JP2016060341A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of achieving both of flat spot resistance and stability during high speed travel.SOLUTION: A pneumatic tire comprises: a belt layer 7 formed by arranging and inclining a cord in a tire peripheral direction on an outer peripheral side of a carcass layer 4 on a tread part 3; and a belt reinforcement layer 9 formed by arranging an organic fiber cord on the outer peripheral side of the belt layer, along the tire peripheral direction. As the organic fiber cord forming the belt reinforcement layer, a cord formed of aliphatic polyamide whose glass transition temperature is 90-170°C, and intermediate extension degree of the organic fiber cord is 5.0-15.0%, is used.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. Conventionally, general-purpose nylon fibers (aliphatic polyamide fibers) represented by nylon 66, nylon 6 and the like have been used for the fiber cords of the belt reinforcing layer. However, the belt reinforcement layer using general-purpose nylon fiber has a characteristic that distortion due to high heat generated during high-speed running is set, so that a so-called flat spot phenomenon that causes the tire to vibrate during re-running tends to occur. .

  Patent Document 1 suggests application of polyethylene naphthalate, polyethylene terephthalate, etc. having higher elasticity and higher glass transition temperature than general-purpose nylon fibers to improve the flat spot phenomenon, and polyethylene terephthalate and polyethylene are used as reinforcing elements for the belt reinforcement layer. The use of naphthalate is disclosed. In Patent Document 2, the belt reinforcing layer is composed of a composite cord formed by twisting a yarn made of nylon 46 having a glass transition temperature higher than that of a general-purpose nylon fiber and a yarn made of an aramid fiber, and has high-speed durability. And improving flat spot resistance. Patent Document 3 discloses that the belt reinforcing layer is composed of a composite cord formed by twisting a yarn made of polyethylene naphthalate and a yarn made of polyethylene terephthalate to improve steering stability and high-speed durability. Has been.

  On the other hand, 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-A-2003-320813 JP 2009-132324 A JP 2014-108675 A International Publication No. 2009/113590

  Polyethylene naphthalate has a higher glass transition temperature than general-purpose nylon fibers and improves flat spot resistance, but its elasticity is high and its elongation at low loads is small. As a result, the belt is not uniformly expanded, which makes it difficult to improve steering stability during high-speed traveling.

  An object of the present invention is to provide a pneumatic tire that can achieve both flat spot resistance and steering stability during high-speed traveling.

  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. In the pneumatic tire provided with the arranged belt reinforcing layers, the organic fiber cord used for the belt reinforcing layer is made of an aliphatic polyamide having a glass transition temperature of 90 to 170 ° C. and an intermediate elongation of 5.0. It is ˜15.0%. Here, the aliphatic polyamide is a polyamide containing an aliphatic skeleton polymerized using an aliphatic diamine and / or an aliphatic dicarboxylic acid, and the aliphatic has a cyclic structure as well as a chain structure. Also included are alicyclics with

  According to the present invention, since the restoration property of the organic fiber cord is improved by configuring the belt reinforcing layer using the organic fiber cord made of the aliphatic polyamide having the specific glass transition temperature, the flat spot resistance is improved. Can be improved. In addition, by using an aliphatic fiber cord having such a high glass transition temperature and an organic fiber cord in which the intermediate elongation is set within the predetermined range, it is possible to follow expansion at the time of tire molding, and at the time of high-speed running Steering stability can be improved. Therefore, both flat spot resistance and steering stability during high-speed traveling can be achieved.

1 is a half sectional view of a pneumatic radial tire according to 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 (equatorial plane) outside the belt layer in the tire radial direction. That is, the organic fiber cord of the belt reinforcing layer extends substantially parallel to the tire circumferential direction, that is, at an angle of approximately 0 ° (preferably an angle of 5 ° or less), and the cord is spaced at a predetermined interval in the tire width direction. Are arranged in 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).

  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 to obtain a tagging effect that increases the rigidity and belt restraint force in the tire circumferential direction and radial direction, and lifts the belt due to centrifugal force during high-speed running Suppresses diameter growth, belt end distortion, and improves 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 yarn 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 is more preferably 100 ° C. or higher, and further preferably 120 ° C. or higher. Increasing the stretch ratio of the aliphatic polyamide increases the orientation and 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. 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.

  The aliphatic polyamide according to the present embodiment having the glass transition temperature is a polyamide including an aliphatic skeleton, and does not include an aramid including only 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.

  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 yarn comprising the aliphatic polyamide according to this embodiment is 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. be able to.

  In the organic fiber cord used for the belt reinforcing layer according to the present embodiment, the intermediate elongation is set in the range of 5.0 to 15.0%. When the organic fiber cord has an intermediate elongation of 5.0% or more, it can follow the expansion of the tire at the time of tire molding, enables uniform expansion of the belt, and improves driving stability at high speeds. Can be increased. When the intermediate elongation of the organic fiber cord is 15.0% or less, it is possible to increase the tagging effect of the belt reinforcing layer and improve the handling stability during high-speed running. The intermediate elongation of the organic fiber cord is preferably 7.0 to 13.0%, more preferably 10.0 to 13.0%. The intermediate elongation is set by, for example, adjusting the cord structure or the number of twists according to the elastic modulus of the aliphatic polyamide constituting the cord, or a known adhesion treatment such as an RFL (resorcin-formalin-latex) treatment liquid. It can be performed by adjusting the type of liquid and the amount of adhesion, and can be set within the above range. Here, the intermediate elongation is measured according to JIS L1017.

