Spiral distributor, blowing head, blown film plant, method for producing a blown film

Abstract

Helical distributor (1, 30, 40) for a blowing head of a film extrusion plant, with a central axis (4, 37) which runs in the blowing direction, and with an extrusion direction which is parallel to the central axis (4, 37) in the case of an axial helical distributor, radial in the case of a radial helical distributor (30) and projectable onto the axis in the case of a conical helical distributor, a. where pre-distribution channels all around lead into the beginnings of spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207), b. wherein the helical channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) run at an angle to the extrusion direction, such that c. a first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) begins at a start, after an initial section (15, 56, 57, 58, 221, 236) passes a second, directly adjacent spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) downstream at its start and continues in a further section downstream of its initial section (15, 56, 57, 58, 221, 236) and its further section, d. so that, during operation of the blow head, melt exiting from the second helical channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) beyond a sealing end edge (214, 220, 235) that seals against overflow, can flow over the downstream further section of the first helical channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) in the extrusion direction during the first helical channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207), beyond a sealing end edge (214, 220, 235) that seals against overflow, can flow over the downstream further section of the first helical channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207), e. so that at the spiral distributor (1, 30, 40) i. an initial zone is formed in which initial sections (15, 56, 57, 58, 221, 236) of the helical channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) are located, which have a sealing gusset zone (13, 108, 217) upstream in the extrusion direction and are therefore not yet open to flow from other helical channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) located upstream in the extrusion direction, but melt can flow to downstream helical channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) are to be submitted, and subsequently ii. an overflow zone (218, 219) in which only overflowed further sections of the helical channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) are located, characterized in that iii. the first spiral canal (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) 1. has a course with a circular cross-section in the initial zone and 2. exhibits a development in its course with respect to the circular cross-section - for example, an unsteady development - whereby the first helical channel deviates from a circular cross-section later in the course in the initial zone and / or in the overflow zone.

Description

[0001] The invention relates to a spiral distributor for a blow head of a film extrusion line, a blow head for such a blown film line, a blown film line and a method for producing a blown film.

[0002] The die head is the extrusion tool and thus the technological core of a blown film extrusion line, also known as a blown film line. Regardless of its specific design, the die head's function is to shape the melt. The melt reaches the die head from one or more melt strands at the die inlet and should exit the die head with a uniform, thermally and mechanically homogeneous melt distribution across the annular gap-shaped exit cross-section downstream at the die outlet.

[0003] The designs of blow heads commonly used today can be roughly divided into two groups: on the one hand, the group of spiral distributors in cylindrical or conical form, and on the other hand, the group of radial spiral distributors, which are also called spiral distributors.

[0004] DE 103 60 360 A1 shows a blowing head for a nine-layer film.

[0005] The book "Extrusion Tools for Plastics and Rubber: Types, Design, and Calculation Options / Walter Michaeli, with the collaboration of Ulrich Dombrowski ..., second, completely revised, and expanded edition; Munich, Vienna; Hanser-Verlag 1991, ISBN 3-446-15637-2" shows various spiral distributor tools, particularly starting on page 159. On page 160, lines 4f, the book describes that the complete avoidance of weld lines and flow marks is one of the main advantages of a melt distributor system.

[0006] DE 199 24 540 C1 discloses an axial spiral distributor with a cylindrical spiral carrier and a surrounding smooth counter body.

[0007] Another axial spiral distributor can be found in WO 88 / 01226 A1, where the spiral carrier is also cylindrical and surrounded by a smooth counter body.

[0008] US Pat. No. 6,866,498 B2 shows a conical spiral distributor in which outlets from a pre-distributor initially lead into pivoted supply grooves. Each supply groove has an end region where it closes. The melt is thereby forced into a spiral channel beginning downstream. The spiral channels on the spiral carrier run linearly in the developed configuration. The counter body is smooth.

[0009] What all die heads have in common is that the melt stream delivered by the extruder is first divided into several individual streams. The individual streams are brought together as seamlessly as possible by means of a spiral distributor. Star- and ring-shaped distributor systems are predominantly used for this purpose. These so-called pre-distributors open into the spiral channels, which are incorporated into a spiral carrier. In the case of an axial, i.e. cylindrical or conical, spiral distributor, a spiral carrier is a central and / or surrounding body. In the case of a radial spiral distributor, the spiral carrier has the shape of one or two plates. The spiral channels encircle the spiral carrier in the form of a multiple thread or are arranged on the plate in the form of a multiple spiral.

[0010] Blow heads for multi-layer film tubes have several spiral distributors.

[0011] There may also be coils in the counter body, in which case the coils in the counter body are directed towards the coil carrier, so that two coil carriers together form the coil distributor.

[0012] In general, the channel depth of each spiral channel decreases to zero in the extrusion direction. The gap between the spiral carrier and the counter-body increases correspondingly. This causes a melt stream flowing in a spiral channel to continuously divide into two parts: one part that flows over the overflow bars between two spiral channels; the other part that follows the course of the spiral channels. As the extrusion direction progresses, the proportion of overflow increases relative to the channel flow.

[0013] By superimposing the overflow with the channel flows, so-called “weld lines” are avoided and, in addition to the desired mechanical homogeneity, a high thermal homogeneity of the melt is achieved.

[0014] US 3,809,515 A discloses radial spiral distributors with three different geometries: In a first embodiment, the spiral channels on the plate-shaped spiral carrier are each opposite a spiral channel in the plate-shaped counter-body. This results in a round cross-section over the length of the spiral distributor, whereby a round cross-section in a broader sense also includes the lens shape formed by the opposing, flattening spiral channels. In a second embodiment, the two spiral channels beginning opposite each other are to have a different pitch, so that the overlap shifts immediately from the beginning of the spiral channels. The development of the channel cross-section over the channel length is constant, so that with a radial section (cf. Fig. 10 of US Pat. No. 3,809,515 A) the offset between the upper and lower partial cross-sections increases evenly from ring to ring. A third embodiment discloses double spiral channels on a spiral carrier with a smooth counter-body.

[0015] EP 1 426 163 A2 discloses different shapes and arrangements for the spiral channel in the mandrel-shaped spiral carrier opposite spirals in the counter body.

[0016] The invention is based on the object of providing an improved spiral distributor.

