Evaluation method for tire water removal and tire

Abstract

To provide a method for evaluating water repellency with an irregularity at a tire surface in a micro scale, and to provide a tire that has excellent on-ice gripping performance.SOLUTION: A method for evaluating tire water repellency includes: an imaging step of imaging a tire running on a transparent or translucent plate on which a water screen is formed from a lower side of the transparent or translucent plate; an image processing step of dividing each snapshot image of the filmed video into regions of an actual ground contact part, a water screen part and a space part; and a calculation step of providing a ratio between the actual ground contact part and the water screen part.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for evaluating tire water removal and to tires. [Background technology]

[0002] When observing the contact condition of a tire during driving, a method is generally used in which the tire is driven on a glass plate and the part of the tire that touches the glass plate is filmed from below with a video camera. However, the water removal at the microscale due to the unevenness of the tire surface has not been evaluated (see Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-128196 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present invention aims to solve the aforementioned problems and provide a method for evaluating water removal at a microscale due to irregularities on the tire surface, and a tire with excellent grip performance on ice. [Means for solving the problem]

[0005] The present invention includes a photographing step of photographing a tire running on a transparent or translucent plate on which a water film has been formed, from below the transparent or translucent plate, Image processing steps for each snapshot image of the captured video, separating it into regions of the actual ground contact area, the water film area, and the empty space area, This invention relates to a method for evaluating tire water removal, which includes a calculation step to determine the ratio of the actual contact area to the water film area. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a method for evaluating the water repellency at the microscale due to the unevenness on the tire surface. Further, it is possible to provide a tire having excellent grip performance on ice.

Brief Description of the Drawings

[0007] [Figure 1] An example of a schematic diagram for photographing the grounding state (ground contact part) of a tire in a stationary state, a running state, etc. in the method for evaluating the water repellency of the tire of the present invention [Figure 2] In the photographing step, (a) a still image obtained by photographing the ground contact part 112 of the tire 111 in a sufficiently stationary state on a transparent or translucent plate 102 having a water film 103 formed thereon, (b) the luminance distribution of the still image [Figure 3] Three snapshot images extracted from a moving image obtained by photographing the change in the grounding state of the tire 111 running on a transparent or translucent plate 102 having a water film 103 formed thereon from below the transparent or translucent plate 102 [Figure 4] Figs. (a) and (b) schematically showing an image in which the area of the actual ground contact part determined in the image processing step first occupies 1.0 area% or more in the snapshot image [Figure 5] An example of the tire of the present invention [Figure 6] An enlarged view near the tread 4 of FIG. 5

Modes for Carrying Out the Invention

[0008] <Method for Evaluating Tire Water Repellency> The present invention includes a photographing step of photographing a tire running on a transparent or translucent plate having a water film formed thereon from below the transparent or translucent plate, an image processing step of separating each snapshot image of the photographed moving image into regions of an actual ground contact part, a water film part, and a space part, and a calculation step of obtaining the ratio between the actual ground contact part and the water film part, and is a method for evaluating the water repellency of a tire.

[0009] In a tire traveling on a water film, among the contact surfaces between the tire and the road surface, the area where no water film exists between the tire and the road surface greatly contributes to the grip performance. It is considered that the faster the water film between the tire and the road surface is removed due to the irregularities on the tire surface, the better the grip performance on ice. According to the present invention, by separating the tire traveling on the water film into a grounded portion, a water film portion, and a space portion, it is possible to confirm whether a water film exists between the tire and the road surface among the contact surfaces between the tire and the road surface. Furthermore, by obtaining the ratio between the grounded portion and the water film portion, the removal of the water film between the tire and the road surface is performed, and the speed of grounding with the road surface can be quantitatively evaluated. For the above reasons, it is possible to provide a method for evaluating the water repellency at the microscale due to the irregularities on the tire surface.

[0010] In addition, in the method for evaluating tire water repellency, the order of the photographing step, the image processing step, and the calculation step is not particularly limited and can be performed in any order. Among them, it is preferable to perform them in the order of photographing step → image processing step → calculation step.

[0011] An example of the method for evaluating tire water repellency of the present invention will be described below, but the present invention is not limited to the following method.

[0012] In the photographing step, a tire traveling on a transparent or translucent plate on which a water film is formed is photographed as a moving image from below the transparent or translucent plate. Also, from the viewpoint of facilitating the acquisition of the binarization threshold value in the "acquisition step of the grounded portion" described later, in addition to the above moving image, it is preferable to acquire a still image of a tire stationary on a transparent or translucent plate on which a water film is formed, photographed from below the transparent or translucent plate.

[0013] FIG. 1 shows an example of a schematic diagram for photographing the grounding state of a tire such as a stationary state and a traveling state in the method for evaluating tire water repellency of the present invention. The tire contact imaging device 101 shown in Figure 1 comprises a transparent or translucent plate 102 through which a vehicle (not shown) can pass, a water film 103 formed on the transparent or translucent plate 102, and an imaging device 104 positioned below the transparent or translucent plate 102.

[0014] Figure 1 is a schematic diagram showing the contact state of a tire 111 (a tire mounted on a vehicle not shown) stationary on a transparent or translucent plate 102 on which a water film 103 has formed, or a tire 111 running on a transparent or translucent plate 102 on which a water film 103 has formed, as photographed from below the transparent or translucent plate 102.

[0015] The tire to which the tire water removal evaluation method of the present invention can be applied is not particularly limited and can be applied to both pneumatic and non-pneumatic tires. It can be applied to summer tires, winter tires, all-season tires, etc. Examples of winter tires include studless tires, snow tires, and studded tires. It can also be applied to passenger car tires, large passenger car tires, large SUV tires, heavy-duty tires for trucks and buses, light truck tires, motorcycle tires, racing tires, etc. There are no restrictions on the size of the tires to which it can be applied; it can be applied to tires of any size.

[0016] In particular, it is well-suited for winter tires. In this case, it allows for quantitative evaluation of the water removal performance of the water film created by the uneven surface of the tire, which is important for winter tires.

[0017] In the method for evaluating tire water removal, the vehicle speed is not particularly limited, but from the viewpoint of being able to observe the water removal process due to the unevenness of the tire surface, it is preferably 0.1 km / h or more, more preferably 1 km / h or more, even more preferably 5 km / h or more, and also preferably 50 km / h or less, more preferably 30 km / h or less, and even more preferably 20 km / h or less.

[0018] In the method for evaluating tire water removal, the load applied to a single tire is not particularly limited, but from the viewpoint of being able to observe the water removal process due to the unevenness of the tire surface, it is preferably 150 kg or more, more preferably 250 kg or more, even more preferably 375 kg or more, and also preferably 800 kg or less, more preferably 700 kg or less, and even more preferably 600 kg or less.

[0019] The transparent or translucent plate 102 is not particularly limited and can be used as long as it is transparent or translucent enough to allow for photography of the contact state of the stationary or moving tire 111 on the water film 103 from a position below it. The transparent or translucent plate 102 can be, for example, a transparent or translucent glass plate, an acrylic plate, or the like. Examples of the glass plate include tempered glass.

[0020] The transparent or translucent plate 102 is not particularly limited in its transmittance, as long as it is transparent or translucent enough to allow imaging of the tire 111's contact with the ground. It also includes colorless transparent, translucent, colored transparent, colored translucent, etc. In particular, the transparent or translucent plate 102 preferably has a transmittance of 60 or more, and more preferably 65 or more. The upper limit of the transmittance is usually 100 or less, but is not limited to this. The transmittance can be measured, for example, using the transmittance (L* value) of a spectrophotometer.

[0021] The thickness of the transparent or translucent plate 102 should be set appropriately so as to withstand tire movement and allow sufficient imaging of the contact area 112 of the tire 111 by the imaging device 104 from below. In particular, from the viewpoint of strength and the ability to image the tire, the upper limit of the thickness is preferably 30 mm or more, more preferably 40 mm or more, and even more preferably 50 mm or more, and the lower limit is preferably 200 mm or less, more preferably 100 mm or less, and even more preferably 80 mm or less.

[0022] Any material capable of forming a water-containing film on a transparent or translucent plate 102 can be used to form the water film 103. In particular, from the viewpoint of taking images with good water removal performance, it is desirable to use a water film 103 formed from a suspension.

[0023] The suspension is not particularly limited, and for example, a white suspension can be used. The white suspension is not particularly limited and may be a mixture of white paint and water, or a mixture of milk and water. The concentration of the white suspension can be appropriately selected considering the image to be obtained. For example, in the case of a mixture of white paint and water, the concentration of the white paint may be 0.1 to 1.0% by mass, and in the case of a mixture of milk and water, for example, the concentration of the milk may be 10 to 50% by mass.

[0024] When a white suspension is used as the water film 103, the outline of the contact area 112 is clearly visible because the tire 111 is black and the white suspension is white. In addition, the effect of shielding from ambient light is greatly enhanced, so the illumination of the contact area 112 is not overpowered by ambient light, and the image of the contact area 112 is not darkened but clearly visible.

[0025] The thickness of the water film 103 is not particularly limited, and is, for example, 1 to 10 mm, preferably 4 to 6 mm. Within this range, it tends to be preferable to obtain effects such as shielding from ambient light and enhancing contrast.

[0026] The imaging device 104 can be used as long as it is capable of photographing the contact area 112 of the tires 111 of a stationary or moving vehicle on a transparent or translucent plate 102 on which a water film 103 is formed, and various cameras such as still image cameras and video cameras can be used. In particular, it is desirable to use a high-speed camera as the imaging device 104, from the viewpoint of being able to observe the water removal process due to the unevenness of the tire surface. Examples of such high-speed cameras include digital high-speed cameras.

[0027] In this invention, a high-speed camera is a camera capable of continuously capturing more than 30 frames per second.

