Method for manufacturing vehicle pneumatic tires

Abstract

The invention relates to a method for manufacturing a vehicle pneumatic tire, comprising the process steps of: a) manufacturing or providing a vehicle pneumatic tire blank, comprising: i) a carcass blank comprising a plurality of reinforcing elements embedded in a first vulcanizable rubber compound, ii) a tread blank arranged radially above the carcass blank, and iii) an inner layer blank arranged radially below the carcass blank, comprising a second vulcanizable rubber compound comprising at least one butyl rubber and / or halobutyl rubber, b) applying an aqueous dispersion to the surface of the inner layer blank to obtain a prepared vehicle pneumatic tire blank, wherein the aqueous dispersion comprises one or more dispersed polysiloxane particles.c) Vulcanizing the prepared vehicle pneumatic tire blank in a vulcanization mold to obtain a vehicle pneumatic tire, wherein the surface of the tire inner layer obtained from the inner layer blank is at least partially coated with polysiloxane particles, and d) applying a sealant composition to an application area of ​​the surface of the tire inner layer coated with polysiloxane particles.

Description

[0001] The invention relates to a method for manufacturing a vehicle pneumatic tire and a vehicle pneumatic tire manufactured therein.

[0002] A vehicle's tires have a significant impact on its driving safety characteristics. Tire failures while driving have always been a major safety risk on the road. A complete puncture in a standard pneumatic tire can lead to an unintended loss of pressure, forcing the driver to change the tire, often in the dangerous environment of the immediate vicinity of the road.

[0003] To circumvent this problem, so-called self-sealing pneumatic tires were developed, which are now commercially available from various manufacturers. In these self-sealing tires, an additional sealing layer, sometimes also referred to as a "sealant," located inside the tire beneath the tread, ensures that any puncture in the tread area seals the resulting opening, preventing air from escaping and at least slowing down the associated pressure loss. General information on the technological background is disclosed, for example, in US 4287928 A, EP 3175975 B1, EP 3085523 B1, WO 2022237250 A1, and US 4263075 A.

[0004] Self-sealing pneumatic tires and the sealants used for them are well-known to those skilled in the art. In the prior art, the sealant composition is typically applied to the already vulcanized pneumatic tire. For those skilled in the art, it is crucial that sufficient adhesion exists between the sealant composition and the interior of the pneumatic tire, particularly the inner tire liner. To this end, prior art usually involves a separate pre-cleaning of the inner tire liner before the sealant composition is applied, in order to maximize the adhesion of the resulting bond and prevent, for example, contaminants from locally reducing the bond strength.

[0005] With increasing awareness of the need for more sustainable economic practices and a more careful use of fossil resources, the recycling of pneumatic vehicle tires has come into sharper focus in recent years, with various approaches and concepts for recycling old pneumatic vehicle tires being known. However, with regard to self-sealing pneumatic tires, most relevant recycling processes have in common that, for efficient recycling, the sealant composition usually has to be removed from the tire before it can be recycled.

[0006] Removing the sealant from the tire becomes increasingly difficult the stronger the bond between the sealant and the tire's inner liner. Thus, the high adhesion between the sealant and the inner liner, desirable in the production of new self-sealing tires, negatively impacts their recyclability at the end of their service life. This creates a conflict of objectives for self-sealing tires between the performance characteristics of new tires, which require a firm bond between the sealant and the tire's recyclability at the end of its lifespan.

[0007] The primary object of the present invention was to eliminate or at least reduce the disadvantages of the prior art.

[0008] In particular, the object of the present invention was to provide a method for manufacturing a vehicle tire and a corresponding vehicle tire which has excellent self-sealing properties when used on a vehicle, especially with regard to a reliable hold of the sealant composition on the inside of the tire, but which is also particularly time- and cost-efficient to recycle, since the sealant composition can be removed as easily as possible in the course of typical recycling processes.

[0009] Accordingly, the object of the present invention was to identify, by suitable means or methods, an optimal solution to the existing conflict of objectives between the durability of the resulting composite of vehicle pneumatic tire and sealant composition and the subsequent removability of the sealant composition.

