Composition of rubber and tire
Patent Information
- Application Number
- BRPI0906951
- Authority / Receiving Office
- BR · BR
- Patent Type
- Patents
- Current Assignee / Owner
- Publication Date
- 2026-08-11
- Estimated Expiration
- Not applicable · inactive patent
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Abstract
Description
The present invention relates to a rubber composition suitable as a tire tread element, more specifically to a rubber composition that is prepared using precipitated silica having a specific structure as a reinforcing filler and that is improved in low heat buildup and abrasion resistance, and to a tire prepared using the same. Previous Technique Carbon black has been used to date as a reinforcing filler for rubber. This is because carbon black can provide rubber compounds with high abrasion resistance. In recent years, as resource and energy savings are socially demanded, low heat buildup in tire rubber has become sought after, as well as for the purpose of saving fuel consumption in cars. When low heat buildup is to be achieved using carbon black alone, it is considered that the proportion of carbon black in the compound is reduced or a carbon black with a large particle diameter is used, but in both cases, it is known that the reinforcement, abrasion resistance, and grip on a wet road surface are reduced. On the other hand, silica is known to be used as a filler to improve low heat buildup (refer, for example, to patent documents 1 to 4).However, silica particles tend to be aggregated by virtue of a hydrogen bond with a silane group, which is a surface functional group of silica, and a silane group is inferior in wetting capacity. 2 / 22 molecules of rubber are affected by a -OH group that has hydrophilicity, which impairs the dispersion of silica in the rubber. The kneading time has to be prolonged in order to mitigate the above problem. Furthermore, the Mooney viscosity of a rubber compound is increased due to insufficient silica dispersion in the rubber, and a defect that the rubber compound is inferior in processability, such as extrusion, has been involved in this. Additionally, since the surface of a silica particle is acidic, the silica adsorbs a basic substance used as a vulcanization accelerator in the vulcanization of a rubber compound, thus preventing the rubber compound from being sufficiently vulcanized, so the defect that the elastic modulus is not improved has been involved in this. A silane coupling agent has been developed to mitigate the above defects, but the silica dispersion has not yet reached a sufficiently high level, and it has been particularly difficult to obtain an industrially good dispersion of silica particles. Therefore, attempts are being made to mix a treated silica surface with a hydrophobicity-promoting agent in order to accelerate the reaction of a silane coupling agent (patent document 5). Furthermore, patent document 6 reveals the use of hydrophobic precipitated silica. However, since precipitated silica subjected to complete hydrophobicity treatment is used, the surface silanol groups to react with a silane coupling agent disappear, and therefore the defect that the rubber is not sufficiently reinforced has been involved in this. In addition, the silica, which has a diameter... 3 / 22 of an increased particle size is used to improve low heat buildup, but in this case, the silica is reduced in a specific surface area by increasing the particle diameter, deteriorating the reinforcing property. Patent document 7 discloses the use of silica that has a specific shape, but the low heat buildup and abrasion resistance of a rubber compound are not sufficiently high. Patent Document 1: Japanese Patent Application Open to the Public Hei 6 No. 248116 Patent Document 2: Japanese Patent Application Open to the Public Hei 7 No. 70369 Patent Document 3: Japanese Patent Application Open to the Public Hei 8 No. 245838 Patent document 4: Japanese Patent Application Open to the Public 3 No. 252431 Patent Document 5: Japanese Patent Application Open to the Public Hei 6 No. 248116 Patent Document 6: Japanese Patent Application Open to the Public Hei 6 No. 157825 Patent Document 7: Japanese Public Patent Application No. 2006-37046 DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention provides a rubber composition that is improved by the dispersion of precipitated silica in a rubber composition and improved both in low heat buildup and abrasion resistance, and which is suitable as a tire tread element and a tire prepared using the same. Ways to Solve the Problems 4 / 22 The present inventors have found that, in a rubber composition containing precipitated silica, low heat