JP2008303360A - Rubber composition for base tread and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a base tread, in which the content of materials derived from non-petroleum resources is made higher to satisfactorily take saving resources and protection of the environment into consideration and which copes with all of gripping property, rolling resistance and durability when a tread part is worn and to provide a pneumatic tire. <P>SOLUTION: The rubber composition for the base tread contains: a natural rubber component composed of 5-85 mass% natural rubber and 95-15 mass% epoxidized natural rubber; silica of 20-100 parts mass on the basis of 100 parts mass natural rubber component; and a silane compound of 4-16 parts mass, which is represented by the formula: (X)<SB>n</SB>-Si-Y<SB>(4-n)</SB>(wherein X represents a methoxy or ethoxy group; Y represents a phenyl or linear or branched alkyl group; n is an integer of 1-3), on the basis of 100 parts mass silica. The pneumatic tire has the base tread rubber made with this rubber composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition used for a tire, and more particularly to a rubber composition for a base tread of a pneumatic tire. Moreover, this invention relates to a pneumatic tire provided with the base tread rubber which consists of the said rubber composition.

  Conventionally, a rubber composition for a tire base tread is blended with styrene butadiene rubber (SBR) or polybutadiene rubber in addition to natural rubber (NR) exhibiting excellent rolling resistance, and when the tread portion is worn. Carbon black has been blended to satisfy grip, rolling resistance and durability. These styrene butadiene rubber (SBR), polybutadiene rubber and carbon black are all materials derived from petroleum resources.

  However, in recent years, environmental issues have become more important and regulations on carbon dioxide emissions have been strengthened. In addition, since the existing amount of petroleum is limited, the use of raw materials derived from petroleum resources is limited. This environment-oriented orientation is no exception in the tire field, and the development of rubber compositions for base treads in which some or all of the petroleum-derived raw materials currently used are replaced with raw materials derived from non-petroleum resources. Is required.

  For example, Patent Document 1 discloses an eco-tire using silica or the like as a non-petroleum resource as an alternative raw material for carbon black. However, when a white filler such as silica is used instead of carbon black in the rubber composition for the base tread, the grip characteristics, rolling resistance and durability when the tread is worn are the important characteristics of the base tread. It was difficult to achieve both.

  By the way, Patent Documents 2 to 5 disclose techniques for blending a silylating agent into a rubber composition for a tire tread or a rubber composition for a sidewall for the purpose of improving grip properties or water repellency. ing. However, in the base tread, the grip performance, rolling resistance and durability when the tread portion is worn are not considered, and there is room for improvement.

As described above, in the rubber composition in which the raw material derived from petroleum resources is replaced with the raw material derived from non-petroleum resources, the base tread is designed to achieve both grip, rolling resistance and durability when the tread portion is worn. The present condition is that the rubber composition used suitably for rubber | gum is not obtained.
JP 2003-63206 A Japanese Unexamined Patent Publication No. 7-118454 JP 7-292158 A JP-A-9-87427 Japanese Patent Laid-Open No. 10-60175

  The present invention has been made in order to solve the above-mentioned problems, and the purpose of the present invention is to sufficiently consider resource saving and environmental protection by increasing the content ratio of materials made of resources other than petroleum. In addition, a rubber composition for base tread that achieves both grip performance, rolling resistance and durability when the tread portion is worn, and a pneumatic tire including the base tread rubber made of the rubber composition are provided. That is.

  The present inventor has provided a rubber composition having a good balance between wear resistance and wet performance among fillers derived from non-petroleum resources, and also epoxidized natural rubber (NR) to natural rubber (NR). ENR) has been found to be able to balance wet performance and rolling resistance performance. However, since the epoxidized natural rubber (ENR) has a higher polarity than the natural rubber, the compounded silica is localized in the ENR layer, and the wear resistance of the rubber is lowered. In addition, since the silica is localized in the ENR layer having a higher glass transition point, there is a problem in that the loss tangent (tan δ) in the high temperature region increases and the rolling resistance decreases.

