JP3600675B2 - Tread rubber composition for studless tires - Google Patents

Description

【００２８】
【表２】

【００２９】
カーボンブラック：東海カーボン（株）製のＮ２２０
炭酸カルシウム（１）：粒子径０．０４μｍで表面が脂肪酸（主にステアリン酸）によって処理されている白石カルシウム（株）の白艶華ＣＣ
炭酸カルシウム（２）：粒子径０．０４μｍで表面が脂肪酸（主にステアリン酸）によって処理されている竹原化学（株）のネオライトＳ
チタネート系カップリング剤：味の素（株）製のプレンアクトＴＴＳ（イソプロピルトリイソステアロイルチタネート）
プロセスオイル：出光興産（株）製のダイアナプロセスＰＳ３２
ワックス：大内新興化学（株）製のサンノックワックス
老化防止剤：精工化学社製のオゾノン６Ｃ
加硫促進剤：大内新興化学社製のノクセラ−ＮＳ
＜評価結果＞
実施例３と比較例２および比較例３との比較から、炭酸カルシウムおよびチタネート系カップリング剤を組み合わせると、撥水性および氷上性能が大幅に向上することがわかる。
【００３０】
実施例１〜４と比較例４との比較から、炭酸カルシウムの添加量の増加に従って接触角が増大し、氷上性能が向上するが、添加量が４０部より多いと（比較例４）、耐摩耗性能が著しく低下してしまうことがわかる。
実施例３および実施例６〜８から、チタネート系カップリング剤の添加量の増加に従って接触角が増大し、氷上性能が向上することがわかる。
【００３１】
実施例３および実施例５から、炭酸カルシウムの種類を変更しても同等の性能が得られることがわかる。
以上のように、実施例では補強性の低下を最小限に抑えながら、撥水性および氷上性能が向上することがわかる。
【００３２】
【発明の効果】
本発明のスタッドレスタイヤ用トレッドゴム組成物は、凍結路面においても優れたグリップ性を発揮するスタッドレスタイヤを得ることができる。
炭酸カルシウムの平均粒子径が１μｍ以下であるので補強性の低下は少ない。
脂肪酸および／または界面活性剤で表面処理されている炭酸カルシウムを含むトレッドゴム組成物は、ゴム組成物中の炭酸カルシウムの分散性が向上し、炭酸カルシウムがトレッドゴム組成物中に均一に分散することができる。
【００３３】
前記チタネート系カップリング剤がアルコキシチタネートであると、撥水性がさらに向上し、凍結路面においてもより優れたグリップ性を発揮することができる。
前記アルコキシチタネートがイソプロピルトリイソステアロイルチタネートであると、撥水性が最も向上し、凍結路面においてもよりいっそう優れたグリップ性を発揮することができる。
【図面の簡単な説明】
【図１】接触角の定義を示す説明図である。
【図２】接触角測定装置のブロック図である。
【符号の説明】
１ ゴム
２ 水滴[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tread rubber composition for a studless tire.
[0002]
[Prior art]
In order to prevent dust pollution due to spiked tires, the ban on spiked tires has been legislated, and studless tires have been used in cold regions instead of spiked tires. As a result of improvements, studless tires have been developed that have grip properties similar to spike tires on snow, but may be inferior to spiked tires on frozen road surfaces.
[0003]
On a road surface having a very small friction coefficient, such as a frozen road surface, factors that affect the grip performance of the studless tire include an adhesive friction force between the tread rubber and the road surface, a digging-up friction force, and the like.
In order to increase the adhesive frictional force, the rubber itself affects the adhesive frictional force. For example, it is also effective to soften the rubbery material to increase the contact area between the tire and the road surface. In order to soften the rubber, the amount of a filler is reduced, a rubber such as butadiene rubber or isoprene rubber, which hardly cures even at a low temperature, or a softening agent is added. However, rubber cannot be extremely softened from the viewpoint of steering stability and abrasion resistance on a frozen road surface. That is, softening the rubber is not sufficient from the viewpoint of balance between steering stability and wear resistance.
[0004]
In order to increase the excavation frictional force, the tread pattern and the surface morphology of the tread rubber are important. Spike tires have a large digging frictional force, but studless tires are also devised to increase the unevenness of the tread surface by using foamed rubber or mixing organic fibers in order to increase the digging up frictional force, which is also effective on frozen road surfaces. Further, the unevenness of the tread surface eliminates a water film generated between the tread surface and the frozen road surface, and thus has an effect of indirectly increasing the adhesive friction force. However, in the method of increasing the unevenness of the tread surface, there is a limit in increasing the actual contact area and a limit in increasing the adhesive friction force.
[0005]
As described above, the current studless tires have performance comparable to spike tires in terms of snow performance including grip, but on frozen road surfaces, grip performance may be inferior to spike tires. There is a need for improvement.
As an example of such improvement, the present applicant has previously proposed a rubber composition for a tread containing a silylating agent in Japanese Patent Application Laid-Open No. Hei 7-118452, and has obtained an effect of improving grip properties by the present invention. It has been desired to further improve the grip during braking.
[0006]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to provide a tread rubber composition used for a studless tire exhibiting more excellent grip even on a frozen road surface.
[0007]
[Means for Solving the Problems]
The inventor of the present application has changed the silylating agent to a titanate-based coupling agent in order to improve the gripping property during braking on a frozen road surface, and conducted intensive studies on the use of this with other components. The present invention has been achieved based on the finding that the type and the amount of the component are important, and the finding that the balance between the gripping property and the reinforcing property is important when determining the type and the amount of the other components.
[0008]
That is, the tread rubber composition for a studless tire of the present invention includes a diene rubber composed of at least one of natural rubber and a diene synthetic rubber, calcium carbonate, and a titanate coupling agent. The compounding ratio is 5 to 40 parts by weight of the calcium carbonate and 0.05 to 8 parts by weight of the titanate coupling agent with respect to 100 parts by weight of the diene rubber , and the average particle diameter of the calcium carbonate is It is 1 μm or less .
