JP2022184189A - Rubber composition and tire - Google Patents

Abstract

To provide a rubber composition excellent in cut resistance.SOLUTION: The rubber composition of the present invention includes: a rubber constituent containing a natural rubber, and polybutadiene (high-cis butadiene rubber) having a cis-1,4 bond content of 90 mass% or more; and a cyclic polyol compound having a hydrocarbyl group, wherein the content of the natural rubber is 20-70 mass%, and the content of the high-cis butadiene rubber is 30-80 mass% in the rubber constituent, and the content of the cyclic polyol compound having a hydrocarbyl group is 0.1-3 pts.mass with respect to 100 pts.mass of the natural rubber.SELECTED DRAWING: None

Description

The present invention relates to rubber compositions and tires.

Various components are also used as additives for rubber compositions in order to improve the functions of rubber compositions and crosslinked rubbers obtained by crosslinking them.
For example, in Patent Document 1, (A) per 100 parts by weight of rubber selected from natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, isoprene rubber, acrylonitrile-butadiene copolymer rubber, chloroprene rubber, butyl rubber and halogenated butyl rubber, (B) 0.5 to 10 parts by weight of carbohydrate, (C) 0.5 to 10 parts by weight of methoxylated methylol melamine resin, and (D) 0.05 to 1 part by weight of cobalt carboxylate salt in terms of cobalt content. , discloses techniques for improving adhesion and rubber hardness in vulcanization adhesion to steel cords.
Further, in Patent Document 2, a rubber composition contains a specific diene rubber and silica having a glass transition point and a CTAB adsorption specific surface area defined within a specific range, thereby improving wear resistance and wet performance and a technique that achieves compatibility with on-ice performance is disclosed.

However, the technology disclosed in Patent Document 1 is inferior in cut resistance and wear resistance under severe conditions (high-severity conditions), and further improvements are made considering its application to rubber articles such as tires. was desired.
Also, with regard to the technique disclosed in Patent Document 2, since the rubber composition has low elasticity, a sufficient effect cannot be obtained with respect to the cut resistance of the rubber composition after vulcanization, and further improvement is needed. was desired.

Therefore, in recent years, techniques have been developed to add a compound having a polyol structure, such as sorbitol, to a rubber composition for the purpose of improving the cut resistance of the rubber composition.
According to this technique, it is possible to improve the cut resistance as compared with the conventional art without deteriorating physical properties such as low heat build-up.

JP-A-07-118457 JP 2016-47888 A

As described above, it was found that adding a compound having a polyol structure, such as sorbitol, to a rubber composition has a certain effect of improving cut resistance.
However, with respect to cut resistance, further improvement has been desired so that a high level of cut resistance can be achieved even under severe conditions such as the tread portion and sidewall portion of tires for construction vehicles and tires for trucks and buses.

Therefore, an object of the present invention is to provide a rubber composition having excellent cut resistance. Another object of the present invention is to provide a tire having excellent cut resistance.

The present inventors have made intensive studies to achieve better cut resistance. By adding a small amount of a cyclic polyol compound having a hydrocarbyl group to a rubber composition containing a large amount of natural rubber as a rubber component, the strength of the rubber is increased and the proportion of the high-cis-butadiene rubber in the rubber component is increased. The inventors have found that the cut resistance can be greatly improved by this.

That is, the rubber composition of the present invention comprises a rubber component containing natural rubber and polybutadiene (high cis-butadiene rubber) having a cis-1,4 bond content of 90% by mass or more, a cyclic polyol compound having a hydrocarbyl group, including
In the rubber component, the content of natural rubber is 20 to 70% by mass, and the content of the high-cis-butadiene rubber is 30 to 80% by mass,
A content of the cyclic polyol compound having a hydrocarbyl group is 0.1 to 3 parts by mass with respect to 100 parts by mass of the natural rubber.
By providing the above configuration, excellent cut resistance can be achieved.

In the rubber composition of the present invention, the hydrocarbyl group-containing cyclic polyol compound is preferably a hydrocarbyl ester group-containing cyclic polyol compound. This is because more excellent cut resistance can be achieved.

