SELF-SEALING TIRE SEALANT AND PNEUMATIC VEHICLE TIRE CONTAINING THE TIRE SEALANT

Description

[0001] The invention relates to a self-sealing tire sealant and a pneumatic vehicle tire containing the tire sealant.

[0002] Self-sealing pneumatic vehicle tires are known, for example, from DE 10 2006 059 286 A1 by the applicant. In this case, standard tire designs are subsequently provided with a layer of sealant. The self-sealing sealant is a self-adhesive, viscous sealing compound that is applied as a layer from the radially inside projection area of ​​the belt package to the radially innermost tire layer, the largely airtight inner layer. The sealant layer is capable of independently sealing punctures up to five millimeters in diameter. After a puncture has penetrated the tread and through the inner layer, the sealant completely encloses the penetrated foreign body, sealing the interior from the environment and thus preventing a loss of air pressure in the tire. The driver of the vehicle is not forced to immediately replace the defective tire with a full-size spare tire or an emergency spare tire.

[0003] The sealant is characterized by airtightness, strong tackiness and balanced flow behavior, whereby the property profile is designed for use in pneumatic car tires with an internal pressure of 2 to 2.5 bar.

[0004] From the document US 4 895 610 A a self-sealing tire sealant is known which contains a polyolefin, a rubber and a crosslinking agent.

[0005] The object of the present invention is to provide, based on the prior art, a self-sealing tire sealant which is suitable for tires with a high internal pressure, in particular 3.5 bar and more.

[0006] The sealant should have an optimal combination of properties in terms of viscosity, flow behavior, elasticity and stickiness.

[0007] This task is solved by the sealant containing at least the following components: 10 to 30 wt.% of at least one polyolefin and 35 to 60 wt.% of at least one rubber and 1.0 to 3.0 wt.% of at least one crosslinker, wherein the crosslinker is selected from the group consisting of polymethylol resin and divinylbenzene and quinones, wherein the quinone is preferably a quinone dioxime, and 1.8 to 5.0 wt.% of at least one crosslinking initiator, wherein the crosslinking initiator is lead oxide or another metal oxide or a peroxidic compound, wherein the peroxidic compound is preferably selected from the group consisting of diaroyl peroxides, diacyl peroxides and peroxy esters.

[0008] By combining the components in the specified quantities, the sealant exhibits optimal flow behavior, optimal viscosity and elasticity, and optimal tackiness. This property profile ensures that the sealant continues to seal when used in tires with an internal pressure of 3.5 bar and above, while simultaneously preventing flow from the puncture site. The sealant exhibits an increased viscosity, particularly due to the increased amounts of crosslinker, crosslinking initiator, and rubber, and a lower amount of polyolefin compared to the state of the art.

[0009] With the present invention it is thus possible to design self-sealing tires even with a high internal pressure.

[0010] The weight percentages refer to the total amount of sealant. The terms "sealant" and "tire sealant" are used synonymously in the present invention and refer to self-sealing (automatically sealing) sealant compositions, unless expressly stated otherwise.

[0011] The tire sealant according to the invention can be produced by methods known in the art.

[0012] A further subject of the present invention is a pneumatic vehicle tire which has the tire sealant according to the invention, including all the aforementioned embodiments, at least on the inner surface opposite the tread.

[0013] The pneumatic vehicle tire according to the invention is particularly designed to operate at an internal pressure of 3.5 bar or more. This can be any tire type that operates with such an internal pressure, such as, in particular, van tires, truck tires, and industrial tires.

[0014] The components of the sealant according to the invention are explained in more detail below.

[0015] According to the present invention, the self-sealing tire sealant contains 10 to 30 wt.% of at least one polyolefin. Preferably, the amount of the at least one polyolefin is 15 to 30 wt.%, for example 25 wt.%.

[0016] With an amount of 10 to 30 wt.%, preferably 15 to 30 wt.%, optimal flow behavior, in particular optimal viscosity, is achieved with simultaneous good manufacturability (processability) and tackiness of the sealant.

[0017] The at least one polyolefin preferably has a number average molecular weight distribution Mn according to GPC of 400 to 2500 g / mol, particularly preferably 800 to 2500 g / mol, very particularly preferably 800 to 1600 g / mol, again preferably 1200 to 1600 g / mol, again particularly preferably 1200 to 1400 g / mol, for example 1300 g / mol.

