Hybrid cord and method for manufacturing the same

Abstract

This invention discloses a hybrid cord and a method for manufacturing the same, which eliminates the non-uniformity caused by the difference in fineness between two different filaments by pre-twisting a low-modulus first yarn, reduces the difference in twist index between the low-modulus first yarn and the high-modulus second yarn, ensures functional uniformity and maintains better functional balance, and has not only high strength but also strong adhesion to rubber and excellent fatigue resistance, thereby realizing high performance and weight reduction of tires.

Description

Technical Field

[0001] The present invention relates to a hybrid cord for tire reinforcement and a method for manufacturing the same, and more particularly, to a hybrid cord suitable for application to a cap ply of a high-performance tire and an electric vehicle tire with high strength utilization rate and a method for manufacturing the same.

Background Art

[0002] As vehicles become more high-performance, the number of vehicles traveling at speeds exceeding 120 km / h is increasing. Therefore, a tire cord that can maintain the handling safety and durability of tires even during high-speed driving is required.

[0003] A tire cord is a fiber cord used as a reinforcing material for a tire and is classified according to the part and role where it is used. A tire is composed of a carcass part that supports the entire tire, a belt part that achieves the role of ensuring the contact area and the edge part, and a cap ply part that prevents deformation of the belt part. As the driving speed of an automobile increases, problems such as deformation of the belt part of the tire and deterioration of the riding comfort have occurred. Therefore, the importance of the cap ply for preventing deformation of the belt part has increased.

[0004] As a tire cord for a cap ply, a nylon cord and a nylon / aramid hybrid cord are mainly used. Compared with a nylon cord, a nylon / aramid hybrid cord contains aramid having a higher modulus than nylon, so an improvement in physical properties such as high strength and excellent fatigue resistance can be expected. However, since the fineness of the aramid raw yarn and the fineness of the nylon raw yarn constituting the hybrid cord are different, when making a balanced cord with the same number of twists, the characteristics expected of the hybrid cord cannot be achieved 100%, and uniform physical properties and high fatigue resistance cannot be obtained.

[0005] In other words, when an external force is applied, not all filaments can act simultaneously, and certain filaments resist first, resulting in a problem where the final physical properties are lower. Therefore, in the case of hybrid cords, in order to have high fatigue resistance and uniform physical properties, it is advantageous to manufacture tire cords with an unbalanced structure in which the number of twists differs depending on the physical properties. Existing unbalanced hybrid cords have been manufactured using ring twisting machines, but cords manufactured by ring twisting machines have the problem of low strength utilization due to the large amount of friction generated by the anti-ballooning ring and the long thread path.

[0006] To solve these problems, a direct cabler that can increase the strength utilization rate of tire cord must be used. However, with a direct cabler, the upper and lower twists are performed simultaneously, so it is not possible to make the number of lower twists different for each ply during twisting, which limits the production of tire cords with an unbalanced configuration. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent No. 09653571A [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention aims to overcome the problems of the prior art described above, and one objective of the present invention is to provide a hybrid cord that not only has high strength and high modulus but also excellent fatigue resistance, thereby achieving high performance in tires.

[0009] Another object of the present invention is to provide a method for manufacturing a hybrid cord that can realize high performance tires by having high strength and excellent fatigue resistance. [Means for solving the problem]

[0010] One aspect of the present invention for solving the above-mentioned problems is a hybrid cord in which a first yarn that is pre-twisted and has a low modulus and a second yarn that is not twisted and has a higher modulus than the first yarn are simultaneously twisted together, wherein the ratio (K1 / K2) of the first twist index (K1) calculated by the following formula 1 and the second twist index (K2) calculated by the following formula 2 is 0.94 to 1.24, and the strength utilization rate of the hybrid cord is 70% or more.

[0011] (Math 1) K1 = (T1 + T2) / 10 × A 0.5 T1: Number of twists in the first yarn T2: Number of twists at the end of the first yarn A: Denier of the first yarn

[0012] (Math 2) K2 = T3 / 10 × B 0.5 T3: Number of twists in the second yarn B: Denier of the second yarn

[0013] The initial twist count of the first yarn may be 3-25% of the initial twist count of the second undertwist yarn.

[0014] The number of twists in the first yarn and the second yarn during the initial twisting and upper twisting stages may be 200 to 500 TPM.

