Duplex cord for use as a strengthening agent in a belt bandage of a vehicle pneumatic tire

Description

[0001] The invention relates to a duplex cord for use as a reinforcement in a belt bandage of a pneumatic vehicle tire, a composite material comprising corresponding duplex cords, a vulcanized composite material producible therefrom, a corresponding vehicle tire made of these materials and the use of corresponding duplex cords in the belt bandage of a pneumatic vehicle tire for improving the high-speed properties and the rolling resistance properties.

[0002] The subject matter of the invention is defined in the appended claims.

[0003] The development and production of high-performance vehicle tires is an area in which there is a constant need to further improve state-of-the-art components. One tire component that is particularly important for optimizing the high-speed performance of vehicle tires is the so-called reinforcement cords, which are used as strength members in the belt bandage of a pneumatic vehicle tire. These reinforcement cords serve, among other things, to ensure the necessary stiffness in the tire and, with their mechanical properties, significantly influence the tire's subsequent running characteristics, particularly through their hysteresis behavior and the resulting force-strain curve for the reinforcement cords.

[0004] Currently, high-modulus triplex cords are used for particularly high-performance pneumatic vehicle tires, which are optimized for high-speed performance. These cords consist of two relatively high-modulus aramid yarns and one low-modulus nylon yarn twisted together. The helical twist allows for elongation of the aramid at relatively low forces, which is necessary to prevent unwanted deformation during the tire manufacturing process, especially during molding.

[0005] Although established triplex cords enable the production of pneumatic vehicle tires with advantageous performance characteristics, these triplex cords are often perceived as having disadvantages. Manufacturing from three individual yarns requires a comparatively complex and cost-intensive two-stage twisting process, during which the rather brittle aramid is subjected to two mechanical stresses, which should generally be avoided. In addition, triplex cords are often comparatively thick, which is perceived as detrimental to temperature development during later use of the vehicle tire and thus ultimately also to high-speed performance. Furthermore, the hysteresis behavior of such triplex cords sometimes worsens the rolling resistance of the corresponding vehicle tires.

[0006] As an alternative to triplex cords, so-called duplex cords are also known from the state of the art. These consist of only two yarns twisted together, making them significantly easier to manufacture. Duplex cords are also typically thinner than triplex cords. The disadvantage of duplex cords, which often limits their use in high-performance tires for high-speed applications, is that their stress-elongation behavior is often perceived as inferior to triplex cords, particularly because the required high modulus of the entire cord is not achieved.

[0007] Duplex cords and triplex cords are generally known from the state of the art.

[0008] EP 3 031 623 A1 discloses a hybrid cord for use as a reinforcement in a belt bandage of a pneumatic vehicle tire. The hybrid cord consists of a high-modulus yarn with a fineness of at least 1100 dtex and a low-modulus yarn with a fineness of at most 550 dtex, the yarns being end-twisted together. The low-modulus yarn furthermore has a force, standardized to its fineness and determined according to ASTM D885, which is less than 150 mN / tex at an elongation of 1% and less than 200 mN / tex at an elongation of 2%. The high-modulus yarn furthermore has a force, standardized to its fineness and determined according to ASTM D885, which is greater than 300 mN / tex at an elongation of 1% and greater than 500 mN / tex at an elongation of 2%.The hybrid cord is designed to be cost-effective to produce, enable problem-free tire construction, and, when used in a belt bandage, contribute to improved high-speed capability of the tire.

[0009] EP 3 441 237 A1 discloses another hybrid cord for use as a reinforcement in a reinforcement layer, in particular a belt bandage, of a pneumatic vehicle tire. This hybrid cord consists of a high-modulus yarn and a low-modulus yarn, wherein the yarns are end-twisted with each other and wherein the hybrid cord has an asymmetrical construction. The high-modulus yarn has a fineness of greater than 2500 dtex, wherein the fineness of the high-modulus yarn is at least twice the fineness of the low-modulus yarn. The hybrid cord is intended to exhibit improved fatigue resistance while maintaining good high-speed properties of the pneumatic vehicle tire.

