Process for Producing a Laminate

Abstract

The present invention relates to a process for laminating a first substrate, which comprises a thermoplastic polymer material surface, and wherein the first substrate preferably is a thermoplastic polymer film, to a second substrate, wherein the second substrate preferably is a non-woven or woven fabric, wherein the thermoplastic polymer material surface is activated by irradiation with a laser beam prior to laminating the two substrates to each other as well as a device for carrying out such a process.

Claims

1. A process for bonding at least one first substrate, which comprises a thermoplastic polymer material surface, to at least one second substrate without an adhesive to form a laminate, comprising (a) irradiating the thermoplastic polymer material surface of the first substrate with electromagnetic radiation in form of a laser beam such that the thermoplastic polymer material surface of the first substrate is at least locally heated to a softened state; and (b) laminating the laser irradiated softened thermoplastic polymer material surface of the first substrate to the second substrate.

2. The process according to claim 1, wherein the process does not involve cooling the first substrate during or after irradiation with the laser beam.

3. The process according to claim 1, wherein the first substrate is a thermoplastic polymer film.

4. The process according to claim 1, wherein the second substrate is a non-woven or woven fabric.

5. The process according to claim 1, wherein the laser beam is directed to the thermoplastic polymer material surface of the first substrate by a polygonal mirror, which is pivotable around a rotation axis.

6. The process according to claim 5, wherein the laser beam is focused prior or after having been directed by the polygonal mirror.

7. The process according to claim 1, wherein the process is a continuous process; the first and second substrates are transported in a feed direction; and the laser beam is guided over the thermoplastic polymer material surface of the first substrate in a line pattern and/or essentially orthogonal to the movement direction of the first substrate.

8. The process according to claim 1, wherein the laser beam is guided through a photomask for patterning the thermoplastic polymer material surface of the first substrate.

9. The process according to claim 1, wherein the laser beam projection impinges on the thermoplastic polymer material surface of the first substrate less than 10 cm before the site where the two substrates are brought into contact with each other.

10. The process according to claim 1, wherein the laser beam projection impinges on the thermoplastic polymer material surface of the first substrate less than 1 cm before the site where the two substrates are brought into contact with each other.

11. The process according to claim 1, wherein the laser beam is guided over the thermoplastic polymer material surface of the first substrate and adapted to a movement speed of the first substrate such that time period between irradiation and lamination is essentially identical for each point on the thermoplastic polymer material surface.

12. The process according to claim 1, wherein the laser (a) operates at a wavelength in the range of 1 to 12 m; and/or (b) is a carbon dioxide laser; and/or (c) is deflected onto the thermoplastic polymer material surface of the first substrate at an angle of up to about 90 relative to the feed direction of the first substrate.

13. The process according to claim 1, wherein the thermoplastic polymer material is a polyolefin.

14. The process according to claim 1, wherein step (b) is carried out by use of a roll laminator or nip station.

15. The process according to claim 1, wherein only previously defined areas of the first substrate thermoplastic polymer material are irradiated by the laser beam.

16. A device for laminating at least one first substrate, the at least one first substrate being a thermoplastic polymer film comprising a thermoplastic polymer material surface, to at least one second substrate, wherein the at least one second substrate is a non-woven or woven fabric, comprising: (a) at least one transporting means to transport the at least one first substrate, the at least one second substrate or both in a feed direction; (b) a laser for generating a laser beam and irradiating the thermoplastic polymer material surface such that it is at least locally heated to a softened state, wherein the laser beam is guided such that it has a contact point on the thermoplastic polymer material surface that is moved relative to the surface in a projection movement direction, wherein the projection movement direction is at least temporarily angled relative to the feed direction, to allow heating the thermoplastic polymer material surface during movement of the first substrate in the feed direction and before lamination to the second substrate, wherein the laser beam comprises infrared radiation of a wavelength in the range of 5 to 10 m; (c) a laminating unit to laminate the at least one first substrate with its softened thermoplastic polymer material surface side to the at least one second substrate.

17. The device according to claim 16, wherein the device further comprises (a) a laser beam deflection unit to deflect the laser beam to and guide it over the thermoplastic polymer material surface, wherein the laser beam deflection unit comprises a polygonal mirror; and/or (b) a laser beam focusing means to focus the laser beam; and/or (c) a photomask for patterning the surface of the thermoplastic polymer material surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG. 1 is a schematic view of an apparatus according to the invention.

[0055] FIG. 2 is a sectional view through the section line A-A of the device of FIG. 1 in a snapshot.

[0056] FIG. 3 is the sectional view of FIG. 2 after the expiration of a time period t1.

[0057] FIG. 4 is the sectional view of FIG. 2 after the expiration of a time period t2.

[0058] FIG. 5 is a schematic view of an apparatus according to the invention.

