Sealant composition and tire using same

Abstract

To provide a solution to a problem of sealing property to a through hole formed when a foreign matter such as a nail is stuck to a tread section.SOLUTION: The above problem was solved by a sealant material composition which is a sealant material composition constituting a sealant layer of a pneumatic tire having a sealant layer on an inner surface of the tire, comprising a rubber component, a tackifier, a plasticizer and a cross-linking component, and having an adhesive strength to steel materials of 12 N or more.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] A pneumatic tire is known in which a sealant layer is provided on the radially inner side of an inner liner layer in a tread portion of the tire. In such a pneumatic tire, when a foreign object such as a nail penetrates the tread portion, the sealant material flows into the through hole, thereby exerting a sealing property, suppressing a decrease in air pressure, and enabling the tire to continue running.

[0003] It is known that the improvement of the sealing property can be generally achieved by using butyl rubber as the rubber component and blending a large amount of plasticizer to reduce the viscosity of the sealant and make it easier for the sealant to flow into the through holes. For example, the following patent document discloses a sealant composition for forming a sealant layer of a pneumatic tire having a sealant layer on the inner surface of the tire, characterized in that 1 to 40 parts by mass of a crosslinking aid, 50 to 400 parts by mass of a liquid isobutylene-isoprene copolymer having a molecular weight of 10,000 to 60,000, and 1 to 40 parts by mass of an organic peroxide are blended with 100 parts by mass of halogenated butyl rubber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6583456 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a sealant material composition which can provide a more improved sealing performance for a through hole formed when a foreign object such as a nail penetrates a tread portion than that of the prior art. [Means for solving the problem]

[0006] As a result of extensive research, the inventors have discovered that a sealant composition containing a rubber component, a tackifier, a plasticizer and a cross-linking component, and having an adhesive strength to steel materials set to a specific value or greater, can solve the above-mentioned problems, and have thus completed the present invention.

[0007] The present invention provides a sealant material composition that constitutes a sealant layer of a pneumatic tire having a sealant layer on the inner surface of the tire, the sealant material composition comprising a rubber component, a tackifier, a plasticizer and a crosslinking component, and having an adhesive strength to steel materials of 12 N or more. Effect of the Invention

[0008] The sealant composition of the present invention contains a rubber component, a tackifier, a plasticizer, and a cross-linking component, and is characterized by having an adhesive strength to steel materials of 12 N or more. According to the above configuration, even if the viscosity of the sealant composition is high, the sealability against a through hole formed when a foreign object such as a nail penetrates the tread portion can be sufficiently improved compared to the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will now be described in further detail. (Rubber component) Examples of the rubber component used in the present invention include diene rubbers such as natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene-diene terpolymer (EPDM), and butyl rubber. These may be used alone or in combination of two or more. Among these, from the viewpoint of improving the effects of the present invention, the rubber component is preferably NR, IR, SBR, BR or a blend thereof.

[0010] (tackifier) The tackifier used in the present invention may, for example, be a hydrocarbon resin. Examples of hydrocarbon resins include petroleum-based resins such as aromatic hydrocarbon resins produced by polymerizing components obtained by processing crude oil such as distillation, cracking, and modification, or saturated or unsaturated aliphatic hydrocarbon resins. Examples of petroleum-based resins include C5 petroleum resins (aliphatic petroleum resins polymerized from fractions such as isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, and pentene), C9 petroleum resins (aromatic petroleum resins polymerized from fractions such as α-methylstyrene, o-vinyltoluene, m-vinyltoluene, and p-vinyltoluene), and C5C9 copolymer petroleum resins.

[0011] The glass transition temperature (Tg) of the tackifier is preferably higher than 0° C. By specifying Tg in this manner, flowability is improved. The glass transition temperature (Tg) referred to in the present invention refers to the midpoint temperature of the transition region measured by differential scanning calorimetry (DSC) at a temperature rise rate of 20° C. / min. More preferably, the Tg is 30° C. or higher and 90° C. or lower. The number average molecular weight of the tackifier is preferably 400 to 2000. By having the number average molecular weight in this range, the adhesive strength is improved.

