Method for tracking process parameters in the manufacture of rubber products

Description

[0001] The invention relates to a method for tracking process parameters in the production of rubber products and an extrusion line for implementing the method. Also disclosed are an unvulcanized rubber product and a vulcanized rubber product that can be produced therefrom.

[0002] The subject matter of the invention is defined in the appended claims.

[0003] In many areas of technology, it is of great importance to carefully document the process parameters and information on the raw materials during product manufacture in order to enable sufficient quality control and / or to meet regulatory requirements. This necessity is particularly evident in the production of vehicle tires, for example pneumatic vehicle tires. Modern pneumatic vehicle tires are high-performance products that require careful quality control. Due to the high safety relevance, it is also necessary to be able to conduct efficient root cause research in the event of a product defect and, at the same time, to reliably remove other products from the market that could potentially have the same safety defect. A method and system for marking batches of soft elastomers for tire production is disclosed in patent application WO 2018 217082 A.

[0004] In the tire manufacturing sector, however, it is often perceived as a disadvantage that tracking process information in the extrusion processes used in the tire industry is often difficult, particularly due to the complex post-processing after the rubber exits the extruder. Current technology generally does not allow for a direct, sufficiently reliable correlation between the resulting product and the relevant extruder process parameters between the molding of the hot rubber mass at the extruder head and the packaging process at the end of the extrusion line.

[0005] To date, the specialist in the manufacture of rubber products for pneumatic vehicle tires, in particular in the molding of unvulcanized treads, has often had to rely on rough estimates based on his experience in order to enable at least a minimum level of documentation for the molded products.

[0006] This potentially leads to the fact that extruded products, for example unvulcanized treads or the vulcanized products subsequently manufactured from them, cannot be traced back to the exact extrusion time, or at least not sufficiently, and that the associated process information, for example regarding the extrusion parameters used, in particular the melt temperature and pressure, or the composition of the compounds used, can often not be unambiguously assigned to these products afterwards.

[0007] The problem described above is made more difficult, particularly in the production of pneumatic vehicle tires, by the fact that the so-called green products, i.e. the unvulcanized rubber products obtained at the end of a typical extrusion line, must then undergo a specific chemical crosslinking reaction in order to ultimately be combined with other components and used in a high-performance product, i.e. a pneumatic vehicle tire. This makes the labeling of corresponding unvulcanized rubber products difficult, even at the end of the extrusion line, since, for example, the application of identifying paint or stickers to the unvulcanized rubber product is problematic. Depending on the adhesive, this can potentially locally impair vulcanization and / or subsequent bonding with other tire components.

[0008] Such marking on surfaces that will be visible in the subsequent vehicle tire can also lead to undesirable discoloration in the final product, which, although not safety-relevant, could lead to lower acceptance of the product by the end customer. Likewise, for most unvulcanized rubber products, there are many arguments against mechanical marking using conventional methods, as the resulting macroscopic irregularities could, depending on the location of application, reduce the strength of the bond with other tire components during subsequent processing, or could remain as unwanted visual defects on the outside of the pneumatic vehicle tire.

[0009] In light of the problems described above, the tracking of process information in the production of components for vehicle tires is in practice often still carried out via rudimentary, paper-based systems, so that at least rough process information in the form of a written note can be attached to individual non-crosslinked rubber products and the transport devices used for transport.

[0010] Against this background, the primary object of the above invention was to provide a method for tracking process parameters in the production of rubber products, which eliminates or at least reduces the disadvantages of the prior art described above.

[0011] One of the tasks was to specify a method for tracking process parameters in the manufacture of rubber products that could be implemented in such a way that the process parameters of the manufacture, in particular the extrusion process, could be correlated very precisely with the respective parts of the unvulcanized rubber product.

[0012] In addition, it was a task that the method to be specified for tracking process parameters in the manufacture of rubber products leaves no or essentially no traces after vulcanisation of the unvulcanised rubber products, at least no traces visible to the naked eye.

