JP5746563B2 - Rubber chipping resistance evaluation method - Google Patents

Description

  The present invention relates to a rubber chipping resistance evaluation method capable of easily and accurately evaluating the rubber chipping resistance of rubber having various compositions.

  One of the factors affecting tire life and tire strength is the resistance to chipping of rubber in tread rubber and sidewall rubber. Rubber chipping occurs and early tire replacement is unavoidable.

  Therefore, various rubbers have been developed to improve the resistance to chipping of rubber. Conventionally, as an evaluation method for the resistance to chipping of rubber, for example, “Calculation rubber and thermoplastic rubber-Determination of tensile properties” of JIS K6251. The tensile strength and elongation at break of a dumbbell-shaped test piece are measured, and the fracture energy is calculated therefrom and evaluated based on the magnitude.

  However, the evaluation method based on this tensile test often becomes inconsistent with the rubber chipping phenomenon of tires that occurs in the market, and there is a problem that the superiority or inferiority of the rubber chipping performance cannot be accurately evaluated.

  In addition, a hitting test in which a tire is actually hit with a hammer is manually performed, and evaluation of superiority or inferiority based on how the rubber is chipped at that time, the size of the rubber chip, or the like is also performed in part. However, it is difficult to say that this is practical because it requires a lot of time and effort, such as requiring many hits before the rubber is missing. Moreover, since this is inferior in reproducibility, it is difficult to expect accurate evaluation.

  Patent Document 1 below proposes a test apparatus that evaluates the strength and durability of a member in a side portion by hitting the side portion of a tire using a pendulum having a striking piece at the tip.

JP-A-6-273299

  Therefore, the present invention uses a pendulum provided with a hitting piece at the tip, hits the front surface of the rubber test piece supported by the support, and shapes and states of hitting portions of the rubber test piece, hitting piece shape, and hitting Based on specifying the location, etc., it has an accuracy close to the evaluation of rubber chipping of tires on the market, can easily and accurately evaluate the superiority or inferiority of rubber chipping performance, and can shorten the test time The object is to provide a method for evaluating the resistance to chipping of rubber.

In order to solve the above-mentioned problem, the invention of claim 1 of the present application is characterized in that the striking piece of the pendulum in which the striking piece is provided at the other end of the arm whose one end is pivotally supported by the horizontal axis i is provided by a support. A rubber chipping resistance evaluation method for evaluating the resistance to rubber chipping from the falling energy of the pendulum and the state of rubber chipping of the rubber test piece by colliding with the front surface of the supported rubber test piece,
The rubber test piece has a rectangular block shape surrounded by the front and rear surfaces, the upper and lower surfaces, and both side surfaces, and the front surface is supported in parallel with the axis i direction, and the front upper edge where the front surface and the upper surface intersect with each other. A plurality of cuts extending perpendicularly to the direction of the axis i downward from the upper surface are provided in the front upper corner portion including the cut formation regions that are spaced at equal intervals in the direction of the axis i.
The striking piece of the pendulum has a facing surface facing the front surface at the time of collision, a lower surface facing downward, and a lower corner portion where the facing surface and the lower surface intersect at an angle θ of 60 to 100 °, and the arm When the vertical line passing through the vertical line extending from the axis i or immediately after passing the vertical line, the lower corner portion collides with the front surface and the notch formation region,
The rubber test piece is preheated so that the temperature at the time of collision is 80 to 100 ° C.

  In the invention of claim 2, the front surface of the rubber test piece is supported so as to be separated from the lower corner portion of the hitting piece at the time of passing the vertical line by a distance L of 0 to 6.0 mm. The striking piece of the pendulum is characterized by colliding with the rubber test piece when passing through the vertical line or immediately after passing through the vertical line.

The invention of claim 3 is a vertical depth from the upper surface of the rubber specimen Tatefuka of Hb is 5 to 10 mm, the horizontal depth Ha is a longitudinal depth from the front surface 5 It is characterized by 10 mm and a cut width t of 0.5 mm or less.

