VEHICLE TIRES WITH BELT BANDAGE

Description

[0001] The invention relates to a vehicle tire having a belt bandage, wherein the belt bandage comprises strength members, wherein the strength members comprise hybrid cords which are arranged parallel to one another within the layer and wherein the hybrid cords each contain at least one yarn of polyethylene terephthalate (PET) and at least one yarn of polyamide.

[0002] Reinforcing elements for various elastomer products are well known. For example, pneumatic vehicle tires use a belt bandage consisting of one or more layers, covering the belt edges, and containing parallel and essentially circumferentially extending reinforcements in the form of cords embedded in the rubber. This belt bandage serves to prevent tire lift due to the centrifugal forces occurring during driving, particularly during high-speed use.

[0003] During tire production, the bandage is applied in the form of layers, strips, or individual cords with reinforcements embedded in an unvulcanized rubber compound, which are wound or spooled onto the belt. The reinforcements are embedded in the rubber by passing a group of essentially parallel, thread-like reinforcements, which are usually pretreated thermally and / or with an impregnation for better adhesion to the embedding rubber in a manner known to the expert, longitudinally through a calender or extruder to be coated with the rubber compound. During cambering with previously used devices and vulcanization of the tire, the tire generally stretches by up to 2% in the shoulder area due to the elevation and by up to 4% in the center area compared to the unvulcanized green blank when the green blank is wound on a flat drum.Newer building drums require only a lower elongation of approximately 2% maximum during tire production. More modern equipment allows for less elevation. Another problem is the shrinkage behavior of the respective cord material at elevated temperatures. Lower shrinkage results in greater dimensional stability of the vehicle tire and thus better flat spot behavior (= reversible plastic flattening of the ground contact patch when parked), as is familiar to experts.

[0004] The cords of the tire bandage should allow sufficient elevation during tire production and in the vulcanization mold to allow precise tire molding, and they should ensure good high-speed performance after the tire's completion. To meet these requirements, the cords should be able to be stretched up to an elongation of approximately 3% with moderate force, and beyond this point, only with very high force.

[0005] US Pat. No. 7,252,129 B2 discloses a hybrid cord consisting of aramid fibers and another fiber selected from the group consisting of polyester, nylon, and rayon. This hybrid cord ensures reduced separation of the individual threads of the reinforcement layer.

[0006] KR 100829260 B1 and KR 100829261 describe hybrid cords made of PET (polyethylene terephthalate) and nylon, which are end-twisted at 270 to 330 t / m (330 turns per meter) and treated with a double dip. Compared to a single-dipped nylon cord, this results in a reduction in elongation at 45 N and lower shrinkage at 180 °C. The influence on the shrinkage force is not disclosed in these documents.

[0007] Hybrid cords made of polyester and polyamide are also described in WO 2014 / 001039 A1, WO 2015 / 137901 A1 and WO 2017 / 048208 A1.

[0008] WO 2011 / 147635 A1 discloses the use of recycled PET, particularly in the carcass ply of vehicle tires. A very similar use is also disclosed in EP 2 708 380 A1.

[0009] The present invention is based on the object of providing a vehicle tire of the type mentioned above, comprising a belt bandage, which exhibits further improvements in shrinkage behavior and thus, in particular, improved high-speed performance. At the same time, the tire should be produced as sustainably as possible and exhibit improved rolling resistance properties.

[0010] This problem is solved by using recycled PET (rPET).

[0011] Surprisingly, it was found that using recycled PET as a reinforcement material results in a further improvement in shrinkage behavior (greater shrinkage) than using PET originally made from petroleum, i.e., non-recycled PET. This also results in improved properties in the belt bandage of the vehicle tire according to the invention: The vehicle tire according to the invention exhibits improved high-speed capability. Possible cord compression at the belt edge no longer occurs or is significantly reduced, resulting in fewer cord breaks. Furthermore, the use of recycled PET has ecological and economic advantages. This avoids the production of new (non-recycled) petroleum-based materials, thus avoiding a burden on the finite resource of petroleum.

[0012] For the purposes of this invention, "recycled PET" refers to PET obtained from old PET products such as PET bottles or other PET articles, particularly through remelting. Significant degradation and rebuilding of the polymers does not occur. The direct starting material for recycled PET is not petroleum, but rather bottles or other PET articles.

