JP7402735B2 - Rubber compositions and tires - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition and a tire.

In order to provide rubber compositions and pneumatic tires with good compatibility with fillers such as carbon black and silica, from monomers comprising, for example, at least one conjugated diene monomer and optionally at least one vinyl aromatic monomer. Functionalized elastomers have been disclosed that include a derivatized polymer backbone; and functional groups attached to the backbone, the functional groups including polydentate ligands capable of complexing with metal ions. (See Reference 1).

Japanese Patent Application Publication No. 2013-136747

However, as disclosed in Patent Document 1, vulcanized rubber obtained from a rubber composition containing a functionalized elastomer containing a polydentate ligand capable of complexing with a metal ion and a metal compound consisting of a divalent metal ion is , crack resistance was insufficient.
An object of the present invention is to provide a tire that has both high crack resistance and excellent fuel efficiency, and a rubber composition from which the tire can be obtained, and to solve the object.

<1> A rubber composition comprising a rubber component containing a polymer having a monodentate pyridyl group, a metal compound containing a trivalent metal ion, a filler, and sulfur.

<2> In <1>, the trivalent metal ion is at least one selected from the group consisting of iron ions, copper ions, aluminum ions, cobalt ions, manganese ions, titanium ions, rubidium ions, and nickel ions. The rubber composition described above.
<3><1> or <2> wherein the metal compound is at least one selected from the group consisting of chlorides, nitrates, bromides, sulfates, carbonates, phosphates, complexes, and organic acid salts. The rubber composition described in .
<4> The rubber composition according to any one of <1> to <3>, wherein the metal compound is blended in an amount of 0.1 to 10 parts by mass based on 100 parts by mass of the rubber component.
<5> The rubber composition according to any one of <1> to <4>, wherein the content of the polymer in the rubber component is 10 to 100% by mass.

<6> A tire using the rubber composition according to any one of <1> to <5>.

According to the present invention, it is possible to provide a tire that has both high crack resistance and excellent fuel efficiency, and a rubber composition from which the tire can be obtained.

<Rubber composition>
The rubber composition of the present invention is formed by blending a rubber component containing a polymer having a pyridyl group, a metal compound containing a trivalent metal ion, a filler, and sulfur.
Hereinafter, a polymer having a pyridyl group may be referred to as a "specific polymer". Further, a metal compound containing a trivalent metal ion is sometimes referred to as a "specific metal compound."

The reason why the tire obtained from the rubber composition having the above structure achieves both high crack resistance and excellent fuel efficiency is not clear, but it is presumed to be due to the following reason.
The specific polymer functions as a polymer containing monodentate ligands. By vulcanizing a rubber component containing such a polymer in the presence of a specific metal compound, a pyridine-metal coordination bond is formed, and the coordination bond is a bond that can be dissociated and reformed (sacrificial bond). ). On the other hand, it is thought that a covalent crosslinking bond (vulcanization bond) is formed between the rubber component and sulfur.
Although it is not clear how these two types of bonds specifically act, the coordination bonds dissociate preferentially over the sulfur crosslinks, so that the tire obtained by vulcanizing the rubber composition has the following properties: It is thought that it achieves both high crack resistance and excellent fuel efficiency.
Hereinafter, details of the rubber composition of the present invention will be explained.

[Rubber component]
The rubber component includes a polymer (specific polymer) having a pyridyl group.
Here, "a polymer having a pyridyl group" means a "polymer having a monodentate pyridyl group". That is, it means that the polymer has a monodentate pyridyl group, and polymers having polydentate bipyridyl groups, terpyridyl groups, etc. are excluded.
Specific polymers include, for example, poly(2-vinylpyridine), poly(4-vinylpyridine), 2-vinylpyridine/styrene copolymer, 4-vinylpyridine/styrene copolymer, 2-vinylpyridine/styrene- Examples include butadiene copolymer rubber, 4-vinylpyridine/styrene-butadiene copolymer rubber, and 4-vinylpyridine/methacrylate copolymer.
The specific polymer can be produced by, for example, reacting a diene polymer such as a styrene-butadiene copolymer with a compound having a pyridyl group and introducing a pyridyl group into the molecular chain end or main chain of the diene polymer. Obtainable. Moreover, a commercially available product may be used as the specific polymer.
In the present invention, the main chain of a polymer means a linear molecular chain in which all other molecular chains (long molecular chains, short molecular chains, or both) are connected like pendants. See section 1.34 of "Glossary of Basic Terms in Polymer Science IUPAC Recommendations 1996", Pure Appl. Chem., 68, 2287-2311 (1996)]

Examples of the compound having a pyridyl group include vinylpyridine, chloropyridine, chloromethylpyridine, pyridinecarbaldehyde, pyridine, and isonicotinic acid ester.
Among the above, from the viewpoint of greatly improving the crack resistance of tires, it is preferable that the specific polymer is a modified diene rubber whose molecular main chain is modified with a compound having a pyridyl group, and the modified diene rubber is , modified styrene-butadiene copolymer rubber (styrene-butadiene copolymer rubber having a pyridyl group in the molecule main chain) is more preferable.