[0012] (Plasticizer) Examples of the plasticizer used in the present invention include carboxylate plasticizers, phosphate plasticizers, sulfonate plasticizers, oils, and liquid rubbers. Examples of the carboxylate plasticizer include known phthalates, isophthalates, tetrahydrophthalates, adipates, maleates, fumarate, trimellitates, linoleates, oleates, stearates, and ricinoleates. Examples of the phosphate plasticizer include known trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri-(2-ethylhexyl) phosphate, 2-ethylhexyl diphenyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, isodecyl diphenyl phosphate, tricresyl phosphate, tritolyl phosphate, trixylenyl phosphate, tris(chloroethyl) phosphate, and diphenyl mono-o-xenyl phosphate. The sulfonate ester plasticizers include known benzenesulfonylamide, toluene Sulfonamide, N-ethyl-toluenesulfonamide, N-cyclohexyl-p-toluenesulfonamide, etc. Examples of the oil include mineral oils such as known paraffin-based process oil, naphthene-based process oil, and aromatic process oil. Examples of liquid rubber include liquid polyisoprene, liquid polybutadiene, and liquid polystyrene butadiene, and the weight average molecular weight is preferably 1000 to 100000, and more preferably 1500 to 75000. The average molecular weight in the present invention means a number or weight average molecular weight converted into polystyrene analyzed by gel permeation chromatography (GPC). The liquid rubber used in the present invention is liquid at 23°C. Therefore, it is distinguished from the above-mentioned rubber component that is solid at this temperature. Among the above, from the viewpoint of improving the effects of the present invention, oil or liquid rubber is preferred as the plasticizer.

[0013] (crosslinking component) Examples of the crosslinking component used in the present invention include sulfur and vulcanization accelerators, which are components that improve sealing properties. Examples of the vulcanization accelerator used in the present invention include known guanidine-based, thiazole-based, sulfenamide-based, thiourea-based, dithiocarbamate-based, xanthogenate-based, and thiuram-based vulcanization accelerators, and among these, one or more types selected from thiazole-based vulcanization accelerators, sulfenamide-based vulcanization accelerators, thiourea-based vulcanization accelerators, and thiuram-based vulcanization accelerators are preferred.

[0014] (Mixing ratio of sealant composition) In a preferred embodiment, the sealant composition of the present invention comprises 100 parts by mass of the rubber component, and contains less than 30 parts by mass of a tackifier, 20 to 150 parts by mass of a plasticizer, 0.1 to 10 parts by mass of sulfur, and 0.1 to 10 parts by mass of a vulcanization accelerator. When the amount of the tackifier is less than 30 parts by mass per 100 parts by mass of the rubber component, the effects of the present invention are enhanced, and the viscosity temperature dependency and storage stability of the sealant composition are improved. The amount of the tackifier is preferably 1 to 29 parts by mass, and more preferably 10 to 29 parts by mass. In an embodiment different from the above, from the viewpoint of improving the adhesive strength between the nail or the like and the tackifier, the tackifier may be blended in an amount of more than 90 parts by mass per 100 parts by mass of the rubber component. In this embodiment, the amount of the tackifier is preferably more than 90 parts by mass and not more than 150 parts by mass. When the blending amount of the plasticizer is 20 parts by mass or more per 100 parts by mass of the rubber component, the sealing property is further improved. On the other hand, when the blending amount of the plasticizer is 150 parts by mass or less, the adhesive strength to the steel material is increased. The blending amount of the plasticizer is more preferably 30 to 90 parts by mass. In addition, when the blending amount of sulfur or vulcanization accelerator is in the range of 0.1 to 10 parts by mass, the sealant material composition of the present invention can be dynamically crosslinked when sulfur is blended as a crosslinking component.

[0015] (Other ingredients) The sealant material composition of the present invention may contain various additives other than the above-mentioned components, such as a vulcanizing or crosslinking agent, a vulcanizing or crosslinking accelerator, zinc oxide, an antiaging agent, and carbon black. Such additives may be kneaded to form a composition by a general method, and the amounts of these additives may be conventionally used as long as they do not go against the object of the present invention.

[0016] The sealant composition of the present invention preferably has a complex viscosity of 1000 Pa·s or more at 30° C. By having a complex viscosity of 1000 Pa·s or more at 30° C., the sealant composition does not flow excessively, exhibits excellent flowability, and can prevent deterioration of sealing properties. The complex viscosity at 30° C. is preferably 3000 to 15000 Pa·s, and more preferably 5000 to 10000 Pa·s. The complex viscosity can be measured by the method described in ASTM D4440.

[0017] The sealant composition of the present invention must have an adhesive strength to ferrous materials of 12 N or more. By having an adhesive strength to ferrous materials of 12 N or more, even if the complex viscosity of the sealant composition is as high as described above, the sealant composition can have a sufficiently improved sealing performance against a through hole formed when a foreign object such as a nail penetrates the tread portion, as compared to the prior art. On the other hand, if the adhesive strength is less than 12 N, the sealant composition cannot exhibit sufficient sealing performance. In the present invention, the adhesive strength of the sealant composition to ferrous materials means the adhesive strength of the sealant composition to ferrous materials after vulcanization. The adhesive strength to the ferrous material is preferably 12 to 25N, and more preferably 15 to 20N. The adhesive strength can be measured using a Picmataq tester manufactured by Toyo Seiki Seisakusho Co., Ltd. The measurement conditions are as follows. Contact crimp force: 4.9N Crimping time: 10 seconds Crimping speed: 50cm / min Peeling speed: 125cm / min Other side: Steel material (carbon concentration can be in the normal range, for example, 0.0218-2.14%)

