JP2006241315A - Rubber composition for pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition which maintains a high wet braking performance and improves vulcanization productivity and fuel cost. <P>SOLUTION: This rubber composition for pneumatic tires, comprising (A) 100 pts.wt. of a dienic rubber containing an aromatic vinyl copolymer having a Tg of ≥-40°C in an amount of at least ≥40 wt%, (B) (i) 30 to 120 pts.wt. of silica having N<SB>2</SB>SA of 100 to 300 m<SP>2</SP>/g and (ii) carbon black having N<SB>2</SB>SA of 80 to 200 m<SP>2</SP>/g in a total amount of 50 to 120 pts.wt. with the silica, (C) 1 to 6 pts.wt. of diethylene glycol, and (D) a vulcanizing agent, is obtained by kneading the components excluding at least the vulcanizing agent and the diethylene glycol in a closed mixer at a releasing temperature of 140 to 165°C in the first process and then kneading the components comprising at least the vulcanizing agent and the diethylene glycol at a temperature of 80 to 110°C in the second process. The pneumatic tire using the same. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber composition for a pneumatic tire, and more particularly, for a pneumatic tire that maintains high wet braking performance without impairing fracture characteristics and heat aging resistance, and has improved vulcanization productivity and fuel efficiency. The present invention relates to a rubber composition and a pneumatic tire using the same.

  As a high-performance tire cap compound, there is a demand for a rubber composition that balances high wet performance, low fuel consumption, and wear resistance at a high level. Conventionally, the amount of silica compounded is increased or a specific polymer is used. Corresponding with the compounding design. However, if the amount of silica compounded in the rubber composition is increased, the vulcanization speed becomes slower, the vulcanization time becomes longer, the productivity is deteriorated, and the amount of expensive vulcanization accelerator must be increased. Therefore, these solutions are required in practice.

  For the problem of slowing down the vulcanization speed, there are cases where the addition amount of the vulcanization accelerator is increased or a specific vulcanization accelerator is used. This is a compound of the belt layer inside the tire. / May adversely affect adhesion between metals. There are also cases where glycols are added as an activator and the silica surface is covered with glycols to prevent adsorption of the vulcanization accelerator to silica and prevent a decrease in vulcanization speed. If the agent is blended in an amount that sufficiently compensates for the vulcanization delay, there is a problem in that the breaking properties of the rubber are lowered.

  In Patent Document 1, a polyalkylene glycol having a weight average molecular weight of 200 to 20000 is kneaded with a solution-polymerized diene rubber and mixed at a maximum temperature of 120 to 170 ° C. to improve fuel efficiency and increase the vulcanization speed. However, if polyalkylene glycol is blended in an amount sufficient to improve the vulcanization rate, the breaking properties of the rubber may be lowered, which is not preferable.

  Patent Document 2 proposes that polyethylene glycol is blended with a diene rubber containing a specific SIBR to improve wet performance / low fuel consumption / processability, but the mixing method is also normal, and polyethylene glycol is added. If a sufficient amount is added to improve the vulcanization speed, the breaking properties of the rubber may be lowered, which is not preferable.

  In Patent Document 3, polyethylene glycol and an inorganic filler are mixed in advance with diene rubber to prevent adsorption of the vulcanization accelerator to silica, thereby providing excellent workability and excellent wet grip and low fuel consumption. Although it is described that a rubber can be obtained, it is not preferable to add polyethylene glycol in an amount sufficient to improve the vulcanization speed because the rubber breaking property may be lowered.

  In Patent Document 4, polyethylene glycol, particularly rubber / silica / coupling agent, is mixed in rubber at 130 to 140 ° C., polyethylene glycol is mixed at 150 to 170 ° C., and sulfur / vulcanized. It is disclosed that processability (viscosity), wet grip, and low fuel consumption can be improved by blending polyethylene glycol into the rubber composition by a method comprising Step 3 of mixing an accelerator.

Japanese Patent Laid-Open No. 9-3245 JP 2002-88193 A Japanese Patent Laid-Open No. 11-343366 JP 2002-121327 A

  Accordingly, an object of the present invention is to maintain a high wet braking performance without impairing fracture characteristics and heat aging resistance, and to use a rubber composition for a pneumatic tire with improved vulcanization productivity and fuel efficiency, and the same. It is to provide a pneumatic tire.

