JP2017019461A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing rolling resistance while improving flat spot resistance.SOLUTION: A pneumatic tire includes: a belt layer 7 where cords are obliquely arranged in the tire circumferential direction on the outer peripheral side of a carcass layer 4 in a tread part 3; and a belt reinforcement layer 9 where organic fiber cords are arranged along the tire circumferential direction on the outer peripheral side of the belt layer. There is used as the organic fiber cord of the belt reinforcement layer, a cord which comprises an aliphatic polyamide fiber, and where the product of 2% extension time load (cN/dtex) and loss tangent tan δ at 100°C is 0.035-0.044.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  For the purpose of improving the high speed durability of a tire, it is known to provide a belt reinforcing layer formed by arranging fiber cords substantially parallel to the tire circumferential direction on the outer peripheral side of the belt layer. As organic fiber cords forming the belt reinforcing layer, general-purpose nylon fibers (aliphatic polyamide fibers) represented by nylon 66, nylon 6 and the like are generally used.

  However, the belt reinforcement layer using general-purpose aliphatic polyamide fibers has a characteristic that distortion due to high heat generated during high-speed running is set, which causes the tire to vibrate when re-running after running for a long time. The so-called flat spot phenomenon is likely to occur. On the other hand, when an organic fiber cord having a glass transition temperature and rigidity higher than that of nylon 66 such as polyethylene-2,6-naphthalate (PEN) fiber is used, the flat spot resistance is improved. Thus, it has been found that due to the high rigidity, the energy loss with respect to deformation during rolling of the tire increases, and the rolling resistance increases.

  Incidentally, Patent Document 1 discloses that the rolling resistance is reduced by setting the loss tangent tan δ at 120 ° C. of a cord using a general-purpose polyamide fiber such as nylon 66 fiber to 0.065 or less. . However, with general-purpose polyamide fiber cords, it is difficult to achieve both flat spot resistance and reduction in rolling resistance. Patent Document 2 uses a PEN fiber cord having a loss tangent tan δ at 25 ° C. of 0.06 to 0.09 as a belt reinforcing layer, and Patent Document 3 has a loss tangent tan δ of 0 at 60 ° C. It is disclosed that the rolling resistance is reduced by using a cord such as polyethylene terephthalate (PET) fiber that is .1 or less for a belt reinforcing layer. However, a highly rigid fiber cord such as PEN or PET cannot be said to have a sufficient rolling resistance reduction effect, and further improvement is required.

  Patent Document 4 discloses an aliphatic polyamide having excellent heat resistance, fluidity, toughness, low water absorption and rigidity and having a high melting point, and the aliphatic polyamide has a glass transition temperature of 90 to 170 ° C. It is described. However, this document is mainly intended for resin parts such as an air intake system part and a cooling system part of an automobile, and is not suggested for application to a fiber cord constituting a belt reinforcing layer of a tire.

JP 2002-103913 A JP 2003-237308 A Japanese Patent Laying-Open No. 2005-075290 International Publication No. 2009/113590

  An object of the present invention is to provide a pneumatic tire capable of reducing rolling resistance while improving flat spot resistance.

  The pneumatic tire according to the present invention includes a belt layer in which cords are inclinedly arranged with respect to the tire circumferential direction on the outer circumferential side of the carcass layer in the tread portion, and an organic fiber cord on the outer circumferential side of the belt layer along the tire circumferential direction. A pneumatic tire provided with an arranged belt reinforcing layer, wherein the organic fiber cord of the belt reinforcing layer is a cord made of an aliphatic polyamide fiber, and has a 2% elongation load (cN / dtex) and a temperature of 100 ° C. A code having a product of loss tangent tan δ at 0.035 to 0.044 is used.

  According to the present invention, an organic fiber cord made of aliphatic polyamide fiber is used for the belt reinforcing layer, and the product of the load at 2% elongation and the loss tangent tan δ at a temperature of 100 ° C. is set within the above range. The rolling resistance can be reduced while improving the flat spot property.

It is a half sectional view of the pneumatic tire of an embodiment.