[0010] The inventors of the present invention have now found that the problems described above can surprisingly be solved if, during the vulcanization of the vehicle pneumatic tire, a silicone-based dispersion is applied to the inner layer of the tire, such that after vulcanization a surface is obtained that is at least partially covered with polysiloxane particles, if the sealant composition is applied directly to this surface covered with polysiloxane particles, as defined in the claims.

[0011] The invention is based on the realization that, in order to resolve the conflict of objectives described above, a technical aid can be used synergistically, which in some cases is actually used for a different purpose in tire manufacturing.

[0012] This involves the use of an aqueous dispersion of polysiloxane particles, which, along with other compositions with comparable effects (sometimes referred to as "lubricants" by those skilled in the art), is used in some manufacturing processes for pneumatic vehicle tires to optimize the boundary layer between the unvulcanized tire blank and the vulcanization mold used for vulcanization. The aqueous dispersion serves, in particular, to facilitate the efficient removal of the vulcanized tire from the mold after vulcanization and, especially, to prevent rubber residue from adhering to the mold.

[0013] In the prior art, when using "lubricants", it is generally common to remove the "lubricant" residues remaining on the surface of the vehicle tire after vulcanization, in particular using material-removing processes such as strong brushing or laser-based cleaning, whereby in the case of self-sealing tires the intention is in particular to optimize adhesion as described above.

[0014] The inventors of the present invention have now found that, surprisingly, contrary to existing prejudices, it is possible to dispense with this cleaning step and apply the sealant composition directly to the surface covered with polysiloxane particles, provided that a specific aqueous dispersion based on polysiloxane particles is used as a "lubricant".

[0015] Surprisingly, sufficient adhesion is achieved between typical sealant compositions and the tire surface coated with polysiloxane particles, enabling reliable operation and the production of high-performance, self-sealing pneumatic tires. At the same time, excellent recyclability is achieved for these self-sealing tires, as the sealant composition can be easily removed during recycling processes, thus saving time and money, for example, using typical mechanical separation methods.

[0016] The aforementioned problems are thus solved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention are described in the dependent claims and the following descriptions.

[0017] Such embodiments, which are hereinafter referred to as preferred, are combined in particularly preferred embodiments with features of other embodiments referred to as preferred. Combinations of two or more of the embodiments referred to below as particularly preferred are therefore especially preferred. Also preferred are embodiments in which a feature of one embodiment, referred to as preferred to any extent, is combined with one or more further features of other embodiments, which are referred to as preferred to any extent. Features of preferred vehicle pneumatic tires result from the features of preferred methods.

[0018] Insofar as mass fractions are specified below, they are generally expressed in the industry as combined mass fractions of one or more components, thus indicating that the combined mass fraction of the respective components meets the relevant criteria. The unit phr (parts per hundred parts of rubber by weight) used here is the standard unit of measurement in the rubber industry for compound formulations. It specifies the mass fractions of the components in the rubber compound relative to the mass of the high-molecular-weight rubbers present in the compound (weight-average molar mass Mw according to GPC greater than 60,000 g / mol), where the combined mass fraction of the high-molecular-weight rubbers corresponds to 100 phr.

[0019] The invention relates in particular to a method for manufacturing a vehicle pneumatic tire, comprising the following process steps: a) Manufacture or supply of a vehicle pneumatic tire blank, comprising: i) a carcass blank comprising a multitude of reinforcing elements embedded in a first vulcanizable rubber compound, ii) a tread blank arranged radially above the carcass blank, and iii) an inner layer blank arranged radially below the carcass blank, comprising a second vulcanizable rubber compound comprising at least a butyl rubber and / or halobutyl rubber, b) Applying an aqueous dispersion to the surface of the inner layer blank to obtain a prepared vehicle pneumatic tire blank, wherein the aqueous dispersion comprises one or more dispersed polysiloxane particles, c) Vulcanizing the prepared vehicle pneumatic tire blank in a vulcanization mold to obtain a vehicle pneumatic tire, wherein the surface of the tire inner layer obtained from the inner layer blank is at least partially coated with polysiloxane particles, and d) Application of a sealant composition to an application area of ​​the surface of the tire inner layer coated with polysiloxane particles.

