DE10130759A1 - Plastifier system comprises a worm which rotates in a cylinder, a melt zone section and a homogenising zone section - Google Patents

Abstract

A plastifier system comprises a worm (30,40) which can rotate in a cylinder (11), a melt zone section (23) and a homogenisation zone section (24). The latter has a barrier cutting section (65) connection to the worm. The cylinder inner wall (50) has a longitudinally running spiral groove (52). The width and/or depth of the groove varies in the longitudinal direction. The cylinder is a one piece unit, and the plastic material cutting section has primary and secondary channels.

Description

The present invention relates to a plasticizing system a snail, preferably a barrier snail, and one Cylinder in which the screw is rotatably held and closed at least one melting zone longitudinal section and a homogeneity nisierzonen-longitudinal section, wherein in the Homogeni sierzonen longitudinal section to the screw a barrier shear part or connects a Maddock shear part. The invention relates also a mixing system for liquids, preferably art  melt the fabric, with a barrier shear part or a Mad dock shear part, which is rotatably held in a cylinder. The invention further relates to a method for processing of plastic material with a single screw plasticizer system, preferably a single screw extruder or one Screw piston injection molding machine, the one in a cylinder rotatable screw, preferably a barrier screw, and an adjoining barrier shear member or Maddock shear part, wherein the plasticizing system Melting zone longitudinal section and a homogenizing zone Has longitudinal section and the shear part a first and egg has a second channel.

Plasticizing systems of the aforementioned type, in particular a screw extruders, for example in "The single screw Extruder, basics and system optimization "VDI-Verlag GmbH, Düsseldorf 1997 described. Because of the increasing lei The ability of single-screw extruders to do this is required Lich, so-called mixed and / or shear parts in extruder cutting ken to integrate. These mixed and / or shear parts (hereinafter referred to as mixing elements) follow the Melting zone or plasticizing zone and ensure a Homogenization of the melt supplied. Because of the high The performance of current single-screw extruders can achieve this homogeneity This is because the extruder screw is no longer used alone to be achieved.

Plasticizing systems, in particular single-screw plasticizing systems are also used for so-called screw piston injection molding machines used, the problems of plasticizing and mixing are essentially the same. In contrast to  continuously operated single screw extruder is at Screw piston injection molding machines with rotating screw plasticizes the polymer, the screw against the för the direction is axially shifted. Then at most stationary screw by rapid axial displacement of the acting as a piston, the melt produced in a ge closed injection mold. This cycle will continuously repeated, parallel to the cooling of the injection molding some of the next plasticizing phase can already take place. The For the sake of simplicity, however, only the Single-screw extruder referred to.

Single-screw extruders are also used in the preparation of be already liquid polymer melts used. Here, the Melt different additives (additives) added and mixed homogeneously, with the additives the egg improve properties of the polymer in the desired manner.

Different single screw mixing systems and their functions references are, for example, in the above-mentioned publication chung on pages 279 to 307. As a mixed or Shear parts are nowadays, for example, barrier Mixing elements are used, which have the melt in cylinders mix smooth inner surfaces. The barrier mixing element is based on the same principle as the so-called barrier screw builds so that at least two channels are formed, one the two towards one end (inlet channel) and the other towards the are open at the other end (outlet channel). More mixing systems me who do not use a barrier mixing element and where the um giving cylinder has a profiled inner surface are for example the "Transfer Mix" from Tröster to Plasti  fection and mixing of rubber and other highly viscous Melting, the "3-D mixer" from Barmag for mixing Polymer melts, the company's "cavity transfer mixer" (CDM) Rapra for mixing polymer melts or the "Staromix" of Company maturing houses for mixing polymer melts.

One disadvantage of the aforementioned mixing systems is one exception of the Transfermix system in that it has no self-funding Afford. As a result, they have no pressure build-up capacity, i. H. high pressure losses with high throughputs and / or with ver The result is high-tenacity melts. Furthermore, the Manufacturing costs of these mixing elements are relatively high.

