Code and method for manufacturing the same

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 same, a composite (or reinforcing material) containing said cord, and a tire.

Background Art

[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 and the like. However, mechanical properties such as fiber strength and elastic modulus are still insufficient depending on the intended application, and continuous efforts have been made to provide fibers with more excellent properties.

[0003] On the other hand, aramid fibers are also used for cords which are tire reinforcing materials. For example, a tire cord is produced by final twisting nylon fibers and aramid fibers together. However, nylon is a fiber with a relatively low modulus, and has the disadvantage of undergoing extremely large deformation under tensile (external) force. In contrast, aramid fibers have a relatively high modulus, so their deformation under tensile (external) force is small. This difference in properties arises from the molecular chain conformation and microstructure of each fiber. Specifically, aramid having linear polymer chains forms hydrogen bonds between molecular chains, resulting in a relatively high crystallinity and thus a high modulus.

[0004] In consideration of this point, there is a need to develop an aramid fiber with an improved microstructure and an article (e.g., cord) containing the same, so that the tire cord can exhibit small deformation against external force.

Summary of the Invention

Problem to be Solved by the Invention

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

[0006] Another object of this application is to provide a tire cord having excellent mechanical properties (e.g., tensile properties).

[0007] Another object of this application is to provide a tire cord that has high resistance to deformation when external forces are applied, such as having a low creep rate (Creep Strain (%)).

[0008] The above-mentioned and other objectives of this application can all be resolved by the invention described in detail below. [Means for solving the problem]

[0009] A specific example of this application provides a cord comprising two different types of under-twisted yarns, one of which is formed by twisting a para-aramid fiber that satisfies predetermined properties; and a method for producing the same.

[0010] Specifically, the inventors of this application have experimentally confirmed that, for example, when manufacturing cords used as reinforcing materials for tires, if para-aramid fibers with excellent mechanical properties (e.g., tensile properties) are used, a cord formed to include the para-aramid fibers of this application (described later) exhibits superior mechanical properties (e.g., strength, strength, and / or elongation) and has a lower creep rate (Creep Strain (%)) than a cord without these fibers, thereby completing the present invention.

[0011] In this specification, “cord” may mean an article comprising at least two or more fibers that are different from each other. For example, the cord may mean a hybrid cord comprising at least two or more different undertwisted yarns. Such a cord may be a compound yarn formed by twisting together (i.e., overtwisting) two or more undertwisted yarns.

[0012] In the specific examples of this application, the cord may be a raw cord or a dipped cord. A dipped cord means a cord in which a coating agent, such as an adhesive, is coated onto the fibers (plywood). Conversely, a cord containing at least two or more fibers in which no coating agent is coated onto the fibers may be called a raw cord. In the specific examples of this application, the cord has a plywood structure in which at least a first under-twisted yarn and a second upper-twisted yarn are twisted together (i.e., the under-twisted yarns are twisted together).

[0013] In this specification, “under-twist” means twisting a yarn or filament in either direction, and “under-twisted yarn” can mean a single ply of yarn, i.e., a single yarn, made by twisting a yarn or filament in either direction. While not particularly limited, the under-twist can mean, for example, a clockwise or counterclockwise twist.

[0014] Furthermore, in this specification, "plied yarn" can mean a yarn made by twisting two or more under-twisted yarns together in one direction. Over-twist can mean a twist in the opposite direction to the under-twist. For example, over-twist can mean a counter-clockwise or clockwise twist.

[0015] A pre-twisted or plied yarn manufactured by applying a twist in a certain direction may have a predetermined number of twists. In this case, "number of twists" refers to the number of twists per meter, and its unit may be TPM (Twist Per Meter).

[0016] The following provides a more detailed explanation of the code of this application and its manufacturing method.

[0017] In one example relating to this application, the application relates to a cord containing para-aramid fibers. The cord can be used as a reinforcement for rubber, more specifically, as a reinforcement for tires, although this is not particularly limited.

[0018] Specifically, the cord may be formed by twisting together a para-aramid fiber (A) that satisfies the characteristics described later and a different type of fiber (B) that is different from the para-aramid fiber.

[0019] Specifically, the para-aramid fibers used to form the aforementioned cord are para-aramid fibers that (i) have a crystallinity of 67% or more, (ii) have a crystal size of 5.8 to 7.0 nm based on 110 plane, (iii) have a total fineness of 200 to 1,600 denier (de), and (iv) have 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 for fibers obtained after normal spinning, coagulation, and drying, and are measured values ​​for fibers in a state where no heat treatment process, which can be added to the fiber manufacturing method, is performed.

[0021] As described above, when a para-aramid fiber (A), which has a large crystal size and high degree of crystallinity and exhibits excellent mechanical properties (e.g., tensile properties), is twisted with a different fiber (B) to produce a cord, a cord with excellent mechanical properties (e.g., strength, tensile strength, and / or elongation) and a low creep rate (Creep Strain (%)) can be provided, as can be confirmed from the experiments described later.

[0022] In one example, para-aramid fibers having such properties may be formed from a para-aramid polymer produced by a predetermined polymerization method. Specifically, the para-aramid fibers can be provided by a method for producing para-aramid fibers, comprising the steps of: filtering 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 diacid halide to a reactor containing the slurry in three or more installments and reacting them 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 of the cooling water at the cooling water inlet and outlet for cooling the reactor is controlled to within 50°C during the primary and secondary additions of the aromatic diacid halide.

[0023] This manufacturing method minimizes the amount of residual inorganic impurities in the final para-aramid polymer by removing impurities from the reaction raw materials, thereby providing para-aramid fibers with excellent mechanical strength.

[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 listed reaction raw materials can be filtered to remove impurities contained in that raw material. For example, in the step of filtering the reaction raw materials to remove impurities, the organic solvent, inorganic salt, aromatic diamine, and aromatic diacid halide can each be filtered to prepare reaction raw materials from which impurities have been removed.

[0025] In the step of filtering the reaction raw material to remove impurities, the reaction raw material may 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. Said diameter may be the major axis length of the filtration pores of the filter. 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 with said 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 said inorganic impurities may be 0 ppb or more.

[0026] The order in which the step of filtering the reaction raw material to remove impurities is performed is not particularly limited. Specifically, the step of filtering the reaction raw material to remove impurities may be performed before the step of forming the slurry, or may be performed during the step of forming the slurry. As an example, when the step of filtering the reaction raw material to remove impurities is performed during the step of forming the slurry, after producing a mixed solvent containing an organic solvent and an inorganic salt, the mixed solvent is filtered to prepare the mixed solvent, and an aromatic diamine from which impurities have been removed by separate filtration is added to said mixed solvent to form the slurry.

[0027] On the other hand, in the step of forming the slurry, in order to increase the polymerization degree of the para-aramid polymer, an inorganic salt may be added to an organic solvent to produce a mixed solvent.

[0028] The inorganic salt contained in said mixed solvent may include an alkali metal halide salt or an alkaline earth metal halide salt. As an example, said inorganic salt may include one or more selected from the group consisting of CaCl₂, LiCl, NaCl, KCl, LiBr and KBr. Such an inorganic salt may be contained in an amount of 0.01 to 15% by weight, 0.05 to 13% by weight, 0.1 to 11% by weight, or 1 to 10% by weight based on the total weight of said mixed solvent.

[0029] The organic solvent contained in the mixed solvent may include one or more 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 included in an amount equal to the remainder after 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 can be mixed so that the aromatic diamine content in the slurry is 0.5 to 10% by weight.