Further, in the rubber composition of the present invention, the cyclic polyol compound having hydrocarbyl groups preferably has two or more hydroxyl groups. This is because more excellent cut resistance can be achieved.

［式中、Ａは炭素数６～３０のヒドロカルビルエステル基又は炭素数６～３０のヒドロカルビルエーテル基であり、Ｘ_１、Ｘ_２、Ｘ_３及びＸ_４はそれぞれ独立して－ＯＨ又は－Ｒ（ここで、－Ｒは－Ｈ又は－ＣＨ_２ＯＨである）であり、但し、Ｘ_１、Ｘ_２、Ｘ_３及びＸ_４のうち少なくとも３つは－ＯＨである］で表わされる化合物であることが好ましく、前記ヒドロカルビル基を有する環状ポリオール化合物は、式（１）中のＡのヒドロカルビル基部分の炭素数が１２～２４であることがより好ましい。より優れた耐カット性を実現できるためである。 Further, in the rubber composition of the present invention, the cyclic polyol compound having a hydrocarbyl group has the following formula (1):

[In the formula, A is a hydrocarbyl ester group having 6 to 30 carbon atoms or a hydrocarbyl ether group having 6 to 30 carbon atoms, and X ₁ , X ₂ , X ₃ and X ₄ are each independently -OH or -R( wherein —R is —H or —CH ₂ OH), provided that at least three of X ₁ , X ₂ , X ₃ and X ₄ are —OH. More preferably, the cyclic polyol compound having a hydrocarbyl group has 12 to 24 carbon atoms in the hydrocarbyl group portion of A in formula (1). This is because more excellent cut resistance can be achieved.

Furthermore, in the rubber composition of the present invention, the melting point of the cyclic polyol compound having hydrocarbyl groups is preferably 40 to 100°C. This is because the cut resistance at high temperatures can be improved.

Furthermore, it is preferable that the rubber composition of the present invention further contains a filler containing at least carbon black. This is because better wear resistance can be achieved while maintaining good cut resistance.

Further, in the rubber composition of the present invention, the carbon black content is preferably 20 to 60 parts by mass with respect to 100 parts by mass of the rubber component. This is because better wear resistance can be achieved without deteriorating low heat build-up.

Furthermore, for the rubber composition of the present invention, it is preferred that the carbon black has a grade of ISAF, SAF, FEF or HAF. This is because better cut resistance and wear resistance can be achieved.

A tire of the present invention is characterized by using the rubber composition described above in at least one of a tread portion and a sidewall portion.
By providing the above configuration, excellent cut resistance can be achieved.

Moreover, the tire of the present invention is preferably a tire for passenger cars, a tire for trucks and buses, or a tire for construction vehicles. This is because there is a large merit due to the effect of improving the cut resistance.

ADVANTAGE OF THE INVENTION According to this invention, the rubber composition excellent in cut resistance can be provided. Further, according to the present invention, it is possible to provide a tire having excellent cut resistance.

Embodiments of the present invention will be specifically described below by way of illustration.
<Rubber composition>
The rubber composition of the present invention includes a rubber component containing natural rubber and polybutadiene (high cis-butadiene rubber) having a cis-1,4 bond content of 90% by mass or more, and a cyclic polyol compound having a hydrocarbyl group. It is a rubber composition.

(rubber component)
As described above, the rubber component contained in the rubber composition of the present invention contains natural rubber and polybutadiene (high cis-butadiene rubber) having a cis-1,4 bond content of 90% by mass or more. By using natural rubber together with a cyclic polyol compound having a hydrocarbyl group, which will be described later, excellent cut resistance, reinforcing properties, abrasion resistance, and the like can be obtained. In addition, by containing high-cis-butadiene rubber as a rubber component and adjusting the content with the natural rubber in an appropriate range, the cut resistance can be further enhanced.

Here, the content of natural rubber in the rubber component is 20 to 70% by mass. This is because when the content of the natural rubber is 20% by mass or more, cut resistance and wear resistance can be reliably improved when used together with a cyclic polyol compound having a hydrocarbyl group, which will be described later. On the other hand, by setting the content of the natural rubber to 70% by mass or less, the cut resistance improvement effect of the high-cis-butadiene rubber, which will be described later, is not impaired. From the same point of view, the content of natural rubber in the rubber component is preferably 30 to 70% by mass, more preferably 40 to 60% by mass or more.

