Sealant material composition and tire using the same

Abstract

To solve the problems in prior art about sealability with respect to a through hole formed when a foreign matter, such as a nail, sticks into a tread part, and peeling of a sealant material after being subjected to deterioration.SOLUTION: A sealant material composition includes: (A) a rubber composition composed of 50-100 pts.mass of natural rubber and / or synthetic isoprene rubber and 0-50 pts.mass of styrene-butadiene copolymer rubber, butadiene rubber, or a mixture of these; (B) a vulcanization accelerator; and (C) sulfur, where the (B) vulcanization accelerator / the (C) sulfur (mass ratio) is 2.5 or more.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In a pneumatic tire, a pneumatic tire having a sealant layer provided on the inner diameter side in the tire radial direction of the inner liner layer in the tread portion is known. In such a pneumatic tire, when a foreign object such as a nail pierces the tread portion, the sealant material composition flows into the through hole, thereby exhibiting a sealing property, suppressing a decrease in air pressure, and enabling driving to be maintained. Examples of the sealant material composition are disclosed in Patent Documents 1 to 4 below.

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] The sealant material composition is required to have fluidity for ensuring sealing performance and not to peel off due to deterioration during driving. It has been found that the peeling occurs due to the progress of curing by crosslinking of the sealant material composition due to deterioration, a decrease in adhesive force, and shrinkage of the sealant material composition. However, in the prior art, there is room for improvement in the fluidity in the initial stage or after deterioration and the peeling. The present invention aims to solve the above problems, ensure appropriate fluidity in the initial stage or after deterioration, and sufficiently suppress peeling after deterioration, and provides a sealant material composition and a tire using the same.

Means for Solving the Problems

[0005] As a result of intensive research, the inventors of the present invention have found that a sealant material 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 can solve the above problems, and thus the present invention has been completed.

[0006] That is, the present invention is a sealant material composition constituting the sealant layer of a pneumatic tire having a sealant layer on the inner surface of the tire, (A) A rubber component composed 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, butadiene rubber or a mixture thereof, (B) A vulcanization accelerator, and (C) Sulfur are included, and the (B) vulcanization accelerator / the (C) sulfur (mass ratio) is 2.5 or more. The present invention provides a sealant material composition characterized by the above.

Effects of the Invention

[0007] The sealant material composition of the present invention comprises, based on 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, and sets the ratio of the (B) vulcanization accelerator to the (C) sulfur (mass ratio) to 2.5 or more. By setting the ratio of the (B) vulcanization accelerator to the (C) sulfur (mass ratio) to 2.5 or more, appropriate fluidity at the initial stage or after deterioration is ensured. Further, for example, even if the curing due to crosslinking of the sealant material composition progresses with aging deterioration, the softness of the natural rubber and / or synthetic isoprene rubber, which is the main component of the (A) rubber component, compensates for the curing due to the crosslinking, and as a result, it is presumed that the reduction in the adhesive force and shrinkage of the sealant material composition can be suppressed, and peeling after deterioration can be sufficiently suppressed.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the present invention will be described in more detail. (A) Rubber component The (A) rubber component used in the present invention is mainly composed of natural rubber (NR) and / or synthetic isoprene rubber (IR). Further, the (A) rubber component can also be blended with styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), or a mixture thereof. Further, the (A) rubber component may be end-modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, etc., or may be epoxidized. The weight average molecular weight (Mw) of the (A) rubber component is not particularly limited, but for reasons such as more excellent effects of the present invention, it 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. In this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are standard polystyrene conversion values obtained by gel permeation chromatography (GPC) measurement.

[0009] The rubber component (A) used in the present invention is composed of 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 in total.

[0010] (B) Vulcanization accelerator and (C) sulfur Examples of the vulcanization accelerator (B) used in the present invention include known sulfenamide - type, thiazole - type, guanidine - type, thiourea - type, dithiocarbamate - type, xanthate - type, and thiuram - type vulcanization accelerators. Among them, from the viewpoint of improving the effects of the present invention, one or more selected from sulfenamide - type vulcanization accelerators and thiazole - type vulcanization accelerators are preferred. Since the sealant material composition of the present invention contains (C) sulfur, it is also possible to perform dynamic cross - linking.

[0011] (Mixing ratio of the sealant material composition) In the sealant material composition of the present invention, the blending amount of the vulcanization accelerator (B) 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, based on 100 parts by mass of the rubber component (A). Also, in the sealant material composition of the present invention, the blending amount of sulfur (C) 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, based on 100 parts by mass of the rubber component (A). In addition, in the sealant material composition of the present invention, it is necessary that the (B) vulcanization accelerator / (C) sulfur (mass ratio) is 2.5 or more. If the ratio is less than 2.5, it is impossible to sufficiently achieve ensuring appropriate fluidity at the initial stage or after deterioration and suppressing peeling after deterioration. The (B) vulcanization accelerator / (C) sulfur (mass ratio) is preferably 5 or more, more preferably 10 or more, and particularly preferably 10 to 20. In the preferable range of the above - mentioned mixing ratio, the effects of the present invention are exhibited more favorably.