[0013] For the purposes of the present invention, cords are linear structures consisting of two or more twisted yarns. A hybrid cord is a cord in which two or more different yarns are twisted together. For the purposes of the present invention, a yarn, based on DIN 60900, is a linear structure consisting of individual filaments or fibers.

[0014] The unit "dtex" is familiar to those skilled in the art and is a measure of weight per length. The lower the count in dtex, the lighter the corresponding yarn or cord.

[0015] According to the invention, the yarn made of recycled PET has a fineness of 200 to 1670 dtex, preferably 200 to 1350 dtex.

[0016] With such finenesses of the yarn made of recycled PET in the hybrid cord in the belt bandage of the tire according to the invention, particularly good high-speed capabilities are achieved while simultaneously reducing weight and thus improving rolling resistance.

[0017] According to the invention, the polyamide yarn has a fineness of 200 to 1400 dtex, preferably 200 to 1000 dtex.

[0018] With such finenesses of the yarn polyamide in the hybrid cord in the belt bandage of the tire according to the invention, particularly good high-speed capabilities are achieved, among other things, in comparison with cords made of 100 wt.% nylon, while at the same time reducing weight and thus improving rolling resistance.

[0019] According to the invention, the hybrid cord of the belt bandage has a total fineness (total fineness) of 400 to 2900 dtex, preferably 400 to 2200 dtex.

[0020] With such total fineness of the hybrid cord in the belt bandage of the tire according to the invention, particularly good high-speed capabilities are achieved while simultaneously reducing weight and thus improving rolling resistance.

[0021] According to advantageous embodiments of the invention, the recycled PET yarn and the polyamide yarn are end-twisted together at a twist density of 200 to 700 t / m, preferably 300 to 600 t / m, to form the hybrid cord. This results in very good fatigue resistance, so that the tire has very good durability.

[0022] The cord density of the belt bandage is 50 to 150 epdm, preferably 50 to 120 epdm. This density ensures sufficient strength for use in pneumatic vehicle tires.

[0023] The inventive use of rPET and polyamide in the belt bandage allows for a reduction in the number of cords relative to the tire width (epdm = ends per decimeter) and / or the ply thickness, which in turn provides advantages in rolling resistance. At the same time, this results in greater dimensional stability and thus improved flat spot behavior.

[0024] According to a particularly advantageous embodiment of the invention, the recycled PET yarn has a fineness of 1000 to 1200 dtex, and the polyamide yarn has a fineness of 900 to 1000 dtex. This achieves particularly good properties for achieving the object underlying the invention, as can be seen in Table 1 below.

[0025] Preferably, the recycled PET yarn and the polyamide yarn are end-twisted together at 300 to 380 t / m to form the hybrid cord. This achieves very good fatigue resistance.

[0026] According to the invention, the cord thread density in the belt bandage is 50 to 150 epdm, preferably 70 to 120 epdm.

[0027] The cord density, which is adapted to the fineness, results in optimal properties with regard to the technical task and in particular high-speed capability, dimensional stability - and thus flatspot behavior - and rolling resistance behavior.

[0028] According to another particularly advantageous embodiment of the invention, the recycled PET yarn has a fineness of 200 to 360 dtex, and the polyamide yarn has a fineness of 200 to 360 dtex. This achieves particularly good properties for achieving the object underlying the invention, as can be seen in Table 2 below. At the same time, these finenesses allow for particularly thin layers in the belt bandages of vehicle tires according to the invention. This further optimizes the rolling resistance behavior.

[0029] Preferably, the recycled PET yarn and the polyamide yarn are end-twisted together at 500 to 600 t / m to form the hybrid cord. This achieves very good fatigue resistance.

[0030] The cord thread density in the belt bandage is preferably 100 to 150 epdm, particularly preferably 110 to 130 epdm.

[0031] The cord density, which is adapted to the fineness, results in optimal properties with regard to the technical task and in particular high-speed capability, dimensional stability - and thus flatspot behavior - and rolling resistance behavior.

