JP7069752B2 - Rubber composition for tires and tires - Google Patents

Description

The present invention relates to a tire rubber composition and a tire having a tire member composed of the tire rubber composition.

In recent years, the characteristics required for automobile tires have become diverse, and among them, the demand for low fuel consumption is increasing for the purpose of saving fuel consumption of automobiles due to the social demand for energy saving. High-load tires mounted on trucks and buses are required to have high fracture resistance so that they can withstand use under harsh conditions, and natural rubber is often used. Even in such tires, The demand for low fuel consumption is increasing.

A technique for blending silica or the like with a rubber composition for a tire is known in order to improve fuel efficiency, but the blending of silica causes problems such as a decrease in vulcanization rate (vulcanization delay) and deterioration of silica dispersibility. Occurs.

It is known that a predetermined amine-added salt or the like is added in order to suppress the vulcanization delay (Patent Document 1).

Japanese Unexamined Patent Publication No. 2001-139727

However, the addition of the amine-added salt of Patent Document 1 has a problem that the scorch time is shortened and the molding processability is deteriorated.

In the present invention, a rubber composition containing natural rubber as a main rubber component and containing silica is excellent in low fuel consumption and breaking strength, and further has molding processability (securing molding time) and vulcanization rate (vulcanization time). It is an object of the present invention to provide a rubber composition for a tire that also achieves (shortening), and to provide a tire having a tire member composed of the rubber composition.

As a result of diligent studies, the present inventor has made a rubber composition containing silica with respect to a rubber component containing 50% by mass or more of natural rubber, styrene-butadiene rubber and butadiene rubber, thereby further containing aminoguanidine weak acid salt. We have found that the problem can be solved, and after further studies, we have completed the present invention.

That is, the present invention
[1] A rubber composition for a tire, which comprises 50% by mass or more of natural rubber, a rubber component containing styrene-butadiene rubber and butadiene rubber, silica, and a weak acid salt of aminoguanidine.
[2] The rubber composition for a tire according to the above [1], wherein the aminoguanidine weak acid salt is at least one selected from the group consisting of aminoguanidine bicarbonate and aminoguanidine phosphate.
[3] The rubber composition for a tire according to the above [1] or [2], wherein the content of the weak acid salt of aminoguanidine is 0.01 to 10 parts by mass with respect to 100 parts by mass of the rubber component.
[4] The rubber composition for a tire according to any one of [1] to [3] above, wherein the content of silica is 5 parts by mass or more with respect to 100 parts by mass of the rubber component.
[5] The rubber composition for a tire according to any one of the above [1] to [4], wherein the content of styrene-butadiene rubber in the rubber component is 5% by mass or more.
[6] The rubber composition for a tire according to any one of the above [1] to [5], further comprising carbon black.
[7] A tire having a tire member composed of the rubber composition for a tire according to any one of the above [1] to [6].
Regarding.

According to the present invention, it is possible to provide a rubber composition for a tire which is excellent in fuel efficiency and breaking strength, and also has both molding processability (securing of molding time) and vulcanization speed (shortening of vulcanization time). And, it is possible to provide a tire having a tire member composed of this rubber composition.

One embodiment is a rubber composition for a tire, which comprises 50% by mass or more of natural rubber, a rubber component containing styrene-butadiene rubber and butadiene rubber, silica, and a weak acid salt of aminoguanidine.

Another embodiment is a tire having a tire member made of the rubber composition for a tire.

Although not intended to be bound by theory, the following can be considered as a mechanism for obtaining a predetermined effect in the present embodiment. That is, silica can improve fuel efficiency and fracture strength, but on the other hand, its silanol group adsorbs a vulcanization accelerator, so that the vulcanization time tends to be too long. However, when aminoguanidine weak acid salt (carbonate, phosphate) is added, the increase in vulcanization time is suppressed even when silica is blended, and as a result, fuel efficiency, breaking strength, and molding processability (molding) are suppressed. It is considered that (securing time) and vulcanization rate (shortening of vulcanization time) will be improved in a well-balanced manner. Also, due to its strong polarity, aminoguanidine not only aids in the dispersion of silica, but also aids in the hydrolysis reaction of the coupling agent, resulting in higher silica-polymer reactivity, through which It is presumed that the improvement of the dispersibility of silica will be achieved and the fuel efficiency will be realized. Furthermore, the improvement of the reactivity between silica and polymer by aminoguanidine leads to the reinforcement of the interface between the styrene-butadiene rubber and the other rubbers, and it is considered that the strength is further improved.

<Rubber component>
In the present embodiment, the rubber component contains natural rubber (NR), styrene-butadiene rubber (SBR) and butadiene rubber (BR). The rubber component may contain rubber other than these, and the rubber is not particularly limited, and any rubber conventionally used in the tire industry can be preferably used. Examples of the rubber component that can be contained in addition to NR, SBR and BR include isoprene-based rubber containing polyisoprene rubber (IR), styrene isoprene rubber (SIR), styrene isoprene butadiene rubber (SIBR), and chloroprene rubber (CR). Diene rubber such as acrylonitrile butadiene rubber (NBR), halogenated butyl rubber containing butyl rubber (IIR), brominated butyl rubber (Br-IIR), chlorinated butyl rubber (Cl-IIR) and fluorinated butyl rubber (F-IIR), etc. Butyl rubber can be mentioned. These rubber components other than NR, SBR and BR may be used alone or in combination of two or more.

