CA2297696A1 - Process for controlling the diameter of a blown film web, blown up into a blown film bubble with a vertical center line between a pair of forward draw rolls and a pair of take-offrolls - Google Patents
Process for controlling the diameter of a blown film web, blown up into a blown film bubble with a vertical center line between a pair of forward draw rolls and a pair of take-offrolls Download PDFInfo
- Publication number
- CA2297696A1 CA2297696A1 CA002297696A CA2297696A CA2297696A1 CA 2297696 A1 CA2297696 A1 CA 2297696A1 CA 002297696 A CA002297696 A CA 002297696A CA 2297696 A CA2297696 A CA 2297696A CA 2297696 A1 CA2297696 A1 CA 2297696A1
- Authority
- CA
- Canada
- Prior art keywords
- blown
- bubble
- blown film
- pair
- rolls
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/28—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of blown tubular films, e.g. by inflation
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
Abstract
For the purpose of re-stretching, a blown film web is blown up into a blown film bubble between a pair of forward draw rolls and a pair of take-off rolls, after the blown film web has been heated in the inlet area of the blown film bubble. To hold the gas pressure in the blown film bubble constant or at such a value that the blown film web, hauled off the film bubble, exhibits a width equal to the desired width without having to refill through continuous injection of blowing air, water or a liquid with a different boiling point is filled into the film tube. The liquid collects above the pair of take-off rolls. The liquid is heated to a temperature exceeding its boiling point until the necessary pressure is reached in the blown film bubble.
Description
PROCESS FOR CONTROLLING THE DIAMETER OF A BLOWN FILM WEB, BLOWN
UP INTO A BLOWN FILM BUBBLE WITH A VERTICAL CENTER LINE BETWEEN
A PAIR OF FORWARD DRAW ROLLS AND A PAIR OF TAKE-OFF ROLLS
The invention relates to a process for controlling the diameter of a blown film web, blown up into a blown film bubble with a vertical center line between a pair of forward draw rolls and a pair of take-off rolls, in which process the blown film web is pulled off continuously from the blown film bubble by means of the pair of take-off rolls and laid flat by means of two flat-laying units, which are arranged in the shape of a wedge and taper off in the direction of the intake slit of the pair of take-off rollers, and in which process the blown film web is heated in the inlet area of the bubble.
There are cases in which a plastic blown film web, produced in the blown film extrusion process and wound up into a roll, is stretched by blowing up again into a bubble and heating in order to achieve other properties or to improve strength values. In so doing, the heating is conducted at temperatures that are necessary to achieve the desired modified film properties.
Preferably the blown-up blown film web is heated in the area of its inflow into the bubble up to approximately its heat deformation temperature (glass transition temperature). The blown film web, pulled in by the pair of forward draw rolls, is blown up using injection needles. In this process the injection needles can be arranged so as to travel along or rotate in order to maintain the air pressure in the blown film bubble.
In blowing up and stretching the blown film web in a blown film bubble, the blown film web, which is pulled off the blown film bubble and laid flat, cannot be prevented from dragging along the air through the pair of take-off rollers so that the air volume changes in the bubble. As the air volume decreases, the blown film web is also stretched less in the blown film bubble so that the diameter of the bubble or the width of the flat-laid blown film web, hauled off the blown film bubble, decreases. This decrease in air volume can be balanced by continuously feeding in blowing air using injection needles, a feature that is associated, however, with a perforation of the bubble, which is absolutely undesired.
The object of the invention is to propose a process, in which the gas pressure in the bubble can be held constant or at such a value that the blown film web, hauled off the bubble, exhibits a width equivalent to the desired width without having to constantly refill the blowing air through injections.
The invention solves this problem with a process of the type described in the introductory part in that the film tube is filled with water or a liquid that has a different boiling point and that collects above the pair of forward draw rolls and that the liquid is heated to temperatures exceeding its boiling point until a specific pressure is reached in the blown film bubble.
Thus, it is no longer necessary, according to the process of the invention, to refill compressed air through injections into the blown up film tube or the blown film bubble. A pressure loss in the blown film bubble is balanced, according to the invention, by the steam pressure of the liquid in the blown up blown film. The liquid can be heated, as necessary, through the film wall with radiant energy to temperatures exceeding the boiling point so
UP INTO A BLOWN FILM BUBBLE WITH A VERTICAL CENTER LINE BETWEEN
A PAIR OF FORWARD DRAW ROLLS AND A PAIR OF TAKE-OFF ROLLS
The invention relates to a process for controlling the diameter of a blown film web, blown up into a blown film bubble with a vertical center line between a pair of forward draw rolls and a pair of take-off rolls, in which process the blown film web is pulled off continuously from the blown film bubble by means of the pair of take-off rolls and laid flat by means of two flat-laying units, which are arranged in the shape of a wedge and taper off in the direction of the intake slit of the pair of take-off rollers, and in which process the blown film web is heated in the inlet area of the bubble.
