阅读说明：本技术 挤出设备和挤出方法 (Extrusion apparatus and extrusion method ) 是由 利奥波德·魏尔迈尔 于 2019-08-29 设计创作，主要内容包括：本发明涉及一种用于将具有至少两个空腔的PVC型材,尤其窗型材共挤出的挤出设备,其中所述挤出设备包括喷嘴设备(22),所述喷嘴设备具有至少一个用于第一热塑性材料的第一流动通道(31)和至少一个用于第二热塑性材料的第二流动通道(33),所述流动通道(31、33)在所述喷嘴设备(22)的内部中直至汇聚部(36)都分开地设置,并且所述流动通道(31、33)沿着挤出方向(E)在所述汇聚部(36)下游形成共同的流动通道(37),其特征在于,用于新材料的第一流动通道(31)具有大于所述喷嘴设备(22)的轴向长度的一半的长度,尤其所述流动通道的轴向长度,或所述流动通道(31、33)的所述汇聚部(36)距所述型材(1)的出口的轴向距离小于所述喷嘴设备(22)的轴向长度的12％。本发明还涉及一种挤出方法。(The invention relates to an extrusion device for coextrusion of PVC profiles, in particular window profiles, having at least two cavities, wherein the extrusion device comprises a nozzle device (22) having at least one first flow channel (31) for a first thermoplastic material and at least one second flow channel (33) for a second thermoplastic material, wherein the flow channels (31, 33) are arranged separately in the interior of the nozzle device (22) up to a convergence (36), and wherein the flow channels (31, 33) form a common flow channel (37) downstream of the convergence (36) in an extrusion direction (E), characterized in that the first flow channel (31) for new material has a length which is greater than half the axial length of the nozzle device (22), in particular the axial length of the flow channel, or the axial distance of the convergence (36) of the flow channel (31, 33) from the outlet of the profile (1) is less than 12% of the axial length of the nozzle device (22). The invention also relates to an extrusion method.)

1. Extrusion device for coextrusion of PVC profiles, in particular window profiles, having at least two cavities, wherein the extrusion device comprises a nozzle device (22) having at least one first flow channel (31) for a first thermoplastic material and at least one second flow channel (33) for a second thermoplastic material, the flow channels (31, 33) being arranged separately in the interior of the nozzle device (22) up to a convergence (36), and the flow channels (31, 33) forming a common flow channel (37) downstream of the convergence (36) in an extrusion direction (E),

it is characterized in that the preparation method is characterized in that,

the first flow channel (31) for new material has a length greater than half the axial length of the nozzle device (22), in particular the axial length of the flow channel, and/or the axial distance of the converging portion (36) of the flow channel (31, 33) from the outlet of the profile (1) is less than 12% of the axial length of the nozzle device (22).

2. Extrusion apparatus according to claim 1, wherein the convergence (36) of the flow channels (31, 33) is configured such that at the nozzle outlet (25) of the common flow channel (37) from the nozzle apparatus (22) the ratio of wall thickness expansion (W) to length expansion (L) is 1.01 to 1.3, preferably 1.1.

3. Extrusion apparatus according to claim 1 or 2, wherein the at least one flow channel (31) for the first thermoplastic material and the at least one flow channel (33) for the second thermoplastic material converge in a distance of between 20mm and 50mm upstream of the nozzle end face (25) into at least one common flow channel (37) for the first thermoplastic material and the second thermoplastic material.

4. Extrusion apparatus according to any of the preceding claims, wherein the at least one first flow channel (31) for the first thermoplastic material is not divided on flat visible faces (8, 9) except at profile corners.

5. Extrusion apparatus according to one of the preceding claims, wherein the nozzle inflow region (39) is connected to at least one main extruder (20) and the coextrusion apparatus (21).

6. Extrusion apparatus according to at least one of the preceding claims, wherein the average inclination of the first flow channel (31) with respect to the extrusion direction (E) is 5 ° to 50 °, in particular 10 ° to 25 °.

7. Extrusion apparatus according to at least one of the preceding claims, wherein the two thermoplastic materials are PVC materials with different compositions.

8. Extrusion apparatus according to at least one of the preceding claims, characterized in that in the region of the convergence of the two flow channels at the visible face (8, 9), the gap height of the first flow channel (31) for new material is greater than the gap height of the second flow channel in this region.