[0013] It was an object of the present invention that the method to be specified for tracking process parameters in the production of rubber products should reduce the need for a paper-based labeling system and enable reliable identification of the unvulcanized rubber product and an assignment to the process parameters used in production over large parts of the manufacturing process of pneumatic vehicle tires.

[0014] It was desirable that the tracking of process parameters should be possible even after long storage of the unvulcanized rubber products.

[0015] In addition, it was a requirement that the solution to be specified should not create any chemical incompatibilities with the unvulcanized rubber product, especially not during the subsequent vulcanization process.

[0016] It was desirable that the method to be specified for tracking process parameters in the manufacture of rubber products should not require the use of color or potentially harmful substances.

[0017] Furthermore, the method to be specified for tracking process parameters in the manufacture of rubber products should ideally be designed in such a way that it can be operated with a high throughput in order to be particularly time- and cost-efficient.

[0018] Advantageously, the method to be specified for tracking process parameters in the manufacture of rubber products should be particularly easy to integrate into the other production steps in the manufacture of pneumatic vehicle tires.

[0019] It was desirable that the process to be specified should be particularly safe to operate, with an additional requirement that environmental pollution with emissions or particulate dust be minimized.

[0020] In addition, it was a task to specify an unvulcanized rubber product which makes information about the process parameters used in its production traceable, but which does not impose any restrictions on the bonding with other

[0021] Rubber components still have visible defects on the surface.

[0022] Based on this, it was a supplementary task to specify a vulcanised rubber product which can be manufactured from the unvulcanised rubber product and which no longer includes, or essentially no longer includes, any markings visible to the naked eye which were aimed at the tracking of the information previously included.

[0023] In light of the above statements, it was a supplementary object of the present invention to provide a device for producing corresponding unvulcanized rubber products, with which in particular the method to be specified for tracking process parameters in the production of rubber products can be carried out particularly efficiently.

[0024] The inventors of the present invention have now recognized that the objects described above can surprisingly be achieved if the green rubber product, ie the unvulcanized rubber product, is marked in a specific form as defined in the claims.

[0025] For this purpose, the surface of the unvulcanized rubber product is marked, preferably while still warm. The marking, which includes information about one or more manufacturing process parameters and / or is linked to this information via a data processing system, can expediently be implemented as a machine-readable marking, i.e., with a machine-readable code.

[0026] The inventors of the present invention have recognized that this marking must be applied by creating depressions on the surface. However, to achieve the above-described objectives, it is essential that the created depressions have a maximum depth.

[0027] With appropriate markings, it is advantageously possible to obtain unvulcanized rubber products that, after vulcanization, no longer show any, or essentially no, traces of the previously applied marking on their surface that are visible to the naked eye. This makes it possible to enable efficient tracking of process parameters during the production of rubber products without adversely affecting the optical quality and material properties of the resulting vulcanized rubber product.

[0028] The above-mentioned objects are accordingly achieved by methods for tracking process parameters in the manufacture of rubber products and corresponding devices, as defined in the claims. Preferred embodiments of the invention emerge from the subclaims and the following statements.

[0029] Such features of inventive objects, which are designated as preferred below, are combined in particularly preferred embodiments with other features designated as preferred. Combinations of two or more of the embodiments designated as particularly preferred below are thus very particularly preferred. Likewise preferred are embodiments in which a feature designated as preferred to any extent is combined with one or more further features designated as preferred to any extent. Features of preferred unvulcanized rubber products and the vulcanized rubber products producible therefrom, as well as preferred devices according to the invention, also emerge from the features of preferred methods.

[0030] The invention relates to a method for tracking process parameters in the production of rubber products, in particular unvulcanized treads for pneumatic vehicle tires, comprising the steps: a) producing an unvulcanised rubber product comprising a crosslinkable rubber mixture, and b) applying a marking to a surface of the unvulcanised rubber product, wherein the marking comprises information about one or more process parameters of the production and / or is linked to information about one or more process parameters of the production via a data processing system, wherein the marking is applied by creating depressions on the surface using a material-removing process and / or an indenting process, the depressions created having a depth of 100 µm or less.