[0031] As the aromatic diamine, one or more selected from the group consisting of p-phenylenediamine, 4,4'-oxydianiline, 2,6-naphthalenediamine, 1,5-naphthalenediamine, and 4,4'-diaminobenzanilide can be used.

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

[0033] As the aromatic diacid halide, one or more 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 can be used.

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

[0035] The polymerization reaction between the aromatic diamine and the aromatic diacid halide proceeds rapidly and exothermally. Therefore, conventionally, a portion of the aromatic diacid halide was added first to perform prepolymerization, and then the remaining aromatic diacid halide was added to minimize the difference in the degree of polymerization between the final polymers.

[0036] In the aforementioned manufacturing method, by using reaction raw materials from which impurities have been removed, and by controlling the conditions and method of introducing the reaction raw materials, it is possible to provide para-aramid fibers that not only have little difference in the degree of polymerization between polymers, but also have a large crystal size and high crystallinity.

[0037] Specifically, in the above manufacturing method, instead of the conventional method of adding aromatic diacid halides in two separate steps, aromatic diacid halides are added in three or more separate steps, and the temperature difference between the cooling water entering and leaving the reactor is controlled to within 50°C during the primary and secondary addition of aromatic diacid halides, thereby providing para-aramid fibers with the desired large crystal size and high crystallinity.

[0038] Specifically, in the step of forming the polymer, a reactor that allows cooling water to enter and exit is used.

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

[0040] In the step of forming the polymer, aromatic diacid halides are added to the reactor containing the slurry in three or more separate additions. In particular, the aromatic diacid halides can be added in primary and secondary additions while the temperature difference of the cooling water between the reactor's cooling water inlet and outlet is controlled to 0°C to 50°C.

[0041] More specifically, when the aromatic diacid halide is added as a primary agent, the temperature difference of the cooling water 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 at the cooling water inlet and outlet to within 50°C, the stirring speed of the reactor can be adjusted to 10-1000 rpm, 10-900 rpm, 10-700 rpm, or 10-500 rpm while the cooling water is circulating within the reactor.

[0043] The content of the primary aromatic diacid halide can be adjusted to 20-40 mol% or 25-35 mol% of the total content of the aromatic diacid halides added. Within this range, a prepolymer having molecular chains of appropriate length can be formed.

[0044] After adding aromatic diacid halides, prepolymerization can be carried out by stirring at a temperature of 0°C to 45°C for 1 to 30 minutes or 5 to 15 minutes.

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

[0046] The content of the secondarily added aromatic diacid halide can be adjusted to 20-75 mol%, 40-75 mol%, or 50-70 mol% relative to the total content of the added aromatic diacid halide. Within this range, polymers can be formed that provide fibers with large crystal size and high crystallinity while minimizing the difference in the degree of polymerization between polymers.

[0047] After secondarily adding aromatic diacid halides, polymerization can be carried out by stirring at a temperature of 0°C to 45°C for 1 to 30 minutes or 5 to 15 minutes.

[0048] Subsequently, the remaining aromatic diacid halide can be added in one or more fractional additions, followed by additional polymerization to ultimately produce a para-aramid polymer. This additional polymerization may be carried out by stirring at a temperature of 0°C to 45°C for 5 minutes to 1 hour or 10 minutes to 40 minutes.

[0049] After the step of forming the polymer, one or more of the following steps may be performed, regardless of the order described: separating the generated polymer from the polymerization reaction system, washing the polymer, neutralizing the polymer, and grinding the polymer.

[0050] The para-aramid polymer has 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 also be 9.0 dl / g or less.

[0051] Furthermore, 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 a smaller deviation in the intrinsic viscosity of the para-aramid polymer is advantageous, the lower limit of the intrinsic viscosity deviation may be 0 dl / g or greater.

[0052] The aforementioned intrinsic viscosity deviation can be determined by dividing the para-aramid polymer, after washing and drying, into three groups using standard sieves with mesh sizes of 1 mm and 2 mm: 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. After measuring the intrinsic viscosity of each group, the difference between the maximum and minimum values ​​of the average intrinsic viscosity of the three groups can be calculated.

[0053] Since the para-aramid polymer is manufactured from reaction raw materials from which impurities have been removed, the amount of residual inorganic impurities in the polymer may be very small or nonexistent. 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(para-phenylene-4,4'-biphenylene-dicarbonylamide), poly(para-phenylene-2,6-naphthalenedicarbonylamide), or copolymers thereof. For example, the para-aramid polymer may be poly(para-phenylene terephthalamide).

[0055] On the other hand, in the step of manufacturing the fibers, the spinning dope containing the polymer produced in the step of forming the polymer is spun to provide the fibers.

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

[0057] The viscosity of the spinning dope used to produce fibers increases as the concentration of para-aramid polymer in the spinning dope increases. However, when the concentration of para-aramid polymer exceeds the critical concentration, the viscosity of the spinning dope decreases rapidly. At this point, the spinning dope changes from optical isotropic to optical anisotropic without forming a solid phase. Optical anisotropic dope can provide high-strength para-aramid fibers without a separate drawing process due to its structural and functional properties. Therefore, it is preferable that the concentration of para-aramid polymer in the spinning dope exceeds the critical concentration, but if the concentration is excessively high, the viscosity of the spinning dope may become excessively low. For this reason, the spinning dope may contain para-aramid polymer in an amount of 10 to 25% by weight relative to the total weight of the spinning dope.

[0058] In the stage of manufacturing the aforementioned fibers, a spinning process can be carried out to spin the spinning dope.

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

[0060] The aforementioned air-gap wet spinning method involves creating an air gap between the spinneret and the surface of the coagulation bath. Through this air-gap wet spinning method, the spinning dope can be spun through the spinneret, across the air gap, and into a coagulation bath containing the coagulation solution.

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

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

[0063] Specifically, the spinneret can be equipped with 50 to 3000, 100 to 2000, 120 to 1500, or 500 to 1200 holes. Within this range, it is possible to provide para-aramid fibers that have a large crystal size and high crystallinity and exhibit excellent tensile properties.

[0064] The diameter of the holes formed in the spinneret can only be adjusted to an appropriate size to improve molecular orientation on both the surface and inside of the filament. Therefore, the diameter of the holes in the spinneret can be adjusted to between 50 μm and 100 μm.

[0065] In the spinning process, 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 spinning speeds of 80-800 m / min, 100-800 m / min, 300-800 m / min, 500-700 m / min, 550-660 m / min, 580-650 m / min, 580-640 m / min, or 590-610 m / min. Within this range, it is possible to provide para-aramid fibers that exhibit excellent tensile properties due to their large crystal size and high crystallinity.

[0067] The dope spun through the aforementioned spinneret is obtained as an unsolidified filament in which sulfuric acid is distributed on a matrix in which para-aramid polymers are uniformly distributed. Such an unsolidified filament can solidify by passing through an air gap and into a solidification tank containing a solidification solution.

[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 (dry N2). The length of the air gap is adjustable from 0.1 to 15 cm.

[0069] The doped yarn, spun from the spinneret and passed through the air gap, forms a filament as it passes through the solidification tank, with the sulfuric acid inside being removed. At this time, if the sulfuric acid is removed too rapidly from the surface of the filament, the surface of the filament solidifies before the sulfuric acid contained inside can escape, which can reduce the uniformity between the inside and outside of the filament. Therefore, it is preferable that the solidification liquid entering the solidification tank is an aqueous sulfuric acid solution containing sulfuric acid.