[0028] The frame rate (shooting speed) of the high-speed camera is preferably 1,000 to 50,000 fps (frames per second), and more preferably 1,500 to 40,000 fps. The shutter speed of the high-speed camera is not particularly limited, but is preferably 20.1 μs or less.

[0029] While the illuminance is not particularly limited, from the viewpoint of being able to observe how water is removed due to the unevenness of the tire surface, it is preferably 10,000 lux or more, more preferably 50,000 lux or more, even more preferably 100,000 lux or more, and also preferably 500,000 lux or less, more preferably 400,000 lux or less, and even more preferably 300,000 lux or less.

[0030] From the viewpoint of being able to observe how water is removed due to the irregularities on the tire surface, it is desirable for the imaging device 104 to capture a narrow field of view. The field of view (part) to be imaged is preferably 5.0 cm. 2 More preferably 3.0 cm 2 More preferably 2.0 cm 2 The following applies, and there is no particular lower limit; the narrower the field of view, the more desirable, for example, 0.01 cm. 2 Above, 0.05cm 2 More than 0.1cm 2 That's fine too.

[0031] The imaging device 104 may be controlled and operated by a computer to capture still images and videos. The computer may control the imaging device 104 and also function as a data processing device that processes the captured data from the imaging device 104, and a display device that displays the contact status of the tire 111 based on the processed data processed by the data processing device.

[0032] The photographing device 101, which captures images of the tire contact with the ground, may be equipped with a lighting device as appropriate, in order to capture high-contrast still images and videos using the imaging device 104.

[0033] In the image processing step, the image acquired in the shooting step is separated into regions of actual contact area, water film area, and empty space area. The above image processing step is not particularly limited, but preferably consists of a "actual contact area acquisition step" that determines a threshold for separating the actual contact area from the non-actual contact area (the region combining the water film area and the empty space area, i.e., the region other than the actual contact area), and a "empty space area acquisition step" that determines a threshold for separating the empty space area from the non-empty space area (the region combining the actual contact area and the water film area). In the above tire water removal evaluation method, the order in which the actual contact area acquisition step and the empty space area acquisition step are performed is not particularly limited, and either step may be performed first, or they may be performed separately or simultaneously.

[0034] In this invention, the "actual contact area" refers to the region where the tire is actually in contact with the road surface, that is, the region where there is no water film between the tire and the road surface. The "water film area" refers to the region where the tire is not in contact with the road surface at a microscale, that is, the region where a water film exists between the tire and the road surface. The "empty area" refers to the region where the tire is not visible, that is, the region that the tire has not reached or has driven past. The "non-actual contact area" refers to the region that combines the "water film area" and the "empty area," that is, the remaining region after excluding the "actual contact area" from the entire snapshot image.

[0035] The step of acquiring the actual contact area can be performed by determining a binarization threshold for separating the actual contact area from the non-contact area (the region combining the water film area and the empty space area) of a still image taken from below the transparent or translucent plate 102, which has a water film 103 formed on it, based on the image taken in the shooting step.

[0036] In the step of acquiring the actual ground contact portion, it is desirable that the binarization threshold that separates the actual ground contact portion from the non-ground contact portion (the region combining the water film portion and the empty portion) is the value that shows the highest frequency in the brightness distribution of the still image captured in the shooting step. If there are two or more values ​​that show the highest frequency, it is desirable that the smaller value be used as the highest frequency. In addition, it is generally desirable that the lower limit of the brightness is 0 or greater, and the upper limit is generally desirable that it is 255 or less.

[0037] The still image captured in the aforementioned shooting step is preferably an image of a tire stationary on a transparent or translucent plate, taken from below the transparent or translucent plate. Furthermore, the binarization threshold in the step of acquiring the actual contact area is preferably determined for each tire.

[0038] Figure 2 shows (a) a still image of the contact area 112 of a tire 111 that is sufficiently still on a transparent or translucent plate 102 on which a water film 103 has been formed, taken during the shooting step, and (b) a figure showing the brightness distribution extracted from the image during the image processing step.

[0039] (a) is a still image obtained by photographing the contact area 112 of the tire 111 from below the transparent or translucent plate 102, using an imaging device 104, while the vehicle, with the tire 111 mounted on a transparent or translucent plate 102 on which a water film 103 has been formed, is sufficiently stationary. (b) is a figure obtained by extracting the brightness distribution from the image in (a).

[0040] Specifically, in Figure (b), for example, the luminance value indicating the maximum frequency (number of pixels) can be used as the binarization threshold, allowing the tire to be separated into the actual contact area and the non-contact area. In this case, it is desirable to designate the area below the binarization threshold as the actual contact area and the area above the binarization threshold as the non-contact area. In the example in Figure 2, the binarization threshold is 52, and the area with a luminance of 52 or less can be designated as the actual contact area of ​​the tire.

[0041] The spatial portion acquisition step can be performed by determining a binarization threshold for each snapshot image of the video captured in the shooting step, which separates the spatial portion from the non-spatial portion (the region combining the water film portion and the actual ground contact portion).

[0042] In the acquisition step for the spatial portion, the binarization threshold is determined by a different method than the one used in the acquisition step for the actual ground portion. In particular, it is desirable to determine the binarization threshold that separates the spatial portion from the non-spatial portion (the region combining the actual ground portion and the water film portion) by discriminant analysis, i.e., Otsu's binarization (see, for example, Nobuyuki Otsu, "Automatic Threshold Selection Method Based on Discriminant and Least Squares Criteria," IEICE Transactions on Electronics, Information and Communication Engineers, Vol. J63-D, No. 4, pp. 346-356 (1980)).

[0043] Here, a "snapshot image" refers to a still image of each frame that makes up the captured video, and the captured video is composed of all the snapshot images. In this invention, a "captured video" refers to a video in which recording begins before the tire passes over a transparent or translucent plate and continues until the tire has completely passed over the plate, and in which no objects other than the tire and the water film are reflected.

[0044] In the spatial portion acquisition step, it is desirable to determine a binarization threshold for all snapshot images constituting the video captured in the shooting step, separating them into a spatial portion and a non-spatial portion (the region combining the actual ground contact portion and the water film portion), thereby separating them into the spatial portion and the non-spatial portion.

[0045] Typically, the binarization threshold determined in the spatial portion acquisition step is greater than the binarization threshold determined in the actual contact portion acquisition step. Furthermore, since the binarization threshold is determined for each snapshot image in the spatial portion acquisition step, the determined thresholds are not identical and are usually different. On the other hand, it is desirable that the binarization threshold determined in the actual contact portion acquisition step be a common value across all snapshot images. Specifically, in the example in Figure 2, the area with a brightness of 52 or less represents the actual contact portion of the tire, and this threshold of 52 or less does not vary from snapshot image to snapshot.

[0046] The spatial portion acquisition step can be performed, for example, by first capturing a video of a moving tire 111 from the moment the tire 111 enters the shooting position until it leaves the shooting position, and then determining a binarization threshold for each of the snapshot images that make up that video, using methods such as Otsu's binarization.

[0047] The method of driving tire 111 is not particularly limited, such as driving in a straight line from the moment tire 111 enters the shooting position until it exits, but driving in a straight line is preferable.

[0048] Figure 3 shows three snapshot images extracted from a video taken from below the transparent or translucent plate 102, showing the change in the contact state of a tire 111 as it travels on the transparent or translucent plate 102 on which a water film 103 has formed. The areas with a binarization threshold (52 in the case of Figure 2) determined in the acquisition step of the actual contact area are shown as black areas, and the areas with a binarization threshold determined in the acquisition step of the empty area are shown as white areas.

[0049] Figure 3(a) is an example of a snapshot image of the initial contact point 112 when the tire 111 enters the video recording position while driving, (b) is an example of a snapshot image of the contact point 112 at the midpoint of the recording position, and (c) is an example of a snapshot image of the final contact point 112 at the recording position.

[0050] The calculation step can be performed by determining the ratio of the actual ground contact area to the water film area in each snapshot image of the captured images. In particular, it is desirable to determine the area ratio of the area occupied by the combined area of ​​the actual ground contact area and the water film area out of 100% (area %) of the total area of ​​the snapshot image. It is especially desirable to determine the area ratio of the combined area of ​​the actual ground contact area and the water film area out of 100% (area %) of the total area of ​​the first snapshot image in which the area of ​​the actual ground contact area exceeds a predetermined percentage. Note that the method for calculating the ratio of the actual ground contact area to the water film area is not limited to the method described above. For example, it may be a method that determines the area ratio of the area occupied by the actual ground contact area out of the area of ​​the combined area of ​​the actual ground contact area and the water film area.

[0051] In the calculation step described above, first, the first snapshot image in which the area of ​​the actual ground contact portion exceeds a predetermined proportion is extracted from all snapshot images. For example, in the case of Figure 2, the first snapshot image in which the area below the threshold of 52 exceeds a predetermined proportion is extracted.

[0052] The aforementioned "predetermined ratio" can be selected as appropriate. In particular, it is desirable that the area of ​​the actual contact area be 1.0% (area %) or more of the snapshot image consisting of the area of ​​the actual contact area, the water film area, and the space area.

[0053] In this invention, "first snapshot image" means the first snapshot image among all snapshot images in which the area of ​​the actual ground contact portion exceeds a predetermined percentage. That is, all snapshot images from the snapshot image at the start of the video up to immediately before the first snapshot image have an area of ​​the actual ground contact portion that is less than the predetermined percentage. For example, if the first snapshot image is the image at the first moment in which the area of ​​the actual ground contact portion exceeds 1.0% of 100% (area %) of all snapshot images, and the snapshot images follow in the order of snapshot image 1 (where the area of ​​the actual ground contact portion occupies 0.1%) → snapshot image 2 (where it occupies 0.4%) → snapshot image 3 (where it occupies 1.1%) → snapshot image 4 (where it occupies 1.5%), then the first snapshot image in which it exceeds 1.0% is snapshot image 3.

