Rubber composition for pneumatic tires and pneumatic tire

Abstract

To provide a rubber composition for pneumatic tires which contains sustainable recycled process oil and can serve as a raw material of a vulcanized rubber having excellent rupture strength and low tanδ.SOLUTION: Provided is a rubber composition for pneumatic tires containing recycled process oil, wherein the recycled process oil has a kinematic viscosity of 5 mm2 / s or more as measured at 100°C. It is preferred that the recycled process oil has a number average molecular weight of 500 and a weight average molecular weight of 600 or more. It is preferred that the recycled process oil contains 50% or more of a paraffin component and has a flash point of 250°C or higher. It is preferred that the recycled process oil has a glass transition point of higher than -80°C. It is preferred that the recycled process oil is derived from compressor operating oil.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition for a pneumatic tire and a pneumatic tire. [Background technology]

[0002] The majority of the materials constituting pneumatic tires are vulcanized rubber, which is produced by vulcanizing and molding a rubber composition for pneumatic tires obtained by kneading and mixing fillers, sulfur, and the like with a rubber component. Conventionally, when mixing compounding agents such as fillers into the rubber component, process oils are often used to lubricate the kneading. However, from the perspective of sustainable material substitution, many attempts have been made to replace process oils produced from petroleum with vegetable oils, etc.

[0003] In the following Patent Document 1, the kinetic viscosity at 75°C is 5mm 2 / s or more 100mm 2 The document describes a process oil having a viscosity specific gravity constant of 0.700 or more and 0.900 or less, an absorbance at 198 nm of more than 3 and 3.6 or less, an absorbance at 228 nm of 1.6 or more and 3.5 or less, and an aniline point of 100°C or more and 200°C or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7061942 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology described in Patent Document 1 aims to achieve both weather resistance and bleeding resistance, but uses process oil produced from petroleum as is, and there is room for improvement from a sustainability perspective.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a rubber composition for pneumatic tires that contains sustainable recycled process oil and that serves as a raw material for vulcanized rubber that has excellent breaking strength and low tan δ. [Means for solving the problem]

[0007] The above problem can be solved by the following configuration. That is, the present invention is a rubber composition for pneumatic tires containing recycled process oil, wherein the recycled process oil has a kinetic viscosity of 5 mm when measured at 100°C. 2 / s or more.

[0008] In the rubber composition for pneumatic tires (1), the recycled process oil preferably has a number average molecular weight of 500 and a weight average molecular weight of 600 or more.

[0009] In the rubber composition for pneumatic tires (1) or (2), the recycled process oil is preferably a rubber composition for pneumatic tires (3) having a paraffin content of 50% or more and a flash point of 250° C. or more.

[0010] In any one of the rubber compositions for pneumatic tires (1) to (3), the recycled process oil is preferably a rubber composition for pneumatic tires (4) having a glass transition point higher than -80°C.

[0011] In any one of the rubber compositions for pneumatic tires (1) to (4), the recycled process oil is preferably a rubber composition for pneumatic tires (5) that is derived from compressor hydraulic oil.

[0012] The present invention also relates to a pneumatic tire (6) comprising at least a vulcanized rubber of any one of the rubber compositions for pneumatic tires (1) to (5). Effect of the Invention

[0013] As mentioned above, from the viewpoint of sustainable material substitution, many attempts have been made to replace process oils produced from petroleum with vegetable oils, etc. However, rubber compositions for pneumatic tires using vegetable oils have significantly lower unvulcanized rubber properties and vulcanized properties than conventional process oils, so the reality is that substitution has not progressed very far. The main reason for this is thought to be the significant difference in composition between vegetable oils, which are composed of triglycerides, and process oils, which are composed of hydrocarbons such as paraffin.

[0014] Therefore, the present inventors focused on recycled process oil produced by subjecting used process oil to a recycling process, and conducted extensive research into a rubber composition for pneumatic tires that contains recycled process oil, which can suppress the deterioration of the physical properties of the finally obtained vulcanized rubber, compared to unused process oil. As a result, (i) a kinetic viscosity measured at 100°C of 5 mm 2 The present inventors have found that a rubber composition for pneumatic tires containing recycled process oil with a molecular weight of 100 / s or more can be used as a raw material for vulcanized rubber having excellent breaking strength and low tan δ, even when compared with a rubber composition for pneumatic tires containing unused process oil.