[0018] A polyolefin with the mentioned ranges for the Mn is particularly suitable to create the desired flowability while simultaneously providing a sealing effect of the sealant in the event of a puncture.

[0019] It is particularly preferred that the at least one polyolefin is at least one polybutene.

[0020] This adjusts the stickiness of the finished sealant and determines the flowability in the production process as well as the local strength of the finished sealant.

[0021] It can also be a mixture of two or more polybutenes, each with a Mn of 400 to 2500 g / mol, whereby the polybutenes can differ in Mn.

[0022] Suitable polybutenes, also called polyisobutenes, are available, for example, under the trade name Indopol® Polybutene from INEOS Capital Limited. A mixture of at least one polybutene with at least one other polyolefin is also conceivable.

[0023] According to a particularly advantageous development of the invention, the at least one polyolefin has a chlorine content of less than or equal to 5 mg / kg, preferably less than or equal to 3 mg / kg. This figure refers to mg of chlorine per kg of polyolefin. In a preferred embodiment of the invention, the self-sealing tire sealant contains at least one polyolefin with a chlorine content of less than or equal to 1.5 mg / kg, particularly preferably less than 1 mg / kg. The polyolefin is preferably a polybutene.

[0024] According to a particularly preferred embodiment of the invention, the sealant thus contains at least one polybutene with a chlorine content of less than or equal to 5 mg / kg, preferably less than or equal to 3 mg / kg, particularly preferably less than 1 mg / kg. Suitable polybutenes, also called polyisobutenes, are known, for example, under the trade name Glissopal® from BASF. Glissopal® V-500, V-640, or V-190 are particularly suitable.

[0025] According to the present invention, the self-sealing tire sealant contains 35 to 60 wt.% of at least one rubber. The amount of the at least one rubber is preferably 40 to 60 wt.%, particularly preferably 50 to 55 wt.%, for example 52 wt.%, based on the total amount of sealant.

[0026] The rubber used here is raw rubber, so the uncrosslinked sealant can contain both devulcanized rubber from recycled rubber residues and unvulcanized rubber.

[0027] The rubber can be any type of rubber known to those skilled in the art. A mixture of different rubbers is also conceivable.

[0028] According to a preferred embodiment of the invention, the rubber in process step a) is natural rubber (NR) and / or butadiene rubber (BR) and / or isoprene rubber (IR) and / or styrene-butadiene rubber (SBR) and / or polychloroprene (CR) and / or butyl rubber (IIR) and / or bromobutyl rubber (BIIR) and / or chlorobutyl rubber (CIIR). These rubber types are particularly well suited for the processing temperatures during the production of the tire sealant and later during application in the tire.

[0029] Particularly preferred is at least butyl rubber (IIR). Butyl rubber is particularly suitable because it has a comparatively high level of airtightness.

[0030] It is clear to the person skilled in the art that all of the above-mentioned components in the crosslinked sealant are present at least partially in chemically modified form, in particular as derivatives.

[0031] In particular, by combining a crosslinker with a crosslinking initiator in the amounts specified according to the invention, a particularly effective tire sealant is obtained which seals quickly in the event of a puncture and is optimized for tires with a high internal pressure.

[0032] According to the present invention, the self-sealing tire sealant contains 1.0 to 3.0 wt.% of at least one crosslinker. The amount of the at least one crosslinker is preferably 1.5 to 3.0 wt.%, particularly preferably 1.5 to 2.5 wt.%, based on the total amount of sealant.

[0033] According to the invention, the crosslinker is selected from the group consisting of polymethylol resin, divinylbenzene, and quinones. The quinone is preferably a quinone dioxime, for example dibenzoylquinone dioxime or para-benzoquinone dioxime. Para-benzoquinone dioxime is particularly preferred.

[0034] The preferred and particularly preferred crosslinkers achieve extremely rapid crosslinking at relatively low temperatures. This allows the sealant to set quickly after application of the material to the tire.

[0035] According to the present invention, the self-sealing tire sealant contains 1.8 to 5.0 wt.% of at least one crosslinking initiator.

[0036] The amount of the at least one crosslinking initiator is preferably 2.0 to 4.0 wt.%, particularly preferably 2.5 to 3.5 wt.%, based on the total amount of sealant.

[0037] The crosslinking initiator is a chemical compound that initiates the crosslinking of the sealant. The crosslinking initiator is lead oxide or other metal oxides, or a peroxide compound.

