WO2008043715A1

WO2008043715A1 - Film blowing die for concentric spiralling

Info

Publication number: WO2008043715A1
Application number: PCT/EP2007/060589
Authority: WO
Inventors: Berthold Moorkamp
Original assignee: Windmöller & Hölscher Kg
Priority date: 2006-10-09
Filing date: 2007-10-05
Publication date: 2008-04-17
Also published as: DE102006047996A1

Abstract

The invention describes a film blowing die (1, 21, 41) for the extrusion of film tubes (18) from film with at least two layers of plastic. This film blowing die (1, 21, 41) has a central preliminary manifold (20, 40), by means of which (20, 40) the material for the at least one layer of plastic can be fed to a first gap (26, 46) for directing an individual flow, which opens out into a die gap (17) for directing a number of individual flows. What is novel and inventive is at least one further, second gap (66a, 66b) for directing an individual flow, which opens out into a die gap (17) for directing a number of individual flows and to which (66a, 66b) the melt can be fed without having passed the central preliminary manifold (20, 40).

Description

Blow head for concentric winding

The invention relates to a blow head for the extrusion of film with at least two plastic layers, a retrofit kit for a blow head, and a method for operating a blown film plant.

Blown heads for the extrusion of multilayer plastic film are known. Thus, document EP 0 568 544 B1 shows such a blow head in FIG. This is constructed according to the so-called "stack-die principle", that is, the melt flows, which later form a single layer of the multilayer film, are each fed in the radial direction of the blow head "from outside" to a gap for directing a single flow. This gap is usually formed by an upper and lower plate. These plates are traversed by the mentioned melt supply lines, whereby these usually pass into spirals upon reaching the gap, so that the melt flow of the individual layers in the gap is "flattened" and thus anticipates the later flat shape of the film. This is because several pairs of functionalities from such upper and lower plates are stacked on top of one another, with their respective column leading to a single flow into the same gap - usually called the nozzle gap - leading to multiple single flow flows Art merged, in which they later form the multilayer film.

However, it has been shown that stack die blow heads, due to their design principle, have a high overall height. However, this great height is undesirable when heat-sensitive Folienmatehalien extruded and thus be passed through a correspondingly long nozzle gap.

For this reason, increasingly used in recent years blow heads with central pre-distributor, which build shorter with an equal number of melt layers. Such devices are shown for example in the publications DE 102 04 897 A1 and DE 199 23 973 A1. The blow heads shown in the two aforementioned publications have so-called central pre-distributor for the melt. Such blow heads with central pre-distributors usually have the following characteristics:

A common pre-distributor called component, which is flowed through by melt for different plastic layers and in the direction in which the film tube leaves the blow head [along the main axis of symmetry of the blow head (z)], the remaining components of the blow head upstream.

In the radial direction of the blow head in its center are central cavities, of which several melt distribution lines are shown. These supply lines extend from the central cavities ("star-shaped"), ie predominantly in the radial direction, thereby leaving the pre-distributor and usually opening into a helix which inserts either into one or both of the gap forming an individual flow In this gap, the melt flow already assumes the flat shape of the later sheet, but a multilayer blowing head of this type contains a plurality of such columns for conducting a single flow, respectively directing the melt flow forming a film layer for conducting a single flow then open into a common gap for conducting a plurality of individual flows, in which the individual melt flows are combined to form a not yet solidified or cured film composite.

It should also be mentioned that the blow heads of the aforementioned type also occur in various embodiments. Thus, the document DE 199 23 973 A1 shows a blowing head with a common gap to the line a plurality of individual flows to which the individual flows in the radial direction (r) of the blow head from both directions is fed through gaps for directing the individual flows. In the document DE 102 04 897 A1, this supply line initially takes place exclusively from one direction, namely in the radial direction of the blow head from the outside.

