Sealant material composition and tire using same

Abstract

The present invention provides a sealant material composition which constitutes a sealant layer of a pneumatic tire that is provided with the sealant layer on the inner surface of the tire. This sealant material composition is characterized by containing (A) a rubber component which is composed of 50-100 parts by mass of a natural rubber and / or a synthetic isoprene rubber, and 0-50 parts by mass of a styrene-butadiene copolymer rubber, a butadiene rubber, or a mixture thereof, (B) a vulcanization accelerator, and (C) sulfur, and is also characterized in that the ((B) vulcanization accelerator) / ((C) sulfur) ratio (mass ratio) is 2.5 or more.

Description

Sealant composition and tire using same

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

[0002] There is known a pneumatic tire having a sealant layer provided radially inward of an inner liner layer in the tread portion of the tire. In such a pneumatic tire, when a foreign object such as a nail penetrates the tread portion, the sealant composition flows into the through-hole, thereby providing a seal and preventing a decrease in air pressure, thereby enabling the tire to continue running. Examples of such sealant compositions are disclosed in Patent Documents 1 to 4 listed below.

[0003] Patent No. 5646474 Patent No. 5651109 Patent No. 5525522 Patent No. 5738897

[0004] The sealant composition is required to have flowability that ensures sealing performance and not peel off due to deterioration caused by driving. It has been found that peeling occurs when deterioration progresses as the sealant composition hardens due to crosslinking, reducing adhesive strength and causing shrinkage of the sealant composition. However, the prior art has room for improvement in terms of flowability at the initial stage or after deterioration, and in preventing peeling. The present invention aims to solve the above problems and provide a sealant composition that ensures appropriate flowability at the initial stage or after deterioration and can sufficiently prevent peeling after deterioration, as well as a tire using the same.

[0005] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by a sealant composition in which a vulcanization accelerator and sulfur are blended with a rubber component having a specific composition, and the blending ratio of the vulcanization accelerator and the sulfur is specified, thereby completing the present invention.

[0006] That is, the present invention provides a sealant material composition for constituting a sealant layer of a pneumatic tire having a sealant layer on the inner surface of the tire, the sealant material composition comprising: (A) a rubber component consisting of 50 to 100 parts by mass of natural rubber and / or synthetic isoprene rubber, and 0 to 50 parts by mass of a styrene-butadiene copolymer rubber, a butadiene rubber, or a mixture thereof; (B) a vulcanization accelerator; and (C) sulfur, wherein the (B) vulcanization accelerator / (C) sulfur (mass ratio) is 2.5 or more.

[0007] The sealant composition of the present invention comprises a rubber component consisting of 50 to 100 parts by mass of (A) natural rubber and / or synthetic isoprene rubber, and 0 to 50 parts by mass of styrene-butadiene copolymer rubber, butadiene rubber, or a mixture thereof, blended with (B) a vulcanization accelerator and (C) sulfur, with the (B) vulcanization accelerator / (C) sulfur (mass ratio) set to 2.5 or greater. By setting the (B) vulcanization accelerator / (C) sulfur (mass ratio) to 2.5 or greater, appropriate flowability is ensured, both initially and after deterioration. Furthermore, even if the sealant composition progresses in hardening due to crosslinking over time, for example, the softness of the natural rubber and / or synthetic isoprene rubber, which is the primary component of the (A) rubber component, compensates for the hardening due to crosslinking. As a result, the sealant composition is presumably able to suppress a decrease in adhesion and shrinkage, and to adequately suppress peeling after deterioration.

[0008] The present invention will be described in further detail below. (A) Rubber Component The (A) rubber component used in the present invention is primarily composed of natural rubber (NR) and / or synthetic isoprene rubber (IR). The (A) rubber component can also contain styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), or a mixture thereof. The (A) rubber component may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, or hydroxyl group, or may be epoxidized. The weight-average molecular weight (Mw) of the (A) rubber component is not particularly limited, but is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000, to achieve superior effects of the present invention. In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated as standard polystyrene obtained by gel permeation chromatography (GPC) measurement.

