DE102011002279A1 - Method and device for producing a rubber component - Google Patents

Abstract

The invention relates to a method and a device for producing a tire component, in which an intermediate mixture is prepared in a kneader (1) in a temperature-homogeneous manner and then fed to an extrusion unit (2). This means that there is no need for a rolling mill and the necessary preparation can be carried out in a single step.

Description

The invention relates to a process for the preparation of a rubber component, for example a tire component or a tread, in which an intermediate mixture is mixed in one process step and subsequently fed to an extrusion unit, in particular as a discharge extruder. Furthermore, the invention relates to a device for carrying out the method.

Modern processes for the production of rubber compounds for tire production use rolling mills in conjunction with internal mixers in which the mixing components rubber, filler, plasticizer and chemicals are entered manually or fully automatically. The operation of the internal mixer is discontinuous due to the closed mixing chamber. After ready mixing of a batch, it is ejected to a rolling mill and the internal mixer is re-filled for a new cycle.

The mixture is homogenized on the rolling mill and cooled. Depending on the further processing, the forming on the roller mixture skins are removed as plates or cut into endless strips and fed to a fur cooling system. In this plant, the strips are finally cooled and treated for further storage with release agent.

Especially for mixtures with high filler contents very high temperatures in the range of 140 to 170 ° C are achieved during the mixing process. These high temperatures do not allow the addition of crosslinking chemicals such as accelerators, peroxides and vulcanizing resins due to their temperature sensitivity. For these mixtures, a second mixing stage is followed on the rolling mill or in the internal mixer. In this, temperatures above 120 ° C are avoided.

The two-stage process is used for blends with high filler levels, small amounts of plasticizer or high active carbon black. The masterbatch, after molding, is stored for several hours and allowed to cool, before being fed again to the internal mixer in the final mixing stage together with the crosslinking chemicals.

For the homogenization and shaping of the hot mixture, rolling mills are used after the internal mixer. In practice, variants are already known in which extruders have taken over the function of the rolling mill.

The internal mixer empties into a shaft that can hold several batches. This mixing buffer allows the extruder to run continuously. The tasks of the extruder consist in the absorption, cooling and shaping of the mixture. Single-screw extruders and short twin-screw extruders are used.

In tire production, a distinction is made in the further processing of the mixtures to the profile of the cold and the heat extrusion. In cold extrusion, the intermediate mixture is placed cold in the forming extruder. The Ausformextruder is usually a so-called cross-flow mixer. In the heat extrusion, the mixture must be homogenized and mixed again before forming due to high natural rubber content, and then transferred continuously in a heat in the so-called heat extruder. For this purpose one sets u. a. Porkchop extruders, which continuously preheat the intermediately stored mixture and transfer to one or more successive rolling mills. The mixture is remixed and transferred via a buffer with subsequent transfer belt to the heat extruder.

Furthermore, in the DE 40 14 408 C1 described the processing in a closed working space, in which a rotating and oscillating movement is used. Such a single-screw conveyor machine, also referred to as a co-kneader, performs a synchronous reciprocating movement in the axial direction per revolution. The kneading blades on the auger shaft work together with fixed kneading teeth or pins in the kneader housing. This shears the raw material components between the kneading blades and the kneading teeth. Due to the working principle, a good mixing effect results through optimal distribution of the starting materials.

As a disadvantage, when mixing over rolling mills, the large space requirement, the high investment costs and personnel expenses.

The invention has for its object to simplify the production of rubber components, in particular of tire components, significantly.

This object is achieved by a method according to the features of claim 1, characterized in that the intermediate mixture is processed in a kneader temperature homogeneous and then fed to the extrusion unit. This can be dispensed in a surprisingly simple manner required by the prior art rolling mill by the kneader, the required preparation in one performs single work step. It has been shown that both the desired homogenization and the thorough mixing of the already existing mixture can be realized in an efficient manner in the kneader, contrary to the prejudices prevailing in the art. For the purposes of the present invention, the term mixture is intended to include a treatment for the targeted optimization of the property profiles both with and without the admixture of additives, such as, for example, fillers or additives.

The mixing section could be used to increase the pressure to transfer the mixture to the extrusion unit with a relative overpressure. In contrast, it is particularly advantageous if the mixture is transferred after a pressure equalization with respect to the atmosphere of the kneader to the extrusion unit by the handover of the kneader is open to the extrusion unit. In this way, volatile components can escape, so that an impairment of the molding process is avoided. The pressure compensation can take place both in the region of the mixing section and in a transfer area.