9. An extrusion method for coextrusion of PVC profiles, in particular window profiles, having at least two cavities,

-wherein the first thermoplastic material is guided in at least one flow channel (31) in the nozzle device (22); and

-guiding a second thermoplastic material in at least one second flow channel (33) of the nozzle device (22),

-wherein a first thermoplastic material from the at least one first flow channel (31) and a second thermoplastic material from the at least one second flow channel (33) converge into a common flow channel (37) at a convergence (36) such that a profile (1) leaving the nozzle device (22) has layers of the first and second thermoplastic materials, and

-guiding the material in the first flow channel (31) for new material over a length greater than half the axial length of the nozzle device (22), in particular over the axial length of the flow channel, or the convergence (36) of the guided material in the flow channel (31, 33) is achieved in a manner less than 12% of the axial length of the nozzle device (22) measured from the outlet.

10. The extrusion process of claim 9, wherein the first thermoplastic material and the second thermoplastic material are comprised of two different polyvinyl chloride (PVC) formulations.

11. Extrusion process according to claim 9 or 10, characterized in that the profile (1) has a temperature between 190 ℃ and 210 ℃ at the exit from the nozzle device (22).

12. Extrusion process according to at least one of claims 9 to 11, characterized in that the pressure drop with respect to the outlet of the profile is between 250bar and 450bar, in particular between 300bar and 390 bar.

13. Extrusion process according to at least one of claims 9 to 12, characterized in that the melt velocity of the polymer melt of the profile (1) at the outlet is between 1 and 6m/min, in particular between 2.5 and 5 m/min.

14. Extrusion process according to at least one of claims 9 to 13, characterized in that two layers (6, 7) are at least partially applied onto the outer wall of the profile (1), wherein the thickness of the outer layer (6) on the visible faces (8, 9) is at least 50% of the total wall thickness.

15. Extrusion process according to at least one of claims 9 to 14, characterized in that at the nozzle outlet (25) of the common flow channel (37) exiting the nozzle device (22) the ratio of wall thickness expansion to length expansion is 1.01 to 1.3, in particular 1.1.

Technical Field

The invention relates to an extrusion device having the features of claim 1 and an extrusion method having the features of claim 9.

Background

It is known to use extrusion equipment with a nozzle system to co-extrude at least two different thermoplastic resin formulations, for example PVC rigid formulations for making profiles.

In this case, relatively high-quality PVC preparations are provided on the visible side and on the areas of the profiles exposed to weathering and solar radiation. Relatively inexpensive ingredients or formulations are used for the remaining cross-sectional area of the profile.

The cheaper parts can for example consist of recycled materials, for example by means of regrind consisting of ground profiles, or can have an inherent formulation in which less stabilizer and/or more chalk is contained for cost reasons. In this cheaper composition, the color is not critical, since the color is not visible in the finished profile. Since this cheaper composition can always only be used in the inner region of the profile or in the outer region which is hardly exposed to solar radiation, the component is referred to as "core material". While high quality formulations are called "new materials".

Because the cost of regrind is only about 40% and the cost of a normal alternative formulation is only about 80% compared to a high quality window formulation, a high share of inexpensive ingredients is desired. The technical limits are determined by the minimum requirements that the profile must comply with. On the one hand, this relates to the strength properties and weather resistance of the profile, and on the other hand to the appearance, such as color and surface quality.

The simplest form of coextrusion relates to profiles in which the inner wall and in the case of frame profiles also the outer wall facing the wall or in the case of wing profiles the outer wall facing the glass pane is formed from a core material. In this case, the proportion by weight of the core material in the main window profile is approximately 30% to 40%.

This weight fraction becomes higher if the two visible sides and the outer wall of the profile facing the glass are also coextruded, that is to say the exposed outer layer of 1/3, which is approximately the total wall thickness, is formed from the new weather-resistant material and the inner layer of these visible sides, that is to say approximately 2/3 of the total wall thickness, is formed from the core material. In this case, the proportion by weight of the core material is up to about 70% in the main window profile.

