EP2956284A1

EP2956284A1 - Single-screw plasticator and set of a series; method for plasticating a starting material

Info

Publication number: EP2956284A1
Application number: EP14712191.7A
Authority: EP
Inventors: Tim Carsten Pohl
Original assignee: Reifenhaeuser GmbH and Co KG Maschinenenfabrik
Current assignee: Reifenhaeuser GmbH and Co KG Maschinenenfabrik
Priority date: 2013-02-15
Filing date: 2014-02-16
Publication date: 2015-12-23
Also published as: WO2015113529A9; US20150367532A1; WO2015113529A1; DE102013002559A1; CN105142876B; DE102013002559B4; CN105142876A; DE112014000840A5

Abstract

To increase the output, the diameter of the screw is generally increased in accordance with the physical laws of similarity. The length-to-diameter ratio remains the same, or the extruder becomes longer. This has the effect that the engineer seeks to use an extruder with a small screw diameter. The invention addresses the problem of presenting a universal concept of a single-screw plasticator. The invention discloses a compact screw with a diameter of at least 150 mm and with an effective length L that has in relation to the screw diameter D a ratio L/D of 1 to 8.

Description

SCROLL PLASTICIZER AND SET OF A SERIES; METHOD FOR PLASTICIZING AN OUTLET MATERIAL

[Ol] The invention relates to a single-screw plasticizing machine for conveying, melting, homogenizing and pressure building - ie plasticizing - a starting material, as well as a method for conveying, melting, homogenizing and pressure build-up - ie plasticizing - a starting material.

[02] The "starting material" comprises, in particular, plastics, in particular thermoplastic polymers, optionally with powdery and fibrous additives, as well as food masses. [03] The "single-screw plasticizing machine" may, above all, be an extruder, so that the invention is based on all relates to a single-screw extruder for thermoplastic polymers and a method for plasticizing thermoplastic polymers with such an extruder.

[04] Single-screw plasticizing machines are widely known in the art. A detailed explanation of their structure and the flow calculation can be found in Schöppner, Volker "Process Engineering of Extrusion Systems" in the publication series "Progress Reports VDI", Series 3, No. 715. Dusseldorf, VDI Verlag 2001, ISBN 3-18-371503- 1, in chapter 4.2.

[05] A concrete proposal of a single-screw plasticizing machine can be found in DE 102 17 686 A1.

[06] Single-screw plasticizing machines are often found, for example, in the form of extruders or in plastic injection molding machines. Within the extruder, those which are part of a plant for the production of profiles, tubes, films, blow moldings, plates, filaments, nonwovens, tapes, Semi-finished products, hoses, cables, granules, compound or semifinished foam products can be o-.

[07] Numerous requirements are placed on a plasticizing machine: in order to maintain the best possible discharge rate, it should be possible to maintain a constant delivery rate, even at different backpressures. It should also achieve a good homogeneity of the starting material to be processed at an optimally predetermined extrusion temperature. In addition, he should be able to process as broad a spectrum of materials as possible, but at the same time have low energy consumption and thus save resources as a whole. And in addition to the usual requirements for the best possible price-performance ratio, a small footprint, low noise, high availability, wear resistance and ease of maintenance, he should be able to scale up. The latter is of particular interest to the manufacturer of an extruder in order to be able to offer reliable extruders for a wide variety of throughputs and plastics.

Since the time of industrialization, extruders are built so that at a given screw diameter depending on the process conditions, a corresponding throughput or throughput range is achieved, ie depending on the pressure, type of polymer used, molding mass temperature, homogeneity, etc.

[09] When the throughput is to be increased while maintaining the other process conditions, the screw diameter is usually increased in accordance with the physical laws of similarity. The length to diameter ratio, which is commonly referred to in the art as L / D, remains the same or the extruder becomes longer due to meltdown and dwell time problems. As a result, the engineer strives to use an extruder with the smallest possible screw diameter. [10] In order to increase the output power rh, the free channel volume must always be increased and the dwell time adjusted accordingly in order to fully fill the material. to melt constantly. However, the screw channel volume can not be increased arbitrarily because the screw still has to transmit the required drive torque. Ultimately, therefore, the screw diameter must be larger.

