DE102005038730A1 - Improved airflow at the film bubble - Google Patents

Abstract

The invention describes an extrusion device (1) for extruding a film tube in a transport direction (z). Said extrusion device (1) comprises a nozzle head with an annular gap from which melt material emerges, which solidifies on the frost line during transport and then forms the film tube, and is provided with a distribution device for distributing melt material onto the annular gap. Furthermore, this includes a take-off device with which the film tube can be removed, and at least one guide element arranged between the nozzle head and the take-off device, which guides components of the film tube along a path. DOLLAR A New and inventive is that the at least one guide element contains at least one porous, preferably microporous, material and that the at least one guide element is arranged in the transport direction (z) of the film tube between the distribution device and the frost line.

Description

The The invention relates to an extrusion device for the extrusion of a Foil tube according to the preamble of claim 1 and a Process for the extrusion of a film tube according to the preamble of Claim 11.

Foil hoses are produced in extrusion devices, as for example from the patent DE 100 48 862 C1 the applicant are known. There, a nozzle head is shown, which is supplied via melt-supplying lines plastic melt, which is distributed annularly within the nozzle head with a distribution device. Starting from the melt-feeding lines, the melt is pressed in the transport direction z through an annular gap. Subsequently, the annular melt solidifies to a film tube, which is initially transported further in the transport direction z. The plane at which the melt solidifies into a film tube is called a frost line. After solidification, the film tube is withdrawn with a take-off device in the transport direction z. Between the nozzle head and the take-off device, the already solidified film tube is generally guided by guide elements, which can be found, for example, on so-called flattening devices or calibrating devices.

at Try to measure the throughput through the nozzle head, ie the production speed, to increase, was observed that the melt after leaving the die gap not yet sufficiently solidified, so that these flexing movements executing, to a variation of the film tube diameter or the film thickness of the film tube leads. Production output from well-known Extrusion devices is so limited.

The The object of the present invention is therefore an extrusion device and to propose a method by which the production speed increase leaves, without the quality the film tube impaired becomes.

According to the invention this Task by the features of the characterizing parts of claims 1 and 11 solved.

Thereby, that the at least one guide element a porous one Material may be at its the film tube or the Melt facing side form an air cushion. This air cushion prevents that a melt in touching Contact with the guide element occurs. This surprising realization make it possible, such a guide element even in areas where the melt is not yet has solidified sufficiently, ie in particular between the nozzle head and frost line. The pores can be integrated into the material in a variety of ways contribute. Thus, machining methods are conceivable. Pores can too be generated with matter rays such as electron beams. It can but also materials are used, even without a treatment are porous. It may be of particular advantage to provide such guide elements within the nozzle head in areas where it is intended that the melt does not cool yet. Such an arrangement of a guide element is preferred at the end of the annular Gap. Through the air cushion, the melt is no longer in Contact with components of the nozzle head whereby the otherwise observed melt deposits on the die lip be avoided.

In preferred embodiment this is at least a guide element acted upon by a pressurized fluid. The fluid may then pass through the porous material in the direction of the melt. By a variation of the pressure can thus melt and their transport routes are specifically influenced. As fluid is doing a gas or gas mixture, in particular air, is preferred. It can, however a liquid be used as a fluid. Such a liquid, for example water, can be used advantageously for cooling the outer surface of the Foil tube can be used.

The fluid is preferably provided by at least one pressure source and / or a pressure reservoir. An applicable pressure source may be a simple compressed air generator, which communicates with the guide elements via a compressed air line. Compressed air reservoirs can be temporary storage, for example compressed air tanks, in which pressurized fluid can be stored. To the strength of the air Polsters, which leads the melt to be able to adjust, it is provided that the pressure on the fluid is variable.

In An advantageous embodiment of the invention is the guide element and / or the fluid temperature controlled. In this way, the cooling behavior be influenced by the melt. In general, the melt cooled, However, it may also be advantageous to melt, at least locally, to warm, to a slight "melting" of the melt to reach. This is caused by warming the guide elements and / or of the fluid. The heating the guide elements may be further provided to deposits such as to avoid paraffin. It can be provided on the perimeter the melt several guide elements provide, in which case over seen the scope of the guide elements and / or the fluid are partially temperature controlled. In this way can the strength later Slide over the extent can be influenced. Such an influence on the Geometric properties of the film tube is also referred to as "profile control".

