min at 80° C.

(96) A 2.sup.nd similar line coating with Elastosil RT 620 was applied rectangular to the first line coating to form a grid coating. After coating the structure was cured again at 80° C. for 3 min.

(97) An additional circular elastomeric coating with Elastosil RT 620 was applied on the sample through a lasercut circle on a 100 micron thick paper.

(98) FIG. 18 shows the obtained film assembly comprising an elastomeric support material in the form of a grid coating and in the centre of the film assembly an additional circular elastomeric coating as sealing member.

Example 2B3

(99) The film assembly of Example 2B2 was circularly cut out and bonded to a plastic disc with 10 mm opening and having an inner tube. The film assembly was placed onto the plastic disc in such a way that the sealing member was congruent with the opening of the inner tube, thereby forming a check valve. A schematic drawing of this check valve is shown in FIG. 19.

(100) The closed state of the valve is shown on the left hand side of FIG. 19. The elastomeric support material is in its relaxed state and the sealing member closes the opening of the tube, see also FIG. 20. From the outside to the inside, when the vent was closed, the penetration of e.g. water, water vapour and oils, into the inner area was prevented. From the inside to the outside the vent is closed by the elastomeric coating forming the sealing member over the inner tube, preventing the release of e.g. air, water, water vapour and oils, from within the inner tube. This is shown in the left hand drawing of FIG. 19, in which the arrows representing airflow and moisture transport do not cross the sealing member part of the film assembly. Increasing the inner gas pressure causes the film assembly to stretch. From the inside, once a desired pressure is reached the sealing member is lifted from the opening of the tube and the vent opens to equilibrate pressure, see right hand side of FIG. 19. As can be seen from FIG. 22, if the difference between the inner and outer pressure in this example is higher than 20 mbar, the vent opens. The open state of the vent can also be seen from FIG. 21. The elastomeric support material is then in its stretched state. Air and/or moisture, for instance, may flow from the interior of the valve through venting areas adjacent to the sealing member and through the parts of the film assembly not covered by the sealing member to the outside. If equilibrium in pressure is reached, the elastomeric support material returns to its relaxed state, causing the sealing member to lower onto the opening of the tube, and closing the valve again.

Example 2B4

(101) The film assembly of Example 2B1 was circularly cut out and bonded to a valve substrate to provide a switchable valve. FIG. 34A shows the bond area 30 at the perimeter of the circular film assembly, which was continuous around the entire perimeter of the circular film assembly, to a valve substrate. FIGS. 34B and C show the cross-section of the switchable valve at plane 32 of FIG. 34A.

(102) Referring to FIG. 34B, film assembly 10 was attached to the base 28 of a valve substrate 20 at the bond area 30. The valve substrate may be a plastic material, such as a molded plastic. The bond area 30 attached the elastomeric support material of the film assembly to the base 28 of the valve substrate 20. The elastomeric support material was on the face of the film assembly 10 directed inward towards and adjacent to the valve substrate 20 and the structured or compacted film was on the opposite side facing outward from the valve substrate.

(103) The valve substrate 20 had a first opening 22 and second openings 24. The first opening 22 can be formed by a tube inserted into the valve substrate. Alternatively, the valve substrate 20 may be molded to provide first opening 22 as a channel through a protuberance 26 which projects from the base 28 of the valve substrate as shown in FIGS. 34B and C. The film assembly 10 was bonded onto the base 28 of the valve substrate 20 in such a way that a portion of the film assembly was congruent with the surface of protuberance 26 surrounding the first opening 22 and through which opening 22 emerges, thereby forming a sealing member 25 over first opening 22 to provide a switchable valve 5.

(104) The closed state of the switchable valve is shown in FIG. 34B. The elastomeric support material was in its relaxed state and the film assembly 10 was located adjacent to and in contact with the protuberance 36 closing the first opening 22. From the outside to the inside, when the vent was closed, the penetration of e.g. liquid water, water vapour and oils, through the film assembly 10 into the inner area 29 of the switchable valve was prevented. From the inside to the outside, gases such as air or water vapour may exit inner area 29 through the sealing member 25 of the film assembly 10 in the direction of the arrow shown. Increasing the first fluid pressure causes the film assembly 10 to stretch.

