WO2017003307A1

WO2017003307A1 - Manifold for the heads of an extruder, and related method for producing plastic products using such an extruder

Info

Publication number: WO2017003307A1
Application number: PCT/PL2015/000104
Authority: WO
Inventors: Włodzimierz PIŁACIŃSKI; Janusz ROSŁOŃ
Original assignee: Secura B.C. Sp. Z O.O.
Priority date: 2015-06-29
Filing date: 2015-06-29
Publication date: 2017-01-05

Abstract

Manifold for the heads of an extruder for highly efficient plastic extrusion consisting of a homogenization module and a distribution module, through which a polymeric raw material flows successively. Also disclosed is a method for the production of plastic products using such a manifold.

Description

MANIFOLD FOR THE HEADS OF AN EXTRUDER, AND RELATED METHOD FOR

PRODUCING PLASTIC PRODUCTS USING SUCH AN EXTRUDER The present invention relates to a manifold for the heads for highly efficient plastic extrusion.

Production of plastic products through extrusion method is based on the work of a machine called an extruder. This is an apparatus in which a process of melting and homogenization of a polymer as well as its mixing with the used additives such as for example dyes or fillers takes place.

The corresponding operating head is mounted at the exit of the extruder, to which the shaft with the perpetual screw within the extruder gradually pushes the molten raw material. At this point, the melt polymer is subjected to a final molding in the head. The extruders have been used for the production of nonwoven filters for liquids for many years. In the so-called melt-blown technology, a stream of molten polypropylene is fed through the extruder to the head and there subjected to blowing by the means of a stream of hot air. The special construction of the head for forming the fibers allows the controlled production of thin polymeric fibrils, which then form a filtration layer and perpetuate its shape through interconnecting fibrils during cooling.

US200100&642 description discloses an extruder die head, which comprises an internal cylindrical mandrel and a jacket, which envelops concentrically said mandrel. Between said mandrel and jacket an annular channel is formed, that empties into a die slit. The invention also comprises at least one line, which empties into the annular channel in the area opposite the die slit nozzle and which feeds the melt. To prevent a slit between the central mandrel and the jacket enclosing said mandrel, where the polymer melt could accumulate and deposit, the mandrel is made as one piece with a flange-shaped foot. The jacket rests with its bottom face sealingly on the annular surface of the flange-shaped foot and is connected, for example fastened to the same. The annular channel extends from the peripheral surface of the mandrel to the flange-shaped foot up to the transition region. The line, feeding in a melt, empties into this transition region. In US4203715 is described a rotating joint for extrusion die with two or more thermoplastic layers of a consistent uniformity of distribution. This assembly includes a stationary manifold for receiving two or more thermoplastic streams and conveying the streams to discharge openings in the manifold, and a cylindrical conduit rotatably connected to the manifold, the conduit having intake openings aligned with discharge openings in the stationary base for receiving and conveying thermoplastic streams from the base to an extrusion die and an axial channel aligned with an axial channel in the stationary manifold for receiving and conveying one of the thermoplastic streams to the die.

JPS5970523 describes an extrusion die equipped with a sub-die, and a manifold formed between the form front wall of the mold plate and the rear wall of the side mold, which serves to close the entire envelope path for extrusion resin and the manifold connects under jacket the flow path of the resin arranged on the rear wall of the mold. In addition, there is a thin edge, on the front side of the mold, formed circularly between the fitting cavity and a covered slit for extruding the resin and adjusting screws in contact with the edge. The thickness of the resin layer can be changed by deforming the edge by adjusting screws. The thickness of the resin layer extruded in the slit can be uniformed by corresponding adjustment of the screwing degree of each of the plurality of adjusting screws.

The solution described in JPH02225021 is aimed to provide a process to easily obtain a multilayer product by a melt-blown technology, in which a plurality of disc rings are concentrically vertically mounted around the core, which ensures the connection with the final surface of the flow path generated by the gradually increasing slit which is formed by part of the barrier portion between the manifolds adjacent to each other and the portion of the flat surface of the counterpart adjacent to the disc ring, towards the inside of each ring in the flow path of the resin.