[0015] In the present invention, the regenerated process oil is (ii) Reclaimed process oil having a number average molecular weight of 500 and a weight average molecular weight of 600 or more; (iii) Reclaimed process oil having a paraffin content of 50% or more and a flash point of 250°C or more; (iv) Reclaimed process oil having a glass transition temperature greater than -80°C; When compounded with a rubber composition for a pneumatic tire, it is preferable because it can become a raw material for vulcanized rubber having excellent breaking strength and low tan δ.

[0016] In the present invention, the regenerated process oil is particularly (v) Reclaimed process oils derived from compressor hydraulic fluids; When the rubber composition for a pneumatic tire is blended with the above-mentioned terpolymer, it is more preferable since it can become a raw material for a vulcanized rubber having an even more excellent breaking strength and an even lower tan δ. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The rubber composition for pneumatic tires according to the present invention contains recycled process oil. In the present invention, recycled process oil means a process oil obtained by recycling process oil used as industrial lubricant at least once. Examples of industrial lubricant oil include compressor working oil used for the purpose of suppressing wear and cooling during compressor operation, electrical insulating oil that plays a role in insulating and cooling electrical equipment such as transformers, cables, and capacitors, and metal processing oil used for the purpose of suppressing friction and cooling during cutting of metals. In particular, in the present invention, when recycled process oil derived from compressor working oil produced by recycling compressor working oil is blended into the rubber composition for pneumatic tires, it is more preferable because it can become a raw material for vulcanized rubber having excellent breaking strength and lower tan δ.

[0018] The regenerated process oil can be produced, for example, by subjecting the above-mentioned used industrial lubricating oil to regeneration treatments such as dehydration, removal of oxides, and filtration. In the present invention, the regenerated process oil may contain an antioxidant, for example, by being added during the regeneration treatment.

[0019] The kinetic viscosity when measured at 100°C is 5mm 2 When recycled process oil having a kinetic viscosity of 10 mm / s or more is blended into a rubber composition for pneumatic tires, the resulting vulcanized rubber has excellent breaking strength and can be used as a raw material for vulcanized rubber having a low tan δ. 2 / s or more, and the kinematic viscosity of the recycled process oil used is 15 mm when measured at 100 °C. 2 / s or more, it is more preferable because it is possible to produce a vulcanized rubber having even better breaking strength and even lower tan δ. The method for measuring the kinetic viscosity of the recycled process oil will be described later.

[0020] In the present invention, the regenerated process oil is (ii) Reclaimed process oil having a number average molecular weight of 500 and a weight average molecular weight of 600 or more; (iii) Reclaimed process oil having a paraffin content of 50% or more and a flash point of 250°C or more; (iv) Reclaimed process oil having a glass transition temperature greater than -80°C; When blended with a rubber composition for pneumatic tires, it is preferable because it can be a raw material for vulcanized rubber with excellent breaking strength and low tan δ. The method for measuring the number average molecular weight and weight average molecular weight of the recycled process oil, the component ratio of paraffin components in the oil, the flash point, and the glass transition point will be described later.

[0021] From the viewpoint of producing a vulcanized rubber having excellent breaking strength and low tan δ, the content of the recycled process oil to be blended in the rubber composition for a pneumatic tire according to the present invention is preferably 1 to 20 parts by mass, and more preferably 10 to 20 parts by mass, when the total amount of the rubber components is 100 parts by mass.

[0022] The rubber composition for pneumatic tires according to the present invention contains a diene rubber as a rubber component in addition to the recycled process oil. Examples of the diene rubber include emulsion-polymerized polystyrene butadiene rubber (hereinafter also referred to as "E-SBR") obtained by emulsion polymerization (radical polymerization) in water and solution-polymerized polystyrene butadiene rubber (hereinafter also referred to as "S-SBR"), natural rubber, isoprene rubber, butadiene rubber, and the like.

[0023] The rubber composition for pneumatic tires according to the present invention may contain carbon black as a filler. Carbon black may be, for example, SAF, ISAF, HAF, FEF, GPF, or other carbon blacks commonly used in the rubber industry, as well as conductive carbon blacks such as acetylene black and ketjen black. The rubber composition for pneumatic tires according to the present invention preferably contains 1 to 60 parts by mass, and more preferably 30 to 60 parts by mass, of carbon black when the total amount of the rubber components is taken as 100 parts by mass.