[0031] The method according to the invention is used to track process parameters in the production of rubber products and is particularly suitable for use in the production of unvulcanized treads and other components of pneumatic vehicle tires.

[0032] In step a) of the process according to the invention, an unvulcanized rubber product comprising a crosslinkable rubber mixture is produced. The resulting unvulcanized rubber product is also referred to as a green rubber product.

[0033] A marking is then applied to the surface of this unvulcanized rubber product. This marking can, for example, directly contain information about one or more manufacturing process parameters. This could, for example, be the time of manufacture, represented by the time.

[0034] In particularly preferred embodiments, however, the applied marking can be linked to a data processing system, for example, a computer, with information about one or more manufacturing process parameters. In this case, the marking expediently contains link information, for example, in the form of a QR code, which, when read, causes a data processing system to retrieve a specific data set stored on a storage unit, which includes one or more manufacturing process parameters.

[0035] According to the invention, the marking is applied by creating depressions in the surface using a specific method. Material-removing methods, for example milling and / or indentation methods, for example with an embossing stamp, have been identified as generally suitable for this purpose, with material-removing methods being preferred. In the inventors' opinion, it is essential that the depressions created have a maximum depth of 100 µm. Based on the inventors' own experiments, above this maximum depth, the processing properties in the marked area are potentially adversely affected, and after vulcanization, deeper depressions can in many cases still be perceived with the naked eye. A method according to the invention is preferred in which all of the depressions created have a depth of 100 µm or less.

[0036] In the inventors' own experiments, however, it has proven particularly advantageous to make the depressions even shallower. This made it possible to reduce the influence of the marking on the surface properties of the marked area and, in particular, to achieve a substantially complete disappearance of the marking after the vulcanization step. A method according to the invention is preferred, wherein the depressions produced, preferably all of the depressions produced, have a depth of 70 µm or less, preferably 50 µm or less, particularly preferably 30 µm or less.

[0037] In principle, the method according to the invention advantageously does not require any minimum depth for the depressions produced. In practice, in fact, it usually depends solely on the accuracy of the sensors that are later to be used to read the marking. If particularly high-quality sensors with a high level of detection accuracy are used, even very small depressions can be used. However, with a view to efficient process control, it has proven particularly advantageous to provide a certain minimum depth so that the marking can be easily read even with comparably inexpensive sensors, since there is a sufficiently high contrast. A method according to the invention is therefore preferred, wherein the depressions produced, preferably all of the depressions produced, have a depth of at least 5 µm, preferably at least 10 µm, particularly preferably at least 20 µm.

[0038] In light of the above, the inventors also suggest that the depressions created should not be chosen to be too wide. Although, in the inventors' estimation, this is rather a secondary aspect with regard to the later recognizability of the marking, in the case of particularly wide depressions, especially if they are located at the upper end of the maximum depth and the vulcanization process is carried out poorly, an unwanted marking can remain on the surface. Thus, a method according to the invention is preferred, wherein the depressions created, preferably all of the depressions created, have a width of 1000 µm or less, preferably 800 µm or less, particularly preferably 600 µm or less, at the opening.

[0039] Of the options for the information content of the marking defined above, it is explicitly preferred if the marking is designed such that it is linked to information about one or more process parameters via a data processing system. Such an embodiment is particularly advantageous because the process parameters can thus be processed, adapted, and further processed particularly efficiently using the data processing system, so that the marked unvulcanized rubber product can also be correlated with data derived from the information about the at least one process parameter during the manufacturing process. Accordingly, a method according to the invention is preferred, wherein the marking is linked to information about one or more manufacturing process parameters via a data processing system.

[0040] A corresponding system can advantageously be implemented using a QR code or a data matrix code, which comprises connection information that causes a reading data processing device to establish a corresponding connection, for example, to a specific memory segment on a storage unit. Therefore, a method according to the invention is preferred, wherein the marking is a machine-readable marking. In particular, a method according to the invention is preferred, wherein the marking comprises a QR code, a bar code, or a data matrix code, preferably a data matrix code.

