JP5472772B2 - Clinch rubber composition and pneumatic tire using the same - Google Patents

Description

  The present invention relates to a tire clinch rubber composition in which vegetable wax is blended with natural rubber, and a pneumatic tire using the same.

  When the tire is mounted on the rim, the clinch rubber of the tire located in the chafing part with the rim has a function to transmit driving force from the rim when the tire travels and a function to hold the tire load, so it has high hardness and heat resistance Aging characteristics are required, and in addition, wear resistance is required to reduce rubber wear due to rubbing with the rim due to repeated deformation during tire travel.

  The rigidity, hardness and strength of the clinch rubber have a great influence on the steering stability performance during running. On the other hand, clinch rubber also needs to exhibit elongation at break so that tire toe chipping often occurs at the time of tire replacement does not occur. Here, the clinch rubber refers to a rubber member disposed in a region in contact with the rim in the region of the bead portion from the sidewall of the tire.

  Aiming to reduce fuel consumption and weight, the tire structure has been simplified, rubber gauges have been made thinner, and cords have been made lighter, and the performance required for each rubber compound has become even more stringent. There is a demand for a rubber composition that exhibits excellent handling stability at the time and elongation properties in a well-balanced manner.

  Currently marketed tires are made up of raw materials comprising more than half of the total weight of petroleum resources. For example, a general passenger car tire contains about 20% synthetic rubber, about 20% carbon black, a softening agent, synthetic fiber, etc. with respect to the total weight of the tire. Consists of raw materials.

  In recent years, emphasis has been placed on environmental issues and regulations on the suppression of carbon dioxide emissions have been strengthened. Petroleum raw materials are limited and the supply amount has been decreasing year by year. Therefore, it is desired to develop a rubber compound for tires using natural raw materials that satisfy the same or more required characteristics as those of conventional petroleum-based materials.

  As for clinch rubber that requires severe performance as described above, a highly hard rubber composition made of polybutadiene rubber containing 5% by weight or more of syndiotactic crystals is disclosed (Patent Document 1).

Furthermore, carbon black and silica are used as a reinforcing agent blended in the tire rubber composition. Here, when carbon black is blended alone with the rubber composition, the elongation at break is lowered, and when silica is blended alone, there is a problem that the steering stability performance under severe conditions is poor. Therefore, in order to compensate for the disadvantages that occur when carbon black and silica are blended alone, a specific amount of carbon black material containing silica is blended in the tire tread to achieve both low rolling resistance and wear resistance. Has been disclosed (Patent Document 2). However, even if this technique is applied to a clinch rubber that is required to have high rigidity and high hardness, it is impossible to improve steering stability and stretch physical properties in a well-balanced manner.
Japanese Patent Laid-Open No. 7-118444 JP 2000-198883 A

The clinch rubber efficiently transmits the driving force from the rim when the tire travels and contributes to maintaining the tire load . The present invention provides a clinch rubber composition that retains substantially the same level of properties as a rubber composition using conventional petroleum-based raw materials . Furthermore, the present invention provides a pneumatic tire using the clinch rubber composition.

  In the present invention, 15 to 90 parts by mass of silica and 3 to 15 parts by mass of vegetable wax are blended with respect to 30 to 90% by mass of natural rubber component and 100 parts by mass of 10 to 70% by mass of epoxidized natural rubber. A clinch rubber composition for tires. The vegetable wax is preferably carnauba wax. The tire clinch rubber composition preferably contains 3 parts by mass or more of a silane coupling agent with respect to 100 parts by mass of silica.

  Another embodiment of the present invention includes a toroidal carcass that is folded back and engaged with a pair of left and right bead cores, a belt layer that is disposed on the crown portion of the carcass, a tread layer that is disposed outside the belt layer, Furthermore, it has a clinch rubber disposed in a region in contact with the rim from the bead portion to the side wall portion, and the clinch rubber is a pneumatic tire made of the clinch rubber composition.

By adopting the above-described configuration, the present invention provides a clinch rubber composition that retains substantially the same level of characteristics as a rubber composition using conventional petroleum-based raw materials, and a pneumatic tire using the same. . In addition, the present invention adopts the above-described configuration to efficiently transmit the driving force from the rim when the tire travels, has high strength and excellent weather resistance (ozone crack resistance), and further when the tire travels. A clinched rubber composition with less rubber wear, that is, excellent wear resistance, and a pneumatic tire using the same, can be obtained by rubbing against the rim due to repeated deformation.

  In the present invention, 15 to 90 parts by mass of silica and 3 to 15 parts by mass of vegetable wax are blended with respect to 30 to 90% by mass of natural rubber component and 100 parts by mass of 10 to 70% by mass of epoxidized natural rubber. A clinch rubber composition for tires.