(105) In an alternative embodiment, the film assembly of Example 2B2 may be used in which the sealing member comprises an additional circular elastomeric coating. In such an embodiment, from the outside to the inside, when the vent was closed, the penetration of e.g. liquid water, water vapour and oils, through the film assembly into the inner area of the switchable valve was prevented. From the inside to the outside venting of gases such as air or water vapour through the sealing member is reduced compared to the embodiment of the film assembly of Example 2B1, due to the presence of the elastomeric coating forming the sealing member. In those embodiments in which the elastomeric coating prevents the passage of gases such as air or water through the sealing member, a check valve is obtained.

(106) From the inside of switchable valve 5, once a desired pressure is reached, the sealing member 25 portion of the film assembly 10 was lifted from the first opening 22 allowing fluid communication between the first opening 22 and second openings 24 as shown in FIG. 34C. The second openings were in fluid communication with the outside of the switchable valve i.e. the environment external to the inner area of the switchable valve. This represents the open state of the switchable valve.

(107) The second openings 24 were channels through the base 28 of the valve substrate. The second openings 24 were located on base 28 between the protuberance 26 containing the first opening 22 and the bond area 30 in a second venting area. In an alternative embodiment not shown in FIGS. 34B and C, the second openings could be located elsewhere on the valve substrate, as long as they were present in the second venting area and could enter into fluid communication with the first opening upon removal of the sealing member. For instance, the second openings could be located in a side wall (not shown) of the valve substrate to which the perimeter of the film assembly could be attached. In such an embodiment, in the open state of the switchable valve, the fluid would vent through the second openings in a stream perpendicular to the stream flowing through the first opening. This is in contrast to the embodiment shown in FIG. 34C in which the fluid venting through the second openings is a countercurrent stream to that leaving inner area via the first opening.

(108) Returning to FIG. 34C, in the open state, the expansion of the film assembly 10 released the sealing member 25 from the first opening 22 allowing the pressure in the inner area 29 of the switchable valve to equilibrate with the outside through second openings 24 of the second vent area in the direction of the arrows shown. The elastomeric support material of the film assembly 10 was then in its stretched state. Gaseous and liquid fluids such as one or more of air, moisture and liquid water, for instance, may flow from the interior area 29 of the valve through the second vent area adjacent to the sealing member to the outside of the valve via second openings 24. If equilibrium between the internal and external pressures of the switchable valve is reached, the elastomeric support material returns to its relaxed state, causing the sealing member 25 to lower onto the first opening 22, and closing the switchable valve again.

Example 2B5

(109) The film assembly of Example 2B1 was circularly cut out and bonded to a valve substrate to provide a switchable valve. FIG. 35A shows the bond areas 30 at the perimeter of the circular film assembly, which were discontinuous around the perimeter of the circular film assembly, such that non-bonded areas 34 between the film assembly and valve substrate at the perimeter of the film assembly were present. FIGS. 35B and C show the cross-section of the switchable valve at plane 32 of FIG. 35A, while FIG. 36 shows a representation of a three dimensional view of the switchable valve in the open state.

(110) Referring to FIG. 35B, film assembly 10 was attached to the base 28 of a valve substrate 20. Bond areas (not shown in the cross-section of FIG. 35B) attached the elastomeric support material of the film assembly 10 to the base 28 of the valve substrate 20. The elastomeric support material was on the face of the film assembly 10 directed inward towards and adjacent to the valve substrate 20 and the structured film of the film assembly 10 was on the opposite side facing outward from the valve substrate.

(111) The valve substrate 20 had a first opening 22. The first opening 22 was formed by a hole to provide a channel through the base 28 of the valve substrate 20 to inner area 29. The film assembly 10 was bonded onto the base 28 of the valve substrate 20 in such a way that in a relaxed state the film assembly was congruent and in contact with the surface of the base 28 through which the first opening 22 emerges, thereby forming a sealing member 25 over first opening 22 to provide a switchable valve 5.