In another, also particularly promising modification of the flow rate in the kneader is kept substantially constant by the axial position and / or the angular position of a screw conveyor of the kneader are detected and the rotational speed is adjusted accordingly, ie varies cyclically in one revolution of the screw conveyor , Thus, the flow rate and the exiting flow is kept constant in order to compensate for or counteract the pulsation caused by the screw conveyor. In this way, a constant throughput can be achieved without an additional material buffer.

Furthermore, the object of the invention is still achieved with a device for producing a rubber component, in particular a truck tread, with a mixing section for an intermediately stored mixture and with a particular designed as Austragsextruder extrusion unit in that the mixing section a kneader with a rotationally movable and oscillating drivable screw conveyor having. As a result, a homogeneous mixing of the temperature is achieved, which makes a customary in the prior art extruder as well as a downstream of the extruder mill dispensable. In this way, both the space required and the control effort as well as the manufacturing costs and the staff can be reduced.

In this case, the kneader according to the invention can be connected in an open process chain by means of per se known conveying means with the extrusion unit. In contrast, it is particularly advantageous if the kneader is connected to the extrusion unit to form a structural unit in order to realize particularly compact dimensions and to further reduce the control effort.

A particularly advantageous embodiment of the invention is also achieved in that the mixing section has the kneader and a volumetric pump arranged in the conveying direction for pressure stabilization, so as to be independent of the possible pressure increase by the kneader a constant pressure in the transfer of the mixture to the extrusion unit sure.

It proves to be particularly practical if the kneader has a feed roll which is arranged in particular in the feed area of the feed screw and which permits continuous feeding, in particular when the mixture is supplied in the form of hides. This can be driven by a drive common to the kneader.

Furthermore, it is alternatively possible to feed the mixture in granulated form in the kneader. Here it is possible to add even powdered additives already in the feeder.

For this purpose, an embodiment of the kneader is preferably also suitable, in which the draw-in area has a shaping acting as a draw-in curve for deflecting the supplied component in the direction of the axis of rotation of its screw conveyor, so as to achieve optimized feeding of the mixture. The mixing flow is thus already impressed by the pull-in curve a movement component with a direction of action parallel to the auger axis.

This movement of the feed roller can take place parallel to the longitudinal axis of the kneader according to another, particularly useful embodiment according to the oscillating movement of the kneader, so that the feed roller, the movement of the screw conveyor, in particular also by means of a common drive is moved. An undesirable accumulation of material in the end regions of the feed roller due to the oscillating movement of the kneader can be counteracted so effectively.

Another, also particularly useful modification is achieved in that the kneader has a section intended for pressure increase, which is free of shear pins engaging in the kneading blades, so as to achieve a controlled pressure build-up in this section. On a downstream pump can be dispensed with and the production cost can be further reduced.

For this purpose, it has already proved to be particularly useful when the section with the screw conveyor rotatably and axially movably connected. By a corresponding axial bearing the transmission of the oscillating screw conveyor motion is avoided on this section. By the storage of this section as a single degree of freedom allows a rotational movement, a transmission of the linear movement of the screw conveyor is avoided on the connected thereto only rotatably connected by a sliding guide portion. An additional drive for the section can therefore be dispensed with.

In another, likewise particularly practical modification, the kneader and / or a transfer area connecting the kneader to the extrusion aggregate has a plurality of degassing openings. This ensures a defined degassing, by which the volatile constituents can be fed to a targeted after-treatment.

Furthermore, it is particularly useful if the kneader has a feed for a heat transfer fluid, so as to achieve a temperature compensation within the mixture. In particular, this liquid can be supplied to influence the mixing temperature in the desired manner on their evaporation.

Another possibility for controlling the temperature is realized in that the screw conveyor at least partially encloses a cavity, which is connected to recesses on the circumference of the screw conveyor and the supply of a heat transfer fluid is used. For example, by feeding the screw conveyor through the cavity into the hollow kneading blades, the temperature can be effectively adjusted to the mixture without the direct action of a fluid.

In another advantageous modification, the kneader has a drive shaft, which is axially guided by a hollow shaft of a transmission of the extrusion unit, so as to secure by the design of the device as a piggyback unit advantageous space conditions and accordingly to reduce the space requirement.