[0054] For example, if the threshold determined in the spatial portion acquisition step is 60, it is possible to determine the percentage (%) of the area where the threshold is 60 or less within 100% (area %) of the initial snapshot image, that is, the percentage (area %) of the area occupied by the sum of the actual ground contact portion and the water film portion within 100% (area %) of the initial snapshot image.

[0055] Figures 4(a) and 4(b) schematically show the results of the initial snapshot image extraction process for different tires, where the actual contact area is represented by a black area, the empty space by a white area, the water film by a shaded area, and the combined area of ​​the actual contact area and the water film by a dashed line.

[0056] Specifically, Figures 4(a) and 4(b) schematically show images in which the area (percentage) of the actual ground contact portion, determined in the actual ground contact portion acquisition step to be 52 or less, first occupies 1.0 area % or more of the snapshot image. The black area schematically shows the area of ​​the actual ground contact portion in the initial 100% area of ​​the snapshot image that is 52 or less, determined in the actual ground contact portion acquisition step. The white area schematically shows the area of ​​the empty portion in the initial 100% mass of the snapshot image that is greater than the threshold 60, determined in the empty portion acquisition step. The area enclosed by the dashed line schematically shows the area of ​​the empty portion in the initial 100% mass of the snapshot image that is 60 or less, determined in the empty portion acquisition step. Furthermore, the shaded area schematically shows the area that satisfies the threshold of 60 or less, determined in the empty portion acquisition step, determined in the initial 100% mass of the snapshot image, and is greater than the threshold 52, determined in the actual ground contact portion acquisition step.

[0057] In Figure 4(a), compared to (b), the proportion of the area below the binarization threshold determined in the spatial portion acquisition step (the proportion of the area enclosed by the dashed line, i.e., the combined area of ​​the actual contact area and the water film) within the overall initial snapshot image (100% (area %)) is smaller. In such cases, the tire in (a) can be evaluated as having a faster water removal rate than the tire in (b).

[0058] The area percentage of the actual ground contact area, the area percentage of the water film area, the area percentage of the empty space area, and the area percentage of the combined area of ​​the actual ground contact area and the water film area within the entire snapshot image (100% (area %)) can be measured using image processing techniques.

[0059] <Tires> The present invention relates to a tire having a tread, The tire is one in which the area ratio S (% (area %)) and the tread thickness T (mm) obtained by the aforementioned tire water removal evaluation method satisfy the following formulas (1) and (2). (1) S<30 (2) S × T ≤ 400

[0060] The aforementioned tires have excellent grip performance on ice. The mechanism by which these effects are obtained is not clear, but it is speculated to be as follows. By quickly removing the water film between the tire and the ice, the time that the tire tread rubber is in contact with the ice increases (Equation (1)). Furthermore, by reducing the thickness of the tread rubber, heat accumulation inside the rubber can be suppressed, and even if the time that the tire surface is in contact with the ice increases, the generation of a new water film formed by the melting ice can be suppressed (Equation (2)), so it is presumed that good ice grip performance will be achieved.

[0061] The aforementioned tire, in particular, is photographed from below the transparent or translucent plate on which a water film has been formed, as the tire is running. Image processing steps for each snapshot image of the captured video, separating it into regions of the actual ground contact area, the water film area, and the empty space area, A method for evaluating tire water removal, which includes a calculation step of determining the ratio of the actual contact area to the water film area, The aforementioned aqueous film is formed in a suspension. In the image processing step described above, the binarization threshold for separating the area into the actual ground contact area and the area outside the actual ground contact area is the value that shows the highest frequency in the luminance distribution, the binarization threshold for separating the area into the spatial area and the area outside the spatial area is determined by discriminant analysis, and all snapshot images constituting the captured video are separated into the areas of the actual ground contact area, the water film area, and the spatial area. In the calculation step described above, for the first snapshot image in which the area of ​​the actual ground contact portion is 1.0% (area %) or more of the snapshot image, the area percentage (area %) of the total area of ​​the first snapshot image, which is the sum of the area of ​​the actual ground contact portion and the water film portion, is calculated. It is desirable that the tire satisfies the above formulas (1) and (2), where the area ratio S (% (area %)) and the tread thickness T (mm) are determined by the tire water removal evaluation method.

[0062] The present invention relates to a tire having a tread. The tread is made of a rubber composition for treads.

[0063] Tread rubber compositions contain rubber components. The rubber component usable in tread rubber compositions is a component that contributes to crosslinking, and generally, it is a polymer with a weight-average molecular weight (Mw) of 10,000 or more that is not extracted by acetone. The rubber component is in a solid state at room temperature (25°C).

[0064] The weight-average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and also preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Within this range, a better effect tends to be obtained.

[0065] In this specification, the weight-average molecular weight (Mw) can be determined by converting the measured values ​​obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation) to standard polystyrene equivalents.

[0066] Examples of rubber components include isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). Butyl rubber and fluororubber are also examples. These may be used individually or in combination of two or more. Among these, isoprene rubber, BR, and SBR are preferred from the viewpoint of obtaining better effects, with isoprene rubber and BR being more preferred.

[0067] The rubber component may be either unmodified rubber or modified rubber. The modified rubber can be any rubber having a functional group that interacts with a filler such as silica. Examples include end-modified rubber (end-modified rubber having the functional group at the end) in which at least one end of the rubber is modified with a compound (modifier) ​​having the functional group, main-chain modified rubber having the functional group in the main chain, main-chain end-modified rubber having the functional group in both the main chain and the end (for example, main-chain end-modified rubber having the functional group in the main chain and at least one end modified with the modifier), and end-modified rubber that is modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and in which hydroxyl groups or epoxy groups are introduced.

[0068] Examples of the above functional groups include amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, and the like. These functional groups may have substituents. Among these, amino groups, alkoxy groups, and alkoxysilyl groups are preferred. The above amino group is not particularly limited, but an amino group in which the hydrogen atoms of the amino group are substituted with an alkyl group having 1 to 6 carbon atoms is preferred. The above alkoxy group is not particularly limited, but an alkoxy group having 1 to 6 carbon atoms is preferred. The alkoxysilyl group is not particularly limited, but an alkoxysilyl group having 1 to 6 carbon atoms is preferred.

[0069] Furthermore, hydrogenated rubber can also be used as the rubber material.

[0070] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. For NR, common types used in the rubber industry can be used, such as SIR20, RSS#3, and TSR20. For IR, there are no particular limitations; common types used in the rubber industry can be used, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. Modified isoprene-based rubbers having similar functional groups to the modified rubbers mentioned above can also be used. These may be used individually or in combination of two or more types.

[0071] When the tread rubber composition contains isoprene-based rubber, the isoprene-based rubber content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. The upper limit is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. Within the above range, better effects tend to be obtained.

[0072] BR is not particularly limited, and for example, high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using a rare-earth catalyst (rare-earth BR) can be used. These may be used individually or in combination of two or more. In particular, it is preferable that the BR contains high-cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more. The cis content can be measured by infrared absorption spectroscopy.

[0073] Furthermore, both unmodified and modified BR can be used. Modified BR can be those which have functional groups similar to those introduced in the modified rubber. Hydrogenated butadiene rubber can also be used as BR.

[0074] For example, products from companies such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation can be used as BRs.

[0075] When the tread rubber composition contains BR, the BR content in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, and particularly preferably 60% by mass or more. The upper limit is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less. Within the above range, a better effect tends to be obtained.

[0076] The SBR is not particularly limited; for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc., can be used. These may be used individually or in combination of two or more types.

[0077] The styrene content of SBR is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. The styrene content is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 10% by mass or less. The effect tends to be better obtained by keeping it within the above range. In this specification, the styrene content is defined as follows: 1 It can be measured by 1H-NMR.

[0078] The amount of vinyl bonding in SBR is preferably 20% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, and particularly preferably 42% by mass or more. The amount of vinyl bonding is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less. By keeping it within the above range, better effects tend to be obtained. In this specification, the amount of vinyl bond (amount of 1,2-bonded butadiene units) can be measured by infrared absorption spectroscopy.

[0079] For example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Co., Ltd. can be used.

[0080] When the tread rubber composition contains SBR, the SBR content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. Within the above range, better effects tend to be obtained.

[0081] From the viewpoint of obtaining better performance, it is desirable for the tread rubber composition to include a water-soluble filler.

[0082] The median particle size (median diameter, D50) of the water-soluble filler is preferably 0.4 μm or larger, more preferably 0.6 μm or larger, and even more preferably 1.0 μm or larger. The upper limit is preferably 200 μm or smaller, more preferably 150 μm or smaller, even more preferably 50 μm or smaller, and particularly preferably 20 μm or smaller. Within the above range, better effects tend to be obtained. In this specification, the median particle size of a water-soluble filler can be measured by laser diffraction, and refers to the particle size of the 50% integrated value in the mass-based particle size distribution curve obtained by laser diffraction scattering. The median particle size of water-soluble fillers is measured by the following method. [Measurement of median particle size (median diameter) of water-soluble fillers] The measurement will be performed using the SALD-2000J model manufactured by Shimadzu Corporation, employing the laser diffraction method. The operating procedure is as follows: <Measurement Procedure> A water-soluble filler is dispersed at room temperature in a mixed solution of a dispersion solvent (toluene) and a dispersant (10% by mass of di-2-ethylhexyl sodium sulfosuccinate / toluene solution). The resulting dispersion is stirred for 5 minutes while being irradiated with ultrasound to obtain a test solution. The test solution is transferred to a batch cell and measured after 1 minute. (Refractive index: 1.70-0.20i)

[0083] Examples of water-soluble fillers include water-soluble inorganic salts and water-soluble organic substances. These may be used individually or in combination of two or more.