buildup is achieved by providing the precipitated silica with a specific structure and that, at the same time, the rubber composition is improved in abrasion resistance and reinforcing properties, and thus the present invention has been completed. The rubber composition of the present invention is a rubber composition that is prepared by combining natural rubber and / or diene-based synthetic rubber with structural precipitated silica, a silane coupling agent that has a specific structure, and carbon black, and mixing them together. The precipitated silica used in the present invention is characterized by having a structure (primary aggregation) that can be shown by the following index. That is, an adsorption surface area of cetyltrimethylammonium bromide (CTAB) (m2 / g) and the mode Aacem diameters (mm) of primary aggregates determined by acoustic measurement of particle size distribution satisfy equation (I) shown below: Aac> -0.76 X (CTAB) + 274 (I) and the loss of ignition (% mass reduction when heated to 50°C for 3 hours) and the loss of heating (% mass reduction when heated to 105°C for 2 hours) preferably satisfy equation (II) shown below: (loss of ignition) - (loss of heating) f 3 (II) A rubber composition containing the precipitated silica above may allow low heat buildup to be compatible with abrasion resistance. The precipitated silica used in the present invention is obtained by a method in which the precipitated silica is deposited and precipitated by neutralization. 5 / 22 of an aqueous solution of an alkali salt of silicic acid, such as sodium silicate, with a mineral acid, such as sulfuric acid and the like, a method according to a production method for so-called precipitated silica. Effects of the Invention According to the present invention, a rubber composition is obtained that excels in low heat accumulation and, when used as a tire tread element, the tire excels in both low heat accumulation and abrasion resistance, which are antinomic issues and can contribute significantly to energy savings. Brief Explanation of the Drawing Figure 1 is a graph showing the relationship between CTAB of precipitated silicas used in the examples and in the comparative examples and Aac. Method for Putting the Invention into Practice The rubber component used in the rubber composition of the present invention is natural rubber and / or diene-based synthetic rubber. Specific examples of diene-based synthetic rubber include synthetic polyisoprene rubber, polybutadiene rubber, a styrene-butadiene rubber, and the like. The above rubber components may be used alone or in a mixture of two or more species thereof. The structural precipitated silica used in the present invention can be characterized by the fact that its characteristic values, measured by a method commonly used to measure silica and carbon black, satisfy the following relationships. In other words, it is a precipitated silica in which a specific surface area for bromide adsorption 6 / 22 cetyltrimethylammonium (CTAB) (m2 / g) and a diameter Aac(mm) of the mode in the number of primary aggregates determined by an acoustic measurement of the particle size distribution satisfy equation(I) shown below: Aac> -0.76 X (CTAB) + 274 (I) and in which an ignition loss (mass reduction of % when heated to 750°C for 3 hours) and a heating loss (mass reduction of % when heated to 105°C for 2 hours) preferably satisfy equation (II) shown below: (loss of ignition) - (loss of heating) 3 (II) The specific surface area of cetyltrimethylammonium bromide (CTAB) adsorption is a specific surface area (m² / g) of precipitated silica calculated from the amount of cetyltrimethylammonium bromide adsorbed onto a surface of precipitated silica. CTAB can be measured according to a method described in ASTM document D3765-92. The method described in ASTM document D3765-92 is a method for measuring the CTAB of carbon black and, therefore, will be slightly modified. That is, a standard carbon black product is not used and a standard solution of cetyltrimethylammonium bromide (hereinafter abbreviated to CE-TRAB) is prepared. This solution is used to standardize an OT solution of precipitated silica (sodium di-2-ethylhexylsulfosuccinate) to calculate a specific surface area from an amount of CE-TRAB adsorption, assuming that a cross-sectional area of adsorption per molecule of CE-TRAB on a surface of precipitated silica is 0.35 nm2. The precipitated silica used in the present invention has a CTAB of 50 to 250 m² / g, preferably of 7 / 22 100 to 200 m² / g. If the CTAB is less than 50 m² / g, the rubber composition is likely to be significantly reduced in a storage module, and if it is greater than 250 m² / g, the