JP2013159769A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire that can improve low fuel consumption, abrasion resistance, mechanical strengths and vulcanization stability and a pneumatic tire using the rubber composition for tire in each member (especially tread) of the tire.SOLUTION: A rubber composition for a tire comprises a modified natural rubber having a phosphorus content of ≤200 ppm, a butadiene rubber, a compound represented by formula (1) [wherein p is an integer of 2-8] and/or formula (2) [wherein q is an integer of 2-8; Mis a metal ion: r is its valence], carbon black and a compound represented by formula (A) [wherein Y is 2-10C alkylene; Rand Rare the same or different and each a nitrogen atom-containing monovalent organic group].

Description

The present invention relates to a rubber composition for a tire and a pneumatic tire using the same.

Currently, in the transportation industry, tires with excellent fuel efficiency are desired for reasons such as rising fuel costs and increased costs due to the introduction of environmental regulations. As one of the methods for improving the low fuel consumption, a method of replacing carbon black as a filler with silica is known. However, although this method can improve fuel efficiency, there is a problem that wear resistance is lowered.

In Patent Documents 1 to 3, for the purpose of improving fuel economy, in a compound containing silica, a specific polar group is added to rubber so as to have affinity with silica, thereby improving dispersibility of silica and reducing fuel consumption. Although a method for obtaining a rubber composition having excellent properties is described, provision of other methods is also demanded.

JP 2001-114939 A JP 2005-126604 A JP 2005-325206 A

The present invention solves the above-mentioned problems and improves the fuel efficiency, wear resistance, mechanical strength, vulcanization stability of the tire, and the tire rubber composition. An object of the present invention is to provide a pneumatic tire used for a tread.

［式（１）中、ｐは２〜８の整数を表す。式（２）中、ｑは２〜８の整数を表す。Ｍ^ｒ＋は金属イオンを表し、ｒはその価数を表す。］

［式（Ａ）中、Ｙは、炭素数２〜１０のアルキレン基、Ｒ^１０及びＲ^１１は、同一若しくは異なって、チッ素原子を含む１価の有機基を表す。］
式（２）中のＭ^ｒ＋で表される金属イオンが、リチウムイオン、ナトリウムイオン、カリウムイオン、セシウムイオン、コバルトイオン、銅イオン、又は亜鉛イオンであることが好ましく、リチウムイオン、ナトリウムイオン、又はカリウムイオンであることがより好ましい。 The present invention relates to a modified natural rubber having a phosphorus content of 200 ppm or less, a butadiene rubber, a compound represented by the following formula (1) and / or the following formula (2), carbon black, and the following formula (A). The rubber composition for tires containing the compound represented by these.

[In formula (1), p represents the integer of 2-8. In formula (2), q represents an integer of 2 to 8. M ^{r +} represents a metal ion, and r represents its valence. ]

[In Formula (A), Y is an alkylene group having 2 to 10 carbon atoms, and R ¹⁰ and R ¹¹ are the same or different and each represents a monovalent organic group containing a nitrogen atom. ]
It is preferable that the metal ion represented by ^{Mr +} in Formula (2) is a lithium ion, a sodium ion, a potassium ion, a cesium ion, a cobalt ion, a copper ion, or a zinc ion, and a lithium ion, a sodium ion, or More preferred is potassium ion.

The tire rubber composition preferably has a modified natural rubber content of 60% by mass or more and a butadiene rubber content of 5 to 40% by mass in 100% by mass of the rubber component.

In the tire rubber composition, the total content of the modified natural rubber and butadiene rubber in 100% by mass of the rubber component is preferably 80% by mass or more.

In the tire rubber composition, the content of the compound represented by the formula (A) is 0.05 to 12 parts by mass with respect to 100 parts by mass of the rubber component, and the content of carbon black is 100 parts by mass of the rubber component. 10 to 90 parts by mass with respect to parts, and the total content of the compounds represented by the above formula (1) and the following formula (2) is 0.2 to 10 parts by mass with respect to 100 parts by mass in total of carbon black and silica. Part.

The nitrogen content of the modified natural rubber is preferably 0.3% by mass or less, and the gel content measured as a toluene insoluble content is preferably 20% by mass or less.

In the modified natural rubber, the natural rubber latex is saponified to obtain a saponified natural rubber latex (A), and the obtained saponified natural rubber latex has a phosphorus content of 200 ppm or less. It is preferable that it is what was obtained by the manufacturing method including the process (B) wash | cleaned until it becomes.

The tire rubber composition is preferably used as a tread rubber composition.

The present invention also relates to a pneumatic tire produced using the rubber composition. The pneumatic tire is preferably a truck / bus tire.

According to the present invention, a modified natural rubber, a butadiene rubber, a compound represented by the above formula (1) and / or the above formula (2), carbon black, and a compound represented by the above formula (A) Therefore, low fuel consumption, wear resistance, mechanical strength, and vulcanization stability can be improved. By using the rubber composition for each member (particularly, tread) of the tire, a pneumatic tire excellent in low fuel consumption, wear resistance, and mechanical strength can be provided with high productivity.

