PROCESS FOR INTRODUCING PERFORATIONS INTO LAMINATES COMPRISING SILICONE GELS

Abstract

Described is a process for introducing perforations in a laminate that comprises a silicone gel. The process includes the following steps: bringing an array of perforating elements in contact with a deformable layer of a laminate that at least includes a substrate layer, a layer comprising a silicone gel and a deformable layer, wherein said deformable layer covers said layer including the silicone gel; applying ultrasonic energy to said laminate in order to simultaneously introduce a plurality of perforations into said laminate, while providing deformed portions in said deformable layer, wherein said deformed portions penetrate into the plurality of perforations in said laminate; after having introduced said plurality of perforations into said laminate, keeping said deformable layer in contact with said layer including the silicone gel, such that said deformed portions remain penetrating into said plurality of perforations, for at least 12 hours.

Claims

1. A process for introducing a plurality of perforations into a laminate, wherein said process comprises at least the following steps: i. providing a laminate, said laminate comprising at least one substrate layer, said substrate layer being in contact with at least one layer comprising a silicone gel: said laminate further comprising, in contact with said layer comprising silicone gel layer, at least one deformable layer; ii. providing an ultrasonic welding device comprising an array of perforating elements suitable for introducing perforations into at least said substrate and said layer comprising silicone gel; iii. bringing said array of perforating elements in contact with said deformable layer of said laminate; iv. applying ultrasonic energy to said laminate in order to simultaneously introduce a plurality of perforations into at least said substrate and said layer comprising silicone gel, while introducing deformed portions in said deformable layer, wherein said deformed portions essentially correspond to the shape of the perforating elements, further wherein said deformed portions at least partly penetrate into the perforations so created; v. after having introduced said plurality of perforations into said laminate, keeping said deformable layer in contact with said layer comprising silicone layer, such that said deformed portions remain penetrating into said plurality of perforations, for at least 12 hours.

2. The process according to claim 1, wherein said substrate layer of the laminate is a polymer layer.

3. The process according to claim 1, wherein the thickness of said substrate layer is from 5 μm to 200 μm.

4. The process according to claim 1, wherein said substrate layer is in contact with at least one further layer that is positioned farther away from said layer comprising silicone gel.

5. The process according to claim 1, wherein a silicone composition, precursor or silicone gel is brought into contact with the substrate layer in a process step (0) that occurs prior to step (i).

6. The process according claim 5, wherein the time from the moment of joining said substrate layer with a silicone composition, precursor or silicone gel in a step (0) and the moment of applying ultrasonic energy to the laminate in order to simultaneously introduce a plurality of perforations into said laminate is not more than 12 hours.

7. The process according to claim 1, wherein said layer comprises the silicone gel, wherein the silicone gel is based on a two-component silicone composition.

8. The process according to claim 1, wherein atho softness/penetration depth of said silicone gel is from 3 mm to 20 mm.

9. The process according to claim 1, wherein the amount of silicone gel per square meter is from 10 g/m.sup.2 to 500 g/m.sup.2.

10. The process according to claim 1, wherein said perforations have a diameter of from 0.5 mm to 20 mm.

11. The process according to claim 1, wherein the melting point of said deformable film is from 120 to 230° C.

12. The process according to claim 1, wherein said deformable layer comprises a material selected from the group consisting of polypropylene, polyester, polycarbonate, and polyamide or a combination thereof.

13. The process according to claim 1, wherein after the time period indicated in step (v), the process further comprises the step of removing said deformable layer from said layer comprising silicone gel.

Description

DESCRIPTION OF THE FIGURES

[0068] FIG. 1: schematically shows an ultrasonic welding device comprising, among others, a sonotrode/horn (10) and an opposed perforation element (13) that can be used to introduce perforations into a laminate (1).

[0069] FIG. 2: shows an apparatus known from the art for continuously introducing perforations into a laminate. A rotating drum (12) comprising perforation elements (13), in conjunction with the sonotrode (14), introduces perforations into a laminate (1).

[0070] FIG. 3: shows the cone (dimension and positioning) used in the standard for measuring the softness/penetration of a given silicone gel. The measurement method is described in detail above.

[0071] FIG. 4: illustrates the process according to an embodiment of the invention: in which a rotating drum (12) with an array of perforation elements (e.g. pins) introduces an array of perforations into a laminate (11), said laminate comprising a paper layer (60), a substrate layer (50) and a silicone layer (40), wherein a deformable film (20) (i.e. a film that can be deformed by the perforation elements but is not molten by the ultrasonic energy input) is placed in contact with the rotating drum such that the array of perforation elements create a corresponding pattern of deformed portions (or imprints) in the deformable film which deformed portions penetrate into the perforations (30) of the laminate and thereby keep any “surplus” silicone gel (40) that has been pushed away and aggregates around the edges of the perforations from occluding the perforations.

[0072] FIGS. 5A-C: show a microscopic image of a perforated laminates having the layer structure as schematically shown in FIG. 4 [polyurethane substrate layer (“PU film”) and silicone coating], wherein, in FIG. 5A, the silicone layer has a grammage of 500 g/m2 and a comparatively high softness/penetration depth of 14.5 mm and the deformable film [laminate of polyethylene (PE) film and polyamide (PA) film, wherein the PE film functions as a processing aid, i.e. release liner against the silicone and the PA film is the deformable film] as deformed (having deformed portions that penetrate into the perforations) was removed immediately after the perforating step (process not in accordance with the present invention).

[0073] As is apparent from FIG. 5A, after 72 hours, the silicone gel completely occluded the peroration holes in the PU film. By contrast, in FIGS. 5B and 5C (otherwise same laminate and process), the deformable film [laminate of polyethylene (PE) film and polyamide (PA) film as described above] was removed after 72 hours. As can be seen from FIGS. 5B and 5C vis-à-vis FIG. 5A, implementing the step of introducing a deformable film and of keeping the deformable (or deformed) film in the perforations for at least 12 hours, preferably at least 24 hours, minimizes occlusion of the perforations by the silicone gel.

[0074] FIG. 6: shows a microscopic image of a perforated laminate having the layer structure as schematically shown in FIG. 4 (PU layer and silicone coating), wherein, in FIG. 6A, the silicone layer has a grammage of 100 g/m2 and a comparatively low softness/penetration depth of 5 mm to 6 mm, wherein the deformable film [laminate of polyethylene (PE) film and polyamide (PA) film as described above in connection with FIG. 5] as deformed and penetrating into the perforations was removed directly after the perforating step. By contrast, in FIG. 6B (otherwise same laminate and process), the deformable film [laminate of polyethylene (PE) film and polyamide (PA) film, same as above] was removed after 72 hours. As is apparent from a comparison of FIGS. 6A and 6B, the occlusion effect (i.e. movement of silicone gel into the perforations) is substantially avoided by the use of the deformable film (i.e. by keeping the deformable/deformed film after the perforation step).

[0075] All perforated products discussed above were analysed visually using polarized light microscopy. The distance between two perforations (in all analysed products) is approximately 3 mm (centre-to centre distance). All microscopic images in the above examples have been taken from the polyurethane film side of the laminate.