Also, the content of the high-cis butadiene rubber in the rubber component is 30 to 80% by mass. When the high-cis-butadiene rubber is 30% by mass or more, the strength of the rubber component can be increased, and cut resistance and abrasion resistance can be improved. On the other hand, by setting the content of the high-cis-butadiene rubber to 80% by mass or less, the effect of improving the cut resistance when used together with the natural rubber and the cyclic polyol compound having a hydrocarbyl group described below is not impaired. From the same point of view, the content of the high-cis butadiene rubber in the rubber component is preferably 30 to 70% by mass, more preferably 40 to 60% by mass or more.

The rubber component may contain any synthetic rubber in addition to the natural rubber and the high-cis-butadiene rubber.
For example, the rubber component preferably contains a diene-based synthetic rubber in order to obtain excellent cut resistance and abrasion resistance.

Examples of the diene-based synthetic rubber include synthetic polyisoprene (IR) and styrene/butadiene copolymer rubber (SBR). The diene-based synthetic rubber in the rubber component may be contained singly or as a blend of two or more. In addition, the rubber component may contain a non-diene synthetic rubber depending on the performance required.

The rubber component containing the natural rubber and the high-cis-butadiene rubber may be modified with a modifying agent. Modifiers used for modification include, for example, compounds containing nitrogen, oxygen, and silicon.

(Cyclic polyol compound having hydrocarbyl group)
In addition to the rubber component described above, the rubber composition of the present invention further contains 0.1 to 3 parts by mass of a cyclic polyol compound having a hydrocarbyl group with respect to 100 parts by mass of natural rubber in the rubber component. .
A cyclic polyol compound having a hydrocarbyl group contained in the rubber composition can greatly improve the cut resistance of the rubber composition of the present invention. Further, by increasing the interaction between the rubber molecules of the rubber component and the agent described later, the physical properties of the rubber after cross-linking can be homogenized, and as a result, the reinforcing properties and wear resistance can also be improved.
Furthermore, since the cyclic polyol compound having a hydrocarbyl group has fewer hydrophilic sites than compounds such as sorbitol, self-aggregation in the rubber composition can be suppressed, and as a result, the elongation fatigue property of the rubber composition is improved. can be maintained well.

Here, the content of the cyclic polyol compound having a hydrocarbyl group is 0.1 to 3 parts by mass with respect to 100 parts by mass of the natural rubber, and 0.1 part by mass with respect to 100 parts by mass of the natural rubber. If it is less than 100%, the amount of the cyclic polyol compound is too small to obtain a sufficient effect of improving cut resistance, and a sufficient effect of elongation fatigue resistance cannot be obtained. On the other hand, when the content of the cyclic polyol compound having a hydrocarbyl group exceeds 3 parts by mass with respect to 100 parts by mass of the natural rubber, the amount of the cyclic polyol compound becomes too large. self-aggregation occurs, which may lead to deterioration of physical properties such as elongation fatigue.
From the same viewpoint, the content of the cyclic polyol compound having a hydrocarbyl group is preferably 0.1 to 2 parts by mass, more preferably 0.3 to 1.5 parts by mass, based on 100 parts by mass of the natural rubber. is more preferable.

Here, the cyclic polyol compound having hydrocarbyl groups preferably has two or more hydroxyl groups, preferably three or more hydroxyl groups. This is because, by having many hydroxyl groups, the interaction between the rubber component and the additive is exhibited more strongly, and more excellent cut resistance can be achieved.

Furthermore, the cyclic polyol compound having a hydrocarbyl group is preferably a cyclic polyol compound having a hydrocarbyl ester group. This is because more excellent elongation fatigue resistance and cut resistance can be achieved.

で表わされる化合物であることがより好ましい。 Furthermore, the cyclic polyol compound having a hydrocarbyl group has the following formula (1):

A compound represented by is more preferable.