However, such a high proportion of inexpensive components is associated with disadvantages in fillet welding. Profiles such as window profiles are welded as rectangular frames, wherein first the four frame legs are cut into beveled connections. During welding, the ramp surface is heated to approximately 220 ℃ so that the profile softens there. Then, the scarfed surfaces are pressed against each other, that is, welded and cooled. Here, a weld seam is formed, which projects outwards and inwards, since the profile is shortened by approximately 1.5mm during welding. The weld is then removed so that a slightly shaded seam is formed. In the shadow seams, the core material must not be visible, since the color difference is perceived as disturbing visually and the weathering resistance is also reduced, which can lead to cracks in the corner regions after a long service time.

Disclosure of Invention

The object of the present invention is therefore to provide an extrusion device which makes it possible to co-extrude complex PVC profiles with two layers composed of two different thermoplastic materials, namely PVC, wherein the outer layer can have a greater thickness than the inner layer.

This object is achieved by an extrusion apparatus having the features of claim 1.

The extrusion device is used for co-extruding the PVC profile with at least two cavities, in particular window profiles. The extrusion device has a nozzle device with at least one first flow channel for the first thermoplastic material and at least one second flow channel for the second thermoplastic material. The thermoplastic material is a PVC material which can have different properties, for example due to different formulations.

In one embodiment, the length of the first flow channel for new material is greater than half the axial length (measured along the extrusion direction) of the nozzle apparatus. In this case, the length can be, in particular, an axial length, i.e. a length projected onto an axis of the extrusion direction. In any case, it should be ensured that: the length based on the flow history in the polymeric material comprises a defined shear history.

Alternatively or additionally, in one embodiment, the axial distance between the converging portion of the flow channel from the outlet of the profile can be less than 12% of the axial length of the nozzle device. This means that the converging portion of the flow passage is located relatively close to the nozzle outlet. Due to the longer flow path, the wall thickness expansion is relatively reduced compared to the length expansion.

The flow channels are arranged separately in the interior of the nozzle device up to the convergence. In the flow direction, the flow channels form a common flow channel downstream of the convergence, which then opens into the nozzle outlet on the end face of the nozzle device.

The convergence of the flow channels is designed in such a way that at the nozzle outlet of the common flow channel, which exits the nozzle device, the ratio of the wall thickness expansion to the length expansion is 1.01 to 1.3, preferably 1.1. Thus, the wall thickness expansion is always slightly greater than the length expansion.

Wall thickness expansion is defined as the ratio between the wall thickness of the shear pattern and the wall thickness of the profile pattern. The length expansion is defined as the ratio between the length of the individual walls on the shear pattern and the length of these walls on the profile pattern. A shear pattern is understood to be a short melt section of approximately 20mm in length, which is cut off with a wide doctor blade nozzle at the end face of the nozzle device during the extrusion process, even before the profile is guided through the calibration section. The melt sections were air-cooled at room temperature, thereby hardening them. In contrast, in the profile pattern, the section of the profile which is to be guided through the calibration section is sawn off. The length of the profile section is also approximately 20mm here. This means that in a typical PVC moulding tool the outlet gap of the nozzle is always smaller on average than the wall thickness to be achieved on the profile pattern. The length of the profile wall at the nozzle outlet is, on average, always greater than the length to be achieved on the profile pattern.

In the same plastic class (here PVC) and rheological boundary conditions, the wall thickness expansion and length expansion are essentially related to the flow channel geometry and the convergence of the flow channel. Thereby, the ratio of expansion is also characteristic of the geometry in particular and vice versa.

In one embodiment, the at least one flow channel for the first thermoplastic material and the at least one flow channel for the second thermoplastic material converge into at least one common flow channel in a distance of between 20mm and 50mm upstream of the nozzle end face. This also achieves: the flow channel has a sufficient length.

In one embodiment, the at least one first flow channel for the first thermoplastic material on the flat visible face is not divided by the retaining web. Surface effects such as gloss streaks and waviness are thus avoided.

Furthermore, in one embodiment, the nozzle inflow region is connected to at least one main extruder and the coextrusion device.

In another embodiment, the average inclination of the first flow channel 31 with respect to the extrusion direction is between 5 ° and 50 °, in particular between 10 ° and 25 °. It is also relevant here that a defined shear history can be formed in the flow channel.

It is also possible that the two thermoplastic materials are PVC materials with different compositions.

In a further embodiment, in the region of the visible face (8, 9) of the window profile at the combination of the two flow channels, the gap height of the first flow channel (31) for the new material is greater than the gap height of the second flow channel in this region.

The object is also achieved by an extrusion process having the features of claim 9.

