JP2009024119A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition, which is suitably used for a joint tape for inner liner capable of surely preventing penetration of a release agent through an inner liner joint part to prevent a failure resulting from a trouble in tire manufacturing, and further improving durability of a tire by improving the heat resistance of the joint tape. <P>SOLUTION: The rubber composition includes 75-95 pts.wt. of halogenated butyl rubber or a blend of halogenated butyl rubber and butyl rubber and 25-5 pts.wt. of diene-based rubber as rubber components and carbon black, and has a 200% elongation modulus of 0.2-0.3 MPa in an unvulcanized state, and a modulus retention rate of 30-55% after 1 minute in the 200% elongated state. The pneumatic tire comprises a joint part 3 of an inner liner 10 on the tire inner surface, which is covered with a joint tape 4 composed of the rubber composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition used for a joint tape of an inner liner joint portion of a tubeless tire, and a pneumatic tire using the joint tape.

  In general, for tubeless tires, butyl rubber or halogenated butyl rubber, which is non-breathable on the inner surface of the tire, is used as a main rubber component in order to prevent the pressure inside the tire from permeating outside the tire and reducing the internal pressure. An inner liner made of a rubber composition is provided.

  Normally, tubeless tires are formed by laminating members such as inner liners, carcass, belts, and treads on a molding drum to form an unvulcanized tire, which is inserted into the mold and expanded by shaving using a bladder or the like. The product tire is vulcanized by being deformed and heated while being pressed against the molding surface, but in order to improve the releasability from the bladder after vulcanization, the entire inner liner on the inner surface of the unvulcanized tire is water-soluble. A release agent such as sex is applied.

  When the release agent is applied to the inner surface of the unvulcanized tire in this way, the release agent penetrates into the joint part of the inner liner or the joint part entrains the release agent, and the joint part is Problems such as opening or air trapping at the intrusion part of the release agent are caused, which contributes to air leakage of the tubeless tire and deterioration of the durability of the tire.

  To deal with this problem in the joint part, for example, after covering the joint part of the inner liner with a joint tape comprising a rubber composition containing carbon black, a plasticizer and a resin on halogenated butyl rubber, a release agent is applied to the inner surface of the tire. It is disclosed to prevent the release agent from entering the joint portion by applying (Patent Document 1).

The inner liner rubber composition is composed of halogenated butyl rubber and diene rubber as rubber components, and the modulus at 200% elongation when unvulcanized is set to 0.2 to 0.4 MPa. It has been proposed to solve the above problem (Patent Document 2).
Japanese Patent Laid-Open No. 7-9807 Japanese Patent Laid-Open No. 2007-9121

  However, in the technique described in Patent Document 1, since halogenated butyl rubber is used alone as a rubber component, the adhesiveness (tackiness) between the inner liner and the joint tape is poor, and the joint tape is peeled off by the tire before vulcanization. In some cases, the release agent permeates from the peeled portion, and the above problem has not been sufficiently solved.

  Further, even with the technique described in Patent Document 2, the problem that the inner liner is peeled off due to the expansion deformation at the time of tire vulcanization and the release agent enters the liner joint portion has not yet been solved.

  Therefore, the object of the present invention is to reliably prevent the release agent from entering from the inner liner joint part, to prevent a failure due to a failure during tire manufacture, and to improve the heat resistance of the joint tape. An object of the present invention is to provide a rubber composition that can be suitably used for a joint tape of an inner liner that can improve the durability of a tire.

  As a result of various investigations in view of the above, the present invention provides a rubber composition having a specific range of unvulcanized modulus characteristics in a butyl halide compounded system and further improving tackiness to solve the above problems. The present invention was completed.

  That is, the present invention comprises carbon black containing 75 to 95 parts by weight of a halogenated butyl rubber or a blend of halogenated butyl rubber and butyl rubber and 25 to 5 parts by weight of a diene rubber as a rubber component. The rubber composition is characterized in that the modulus at 200% elongation is 0.2 to 0.3 MPa and the modulus retention after 1 minute in the 200% stretched state is 30 to 55%.

  In the rubber composition of the present invention, the total amount of carbon black having an iodine adsorption of 15 to 55 g / kg and a DBP absorption of 75 to 125 ml / 100 g and a white filler for rubber is 100 parts by weight of the rubber component. It is preferable to contain -70 weight part.

