Hybrid cord and method for manufacturing hybrid cord

Abstract

The present invention provides a method for manufacturing a hybrid cord, the method comprising the steps of: preparing a high-strength fiber and a thermoplastic fiber; co-twisting the high-strength fiber and the thermoplastic fiber by a direct cabler to produce a raw cord; and thermally treating the raw cord to manufacture a dip cord, wherein the high-strength fiber has a yarn strength of 15 g / d or more and a cutting elongation of less than 10%, and the thermoplastic fiber has a yarn strength of 5 g / d to 10 g / d, a melting temperature of 220°C or higher, and a cutting elongation of 12% or more.

Description

Hybrid code and method of manufacturing hybrid code

[0001] The present invention relates to a method for manufacturing a hybrid capply reinforcement material by applying different modulus ratios for each section of a hybrid capply reinforcement material of high modulus-low modulus fibers and reflecting characteristic manufacturing conditions and physical property conditions, and more specifically, to an efficient, uniformly improved, high-performance pneumatic radial tire using the hybrid capply reinforcement material.

[0002]

[0003] Until now, aramid hybrid cap ply reinforcement materials used as reinforcing belts in high-performance tires have been applied based on the ratio of initial modulus and modulus at break.

[0004] Representative prior patents related to the aramid hybrid mentioned above include Sumitomo Rubber Tokukaihei 01-247204 and Michelin's US 7,222,481, both of which define only the initial modulus and the final modulus.

[0005] In theory, the initial modulus is defined as the slope of the tangent line when the strain is 0 in the stress-strain curve. However, when drawing a tangent line at point 0 in the measurement graph of an actual tire cap ply reinforcement (hereinafter referred to as “cord”), a problem occurs in which a very low slope is obtained. To prevent this, a specific section must be determined and the tangent (tan α) slope value must be obtained, but the section for this is not mentioned in the above literature.

[0006] In fact, it is not clear whether the slope of the tangent line at strain 0 can accurately represent the initial modulus value under the superload condition of 0.5 cN / tex or 0.05 g / d in a general tensile test, and in the existing superload condition or micro-displacement section, the stress is not evenly distributed due to the structural characteristic of insufficient focusing force below a certain load of the fiber bundle forming the cord, and structural deformation occurs in which the focusing force of the filaments is enhanced, so it seems that there are many insufficient parts in defining the initial modulus of the material under superload conditions in a tensile test.

[0007] Due to this phenomenon, the modulus in the initial microsection has a lower value than the originally desired characteristic value, and in fact, when a tensile test is performed with only the aramid cord under the initial load condition of 0.05 g / d and the slope of the tangent line at the origin, i.e. the initial modulus, is obtained in the microsection from the origin, the ratio with the final modulus may sometimes be as high as 1:10, which may be an undesirable result.

[0008] To resolve these errors, this patent conducts a tensile test by applying an initial load twice that of the existing one, and defines the initial modulus as the tangent line at the strain of 0 at this time. By defining the initial load at this time as 0.10 g / d, the patent seeks to define the initial modulus that can represent the overall material characteristics.

[0009] Furthermore, Michelin's aramid hybrid cord manufacturing technology is applied to tires by twisting and heat-treating the yarn so that the ratio of the initial modulus to the final modulus is 10 or more.

[0010] Specifically, it is common to use bundles of aramid fibers of 900 to 2,000 denier and bundles of polyamide 66 fibers of 700 to 1,500 denier by twisting them together at 1 to 2 plies each, and by giving different twists to the aramid yarn and nylon yarn, so that the polyamide 66 yarn is structurally composed as a core and the aramid yarn as a covering. At this time, in order to manufacture nylon as a core and aramid as a covering, the twist of the aramid yarn must be given relatively more than that of the nylon, or even the twist of the nylon must be given in the opposite direction to that of the aramid.

[0011] The above-described method has the disadvantage of being difficult to manufacture using a direct cabler method, and since a ring twister must be used, the manufacturing time is long and the process loss is large, and in order to maintain the core-covering structure formed during the above-described double-twisting process, the tension must be very low during subsequent dipping and heat treatment.

[0012] The aramid-polyamide 66 hybrid cord obtained in this way has a ratio of the initial modulus to the modulus at break of 10 or more, and at this time, an inflection point (transition point) due to the difference between the initial modulus and the final modulus exists at a tensile strain of 0.01 to 0.07.

[0013] Figure 1 shows a stress-strain curve of an aramid-polyamide 66 hybrid cord manufactured by the above-described method.

[0014] Referring to the above drawing 1, the initial modulus (E initial ) is 14 gf / d, and the final modulus (E terminal) is 257 gf / d, and the ratio of the initial modulus to the final modulus is 18.3. However, since fiber materials such as textile cords are not solid but rather a collection of thin fibers, there may be a very large error in measurement, so it is insufficient to simply limit the physical properties to the ratio of the initial modulus to the final modulus.

[0015] In addition, in the aramid-polyamide 66 hybrid cord, an excessively low initial modulus has the disadvantage of causing product-to-product variation in subsequent processes including the rolling process, and if the tension is artificially lowered during the heat treatment process of the cord to have a low initial modulus, there is also the problem of increasing the variation in the physical properties of each cord.

[0016] The early part of the stress-strain curve has a low initial modulus for ease of manufacturing, which is relatively too low compared to the process conditions, so it can easily be deformed when subjected to tensile force in the direction of the code axis during the process, which can have disadvantages in terms of dimensional stability during the manufacturing process, and the difference in physical properties between codes that occurs during the code manufacturing process can also have disadvantages in that it can affect the uniformity and dimensions of the finished tire.