[0015] The first yarn may have a fineness of 800 to 1700 denier, and the second yarn may have a fineness of 1000 to 2000 denier.

[0016] The first yarn may be nylon yarn, and the second yarn may be aramid yarn.

[0017] Another aspect of the present invention for achieving the above-described object is a tire including a pair of parallel bead cores, one or more radial carcass layers wound around the bead cores, a belt layer laminated on the outer peripheral side of the carcass layer, and a circumferential cap ply formed on the outer peripheral side of the belt layer, wherein the cap ply includes the hybrid cord according to any one of claims 1 to 5.

[0018] Still another aspect of the present invention for achieving the above-described object includes the steps of preparing two or more types of yarns having different moduli, wherein the modulus of the first yarn is smaller than the modulus of the second yarn; twisting the first yarn to perform pre-twisting; simultaneously performing under-twisting and over-twisting on the pre-twisted first yarn and the second yarn that has not been twisted to produce a ply yarn; and dipping the ply yarn in an adhesive solution and drying and heat-treating the ply yarn. The ratio (K1 / K2) of the first twist index (K1) calculated by the following mathematical formula 1 and the second twist index (K2) calculated by the following mathematical formula 2 is 0.94 to 1.24. The present invention relates to a method for manufacturing a hybrid cord.

[0019] (Equation 1) K1=(T1+T2) / 10×A 0.5 T1: Number of under-twists of the first yarn T2: Number of pre-twists of the first yarn A: Fineness (Denier) of the first yarn

[0020] (Equation 2) K2=T3 / 10×B 0.5 T3: Number of under-twists of the second yarn B: Fineness (Denier) of the second yarn

[0021] In the present invention, the pre-twisting of the first yarn is performed in the first twist direction, the under-twisting of the first yarn is performed in the second twist direction, the under-twisting of the second yarn is performed in the third twist direction, and the second twist direction and the third twist direction may be the same as or different from the first twist direction.

[0022] The upper twist of the first and second yarns is carried out in the fourth twisting direction, and the fourth twisting direction may be in the opposite direction to the second and third twisting directions.

[0023] The initial twist count of the first yarn may be at a level of 3 to 25% of the initial twist count of the second lower yarn.

[0024] The first yarn may be nylon yarn, and the second yarn may be aramid yarn. [Effects of the Invention]

[0025] According to the present invention, the process of forming the first and second under-twisted yarns (i.e., the under-twisting process) and the process of forming a combined yarn with the first and second under-twisted yarns (i.e., the over-twisting process) are carried out by a single twisting machine (e.g., a direct cabler), thereby improving the productivity of hybrid cords and reducing manufacturing costs. Furthermore, since hybrid cords with an unbalanced structure can be manufactured using a direct cabler, the strength, adhesive strength, and strength utilization rate of the hybrid cords can be improved.

[0026] This invention eliminates structural inconsistencies caused by the difference in fineness between the two different yarns by pre-twisting a low-modulus first yarn, thereby reducing the difference in twist index between the aramid yarn and the nylon yarn, and thus obtaining a hybrid cord with improved strength and fatigue resistance that is more functionally balanced. [Brief explanation of the drawing]

[0027] [Figure 1] These are the stress-strain curves (SS curves) for the hybrid cords obtained in Example 1 and Comparative Examples 1 and 2. [Modes for carrying out the invention]

[0028] The present invention will be described in more detail below.

[0029] In this specification, the term "cord" may mean a hybrid cord comprising two or more different types of fibers. The hybrid cord may also mean a dipped cord coated with a coating agent such as an adhesive.

[0030] In this specification, "pre-ply twisting" means imparting a predetermined twist to the yarn for manufacturing hybrid cords before performing the under-twist and over-twist.

[0031] In this specification, “ply twist” means twisting a yarn or filament in one direction, and “ply twisted yarn” may mean a single yarn, i.e., a single yarn, made by twisting a yarn or filament in one direction. The first ply twisted yarn is a yarn obtained by ply twisting a first yarn that has been pre-twisted, and the second ply twisted yarn is a yarn obtained by ply twisting a second yarn that has not been twisted.

[0032] In this specification, "number of undertwists of the first yarn" refers to the number of undertwists of the first yarn excluding the lead twist.

[0033] In this specification, "cable twist" means twisting the first and second under-twisted yarns in either one direction to create a combined twisted yarn (raw cord).