In the above formula (1), A is a hydrocarbyl ester group having 6 to 30 carbon atoms or a hydrocarbyl ether group having 6 to 30 carbon atoms, and the hydrocarbyl group portion of A preferably has 12 to 24 carbon atoms. . When the number of carbon atoms in the hydrocarbyl group portion of A in formula (1) is in the range of 12 to 24, cut resistance is further improved while maintaining good extension fatigue resistance.
As for A in formula (1), the first atom from the ring portion (that is, the atom bonded to the ring) or the second atom from the ring portion is preferably an oxygen atom. A whose first atom from the ring portion is an oxygen atom includes, for example, groups represented by —OA′ and —O—CO—A″, and the second atom from the ring portion is Examples of A which is an oxygen atom include groups represented by —CH ₂ —OA″ and —CH ₂ —O—CO-A′″, where A′ has 6 to 6 carbon atoms. Preferably, 30 hydrocarbyl groups, A'' is a hydrocarbyl group having 5 to 29 carbon atoms, A''' is a hydrocarbyl group having 4 to 28 carbon atoms, and A', A'' and A''' is more preferably a hydrocarbyl group having 12 to 24 carbon atoms.

Further, in the above formula (1), X ₁ , X ₂ , X ₃ and X ₄ are each independently —OH or —R (where —R is —H or —CH ₂ OH), provided that at least three of X ₁ , X ₂ , X ₃ and X ₄ are —OH. When three or more of X ₁ , X ₂ , X ₃ and X ₄ are —OH, the cut resistance of the rubber composition is further improved.

で表わされる化合物が更に好ましく、上記式（２）で表わされる化合物が特に好ましい。
なお、式（２）及び式（３）中、ｎは自然数であり、１１～２３の範囲が好ましい。
前記変性環状ポリオール化合物として、上記式（２）又は式（３）で表わされる化合物を配合することで、耐カット性をより向上させることができる。 Furthermore, among the compounds represented by the above formula (1), the following formula (2) or formula (3):

A compound represented by is more preferable, and a compound represented by the above formula (2) is particularly preferable.
In formulas (2) and (3), n is a natural number, preferably in the range of 11-23.
By blending the compound represented by the above formula (2) or (3) as the modified cyclic polyol compound, cut resistance can be further improved.

The cyclic polyol compound having a hydrocarbyl group is not particularly limited. It can be obtained by reacting an aliphatic alcohol or an aliphatic carboxylic acid such as lauric acid, myristic acid, palmitic acid, stearic acid, or oleic acid.

Specific examples of the cyclic polyol compound having a hydrocarbyl group include ester compounds such as sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, octyl-β- Ether compounds such as D-glucopyranoside, decyl-β-D-glucopyranoside, dodecyl-β-D-glucopyranoside, tetradecyl-β-D-glucopyranoside, and hexadecyl-β-D-glucopyranoside. These compounds may be used individually by 1 type, and may be used in combination of 2 or more type.
Further, among these compounds, the cyclic polyol compound having a hydrocarbyl group is preferably sorbitan monostearate (sorbitan monoester) from the viewpoint of achieving a higher level of both elongation fatigue resistance and cut resistance. .

Furthermore, the melting point of the cyclic polyol compound having hydrocarbyl groups is preferably 40 to 100°C, more preferably 45 to 90°C. This is because when the melting point of the cyclic polyol compound having a hydrocarbyl group is 100° C. or lower, the solubility during kneading and vulcanization reactions can be improved, and when it is 40° C. or higher, cut resistance at high temperatures can be enhanced. .

(filler)
The rubber composition of the present invention preferably further contains a filler containing at least carbon black in addition to the rubber component and the cyclic polyol compound described above.
By including a filler containing at least carbon black together with the rubber component, the properties of the vulcanized rubber composition, such as cut resistance and abrasion resistance, can be further enhanced.

Here, the type of carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, N339, IISAF, ISAF, and SAF grade carbon blacks. From the viewpoint of further improving wear resistance and cut resistance, it is preferable to use ISAF, SAF, FEF or HAF grade carbon black. These carbon blacks may be used individually by 1 type, and may use 2 or more types together.
Further, the carbon black may have a nitrogen adsorption specific surface area (N ₂ SA, measured according to JIS K 6217-2:2001) of 20 to 250 m ² /g, and 30 to 200 m ² . /g can be used, and those of 30 to 150 m ² /g can be used.
Further, the carbon black has a dibutyl phthalate (DBP) oil absorption (measured by the method described in JIS K 6217-4:2001 "Determination of DBP absorption") of 50 to 200 cm ³ /100 g. of 60 to 150 cm ³ /100 g can be used.

