JP4923532B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire. More specifically, while using a polyolefin ketone fiber cord as a carcass cord for forming a carcass layer, good durability at a level equivalent to or exceeding that when a rayon fiber cord is used. And a novel pneumatic tire capable of realizing good steering stability.

  Conventionally, as a carcass cord that forms a pneumatic tire, the number of twists of the cord and the number of twists of the cord have been made different to improve the fatigue resistance while maintaining the strength of the cord and ensuring the rigidity. Specifically, it has been practiced to set the number of lower twists to be smaller and to increase the number of upper twists than the number of lower twists.

  For example, as a proposal to become such a technical idea, it is made of polyolefin ketone fiber, and for rubber reinforcement that the strength and fatigue resistance are highly balanced by specifying each of the lower twist and the upper twist in a specific range A cord has been proposed (Patent Document 1). Specifically, for example, as shown in the examples, the number of lower twists is 13 to 37 times / 10 cm with respect to the number of upper twists of 39 times / 10 cm. Examples of polyolefin ketone fiber cords are disclosed.

  However, in the case of this proposal, by reducing the number of lower twists, even when the same fiber yarn (raw material yarn) is used, the cord diameter as a twisted cord becomes smaller, that is, becomes thinner, resulting in a unit carcass width. When the same number of cords are driven in, the distance between the cords becomes larger, and as a result, for example, the same or more than when using almost the same rayon fiber twist cord, It is difficult to ensure good handling stability. In other words, when the cord becomes thinner and the distance between the cords becomes larger, the amount of rubber used in the carcass layer increases, and when this amount of rubber increases, the handling responsiveness deteriorates and good steering stability is achieved. There was a problem that it could not be secured.

  In addition, the carcass layer is composed of at least two radial plies reinforced with fiber cords, and the twist coefficient of each of the outer ply and the inner ply is within a specific range, so that the strength particularly during run-flat running And a proposal to balance fatigue resistance (Patent Document 2).

However, this proposal is only a proposal regarding the structural difference between the cords of the outer ply and the inner ply, particularly focusing on the strength and fatigue resistance at the time of run-flat, and is a problem during normal running that is problematic in the present invention. Paying attention to durability and handling stability, it was also not related to the upper twist / lower twist structure of the carcass cord as a single body.
JP 2004-308024 A JP 2001-63308 A

  In view of the above points, the object of the present invention is to provide a pneumatic tire having excellent driving stability and good durability to the same level or even higher than when a rayon fiber cord is used. It is intended to be provided in pneumatic tires using polyolefin ketone fiber cords.

The pneumatic tire of the present invention that achieves the above-described object has the following configuration (1).
(1) It consists of a polyolefin ketone fiber represented by the following formula (a), has a heat shrinkage stress value at a dry heat of 150 ° C. of 0.19 cN / dtex or more and 0.81 cN / dtex or less , and a lower twist coefficient A carcass layer including a twisted cord in which a ratio R (= N ₂ / N ₁ ) of N ₁ and an upper twist coefficient N ₂ is 1.20 ≦ R ≦ 1.70, and an upper twist coefficient N ₂ is 1600 or more and 2300 or less A pneumatic tire characterized by having one ply or more.
_{- (CH 2 -CH 2 -CO)} n- (R-CO-) m- ............ formula (a)

Here, in the formula (a), the relationship between n and m is represented by the following formula (b), and R is an alkylene group having 3 or more carbon atoms.
1.05 ≧ (n + m) /n≧1.00 Expression (b)
Also,
N ₁ = T ₁ × √ (D ₁ /1.111)
N ₂ = T ₂ × √ (D ₂ /1.111)
Here, N ₁ : Lower twist coefficient,
N ₂ : Upper twist coefficient,
D ₁ : Number of decitex displayed on the lower twisted yarn,
D ₂ : Number of display decitex of the upper twisted yarn,
T ₁ : the number of twists of the twisted yarn (times / 10 cm),
T ₂ : Number of upper twists (twice / 10 cm)

  According to the first aspect of the present invention, in a pneumatic tire using a polyolefin ketone fiber cord, compared with the case where a rayon fiber cord is used, the steering stability and the good level which are excellent to the same level or more than that are used. A pneumatic tire having durability can be provided.

Hereinafter, the pneumatic tire of the present invention will be described in more detail.
It is important that the pneumatic tire of the present invention first comprises a polyolefin ketone fiber represented by the following formula (a).