[0024] It is also preferable to contain silica as a filler. As the silica, wet silica, dry silica, sol-gel silica, surface-treated silica, etc., which are generally used for rubber reinforcement, are used. Among them, wet silica is preferable. When the total amount of the rubber component is 100 parts by mass, it is preferable to compound 1 to 150 parts by mass of silica, and more preferably 50 to 100 parts by mass.

[0025] When silica is contained as a filler, it is also preferable to contain a silane coupling agent together. The silane coupling agent is not particularly limited as long as it contains sulfur in the molecule, and various silane coupling agents that are compounded together with silica in rubber compositions can be used. Examples of the silanes include sulfide silanes such as bis(3-triethoxysilylpropyl)tetrasulfide (e.g., "Si69" manufactured by Degussa), bis(3-triethoxysilylpropyl)disulfide (e.g., "Si75" manufactured by Degussa), bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, and bis(2-trimethoxysilylethyl)disulfide; mercaptosilanes such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropyldimethylmethoxysilane, and mercaptoethyltriethoxysilane; and protected mercaptosilanes such as 3-octanoylthio-1-propyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane. The amount of the silane coupling agent blended is preferably 1 to 20 parts by mass, and more preferably 1 to 10 parts by mass, per 100 parts by mass of silica.

[0026] The rubber composition for pneumatic tires according to the present invention can contain, in addition to diene rubber, recycled process oil, carbon black, silica and a silane coupling agent, vulcanization compounding agents, antioxidants, stearic acid, softeners such as wax and oil, processing aids and the like.

[0027] As the age resistor, age resistors generally used for rubber, such as aromatic amine-based age resistors, amine-ketone-based age resistors, monophenol-based age resistors, bisphenol-based age resistors, polyphenol-based age resistors, dithiocarbamate-based age resistors, and thiourea-based age resistors, may be used alone or in appropriate mixtures.

[0028] Examples of vulcanization compounding agents include vulcanizing agents such as sulfur and organic peroxides, vulcanization accelerators, vulcanization acceleration assistants, and vulcanization retarders.

[0029] The sulfur as a vulcanization compounding agent may be any ordinary rubber sulfur, such as powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur, etc. Considering the rubber physical properties and durability after vulcanization, the amount of sulfur is preferably 1 to 10 parts by mass, more preferably 1 to 5 parts by mass, calculated as the sulfur content, when the total amount of the rubber components is 100 parts by mass.

[0030] As the vulcanization accelerator, those vulcanization accelerators usually used for rubber vulcanization, such as sulfenamide-based vulcanization accelerators, thiuram-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiourea-based vulcanization accelerators, guanidine-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators, may be used alone or in appropriate mixtures.

[0031] The rubber composition for pneumatic tires according to the present invention can be obtained by kneading diene rubber, recycled process oil, carbon black, silica, and a silane coupling agent, as well as vulcanization compounding agents, antioxidants, stearic acid, softeners such as wax and oil, processing aids, and the like, using a kneading machine typically used in the rubber industry, such as a Banbury mixer, kneader, or roll.

[0032] The method for compounding each of the above components is not particularly limited, and may be any of a method in which the compounding components other than the vulcanization compounding agents such as the sulfur-based vulcanizing agent and the vulcanization accelerator are previously mixed to prepare a master batch, and the remaining components are added and further kneaded, a method in which the components are added in any order and kneaded, and a method in which all the components are added simultaneously and kneaded.

[0033] The rubber composition for pneumatic tires according to the present invention contains sustainable recycled process oil, and is therefore useful for pneumatic tire applications that are environmentally conscious. Furthermore, a pneumatic tire that includes at least a vulcanized rubber of the rubber composition for pneumatic tires according to the present invention is excellent in breaking strength and low tan δ in addition to sustainability. Therefore, the rubber composition for pneumatic tires according to the present invention is particularly useful for pneumatic tire tread applications. EXAMPLES

[0034] Examples specifically illustrating the configuration and effects of the present invention will be described below. The evaluation items in the examples were evaluated based on the following evaluation conditions for the rubber samples obtained by heating and vulcanizing each rubber composition at 160°C for 20 minutes.