According to JPH02225021, the inlet portion of the resin are on an outer peripheral portion of each mating surface which is formed by at least two vertically mounted disc rings. Preferably, the number of openings is from 2 to 8. Special manifolds 5 are engraved on the opening side towards the flow path of the resin on one side of the flat surface of a flat mating surface. The slit which is formed by a barrier part between the manifolds adjacent to each other on a flat mating surface portion of the disc ring, is formed so as to gradually increase to the inside of the ring, so that the liquid resin gradually leaks from the manifolds ensuring the total unification of the resin at the end surface of the flow path, and after the change in flow direction into the axial direction of the nozzle, they communicate with the resin flow channel. In this case, the depth of the manifold varies according to the slit in the barrier part, so as to maintain a constant flow rate of the resin.

EP0091235 description presents a die head including an inlet for receiving a continuous supply of plastics material to be extruded and a duct distribution system for directing said material from said inlet to an extrusion outlet or outlets of the head. The duct distribution system forms a "family tree" system arranged to direct said plastics material supplied to said inlet to spaced apart locations adjacent said outlet or outlets via paths of substantially equal lengths.

The current method for producing the fibers and hence the filters was limited by the construction of the head, which was small, and allowed only the limited flow of evenly molten polymer. In certain applications, for example by the highly efficient accelerated production of the filters the production simultaneously several times larger quantities of polymer fibers is required. This requires the development of a new type of spray head supplied with a much larger stream of the molten polymer. In the course of tests a special design of a highly efficient head for the formation of polypropylene fibers has been developed, which managed to stabilize the molten polymer and hot air flows as well as temperature field. A disadvantage of this head is a continuous formation of different fibers in the . various sections of the head instead of fibers having the same characteristics. Surprisingly, it was found that beyond the production head the suitable design of a manifold connecting the extruder to the head is also necessary. Earlier no structure of the manifold has been analyzed while it was brought to a regular thermally insulated passageway. In known solutions, the polymer flowing through a typical manifold is subjected to a different secondary processes that lead to non-uniform and non-even feed of the entire length of the forming head of the fiber and further the final product.

The present invention relates to a manifold head for highly efficient plastic extrusion, which consists of a homogenization module and a distribution module, through which a polymeric material flows successively.

Preferably, the homogenization module consists of a cylindrical section with bottoms (2) and is equipped with a mixer (6) having a structure composed of an inner cylinder (7, 8) mounted to a central shaft (5) on the outer surface by the means of supports (10) with ribbon mixers (11 , 12). In a preferred embodiment the ribbon mixers (11 , 12) on the surface of the inner cylinders have opposite dead centers and are designed to rotate with the mixer to scrape the raw material to the sides of the distribution unit heated by heaters from the inside to the outside, wherein the edges of the ribbon mixers (11 , 12) reach not more than 0.5 mm from the inner surface of the cylindrical portion of the manifold body.

In a preferred embodiment of the manifold the inner cylinders are separated by an slit having a width of 5 to 35 mm.

In another preferred embodiment of the manifold the supports (10) supporting the inner cylinders on the central shaft (5) also act as mixers for the raw material flowing axially in the inner cylinders.

In another preferred embodiment of the manifold the heaters (13, 14) with temperature control are installed on the cylindrical surface of the homogenization module.

In another preferred embodiment of the manifold there is a mixer inside the homogenization module providing circular motion of the raw material together with helicoidal motion and the homogenization module is thermally insulated.

In another preferred embodiment the manifold comprises helical correction valves to further control the raw material yield in the various distribution channels.

Preferably the distribution module is in a form of a rectangular block and has at least two heaters (13, 14) on the top and bottom surfaces provided with temperature control system.

