JP2007009160A - Rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition capable of reducing the rolling resistance based on the vulcanization behavior of a rubber composition by grasping the relationship between the vulcanization behavior of the rubber composition and the rolling resistance.
SOLUTION: 0.5 to 5 parts by weight of sulfur, a vulcanization accelerator, and a nitrogen adsorption specific surface area (N ₂ SA) with respect to 100 parts by weight of a diene rubber component containing 40 parts by weight or more of styrene butadiene rubber. In a rubber composition containing carbon black of 60 to 120 m ² / g, 10% vulcanization time (t10) and 90% vulcanization time (t90) obtained from a vulcanization curve measured at 160 ° C. It is a rubber composition characterized by satisfying both the conditions of (t90−t10) / t10 ≦ 1 and 2 <t10.
[Selection figure] None

Description

  The present invention relates to a rubber composition, and more particularly to a rubber composition that can be used for a tire tread to reduce rolling resistance of a tire and a pneumatic tire to which the rubber composition is applied.

  In recent years, development of fuel-efficient tires has been promoted as a social demand for energy saving. As one of the countermeasures, tire weight reduction, longer life, and reduction of tire rolling resistance, that is, hysteresis loss of rubber composition The reduction of heat resistance, low heat generation, etc. are being studied.

  However, in the former, the thinning of the tire has reached the limit, causing problems of wear resistance and steering stability deterioration, and in the latter, solution polymerization and emulsion polymerization styrene butadiene rubber with adjusted polymer microstructure, carbon black, Many studies have been made on reducing rolling resistance from a rubber compounding surface by combining additives such as reinforcing agents such as silica, chain transfer agents and processing aids.

For example, it is disclosed to improve rolling resistance and wet skid performance and improve wear resistance by blending nationally specified carbon black and silica with emulsion-polymerized styrene butadiene rubber of specific styrene content and molecular weight ( Patent Document 1) and many of these technical improvements have the effect of reducing rolling resistance.
JP 2002-241542 A

  Conventionally, as described above, many studies have been made on improvement of polymers and blending techniques, improvement of reinforcing agents such as carbon black and silica, improvement of additives, vulcanization system changes and variables. However, the rubber properties from the viewpoint of vulcanization behavior of rubber, especially rolling resistance has not been sufficiently studied, and the relationship between vulcanization behavior and rolling resistance has not been grasped.

  The present invention has been made in view of the above points, and by grasping the relationship between the vulcanization behavior of a rubber composition and the rolling resistance, it is intended to reduce the rolling resistance based on the vulcanization behavior of the rubber composition. A rubber composition that can be used is provided.

  As a result of intensive investigations on the relationship between vulcanization behavior and rolling resistance for rubber compositions mainly used for tire treads, the present inventors have found that 10% vulcanization time (t10) and 90% vulcanization time (t90). A rubber composition in which t10 is in a predetermined range with respect to t90, and t10 and t90 are in a predetermined relationship with each other. It has been found that it is advantageous for resistance.

That is, in the present invention, 0.5 to 5 parts by weight of sulfur, a vulcanization accelerator, and a nitrogen adsorption specific surface area (N ₂ SA) with respect to 100 parts by weight of a diene rubber component containing 40 parts by weight or more of styrene butadiene rubber. ) In a rubber composition containing carbon black having 60 to 120 m ² / g, 10% vulcanization time (t10) and 90% vulcanization time (t90) obtained from a vulcanization curve measured at 160 ° C. Is a rubber composition characterized by satisfying both the conditions of (t90−t10) / t10 ≦ 1 and 2 <t10.

  In the rubber composition of the present invention, 1.3 to 2.2 parts by weight of a sulfenamide-based vulcanization accelerator and 0 to guanidine-based vulcanization accelerator are used as the vulcanization accelerator with respect to 100 parts by weight of the rubber component. It is preferable that the total amount is 2.4 parts by weight or less.

