JP3591751B2 - Rubber composition - Google Patents

Description

【００３２】
上記表１に示すカーボンブラックおよび試料１〜５を用いて、下記の表２に示す配合処方（重量部）に従い各種ゴム組成物を調製した。
得られたゴム組成物について、ヒステリシスロス、ウエットスキッド抵抗および耐摩耗性を以下のようにして評価した。
【００３３】
（イ）ヒステリシスロス（ｔａｎδ（５０℃））
米国レオメトリックス社製の動的スペクトロメータを使用し、５０℃にて動的剪断歪み（振幅１．０％、周波数１５Ｈｚ）を与えてｔａｎδ値を測定し、比較例１における値を１００として指数表示した。従って、数値が小さい程ヒステリシスロスが小さく良好であることを示す。
【００３４】
（ロ）ウエットスキッド抵抗
ポータブルスキッドレジスタンステスターを用いて、室温にて湿潤コンクリート路面に対する有効摩擦係数μを求め、比較例１における値を１００として指数表示した。従って、数値が大きい程ウエットスキッド抵抗が大きく良好であることを示す。
【００３５】
（ハ）耐摩耗性
ランボーン摩耗法により測定した。負荷荷重が２．０ｋｇ、室温におけるスリップ率５０％における摩耗量を測定し、それらの逆数を用いて、比較例１における値を１００として指数表示した。従って、数値が大きい程耐摩耗性が良好であることを示す。
得られた結果を下記の表２に併記する。
【００３６】
【表２】

１）日本合成ゴム（株）製 アロマオイル３７．５ｐｈｒの油展スチレンブタジエンゴム
２）日本合成ゴム（株）製 ポリブタジエンゴム
３）東海カーボン（株）製 シースト７Ｈ
４）日本シリカ（株）製 ニプシルＡＱ
５）ドイツのデグサ社製 Ｓｉ６９
６）ジフェニルグアニジン
７）Ｎ−ｔｅｒｔ−ブチル−２−ベンゾチアゾリルスルフェンアミド
【００３７】
表２に示す評価結果から以下のことが確かめられた。
沈降法によりシリカを表面に付着させたカーボンブラックを用いたゴム組成物（比較例４）は、シリカとカーボンブラックとを単純なブレンド状態で配合したゴム組成物（比較例３）と効果の面でさほど差がなかった。これに対し、実施例１〜３のゴム組成物は、いずれも耐摩耗性を実質的に損なうことなく低燃費性能とウエットスキッド抵抗とが大幅に改善された。このことは、表２に示す耐摩耗性とヒステリシスロス（ｔａｎδ（５０℃））との関係からも明らかである。
【００３８】
【発明の効果】
以上説明してきたように本発明のゴム組成物においては、ゾル−ゲル法によるシリカコーティングカーボンブラックを所定量配合したことにより、耐摩耗性と低燃費性能およびウェットスキッド抵抗とを良好に両立させることができる。また、ゾル−ゲル法によるシリカコーティング前のカーボンブラックに低温プラズマ処理を施すことにより、あるいは所定量のシランカップリング剤を配合することにより、かかる効果をより高めることができる。
【図面の簡単な説明】
【図１】実施例、参考例および比較例におけるｔａｎδと耐摩耗性との関係を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improved silica-containing rubber composition, and more particularly, when applied to a tire, particularly to a tread, has significantly lower fuel consumption performance and friction on wet road surfaces than conventional silica-containing rubber compositions. The present invention relates to a rubber composition capable of improving resistance (wet skid resistance) and abrasion resistance.
[0002]
[Prior art]
Conventionally, carbon black has been used as a reinforcing filler for rubber. This is because carbon black has high reinforcing properties and excellent wear resistance as compared with other fillers. However, in recent years, under the social demands for energy saving and resource saving, it has been required at the same time to reduce fuel consumption by using compound rubber in order to save fuel consumption of automobiles. Here, it is generally known that reducing the rolling resistance of the tire reduces the fuel consumption of the vehicle, resulting in a so-called fuel-efficient tire. It is also known that the rolling resistance of a tire can be reduced by using a material having a small hysteresis loss for the tread rubber of the tire.
