Tire tread splice cement

Abstract

To solve the following problem that: although styrene-butadiene copolymer rubber have been used widely in cap treads as a result of the recent demand for low-heat-generating tires, if a conventional splice cement based mainly on natural rubber is used, the adhesiveness (tackiness) before vulcanization and the post-vulcanization adhesion are insufficient.SOLUTION: The above problem is solved by a tire tread splice cement in which 20 to 80 pts.mass of carbon black and 5 pts.mass or more of a butylphenol-acetylene resin are incorporated into 100 pts.mass of diene rubber containing 97 pts.mass or more of styrene-butadiene copolymer rubber having a glass transition temperature of -40°C or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a cement for tire tread splices.

Background Art

[0002] Conventionally, the cap tread of a tire has been formed by extruding an unvulcanized rubber composition from an extruder to obtain a strip material, cutting this strip material to a certain length, winding it annularly on a forming drum, joining both ends to each other, and then vulcanizing and molding. As this joining method, a splice cement is applied to the joining (splice) part at both ends and then bonded together (for example, Patent Documents 1 to 4 below). On the other hand, in response to the recent demand for low heat generation in tires, styrene-butadiene copolymer rubber is widely used in cap treads. However, when using a splice cement mainly composed of natural rubber as disclosed in Patent Documents 1 to 4 below, there are problems that the adhesiveness (tackiness) before vulcanization and the adhesiveness after vulcanization are insufficient.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a cement for tire tread splices that enhances the adhesiveness (tackiness) before vulcanization and the adhesiveness after vulcanization.

Means for Solving the Problem

[0005] As a result of intensive research, the inventors of the present invention have found that a cement for tire tread splice containing a diene rubber containing a styrene-butadiene copolymer rubber having a specific glass transition temperature range, carbon black, and butylphenol-acetylene resin in specific amounts can solve the above problems, and thus have completed the present invention.

[0006] That is, the present invention provides a cement for tire tread splice, which is characterized in that 20 to 80 parts by mass of carbon black and 5 parts by mass or more of butylphenol-acetylene resin are blended with 100 parts by mass of a diene rubber containing 97 parts by mass or more of a styrene-butadiene copolymer rubber having a glass transition temperature of -40°C or lower.

Effect of the Invention

[0007] The cement for tire tread splice of the present invention is characterized in that 20 to 80 parts by mass of carbon black and 5 parts by mass or more of butylphenol-acetylene resin are blended with 100 parts by mass of a diene rubber containing 97 parts by mass or more of a styrene-butadiene copolymer rubber having a glass transition temperature of -40°C or lower. Therefore, even if the tire tread is mainly composed of a styrene-butadiene copolymer rubber, both the tackiness before vulcanization and the adhesiveness after vulcanization can be enhanced.

Mode for Carrying Out the Invention

[0008] Hereinafter, the present invention will be described in more detail.

[0009] (Diene Rubber) The diene rubber used in the present invention is mainly composed of styrene-butadiene copolymer rubber (SBR). The blending amount of the SBR is 97 parts by mass or more when the total amount of the diene rubber is 100 parts by mass, and preferably all of the diene rubber consists of SBR. The weight average molecular weight (Mw) of the SBR is preferably 350,000 or more because the effects of the present invention are more excellent. In this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are values in terms of standard polystyrene obtained by gel permeation chromatography (GPC) measurement. From the viewpoint of improving the effects of the present invention, the glass transition temperature (Tg) of the SBR is preferably -40°C or lower, more preferably -45°C or lower, and particularly preferably -50°C or lower. The glass transition temperature (Tg) referred to in the present invention means the temperature at the midpoint of the transition region measured by a thermogram under the condition of a heating rate of 20°C / min by differential scanning calorimetry (DSC).

[0010] (Carbon black) Specific examples of the carbon black used in the present invention include furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF. These may be used alone or in combination of two or more. From the viewpoint of improving the effects of the present invention, the carbon black preferably has a nitrogen adsorption specific surface area (N2SA) of 50 to 150 m 2 / g, and more preferably 70 to 150 m 2 / g. The nitrogen adsorption specific surface area (N2SA) is a value measured in accordance with JIS K 6217-2:2001 "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method".

[0011] (Butylphenol acetylene resin) The cement for tire tread splice of the present invention contains a butylphenol acetylene resin. The butylphenol acetylene resin is known and commercially available products can be used. For example, products such as Colesin manufactured by BASF can be mentioned. From the viewpoint of improving the effects of the present invention, the butylphenol acetylene resin used in the present invention preferably has a softening point of 135 - 150°C.