From the viewpoint of further improving the crack resistance and fuel efficiency of the tire, the weight average molecular weight (Mw) of the specific polymer is preferably 10,000 to 5,000,000, and preferably 50,000 to 3,000. ,000 is more preferable, and even more preferably 100,000 to 1,000,000.
From the viewpoint of further improving the crack resistance and fuel efficiency of the tire, the molecular weight distribution (Mw/Mn) of the specific polymer is preferably 1.00 to 5.00, and preferably 1.01 to 4.50. It is more preferably 1.02 to 4.00.

From the viewpoint of further improving the crack resistance and fuel efficiency of the tire, the amount of vinyl bonds in the butadiene portion of the specific polymer is preferably 5 to 70%, more preferably 5 to 65%.
From the viewpoint of further improving the crack resistance and fuel efficiency of the tire, the amount of bound styrene in the specific polymer is preferably from 0 to 40% by mass, more preferably from 0 to 38% by mass, and from 0 to 38% by mass. More preferably, it is 35% by mass.

The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw/Mn) of a specific polymer can be determined by gel permeation chromatography (GPC) using polystyrene as a standard substance.
The amount of vinyl bonds in the butadiene moiety of the specific polymer can be determined by the Morello method, and the amount of bound styrene can be determined from the integral ratio of ^{the 1} H-NMR spectrum.

In addition to the specific polymer, the rubber components include natural rubber (NR); polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), It may contain one or more synthetic rubbers such as chloroprene rubber (CR) and halogenated butyl rubber.

The content of the specific polymer in the rubber component is not particularly limited, but from the viewpoint of improving the crack resistance and fuel efficiency of the tire, it is preferably 1 to 100% by mass, and 10 to 100% by mass. It is more preferably 10 to 80 mass %, even more preferably 10 to 60 mass %, and may be 100 mass %.

[Metal compound containing trivalent metal ion]
The rubber composition of the present invention contains a metal compound (specific metal compound) containing a trivalent metal ion.
The valence of the metal ions in the specific metal compound may change from trivalent to divalent during kneading or after vulcanization of the rubber composition depending on the stability of the specific metal compound. A metal compound containing a trivalent metal ion is used when blending the constituent components of the composition. Unless a metal compound containing a trivalent metal ion is used during blending, the resulting tire will not have both excellent crack resistance and high crack resistance.

The amount of the specific metal compound blended is preferably 0.1 to 10 parts by weight per 100 parts by weight of the rubber component.
When the content of the specific metal compound is 0.1 part by mass or more with respect to 100 parts by mass of the rubber component, the crack resistance and fuel efficiency of the tire are improved, and when the content is 10 parts by mass or less, the rubber composition and In comparison, agglomerates of highly polar specific metal compounds are less likely to occur, and a decrease in crack resistance caused by such agglomerates can be suppressed.
The amount of the specific metal compound added to 100 parts by mass of the rubber component is preferably 0.1 to 5 parts by mass, more preferably 0.1 to 3 parts by mass.

Trivalent metal ions of the specific metal compound include, for example, iron ions (Fe ³⁺ ), copper ions (Cu ³⁺ ), aluminum ions (Al ³⁺ ), cobalt ions (Co ³⁺ ), manganese ions (Mn ³⁺ ), and titanium ions. (Ti ³⁺ ), rubidium ion (Ru ³⁺ ), nickel ion (Ni ³⁺ ), and the like. The trivalent metal ion is preferably at least one selected from the group of these metal ions.
Among the above, from the viewpoint of further improving the crack resistance and fuel efficiency of the tire, the trivalent metal ions are preferably iron ions, aluminum ions, and nickel ions, more preferably iron ions or aluminum ions, and iron ions. is even more preferable.

Examples of the specific metal compound include at least one selected from the group consisting of chlorides, nitrates, bromides, sulfates, carbonates, phosphates, complexes, and organic acid salts, and hydrates thereof. It's okay.
Examples of chlorides include iron (III) chloride [FeCl ₃ ], aluminum chloride [AlCl ₃ ], copper (III) chloride [CuCl ₃ ], rubidium chloride [RuCl ₃ ], cobalt chloride [CoCl ₃ ], and nickel chloride. Examples include [NiCl ₃ ], among which iron (III) chloride [FeCl ₃ ] is preferred.