In addition, although the content of the carbon black is not particularly limited, it is preferably 20 to 80 parts by mass, more preferably 25 to 70 parts by mass, with respect to 100 parts by mass of the rubber component. More preferably, it is 30 to 65 parts by mass. If the content of the carbon black is 20 parts by mass or more with respect to 100 parts by mass of the rubber component, the wear resistance can be further improved, and if it is 80 parts by mass or less, the deterioration of low heat build-up is more assured. can be suppressed.

Also, the filler preferably contains silica. This is because better cut resistance and performance on ice can be obtained.
Examples of the silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred. These silicas may be used individually by 1 type, and may use 2 or more types together.
Furthermore, the wet silica may be precipitated silica. In addition, precipitated silica means that in the early stage of production, the reaction solution is reacted at a relatively high temperature and in a neutral to alkaline pH range to grow primary silica particles, and then controlled to the acidic side to aggregate the primary particles. It is the silica obtained as a result of

Furthermore, the silica is not particularly limited, but may have, for example, a CTAB specific surface area (cetyltrimethylammonium bromide adsorption specific surface area) of 70 m ² /g or more and 250 m ² /g or less. The CTAB specific surface area means a value measured according to ASTM D3765-92. However, the adsorption cross-sectional area per molecule of cetyltrimethylammonium bromide on the silica surface is 0.35 nm ² , and the specific surface area (m ² /g) calculated from the adsorption amount of CTAB is defined as the CTAB specific surface area.
Moreover, the BET specific surface area of the silica can be 100 m ² /g or more and 250 m ² /g or less. The BET specific surface area is a specific surface area determined by the BET method, and can be measured according to ASTM D4820-93 in the present invention.

The silica content is preferably 5 to 100 parts by mass, more preferably 10 to 50 parts by mass, and further preferably 10 to 45 parts by mass with respect to 100 parts by mass of the rubber component. preferable. If the silica content is 5 parts by mass or more with respect to 100 parts by mass of the rubber component, the wear resistance and performance on ice of the vulcanized rubber composition can be further improved. It is possible to suppress deterioration of processability and deterioration of low rolling resistance of the rubber composition.

In addition to the carbon black and silica described above, the filler may be the following general formula (XX):
_{nM.xSiOy.zH2O (} XX)
[In the formula, M is a metal selected from the group consisting of aluminum, magnesium, titanium, calcium and zirconium, oxides or hydroxides of these metals, and hydrates thereof, or carbonates of these metals is at least one selected; n, x, y and z are each an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10]. can also include
Examples of the inorganic compound represented by the general formula (XX) include alumina (Al ₂ O ₃ ) such as γ-alumina and α-alumina, alumina monohydrate (Al ₂ O ₃ ·H ₂ O) such as boehmite and diaspore, Aluminum hydroxide [Al(OH) ₃ ] such as gibbsite and bayerite, aluminum carbonate [Al ₂ (CO ₃ ) ₃ ], magnesium hydroxide [Mg(OH) ₂ ], magnesium oxide (MgO), magnesium carbonate (MgCO ₃ ), talc ( _{3MgO.4SiO.sub.2.H.sub.2O} ), attapulgite (5MgO.8SiO.sub.2.9H.sub.2O ₎ , titanium white ( _TiO.sub.2 ), titanium black ( _{TiO.sub.2n - 1} ), calcium oxide (CaO), water _Calcium oxide [Ca(OH) ₂ ], _{magnesium aluminum} oxide ( _{MgO.Al2O3 ) ,} clay ( _Al2O3.2SiO2 ), kaolin ( _{Al2O3.2SiO2.2H2O} ), _pyrophyl Light ( _{Al2O3.4SiO2.H2O ) ,} bentonite _{( Al2O3.4SiO2.2H2O} ) _{, aluminum} silicate _{( Al2SiO5 , Al4.3SiO4.5H2O} , _{etc. )} , magnesium silicate ( _Mg2SiO4 , _MgSiO3 , _etc. ) _, calcium silicate ( _{Ca2SiO4 ,} etc.), aluminum calcium silicate ( _{Al2O3.CaO.2SiO2 , etc.} ), magnesium calcium silicate ( _CaMgSiO4 ), calcium _carbonate ( _CaCO3 ), zirconium oxide ( _ZrO2 ), zirconium hydroxide [ZrO(OH) _2.nH2O ], zirconium carbonate [Zr( _CO3 ) ₂ ], and various zeolites. Mention may be made of crystalline aluminosilicates containing compensating hydrogen, alkali metals or alkaline earth metals, and the like.
From the viewpoint of the balance between wear resistance and wet performance, the inorganic compound of formula (XX) preferably has an average particle size of 0.01 to 10 μm, more preferably 0.05 to 5 μm.