In particularly preferred embodiment this is at least a guide element arranged within the film tube or the film bubble. This is the room for the melt is confined inwards, allowing flexing movements in These directions can be effectively avoided. To spread the Melt to the outside From this side, a strong fluid flow can be prevented against the Melt be directed. This fluid flow can escape from blowing nozzles.

In However, further embodiment of the invention can also outside the film tube or the annular melt guide elements to the leadership be arranged the melt. The guide elements can be in Transport direction of the melt or the film tube Seen also be arranged alternately inside and outside. Depending on Strength the air cushion and depending on the thickness of the subsequent film or the diameter of the film tube, the guide elements also transversely to the transport direction the melt relative to the nozzle head slidably provided.

Advantageous is it when the guide elements with the melt facing surface parallel to the transport direction run the melt. The melt can already be in this case be guided in a form the later Foil tube corresponds.

It However, it is also known that the melt or even the film tube can be stretched or stretched to influence the geometric, mechanical and also the optical properties to be able to. With the guide elements an extrusion device according to the invention let yourself not just melt, but also to steer a certain way. Thus, the melt can also dilated, that is the diameter of the later Foil tube can be increased. For this reason, in a further advantageous embodiment the invention provided that, in the transport direction of the melt seen, the melt-facing surface of the at least one guide element has a different distance from the axis of the later film tube. The guide elements can so weird to be hired or inclined surfaces to have. The surfaces can but also curved be so that the melt are guided on a curved path can. The guide elements can for example, attached to the nozzle head be that they are in their positions and / or in their inclinations change to let. In this way, film hoses with different Make diameters with the same extrusion device. To This purpose can also be the entirety of the guide elements on the inside or the outside of the film tube are varied in diameter.

In a preferred embodiment include the guide elements at least partially sintered material. This material can be sintered ceramic or sintered metal. Also leave materials of other classes to sinter. Such sintered materials are characterized that they become porous in their manufacturing process and thus in operation a fluid can pass through these pores. Usually wise such sintered materials have a very high density of such pores, which also have small diameters (microporosity). A preferred medium Pore size is between 5 and 100 microns, especially between 10 and 60 Micrometers. Other materials may also have these properties such as a sheet that has a lot of fine holes, so that a similar one porosity arises. As a result, the fluid spreads evenly the melt facing surface of the guide elements.

Other embodiments of the invention will become apparent from the subject description and the Claims out.

The individual figures show:

1 Side view of a first embodiment of an extrusion device according to the invention

2 Side view of a second embodiment of an extrusion device according to the invention

1 shows a schematic representation of an extrusion device according to the invention 1 in the side view. On the structure and operation of the nozzle head 3 has already been briefly mentioned in the introductory description. For a more detailed explanation reference is made to earlier patents or patent applications, for example to the DE 100 48 862 C1 , The nozzle head 3 has an annular gap, not visible in this view, through which the plastic melt exits the nozzle head and immediately begins to cool, since the ambient air is usually colder compared to the temperatures prevailing in the nozzle head. As a result, the melt solidifies and then forms a film tube 2 , In this case, the melt or the film tube is transported in the transport direction z, wherein the temperature distribution is assumed to be static. Therefore, it can be said that the solidification of a plane takes place which is substantially orthogonal to the transport direction z. This level is in the 1 and 2 through the frost line 4 shown. Below this frost line is therefore the not yet solidified melt 6 in front.

To this melt 6 to be able to lead are (see 1 and 2 ) between nozzle head 3 and the frost line 4 guide elements 8th inside the film tube 2 arranged, which contain microporous material. It can also be a single, cone-shaped guide element. These guide elements are supplied via lines not shown with a pressurized fluid, which is provided by pressure generators and / or accumulators available, so that this fluid passes through the pores of the microporous material, resulting in the melt 6 facing walls of the guide elements 8th Training fluid posters. As these fluid pads over the surfaces of the guide elements 8th have very uniform pressure distribution, the melt can 6 be kept at a constant distance to these surfaces. This fluid cushion is in the figures with the numeral 7 designated.