  The present inventor has found that a silane compound (silylating agent) may be added to the rubber composition in order to solve the above problems, and has completed the present invention. That is, the present invention is as follows.

The present invention includes 20 to 100 parts by mass of silica with respect to 100 parts by mass of a natural rubber component consisting of 5 to 85% by mass of natural rubber and 95 to 15% by mass of epoxidized natural rubber, and The following general formula (1):
(X) _n -Si-Y _(4-n) (1)
(In the above general formula (1), X represents a methoxy group or an ethoxy group, Y represents a phenyl group or a linear or branched alkyl group, and n represents an integer of 1 to 3).
It is a rubber composition for base treads containing 4-16 mass parts of silane compounds represented by these. Here, the rubber composition for a base tread of the present invention may further contain 60 parts by mass or less of polybutadiene rubber and / or styrene butadiene rubber with respect to 100 parts by mass of the natural rubber component. Moreover, it is preferable that the rubber composition for base treads of this invention further contains 4-20 mass parts silane coupling agents with respect to 100 mass parts of said silica.

  Furthermore, this invention provides a pneumatic tire provided with the base tread rubber which consists of the said rubber composition.

  According to the present invention, by increasing the content ratio of materials made from non-petroleum resources, consideration for resource saving and environmental protection is sufficient, and gripping properties and rolling resistance when the tread portion is worn are sufficient. And a rubber composition for a base tread that achieves both compatibility and durability, and a pneumatic tire including a base tread rubber made of the rubber composition.

The rubber composition for a base tread of the present invention is based on 100 parts by mass of a natural rubber component consisting of 5 to 85% by mass of natural rubber (NR) and 95 to 15% by mass of epoxidized natural rubber (ENR). 20 to 100 parts by mass of silica, and with respect to 100 parts by mass of silica, the following general formula (1):
(X) _n -Si-Y _(4-n) (1)
(In the above general formula (1), X represents a methoxy group or an ethoxy group, Y represents a phenyl group or a linear or branched alkyl group, and n represents an integer of 1 to 3).
4 to 16 parts by mass of a silane compound represented by the formula: Hereafter, each component which the rubber composition for base treads of this invention contains is demonstrated in detail.

<Rubber component>
The rubber composition for a base tread of the present invention contains a natural rubber component, and the natural rubber component contains 5 to 85% by mass of natural rubber (NR) and 95 to 15% by mass of epoxidized natural rubber ( ENR).

  As the natural rubber (NR), those conventionally used in the rubber industry can be used, and examples thereof include natural rubber of grades such as KR7 and TSR20.

  The content of natural rubber (NR) in the natural rubber component is 5 to 85% by mass. If the content of the natural rubber (NR) in the natural rubber is less than 5% by mass, the rubber strength tends to be insufficient. Moreover, when the said content rate exceeds 85 mass%, there exists a tendency for abrasion resistance not to be enough. The content of natural rubber (NR) in the natural rubber is preferably 10 to 50% by mass, and more preferably 10 to 40% by mass.

  The rubber composition for base treads of the present invention contains epoxidized natural rubber (ENR) as a natural rubber component. Epoxidized natural rubber (ENR) is obtained by epoxidizing an unsaturated double bond of natural rubber (NR), and its molecular cohesion is increased by epoxy groups that are polar groups. Therefore, the glass transition temperature (Tg) is higher than that of natural rubber, and the mechanical strength, abrasion resistance, and air permeation resistance are excellent. In particular, when silica is compounded in the rubber composition, due to the reaction between the silanol group on the silica surface and the epoxy group of the epoxidized natural rubber, the same degree as when carbon black is compounded in the rubber composition. The mechanical strength and wear resistance can be obtained.