Here, the total content of the filler is not particularly limited, but is preferably 20 to 150 parts by mass, more preferably 30 to 120 parts by mass, with respect to 100 parts by mass of the rubber component. More preferably, 40 to 100 parts by mass is particularly preferable. This is because, by optimizing the amount of the filler, tire characteristics such as wear resistance, cut resistance, and low loss can be further improved.

Furthermore, the content of carbon black with respect to the content of silica (content of carbon black/content of silica) is preferably 0.1 to 15, more preferably 0.5 to 1.5. is more preferably 0.7 to 1.2. Another preferred example is 4 to 15, more preferably 7 to 13.
When the content mass ratio of the carbon black to the silica content is 0.1 or more, it is possible to obtain better wear resistance and reinforcement, and the content of the carbon black to the silica content When the mass ratio is 15 or less, excellent cut resistance can be obtained without deteriorating low heat build-up.

(other ingredients)
The rubber composition of the present invention comprises the above-mentioned rubber component, a cyclic polyol compound having a hydrocarbyl group, a filler, and a linear polyhydric alcohol as an optional component. agents can be included as other ingredients. For other components, for example, silane coupling agents, cross-linking agents, vulcanization accelerators, polyethylene glycol, softening agents, resins, anti-aging agents, zinc white, etc., are appropriately selected within a range that does not impair the purpose of the present invention. can be included as Commercially available products can be suitably used as these compounding agents.

Moreover, when silica is contained as the filler mentioned above, it is preferable to further contain a silane coupling agent. This is because the effects of silica on cut resistance, reinforcement, and loss reduction can be further improved. In addition, a well-known thing can be used suitably for a silane coupling agent.
Examples of the silane coupling agent include bis(triethoxysilyl)propylpolysulfide, bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilyl) propyl) disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3- Mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N- dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyltetrasulfide, 3-triethoxysilylpropylbenzothiazolyltetrasulfide, 3 -triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethyl thiocarbamoyltetrasulfide, dimethoxymethylsilylpropylbenzothiazolyltetrasulfide and the like. These silane coupling agents may be used singly or in combination of two or more.

Furthermore, although the content of the silane coupling agent varies depending on the type of silane coupling agent, etc., the content of the silica is preferably 0.2 or less, and preferably 0.1. It is more preferably 0.09 or less, more preferably 0.09 or less. This is because the cut resistance of the rubber composition can be further improved by reducing the content of the silane coupling agent to the content of the silica by a mass ratio of 0.2 or less.

The cross-linking agent is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include sulfur-based cross-linking agents, organic peroxide-based cross-linking agents, inorganic cross-linking agents, polyamine cross-linking agents, resin cross-linking agents, sulfur compound-based cross-linking agents, and oxime-nitrosamine-based cross-linking agents. Among these cross-linking agents, a sulfur-based cross-linking agent (vulcanizing agent) is more preferable as a rubber composition for tires.
The content of the cross-linking agent is not particularly limited and can be appropriately selected depending on the intended purpose.