  Hereinafter, embodiments of the present invention will be described in detail.

  The pneumatic tire according to the present embodiment is characterized by the configuration of the belt reinforcing layer disposed on the outer peripheral side of the belt layer. The belt reinforcing layer is made of an organic fiber cord arranged along the tire circumferential direction on the outer side in the tire radial direction of the belt layer, and is a layer including the organic fiber cord and a covering rubber covering the organic fiber cord. The organic fiber cords of the belt reinforcing layer extend substantially parallel to the tire circumferential direction, that is, at an angle of approximately 0 ° (preferably an angle of 5 ° or less), and the cords are arranged at predetermined intervals in the tire width direction. Has been. Such a belt reinforcing layer may be a cap ply that covers the entire width direction of the belt layer, or an edge ply that covers the belt end.

  FIG. 1 is a half sectional view of a pneumatic radial tire for passenger cars as an example of a pneumatic tire. The tire includes a pair of left and right bead portions (1) and sidewall portions (2), and a tread portion (3) provided between both sidewall portions (2). A carcass layer (4) extending in a toroidal shape is provided between the parts (1). In this example, the tire has a symmetrical structure with respect to the tire equator CL.

  The carcass layer (4) passes through the sidewall portion (2) from the tread portion (3), and is locked by folding back from the inside to the outside at the bead core (5) in the bead portion (1). The carcass layer (4) is composed of at least one ply formed by arranging carcass cords made of organic fibers substantially perpendicular to the tire circumferential direction.

  A belt layer (7) is disposed on the outer peripheral side of the carcass layer (4) in the tread portion (3) (that is, on the outer side in the tire radial direction). The belt layer (7) is provided so as to overlap the outer periphery of the crown portion of the carcass layer (4), and can be constituted by one or a plurality of belts. In this example, the inner first belt (7A) And the outer second belt (7B). The belt layer (7) is formed by inclining steel cords at a constant angle with respect to the tire circumferential direction and arranging them at predetermined intervals in the tire width direction, and between the two belts (7A) (7B). The steel cords are arranged so as to cross each other.

  A belt reinforcing layer (9) is provided between the belt layer (7) and the tread rubber portion (8) on the outer peripheral side of the belt layer (7) (that is, the outer side in the tire radial direction). In this example, the belt reinforcing layer (9) is a cap ply that covers the belt layer (7) with its full width, and is made of an organic fiber cord arranged substantially parallel to the tire circumferential direction. The belt reinforcement layer (9) tightens the belt layer (7) in the circumferential direction, obtains a tagging effect that increases the rigidity in the tire circumferential direction and the radial direction and the belt restraining force, and generates the belt layer (7 ) Rise and diameter growth, and distortion at the end of the belt layer (7), thereby improving high-speed durability and steering stability.

  Hereinafter, the organic fiber cord constituting the belt reinforcing layer will be described in detail.

  In this embodiment, the organic fiber cord used for the belt reinforcing layer is made of an aliphatic polyamide fiber yarn. An aliphatic polyamide is a polyamide containing an aliphatic skeleton, and does not include an aramid consisting only of an aromatic skeleton. The aliphatic polyamide is polymerized using an aliphatic diamine and / or an aliphatic dicarboxylic acid, and the aliphatic here includes not only a chain structure but also an alicyclic group having a cyclic structure. It is a concept. Further, it may be polymerized by using an aromatic diamine and / or an aromatic dicarboxylic acid together with an aliphatic diamine and / or an aliphatic dicarboxylic acid.

  The organic fiber cord is preferably made of an aliphatic polyamide fiber having a glass transition temperature (Tg) of 90 to 170 ° C. Thus, by using the aliphatic polyamide fiber having a high glass transition temperature, the restoration property of the organic fiber cord is improved, and thus the flat spot resistance can be improved. Further, since heat resistance can be imparted to the belt reinforcing layer, it is advantageous for handling stability and high speed durability during high speed running. The lower limit of the glass transition temperature of the aliphatic polyamide fiber is more preferably 100 ° C. or higher, and further preferably 120 ° C. or higher. Increasing the stretch ratio of the aliphatic polyamide fiber increases the orientation and improves the crystallinity, thereby increasing the glass transition temperature. However, if the orientation is raised too much, it becomes hard and tends to cause fluff and filament breakage during processing such as the spinning process, resulting in a decrease in yarn productivity. Therefore, the glass transition temperature is preferably 170 ° C. or lower, more preferably 160 ° C. or lower. Here, the glass transition temperature is measured according to JIS K7121.