According to the present invention, (A) 100 parts by weight of a diene rubber containing at least 40% by weight or more of an aromatic vinyl copolymer having a glass transition point (Tg) of −40 ° C. or higher, (B) (i) a nitrogen adsorption ratio 30 to 120 parts by weight of silica having a surface area (N ₂ SA) of 100 to 300 m ² / g and (ii) carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 80 to 200 m ² / g in total amount with silica A rubber composition containing 50 to 120 parts by weight, (C) 1 to 6 parts by weight of diethylene glycol and (D) a vulcanizing compound, and at least 140 components excluding the vulcanizing compound and diethylene glycol in the first step. Obtained by kneading in a closed mixer at a release temperature of 165 ° C. to 165 ° C., and then kneading the components containing at least the vulcanizing compound and diethylene glycol at a temperature of 80 ° C. to 110 ° C. in the second step. Pneumatic tire rubber composition and a pneumatic tire using the same are provided.

  In order to solve the above problems, the inventors of the present invention blend a specific amount of specific silica / carbon black with a specific diene rubber, and first add components other than the vulcanized compound and diethylene glycol at 140 to 165 ° C. After mixing in this step, by adding the vulcanizing compound and diethylene glycol in the second step, high wet performance and low fuel consumption performance can be achieved without reducing vulcanization productivity, rupture properties and heat aging resistance. It has been found that a rubber composition can be obtained.

As described above, according to the present invention, an aromatic vinyl copolymer having a glass transition point (Tg) of −40 ° C. or higher (for example, at least one of a styrene-butadiene copolymer, a styrene-isoprene-butadiene copolymer, etc.). Silica 30 having (B) nitrogen adsorption specific surface area (N ₂ SA) of 100 to 300 m ² / g (preferably 110 to 250 m ² / g) in 100 parts by weight of diene rubber (A) containing at least 40% by weight 50 to 120 parts by weight (preferably 60 to 120 parts by weight) of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 80 to 200 m ² / g (preferably 100 to 250 m ² / g) and silica. To 100 parts by weight), (C) 1 to 6 parts by weight (preferably 1.5 to 4 parts by weight) of diethylene glycol, and (D) a vulcanizing compound, preferably sulfur / vulcanization acceleration. A vulcanization blend comprising sulfur having a ratio of 1 / 1.2 to 1 / 1.7 (more preferably 1 / 1.2 to 1 / 1.5 (weight ratio)) and at least one vulcanization accelerator. In the first step, the rubber composition obtained by blending the agent with rubber, silica, carbon, and other compounding agents excluding at least the vulcanizing compounding agent and diethylene glycol is 140 to 165 using a closed kneader. To obtain a desired rubber composition by kneading at a release temperature of 0 ° C., followed by step 2 of kneading at least a component containing a vulcanizing compound and diethylene glycol at a temperature of 80 ° C. to 110 ° C. Can do.

  In the present invention, the rubber used as component (A) has a glass transition point (Tg) of -40 ° C or higher, preferably -35 ° C to -15 ° C (Tg is a DuPont differential thermal analyzer (DSC), ASTM D3418- A diene rubber containing 40% by weight or more, preferably 45 to 80% by weight of an aromatic vinyl copolymer at a temperature rising rate of 10 ° C./min. As an aromatic vinyl copolymer having a Tg of −40 ° C. or higher used as the component (A), a styrene-butadiene copolymer rubber (SBR), a styrene-isoprene-butadiene copolymer (SIBR) or the like may be used alone or in combination. Can be used as any mixture of As other diene rubbers, natural rubber (NR), polyisoprene rubber (IR), various polybutadiene rubbers (BR), SBR having a Tg of less than -40 ° C, etc. can be used. It can be used as a mixture of the above. If the amount of the aromatic vinyl copolymer having a Tg of −40 ° C. or higher is too small, the wet braking performance cannot be exhibited, which is not preferable.