[11] To avoid the disadvantage of space-intensive extruders, fast-rotating single-screw extruders have been developed over the last decade. Customary practice is extruders with a diameter D of 35 mm to 100 mm and with a cylinder length L of 30 D to 40 D, and with a peripheral speed of about 1 m / s.

The disadvantage is that the material is severely sheared by the high peripheral speeds, the melting temperature is high due to the process and the processing window is narrow.

[13] Ultimately, however, all customary concepts struggle to provide an actual helix-diameter-independent universal extruder that is freely scalable using similarity laws. There are several reasons for this: firstly, the delivery rate depends on the coefficients of friction between polymer and steel and within the polymer, which makes it dependent on the channel depth, the channel width and the polymer properties, ie there is no real physical similarity, because and adhesion behavior is not reproducible in terms of similarity theory. Then, the melting performance is not exactly proportional to the residence time and the shear energy. Finally, various polymers are not physically similar in viscosity, melting point, friction, and morphology.

Therefore, nowadays, with individualized experience and process know-how, extruders are optimally adapted to the respective task. Specifically, the person skilled in the art begins the design process of an extruder for boundary conditions to be achieved by using a small, proven extruder as the starting geometry, starting with the physical geometry of this initial geometry Applying similarity laws, and then improving the performance of the extruder in subsequent iterative refinement steps. It can not be guaranteed that the extruder thus constructed achieves the result quality of the proven extruder with the initial geometry. [15] In practice, extruders are in the parameter ranges

Peripheral speed 0.05 to 1.5 m / s, high speed> 1.0 m / s

L / D 16 to 36 (sometimes up to 40)

h / D 1/5 to 1/20

Gear number i 1 to 2 and

Diameter D 18 to 250 (some to 350) become known.

[16] In Gerhard Schenkel: Kunststoff-Extrudertechnik, 2nd edition of the book "Schneckenpressen für Kunststoffe", Carl Hanser Verlag, Munich, 1963, various calculations for understanding the mechanical model laws are presented on pages 167-169 L / D ratio of the extruder modeled similarly to other values is given in an example as about 3.2 at a diameter D of 150 mm On page 169 it is mentioned that in such calculations "considerably shorter screws" are used However, this theoretical "suggestion can not be regarded as a viable solution to the problem." [17] The practice has seen this as well: Since the 1970s, especially in view of the introduction of Nutbuchsenextrudern and high-speed single-screw extruders, corresponding geometries are The low throughput in relation to the high back pressure due to of the large screw diameter. For more than 40 years now, experts have been endeavoring to obtain a high output from the smallest and longest possible extruders, ie with a high L / D ratio. In practice, since the 70s For example, the screw length from about 20 L / D even up to 40 L / D for fast-rotating screws (called fast-rotating screws, those running at a peripheral speed of> 1 m / s) is being developed.

[18] In the field of hot rubber extruders or rubber extruders in general, there can be very short, large diameter extruders such as those mentioned in Lothar Köster: Practice of Rubber Extrusion, Carl Hanser Verlag, Munich, ISBN 978-3-446-40772 -5, table on page 5; also confirmed by James White, Helmut Potente: Screw Extrusion, Hanser Verlag, ISBN 3-446-19624-2. There, it is discussed that rubber extruders are designed significantly shorter and the temperature is controlled with water instead of electrically or with Öltempertierung in Kunststoffxtrudern. When the rubber is preheated to the extruder (addition temperature = 60-90 ° C), the hot fed extruder is reduced from 14-20 L / D to 6-12 L / D.

[19] However, the extruders for rubber or hot rubber have nothing to do with the genus of the present invention because the extruders for rubber or hot rubber are not concerned with melting and plasticizing a starting material. After all, a rubber or warm rubber already has the original properties required. As a result, a rubber is filled into the extruder at room temperature, for example, and usually leaves the extruder at between 90 ° C and 130 ° C. If too high a temperature is reached, then the rubber quickly damages. The processing temperature is below 130 ° C. In addition, rubber does not experience any phase transformation solid / liquid during processing. In addition, rubber is usually supplied in strip form to an extruder, so no compaction is required as in the addition of granules of thermoplastic polymers. Rather, the rubber extruder has the primary task of continuously conveying, to heat the rubber evenly and to build up an extrusion pressure.