[0018] The sealant composition of the present invention can be provided as a sealant layer on the tire radial inner side of the inner liner layer in the tread portion of a pneumatic tire. The sealant layer can be formed by vulcanizing the sealant made of the sealant composition of the present invention, molding it into a sheet, and attaching it to the entire circumference of the inner surface of the tire. Alternatively, the sealant layer can be formed by vulcanizing the sealant, molding it into a string or strip, and attaching it in a spiral shape to the inner surface of the tire. When a foreign object such as a nail penetrates the tread portion, the sealant constituting the sealant layer flows into the through hole, thereby suppressing the decrease in air pressure and enabling the vehicle to continue running. The sealant layer has a thickness of, for example, 0.5 mm to 5.0 mm. EXAMPLES

[0019] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, "parts" means "parts by mass".

[0020] Examples 1 to 5 and Comparative Example 1 A sealant composition was obtained by kneading the components (parts by mass) shown in Table 1 for 40 minutes in a 1.7-liter closed Banbury mixer. The resulting sealant composition was then press-vulcanized in a specified mold at 180°C for 10 minutes to obtain a sealant having a thickness of 3 mm.

[0021] The adhesive strength of the sealant composition obtained above was measured by the method described above. The complex viscosity at 30° C. of the sealant composition obtained above was measured by the method described above.

[0022] A test tire was manufactured by attaching the above sealant material to a pneumatic tire having a tire size of 215 / 55R17, a tread portion, a pair of sidewall portions, and a pair of bead portions, and having a sealant layer made of a sealant on the tire radial direction inside of the inner liner layer in the tread portion. The following physical properties were measured for the test tire obtained.

[0023] Sealability: The test tire was mounted on a wheel with a rim size of 17x7J, the initial air pressure was set to 250kPa, a 4mm nail was driven into the tread, and after removing it, the tire was left for one hour and the air pressure was then measured. The evaluation results were shown as follows: if the air pressure after leaving it was between 230kPa and 250kPa, it was indicated with "◯", if the air pressure after leaving it was between 200kPa and 230kPa, it was indicated with "△", and if the air pressure after leaving it was less than 200kPa, it was indicated with "X".

[0024] The results are shown in Table 1.

[0025] [Table 1]

[0026] *1:NR(SIR20) *2: SBR (Nipol 1502 manufactured by Zeon Corporation) *3: Tackifier (T-REZ RC115, C5 petroleum resin, manufactured by ENEOS Corporation) *4: Plasticizer (Diana Process Oil NP250 (naphthenic process oil) manufactured by Idemitsu Kosan Co., Ltd.) *5: Sulfur (Kinka-jirushi oil-filled fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.) *6: Vulcanization accelerator DM-PO (Sansera DM-PO manufactured by Sanshin Chemical Industry Co., Ltd.)

[0027] As can be seen from the results in Table 1, the sealant composition of each Example contained a rubber component, a tackifier, a plasticizer and a crosslinking component, and had an adhesive strength of 12 N or more to steel materials, and therefore exhibited excellent sealing properties. In contrast, in Comparative Example 1, the adhesive strength to the steel material was 9.4 N, which is below the lower limit defined by the present invention, and therefore the sealing performance was deteriorated.

Claims

1. A sealant material composition constituting a sealant layer of a pneumatic tire having a sealant layer on an inner surface of the tire, comprising: Contains a rubber component, a tackifier, a plasticizer and a crosslinking component, The adhesive strength to steel materials is 12N or more, The rubber component is natural rubber, synthetic isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, or a blend thereof; The crosslinking component includes a vulcanization accelerator, and the vulcanization accelerator is at least one selected from a thiazole-based vulcanization accelerator, a sulfenamide-based vulcanization accelerator, a thiourea-based vulcanization accelerator, and a thiuram-based vulcanization accelerator. A sealant material composition comprising:

2. 2. The sealant material composition according to claim 1, wherein the complex viscosity at 30° C. is 1,000 Pa·s or more.

3. 3. The sealant material composition according to claim 1, wherein the tackifier is a hydrocarbon resin.

4. 4. The sealant composition according to claim 1, wherein the amount of the tackifier is less than 30 parts by mass based on 100 parts by mass of the rubber component.

5. 5. The sealant material composition according to claim 1, wherein the plasticizer is an oil or a liquid rubber.

6. 6. The sealant material composition according to claim 1, wherein the blending amount of the plasticizer is 20 to 150 parts by mass based on 100 parts by mass of the rubber component.

7. 7. The sealant material composition according to claim 1, wherein the crosslinking component contains sulfur and a vulcanization accelerator.

8. 8. The sealant composition according to claim 7, wherein the amount of the sulfur is 0.1 to 10 parts by mass based on 100 parts by mass of the rubber component.

9. A tire using the sealant material composition according to any one of claims 1 to 8.

Images