Sealant composition and pneumatic tire using same

Abstract

To provide a composition for a sealant which is excellent in producibility (coating speed) and sealing characteristics, and a pneumatic tire using the same.SOLUTION: A composition for a sealant contains, with respect to 100 pts.mass of a solid rubber component containing diene-based rubber, 95-150 pts.mass of a hydrocarbon resin, 20-60 pts.mass of a liquid plasticizer, and 5-30 pts.mass of a filler having a DBP absorption amount of 110 cm3 / 100 g or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sealant composition and a pneumatic tire using the same. [Background technology]

[0002] A sealant composition may be applied to the inner surface of a pneumatic tire to seal the tire when the tire is punctured by a foreign object such as a nail.

[0003] For example, Patent Document 1 describes such a sealant composition characterized by comprising at least an unsaturated diene elastomer as a main elastomer; a thermoplastic hydrocarbon plasticizer resin having a mass content of between 30 phr and 90 phr; a liquid plasticizer having a Tg (glass transition temperature) lower than −20° C. and having a mass content of between 0 and 60 phr; and 0 to less than 30 phr of a filler. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2011-529972 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the sealant composition described in Patent Document 1 has high viscosity at application temperatures (e.g., 80 to 160°C), which places a load on the application device, making it necessary to reduce the application speed, leaving room for improvement in production efficiency.

[0006] In view of the above, an object of the present invention is to provide a sealant composition that is excellent in production efficiency (application speed) and sealing properties. [Means for solving the problem]

[0007] In order to solve the above problems, the sealant composition of the present invention comprises 100 parts by mass of a solid rubber component containing a diene rubber, 95 to 150 parts by mass of a hydrocarbon resin, 20 to 60 parts by mass of a liquid plasticizer, and a DBP absorption of 110 cm 3 The filler having a viscosity of 1000 mg / 100 g or less is contained in an amount of 5 to 30 parts by mass.

[0008] The hydrocarbon resin may be at least one selected from the group consisting of petroleum-based resins, styrene-based resins, and terpene-based resins.

[0009] The liquid plasticizer may be an oil or a liquid rubber.

[0010] The pneumatic tire according to the present invention is formed using the above sealant composition. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a sealant composition that is excellent in production efficiency (application speed) and sealing properties. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view of a pneumatic tire according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Matters relating to the implementation of the present invention will be described in detail below.

[0014] The sealant composition according to the present embodiment comprises 100 parts by mass of a solid rubber component containing a diene rubber, 95 to 150 parts by mass of a hydrocarbon resin, 20 to 60 parts by mass of a liquid plasticizer, and a DBP absorption of 110 cm 3 The filler having a viscosity of 1000 mg / 100 g or less is contained in an amount of 5 to 30 parts by mass.

[0015] The solid rubber component according to the present embodiment contains a diene rubber, and the content of the diene rubber is preferably 50% by mass or more, and more preferably 80% by mass or more. Here, in this specification, "solid" means that it does not have fluidity at 23°C.

[0016] Examples of diene rubbers include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and styrene-isoprene-butadiene copolymer rubber. Furthermore, copolymers may be alternating copolymers, block copolymers, or random copolymers. These solid rubbers may be used alone or in combination of two or more.

[0017] The solid rubber component may contain a rubber component other than diene rubber, such as butyl rubber.

[0018] The hydrocarbon resin used in the sealant composition of this embodiment is a polymer essentially based on carbon and hydrogen. For example, it may be based on aliphatic, alicyclic, aromatic, or hydrogenated aromatic monomers, or it may be aliphatic / aromatic, i.e., based on aliphatic and / or aromatic monomers. The hydrocarbon resin may be a petroleum-based resin or a non-petroleum-based resin (natural or synthetic resin).

[0019] Preferred examples of hydrocarbon resins include petroleum-based resins, styrene-based resins, and terpene-based resins.