[0084] Examples of water-soluble inorganic salts include metal sulfates such as magnesium sulfate, sodium sulfate, and potassium sulfate; metal chlorides such as potassium chloride, sodium chloride, calcium chloride, and magnesium chloride; metal hydroxides such as potassium hydroxide and sodium hydroxide; carbonates such as potassium carbonate, sodium carbonate, and calcium bicarbonate; and phosphates such as sodium hydrogen phosphate and sodium dihydrogen phosphate.

[0085] Examples of water-soluble organic substances include lignin derivatives and sugars. Suitable lignin derivatives include lignin sulfonic acid and lignin sulfonate salts. The lignin derivative may be obtained by either the sulfite pulp method or the kraft pulp method.

[0086] Examples of ligninsulfonates include alkali metal salts, alkaline earth metal salts, ammonium salts, and alcoholamine salts of ligninsulfonic acid. Among these, alkali metal salts (potassium salts, sodium salts, etc.) and alkaline earth metal salts (calcium salts, magnesium salts, lithium salts, barium salts, etc.) of ligninsulfonic acid are preferred.

[0087] The lignin derivative preferably has a sulfonation degree of 1.5 to 8.0 / OCH3. In this case, the lignin derivative includes ligninsulfonic acid and / or ligninsulfonate salts in which at least a portion of lignin and / or its decomposition products are substituted with sulfon groups (sulfonated groups), and the sulfon groups of the ligninsulfonic acid may be in an unionized state, or the hydrogen of the sulfon group may be substituted with an ion such as a metal ion. The sulfonation degree is more preferably 3.0 to 6.0 / OCH3. The effect tends to be more favorably obtained by keeping it within the above range.

[0088] The degree of sulfonation of lignin derivative particles (the lignin derivatives that constitute the particles) is the rate of introduction of sulfo groups and can be calculated using the following formula. Sulfonation degree ( / OCH3) = S (moles) in the sulfone group in the lignin derivative / methoxyl group (moles) in the lignin derivative

[0089] Sugars have no particular restrictions on the number of carbon atoms they consist of and can be monosaccharides, oligosaccharides, or polysaccharides. Examples of monosaccharides include trisaccharides such as aldotrioose and ketotriose; tetrasaccharides such as erythrose and threose; pentoses such as xylose and ribose; hexoses such as mannose, allose, altrose, and glucose; and heptasaccharides such as sedoheptulose. Examples of oligosaccharides include disaccharides such as sucrose and lactose; trisaccharides such as raffinose and melegitose; tetrasaccharides such as acarbose and stachyose; and oligosaccharides such as xylooligosaccharides and cellooligosaccharides. Examples of polysaccharides include glycogen, starch (amylose, amylopectin), cellulose, hemicellulose, dextrin, and glucan.

[0090] Among water-soluble fillers, water-soluble inorganic salts are preferred, metal sulfates are more preferred, and magnesium sulfate is even more preferred. Among magnesium sulfates, anhydrous magnesium sulfate, magnesium sulfate dihydrate, and magnesium sulfate trihydrate are preferred, and anhydrous magnesium sulfate is more preferred. Sodium sulfate is also preferred, and anhydrous sodium sulfate is even more preferred.

[0091] In the tread rubber composition, the water-soluble filler content is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 30 parts by mass or more, and particularly preferably 60 parts by mass or more, per 100 parts by mass of the rubber component. It is also preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less. The effect tends to be more favorably obtained by keeping it within the above range.

[0092] From the viewpoint of obtaining better performance, it is desirable for the tread rubber composition to contain vulcanized rubber particles.

[0093] Vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder as defined in JIS K 6316:2017 can be used. From the standpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. These may be used individually or in combination of two or more types.

[0094] Commercially available vulcanized rubber particles can be used, including those from Lehigh, Muraoka Rubber Industries, and others. Note that, in this specification, vulcanized rubber particles are not included in the rubber component.

[0095] The average particle size of the vulcanized rubber particles is preferably 5 μm or more, more preferably 8 μm or more, even more preferably 10 μm or more, and also preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. Within the above range, a better effect tends to be obtained. The average particle size of vulcanized rubber particles is the mass-based average particle size calculated from the particle size distribution measured in accordance with JIS Z 8815:1994.

[0096] The content of vulcanized rubber particles is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more, per 100 parts by mass of rubber component. It is also preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 100 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0097] From the viewpoint of obtaining better performance, it is preferable to incorporate a surface roughening agent into the tread rubber composition.

[0098] The surface roughening agent is not particularly limited, but examples include eggshell powder, short fibers, zinc oxide whiskers, hull powder, shirasu granules, crushed walnuts, volcanic ash, and iron fine particles. In addition, rubber powders such as recycled rubber and vulcanized rubber powder can also be used as surface roughening agents. These may be used alone or in combination of two or more. Among these, eggshell powder is preferred. Eggshell powder is obtained by crushing eggshells, and its main component is calcium carbonate.

[0099] The average particle size of the surface roughening agent (preferably eggshell powder) is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 10 μm or more. There is no particular upper limit, but it is preferably 150 μm or less, more preferably 100 μm or less, even more preferably 70 μm or less, and especially preferably 50 μm or less. When the particle size is within the above range, the effect tends to be better. The average particle size of the surface roughening agent (eggshell powder) is measured using a particle size distribution analyzer.

[0100] For eggshell powder, products from companies such as Green Techno 21 Co., Ltd. and Kewpie Corporation can be used.

[0101] In the tread rubber composition, the content of the surface roughening agent is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more, per 100 parts by mass of the rubber component. Also, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less. When the content is within the above range, a better effect tends to be obtained. The content of eggshell powder is also preferably within a similar range.

[0102] From the viewpoint of obtaining better performance, it is desirable for the rubber composition for the tread to include an inorganic filler.

[0103] The inorganic filler is not particularly limited, and materials known in the rubber field can be used, such as silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica.

[0104] In the rubber composition for tread, the content of the inorganic filler is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, still more preferably 55 parts by mass or more, particularly preferably 60 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, still more preferably 80 parts by mass or less, particularly preferably 70 parts by mass or less. When it is within the above range, the effects can be preferably obtained.

[0105] Among the inorganic fillers, silica is desirable from the viewpoint of obtaining better effects. The silica is not particularly limited, and examples thereof include dry-process silica (anhydrous silica), wet-process silica (hydrous silica), and the like. Among them, wet-process silica is preferred because of its large number of silanol groups.

[0106] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 30 m 2 / g or more, more preferably 100 m 2 / g or more, still more preferably 125 m 2 / g or more. Also, the N2SA of the silica is preferably 300 m 2 / g or less, more preferably 250 m 2 / g or less, still more preferably 200 m 2 / g or less. When it is within the above range, the effects can be preferably obtained. Note that the N2SA of the silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0107] As the silica, for example, products of Degussa, Rhodia, Tosoh Silica Corporation, Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0108] In the tread rubber composition, the silica content is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, and particularly preferably 100 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but for example, it may be 300 parts by mass or less, 200 parts by mass or less, or 150 parts by mass or less. When the content is within the above range, the effect is preferably obtained.

[0109] From the viewpoint of obtaining better performance, it is desirable for the rubber composition for the tread to contain carbon black.

[0110] While not particularly limited, examples of carbon black include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nippon Chemical Carbon Co., Ltd., and Columbia Carbon Corporation. These can be used individually or in combination of two or more types.

[0111] The specific surface area (N2SA) of carbon black for nitrogen adsorption is 30 m². 2 Preferably 50m / g or more. 2 More preferably 70m 2 More preferably, the amount of N2SA is 200m 2 Preferably less than / g, 150m 2 More preferably less than / g, 130m 2 More preferably less than / g, and 120m 2 A value of less than / g is particularly preferable. Within this range, better effects tend to be obtained.

[0112] In the tread rubber composition, the carbon black content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0113] Other fillers that can be used besides silica, carbon black, and water-soluble fillers include, for example, poorly dispersible fillers.

[0114] Examples of poorly dispersible fillers include microfibrillated plant fibers, short fibrous cellulose, and gel-like compounds. Among these, microfibrillated plant fibers are preferred.

[0115] As the above-mentioned microfibrillated plant fiber, cellulose microfibrils are preferred in that they provide good reinforcing properties. The cellulose microfibrils are not particularly limited as long as they are derived from natural products, and examples include resource biomass such as fruits, grains, and root vegetables; wood, bamboo, hemp, jute, and kenaf, as well as waste biomass such as pulp, paper, cloth, agricultural residues, food waste, and sewage sludge obtained from these raw materials, unused biomass such as rice straw, wheat straw, and thinned wood, and cellulose produced by sea squirts, acetic acid bacteria, etc. One type of these microfibrillated plant fiber may be used, or two or more types may be used in combination.

[0116] In this specification, cellulose microfibrils typically refer to cellulose fibers having an average fiber diameter of 10 μm or less, and more typically, cellulose fibers having a microstructure with an average fiber diameter of 500 nm or less, formed by an aggregate of cellulose molecules. Typical cellulose microfibrils are formed, for example, as aggregates of cellulose fibers having the average fiber diameter described above.

[0117] The rubber composition for the tread preferably contains a silane coupling agent. The silane coupling agent is not particularly limited and includes, for example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl) trisulfide, bis(4-trimethoxysilylbutyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, and 3-trimethoxysilylpropyl-N Examples include sulfide compounds such as N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto compounds such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyl compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products include those from companies such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd. These can be used individually or in combination of two or more types.

[0118] In the tread rubber composition, the silane coupling agent content is preferably 0.1 parts by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, based on 100 parts by mass of silica (100 parts by mass of total amount of silica constituting the surface-modified silica and other silica contained therein). The upper limit of the content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0119] The rubber composition for the tread preferably contains a plasticizer. Here, a plasticizer is a material that imparts plasticity to rubber components, and examples include liquid plasticizers (plasticizers that are in a liquid state at room temperature (25°C)) and resins (resins that are in a solid state at room temperature (25°C)).