<Rubber component>
The rubber component is basically a mixture of a natural rubber component and an epoxidized natural rubber. Here, natural rubber is mainly composed of cis 1,4 polyisoprene, but trans 1,4 polyisoprene can be mixed according to the required characteristics.

  The rubber component contains epoxidized natural rubber (hereinafter also referred to as “ENR”). Conventional methods can be employed for epoxidizing natural rubber. For example, the chlorohydrin method, direct oxidation method, hydrogen peroxide method, alkyl hydroperoxide method, peracid method and the like can be used. Examples of the peracid method include a method in which natural rubber is reacted with an organic peracid such as peracetic acid or performic acid.

  The epoxidation rate of the natural rubber is preferably 5 mol% or more, and more preferably 10 mol% or more. When the epoxidation rate of the natural rubber is less than 5 mol%, the glass transition temperature (Tg) of the epoxidized natural rubber is low, and high rigidity, high hardness, and wear resistance cannot be obtained. On the other hand, the epoxidation rate of natural rubber is preferably 65 mol% or less, and more preferably 60 mol% or less. If the epoxidation rate exceeds 65 mol%, the hardness tends to increase excessively and the bending fatigue resistance tends to decrease significantly. Here, the epoxidation rate is defined as the ratio (mol%) of the reaction of the epoxy compound with respect to the entire double bond of the natural rubber.

  The content of natural rubber in the rubber component is preferably 30% by mass or more, and more preferably 40% by mass or more. The natural rubber component is 90% by mass or less, preferably 80% by mass or less. On the other hand, epoxidized natural rubber is the remainder of the rubber component in a two-component system with natural rubber, and is mixed in the range of 10 to 70% by mass. When the content of the epoxidized natural rubber is less than 10% by mass, the wear resistance is not sufficiently improved.

<Other rubber components>
Rubber components other than natural rubber and epoxidized natural rubber, such as styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile Butadiene rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (X-IIR) and the like can be mixed within a range of 20% by mass or less. However, from the viewpoint of environmental considerations, the smaller the amount, the better.

<Plant wax>
The vegetable waxes, mosquito Runabawakkusu virtuous preferable. The content of the vegetable wax is 3 parts by mass or more, preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. When the content of the vegetable wax is less than 3 parts by mass, the effect of improving weather resistance, that is, ozone crack resistance is small. The vegetable wax content is 15 parts by mass or less, preferably 10 parts by mass or less. If the content of the vegetable wax exceeds 15 parts by mass, the rubber hardness is lowered and the wear resistance and rolling resistance index are lowered.

<Silica>
Silica has a BET specific surface area (hereinafter referred to as BET) of preferably 80 m ² / g or more, and more preferably 100 m ² / g or more. When the BET of silica is less than 80 m ² / g, the wear resistance tends to be extremely lowered. Further, BET of silica is preferably 300 meters ² / g or less, more preferably 250m ² / g. When the BET of silica exceeds 300 m ² / g, dispersion in rubber becomes difficult and various performances tend to be lowered.

  The DBP adsorption amount of silica is preferably 70 to 200 ml / 100 g. The lower limit of the DBP adsorption amount is more preferably 90 ml / 100 g, and the upper limit is more preferably 150 ml / 100 g. If the DBP adsorption amount is less than 70 ml / 100 g, the rigidity required for steering stability tends to decrease, and if it exceeds 200 ml / 100 g, the elongation tends to deteriorate and the processability during production tends to deteriorate.

  The compounding quantity of a silica is 15 mass parts or more with respect to 100 mass parts of rubber components, Preferably it is 30 mass parts or more. When the silica content is less than 15 parts by mass, the rigidity and hardness are not sufficient, and the strength is also lowered. On the other hand, the blending amount is 90 parts by mass or less, preferably 80 parts by mass or less. When the content of silica exceeds 90 parts by mass, the hardness is excessively increased and the bending fatigue resistance tends to be greatly reduced.

<Silane coupling agent>
In the present invention, it is preferable to use a silane coupling agent in combination with silica. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica 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-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-tri Methoxysilylethyl) trisulfide, 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-dimethylthiocarbamoyltetra Sulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate mono Sulfide type such as sulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane and other mercaptotypes, vinyltriethoxysilane, vinyltrimethoxy Vinyl-based silane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) amino Amino group such as propyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyl Glycidoxy type such as diethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyl Examples include chloro-based compounds such as triethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane. These silane coupling agents may be used alone or in combination of two or more.

  In particular, Si69 (bis- (3-triethoxysilylpropyl) tetrasulfide), Si266 (bis- (3-triethoxysilylpropyl) disulfide) manufactured by Degussa, etc. can be mentioned, but because of good workability, Of these, Si266 is preferably used.

