Rubber composition for tires and tires using the same

Abstract

To provide a tire for heavy load having excellent abrasion resistance and long tire life, low heat-generating properties, and improved abrasion resistance and chipping resistance.SOLUTION: There is provided a rubber composition for a tire which is obtained by blending 30 to 70 pts.mass of silica satisfying the following expressions (A) and (B), 0 to 20 pts.mass of carbon black having a nitrogen adsorption specific surface area (N2SA) of 50 to 300 m2 / g and 0.5 to 5.0 pts.mass of zinc oxide based on 100 pts.mass of a rubber including 60 pts.mass or more of an isoprene-based rubber. Expression (A): y≤0.38x+120, Expression (B): 210≤x≤ 250 (x represents the CTAB specific surface area of the silica (m2 / g) and y represents the DBP oil absorption of the silica (ml / 100 g).)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for tires and a tire using the same, and more specifically, to a rubber composition that is low in heat generation and can improve abrasion resistance and chipping resistance, and a tire using the same. [Background technology]

[0002] Heavy-duty tires used for trucks and buses require excellent wear resistance and a long tire life. On the other hand, tires are required to have low rolling resistance due to stricter international standards such as the UN / ECE's R-117 standard and stricter greenhouse gas (GHG) regulations by the US Environmental Protection Agency (EPA). Adding silica is effective in reducing rolling resistance, but this comes with the problem of reduced wear resistance. Conversely, adding small-particle silica can improve wear resistance, but this worsens heat generation. Thus, these two performance characteristics are mutually exclusive, and achieving both simultaneously is difficult. Another performance requirement for heavy-duty tires is chipping resistance. One way to improve chipping resistance is to soften the tread rubber, but this comes at the expense of wear resistance and heat generation. Based on the above, it is recognized in this industry that achieving low heat generation, as well as improved wear resistance and chipping resistance, is an extremely difficult task.

[0003] For example, Patent Document 1 below describes a rubber component and an average primary particle diameter X (nm) and nitrogen adsorption specific surface area Y (m²) that satisfy the following three equations. 2 A rubber composition for tires containing silica having ( / g) is disclosed. Y≧370-9.0X 10.0 ≤ X ≤ 28.0 30 ≤ Y ≤ 500 However, conventional technologies do not disclose any technical concept for achieving wear resistance, low heat generation, and chipping resistance simultaneously by using silica that has a specific relationship between the CTAB specific surface area and the DBP oil absorption amount. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 5840971 [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, the object of the present invention is to provide a rubber composition that is low in heat generation and can improve abrasion resistance and chipping resistance, and a tire using the same. [Means for solving the problem]

[0006] As a result of diligent research, the inventors of this invention discovered that the above problems can be solved by blending specific amounts of silica and zinc oxide, which have a specific relationship between the CTAB specific surface area and the DBP oil absorption amount, into rubber containing isoprene-based rubber, and thus completed the present invention.

[0007] In other words, the present invention provides 100 parts by mass of rubber containing 60 parts by mass or more of isoprene-based rubber, 30 to 70 parts by mass of silica satisfying the following formulas (A) and (B), and a nitrogen adsorption specific surface area (N2SA) of 50 to 300 m². 2 The present invention provides a tire rubber composition characterized by comprising 0 to 20 parts by mass of carbon black at a concentration of / g (where the total amount of silica and carbon black is 40 to 70 parts by mass) and 0.5 to 5.0 parts by mass of zinc oxide. Equation (A): y ≤ 0.38 x + 120 Formula (B): 210 ≦ x ≦ 250 (In formulas (A) and (B) above, x is the CTAB specific surface area of ​​the silica (m²) 2 The value shown is ( / g), and y represents the DBP oil absorption capacity of the silica (ml / 100g). [Effects of the Invention]

[0008] The rubber composition for tires of the present invention contains 30 to 70 parts by mass of silica satisfying the above formulas (A) and (B), 0 to 20 parts by mass of carbon black having a nitrogen adsorption specific surface area (N2SA) of 50 to 300 m 2 / g (where the total amount of the silica and the carbon black is 40 to 70 parts by mass), and 0.5 to 5.0 parts by mass of zinc oxide, based on 100 parts by mass of rubber containing 60 parts by mass or more of isoprene rubber. Therefore, it is possible to provide a rubber composition having low heat generation and capable of improving abrasion resistance and chipping resistance, and a tire using the same.

