EP0310602A1

EP0310602A1 - Method and extruder head for manufacturing extrusion products from melted plastic

Info

Publication number: EP0310602A1
Application number: EP87902520A
Authority: EP
Inventors: Kari Kirjavainen
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-04-04
Filing date: 1987-04-03
Publication date: 1989-04-12
Also published as: ES2004134A6; JPH01501925A; FI79802B; FI861457A; FI861457A0; FI79802C; CN87102620A; WO1987005856A1; KR880701172A

Abstract

Des produits d'extrusion, tels que des câbles, des conduites, des films soufflés etc. constitués de plusieurs couches d'un matériau sont généralement fabriqués en utilisant des ajutages à plusieurs couches, dans lesquels les masses du matériau sont divisées en plusieurs composantes d'écoulement, lesquelles sont ensuite à nouveau fondues, afin de produire une structure tubulaire. L'inconvénient de ce procédé est que des saillies inutiles et des rayures risquent d'apparaître à l'endroit de fusion des composantes d'écoulement. Dans le procédé d'extrusion de la présente invention, les masses en écoulement sont homogénisées par des rotors tournant entre des plaques placées les unes sur les autres, les masses de plastique étant introduites dans les espaces des rotors à partir des périphéries des rotors puis acheminées vers les bords internes circulaires des rotors d'où elles se dirigent ensuite en un écoulement tubulaire dans les ajutages. Les matériaux utilisés dans ledit procédé de fabrication, tels que des plastiques, des colorants, des générateurs de mousse, des gaz, des agents de vulcanisation et d'autres substances chimiques, sont appliqués aux périphéries des rotors et mélangés par la rotation des rotors, le résultat étant un mélange homogène et un produit tubulaire de qualité uniforme.Extrusion products, such as cables, pipes, blown films, etc. made up of several layers of a material are generally manufactured using multi-layer nozzles, in which the masses of the material are divided into several flow components, which are then melted again, in order to produce a tubular structure. The disadvantage of this method is that unnecessary protrusions and scratches may appear at the point of fusion of the flow components. In the extrusion process of the present invention, the flowing masses are homogenized by rotors rotating between plates placed on top of each other, the plastic masses being introduced into the spaces of the rotors from the peripheries of the rotors and then conveyed towards the circular internal edges of the rotors from where they then flow into a tubular flow in the nozzles. The materials used in said manufacturing process, such as plastics, dyes, foam generators, gases, vulcanizing agents and other chemical substances, are applied to the peripheries of the rotors and mixed by the rotation of the rotors, the result being a homogeneous mixture and a tubular product of uniform quality.

Description

METHOD AND EXTRUDER HEAD FOR MANUFACTURING EXTRUSION PRODUCTS FROM MELTED PLASTIC

In the manufacturing of extrusion products composed of several material layers, e.g. cables, bottles, pipes or blown films, it is necessary that the various layers have uniform thickness and that the additives contained in the plastic mass be evenly distributed in the product. The additives, which are either premixed in the moulding compounds or introduced during the extrusion phase by pumping, have a tendency - due to differences in pressure, speed and temperature gradients - to be separated from the mass and deposited on the surfaces of the mass flow channels. When the manufacturing process uses an extruder head that combines different mass flow components, the product shows stripes or seams along the lines where the components were merged. In current practice, the additives are usually pumped into mixer units incorporated in the extruder machine, the flow components being passed from the mixer units into the mass distributors.

The method of the invention employs ring-shaped rotors sandwiched between plates placed on top of each other, the mass being introduced at the rotor periphery and spread on both sides of the rotor toward the circular inner edge of the rotor, from where it proceeds in a tubular formation into the extruder nozzles. The rotors are rotated either by the kinetic energy of the moving mass or by an external force. The various components of the mass are mixed in the narrow spaces between the rotors and the plates, the mixed mass being thus directly output as a tubular flow, obviating the need for merging separate flow components. Therefore, the product is free of seams and stripes and has uniform thickness as well as a centric structure.

Figure 1 represents a cross-section of a three-layer embodiment of the extruder head of the invention.

Figure 2 represents the extruder head of figure 1 in lateral view. Figure 3 represents a rotor as used in the extruder head.

Figure 4 represents a supply channel arrangement that may be used instead of that in figure 2.

Figure 5 represents another embodiment of the extruder head of the invention in lateral view.

In figure 1, the masses are supplied via the channels 8 provided between the plates 1a-1d to the peripheries of the rotors 2a-2c. The plastic mass may be fed in by means of the presses used for melting and pressurizing the plastic materials; the other substances may be supplied e.g. by means of geared pumps. From the channel 8, the masses proceed into the input slit 9 and further into the bearing groove 10, from where they are introduced into the narrow spaces between the rotors and the plates, where the various mass components are mixed and passed further towards the central openings of the rotors. As the masses flowing from each side of the rotor are merged at the edge of the opening, they form a two-layer tubular flow, which is directed into the nozzles 3. using e.g. a device consisting of four plates 1a-1d and three rotors 2a-2c. With such a device it is possible to produce tubular structures consisting of as many as six layers, depending on the materials pumped into the supply channels. Channel 5 is used for the input of liquids and gases.