Examples of the bromide include iron(III) bromide [FeBr ₃ ]. Examples of the sulfate include iron(III) [Fe ₂ (SO ₄ ) ₃ ]. Examples of the carbonate include aluminum carbonate [Al ₂ (CO ₃ ) ₃ ]. Examples of the phosphate include iron phosphate [FePO ₄ ].

Examples of the nitrate include iron (III) nitrate [Fe(NO ₃ ) ₃ ], aluminum nitrate [Al(NO ₃ ) ₃ ], nickel nitrate, and the like, with iron (III) nitrate being preferred.
Examples of the complex include iron acetylacetone complexes, iron bipyridyl complexes, iron carbonyldiene complexes, and iron acetylacetone complexes, among which iron acetylacetone complexes are preferred.
Examples of the organic acid salt include saturated or unsaturated fatty acid salts having 2 to 20 carbon atoms, and the hydrocarbon chain of the fatty acid salt may be linear or branched. Specifically, examples thereof include iron(III) hydroxide acetate [Fe(OH)( _CH3COO ) ₂ ], iron(III) stearate, iron carbonate, and the like, with iron stearate being preferred.

Among the above, from the viewpoint of improving the crack resistance and fuel efficiency of the tire, the specific metal compound is preferably a chloride, and is composed of iron ions, copper ions, aluminum ions, cobalt ions, rubidium ions, and nickel ions. More preferably, it is a chloride containing at least one selected from the group consisting of iron(III) chloride [FeCl ₃ ].

〔filler〕
The rubber composition of the present invention contains a filler.
When the rubber composition contains a filler, the mechanical strength of the vulcanized rubber can be improved, and the wear resistance, crack resistance, etc. of the tire can be improved.
The filler is not particularly limited, and for example, a reinforcing filler that reinforces the rubber composition is used. Examples of reinforcing fillers include silica and carbon black, and either silica or carbon black may be used alone, or both silica and carbon black may be used.

(silica)
The silica is not particularly limited, and general grade silica, special silica surface-treated with a silane coupling agent, etc. can be used depending on the purpose. It is preferable to use wet silica as the silica, for example. These may be used alone or in combination of two or more.

(Carbon black)
Carbon black is not particularly limited and can be appropriately selected depending on the purpose. Carbon black is preferably of FEF, SRF, HAF, ISAF, and SAF grade, and more preferably of HAF, ISAF, and SAF grade. These may be used alone or in combination of two or more.

The content of the filler in the rubber composition of the present invention is preferably 10 to 100 parts by mass, and 30 to 80 parts by mass, based on 100 parts by mass of the rubber component, from the viewpoint of crack resistance of the resulting tire. It is more preferable that it is part.

〔sulfur〕
The rubber composition of the present invention contains sulfur.
When the rubber composition contains sulfur, crosslinking (vulcanization) proceeds quickly and at low cost by heating the rubber composition, unlike crosslinking using peroxide, resulting in excellent supply stability.
Sulfur is not particularly limited, and examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.
In the rubber composition of the present invention, the sulfur content is preferably 0.1 to 10 parts by mass based on 100 parts by mass of the rubber component. When the sulfur content is 0.1 parts by mass or more, vulcanization can be sufficiently progressed, and when the sulfur content is 10 parts by mass or less, the aging resistance of the vulcanized rubber can be suppressed.
The content of sulfur in the rubber composition is more preferably 0.3 to 7 parts by mass, and even more preferably 0.5 to 4 parts by mass, based on 100 parts by mass of the rubber component. By setting this range, both the covalent crosslinking bond (vulcanized bond) bonded between the rubber component and sulfur and the coordinate bond bonding bonding between the pyridyl group and the specific metal compound are formed. It is easy to use, and it is easy to greatly improve crack resistance and fuel efficiency.

The rubber composition of the present invention includes a rubber component containing a specific polymer, a specific metal compound, a filler, and sulfur, and, if necessary, compounding agents commonly used in the rubber industry, such as softeners, resins, Wax, stearic acid, anti-aging agents, vulcanization accelerators, etc. may be appropriately selected and contained within the range that does not impair the purpose of the present invention.