[0070] Specifically, the coagulation solution contained in the coagulation tank may be an aqueous sulfuric acid solution obtained by adding sulfuric acid to water. In addition, monohydric alcohols such as methanol, ethanol, or propanol; dihydric alcohols such as ethylene glycol or propylene glycol; or trihydric alcohols such as glycerol may be added to the coagulation solution as needed.

[0071] The temperature of the solidifying solution is preferably 1 to 10°C. If the temperature of the solidifying solution is excessively low, sulfuric acid may not escape easily from the filament. If the temperature of the solidifying solution is excessively high, sulfuric acid may escape rapidly from the filament, reducing the uniformity of the filament.

[0072] A solidification tube may be formed at the bottom of the solidification tank. The solidification tube is connected to the solidification tank, and a number of nozzles may be formed in the solidification tube. In this case, the nozzles are connected to a predetermined jet device, and the solidified liquid sprayed from the jet device is sprayed onto the filament passing through the solidification tube via the nozzles. Preferably, the number of nozzles are aligned so that the solidified liquid is sprayed symmetrically onto the filament. The spray angle of the solidified liquid is preferably 0 to 85° with respect to the axial direction of the filament, and in particular, a spray angle of 20 to 40° is appropriate in commercial production processes.

[0073] In the stage of manufacturing the aforementioned fibers, following the solidification step, a water washing step may be performed to remove any sulfuric acid remaining on the solidified filaments.

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

[0075] The washing process may be carried out in multiple stages. For example, the solidified filament can be first washed with a 0.1 to 1.5% by weight aqueous caustic solution, and then secondarily washed with a dilute aqueous caustic solution.

[0076] In the stage of manufacturing the fibers, following the coagulation and washing steps, a drying step may be performed to adjust the moisture content remaining in the filaments.

[0077] The drying process may be carried out by adjusting the time the filament is in contact with the heated drying roll, or by adjusting the temperature of the drying roll.

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

[0079] Furthermore, the para-aramid fiber may include a plurality of monofilaments and have a total fineness of 200-1,600 de, 200-400 de, 800-1,000 de, 1,000-1,100 de, or 1,400-1,600 de.

[0080] Para-aramid fibers produced by this manufacturing method have a large crystal size, exhibit high crystallinity and orientation, and can exhibit excellent mechanical properties (e.g., tensile properties).

[0081] The para-aramid fibers can have an increased crystal size when manufactured by the above manufacturing method.

[0082] For example, the para-aramid fiber may have a crystal size 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 based on the 110 plane, and may also be 7.0 nm or less, 6.8 nm or less, 6.7 nm or less, or 6.6 nm or less. Alternatively, the para-aramid fiber may have a crystal size of 5.0 nm or more, 5.5 nm or more, or 5.6 nm or more based on the (200) plane, and may also be 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 determined from the X-ray diffraction pattern, and for more detailed measurement methods, refer to the methods described in the test examples below. The para-aramid fiber can have a high degree of crystallinity when manufactured by the above manufacturing method.

[0084] Specifically, the para-aramid fibers 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, and 75.0% or more, and may also 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 aforementioned degree of crystallinity is determined by analysis of the X-ray diffraction pattern. For more detailed measurement methods, please refer to the methods described in the test examples below.

[0086] The para-aramid fibers produced by the manufacturing method described above can exhibit a high degree of orientation. In other words, 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 of 2° or more, 3° or more, 4° or more, 5° or more, 6° or more, or 7° or more based on the (110) plane. Furthermore, the orientation angle of 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. In addition, the para-aramid fiber may have an orientation angle of 2° or more, 3° or more, 4° or more, 5° or more, 6° or more, 7° or more, or 8° or more based on the (200) plane. Furthermore, 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 the orientation angle analyzed from the X-ray diffraction pattern, and for more detailed measurement methods, please refer to the methods described in the test examples below.

[0089] The para-aramid fibers, when manufactured by the aforementioned manufacturing method, can have their crystalline parameters minimized.

[0090] For example, the para-aramid fiber may have crystalline defects of 1.00% or more, or 1.30% or more, and may also have 1.85% or less, 1.80% or less, 1.70% or less, or 1.60% or less.

[0091] The aforementioned crystal defects are those analyzed from the X-ray diffraction pattern. For more detailed measurement methods, please refer to the methods described in the test examples below.

[0092] The aforementioned para-aramid fibers can exhibit excellent tensile properties due to their large crystal size and high degree of crystallinity.

[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 may also have a tensile strength of 30 g / d or less, or 28 g / d or less. Furthermore, the para-aramid fiber may 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 may also have a Young's modulus of 900 g / d or less, 880 g / d or less, or 860 g / d or less. Finally, the para-aramid fiber may 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 may also have an elongation of 4.5% or less, or 4.0% or less.

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

[0095] Cord exhibits different properties (physical properties) depending on its thickness. For example, when the cord is used as a tire reinforcement, a thicker cord improves tire performance in terms of strength and modulus, but the thickness of the rubber covering the cord fabric increases, leading to a larger tire size and thus increased weight. Therefore, it is unsuitable for tires where fuel efficiency and weight reduction are important. Conversely, a thinner cord is advantageous for reducing tire weight, but its strength and modulus are lower, preventing it from fully performing as a reinforcement. In this application, these points are taken into consideration, and the fineness of the fibers forming the cord (each fiber forming the under-twisted yarn) is appropriately adjusted.

[0096] In one example, the para-aramid fiber or the pre-twisted yarn (first pre-twisted yarn) formed therefrom may 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. Para-aramid fibers of 900 to 1100 denier or 1400 to 1600 denier can be used as pre-twisted yarn, although this is not particularly limited.

[0097] In one example, the dissimilar fiber or the under-twisted yarn (second under-twisted yarn) formed therefrom may have a fineness of 600 to 2000 denier (de). For example, the lower limit of the fineness of the dissimilar 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, dissimilar fibers of 700 to 900 denier or 1100 to 1400 denier may be used as under-twisted yarn.

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

[0099] The degree of twist in the undertwist yarn and / or the twist between undertwist yarns (i.e., overtwist) affects the physical properties of the cord. Generally, a high twist results in a form with a helical inclination in the vertical direction of the cord, increasing elongation (or break elongation, or mid-length elongation), decreasing modulus, and lowering tensile strength (or strength) due to the external force applied by the twist. Conversely, a low twist results in a form where the fibers are well aligned in the cord direction (a form with a low helical inclination value in the vertical direction of the cord), resulting in higher strength (or strength) and modulus compared to a high twist, but lower elongation. In this application, taking these points into consideration, the number of twists in each undertwist yarn and the number of twists between undertwist yarns are adjustable.

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

[0101] In the specific example of this application, the number of twists of the first under-twisted yarn containing (A) para-aramid fibers (first twist count), or the number of twists of the second under-twisted yarn containing different fibers (second twist count), 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 also be 390TPM or higher, 400TPM or higher, 410TPM or higher, 420TPM or higher, 430TPM or higher, 440TPM or higher, 450TPM or higher, 460TPM or higher, 470TPM or higher, 480TPM or higher, 490TPM or higher, 500TPM or higher, 510TPM or higher, 520TPM or higher, 530TPM or higher, 540TPM or higher, 550TPM or higher, 560TPM or higher, 570TPM or higher, 580TPM or higher, or 590TPM or higher. And the upper limit of the twist count is, for example, 590TPM or less, 580TPM or less, 570TPM or less, 560TPM or less, 550TPM or less, 540TPM or less, 530TPM or less, 520TPM or less, 510TPM or less, 500TPM or less, 490TPM or less, 480TPM or less, 470TPM or less, 460TPM or less, 450TPM or less, 440TPM or less, 430T It may also be ≤PM, ≤420TPM, ≤410TPM, ≤400TPM, ≤390TPM, ≤380TPM, ≤370TPM, ≤360TPM, ≤350TPM, ≤340TPM, ≤330TPM, ≤320TPM, ≤310TPM, ≤300TPM, ≤290TPM, ≤280TPM, ≤270TPM, or ≤260TPM.