[0009] The rubber component (A) used in the present invention contains 50 to 100 parts by mass, preferably 50 to 80 parts by mass, of NR and / or IR, and 0 to 50 parts by mass, preferably 20 to 50 parts by mass, of SBR, BR, or a mixture thereof, based on 100 parts by mass of the entire rubber component (A).

[0010] (B) Vulcanization Accelerator and (C) Sulfur Examples of the (B) vulcanization accelerator used in the present invention include known sulfenamide, thiazole, guanidine, thiourea, dithiocarbamate, xanthogenate, and thiuram vulcanization accelerators, and among these, from the viewpoint of improving the effects of the present invention, one or more selected from sulfenamide vulcanization accelerators and thiazole vulcanization accelerators are preferred. The sealant composition of the present invention is also capable of dynamic crosslinking because it contains (C) sulfur.

[0011] (Ratio of Compounding in Sealant Composition) In the sealant composition of the present invention, the compounding amount of the (B) vulcanization accelerator is, for example, 1 to 5 parts by mass, preferably 1 to 4 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the (A) rubber component. In the sealant composition of the present invention, the compounding amount of the (C) sulfur is, for example, less than 0.5 parts by mass, preferably 0.1 to 0.4 parts by mass, and more preferably 0.15 to 0.3 parts by mass, per 100 parts by mass of the (A) rubber component. In the sealant composition of the present invention, the (B) vulcanization accelerator / (C) sulfur (mass ratio) must be 2.5 or more. If this ratio is less than 2.5, it is difficult to ensure appropriate flowability initially or after aging, and it is difficult to sufficiently suppress peeling after aging. The (B) vulcanization accelerator / (C) sulfur (mass ratio) is preferably 5 or more, more preferably 10 or more, and particularly preferably 10 to 20. When the blending ratio is within the preferred range, the effects of the present invention are more effectively exhibited.

[0012] From the viewpoint of improving the effect, the sealant composition of the present invention preferably contains magnesium oxide, and the BET specific surface area of ​​the magnesium oxide is 20 to 200 m ２ / g. The BET specific surface area of ​​magnesium oxide is the specific surface area of ​​magnesium oxide measured by nitrogen gas adsorption according to the single-point method of JIS Z8830. The compounding amount of the magnesium oxide is, for example, less than 1.0 part by mass, and preferably 0.1 to 0.5 parts by mass, per 100 parts by mass of the rubber component (A).

[0013] The sealant composition of the present invention may preferably contain a tackifier. Examples of tackifiers include hydrocarbon resins. Examples of hydrocarbon resins include petroleum-based resins, such as aromatic hydrocarbon resins produced by polymerizing components obtained by processes such as distillation, cracking, and modification of crude oil, and saturated or unsaturated aliphatic hydrocarbon resins. Examples of petroleum-based resins include C5 petroleum resins (aliphatic petroleum resins obtained by polymerizing fractions such as isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, and pentene), C9 petroleum resins (aromatic petroleum resins obtained by polymerizing fractions such as α-methylstyrene, o-vinyltoluene, m-vinyltoluene, and p-vinyltoluene), and C5C9 copolymer petroleum resins. Furthermore, the glass transition temperature (Tg) of the hydrocarbon resin is preferably higher than 0°C. By specifying the Tg in this way, flowability is improved. The glass transition temperature (Tg) referred to in the present invention refers to the temperature at the midpoint of the transition region when a thermogram is measured by differential scanning calorimetry (DSC) at a heating rate of 20°C / min. A more preferred Tg is 30°C or higher and 90°C or lower. The number average molecular weight of the hydrocarbon resin is preferably 400 to 2,000. Having a number average molecular weight within this range improves adhesive strength. The blending amount of the hydrocarbon resin is preferably 10 to 90 parts by mass, more preferably 20 to 60 parts by mass, per 100 parts by mass of the (A) rubber component.