unvulcanized rubber composition is likely to have a higher viscosity. A diameter (acoustic particle size distribution diameter) measured as a particle diameter of precipitated silica using acoustic particle size distribution measuring equipment is an index for the development of a constitutive property. Precipitated silica particles contain particles prepared by primary aggregation of fine particles and slightly contain particles prepared by secondary aggregation of the above particles. The measurement of particle size distribution using acoustic measuring equipment is carried out after subjecting a 0.01M KCl aqueous solution of precipitated silica to an ultrasonic wave dispersion treatment for 5 minutes to remove bubbles and break up secondary aggregates. Particle diameters of primary aggregates of precipitated silica and their particle number distribution are obtained, and assuming that, among them, the particle diameter observed at the highest frequency is fixed at Aac(nm), the rubber composition is improved in both low heat accumulation and abrasion resistance when the following equation is satisfied. Aac> -0.76 X (CTAB) + 274 (I) When Aac does not meet the above condition, the rubber composition is reduced in both low heat accumulation and abrasion resistance. Furthermore, Aac is preferably 1 µm or less. If it is greater than 1 µm, the precipitated silica becomes a core for fracture, and is 8 / 22 It is likely that the kinetic properties of the rubber compound will be damaged. Furthermore, the difference between a reduction (%) in the mass of precipitated silica used in the present invention when heated and a reduction (%) in its mass when ignited is preferably: (loss of ignition) - (loss of heating)3 (II) The loss on heating and the loss on ignition are measured according to a test method for compounding rubber ingredients in document JIS K6220-1, in which the loss on heating is a reduction (%) in mass when typically heated to 105 ± 2°C for 2 hours, and the loss on ignition is a reduction (%) in mass when typically ignited to 750 ± 25°C for 3 hours. The amount of precipitated silica used in the present invention is preferably 10 to 150 parts by mass based on 100 parts by mass of the rubber component. The precipitated silica used in the present invention is produced according to a production process for precipitated silica. For example, a reaction vessel pre-filled with a fixed amount of hot water is charged with sodium silicate and sulfuric acid while controlling the pH and temperature in order to obtain a semi-fluid paste of precipitated silica after the fixed time has elapsed. Then, the semi-fluid paste of precipitated silica is separated by filtration through a filtering device capable of washing a mass, such as a filter press, and washed to remove by-produced electrolytes, and then a semi-fluid paste is prepared from the resulting mass of precipitated silica and dried by means of a dryer. 9 / 22 such as a spray dryer, in order to obtain precipitated silica. In the present invention, a silane coupling agent is preferably used. The silane coupling agent is reacted with silanol groups that remain on a precipitated silica surface and with the rubber component so as to act as a bridge linking agent with the rubber and form a reinforcing phase. The silane coupling agent used in the present invention is at least one selected from the group consisting of compounds represented by the formulas shown below: AmB3_mSi- (CH2)a-Sb- (CH2)a-SiAmB3_m(III) (where A is CnH2n+iO (n is an integer from 1 to 3) or a chlorine atom; B is an alkyl group having from 1 to 3 carbon atoms; m is an integer from 1 to 3; a is an integer from 1 to 9; b is an integer of 1 or more and may have distribution; provided that when m is 1, two B may be the same or different, and that when m is 2 or 3, two or three A may be the same or different); AmB3_mSi-(CH2)cY (IV) (where A is CnH2n+iO (n is an integer from 1 to 3) or a chlorine atom; B is an alkyl group having from 1 to 3 carbon atoms; Y is a mercapto group, a vinyl group, an amino group, a glycidoxy group or an epoxy group; m is an integer from 1 to 3; c is an integer from 0 to 9; provided that, when m is 1, two B may be the same or different and that, when m is 2 or 3, two or three A may be the same or different); and AmB3_mSi-(CH2)a-Sb-Z (V) where A is CnH2n+iO (n is an integer from 1 to 3) or a chlorine atom; B is an alkyl group having from 1 to 3 carbon atoms; Z is a benzothiazolyl group, a group 10 / 22 N,N-dimethylthiocarbamoyl or a methacryloyl group; m is an integer from 1 to 3; a is an integer from 1 to 9; b is an integer of 1 or more and may have a distribution; provided that, when m is 1, two