[0020] Examples of petroleum resins include aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic copolymer petroleum resins. Aliphatic petroleum resins are resins obtained by cationic polymerization of unsaturated monomers such as isoprene and cyclopentadiene, which are petroleum fractions having 4 to 5 carbon atoms (C5 fractions) (also referred to as C5 petroleum resins), and may be hydrogenated. Aromatic petroleum resins are resins obtained by cationic polymerization of monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions having 8 to 10 carbon atoms (C9 fractions) (also referred to as C9 petroleum resins), and may be hydrogenated. Aliphatic / aromatic copolymer petroleum resins are resins obtained by copolymerizing the C5 fraction and C9 fraction (also referred to as C5 / C9 petroleum resins), and may be hydrogenated.

[0021] Examples of styrene-based resins include α-methylstyrene homopolymers, styrene / α-methylstyrene copolymers, styrene-based monomer / aliphatic monomer copolymers, α-methylstyrene / aliphatic monomer copolymers, and styrene-based monomer / α-methylstyrene / aliphatic monomer copolymers.

[0022] Examples of the terpene resin include polyterpene and terpene-phenol resin.

[0023] The softening point of the hydrocarbon resin is not particularly limited, but is preferably 80 to 150° C., and more preferably 80 to 120° C. In this specification, the "softening point" refers to a value measured in accordance with JIS K2207 (ring and ball method).

[0024] The weight-average molecular weight of the hydrocarbon resin is not particularly limited, but is preferably 500 to 3000, and more preferably 500 to 2500. Herein, the weight-average molecular weight refers to the value measured by gel permeation chromatography (GPC) as a weight-average molecular weight converted into polystyrene.

[0025] The content of the hydrocarbon resin is 95 to 150 parts by mass, preferably 95 to 125 parts by mass, and more preferably 95 to 115 parts by mass, per 100 parts by mass of the solid rubber component. When the content of the hydrocarbon resin is 95 parts by mass or more, excellent production efficiency (application speed) is likely to be obtained. When the content of the hydrocarbon resin is 150 parts by mass or less, cracks are less likely to occur in the sealant layer formed by applying the sealant composition.

[0026] Examples of liquid plasticizers include oil and liquid rubber. In this specification, the term "liquid" means that the plasticizer has fluidity at 23°C.

[0027] As the oil, various oils that are generally compounded in rubber compositions can be used, such as mineral oils such as paraffin oil, naphthenic oil, and aromatic oil.

[0028] Examples of liquid rubbers include liquid isoprene rubber, liquid butadiene rubber, liquid styrene butadiene rubber, liquid isoprene butadiene rubber, liquid isoprene styrene rubber, liquid isoprene butadiene styrene rubber, liquid isobutylene, and liquid ethylene propylene diene rubber (EPDM). These liquid rubbers may be modified by carboxylation, methacrylation, or the like. These liquid rubbers may be used alone or in a blend of two or more.

[0029] The content of the liquid plasticizer is 20 to 60 parts by mass, preferably 20 to 50 parts by mass, and more preferably 30 to 50 parts by mass, per 100 parts by mass of the solid rubber component. When the content of the liquid plasticizer is 20 parts by mass or more, cracks are less likely to occur in the sealant layer formed by applying the sealant composition. When the content of the liquid plasticizer is 60 parts by mass or less, migration of the liquid plasticizer to members adjacent to the sealant composition is less likely to occur.

[0030] The DBP absorption of the filler is 110 cm 3 / 100g or less, 90cm 3 / 100g or less is preferable, 60cm 3 The type of filler is not particularly limited, and examples thereof include carbon black, bituminous coal, silica, etc., which may be used alone or in combination of two or more. 3 When the viscosity is 100 g or less, the fluidity of the sealant composition is easily obtained, and by adsorbing the liquid plasticizer, the liquid plasticizer is easily prevented from migrating to a member adjacent to the sealant composition.