[0102] In one example, the number of twists (first twist count) of the undertwist yarn containing the para-aramid fiber (first undertwist yarn) and the number of twists (second twist count) of the undertwist yarn of the different fiber (second undertwist yarn) may be the same or different. For example, a cable cord twist machine or a ring twister may be used to assign such twist counts, but having the same twist count for each undertwist yarn means that the twist count setting for each undertwist yarn is the same when using the equipment. However, depending on the equipment or process conditions (e.g., some untwisting may occur during the drying stage after immersion in the adhesive solution), there may be a difference of approximately 15%, 10%, or 5% in the twist count from the set value.

[0103] In one example, the cord may be formed by over-twisting the first and second under-twist yarns within the range of 250 to 600 TPM. For example, when the first and second under-twist yarns described above are over-twisted together, the number of twists (third twist count) 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. It may also be 410TPM or higher, 420TPM or higher, 430TPM or higher, 440TPM or higher, 450TPM or higher, 460TPM or higher, 470TPM or higher, 480TPM or higher, 490TPM or higher, 500TPM or higher, 510TPM or higher, 520TPM or higher, 530TPM or higher, 540TPM or higher, 550TPM or higher, 560TPM or higher, 570TPM or higher, 580TPM or higher, or 590TPM or higher. And the upper limit of the twist count is, for example, 590TPM or less, 580TPM or less, 570TPM or less, 560TPM or less, 550TPM or less, 540TPM or less, 530TPM or less, 520TPM or less, 510TPM or less, 500TPM or less, 490TPM or less, 480TPM or less, 470TPM or less, 460TPM or less, 450TPM or less, 440TPM or less, 430T It may also be ≤PM, ≤420TPM, ≤410TPM, ≤400TPM, ≤390TPM, ≤380TPM, ≤370TPM, ≤360TPM, ≤350TPM, ≤340TPM, ≤330TPM, ≤320TPM, ≤310TPM, ≤300TPM, ≤290TPM, ≤280TPM, ≤270TPM, or ≤260TPM.

[0104] In one example, the number of twists of the first and second undertwisted yarns (i.e., the number of twists during undertwisting) and the number of twists during overtwisting may be the same or different. In the specific example of this application, the number of twists during undertwisting and the number of twists during overtwisting can be set to be the same. However, in some cases, the number of twists during undertwisting and the number of twists during overtwisting may be slightly different in the final product. Specifically, in the case of a CC twisting machine (Cable Corder Twist machine) used in the manufacture of cord, it is driven by one motor. The yarn in the creel passes through a disk connected to the motor and is connected to a regulator (the section where undertwisted yarns meet and overtwisting takes place), and the yarn in the port passes through a tension adjustment guide roll and is connected to the regulator. At this time, the regulator to which the yarn coming out of the disk is connected rotates together with the rotation of the motor. As a result of this mechanical motion, the rotation of the motor adds a pre-twist to the yarn in the connected creel and port sections, and the regulator twists the pre-twisted yarns together to create a top twist. In this way, raw cord is manufactured as twist is generated by the rotational motion of the motor, but even when the number of twists in the pre-twist and top twist are set to be the same, the number of twists in the top twist and pre-twist may differ slightly due to friction generated by winding tension and guide rollers.

[0105] As described above, the cord of this application includes a first under-twist yarn and a second under-twist yarn having a predetermined number of twists, and is formed by twisting the first under-twist yarn and the second under-twist yarn together. At this time, the first under-twist yarn and the second under-twist yarn are formed as the filaments for forming the first under-twist yarn and the filaments for forming the second under-twist yarn are simultaneously under-twisted by a CC twisting machine (e.g., a cable corder twist machine) or a ring twisting machine. Therefore, the twisting direction of the first under-twist yarn (first twisting direction) and the twisting direction of the second under-twist yarn (second twisting direction) may be the same. Furthermore, when using a CC twisting machine (for example, a cable corder twist machine) or a ring twisting machine, the top twist may be performed continuously and simultaneously with the bottom twist, but the twisting direction of the top twist (i.e., the third twisting direction) may be opposite to the first twisting direction (or second twisting direction).

[0106] In the specific example of this application, the content ratio of the first under-twisted yarn to the second under-twisted yarn can be appropriately adjusted to a level that can achieve the objectives of this application. For example, based on a total weight of 100% by weight of the first under-twisted yarn and the second under-twisted yarn contained in the cord, specifically the low cord, the content of the first under-twisted 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 under-twisted yarn can be determined according to the content of the first under-twisted yarn as described above.

[0107] In one example, the cord may be a 2-ply or 3-ply cord. For example, the cord may have a 2-ply structure in which one first under-twisted yarn and one second under-twisted yarn are twisted together. Alternatively, the cord may have a 3-ply structure in which two first under-twisted yarns of the fineness described above and one second under-twisted yarn having the fineness described above are twisted together.

[0108] In a specific example of this application, when the first undertwisted yarn (undertwisted yarn containing para-aramid fibers) forms a plied yarn together with the second undertwisted yarn (undertwisted yarn containing different fibers), the length ratio of the first undertwisted yarn to the second undertwisted yarn (length of the first undertwisted yarn (L1) / length of the second undertwisted yarn (L2)), measured after untwisting the top twist of the plied yarn (low cord or dip cord), may be in the range of 1.0 to 1.10 times.

[0109] Such a length ratio (length of the first undertwist (L1) / length of the second undertwist (L2)) results in a longer first undertwist (undertwist containing para-aramid fibers), which has a higher modulus. This allows the properties of the second undertwist (e.g., nylon), which has a lower modulus, to manifest initially in the stress-strain curve pattern (SS Curve Pattern) that indicates the tensile properties of the cord. While this characteristic helps reduce non-uniformity of the tire's shape during tire manufacturing, in the case of a cap ply wound circumferentially around the tire, for example, a high initial modulus of the cord may prevent the tread from functioning properly against the expansion pressure during tire molding. Therefore, in the SS Curve Pattern of a cap ply cord, the initial manifestation of a low modulus characteristic may be more effective in tire manufacturing. After tire manufacturing, a high modulus must manifest to prevent belt cord detachment during high-speed driving and maintain ground contact. For this reason, the manifestation of a high modulus after the elongation section worn down during tire manufacturing may be more effective in terms of tire performance. Therefore, a cord manufactured by varying the lengths of the first and second undertwists, which have different moduli, can be very effective from both a manufacturing and performance standpoint for tires.

[0110] If the length ratio of the first and second undertwists (length of the first undertwist (L1) / length of the second undertwist (L2)) is less than 1.0, the first undertwist, which has a higher modulus, becomes shorter, and the aramid properties appear first, which can be detrimental to tire manufacturing. Furthermore, the high initial modulus significantly reduces fatigue performance under repeated tensile and compressive stress. If the length ratio of the first and second undertwists (length of the first undertwist (L1) / length of the second undertwist (L2)) exceeds 1.10, the first and second undertwists will experience separate forces during cord tensioning, which can result in lower final cord strength.