The rubber composition for tires of the present invention includes a modified natural rubber, a butadiene rubber, a compound represented by the above formula (1) and / or the above formula (2), carbon black, and the above formula (A). And the compounds represented.

Modified natural rubber (HPNR) with a phosphorus content of 200 ppm or less has a property that it is difficult to generate heat because the phospholipids contained in the natural rubber (NR) are reduced and removed (preferably the protein and gel are also removed). Therefore, further reduction in fuel consumption can be achieved compared to the use of NR. However, it has been clarified by the inventor's research that wear resistance decreases when HPNR is used. As a result of intensive studies by the inventor on this newly generated problem, by blending butadiene rubber (BR) with HPNR, it is possible to improve fuel efficiency while maintaining good wear resistance. I found out that As a result of further studies, it is possible to further improve fuel efficiency by blending carbon black and the compound represented by the above formula (1) and / or the above formula (2) in addition to HPNR and BR. I found out that However, the use of these components in combination has revealed that the scorch time is shortened, the vulcanization stability is inferior, the wear resistance, and the mechanical strength are reduced. As a result of intensive studies by the inventor on this newly generated problem, by adding the compound represented by the above formula (A) together with the above components, the fuel consumption is further improved and the wear resistance is improved. It has been found that the property, mechanical strength and vulcanization stability can be greatly improved, and the fuel efficiency, wear resistance, mechanical strength and vulcanization stability can be improved in a well-balanced manner.
In the present specification, excellent vulcanization stability means that early vulcanization hardly occurs (excellent scorch stability), and can be evaluated by, for example, the method described in Examples.

In the present invention, modified natural rubber (HPNR) having a phosphorus content of 200 ppm or less is used as the rubber component.

The modified natural rubber (HPNR) has a phosphorus content of 200 ppm or less. If it exceeds 200 ppm, the amount of gel increases during storage, tan δ of the vulcanized rubber increases and the fuel efficiency deteriorates, or the Mooney viscosity of the unvulcanized rubber increases and the processability deteriorates. The phosphorus content is preferably 150 ppm or less, and more preferably 100 ppm or less. Here, the phosphorus content can be measured by a conventional method such as ICP emission analysis. Phosphorus is derived from phospholipids (phosphorus compounds).

In the modified natural rubber, the nitrogen content is preferably 0.3% by mass or less, and more preferably 0.15% by mass or less. When the nitrogen content exceeds 0.3% by mass, the Mooney viscosity increases during storage and the processability tends to deteriorate, and the fuel efficiency may also deteriorate. The nitrogen content can be measured by a conventional method such as Kjeldahl method. Nitrogen is derived from protein.

The gel content in the modified natural rubber is preferably 20% by mass or less, more preferably 10% by mass or less, and still more preferably 7% by mass or less. If it exceeds 20% by mass, the Mooney viscosity tends to increase and the processability tends to deteriorate, and the fuel efficiency may deteriorate. The gel content means a value measured as an insoluble content with respect to toluene which is a nonpolar solvent, and may be simply referred to as “gel content” or “gel content” below. The measuring method of the content rate of a gel part is as follows. First, a natural rubber sample is soaked in dehydrated toluene, light-shielded in the dark and left for 1 week, and then the toluene solution is centrifuged at 1.3 × 10 ⁵ rpm for 30 minutes to obtain an insoluble gel content and a toluene soluble content. Isolate. Methanol is added to the insoluble gel and solidified, and then dried, and the gel content is determined from the ratio between the mass of the gel and the original mass of the sample.

The modified natural rubber is preferably substantially free of phospholipids. “Substantially no phospholipid is present” represents a state in which a natural rubber sample is extracted with chloroform and a peak due to phospholipid does not exist at −3 ppm to 1 ppm in ³¹ P NMR measurement of the extract. The peak of phosphorus present at -3 ppm to 1 ppm is a peak derived from the phosphate structure of phosphorus in the phospholipid.

As a method for producing the modified natural rubber, for example, the production method described in JP 2010-138359 A, that is, the step (A) of obtaining a saponified natural rubber latex by saponifying the natural rubber latex, and the obtained Examples of the method include a step (B) of washing the saponified natural rubber latex until the phosphorus content in the rubber is 200 ppm or less. Specifically, first, a natural rubber latex is saponified with an alkali to prepare a saponified natural rubber latex, and then the agglomerated rubber obtained by agglomerating the saponified natural rubber latex contains phosphorus to the rubber content. A modified natural rubber (saponified natural rubber) can be produced by a method of repeatedly washing with water until the rate becomes 200 ppm or less and drying.

According to the above production method, the phosphorus compound separated by saponification is washed away, so that the phosphorus content of the natural rubber can be suppressed. Moreover, since the protein in natural rubber is decomposed by the saponification treatment, the nitrogen content of the natural rubber can be suppressed.