[0120] In the rubber composition for treads, the plasticizer content (total amount of plasticizer) is preferably 10 parts by mass or more, more preferably 25 parts by mass or more, even more preferably 35 parts by mass or more, particularly preferably 40 parts by mass or more, and most preferably 55 parts by mass or more, per 100 parts by mass of rubber component. The upper limit is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0121] The liquid plasticizer (a plasticizer that is in a liquid state at room temperature (25°C)) that can be used in the tread rubber composition is not particularly limited, and it is desirable to use oil, liquid polymers (liquid resins, liquid diene polymers, liquid farnesene polymers, etc.). In particular, it is preferable to include a liquid polymer from the viewpoint of obtaining better effects. These may be used alone or in combination of two or more.

[0122] In the rubber composition for treads, the liquid plasticizer content is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, particularly preferably 35 parts by mass or more, and most preferably 50 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0123] Examples of oils include process oils, vegetable oils, or mixtures thereof. Examples of process oils include paraffinic process oils, aromatic process oils, and naphthenic process oils. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Alternatively, waste cooking oil recovered from the use of the above vegetable oils as cooking oil may also be used. Commercial products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Ltd. can be used. Among these, process oils (paraffinic process oils, aromatic process oils, naphthenic process oils, etc.) and vegetable oils are preferred.

[0124] In the tread rubber composition, the oil content is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, particularly preferably 35 parts by mass or more, and most preferably 50 parts by mass or more, per 100 parts by mass of rubber component. The upper limit is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less. Within the above range, a better effect tends to be obtained. Note that the oil content includes the amount of the rubber expander used in the oil-applied rubber.

[0125] Examples of liquid polymers include terpene resins (including terpene phenol resins and aromatically modified terpene resins), rosin resins, styrene resins, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, coumarone-indene resins (including coumarone and indene-only resins), phenolic resins, olefin resins, polyurethane resins, and acrylic resins. Hydrogenated versions of these resins can also be used.

[0126] Examples of liquid polymers include liquid diene polymers that are liquid at 25°C, such as liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid farnesene polymer, and liquid farnesene-butadiene copolymer. These polymers may have polar groups attached to their ends or main chains. Hydrogenated versions of these polymers are also available.

[0127] In the rubber composition for treads, the liquid polymer content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0128] Examples of resins that can be used in tread rubber compositions (resins that are solid at room temperature (25°C)) include aromatic vinyl polymers, coumarone indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins, all of which are solid at room temperature (25°C). The resins may also be hydrogenated. These may be used individually or in combination of two or more. Among these, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred.

[0129] In the rubber composition for treads, the resin content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0130] The softening point of the above resin is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 60°C or higher. The upper limit is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower. Within the above range, the effect tends to be better obtained. The softening point of the above resin is the temperature at which the sphere drops when the softening point specified in JIS K6220-1:2001 is measured using a ring-type softening point measuring device.

[0131] The above-mentioned aromatic vinyl polymer is a polymer containing aromatic vinyl monomers as constituent units. Examples include resins obtained by polymerizing α-methylstyrene and / or styrene, specifically, homopolymers of styrene (styrene resin), homopolymers of α-methylstyrene (α-methylstyrene resin), copolymers of α-methylstyrene and styrene, copolymers of styrene and other monomers.

[0132] The above-mentioned coumarone-indene resin is a resin that contains coumarone and indene as the main monomer components that constitute the resin's backbone (main chain). Other monomer components that may be included in the backbone besides coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0133] The coumarone resin described above is a resin that contains coumarone as the main monomer component that constitutes the resin's backbone (main chain).

[0134] The above-mentioned indene resin is a resin that contains indene as the main monomer component that constitutes the resin's backbone (main chain).

[0135] As the phenolic resin mentioned above, known polymers such as those obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural using an acid or alkali catalyst can be used. Among these, those obtained by reaction with an acid catalyst (such as novolac-type phenolic resins) are preferred.

[0136] Examples of the rosin resins mentioned above include natural rosin, polymerized rosin, modified rosin, their ester compounds, and rosin-based resins represented by their hydrogenated products.

[0137] Examples of the above petroleum resins include C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, and hydrogenated versions thereof. Among these, DCPD resins and hydrogenated DCPD resins are preferred.

[0138] The above-mentioned terpene resins are polymers containing terpenes as constituent units. Examples include polyterpene resins obtained by polymerizing terpene compounds, and aromatically modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. As aromatically modified terpene resins, terpene-phenol resins made from terpene compounds and phenolic compounds, terpene-styrene resins made from terpene compounds and styrene compounds, and terpene-phenol-styrene resins made from terpene compounds, phenolic compounds, and styrene compounds can also be used. Examples of terpene compounds include α-pinene and β-pinene, examples of phenolic compounds include phenol and bisphenol A, and examples of aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.).

[0139] The above-mentioned acrylic resin is a polymer containing acrylic monomers as constituent units. Examples include styrene-acrylic resins such as styrene-acrylic resin, which have carboxyl groups and are obtained by copolymerizing an aromatic vinyl monomer component with an acrylic monomer component. Among these, solvent-free carboxyl group-containing styrene-acrylic resins can be suitably used.

[0140] Examples of plasticizers that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Industries, Ltd.

[0141] The rubber composition for the tread may contain processing aids. Examples of processing aids include metal salts (compounds in which the hydrogen atoms of an acid are replaced by metal ions), fatty acid amides, amide esters, and fatty acid esters. These may be used individually or in combination of two or more. Among these, metal salts and fatty acid amides are preferred, and metal salts are more preferred.

[0142] Examples of metals used in metal salts include alkali metals such as potassium and sodium, and alkaline earth metals such as calcium and barium. Magnesium, zinc, nickel, and molybdenum can also be used. Among these, alkali metals are preferred.

[0143] Acids used in metal salts include fatty acids such as lauric acid, myristic acid, and palmitic acid. Boric acid, carbonic acid, hydrochloric acid, nitric acid, and sulfuric acid can also be used.

[0144] Commercially available processing aids include products from companies such as Kishida Chemical Co., Ltd., Ken-ei Pharmaceutical Co., Ltd., Structol, and Performance Additives.

[0145] In the tread rubber composition, the content of processing aids is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, and also preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, a better effect tends to be obtained.

[0146] The rubber composition for the tread preferably contains an anti-aging agent from the viewpoint of crack resistance, ozone resistance, etc.

[0147] While not particularly limited, the following are examples of anti-aging agents: naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, and N,N′-di-2-naphthyl-p-phenylenediamine. Examples of anti-aging agents include p-phenylenediamine-based anti-aging agents such as amines; quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis, tris, and polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and polymers of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercial products such as those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Co., Ltd. can be used.

[0148] In the tread rubber composition, the content of the anti-aging agent is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less.

[0149] The tread rubber composition may contain stearic acid. In the rubber composition, the stearic acid content is preferably 0.5 to 10 parts by mass or more, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0150] In addition, conventionally known stearic acid can be used, such as products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Corporation, Chiba Fatty Acid Co., Ltd.

[0151] The tread rubber composition may also contain zinc oxide. In the tread rubber composition, the zinc oxide content is preferably 0.5 to 10 parts by mass, more preferably 1 to 3 parts by mass, per 100 parts by mass of the rubber component.

[0152] In addition, conventionally known zinc oxides can be used, such as products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd.

[0153] Wax may be added to the rubber composition for the tread. In the rubber composition for treads, the wax content is preferably 0.5 to 10 parts by mass, more preferably 2 to 5 parts by mass, per 100 parts by mass of rubber components.

[0154] The type of wax used is not particularly limited and includes petroleum-based waxes, natural waxes, and synthetic waxes obtained by refining or chemically processing multiple waxes. These waxes may be used individually or in combination of two or more types.

[0155] Examples of petroleum-based waxes include paraffin wax and microcrystalline wax. Examples of natural waxes are not limited to those derived from non-petroleum resources, and include plant-based waxes such as candelilla wax, carnauba wax, wood wax, rice wax, and jojoba wax; animal-based waxes such as beeswax, lanolin, and whale wax; mineral waxes such as ozokerite, ceresin, and petrolactam; and refined products thereof. Commercially available products include those from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd.

[0156] Sulfur may be added to the tread rubber composition in order to form appropriate cross-linked chains in the polymer chains and to impart the aforementioned balance of performance.

[0157] In the tread rubber composition, the sulfur content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 part by mass or more, per 100 parts by mass of the rubber component. The content is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0158] Examples of sulfur commonly used in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. Commercially available products include those from Tsurumi Chemical Industries, Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Co., Ltd., Flexis Co., Ltd., Nippon Dry Distillation Co., Ltd., and Hosoi Chemical Industry Co., Ltd. These can be used individually or in combination of two or more types.

[0159] The tread rubber composition may contain a vulcanization accelerator. In a rubber composition for treads, the content of the vulcanization accelerator is usually 0.3 to 10 parts by mass, preferably 0.5 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0160] There are no particular restrictions on the type of vulcanization accelerator; commonly used ones can be used. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diortotrilguanidine, and orthotrilbiguanidine. These may be used individually or in combination of two or more. Among them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

[0161] In addition to the above-mentioned components, the tread rubber composition may also contain, as appropriate, conventional additives used in the field of application, such as mold release agents and pigments. In the tread rubber composition, the content of the additives is preferably 0.5 to 10 parts by mass, more preferably 2 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0162] Known methods can be used to manufacture the rubber composition for treads. For example, it can be manufactured by kneading each component using a rubber kneading device such as an open roll or Banbury mixer, and crosslinking as needed. The kneading conditions are as follows: the kneading temperature is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes.