[0017] According to a first aspect of the present invention, this object is achieved by a spiral distributor for a blow head of a film extrusion line, having a central axis which runs in the blowing direction and having an extrusion direction which is parallel to the central axis in the case of an axial spiral distributor, radial in the case of a radial spiral distributor and projectable onto the axis in the case of a conical spiral distributor, wherein pre-distribution channels all around open into the beginnings of spiral channels, wherein the spiral channels run at an angle to the extrusion direction, so that a first spiral channel begins at a beginning, after an initial section passes a second, directly adjacent spiral channel downstream at its beginning and continues in its further section downstream of its initial section and its further section,so that in the course of the first spiral channel beyond a sealing end edge sealing against overflow during operation of the die head, melt emerging from the second spiral channel can flow over the further downstream section of the first spiral channel in the extrusion direction, so that at the spiral distributor, • an initial zone is formed in which initial sections of the spiral channels are located, which - in the extrusion direction - have a sealing interstices zone upstream and therefore cannot yet be overflown by other spiral channels upstream in the extrusion direction, but are themselves intended to deliver melt by way of overflow to downstream spiral channels, and subsequently • an overflow zone is created in which only further overflowing sections of the spiral channels are located, The spiral distributor is characterized in that the first spiral channel • has a course with a circular cross-section in the initial zone and • has an unsteady development over its course with regard to the circular cross-section, so that the first spiral channel deviates from a circular cross-section later in the course in the initial zone and / or in the overflow zone.

[0018] The invention is based on the following finding:

[0019] Despite numerous efforts, the state of the art has so far failed to achieve clean melt flow from the initial section of the spiral channels, especially when changing the melt, where, for example, the color or even just the melt composition may be altered. This is because spiral channels typically have a cross-section that is not ideal for flow. For example, the relatively common D-shaped cross-section of spiral channels, according to the inventor's findings, creates a dead zone in the flow, which requires considerable flushing effort if a different melt is to be processed.

[0020] When considering the “cross-sectional shape”, the cross-section perpendicular to the direction of travel along a spiral channel is generally considered.

[0021] A D-shaped cross-section is most commonly found when the counter body is smooth and a channel is provided in the surface on the side of the spiral carrier, with a cross-section with a chord and a curved line, namely with the chord as the open end of the spiral channel directed towards the counter body and with some kind of curved line, which at both of its points of impact on the chord each has a maximum of 90° to the chord.

[0022] With regard to the dead zone in the flow, the point of impact of the curved line on the chord that is located upstream is particularly relevant.

[0023] In addition, depending on the direction of the spiral channels, imperfect results often occur in their initial area:

[0024] A well-known problem with existing blow heads with an axial spiral distributor is that the spiral carrier, beyond the beginning of the spiral channel, is tightly fitted into a cylindrical bore of the usually smooth outer counter body. This creates an annular gap-shaped channel with the counter body for the melt escaping from the spiral channels and thus overflowing the adjacent spiral channels in their further sections.

[0025] The area of ​​the spiral distributor where the pre-distributor channels are routed to the beginning of the spiral distributor's spiral channels is often referred to as the "gusset area" or "gusset zone." In this gusset area, the pre-distributor channels are designed as closed channels due to the tight fit between the spiral carrier and the counter body.

[0026] The gusset zone usually runs with a zigzag contour around the spiral carrier and is usually geometrically defined by two edges of the sealing fit. These are explained below, using the example of an axial spiral distributor for ease of description:

[0027] First, there is a predominantly horizontally extending, longer edge between the spiral channel and the mostly smooth outer circumferential surface of the spiral carrier, specifically along the upstream edge of the spiral channel. This edge, as the edge of the spiral channel, runs approximately from its beginning to approximately the beginning of the overlap with the adjacent spiral channel, viewed in the direction of rotation of the spiral channel. In the wording of the present application, this edge thus extends over the "initial section" of the spiral channel.

[0028] The horizontally running edge forms a corner with the mostly smooth outer circumference of the spiral support in cross-section—cut perpendicular to the direction of the spiral channel. In this corner, wall shear stresses are significantly lower than in the rounded areas of the spiral channel cross-section. As a result, the melt has a comparatively long residence time in this area.

[0029] On the other hand, there is a predominantly vertical edge that extends axially in the area of ​​the beginning of the overlap between the first and second spiral channel, which, viewed in the direction of rotation of the first spiral channel, is located immediately adjacent to the first spiral channel. In the above-mentioned wording, the beginning of the overlap is the "transition section" of the first spiral channel, i.e., the area where the initial section of the first spiral channel transitions into the further section of the first spiral channel.

[0030] The vertical edge forms the boundary of the flow channel at the beginning of the overflow web between the two aforementioned spirals. The volume flow flowing over this web between the two spirals in the area of ​​the vertical edge is low and is further slowed by the vertical edge itself. In other words, similar to the horizontal edge, the wall shear stresses in the area of ​​the vertical edge are significantly lower than in the other areas of the overflow web between the spiral channels. Therefore, comparatively long melt residence times also occur in this area.

[0031] The problem described above is exacerbated by the fact that, as the extrusion die heats up, the outer counter-body expands more than the central coil carrier due to its larger diameter, creating an increasingly large gap between the two, into which the plastic melt can flow, where a seal should be present, at least when cold. Due to the long residence time of the melt in this area, it can thermally degrade. Deposited particles are then occasionally swept along by the flowing melt and lead to defects in the melt. For similar reasons, color changes can adversely affect the film by producing streaks.

[0032] In radial spiral distributors, the two edges mentioned above are found in the radial direction and in the circumferential direction of the spiral carrier plate.

[0033] In summary, the state-of-the-art geometric design of the gusset area, particularly the geometry of the two edges, leads to significantly longer residence times due to the melt's adhesion to the wall, resulting in an inhomogeneous film structure. The corresponding defects are often referred to as "spiral stripes."

[0034] The long residence times also mean, among other things, a comparatively long rinsing time when the recipe changes, especially when the color changes.

[0035] There are therefore two problems in the initial sections that can lead to streaking in the film, whereby the invention proposed here focuses more on the problem of long rinsing times.

[0036] The invention proposed here generally solves the problem of the initial sections by providing the spiral channels with a circular cross-section in the initial zone, i.e. in the section in which the spiral channels are not overflowed by upstream sections of other spiral channels.

[0037] During prototype tests by the inventor, it was found that even in the otherwise problematic initial section of a spiral duct, a significantly improved, more uniform flow occurs than in the otherwise usual cross-sectional profiles, especially than in the otherwise widespread D-shaped cross-sectional profile.

[0038] The highlight of the invention is that the round cross-section is used specifically in the problematic area.

[0039] In this regard, it should be explained that the “cross-section” is to be understood as the area which appears in a section perpendicular to the axis of the spiral channel.

