JP2008127400A - Rubber composition for chafer and tire having chafer using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition for a chafer, excellent in all of processability, roll winding properties, low exothermic properties, rim rubbing abrasion resistance and chipping resistance of rubber while maintaining hardness and a tire having a chafer using the same. <P>SOLUTION: The rubber composition for a chafer comprises a rubber component composed of 40-70 wt.% of a butadiene rubber having a viscosity in a toluene solution at 25°C of 50-155 cps and a molecular weight distribution of 2.9-4.0 and has a Mooney viscosity at 130°C before curing of ≤70, a JIS-A hardness at 23°C after curing of 65-80 and a dissipation factor (Tanδ) measured at 70°C and at a dynamic strain 2% of ≤0.13. The tire has a chafer using the same. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition for chafers and a tire having a chafer using the same.

  The need for heavy-duty radial tires (TBR) used for trucks and buses has long been regarded as important for wear resistance, and many TBRs with excellent wear resistance have been proposed. Fuel economy has also been emphasized. In order to improve the fuel efficiency of each member constituting the tire, various attempts have been made to reduce the heat generation of the rubber. In particular, members having a large contribution regarding fuel efficiency are members having a large occupied volume such as treads, sidewalls, belts, belt cushions, bead packings, chafers, and the like. In order to improve fuel economy in each member, for example, a method of reducing the carbon black, a method of increasing the vulcanizing agent, a method using silica, etc. are used, but the chafer part has a bead durability. Therefore, it is a member that is difficult to apply these methods.

  At present, in order to improve fuel efficiency while maintaining bead durability in the chafer portion, the chafer portion is filled with carbon black having a small particle diameter and developed particle connection (for example, see Patent Document 1). However, if such a carbon black is filled in a large amount of the rubber composition for chafers containing a large amount of butadiene rubber, the elasticity of the raw rubber before vulcanization becomes too strong, and the extrusion process This causes the problem that it cannot be wound on the roll and cannot be processed.

JP 2001-226526 A

  The present invention provides a rubber composition for chafers excellent in processability, roll wrapping property, low heat generation, rim rubbing wear resistance and rubber chipping resistance while maintaining hardness, and a chafer using the same. It aims at providing the tire which has.

  The present invention includes a rubber component containing 40 to 70% by weight of a butadiene rubber having a toluene solution viscosity of 50 to 155 cps and a molecular weight distribution of 2.9 to 4.0 at 25 ° C., and Mooney before curing at 130 ° C. A chafer having a loss tangent (Tan δ) of 0.13 or less after curing measured under conditions of a viscosity of 70 or less, a JIS-A hardness after curing at 23 ° C. of 65 to 80, 70 ° C. and a dynamic strain of 2%. The present invention relates to a rubber composition.

  The rubber component preferably further contains 30% by weight or more of natural rubber and / or isoprene rubber.

  The present invention also relates to a tire having a chafer using the chafer rubber composition.

  According to the present invention, a rubber component containing a predetermined amount of a predetermined butadiene rubber is included, and the Mooney viscosity, JIS-A hardness and loss tangent are set in predetermined ranges, so that processability, roll winding property, and low heat generation are achieved. It is possible to provide a rubber composition for a chafer which is excellent in all of the properties, rim rubbing wear resistance and rubber chipping resistance, and a tire having a chafer using the same.

  The rubber composition for chafers of the present invention contains a rubber component.

  The rubber component contains butadiene rubber (BR).

  In general, there are toluene solution viscosity and molecular weight distribution representing the degree of branching of the molecular structure in terms of BR characteristics. Generally, in order to improve wear resistance, the toluene solution viscosity is increased and the molecular weight distribution is increased. Is effective, and the reverse is preferable for improving roll processability.

  Therefore, in general, commercially available BR is classified into two types, one having a low toluene solution viscosity and a large molecular weight distribution (excellent processability) and one having a large toluene solution viscosity and a small molecular weight distribution (excellent wear resistance). Be divided.

  The BR used for the present invention, unlike any conventional type, has a large toluene solution viscosity and a large molecular weight distribution.

  Specifically, the 5% toluene solution viscosity (T-CP) at 25 ° C. of BR is 50 cps or more, preferably 70 cps or more. When the T-CP of BR is less than 50 cps, the abrasion resistance (rim abrasion resistance) as the chafer rubber composition is lowered. The T-CP of BR is 155 cps or less, preferably 135 cps or less. When the T-CP of BR exceeds 155 cps, the Mooney viscosity becomes too large and roll processability is deteriorated.