[0163] The tire of the present invention is manufactured by a conventional method using the above-mentioned tread rubber composition. For example, an unvulcanized tire is formed by extruding a rubber composition containing various materials into the shape of a tread at the unvulcanized stage, and then molding it together with other tire components on a tire molding machine in a conventional manner. A tire is then obtained by heating and pressurizing this unvulcanized tire in a vulcanizing machine.

[0164] The tire of the present invention satisfies the following formula (1) when the area ratio S (% (area %)) determined by the tire water removal evaluation method described above. (1) S<30 S is preferably 28% or less, more preferably 25% or less, even more preferably 21% or less, and particularly preferably 18% or less. The lower limit of S is not particularly limited, but is preferably 5% or more, more preferably 9% or more, even more preferably 12% or more, and particularly preferably 15% or more. When it is within the above range, the effect tends to be better obtained.

[0165] The aforementioned tire satisfies the following formula (2) in terms of area ratio S (%) and tread thickness T (mm). (2) S × T ≤ 400 (Unit: %·mm) S×T is preferably 380 or less, more preferably 360 or less, even more preferably 286 or less, particularly preferably 252 or less, and most preferably 234 or less. The lower limit of S×T is not particularly limited, but is preferably 100 or more, more preferably 130 or more, even more preferably 150 or more, and particularly preferably 170 or more. When it is within the above range, the effect tends to be better obtained.

[0166] In the aforementioned tire, the area ratio S is preferably the area ratio (%) obtained in the third step of the evaluation method for tire water removal that satisfies the following conditions (1) to (4). (1) A water film is formed in the suspension. (2) In the first step, the brightness value that shows the highest frequency in the brightness distribution of the still image is determined as a binarization threshold that separates the actual grounded portion from the non-grounded portion or the empty portion. (3) In the second step, the binarization threshold is determined by Otsu's binarization. (4) In the third step, the snapshot image in which the area of ​​the actual ground contact portion below the binarization threshold determined in the first step is 1.0% (area %) or more is taken as the first snapshot image.

[0167] From the viewpoint of obtaining better performance, it is desirable that the tread thickness T (mm) of the aforementioned tire satisfies the following formula. 5.0 ≤ T ≤ 18.0 The lower limit of T is preferably 6.0 mm or more, more preferably 9.0 mm or more, and even more preferably 11.0 mm or more. The upper limit is preferably 16.0 mm or less, more preferably 14.0 mm or less, and even more preferably 13.0 mm or less. Within the above range, a better effect tends to be obtained.

[0168] In the aforementioned tire, the tread thickness T refers to the maximum dimension (maximum thickness of the tread portion) among the thicknesses of each tread at each point on the tread surface. The thickness at each point on the tread surface is a value measured along the normal to the tread surface at that point, and the tread thickness T is the maximum thickness at each point. The thickness at each point is the distance from the tread surface to the interface on the outermost side of the tire of the reinforcing layer, which includes other fibrous materials such as the belt layer and carcass layer, in a cross-section cut by a plane containing the tire axis. In areas with grooves, it is the straight-line distance from the plane formed by the straight line connecting the outermost ends of the grooves in the radial direction of the tire. Specifically, in the case of a two-layer tread structure consisting of a cap layer and a base layer as shown in Figures 5 and 6 below, the thickness at each point means the distance from the tread surface 24 to the interface on the outermost side of the tire of the band 18. Also, in the case of a tire that uses a single-layer tread structure or a tread with a structure of three or more layers instead of the two-layer tread structure, the thickness at each point means the distance from the tread surface to the interface on the outermost side of the tire of the band, similar to the two-layer tread structure. In this invention, the tread portion may be formed of only one cap rubber layer, or it may be made of two layers by providing a base rubber layer inside the cap rubber layer, or it may be made of three layers, or even four or more layers.

[0169] In this specification, unless otherwise specified, the tread thickness T is a value obtained by disassembling the tire and measuring the thickness T.

[0170] In the aforementioned tire, from the viewpoint of obtaining a better effect, it is desirable that the land ratio L (%) and the area ratio S (%) satisfy the following formula. L / S ≥ 2.0 (Unit: Dimensionless) The lower limit of L / S is preferably 2.3 or higher, more preferably 2.5 or higher, and even more preferably 2.7 or higher. The upper limit is preferably 3.5 or lower, more preferably 3.2 or lower, and even more preferably 3.0 or lower. Within the above range, better effects tend to be obtained.

[0171] In the aforementioned tire, from the viewpoint of obtaining better performance, it is desirable that the land ratio L (%) satisfies the following formula. L≧50% The lower limit of the land ratio is preferably 65% ​​or more, more preferably 68% or more, and even more preferably 70% or more. The upper limit of the land ratio is preferably 90% or less, more preferably 85% or less, even more preferably 82% or less, and particularly preferably 80% or less. Within the above range, the effect tends to be better obtained.

[0172] In this specification, if the tire is a pneumatic tire, the land ratio (L) is calculated from the contact patch shape under normal rim, normal internal pressure, and normal load conditions. In the case of a non-pneumatic tire, it can be measured similarly without requiring normal internal pressure.

[0173] A "standard rim" refers to the rim specified for each tire within the standards system that the tire is based on. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." Refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. In the case of tires not specified in the standards, it refers to the rim with the smallest diameter and the narrowest rim width among rims that can be mounted on and can maintain internal pressure, i.e., rims that do not cause air leakage between the rim and tire.

[0174] "Regular internal pressure" refers to the air pressure specified for each tire by the aforementioned standards. For JATMA, it is the maximum air pressure; for ETRTO, it is "INFLATION PRESSURE"; for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is "INFLATION PRESSURE." Similar to "regular rim," refer to JATMA, ETRTO, and TRA in that order and follow the respective standards. In the case of tires not specified in the standards, it refers to the regular internal pressure (but 250 kPa or higher) of another tire size (specified in the standards) that uses the aforementioned regular rim as the standard rim. If multiple regular internal pressures of 250 kPa or higher are listed, refer to the lowest value among them.

[0175] "Regular load" refers to the load specified for each tire in the tire standard system, including the standard on which the tire is based. For JATMA, it refers to the maximum load capacity; for ETRTO, it refers to "LOAD CAPACITY"; and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." Similar to the "regular rim" and "regular internal pressure" mentioned above, refer to JATMA, ETRTO, and TRA in that order and follow the respective standards. For tires not specified in the standards, the regular load W is calculated as follows: L We seek. V = {(Dt / 2)} 2 -(Dt / 2-Ht) 2} × π × Wt W L = 0.000011 × V + 175 W L :Normal load (kg) V: Virtual volume of the tire (mm²) 3 ) Dt: Tire outer diameter (mm) Ht: Tire section height (mm) Wt: Tire section width (mm)

[0176] The "contact shape" can be obtained by mounting the tire onto a standard rim, applying the standard internal pressure, letting it stand at 25°C for 24 hours, then applying ink to the tire tread surface, applying the standard load, pressing it onto cardboard (camber angle 0°), and transferring the result to the paper. The tire is rotated 72° in the circumferential direction, and the shape is transferred at five points. In other words, the contact shape is obtained five times. At this time, for the five contact shapes, the parts that are interrupted by grooves in the contour are smoothly connected, and the resulting shape is taken as the virtual contact surface. The land ratio (L) is calculated as: average area of ​​the five contact shapes (inked areas) transferred to the cardboard / (average area of ​​the virtual contact surface from the five contact shapes) × 100 (%).

[0177] In the aforementioned tire, it is desirable that the tread rubber composition (rubber composition after vulcanization) constituting the tread has an acetone extraction amount A (mass%) that satisfies the following formula. A≧17% by mass The lower limit of A is preferably 20% by mass or more, and more preferably 23% by mass or more. The upper limit is preferably 34% by mass or less, more preferably 31% by mass or less, and even more preferably 28% by mass or less. When the amount is within the above range, the effect tends to be better. In this invention, the amount of acetone extracted (A) is measured for the rubber composition (sample) using the method for measuring the amount of acetone extracted in accordance with JIS K 6229:2015 (unit: mass %) of the rubber composition (sample).

[0178] An example of the tire of the present invention, which has a tread made of a tread rubber composition, will be explained with reference to Figure 5. In Figure 5, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the plane of the paper is the circumferential direction of the tire 2. The tread portion 4 comprises a cap layer 30 and a base layer 28.

[0179] Although Figure 5 shows an example of a two-layer tread section 4 consisting of a cap layer 30 and a base layer 28, a single-layer tread or a tread section with three or more layers may also be used.

[0180] In tire 2, each sidewall 6 extends radially inward from the edge of the tread 4. The radially outer portion of this sidewall 6 is joined to the tread 4. The radially inner portion of this sidewall 6 is joined to the clinch 10. This sidewall 6 can prevent damage to the carcass 14.

[0181] Each wing 8 in Figure 5 is located between the tread 4 and the sidewall 6. The wing 8 is joined to both the tread 4 and the sidewall 6, respectively.

[0182] Each clinch 10 is located approximately radially inward of the sidewall 6. In the axial direction, the clinch 10 is located outward from the bead 12 and the carcass 14.

[0183] Each bead 12 is located axially inward of the clinch 10. The bead 12 comprises a core 32 and an apex 34 extending radially outward from the core 32. The core 32 is preferably ring-shaped and contains a wound non-stretchable wire. The apex 34 tapers radially outward.

[0184] The carcass 14 is provided with a carcass ply 36. In this tire 2, the carcass 14 consists of one carcass ply 36, but it may be composed of two or more.

[0185] In this tire 2, the carcass ply 36 spans between the beads 12 on both sides and runs along the tread 4 and sidewall 6. The carcass ply 36 is folded axially from the inside to the outside around each core 32. This folding gives the carcass ply 36 a main portion 36a and a pair of folded portions 36b. In other words, the carcass ply 36 comprises a main portion 36a and a pair of folded portions 36b.