[01] Thermoplastics, on the other hand, are processed at 170 ° C to 350 ° C. As described in the preamble of the present claims they are additionally compacted and melted in the extruder - so it is imperative that a phase transformation solid / liquid instead.

The invention has for its object to provide the prior art an improvement or an alternative.

[21] According to a first aspect of the present invention, this object is achieved by a single-screw plasticizing machine for conveying, melting and homogenizing plastic, wherein the single-screw plasticizing machine has a screw with a screw diameter and an effective length, and wherein the screw-in Plasticizing machine is adapted to rotate the worm in operation by means of a controller with a peripheral speed, wherein two or all three of the following parameter ranges are met, namely that:

The screw diameter D is at least 150 mm, in particular 200 mm to 800 mm,

The effective length L to the screw diameter D has a ratio L / D of 1 to 8, or

• The controller is adapted to operate the screw at a peripheral speed of less than 1.5 m / s, preferably below 1.0 m / s, more preferably between 0.05 m / s and 1.0 m / s ,

Within the specified parameter ranges, the following intermediate values are to be understood as concrete with disclosed, so that the above interval limits can be optionally restricted by the following:

• The screw diameter D should alternatively be at least 150, 200, 300, 400, 500, 600, 700 or 800 mm and / or • The screw diameter D should alternatively be at most 500, 600, 700, 800 mm or more and / or

• the ratio L / D should alternatively be at most 8, 7, 6, 5, 4, 3 or 2 and / or

The ratio L / D should alternatively be at least 1, 2, 3, 4, 5, 6 or 7 and / or the peripheral speed should in the alternative be at most 1.0, 0.9, 0.8, 0.7, 0, 6 or 0.5 m / s and / or

• In the alternative, the peripheral speed should be at least 0.001, 0.05, 0, 1, 0.2, 0.3, 0.4 or 0.5 m / s.

[22] The following is explained conceptually: [23] The single-screw plasticizing machine is then "set up" to melt and homogenize the relevant starting material, ie a thermoplastic, if it is in any case designed to achieve a temperature range required for it at about 150 ° C or 160 ° C, rather even at about 170 ° C. The machine must therefore be set up to convey, melt and homogenize the plastic at 160 ° C., 170 ° C. or more Have active heating means, which is directed to the plastic stream in the course of the effective length L of the screw, especially an electric heater and / or a water heater and / or other fluid heating, such as an oil heater. Preferably, a shutdown is provided which signals an alarm or even automatically shuts off the producing machine when on or in the we ksamen length L a temperature below or even set only, which is in the range of about 100 ° C, for example, of about 130 ° C or above 140 ° C, especially at about 150 ° C, but preferably below 170 ° C. [25] The "screw diameter" D is the diameter which is commonly used in the calculation of the design, which is the inside diameter of the cylinder surrounding the screw.

[26] The term "effective length" L refers to the size commonly referred to in the calculation and design as size L. The size L refers to the effective length of the screw, which normally extends from the front edge of the funnel until the start of the screw tip, ie until the transition from the screw geometry to the tip.

[27] The cylinder is either smooth inside over the length L, which in the context of the present disclosure means a surface roughness of not more than 0.1 mm; or, within the length L, there is a smooth portion and a rough portion, for example, with a rough inner surface in the intake area of the extruder for improving the conveyance of solids. A rough surface may, for example, grooves, grooves, helix or have other macroscopic profiling, especially as known from the prior art and / or arranged regularly.

[28] The "control" should include any control, which is to be understood as a subset of a regulation.Whenever in the context of the present patent application of a control is spoken, should therefore be a "control, in particular regulation" to understand. As control parameters, in particular the speed, the temperature, the pressure-speed behavior and the speed-throughput behavior come into consideration.

[29] It is crucial for the realization of the invention that the single-screw plasticizing machine makes possible an operating point by means of its control, which lies within the value limits claimed here. This can easily be fulfilled even if the control is additionally designed to operate the single-screw plastifying machine with an alternative operating point, which lies outside the value limits claimed here. [30] The "peripheral velocity" is the tangential velocity of any point on the outermost diameter of the screw at the operating angular velocity of the screw, the peripheral velocity thus being the product of the angular velocity of the screw in service and the screw diameter D, for calculation It is assumed that the remaining gap width between the outermost circumference of the screw and the inner diameter of the cylinder is zero.