  In the present embodiment, the fineness of the organic fiber cord (also referred to as nominal fineness or display fineness) is preferably 900 to 4000 dtex. When the fineness is 900 dtex or more, the restraining force by the belt reinforcing layer can be maintained without increasing the number of cords to be driven. Further, since the fineness is 4000 dtex or less, the rigidity is not excessively increased and the belt is prevented from being sunk into the belt, so that it is possible to suppress a decrease in steering stability during high speed traveling. The fineness of the organic fiber cord is preferably 1200 to 3800 dtex, more preferably 1500 to 3500 dtex.

  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 (number of upper twists) T is not particularly limited, and may be, for example, 10 to 50 times / 10 cm or 15 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.

  Using the organic fiber cords as described 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 resulting raw tire is vulcanized to form 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-in cords) can be appropriately set according to the cord strength and the like, and is not particularly limited, but is preferably 15 to 50/25 mm.

  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.

  -Tensile strength and elongation: According to JIS L1017, after standing for 24 hours under constant temperature conditions of 20 ° C. and 65% RH, the tensile strength and elongation are determined using a tensile tester, and the tensile strength is determined from the fineness of the sample. As well as calculating the elongation. In addition, the yarn physical properties in Table 1 are measured values in a non-twisted state of the yarn constituting the cord (including a state in which a slight twist is applied so that the filament does not come apart in the measurement).

  Intermediate elongation: according to JIS L1017, the sample was allowed to stand for 24 hours under constant temperature conditions of 20 ° C. and 65% RH, and then the elongation of the sample at a constant load was measured using a tensile tester. The load was a value obtained by multiplying the fineness (dtex) of the sample by 0.023 N / dtex.

  -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".

  ・ Flat spot resistance: A test tire incorporated with an internal pressure of 200 kPa is mounted on a test vehicle with a displacement of 2000 cc, the load per tire is 4.31 kN, and the vehicle is run at a speed of 100 km / h for 1 hour, then 16 hours. Allowed to stand. 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 Example 1 being 10 points. The smaller the number of points, the smaller the vibration, and thus the better the flat spot resistance.

  ・ High-speed steering stability: A test tire incorporated with an internal pressure of 200 kPa is mounted on a test vehicle with a displacement of 2000 cc, runs on a dry road test course, steerability during lane change and cornering at a speed of 100 km / h, and straight ahead Time stability is evaluated by sensory evaluation by one skilled test driver. This sensory evaluation is indicated by an index with the pneumatic tire of Comparative Example 1 as a reference (100), and the higher this index, the better the high-speed steering stability.

[Examples and Comparative Examples]
A pneumatic radial tire for passenger cars having a tire size of 195 / 65R15 and provided with 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 18 / 25.4 mm, and the cord angle was + 25 ° / −25 °). The carcass layer was one ply of polyester fiber 1670 dtex / 2 cord arranged at 23 pieces / 25 mm. The number of organic fiber cords driven into the belt reinforcing layer was 20/25 mm.

  In Table 1, “Ny66” indicates nylon 66, and “PEN” indicates polyethylene naphthalate. “High Tg-PA” is an aliphatic polyamide having a glass transition temperature higher than that of nylon 66, prepared by the hot melt polymerization method described in International Publication No. 2009/113590 [0057] to [0062]. A yarn produced by melt spinning according to a conventional method. Each of the cords of the examples and comparative examples has a double twisted structure obtained by twisting two twisted lower twisted yarns. In addition, the twist number in the table | surface about a double twist structure showed the number of upper twists, and the number of lower twists was set to the same number as the number of upper twists.

  Using each of the obtained tires, flat spot resistance and high-speed steering stability were evaluated. The results are shown in Table 1.

  As shown in Table 1, in Examples 1 to 4, the flat spot resistance is improved as compared with Comparative Example 2 using nylon 66, and compared to Comparative Example 1 using PEN. High-speed steering stability was improved while maintaining flat spot resistance. On the other hand, in Comparative Example 3, the glass transition temperature of the aliphatic polyamide constituting the organic fiber cord was 82 ° C., which was not specified, and thus the effect of improving the flat spot resistance was insufficient. In Comparative Example 4, since the glass transition temperature of the aliphatic polyamide constituting the organic fiber cord was 175 ° C., which was not specified, the productivity of the yarn was reduced, the tensile strength was small, and the high speed steering stability was improved. Was not obtained. In Comparative Example 5, although the flat spot resistance was improved as compared to Comparative Example 2, the intermediate elongation of the organic fiber cord was 4.5% outside the specified range, so it was not possible to follow the expansion of the tire at the time of molding, The high-speed steering stability was inferior because the belt was unevenly expanded. In Comparative Example 6, the intermediate elongation of the organic fiber cord was 17.9%, which was not specified, so the tagging effect by the belt reinforcing layer was small and the high-speed steering stability was poor.

  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 (2)

  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 the pneumatic tire, the organic fiber cord used for the belt reinforcing layer is made of an aliphatic polyamide having a glass transition temperature of 90 to 170 ° C. and an intermediate elongation of 5.0 to 15.0%. Tires.   The pneumatic tire according to claim 1, wherein a nominal fineness of the organic fiber cord is 900 to 4000 dtex.

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