Vehicle tire

Abstract

The invention relates to a vehicle tire (10), comprising a tread (12) and a first belt ply (14), which is arranged underneath the tread (12) and lies closest to the tread (12), and a second belt ply (16), which is arranged underneath the first belt ply (14). The first belt ply (14) is produced by vulcanization in a first vulcanizable rubber mixture, which may comprise methylene donors, namely melamine-based compounds, in particular hexamethoxymethylmelamine (HMMM), and comprises methylene acceptors. The second belt ply (16) is produced by vulcanization in a second vulcanizable rubber mixture, which comprises methylene donors, namely melamine-based compounds, in particular hexamethoxymethylmelamine (HMMM), and methylene acceptors, wherein the ratio of the amount of methylene donors to the amount of methyl acceptors in the first vulcanizable rubber mixture is smaller than in the second vulcanizable rubber mixture.

Description

[0001] Vehicle tires

[0002] Description

[0003] The invention relates to a vehicle tire comprising a tread and a first belt layer arranged below the tread, as well as a second belt layer arranged below the first belt layer.

[0004] The automotive industry is among the sectors that have faced fundamental challenges since the beginning of the 21st century, while simultaneously being shaped by numerous technological innovations. Growing customer awareness of environmental aspects such as emissions profiles and resource efficiency necessitates new concepts for mobility. At the same time, the demand for improved vehicle performance and the requirements for driving safety are increasing. Meeting these challenges is not solely the responsibility of vehicle manufacturers. In practice, many of these aspects are significantly influenced by tire properties, making tire optimization a crucial area for innovation.

[0005] Several relevant properties of vehicle tires, such as wet grip and abrasion resistance, are closely linked to the rubber composition of the tread. However, the physical and chemical properties of other tire components, such as the materials used in the belt plies, also influence the performance characteristics of vehicle tires. Against this background, much research focuses on optimizing the properties of the various rubber compounds and their additives used in vehicle tires.

[0006] Given the detailed coordination of the various rubber compounds to meet different requirements and their sometimes very different chemical compositions, a new aspect is increasingly coming into focus in the inventors' development work. After the construction of the vehicle tire blank, potentially very different rubber compounds come into contact. Within the vehicle tire blank and during its vulcanization at elevated temperatures, but also later in use as a vulcanized vehicle tire, diffusion of individual components of the rubber compounds occurs between the contacting tire components and into the surrounding components.

[0007] This reduces the proportion of migrating compounds in the original tire component, while the concentration in adjacent tire components can increase. This can lead to the undesirable introduction of chemical components into the surrounding rubber compounds.

[0008] In tests, an undesirable tendency to migrate has been observed, particularly for some melamine-based compounds. Such melamine-based compounds, especially hexamethoxymethylmelamine (HMMM), are used as methylene donors in the production of vehicle tires. These methylene donors are used especially in the vulcanizable rubber compounds of reinforcement layers, particularly the belt layers, where they act together with complementary methylene acceptors, such as resorcinol, as part of so-called methylene acceptor-methylene donor pairs. In many cases, these methylene acceptor-methylene donor pairs contribute to the advantageous bonding of textile or metallic reinforcing materials embedded in the respective vulcanizable rubber compounds.Melamine-based compounds, especially hexamethoxymethylmelamine (HMMM), are also used in some cases without complementary methylene acceptors.

[0009] Hexamethoxymethylmelamine (HMMM) is one of the most established methylene donors in the field of technology and is preferred for use in methylene acceptor-methylene donor pairs for numerous reasons. However, investigations by the inventors have shown that HMMM has a relatively high tendency to migrate from the vulcanizable rubber compounds of the reinforcement layers into the surrounding tire components, particularly during the vulcanization process. The presence of HMMM and other melamine-based compounds is undesirable in many tire components, especially in the tread, from where it can be released into the environment, particularly through the well-known abrasion process of vehicle tires.

[0010] The primary objective of the present invention was to eliminate or at least reduce the disadvantages of the prior art. In particular, it was an objective of the present invention to provide a vehicle tire in which the release of HMMM and other melamine-based compounds into the environment is eliminated or at least reduced.