[0031] The content of the filler is 5 to 30 parts by mass, and preferably 10 to 30 parts by mass, per 100 parts by mass of the solid rubber component.

[0032] As the carbon black and bituminous coal, various known types can be used.

[0033] As the silica, wet silica such as wet precipitation silica or wet gel silica is preferably used. In addition to silica, a silane coupling agent such as sulfide silane or mercapto silane may be further blended. When a silane coupling agent is blended, the blending amount is preferably 2 to 20 mass % relative to the blending amount of silica.

[0034] The sealant composition according to this embodiment may contain a crosslinking compounding agent. When a crosslinking compounding agent is contained, the sealant composition crosslinks after application to the inside of a tire, reducing the fluidity of the sealant composition and facilitating the adhesion to the inner surface of the tire and the formation of a uniform sealant layer.

[0035] Examples of crosslinking compounding agents include vulcanizing agents and vulcanization accelerators. Examples of vulcanizing agents include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the compounding amount is preferably 0.1 to 2 parts by mass, more preferably 0.1 to 1 part by mass, and even more preferably 0.1 to 0.5 parts by mass, per 100 parts by mass of the rubber component.

[0036] Examples of vulcanization accelerators include sulfenamide vulcanization accelerators, thiuram vulcanization accelerators, thiazole vulcanization accelerators, thiourea vulcanization accelerators, guanidine vulcanization accelerators, and dithiocarbamate vulcanization accelerators. Among these, sulfenamide vulcanization accelerators, thiazole vulcanization accelerators, and guanidine vulcanization accelerators are preferred. Two or more of these may be used in combination. When two or more are used in combination, it is preferred to use a guanidine vulcanization accelerator in combination with a sulfenamide vulcanization accelerator and / or a thiazole vulcanization accelerator.

[0037] Examples of sulfenamide vulcanization accelerators include N-cyclohexyl-2-benzothiazolylsulfenamide (abbreviation: CZ), N-tert-butyl-2-benzothiazolylsulfenamide (abbreviation: NS), N-oxydiethylene-2-benzothiazolylsulfenamide (abbreviation: OBS), and N,N-diisopropyl-2-benzothiazolesulfenamide (abbreviation: DZ).

[0038] Examples of the guanidine vulcanization accelerator include 1,3-diphenylguanidine (abbreviation: D) and di-O-tolylguanidine (abbreviation: DT).

[0039] Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole (abbreviation: MBT), dibenzothiazyl disulfide (also known as di-2-benzothiazolyl disulfide, abbreviation: MBTS), salts of 2-mercaptobenzothiazole (zinc salt (abbreviation: ZnMBT), sodium salt (abbreviation: NaMBT), cyclohexylamine salt (abbreviation: CMBT), etc.), and 2-(4'-morpholinodithio)benzothiazole (abbreviation: MBDS).

[0040] The content of the sulfenamide vulcanization accelerator is not particularly limited, but is preferably 0.1 to 3 parts by mass, and more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the rubber component.

[0041] The content of the guanidine vulcanization accelerator is not particularly limited, but is preferably 0.1 to 3 parts by mass, and more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the rubber component.

[0042] The content of the thiazole vulcanization accelerator is not particularly limited, but is preferably 0.1 to 3 parts by mass, and more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the rubber component.

[0043] The content of the vulcanization accelerator (the total amount when two or more types are blended) is preferably 0.1 to 3 parts by mass, more preferably 1.0 to 2.5 parts by mass, and even more preferably 1.5 to 2.0 parts by mass, per 100 parts by mass of the rubber component. When the content of the vulcanization accelerator is 0.1 part by mass or more, the sealant composition is easily fixed to the inner surface of the tire. When the content of the vulcanization accelerator is 3 parts by mass or less, excellent production efficiency (application speed) is easily achieved.

[0044] Compounding agents other than crosslinking compounding agents may include compounding chemicals such as process oil, processing aids, zinc oxide, stearic acid, softeners, plasticizers, resins, waxes, and antioxidants that are commonly used in the rubber industry and may be appropriately compounded within normal ranges.