[0017] Meanwhile, Korean Patent No. 10-1580352 describes a hybrid aramid and nylon in which the twists of the aramid and nylon yarns are identical. However, when measured using testing methods corresponding to ASTM D885 and D1423, the twist count varies depending on the length change of the nylon during heat treatment, even if the same number of turns is reflected during manufacturing.

[0018] In other words, it is extremely difficult for aramid and nylon of Hayeon to have the same twist number measurement value based on the dip cord, and it is also difficult to numerically define what it means to have the same twist number.

[0019] The ASTM D1423 test method reflects the following equation 1 for both the upper and lower edges:

[0020] [Formula 1]

[0021]

[0022] In the above formula,

[0023] T is the number of twists (twists per unit length),

[0024] R is the number of twist turns in the meter,

[0025] L represents the initial length when measured before the sea level rise.

[0026] In the case of aramid hybrid, if the same length of yarn is spun using a direct cabler and then weaved and heat-treated to produce a hybrid cord, the following errors may occur.

[0027] When inputting, both aramid and nylon are input with the same length and number of turns, so after the first twist, the number of turns in the second twist is the same. However, after the actual first twist, the initial length of each aramid and nylon changes differently when measuring the second twist.

[0028] Aramid does not shrink under heat, but nylon shrinks under heat, so when actually measured, the L value of nylon will be shorter, and when measured according to the ASTM D1423 mentioned above, the twist number of nylon may be higher. On the other hand, if excessive tension is applied during heat treatment so that the aramid goes to the core and the nylon covers the outside, the L value of nylon will increase, so the twist number may be lower.

[0029] Since these characteristics are well-known facts that arise when setting the properties of the final Dip fabric, it is difficult to judge whether they improve the performance of any tire or improve manufacturability.

[0030] In addition, Korean Patent No. 10-1353700 discloses that the difference between the elongation at break of a high modulus aramid and the elongation at break of nylon afterward is within 3% when the manufactured hybrid cord is tensile broken, and Korean Patent No. 10-1602605 discloses that when aramid and nylon are simultaneously twisted through a direct cabler, the lengths of the inputs are different, and the lengths of the hybrid tire cords manufactured afterward are also different, but none of these can be said to be unique manufacturing processes developed to improve tire performance.

[0031] There is a need for a method for manufacturing a hybrid cord that secures stable aramid hybrid properties, is efficient, and has improved uniformity when applied to radial tires.

[0032] <Prior Art Literature>

[0033] Republic of Korea Patent No. 10-0668633

[0034]

[0035] In order to solve the above problem, one aspect of the present invention provides a method for manufacturing a hybrid cord, comprising the steps of: preparing a high-strength fiber and a thermoplastic fiber; twisting the high-strength fiber and the thermoplastic fiber with a direct cabler to manufacture a raw material cord; and heat-treating the raw material cord to manufacture a dip cord; wherein the high-strength fiber has a yarn strength of 15 g / d or more and a breaking elongation of less than 10%, and the thermoplastic fiber has a yarn strength of 5 to 10 g / d, a melting temperature of 220°C or more, and a breaking elongation of 12% or more.

[0036] In addition, one aspect of the present invention provides a hybrid capply reinforcement (hereinafter referred to as “hybrid cord”) manufactured by the method for manufacturing the hybrid cord.

[0037] In addition, one aspect of the present invention provides a pneumatic radial tire including the hybrid code.

[0038] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0039]

[0040] One aspect of the present invention provides a hybrid cord characterized by including: a thermoplastic fiber disposed in a core and having a yarn strength of 5 g / d to 10 g / d and a breaking elongation of 12% or more; and a high-strength fiber covering the thermoplastic fiber and having a yarn strength of 15 g / d or more and a breaking elongation of less than 10%.

[0041] In one embodiment of the present invention, the high-strength fiber may be composed of one or more of PPTA, wholly aromatic polyester, and PPTA / DPE.

[0042] In one embodiment of the present invention, the thermoplastic fiber may be composed of at least one of polyamide and polyester.

[0043] In one embodiment of the present invention, the density ratio of the thermoplastic fiber to the high-strength fiber may be 1:0.78 to 1:0.96.

[0044] In one embodiment of the present invention, the draw ratio of the thermoplastic fiber may be 5.4 to 5.8.

[0045] In one embodiment of the present invention, a fiber having a strength of 11 g / d or more, a twist coefficient of 250 to 500 TPM, and expressed by the following equation 2 (α) d ) can have 140 to 210.

[0046] [Formula 2]

[0047]

[0048] (In the above formula, is the twist coefficient based on denier, and T is TPM (Twist per meter). is the quantitative fineness in denier units of the hybrid code)

[0049] In one embodiment of the present invention, a modulus transition point exists at a strain of 0.01 to 0.03, the modulus in a region before the modulus transition point is 30 to 70 g / d, and the modulus in a region after the modulus transition point can reach a saturation region at a level of 150 to 250 g / d.

[0050] One aspect of the present invention provides a pneumatic radial tire characterized by including a hybrid cord.

[0051] One aspect of the present invention comprises the steps of: preparing the high-strength fiber and the thermoplastic fiber; twisting the high-strength fiber and the thermoplastic fiber with a direct cabler to produce a raw cord; and heat-treating the raw cord to produce a dip cord.