[0041] In principle, all possible information can be stored as information about the at least one process parameter. However, information about specific process parameters, which experience has shown should be tracked, has proven particularly advantageous, particularly in the field of vehicle tire production. Thus, a method according to the invention is preferred, wherein the information about one or more process parameters includes information about the time of production, the production temperature, the pressure, the profile geometry, the weight, the operating parameters of the extruder, and / or the composition of the crosslinkable rubber mixture.

[0042] Even though the negative impact of the surface treatment on the subsequent processability of the unvulcanized rubber product is advantageously minimized in the process according to the invention, it has proven particularly advantageous not to apply the marking to a surface that is to be bonded to other parts of the vehicle tire at a later stage. This not only ensures a high quality of the bond, but also makes particularly effective use of the advantage of the process according to the invention that the marking is no longer visible after vulcanization. Therefore, a process according to the invention is preferred in which the marking is applied to a surface of the unvulcanized rubber product that is visible during use of the vulcanized rubber product.

[0043] As explained above, there is fundamentally a wide range of possible methods for producing the necessary indentations for the marking. In their own experiments, however, the inventors have found that the use of lasers is particularly preferred because they allow particularly fine structures to be produced in a particularly controlled manner. The inventors have succeeded in identifying lasers and suitable wavelengths that have excellent interaction with the material to be processed and with which the marking can be applied particularly well and precisely using the method according to the invention. A method according to the invention is therefore preferred in which the marking is applied by producing indentations on the surface using a laser, the laser preferably being a CO2 laser or a fiber laser.A method according to the invention is preferred, wherein the laser has a wavelength in the range of 0.5 to 11 µm, preferably in the range of 1.06 to 10.6 µm.

[0044] As explained above, the method according to the invention can, in principle, be used for a variety of unvulcanized rubber products. However, its use for marking unvulcanized treads that are later to be used in the production of vehicle tires has proven particularly advantageous. This method is particularly advantageous because, with regularly extruded, unvulcanized treads, there is a particularly high need to document the process parameters particularly accurately. Accordingly, a method according to the invention is preferred wherein the unvulcanized rubber product is an unvulcanized tread for vehicle tires, in particular pneumatic vehicle tires.

[0045] In principle, the process according to the invention is suitable for essentially all rubber products, in particular all rubber products used in the manufacture of vehicle tires. In addition to extruded products such as treads, it can also be used, for example, for carcass plies and similar calendered products. Corresponding carcass plies comprise not only the rubber mixture but also so-called reinforcement cords, thus constituting composite materials. However, a process according to the invention is preferred in which the unvulcanized rubber product consists of the crosslinkable rubber mixture.

[0046] Even though the inventors of the present invention have no reason to believe that the process they have developed cannot be applied essentially to all crosslinkable rubber mixtures, they have been able to identify, through their own experiments, preferred compositions for crosslinkable rubber mixtures with which the process according to the invention and the marking to be carried out can be reliably carried out and with which, moreover, unvulcanized rubber products can be obtained in which the chemical properties, in particular the flow properties of the crosslinkable rubber mixture, are so pronounced that the applied marking disappears completely or almost completely during the subsequent vulcanization step. In this respect, a process according to the invention is preferred, wherein the crosslinkable rubber mixture comprises at least one diene rubber.wherein the deinked rubber is preferably selected from the group consisting of natural polyisoprene, synthetic polyisoprene, epoxidized polyisoprene, butadiene rubber, solution-polymerized styrene-butadiene rubber, emulsion-polymerized styrene-butadiene rubber, polynorbornene, ethylene-propylene-diene rubber, nitrile rubber, acrylate rubber, silicone rubber, polysulfide rubber, epichlorohydrin rubber, styrene-isoprene-butadiene terpolymer, hydrogenated acrylonitrile-butadiene rubber, isoprene-butadiene copolymer and hydrogenated styrene-butadiene rubber, wherein the deinked rubber is particularly preferably selected from the group consisting of natural polyisoprene (NR), synthetic polyisoprene (IR), Butadiene rubber (BR), solution-polymerized styrene-butadiene rubber (SSBR), and emulsion-polymerized styrene-butadiene rubber (ESBR). Also preferred is a process according to the invention wherein the crosslinkable rubber mixture comprises 2.5 to 8.0 phr of sulfur.and / or, wherein the crosslinkable rubber mixture comprises 0.1 to 100 phr of one or more fillers, wherein the fillers are selected from the group consisting of polar and non-polar fillers, preferably selected from the group consisting of carbon black, aluminum hydroxide, titanium dioxide, magnesium oxide, pyrogenic silica and phyllosilicates, particularly preferably selected from the group consisting of carbon black and pyrogenic silica.

