Eco-friendly pneumatic passenger car radial tire with improved steering stability

Abstract

The PET cord for manufacturing a cap ply and the cap ply manufactured using same according to the present invention have low heat shrinkage characteristics and a moderately low modulus even at high temperatures compared to PET having general heat shrinkage characteristics and high-temperature modulus, and exhibits a low modulus in a low elongation range, thereby solving disadvantages in the manufacturing process and providing higher reinforcement than nylon. In addition, the tire according to the present invention in which the bonding relationship between the tread and steel belt layer adjacent to the cap ply is adjusted can overcome the physical limitations that may occur when PET is used as a cord material of the cap ply.

Description

Eco-friendly pneumatic passenger radial tire with improved handling stability

[0001] The present invention relates to a PET cord for a cap ply and a tire including the same, and more particularly, to a PET cord for a cap ply and a tire including the same, which can bring about the effects of constant steering stability, reduced rolling resistance, and improved wear rate by applying a PET cord having novel properties.

[0002] The cap ply is a fiber cord attached to the top of the steel belt of a radial tire, and it is a component that provides stability to the radial tire. More specifically, the cap ply reduces the defect rate by inducing adhesion of the steel belt semi-finished products during the tire manufacturing process based on the shrinkage force generated at high temperatures and excellent adhesiveness. It also adjusts the shape of the foot shape and contributes to improving high-speed driving stability by preventing the increase in the overall diameter (OD) due to centrifugal force generated during driving. As the radial tire market expands, the usage of fiber cord used as the cap ply of radial tires is also increasing.

[0003] Nylon-66 is the most commonly used material for the cap ply, and is known to exhibit excellent adhesion even under harsh conditions, making it advantageous for high-speed driving durability. However, cap ply made of nylon-66 has a relatively low elastic modulus, making it difficult to suppress the increase in OD caused by centrifugal force during driving.

[0004] To solve the above problem, lowering the angle of the steel belt during tire manufacturing can be considered. However, when the angle of the steel belt is lowered, the tensile force distributed to the steel belt cord increases, so although OD growth can be suppressed, the strain energy density (SED) applied to the end of the belt cord also increases, so there is a problem that separation due to heat generation easily occurs, so there is a limitation.

[0005] When using a hybrid cap ply manufactured by twisting nylon-66 aramid, durability and tire OD growth can be suppressed during high-speed driving even when the angle of the steel belt is high, such as 28 degrees or more. However, the para-aramid fiber used as a material is traded at a high price due to the limited supply and difficult manufacturing process, which is disadvantageous in terms of manufacturing cost.

[0006] Meanwhile, PET, rather than aliphatic amides (N66, N6) or aromatic amides (P-aramid), could be considered as a material for the cap fly. PET is readily available and inexpensive, so it doesn't pose manufacturing cost issues. Furthermore, its higher modulus compared to nylon makes it effective in suppressing deformation, which increases the OD in the circumferential direction during high-speed operation.

[0007] However, since PET has a lower breaking elongation than Nylon, if the circumferential tensile force due to centrifugal force during driving is excessively applied to the cap ply rather than the steel belt, problems such as cutting of the cap ply or destruction of the tire due to repeated tensile deformation may occur.

[0008] In addition, because PET contains ester bonds, it is vulnerable to decomposition under alkaline conditions, lacks functional groups that can form secondary bonds including hydrogen bonds, and has steric hindrance due to benzene rings within the polymer chain, which is unfavorable for adhesion.

[0009] In addition, since PET has lower chain mobility than nylon, it is common for the initial modulus to be greater than that of nylon. This can prevent the green tire from being smoothly tensioned in the circumferential direction of the tread during shaping in the mold, which can cause manufacturing defects such as the outer diameter of the cure tire becoming smaller than the originally designed value or the appearance becoming distorted. In particular, when the outer diameter of the cure tire is reduced, problems may arise that go beyond the OD range for each tire standard defined by ETRTO, FMVSS, JIS, etc.

[0010] As a prior art applying a cap ply using PET cord, there exist Japanese Patent No. 4397207 (registered on October 30, 2009), Japanese Patent No. 5493590 (registered on March 14, 2014), and Japanese Patent No. 7151217 (registered on October 3, 2020). The PET cord according to the above prior art focuses on preventing the diameter of the tire from increasing during high-speed driving by using the modulus as high as possible. However, when the modulus is increased as in the prior art, the deep cord in the cap ply has a relatively high heat shrinkage rate and a low twist coefficient, so that the tire is manufactured under a high tensile force during curing, and as a result, the OD decreases rapidly after being removed from the curing mold, which inevitably causes side effects such as unsuitable appearance and a decrease in the outer diameter of the cured tire compared to the expected.

[0011] To address this, it is necessary to develop a PET cord for cap plies that has a low modulus in the low elongation range, an appropriate modulus in the low heat shrinkage / force use range, or a balance of LASE (Load at Static Elongation).

