Cord and its manufacturing method

Abstract

The present application relates to a cord containing para-aramid fibers, a method for producing the cord, and a reinforcing material and a tire containing the cord. Specifically, the cord contains para-aramid fibers that have a large crystal size and a high degree of crystallinity and thus have excellent mechanical properties, and therefore has high resistance to deformation due to external forces, and therefore can be usefully used as a tire reinforcing material.

Description

[Technical Field]

[0001] The present application relates to a cord containing para-aramid fibers, a method for producing the cord, a composite (or reinforcement material) and a tire containing the cord. [Background technology]

[0002] Aramid fibers composed of an aromatic dicarboxylic acid component and an aromatic diamine component, particularly para-aramid fibers such as polyparaphenylene terephthalamide (PPTA) fibers, are excellent in strength, elastic modulus, and heat resistance and are widely used in industrial applications, medical applications, etc. However, the mechanical properties of the fibers, such as strength and elastic modulus, are still insufficient depending on the application, and efforts are being made to provide fibers with better physical properties.

[0003] Meanwhile, aramid fibers are also used in tire cords, which are reinforcement materials. For example, tire cords are made by plying nylon and aramid fibers together. However, nylon has a relatively low modulus, which means it deforms significantly when subjected to tension (external force). In contrast, aramid fibers have a relatively high modulus, which means they deform less when subjected to tension (external force). These differences in properties are due to the shape and microstructure of the molecular chains that make up each fiber. Specifically, aramid, which has linear polymer chains, has a relatively high degree of crystallinity due to hydrogen bonding between the molecular chains, resulting in a high modulus.

[0004] Considering this point, it is necessary to develop aramid fibers and articles (e.g., cords) containing the same with improved microstructure so that tire cords can exhibit small deformations against external forces. Summary of the Invention [Problem to be solved by the invention]

[0005] One object of the present application is to provide an article (e.g., a cord) containing, as a component, para-aramid fibers that have a large crystal size and a high degree of crystallinity and exhibit excellent mechanical properties (e.g., tensile properties).

[0006] Another object of the present application is to provide a tire cord having excellent mechanical properties (eg, tensile properties).

[0007] A further object of the present application is to provide a tire cord that has high resistance to deformation when an external force is applied, such as a low creep rate (Creep Strain (%)).

[0008] The above and other objects of the present application can all be achieved by the invention of the present application as described in detail below. [Means for solving the problem]

[0009] According to a specific example of the present application, there is provided a cord including two different types of first twisted yarns, one of which is formed by twisting a para-aramid fiber that satisfies predetermined properties; and a method for manufacturing the cord.

[0010] Specifically, the inventors of the present application have experimentally confirmed that when para-aramid fibers having excellent mechanical properties (e.g., tensile properties) are used in the manufacture of cords to be used as reinforcement materials for tires and the like, a cord formed to contain the para-aramid fibers of the present application described below can exhibit better mechanical properties (e.g., tenacity, strength and / or elongation) and have a lower creep rate (Creep Strain (%)) than a cord formed without the para-aramid fibers, and have thus completed the present invention.

[0011] As used herein, the term "cord" may refer to an article containing at least two or more different fibers. For example, the cord may refer to a hybrid cord containing at least two or more different ply-twisted yarns. Such a cord may be a plied yarn formed by twisting together (i.e., ply-twisting) two or more ply-twisted yarns.

[0012] In a specific example of the present application, the cord may be a raw cord or a dipped cord. A dipped cord refers to a fiber (plied yarn) coated with a coating agent such as an adhesive. Conversely, a cord containing at least two fibers without a coating agent on the fibers may be referred to as a raw cord. In a specific example of the present application, the cord has a plied yarn structure in which at least a first ply yarn and a second ply yarn are ply-twisted together (i.e., made by twisting ply yarns together).

[0013] As used herein, "first twist" refers to twisting yarns or filaments in one direction, and "first twist yarn" refers to a single ply of yarn, i.e., a single yarn, made by twisting yarns or filaments in one direction. While not particularly limited, the first twist may refer to, for example, a clockwise or counterclockwise twist.

[0014] Also, as used herein, "plied yarn" may refer to a yarn made by twisting two or more ply-twisted yarns together in one direction. Ply twist may refer to a twist in the opposite direction to the twist in which the ply twist is made. For example, ply twist may refer to a counterclockwise or clockwise twist.

[0015] A ply-twisted yarn or plied yarn produced by twisting in a certain direction can have a predetermined twist count. Here, "twist count" refers to the number of twists per meter, and its unit may be TPM (Twist Per Meter).

[0016] The cord of the present application and its manufacturing method will be described in more detail below.

[0017] In one embodiment, the present application relates to a cord comprising para-aramid fibers, which can be used as a reinforcement material for rubber, more specifically, a reinforcement material for tires, without being limited thereto.

[0018] Specifically, the cord may be formed by twisting together para-aramid fibers (A) that satisfy the properties described below and different fibers (B) that are different from the para-aramid fibers.

[0019] Specifically, the para-aramid fibers used to form the cords are para-aramid fibers having (i) a crystallinity of 67% or more, (ii) a crystal size of 5.8 to 7.0 nm based on 110 plane, (iii) a total fineness of 200 to 1,600 denier (de), and (iv) a tensile strength of 22 g / d or more.

[0020] In this specification, unless otherwise specified, physical properties such as tensile properties and microstructure measurements of para-aramid fibers are values measured on fibers obtained after normal spinning, coagulation, and drying, and are values measured on fibers in a state where a heat treatment step that can be added to a fiber manufacturing method is not performed.

[0021] When a cord is produced by twisting the para-aramid fiber (A), which has a large crystal size and high crystallinity and can exhibit excellent mechanical properties (e.g., tensile properties) as described above, with a heterogeneous fiber (B), a cord having excellent mechanical properties (e.g., tenacity, strength, and / or elongation) and a low creep rate (Creep Strain (%)) can be provided, as confirmed by the experiments described below.

[0022] In one example, the para-aramid fiber having such properties may be formed from a para-aramid polymer produced by a predetermined polymerization method. Specifically, the para-aramid fiber can be provided by a method for producing a para-aramid fiber, the method comprising the steps of: filtering reaction materials to remove impurities; adding an aromatic diamine to a mixed solvent containing an organic solvent and an inorganic salt to form a slurry; adding an aromatic diacid halide to a reactor containing the slurry in three or more divided portions and reacting the mixture to form a para-aramid polymer; and spinning a spinning dope containing the para-aramid polymer to produce fibers, wherein, in the step of forming the polymer, the temperature difference between the cooling water inlet and outlet for cooling the reactor during the first and second additions of the aromatic diacid halide is controlled to within 50°C.

[0023] This manufacturing method can provide para-aramid fibers with excellent mechanical strength by minimizing the amount of inorganic impurities remaining in the final para-aramid polymer through the step of removing impurities from the reaction raw materials.

[0024] The reaction raw materials include an organic solvent, an inorganic salt, an aromatic diamine, and an aromatic diacid halide. In the step of filtering the reaction raw materials to remove impurities, at least one of the reaction raw materials can be filtered to remove impurities contained in the raw material. For example, in the step of filtering the reaction raw materials to remove impurities, the organic solvent, the inorganic salt, the aromatic diamine, and the aromatic diacid halide can each be filtered to prepare a reaction raw material from which impurities have been removed.

[0025] In the step of filtering the reactant materials to remove impurities, the reactant materials can be filtered using a filter having a diameter of 0.01 to 1.0 μm, 0.03 to 0.7 μm, or 0.05 to 0.5 μm. The diameter may be the major axis length of the filter holes. By using a filter having such a diameter, the content of inorganic impurities in the reaction system can be reduced to 1 ppm or less. Furthermore, by using a filter having such a diameter, the content of inorganic impurities in the polymerized polymer can be reduced to 50 ppb or less. The lower limit of the content of inorganic impurities may be 0 ppb or more.

[0026] The order in which the step of filtering the reactants to remove impurities is performed is not particularly limited. Specifically, the step of filtering the reactants to remove impurities may be performed before or during the step of forming the slurry. For example, when the step of filtering the reactants to remove impurities is performed during the step of forming the slurry, a mixed solvent containing an organic solvent and an inorganic salt may be prepared, and the mixed solvent may be filtered to prepare the mixed solvent. The aromatic diamine, which has been separately filtered to remove impurities, may be added to the mixed solvent to form the slurry.

[0027] Meanwhile, in the step of forming the slurry, a mixed solvent may be prepared by adding an inorganic salt to an organic solvent in order to increase the degree of polymerization of the para-aramid polymer.

[0028] The inorganic salt contained in the mixed solvent may include an alkali metal halide salt or an alkaline earth metal halide salt. For example, the inorganic salt may include one or more selected from the group consisting of CaCl, LiCl, NaCl, KCl, LiBr, and KBr. The inorganic salt may be contained in an amount of 0.01 to 15 wt %, 0.05 to 13 wt %, 0.1 to 11 wt %, or 1 to 10 wt %, based on the total weight of the mixed solvent.

[0029] The organic solvent contained in the mixed solvent may include at least one selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, hexamethylphosphoamide, N,N,N',N'-tetramethylurea, N,N-dimethylformamide, and dimethyl sulfoxide. The organic solvent may be contained in an amount equal to the remaining amount excluding the inorganic salt based on the total weight of the mixed solvent.

[0030] In the step of forming the slurry, the mixed solvent and the aromatic diamine may be mixed so that the content of the aromatic diamine in the slurry is 0.5 to 10 wt %.

[0031] The aromatic diamine may be at least one selected from the group consisting of p-phenylenediamine, 4,4'-oxydianiline, 2,6-naphthalenediamine, 1,5-naphthalenediamine, and 4,4'-diaminobenzanilide.

[0032] Next, in the step of forming the para-aramid polymer, an aromatic diacid halide may be added to the previously prepared slurry and reacted to prepare the para-aramid polymer.