In particular, through the introduction of blow heads with central pre-distributor, it has become possible to equip multilayer film composites with layers of more sensitive material, since the height of these blow heads as mentioned is relatively low and thus the thermal load on the film remains limited. However, in recent years, there has been a demand for novel film composites in which thermally highly susceptible substances are combined with substances which require higher temperatures when they are processed in the die. Examples include composites containing both EVOH and polyester layers. This material composition actually requires the use of a blow head with a central pre-distributor. However, the design of this die also heated the temperature-sensitive EVOH to at least a similar temperature as the polyester and, in many cases, damaged it. The object of the present invention is therefore to propose a blow head with which composite films made of materials with different temperature behavior can be better produced.

The present invention is based on an arbitrary embodiment of a blowing head with a central predistributor and achieves the object by the characterizing features of claim 1.

The invention makes use of the fact that the stack die blowpipes just do not have any central predistributors and that, as a rule, the melt is supplied to them in the radial direction. It is therefore possible to decouple the temperature of the melt of the two parts of the blow head better thermally from each other. This applies both in the cases where the stack die part of the die is the melt with the higher temperature in the central Ringpalt introduces, as well as in the case in which he brings the melt of higher temperature.

In the former case, it makes sense to arrange the stack die die in the transport direction of the melt (z) in front of the die with central pre-distributor. In this case too, the more sensitive extrudate mass passing through the pre-distributor is protected in a more satisfactory manner than in the prior art from the higher temperature of the other melt. In the latter case, it is preferable that the stack die in the transport direction of the melt (z) follows the part with the central pre-distributor. The stack die then delivers the low melting temperature sensitive materials to the already cooling layers of the higher melting materials. For a general explanation of the nomenclature of the present document, it should be mentioned that the first and second columns for conducting a single flow usually have the same function: They convert the single flow, which is initially guided by one or more melt lines, into a "flat" state and then direct this individual flow into the central gap, as a rule the gaps have helices, but sleeves are also known for distributing the melt in the gap.

The difference between the first and two columns is therefore that the first column is supplied with melt via a central pre-distributor and the second column is not. In general, the second column should be supplied via radial distributor with melt. In this context, tests have shown that the so-called deer antler form is to be preferred. The terms radial distributor and deer antler are explained in more detail below in the present description. However, it is also possible to supply the second column in other ways, such as by means of a plurality of evenly distributed over the circumference of the blower head, radially to the gap to running melt lines.

Another common feature of the first and second column is that they are often limited by two plates. In particular, in the stack-this offers itself due to their arrangement, the designation upper and lower plate. A Functional unit of such an upper and lower plate is referred to below Radialverteilungseinschub. In order to ensure better manufacturability, modularity and thermal separability of such stack dies, it is advantageous if the melt feed lines for a second gap extend exclusively in its radial distribution insert. Even more advantageous is the restriction of the melt lines to a plate or a component.

The application of the teachings of the present invention is particularly well suited for retrofitting existing blow heads. In this case, a retrofit kit can be constructed according to the Stack-Die-Phnzip and expand a blow head with a central pre-distributor. It can also be a stack die with a

Retrofit kit, which has a central pre-distributor to be retrofitted.

The blow heads resulting in this way then have the advantages already described above, especially in the manufacture of more complicated

Material networks on. In general, the provision of retrofit kits, which increases the number of layers that can be produced with a blow head, meets the increasing demand for multi-layered film that is just the same as the old one

Blasköpfen just can not be made, after. The retrofitting according to the invention brings with it further advantages.

Conveniently, the retrofitting of a blow head with a central pre-distributor with a stack-the-retrofit kit, since the extension of a blow head with central pre-distributor with a retrofit kit of the same type would entail extensive mechanical engineering problems.

