JP2009007511A - Diene-based rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica-filled diene-based rubber composition that is suitably used as a vulcanization molding material for a tread part of a pneumatic tire or the like, increases a vulcanization rate and can give a vulcanized product having an excellent balance of viscoelastic properties. <P>SOLUTION: A diene rubber composition comprising diene rubber, silica, a silane coupling agent and a tetrazole derivative represented by the formula (wherein n is an integer of 4-10) achieves the object. The diene rubber composition comprises 20-100 pts.wt. silica per 100 pts.wt. diene rubber and the silane coupling agent and the tetrazole derivative each in an amount of 2-15 wt.% based on the weight of silica. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a diene rubber composition. More specifically, the present invention relates to a silica-containing diene rubber composition that is suitably used as a vulcanization molding material for a tread portion of a pneumatic tire.

In recent years, the performance required for pneumatic tires has been various, and has become higher-dimensional. For example, there is a strong demand for reducing tire rolling resistance due to market needs for low fuel consumption, and in terms of safety, improvements in braking performance and driving stability on wet road surfaces are also required. In order to achieve both such low rolling resistance and high wet resistance (wet performance), silica has conventionally been used as a rubber filler in the tread portion of a tire or the like instead of carbon black.
Journal of the Adhesion Society of Japan, Vol. 17, No. 5, 197 (2001)

  Further, in recent years, the amount of silica is greatly increased, and accordingly, problems such as a decrease in the vulcanization rate and deterioration in dispersibility due to the promotion of aggregation between silicas have been observed. Furthermore, since a long mixing time is required to increase the reactivity of silica, there is a concern about a decrease in productivity. In order to solve these problems, if the affinity between the diene rubber and silica can be increased, the diene rubber composition can satisfy the required tire performance while reducing the mixing time and improving the productivity. Things can be provided.

  An object of the present invention is a silica-containing diene rubber composition that is suitably used as a vulcanization molding material for a tread portion of a pneumatic tire, which increases the vulcanization speed and has a good balance of viscoelastic properties. It is to provide what can give a vulcanizate.

(ここで、nは4〜10の整数である)で表わされるテトラゾール誘導体を含有してなるジエン系ゴム組成物によって達成され、このジエン系ゴム組成物は、ジエン系ゴム100重量部当り20〜100重量部のシリカ、シリカ重量に対してそれぞれ2〜15重量％の割合で用いられたシランカップリング剤およびテトラゾール誘導体よりなる。 The object of the present invention is to provide diene rubber, silica, silane coupling agent and general formula

(Where n is an integer of 4 to 10), and is achieved by a diene rubber composition comprising 20 to 20 parts by weight of 100 parts by weight of diene rubber. It consists of 100 parts by weight of silica and a silane coupling agent and a tetrazole derivative used at a ratio of 2 to 15% by weight with respect to the silica weight.

  The diene rubber composition according to the present invention adds a tetrazole derivative having a high affinity with the diene rubber, thereby controlling the delay of the vulcanization speed in the silica mass blending system and increasing the vulcanization speed. Since a vulcanizate having an excellent balance of viscoelastic properties is provided, it can be suitably used as a vulcanization molding material for tread portions such as cap treads and under treads of pneumatic tires. In particular, it is suitable as a vulcanization molding material for cap treads containing high silica. As a result, it is possible to obtain a pneumatic tire that satisfies the required tire performance of the tread portion while shortening the vulcanization reaction time and improving the productivity.

  Diene rubbers include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), nitrile rubber (NBR), styrene butadiene rubber (SBR), etc. Or as a blend rubber, preferably NR, BR, SBR or a blend rubber thereof. As SBR, either emulsion polymerization SBR (E-SBR) or solution polymerization SBR (S-SBR) can be used.

As the silica, those having a BET specific surface area of 30 to 200 m ² / g, preferably 50 to 150 m ² / g are generally used. These include the pyrolysis method of halogenated silicic acid or organosilicon compounds and the dry method of silica and sodium silicate pyrolysis method, which is produced by heating and reducing silica sand and air-oxidizing the evaporated SiO. Wet process silica to be produced, etc., and wet process silica is preferably used in terms of cost and performance. Actually, a commercial product marketed for the rubber industry can be used as it is.

  The addition ratio is 20 to 100 parts by weight, preferably 30 to 90 parts by weight per 100 parts by weight of the diene rubber. When the addition ratio of silica is less than this, the characteristics required of silica as a filler, i.e., low rolling resistance and wet resistance performance are not sufficiently exhibited, while when used at an addition ratio higher than this, Workability will deteriorate.