[0033] The aromatic diacid halide may be at least one selected from the group consisting of terephthaloyl dichloride, [1,1'-biphenyl]-4,4'-dicarbonyl dichloride, 4,4'-oxybis(benzoyl chloride), naphthalene-2,6-dicarbonyl dichloride, and naphthalene-1,5-dicarbonyl dichloride.

[0034] The aromatic diacid halide reacts with the aromatic diamine in a molar ratio of 1:1, so the molar ratio of the aromatic diacid halide to the aromatic diamine may be about 0.9 to 1.1.

[0035] The polymerization reaction between the aromatic diamine and the aromatic diacid halide proceeds at a rapid rate and generates heat. Therefore, in the past, a portion of the aromatic diacid halide was first added to perform prepolymerization, and then the remaining aromatic diacid halide was added to minimize the difference in degree of polymerization between the final polymers.

[0036] The above-mentioned production method is a step ahead of conventional methods, and uses reactant materials from which impurities have been removed, and by controlling the conditions and method for adding the reactant materials, it is possible to provide para-aramid fibers that not only have a small difference in polymerization degree between polymers but also have a large crystal size and a high degree of crystallinity.

[0037] Specifically, in the production method, instead of the conventional method of adding the aromatic diacid halide in two separate additions, the aromatic diacid halide is added in three or more separate additions, and the temperature difference between the cooling water entering and leaving the reactor during the first and second additions of the aromatic diacid halide is controlled to within 50°C, thereby providing para-aramid fibers having a desired large crystal size and high crystallinity.

[0038] Specifically, in the step of forming the polymer, a reactor into which cooling water can be introduced is used.

[0039] In the step of forming the slurry, the slurry may be prepared in a reactor, or may be prepared in a vessel other than the reactor and then introduced into the reactor.

[0040] In the step of forming the polymer, the aromatic diacid halide is added to the reactor containing the slurry in three or more divided portions. In particular, the aromatic diacid halide can be added in the first and second portions while the temperature difference between the cooling water inlet and outlet of the reactor is controlled to 0°C to 50°C.

[0041] More specifically, during the first addition of the aromatic diacid halide, the temperature difference between the cooling water inlet and outlet can be controlled to 0°C to 50°C, 0°C to 40°C, 0°C to 35°C, or 0°C to 30°C.

[0042] In order to control the temperature difference of the cooling water between the cooling water inlet and outlet to within 50°C, the stirring speed of the reactor can be adjusted to 10 to 1000 rpm, 10 to 900 rpm, 10 to 700 rpm, or 10 to 500 rpm while the cooling water is circulating in the reactor.

[0043] The content of the aromatic diacid halide initially added can be adjusted to 20 to 40 mol % or 25 to 35 mol % based on the total content of the aromatic diacid halide added. Within this range, a prepolymer having a molecular chain of an appropriate length can be formed.

[0044] After the aromatic diacid halide is initially added, the mixture is stirred at a temperature of 0°C to 45°C for about 1 to 30 minutes or 5 to 15 minutes to carry out prepolymerization.

[0045] Next, in order to again control the temperature difference of the cooling water between the cooling water inlet and the outlet to within 50°C, the stirring speed of the reactor can be adjusted to 10 to 1000 rpm, 10 to 900 rpm, 10 to 700 rpm, or 10 to 500 rpm while the cooling water is circulating in the reactor.

[0046] The content of the aromatic diacid halide added secondarily can be adjusted to 20 to 75 mol%, 40 to 75 mol%, or 50 to 70 mol% based on the total content of the aromatic diacid halide added. Within this range, it is possible to form a polymer capable of providing fibers with large crystal size and high crystallinity while minimizing the difference in polymerization degree between polymers.

[0047] After the aromatic diacid halide is secondarily added, the mixture can be stirred at a temperature of 0°C to 45°C for about 1 to 30 minutes or 5 to 15 minutes to carry out polymerization.

[0048] Thereafter, the remaining amount of aromatic diacid halide is added in one or more divided portions, and then additional polymerization is carried out to finally produce a para-aramid polymer. The additional polymerization may be carried out at a temperature of 0°C to 45°C with stirring for about 5 minutes to 1 hour or 10 minutes to 40 minutes.

[0049] The step of forming the polymer may be followed by one or more of the steps of separating the produced polymer from the polymerization reaction system, washing the polymer, neutralizing the polymer, and pulverizing the polymer, regardless of the order described.

[0050] The para-aramid polymer may have an intrinsic viscosity of 4.0 dl / g or more, 5.0 dl / g or more, or 5.3 dl / g or more, and may have an intrinsic viscosity of 9.0 dl / g or less.

[0051] The para-aramid polymer may have an intrinsic viscosity deviation of 1.0 dL / g or less, 0.9 dL / g or less, or 0.8 dL / g or less. Since the smaller the deviation of the intrinsic viscosity of the para-aramid polymer, the more advantageous it is, the lower limit of the intrinsic viscosity deviation may be 0 dL / g or more.

[0052] The intrinsic viscosity deviation can be determined by dividing the para-aramid polymer that has been washed and dried into a group of 2 mm or more, a group of 1 mm or more and less than 2 mm, and a group of less than 1 mm using standard sieves with mesh sizes of 1 mm and 2 mm, measuring the intrinsic viscosity of each group, and then calculating the difference between the maximum and minimum average intrinsic viscosities of the three groups.

[0053] The para-aramid polymer may be produced from impurity-removed reactant materials, so that the amount of inorganic impurities remaining in the polymer may be very small or zero. For example, the content of inorganic impurities in the polymer may be 50 ppb or less.

[0054] The para-aramid polymer may be poly(para-phenylene terephthalamide), poly(4,4'-benzanilide terephthalamide), poly(paraphenylene-4,4'-biphenylene-dicarbonylamide), poly(paraphenylene-2,6-naphthalenedicarbonylamide), or copolymers thereof. As an example, the para-aramid polymer may be poly(para-phenylene terephthalamide).

[0055] Meanwhile, in the step of producing the fiber, a spinning dope containing the polymer produced in the step of forming the polymer is spun to provide the fiber.

[0056] The solvent for the spinning dope can be sulfuric acid having a concentration of 97 to 102% by weight, and chlorosulfuric acid or fluorosulfuric acid may be used instead of sulfuric acid.

[0057] The viscosity of a spinning dope for producing fibers increases as the concentration of para-aramid polymer in the spinning dope increases. However, when the concentration of para-aramid polymer exceeds a critical concentration, the viscosity of the spinning dope decreases rapidly. At this time, the spinning dope changes from optically isotropic to optically anisotropic without forming a solid phase. Due to its structural and functional properties, an optically anisotropic dope can produce high-strength para-aramid fibers without a separate drawing process. Therefore, it is preferable that the concentration of para-aramid polymer in the spinning dope exceeds the critical concentration. However, if the concentration is too high, the viscosity of the spinning dope may become too low. Therefore, the spinning dope may contain para-aramid polymer in an amount of 10 to 25 wt% based on the total weight of the spinning dope.

[0058] In the step of producing the fiber, a spinning process of spinning the spinning dope may be performed.

[0059] In the spinning step, the spinning dope can be spun into filaments by air gap wet spinning.

[0060] Air-gap wet spinning is a method in which an air gap is provided between a spinneret and the surface of a coagulation bath. In this air-gap wet spinning method, the spinning dope passes through the spinneret and the air gap and is spun into a coagulation bath containing a coagulation liquid.

[0061] In the spinning process, the thickness of the fiber can be controlled by the pressure and spinning speed when the spinning dope is extruded through the spinneret.

[0062] The spinneret may have a number of holes through which the spinning dope can be spun.

[0063] Specifically, the spinneret may have 50 to 3000, 100 to 2000, 120 to 1500, or 500 to 1200 holes. Within these ranges, a para-aramid fiber having a large crystal size and high crystallinity and exhibiting excellent tensile properties can be provided.

[0064] The diameter of the holes formed in the spinneret must be adjusted to an appropriate size to improve the molecular orientation on both the surface and the interior of the filament. For this reason, the diameter of the holes in the spinneret can be adjusted to 50 μm or more and 100 μm or less.

[0065] In the spinning step, the spinning dope can be spun at a spinning speed of 80 m / min or more and 800 m / min or less.

[0066] Specifically, the spinning dope can be spun at a spinning speed of 80 to 800 m / min, 100 to 800 m / min, 300 to 800 m / min, 500 to 700 m / min, 550 to 660 m / min, 580 to 650 m / min, 580 to 640 m / min, or 590 to 610 m / min. Within such a range, a para-aramid fiber having a large crystal size and a high degree of crystallinity and therefore excellent tensile properties can be provided.

[0067] The dope spun through the spinneret is obtained as uncoagulated filaments in which sulfuric acid is distributed on a matrix in which the para-aramid polymer is uniformly distributed. Such uncoagulated filaments can be coagulated by passing through an air gap and a coagulation bath containing a coagulation liquid.

[0068] The air gap may be an air layer or an inert gas layer. For example, the air gap may be a nitrogen layer supplied with dry nitrogen. The length of the air gap can be adjusted to 0.1 to 15 cm.

[0069] The dope spun from the spinneret and passed through the air gap passes through a coagulation bath, where sulfuric acid is removed from the dope to form filaments. If sulfuric acid is rapidly removed from the surface of the filament, the surface of the filament may coagulate before the sulfuric acid contained therein can escape, resulting in reduced uniformity between the interior and exterior of the filament. Therefore, the coagulation liquid entering the coagulation bath is preferably an aqueous sulfuric acid solution containing sulfuric acid.

[0070] Specifically, the coagulation liquid contained in the coagulation bath may be an aqueous sulfuric acid solution obtained by adding sulfuric acid to water. If necessary, the coagulation liquid may further contain a monohydric alcohol (monol) such as methanol, ethanol, or propanol, a dihydric alcohol (diol) such as ethylene glycol or propylene glycol, or a trihydric alcohol (triol) such as glycerol.

[0071] The temperature of the coagulation liquid is preferably 1 to 10° C. If the temperature of the coagulation liquid is too low, sulfuric acid may not easily escape from the filaments. If the temperature of the coagulation liquid is too high, sulfuric acid may rapidly escape from the filaments, resulting in a decrease in the uniformity of the filaments.