[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 specific examples of this application, such control of the length ratio may be achieved by adjusting the magnitude of the tension applied to the filaments forming the first undertwist and the filaments forming the second undertwist during the undertwist and / or overtwisting processes for manufacturing the cord. For example, when undertwisting and overtwisting are performed, the length of the first undertwist can be made longer than the length of the second undertwist by making the magnitude of the tension applied to the para-aramid fibers (forming the first undertwist) smaller than the tension applied to the dissimilar fibers forming the second undertwist.

[0113] In one example, the cord may further include coating layers formed on the first and second under-twisted yarns. That is, the cord may include a raw cord and a coating layer formed on the raw cord.

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

[0115] The coating layer may be configured to impart predetermined properties to the cord or to reinforce the properties of the cord. For example, the coating layer may be a layer capable of imparting adhesive functionality to the cord, but the properties imparted or reinforced by the coating layer are not limited to adhesive functionality alone.

[0116] In one example, the coating layer may be formed from an adhesive (composition). In one non-limiting example, the coating layer may contain 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 forming the coating layer are not limited to those described above.

[0117] The adhesive composition may contain an aqueous or non-aqueous solvent, although this is not particularly limited. Such an adhesive allows the fiber cord to exhibit improved adhesion to other adjacent components in tire reinforcement applications.

[0118] In one example, a cord with a coating layer formed on it, i.e., a dip cord, may contain a coating layer (or coating component) in a range of 1 to 10% by weight relative to its total weight (100% by weight, including the total content of fiber components and coating components). 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 the specific example of this application, the first under-twist of the cord can exhibit predetermined crystalline properties. Specifically, the coating layer can be formed by applying predetermined tension and heat, as in the manufacturing method described later. During this process, the microstructure of the para-aramid fibers changes, such as by further increasing the crystal size of the para-aramid fibers. As can be confirmed from the experiments described later, when the crystal size of the para-aramid fibers increases further, the creep rate can become even lower.

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

[0121] In one example, the para-aramid fibers contained within the dip cord may have a crystal size based on the (200) plane 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 also 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 crystal size based on the (200) plane of the para-aramid fibers contained within the dip cord can be measured by separating the para-aramid fibers from the dip cord and measuring the inner portion where the coating solution is not applied, as will be described later.

[0122] In one example, the para-aramid fibers contained within the dip cord have 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. It may be 79.5% or higher, and its upper limit 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 degree of crystallinity of the para-aramid fibers contained in the dip cord can be measured by separating the para-aramid fibers from the dip cord and measuring the inner portion where the coating liquid is not applied, as will be described later.

[0123] Thus, in this application, a low cord is manufactured using para-aramid fibers with relatively large crystal size and degree of crystallinity, and a coating layer is formed on the low cord by applying heat treatment and tension. As a result, the para-aramid fibers contained in the dip cord also exhibit larger values. Consequently, the degree of deformation of the fibers and cord can be improved, as can be confirmed from the creep rate described later.

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

[0125] In one example, the creep strain (%) of the code may be 3.0% or less. Specifically, the code 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 is a deformation of a material in response to a constant load and temperature, and is different from elongation, measuring the deformation until the material breaks or breaks while the load is continuously increased. Elongation rate measures how much a material can stretch, and is generally calculated as the length the material stretches before it breaks or snaps. In contrast, creep strain indicates the rate of deformation under a fixed load. Therefore, high creep strain means that the shape of the product deforms significantly under a constant load. Consequently, if cords with high creep strain are used, the likelihood of deformation such as tire deformation due to prolonged parking increases.

[0126] As described later, creep strain (%) is measured by applying a load (tension) of 0.8 g / d (where d is denier and g is the unit of weight) to the cord at 80°C for 24 hours according to ASTM D2990, and can be said to represent the rate of change in the length of the cord (rate of deformation in the direction of the load) confirmed under the above conditions. According to a specific example of this application, the cord may be subjected to a predetermined pretreatment before such creep strain measurement. For example, the creep strain on the cord can be measured after pretreatment in which the cord is stored under constant temperature and humidity conditions (controlled at 20±2°C and humidity: 65±5%) for 24 hours and a load (tension) of 0.01 g / d (where d is denier and g is the unit of weight) is applied to the cord at 180°C for 15 minutes.

[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. The upper limit is not particularly limited, but for example, it may be 40 kgf or less, 35 kgf or less, or 30 kgf or less. The strength of the cord can be measured by ASTM D885, as described later. In this case, the cord may be a dip cord.

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

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

[0130] In other examples relating to this application, this application relates to a method for manufacturing the aforementioned code. The aforementioned code can be manufactured by the aforementioned manufacturing method. Therefore, any descriptions of redundant configurations or characteristics of the aforementioned code will be omitted in the description of the manufacturing method described later.

[0131] In one specific example of this application, the method for manufacturing the cord may include the steps of: preparing para-aramid fibers having a crystallinity of 67% or more, a crystal size of 5.8 to 7.0 nm based on the (110) plane, a total fineness of 200 to 1600 denier, and a tensile strength of 22 g / d or more; and top-twisting together a first under-twisted yarn formed by twisting the para-aramid fibers and a second under-twisted yarn formed by twisting a different type of fiber from the para-aramid fibers to form a cord which is a combined twisted yarn.

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

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

[0134] In the above method, the first and second under-twisted yarns can be twisted together to form a cord with a twist count of 250 to 600 TPM. The specific twist count during the twisting process is as described above.

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

[0136] The method for applying the coating layer-forming composition (coating liquid) onto the low-coat is not particularly limited, and immersion or spraying methods can be used.

[0137] For example, the method may include a step of spraying a coating layer forming composition (coating liquid) onto a plied yarn (low cord). In other words, the method can form a coating layer by spraying a coating layer forming composition (coating liquid) onto a plied yarn.

[0138] In other examples, the method may include the step of dipping a plied yarn (raw cord) into a coating layer forming composition (coating liquid). That is, the method can form a coating layer by dipping the plied yarn into a coating layer forming composition (coating liquid). When the plied yarn is dipped into the coating layer forming composition (coating liquid), the specific method of dipping the plied yarn into the coating layer forming composition is not particularly limited. For example, a method can be used in which the plied yarn or a fiber substrate containing it is transported using a roll while the plied yarn is dipped into a coating bath filled with the coating layer forming composition. A cord coated with the coating layer forming composition after dipping may be called a dipped cord.

[0139] In one example, the formation of the coating layer may be carried out by transferring 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 forming step (process) may include one or more of the processes of transferring the cord, dipping (or spraying), and heat treatment. Specifically, the coating layer forming step (process) may include applying a predetermined amount of tension to a plied yarn to which the coating layer forming composition has already been applied and then heat treating it; applying a predetermined amount of tension to the plied yarn and then applying the coating layer forming composition and then heat treating it; or applying a predetermined amount of tension to the plied yarn and then transferring, applying the coating layer forming composition and then heat treating it.

[0140] In the specific example of this 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 in the 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 may include two or more heat treatment steps. Specifically, the method may 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 may 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 temperature of the first heat treatment may be in the range of 70 to 180°C, and the temperature of the second heat treatment may be in the range of 200 to 250°C. Here, the first heat treatment performed at a relatively lower temperature may be called the drying process, and the second heat treatment performed at a relatively higher temperature may be called the cruing process.

[0143] In one example, the formation of the coating layer may be carried out by applying tension to the twisted yarn (raw cord).