[0052] In one embodiment of the present invention, in the step of manufacturing the raw code, the high-strength fiber may be introduced at an introduction length of 0.99 to 1.015 compared to the thermoplastic fiber.

[0053] In one embodiment of the present invention, in the step of manufacturing the raw code, the high-strength fiber may be placed on the pot yarn of the direct cable, and the thermoplastic fiber may be placed on the creel yarn of the direct cable.

[0054] In one embodiment of the present invention, the thermal shrinkage rate of the raw code may be 2.5 to 6%.

[0055] In one embodiment of the present invention, the step of heat-treating the raw cord to manufacture a dip cord may be performed so that the dip cord shrinks by 0.5 to 3% compared to the raw cord.

[0056]

[0057] The method for manufacturing a hybrid cord according to the present invention can improve the manufacturability of the hybrid cord and the processability of the tire, thereby resolving differences in tire performance such as deviations in the physical properties of the hybrid cord, uniformity, and driving performance, thereby improving the performance of the tire.

[0058] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the composition of the invention described in the claims.

[0059]

[0060] Figure 1 is a stress-strain curve of a conventional aramid hybrid cord.

[0061] Figure 2 is a flowchart of a hybrid code manufacturing method of the present invention.

[0062] Figure 3 is a Stress-Strain curve of a hybrid code according to one embodiment of the present invention.

[0063] Figure 4 is a stress-strain curve of a hybrid code of one embodiment of the present invention.

[0064] FIG. 5 is a schematic cross-sectional view of a radial tire according to one embodiment to which the eco-friendly hybrid code of the present invention can be applied.

[0065]

[0066] A most preferred embodiment of the present invention comprises: a thermoplastic fiber disposed in a core, having a yarn strength of 5 g / d to 10 g / d and a breaking elongation of 12% or more; and a high-strength fiber covering the thermoplastic fiber, having a yarn strength of 15 g / d or more and a breaking elongation of less than 10%.

[0067]

[0068] Hereinafter, the present invention will be described with reference to the attached drawings. However, the present invention can be implemented in various different forms and is therefore not limited to the embodiments described herein. In the drawings, irrelevant parts have been omitted for clarity of description, and similar parts have been designated with similar reference numerals throughout the specification.

[0069] Throughout the specification, when a part is said to be "connected (connected, contacted, joined)" to another part, this includes not only cases where it is "directly connected," but also cases where it is "indirectly connected" with another part in between. Furthermore, when a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0070] The terminology used herein is merely used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0071] In this application, the term "hybrid cord" means a composite cord composed of two or more materials with different properties.

[0072] As used herein, the term "core yarn" refers to a single yarn positioned in the core of a hybrid cord. As used herein, the term "covering yarn" refers to a single strand or multiple strands of yarn wound around the core yarn.

[0073] In this paper, twisting yarn or filaments in a counterclockwise direction is called Z-twist, and twisting yarn or filaments in a clockwise direction is called S-twist.

[0074] The single yarn produced by twisting filaments in this invention is called "cabled yarn", and "cabled yarn" means a yarn produced by twisting two or more single yarns together in one direction.

[0075] In this application, the “initial modulus” of the hybrid code refers to the slope of the tangent line at the origin after the initial load is applied.

[0076] In this application, the “intermediate modulus” of the hybrid code means the modulus at the point where the tangent slope of the stress-strain curve of the hybrid code decreases from the initial modulus section and then begins to increase.

[0077] In this application, the “final modulus” of a hybrid cord is defined as the slope of the tangent line in the stress-strain curve of the hybrid cord that matches the elongation corresponding to the breakage of the cord.

[0078] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0079]

[0080] Conventional aramid-polyamide 66 hybrid cords have a problem in manufacturing cords because they maintain a very low initial modulus in order to achieve a high ratio of initial modulus to final modulus, which is a characteristic, and thus increase manufacturing costs.

[0081] For example, when a structure is formed in which polyamide 66 yarn is positioned in the core and an aramid yarn covers it, a method is generally used in which the twist number (ply twist) of each ply is different in the twisting machine and the tension is almost eliminated during the heat treatment process after dipping, thereby inducing self-shrinkage of the polyamide 66 to manufacture an aramid-polyamide 66 cord of a core-covering structure. However, since the overall process must proceed without tension, there is a disadvantage in that a very slow process speed must be maintained, and there is a large deviation in the physical properties, such as the intermediate elongation of each cord strand.

[0082] Additionally, very low initial modulus makes it difficult to maintain uniform properties during the rolling process and cutting / molding process that apply tensile force during the tire manufacturing process, which can ultimately have a negative impact on the uniformity of physical properties of the tire.

[0083] In addition, in order to easily and efficiently manufacture para-aramid-nylon 66 hybrid cords, a method of using general nylon 66 yarn and para-aramid by direct cable twisting is being widely used. However, in this case, there is a disadvantage that the initial modulus of the SS curve may become excessively high.

[0084] In particular, in the case of deep cords manufactured by twisting a hybrid cord using a direct cabler such as Allma CC4 and then heat-treating it after weaving, if the number of twists of each aramid and nylon 66 ply is the same in the top twist and the bottom twist, a complete core-covering structure is not realized between the nylon and the aramid, and they have an equal twist path. In this case, the modulus in the early and mid-stages becomes excessively high, which has the disadvantage that the belt lift ratio, which increases the circumference of the belt section during the vulcanization process of tire manufacturing, must be increased only to a very limited extent. If the belt lift ratio exceeds 2%, the probability of non-conformity may actually increase significantly.

