Heavy-duty tire

Abstract

To solve the problem in which heavy-duty tires for use including traveling under heavy-load conditions or tires for construction vehicles such as dump trucks that primarily operate off-road typically undergo long vulcanization times of 1-10 hours due to their large size, but there is concern that the long vulcanization causes deterioration of heat generation properties and other physical properties.SOLUTION: A heavy-duty tire comprises a rubber component containing a diene-based rubber and carbon black, in which 1-50 mass% of the total carbon black is acetylene black, the nitrogen adsorption specific surface area (N2SA) of the acetylene black is 60 m2 / g or more, and the tread gauge Ga is 21.5 mm or more.The heavy-duty tire solves the problem.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heavy-duty tire, and more particularly to a heavy-duty tire that is excellent in productivity while maintaining physical properties such as heat buildup, tensile strength, and abrasion resistance. [Background technology]

[0002] When manufacturing heavy-duty tires that are used under heavy load conditions or tires for construction vehicles such as dump trucks that are primarily used off-road, long vulcanization times of 1 to 10 hours are typically required due to the large tire sizes. However, prolonged vulcanization can lead to problems such as deterioration of heat buildup and other physical properties. Attempts have been made to solve this problem, such as vulcanization at low temperatures, but this further lengthens the vulcanization time, resulting in another problem of reduced productivity.

[0003] While the techniques of compounding conductive carbon black into rubber compositions for tires are disclosed in, for example, Patent Documents 1 to 3 listed below, they do not disclose any technical idea of ​​shortening the vulcanization time for large, heavy-duty tires to improve productivity while maintaining physical properties such as heat buildup, tensile strength, and abrasion resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-188672 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-2206 [Patent Document 3] Patent No. 5635291 Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heavy-duty tire that is excellent in productivity while maintaining physical properties such as heat buildup, tensile strength, and abrasion resistance. [Means for solving the problem]

[0006] The present invention relates to a heavy-duty tire having a tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, a pair of bead portions disposed on the tire radially inward side of the pair of sidewall portions, and a carcass layer mounted between the pair of bead portions, wherein the tread portion is provided with a cap tread that forms the ground contact surface of the tread portion, the composition that forms the cap tread contains a rubber component including a diene rubber and carbon black, acetylene black accounts for 1 to 50 mass % of the total carbon black, and the nitrogen adsorption specific surface area (N2SA) of the acetylene black is 60 m 2 / g or more, and the tread gauge of the heavy duty tire is 21.5 mm or more. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a heavy-duty tire that is excellent in productivity while maintaining physical properties such as heat buildup, tensile strength, and abrasion resistance.

[0008] In the present invention, by replacing a portion of the carbon black in the composition constituting the cap tread with acetylene black, which has a high thermal diffusivity, the thermal diffusivity of large, heavy-duty tires themselves is increased, shortening the vulcanization time and improving tire productivity. At the same time, by specifying the amount of acetylene black replaced and the nitrogen adsorption specific surface area (N2SA), it is possible to maintain physical properties such as heat buildup, tensile strength, and abrasion resistance at levels sufficient for practical use. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a meridian cross-sectional view of a heavy-duty tire. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will now be described in more detail, with a first description being given of the composition constituting the cap tread.

[0011] (rubber component) The rubber component used in the present invention contains a diene rubber. The diene rubber used in the present invention can be any diene rubber that can be compounded into a rubber composition for heavy-duty tires, such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and ethylene-propylene-diene terpolymer (EPDM). These may be used alone or in combination of two or more. There are no particular limitations on the molecular weight or microstructure, and the rubber may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl, or the like, or may be epoxidized. The molecular weight of the diene rubber is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000. In this specification, the molecular weight is a weight average molecular weight (Mw) calculated as a standard polystyrene equivalent obtained by gel permeation chromatography (GPC) measurement.