Embodiments for Carrying out the Invention

[0009] Hereinafter, the present invention will be described in more detail.

[0010] The rubber used in the present invention needs to contain 60 parts by mass or more of isoprene rubber when the total amount is 100 parts by mass. If the amount of the isoprene rubber is less than 60 parts by mass, the effects of the present invention cannot be achieved. Examples of the isoprene rubber include natural rubber (NR), synthetic isoprene rubber (IR), or a combination thereof. In addition to NR and IR, other diene rubbers can also be used. For example, butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), etc. can be mentioned. These may be used alone or in combination of two or more. Further, their molecular weight and microstructure are not particularly limited, and they may be end-modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, etc., or may be epoxidized.

[0011] The silica used in the present invention needs to satisfy the following formulas (A) and (B).

[0012] Formula (A): y ≦ 0.38x + 120 Formula (B): 210 ≦ x ≦ 250 (In the above formulas (A) and (B), x represents the CTAB specific surface area (m 2 / g) of the silica, and y represents the DBP oil absorption amount (ml / 100g) of the silica.)

[0013] As described above, in the art, it has been recognized that it is extremely difficult to achieve low heat generation and improve abrasion resistance and chipping resistance. However, according to the studies of the present inventors, it has been found that by using silica having specific colloidal properties, the problem can be solved.)

[0014] The silica having specific colloidal properties capable of solving the above problems has been found through numerous trials and errors by the present inventors.) That is, in order to achieve low heat generation and improve abrasion resistance and chipping resistance, first, it has been found that setting the ranges of the CTAB specific surface area (m 2 / g) and DBP oil absorption amount (ml / 100g) of the silica is effective. Furthermore, regarding what ranges of CTAB specific surface area (m 2 / g) and DBP oil absorption amount (ml / 100g) should be given to the silica, about 100 silicas were examined, and the above formulas (A) and (B) were derived by linear regression using the least squares method.)

[0015] In the present invention, it is more preferable that the above formulas (A) and (B) are the following formulas (A-2) and (B-2).) Formula (A-2): y ≤ 0.38x + 110 Formula (B-2): 210 ≤ x ≤ 250

[0016] Also in the present invention, it is more preferable to satisfy the above formulas (A) and (B) and the following formula (C).) Formula (C): y ≥ 0.38x + 70

[0017] The silica used in the present invention can be produced by a method having the following steps i) to vi), for example, as described in JP-A-2020-26363.)

[0018] i) The process of adjusting the alkali silicate aqueous solution to, for example, pH 9.5-12 and charging it into the reaction vessel. ii) A neutralization reaction step including the step of simultaneously adding an alkaline silicate aqueous solution and a mineral acid dropwise, and the step of adding only the mineral acid dropwise without adding the alkaline silicate aqueous solution. iii) A neutralization reaction step in which an aqueous alkali silicate solution and a mineral acid are added dropwise simultaneously, provided that the flow rates of each are independently within the range of 20-80% of the flow rate in the simultaneous addition step ii). iv) A step in which only mineral acid is added dropwise without adding an alkaline silicate aqueous solution, bringing the pH to < 7 and stopping the neutralization reaction. However, steps i) to iv) are carried out while stirring and / or circulating the reaction slurry and maintaining a temperature in the range of 70 to 90°C, and steps ii) to iii) are carried out while maintaining a pH in the range of 9.5 to 12. v) A step of filtering the obtained hydrated silica slurry and washing it with water in an amount equal to or greater than the amount of the obtained hydrated silica cake, vi) A drying process, and a process to adjust the particle size as necessary.

[0019] For the alkaline silicate solution, commercially available sodium silicate can be used, and sulfuric acid is an example of a mineral acid.