  The invention according to claim 4 is characterized in that the number of the cuts arranged in the collision range where the lower corner portion of the hitting piece collides with the rubber test piece is three or four.

  As described above, the present invention makes the striking piece provided at the end of the pendulum collide with the front surface of the rubber test piece. Evaluate.

  At this time, the front upper corner portion where the upper surface and the front surface of the rubber test piece intersect with each other has a plurality of cuts extending at a right angle to the axial center i direction downward from the upper surface at equal intervals in the axial center i direction. A notch forming region is provided, and the lower corner portion of the striking piece collides with the front of the rubber test piece in the notch forming region. Moreover, the rubber test piece is preheated so that the temperature at the time of the collision is 80 to 100 ° C.

  Thus, by forming a notch formation region in the rubber test piece, striking this notch formation region at the lower corner portion of the striking piece, and heating the temperature of the rubber test piece to 80 ° C. or higher, the rubber Chipping can be promoted and generated, and the phenomenon of rubber chipping in the market can be reproduced easily and accurately. Further, since the test can be performed with a single hit, the test time and labor can be improved.

  Also, rubber chipping can be generated by amplifying, such as the difference in rubber chipping performance appearing as a difference in the large rubber chipping state (for example, the size of the rubber chipping). This can be performed with higher accuracy.

It is a front view which shows the testing apparatus used for the rubber chipping-resistant performance evaluation method of this invention. It is a perspective view which shows a rubber test piece. It is sectional drawing explaining the collision state to the rubber test piece by a striking piece. It is sectional drawing which shows the other example of a hit piece. It is a perspective view which shows the example of the rubber | gum missing state of a rubber test piece.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the test apparatus 1 according to the present embodiment has a support 3 that supports a rubber test piece 2 and a striking piece 5 of a pendulum 4 that collides with the rubber test piece 2 that is supported to cause a lack of rubber. And a pendulum impact tool 6 for generating

  The pendulum impact tool 6 includes a stand 7 having a column 7B raised on a base 7A, and a pendulum 4 that is pivotably supported by a horizontal support shaft 8 provided at the upper end of the column 7B. With The pendulum 4 includes an arm 9 whose one end is pivotally supported by an axis i of the support shaft 8 and the striking piece 5 provided at the other end of the arm 9. In the present embodiment, the stand 7 is provided with a display unit 10 for displaying the swing angle α of the arm 9 with the vertical line X extending from the axis i being 0 °.

  The striking piece 5 comprises a striking piece main body 5A on the front side that collides with the front surface Sa1 of the rubber test piece 2, and a weight part 5B on the rear side thereof, and the weight part 5B is configured such that its weight can be adjusted. Has been.

  Further, as shown in FIG. 2, the striking piece main body 5A has a lower corner portion Q where a facing surface K1 facing the front surface Sa1 and a lower surface K2 facing downward intersect at an angle θ of 60 to 100 ° at the time of collision. . In this example, a case where the hitting piece main body 5A has a rectangular parallelepiped shape and the angle θ is 90 ° is exemplified.

  The rubber test piece 2 has a rectangular block shape surrounded by the front and rear surfaces Sa1 and Sa2, the upper and lower surfaces Sb1 and Sb2, and both side surfaces Sc and Sc, and the front surface Sa1 is directed parallel to the axis i direction. Supported by the support 3. The support 3 is not particularly restricted as long as the rubber test piece 2 does not move at the time of impact (at the time of impact). In this example, a so-called vise is used and the bottom plate 11 that receives the lower surface Sb2 is used. The rubber test piece 2 is held between the side plates 12 and 12 that receive the side surfaces Sc and Sc and the back plate 13 that receives the rear surface Sa2.

