DE19728522C2 - Method and device for producing single or multi-layer tubular films made of thermoplastic - Google Patents

Description

The invention relates to a method for producing single or multilayer tubular films made of thermoplastic Plastic, in which the plastic is plasticized and in one Tool is formed into a tube and out of the tool an annular gap emerges vertically downwards and one Hose bubble forms and the hose bubble at the other end squeezed and laid flat, the hose in the Area of the inner tube bladder filled with supporting air and cooled and cooled from the outside and calibrated outside.

Furthermore, the invention relates to a device to carry out the process for making one or multilayer tubular films made of thermoplastic Plastic.

It is for making biaxially stretched tubular films required the extruded from the tool Cool the tubular film very quickly and very evenly, so that the molecular structure maintains its amorphous structure, until the tubular film is squeezed out with a possible tolerance in order to be subsequently drawn. A Tolerance-neutral squeezing means that, for example, none  Material accumulation on the inside of the pinch fold as a result insufficient cooling occurs, for example.

In known methods, such as in DE-OS 20 63 612 and in US 3,456,044 described, the external cooling of the from Extruded hose emerging from the tool usually by means of water showers or by extrusion in a water bath or by a combination of these two means. In addition, the hose calibrated on the outside. Furthermore, the will mechanically exiting the annular gap of the tool stabilized and formed a tube bladder that with a Liquid, support air or support gas is filled. This Liquid, supporting air or the supporting gas also cool. It however, it has been found that these are known Internal cooling systems are not sufficient to be available in the a sufficient cooling of the standing dwell times To reach the inside of the hose. This leads to the fact that Inner tube, especially slow when using crystallizing thermoplastics, still in amorphous-ductile Condition, causing injury as well Thickness fluctuations, especially in the area of the edges when Squeezing the hose can come. Such Fluctuations in thickness make it difficult to process the Hose to biaxially oriented, if necessary heat-set tubular film according to known methods, such as she prefers for the production of cooked and cooked sausages is used.

DE-OS 19 48 797 describes a method for producing multilayer tubular films made of thermoplastic Plastic known in which the hose is vertically down emerges from a mold and the hose with supporting air is filled and inside with an additional imported coolant is cooled. Inside the The support body provided to support the bladder Hose bladder. The coolant introduced inside starts up the hose bubble down and is collected here again. Evaporation of the coolant film does not take place  would also lead to inflation of the tubular film, which is not desired.

From GB 1123318 is a method and an apparatus for Manufacture of tubular films known, the tubular film generated by subtracting in the vertical direction, Outside cooling rings are available and support air in the form a gaseous liquid mist in the hose bladder is blown in to inflate the same. So far the Liquid mist condenses and accumulates in front of the From here, he can exit the tubular film via a nozzle Suction line can be removed again, however, if in doubt supporting air also undesirably emerges again.

The object of the invention is therefore in particular Provision of a method and an apparatus for Internal cooling of an extruded film tube with a such cooling rate that when squeezing the Hose blister no pinch folds on the edges as a result plastic-ductile deformation of the inside of the hose occurs. Furthermore, the task is to achieve one uniform and, if possible, completely amorphous structure of the film tube manufactured according to the method.  

The invention solves the problem at Generic method for producing a tubular film in such a way that on the inner wall of the hose in the area sprayed a finely atomized liquid into the bladder and the liquid with intensive cooling of the Inner wall of the hose evaporates at least partially and the condensate or the liquid runs down inside the bladder and above the pinch in the bladder collects and the condensate and liquid from the Collection area is suctioned off.

According to the invention, the extruded tubular film succeeds immediately after leaving the annular gap quickly and cool evenly and thus the molecular structure of the To retain plastic in an amorphous structure, so that subsequently, after cooling, a desired stretching of the Foil can be made. The extruded hose can be formed in one or more layers. As raw materials can all be processed in the extrusion process thermoplastics are used, in particular Polyamides, polyesters, polyethylenes, ethylene vinyl alcohol Copolymers, copolymers of ethylene and blends thermoplastics, preferably poly E-caprolactam and copolyamides based on e-caprolactam.

The method according to the invention can be particularly advantageous for the production of smaller tubular films with diameters from 20 mm to 200 mm with wall thicknesses from 200 µm to 600 µm deploy. According to the invention, internal cooling proposed in the area of the bladder, cooling by spraying and evaporating suitable liquids with subsequent condensation as far as the liquid evaporates is done. The process can be open or closed Cycle. It is also possible to use internal cooling a liquid to be exchanged and is cooled outside again.  

Advantageous developments of the invention are the characteristic features of claims 2 to 12 can be removed.

As a liquid for spraying the inner wall of the hose preferably water is used which evaporates at approx. 100 ° C. Since the temperature of the extruded from the annular gap of the Tool emerging hose up to 300 ° C and more each according to material, is a correspondingly massive Evaporation of the sprayed liquid enables and thus intensive cooling of the inner wall of the hose. On Other suitable inert ones may be used instead of water Liquids are sprayed that have a corresponding have suitable evaporation temperature.