The present invention also provides a method for producing plastic products using an extruder in which the homogenizing unit is fed by molten polymer stream with the optional additives as fillers or plasticizers to completely fill the reservoir portion with the raw material, then the melt polymer is skimmed by the means of the mixer from the cylindrical surface and maintained in a stable temperature and introduced into the central tube through which the raw material flows from both outer ends towards the center and flows out the central aperture to the formation of the helicoidal circulating flow of the molten raw material inside the homogenization module, the melt polymer is mixed, and the composition and temperature is averaged using additional supports inside the central cylinders and then fresh raw material flow is introduced into the homogenization module and is mixed with the raw material circulating in the homogenization module, and then is heated and thoroughly mixed before exiting the homogenization module through a discharge connection, whereupon the so prepared material is then transported to the distribution unit which is heated in a controlled manner to provide constancy of the temperature of the distribution module block and the raw material passing through the distribution module retains its original temperature and rheological properties, whereupon the raw material is fed to the raw material end receivers installed at the outputs of the distribution module.

The manifold of a new, special construction made it possible to eliminate these undesirable effects. The manifold of the new design process occurs continuously mixing and plasticizing the raw material, which ensures the uniform physical properties of the polymer until the entry of the same polymer to the blow to the head. By the design of high performance head it is now possible to uniformly process large quantities of raw materials without the formation of defects in the products and maintaining continuous control over the quality of the filaments formed and thereby produced filters. Furthermore, a new design is suitable for use in processing other types of plastic with extruders and high operating heads.

The invention has been described in reference to the drawings, in which:

Figure 1 shows schematically a cross section of the manifold MH,

Figure 2 shows a cross section AA for MH

Figure 3 shows a cross section of the distribution module (MR) of the three sets of raw material,

Figure 4 shows a cross-sectional view along the BB unit of the distribution of the central distribution channel (4b).

The components responsible for the flow of material between two consecutive points in the system from the point of view of fluid mechanics are simply channels. Their primary function is to always provide the proper amount of fluid between the beginning and the end of the channel. In operating plastics can plasticized on the function of the flow channel are additionally imposed restrictions related to ensure the quality of the transported material. The quality includes the rheological behavior of the respective material in the liquid state. On the one hand, material requires the handling of a fluid and on the other hand ensure the quality of the product resulting after cooling to the solid state material. Problems relating to the flow channel due to the large viscosity of molten polymers, generally of high pressure processing and the variability in material depending on the state and type of polymer. The molten polymers exhibit high volatility of such an important parameter as viscosity depending on temperature, shear rate and pressure.

Flows in the channels take place generally in the range of laminar flow, and so can be analyzed.

The implementation of the flow through a transport channel from one point to another point does not pose major problems with its design. The solution is usually limited to, the channel is performed in a pressure drop greater than the acceptable from the point of view of strength of the calling flow, or the pressure applied at the entrance to the channel. It should be noted that the flow resistances are added together resulting in the need to bring the polymer under considerable pressure of up to 100 MPa often, so it is not a question that can be underestimated. The solution of this problem is made by adjusting the cross-section of the flow channel corresponding to its length.

Simple in terms of hydraulic single-channel solution, however, requires attention to ensure quality plastic, covering the following aspects:

Ensuring the maintenance of a stable temperature to assure optimal flow conditions. Not too low, because the resistance and the pressure will rise leading to a spot overheating of the material due to friction. Not too high, because the overheating of the plastic degrades, strongly associated with exposure time.

Ensuring a constant uniform flow without stopping and stasis stream. In this case, in turn, preferred channels are narrower intensifying speed, since a positive effect, inter alia, the movement of the boundary layer. The most preferred channels are circular. Any arches collapse and connections should be smooth liquid to prevent the emergence of local bottlenecks leading to degradation of the material.

The channels may also fulfill the functions associated with the processing and preparation of a polymer such as:

· To orient the flow in order to orient the internal structures of the final product.

• The hash function in order to adequately mixed material and its components. This applies in the case of addition of the components downstream of an extruder (e.g. reactive ingredients shear sensitive)

· The hash function in order to detach the boundary layer and higher homogenization material (material at the walls is warmer and a poor guide to not transmit the heat to the inside of the channel - it is noted that the wall material has different characteristics than in the middle of the stream) material flowing in the channel begins in a way to stabilize and vary depending on where in the stream of flowing.

· Calling the plastic traffic associated with the need to avoid stagnation and degradation of local materials.