[31] A screw of the shape proposed here has a surprisingly short effective length L, but a surprisingly large screw diameter D. Not only a considerable reduction in the required installation space is achieved with it, but above all a great deal of freedom in the adaptation of the Obtained screw geometry to the respective procedural tasks. In order to change the desired throughput, the design can simply change the length at a constant diameter. This is at the same time a considerable departure from the idea of Gerhard Schenkel, who speaks of increasing the diameter for the same length. The big advantage of the present invention is in contrast to keep the diameter large and change the length. Thus, it is possible to adjust the extruder output by a comparatively small change in the screw length without changing the melt properties.

[32] It is proposed that the single-screw plasticizing machine in the machine direction beyond the effective length of the screw has a melt pump which is designed to generate a pressure build-up during operation.

[33] Melt pumps as such are known in the market for extruders of the type relevant here. Thus, the extruder screw can convey the melt directly into a melt pumping chamber, which is attached to the front of the screw tip as a continuation of the cylinder. There are two mutually toothed axially parallel rollers whose axes are perpendicular to the extrusion, so machine, direction. You can adjustable rotation and with adjustable rotational speed so that they adjust the melt back pressure at the screw tip, thus providing another opportunity to influence the pressure and flow profile in the extruder. As a rule, a melt pump is used to reduce the back pressure of the screw or to take over part of the pressure build-up. Often there are pressure sensors both in front of and behind the roller pair.

[34] According to the current state of knowledge, a melt pump seems sensible above all from about 200 bar extrusion resistance.

In the case of an extruder, which is used as part of a plant for producing spunbonded fabric, the use of a melt pump already makes sense from about 100 to 150 bar extrusion resistance.

Another advantage is that a melt pump is a structurally favorable variant to change from relatively large screw diameter to a relatively smaller connection cross-section for the further transport of the melt beyond the melt pump.

[37] Often there is a sieve in front of and / or behind the melt pump. A sieve, which is located in front of the melt pump, often serves to protect the melt pump and can be designed as a fairly coarse sieve. Often there is a screen changer in front of and behind the melt pump. [38] The use of a melt pump in combination with a slow-running short extruder with a comparatively large screw diameter - as proposed above as a single screw plasticising machine - constructively counteracts the disadvantage of the disproportionately increasing axial pressure. Due to the degree of freedom gained, the melt backflow fraction can also be altered by adapting the screw inlet pressure and the material homogeneity can be adapted to the requirement. [39] For the sake of completeness, it should be emphasized that the single-screw plasticizing machine does not necessarily require a melt pump in order to build up the desired pressure. Rather, an extruder, for example, can build up the desired pressure even without a melt pump. [40] Thus, the advantage of a space-saving short extruder with large screw diameter, a melt pump is added to the screw tip, so that the extrusion pressure can be adjusted to the desired level. This can be done, for example stepless or stepped. By controlling the extrusion pressure, the extruder user gets an additional degree of freedom to change the melt temperature or the material homogeneity.

[41] According to a second aspect of the present invention, the object is achieved by a single-screw plasticizing machine suitable and arranged for conveying, melting and homogenizing a raw material, the single-screw plasticizing machine having a screw with a screw diameter and an effective length, and wherein the single-screw plasticizing machine is adapted to rotate the screw in operation by means of a peripheral speed control, in particular a single-screw plasticising machine as described above, wherein the machine is characterized in that in the range of the effective length L of the screw and / or in the region of a screw tip beyond the effective length L, a pressure reducer is provided, through which the screw extends with a part of its axial length into a pressure-reduced area during operation, in particular into an area with ambient pressure during operation.

[42] The effective area of the axial pressure on the screw can be reduced by reducing the effective area. This area reduction can be effected by a change in the diameter of the screw and / or a change in the inflow cross section of the downstream of the plasticizing machine. [43] Thus, as an alternative to a melt pump, it is conceivable that an extrusion tool is placed at the end of the screw cylinder so that an extrudate is formed following the screw channel.

[44] An extrusion die may include an annular die, for example, set to produce an annular extrudate, such as a tube, or a granulating head may be provided there, for example.