In the rubber composition of the present invention, the content of the modified natural rubber in 100% by mass of the rubber component is preferably 60% by mass or more, more preferably 70% by mass or more, and further preferably 75% by mass or more. If it is less than 60% by mass, fuel economy may not be sufficiently improved. The content is preferably 95% by mass or less, more preferably 90% by mass or less. If it exceeds 95% by mass, the wear resistance and vulcanization stability may be deteriorated.

In the present invention, butadiene rubber (BR) is used together with the modified natural rubber. The BR is not particularly limited. For example, BR having a high cis content (BR having a cis content of 90% by mass or more), BR containing syndiotactic polybutadiene crystals, butadiene rubber synthesized using a rare earth element-based catalyst ( Hereinafter, it is also referred to as rare earth BR). Of these, BR having a high cis content (preferably a BR having a cis content of 95% by mass or more) is preferable because of its high effect of improving fuel economy, mechanical strength, and abrasion resistance.

The content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more. If it is less than 5% by mass, the wear resistance may be deteriorated. The BR content is preferably 40% by mass or less, more preferably 30% by mass or less, and still more preferably 25% by mass or less. If it exceeds 40% by mass, the fuel economy may not be sufficiently improved.

The total content of the modified natural rubber and BR in 100% by mass of the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass. If it is less than 80% by mass, the fuel economy, wear resistance, mechanical strength, and vulcanization stability may not be improved in a well-balanced manner.

Examples of the rubber component used in the present invention other than HPNR and BR include natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), and chloroprene rubber (CR). And diene rubbers such as acrylonitrile butadiene rubber (NBR). A rubber component may be used independently and may use 2 or more types together.

［式（１）中、ｐは２〜８の整数を表す。式（２）中、ｑは２〜８の整数を表す。Ｍ^ｒ＋は金属イオンを表し、ｒはその価数を表す。］ In the present invention, a compound represented by the following formula (1) and / or the following formula (2) is used.

[In formula (1), p represents the integer of 2-8. In formula (2), q represents an integer of 2 to 8. M ^{r +} represents a metal ion, and r represents its valence. ]

The compound represented by the above formula (2) can be produced by any known method. Specifically, a method of reacting a haloalkylamine with sodium thiosulfate, reacting a potassium salt of phthalimide with a dihaloalkane, reacting the resulting compound with sodium thiosulfate, and then reacting the resulting compound with The method of hydrolyzing is mentioned.

Specifically, when q is a compound of 6, for example, a method of reacting 6-halohexylamine with sodium thiosulfate, a compound obtained by reacting a potassium salt of phthalimide with 1,6-dihalohexane And a method in which sodium thiosulfate is reacted and then the resulting compound is hydrolyzed.

When q is a compound of 3, for example, a method in which 3-halopropylamine and sodium thiosulfate are reacted, a potassium salt of phthalimide and 1,3-dihalopropane are reacted, Examples include a method of reacting with sodium thiosulfate and then hydrolyzing the obtained compound.

The compound represented by the above formula (1) can be produced, for example, by reacting the compound represented by the above formula (2) with a protonic acid.

In the present invention, a mixture of the compound represented by the above formula (1) and the compound represented by the above formula (2) can also be used. Such a mixture is obtained by mixing a compound represented by the above formula (1) and a compound represented by the above formula (2), a metal alkali (a metal-containing hydroxide, carbonate, and A method in which a part of the compound represented by the above formula (1) is metallated using a bicarbonate, a method of neutralizing a part of the compound represented by the above formula (2) using a protonic acid Can be manufactured. The compound represented by the above formula (1) and the compound represented by the above formula (2) thus produced can be taken out from the reaction mixture by operations such as concentration and crystallization, The compound represented by the formula (1) and the compound represented by the above formula (2) usually contain about 0.1 to 5% of water. In the present invention, only the compound represented by the above formula (1) can be used, or only the compound represented by the above formula (2) can be used. Moreover, the compound represented by the multiple types of compound represented by said Formula (1) and the said Formula (2) can also be used together.

In formula (1), p represents an integer of 2 to 8, and 2 to 5 are preferable. In formula (2), q represents an integer of 2 to 8, preferably 2 to 5.

As the metal ion represented by ^{Mr +} , lithium ion, sodium ion, potassium ion, cesium ion, cobalt ion, copper ion and zinc ion are preferable, lithium ion, sodium ion and potassium ion are more preferable, and sodium ion is still more preferable. . r represents the valence of the metal ion, and is not limited as long as it is possible in the metal. When the metal ion is an alkali metal ion such as lithium ion, sodium ion, potassium ion or cesium ion, r is usually 1, and when the metal ion is cobalt ion, r is usually 2 or 3. When the metal ion is a copper ion, r is usually an integer of 1 to 3, and when the metal ion is a zinc ion, r is usually 2. According to the said manufacturing method, although the sodium salt of the compound represented by the said Formula (1) is obtained normally, it can convert into metal salts other than a sodium salt by performing a cation exchange reaction.