B's may be the same or different and that, when m is 2 or 3, two or three A's may be the same or different). To be specific, the silane coupling agent represented by formula (III) includes bis-(3-triethoxysilylpropyl) tetrasulfide, bis-(3-trimethoxysilylpropyl) tetrasulfide, bis-(3-methyldimethoxysilylpropyl) tetrasulfide, bis-(3-triethoxysilylethyl) tetrasulfide, bis-(3-triethoxysilylpropyl) disulfide, bis-(3-trimethoxysilylpropyl) disulfide and bis-(3-triethoxysilylpropyl) trisulfide; The silane coupling agent represented by formula (IV) includes 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, glycidoxypropyltrimethoxysilane and glycidoxypropylmethyldiethoxysilane; and the silane coupling agent represented by formula (V) includes 3-trimethoxysilylpropyl-N,N-dimethylthiocarbomoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide and 3-trimethoxysilylpropylmethacryloyl monosulfide.The preferred usage quantity of the silane coupling agent is 1 to 20% by mass based on the proportion of precipitated silica. If the usage proportion is less than 1% by mass, a sufficiently high coupling effect is not obtained in a given case, e.g. 11 / 22 if it exceeds 20% by mass, polymer gelation is carried out in a specific case. In the rubber composition of the present invention, carbon black can be used as a reinforcing filler together with precipitated silica. The abrasion resistance of the rubber composition can be improved by the addition of carbon black. The amount of carbon black used is preferably 80 parts by mass or less based on 100 parts by mass of the rubber component, and the total composition amount obtained by adding the carbon black and precipitated silica is preferably 120 parts by mass or less. Controlling the total composition amount to 120 parts by mass or less based on 100 parts by mass of the rubber component makes it possible to sufficiently improve low heat buildup and abrasion resistance. The rubber composition of the present invention can be suitably supplemented, if necessary, with compositional ingredients commonly used in the rubber industry, such as, for example, other reinforcing fillers, vulcanizing agents, vulcanization accelerators, antioxidants, emollients, and the like. The rubber composition of the present invention is obtained by kneading the components in an open-type mixer, such as a cylinder, and an internal mixer, such as a Banbury mixer, and is vulcanized after being subjected to molding processing and can be applied to various rubber products. The tire of the present invention is characterized by the application of the rubber compound described above to a tread element. The tire prepared using the rubber compound described above for an element The 12 / 22 tread pattern has low rolling resistance since the rubber compound has low heat buildup, and is excellent in abrasion resistance. Ordinary air or air in which a partial pressure of oxygen is altered, or an inert gas such as nitrogen, can be used for the gas charged in the tire of the present invention. EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is by no means limited to the following examples. In the following examples and comparative examples, the physical properties of precipitated silica and the low heat accumulation and abrasion resistance of the rubber compound were measured and evaluated by the following methods. Physical properties of precipitated silica: (1) Measurement of the acoustic particle size distribution diameter: A 0.01M KCl aqueous solution of each precipitated silica was subjected to dispersion treatment for 5 minutes using an ultrasonic wave to remove bubbles, and then the Aac mode (mm) in diameters of primary aggregates of precipitated silica was measured using a DT1200 acoustic particle size distribution measuring instrument (manufactured by Dispersion Technology, Inc.). (2) CTAB measurement: The CTAB was measured according to a method described in ASTM document D3765-92. The method described in ASTM document D3765-92 is a method for measuring the CTAB of carbon black and, therefore, was slightly modified. That is, IRB No. 3 (83.0 m² / g), which was a standard product of 13 / 22 carbon black was not used, and a standard solution of cetyltrimethylammonium bromide (hereinafter abbreviated to CE-TRAB) was prepared separately. This solution was used to standardize an OT solution of precipitated silica (sodium di-2-ethylhexylsulfosuccinate) in order to calculate a specific surface area (m² / g) of an adsorbent ratio of CE-TRAB, assuming that the adsorbent cross-sectional area per molecule of CE-TRAB on a precipitated silica surface was 0.35 nm. This is because carbon black and precipitated silica are considered to be