Materials Distribution Channels pose further problems to solve.

Supplying an appropriate amount of material from the supply to the respective reception points, but may be an amount unequal, but the most common problem is the flow of the same amount of material through different channels of different lengths and shapes. We must also remember that the performance of the transport channels is additionally determined flow parameters - e.g. channel thinner, if the viscosity of materials in the fall, due to the shear rate, can flow more plastic than with a larger cross-section of the channel where material parameters did not change in the way so important.

The issues of molten polymer is important to ensure that the material had the necessary parameters such as temperature and viscosity.

In general, to achieve a satisfactory design solution is possible in a relatively simple systems by analyzing sections and so-called, similarity analysis parameters of the transport channels. The next step is usually experimental correction system. Because of the variability satisfactory solutions are achieved for specific: plastic, temperature and flow rate of the polymer.

If you change either of these factors developed solution can behave in a way far different and cannot meet the initial assumptions.

These remarks apply to systems that could be called a fixed flow positive.

To become independent of some of the problems mentioned above can be used in flow systems active elements aimed at independence from eg. The parameters material. These elements will, for example. Metering pump that will allow the flow of indeterminacy marginalized and ensure its stability. Such means could be a dynamic mixer plastic to prevent stagnation in the channels.

Construction of a new type of manifold is the two-module design. The first module provides averaging the composition, temperature, and consequently, viscosity of the molten polymer feed, while the second module provides a uniform distribution of polymer melt to each receiver in such a way as to ensure the required flow distribution of the raw material enters the receiving elements. The design of the module homogenisation is explained with diagrams. MH cross section of the manifold shown schematically in Figure 1. Module homogenization (MH) has a tank structure and its body 1 is made preferably cylindrical in shape. The ends 2 at the both ends of the tank MH fastened to the central part provide improved mechanical strength for the case of extremely high pressure gas in the MH. Input 3 raw material for the MH and output 4 are located on the side walls of the body MH on opposite sides. Along the axis of the body shaft 5 extends MH stirred 6. The agitator has two cylindrical parts 7 and 8 are fixedly mounted on the shaft 5. Between the two is theslit9. The stiffness of the connection cylindrical portion stirred provide support 10. On the outer surface of each of the tubular portions of the agitator are the four sections of the web 11 and the agitator 12 at intervals of 90 °. The outer edges of the strip- like agitator reach close as possible to the inner wall of the housing MH and its length has a length of the cylindrical mixer. The bands on one of the cylindrical parts have opposite twists than the web on the second cylindrical portion.MH body is heated by two band heaters 13 and 14. MH body temperature measurement is performed by a thermocouple 15, which allows control of the heaters. The MH is covered by a layer of thermal insulation not shown in Figure 1. The cross section AA for MH is shown in Figure 2. It shows the cross- section of four mixers 21-24 ribbon on the outer surface of the cylindrical portion 25. Fig.3. Is presented the cross section of the distribution module (MR) of the three receivers material. MR is formed in the block, preferably a metal with a substantially plane top and bottom surfaces. The side wall is attached to the inlet connector 31 , through which a polymeric material goes to the primary channel 32. The primary channel is hollow in a block unit MR and terminates in a cap 33. In the main channel are derived in a number of distribution channels such as the required number of sets of raw material, in Figure 3 are the three channels 34a-34c. At the outlets of the distribution channels are slots 35a-35c to mount receivers raw material. For adjustment of the amount of raw material transported the manifold is carried out by means of a valve screw jacks which are indicated 36a-36c. Figure 4. Shows a cross section BB module distribution along the central distribution channel 44b. The temperature distribution module maintains two flat electric heaters 41 and 42 adjacent to the upper and to the lower surface of the MR. The MR together with the heater is covered with an insulating layer as shown in Figure 4. Under an insulating layer are knobs 43 of the final regulatory screws to correct the amount of flowing gas.

Example of the manifold to the heads for high extrusion of plastics is described using the diagrams in Figure 1 to Figure 4.