[0010] DE 10 2008 037 615 A1, for example, discloses hybrid cords for use as strength members in a belt bandage with specific initial twist numbers of the respective yarns.

[0011] EP 1 878 591 B1 discloses a layer of reinforcements embedded in an unvulcanized rubber mixture for the belt bandage of pneumatic vehicle tires, wherein a maximum fineness is defined in the reinforcements for the yarn with the high modulus of elasticity.

[0012] EP 2 055 817 A1 discloses a tire having at least one cord, wherein the yarns of the cord are formed from specific materials.

[0013] EP 2 065 222 B1 discloses a pneumatic vehicle tire with reinforcing 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.

[0014] EP 3 006 228 B1 discloses a hybrid cord, wherein the high modulus yarn is a filament yarn and the low modulus yarn is a staple fiber yarn.

[0015] EP 3 196 343 B1 discloses a hybrid cord with a core-covering structure, wherein the hybrid cord is defined by a specific twist number as well as a specific tensile strength and a specific Young's modulus of the high modulus yarn.

[0016] EP 3 365 187 B1 discloses a carcass for pneumatic tires comprising a plurality of two-layer hybrid cords, wherein the hybrid cords have a specific nylon content, a specific total linear density value and a predetermined degree of twist.

[0017] US 2018 / 0099529 A1 discloses a reinforcing element wherein a high modulus yarn and a low modulus yarn are twisted together in a specific manner.

[0018] WO 2014 / 104680 A1 discloses a hybrid cord comprising twisted nylon and twisted aramid yarn, which in turn are end-twisted together.

[0019] WO 2018 / 075305 A1 discloses a hybrid cord in which a nylon yarn and an aramid yarn have the same twist and approximately the same length.

[0020] The object of the present invention was to overcome or at least reduce the disadvantages known from the prior art.

[0021] In particular, it was the object of the present invention to provide a reinforcing cord for use as a strength member in a belt bandage of a pneumatic vehicle tire, which reduces or even completely eliminates the disadvantages known for triplex cords.

[0022] In particular, the specified reinforcement cord should be lighter and more cost-effective to produce than corresponding triplex cords, while maintaining as similar a force-elongation behavior as possible. Furthermore, the specified reinforcement cord should ideally have a smaller diameter and a lower total fineness value, while maintaining as similar a force-elongation behavior as possible.

[0023] In comparison to the duplex cords known from the state of the art, the task was to provide a reinforcement cord which has excellent force-elongation properties corresponding to those of triplex cords known from the state of the art.

[0024] The task was to specify a reinforcement cord which is particularly suitable for use in pneumatic vehicle tires which are optimized for high-speed applications.

[0025] An additional requirement was that the reinforcement cord to be specified should ideally be producible using conventional manufacturing processes and should have the highest possible chemical compatibility with the sulfur-curable compositions commonly used in pneumatic vehicle tires.

[0026] It was a supplementary object of the present invention that the reinforcement cord to be specified should lead to improved rolling properties, in particular to a more favorable rolling resistance.

[0027] The inventors of the present invention have now recognized that the above objects can surprisingly be achieved by providing a duplex cord as the reinforcement cord, as defined in the appended claims. In particular, the inventors of the present invention have recognized that a favorable force-elongation behavior for the duplex cord can surprisingly be achieved by using a different yarn than the higher-modulus yarns commonly used in the prior art, such as aramid, which yarn has a significantly higher modulus than the prior art.

[0028] In this respect, however, the inventors of the present invention have also recognized that in order to obtain force-elongation properties comparable to those of triplex cords known from the prior art, a certain ratio between the finenesses of the two yarns used in the duplex cord must also be set, so that the very high modulus first yarn should have a fineness that is not too significantly higher than that of the second yarn.