[0035] (Breaking strength of vulcanized rubber) A tensile test (dumbbell No. 3) was carried out in accordance with JIS K6251 to measure the breaking strength of the vulcanized rubber. The evaluation was expressed as an index with the value of Comparative Example 1 set to 100 for Comparative Examples 2-3 and Example 1, an index with the value of Comparative Example 4 set to 100 for Comparative Examples 5-6 and Example 2, and an index with the value of Comparative Example 7 set to 100 for Comparative Examples 8-9 and Example 3. A larger value indicates better breaking strength of the vulcanized rubber.

[0036] (tan δ of vulcanized rubber) For each measurement sample obtained by molding the vulcanized rubber into a predetermined shape, the storage modulus (E') and loss modulus (E") were measured using a dynamic viscoelasticity measuring device (product name "Fully Automatic Viscoelasticity Analyzer VR-7110", manufactured by Ueshima Seisakusho Co., Ltd.), and tan δ at 0°C was determined. The evaluation was expressed as an index with the value of Comparative Example 1 set to 100 for Comparative Examples 2-3 and Example 1, an index with the value of Comparative Example 4 set to 100 for Comparative Examples 5-6 and Example 2, and an index with the value of Comparative Example 7 set to 100 for Comparative Examples 8-9 and Example 3. The larger the value, the lower the tan δ of the vulcanized rubber and the more excellent the fuel efficiency when made into a pneumatic tire. The measurement conditions are as follows: Measurement sample size: length 40mm, width 3mm, thickness 2mm Measurement mode: Tensile mode Measurement temperature: 0℃, 60℃ Frequency: 100Hz Dynamic Distortion: 0.15%

[0037] (Recycled Process Oil) The following three types of regenerated process oil were prepared: Regenerated process oil 1: Compressor hydraulic oil used for purposes such as reducing wear and cooling during compressor operation has been regenerated through processes such as dehydration, removal of oxides, and filtration. Contains antioxidants. Regenerated Process Oil 2: Electrical insulating oil that serves as insulation and cooling for electrical equipment such as transformers, cables, and capacitors, which has been regenerated through processes such as dehydration, oxide removal, and filtration. Regenerated process oil 3: Metalworking oil used for purposes such as reducing friction and cooling when cutting metals, etc., which has been regenerated through processes such as dehydration, oxide removal, and filtration.

[0038] The kinematic viscosity, number average molecular weight, weight average molecular weight, composition of paraffin components in the process oil, flash point, and glass transition point of the above-mentioned regenerated process oils 1 to 3 and unused process oil 1 (product name "Process P200", manufactured by JX Nippon Oil & Energy Corporation) were measured by the following methods.

[0039] (Kinematic viscosity of recycled process oil) Kinematic viscosity (mm) at 100℃ and 40℃ according to JIS K2283 2 / s) was measured. (Number average molecular weight (Mn) and weight average molecular weight (Mw) of recycled process oil) The number average molecular weight and the weight average molecular weight were measured by GPC under the following conditions: Column temperature: 40℃ Mobile phase: Tetrahydrofuran Flow rate: 1.0ml / min Column: Plgel 5μ500Å+100Å+50Å(3 columns) Injection volume: 40μL Sample concentration: 2g / L Detector: RI (Amount of paraffin in recycled process oil) The calculation was performed according to the Kurtz method described in Journal of the Society of Rubber Science and Technology of Japan, Vol. 50, No. 10 (1977). (Flash point of regenerated process oil) Measurements were performed in accordance with JIS K2283. (Glass transition temperature of recycled process oil (Tg(℃))) The measurements were performed using a differential scanning calorimeter [DSC] (product name: X-DSC 7000, manufactured by Hitachi High-Tech Science Corporation) at a heating rate of 20° C. / min.

[0040] Table 1 shows the physical properties of the regenerated process oils 1 to 3 and the virgin process oil 1.

[0041] [Table 1]

[0042] (Preparation of Rubber Composition for Pneumatic Tires) According to the compounding recipe in Table 1-3, the rubber compositions of Examples 1-3 and Comparative Examples 1-9 were compounded and kneaded using a normal Banbury mixer to prepare a rubber composition for a pneumatic tire. Each compounding ingredient listed in Table 1-3 is shown below (in Table 1-4, the compounding amount of each compounding ingredient is shown in parts by mass relative to 100 parts by mass of the rubber component).

