Braided cord for use as a reinforcing member in a belt of a vehicle pneumatic tire

Abstract

This invention relates to a double-strand cord used as a reinforcing member in the belt loop of a vehicle pneumatic tire, comprising only two yarns twisted together at their ends, wherein the first yarn has a Z value of 600 mN / tex or greater, and wherein the second yarn has a Z value of 75 mN / tex or less and a Y value of 150 mN / tex or less, wherein Z is the force normalized to the yarn linear density at 1% elongation in a force-elongation diagram, wherein Y is the force normalized to the yarn linear density at 4% elongation in a force-elongation diagram, and wherein the quotient X of the linear density of the first yarn divided by the linear density of the second yarn is in the range of 1.0 to 1.3.

Description

Technical Field

[0001] The present invention relates to a double-strand cord used as a reinforcing member in the belt band of a pneumatic tire for a vehicle, a composite material comprising the corresponding double-strand cord, a vulcanized composite material that can be produced therefrom, a corresponding vehicle tire made of these materials, and the use of the corresponding double-strand cord in the belt band of a pneumatic tire for improving high-speed characteristics and rolling resistance characteristics. Background Technology

[0002] The development and manufacture of high-performance vehicle tires is an area where further improvements to known components in existing technologies are continuously needed. A tire component particularly important for optimizing the high-speed characteristics of vehicle tires is the so-called reinforcing cord, which serves as a reinforcing member in the belt loops of a pneumatic vehicle tire. These reinforcing cords are used specifically to ensure the necessary stiffness in the tire, and their mechanical properties, particularly through hysteresis characteristics and the curves of the reinforcing cords in the resulting force-elongation diagram, significantly influence the driving characteristics of the subsequent tire.

[0003] In the prior art, for particularly high-performance pneumatic tires for vehicles, especially optimized for high-speed performance, high-modulus three-ply cords are currently used, consisting of two relatively high-modulus aramid yarns and one low-modulus nylon yarn twisted together. Here, the helical twist allows the aramid to stretch under relatively low forces, which is necessary to avoid any undesirable deformation during the tire manufacturing process, especially when introduced into the mold.

[0004] While existing three-ply cords enable the manufacture of pneumatic tires with advantageous performance characteristics, they are also generally considered to have drawbacks. Production from three individual yarns requires a relatively complex and costly two-stage twisting process, in which the rather brittle aramid undergoes mechanical stress twice, which should ideally be avoided. Furthermore, three-ply cords typically have a relatively large thickness, which is considered detrimental to temperature development during later stages of tire operation and therefore ultimately to high-speed performance. Additionally, the hysteresis characteristics of such three-ply cords can, in some cases, worsen the rolling resistance of the corresponding tire.

[0005] As an alternative to three-ply cords, existing technology also discloses so-called two-ply cords, in which only two yarns are twisted together, and therefore their production is simpler. Here, two-ply cords are generally also finer than three-ply cords. The disadvantage of two-ply cords is that their force-elongation characteristics are generally considered inferior compared to three-ply cords, particularly in not achieving the high modulus required for the entire cord, which in many cases limits their use in high-performance tires for high-speed applications.

[0006] In principle, double-strand and triple-strand cords are known in the prior art.

[0007] For example, DE 10 2008 037 615 A1 discloses a hybrid cord used as a reinforcing member in a belt band, wherein each yarn has a specific initial twist number.

[0008] EP 1 878 591 B1 discloses a reinforcing member embedded in an uncured rubber compound for a belt band of a vehicle pneumatic tire, wherein a maximum linear density of yarn with a high modulus of elasticity is defined in the reinforcing member.

[0009] EP 2 055 817 A1 discloses a tire having at least one cord, wherein the yarn of the cord is formed from a specific material.

[0010] EP 2 065 222 B1 discloses a vehicle pneumatic tire with reinforced cords, wherein the high modulus yarn has an elastic modulus of not less than 10,000 MPa, and the low modulus yarn is nylon 46.

[0011] EP 3 006 228 B1 discloses a hybrid cord in which the high-modulus yarn is a filament yarn and the low-modulus yarn is a staple fiber yarn.