In the present invention, the component (B) has a nitrogen adsorption specific surface area (N ₂ SA) of 100 to 300 m ² / g, preferably 110 to 250 m ² / g of silica, 30 to 120 parts by weight, preferably 30 to 80 parts by weight. When the nitrogen adsorption specific surface area (N ₂ SA) of 80 m ² / g or more, preferably 50 to 120 parts by weight of carbon black 100 to 250 m ² / g in a total amount of silica, preferably 60 to 100 parts by weight blended To do. The range of N ₂ SA is necessary for maintaining the fracture characteristics. If the blending amount of silica is too small, wet braking performance deteriorates, which is not preferable. Conversely, if it is too large, workability during kneading deteriorates. Therefore, it is not preferable. On the other hand, if the amount of carbon black is too small, the reinforcing property is lowered, and if it is too large, the workability at the time of kneading deteriorates like silica, which is not preferable.

  In the rubber composition of the present invention, diethylene glycol is added as component (C) in an amount of 1 to 6 parts by weight, preferably 1.5 to 4 parts by weight, per 100 parts by weight of the diene rubber. If this amount is too small, the effect of accelerating vulcanization will be small, and conversely if too large, the fracture characteristics will be reduced, which is not preferable.

  In the rubber composition of the present invention, for example, sulfur and at least one vulcanization accelerator are blended as a vulcanizing compound in accordance with a conventional method. Although there is no limitation in particular in the composition and usage-amount of the vulcanization | cure type | system | group compounding agent to be used, the ratio (weight ratio) of sulfur / vulcanization accelerator is preferably 1 / 1.2 to 1 / 1.7, 1/1 2 to 1 / 1.5 is more preferable. If the amount of sulfur is too small at this ratio, the vulcanization rate is slow, which is not preferable. On the other hand, if the amount is too large, the heat aging resistance deteriorates, which is not preferable. The vulcanization accelerator to be used is not particularly limited. For example, N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, diphenylguanidine or the like is used alone or in a blend. can do.

  When mixing the rubber composition according to the present invention, first, as a first step (ie, step 1), 140 components of a vulcanizing compound and a component excluding diethylene glycol, ie, rubber, silica, carbon black and other compounding agents are added. Kneading in a closed kneading machine (for example, Banbury mixer) at a discharge temperature of ˜165 ° C., preferably 145 ° C. to 160 ° C., and then adding a component containing at least a vulcanizing compound and diethylene glycol in step 2 to 80 ° C. It knead | mixes at the temperature of -110 degreeC, Preferably it is 90-100 degreeC. In addition, since diethylene glycol is liquid at normal temperature, it is preferable to mix it with some silica or carbon black or the like separately from the above vulcanizing compound.

  In addition to the above-described essential components, the rubber composition according to the present invention includes other reinforcing agents (fillers) other than carbon black and silica, vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, and anti-aging. Various additives that are generally blended for tires such as additives and plasticizers, and other general rubbers can be blended, and such additives are kneaded and vulcanized by a general method to obtain a composition. Can be used to vulcanize or crosslink. The blending amounts of these additives may be conventional conventional blending amounts as long as the object of the present invention is not adversely affected.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Examples 1-3 and Comparative Examples 1-3
Sample preparation In the formulation shown in Table I, the components excluding diethylene glycol, vulcanization accelerator and sulfur were kneaded for 5 minutes in a 1.7 liter closed mixer, and when reaching 160 to 165 ° C, the master batch was released. Obtained. Diethylene glycol, a vulcanization accelerator and sulfur were kneaded with this master batch at a temperature of 100 to 105 ° C. with an open roll to obtain a rubber composition. Using this rubber composition, unvulcanized physical properties were evaluated by the following test methods. The results are shown in Table I.

  Next, the obtained rubber composition was vulcanized in a 15 × 15 × 0.2 cm mold at 160 ° C. for 20 minutes to prepare a vulcanized rubber sheet. The physical properties of the vulcanized rubber were measured by the following test methods. It was measured. The results are shown in Table I.

Rubber physical property evaluation test method Vulcanization rate T95: Measured at 160 ° C. using RLRIII type manufactured by Toyo Seiki Co., Ltd. The smaller this number, the faster the vulcanization rate.
Elongation at break: Elongation at break was measured according to JIS6301. The index was displayed with the value of Comparative Example 1 as 100. Larger numbers indicate better fracture characteristics.
tan δ (40 ° C.) (index): Measured under measuring conditions of initial strain 10% and dynamic strain 2% using Toyo Seiki's viscoelasticity spectrometer. Smaller numbers indicate better fuel economy.