The median diameter of the compound represented by the above formula (1) and the compound represented by the above formula (2) is preferably in the range of 0.05 to 100 μm, more preferably in the range of 1 to 100 μm. Such median diameter can be measured by a laser diffraction method.

The compound represented by the above formula (1) and the compound represented by the above formula (2) may be used after being previously mixed with a carrier. Examples of the supporting agent include “inorganic fillers and reinforcing agents” described on pages 510 to 513 of “Rubber Industry Handbook <Fourth Edition>” edited by the Japan Rubber Association. Among them, carbon black, silica, calcined Clay and aluminum hydroxide are preferred. Although the usage-amount of a support agent is not specifically limited, The range of 10-1000 mass parts is preferable with respect to 100 mass parts of total amounts of the compound represented by the said Formula (1) and / or the said Formula (2).

The total content of the compounds represented by the above formula (1) and the above formula (2) is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass with respect to a total of 100 parts by mass of carbon black and silica. Part or more, more preferably 1 part by weight or more. If it is less than 0.2 parts by mass, the fuel economy may not be sufficiently improved. The total content is preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and still more preferably 5 parts by mass or less with respect to 100 parts by mass of the total of carbon black and silica. If it exceeds 10 parts by mass, the mechanical strength, wear resistance, and vulcanization stability may be deteriorated.

In the present invention, carbon black is used. Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 20 m ² / g or more, more preferably 30 m ² / g or more. If it is less than 20 m ² / g, sufficient reinforcing properties cannot be obtained, and mechanical strength and wear resistance tend to decrease. Further, the N ₂ SA of the carbon black is preferably 100 m ² / g or less, more preferably 60 m ² / g or less. If it exceeds 100 m ² / g, the fuel efficiency tends to deteriorate. Further, the dispersibility tends to be inferior, and the wear resistance and mechanical strength tend to decrease.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

Carbon black has a dibutyl phthalate oil absorption (DBP) of preferably 50 ml / 100 g or more, more preferably 90 ml / 100 g or more. If it is less than 50 ml / 100 g, the fuel efficiency tends to deteriorate.
The DBP of carbon black is preferably 160 ml / 100 g or less, more preferably 140 ml / 100 g or less. When it exceeds 160 ml / 100 g, there exists a tendency for abrasion resistance and mechanical strength to fall.
In addition, DBP of carbon black is calculated | required by the measuring method of JISK6217-4.

The content of carbon black is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and still more preferably 35 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, the mechanical strength and wear resistance may not be sufficiently improved. The content of the carbon black is preferably 90 parts by mass or less, more preferably 60 parts by mass or less. If it exceeds 90 parts by mass, fuel efficiency may be deteriorated.
In the present invention, together with carbon black, modified natural rubber, butadiene rubber, a compound represented by the above formula (1) and / or the above formula (2), and a compound represented by the above formula (A) By using in combination, fuel economy, abrasion resistance, mechanical strength, and vulcanization stability can be improved. Therefore, it is not necessary to reduce the amount of carbon black in order to improve the fuel efficiency, and the carbon black content can be adjusted to the above-mentioned amount, so that the decrease in mechanical strength and wear resistance can be suppressed, and the fuel efficiency can be reduced. Properties, wear resistance, mechanical strength, and vulcanization stability are well-balanced.

［式（Ａ）中、Ｙは、炭素数２〜１０のアルキレン基、Ｒ^１０及びＲ^１１は、同一若しくは異なって、チッ素原子を含む１価の有機基を表す。］ In the present invention, a compound represented by the following formula (A) is blended as a vulcanizing agent.
By blending a compound represented by the following formula (A), the rubber composition can have a CC bond having high binding energy and high thermal stability. By blending the compound represented by the following formula (A) together with the compound represented by (1) and / or the above formula (2) and carbon black, low fuel consumption, wear resistance, mechanical strength, Sulfur stability can be improved in a well-balanced manner. In addition, you may mix | blend sulfur with the compound represented by a following formula (A).

[In Formula (A), Y is an alkylene group having 2 to 10 carbon atoms, and R ¹⁰ and R ¹¹ are the same or different and each represents a monovalent organic group containing a nitrogen atom. ]

The alkylene group for Y (having 2 to 10 carbon atoms) is not particularly limited, and examples thereof include linear, branched, and cyclic groups. Among them, a linear alkylene group is preferable. As for carbon number, 4-8 are preferred. When the number of carbon atoms in the alkylene group is 1, the thermal stability tends to be poor, and the effect of having an alkylene group tends not to be obtained. When the number of carbon atoms is 11 or more, -S-S-YSS- It tends to be difficult to form a crosslinked chain represented by

Examples of the alkylene group satisfying the above conditions include ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, decamethylene group and the like. Among these, a hexamethylene group is preferable because a bridge represented by —S—S—Y—S—S— is smoothly formed between the polymers and is thermally stable.

