JP2011063766A - Rubber composition for breaker cushion, and tire for truck and bus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for breaker cushion having excellent low-fuel-economy performance and excellent in rubber-reinforcing performance (tire durability) as well, and to provide tires for trucks and buses having such breaker cushions produced using the same. <P>SOLUTION: The rubber composition for breaker cushion includes: a rubber component; and a silicate compound. In the rubber composition, it is preferable that the rubber component is natural rubber or an epoxidized natural rubber, and the silicate compound is preferably 1-100 in polymerization degree. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a rubber composition for a breaker cushion, and a truck / bus tire using the same.

In recent years, in the transportation industry, tires with excellent fuel efficiency have been desired because of increased costs associated with soaring fuel costs and increased costs due to the introduction of environmental regulations. In tires, especially truck and bus tires, when giving fuel efficiency to rubber compound, it is difficult to give excellent fuel efficiency to the tread because of wear performance, but wear performance is not required. In the case of a breaker cushion or the like, it is possible to provide excellent fuel efficiency by a method such as blending silica.

However, if silica is increased and carbon black is reduced to that extent to reduce fuel consumption (excellent fuel efficiency cannot be achieved with silica addition unless carbon black is reduced), the rubber's reinforcement will decrease. This may cause a decrease in tire durability. For this reason, as compared with such a method, it is desired to provide a technique capable of obtaining excellent fuel efficiency while maintaining rubber reinforcement.

Patent Document 1 proposes improving the grip properties on a frozen road surface by using an alkoxysilane compound in a rubber composition for a tire tread. Patent Document 2 proposes that chipping resistance can be improved by using an alkoxysilane compound in a rubber composition for a tread.

However, there is still room for improvement in obtaining excellent fuel efficiency while maintaining rubber reinforcement (tire durability). Moreover, application to a breaker cushion has not been studied.

JP-A-9-87427 JP-A-8-337688

The present invention solves the above-mentioned problems and has a rubber composition for a breaker cushion that has excellent fuel efficiency and at the same time is excellent in rubber reinforcement (tire durability performance), and a breaker cushion manufactured using the same. The object is to provide a tire for trucks and buses having the following.

The present invention relates to a rubber composition for a breaker cushion containing a rubber component and a silicate compound.

（式（Ｉ）において、Ｒ^１は、同一若しくは異なって、置換されていてもよいアルキル基、アリール基、アルケニル基、アルキニル基、アルコキシ基又はアリールオキシ基を表す。Ｒ^２は、同一若しくは異なって、置換されていてもよいアルキル基、アリール基、アルケニル基又はアルキニル基を表す。ｎは、１〜１００の数である。） The silicate compound is preferably a compound represented by the following formula (I) or a partial hydrolyzate thereof.

(In Formula (I), R ¹ is the same or different and represents an optionally substituted alkyl group, aryl group, alkenyl group, alkynyl group, alkoxy group or aryloxy group. R ² is the same or different. And represents an optionally substituted alkyl group, aryl group, alkenyl group or alkynyl group, where n is a number from 1 to 100.)

The present invention also relates to a truck / bus tire having a breaker cushion manufactured using the rubber composition.

According to the present invention, since it is a rubber composition for a breaker cushion containing a rubber component and a silicate compound, by applying the rubber composition to a breaker cushion of a tire, excellent low fuel consumption performance and rubber reinforcement ( It is possible to provide a truck / bus tire having tire durability performance).

The rubber composition for a breaker cushion of the present invention contains a rubber component and a silicate compound. In truck and bus tires with improved fuel efficiency, a breaker cushion with silica added may be used. In this silica formulation, a silicate compound is further added, or silica is replaced with a silicate compound. As a result, further excellent fuel efficiency can be obtained.

In addition, the addition or substitution of the silicate compound does not reduce the hardness, so that the steering stability does not deteriorate. Furthermore, addition or substitution of a silicate compound does not reduce rubber strength or elongation, so that good fuel economy performance and good tire durability performance can be obtained.

The rubber components that can be used in the rubber composition of the present invention include natural rubber (NR), epoxidized natural rubber (ENR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), ethylene propylene diene. Examples thereof include diene rubbers such as rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), and halogenated butyl rubber (X-IIR). Among these, from the viewpoint of achieving both low fuel consumption performance and tire durability performance, NR and ENR are preferably used, and NR is more preferably used. These may be used alone or in combination of two or more.

When the rubber composition contains NR, the content of NR in 100% by mass of the rubber component is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and most preferably 100%. % By mass. If it is less than 60% by mass, the mechanical strength tends to decrease and the durability of the tire tends to decrease.