[0012] (carbon black) The carbon black used in the present invention contains acetylene black. Acetylene black is a type of carbon black obtained by pyrolysis of acetylene gas. In the present invention, it is necessary that the acetylene black accounts for 1 to 50% by mass of the total carbon black. If the acetylene black accounts for less than 1% by mass of the total carbon black, the blending amount is too small to achieve the effects of the present invention, and conversely, if it exceeds 50% by mass, physical properties such as tensile strength will decrease. In the present invention, the acetylene black preferably accounts for 1 to 50% by mass, and more preferably 1 to 25% by mass, of the total carbon black. In addition, the nitrogen adsorption specific surface area (N2SA) of acetylene black is 60m 2 / g or more. The nitrogen adsorption specific surface area (N2SA) of acetylene black is 60m 2 If it is less than 1 / g, the abrasion resistance and cut resistance will decrease. From the viewpoint of improving the effect of the present invention, the nitrogen adsorption specific surface area (N2SA) of acetylene black is 80m 2 / g or more, and 2 The upper limit of the nitrogen adsorption specific surface area (N2SA) of acetylene black is not particularly limited, but it is preferably 140 m 2 / g or less. In the present invention, carbon black other than acetylene black can also be used. From the viewpoint of improving the effects of the present invention, the carbon black other than acetylene black should have a nitrogen adsorption specific surface area (N2SA) of 50 to 135 m 2 / g, and 80 to 135m 2 More preferably, it is / g. The nitrogen adsorption specific surface area (N2SA) is a value measured in accordance with JIS K 6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0013] (mixing ratio) In order to improve the effects of the present invention, the composition constituting the cap tread of the present invention preferably contains 10 to 80 parts by mass, and more preferably 40 to 80 parts by mass, of carbon black per 100 parts by mass of the rubber component. Note that the term "carbon black" as used herein includes acetylene black and carbon black other than acetylene black.

[0014] (Other ingredients) In addition to the above-mentioned components, the composition constituting the cap tread of the present invention may contain various additives that are generally compounded in rubber compositions for cap treads, such as vulcanizing or crosslinking agents; vulcanizing or crosslinking accelerators; various fillers such as silica, clay, talc, calcium carbonate, and aluminum hydroxide; antioxidants; curing agents; silane coupling agents, and plasticizers, and these additives can be kneaded by a general method to form a composition, which can then be used for vulcanization or crosslinking. The amounts of these additives that can be compounded may be conventional amounts, as long as they do not contradict the object of the present invention. For example, the total amount of carbon black and filler is preferably 40 to 80 parts by mass per 100 parts by mass of the rubber component, and the blending amount of plasticizer is preferably 0 to 5 parts by mass per 100 parts by mass of the rubber component.

[0015] The heavy-duty tire of the present invention is excellent in productivity while maintaining physical properties such as heat buildup, tensile strength, and abrasion resistance, and is therefore suitable for use as a large-sized heavy-duty tire or a tire for construction vehicles primarily used for off-road driving, such as dump trucks. The heavy-duty tire of the present invention is also preferably a pneumatic tire, which can be filled with air, an inert gas such as nitrogen, or other gases. As for the size of the heavy duty tire of the present invention, if the tread gauge is 21.5 mm or more, the effect of shortening the vulcanization time and improving productivity is particularly great.

[0016] Next, the tread gauge will be described. The tread gauge corresponds to the length of the longest perpendicular line formed when a perpendicular line is drawn from any measurement point on the profile of the cap tread to the belt layer in a cross section taken in the tire meridian direction. FIG. 1 is a meridian cross-sectional view of a heavy-duty tire for explaining a tread gauge. 1, the heavy-duty tire comprises a tread portion 3 extending in the circumferential direction of the tire and forming an annular shape, a pair of sidewall portions 2 arranged on both sides of the tread portion 3, a pair of bead portions 1 arranged radially inward of the pair of sidewall portions 2, and a carcass layer 4 mounted between the pair of bead portions 1, 1. Ends of the carcass layer 4 are folded back and wrapped around bead cores 5 and bead fillers 6 from the inside to the outside of the tire. The tread portion 3 includes a cap tread rubber 30 that forms the contact surface of the tread portion, and an undertread rubber 31 that is provided on the inner side of the cap tread rubber 30 in the tire radial direction. The bead filler 6 is composed of two members, an upper bead filler 62 located on the outer side in the tire radial direction, and a lower bead filler 64 located on the inner side in the tire radial direction relative to the upper bead filler 62. Additionally, a belt layer 7 is disposed around the tire on the outside of the carcass layer 4. Belt cushions 8 are disposed on both ends of the belt layer 7. An inner liner 9 is provided on the inner surface of the heavy-duty tire to prevent air filled inside the tire from leaking to the outside, and a tie rubber 10 for bonding the inner liner 9 is laminated between the carcass layer 4 and the inner liner 9. The tire radial direction is the direction perpendicular to the tire rotation axis, the tire radial inner side refers to the direction approaching the tire rotation axis, and the tire radial outer side refers to the direction away from the tire rotation axis. The tread gauge Ga corresponds to the length of the longest perpendicular line drawn from any measurement point on the cap tread 30 toward the belt layer 7 in a cross-sectional view taken along the tire meridian direction. In the embodiment shown in FIG. 1, since the undertread 31 is provided, the tread gauge Ga is the length of the longest perpendicular line drawn from the tread surface of the cap tread 30 toward the undertread 31 in a cross-sectional view taken along the tire meridian direction. If the undertread 31 is not provided, the tread gauge Ga is the length of the longest perpendicular line drawn from the contact surface of the cap tread 30 toward the belt layer 7 in a cross-sectional view taken along the tire meridian direction.