There are cases in which a plastic blown film web, produced in the blown film extrusion process and wound up into a roll, is stretched by blowing up again into a bubble and heating in order to achieve other properties or to improve strength values. In so doing, the heating is conducted at temperatures that are necessary to achieve the desired modified film properties.
Preferably the blown-up blown film web is heated in the area of its inflow into the bubble up to approximately its heat deformation temperature (glass transition temperature). The blown film web, pulled in by the pair of forward draw rolls, is blown up using injection needles. In this process the injection needles can be arranged so as to travel along or rotate in order to maintain the air pressure in the blown film bubble.
In blowing up and stretching the blown film web in a blown film bubble, the blown film web, which is pulled off the blown film bubble and laid flat, cannot be prevented from dragging along the air through the pair of take-off rollers so that the air volume changes in the bubble. As the air volume decreases, the blown film web is also stretched less in the blown film bubble so that the diameter of the bubble or the width of the flat-laid blown film web, hauled off the blown film bubble, decreases. This decrease in air volume can be balanced by continuously feeding in blowing air using injection needles, a feature that is associated, however, with a perforation of the bubble, which is absolutely undesired.
The object of the invention is to propose a process, in which the gas pressure in the bubble can be held constant or at such a value that the blown film web, hauled off the bubble, exhibits a width equivalent to the desired width without having to constantly refill the blowing air through injections.
The invention solves this problem with a process of the type described in the introductory part in that the film tube is filled with water or a liquid that has a different boiling point and that collects above the pair of forward draw rolls and that the liquid is heated to temperatures exceeding its boiling point until a specific pressure is reached in the blown film bubble.
Thus, it is no longer necessary, according to the process of the invention, to refill compressed air through injections into the blown up film tube or the blown film bubble. A pressure loss in the blown film bubble is balanced, according to the invention, by the steam pressure of the liquid in the blown up blown film. The liquid can be heated, as necessary, through the film wall with radiant energy to temperatures exceeding the boiling point so
2 that a drop in the air pressure is equalized by the steam pressure of the liquid.
Water is the preferred liquid. It is especially advantageous to treat the blown film wall with water or water vapor when the blown film or at least the inside wall is made of polyamide. Then the polyamide films are made largely steam-tight through a water or water vapor treatment so that such films are especially suitable for packaging of food.
Instead of water, liquid having a low boiling point and preferably having a lower boiling point can also be used.
The liquid collecting in the blown-up film tube above the pair of forward draw rolls can be fed radiant energy, for example, using an infrared radiator.
However, it is especially advantageous to feed heat to the liquid using microwaves, such as those used in microwave heaters.
A preferred embodiment provides that the diameter of the blowm film bubble or the width of the flat-laid film, drawn off the bubble, is measured and in accordance with the measured deviation of the diameter from the desired diameter of the blown film bubble or the width from the desired width, heat is fed to the liquid by means of radiant energy.
A device for carrying out the process of the invention comprising a frame-mounted driven pair of forward draw rolls for a flat-lying film webs comprising an opposite, stationarily mounted, and driven pair of take-off rolls for the flat-laid blown film web, which is hauled off the blown-up film bubble and upstream of
Water is the preferred liquid. It is especially advantageous to treat the blown film wall with water or water vapor when the blown film or at least the inside wall is made of polyamide. Then the polyamide films are made largely steam-tight through a water or water vapor treatment so that such films are especially suitable for packaging of food.
Instead of water, liquid having a low boiling point and preferably having a lower boiling point can also be used.
The liquid collecting in the blown-up film tube above the pair of forward draw rolls can be fed radiant energy, for example, using an infrared radiator.
However, it is especially advantageous to feed heat to the liquid using microwaves, such as those used in microwave heaters.
A preferred embodiment provides that the diameter of the blowm film bubble or the width of the flat-laid film, drawn off the bubble, is measured and in accordance with the measured deviation of the diameter from the desired diameter of the blown film bubble or the width from the desired width, heat is fed to the liquid by means of radiant energy.