[45] If the screw protrudes through a pressure reducer, then the effective length L of the screw is only in the area between the hopper and the pressure reducer. In this case, therefore, the effective length L of the screw is shorter than the range of the screw geometry.

[46] It is proposed that an annular gap of the annular gap nozzle lies in alignment with a channel between the screw and the cylinder. In such an embodiment, an otherwise suitable transitional component between the melt in its path along the screw and its path through the tool is omitted with suitable construction.

[47] If an extrusion tool is provided at the end of the screw cylinder, then it is suggested that it starts still upstream of the screw tip, ideally immediately adjacent to a screw-top screw cylinder, so that the screw tip and / or a part of the screw in front of the screw tip and / or a snail on its front side of the worm tip supporting abutment protrude into the tool or even protrude into or through a nozzle of the tool. The screw is then with appropriate design partially in the ambient pressure range.

[48] According to a third aspect of the present invention, the stated object solves a single-screw plasticizing machine suitable and arranged for conveying, melting and homogenizing a starting material, wherein the single-screw Plasticizing machine having a screw with a screw diameter and an effective length, and wherein the single screw plasticizing machine is adapted to rotate the screw in operation by means of a peripheral speed control, in particular a single screw plasticising machine as described above, the machine being characterized in that an extrusion tool is connected in the machine direction beyond a cylinder of the screw, wherein the extrusion tool is configured to produce granules during operation and has a perforated disk for producing a strand and a knife for cutting the strand, the knife rotating with the screw is arranged, in particular at the Schneckenspitze.

[49] Such an embodiment can be made very inexpensive and spatially compact. In addition, regardless of the speed of rotation of the screw, the granules are always cut essentially the same size, because as the rotational speed increases, not only does the conveyed mass throughput increase, but the speed of the knife also increases in its orbit.

[50] In a preferred embodiment, the controller is adapted to operate the screw at a peripheral speed of less than 1.5 m / s, in particular with a peripheral speed of at most 1.0 m / s, 0.9 m / s, 0 , 8 m / s, 0.7 m / s, 0.6 m / s or 0.5 m / s. Such an embodiment turns away from the fast-running screws and achieves a low extrusion temperature through a low peripheral speed.

[51] With regard to the effective length L, it is proposed that this take an amount between 300 mm and 2,400 mm. The two limits are to be understood as being included in the interval. Moreover, in a preferred embodiment, the limits are not to be understood as sharp boundaries, but rather as approximate limits. The inventor also has successful calculations and prototype experiments with an effective Length L of up to less than 300 mm. Even with regard to the upper interval limit, it does not appear from the previous experiments that the interval according to the invention should necessarily end there abruptly.

[52] Incidentally, the same applies with regard to the interval limits, also with regard to the specified screw diameter D with its interval limits analogously, and also analogously for the interval limits of the ratio L / D.

[53] The lower limit and / or the upper limit of the value interval of the effective length L may alternatively be 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 1,000 mm, 1,100 mm, 1,200 mm, 1,300 mm, 1,400 mm, 1,500 mm, 1,600 mm, 1,700 mm, 1,800 mm, 1,900 mm, 2,000 mm, 2,100 mm, 2,200 mm and 2,300 mm are understood as being disclosed, likewise preferably in each case as approximate limits.

[54] With regard to the ratio between the screw diameter D and the channel depth h of the screw channel, a ratio D / h of 20 to 150 is proposed, whereby the two interval limits do not have to be understood as sharp ends of the useful interval according to the invention, but only as possible retraction positions within the framework of the patentability.

Conceptually, let the channel depth h be understood as the radial distance between the screw root and the inner diameter of the cylinder surrounding the screw, so that the inner diameter of the cylinder (ie the "screw diameter D") from the diameter of the screw from Schneckengrund to Schneckengrund and is composed of twice the channel depth h as a sum.

[56] Also, the large ratio D / h again contributes to a very large in Schneckenendurchmesser sized and therefore correspondingly short screw, so a snail with a rather stocky shape. [57] It is suggested that the snail is more motile. It may for example have two flights or more than two flights, in particular three, four, five, six, seven or eight flights. With regard to the number of gears, it is taken into account that a two-part gear at a barrier zone should be considered as exactly one gear.