[0047] The phr specification corresponds to the parts per hundred rubber specification commonly used in the rubber industry, where the mass information is based on one hundred parts by mass of the rubber contained in the mixture.

[0048] Even though the production of the unvulcanized rubber product, as explained above, can also be carried out, for example, by calendering or similar methods, it is explicitly preferred, with a view to efficient process control, if the production takes place via extrusion, in particular because this allows a continuous process to be implemented particularly efficiently. Accordingly, a process according to the invention is preferred, wherein the production in step a) comprises the extrusion of a crosslinkable rubber mixture from an extruder.

[0049] According to the inventors' findings, it is in principle possible to apply the marking according to the invention spatially and / or temporally separate from the production of the unvulcanized rubber product. However, according to the inventors' findings, this usually requires very precise and complex tracking of the unvulcanized rubber products in order to subsequently assign them reliably and precisely to the process parameters prevailing during production. In the inventors' opinion, it is particularly advantageous if, in contrast, the marking is carried out immediately after the production of the unvulcanized rubber product. This significantly simplifies the error-free documentation of the relevant process parameters in connection with the unvulcanized rubber product and the marking on the unvulcanized rubber product.Furthermore, the inventors of the present invention have recognized that the processability of the unvulcanized rubber product is significantly improved in many cases with the processing methods used for marking immediately after production, for example, when indentation methods are used, which particularly benefit from a lower viscosity of the crosslinkable rubber mixture. Therefore, a method according to the invention is preferred, wherein the application of the marking takes place spatially and temporally immediately after the production of the unvulcanized rubber product.

[0050] In this respect, it is considered particularly advantageous to mark the unvulcanized rubber product while it is still warm. Therefore, a method according to the invention is preferred, wherein the temperature of the unvulcanized rubber product during the application of the marking is 60°C or more, preferably 70°C or more, particularly preferably 80°C or more, with the temperature of the unvulcanized rubber product during the application of the marking most preferably being in the range of 70 to 140°C.

[0051] With regard to the achievable throughput and correspondingly the cost-effectiveness of the process, it has proven particularly advantageous that the process according to the invention can be operated as a continuous process when used in an extrusion line. The embodiment described above as preferred can be implemented particularly efficiently when the marking to be carried out according to the invention in the extrusion line does not take place too far away from the extruder head. A process according to the invention is preferred, wherein the process is carried out in a continuously operated extrusion line, wherein the application of the marking preferably takes place in a region of the extrusion line that is 3 to 20 m, preferably 4 to 10 m, particularly preferably 5 to 8 m, from the extruder head.

[0052] The marking applied in the method according to the invention is naturally the result of very fine processing that requires a great deal of care and precision. Particularly when selecting particularly small recess depths, it cannot be ruled out that the marking will be applied inadequately and that the necessary readability of the applied marking will not be guaranteed. To counteract this problem, the inventors of the present invention propose providing a further step in the method according to the invention in which the readability of the applied marking is checked by a testing device, preferably immediately after the marking and / or at the end of the extrusion line. If this test shows that the readability does not meet the requirements, for example, another marking that meets the necessary requirements can be applied immediately.A method according to the invention is preferred, additionally comprising the step: c) checking the readability of the applied marking by means of a testing device.

