Preheating a polymer bale

Abstract

The invention relates to the problem of dividing a cold rubber bale, the heating of the rubber bales to improve their division, and the associated problem of inhomogeneous heating and poor division despite heating. The invention proposes that the at least one rubber bale be heated several times in a microwave tunnel using microwaves.

Description

[0001] The invention relates to a method for mixing rubber for the production of a tread of a tire, in particular a vehicle pneumatic tire, and to the production of a tread of a tire, in particular a vehicle pneumatic tire.

[0002] In the production of tires, especially pneumatic vehicle tires, the individual components, such as the carcass and the tread, are initially manufactured separately. Various raw materials are used in the production of the tread, including large quantities of rubber—some natural, some synthetic—as well as other raw materials such as carbon black, silicon dioxide, silanes, and other additives. These raw materials are then mixed in specific proportions according to a predetermined recipe, depending on the desired properties of the tread. This mixture is then extruded into long strips to obtain the tread semi-finished product for tire manufacturing.

[0003] For the production of the tread, the rubber, whether natural rubber or other types, is usually delivered in large bales. These must then be added to the other raw materials according to the proportions specified in the desired recipe. For this, the rubber must first be processed, for example, by cutting it, so that the correct quantity can be added to the mixture in the correct proportions, along with the other raw materials. Such processing of the rubber before mixing is necessary because the rubber bale is delivered cold and is therefore very hard. This is due to the fact that the rubber bale is stored outdoors or that long transport routes in cold conditions are involved.

[0004] It is now difficult to portion the hard rubber in such a way that the correct amount of rubber can be added to the mixture.

[0005] For this reason, it is possible to heat the rubber using microwave systems. Microwave tunnels are used for this purpose, into which the cold rubber bale is inserted on one side and, after being heated by the microwaves, removed on the other side. The aim is to make the rubber less hard and thus easier to portion into the correct quantity. However, a problem with this technology is that the rubber bales heated in a microwave tunnel do not have a homogeneous temperature, and some parts of the bale are too hot, which can even lead to fires. Portioning must also take place promptly after heating, otherwise the benefit of the heating process is lost. Mixing with the other ingredients usually follows as soon as possible.

[0006] The object of the invention is therefore to provide a less hard rubber ball for portioning and mixing with the other raw materials of the tread for the production of the tread, in which, however, the heating is more homogeneous or a more homogeneous temperature is present.

[0007] This problem is solved by a method for mixing raw materials for a tire tread as described below, particularly according to claim 1. The problem is also solved by a method for producing a tread as a semi-finished product in the form of a strip as described below, particularly according to claim 8. The problem is further solved by a microwave device as described below, particularly according to claim 9. Further solutions, and in particular advantageous embodiments of the aforementioned solutions, are presented in the further claims and in the following description.

[0008] The core of the invention lies initially in the fact that at least one ball of rubber is inserted into the microwave tunnel several times.

[0009] The problem is solved by a process for mixing raw materials for the tread of a tire, particularly a pneumatic vehicle tire. This mixture can then be used to manufacture, especially by extrusion, the tire tread, or at least to produce a tread strip semi-finished product in the form of a strip, particularly an endless one. Such a strip is significantly longer than required for the tire, and multiple tire treads can be produced from a single strip, hence the term "endless strip."

[0010] According to the invention, one of the raw materials for the tread is rubber. In particular, the rubber can be natural rubber or synthetic rubber, such as butadiene rubber. Advantageously, another raw material can be a different type of rubber. Advantageously, one of the raw materials can be carbon black, silica, carbon, or chalk. The present invention deals solely with the raw material of rubber, which is a polymer and exhibits the aforementioned problems in further processing.

[0011] According to the invention, the raw material rubber is initially available in bales. Advantageously, a bale is understood to be a conglomerate of rubber as the starting material, having a volume of at least 0.75 m³. 3 and / or a maximum of 1.25m 3 , especially approximately 1m 3 , especially from 1m 3The invention features a recipe for the tread strip, based on specific proportions of the different raw materials, including the proportion of rubber present in bales. Accordingly, the quantities of the raw materials are predetermined, and the mixing is carried out based on these predetermined quantities.