  As the epoxidized natural rubber (ENR), a commercially available product may be used, or an epoxidized natural rubber (NR) may be used. The method for epoxidizing NR is not particularly limited, and examples thereof include a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, and a peracid method. Examples of the peracid method include a method of reacting an organic peracid such as peracetic acid or formic acid with natural rubber.

  The epoxidation rate of the epoxidized natural rubber (ENR) is not particularly limited, but is preferably 5 mol% or more, and more preferably 10 mol% or more. When the epoxidation rate of ENR is less than 5 mol%, the effect of ENR compatibility with NR tends to decrease. The epoxidation rate of the epoxidized natural rubber (ENR) is preferably 60 mol% or less, and more preferably 50 mol% or less. When the epoxidation rate of ENR exceeds 60 mol%, the rubber strength tends to be insufficient. The epoxidation rate of the epoxidized natural rubber (ENR) means (number of epoxidized double bonds) / (number of double bonds before epoxidation). Specifically, ENR (ENR25) having an epoxidation rate of 25 mol%, ENR (ENR50) having an epoxidation rate of 50 mol%, and the like can be suitably used.

  In the present invention, only one ENR may be used, or two or more ENRs having different epoxidation rates may be used.

  The content of epoxidized natural rubber (ENR) in the natural rubber component is 15 to 95% by mass. If the ENR content is less than 15% by mass, the wear resistance tends to be insufficient. Further, when the ENR content exceeds 95% by mass, the strength tends to be insufficient.

  The rubber composition for a base tread of the present invention may contain a diene synthetic rubber in addition to the natural rubber component described above. Examples of the diene-based synthetic rubber include styrene butadiene rubber (SBR), polybutadiene rubber (BR), styrene isoprene copolymer rubber, isoprene rubber (IR), butyl rubber (IIR), chloroprene rubber (CR), acrylonitrile butadiene rubber ( NBR), halogenated butyl rubber (X-IIR), and halides of copolymers of isobutylene and p-methylstyrene. Among these, polybutadiene rubber (BR), styrene butadiene rubber (SBR), and combinations thereof can be suitably used for achieving both rolling resistance performance and durability.

  When the rubber composition for base treads of this invention contains a diene type synthetic rubber, it is preferable that content of a diene type synthetic rubber shall be 60 mass% or less with respect to 100 mass parts of natural rubber components. However, in consideration of resource saving and environmental protection, it is more preferable not to include a diene synthetic rubber from the viewpoint of increasing the content of non-petroleum resources.

<Silica>
The rubber composition for base treads of the present invention contains silica. Silica functions as a reinforcing filler, and the wet performance of the resulting base tread rubber can be improved by blending silica.

  Silica may be prepared by a wet method or may be prepared by a dry method.

Silica has a BET specific surface area of preferably 40 m ² / g or more, and more preferably 80 m ² / g or more. When the BET specific surface area of silica is less than 40 m ² / g, the wear resistance performance tends to decrease. Further, BET specific surface area of silica is preferably not more than 400 meters ² / g, more preferably at most 300m ² / g. When the BET specific surface area of silica exceeds 400 m ² / g, when zinc oxide is blended, the dispersibility of zinc oxide tends to be inferior. Specifically, Ultrazil VN2 (BET specific surface area: 125 m ² / g) or Ultrazil VN3 (BET specific surface area: 210 m ² / g) manufactured by Degussa can be suitably used.

  The content of silica is 20 parts by mass or more with respect to 100 parts by mass of the natural rubber component. If the content of silica is less than 20 parts by mass, the tear strength tends to be insufficient. The content of silica is more preferably 25 parts by mass or more with respect to 100 parts by mass of the natural rubber component. Moreover, 100 mass parts or less are preferable with respect to 100 mass parts of natural rubber components, and, as for content of a silica, 90 mass parts or less are more preferable. When the silica content exceeds 100 parts by mass, the bending crack resistance tends to be inferior.