  Further, the rubber test piece 2 is provided with a notch forming region Y at a front upper corner portion P including a front upper edge Pe where the front surface Sa1 and the upper surface Sb1 intersect. This notch forming region Y is a region where a plurality of notches 15 extending downward from the upper surface Sb1 at right angles to the direction of the axis i are formed at equal intervals in the direction of the axis i.

  The notch 15 is an incision opened at the front surface Sa1 and the upper surface Sb1, and the vertical depth Hb from the upper surface Sb1 is smaller than the height HB of the rubber test piece 2 and the lateral depth from the front surface Sa1. Ha is set to be smaller than the depth HA of the rubber test piece 2. The notch width t of the notch 15 is 0.5 mm or less, and the wall surfaces of the notch 15 are substantially in pressure contact with each other when mounted on the support 3. The vertical depth Hb is set to 5 to 10 mm, and the horizontal depth Ha is set to 5 to 10 mm.

  Then, the test apparatus 1 is used to generate a rubber chip at the front upper corner portion P of the rubber test piece 2, and the dropping energy of the pendulum 4 at that time and the rubber test piece 2 in the rubber test piece 2 as shown in FIG. From this, the rubber chipping resistance is evaluated. Although not particularly defined as a state of lack of rubber, as shown in the figure, for example, the maximum width VLc in the direction of the axis i of the portion V where the lack of rubber occurs, the maximum vertical depth VLb from the upper surface Sb1, and the maximum from the front surface Sa1. The size of the rubber chip such as the lateral depth VLa and the weight of the chipped rubber can be evaluated as an index.

  Specifically, the pendulum 4 is swung down from a predetermined swing-up height position, and the lower corner portion Q of the striking piece 5 is placed on the front surface Sa1 and the notch forming region of the rubber test piece 2 as shown in FIG. Collide with Y. At this time, the arm 9 performs the collision at a time T1 when the arm 9 passes through the vertical line X, or T2 immediately after the vertical line passes. Specifically, the rubber test piece 2 is attached to the position where the distance L from the lower corner portion Q to the front surface Sa1 of the rubber test piece 2 at the time T1 when passing through the vertical line is 6.0 mm or less and caused to collide. . Therefore, T2 immediately after passing through the vertical line means a range from the time T1 when passing through the vertical line until the hit piece 5 moves a distance L of 6.0 mm forward.

  Here, when the striking piece 5 does not collide (line contact) with the front surface Sa1 at the lower corner portion Q, but collides with the opposing surface K1 (surface contact), the contact area increases. As a result, the impact is reduced and rubber chips cannot be generated. Further, when the hitting piece 5 is caused to collide before passing through the vertical line, the collision energy vector is directed obliquely downward, so that the ratio of energy related to the rubber chipping of the front upper corner portion P is reduced, Reduces the effect of rubber chipping. Therefore, in order to enhance the effect of promoting rubber chipping, the collision energy vector is caused to collide at least at the time of passing through the vertical line T1 so that the vector of the collision energy does not face obliquely downward. It is desirable to collide and direct the collision energy vector diagonally upward. If the collision is too far from T1 when passing through the vertical line, the fall energy itself decreases, so the distance L is preferably 6.0 mm or less.

  Further, if the angle θ of the lower corner portion Q is too large, the impact is alleviated and the effect of promoting rubber chipping is reduced, and conversely if too small, the rubber is damaged at the edge of the lower corner portion Q, It becomes impossible to accurately reproduce the phenomenon of missing rubber in the market. From such a viewpoint, the angle θ is preferably in the range of 60 to 100 ° described above.

