DE4115229C2 - Method and device for producing multilayer tubular films or tubes - Google Patents

Description

The invention relates to devices according to the preamble of claim 1 and a method of manufacturing multilayer films and tubes.

Devices for producing multilayer are in the prior art Blown films or tubes known. The publications EP 0 017 501 A1 and EP 0 074 812 A2 describe various embodiments of such devices and the corresponding procedure. Such devices mostly contain a mandrel around which concentrically formed laminate plates are arranged are from which different material melts in the space between the mandrel and laminated sheets are pressed. The hose or the pipe forms in the multi-layer channel between the mandrel and the layer plate ten out. By injecting different material melts into different axial position, multilayer tubular films are created or pipes. A problem with such devices is uniform To produce material flow in the circumferential direction, so that even layer thicknesses can be achieved in the circumferential direction. The publications mentioned above show different ways to solve the problem by ver different locations of the supply channels pressure changes are provided. al len these devices has in common that the material feeds Nozzle in which the tube or hose is formed over long distances stretches that extend substantially in the axial direction and the training a homogeneous flow of material into the multi-layer channel is not guaranteed len.

The longer feed channels to the multilayer channel have the disadvantage of one Build up high pressure, have long dwell times and become more difficult to clean.  

The nozzles required for molding a single layer are coaxial Mandrel arranged, with cylinders comprising several parts for each layer be used. The disassembly of such nozzles, namely the removal of the coaxial cylinder, is usually a difficult and lengthy task. This can take 1 to 2 days.

It is also difficult to maintain accurate gap widths. This sets separa te adjustment and very precise finishing with exact grinding zy Lindward cut surfaces ahead.

FR 2625941 A also makes nozzles for the production of multilayer films known in which annular distributor disks coincide in the axial direction be applied, with disk-shaped distributor disks with radial ver set feed holes are used, from which the material melt through an essentially radial gap inwards to a central ko axial multilayer gap flows. In this known device is a even distribution of the flow and thus an outflow with the same Density and equal pressure in the inner multi-layer channel problematic. It can also be caused by a non-forced flow Guidance to materials with high dwell time with materials sensitive to dwell time time and thus come to the dismantling.

DE 39 02 270 A1 describes a method and an apparatus for the manufacture position of co-extruded tubular films in the case of a multitude of layer plates are stacked on top of each other. The material waste is via distribution channels fed radially from the outside and a single radial flow channel introduced into the multi-layer channel. An even, homogeneous material electricity in the multi-layer channel can hardly be reached.

According to DE 23 29 792 A1, a method and devices are known which initiate a melt flow centrally and the melt over several very complex spiral plates lead to the outside and to egg nem essential in relation to the radius of the melt flow supplied larger ring cross-section. The same applies to the device according to the DE 24 26 677 A1.  

Nozzles of this design have the disadvantage that they are only for larger nozzles outlet diameter can be used and also longer Melt channels for the supply of the melt to the layer plates are required countries. The design effort for the production of multi-layer fo lien with 5 to 10 layers disproportionately large and complex.

The nozzles known from the prior art have many disadvantages, such as

• - large dimensions,
• - large weights,
• - difficult manufacture,
• - high investment costs,
• - complicated assembly, disassembly and cleaning, so high Maintenance costs,
• - long flow paths,
• - high pressure build-up,
• - Long dwell time and thus the risk of sensitive fragments being broken down Materials.

The object of the invention is a device and an associated method ren to create, in which the disadvantages mentioned above are avoided. in the all should be special for the quality of an optimal melt distribution be shaped into a laminated board.

This object is achieved by the features of claim 1 and claim 10 solved.

Advantageous further developments are the subject of dependent claims.

According to the invention, the device consists of annular individual elements built up. The individual elements are designed as layer plates, some Distribution channel which has the material entering from one side from the outside melt distributed in a ring, the distribution channel in the circumferential direction is rejuvenated. The taper serves to circumferentially flow with flowing material direction after leaving the distribution channel to ensure the same pressure len, depending on the location, the same amount of material over ironing zones and one Pressure equalization channel with homogeneous flow in the inside push the layer channel in. In the invention, the multilayer channel formed between a mandrel and the layer plates be, then the flow of material through these plates done from the outside in.  

The multilayer channel should be in the outflow direction of the film or the location expand, since the material flow increases with the number of layers. Makes the individual elements are the same size and the mandrel in the above-mentioned version conical, then there is also a simple standardization of the layered plates possible what the cost of fixtures for different layers settles. By means of the same layer plates, the device can also be used Assemble the need for the layer structure. That has the advantage of one further standardization, which is the price of devices according to the invention continues to lower.

It is also convenient to have different distribution channels in different directions to lay in order to achieve an even distribution of material. Be the following two versions are preferred. At the first execution shape expand from the feed hole in the opposite circumferential direction two distribution channels. In the second embodiment is a distribution channel provided that it spirals more than 360 ° around the center of the ring-shaped laminated sheets twists.