[0012] (Mixing ratio of cement for tire tread splice) The cement for tire tread splice of the present invention is characterized in that 20 to 80 parts by mass of carbon black and 5 parts by mass or more of butylphenol acetylene resin are blended based on 100 parts by mass of diene rubber. When the blending amount of carbon black is less than 20 parts by mass based on 100 parts by mass of diene rubber, the adhesiveness after vulcanization deteriorates. Conversely, when it exceeds 80 parts by mass, the tackiness (tack) before vulcanization deteriorates. When the blending amount of butylphenol acetylene resin is less than 5 parts by mass based on 100 parts by mass of diene rubber, the addition amount is too small to achieve the effects of the present invention. The blending amount of the carbon black is preferably 30 to 70 parts by mass based on 100 parts by mass of diene rubber. The blending amount of the butylphenol acetylene resin is preferably 5 to 30 parts by mass, more preferably 10 to 25 parts by mass based on 100 parts by mass of diene rubber.

[0013] (Other components) In the cement for tire tread splice in the present invention, in addition to the above-mentioned components, vulcanizing or crosslinking agents; vulcanizing or crosslinking accelerators; zinc oxide; anti-aging agents; plasticizers; various fillers such as silica, calcium carbonate, talc, clay, etc.; silane coupling agents; and other various additives generally blended in cement for tire tread splice can be blended. Such additives can be kneaded by a general method to form a composition and can be used for vulcanization or crosslinking. The blending amounts of these additives can also be set to conventional general blending amounts as long as they do not conflict with the object of the present invention.

[0014] Using the cement for tire tread splice of the present invention, the tire cap tread can be formed as follows. An unvulcanized rubber composition for the cap tread is extruded from an extruder to obtain a strip material, the strip material is cut to a certain length, preferably at 100 ° C or lower, wound annularly on a forming drum, and then at least one end of the strip material is dissolved and applied with the cement for tire tread splice using an organic solvent such as toluene, the end portions of the strip material are joined to each other, and vulcanized and formed. In addition, a suitable tire tread composition when using the cement for tire tread splice of the present invention is exemplified below. (Rubber composition for tire cap tread mainly composed of SBR as rubber component) Examples of the formulation include 5 to 100 parts by mass of carbon black, 5 to 100 parts by mass of silica when using silica, and 3 to 30 parts by mass of plasticizer with respect to 100 parts by mass of a diene rubber containing 70 parts by mass or more of SBR. (Rubber composition for tire cap tread mainly composed of NR as rubber component) Examples of the formulation include 5 to 100 parts by mass of carbon black, 5 to 100 parts by mass of silica when using silica, and 3 to 30 parts by mass of plasticizer with respect to 100 parts by mass of a diene rubber containing 70 parts by mass or more of NR. In addition, as components other than the above, components usually blended in conventional rubber compositions for tire cap treads can be blended without limitation. For example, vulcanizing or crosslinking agents; vulcanizing or crosslinking accelerators; zinc oxide; antioxidants; plasticizers; various fillers; silane coupling agents, etc. can be blended as appropriate.

Examples

[0015] Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples.

[0016] (Preparation of cement for tire tread splice) In the formulation (parts by mass) shown in Table 1, the components excluding the vulcanization accelerator and sulfur were kneaded in a 1.5-liter closed mixer for 3 minutes, and discharged when the temperature reached 130 ± 5°C to obtain a masterbatch. After kneading the vulcanization accelerator and sulfur into this masterbatch on an open roll, a sheet with a thickness of 1 mm was obtained. Next, after cutting the obtained sheet, it was immersed in 9 times the mass of toluene for 12 hours, and then mixed with a stirrer for about 4 hours to obtain a cement for various tire tread splices.

[0017] (Preparation of Rubber Composition for Cap Tread) In the formulation (parts by mass) shown in Table 2, the components excluding the vulcanization system (vulcanization accelerator, sulfur) were kneaded in a 1.7-liter closed Banbury mixer for 5 minutes, then discharged outside the mixer and cooled to room temperature. Subsequently, the composition was put back into the same Banbury mixer, the vulcanization system was added and kneaded to obtain an unvulcanized rubber composition. Two types of rubber compositions, SBR-based or NR-based, were prepared as the rubber composition.

[0018] (Fabrication of Test Tires) Test tires were fabricated with a common tire size of 215 / 70R16 and a cap tread of NR-based or SBR-based formed by the molding method shown below. The unvulcanized rubber compositions for various cap treads were extruded from an extruder to obtain a strip material with a bottom width of 210 mm and a thickness of 10 mm. This strip material was cut at 30°C to a length of 2100 mm, wound annularly on a molding drum, and then an appropriate amount of the cement for various tire tread splices was applied to one end of the strip material to join the strip materials to each other and vulcanization-molded at 180°C. In each example and comparative example, other members other than the cap tread were the same.