When composites are to be made from materials having widely different temperature behaviors, the use of means for thermally separating components defining a second gap and members defining a first gap is advantageous because favorable extrusion techniques for such composite films have particularly high temperature gradients between them Provide columns. Such means for thermal separation may consist of ceramic, but they may also contain air gaps or comprise other insulating material. Further embodiments of the invention will become apparent from the description and the claims. The individual figures show:

Fig. 1 shows a section through a stack die Blaskopf

Fig. 2 shows a section through a Radialverteilungseinschub an advantageous Blaskopfes

3 shows a section through a blow head with a central pre-distributor. FIG. 4 shows a section through a further blow head with a central blower head

preliminary distributor

5 shows a section through a blow head according to the invention, FIG. 6 shows an advantageous radial distribution system

1 shows a section through a stack die blow head 1. The cutting plane is spanned by the axial and radial coordinates z, r of the blow head. The axial components z at the same time indicate the conveying direction of the melt in the die. The stack-die Blaskopf 1 is supported on a foot 2, which also contains part of the infrastructure required for the blow head (cooling air, power, sensor and control lines). The part of the infrastructure, which is intended for the interior of the film bubble, passes into the inner tube 3, which passes, for example, the air for internal cooling to the internal cooling 13. The inner tube 3 in turn extends within the lower 4, middle 5 and upper 6 inner mandrel of the blow head 1. The inner mandrels 4,5,6 also limit the nozzle gap for conducting a plurality of individual flows 17 inwardly and form the Blaskopfinnere in the radial direction r of the blow head 1 ,

The melt is supplied to the shown stack die blow head in the radial direction r from the outside, wherein the outside of the blow head 1 extending lines are not shown.

The forwarding of the melt in the Blaskopf take over the

Melting lines or radial distribution lines 14, in the present

Sectional drawing (Figure 1) can be seen only in cross section. It is not shown that the course of these lines 14 just radial components r so that the lines 14, the melt the coils 15 and thus the second columns for guiding a single flow 16 supply.

The lines 14, the coil 15 and the second column 16 are limited in the illustrated embodiment of a stack die Blaskopfes each of the upper and lower plate 10, 1 1 of a Radialverteilungseinschubs 12. The illustrated blow head 1 has five such Radialverteilunginsschübe 12 and thus also five such column for conducting individual flows 16. All of these gaps open into the gap for directing a single flow 17 in which the various melt flows are combined to form a composite. At the axial end of the blow head, the melt composite passes through the nozzle 19 formed by the inner and outer extrusion lip and cools down to the film bubble 18.

FIG. 2 shows an advantageous course of melt lines 14 in a radial distribution insert 12, often referred to as stag antlers. Here, FIG. 2 is to be understood as a section through such a radial distribution insert 12. The cutting plane is spanned by the radial and angular coordinates φ of the blow head. The specific nature of the course and branches of the radial distribution line 14 is similar to a deer antler. First, the melt at the transfer point A is transferred from an unillustrated outside of the blow head, preferably between an extruder and the blow head 1 extending line to the running within the Radialverteilungseinschubs 12 and thus within the Blaskopfes 1 radial distribution line 14. These

Radial distribution line branches to bring the melt as evenly as possible at different locations to the second gap 16 for conducting a single flow. Upon reaching this gap 16 at point B, the melt line 14 is in the present embodiment in the coil 15 via.

Important for the great quality of the described type of radial distributor is that the distance between the point A and the points B is the same in all branches. In this way it is ensured that the pressure drop in all branches is the same and the melt on the gap reached the different points B with the same pressure. The dashed circle 35 indicates the radial extent of the second gap for conducting a single flow.

3 shows a blowing head 21 with a central pre-distributor 20. This is located - in a characteristic way - at the foot of the blow head and is arranged centrally in the radial direction r.

The central pre-distributor 20, the melt is fed via main melt lines 24 a to f. For illustrative reasons, only one melt feed line 24 is shown as representative. The pre-distributor consists here of different layered superimposed components 20a to 20g. Each later melt layer is also associated with a central cavity 24 a to f, into which the respective main melt line 22 a to f opens. Of these cavities 24 a to g, the melt distribution lines 25 a-g are branched off. It should be noted that several melt distribution lines branch off from each cavity, only one of which is shown. This measure also has the goal of providing the first column for conducting a single flow 26a to 26g along its extent in the direction of the angular coordinates φ as uniformly as possible with melt. Upon reaching these gaps 26a to 26f, the melt distribution lines 25a-f merge into coils 15. After the individual flows of the melt in the columns 26a to 26g have been brought into their flat shape in the development, they reach the nozzle gap for conducting a plurality of individual flows 17 and are finally extruded through the nozzle 19.