[0011] This problem is solved by a vehicle tire having the features of claim 1. Further developments and advantageous embodiments of the invention are set forth in the dependent claims.

[0012] The vehicle tire comprises a tread and a first belt layer located beneath the tread and closest to the tread, as well as a second belt layer located beneath the first belt layer. Further belt layers may be provided beneath these.

[0013] According to the invention, the first belt layer is produced by vulcanization in a first vulcanizable rubber mixture which may have methylene donors, namely melamine-based compounds, in particular hexamethoxymethylmelamine (HMMM), and methylene acceptors, and the second belt layer is produced by vulcanization in a second vulcanizable rubber mixture which has methylene donors, namely melamine-based compounds, in particular hexamethoxymethylmelamine (HMMM), and methylene acceptors, wherein the ratio of the amount of methylene donors to the amount of methyl acceptors in the first vulcanizable rubber mixture is smaller than in the second vulcanizable rubber mixture.

[0014] Typically, the vulcanization of the vehicle tire, including the tread and belt layers, takes place in a single vulcanization step.

[0015] According to the invention, in the vulcanizable rubber mixture of the second belt layer, during the vulcanization process the methylene donors, i.e. the melamine-based compounds, in particular hexamethoxymethylmelamine (HMMM), react with the complementary methylene acceptors and form chemical bonds between the polymer chains of the rubber.

[0016] The reaction between, for example, HMMM as a methylene donor and, for example, resorcinol as a methylene acceptor, typically occurs in the presence of sulfur and under heat. During heating, the methoxymethyl groups of HMMM cleave off, and the resulting reactive groups can react with the hydroxyl groups of resorcinol to form a cross-link. The exact reaction mechanism can be complex and depends on various factors such as temperature, pressure, and the composition of the mixture. However, the end result is a cross-linked structure that improves the desired mechanical and thermal properties of the vulcanized rubber.

[0017] The aforementioned reaction also occurs in the vulcanizable rubber compound of the first belt layer, provided that methylene donors are present there from the outset.

[0018] As already mentioned, the inventors discovered in experiments that the reaction in question does not proceed completely during vulcanization, so that unreacted melamine-based compounds, in particular hexamethoxymethylmelamine (HMMM), undesirably diffuse into adjacent tire components, especially the tread, even during the vulcanization process. This is where the invention comes into play. By providing a first belt layer between the second belt layer and the tread, which is vulcanized into or into the tread, the first belt layer is vulcanized into the tread.When a vulcanizable rubber compound is produced which may contain methylene donors – and if these are present – ​​the ratio of the amount of methylene donors to the amount of methyl acceptors in this first vulcanizable rubber compound is smaller than in the second vulcanizable rubber compound, which is ensured according to the invention by an excess of methyl acceptors compared to the methylene donors in the first rubber compound, the methylene donors diffusing from the vulcanizable rubber compound of the second belt layer into the vulcanizable rubber compound of the first belt layer react during vulcanization with the methylene acceptors present in the vulcanizable rubber compound of the first belt layer in the aforementioned excess and are thus at least largely chemically bound.

[0019] This ensures that the first belt layer closest to the tread has fewer unbound methylene donors after vulcanization, thus preventing or at least significantly reducing the diffusion of such methylene donors into the tread. This prevents melamine-based compounds, especially hexamethoxymethylmelamine (HMMM), from leaching into the environment via the tread, even if the tread wears down during subsequent use.

[0020] A further advantage is that even methylene donors, i.e., melamine-based compounds, especially hexamethoxymethylmelamine (HMMM), which may still be present unreacted in the second belt layer even after vulcanization, would first have to diffuse through the entire first belt layer to reach the tread. The first belt layer thus forms an additional barrier between the tread and the second belt layer, slowing down the diffusion of melamine-based compounds, particularly hexamethoxymethylmelamine (HMMM), from the second belt layer into the tread.The barrier effect is advantageously further enhanced by unreacted methylene acceptors present in the first belt layer, which can chemically interact with the methylene donors diffusing into the first belt layer, i.e., the melamine-based compounds, especially hexamethoxymethylmelamine (HMMM), and thus significantly reduce the diffusion rate of the melamine-based compounds, especially hexamethoxymethylmelamine (HMMM).