Other variations are also possible in which the melt does not go through one but flows through several holes and thus a lot multiplication of the channel shapes described below results.

It is particularly advantageous that the layer plates are simply taken apart are so that the ducts can be easily cleaned and the maintenance costs correspond can be lowered accordingly. An embodiment is advantageous for these purposes sticky, with one side of the layer plate is open, so that the melt leading Channels are easily accessible. It is provided that the bottom of a Layer plate formed by the opposite side of the adjacent layer plate to close the otherwise open melt-carrying channel. Around To keep the cooling of the melt as low as possible can be in or on the Layer plates also provide heating elements. For generation certain desired temperature gradients, is also possible different Place heating elements in the upper and lower part of laminated panels.

Advantages and features of the invention also result from the description of the following embodiments in connection with the claims  and the drawing. Show it:

Fig. 1 shows a device according to the invention;

FIG. 2 shows a layer plate of the device from FIG. 1;

Figure 3 shows an embodiment with five elements and different types of layer plates.

FIG. 4 shows a layer plate of the device according to FIG. 3;

Figure 5 is a section through a laminated board with separable upper and lower part to illustrate the installation of heater elements.

Fig. 1 shows a basic embodiment of a device according to the invention. A base plate 12 is attached to a central mandrel 11 and axially secured by a nut or flange 13 . The parts 11 , 12 , 13 can also be formed in one piece. On the base plate 12 , layer plates 15 are set up. A cover plate 18 is arranged thereon. The layer plates 15 are secured with dowel pins 20 against shifting. The plates 12 , 15 and 18 are pressed together with tie rods 22 .

A die 24 is screwed onto the cover plate 18 by means of screws 26 . A mandrel 32 is constructed centrally on the mandrel holder 11 , which represents the inner shape of the blown film tube. Lateral set screws 28 are used to set a nozzle gap 30 . Heating tapes 34 are attached to and heat the exterior wall of the device. In a preferred embodiment, thermocouples can also be provided for temperature control.

FIG. 2 schematically shows a top view of a layer plate 15 as used in FIG. 1. In Fig. 2 the material flow is indicated by arrows. The melt flows into a distribution channel 43 through a feed bore 41 . This surrounds the center in a circle. In the direction of flow, the distribution channel 43 has a narrowing cross section. From the feed hole 41 , the plastic mass is distributed to the right and left into the distribution channel 43 . A point 45 is designated in FIG. 1 opposite the feed channel 41 . At point 45 there is a wall with which the two opposite directions of flow are separated. A heart-shaped course of the wall can also be provided here, which ends at point 45 for a defined outflow on the opposite side. Such a distribution channel corresponds to that of a clothes hanger channel known to the person skilled in the art in the case of a slot die. Due to the pressure conditions in the distribution channel 43 , the material melt is pressed into an ironing zone 47 . Then the material melt is evenly distributed in the circumferential direction and can then be continued. The calculation of the annular narrowing distribution channel 43 with the subsequent bracket zone 47 is carried out according to the same laws as the calculation of a flat film nozzle with clothes hanger zone.

The melt flows from the distribution channel 43 into the ironing zone 47 , which is wider in the inlet area and narrower in the area of the point 45 . The purpose of this design is to provide a melt flow at the same speed and pressure at the exit of this ironing zone 47 and at the entrance to a flow-symmetrical pressure compensation chamber 49 following the flow by means of different flow resistance. In the pressure compensation chamber 49 , the volume of the melt increases so that remaining pressure differences are compensated. Here, the melt flows through a melt channel 50 , which acts as an ironing zone, into a multilayer channel 52 in the radial or, preferably, also axially conical direction. In the multi-layer channel 52 , the stacked melt flows from different layer plates 15 , 18 with a coating thickness corresponding to the further loading thickness increasing ring channel until the hose at the nozzle gap 30 leaves the device 10 .

The embodiment shown in Fig. 1 and Fig. 2 already shows the essential characteristics of the invention. The device 10 is built up by stacking layer plates, the distribution of the plastic mass or material melt occurs primarily through the configuration of the layer plates due to the tapered distributor channel 43 in connection with the ironing zone 47 and the pressure compensation channel 49 . In Fig. 1 it is shown that the multi-layer channel 52 is increasingly widespread in the axial direction Rich to accommodate the larger material flow. This is achieved in that the layer plates 15 are given a larger diameter in the direction of flow. However, for standardization or for realizing other types of structures, it is expedient to make the laminated panels of the same size. Then the mandrel 11 must be correspondingly conical and taper in the counterflow direction.