[0014] The sealant composition of the present invention may preferably contain an inorganic filler. Examples of the inorganic filler include one or more selected from calcium carbonate, talc, and clay. The amount of the inorganic filler is preferably 1 to 20 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the rubber component (A).

[0015] (Other Components) The sealant composition of the present invention may contain various additives other than those described above, such as vulcanizing or crosslinking agents, vulcanizing or crosslinking accelerators, zinc oxide, antioxidants, and plasticizers. These additives can be kneaded into a composition by a conventional method, and the amounts of these additives may be conventional amounts as long as they do not deviate from the object of the present invention. When a plasticizer is added, the amount is preferably 20 to 90 parts by mass per 100 parts by mass of the rubber component (A).

[0016] The sealant composition of the present invention can be applied as a sealant layer on the radially inner side of the inner liner layer in the tread portion of a pneumatic tire. The sealant layer can be formed by applying a sealant composed of the sealant composition of the present invention molded into a sheet around the entire circumference of the tire's inner surface. Alternatively, the sealant layer can be formed by applying a sealant composed of the sealant composition of the present invention molded into a string or strip shape to the tire's inner surface in a spiral shape. The sealant can be a vulcanizate. When a foreign object such as a nail penetrates the tread portion, the sealant constituting the sealant layer flows into the hole, thereby suppressing a decrease in air pressure and enabling the vehicle to continue driving. The sealant layer has a thickness of, for example, 0.5 mm to 5.0 mm.

[0017] 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."

[0018] Examples 1 to 15 and Comparative Examples 1 to 2: The formulations (parts by mass) shown in Table 1 were kneaded in a 1.7-liter internal Banbury mixer for 40 minutes to obtain a rubber composition. The obtained rubber composition was then press-vulcanized in a specified mold at 180°C for 10 minutes to obtain a sealant material with a thickness of 3 mm. Hereinafter, the obtained sealant material will be referred to as the initial sealant material. The initial sealant material obtained above was also subjected to moist heat aging under the following conditions. Hereinafter, the obtained sealant material will be referred to as the sealant material after moist heat aging. Moisture aging conditions: temperature 70°C, relative humidity 96%, period 30 days. The following properties were examined for the initial sealant material and the sealant material after moist heat aging.

[0019] Flowability (Creep) Creep measurements were carried out under the following conditions. Measuring device: ARES-G2 dynamic viscoelasticity measuring instrument manufactured by TA Instruments Jig: 8 mm diameter parallel plate Sample thickness: 1.2 mm Shear stress: 3000 Pa Time: 60 minutes If the creep is 100 or less, the degree of hardening is large, the flowability decreases, and sealing properties cannot be maintained. On the other hand, if the creep is 9000 or more, there is excessive flowability, causing problems such as flowing toward the center of the tire tread width direction during driving. The unit of creep is %.

[0020]

[0043] Flowability and Peeling Property (Evaluation on Actual Vehicle)

[0044] In a pneumatic tire having a tire size of 215 / 55R17, including a tread portion, a pair of sidewall portions, and a pair of bead portions, and having a sealant layer made of a sealant material on the tire radially inner side of the inner liner layer in the tread portion, the above sealant material was applied as the sealant layer to produce various test tires. The following tests were carried out on the obtained test tires. The test tire immediately after production is called the initial test tire, and the test tire that was subjected to the aging treatment under the above-mentioned humid heat aging conditions is called the humid heat aged test tire.

[0021] Flowability (Evaluation on Actual Vehicle) Test tires were mounted on wheels with a rim size of 17x7J and mounted on a drum testing machine. A high-deflection test was performed for 80 hours under conditions of an air pressure of 160 kPa, a load of 8.5 kN, and a running speed of 80 km / h. The flow and peeling states of the sealant were then examined. The evaluation results were evaluated as flowing when the thickness of the 3 mm sealant at each position from the sealant edge was 1.5 mm or less after the test. A case in which no flow was observed at a position 0.5 cm from the sealant edge was indicated by "◎", a case in which no flow was observed at a position 1 cm from the sealant edge was indicated by "◯", a case in which flow was observed at a position 1 cm from the sealant edge but not at a position 2 cm from the sealant edge was indicated by "△", and a case in which flow was observed at a position 2 cm from the sealant edge was indicated by "X".