different on a surface and therefore different in an adsorbent ratio of CE-TRAB even if they have the same surface area. (3) Measurement of loss on heating and loss on ignition: A sample of precipitated silica was weighed and heated to 105 ± 2°C for 2 hours in the case of loss on heating and to 750 ± 25°C for 3 hours in the case of loss on ignition, and then the masses were measured in order to represent the difference of a sample mass before heating in % based on its mass before heating. (4) Low heat accumulation: The tan δ values were measured at a temperature of 60°C, a distortion of 1%, and a frequency of 50 Hz using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho Ltd.). They were shown by an index, where the value in Comparative Example 1 was set at 100. The higher the value above, the better the low heat accumulation. (5) Abrasion resistance: The amount of abrasion at a 60% slip rate at ambient temperature was measured using a Lambourn abrasion tester, according to the document. 14 / 22 JIS K6264, and an inverse number of the amount of abrasion was shown by an index, where the value in Comparative Example 1 was set at 100. The higher the numerical value above, the better the abrasion resistance. Production of precipitated silica: Example of Production A A jacketed stainless steel reaction vessel with a volume of 180 L, equipped with a stirrer, was filled with 93 L of water and 0.6 L of an aqueous solution of sodium silicate (SiC2 160 g / L, SiO2 / Na2O mole ratio: 3.3) and heated to 96°C. The concentration of Na2O in the resulting solution was 0.005 mol / L. While the above solution was maintained at a temperature of 96°C, the same aqueous sodium silicate solution was added in increments simultaneously, as described above, at a flow rate of 540 ml / minute, and sulfuric acid (18 mol / L) at a flow rate of 24 ml / minute. A Na₂O concentration in the reaction solution was maintained in a range of 0.00 to 0.01 mol / L by controlling the flow rates in order to effect the neutralization reaction. The solution began to become hazy midway through the reaction and increased in viscosity after 47 minutes, and the solution was transformed into a gelatinous consistency. The addition was continued, and the reaction was terminated after 90 minutes. After the reaction was complete, the temperature of the reaction liquid was maintained at 96°C for 30 minutes. The silica concentration in the resulting solution was 55 g / L.Next, sulfuric acid at the concentration described above was added until the pH of the solution was 3 to obtain a semi-fluid silica paste. The semi-fluid silica pulp thus obtained was filtered using a filter press, and the solid body... 15 / 22 filtrate was washed with water until a wet mass was obtained. Then, the wet mass was transformed into a semi-fluid paste using an emulsification apparatus, and the semi-fluid paste was dried using a spray dryer to obtain precipitated silica A. Example of Production B The same container used in Production Example A was filled with 93 L of water and 0.6 L of aqueous sodium silicate solution, which were the same raw materials used in Production Example A, and heated to 90°C. The concentration of Na2U in the resulting solution was 0.005 mol / L. While the above solution was maintained at a temperature of 90°C, the same aqueous sodium silicate solution described above was added simultaneously in drops, at a flow rate of 540 ml / minute, and sulfuric acid (18 mol / L) at a flow rate of 24 ml / minute. A concentration of Na2O in the reaction solution was maintained in a range of 0.00 to 0.01 mol / L by controlling the flow rates in order to effect the neutralization reaction. The solution began to become hazy midway through the reaction and increased in viscosity after 47 minutes, and the solution was transformed into a gelatinous consistency. The addition was continued, and the reaction was terminated after 90 minutes. After the reaction was complete, the temperature of the reaction liquid was maintained at 96°C for 30 minutes. The silica concentration in the resulting solution was 55 g / L.Next, sulfuric acid at the concentration described above was added until the pH of the solution was 3 to obtain a semi-fluid silica paste. Then, precipitated silica B was obtained using the same method as in Production Example A. 16 / 22 Example of Production C The same container used in Production Example A was filled with 93 L of water and 0.6 L of aqueous sodium silicate solution, which were the same raw materials used in Production Example A, and heated to 84°C. The concentration of Na2O in the resulting solution was 0.005 mol / L. While the above solution was maintained at a temperature of 