[0144] For example, the tension applied to the twisted 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. 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 by applying tension, the coating layer formation step can be used to mean that the twisted yarn, to which the coating layer forming composition has already been applied, is heat-treated by applying tension of the magnitude described above. More specifically, the coating layer formation step (process) performed by applying tension can be used to mean that the twisted yarn, to which the coating layer forming composition has been applied and which has undergone a first heat treatment, is heat-treated by applying tension of the magnitude described above. In the case of heat treatment in which high temperatures are applied, especially in the case of the second heat treatment, it is important to satisfy the tension range described above because it greatly affects the final physical properties of the cord. Therefore, the tension in the range described above is maintainable at least during the heat treatment, more specifically during the second heat treatment, and may be the same or different (slightly modified) during the transfer and immersion (spray) for coating layer formation, and the first heat treatment process.

[0146] As described above, when heat and tension are applied, the tension causes the molecular chains to be more oriented toward the fiber axis, and the heat sets this orientation, thus allowing the microstructure to change. Because heat and / or tension are applied during the dipping process, the microstructure of the para-aramid fibers in the dip cord has a larger crystal size compared to the filament state. As described above, this application uses para-aramid filaments with a higher degree of crystallinity, and in addition, the dipping process further increases the degree of crystallinity of the dip cord para-aramid fibers, thereby reducing the degree of deformation under external forces (i.e., increasing deformation resistance). This is confirmed by the creep rate (Creep Strain (%)) described above.

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

[0148] For example, a primary immersion, a secondary immersion, and a heat treatment may be performed in sequence. In this case, the heat treatment may include a primary heat treatment (e.g., drying) and / or a secondary heat treatment (e.g., curing) in sequence.

[0149] In other examples, primary immersion, heat treatment, secondary immersion, and heat treatment may be performed in sequence. In this case, the heat treatment performed between primary and secondary immersion may be a drying process performed at a relatively low temperature, and the heat treatment performed after secondary immersion may be a curing process performed at a relatively high temperature.

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

[0151] In one example, the method may be a method of producing a combined twisted yarn by over-twisting the first and second under-twisted yarns in a third twisting direction after or simultaneously with the production of such under-twisted yarns. In this case, the first twisting direction and the second twisting direction may be the same, while the first twisting direction and the third twisting direction may be different from each other.

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

[0153] In one example, the method may be a method of forming a base twist yarn by giving the fibers (filaments) that form the base twist yarn a twist count in the range of 250 to 600 TPM. That is, the twist count given to the first and second base twist yarns is in the range of 250 to 600 TPM.

[0154] In one example, the method can form a combined yarn by twisting the first and second under-twisted yarns together with a twist count in the range of 250 to 600 TPM.

[0155] In a specific example of this application, the method may be a method of controlling the amount of tension applied to the aramid fibers (forming the first undertwist) when undertwisting and / or overtwisting is performed to be less than the tension applied to the dissimilar fibers (forming the second undertwist). This makes it possible to adjust the length ratio of the first undertwist to the second undertwist (length of the first undertwist (L1) / length of the second undertwist (L2)), measured after untwisting the overtwist with respect to the combined twisted yarn (raw cord or dip cord), to a range of 1.0 to 1.10 times.

[0156] In relation to the manufacturing method of this application, in addition to the above, the description of the structure, characteristics, and manufacturing of the cord and the under-twisted yarn that forms it is omitted as it is as described above in relation to the cord.

[0157] In a specific example of this application, the method for producing the cord may further include a method for producing (preparing) the para-aramid fibers described above. For example, the para-aramid fibers can be produced by the method described above, and the method for producing the cord may further include a process (or method) for producing para-aramid fibers, comprising 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 diacid halide to a reactor containing the slurry in three or more installments and reacting them to form a para-aramid polymer; and spinning a spinning dope containing the para-aramid polymer to produce fibers. Here, in the step of forming the polymer, the temperature difference of the cooling water between the cooling water inlet and outlet for cooling the reactor during the primary and secondary additions of the aromatic diacid halide can be controlled to within 50°C.

[0158] The specific process for manufacturing para-aramid fibers is the same as described above, so it will be omitted here.

[0159] In yet another example relating to this application, the application relates to a rubber composite or rubber reinforcement comprising the cord. The rubber composite or rubber reinforcement may further include a rubber substrate such as a rubber sheet, in addition to the cord described above.

[0160] In yet another example relating to this application, the application relates to a tire including the aforementioned cord. The tire may have a commonly known configuration such as a tread, shoulder, sidewall, cap ply, belt, carcass (or body ply), inner liner, bead, etc. [Effects of the Invention]

[0161] This application provides a cord containing para-aramid fibers as the under-twist component, which have a large crystal size and high degree of crystallinity and exhibit excellent mechanical properties (e.g., tensile properties). The cord has high resistance to deformation under external force and can be used as a tire reinforcement. [Modes for carrying out the invention]

[0162] The function and effects of the invention will be explained in more detail below through specific embodiments of the invention. However, these are presented as examples of the invention and do not limit the scope of the invention in any way.

[0163] Experiment 1: Evaluation of para-aramid polymers and fibers 1. Manufacturing and property evaluation of para-aramid polymers The physical properties of the para-aramid polymers obtained in the following synthesis examples were measured using the method described below.

[0164] (1) Measurement of intrinsic viscosity The intrinsic viscosity of the polymer was measured using Equation 1 below.

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

[0166] In equation 1 above, ln is the 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 This is the ratio of the flow time between the polymer solution and the solvent, measured using a capillary viscometer at 30°C.

[0167] (2) Measurement of intrinsic viscosity deviation After washing and drying, the polymers were separated into three groups using standard sieves with mesh sizes of 1 mm and 2 mm, respectively: a group of 2 mm or larger, a group of 1 mm to less than 2 mm, and a group of less than 1 mm.

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

[0169] (3) Content of inorganic impurities

[0170] The inorganic impurity content in para-aramid polymers was measured by the following method: After completely decomposing a 1g sample by acid treatment, the concentration of ionized and residual inorganic impurities in the sample was measured using an inductively coupled plasma atomic emission spectrophotometer.

[0171] Synthesis Example 1: Production of Para-aramid Polymer (PPTA-1) As 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 from the reaction raw materials.

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

[0173] Next, TPC equivalent to 30 mol% of the molar amount of PPD was added to the reactor, which had been cooled to 30°C, and the reaction was allowed to proceed for 10 minutes. During this time, the stirring speed of the reactor was adjusted to approximately 200 rpm to control the temperature difference of the cooling water between the inlet and outlet to within approximately 20°C.

[0174] Subsequently, TPC equivalent to 60 mol% of the molar amount of PPD was added to the reactor, which had been cooled again to 30°C, and the reaction was allowed to proceed for 30 minutes. During this time, the stirring speed of the reactor was adjusted to approximately 200 rpm, and the temperature difference of the cooling water between the cooling water inlet and outlet was controlled to be within approximately 20°C.

[0175] Finally, TPC equivalent to 10 mol% of the molar amount of PPD was added to a reactor cooled to 30°C, and the reaction was carried out for 30 minutes to produce a para-aramid polymer.

[0176] To the solution containing the para-aramid polymer, water and NaOH were added to neutralize the acid. Next, the para-aramid polymer was pulverized, and the polymerization solvent contained in the para-aramid polymer was extracted using water. Dehydration and drying were then performed to finally obtain PPTA-1.