  Examples of the aliphatic polyamide according to a preferred embodiment include polyamides disclosed in WO2009 / 113590. That is, (a) a dicarboxylic acid containing at least 50 mol% of an alicyclic dicarboxylic acid and (b) at least 50 mol% of a diamine containing a diamine having a substituent branched from the main chain were polymerized, Polyamide.

  As said alicyclic dicarboxylic acid, carbon number of cyclic structures, such as 1, 4- cyclohexane dicarboxylic acid, 1, 3- cyclohexane dicarboxylic acid, and 1, 3- cyclopentane dicarboxylic acid, is 3-10, for example. Examples include at least one selected from alicyclic dicarboxylic acids, and 1,4-cyclohexanedicarboxylic acid is preferable. The dicarboxylic acid may be composed only of an alicyclic dicarboxylic acid, and for example, a chain fatty acid such as adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, and hexadecanedioic acid. An aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid may be used in combination. As the dicarboxylic acid other than the alicyclic dicarboxylic acid, a chain aliphatic dicarboxylic acid having 10 to 18 carbon atoms is more preferable.

  For the diamine, examples of the substituent branched from the main chain include alkyl groups having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group. Preferably, it is a methyl group. Examples of the diamine having a substituent branched from the main chain include 2-methylpentamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, and 2-methyloctamethylene. Examples thereof include at least one selected from branched saturated aliphatic diamines having 3 to 20 carbon atoms such as diamine, and 2-methylpentamethylenediamine is preferable. The diamine may be composed only of a diamine having a substituent branched from the main chain. For example, at least one selected from linear saturated aliphatic diamine, alicyclic diamine, and aromatic diamine is used in combination. May be.

  A method for producing the aliphatic polyamide by polymerizing the dicarboxylic acid (a) and the diamine (b) is not particularly limited, but a hot melt polymerization method is preferably used. In the hot melt polymerization method, an aqueous solution or water suspension of dicarboxylic acid and diamine, or an aqueous solution or water suspension of a mixture of dicarboxylic acid and diamine salt and other components was heated to maintain a molten state. This is a method of polymerizing as it is. The polymerization form may be batch or continuous. Examples of the polymerization apparatus include an autoclave reactor, a tumbler reactor, and an extruder reactor such as a kneader.

  The aliphatic polyamide fiber can be produced by melt spinning according to a conventional method using the above aliphatic polyamide or an aliphatic polyamide composition obtained by adding various additives to the aliphatic polyamide. An organic fiber cord as a dip-treated cord is prepared by applying a twist to the obtained yarn made of aliphatic polyamide fiber to produce a raw cord, and subjecting the raw cord to a dip treatment using a known adhesive treatment liquid Is obtained.

  In the organic fiber cord used for the belt reinforcing layer according to the present embodiment, the product (P = S × L) of the 2% elongation load (S) (cN / dtex) and the loss tangent tan δ (L) at a temperature of 100 ° C. 0.035 to 0.044. Since the product (P) is 0.035 or more, the hoop effect of the belt reinforcing layer at the time of high speed traveling can be enhanced, so that the tire durability can be improved. When the product (P) is 0.044 or less, it is possible to reduce energy loss with respect to deformation during tire rolling, and to reduce rolling resistance. Moreover, when the product (P) is 0.044 or less, the cord is hardly melted when the tire rolls, and the flat spot resistance can be improved.

  The load at 2% elongation of the organic fiber cord is a load at 2% elongation at 20 ° C. as a dip-treated cord, and the tensile load (cN) measured at 2% according to JIS L1017 is the nominal fineness ( dtex) divided by.