[0020] The method according to the invention serves to manufacture a pneumatic vehicle tire, in particular a self-sealing pneumatic vehicle tire. The manufactured pneumatic vehicle tires can, in principle, be for a wide range of applications, for example, also for motorcycles. However, the method according to the invention is particularly relevant for the manufacture of pneumatic vehicle tires for passenger cars or trucks. A method according to the invention is therefore preferred in which the pneumatic vehicle tire is a passenger car or truck tire, preferably a passenger car tire.

[0021] In the inventive method, a vehicle tire blank is first produced using a typical process. For this, a person skilled in the art can refer to methods known from the prior art. With regard to its structure, the vehicle tire blank to be produced initially corresponds to a typical vehicle tire blank. This means, in particular, that the unvulcanized vehicle tire blank comprises a carcass blank with reinforcing elements embedded in a vulcanizable rubber compound, above which the unvulcanized tread is arranged, while the inside of the vehicle tire blank is covered by the inner layer blank, from which the inner tire layer is to be obtained after vulcanization, which is primarily responsible for the airtightness of the manufactured vehicle tire.

[0022] For the first vulcanizable rubber compound, i.e., the vulcanizable rubber compound used for rubberizing the reinforcing elements, the person skilled in the art can, as well as for the vulcanizable rubber compound used in the tread blank, refer to all vulcanizable rubber compounds known from the prior art. However, the decisive factor for the interaction underlying the invention between the subsequent tire inner layer, the lubricant used, and the sealant composition is the nature of the tire inner layer, which, in the inventors' opinion, must comprise at least butyl rubber or halobutyl rubber, both of which are thoroughly familiar to those skilled in the art in the field of tire manufacturing.

[0023] In practice, the inner layer blank in the vehicle tire blank will line the entire inward-facing surface to achieve the most complete sealing effect possible in the subsequent vehicle tire. A preferred method according to the invention is therefore one in which the radially inner surface of the vehicle tire blank is substantially completely covered by the inner layer blank.

[0024] The inventors have succeeded in identifying particularly suitable materials for the composition of the second vulcanizable rubber compound used in the inner layer blank, which, in combination with the subsequently applied aqueous dispersion, achieves a good balance between the adhesion of the sealant composition and its removability. A preferred method according to the invention is one in which the second vulcanizable rubber compound comprises butyl rubber and / or halobutyl rubber in a combined mass fraction in the range of 70 to 100 phr, preferably in the range of 80 to 100 phr, and particularly preferably in the range of 90 to 100 phr. An additionally or alternatively preferred method according to the invention is one in which the second vulcanizable rubber compound comprises halobutyl rubber, preferably chlorobutyl rubber or bromobutyl rubber.A preferred method according to the invention is additionally or alternatively a method wherein the second vulcanizable rubber mixture comprises one or more fillers, preferably in a combined mass fraction of 30 phr or more, more preferably of 40 phr or more, particularly preferably of 60 phr or more, wherein the filler is preferably selected from the group consisting of carbon black and amorphous silicon dioxide, for example precipitated amorphous silicon dioxide, preferably carbon black.

[0025] In process step b), a so-called "lubricant," sometimes also referred to as a "tire release agent," is applied to the surface of the inner layer blank, i.e., before vulcanization. According to the inventors, however, not just any tire release agent can be used to achieve the desired beneficial effect of the sealant composition being easily removable during the recycling of the vehicle tires. Rather, it is necessary to use an aqueous dispersion as the tire release agent that is "silicone-based" and comprises appropriately dispersed polysiloxane particles. Based on the inventors' experiments, it is assumed that the advantages of the process according to the invention do not depend on the choice of a specific polysiloxane in this context, due to the generally very similar macroscopic properties of polysiloxanes.