[0019] (Measurement of Splice Performance) The test tires obtained above were mounted on a rim with a rim size of 16 × 7JJ, the air pressure was set to 200 kPa, and four test tires each were attached to a passenger car with a displacement of 2000 cc and driven in a 10-km circular turn at a speed of 20 km / h. The state of the tire cap tread after driving was evaluated according to the following evaluation criteria. 5 points: No crack generation 4 points: Cracks less than 1 mm generated 3 points: Cracks 1 mm or more and less than 5 mm generated 2 points: Cracks 5 mm or more and less than 10 mm generated 1 point: Cracks 10 mm or more generated

[0020] (Measurement of tack performance) The strip material before vulcanization was attached to a PICMA II type tack tester manufactured by Toyo Seiki Seisakusho Co., Ltd. On the other hand, an appropriate amount of cement for tire tread splicing was applied to another rubber, and this was pressure-bonded to the strip material. The force (N) when peeling vertically was measured under the conditions of a pressure-bonding speed of 500 mm / min, a pressure-bonding load of 4.9 N, a pressure-bonding time of 0.5 seconds, and a peeling speed of 1250 mm / min. The results were shown as an index with the value of the standard example set to 100. A larger index means better tack performance.

[0021] The results are shown together in Table 1.

[0022]

Table 1

[0023] *1: NR (RSS#3) *2: BR (Nipol BR1220 manufactured by Zeon Corporation, Japan) *3: SBR1 (SBR1 prepared by the following manufacturing method, glass transition temperature = -30°C, weight average molecular weight = 300,000) *4: SBR2 (Nipol 1502 manufactured by Zeon Corporation, Japan, glass transition temperature = -55°C, weight average molecular weight = 300,000) *5: SBR3 (SBR3 prepared by the following manufacturing method, glass transition temperature = -55°C, weight average molecular weight = 450,000) *6: Carbon black (product name Seast KH manufactured by Tokai Carbon Co., Ltd., nitrogen adsorption specific surface area (N2SA) = 93 m 2 / g) *7: Butylphenol acetylene resin (p-tert-butylphenol acetylene resin manufactured by BASF Co., Ltd., product name Colesin) *8: Zinc Oxide (Three types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.) *9: Antioxidant (SANTOFLEX 6PPD manufactured by Flexsys) *10: Process Oil (Diana Process Oil NH-70S manufactured by Idemitsu Kosan Co., Ltd.) *11: Sulfur (Micronized sulfur for gold printing oil manufactured by Tsurumi Chemical Industry Co., Ltd.) *12: Vulcanization Accelerator 1 CBS (Sunceler NS-G manufactured by Sanshin Chemical Industry Co., Ltd.) *13: Vulcanization Accelerator 2 DPG (Senceler D-G manufactured by Sanshin Chemical Industry Co., Ltd.)

[0024] Method for manufacturing SBR1 Into an autoclave equipped with a stirrer, 4000 g of cyclohexane, 7.6 g of 2,2-bis(tetrahydrofuryl)propane, 329.4 g of 1,3-butadiene, and 157.5 g of styrene were charged under a nitrogen atmosphere. After that, 8.2 mL of n-butyllithium (1.60 mol / L hexane solution) was added as an initiator, and polymerization was started at 40°C. Ten minutes after the start of polymerization, 172.1 g of 1,3-butadiene and 18.3 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 60°C. After the continuous addition was completed, the polymerization reaction was continued for another 20 minutes. After confirming that the monomer conversion rate was in the range of 95% to 100%, methanol in an amount corresponding to twice the molar amount of the n-butyllithium used was added as a polymerization terminator to obtain a solution containing solution-polymerized SBR. Then, 5.82 g of 2,6-di-tert-butyl-p-cresol was added to the obtained solution. Next, the solvent was removed by steam stripping, and a solid conjugated diene rubber was obtained by drying with a hot roll adjusted to 110°C.

[0025] Method for manufacturing SBR3 Into an autoclave equipped with a stirrer, 4000 g of cyclohexane, 8.1 g of 2,2 - bis(tetrahydrofuryl)propane, 261.1 g of 1,3 - butadiene and 230.8 g of styrene were charged under a nitrogen atmosphere. After that, 7.9 mL of n - butyllithium (1.60 mol / L hexane solution) was added as an initiator, and polymerization was started at 40°C. Ten minutes after the start of polymerization, 128.6 g of 1,3 - butadiene and 62.8 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 60°C. After the continuous addition was completed, the polymerization reaction was continued for another 20 minutes. After confirming that the monomer conversion rate was in the range of 95% to 100%, as a polymerization terminator, an amount of methanol corresponding to twice the molar amount of the used n - butyllithium was added to obtain a solution containing solution - polymerized SBR. Then, 5.83 g of 2,6 - di - tert - butyl - p - cresol was added to the obtained solution. Next, the solvent was removed by steam stripping and dried with a hot roll adjusted to 110°C to obtain a solid conjugated diene rubber.