  The load at 2% elongation of the organic fiber cord is preferably 0.79 to 0.90 cN / dtex. More preferably, it is 0.82-0.90 cN / dtex. When the load at 2% elongation is 0.79 cN / dtex or more, it is possible to increase the belt restraint force as a tagging effect and enhance the effect of improving tire durability. By being 0.90 cN / dtex or less, the cord of the belt reinforcing layer can be prevented from biting into the belt layer when the tire is expanded at the time of tire vulcanization molding, and the effect of improving tire durability can be enhanced. Moreover, the energy loss with respect to the deformation | transformation at the time of tire rolling can be made small, and the reduction effect of rolling resistance can be heightened. The value of the load at 2% elongation can be determined, for example, by adjusting the elastic modulus of the aliphatic polyamide fiber constituting the organic fiber cord, or by adjusting the cord structure or the number of twists. By increasing the number of twists, the load at 2% elongation can be reduced.

  The loss tangent tan δ at a temperature of 100 ° C. of the organic fiber cord is a loss tangent tan δ as a dip-treated cord at a temperature of 100 ° C. measured at a frequency of 10 Hz, an initial load of 6.47 N / line and a dynamic strain of 5%. Although this tan-delta in 100 degreeC is not specifically limited, It is preferable that it is 0.035-0.060, More preferably, it is 0.039-0.055.

  The value of tan δ is adjusted, for example, by adjusting conditions such as processing temperature, tension, speed and time during stretching of the aliphatic polyamide fiber constituting the organic fiber cord, and adjusting the molecular weight and crystallinity of the aliphatic polyamide. Stretching, heat setting as needed after spinning, adjusting the conditions such as the treatment liquid composition, treatment temperature, tension, speed and time at the time of dip treatment using the adhesion treatment liquid, the fineness and twist number of the cord It can be performed by adjusting the value, and can be set within the above range. For example, tan δ tends to decrease by lowering the spinning speed. In addition, when an aliphatic polyamide fiber cord having a high glass transition temperature as described above is used, it is easy to lower tan δ at 100 ° C. compared to a general-purpose aliphatic polyamide fiber cord, which is advantageous. That is, in the general-purpose aliphatic polyamide fiber cord, the tan δ peak temperature is around 100 ° C., whereas in the above-mentioned aliphatic polyamide fiber cord having a high glass transition temperature, the tan δ peak is at a higher temperature. It is easy to reduce tan δ.

  The cord structure of the organic fiber cord of the present embodiment may be a single twisted structure in which a yarn formed by bundling a large number of aliphatic polyamide filaments is given a unidirectional twist, or alternatively, the aliphatic polyamide filament yarn may be a Z direction. A twisted structure is obtained by twisting the two twisted yarns into a twisted direction and twisting them in the S direction opposite to the twisted direction. For example, a double twisted structure in which two twisted yarns are twisted together But you can. The number of twists (the number of upper twists) is not particularly limited, and may be, for example, 10 to 50 times / 10 cm, 15 to 45 times / 10 cm, or 25 to 40 times / 10 cm. In addition, about the number of lower twists, it can be normally set to the same value as the number of upper twists.

  In the present embodiment, the nominal fineness (also referred to as display fineness) of the organic fiber cord is not particularly limited, and may be 900 to 5000 dtex or 1500 to 4500 dtex, for example. Here, the nominal fineness of the organic fiber cord is the total nominal fineness of all the yarns when a plurality of yarns are twisted together.

  Using the organic fiber cord composed of the above, a raw tire (green tire) is produced in a state where the belt reinforcing layer is wound around the outer peripheral side of the belt layer, and the obtained raw tire is vulcanized at, for example, 150 to 180 ° C. By doing so, a pneumatic tire is obtained. When the belt reinforcing layer is formed on the belt layer, one or a plurality of the above organic fiber cords are aligned and rubber-coated, or the organic fiber is wound on the belt layer of the green tire in a spiral manner A wide rubberized sheet with cords aligned may be wound around the belt layer. Preferably, it is wound around the former spiral.