[58] At this point, it should be expressly pointed out that in the context of the present patent application, any statement with an indefinite number article, ie for example "a", "two", etc. should be understood as an "at least" indication, provided that It does not follow from the context in question that there should only be understood as an "exact" expression, for example "exactly one", "exactly two" etc.

[59] The pitch t is found as the distance between two adjacent worm walls of the same channel in a longitudinal section along the worm.

[60] The screw preferably has a modular connection device. It can then be kept and offered with particularly easy measures different screw lengths.

[61] The maintenance of the screw is greatly facilitated if a cylinder surrounding the screw has a segmented structure. Any cylinder which is not formed from a one-piece hollow cylinder is to be understood as being "segmented." Above all, it should be remembered that the cylinder has two or more segments, so that the cylinder is axially segmented, that is to say in the length of several The worm may then be tempered from the inside, for example via a cooling fluid guide or via a heating fluid guide In the case of a temperature-controlled worm, a temperature sensor is preferably additionally present to enable the thermal feedback of the worm plasticizing material on the surface of the screw with capture. [63] A preferred embodiment of the screw has a worm shaft with a recess which has a back pressure bearing or is adapted to receive a back pressure bearing.

[64] The worm can have a worm shaft, which is designed as a worm mandrel.

[65] It has already been explained that the machine is preferably a single-screw extruder.

[66] Extruders are used in many areas of the plastics processing industry. In particular, consider an extruder which conveys, melts and homogenizes thermoplastic materials to subsequently direct the plastic melt to a forming die for forming a continuous product. The products are, for example, profiles, tubes, films, blow moldings, plates, filaments, nonwovens, tapes, semi-finished products, hoses, cables, granules, compound or semifinished foam products. [67] Alternatively, it is easy to imagine that the machine is, for example, a plastic injection molding machine, in particular having a central injection piston. In a plastic injection molding machine, the plasticizing screw is usually mounted longitudinally displaceable. With increasing amount of plastic granules conveyed, this is collected at the end of the screw in the plasticized state until the required amount is accumulated for injection into the Spritzgusskavität. To collect the plastic melt in front of the screw tip, the screw moves axially back during the plastification process. This increases the required overall length even beyond the pure screw length.

[68] It can easily be seen that such a machine also benefits greatly from a screw whose geometry has a rather compact shape, in particular a short overall length. [69] According to a fourth aspect of the present invention, the stated object solves a single-screw plasticizing machine for conveying, melting and homogenizing plastic, the single-screw plasticizing machine having a screw with a screw diameter and an effective length, and wherein the screw-in Plasticizing machine is adapted to rotate the worm in operation by means of a controller with a peripheral speed, so that in operation, taking into account a number of flights of the worm an established mass flow m of the plastic results, the effective length L of 200 mm to 2000 mm and wherein in operation the ratio between the mass flow m and the effective length L is between 0.25 kg / (h * mm) and 1.4 kg / (h * mm), in particular at least 0.5 kg / (h * mm) ,

[70] It should be emphasized that a single-screw plasticising machine designed in this way can additionally be equipped with all the features described above.

[71] It should also be emphasized that even the specified interval limits do not have to be sharp. On the contrary, values slightly above or below are to be regarded as being within the scope of the invention.

[72] It is explained in terms of the "mass flow" that it should correspond to the variable which is usually designated by the parameter rh in the calculation and design .. Designs with parameter ratios are proposed in the development of the extruders used in the prior art described at the outset which, given the order of the ordinate throughput and the effective length of the extruder on the abscissa in a Cartesian coordinate system, will essentially give a straight line, but this straight line will not pass through the zero point of the coordinate system, nor does it require a desired throughput of For example, starting at 200 kg / h, an extruder length of about 1,500 mm and upwards can be achieved. On the other hand, significantly shorter extruders can be produced with the value range proposed here, at the same required throughput of 200 kg / h, for example Extruder with a length of only about 200 mm to 800 mm, with diameters D of about 400 mm and about 100 mm.