Against this background, the object of the invention is the plasticizing system of the aforementioned type and the mixing system of the aforementioned type so that a throughput increase hung, a decrease in melt temperature, an improvement tion of the pressure build-up capacity and an improvement of the Ver workability of wall-sliding melts can be achieved, the Manufacturing costs are to be kept low.

The object underlying the invention is in the Pla Stification system of the aforementioned type solved in that the Cylinder on its inner wall in the area of the homogenizing zone Longitudinal section at least one groove running in the longitudinal direction having.

In other words, the object of the invention is achieved by a Combination of a barrier shear part and a cylinder dissolves the grooves in the mixing zone or in the homogenizing zone in the cylinder inner wall.  

The grooves in the inner surface of the cylinder make it in the inlet channel of the barrier-shear part entering the melt quasi time held down wisely, thereby also in small portions divided, then rinsed out of the grooves and finally with the rest of the melt in the outlet channel of the bar riere-shear part mixed. Through this additional division the melt flow is the mixing process in barrier-shear sharing greatly improved.

In addition, melting tends to slide through the wall the local "hooking" of the melt in the groove of the cylinder probably better axially conveyed, which is an improvement in pressure entails building capacity, as well as in the circumferential direction mixed much better by additional divisions.

Finally, the manufacturing effort for those in the Zylin the inside of the grooves due to the use of known method low, so that the manufacturing cost only insignificant compared to previous cylinder production costs Lich increase.

In a preferred development of the invention extends the groove is helical. Preferably, several are in the circumferential direction tion spaced grooves are provided. Beson preferably the width and / or the depth of the varies Longitudinal groove (s).

These measures have changed in practice with a view to Mixing performance of the shear part as particularly advantageous exposed. In addition, self-cleaning is improved sert.  

In a preferred development of the invention, the Snail designed as a barrier screw and has the Zylin on its inner wall in the area of the melting zone Longitudinal section at least one groove, which is parallel to Longitudinal axis or helical extends. Preferably the Groove in the melting zone longitudinal section seamlessly into the groove in the longitudinal section of the homogenizing zone.

The combination of a barrier screw and a grooved cylinder in the melting zone longitudinal section with a barrier shear part and grooved cylinder brings with a single screw plastifi ornamental system extraordinarily good results with regard to the Overall throughput. The throughput in the melting zone Longitudinal section can be increased significantly without a Ver deterioration of the homogenization of the melt.

In a preferred development, the cylinder is in one piece educated.

This measure has the advantage that the manufacturing costs ge can be lowered. Are the grooves in the melting zone longitudinal section and into one another in the longitudinal section of the homogenizing zone trained temporarily, the manufacturing costs can further be lowered.

The plasticizing system can be a single screw Extruder for the preparation of polymer melts, one screw extruder for plasticizing polymers or a Acting screw piston injection molding machine. At this point however, it should be noted that this list is not exhaustive and is complete. Of course, other sy  steme benefit from the invention, the solid material on melt, or process such a melt.

The object underlying the invention is in the mixing System of the type mentioned solved in that the Zy linder ver on an inner wall at least one in the longitudinal direction has running groove.

The mode of operation and the advantages of such a mixing system were previously related to the plasticizing system explained, so that it is not shown again can be.

The object underlying the invention is also achieved by a Process for processing plastic material, in particular solved for extruding plastic material from that before mentioned mixing system or plasticizing system according to the invention is performed. In particular, the melt flow is in the range of the homogenizing zone longitudinal section by one in the cylinder intended groove divided into partial flows.

The method according to the invention leads to the above divide so that they are not repeated can.

Further advantages and refinements of the invention result from the description and the accompanying drawing.

It is understood that the above and the following standing features to be explained not only in each specified combination, but also in other combinations  or can be used alone, without the scope of to leave the present invention.

The invention will now be described using an exemplary embodiment With reference to the drawing explained. Show:

Figure 1 is a schematic sectional view of a screw plasticizing extruder.

Figs. 2a and 2b show two different shear sub-types, namely a barrier shear section (Fig. 2a) and a Mad dock shear part (Fig. 2b);

Fig. 3a shows a schematic cross-sectional view of the extruder in the region of Aufschmelzzonen- and Homogenisierzonen longitudinal section, and

Fig. 3b is a schematic representation of a section of the cylinder inner wall.