[0022] Peeling property After the flowability test (evaluation on an actual vehicle), the sealant was visually inspected for peeling. Peeling property was evaluated for the test tires after aging under moist heat.

[0023] The results are shown in Table 1.

[0024]

[0025] *1: NR (SIR20) *2: SBR (Nipol 1502 manufactured by Nippon Zeon Co., Ltd.) *3: Hydrocarbon resin (T-REZ RC115 manufactured by ENEOS Corporation, C5 petroleum resin) *4: Naphthenic oil (Diana Process Oil NP250 (naphthenic process oil) manufactured by Idemitsu Kosan Co., Ltd.) *5: Sulfur (Kinka-ji oil-containing fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.) *6: Sulfenamide vulcanization accelerator CZ (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *7: Sulfenamide vulcanization accelerator NS (trade name Noccela NS-P manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *8: Thiazole vulcanization accelerator DM (Suncerer DM-PO manufactured by Sanshin Chemical Industry Co., Ltd.) *9: Calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) *10: Magnesium oxide-1 (Kyowamag 30 manufactured by Kyowa Chemical Industry Co., Ltd., BET specific surface area = 42 m ２ / g) *11: Magnesium oxide-2 (Kyowamag 150 manufactured by Kyowa Chemical Industry Co., Ltd., BET specific surface area = 144 m ２ / g)

[0026] The results in Table 1 indicate that the sealant compositions of each Example contained a rubber component consisting of (A) 50 to 100 parts by mass of natural rubber and / or synthetic isoprene rubber, and 0 to 50 parts by mass of styrene-butadiene copolymer rubber, butadiene rubber, or a mixture thereof, (B) a vulcanization accelerator, and (C) sulfur. Since the (B) vulcanization accelerator / (C) sulfur (mass ratio) was 2.5 or higher, appropriate flow properties were ensured initially and after aging, and peeling after aging was sufficiently suppressed. In contrast, in Comparative Example 1, the (B) vulcanization accelerator / (C) sulfur (mass ratio) was 2.0, so flow properties deteriorated after moist heat aging in an actual vehicle test, and peeling of the sealant was also observed after moist heat aging. In Comparative Example 2, the (B) vulcanization accelerator / (C) sulfur (mass ratio) was 1.7, so the initial sealant flow properties deteriorated in both creep and actual vehicle tests.

[0027] The present invention includes the following embodiments. Embodiment 1: A sealant material composition for forming a sealant layer of a pneumatic tire provided on the inner surface of the tire, the sealant material composition comprising: (A) a rubber component consisting of 50 to 100 parts by mass of natural rubber and / or synthetic isoprene rubber, and 0 to 50 parts by mass of a styrene-butadiene copolymer rubber, a butadiene rubber, or a mixture thereof; (B) a vulcanization accelerator; and (C) sulfur, wherein the (B) vulcanization accelerator / (C) sulfur (mass ratio) is 2.5 or more. Embodiment 2: The sealant material composition according to Embodiment 1, wherein the (B) vulcanization accelerator is a sulfenamide-based and / or thiazole-based vulcanization accelerator. Embodiment 3: The sealant material composition according to Embodiment 1 or 2, wherein the (B) vulcanization accelerator / (C) sulfur (mass ratio) is 5 or more. Embodiment 4: The sealant material composition according to any one of Embodiments 1 to 3, wherein the (B) vulcanization accelerator / (C) sulfur (mass ratio) is 10 or more. Embodiment 5: The sealant material composition according to any one of Embodiments 1 to 4, further comprising magnesium oxide, wherein the amount of the magnesium oxide blended is less than 1.0 part by mass per 100 parts by mass of the rubber component.Embodiment 6: The sealant material composition according to any one of Embodiments 1 to 5, wherein the amount of the (C) sulfur blended is less than 0.5 parts by mass per 100 parts by mass of the rubber component.Embodiment 7: The sealant material composition according to any one of Embodiments 1 to 6, further comprising a hydrocarbon resin as a tackifier, wherein the amount of the hydrocarbon resin blended is 10 to 90 parts by mass per 100 parts by mass of the (A) rubber component.Embodiment 8: The sealant material composition according to any one of Embodiments 1 to 7, further comprising one or more inorganic fillers selected from calcium carbonate, talc, and clay.Embodiment 9: The sealant composition according to any one of Embodiments 1 to 8, wherein the (A) rubber component comprises, based on 100 parts by mass of the entire rubber component, 50 to 80 parts by mass of natural rubber and / or synthetic isoprene rubber, and 20 to 50 parts by mass of styrene-butadiene copolymer rubber, butadiene rubber, or a mixture thereof.Embodiment 10: The sealant composition according to any one of Embodiments 1 to 9, wherein the (B) vulcanization accelerator is a sulfenamide vulcanization accelerator.Embodiment 11: The sealant composition further comprises magnesium oxide, the magnesium oxide having a BET specific surface area of ​​20 to 200 m. ２ / g. Embodiment 12: The sealant material composition according to any one of embodiments 1 to 11, further comprising a hydrocarbon resin as a tackifier, wherein the hydrocarbon resin is a petroleum-based resin. Embodiment 13: A tire using the sealant material composition according to any one of embodiments 1 to 12.