  Further, by providing the notch forming region Y in the front upper corner portion P, it is possible to promote the chipping of rubber. At this time, it is preferable that the number of the notches 15 arranged in the collision range J (shown in FIG. 2) in which the impact piece 5 collides with the rubber test piece 2 is 3 or 4, and less than 3. In this case, the rigidity of the rubber is still high, and the effect of promoting rubber chipping cannot be obtained sufficiently. On the other hand, if the number exceeds four, it becomes easy to cause rubber chipping, and it becomes difficult to identify the difference in rubber chipping resistance based on the difference in rubber blending. The height Hp (collision height Hp) from the upper surface Sb1 of the collision position Pj where the lower corner portion Q collides with the front surface Sa1 is preferably 50% or less of the vertical depth Hb of the notch 15. Thereby, the rubber chipping to the front upper corner portion P can be further promoted.

  Further, if the size of the notch 15, that is, the vertical depth Hb and the horizontal depth Ha, are too large, the rubber part divided between the notches 15 and 15 is easy to move, the impact is alleviated, and the rubber is not easily chipped. The effect of promoting rubber chipping is reduced. On the other hand, if the vertical depth Hb and the horizontal depth Ha are too small, the amount of rubber chipping decreases, and it becomes difficult to identify the difference in rubber chipping resistance based on the difference in rubber blending. From such a viewpoint, the vertical depth Hb and the horizontal depth Ha are preferably in the range of 5 to 10 mm, and more preferably, the vertical depth Hb and the horizontal depth Ha are set equal.

  The rubber test piece 2 needs to be preheated so that the temperature at the time of the collision is 80 to 100 ° C., and this heating weakens the fracture strength and promotes rubber chipping. If the temperature is less than 80 ° C., the effect of promoting the lack of rubber cannot be sufficiently obtained. Conversely, if the temperature exceeds 100 ° C., the rubber vulcanization degree and the like change due to the heating itself. A fear arises, and it becomes difficult to accurately evaluate the rubber chipping resistance performance of the rubber test piece 2. In addition, the said temperature is the temperature of the surface of rubber test piece 2, and an inside, Comprising: For example, using the well-known oven, the said heating can be performed by leaving it to stand in the said temperature range for 3 hours or more.

  FIG. 4 shows another example of the impact piece main body 5A. In this example, the hitting piece main body 5A is formed such that the lower corner portion Q projects forward. In such a case, as shown in the figure, the lower corner portion Q can collide with the front surface Sa1 at the time of passing through the vertical line T1. Therefore, in this example, the rubber test piece 2 is supported with the distance L = 0 mm.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  In order to confirm the effect of the present invention, using the test apparatus 1, a rubber chip test according to the present invention was performed on the five types of rubber compositions A to E shown in Table 1 based on the following specifications. And from the rubber | gum chipped state of the rubber test piece at that time, the rubber | gum chipping resistance performance of each rubber composition AE was evaluated, and the result was described in Table 2 as Example 1. FIG. In addition, the said evaluation measured the weight of the rubber | gum which was missing by the rubber | gum chip | tip test, and is represented by the index | exponent which set the rubber composition D to 100. The smaller the value, the better the rubber chipping resistance.

"Test specifications"
<Test equipment>
・ Pendulum arm length = 450mm
・ Weight of striking piece = 300g
・ Swing angle α = 90 °
・ Size of the striking piece body (cuboid: height = 29 mm, depth = 29 mm, width 39 mm in the direction of the axis i)
・ Angle of lower corner Q: θ = 90 °
<Rubber specimen>
-Size of rubber test piece (cuboid: height HB = 24 mm, depth HA = 39 mm, width W in the i-axis direction = 59 mm)
・ Size of notch (vertical depth Hb = 7.0 mm, lateral depth Ha = 7.0 mm, notch width t = 0.2 mm)
・ Incision interval = 13 mm
<Collision situation>
-Collision with T2 immediately after passing the vertical line (L = 2.0mm)
-Collision (line contact) at lower corner Q
・ Collision height Hp = 3.5mm (0.5 × Hb)
・ Number of notches arranged in the collision range = 3 <warming condition>
・ Temperature = 80 ℃