For the mechanical structure of this blowing head 21 is still to say the following: The central pre-distributor 20 is surrounded by the Hauptumlenkstück 23. The column for directing a single flow 26a to 26f are formed by the main deflector 23, the deflectors 27 af and the jacket 28. Before it enters the atmosphere, the nozzle gap 17 is delimited by the inner mandrel 31, the inner ring 30 and the outer ring 29. The inner mandrel 31 has further inner parts 32 to 34. The mechanical structure of the blow head 41 in Figure 4 initially acts clearer than the mechanical structure of the blow head 21: About the Hauptumlenkstück 43, the further deflecting 47 are arranged af. The outer ring 50 and the inner ring 49 follow these deflecting pieces. The inner tube 51 provides space for the feed lines for the interior of the film bubble 18.

The column for directing a single flow 46 a to f are again limited by the deflection pieces 43 and 47 a-f and the rings 49,50. Compared to the blowing head 21, it is noticeable that the gaps for directing a single flow 47 b to f open on both sides of the melt flowing through the nozzle gap for conducting a plurality of individual flows 17. Only the first individual gap 26 a in the main flow direction z of the melt passes directly and thus individually into the die gap 17. In this way, it is also possible to merge seven melt layers, but to keep the distance between the junctions of the individual gaps 26 a to f in the nozzle gap 17 and the outlet of the melt from the nozzle 19 substantially lower than in the blowing head 21. This fact protects the film material. The blow head 41 shown in FIG. 4 also has a central predistributor 40, this not comprising different components exclusively assigned to it, such as the predistributor 20 of the blow head 21 with its parts 20 a-g. Rather, the central pre-distributor 40, which is designated merely by an arrow, is pronounced as part of the main deflecting piece 43 and of the deflecting pieces 47 a-f. However, a comparison of the two blow heads 21 and 41 or pre-distributor 20 and 40 reveals basic functional similarities:

The main melt lines 22 af and 42 af bring the melt to cavities 24 and 44 af, which are positioned in the radial direction r of the blow head best exactly in the center of the nozzle ring. In the exemplary embodiments shown, the main melt lines extend predominantly in the radial direction r. However, it also seems possible to supply the cavities by predominantly in the z-direction running main melt lines. These cavities supply melt distribution lines 25 and 45 af, which usually branch off in a star-like manner from the cavities and open again into the first gaps 26 and 46 for conducting a single flow. The purpose of the central positioning of the cavities 24, 44 in the central predistributor is that the various star-shaped melt distribution lines 25 and 45 branching off from one cavity, which conduct a melt flow and which open into a gap 26 or 46 for conducting a single flow, from the cavity are the same length until the gap. In this way, the melt of a nten melt layer in all its associated melt distribution lines 25a-f and 45a-f experiences the same pressure loss. In this way, a desired film quality is ensured. In general, the cavities are 24 af or 44 af in the z-direction below the beginning of the column 26 or 46 af.

FIG. 5 shows a blow head 61 according to the invention, whose lower components in the z-direction are initially identical to the corresponding components of the blow head 41:

The deflecting pieces 47a are "stacked" on the main deflecting piece 43 and create the prerequisite for the extrusion of a seven-layered film. However, these components in the main flow direction of the melt (or the axial direction of the blowing head) are not followed by the closing rings 49 and 50 as in the die 41, but the two plates 63 and the outer ring 67. These components 63 and 67 have a similar function as the upper and lower plates 10 and 1 1 of the Stack DIE Blaskopfes 1: they define the second column 66 a They also limit their associated melt distribution lines 62, which again are designed as radial distributors, ie the same or similar to those in Figure 2 or below in Figure 6. In this context, it is especially important that these two columns for conducting a single flow 66 a, b, the melt is not just received via the central pre-distributor 40 and so that second column in the language of this document are. The first column 46 a to f are supplied from the central pre-distributor. The bracket 69 indicates that the plates 63 and the outer ring 67 components of a retrofit kit may be, in the present case a Seven-layer blown head extended to a nine-layer blown head. The screw 64 is a fastener that adequately anchors the retrofit kit 69.