That is, the polyolefin ketone fiber is, for example, disclosed in JP-A-1-124617, JP-A-2-112413, US Pat. No. 5,194,210, JP-A-9-324377, JP-A-2001-115007, or Although it can be obtained by melt spinning or wet spinning disclosed in JP-A-2001-131825, etc., it is particularly important in the present invention to use a polyolefin ketone fiber having a structure represented by the following formula (a). It is.
_{- (CH 2 -CH 2 -CO)} n- (R-CO-) m- ............ formula (a)

Here, in the formula (a), the relationship between n and m is represented by the following formula (b), and R is an alkylene group having 3 or more carbon atoms.
1.05 ≧ (n + m) /n≧1.00 Expression (b)

  If the m fraction (alkylene unit other than ethylene) of the polyolefin ketone fiber is increased, the tire traveling growth is increased, and the durability is remarkably lowered. This is thought to be because the crystal structure of the spun fiber changes with an increase in m units, and the secondary binding force between the molecular chains decreases.

  Here, it is more preferable to use an alternating copolymer consisting essentially of ethylene and carbon monoxide, where m = 0. In order to produce such a polyolefin ketone fiber, a wet spinning method is used. Is preferred.

Furthermore, it is important that the twisted cord of the polyolefin ketone fiber used in the present invention has a heat shrinkage stress value at a dry heat of 150 ° C. of 0.19 cN / dtex or more and 0.81 cN / dtex or less .

  The heat shrinkage stress value at a dry heat of 150 ° C. is used as a standard parameter for the tire temperature in the post-cure inflation (PCI) process in which a predetermined air pressure is applied immediately after the tire is removed from the mold after vulcanization. Is gradually cooled from 150 ° C. or higher, so that the tire dimensions change depending on the heat shrinkage stress value generated in the process, and the heat shrinkage stress value at a dry heat of 150 ° C. is one criterion. This is significant in that it affects the level of dimensional change.

  That is, if the polyolefin ketone fiber having the above-described heat shrinkage stress characteristics is used for the carcass cord, the heat shrinkage stress generated in the tire vulcanization process is higher than, for example, conventional polyethylene terephthalate (PET) fiber (generally, In PET, 0.07 to 0.18 cN / dtex), after vulcanization, there is less dimensional change in the post-cure inflation (PCI) process in which a predetermined air pressure is applied after the tire is taken out of the mold. This makes it possible to manufacture a pneumatic tire having characteristics with high accuracy according to expected performance.

In particular, a preferable range of the heat shrinkage stress value at 150 ° C. dry heat is 0.19 cN / dtex or more and 0.69 cN / dtex or less.

  In the present invention, it is important that the carcass twisted cord made of polyolefin ketone fiber is formed by twisting a plurality of multifilament yarns such as 1100 to 2200 dtex made of 100% polyolefin ketone fiber. Furthermore, in that case, it is important to make the structure of the lower twist and the upper twist as follows.

That is, the ratio R (= N ₂ / N ₁ ) between the lower twist coefficient N ₁ and the upper twist coefficient N ₂ is set to 1.20 ≦ R ≦ 1.70, and the upper twist coefficient N ₂ is It is in the region of 1600 or more and 2300 or less.

According to the above-described structure of the lower twist and the upper twist of the present invention, the technical idea will be described with reference to the drawings. FIG. 1 is a schematic model diagram for explaining the technical idea of the present invention, and FIG. When the number of twists of the lower twisted yarn 4 is reduced and the carcass twisted cord 3 is formed by twisting two of the lower twisted yarns 4 as a technical idea of the prior art, the diameter of the lower twisted yarn is reduced. It shows that the diameter of the twisted cord 3 is reduced and the interval W ₁ between the twisted cords 3 is increased. 2 is a carcass rubber part. On the other hand, in the present invention, as shown in the model in FIG. 1 (b), the lower twist coefficient N ₁ is smaller than the upper twist coefficient N ₂ by a specific ratio, so that the same polyolefin ketone multifilament yarn is used. Even when is used, the distance between the twisted cords 3 becomes small as shown by W ₂ . Accordingly, the amount of rubber used in the carcass layer can be reduced, which can realize good handling responsiveness and good steering stability.

From the above viewpoint, when the ratio R (= N ₂ / N ₁ ) is less than 1.20, good steering stability can be obtained, but the amount of cord used increases, which is not preferable in terms of price. If it is larger than 1.70, the amount of rubber between the cords / cords increases, the elastic modulus of the cords cannot be utilized, and it becomes difficult to obtain good steering stability, which is not preferable.