[0012] EP 3 196 343 B1 discloses a hybrid cord with a core-spun structure, wherein the hybrid cord is defined by a specific twist number of a high-modulus yarn, as well as a specific tensile strength and a specific Young's modulus.

[0013] EP 3 365 187 B1 discloses a carcass for a pneumatic tire having multiple double-layered hybrid cords, wherein these hybrid cords have a specific nylon content, a specific overall linear density value and a predetermined twist.

[0014] US 2018 / 0099529 A1 discloses a reinforcing element in which high-modulus yarns and low-modulus yarns are twisted together in a specific manner.

[0015] WO 2014 / 104680 A1 discloses a hybrid cord comprising twisted nylon and twisted aramid yarns, which are then twisted together at the ends.

[0016] WO 2018 / 075305 A1 discloses a hybrid cord in which nylon yarn and aramid yarn have the same twist and approximately equal length. Summary of the Invention

[0017] The purpose of this invention is to overcome or at least reduce the disadvantages known in the prior art.

[0018] In particular, the object of the present invention is to specify a reinforcing cord used as a reinforcing member in the belt band of a vehicle pneumatic tire, which reduces or even completely eliminates the known disadvantages of three-strand cords.

[0019] Specifically, the reinforcing cord to be specified should be easier and more cost-effective to produce than the corresponding three-strand cord, while having the most similar force-elongation characteristics possible. Furthermore, the reinforcing cord to be specified should ideally have a relatively small diameter and a relatively low overall linear density value, while having the most similar force-elongation characteristics possible.

[0020] On the other hand, compared with the known double-strand cords in the prior art, the objective is to specify a reinforced cord that has superior force-elongation characteristics, comparable to those of the known triple-strand cords in the prior art.

[0021] In this regard, the aim is to specify a reinforcing cord that is particularly suitable for such vehicle pneumatic tires optimized for high-speed applications.

[0022] In this case, the additional requirement is that the specified reinforcing cord should ideally be manufactured using conventional production processes and should have the highest possible chemical compatibility with conventional sulfur-curable compositions used in vehicle pneumatic tires.

[0023] A further objective of this invention is to specify that the reinforcing cord should produce improved rolling characteristics, particularly more favorable rolling resistance.

[0024] The inventors of this invention have now discovered that the above-mentioned objectives can be unexpectedly achieved by providing a double-strand cord as defined in this invention as the reinforcing cord. In particular, the inventors of this invention have discovered that the advantageous force-elongation characteristics of the double-strand cord can be unexpectedly achieved by using a different yarn with a significantly increased modulus compared to the prior art, compared to the higher modulus yarns (such as aramids) commonly used in the prior art.

[0025] However, in this respect, the inventors of this invention have also discovered that in order to obtain force-elongation characteristics comparable to those of three-ply cords known in the prior art, a certain ratio must be established between the linear densities of the two yarns used in the double-ply cord, which means that the linear density of the first yarn with a very high modulus should not be much higher than that of the second yarn.

[0026] The aforementioned objectives are achieved accordingly through double-strand cords, composite materials, vulcanized composite materials, vehicle tires, and applications as defined in this invention. Preferred configurations according to the invention will become apparent from the following description.

[0027] Those features described below as preferred in the invention's double-strand cord, composite material, vulcanized composite material, vehicle tire, and applications are combined with other features described as preferred in particularly preferred embodiments. Therefore, combinations of two or more embodiments described below as particularly preferred are highly preferred. Embodiments in which features described as somewhat preferred are combined with one or more other features described as somewhat preferred are also preferred. The preferred features of the invention's composite material, vulcanized composite material, vehicle tire, and applications derive from the preferred features of the double-strand cord.

[0028] This invention relates to a double-strand cord used as a reinforcing member in the belt loop of a vehicle pneumatic tire, which consists of only two yarns with their ends twisted together.

[0029] The first yarn has a Z value of 600 mN / tex or greater, and

[0030] The second yarn has a Z value of 75 mN / tex or less and a Y value of 150 mN / tex or less.