[0053] As a useful further development of the method according to the invention, the inventors of the present invention propose that the applied marking can be read by a reading device, which in the preferred embodiment can also be the testing device used for testing, in order to obtain information about the at least one process parameter. This can occur, for example, when an unvulcanized rubber product is fed for further processing with other rubber products after prior storage. In the preferred method according to the invention, the read information is correlated with other information that matches the other rubber semi-finished products, thereby creating a data set that includes information about the product obtained through processing. Such a data set can then be saved and is available after the final product has been manufactured.In particularly preferred embodiments, a final marking can now also be applied to the surface of the entire rubber product, which contains the information stored in the data set or can be correlated with it via a data processing system, analogous to the procedure described above. Thus, a method according to the invention is preferred, additionally comprising the steps: d) reading the applied marking by a reading device to obtain the information about the one or more process parameters, e) correlating the information about the one or more process parameters of the unvulcanised rubber product with information relating to one or more further rubber semi-finished products which are to be processed together with the unvulcanised rubber product to form an overall rubber product, to obtain a data set, and f) storing the data set in a storage unit of a data processing system, and optionally g) applying a final marking to a surface of the overall rubber product, wherein the final marking comprises information about the data set and / or is linked to information about the data set via a data processing system.

[0054] The inventors of the present invention propose that the testing device and / or the reading device should each have an optical sensor with which they can read the marking. As explained above, it is preferred if the testing device and the reading device are formed by the same device. A method according to the invention is therefore preferred, wherein the testing device has an optical sensor which is connected to a device for data processing. A method according to the invention is also preferred, wherein the reading device has an optical sensor which is connected to a device for data processing. A method according to the invention is also preferred, wherein the testing device and the reading device are separate devices or are formed by the same device.

[0055] In light of the above explanations, it is apparent to the person skilled in the art that in the preferred process according to the invention, the semi-finished rubber products are preferably components of a vehicle tire which are correspondingly assembled to form a vehicle tire.

[0056] A preferred method according to the invention is preferred, wherein the one or more semi-finished rubber products are components of a vehicle tire, in particular a pneumatic vehicle tire, and wherein the overall rubber product is a vehicle tire, in particular a pneumatic vehicle tire.

[0057] Based on the method according to the invention, the correspondingly processed unvulcanized rubber product can then be converted into a corresponding rubber product by vulcanization. For the vulcanization, the methods customary in the field of technology are used. However, according to the inventors' findings, it is particularly advantageous to provide certain temperatures for the vulcanization, which in particular should not be set too low, in order to promote the completely fading of the marking applied to the unvulcanized rubber products when the material is sufficiently flowable, so that it is no longer visible or essentially no longer visible to the naked eye. Therefore, a method according to the invention is preferred, additionally comprising the step: h) vulcanizing the unvulcanized rubber product to obtain a vulcanized rubber product.

[0058] A process according to the invention is preferred, wherein the vulcanization of the unvulcanized rubber product takes place at a temperature in the range from 110 to 170 °C, preferably in the range from 120 to 160 °C.

[0059] After extensive testing, the inventors of the present invention propose adapting the marking to the subsequent vulcanization process such that the resulting marking essentially fades completely and is therefore almost imperceptible. In this respect, a method according to the invention is preferred, wherein the marking after vulcanization of the unvulcanized rubber product has a total volume reduced by 75% or more, preferably 85% or more, particularly preferably 95% or more, and most particularly preferably 98% or more, compared to the total volume of the depressions produced in step b).In this respect, a method according to the invention is also preferred, wherein the depressions of the marking after vulcanization of the unvulcanized rubber product have a depth reduced by 75% or more, preferably 85% or more, particularly preferably 95% or more, very particularly preferably 98% or more, compared to the marking produced in step b).