[0034] In this specification, the term "plied yarn" refers to yarn made by twisting two or more under-twisted yarns together in one direction, and is also called "raw cord."

[0035] In this specification, "cord" refers to a plied yarn containing adhesive so that it can be readily applied to rubber products, and is also called "dipped cord." A fabric containing adhesive obtained by weaving plied yarn and then dipping the fabric in an adhesive solution is also included in the definition of "cord."

[0036] In this specification, "twist number" means the number of twists per meter, and its unit may be TPM (Twist Per Meter). In this invention, the twist number can be measured by the method specified in ASTM D-885, for example, using a D314 device manufactured by Zweigle.

[0037] One aspect of the present invention for solving the above-mentioned problems is: This invention relates to a hybrid cord containing two or more yarns with different moduli, wherein a pre-ply twisted first yarn with a lower modulus and a second yarn with a higher modulus than the first yarn are simultaneously twisted together in an unbalanced structure.

[0038] The present invention can overcome the functional drawbacks caused by the denier difference between two filaments with different moduli by pre-twisting the nylon filament, thereby improving the strength, fatigue resistance, and adhesive strength of the cord. Furthermore, the present invention can improve the strength utilization rate of a hybrid cord by pre-twisting the first yarn (e.g., nylon yarn) to create an unbalanced structure using a direct cabler that can increase the strength utilization rate.

[0039] In this invention, the first yarn and the second yarn have different moduli, and the first yarn has a lower modulus than the second yarn.

[0040] The first yarn with a low modulus may be a nylon yarn. The usable nylon filament can be one selected from the group consisting of nylon 6, nylon 66, and nylon 6.10, nylon 5, 6, and nylon 4, 10, and nylon 66 can be used, with nylon 66 being preferred.

[0041] The second yarn, which has a relatively high modulus, may be selected from the group consisting of aramid, aromatic polyamide, all-aromatic polyester, and mixtures thereof. According to a preferred embodiment of the present invention, the second yarn is poly(p-phenylene terephthalamide). High-modulus aramid yarns are advantageous materials for suppressing the flat spot phenomenon that causes tire deformation because the amount of change in modulus is small at room temperature and high temperature.

[0042] In one embodiment, the first yarn may be a nylon yarn having a fineness of 800 to 1700 denier, and the second yarn may be an aramid yarn having a fineness of 1000 to 2000 denier. For example, the fineness of the aramid yarn used for twisting may be 1000 denier, 1500 denier, or 2000 denier, and the fineness of the nylon yarn may be 840 denier, 1260 denier, or 1680 denier.

[0043] In one embodiment, the hybrid cord according to the present invention is a hybrid type of first yarn and second yarn, in which the first yarn to which a twist has been applied and the second yarn to which an untwisted yarn has not been applied are simultaneously under-twisted by a single twisting machine (e.g., a direct cabler) to form the first under-twisted yarn and the second under-twisted yarn, and at the same time (i.e., continuously) the first under-twisted yarn and the second under-twisted yarn are over-twisted together to form a combined twisted yarn (raw cord).

[0044] In this invention, the number of twists refers to the number of twists at that stage, regardless of the twisting direction. Since the first under-twisted yarn is a yarn that is under-twisted after being pre-twisted, the number of twists of the first under-twisted yarn obtained at the under-twisting stage and the number of twists of the first under-twisted yarn are not the same depending on the twisting direction. However, if we consider only the under-twisting stage, the number of under-twists of the first yarn and the number of under-twists of the second yarn can be made the same.

[0045] The twist direction of the first yarn's initial twist may be the same as or different from the twist direction of the first and second undertwisted yarns. The first and second undertwisted yarns may have the same twist direction, and the upper twist direction may be opposite to the twist direction of the first and second undertwisted yarns.

[0046] The first twist index (K1) of the first undertwist yarn is calculated by formula 1 below, and the second twist index (K2) of the second undertwist yarn is calculated by formula 2 below. The ratio of the first twist index (K1) to the second twist index (K2) (K1 / K2) may be in the range of 0.94 to 1.24. If the ratio of the first twist index (K1) to the second twist index (K2) (K1 / K2) is less than 0.94, a functional imbalance will occur in the cord, making it difficult to achieve the objective of the present invention. If the ratio of the first twist index (K1) to the second twist index (K2) (K1 / K2) exceeds 1.24, the degree of non-uniformity of both yarns will increase during the twisting stage, which may reduce workability. In one embodiment, the first twist index (K1) calculated by the following formula 1 for the first undertwisted yarn and the second twist index (K2) calculated by the following formula 2 for the second undertwisted yarn may each be between 1070 and 1450.