The rubber composition of the present invention contains a silicate compound. As a result, excellent fuel efficiency can be obtained without sacrificing the durability of the tire. Therefore, it is possible to obtain a tire that has excellent fuel efficiency performance and at the same time excellent tire durability performance and excellent steering stability. In addition, in the use of the silicate compound, the silica is replaced with a silicate compound rather than further adding the silicate compound to the compound containing silica (for example, the silica is replaced with a silicate compound corresponding to an equivalent amount of silica). ) Can suppress heat generation more and can achieve good fuel efficiency.

Examples of the silicate compound include oligomers (silicones) having a polysiloxane bond in the main chain, and those in which a part of substituents of the main chain of the polysiloxane bond are hydrolyzed to become OH groups are also included.

（式（Ｉ）において、Ｒ^１は、同一若しくは異なって、置換されていてもよいアルキル基、アリール基、アルケニル基、アルキニル基、アルコキシ基又はアリールオキシ基を表す。Ｒ^２は、同一若しくは異なって、置換されていてもよいアルキル基、アリール基、アルケニル基又はアルキニル基を表す。ｎは、１〜１００の数である。） Preferred silicate compounds include compounds represented by the following formula (I) having a polysiloxane bond, and partial hydrolysates thereof.

(In Formula (I), R ¹ is the same or different and represents an optionally substituted alkyl group, aryl group, alkenyl group, alkynyl group, alkoxy group or aryloxy group. R ² is the same or different. And represents an optionally substituted alkyl group, aryl group, alkenyl group or alkynyl group, where n is a number from 1 to 100.)

R ¹ is an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or An aryloxy group having 6 to 12 carbon atoms is preferred, and these may be optionally substituted. More preferably, it is an unsubstituted alkoxy group, an alkyl group, an aryloxy group, still more preferably an alkoxy group, particularly preferably an ethoxy group, a methoxy group, and most preferably a methoxy group.

R ² is preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms, and these are optionally substituted. May be. More preferably, it is an unsubstituted alkyl group having 1 to 5 carbon atoms, more preferably a methyl group, an ethyl group, and most preferably a methyl group.

The repeating unit n (average value) is usually a number in the range of 1 to 100, preferably 2 to 50, more preferably 3 to 30. The compound represented by the above formula (I) is present in the form of a monomer, in the form of a long chain, and in the form of any branched oligomer long chain, depending on the value of n.

The partial hydrolyzate of the compound represented by the above formula (I) is one in which at least one of R ¹ and R ² is converted to an OH group by hydrolysis.

Examples of the silicate compound in the present invention include alkyl silicates conventionally referred to as methyl silicate and ethyl silicate (SiO ₂ content is usually 50 to 60% by mass). Alkyl silicate is normally a colorless and transparent liquid, but forms solid silica when the hydrolysis / condensation reaction proceeds completely. The silicate compound in the present invention also reacts with an alkoxysilyl group (for example, reacts with an alkoxysilyl group in a silane coupling agent) to form a siloxane bond.

The content of the silicate compound is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 1 part by mass, the effect of blending the silicate compound tends to be insufficient. Moreover, the said content becomes like this. Preferably it is 15 mass parts or less, More preferably, it is 10 mass parts or less. When the amount exceeds 15 parts by mass, an effect commensurate with the increase in cost cannot be obtained, and the processability of rubber tends to deteriorate.

You may mix | blend a silica with the rubber composition of this invention. By blending silica, good fuel efficiency can be obtained. The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups. Silica may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of the silica is preferably 50 m ² / g or more, more preferably 100 m ² / g or more, and still more preferably 150 m ² / g or more. If it is less than 50 m ² / g, since the reinforcing property is small, the durability performance of the tire may not be sufficiently improved. Further, N ₂ SA of silica is preferably 400 m ² / g or less, more preferably 300 m ² / g or less, and further preferably 250 m ² / g or less. When it exceeds 400 m ² / g, silica dispersibility, rubber processability, and tire durability tend to be deteriorated.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of the silica is preferably 3 parts by mass or more, more preferably 6 parts by mass or more with respect to 100 parts by mass of the rubber component. When the content of silica is less than 3 parts by mass, the effect due to the blending of silica tends to be insufficient. The silica content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. When the silica content exceeds 50 parts by mass, the dispersibility of silica and the processability of rubber tend to deteriorate.