[0177] The intrinsic viscosity of the PPTA-1 produced in this manner was 5.4 dl / g, and the inorganic impurity content in the polymer was 48 ppb. Furthermore, using standard sieves with mesh sizes of 1 mm and 2 mm, the PPTA-1 was classified into three groups: those with mesh sizes of 2 mm or more, those with mesh sizes between 1 mm and 2 mm, and those with mesh sizes less than 1 mm. After measuring the intrinsic viscosity of each group, the deviation of the intrinsic viscosity, calculated by the difference between the maximum and minimum values ​​of 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 consisting 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 to the slurry to a concentration of 3% by weight, thereby producing a slurry.

[0179] Next, TPC equivalent to 30 mol% of the molar amount of PPD was added to a reactor cooled to 0°C, and the reaction was carried out at 5°C for 30 minutes.

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

[0181] To the solution containing the para-aramid polymer, water and NaOH were added to neutralize the acid. Next, the para-aramid polymer was pulverized, and the polymerization solvent contained in the para-aramid polymer was extracted using water. Dehydration and drying were then performed to finally obtain PPTA-2.

[0182] The intrinsic viscosity of the PPTA-2 produced in this manner was 5.4 dl / g, and the inorganic impurity content in the polymer was 3150 ppb. Furthermore, using standard sieves with mesh sizes of 1 mm and 2 mm, the PPTA-2 was classified into three groups: one with a mesh size of 2 mm or more, one with a mesh size of 1 mm or more but less than 2 mm, and one with a mesh size of less than 1 mm. After measuring the intrinsic viscosity of each group, the deviation of the intrinsic viscosity, calculated by the difference between the maximum and minimum average intrinsic viscosities for the three groups, was 1.3 dl / g.

[0183] 2. Manufacturing and property evaluation of para-aramid fibers The physical properties of the para-aramid fibers obtained in the following manufacturing examples and comparative manufacturing examples were measured using the method described below, and the results are shown in Table 1.

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

[0185] (2) Tensile properties Para-aramid fibers produced by the manufacturing example and comparative manufacturing example were cut to a length of 250 mm and twisted with TM (twist multiplier) 1.1 to prepare samples, which were then stored for 14 hours at a relative humidity of 55% and a temperature of 23°C.

[0186] Next, following the ASTM D885 standard test method, the sample was mounted on an Instron Engineering Corp. (Canton, Mass) testing machine. One end of the fiber was fixed, and the initial load was set to 1 / 30 g of the fineness (fineness × 1 / 30 g). The other end was then stretched at a speed of 25 mm / min, and the tensile load (g) and elongation (strain) at which the fiber broke were measured. The strength (g / d) was obtained by dividing the measured tensile load by the fineness, and Young's modulus was determined from the slope of the stress-deformation curve of the para-aramid fiber obtained under the tensile load measurement conditions.

[0187] (3) X-ray diffraction (XRD) analysis The microstructure of para-aramid fibers produced using the manufacturing example and comparative manufacturing example was analyzed by X-ray diffraction pattern analysis.

[0188] Para-aramid fibers produced by the manufacturing example and comparative manufacturing example were cut to a length of 20-30 mm, aligned as precisely as possible, and then attached to a holder to prepare the sample. The prepared sample was suspended from a sample attachment so that the β-position was at 0°. The voltage and current of the warmed-up XRD measuring 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 then set as follows.

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

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

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

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

[0193] ii) Crystallinity (Xc) The degree of crystallinity was determined by the ratio of crystalline peaks to amorphous peaks using the aforementioned X-ray diffraction pattern.

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

[0195] iv) Crystallographic defects (Paracrystalline parameter; g II) Para-aramid fibers produced by the manufacturing example and comparative manufacturing example were cut to a length of 20-30 mm, aligned as much as possible, and then attached to a holder to prepare the sample. The prepared sample was suspended from a sample attachment so that the β-position was at 0°. The voltage and current of the warmed-up XRD measuring 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 [Step / scan time is sufficient to allow sufficient beam exposure time to achieve 2,000 CPS, as the peak intensity is slight].

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

[0198] <Expression 2> JPEG0007920436000001.jpg25116

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

[0200] Manufacturing Example 1: Production of Para-Aramid Fibers A spinning dope was prepared by dissolving PPTA-1 obtained in Synthesis Example 1 in 99.8% by weight sulfuric acid at a concentration of 19% by weight relative to the total weight of the spinning dope.

[0201] The aforementioned spinning dope was spun at a speed of 650 m / min through a spinneret with 133 holes, and then solidified in a solidification tank after passing through an air gap to produce a filament.

[0202] The solidified series of filaments were washed with water to remove any remaining sulfuric acid, etc., on them, then dried and wound up to obtain para-aramid fibers with a monofilament fineness of 1.47 de and a total fineness of 213 de.

[0203] Manufacturing Example 2: Production of Para-Aramid Fibers A spinning dope was prepared by dissolving PPTA-1 obtained in Synthesis Example 1 in 99.8% by weight sulfuric acid at a concentration of 19% by weight relative to the total weight of the spinning dope.

[0204] The aforementioned spinning dope was spun at a speed of 620 m / min through a spinneret with 665 holes, and then solidified in a solidification tank after passing through an air gap to produce a filament.

[0205] The solidified filament was washed with water to remove any remaining sulfuric acid, etc., from the filament, then dried and wound up to obtain a para-aramid fiber with a monofilament fineness of 1.43 de and a total fineness of 988 de.

[0206] Manufacturing Example 3: Production of Para-Aramid Fibers A spinning dope was prepared by dissolving PPTA-1 obtained in Synthesis Example 1 in 99.8% by weight sulfuric acid at a concentration of 20% by weight relative to the total weight of the spinning dope.

[0207] The aforementioned spinning dope was spun at a speed of 600 m / min through a spinneret with 665 holes, and then solidified in a solidification tank after passing through an air gap to produce a filament.

[0208] The solidified filament was washed with water to remove any remaining sulfuric acid, etc., on it, then dried and wound up to obtain a para-aramid fiber having a monofilament fineness of 1.50 de and a total fineness of 1022 de.

[0209] Manufacturing Example 4: Production of Para-Aramid Fibers A spinning dope was prepared by dissolving PPTA-1 obtained in Synthesis Example 1 in 99.8% by weight sulfuric acid at a concentration of 19% by weight relative to the total weight of the spinning dope.

[0210] The aforementioned spinning dope was spun at a speed of 650 m / min through a spinneret with 1000 holes, and then solidified in a solidification tank after passing through an air gap to produce a filament.

[0211] The solidified filament was washed with water to remove any remaining sulfuric acid, etc., and then dried and wound up to obtain a para-aramid fiber having a monofilament fineness of 1.54 de and a total fineness of 1550 de.

[0212] Comparative manufacturing example 1: Manufacturing of para-aramid fibers A spinning dope was prepared by dissolving PPTA-2 obtained in Synthesis Example 2 in 99.8% by weight sulfuric acid at a concentration of 19% by weight relative to the total weight of the spinning dope.

[0213] The aforementioned spinning dope was spun at a speed of 600 m / min through a spinneret with 1000 holes, and then solidified in a solidification tank after passing through an air gap to produce a filament.

[0214] The solidified filament was washed with water to remove any remaining sulfuric acid, etc., and then dried and wound up to obtain a para-aramid fiber with a monofilament fineness of 1.49 de and a total fineness of 1527 de.