Further, as Comparative Example 1, in accordance with JIS K6251 “vulcanized rubber and thermoplastic rubber—How to obtain tensile properties”, dumbbell-shaped test pieces using the rubber compositions A to E were prepared, and their tensile strengths were obtained. And elongation at break were measured. And while calculating fracture energy from a following formula, the calculation result is represented by the index | exponent which made the rubber composition D 100. FIG.
(Fracture energy) = (Tensile strength) × (Elongation at cutting) / 2

  Pneumatic tires (tire size 11R22.5) employing the rubber compositions A to E as tread rubbers were prepared, and the rubber chipping resistance of each rubber composition A to E was evaluated by actual vehicle running (market evaluation) )did. In the market evaluation, it was obtained that the rubber chipping resistance was superior as it went to the left in the order of A> B> C> D> E.

  As shown in Comparative Example 1, the evaluation method based on the tensile test of JIS K6251 often does not match the market evaluation, and the superiority or inferiority of the rubber chipping resistance cannot be accurately evaluated. In contrast, in Example 1 according to the present invention, it can be confirmed that an evaluation consistent with the market evaluation can be obtained.

Further, a rubber chipping test was performed based on the trial use in Table 3, and the rubber chipping resistance performance of each of the rubber compositions A to E was similarly evaluated.

  As shown in Comparative Examples 2 to 4, when no notch is formed, when preheating is not performed, when the hitting portion is an opposing surface (planar surface), the rubber chipping is not sufficiently promoted and the rubber chipping is not performed. The evaluation accuracy is reduced.

2 Rubber test piece 3 Support tool 4 Pendulum 5 Strike piece 9 Arm 15 Notch K1 Opposing surface K2 Lower surface P Front upper corner portion Pe Front upper edge Q Lower corner portion Sa1 Front surface Sa2 Rear surface Sb1 Upper surface Sb2 Lower surface Sc Side surface X Vertical line Y Notch Formation area

Claims (4)

The striking piece of the pendulum provided with a striking piece on the other end of the arm pivoted at one end at a horizontal axis i is collided with the front surface of the rubber test piece supported by the support, and the pendulum drop energy And a rubber chipping resistance evaluation method for evaluating the rubber chipping resistance performance from the rubber chipping state of the rubber test piece,
The rubber test piece has a rectangular block shape surrounded by the front and rear surfaces, the upper and lower surfaces, and both side surfaces, and the front surface is supported in parallel with the axis i direction, and the front upper edge where the front surface and the upper surface intersect with each other. A plurality of cuts extending perpendicularly to the direction of the axis i downward from the upper surface are provided in the front upper corner portion including the cut formation regions that are spaced at equal intervals in the direction of the axis i.
The striking piece of the pendulum has a facing surface facing the front surface at the time of collision, a lower surface facing downward, and a lower corner portion where the facing surface and the lower surface intersect at an angle θ of 60 to 100 °, and the arm When the vertical line passing through the vertical line extending from the axis i or immediately after passing the vertical line, the lower corner portion collides with the front surface and the notch formation region,
The rubber test piece is preliminarily heated so that the temperature at the time of collision is 80 to 100 ° C.   The front surface of the rubber test piece is supported so as to be separated by a distance L of 0 to 6.0 mm from the lower corner portion of the striking piece when passing through the vertical line. The rubber chipping resistance evaluation method according to claim 1, wherein the rubber test piece collides with the rubber test piece when passing or immediately after passing through a vertical line. The incision has a vertical depth Hb of 5 to 10 mm from the upper surface of the rubber test piece in the vertical direction , a lateral depth Ha of 5 to 10 mm from the front surface in the front-rear direction , and a notch width t. The rubber chipping resistance evaluation method according to claim 1 or 2, wherein the evaluation is 0.5 mm or less.
  4. The resistance to resistance according to claim 1, wherein the number of the cuts arranged in a collision range in which the lower corner portion of the hitting piece collides with the rubber test piece is 3 or 4. 5. Rubber chip performance evaluation method.

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