Rubber composition for a tire, vulcanized product and use of the vulcanized product in a protective tread of an pneumatic tire

Abstract

Rubber composition for a tire, including: 70 to 180 parts by mass of soot with a specific nitrogen adsorption surface area (N2SA) of 100 to 500 m² 2 / g; and 5 to 50 parts by mass of a terpene phenolic resin with an acid number of 30 to 150 mg KOH / g and a hydroxyl number of 5 to 120 mg KOH / g, per 100 parts by mass of a diene rubber comprising a styrene-butadiene copolymer rubber.

Description

Technical field

[0001] The present invention relates to a rubber composition for a tire, a vulcanized product and a use of the vulcanized product in a protective tread of a pneumatic tire, and in particular relates to a rubber composition for a tire which can improve dry grip performance, increase fracture toughness, exhibit excellent abrasion resistance and suppress the temperature dependence of hardness. State of the art

[0002] Generally, racing tires are required to perform various functions. In particular, they must exhibit excellent steering stability (dry grip) on a dry road surface at high speeds and also suppress changes in their performance (wear and heat-induced loss of grip) during prolonged high-speed cornering.

[0003] To improve dry grip performance, for example, a filler with a high specific surface area or a resin with a high softening point is added in large quantities.

[0004] However, if a filler with a high specific surface area is added in a large quantity, the tensile strength decreases, leading to a deterioration in abrasion resistance. Conversely, if a resin with a high softening point is added in a large quantity, temperature dependence of the hardness occurs, and the heat-related loss of grip performance worsens, resulting in a reduction in race time.

[0005] As an attempt to improve dry grip performance, patent document 1, for example, describes a rubber composition in which silica with a high specific surface area, a resin component with a high Tg, and a resin component with a low Tg are added to a diene rubber.

[0006] However, it is difficult for technology to improve both the temperature dependence of the hardness and the abrasion resistance.

[0007] On the other hand, a tire for driving on a dry road surface and a tire for driving on a wet road surface are prepared as racing tires, and the optimal tire for each of these is selected according to the weather and road surface conditions at the time of driving. Here, the racing tire for driving on a wet road surface contains a large amount of a polymer with a high glass transition temperature (high Tg polymer), a resin with a high softening point (high softening point resin), and / or a filler with a high specific surface area to increase wet grip performance.

[0008] However, adding a large quantity of a polymer with a high Tg or a resin with a high softening point causes problems of excessively increasing the Tg of the compound and reducing the heat-up performance (wet grip performance at low temperatures).

[0009] On the other hand, adding a large quantity of a filler with a high specific surface area poses problems of decreasing fracture strength and thus causes a deterioration in abrasion resistance.

[0010] As an attempt to improve wet grip performance, patent document 1, for example, describes a rubber composition in which silica with a high specific surface area, a resin component with a high Tg, and a resin component with a low Tg are added to a diene rubber.

[0011] However, it is technically difficult to improve both wet grip performance and abrasion resistance. Patent document 2 describes a pneumatic tire with improved wet grip, dry grip, and wear resistance in a balanced manner. Patent document 3 describes a synthetic rubber-like compound with high tackiness. List of oppositions patent literature Patent document 1: JP 2007- 186 567 A Patent document 2: JP 2016- 56 236 A Patent document 3: DE 16 94 829 A Brief description of the invention: Technical problem

[0012] Therefore, one problem of the present invention is to provide a rubber composition for a tire that can improve dry grip performance, increase fracture toughness, exhibit excellent abrasion resistance and suppress the temperature dependence of hardness, and a pneumatic tire that uses this. Solution to the problem

[0013] As a result of careful research, the inventors have found that the problem described above can be solved by adding a specific amount of carbon black with a specific nitrogen adsorption surface (N2SA) and a specific amount of a terpene phenolic resin with a specific acidity range and a specific hydroxyl number range to a diene rubber containing a styrene-butadiene copolymer rubber, thus completing the present invention.

[0014] The configuration of the present invention, which can solve the problem, is illustrated by the following features. Furthermore, the configuration of an embodiment that is not within the scope of protection is illustrated in the following description.

[0015] The invention relates to a rubber composition for a tire, comprising: 70 to 180 parts by mass of soot with a specific nitrogen adsorption surface area (N2SA) of 100 to 500 m² 2 / g; and 5 to 50 parts by mass of a terpene phenolic resin with an acid number of 30 to 150 mg KOH / g and a hydroxyl number of 5 to 120 mg KOH / g, per 100 parts by mass of a diene rubber containing a styrene-butadiene copolymer rubber.

[0016] In one embodiment, the styrene-butadiene copolymer rubber has a styrene content of 30 percent by mass or more.

[0017] In one embodiment, the rubber composition further comprises a liquid aromatic vinyl-conjugated diene rubber with a glass transition temperature (Tg) of -40 °C or higher, in addition to the styrene-butadiene copolymer rubber. Advantageous effects of the invention

[0018] The rubber composition for a tire according to the invention contains: 70 to 180 parts by mass of soot with a specific nitrogen adsorption surface area (N2SA) of 100 to 500 m² 2 / g; and 5 to 50 parts by mass of a terpene phenolic resin with an acid number of 30 to 150 mg KOH / g and a hydroxyl number of 5 to 120 mg KOH / g, per 100 parts by mass of a diene rubber containing a styrene-butadiene copolymer rubber.

[0019] Thus, it is possible to provide a rubber compound for a tire that can improve dry grip performance, increase fracture resistance, exhibit excellent abrasion resistance and suppress the temperature dependence of hardness, and a pneumatic tire that uses this.