Homogenizing module (MH) is supplied with molten polymer stream with the optional additives as fillers and plasticizers entrance (3). The receptacle portion (1) is completely filled with material. A central shaft (5) is driven by a motor with a gear which is not shown in the diagrams. Movement of the agitator (6) mounted on the shaft (5) will scrape the polymer from the cylindrical surface (1) maintained at a stable temperature by grzalkom (13 and 14) and putting it into the designed using the central tube (7, 8). Inside the raw material flows from both outer ends towards the center and leaves the central slit (9). As a result, it formed a helicoidal flow of the circulating molten raw materials in the interior of MH. The mixing, averaging composition and temperature provide further support (10) inside the central cylinder. MH stream is introduced into the fresh feedstock is mixed with the raw material circulating in the MH, heats up and thoroughly mixed before exiting MH discharge port (4). MH construction eliminates formation inside MH zones residual raw material and zones of overheating, and thus provides a very homogeneous material at the outlet of the MH. Edited material then passes into the distribution module MR (Figure 3.), Which is heated in a controlled manner to maintain the integrity block temperature MR. As a result, the raw material passing through the MR channels 2, 4a, 4b, 4c retains its original temperature and thereby their rheological properties. The diameters and length of the main channel and distribution channels are defined for the projected performance of individual receivers by calculating art hydraulic hoses.

Claims

1. A manifold for the heads for highly efficient plastic extrusion, characterized in that said manifold consists of a homogenization module and a distribution module, through which a polymeric raw material flows successively.

2. The manifold according to claim 1, wherein the homogenization module consists of a cylindrical section with bottoms (2) and is equipped with a mixer (6) having a structure composed of an inner cylinder (7, 8) mounted to a central shaft (5) by the means of supports (10) with ribbon mixers (11, 12) on the outer surface.

3. The manifold according to claim 2, wherein the ribbon mixers (11 , 12) on the surface of the inner cylinders have opposite directions and are designed to rotate with the mixer to skim the raw material at the sides of the distribution unit heated by the heaters from the center to the sides.

4. The manifold according to claim 3, wherein the edges of the ribbon mixers (11, 12) extend less than 0.5 mm from the inner surface of the cylindrical portion of the manifold body.

5. The manifold according to any of claims 1-4, wherein the inner cylinders are separated by a slit having a width of 5 to 35 mm.

6. The manifold according to any of claims 1-5, wherein the supports (10) supporting the inner cylinders on the central shaft (5) also act as mixers for the raw material flowing axially in the inner cylinders.

7. The manifold according to any of claims 1-6, wherein the heaters (13, 14) with temperature control are installed on the cylindrical surface of the homogenization module.

8. The manifold according to any of claims 1-7, wherein there is a mixer inside the homogenization module providing circular motion of the raw material together with helicoidal motion.

9. The manifold according to any of claims 1-8, wherein the homogenization module is thermally insulated.

10. The manifold according to any of claims 1-9, wherein said manifold comprises helical correction valves to further control the raw material yield in the various distribution channels.

11. The manifold according to any of claims 1-9, wherein the distribution module is in the form of a rectangular block and has at least two heaters (13, 14) provided with temperature control system on the top and bottom surfaces.

12. A method for producing plastic products using an extruder in which the homogenizing unit is fed by molten polymer flow with the optional additives as fillers or plasticizers to completely fill the reservoir portion with the raw material, then the melt polymer is skimmed by the means of the mixer from the cylindrical surface and maintained in a stable temperature and introduced into the central tube through which the raw material flows from both outer ends towards the center and flows out the central slit to the formation of the helicoidal circulating flow of the molten raw material inside the homogenization module, the melt polymer is mixed, and the composition and temperature is averaged using additional supports inside the central cylinders and then fresh raw material flow is introduced into the homogenization module and is mixed with the raw material circulating in the homogenization module, and then it is heated and thoroughly mixed before exiting the homogenization module through a discharge connection, whereupon the so prepared material is then transported to the distribution unit which is heated in a controlled manner to provide constancy of the temperature of the distribution module block and the raw material passing through the distribution module retains its original temperature and rheological properties, whereupon the raw material is fed to the raw material end receivers installed at the outputs of the distribution module.