[0021] It can be advantageous if the percentage by weight of methylene acceptors in the total weight of the first vulcanizable rubber compound is equal to the percentage by weight of methylene acceptors in the total weight of the second vulcanizable rubber compound. However, to ensure that the ratio of methylene donors to methyl acceptors according to the invention is lower in the first vulcanizable rubber compound than in the second, the first vulcanizable rubber compound must therefore have a lower percentage by weight of methylene donors than the second vulcanizable rubber compound.

[0022] It can be advantageous if the percentage by weight of the methylene acceptors in the total weight of the first vulcanizable rubber mixture is greater than the percentage by weight of the methylene acceptors in the total weight of the second vulcanizable rubber mixture, preferably at least 10% greater, particularly preferably at least 25% greater, and even more preferably at least 50% greater.

[0023] It can be advantageous if the percentage by weight of methylene donors in the total weight of the first vulcanizable rubber compound is smaller than the percentage by weight of methylene acceptors in the total weight of the second vulcanizable rubber compound, preferably by at least 10%, particularly preferably by at least 25%, even more preferably by at least 50%, and still more preferably by at least 75%. It can be particularly advantageous if the first vulcanizable rubber compound contains no methylene donors.

[0024] A mixture of differently methylated melamine cores is preferably used as HMMM. On average, between 5.4 and 5.6 of the six possible positions are methylated. Melamine consists of six nitrogen atoms, each of which carries three hydrogen atoms. In hexamethoxymethylmelamine, each nitrogen atom is largely replaced by a methoxymethyl group (CH₂OCH₃). If, on average, between 5.4 and 5.6 of the six possible positions are methylated, this means that most melamine cores have a methoxymethyl group at almost all six positions, although some melamine cores may exhibit slightly less methylation. The species that are not 6-fold methylated are significantly more reactive, which is preferred for the rubber compounds used according to the invention. A methylation level of less than e is therefore preferred.

[0025] It can be advantageous if resorcinol, precondensates of resorcinol, resorcinol-formaldehyde resins, p-phenylenediamine, novolac resins and / or alkyl phenol resins can be used as methylene acceptors.

[0026] For many applications, the use of resorcinol and / or resorcinol precondensates, especially resorcinol-formaldehyde resins, is advantageous. These precondensates are formed primarily by the reaction of resorcinol with formaldehyde under controlled conditions to obtain a prepolymerized product.

[0027] For certain applications, the use of a resin known under the trade name Alvonol is advantageous. This resin is a modified phenolic resin.

[0028] Novolak resins are phenol-formaldehyde resins produced by the condensation reaction of phenol with formaldehyde under acidic conditions. The vehicle tire according to the invention can be a passenger car tire or, preferably, a truck tire. The general structure is known to those skilled in the art. Preferably, the vehicle tire is a truck tire, particularly preferably of radial construction.

[0029] It can be advantageous if the first belt layer and the second belt layer form a belt consisting of a total of four belt layers.

[0030] The invention is explained below with reference to an embodiment shown in the drawing. The single figure shows a partial cross-section through half of a vehicle tire 10 in the area of ​​the belt 22 and the tread 12.

[0031] This is a radial vehicle tire 10 for trucks in a standard construction with a carcass 24 with steel cords as reinforcing elements, an airtight inner layer 26, a multi-layered belt 22 and a profiled tread 12.

[0032] The belt 22 has four belt layers 14, 16, 18 and 20, namely a first belt layer 14 arranged under the running strip 12 and closest to the running strip 12, a second belt layer 16 arranged under the first belt layer 14, a third belt layer 18 arranged under the second belt layer 16 and a fourth belt layer 20 arranged under the third belt layer 18. The first belt layer 14 thus forms the radially outermost belt layer 14.

[0033] Belt layers 14, 16, 18, 20 each consist of reinforcing steel cord embedded in a rubber compound.