R ¹⁰ and R ¹¹ are not particularly limited as long as they are monovalent organic groups containing a nitrogen atom, but those containing at least one aromatic ring are preferred, and N—C (= Those containing a linking group represented by S)-are more preferred. Moreover, although linear, branched, and cyclic | annular may be sufficient, a branched shape is preferable.

R ¹⁰ and R ¹¹ may be the same or different, but are preferably the same for reasons such as ease of production.

Examples of the compound satisfying the above conditions include 1,2-bis (N, N′-dibenzylthiocarbamoyldithio) ethane, 1,3-bis (N, N′-dibenzylthiocarbamoyldithio) propane, 1, 4-bis (N, N′-dibenzylthiocarbamoyldithio) butane, 1,5-bis (N, N′-dibenzylthiocarbamoyldithio) pentane, 1,6-bis (N, N′-dibenzylthio) Carbamoyldithio) hexane, 1,7-bis (N, N′-dibenzylthiocarbamoyldithio) heptane, 1,8-bis (N, N′-dibenzylthiocarbamoyldithio) octane, 1,9-bis (N , N′-dibenzylthiocarbamoyldithio) nonane, 1,10-bis (N, N′-dibenzylthiocarbamoyldithio) decane and the like. Among these, 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane is preferable because it is thermally stable and has excellent polarizability.

The content of the compound represented by the formula (A) is preferably 0.05 parts by mass or more, more preferably 0.08 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.05 parts by mass, sufficient fuel economy, wear resistance, mechanical strength, and vulcanization stability may not be obtained. The content of the compound represented by the formula (A) is preferably 12 parts by mass or less, more preferably 11 parts by mass or less. If it exceeds 12 parts by mass, fuel economy, mechanical strength, and vulcanization stability may be deteriorated.

In addition to the above components, the rubber composition of the present invention includes compounding agents generally used in the production of rubber compositions, such as reinforcing fillers such as silica and clay, silane coupling agents, zinc oxide, and stearic acid. Further, processing aids, various anti-aging agents, softening agents such as oil, vulcanizing agents such as wax and sulfur, vulcanization accelerators, and the like can be appropriately blended.

Examples of silica include dry process silica (anhydrous silica), wet process silica (hydrous silica), and wet process silica is preferred because it has many silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 120 m ² / g or more, more preferably 150 m ² / g or more. If it is less than 120 m ² / g, sufficient reinforcing properties cannot be obtained, and sufficient mechanical strength and abrasion resistance tend to be not obtained. Further, N ₂ SA of silica is preferably 250 m ² / g or less, more preferably 200 m ² / g or less. When it exceeds 250 m < ² > / g, the viscosity of an unvulcanized rubber composition will become high and there exists a tendency for workability to deteriorate. The _N 2 SA of silica is a value determined by the BET method in accordance with ASTMD3037-81.

When silica is contained, the content of silica is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 5 parts by mass, the fuel economy, mechanical strength, and wear resistance may not be improved in a well-balanced manner. The content of silica is preferably 90 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 30 parts by mass or less. When it exceeds 90 parts by mass, the viscosity of the unvulcanized rubber composition increases, and the fuel economy and processability tend to deteriorate.

The total content of carbon black and silica is preferably 10 parts by mass or more, more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, the fuel economy, mechanical strength, and wear resistance may not be improved in a well-balanced manner. The total content is preferably 100 parts by mass or less, more preferably 70 parts by mass or less. If it exceeds 100 parts by mass, fuel economy and processability may be deteriorated.
In the present invention, together with carbon black, modified natural rubber, butadiene rubber, a compound represented by the above formula (1) and / or the above formula (2), and a compound represented by the above formula (A) By using in combination, fuel economy, abrasion resistance, mechanical strength, and vulcanization stability can be improved. Therefore, it is not necessary to reduce the amount of carbon black and silica in order to improve fuel efficiency, and the total content of carbon black and silica can be adjusted to the above amount, so that the mechanical strength and wear resistance are reduced. It is possible to suppress the fuel consumption, wear resistance, mechanical strength, and vulcanization stability in a well-balanced manner.

When silica is contained, it is preferable to contain a silane coupling agent together with silica.
As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry, and examples thereof include sulfide systems such as bis (3-triethoxysilylpropyl) disulfide, 3- Mercapto type such as mercaptopropyltrimethoxysilane, vinyl type such as vinyltriethoxysilane, amino type such as 3-aminopropyltriethoxysilane, glycidoxy type of γ-glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxy Examples thereof include nitro compounds such as silane and chloro compounds such as 3-chloropropyltrimethoxysilane. Of these, sulfide systems are preferred. The content of the silane coupling agent is preferably 3 to 15 parts by mass with respect to 100 parts by mass of silica.

Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerator. Agents. Of these, sulfenamide vulcanization accelerators are preferred.