[0085] To achieve the same stable belt lift rate (typically 2.5 to 4%, strain 0.025 to 0.04) as tires using conventional nylon cap plies, the modulus must be kept low, at least to around 3%.

[0086] As described above, when the twist number of aramid and nylon 66 is the same as in Korean Patent Nos. 10-1580352 and 10-1740769, excessive tension is applied at low elongation, which may cause defects during tire manufacturing.

[0087] Therefore, the strain ranges of the hybrid code (0.01-0.02), 0.02-0.04, and subsequent strain ranges must be evaluated separately, and a nonlinear approach must be adopted. Furthermore, the above-mentioned prior art fails to specify the more important manufacturing conditions for nylon yarn and the application conditions for direct cablers.

[0088]

[0089] To solve the above-described problem, one aspect of the present invention provides a method for manufacturing a hybrid code.

[0090] Figure 2 is a flowchart of a method for manufacturing a hybrid code of the present invention.

[0091] *Referring to FIG. 2, the method for manufacturing a hybrid cord of the present invention includes a step of preparing high-strength fibers and thermoplastic fibers (S10); a step of twisting the high-strength fibers and thermoplastic fibers with a direct cabler to manufacture a raw cord (S20); and a step of heat-treating the raw cord to manufacture a dip cord (S30).

[0092] In addition, the high-strength fiber may have a yarn strength of 15 g / d or more and a breaking elongation of less than 10%, and the thermoplastic fiber may have a yarn strength of 5 g / d to 10 g / d, a melting temperature of 220°C or more, and a breaking elongation of 12% or more.

[0093] In one embodiment of the present invention, the high-strength fiber may be composed of one or more of PPTA, wholly aromatic polyester, and PPTA / DPE, and the thermoplastic fiber may be composed of one or more of polyamide and polyester.

[0094] In one embodiment of the present invention, the high-strength fiber may be a high-strength / high-strength super fiber such as para-aramid (trade names Kevlar, Twaron, Heracron, Alkex, etc.), DPE / PPTA (trade name Technora), or wholly aromatic liquid crystal polyester (trade name Vectran, etc.), and the thermoplastic fiber may be a polyamide (nylon 66, nylon 6, nylon 56, nylon 46, nylon 410) or polyester (polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene furanoate, etc.).

[0095] In one embodiment of the present invention, the high-strength fiber may be a para-aramid, for example, poly p-phenyleneterephtalamide (PPTA) which has the property of exhibiting liquid crystals at a specific concentration of a solution dissolved in concentrated sulfuric acid and which can be obtained through wet spinning.

[0096] In one embodiment of the present invention, the high-strength fiber may be DPE / PPTA (Co-poly 3,4'-diphenylether / para-phenylene therephtalate), which is one of aromatic polyamides, which has an isotropic property rather than a liquid crystal property when dissolved in a solvent, and has a property of developing a microstructure by stretching more than 10 times during a heat treatment process after wet spinning.

[0097] In one embodiment of the present invention, the high-strength fiber may be a wholly aromatic polyester (poly arylate) having thermotropic liquid crystal properties and being a high-strength fiber obtained through melt spinning.

[0098] In one embodiment of the present invention, it may be preferable to use the thermoplastic fiber as an aliphatic polyamide series or a semi-aromatic polyester (typically polyethylene terephthalate).

[0099] The materials described above can be hybridized to perform their respective roles in tires.

[0100] In passenger car and light truck tires, it is desirable to use a material with a high modulus on a steel belt to suppress changes in driving stability due to changes in the contact area and increased ground clearance caused by an increase in the circumference of the tire tread due to centrifugal force during high-speed driving.

[0101] However, looking at the current tire manufacturing process, the circumference or diameter of the green tire must be smaller than the circumference or diameter of the mold in order for the tire to be manufactured smoothly, so there are problems that make tire manufacturing impossible when high-strength, high-modulus materials such as para-aramid are used solely as cap ply.

[0102] To solve these problems, it was common in the past to manufacture hybrid cords in a two-step process using ring twisters, etc., but in this case, as described above, there were the disadvantages of the hybrid cord's physical properties becoming uneven (the physical property deviation becoming large), the initial modulus becoming too low, making it difficult to express the characteristics of high-strength materials such as aramid even under design conditions with a belt lift rate of about 4%, and the manufacturing process becoming complicated.

[0103] The methods disclosed in Korean Patent No. 10-1580352 or 10-1740769, which are intended to improve these shortcomings, also had unrealistic differences, such as an initial modulus that was too high and a value that was different from the physical properties or characteristic values ​​of the hybrid cord to be actually used.

[0104] In addition, Korean Patent No. 10-1353700 discloses a hybrid cord prepared so that, in the load-tensile curve of the tensile test result of the hybrid cord, the high-strength, high-elasticity fiber ply (aramid) breaks first, and the thermoplastic fiber ply (nylon 66) breaks within 3% from that point. However, this is an area that is already sufficiently achievable with existing technology, and when using the aramid hybrid cord for the cap ply of a tire, the high-strength, high-elasticity fiber ply loses its original function at the point where the breakage occurs, so it cannot be regarded as a necessary condition for achieving the performance of a high-performance tire in relation to tire performance. For example, when thermoplastic fibers are plied, the breaking elongation of the thermoplastic fibers may be expressed very effectively, so that the high-strength fibers may break together, or the breaking may occur first due to the core-covering structure. Conversely, if the thermoplastic fibers have a very high breaking elongation, the breaking of the thermoplastic fibers may occur 3% after the breaking of the high-strength, high-elasticity fibers. However, since this is a safety factor issue that already exceeds the performance range of the tire, it is difficult to link it to performance.