But that the melt 6 does not dodge to the outside, it is according to the in 1 shown embodiment provided that the melt 6 From the outside with blowing air is applied, by blowing air nozzles 5 flows in the current direction A. Of course, the use of the blowing air nozzles is not limited to air, but also any fluid can be used.

In the embodiment according to 2 are also outside the annular melt 6 guide elements 8th' arranged containing microporous material. The operation of the guide elements 8th' corresponds to the guide elements 8th , so that the melt between two fluid pads, such as air cushions, out.

The in the 1 and 2 shown guide elements 8th and 8th' can be configured and arranged differently. So can several guide elements 8th and or 8th be arranged in the circumferential direction of the annular melt or the film tube, so that they occupy the surface of an imaginary pipe section. Also, in each case a single tubular piece-shaped guide element 8th respectively 8th ' be provided. Along the direction z, the guide elements 8th . 8th' have a cone-shaped arrangement, as in the 1 and 2 can be seen.

Another inventive embodiment, which with one of the in the 1 and 2 shown embodiments can be combined in the 3 shown. This figure shows a section through a nozzle head 3 , Furthermore, the annular channel 9 visible, through which the melt 6 is transported in the direction of z. More precisely, the melt is 6 pressurized, passing through the open end of the annular channel 9 that is, through the annular gap 10 , in the direction of z enters the open air. On its inner side is the annular channel with guide elements 11 , their structure and function with those of the guide elements 11 are comparable, occupied. This will cause the melt 6 in the area of the guide elements 11 not by contact with the side walls of the annular channel 9 guided, but by air cushion. The guide elements 10 can thereby with their upper edges flush with the annular gap 10 issue. Due to the contactless guidance of the melt, a considerably reduced deposition of plastic material in the area of the annular gap occurs 10 , It can be in the circumferential direction of annular channel 9 several guide elements 11 or a single tubular piece-like guide element can be arranged. Furthermore, alternatively or additionally, such guide elements 11 also on or in the outer wall of the annular channel 9 be arranged.

Claims (12)

Extrusion device ( 1 ) for the extrusion of a film tube in a transport direction (z), which ( 1 ) - a nozzle head with an annular gap from which emerges melt material which solidifies in the course of transport on the frost line and then forms the film tube, and with a distribution device for distribution of melt material on the annular gap, - a take-off device with which the Foil tube is transportable, and - at least one arranged between the nozzle head and the extraction device guide element, which carry components of the film tube along a path, comprises, characterized - That the at least one guide element contains at least one porous, preferably microporous material, and - that the at least one guide element in the transport direction (z) of the film tube between the distribution device and the frost line is arranged. Extrusion device according to claim 1, characterized that the at least one guide element in the transport direction (z) of the film tube between the annular gap and the frost line is arranged. Extrusion device according to claim 1, characterized that the at least one guide element with a pressurized fluid can be acted upon, so that the fluid in the direction of the melt material through the porous material passes. Extrusion device according to the preceding claim, characterized in that at least one pressure source and / or at least one pressure reserve is provided which / s the under Pressure fluid available provides. Extrusion device according to one of the two preceding Claims, characterized in that the pressure on the fluid changeable is. Extrusion device according to one of the preceding Claims, characterized in that the at least one guide element and / or the fluid is temperature-controlled. Extrusion device according to one of the preceding Claims, characterized in that the guide elements are inside the Foil tube are arranged. Extrusion device according to one of the preceding Claims, characterized in that the guide elements are outside the film tube are arranged. Extrusion device according to one of the preceding Claims, characterized in that the film tube surface facing the at least one guide element runs parallel to the transport direction (z) of the film tube. Extrusion device according to one of claims 1 to 8, characterized in that the film tube facing surface the at least one guide element in the direction of transport (z) a different distance to the axis of the film tube has. Extrusion device according to one of the preceding Claims, characterized in that the porous material is sintered material is. Process for the extrusion of a film tube in a transport direction (z), in which - Melting material from one annular Gap of a nozzle head exit, - Melting material chilled so that it solidifies in the course of transport and subsequently forms the film tube, - The film tube removed will and - between the nozzle head and the extractor components of the film tube along led a way become, characterized, - that the film tube in an area led is at least partially melted material, and - that the film tube is guided with at least one guide element, which is at least a porous, preferably microporous Contains material.