[0047] (Math 1) K1 = (T1 + T2) / 10 × A 0.5 T1: Number of twists in the first yarn T2: Number of twists at the end of the first yarn A: Denier of the first yarn

[0048] (Math 2) K2 = T3 / 10 × B 0.5 T3: Number of twists in the second yarn B: Denier of the second yarn

[0049] The number of twists at the beginning of the first yarn may be at a level of 3-25% of the number of twists at the end of the second undertwist yarn. The twist directions of the beginning and undertwist yarns may be the same, but are not limited to this and may be different. For example, if a first yarn (e.g., nylon yarn) is given a beginning twist of 50 TPM in the Z direction, and then the pre-twisted nylon yarn is placed on the creel of a direct cabler, and the aramid yarn is placed in a pot and twisted at 300 TPM, a hybrid raw cord can be produced consisting of nylon yarn and aramid yarn with different total twist counts: 300 TPM for the top twist, 300 TPM for the undertwist aramid, and 350 TPM for the undertwist nylon (sum of the number of twists at the beginning and the undertwist).

[0050] For example, the pre-twisted first yarn may contain nylon fibers (filaments) having a fineness of 800 to 1700 denier (de). For example, the lower limit of the fineness of the first yarn may be 800 denier or more, 900 denier or more, 1000 denier or more, 1050 denier or more, 1100 denier or more, 1150 denier or more, 1200 denier or more, 1250 denier or more, 1300 denier or more, 1350 denier or more, or 1400 denier, 1500 denier or more.

[0051] Furthermore, the upper limit of the fineness of the first yarn may be, for example, 1700 denier or less, 1650 denier or less, 1600 denier or less, 1550 denier or less, 1500 denier or less, 1450 denier or less, 1400 denier or less, 1350 denier or less, 1300 denier or less, 1250 denier or less, 1200 denier or less, 1150 denier or less, 1100 denier or less, or 1050 denier or less, 1000 denier or 900 denier or less. In a preferred embodiment, the fineness of the first yarn may be 840 denier, 1260 denier or 1680 denier.

[0052] The second yarn may contain fibers (filaments) having a fineness of 1000 to 2000 denier. For example, the lower limit of the fineness of the second yarn may be 1000 denier or more, 1100 denier or more, 1200 denier or more, 1300 denier or more, 1400 denier or more, 1450 denier or more, 1500 denier or more, 1550 denier or more, 1600 denier or more, or 1650 denier or more, 1700 denier or more, 1750 denier or more, 1800 denier or more, or 1900 denier or more.

[0053] Furthermore, the upper limit of the fineness of the second yarn may be, for example, 2000 denier or less, 1900 denier or less, 1800 denier or less, 1700 denier or less, 1650 denier or less, 1600 denier or less, 1550 denier or less, 1500 denier or less, or 1450 denier or less. In a preferred embodiment, the fineness of the second yarn may be 1000 denier, 1500 denier, or 2000 denier.

[0054] According to the present invention, since the aramid yarn and the nylon yarn have substantially the same twist index and length in the final tire cord, the two yarns exhibit similar behavior in terms of strength and fatigue performance.

[0055] Specifically, the twist count of the first under-twisted yarn containing the nylon yarn may be 200 to 500 TPM. According to the present invention, when performing under-twisting and over-twisting for the production of the plied yarn (raw cord), the same twist count is applied within the range of 200 to 500 TPM.

[0056] However, when subsequent dipping, drying, and heat treatment processes are carried out sequentially to apply adhesive, unintended untwisting may occur, resulting in a difference of up to 15% in the undertwist and overtwist compared to the initially set twist count. Generally, a higher twist count in filament yarn reduces strength but increases fatigue resistance. Conversely, a lower twist count in filament yarn increases strength but decreases fatigue resistance.