[0017] In the present invention, the tread gauge Ga is 21.5 mm or more, and from the viewpoint of shortening the vulcanization time and enhancing the effect of improving productivity, the tread gauge Ga is preferably 60 mm or more, and more preferably 80 mm or more. The tire size of the heavy duty tire of the present invention is preferably, for example, 33 inches or more, more preferably 49 inches or more, in terms of the inch size of the rim wheel to which it is attached. [Example]

[0018] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0019] Standard Example 1, Examples 1 to 3, and Comparative Examples 1 to 4 Sample preparation In the formulation (parts by mass) shown in Table 1, the components excluding the vulcanization system (vulcanization accelerator, sulfur) were mixed for 5 minutes in a Banbury mixer at 80°C. Next, the vulcanization system was added and mixed using a roll to obtain a rubber composition. Each obtained rubber composition (unvulcanized) was press-vulcanized in a mold at 145°C for 45 minutes to prepare vulcanized rubber test pieces, which were then evaluated as follows.

[0020] Thermal Conductivity: The thermal diffusivity of the vulcanized rubber test pieces prepared as described above was measured using a high-speed blow point tester manufactured by Toyo Seiki Seisakusho, Ltd. The results were expressed as an index, with the value of Control Example 1 being 100. A larger index indicates a higher thermal diffusivity and better thermal conductivity.

[0021] Heat durability: For the vulcanized rubber test pieces prepared as described above, the loss tangent tanδ(60°C) at a temperature of 60°C was measured using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho, Ltd.) under conditions of an initial strain of 10%, an amplitude of ±2%, and a frequency of 20 Hz, and heat buildup durability was evaluated. The results are expressed as an index, with the value for Reference Example 1 being 100. A larger index indicates lower heat buildup.

[0022] Tensile strength: The vulcanized rubber test pieces prepared as described above were subjected to a tensile test (TB) at room temperature in accordance with JIS K6251 (JIS No. 3 dumbbell). The results were expressed as an index, with the value of Standard Example 1 set at 100. The higher the index, the higher the tensile strength. A tensile strength index of 95 or higher can be considered to have sufficient tensile strength for practical use.

[0023] Abrasion resistance: The abrasion loss of the vulcanized rubber test pieces prepared as described above was measured using a Pico abrasion tester in accordance with ASTM-D2228. The results were expressed as an index, with the value of Standard Example 1 being 100. A higher index indicates higher abrasion resistance.

[0024] Productivity: Each rubber composition (unvulcanized) prepared as described above was vulcanized in a mold. The degree of vulcanization was judged to have reached its peak when air bubbles disappeared from the unvulcanized rubber (blow point), and the time from the start of vulcanization to the blow point was measured. The results were expressed as an index, with the value for Reference Example 1 being 100. A smaller index indicates a shorter vulcanization time and higher productivity. The tread gauge Ga was 80 mm, and the size of the rim wheel used was 33 inches.

[0025] The results are shown in Table 1.

[0026] [Table 1]