In Fig. 1, a single-screw plasticizing extruder for extruding a plastic material is identified by the reference numeral 10 . The single-screw plasticizing extruder 10 (hereinafter referred to simply as extruder for the sake of simplicity) comprises a tubular cylinder 11 , which in the present embodiment is composed of tubular cylinder assemblies 12 , 14 and 16 . The connection of the two units 14 and 16 takes place via a flange 17 , while the two cylinder units 12 and 14 are formed in one piece. Of course, it is also conceivable to form these two cylinder assemblies 12 , 14 in two parts and also to connect them to one another via a flange 17 .

The cylinder 11 is divided into several functional longitudinal sections, namely a filling zone 21 , to which a feed zone 22 , a melting zone 23 , a homogenizing zone 24 and finally a shaping zone 25 are connected downstream. In FIG. 1, the filling zone 21 forms the right end and the shaping zone 25 the left end of the cylinder 11 .

Within the cylinder 11 , a screw 30 is mounted coaxially to this, wherein for the sake of clarity neither the screw drive nor the screw bearing are shown. The figure shows, however, that the screw 30 is formed in the region of the melting zone 23 as a so-called barrier screw 40 . The barrier screw 40 is characterized in that, in addition to a main web 44, it also has a so-called barrier web 46 . The main web 44 forms with the following downstream barrier wall 46 has a melt channel 48 and to the upstream barrier web 46 following a solids channel 49th The figure also shows that the width of the solids channel 49 to the downstream end of the Barriereschnec ke 40 decreases, while that of the melt channel 48 increases. The special functioning of the barrier screw 40 is based in particular on the fact that the gap between the cylinder inner wall and the main web 44 is smaller than the gap between the barrier screw 40 and the cylinder inner wall. This can be seen particularly well in Fig. 3a, in which a barrier screw with two pairs of channels is shown in cross section. Are clearly visible in this Fig. 3a, the two diametrically opposed main webs 44 and also the two diametrically opposite lands 46 barrier. In Fig. 3a, the gap between the main web 44 and an inner wall 50 of the cylinder 11 with δ _S and the gap between the barrier web 46 and the inner wall 50 is marked with δ _Ü . In the case of barrier screws, δ _{S is} always smaller than δ _Ü . As already mentioned, seen in the direction of rotation between a barrier web 46 and a main web 44, the solids channel 49 and between a main web 44 and a subsequent barrier web 46 of the Schmelzeka channel 48 is formed. In the two-channel embodiment shown here, two such solid channels 49 and two melt channels 48 are provided. With regard to the func- ,

The screw 30 itself extends from the screw shaft and from the filling zone 21 to the end of the homogenizing zone 24 . An opening 27 is provided in the assembly 12 of the cylinder 11 in the area of the filling zone 21 , which enables a connection from the outside into the interior of the cylinder 11 . In order to facilitate the supply of starting material, a funnel 28 is attached to the opening 27 .

Fig. 1 also shows that the assembly 12 has 11 grooves on the inner wall of the cylinder, two of these nu shown in Fig. 1 and marked with the reference numeral 33 are marked. Usually, a plurality of axially running ver, evenly spaced grooves 33 in the circumferential direction are provided. The depth of the grooves 33 is maximum in the loading zone 21 and generally decreases evenly in the conveying direction. At the end of the feed zone 22 , the groove depth is minimal.

The cylinder 11 is surrounded in the feed zone 22 by ring-shaped or helical cooling channels 35 , with neither the coolant inlet nor the coolant outlet being shown in the figure for the sake of clarity. In the simplest case, the cooling can be done by free convection of the surrounding air.

The tubular cylinder assembly 14 is surrounded by schematically represented heating elements 38 , the heating elements 38 extending over the entire length of this unit, so that both the melting zone 23 and the Homogenisierzo ne 24 can be heated via such heating elements 38 . In the present embodiment, a plurality of heating elements 38 are arranged one behind the other in the longitudinal direction. Another Heizele element 38 also surrounds the third assembly 16 in the region of the molding zone 25 . The heating elements can also be provided with cooling elements in order to dissipate any excess frictional heat which may arise at higher screw speeds.