Therein, the

-guiding a first thermoplastic material in at least one flow channel in a nozzle device; and is

-guiding a second thermoplastic material in at least one second flow channel of the nozzle device,

-wherein the first thermoplastic material from the at least one first flow channel and the second thermoplastic material from the at least one second flow channel converge into one common flow channel, so that the profile exiting from the nozzle device has layers of the first thermoplastic material and the second thermoplastic material, and

-guiding new material in the first flow channel for new material over a length exceeding half the axial length of the nozzle device, in particular over the axial length of the flow channel, and/or measuring the convergence of the new material guided in the flow channel from the outlet in a manner less than 12% of the axial length of the nozzle device. This means that the convergence of the melt is relatively close to the outlet.

The first thermoplastic material and the second thermoplastic material can be composed of two different polyvinyl chloride (PVC) formulations.

In one embodiment, the profile has a temperature between 190 ℃ and 210 ℃ at the outlet from the nozzle device. The pressure drop with respect to the profile outlet can be between 250 and 450bar, in particular between 300 and 390 bar. And, at the outlet, the melt speed of the polymer melt of the profile can be between 1m/min and 6m/min, in particular between 2.5m/min and 5 m/min.

In another embodiment, the two layers are applied at least partially to the outer wall of the profile, i.e. to the wall of the extrusion which is exposed to sunlight when mounted, wherein the thickness of the outer layer on the visible side is at least 50% of the total wall thickness.

The ratio of the wall thickness expansion to the length expansion at the nozzle outlet of the common flow channel from the nozzle device can also be 1.01 to 1.3, in particular 1.1.

Drawings

The invention is explained in detail below with reference to the drawings according to embodiments. In particular, the different nozzle configurations and the extruder arrangements required for this are described in terms of exemplary window profiles according to the figures. Shown here are:

fig. 1 shows a frame profile in a co-extrusion embodiment with three outer walls of two parts, wherein the thickness of the outer layer is about 30% of the total wall thickness.

Fig. 2 shows the same frame profile in a co-extrusion embodiment, with three outer walls consisting of two parts, wherein the thickness of the outer layers of the two visible faces is about 70% of the total wall thickness.

FIG. 3 shows a cross section of a weld seam after fillet welding, the profile according to FIG. 1-approximately 30% of the total layer thickness is composed of new material;

FIG. 4 shows a cross section of a weld seam after removal of the weld bead, the profile according to FIG. 1-approximately 30% of the total layer thickness is made up of new material;

FIG. 5 shows a cross section of a weld seam after removal of the weld bead, the profile according to FIG. 2-approximately 70% of the total layer thickness is made up of new material;

FIG. 6 shows an overview of one embodiment of a main extruder, a coextrusion apparatus and a nozzle apparatus;

FIG. 6A shows a schematic of wall thickness expansion and length expansion of the profile at the exit from the nozzle apparatus;

fig. 7 shows a vertical section through an embodiment of a nozzle device for manufacturing a profile according to fig. 2;

fig. 8 shows a cross-sectional view of the nozzle device according to fig. 7 against the extrusion direction, section a-B referring to fig. 7;

FIG. 9 illustrates a front view of one embodiment of a nozzle inlet plate of the nozzle apparatus;

FIG. 10 illustrates a front view of another embodiment of a nozzle inlet plate of the nozzle apparatus;

fig. 11 shows a three-dimensional view of a channel guide in an extrusion tool;

FIG. 12 shows a detail of the convergence of the two flow channels;

FIG. 13 shows a cross-sectional view of a channel for an extrusion profile;

fig. 14 shows a cross-sectional view through an extrusion with two different layers.

Detailed Description

Fig. 1 shows in cross section a profile 1 made of PVC, i.e. a window frame profile with more than two, here eight cavities 12 in a coextrusion version, wherein a relatively very low-cost core material, i.e. about 75%, is used compared to new materials.

The profile 1 has two visible faces 8, 9: the visible surface is the outer wall of the profile 1 that is visible from the outside and from the room when the window is installed.

The three outer walls, which are in significant contact with the sunlight, have two layers 6, 7 at least in part here, i.e. one layer 6 is "coextruded" onto the other layer 7. The outer layer 6 has a thickness of about 1/3 a of the total wall thickness, i.e. about 0.7 to 1.0mm, and is made of the new material.