[0012] [Prior Art Literature]

[0013] [Patent Document]

[0014] (Patent Document 1) Japanese Patent No. 4397207 (registered on October 30, 2009)

[0015] (Patent Document 2) Japanese Patent No. 5493590 (registered on March 14, 2014)

[0016] (Patent Document 3) Japanese Patent No. 7151217 (registered on October 3, 2020)

[0017] The object of the present invention is to disclose a PET cord for manufacturing a cap ply, a cap ply manufactured using the same, and a tire, which can solve the above problems that may arise when using PET as a material while suppressing an increase in OD due to high-speed driving by applying a PET cord instead of nylon-66, which was used as a cap ply in a conventional pneumatic passenger radial tire.

[0018] In order to solve the above object, the present invention provides a cord made of polyethylene terephthalate (PET) material immersed in a dipping solution, wherein the cord has a quantitative fineness of 1000 to 3500 denier, and when a tensile stress of 0.7 g / d is applied at 160°C, the elongation is 1.7% to 3.5% and the elastic modulus is 27.8 g / d or less, and when a tensile stress of 1.0 g / d is applied at room temperature, the elongation is 1.3% to 3.3% and the elastic modulus satisfies the range of 35 g / d to 60 g / d, and when a tensile stress of 1.0 g / d is applied at room temperature, the elastic modulus at a specific elongation is less than 2.7 times the elastic modulus at the same elongation when a tensile stress of 0.7 g / d is applied at 160°C, and the tensile strength at room temperature is 7.0 gf / d or more, and when a tensile stress of 1.0 g / d is applied at the ... a tensile stress of 0.7 g / d at 160°C, and the tensile strength at room temperature is 7.0 gf / d or more, and when a tensile stress of 0.7 g / d is applied at 160°C, the elastic modulus at a specific elongation is less than 2. A PET cord for manufacturing a cap fly is disclosed, characterized in that the tensile strength at 160°C is 4.0 gf / d or more, the tensile strength at 160°C exceeds 50% of the tensile strength at room temperature, the maximum elastic modulus on the stress-strain curve during tension at 160°C is 35 to 55 gf / d, the shrinkage rate is 1.1% or less under the condition of applying an initial load of 0.05 g / d for 2 minutes at 177°C, and the elastic modulus in the 0 to 2.5% strain range under room temperature tension conditions is 20 to 70 gf / d.

[0019] As an example, the PET cord for manufacturing the cap fly can be manufactured by single-filament or double-filament PET filaments having a denier of 900 to 1500.

[0020] As an example, the PET cord for manufacturing the cap fly may be manufactured by double-splicing, and may have a twist factor of 120 to 200 according to the following equation 1.

[0021] (Formula 1)

[0022]

[0023] * TPM = Twist per Meter

[0024] * Cord Fineness = Quantitative fineness

[0025] As an example, the PET cord for manufacturing the cap fly may be manufactured as a single yarn and may have a twist coefficient of 60 to 200 according to the above formula 1.

[0026] As an example, the PET code for manufacturing the cap fly may have a breaking elongation of 13% or more when stretched at room temperature, a breaking elongation of 12% or more when stretched at 160°C, and a maximum elastic modulus when stretched at 160°C within a strain range of 6.5 to 10%.

[0027] As an example, the PET code for manufacturing the cap fly may have a surface defoaming unit (DPU) of 3% to 7%.

[0028] As an example, the PET constituting the PET code for manufacturing the cap fly may be derived from petroleum, biomass, or recycled PET.

[0029] In addition, the present invention discloses a cap fly semi-finished product, which is a sheet or strip manufactured by rolling or extruding a PET cord for cap fly manufacturing through a weaving process, wherein PET cords are arranged at intervals ranging from 0.19 to 0.5 mm within the sheet or strip.

[0030] In addition, the present invention discloses a tire manufactured by providing the cap ply semi-finished product between a tread rubber and a steel belt layer, characterized in that the change in outer diameter (OD) before and after curing is within 5 mm.

[0031] As an example, the tread rubber includes a sub tread rubber and a cap tread rubber, and the sub tread rubber and the cap tread rubber include a reinforcing resin and a resin crosslinking agent, and the resin crosslinking agent provides a methylene group upon decomposition, but the amount of free amine released during this process may be less than 0.5 moles per 1 mole of the resin crosslinking agent.

[0032] As an example, the resin crosslinker may decompose to provide a methylene group without releasing a free amine.

[0033] As an example, a tire characterized in that the resin crosslinking agent is at least one of hexamethoxymethylmelamine (HMMM) and pentamethoxymethylmelamine (PMMM).

[0034] As an example, the tread rubber may have a thickness from the PET cord-rubber interface to the tread block of less than 13 mm, and a thickness from the PET cord-rubber interface to the surface of the main groove of less than 6.5 mm.

[0035] As an example, the tread rubber may have a sea-island ratio of 50% to 68%.

[0036] As an example, the belt lift ratio of the tire may range from 1.8 to 3.2%.

[0037] As an example, the angle of the steel belt may be 24° to 30°.

[0038] As an example, a section within 30 mm from the outermost edge of both sides of the steel belt toward the inside in the tire width direction may have a gap of 0.05 mm or more secured from the adjacent cap ply cord.

[0039] The PET cord for manufacturing a cap ply according to the present invention and the cap ply manufactured using the same have lower heat shrinkage characteristics and a moderately low modulus even at high temperatures compared to PET having general heat shrinkage characteristics and a high temperature modulus, and have a low modulus in a low elongation range, thereby resolving disadvantages in the manufacturing process and having higher reinforcing properties than nylon.