(Natural rubber)
The NR is not particularly limited, and for example, general ones (non-modified NR) in the tire industry such as SIR20, RSS # 3, and TSR20 can be used, as well as epoxidized natural rubber (ENR) and hydrogenation. Modified natural rubber such as natural rubber (HNR), grafted natural rubber, deproteinized natural rubber (DPNR), and high-purity natural rubber can also be used.

The content of NR in the rubber component is 50% by mass or more. The rubber component of the present invention contains NR as a main component in the rubber component so that it can exhibit sufficient fracture resistance even when used as a tire for a high load vehicle. The content of NR is preferably 51% by mass or more, more preferably 52% by mass or more, more preferably 53% by mass or more, still more preferably 54% by mass or more, still more preferably 55% by mass or more. Further, from the viewpoint of fuel efficiency, the content is preferably 80% by mass or less, more preferably 75% by mass or less, more preferably 70% by mass or less, more preferably 65% by mass or less, and more preferably 60% by mass or less. More preferred.

(Styrene butadiene rubber)
The SBR is not particularly limited, and is, for example, an unmodified emulsified polymerized styrene-butadiene rubber (E-SBR), a solution-polymerized styrene-butadiene rubber (S-SBR), and a modified modified emulsified styrene-butadiene rubber (modified E-SBR). ) And modified SBR such as modified solution-polymerized styrene-butadiene rubber (modified S-SBR). Examples of the modified SBR include modified SBRs having modified terminals and / or main chains, modified SBRs coupled with tin, silicon compounds and the like (condensates, those having a branched structure, etc.) and the like. Further, as the SBR, there are an oil-extending type in which the flexibility is adjusted by adding a spreading oil and a non-oil-extending type in which no extending oil is added, and both of them can be used. For example, those manufactured by JSR Corporation, those manufactured by Asahi Kasei Chemicals Co., Ltd., those manufactured by Nippon Zeon Corporation, and the like can be used.

The styrene content of SBR is preferably 15.0% by mass to 40.0% by mass. From the viewpoint of rubber strength and grip performance, the styrene content is preferably 20.0% by mass or more, more preferably 25.0% by mass or more, further preferably 30.0% by mass or more, and further preferably 35.0% by mass or more. preferable. The styrene content of SBR is preferably 39.0% by mass or less from the viewpoint of fuel efficiency. The styrene content of SBR is a value calculated by ¹ H-NMR measurement.

The vinyl content (1,2-bonded butadiene unit amount) of SBR is preferably 10.0 to 30.0%. The vinyl content is preferably 13.0% or more, more preferably 15.0% or more, from the viewpoint of rubber strength and grip performance. The vinyl content is preferably 25.0% or less, more preferably 20.0% or less, from the viewpoint of fuel efficiency. The vinyl content of SBR is a value measured by infrared absorption spectrum analysis.

When SBR is contained, the content in the rubber component is more preferably 5% by mass or more, more preferably 7% by mass or more, and more preferably 10% by mass or more because the effect of the present embodiment can be exhibited more satisfactorily. More preferred. The SBR content is preferably 30% by mass or less, preferably 25% by mass or less, and even more preferably 20% by mass or less. When an oil-extended type SBR is used as the SBR, the content of the SBR itself as a solid content contained in the oil-extended type SBR is defined as the content of the SBR in the rubber component.

(Butadiene rubber)
The BR is not particularly limited, and any BR usually used in this field can be preferably used. For example, high cis-1,4-polybutadiene rubber (high cis BR), rare earth butadiene rubber synthesized using a rare earth element catalyst (rare earth BR), and butadiene rubber containing 1,2-syndiotactic polybutadiene crystals (SPB). Various BRs such as contained BR) and modified butadiene rubber (modified BR) can be used. As such a BR, for example, one manufactured by Ube Kosan Co., Ltd., one manufactured by Nippon Zeon Co., Ltd., one manufactured by Lanxess Corporation, or the like can be preferably used.

High cis BR is a butadiene rubber having a cis-1,4 bond content of 90% by mass or more. Among them, those having a cis-1,4 bond content of 95% by mass or more, more preferably 96% by mass or more, further preferably 97% by mass or more, and 98% by mass or more. Is even more preferable. By containing HISIS BR, low temperature characteristics and wear resistance can be improved. The cis-1,4 bond content in BR is a value calculated by infrared absorption spectrum analysis.

The rare earth BR is synthesized using a rare earth element catalyst and has a vinyl content (1,2 bond butadiene unit amount) of 1.8% by mass or less, preferably 1.0% by mass or less, and more preferably 0.8. Those having a mass% or less and a cis content (cis-1,4 bond content) of 90% by mass or more, preferably 93% by mass or more, and more preferably 95% by mass or more can be preferably used. When the vinyl content and the cis-1,4 bond content are within the above ranges, the effect of excellent fracture elongation and wear resistance of the obtained rubber composition can be obtained. The vinyl content and cis content of the rare earth BR are values measured by infrared absorption spectrum analysis.

As the rare earth element catalyst used for the synthesis of the rare earth BR, a known one can be used, for example, a lanthanum series rare earth element compound, an organic aluminum compound, an aluminoxane, a halogen-containing compound, and a catalyst containing a Lewis base if necessary. Can be given.