When the upper twist coefficient N ₂ is smaller than 1600, it is difficult to exhibit basic performance as a carcass twisted cord. On the other hand, when the upper twist coefficient N ₂ is larger than 2300, the elastic modulus at low load becomes small. Also, it is not desirable from the viewpoint of productivity and cost of the twisting process. The upper twist coefficient N ₂ of 1600 or more and 2300 or less is about 29.2 times / 10 cm (N ₂ ) in terms of the number of upper twists of two 1700 decitex polyolefin ketone fiber yarns. Is equal to or greater than about 41.9 times / 10 cm (when N ₂ is equal to 2300).

  The pneumatic tire of the present invention is configured to have one or more ply of carcass layers including the above-described carcass cords of polyolefin ketone fibers.

  The thickness (single fiber fineness) of the single fiber constituting the polyolefin ketone multifilament yarn is not particularly limited, but is preferably 0.5 to 7 dtex according to various findings of the present inventors. Preferably it is in the range of 1 to 4.5 dtex.

  When the single fiber fineness is less than 0.5 dtex, fluffing may occur frequently at the raw fiber stage such as the yarn-making process, the twisting process, and the weaving process, and the cord strength is generally lowered. On the other hand, if it exceeds 7 dtex, the polyolefin ketone fiber is generally produced by a wet spinning method, but the skin surface structure on the fiber surface is prominent, and the structure is prone to fibrillation. Generally, it should be avoided because it leads to a decrease in strength of the twisted cord.

A polyolefin ketone fiber having a heat shrinkage stress value at a dry heat of 150 ° C. of 0.19 cN / dtex or more and 0.81 cN / dtex or less is subjected to an appropriate heat treatment after the formation of the fiber. In the present invention, it can be incorporated into a tire manufacturing process (carcass manufacturing process) and is not particularly limited. For example, by a combination of heat treatment conditions as described below, etc. It can be obtained.

That is, in order to form a twisted cord made of polyolefin ketone fiber in the carcass layer, RFL (resorcin-formalin-latex as an adhesive) is used in order to improve the adhesiveness with rubber which is another material constituting the carcass. ) In general, a step of applying a liquid is provided. After the strand cord made of polyolefin ketone fiber is immersed in the RFL liquid and attached to the RFL liquid, a tension heat treatment is performed for drying and fixing the RFL liquid. By carrying out under special conditions, a polyketone fiber having a heat shrinkage stress value at a dry heat of 150 ° C. of 0.19 cN / dtex or more and 0.81 cN / dtex or less can be obtained.

  Specifically, for example, the tension heat treatment is performed in two zones, a heat setting zone (heat setting zone) and a fixing zone (normalizing zone). In particular, the heat setting zone is 190 ° C. to 260 ° C. × The tension applied to the cord under 60 seconds to 180 seconds is performed in the condition range of 0.20 cN / dtex to 1.50 cN / dtex, and the fixing zone is applied to the cord under 190 ° C. to 260 ° C. × 60 seconds to 180 seconds. It is important to perform the tension under a condition of 0.015 cN / dtex or more. In particular, the heat treatment zone (heat set zone) and the fixing zone (normalizing zone) are preferably treated at 200 to 240 ° C. for 60 to 160 seconds.

  Regarding the conditions of the tension heat treatment, it is important to perform the tension heat treatment so that the tension of the heat setting zone in the above range is higher than the tension of the fixing zone.

  The adhesion amount of resorcin / formalin / latex (attachment amount of active solid component) is preferably 7% by weight or less (weight of carcass layer), and particularly, the adhesion amount is 3.0% by weight or more. 6.0 wt% or less is preferable.

   Hereinafter, specific configurations and effects of the pneumatic tire cord of the present invention will be described based on examples. The heat shrinkage stress, durability, and steering stability at a dry heat of 150 ° C. are measured and determined as follows.

(1) Heat shrinkage stress at 150 ° C. dry heat:
A fiber cord was attached to a chuck with an interval of 250 mm, and the sample length (between chucks) in a state where a load of (display decitex number × 0.45) mN was applied was used as a test length.

  While maintaining the test length, the temperature was increased according to the following temperature increase pattern, and the heat shrinkage stress generated at 150 ° C. was measured. The measurement was performed by setting n number to 2 and taking the average value.

Heating pattern ・ Raise the temperature from room temperature to 40 ° C in 1 minute and hold for 1 minute.
-Then, it heated up to 250 degreeC with the temperature increase rate of 5 degree-C / min.

(2) Durability:
Indoor load durability evaluation was performed using the tire manufactured by each Example and the comparative example. The durability of Comparative Example 1 using a rayon tire cord was evaluated with reference to (100), and each Example and Comparative Example were determined. The larger this value, the better.

(3) Steering stability:
A 3.0 liter sports car is fitted with tires manufactured in each of the examples and comparative examples to form a state equivalent to four adult passengers and actually run on the test course to feel the handling stability. Evaluation was performed. Evaluation was made based on the handling stability of Comparative Example 1 using a rayon tire cord as a reference (100), and each Example and Comparative Example were determined. The larger this value, the better.

Examples 1-5, Comparative Examples 1-8
Pneumatic tires with a tire size of 225 / 45ZR17, as shown in detail in Table 1, each fiber cord in which the yarn type, 150 ° C. heat shrinkage stress value, lower twisting condition, upper twisting condition, etc. were changed to the carcass layer The above-mentioned durability and steering stability were evaluated.

  In Examples 1 to 5 and Comparative Examples 2 to 8, two multifilament yarns having a yarn fineness of 1670 dtex are twisted to form a double yarn to form a carcass twisted cord.

  In Comparative Example 1, two 1840 dtex rayon fiber yarns are twisted to form a twin yarn to form a carcass twisted cord.

  Comparative Example 3 uses an aramid fiber cord. Except for Comparative Example 1 and Comparative Example 3, all of them use polyolefin ketone fiber (indicated as POK fiber in Table 1) cord.

  The heat shrinkage stress at 150 ° C. of dry heat of polyolefin ketone fiber yarns, etc., is different from the heat treatment zone as the tension heat treatment conditions performed after the immersion adhesion treatment of RFL (resorcin-formalin-latex) liquid in order to make various differences. (Heat set zone) and fixing zone (normalizing zone) conditions were appropriately combined and changed. The details (yarn tension during processing × temperature × time) are as shown in Table 2, respectively.

  In each example and comparative example, the amount of resorcin-formalin-latex deposited was about 5% by weight (vs. carcass cord weight).

  As can be seen from these examples and comparative examples, according to the pneumatic tire of the present invention, polyolefin ketone fibers having the characteristics of high strength and high elastic modulus are used, and the conventional rayon fiber cord is used for running durability. A pneumatic tire capable of improving steering stability while maintaining or exceeding that of using a tire is realized.

FIG. 1 is a schematic cross-sectional model diagram illustrating a state of a carcass cord in a carcass layer. FIG. 1A schematically illustrates a cross section of the carcass layer when the number of twists of the lower twisted yarn is small. (B) shows a model of a cross section of the carcass layer when the number of twists of the lower twisted yarn is large.

Explanation of symbols

1: carcass layer 2: carcass rubber portion 3: carcass ply cords 4: twist yarn W _1, W _2: distance between the carcass ply cords

Claims (1)

It consists of a polyolefin ketone fiber represented by the following formula (a), has a heat shrinkage stress value at a dry heat of 150 ° C. of 0.19 cN / dtex or more and 0.81 cN / dtex or less , and a lower twist coefficient N ₁ is the ratio _{R (= N 2 / N 1} ) is 1.20 ≦ R ≦ 1.70 above twist factor N _2, 1-ply carcass layer comprising a twisted cord above twist factor N ₂ is 1600 or more 2300 or less A pneumatic tire characterized by having the above.
_{- (CH 2 -CH 2 -CO)} n- (R-CO-) m- ............ formula (a)
Here, in the formula (a), the relationship between n and m is represented by the following formula (b), and R is an alkylene group having 3 or more carbon atoms.
1.05 ≧ (n + m) /n≧1.00 Expression (b)
Also,
N ₁ = T ₁ × √ (D ₁ /1.111)
N ₂ = T ₂ × √ (D ₂ /1.111)
Here, N ₁ : Lower twist coefficient,
N ₂ : Upper twist coefficient,
D ₁ : Number of decitex displayed on the lower twisted yarn,
D ₂ : Number of display decitex of the upper twisted yarn,
T ₁ : the number of twists of the twisted yarn (times / 10 cm),
T ₂ : Number of upper twists (twice / 10 cm)

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