[0072] A coagulation tube may be formed at the bottom of the coagulation bath. The coagulation tube may be connected to the coagulation bath and may have multiple injection ports. In this case, the injection ports are connected to a predetermined jet device, and the coagulation liquid injected from the jet device is injected through the injection ports onto the filaments passing through the coagulation tube. The multiple injection ports are preferably aligned so that the coagulation liquid can be injected symmetrically with respect to the filaments. The injection angle of the coagulation liquid is preferably 0 to 85° with respect to the axial direction of the filaments, and a jet angle of 20 to 40° is particularly suitable for commercial production processes.

[0073] In the step of producing the fiber, the coagulation step may be followed by a water washing step to remove sulfuric acid remaining in the coagulated filaments.

[0074] The water washing step may be carried out by spraying water or a mixed solution of water and an alkaline solution onto the solidified filaments.

[0075] The water-washing step may be performed in multiple stages. For example, the coagulated filaments may be first washed with a 0.1 to 1.5 wt % aqueous caustic solution, and then second washed with a more diluted aqueous caustic solution.

[0076] In the step of producing the fiber, the coagulation and washing steps may be followed by a drying step to adjust the moisture content remaining in the filaments.

[0077] The drying step may be carried out by adjusting the time the filaments are in contact with a heated drying roll or by adjusting the temperature of the drying roll.

[0078] The monofilaments constituting the finally obtained para-aramid fibers can have a fineness of 1.0 to 2.5 de (denier).

[0079] The para-aramid fiber includes a plurality of the monofilaments and can have a total fineness of 200 to 1,600 de, 200 to 400 de, 800 to 1,000 de, 1,000 to 1,100 de, or 1,400 to 1,600 de.

[0080] The para-aramid fibers produced by such a production method have a large crystal size, and exhibit high crystallinity and orientation, and can exhibit excellent mechanical properties (for example, tensile properties).

[0081] The para-aramid fibers can have an increased crystal size by being produced by the above-mentioned production method.

[0082] For example, the para-aramid fiber may have a crystal size based on the (110) plane of 5.8 nm or more, 5.9 nm or more, 6.0 nm or more, 6.1 nm or more, or 6.2 nm or more, and 7.0 nm or less, 6.8 nm or less, 6.7 nm or less, or 6.6 nm or less. Also, the para-aramid fiber may have a crystal size based on the (200) plane of 5.0 nm or more, 5.5 nm or more, or 5.6 nm or more, and 6.5 nm or less, 6.4 nm or less, 6.3 nm or less, or 6.2 nm or less.

[0083] The crystal size is a crystal size analyzed from an X-ray diffraction pattern, and for a more detailed measurement method, the method described in the test examples described later can be referred to. The para-aramid fiber produced by the production method can have a high degree of crystallinity.

[0084] Specifically, the para-aramid fiber may have a crystallinity of 67% or more, 67.5% or more, 68% or more, 68.5% or more, 69% or more, 69.5% or more, 70% or more, 70.5% or more, 71% or more, 71.5% or more, 72% or more, 72.5% or more, 73.0% or more, 73.5% or more, 74.0% or more, 74.5% or more, or 75.0% or more, and may be 78% or less, 77.5% or less, 77.0% or less, 76.5% or less, 76.0% or less, 75.5% or less, 75% or less, 74.5% or less, 74.0% or less, 73.5% or less, or 73% or less.

[0085] The crystallinity is determined by analyzing an X-ray diffraction pattern, and for more detailed measurement methods, the methods described in the test examples below can be referred to.

[0086] The para-aramid fibers produced by the above-described production method can exhibit a high degree of orientation, that is, the para-aramid fibers can have a high degree of orientation and a small orientation angle.

[0087] For example, the para-aramid fiber may have an orientation angle with respect to the (110) plane of 2° or more, 3° or more, 4° or more, 5° or more, 6° or more, or 7° or more. The orientation angle with respect to the (110) plane may be 12° or less, 11.5° or less, 11° or less, 10.5° or less, 10° or less, 9.5° or less, 9.4° or less, 9.3° or less, 9.2° or less, 9.1° or less, or 9.0° or less. The para-aramid fiber may have an orientation angle with respect to the (200) plane of 2° or more, 3° or more, 4° or more, 5° or more, 6° or more, 7° or more, or 8° or more. The orientation angle based on the (200) plane may be 13° or less, 12° or less, 11.5° or less, 11.4° or less, 11.3° or less, 11.2° or less, 11.1° or less, 11° or less, 10.5° or less, 10.4° or less, or 10.3° or less.

[0088] The orientation angle is an orientation angle analyzed from an X-ray diffraction pattern, and for more detailed measurement methods, the methods described in the test examples below can be referred to.

[0089] The para-aramid fiber can minimize the paracrystalline parameter by being manufactured by the above manufacturing method.

[0090] For example, the para-aramid fiber may have a crystal defect content of 1.00% or more, or 1.30% or more, or 1.85% or less, 1.80% or less, 1.70% or less, or 1.60% or less.

[0091] The crystal defects are crystal defects analyzed from an X-ray diffraction pattern, and for more detailed measurement methods, the methods described in the test examples below can be referred to.

[0092] The para-aramid fibers have a large crystal size and a high degree of crystallinity, and therefore can exhibit excellent tensile properties.

[0093] For example, the para-aramid fiber may have a tensile strength of 22 g / d or more, 22.5 g / d or more, 23 g / d or more, 23.5 g / d or more, 24 g / d or more, or 25 g / d or more, and 30 g / d or less, or 28 g / d or less. The para-aramid fiber may also have a Young's modulus of 750 g / d or more, 760 g / d or more, 780 g / d or more, 790 g / d or more, 800 g / d or more, or 810 g / d or more, and 900 g / d or less, 880 g / d or less, or 860 g / d or less. The para-aramid fiber may also have an elongation of 2.0% or more, 2.5% or more, 3.0% or more, 3.1% or more, 3.2% or more, 3.3% or more, or 3.4% or more, and 4.5% or less, or 4.0% or less.

[0094] The tensile properties such as the tensile strength, Young's modulus, and elongation are tensile properties measured by the ASTM D885 standard test method for a sample having a twist multiplier of 1.1. For more detailed measurement methods, please refer to the methods described in the test examples below.

[0095] Cords exhibit different properties depending on their thickness. For example, when the cord is used as a tire reinforcement material, a thicker cord improves tire performance in terms of strength and modulus, but the thickness of the rubber covering the top and bottom of the cord fabric increases, resulting in a larger tire size and increased weight. Therefore, it is unsuitable for tires where fuel economy and weight reduction are important. Furthermore, a thinner cord is advantageous for reducing tire weight, but its strength and modulus decrease, preventing it from fully performing as a reinforcement material. In this application, taking these points into consideration, the fineness of the fibers forming the cord (each fiber forming the first twist yarn) is appropriately adjusted.

[0096] In one example, the para-aramid fiber or the first twisted yarn (first twisted yarn) formed therefrom can have a fineness of 200 to 1600 denier (de). For example, the lower limit of the fineness of the para-aramid fiber may be 300 denier or more, 400 denier or more, 500 denier or more, 600 denier or more, 700 denier or more, 800 denier or more, 900 denier or more, 1000 denier or more, or 1100 denier or more, and the upper limit may be, for example, 1500 denier or less, 1400 denier or less, 1300 denier or less, 1200 denier or less, 1100 denier or less, or 1000 denier or less. Although not particularly limited, para-aramid fiber of 900 to 1100 denier or 1400 to 1600 denier can be used as the first twisted yarn.

[0097] In one example, the heterogeneous fiber or the first twist yarn (second first twist yarn) formed therefrom may have a fineness of 600 to 2000 denier (de). For example, the lower limit of the fineness of the heterogeneous fiber may be 650 denier or more, 700 denier or more, 750 denier or more, 800 denier or more, or 850 denier or more. The upper limit may be, for example, 1900 denier or less, 1800 denier or less, 1700 denier or less, 1600 denier or less, 1500 denier or less, 1400 denier or less, 1300 denier or less, 1200 denier or less, 1100 denier or less, 1000 denier or less, or 900 denier or less. Although not particularly limited, heterogeneous fibers of 700 to 900 denier or 1100 to 1400 denier may be used as the first twist yarn.

[0098] The type of the different fiber (B) to be twisted together with the para-aramid fiber (A) to form the cord is not particularly limited, and for example, nylon fiber or polyester fiber can be used to manufacture the cord. In other words, the cord of the present application may be formed by twisting together a first twist yarn containing para-aramid fiber and a first twist yarn containing a different fiber such as nylon fiber or polyester fiber.

[0099] The degree of twist of the ply twist yarns and / or the twist between the ply twist yarns (i.e., the ply twist) affects the physical properties of the cord. Generally, when the twist is high, the cord has a helical inclination in the vertical direction, which increases the elongation (or elongation at break or elongation at midpoint), decreases the modulus, and the external force caused by the twist reduces the tensile strength (or tenacity). Conversely, when the twist is low, the fibers are well aligned in the cord direction (a form in which the helical inclination value in the vertical direction of the cord is low), which results in higher strength (or tenacity) and modulus but lower elongation compared to a high twist. In this application, taking these points into consideration, the number of twists in each ply twist yarn and the number of twists between the ply twist yarns can be adjusted.

[0100] In one example, the (A) para-aramid fiber may be a first twisted yarn (first twisted yarn) twisted at 250 to 600 TPM, and the (B) heterogeneous fiber may be a second twisted yarn (second twisted yarn) twisted at 250 to 600 TPM. The cord may be formed by twisting the first twisted yarn and the second twisted yarn together.