The Fig. 1 can be further appreciated that the screw 30 has 24 a mixing and shearing element 60 in the region of the homogenizing. This mixing and shearing element 60 is divided into two shearing parts 62 , 64 and a mixing part 66 in the exemplary embodiment lying before, which are arranged on the screw 30 in the longitudinal direction one behind the other. The two shear parts 62 , 64 are so-called barrier shear parts 65 , while the mixing part 66 is designed as a diamond mixing part 67 .

Both barrier-shear parts 65 are constructed similarly and, like the barrier screw 40 described above, comprise a main web 71 and a downstream barrier web 73 , which are clearly shown in FIG. 2a. The main ridge 71 forms with the upstream barrier wall 73 an inlet channel 75 and centering ridge with the downstream bar 73 an outlet channel 77th The inlet channel 75 is open to the upstream end of the mixing and shearing element 60 , while the outlet channel 77 is open to the opposite end. However, the other two respective ends of the channels are closed.

As with the barrier screw 40 , the gap (δ _Ü ) between the barrier web 73 and the cylinder inner wall is also larger than that (δ _S ) between the main web 71 and the cylinder inner wall in the barrier shear part.

The general functioning of such a barrier-shear part 65 and the diamond mixing part 67 are described in the above-mentioned publication "The single-screw extruder" example on pages 125 to 131. For simplicity, the disclosure content of this section is included in the present description by reference.

In addition to the barrier shear part already described, alternatively a shear part of the "Maddock" type can also be used, which is identified in FIG. 2b by the reference number 65 '. This type of shear part works in a similar way to the barrier shear part (also referred to as Maillefer shear part), but the webs are not helical, but run in the longitudinal direction parallel to the longitudinal axis. A corresponding disclosure of the mode of operation can be found in the above-mentioned publication.

According to the invention, grooves 52 are now formed in the inner wall 50 of the cylinder 11 in the region of the homogenization zone 24 . In the present embodiment in FIG. 3a, a total of eight grooves 52 are provided, which are first in the axial direction and are evenly spaced apart in the circumferential direction of the cylinder. Furthermore, the grooves have a rectangular cross section in the example shown. However, other cross-sectional shapes are also possible. It is particularly advantageous, however, to design the grooves 52 such that there are no sharp edges or corners. By way of example only, a single groove 52 'with rounded edges is shown in FIG. 3a. Of course, it is also conceivable and advantageous, as shown instead of a plurality of axial grooves 52, one or more helical grooves 52 'in Fig. 3b schematically provided.

The grooves 52 have a width that can be approximately the same size range as the width of the main and barrier webs 44 , 71 and 46 , 73 . The depth of the grooves 52 must be selected depending on the application, care being taken that the depth in the melting zone is not too great, since otherwise the function is expected to deteriorate. Both the groove depth and the groove width can vary in the longitudinal direction of the cylinder 11 , the groove depth preferably being in the downstream end region of the melting zone 23 .

The grooves 52 in the homogenization zone 24 are flat and extend to the downstream end of the barrier-shear part 64 with essentially the same groove depth. The groove depth is then reduced in the downstream direction to zero. Grooves may also be present in the area of the mixing part 66 . The functioning of the barrier-shear part 65 in combination with the grooves 52 will be briefly explained below:
The melt generated in the melting zone 23 is conveyed into the Ho mogenisierzone. There it arrives in the inlet channel 75 of the barrier shear part 65 . Through the grooves 52 in the inner cylinder wall 50 , this melt is quasi temporarily held firmly and thereby additionally divided into small portions. Then these small portions are rinsed out again from the nu 52 and finally mixed with the rest of the melt, which was pressed through the gap between the barrier web and the inner wall into the outlet channel, in the outlet channel of the barrier shear.

This additional division of the melt flow leads to a considerable improvement in the mixing process in the homogenizing zone 24 .

The inventor has now found that, surprisingly, no deposits form in the grooves 52 (provided the groove depth is not chosen too large). Such deposits would otherwise significantly deteriorate the quality of the homogenization.