Examples of the SPB-containing BR include those in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR, but are dispersed after being chemically bonded to BR. The complex elastic modulus tends to be improved because the crystals are chemically bonded to the rubber component and then dispersed.

Modified BRs include modified BRs with modified terminals and / or backbones, modified BRs coupled with tin, silicon compounds, etc. (condensates, those with a branched structure, etc.), and functional groups that interact with silica. Examples thereof include modified BR having a terminal and / or main chain modified by the above, particularly modified BR having at least one selected from the group consisting of a silyl group, an amino group, an amide group, a hydroxyl group, and an epoxy group. By using the modified BR, the effect of strengthening the interaction with the filler and excellent fuel efficiency can be obtained.

When BR is contained, the content in the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more from the viewpoint of wear resistance. The BR content is preferably 40% by mass or less, more preferably 35% by mass or less, still more preferably 30% by mass or less, from the viewpoint of molding processability.

<Silica>
The rubber composition for a tire according to the present embodiment is characterized by containing silica as a filler. By containing silica, the effect of improving fuel efficiency can be preferably obtained, and high reinforcing properties can be obtained.

Silica is generally difficult to disperse in a rubber composition, but according to the rubber composition containing the aminoguanidine weak acid salt of the present embodiment, it can be dispersed well and the excellent rubber performance is balanced. It can be expressed well.

The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), and the like, which are common in the tire industry, can be used. Of these, hydrous silica prepared by a wet method is preferable because it has a large number of silanol groups. Silica may be used alone or in combination of two or more.

The N ₂ SA of silica is preferably 70 m ² / g or more, more preferably 80 m ² / g or more, and even more preferably 90 m ² / g or more. The upper limit of N ₂ SA is not particularly limited, but from the viewpoint of ease of handling, for example, 500 m ² / g or less is preferable, 400 m ² / g or less is more preferable, and 300 m ² / g or less is preferable. More preferably, 280 m ² / g or less is more preferable, 250 m ² / g or less is more preferable, and 230 m ² / g or less is further preferable. By using silica within the above range for N ₂ SA, fuel efficiency and moldability can be improved in a well-balanced manner. The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica with respect to 100 parts by mass of the rubber component is preferably within a predetermined range from the viewpoint of silica dispersibility, fuel efficiency, moldability and the like, and is, for example, 5 to 50 parts by mass. The silica content is preferably 6 parts by mass or more, more preferably 7 parts by mass or more, more preferably 8 parts by mass or more, still more preferably 9 parts by mass or more, still more preferably 10 parts by mass or more. The silica content is preferably 45 parts by mass or less, more preferably 40 parts by mass or less, more preferably 35 parts by mass or less, still more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less.

<Other fillers>
As the filler, other fillers may be used in addition to silica. The filler is not particularly limited, and any filler generally used in this field such as carbon black, aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, talc, and clay is used. be able to. These fillers may be used alone or in combination of two or more. When a filler other than silica is used, carbon black is preferable from the viewpoint of rubber strength. That is, the filler preferably contains silica and carbon black, or is preferably composed only of silica and carbon black.

(Carbon black)
The carbon black is not particularly limited, and general ones in the tire industry such as GPF, FEF, HAF, ISAF, and SAF can be used.

The carbon black N ₂ SA is preferably 50 m ² / g or more, more preferably 70 m ² / g or more, still more preferably 90 m ² / g or more, from the viewpoint of obtaining sufficient reinforcing property and wear resistance. Further, carbon black N ₂ SA is preferably 500 m ² / g or less, more preferably 450 m ² / g or less, further preferably 300 m ² / g or less, and even more preferably 250 m ² from the viewpoint of excellent dispersibility and less heat generation. It is more preferably / g or less. The carbon black N ₂ SA is a value measured in accordance with JIS K 6217-2: 2001.

From the viewpoint of wear resistance, the DBP oil absorption amount of carbon black is preferably 50 ml / 100 g or more, and more preferably 100 ml / 100 g or more. Further, the DBP oil absorption amount of carbon black is preferably 250 ml / 100 g or less, more preferably 200 ml / 100 g or less, and more preferably 150 ml / 100 g or less from the viewpoint of grip performance. The amount of DBP oil absorbed by carbon black is a value measured according to JIS K 6217-4: 2008.

When carbon black is contained, the content of the rubber component with respect to 100 parts by mass is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and 15 parts by mass or more from the viewpoint of obtaining sufficient reinforcing property and abrasion resistance. Is more preferable, 20 parts by mass or more is more preferable, 25 parts by mass or more is more preferable, and 30 parts by mass or more is further preferable. The content of carbon black is preferably 80 parts by mass or less, preferably 75 parts by mass or less, preferably 70 parts by mass or less, and 65 parts by mass or less from the viewpoint of molding processability, low fuel consumption and wear resistance. It is preferably 60 parts by mass or less, preferably 55 parts by mass or less, preferably 50 parts by mass or less, preferably 45 parts by mass or less, and further preferably 40 parts by mass or less.