[0057] In the present invention, the number of undertwists of the nylon yarn (excluding the number of initial twists) and the aramid yarn may be 200 TPM or more, 210 TPM or more, 220 TPM or more, 230 TPM or more, 240 TPM or more, 250 TPM or more, 260 TPM or more, 270 TPM or more, 280 TPM or more, 290 TPM or more, 300 TPM or more, 310 TPM or more, 320 TPM or more, 330 TPM or more, 340 TPM or more, 350 TPM or more, 360 TPM or more, 370 TPM or more, 380 TPM or more, 390 TPM or more, 400 TPM or more, 410 TPM or more, 420 TPM or more, 430 TPM or more, 440 TPM or more, 450 TPM or more, 460 TPM or more, 470 TPM or more, 480 TPM or more, or 490 TPM or more, respectively.

[0058] Furthermore, the upper limit of the number of undertwists for the nylon yarn (excluding the number of initial twists) and the aramid yarn may be, for example, 500 TPM or less, 490 TPM or less, 480 TPM or less, 470 TPM or less, 460 TPM or less, 450 TPM or less, 440 TPM or less, 430 TPM or less, 420 TPM or less, 410 TPM or less, 400 TPM or less, 390 TPM or less, 380 TPM or less, 370 TPM or less, 360 TPM or less, 350 TPM or less, 340 TPM or less, 330 TPM or less, 320 TPM or less, 310 TPM or less, 300 TPM or less, 290 TPM or less, 280 TPM or less, 270 TPM or less, 260 TPM or 250 TPM or less, 240 TPM or less, or 230 TPM or less.

[0059] As described above, the hybrid cord of the present invention includes a first under-twisted yarn and a second under-twisted yarn that are pre-twisted and have a predetermined number of twists, and is formed by twisting the first under-twisted yarn and the second under-twisted yarn together. Here, the first yarn for forming the first under-twisted yarn and the second yarn for forming the second under-twisted yarn are simultaneously under-twisted by a direct cabler, respectively, so the twisting direction of the first under-twisted yarn (second twisting direction) and the twisting direction of the second under-twisted yarn (third twisting direction) may be the same. Furthermore, when using a direct cabler twisting machine (for example, a direct cabler), under-twisting and over-twisting can be performed continuously and simultaneously following the under-twisting. Here, the twisting direction of the over-twist (i.e., the fourth twisting direction) may be opposite to the second twisting direction (or third twisting direction).

[0060] A hybrid cord according to one embodiment of the present invention may further include an adhesive coated on the nylon undertwist yarn and the aramid undertwist yarn to improve adhesion to the tire. Such a coating layer may be formed on at least a portion of the undertwist yarn described above. The method for forming the coating layer is not particularly limited, and for example, the coating layer can be formed by known dipping or spraying methods.

[0061] The coating layer may be formed from an adhesive composition. For example, the coating layer may contain or be formed from a resorcinol formaldehyde latex (RFL) adhesive, epoxy adhesive, or urethane adhesive.

[0062] The hybrid cord of the present invention has a dry heat shrinkage rate of 1.0 to 3.0%. If the dry heat shrinkage rate falls outside this range, the cord may shrink significantly due to the increase in the internal temperature of the tire during high-speed driving, which can reduce the dimensional stability of the cord and degrade the performance of the tire.

[0063] The dry heat shrinkage rate of the hybrid cord of the present invention may be 1.0% or more. For example, the dry heat shrinkage rate may be 1.1% or more, 1.2% or more, 1.3% or more, 1.4% or more, 1.5% or more, 1.6% or more, 1.7% or more, 1.8% or more, 1.9% or more, or 2.0% or more. The dry heat shrinkage rate of the hybrid cord may be 3.0% or less. For example, the dry heat shrinkage rate may be 2.9% or less, 2.8% or less, 2.7% or less, 2.6% or less, 2.5% or less, 2.4% or less, 2.3% or less, or 2.2% or less.

[0064] The strength of the hybrid cord of the present invention may be 35 kgf or more. Specifically, the strength may be, for example, 35 kgf or more, 36 kgf or more, 37 kgf or more, 38 kgf or more, 39 kgf or 40 kgf or more.

[0065] In the present invention, the strength utilization rate of the hybrid twisted yarn (raw cord) is 70% or more, more preferably 75% or more. The strength utilization rate of the hybrid cord may be 70% or more. For example, the strength utilization rate may be 71.0% or more, 72.0% or more, 73.0% or more, 74% or more, 75% or more, 76% or more, 77% or more, 78% or more, 79% or more, or 80% or more.