[0186] Although not shown in the diagram, the carcass ply 36 preferably consists of a number of parallel cords and topping rubber. The absolute value of the angle that each cord makes with respect to the equatorial plane is preferably between 75° and 90°. In other words, it is preferable that the carcass 14 has a radial structure.

[0187] The belt layer 16 in Figure 5 is located radially inward of the tread 4. The belt layer 16 is laminated with the carcass 14. The belt layer 16 reinforces the carcass 14. The belt layer 16 consists of an inner layer 38 and an outer layer 40. As is clear from Figure 1, it is desirable that the width of the inner layer 38 is slightly larger than the width of the outer layer 40 in the axial direction. In this tire 2, the axial width of the belt layer 16 is preferably 0.6 times or more, and preferably 0.9 times or less, the cross-sectional width of the tire 2 (see JATMA).

[0188] Although not shown in the diagram, it is desirable that each of the inner layer 38 and the outer layer 40 consists of a number of parallel cords and topping rubber. In other words, the belt layer 16 contains a number of parallel cords. Each cord is inclined with respect to the equatorial plane. The general absolute value of the inclination angle is between 10° and 35°. The inclination direction of the cords of the inner layer 38 with respect to the equatorial plane is opposite to the inclination direction of the cords of the outer layer 40 with respect to the equatorial plane.

[0189] The tire 2 has a tread 4 made of the aforementioned tread rubber composition.

[0190] In Figure 5, band 18 is located radially outside the belt layer 16. In the axial direction, band 18 has a width equal to the width of the belt layer 16. Band 18 may have a width greater than the width of the belt layer 16.

[0191] Although not shown in the diagram, the band 18 preferably consists of a cord and a topping rubber. The cord is wound in a spiral shape. This band 18 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is preferably 5° or less, and more preferably 2° or less. Since the belt layer 16 is restrained by this cord, lifting of the belt layer 16 is suppressed.

[0192] The belt layer 16 and band 18 in Figure 5 constitute the reinforcing layer. The reinforcing layer may also be composed of the belt layer 16 alone.

[0193] Figure 6 is a magnified view of the area around tread 4 in Figure 5. In Figure 6, T1 represents the tread thickness at a predetermined point on the tread surface 24, and is a value measured along the normal to the tread surface 24 at that point. The tread thickness T is the maximum thickness at each point (the maximum thickness of the tread portion).

[0194] Furthermore, the tire 2 preferably satisfies the following conditions: the thickness T (mm) of the tread 4, the area ratio S (%) determined by the tire water removal evaluation method, and the resin component content of the tread, with S × T ≤ 380, and more preferably S × T ≤ 360. Furthermore, it is desirable that the land ratio L (%) and tread thickness T (mm) of tire 2 satisfy the formula "L / T ≥ 200". In addition, it is desirable that the acetone extraction amount AE (mass%) of the rubber composition constituting the tread 4 (rubber composition after vulcanization) satisfy the formula "AE ≥ 20.0".

[0195] The inner liner 20 is located inside the carcass 14. The inner liner 20 is bonded to the inner surface of the carcass 14. Typical base rubbers for the inner liner 20 are butyl rubber or halogenated butyl rubber. The inner liner 20 maintains the internal pressure of the tire 2.

[0196] Each chafer 22 is located near the bead 12. In this embodiment, it is preferable that the chafer 22 consists of cloth and rubber impregnated into the cloth. The chafer 22 may be integrated with the clinch 10.

[0197] In this tire 2, the tread 4 is provided with main grooves 42 as grooves 26. As shown in Figure 5, this tread 4 has multiple main grooves 42, specifically three. These main grooves 42 are spaced apart in the axial direction. The three main grooves 42 in this tread 4 form four ribs 44 that extend in the circumferential direction. In other words, the space between the ribs 44 is the main groove 42.

[0198] Each main groove 42 extends in the circumferential direction. The main grooves 42 are continuous and uninterrupted in the circumferential direction. The main grooves 42 facilitate the removal of water present between the road surface and the tire 2, for example, in rainy weather. As a result, even when the road surface is wet, the tire 2 can maintain sufficient contact with the road surface. [Examples]

[0199] The following examples (implementations) are considered preferable for implementation, but the scope of the present invention is not limited to these examples.

[0200] The following tables show the results of examining tires obtained by varying the formulations using the various chemicals listed below, and calculating the results based on the evaluation method described below.

[0201] (Rubber component) NR:TSR20 BR: BR730 (High-Cys BR, cis content: 97% by mass) manufactured by JSR Corporation.

[0202] (Chemicals other than rubber components) Silica: Evonik Degussa's UltraSil VN3 (N2SA: 175m 2 / g) Carbon black: Dia Black I (N220, N2SA) manufactured by Mitsubishi Chemical Corporation: 114ml 2 ( / g, DBP 114ml / 100g) Magnesium sulfate 1: Magnesium sulfate manufactured by Maiko Chemical Industries Co., Ltd. (Median particle size: 1 μm) Magnesium sulfate 2: Magnesium sulfate manufactured by Maiko Chemical Industries Co., Ltd. (Median particle size: 50 μm) Magnesium sulfate 3: Magnesium sulfate manufactured by Maiko Chemical Industries Co., Ltd. (Median particle size: 100 μm) Magnesium sulfate 4: Magnesium sulfate manufactured by Maiko Chemical Industries Co., Ltd. (Median particle size: 150 μm) Vulcanized rubber particles 1: Rubber powder manufactured by Muraoka Rubber Industry Co., Ltd. (average particle size: 10 μm) Vulcanized rubber particles 2: Rubber powder manufactured by Muraoka Rubber Industry Co., Ltd. (average particle size: 50 μm) Vulcanized rubber particles 3: Rubber powder manufactured by Muraoka Rubber Industry Co., Ltd. (average particle size: 100 μm) Vulcanized rubber particles 4: Rubber powder manufactured by Muraoka Rubber Industry Co., Ltd. (average particle size: 150 μm) Eggshell powder 1: Eggshell powder manufactured by Green Techno 21 Co., Ltd. (average particle size 10 μm) Eggshell powder 2: Eggshell powder manufactured by Green Techno 21 Co., Ltd. (average particle size 50 μm) Eggshell powder 3: Eggshell powder manufactured by Green Techno 21 Co., Ltd. (average particle size 100 μm) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by EVONIK-DEGUSSA Oil: Diana Process AH-24 (aroma oil) manufactured by Idemitsu Kosan Co., Ltd. Resin: SYLVARES SA85 manufactured by Arizona Chemical Corporation (a copolymer of α-methylstyrene and styrene, a resin that is solid at room temperature) Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Anti-aging agent: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Processing aid: ULTRA-FLOW 440 (zinc fatty acid) manufactured by Performance Additives. Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industries Co., Ltd. Vulcanization accelerator CZ: Noxellar CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator DPG: Noxellar D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Liquid polymer: RICON130 (polybutadiene, Mn2500) manufactured by CRAY VALLEY.

[0203] <Manufacturing of test tires> According to the formulations shown in each table, the chemicals other than sulfur and vulcanization accelerators are mixed for 4 minutes at 160°C using a 16L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a mixture. Next, sulfur and a vulcanization accelerator are added to the resulting mixture, and the mixture is kneaded using an open roll at 80°C for 4 minutes to obtain an unvulcanized polymer composition. The resulting unvulcanized polymer composition is molded into a tread shape and bonded together with other tire components on a tire molding machine to form an unvulcanized tire. Then, it is vulcanized at 170°C for 12 minutes to produce a test tire (size: 195 / 65R15).

[0204] Assuming test tires obtained from compositions with varying formulations according to each table, the results calculated based on the tire water removal evaluation method and ice grip performance evaluation method described below are shown in each table. The standard formulation is as follows: Table 1: Formulation 1-14 Table 2: Formulation 2-10 Table 3: Formulation 3-9

[0205] <Evaluation method for tire water removal> (1) In the shooting step, under the following experimental conditions, still images and videos of each test tire are taken using the tire contact state shooting device 101 shown in Figure 1, in the manner shown in Figures 2 to 4. (Experimental conditions) Load on one tire: 375 kg Tires: 195 / 65R15 (approximately 100km of break-in driving completed) Vehicle speed: 5 km / h when passing the high-speed camera (during video recording) Glass thickness: 60mm Water film thickness: 4mm Suspension water: Prepared by mixing white paint with water (32 ml of paint per 8 L of water; paint type: Sakura Poster Color White) High-speed camera: NAC ACS-1 M60 High-speed camera settings : Shooting at 30,000 fps : Gain Gamma Mid : Shutter (exposure time) open Lens used: 100mm F2.8 Ultra Macro APO lens Lens settings : Aperture f4 Magnification: 3.4x (using a 2x teleconverter) Illuminance: 100,000 lux Field of view: 1.5cm x 1.2cm

[0206] (2) In the image processing step, the binarization threshold is obtained using the following procedure. (2-1) In the step of acquiring the actual ground contact portion, the value showing the highest frequency in the brightness distribution of the still image captured in the above shooting step is used as the binarization threshold that separates the actual ground contact portion from the other portion (the region combining the water film portion and the space portion). (2-2) In the spatial portion acquisition step, for each snapshot image of the video captured in the above shooting step, the binarization threshold obtained by discriminant analysis is used as the binarization threshold that separates the spatial portion from the non-spatial portion (the region combining the actual ground contact portion and the water film portion).

[0207] (3) In the calculation step, for each snapshot image of the video, the area ratio of the area occupied by the actual ground contact portion and the water film portion combined out of the total area of ​​the first snapshot image in which the area of ​​the actual ground contact portion is 1.0% (area %) or more is calculated.

[0208] In Tables 1-3, tires with an area percentage S(%) of less than 30.0%, as determined by the above tire water removal evaluation method, can be evaluated as having good water removal, particularly at the microscale due to surface irregularities.