<Silane coupling agent>
Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. Examples of such a silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, and bis ( 3-Trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2- Triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxy) Cyrilbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, Bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, N- Dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl Silane coupling agents having sulfide groups such as tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-trimethoxysilylpropylmethacrylate monosulfide; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, silane coupling agent having a mercapto group such as NXT-Z100, NXT-Z45, NXT manufactured by Momentive; vinyltriethoxysilane, vinyltrimethoxysilane, etc. Sulfide coupling agent with vinyl group; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, A silane coupling agent having an amino group such as 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane; γ-glycidoxypropyltriethoxysilane, γ- Glycydoxy-based silane coupling agents such as glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane; 3-nitropropyltrimethoxysilane, 3-nitropropyl Nitro-based silane coupling agents such as triethoxysilane; chloro-based silanes such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane Coupling agent; etc. These silane coupling agents may be used alone or in combination of two or more. Of these, sulfide-based and mercapto-based materials are preferable because they have a strong bond with silica and are excellent in fuel efficiency. Further, it is preferable to use the mercapto system from the viewpoint that the fuel efficiency characteristics and the wear resistance can be suitably improved.

When the silane coupling agent is contained, the content with respect to 100 parts by mass of silica is more preferably 1.0 part by mass or more, and 2.0 parts by mass, because sufficient silica dispersibility and effects such as viscosity reduction can be obtained. More than parts by mass is more preferable, more than 4.0 parts by mass is more preferable, and more than 6.0 parts by mass is further preferable. Further, the content of the silane coupling agent is preferably 20.0 parts by mass or less, preferably 18.0 parts by mass or less, for the reason that a sufficient coupling effect and silica dispersion effect are efficiently obtained to ensure reinforcing property. Is more preferable, and 15.0 parts by mass or less is further preferable.

<Pimagedine weak acid salt>
The rubber composition for a tire according to the present embodiment is characterized by containing a weak acid salt of aminoguanidine.

In the present embodiment, the aminoguanidine weak acid salt is a salt composed of aminoguanidine and a weak acid, and the guanidine moiety of the aminoguanidine forms a salt with the weak acid. The aminoguanidine weak acid salt may be a salt consisting of one molecule of weak acid and one molecule of aminoguanidine, or may be a salt consisting of one molecule of weak acid and two molecules of aminoguanidine.

The aminoguanidine weak acid salt is not particularly limited as long as it can exhibit the effects of the present embodiment. As the weak acid used for the aminoguanidine weak acid salt, any organic acid or inorganic acid can be used, but an inorganic acid is preferable. Specific examples of the aminoguanidine weak acid salt include aminoguanidine bicarbonate composed of aminoguanidine and carbonic acid (aminoguanidine bicarbonate), aminoguanidine phosphate composed of aminoguanidine and phosphoric acid, and the like. Such aminoguanidine weak acid salt may be used alone or in combination of two or more. Among them, bicarbonate can exert the effect of the present embodiment better by containing aminoguanidine weak acid salt, has excellent fuel efficiency and breaking strength, and has both molding processability and brewing speed. It preferably contains at least one selected from the group consisting of aminoguanidine and aminoguanidine phosphate. Further, as the aminoguanidine weak acid salt, aminoguanidine bicarbonate is preferable, aminoguanidine phosphate is preferable, or aminoguanidine bicarbonate and aminoguanidine phosphate are preferable.

The aminoguanidine weak acid salt of the present embodiment can be obtained by a known method, and examples thereof include a method of mixing aminoguanidine bicarbonate and a weak acid. Commercially available products can be used for aminoguanidine bicarbonate and weak acid. For example, one manufactured by Tokyo Chemical Industry Co., Ltd. can be used.

The content of aminoguanidine weak acid salt with respect to 100 parts by mass of the rubber component is preferably 0.01 to 10 parts by mass. The content of the aminoguanidine weak acid salt is preferably 0.05 parts by mass or more, more preferably 0.10 parts by mass or more, more preferably 0.30 parts by mass or more, still more preferably 0.50 parts by mass or more. The content of the weak acid salt of aminoguanidine is preferably 9 parts by mass or less, more preferably 7 parts by mass or less, more preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and more preferably 2.5 parts by mass or less. It is preferably 2.0 parts by mass or less, and more preferably 2.0 parts by mass or less. Within such a range, the effect of the present embodiment can be more satisfactorily exhibited.

<Plasticizer>
The rubber composition for a tire according to the present embodiment may further contain a plasticizer.

The plasticizer is not particularly limited, and general plasticizers in the rubber industry and those used as softeners can be used, and are known as, for example, resins, oils, liquid polymers, and low-temperature plasticizers. Includes all. The plasticizer may be used alone or in combination of two or more. Among them, resins, oils, and liquid polymers are preferable, resins and oils are more preferable, and only resins and oils are more preferable, because the effects of the present embodiment can be more favorably exhibited.

(resin)
The resin is not particularly limited, and any resin usually used in the rubber industry can be preferably used. For example, a terpene resin, a hydrogenated terpene resin, a C5-C9 resin, and a styrene / α-methyl resin can be preferably used. Examples thereof include styrene copolymer resin, adhesive resin, crosslinkable resin, and compatible resin.

The softening point of these resins is preferably in the range of −20 to 180 ° C. from the viewpoint of preferably exerting the function as a plasticizer. The upper limit of the softening point is preferably 170 ° C. or lower, more preferably 150 ° C. or lower, and even more preferably 130 ° C. or lower. The lower limit of the softening point is preferably −10 ° C. or higher, more preferably −5 ° C. or higher. In the present specification, the softening point of the resin is the temperature at which the softening point defined in JIS K 6220-1 is measured by a ring-ball type softening point measuring device and the ball drops.