Figure 2 shows a lateral view of an extruder head as provided by the invention, comprising the plates 1, provided with vanes 6 (corresponding to the guide vanes of a radial turbine) attached to the rotor chamber surfaces, the rotors 2, provided with vanes 7 (corresponding to the runner vanes of a radial turbine) arranged in a converse angle, the channel system 4 for the supply of plastic mass and a channel 5 for the supply of additives. The rotors shown in the figure rotate freely with the flow of the plastic mass at a speed corresponding to the speed of the mass flow. The vanes 6,7 attached to the plates 1 and the rotors 2 effectively mix the masses supplied into the rotor spaces and cause them to move toward the central openings of the rotors. The drawings do not show the auxiliary devices needed for purposes like heating, mounting etc., which are irrelevant to the principle of the invention.

Figure 3 shows the structure of the rotor 2 in greater detail. The groove 11 at the rotor periphery is for the bearing balls supporting the rotor.

Figure 4 shows an alternative supply channel arrangement, in which the supply channel 12 forks into two branches directly communicating with the input slit 9 so that the supply pressure is evenly distributed over the whole periphery of the rotor. Thus, in principle, there are an infinite number of points from which the masses are introduced into the rotor space.

Figure 5 shows an embodiment of the invention in which the rotors are driven by means of gears 14, which are attached to the shafts 13. In this case the rotor periphery must be provided with a gear track instead of the groove shown in figure 3.

This solution may be applied in cases when for some reason the mass flow does not impart a sufficiently high or low speed to the rotor to achieve the desired result. This applies to cases when e.g. the temperature or the degree of treatment or mixing of the plastic mass is to be changed by changing the speed of rotation of the rotors.

The method of the invention can be used in a wide variety of applications in the plastic industry and the manufacture of extrusion products in general, to mix together different materials, whether liquid, melted, pastelike, gaseous etc., in order to produce rotationally symmetric structures consisting of several layers, the number of which may vary. It is also possible to pump in the same material via all the supply channels. In this case, the desired additives may be supplied to the desired rotors or just one side of the rotor to produce different layer structures. Further, the number of plates 1 and rotors 2 can easily be increased, since this does not involve increased requirements regarding resistance to pressure and since all the rotors can be driven by the same power transmission shafts.

The geared pumps used for supplying additives can also be integrated between the plates 1, and so can the screw extrusion devices used for supplying plastic materials. The latter devices may be very small and rotate at high speeds, since the final plasticity of the mass is achieved by means of the rotors 2 and since the supply channels can also be utilized to raise the mass temperature to the desired level. By adjusting the rotational speed of the rotors, the frictional heat can be controlled to regulate the final temperature of the mass. In this way, a system is provided in which the thermal time constants are very short and the mass is of uniform quality in the thermal respect as well.

Claims

1. Method for manufacturing tubular extrusion products from melted plastic mass by means of an extruder head, c h a r a c t e r i z e d in that liquid or composite liquid/gaseous masses are caused to flow between the surfaces of the stator plates (1) and the rotors (2) of an extruder head comprising at least two stator plates (1) and at least one rotor (2) placed between them, from the rotor periphery inwards in the direction of the radius and into the nozzles of the extruder head. whereby the flowing masses are mixed by means of guide vanes (6) attached to the stator surfaces and runner vanes (7) attached to the rotor surfaces, said vanes being arranged according to the principle of the radial turbine, the masses emerging from these mixing zones being passed on to the circular inner edge of the rotor and, in a tubular formation, further into the nozzle (3).

2. Method according to claim 1, c h a r a c t e r i z e d in that the mass flow is applied to the periphery of the rotor (2) from at least two locations placed radially symmetrically relative to the rotor.

3. Method according to claim 1 or 2, c h a r a c t e r i z e d in that the energy rotating the rotors is substantially derived from the mass flow by means of guide vanes (6) attached to the stator surfaces and runner vanes (7) attached to the rotor surfaces.

4. Method according to claim 1 or 2, c h a r a c t e r i z e d in that a substantial part of the energy required for rotating the rotors is supplied by an external force applied to the rotor peripheries from at least two points located radially symmetrically to the rotor.

5. Extruder head for applying the method of claim 1, c h a r a c t e r i z e d in that it comprises at least three stator plates (1) and two rotors (2) as well as the channels (4) for supplying liquid or composite liquid/gaseous masses to the periphery of both faces of the plates (1) and the rotors (2) and into the mixing zones between them, and that the stator surfaces are provided with guide vanes (6) and the rotor surfaces with runner vanes (7). said vanes being arranged in the mixing zone according to the prinicple of the radial turbine, and that the masses flowing out of the mixing zones are merged at the edge of the central opening of the rotor to form a tubular flow.

6. Extruder head according to claim 5. c h a r a c t e r i z e d in that the mass flow channels (4) extend to the periphery of the rotor (2) in at least two locations placed radially symmetrically relative to the rotor.

7. Extruder head according to claim 5 or 6, c h a r a c t e r i z e d in that the rotors (2) are rotated by means of at least two power transmission devices, such as gear assemblies, arranged radially symmetrically on the rotor peripheries.

8. Extruder head according to claim 5, 6 or 7, c h a r a c t e r i z e d in that it comprises as many rotors (2a-2c) as there are material layers in the product to be manufactured.