The inner layer 7 is composed of a core material. The respective outer wall and the smaller profile sections as well as the inner wall are formed in a single layer in this profile 1. When the windows are installed, they are facing the wall or are located inside the profile and are thus no longer visible.

As shown in the tests, in the coextrusion device 22 mentioned for these profiles 1, the thickness of the outer layer 6 cannot be increased at will, i.e. from 1/3 to, for example, 2/3 of the total wall thickness.

Fig. 2 shows the profile 1 according to fig. 1, but with a medium-high proportion of core material, i.e. approximately 60%.

In this case, the three outer walls which are in significant contact with the sunlight are also constructed from two layers 6, 7, i.e. they are coextruded.

The main difference to the profile 1 according to the embodiment in fig. 1 is that the thickness of the outer layer 6 is about 2/3, i.e. about 1.5mm to 2.0mm, of the total wall thickness, and the outer layer 6 is made of the new material. The inner layer 7 is composed of a core material. The respective outer wall and the smaller profile sections as well as the inner wall 4 are also designed in a single layer. When the windows are installed, they again face the wall or are located inside the profile and are thus no longer visible.

As mentioned above, the requirement for a greater thickness of the outer layer 6 is based on fillet welding. During welding, the profile 1 is heated above the melting temperature in the mitre region and then pressed against one another, wherein the two frame legs are each shortened by approximately 1.5 mm. A weld bead 10 (see fig. 3) is produced on the visible face, which is removed so that a shadow seam 11 (see fig. 4, 5) of about 4mm width and 0.5mm depth is produced. If the core material is exposed in the shaded seam 11, this may indicate a quality loss, as will be explained below.

Fig. 3 shows a weld bead 10 in cross section, which is produced after fillet welding of the outer walls of the two layers of the profile (on the inner visible surface 9). The relevant outer wall is shown below in fig. 1, which is directed outwards when the window is installed in the house wall. The weld bead 10 is substantially symmetrical about an axis not shown in fig. 3 in a vertically and horizontally extending manner. During welding, the two frame legs are displaced by approximately 1.5mm relative to each other, so that excess viscous material is pushed out from the interior of the wall and forms a weld bead 10 on both sides. If the inner wall 4 (see fig. 1) projecting at right angles hinders the pushing into the interior of the profile, more material is pushed outwards, the outer beads then being larger than the inner beads.

After the four welds of the rectangular frame have cooled, the weld beads are removed.

In the machine, all welds are "cleaned", i.e. the weld bead 11 is removed. The chips are removed in the mitered plane on both visible faces, so that a shadow seam 11 is produced, as shown in fig. 4.

As can be seen in fig. 4, the separation layer between the new material 2 and the core material 7 is cut through the hatched slits 11 so that the core material 7 is also directly outside and visible. This is undesirable, for example in the case of color deviations, because the core material 7 can have a greater distinction from the new material 2 both in terms of color and in terms of environmental resistance. Sometimes even fail to reliably follow the required characteristic values (e.g. environmental resistance, long-term stability).

If the layer thickness of the outer layer consisting of the new material 2 is made thicker on the visible faces 8, 9, i.e. more than 50% of the total wall thickness, preferably about 60 to 70%, see fig. 5, the core material is not cut open with high safety when removing the bead 10. The quality of the window is therefore of higher quality, since the color difference does not interfere with the visual impression, nor does the core material be damaged by environmental influences, so that fractures after long service times of 20 years or more can be reliably avoided.

Fig. 6 shows a per se known arrangement of a main extruder 20, a coextrusion device 21 and a nozzle device 22.

The main extruder 20 is oriented coaxially with the entire successor of the extrusion line and serves to formulate the components having a larger share in the respective profile 1. The co-extrusion device 21, which is used to formulate the other ingredients, is inclined to the main extruder at an angle of about 30 °.

The two extruders 20, 21 feed the formulated PVC melt into a nozzle device 22, i.e. first into a nozzle inlet plate 24. The nozzle arrangement 22 has a plurality of nozzle plates 23, which are arranged perpendicular to the extrusion direction E.

According to the embodiment of the conveying channels 32, 35 (see fig. 7) in the nozzle inlet plate 24, in principle each of the extruders 20, 21 is able to process a core formulation for the inner wall 4, the three co-extruded outer walls 7 and the inner side of the outer wall 3 and some other profiled regions 3. In the embodiment shown, this is done by the main extruder 20.