  When the silica and the silane coupling agent are contained, the amount of the silane coupling agent is preferably 3 parts by mass or more and more preferably 4 parts by mass or more with respect to 100 parts by mass of silica. When the content of the silane coupling agent is less than 3 parts by mass, it becomes difficult to disperse silica, and various performances, particularly wear resistance, tend to be lowered. Moreover, 20 mass parts or less are preferable and, as for content of a silane coupling agent, 15 mass parts or less are more preferable. When the content of the silane coupling agent exceeds 20 parts by mass, the crosslink density increases, chipping resistance decreases, and the cost tends to increase.

<Other ingredients>
In addition to the rubber component, vegetable wax, silica, and silane coupling agent, the clinch rubber composition of the present invention contains compounding agents conventionally used in the rubber industry, such as sulfur, stearic acid, zinc oxide, vulcanized An accelerator and the like may be contained.

  As sulfur, sulfur generally used in the rubber industry during vulcanization can be used. 0.5 mass part or more is preferable with respect to 100 mass parts of rubber components, and, as for content of sulfur, 0.8 mass part or more is more preferable. If the sulfur content is less than 0.5 parts by mass, the rubber tends to be too soft and the wear resistance tends to be greatly reduced. Moreover, 4 mass parts or less are preferable, and, as for sulfur content, 3 mass parts or less are more preferable. When the sulfur content exceeds 4 parts by mass, the hardness of the rubber is excessively increased, and not only a sufficient grip performance cannot be obtained, but also the wear resistance tends to be lowered. In the rubber composition for clinch of the present invention, vulcanization accelerators such as sulfur and sulfenamide are suitably blended as vulcanizing agents.

  The ratio (A / S) of the amount of sulfur (S) to the amount of vulcanization accelerator (A) is preferably 1/4 to 1/1. When the blending ratio is less than 1/4, the crosslinked form of the obtained rubber composition is greatly changed, the steering stability performance is inferior, and the elongation at break tends to decrease. On the other hand, when the blending ratio exceeds 1/1, the physical property change of the rubber composition due to running becomes large, which is not desirable.

<Pneumatic tire>
The pneumatic tire of the present invention is manufactured by a normal manufacturing method using the rubber composition of the present invention for clinching.

  FIG. 1 is a cross-sectional view of the right half of a radial tire for a passenger car. In FIG. 1, the tire T has a tread portion 1, a side wall portion 4 and a bead portion 5. Further, a carcass ply 3 in which the ends of the pair of bead cores 9 are wound back from the inside to the outside and both ends are locked, and a ply in which cords are arranged at an angle of 10 ° to 40 ° in the tire circumferential direction outside the crown portion of the carcass ply. And a bead apex 6 which is disposed between the carcass ply main body and the folded end thereof and reinforces the bead portion. The bead apex is preferably made of high-hardness rubber whose thickness gradually decreases from the upper side of the bead core 9 toward the side wall. Further, when the tire is mounted on the rim 7, the clinch rubber 8 is disposed at a position where the tire contacts the rim base portion and the rim flange 7 a. This clinch rubber is a component part of the tire that transmits a driving force from the rim during running of the tire and receives a heavy load and a very strong thermal history due to repeated deformation of the tire. The clinch rubber 8 generally has a structure in which the outer surface in the thickness direction contacts at least in the vicinity of the rim flange 7a, and the inner side in the thickness direction is adjacent to the folded end of the carcass ply and / or the bead apex. The upper end of the clinch rubber is positioned below the maximum width position of the side wall, and the lower end is configured to be positioned in a region adjacent to the rim base. The present invention employs the above-mentioned clinch rubber composition for this clinch rubber.

  In addition, although the structure of the typical pneumatic tire for passenger cars was shown in FIG. 1, the structure can be changed suitably. Furthermore, the present invention can also be applied to heavy vehicle tires, truck bus tires, and light truck tires.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to an Example.

Examples 1 to 3 and Comparative Example 1
1 part by weight of petroleum-based wax, 3 parts by weight to 15 parts by weight of carnauba wax, and 2 parts by weight of anti-aging agent with respect to 100 parts by weight of the rubber components and the blending contents shown in Table 1 excluding sulfur and vulcanization accelerator 2 parts by mass of stearic acid and 3 parts by mass of zinc oxide are mixed and kneaded in a banbury at about 150 ° C. for 5 minutes. Thereafter, sulfur and a vulcanization accelerator were added to the obtained rubber composition in amounts shown in Table 1, and kneaded with a biaxial open roll at about 80 ° C. for 5 minutes.

    Using the obtained clinch rubber composition, a tire was molded by a normal production method, and vulcanized under the conditions of 175 ° C., 12 minutes, 20 kgf to produce a 195 / 65R15 passenger car tire.

