PNEUMATIC VEHICLE TIRES

Description

[0001] The invention relates to a pneumatic vehicle tire of radial design with a tread, a radial carcass, a belt assembly with at least two belt plies and with at least one belt bandage ply which is arranged radially outside the belt, wherein the belt bandage ply comprises cords of at least two multifilament yarns twisted together, which are arranged parallel to one another within the belt bandage ply and wherein the multifilament yarns consist of recycled polyethylene terephthalate (rPET).

[0002] Such a pneumatic vehicle tire is known from EP 257 62 45 B1. Recycled PET (rPET) is not obtained directly from fossil raw materials, but is 100% recovered from previously used PET products, such as PET beverage bottles. The previously used PET material is cleaned, shredded, and melt-spun into a fiber, which is then further processed into multifilament yarns and cords. This reuse of PET waste for reinforcements in pneumatic vehicle tires is environmentally friendly and resource-efficient.

[0003] Single or multi-layer belt bandages are well known to those skilled in the art.

[0004] Furthermore, EP 1 671 813 B1 discloses the use of a PET cord for the belt bandage plies of pneumatic vehicle tires, which cord has a modulus of elasticity of not less than 2.5 mN / dtex% under a load of 29.4 N, measured at 160°C. Furthermore, the cord is treated with an adhesion-promoting composition comprising a thermoplastic polymer, a thermosetting, aqueous polyurethane resin, and an epoxy resin compound. It is also common practice to use nylon cords, particularly PA 6.6, in the bandage plies of a pneumatic vehicle tire. Due to the comparatively low tensile modulus of nylon cords, it is necessary for certain applications, particularly when the high-speed durability of the tire is important, to provide two bandage plies with nylon cords as reinforcements.The main function of tire bandages is to prevent relative movements at the lateral belt ply edges in order to avoid separation of the belt ply edges.

[0005] DE 10 2010 036 760 A1 discloses a pneumatic vehicle tire with at least one belt bandage layer containing PET cords. The PET cord exhibits an elongation of 3% to 5% at a force of 1.56 cN / dtex at 20°C and an elongation of 7% to 9% at 160°C. The sum of the breaking elongation of the PET cord and the heat shrinkage, determined at 180°C, with a pre-tension force of 0.01 cN / dtex and a duration of two minutes, is greater than 20%. The PET cord exhibits a heat shrinkage, determined at 180°C, with a pre-tension force of 0.01 cN / dtex and a duration of two minutes, of greater than 2.5%. The PET cord prevents belt edge separation, ensures good high-speed durability and a long tire life, and reduces the flat spot effect.

[0006] The invention is based on the object of providing an rPET cord for the belt bandage layer(s) which, even in the case of a single-layer design of the bandage, ensures that the tire has good high-speed durability, a long service life and a reduced flat spot effect.

[0007] The object is achieved according to the invention by a pneumatic vehicle tire according to claim 1.

[0008] A belt bandage layer in a pneumatic vehicle tire provided with such an rPET cord is environmentally friendly, effectively prevents belt edge separation, ensures good high-speed durability, a long tire life, and reduces the flat spot effect.

[0009] A filament yarn made from recycled PET (rPET) typically has a lower modulus than a filament yarn made from non-recycled PET. The rPET cord properties according to the invention are surprisingly achieved by a net draw (the sum of the draw of the reinforcement in the individual ovens during the conversion process) of 3% to 6%, preferably 3.5% to 5%. A cord made from non-recycled PET with a comparable tensile modulus undergoes a maximum net draw of 1.5%. The conversion process involving the draw of corresponding reinforcements is well known to those skilled in the art.

[0010] Some cord parameters are particularly important for achieving these effects. For example, the total fineness of the cord is important; the rPET cord according to the invention should have a total fineness between 500 dtex and 6000 dtex, in particular between 500 dtex and 3500 dtex. Furthermore, the rPET cord should have a cord twist between 150 tpm and 650 tpm, in particular between 200 tpm and 650 tpm.

[0011] An arrangement of the inventive rPET cord in the tire bandage layer with 60 epdm to 160 epdm, particularly with 80 epdm to 140 epdm, has proven particularly advantageous for preventing belt ply edge separation, ensuring good high-speed durability, and a long tire life. Only a single tire bandage layer is required.

[0012] In a further embodiment, a pneumatic vehicle tire according to the invention has a multi-layer, in particular 2-layer belt bandage.

[0013] Further features, advantages and details of the invention will now be described in more detail with reference to the drawing, which illustrates an embodiment. The single figure shows, Fig. 1 , schematically a cross-section through a pneumatic vehicle tire.