[0066] The method for manufacturing the hybrid cord of the present invention will be described in more detail below.

[0067] In manufacturing a hybrid cord according to the present invention, two or more yarns with different moduli are prepared, wherein the modulus of the first yarn is smaller than the modulus of the second yarn. Then, the first yarn is pre-twisted by applying a twist, and then the pre-twisted first yarn and the untwisted second yarn are simultaneously subjected to under-twisting and over-twisting to produce a plied yarn. Optionally, the plied yarn may further be immersed in an adhesive solution, dried, and heat-treated.

[0068] In the method of the present invention, the ratio (K1 / K2) of the first twist index (K1) calculated by the following formula 1 and the second twist index (K2) calculated by the following formula 2 can be set to 0.94 to 1.24.

[0069] (Math 1) K1 = (T1 + T2) / 10 × A 0.5 T1: Number of twists in the first yarn T2: Number of twists at the end of the first yarn A: Denier of the first yarn

[0070] (Math 2) K2 = T3 / 10 × B 0.5 T3: Number of twists in the second yarn B: Denier of the second yarn

[0071] The first yarn may be nylon yarn, and the second yarn may be aramid yarn.

[0072] When a low modulus first yarn (e.g., nylon yarn) is pre-twisted, the twisting direction may be the S direction or the Z direction. The number of pre-twisted strands of the first yarn may be at a level of 3 to 25% of the number of undertwisted strands of the second undertwisted yarn (e.g., aramid yarn).

[0073] As an example, first, a first yarn with a low modulus is pre-twisted to a level of 3-25% of the undertwist count of the second undertwist yarn. Next, the first yarn of 800-1700 denier and the second yarn of 1000-2000 denier are fed into a cable cord twisting machine (direct cabler) that performs both undertwisting and overtwisting. In the cable cord twisting machine, the steps of undertwisting the first yarn to obtain the first undertwist yarn and undertwisting the second yarn to obtain the second undertwist yarn are performed simultaneously, and the step of overtwisting the first and second undertwist yarns together to form a combined yarn is performed almost simultaneously (continuously) with the undertwisting steps of the first and second yarns. The twisting direction of the overtwist is the opposite direction to the twisting direction of the undertwist, and when the undertwisting and overtwisting are performed simultaneously, the same number of twists can be applied within the range of 200-500 TPM.

[0074] The present invention allows for the production of a hybrid cord by further steps of immersing a plied yarn (raw cord), drying it, and heat-treating it after the plied yarn has been manufactured. The hybrid cord of the present invention (i.e., dip cord) can be produced by immersing the plied yarn in the adhesive solution, drying the plied yarn impregnated with the adhesive solution, and then heat-treating the dried plied yarn. Here, an RFL solution (Resorcinol Formaldehyde Latex) or an epoxy-based adhesive composition liquid can be used as the adhesive solution.

[0075] The temperature and time of the drying process vary depending on the composition of the adhesive solution, but are typically carried out at 70-200°C for 30-120 seconds. The heat treatment process can be carried out at 200-250°C for 30-120 seconds. Through these processes, the adhesive components of the adhesive solution coat the surface of the twisted yarn, thereby increasing the adhesion between the hybrid cord of the present invention and the other components of the tire.

[0076] On the other hand, although the twisting machine is set up to perform both the undertwist and overtwist with the same number of twists, a twisting phenomenon may occur during the process in which the plied yarn produced by the twisting machine is immersed in an adhesive solution, dried, and heat-treated. In order to minimize such a twisting phenomenon and to prevent excessive shrinkage of the nylon yarn, it is preferable that the tension applied to the plied yarn during the continuous immersion, drying, and heat treatment stages is 0.4 kg / cord or more.

[0077] Another aspect of the present invention relates to a tire including the hybrid cord (dip cord) described above. For example, the hybrid cord of the present invention can be used for manufacturing the cap ply layer of a tire.

[0078] The present invention will be described in more detail below based on examples. However, the following examples are provided solely to aid in understanding the present invention and do not limit the scope of the rights of the present invention.