A device for carrying out the process of the invention comprising a frame-mounted driven pair of forward draw rolls for a flat-lying film webs comprising an opposite, stationarily mounted, and driven pair of take-off rolls for the flat-laid blown film web, which is hauled off the blown-up film bubble and upstream of
3 which are flat-laying units, for example flat-laying plates, which are arranged in the shape of a wedged comprising units for blowing up the blown film web between the pairs of forward draw and take-off rolls into a film bubbled comprising units for heating the blown-up blown film web: and comprising units for measuring the diameter of the bubble or the width of the flat-laid blown film web, hauled off the film bubble, characterized in that above the pair of take-off rolls there is a radiator, which heats a liquid in the blown-up film tube and that there is a controller, which feeds energy to the radiator in accordance with the deviation of the measured diameter from the diameter of the blown film bubble or the measured width from the desired width of the flat-laid blown film web.
One embodiment of the invention is explained in detail below with reference to the drawing, in which the single figure is a diagrammatic side view of the device according to the invention.
A flat-lying plastic blown film web 1 is hauled off a supply roll (not illustrated), mounted in an unwinding unit, in the direction of the arrow A by a pair of forward draw rolls and the following deflecting rolls 2, which are mounted in a frame 3. The blown film web is guided by means of deflecting rolls through a hot water bath 4, where the blown film web 1 is preheated. The blown film web 1 is pulled forward by means of forward draw rolls or pairs of forward draw rolls 5, 6, whose rolls or rollers can be heated. To guarantee a good infeed of the blown film web 1 into the blown film bubble 7 or the preceding, blown-up tube segment 8, there are behind the outlet slit of the pair of forward draw rolls 6 guide plates 9, which are arranged in the shape of a wedge and can also be provided with rolls or friction-reducing material. The guide plates 9, which expand in the shape of a
One embodiment of the invention is explained in detail below with reference to the drawing, in which the single figure is a diagrammatic side view of the device according to the invention.
A flat-lying plastic blown film web 1 is hauled off a supply roll (not illustrated), mounted in an unwinding unit, in the direction of the arrow A by a pair of forward draw rolls and the following deflecting rolls 2, which are mounted in a frame 3. The blown film web is guided by means of deflecting rolls through a hot water bath 4, where the blown film web 1 is preheated. The blown film web 1 is pulled forward by means of forward draw rolls or pairs of forward draw rolls 5, 6, whose rolls or rollers can be heated. To guarantee a good infeed of the blown film web 1 into the blown film bubble 7 or the preceding, blown-up tube segment 8, there are behind the outlet slit of the pair of forward draw rolls 6 guide plates 9, which are arranged in the shape of a wedge and can also be provided with rolls or friction-reducing material. The guide plates 9, which expand in the shape of a
4 wedge, lead to a gentler transition of the forward drawn flat-lying web to the blown-up film tube 8.
A liquid 20 is filled into the bottom region of the blown-up tube segment 8 using injection needles. The liquid is supported on the side by guide plates 9 so that it collects in the bottom wedge-shaped region of the blown up tube segment 8.
Another possibility of filling a liquid into the tube segment consists of pulling a flat-lying film web through the forward draw rolls, pre-opening slightly said forward draw rollers by hand and pouring water in, then moving the film web to the pair of nip rolls and finally evaporating the water in the tube segment so that the tube is blown up.
Two permanent heating rings 10, 11, which can comprise infrared heating rings, are spaced adequately above the pair of forward draw rolls 6 or the guide plates 9. The bottom heating ring radiates uniform heat onto the blown-up film tube 8, which travels through said ring. The heating ring 11 is divided in the circumferential direction into heating sectors, which can be controlled separately, so that they can differentially heat the circumference of the film tube passing through said ring, if this should be necessary to compensate for the varying wall thicknesses. The differential heating of a film tube via its circumference to compensate for fluctuations in thickness is known and does not need, therefore, to be described here in detail. Above the heating ring 11, which can be heated sector by sector, there is a conventional cooling ring 12, from whose circular outlet slit, facing the blown film bubble 7, cooling air is blown onto the film bubble 7.
The film tube, blown up into a film bubble 7, is hauled off by a pair of take-off rolls 13, which is arranged vertically over the pair of forward draw rolls 6, for example mounted stationarily on the ceiling of a factory. Upstream of the pair of take-off rolls 13 are plate-shaped flat-laying units 14, which are arranged in the shape of a wedge and which taper off in the direction of the intake slit of the pair of take-off rollers 13. The plate-shaped flat-laying units 14 are stationarily mounted or held in a manner that is not illustrated.