  The molecular weight distribution (Mw / Mn) of BR is 2.9 or more, preferably 3.1 or more. When Mw / Mn is less than 2.9, roll winding property is lowered. The Mw / Mn of BR is 4.0 or less, preferably 3.8 or less. When Mw / Mn of BR exceeds 4.0, the wear resistance (rim rubbing wear resistance) as a rubber composition for chafers is lowered.

  The rubber composition for chafers using BR satisfying these characteristics is the case where the grade of carbon black used is changed to a low grade in order to balance wear resistance and rubber chipping resistance. However, it will have favorable roll winding property, and it becomes possible to obtain the rubber composition for chafers excellent in abrasion resistance, rubber chipping resistance and roll winding property.

  The content of BR in the rubber component is 40% by weight or more, preferably 45% by weight or more. If the BR content is less than 40% by weight, the wear resistance (rim rubbing wear resistance) of the rubber composition for chafers is lowered. The BR content is 70% by weight or less, preferably 65% by weight or less. When the BR content exceeds 70% by weight, the Mooney viscosity becomes too large, and the roll processability decreases.

  In addition to BR, the rubber component preferably contains natural rubber (NR) and / or isoprene rubber (IR) for the purpose of improving low severity abrasion resistance and rubber chipping resistance.

  As NR, grades such as TSR20, RSS # 3 and the like which are usually used in the rubber industry can be used.

  Moreover, what is normally used in the rubber industry can also be used as IR.

  The content of NR and / or IR in the rubber component is preferably 30% by weight or more, and more preferably 40% by weight or more. When the content of NR and / or IR is less than 30% by weight, the tip of the chafer tends to be missing when assembling the rim even if the hardness is within a predetermined range. The content of NR and / or IR is preferably 60% by weight or less, and more preferably 55% by weight or less. When the content of NR and / or IR exceeds 60% by weight, the wear resistance (rim rubbing wear resistance) of the rubber composition for chafer tends to be lowered.

  As the rubber component, in addition to BR, NR and IR, for example, styrene butadiene rubber (SBR), butyl rubber (IIR), halogenated butyl rubber (X-IIR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), Examples include ethylene propylene diene rubber (EPDM) and halides of copolymers of isomonoolefin and paraalkyl styrene. These can be used alone or in combination of two or more in combination with BR, NR, IR, etc. May be. Of these, SBR is preferred because of its low severity abrasion resistance and improved rubber chipping resistance.

  When using SBR, the content of SBR in the rubber component is preferably 5% by weight or more, and more preferably 10% by weight or more. When the SBR content is less than 5% by weight, the rubber chipping resistance tends to be not improved. The SBR content is preferably 30% by weight or less, more preferably 20% by weight or less. If the SBR content exceeds 30% by weight, the rubber tends to generate heat.

  Carbon black can be blended with the rubber component in the rubber composition of the present invention.

  The carbon black is obtained by an ordinary carbon black production method, and is preferably a hard carbon black of ISAF class or less in order to balance the wear resistance and the rubber chipping resistance.

  The iodine adsorption amount (IA) of carbon black is preferably 60 g / kg or more, and more preferably 70 g / kg or more. If the IA of the carbon black is less than 60 g / kg, the wear resistance (rim scuff wear resistance) as a chafer rubber composition tends to decrease. The IA of carbon black is preferably 135 g / kg or less, and more preferably 125 g / kg or less. If the IA of the carbon black exceeds 135 g / kg, the rubber tends to generate heat or roll processability tends to decrease.

  When carbon black is used, the compounding amount of carbon black is preferably 45 parts by weight or more and more preferably 50 parts by weight or more with respect to 100 parts by weight of the rubber component. When the blending amount of carbon black is less than 45 parts by weight, the wear resistance (rim rubbing wear resistance) as a chafer rubber composition tends to be lowered. The amount of carbon black is preferably 75 parts by weight or less, more preferably 65 parts by weight or less. If the blending amount of the carbon black exceeds 75 parts by weight, the rubber tends to generate heat or roll processability tends to decrease.

  In addition to the rubber component and carbon black, the rubber composition for chafers of the present invention includes compounding agents usually used in the rubber industry, such as zinc oxide, stearic acid, various anti-aging agents, wax, sulfur and the like. Vulcanizing agents, various vulcanization accelerators, and the like can be appropriately blended.

  The rubber composition for a chafer of the present invention is produced by a general method. That is, the rubber composition for a chafer of the present invention can be produced by kneading the compounding agent and, if necessary, the additive with a Banbury mixer, a kneader, an open roll or the like, and then vulcanizing.

