Self-sealing tire sealant, method for producing a self-sealing tire sealant and vehicle tires containing the tire sealant

Description

[0001] The invention relates to a self-sealing tire sealant, a method for producing 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. Here, 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 inner side in the 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 occurred through 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 a temporary spare tire.

[0003] The sealant is characterized by airtightness, strong adhesiveness and balanced flow behavior.

[0004] WO 2008 / 141848 A1 discloses a process for producing a tire sealant, which is made from two sealant components A and B. Component A is a highly viscous component containing at least one rubber. The rubber used, in particular butyl rubber, has a high viscosity compared to the sealant, which must first be reduced to produce the finished sealant (mixing with component B).

[0005] DE 102007028932 A1 discloses a pneumatic vehicle tire whose sealant can be based on polyurethane or a viscous mixture based on a butyl rubber, a polybutene or based on silicone.

[0006] DE 102013110890 AI discloses a method for producing a pneumatic vehicle tire having a self-sealing tire sealant pre-applied to the interior thereof on the inner surface opposite the tread. The method comprises at least the following process steps: mixing at least microspheres and at least one polybutene solution to produce a component B; mixing at least one polymer and at least one crosslinker to produce a component A; mixing component A and component B to produce a microsphere-containing and / or expandable graphite-containing tire sealant at a temperature of 90 to 140°C; and applying the tire sealant to the inner surface of a vulcanized pneumatic vehicle tire opposite the tread.

[0007] Depending on the other components, especially low-viscosity components, contained in the tire sealant, health and environmental concerns may arise. The sealant's components should also be compatible with the other tire components.

[0008] The present invention is therefore based on the object of providing a self-sealing tire sealant that is comparatively safe for health and the environment without adversely affecting the properties of the tire sealant. In particular, it should continue to exhibit good flowability and sealing effect.

[0009] This task is solved by the sealant containing at least one polyolefin with a chlorine content of less than or equal to 5 mg / kg.

[0010] Surprisingly, it has been found that the same flow and sealing properties, as well as tackiness, are achieved by using a polyolefin with a low chlorine content in the tire sealant. The tire sealant according to the invention is safe for health and the environment due to its comparatively low chlorine content. A high chlorine content results in the formation of hydrochloric acid (HCl), which can escape from the sealant over an extended period, e.g., in the form of vapors. The released hydrochloric acid is one reason for the potential environmental and health risks of sealants with a high chlorine content in their components.

[0011] Self-sealing tire sealants are known to those skilled in the art. As mentioned above, these can be based on butyl rubber and polybutene (a polyolefin). A more precise specification of polybutene with regard to impurities and secondary components, particularly with regard to chlorine content, is not available in the prior art in connection with tire sealants.

[0012] According to the present invention, the self-sealing tire sealant contains at least one polyolefin with 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.

[0013] The at least one polyolefin of the tire sealant preferably has a number average molecular weight distribution Mn according to GPC of 800 to 2500 g / mol, particularly preferably 1200 to 1600 g / mol, very particularly preferably 1200 to 1400 g / mol, for example 1300 g / mol.

[0014] A polyolefin with a Mn of 800 to 2500 g / mol is particularly suitable for producing the desired flowability while simultaneously providing a sealing effect of the sealant in the event of a puncture.

[0015] It is particularly preferred that the polyolefin be at least one polybutene. This determines the tackiness of the finished sealant and determines the flowability during the production process as well as the local stability of the finished sealant.

[0016] It can also be a mixture of two or more polybutenes.

[0017] A mixture of at least one polybutene with at least one other polyolefin is also conceivable.

[0018] 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. 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.

[0019] The sealant of the pneumatic vehicle tire according to the invention particularly preferably contains 65 to 75 wt.% of at least one polybutene having a chlorine content of less than or equal to 5 mg / kg.

[0020] The sealant preferably also contains: At least one rubber and at least one filler and at least one tackifier and at least one crosslinker and at least one crosslinking initiator.

[0021] According to an advantageous embodiment of the invention, the sealant contains the components in the following amounts: 65 to 75 wt% of at least one polybutene having a chlorine content of less than or equal to 5 mg / kg and 9 to 14.9 wt% of at least one rubber and 5 to 8.9 wt% of at least one filler and 2 to 3.5 wt% of at least one tackifier and 0.4 to 0.8 wt% of at least one crosslinker and 0.5 to 1.2 wt% of at least one crosslinking initiator.

[0022] The information in wt.% refers to the total amount of sealant.

[0023] The sealant is therefore preferably based on the crosslinking of a rubber with a crosslinking agent.

[0024] It is clear to the person skilled in the art that the components mentioned are present in the crosslinked sealant at least partially in chemically modified form, in particular as derivatives.

[0025] The rubber can be any type of rubber known to those skilled in the art. A mixture of different rubbers is also conceivable.

[0026] 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).

[0027] These rubber types are particularly well suited to the processing temperatures during the production of the tire sealant and later during application in the tire.