The blown film web, which is laid flat by the pair of take-off rollers or rolls 13, travels through a width measuring unit 15, which measures the width of the flat-laid blown film web, hauled off the film bubble 7. The blown film web, which is laid flat again, is fed over deflecting rolls 16 to a wind-up unit or reprocessing units.
The guide plates 9 or the windows of the guide plates 9 have microwave radiating units 21, which can be fastened to the guide plates 9 or in a manner that is not illustrated to holders of the frame 23.
The width measuring unit 15 sends its measurement signals over a line 30 to the control and regulating unit 31, which comprises a computer and which compares the measured actual width of the flat-laid blown film web with the stored desired width and generates control signals in accordance with the deviation of the actual width from the desired width, and feeds them over the line 32 to the microwave units 21.
Blowing air can be fed, as necessary, to the wall of the blown film bubble using injection needles 36. The feeding of blowing air into the film bubble 7 using injection needles, which travel along over a specific stretch and which are inserted at the start of the stretch and extracted again at the end of the stretch, is known and does not have, therefore, to be described here in detail.
A liquid 20 is filled into the bottom region of the blown-up tube segment 8 using injection needles. The liquid is supported on the side by guide plates 9 so that it collects in the bottom wedge-shaped region of the blown up tube segment 8.
Another possibility of filling a liquid into the tube segment consists of pulling a flat-lying film web through the forward draw rolls, pre-opening slightly said forward draw rollers by hand and pouring water in, then moving the film web to the pair of nip rolls and finally evaporating the water in the tube segment so that the tube is blown up.
Two permanent heating rings 10, 11, which can comprise infrared heating rings, are spaced adequately above the pair of forward draw rolls 6 or the guide plates 9. The bottom heating ring radiates uniform heat onto the blown-up film tube 8, which travels through said ring. The heating ring 11 is divided in the circumferential direction into heating sectors, which can be controlled separately, so that they can differentially heat the circumference of the film tube passing through said ring, if this should be necessary to compensate for the varying wall thicknesses. The differential heating of a film tube via its circumference to compensate for fluctuations in thickness is known and does not need, therefore, to be described here in detail. Above the heating ring 11, which can be heated sector by sector, there is a conventional cooling ring 12, from whose circular outlet slit, facing the blown film bubble 7, cooling air is blown onto the film bubble 7.
The film tube, blown up into a film bubble 7, is hauled off by a pair of take-off rolls 13, which is arranged vertically over the pair of forward draw rolls 6, for example mounted stationarily on the ceiling of a factory. Upstream of the pair of take-off rolls 13 are plate-shaped flat-laying units 14, which are arranged in the shape of a wedge and which taper off in the direction of the intake slit of the pair of take-off rollers 13. The plate-shaped flat-laying units 14 are stationarily mounted or held in a manner that is not illustrated.
The blown film web, which is laid flat by the pair of take-off rollers or rolls 13, travels through a width measuring unit 15, which measures the width of the flat-laid blown film web, hauled off the film bubble 7. The blown film web, which is laid flat again, is fed over deflecting rolls 16 to a wind-up unit or reprocessing units.
The guide plates 9 or the windows of the guide plates 9 have microwave radiating units 21, which can be fastened to the guide plates 9 or in a manner that is not illustrated to holders of the frame 23.
The width measuring unit 15 sends its measurement signals over a line 30 to the control and regulating unit 31, which comprises a computer and which compares the measured actual width of the flat-laid blown film web with the stored desired width and generates control signals in accordance with the deviation of the actual width from the desired width, and feeds them over the line 32 to the microwave units 21.
Blowing air can be fed, as necessary, to the wall of the blown film bubble using injection needles 36. The feeding of blowing air into the film bubble 7 using injection needles, which travel along over a specific stretch and which are inserted at the start of the stretch and extracted again at the end of the stretch, is known and does not have, therefore, to be described here in detail.
Claims (4)
1. Process for controlling the diameter of a blown film web, blown up into a bubble with a center line between a pair of forward draw rolls and a pair of take-off rolls, in which process the blown film web is pulled off continuously by means of the pair of take-off rolls from the bubble and laid flat by means of two flat-laying units, which are arranged in the shape of a wedge and taper off in the direction of the intake slit of the pair of take-off rolls, and in which process the blown film web is heated in the inlet area of the bubble and the air or gas pressure in the film blown bubble is held essentially constant, characterized in that the film tube is filled with water or a liquid that has a different boiling point and that collects above the pair of forward draw rolls and that the liquid is heated to temperatures exceeding its boiling point until a specific pressure is reached in the blown film bubble.