Examples of the sulfenamide vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N And '-dicyclohexyl-2-benzothiazolylsulfenamide (DZ). Of these, CBS is preferable.

The content of the vulcanization accelerator is preferably 0.05 parts by mass or more, more preferably 0.08 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.05 parts by mass, mechanical fatigue tends to occur, durability is lowered, and there is a tendency that compatibility with low fuel consumption is difficult. The content of the vulcanization accelerator is preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 2.0 parts by mass or less, and particularly preferably 1.7 parts by mass or less. . If it exceeds 4.0 parts by mass, sufficient fuel economy, abrasion resistance, mechanical strength, and vulcanization stability (particularly vulcanization stability) may not be obtained.

The sulfur content is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.05 parts by mass, mechanical fatigue tends to occur, durability is lowered, and there is a tendency that compatibility with low fuel consumption is difficult. The sulfur content is preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 2.0 parts by mass or less, and particularly preferably 1.5 parts by mass or less. If it exceeds 4.0 parts by mass, sufficient fuel economy, abrasion resistance, mechanical strength, and vulcanization stability (particularly vulcanization stability) may not be obtained.
In the present invention, modified natural rubber, butadiene rubber, a compound represented by the above formula (1) and / or the above formula (2), carbon black, and a compound represented by the above formula (A) By using in combination, fuel economy, abrasion resistance, mechanical strength, and vulcanization stability can be improved. Therefore, it is not necessary to increase the amount of sulfur to improve fuel efficiency, and the sulfur content can be adjusted to the above amount, so that a decrease in vulcanization stability can be suppressed, and fuel efficiency and wear resistance are reduced. , Mechanical strength and vulcanization stability are well balanced.

The oil content is preferably 8 parts by mass or less, more preferably 5 parts by mass or less, further preferably 1 part by mass or less, particularly preferably 0.1 parts by mass or less, and most preferably 0 part by mass (not contained). is there. If it exceeds 8 parts by mass, the mechanical strength and wear resistance may be deteriorated.

As a method for producing the rubber composition of the present invention, a known method can be used. For example, the above components are kneaded using a rubber kneader such as an open roll, a Banbury mixer, a closed kneader, and then added. It can be manufactured by a method of sulfurating.

The rubber composition of the present invention can be suitably used for each member (particularly tread) of a tire.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, if necessary, a rubber composition containing various additives is extruded in accordance with the shape of each member (particularly, tread) of the tire at an unvulcanized stage, and a normal method is performed on a tire molding machine. After being formed by bonding together with other tire members to form an unvulcanized tire, the tire can be manufactured by heating and pressing in a vulcanizer.

The tire of the present invention is suitably used as a truck / bus tire.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

(Production Example 1) (Production of sodium salt of S- (3-aminopropyl) thiosulfuric acid)
The gas in the reaction vessel was replaced with nitrogen gas. The reaction vessel was charged with 25 g (0.11 mol) of 3-bromopropylamine bromate, 28.42 g (0.11 mol) of sodium thiosulfate pentahydrate, 125 ml of methanol and 125 ml of water. The mixture was refluxed at 70 ° C. for 4.5 hours. The reaction mixture was allowed to cool and methanol was removed under reduced pressure. To the obtained residue, 4.56 g of sodium hydroxide was added, and the resulting mixture was stirred at room temperature for 30 minutes. After completely removing the solvent under reduced pressure, 200 ml of ethanol was added to the residue and refluxed for 1 hour. By-product sodium bromide was removed by hot filtration. The filtrate was concentrated under reduced pressure until crystals precipitated, and then allowed to stand. The crystals were removed by filtration and washed with ethanol and then hexane. The obtained crystals were vacuum-dried to obtain S- (3-aminopropyl) thiosulfuric acid sodium salt (compound represented by the following formula).
¹ H-NMR (270.05 MHz, MeOD) δ _ppm : 3.1 (2H, t, J = 6.3 Hz), 2.8 (2H, t, J = 6.2 Hz), 1.9-2. 0 (2H, m)
The median diameter (50% D) of the sodium salt of the obtained S- (3-aminopropyl) thiosulfuric acid was measured by a laser diffraction method (measurement procedure is as follows) using SALD-2000J type manufactured by Shimadzu Corporation. However, the median diameter (50% D) was 66.7 μm. The obtained sodium salt of S- (3-aminopropyl) thiosulfuric acid was pulverized to prepare a sodium salt of S- (3-aminopropyl) thiosulfuric acid having a median diameter (50% D) of 14.6 μm. . The sodium salt of S- (3-aminopropyl) thiosulfate having a median diameter (50% D) of 14.6 μm was used in the following examples.
<Measurement operation>
The obtained sodium salt of S- (3-aminopropyl) thiosulfuric acid was added to a mixed solution of the following dispersion solvent (toluene) and a dispersant (10% by mass sodium di-2-ethylhexyl sulfosuccinate / toluene solution) at room temperature. The dispersion was stirred for 5 minutes while irradiating the obtained dispersion with ultrasonic waves to obtain a test solution. The test solution was transferred to a batch cell and measured after 1 minute. (Refractive index: 1.70-0.20i)
The pH of the aqueous solution obtained by dissolving 10.0 g of sodium salt of S- (3-aminopropyl) thiosulfuric acid in 30 ml of water was 11-12.