[0101] In specific examples of the present application, the twist number (first twist number) of the (A) first twisted yarn containing para-aramid fiber or the twist number (second twist number) of the (B) second twisted yarn containing a heterogeneous fiber is 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, It may be 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, 490 TPM or more, 500 TPM or more, 510 TPM or more, 520 TPM or more, 530 TPM or more, 540 TPM or more, 550 TPM or more, 560 TPM or more, 570 TPM or more, 580 TPM or more, or 590 TPM or more. The upper limit of the twist number is, for example, 590 TPM or less, 580 TPM or less, 570 TPM or less, 560 TPM or less, 550 TPM or less, 540 TPM or less, 530 TPM or less, 520 TPM or less, 510 TPM or less, 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 The pressure may be 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, or 260 TPM or less.

[0102] In one example, the twist number (first twist number) of the ply-twisted yarn containing the para-aramid fiber (first ply-twisted yarn) and the twist number (second twist number) of the ply-twisted yarn containing the heterogeneous fiber (second ply-twisted yarn) may be the same or different. Such twist numbers can be imparted using, for example, a cable cord twist machine (CC twister) or a ring twister. The same twist number for each ply-twisted yarn means that the same twist number is set for each ply-twisted yarn when using the machine. However, depending on equipment or process conditions (e.g., slight unwinding may occur during the drying stage after immersion in the adhesive solution), the twist number may differ by approximately 15%, 10%, or 5% from the set value.

[0103] In one example, the cord may be formed by second twisting the first twisted yarn and the second twisted yarn within a range of 250 to 600 TPM. For example, when the first and second twisted yarns are second twisted together, the twist number (third twist number) may be 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, 490 TPM or more, 500 TPM or more, 510 TPM or more, 520 TPM or more, 530 TPM or more, 540 TPM or more, 550 TPM or more, 560 TPM or more, 570 TPM or more, 580 TPM or more, or 590 TPM or more. The upper limit of the twist number is, for example, 590 TPM or less, 580 TPM or less, 570 TPM or less, 560 TPM or less, 550 TPM or less, 540 TPM or less, 530 TPM or less, 520 TPM or less, 510 TPM or less, 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 The pressure may be 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, or 260 TPM or less.

[0104] In one example, the number of twists of the first and second ply twist yarns (i.e., the number of twists in ply twist) and the number of twists in ply twist may be the same or different. In a specific example of the present application, the number of twists in ply twist and the number of twists in ply twist may be set to be the same. However, in some cases, the number of twists in ply twist and the number of twists in ply twist may be slightly different in the final product. Specifically, a cable cord twist machine (CC twisting machine) used in cord manufacturing is driven by a single motor. The raw yarn in the creel passes through a disk connected to the motor and is connected to a regulator (the section where the ply twist yarn and the ply twist yarn meet and perform the ply twisting), and the raw yarn in the port passes through a tension-adjusting guide roll and is connected to the regulator. At this time, the regulator to which the raw yarn coming out of the disk is connected rotates together with the rotation of the motor. As a result of this mechanical movement, the rotation of the motor applies a first twist to the raw yarn in the connected creel section and the raw yarn in the port section, and the regulator twists the first twisted yarns together to create a final twist. In this way, the raw cord is manufactured as twisting occurs due to the rotational movement of the motor, but even when the same number of twists is applied (set) for the first twist and the final twist, the number of twists for the final twist and the first twist may differ slightly due to friction generated by the winding tension and the guide rollers, etc.

[0105] As described above, the cord of the present application includes a first ply yarn and a second ply yarn having a predetermined twist number, and is formed by twisting the first ply yarn and the second ply yarn together. In this case, the first ply yarn and the second ply yarn are formed as the filaments for forming the first ply yarn and the filaments for forming the second ply yarn are simultaneously ply-twisted by a CC twisting machine (e.g., a cable corder twist machine) or a ring twisting machine. Therefore, the twist direction of the first ply yarn (first twist direction) and the twist direction of the second ply yarn (second twist direction) may be the same. When a CC twisting machine (e.g., a cable corder twist machine) or a ring twisting machine is used, the first twist may be followed by the final twist simultaneously, and the twisting direction of the final twist (i.e., the third twisting direction) may be opposite to the first twisting direction (or the second twisting direction).

[0106] In a specific example of the present application, the content ratio of the first ply twist yarn to the second ply twist yarn can be appropriately adjusted to a level that can achieve the object of the present application. For example, based on 100% by weight of the total weight of the first ply twist yarn and the second ply twist yarn included in the cord, specifically the low cord, the content of the first ply twist yarn may be 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, or 90% by weight or more. The upper limit may be, for example, 90% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, or 10% by weight or less. The content of the second twisted yarn can be determined depending on the content of the first twisted yarn described above.

[0107] In one example, the cord may be a two-ply or three-ply cord. For example, the cord may have a two-ply structure in which one first ply twisted yarn described above and one second ply twisted yarn described above are ply-twisted together. Alternatively, the cord may have a three-ply structure in which two first ply twisted yarns having the above-mentioned finenesses and one second ply twisted yarn having the above-mentioned finenesses are ply-twisted together.

[0108] According to a specific example of the present application, when the first ply twisted yarn (ply twisted yarn containing para-aramid fiber) forms a plied yarn together with the second ply twisted yarn (ply twisted yarn containing a different fiber), the length ratio of the first ply twisted yarn to the second ply twisted yarn (length of the first ply twisted yarn (L1) / length of the second ply twisted yarn (L2)) measured after untwisting the ply twist on the plied yarn (low cord or dipped cord) may be in the range of 1.0 to 1.10.

[0109] This length ratio (length of first ply twist yarn (L1) / length of second ply twist yarn (L2)) allows the first ply twist yarn (ply twist yarn containing para-aramid fiber) with a higher modulus to be longer, thereby initially exhibiting the properties of the second ply twist yarn (e.g., nylon), which has a lower modulus, in the stress-strain curve pattern (SS curve pattern), which indicates the tensile properties of the cord. This characteristic plays a role in reducing unevenness in the tire shape during tire manufacturing. However, in the case of a cap ply, which is wound circumferentially around a tire, if the initial modulus of the cord is high, it may not function properly in the tread portion due to resistance to the expanding pressure during tire molding. Therefore, initially exhibiting a low modulus characteristic in the SS curve pattern of the cap ply cord may be more effective for tire manufacturing. After tire manufacturing, a high modulus must be exhibited to prevent belt cord separation during high-speed driving and maintain ground contact. Therefore, exhibiting a high modulus after the elongation section consumed during tire manufacturing may be more effective in terms of tire performance. Therefore, a cord manufactured by varying the lengths of the first ply twisted yarn and the second ply twisted yarn, which have different moduli, can be very effective in terms of tire manufacturing and performance.

[0110] If the length ratio of the first ply twist yarn to the second ply twist yarn (length of first ply twist yarn (L1) / length of second ply twist yarn (L2)) is less than 1.0, the first ply twist yarn, which has a high modulus, becomes shorter, causing the physical properties of aramid to appear first, which can be detrimental to tire manufacturing, and the high initial modulus significantly reduces fatigue performance under repeated tension and compression.Furthermore, if the length ratio of the first ply twist yarn to the second ply twist yarn (length of first ply twist yarn (L1) / length of second ply twist yarn (L2)) is more than 1.10, the first ply twist yarn and the second ply twist yarn are subjected to separate forces when the cord is pulled, which can reduce the final strength of the cord.

[0111] Specifically, the lower limit of the length ratio may be, for example, 1.01 or more, 1.02 or more, 1.03 or more, 1.04 or more, or 1.05 or more, and the upper limit may be, for example, 1.09 or less, 1.08 or less, 1.07 or less, 1.06 or less, or 1.05 or less.

[0112] In a specific example of the present application, such control of the length ratio may be achieved by adjusting the amount of tension applied to the filaments forming the first ply yarn and the filaments forming the second ply yarn during the ply twist and / or ply twist steps to produce the cord. For example, when ply twist and ply twist are performed, the amount of tension applied to the para-aramid fiber (forming the first ply yarn) can be made less than the tension applied to the heterogeneous fiber forming the second ply yarn, thereby making the length of the first ply yarn longer than the length of the second ply yarn.

[0113] In one example, the cord may further include a coating layer formed on the first ply yarn and the second ply yarn, i.e., the cord may include a raw cord and a coating layer formed on the raw cord.

[0114] The coating layer refers to a layer formed from a coating solution capable of exhibiting a predetermined function. Such a coating layer may be formed on at least a portion of the first twisted yarn. The method for forming the coating layer is not particularly limited, and the coating layer may be formed, for example, by a known dipping or spraying method.

[0115] The coating layer may be configured to impart predetermined properties to the cord or reinforce the properties of the cord. For example, the coating layer may be a layer that can impart an adhesive function to the cord, but the properties imparted or reinforced by the coating layer are not limited to adhesive function only.

[0116] In one example, the coating layer may be formed from an adhesive (composition). In one non-limiting example, the coating layer may include or be formed from a resorcinol formaldehyde latex (RFL) adhesive (composition), an epoxy adhesive (composition), or a urethane adhesive (composition). In another example, the coating layer may be formed from an adhesive that does not contain an RFL component. However, the adhesive components that form the coating layer are not limited to those described above.

[0117] Although not limited thereto, the adhesive composition may contain an aqueous or non-aqueous solvent, and such adhesives may provide improved adhesion of the textile cord to adjacent components in tire reinforcement applications.

[0118] In one example, a cord on which a coating layer has been formed, i.e., a dipped cord, can contain 1 to 10% by weight of the coating layer (or coating component) relative to its total weight (100% by weight, which is the total content including the fiber component and the coating component). For example, the upper limit of the coating layer content may be 9% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, or 3% by weight or less, and the lower limit may be 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 6% by weight or more, 7% by weight or more, 8% by weight or more, or 9% by weight or more.

[0119] In a specific example of the present application, the first twisted yarn of the cord may exhibit predetermined crystalline characteristics. Specifically, the coating layer may be formed by applying a predetermined tension and heat, as in the manufacturing method described below. During this process, the microstructure of the para-aramid fiber may change, such as the crystal size of the para-aramid fiber becoming larger. As confirmed by the experiment described below, the creep rate may be reduced as the crystal size of the para-aramid fiber becomes larger.