[0032] According to another particularly advantageous embodiment of the invention, the recycled PET yarn has a fineness of 700 to 800 dtex, and the polyamide yarn has a fineness of 680 to 780 dtex. This achieves particularly good properties for achieving the object underlying the invention. Even with these finenesses, thinner layers can be achieved in the belt bandages of vehicle tires according to the invention, compared to cords made of 100 wt.% nylon. This further optimizes the rolling resistance behavior.

[0033] Preferably, the recycled PET yarn and the polyamide yarn are end-twisted together at 350 to 450 t / m to form the hybrid cord. This achieves very good fatigue resistance.

[0034] The preferred cord density in the belt bandage is 50 to 80 epdm. The cord density, which is adapted to the gauge, results in optimal properties with regard to the technical task, particularly high-speed capability, dimensional stability—and thus flat-spot behavior—and rolling resistance behavior.

[0035] According to another particularly advantageous embodiment of the invention, the recycled PET yarn has a fineness of 500 to 600 dtex, and the polyamide yarn has a fineness of 430 to 530 dtex. This achieves particularly good properties for achieving the object underlying the invention. Even with these finenesses, thinner layers can be achieved in the belt bandages of vehicle tires according to the invention, compared to cords made of 100 wt.% nylon. This further optimizes rolling resistance and achieves increased dimensional stability.

[0036] Preferably, the recycled PET yarn and the polyamide yarn are end-twisted together at 400 to 500 t / m to form the hybrid cord. This achieves very good fatigue resistance.

[0037] The preferred cord density in the belt bandage is 70 to 100 epdm. The cord density, which is adapted to the gauge, results in optimal properties with regard to the technical task, particularly high-speed capability, dimensional stability—and thus flat-spot behavior—and rolling resistance behavior.

[0038] The polyamide of the polyamide yarn is selected from the group consisting of polyamide 6 (PA 6), polyamide 66 (PA 66), polyamide 12 (PA 12), polyamide 11 (PA 11), polyamide 1313 (PA 1313), polyamide 4 (PA 4), polyamide 7 (PA 7), polyamide 8 (PA 8), polyamide 9 (PA 9), polyamide 46 (PA 46), polyamide 610 (PA 610), polyamide 612 (PA 612), polyamide 69 (PA 69) and polyamide 66 / 6 (PA 66 / 6).

[0039] The use of PA 6 and / or PA 66 is preferred, the use of PA 66 (nylon) is particularly preferred.

[0040] Using PA 66 as the material for the polyamide yarn results in particularly good properties with regard to the underlying task.

[0041] According to advantageous embodiments of the invention, the weight fraction of recycled PET in the hybrid cord is 40 to 60%. This optimally solves the problem underlying the invention, and the hybrid cord, with the recycled PET, contains a significant proportion of sustainable material.

[0042] To ensure reliable adhesion of textile reinforcements to the rubber, it is advisable for the hybrid cords to be impregnated with an adhesive to ensure the adhesion of the reinforcements to the rubber. For example, this impregnation can be achieved with an RFL dip (resorcinol-formaldehyde latex) in a one- or two-bath process. However, all other impregnation processes and adhesives known to those skilled in the art are also conceivable, particularly dips that are free of resorcinol and formaldehyde.

[0043] Furthermore, further and customary pretreatment processes known to the person skilled in the art can be carried out, such as, in particular, hot stretching of the cords.

[0044] The belt bandage is preferably designed as a single-layer or multi-layer bandage at an angle between 0° and 5° to the circumferential direction, with single-layer being particularly preferred. "Designed" in this context means that it is wound in a single-layer or multi-layer manner in the circumferential direction, preferably a single-layer.

[0045] The yarn made from recycled PET can be twisted in the S or Z direction.

[0046] The polyamide yarn can be twisted in the S or Z direction.

[0047] Advantageously, the yarns have the same twist direction. Therefore, they are both preferably twisted in either the S or Z direction.

[0048] Advantageously, the twist direction of the hybrid cord is opposite to the twist direction of the yarns. This results in improved and more consistent quality in terms of the strength of the cords and thus of the belt bandage.

[0049] Embodiments and further advantages of the invention are explained in more detail in connection with the following Tables 1 and 2.

[0050] The examples according to the invention are marked with "E" and are exemplary and particularly advantageous constructions of hybrid cords of the belt bandage of the vehicle tire according to the invention.