[0040] In addition, the tire according to the present invention can overcome the limitations in physical properties that may arise from using PET as a cord material for the cap ply by controlling the bonding relationship between the cap ply and the adjacent tread and steel belt layer.

[0041] Figure 1 is a drawing showing the general structure of a tire.

[0042] Figure 2 is a graph showing a stress-strain curve under room temperature tensile conditions for a PET code for a cap fly according to the present invention.

[0043] Figure 3 is a graph showing the stress-strain curve and elastic modulus under high temperature (160°C) tensile conditions for a PET code for a cap fly according to the present invention.

[0044] Fig. 4 is a cross-sectional view for confirming the thickness of tread rubber in a tire according to an example of the present invention.

[0045] FIG. 5 is a cross-sectional view for confirming the gap between the steel belt and the cap ply cord in the tire according to an example of the present invention.

[0046] As mentioned above, existing technologies have focused only on the high modulus of PET compared to nylon, and in particular, they judge that only the elastic modulus (the slope of the tangent at a specific point on the stress-strain curve) at a specific load applied to the cord is important. However, in reality, when using PET as a cap ply, it is desirable to determine whether it has a low modulus that can offset the unevenness in deformation occurring during the manufacturing process, has the modified physical properties (2-5% elongation effect) after vulcanization, and has a superior effect of the belt package increasing the diameter of the tire due to centrifugal force compared to existing nylon in the deformation occurring during driving.

[0047] As a result of repeated research from the above-mentioned perspective, the applicant has developed a PET code for manufacturing a cap fly according to the present invention.

[0048] Hereinafter, the PET code for manufacturing a cap fly according to the present invention will be described in detail.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

[0050] Throughout this specification, whenever 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.

[0051] The PET cord for manufacturing a cap fly according to the present invention may have an adhesive (dipping liquid) immersed on its surface. The adhesive may be attached to the surface of the PET cord by weaving the cap fly using the PET cord and then dipping and curing it in the adhesive liquid. At this time, the adhesive amount (Dip Pick Up, DPU) is preferably 3% to 7% to improve adhesion to rubber.

[0052] If the DPU is less than 3%, it is disadvantageous in suppressing the decomposition of PET polymer due to the diffusion of chemicals including free amines from the compound, and if it exceeds 7%, it is disadvantageous because the adhesive layer itself acts as a weak point due to excessive adhesive layer thickness, making it easy for failure to occur in the adhesive layer.

[0053] The above adhesive may be any known dipping solution that can be generally used in the cap fly manufacturing process, and may be attached by a conventional dipping process.

[0054] As an example, the dipping process may sequentially attach two or more types of dipping liquids to the PET code, and the step of attaching each dipping liquid may include immersion, drying, and heat treatment processes.

[0055] According to a preferred embodiment, the dipping process may use an epoxy dip as the first dipping and a Resorcinol Formaldehyde Latex (RFL) system as the second dipping, and may be sequentially dipped through a continuous dipping machine capable of configuring two dip baths. At this time, the epoxy dip may include soft water, polyglycidyl ether, and caprolactam blocked diisocyanate, and the RFL aqueous solution as the second dipping liquid may include soft water, sodium hydroxide (NaOH), novolak resin, formaldehyde, and latex aqueous dispersion. The dipping liquid may also include a dispersant, an antifoaming agent, a thickener, a surfactant, etc., as needed.

[0056] During the above dipping process, the PET cord can form a chemical bond with the dipping solution, and when two or more dipping solutions are used, chemical bonding between the dipping solutions can also occur. In addition, the tension of the PET cord can be adjusted during the heat treatment process. It is preferable that the PET cord undergoes heat shrinkage and heat setting during the heat treatment process. By appropriately controlling the tension, temperature, and time during the heat treatment process, a PET cord having a desired microstructure and physical properties can be manufactured.

[0057] However, the present invention is not limited to the dipping liquid of the above embodiment, and other types of dipping liquids, for example, Pexul dip may be used as the first dipping liquid, or alternative compositions of RF resins composed of phenol resin-long-chain aldehyde, phenol resin-benzene aldehyde, phenol resin modified with epoxy and HMMM (Hexa methoxy methyl melamine), or PMMM (Penta methoxy methyl melamine) may be used as the second dipping liquid, alternative compositions composed of phenol resin modified with epoxy and long-chain aldehyde, or isocyanate, alternative compositions composed of crosslinked acrylic resin and polyol and isocyanate, etc. may be used.

[0058] In addition, the PET cord for manufacturing the cap fly may have a quantitative fineness ranging from 1000 to 3500 denier. When the quantitative fineness is less than 1000 denier, a high EPI must be applied to secure reinforcement due to the low cord diameter, which has the disadvantage of adversely affecting rolling workability, and when the quantitative fineness is 3500 denier or more, as the cord diameter increases, the thickness of the rolled product also increases, which adversely affects weight reduction and reduction of rolling resistance.

[0059] In addition, the quantitative fineness of the PET code for manufacturing the cap fly can be achieved by using 900 to 1500 denier polyethylene terephthalate (PET) filaments by double plying them or by twisting them into 1 ply without a plying process to form a D / 1 structure.