In FIG. 3, a slightly different embodiment is shown with five layer plates. The nozzle is constructed in a similar manner to the nozzle according to FIG. 1. The same reference symbols here mean the same elements with the same function. The difference is above all in the layer plates 60 , the flow guide is recognizable in the top view according to FIG. 4. Through a guide bore 62 , the melt flows into a distribution channel 64 which , in this exemplary embodiment, surrounds the center in a spiral shape, so that more than 360 ° is enclosed. In this embodiment according to the invention, there is an overlap of the outer channel and the channel course lying further inside. In the direction of the arrow, the distributor channel 64 tapers more and more in accordance with the reduced flow rate. In the spiral surrounding area there are web 66 which act as an ironing zone and via which the melt passes from the outer channel into the inner channel. This Spiralver divider or "linear spiral distributor" is designed mathematically according to the principles known to the person skilled in the art of the spiral coil distributors of conventional single or multi-layer blown films.

Concentric to the distribution channel 64 , a web 67, which is effective together with the web 66 as a bracket zone, is attached, via which the melt flows at the same speed and pressure into the pressure compensation chamber 68 located further inside. In the pressure equalization chamber 68 , the volume increases, which compensates for remaining pressure differences. From here, the melt flows radially inward through a parallel melting channel 70 , which acts as an ironing zone, into the multilayer channel 52 .

The heating of the device was accomplished in the previous embodiments by heating tapes were attached to the periphery. An alternative solution with integrated heating elements 78 , 79 and 80 , 81 is shown in FIG. 5. An integrated installation of heating elements is advantageous because you can adjust the heating individually, while when heating with external heating tapes, the temperature can be set essentially only for all plates.

Because of the different melting points of polymers, it is often desirable, the individual melt channels with different Driving temperatures, the temperature for each material is optimized.

This is possible due to the split design of each layer plate. From Fig. 5 it can be seen that here the layer plates are divided into an upper part 74 and a lower part 76 . The plate is constructed on the paper guide plate is equal to the layer 60 of Fig. 3 and Fig. 4.

The heating elements 78 and 79 are now arranged in the upper part 74 and the two heating elements 80 and 81 are arranged in the lower part 76 . Separate thermocouples 83 and 84 for the upper part 74 and lower part 76 are used to regulate different temperatures. Narrow pads 86 and 87 , which can consist of thermally good insulating material, ensure thermal separation of the various layer plates formed from upper part 74 and lower part 76 , so that the temperature for the individual melts can be adjusted independently of one another in the large area ,

The temperature of the layer plate halves 74 and 76 must be the same, e.g. B. to 200 ° C, set so that the melt in channel 68 with the same temperature, z. B. with 200 ° C, is performed. The temperature of the layer plates halves 71 and 72 must be even at a slightly higher temperature, e.g. May be set as 210 ° C in the channel 73 to a temperature of eg. B. to guarantee 210 ° C.

From Fig. 1 and Fig. 3 it can be seen that the layer plates are arranged so that their feed holes are charged with melt material on different sides. This measure compensates for tolerances, and a further improvement in the uniformity of the tube or tube thickness is ensured in this way.

With all of the exemplary embodiments, a method can be carried out in which the Spray material is guided through a tapered distribution channel.  

This step will result in an even distribution of material in circumference direction ensured.

The features essential to the invention and their advantages become clear from the exemplary embodiments shown. The invention is characterized by a particularly flat, disk-shaped structure of the individual melt-guiding elements, the so-called layer plates. The distribution of the melt entering through a feed opening into an even radial flow in the circumferential direction occurs through a distribution channel that decreases in the flow direction in cooperation with a subsequent ironing zone or a web. This design enables devices according to the invention to be very compact and to be executable. In addition, the invention allows a ge compared to conventional multi-layer nozzles unusually easy assembly and disassembly due to the disc-shaped structure. As can be seen directly from Fig. 1 and Fig. 3, the melt-carrying channels are exposed by disassembly of the single layer plates, so that simple cleaning is possible. In the example corresponding to FIG. 5, it is also shown that the melt-guiding channels can also be exposed by a separability of the layer elements in an upper part 14 and a lower part 16 , thus also making a maintenance-friendly device possible.

The total length of the melt-guiding channels and the material-covered Surface is in the invention compared to conventional ways in conventional Nozzles greatly reduced. There is only a relatively short inlet cross-section large diameter. This creates the necessary pressure build-up for delivery the material through the distribution space for the melt much less and with the advantage of a lower pressure build-up in the extruder or through the melt pump.

Despite the simple structure, a forced flow is possible while avoiding dead zones and a radial flow that is uniform over the circumference with regard to the speed and pressure distribution, by combining the following features:

• 1. Layered construction of the nozzles;  
• 2. Radial inlet of the flow from the outside into the layer plate;
• 3. Guide the melt inwards into a pre-distribution channel with a continuously decreasing cross section;
• 4. Overflow of the melt from the pre-distribution channel into a compensation gap or an ironing zone, the geometry of the pre-distribution channel and the ironing zone is to be calculated so that the melt at the end of the ironing zone with the same pressure and the same speed in the printout common room entry;
• 5. A concentric pressure equalization space;
• 6. A radial, parallel channel from the pressure equalization chamber into a conc trical internal multilayer channel, which from the layer plate and the inner mandrel is formed.