[0029] The aforementioned objects are accordingly achieved by duplex cords, composite materials, vulcanized composite materials, vehicle tires, and uses as defined in the claims. Preferred embodiments of the invention emerge from the subclaims and the following statements. Those features of duplex cords, composite materials, vulcanized composite materials, vehicle tires, and uses according to the invention that are designated as preferred below are combined in particularly preferred embodiments with other features designated as preferred. Combinations of two or more of the embodiments designated as particularly preferred below are therefore very particularly preferred. Likewise preferred are embodiments in which a feature designated as preferred to any extent is combined with one or more further features that are designated as preferred to any extent.Features of preferred composite materials according to the invention, vulcanized composite materials, vehicle tires and uses result from the features of preferred duplex cords.

[0030] The invention relates to a duplex cord for use as a reinforcement in a belt bandage of a pneumatic vehicle tire, consisting of exactly two yarns twisted together at the ends, wherein the first yarn has a value for Z of 600 mN / tex or more, and wherein the second yarn has a value for Z of 75 mN / tex or less and a value for Y of 150 mN / tex or less, where Z is the force normalized to the fineness of the yarn at which an elongation of 1% is obtained in the force-elongation diagram, where Y is the force normalized to the fineness of the yarn at which an elongation of 4% is obtained in the force-elongation diagram, where the quotient X of the fineness of the first yarn divided by the fineness of the second yarn is in the range from 1.0 to 1.3, and where the force-elongation diagram is recorded using a Zwick tensile testing machine in accordance with ASTM D885 / D885M 2014.

[0031] The duplex cord according to the invention is suitable for use as a reinforcement in a belt bandage of a pneumatic vehicle tire and is particularly preferred for this use.

[0032] The duplex cord consists of exactly two yarns twisted together at the ends. This means that no other yarn is contained in the duplex cord.

[0033] According to the invention, the first yarn has a specific value for Z, where Z is the force normalized to the yarn's fineness at which an elongation of 1% is obtained in the force-elongation diagram. The value Z correlates accordingly with the yarn's modulus, with the chosen definition using the chord modulus being a representation of this property familiar to those skilled in the art, which allows for a particularly meaningful definition of the materials. The first yarn is thus a particularly high-modulus yarn, which in particular has a higher chord modulus than the aramid yarns used in prior art reinforcement cords.

[0034] The second yarn is a low-modulus yarn. In accordance with expert understanding, to adequately define the second yarn, not only the Z value for the tendon modulus at an elongation of 1% is specified, but also the Y value as the tendon modulus at an elongation of 4%.

[0035] The Y and Z values ​​are determined in accordance with expert understanding from the force-strain diagram and can be calculated using the known yarn count. For the purposes of the present invention, the force-strain diagram used to determine Y and Z is recorded using a Zwick tensile testing machine in accordance with the 2014 ASTM D885 / D885M standard.

[0036] In the duplex cord according to the invention, the counts of the first and second yarns are specifically matched to achieve a force-elongation behavior equivalent to that of a triplex cord. This is achieved via the quotient X, which is calculated by dividing the count of the first yarn by the count of the second yarn. According to the inventors' assessment, the quotient X must be within the specified range to reliably obtain a duplex cord according to the invention that meets the stated objectives.

[0037] The term "count" is clear to textile experts and is sometimes referred to as linear density. This value correlates with the thickness or strength of a yarn and represents a length-related mass, usually expressed in units of tex or dtex.

[0038] With duplex cords according to the invention, the objects defined above are achieved and reinforcing cords are obtained as strength members, the use of which in the belt bandage of a pneumatic vehicle tire can be used to obtain high-performance tires having excellent high-speed properties.

[0039] The inventors of the present invention have come to the conclusion that it is particularly advantageous if the ratio of the finenesses is set to very specific values, whereby the high-modulus first yarn should ideally have values ​​that lie within a certain range just above the fineness of the second yarn. In particular with duplex cords according to the invention, in which the quotient X is approximately 1.15, a force-elongation behavior was observed that was particularly similar to that of a triplex cord acting as a reference system. Accordingly, a duplex cord according to the invention is preferred, wherein the quotient X of the fineness of the first yarn divided by the fineness of the second yarn is in the range from 1.05 to 1.25, preferably in the range from 1.1 to 1.2, particularly preferably in the range from 1.13 to 1.17.