<Method for producing rubber composition>
The method for producing a rubber composition of the present invention includes a rubber component containing a polymer having a pyridyl group, a metal compound containing trivalent metal ions, and a filling amount of 1 to 10 parts by mass based on 100 parts by mass of the rubber component. The method includes a kneading step of kneading the agent and sulfur.
In the kneading step, other components that may be included in the rubber composition of the present invention, such as oil, wax, vulcanization accelerator, anti-aging agent, etc., may be further added and kneaded. The kneading step may be performed once or may be divided into two or more times. The kneading may be carried out using a kneading machine such as a Banbury mixer, a roll, an internal mixer, a single-screw extrusion kneader, or a twin-screw extrusion kneader.

<Tires>
The tire (pneumatic tire) of the present invention is made using the rubber composition of the present invention.
Since the tire of the present invention uses the rubber composition of the present invention, it has both high crack resistance and excellent fuel efficiency.
Depending on the type and components of the tire to which it is applied, the tire may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or it may be obtained by vulcanizing the unvulcanized rubber composition after a pre-vulcanization process, etc. After obtaining a semi-vulcanized rubber from a product, the semi-vulcanized rubber may be molded using the semi-vulcanized rubber, and then further vulcanized. Among various tire members, it is preferable to apply the present invention to tread members from the viewpoint of achieving an excellent balance between wear resistance and on-ice performance. Note that as the gas to fill the tire, in addition to normal air or air with adjusted oxygen partial pressure, inert gas such as nitrogen, argon, helium, etc. can be used.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but these Examples are intended to illustrate the present invention and are not intended to limit the present invention in any way.

<Production Example 1: Synthesis of modified SBR (biPy)>
Step (i): In a glass bottle with an inert atmosphere, cyclohexane (240 g), butadiene/cyclohexane solution (25% by mass, 194 g), styrene/cyclohexane solution (27% by mass, 46 g), 4-methylstyrene (480 mg) ) and mixed, then 2,2-di-(2-tetrahydrofuryl)propane/cyclohexane solution (1M, 0.35mL) and n-butyllithium (1.6M, 0.32mL) were added. The mixture was gently shaken at 50° C. for 1 hour to complete polymerization and confirm the formation of a conjugated diene polymer.
In step (ii), N,N,N',N'-tetramethylethylenediamine (418 mg), sec-butyllithium (1.0M, 3.6 mL) was added thereto, and the mixture was shaken at 50°C for 1 hour.
In step (iii), a bipyridyl/tetrahydrofuran solution (0.5 M, 10.8 mL) was added to the solution containing the conjugated diene polymer obtained in step (ii), and the mixture was shaken at 50° C. for 1 hour.
After that, 0.5 mL of an isopropanol solution (BHT concentration: 5% by mass) of 2,6-di-t-butyl-p-cresol (BHT) was added to the obtained polymer cement, and the mixture was reprecipitated with isopropanol and the pressure was reduced. By drying, a modified styrene-butadiene copolymer into which the desired bipyridyl was introduced was obtained.

<Production Example 2: Synthesis of modified SBR (Py)>
Perform the same procedure up to step (ii) in Production Example 1, add pyridine/tetrahydrofuran solution (0.5 M, 10.8 mL) to the obtained solution containing the conjugated diene polymer, and shake at 50 ° C. for 1 hour. Ta.
Thereafter, reprecipitation and drying under reduced pressure were carried out in the same manner as in Production Example 1 to obtain a modified styrene-butadiene copolymer into which the desired pyridine was introduced.

<Preparation of rubber composition and production of vulcanized rubber>
[Preparation of rubber composition]
Each component was blended and kneaded according to the formulation in Table 2 to obtain rubber compositions of Examples and Comparative Examples. The prepared rubber composition was vulcanized to obtain vulcanized rubber.
When producing a tire, for example, a tire (tire size: 195/65R15) may be produced using the prepared rubber composition as tire case rubber.

<Evaluation>
(1) Fuel efficiency evaluation Loss tangent (tan δ) was measured at a temperature of 50° C., a frequency of 15 Hz, and a strain of 10% using a viscoelasticity measuring device “Ares G2” manufactured by TA Instruments. The value of tan δ was expressed as an index by taking its reciprocal and setting the value of Comparative Example 2 as 100. The smaller the index value, the better the fuel efficiency.
An index of less than 90 is acceptable. The results are shown in Table 2.
Fuel efficiency index = (tan δ of vulcanized rubber of comparative example 2/tan δ of each vulcanized rubber) x 100

(2) Crack resistance evaluation For vulcanized rubber samples, a 0.5 mm crack is made in the center of the JIS No. 3 test piece, and fatigue is repeatedly applied at a constant strain of 40 to 100% at room temperature until the sample breaks. The number of times was measured and evaluated.
In Table 2, the index is expressed when Comparative Example 2 is taken as 100, and the larger the index value, the better the crack resistance is.