[0060] As a preferred example of the quantitative fineness of the PET code for manufacturing the above cap fly, it may be any one selected from the group consisting of 500D / 2, 850D / 2, 1000D / 2, 1300D / 2, 1500D / 2, 1000D / 1, 1300D / 1, 1500D / 1, 2000D / 1, and 3000D / 1, and more preferably 1000D / 2, but is not limited thereto.

[0061] At this time, the PET material constituting the filament may be petroleum-derived PET, biomass, or recycled PET.

[0062] The PET code for the cap fly may have a twist factor of 120 to 200 calculated according to the following equation 1 when manufactured by double-splicing, and may have a twist factor of 60 to 200 when manufactured by single-splicing.

[0063] (Formula 1)

[0064]

[0065] * TPM = Twist per Meter

[0066] * Cord Fineness = Quantitative fineness

[0067] The above twist coefficient, when increased, can lower the initial modulus or low elongation tensile stress, but when shrinkage occurs in the fibers constituting the cord, it becomes a factor that further increases the shrinkage rate and shrinkage force. For this reason, it is desirable to adjust the twist coefficient within an appropriate range, and when it is in the range of 120 to 200 in the case of a two-ply configuration as described above, and when it is in the range of 60 to 200 in the case of a single-ply configuration, it is easy to obtain the tensile properties and heat shrinkage characteristics required for the PET cord for manufacturing a cap ply according to the present invention.

[0068] In addition, the PET cord for manufacturing the cap ply may have an elongation of 1.3% to 3.3% and an elastic modulus of 35 g / d to 60 g / d when a tensile stress of 1.0 g / d is applied at room temperature. If the elongation under the above conditions is 1.3% or less, there is a high possibility that unsuitability may occur during tire manufacturing due to excessively high modulus, and if it is 3.5% or more, after tire manufacturing, the effect of suppressing diameter increase due to centrifugal force during driving is not sufficient in terms of tire performance, and the effect of improving in-plane stiffness is not sufficient due to the low modulus.

[0069] In addition, the PET cord for manufacturing the cap ply has an elongation of 1.7% to 3.5% and an elastic modulus of 27.8 g / d or less when a tensile stress of 0.7 g / d is applied at 160°C, and when a tensile stress of 1.0 g / d is applied at room temperature, the elastic modulus at a specific elongation is preferably less than 2.7 times the elastic modulus at the same elongation when a tensile stress of 0.7 g / d is applied at 160°C. If it is 2.7 times or more, the difference in elastic modulus between room temperature conditions and high temperature conditions becomes excessively large, causing a change in physical properties due to heat generated during high-speed driving, which adversely affects the performance of the tire.

[0070] In addition, the PET cord for manufacturing the cap ply preferably has a tensile strength at room temperature of 7.0 gf / d or more, a tensile strength at 160°C of 4.0 gf / d or more, and a tensile strength ratio at 160°C of more than 50% of the tensile strength at room temperature. As described above, by securing a ratio of high-temperature tensile strength to room-temperature tensile strength, or a retention rate, of 50% or more, it is possible to prevent rapid changes in the properties of the PET cap ply cord and rapid changes in the characteristics of the tire even when the temperature of the tire changes depending on the driving conditions.

[0071] In addition, the PET cord for manufacturing a cap fly according to the present invention has a breaking elongation of 13% or more when stretched at room temperature, a breaking elongation of 12% or more when stretched at 160°C, and a maximum elastic modulus range when stretched at 160°C can exist within a strain range of 6.5 to 10%.

[0072] If the maximum elastic modulus section appears at a strain exceeding 10%, there is a disadvantage in that the elastic modulus actually required within the tire cannot be used, and if the maximum elastic modulus section appears at a strain less than 6.5%, it may exhibit characteristics that are unfavorable to riding comfort due to the high modulus in the low usage area.

[0073] In addition, the PET cord for manufacturing a cap fly according to the present invention preferably has a maximum elastic modulus in the range of 35 gf / d to 55 gf / d when stretched at 160°C.

[0074] If the maximum elastic modulus is less than 35 gf / d, it means that the physical properties deteriorate significantly at high temperatures, so there is a disadvantage that its role as a cap ply may be reduced in high-speed driving, harsh driving, or summer conditions, and if it exceeds 55 gf / d, there is a possibility that the ride comfort may be reduced due to the high modulus.

[0075] In addition, it is preferable that the PET cord for manufacturing the cap ply has an elastic modulus of 20 g / d to 70 g / d in a deformation range of 0 to 2.5%, thereby preventing excessive tensile force from being applied to the cap ply while the green tire is vulcanized in the mold, thereby preventing product unsuitability due to OD reduction.

[0076] In addition, it is preferable that the PET code for manufacturing the cap fly has a shrinkage rate of 1.1% or less under the condition of applying an initial load of 0.05 g / d for 2 minutes at 177°C.

[0077] The above shrinkage ratio can be measured using a heat export rate / force tester such as Testrite.

[0078] The PET cord for manufacturing cap plies of the present invention having the above properties has lower heat shrinkage characteristics and a moderately low high-temperature modulus compared to conventional ones, and has a low modulus in the low-elongation range, so that it can reduce the occurrence of defects that may occur during the manufacturing process, while still having a low-temperature / high-temperature modulus (elasticity) that is higher than that of nylon, so that it can secure higher high-speed driving stability and durability than nylon.