[0009]
It is preferable that the calcium carbonate is surface-treated with a fatty acid and / or a surfactant.
Preferably, the titanate-based coupling agent is an alkoxy titanate.
The alkoxy titanate may be isopropyl triisostearoyl titanate.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The tread rubber composition for a studless tire of the present invention contains a diene rubber, calcium carbonate, and a titanate coupling agent.
The diene rubber comprises at least one of natural rubber and diene synthetic rubber. Specific examples of the diene-based synthetic rubber include styrene-butadiene rubber (SBR), butadiene rubber (BR), and diene-based synthetic rubber such as isoprene rubber (IR). One or two or more of these diene rubbers can be used as needed.
[0011]
Calcium carbonate is usually used as an inexpensive bulking agent to increase the volume of rubber, plastic products, etc., to reduce costs, or to impart appropriate plasticity to unvulcanized rubber and improve processability. Have been. However, in the present invention, calcium carbonate is used together with a titanate-based coupling agent to increase water repellency and enhance grip on a frozen road surface. This is apparent from the fact that the rubber composition containing calcium carbonate has higher water repellency and grip on a frozen road surface than the rubber composition containing only carbon black.
[0012]
The average particle diameter of the calcium carbonate, from the viewpoint of not impairing the reinforcing effect of the carbon black, Ri average particle diameter of 1μm der less, more preferably 0.001 to 0.5 [mu] m, most preferably 0.01 to 0.1 μm. If the average particle size is more than this, the reinforcing property may be reduced. Further, when the calcium carbonate is surface-treated with a fatty acid and / or a surfactant, the dispersibility of the calcium carbonate in the rubber composition is improved, and the calcium carbonate is preferably dispersed uniformly in the tread rubber composition. .
[0013]
Fatty acids used for the surface treatment of calcium carbonate are not particularly limited. Specific examples of fatty acids include stearic acid, oleic acid, palmitic acid and the like. One or two or more of these fatty acids can be used as needed. Among them, stearic acid is preferable as the fatty acid.
The surfactant used for the surface treatment of calcium carbonate is not particularly limited. Specific examples of the surfactant include inorganic salts and organic salts of fatty acids such as stearic acid, oleic acid, and palmitic acid. One or two or more of these surfactants can be used as needed.
[0014]
The amount of calcium carbonate in the tread rubber composition is 5 to 40 parts by weight of calcium carbonate based on 100 parts by weight of the diene rubber. The amount of calcium carbonate is preferably 7 to 35 parts by weight, more preferably 8 to 25 parts by weight, based on 100 parts by weight of the diene rubber. If the amount of calcium carbonate is out of this range, the water repellency and grip on a frozen road surface will be low.
[0015]
The titanate-based coupling agent is used together with calcium carbonate to improve the water repellency by converting a hydrophilic portion having an active hydrogen such as a hydroxyl group, an amino group and a carboxyl group in the rubber composition into a hydrophobic portion, thereby improving freezing. The grip on the road surface is improved.
The titanate-based coupling agent is not particularly limited, and examples thereof include an alkoxy titanate, which is preferable because water repellency is further improved and more excellent grip properties can be exhibited even on a frozen road surface.
[0016]
Specific examples of the alkoxy titanates include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridodecyl phosphite) titanate, tetra (2,2-diallyloxy) Methyl-1-butyl) bis (ditridodecyl) phosphite titanate and the like can be mentioned. These alkoxy titanates may be used alone or, if necessary, in combination of two or more. Above all, it is preferable that the alkoxy titanate is isopropyl triisostearoyl titanate, since the water repellency is most improved and even more excellent grip properties can be exhibited even on a frozen road surface.
[0017]
The mixing amount of the titanate coupling agent in the tread rubber composition is 0.05 to 8 parts by weight of the titanate coupling agent based on 100 parts by weight of the diene rubber. The compounding amount of the titanate coupling agent is preferably 0.1 to 6 parts by weight of the titanate coupling agent with respect to 100 parts by weight of the diene rubber, and more preferably the titanate coupling with respect to 100 parts by weight of the diene rubber. 0.5 to 5 parts by weight, most preferably 1 to 4 parts by weight of a titanate coupling agent. If the amount of the titanate-based coupling agent is too small, the effect of improving the water repellency and the grip on a frozen road surface cannot be expected by the compounding. Also, if the amount of the titanate-based coupling agent is too large, unreacted titanate-based coupling agents that do not react with active hydrogen such as hydroxyl group, amino group and carboxyl group in the rubber composition increase, and the rubber hardness decreases. Cost is high.