[0040] In a very typical design for an axial spiral distributor with an internal spiral carrier and a counter body surrounding it on the outside, the spiral channel has a D-shaped cross-section in which the straight side of the cross-sectional shape—that is, the chord spanning the open surface of the spiral channel, which essentially continues the smooth surface of the spiral carrier—is directed toward the counter body, usually lying essentially parallel to it, while the rounded side of the turning channel cross-section runs within the body of the spiral carrier. Looking at the surface of the cylindrical spiral carrier, one sees an open spiral channel with a rounded profile and with its widest point precisely in the imaginary, continued course of the cylindrical surface of the spiral carrier.The transition between the spiral channel and the surface of the spiral carrier is sharp-edged both upstream and downstream – in each case relative to the extrusion direction. The curved line created by the spiral channel in its cross-section meets the chord at approximately a right angle in a D-shape, and at an acute angle in a C-shape or lens-shape.

[0041] The present invention understands the term “round cross-section” to mean that the upstream bottom course of the spiral channel is rounded.

[0042] This can be done in two different ways:

[0043] Firstly, which is the preferred embodiment of the invention, the spiral channel cross-section can continue outside the spiral carrier, especially in the counter body. The inventor's prototype tests have shown that arranging the channel edge of the spiral channel facing upstream of the extrusion direction and a counterpart in the counter body offers considerable advantages. In such a design, at least one channel edge of the spiral channel on the spiral carrier side and the spiral channel located in the counter body face each other.

[0044] On the other hand, the spiral channel can have a curved line which, when it hits the tendon, forms an obtuse angle with the tendon, i.e. an angle greater than 90°, preferably over 120° or 135°, but less than 180°.

[0045] Depending on the structural design, the curved line can continue over an intermediate part or run in a one-piece spiral carrier.

[0046] The following terminology is further explained regarding the invention presented:

[0047] The "blowing direction" should be the direction in which a system would blow out the film in tube form when using a spiral distributor. Normally, this will be perpendicular to the plane of the annular gap. Generally, it will be vertical; in modern systems, it will be vertically upward, because the blowing and removal now occur against gravity.

[0048] In the case of an axial spiral distributor, particularly in the form of a cylindrical spiral distributor or in the form of a conical spiral distributor, the central axis, which runs in the blowing direction, even gives the distributor its name.

[0049] In a radial spiral distributor, however, the plate is positioned horizontally. The melt flow flows either from the outside to the inside or from the inside to the outside, but is always redirected for blowing out. The blowing direction is therefore also vertical, perpendicular to the plate of the radial spiral distributor.

[0050] The "extrusion direction" is a fictitious direction. Whether every single particle in the flowing melt will actually flow exactly in the extrusion direction is more than questionable. Therefore, the extrusion direction should be understood here as a purely geometric, theoretical direction. The extrusion direction refers to the intended main direction within the spiral distributor. It is often also referred to as the distributor flow direction. The actual overflow in the annular gap does not exactly follow the theoretical extrusion direction.

[0051] In the case of a cylindrical spiral distributor, the extrusion direction is understood to be parallel to the blowing direction, since the melt flow can theoretically flow along straight lines on the outer surface of the cylinder in the blowing direction.

[0052] In the case of a conical spiral distributor, the global extrusion direction is also parallel to the blowing direction. This is because the inclinations of the individual theoretical melt flows over the circumference of a conical spiral distributor add up to form a straight line coaxial with the central axis.

[0053] However, in the conical spiral distributor, the theoretically shortest path for flow along the surface of the truncated cone is now at an angle to the central axis. The set of these straight lines, which extend diagonally upwards along the shortest path to the central axis, along the surface of the truncated cone are to be understood as the local extrusion direction.

[0054] The extrusion direction is to be understood as a virtual flow direction. It is defined here only to describe the angular deflection of the melt channels, uniformly for axial and radial spiral distributors.

[0055] In the case of a radial spiral distributor, the “extrusion direction” is understood to be the set of radially running straight lines.

[0056] The "intersection zone" is the area on the spiral distributor where outlets for the melt streams are located. The melt is divided into many small streams through the pre-distributor outlets, i.e., the pre-distributor orifices, and reaches the actual spiral section. Within the intersection zone, no overflow of melt in the extrusion direction out of the spiral channels is planned. Rather, the intersection zone seals against overflow.

[0057] In this context, it should be noted that "sealing" in this sense does not necessarily require complete tightness. Rather, a slight overflow can already occur there, which in practice can occur with axial spiral distributors, for example, simply because the outer counter body expands more than the inner spiral carrier when the temperature rises. Based on the sealing end edge on the spiral carrier surface described above, a person skilled in the art can easily differentiate which zones are intended for sealing and which zones for overflow.

[0058] The "beginning" of the spiral channels is primarily understood to be the point from which the spiral channel runs at least substantially in its direction of travel in the further section and / or in the initial section. In the prior art, the latter two directions are identical. In this embodiment, a difference between these two directions can be observed.

[0059] In an extended definition, the “beginning” of a spiral duct can also be understood as the point in the duct course from which the distribution duct no longer feeds several spiral ducts, but only one spiral duct.

[0060] The "angle" described several times is an angle between 0° and 90°, i.e., an acute angle. In other words, this means that in an axial spiral distributor, the spiral channel in a shell development would exhibit such an angle relative to the central axis and the extrusion direction. In a radial spiral distributor, the angle is measured locally relative to a radial jet.

[0061] “Downstream” refers to a point that is further in the direction of extrusion than an upstream point.

[0062] As a result, the design of the spiral distributor has been modified, which has a positive impact on both the system and the quality of the produced film. The spiral distributor presented here can be produced very cost-effectively. The bottom line is a previously unattained ratio of low technical complexity of the film extrusion system to high film quality.

[0063] The invention differs from EP 1 426 163 A2 in that, in its first embodiment, this document – ​​by chance while pursuing a different goal – arranges D-shaped spiral channels in the outer counter body of an axial spiral distributor over the entire height of the spiral distributor, i.e., both in the initial zone and without any changes in the overflow zone. While this achieves a circular cross-section for the spiral channels in the initial zone, it is considerably more complex and costly to manufacture than the invention presented here. It evidently failed to recognize the technical effect.

[0064] The situation is similar with US 3 809 515 A: There, the spiral channels run in the spiral carrier of the radial spiral distributor shown in a first embodiment (shown in the Fig. 1 to 5) also extends over both the initial zone and the overflow zone. This also results in considerable manufacturing effort and associated costs. Because the spirals are usually milled with high precision into the solid material. The fact that the channel geometry is practically irrelevant beyond the initial area has only been revealed by this invention.