[0012] From the perspective of improving the effect, it is preferable to blend magnesium oxide in the sealant composition of the present invention, and the BET specific surface area of magnesium oxide is more preferably 20 to 200 m 2 / g. The BET specific surface area of magnesium oxide is the specific surface area of magnesium oxide by adsorption of nitrogen gas, which is measured by the one-point method of JIS Z8830. The blending amount of the magnesium oxide is, for example, less than 1.0 part by mass with respect to 100 parts by mass of the rubber component (A), and preferably 0.1 to 0.5 part by mass.

[0013] As a preferred form, the sealant composition of the present invention can be blended with a tackifier. Examples of the tackifier include hydrocarbon resins. Examples of the hydrocarbon resin include aromatic hydrocarbon resins or petroleum resins such as saturated or unsaturated aliphatic hydrocarbon resins produced by polymerizing components obtained by treating crude oil by distillation, decomposition, reforming, etc. Examples of the petroleum resin include C5 petroleum resin (an aliphatic petroleum resin polymerized from fractions such as isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, and pentene), C9 petroleum resin (an aromatic petroleum resin polymerized from fractions such as α-methylstyrene, o-vinyltoluene, m-vinyltoluene, and p-vinyltoluene), and C5C9 copolymer petroleum resin. Also, the glass transition temperature (Tg) of the hydrocarbon resin is preferably higher than 0°C. By defining Tg in this way, the fluidity is improved. The glass transition temperature (Tg) referred to in the present invention is the temperature at the midpoint of the transition region, where the thermogram is measured by differential scanning calorimetry (DSC) under the condition of a heating rate of 20°C / min. More preferably, the Tg is 30°C or higher and 90°C or lower. Also, the number average molecular weight of the hydrocarbon resin is preferably 400 to 2000. By having a number average molecular weight in this range, the adhesive force is improved. The blending amount of the hydrocarbon resin is preferably 10 to 90 parts by mass with respect to 100 parts by mass of the rubber component (A), and more preferably 20 to 60 parts by mass.

[0014] Further, as a preferred embodiment, the sealant material composition of the present invention can be blended with an inorganic filler. Examples of the inorganic filler include one or more selected from calcium carbonate, talc, and clay. The blending amount of the inorganic filler is preferably 1 to 20 parts by mass, more preferably 5 to 15 parts by mass, based on 100 parts by mass of the rubber component (A).

[0015] (Other components) In the sealant material composition of the present invention, various additives such as vulcanizing or crosslinking agents, vulcanizing or crosslinking accelerators, zinc oxide, anti-aging agents, and plasticizers can be blended in addition to the above-described components. Such additives can be kneaded by a general method to form a composition, and 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. When a plasticizer is blended, it is preferably 20 to 90 parts by mass based on 100 parts by mass of the rubber component (A).

[0016] The sealant material composition of the present invention can be provided as a sealant layer on the inner diameter side in the tire radial direction of the inner liner layer in the tread portion in a pneumatic tire. The sealant layer can be formed by attaching a sealant material made of the sealant material composition of the present invention formed in a sheet shape over the entire circumference of the inner surface of the tire. Alternatively, the sealant layer can also be formed by spirally attaching a sealant material made of the sealant material composition of the present invention and formed in a string shape or a strip shape to the inner surface of the tire. The sealant material can be a vulcanizate. When a foreign object such as a nail pierces the tread portion, the sealant material constituting the sealant layer flows into the through hole, thereby suppressing a decrease in air pressure and enabling driving to be maintained. The sealant layer has a thickness of, for example, 0.5 mm to 5.0 mm.

Examples

[0017] 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. In the following examples, "part(s)" means "part(s) by mass".

[0018] Examples 1 to 15 and Comparative Examples 1 to 2 In the formulation (parts by mass) shown in Table 1, kneading was carried out for 40 minutes using a 1.7-liter sealed Banbury mixer to obtain a rubber composition. Next, the obtained rubber composition was press-vulcanized at 180°C for 10 minutes in a predetermined mold to obtain a sealant material with a thickness of 3 mm. Hereinafter, the obtained sealant material is referred to as the initial sealant material. In addition, the initial sealant material obtained above was subjected to damp heat deterioration under the following conditions. Hereinafter, the obtained sealant material is referred to as the sealant material after damp heat deterioration. Damp heat deterioration 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 damp heat deterioration.