  Furthermore, the effect of this invention can be improved as the Mooney viscosity (JIS K6300 ML1 + 8, 125 degreeC) of halogenated butyl rubber and butyl rubber is 27-37.

  The diene rubber is preferably natural rubber or polyisoprene rubber.

  The pneumatic tire according to the present invention is characterized in that the inner liner joint portion on the inner surface of the tire is covered with a joint tape made of the rubber composition.

  With the rubber composition according to the present invention, the modulus of unvulcanized (green modulus) and the modulus retention rate (stress relaxation rate) in the stretched state are within an appropriate range, and the tackiness is further improved, thereby improving the It is excellent in adhesiveness, and by using butyl rubber as a main rubber component, it has excellent heat resistance, so that deterioration of the joint tape due to heat generation during traveling can be suppressed.

  As a result, tires in which the joint portion of the inner liner is covered with a joint tape made of this rubber composition reliably prevent the joint tape from peeling off during the production process and storage of unvulcanized tires, and the above problems during tire production. This eliminates the problem based on the intrusion of the mold release agent into the joint part and improves the durability of the tire. Further, the improvement of the heat resistance of the joint tape suppresses the curing of the rubber, prevents a failure due to the occurrence of cracking or peeling of the tape, and improves the durability of the tire.

  The rubber composition of the present invention is used as a rubber component at 100 parts by weight consisting of 75 to 95 parts by weight of halogenated butyl rubber or a blend of halogenated butyl rubber and butyl rubber, and 25 to 5 parts by weight of diene rubber.

  Examples of the halogenated butyl rubber (halogenated IIR) include chlorinated butyl rubber (CIIR) and brominated butyl rubber (BIIR). One kind may be used, or two or more kinds may be used in combination.

  In the present invention, halogenated IIR may be used alone as the butyl rubber component, but a blend of halogenated IIR and butyl rubber (IIR) can be used. Butyl rubber is excellent in non-breathability, heat resistance, weather resistance, etc., but is inferior in vulcanization speed and adhesiveness with other rubbers. By using a blended IIR with IIR, the non-breathability and heat resistance of IIR In addition, the vulcanization speed can be increased while ensuring the property, weather resistance, etc., and the co-vulcanizability and adhesion with other rubbers can be improved.

  The halogenated butyl rubber and butyl rubber preferably have a Mooney viscosity (JIS K6300 ML1 + 8, 125 ° C.) of 27 to 37. Thereby, it becomes easy to adjust the green modulus and the stress relaxation rate of the rubber composition to a range suitable for the use conditions of the joint tape.

  As the diene rubber, natural rubber (NR), polyisoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR), and the like can be used. One type may be used, or two or more types may be used in combination. You can also. Among them, NR or IR is preferable from the viewpoint of optimizing the green modulus and good tackiness and improving the adhesiveness and workability of the halogenated butyl rubber.

  In the present invention, when the blending amount of the butyl rubber in the rubber component is less than 75 parts by weight, the diene rubber component is increased and the tackiness is increased and improved, but the heat resistance is lowered and the resin is easily cured. Reduce tire durability. Further, when the diene rubber component is reduced by exceeding 95 parts by weight of the butyl rubber, tackiness is lowered, so that problems such as peeling of the joint tape and lifting of the tire at the time of tire molding or before vulcanization are easily caused.

  From this viewpoint, the rubber composition of the present invention has a modulus at 200% elongation when unvulcanized of 0.2 to 0.3 MPa, and a modulus retention after 30 minutes of 200% elongation is 30 to 30%. The range is 55%.

  Thus, by making the green modulus and stress relaxation within the appropriate ranges, it is possible to achieve both the tackiness and extension characteristics of the joint tape, and to prevent problems such as peeling of the tape at the time of tire expansion deformation and after expansion deformation.

  Here, the reason why the green modulus at the time of 200% elongation is adopted is that the expansion rate may be locally 150 to 250% in the joint tape portion in a general tire molding and vulcanization process. .

  The rubber composition of this invention contains carbon black and the white filler for rubber | gum, and the compounding quantity can be 55-70 weight part with respect to 100 weight part of rubber components in total of both.

  Carbon black is not particularly limited as long as it is usually used for rubber, but carbon having an iodine adsorption amount (IA) of 15 to 55 g / kg and a DBP absorption amount of 75 to 125 ml / 100 g. Black is preferable for cell rolling while achieving both the above-described tackiness and elongation characteristics. For example, carbon blacks such as FEF, GPF, and SRF are preferable examples. These carbon blacks may be used alone or in combination of two or more.