Hereinafter, various chemicals used in Production Example 2 will be described together. In addition, the chemical | medical agent refine | purified according to the usual method as needed.
Natural rubber latex: Field latex obtained from Taitex Co., Ltd. Surfactant: Emal-E (Polyoxyethylene lauryl ether sodium sulfate) manufactured by Kao Corporation
NaOH: NaOH manufactured by Wako Pure Chemical Industries, Ltd.

(Production Example 2) (Synthesis of saponified natural rubber)
After adjusting the solid rubber latex solids concentration (DRC) to 30% (w / v), 1000 g of natural rubber latex was added with 10 g of Emal-E and 20 g of NaOH, followed by saponification at room temperature for 48 hours. Natural rubber latex was obtained. Water was added to the latex to dilute to DRC 15% (w / v), and then formic acid was added with slow stirring to adjust the pH to 4.0 to 4.5 to cause aggregation. The agglomerated rubber was pulverized, washed repeatedly with 1000 ml of water, and then dried at 110 ° C. for 2 hours to obtain a solid rubber (saponified natural rubber (HPNR)).

Nitrogen content, phosphorus content, and gel content were measured by the methods shown below for HPNR obtained in Production Example 2 and TSR used in the evaluation of the rubber composition described below. The results are shown in Table 1.

(Measurement of nitrogen content)
The nitrogen content was measured using CHN CORDER MT-5 (manufactured by Yanaco Analytical Industries). For the measurement, first, a calibration curve for determining the nitrogen content was prepared using antipyrine as a standard substance. Next, about 10 mg of natural rubber obtained in each production example was weighed, and an average value was obtained from the measurement results of three times to obtain the nitrogen content of the sample.

(Measurement of phosphorus content)
The phosphorus content was determined using an ICP emission spectrometer (ICPS-8100, manufactured by Shimadzu Corporation).
In addition, ³¹ P-NMR measurement of phosphorus uses an NMR analyzer (400 MHz, AV400M, manufactured by Nippon Bruker Co., Ltd.), and uses a measurement peak of P atom in an 80% aqueous phosphoric acid solution as a reference point (0 ppm), and raw rubber with chloroform. More extracted components were purified, dissolved in CDCl ₃ and measured.

(Measurement of gel content)
A raw rubber sample 70.00 mg cut to 1 mm × 1 mm was weighed, 35 mL of toluene was added thereto, and the mixture was allowed to stand in a cool dark place for 1 week. Subsequently, centrifugation was performed to precipitate a gel component insoluble in toluene, the soluble component of the supernatant was removed, and only the gel component was solidified with methanol, and then dried and the mass was measured. The gel content (mass%) was determined by the following formula.
Gel content (mass%) = [mass mg after drying / mg of initial sample] × 100

As shown in Table 1, the saponified natural rubber (HPNR) had a reduced nitrogen content, phosphorus content, and gel content as compared to TSR. Moreover, in the ³¹ P NMR measurement of the extract extracted from HPNR obtained in the production example, no peak due to phospholipid was detected at -3 ppm to 1 ppm.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR20
HPNR: Saponified natural rubber (HPNR) prepared in Production Example 2 above
BR: Nipol BR1220 manufactured by Zeon Corporation (cis content: 97% by mass, vinyl content: 1.0% by mass)
Carbon Black: Diamond Black E (FEF, N ₂ SA: 41 m ² / g, DBP: 115 ml / 100 g) manufactured by Mitsubishi Chemical Corporation
Compound 1: Compound silica prepared in Production Example 1 Ultrasil VN3 (N ₂ SA: 175 m ² / g) manufactured by Evonik Degussa
Silane coupling agent: Si69 manufactured by Evonik Degussa
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Zinc oxide wax manufactured by Mitsui Mining & Smelting Co., Ltd .: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
VP KA9188: Vulcuren VP KA9188 (1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane) (vulcanizing agent) manufactured by LANXESS
Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd .: Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples and Comparative Examples According to the formulation shown in Table 2 (note that the compounding amount in () of compound 1 indicates the compounding amount of compound 1 with respect to 100 parts by mass of carbon black and silica in total), a 1.7 L Banbury mixer was used. The materials other than sulfur, VP KA9188 and vulcanization accelerator were kneaded for 3 minutes at 150 ° C. to obtain a kneaded product. Next, sulfur, VP KA9188 and a vulcanization accelerator were added to the kneaded material obtained and kneaded for 5 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized with a 2 mm thick mold at 150 ° C. for 35 minutes to obtain a vulcanized rubber composition.

The following evaluation was performed about the obtained unvulcanized rubber composition and vulcanized rubber composition. The results are shown in Table 2.