[0031] Where Z is the force normalized to yarn linear density when 1% elongation is obtained in the force-elongation diagram.

[0032] Where Y is the force normalized to yarn linear density when 4% elongation is obtained in the force-elongation diagram, and

[0033] The quotient X, which is the linear density of the first yarn divided by the linear density of the second yarn, is in the range of 1.0 to 1.3.

[0034] The double-strand cord according to the invention is suitable for use as a reinforcing member in the belt band of a vehicle pneumatic tire, and is particularly preferred for this purpose.

[0035] This double-strand cord consists of only two yarns twisted together at their ends. This means that there are no other yarns in this double-strand cord.

[0036] According to the invention, the first yarn has a specific Z value, where Z is the force normalized to the yarn linear density at 1% elongation in the force-elongation diagram. Accordingly, the value Z is related to the yarn modulus, and the definition chosen by the chord modulus is a representation of this characteristic conventionally used by those skilled in the art, and allows for a particularly meaningful definition of the material. Therefore, the first yarn is a particularly high-modulus yarn, specifically having a higher chord modulus than the aramid yarns used in prior art reinforcing cords.

[0037] The second yarn is a low-modulus yarn. As understood by those skilled in the art, in order to fully define the second yarn, not only is the value Z of the chord modulus at 1% elongation specified, but also the value Y of the chord modulus at 4% elongation is specified.

[0038] The Y and Z values ​​are determined from the force-elongation diagram as understood by those skilled in the art, and can be calculated using known yarn linear densities. In the context of this invention, the force-elongation diagram used to determine Y and Z is recorded using a tensile testing machine from Zwick, according to the 2014 standard ASTM D885 / D885M.

[0039] In the double-ply cord according to the invention, the linear densities of the first and second yarns are also specifically matched to achieve a force-elongation characteristic comparable to that of a three-ply cord. This is accomplished by a quotient X, which is calculated by dividing the linear density of the first yarn by the linear density of the second yarn. According to the inventors, the quotient X must be within a specified range in order to easily obtain a double-ply cord according to the invention that achieves the intended purpose.

[0040] The term linear density is familiar to those skilled in the field of textiles. This parameter relates to the thickness of the yarn and represents the mass per unit length, usually expressed in tex or dtex.

[0041] By means of the double-strand cord according to the invention, the objectives defined above are achieved and a reinforced cord as a reinforcing member is obtained, the use of which in the belt band of a vehicle pneumatic tire enables the acquisition of a high-performance tire with superior high-speed characteristics.

[0042] The inventors of this invention have determined that it is particularly advantageous to set the ratio of linear densities to very specific values, wherein the high-modulus first yarn should ideally have a value within a certain range that is slightly higher than that of the second yarn. In particular, in the case of a bi-ply cord according to the invention, where the quotient X is approximately 1.15, the observed force-elongation characteristics are particularly similar to those of a tri-ply cord serving as a reference system. Accordingly, a bi-ply cord according to the invention is preferred, wherein the quotient X of the linear density of the first yarn divided by the linear density of the second yarn is in the range of 1.05 to 1.25, preferably in the range of 1.1 to 1.2, and particularly preferably in the range of 1.13 to 1.17.

[0043] The inventors of this invention have found that selecting a particularly high-modulus first yarn is especially advantageous, because the result is an unexpectedly high-performance double-strand cord, whose force-elongation characteristics are advantageously comparable to those of a triple-strand cord using yarns made from conventional high-modulus materials (e.g., aramids). Specifically, the preferred double-strand cord according to the invention has a Z-value of 650 mN / tex or greater, preferably 700 mN / tex or greater.

[0044] Furthermore, the inventors proposed selecting a second yarn with the smallest possible modulus, such that the moduli of the two yarns used differ significantly. With this corresponding construction, bi-ply cords according to the invention are conventionally obtained, and these bi-ply cords can be processed particularly easily and efficiently. Therefore, bi-ply cords according to the invention are preferred, wherein the second yarn has a Z value of 65 mN / tex or less, preferably 55 mN / tex or less, and / or wherein the second yarn has a Y value of 140 mN / tex or less, preferably 135 mN / tex or less.