The weight average molecular weight (Mw) of these resins is preferably within a predetermined range from the viewpoint of obtaining good molding processability and ensuring rubber hardness. Specifically, Mw is preferably 120,000 or less, more preferably 10,000 or less, and even more preferably 5000 or less. Further, Mw is preferably 200 or more, more preferably 250 or more, further preferably 300 or more, still more preferably 350 or more. In the present specification, the resin Mw is a gel permeation chromatograph (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-manufactured by Tosoh Corporation. It is a value obtained by standard polystyrene conversion based on the measured value by M).

≪Styrene / α-methylstyrene copolymer resin≫
The styrene / α-methylstyrene copolymer resin is a resin obtained by polymerizing styrene and α-methylstyrene.

≪Hydrogenated terpene resin≫
The hydrogenated terpene-based resin is obtained by hydrogenating (hydrogenating) the terpene-based resin. The hydrogenation treatment to the terpene resin can be performed by a known method.

The hydrogenated terpene resin is not particularly limited, and is, for example, a polyterpene resin composed of at least one selected from terpene raw materials such as α-pinene, β-pinene, limonene, and dipentene, and a terpene compound and an aromatic compound as raw materials. Examples thereof include terpene-based resins such as aromatic-modified terpene resins and terpene phenolic resins made from terpene compounds and phenolic compounds, which have been subjected to hydrogenation treatment. Here, examples of the aromatic compound used as a raw material for the aromatic-modified terpene resin include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene, and examples of the phenolic compound used as a raw material for the terpene phenol resin include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples include phenol, bisphenol A, cresol, xylenol and the like.

≪Adhesive resin≫
The pressure-sensitive adhesive resin is usually an oligomer having a property of being compatible with a rubber component or at least semi-compatible with a rubber component and having a molecular weight of several hundred to several tens of thousands. By blending the adhesive resin, the adhesiveness (molding processability) of the unvulcanized product at the time of tire molding is improved. Here, the adhesive resin is not particularly limited, and any resin other than those described above, which is usually used in the rubber industry, can be preferably used, for example, a phenol-based resin, a Kumaron inden resin, and a terpene-based resin. Examples thereof include resins, styrene resins, acrylic resins, rosin-based resins, and dicyclopentadiene resins (DCPD resins). Examples of the phenolic resin include those manufactured by BASF and Taoka Chemical Industry Co., Ltd., and examples of the Kumaron Inden resin include those manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. and JXTG Energy Co., Ltd. As the styrene resin, for example, one manufactured by Arizona chemical can be used. As the terpene-based resin, for example, those manufactured by Arizona Chemical Co., Ltd., Yasuhara Chemical Co., Ltd., and the like can be used. As the rosin-based resin, for example, those manufactured by Harima Chemicals Co., Ltd., Arakawa Chemicals Co., Ltd., and the like can be used. Among them, it is preferable to use a phenol-based resin, a Kumaron inden resin, a terpene-based resin, and an acrylic resin because of their excellent grip performance.

≪Liquid resin≫
As the resin, a liquid resin (liquid resin) can be preferably used from the viewpoint of satisfactorily exerting the effect as a plasticizer. Here, the liquid resin means a resin that has not been cured at room temperature (25 ° C.).

As the liquid resin, for example, a liquid Kumaron indene resin, a liquid terpene resin, or the like can be preferably used. Of these, liquid Kumaron indene resin is preferable.

The liquid kumaron inden resin contains kumaron and inden as monomer components constituting the skeleton (main chain) of the resin. In addition, examples of the monomer component contained in the skeleton other than kumaron and indene include styrene, α-methylstyrene, methylindene, vinyltoluene and the like. The softening point of the liquid Kumaron inden resin is preferably −20 to 45 ° C. The upper limit is preferably 40 ° C. or lower, more preferably 35 ° C. or lower. The lower limit is preferably −10 ° C. or higher, more preferably −5 ° C. or higher. As the liquid kumaron indene resin, for example, one manufactured by Rutgers Chemicals can be preferably used.

(oil)
The oil is not particularly limited, and any oil usually used in the rubber industry can be preferably used, and examples thereof include process oils, vegetable oils and fats, and animal oils and fats. Examples of the process oil include paraffin-based process oils, naphthen-based process oils, and aromatic process oils. Vegetable oils and fats include castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut oil, rosin, pine oil, pineapple, tall oil, corn oil, rice oil, sesame oil, olive oil, sunflower. Examples include oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, safflower oil, and tung oil. Examples of animal fats and oils include oleyl alcohol, fish oil, and beef tallow. Of these, process oils are preferable because they are advantageous in processability, and process oils (low PCA content) having a low content of polycyclic aromatic compounds (PCA) are preferable because they reduce the burden on the environment. Process oil) is preferred.

Low PCA content process oils include Treated Distillate Aromatic Extract (TDAE), which is a re-extracted oil aromatic process oil, aroma substitute oil, which is a mixture of asphalt and naphthenic oil, and mild extraction solutions: MES. ), Heavy naphthenic oil, etc.