[0079] In addition, the present invention discloses a cap fly semi-finished product, which is a sheet or strip manufactured by rolling or extruding the PET code for manufacturing the cap fly after a weaving process, and in which the PET code is arranged at intervals ranging from 0.19 to 0.5 mm within the sheet or strip.

[0080] The above cap ply semi-finished product can suppress the increase in OD of the tire due to centrifugal force compared to the nylon-66 cord by applying the PET cord for manufacturing the cap ply described above.

[0081] Furthermore, compared to cap ply manufactured with conventional PET cord having a heat shrinkage rate of 1.5% or more, it can contribute to lowering the defect rate, which is a problem when using PET cord, by suppressing deformation of the tire after curing so that it does not occur significantly compared to the mold size.

[0082] In the above cap ply semi-finished product, if the gap between PET codes exceeds 0.5 mm, the reinforcing effect may be insufficient, and if it is 0.19 mm or less, the effect of rubber penetration or rubber bridge centered on the PET cap ply layer may be halved, causing tread chunking to occur during high-speed driving, and there is concern that the cracks that occur may easily propagate.

[0083] In addition, the present invention discloses a tire characterized in that a cap ply semi-finished product is manufactured by being provided between a tread rubber and a steel belt layer, and the change in the outer diameter (OD) of the tire before and after vulcanization is within 5 mm.

[0084] The above tire can effectively suppress OD changes during high-speed driving while improving productivity by using the cap ply semi-finished product according to the present invention and the PET cord included in the semi-finished product, and in the tire manufacturing process, the OD changes before and after curing can be suppressed to within 5 mm, preferably within 3 mm, thereby preventing defects from occurring during the tire manufacturing process.

[0085] In the above tire, the tread rubber is configured such that one side comes into contact with the upper part of the cap ply and the opposite side comes into contact with the road surface, and after the green tire is vulcanized, it forms a bond with the cap ply as firmly as possible.

[0086] The cap tread and sub tread in the tread rubber may include a reinforcing resin, and may include a resin crosslinking agent that acts as a methylene donor for crosslinking of the reinforcing resin. At this time, the resin crosslinking agent provides a methylene group while being decomposed during the vulcanization process, but the amount of free amine released during this process may be less than 0.5 mol per 1 mol of the resin crosslinking agent, and preferably, no amine may be released.

[0087] If an amine-based resin crosslinking agent such as hexamethylenetetraamine (HMTA) exists in the tread rubber, the HMTA may decompose during vulcanization, releasing a large amount of free amine at 0.5 mol or more per mol of the resin crosslinking agent. The free amine may cause aminolysis or hydrolysis with the PET in the cap ply, thereby decomposing the filament surface of the PET cord. This may drastically reduce the adhesive properties of the cap ply cord, causing cracks and separation in the cap ply cord during driving, which may reduce the driving durability, and the deterioration of the tensile properties may cause problems such as breakage due to centrifugal force during driving and cap ply tearing due to impact in poor road conditions (e.g., potholes).

[0088] As a preferred example of the resin crosslinking agent that does not release the above free amine, a melamine-based resin crosslinking agent may be used, and more preferably, at least one of hexamethoxymethylmelamine (HMMM) and pentamethoxymethylmelamine (PMMM) may be used.

[0089] The tread rubber may have a pattern, and the pattern may include grooves, which are portions that are dug out and do not come into contact with the ground, and blocks that come into contact with the ground. The tire according to the present invention can appropriately control the heat transferred to the cap ply by controlling the depth of the grooves or the area of ​​the blocks, thereby complementing the physical limitations of PET cord for the cap ply, which is relatively vulnerable to heat.

[0090] Due to the above pattern, the thickness of the tread rubber may vary depending on the location on the tread surface, more specifically, the presence or absence of grooves or blocks. As an example, FIG. 4 is an exemplary cross-section of a tire having main grooves and tread blocks, and in the tire according to the present invention, the thickness is preferably less than 13 mm from the PET cord-rubber interface in the cap ply to the tread block surface, and less than 6.5 mm from the PET cord-rubber interface to the surface of the main groove.

[0091] As configured as above, heat accumulated in the cap fly-tread compound is suppressed while heat dissipation is promoted, so that adhesive properties can be maintained even in situations where high temperature conditions are maintained.

[0092] In addition, in the above tire, it is preferable that the sea-island ratio of the tread be 50% to 68%. The sea-island ratio of 100% means a slick tire without grooves or kerfs, and 50% means that the ratio of the area of ​​the tread block that contacts the road surface to the area of ​​the part that does not contact the road surface, such as the grooves or kerfs, is 50:50.

[0093] If the above-mentioned actual contact ratio exceeds 68%, it may be disadvantageous for heat dissipation, which may result in disadvantageous results in high-speed driving durability, and if it is less than 50%, it may be disadvantageous for handling stability such as wear and dry handling.