[0028] Particularly preferred is at least butyl rubber (IIR). Butyl rubber is particularly suitable because it has a comparatively high level of airtightness.

[0029] The filler may be any filler known to the person skilled in the art, such as in particular carbon black and / or silica.

[0030] 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 properties are improved.

[0031] This may be any type of carbon black known to the person skilled in the art, such as in particular and preferably a carbon black of type N326.

[0032] A tackifier is understood to be a substance that increases the adhesiveness of the sealant. Preferably, the tackifier is at least one adhesive resin selected from the group consisting of alkyl resins and phenolic resins and gum resin, in particular tetrahydroabeitic acid and / or rosin and / or balsam resin, and coresin and aromatic resins and terpene oligomers and coumarone-indene resins.

[0033] In particular, the combination of a crosslinker with a crosslinking initiator results in a particularly effective tire sealant that seals quickly in the event of a puncture.

[0034] According to a preferred embodiment of the invention, the crosslinker is selected from the group comprising, particularly preferably consisting of, polymethylol resin and divinylbenzene and quinones. The quinone is preferably a quinone dioxime, for example dibenzoylquinone dioxime or para-benzoquinone dioxime. Para-benzoquinone dioxime is particularly preferred.

[0035] The preferred and particularly preferred crosslinkers achieve extremely rapid crosslinking at relatively low temperatures. This allows for the use of low-viscosity formulations in the sealant production process, which quickly solidify after the material is applied to the tire.

[0036] The crosslinking initiator is a chemical compound that initiates the crosslinking of the sealant. The crosslinking initiator can, for example and preferably, be lead oxide or other metal oxides or a peroxide compound.

[0037] A peroxide compound is a chemical compound that contains at least one peroxide unit, i.e., -OO- (where O = oxygen). Multiple peroxides can also be used. The peroxide(s) are preferably selected from the group consisting of diaroyl peroxides, diacyl peroxides, and peroxy esters.

[0038] The sealant may also contain other components, such as plasticizers, such as oil(s), and optionally other additives, such as color pigments and / or zinc oxide and / or sulfur and / or microspheres and / or glass beads and / or plastic particles.

[0039] The oil can be any oil known to the person skilled in the art, such as, in particular, 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.

[0040] When using mineral oil, this 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.

[0041] The sealant preferably does not contain any substance having a chlorine content of greater than 5 mg / kg based on the respective substance, ie it is preferably free of such substances, particularly preferably free of polybutene having a chlorine content of greater than 5 mg / kg based on the respective polybutene.

[0042] Thus, the chlorine content relative to the total amount of sealant is preferably adjusted by the polybutene(s) used as described above.

[0043] Another object of the present invention relates to a process for producing a tire sealant, which comprises at least the following process steps: a) mixing at least one rubber with at least one filler to produce a masterbatch; and b) mixing the masterbatch with at least one polyolefin having a chlorine content of less than or equal to 5 mg / kg to produce a component A; and c) providing a component B containing at least one crosslinking initiator; and d) mixing component A and component B to produce the tire sealant.

[0044] The above statements apply to all components unless explicitly stated otherwise.

[0045] According to the invention, in process step a), a masterbatch is first produced, which contains at least one rubber and at least one filler. All the above statements apply to the rubber and filler. Particularly preferably, at least butyl rubber (IIR) is used in process step a). Butyl rubber is particularly suitable because it has a comparatively high airtightness.

[0046] In process step a), further components as described above can be added, such as processing aids, in particular tackifiers and / or at least one plasticizer and optionally further additives.

[0047] Process step a) can be carried out in one or more mixing stages.

[0048] In process step a), preferably and in particular, at least one crosslinker may be added, whereby reference is also made to the statements already made regarding the crosslinker(s).

[0049] The masterbatch produced in step a) is mixed in process step b) with at least one polyolefin having a chlorine content of less than or equal to 5 mg / kg, thereby producing component A.

[0050] The at least one polyolefin is particularly preferably at least one polybutene, as also stated above for the sealant. This determines the tackiness of the finished sealant and determines the flowability of component A in the production process, as well as the local stability of the finished sealant. Preference is given to at least one polyolefin, preferably polybutene, with a number-average molecular weight distribution Mn according to GPC of 800 to 2500 g / mol, particularly preferably 1200 to 1600 g / mol, again particularly preferably 1200 to 1400 g / mol, in particular, for example, 1300 g / mol.

[0051] Component A in process step b) is preferably produced in a kneading extruder or a twin-screw extruder. This ensures sufficient mixing of the almost solid masterbatch with the low-viscosity polyolefin. These extruders are therefore particularly suitable for processing high viscosities. However, other suitable devices are also conceivable.

[0052] The production of component A in process step b) is particularly preferably carried out in a twin-screw extruder.

[0053] According to the invention, in process step c) a component B containing at least one crosslinking initiator is provided, for which reference is made to the above statements.