(112) FIG. 35B shows the switchable vent in the closed position. From the outside to the inside, when the switchable vent was closed, the penetration of e.g. liquid water, water vapour and oils, through the film assembly 10 into the first area 29 of the switchable valve was prevented. From the inside to the outside, gases such as air or water vapour may exit first area 29 through the film assembly 10 in the direction of the arrow shown.

(113) In an alternative embodiment, the film assembly of Example 2B2 may be used in which the sealing member comprises an additional circular elastomeric coating. In such an embodiment, from the outside to the inside, when the vent was closed, the penetration of e.g. liquid water, water vapour and oils, through the film assembly into the inner area of the switchable valve was prevented. From the inside to the outside venting of gases such as air or water vapour through the sealing member is reduced compared to the embodiment of the film assembly of Example 2B1, due to the presence of the elastomeric coating forming the sealing member. In those embodiments in which the elastomeric coating prevents the passage of gases such as air or water through the sealing member, a check valve is obtained.

(114) Increasing the first fluid pressure causes the film assembly 10 to stretch. From the inside, once a desired pressure is reached the sealing member 25 portion of the film assembly 10 is lifted from the first opening 22. The film assembly 10 is also lifted from the base 28 of the valve substrate 20 forming second openings 24 at the non-bonded areas of the perimeter allowing fluid communication between the inner area 29 and outside of the switchable valve via the second vent area formed between the base 28 and the film assembly 10 as shown in FIG. 35C. In the open state, the expansion of the film assembly can release the sealing member from the first opening 22 allowing the pressure in the first area 29 of the switchable valve 5 to equilibrate with the outside in the direction of the arrows shown. The elastomeric support material of the film assembly is then in its stretched state.

(115) FIG. 36 shows a representation of an external three dimensional view of the switchable valve 5 in the open state. The second openings 24 formed in the non-bonded areas of the circular film assembly are shown. The second openings 24 are in fluid communication with the outside of the switchable valve i.e. the environment external to the first area of the switchable valve. Fluids such as one or more of air, water vapour and liquid water, for instance, may flow from the interior area of the valve through the second vent area between film assembly 10 and base 28 to the outside via second openings 24. If equilibrium between the internal and external pressure of the switchable valve is reached, the elastomeric support material returns to its relaxed state, causing the sealing member to lower onto the base 28, sealing the first opening and second openings 24, and closing the valve again.

Example 2D1

(116) The obtained compacted film of Example 2D (see FIG. 23) was coated with an elastomeric support material to form a film assembly. A 100 micron paper was lasercut with slots of 100 micron width and a distance of about 1 mm. Wacker Elastosil RT 620 Silicones component A and B were mixed at a weight ratio of 9:1 and the material was pressed through the slots of the paper. The material was cured in an oven for 3 min at 80° C.

(117) FIG. 24 shows on the right hand side the compacted film of Example 2D with elastomeric line coatings. On the left hand side the film assembly is shown after the first stretch cycle. Periodic wrinkle pattern occur between the elastomeric lines.

Example 3

(118) An ePTFE membrane was made by processes known in the art for example US20140120286 A1. The membrane had an average ATEQ airflow of 500 l/hr (at 70 mbar test pressure), a thickness of 25 μm and a mass/area of 6.5 g/m.sup.2.

(119) The membrane was adhered to a prestretched PDMS (Elastosil RT620, Wacker silicones) sheet with slight pressure. The PDMS sheet was relaxed in longitudinal direction as can be seen in following Table 2.

(120) TABLE-US-00002 TABLE 2 3A (reference) 3B Processing type — Longitudinal Processing ratio [%] 100 300 Processing temperature [° C.] 20 20 Elastic substrate — Elastosil RT 620 Elastic substrate surface — smooth Structure density direction x — 0.0/mm Structure density direction y — 0.0/mm

Example 3B1

(121) The film of Example 3B was bonded to a 12 mm Polyurethane hotmelt grid material (Protechnic, France) in a heatpress at 100° C. for 5 s and 3 bar pressure. After cooling the sample was removed from the substrate it was compacted on. At removal the compacted parts of the film in between the grid unfolded and a controlled 3D patterned surface was obtained. The parts of the compacted film being bonded to the grid are still in their compacted state.