[0020] Steps ii) and iii) should ideally be completed in a total of approximately 80 to 140 minutes.

[0021] The filtration and washing of the hydrated silica in step v) can be carried out using, for example, a filter press.

[0022] The process in step vi) can be carried out by known means; for example, the drying process can be carried out using a spray dryer, and the particle size adjustment process can be carried out using a compression roll, etc.

[0023] In this specification, the CTAB specific surface area is determined in accordance with JIS K6217-3, and the DBP oil absorption amount is determined in accordance with JIS K6217-4 Oil Absorption Method A.

[0024] (Carbon black) The carbon black used in the present invention preferably has a nitrogen adsorption specific surface area (N2SA) of 50 to 300 m 2 / g, more preferably 80 to 250 m 2 / g. The nitrogen adsorption specific surface area (N2SA) is a value determined in accordance with JIS K6217-2.

[0025] (Mixing ratio of rubber composition for tires) The rubber composition of the present invention comprises, per 100 parts by mass of rubber, 30 to 70 parts by mass of silica satisfying the formulas (A) and (B), 0 to 20 parts by mass of carbon black having a nitrogen adsorption specific surface area (N2SA) of 50 to 300 m 2 / g (provided that the total amount of the silica and the carbon black is 40 to 70 parts by mass), and 0.5 to 5.0 parts by mass of zinc oxide. When the amount of silica is less than 30 parts by mass, the abrasion resistance deteriorates, and when it exceeds 70 parts by mass, the heat generation property deteriorates. When the amount of the carbon black exceeds 20 parts by mass, the heat generation property deteriorates. When the N2SA of the carbon black is less than 50 m 2 / g, the abrasion resistance deteriorates, and when it exceeds 300 m 2 / g, the heat generation property deteriorates. Also, when the total amount of the silica and the carbon black is less than 40 parts by mass, the abrasion resistance deteriorates, and when it exceeds 70 parts by mass, the heat generation property deteriorates. Further, when the total amount of the zinc oxide is outside the range of 0.5 to 5.0 parts by mass, the heat generation property, abrasion resistance, and chipping resistance cannot be improved.

[0026] In the rubber composition of the present invention, the amount of silica satisfying the formulas (A) and (B) is more preferably 35 to 65 parts by mass per 100 parts by mass of rubber. The nitrogen adsorption specific surface area (N2SA) is 50 to 300 m 2The amount of carbon black added per gram is more preferably 1 to 15 parts by mass per 100 parts by mass of rubber. The nitrogen adsorption specific surface area (N2SA) of the carbon black is 80-250 m². 2 It is even more preferable that it be / g.

[0027] (Other ingredients) In addition to the components mentioned above, the rubber composition of the present invention may contain various additives commonly used in rubber compositions, such as vulcanizing or crosslinking agents; vulcanizing or crosslinking accelerators; various fillers such as clay, talc, and calcium carbonate; antioxidants; and plasticizers. These additives can be mixed in a conventional manner to form a composition which can then be used for vulcanization or crosslinking. The amounts of these additives can also be conventional amounts, as long as they do not contradict the purpose of the present invention.

[0028] The rubber composition of the present invention preferably has a hardness of 63 or higher at 20°C and a loss compliance of 35.0 or lower at 60°C. Satisfying these conditions further improves abrasion resistance, low heat generation, and chipping resistance. The hardness is more preferably between 65 and 75, and the loss compliance is more preferably between 5.0 and 30.0. The hardness was measured in accordance with JIS K6253, and the loss compliance was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho under the conditions of a temperature of 60°C, a frequency of 20Hz, an amplitude of 2%, and an initial strain of 10% (N / PA).