Preferably, the kneader in the axial direction of the screw conveyor can be assigned a lateral feed for other components so as to be able to supply the mixture, if necessary, further components. In this case, the feed is not limited to fluids, but is also suitable, for example, for powdered rubber, so that optionally can be dispensed with an internal mixer.

Further, according to a preferred variant, the mixing section following the kneader in the process direction on a variable-temperature section, in which the mixture is formed into a tube with variably adjustable wall thickness and then slit and folded. The fact that the tube is slotted for degassing the air in the core and opened to the rubber skin, the entrapped by the axial movement of the kneader shaft in the core of each solid profile at least for production start air entrapment with unfolded tube to the atmosphere.

The invention allows for various embodiments. To further clarify its basic principle, one of them is shown in the drawing and will be described below. This shows in

1 the procedure according to the prior art;

2 a schematic diagram of a method according to the invention;

3 a variant of the method according to the invention also in a schematic representation;

4 a kneader intended for producing a rubber component in a partially sectioned plan view;

5 the in 4 shown kneader in a perspective view.

1 shows schematically a process known in the prior art process in tire production for further processing of the mixtures to the profile by heat extrusion. In the heat extrusion, the mixture must be homogenized and mixed again before forming due to high natural rubber content, and then transferred continuously in a heat in the so-called heat extruder. For this purpose, a so-called Porkchop extruder 11 used, which continuously preheats the intermediately stored mixture and to one or more successive rolling mills 12 . 13 passes. The mixture is mixed and passed through a buffer with subsequent transfer belt to a running as a heat extruder extrusion unit 2 to hand over.

2 shows a schematic representation of the method according to the invention in a first variant, in which the intermediately stored mixture in a kneader 1 temperature homogenously processed and then the extrusion unit 2 is supplied. As can be seen, can be dispensed with a rolling mill, because the kneader 1 Perform the required treatment in a single step. The feeding of the mixture to the extrusion unit 2 takes place by means of a known conveyor belt 3 so as to achieve at the same time a pressure equalization of the mixture to the atmosphere.

In contrast, can be dispensed with such a conveyor belt when the kneader 1 according to a in 3 shown variant such with the extrusion unit 2 connected to that, the processed, from the kneader 1 leaving mixture the extrusion unit 2 is fed directly by the outlet of the kneader 1 to the extrusion unit 2 flanged and the kneader 1 with the extrusion unit 2 is connected to a unit. Here, the mixture with an overpressure to the extrusion unit 2 to hand over.

Complementary shows 4 a kneader dedicated to the manufacture of a rubber component 1 in a partially sectioned plan view, which with a in the conveying direction behind this arranged volumetric pump 4 connected to the pressure stabilization. With the help of the pump 4 is independent of the possible pressure increase by the kneader 1 a constant pressure in the transfer of the mixture to the in the 2 and 3 shown extrusion unit 2 ensured.

In 5 is a modification of the in 4 shown kneader 1 recognizable, in which the kneader 1 a feed roller arranged in the catchment area of the screw conveyor 5 having. As a result, a continuous supply is achieved in particular in the supply of the mixture in the form of skins. Alternatively, the mixture can be kneader 1 be supplied in granulated form to add even powdered additives already in the feeder. The feed roller 5 can through one with the kneader 1 common drive 6 be driven movably. By acting in the catchment area as a pull-in curve molding 7 For deflecting the supplied component in the direction of the axis of rotation of the screw conveyor, in addition, an optimized supply of the mixture is achieved and the mixing flow is imparted with a movement component with a direction of action parallel to the screw conveyor axis.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4014408 C1 [0009]

Claims (28)