(122) FIG. 25 shows an image of the obtained film assembly with released sections having semi-spherical shape.

Example 4

(123) An ePTFE membrane was made by processes known in the art, for example in US 2007/0012624 A1. The membrane had an average mass/area of 0.5 g/m.sup.2 and a thickness of about 0.6 μm.

(124) PDMS (Elastosil RT 620) was used as elastic substrate. The membrane was adhered to the elastic substrate in a prestretched state with slight pressure using the rotatable elastic carrier belt of Example D2 above (see also FIG. 2). The elastic substrate was relaxed in the transverse upon rotation. Example 4D was compacted over its potential to be compacted, and a periodic delamination of the film from the elastic substrate occurred. The structure density for example 4D is 125 per mm.

(125) SEM images of Examples 4A, 4B and 4C are shown in FIGS. 26 to 28. Results and processing conditions are given in Table 3 below.

(126) TABLE-US-00003 TABLE 3 4A (ref- erence) 4B 4C 4D Processing type — transverse transverse transverse Processing ratio 100 250 625 1560 [%] 1pass 2pass 3pass Processing 20 20 20 20 temperature [° C.] Elastic substrate — Elastosil Elastosil Elastosil RT 620 RT 620 RT 620 Elastic substrate — smooth smooth smooth surface Structure density — 0.0/mm 0.0/mm 125/mm direction x Structure density — 0.0/mm 0.0/mm  0.0/mm direction y

Example 5

(127) Example 5 is a structured film obtained by the exemplary process for the formation of a structured porous film as described above. An ePTFE membrane was made by processes known in the art, for example U.S. Pat. No. 3,953,566. The membrane had an average matrix tensile strength of 10 N/mm.sup.2 in machine direction and 25 N/mm.sup.2 in transverse direction, an airflow of 8 Gurley seconds, a bubble point of 1.5 bar, a thickness of 35 μm, mass/area of 17 g/m.sup.2, and mean flow pore size of 0.18 μm.

(128) A Bicomponent Copolyester Spunbond was used as support material. To adhere the support material to the membrane samples a polyurethane hot melt web adhesive (Article Number: D6C8F 10 g/m.sup.2; Company: Protechnic (France)) was used. The web adhesive was pre-applied to the support material in a heat press at 120° C. and 5 psi (0.34 bar) areal pressure at 15 seconds dwell time. The support material with pre-adhered adhesive layer was placed on top of the membrane, the adhesive layer facing towards the membrane. A 10 mm thick, 150 mm diameter silicone sheet (Elastosil RT620) was preheated in an oven to reach 150° C. The upper silicone sheet was placed on top of the support material. An aluminium rod with a diameter of 80 mm and a mass of 5 kg was placed on top of the upper silicone sheet for 10 s to create a bond between the membrane sample and the support material.

(129) After 10 s the rod and upper silicone sheet were removed and the sample was cooled for 3 min before removing from the lower silicone sheet material.

(130) The elastic substrate of a device according to FIG. 1 is stretched to the desired processing ratio with air inflation. After reaching the desired stretched state, a valve is closed to keep the processing ratio on a constant state. The film sample is applied on the stretched elastic substrate and a force is applied with a rubber roller to adhere the film sample to the elastic substrate.

(131) After sufficient adhesion is achieved, the air valve is opened to release the inner pressure that stretches the elastic substrate.

(132) A typical processing time was 3 seconds for Elastosil RT620 inflated to a processing ratio of 200%. The elastic substrate retracts back to its original unstretched, flat shape. The adhered film retracts with the elastic substrate, but is structured after the process.

(133) Processing details and results are given in Table 4 below. FIG. 29 shows the determination of the structure density of the film (left hand side), and a surface topography of the film right hand side).

(134) TABLE-US-00004 TABLE 4 Example 5 processing type biaxial Processing ratio (%) 300 processing temp. (° C.) 20 elastic substrate Elastosil RT620 elastic substrate surface smooth airflow ATEQ - up (l/h) 105.90 airflow ATEQ - down (l/h) 101.80 structure height (μm) 890 structure density, direction x 1.5/mm structure density, direction y 1.5/mm Area increase factor (calc. 9 from proc. ratio(s))