  Wet braking performance (index): tires (size: 205 / 60R15) used for cap treads using the rubber compositions of Examples and Comparative Examples were measured, and braking distances on wet road surfaces from 100 km / h were measured. The value of Comparative Example 1 was taken as 100 and displayed as an index. Larger numbers indicate shorter braking distances and better wet performance.

Table I footnote * 1: VBR5025 manufactured by SBR-1 Bayel (Tg = -21 ° C., oil exhibition 37.5 phr)
* 2: SBR-2 NIPOL 1712 manufactured by Nippon Zeon Co., Ltd. (Tg = −51 ° C., oil exhibition 37.5 phr)
* 3: NR TSR
* 4: BR1220 manufactured by BR Nippon Zeon Co., Ltd.
* 5: Silica-2 165GR manufactured by RHODIA (N ₂ SA = 140 m ² / g)
* 6: Carbon black N234 manufactured by Showa Cabot Co., Ltd. (N ₂ SA = 112 m ² / g)
* 7: Diethylene glycol Diethylene glycol manufactured by Nippon Shokubai Co., Ltd. * 8: Silane coupling agent Coupling agent Si69 manufactured by DEGUSSA
* 9: Zinc Hana 3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. * 10: Stearic acid Industrial stearic acid manufactured by Nippon Oil & Fats Co., Ltd. * 11: Anti-aging agent SANTOFLEX 6PPD manufactured by Flexis Co., Ltd.
* 12: Paraffin wax manufactured by Wax Nippon Seiwa Co., Ltd. * 13: Oil Aroma oil manufactured by Showa Shell Sekiyu KK * 14: Sulfur Differential Sulfur with 5% oil manufactured by Tsurumi Chemical Co., Ltd. * 15: Vulcanization accelerator N-cyclohexyl-2-benzothiazolylsulfenamide manufactured by Flexis

  As shown in Table I, in Comparative Example 1, the blending is within the scope of the present invention, but the charging step of diethylene glycol is step 1, so the vulcanization rate is slow and improvement is desired.

  On the other hand, in Example 1, since the charging step of diethylene glycol was set to process 2, the vulcanization speed could be increased. Further, by adding diethylene glycol in step 2, the blending amount can be reduced, and the elongation at break is also improved. Example 2 shows that the fuel efficiency can be further improved by increasing the blending amount of diethylene glycol. Example 3 is an example in which the amount of sulfur is increased with respect to the vulcanization accelerator. Although further improved, the heat aging resistance (M300 change rate) tends to decrease slightly.

  On the other hand, Comparative Example 2 shows that excessive addition of diethylene glycol is accompanied by a decrease in elongation at break, and Comparative Example 3 shows that the rubber component used is the present invention even if the amount and input of diethylene glycol are within the scope of the present invention. If it is out of the range, the wet performance is not exhibited.

  Since the rubber composition according to the present invention can provide a rubber composition having high wet performance and low fuel consumption without deteriorating vulcanization productivity, compound breaking characteristics, and heat aging resistance, it can be used for tire treads. It is useful for use as a rubber composition or the like.

Claims (3)

(A) 100 parts by weight of a diene rubber containing at least 40% by weight or more of an aromatic vinyl copolymer having a glass transition point (Tg) of −40 ° C. or higher, (B) (i) a nitrogen adsorption specific surface area (N ₂ SA) 30 to 120 parts by weight of silica having a molecular weight of 100 to 300 m ² / g and (ii) 50 to 120 parts by weight of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 80 to 200 m ² / g in total with silica, (C) A rubber composition containing 1 to 6 parts by weight of diethylene glycol and (D) a vulcanizing compound, and at least a component excluding the vulcanizing compound and diethylene glycol is released at 140 ° C. to 165 ° C. in the first step. Pneumatic tire obtained by kneading in a closed mixer at a temperature, and then kneading at least a vulcanizing compound and a component containing diethylene glycol at a temperature of 80 to 110 ° C. in the second step Rubber composition.   The rubber composition according to claim 1, wherein the vulcanizing compound contains sulfur and at least one vulcanization accelerator in a sulfur / vulcanization accelerator ratio of 1 / 1.2 to 1 / 1.7 (weight ratio). object.   A pneumatic tire using the rubber composition according to claim 1.