(Liquid polymer)
The liquid polymer is preferably a liquid polymer having a polystyrene-equivalent weight average molecular weight of 1.0 × 10 ³ to 2.0 × 10 ⁵ as measured by gel permeation chromatography (GPC). Within such a range, fracture characteristics, durability, and moldability tend to be well-balanced.

The liquid polymer is not particularly limited, and any one usually used in the rubber industry can be preferably used, and examples thereof include liquid SBR, liquid BR, liquid IR, and liquid SIR. Of these, it is particularly preferable to use liquid SBR because it can improve durability and grip performance in a well-balanced manner.

(Low temperature plasticizer)
The low-temperature plasticizer is not particularly limited, and any one usually used in the rubber industry can be preferably used. For example, dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA) can be used. ), Di2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), Dioctyl Sevacinate (DOS), Tributyl Phosphate (TBP), Trioctyl Phosphate (TOP), Triethyl Phosphate (TEP), Trimethyl Phosphate (TMP), Timidin Triphosphate (TTP), Tricrecil Phosphate (TPP) TCP), ester-based plasticizers such as trixylenyl phosphate (TXP), and the like. Among them, DOS and TOP are preferable from the viewpoint of the balance between the plastic effect and the wear resistance at low temperature, and DOS is preferable because it is excellent in fuel efficiency.

The freezing point of the low-temperature plasticizer is preferably −50 ° C. or lower, more preferably −70 ° C. or lower, from the viewpoint of a sufficient grip improving effect. Further, the lower limit of the freezing point of the low-temperature plasticizer is not particularly limited.

The viscosity of the low-temperature plasticizer at 25 ° C. is preferably 30 mPa · s or less, and more preferably 20 mPa · s or less, from the viewpoint of a sufficient grip improving effect. Further, the lower limit of the viscosity of the low temperature plasticizer is not particularly limited.

(Content)
The content of the plasticizer with respect to 100 parts by mass of the rubber component can be within a predetermined range from the viewpoint of fuel efficiency and wear resistance. The content of the plasticizer is, for example, preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more. The content of the plasticizer is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, further preferably 40 parts by mass or less, further preferably 30 parts by mass or less, still more preferably 20 parts by mass or less, and further preferably 10 parts by mass. Less than a portion is more preferable. The content of the plasticizer includes not only the oil component contained in the oil-extended rubber and the insoluble sulfur, but also the post-filled oil (an oil compounded separately from the oil component contained in the oil-extended rubber and the insoluble sulfur). ..

The content of the resin in the plasticizer is, for example, preferably 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 10 parts by mass or more. The content of the resin is, for example, preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less.

Of the plasticizers, the oil content is, for example, preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 10 parts by mass or more. The content of the oil is, for example, preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less.

<Other compounding agents>
In addition to the above-mentioned components, the rubber composition according to the present embodiment includes compounding agents generally used for producing the rubber composition, for example, zinc oxide, stearic acid, an antioxidant, a wax, a vulcanizing agent, and the like. A vulcanization accelerator or the like can be appropriately added.

(Anti-aging agent)
The anti-aging agent is not particularly limited, and any of those usually used in the rubber industry can be preferably used. For example, an amine / ketone-based anti-aging agent, an imidazole-based anti-aging agent, and an amine-based anti-aging agent can be used. , Phenolic anti-aging agents, sulfur-based anti-aging agents, phosphorus-based anti-aging agents and the like. The anti-aging agent may be used alone or in combination of two or more.

When the anti-aging agent is contained, the content of the rubber component with respect to 100 parts by mass is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more. The content of the antiaging agent is preferably 7 parts by mass or less, more preferably 5 parts by mass or less. Within such a range, the effect of the present embodiment can be more satisfactorily exhibited.

(wax)
The wax is not particularly limited, and any wax usually used in the rubber industry can be preferably used, and examples thereof include paraffin waxes manufactured by Nippon Seiro Co., Ltd. and Paramelt Co., Ltd. The wax may be used alone or in combination of two or more.

When wax is contained, the content of the rubber component with respect to 100 parts by mass is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and further preferably 1.2 parts by mass or more. Further, 3.0 parts by mass or less is preferable, 2.5 parts by mass or less is more preferable, and 2.0 parts by mass or less is further preferable. Within such a range, the effect of the present embodiment can be more satisfactorily exhibited.

(Vulcanizing agent)
The vulcanizing agent is not particularly limited, and known vulcanizing agents can be used, and examples thereof include sulfur, organic peroxides, resin vulcanizing agents, and metal oxides such as magnesium oxide. Of these, it is preferable to use sulfur. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur and the like, all of which are preferably used. The vulcanizing agent may be used alone or in combination of two or more.

When sulfur is contained as a vulcanizing agent, the content with respect to 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more. The sulfur content is preferably 7 parts by mass or less, more preferably 5 parts by mass or less. Within such a range, the effect of the present embodiment can be more satisfactorily exhibited.

(Vulcanization accelerator)
The vulcanization accelerator is not particularly limited, and known vulcanization aids can be used, for example, sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, and aldehyde-amine. Examples thereof include a system or an aldehyde-ammonia system, an imidazoline system, or a xanthate system vulcanization accelerator. Of these, sulfenamide-based and guanidine-based are preferable because the scorch time and vulcanization time can be well-balanced. The vulcanization accelerator may be used alone or in combination of two or more.