The sprayed and evaporated liquid flows as Condensate along the inside of the hose and collects on lower end of the hose bladder in front of the squeezing area. Also liquid that has not evaporated collects here. The level of Collection point is by suction of the liquid and the Condensate adjusted and regulated.

The target surface and the intensity of the atomized Liquid for cooling the inner wall of the hose can be in Adaptation and dependency of the raw material - thermoplastic Plastics -, the structure of the hose, the throughput, the thickness, the tube shape - neck-in, neutral, bulged -, the melt temperature of the raw material at the tool outlet, the type and intensity of the external cooling of the hose and the Calibration can be set and regulated. In particular is it is possible to attack the surface of the atomized liquid on the inner wall of the hose in terms of size and / or location with respect to the outlet of the hose from the Set and / or regulate the annular gap of the tool. It is also proposed the intensity of the cooling of the Inner wall of the hose by regulating the amount and the Adjust the temperature of the atomized liquid and / or to regulate.  

The external cooling of the hose is done in a known manner made either after exiting the annular gap of the Tools using sprayed water using water showers, especially in connection with calibration devices or by direct entry into a water bath or through a Combination of these two measures, the spraying of Water as the first cooling section and passing through one Water bath is selected as the second cooling section. Also the Installation of underwater showers is possible.

With the measures according to the invention it is achieved that the Cross section of the hose from the exit from the annular gap of the Tools up to squeezing in the area of the passage the hose bladder is evenly cooled from the inside and outside is such that when the pinch is reached as little as possible or no temperature gradient in the cross section there is more of the film.

Furthermore, the hose is also passed through the Tempering tempered, for example by a Water bath is performed. The one so cooled and then Squeezed tube has a very uniform amorphous Structure on that for subsequent stretching Requirement is.

As a device for performing the invention Process is known from plants for Tubular film production with vertically downward Deduction and operation according to the generic term of claim 9 went out.

To form an intensive internal cooling, the Generic device in such a way that a pipe is passed through the tool, at the end of which a Internal spray body attached to atomize the liquid which is positioned so that it comes out of the tool protrudes and ends within the tubular bubble to be formed, and the internal spray body through the tube  can be supplied with the liquid by means of a pump and the another an exhaust pipe through the tool and out of the Tool out until close to the squeeze device to suck the condensate out of the hose bladder.

For an adaptation to different raw materials, Extrusion conditions, tube shapes and tube thicknesses proposed in the device according to the invention both the internal spray body as well as the suction pipe in height training adjustable. Likewise, different Internal spray bodies are used and also the Internal spray body with regard to the dispensed amount of the atomized Liquid are regulated.

In a preferred embodiment of the internal spray device for the internal cooling of the hose is proposed that Suction tube concentric within the tube that the Support air supply in the hose bladder is used to arrange and lead through.

Advantageous further developments of the device are characterizing features of subclaims 10 to 14 removable. Internal cooling and external cooling are according to the invention to each other to make the uniform Cooling of the hose across the cross section to Squeeze to achieve the desired level. In particular, there should be no squeezing Temperature gradient be more present in the tubular film, which is negative, for example due to thick points would make itself noticeable and thus in the following Stretching disturbs.

The invention is illustrated and explained below with the aid of a schematic illustration of the cooling of the extruded thermoplastic hose in FIG. 1.

The plasticizing device for the thermoplastic material for producing a single or multi-layer tubular film is not shown. The plasticizing device is followed by the film blowing head in the form of the tool 10 , which is shown schematically here, with the annular gap 11 , from which freshly extruded tube 1 emerges with a melt temperature at the tool outlet of up to more than 300 ° C., depending on the thermoplastic used . The tube 1 emerging from the annular gap 11 must be cooled very quickly and very uniformly in order to maintain the amorphous structure of the molecular structure in order to achieve a tolerance-neutral squeezing without material accumulation on the inside of the pinch fold for the subsequent stretching.

Through the tool 10 , a channel 12 is formed here concentrically to the annular gap 11 , in which the tube 13 is passed concentrically to form an annular channel 14 . The ring channel 14 is used to supply support air 15 for filling the hose bladder 1 a and stabilizing the same. The supporting air 15 is fed to the annular channel 14 via the flange part 19 . The tube 13 is cantilevered at the outlet end of the tool 10 , where the hose 1 exits the annular gap 11 , and is equipped with the internal spray body 16 at its end. Within the tube 13 , a further suction pipe 17 is guided concentrically to form a further annular channel 13 a, the suction pipe 17 being extended through the spray head 16 in the direction of the pinch roller pair 24 . Through the annular channel 13 a formed between the suction pipe 17 and the pipe 13 , water 18 is guided into the spray head 16 , which emerges from the spray head 16 with atomization and meets the inner wall of the hose 1 . The water 18 is fed to the spray head 16 via a channel 13 a by means of a pump, which is not shown in detail. The tube bladder 1 a that forms in the withdrawal direction V after exiting the tool 10 is guided at the end through the nip 25 , which is formed by the two nip rollers 24 , and then the flat tubular film 1 b is pulled off in the direction of the arrow. The squeezing device 24 is arranged in a spray water tank 22 with water 23 such that it is completely in the water, including the last part of the hose bladder. The water level 23 a of the spray water tank 22 is adjustable.