Due to the local "hooking" of the melt in the grooves 52 of the cylinder 11 in the homogenizing zone 24 , wall-melting melts are better conveyed axially with the result of an improvement in the pressure build-up capacity. Furthermore, such melts are mixed much better in the circumferential direction by additional conditions. By improving the axial conveyance of the melt, a reduction in the pressure level can also be achieved.

A more detailed general description of the function of a barrier-shear part and a diamond mixing part without grooves 52 is found in the already mentioned publication "The One Screw Extruder - Basics and System Optimization -", for example on pages 125 to 131, so that reference is made to it can be.

After all, it turns out that the combination of a barrier-shear part 65 with grooves 52 in the cylinder inner wall in the Ho mogenisierzone 24 enables a significant increase in the performance of the extruder, since the throughput can be increased by the significantly better mixing performance in the homogenizing zone.

In the end it should be pointed out again that the fiction moderate mixing system (shear part with cylinder groove) not only in the single-screw plasticizing extruder shown can, but also in other plasticizing systems, for example also with injection molding machines.

Claims (13)

1. Plasticizing system with a screw ( 30 , 40 ) and a cylinder ( 11 ) in which the screw ( 40 ) is rotatably held and which has at least one melting zone longitudinal section ( 23 ) and a homogenizing zone longitudinal section ( 24 ), wherein a barrier shear part ( 65 ) or Mad dock shear part ( 65 ') adjoins the screw ( 40 ) in the homogenizing zone longitudinal section ( 24 ), characterized in that the cylinder ( 11 ) on its inner wall ( 50 ) in the region of the Homogenizing zone longitudinal section ( 24 ) has at least one longitudinally extending groove ( 52 ). 2. Plasticizing system according to claim 1, characterized in that the groove ( 52 ) extends helically. 3. plasticizing system according to claim 1 or 2, characterized in that a plurality of circumferentially spaced grooves ( 52 ) are provided. 4. Plasticizing system according to one of the preceding claims, characterized in that the width and / or the depth of the groove (s) ( 52 ) varies in the longitudinal direction. 5. Plasticizing system according to one of the preceding claims, characterized in that the screw is designed as a barrel screw, and the cylinder ( 11 ) on its inner wall ( 50 ) in the region of the melting zone longitudinal section ( 23 ) has at least one groove ( 52 ). has, which extends parallel to the longitudinal axis or helically. 6. Plasticizing system according to claim 5, characterized in that the groove ( 52 ) in the melting zone longitudinal section ( 23 ) passes seamlessly into the groove ( 52 ) in the homogenizing zone longitudinal section ( 24 ). 7. Plasticizing system according to one of the preceding claims, characterized in that the cylinder ( 11 ) is formed in one piece. 8. Plasticizing system according to one of the preceding claims che, characterized in that it is a single screw Extruder for processing polymer melts, one screw extruder for plasticizing polymers or is a screw piston injection molding machine. 9. Mixing system for liquids, preferably plastic melts, with a barrier shear part ( 65 ) or a Maddock shear part ( 65 ') which is rotatably held in a cylinder ( 11 ), characterized in that the cylinder ( 11 ) on an inner wall ( 50 ) has at least one longitudinally extending groove ( 52 ). 10. Mixing system according to claim 9, characterized in that the groove ( 52 ) extends helically. 11. Mixing system according to claim 9 or 10, characterized in that a plurality of circumferentially spaced grooves ( 52 ) are provided. 12. Mixing system according to one of claims 9-11, characterized in that the width and / or the depth of the groove (s) ( 52 ) varies in the longitudinal direction. 13. Process for processing plastic material with egg a single-screw plasticizing system, preferably one Single screw extruder or a screw piston Injection molding machine, the one rotatable in a cylinder holding snail, preferably a barrier snail, and an adjoining barrier shear part or a Maddock shear part, wherein the plasticizing system a melting zone longitudinal section and a homogeneity Sierzonen longitudinal section and the shear part one has first and a second channel, characterized records that in the area of the homogenizing zone longitudinal section of melt flow through at least one in the cylin the intended groove is divided into partial flows.