<Silane compound>
The rubber composition for base treads of the present invention contains a silane compound. By adding the silane compound, it is possible to obtain a rubber composition in which the gripping property, rolling resistance and durability when the tread portion is worn are achieved. Such an effect is considered to be caused by the silane compound reducing the polarity of silica.

Here, the silane compound in the present invention is the following general formula (1):
(X) _n -Si-Y _(4-n) (1)
(In the above general formula (1), X represents a methoxy group or an ethoxy group, Y represents a phenyl group or a linear or branched alkyl group, and n represents an integer of 1 to 3).
It is a silane compound represented by these.

  X in the general formula (1) is more preferably an ethoxy group because it is more compatible with the natural rubber component. For the same reason, Y in the general formula (1) is more preferably a phenyl group. Moreover, n in the said General formula (1) is an integer of 1-3. When n is 0, X does not exist, and the reactivity of the silane compound tends to increase too much. When n is 4, Y does not exist and the reactivity of the silane compound tends to decrease.

  Specific examples of the silane compound represented by the general formula (1) include, for example, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, and phenyl. Examples include triethoxysilane, diphenyldiethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane, and trifluoropropyltrimethoxysilane. These silane compounds may be used alone or in combination of two or more. Phenyltriethoxysilane is preferred because it is compatible with rubber and can reduce costs.

  Content of a silane compound is 4 mass parts or more with respect to 100 mass parts of silica, Preferably it is 5 mass parts or more. When the content of the silane compound is less than 4 parts by mass, the flex crack resistance tends to be lowered. Moreover, content of a silane compound is 16 mass parts or less with respect to 100 mass parts of silica, Preferably it is 15 mass parts or less. When the content of the silane compound exceeds 16 parts by mass, the wear resistance performance tends to decrease.

<Silane coupling agent>
It is preferable to mix | blend a silane coupling agent with the rubber composition for base treads of this invention with a silica. As the silane coupling agent, a conventionally known silane coupling agent can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4- Triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxy Silylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) ) Resulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3 -Trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-tri Ethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthio Sulfide systems such as rubamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-trimethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane Mercapto series such as 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; Vinyl series such as vinyltriethoxysilane and vinyltrimethoxysilane; 3-aminopropyltriethoxysilane 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxy Amino systems such as silane; glycidoxy systems such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane Nitro compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltri Chloro-based compounds such as ethoxysilane; These silane coupling agents may be used alone or in combination of two or more.

  Of these, Si69 (bis (3-triethoxysilylpropyl) tetrasulfide), Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa are preferably used because of their good processability. It is done.

  4 mass parts or more are preferable with respect to 100 mass parts of silica, and, as for content of a silane coupling agent, 5 mass parts or more are more preferable. When the content is less than 4 parts by mass, the effect of improving the bending crack resistance tends to be difficult to obtain. Moreover, 20 mass parts or less are preferable with respect to 100 mass parts of silica, and, as for content of a silane coupling agent, 15 mass parts or less are more preferable. When it exceeds 20 mass parts, it exists in the tendency for the improvement effect of a bending crack-proof performance to be hard to be acquired.

<Carbon black>
The rubber composition for base treads of the present invention may contain carbon black. The BET specific surface area of carbon black is preferably 60 m ² / g or more, and more preferably 80 m ² / g or more. If the BET specific surface area of carbon black is less than 60 m ² / g, the effect of improving the flex crack resistance tends to be difficult to obtain. Further, BET specific surface area of the carbon black is preferably 150 meters ² / g or less, more preferably 130m ² / g. When the BET specific surface area of carbon black exceeds 150 m ² / g, workability tends to deteriorate.

  When the rubber composition for base treads of the present invention contains carbon black, the content thereof is preferably 20 parts by mass or less, and 15 parts by mass or less with respect to 100 parts by mass of the natural rubber component. More preferred. By adding carbon black, it is possible to further improve rubber strength and rubber hardness. However, from the viewpoint of resource saving and environmental protection, it is preferable not to contain carbon black.