[0003]
On the other hand, due to recent demands for running stability, a rubber material having a large wet skid resistance has been strongly desired. However, the wet skid resistance and the above-mentioned low rolling resistance of the tire have a trade-off relationship, and it is extremely difficult to satisfy both the characteristics.
[0004]
Therefore, various silica-containing rubber compositions have been proposed from the standpoint of achieving a balance between the two, for example, JP-A-3-252431, JP-A-3-252433, JP-A-4-224840, JP-A-5-271777. As disclosed in JP-A-5-51484, JP-A-7-1908, and JP-A-7-48476, the rubber composition containing silica can improve wet skid resistance and low fuel consumption performance. Has been stated.
[0005]
[Problems to be solved by the invention]
However, since silica does not have a strong structure unlike carbon black, there is a problem that abrasion resistance is deteriorated. By the way, recently, it has been proposed that low hysteresis loss (high temperature tan δ), wet skid resistance, electric resistance and dispersibility can be improved by blending carbon black having silica adhered to its surface into a rubber composition. However, such a silica surface-treated carbon black is produced by mixing carbon black during the production of general wet silica, and the bonding between silica and carbon black is performed. Was not always sufficient, and was limited to some combinations. Therefore, even if this silica surface-treated carbon black is added to the rubber composition of the tire tread, it is still insufficient in terms of achieving both low fuel consumption performance and wet skid resistance without impairing abrasion resistance. there were.
[0006]
Accordingly, an object of the present invention is to provide a rubber composition that achieves both good abrasion resistance, low fuel consumption performance, and wet skid resistance by using silica-coated carbon black in which silica is sufficiently chemically bonded to the carbon black surface. To provide.
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the above object can be achieved by blending carbon black coated on the surface with silica using a sol-gel method into a rubber composition. Thus, the present invention has been completed.
[0008]
That is, the rubber composition of the present invention is blended with 100 to 100 parts by weight of natural rubber and / or a diene-based synthetic rubber, and 10 to 100 parts by weight of carbon black whose surface is coated with silica using a sol-gel method. The carbon black whose surface is coated with silica using the sol-gel method is subjected to a low-temperature plasma treatment.
[0009]
To make the bond between the silica and the carbon black surface stronger, the carbon black may be subjected to a low-temperature plasma treatment. The rubber composition of the present invention preferably contains a silane coupling agent in an amount of 1 to 15% by weight based on the carbon black coated on the surface of the silica, and the silica in the carbon black coated on the surface of the silica. Preferably, the amount is from 1 to 40% by weight.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
As the rubber component in the present invention, natural rubber (NR) or synthetic rubber can be used alone or in combination. Examples of the synthetic rubber include synthetic polyisoprene rubber, polybutadiene rubber (BR), styrene butadiene rubber (SBR), and the like.
[0011]
As the carbon black used as the reinforcing filler in the present invention, SAF, ISAF, HAF, FEF grade carbon black can be preferably used, and preferably, dibutyl phthalate oil absorption (DBP) is 60 to 220 ml / 100 g, and nitrogen is used. It is preferable to use one having an adsorption specific surface area of 50 to 230 m ² / g. Note that DBP is a value determined in accordance with ASTM D2414-93, and N ₂ SA is a value determined in accordance with ASTM D4820.
[0012]
Next, a method for producing carbon black having silica coated on its surface using the sol-gel method according to the present invention (hereinafter abbreviated as “silica-coated carbon black”) will be specifically described.