[0060] It will be apparent to those skilled in the art that the unvulcanized rubber product that can be obtained using the process according to the invention is also particularly advantageous in itself. Due to its specific design, it can be converted by vulcanization into a vulcanized rubber product in which a previously existing marking, in which important process information (or information relating to this information) could have been stored, is no longer or essentially no longer visible, so that the end products produced therefrom have virtually no visual defects.The invention thus also relates to an unvulcanized rubber product comprising a crosslinkable rubber mixture, wherein the unvulcanized rubber product has on a surface a marking consisting of depressions with a depth of 100 µm or less, wherein the marking comprises information about one or more process parameters of the production of the unvulcanized rubber product and / or is linked via a data processing system to information about one or more process parameters of the production of the unvulcanized rubber product.

[0061] The disclosure also relates to a vulcanized rubber product, in particular vehicle tires, producible by vulcanizing an unvulcanized rubber product according to the invention and / or producible by a process according to the invention.

[0062] As explained above, numerous different devices are generally suitable for producing the unvulcanized rubber product. However, in the opinion of the inventors, the use of an extrusion line is explicitly preferred, particularly with regard to efficient process control. The inventors of the present invention propose equipping this line in such a way that it can be used to carry out the process according to the invention and to achieve the advantages described above.The invention thus also further relates to a device for producing an unvulcanized rubber product, preferably an extrusion line for producing an unvulcanized rubber product, in particular for carrying out the method according to the invention, comprising one or more tools which are designed to produce a marking consisting of depressions on the surface of an unvulcanized rubber product using a material-removing method and / or an indenting method, so that the depressions produced have a depth of 100 µm or less.

[0063] A device according to the invention is preferred, wherein the device is an extrusion line and wherein the one or more tools are arranged in a region of the extrusion line which is spaced 3 to 8 m, preferably 4 to 7 m, from the extruder head.

[0064] Also preferred is a device according to the invention, wherein the one or more tools are lasers, preferably CO2 lasers or fiber lasers.

[0065] Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying drawings. Fig. 1 a schematic flow diagram of the method according to the invention in a preferred embodiment.

[0066] Fig. 1 shows a schematic flow diagram of an exemplary method according to the invention, which the inventors consider to be particularly advantageous. Using these and comparable methods, the inventors were able to mark various unvulcanized rubber products, in particular treads of pneumatic vehicle tires, whereby these rubber products, after vulcanization, essentially no longer exhibited any traces of the previous marking on their surface that were visible to the naked eye. This assessment was carried out qualitatively by visual inspection of the manufactured vulcanized rubber products by workers familiar with tire production from a distance of approximately one meter. In this case, the remaining traces of the previous marking were at best only registered when the assessors were actively informed of the location of the previous marking.

[0067] In the Fig. 1 In the exemplary method presented, in step 101, an unvulcanized tread is produced which consists entirely of a crosslinkable rubber mixture which, in addition to sulfur and filler, primarily consists of SSBR. The corresponding unvulcanized tread is extruded from an extruder head on a continuously operating extrusion line. In step 102, a marking is applied to the surface of the unvulcanized tread. The application is carried out using a CO2 laser or a fiber laser with a wavelength in the infrared range, which is arranged approximately 5 m behind the exit of the extruder head.

[0068] The marking was applied by laser-assisted creation of indentations on the surface, with each indentation having a depth of 10–50 µm. This method creates a machine-readable marking in the form of a DataMatrix code containing connection information that guides a corresponding readout device to a specific part of a storage unit, where, in practical applications, the relevant process parameters of interest for the respective process are stored.

[0069] The marking is applied to the side of the tread that will later receive the profile during vulcanization and tire production, and will therefore be visible during subsequent use. At the time of marking, the temperature of the unvulcanized rubber product is approximately between 70 and 80°C, which has proven to be a suitable temperature range, especially when using a laser.

[0070] In step 103 Subsequently, at the end of the extrusion line, the applied marking is checked for readability. However, this can probably be considered optional for many subsequent practical processes. For the selected depth ranges, sufficiently good contrast and adequate readability were observed in all experiments.