[0012] According to the invention, in the process at least one bale of rubber, as one of the raw materials for the mixture, is first pretreated in a microwave tunnel. This pretreatment comprises at least one pretreatment of the at least one bale of rubber by heating using microwaves, which are generated, in particular, in a controllable manner, in the microwave tunnel.

[0013] The invention is now characterized in that the at least one ball of rubber is heated several times by means of microwaves in the microwave tunnel.

[0014] Furthermore, according to the invention, the at least one heated ball of rubber is then divided into the predetermined quantity, in particular by cutting the at least one heated ball. According to the invention, the divided quantity of rubber is then mixed with the predetermined quantities of the other raw materials.

[0015] By heating the bale multiple times, each heating phase can be shorter or less intense, and by heating it multiple times, it can be achieved that the bale is heated more homogeneously, and it can also be achieved that the bale is not heated too much during each heating phase.

[0016] Advantageously, at least two bales of rubber are heated using microwaves in the microwave tunnel, with each bale being heated several times alternately using microwaves in the microwave tunnel. Advantageously, a plurality of bales of rubber are heated using microwaves in the microwave tunnel, with each bale being heated several times alternately using microwaves in the microwave tunnel. Advantageously, exactly two bales of rubber are heated using microwaves in the microwave tunnel, with each bale being heated several times alternately using microwaves in the microwave tunnel.

[0017] Advantageously, the at least two rubber bales are inserted into and removed from the microwave tunnel from opposite sides. This allows one of the at least two rubber bales to be inserted into and removed from one side of the microwave tunnel, while a second bale can be inserted into and removed from another side, for example, the side opposite the first.

[0018] Advantageously, the at least one bale, in particular each bale, is heated at least three times, in particular at least four times, in particular at least ten times, and / or at most ten times using microwaves in the microwave tunnel.

[0019] Advantageously, at least one bale, in particular each bale, is temporarily stored outside the microwave tunnel between heating, in particular for at least one minute, in particular for at least five minutes, and / or for a maximum of sixty minutes, in particular for a maximum of thirty minutes.

[0020] Advantageously, at least one bale, in particular each one, is heated for at least five minutes and / or a maximum of thirty minutes and / or at a minimum of 500 MHz and / or a maximum of 25000 MHz using microwaves in the microwave tunnel.

[0021] In particular, the duration of heating and / or the frequency of heating is selected based on the material of the bale and / or the input temperature.

[0022] Advantageously, the at least one bale, in particular each bale, is first heated by microwaves in the microwave tunnel at a first power level between 500 MHz and 10000 MHz, in particular for at least five minutes and / or a maximum of thirty minutes, and then at a second power level, which is at least 110%, in particular 150%, in particular 200%, of the first power level, in particular a second power level between 1000 MHz and 25000 MHz, in particular for at least five minutes and / or a maximum of thirty minutes.

[0023] Advantageously, at least one bale, in particular each bale, is temporarily stored outside the microwave tunnel for at least five minutes and / or a maximum of 30 minutes between heating with the first power and with the second power.

[0024] Advantageously, the temperature of each bale is measured after heating with microwaves in the microwave tunnel and / or the moisture content of each bale is measured after heating with microwaves in the microwave tunnel, wherein, in particular, based on the measured temperature and / or moisture content of a bale, a duration of the bale in the subsequent heating phase with microwaves in the microwave tunnel is selected and / or, in particular, based on the measured temperature and / or moisture content of a bale, a power output of the subsequent heating phase with microwaves in the microwave tunnel for the bale is selected and / or a duration of intermediate storage before the subsequent heating phase with microwaves in the microwave tunnel is selected.

[0025] Advantageously, the at least one bale, in particular each bale according to claim 2, is heated at least once more with a further power using microwaves in the microwave tunnel after heating with the second power, wherein the further power, in particular the further powers, of the at least one further heating is each at least 10% higher than the preceding power.

[0026] The problem is also solved by a method for manufacturing a tread strip, wherein the tread strip is a semi-finished tool in the form of a strip, particularly an endless strip. Such a strip is significantly longer than required for the tire, and several tread strips of a tire are produced from a single strip, hence the term "endless strip." According to the invention, a mixture is first produced, and then this mixture is extruded into a tread strip semi-finished tool.