  Thus, the properties required of silica and dispersibility with diene rubbers (silica has poor affinity with rubber polymers, and silica in rubber forms hydrogen bonds through silanol groups, and silica is incorporated into rubber. In order to increase (having the property of reducing dispersibility), a silane coupling agent is used in a proportion of 2 to 15% by weight, preferably 5 to 10% by weight, based on the weight of silica. Examples of the silane coupling agent include polysulfide silane coupling agents having an alkoxysilyl group that reacts with a silanol group on a silica surface and a sulfur chain that reacts with a polymer, such as bis (3-triethoxysilylpropyl) tetrasulfide, bis (2 -Triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide and the like are preferably used. If the proportion of silane coupling agent used is less than this, the properties required of silica and dispersibility with diene rubber will not be fully exhibited, while if it is used in a proportion higher than this, workability will deteriorate. To come.

  In the silica-containing diene rubber composition of the present invention, in order to increase the vulcanization rate and give a vulcanizate having excellent viscoelastic properties, the tetrazole derivative represented by the above general formula is further added to the silica weight. 2 to 15% by weight, preferably 2 to 10% by weight is added. When the use ratio is less than this, the effect of adding the tetrazole derivative is not sufficiently exhibited. On the other hand, when the use ratio is higher than this, the scorch is quickened and the workability is deteriorated.

と脂肪族モノカルボン酸C_nH_2n+1COOH(n：4〜10)またはその酸ハライドとの縮合反応生成物として得られる。 Such tetrazole derivatives include 5-amino-1H-tetrazole, which is a 5-amino substitution of tetrazole, which is a tautomer of 1H-tetrazole and 2H-tetrazole.

And an aliphatic monocarboxylic acid C _n H _{2n + 1} COOH (n: 4 to 10) or an acid halide thereof.

  Aliphatic monocarboxylic acids include n: 4-10 pentanoic acid (valeric acid), hexanoic acid (n-caproic acid), heptanoic acid (enanthic acid), octanoic acid (caprylic acid), nonanoic acid (pelargonic acid) ), 2-ethylheptanoic acid, decanoic acid (capric acid), undecanoic acid (undecylic acid), and other linear or branched monocarboxylic acids. The range of the alkyl group chain length n of such a carboxylic acid is specified from the viewpoint of compatibility with diene rubber, and when n is 3 or less, the compatibility with rubber is inferior and tetrazole derivatives are mixed. On the other hand, when n is 11 or more, the rubber hardness increases.

  These aliphatic monocarboxylic acids or acid halides thereof such as acid chloride and 5-amino-1H-tetrazole are subjected to condensation reaction in the presence of a dehydration catalyst such as dicyclohexylcarbodiimide or a dehydrohalogenation catalyst, dimethylformamide, An aprotic polar solvent such as diethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone or the like is used as a reaction solvent, and the reaction can be easily performed at about 15 to 25 ° C.

Patent Document 1 below has proposed a filler-containing rubber composition having excellent heat resistance while maintaining excellent strength characteristics by using a bismercaptooxadiazole compound as a heat-resistant crosslinking agent together with sulfur. There is also a description that a heterocyclic group such as a tetrazole group is used as a linking group for the bismercaptooxazole group, but it is different from the tetrazole derivative used in the present invention. In addition, examples of the filler compounded in the rubber composition include carbon black, silica and the like, and it is said that a silane coupling agent and the like can be blended if necessary. However, a preferable filler is carbon black. ing.
JP 2006-328310 A

  In the diene rubber composition, in addition to the above essential components, a compounding agent generally used as a rubber compounding agent, for example, a vulcanizing agent such as sulfur depending on the type of the diene rubber, thiazole , Sulfenamide, guanidine, thiuram and other vulcanization accelerators, carbon black and other reinforcing agents, talc, clay, graphite, calcium silicate and other fillers, stearic acid, paraffin wax, aroma oil, etc. Processing aids, zinc oxide, anti-aging agents, plasticizers and the like are appropriately added and used as necessary. As the carbon black, carbon black such as SAF, ISAF and HAF is used in a ratio of about 40 parts by weight or less, preferably about 10 to 20 parts by weight per 100 parts by weight of the diene rubber.

  The composition is prepared by kneading by a general method using a kneader such as a kneader or a Banbury mixer, or an open roll, and the obtained composition is subjected to vulcanization or crosslinking.

  Next, the present invention will be further described with reference to examples, but it goes without saying that the scope of the present invention is not limited by these examples.

Reference Example In a eggplant flask having a volume of 100 ml, 1.93 g (12.2 mmol) of nonanoic acid was charged and dissolved in 10 ml of dimethylformamide. 0.42 g (12.2 mmol) of 5-amino-1H-tetrazole was added thereto, and while cooling to 0 ° C., 2.6 g (12.9 mmol) of a dicyclohexylcarbodiimide condensing agent dissolved in 5 ml of dimethylformamide was slowly added dropwise to room temperature conditions. Reacted below. After completion of the reaction, the filtrate obtained by removing the solid matter by filtration is concentrated under reduced pressure, the residue is dissolved in chloroform, and the chloroform solution is washed with a saturated aqueous sodium bicarbonate solution, a 2M aqueous citric acid solution, a saturated aqueous sodium bicarbonate solution, and water in this order. After the organic layer was dried over anhydrous sodium sulfate, the solution was concentrated under reduced pressure. The residue was recrystallized from n-hexane to obtain the desired tetrazole derivative (n = 8; melting point 79 ° C.).