Examples of the sulfenamide-based vulcanization accelerator include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), N, N. '-Dicyclohexyl-2-benzothiazolyl sulfenamide (DZ) and the like can be mentioned. Of these, N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS) is preferable.

Examples of the guanidine-based vulcanization accelerator include 1,3-diphenylguanidine (DPG), dioltotrilguanidine, orthotrilbiguanidine and the like. Of these, 1,3-diphenylguanidine (DPG) is preferable from the viewpoint of shortening the vulcanization time.

In the present embodiment, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) and 1,3-diphenylguanidine (CBS) and 1,3-diphenylguanidine (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)) and 1,3-diphenylguanidine (CBS) and 1,3-diphenylguanidine as vulcanization accelerators can be used as vulcanization accelerators because the effects of the present embodiment can be better exerted. It is more preferable to use only DPG).

When the vulcanization accelerator is contained, the content of the rubber component with respect to 100 parts by mass is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, still more preferably 2.0 parts by mass or more. The content of the vulcanization accelerator is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and further preferably 3.5 parts by mass or less. Within such a range, the effect of the present embodiment can be more satisfactorily exhibited.

<Manufacturing of rubber compositions for tires>
The rubber composition for a tire of the present embodiment is produced by a known method. For example, it can be produced by a method of kneading each of the above components with a Banbury mixer, a kneader, an open roll, or the like, and then vulcanizing. In kneading, components other than the vulcanizing agent and the vulcanization accelerator can be kneaded first, and then the vulcanizing agent and the vulcanization accelerator can be added to the obtained kneaded product and kneaded. The method for blending the aminoguanidine weak acid salt is also not particularly limited and can be blended as it is as a powder. However, other than such a blending method, for example, a method of dissolving in a solvent and blending as a solution, or It can also be blended by a method of blending as an emulsion solution.

<Rubber composition for tires>
The rubber composition for a tire of the present embodiment can be used for each tire member such as a tread, an under tread, a carcass, a sidewall, and a bead of a tire. In particular, since it is excellent in fuel efficiency, fracture strength and wear resistance, it is preferable to use a tire having a tread made of the rubber composition for a tire of the present embodiment.

<Manufacturing of tires>
The tire of the present embodiment can be manufactured by a usual method using the rubber composition for a tire. That is, the rubber composition for a tire is extruded according to the shape of a tire member such as a tire tread at the unvulcanized stage, molded by a normal method on a tire molding machine, and pasted together with other tire members. Combine to form an unvulcanized tire. The tire of the present embodiment can be manufactured by heating and pressurizing the unvulcanized tire in a vulcanizer. The vulcanization temperature is not particularly limited as long as it is a vulcanization temperature that is common in the tire industry, and is, for example, 120 ° C. or higher and 200 ° C. or lower, preferably 140 ° C. or higher, and preferably 180 ° C. or lower.

<Tire>
The tire of the present embodiment may be a pneumatic tire or a non-pneumatic tire, but is preferably a pneumatic tire. Pneumatic tires can be used for various tires such as passenger car tires, truck / bus tires, two-wheeled vehicle tires, competition tires and other high-performance tires, and run flat tires, but the main rubber component is natural rubber. Since it has high fracture resistance, it can be suitably used as a tire for high-load vehicles such as trucks and buses.

<Others>
In the present specification, when the numerical range is expressed as "10 to 100", the numerical range means that the values at both ends thereof are included unless otherwise specified.

Although the present embodiment will be described based on the examples, the present embodiment is not limited to the examples.

The various chemicals used in Examples and Comparative Examples are shown below.
Natural rubber (NR): TSR20
Styrene-butadiene rubber (SBR): SBR1502 manufactured by JSR Corporation
Butadiene rubber (BR): UBEPOL BR15H manufactured by Ube Kosan Co., Ltd.
Carbon black (CB): N220
Silica: Ultrasil VN3 manufactured by Evonik ((175m ² / g))
Silane coupling agent (coupling agent): Si266 (bis (3-triethoxysilylpropyl) polysulfide) manufactured by Evonik Industries, Inc.
Anti-aging agent: Crack 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Wax: Ozo Ace 0355 manufactured by Nippon Seiro Co., Ltd.
Zinc Oxide Sulfur Vulcanization Accelerator 1: N-Cyclohexyl-2-benzothiazolyl sulphenamide (CBS)
Vulcanization accelerator 2: 1,3-diphenylguanidine (DPG)
Aminoguanidine Weak Acid 1 (AG Weak Acid 1): Aminoguanidine Phosphate Aminoguanidine Weak Acid 2 (AG Weak Acid 2): Aminoguanidine Hydrocarbonide Aminoguanidine Hydrochloride (AG Hydrochloride)

Examples 1 to 6 and Comparative Examples 1 to 6
Among the formulation contents shown in Table 1, various chemicals (excluding sulfur and vulcanization accelerators 1 and 2) are kneaded with a Banbury mixer to obtain a kneaded product. Next, using an open roll, sulfur and vulcanization accelerators 1 and 2 are added to the obtained kneaded product and kneaded to obtain an unvulcanized rubber composition.