84°C, the same aqueous sodium silicate solution described above was added simultaneously in drops, at a flow rate of 540 ml / minute, and sulfuric acid (18 mol / L) at a flow rate of 24 ml / minute. A concentration of NasO in the reaction solution was maintained in a range of 0.00 to 0.01 mol / L by controlling the flow rates in order to effect the neutralization reaction. The solution began to become hazy midway through the reaction and increased in viscosity within 48 minutes, and the solution was transformed into a gelatinous consistency. The addition was continued, and the reaction was terminated in 90 minutes. After the reaction was complete, the temperature of the reaction liquid was maintained at 84°C for 30 minutes. The silica concentration in the resulting solution was 55 g / L.Next, sulfuric acid at the concentration described above was added until the pH of the solution was 3 to obtain a semi-fluid silica paste. Then, precipitated silica C was obtained by the same method as in Production Example A. Production Example D. The same container used in Production Example A was filled with 93 L of water and 0.6 L of aqueous sodium silicate solution, which were the same raw materials used in Production Example A, and 17 / 22 heated to 90°C. The concentration of Na2O in the resulting solution was 0.005 mol / L. While the above solution was maintained at a temperature of 90°C, the same aqueous sodium silicate solution described above was added simultaneously in drops, at a flow rate of 540 ml / minute, and sulfuric acid (18 mol / L) at a flow rate of 24 ml / minute. A Na2O concentration in the reaction solution was maintained in a range of 0.00 to 0.01 mol / L by controlling the flow rates in order to effect the neutralization reaction. The solution began to become hazy midway through the reaction and increased in viscosity after 47 minutes, and the solution was transformed into a gelatinous consistency. The addition was continued, and the reaction was terminated after 90 minutes. After the reaction was complete, the temperature of the reaction liquid was maintained at 90°C for 60 minutes. The silica concentration in the resulting solution was 55 g / L.Next, sulfuric acid at the concentration described above was added until the pH of the solution was 3 to obtain a semi-fluid silica paste. Then, precipitated silica D was obtained by the same method as in Production Example A. Production Example E: The same container used in Production Example A was filled with 93 L of water and 0.6 L of the aqueous sodium silicate solution, which were the same raw materials used in Production Example A, and heated to 78°C. The concentration of Na2O in the resulting solution was 0.005 mol / L. While the above solution was maintained at a temperature of 78°C, the same aqueous solution of sodium silicate described 18 / 22 above, at a flow rate of 540 ml / minute, and sulfuric acid (18 mol / L) at a flow rate of 24 ml / minute. A concentration of Na2O in the reaction solution was maintained in a range of 0.00 to 0.01 mol / L by controlling the flow rates in order to effect the neutralization reaction. The solution began to become cloudy midway through the reaction and increased in viscosity over 49 minutes, and the solution was transformed into a gelatinous consistency. The addition was continued, and the reaction was terminated after 90 minutes. After the reaction was complete, the temperature of the reaction liquid was maintained at 78°C for 60 minutes. The silica concentration in the resulting solution was 55 g / L. Then, sulfuric acid at the concentration described above was added until the pH of the solution was 3 to obtain a semi-fluid silica paste. Next, precipitated silica E was obtained using the same method as in Production Example A.Example Production F: The same container used in Example Production A was filled with 93 L of water and 0.6 L of aqueous sodium silicate solution, which were the same raw materials used in Example Production A, and heated to 65°C. The concentration of Na2O in the resulting solution was 0.005 mol / L. While the above solution was maintained at a temperature of 65°C, the same aqueous sodium silicate solution described above was added simultaneously in drops, at a flow rate of 540 ml / minute, and sulfuric acid (18 mol / L) at a flow rate of 24 ml / minute. A concentration of Na2O in the reaction solution was maintained in a range of 0.00 to 0.01 mol / L by controlling the flow rates in order to effect 19 / 22 the neutralization reaction. The reaction solution began to become hazy in the middle of the reaction and increased in viscosity within 50 minutes, and the solution was transformed into a gelatinous consistency. The