  And it can be set as the pneumatic tire which is excellent in low rolling resistance by applying the said rubber composition to a tread part.

  In the rubber composition of the present invention, the longer the time t10 is spent with respect to t90, the more heat is applied to the polymer when it is not vulcanized, and then the polymer is heated to some extent. It is presumed that the rubber properties are improved and the rolling resistance is reduced by making the crosslinking density appropriate by the rapid progress of sulfur.

  According to the rubber composition of the present invention, it is possible to reduce rolling resistance and maintain rubber characteristics such as wear resistance and wet skid performance. A pneumatic tire using this rubber composition is economical as a fuel-efficient tire. It will have a positive effect.

The rubber composition of the present invention comprises 0.5 to 5 parts by weight of sulfur, a vulcanization accelerator, and a nitrogen adsorption ratio with respect to 100 parts by weight of a diene rubber component containing 40 parts by weight or more of styrene butadiene rubber (SBR). Carbon black having a surface area (N ₂ SA) (measured value according to ASTM D3037) of 60 to 120 m ² / g is included as a constituent component.

  SBR is not limited by polymerization method, microstructure such as styrene content, vinyl content, molecular weight, or presence / absence of terminal modification by a functional group such as a hydroxyl group or amino group, but it is not limited in strength, low heat build-up, It can be used by selecting from SBR obtained by solution polymerization or emulsion polymerization conventionally used for tire treads and the like, which is excellent in wear and workability. The SBR is preferably contained in an amount of 40 parts by weight or more, preferably 50 parts by weight or more as a main rubber component, in view of the basic rubber characteristics of the tread rubber.

  The SBR has, for example, a styrene content of 15 to 45% by weight, more preferably 20 to 40% by weight, and a vinyl content of about 30 to 60% by weight, which is advantageous for rolling resistance and wear resistance. It is. If the amount of styrene exceeds 45% by weight, the glass transition temperature (Tg) increases and the wet performance is maintained, but the rolling resistance increases and the wear resistance tends to decrease. By setting the range, the TBR of SBR can be set to an appropriate range.

  In this invention, it can comprise with the blend rubber which uses the said SBR as a main rubber component, and if it is diene rubbers other than said SBR as another rubber component in this case, it will not restrict | limit in particular. Examples of these diene rubbers include natural rubber (NR), SBR other than the above SBR, butadiene rubber (BR), isoprene rubber (IR), nitrile rubber (NBR), and the like, one or two of these. It is selected from the above and blended.

  The rubber composition of the present invention contains 0.5 to 5 parts by weight, preferably 1 to 3 parts by weight of sulfur such as powdered sulfur for rubber and oil-treated sulfur as a vulcanizing agent with respect to 100 parts by weight of the rubber component. . If the amount of sulfur is less than 0.5 parts by weight, the vulcanization rate is slow and the crosslinking density is low, and if it exceeds 5 parts by weight, the hardness of the vulcanized rubber increases, which adversely affects rolling resistance and wear resistance, and there is a problem of reversion. Will arise.

  Examples of the vulcanization accelerator include N-cyclohexyl-2-benzothiazolylsulfenamide (CZ), N-tert-butyl-2-benzothiazolylsulfenamide (NS), N, N-dicyclohexyl-2-benzo Sulfenamides such as thiazolesulfenamide (DZ), guanidines such as 1,3-diphenylguanidine (D) and 1,3-di-O-tolylguanidine (DT), di-2-benzothiazolyl Examples thereof include thiazole type vulcanization accelerators such as disulfide (DM) and 2-mercaptobenzothiazole (M), and thiuram type vulcanization accelerators such as tetramethylthiuram disulfide (TT).

  In the rubber composition of the present invention, in the vulcanization accelerator, 1.3 to 2.2 parts by weight of a sulfenamide-based vulcanization accelerator and guanidine-based vulcanization are added to 100 parts by weight of the diene rubber component. It is preferable to use 0 to 0.5 parts by weight of a sulfur accelerator, and the total amount of both is preferably 2.4 parts by weight or less.