Details of the components in Table 2 are as follows.
1. Rubber component (1) Unmodified SBR: Manufactured by Asahi Kasei Chemicals Co., Ltd., trade name "TUFDENE 3835"
(2) Modified SBR (biPy): Modified styrene-butadiene copolymer produced in Production Example 1 (3) Modified SBR (Py): Modified styrene-butadiene copolymer produced in Production Example 2

2. Metal compound (1) FeCl ₃ : metal compound containing trivalent metal ion, iron chloride (III)
(2) ZnCl ₂ : Metal compound containing divalent metal ions, zinc chloride (II)

3. Various components (1) Filler: N234 grade carbon black, manufactured by Asahi Carbon Co., Ltd., product name "#78"
(2) Oil: Manufactured by Fuji Kosan Co., Ltd., product name “Aromax #3”
(3) Anti-aging agent: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name "Nocrac 6C"
(4) Wax: Manufactured by Seiko Kagaku Co., Ltd., product name “Suntite”
(5) Vulcanization accelerator: Manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name “Noxeler CZ-G”

Number average molecular weight (Mn), weight average molecular weight (Mw), molecular weight distribution (Mw/Mn), amount of bound styrene, and butadiene moiety of each polymer of unmodified SBR, modified SBR (biPy), and modified SBR (Py). The amount of vinyl bonds is shown in Table 1.
The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw/Mn) were determined by gel permeation chromatography (GPC) using polystyrene as a standard substance.
The amount of vinyl bonds in the polymer was measured by the Morello method, and the amount of bonded styrene was determined from the integral ratio of the ¹ H-NMR spectrum.

As can be seen from Table 2, the vulcanized rubber obtained from the rubber composition of Comparative Example 1, which did not use a polymer having a pyridyl group, had a significantly lower fuel efficiency index and was not excellent in crack resistance.
Similarly, the vulcanized rubbers obtained from the rubber compositions of Comparative Examples 2 and 3 in which a polymer having a bipyridyl group was used instead of a polymer having a pyridyl group were metal compounds containing trivalent metal ions. By adding , the fuel efficiency index decreased and the crack resistance significantly decreased.
Even if a polymer having a pyridyl group is used, a rubber composition containing no metal compound (Comparative Example 4) and a rubber composition in which the metal species of the metal compound is a divalent metal ion (Comparative Example 5) can be used. The vulcanized rubber had a low fuel efficiency index and was not excellent in crack resistance.
On the other hand, the vulcanized rubber obtained from the rubber composition of the example exhibited significantly excellent crack resistance while suppressing the decrease in fuel efficiency index. By applying such vulcanized rubber to tires, it is expected that tires that have both high crack resistance and excellent fuel efficiency can be obtained.

By using the rubber composition of the present invention, it is possible to obtain a tire that has both high crack resistance and excellent fuel efficiency. It is suitably used in various tires for trucks and heavy loads (trucks/buses, off-the-road tires (mining vehicles, construction vehicles, small trucks, etc.)). In particular, the rubber composition of the present invention is suitable for use in passenger cars, light passenger cars, light trucks, heavy-duty tires {trucks and buses, off-the-road tires (mining vehicles, construction vehicles, light trucks, etc.)}, etc. Suitable for use in tire cases, tread members, etc. of various tires.
Examples of case members include side walls, side reinforcing rubber, belts, chafers, beads, stiffeners, inner liners, etc., and examples of tread members include cap treads, base treads, etc.
The rubber composition of the present invention is also applicable to uses other than tires. Applications other than tires include anti-vibration rubber, anti-vibration rubber, crawlers, belts, hoses, etc.

Claims (5)

A rubber component containing a polymer having a pyridyl group;
a metal compound containing a trivalent metal ion;
filler and
sulfur and
A rubber composition comprising:
The polymer having a pyridyl group is a modified styrene-butadiene copolymer rubber whose molecular main chain is modified with a compound having a monodentate pyridyl group,
A rubber composition, wherein the trivalent metal ion is at least one selected from the group consisting of iron ions, copper ions, aluminum ions, cobalt ions, manganese ions, titanium ions, rubidium ions, and nickel ions. The rubber composition according to claim 1 , wherein the metal compound is at least one selected from the group consisting of chlorides, nitrates, bromides, sulfates, carbonates, phosphates, complexes, and organic acid salts. The rubber composition according to claim 1 or 2 , wherein the amount of the metal compound blended is 0.1 to 10 parts by mass based on 100 parts by mass of the rubber component. The rubber composition according to any one of claims 1 to 3 , wherein the content of the polymer in the rubber component is 10 to 100% by mass. A tire using the rubber composition according to any one of claims 1 to 4 .