[0059] FIG. 6 is a sectional view through the section line A-A of the device of FIG. 5 in a snapshot.

[0060] FIG. 7 is the sectional view of FIG. 6 after the expiration of a time period t1.

[0061] FIG. 8 is the sectional view of FIG. 6 after the expiration of a time period t2.

[0062] FIG. 1 shows a schematic view of a device of the invention 1 for continuous bonding a second substrate 2, which is by way of example in the form of a non-woven or woven fabric, with a first sheet-shaped substrate 4, which is by way of example made of a thermoplastic polymer material. The second sheet-shaped substrate 2 is in this case on a supply roll 3 and is fed by means of a not further described feed device comprising a drive and a plurality of deflection and/or guiding rollers. The second substrate 2 is transported towards a pressure unit 7 for pressing one side of the second substrate 2 to the first substrate 4.

[0063] The first substrate 4, in turn, is in this case on a supply roll 5 and is fed by means not described in detail also with a feed device in a feed direction 6 of the pressure unit 7. Immediately before reaching the pressure unit 7, the surface of the first substrate 4, which is intended to come in contact with the second substrate 2 is heated by means of a laser beam 11 with a wavelength range between 9 to 10 microns, which is emitted from a laser unit 10. The laser unit 10 shown comprises by way of example a CO.sub.2 laser with a power in the range between 500 and 1500 W. In addition, the CO.sub.2 laser is operated continuously or nearly continuously. To guide the laser beam 11 on the surface of the first substrate 4 a deflection unit 12 is provided which includes in particular a rotatably mounted polygon mirror 13. The polygon mirror 13 has a drive in the form of servomotors to drive the polygon mirror 13 at a desired rotational speed. In addition, the deflection unit may comprise a focusing device, which is not shown. The deflection unit 12 in particular in combination with the rotatably mounted polygon mirror 13 provides a way to deflect the laser beam 11 and to guide it over the surface of the first substrate 4 such that its projection is moved in a relative movement with respect to the surface in a projection movement direction over the surface of the first substrate 4 to allow heating of the first substrate 4 and convert it into a softened state. The deflection unit 12 is designed such that it guides at least temporarily the laser beam 11 over the surface of the first substrate 4 such that the projection movement direction moves at an angle to the feed direction to allow heating of the surface area during its movement in the feed direction. In order to obtain the desired temperature of the surface of the first substrate 4, also a temperature sensor 16 is provided, which determines the temperature of the upper surface immediately before the pressure unit 7. Furthermore, a beam trap 14 is provided in order to block in a controlled manner laser irradiation transmitted through the first substrate 4. For controlling the apparatus 1, both feeding means, the laser unit 10, the deflection unit 12 and the temperature sensor 16 are connected to a control unit 15. This control unit can match the feed rates of the substrates 2, 4 and the speed of the laser beam 11 across the surface of the first substrate 4 to each other, so that the surface of the first substrate 4 is heated to the desired temperature.

[0064] Subsequently, the softened surface of the first substrate 4 is contacted with the second substrate 2 in the pressure unit 7. For pressing, both substrates 2, 4 are fed to the pressure unit 7 wherein a press roller 8 and a corresponding bedroll 9 press both substrates 2, 4 together.

[0065] FIG. 2 shows a sectional view through the section line A-A of the apparatus of FIG. 1, with the cut extending through the press roller 8 and the sectional area is parallel to the surface of the first substrate 4. The device 1 is here shown in a photographic snapshot to illustrate the irradiation of the first substrate 4 by the laser unit 10 and the deflection unit 12. The laser beam 11 impinges on the surface of the first substrate 4 in a projection 19, wherein the energy input results in a heating of the surface. For further heating the surface, the laser beam 11 is deflected by means of the deflection unit 12 such that its projection 19 is moved over the surface in a projection movement direction 17. This active projection movement relative to the surface is independent of a movement of the substrate in the feed direction 6. In the shown embodiment, the projection movement direction 17 is substantially orthogonal to the feed direction 6.

[0066] FIG. 3 shows the sectional view of FIG. 2 after a time period t1, during which the laser beam 11 has been guided over the first substrate 4 such that the projection 19 shown in FIG. 2 has been moved from the first side edge of the substrate 4 to the opposite second side edge relative to the surface following the above described active projection movement direction. Further, the first substrate 4 has been moved during the irradiation in the feed direction 6, so that a projection line in form of a parallelogram extends over the surface, even though the projection movement direction 17 is substantially orthogonal to the feed direction 6. The movement of the first substrate 4 in the feed direction 6 has thus resulted in a passive projection movement across the surface. By means of the above described focusing means the width of the projection line 21 has been set to a projection width 20 of about 8 mm.