[0120] In one example, the para-aramid fibers contained in the dipped cord may have a (110) plane crystal size of 7.2 nm or more, 7.3 nm or more, 7.4 nm or more, 7.5 nm or more, 7.6 nm or more, 7.7 nm or more, 7.8 nm or more, 7.9 nm or more, 8.0 nm or more, 8.1 nm or more, 8.2 nm or more, 8.3 nm or more, 8.4 nm or more, 8.5 nm or more, 8.6 nm or more, 8.7 nm or more, 8.8 nm or more, 8.9 nm or more, or 9.0 nm or more. The upper limit of the crystal size may be, for example, 10.0 nm or less, 9.5 nm or less, or 9.0 nm or less. The (110) plane crystal size of the para-aramid fibers contained in the dipped cord can be measured by separating the aramid from the dipped cord and measuring the inner portion to which the coating liquid is not applied, as described below.

[0121] In one example, the para-aramid fibers contained in the dipped cord may have a (200) plane crystal size of 5.5 nm or more, 5.6 nm or more, 5.7 nm or more, 5.8 nm or more, 5.9 nm or more, 6.0 nm or more, 6.2 nm or more, 6.3 nm or more, or 6.4 nm or more, and may be 6.5 nm or less, 6.4 nm or less, 6.3 nm or less, 6.2 nm or less, 6.1 nm or less, or 6.0 nm or less. The (200) plane crystal size of the para-aramid fibers contained in the dipped cord can be measured by separating the para-aramid fibers from the dipped cord and measuring the inner portion to which the coating liquid is not applied, as described below.

[0122] In one example, the para-aramid fiber contained in the dipped cord has a crystallinity of 72% or more, 72.5% or more, 73.0% or more, 73.5% or more, 74.0% or more, 74.5% or more, 75.0% or more, 75.5% or more, 76.0% or more, 76.5% or more, 77.0% or more, 77.5% or more, 78.0% or more, 78.5% or more, 79.0% or more, or may be 79.5% or more, and the upper limit thereof may be, for example, 80% or less, 79.5% or less, 79.0% or less, 78.5% or less, 78.0% or less, 77.5% or less, 77.0% or less, 76.5% or less, 76.0% or less, 75.5% or less, 75% or less, 74.5% or less, 74.0% or less, 73.5% or less, 73% or less, or 72.5% or less. The crystallinity of the para-aramid fibers contained in the dipped cord can be measured by separating the para-aramid fibers from the dipped cord and measuring the inner portion to which the coating liquid is not applied, as will be described later.

[0123] In this manner, in the present application, a raw cord is manufactured using para-aramid fibers with relatively large crystal size and crystallinity, and a coating layer is formed on the raw cord by heat treatment and tension, so the para-aramid fibers contained in the dipped cord also exhibit larger values. As a result, the degree of deformation of the fibers and cord can be improved, as confirmed by the creep rate described below.

[0124] In the specific example of the present application, the code of the above configuration can exhibit the following characteristics:

[0125] In one example, the creep rate (creep strain (%)) of the cord may be 3.0% or less. Specifically, the cord may satisfy a creep strain (%) of 2.9% or less, 2.85% or less, 2.8% or less, 2.75% or less, 2.7% or less, 2.65% or less, 2.6% or less, 2.55% or less, 2.5% or less, 2.45% or less, 2.4% or less, 2.35% or less, 2.3% or less, 2.25% or less, or 2.20% or less. Although not particularly limited, the lower limit of the creep strain (%) may be, for example, 1.5% or more or 2.0% or more. Creep strain indicates the deformation of a material in response to a constant load and temperature, and is different from elongation, which measures the deformation until the material breaks or breaks while the load is continuously increased. Elongation measures the extent to which a material can be stretched, and is generally expressed as the length the material can stretch before breaking or breaking. In contrast, creep strain indicates the rate of deformation under a fixed load. Therefore, a high creep strain means that the product undergoes significant deformation under a constant load. Therefore, when cords with high creep strain are used, there is a greater possibility that tire deformation will occur due to long-term parking.

[0126] As described below, creep strain (%) is measured by applying a load (tension) of 0.8 g / d (where d is the denier and g is the weight unit) to a cord at 80°C for 24 hours according to ASTM D2990. It can refer to the rate of change in length of the cord (the rate of deformation in the load direction) determined under these conditions. According to a specific example of the present application, the cord may be pretreated before measuring the creep strain. For example, the cord may be stored under constant temperature and humidity conditions (controlled at 20±2°C and 65±5% humidity) for 24 hours, and then pretreated by applying a load (tension) of 0.01 g / d (where d is the denier and g is the weight unit) to the cord at 180°C for 15 minutes. The creep strain of the cord can then be measured.

[0127] In one example, the cord may have a strength of 24.0 kgf or more. Specifically, the strength of the cord may be, for example, 24.5 kgf or more, 25.0 kgf or more, 25.5 kgf or more, 26.0 kgf or more, 26.5 kgf or more, 27.0 kgf or more, 27.5 kgf or more, 28.0 kgf or more, 28.5 kgf or more, 29.0 kgf or more, 29.5 kgf or more, or 30.0 kgf or more. There is no particular upper limit, but the strength may be, for example, 40 kgf or less, 35 kgf or less, or 30 kgf or less. The strength of the cord can be measured according to ASTM D885, as described below. In this case, the cord may be a dipped cord.

[0128] In one example, the strength of the cord may be 13.0 g / d or more. Specifically, the strength of the cord may be, for example, 13.5 g / d or more, 14.0 g / d or more, 14.5 g / d or more, 15.0 g / d or more, 15.5 g / d or more, 16.0 g / d or more, 16.5 g / d or more, 17.0 g / d or more, 18.0 g / d or more, 18.5 g / d or more, 19.0 g / d or more, or 19.5 g / d or more. The upper limit is not particularly limited, but may be, for example, 25 g / d or less or 20 g / d or less. The strength of the cord can be measured according to ASTM D885, as described below. Here, the cord may be a dipped cord.

[0129] In one example, the elongation of the cord (elongation at break) may be 7.0% or more. Specifically, the elongation of the cord may be, for example, 7.5% or more, 8.0% or more, 8.5% or more, 9.0% or more, 9.5% or more, or 10% or more. The upper limit is not particularly limited, but may be, for example, 15% or less. The elongation of the cord can be measured according to ASTM D885, as described below. Here, the cord may be a dipped cord.

[0130] In another embodiment, the present application relates to a method for manufacturing the cord described above. The cord described above can be manufactured by the manufacturing method. Therefore, among the descriptions of the characteristics of the cord described above, descriptions of the configuration and characteristics that overlap with the description of the manufacturing method described below will be omitted.

[0131] In one embodiment of the present application, the method for manufacturing the cord includes the steps of: preparing para-aramid fibers having a crystallinity of 67% or more, a (110) plane crystal size of 5.8 to 7.0 nm, a total fineness of 200 to 1600 denier, and a tensile strength of 22 g / d or more; and second-twisting together a first first-twisted yarn formed by twisting the para-aramid fibers and a second first-twisted yarn formed by twisting a different fiber from the para-aramid fibers, to provide a cord that is a doubled-twisted yarn.

[0132] In the above method, the first twisted yarn can be produced by twisting the para-aramid fiber at 250 to 600 TPM. The specific number of twists for the first twisted yarn is as described above.

[0133] In the above method, the second twisted yarn can be produced by twisting the different fibers at 250 to 600 TPM. The specific number of twists for the second twisted yarn is as described above.

[0134] In the method, the first twisted yarn and the second twisted yarn are final twisted at a twist rate of 250 to 600 TPM to form a cord. The specific twist rate during final twisting is as described above.

[0135] In one example, the method may further include forming a coating layer on the ply-twisted yarn (raw cord). Here, "forming a coating layer" may mean that a coating layer-forming composition (coating liquid) is applied to the raw cord. The applied coating layer-forming composition may be subjected to a heat treatment such as drying or curing, as described below. In this case, the coating layer may mean a layer obtained by the heat treatment.

[0136] The method for applying the coating layer-forming composition (coating liquid) onto the raw cord is not particularly limited, and a dipping or spraying method can be used.

[0137] For example, the method may include spraying a coating layer-forming composition (coating liquid) onto a plied yarn (raw cord). That is, the method may form a coating layer by spraying the coating layer-forming composition (coating liquid) onto the plied yarn.

[0138] In another example, the method may include immersing a ply-twisted yarn (raw cord) in a coating layer-forming composition (coating liquid). That is, the method may form a coating layer by immersing the ply-twisted yarn in the coating layer-forming composition (coating liquid). When the ply-twisted yarn is dipped in the coating layer-forming composition (coating liquid), the specific method for immersing the ply-twisted yarn in the coating layer-forming composition is not particularly limited. For example, a method may be used in which the ply-twisted yarn or a fiber substrate containing the ply-twisted yarn is transported using a roll while the ply-twisted yarn is immersed in a coating bath filled with the coating layer-forming composition. A cord coated with the coating layer-forming composition after immersion may be referred to as a dipped cord.

[0139] In one example, the coating layer may be formed through transporting the cord, applying (spraying or dipping) the coating layer-forming composition to the cord, and / or a subsequent heat treatment process. For example, the coating layer formation step (process) may include one or more of the following processes: transporting the cord, dipping (or spraying), and heat treatment. Specifically, the coating layer formation step (process) may include applying a predetermined amount of tension to the plied / twisted yarn already coated with the coating layer-forming composition and then heat treating it; applying the coating layer-forming composition to the plied / twisted yarn under a predetermined amount of tension and then heat treating it; or transporting the plied / twisted yarn, applying the coating layer-forming composition, and then heat treating it under a predetermined amount of tension.

[0140] In a specific example of the present application, the heat treatment may be performed at a temperature within a predetermined range. For example, the heat treatment may be performed at a temperature of 50° C. or higher, specifically, at a temperature within a range of 60 to 350° C. Although not particularly limited, the heat treatment may be performed for 10 to 300 seconds.

[0141] In one example, the method can include two or more heat treatment steps. Specifically, the method can include a first heat treatment step performed at a temperature of 70 to 180° C. and a second heat treatment step performed at a temperature of 200 to 250° C. The duration of the heat treatment is not particularly limited, but for example, each of these heat treatments can be performed for about 30 to 300 seconds.