  When n = 1, acetic acid is used as a carboxylic acid, when n = 4, pentanoic acid is used as a starting material, and when n = 10, undecanoic acid is used as a starting material. It was.

Example 1
SBR (Zeon Nippon NS440) 96.3 parts by weight
BR (Nipol BR 1220) 30.0 〃
Carbon black 10.0 〃
(Cabot Japan Product Show Black N234)
Silica (Zeosil 165GR) 60.0 〃
Silane coupling agent (Degusa Si69) 6.0 〃
Zinc oxide (3 types of Zinc Chemical products zinc oxide) 2.0 〃
Stearic acid (beef stearic acid from Japanese fat products) 1.0 1.0
Anti-aging agent (Flexis product SANTOFLEX 6PPD) 2.0 〃
Aroma oil (Showa Shell Petroleum Product Extract No. 4 S) 10.0 〃
Tetrazole derivative (alkyl group chain length n = 4) 3.0 〃
Sulfur (Tsurumi Chemical Co., Ltd. fine powdered sulfur with Jinhua seal oil) 2.0 〃
Vulcanization accelerator CBS (Ouchi Emerging Chemical Industries Noxeller CZ-G) 2.0 〃
Vulcanization accelerator DPG (Sumitomo Chemical Product Soxinol DG) 1.0 〃
In the blending of the above components, each component except the vulcanization accelerator and sulfur was kneaded for 5 minutes with a 1.7 L closed Banbury mixer to obtain a master batch. This master batch was kneaded with a vulcanization accelerator and sulfur with an open roll to obtain an unvulcanized rubber composition.

Using this unvulcanized rubber composition, the characteristics of the unvulcanized rubber were evaluated or measured by the following test method. Next, this unvulcanized rubber composition was subjected to press vulcanization at 160 ° C. for 20 minutes in a 15 × 15 × 0.2 mm mold, and the obtained vulcanized rubber sheet was vulcanized by the following test method. Rubber physical properties were measured.
Dispersion state of unvulcanized rubber: Visual confirmation of dispersion state of unvulcanized rubber after mixing
(◎: very good, ○: good, ×: poor dispersion)
Wet performance: Initial strain using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho
Loss tangent (tanδ) at 10%, amplitude ± 2%, frequency 20 Hz, temperature 0 ° C
Measured and displayed in index display with the value of Comparative Example 2 as 100
The larger the value, the larger the Tanδ and the higher the wet performance. Rolling resistance: Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, initial strain 10%, amplitude
Measure loss tangent (tanδ) at ± 2%, frequency 20Hz, temperature 60 ° C, and display in index display with the value of Comparative Example 2 as 100
The smaller the value, the lower the Tanδ and the lower the rolling resistance. Hardness: Measured according to JIS K6253 and displayed in index notation with the value of Comparative Example 2 being 100.
The larger the value, the higher the hardness. Vulcanization rate: JIS K6300 compliant (measures the time to reach 30% vulcanization at 160 ° C)

Example 2
In Example 1, 100 parts by weight of SBR (NS440) was used, and BR was not used.

Examples 3-4, Comparative Example 1
In Example 1, as a tetrazole derivative Example 3: Alkyl group chain length n = 8
Example 4: Alkyl group chain length n = 10
Comparative Example 1: Alkyl chain length n = 1
Were used in the same amount.

Comparative Example 2
In Example 1, no tetrazole derivative was used.

The results obtained in the above examples and comparative examples are shown in the following table.
table
Evaluation / Measurement Items Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2
Dispersion state of unvulcanized rubber ○ ◎ ◎ ◎ × ○
Wet performance 101 110 106 107 97 100
Rolling resistance 98 94 95 94 103 100
Hardness 100 100 100 103 100 100
Vulcanization rate (min) 5.8 5.4 5.6 5.5 6.0 6.0

Claims (4)

Diene rubber, silica, silane coupling agent and general formula

A diene rubber composition comprising a tetrazole derivative represented by the formula (where n is an integer of 4 to 10).   The diene rubber composition according to claim 1, wherein 20 to 100 parts by weight of silica per 100 parts by weight of the diene rubber and 2 to 15% by weight of a silane coupling agent and a tetrazole derivative are used based on the weight of the silica.   The diene rubber composition according to claim 1 or 2, which is used as a vulcanization molding material for a tread portion of a pneumatic tire.   A pneumatic tire having a tread portion vulcanized and molded from the diene rubber composition according to claim 3.