Sealant composition and pneumatic tire using same

Abstract

To provide a composition for a sealant which is excellent in heat generation performance, rigidity, 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 0.1-10 pts.mass of a cellulose nanofiber.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 a method for applying particles (11) to the inner wall of a tire comprising two sidewalls (3), a crown (2) having a tread radially outward, a carcass-type reinforcing structure (7) and at least one crown reinforcement (6), the inner surfaces of each sidewall (3) and the crown (2) forming an inner wall, at least a portion of which is covered with at least one layer (10) of a self-sealing composition, in which the particles (11) are applied to the self-sealing composition layer by a flocking method after the tire has been cured. [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 invention described in Patent Document 1 applies particles to the self-sealing composition layer after the tire has been cured in order to keep the tire structure completely intact, and the sealing properties leave room for improvement.

[0006] Furthermore, when the sealant composition is applied to the inner surface of a tire, if the viscosity of the sealant composition is low, the composition may not adhere to the applied area and may flow, making it impossible to apply the composition uniformly.

[0007] Furthermore, when the sealant composition is applied to the inner surface of a tire, hysteresis loss increases during tire rolling, and heat generation performance may deteriorate.

[0008] In view of the above, an object of the present invention is to provide a sealant composition that is excellent in heat generation performance, rigidity, and sealing properties. [Means for solving the problem]

[0009] In order to solve the above problems, the sealant composition of the present invention contains 95 to 150 parts by mass of a hydrocarbon resin, 20 to 60 parts by mass of a liquid plasticizer, and 0.1 to 10 parts by mass of cellulose nanofibers relative to 100 parts by mass of a solid rubber component containing a diene rubber.

[0010] The hydrocarbon resin may be at least one selected from the group consisting of petroleum-based resins, styrene-based resins, and terpene-based resins.

[0011] The liquid plasticizer may be an oil or a liquid rubber.

[0012] The pneumatic tire according to the present invention is formed using the above sealant composition. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a sealant composition that is excellent in heat generation performance, rigidity, and sealing properties. [Brief explanation of the drawings]

[0014] [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

[0015] Matters relating to the implementation of the present invention will be described in detail below.

[0016] The sealant composition according to this embodiment contains 95 to 150 parts by mass of a hydrocarbon resin, 20 to 60 parts by mass of a liquid plasticizer, and 0.1 to 10 parts by mass of cellulose nanofibers relative to 100 parts by mass of a solid rubber component containing a diene rubber.

[0017] 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.

[0018] 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 a blend of two or more. Among these, natural rubber (NR), isoprene rubber (IR), and butadiene rubber (BR) are preferred, and a combination of natural rubber (NR) or isoprene rubber (IR) with butadiene rubber (BR) is preferred.

[0019] The solid rubber component may contain a rubber component other than diene rubber, such as butyl rubber.

[0020] 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).

[0021] Preferred examples of hydrocarbon resins include petroleum-based resins, styrene-based resins, and terpene-based resins.

[0022] 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.

[0023] 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.

[0024] Examples of the terpene resin include polyterpene and terpene-phenol resin.

[0025] 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).

[0026] 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.

[0027] 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.

[0028] Examples of liquid plasticizers include oil and liquid rubber. In this specification, the term "liquid" means that the plasticizer has fluidity at 23°C.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] Cellulose nanofibers may have a nano-sized fiber diameter, preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 1 to 60 nm. Furthermore, the fiber length of the cellulose nanofiber is not particularly limited, but is preferably 100 μm or less, more preferably 10 μm or less, and even more preferably 100 nm to 10 μm. Cellulose nanofibers are obtained by defibrating cellulose fibers. The defibration method is not particularly limited, and any known method may be used. The cellulose fibers to be defibrated are not particularly limited, and cellulose fibers (pulp) prepared from various natural plant fibers such as wood, rice husks, straw, and bamboo can be used. Here, the average fiber diameter and average fiber length are determined by randomly selecting 10 cellulose fibers from a scanning electron microscope (SEM) image, measuring the short diameter, and taking the arithmetic mean of the measured short diameters. The average fiber length is determined by taking the arithmetic mean of the measured long diameters.