[0045] The sealant composition according to this embodiment can be produced using a kneader that is commonly used in the rubber industry.

[0046] In the first step, the hydrocarbon resin and the compounding ingredients excluding the cross-linking compounding ingredients are added, and the kneaded mixture is kneaded while increasing its temperature. The discharge temperature at this time is not particularly limited, but is preferably 120 to 160°C.

[0047] Examples of the kneading machine used in the first step include a Banbury mixer, a roll mill, and a kneading extruder.

[0048] In the second step, the hydrocarbon resin and cross-linking compounding agents are added to the kneaded product obtained in the first step and kneaded. The discharge temperature is not particularly limited, but is preferably higher than the softening point of the hydrocarbon resin, more preferably at or below the softening point +10°C, and even more preferably at or below the softening point +5°C. As a guideline for the discharge temperature, for example, 80 to 120°C is preferred, and 90 to 110°C is more preferred. By kneading at a temperature higher than the softening point of the hydrocarbon resin, excellent dispersibility of the resin is likely to be obtained.

[0049] Examples of the kneader used in the second step include kneader extruders such as a twin-screw kneader extruder and a co-kneader.

[0050] The rubber composition obtained by the production method according to this embodiment can be used for tires, and can be applied as a sealant layer to the inside of pneumatic tires of various uses and sizes, such as passenger car tires and large tires for trucks and buses. Tires can be obtained by vulcanizing and molding a green tire (unvulcanized tire) prepared according to a conventional method.

[0051] An embodiment of a tire having a sealant layer will be described with reference to Fig. 1. The tire 1 includes an annular tread 2 that comes into contact with the road surface, a pair of left and right beads 3, 3 located inside the tread 2 in the tire radial direction RD, and a pair of left and right sidewalls 4, 4 located between the tread 2 and the beads 3, 3. The tire 1 includes a bead core 5 embedded in the bead 3, a carcass ply 6 that extends toroidally between the left and right beads 3, 3, a belt 7 and tread rubber 8 provided on the outer circumferential side of the carcass ply 6 in the tread 2, an inner liner 9 provided on the tire inner surface side of the carcass ply 6, and a sealant layer 10 provided on the tire inner surface side of the inner liner 9.

[0052] The sealant layer 10 is provided on the inner surface 1A of the tire 1, specifically, overlapping the inside of the inner liner 9. In this example, the sealant layer 10 is provided on the tire inner surface 1A of the tread 2 from one end to the other end in the tire axial direction AD. In this way, the sealant layer 10 is preferably provided over the entire inner surface of the tread 2, and may be provided only on the inner surface of the tread 2, or may be provided over a wider range including the inner surface of the tread 2. In other words, the sealant layer 10 is preferably provided on the inner surface 1A of the tire 1 including the inner surface of the tread 2.

[0053] The method for forming the sealant layer is not particularly limited, but for example, the obtained sealant composition is heated to, for example, 80 to 160°C, applied to the inside of a tire using an application device, and then left at room temperature, whereby the fluidity of the sealant composition decreases and it is fixed to the inside of the tire, thereby forming a sealant layer.

[0054] The type of pneumatic tire according to this embodiment is not particularly limited, and may be any of various types of tires such as tires for passenger cars and heavy-duty tires used for trucks, buses, etc. [Explanation of symbols]

[0055] 1... tire, 2... tread, 3... bead, 4... sidewall, 5... bead core, 6... carcass ply, 7... belt, 8... tread, 9... inner liner, 10... sealant layer, 1A... tire inner surface, RD... tire radial direction, AD... tire axial direction [Example]

[0056] Examples of the present invention will be shown below, but the present invention is not limited to these examples.