[0038] A peroxidic compound is a chemical compound that contains at least one peroxide unit, i.e. -OO- (where O = oxygen). It is also possible to use several peroxides. The peroxide(s) are preferably selected from the group consisting of diaroyl peroxides, diacyl peroxides and peroxyesters. The crosslinking initiator can be added as a pure substance or in a mixture with, for example, a stabilizer. In the case of a mixture, for example of 50 wt.% dibenzoyl peroxide and 50 wt.% dibutyl maleate as stabilizer, only the amount of peroxide contained is included in the amount of crosslinking initiator, i.e., for example, accompanying substances such as dibutyl maleate are not included in the above-mentioned amounts of at least one crosslinking initiator.

[0039] The sealant may also contain other components, such as fillers, tackifiers, plasticizers, such as oil(s), and optionally other additives, such as color pigments and / or zinc oxide and / or sulfur.

[0040] The plasticizer can be any plasticizer known to the person skilled in the art, in particular oils, such as aromatic, naphthenic or paraffinic mineral oil plasticizers, such as MES (mild extraction solvate) or RAE (residual aromatic extract) or TDAE (treated distillate aromatic extract), or rubber-to-liquid oils (RTL) or biomass-to-liquid oils (BTL), preferably with a polycyclic aromatics content of less than 3% by weight according to method IP 346. Mineral oils are particularly preferred as plasticizers.

[0041] When using mineral oil, it is preferably selected from the group consisting of DAE (Distilled Aromatic Extracts) and / or RAE (Residual Aromatic Extract) and / or TDAE (Treated Distilled Aromatic Extracts) and / or MES (Mild Extracted Solvents) and / or naphthenic oils.

[0042] According to a preferred embodiment of the invention, the sealant also contains at least one filler, in particular at least one active filler.

[0043] The filler may be any filler known to the person skilled in the art, such as, in particular, reinforcing fillers such as carbon black and / or silica, whereby precipitated silicas are particularly meant and preferred, which are known as fillers for tire rubber mixtures.

[0044] Furthermore, the sealant may contain magnetic fillers, such as ferromagnetic metals, such as iron, nickel, cobalt, strontium, barium and gadolinium, and / or their compounds, such as in particular iron compounds, in particular iron oxides, such as magnetite (Fe 3 O 4 ) or ferrites.

[0045] Furthermore, other reinforcing and non-reinforcing fillers are conceivable, in particular silicon oxide-based fillers such as silicates or sand or glass beads, as well as possibly reinforcing fillers such as graphite and graphene and so-called "carbon-silica dual-phase fillers", as well as microspheres or plastic particles or recycled residues of foams.

[0046] “Carbon blacks” include both industrial carbon blacks and pyrolysis carbon blacks.

[0047] According to a preferred embodiment of the invention, the filler comprises at least one carbon black. This has the advantage of increasing the cohesion of the sealant and reducing its stickiness during the manufacturing process. At the same time, the sealant's stability and tear resistance are improved.

[0048] In principle, all types of carbon black known to the person skilled in the art can be considered as carbon blacks within the scope of the present invention.

[0049] According to an advantageous embodiment of the invention, a carbon black is used which has an iodine adsorption number according to ASTM D 1510 of 20 to 180 g / kg, particularly preferably 30 to 140 g / kg, and a DBP number according to ASTM D 2414 of 30 to 200 ml / 100 g, preferably 90 to 180 ml / 100 g, particularly preferably 110 to 180 ml / 100 g.

[0050] According to a further preferred embodiment of the invention, a carbon black of the type N326 is used.

[0051] A mixture of two or more carbon blacks is also conceivable.

[0052] According to a further preferred embodiment of the invention, the filler comprises at least one silica.

[0053] This achieves optimal reinforcement of the sealant and enables good viscosity control and adjustment. Furthermore, the use of at least one silica increases the cohesion of the sealant and reduces its tackiness during the manufacturing process. At the same time, the sealant's in-place strength and tear properties are improved.

[0054] A mixture of two or more silicas is also conceivable.

[0055] The silicas can be those known to those skilled in the art and suitable as fillers for tire rubber compounds. Thus, for example, silicas of the type Ultrasil®< VN3 (trade name) from Evonik, as well as silicas with a comparatively low BET surface area (such as Zeosil®< 1115 or Zeosil®< 1085 from Solvay), as well as highly dispersible silicas, so-called HD silicas (e.g. Zeosil®< 1165 MP from Solvay) can be used.