[0043] SBR (E-SBR (emulsion polymerized SBR)): Product name "SBR1502" (manufactured by ENEOS Materials Co., Ltd.) ·NR (natural rubber): STR20 BR (high cis 1,4-polybutadiene): Product name "BR1280" (manufactured by LG Chem, Ltd.) Carbon black (CB) (HAF): Product name "N339 Seast KH" (manufactured by Tokai Carbon Co., Ltd.) Silica: Product name "Nipsil AQ" (manufactured by Tosoh Corporation) Silane coupling agent: Product name "Si69" (manufactured by Degussa) Wax: Product name "OZOACE0355" (manufactured by Nippon Seiro Co., Ltd.) Stearic acid: Trade name "Lunac S-20" (manufactured by Kao Corporation) Zinc oxide: Product name "Zinc oxide type 2" (manufactured by Mitsui Mining & Smelting Co., Ltd.) Anti-aging agent: Product name "Nocrac 6C" (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Vulcanization accelerator 1: Product name "Noccelaer D" (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Vulcanization accelerator 2: Trade name "Sokushinol CZ" (manufactured by Sumitomo Chemical Co., Ltd.) Sulfur: Product name: Powdered sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0044] [Table 2]

[0045] From the results in Table 2, in the rubber composition for pneumatic tires containing 100 parts by mass of SBR as a rubber component, the vulcanized rubber of Example 1 containing recycled process oil 1 had improved breaking strength and tan δ compared to the vulcanized rubber of Comparative Example 1 containing unused process oil. On the other hand, the vulcanized rubber of Comparative Example 3 containing recycled process oil 2 had improved breaking strength but worsened tan δ compared to the vulcanized rubber of Comparative Example 1 containing unused process oil. In addition, the vulcanized rubber of Comparative Example 2 containing recycled process oil 3 had worse breaking strength and tan δ compared to the vulcanized rubber of Comparative Example 1 containing unused process oil.

[0046] [Table 3]

[0047] From the results in Table 3, in the rubber composition for pneumatic tires containing 50 parts by mass of SBR and 50 parts by mass of NR as the rubber components, the vulcanized rubber of Example 2 containing recycled process oil 1 had improved breaking strength and tan δ compared to the vulcanized rubber of Comparative Example 1 containing unused process oil. On the other hand, the vulcanized rubber of Comparative Example 6 containing recycled process oil 2 and the vulcanized rubber of Comparative Example 5 containing recycled process oil 3 had improved breaking strength but worsened tan δ compared to the vulcanized rubber of Comparative Example 1 containing unused process oil.

[0048] [Table 4] From the results in Table 4, in the rubber composition for pneumatic tires containing 50 parts by mass of SBR and 50 parts by mass of BR as the rubber components, the vulcanized rubber of Example 3 containing recycled process oil 1 had improved breaking strength and tan δ compared to the vulcanized rubber of Comparative Example 1 containing unused process oil. On the other hand, the vulcanized rubber of Comparative Example 9 containing recycled process oil 2 and the vulcanized rubber of Comparative Example 8 containing recycled process oil 3 had deteriorated breaking strength and tan δ compared to the vulcanized rubber of Comparative Example 1 containing unused process oil.

Claims

1. A rubber composition for pneumatic tires containing recycled process oil, The regenerated process oil has a kinetic viscosity of 5 mm when measured at 100°C. ２ / s or more.

2. 2. The rubber composition for a pneumatic tire according to claim 1, wherein the recycled process oil has a number average molecular weight of 500 and a weight average molecular weight of 600 or more.

3. 2. The rubber composition for a pneumatic tire according to claim 1, wherein the recycled process oil has a paraffin content of 50% or more and a flash point of 250° C. or more.

4. The rubber composition for pneumatic tires according to claim 1, wherein the recycled process oil has a glass transition point higher than -80°C.

5. The rubber composition for a pneumatic tire according to claim 1 , wherein the recycled process oil is a recycled process oil derived from compressor hydraulic oil.

6. A pneumatic tire comprising at least a vulcanized rubber of the rubber composition for pneumatic tires according to claim 1.

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