In the present invention, by using the sol-gel method, carbon black is bonded to silica via oxygen-containing functional groups (hydroxyl group, quinone group, carboxyl group, etc.) present on the surface. Such a bond can sufficiently occur even with untreated carbon black, but the more oxygen-containing functional groups present on the surface of the carbon black, the more the bond with silica increases, which is preferable. Therefore, in the present invention, in order to further increase the bonding of silica to the surface of the carbon black, it is preferable to subject the carbon black to a low-temperature plasma treatment.
[0013]
Introduction of a functional group by low-temperature plasma treatment is described in, for example, Japanese Patent Publication No. 5-18339, publication "Coloring Material" (60 (6), 342, 1987), and the like. It is possible to introduce oxygen-containing functional groups on the surface.
[0014]
Power sources for generating plasma include high frequency, microwave, direct current, and alternating current, and discharge types include glow discharge, corona discharge, and boxer charger due to inductive load or capacitive load. is not.
[0015]
The atmosphere gas at the time of plasma irradiation can be used alone or as a mixture of two or more of H ₂ O, oxygen, air, carbon dioxide, carbon monoxide, hydrogen, nitrogen, argon, helium and the like. It is preferable to use H ₂ O, oxygen, and air for the purpose of efficiently introducing an oxygen-containing functional group into the polymer. H ₂ O is more preferable from the viewpoint of preventing carbon black ashing during plasma irradiation.
[0016]
The pressure of the atmospheric gas in the reaction system is 10 ^{−2 to 5} Torr, preferably 10 ^{−2 to 3} Torr. If the pressure is too high, the plasma becomes unstable, and the amount of oxygen-containing functional groups introduced into the carbon black surface decreases, so that the increase in the amount of silica coated in the next sol-gel process according to the present invention is not sufficient. .
[0017]
Next, it is generally known that the sol-gel method has a simple reaction mechanism and is excellent in uniformity in surface coating of metal, glass, ceramic and the like. In the present invention, this sol-gel method is used for coating silica with carbon black, and such sol-gel coating on carbon black is a technique not yet known. On the other hand, the method of adhering silica to the surface of carbon black described in Japanese Patent Application Laid-Open No. 8-277347 describes that, as described, silica adheres only to a very small part of the surface of carbon black, Since black is considered to be physically attached, there is no actual difference from a simple blend of silica and carbon black generally used in the rubber industry.
[0018]
As the sol-gel method in the present invention, a method usually used can be basically applied, but as a raw material, water glass, various alkoxysilanes SiR _n (OR) _4-n (R: alkyl group), gas phase Typical examples include silica, but are not particularly limited thereto. However, from the viewpoint of the reaction rate, tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and tetra-n-propoxysilane are preferable. Also, usually sol - As used gel method, it may be added an _alcohol, H 2 O, HCl, if necessary the _NH 4 Cl or the like.
[0019]
Further, the molar ratio (H ₂ O / Si) of H ₂ O to be added and Si in the raw material is preferably 25 or more, and more preferably 50 or more. If the concentration of Si is too high, silica precipitates on the surface other than the carbon black surface, and a sample substantially consisting of the required silica-coated carbon black cannot be obtained.
[0020]
The silica and the carbon black in the silica-coated carbon black obtained by the sol-gel method in this way have extremely good chemical bonds, and when this is blended with the rubber composition, simple blending or physical adhesion is not achieved. Has a distinctly different superior effect. In the sol-gel method of the present invention, as is known as a so-called general sol-gel method, a process in which raw material Si sources are hydrolyzed and dehydrated and condensed to form a sol, and then gelled on the surface of carbon black. In addition, after the raw material Si source monomer chemically bonds to the carbon black surface, the raw material monomer repeats dehydration condensation based on the site, and a process of coating the carbon black surface with silica may occur.
[0021]
The amount of silica in the silica-coated carbon black is preferably from 1 to 40% by weight, and more preferably from 2 to 30% by weight. If the amount of silica is less than 1% by weight, the effect of improving wet skid resistance and low fuel consumption performance is insufficient. On the other hand, if it exceeds 40% by weight, no improvement in the effect is observed. The amount of silica is determined from the amount of ash obtained by completely burning silica-coated carbon black in an electric furnace.