[0020] Furthermore, the rubber composition for a tire according to the alternative embodiment, which is not covered by the scope of protection, contains: from 75 to 200 parts by mass silica with a specific CTAB surface area of ​​100 to 400 m² 2 / g; and 5 to 50 parts by mass of a terpene phenolic resin with an acid number of 30 mg KOH / g or more and a hydroxyl number of 5 mg KOH / g or more, per 100 parts by mass of a diene rubber containing a styrene-butadiene copolymer rubber with a glass transition temperature (Tg) of -20 °C or higher.

[0021] Thus, it is possible to provide a rubber compound for a tire that improves wet grip performance, maintains or increases warm-up performance (wet grip performance at low temperatures) and fracture toughness, and has excellent abrasion resistance, and a pneumatic tire that uses this. Description of embodiments

[0022] The present invention is described in more detail below. Dien rubber

[0023] The diene rubber used in the invention contains a styrene-butadiene copolymer rubber (SBR) as a key component. If the total amount of the diene rubber used in the first invention is taken to be 100 parts by mass, the amount of SBR is preferably 60 to 100 parts by mass and more preferably 80 to 100 parts by mass. In addition to the SBR, any diene rubber that can be blended into ordinary rubber compositions can be used in the first invention, and examples include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile butadiene copolymer rubber (NBR), and ethylene propylene diene terpolymer (EPDM). These can each be used individually, or two or more types can be used in combination. Furthermore, their molecular weight and microstructure are not particularly restricted.The diene rubber can be terminally modified or epoxidized with an amine, amide, silyl, alkoxysilyl, carboxyl or hydroxyl group.

[0024] The SBR used in the invention preferably has a styrene content of 30% by mass or more. By achieving such a styrene content, the glass transition temperature (Tg) of the SBR increases, and the dry-handling performance can be improved. Furthermore, the styrene content is preferably 35 to 50% by mass.

[0025] The diene monomer used in the alternative embodiment, which is not covered by the scope of protection, contains a styrene-butadiene copolymer rubber (SBR) with a glass transition temperature (Tg) of -20 °C or higher as a substantial component. If the total amount of diene monomer used in the second invention is assumed to be 100 parts by mass, the proportion of SBR with a Tg of -20 °C or higher can be determined by appropriately considering various conditions, such as air temperature and weather, for example, in a racing application. The amount of SBR added can be 100 parts by mass, is preferably 15 to 85 parts by mass, more preferably 25 to 75 parts by mass, and particularly preferably 30 to 70 parts by mass. In addition to the SBR with a Tg of -20 °C or higher, any diene monomer rubber that can be blended into ordinary rubber compositions can be used in the second invention.Examples include SBR with a Tg of less than -20 °C, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile butadiene copolymer rubber (NBR), and ethylene propylene diene terpolymer (EPDM). These can each be used individually, or two or more types can be used in combination. Furthermore, their molecular weight and microstructure are not particularly restricted. The diene rubber can be terminally modified or epoxidized with an amine, amide, silyl, alkoxysilyl, carboxyl, or hydroxyl group. In the SBR with a Tg of -20 °C or higher, the Tg is also preferably from -18 to -8 °C. Furthermore, the Tg referred to in the second invention is a glass transition temperature of the SBR in a state in which it is free of an oil-diluting component (oil).The glass transition temperature (Tg) is determined by thermographing using differential scanning calorimetry (DSC) at a temperature rise rate of 20 °C / minute, and the temperature at the midpoint of the transition region is defined as the glass transition temperature.

[0026] The SBR with a glass transition temperature (Tg) of -20 °C or higher, used in the alternative embodiment not covered by the protected scope, preferably has a styrene content of 30% by mass or more. Achieving such a styrene content increases the glass transition temperature (Tg) of the SBR and thus improves its dry-handling performance. Furthermore, a styrene content of 33 to 50% by mass is preferred. soot

[0027] The carbon black used in the invention must have a specific nitrogen adsorption surface area (N2SA) of 100 to 500 m². 2 exhibit / g. If the specific nitrogen adsorption surface (N2SA) of the soot is less than 100 m² 2As the weight per gram decreases, dry grip performance decreases and breaking strength decreases, leading to a deterioration in abrasion resistance.

[0028] If the specific nitrogen adsorption surface (N2SA) of the soot is 500 m² 2 If the value of / g is exceeded, the tensile strength decreases along with a deterioration of the carbon dispersion, leading to a deterioration of the abrasion resistance.

[0029] Another preferred specific nitrogen adsorption surface area (N2SA) of the carbon black used in the invention is 130 to 400 m². 2 / g. The nitrogen adsorption surface area (N2SA) of the soot is a value calculated according to JIS K6217-2. Silica

[0030] The silica used in the alternative embodiment, which is not covered by the scope of protection, must preferably have a specific CTAB surface area of ​​100 to 400 m². 2 exhibit / g.

[0031] If the specific CTAB surface area of ​​the silica is less than 100 m² 2 As the weight of the indentation decreases, the breaking strength decreases, leading to a deterioration in abrasion resistance.

[0032] If the specific surface area of ​​silica is 400 m² 2 If the viscosity exceeds / g, it becomes too high, leading to processing difficulties.

[0033] Another preferred specific CTAB surface area of ​​the silica used in the second invention is 140 to 350 m². 2 / G.