<Other ingredients>
In addition to the components described above, the rubber composition for base treads of the present invention includes other additives such as vulcanizing agents, vulcanization accelerators, stearic acid, oils, waxes, anti-aging agents, zinc white (zinc oxide). ) And the like.

  As the vulcanizing agent, an organic peroxide or a sulfur-based vulcanizing agent can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, and di-t-butyl peroxide. , T-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoyl) Peroxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 or 1,3-bis (t-butylperoxypropyl) benzene, di-t-butylperoxy- Diisopropylbenzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, 1,1-di t- butyl peroxy-3,3,5-trimethyl siloxane, and the like can be used n- butyl-4,4-di -t- butyl peroxy valerate. Of these, dicumyl peroxide, t-butylperoxybenzene and di-t-butylperoxy-diisopropylbenzene are preferred. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred. These vulcanizing agents may be used alone or in combination of two or more.

  Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Those containing at least one of them can be used. Examples of the sulfenamide system include CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (N-tert-butyl-2-benzothiazylsulfenamide), N, N-dicyclohexyl-2- Sulfenamide compounds such as benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, and N, N-diisopropyl-2-benzothiazolesulfenamide can be used. Examples of the thiazole group include MBT (2-mercaptobenzothiazole), MBTS (dibenzothiazyl disulfide), sodium salt of 2-mercaptobenzothiazole, zinc salt, copper salt, cyclohexylamine salt, 2- (2,4-dinitro). Thiazole compounds such as phenyl) mercaptobenzothiazole and 2- (2,6-diethyl-4-morpholinothio) benzothiazole can be used. Examples of thiurams include TMTD (tetramethyl thiuram disulfide), tetraethyl thiuram disulfide, tetramethyl thiuram monosulfide, dipentamethylene thiuram disulfide, dipentamethylene thiuram monosulfide, dipentamethylene thiuram tetrasulfide, dipentamethylene thiuram hexasulfide. Further, thiuram compounds such as tetrabutylthiuram disulfide and pentamethylenethiuram tetrasulfide can be used. As the thiourea series, for example, thiourea compounds such as thiacarbamide, diethylthiourea, dibutylthiourea, trimethylthiourea, diortolylthiourea and the like can be used. Examples of guanidine-based compounds include guanidine-based compounds such as diphenylguanidine, diortolylguanidine, triphenylguanidine, orthotolylbiguanide, and diphenylguanidine phthalate. Examples of dithiocarbamate include zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc diamyldithiocarbamate, zinc dipropyldithiocarbamate , Complex salt of zinc pentamethylenedithiocarbamate and piperidine, zinc hexadecyl (or octadecyl) isopropyldithiocarbamate, zinc dibenzyldithiocarbamate, sodium diethyldithiocarbamate, piperidine pentamethylenedithiocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, diamyl Di, such as cadmium dithiocarbamate And the like can be used Okarubamin acid compound. As the aldehyde-amine system or aldehyde-ammonia system, for example, an aldehyde-amine system or aldehyde-ammonia system compound such as acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde-ammonia reaction product, etc. is used. can do. As the imidazoline-based compound, for example, an imidazoline-based compound such as 2-mercaptoimidazoline can be used. As the xanthate type, for example, a xanthate type compound such as zinc dibutylxanthate can be used. These vulcanization accelerators may be used alone or in combination of two or more.

  As the anti-aging agent, amine-based, phenol-based, imidazole-based, carbamic acid metal salts, and the like can be appropriately selected and used.

  As the oil, for example, process oil, vegetable oil and fat, and a mixture thereof can be used. Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil. Vegetable oils include castor oil, cottonseed oil, rapeseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pineapple oil, tall oil, corn oil, rice bran oil, beet flower oil, Sesame oil, olive oil, sunflower oil, palm kernel oil, coconut oil, jojoba oil, macadamia nut oil, safflower oil, tung oil, and the like.