[0040] The inventors of the present invention have recognized that it is particularly advantageous to select a particularly high-modulus first yarn, since this surprisingly allows for particularly high-performance duplex cords to be obtained, the resulting force-elongation behavior of which is advantageously comparable to that of triplex cords in which multiple yarns made of conventional high-modulus material, for example, aramid, are used. A duplex cord according to the invention is preferred, wherein the first yarn has a Z value of 650 mN / tex or more, preferably 700 mN / tex or more.

[0041] Furthermore, the inventors propose selecting the second yarn with the smallest possible modulus, so that there is deliberately a large difference between the moduli of the two yarns used. With a corresponding structure, duplex cords according to the invention are regularly obtained that are particularly easy and efficient to process. Therefore, a duplex cord according to the invention is 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.

[0042] In the course of their development work, the inventors of the present invention succeeded in identifying particularly suitable materials that can be used as the first or second yarn in duplex cords according to the invention. For the high-modulus yarn, specific, particularly high-modulus aramid (also referred to as HM aramid) optimized in terms of its modulus, as well as the material known as Zylon, have proven particularly suitable. These materials differ significantly in their modulus from the regular aramid commonly used in the prior art for duplex cords. With regard to the low-modulus second yarn, polyamides have proven particularly suitable, with the material known as nylon being particularly preferred, in particular nylon PA6.6.

[0043] A duplex cord according to the invention is therefore preferred, wherein the first yarn comprises a material selected from the group consisting of aromatic polyamides, in particular poly(p-phenylene terephthalamide), and polyoxazoles, in particular poly(p-phenylene-2,6-benzobisoxazole), wherein the first yarn preferably consists of this material. A duplex cord according to the invention is therefore particularly preferred, wherein the first yarn consists of poly(p-phenylene terephthalamide) or poly(p-phenylene-2,6-benzobisoxazole). The specific configuration of these materials as a particularly high-modulus embodiment follows from the value for Z defined above.

[0044] Accordingly, a duplex cord according to the invention is also preferred, wherein the second yarn comprises a material selected from the group consisting of polyamides, in particular polyhexamethylene adipamide, wherein the second yarn preferably consists of this material.

[0045] According to the inventors' assessment, to obtain particularly high-performance duplex cords according to the invention, the first and second yarns should each have a fineness above 1000 dtex. With regard to the thickness of the resulting duplex cord, the inventors propose certain upper limits above which greater heat development may occur during subsequent use in the vehicle tire. In this respect, a duplex cord according to the invention is preferred, wherein the first yarn has a fineness in the range of 1000 to 3000 dtex, preferably in the range of 1500 to 2000 dtex. Likewise preferred is a duplex cord according to the invention, wherein the second yarn has a fineness in the range of 1000 to 2000 dtex, preferably in the range of 1300 to 1700 dtex.

[0046] Based on the above information, the inventors believe that the overall fineness of the duplex cord should ideally also be within a certain medium range. Therefore, a duplex cord according to the invention is preferred, wherein the duplex cord has a fineness in the range of 2500 to 4000 dtex, preferably in the range of 2800 to 3500 dtex.

[0047] In the course of development, the inventors of the present invention were able to identify a force-strain profile that can be adjusted with duplex cords according to the invention and whose behavior is particularly similar to that of triplex cords for high-speed applications. Using such preferred duplex cords, vehicle tires can be produced that are particularly advantageous for these high-speed applications and, in particular, exhibit the necessary stiffness.

[0048] A duplex cord according to the invention is preferred, wherein the duplex cord has the following force-elongation properties: 13 to 17 N at 1% elongation, 29 to 33 N at 2% elongation, 57 to 63 N at 3% elongation, 102 to 112 N at 4% elongation, 160 to 180 N at 5% elongation, 240 to 280 N at 6% elongation.