The Mooney viscosity (ML _{1 +} 4/130 ° C.) of the rubber composition for chafers before curing at 130 ° C. (unvulcanized state) is 70 or less, preferably 65 or less. When ML _{1 +} 4/130 ° C. exceeds 70, the Mooney viscosity is too large and roll processability is deteriorated. Moreover, ML1 ₊ 4/130 degreeC has 45 or more preferable, and 50 or more is more preferable. When ML _{1 +} 4/130 ° C. is less than 45, the wear resistance (rim rubbing wear resistance) as a chafer rubber composition tends to be lowered.

  The JIS-A hardness after curing of the rubber composition for chafers of the present invention at 23 ° C. is 65 or more, preferably 68 or more. When the JIS-A hardness is less than 65, the abrasion resistance (rim abrasion resistance) and bead durability as the chafer rubber composition are lowered. The JIS-A hardness is 80 or less, preferably 77 or less. When the JIS-A hardness exceeds 80, the chafer part is too hard and the chafer tip is missing when the rim is assembled. Here, bead durability refers to the occurrence of cracks starting from the ply, steel cord, and organic fiber winding ends, and breaking down to the inner liner, and to the outer chafer and sidewall. It shows the durability against breaking.

  The loss tangent (Tanδ) after curing of the rubber composition for a chafer of the present invention measured under the conditions of 70 ° C. and dynamic strain of 2% is 0.13 or less, preferably 0.12 or less. If Tan δ exceeds 0.13, not only low heat build-up will be reduced, but also the improvement effect of fuel efficiency will not be seen. Tan δ is preferably 0.07 or more, and more preferably 0.08 or more. If Tan δ is less than 0.07, sufficient hardness as a chafer rubber composition cannot be obtained, and it tends to be impossible to ensure wear resistance and bead durability.

  The rubber composition for chafers of the present invention is applied to chafers, and by doing so, a tire that can improve fuel efficiency while maintaining roll processability during production can be obtained.

  The tire of the present invention is produced by an ordinary method using the chafer rubber composition of the present invention. That is, the rubber composition for a chafer of the present invention blended with various compounding agents as necessary is extruded according to the shape of the chafer at an unvulcanized stage, and is subjected to a normal method on a tire molding machine. After forming and bonding together with other tire members to form an unvulcanized tire, the tire of the present invention can be produced by heating and pressing in a vulcanizer.

  The tire of the present invention is a fuel-efficient tire while maintaining bead durability and rim rubbing wear resistance, particularly by making it a heavy duty tire for trucks and buses that require bead durability and rim rubbing wear resistance. The effect that it can be made is obtained.

  The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Next, the chemical | medical agent used by the Example and the comparative example is demonstrated.
Natural rubber (NR): TSR20
Butadiene rubber 1 (BR1): BR150B manufactured by Ube Industries, Ltd.
Butadiene rubber 2 (BR2): BR150 manufactured by Ube Industries, Ltd.
Butadiene rubber 3 (BR3): BR A manufactured by Ube Industries, Ltd.
Butadiene rubber 4 (BR4): BR01 manufactured by JSR Corporation
Butadiene rubber 5 (BR5): BR B manufactured by Ube Industries, Ltd.
Styrene butadiene rubber (SBR): SBR1502 manufactured by JSR Corporation
Carbon Black: Show Black N220 manufactured by Cabot Japan
Zinc oxide: Zinc oxide stearic acid manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent: Anti-aging agent 6C (N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine) manufactured by Flexis
Wax: Ozoace wax manufactured by Nippon Seiwa Co., Ltd. Sulfur: Sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Accelerator TBBS (N-tert-butyl-2-benzothia manufactured by Seiko Chemical Co., Ltd.) Zolylsulfenamide)

(Toluene solution viscosity measurement)
BR is dissolved in toluene, a 5% toluene solution is prepared, and the viscosity of the toluene solution (T-CP) is calculated from the flow time of the kinematic viscometer using a Canon Fencer type kinematic viscometer (# 400) and measured. T-CP under a temperature of 25 ° C. was estimated.

(Molecular weight measurement)
The weight average molecular weight (Mw) and number average molecular weight (Mn) in terms of polystyrene were measured by gel permeation chromatography (GPC), and the molecular weight distribution (Mw / Mn) of butadiene rubbers 1 to 5 was calculated.

  The results of the measurement for BR are shown in Table 1.