[0142] In one example, the temperature at which the first heat treatment is performed may be lower than the temperature at which the second heat treatment is performed. Specifically, the first heat treatment temperature may be in the range of 70 to 180° C., and the second heat treatment temperature may be in the range of 200 to 250° C. Here, the first heat treatment performed at a relatively low temperature may be referred to as a drying process, and the second heat treatment performed at a relatively high temperature may be referred to as a cruing process.

[0143] In one example, the coating layer may be formed by applying tension to a ply-twisted yarn (raw cord).

[0144] For example, the tension applied to the plied yarn may be 0.1 kg / cord or more, 0.2 kg / cord or more, 0.3 kg / cord or more, 0.4 kg / cord or more, 0.5 kg / cord or more, 0.6 kg / cord or more, 0.7 kg / cord or more, 0.8 kg / cord or more, or 0.9 kg / cord or more, and the upper limit may be, for example, 1.5 kg / cord or less, 1.4 kg / cord or less, 1.3 kg / cord or less, 1.2 kg / cord or less, 1.1 kg / cord or less, 1.0 kg / cord or less, 0.9 kg / cord or less, 0.8 kg / cord or less, 0.7 kg / cord or less, 0.6 kg / cord or less, 0.5 kg / cord or less, 0.4 kg / cord or less, 0.3 kg / cord or less, or 0.2 kg / cord or less.

[0145] In one example, when the coating layer formation step (process) is performed under tension, the coating layer formation step (process) can be used to mean a step of applying a tension of the above-mentioned magnitude to a plied / twisted yarn that has already been coated with a coating layer-forming composition and then heat-treating it. More specifically, the coating layer formation step (process) performed under tension can mean a step of applying a tension of the above-mentioned magnitude to a plied / twisted yarn that has been subjected to a first heat treatment after being coated with a coating layer-forming composition and then heat-treating it. Heat treatments involving high temperatures, particularly the second heat treatment, can significantly affect the final physical properties of the cord, so it is important to satisfy the above-mentioned tension range. Therefore, the tension within the above-mentioned range can be maintained at least during the heat treatment, more specifically the second heat treatment. The tension within the above-mentioned range can be maintained during at least the heat treatment, more specifically the second heat treatment. The transport and immersion (spraying) steps for coating layer formation and the first heat treatment process can be the same or different (slightly modified).

[0146] As described above, when heat and tension are applied, the molecular chains are more oriented toward the fiber axis due to the tension, and this orientation is set by heat, which can change the microstructure. Because heat and / or tension are applied during the dipping process, the microstructure of the para-aramid fiber in the dipped cord has a larger crystal size than that in the raw yarn state. As described above, the present application uses para-aramid yarn with a higher degree of crystallinity. In addition, the crystallinity of the dipped cord para-aramid fiber is increased by the dipping process, which can reduce the degree of deformation due to external forces (i.e., increase deformation resistance). This is confirmed by the creep rate (Creep Strain (%)) described above.

[0147] In one example, the dipping or spraying may be performed one or more times. When the dipping or spraying is performed two or more times, the components of the coating layer-forming composition used for each dipping or spraying may be the same or different.

[0148] For example, a first immersion, a second immersion, and a heat treatment may be performed in sequence, and the heat treatment may include a first heat treatment (e.g., drying) and / or a second heat treatment (e.g., curing) in sequence.

[0149] In another example, the steps of first dipping, heat treatment, second dipping and heat treatment may be performed in this order, in which the heat treatment performed between the first and second dipping may be a drying step performed at a relatively low temperature, and the heat treatment performed after the second dipping may be a curing step performed at a relatively high temperature.

[0150] In one example, the method may involve first twisting para-aramid fibers (filaments) in a first twist direction to produce a first twisted yarn, while simultaneously twisting a different type of fiber (filament) in a second twist direction to produce a second twisted yarn.

[0151] In one example, the method may involve producing a doubled-twisted yarn by second-twisting the first and second ply-twisted yarns in a third twist direction after or simultaneously with the production of the ply-twisted yarn, in which case the first twist direction and the second twist direction may be the same, and the first twist direction and the third twist direction may be different from each other.

[0152] According to a specific example of the present application, a twisting machine that simultaneously performs first twisting and final twisting, such as a cable corder, is used to manufacture a doubled twisted yarn. For example, when manufacturing a cord, a first first twisted yarn forming filament (para-aramid filament yarn) and a second first twisted yarn forming filament (e.g., nylon or polyester) are simultaneously first twisted by a single twisting machine (e.g., cable corder) to form the first first twisted yarn and the second first twisted yarn, and therefore the twist direction of the first first twisted yarn (first twist direction) and the twist direction of the second first twisted yarn (second twist direction) may be the same. Furthermore, in a specific example of the present application in which twisting is performed using a twisting machine such as a cable corder that is capable of simultaneously performing first twisting and final twisting, final twisting may be performed continuously following the first twisting, and the twisting direction of such final twisting (i.e., the third twisting direction) may be opposite to the first twisting direction (or the second twisting direction).

[0153] In one example, the method may be a method of forming a first twisted yarn by imparting a twist number in the range of 250 to 600 TPM to the fibers (filaments) forming the first twisted yarn, i.e., the twist number imparted to the first and second first twisted yarns is in the range of 250 to 600 TPM.

[0154] In one example, the method can form a plied yarn by second twisting the first ply yarn and the second ply yarn at a twist rate in the range of 250 to 600 TPM.

[0155] In a specific example of the present application, the method may be a method of controlling the magnitude of tension applied to the aramid fiber (forming the first ply twisted yarn) during first twisting and / or second twisting so that it is smaller than the tension applied to the different fiber (forming the second ply twisted yarn).This allows the length ratio of the first ply twisted yarn to the second ply twisted yarn (length of first ply twisted yarn (L1) / length of second ply twisted yarn (L2)) measured after untwisting the ply twist for a plied yarn (low cord or dipped cord) to be adjusted within the range of 1.0 to 1.10.

[0156] In addition to the above description in relation to the manufacturing method of the present application, the description of the structure, characteristics, manufacturing, etc. of the cord and the first twist yarn forming the cord is the same as that described above in relation to the cord, so it will be omitted here.

[0157] In a specific example of the present application, the method for producing a cord may further include a method for producing (preparing) the para-aramid fiber described above. For example, the para-aramid fiber may be produced by the method described above, and the method for producing a cord may further include a step of filtering the reaction raw materials to remove impurities; a step of adding an aromatic diamine to a mixed solvent containing an organic solvent and an inorganic salt to form a slurry; a step of adding an aromatic diacid halide to a reactor containing the slurry in three or more divided portions and reacting the mixture to form a para-aramid polymer; and a step of spinning a spinning dope containing the para-aramid polymer to produce a fiber. Here, in the step of forming the polymer, the temperature difference between the cooling water inlet and outlet for cooling the reactor during the first and second additions of the aromatic diacid halide may be controlled to within 50°C.

[0158] The specific process for producing para-aramid fibers is the same as that described above, so the description will be omitted.

[0159] In yet another embodiment of the present application, the present application relates to a rubber composite or a rubber reinforcing material including the cord. The rubber composite or the rubber reinforcing material may further include a rubber substrate such as a rubber sheet in addition to the cord.

[0160] In yet another example of the present application, the present application relates to a tire including the cord, which may have a commonly known configuration such as a tread, shoulders, sidewalls, cap plies, belts, carcass (or body plies), inner liner, beads, etc. [Effects of the Invention]

[0161] According to the present application, there is provided a cord containing, as a ply-twisted yarn component, para-aramid fibers having a large crystal size, a high degree of crystallinity, and excellent mechanical properties (e.g., tensile properties). The cord has high resistance to deformation due to external forces and can be used as a tire reinforcement material. DETAILED DESCRIPTION OF THE INVENTION

[0162] The functions and effects of the present invention will be described in more detail below through specific examples of the present invention, but these are presented as examples of the present invention and do not limit the scope of the invention in any way.

[0163] Experiment 1: Evaluation of para-aramid polymers and fibers 1. Production of para-aramid polymer and evaluation of its properties The physical properties of the para-aramid polymers obtained in the following synthesis examples were measured by the methods described below.

[0164] (1) Measurement of intrinsic viscosity The intrinsic viscosity of the polymer was measured according to the following equation 1.

[0165] <Expression 1> IV=ln(η rel ) / C

[0166] In the above formula 1, ln is a natural logarithm function, C is the concentration of the polymer solution (a solution in which 0.5 g of polymer is dissolved in 100 mL of 98 wt % concentrated sulfuric acid), and the relative viscosity (η rel ) is the ratio of the flow times between the polymer solution and the solvent measured with a capillary viscometer at 30°C.

[0167] (2) Measurement of intrinsic viscosity deviation The polymer that had been washed with water and dried was separated into a group of 2 mm or more, a group of 1 mm or more and less than 2 mm, and a group of less than 1 mm using standard sieves with opening sizes of 1 mm and 2 mm, respectively.

[0168] Thereafter, the intrinsic viscosity of each group was measured, and the difference between the maximum and minimum values of the average intrinsic viscosity of the three groups was calculated to determine the intrinsic viscosity deviation of the polymer.

[0169] (3) Inorganic impurity content

[0170] The content of inorganic impurities in the para-aramid polymer was measured by the following method: 1 g of a sample was treated with acid to completely decompose it, and then the concentration of ionized inorganic impurities remaining in the sample was measured using an inductively coupled plasma atomic emission spectrophotometer.

[0171] Synthesis Example 1: Production of para-aramid polymer (PPTA-1) The reaction raw materials, N-methyl-2-pyrrolidone (NMP), CaCl2, p-phenylenediamine (PPD) and terephthaloyl chloride (TPC), were passed through a filter with a diameter of 0.1 μm to remove impurities in the reaction raw materials.