The total content of the silicate compound and 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 in terms of SiO ₂ . If it is less than 5 mass parts, there exists a tendency that the effect by the mixing | blending of a silicate compound and a silica cannot fully be acquired. Moreover, the said total content becomes like this. Preferably it is 50 mass parts or less, More preferably, it is 30 mass parts or less. When it exceeds 50 parts by mass, the dispersibility of silica and the processability of rubber tend to deteriorate.

The rubber composition of the present invention preferably contains a silane coupling agent. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-tri Sulfide series such as ethoxysilylpropyl) trisulfide and bis (3-triethoxysilylpropyl) disulfide, mercapto series such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxy Silane and other vinyl-based materials, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane and other glycidoxy-based materials, 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane And chloro-based compounds such as Toro-based, 3-chloropropyltrimethoxysilane, and 3-chloropropyltriethoxysilane. Product names include Si69, Si75, Si363 (Degussa), NXT, NXT-LV, NXT-ULV, NXT-Z (Momentive Performance Materials). Of these, bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide are preferable. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 3 parts by mass or more and more preferably 8 parts by mass or more with respect to 100 parts by mass of the total content of the silicate compound and silica (in terms of SiO ₂ ). When the content of the silane coupling agent is less than 3 parts by mass, the rubber strength is greatly reduced, and the tire durability tends to deteriorate. Moreover, 15 mass parts or less are preferable, and, as for content of the said silane coupling agent, 10 mass parts or less are more preferable. When content of a silane coupling agent exceeds 15 mass parts, there exists a tendency for the effect corresponding to the raise of cost not to be acquired.

The rubber composition of the present invention preferably contains carbon black. By blending carbon black, it is possible to enhance the reinforcement. Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited.

As described above, when carbon black and silica are used in combination, the fuel efficiency cannot be improved unless the carbon black is reduced by the amount of silica added. Therefore, when carbon black is blended in the rubber composition of the present invention containing a silicate compound without reducing the weight, it is expected that the fuel efficiency performance deteriorates in exchange for the improvement of the reinforcing property. However, even if carbon black is blended with the rubber composition of the present invention, deterioration of fuel efficiency can be suppressed. This is thought to be because when carbon black is kneaded with a silicate compound, the carbon black reacts with the silicate compound and silica adheres to the surface of the carbon black.

The blending ratio of the silicate compound and carbon black (mass of silicate compound / mass of carbon black, hereinafter referred to as blending ratio) is preferably 1/30 or more, more preferably 1/25 or more. If the blending ratio is less than 1/30, fuel efficiency tends to deteriorate. This is presumably because the silicate compound cannot sufficiently react with carbon black. Further, the blending ratio is preferably 2/3 or less, more preferably 1/2 or less. If the blending ratio exceeds 2/3, the rubber strength tends to decrease.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 15 m ² / g or more, and more preferably 30 m ² / g or more. When N ₂ SA is less than 15 m ² / g, there is a tendency that sufficient reinforcing properties cannot be obtained. Also, _N 2 SA of carbon black is preferably ^{80 m} 2 / g or less, ^{60 m} 2 / g or less is more preferable. When N ₂ SA exceeds 80 m ² / g, the viscosity at the time of unvulcanization becomes very high, and the processability of rubber tends to deteriorate. In addition, the fuel efficiency performance tends to deteriorate.
The nitrogen adsorption specific surface area of carbon black is determined by the A method of JIS K6217.

The content of carbon black is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 5 parts by mass, sufficient reinforcing properties tend not to be obtained. Further, the content of carbon black is preferably 60 parts by mass or less, more preferably 50 parts by mass or less with respect to 100 parts by mass of the rubber component. If it exceeds 60 parts by mass, fuel efficiency tends to deteriorate.

In addition to the above components, the rubber composition includes a compounding agent conventionally used in the rubber industry, for example, a filler such as clay, oil or plasticizer, wax, stearic acid, antioxidant, ozone deterioration inhibitor, Anti-aging agents, vulcanization accelerators, vulcanizing agents such as zinc oxide, peroxides, sulfur and sulfur-containing compounds, vulcanization accelerators and the like may be contained.

Examples of the vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N′-dicyclohexyl-2- Examples include benzothiazolylsulfenamide (DZ), mercaptobenzothiazole (MBT), dibenzothiazolyl disulfide (MBTS), and diphenylguanidine (DPG). Among them, it is preferable to use TBBS because it has excellent vulcanization characteristics and has a large effect of improving fuel efficiency and tire durability.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The rubber composition of the present invention is used for a breaker cushion. The breaker cushion is adjacent to the outer end in the tire axial direction of the breaker provided inside the tread and located between the outer end of the breaker and the carcass, or between the breaker and the carcass. And a portion arranged over the entire inside of the breaker. A specific example of the breaker cushion is shown in FIG. 1 of JP-A-2009-137438.