addition was continued, and the reaction was completed in 90 minutes. After the reaction was complete, the temperature of the reaction liquid was maintained at 65°C for 60 minutes. The silica concentration in the resulting solution was 55 g / L. Then, sulfuric acid with the concentration described above was added until the pH of the solution was 3 in order to obtain a semi-fluid silica paste. Then, precipitated silica F was obtained by the same method as in Production Example A. Example of Production G The same container used in Production Example A was filled with 8.6 L of water and 0.5 L of aqueous sodium silicate solution, which were the same raw materials used in Production Example A, and heated to 96°C. The concentration of Na2O in the resulting solution was 0.005 mol / L. While the above solution was maintained at a temperature of 96°C, the same aqueous sodium silicate solution described above was added simultaneously in drops, at a flow rate of 615 ml / minute, and sulfuric acid (18 mol / L) at a flow rate of 27 ml / minute. A concentration of Na2O in the reaction solution was maintained in a range of 0.00 to 0.01 mol / L by controlling the flow rates in order to effect the neutralization reaction. The solution began to become hazy in the middle of the reaction and increased in viscosity within 40 minutes, and the solution was transformed into a gelatinous consistency. The addition was continued, and the reaction was terminated in 90 minutes. After the reaction was complete, the temperature of the liquid The 20 / 22 reaction was maintained at 96°C for 30 minutes. The silica concentration in the resulting solution was 62 g / L. Then, sulfuric acid with the concentration described above was added until the pH of the solution was 3, in order to obtain a semi-fluid silica paste. Subsequently, the precipitated silica G was obtained by the same method as in Production Example A. Examples 1 to 7 and Comparative Examples 1 to 2 The rubber compositions comprising rubber components and composition ingredients of the species and proportions shown in Table 1 were prepared according to an ordinary method using precipitated silicas A to G produced respectively in Production Examples A to G in Examples 1 to 7, Nipsil AQ, manufactured by Tosoh Silica Corporation in Comparative Example 1, and ULTRASIL VN2, manufactured by Degussa AG in Comparative Example 2. The physical properties of the precipitated silica and vulcanized rubber used in the respective examples are shown in Table 2. Table 1 Mixture composition Parts by mass SBR*1 BR*2 *3 Carbon black Precipitated silica*4 Organic silicon Stearic acid Antioxidant 6C*6 Zinc oxide Vulcanization accelerator DGP*7 96.25 30 15 65 5.2 2 1.5 3 0.5 21 / 22 Vulcanization accelerator NS*8 1 Sulfur 1.5 Notes: * 1: SBR #120 (manufactured by JSR Corporation); subjected to an oil extension by an aromatic oil of 37.5 parts by mass based on 100 parts by mass of the rubber component * 2: BR 150L (manufactured by Ube Industries, Ltd.) * 3: Seast KH (N339) (manufactured by Tokai Carbon Co., Ltd.) * 4: described in Production Examples A to G for precipitated silica * 5: Silane coupling agent Si75 (manufactured by Degussa Ag.) * 6: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine * 7: Diphenylguanidine * 8: Nt-butyl-2-benzothiazylsulfenamide Table 2 Example Comparative Example 1 2 3 4 5 6 7 1 2 Precipitated silica species ABCDEFG Nipsil AQ ULTRSIL CTAB (m2 / g) Particle distribution diameter 112 134 157 127 172 210 80 147 105 Aac (nm) -0.76 X CTAB 208 178 158 192 149 125 213 35 74 + 274 189 172 155 177 143 114 212 162 194 Loss on ignition - 2.6 2.6 2.1 2.2 2.9 2.9 2.8 2.3 3.3 22 / 22 Heat loss (% by mass) Low heat accumulation (index) 125 116 113 118 117 111 128 100 117 Abrasion resistance 112 109 109 114 116 123 101 100 85 The relationship between the CTAB of the precipitated silicas used in the examples and in the comparative examples and the acoustic particle size distribution diameters 5 Aa is shown by a graph in Figure 1. It can be seen that, in the precipitated silicas used in the examples, Aa is in a higher position than the straight line of Y (Aac) = -0.76 x (CTAB) + 274 and satisfies equation (I) described above and that, on the other hand, the precipitated silicas used in the examples have a smaller Aac. Furthermore, it can be seen from the results shown in Table 2 that, in the precipitated silica used in the examples, the difference between the loss on ignition and the loss on heating also satisfies equation 15 (II) described above. Rubber compounds in which low heat buildup and abrasion resistance are well balanced and improved were obtained using the precipitated silica described above.