[0033] The content of cellulose nanofibers is 0.1 to 10 parts by mass, preferably 0.5 to 8 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the solid rubber component. When the cellulose nanofiber content is 0.1 part by mass or more, the sealant composition has appropriate viscosity, adheres to the applied area, and does not easily flow, and when the content is 10 parts by mass or less, excellent heat generation performance is likely to be obtained.

[0034] The sealant composition according to this embodiment may contain a filler other than cellulose nanofibers. The type of filler is not particularly limited, and examples thereof include carbon black, bituminous coal, and silica.

[0035] The content of the filler (including cellulose nanofibers) is not particularly limited, but is preferably 0.1 to 30 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of the solid rubber component.

[0036] As the carbon black and bituminous coal, various known types can be used.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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).

[0042] Examples of the guanidine vulcanization accelerator include 1,3-diphenylguanidine (abbreviation: D) and di-O-tolylguanidine (abbreviation: DT).

[0043] 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).

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] The sealant composition according to this embodiment can be produced using a kneader that is commonly used in the rubber industry.

[0050] 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.

[0051] Examples of the kneading machine used in the first step include a Banbury mixer, a roll mill, and a kneading extruder.

[0052] 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.

[0053] Examples of the kneader used in the second step include kneader extruders such as a twin-screw kneader extruder and a co-kneader.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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]

[0059] 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]

[0060] Examples of the present invention will be shown below, but the present invention is not limited to these examples.

[0061] 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 kneaded mixture (discharge temperature = 90°C) to prepare a rubber composition.

[0062] Details of each component in Table 1 are as follows: IR: JSR Corporation "IR2200" BR: Ube Industries, Ltd. "UBEPOL BR150B" Carbon black: "Seast 7HM" manufactured by Tokai Carbon Co., Ltd. Cellulose nanofiber: "BiNFi-s Dry Powder" manufactured by Sugino Machine Co., Ltd., fiber diameter = 10-50 nm, fiber length = 10 μm or less 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"

[0063] Each rubber composition thus obtained was evaluated for sealing ability after nail removal, rigidity, and heat generation performance according to the following methods.

[0064] 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.

[0065] Stiffness: The loss factor (40°C tanδ) was measured using a Montech D-RPA3000 under conditions of a temperature of 40°C, a frequency of 1 Hz, and a strain of 25%. The result is expressed as an index, with Comparative Example 1 being set at 100. The higher the index, the higher the viscosity at 40°C, and the less likely it is to flow when applied to the inner surface of a tire.

[0066] Heat generation performance: The loss factor 60°C tan δ was measured using a Montech D-RPA3000 under conditions of a temperature of 60°C, a frequency of 10 Hz, and a strain of 1%. The results are expressed as an index, with the result of Comparative Example 1 being set at 100. The smaller the index, the more excellent the heat generation performance.

[0067] [Table 1]

[0068] The results are shown in Table 1. Each example had excellent sealing properties after nail removal, and compared to Comparative Example 1, was also excellent in rigidity and heat generation performance.

Claims

1. A sealant composition used to form a sealant layer on the inner surface of a tire, comprising: per 100 parts by mass of a solid rubber component containing 80% by mass or more of at least one diene rubber selected from the group consisting of natural rubber, isoprene rubber, and butadiene rubber, 95 to 150 parts by mass of a hydrocarbon resin, 20 to 60 parts by mass of a liquid plasticizer, Contains 0.1 to 10 parts by mass of cellulose nanofibers, A sealant composition, wherein the liquid plasticizer is an oil.

2. 2. The sealant composition according to claim 1, wherein the hydrocarbon resin is at least one selected from the group consisting of petroleum-based resins, styrene-based resins, and terpene-based resins.

3. A pneumatic tire having a sealant layer formed on an inner surface of the tire using the sealant composition according to claim 1 or 2.

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