[0034] The invention provides that the first belt layer 14 is produced by vulcanization in or with a vulcanizable rubber mixture which does not contain methylene donors, namely no melamine-based compounds, in particular no hexamethoxymethylmelamine (HMMM), and that the second belt layer 16 is produced by vulcanization in or with a vulcanizable rubber mixture which contains methylene donors, namely melamine-based compounds, in particular hexamethoxymethylmelamine (HMMM).

[0035] The third belt layer 18 and the fourth belt layer 20 also feature melamine-based compounds, in particular hexamethoxymethylmelamine (HMMM), as methylene donors.

[0036] The vulcanizable rubber compounds for the production of both the first belt layer 14 and the second belt layer 16 contain methylene acceptors, in particular resorcinol, wherein the ratio of the amount of methylene donors to the amount of methyl acceptors in the first vulcanizable rubber compound is smaller than in the second vulcanizable rubber compound. The further belt layers 16, 18 may also contain methylene acceptors, in particular resorcinol.

[0037] Even if the vehicle tire 10 is only partially shown, the components that are not shown or not shown completely are known to the expert.

[0038] The vehicle tire 10 shown in Fig. 1 consists of various layers and materials and comprises: a) the tread 12, which can also be referred to as the running surface, and which, as the outermost part of the vehicle tire 10, forms the contact surface with the road. The tread 12 is usually made of a predetermined rubber compound designed for optimal traction, abrasion resistance, and grip. The tread 12 may also have a pattern of tread blocks, grooves, and sipes, which vary depending on the intended use of the vehicle tire 10; b) the multi-layered belt 22 arranged beneath the tread 10, which consists of several belt layers 14, 16, 18, 20 arranged one above the other to increase the stability and strength of the vehicle tire 10.Each belt layer 14, 16, 18, 20 comprises reinforcing threads, in particular reinforced steel wire, so-called steel cords, and is designed to ensure a uniform distribution of loads across the tread 12 of the vehicle tire 10. The belt layers 14, 16, 18, 20, with their reinforcing threads, are embedded in the preferably different vulcanizable rubber compounds to improve the tensile strength and durability of the vehicle tire 10. According to the invention, the rubber compounds of at least the first belt layer 14 and the second belt layer 16 differ. The tire blank, which contains the belt layers 14, 16, 18, 20 with the reinforcing threads, is then placed in the vulcanization mold and the vulcanization process is carried out.During the vulcanization process, the belt plies 14, 16, 18, 20, including reinforcing threads, are cross-linked with the respective rubber compound and become an integral part of the vehicle tire 10. c) Sidewalls 28, which form the lateral parts of the vehicle tire 10 between the tread 12 and the rim (not shown). They typically consist of flexible rubber and contribute to ensuring the lateral stiffness of the vehicle tire 10, as well as absorbing impact loads and transmitting lateral forces. d) The carcass 24, which is the basic structure of the vehicle tire 10 and consists of several layers of textile or steel cords embedded in rubber. In radial tires, these textile or steel cords run radially, i.e., perpendicular to the tread 12 from bead to bead. The carcass 24 bears the main load of the vehicle tire 10 and determines its load-bearing capacity and flexibility.e) an inner liner, which is an airtight inner layer 26 made of special rubber that lines the inside of the vehicle tire 10 and prevents air from escaping. It helps maintain tire pressure and supports the safety and stability of the vehicle. f) bead cores (not shown) made of high-strength wire ropes that connect the vehicle tire 10 to the rim. They ensure that the vehicle tire 10 is firmly seated on the rim and prevent it from slipping or coming loose while driving.