[73] According to a fifth aspect of the invention proposed here, the stated object solves a method for plasticizing a starting material in the form of plastic, in particular plastic granules, by means of a single-screw plasticizing machine as described above, wherein the control preferably uses the screw Circumferential speed of less than 1.5 m / s operates, in particular of less than 1.0 m / s. It goes without saying that this interval limit should also be understood as a non-sharp boundary. [74] Depending on the polymer and application, the extruder operates at a desired speed and throughput range. The ratio of maximum flow rate to minimum flow rate is usually between 5: 1 and 20: 1. Above the maximum flow rate, the farsighted engineer plans a speed reserve of typically about 10% to 20%. The upper circumferential speed limit specified in the invention as the design basis relates in particular to the desired maximum upper rpm range, and it may also be fundamentally sensible to process shear-sensitive polymers with lower circumferential speeds.

[75] According to a sixth aspect of the present invention, the stated object solves a set of a series comprising two single-screw plasticizing machines as described above, wherein both have a maximum deviation of 10% the same ratio between the mass flow m and the effective length L.

[76] For clear understanding, see

Figure 1 in a schematic longitudinal section of an extruder with a hopper and in Figure 2 in a schematic longitudinal section of a screw tip two alternatively usable, exemplary different tools shown.

The screw in Figure 1 has within its effective length L three zones, first with a channel depth hl, then a transition region and finally with a channel depth h2, and with a screw diameter D and a rotational speed n. The peripheral speed is calculated to the Product of D, n and π.

[78] The extrusion direction runs from left to right.

[79] Currently favored parameter ranges for a squat snail of the invention presented here are mainly at

Peripheral speed 0.05 to 1.0 m / s

L / D 1 to 8

h / D 1/20 to 1/150

Number of gears i 2 to 20 and / or

Diameter D 150 to 800.

[80] At first glance, according to the current state of development, the practically most meaningful screw diameter range starts at about 300 mm or less - smaller values appear to make sense especially with an extruder without a melt pump - and goes up to approx. 500 mm or more.

[81] Finally, by skillfully choosing the screw diameter, it is possible to transfer the throughput range known today to an effective screw length of less than 2,000 mm.

The screw 1 in Figure 2 extends in a cylinder 2. It has along an extrusion direction 3, first a cylindrical part 4 and then a screw tip 5 on. [83] A gear 6 is formed between the screw 1 and the cylinder 2. During operation, the screw 1 during operation conveys the molten plasticized plastic in the extrusion direction 3.

[84] The cylinder 2 terminates even before the start of the screw tip 5. A tool is connected to its end 7, namely, for example (shown in the upper half of FIG. 2), a tapering of the channel 6 to form an annular gap nozzle 8, so that in operation Machine (not shown in full) a tube 9 is extruded; or there are, for example (shown below in Figure 2) a perforated plate 10 for extruding a plurality of melt strand 1 1 (shown by way of example) and a following, on the rotating in operation screw 1 mitrotierend fixed knife 12 for cutting the melt strands 1 1 in granules 13th , 14 (numbered as an example).

[85] The screw 1 protrudes from a pressure area 15 upstream of the tool through the tool into an area 16 with ambient pressure. The tool forms the nozzle with the cylindrical part of the screw 1. The screw tip 5 is completely in the pressure-reduced area, and it protrudes part of the cross-sectional area of the screw 1 to the outside.

Claims

Single-screw extruder, suitable and adapted for conveying, melting and homogenizing a starting material, in particular a thermoplastic polymer, wherein the Einschnecken-plasticizing a screw having a screw diameter and an effective length, and wherein the Einschnecken -Plastifizier- machine is set to rotate the worm in operation by means of a controller with a peripheral speed, characterized in that

• The screw diameter D is at least 150 mm, in particular 200 mm to 800 mm, and that

• the effective length L to the screw diameter D has a ratio L / D of 1 to 8.

Single-screw extruder, suitable and arranged for conveying, melting and homogenizing a starting material, in particular a thermoplastic polymer, wherein the single-screw plasticizing machine has a screw with a screw diameter and an effective length, and wherein the single screw -Plastifizier- machine is set to rotate the worm in operation by means of a controller with a peripheral speed, characterized in that

The screw diameter D is at least 150 mm, in particular 200 mm to 800 mm, and that

• The controller is adapted to operate the screw at a peripheral speed of less than 1.5 m / s, preferably less than 1.0 m / s, more preferably between 0.05 m s and 1, 0 m / s.

• the effective length L to the screw diameter D has a ratio L / D of 1 to 8 and that

Single-screw plasticizing machine according to two or all three of the preceding claims.