2. Process, as claimed in claim 1, characterized in that the diameter of the bubble or the width of the flat-laid tube that is hauled off the bubble is measured and the radiant energy is fed to the liquid for the purpose of heating it in accordance with the measured deviation of the diameter from the desired diameter of the film bubble or the width from the desired width.
3. Process as claimed in claim 1 or 2, characterized in that the heat is fed to the liquid by means of microwaves.
4. Device for carrying out the process, as claimed in claim 1, comprising a frame mounted, driven pair of forward draw rolls for a flat-lying blown film web, comprising an opposite, stationarily mounted, and driven pair of take-off rolls for the flat-laid blown film web, which is hauled off the blown-up film bubble and upstream of which are flat-laying units, preferably flat-laying plates, which are arranged in the shape of a wedge, comprising units for blowing up the blown film web between the pairs of forward draw and take-off rolls into a film bubble, comprising units for heating the blown-up blown film web and comprising units for measuring the diameter of the blown bubble or the width of the flat-laid blown film web, hauled off the film bubble, characterized in that above the pair of forward draw rolls there is a radiator, which heats a liquid in the blown up film tube and that there is a control and regulating unit, which feeds the energy to the radiator in accordance with the deviation of the measured diameter from the diameter of the blown film bubble or the measured width from the desired width of the flat-laid blown film web.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19904529A DE19904529C2 (en) | 1999-02-04 | 1999-02-04 | Method for regulating the diameter of a tubular film web inflated between a pair of preferred rollers and a pair of pulling rollers to form a tubular film bubble with a vertical center line |
| DE19904529.1 | 1999-02-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2297696A1 true CA2297696A1 (en) | 2000-08-04 |
Family
ID=7896429
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002297696A Abandoned CA2297696A1 (en) | 1999-02-04 | 2000-02-03 | Process for controlling the diameter of a blown film web, blown up into a blown film bubble with a vertical center line between a pair of forward draw rolls and a pair of take-offrolls |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP1025979A3 (en) |
| JP (1) | JP2000225644A (en) |
| BR (1) | BR0000299A (en) |
| CA (1) | CA2297696A1 (en) |
| DE (1) | DE19904529C2 (en) |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2372688A1 (en) * | 1976-12-06 | 1978-06-30 | Flax V | Dilation of reheated thermoplastic tubing by hydrostatic pressure - to simplify mfr. of heat shrinkable film |
| DE3119006C2 (en) * | 1981-05-13 | 1983-09-01 | Windmöller & Hölscher, 4540 Lengerich | Device for injecting air or gas into a tubular film web |
| US4536365A (en) * | 1983-12-22 | 1985-08-20 | American Cyanamid Company | Process for the manufacture of equally biaxially oriented film |
| AT387540B (en) * | 1984-08-20 | 1989-02-10 | Muanyagipari Kutato Intezet | METHOD AND DEVICE FOR THE PRODUCTION OF HEAT-SHRINKING TUBE FILMS ORIENTED IN TWO DIRECTIONS |
| CA2028206A1 (en) * | 1989-10-27 | 1991-04-28 | Jacob Wajsbrot | Process for the manufacturing of a mechanically conditioned thermoplastic film with biaxially recoverable stresses |
| JP2786082B2 (en) * | 1993-08-10 | 1998-08-13 | 積水化学工業株式会社 | Automatic size change control system in inflation molding line |
| FR2736861B1 (en) * | 1995-07-18 | 1997-09-19 | Plastiques De La Deome | METHOD AND INSTALLATION FOR PROVIDING TWO-STRETCHING OF A PRIMARY SHEATH |
-
1999
- 1999-02-04 DE DE19904529A patent/DE19904529C2/en not_active Expired - Fee Related
-
2000
- 2000-01-12 EP EP00100524A patent/EP1025979A3/en not_active Withdrawn
- 2000-02-03 CA CA002297696A patent/CA2297696A1/en not_active Abandoned
- 2000-02-03 BR BR0000299-2A patent/BR0000299A/en not_active Application Discontinuation
- 2000-02-04 JP JP2000027894A patent/JP2000225644A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP1025979A2 (en) | 2000-08-09 |
| BR0000299A (en) | 2000-10-17 |
| JP2000225644A (en) | 2000-08-15 |
| EP1025979A3 (en) | 2001-03-07 |
| DE19904529C2 (en) | 2002-03-14 |
| DE19904529A1 (en) | 2000-08-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |