JP2020111632A - Vulcanized rubber composition for tire tread, tire provided with vulcanized rubber composition and evaluation method of vulcanized rubber composition for tire tread - Google Patents

Abstract

To provide a vulcanized rubber composition for a tire tread having high robustness with respect to abrasion resistance, a tire provided with the vulcanized rubber composition and an evaluation method of the vulcanized rubber composition for a tire tread.SOLUTION: Provided is a vulcanized rubber composition for a tire tread. When a regression equation that defines an abrasion amount Z of the rubber sample 2 relative to the rolling velocity V and the abrasion energy E is calculated, when an abrasion test of rolling with a cylindrical rubber sample 2 pressed against a pseudo road surface 8 is performed a plurality of times by varying the rolling velocity of the rubber sample 2 and abrasion energy E acted the rubber sample 2, in the range where the rolling velocity V of the rubber sample 2 is 2.5 to 25 (km/h), a first gradient e of the abrasion amount Z relative to the abrasion energy E of the regression equation is 1.8 or smaller.SELECTED DRAWING: Figure 5

Description

The present invention relates to a vulcanized rubber composition suitable for use in a tire tread, a tire including the vulcanized rubber composition, and a method for evaluating the vulcanized rubber composition.

Conventionally, in order to use a vulcanized rubber composition for a tire tread, it has been attempted to evaluate the wear resistance performance of the vulcanized rubber composition. For example, Patent Document 1 below proposes a method of evaluating the wear resistance performance of a rubber material by causing a cylindrical rubber material to rotate and run on a simulated road surface to cause wear.

JP, 2016-218017, A

However, the rubber composition evaluated by the evaluation of Patent Document 1 may have different evaluation results under the conditions different from the conditions used for the evaluation, and the rubber composition suitable for various conditions of actual vehicle running. Could not be identified.

The present invention has been devised in view of the above circumstances, a vulcanized rubber composition for a tire tread having high robustness with respect to abrasion resistance, a tire provided with this vulcanized rubber composition, and a tire tread. The main object of the present invention is to provide a method for evaluating a vulcanized rubber composition for use.

The present invention is a vulcanized rubber composition for a tire tread, in which a cylindrical rubber sample is subjected to a wear test in which it is pressed against a simulated road surface to cause rolling, and acts on the rolling speed and the rubber sample of the rubber sample. When a regression equation that defines the amount of wear of the rubber sample with respect to the rolling speed and the wear energy when the wear energy is changed a plurality of times is calculated, the rolling speed of the rubber sample is 2. In the range of 5 to 25 (km/h), the first slope of the wear amount with respect to the wear energy of the regression equation is 1.8 or less.

In the vulcanized rubber composition for a tire tread of the present invention, the wear energy acting on the rubber sample is in the range of 40 to 350 (J/m ² ), of the wear amount with respect to the rolling speed of the regression equation. It is desirable that the second inclination is within ±0.4.

In the vulcanized rubber composition for tire tread of the present invention, it is desirable that the first slope of the regression equation is 1.6 or less.

In the vulcanized rubber composition for tire tread of the present invention, it is desirable that the first slope of the regression equation is 1.5 or less.

In the vulcanized rubber composition for tire tread of the present invention, it is desirable that the first slope of the regression equation is 1.4 or less.

In the vulcanized rubber composition for tire tread of the present invention, it is desirable that the second slope of the regression equation is within ±0.3.

In the vulcanized rubber composition for tire tread of the present invention, it is desirable that the second slope of the regression equation is within ±0.2.

In the vulcanized rubber composition for tire tread of the present invention, it is desirable that the second slope of the regression equation be within ±0.1.

The present invention is preferably a tire including the vulcanized rubber composition for the tire tread described above.

The present invention is a method for evaluating a vulcanized rubber composition for a tire tread, in which a cylindrical rubber sample is subjected to a wear test of rolling by pressing against a pseudo road surface, and from the results of the test process. Including the evaluation step for evaluating the wear resistance performance of the rubber sample, the test step, the abrasion test is performed a plurality of times by changing the rolling energy of the rubber sample and the abrasion energy acting on the rubber sample, the evaluation. The step, when calculating a regression equation that defines the amount of wear of the rubber sample with respect to the rolling speed and the wear energy, in the range of the rolling speed predetermined, for the wear energy of the regression equation It is characterized in that the first inclination of the wear amount is evaluated.

In the method for evaluating a vulcanized rubber composition for a tire tread of the present invention, the evaluation step includes a second slope of the wear amount with respect to the rolling speed of the regression equation in a predetermined range of the wear energy. It is desirable to evaluate.

In the rubber composition for a tire tread of the present invention, a cylindrical rubber sample is subjected to a wear test in which the rubber sample is pressed against a simulated road surface to roll, and the rolling speed of the rubber sample and the wear energy acting on the rubber sample are changed. When a regression equation that defines the amount of wear of the rubber sample with respect to the rolling speed and the wear energy when it is performed a plurality of times is calculated, the rolling speed of the rubber sample is 2.5 to 25 (km/km In the range of h), the first slope of the wear amount with respect to the wear energy of the regression equation is 1.8 or less. Such a rubber composition for a tire tread has good wear resistance performance under various conditions of actual vehicle running, and can have high robustness with respect to wear resistance performance.

In the evaluation method of the vulcanized rubber composition for the tire tread of the present invention, the test step is performed a plurality of times by changing the rolling speed of the rubber sample and the abrasion energy acting on the rubber sample in the abrasion test, and the evaluation step is When calculating a regression equation that defines the amount of wear of the rubber sample with respect to the rolling speed and the wear energy, in the range of the rolling speed predetermined of the rubber sample, the wear energy of the regression equation The first slope of the wear amount with respect to is evaluated. Such a method for evaluating a vulcanized rubber composition for a tire tread can accurately evaluate wear resistance performance under various conditions of actual vehicle running.

1 is a perspective view showing an embodiment of a tester for carrying out a wear test of a vulcanized rubber composition for a tire tread of the present invention. 1 is a flowchart showing an embodiment of a method for evaluating a vulcanized rubber composition for tire tread of the present invention. It is a flowchart of a test process. It is a flowchart of an evaluation process. It is a graph which shows an example of a regression equation. It is a graph which shows an example of the 1st slope e of a regression equation. It is a graph which shows an example of the 2nd slope v of a regression equation.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing a testing machine 1 for performing an abrasion test on a vulcanized rubber composition for a tire tread according to this embodiment. As shown in FIG. 1, a vulcanized rubber composition for a tire tread is prepared, for example, as a cylindrical rubber sample 2. The rubber sample 2 may be, for example, integrally manufactured in a cylindrical shape, or may be manufactured in a sheet shape and attached to the periphery of a cylindrical core material.

The test machine 1 of the present embodiment is for evaluating the wear resistance performance of the vulcanized rubber composition for the tire tread from the wear state of the rubber sample 2. The tester 1 includes, for example, a turntable 3 for rotating the rubber sample 2, a support section 4 for supporting the rubber sample 2, and a base 5 for supporting the turntable 3 and the support section 4.

The rubber sample 2 has, for example, a hole portion 6 into which the support portion 4 is inserted, provided in the center of a cylinder. Such holes 6 serve to rotatably support the rubber sample 2 by the support 4.

The outer diameter of the rubber sample 2 is preferably 50 to 120 mm. The width w of the rubber sample 2 is preferably 15 to 22 mm. When the rubber sample 2 is manufactured in a sheet shape, the thickness t of the rubber sample 2 is preferably 0.5 to 4 mm. With such a rubber sample 2, the wear state can be accurately measured.

The turntable 3 of the present embodiment includes a disc-shaped turntable 7 and a pseudo road surface 8 fixed on the turntable 7. The rotary table 7 is fixed to, for example, an upper end side of a vertical shaft 9 protruding upward from the base 5. The lower end of the vertical shaft 9 is fixed to, for example, an electric motor (not shown) built in the base 5. The electric motor is preferably controlled to rotate the rotary table 7 at an arbitrary rotation speed. In such a turntable 3, the rotational speed of the simulated road surface 8 can be freely changed, and the rolling speed V of the rubber sample 2 can be arbitrarily changed.

The rolling speed V of the rubber sample 2 is preferably 0.1 to 120 km/h, more preferably 1 to 50 km/h. The turntable 3 capable of reproducing such a rolling speed V can change the rolling speed V of the rubber sample 2 and perform a wear test corresponding to various conditions of actual vehicle running.

The pseudo road surface 8 is formed of, for example, a grindstone. The grindstone count of the pseudo road surface 8 is preferably 60 to 240. Such a pseudo road surface 8 can efficiently wear the rubber sample 2. The simulated road surface 8 may be, for example, asphalt or concrete. During the abrasion test, for example, sand may be sprinkled on the simulated road surface 8.

The support part 4 includes, for example, a horizontal shaft 10 that is inserted into the hole 6 of the rubber sample 2 and a cylinder 11 that moves the horizontal shaft 10. The horizontal shaft 10 is provided with, for example, measuring means (not shown) capable of measuring the lateral force F1, the ground load P, and the longitudinal force F2 acting on the rubber sample 2.

The cylinder 11 preferably moves the horizontal shaft 10 in the vertical direction. In such a cylinder 11, the ground load P on the pseudo road surface 8 of the rubber sample 2 can be set arbitrarily. The ground contact load P is applied such that the average pressure in the ground contact surface is preferably 0.1 to 1 MPa, more preferably 0.2 to 0.8 MPa. The cylinder 11 capable of reproducing such a ground contact load P can set an average ground contact pressure of an actual vehicle, and can perform a wear test corresponding to various conditions of actual vehicle travel.

The cylinder 11 is preferably supported on the base 5 so as to be rotatable about a vertical axis. In such a cylinder 11, the slip angle θ of the rubber sample 2 with respect to the pseudo road surface 8 can be arbitrarily set. In such a cylinder 11, the lateral force F1 acting on the rubber sample 2 can be arbitrarily changed based on the ground load P and the slip angle θ. Here, the relationship between the lateral force F1 acting on the rubber sample 2, the ground contact load P, and the slip angle θ is preferably obtained in advance by a preliminary test or the like by a conventionally known method.

Next, with reference to FIG. 1, a method for evaluating the vulcanized rubber composition for the tire tread of the present embodiment using the above-described tester 1 will be described. FIG. 2 is a flow chart showing a method for evaluating a vulcanized rubber composition for a tire tread according to this embodiment. As shown in FIG. 2, in the evaluation method of the present embodiment, the rubber sample 2 is subjected to a wear test in which the rubber sample 2 is pressed against the pseudo road surface 8 to roll it, and a rubber is obtained from the results of the test step S1. The evaluation step S2 for evaluating the abrasion resistance performance of the sample 2 is included.

FIG. 3 is a flowchart showing the test process S1. As shown in FIG. 3, in the test process S1 of this embodiment, first, a preparation process S11 is performed. In the preparation step S11, for example, the rubber sample 2 is prepared.

The rubber sample 2 of the present embodiment is manufactured in a sheet shape and is attached around a cylindrical core material. It is desirable that the rubber samples 2 are prepared in a number equal to or more than the number of times of the abrasion test step S12 performed after the preparation step S11 in the test step S1. The relationship between the lateral force F1 acting on the rubber sample 2, the ground contact load P, and the slip angle θ may be obtained in this preparation step S11. Such a rubber sample 2 can be subjected to a wear test under a plurality of conditions.

The abrasion test step S12 of this embodiment is performed a plurality of times by changing at least one of the rolling speed V, the ground contact load P, and the slip angle θ of the rubber sample 2. In the wear test step S12, first, the rolling speed V of the rubber sample 2 and the wear energy E acting on the rubber sample 2 are set based on predetermined conditions.

Here, the wear energy E of the rubber sample 2 is calculated, for example, by the lateral force F1 acting on the rubber sample 2 and the slip angle θ based on the following mathematical formula 1.

Since the relationship between the lateral force F1 acting on the rubber sample 2 and the ground load P and the slip angle θ is obtained in advance, the wear energy E of the rubber sample 2 is the ground load P and the slip angle θ of the rubber sample 2. It can be set arbitrarily by changing.

In the wear test step S12, a wear test is performed in which the cylindrical rubber sample 2 is pressed against the pseudo road surface 8 to roll under the above-mentioned conditions. Such a wear test step S12 can accurately reproduce the wear state due to actual vehicle travel.

In the test process S1, it is desirable that after the wear test process S12, a judgment process S13 for judging whether to perform the wear test under different conditions is performed. That is, the determination step S13 of the present embodiment determines whether the abrasion test has been performed multiple times.

In the determination step S13, for example, when it is determined that the abrasion test is performed under different conditions, the rolling speed V of the rubber sample 2 and the abrasion energy E acting on the rubber sample 2 are changed, and the abrasion test step S12 is performed again. Be seen. In the determining step S13 of the present embodiment, if it is determined that the wear test of a predetermined number of times is completed, the test step S1 is ended.

ここで、ａ〜ｄは、フィッティングパラメータである。 FIG. 4 is a flowchart of the evaluation step S2. As shown in FIG. 4, in the evaluation step S2 of the present embodiment, first, a regression equation calculation step S21 that calculates a regression equation based on the results of a plurality of wear tests is performed. In the regression formula calculating step S21, for example, a regression formula that defines the wear amount Z of the rubber sample 2 with respect to the rolling speed V and the wear energy E is calculated based on the following formula 2.

Here, a to d are fitting parameters.

FIG. 5 is a graph showing an example of the regression equation. In FIG. 5, the wear amount Z is shown on the plane defined by the rolling speed V axis and the wear energy E axis. All axes in FIG. 5 are each represented as a logarithmic axis. As shown in FIG. 5, the regression equation of the present embodiment defines one curved surface based on the results of a plurality of wear tests.

As shown in FIG. 4, in the evaluation step S2 of the present embodiment, after the regression equation calculation step S21, the first slope e of the wear amount Z with respect to the wear energy E of the regression equation obtained by Equation 2 and An inclination calculation step S22 of determining the second inclination v of the wear amount Z with respect to the rolling speed V is performed.

The first slope e of the regression equation is calculated based on the following Equation 3 by using two wear energies E ₁ and E _{2 at} the same rolling speed V and two wear amounts Z ₁ and Z ₂ corresponding to them. To be done.

The second slope v of the regression equation is calculated, for example, from the following Equation 4 using two rolling speeds V ₁ and V _{2 at} the same wear energy E and two corresponding wear amounts Z ₁ and Z _2. To be done.

In the evaluation step S2 of the present embodiment, after the inclination calculation step S22, a wear evaluation step S23 for evaluating the calculated first inclination e and second inclination w is performed. In the wear evaluation step S23 of the present embodiment, first, the first slope e of the regression equation is evaluated in the range of the rolling speed V determined in advance.

FIG. 6 is a graph showing an example of the first slope e of the regression equation. The horizontal axis of FIG. 6 represents the rolling speed V as a logarithmic axis, and the vertical axis represents the first slope e. As shown in FIG. 6, the range of the predetermined rolling speed V is, for example, 2.5 to 25 (km/h). It can be said that the rubber sample 2 having a small first slope e of the regression equation in such a range of the rolling speed V has high robustness with respect to wear resistance performance.

In the wear evaluation step S23 of the present embodiment, next, the second slope v of the regression equation is evaluated in the range of the predetermined wear energy E.