[0079] Examples Example 1 Prior to performing the under-twist and top-twist of the hybrid cord, 1260d nylon yarn was pre-twisted in the Z direction at 30 TPM. Then, the 1500d aramid yarn and the pre-twisted 1260d nylon yarn were fed into a cable cord twisting machine (Allma's Direct Cabler) to simultaneously perform the under-twist and top-twist to produce a combined twisted yarn. Here, the under-twist direction of the nylon yarn and the aramid yarn were the same, in the Z direction, with the same number of twists at 300 TPM, while the top-twist direction was in the S direction, with a number of twists at 300 TPM.

[0080] Next, the plied yarn was immersed in a resorcinol-formaldehyde-latex (RFL) adhesive solution. The plied yarn impregnated with the RFL adhesive solution was dried at 160°C for 100 seconds and then heat-treated at 240°C for 100 seconds to produce a hybrid cord.

[0081] Examples 2 and 3 Prior to performing the under-twist and over-twist, the nylon yarn was pre-twisted, and a hybrid cord was manufactured in the same manner as in Example 1, except that the number of pre-twists (10 TPM, 50 TPM), the number of twists in the nylon under-twist yarn, or the ratio of the twist index of the aramid yarn to the twist index of the nylon yarn were varied as shown in Table 1 below.

[0082] Comparative Example 1 A hybrid cord was manufactured using the same method as in Example 1, except that untwisted 1260d nylon yarn was used.

[0083] Comparative Example 2 A hybrid cord was manufactured in the same manner as in Example 1, except that 1500d aramid yarn and 1260d nylon yarn were fed into a ring twister for initial twisting (300 TPM / 330 TPM), followed by initial twisting (300 TPM) on each.

[0084] Comparative Example 3 A hybrid cord was manufactured in the same manner as in Example 1, except that the nylon yarn was pre-twisted (pre-twisted) prior to the lower and upper twisting processes, with a pre-twist count of 110 TPM.

[0085] Test example To evaluate whether the physical properties of the hybrid cords obtained from the above-mentioned test examples and comparative examples are suitable for cap ply applications, the strength, fatigue resistance, and strength utilization rate of the cords were measured by the following methods, and the results are shown in Table 1 below.

[0086] *Strong (kgf) Ten samples, each 250 mm long, were prepared for the hybrid cord. The strength of each sample was then measured using an Instron testing machine (Instron Engineering Corp., Canton, Mass) by applying a tensile speed of 300 m / min to each sample, following the ASTM D885 / D885M-10a (2014) test method (leaving the samples in a constant temperature and humidity chamber at 25°C and 65% RH for 24 hours). The strength was calculated as the average strength of the ten samples.

[0087] *Fatigue resistance (%) Fatigue tests were conducted using a belt fatigue tester, which is commonly used for fatigue testing of tire cords. After the tests, residual strength was measured to compare fatigue resistance. The fatigue test conditions were RT, load of 80 kg, and 37,500 rotations. After the fatigue tests, the rubber and cord were separated and the residual strength was measured. The residual strength was measured using a standard tensile strength tester.

[0088] *Strong utilization rate (%) : - Strength utilization rate of plied yarn (raw cord) (%) = Strength of raw cord / (Strength of 1st yarn + Strength of 2nd yarn) × 100 - Code (DIP code) strength utilization rate (%) = DIP code strength / (Strength of 1st yarn + Strength of 2nd yarn) × 100

[0089] [Table 1]

[0090] As can be seen from the test results in Table 1, in the present invention (Examples 1-4), in which a pre-twist is applied to the nylon yarn to have a certain range of twists, and the pre-twisted nylon yarn and the unpre-twisted aramid yarn are simultaneously over-twisted and under-twisted in a direct cable twister to produce raw cord, it can be confirmed that the hybrid cord has superior strength, strength utilization rate, and fatigue resistance compared to the comparative example. In particular, it can be seen that the examples have superior fatigue resistance compared to Comparative Example 1, in which the nylon yarn was not pre-twisted, and that the examples have superior strength utilization rate compared to Comparative Example 2, in which a ring twisting machine other than a cable cord twisting machine (direct cable twister) was used.