[0094] The above steel belt layer is configured to closely contact the lower part of the cap ply, and plays a role in maintaining the flatness of the tire tread and maintaining the contact pressure evenly when the tire is in contact with the ground, and can secure driving stability and steering stability by suppressing changes in the contact shape and tire diameter due to the centrifugal force in the circumferential direction that occurs during driving, and can induce effective directional change and straight-line driving by transmitting the lateral force between the road surface and the tire from the lateral force that occurs at the contact surface. The performance of the above steel belt layer may be affected by the angle of the belt cord constituting the belt layer, the spacing between the belt layers, the volume fraction between the steel belt cord and the skim compound constituting the belt layer, the skim compound, and the respective structures and properties of the steel belt, and the steel belt layer in the tire according to the present invention can compensate for the limitations of the properties of the PET used in the cap ply by adjusting the belt lift rate or angle.

[0095] In the above steel belt layer, the belt lift ratio, which is the tensile strain ratio in the circumferential direction of the belt layer during the curing process from the green tire after molding, may be in the range of 1.8 to 3.2%, preferably 2.0 to 2.9%. This is a lower value than the belt lift ratio of 3% or more secured in most passenger car tires (PCR), and by preventing excessive tensile stress from being applied to the cap ply, the durability of the cap ply can be improved.

[0096] In addition, in the above tire, the angle of the steel belt may be 23˚ to 33˚, preferably 24˚ to 30˚. By setting the steel belt angle within the above range, the tension applied to the PET cord for the cap ply can be appropriately distributed, while suppressing OD growth due to centrifugal force during driving.

[0097] In addition, in the steel belt, a section within 30 mm from the outermost edge of both sides toward the inside in the tire width direction may have a gap of 0.05 mm or more with the adjacent cap ply cord. In this regard, Fig. 5 is a drawing showing a section of 30 mm from the outermost edge of one side of the steel belt toward the inside in the tire width direction. According to Fig. 5, it can be confirmed that in the 30 mm section, the steel belt and the cap ply cord are not in direct contact and have a gap of 0.05 mm or more.

[0098] By ensuring the above spacing, it is possible to prevent the problem of the cap fly code and steel belt being positioned too close to each other when vulcanization is completed, which is detrimental to the driving durability characteristics due to the occurrence and propagation of cracks during driving.

[0099] Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. However, these embodiments are intended to illustrate the present invention more specifically, and it will be apparent to those skilled in the art that the scope of the present invention is not limited thereby.

[0100] Experimental Example 1: Manufacturing and property verification of PET cap fly

[0101] Manufacturing Example 1

[0102] PET cord for cap ply (PET 1000D / 2 for cap ply) was manufactured by double-splicing 1000 denier polyethylene terephthalate filaments according to the manufacturing process of conventional textile cords and manufacturing them under conditions that satisfy the property ranges presented in this specification.

[0103] Comparative Manufacturing Example 1

[0104] According to the conventional carcass cord manufacturing process, PET cord for carcass (PET 1000D / 2 for carcass) was manufactured by double-splicing 1000 denier polyethylene terephthalate filaments.

[0105] Comparative Manufacturing Example 2

[0106] A commercially available nylon-66 cord for cap fly was prepared.

[0107] For the cap plies according to the above-described Manufacturing Example 1, Comparative Manufacturing Example 1, and Comparative Manufacturing Example 2, the pullout force according to ASTM D4776, the elongation under room temperature tensile conditions, and the elastic modulus under high temperature tensile conditions were measured, and the results are shown in Table 1 below.

[0108] [Table 1]

[0109] [Correction pursuant to Rule 91, June 19, 2025]

[0110] According to Table 1 above, it can be confirmed that the PET cord for cap fly according to Manufacturing Example 1 exhibits higher tensile strength, higher room temperature elongation, and lower high temperature elasticity compared to the PET cord according to Comparative Manufacturing Example 1, and exhibits lower room temperature elongation and higher high temperature elasticity compared to the nylon cord according to Comparative Manufacturing Example 2.

[0111] In addition, the PET code for cap fly according to the above-mentioned manufacturing example 1 was deformed in the longitudinal direction until fracture in room temperature and high temperature (160°C) environments, and the stress-strain curve was recorded, and the results were as shown in Figs. 2 and 3.

[0112] Fig. 2 is a Stress-Strain Curve under room temperature tensile conditions, and according to Fig. 2, it can be confirmed that the PET cord for cap ply according to Manufacturing Example 1 has a tensile strength of 7.0 gf / d or more at room temperature and a breaking elongation of 13% or more.

[0113] FIG. 3 is a Stress-Strain Curve and elastic modulus under high temperature (160°C) tensile conditions. According to FIG. 3, it can be confirmed that the PET cord for cap ply according to Manufacturing Example 1 has a tensile strength of 7.0 gf / d or more at high temperature, an elongation at break of 12% or more, and a maximum elastic modulus range of 35 to 55 gf / d within a strain range of 6.5 to 10%.

[0114] In addition, when comprehensively examining the above drawings 2 and 3, it can be confirmed that the PET code for cap fly according to Manufacturing Example 1 has a ratio of tensile strength at 160°C to tensile strength at room temperature exceeding 50%.