[0034] The specific CTAB surface area of ​​silica is determined according to JIS K6217-3. Terpene phenol resin

[0035] The terpene phenolic resin used in the alternative embodiment of the invention, which is not covered by the scope of protection, must have an acid number of 30 mg KOH / g or more and a hydroxyl number of 5 mg KOH / g or more. If the acid number is less than 30 mg KOH / g, neither the dry grip performance nor the temperature dependence of the hardness can be improved in the first invention, and neither the wet grip performance nor the abrasion resistance can be improved in the second invention. Furthermore, the phenol content decreases if the hydroxyl number is less than 5 mg KOH / g, and the effects of the invention and the alternative embodiment, which is not covered by the scope of protection, cannot be achieved. According to the invention, the acid number is between 30 and 150 mg KOH / g and the hydroxyl number is between 5 and 120 mg KOH / g.

[0036] Another preferred acid number is 40 to 150 mg KOH / g.

[0037] Furthermore, another preferred hydroxyl value is between 45 and 120 mg KOH / g.

[0038] A terpene phenolic resin is obtained by reacting a terpene compound and a phenol, and any terpene phenolic resin can be used as long as it is known and meets the acid number and hydroxyl number conditions in the invention and the alternative embodiment which is not within the scope of protection.

[0039] Furthermore, the terpene phenol resin used in the invention and the alternative embodiment, which is not covered by the scope of protection, has a softening point of preferably 85 to 180 °C.

[0040] It should be noted that the acid value and hydroxyl value can be measured according to JIS K 0070: 1992. Additionally, the softening point can be measured according to JIS K 6220-1: 2001.

[0041] The terpene phenol resin used in the invention and the alternative embodiment, which is not covered by the scope of protection, is commercially available. Examples of the terpene phenol resin include Tamanol 803L, available from Arakawa Chemical Industries, Ltd., (acid value = 50 mg KOH / g, hydroxyl value = 15 mg KOH / g) and Tamanol 901 (acid value = 50 mg KOH / g, hydroxyl value = 45 mg KOH / g). Liquid aromatic vinyl-conjugated diene rubber

[0042] In the invention, a liquid aromatic vinyl-conjugated diene monomer rubber with a glass transition temperature (Tg) of -40 °C or higher is preferably added. Adding such a liquid aromatic vinyl-conjugated diene monomer rubber increases the glass transition temperature (Tg) of the rubber composition and can improve its dry grip performance. Furthermore, the liquid aromatic vinyl-conjugated diene monomer rubber tends to conform to the diene monomer rubber and thus exhibits its effect.

[0043] From the perspective of improving dry grip performance, the liquid aromatic vinyl-conjugated diene rubber is preferably a liquid styrene-butadiene copolymer (liquid SBR). A liquid SBR with a weight-average molecular weight of 1000 to 100,000, and preferably 2000 to 80,000, can be used. The "weight-average molecular weight" in the present invention refers to a weight-average molecular weight determined by gel permeation chromatography (GPC) based on calibration with polystyrene. For the glass transition temperature (Tg), a thermograph is used to measure by differential scanning calorimetry (DSC) at a temperature rise rate of 20 °C / min, and the temperature at the midpoint of the transition region is defined as the glass transition temperature.

[0044] It should be noted that the liquid rubber used in the invention is liquid at 23 °C. It therefore differs from diene rubber, which is solid at this temperature.

[0045] The amount of liquid vinyl-conjugated diene rubber added is preferably 20 to 80 parts by mass and further preferably 30 to 70 parts by mass per 100 parts by mass of the diene rubber. Sulfur-containing silane adhesion improver

[0046] In the alternative embodiment, which is not covered by the scope of protection, a sulfur-containing silane adhesion promoter, represented by the formula (100) below, is preferably added.

[0047] The wet grip performance can be further improved by adding such a sulfur-containing silane adhesion promoter. (A) a (B) b (C) c (D) d (R1) e SiO (4-2a-b-c-d-e) / 2 (100) where A represents a divalent organic group with a sulfide group, B represents a monovalent hydrocarbon group with 5 to 10 carbon atoms, C represents a hydrolyzable group, D represents an organic group with a mercapto group, R1 represents a monovalent hydrocarbon group with 1 to 4 carbon atoms, and a to e satisfy the relationships: 0 ≤ a < 1, 0 < b < 1, 0 < c < 3, 0 ≤ d < 1, 0 ≤ e < 2, and 0 < 2a + b + c + d + e < 4, provided that a and d are not simultaneously 0.

[0048] The sulfur-containing silane adhesion promoter (polysiloxane), represented by formula (100), and the manufacturing process thereof are publicly known and disclosed, for example, in WO 2014 / 002750.

[0049] In the formula (100) above, A represents a divalent organic group with a sulfide group. Among these, a group represented by the formula (120) below is preferred. *-(CH2) n -Sx -(CH2) n -* (120)

[0050] In the above formula (120) n represents an integer from 1 to 10, of which an integer from 2 to 4 is preferred.

[0051] In the above formula (120) x represents an integer from 1 to 6, among which an integer from 2 to 4 is preferred.

[0052] In the formula above (120), * indicates a bonding position. Specific examples of the group represented by the formula above (120) include *-CH2-S2-CH2-*, *-C2H4-S2-C2H4-*, *-C3H6-S2-C3H6-*, *-C4H8-S2-C4H8-*, *-CH2-S4-CH2-*, *-C2H4-S4-C2H4-*, *-C3H6-S4-C3H6-*, *-C4H8-S4-C4H8-*.

[0053] In the above formula (100), B represents a monovalent hydrocarbon group with 5 to 20 carbon atoms, and specific examples include a hexyl group, an octyl group, and a decyl group. B is preferably a monovalent hydrocarbon group with 5 to 10 carbon atoms.