FIG. 6 shows an advantageous course of a melt distribution line 55, as may be embodied in a radial distribution insert 12 or in one or more plate 63 or outer ring 67. The course of the melt distribution line 55 is similar to the course of the melt distribution line 14, wherein it can be clearly seen in FIG. 6 that the line runs in two planes. The distance between the one transfer point between outer (not shown) and inner melt line / radial distribution line 55 and the (here) eight transition points B between this line 55 and its associated gap for conducting a single flow is the same for all eight transition points B. A synopsis, in particular of FIGS. 5, 6 and optionally 2, illustrates that it is possible to make the melt lines 62, which supply the second gaps a, b with melt, relatively short (distance between points A and B). However, these melt lines already lead the melt for the eighth and ninth layer of the film composite. The melt supply lines 42g, f and 45g, f of the sixth and seventh first gaps 46g, f are much longer. This can be extruded through the second column in the present embodiment with the same pressure more melt, which can be used in multilayer films, for example, for a higher extrusion speed. Again, this is one of the benefits of the present invention.

Of course, the length of the melt feed lines is mathematically related to their volume. In the application of the invention, it is favorable if the first columns 26, 46 for conducting a single flow, which are fed by a central predistributor, are moved to second columns 16, if the distance - or the line volume - between the transition of the central Cavity 24 to the melt distribution line D and the transition F of the melt distribution line 25 in the second gap 26 is longer than the Distance between points A and B of a radial distribution system (see Figure 3).

LIST OF REFERENCE NUMBERS

Stack the die

Foot and feed part

inner tube

Lower inner spine

Middle inner thorn

Upper inner thorn

Inner nozzle lip

Outer nozzle lip

outside Dorn

Upper plate

Lower plate

Radial distribution slot

internal cooling

Radial distribution lines

Wendel second gap for directing a single flow

Nozzle gap for the conduction of several individual flows

film bubble

Nozzle a-f Central pre-distributor

Blow head with central pre-distributor A-F main melt lines

Main diverter a-f Cavity a-f Melt distribution ducts a-f First column a-f diverters

coat

outer ring

Claims

claims

1. Blaskopf (1, 21, 41) for the extrusion of film tubes (18) made of film with at least two plastic layers, which has a central pre-distributor (20,40), via which (20,40) the material for the at least one plastic layer one first gap (26,46) can be supplied to conduct a single flow, which opens into a nozzle gap (17) for conducting a plurality of individual flows, characterized by

at least one further second gap (16) for conducting a single flow,

- The flows into a nozzle gap (17) for conducting a plurality of individual flows and

- Which (16) the melt can be fed without having passed the central pre-distributor (20,40).

2. Blow head according to claim 1, characterized in that

the at least one second gap (16) for conducting a single flow,

- In a nozzle gap for conducting a plurality of individual flows (17) opens and

- Which (16) the material can be fed without the central pre-distributor (20,40) to have passed

- In the transport direction of the film melt (z) after the at least one first gap (26,46) which is fed via the central pre-distributor, is arranged.

3. Blaskopf according to claim 2, characterized in that all the second column (16) for directing a single flow in the transport direction (z) of the film melt in the nozzle gap behind all the first columns (26,46) are arranged to conduct a single flow.

4. Blow head according to one of the preceding claims, characterized in that at least one second gap (16) in a Radialverteilungseinschub (12), the (12) is assigned at least one melt supply line (25) which extends through any Radialverteilungseinschub (12) which is associated with another melt line (25).

5. Blowing head according to one of the preceding claims, characterized in that at least one second gap (16) in a Radialverteilungseinschub (12) extends, in which a melt distribution system (14) extends, with the second gap melt is zuleitbar and that the melt in Transition region (A) between the melt distribution system (14) and feed lines with which the melt is brought to the radial distribution system (14) is conveyed mainly in the radial direction (r) of the die.