[0051] The references are a nylon cord, which is commonly used in the belt bandage of vehicle tires, and a hybrid cord made of original PET and PA 6.6.

[0052] The measurements were carried out using the following methods: Breaking force and elongation at break, force and tensile strength at 4% and 6% elongation, elongation at 45 N, shrinkage at 180 °C and shrinkage force based on ASTM D 855

[0053] The properties given in the unit N / dm refer to the measured properties of the cord, which were extrapolated using the possible number of cords in the belt bandage per tire width (epdm = ends per decimeter) also given in the tables. Table 1 Characteristic Unit Ref. 1 a)< Ref. 2 b)< E1 c)< PA 66 1400x2 290 t / m end twist Hybrid cord PET 1100x1 / PA 66 940x1 340 t / m end twist Hybrid cord rPET 1100x1 / PA 66 940x1 340 t / m end twist Breaking strength N 226 139 141 Elongation at 45 N % 5,9 3,6 3,9 Force (4% elongation) N 30 50 48 Force (4% elongation) N / dm 3300 4000 3840 Tensile strength (4% elongation) mN / dtex 10,7 24,5 23,5 Force (6% elongation) N 46 78 76 Force (6% elongation) N / dm 5060 6240 6080 Tensile strength (6% elongation) mN / dtex 16,4 38,2 37,3 Elongation at break % 19 11 12 Shrinkage at 180°C % 5,0 5,2 6,3 diameter mm 0,64 0,57 0,57 a)< PA 66: Nylon, single yarn, Z twist; cord PA 66 1400x2, S twist b)< non-recycled PET and PA 66 yarn, each with Z twist, hybrid cord PET 1100x1 / PA 66 940x1, S twist c)< rPET: recycled PET; rPET and PA 66 yarn, each with Z twist, hybrid cord rPET 1100x1 / PA 66 940x1, S twist

[0054] Table 1 shows that the hybrid cord made of recycled PET and polyamide (E1) contained in the belt bandage according to the invention surprisingly exhibits greater shrinkage than a cord made of PA 66 and non-recycled PET (Ref. 2). The surprisingly significantly improved shrinkage behavior of the hybrid cord in the belt bandage results in improved high-speed performance in the vehicle tire. Possible cord compression at the belt edge no longer occurs or is significantly reduced, resulting in fewer cord breaks.

[0055] Compared to a standard nylon cord for the belt bandage from the state of the art (Ref. 1), higher forces and tensile strengths are achieved at 4 and 6% elongation, respectively. This allows the reinforcements in the belt bandage to be used with a smaller diameter and in a smaller number (relative to the tire width). As shown in Table 1, starting from 110 epdm of standard nylon cords, the number can be reduced with a hybrid cord made of PET and nylon, and, for example, with 80 epdm, the above-mentioned improved properties can be achieved despite the lower epdm.

[0056] The smaller number of cords allows the individual cords to be spaced further apart within the belt bandage. This results in less shear stress in the surrounding rubber matrix, which in turn improves durability.

[0057] At the same time, this leads to better flat spot behavior and thus improved dimensional stability, since there is less shrinking material in the tire overall.

[0058] Due to the smaller diameter of the cords compared to Ref. 1, the overall belt bandage can be made thinner, and less rubber compound is required. This improves the rolling resistance behavior of the tire according to the invention.

[0059] This also reduces the fineness and thus the weight per length of the hybrid cord. While Ref. 1 has a total fineness of 2800 dtex, the exemplary PET and nylon construction achieves a fineness of 2040 dtex. The weight savings improve the rolling resistance behavior of the tire according to the invention.

[0060] While the advantages resulting from the lower weight, smaller number, and smaller diameter apply to both non-recycled PET and recycled PET, the aforementioned increased shrinkage and the associated benefits are only achieved with recycled PET (invention).

[0061] E2 is another example according to the invention with a significantly lower fineness and thus further advantages in terms of rolling resistance. As can be seen in Table 2, this also achieves the advantages described for E1 compared to the respective references.

[0062] This construction also improves the shrinkage and tensile strength properties that are important for the belt bandage.