[0029] The rubber composition of the present invention is low-heat generating and can improve abrasion resistance and chipping resistance, making it suitable for use in the tread rubber of tires, particularly heavy-duty tires. Furthermore, the tire of the present invention is preferably a pneumatic tire and can be filled with air, an inert gas such as nitrogen, and other gases. [Examples]

[0030] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0031] Reference example, Examples 1-2, and Comparative Examples 1-7 Sample preparation In the formulations (parts by mass) shown in Table 1, the components excluding the vulcanization accelerator and sulfur were kneaded in a 1.7-liter sealed Banbury mixer for 5 minutes, and the rubber was released from the mixer and cooled to room temperature. Next, the rubber was put back into the mixer, the vulcanization accelerator and sulfur were added, and kneaded further to obtain a rubber composition. The obtained rubber composition was then press-vulcanized in a predetermined mold at 148°C for 30 minutes to obtain vulcanized rubber test pieces, and the physical properties of the unvulcanized rubber composition and the vulcanized rubber test pieces were measured using the test method described below.

[0032] Generating properties: Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., tanδ(60°C) was measured under the conditions of initial strain 10%, amplitude ±2%, frequency 20Hz, and temperature 60°C. The results are shown exponentially, with the reference example value set to 100. A higher value indicates lower generating properties, and a value of 95 or higher can be judged as sufficiently low generating properties.

[0033] Abrasion Resistance: The Lamborn abrasion index was measured using a Lamborn abrasion tester (manufactured by A&D Co., Ltd.) under the conditions of a load of 30N, a slip ratio of 10%, a time of 15 minutes, and room temperature. The results are expressed as an index with the value of the reference example set to 100. A higher index indicates better abrasion resistance, and a value of 105 or higher indicates excellent abrasion resistance.

[0034] Chipping resistance: The elongation at break was measured at 100°C in accordance with JIS K6251. The results are expressed as an index, with the value of the reference example set to 100. A higher index indicates a higher elongation at high temperatures and superior chipping resistance; a value of 105 or higher indicates excellent chipping resistance.

[0035] Hardness and loss compliance: Measured using the measurement method described above.

[0036] The results are shown in Table 1.

[0037] [Table 1]

[0038] *1:NR(STR20) *2: BR (NIPOL BR1220 manufactured by Nippon Zeon Co., Ltd.) *3: Carbon black (product name Showblack N220, manufactured by Cabot Japan, nitrogen adsorption specific surface area (N2SA) = 110m²) 2 / g) *4: Silica A (Solvay ZEOSIL 1165MP, CTAB specific surface area = 160m²) 2 / g, DBP oil absorption = 195ml / 100g) *5: Silica B (ZEOSIL Premium 200MP manufactured by Solvay, CTAB specific surface area = 203 m²) 2 / g, DBP oil absorption = 209ml / 100g) *6: Silica C (Solvay VHSA, CTAB specific surface area = 270 m²) 2 / g, DBP oil absorption = 230ml / 100g) *7: Silica D (Solvay ZEOSIL HRS 200MP, CTAB specific surface area = 199 m²) 2 / g, DBP oil absorption = 182ml / 100g) *8: Silica prepared based on the processes of Silica E (i) to vi) above. CTAB specific surface area = 241 m² 2 / g, DBP oil absorption = 203ml / 100g) *9: Silica F prepared based on the processes described in (i) to (vi) above. CTAB specific surface area = 223 m² 2 / g, DBP oil absorption = 184ml / 100g) *10: Silane coupling agent (Si69 manufactured by Evonik DeGussa, bis(3-triethoxysilylpropyl)tetrasulfide) *11: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu K.K.) *12: Stearic acid (YR bead stearic acid manufactured by NOF Corporation) *13: Anti-aging agent 6C (Santoflex 6PPD manufactured by Flexis) *14: Zinc oxide (3 types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd.) *15: Vulcanization accelerator NS (Noxellar NS-F, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *16: Sulfur (Finely powdered sulfur containing Kinka oil, manufactured by Tsurumi Chemical Industries Co., Ltd.)