  Examples of the white filler for rubber include calcium carbonate, magnesium carbonate, clay, zinc white, talc, and mica, among which clay and surface-treated clay are preferable.

  When the total amount of the carbon black and white filler is less than 55 parts by weight, the tackiness is good, but the green modulus is low, it becomes easy to stretch when applied, adversely affects joint disengagement and workability, and vulcanizes. Later rubber strength also decreases. On the other hand, if the amount exceeds 70 parts by weight, the green strength and modulus will be increased, so that the workability of application will be reduced, the tackiness will be reduced and the tape will be easily peeled off. Is likely to occur.

  The rubber composition of the present invention includes, in addition to the rubber component and carbon black, a tackifier such as zinc white, stearic acid, a plasticizer, and a resin that are commonly used in the rubber industry, a softening agent such as wax and oil, Rubber compounding agents such as anti-aging agents, sulfur vulcanizing agents, vulcanization accelerators, etc. are properly blended and used within the normal range, and ordinary methods using rubber kneaders such as ordinary Banbury mixers and kneaders The rubber composition is prepared by kneading.

  The rubber composition is processed into a tape shape using a rubber roll, a calendar device, a cutting device, or the like, and is pasted so as to cover the joint portion of the inner liner of the tire inner surface in the tire molding process. Although the thickness and width of the tape are not particularly limited, the thickness is about 0.1 to 2 mm and the width is about 10 to 30 mm, and the tape is appropriately processed according to the tire size and application.

  In the pneumatic tire of the present invention, the joint portion of the inner liner on the inner surface of the unvulcanized tire is covered with the joint tape, and then a release agent is applied to the inner surface of the unvulcanized tire, followed by vulcanization by a conventional method. Manufactured by doing.

  In the pneumatic tire of the present invention, the joint portion of the inner liner covers the joint tape 4 on the so-called butt joint portion 3 in which both ends 1 and 2 of the inner liner 10 are abutted and joined as shown in FIG. In addition, as shown in FIG. 2, a tire having both types of inner liner joint that covers the joint tape 9 on the so-called overlapping joint portion 8 in which both ends 5 and 6 of the inner liner 20 are overlapped and joined is applied. The

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by this.

  The rubber composition of each Example and Comparative Example in which the following rubber components and compounding agents were blended according to the blending amounts (parts by weight) shown in Table 1 were kneaded using a normal 20 liter Banbury mixer, and each rubber composition. Was prepared.

  About each obtained rubber composition, 200% green modulus, modulus retention after 1 minute in 200% stretched state, tackiness, tire moldability, heat resistance, and presence / absence of cracks in tape after actual running test The following test method evaluated. The results are shown in Table 1. The Mooney viscosity (ML1 + 8, 125 ° C.) is a value measured according to JIS K6300.

The rubber component and compounding agent are as follows.
・ Natural rubber (NR): RSS # 3
Isoprene rubber (IR): JSR Corporation “IR2200”
Brominated butyl rubber (BIIR): “Bromobutyl 2255” manufactured by ExxonMobil, ML1 + 8, 125 ° C. = 46
Brominated butyl rubber (BIIR): “Bromobutyl 2222” manufactured by ExxonMobil, ML1 + 8, 125 ° C. = 31
Butyl rubber (IIR): “Butyl 365” manufactured by ExxonMobil, ML1 + 8, 125 ° C. = 32
Carbon black (CB-GPF): “Seast V”, Tokai Carbon Co., Ltd. (IA = 26 g / kg, DBP absorption amount = 87 ml / 100 g)
・ Clay: Shiraishi Calcium Co., Ltd. “Hard Top Clay”
Paraffin oil: “JOMO Process P200” manufactured by Japan Energy
・ Zinc flower: Mitsui Kinzoku Co., Ltd. Zinc flower No. 3 ・ Stearic acid: Kao Lunac S-20
・ Tackifier: “Escollets 1102” manufactured by ExxonMobil
・ Sulfur: Tsurumi Chemical Co., Ltd. “5% oil-treated powder sulfur”
・ Vulcanization accelerator DM: Ouchi Shinsei Chemical Co., Ltd. Noxeller DM-P

[200% green modulus (MPa)]
An unvulcanized rubber sheet having a thickness of 3 mm was prepared using a test roll, and this sheet was punched with a No. 1 dumbbell defined in JIS K6251. Using an autograph manufactured by Shimadzu Corporation, the tensile speed was 50 mm / min. A tensile test was performed and the modulus at 200% elongation was measured.