[0056] Furthermore, a mixture of the fillers mentioned is conceivable and preferred, such as in particular at least one industrial carbon black in combination with at least one silica, which also results in the advantages mentioned.

[0057] According to an advantageous embodiment of the invention, the amount of the at least one filler is 0.1 to 20 wt.%, preferably 2 to 12 wt.%, for example 5 to 10 wt.%, based on the total amount of sealant.

[0058] According to a particularly advantageous embodiment of the invention, the sealant contains 2.0 to 20, preferably 2 to 12 wt.% of at least one filler selected from carbon blacks, silicas and magnetic particles, wherein carbon blacks include industrial carbon blacks and pyrolysis carbon blacks.

[0059] Fillers such as carbon black and / or silica strengthen the sealant, especially at low elongations. Furthermore, the network exhibits high temperature stability.

[0060] Magnetic particles make it possible to optimize the flow behavior of metallic piercing objects, such as iron nails.

[0061] According to a further embodiment of the invention, no filler, i.e. 0 wt.% filler, is contained.

[0062] According to advantageous embodiments, the sealant contains at least one tackifier, particularly in the case where the sealant does not already exhibit sufficient tackiness due to the components it contains, in particular the polymers. "Tackifier" is understood to mean, in principle, any substance that increases the tackiness of the sealant.

[0063] The amount of at least one tackifier is preferably 2.0 to 20 wt.% based on the total amount of sealant.

[0064] According to advantageous embodiments of the invention, the tackifier is at least one hydrocarbon resin.

[0065] It is clear to the person skilled in the art that hydrocarbon resins are polymers composed of monomers, whereby the hydrocarbon resin is formally composed of derivatives of the monomers by linking the monomers to one another.

[0066] In the context of the present application, the term "hydrocarbon resins" encompasses resins which contain carbon atoms and hydrogen atoms and may optionally contain heteroatoms, such as, in particular, oxygen atoms.

[0067] The hydrocarbon resin can be a homopolymer or a copolymer. In the present application, a homopolymer is defined as a polymer that, according to Römpp Online (excerpt from January 2, 2017, article last updated in August 2008), "is formed from monomers of only one type."

[0068] For the purposes of the present invention, a copolymer is understood to mean a polymer composed of several, i.e., two or more, different monomers. For the purposes of the present invention, the hydrocarbon resin can therefore also be, for example, a copolymer of three different monomers.

[0069] The monomers may be all monomers of hydrocarbon resins known to the person skilled in the art, such as aliphatic monomers, in particular aliphatic C 5 monomers, other unsaturated compounds which can be cationically polymerized, containing aromatics and / or terpenes and / or alkenes and / or cycloalkenes.

[0070] Preferred monomers are in particular C 5 and C 9 monomers.

[0071] The aromatics (aromatic monomers) can be, for example, alpha-methylstyrene and / or styrene and / or vinyltoluene and / or indene and / or coumarone and / or methylindene and / or methylcoumarone and / or phenol. The aromatic monomers are preferably alpha-methylstyrene and / or styrene and / or vinyltoluene and / or indene and / or coumarone and / or methylindene and / or methylcoumarone.

[0072] According to Römpp Online, the term "olefins" is the "group name for acyclic and cyclic aliphatic hydrocarbons with one or more reactive C=C double bonds in the molecule, which are now better referred to as alkenes or cycloalkenes, and in a broader sense also as a name for their substituted derivatives...." For the purposes of the present invention, unsaturated terpenes, alkenes, and cycloalkenes are therefore summarized under the generic term "olefins."

[0073] The alkenes can be, for example, 1-butene and / or 2-butene and / or butadiene.

[0074] According to a preferred embodiment of the invention, the hydrocarbon resin is at least one aliphatic resin, i.e., a resin that does not contain any aromatic ring systems. Such a resin consists of 100 wt. % aliphatic monomers or their derivatives.

[0075] According to a further embodiment of the invention, the resin consists of 10 to 99 wt.%, preferably 50 to 99 wt.%, particularly preferably 70 to 99 wt.%, of aliphatic monomers and 1 to 90 wt.%, preferably 1 to 50 wt.%, particularly preferably 1 to 30 wt.% of aromatic monomers.

[0076] According to a preferred embodiment of the invention, the hydrocarbon resin is at least one resin composed of at least C5 monomers and is known to those skilled in the art as a so-called C5 resin. This achieves particularly good sealant properties, in particular optimized flow behavior combined with good tackiness.

