DEVICE AND PROCESS TO PERMIT MONOAXIAL CHANGES IN THE LENGTH OF FILM WEBS

Abstract

In the case of a device to permit the monoaxial length change of film webs in machine direction, which comprises at least one processing gap delimited by two rolls via which a film web is routed in machine direction, whereby the first roll in film transport direction exhibits a first peripheral speed and the second roll in film transport direction exhibits a second peripheral speed, in order to produce film webs with low transverse neck-in as well as reduced edge build-up and to improve the flatness of the film web.

Claims

1. A device to permit a monoaxial length change of film webs in a machine direction, the device comprising: at least one processing gap delimited by first and second rolls via which a film web is routed in the machine direction, whereby the first roll in a film transport direction exhibits a first peripheral speed and the second roll in a film transport direction exhibits a second peripheral speed wherein at least one of the rolls is an air-flow roll through which air flows from the outside in.

2. The device in accordance with claim 1, wherein a negative pressure source can be connected up to the air-flow roll and therefore a negative pressure can be applied to the air-flow roll.

3. The device in accordance with claim 2, wherein different degrees of negative pressure can be applied to the air-flow roll along a length of the air-flow roll.

4. The device in accordance with claim 1, wherein the at least one air-flow roll is combineable with a temperature control.

5. The device in accordance with claim 1, wherein the first roll in the film transport direction exhibits a lower peripheral speed than the second roll in the film transport direction and the length change to the film web is a positive one.

6. The device in accordance with claim 1, wherein the first roll in the film transport direction exhibits a higher peripheral speed than the second roll in the film transport direction of the film web and the length change to the film web is a negative one.

7. The device in accordance with claim 1, wherein the first roll in the film transport direction and the second roll in the film transport direction of the film web exhibit the same peripheral speed.

8. The device in accordance with claim 1, wherein the device is an integral part of an orientation line.

9. The device in accordance with claim 8, wherein further rolls of the orientation line are designed as air-flow rolls with and without applied negative pressure.

10. The device in accordance with claim 8, wherein the orientation line is located in-line within a blown film line.

11. A blown film line for production of a tubular film, wherein the device in accordance with claim 1 is located in-line within a blown film line.

12. The blown film line in accordance with claim 11, wherein the device is located in the film transport direction downstream of the pair of take-off rolls and upstream or downstream of turning bars of the blown film line.

13. The blown film line in accordance with claim 11, wherein the blown film line includes a plurality of devices.

14. A process to permit the monoaxial length alteration of film webs in a machine direction, whereby a film web is routed through at least one processing gap delimited by first and second rolls, whereby the first roll in a film transport direction exhibits a first peripheral speed and the second roll in the film transport direction exhibits a second peripheral speed wherein the film web experiences a change in length in the processing gap and wherein at least one of the first and second rolls is an air-flow roll through which air flows from the outside in and whereby the air that accumulates between the air-flow roll and the film web flows out through the air-flow roll, and the film web lays direct on the air-flow roll.

15. The process in accordance with claim 14, wherein the film is subjected during production on a blown film line to a film thickness regulation, so that the thickness profile of the film tube produced with the blown film line is regulated such that the specified thickness profile exhibits deviations from a uniform film thickness, which serves to compensate for film thickness changes across the film width which occur during the downstream monoaxial orientation in the machine direction so that the film web is produced as a result of orientation whose transverse thickness profile has limited deviations from the average film thickness across the entire width of the film web.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The drawings show:

[0062] FIG. 1 shows an orientation line with the disclosed-design device to permit monoaxial changes to the length of a film web in machine direction, and

[0063] FIG. 2 shows a device to permit monoaxial changes to the length of a film web in machine direction

DETAILED DESCRIPTION

[0064] FIG. 1 shows the disclosed-design device to permit monoaxial changes to the length of a film web in machine direction within an orientation line, also known as an MDO line, as an application possibility of the disclosed-design device.

[0065] The film web (1) is introduced into the orientation line from above. It is then routed via a heating section (2) with heated rolls (3). The film web (1) is then routed to the disclosed-design device for length change (4), here the orientation unit (4), with the rolls (5), here the orientation rolls with the processing gap in between, here the orientation gap (6), and is oriented. The diameter of the orientation rolls (5) can be smaller than that of the heated rolls. The film web (1) is subsequently routed to an annealing section (7) with annealing rolls (8) for tempering, followed by a cooling section (9) with cooling rolls (10). The film (1) finally exits the MDO system and can be wound with the winder. The film web is held securely on the different rolls by means of lay-on rolls (11).

[0066] FIG. 2 shows the device for length change (4) of the orientation line in detail. The film web (1) is routed over the first orientation roll (5a) to the second orientation roll (5b). The orientation gap (6) is located between the orientation rolls (5a) and (5b). In this orientation line, the second orientation roll (5b) has a higher peripheral speed than the first orientation roll (5a) so that a positive length alteration results. The lay-on rolls (11) serve to additionally fix the film web (1) on the orientation rolls (5a) and (5b).

[0067] The film web (1) then exits the disclosed-design device (4). The orientation roll (5b) is designed in accordance with the disclosure as an air-flow roll with the possibility of connecting up a negative pressure source, not shown here. The orientation roll (5a) and the orientation roll (5b) can also be designed in addition as tempering rolls. In that case, the orientation roll (5b) is a combination of air-flow roll and tempering roll.

[0068] Dependent on the orientation task, individual lay-on rolls (11) or all of them can be omitted.

[0069] Orientation lines can also have more than two orientation rolls (5) and thus have more disclosed-design devices (4).

[0070] The orientation line can have two, three or more heated rolls, orientation rolls, annealing rolls or cooling rolls in each case.

LEGEND

[0071] 1 Film web

[0072] 2 Heating section

[0073] 3 Heated rolls

[0074] 4 Device for length change/orientation unit

[0075] 5 Rolls/orientation rolls

[0076] 5a First roll/orientation roll

[0077] 5b Second orientation roll/roll

[0078] 6 Processing gap/orientation gap

[0079] 7 Annealing section

[0080] 8 Annealing rolls

[0081] 9 Cooling section

[0082] 10 Cooling rolls

[0083] 11 Lay-on rolls