[0022]
In the present invention, the amount of the silica-coated carbon black in the rubber composition is 10 to 100 parts by weight, preferably 10 to 80 parts by weight. If the amount is less than 10 parts by weight, the effect of improving wet skid resistance and fuel efficiency is not sufficient, while if it exceeds 100 parts by weight, fuel efficiency deteriorates. Incidentally, carbon black and / or silica can be added to the rubber composition of the present invention. In this case, the total number of parts of the silica-coated carbon black, silica and carbon black is preferably 120 parts by weight or less. If it exceeds 120 parts by weight, not only does the fuel economy performance deteriorate, but the rubber becomes hard and workability is poor.
[0023]
Furthermore, in the rubber composition of the present invention, it is preferable that the silane coupling agent is contained in an amount of 1 to 15% by weight based on the silica-coated carbon black. If the amount of the silane coupling agent is less than 1% by weight, the coupling effect is small, while if it exceeds 15% by weight, gelation of the polymer is caused, which is not preferable.
[0024]
Such a silane coupling agent is not particularly limited as long as it is generally used in the rubber industry. Specifically, bis (3-triethoxysilylpropyl) polysulfide (S number of polysulfide portion: 2 to 8), γ-mercaptopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltri Methoxysilane is preferred.
[0025]
In the rubber composition of the present invention, in addition to the above rubber component, silica-coated carbon black, and silane coupling agent, if necessary, a softening agent, an antioxidant, a vulcanizing agent, a vulcanization accelerator, a vulcanizing accelerator, A compounding agent usually used in the rubber industry, such as a sulfuric acid accelerating aid, can be appropriately compounded.
[0026]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
According to the conditions shown in Table 1 below, untreated N234 carbon black, silica-coated carbon black by a sol-gel method (sample Nos. 2 to 5), and carbon black having silica adhered to the surface by a sedimentation method for comparison (Sample No. 1) were prepared respectively. The specific low-temperature plasma treatment, the specific sol-gel method, and the sedimentation method were performed as follows.
[0027]
Low-temperature plasma conditions A plasma experiment apparatus obtained by improving a rotary evaporator was used, and an NFG-150 manufactured by Nippon Dempa Kogyo Co., Ltd. having an oscillation frequency of 13.56 MHz was used as a high-frequency generator.
N234 carbon black (non-granulated product) dried under reduced pressure is put into a reaction vessel, and a vacuum (10 ⁻² Torr or less) is applied by using an oil diffusion vacuum pump, and then steam is introduced up to 1 Torr and plasma is irradiated for 1 hour. did. At this time, the energy (W / FM) of the plasma applied to the atmosphere gas was controlled as shown in Table 1 by changing the flow rate of the steam.
[0028]
Sol - gel method <br/> tetraethoxysilane (TEOS) 20 g, in 1 liter flask containing water 400g of hydrochloric acid or _NH 4 Cl was added, the pH value of 2.5 or 9.8 as shown in Table 1 Was adjusted to be a sol-gel reaction mother liquor. To this, 50 g of untreated N234 carbon black (ungranulated product) (sample No. 2) or plasma-treated carbon black (samples 3 to 5) was added, stirred at 80 ° C. for 15 minutes, and then stirred at room temperature for 72 hours. After filtering, drying and crushing lightly, each sample was obtained.
[0029]
A slurry of sedimentation method N234 carbon black was prepared, heated to 80 ° C., and then sodium silicate (SiO ₂ / Na ₂ O = 3.4) was added dropwise over 2 hours. At this time, sulfuric acid was simultaneously added dropwise so that the pH of the system was maintained at 9.5. After the sodium silicate was dropped, only sulfuric acid was dropped until the pH reached 4, followed by filtration, washing with water, and drying to obtain a target product (sample 1).