Moreover, when sulfur is used as the cross-linking agent, it is preferable that a vulcanization accelerator is included. As the vulcanization accelerator, a conventionally known one can be used, and it is not particularly limited. -butyl-2-benzothiazylsulfenamide), TBSI (Nt-butyl-2-benzothiazylsulfenimide) and other sulfenamide-based vulcanization accelerators; DPG (diphenylguanidine) and other guanidines thiuram-based vulcanization accelerators such as tetraoctylthiuram disulfide and tetrabenzylthiuram disulfide; and zinc dialkyldithiophosphate. The sulfur content is preferably less than the sulfur content, and more preferably about 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition of the present invention preferably further contains glycerol monostearate from the viewpoint of shortening the scorch time and further improving the workability such as increasing the vulcanization speed during tire production.

The content of the glycerol monostearate is 0.1 parts by mass or more, preferably 0.3 parts by mass or more, and more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component. . If it is less than 0.1 part by mass, the effects of the present invention may not be obtained satisfactorily. The content is 3.5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 2.5 parts by mass or less. If it exceeds 3.5 parts by mass, the scorch time tends to be too short.

Furthermore, the content of the polyethylene glycol is 0.1 parts by mass or more, preferably 0.3 parts by mass or more, and more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 0.1 part by mass, the effects of the present invention may not be obtained satisfactorily. The content is 3.5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 2.5 parts by mass or less. If it exceeds 3.5 parts by mass, the scorch time tends to be too short.

Furthermore, the rubber composition of the present invention can also contain a softening agent from the viewpoint of increasing the flexibility of the rubber and realizing better wet performance and ice performance. As the softener, conventionally known ones can be used, and there is no particular limitation, but petroleum-based softeners such as aroma oil, paraffin oil, and naphthenic oil, palm oil, castor oil, cottonseed oil, soybean oil, and the like can be used. of vegetable softeners. At the time of use, one of these may be used singly or two or more may be appropriately selected and used.
When the softener is contained, from the viewpoint of ease of handling, among the above softeners, those that are liquid at room temperature such as 25 ° C., for example, petroleum softeners such as aroma oil, paraffin oil, naphthenic oil It is preferable to contain

Furthermore, the rubber composition of the present invention can contain a resin from the viewpoint of increasing the flexibility of the rubber and realizing better wet performance and performance on ice. As the resin, various natural resins and synthetic resins can be used. Specifically, rosin-based resins, terpene-based resins, petroleum-based resins, phenol-based resins, coal-based resins, xylene-based resins, etc. are used. preferably. These resins may be used individually by 1 type, and may use 2 or more types together.

In addition, the manufacturing method of the rubber composition of the present invention is not particularly limited. For example, the rubber component, the filler containing at least silica, the cyclic polyol compound having a hydrocarbyl group, and other optionally blended components are blended and kneaded by a known method. can be obtained by

<Tire>
The tire of the present invention is characterized by using the vulcanized rubber composition of the present invention described above in at least one of the tread portion and the sidewall portion. By applying the rubber composition of the present invention to the tread portion and/or the sidewall portion, excellent cut resistance can be achieved.
Here, the tire of the present invention can be used, for example, as a tire for construction vehicles, a tire for trucks and buses, a tire for aircraft, and a tire for passenger vehicles. A tire is preferred. This is because the rubber composition used as the material for the tread portion and the sidewall portion is excellent in cut resistance, and has great advantages when used as the tire described above.

When the vulcanized rubber composition of the present invention described above is used in the tread portion, the structure described in the following publications, for example, can be employed as the structure of the tread.
JP 2016-203842, JP 2009-196527, JP 2000-225815, JP 2000-264019, JP 2003-211921, WO 2014/196409

The tire of the present invention is not particularly limited except that the vulcanized rubber composition of the present invention is used for at least one of the tread portion and the sidewall portion of the tire, and is manufactured according to a conventional method. be able to. As the gas to be filled in the tire, in addition to normal air or air with adjusted oxygen partial pressure, inert gas such as nitrogen, argon, and helium can be used.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

(Example, Comparative Example)
According to the formulation shown in Table 1, rubber composition samples were prepared by blending and kneading in a conventional manner.
Each sample obtained was vulcanized and then subjected to the following evaluations (1) and (2).