[0172] Under a nitrogen atmosphere, a mixed solvent of NMP as an organic solvent and CaCl2 as an inorganic salt in a weight ratio of 92:8 was placed in a reactor, and PPD was added so that the concentration of PPD in the slurry was 5 wt %, to produce a slurry.

[0173] Next, TPC equivalent to 30 mol% of the number of moles of PPD was added to the reactor cooled to 30°C, and the reaction was carried out for 10 minutes. During this time, the stirring speed of the reactor was adjusted to about 200 rpm, and the temperature difference of the cooling water between the cooling water inlet and outlet was controlled to be within about 20°C.

[0174] Thereafter, TPC equivalent to 60 mol% of the moles of PPD was added to the reactor cooled to 30°C again, and the reaction was carried out for 30 minutes. At this time, the stirring speed of the reactor was adjusted to about 200 rpm, and the temperature difference of the cooling water between the cooling water inlet and outlet was controlled to be within about 20°C.

[0175] Finally, TPC equivalent to 10 mol % of the number of moles of PPD was added to the reactor cooled to 30° C., and the mixture was reacted for 30 minutes to produce a para-aramid polymer.

[0176] Water and NaOH were added to the solution containing the para-aramid polymer to neutralize the acid. Next, the para-aramid polymer was pulverized, and then the polymerization solvent contained in the para-aramid polymer was extracted with water, followed by dehydration and drying to finally obtain PPTA-1.

[0177] The intrinsic viscosity of the polymer PPTA-1 thus produced was 5.4 dL / g, and the content of inorganic impurities in the polymer was 48 ppb. Using standard sieves with 1 mm and 2 mm mesh sizes, the polymer was classified into a group of 2 mm or more, a group of 1 mm or more but less than 2 mm, and a group of less than 1 mm. The intrinsic viscosity of each group was measured, and the deviation of the intrinsic viscosity calculated by the difference between the maximum and minimum values for the average intrinsic viscosity of the three groups was 0.85 dL / g.

[0178] Synthesis Example 2: Production of para-aramid polymer (PPTA-2) Under a nitrogen atmosphere, a mixed solvent of NMP as an organic solvent and CaCl2 as an inorganic salt in a weight ratio of 86:14 was placed in a reactor, and PPD was added so that the concentration of PPD in the slurry was 3 wt % to produce a slurry.

[0179] Next, TPC equivalent to 30 mol % of the number of moles of PPD was added to the reactor cooled to 0°C, and the mixture was reacted at 5°C for 30 minutes.

[0180] After 30 minutes, the temperature difference between the cooling water at the cooling water inlet and outlet was 65°C, and TPC equivalent to 60 mol% of the number of moles of PPD was added to the reactor, followed by a reaction at 5°C for 20 minutes. Then, TPC equivalent to 10 mol% of the number of moles of PPD was added to the reactor, followed by a reaction at 5°C for 5 minutes to produce a para-aramid polymer.

[0181] Water and NaOH were added to the solution containing the para-aramid polymer to neutralize the acid. Next, the para-aramid polymer was pulverized, and then the polymerization solvent contained in the para-aramid polymer was extracted with water, followed by dehydration and drying to finally obtain PPTA-2.

[0182] The intrinsic viscosity of the PPTA-2 thus produced was 5.4 dL / g, and the content of inorganic impurities in the polymer was 3150 ppb. Using standard sieves with 1 mm and 2 mm mesh sizes, the polymer was classified into groups of 2 mm or more, 1 mm or more but less than 2 mm, and less than 1 mm. The intrinsic viscosity of each group was measured, and the difference between the maximum and minimum average intrinsic viscosities for the three groups was calculated. The deviation of the intrinsic viscosity was 1.3 dL / g.

[0183] 2. Production of para-aramid fiber and evaluation of its properties The physical properties of the para-aramid fibers obtained in the following Production Examples and Comparative Production Examples were measured by the methods described below, and the results are shown in Table 1.

[0184] (1) Denier (de) The fineness is expressed in denier (de) as the weight (g) of 9000 m of yarn and was measured according to ASTM D1577.

[0185] (2) Tensile properties The para-aramid fibers produced in the Production Examples and Comparative Production Examples were cut into lengths of 250 mm and twisted at a TM (twist multiplier) of 1.1 to prepare samples, which were then stored at a relative humidity of 55% and a temperature of 23°C for 14 hours.

[0186] Next, according to the ASTM D885 standard test method, the sample was mounted on an Instron testing machine (Instron Engineering Corp., Canton, Mass.), one end of the fiber was fixed, and an initial load was set to 1 / 30 g of the fineness (fineness x 1 / 30 g). The other end was pulled at a rate of 25 mm / min to measure the tensile load (g) and elongation (strain) at which the fiber broke. The measured tensile load was divided by the fineness to determine the strength (g / d), and the Young's modulus was calculated from the slope of the stress-strain curve of the para-aramid fiber obtained under the tensile load measurement conditions.

[0187] (3) X-ray diffraction (XRD) analysis The microstructures of the para-aramid fibers produced in the Production Examples and Comparative Production Examples were analyzed by X-ray diffraction patterns.

[0188] The para-aramid fibers produced in the Production Examples and Comparative Production Examples were cut to lengths of 20-30 mm, aligned as evenly as possible, and then attached to a holder to prepare samples. The prepared samples were suspended from a sample attachment so that the β-position was at 0°. The voltage and current of the warmed-up XRD measurement instrument were gradually increased to the measurement conditions of 50 kV and 180 mA, and the equatorial pattern was measured. The main measurement conditions were set as follows:

[0189] Goniometer, Continuous scan mode, Scan angle range: 10~40°, Scan speed: 2.

[0190] In the scanned profile, the 2θ positions of two peaks appearing between 20-21° and 22-23° were measured. The measured profile was processed using a multi-peak separation method program.

[0191] After specifying a background in a straight line from 2θ 15 to 35°, two crystalline peaks were separated to obtain an X-ray diffraction pattern.

[0192] i) Apparent crystal size (ACS) Using the X-ray diffraction pattern, the apparent crystal size (ACS) was calculated using the Scherrer equation with factors [2θ Position, Intensity, Full Width at Half Maximum (FWHM)] when K for each crystal plane is 1. Here, the apparent crystal size (ACS) means the average size of the crystals on that plane.

[0193] ii) Crystallinity (Xc) Using the X-ray diffraction pattern, the crystallinity was determined from the ratio of the crystalline peak to the amorphous peak.

[0194] iii) Orientation angle (OA) After performing an azimuthal scan (scanning of the azimuthal angle) at the position of each plane in the X-ray diffraction pattern, the full width at half maximum (FWHM) of each peak was determined to determine the orientation angle.

[0195] iv) Crystal defects (Paracrystalline parameter; g II) The para-aramid fibers produced in the Preparation Examples and Comparative Preparation Examples were cut to lengths of 20-30 mm, aligned as evenly as possible, and then attached to a holder to prepare samples. The prepared samples were suspended from a sample attachment so that the β-position was at 0°. The voltage and current of the warmed-up XRD measurement instrument were gradually increased to the measurement conditions of 50 kV and 180 mA, and the meridional pattern was measured. The main measurement conditions were set as follows:

[0196] Goniometer, continuous scan mode, scan angle range: 10-40°, scan speed: 0.5 [The step / scan time is set to provide sufficient beam exposure time to obtain 2,000 CPS, as the peak intensity is small].

[0197] The 2θ position of the peak (002 plane) appearing between 10 and 15° in the scanned profile was measured. The measured profile was substituted into the Hosemann equation (Equation 2) below to derive the paracrystalline parameter.

[0198] <Expression 2> JPEG2025526481000001.jpg25116

[0199] In the above formula 2, δs is the dispersion of the diffraction peak, L is the crystal size, d is the spacing of the lattice plane, and m is the order of the diffraction peak.

[0200] Manufacturing Example 1: Manufacturing of para-aramid fiber A spinning dope was prepared by dissolving PPTA-1 obtained in Synthesis Example 1 in 99.8 wt % sulfuric acid in an amount of 19 wt % based on the total weight of the spinning dope.

[0201] The spinning dope was spun through a spinneret with 133 holes at a speed of 650 m / min, and solidified in a coagulation bath through an air gap to produce filaments.

[0202] The coagulated series of filaments was washed with water to remove sulfuric acid and the like remaining on the filaments, and then dried and wound up to obtain para-aramid fibers having a monofilament fineness of 1.47 de and a total fineness of 213 de.

[0203] Manufacturing Example 2: Manufacturing of para-aramid fiber A spinning dope was prepared by dissolving PPTA-1 obtained in Synthesis Example 1 in 99.8 wt % sulfuric acid in an amount of 19 wt % based on the total weight of the spinning dope.

[0204] The spinning dope was spun through a spinneret with 665 holes at a speed of 620 m / min, and solidified in a coagulation bath through an air gap to produce filaments.

[0205] The coagulated filaments were washed with water to remove sulfuric acid and the like remaining on the filaments, and then dried and wound up to obtain para-aramid fibers having a monofilament fineness of 1.43 de and a total fineness of 988 de.

[0206] Manufacturing Example 3: Manufacturing of para-aramid fiber A spinning dope was prepared by dissolving PPTA-1 obtained in Synthesis Example 1 in 99.8 wt % sulfuric acid in an amount of 20 wt % based on the total weight of the spinning dope.

[0207] The spinning dope was spun through a spinneret with 665 holes at a speed of 600 m / min, and solidified in a coagulation bath through an air gap to produce filaments.

[0208] The coagulated filaments were washed with water to remove sulfuric acid and other substances remaining on the filaments, and then dried and wound up to obtain para-aramid fibers having a monofilament fineness of 1.50 de and a total fineness of 1022 de.

[0209] Manufacturing Example 4: Manufacturing of para-aramid fiber A spinning dope was prepared by dissolving PPTA-1 obtained in Synthesis Example 1 in 99.8 wt % sulfuric acid in an amount of 19 wt % based on the total weight of the spinning dope.

[0210] The spinning dope was spun through a spinneret with 1000 holes at a speed of 650 m / min, and solidified in a coagulation bath through an air gap to produce filaments.