[0065] In a second embodiment (shown in the Fig. 6 to 10) of US Pat. No. 3,809,515 A, however, disclose spiral channels in the counter body with a different course than the spiral channels in the spiral carrier. Thus, the document does not teach a spiral channel "course with a circular cross-section," but only a singular point with a circular cross-section at the very beginning of the spiral channels.

[0066] Furthermore, it's not even clear whether this point lies within the initial section—rather, it appears to be located at the beginning of the spiral channels, but before the beginning of the initial sections. Thus, in US Pat. No. 3,809,515 A, this point with a circular cross-section is apparently not present at the critical location downstream of the seal's end edge.

[0067] Optional advantageous embodiments of the present invention are described below:

[0068] In a preferred embodiment, the circular cross-section ends earlier than the first spiral channel, particularly in a tapered manner. The first spiral channel has a specific length from the point where it passes the seal's end edge, namely the sum of an initial section plus its subsequent section. The purpose of the possible design feature presented here is that the spiral channel loses its circular cross-section before the end of the subsequent section.

[0069] The circular cross-section can be transformed into another cross-section, particularly in a smooth or stepped transition, for example, the conventionally known and most commonly used D-shaped cross-section. The earlier the circular cross-section ends before the end of the first spiral channel, the more cost-effectively the spiral distributor can be produced.

[0070] One embodiment provides that after the spiral channel enters the overflow zone, i.e., after passing the sealing end edge to the adjacent spiral channel, a spiral is terminated in the counter body, i.e., either ending gradually or tapering off smoothly, so that the cross-section of the spiral channel is reduced to the cross-section in the spiral carrier, whereas in the initial section, the cross-section was added from the channel profile in the spiral carrier on the one hand and the channel profile in the counter body on the other. In such a case, the conventional D-shape of the spiral channel can be retained unchanged in the spiral carrier, for example in the mandrel in the case of an axial spiral distributor or conical spiral distributor, while only the counter body is designed to have milled spirals along the course of the initial zone, which taper off or suddenly end in the overflow zone. This even offers a cost-effective retrofitting of existing die heads.

[0071] By a circular cross-section "over the course of the initial zone", the present invention means that a significant part, preferably the predominant part, of the initial section of the spiral distributor should be shaped in such a way, in particular at least three-quarters of the course, especially the entire course; and / or should already be designed in this way directly at the beginning of the initial section.

[0072] According to a second aspect of the present invention, the stated object is achieved by a spiral distributor for a blow head of a film extrusion line, having a central axis which runs in the blowing direction and having an extrusion direction which is parallel to the central axis in the case of an axial spiral distributor, radial in the case of a radial spiral distributor and projectable onto the axis in the case of a conical spiral distributor, wherein pre-distribution channels all around open into the beginnings of spiral channels, wherein the spiral channels run at an angle to the extrusion direction, so that a first spiral channel begins at a beginning, after an initial section passes a second, directly adjacent spiral channel downstream at its beginning and continues in a further section downstream of its initial section and its further section,so that in the course of the first spiral channel beyond a sealing end edge sealing against overflow during operation of the die head, melt emerging from the second spiral channel can overflow the further downstream section of the first spiral channel in the extrusion direction, so that an initial zone is formed on the spiral distributor, in which initial sections of the spiral channels are located, which have a sealing interstices zone upstream in the extrusion direction and are therefore not yet overflowable by other spiral channels located upstream in the extrusion direction, but are themselves intended to deliver melt by way of overflow to downstream spiral channels, and thereafter an overflow zone is formed, in which only further sections of the spiral channels over which are overflowed are located, wherein the spiral distributor is characterized in that on a counter body which is opposite the two spiral channels,in the initial zone, a counter-body spiral channel is formed, which ends, in particular runs out, upstream of the first spiral channel in the extrusion direction.

[0073] The variant with the coils in the counter body, whereby the coil carrier is preferably designed as a mandrel, has already been explained above.

[0074] The inventor's prototype tests have shown that when implementing the second aspect of the invention, the first aspect does not even have to be implemented at the same time in order to achieve an advantage.

[0075] It goes without saying that a particularly great advantage is achieved when both aspects are realized simultaneously.

[0076] In a preferred embodiment, the counter-body spiral channel runs opposite the first spiral channel in the counter-body. This is particularly the case if the counter-body spiral channel is opposite the spiral channel over its entire length. Projecting the counter-body spiral channel onto the spiral channel thus results in at least a slight overlap, preferably the same overlap throughout, or even congruence.

[0077] Preferably, the counter-body spiral channel forms a round cross-section with the first spiral channel, especially a circular cross-section. The circular cross-section has proven to be a very good cross-sectional shape in the inventor's experiments. A circular cross-section is understood in particular to mean that the cross-section at the upstream inlet, i.e., at the transition edge from the spiral channel profile to the spiral carrier surface, results in an approximately or even precisely circular shape, whether in the precise arrangement of the two profiles relative to one another or deviating from the ideal circular shape by an offset in the width of the slot remaining between them, which leads to the annular slot nozzle.

[0078] It is proposed that a circular cross-section is composed of two partially circular partial cross-sections, wherein the two partial cross-sections can in particular consist of two semicircular partial cross-sections and can be provided on the one hand by the part of the spiral channel on the spiral carrier side, and on the other hand by the part of the spiral channel formed by the counter body.

[0079] The first spiral channel can already have a circular cross-section at its beginning.

[0080] It has already been explained that the first spiral channel preferably has a round cross-section at the beginning of its initial section, i.e. at least downstream of the edge which ends the sealing interstices area.

[0081] In one embodiment, the first spiral channel has a circular cross-section over the entire initial section.

[0082] At the beginning, or at least at the beginning, of the overflow zone, the circular cross-section can end, particularly where it runs out. There, the complex geometry of the circular cross-section is no longer required to the same extent for the achievable film quality as in the initial section—that is, in the initial zone, viewed on a die head scale.

[0083] In a preferred embodiment, two spiral channels, but preferably all spiral channels, are each formed as described above in the initial zone, i.e. they have an opposite, associated spiral and / or have a round cross-section.

[0084] Generally, it should be noted at this point that, in the context of this application, the indefinite numerical term "a" is not intended to be understood as a limiting term, in the sense of "exactly one." Rather, any numerical specification always means that this number is to be understood as a minimum, unless it is clear from the respective context that "exactly" the specified numerical specification is intended to be present.