[0019] Flowability (creep) Creep measurement was carried out according to the following conditions. Measuring device: Dynamic viscoelasticity measuring instrument ARES-G2 manufactured by TA Instruments Jig: Parallel plate with a diameter of 8 mm Sample thickness: 1.2 mm Shear stress: 3000 Pa Time: 60 minutes When the creep is 100 or less, the degree of curing is large and the flowability decreases, and the sealing property cannot be maintained. Also, when the creep is 9000 or more, it has excessive flowability and problems such as flowing out toward the center in the width direction of the tire tread during running occur. The unit of creep is %.

[0020] Flowability and peelability (evaluation on actual vehicle) An inflated tire having a tire size of 215 / 55R17, comprising 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 inner side in the tire radial direction of the inner liner layer in the tread portion. Various test tires were manufactured by attaching the sealant material as the sealant layer. The following tests were conducted on the obtained test tires. Note that the test tire immediately after production is called the initial test tire, and the test tire subjected to deterioration treatment under the above wet heat deterioration conditions is called the test tire after wet heat deterioration.

[0021] Flowability (in-vehicle evaluation) The test tire was assembled onto a wheel with a rim size of 17×7J and mounted on a drum tester. A high deflection test was carried out for 80 hours with an air pressure of 160 kPa, a load of 8.5 kN, and a running speed of 80 km / h. After that, the flow state and peeling state of the sealant material were examined. The evaluation result was regarded as "flowed" when the thickness of the 3-mm sealant material became 1.5 mm or less at each position from the end of the sealant material after the test. "◎" was used to indicate the case where no flow was observed at a position 0.5 cm from the end of the sealant, "○" was used to indicate the case where no flow was observed at a position 1 cm from the end of the sealant, "△" was used to indicate the case where flow was observed at a position 1 cm from the end of the sealant and no flow was observed at a position 2 cm, and "×" was used to indicate the case where flow was observed at a position 2 cm from the end of the sealant.

[0022] Peelability After the test of the above flowability (in-vehicle evaluation), the presence or absence of peeling of the sealant material was visually examined. The peelability was examined for the test tire after wet heat deterioration.

[0023] The results are shown in Table 1.

[0024]

Table 1

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

[0026] From the results in Table 1, it was found that the sealant material compositions of each example contain (A) 50 to 100 parts by mass of natural rubber and / or synthetic isoprene rubber, and a rubber component composed of 0 to 50 parts by mass of styrene-butadiene copolymer rubber, butadiene rubber or a mixture thereof, (B) a vulcanization accelerator, and (C) sulfur, and since the (B) vulcanization accelerator / (C) sulfur (mass ratio) is 2.5 or more, appropriate fluidity can be ensured in the initial stage or after deterioration, and peeling after deterioration can also be sufficiently suppressed. In contrast, in Comparative Example 1, since the (B) vulcanization accelerator / (C) sulfur (mass ratio) is 2.0, the fluidity after hygrothermal deterioration in the actual vehicle evaluation deteriorated, and peeling of the sealant material was also observed after hygrothermal deterioration. In Comparative Example 2, since the (B) vulcanization accelerator / (C) sulfur (mass ratio) is 1.7, the fluidity of the initial sealant material deteriorated both in creep and in the actual vehicle evaluation.

[0027] The present invention includes the following embodiments. Embodiment 1: A sealant material composition constituting the sealant layer of a pneumatic tire having a sealant layer on the inner surface of the tire, (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 containing the above, and the (B) vulcanization accelerator / the (C) sulfur (mass ratio) is 2.5 or more A sealant material composition characterized by this. 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 / the (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 / the (C) sulfur (mass ratio) is 10 or more. Embodiment 5: The sealant material composition according to any one of Embodiments 1 to 4, wherein the sealant material composition further contains magnesium oxide, and the compounding amount of the magnesium oxide is less than 1.0 part by mass with respect to 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 compounding amount of the (C) sulfur is less than 0.5 part by mass with respect to 100 parts by mass of the rubber component. Embodiment 7: The sealant material composition according to any one of Embodiments 1 to 6, wherein the sealant material composition further contains a hydrocarbon resin as a tackifier, and the compounding amount of the hydrocarbon resin is 10 to 90 parts by mass with respect to 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 at least one selected from calcium carbonate, talc, and clay as an inorganic filler. Embodiment 9: A tire using the sealant material composition according to any one of Embodiments 1 to 8.

Claims

1. A sealant material composition constituting the sealant layer of a pneumatic tire having a sealant layer on the inner surface of the tire, (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 which contains, and the (B) vulcanization accelerator / the (C) sulfur (mass ratio) is 2.5 or more A sealant material composition 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 (B) vulcanization accelerator / the (C) sulfur (mass ratio) is 5 or more.

4. The sealant material composition according to claim 1, wherein the (B) vulcanization accelerator / the (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 one or more selected from calcium carbonate, talc and clay as an inorganic filler.

9. A tire using the sealant material composition according to claim 1.

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