[0027] The methods according to the invention enable a significantly more homogeneous temperature to be achieved in the rubber bale, thereby facilitating better division of the rubber into a specific quantity. Furthermore, the implementation can be easily integrated into existing production processes, so that the improvement in homogeneity and the improvement in divisibility can be achieved without negatively impacting cycle times.

[0028] The problem is also solved by a microwave device for heating a bale of rubber, in particular a bale as previously described. In particular, the inventive process step of heating the aforementioned mixing process according to the invention can be carried out using the microwave device. The microwave device comprises a microwave with at least two inlets, in particular in the form of an opening in the microwave. Furthermore, at least one, in particular exactly one, conveyor belt is assigned to each of the inlets, in particular arranged at the inlets of the microwave. Each conveyor belt is configured to move a bale stored on the conveyor belt through the inlet into the microwave and to move it out of the microwave through the inlet to an intermediate storage position outside the microwave. The conveyor belt is thus, for example,The conveyor belt is not only designed to move in one direction, but also in the opposite direction. Previously, only a conveyor belt capable of moving in one direction was provided. Therefore, in the prior art, the microwave oven has only one inlet and one outlet, with the conveyor belt at the inlet solely designed to move a bale through the inlet into the microwave oven, and the conveyor belt at the outlet solely designed to convey the bale out of the microwave oven on the side opposite the inlet.

[0029] Advantageously, the microwave is configured to direct microwave radiation, in particular variable and / or adjustable, between 500 MHz and 25000 MHz, onto the bale inside the microwave, and / or the microwave device has at least one temperature sensor, which is in particular configured to measure the temperature of a bale in the intermediate storage position, and / or the microwave device has at least one moisture sensor, which is in particular configured to measure the moisture of a bale in the intermediate storage position.

[0030] Further advantageous embodiments will become apparent from the following description of an exemplary embodiment with reference to the accompanying schematic figures. These show: Fig. 1 a microwave device and a method according to the prior art and Fig. 2 a microwave device according to the invention and part of the method according to the invention.

[0031] The exemplary embodiments are depicted in sketch form in the figures, so that individual features of the invention are particularly easy and clear to see. The proportions do not need to be realistically represented. Identical elements in the figures are labelled with the same reference numerals.

[0032] In the Fig. Figure 1 is a microwave device 1 as known from the prior art. The microwave device 1 comprises a microwave chamber 2, which includes means 4 by means of which material located inside the microwave chamber can be irradiated with microwaves. For this purpose, the material can be conveyed into the interior of the microwave chamber 2 via an inlet opening 5 of the microwave chamber 2. After irradiation with the microwaves, the material can then be conveyed out of the interior of the microwave chamber 2 through an outlet opening 6 of the microwave chamber 2. Such material can be a bale 3, which rests on a conveyor belt 7 running through the microwave chamber 2 in a single direction and is thus conveyed into the interior of the microwave chamber 2, heated there by the microwaves, and then conveyed out the other side, the outlet side 6, again on the conveyor belt 7.

[0033] The microwave device 1 according to the invention is now in Fig.Figure 2 illustrates this. It is essential that at least two conveyor belts are present, namely a first conveyor belt 7 and a second conveyor belt 8. It is further essential that these conveyor belts 7 and 8 can transport material in both directions. Finally, it is essential that the microwave oven 2 has at least two inlet openings 5 ​​and 6, namely one inlet opening 5 and 6 for each conveyor belt 7 and 8.This allows a first bale 3, located on the first conveyor belt 7, to be conveyed into the interior of the microwave 2 through the first inlet opening 5 and, after initial heating, conveyed back out through the first inlet opening 5 to an intermediate storage position outside the microwave 2. Subsequently, a second bale 3, located on the second conveyor belt 8, is conveyed into the interior of the microwave 2 through the second inlet opening 6 and, after initial heating, is conveyed back out through the second inlet opening 6 to an intermediate storage position outside the microwave 2. Following this, the first bale 3, located on the first conveyor belt 7, can once again be conveyed into the microwave 2.

[0034] By heating the bales multiple times, each heating phase can be shorter or less intense. This also ensures that the bales are heated more homogeneously and that they are not overheated during each heating phase. In particular, intermediate storage and repeated heating allow the bales to reach a homogeneous target temperature between 25°C and 50°C.