(evaluation)
(1) Cut resistance For each sample of Examples and Comparative Examples, after vulcanization treatment, a pure shear type test piece was prepared, and a test piece was cut using a tensile tester (Shimadzu Corporation). A notch was made in the tensioned state to observe how the crack propagated, and the energy release rate (transition energy) at which the crack propagation speed increased discontinuously was measured.
For evaluation, the reciprocal of the transition energy of each measured sample was calculated. Table 1 shows exponential values when the reciprocal of the transition energy of the sample of the comparative example is set to 100. It should be noted that the larger the numerical value in Table 1, the better the cut resistance.

*1 Butadiene rubber: “UBEPOL BR150L” manufactured by Ube Industries, Ltd., cis-1,4 bond content is 98% by mass
*2 Carbon black: SAF grade carbon black *3 Silica: manufactured by Tosoh Silica Industry Co., Ltd., trade name “Nipsil AQ”
* 4 Silane coupling agent: Bis (triethoxysilyl) propyl polysulfide, manufactured by Shin-Etsu Chemical Co., Ltd. * 5 Sorbitan: Sorbitan monostearate, manufactured by Kao Corporation, "Rheodol AS-10V", 3 hydroxyl groups
* 6 Anti-aging agent: N-isopropyl-N'-phenyl-p-phenylenediamine, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., "Nocrac 6C"
In addition, in Table 1, the same amounts of process oil, stearic acid, zinc white, and anti-aging agent are included in each example and comparative example in addition to the described compounding components.
Moreover, the amount of the vulcanization accelerator compounded is the total amount of the vulcanization accelerators compounded.

The results in Table 1 show that the rubber compositions of Examples are superior in cut resistance to the rubber compositions of Comparative Examples.

ADVANTAGE OF THE INVENTION According to this invention, the rubber composition excellent in cut resistance can be provided. Further, according to the present invention, it is possible to provide a tire having excellent cut resistance.

Claims (11)

A rubber component containing natural rubber and polybutadiene (high cis-butadiene rubber) having a cis-1,4 bond content of 90% by mass or more, and a cyclic polyol compound having a hydrocarbyl group,
In the rubber component, the content of natural rubber is 20 to 70% by mass, and the content of the high-cis-butadiene rubber is 30 to 80% by mass,
A rubber composition, wherein the content of the cyclic polyol compound having hydrocarbyl groups is 0.1 to 3 parts by mass with respect to 100 parts by mass of the natural rubber. 2. The rubber composition according to claim 1, wherein the cyclic polyol compound having hydrocarbyl groups is a cyclic polyol compound having hydrocarbyl ester groups. 2. The rubber composition according to claim 1, wherein the cyclic polyol compound having hydrocarbyl groups has two or more hydroxyl groups. The cyclic polyol compound having a hydrocarbyl group has the following formula (1):

[In the formula, A is a hydrocarbyl ester group having 6 to 30 carbon atoms or a hydrocarbyl ether group having 6 to 30 carbon atoms, and X ₁ , X ₂ , X ₃ and X ₄ are each independently -OH or -R( wherein —R is —H or —CH ₂ OH), provided that at least two of X ₁ , X ₂ , X ₃ and X ₄ are —OH. The rubber composition according to claim 1, characterized by: 5. The rubber composition according to claim 4, wherein the hydrocarbyl group-containing cyclic polyol compound has 12 to 24 carbon atoms in the hydrocarbyl group portion of A in formula (1). The rubber composition according to any one of claims 1 to 5, wherein the cyclic polyol compound having hydrocarbyl groups has a melting point of 40 to 100°C. The rubber composition according to any one of claims 1 to 6, further comprising a filler containing at least carbon black. 8. The rubber composition according to claim 7, wherein the content of said carbon black is 20 to 60 parts by mass with respect to 100 parts by mass of said rubber component. 9. Rubber composition according to claim 7 or 8, characterized in that the carbon black has a grade of ISAF, SAF, FEF or HAF. A tire characterized by using the rubber composition according to any one of claims 1 to 9 in at least one of a tread portion and a sidewall portion. 11. Tire according to claim 10, characterized in that said tire is a tire for passenger cars, a tire for trucks and buses or a tire for construction vehicles.