[0026]

Table 2

[0027] *14: NR (RSS#3) *15: SBR (Nipol 1502 manufactured by Zeon Corporation, Japan) *16: Carbon black (trade name Seast KH manufactured by Tokai Carbon Co., Ltd.) *17: Silica (trade name 1165MP manufactured by Solvay) *18: Silane coupling agent (Si69 manufactured by Evonik Degussa) *19: Process oil (Diana Process Oil NH - 70S manufactured by Idemitsu Kosan Co., Ltd.) *20: Zinc oxide (Zinc oxide No. 3 manufactured by Shodo Chemical Industry Co., Ltd.) *21: Sulfur (Jin Hua Indian Ink Micro - Powder Sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.) *22: Vulcanization accelerator (Sunceler NS - G manufactured by Sanshin Chemical Industry Co., Ltd.)

[0028] From the results in Table 1, for 100 parts by mass of a diene rubber containing 97 parts by mass or more of a styrene-butadiene copolymer rubber having a glass transition temperature of -40°C or lower, 20 to 80 parts by mass of carbon black and 5 parts by mass or more of a butylphenol-acetylene resin are blended. Therefore, even if the rubber component of the rubber composition for a tire cap tread is mainly SBR, the tackiness (tack) before vulcanization and the adhesiveness after vulcanization are improved compared to Standard Example 1. On the other hand, in Comparative Examples 1 to 3, the blending amount of SBR is less than the lower limit defined in the present invention, and the glass transition temperature of SBR exceeds the upper limit defined in the present invention. Therefore, the adhesiveness after vulcanization decreased. In Comparative Example 4, the blending amount of carbon black is less than the lower limit defined in the present invention, and the glass transition temperature of SBR exceeds the upper limit defined in the present invention. Therefore, the adhesiveness after vulcanization decreased. In Comparative Example 5, the blending amount of carbon black exceeds the upper limit defined in the present invention, and the glass transition temperature of SBR exceeds the upper limit defined in the present invention. Therefore, no significant improvement was observed in tackiness and adhesiveness after vulcanization. In Comparative Example 6, since no butylphenol-acetylene resin was blended, both tackiness and adhesiveness after vulcanization decreased.

[0029] The present invention includes the following forms. Embodiment 1: A cement for a tire tread splice, characterized in that 20 to 80 parts by mass of carbon black and 5 parts by mass or more of a butylphenol-acetylene resin are blended with respect to 100 parts by mass of a diene rubber containing 97 parts by mass or more of a styrene-butadiene copolymer rubber having a glass transition temperature of -40°C or lower. Embodiment 2: The cement for a tire tread splice according to Embodiment 1, characterized in that the weight average molecular weight of the styrene-butadiene copolymer rubber is 350,000 or more. Embodiment 3: An unvulcanized rubber composition is extruded from an extruder to obtain a strip material, the strip material is cut into a certain length, wound annularly on a forming drum, and then a cement for tire tread splicing is applied to at least one end of the strip material to join the strip materials to each other, and vulcanized and molded. In a method for molding a tire cap tread, the cement for tire tread splicing is the cement for tire tread splicing according to Embodiment 1 or 2. A method for molding a tire cap tread, characterized in that. Embodiment 4: A tire using the cement for tire tread splicing according to Embodiment 1 or 2.

Claims

1. A cement for tire tread splice, characterized in that, based on 100 parts by mass of a diene rubber containing 97 parts by mass or more of a styrene-butadiene copolymer rubber having a glass transition temperature of -40°C or lower, 20 to 80 parts by mass of carbon black and 5 parts by mass or more of a butylphenol acetylene resin are blended.

2. The cement for tire tread splice according to Claim 1, characterized in that the weight average molecular weight of the styrene-butadiene copolymer rubber is 350,000 or more.

3. In a method for forming a tire cap tread, an unvulcanized rubber composition is extruded from an extruder to obtain a strip material, the strip material is cut to a certain length, wound annularly on a forming drum, and then a cement for tire tread splice is applied to at least one end of the strip material to join the strip materials to each other and vulcanize and form. The method for forming a tire cap tread, characterized in that the cement for tire tread splice is the cement for tire tread splice according to Claim 1.

4. A tire using the cement for tire tread splice according to Claim 1.

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