[0054] In the preceding formula (100), C represents a hydrolyzable group, and specific examples include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Among these, a group represented by the following formula (130) is preferred. *-OR 2 (130)

[0055] In the above formula (130) R represents 2This represents an alkyl group with 1 to 20 carbon atoms, an aryl group with 6 to 10 carbon atoms, an aralkyl group (arylalkyl group) with 6 to 10 carbon atoms, or an alkenyl group with 2 to 10 carbon atoms, of which an alkyl group with 1 to 5 carbon atoms is preferred. Specific examples of the alkyl group with 1 to 20 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, and an octadecyl group. Specific examples of the aryl group with 6 to 10 carbon atoms include a phenyl group and a tolyl group. Specific examples of the aralkyl group with 6 to 10 carbon atoms include a benzyl group and a phenylethyl group. Specific examples of alkenyl groups with 2 to 10 carbon atoms include a vinyl group, a propenyl group, and a pentenyl group.

[0056] In the above formula (130), * indicates a binding position.

[0057] In the preceding formula (100), D represents an organic group containing a mercapto group. Among these, a group represented by the following formula (140) is preferred. *-(CH2) m -SH (140)

[0058] In the above formula (140) m represents an integer from 1 to 10, with an integer from 1 to 5 being preferred.

[0059] In the formula (140) above, * indicates a bonding position. Specific examples of the group represented by the formula (140) above include *-CH2SH, *-C2H4SH, *-C3H6SH, *-C4H8SH, *-C5H 10 SH, *-C6H 12 SH, *-C7H 14 SH, *-C8H 16 SH, *-C9H 18 SH, and *-C 10 H 20 SH one.

[0060] In the above formula (100), R1 represents a monovalent hydrocarbon group with 1 to 4 carbon atoms.

[0061] In the above formula (100) a to e satisfy the following relationships: 0 ≤ a < 1, 0 < b < 1, 0 < c < 3, 0 ≤ d < 1, 0 ≤ e < 2, and 0 < 2a + b + c + d + e < 4, provided that a and d are not simultaneously 0.

[0062] In the above formula (100), a is preferably 0 < a ≤ 0.50 from the point of view of improving the effect of the alternative embodiment which is not within the scope of protection.

[0063] In the above formula (100), b is preferably 0 < b and more preferably 0.10 ≤ b ≤ 0.89 from the point of view of improving the effect of the alternative embodiment which is not within the scope of protection.

[0064] In the above formula (100), c is preferably 1.2 ≤ c ≤ 2.0 from the point of view of improving the effect of the alternative embodiment which is not within the scope of protection.

[0065] In the above formula (100), d is preferably 0.1 ≤ d ≤ 0.8 from the point of view of improving the effect of the alternative embodiment which is not within the scope of protection.

[0066] The weight-average molecular weight of the polysiloxane, from the perspective of improving the performance of the alternative embodiment which is not within the scope of protection, is preferably 500 to 2300, more preferably 600 to 1500. The molecular weight of the polysiloxane in the alternative embodiment which is not within the scope of protection is determined by gel permeation chromatography (GPC) using toluene as a solvent, based on a calibration with polysiloxane.

[0067] The mercapto weight equivalent of the polysiloxane, determined by the acetic acid / potassium iodide / potassium iodide addition / sodium thiosulfate solution titration method, is preferably 550 to 700 g / mol and more preferably 600 to 650 g / mol from the point of view of excellent vulcanization reactivity.

[0068] From the point of view of improving the effect of the alternative embodiment, which is not covered by the scope of protection, the polysiloxane is preferably a polysiloxane with 2 to 50 siloxane units (-Si-O-).

[0069] It should be noted that other metals besides a silicon atom (e.g. Sn, Ti and Al) are not present in the main chain of the polysiloxane.

[0070] The process for producing polysiloxane is publicly known and can be carried out, for example, according to the process disclosed in WO 2014 / 002750.

[0071] It should be noted that the silane adhesion promoter used in the alternative embodiment, which is not covered by the scope of protection, may also use other sulfur-containing silane adhesion promoters than those mentioned above. Examples of such sulfur-containing silane coupling agents are bis-(3-triethoxysilylpropyl)tetrasulfide, bis-(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, γ-mercaptopropyltriethoxysilane, and 3-octanoylthiopropyltriethoxysilane.

[0072] The amount of the sulfur-containing silane adhesion promoter added, represented by formula (100), is preferably from 2 to 20 wt% and even more preferably from 7 to 15 wt%, based on the amount of silica. Mixing ratio of the rubber composition according to the invention

[0073] The rubber composition according to the first invention contains: 50 to 200 parts by mass of carbon black with a specific nitrogen adsorption surface area (N2SA) of 100 to 500 m² 2 / g; and 5 to 50 parts by mass of a terpene phenolic resin with an acid number of 30 mg KOH / g or more and a hydroxyl number of 5 mg KOH / g or more, per 100 parts by mass of a diene rubber.

[0074] If the amount of carbon black added is less than 50 parts by mass, the heat build-up decreases, the dry grip performance deteriorates, and conversely, if the amount added exceeds 200 parts by mass, the fracture toughness decreases and the abrasion resistance deteriorates.

[0075] If the amount of terpene phenol resin added is less than 5 parts by mass, the amount is insufficient, and the effect of the first invention cannot be achieved. Conversely, if the mixture exceeds 50 parts by mass, the temperature dependence of the hardness deteriorates, the fracture toughness decreases, and the abrasion resistance deteriorates.