FIG. 7 is a graph showing an example of the second slope v of the regression equation. The horizontal axis of FIG. 7 represents the wear energy E as a logarithmic axis, and the vertical axis represents the second slope v. As shown in FIG. 7, the predetermined range of wear energy E is, for example, 40 to 350 (J/m 2 ). It can be said that the rubber sample 2 having a small change in the second slope v of the regression equation in such a range of the wear energy E has high robustness with respect to wear resistance performance.

Next, a vulcanized rubber composition suitable for use in the tire tread evaluated by the above-described evaluation method and a tire including the vulcanized rubber composition will be described.

The vulcanized rubber composition for tire tread of the present embodiment has a first slope e of the regression equation of 1.8 or less when the rolling speed V of the rubber sample 2 is in the range of 2.5 to 25 (km/h). Is. The first slope of the regression equation is preferably 1.6 or less, more preferably 1.5 or less, and further preferably 1.4 or less. Such a vulcanized rubber composition has good wear resistance performance under various conditions of actual vehicle running, and can have high robustness with respect to wear resistance performance. Therefore, a tire provided with this vulcanized rubber composition can exhibit excellent wear resistance performance regardless of the state of use.

In the vulcanized rubber composition for tire tread of the present embodiment, the second slope v of the regression equation is within ±0.4 when the wear energy E is in the range of 40 to 350 (J/m2). The second slope v of the regression equation is preferably within ±0.3, more preferably within ±0.2, and even more preferably within ±0.1. Such a vulcanized rubber composition has good wear resistance performance under various conditions of actual vehicle running, and can have higher robustness with respect to wear resistance performance. Therefore, a tire provided with this vulcanized rubber composition can exhibit excellent wear resistance performance regardless of the state of use.

The vulcanized rubber composition for a tire tread preferably has a loss tangent tan δ at 30° C. of 0.11 or less. Such a vulcanized rubber composition suppresses heat generation of the rubber and is unlikely to reach a high temperature, and thus has a small change in physical properties and can have higher robustness with respect to abrasion resistance.

Here, the loss tangent tan δ is a value measured by using a viscoelasticity spectrometer under the following conditions according to JIS-K6394.
Initial strain: 10%
Amplitude: ±2%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 30℃

The rubber component of the vulcanized rubber composition for tire tread is, for example, natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile butadiene rubber. A diene rubber such as (NBR) is adopted. The diene rubber may be used alone, but it is desirable to use two or more kinds in combination. The diene rubber of the present embodiment is a combination of three types of NR, SBR and BR. Such a vulcanized rubber composition can exhibit excellent wear resistance performance.

The content of NR in 100% by mass of the rubber component is preferably 25% by mass or less, and more preferably 20% by mass or less. The vulcanized rubber composition having such an NR content can further improve the wear resistance performance.

The content of SBR in 100% by mass of the rubber component is preferably 60% by mass or more, and more preferably 65% by mass or more. The SBR content in 100% by mass of the rubber component is preferably 80% by mass or less, more preferably 75% by mass or less. The vulcanized rubber composition having such an SBR content can further improve the wear resistance performance.

The content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more. Further, the content of BR in 100% by mass of the rubber component is preferably 25% by mass or less, and more preferably 20% by mass or less. The vulcanized rubber composition having such a BR content can further improve the wear resistance performance.

The vulcanized rubber composition includes, for example, carbon black, silica, a silane coupling agent, a softening agent such as oil, a wax, an antioxidant, a vulcanizing material such as stearic acid, zinc oxide and sulfur, and a vulcanization accelerator. It may be appropriately blended.

Although a particularly preferred embodiment of the present invention has been described above in detail, the present invention is not limited to the above-described embodiment and can be modified into various modes and carried out.

A plurality of types of vulcanized rubber compositions having different rubber components were prototyped and evaluated by the evaluation method of FIGS. 2 to 4 using the tester of FIG. In the abrasion test of the vulcanized rubber composition, the ground contact load was kept constant at 40 N, the rolling speed was 2.5 km/h, 12 km/h and 25 km/h, and the slip angle was 3° and 5.5. The test was conducted under a total of 9 conditions of 3 levels of ° and 9°.