[0027] *1:NR(SIR20) *2: E-SBR (Nipol BR 1220 manufactured by Nippon Zeon Co., Ltd.) *3: Acetylene black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd., nitrogen adsorption specific surface area (N2SA) = 82m 2 / g) *4: Carbon black A (product name: Show Black S118, manufactured by Cabot Japan Co., Ltd., nitrogen adsorption specific surface area (N2SA) = 148 m 2 / g) *5: Carbon black B (manufactured by Cabot Japan, trade name Show Black N234, nitrogen adsorption specific surface area (N2SA) = 114 m 2 / g) *6: Carbon black C (product name: Show Black N339, manufactured by Cabot Japan Co., Ltd., nitrogen adsorption specific surface area (N2SA) = 88 m 2 / g) *7: Silica (Zeosil 1085GR manufactured by Solvay Japan, nitrogen adsorption specific surface area (N2SA) = 90m 2 / g, CTAB specific surface area=80m 2 / g) *8: Silane coupling agent (Si69, manufactured by Evonik Degussa, bis(3-triethoxysilylpropyl)tetrasulfide) *9: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu Co., Ltd.) *10: Processing aid (STRUKTOL A50P, manufactured by STRUKTOL) *11: Stearic acid (NOF Corporation Stearic Acid YR) *12: Anti-aging agent (Flexis SANTOFLEX 6PPD) *13: Zinc oxide (Zinc oxide type 3 manufactured by Seido Chemical Industry Co., Ltd.) *14: Vulcanization accelerator CZ (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *15: Vulcanization accelerator NS (Sanceler NS-G manufactured by Sanshin Chemical Industry Co., Ltd.) *16: Sulfur (Karuizawa Refinery Co., Ltd. oil refinery processing sulfur)

[0028] Standard Example 2, Examples 4-5 and Comparative Examples 5-8 The above "Standard Example 1, Examples 1 to 3, and Comparative Examples 1 to 4" were repeated except that the formulations were changed as shown in Table 2 (parts by mass). The results are shown in Table 2. Examples 4 to 5 and Comparative Examples 5 to 8 are compared with Standard Example 2.

[0029] [Table 2]

[0030] From the results in each table, it can be seen that in each example, the cap tread composition contains a rubber component containing a diene rubber and carbon black, the acetylene black accounts for 1 to 50 mass % of the total carbon black, and the nitrogen adsorption specific surface area (N2SA) of the acetylene black is 60 m 2 / g or more and the tread gauge of the heavy-duty tire is 21.5 mm or more, it can be seen that the productivity is excellent while maintaining physical properties such as heat buildup, tensile strength, and abrasion resistance. On the other hand, in Comparative Examples 1 and 5, the acetylene black accounted for 83 mass % of the total carbon black, and therefore the tensile strength and abrasion resistance were reduced. Comparative Examples 2 to 4 and 7 to 8 are systems in which acetylene black is not used, but multiple types of carbon black are blended, or silica is blended, so that heat buildup or tensile strength is reduced, and no improvement in productivity is observed.

[0031] The present disclosure encompasses the following inventions. Invention [1]: A heavy-duty tire having a tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, a pair of bead portions arranged on the tire radially inner side of the pair of sidewall portions, and a carcass layer mounted between the pair of bead portions, wherein the tread portion is provided with a cap tread that forms the tread surface of the tread portion, The composition constituting the cap tread contains a rubber component including a diene rubber and carbon black, acetylene black accounts for 1 to 50 mass% of the total mass of the carbon black; The nitrogen adsorption specific surface area (N2SA) of the acetylene black is 60m 2 / g or more, and The tread gauge of the heavy duty tire is 21.5 mm or more A heavy-duty tire characterized by: Invention [2]: A heavy-duty tire according to Invention 1, characterized in that the amount of carbon black blended is 10 to 80 parts by mass per 100 parts by mass of the rubber component. Invention [3]: The nitrogen adsorption specific surface area (N2SA) of the carbon black other than the acetylene black is 50 to 135 m 2 / g. [Explanation of symbols]

[0032] 1 Bead section 2 Sidewall 3 Tread section 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 8 Belt Cushion 9 Inner liner 10 Thai Rubber 30 Cap tread rubber 31 Undertread rubber 62 Upper bead filler 64 Lower bead filler Ga Tread Gauge

Claims

1. A heavy-duty tire having a tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, a pair of bead portions disposed on the tire radially inner side of the pair of sidewall portions, and a carcass layer mounted between the pair of bead portions, wherein the tread portion is provided with a cap tread that forms the tread surface of the tread portion, The composition constituting the cap tread contains a rubber component including a diene rubber and carbon black, acetylene black accounts for 1 to 50 mass% of the total mass of the carbon black; The nitrogen adsorption specific surface area (N ２ SA) is 60m ２ / g or more, and The tread gauge of the heavy duty tire is 21.5 mm or more. A heavy-duty tire characterized by:

2. 2. The heavy-duty tire according to claim 1, wherein the amount of the carbon black blended is 10 to 80 parts by mass per 100 parts by mass of the rubber component.

3. The nitrogen adsorption specific surface area (N ２ SA) is 50 to 135 m ２ 2. The heavy duty tire according to claim 1, wherein the tensile strength is 1 / g.

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