[0045] During the development process, the inventors of this invention have successfully identified particularly suitable materials for use as the first or second yarn in the biply cord according to the invention. For high-modulus yarns, specific, particularly modulus-optimized, extra-high modulus aramids (also known as HM aramids) and materials called Zylon have proven particularly suitable. These materials differ significantly in modulus from conventional aramids commonly used in biply cords in the prior art. For low-modulus second yarns, polyamides have proven suitable, with materials called nylon being particularly preferred, especially nylon PA 6.6.

[0046] Therefore, a preferred embodiment is the bi-ply cord according to the invention, wherein the first yarn comprises a material selected from the group consisting of aromatic polyamides, particularly poly(p-phenylene terephthalamide), and polyoxazoles, particularly poly(p-phenylene-2,6-benzobisoxazole), the first yarn preferably being composed of such a material. Therefore, a particularly preferred embodiment is the bi-ply cord according to the invention, wherein the first yarn is composed of poly(p-phenylene terephthalamide) or poly(p-phenylene-2,6-benzobisoxazole). The specific construction of these materials, as particularly high-modulus embodiments, is derived here from the Z-value defined above.

[0047] Accordingly, a double-strand cord according to the invention is also preferred, wherein the second yarn comprises a material selected from the group consisting of polyamide, particularly polyhexamethylene adipamide, and the second yarn is preferably composed of such material.

[0048] According to the inventors' assessment, in order to obtain the particularly high-performance biply cord according to the invention, the first and second yarns should each have a linear density value greater than 1000 dtex. The inventors have proposed specific upper limits considering the thickness of the resulting biply cord, exceeding which stronger thermal expansion is more likely to occur during subsequent use of the vehicle tire. In this regard, a biply cord according to the invention is preferred, wherein the linear density of the first yarn is in the range of 1000 to 3000 dtex, preferably in the range of 1500 to 2000 dtex. Equally preferred is a biply cord according to the invention, wherein the linear density of the second yarn is in the range of 1000 to 2000 dtex, preferably in the range of 1300 to 1700 dtex.

[0049] Based on the above statements, the inventors have determined that the overall linear density of the double-strand cord should ideally also be within a specific intermediate range. Therefore, the double-strand cord according to the invention is preferred, wherein the linear density of the double-strand cord is in the range of 2500 to 4000 dtex, preferably in the range of 2800 to 3500 dtex.

[0050] During development, the inventors of this invention were able to determine a force-elongation curve that can be established using the bi-ply cord according to the invention, and whose characteristics are particularly similar to those of triple cords used for high-speed applications. Accordingly, this preferred bi-ply cord can be used to produce vehicle tires that are particularly advantageous for these high-speed applications and possess the required stiffness.

[0051] Preferably, the double-strand cord according to the invention has the following force-elongation characteristics:

[0052] At 1% elongation, it is 13 to 17 N.

[0053] At 2% elongation, the N is 29 to 33.

[0054] At 3% elongation, it is 57 to 63 N.

[0055] At 4% elongation, it is 102 to 112 N.

[0056] At 5% elongation, it is 160 to 180 N.

[0057] At 6% elongation, it is 240 to 280 N.

[0058] Although the inventors have assessed that the double-ply cord according to the invention is relatively flexible in terms of the twisting between the yarns, the inventors, based on their available knowledge, have proposed specific twist coefficients to produce particularly suitable double-ply cords according to the invention. That is, preferred double-ply cords according to the invention have a twist coefficient in the range of 150 to 200, more preferably in the range of 170 to 230, and particularly preferably in the range of 185 to 215.

[0059] In view of the foregoing, it is apparent that the present invention also relates to a composite material comprising one or more double-stranded cords according to the invention. Therefore, the present invention also relates to a composite material, particularly for manufacturing belt bands for pneumatic tires of vehicles, comprising one or more double-stranded cords according to the invention, which are at least partially covered by a crosslinkable rubberized compound.