[0014] The Fig.1The pneumatic vehicle tire shown is a tire for passenger cars of radial design and has a tread 1, sidewalls 2, bead regions 3 with bead cores 4 and bead profiles 5, a carcass ply 6 which runs around the two bead cores 4, an inner layer 7 and a belt assembly 8 arranged between the carcass ply 6 and the tread 1. In the embodiment shown, the belt assembly 8 has two belt layers 8a and 8b, which can consist, in a known manner, of steel cord reinforcements embedded in a rubber mixture and running parallel to one another. The steel cords in one belt layer 8a run crossed with the steel cords in the other belt layer 8b and enclose one of the usual angles in the order of 20° to 35° with the tire circumferential direction.Radially outside the two belt layers 8a, 8b there is a bandage layer 9 - a cap-ply layer - which is formed by continuously and spirally winding a cord 10 made of rPET (recycled polyethylene terephthalate) in the circumferential direction of the tire and covers the lateral edges of the belt assembly 8.

[0015] According to the invention, an rPET cord 10 of construction 1100 dtex x 2 or 1440 dtex x 2 or 720 dtex x 2 or 550 dtex x 2 or 1670 dtex x 2 is used, which has the following properties: Under the action of a force of 1.56 cN / dtex, at a temperature of 20°C, the elongation of the cord 10 is between 2% and 5%, at a temperature of 120°C between 6% and 9%. At a pretension force of 0.01 cN / dtex acting over a period of two minutes and at a temperature of 180°C, the sum of the elongation at break and the thermal shrinkage is greater than 17%. Furthermore, the heat shrinkage at 180°C and under a pre-tensioning force of 0.01 cN / dtex, applied for two minutes, is greater than 2.5%. The net stretch (the sum of the stretching of the reinforcement in the individual ovens during the conversion process) is in the range of 3% to 6%, preferably in the range of 3.5% to 5%.

[0016] The rPET cord 10 according to the invention has a total fineness between 1100 dtex and 3340 dtex. In particular, the rPET cord 10 is used with a cord twist between 150 and 650 tpm (turns per meter), in particular between 200 tpm and 650 tpm.

[0017] The mutual spacing during winding of the rPET cord 10 to form the belt bandage is adjusted such that the finished bandage layer has a density of between 60 and 160 epdm (ends per decimeter). In a preferred embodiment of the invention, the bandage layer 9 has a density of between 80 epdm and 140 epdm.

[0018] A tire with a single tire ply 9 constructed according to the invention exhibits high-speed durability comparable to tires with known two-ply tire designs using nylon 6.6 as the reinforcement. A further advantageous effect of the tire ply according to the invention is its improved robustness against impact loads, without the risk of cord breakage in the belt plies. Compared to the commonly used nylon cords, the flat spot effect (a temporary deformation of the tire's footprint when parked) is significantly reduced in a tire constructed according to the invention and is more environmentally friendly than conventional cords. List of reference symbols

[0019] 1Tread 2Sidewall 3Bead area 4Bead core 5Bead profile 6Carcass ply 7Inner layer 8Belt assembly 8aBelt ply 8bBelt ply 9Bandage ply 10rPET cord

Claims

1. Pneumatic vehicle tire of radial construction having a tread (1), a radial carcass, a belt bandage (8) having at least two belt plies (8a, 8b) and having at least one belt bandage ply (9), which is arranged radially outside the bandage, wherein the belt bandage ply (9) comprises cords of at least two multifilament yarns twisted together which are arranged parallel to one another inside the belt bandage ply (9) and wherein the multifilament yarns are made of recycled polyethylene terephthalate (rPET), wherein at a force of 1.56 cN / dtex the rPET cord (10) has an elongation of 2% to 5% at 20°C and an elongation of 6% to 9% at 120°C, wherein the sum of the breaking elongation of the rPET cord (10) and the heat shrinkage determined at 180°C at a preload force of 0.01 cN / dtex and a time of exposure of two minutes is greater than 17%, wherein the rPET cord (10) has a heat shrinkage determined at 180°C at a preload force of 0.01 cN / dtex and a time of exposure of two minutes of greater than 2.5% and wherein the net stretch of the rPET cord (10) is in a range from 3% to 6%, preferably in a range from 3.5% to 5%.

2. Pneumatic vehicle tire according to Claim 1, characterized in that the rPET cord (10) has an overall fineness of between 500 dtex and 6000 dtex, preferably between 500 dtex and 3500 dtex.

3. Pneumatic vehicle tire according to Claim 1 or 2, characterized in that the rPET cord (10) has a cord twist between 150 tpm and 650 tpm, preferably between 200 tpm and 650 tpm.

4. Pneumatic vehicle tire according to one or more of Claims 1 to 3, characterized in that the rPET cord (10) has the construction rPET 550 dtex x2, rPET 1100 dtex x 2, rPET 1440 dtex x 2, rPET 720 dtex x 2 or rPET 1670 dtex x2.

5. Pneumatic vehicle tire according to one or more of Claims 1 to 4, characterized in that the rPET cord (10) is arranged in the belt bandage ply (9) with 60 epdm to 160 epdm, in particular with 80 epdm to 140 epdm.