In principle, it is also possible in the nozzle inlet plate 24 to exchange the distribution of the two PVC materials on the two extruders 20, 21 by changing the conveying channels 32, 35. If the new material is processed by the main extruder 20, it is expedient if the nozzle inlet plate is constructed in two parts, rather than a single nozzle inlet plate 24.

The coextrusion device 21 does not have to be arranged at the same height as the main extruder 20. The coextrusion device can also be arranged obliquely above the main extruder and then fed from above into the nozzle inlet plate 24.

It has been found that the known extrusion devices cannot be used to form a thicker layer 6 on the profile 1 at about 2mm on the outside and a layer 7 at about 1mm or less on the inside. It has been determined that in such coextruded profiles too little length expansion and/or too high wall thickness expansion can be expected. In particular, the ratio of wall thickness expansion to length expansion becomes worse to values much higher than 1.2.

Expansion (also referred to as swell in english) is understood here as the property of melt elasticity, which is a property of polymer melts. For example, if the polymer melt is extruded from a cylindrical tube at a low reynolds number, the diameter of the exiting profile is significantly larger than the outlet profile of the nozzle device; the profile expands due to the adjustment of the velocity profile.

The expansion is caused by reducing the normal stress transverse to the shear direction. These normal stresses are pressed against the walls of the flow channels 31, 33 and the common flow channel 37. After leaving the nozzle device 22, the polymer can be relieved of stress and expanded.

In the hollow-chamber profile 1 referred to here, the expansion is a two-dimensional effect, since the length expansion L (expansion of the length of the individual walls) is formed differently from the wall thickness expansion W (expansion of the thickness of the profile wall).

This is schematically illustrated in fig. 6A for a strongly simplified profile 1 without coextruded layers, the section view being directed perpendicular to the extrusion direction E.

In the test, the free exit of the profile 1 from the nozzle device 22 was used when fine-tuning the nozzle device 22: a short melt section of approximately 20mm in length is cut off with a wide doctor blade on the end face of the nozzle device 22 and air-cooled at room temperature, just before the profile 1 is guided through the calibrating section (not shown here). Ideally, all the walls are longer and thicker than the calibrated normally stripped profile sections.

The reasons may be: the new material fed to the nozzle in the downstream region of the forming section 38 has too little time to relax and still clearly "remembers" the thicker shape in the feed channel 32 and tries to adopt this shape again approximately. Thicker coextruded layers have a greater effect on bulk expansion than thinner coextruded layers. This expansion behavior naturally also applies to the coextruded outer wall according to fig. 1 with a thin outer layer: the expansion behavior of the thicker inner layer is also dominant here in the overall expansion. However, this expansion is relatively small, since the melt has flowed for a relatively long time through the long flow channel 33 with small gap thickness variations and the memory of the flow cross section in the conveying channel 34 is significantly reduced.

PVC material at 190 ℃ and210leaving the nozzle arrangement 22 at a temperature between c. The pressure drop with respect to the outlet is between 250bar and 450bar, in particular between 300bar and 390 bar. In this region, the melt velocity of the PVC melt is from 1m/min to 6m/min, in particular from 2.5m/min to 5 m/min.

The application of an outer layer having a relatively thick thickness is possible with the embodiment shown in fig. 7. Both the new material for the outer layer 6 and the core material for the inner layer 7 have been supplied to the nozzle 39 in the inflow region.

Thus, there is a first flow channel 31 for the first thermoplastic material and a second flow channel 33 for the second thermoplastic material, wherein the flow channels 31, 33 are arranged separately in the interior of the nozzle device 22 up to a convergence 36, and the flow channels 31, 33 form a common flow channel 37 downstream of the convergence 36 in the extrusion direction E.

Thus, a long shaping section of the nozzle 38 is provided for the two layers 6, 7, wherein only a small change in the gap height of the two flow channels 31, 33 has to be made again. Thus, both materials have sufficient time to relax so that internal stresses can be reduced as much as possible. As a result, all wall regions of the outer wall have a similar expansion, so that no waves and differences in gloss occur in the edge regions of the profile 1.