A vulcanized rubber composition is produced by molding the unvulcanized rubber composition into a desired shape and press vulcanizing under the condition of 170 ° C. The vulcanization time is twice as long as the vulcanization characteristic t90 at 170 ° C. determined below.

The unvulcanized rubber composition is extruded by an extruder equipped with a tread-shaped base, bonded together with other tire members to form an unvulcanized tire, and press-vulcanized under the condition of 170 ° C. To manufacture a test tire (size: 195 / 65R15).

<Formability>
The unvulcanized rubber composition was subjected to a vulcanization test at a measurement temperature of 130 ° C. using a vibration type vulcanization tester (curast meter) described in JIS K 6300, and the time and torque were plotted. Obtain a vulcanization rate curve. When the minimum value of the torque of the vulcanization rate curve is ML, the maximum value is MH, and the difference (MH-ML) is ME, the time t10 (scorch time) (minutes) to reach ML + 0.1ME is read. The scorch time of the standard comparative example is set to 100, and the index is displayed by the following formula. The larger the value, the longer the scorch time and the better the moldability.
(Formability index) =
{(Scorch time of each formulation) / (Scorch time of standard comparison example)} x 100

<Vulcanization rate>
For the unvulcanized rubber composition, the vulcanization characteristic t90 at 170 ° C. is determined using a viscoelasticity measuring device (manufactured by Alpha Technologies, trade name: RPA2000) and used as the vulcanization time. The vulcanization time of the standard comparative example is set to 100, and the index is expressed by the following formula. The larger the value, the shorter the vulcanization time.
(Vulcanization rate index) = {(Vulcanization time of standard comparative example) / (Vulcanization time of each formulation)} × 100

<Break strength>
Using a No. 6 dumbbell type test piece made of a vulcanized rubber composition, perform a tensile test in an atmosphere of 25 ° C. in accordance with JIS K 6251: 2010 "Vulcanized rubber and thermoplastic rubber-How to determine tensile properties". This is carried out, and the breaking strength TB (MPa) and the elongation at break EB (%) are measured. Then, the value of TB × EB / 2 (MPa%) is calculated. The calculated value is converted into an exponent with the reference comparison example as 100 by the following formula. The larger the value, the better the fracture strength.
(Fracture strength index) = {(value of each formulation) / (value of standard comparative example)} × 100

<Fuel efficiency>
For the vulcanized rubber composition, using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent of each formulation under the conditions of a temperature of 50 ° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz ( (Tanδ _{50 ° C.} ) is measured, the fuel efficiency index of the standard comparative example is set to 100, and the fuel efficiency of each formulation is displayed as an index by the following formula. The larger the value, the smaller the rolling resistance and the better the fuel efficiency.
(Fuel efficiency index) =
{(Tanδ 50 ° C of standard comparative example) / (tanδ _{50 ° C} of each formulation)} × 100

By performing each of the above tests based on the formulation contents in Table 1, each index or a value close to it can be obtained.

In the present embodiment, the target value of the molding processability index is 98 or more, and the target value of the vulcanization rate index is 100 or more. Further, the fracture strength index and the fuel efficiency index exceed 100, and the larger the index, the more desirable.

Claims (8)

A rubber composition for a tire obtained by blending 50% by mass or more of natural rubber, a rubber component containing styrene-butadiene rubber and butadiene rubber, silica, and a weak acid salt of aminoguanidine .
The styrene-butadiene rubber contains unmodified emulsion-polymerized styrene-butadiene rubber or unmodified solution-polymerized styrene-butadiene rubber.
A rubber composition for a tire in which the aminoguanidine weak acid salt is aminoguanidine bicarbonate .
[However, the rubber compositions for tires (a), (b), (c) and (d) below are excluded:
(A) Rubber composition for tires containing zinc phosphate,
(B) A rubber composition for a tire containing a compound represented by the following formula (1),

(N is 1 or 2)
(C) A rubber composition for a tire containing 1 to 25 parts by mass of an antimony oxide compound with respect to 100 parts by mass of the rubber component.
(D) A rubber composition for a tire containing 10 to 40% by mass of a modified styrene-butadiene rubber having a styrene content of 21% by mass or less. ] A rubber composition for a tire comprising 50% by mass or more of natural rubber, a rubber component containing styrene-butadiene rubber and butadiene rubber, silica, and a weak acid salt of aminoguanidine.
The styrene-butadiene rubber is a styrene-butadiene rubber having a styrene content of 23.5% by mass or more.
A rubber composition for a tire, wherein the butadiene rubber is a butadiene rubber having a cis-1,4-bond content of 90% by mass or more and a 1,2-bonded butadiene unit amount of 0.8% by mass or less. The rubber composition for a tire according to claim 2 , wherein the aminoguanidine weak acid salt is aminoguanidine bicarbonate. The rubber composition for a tire according to any one of claims 1 to 3, wherein the content of the aminoguanidine weak acid salt is 0.01 to 10 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition for a tire according to any one of claims 1 to 4 , wherein the content of silica is 5 parts by mass or more with respect to 100 parts by mass of the rubber component. The rubber composition for a tire according to any one of claims 1 to 5 , wherein the content of styrene-butadiene rubber in the rubber component is 5% by mass or more. The rubber composition for a tire according to any one of claims 1 to 6 , further comprising carbon black. A tire having a tire member composed of the rubber composition for a tire according to any one of claims 1 to 7 .