(Low fuel consumption)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), tan δ of each compounding (vulcanized rubber composition) was measured under conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%. The tan δ in Example 1 was set to 100, and the index was displayed by the following calculation formula. The larger the index, the better the fuel efficiency.
(Low fuel consumption index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Abrasion resistance)
Using a Lambourn abrasion tester, the Lambourn abrasion amount of each compound (vulcanized rubber composition) was measured under the conditions of a temperature of 20 ° C., a slip ratio of 20% and a test time of 2 minutes. Then, the volume loss amount was calculated from the measured amount of lamborn wear, and the volume loss amount of each formulation was displayed as an index according to the following formula. In addition, it shows that it is excellent in abrasion resistance, so that a Lambourn abrasion index is large.
(Lambourn wear index) = (volume loss amount of Comparative Example 1) / (volume loss amount of each formulation) × 100

(Mechanical strength)
In accordance with JIS K6251 “vulcanized rubber and thermoplastic rubber—how to obtain tensile properties”, a tensile test was conducted using No. 3 dumbbell-shaped test pieces made of each vulcanized rubber composition, and the breaking strength (TB) and The elongation at break (EB) was measured and the fracture energy (TB × EB / 2) was calculated. And the breaking energy of the comparative example 1 was set to 100, and the breaking energy of each combination was indicated by an index by the following calculation formula. The larger the index, the higher the mechanical strength, the better the cut resistance and the separation resistance, and the better the durability as a tire.
(Strength index) = (Fracture energy of each formulation) / (Fracture energy of Comparative Example 1) × 100

(Vulcanization stability)
Using a curast meter, a test piece made of an unvulcanized rubber composition was vulcanized while applying vibration at 160 ° C., thereby measuring a time T10 (min) at which the torque increased by 10%. And T10 of the comparative example 1 was set to 100, and T10 of each mixing | blending was displayed as an index | exponent with the following formulas. The larger the index, the longer the scorch time and the better the vulcanization stability.
(T10 index) = (T10 of each formulation) / (T10 of Comparative Example 1) × 100

From the results of Table 2, modified natural rubber (HPNR), butadiene rubber, the compound represented by the above formula (1) and / or the above formula (2) (compound 1), carbon black, and the above formula ( The example containing the compound represented by A) (VP KA9188) was able to improve fuel economy, wear resistance, mechanical strength, and vulcanization stability.

Claims (11)

Represented by a modified natural rubber having a phosphorus content of 200 ppm or less, a butadiene rubber, a compound represented by the following formula (1) and / or the following formula (2), carbon black, and the following formula (A) A tire rubber composition comprising a compound.

[In formula (1), p represents the integer of 2-8. In formula (2), q represents an integer of 2 to 8. M ^{r +} represents a metal ion, and r represents its valence. ]

[In Formula (A), Y is an alkylene group having 2 to 10 carbon atoms, and R ¹⁰ and R ¹¹ are the same or different and each represents a monovalent organic group containing a nitrogen atom. ] The tire rubber composition according to claim 1, wherein the content of the modified natural rubber in 100% by mass of the rubber component is 60% by mass or more and the content of the butadiene rubber is 5 to 40% by mass. The tire rubber composition according to claim 1 or 2, wherein the total content of the modified natural rubber and butadiene rubber in 100% by mass of the rubber component is 80% by mass or more. The content of the compound represented by the formula (A) is 0.05 to 12 parts by mass with respect to 100 parts by mass of the rubber component, and the content of carbon black is 10 to 90 parts by mass with respect to 100 parts by mass of the rubber component. Part, the total content of the compound represented by the formula (1) and the following formula (2) is 0.2 to 10 parts by mass with respect to 100 parts by mass in total of carbon black and silica. The tire rubber composition according to any one of the above. The metal ion represented by ^{Mr <+>} in Formula (2) is a lithium ion, a sodium ion, a potassium ion, a cesium ion, a cobalt ion, a copper ion, or a zinc ion, The any one of Claims 1-4 Rubber composition for tires. The tire rubber composition according to any one of claims 1 to 5, wherein the metal ion represented by ^{Mr +} in the formula (2) is a lithium ion, a sodium ion, or a potassium ion. The tire rubber according to any one of claims 1 to 6, wherein the modified natural rubber has a nitrogen content of 0.3 mass% or less and a gel content measured as a toluene insoluble content is 20 mass% or less. Composition. In the modified natural rubber, the natural rubber latex is saponified to obtain a saponified natural rubber latex (A), and the phosphorus content of the obtained saponified natural rubber latex in the rubber is 200 ppm or less. The tire rubber composition according to any one of claims 1 to 7, which is obtained by a production method including the step (B) of washing until The tire rubber composition according to any one of claims 1 to 8, which is used as a tread rubber composition. The pneumatic tire produced using the rubber composition in any one of Claims 1-9. The pneumatic tire according to claim 10, which is a truck / bus tire.