Thus, the axial distance of the converging portion 36 of the flow channel 31, 33 from the outlet of the profile 1 can be less than 12% of the axial length of the nozzle device 22 of the nozzle. This means that the convergence of the flow channels 31, 33 is located relatively close to the nozzle outlet. The length of the flow channels 31, 33 can also be greater than half the axial length of the nozzle device 22 (measured in the extrusion direction E). In this case, the length can be, in particular, an axial length, i.e. a length projected onto an axis of the extrusion direction. In any case, it should be ensured that: the length based on the flow history in the polymer material comprises a defined shear history (schervargeschichte).

The convergence 36 of the flow channels 31, 33 in the nozzle device 22 is designed in such a way that at the outlet of the common flow channel 37 from the nozzle device 22, a ratio of the wall thickness expansion W to the length expansion L of 1.01 to 1.3, preferably 1.1, results. This means that the wall thickness expansion W is slightly greater than the length expansion L.

The flow channels 31, 33 depicted in fig. 7 run in a manner allowing for different thicknesses of the outer layer, preferably in the range of 25% to 70% of the total wall thickness. Through this course of the flow channels 31, 33, it is therefore possible to extrude the two profile shapes according to fig. 1 and 2, i.e. the thin outer layer 6 in the flanged region of the profile according to fig. 1, without problems.

In fig. 11 and 12, the spatial arrangement of the flow channels 31, 33 is clearly shown in a further embodiment.

Fig. 8 shows a sectional view against the extrusion direction of the nozzle according to fig. 7. Section a-B is shown in fig. 7. The two flow channels 31, 33 converge further downstream of the convergence 36 of the two into a common flow channel 37, wherein the two flow channels 31, 33 run slightly obliquely and also slightly conically with respect to the extrusion direction E.

The first flow channel 31 can be inclined, for example, by 5 ° to 50 °, in particular by 10 ° to 25 °, with respect to the extrusion direction. The angle is determined from the convergence 36.

The flow channel 31 of the outer layer of new material is continuous over the entire width. The flow channel 33 for the inner layer of core material is interrupted by two retaining webs 40.

The continuous flow channel 31 leads to a uniform surface of the outer layer on the visible side 8, 9 of the profile 1. Irregularities in the form of retaining webs or edges in the flow channel 31 should be avoided as much as possible, since even if they are located further upstream of the nozzle device 22, gloss streaks or slight undulations on the surface of the profile 1 inevitably occur.

If a division in the flow channel 31 is still required to reduce the cross flow, this division should not take place in the region of the flat wall sections, but rather at locations where the outer wall has a bend with a comparatively small radius of curvature (see also fig. 14).

The surface of the coextruded outer wall facing the cavity 12 has low requirements with regard to the surface quality, so that the associated flow channel 33 for the inner layer can be easily interrupted by the retaining web 40. The retaining webs 40 serve to statically stabilize the relatively thin separating wall 41 between the two flow channels 31, 33.

Significant melt pressures of up to about 450bar occur in the nozzle arrangement 22. Especially at start-up and shut-down of the extrusion line, the following can occur: one extruder conveys material and the other does not. That is to say that already a significant melt pressure (Massedruck) is about to occur in the flow channel and in the flow channel beside it is almost zero. A large pressure difference of 100bar and more on both sides of the partition wall 41 places higher demands on the mechanical stability of the nozzle arrangement 22. In the present case, the bending of the partition wall 41 is prevented by the two retaining webs 40. The force is directed into the core region of the nozzle arrangement 22, for which purpose corresponding retaining webs are provided in the further, internally located flow channels. In any case, the stability towards the outer face 42 of the nozzle is sufficient, since the distance of the flow channels from the outer face is always greater than 30 mm.

The course of the flow and transport channels 31, 32, 33, 34, 35 is described in each case for the two-layer construction of the coextruded outer wall 5. It is clear that this principle run of flow channels can be applied even in coextruded walls of three or more layers.

Fig. 9 shows a front view of the nozzle inlet plate 24 against the extrusion direction E for the case "new material from the coextrusion device 21" as described above. Shown in fig. 6: the coextrusion device 21 is fed laterally into the nozzle device 22. The circular feed channel 42 extends horizontally in the nozzle inlet plate 24 and is slightly inclined with respect to its end face. Three conveying channels 44 sink into the end face of the nozzle device 22, said conveying channels 44 feeding the flow channel 31 for new material of the outer layer and of some small profile sections. The new material from the coextrusion device 21 flows first through the feed channel 42, then through the delivery channel 44 and finally into the flow channel 31, which is not shown in fig. 9. These flow channels 31 project perpendicularly from the plane of the drawing.