[0039] These components can vary depending on the tire type and intended use, and some vehicle tires 10 may have additional layers or technologies such as sidewall protection or reinforcements for impact resistance. The vehicle tire 10 according to the invention is a vulcanization product. The vulcanization of vehicle tires 10 is an important process that serves to improve the physical properties of the rubber in order to increase the durability, strength, and performance of the vehicle tire 10. Typically, the vulcanization of vehicle tires 10 works as follows: a) Preparation of the rubber compounds: First, special rubber compounds are produced, consisting of natural or synthetic rubber, various fillers, plasticizers, crosslinking agents such as the aforementioned methylene donors and acceptors, and other additives. These compounds are thoroughly mixed to ensure a homogeneous composition.The mixing process comprises several mixing steps. b) Shaping the tire blank: The rubber compounds are then placed into the mold of a tire blank, which has the rough shape of the final vehicle tire 10. This blank typically contains the tread 12, sidewalls 28, belt plies 14, 16, 18, 20, carcass 24, and bead area of ​​the vehicle tire 10, but it is not yet fully formed or vulcanized. c) Vulcanization process: The tire blank is placed in a mold and then immersed in a vulcanizing formula that generates heat and pressure. Typically, the tire blank is vulcanized at temperatures of approximately 140°C to 180°C while simultaneously being held under high pressure. The vulcanization process usually takes several minutes to several hours, depending on the size and type of tire.d) Crosslinking of polymer chains: During the vulcanization process, the crosslinking agents in the rubber compounds, typically sulfur, react with the polymer chains of the rubber. This reaction forms chemical bonds between the polymer chains and crosslinks them together, resulting in improved elastic properties and greater resistance to wear, cracking, and deformation of the rubber. e) Cooling and curing: After the vulcanization process is complete, the vulcanized tire is removed from the mold and cooled. During cooling, the rubber cures and retains its new shape and structure.

[0040] The vulcanized tire then undergoes further processing to achieve its final shape and surface finish. This can include cutting and trimming excess material, applying tread patterns, and adding markings or prints. Finally, the tire is thoroughly inspected to ensure it meets quality standards before being released for sale.

Claims

Claims 1. Vehicle tire (10) comprising a tread (12) and a first belt layer (14) arranged beneath the tread (12) and closest to the tread (12), as well as a second belt layer (16) arranged beneath the first belt layer (14), characterized in that the first belt layer (14) is produced by vulcanization in a first vulcanizable rubber compound which may contain methylene donors, namely melamine-based compounds, in particular hexamethoxymethylmelamine (HMMM), and methylene acceptors, and that the second belt layer (16) is produced by vulcanization in a second vulcanizable rubber compound which contains methylene donors, namely melamine-based compounds, in particular hexamethoxymethylmelamine (HMMM), and methylene acceptors.where the ratio of the amount of methylene donors to the amount of methyl acceptors in the first vulcanizable rubber mixture is smaller than in the second vulcanizable rubber mixture.

2. Vehicle tire (10) according to claim 1 , characterized in that the percentage by weight of the methylene acceptors in the total weight of the first vulcanizable rubber compound is equal to the percentage by weight of the methylene acceptors in the total weight of the second vulcanizable rubber compound.

3. Vehicle tire (10) according to claim 1, characterized in that the percentage by weight of the methylene acceptors in the total weight of the first vulcanizable rubber compound is greater than the percentage by weight of the methylene acceptors in the total weight of the second vulcanizable rubber compound, preferably at least 10% greater, particularly preferably at least 25% greater, even more preferably at least 50% greater.

4. Vehicle tire (10) according to one of the preceding claims, characterized in that the percentage by weight of the methylene donors in relation to the total weight of the first vulcanizable rubber compound is less than the percentage by weight of the methylene acceptors in relation to the total weight of the second vulcanizable rubber compound, preferably at least 10% smaller, particularly preferably at least 25% smaller, more preferably at least 50% smaller, and even more preferably at least 75% smaller.

5. Vehicle tire (10) according to one of the preceding claims, characterized in that the first vulcanizable rubber compound does not have methylene donors.

6. Vehicle tire (10) according to one of the preceding claims, characterized in that resorcinol, precondensates of resorcinol, resorcinol-formaldehyde resins, p-phenylenediamine, novolac resins and / or alkyl phenol resins can be used as methylene acceptors.

7. Vehicle tire (10) according to one of the preceding claims, characterized in that the vehicle tire (10) is a truck tire, preferably of radial design.

8. Vehicle tire (10) according to claim 7, characterized in that the first belt layer (14) and the second belt layer (16) form a belt (22) which consists of a total of four belt layers (14, 16, 18, 20).

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