[0211] The coagulated filaments were washed with water to remove sulfuric acid and other substances remaining on the filaments, then dried and wound up to obtain para-aramid fibers having a monofilament fineness of 1.54 de and a total fineness of 1550 de.

[0212] Comparative Manufacturing Example 1: Manufacturing of para-aramid fiber A spinning dope was prepared by dissolving PPTA-2 obtained in Synthesis Example 2 in 99.8 wt % sulfuric acid in an amount of 19 wt % based on the total weight of the spinning dope.

[0213] The spinning dope was spun through a spinneret with 1000 holes at a speed of 600 m / min, and solidified in a coagulation bath through an air gap to produce filaments.

[0214] The coagulated filaments were washed with water to remove sulfuric acid and other substances remaining on the filaments, and then dried and wound up to obtain para-aramid fibers having a monofilament fineness of 1.49 de and a total fineness of 1527 de.

[0215] In addition, when the spinning speed of PPTA-2 obtained in Synthesis Example 2 was set to be the same as that of Production Example 4, various physical properties were poor. Therefore, PPTA-2 was produced so as to have the same level of fineness as the para-aramid fiber of Production Example 4, and the spinning speed was adjusted to a speed optimized for PPTA-2 obtained in Synthesis Example 2.

[0216] [Table 1]

[0217] *In Table 1, the crystal size refers to the crystal size based on the (110) plane and the crystal size based on the 200 plane, and the orientation angle refers to the orientation angle based on the (110) plane and the orientation angle based on the (200) plane.

[0218] Referring to Table 1, it can be seen that the para-aramid fiber according to one embodiment of the present application is formed from a para-aramid polymer produced by using impurity-removed reactant materials and controlling the conditions and method for adding the reactant materials, and can be provided as high-quality para-aramid fibers of various grades.

[0219] Specifically, when comparing Preparation Examples 1, 2, and 4, which provide para-aramid fibers with a standard tenacity of about 20 to 24 g / d, with Comparative Preparation Example 1, it is confirmed that Preparation Examples 1, 2, and 4 exhibit larger crystal size, higher crystallinity, and higher orientation than Comparative Preparation Example 1, and also have better Young's modulus.

[0220] Furthermore, Production Example 3, which provides high tenacity para-aramid fibers having a strength of 25 g / d or more, also exhibits a large crystal size, a high degree of crystallinity, and a high degree of orientation, and is confirmed to have excellent tensile properties.

[0221] Experiment 2: Cord manufacturing and physical property evaluation Para-aramid filament yarns were produced through the same process as in the Production Example and Comparative Production Example described in Experiment 1, and the total fineness was controlled to a similar level of 1,000 (±50 or less) denier. Each of the produced para-aramid filament yarns was fed into a cable cord twisting machine (Allma Cable Corder) together with an 840 denier nylon filament yarn, and Z-direction first twisting and S-direction second twisting were simultaneously performed to produce a 2-ply cabled yarn (low cord). At this time, the cable cord twisting machine was set to a twist rate of 360 TPM (twist per meter) for the first twisting and second twisting. By adjusting the tensions applied to the nylon filament yarn and the para-aramid filament yarn, respectively, the ratio of the length of the para-aramid single yarn (first twist yarn) to the length of the nylon single yarn (first twist yarn) in the doubled and twisted yarn (low cord) (= the length of the para-aramid single yarn (L A ) / Nylon single yarn length (L N )) was set to 1.01. At this time, to determine the length ratio of the para-aramid single yarn and the nylon single yarn, a load of 0.05 g / d was applied to a 1-meter-long plied yarn (low cord) sample to untwist the upper twist and separate the para-aramid single yarn and the nylon single yarn. The lengths of the para-aramid single yarn and the nylon single yarn were then measured with a load of 0.05 g / d applied. The low cord manufactured as described above contains about 40 to 50% by weight of a first ply yarn (containing para-aramid fiber) and about 50 to 60% by weight of a second ply yarn (containing nylon fiber).

[0222] Next, the ply-twisted yarn (raw cord) was dipped in a resorcinol-formaldehyde-latex (RFL) adhesive solution containing 2.0 wt% resorcinol, 3.2 wt% formalin (37%), 1.1 wt% sodium hydroxide (10%), 43.9 wt% styrene / butadiene / vinylpyridine (15 / 70 / 15) rubber (41%), and water. The ply-twisted yarn (raw cord) containing the RFL solution was dried at 150°C for 100 seconds and heat-treated (cured) at 240°C for 100 seconds to complete the dipped cord. The tension applied to the ply-twisted yarn during the dipping, drying, and heat-treatment processes was 0.6 kg / cord. The content of the coated adhesive relative to the total weight of the manufactured dipped cord was approximately 4.5-5.0 wt%.

[0223] The dipped cord thus prepared was measured for the following properties, which are shown in Table 2.

[0224] (1) Crystal size and crystallinity based on the (110) and (200) planes of the para-aramid first twist yarn contained in the dip cord The para-aramid first twisted yarn was separated from the dipped cord, and the crystallinity of the inner part, to which the coating liquid was not applied, was measured in the same manner as in the measurement of the raw yarn microstructure described in Experiment 1.

[0225] (2) Creep Strain (%) of the dipped cord According to ASTM D885, the dipped cord specimens were left at constant temperature and humidity (temperature: 20±2°C, humidity: 65±5% as per ASTM D885) for 24 hours, and then pre-treated (dried) by applying a temperature of 180°C and a load of 0.01g / d for 15 minutes. Since different fiber components (e.g., nylon) can deform due to moisture, this pre-treatment was carried out to measure creep strain (%) reproducibly.

[0226] After this process, the hybrid dipped cord was subjected to creep evaluation according to ASTM D2990 to measure creep strain (%) as a function of time. Specifically, a load of 0.8 g / d was applied to the cord at 80°C for 24 hours, and the rate of change (deformation rate) in the direction of the load (longitudinal direction) was measured (Creep strain (%) after 24 hours).

[0227] (3) Dipped cord strength (kgf), strength (breaking strength) (g / d) and elongation (breaking elongation) (%) Ten 500 mm long samples were prepared for each dipped cord. The strength, breaking strength, and breaking elongation of each sample were measured using an Instron testing machine (Instron Engineering Corp., Canton, Mass.) at a tensile speed of 300 m / min according to the test methods of ASTM D885 and ASTM D885M-10a (2014). The arithmetic mean values of the strength, breaking strength, and breaking elongation of each of the 10 samples were then calculated.

[0228] [Table 2]

[0229] Referring to Table 2, it can be seen that the cords of Examples 1 to 4, which contain para-aramid fibers having large crystal sizes and high crystallinity and thus excellent mechanical properties, have lower creep rates and higher resistance to deformation against external forces than those of Comparative Example 1.

Claims

1. A cord formed by twisting together a first twisted yarn formed by twisting para-aramid fibers having a crystallinity of 67% or more, a (110) plane based crystal size of 5.8 to 7.0 nm, a total fineness of 200 to 1600 denier, and a tensile strength of 22 g / d or more; and a second twisted yarn formed by twisting a different type of fiber different from the para-aramid fibers.

2. The cord of claim 1 , wherein the heterogeneous fibers comprise nylon fibers or polyester fibers.

3. The cord of claim 1 further comprising a coating layer formed on the first ply twist yarn and the second ply twist yarn.

4. The cord according to claim 3, wherein the cord satisfies a creep strain of 3.0% or less.

5. The first twisted yarn is a twisted yarn obtained by imparting a twist of 250 to 600 TPM to the para-aramid fiber, The cord according to claim 1, wherein the second twisted yarn is a twisted yarn obtained by imparting a twist of 250 to 600 TPM to the heterogeneous fiber.

6. The cord according to claim 1, wherein the cord is formed by final twisting a first ply yarn and a second ply yarn with a twist number of 250 to 600 TPM.

7. Preparing para-aramid fibers having a crystallinity of 67% or more, a crystal size based on the (110) plane of 5.8 to 7.0 nm, a total fineness of 200 to 1600 denier, and a tensile strength of 22 g / d or more; and The method for manufacturing a cord includes a step of final twisting together a first first twist yarn formed by twisting the para-aramid fiber and a second first twist yarn formed by twisting a different type of fiber different from the para-aramid fiber to form a cord that is a double-twisted yarn.

8. The method for manufacturing a cord according to claim 7 , wherein the heterogeneous fibers include nylon fibers or polyester fibers.

9. The method for manufacturing a cord according to claim 7 , further comprising the step of forming a coating layer on the ply-twisted yarn.

10. The method for manufacturing a cord according to claim 9, wherein the cord satisfies a creep strain of 3.0% or less.

11. The para-aramid fiber is twisted at 250 to 600 TPM to produce the first twisted yarn; The method for manufacturing a cord according to claim 7, wherein the second twisted yarn is manufactured by giving a twist of 250 to 600 TPM to the heterogeneous fiber.

12. 8. The method for manufacturing a cord according to claim 7, wherein the cord is formed by final twisting the first twisted yarn and the second twisted yarn at a twist rate of 250 to 600 TPM.

13. The step of preparing the para-aramid fiber includes: The method includes the steps of filtering the reaction raw materials to remove impurities; adding an aromatic diamine to a mixed solvent containing an organic solvent and an inorganic salt to form a slurry; adding an aromatic diamine to a reactor containing the slurry in three or more divided portions and reacting the mixture to form a para-aramid polymer; and spinning a spinning dope containing the para-aramid polymer to produce fibers, 8. The method for producing a cord according to claim 7, wherein in the step of forming the polymer, a temperature difference between a cooling water inlet and a cooling water outlet for cooling the reactor during the first and second additions of the aromatic diacid halide is controlled to within 50°C.

14. The method for manufacturing a cord according to claim 13, wherein the step of filtering the reaction raw material to remove impurities includes filtering the reaction raw material using a filter having a diameter of 0.01 to 1.0 μm.

15. The method for producing a cord according to claim 13, wherein the stirring speed of the reactor is adjusted to 10 to 1000 rpm during the second addition of the aromatic diacid halide.

Images