The tire for trucks and buses of the present invention is produced by an ordinary method using the rubber composition. That is, if necessary, a rubber composition containing various additives is extruded in accordance with the shape of the breaker cushion at an unvulcanized stage, molded on a tire molding machine by a normal method, and other tires. The tires for trucks and buses of the present invention can be manufactured by pasting together with the members to form an unvulcanized tire and then heating and pressing in a vulcanizer.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: RSS # 3
Carbon Black: Show Black N550 (N ₂ SA: 42 m ² / g) manufactured by Showa Cabot Corporation
Silica: Ultrasil VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Silicate compound (1): MS56S manufactured by Mitsubishi Chemical Corporation (R ² = CH ₃ , R ¹ = OCH _{3 in} the formula (I), average value of n = about 16, SiO ₂ content 59 ± 1.0 Mass% (SiO ₂ conversion)
Silicate compound (2): MS58B30 manufactured by Mitsubishi Chemical Corporation (in the above formula (I), R ² = C ₄ H ₉ , R ¹ = CH ₃ , average value of n = about 15, SiO ₂ content 52 ± 3) .0 mass% (in terms of SiO ₂ ))
Anti-aging agent: Non-flex RD manufactured by Seiko Chemical Co., Ltd.
Stearic acid: Zinc stearate manufactured by NOF Corporation: Zinc Hua No. 1 60% insoluble sulfur manufactured by Mitsui Mining & Smelting Co., Ltd .: Seimisulfur manufactured by Nippon Kiboshi Kogyo Co., Ltd. (60% pure sulfur content, oil 40%)
Vulcanization accelerator: Noxeller NS (Nt-butyl-2-benzothiazyl sulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-8 and Comparative Examples 1-2
According to the blending contents shown in Table 1, using a Banbury mixer, materials other than 60% insoluble sulfur and a vulcanization accelerator were kneaded for 5 minutes at 150 ° C. to obtain a kneaded product. Next, 60% insoluble sulfur and a vulcanization accelerator were added to the kneaded product obtained, and kneaded for 3 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a breaker cushion shape, bonded to another tire member, and vulcanized at 150 ° C. for 30 minutes to prepare a test tire.

Using the obtained test tire (vulcanized rubber composition), the following evaluation was performed. Each test result is shown in Table 1.

(Heat generation performance index)
A rubber test piece is collected from a breaker cushion of a test tire and blended under a condition of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2% using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.). The tan δ was measured, and the tan δ of Comparative Example 2 was taken as 100. A lower index indicates less heat generation and better fuel efficiency.
(Heat generation performance index) = (tan δ of each formulation) / (tan δ of Comparative Example 2) × 100

(Durability Index)
A tensile test according to JIS K6251 was performed on the rubber test piece collected from the breaker cushion of the test tire, and the elongation at break was measured. The measurement results are shown as an index according to the following calculation formula, with Comparative Example 1 being 100. The larger the index, the stronger the rubber strength and the better the durability of the tire.
(Durability Performance Index) = (Elongation at Break for Each Formulation) / (Elongation at Break in Comparative Example 1) × 100

In the examples in which the silicate compound was blended, excellent fuel efficiency performance was obtained and the tire durability performance was also good. On the other hand, in Comparative Example 2 in which no silicate compound was blended, the fuel efficiency performance was inferior and the tire durability performance was slightly inferior compared to the Examples. In Comparative Example 1 in which silica, a silane coupling agent and a silicate compound were not blended, the fuel economy performance was greatly inferior and the tire durability performance was also inferior compared with the Examples.

Moreover, it became clear from the comparison of Example 2 and 3 and the comparison of Example 4 and 5 that a low mileage performance can be improved by mix | blending a silicate compound and reducing silica.

Claims (3)

A rubber composition for a breaker cushion, comprising a rubber component and a silicate compound. The rubber composition for a breaker cushion according to claim 1, wherein the silicate compound is a compound represented by the following formula (I) or a partial hydrolyzate thereof.

(In Formula (I), R ¹ is the same or different and represents an optionally substituted alkyl group, aryl group, alkenyl group, alkynyl group, alkoxy group or aryloxy group. R ² is the same or different. And represents an optionally substituted alkyl group, aryl group, alkenyl group or alkynyl group, where n is a number from 1 to 100.) A tire for trucks and buses having a breaker cushion produced using the rubber composition according to claim 1.