[0026] According to the inventors, it is advantageous for the aqueous dispersion to consist as largely as possible of water in its liquid phase. Furthermore, the inventors have also identified suitable ranges for the solids content of the aqueous dispersion. A preferred method according to the invention is one in which the liquid phase of the aqueous dispersion consists of 70% or more, preferably 80% or more, particularly preferably 90% or more, and most preferably 95% or more, of water, based on the mass of the liquid phase. An additionally or alternatively preferred method according to the invention is one in which the aqueous dispersion has a solids content in the range of 30% to 60%, preferably in the range of 40% to 50%.A preferred method is additionally or alternatively a method according to the invention wherein the solid phase of the aqueous dispersion consists of 70% or more, preferably 80% or more, particularly preferably 90% or more, most preferably 95% or more, of polysiloxane particles, based on the mass of the solid phase.

[0027] According to the inventors, to achieve the best possible coverage of the surface with polysiloxane particles, it is advisable to agitate the aqueous dispersion immediately before application, for example by stirring. Application can, in principle, be carried out using a variety of methods, such as a brush. However, the inventors have achieved particularly good results regarding the quality of the resulting polysiloxane-coated surface when applying it with a spray gun. A preferred method according to the invention involves homogenizing the aqueous dispersion before application. An additionally or alternatively preferred method according to the invention involves applying the aqueous dispersion by spraying, preferably with a spray gun.

[0028] Although the beneficial effect of the aqueous dispersion on optimizing the adhesion of the sealant composition is particularly relevant in the areas where the sealant composition is subsequently applied, it is recommended, in order to synergistically utilize the advantageous release effect of the tire release agent, to apply the aqueous dispersion as much as possible over the entire surface of the inner layer blank in order to ensure excellent vulcanizability in the vulcanization mold. A preferred method according to the invention is one in which the aqueous dispersion is applied to 70% or more, preferably 80% or more, particularly preferably 90% or more, most preferably 95% or more, and most preferably substantially 100% of the surface of the inner layer blank.

[0029] The degree of coating of the tire inner layer with polysiloxane particles depends significantly on the application of the aqueous dispersion to the tire inner layer blank. In this respect, the inventors have succeeded in identifying particularly suitable areas with which especially advantageous results can be achieved, both with regard to the release effect from the vulcanization mold and with regard to the adhesion of the sealant composition to the formed surface. A preferred method according to the invention is one in which the aqueous dispersion has a basis weight in the range of 5 to 25 g / m². 2 , preferably in the range of 10 to 20 g / m³ 2 , is applied.

[0030] The appropriately prepared vehicle tire blank is vulcanized in process step c), whereby the inner layer blank is formed into the tire's inner layer, which, as a result of the preceding coating with the aqueous dispersion, is at least partially covered with polysiloxane particles. In their own experiments, the inventors have identified suitable vulcanization temperatures with which excellent results could be achieved in the process according to the invention, particularly with regard to the quality of the surface of the tire's inner layer, which is at least partially covered with polysiloxane particles. A preferred method according to the invention is one in which vulcanization takes place at a temperature in the range of 130 to 200 °C, preferably in the range of 150 to 180 °C.

[0031] The surface of the tire's inner liner is, as defined above, partially coated with polysiloxane particles. This indicates that it would be theoretically possible not to coat the entire inner liner blank with the tire release agent, although, as explained above, this is less preferred. In principle, to optimize the adhesion of the sealant composition, it would be sufficient to provide a coating of polysiloxane particles in the application area, i.e., the area of ​​the tire's inner liner to which the sealant composition is to be applied. However, analogous to the above, it is preferred if the surface of the tire's inner liner is coated with polysiloxane particles as completely as possible.A preferred method according to the invention is wherein the surface of the inner tire layer obtained from the inner layer blank is at least partially covered with polysiloxane particles to 70% or more, preferably 80% or more, particularly preferably 90% or more, very preferably 95% or more, and particularly preferably substantially 100%, based on the surface of the inner tire layer.

[0032] In the parts of the surface that are covered with polysiloxane particles, the density of the polysiloxane particles, i.e., the mass of polysiloxane particles in the upper volume layer of the surface, can vary, depending in particular on the application of the aqueous dispersion and the solids content. In this respect, the inventors propose that it is advantageous to achieve the densest possible coverage, ideally a complete coating, with polysiloxane particles, so that the surface of the tire's inner layer is preferably formed essentially entirely by a layer of polysiloxane particles, especially in the application area relevant for the adhesion of the sealant composition.A preferred method according to the invention is wherein the surface of the tire inner layer obtained from the inner layer blank is covered with polysiloxane particles to 70% or more, preferably 80% or more, particularly preferably 90% or more, very preferably 95% or more, particularly preferably substantially 100%, in the areas covered with polysiloxane particles, especially in the application area.