[0030]
Nitrogen adsorption ratios of untreated N234 carbon black, silica-coated carbon black by sol-gel method (Sample Nos. 2 to 5), and carbon black with silica attached to the surface by sedimentation method (Sample No. 1) for comparison The surface area (N ₂ SA) and ash content (ratio (%) of the residue after standing in an electric furnace at 900 ° C. for 24 hours) are also shown in Table 1 below.
[0031]
[Table 1]

[0032]
Various rubber compositions were prepared from the carbon blacks shown in Table 1 and Samples 1 to 5 in accordance with the formulation (parts by weight) shown in Table 2 below.
The obtained rubber composition was evaluated for hysteresis loss, wet skid resistance and abrasion resistance as follows.
[0033]
(A) Hysteresis loss (tan δ (50 ° C))
Using a dynamic spectrometer manufactured by Rheometrics Co., USA, a tan δ value was measured at 50 ° C. while applying a dynamic shear strain (amplitude: 1.0%, frequency: 15 Hz), and the index in Comparative Example 1 was set to 100. displayed. Therefore, the smaller the numerical value, the smaller the hysteresis loss and the better.
[0034]
(B) Wet skid resistance Using a portable skid resistance tester, the effective friction coefficient μ against a wet concrete road surface was determined at room temperature, and the index in Comparative Example 1 was set to 100 to indicate the index. Therefore, the larger the numerical value, the larger the wet skid resistance and the better.
[0035]
(C) Abrasion resistance Measured by the Lambourn abrasion method. The amount of wear at a load of 2.0 kg and a slip ratio of 50% at room temperature was measured, and the index of the value in Comparative Example 1 was set to 100 using the reciprocal of the wear amount. Therefore, the larger the value, the better the wear resistance.
The results obtained are shown in Table 2 below.
[0036]
[Table 2]

1) Oil-extended styrene-butadiene rubber of 37.5 phr aroma oil manufactured by Nippon Synthetic Rubber Co., Ltd. 2) Polybutadiene rubber manufactured by Nippon Synthetic Rubber Co., Ltd. 3) Seast 7H manufactured by Tokai Carbon Co., Ltd.
4) Nipsil AQ manufactured by Nippon Silica Co., Ltd.
5) Si69 manufactured by Degussa of Germany
6) diphenylguanidine 7) N-tert-butyl-2-benzothiazolylsulfenamide
From the evaluation results shown in Table 2, the following was confirmed.
The rubber composition using carbon black having silica adhered to the surface by the sedimentation method (Comparative Example 4) is different from the rubber composition (Comparative Example 3) in which silica and carbon black are blended in a simple blend state. There was not much difference. In contrast, all of the rubber compositions of Examples 1 to 3 exhibited significantly improved fuel economy and wet skid resistance without substantially impairing wear resistance. This is clear from the relationship between the wear resistance and the hysteresis loss (tan δ (50 ° C.)) shown in Table 2.
[0038]
【The invention's effect】
As described above, in the rubber composition of the present invention, by mixing a predetermined amount of silica-coated carbon black by a sol-gel method, it is possible to achieve both good wear resistance, low fuel consumption performance and wet skid resistance. Can be. Such effects can be further enhanced by subjecting the carbon black before silica coating by the sol-gel method to low-temperature plasma treatment or by blending a predetermined amount of a silane coupling agent.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between tan δ and wear resistance in Examples, Reference Examples and Comparative Examples.

Claims (3)

Against natural rubber and / or diene synthetic rubber 100 parts by weight, the sol - gel method carbon black 10 to 100 parts by weight was applied to the surface of silica with is blended, the sol - silica by gel method A rubber composition, characterized in that carbon black to be coated on the surface has been subjected to low-temperature plasma treatment . The rubber composition according to claim 1, wherein the silane coupling agent is contained in an amount of 1 to 15% by weight based on carbon black coated with silica. The rubber composition according to claim 1 or 2 , wherein the amount of the silica in carbon black having silica coated on the surface is 1 to 40% by weight.

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