  The number of ends of the organic fiber cord in the belt reinforcing layer (the number of driven cords) can be appropriately set according to the cord strength and the like, and may be, for example, 10-50 cords / 25 mm, or 15-30 cords / 25 mm. Good.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples.

[Measurement and test methods]
The measurement methods and test methods in the examples are as follows.

  Glass transition temperature: Measured using Diamond-DSC manufactured by PERKIN-ELMER according to JIS K7121. The measurement condition is that a sample in a molten state obtained by melting the sample on a hot stage (EP80 manufactured by Mettler) is rapidly cooled using liquid nitrogen, solidified to obtain a measurement sample, and the sample is heated using 10 mg of the measurement sample. The glass transition temperature was measured by raising the temperature in the range of 30 to 350 ° C. under a temperature speed of 20 ° C./min.

  -Yarn productivity: At the end of spinning, the yarn was visually observed, and those having no problem with the shape were evaluated as "Good", and those having fluff and filament breakage were evaluated as "X".

  -Load at 2% elongation: According to JIS L1017, after standing for 24 hours under constant temperature conditions of 20 ° C. and 65% RH, a tensile test is performed using a tensile tester, and the tensile load (cN) at 2% elongation is The value divided by the nominal fineness (dtex) was calculated as the load at 2% elongation.

  Tan δ: The loss tangent of the organic fiber cord was measured with a spectrometer manufactured by UBM. Loss tangent in the temperature range from 30 to 200 ° C. under the conditions of a sample length of 20 mm, a frequency of 10 Hz, an initial load of 6.47 N / cord, and a dynamic strain (strain amplitude) of 1 mm (ie, 5%). Was measured and the value at 100 ° C. was determined.

  ・ Flat spot resistance: After mounting a prototype tire incorporating an internal pressure of 200 kPa on a test vehicle (sedan) with a displacement of 2000 cc and running for 1 hour at a speed of 100 km / h with a load per tire set to 4.31 kN And allowed to stand for 16 hours. Then, sensory evaluation with a test driver was performed. The evaluation was performed with respect to the magnitude of vibration in the up-down direction and the front-rear direction at the start of running, and was evaluated in 20 levels from 0 to 20 points, with the magnitude of vibration of the pneumatic tire of Comparative Example 1 being 10 points. The larger the score, the smaller the vibration, and thus the better the flat spot resistance.

  Rolling resistance: The rolling resistance of the tire was measured using a rolling resistance tester under conditions of a tire internal pressure of 200 kPa, a rim size of 15 × 6JJ, a load of 4.2 kN, and a speed of 80 km / h. It displays with the index | exponent which set the comparative example 1 to 100, and rolling resistance is so small that an index | exponent is small, and it is excellent in low-fuel-consumption property.

  Tire durability: In accordance with JIS D4230, using a steel drum testing machine (drum diameter = 1700 mm) with a smooth surface, ambient temperature 40 ° C., tire internal pressure 180 kPa, rim size 15 × 6 JJ, speed 80 km / h ( Evaluation) The evaluation procedure is as follows. After running for 4 hours at a load of 85% of the maximum load specified by JATMA, then for 6 hours at a load of 90% of the maximum load, and further for 24 hours at the maximum load, the appearance and inner surface were investigated and abnormal If not, the vehicle is further run for 24 hours at 120% of the maximum load. At this time, if there is no abnormality in the appearance and the inner surface, the vehicle is further driven at 140% of the maximum load until a failure occurs. According to this evaluation procedure, the travel distance until the failure occurred was obtained and displayed as an index with Comparative Example 1 being 100. It means that it is excellent in tire durability, so that an index | exponent is large.

[Examples and Comparative Examples]
A pneumatic radial tire for passenger cars having a tire size of 175 / 65R15 and having a belt reinforcing layer (9) as shown in FIG. 1 was prototyped. The constitution of the organic fiber cord constituting the belt reinforcing layer (cap ply) is as shown in Table 1 below for each tire of the examples and comparative examples, and the constitution other than the belt reinforcing layer is the same as all common constitutions. did.