[Modulus retention rate after 1 minute of 200% elongation (%)]
In the same manner as described above, an autograph was used to stretch 200% at a pulling speed of 50 mm / min, measure the modulus after 1 minute in the 200% stretched state, and determine the retention rate (%) relative to the modulus at the time of 200% stretching. Asked.

[Tackiness (index)]
Using the above unvulcanized rubber sheet, tackiness was measured by tack tester I (manufactured by Toyo Seiki Seisakusho) to evaluate tackiness. It shows by the index | exponent which sets the adhesive force of Example 1 to 100, and a tackiness is so favorable that a value is large.

[Tire moldability]
100 unvulcanized tires each having a tire size of 11R22.5 14PR were molded. In the 24 hours after the molding of the tire, there are no problems such as peeling of the joint tape (including partial lifting) and opening of the inner liner joint part, “○” indicates that there is no failure, 1-4 indicates “△”, Five or more were evaluated as “x”.

[Heat resistance]
The unvulcanized rubber sheet was left in a hot air circulating dryer adjusted to 140 ° C. The number of days until a crack was generated on the sheet surface when the extracted sheet was bent was measured and evaluated as heat-resistant curability.

[Real driving test]
Attach the 6 tires produced in the above-mentioned evaluation of tire formability to a plurality of large truck rear wheels two by two, run the general road for 100,000 km, remove the tires, and visually check for cracks in the joint tape And observed. A case where no crack occurred in all six tires was evaluated as “◯”, and a case where even one crack occurred was evaluated as “x”.

  As shown in Table 1, the rubber composition of each example according to the present invention has a green modulus and a modulus retention ratio in appropriate ranges, good tackiness, good tire moldability, and excellent heat resistance and durability. Can be improved.

  On the other hand, Comparative Examples 1 to 4 using BIIR having a large ML have a high modulus retention ratio, and the tire moldability is lowered. In particular, Comparative Example 4 in which the amount of NR is increased improves the tackiness but deteriorates the stretch characteristics. However, the balance between the two was not obtained, the heat resistance was poor, and the tape was cracked after running. On the other hand, in Comparative Example 5 containing no NR, the green modulus and tackiness are poor, so the joint tape is easily peeled off and the moldability is poor. In Comparative Example 6 with a small amount of carbon black, the green modulus is lowered and the moldability is lowered due to the opening of the joint portion. On the contrary, in Comparative Example 7 with a large amount of carbon black, both the green modulus and tackiness are deteriorated due to the increase in rubber hardness. It can be seen that the heat resistance is also deteriorated.

  The rubber composition of the present invention can be used for a joint tape of an inner liner of a tubeless tire for passenger cars, light trucks, trucks and buses. Especially, it is used suitably for the tire for heavy loads whose use conditions are severe, and the durability is improved.

It is a joint part sectional view explaining a butt joint. It is a joint part sectional view explaining an overlap joint.

Explanation of symbols

1, 2 ... inner liner end 3 ... joint 4 ... joint tape 10 ... inner liner

Claims (5)

It contains 75 to 95 parts by weight of halogenated butyl rubber or a blend of halogenated butyl rubber and butyl rubber, and 25 to 5 parts by weight of a diene rubber, and contains carbon black as a rubber component. The rubber composition is characterized in that the modulus retention after 1 minute in a 200% stretched state is 30 to 55%. A total of 55 to 70 parts by weight of carbon black having a iodine adsorption of 15 to 55 g / kg and a DBP absorption of 75 to 125 ml / 100 g and a white filler for rubber is contained with respect to 100 parts by weight of the rubber component. The rubber composition according to claim 1. The rubber composition according to claim 1 or 2, wherein Mooney viscosity (JIS K6300 ML1 + 8, 125 ° C) of the halogenated butyl rubber and butyl rubber is 27 to 37. The rubber composition according to any one of claims 1 to 3, wherein the diene rubber is natural rubber or polyisoprene rubber. A pneumatic tire comprising a joint tape made of the rubber composition according to any one of claims 1 to 4 and covering an inner liner joint portion of an inner surface of the tire.

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