  The pneumatic tire of the present invention is a pneumatic tire provided with a base tread rubber made of the rubber composition for a base tread of the present invention. Hereinafter, the pneumatic tire of the present invention will be described with reference to FIG. FIG. 1 illustrates a pneumatic tire according to the present invention. The pneumatic tire 1 includes a tread portion 2 including a cap tread portion 2a and a base tread portion 2b, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends of the tread portion 2, and each sidewall portion 3 It is common to have a structure provided with bead part 4 located in the inner end of the. A carcass 6 is bridged between the bead portions 4, and a belt layer 7 that reinforces the tread portion 2 with a tagging effect is disposed outside the carcass 6 and inside the tread portion 2. .

  The carcass 6 is formed of one or more carcass plies 6a in which the carcass cord is arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator CO. The carcass ply 6a extends from the tread portion 2 to the sidewall portion. 3, the periphery of the bead core 5 of the bead portion 4 is folded back and locked from the inner side to the outer side in the tire axial direction.

  The belt layer 7 is composed of two or more belt plies 7a in which the belt cord is arranged at an angle of, for example, 40 ° or less with respect to the tire equator CO. It is location.

  Further, a bead apex rubber 8 extending radially outward from the bead core 5 is disposed in the bead portion 4, and an inner liner rubber 9 forming a tire lumen surface is adjacent to the inside of the carcass 6. The outside of the carcass 6 is protected by clinch rubber 4G and sidewall rubber 3G.

  The rubber composition for base tread of the present invention is used for the base tread portion 2b.

  The pneumatic tire of the present invention is produced by a conventionally known method using the rubber composition for a base tread of the present invention. That is, the rubber composition for a base tread having the above structure is kneaded and extruded in accordance with the shape of the base tread portion of the tire at an unvulcanized stage, and usually on a tire molding machine together with other members of the tire. By molding by this method, an unvulcanized tire is formed. The pneumatic tire of the present invention can be obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

  In the pneumatic tire of the present invention, the base tread rubber has a higher content ratio of materials composed of non-petroleum resources, and sufficient consideration is given to resource saving and environmental protection, and the grip when the tread portion is worn is obtained. Since the rubber composition in which compatibility, rolling resistance, and durability are compatible is used, it can be suitably used as, for example, a passenger car as an “eco-tyre” that is friendly to the global environment.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these.

<Examples 1-3 and Comparative Examples 1-3>
In accordance with the formulation shown in Table 1, the components other than sulfur and the vulcanization accelerator were kneaded for 3 minutes at a rotational speed of 80 rpm and 150 ° C. using a Kobe Steel 1.7 L Banbury mixer. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded material in the amounts shown in Table 1, and then kneaded at 80 ° C. for 5 minutes using an open roll to obtain an unvulcanized rubber composition. . Next, the unvulcanized rubber composition was vulcanized at 150 ° C. for 30 minutes to prepare vulcanized rubber sheets of Examples 1 to 3 and Comparative Examples 1 to 3.

Moreover, the rubber composition for base treads (base tread part) in the unvulcanized state was pasted together with other members, and press vulcanized at 160 ° C. for 20 minutes, whereby Examples 1 to 3 and Comparative Examples 1 to 3 A pneumatic tire (size: 195 / 65R15) was produced. Such a pneumatic tire has a structure as shown in FIG. 1, and details thereof are as follows.
Carcass: Material Polyester (1670 dtex / 2)
Belt layer: Material Steel cord, structure 1 × 4, angle 22 ° × 22 °
Cap tread / base tread thickness ratio: 80/20