[0063] At the same time, the use of recycled PET is environmentally friendly and conserves resources. Furthermore, recycled PET, like PET obtained directly from fossil raw materials, maintains consistent quality. This ensures consistent product quality.

[0064] According to further exemplary embodiments, the hybrid cord made of recycled PET and polyamide contained in the belt bandage according to the invention has the following constructions: E3: Hybrid cord rPET 720x1 / PA 66 700x1, 400 t / m end twist, 60 epdm E4: Hybrid cord rPET 550x1 / PA 66 470x1, 470 t / m end twist, 80 epdm

[0065] In both E3 and E4, each individual yarn is twisted in the Z direction and the two hybrid cords are each twisted in the S direction. Table 2 Characteristic Unit Ref. 3 d)< Ref. 4 e)< E2 f)< PA 66 470x2 420 t / m end twist Hybrid cord PET 225x1 / PA 66 235x1 550 t / m end twist Hybrid cord rPET 225x1 / PA 66 235x1 550 t / m end twist Breaking strength N 73 30 31 Elongation at 45 N % 5,9 3,6 Force (4% elongation) N 12 14 13 Force (4% elongation) N / dm 1560 1680 1560 Tensile strength (4% elongation) mN / dtex 12,8 30,4 28,3 Force (6% elongation) N 18 20 19 Force (6% elongation) N / dm 2340 2400 2280 Tensile strength (6% elongation) mN / dtex 19,1 43,5 41,3 Elongation at break % 18 14 15 Shrinkage at 180°C % 5,0 5,3 6,4 diameter mm 0,40 0,25 0,25 epdm 130 120 120 d)< PA 66: Nylon, single yarn, twist direction Z; cord PA 66 470x2, twist direction S e)< PET and PA 66 yarn, twist direction Z, hybrid cord PET 225x1 / PA 66 235x1, twist direction S f)< rPET and PA 66 yarn, each twist direction Z, hybrid cord rPET 225x1 / PA 66 235x1, twist direction S

Claims

1. Vehicle tyre comprising a belt bandage, wherein the belt bandage comprises strength members, wherein the strength members comprise hybrid cords arranged parallel to one another within the ply and wherein the hybrid cords each contain at least one yarn made of polyethylene terephthalate (PET) and at least one yarn made of polyamide, wherein the PET is recycled PET (rPET) and the yarn made of recycled PET has a fineness of 200 to 1670 dtex, the yarn made of polyamide has a fineness of 200 to 1400 dtex, the hybrid cord altogether has a fineness of 400 to 2900 dtex, characterized in that the cord thread density of the belt bandage is 50 to 150 epdm.

2. Vehicle tyre according to Claim 1, characterized in that the yarn made of recycled PET has a fineness of 200 to 1350 dtex.

3. Vehicle tyre according to either of Claims 1 or 2, characterized in that the yarn made of polyamide has a fineness of 200 to 1000 dtex.

4. Vehicle tyre according to any of the preceding claims, characterized in that the hybrid cord altogether has a fineness of 400 to 2200 dtex.

5. Vehicle tyre according to any of the preceding claims, characterized in that the yarn made of recycled PET and the yarn made of polyamide are end-twisted together to form the hybrid cord at 200 to 700 t / m, preferably 300 to 600 t / m.

6. Vehicle tyre according to any of the preceding claims, characterized in that the yarn made of recycled PET has a fineness of 1000 to 1200 dtex and the yarn made of polyamide has a fineness of 900 to 1000 dtex.

7. Vehicle tyre according to Claim 6, characterized in that the yarn made of recycled PET and the yarn made of polyamide are end-twisted together to form the hybrid cord at 300 to 380 t / m.

8. Vehicle tyre according to any of Claims 1 to 5, characterized in that the yarn made of recycled PET has a fineness of 200 to 360 dtex and the yarn made of polyamide has a fineness of 200 to 360 dtex.

9. Vehicle tyre according to any of the preceding claims, characterized in that the polyamide is polyamide 66 (PA 66).

10. Vehicle tyre according to any of the preceding claims, characterized in that the weight fraction of the recycled PET in the hybrid cord is 40% to 60%.

11. Vehicle tyre according to any of the preceding claims, characterized in that the cord thread density of the belt bandage is 50 to 120 epdm.