[0085] As already explained above, it is proposed that the spiral duct adopt a D-shaped cross-section in the overflow zone. Such a duct profile is easy to manufacture and has proven itself in numerous commercial applications.

[0086] In addition to the design of the initial zone as described above, it is proposed that the spiral distributor have an overflow promoter for the melt at the beginning, in the initial section, and / or in a transition section of a spiral channel, so that during operation, melt exiting from the second spiral channel at a die head flows over an overflow web in the distributor flow direction to the downstream first spiral channel. Such a design can be found in DE 10 2010 023 203 A.

[0087] A "overflow promoter" is understood to mean any means that is more localized, i.e., not uniformly distributed over the entire length of the spiral channel, that leads to an increase in the flow velocity of the melt in the critical areas, i.e., in particular, an increase in overflow. In particular, measures that reduce the flow resistance for the overflow path or that increase the flow resistance for the channel flow are conceivable.

[0088] It should therefore be expressly understood that this term does not apply if a helix exhibits a continuous flattening along its entire length, as is known in the prior art. Although such a helix also has a smaller channel depth in the transition area than in the initial section, given the length of the helix channel and the relatively short length of the initial section, a uniform flattening cannot be considered an "acceleration measure in or at" the initial section.

[0089] In an advantageous embodiment of the invention, a spiral channel has a bend, a curve, or a pivot in its transition section. With a suitable design, this can lead to a better flushing of an otherwise poorly flushed vertical edge. With a suitable design, it can also be achieved that a greater amount of melt exits the spiral channel and flows downstream over the overflow web.

[0090] Particular attention should be paid to kinks, curves, or deflections, where, for example, the further section of the spiral duct is only slightly deflected relative to the initial section. Initial considerations suggest that angles of even less than 45°, especially less than 30°, relative to the distribution flow direction could easily occur here.

[0091] The advantages described above for a spiral distributor also apply analogously to a blow head for a blown film line which is equipped with a spiral distributor as described above.

[0092] The advantages also apply to a blown film line with an extruder, a blowing head as described above, a flattening device and a take-off device, and preferably with a winding station.

[0093] Finally, the advantages extend to a method for producing a blown film using such a blown film line.

[0094] The invention will be explained in more detail below using exemplary embodiments with reference to the drawings, in which Fig. 1 in a spatial, partially sectioned schematic view of a cylindrical axial spiral distributor according to the prior art, Fig. 2 schematically shows in a radial section one half of a spiral distributor according to the prior art, in which melt is fed radially outward into spiral channels, Fig. 3 a processing according to the state of the art, Fig. 4 schematically shows, in a section perpendicular to a spiral channel course, a first embodiment of its circular cross-section, wherein the spiral channel is composed of a part running in a spiral carrier and a spiral in a counter body over the entire length of an initial zone, Fig. 5 schematically shows a second embodiment of a circular cross-section in a section perpendicular to a spiral channel, Fig. 6 schematically shows a third embodiment of a circular cross-section in a section perpendicular to a spiral channel, Fig. 7 schematically in a section perpendicular to a spiral channel course, in an analogous representation to the Fig. 5 and Fig. 6, three examples of D-shaped cross-sections from the state of the art, Fig. 8 schematically shows possible “beginnings” of spiral distributors in a development of initial sections and further sections as well as Fig. 9 schematically shows in a detail of another development of initial sections and further sections different courses of circular cross-sections.

[0095] The spiral distributor 1 in Fig. 1 is constructed according to the state of the art. It essentially consists of a central spiral carrier 2 designed as a mandrel, which is surrounded by a jacket-shaped counter-body 3. The melt stream delivered by an extruder (not shown) is first divided into several individual streams in a pre-distributor (concealed by an outer surface not shown in section), which flow into spiral-shaped channels. These channels are incorporated into the spiral carrier 2 and encircle it in the form of a multiple thread.

[0096] A central axis 4 is coaxial with an annular outlet nozzle 5 at a downstream end 6 of the spiral distributor 1.

[0097] In a distribution flow direction 7, thus parallel to the local extrusion directions, a channel depth of spiral channels 8, 9 (exemplarily marked) decreases to zero at a channel end 10 (exemplarily marked).

[0098] At the same time, an annular gap 11 between the spiral carrier 2 and the counter-body 3 continuously increases. This causes a melt stream flowing in a spiral channel to continuously divide into two parts: one part that flows over the overflow ribs 12 located between the spiral channels (marked as an example), and the other part that follows the course of the spiral channels 8, 9. As the flow progresses along the spiral channels 8, 9, the flow along the extrusion direction, i.e., the overflow over the overflow ribs, increases.

[0099] The melt leaves the extrusion tool at the outlet nozzle 5 as homogeneously as possible.

[0100] In a gusset area 13 (largely hidden by the surface 21), which seals with its surface against the counter body 3, the spiral channels 8, 9 run from beginnings 14 (exemplarily marked, hidden by the surface 21) via initial sections 15 (exemplarily marked, shown there in full) to transition sections 16 (exemplarily marked) and continuously further in further sections 17 (exemplarily marked).

[0101] In the gusset area 13, there are several areas with rather horizontally running lower edges 18 and vertical edges 19, 20 (marked as examples), which form sealing end edges, in which adhesion of melt is to be feared.

[0102] The radial spiral distributor 30 in Fig. 2, which is also constructed according to the state of the art, essentially consists of a plate 31 as a spiral carrier, into which spiral channels 32 (marked as examples) are introduced, and a counter-plate 33, which is also horizontal, as a counter-body.

[0103] With regard to the risk of flow dead zones in the radial spiral distributor, the horizontal edges 18 and the vertical edges 19, 20 correspond to the circumference of the distributor 30 following edges (not shown) or radial edges (not shown) downstream and with a tangential offset from each spiral channel start (not shown).

[0104] In the radial spiral distributor 30, the plastic melt is guided during operation from pre-distribution channels 34 into the beginnings 35 of the spiral channels 32. In an extrusion direction 36, which is radial toward a central axis 37, while the central axis 37 is parallel to a blowing direction 38, the channel depth of the spiral channels 32 decreases, with an overflow gap 39 becoming larger along the extrusion direction 36.

[0105] When developing sections of the spiral distributor 40 in Fig. 3, which is an embodiment of the invention, the geometry of the spiral channels 41, 42, 43, 44, 45 was modified:

[0106] Starting from a pre-distributor (not shown), outlets 46, 47, 48 are located on the cylindrical axial spiral distributor 40. These open into feed sections 49, 50, 51, with two feed sections 50, 51 being curved towards each other in pairs so that pre-distributor channels arranged in the spiral distributor 40 can be guided more compactly.