Examples 1-4 and Comparative Examples 1-7
<Preparation of rubber composition>
The amount of chemicals other than sulfur listed in Table 2 are shown in Table 2, 3 parts by weight of zinc oxide, 2 parts by weight of stearic acid, 3 parts by weight of anti-aging agent, 1.5 parts by weight of wax, and a closed Banbury mixer. The mixture was kneaded for 4 minutes until the temperature reached 150 ° C. To the obtained kneaded product, sulfur is further added in the amount shown in Table 2, and 1.5 parts by weight of a vulcanization accelerator is added, and the mixture is kneaded for 4 minutes at 40 ° C. using a biaxial open roll. Thus, unvulcanized rubber compositions were prepared. Furthermore, the vulcanized rubber compositions of Examples 1 to 4 and Comparative Examples 1 to 7 were prepared by press vulcanizing the unvulcanized rubber composition for 30 minutes at 150 ° C.

(Mooney viscosity)
A test piece having a width of 4 cm, a length of 4 cm, and a thickness of 7 to 9 mm was prepared from the unvulcanized rubber composition, and manufactured by Shimadzu Corporation according to JIS K 6300 “Testing method for unvulcanized rubber”. Using a Mooney Viscosity Tester “Mooney Viscometer SMV-202”, rotating the small rotor under the temperature condition of 130 ° C. heated by preheating for 1 minute, unvulcanized rubber composition after 4 minutes The viscosity of the product (ML _{1 +} 4/130 ° C.) was measured. In addition, it shows that it is excellent in workability, so that Mooney viscosity is small.

(Roll rollability)
When a 20-inch diameter roll is used and 20 kg of the kneaded product is fed under the conditions of a roll temperature of 60 ° C. and a rotation speed of 15 revolutions / minute, the kneaded product is wound until the temperature of the kneaded product reaches 80 ° C. The evaluation was “possible”, and the case where the roll was not wound was “impossible”, and the roll wrapping property was evaluated.

(Low heat generation)
A test piece having a width of 4 mm, a length of 30 mm, and a thickness of 1.8 to 2.2 mm was cut out from the vulcanized rubber composition, and an initial strain of 10% was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho. The loss tangent (Tanδ) at 70 ° C. was measured under the conditions of 2% strain and 10 Hz frequency. In addition, it shows that the heat | fever of a rubber composition is suppressed and it is excellent, so that Tan (delta) is small.

<Manufacture of tires>
The unvulcanized rubber composition is molded into a chafer shape, bonded together with other tire members on a tire molding machine to form an unvulcanized tire, and press vulcanized for 40 minutes at 151 ° C., Truck and bus tires (TBR, tire size: 11R22.5) of Examples 1 to 5 and Comparative Examples 1 to 7 were manufactured.

(Rubber hardness)
The JIS-A hardness at 23 ° C. of the surface of the chafer part of the manufactured TBR was measured with a durometer type A according to the test method of JIS K 6253 “Hardness test method for vulcanized rubber and thermoplastic rubber”. .

(Rim abrasion resistance)
For the manufactured TBR, the tread part that contacts the road surface was removed by buffing until the tire groove reached 4 mm, and then incorporated into an 8.25 size rim. The test was run for 96 hours under the condition of 58 kN, and then was run for 96 hours under the conditions of an internal pressure of 950 kPa, a speed of 20 km / h, and a load of 68 kN. Thereafter, the vehicle was run for 500 hours under the conditions of an internal pressure of 1000 kPa, a speed of 20 km / h, and a load of 77 kN, and whether or not rim rubbing wear occurred in the chafer portion of the TBR was determined. “None” indicates that rim rubbing has not occurred and is preferable, and “Yes” indicates that rim rubbing has occurred and is not preferable.

(Bead durability)
When running, bead durability was determined in the same manner as the rim rubbing wear resistance except that it was run on the drum. “◯” indicates that rim rubbing has not occurred and is preferable, and “×” indicates that rim rubbing has occurred and is not preferable.

(Rubber resistance)
The manufactured TBR was detached from a 7.50 inch rim three times, and the presence or absence of chipping at the tip of the chafer portion was confirmed. “None” indicates that there is no chipping and is preferable, and “Yes” indicates that there is a chipping and is not preferable.

  The evaluation results are shown in Table 2.

Claims (3)

A rubber component containing 40 to 70% by weight of a butadiene rubber having a toluene solution viscosity at 25 ° C. of 50 to 155 cps and a molecular weight distribution of 2.9 to 4.0,
Mooney viscosity before curing at 130 ° C. is 70 or less,
JIS-A hardness after curing at 23 ° C. is 65-80,
A rubber composition for chafers having a loss tangent (Tan δ) after curing measured at 70 ° C. and 2% of dynamic strain of 0.13 or less. The rubber composition for a chafer according to claim 1, wherein the rubber component further contains 30% by weight or more of natural rubber and / or isoprene rubber. A tire having a chafer using the rubber composition for chafers according to claim 1.