[0018]
The tread rubber composition for a studless tire of the present invention contains calcium carbonate and a titanate-based coupling agent as essential components. For this reason, the water repellency and the grip on a frozen road surface are significantly improved.
The tread rubber composition for a studless tire of the present invention may contain carbon black in order to obtain sufficient hardness when the composition is used for a studless tire.
[0019]
The compounding amount of carbon black in the tread rubber composition is not particularly limited, and is preferably 30 to 80 parts by weight of carbon black based on 100 parts by weight of diene rubber. The compounding amount of carbon black is more preferably 40 to 60 parts by weight, and most preferably 40 to 50 parts by weight, based on 100 parts by weight of the diene rubber. If the amount of the carbon black is too small, abrasion resistance and crack resistance tend to be inferior. If the amount of the carbon black is too large, the rubber is cured, and the obtained tire tends to generate heat during use.
[0020]
In the tread rubber composition for a studless tire of the present invention, if necessary, specifically, a softening agent such as a naphthenic process oil; a vulcanization aid such as zinc oxide and stearic acid; a mercaptobenzothiazole (MBT) Thiazole-based accelerators such as benzothiazyl disulfide (MBTS), N-tert-butyl-2-benzothiazolylsulfenamide (TBBS) and N-cyclohexyl-2-benzothiazylsulfenamide (CBS). Vulcanization accelerators; sulfur; organic fibers; foaming agents; anti-aging agents; The amount of these additives in the tread rubber composition is not particularly limited, and can be appropriately used.
[0021]
As a method for producing the tread rubber composition for a studless tire of the present invention, a known method can be applied. The above components can be obtained by kneading them under a usual method and conditions using a kneader such as a Banbury mixer. The kneading temperature is preferably from 120 to 180 ° C.
The studless tire is obtained by molding and vulcanizing the tread rubber composition for a studless tire described above.
[0022]
【Example】
Hereinafter, specific examples and comparative examples of the present invention will be described, but the present invention is not limited to the following examples.
(Examples 1 to 8 and Comparative Examples 1 to 4)
A tread rubber composition was prepared by kneading the components shown in Tables 1 and 2 below at 150 ° C. for 5 minutes using a Banbury mixer. The performance of a rubber sample obtained by vulcanizing the obtained tread rubber composition at 170 ° C. for 10 minutes was evaluated by the following evaluation method. The results are shown in Tables 1 and 2.
[0023]
<Evaluation method>
1. Rubber hardness The rubber hardness Hs (JIS-A) at 0 ° C. was measured according to the method specified in JIS K6301.
2. Contact angle The contact angle refers to the angle (θ) at which the boundary between the rubber 1 and the water droplet 2 contacts with the water droplet 2 adhered to the surface of the rubber 1 as shown in FIG. Means leakiness. The smaller the contact angle is, the more difficult it is to wet, indicating that the rubber has excellent water repellency.
[0024]
Using the measuring device shown in FIG. 2, the forward contact angle and the receding contact angle are measured, and the contact angle is calculated according to the following equation. Example values displayed. Therefore, a larger value indicates a larger contact angle.
cos θ = 1/2 × (cos θ _a + cos θ _r )
θ: contact angle θ _a : advancing contact angle θ _r : receding contact angle The magnitude of water repellency can be quantitatively expressed by measuring the contact angle between water and the rubber composition, and the larger the contact angle, the better. It means that it is water repellent. Note that the contact angle is measured by the number of samples and the number of measurements so that a difference of the unit value 1 of the average value can be detected at the 5% significance level.
[0025]
3. Stopping distance on ice The studless tire was manufactured using the tread rubber composition (185 / 70R14). These tires were mounted on a front-wheel drive (FF vehicle) type domestic car with a displacement of 2000 cc, and the stopping distance on ice required to stop suddenly during running at a speed of 30 km / h and stop was measured. With the stopping distance of Comparative Example 1 set to 100, values of other Comparative Examples and Examples are displayed. The larger the value, the better the braking resistance.
[0026]
Test location: Skating rink Temperature: 2 ° C
4. Abrasion resistance The wear of the test piece was measured using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho under the conditions of a load of 2.5 kg, a slip ratio of 20% and 40%. The average value at both slip ratios was calculated, and the values of Comparative Examples 1 and 2 were shown as wear indices with Comparative Example 1 being 100. The larger the wear index, the better the wear resistance.
[0027]
[Table 1]