[0054] In process step c), component B preferably contains at least one polyolefin with a chlorine content of less than or equal to 5 mg / kg. This means that at least one polyolefin with a chlorine content of less than or equal to 5 mg / kg is preferably also added to the sealant via component B. This ensures optimal tack, flowability and local stability of the finished sealant and, at the same time, makes it possible to dispense with other components that could pose a greater potential for environmental hazards. By using at least one polyolefin with a chlorine content of less than or equal to 5 mg / kg in both components of the sealant, the total chlorine content of the produced sealant can be determined or set to a particularly low level via the low chlorine content of the polyolefin.

[0055] According to the invention, in process step d) component A and component B are mixed to produce the tire sealant.

[0056] Other process steps and devices are preferably carried out as disclosed in WO 2008 / 141848.

[0057] 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.

[0058] In the following, the invention will be explained using an example. Production of the sealant:

[0059] For example, component A is first produced from a masterbatch and polybutene: In this case, a masterbatch is first produced in an internal mixer, which contains 45 to 50 wt.% butyl rubber, 25 to 30 wt.% carbon black N326, 2 to 5 wt.% MES oil, 2 to 3 wt.% zinc oxide, 8 to 10 wt.% adhesive resin, 2 to 4 wt.% quinone dioxime and 0.5 to 3 wt.% sulfur.

[0060] The wt% refers to the proportion in relation to the total amount of the masterbatch.

[0061] In a twin-screw extruder, 25 to 30 wt.% of the masterbatch is then continuously mixed with 65 to 70 wt.% polybutene (e.g., Glissopal®< V-500, chlorine content < 1 mg / kg) and 1 to 5 wt.% paraffin oil according to process step b), thereby producing component A. The wt.% refers to the proportion relative to the total amount of component A.

[0062] According to a step c), component B containing 70 to 75 wt.% polybutene (e.g. Glissopal ®< V-500) and 25 to 30 wt.% dibenzoyl peroxide solution (50 wt.% dibenzoyl peroxide in dibutyl maleate) is provided, wherein the wt.% relates to the total amount of component B.

[0063] According to a step d), for example, component A and component B are mixed together in a weight ratio of 10 to 1, whereby the sealant is obtained.

[0064] Crosslinking occurs during and after mixing component A and component B.

[0065] The tire sealant thus produced has a low total chlorine content, which is determined by the added polybutenes.

[0066] The tire sealant obtained according to the invention is applied to the inside of a pneumatic vehicle tire by means of known devices.

Claims

1. Self-sealing tyre sealant, characterized in that it contains at least one polyolefin having a chlorine content not more than 5 mg / kg.

2. Tyre sealant according to Claim 1, characterized in that it additionally contains the following constituents: - at least one rubber and - at least one filler and - at least one tackifier and - at least one crosslinker and - at least one crosslinking initiator.

3. Tyre sealant according to Claim 1 or 2, characterized in that the at least one polyolefin has a number-average molecular weight distribution Mn according to GPC of 800 to 2500 g / mol.

4. Tyre sealant according to any of the preceding claims, characterized in that the at least one polyolefin is at least one polybutene.

5. Tyre sealant according to Claim 4, characterized in that it contains 65% to 75% by weight of at least one polybutene having a chlorine content of not more than 5 mg / kg.

6. Tyre sealant according to any of Claims 2 to 5, characterized in that the rubber 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).

7. Tyre sealant according to any of Claims 2 to 6, characterized in that the rubber is at least butyl rubber (IIR).

8. Tyre sealant according to any of Claims 2 to 7, characterized in that the filler comprises at least one carbon black.

9. Tyre sealant according to any of Claims 2 to 8, characterized in that the crosslinker is selected from the group containing polymethylol resin and divinylbenzene and quinones.

10. Tyre sealant according to any of Claims 2 to 9, characterized in that the at least one crosslinking initiator is selected from the group containing lead oxide and other metal oxides and peroxidic compounds.

11. Tyre sealant according to any of Claims 2 to 10, characterized in that the tackifier is a tackifying resin which is selected from the group consisting of alkyl resins and phenolic resins and gum resin, in particular tetrahydroabietic acid and / or rosin and / or balsam resin, and coresin and aromatic resins and terpene oligomers and coumarone-indene resins.

12. Process for producing a tyre sealant which comprises at least the process steps of: a) mixing at least one rubber with at least one filler to produce a masterbatch; and b) mixing the masterbatch with at least one polyolefin having a chlorine content of not more than 5 mg / kg to produce a component A; and c) providing a component B containing at least one crosslinking initiator; and d) mixing component A and component B to produce the tyre sealant.

13. Process according to Claim 12, characterized in that in process step c) component B contains a polyolefin having a chlorine content of not more than 5 mg / kg.

14. Pneumatic vehicle tyre which comprises the tyre sealant according to any of Claims 1 to 11 at least on the inner surface opposite the tread.