[0105] The present invention seeks to improve the above-described points and to improve the method of hybridizing a high-strength, high-modulus (high-elasticity) fiber material with a general-purpose thermoplastic fiber such as nylon and polyester so that it can be an effective method for actual tires.

[0106] In one embodiment of the present invention, the high-strength fiber may be 800 to 2,000 denier, the thermoplastic fiber may be 800 to 2,000 denier, and the thermoplastic fiber may have a draw ratio of 5.4 to 5.8.

[0107] In one embodiment of the present invention, when the high-strength fiber is an aramid fiber and the thermoplastic fiber is nylon 66, the density of the aramid fiber is 1.40, the density of the nylon 66 is 1.15, and the nylon corresponding to the same thickness as 1500 denier of aramid is 1260 denier.

[0108] From this perspective, the cross-sectional area (actual thickness, or volume, not linear density) of high-strength, high-elasticity fibers represented by aramid and the thickness of thermoplastic fibers represented by nylon 66 are prepared by matching them 1:1.

[0109] If possible, the actual thickness should be similar to each other by 95% or less, and in this case, the direct cable can be used to smoothly perform the transmission.

[0110] In the case of aramid fibers, the properties of commercially available products have already been defined, so they will not be discussed separately. However, it is preferable to use a product that is relatively fatigue-friendly, such as Dupont's Kevlar 29 AP.

[0111] Additionally, in the case of nylon 66 to be used as a thermoplastic fiber, it is possible to obtain different physical properties through processes such as spinning. The draw ratio of nylon 66 for general tire cords is set at approximately 5.1 to 5.5, but in this technology, the draw ratio of nylon 66 is set at 5.4 to 5.8, resulting in a characteristic in which the heat shrinkage rate is greater than that of nylon 66 manufactured using conventional methods.

[0112] Due to these characteristics, the hybrid raw material cord (filament) manufactured with direct cable has the advantage of being able to shrink more during the subsequent heat treatment process and being able to be manufactured uniformly with nylon as the core and aramid as the covering.

[0113] In one embodiment of the present invention, the heat shrinkage rate of the raw code may be 2.5% to 6%.

[0114] If the heat shrinkage rate of the raw code is less than 2.5%, it is difficult for the structure to be expressed as nylon as the core and aramid as the covering during the heat treatment process. If the heat shrinkage rate exceeds 6%, the core-covering structure may appear unevenly during the heat treatment process, which may cause unevenness in the physical properties.

[0115] In one embodiment of the present invention, the step (S20) of manufacturing a raw cord by twisting the high-strength fiber and the thermoplastic fiber with a direct cabler may be performed by placing the high-strength fiber on the pot yarn of the direct cabler and placing the thermoplastic fiber on the creel yarn of the direct cabler.

[0116] In direct cablers, the mounting position of the bobbins of high-strength fibers and thermoplastic fibers is also very important.

[0117] In one embodiment of the present invention, aramid can be installed as a pot yarn and nylon 66 can be installed as a creel yarn to perform a double twisting process.

[0118] In direct cablers, the port yarn position is characterized by the formation of large balloons and the application of twist. Because the centrifugal force generated by the balloons can cause changes in the port yarn's length before it meets the krill yarn in the regulator and is braided, it is recommended to use a high-modulus aramid for the port yarn.

[0119] Furthermore, when comparing the twisting process between krill and port yarns, krill yarns are twisted by applying a lot of friction in the regulator of the direct cabler, whereas port yarns are twisted by forming balloons and generate relatively less friction. In this case, if aramid is used in the krill yarn location where friction is high, a relatively uneven twist state can be obtained. Therefore, aramid is applied to port yarns and nylon is applied to krill yarns for twisting.

[0120] In one embodiment of the present invention, the step (S20) of manufacturing a raw material cord by twisting the high-strength fiber and the thermoplastic fiber with a direct cabler may be such that the high-strength fiber is inserted at an insertion length of 0.99 to 1.015 relative to the thermoplastic fiber.

[0121] In one embodiment of the present invention, when the insertion length of the high-strength fiber is less than 0.99 compared to the thermoplastic fiber, there is a disadvantage in that it is difficult to secure the configuration of a hybrid cord having the thermoplastic fiber as a core, and when the insertion length of the high-strength fiber exceeds 1.015, the properties of the hybrid cord may become uneven.

[0122] Due to the nature of direct cablers, the number of turns for port yarn and krill yarn can be given the same value, but after the dip cord is manufactured, a difference in the number of turns in the actual under-twisting may occur due to the change in the length of the thermoplastic fiber. Therefore, it is meaningless to limit the number of twists of thermoplastic fiber and high-strength fiber in the under-twisting process and in the hybrid raw cord before heat treatment (dipping). In addition, it is impossible to give different numbers of turns to port yarn and krill yarn due to facility limitations, so no separate meaning is intended for the process.

[0123] That is, a suitable Z-direction twist can be applied to a bundle of high-strength, high-modulus fibers such as aramid, which have tensile properties close to a straight line and a very high initial modulus, and the same twist can be applied to a thermoplastic fiber including polyamide 66, which has a low initial modulus, and the yarn can be spun with a direct cabler.