[0076] Furthermore, in the rubber composition of the invention, the amount of carbon black added is preferably 70 to 180 parts by mass per 100 parts by mass of the diene rubber.

[0077] The amount of terpene phenol resin added is preferably 10 to 40 parts by mass per 100 parts by mass of the diene rubber. Other components

[0078] The rubber composition in the invention may, in addition to the components described above, contain vulcanizing or crosslinking agents; vulcanizing or crosslinking accelerators; various fillers, such as zinc oxide, silica, clay, talc, and calcium carbonate; aging retarders; plasticizers; and other various additives commonly included in rubber compositions. The additives are kneaded together using a conventional method to obtain a composition that can then be used for vulcanization or crosslinking. The amounts of these additives included may be any amount commonly included in related prior art, as long as this does not hinder the purpose of the invention. It should be noted that silica may not be included in the invention. Mixing ratio of the rubber composition according to an alternative embodiment that is not covered by the scope of protection

[0079] The rubber composition according to the alternative embodiment, which is not covered by the scope of protection, contains: from 75 to 200 parts by mass silica with a specific CTAB surface area of ​​100 to 400 m² 2 / g; and 5 to 50 parts by mass of a terpene phenolic resin with an acid number of 30 mg KOH / g or more and a hydroxyl number of 5 mg KOH / g or more, per 100 mass parts of a diene rubber.

[0080] If the amount of silica added is less than 75 parts by mass, the wet grip performance deteriorates. Conversely, if the mixture exceeds 200 parts by mass, the tensile strength decreases and the abrasion resistance deteriorates.

[0081] If the amount of terpene phenol resin added is less than 5 parts by mass, the amount is insufficient, and the effect of the alternative embodiment, which is not covered by the scope of protection, cannot be achieved. Conversely, if the mixture exceeds 50 parts by mass, the heat-up performance (wet grip performance at low temperatures) decreases, as does the tensile strength and abrasion resistance.

[0082] Furthermore, in the rubber composition of the alternative embodiment, which is not covered by the scope of protection, the amount of silica added is preferably 100 to 180 parts by mass per 100 parts by mass of the diene rubber.

[0083] The amount of terpene phenol resin added is preferably 10 to 40 parts by mass per 100 parts by mass of the diene rubber. Other components

[0084] The rubber composition in the alternative embodiment, which is not within the scope of protection, may, in addition to the components described above, contain vulcanizing or crosslinking agents; vulcanizing or crosslinking accelerators; various fillers, such as zinc oxide, carbon black, clay, talc, and calcium carbonate; aging retarders; plasticizers; and other various additives commonly added to rubber compositions. The additives are kneaded together using a conventional method to obtain a composition that can then be used for vulcanization or crosslinking. The amounts of these additives added may be any amount commonly added in the related prior art, as long as the purpose of the alternative embodiment, which is not within the scope of protection, is not hindered.

[0085] Furthermore, the rubber composition according to an embodiment of the present invention is suitable for the manufacture of a pneumatic tire according to a known method for the manufacture of pneumatic tires and is preferably used in a protector tread, in particular in a racing pneumatic tire protector tread. Examples

[0086] The present invention is described in more detail by means of examples and comparative examples, but the present invention is not limited by these examples. Standard example 1, examples 1 to 5 and comparison examples 1 to 5 Sample preparation

[0087] For the composition (parts by mass) shown in Table 1, the components, with the exception of the vulcanization accelerators and sulfur, were kneaded for 5 minutes in a sealed 1.7 L Banbury mixer. The rubber was then removed from the mixer and cooled to room temperature. The rubber was then placed back into an identical mixer, and the vulcanization accelerators and sulfur were subsequently added to the mixture and further kneaded to obtain a rubber composition. Next, the rubber composition thus obtained was pressure-vulcanized in a predetermined mold at 160 °C for 20 minutes to produce a vulcanized rubber test piece, and then the test procedures shown below were used to measure the physical properties of the vulcanized rubber test piece.

[0088] Dry grip performance: According to JIS K6394, a viscoelasticity spectrometer (available from Toyo Seiki Seisakusho, Co., Ltd.) was used to measure tan δ (100 °C) under the following conditions: initial distortion = 10%; amplitude = ±2%; and frequency = 20 Hz. Dry grip performance was then evaluated based on these measurements. The results are expressed as index values, with the standard example 1 assigned a value of 100. Higher index values ​​indicate better dry grip performance.

[0089] Hardness: Measured at 20 °C and 100 °C according to JIS K6253. The results are expressed as index values, with the standard example 1 assigned a value of 100. Higher index values ​​indicate greater hardness. Smaller differences in hardness, measured at 20 °C and 100 °C, indicate better heat-induced loss of grip performance.