As a result of the evaluation, the first inclination in the rolling speed V range of 2.5 to 25 (km/h) is 1.8 or less, and the second inclination in the wear energy range of 40 to 350 (J/m2). Is within ±0.4, and a vulcanized rubber composition a serving as an example and a vulcanized rubber composition b serving as a comparative example in which the first slope and the second slope are out of the above ranges were confirmed. .. The loss tangent tan δ at 30° C. of the vulcanized rubber composition a was 0.11, and the loss tangent tan δ at 30° C. of the vulcanized rubber composition b was 0.26.

Next, a tire A provided with the vulcanized rubber composition a of the example and a tire B provided with the vulcanized rubber composition b of the comparative example were manufactured. A test vehicle equipped with each tire was used to measure the amount of wear after running 30,000 km on a domestic test course and a foreign test course, respectively, and the ratio of the amount of wear between the domestic test course and the foreign test course was measured. Were calculated respectively. The results of the test are as follows.

Test tire wear rate ratio Example (Tire A) 1.1
Comparative Example (Tire B) 1.9

As a result of the test, the tire of the example has a small difference in the amount of wear between the domestic test course and the foreign test course, compared to the tire of the comparative example, and the vulcanized rubber composition of the example relates to the wear resistance performance. It was confirmed to have high robustness.

2 Rubber sample 8 Pseudo road surface E Wear energy V Rolling speed Z Wear amount e First slope

Claims (11)

A vulcanized rubber composition for a tire tread,
Cylindrical rubber sample, the wear test of rolling by pressing against a pseudo road surface, the rolling speed when the rolling speed of the rubber sample and the abrasion energy acting on the rubber sample are changed a plurality of times, and When calculating a regression equation that defines the amount of wear of the rubber sample with respect to the wear energy, the rolling speed of the rubber sample is in the range of 2.5 to 25 (km/h), The first slope of the wear amount with respect to wear energy is 1.8 or less,
Vulcanized rubber composition for tire tread. The second slope of the wear amount with respect to the rolling speed of the regression equation is within ±0.4 within the range of the wear energy acting on the rubber sample of 40 to 350 (J/m2). A vulcanized rubber composition for the tire tread described. The vulcanized rubber composition for a tire tread according to claim 1 or 2, wherein the first slope of the regression equation is 1.6 or less. The vulcanized rubber composition for tire tread according to claim 1 or 2, wherein the first slope of the regression equation is 1.5 or less. The vulcanized rubber composition for tire tread according to claim 1 or 2, wherein the first slope of the regression equation is 1.4 or less. The vulcanized rubber composition for a tire tread according to claim 2, wherein the second slope of the regression equation is within ±0.3. The vulcanized rubber composition for tire tread according to claim 2, wherein the second slope of the regression equation is within ±0.2. The vulcanized rubber composition for a tire tread according to claim 2, wherein the second slope of the regression equation is within ±0.1. A tire comprising the vulcanized rubber composition for a tire tread according to any one of claims 1 to 8. A method for evaluating a vulcanized rubber composition for a tire tread,
Cylindrical rubber sample, a test step of performing a wear test of rolling by pressing the pseudo road surface, and an evaluation step of evaluating the wear resistance performance of the rubber sample from the results of the test step,
The test step, the abrasion test is performed a plurality of times by changing the rolling speed of the rubber sample and the abrasion energy acting on the rubber sample,
The evaluation step, when calculating a regression equation that defines the amount of wear of the rubber sample with respect to the rolling speed and the wear energy, in the range of the rolling speed determined in advance, the wear of the regression equation Evaluating a first slope of the wear amount with respect to energy,
Evaluation method of vulcanized rubber composition for tire tread. The vulcanized rubber composition for a tire tread according to claim 10, wherein the evaluation step evaluates a second slope of the wear amount with respect to the rolling speed of the regression equation in a predetermined wear energy range. How to evaluate things.

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