The hose 1 emerging from the annular gap 11 is immediately cooled and calibrated on the outside immediately thereafter. For this purpose, a sufficient number of external spray bodies 32 and calibration disks 31 are arranged, cooling using water. The water then runs downward in the direction of arrow V1 on the hose 1 down into the spray water tank 22 , from where it can be recycled again. The external spray bodies are also adjustable and controllable with regard to their spraying performance. The calibration disks 31 are adjustable in diameter, adaptable to the desired diameter of the hose to be produced.

The liquid, here water 18 , which is supplied for the internal cooling via the pipe 13 or the ring channel 13 a and the internal spray body 16 , is sprayed onto the hot inner wall of the hose 1 and evaporates in the process. This intensively cools the inner wall of the hose 1 . The evaporated water then condenses again and then likewise runs downward in the direction of arrow V and collects in the lower region of the hose bladder 1 a in front of the squeezing device 24 as condensate 18 a. In this condensate collection area, the suction pipe 17 is immersed at its end and is sucked off again here by means of a pump and level controller, so that the level 18 b of the condensate 18 a can be set and kept constant. The suction pipe 17 for the condensate suction is arranged adjustable in height.

Likewise, the height of the inner spray body 16 with the tube 13 is adjustable, so that the area to be sprayed on the inside of the hose can be selected in a defined manner. The inner spray body 16 is adjustable in height to adapt and optimize the cooling process depending on the raw material of the single- or multi-layer composite of the tubular film, the throughput, the thickness and the tubular shape, the melt temperature at the exit from the annular gap 11 , the type and intensity of the External cooling and hose calibration.

Claims (14)

1. A method for producing single-layer or multilayer tubular films made of thermoplastic, in which the plastic is plasticized and shaped into a tube in a tool and exits the tool vertically downward through an annular gap and forms a tube bubble and the tube bubble at the other end is squeezed and laid flat, the hose in the area of the hose bladder being filled and cooled inside with supporting air and cooled from the outside and calibrated from the outside, characterized in that on the inner wall of the hose ( 1 ) in the area of the hose bladder ( 1 a ) a finely atomized liquid ( 18 ) is sprayed, and the liquid is at least partially evaporated with intensive cooling of the inner wall of the hose, and the condensate ( 18 a) or liquid that forms in the hose bladder runs down and above the Collect pinch in the bladder t and the condensate and the liquid is sucked out of the collecting area. 2. The method according to claim 1, characterized in that as a liquid for spraying the inner wall of the hose water or another Liquid with a suitable vapor point is used. 3. The method according to claim 1 or 2, characterized in that the level ( 18 b) of the condensate in the collecting area in the hose bladder ( 1 a) is regulated and adjusted by the suction. 4. The method according to any one of claims 1 to 3, characterized in that the surface of the finely atomized liquid ( 18 ) on the inner wall of the hose ( 1 ) with respect to the size and / or position with respect to the exit of the hose from the annular gap ( 11 ) the tool is set and / or regulated. 5. The method according to any one of claims 1 to 4, characterized in that the intensity of cooling the Inner wall of the hose by regulating the amount of atomized liquid adjusted and / or regulated becomes. 6. The method according to any one of claims 1 to 5, characterized in that the hose is cooled on the outside after exiting from the annular gap of the tool by means of sprayed water by means of water showers ( 32 ). 7. The method according to any one of claims 1 to 6, characterized in that the hose as it passes the squeezing is tempered, for example by means of a water bath. 8. The method according to any one of claims 1 to 7, characterized in that as a thermoplastic Plastic for the production of polyaminde tubular films, Polyester, polyethylene, polypropylene or PVDC are used become. 9. Device for performing the method according to one of claims 1 to 8 with a plasticizing device for the thermoplastic and a tool with an annular gap for extruding a tubular film, the tool having a channel for the supply of supporting air in the hose to form the hose bladder and with a device for cooling the outside of the hose and a downstream squeezing device, characterized in that a tube ( 13 ) is guided through the tool, at the end of which an internal spray body 16 is attached for atomizing a liquid, which is positioned so that it protrudes from the tool and ends within the hose bladder to be formed, and the inner spray body can be supplied with the liquid through the tube ( 13 ) by means of a pump and furthermore a suction tube ( 17 ) through the tool and out of the tool up to close to the squeezing device is led to Suck the condensate out of the hose bladder. 10. The device according to claim 9, characterized in that the inner spray body ( 16 ) is adjustable in height. 11. The device according to claim 9 or 10, characterized in that the suction pipe ( 17 ) is adjustable in height. 12. Device according to one of claims 9 to 11, characterized in that the suction tube ( 17 ) is arranged concentrically within the tube ( 13 ) and is guided through the internal spray body ( 16 ). 13. Device according to one of claims 9 to 12, characterized in that a pair of nip rollers (24) is provided as the squeezing device and the nip roller pair (24) is disposed within a water bath (22). 14. Device according to one of claims 9 to 13, characterized in that directly on the outlet side of the tool for the hose with respect to the diameter adjustable outer spray body ( 32 ) and calibration devices ( 31 ) are arranged.