Single-screw plasticizing machine according to one of the preceding claims, characterized in that a melt pump is provided in the machine direction beyond the effective length of the screw, which is adapted to generate a pressure build-up during operation. Single-screw extruder, suitable and arranged for conveying, melting and homogenizing a starting material, in particular a thermoplastic polymer, wherein the single-screw plasticizing machine has a screw with a screw diameter and an effective length, and wherein the single screw -Plastifizier- machine is set to rotate the screw in operation by means of a controller at a peripheral speed, in particular single-screw plasticizing machine according to one of the preceding claims, characterized in that in the range of the effective length L of the screw and / or in the region of a screw tip beyond the effective length L, a pressure reducer is provided, through which the screw extends with part of its axial length into a pressure-reduced region during operation, in particular into an area with ambient pressure during operation.

Single-screw plasticizing machine according to one of the preceding claims, characterized in that an extrusion tool is connected in the machine direction beyond a cylinder of the screw.

Single-screw plasticizing machine according to claim 6 or 7, characterized in that the extrusion die has an annular gap nozzle.

Single-screw plasticizing machine according to one of claims 6 to 8, characterized in that the extrusion tool is set up in operation to produce an annular extrudate, in particular a tube. Single screw extruder, suitable and arranged for conveying, melting and homogenizing a starting material, in particular a thermoplastic polymer, wherein the single screw plasticizing machine has a screw with a screw diameter and an effective length, and wherein the single screw Plasticizer is set to rotate the worm in operation by means of a controller at a peripheral speed, mseselfe 'e single-screw plasticizing machine according to one of claims 1 to

characterized in that in the machine direction beyond a cylinder of the screw, an extrusion tool is connected, wherein the extrusion tool in operation to produce granules is set up and a perforated disc for producing a strand and a knife for cutting the strand, wherein preferably the knife mitdrehend on the Snail is arranged, in particular at the screw tip, or the knife is arranged stationary, wherein the perforated disc can be arranged on the screw.

Single-screw plasticizing machine according to one of the preceding claims, characterized in that the effective length L is between 200 mm and 2,400 mm.

Single-screw plasticizing machine according to one of the preceding claims, characterized in that the screw diameter D to the channel depth h has a ratio D / h of 20 to 150.

Single-screw plastifying machine according to one of the preceding claims, characterized in that the screw is more continuous. Single-screw plasticizing machine according to one of the preceding claims, characterized in that the screw has a modular connecting device.

Single-screw plasticizing machine according to one of the preceding claims, characterized in that a cylinder surrounding the screw has an axially segmented structure.

Single-screw plasticizing machine according to one of the preceding claims, characterized in that the screw has a temperature control.

Single-screw plastifying machine according to one of the preceding claims, characterized in that the screw has a worm shaft with a recess which has a back pressure bearing or is adapted to receive.

Single-screw plasticizing machine according to one of the preceding claims, characterized in that the screw has a worm shaft, which is designed as a worm mandrel.

Single-screw plasticizing machine according to one of claims 1 to 18, characterized in that the machine is a plastic injection molding machine

Single-screw plasticizing machine according to claim 19, characterized in that it comprises a central injection piston.

Single-screw plasticizing machine for conveying, melting and homogenizing starting material, especially single-screw extruder for a thermoplastic polymer, the single-screw plasticizing machine having a screw with a screw diameter D and an effective length L, and the single-screw plasticizing machine being arranged to rotate the worm in operation by means of a controller at a peripheral speed, so that in operation, taking into account a number of gears, an enforced mass flow rh of the starting material results, in particular single-screwing according to one of the preceding claims, characterized in that the effective length L of 200 mm to 2000 mm and that in operation the ratio between the mass flow rh and the effective length L is between 0.25 kg / h / mm and 1.4 kg / h / mm, in particular at least 0.5 kg / h / mm.

Process for plasticising a starting material, in particular a thermoplastic polymer, by means of a single-screw plasticizing machine according to one of the preceding claims, in particular in the form of a single-screw extruder, the control preferably operating the screw at a peripheral speed of less than 1.5 m / s, in particular below 1.0 m / s.

Set of a series, comprising two single-screw plasticizing machines according to one of claims 1 to 21, wherein both have the same ratio between the mass flow rh and the effective length L with a maximum deviation of 10%.