[0057] Examples and Comparative Examples Using a Banbury mixer, in the first step, the components excluding the hydrocarbon resin, sulfur, and vulcanization accelerator were added and kneaded (discharge temperature = 130°C) according to the formulation (parts by mass) shown in Table 1. In the second step, the hydrocarbon resin, sulfur, and vulcanization accelerator were added and mixed to the resulting kneaded mixture (discharge temperature = 90°C) to prepare a rubber composition.

[0058] Details of each component in Table 1 are as follows: IR: JSR Corporation "IR2200" BR: Ube Industries, Ltd. "UBEPOL BR150B" Carbon black 1: "Seast V" manufactured by Tokai Carbon Co., Ltd., DBP = 87 cm 3 / 100g Carbon black 2: "Seast 7HM" manufactured by Tokai Carbon Co., Ltd., DBP = 120 cm 3 / 100g Bituminous coal: Austin Black 325 manufactured by Coal Fillers, Inc., DBP = 60 cm 3 / 100g Liquid plasticizer 1: Oil, JXTG Nippon Oil & Energy Corporation "Process NC140" Liquid plasticizer 2: Liquid polyisoprene rubber, Toray Industries, Inc. "LIR50" Hydrocarbon resin 1: "Petrotack 90" manufactured by Tosoh Corporation, aliphatic / aromatic copolymer petroleum resin, softening point = 95°C, weight average molecular weight = 1600 Hydrocarbon resin 2: KRATON "SYLVATRAXX 4150", terpene resin, softening point = 115°C, weight average molecular weight = 2110 Hydrocarbon resin 3: KRATON "SYLVATRAXX 4401", α-methylstyrene resin, softening point = 85°C, weight average molecular weight = 1200 Zinc oxide: "Zinc oxide type 2" manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Kao Corporation's "Lunac S-20" Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Sumitomo Chemical Co., Ltd.'s "Soxinol DG", a guanidine vulcanization accelerator Vulcanization accelerator 2: Sumitomo Chemical Co., Ltd.'s "Soccinol CZ", a sulfenamide vulcanization accelerator

[0059] The resulting rubber compositions were evaluated for their application speed and sealing properties after nail removal. The evaluation methods were as follows.

[0060] Coating speed: Using a Nordson material coating system, the time required to discharge 1 kg of the obtained rubber composition at a pressure of 4.0 bar was measured and used as the coating speed. The coating speed was expressed as an index, with the coating speed of Comparative Example 1 being set at 100. A larger index indicates a faster coating speed and better manufacturing efficiency.

[0061] Sealing property after nail removal: A pneumatic tire was manufactured with the obtained rubber composition applied to the sealant layer, and a nail was inserted into the tread and then removed. After the nail was removed, the sealing property was evaluated based on whether or not there was air leakage.

[0062] [Table 1]

[0063] The results are shown in Table 1. Comparative Example 1 is an example in which carbon black with a DBP value exceeding the upper limit was used, and Comparative Example 2 is an example in which the hydrocarbon resin content exceeded the upper limit. Compared to Comparative Example 1, Comparative Example 2 had a slower application speed and air leakage when sealing after nail removal.

[0064] On the other hand, Examples 1 to 9 had a faster application speed than Comparative Example 1 and also had excellent sealing properties after the nail was removed.

Claims

1. For 100 parts by mass of a solid rubber component containing 50% by mass or more of a diene rubber, 95 to 150 parts by mass of at least one hydrocarbon resin selected from the group consisting of petroleum-based resins, styrene-based resins, and terpene-based resins, the hydrocarbon resin having a softening point of 80 to 150°C, 20 to 60 parts by mass of a liquid plasticizer which is oil and / or liquid rubber, At least one selected from the group consisting of carbon black, bituminous coal, and silica, having a DBP absorption of 110 cm ３ A sealant composition for pneumatic tires, comprising 5 to 30 parts by mass of a filler having a viscosity of 100 g / 100 g or less.

2. A pneumatic tire formed using the sealant composition according to claim 1.

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