[0060] As will be understood by those skilled in the art, the crosslinkable rubberized compound used herein can be a rubberized compound known in the art and commonly used in the production of pneumatic tires for vehicles. In this regard, it can also be considered that the advantage of the bi-strand cords according to the invention is that they allow for the selection of materials with high chemical compatibility with crosslinkable rubberized compounds known in the art.

[0061] The advantageous properties of the composite material according to the invention can be seen in particular from the fact that it can be used to produce pneumatic tires for vehicles, which have good rolling resistance and the stiffness required for high-speed applications, and optimized hysteresis characteristics. In this case, the composite material according to the invention has properties very similar to those of three-ply cord materials, but it is generally significantly more advantageous for production due to the simpler manufacturing process.

[0062] It has been proven particularly advantageous to use two or more double-stranded cords according to the invention in the corresponding composite material and to arrange them preferably substantially parallel to each other. Here, the parameter familiar to those skilled in the art for describing the corresponding arrangement is EPDM, which specifies the number of reinforcing cords per decimeter in a direction perpendicular to the longitudinal axis of the double-stranded cord. Accordingly, a composite material according to the invention is preferred, wherein the composite material comprises two or more double-stranded cords according to the invention, wherein these double-stranded cords are preferably arranged substantially parallel to each other.

[0063] Preferably, the composite material according to the invention is wherein one or more double-strand cords are completely covered by a crosslinkable rubberized mixture, wherein one or more double-strand cords are preferably completely surrounded by a crosslinkable rubberized mixture.

[0064] Vulcanizing the composite material according to the invention enables the production of a vulcanized composite material according to the invention, which can be used in pneumatic vehicle tires. The composite / vulcanized composite material according to the invention can be used to produce belted / vehicle tires with superior high-speed characteristics and favorable rolling resistance, wherein the double-strand cords according to the invention ensure the necessary stiffness and, due to their smaller diameter compared to similar three-strand cords, contribute to reducing heat accumulation in the corresponding vehicle tire.

[0065] Therefore, the present invention also relates to a vulcanized composite material, which can be produced by vulcanizing the composite material according to the present invention.

[0066] The present invention also discloses a belt band for manufacturing pneumatic tires for vehicles, comprising one or more double-strand cords according to the present invention, composite materials according to the present invention, or vulcanized composite materials according to the present invention.

[0067] The present invention also relates to a vehicle tire, particularly a pneumatic vehicle tire, comprising one or more double-strand cords according to the invention, a composite material according to the invention, or a vulcanized composite material according to the invention.

[0068] Finally, the present invention also relates to the use of one or more double-strand cords according to the present invention in the belt band of a pneumatic tire for improving high-speed characteristics and rolling resistance characteristics. Detailed Implementation

[0069] Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying experimental data.

[0070] V1, used as a reference system, provides a three-ply cord consisting of two conventional aramid yarns and one nylon yarn with a twist of 320 T / m. The linear density of the aramid yarn used is 1680 dtex, and the linear density of the nylon is 470 dtex.

[0071] In the double-strand cord E1 according to the invention, a high-modulus aramid (HM aramid) with a linear density of 1610 dtex is used and twisted with the end of a 1400 dtex nylon yarn.

[0072] The Z-value of high-modulus aramid is 678 mN / tex. The Z-value of nylon is 50 mN / tex, and the Y-value is 135 mN / tex. These values ​​are determined from the yarn force-elongation diagram, which was established according to the 2014 standard ASTM D885 / D885M using a tensile testing machine from Zwick.

[0073] The corresponding reinforcing cords are processed into belt loops in the composite material and are also used in the 245 / 40 ZR18 (“extreme contact” DWS06) tire. Here, the tire with the double-strand cords according to the invention exhibits lower rolling resistance and comparable high-speed characteristics.