Claims
1. Rubber composition composed of precipitated silica, characterized in that, in the precipitated silica, a specific surface area for adsorption of cetyltrimethylammonium bromide (CTAB) (m2 / g) and mode Aac (mm) in primary aggregate diameters determined by an acoustic particle size distribution measurement satisfy equation (I) shown below: 1000 > Aac > -0.76 X (CTAB) + 274 (I) wherein: Aac is 158 nm or more; and a loss of ignition and a loss of heat satisfy equation (II) shown below: 2.1% (by mass) ^ (loss of ignition) - (loss of heating) ^ 3% (by mass) (II), the loss of ignition being % mass reduction when heated at 750 °C for 3 hours and the loss of heating is the % mass reduction when heated at 105 °C for 2 hours.
2. Rubber composition according to claim 1, characterized in that the precipitated silica has a CTAB of 50 to 250 m2 / g.
3. Rubber composition, according to any one of claims 1 or 2, characterized in that the rubber component is at least one rubber selected from natural rubber and / or diene-based synthetic rubber, and the precipitated silica is composed in an amount of 10 to 150 parts by mass based on 100 parts by mass of the rubber component.
4. Rubber composition, according to any one of claims 1 to 3, characterized in that a silane coupling agent is composed in a proportion of 1 to 20% by mass based on a combination amount of precipitated silica. Petition 870190003962, dated 14 / 01 / 2019, pp. 13 / 15 2 / 3 5. Rubber composition according to claim 4, characterized in that the silane coupling agent is at least one selected from the group consisting of: a compound represented by formula (III) shown below: AmB3-mSi-(CH2)a-Sb-(CH2)a-SiAmB3-m (III) wherein A is CnH2n+1O (n is an integer from 1 to 3) or a chlorine atom; B is an alkyl group having from 1 to 3 carbon atoms; m is an integer from 1 to 3; a is an integer from 1 to 9; b is an integer of 1 or more and may have distribution; with the condition that when m is 1, two B may be the same or different and that when m is 2 or 3, two or three A may be the same or different; a compound represented by formula (IV) shown below: AmB3-mSi-(CH2)cY (IV) where A is CnH2n+1O (n is an integer from 1 to 3) or a chlorine atom; B is an alkyl group having from 1 to 3 carbon atoms; Y is a mercapto group, a vinyl group, an amino group, a glycidoxyl group or an epoxy group;m is an integer from 1 to 3; c is an integer from 0 to 9; with the condition that when m is 1, two B can be the same or different and that when m is 2 or 3, two or three A can be the same or different; and a compound represented by the formula (V) shown below: AmB3-mSi-(CH2)a-Sb-Z (V) wherein A is CnH2n+1O (n is an integer from 1 to 3) or a chlorine atom; B is an alkyl group having 1 to 3 carbon atoms; Z is a benzothiazolyl group, an N,N-dimethylthiocarbamoyl group or a methacryloyl group; m is an integer from 1 to 3; a is an integer from 1 to 9; b is an integer of 1 or more and can have distribution; with Petition 870190003962, of 14 / 01 / 2019, page. 14 / 15 3 / 3 condition that when m is 1, two B can be the same or different, and that when m is 2 or 3, two or three A can be the same or different.
6. Rubber composition, according to any one of claims 1 to 5, characterized in that carbon black is added as a reinforcing filler in an amount of 80 parts by mass or less based on 100 parts by mass of the rubber component, and a total combined amount of carbon black and precipitated silica being 120 parts by mass or less.
7. Tire characterized by being prepared by applying the rubber compound as described in any of claims 1 to 6 to any rubber members of the tire.