[0115]

[0116] Experimental Example 2: Comparison of physical properties of tires with cap ply applied

[0117] Using the above-described Manufacturing Example 1, Comparative Manufacturing Example 1, and a commercial nylon-66 material cap ply cord (N66 840D / 2), a cap ply satisfying 27 EPI, i.e., a cord-to-cord spacing of 0.38 mm, was manufactured according to a conventional cap ply manufacturing method. In addition, while changing the type of the cap ply, belt angle, belt lift, and actual contact ratio, Examples 1 to 3, Comparative Examples 1 and 5 were manufactured according to a conventional tire manufacturing method.

[0118] Cured Tire OD, failure rate, dynamic profile (300 kph), high-speed driving durability (ECE R30 V), Ride & Handling overall score, rolling resistance, and weight were measured / evaluated for the above Examples 1 to 3 and Comparative Examples 1 and 5. The composition and evaluation results for each Example and Comparative Example can be summarized as shown in Table 2 below.

[0119] [Table 2]

[0120]

[0121] - Cured Tire OD: This refers to the outer diameter of a green tire after curing. Measurements are made at 2.2 kgf / ㎠ for passenger and SUV tires. The smaller the difference between this and the Mold OD (the outer diameter before curing), the lower the defect rate.

[0122] - Dynamic Profile (300kph): The increase in tire circumference due to high-speed rotation was measured when driving at high speed (300km / h). The lower the value, the better the driving stability.

[0123] - High-speed driving durability: Tests are conducted according to ECE R30 to record the time it can withstand friction. For passenger car tires, it passes if it can withstand 1 hour (1:00).

[0124] - Ride & Handling Comprehensive Score: This is a test in which tires are mounted on an actual vehicle and a test driver performs various driving conditions to comprehensively evaluate ride comfort, noise, and handling characteristics.

[0125] - Rolling resistance: This is a test method that places a tire on a fixed rotating drum and rotates the tire and drum at fixed air pressure, ground pressure, and speed, according to the ISO 28580 standard, and expresses the energy lost at this time as “rolling resistance.”

[0126] The performance of tires manufactured according to each of the following examples and comparative examples is described in more detail with reference to Table 2 above.

[0127] (1) Effects according to cap fly material (Comparative Example 1, Comparative Example 2, and Example 1)

[0128] Compared to Comparative Example 1, which used a cap ply made of nylon 66, Comparative Example 2 and Example 1, which used PET, both showed a reduction of less than half at 300 kph in the Dynamic Profile test. This confirms that applying a cap ply made of PET can have a positive effect on high-speed driving stability.

[0129] Meanwhile, in the case of Comparative Example 2, where the cap fly according to Comparative Manufacturing Example 1 was applied, it was confirmed that the defect rate increased and the high-speed driving durability decreased. This is interpreted to be due to the decrease in Cured OD and high modulus caused by excessive shrinkage characteristics.

[0130] In the case of Example 1, where the cap ply according to Manufacturing Example 1 was applied, it was also shown that the Cured OD was somewhat reduced, but it was not to the extent that it affected the defect rate, and it was confirmed that the high-speed driving durability was also maintained at the same level as Comparative Example 1. Through this, it was confirmed that high-speed driving stability can be improved while maintaining other physical properties simply by replacing the cap ply according to the present invention with the conventional tire according to the present invention while maintaining other conditions the same.

[0131] (2) Effect according to belt angle (Comparative examples 3 and 4, Examples 1 and 2)

[0132] Even when the belt angle changes, there is no significant change in the Dynamic Profile, Cured OD, and failure rate. However, Comparative Example 3 with a belt angle of 22 degrees and Comparative Example 4 with a belt angle of 35 degrees did not meet the high-speed driving durability standard. In Example 2 with a belt angle of 28 degrees, the rolling resistance was reduced and the Ride & handling composite score was higher than in Comparative Examples 3 and 4. Therefore, it can be confirmed that it is required to maintain an appropriate belt angle when applying the cap ply according to the present invention to a tire.

[0133] (3) Effects of belt lift (Examples 2 and 3)

[0134] In the case of Example 3, where the belt lift ratio was reduced to 2.7% compared to Example 2, it was confirmed that the decrease in Cure OD was further suppressed. Accordingly, it was confirmed that it is possible to suppress the shrinkage characteristics of the PET material cap ply by adjusting the belt lift ratio even when the same cap ply is applied.

[0135] (4) Effect according to groove area (actual contact ratio) (Example 3 and Comparative Example 5)

[0136] In Comparative Example 5, where the actual contact ratio was increased to 71%, the Ride & Handling composite score was higher than that of Example 3, but the rolling resistance also increased and it did not pass the high-speed driving durability standard. The above result is interpreted as being due to the heat generated inside the tire during high-speed driving not being sufficiently dissipated due to the reduction in the groove area, and through this, it can be confirmed that the actual contact ratio can also affect the physical properties of the tire when the cap ply according to the present invention is applied to the tire.

[0137]

[0138] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and it is possible to implement various modifications within the scope of the claims and the detailed description of the invention, and this also naturally falls within the scope of the present invention.