Claims

[1] Method for mixing raw materials of a tire tread to produce a mixture, wherein one of the raw materials is rubber and is available as a raw material in the form of a bale, wherein the mixing of the raw materials is carried out according to predetermined quantities of the raw materials in the mixture, wherein the quantities are predetermined on the basis of a selected recipe of the mixture, wherein at least one bale of rubber is pretreated in a microwave tunnel, namely by heating by means of microwaves, the at least one heated bale of rubber is divided into the predetermined quantity and then the divided quantity of rubber is mixed with the predetermined quantities of the other raw materials, characterized by that at least one bale of rubber is heated several times using microwaves in the microwave tunnel. [2] Procedure according to the preceding claim, characterized by, that at least two, in particular a plurality of, in particular exactly two, bales of rubber are heated by means of microwaves in the microwave tunnel, wherein each of the bales is alternately heated several times by means of microwaves in the microwave tunnel. [3] Method according to any of the preceding claims, characterized by , that the at least one bale, in particular each bale of the bales according to claim 2, is heated at least three times, in particular at least four times, in particular at least ten times, and / or at most ten times by means of microwaves in the microwave tunnel and in particular is temporarily stored between heating outside the microwave tunnel for at least one minute, in particular at least five minutes, and at most sixty minutes, in particular at most thirty minutes. [4] Method according to any of the preceding claims, characterized by, that the at least one bale, in particular each bale according to claim 2, is heated for at least five minutes and / or a maximum of thirty minutes and / or at a minimum of 500 MHz and / or a maximum of 25000 MHz by means of microwaves in the microwave tunnel. [5] Method according to any of the preceding claims, characterized by, that the at least one bale, in particular each bale according to claim 2, is first heated by microwaves in the microwave tunnel at a first power level between 500 MHz and 10000 MHz, in particular for at least five minutes and / or a maximum of thirty minutes, and then with a second power level that is at least 110%, in particular 150%, in particular 200%, of the first power level, in particular a second power level between 1000 MHz and 25000 MHz, in particular for at least five minutes and / or a maximum of thirty minutes, and in particular is temporarily stored outside the microwave tunnel between heating with the first power level and with the second power level for at least five minutes and / or a maximum of thirty minutes. [6] Method according to the preceding claim 5, characterized by, that the at least one bale, in particular each bale according to claim 2, is heated at least once more with a further power using microwaves in the microwave tunnel after heating with the second power, wherein the further power, in particular the further powers, of the at least one further heating is each at least 10% higher than the preceding power. [7] Method according to any of the preceding claims, characterized by, that the temperature of each bale is measured after heating by means of microwaves in the microwave tunnel and / or the moisture content of each bale is measured after heating by means of microwaves in the microwave tunnel, wherein, in particular, based on the measured temperature and / or moisture content of a bale, a duration of the bale in the subsequent heating phase by means of microwaves in the microwave tunnel is selected and / or, in particular, based on the measured temperature and / or moisture content of a bale, a power of the subsequent heating phase by means of microwaves in the microwave tunnel for the bale is selected and / or a duration of intermediate storage before the subsequent heating phase by means of microwaves in the microwave tunnel is selected. [8] Method for producing a tread strip as a semi-tool in the form of a strip, wherein a mixture produced according to one of the preceding claims is extruded to form a tread strip semi-tool in the form of a strip. [9] Microwave device for heating a bale of rubber, wherein the microwave device has a microwave with at least two inputs, wherein the inputs are also configured as outputs and at least one conveyor belt is arranged at each input, wherein each conveyor belt is configured to move a bale stored on the conveyor belt through the input into the microwave and to move it out of the microwave through the input to an intermediate storage position outside the microwave. [10] Microwave device according to claim 9, wherein the microwave is configured to direct microwave radiation, in particular variable and / or adjustable, between 500 MHz and 25000 MHz, onto the bale within the microwave, and / or wherein the microwave device has at least one temperature sensor, in particular configured to measure the temperature of a bale in the intermediate storage position, and / or the microwave device has at least one moisture sensor, in particular configured to measure the moisture of a bale in the intermediate storage position.

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