[0107] The outlet sections 49, 50, and 51 are very short and extend only until the spiral channels 41, 42, 43, 44, and 45 have the same geometry. There, at the beginnings 52, 53, and 54, there is a first deflection, namely by just under 90°. The angle can be, for example, approximately 85°.

[0108] At this angle to an extrusion direction 55, the spiral channels 41, 42, 43, 44, 45 initially run straight along their initial sections 56, 57, 58 until they are located downstream, i.e., further advanced projected onto the distributor flow direction 55, from the initial sections 52, 53, 54 of immediately adjacent spiral channels 42, 43, 44, 45. There, they have double deflections 59, 60, 61, which, however, do not lead to a parallel continuation of the spiral channels 41, 42, 43, 44, 45, but rather transition with a slight deflection towards a greater gradient in further sections 62, 63, 64, 65. In the further sections 62, 63, 64, 65, the gradient, i.e. the complementary angle to the distribution flow direction 55 up to 90°, remains the same in the further sections 62, 63, 64, 65, so the spiral channels 41, 42, 43, 44, 45 are again straight there.

[0109] Thus, all distribution channels 41, 42, 43, 44, 45 immediately after crossing critical vertical edges 66, 67, 68 - where their initial sections 56, 57, 58 begin - initially run briefly with a steep gradient and then have a greater constant gradient than the initial section 56, 57, 58.

[0110] This results in a higher gradient even after the transition sections with the double deflections 59, 60, and 61. This gradient has a positive effect on the distribution of the melt and also leads to a higher volume flow at the edges 66, 67, and 68, thus reducing spiral stripes.

[0111] In addition, the vertical edges 66, 67, 68 are significantly shorter than in the prior art due to the initially flat gradient in the initial section 56, 57, 58.

[0112] The comparatively short vertical edges 66, 67, 68 define the beginning of overflow ribs 69 (marked as examples). These are initially very short in the overflow direction, which is parallel to the extrusion direction 55. Thus, a large volume flow of melt can occur here.

[0113] As a result of the subsequently increased pitch of the respective downstream spiral, the overflow web 69 is larger at the next overlap with the next beginning spiral channel and assumes a constant width 70 (marked as an example). This is advantageous for good melt distribution.

[0114] In a preferred embodiment, the spiral channel only rises briefly at a steeper gradient after the vertical edges 66, 67, and 68, and then transitions to a constant, steeper gradient compared to the initial section. This results in a slightly wider web width immediately after the vertical edges. This also has a positive effect on the distribution and leads to a higher volume flow at the edges, thus further reducing spiral stripes.

[0115] It should be expressly mentioned that the proposed profile and cross-sectional geometries can be arranged not only in the spiral carrier, but also in the counter body arranged therefor.

[0116] The Wendelkanal 100 in Fig. 4 is formed on the inner mandrel side by a first channel-like recess 101 on a spiral carrier 102 of a blow head and, with its C-shape (shown as a cross-section), represents almost a typical design of a spiral channel with a D-shaped cross-section.

[0117] During operation of the blow head, molten plastic particles are introduced into a gusset region (108) at a beginning (not shown) of the spiral channel 100. The melt flows in the gusset region within the channels, i.e., in the pre-distribution channels and at the beginnings of the spiral channels 100. Once it has reached the spiral channels 100, the melt follows them helically around the spiral carrier 102, almost or completely leak-free, until the spiral channels 100 pass the previously described downstream sealing end edge 108'. From there, the "initial section" extends, and from there, the spiral channels 100 are no longer closed to the downstream outflow side, but allow the melt to enter an annular slot 105 around the downstream transition edges 103a, 103b in the extrusion direction 104.The annular slot 105 is formed on the radially inner side by a coil carrier surface 106, and on the radially outer side by a counter-body surface 107. Both are essentially cylindrical. The counter-body surface 107 surrounds the coil carrier surface 106. Ideally, it fits so tightly that no offset 112 occurs, although in practice, the offset 112 is usually observed when the coil carrier is heated.

[0118] The initial zone adjoins the illustrated interstices 108. Within the initial zone, which transitions into an overflow zone downstream outside the illustrated area, a helix 110 is incorporated, for example, milled, into a counter body 109 as a further part of the spiral channel 100.

[0119] In the initial section, i.e., beginning with the recess of the sealing coil carrier surface 106 at the seal end edge 108', the annular slot 105 with its dimension 105' is defined as the sum of the dimension 108" of the recess of the vertical seal end edge 108', added to the offset 112. Since the offset is ideally zero, the annular slot dimension 105' is approximately the same as the recess dimension 108''.

[0120] The helix 110 runs congruently opposite a helix carrier-side part 111 of the helix channel 100. Together with the helix carrier-side part 111 of the helix channel 100, the helix 110 thus forms a helix channel 100 with an overall circular cross-section.

[0121] Both profiles are C-shaped, mirror-inverted, and in the example chosen here, each exactly semicircular.

[0122] Overall, the two profile parts form an exactly circular cross-section, with an offset 112 of ideally zero.

[0123] Two D-shapes or further modifications are also readily possible to create a circular cross-section, as long as they allow a channel bottom 100a to run smoothly and continuously on an upstream side.

[0124] It has been shown that with such a design, very few residues remain in an otherwise critical dead zone 113, making it particularly easy to change materials in the melt. Purging times before the change are significantly reduced compared to the state of the art.

[0125] Furthermore, it should be expressly mentioned that the invention can be advantageously applied to both single-layer die heads and multi-layer die heads.

[0126] The second embodiment 120 for a round cross-section provides a spiral channel 121 on one side in a spiral carrier 122, which can be constructed as a cylindrical mandrel. The spiral carrier 122 is arranged opposite a counter-body 123, so that a spiral carrier surface 124 and a counter-body surface 125 upstream of the spiral channel 121 seal each other in the initial section (shown). Downstream of the spiral channel 121, however, the spiral carrier surface 124 is set back by a recess 126, thus clearing an annular slot 127 for overflowing melt toward the annular nozzle (not shown).

[0127] Downstream of the initial section of the spiral channel 121, further spiral channels (not shown) with their additional sections are located in the spiral carrier 122. They are also overflowed by melt emerging from the initial section of the spiral channel 121 and flowing over a downstream edge 128.