Process for producing a rubber component, in particular a tread, in which an intermediate mixture is mixed in one process step and subsequently subjected to an extrusion aggregate (in particular as a discharge extruder) ( 2 ), characterized in that the intermediately stored mixture in a kneader ( 1 ) homogenized temperature and then the extrusion unit ( 2 ) is supplied. A method according to claim 1, characterized in that the mixture after a pressure equalization with respect to the atmosphere of the kneader ( 1 ) to the extrusion unit ( 2 ). Process according to claims 1 or 2, characterized in that the mixture is mixed with an overpressure to the extrusion unit ( 2 ). Method and device according to at least one of the preceding claims, characterized in that the mass flow rate in the kneader ( 1 ) is kept substantially constant by the axial position and / or the angular position of a screw conveyor of the kneader ( 1 ) or calculated and the rotational speed of the screw conveyor is adjusted accordingly. Method according to at least one of the preceding claims, characterized in that the mass flow rate in the kneader ( 1 ) is kept substantially constant by the housing and / or the screw of the kneader ( 1 ) are driven to oscillate in the axial direction of the screw conveyor. Method according to at least one of the preceding claims, characterized in that the mass flow rate in the kneader ( 1 ) is kept substantially constant by the housing volume enclosing the mass at the outlet of the kneader ( 1 ) is changed over a form element. Device for producing a rubber component, in particular a tread, with a mixing section for an intermediate mixture and an extrusion unit (in particular as a discharge extruder) 2 ), characterized in that the mixing section is a kneader ( 1 ) With a screw conveyor, which is rotatably movable and oscillating in the axial direction of the screw driven executed. Device according to claim 7, characterized in that the kneader ( 1 ) with the extrusion unit ( 2 ) is connected to a structural unit. Apparatus according to claim 7 or 8, characterized in that the mixing section of the kneader ( 1 ) as well as in the conveying direction behind the kneader ( 1 ) arranged volumetric pump ( 4 ) for pressure stabilization. Device according to at least one of claims 9 to 10, characterized in that the kneader ( 1 ) arranged in particular in the catchment area of the screw feed roller ( 5 ) having. Apparatus according to claim 10, characterized in that the catchment area acting as a pull-in curve molding ( 7 ) for deflecting the supplied component in the direction of the axis of rotation of the screw conveyor. Apparatus according to claim 10 or 11, characterized in that the feed roller according to the oscillating movement of the kneader ( 1 ) parallel to the longitudinal axis of the kneader ( 1 ) is movable. Apparatus according to claim 12, characterized in that the feed roller ( 5 ) Variable speed to kneader shaft adjustable and or is adjustable. Device according to at least one of claims 7 to 13, characterized in that the kneader ( 1 ) has a pressure increasing portion which is free from shearing pins engaging in the screw shanks. Apparatus according to claim 14, characterized in that the section with the screw conveyor rotatably and axially movably connected and has a bearing, which counteracts the transmission of the oscillating screw conveyor movement on this section. Device according to at least one of claims 7 to 15, characterized in that the kneader ( 1 ) has a plurality of degassing openings. Device according to at least one of claims 7 to 16, characterized in that the kneader ( 1 ) and the extrusion unit ( 2 ) are connected by a transfer area equipped with degassing openings. Device according to at least one of claims 7 to 17, characterized in that the kneader ( 1 ) has a supply for a heat transfer fluid. Device according to at least one of claims 7 to 18, characterized in that the screw conveyor at least partially a cavity for the supply of a heat transfer fluid which is connected to recesses in the kneading wings. Device according to at least one of claims 7 to 19, characterized in that the kneader screw is designed as a drive shaft, which is guided axially through a hollow shaft of a transmission of the extrusion unit. Device according to at least one of claims 7 to 20, characterized in that the kneader ( 1 ) has a lateral feed for other components in the region of the axial extent of the screw conveyor. Device according to at least one of claims 7 to 21, characterized in that the mixing section following the kneader ( 1 ) in the process direction has a variable-temperature section, in which the mixture is formed into a tube with variably adjustable wall thickness and then slit and folded. Device according to at least one of claims 7 to 22, characterized in that the kneader ( 1 ) extruded in the process direction through a molding tool, which forms the mixture into a tube. Device according to at least one of claims 7 to 23, characterized in that a mandrel is formed as an extension of the kneader shaft. Device according to at least one of claims 7 to 24, characterized in that the tube is slotted for degassing the air in the core and opened to the rubber skin. Device according to at least one of claims 7 to 25, characterized in that the housing of the kneader ( 1 ) is designed to be driven to oscillate in the axial direction of the screw conveyor in order to increase the mass throughput in the kneader ( 1 ) to be kept substantially constant. Device according to at least one of claims 7 to 26, characterized in that the housing and the screw of the kneader ( 1 ) are designed to be driven to oscillate in the axial direction of the screw conveyor in order to increase the mass flow rate in the kneader ( 1 ) to be kept substantially constant. Device according to at least one of claims 7 to 27, characterized in that the mass flow rate in the kneader ( 1 ) is kept substantially constant by the housing volume enclosing the mass at the outlet of the kneader ( 1 ) is changed over a form element.

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