  By using a sulfenamide vulcanization accelerator, t10 can be controlled by its vulcanization delay effect, and by using a guanidine vulcanization accelerator in combination, t90, that is, an appropriate vulcanization time can be controlled. By blending these two in appropriate amounts (the guanidine vulcanization accelerator may not be included), t10 and t90 can be easily controlled.

  If the blending amount of the sulfenamide vulcanization accelerator is less than 1.3 parts by weight, the vulcanization retarding effect is insufficient and t10 is shortened, and if it exceeds 2.2 parts by weight, scorch and bloom properties are obtained. It deteriorates and the vulcanization stability decreases, and the processability also deteriorates. As the sulfenamide system, vulcanization accelerators such as CZ, NS, and DZ are preferable.

  On the other hand, when the blending amount of the guanidine vulcanization accelerator exceeds 0.50 parts by weight, the vulcanization speed is increased and t10 is less than 2 minutes, which causes a problem of burning, which is not preferable. As the guanidine series, vulcanization accelerators such as D and DT are preferable.

Further, the rubber composition of the present _invention, carbon black _N 2 SA is 60~120m ² / g is compounded. If the N ₂ SA of the carbon black is less than 60 m ² / g, the wear resistance is insufficient, and if it exceeds 120 m ² / g, the dispersibility during mixing decreases, the heat generation increases and the rolling resistance increases, resulting in low fuel consumption. It is not preferable as a rubber composition. Examples of such carbon black include HAF, ISAF, and SAF, and the blending amount thereof is about 40 to 120 parts by weight with respect to 100 parts by weight of the diene rubber component, and if less than 40 parts by weight, the reinforcing property, Abrasion resistance is reduced, and if it exceeds 120 parts by weight, dispersibility is deteriorated and rubber properties such as rolling resistance cannot be obtained.

  The rubber composition of the present invention has a 10% vulcanization time (t10) and a 90% vulcanization time (t90) obtained from a vulcanization curve measured at 160 ° C. in the above compounding system, (t90-t10). ) / T10 ≦ 1 and 2 <t10 must be satisfied.

  In the rubber composition satisfying this condition, heat is applied to the polymer at the time of unvulcanized as the time taken for t10 with respect to t90 is longer, and then the polymer is heated to some extent. As a result of the rapid progress of vulcanization, the rubber properties are improved by optimizing the crosslinking density, so that the rolling resistance can be reduced and the rubber properties such as wear resistance and wet skid performance can be compatible.

  In the rubber composition of the present invention, in addition to the rubber component and the compounding component, various conventional rubber compounding agents, for example, silica, silane coupling agent, vulcanization acceleration aid, oil, zinc white, stearic acid, A softening agent, an anti-aging agent, clay, calcium carbonate, and the like can be appropriately blended, and the blending amount can be used within a range that does not impair the effects of the present invention.

  The rubber composition of the present invention can be produced according to a conventional method using various kneaders such as a Banbury mixer, roll, kneader, etc. by blending the rubber component and various compounding agents, and includes tire treads and sidewalls. It can be used for tire parts such as bead parts, vibration-proof rubber and various industrial rubber products. In particular, it is suitably used as a tire tread rubber excellent in rolling resistance.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

  The following styrene butadiene rubber (SBR) is used as a rubber component, the following sulfur and various vulcanization accelerators are adjusted in the amounts shown in Table 1, and each rubber composition is mixed using a Banbury mixer with a capacity of 20 liters. A rubber composition was prepared. In addition, in order to adjust the tensile modulus (300% modulus according to JIS K6251) of each rubber composition as an evaluation condition within ± 2 Mpa of 300% modulus of Comparative Example 3 (control), the rubber compositions of other Examples and Comparative Examples The amount of oil blended in the product was varied.