[0128] In cross-section, the spiral channel 121 has a circular cross-section because it is free of projections at an upstream channel base 129 and thus continuous. Furthermore, a curved line 130 of its cross-section meets a chord 132 at an obtuse angle 131 at its upstream end. In the present example, the obtuse angle 131 is approximately 150°.

[0129] The spiral channel 121 can, for example, have been produced with a ball milling cutter with a tilted axis 133.

[0130] The spiral channel 140 also embodies a circular cross-section: On the one hand, in its bottom region 141, which is located upstream, a step-free passage is created, namely from a first partial line 142 to a second partial line 143. On the other hand, and independently, here too there is an obtuse angle 148 between a chord 144 and a composite curved line 145, 146 at an impact point 147 of the curved line 145, 146 on the chord 144.

[0131] The fact that the circular cross-section of the spiral channel 140 is not composed of a single spiral carrier body, but rather an insert 150 is added to a larger spiral carrier body 149 to form the circular cross-section, is not relevant for the interpretation of the geometry of the spiral channel as a “circular cross-section”.

[0132] The D-shaped cross sections 160, 161,162 in Fig. 7 are each known from the prior art. A first D-shaped cross-section essentially has a C-shape 163 in its curved line 164. At an impact point 165, the curved line 164 meets a chord 167 at an acute angle 166 of approximately 85° at the crucial upstream edge of the spiral channel.

[0133] In the second D-shaped cross-section 161, an acute angle 168 is only about 50°. This is more of a lens shape.

[0134] The third D-shaped cross-section 162 features two rectangular extension pieces 169, 170, followed by a C-shaped central arch piece 171. The arch line is composed of the two extension pieces 169, 170 and the C-shaped central arch piece 171. It meets a chord 173 at an acute angle 172.

[0135] In the development 200 (only a selected section is shown) of a spiral distributor, a rather complex pre-distributor channel guide is provided as an example on a surface 201 of a spiral carrier 202 of an axial spiral distributor designed as a mandrel.

[0136] A first pre-distribution channel 203 is provided for conveying melt for four spiral channels 204, 205, 206, and 207. For this purpose, it has a feed 208 (not shown in detail).

[0137] After a first branch 209, a second distribution channel 210 and a third distribution channel 211 are provided, each of which is only intended for the transport of melt for two spiral channels 204, 205 and 206, 207 respectively.

[0138] After a second branching point 212, the melt can ultimately flow into the two spiral channels 204, 205 on the left. Likewise, after a third branching point 213, the melt can flow into the two spiral channels 206, 207 on the right.

[0139] The pre-distribution system shown has sealed channels, although it has already been explained that in practice there is usually no perfect seal between the coil carrier 202 and its counter body (not shown), but that a small leakage flow can occur, which the expert will nevertheless perceive as a sealed pre-distribution system.

[0140] The course of a spiral channel 206 (used here as an example) leads from a beginning past a sealing end edge 214. From there on, a channel edge 216 - upstream with respect to an extrusion direction 215 - is no longer sealed by the spiral carrier surface 201 of a gusset zone 217 and is thus open for melt to flow over from an upstream channel.

[0141] The pre-distribution channels are located upstream. However, these are closed. They lead, among other things, into the adjacent upstream spiral channel 207, so that melt will flow from the channel beyond the seal end edge 214 via a reduced-depth overflow area 218 to the first-mentioned spiral channel 206. The overflow area 218 is offset radially inward by the amount by which the seal end edge 214 jumps radially inward. The radial difference between the overflow area 218 and the surface 201 in the interstices area 217, which is sealed, is thus the radial thickness of the annular gap leading to the annular nozzle (not shown).

[0142] The first-described spiral channel 206 also has a downstream overflow area 219, beginning with another sealing end edge 220.

[0143] An initial section 221 of the turning channel 206 described here begins - viewed in the course of the spiral channel 206 starting from the pre-distribution system - exactly when passing the downstream sealing end edge 220. In the initial section 221 adjoining there, the spiral channel 206 releases melt in the extrusion direction 215 by means of overflow, but is itself protected on its upstream edge 216 from overflow by the sealing surface of the gusset area 217.

[0144] In a narrow sense, the “beginning” of the spiral canal 206 is identical with the beginning of its initial section.

[0145] In a further understanding of the word, the "beginning" of the spiral channel 206 is where the spiral channel 206 first assumes the ultimately assumed direction of travel, starting from a bend end 221; from there, the spiral channel 206 assumes the gradient with which it runs at the beginning of its initial section 221.

[0146] In an even broader interpretation of the term, the “beginning” of the spiral channel 206 is directly at the third branching point 213, because from there on there is no longer a pre-distributor, because from there the water is no longer fed into several spiral channels, but only into a single spiral channel.

[0147] The settlement detail 230 in Fig.9 is intended to pick out and describe an exemplary first spiral channel 231, which is sealed in the gusset region 232 to the downstream direction 233 with respect to a downstream adjacent channel 234, then has its initial section 236 after passing a downstream sealing end edge 235 and, after passing a start 237 of a directly adjacent, upstream second spiral channel 238, continues downstream from its initial section 239 into its further section 240.

[0148] The first spiral channel 231 has a circular cross-section of any desired configuration (preferably as described above using exemplary possible cross-sectional shapes) right at its beginning 241 of the initial section 236. From there, the first spiral channel 231 extends with a length 242 having the same circular cross-section or, for example, with a modified circular cross-section, but with a circular cross-section over the entire length 242.

[0149] The circular cross-section ends at the end 243 of the length 242 of the course.

[0150] However, even beyond the end 243, the first spiral channel 231 continues to extend continuously until it enters the further section downstream of the beginning 237 of the adjacent second spiral channel 238.

[0151] Within the further section 240, the first spiral channel 231 can either have a round cross-section or no round cross-section or partially have a round cross-section.

[0152] The first spiral channel 231 thus has a development over the course of the first spiral channel 231: initially, it has a circular cross-section - during the length 242 - but then no longer, whereby the first spiral channel 231 deviates from a circular cross-section later in its course in the initial zone, i.e. beyond the length 242.

[0153] The development of the circular cross-section from the length 242 with a circular cross-section to the adjoining section without a circular cross-section can be continuous or discontinuous. A continuous development would be a gradual phasing out of the circular cross-section. A discontinuous development would be a sudden end of the circular cross-section or, for example, a jump in the size of the circular cross-section.

[0154] Also independent of the embodiment shown here, it should be formulated: Preferably, a course with a circular cross-section extends into a region of the first spiral channel which is already downstream of the second, immediately adjacent spiral channel, thus reaching quite close to the end of the initial section of the first spiral channel.