[0033] In process step d), a sealant composition is applied to the application area, wherein the application area is any area onto which the sealant composition is applied, provided that this application must take place on the surface coated with polysiloxane particles. In practice, this will mostly be a process according to the invention, wherein the application area is located on the inner side of the vehicle tire blank facing away from the tread blank.

[0034] According to the inventors, typical sealant compositions known from the prior art and commercially available from various manufacturers can advantageously be used as the sealant composition. However, the inventors have succeeded in identifying sealant compositions which, in interaction with the polysiloxane particle-coated surface, exhibit particularly good adhesion while simultaneously offering advantageous removability. A preferred method according to the invention comprises the following, based on the mass of the sealant composition: i) one or more first rubbers selected from the group consisting of butyl rubber and halobutyl rubber, preferably in a combined mass fraction in the range of 9 to 23%, particularly preferably in the range of 10 to 20%, and / or ii) one or more second rubbers selected from the group consisting of diene rubbers different from the first rubbers, preferably polybutadiene rubber, preferably in a combined mass fraction in the range of 50 to 70%, particularly preferably in the range of 55 to 65%, and / or iii) one or more inorganic fillers, wherein the inorganic fillers are preferably selected from the group consisting of carbon black and magnesium oxide, preferably in a combined mass fraction in the range of 3 to 9%, particularly preferably in the range of 4 to 8%, and / or iv) one or more crosslinking agents, wherein the crosslinking agent is preferably selected from the group consisting of peroxides and oximes, for example p-benzoquinone dioximes, preferably in a combined mass fraction in the range of 0.5 to 3%, particularly preferably in the range of 1 to 2.5%.

[0035] A preferred method according to the invention is one in which the sealant composition is applied as a formless mass. Alternatively, a preferred method according to the invention is one in which a sealant layer is formed with the sealant composition.

[0036] In addition to the use of a specific tire release agent, the special feature of the method according to the invention is that the sealant composition is applied to the application area with the polysiloxane-coated surface. This means that, unlike in the prior art, the tire release agent is not removed, but rather the polysiloxane particles remain between the surface of the tire's inner layer and the applied sealant composition. Accordingly, unlike in the prior art, no material-removing cleaning, such as that carried out with brushes or lasers, takes place. A preferred method according to the invention is one in which the surface of the tire's inner layer, which is at least partially coated with polysiloxane particles in the application area, is not treated with a material-removing process between process steps c) and d).A preferred method according to the invention is one in which the surface of the inner tire layer, which is at least partially covered with polysiloxane particles, is not processed in the application area between process steps c) and d), in particular by means of brushes or lasers.

[0037] The inventors' experiments have shown that the surface coated with polysiloxane particles can be superficially cleaned using non-abrasive methods without unduly restricting the advantages of the inventive method and without reverting to vehicle tires that would be disadvantageous with regard to recyclability. It has therefore proven advantageous to forgo such cleaning altogether, and in particular to avoid wet cleaning steps. For essentially all embodiments, a method according to the invention is preferred in which the surface of the tire's inner layer, at least partially coated with polysiloxane particles, is cleaned in the application area between process steps c) and d) using a non-abrasive method, preferably compressed air cleaning.A preferred method according to the invention is one in which the surface of the inner tire layer, which is at least partially covered with polysiloxane particles, is not contacted with a cleaning substance in the application area between process steps c) and d).

[0038] In particularly preferred embodiments of the inventive method, the sealant composition is thus applied directly to the inner tire layer coated with polysiloxane particles, as obtained after vulcanization. In other words, a method according to the invention is particularly preferred in which the sealant composition is applied directly to the surface of the inner tire layer produced in process step c).

[0039] The invention also relates to a vehicle pneumatic tire, manufactured or manufacturable using the method according to the invention.

[0040] The invention and preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying figure. It shows: Fig. 1 a simplified flowchart of the process steps of the process according to the invention.