[0067] FIG. 4 shows the sectional view of FIG. 2 after the expiration of a time period t2, corresponding to a multiple of the time period t1 of FIG. 3, in which, as described above, the laser beam 11 has been guided over the first substrate 4 such that the projection 19 shown in FIG. 2 has been moved from the first side edge of the substrate 4 to the opposite second side edge relative to the surface by means of the above-described active projection movement. By use of the rotatably mounted polygon mirror 13, the laser beam 11 after reaching the second side edge of the substrate 4 is again deflected to the starting point on the first side edge of the substrate 4 and is again guided from there over the surface. The projection movement direction 17 here also extends substantially orthogonal to the feed direction 6. Here, the projection width 20, the time period between reaching two adjacent points on the first side of the substrate 4 and the movement speed of the first substrate 4 in the feed direction 6 are selected such that no point on the surface is doubly irradiated, wherein the projection lines 21, 21, 21, 21 generated by the projection 17 moved across the surface in the time period t2 represent adjacent parallelograms on the surface of the substrate 4. Said parameters are further selected such that the first substrate after the irradiation by the laser beam 11 has, at all irradiated points on a line orthogonal to the feed direction, the same temperature.

[0068] FIG. 5 shows a schematic view of a device of the invention 1 similar to FIG. 1. The difference lies in the presence of a photomask 22 in form of a comb that blends out parts of the incident laser beam 11 that is depicted here in an angle different from that shown in FIG. 1 to bring the point of impact of the laser beam on the substrate surface closer to the pressure unit 7. Although it may be present, the beam trap 14 is not shown in FIG. 5.

[0069] FIG. 6 shows a sectional view through the section line A-A of the apparatus of FIG. 5, with the cut extending through the press roller 8 and the sectional area is parallel to the surface of the first substrate 4. The device 1 is here shown in a photographic snapshot to illustrate the irradiation of the first substrate 4 by the laser unit 10 and the deflection unit 12 through the photomask 22. The laser beam 11 impinges on the surface of the first substrate 4 in a projection 19, wherein the energy application results in a heating of the surface. For further heating the surface, the laser beam 11 is deflected by means of the deflection unit 12 such that its projection 19 is moved over the surface in a projection movement direction 17. This active projection movement relative to the surface is independent of a movement of the substrate in the feed direction 6. In the shown embodiment, the projection movement direction 17 is substantially orthogonal to the feed direction 6.

[0070] FIG. 7 shows the sectional view of FIG. 6 after the time period t1, during which the laser beam 11 has been guided over the first substrate 4 such that the projection 19 shown in FIG. 6 has been moved from the first side edge of the substrate 4 to the opposite second side edge relative to the surface following the above described active projection movement direction. Further, the first substrate 4 has been moved during the irradiation in the feed direction 6, so that an imaginary projection line in form of a parallelogram consisting of alternating parallel areas of irradiated and thus heated and non-irradiated regions in form of short parallel lines has been formed.

[0071] FIG. 8 shows the sectional view of FIG. 6 after the expiration of a time period t2, corresponding to a multiple of the time period t1 of FIG. 7, in which, as described above, the laser beam 11 has been guided over the first substrate 4 such that the projection 19 shown in FIG. 6 has been moved from the first side of the substrate 4 to the opposite second side relative to the surface by means of the above-described active projection movement. By use of the rotatably mounted polygon mirror 13, the laser beam 11 after reaching the second side edge of the substrate 4 is again deflected to the starting point on the first side edge of the substrate 4 and is again guided from there over the surface. The projection movement direction 17 here also extends substantially orthogonal to the feed direction 6. Here, the projection width 20, the time period between reaching two adjacent points on the first side of the substrate 4 and the movement speed of the first substrate 4 in the feed direction 6 are selected such that no point on the surface is doubly irradiated, wherein the projection lines 21, 21, 21, 21 generated by the projection 17 moved across the surface in the time period t2 represent adjacent parallelograms on the surface of the substrate 4. Again, each parallelogram consists of alternating areas of irradiated and non-irradiated (blocked by photomask 22) surface regions that take the form of parallel linear areas. Said parameters are further selected such that the first substrate after the irradiation by the laser beam 11 has, at all irradiated points on a line orthogonal to the feed direction, the same temperature.

LIST OF REFERENCE SIGNS

[0072] 1 device [0073] 2 second substrate [0074] 3 supply roll [0075] 4 first substrate [0076] 5 supply roll [0077] 6 feed direction [0078] 7 pressure unit [0079] 8 press roller [0080] 9 bedroll [0081] 10 laser unit [0082] 11 laser beam [0083] 12 deflection unit [0084] 13 polygon mirror [0085] 14 beam trap [0086] 15 control unit [0087] 16 temperature sensor [0088] 17 projection movement direction [0089] 18 angle [0090] 19 projection [0091] 20 projection width [0092] 21 projection line [0093] 22 photomask (comb)

[0094] All embodiments disclosed herein in relation to the processes of the invention are similarly applicable to the devices described herein and vice versa.