[0124] The method for manufacturing a hybrid cord of the present invention includes a step (S30) of manufacturing a dip cord by heat treating a raw cord.

[0125] The step (S30) of manufacturing the above deep code may be performed after the raw code is subjected to a weaving process, or may be manufactured as a single-end code.

[0126] Therefore, in one embodiment of the present invention, a weaving step may be further included before the step of manufacturing the deep code (S30).

[0127] The Dip system used in the step (S30) of manufacturing the above-described deep code of the present invention is not limited to anything obvious in the technical field of the present invention.

[0128] However, in the case of high-strength / high-elasticity materials such as aramid, it is generally not easy to simply bond with RFL (resorcinol formaldehyde latex), so it is common to use a 2-dip method in which an epoxy first dip is applied using epoxy such as various polyglycidyl ethers from Nagase and Caprolactom blocked diisocyanate such as IL-6 from Grilbond, and then a novolac-series or resol-series RF resin and latex are mixed, but the solids ratio is prepared at about 1:5, and an RFL aqueous solution with basic properties of about pH 9.0 to 11 is applied and heat-treated in the second step.

[0129] In one embodiment of the present invention, the step (S30) of manufacturing a dip cord by heat-treating a raw cord may be performed by adjusting the heat treatment process conditions, such as 3 T (Tesnion, Time, Temp), to suit the heat treatment equipment, so that the resulting hybrid cord raw cord shrinks by 0.5 to 3%.

[0130] It is desirable to make the length of the dip cord shorter by about 0.5 to 3% compared to the input length during the heat treatment process. This is because, as described above, by using a direct cabler using a thermoplastic fiber with a slightly increased elongation, the core-covering structure is not expressed at all in the raw cord state, and after the heat treatment, the thermoplastic fiber can be configured as a core and the high-strength fiber as a covering in a similar manner through shrinkage of the thermoplastic fiber.

[0131] The hybrid cord of the present invention manufactured using the above-described method is preferably in the range of 250 to 500 TPM based on the deep cord, but considering that the twist coefficient varies depending on the quantitative fiber, the twist coefficient of the cable twist may be 140 to 210 according to the following equation 2:

[0132] [Formula 2]

[0133]

[0134] In the above formula, is the twist coefficient based on denier, T is TPM (Twist per meter), is the quantitative fineness in denier units of the hybrid code.

[0135] If the above twist coefficient is less than 140, the strength and processability may be reduced due to insufficient cord focusing power, and structural unevenness may occur during the heat treatment process in which thermoplastic fibers are expressed as the core and high-strength fibers as the covering.

[0136] On the other hand, if excessive twisting is performed with a twist coefficient exceeding 210, excessive fiber concentration may hinder the development of a core-covering structure through a heat treatment process, and a low final modulus value that is insufficient for developing cord strength and final modulus due to the excessive twist angle may result in unfavorable characteristics in terms of strength utilization.

[0137] In the case of the lower twist, for example, in direct cablers such as Saurer's Allma CC4, the twist of pot yarn and krill yarn cannot be significantly different, so there is no difference in the total number of turns. However, in the heat treatment process, the length of the thermoplastic fiber ply changes due to heat setting after shrinkage or tension of the thermoplastic fibers that make up the hybrid cord. Ultimately, when the twist number is measured based on the length before untwisting, as in ASTM D885 and D1423, the high-strength fibers and thermoplastic fibers that make up the lower twist (ply twist) will have different twist numbers.

[0138] In the present invention, as described above, the thermoplastic fiber shrinks, and a length shrinkage of 0.5 to 3.0% exists in the deep cord compared to the hybrid cord raw material, and the range can be limited through the test method of ASTM D1423.

[0139] For example, after untwisting the cable twist and cutting off the nylon portion, the initial length of the aramid ply twist can be reflected in the measurement, and after untwisting another cord, the aramid can be cut off, and the length of the remaining nylon 66 ply can be reflected in the initial length of the nylon ply twist.

[0140] The ASTM D1423 test method reflects the following equation 1 for both the upper and lower edges:

[0141] [Formula 1]

[0142]

[0143] In the above formula,

[0144] T is the number of twists (twists per unit length),

[0145] R is the number of twist turns in the meter,

[0146] L represents the initial length when measured before the sea level rise.

[0147] At this time, nylon and aramid were introduced with almost similar input lengths, but due to the shrinkage of nylon, the length of nylon becomes shorter, and as a result, as shown in the above equation 1 by D1423, at the same number of turns (R in equation 1), the initial length L becomes shorter in nylon than in aramid, so the twist number of the lower yarn must have a larger value in nylon.

[0148] According to the test measurement method according to ASTM D1423, the dip cord should be manufactured so that the twist count of the nylon ply is 0.5 to 3.0% higher than the twist count of the aramid ply.

[0149] Even if the above-described manufacturing method is applied, if the twist number of nylon 66 is lower than that of aramid or the difference is less than 0.5%, the initial modulus of the deep cord becomes too high, which is disadvantageous for processability during tire manufacturing, and if it exceeds 3%, excessive shrinkage of nylon is suspected, and in this case, there is a disadvantage that the section where the physical properties of aramid are expressed becomes too long, so when applied to tires, there is a disadvantage that it is ineffective in suppressing the increase in OD (overall diameter) during high-speed driving.

[0150] One aspect of the present invention provides a hybrid code manufactured by the above manufacturing method.