Claims

1. A sealant material composition for forming a sealant layer of a pneumatic tire having a sealant layer on the inner surface of the tire, comprising: (A) a rubber component consisting of 50 to 100 parts by mass of natural rubber and / or synthetic isoprene rubber, and 0 to 50 parts by mass of styrene-butadiene copolymer rubber, butadiene rubber or a mixture thereof; (B) a vulcanization accelerator; and (C) sulfur, wherein the ratio of (B) vulcanization accelerator / (C) sulfur (mass ratio) is 2.5 or more. The sealant material composition is characterized by this.

2. The sealant material composition according to claim 1, wherein the (B) vulcanization accelerator is a sulfenamide-based and / or thiazole-based vulcanization accelerator.

3. The sealant material composition according to claim 1, wherein the ratio of (B) vulcanization accelerator / (C) sulfur (mass ratio) is 5 or more.

4. The sealant material composition according to claim 1, wherein the ratio of (B) vulcanization accelerator / (C) sulfur (mass ratio) is 10 or more.

5. The sealant material composition according to claim 1, wherein the sealant material composition further contains magnesium oxide, and the blending amount of the magnesium oxide is less than 1.0 part by mass with respect to 100 parts by mass of the rubber component.

6. The sealant material composition according to claim 1, wherein the blending amount of the (C) sulfur is less than 0.5 part by mass with respect to 100 parts by mass of the rubber component.

7. The sealant material composition according to claim 1, wherein the sealant material composition further contains a hydrocarbon resin as a tackifier, and the blending amount of the hydrocarbon resin is 10 to 90 parts by mass with respect to 100 parts by mass of the (A) rubber component.

8. The sealant material composition according to claim 1, wherein the sealant material composition further contains at least one selected from calcium carbonate, talc and clay as an inorganic filler.

9. The sealant material composition according to claim 1, wherein when the total of the (A) rubber component is 100 parts by mass, natural rubber and / or synthetic isoprene rubber is 50 to 80 parts by mass, and styrene-butadiene copolymer rubber, butadiene rubber or a mixture thereof is 20 to 50 parts by mass.

10. The sealant material composition according to claim 1, wherein the (B) vulcanization accelerator is a sulfenamide-based vulcanization accelerator.

11. The sealant material composition further contains magnesium oxide, and the BET specific surface area of the magnesium oxide is 20 to 200 m ２ / g. The sealant material composition according to claim 1, characterized in that.

12. The sealant composition according to claim 1, further comprising a hydrocarbon resin as a tackifier, wherein the hydrocarbon resin is a petroleum resin.

13. A tire using the sealant composition according to claim 1.

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