[0090] Tensile strength: Elongation at break was evaluated at 100 °C in a tensile test according to JIS K6251. The results are expressed as index values, with 100 assigned to standard example 1. Higher index values ​​indicate better tensile strength and abrasion resistance. [Table 1-I] Standard example 1 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 SBR 1*1 137,5 137,5 137,5 137,5 137,5 SBR 2 *2 - - - - - Soot 1 *3 100,0 - 250,0 100,0 100,0 Soot 2 *4 - 100,0 - - - Soot 3 *5 - - - - - Harz 1 *6 20,0 20,0 20,0 - - Harz 2 *7 - - - 20,0 - Harz 3 *8 - - - - 20,0 Harz 4 *9 - - - - - Resin 5 *10 - - - - - Liquid SBR *11 - - - - - Öl *12 20,0 20,0 20,0 20,0 20,0 Stearic acid *13 2,0 2,0 2,0 2,0 2,0 Zinc oxide *14 2,0 2,0 2,0 2,0 2,0 Aging retardants *15 2,0 2,0 2,0 2,0 2,0 Vulcanization accelerator 1*16 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator 2*17 2,0 2,0 2,0 2,0 2,0 Sulfur *18 1,5 1,5 1,5 1,5 1,5 Measurement result Dry grip performance 100 82 169 104 115 Hardness (20 °C) 100 95 163 102 105 Hardness (100°C) 100 94 170 103 102 Breaking strength 100 94 56 99 96 [Table 1-II] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative example 5 SBR 1*1 137,5 137,5 - - - 137,5 SBR 2 *2 - - 137,5 137,5 137,5 - Soot 1 *3 100,0 100,0 100,0 100,0 - 100,0 Soot 2 *4 - - - - - - Soot 3 *5 - - - - 100,0 - Harz 1 *6 - - - - - - Harz 2 *7 - - - - - - Harz 3 *8 - - - - - - Harz 4 *9 20,0 - 20,0 20,0 20,0 70,0 Resin 5 *10 - 20,0 - - - - Liquid SBR *11 - - - 20,0 - - Öl *12 20,0 20,0 20,0 - 20,0 20,0 Stearic acid *13 2,0 2,0 2,0 2,0 2,0 2,0 Zinc oxide *14 2,0 2,0 2,0 2,0 2,0 2,0 Aging retardants *15 2,0 2,0 2,0 2,0 2,0 2,0 Vulcanization accelerator 1*16 1,5 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator 2*17 2,0 2,0 2,0 2,0 2,0 2,0 Sulfur *18 1,5 1,5 1,5 1,5 1,5 1,5 Measurement result Dry grip performance 114 113 120 124 136 154 Hardness (20 °C) 104 105 101 94 109 85 Hardness (100°C) 109 107 102 100 110 78 Breaking strength 101 100 108 107 102 85 * 1: SBR 1 (Nipol NS460, available from ZS Elastomers Co., Ltd.; styrene content = 25 wt%; oil-extended product with 37.5 wt parts of an oil component added to 100 wt parts of an SBR) *2: SBR 2 (Nipol NS522, available from ZS Elastomer Co., Ltd.; styrene content = 39 wt%; oil-extended product with 37.5 wt parts of an oil component added to 100 wt parts of an SBR) *3: Carbon black 1 (SEAST 9, available from Tokai Carbon Co., Ltd.; specific nitrogen adsorption surface area (N2SA) = 142 m² 2 / G) *4: Carbon black 2 (Show Black N339, available from Cabot Japan KK; specific nitrogen adsorption surface area (N2SA) = 94 m² 2 / G) *5: Carbon black 3 (CD2019, available from Columbian Chemicals; specific nitrogen adsorption surface area (N2SA) = 340 m² 2 / G) *6: Resin 1 (Neopolymer 140S, available from JX Energy Corporation; C9 resin) *7: Resin 2 (YS POLYSTER ® T130, available from Yasuhara Chemical Co., Ltd; phenol-modified terpene resin; acid value = 0 mg KOH / g; hydroxyl value = 60 mg KOH / g) *8: Resin 3 (YS POLYSTER ® S145, available from Yasuhara Chemical Co., Ltd; phenol-modified terpene resin; acid value = 0 mg KOH / g; hydroxyl value = 100 mg KOH / g) *9: Resin 4 (Tamanol 803L, available from Arakawa Chemical Industries, Ltd.; terpene phenol resin; acid value = 50 mg KOH / g; hydroxyl value = 15 mg KOH / g) *10: Resin 5 (Tamanol 901, available from Arakawa Chemical Industries, Ltd.; terpene phenol resin; acid value = 50 mg KOH / g; hydroxyl value = 45 mg KOH / g) *11: Liquid SBR (RICON) ® 100 (available from Cray Valley); mean molecular weight = 6400; styrene content = 25 wt%; vinyl content = 70 wt%) *12: Oil (Extract No. 4S, available from Showa Shell Sekiyu KK) *13: Stearic acid (Stearic acid spheres YR, available from NOF Corporation) *14: Zinc oxide (Zinc oxide III, available from Seido Chemical Industry Co., Ltd.) *15: Aging retardant (Santoflex) ® 6PP, available from Solutia Europe) *16: Vulcanization Accelerator 1 (NOCCELER CZ-G, available from Ouchi Shinko Chemical Industrial Co., Ltd.) *17: Vulcanization Accelerator 2: NOCCELER TOT-N, available from Ouchi Shinko Chemical Industrial Co., Ltd.) *18: Sulfur (oil-treated sulfur powder “Golden Flower”, available from Tsurumi Chemical Industry, Co., Ltd.)

[0091] The results shown in Table 1 demonstrate that the rubber compositions of Examples 1 to 5 were obtained by adding a specific amount of carbon black with a specific nitrogen adsorption surface area (N₂SA) and a specific amount of a terpene phenolic resin with a specific acidity range and a specific hydroxyl number range to a diene rubber containing a styrene-butadiene copolymer rubber, thus resulting in improved dry grip performance, increased fracture toughness, excellent abrasion resistance, and suppressed temperature dependence of hardness compared to Standard Example 1. In contrast, the specific nitrogen adsorption surface area (N₂SA) of the carbon black in Comparative Example 1 is smaller than the lower limit specified in the invention. Consequently, the dry grip performance and fracture toughness deteriorated compared to those in Standard Example 1.