[0151] In one embodiment of the present invention, the hybrid cord has a strength of 11 g / denier or more relative to the quantitative fiber, a modulus transition point exists at a strain of 0.01 to 0.03, and in the Secondary Modulus, which is the slope of the tangent line of the SS curve, the modulus of the modulus transition point in a region 1 before the modulus transition point has a value of 30 to 70 g / d, and the modulus after the modulus transition point can reach a saturation region at a level of 150 to 250 g / d.

[0152] FIG. 3 is a stress-strain curve of a hybrid code according to one embodiment of the present invention, and FIG. 4 is a stress-strain curve of a hybrid code according to one embodiment of the present invention.

[0153] Referring to Figures 3 and 4, the Modulus transition point can be confirmed.

[0154] In one embodiment of the present invention, the modulus transition point may exist between Strain 0.01 and 0.03.

[0155] If the above transition point exists below 0.01, excessively high modulus can lead to unsuitable tire shape collapse during the curing process, which transitions from green tires to vulcanized tires. This transition point is critical for hybrid cords that lack this section, as it can prevent tire inflation during curing, leading to defects.

[0156] If the above transition point exists at a strain of 0.03 or more, there may be a disadvantage in that the original purpose of the aramid hybrid cord, which is to suppress OD growth during high-speed driving, is not effective after tire manufacturing.

[0157] Additionally, a secondary modulus of at least 100 g / d must be secured at Strain 0.04. If the value is less than 100 g / d at Strain 0.04, the disadvantage of minimal OD growth inhibition during high-speed driving may occur.

[0158] Also, as can be seen in area 2 of Fig. 4, it is desirable for the secondary modulus to be saturated to a level of 190 g / d or higher. If the maximum secondary modulus is less than 190 g / d, there may be a disadvantage in that the effect of suppressing OD increase during high-speed driving is minimal, and a problem in which cutting may occur under impact from an irregular road surface may occur.

[0159] Here, the tensile test is based on D885, applying an initial load of 0.1 g / d, the crosshead speed is 300 mm / min, using an S Clamp, and using a grip face length of 50 to 70 mm to prevent slipping or cutting at the grip.

[0160]

[0161] One aspect of the present invention provides a pneumatic radial tire comprising the hybrid code.

[0162] Figure 5 is a cross-sectional schematic diagram of a pneumatic radial tire according to one embodiment of the present invention.

[0163] Referring to the above drawing 5, the tire includes a tread portion (1), a sidewall portion (2), and a bead portion (3). A carcass layer (4) is installed between the pair of left and right bead portions (3), and both ends of the carcass layer (4) in the tire width direction are wrapped around the bead portion (5) from the inside to the outside of the tire.

[0164] A steel belt layer (5) and a belt layer (6) are installed on the outer side of the carcass layer (4), and an inner liner (not shown) is placed on the inner side of the carcass layer (4).

[0165] A hybrid code according to one embodiment of the present invention can be applied to the belt layer (6), and specifically, to the cap ply.

[0166]

[0167] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0168]

[0169] <Example>

[0170] Comparative Examples 1 and 2 used Polyamide 66 840D / 2 28EPI and Aramid 1500D / 2 21EPI, respectively, and Comparative Example 3 used Aramid 1500D / 1 + Polyamide 66 1260D / 1 hybrid cord manufactured using a conventional manufacturing method.

[0171] Examples 1 and 2 are hybrid cords of the present invention having two modulus transition points manufactured through the above-described method of double-stranding and heat treatment. Example 1 was manufactured by lowering the quantitative fineness and aiming for weight reduction, and Example 2 was manufactured using the same yarn as Comparative Example 3.

[0172] The structure and properties of each code, and the radial tire (225 / 45R17) manufactured by applying the above codes to the cap ply were used to conduct indoor driving tests and actual vehicle performance tests, and the uniformity, dynamic profile, rolling resistance, high-speed driving durability, handling stability, ride comfort, and noise characteristics were measured using the following methods, and the results are shown in Table 1 below:

[0173] [Performance Evaluation Method]

[0174] * Uniformity is an index value that synthesizes values ​​such as R1H and conicity measured using a uniformity measuring device. Based on Comparative Example 1, a higher value is more advantageous.

[0175] * The rolling resistance was evaluated using the SAE J1269 method, and the RRc value of Comparative Example 1 was expressed as an index based on 100, and a higher index value indicates that it is advantageous for the rolling resistance.

[0176] * High-speed driving durability was evaluated by mounting the tire on a drum-type driving durability tester and rotating the drum, so that the tire and drum rotate in engagement, and the driving conditions of the tire were simulated while increasing the speed in stages. After the start of driving, the speed was increased by 20 km / h to 30 km / h every 10 minutes.

[0177] * The dynamic profile was measured and recorded by measuring the growth of the circumference due to centrifugal force according to the driving speed using a dedicated test facility, and the profile change at each location of the tread section on the shoulder was measured and recorded. The smaller the profile change, the better the performance is judged.

[0178] In Table 1, Comparative Example 1 is expressed as an index of 100, and a value higher than 100 indicates better performance than Comparative Example 1.

[0179] * Steering stability, ride comfort, and noise performance are evaluated as indices based on the values ​​felt by test drivers while driving a vehicle equipped with test tires. Comparative Example 1 has an index of 100, and a higher index indicates better performance. An index of 100 or higher indicates better performance than Comparative Example 1, and an index of 100 or lower indicates worse performance than Comparative Example 1.