[0049] Even though the inventors believe that the duplex cords according to the invention are comparatively flexible with regard to the twist between the yarns, the inventors, based on the knowledge available to them, propose specific twist factors that lead to particularly suitable duplex cords according to the invention. A duplex cord according to the invention is preferred, wherein the duplex cord has a twist factor in the range of 150 to 200, preferably in the range of 170 to 230, particularly preferably in the range of 185 to 215.

[0050] In light of the above, it is clear that the invention also relates to a composite material comprising one or more of the duplex cords according to the invention. The invention thus also relates to a composite material, in particular for use in the manufacture of a belt bandage of a pneumatic vehicle tire, comprising one or more duplex cords according to the invention, which are at least partially covered by a crosslinkable rubber coating mixture.

[0051] In accordance with the expert's understanding, the crosslinkable rubber compounds used here can be the rubber compounds known from the prior art that are regularly used in the production of pneumatic vehicle tires. In this respect, it can also be considered an advantage of the duplex cords according to the invention that they allow a material selection that exhibits high chemical compatibility with the crosslinkable rubber compounds known from the prior art.

[0052] The advantageous properties of the composite material according to the invention are particularly evident in its ability to be used in the manufacture of pneumatic vehicle tires, which offer favorable rolling resistance and the stiffness required for high-speed applications, coupled with optimized hysteresis behavior. Compared to materials using triplex cords, the composite material according to the invention exhibits very similar properties, but is generally significantly cheaper to produce due to the simpler manufacturing process.

[0053] It has proven particularly advantageous to use several duplex cords according to the invention in corresponding composite materials according to the invention and to arrange them preferably substantially parallel to one another. The size familiar to the person skilled in the art for describing such an arrangement is the EPDM,which indicates the number of reinforcing cords per decimetre along a direction perpendicular to the longitudinal axis of the duplex cords. Accordingly, a composite material according to the invention is preferred, wherein the composite material comprises two or more duplex cords according to the invention, wherein the duplex cords are preferably arranged substantially parallel to one another.

[0054] A composite material according to the invention is preferred, wherein the duplex cord(s) are completely covered by the crosslinkable rubber mixture, wherein the duplex cord(s) are preferably completely surrounded by the crosslinkable rubber mixture.

[0055] By vulcanizing the composite material according to the invention, a vulcanized composite material can be obtained that can be used in pneumatic vehicle tires according to the invention. The composite material according to the invention or the vulcanized composite material can be used to produce belt bandages or vehicle tires that have excellent high-speed properties and favorable rolling resistance. The duplex cords according to the invention provide the necessary stiffness and, due to their smaller diameter compared to comparable triplex cords, contribute to reducing heat buildup in the corresponding vehicle tires.

[0056] The invention thus also relates to a vulcanized composite material which can be produced by vulcanizing a composite material according to the invention.

[0057] Also disclosed is a belt bandage for use in the manufacture of a pneumatic vehicle tire, comprising one or more duplex cords according to the invention, a composite material according to the invention or a vulcanized composite material according to the invention.

[0058] The invention also relates to a vehicle tire, in particular a pneumatic vehicle tire, comprising a composite material according to the invention or a vulcanized composite material according to the invention.

[0059] Finally, the invention also relates to the use of a duplex cord according to the invention or several duplex cords according to the invention in the belt bandage of a pneumatic vehicle tire for improving the high-speed properties and the rolling resistance properties.

[0060] Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying experimental data.

[0061] A triplex cord was provided as the reference system V1, comprising two regular aramid yarns and one nylon yarn with a twist level of 320 T / m. The aramid yarns used had a count of 1680 dtex and the nylon count was 470 dtex.

[0062] In the duplex cord E1 according to the invention, a high modulus aramid (HM-aramid) with a fineness of 1610 dtex was used and end-twisted with a nylon yarn with 1400 dtex.

[0063] The Z value of the high-modulus aramid was 678 mN / tex. The Z value of the nylon was 50 mN / tex, and the Y value of the nylon was 135 mN / tex. The corresponding values ​​were determined from the force-strain diagrams of the yarns, which were determined using a Zwick tensile testing machine according to the 2014 ASTM D885 / D885M standard.