The core material flows from the main extruder 20 through the conveying channel 43 and is deformed by the obliquely running wall into an L-shaped cross section of the conveying channel 45. The core tip extends into the L-shaped section. The flow channels 33, 34 for the core material again project from the drawing plane and connect without shoulders to the outer contour 45 and to the contour of the core tip, as can be seen clearly in fig. 9.

Fig. 10 shows a front view of the nozzle inlet plate 24 against the extrusion direction E for the case of core material from the coextrusion device 21. In this case too, the coextrusion device 21 is fed laterally into the nozzle device 22, but in this case the core material is fed.

The circular feed channel 42 again runs in the nozzle inlet plate 24 first horizontally and slightly obliquely to its end face. The feed channel 44, which connects the flow channels 33, 34 for the inner layers and the core region of the profile 1, dips into the end face of the nozzle device 22.

It should be noted that the contour 1 is arranged in a mirror-inverted manner about the vertical plane, i.e. the abrupt change of the frame contour is on the right side of the view. The core material from the coextrusion device 21 flows first through the feed channel 42, then through the transport channel 44 and finally into the flow channels 33, 34 for the inner layers, inner walls and some small profile sections of the coextrusion zone, which are not shown in fig. 9. These flow channels 33, 34 project perpendicularly from the plane of the drawing and are "blunt" loaded here.

The new material from the main extruder 20 is divided into three conveying channels 45 in one or two further nozzle plates, which are connected on the inflow side to the nozzle inlet plate 24 shown and are not shown here, starting from a circular feed channel. That is to say, the core material flows first in a circular feed channel in the extrusion direction E, is divided in two or three nozzle plates in conically tapering channels onto three approximately rectangular transport channels 45, and then flows in the flow channel 31 approximately in the extrusion direction E through the shaping section 38 of the nozzle device.

In fig. 11 and 12, the pressure relationship in the convergence portion of the flow channels 31, 33 is shown in a three-dimensional view. This view supplements the view in fig. 7, wherein reference can be made to the corresponding description.

The view from the front shows the end side 25 of the nozzle. The extrusion direction E is depicted.

Here, the flow channels 31, 33 are shown on the right side of the nozzle. The convergence is carried out at an angle of 5 ° to 50 °, in particular at an angle in the range of 10 ° to 25 °.

The area of the convergence 36 of the flow channels 31, 32 is shown enlarged in fig. 12 and highlighted by a border. The axial distance of the converging portion 36 of the flow channels 31, 32 from the outlet of the profile is less than 12% of the axial length of the nozzle device 22.

In the region of the convergence 36, the pressure is approximately 65 bar. If the convergence 36 is realized slightly axially behind, the pressure is approximately 175 bar.

Fig. 13 shows a sectional view through the profile, wherein the at least one first flow channel for the first thermoplastic material is not divided on the flat visible face, except at the profile corners (see highlighted section).

Fig. 14 shows a sectional view through extrusion 1, in which layers 6, 7 can be clearly seen. The layer 7 consisting of the core material is darker than the layer 6 made of the new material.

List of reference numerals

1 section bar

2 outer wall consisting of a high-quality preparation, also called new material

3 outer wall consisting of inexpensive formulation, also called core material

4 inner wall of core material

6 outer layer of a new material

7 inner layer of core material

8 visible surface of the inside

9 external visible surface

10 bead

11 shadow seam

12 cavity

20 Main extruder

21 Coextrusion device

22 nozzle device

23 nozzle plate

24 nozzle inlet plate

25 end side of nozzle device (outlet profile)

31 first flow channel for new material (outer layer)

32 conveying channel for new material

33 second flow channel for core material (inner layer)

34 flow channel for core material (inner wall)

35 feed channel for core material

36 convergence of the outer and inner layers

37 common flow path for new material and core material

38 nozzle forming section

39 inlet area of nozzle

40 retaining web

41 partition wall between two flow channels

42 opening of a circular feed channel of a coextrusion device

43 round feed channel opening of the main extruder

44 feed channel for the flow channel 31

45 feed channel for the flow channels 33 and 34

E direction of extrusion

L length expansion

Wall thickness expansion of W