[0180] Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Structure Polyamide 66 840D / 2 28 EPIAramid 1500D / 2 21 EPIAramid 1500D / 1 + Polyamide 66 1260D / 128 EPIAramid 1000D / 2 + Polyamide 66 840D / 128 EPIAramid 1500D / 1 + Polyamide 66 1260D / 128 EPI Hybrid Cord Twisting Method Direct cable corder Ring Twister Direct cable corder Direct cable corder Top twist (TPM) S 470 340 340 370 340 Bottom twist (TPM) Z 480 Aramid 345 Nylon 66 290 Aramid 340 Nylon 66 340 Aramid 365 Nylon 66 373 Aramid 338 Nylon 66 345 Strain location of modulus transition point -0.04 0.009 0.02 0.02 Specification 225 / 45R17 Application area Cap ply Application method 1 Ply Weight (kg) 13.4 13.5 13.5 13.4 13. 5 Uniformity 1009596 100101 Dynamic profile 10095939493 Rolling resistance 100102 1039899 High-speed driving durability 1:38 1:59 1:59 1:58 2: 03 Handling safety 100110111115119 Ride comfort 1009695 10099 Noise 1009895 103101

[0181] Referring to Table 1 above, it can be seen that in the case of Comparative Example 1 using polyamide 66, noise and ride comfort are excellent, but high-speed driving durability and handling stability are poor, and in the case of Comparative Example 2 using an aramid cord manufactured using a ring twister, high-speed driving durability and handling stability are good, but uniformity, noise, and ride comfort are poor.

[0182] In addition, in the case of Comparative Example 3, which was manufactured using a Direct cable corder, a previously disclosed technology, but used an aramid-polyamide 66 hybrid cord with the same number of twists between the lower yarns, it showed good results overall in noise, ride comfort, high-speed driving durability, and steering stability dynamic profile, but the rolling resistance showed a disadvantageous value, and it was confirmed that the uniformity was disadvantageous due to the disadvantage in manufacturability.

[0183] In Examples 1 and 2 using aramid-polyamide 66 hybrid cords with new properties and manufacturing methods, high-speed durability, handling safety, dynamic profile, and ride comfort were similar to or superior to those of Comparative Example 3, and uniformity was superior to those of Comparative Examples 1 to 3. In addition, it was found that the deviation in tire characteristics was reduced overall as the deviation in properties was reduced. In addition, it was confirmed that Example 1 showed the best rolling resistance characteristics.

[0184]

[0185] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0186] The scope of the present invention is indicated by the claims described below, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0187]

[0188] <Explanation of symbols>

[0189] 1: Tread section

[0190] 2: Sidewall

[0191] 3: Bead part

[0192] 4: Steel belt layer

[0193] 5: Belt layer

Claims

1. Thermoplastic fibers arranged in the core and having a yarn strength of 5 g / d to 10 g / d and a breaking elongation of 12% or more; and A hybrid cord characterized by comprising a high-strength fiber covering the thermoplastic fiber and having a yarn strength of 15 g / d or more and a breaking elongation of less than 10%.

2. In claim 1, A hybrid cord characterized in that the high-strength fiber is composed of at least one of PPTA, wholly aromatic polyester and PPTA / DPE.

3. In claim 1, A hybrid cord characterized in that the thermoplastic fiber is composed of at least one of polyamide and polyester.

4. In claim 1, A hybrid cord characterized in that the density ratio of the thermoplastic fiber to the high-strength fiber is 1:0.78 to 1:0.

96.

5. In claim 1, A hybrid cord characterized in that the draw ratio of the thermoplastic fiber is 5.4 to 5.

8.

6. In any one of claims 1 to 5, Have a strength of 11 g / d or more, The performance has 250 to 500 TPM, The twist coefficient (α) is expressed by Equation 2 below. d ) A hybrid code characterized by having 140 to 210. [Formula 2] (In the above formula, is the twist coefficient based on denier, and T is TPM (Twist per meter). is the quantitative fineness in denier units of the hybrid code) 7. In any one of claims 1 to 5, There is a modulus transition point at strain 0.01 to 0.03, The modulus in the region prior to the above modulus transition point is 30 to 70 g / d, A hybrid cord characterized in that the modulus in the region after the above modulus transition point reaches a saturation region at a level of 150 to 250 g / d.

8. A pneumatic radial tire comprising the hybrid code of claim 1.

9. A method for manufacturing a hybrid code for manufacturing the hybrid code of claim 1, A step of preparing the high-strength fiber and the thermoplastic fiber; A step of manufacturing a raw material cord by twisting the high-strength fiber and thermoplastic fiber with a direct cabler; and A method for manufacturing a hybrid cord, characterized by including a step of manufacturing a dip cord by heat treating the above raw cord.

10. In claim 9, A method for manufacturing a hybrid cord, characterized in that in the step of manufacturing the above raw cord, the high-strength fiber is introduced at an introduction length of 0.99 to 1.015 compared to the thermoplastic fiber.

11. In claim 9, A method for manufacturing a hybrid cord, characterized in that in the step of manufacturing the above raw cord, the high-strength fiber is arranged in the pot yarn of the direct cabler, and the thermoplastic fiber is arranged in the creel yarn of the direct cabler.

12. In claim 9, A method for manufacturing a hybrid code, characterized in that the heat shrinkage rate of the above-mentioned raw code is 2.5 to 6%.

13. In claim 9, A method for manufacturing a hybrid cord, characterized in that the step of manufacturing a dip cord by heat treating the raw cord is performed so that the dip cord shrinks by 0.5 to 3% compared to the raw cord.

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