6. Blower head according to one of the preceding claims, characterized in that

at least one second gap (16) extends in a radial distribution insert (12) in which a melt distribution system (14) runs, with which melt can be supplied to the second gap (16),

wherein the melt distribution system (14) is located in the radial distribution insert (12) branches and has a plurality of points (B), lead to the leads of the melt distribution system (14) in the gap, and that the distance between the feed line (A) of the melt in the melt distribution system (14) and the point (B ), at which the leads of the melt distribution system (14) open into the gap (16) is the same at all branches.

7. Blowing head according to the preceding claim, characterized in that the melt distribution system (14) in the gap (16) merges into coils (15) and that at least a part of the melt distribution system (14) and the coils (15) in a component (10 , 1 1) runs.

8. Blowing head according to one of the preceding claims, characterized in that at least one melt distribution system (14) for a second gap (16) contains melt lines (14) which extend in planes which have a different height in the axial direction of the blow head (z). exhibit.

9. Blow head according to one of the preceding claims, characterized in that at least one fastening means (64), which passes through at least one component (47a-f), which defines a first gap (26,46), also passes through at least one component (63, 67), which passes through a second gap (16).

10. Blowing head according to one of the preceding claims, characterized in that the volume of the melt supply lines (25) between the takeover point (D) from the central pre-distributor and the point (F) at which the melt distribution lines (25) in one of the first column (26 , 46) for conducting an individual flow, is greater than or equal to the volume of a melt supply line (14) between the supply line (A) and the point (B) of the junctions of the supply lines of the melt distribution system in a second gap (16) Conduction of a single flow.

1 1. Blow head according to one of the preceding claims, characterized by

Thermal severing means disposed between components (47) defining at least one first gap (26, 46) and members (63, 67) defining at least one second gap (16).

12. Retrofit kit (69) for a blow head (1, 21, 41, 61), wherein the blow head has a central pre-distributor (20,40), via which the material for the at least one plastic layer a first gap for directing a single flow (26 , 46) can be supplied, which opens into a nozzle gap (17) for conducting a plurality of individual flows, characterized in that

the components of the retrofit kit (69) delimit at least one further second gap (16) for conducting a single flow,

- Which (16) the melt material can be fed without having passed the central pre-distributor (20,40).

13. Retrofit kit (69) according to the preceding claim, characterized in that the components of the retrofit kit (69) with the retrofitted blower head (1, 21, 41, 61) without a jacket (28), at least part of the components of the retrofit kit (69) encompasses, are connectable.

14. Method for operating a blown film plant,

in which at least two-layered film is produced using a blown head,

in which melt in a blow head (1, 21, 41, 61) is fed via a central pre-distributor (20, 40) to at least one first gap (26, 46) for conducting a single flow,

- Which (26,46) the single flow into a nozzle gap (17) for the line one or more individual flows, characterized in that at least one further second gap (16) for directing a single flow, which also opens into a nozzle gap (17) for conducting a plurality of individual flows, the melt is supplied without these the central pre-distributor (20 , 40) has happened.

15. The method according to the preceding claim, characterized in that between the melt in at least a first gap (26,46) and the melt in at least one second gap (16) for conducting a single flow, a temperature difference of at least 50 ° C.

16. The method according to one of the two preceding claims, characterized in that the melt temperature in at least one first gap (26,46) is lower than the melt temperature in at least one second (16).

17. The method according to any one of the three preceding claims, characterized in that the melt temperature in at least a first gap (26,46) between

200 ° and 260 °, but preferably between 220 ° and 240 ° C, and / or the melt temperature in at least one second gap (16) between 290 ° and 300 ° C.

18. Method according to one of the four preceding claims, characterized in that the melt in at least one first gap (26, 46) is predominantly EVOH, and / or that the melt in at least one second gap (16) is predominantly polyester.

19. The method according to any one of the five preceding claims, characterized in that the extruded film is wound using at least one winding point with reversal of direction.