Method for manufacturing a blown film web as well as a blown film line

Patent metadata

Field	Value
Publication number	US-2016263813-A1
Application number	US-201415029558-A
Country	US
Kind code	A1
Filing date	Oct 15, 2014
Priority date	Oct 15, 2013
Publication date	Sep 15, 2016
Grant date	—

Abstract

In a method for manufacturing blown film web on a blown film line, film is heated above the takeoff device and then treated mechanically. This allows the film to be brought from initial heat to an easy-to-process temperature level with little energy. A horizontally oriented treatment roll path is provided between the takeoff and a reversing device is arranged above the takeoff. In both aspects, controlling is performed to achieve a uniform film gauge after stretching.

First claim

1 . Method for manufacturing a blown film web on a blown film line with the steps:
a. Extruding a film tube; b. Inflating the film tube in a tube forming zone and taking off the double-layer film web with a takeoff roll pair for drawing the film tube longitudinally and transversely; c. Cooling the rising film tube using a means of cooling; d. Laying flat the film tube into a double-layer film web by means of a layflat device; e. Routing double-layer film web further upwards above takeoff roll pair and through a treatment roll path with a means of heating for heating double-layer film web; f. Treating double-layer film web on treatment roll path; namely stretching double-layer film web in a stretching path of treatment roll path; g. Routing double-layer film web through a reversing unit for laying; wherein the additional step of
h. Controlling the film gauge of the double-layer film web stretched monoaxially in the machine direction by means of a predetermined target gauge profile, whereby the film gauge profile of the tube film produced on blown film line is controlled in such a manner that the predetermined target gauge profile has variances from a uniform film gauge that are used to compensate for the change in film gauge over the film width resulting from the subsequent monoaxial stretching in the machine direction so that, by means of stretching, a film with a transverse gauge profile having the least possible variances from the mean film gauge over the entire film width is produced.

2 . Method according to claim 1 , whereby for threading double-layer film web upon startup of blown-film line, a roll of treatment roll path is slid or pivoted from its operating position, and double-layer film web is tensioned after threading by means of sliding or pivoting back.

3 . Method according to claim 1 , wherein in treatment step f, double-layer film web in addition to being stretched, is embossed, irradiated, and/or subjected to corona treatment.

4 . Method according to claim 1 , wherein the extruded tube film is controlled to a predetermined target gauge profile via its circumference by means of a film gauge profile control system.

5 . Method according to claim 1 , wherein the target profile laying resulting from the reversing takeoff is compensated over the film width and continuously adjusted, whereby the assignment of one or several circumferential points and/or sectors of the laid-flat tube film to one or several control zones in the control algorithm is taken into account for controlling the segmented control zone.

6 . Method according to claim 1 , wherein the predetermined target gauge profile is controlled by means of an algorithm from the readings of a measuring device that measures the film gauge across the entire film width after monoaxial stretching in the machine direction.

7 . Method according to claim 1 , wherein the control algorithm for controlling the individual segmented control zones includes a superimposition
of the base profile from the film gauge profile control of the blown-film line; of the stretching profile from the laying of the tube film by means of the reversing takeoff and impacts from the stretching process; and optionally, of the roll profile from the evaluation of the film roll.

8 . Method according to claim 1 , wherein the target gauge profile is set manually in the control system.

9 . Method according to claim 1 , wherein the film is routed to the stretching device in the treatment roll path blocked.

10 . Method according to claim 1 , wherein the tube film is slit open on one or both side(s), folded open, and routed to the stretching device.

11 . Method according to claim 1 , wherein for the purpose of controlling, the film gauge is measured above takeoff roll pair according to the routing of the film web proposed here.

12 . Blown-film line, with an annular nozzle for extruding a film tube, with a tube forming zone for drawing the film tube longitudinally and transversely, with a means of cooling for the rising film tube, with a device for laying the film tube flat into a double-layer film web, and with a takeoff roll pair above the means of cooling for taking off the film tube, whereby the treatment roll path has a stretching section for longitudinal stretching of the double-layer film web,
wherein
a treatment roll path is provided above takeoff roll pair with a means of heating for double-layer film web, and that
the device for performing the process is set up according to claim 1 and
includes a blown film line with a reversing takeoff and at least one subsequent stretching device, as well as at least one winder,
whereby a reversing device is provided above the treatment roll path.

13 . Blown-film line, with an annular nozzle for extruding a film tube, with a tube-forming zone for drawing the film tube longitudinally and transversely, with a means of cooling for the rising film tube, with a device for laying the film tube flat into a double-layer film web, and with a takeoff roll pair above the means of cooling for taking off the film tube, whereby the treatment roll path has a stretching section for longitudinal stretching of the double-layer film web, according to claim 12 ,
wherein above takeoff roll pair, a transversely oriented treatment roll path below a reversing device is provided for double-layer film web.

14 . Blown film line according to claim 12 , wherein the treatment roll path has a temperature control unit that allows the means of heating to heat the double-layer film web initially by less than 80 K.

15 . Blown film line according to claim 12 , wherein the treatment roll path has a heating roll for heating up the double-layer film web for easier treatment within the treatment roll path.

16 . Blown film line according to claim 12 , wherein the stretching section has a length of 120 cm max.

17 . Blown film line according to claim 12 , wherein downstream from the stretching path, the treatment roll path has an annealing roll for relaxing the double-layer film web after stretching.

18 . Blown film line according to claim 12 , wherein the annealing roll has an annealing control unit that allows heating the double-layer film web by less than 30 K.

19 . Blown film line according to one of claim 12 , wherein the treatment roll path has a means of cooling for the double-layer film web.

20 . Blown film line according to claim 12 , wherein the treatment roll path has a control unit for improving layflat; i.e., by transversely stretching the double-layer film web by 0.5% to 5%.

21 . Blown film line according to claim 12 , wherein the treatment roll path has a control unit for stretching; i.e., by stretching the double-layer film web by more than 5%.

22 . Blown film line according to claim 12 , wherein the treatment roll path has a heating roll for the double-layer film web with a temperature step of plus/minus 0 K, or of plus 1 K to plus 80 K or more in the case of fast-running double-layer film webs, when compared to the preceding station in the machine direction, and/or the roll temperature of the takeoff roll.

23 . Blown film line according to claim 12 , wherein the treatment roll path has a stretching roll for the double-layer film web with a temperature step of minus 10 K compared to the preceding station in the machine direction.

24 . Blown film line according to claim 12 , wherein the treatment roll path has a stretching roll, with a sm

Assignees

• Reifenhaeuser Masch

Inventors

• Lettowsky Christoph

Classifications

• B29C48/9105

  of hollow articles · CPC title

• B29C48/0018

  combined with shaping by orienting, stretching or shrinking, e.g. film blowing (B29C48/0017 takes precedence) · CPC title

• B29C55/28 Primary

  of blown tubular films, e.g. by inflation {(extrusion moulding of tubular films B29C48/03)} · CPC title

• B29C48/914

  Cooling drums · CPC title

• B29C48/9135

  of flat articles, e.g. using specially adapted supporting means · CPC title