[0092] Since the amount of carbon black added in comparative example 2 exceeds the upper limit specified in the invention, the fracture strength deteriorated compared to that in standard example 1.

[0093] In comparative examples 3 and 4, the acid number of the terpene phenol resin is lower than the lower limit specified in the invention. Therefore, the fracture toughness deteriorated compared to that in standard example 1.

[0094] Since the amount of terpene phenol resin in comparative example 5 exceeds the upper limit specified in the invention, the temperature dependence of the hardness and the fracture toughness deteriorated compared to those of standard example 1.

[0095] Standard Example 2 (alternative embodiment not covered by the scope of protection), Examples 6 to 10 and Comparative Examples 6 to 10 Sample Preparation

[0096] For the composition (parts by mass) shown in Table 2, the components, with the exception of the vulcanization accelerators and sulfur, were kneaded for 5 minutes in a sealed 1.7 L Banbury mixer. The rubber was then removed from the mixer and cooled to room temperature. The rubber was then placed back into an identical mixer, and the vulcanization accelerators and sulfur were subsequently added to the mixture and further kneaded to obtain a rubber composition. Next, the rubber composition thus obtained was pressure-vulcanized in a predetermined mold at 160 °C for 20 minutes to obtain a vulcanized rubber test specimen. The test procedures shown below were then applied to measure the physical properties of the unvulcanized rubber composition and the vulcanized rubber test specimen.

[0097] Wet grip performance: tan δ (0°C) was measured at a strain deformation of 10 ± 2%, a vibration frequency of 20 Hz, and a temperature of 0°C using a viscoelastic spectrometer (available from Toyo Seiki Seisaku-sho, Ltd.) according to JIS K 6394:2007. The results are expressed as index values, with the standard example 2 assigned a value of 100. Higher index values ​​indicate better wet grip performance.

[0098] Warm-up performance (wet grip performance at low temperatures): In the unvulcanized rubber compound, the average Tg of the added diene monomer, resin component, and oil (including an oil that elongates the diene monomer) was calculated. It should be noted that the average Tg is a value calculated based on the weighted average of the Tg of the components. The results are expressed as index values, with the standard example 2 assigned a value of 100. If the index value is large, an increase in the compound's Tg indicates a deterioration in warm-up performance (wet grip performance at low temperatures).

[0099] Tensile strength: Elongation at break was evaluated at 100 °C in a tensile test according to JIS K6251. The results are expressed as index values, with the standard example 2 assigned a value of 100. Higher index values ​​indicate better tensile strength and abrasion resistance. [Table 2-I] Standard example 2 Comparative example 6 Comparative example 7 Comparative example 8 Comparative example 9 SBR 1*19 137,5 137,5 137,5 137,5 137,5 SBR 2 *20 - - - - - Silica 1 *21 100,0 - 250,0 100,0 100,0 Silica 2 *22 - 100,0 - - - Soot *23 10,0 10,0 10,0 10,0 10,0 Harz 1 *24 20,0 20,0 20,0 - - Harz 2 *25 - - - 20,0 - Harz 3 *26 - - - - 20,0 Harz 4 *27 - - - - - Harz 5 *28 - - - - - Sulfur-containing silane adhesion promoter 1*29 8,0 8,0 20,0 8,0 8,0 Sulfur-containing silane adhesion promoter 2*30 Öl *31 20,0 20,0 20,0 20,0 20,0 Stearic acid *32 2,0 2,0 2,0 2,0 2,0 Zinc oxide *33 2,0 2,0 2,0 2,0 2,0 Aging retardants *34 2,0 2,0 2,0 2,0 2,0 Vulcanization accelerator 1*35 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator 2*36 2,0 2,0 2,0 2,0 2,0 Sulfur *37 1,5 1,5 1,5 1,5 1,5 Measurement result Wet grip performance 100 103 113 103 108 Warm-up power 100 100 100 102 103 Breaking strength 100 94 67 98 94 [Table 2-II] Example 6 Example 7 Example 8 Comparative example 10 Example 9 Example 10 SBR 1*19 137,5 137,5 137,5 137,5 10,0 50,0 SBR 2 *20 - - - - 127,5 87,5 Silica 1 *21 100,0 100,0 100,0 100,0 100,0 100,0 Silica 2 *22 - - - - - - Soot *23 10,0 10,0 10,0 10,0 10,0 10,0 Harz 1 *24 - - - - - - Harz 2 *25 - - - - - - Harz 3 *26 - - - - - - Harz 4 *27 20,0 - 20,0 70,0 20,0 20,0 Harz 5 *28 - 20,0 - - - - Sulfur-containing silane adhesion promoter 1*29 8,0 8,0 - 8,0 - - Sulfur-containing silane adhesion promoter 2*30 - - 8,0 - 8,0 8,0 Öl *31 20,0 20,0 20,0 20,0 20,0 20,0 Stearic acid *32 2,0 2,0 2,0 2,0 2,0 2,0 Zinc oxide *33 2,0 2,0 2,0 2,0 2,0 2,0 Aging retardants *34 2,0 2,0 2,0 2,0 2,0 2,0 Vulcanization accelerator 1*35 1,5 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator 2*36 2,0 2,0 2,0 2,0 2,0 2,0 Sulfur *37 1,5 1,5 1,5 1,5 1,5 1,5 Measurement result Wet grip performance 106 108 113 132 102 109 Warm-up power 97 99 100 114 92 97 Breaking strength 101 100 100 85 101 100 * 19: SBR 1 (trade name TUFDENE ® E680, available from Asahi Kasei Corporation; styrene content t = 36 wt%; oil-diluted product with 37.5 wt parts of an oil component added to 100 wt parts of an SBR; Tg of SBR 1 excluding the oil component = -15 °C) *20: SBR 2 (Nipol NS522, available from ZS Elastomer Co., Ltd.; styrene content = 39 wt%; oil-extended product with 37.5 wt parts of an oil component added to 100 wt parts of an SBR; Tg of SBR excluding the oil component = -25 °C) *21: Silica 1 (Ultrasil ® 7000 g, available from Evonik Industries AG; specific CTAB surface area = 160 m² 2 / G) *22: Silica 2 (Zeosil ® 1085GR, available from Solvay; specific CTAB surface area = 85 m² 2 / G) *23: Soot (Sho Black N339, available from Cabot Japan KK) *24: Resin 1 (Neopolymer 140S, available from JX Energy Corporation; C9 resin) *25: Resin 2 (YS POLYSTER ® T160, available from Yasuhara Chemical Co., Ltd.; phenol-modified terpene resin; acid value = 0 mg KOH / g; hydroxyl value = 60 mg KOH / g) *26: Resin 3 (YS POLYSTER ® S145, available from Yasuhara Chemical Co., Ltd; phenol-modified terpene resin; acid value = 0 mg KOH / g; hydroxyl value = 100 mg KOH / g) *27: Resin 4 (Tamanol 803L, available from Arakawa Chemical Industries, Ltd.; terpene phenol resin; acid value = 50 mg KOH / g; hydroxyl value = 15 mg KOH / g) *28: Resin 5 (Tamanol 901, available from Arakawa Chemical Industries, Ltd.; terpene phenol resin; acid value = 50 mg KOH / g; hydroxyl value = 45 mg KOH / g) *29: Sulfur-containing silane adhesion promoter 1 (Si69 ® , available from Evonik Degussa; Bis(3-Triethoxysilylalkyl)tetrasulfide) *30: Sulfur-containing silane adhesion promoter 2 (compound satisfying the above formula (100), synthesized according to synthesis example 1, disclosed in WO 2014 / 002750; composition formula = (-C3H6-S4-C3H6-) 0,083 (-C8H 17 ) 0,667 (-OC2H5) 1,50 (-C3H6SH) 0,167 SiO 0,75 ; average molecular weight = 860) *31: Oil (Extract No. 4S, available from Showa Shell Sekiyu KK) *32: Stearic acid (Stearic acid spheres YR, available from NOF Corporation) *33: Zinc oxide (Zinc oxide III, available from Seido Chemical Industry Co., Ltd.) *34: Aging retardant (Santoflex) ®6PP, available from Solutia Europe) *35: Vulcanization accelerator 1 (NOCCELER CZ-G, available from Ouchi Shinko Chemical Industrial Co., Ltd.) *36: Vulcanization Accelerator 2: NOCCELER TOT-N, available from Ouchi Shinko Chemical Industrial Co., Ltd.) *37: Sulfur (oil-treated sulfur powder “Golden Flower”, available from Tsurumi Chemical Industry, Co., Ltd.)