In particular, the shorter path length and the much smaller one material-covered surface has the advantage of significantly shorter dwell times in the nozzle. This results in further advantages for the processing of materials sensitive to shear temperature and dwell time.

Problems in the production of multilayer films from materials with under different melting points can be avoided by the Melt channels are heated differently.

As shown in Fig. 5, the upper and lower half of the layer plate can be heated separately. In addition, a separate temperature control can be installed in the upper and lower part with the aim of being able to set the channel carrying the material to a different temperature level for each material.

Due to the simple structure of the device according to the invention Manufacturing costs of the invention are unusually low and far below that of the usual multi-layer nozzle constructed with concentric distributors sen.

A major further advantage is that the laminated sheets for everyone Inner layers can be identical. This will expand one  Nozzle simplified to multiple layers by adding to the layer discs another central mandrel and extended tie rods are coming. On the other hand also through the standardization of the manufacture of the individual panes and inventory is reduced.

Claims (10)

1. Device for the production of multilayer tubular films or tubes from material melts,
which has one or more annular layer plates ( 15 ; 60 ) for supplying the material melt for each one melt layer, the layer plates being attached as spiral distributors concentrically around an internal mandrel ( 32 ) and feeding the individual material melts to a funnel-shaped multilayer channel ( 52 ) , on which the tubular film or the tube is then formed,
and wherein each annular layer plate ( 15 ; 60 ) has at least one distributor channel ( 43 ; 64 ) through which the material melt can be introduced into the multilayer channel, the multilayer channel ( 52 ) between the mandrel ( 32 ) and the layer plates ( 15 ; 60 ) is formed
characterized by
that the molten material can be introduced into the distribution channel ( 43 ; 64 ) of the annular layer plate via external feed bores ( 41 ; 62 );
that at the distribution channel ( 43 ; 64 ) closes a bracket zone ( 47 ; 67 ) radially, via which the material melt flows inwards into an annular pressure compensation channel ( 49 ; 68 );
and that radially inside the pressure equalization channel ( 49 ; 68 ) there is another ring-shaped melting channel ( 50 ; 70 ) which acts as an ironing zone and merges into the multilayer channel ( 52 ). 2. Device according to claim 1, characterized in
that the majority of the layer plates ( 15 ; 60 ) are the same size,
and that the multi-layer channel ( 52 ) is widened in the flow direction in that the mandrel ( 32 ) is conical. 3. Device according to one of claims 1 and 2, characterized in that the device can be assembled in a kit, the number of layer plates ( 15 ; 60 ) according to the desired number of layers of the tubular film or the tube is freely selectable. 4. Device according to one of claims 1 to 3, characterized in that from the feed bore ( 41 ) two distributor channels ( 43 ) extend in the opposite circumferential direction. 5. Device according to one of claims 1 to 3, characterized in that the distributor channel ( 64 ) is wound more than 360 degrees like a spiral around the center of the annular layer plate ( 60 ). 6. The device according to one or more of claims 1 to 5, characterized in that melt-carrying channels in the layer plates ( 15 ; 60 ) are at least partially open and the opening after installation of the layer plate ( 15 ; 60 ) in the device through a surface of a adjacent layer plate ( 15 ; 60 ) is closed. 7. The device according to one or more of claims 1 to 6, characterized in that at least one layer plate is constructed in two parts and in the upper part ( 74 ) and lower part ( 76 ) has independent heating elements ( 78 , 79 , 80 , 81 ). 8. The device according to one or more of claims 1 to 7, characterized in that the feed bores ( 41 ; 62 ) of superimposed layer plates ( 15 ; 62 ) are offset from one another in the circumferential direction. 9. Device according to claims 1 to 8, characterized in that the layer plates ( 15 ; 62 ) are clamped together by tie rods ( 22 ). 10. A process for the production of multilayer films or multilayer pipes, in which at least two different material melts are concentrically combined within a funnel-shaped multilayer channel in succession to form a multilayer material melt in which the material melt is drilled through at least one feed channel through at least one distribution channel and one Melt channel is transported evenly in the circumferential direction in the multilayer channel, characterized in that
that the material melt from the distribution channel ( 43 ; 64 ) is introduced via a bracket zo ne ( 47 ) into a pressure compensation channel ( 49 ; 68 ) radially inwards,
and that the molten material is transported radially inward from the pressure compensation channel ( 49 ; 68 ) into the multilayer channel ( 52 ) via a melting channel ( 50 ; 70 ) designed as a further ironing zone.