[0064] The corresponding reinforcement cords were processed into composite materials to form belt bandages and also used in 245 / 40 ZR18 ("extreme contact" DWS06) tires. The tires with the inventive duplex cords demonstrated lower rolling resistance and comparable high-speed performance.

[0065] Table 1 below shows that the load at specified elongation (LASE) required for a specific elongation in duplex cords according to the invention advantageously matches the values ​​obtained for prior art triplex cords. Table 1 also shows that the overall diameter of the duplex cord according to the invention is significantly smaller than the overall diameter of the reference system and that, accordingly, a thinner ply thickness can be achieved with the same amount of rubber coating over the cord. The duplex cord according to the invention is simpler and more cost-effective to manufacture due to the single-step manufacturing process used ("twist process").

[0066] In light of the data presented below in Table 1, it is also clear to the person skilled in the art that with duplex cords according to the invention, reinforcement cords with a higher modulus than the corresponding triplex cord could also be obtained with the same overall diameter. Table 1 Unit V1 E2 Yarns - 1680x2 (aramid) +470x1 (nylon) 1610x1 (HM-aramid) +1400x1 (nylon) EPDM - 80 90 LASE 2% N 36 31 N / cm 288 279 LASE 4% N 122 107 N / cm 976 963 diameter mm 0,90 0,75 Spacing mm 0,35 0,36 Layer thickness mm 1,30 1,15 Rubber over cord mm 0,20 0,20 twist T / m 320 361 Twist factor - 198 198 Twist process - 2 levels 1 level Fineness quotient X - 7,14 1,15

Claims

1. Duplex cord for use as strength member in a belt bandage of a pneumatic vehicle tire, consisting of exactly two yarns that are twisted together at the ends, wherein the first yarn has a Z value of 600 mN / tex or more, 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, where Z is the force normalized to the linear yarn density at which an elongation of 1% is obtained in the force-elongation diagram, where Y is the force normalized to the linear yarn density at which an elongation of 4% is obtained in the force-elongation diagram, where the quotient X of the linear density of the first yarn divided by the linear density of the second yarn is in the range from 1.0 to 1.3, and where the force-elongation diagram is recorded with a tensile testing machine from Zwick in accordance with the standard ASTM D885 / D885M of 2014.

2. Duplex cord according to Claim 1, 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 from 1.05 to 1.25, preferably in the range from 1.1 to 1.2, particularly preferably in the range from 1.13 to 1.17.

3. Duplex cord according to either of Claims 1 and 2, wherein the first yarn has a Z value of 650 mN / tex or more, preferably 700 mN / tex or more.

4. Duplex cord according to any of Claims 1 to 3, wherein the first yarn comprises a material selected from the group consisting of aromatic polyamides, in particular poly(p-phenyleneterephthalamide), and polyoxazoles, in particular poly(p-phenylene-2,6-benzobisoxazole), the first yarn preferably consisting of this material.

5. Duplex cord according to any of Claims 1 to 4, wherein the first yarn has a linear density in the range from 1000 to 3000 dtex, preferably in the range from 1500 to 2000 dtex.

6. Duplex cord according to any of Claims 1 to 5, wherein the second yarn has a linear density in the range from 1000 to 2000 dtex, preferably in the range from 1300 to 1700 dtex.

7. Composite material, in particular for use in the manufacture of a pneumatic vehicle tire, comprising one or more duplex cords according to any of Claims 1 to 6 which are at least partially covered by a crosslinkable rubberization mixture.

8. Vulcanized composite material, producible by vulcanization of a composite material according to Claim 7.

9. Vehicle tire, in particular pneumatic vehicle tire, comprising a composite material according to Claim 7 or a vulcanized composite material according to Claim 8.

10. Use of a duplex cord or a plurality of duplex cords according to any of Claims 1 to 6 in the belt bandage of a pneumatic vehicle tire for improving the high-speed properties and the rolling resistance properties.