[0100] As can be seen from the results in Table 2, the rubber compositions of Examples 6 to 10 were obtained by adding: a specific amount of silica with a specific CTAB surface area and a specific amount of a terpene phenolic resin with a specific acidity range and hydroxyl number range to a diene rubber containing a styrene-butadiene copolymer rubber with a glass transition temperature (Tg) within a specific range, and thus exhibited improved wet grip performance and warm-up performance (wet grip performance at low temperatures), increased fracture toughness and excellent abrasion resistance compared to standard Example 2.

[0101] In contrast, in comparative example 6, the specific CTAB surface area of ​​the silica is smaller than the lower limit specified in the alternative embodiment, which is not within the scope of protection. Thus, the fracture toughness deteriorated compared to that in standard example 2.

[0102] In comparative example 7, the amount of silica in the mixture exceeded the upper limit specified in the alternative embodiment, which is not covered by the scope of protection. Consequently, the fracture toughness deteriorated compared to that in standard example 2.

[0103] In comparative examples 8 and 9, the acid number of the terpene phenol resin is lower than the lower limit specified in the alternative embodiment, which is not within the scope of protection. Consequently, the heat-up performance (wet grip performance at low temperature) and the impact strength deteriorate compared to those in standard example 2.

[0104] Since the amount of terpene phenol resin in comparative example 10 exceeds the upper limit specified in the alternative embodiment, which is not covered by the scope of protection, the heat-up performance (wet grip performance at low temperature) and the breaking strength deteriorated compared to those in standard example 2.

Claims

[1] Rubber composition for a tire, comprising: 70 to 180 parts by mass of soot with a specific nitrogen adsorption surface area (N2SA) of 100 to 500 m² 2 / g; and 5 to 50 parts by mass of a terpene phenolic resin with an acid number of 30 to 150 mg KOH / g and a hydroxyl number of 5 to 120 mg KOH / g, per 100 parts by mass of a diene rubber comprising a styrene-butadiene copolymer rubber. [2] Rubber composition for a tire according to claim 1, wherein the styrene-butadiene copolymer rubber has a styrene content of 30 wt% or more. [3] Rubber composition for a tire according to claim 1, further comprising a liquid aromatic vinyl-conjugated diene rubber having a glass transition temperature (Tg) of -40 °C or higher in addition to the styrene-butadiene copolymer rubber. [4] Vulcanized product obtainable by vulcanizing a rubber composition according to any one of claims 1 to 3. [5] Use of a vulcanized product according to claim 4 in a protector tread of an pneumatic tire.