  Specifically, the belt layer was made of 2 + 1 × 0.27 mm steel cords (the number of cords to be driven was 17 / 25.4 mm, and the cord angle was + 25 ° / −25 °). The carcass layer was one ply of polyester fiber 1100 dtex / 2 cord arranged at 23 pieces / 25 mm.

  Each of the organic fiber cords constituting the belt reinforcing layer has a twisted structure obtained by twisting two twisted yarns (specifically, 2 twisted yarns made of polyamide fiber having a nominal fineness of 1400 dtex are 2 A twin twist structure obtained by twisting together, the nominal fineness of the cord is 2800 dtex). In Table 1, Ny66 of Comparative Example 1 is nylon 66. In other examples and comparative examples, high Tg-PA was prepared by melt spinning an aliphatic polyamide produced by a hot melt polymerization method described in International Publication No. 2009/113590 [0057] to [0062] according to a conventional method. It was produced. In all the cords, the number of lower twists was set to the same number as the number of twists (upper twist number) in Table 1. Example 1 and Example 3 are examples using cords of the same material and the same fineness. By changing the number of twists, tension at the time of dip treatment, etc., the load at 2% elongation and tan δ are listed in Table 1. Adjusted to the street. The number of driven organic fiber cords was 28/25 mm in both the examples and comparative examples.

  Using each of the obtained tires, flat spot resistance, rolling resistance, and tire durability were evaluated. The results are shown in Table 1.

  As shown in Table 1, when the product of the aliphatic polyamide fiber cord in which the product of the load at 2% elongation and tan δ is set in the range of 0.035 to 0.044 is used, As compared with Comparative Example 1 using the nylon 66 fiber, rolling resistance could be reduced while improving flat spot resistance. In particular, when using a high Tg aliphatic polyamide fiber cord having a glass transition temperature of 90 to 170 ° C., the product of 2% elongation load and tan δ was set within the above range. Compared with Comparative Example 1, the rolling resistance was reduced while significantly improving the flat spot resistance and without impairing the yarn productivity. In addition to the product and glass transition temperature described above, in Examples 1 to 3 in which the load at 2% elongation is set in the range of 0.79 to 0.90 cN / dtex, the rolling resistance is reduced effectively. Tire durability was also significantly improved. The above-mentioned high Tg aliphatic polyamide fiber cord has higher rigidity than general-purpose nylon 66 fiber cords, but has lower rigidity than PEN fiber cords and the like, while having a high glass transition temperature. We think that it is advantageous in reducing rolling resistance while improving.

  In Comparative Example 2, although the flat spot resistance and tire durability are improved, the product of the load at 2% elongation and tan δ is larger than the specified value. It was. Further, in Comparative Example 3, although the flat spot resistance and the rolling resistance were improved, the product of 2% elongation load and tan δ was less than the specified value, so the effect of improving tire durability could not be obtained.

  The present invention can be suitably used for various pneumatic tires including passenger vehicle tires.

3 ... tread part, 4 ... carcass layer, 7 ... belt layer, 9 ... belt reinforcement layer

Claims (3)

A belt layer in which cords are arranged obliquely with respect to the tire circumferential direction on the outer circumferential side of the carcass layer in the tread portion, and a belt reinforcing layer in which organic fiber cords are arranged along the tire circumferential direction on the outer circumferential side of the belt layer. In a pneumatic tire
The organic fiber cord of the belt reinforcing layer is a cord made of an aliphatic polyamide fiber, and a product of 2% elongation load (cN / dtex) and loss tangent tan δ at a temperature of 100 ° C. is 0.035 to 0.044. A pneumatic tire characterized by using a cord.   The pneumatic tire according to claim 1, wherein the organic fiber cord is made of an aliphatic polyamide fiber having a glass transition temperature of 90C to 170C.   The pneumatic tire according to claim 1 or 2, wherein a load at 2% elongation of the organic fiber cord is 0.79 to 0.90 cN / dtex.

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