[0091] Test Example 2 205 / 65R15V tires manufactured by applying the hybrid cords produced in the above examples and comparative examples to the cap ply were mounted on a 2000cc class passenger car. Handling safety and ride comfort were evaluated by skilled drivers on a test course, with a maximum score of 100 points and a scale of 5 points. The results are shown in Table 2 below. Durability was measured using the FMVSS109 P-metric tire endurance test method. Under conditions of 38°C temperature, 85%, 90%, and 100% of the tire's stated load, and a driving speed of 80 km / h for a total of 34 hours, the tire was judged to pass (OK) if no signs of bead separation, cord breakage, belt separation, etc., could be found in any part, including the tread, sidewall, carcass cords, inner liner, and bead. For uniformity testing, experiments were conducted using a high-speed uniformity testing machine (HISUM (HOFMANN RGM-LT3)) while maintaining a constant air pressure (30 psi) from 300 to 1300 rpm.

[0092] [Table 2]

[0093] As can be seen from the results in Table 2 above, the tires of Examples 1 to 3, in which the hybrid cord according to the present invention is applied to the cap ply, are superior in terms of ride comfort, durability, and handling safety compared to Comparative Examples 1 to 3, in which a conventional hybrid cord is applied, and the uniformity of the tire is also improved.

Claims

1. A hybrid cord characterized in that a first yarn, which is pre-twisted and has a low modulus, and a second yarn, which is not twisted and has a higher modulus than the first yarn, are simultaneously twisted together, the ratio (K1 / K2) of the first twist index (K1) calculated by the following formula 1 to the second twist index (K2) calculated by the following formula 2 is 0.94 to 1.24, and the strength utilization rate of the hybrid cord is 70% or more. (Math 1) K1=(T1+T2) / 10×A 0.5 T1: Number of twists in the first yarn T2: Number of twists at the end of the first yarn A: Denier of the first yarn (Math 2) K2=T3 / 10×B 0.5 T3: Number of twists in the second yarn B: Denier of the second yarn

2. The hybrid cord according to claim 1, characterized in that the number of twists at the beginning of the first yarn is at a level of 3 to 25% of the number of twists at the beginning of the second under-twist yarn.

3. The hybrid cord according to claim 1, characterized in that the number of twists in the first yarn and the second yarn during the initial twisting and upper twisting is 200 to 500 TPM.

4. The hybrid cord according to claim 1, characterized in that the first yarn has a fineness of 800 to 1700 denier, and the second yarn has a fineness of 1000 to 2000 denier.

5. The hybrid cord according to claim 1, characterized in that the first yarn is a nylon yarn and the second yarn is an aramid yarn.

6. A tire comprising a pair of parallel bead cores, one or more radial carcass layers wound around the bead cores, a belt layer laminated on the outer periphery of the carcass layer, and a circumferential cap ply formed on the outer periphery of the belt layer, wherein the cap ply comprises a hybrid cord as described in any one of claims 1 to 5.

7. The first yarn has a modulus smaller than the second yarn, and two or more yarns with different moduli are prepared. The first yarn is given a twist and pre-twisted, A step of manufacturing a combined twisted yarn by simultaneously performing under-twisting and over-twisting on a pre-twisted first yarn and a second yarn that has not been twisted, The process includes the steps of immersing the aforementioned twisted yarn in an adhesive solution, drying it, and heat-treating it, A method for manufacturing a hybrid cord, characterized in that the ratio (K1 / K2) of the first twist index (K1) calculated by the following formula 1 and the second twist index (K2) calculated by the following formula 2 is set to 0.94 to 1.

24. (Math 1) K1=(T1+T2) / 10×A 0.5 T1: Number of twists in the first yarn T2: Number of twists at the end of the first yarn A: Denier of the first yarn (Math 2) K2=T3 / 10×B 0.5 T3: Number of twists in the second yarn B: Denier of the second yarn

8. A method for manufacturing a hybrid cord according to claim 7, characterized in that the initial twist of the first yarn is carried out in the first twisting direction, the undertwist of the first yarn is carried out in the second twisting direction, the undertwist of the second yarn is carried out in the third twisting direction, and the second twisting direction and the third twisting direction are the same as or different from the first twisting direction.

9. The upper twist of the first and second yarns is carried out in the fourth twisting direction. The method for manufacturing a hybrid cord according to claim 8, characterized in that the fourth twisting direction is in the opposite direction to the second twisting direction and the third twisting direction.

10. The method for manufacturing a hybrid cord according to claim 8, characterized in that the number of twists at the tip of the first yarn is at a level of 3 to 25% of the number of twists at the bottom of the second under-twisted yarn.

11. A method for manufacturing a hybrid cord according to claim 8, characterized in that the first yarn is a nylon yarn and the second yarn is an aramid yarn.

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