Claims

[1] Spiral distributor (1, 30, 40) for a blow head of a film extrusion plant, with a central axis (4, 37) which runs in the blowing direction, and with an extrusion direction which is parallel to the central axis (4, 37) in the case of an axial spiral distributor, radial in the case of a radial spiral distributor (30) and projectable onto the axis in the case of a conical spiral distributor, a. where pre-distribution channels lead all around into the beginnings of spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207), b. wherein the spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) extend at an angle to the extrusion direction, so that c. a first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) begins at a beginning, after an initial section (15, 56, 57, 58, 221, 236) passes a second, directly adjacent spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) downstream at its beginning and continues in a further section downstream of its initial section (15, 56, 57, 58, 221, 236) and its further section, d. so that in the course of the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) beyond a sealing end edge (214, 220, 235) sealing against overflow, during operation of the die head, melt emerging from the second spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) can flow over the further downstream section of the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) in the extrusion direction, e. so that the spiral distributor (1, 30, 40) i. an initial zone is formed in which initial sections (15, 56, 57, 58, 221, 236) of the spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) are located, which have a sealing interstices zone (13, 108, 217) upstream in the extrusion direction and therefore cannot yet be overflown by other spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) located upstream in the extrusion direction, but melt can itself be overflown to downstream spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) are intended to be submitted, and subsequently ii. an overflow zone (218, 219) is formed in which only further sections of the spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) are located, characterized by , that iii. the first spiral canal (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) 1. has a course with a circular cross-section in the initial zone and 2. has a development - for example, unsteady - over its course with regard to the circular cross-section, whereby the first spiral channel deviates from a circular cross-section later in the course in the initial zone and / or in the overflow zone. [2] Spiral distributor according to claim 1, characterized by that the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) is already present at the beginning of the initial section (15, 56, 57, 58, 221, 236) and from there continues continuously over the said course, preferably over the entire initial section (15, 56, 57, 58, 221, 236) and / or into the further section and / or over the entire further section. [3] Spiral distributor for a blow head of a film extrusion plant, with a central axis (4) which runs in the blowing direction, and with an extrusion direction which is parallel to the central axis (4) in the case of an axial spiral distributor, radial in the case of a radial spiral distributor (30) and projectable onto the axis in the case of a conical spiral distributor, a. whereby pre-distribution channels (34, 203) all around lead into the beginnings of spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207), b. wherein the spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) extend at an angle to the extrusion direction, so that c. a first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) begins at a beginning, after an initial section (15, 56, 57, 58, 221, 236) passes a second, directly adjacent spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) downstream at its beginning and continues in a further section downstream of its initial section (15, 56, 57, 58, 221, 236) and its further section, d. so that in the course of the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) beyond a sealing end edge (214, 220, 235) sealing against overflow, during operation of the die head, melt emerging from the second spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) can flow over the further downstream section of the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) in the extrusion direction, e. so that the spiral distributor i. an initial zone is formed in which initial sections (15, 56, 57, 58, 221, 236) of the spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) are located, which have a sealing interstices zone (13, 108, 217) upstream in the extrusion direction and therefore cannot yet be overflown by other spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) located upstream in the extrusion direction, but melt can itself be overflown to downstream spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) are intended to be submitted, and subsequently ii. an overflow zone is formed in which only further sections of the spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) are located, characterized by , that iii. on a counter-body (3) which is opposite the two spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207), a counter-body spiral channel is formed in the initial zone, which ends, in particular runs out, upstream of the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) in the extrusion direction. [4] Spiral distributor according to claim 3, characterized by that the counter-body spiral channel runs opposite the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207). [5] Spiral distributor according to claim 3 or 4, characterized by that the counter-body spiral channel together with the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) forms a circular cross-section, in particular an O-shaped cross-section, especially an approximate or exact circular cross-section. [6] Spiral distributor according to one of claims 1 or 2 and according to one of claims 3, 4 or 5. [7] Spiral distributor according to one of the preceding claims, characterized by that a circular cross-section is composed of two partially circular or circular cross-sections, in particular of two semi-circular cross-sections. [8] Spiral distributor according to one of the preceding claims, characterized by that a circular cross-section is composed of the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) and a counter-body spiral channel formed on a counter-body (3). [9] Spiral distributor according to one of the preceding claims, characterized by that the spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) has a curved line which, when it meets its chord, forms an obtuse angle with the chord, i.e. an angle greater than 90°, preferably over 120° or 135°, but less than 180°. [10] Spiral distributor according to one of the preceding claims, characterized bythat the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) already has a circular cross-section at its beginning. [11] Spiral distributor according to one of the preceding claims, characterized by that the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) already has a circular cross-section at the beginning of its initial section (15, 56, 57, 58, 221, 236). [12] Spiral distributor according to one of the preceding claims, characterized by that the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) has a circular cross-section over the entire initial section (15, 56, 57, 58, 221, 236), wherein the circular cross-section of the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) can end, in particular run out, at the beginning of the overflow zone. [13] Spiral distributor according to one of claims 1 to 11, characterized bythat the circular cross-section of the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) ends before the beginning of the overflow zone, in particular still runs out in the initial zone, wherein the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) preferably extends continuously with a cross-section deviating from a circular cross-section from its section with a circular cross-section to the further section. [14] Spiral distributor according to one of the preceding claims, characterized by that in the initial zone two spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207), in particular all spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207), have a circular cross-section. [15] Spiral distributor according to one of the preceding claims, characterized bythat in the initial zone two spiral channels (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207), in particular all spiral channels, each have an opposite, associated spiral in the counter body. [16] Spiral distributor according to one of the preceding claims, characterized by that the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207) has a D-shaped cross-section in the overflow zone. [17] Spiral distributor according to one of the preceding claims, characterized bythat the spiral distributor has an overflow promoter for the melt at the beginning, in the initial section (15, 56, 57, 58, 221, 236) and / or in a transition section of the first spiral channel (8, 9, 32, 41, 42, 43, 44, 45, 100, 204, 205, 206, 207), so that during operation at a blow head, melt emerging from the initial section (15, 56, 57, 58, 221, 236) of the second spiral channel flows over an overflow web (12) in the extrusion direction to the downstream first spiral channel. [18] Blow head for a blown film line, with a spiral distributor according to one of the preceding claims. [19] Blown film line, with an extruder, a blowing head according to claim 18, a flattening and a take-off device and preferably with a winding station. [20] A method for producing a blown film using a blown film line according to claim 19.

Images