Details of the various blending components used in the above Examples and Comparative Examples are as follows.
(1) Natural rubber (NR): TSR20
(2) Epoxidized natural rubber (ENR): “ENR25” (epoxidation rate: 25 mol%) manufactured by Kumpoulang Guthrie
(3) Silane compound: “KBE-103” (phenyltriethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd.
(4) Carbon Black: “Show Black N351” manufactured by Showa Cabot
(5) Silica: “Ultrasil VN3” manufactured by Degussa (BET specific surface area: 210 m ² / g)
(6) Silane coupling agent: “Si266” (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
(7) Oil: Soybean oil manufactured by Japan Oilio Co., Ltd. (8) Wax: “Sannokk Wax” manufactured by Ouchi Shinsei Chemical Co., Ltd.
(9) Anti-aging agent: “NOCRACK 6C” (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
(10) Stearic acid: Stearic acid “Kashiwa” manufactured by Nippon Oil & Fats Co., Ltd.
(11) Zinc flower: “Zinc flower No. 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
(12) Sulfur: Powdered sulfur produced by Tsurumi Chemical Industry Co., Ltd. (13) Vulcanization accelerator: “Noxeller NS” (N-tert-butyl-2-benzothiazolylsulfur produced by Ouchi Shinsei Chemical Industry Co., Ltd.) Funamide)
The following tests were performed on the vulcanized rubber sheets and the test pneumatic tires of Examples 1 to 3 and Comparative Examples 1 to 3. The results are shown in Table 1.

(Grip performance)
After removing the cap tread part of the manufactured pneumatic tire for testing, it is mounted on a passenger car equipped with 1800cc class ABS and running on a wet asphalt road surface with a skid number of about 50 at a speed of 100km / h. Stepping on the lock brake, the distance until the passenger car stopped was measured, and the deceleration during the lock brake was calculated. The numerical values shown in Table 1 are relative values when the deceleration of Comparative Example 1 is 100. The larger the value, the better the wet ABS braking performance and the better the grip performance.

(Rolling resistance performance)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent (tan δ) of each vulcanized rubber sheet was measured under conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%. The numerical values in Table 1 are indicated by an index according to the following formula, with the numerical value of Comparative Example 1 being 100. The larger the index, the better the rolling resistance.
Rolling resistance index = (tan δ of Comparative Example 1) / (tan δ of each Example or Comparative Example) × 100
(Abrasion resistance)
The amount of wear of each vulcanized rubber sheet was measured under the conditions of room temperature, applied load of 1.0 kgf, and slip rate of 30% using a Lambone type wear tester. The numerical values in Table 1 indicate the reciprocal of the wear amount as an index with Comparative Example 1 being 100. It shows that abrasion resistance is so high that the said numerical value is large.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic sectional drawing which shows an example of the pneumatic tire of this invention.

Explanation of symbols

  1 tire, 2 tread part, 2a cap tread part, 2b base tread part, 3 sidewall part, 4 bead part, 5 bead core, 6 carcass, 7 belt layer, 8 bead apex rubber, 9 inner liner rubber, 4G clinch rubber.

Claims (4)

20 to 100 parts by mass of silica with respect to 100 parts by mass of a natural rubber component consisting of 5 to 85% by mass of natural rubber and 95 to 15% by mass of epoxidized natural rubber, and
The following general formula (1):
(X) _n -Si-Y _(4-n) (1)
(In the above general formula (1), X represents a methoxy group or an ethoxy group, Y represents a phenyl group or a linear or branched alkyl group, and n represents an integer of 1 to 3).
The rubber composition for base treads containing 4-16 mass parts of silane compounds represented by these.   The rubber composition for base treads according to claim 1, further comprising 60 parts by mass or less of polybutadiene rubber and / or styrene butadiene rubber with respect to 100 parts by mass of the natural rubber component.   The rubber composition for base treads of Claim 1 or 2 which further contains 4-20 mass parts silane coupling agents with respect to 100 mass parts of said silica.   A pneumatic tire provided with the base tread rubber which consists of a rubber composition in any one of Claims 1-3.

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