[0209] <Acetone extraction volume AE (mass%)> The rubber test pieces cut from the tread of the above-mentioned test tire will be subjected to acetone extraction using the method for measuring acetone extraction volume in accordance with JIS K 6229:2015, and the amount of extracted material will be measured.

[0210] <Grip performance on ice> The test tires will be mounted on a vehicle, and the vehicle will be driven on ice under the following conditions to evaluate its ice grip performance. To evaluate ice grip performance, the vehicle will be driven on ice, and the stopping distance (ice braking stopping distance) will be measured when the lock brake is applied at a speed of 30 km / h. The index is displayed with the standard comparison example set to 100 (ice grip performance index). A higher index indicates superior braking performance (ice grip performance) on ice. Temperature: -1 to -6°C

[0211] [Table 1]

[0212] [Table 2]

[0213] [Table 3]

[0214] The present invention (1) includes a photographing step of photographing a tire running on a transparent or translucent plate on which a water film has been formed, from below the transparent or translucent plate, Image processing steps for each snapshot image of the captured video, separating it into regions of the actual ground contact area, the water film area, and the empty space area, This is a method for evaluating tire water removal, which includes a calculation step to determine the ratio of the actual contact area to the water film area.

[0215] The present invention (2) is a method for evaluating tire water removal according to the present invention (1), wherein in the calculation step, the ratio is the area ratio of the area occupied by the sum of the actual contact area and the water film area out of 100% (area %) of the total area of ​​the snapshot image.

[0216] The present invention (3) is a method for evaluating tire water removal according to the present invention (1) or (2), wherein the water film is formed in a suspension.

[0217] The present invention (4) is a method for evaluating tire water removal in any combination of the present inventions (1) to (3), wherein in the calculation step, for the first snapshot image in which the area of ​​the actual contact portion becomes 1.0% (area %) or more of the snapshot image, the area ratio (area %) of the area occupied by the sum of the actual contact portion and the water film portion out of the total area 100% (area %) of the first snapshot image is determined.

[0218] The present invention (5) is a method for evaluating tire water removal in any combination of the present invention (1) to (4), wherein the binarization threshold used in the image processing step to separate the area into the actual contact area and the area other than the actual contact area is the value that shows the maximum frequency in the brightness distribution.

[0219] The present invention (6) is a method for evaluating tire water removal, in which, in the image processing step, a binarization threshold for separating the region into a spatial portion and a region other than the spatial portion is determined by discriminant analysis, in any combination of the present inventions (1) to (5).

[0220] The present invention (7) is a method for evaluating tire water removal, which in the image processing step involves separating all snapshot images constituting the captured video into regions of actual contact area, water film area, and empty space, in any combination of the present inventions (1) to (6).

[0221] The present invention (8) is a tire having a tread, The tire is one in which the area ratio S (%) and the tread thickness T (mm), determined by the following tire water-removal evaluation method, satisfy the following formulas (1) and (2). (1) S<30 (2) S × T ≤ 400 (Method for evaluating tire water removal) A photographic step of photographing a tire running on a transparent or translucent plate on which a water film has formed, from below the transparent or translucent plate, An image processing step of separating each snapshot image of the captured video into regions of a grounded portion, a water film portion, and a space portion, A method for evaluating tire drainage performance, including a calculation step of obtaining the ratio of the grounded portion to the water film portion, where the water film is formed of a suspension, In the image processing step, the binarization threshold for separating the grounded portion and the region other than the grounded portion is the value showing the maximum frequency in the luminance distribution, and the binarization threshold for separating the space portion and the region other than the space portion is determined by the discriminant analysis method, and for all the snapshot images constituting the captured video, they are separated into regions of the grounded portion, the water film portion, and the space portion, In the calculation step, for the first snapshot image in which the area of the grounded portion is 1.0% (area %) or more of the snapshot image, the area ratio (area %) occupied by the total area of the grounded portion and the water film portion in 100% (area %) of the total area of the first snapshot image is obtained, A method for evaluating tire drainage performance.

[0222] The tire according to the present invention (9) is the tire according to the present invention (8) satisfying the following formula. S×T≦380

[0223] The tire according to the present invention (10) is the tire according to the present invention (8) or (9) satisfying the following formula. S×T≦360

[0224] The tire according to the present invention (11) is a tire in any combination with any one of the present inventions (8) to (10) where the land ratio L (%) and the area ratio S (%) satisfy the following formula. L / S≧2.0

[0225] The tire according to the present invention (12) is a tire in any combination with any one of the present inventions (8) to (11) where the acetone extraction amount A (mass %) satisfies the following formula. A≧17.0

[0226] The present invention (13) is a tire in any combination of the present invention (8) to (12), wherein the tread contains 60 parts by mass or more of inorganic filler per 100 parts by mass of rubber component.

[0227] The present invention (14) is a tire in any combination of the tread with any of the present inventions (8) to (13), wherein the silica content per 100 parts by mass of rubber component is 60 parts by mass or more.

[0228] The present invention (15) is a tire in any combination of the tread containing a water-soluble filler with any of the present inventions (8) to (14).

[0229] The present invention (16) is a tire in which the tread contains rubber powder in any combination with any of the present inventions (8) to (15).

[0230] The present invention (17) is a tire in any combination of the tread containing a liquid polymer with any of the present inventions (8) to (16).

[0231] The present invention (18) is a tire in any combination with any of the winter tires described in the present invention (8) to (17). [Explanation of Symbols]

[0232] 101 Device for photographing tire contact status 102 Transparent or translucent plate 103 Water film 104 Imaging device 111 Tires 112 Grounding part 2. Pneumatic tires 3 Side section 4 tread 6 Sidewall 8 Wing 10. Clinch 12 beads 14 Carcass 16 belts 18 bands 20 Inner Liner 22 Chafer 24 Tread surface 26 Groove 28 Base Layer 30 cap layers 32 cores 34 Apex 36 Carcass ply 36a Main section 36b Folded section 38 Inner layer 40 outer layer 42 Main groove 44 Ribs CL Tire 2 equatorial plane T1 Thickness of the tread at a predetermined point on the tread surface 24 Main groove depth of the circumferential main groove 42 formed in the tread 4

Claims

1. A photographic step of photographing a tire running on a transparent or translucent plate on which a water film has formed, from below the transparent or translucent plate, Image processing steps for each snapshot image of the captured video, separating it into regions of the actual ground contact area, the water film area, and the empty space area, A method for evaluating tire water removal, including a calculation step to determine the ratio of the actual contact area to the water film area.

2. The tire water removal evaluation method according to claim 1, wherein in the calculation step, the ratio is the area ratio of the area occupied by the sum of the actual contact area and the water film area out of 100% (area %) of the total area of ​​the snapshot image.

3. The method for evaluating tire water removal according to claim 1, wherein the water film is formed in a suspension.

4. The tire water removal evaluation method according to claim 1, wherein in the calculation step, for the first snapshot image in which the area of ​​the actual contact portion becomes 1.0% (area %) or more of the snapshot image, the area ratio (area %) of the area occupied by the sum of the actual contact portion and the water film portion out of the total area 100% (area %) of the first snapshot image is determined.

5. The tire water removal evaluation method according to claim 1, wherein the binarization threshold used to separate the area into the actual contact area and the area other than the actual contact area in the image processing step is the value that shows the maximum frequency in the brightness distribution.

6. The tire water removal evaluation method according to claim 1, wherein in the image processing step, a binarization threshold for separating the image into a spatial portion and a non-spatial portion is determined by discriminant analysis.

7. The tire water removal evaluation method according to claim 1, wherein in the image processing step, all snapshot images constituting the captured video are separated into regions of actual contact area, water film area, and empty space.

8. A tire having a tread, A tire in which the area ratio S (%) obtained by the following tire water removal evaluation method and the tread thickness T (mm) satisfy the following formulas (1) and (2). (1) S < 30 (2) S × T ≤ 400 (Method for evaluating tire water removal) A photographic step of photographing a tire running on a transparent or translucent plate on which a water film has formed, from below the transparent or translucent plate, Image processing steps for each snapshot image of the captured video, separating it into regions of the actual ground contact area, the water film area, and the empty space area, A method for evaluating tire water removal, which includes a calculation step of determining the ratio of the actual contact area to the water film area, The aforementioned aqueous film is formed in a suspension. In the image processing step described above, the binarization threshold for separating the area into the actual ground contact area and the area outside the actual ground contact area is the value that shows the highest frequency in the luminance distribution, the binarization threshold for separating the area into the spatial area and the area outside the spatial area is determined by discriminant analysis, and all snapshot images constituting the captured video are separated into the areas of the actual ground contact area, the water film area, and the spatial area. In the calculation step described above, for the first snapshot image in which the area of ​​the actual ground contact portion is 1.0% (area %) or more of the snapshot image, the area percentage (area %) of the total area of ​​the first snapshot image, which is the sum of the area of ​​the actual ground contact portion and the water film portion, is calculated. Evaluation method for tire water removal.

9. A tire according to claim 8 that satisfies the following formula. S × T ≤ 380

10. A tire according to claim 8 that satisfies the following formula. S × T ≤ 360

11. The tire according to claim 8, wherein the land ratio L (%) and area ratio S (%) satisfy the following formula. L / S ≥ 2.0

12. The tire according to claim 8, wherein the amount of acetone extracted A (mass%) satisfies the following formula. A ≥ 17.0

13. The tire according to claim 8, wherein the tread contains 60 parts by mass or more of inorganic filler per 100 parts by mass of rubber component.

14. The tire according to claim 8, wherein the tread contains 60 parts by mass or more of silica per 100 parts by mass of rubber component.

15. The tire according to claim 8, wherein the tread contains a water-soluble filler.

16. The tire according to claim 8, wherein the tread contains rubber powder.

17. The tire according to claim 8, wherein the tread contains a liquid polymer.

18. The tire according to claim 8, which is a winter tire.

Images