[0077] The aliphatic C5 monomers can be monomers of the C5 petroleum fraction, e.g., isoprene, and / or monomers of terpenes and / or cycloolefins and / or olefins, such as pentene. C5 means that these monomers are composed of five carbon atoms.

[0078] Furthermore, it is known to the person skilled in the art that the C 5 petroleum fraction may contain, in addition to aliphatic monomers having five carbon atoms, other aliphatic monomers (building blocks) having, for example, four, i.e. C 4 monomers, or six carbon atoms, C 6 monomers.

[0079] According to advantageous embodiments of the invention, the sealant contains 2 to 20 wt.% of at least one hydrocarbon resin as a tackifier. The amount of the at least one hydrocarbon resin is preferably 2 to 10 wt.%, particularly preferably 3.5 to 7 wt.%.

[0080] With such preferred and particularly preferred amounts, the tackiness and viscosity of the sealant are further optimized.

[0081] According to advantageous and exemplary embodiments of the invention, the sealant contains the following components in the following amounts: 10 to 30 wt% of at least one polyolefin, preferably at least one polybutene, and 2.0 to 20 wt% of at least one tackifier and 35 to 60 wt% of at least one rubber and 2.0 to 12 wt% of at least one filler and 1.0 to 3.0 wt% of at least one crosslinker and 1.8 to 5.0 wt% of at least one crosslinking initiator.

[0082] The information in wt.% refers to the total amount of sealant.

[0083] The tire sealant according to the invention can be produced from one or more components by methods known in the art. Mixing preferably takes place in an extruder, preferably a twin-screw extruder.

[0084] Possible process steps and devices are disclosed, for example, in WO 2008 / 141848.

[0085] A further subject of the present invention is a pneumatic vehicle tire which has the tire sealant according to the invention, including all the aforementioned embodiments, at least on the inner surface opposite the tread.

[0086] The layer thickness in the radial direction is from 2 to 8 mm, particularly preferably 3 to 7 mm, most preferably 4 to 5 mm.

[0087] The layer thickness is measured in the radial direction perpendicular to the axial direction.

[0088] The layer thicknesses mentioned achieve an optimal balance between sealing effect and, at the same time, not excessive material consumption and tire weight, which in turn has ecological advantages.

[0089] The sealant consists of the following substances, for example: 52 wt% butyl rubber, 25 wt% polybutene with a Mn of 1300 g / mol, 5.0 wt% aliphatic hydrocarbon resin (C 5 resin), 7.0 wt% carbon black N326 as filler, 2.0 wt% crosslinker 3.0 wt% crosslinking initiator + 3.0 wt% dibutyl maleate as stabilizer 3.0 wt% mineral oil plasticizer.

Claims

1. Self-sealing tyre sealant, characterized in that it contains at least the following constituents: - 10% to 30% by weight of at least one polyolefin and - 35% to 60% by weight of at least one rubber and - 1.0% to 3.0% by weight of at least one crosslinker, wherein the crosslinker is selected from the group consisting of polymethylol resin and divinylbenzene and quinones, wherein the quinone is preferably a quinone dioxime, and - 1.8% to 5.0% by weight of at least one crosslinking initiator, wherein the crosslinking initiator is lead oxide or another metal oxide or a peroxidic compound, wherein the peroxidic compound is preferably selected from the group consisting of diaroyl peroxides, diacyl peroxides and peroxyesters.

2. Tyre sealant according to Claim 1, characterized in that it contains 2.0% to 20% by weight, preferably 2.0% to 12% by weight, of at least one filler.

3. Tyre sealant according to Claim 2, characterized in that the filler is selected from carbon blacks, silicas and magnetic particles, wherein the carbon blacks comprise industrial carbon blacks and pyrolysis carbon blacks.

4. Tyre sealant according to any of the preceding claims, characterized in that it contains 2.0% to 20% by weight of at least one tackifier.

5. Tyre sealant according to Claim 4, characterized in that the tackifier comprises at least one hydrocarbon resin.

6. Tyre sealant according to any of the preceding claims, characterized in that it contains 1.5% to 3.0% by weight of at least one crosslinker.

7. Tyre sealant according to any of the preceding claims, characterized in that it contains 2.0 to 4.0 phr of at least one crosslinking initiator.

8. Pneumatic vehicle tyre comprising the tyre sealant according to any of Claims 1 to 7 at least on the inner surface opposite the tread.