[0041] Fig. Figure 1 shows a schematic representation of the process steps of the method according to the invention in a flowchart. In a first step 100, a vehicle pneumatic tire blank is initially produced, which, in addition to the carcass blank, the inner layer blank arranged on its inner side, and the tread blank arranged above it, may also include other components, in particular sidewall components.

[0042] Prior to vulcanization, a silicone-based aqueous dispersion, such as the commercial product Rhenodiv BP-2864 from RheinChemie Additives, is applied to the inner layer blank in step 102. This dispersion has a solids content of approximately 44%, with the liquid phase consisting predominantly of water. It is applied over the entire surface using a spray gun at a rate of approximately 15 g / m². 2 .

[0043] Following this preparation, the vehicle tire blank is vulcanized in a vulcanization mold in the next step 104 and given a tread pattern. During this process, a surface densely coated with polysiloxane particles forms on the previously prepared surface of the inner layer blank, which is transformed into a tire inner layer through vulcanization.

[0044] After the vulcanized tire is removed from the vulcanization mold, a sealant composition is applied in step 106 to the polysiloxane-coated surface of the inner tire layer below the tread by applying a formless mass, without any intermediate cleaning of the surface, in particular no abrasive cleaning that would remove the polysiloxane particles from the surface of the inner tire layer. This results in a pneumatic tire that, in use, exhibits sufficient bond strength between the sealant composition and the inner tire layer, but is very easily, i.e., easily, recycled in typical recycling processes.in a time- and cost-efficient manner, the sealant composition can be removed, for example by using typical cutting tools, such as a blade, advantageously leaving no or only minor residues. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 4287928 A

[0003] EP 3175975 B1

[0003] EP 3085523 B1

[0003] WO 2022237250 A1

[0003] US 4263075 A

[0003]

Claims

[1] Method for producing a pneumatic vehicle tire, comprising the process steps: (a) manufacturing or providing a green pneumatic vehicle tyre comprising: i) a carcass green comprising a plurality of reinforcements embedded in a first vulcanizable rubber mixture, (ii) a tread blank arranged radially above the carcass blank, and iii) an inner layer blank arranged radially below the carcass blank, comprising a second vulcanizable rubber mixture comprising at least one butyl rubber and / or halobutyl rubber, b) applying an aqueous dispersion to the surface of the inner layer blank to obtain a prepared pneumatic vehicle tire blank, wherein the aqueous dispersion comprises one or more dispersed polysiloxane particles, c) vulcanising the prepared pneumatic vehicle tyre blank in a vulcanisation mould to obtain a pneumatic vehicle tyre, wherein the surface of the tyre inner layer obtained from the inner layer blank is at least partially coated with polysiloxane particles, and d) Applying a sealant composition to an application area of the surface of the tire inner layer coated with polysiloxane particles. [2] The method of claim 1, wherein the second vulcanizable rubber composition comprises the butyl rubber and / or the halobutyl rubber in a combined mass fraction in the range of 70 to 100 phr. [3] A method according to any one of claims 1 or 2, wherein the second vulcanizable rubber composition comprises halobutyl rubber. [4] A method according to any one of claims 1 to 3, wherein the second vulcanizable rubber mixture comprises one or more fillers. [5] A process according to any one of claims 1 to 4, wherein the liquid phase of the aqueous dispersion consists of 70% or more of water, based on the mass of the liquid phase. [6] A process according to any one of claims 1 to 5, wherein the aqueous dispersion has a solids content in the range of 30 to 60. [7] A process according to any one of claims 1 to 6, wherein the solid phase of the aqueous dispersion consists of 70% or more of polysiloxane particles, based on the mass of the solid phase. [8] Method according to one of claims 1 to 7, wherein the surface of the tire inner layer at least partially covered with polysiloxane particles in the application area is cleaned between the method steps c) and d) using a non-material-removing method. [9] Method according to one of claims 1 to 8, wherein the sealant composition is applied directly to the surface of the tire inner layer produced in process step c). [10] Pneumatic vehicle tyres manufactured or producible by the method according to one of claims 1 to 9.

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