[0139] [Explanation of symbols]

[0140] 11: Tire

[0141] 12: Carcass layer

[0142] 13: Code for reinforcing the carcass layer

[0143] 14: Fly Turnup

[0144] 15: Bead area

[0145] 16: Beadcore

[0146] 17: Bead filler

[0147] 18: Belt structure

[0148] 19: Cap Fly

[0149] 20: Belt Fly

[0150] 21,22: Belt code

[0151] 23: Tread

[0152] 24: Edgefly

[0153] 25: Cap Fly Code

[0154] The PET cord for manufacturing a cap fly according to the present invention and the cap fly manufactured using the same have lower heat shrinkage characteristics and a moderately low modulus even at high temperatures compared to PET having general heat shrinkage characteristics and a high temperature modulus, and have a low modulus in a low elongation range, thereby resolving disadvantages in the manufacturing process and having higher reinforcing properties than nylon, and thus are recognized as having industrial applicability.

Claims

1. A code made of polyethylene terephthalate (PET) material immersed in a dipping solution. The above code has a quantitative fineness of 1000 to 3500 denier, When a tensile stress of 0.7 g / d is applied at 160 ℃, the elongation is 1.7% to 3.5% and the elastic modulus is 27.8 g / d or less, When a tensile stress of 1.0 g / d is applied at room temperature, the elongation is 1.3% to 3.3%, and the elastic modulus satisfies the range of 35 g / d to 60 g / d. When a tensile stress of 1.0 g / d is applied at the above room temperature, the elastic modulus at a specific elongation is less than 2.7 times the elastic modulus at the same elongation when a tensile stress of 0.7 g / d is applied at 160 ℃, The tensile strength at room temperature is 7.0 gf / d or more, Tensile strength at 160 ℃ is 4.0 gf / d or more, The tensile strength at 160°C is greater than 50% of the tensile strength at room temperature. The maximum elastic modulus on the stress-strain curve under tension at 160 ℃ is 35 gf / d to 55 gf / d, It has a shrinkage rate of 1.1% or less under the condition of applying a super load of 0.05 g / d for 2 minutes at 177 ℃. A PET cord for manufacturing cap ply, characterized in that the elastic modulus in the 0 to 2.5% strain range under room temperature tensile conditions is in the range of 20 gf / d to 70 gf / d.

2. In paragraph 1, The PET cord for manufacturing the cap fly is characterized in that it is manufactured by single-filament or double-filament PET filament of 900 to 1500 denier.

3. In paragraph 2, The PET code for manufacturing the above cap fly is: A PET cord for manufacturing a cap fly, characterized in that it is manufactured by double-stranding and has a twist factor of 120 to 200 according to the following formula 1. (Formula 1) * TPM = Twist per Meter * Cord Fineness = Quantitative fineness 4. In paragraph 2, The PET code for manufacturing the above cap fly is: A PET cord for manufacturing a cap fly, characterized in that it is manufactured as a single piece and has a twist coefficient of 60 to 200 according to the following formula 1. (Formula 1) * TPM = Twist per Meter * Cord Fineness = Quantitative fineness 5. In paragraph 1, The PET code for manufacturing the above cap fly has a breaking elongation of 13% or more when stretched at room temperature and a breaking elongation of 12% or more when stretched at 160°C. PET cord for manufacturing cap ply, characterized in that the maximum elastic modulus when stretched at 160 ℃ is within a strain range of 6.5 to 10%.

6. In paragraph 1, The PET code for manufacturing the cap fly is characterized in that the surface defoaming amount (DPU) is 3% to 7%.

7. In paragraph 1, PET code for manufacturing the cap fly, characterized in that the PET constituting the PET code for manufacturing the cap fly is derived from petroleum, biomass, or recycled PET as a raw material.

8. A sheet or strip manufactured by rolling or extruding a PET code for manufacturing a cap fly according to any one of clauses 1 to 7, A cap fly semi-finished product characterized in that PET codes are arranged at intervals ranging from 0.19 to 0.5 mm within the above sheet or strip.

9. A tire manufactured by placing a cap ply semi-finished product according to Article 8 between a tread rubber and a steel belt layer, characterized in that the change in outer diameter (OD) before and after curing is within 5 mm.

10. In paragraph 9, The above tread rubber includes sub tread rubber and cap tread rubber, The above sub tread rubber and cap tread rubber contain reinforcing resin and resin crosslinking agent, A tire characterized in that the resin cross-linking agent provides a methylene group when decomposed, and the amount of free amine released during this process is less than 0.5 mol per 1 mol of the resin cross-linking agent.

11. In paragraph 10, A tire characterized in that the resin crosslinking agent provides a methylene group upon decomposition, but does not release a free amine.

12. In paragraph 11, A tire characterized in that the resin crosslinking agent is at least one of hexamethoxymethylmelamine (HMMM) and pentamethoxymethylmelamine (PMMM).

13. In paragraph 9, The above tread rubber has a thickness from the PET cord-rubber interface to the tread block of less than 13 mm, A tire characterized in that the thickness from the PET cord-rubber interface to the surface of the main groove is less than 6.5 mm.

14. In paragraph 9, A tire characterized in that the tread rubber has a sea-island ratio of 50% to 68%.

15. In paragraph 9, A tire, characterized in that the belt lift rate of the tire is in the range of 1.8 to 3.2%.

16. In paragraph 9, A tire characterized in that the angle of the steel belt is 24˚ to 30˚.

17. In paragraph 9, A tire characterized in that a section within 30 mm from the outermost edge of both sides of the steel belt to the inner side in the tire width direction has a gap of 0.05 mm or more secured from the adjacent cap ply cord.

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