[0028]
[Table 2]

[0029]
Carbon black: N220 manufactured by Tokai Carbon Co., Ltd.
Calcium carbonate (1): Shiraishi Calcium Co., Ltd.'s white gloss flower CC having a particle diameter of 0.04 μm and a surface treated with a fatty acid (mainly stearic acid)
Calcium carbonate (2): Neolite S from Takehara Chemical Co., Ltd., having a particle size of 0.04 μm and a surface treated with a fatty acid (mainly stearic acid)
Titanate-based coupling agent: Plenact TTS (isopropyl triisostearoyl titanate) manufactured by Ajinomoto Co., Inc.
Process oil: Diana Process PS32 manufactured by Idemitsu Kosan Co., Ltd.
Wax: Sunnock wax antioxidant manufactured by Ouchi Shinko Chemical Co., Ltd .: Ozonone 6C manufactured by Seiko Chemical Co., Ltd.
Vulcanization accelerator: Noxera NS manufactured by Ouchi Shinko Chemical Co., Ltd.
<Evaluation results>
From a comparison between Example 3 and Comparative Examples 2 and 3, it can be seen that when calcium carbonate and a titanate-based coupling agent are combined, the water repellency and the performance on ice are significantly improved.
[0030]
From a comparison between Examples 1 to 4 and Comparative Example 4, the contact angle increases with an increase in the amount of calcium carbonate added, and the performance on ice is improved. It can be seen that the wear performance is significantly reduced.
Examples 3 and 6 to 8 show that the contact angle increases as the added amount of the titanate-based coupling agent increases, and the performance on ice improves.
[0031]
Example 3 and Example 5 show that the same performance can be obtained even when the type of calcium carbonate is changed.
As described above, it can be seen that in the examples, the water repellency and the performance on ice are improved while the reduction in the reinforcing property is minimized.
[0032]
【The invention's effect】
The tread rubber composition for a studless tire of the present invention can provide a studless tire exhibiting excellent grip properties even on a frozen road surface.
Reduction in the reinforcing properties the average particle size of the calcium carbonate is 1μm or less is small.
In a tread rubber composition containing calcium carbonate surface-treated with a fatty acid and / or a surfactant, the dispersibility of calcium carbonate in the rubber composition is improved, and calcium carbonate is uniformly dispersed in the tread rubber composition. be able to.
[0033]
When the titanate-based coupling agent is an alkoxy titanate, the water repellency is further improved, and excellent grip properties can be exhibited even on a frozen road surface.
When the alkoxy titanate is isopropyl triisostearoyl titanate, the water repellency is most improved, and a more excellent grip property can be exhibited even on a frozen road surface.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a definition of a contact angle.
FIG. 2 is a block diagram of a contact angle measuring device.
[Explanation of symbols]
1 rubber 2 water drop

Claims (4)

Including a diene rubber consisting of at least one of natural rubber and a diene synthetic rubber, calcium carbonate, and a titanate coupling agent, the mixing ratio of the three is based on 100 parts by weight of the diene rubber. A tread rubber composition for a studless tire, comprising 5 to 40 parts by weight of the calcium carbonate and 0.05 to 8 parts by weight of the titanate-based coupling agent , and having an average particle diameter of 1 μm or less . The tread rubber composition for a studless tire according to claim 1 , wherein the calcium carbonate is surface-treated with a fatty acid and / or a surfactant. The tread rubber composition for a studless tire according to claim 1 or 2 , wherein the titanate-based coupling agent is an alkoxy titanate. The tread rubber composition for a studless tire according to claim 3 , wherein the alkoxy titanate is isopropyl triisostearoyl titanate.

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