[SBR, sulfur, vulcanization accelerator]
・ SBR: Asahi Kasei Corporation, TUFDENE 3335
・ Sulfur: Hosoi Chemical Co., Ltd., rubber powder sulfur 150 mesh ・ Vulcanization accelerator CZ: Ouchi Shinsei Chemical Industries, Noxeller CZ
・ Vulcanization accelerator NS: Ouchi Shinsei Chemical Industry, Noxeller NS
・ Vulcanization accelerator D: Ouchi Shinsei Chemical Industries, Noxeller D
・ Vulcanization accelerator DM: Ouchi Shinsei Chemical Industry, Noxeller DM

[Common ingredients (blending amount)]
Carbon black: 70 parts by weight, Showa Cabot, Show Black N330
Aroma oil: Comparative Example 3 is 37.5 parts by weight, others are variable, manufactured by Japan Energy, Process X-140
・ Zinc flower: 2 parts by weight, manufactured by Mitsui Mining & Smelting Co., Ltd., Zinc flower No. 1 ・ Stearic acid: 1 part by weight, manufactured by Kao, industrial stearic acid / anti-aging agent 6C: 2 parts by weight, manufactured by Ouchi Shinsei Chemical Industry, NOCRACK 6C

  About each obtained rubber composition, a vulcanization curve is calculated | required at the temperature of 160 degreeC using the rheometer by the alpha technologies company, RPA2000 type | mold, 10% vulcanization time (t10 (min)) and 90% vulcanization time (T90 (min)) was measured, and the value of (t90-t10) / t10 was calculated. The results are shown in Table 1.

  Next, a radial tire of size 205 / 60R16 in which each rubber composition was applied to the tread portion was manufactured, and the rolling resistance of each tire was evaluated according to the following method. Table 1 shows.

[Rolling resistance]
Using a uniaxial drum tester, the rolling resistance when running on the drum at an internal pressure of 200 kPa, a load load of 400 kg, and a speed of 80 km / h was measured, and the rolling resistance index of each test tire was calculated by the following formula. The smaller the value, the better the fuel efficiency and the better. Rolling resistance (index) = (rolling resistance of each test tire) × 100 / (rolling resistance of the tire of Comparative Example 3)

  As shown in Table 1, in the rubber composition of each example in which t10 is 2 minutes or more and the value of (t90−t10) / t10 is 1 or less, it can be seen that the rolling resistance improvement effect appears clearly. . On the other hand, in Comparative Example 1 in which the blending amount of the vulcanization accelerator D is large, t10 is fast, and in Comparative Example 2 in which the blending amount of the vulcanization accelerator NS is less than 1.3 parts by weight (t90) The result of -t10) / t10 ≦ 1 was not satisfied and the rolling resistance was not improved.

  The rubber composition of the present invention can be suitably used as a tread rubber for low fuel consumption pneumatic tires such as passenger cars, light trucks, trucks / buses and the like.

Claims (3)

0.5 to 5 parts by weight of sulfur, a vulcanization accelerator, and a nitrogen adsorption specific surface area (N ₂ SA) of 60 to 120 m ^{2 with} respect to 100 parts by weight of a diene rubber component containing 40 parts by weight or more of styrene butadiene rubber. In a rubber composition containing carbon black that is / g,
A 10% vulcanization time (t10) and a 90% vulcanization time (t90) obtained from a vulcanization curve measured at 160 ° C. satisfy both the conditions of (t90−t10) / t10 ≦ 1 and 2 <t10. A rubber composition characterized by satisfying. Including 100 parts by weight of the rubber component, 1.3 to 2.2 parts by weight of a sulfenamide vulcanization accelerator and 0 to 0.5 parts by weight of a guanidine vulcanization accelerator as the vulcanization accelerator. The rubber composition according to claim 1, wherein the total amount is 2.4 parts by weight or less. A pneumatic tire, wherein the rubber composition according to claim 1 or 2 is applied to a tread portion.