[0039] From the results in Table 1, the rubber compositions of Examples 1 and 2 contain 60 parts by mass or more of isoprene-based rubber per 100 parts by mass of rubber, 30 to 70 parts by mass of silica satisfying formulas (A) and (B), and a nitrogen adsorption specific surface area (N2SA) of 50 to 300 m². 2 The material is composed of 0 to 20 parts by mass of carbon black (where the total amount of silica and carbon black is 40 to 70 parts by mass) and 0.5 to 5.0 parts by mass of zinc oxide. Compared to the standard example, it exhibits lower heat generation and improved wear resistance and chipping resistance. In contrast, Comparative Examples 1 to 3 cannot satisfy the requirements for heat generation, wear resistance, and chipping resistance because the silica used does not satisfy the requirements for formulas (A) and (B). Comparative Example 4 showed a deterioration in exothermic properties because the amount of silica included exceeded the upper limit specified in the present invention. In Comparative Example 5, the total amount of silica and carbon black exceeded the upper limit specified in the present invention, resulting in poor heat generation. Comparative Example 6 failed to achieve sufficient wear resistance and chipping resistance because the amount of zinc oxide used exceeded the upper limit specified in the present invention. Comparative Example 7 showed poor chipping resistance because the amount of isoprene-based rubber blended was below the lower limit specified in the present invention.

[0040] This disclosure encompasses the following inventions: Invention [1]: 100 parts by mass of rubber containing 60 parts by mass or more of isoprene rubber, 30 to 70 parts by mass of silica satisfying the following formulas (A) and (B), and a nitrogen adsorption specific surface area (N2SA) of 50 to 300 m² 2A tire rubber composition characterized by comprising 0 to 20 parts by mass of carbon black at a concentration of / g (where the total amount of silica and carbon black is 40 to 70 parts by mass) and 0.5 to 5.0 parts by mass of zinc oxide. Equation (A): y ≤ 0.38 x + 120 Formula (B): 210 ≦ x ≦ 250 (In formulas (A) and (B) above, x is the CTAB specific surface area of ​​the silica (m²) 2 The value shown is ( / g), and y represents the DBP oil absorption capacity of the silica (ml / 100g). Invention [2]: The tire rubber composition according to Invention 1, characterized in that the silica satisfies the following formulas (A-2) and (B-2). Equation (A-2): y ≤ 0.38 x + 110 Formula (B-2): 210 ≦ x ≦ 250 Invention [3]: The rubber composition according to Invention 1 or 2, characterized in that the hardness at 20°C is 63 or higher and the loss compliance at 60°C is 35.0 or lower. Invention [4]: ​​A tire having a tread rubber made of the tire rubber composition described in any of Inventions 1 to 3. Invention [5]: A heavy-duty tire using the tire rubber composition described in any of Inventions 1 to 3 as the tread rubber.

Claims

1. For every 100 parts by mass of rubber containing 60 parts by mass or more of isoprene-based rubber, 30 to 70 parts by mass of silica satisfying the following formulas (A), (B), and (C) are added, and the nitrogen adsorption specific surface area (N) is also included. ２ SA) 50-300m ２ A tire rubber composition characterized by comprising 0 to 20 parts by mass of carbon black at a concentration of 1 / g (where the total amount of silica and carbon black is 40 to 70 parts by mass) and 0.5 to 5.0 parts by mass of zinc oxide. Formula (A): y ≦ 0.38 x + 120 Formula (B): 210 ≦ x ≦ 250 Formula (C): y ≧ 0.38 x + 70 (In formulas (A), (B), and (C) above, x is the CTAB specific surface area (m²) of the silica. ２ The value shown is ( / g), and y represents the DBP oil absorption amount of the silica (ml / 100g).

2. The tire rubber composition according to claim 1, characterized in that the silica satisfies the following formulas (A-2) and (B-2). Formula (A-2): y ≦ 0.38 x + 110 Formula (B-2): 210 ≦ x ≦ 250

3. The tire rubber composition according to claim 1, characterized in that the hardness at 20°C is 63 or higher and the loss compliance at 60°C is 35.0 or lower.

4. A tire comprising the tire rubber composition described in claim 1 as the tread rubber.

5. A heavy-duty tire comprising the tire rubber composition described in claim 1 as the tread rubber.

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