[0071] After leaving the extrusion line, the tread is assembled with other rubber semi-finished products, i.e. other tire components, to form a green tire. The applied marking is then applied in step 104 by a reading device with an optical sensor, which was a camera with image recognition software, and thereby retrieved information linking it to its specific storage location on the storage unit. In later practical application, this data would be combined with comparable data on the other semi-finished rubber products and stored in an overall data set that would be correlated with the overall rubber product to be manufactured, for example, using a barcode affixed to the vehicle.

[0072] As part of the experiments carried out by the inventors, the following step 105Vulcanization of the unvulcanized rubber product, which occurs together with the other components of the pneumatic vehicle tire in the green tire, and a profile is imprinted on the outer side of the tread in the usual manner. Vulcanization took place at a temperature of approximately 160°C. This procedure proved sufficient in the inventors' experiments to achieve a substantially complete reduction in the depth of the depressions previously produced for marking purposes. Given that the remaining depressions are almost impossible to measure, this reduction can be estimated at approximately 99%.

Claims

1. Method for tracking process parameters in the production of rubber products, in particular unvulcanized treads for vehicle pneumatic tyres, comprising the steps of: a) producing an unvulcanized rubber product, comprising a crosslinkable rubber mixture, and b) applying an identification to a surface of the unvulcanized rubber product, wherein the identification comprises information about one or more process parameters of production and / or is linked with information about one or more process parameters of production by way of a system for data processing, wherein applying the identification is carried out by producing depressions on the surface using a material-removing method and / or an impressing method, wherein the depressions produced have a depth of 100 µm or less.

2. Method according to Claim 1, wherein the depressions produced, preferably all of the depressions produced, have a depth of 70 µm or less, preferably 50 µm or less, particularly preferably 30 or less.

3. Method according to either of Claims 1 and 2, wherein the identification comprises a QR code, a barcode or a data matrix code, preferably a data matrix code.

4. Method according to any of Claims 1 to 3, wherein applying the identification is carried out by producing depressions on the surface using a laser, wherein the laser is preferably a CO2 laser or a fibre laser.

5. Method according to any of Claims 1 to 4, wherein the temperature of the unvulcanized rubber product during the step of applying the identification is 60°C or more, preferably 70°C or more, particularly preferably 80°C or more, wherein the temperature of the unvulcanized rubber product during the step of applying the identification is very particularly preferably in the range of 70 to 140°C.

6. Method according to any of Claims 1 to 5, additionally comprising the step of: c) checking the readability of the applied identification by means of a checking device.

7. Method according to any of Claims 1 to 6, additionally comprising the steps of: d) reading the applied identification by means of a readout device in order to obtain the information about the one or more process parameters, e) correlating the information about the one or more process parameters of the unvulcanized rubber product with information concerning one or more further semifinished rubber products which are intended to be processed together with the unvulcanized rubber product to form an overall rubber product, in order to obtain a data set, and f) storing the data set in a storage unit of a system for data processing, and optionally g) applying a final identification to a surface of the overall rubber product, wherein the final identification comprises information about the data set and / or is linked with information about the data set by way of a system for data processing.

8. Method according to any of Claims 1 to 7, additionally comprising the step of: h) vulcanizing the unvulcanized rubber product in order to obtain a vulcanized rubber product.

9. Method according to any of Claims 1 to 8, wherein the depressions of the identification after the step of vulcanizing the unvulcanized rubber product have a depth reduced by 75% or more, preferably 85% or more, particularly preferably 95% or more, very particular preferably 98% or more, compared with the identification produced in step b).

10. Device for producing an unvulcanized rubber product, preferably extrusion line for producing an unvulcanized rubber product, in particular for carrying out the method according to any of Claims 1 to 9, comprising one or more tools configured to produce an identification made from depressions on the surface of an unvulcanized rubber product using a material-removing method and / or an impressing method, such that the depressions produced have a depth of 100 µm or less.