(Note 1) NR: RSS # 3.
(Note 2) Epoxidized natural rubber: ENR: epoxidation rate, 25%, manufactured by Kumpoulansuri.
(Note 3) Silica: Degussa VN3: BET: 175 m ² / g, DBP oil absorption: 162 ml / 100 g).
(Note 4) Silane coupling agent: Si266 (bis- (3-triethoxysilylpropyl) disulfide) manufactured by Degussa.
(Note 5) Petroleum wax: OZOACE-0355 manufactured by Nippon Seiwa.
(Note 6) Carnauba wax: Toa Kasei Co., Ltd.
(Note 7) Anti-aging agent: 6C manufactured by Sumitomo Chemical.
(Note 8) Stearic acid: Paulownia made by NOF Corporation.
(Note 9) Zinc oxide: Silver candy R manufactured by Mitsui Kinzoku Co., Ltd.
(Note 10) Sulfur: Sulfur manufactured by Tsurumi Chemical Co., Ltd.
(Note 11) Vulcanization accelerator: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<Characteristic evaluation>
1. Static Ozone Test The above-produced passenger car tire was left in a 50 pphm ozone chamber with an internal pressure of rim 6JJ × 15 and 200 KPa, and the number of days until cracking was measured.

2. Rubber strength No. 3 dumbbell-shaped test piece was prepared from a vulcanized rubber sample, and a tensile test was conducted according to JIS-K6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”. TB) and elongation at break (EB) were measured respectively. “Rubber strength” in Table 1 is a relative value when the rubber strength of Comparative Example 1 is 100, and is calculated by the following formula. A larger rubber strength value indicates a better rubber breaking strength.
Rubber strength = {(TB × EB) of each example} / {(TB × EB) of comparative example 1} × 100
3. High Severity Abrasion Resistance According to JIS-K6264 “Vulcanized Rubber and Thermoplastic Rubber—How to Determine Abrasion Resistance”, surface rotation speed 60 rpm, load load 4 kg with Ueshima Seisakusho Pico Abrasion Tester The test piece was worn for 1 minute, and the mass change before and after the test of each vulcanized rubber specimen was measured. The “high severe wear resistance value (W)” in Table 1 is a relative value when the wear value of Comparative Example 1 is 100, and is calculated by the following formula. The larger the value, the higher the resistance to high severity wear.

W = {mass change of each example} / {mass change of comparative example 1} × 100
4). JIS-A hardness JIS hardness is a vulcanized rubber test piece having a predetermined size prepared from a vulcanized rubber composition, and according to JIS-K62535 “Hardness test method for vulcanized rubber and thermoplastic rubber”. Hardness was measured with Type A.

5. Rolling resistance (RRC) index It was mounted on a rim 6JJ × 15 and measured using an STL rolling resistance tester at an internal pressure of 200 kPa, a speed of 80 km / h, and a load of 4.2 kN. The rolling resistance index obtained by dividing the measured value of rolling resistance by the load is shown as a relative value with the measured value of Comparative Example 1 being 100. Higher values indicate lower rolling resistance and better performance.

<Performance evaluation>
From Table 1, it can be seen that Examples 1 to 3 of the present invention are generally excellent in static ozone test, rubber strength, abrasion resistance and rolling resistance index.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. 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.

  The clinch rubber composition of the present invention does not cause environmental problems because it uses only raw materials of natural resources, and further maintains substantially the same level of characteristics as a rubber composition using conventional petroleum-based raw materials. Therefore, a pneumatic tire to which the rubber composition is applied is adopted as having versatility.

It is sectional drawing of the right half of the radial tire for passenger cars of this invention.

Explanation of symbols

  1 tread part, 2 belt layer, 3 carcass ply, 4 side wall, 5 bead part, 6 bead apex, 7 rim, 7a rim flange, 8 clinch rubber, 9 bead core.

Claims (4)

15 to 90 parts by weight of silica and 3 to 15 parts by weight of carnauba wax as vegetable wax are blended with 30 to 90 parts by weight of natural rubber component and 100 parts by weight of 10 to 70% by weight of epoxidized natural rubber. A clinch rubber composition for tires. The tire clinch rubber composition according to claim 1, wherein 5 to 15 parts by mass of carnauba wax is blended with 100 parts by mass of the rubber component.   The clinching rubber composition for tires according to claim 1, comprising 3 parts by mass or more of a silane coupling agent with respect to 100 parts by mass of silica.   A toroidal carcass that is folded back and locked to a pair of left and right bead cores, a belt layer disposed on the crown portion of the carcass, a tread layer disposed on the outer side of the belt layer, and from the bead portion to the side wall portion. A pneumatic tire having a clinch rubber disposed in a region in contact with a rim, wherein the clinch rubber is made of the clinch rubber composition according to any one of claims 1 to 3.

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