[0074] As is evident from Table 1 below, the force (LASE; "load at a specified elongation") required for a specific elongation of the double-strand cord according to the invention is advantageously and very well comparable to the value obtained from the prior art three-strand cord. Here, it is also evident from Table 1 that the overall diameter of the double-strand cord according to the invention is significantly smaller than the overall diameter of the reference system, and correspondingly, a thinner layer thickness can be formed when the same amount of rubber coating is present on the cord. Furthermore, the production of the double-strand cord according to the invention is easier and more cost-effective due to the use of a one-step manufacturing process ("twisting process").

[0075] Given the data shown in Table 1 below, it will also be apparent to those skilled in the art that, using the double-strand cord according to the invention, a reinforced cord with a higher modulus than the corresponding triple-strand cord can be obtained with the same overall diameter.

[0076] Table 1

[0077]

Claims

1. A double-strand cord used as a reinforcing member in the belt loop of a vehicle pneumatic tire, comprising only two yarns twisted together. The first yarn has a Z value of 600 mN / tex or greater, and The second yarn has a Z value of 75 mN / tex or less and a Y value of 150 mN / tex or less. Where Z is the force normalized to yarn linear density when 1% elongation is obtained in the force-elongation diagram. Where Y is the force normalized to yarn linear density when 4% elongation is obtained in the force-elongation diagram. in, The force-elongation diagrams used to determine Y and Z were recorded according to the 2014 standard ASTM D885 / D885M using a tensile testing machine from Zwick Corporation. The quotient X, which is the linear density of the first yarn divided by the linear density of the second yarn, is in the range of 1.0 to 1.

3.

2. The double-strand cord as described in claim 1, wherein, The quotient X, which is the linear density of the first yarn divided by the linear density of the second yarn, is in the range of 1.05 to 1.

25.

3. The double-strand cord as described in claim 2, wherein, The quotient X, which is the linear density of the first yarn divided by the linear density of the second yarn, is in the range of 1.1 to 1.

2.

4. The double-strand cord as described in claim 2, wherein, The quotient X, which is the linear density of the first yarn divided by the linear density of the second yarn, is in the range of 1.13 to 1.

17.

5. The double-strand cord as described in claim 1, wherein, The first yarn has a Z value of 650 mN / tex or greater.

6. The double-strand cord as described in claim 5, wherein, The first yarn has a Z value of 700 mN / tex or greater.

7. The double-strand cord as described in claim 1, wherein, The first yarn contains materials selected from the group consisting of aromatic polyamides and polyoxazoles.

8. The double-strand cord as described in claim 7, wherein, The first yarn is composed of aromatic polyamide and polyoxazole.

9. The double-strand cord as described in claim 7 or 8, wherein, The aromatic polyamide is poly(p-phenylene terephthalamide).

10. The double-strand cord as described in claim 7 or 8, wherein, The polyoxazole is poly(p-phenylene-2,6-benzobisoxazole).

11. The double-strand cord as claimed in claim 1, wherein, The linear density of the first yarn is in the range of 1000 to 3000 dtex.

12. The double-strand cord as claimed in claim 11, wherein, The linear density of the first yarn is in the range of 1500 to 2000 dtex.

13. The double-strand cord as claimed in claim 1, wherein, The linear density of the second yarn is in the range of 1000 to 2000 dtex.

14. The double-strand cord as claimed in claim 13, wherein, The linear density of the second yarn is in the range of 1300 to 1700 dtex.

15. A composite material comprising one or more double-strand cords as claimed in any one of claims 1 to 14, wherein the double-strand cords are at least partially covered by a crosslinkable rubberized compound.

16. The composite material as described in claim 15, wherein, The composite material is used to manufacture pneumatic tires for vehicles.

17. A vulcanizable composite material, which can be produced by vulcanizing the composite material as described in claim 15 or 16.

18. A vehicle tire comprising one or more double-strand cords as described in any one of claims 1 to 14, a composite material as described in claim 15 or 16, or a vulcanized composite material as described in claim 17.

19. The vehicle tire of claim 18, wherein, The vehicle tires mentioned are pneumatic tires.

20. Use of one or more double-strand cords as described in any one of claims 1 to 14 in the belt band of a vehicle pneumatic tire for improving high-speed characteristics and rolling resistance characteristics.

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