[0215] Furthermore, since the physical properties of PPTA-2 obtained in Synthesis Example 2 were inferior when the spinning speed was the same as in Production Example 4, it was manufactured to have the same level of fineness as the para-aramid fiber in 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] *The crystal sizes in Table 1 above refer to the crystal size based on the (110) plane and the crystal size based on the 200 plane, and the orientation angles refer to the orientation angles based on the (110) plane and the orientation angles based on the (200) plane.

[0218] Referring to Table 1 above, it can be confirmed that para-aramid fibers according to one embodiment of this application can be provided as high-quality para-aramid fibers of various grades by being formed from para-aramid polymers produced by controlling the input conditions and methods of the reaction raw materials, using reaction raw materials from which impurities have been removed.

[0219] Specifically, comparing Production Examples 1, 2, and 4, which provide standard tenacity para-aramid fibers with a strength of approximately 20-24 g / d, with Comparative Production Example 1, it can be confirmed that Production Examples 1, 2, and 4 exhibit larger crystal sizes, higher crystallinity, and higher orientation compared to Comparative Production Example 1, and also have superior Young's modulus.

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

[0221] Experiment 2: Code Manufacturing and Physical Property Evaluation Para-aramid filament yarn was manufactured using the same process as described in Experiment 1 and the comparative manufacturing example, and its total fineness was controlled to a similar level of 1000 (±50 or less) denier. Each of the manufactured para-aramid filament yarns was fed into a cable cord twisting machine (Allma's Cable Cord) together with 840 denier nylon filament yarn, and two-ply cabled yarn (low cord) was manufactured by simultaneously performing Z-direction under-twisting and S-direction over-twisting. At this time, the cable cord twisting machine was set to a twist count of 360 TPM (twists per meter) for under-twisting and over-twisting, and by adjusting the tension applied to the nylon filament yarn and the para-aramid filament yarn respectively, the ratio of the length of the para-aramid single yarn (under-twisted yarn) to the length of the nylon single yarn (under-twisted yarn) in the cabled yarn (low cord) was controlled (= the length of the para-aramid single yarn (L A ) / Length of nylon single yarn (L N The ratio was set to 1.01. At this time, in order to determine the length ratio of para-aramid single yarn and nylon single yarn, a 1m long plied yarn (raw cord) sample was subjected to a load of 0.05 g / d to untwist the upper twist, separating the para-aramid single yarn and nylon single yarn from each other. Then, the lengths of the para-aramid single yarn and nylon single yarn were measured, respectively, while the load of 0.05 g / d was applied. The raw cord manufactured as described above contains approximately 40-50% by weight of a first under-twist yarn (containing para-aramid fibers) and approximately 50-60% by weight of a second under-twist yarn (containing nylon fibers).

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

[0223] The characteristics of the dipped cord manufactured as described above were measured and are shown in Table 2.

[0224] (1) Crystal size and crystallinity of the (110) and (200) plane-based para-aramid undertwisted yarns included in the dip cord. Para-aramid undertwisted yarn was separated from the dip cord, and the crystalline properties of the para-aramid undertwisted yarn were measured in the inner portion that was not coated with the coating solution, using the same method as for measuring the microstructure of the raw yarn described in Experiment 1.

[0225] (2) Creep rate of dipcodes (Creep Strain (%)) According to ASTM D885, the dip cord sample was left for 24 hours under constant temperature and humidity conditions (temperature: 20±2°C, humidity: 65±5% based on ASTM D885). Following this, the cord underwent a pretreatment (drying) by applying a temperature of 180°C and a load of 0.01 g / d for 15 minutes. This pretreatment was performed to ensure reproducible measurement of creep strain (%) in the case of dissimilar fiber components (e.g., nylon), as they can deform due to moisture.

[0226] Following this process, creep evaluation was performed on the hybrid dipped cord using the ASTM D2990 method, and the creep strain (%) over time was measured. 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 applied load (longitudinal direction) was measured (creep strain (CCreep Strain) (%) after 24 hours).

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

[0228] [Table 2]

[0229] Referring to Table 2 above, it can be seen that the codes of Examples 1 to 4, which include para-aramid fibers having a large crystal size and high crystallinity and excellent mechanical properties, have a lower creep rate and greater resistance to deformation against external forces compared to Comparative Example 1.

Claims

1. A first under-twisted yarn formed by twisting a para-aramid fiber having a crystallinity of 67% or more, a crystal size of 5.8 to 7.0 nm relative to the (110) plane, an orientation angle of 2° to 12° relative to the (110) plane, an orientation angle of 2° to 13° relative to the (200) plane, a total fineness of 200 to 1600 denier, and a tensile strength of 22 g / d or more; and a second under-twisted yarn formed by twisting a different type of fiber from the para-aramid fiber; are twisted together to form this yarn. The coating layer formed on the first and second under-twisted yarns further comprises The para-aramid fibers contained within the cord on which the coating layer is formed have a crystallinity of 72% or more, and a crystal size of 7.2 to 10.0 nm relative to the (110) plane. The aforementioned code satisfies the creep strain of 3.0% or less.

2. The code according to claim 1, wherein the aforementioned different fibers include nylon fibers or polyester fibers.

3. The first under-twisted yarn is an under-twisted yarn in which the para-aramid fiber is given a twist of 250 to 600 TPM. The cord according to claim 1, wherein the second under-twisted yarn is an under-twisted yarn in which the different fibers are given a twist of 250 to 600 TPM.

4. The cord according to claim 1, wherein the cord is formed by twisting a first under-twisted yarn and a second under-twisted yarn with a twist count of 250 to 600 TPM.

5. The steps include: preparing para-aramid fibers having a crystallinity of 67% or more, a crystal size of 5.8 to 7.0 nm relative to the (110) plane, an orientation angle of 2° to 12° relative to the (110) plane, an orientation angle of 2° to 13° relative to the (200) plane, a total fineness of 200 to 1600 denier, and a tensile strength of 22 g / d or more; and A step of forming a cord which is a combined twisted yarn by twisting together a first under-twisted yarn formed by twisting the para-aramid fiber and a second under-twisted yarn formed by twisting a different type of fiber than the para-aramid fiber; and, The step includes forming a coating layer on the aforementioned twisted yarn, The step of preparing the para-aramid fibers is as follows: The process 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 diacid halide to the reactor containing the slurry in three or more installments and reacting them to form a para-aramid polymer; and spinning a spinning dope containing the para-aramid polymer to produce fibers. The method for producing the code according to claim 1, wherein, in the step of forming the polymer, the temperature difference of the cooling water at the inlet and outlet for cooling the reactor during the primary and secondary addition of the aromatic diacid halide is controlled to be within 50°C.

6. The method for manufacturing a cord according to claim 5, wherein the dissimilar fibers include nylon fibers or polyester fibers.

7. The first under-twisted yarn is produced by giving the para-aramid fiber a twist of 250 to 600 TPM. The method for manufacturing a cord according to claim 5, wherein the second under-twisted yarn is produced by giving the aforementioned different fibers a twist of 250 to 600 TPM.

8. The method for manufacturing a cord according to claim 5, wherein the first under-twisted yarn and the second under-twisted yarn are twisted together with a twist count of 250 to 600 TPM to form the cord.

9. The method for producing a cord according to claim 5, wherein the step of filtering the reaction raw material to remove impurities includes filtering the reaction raw material using a filter with a diameter of 0.01 to 1.0 μm.

10. The method for producing code according to claim 5, wherein the stirring speed of the reactor is adjusted to 10 to 1000 rpm when the aromatic diacid halide is added as a secondary agent.

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