Sealant composition and tire using the same

Abstract

To address the problem that conventional technology lacks satisfactory sealing performance for a penetration hole formed when a foreign object such as a nail penetrates a tread portion.SOLUTION: A sealant composition comprises: (A) a rubber component composed of natural rubber, synthetic isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, or a mixture thereof; and (B) a hollow body having a true specific gravity of 0.3 or less and an average particle diameter of 20 μm to 200 μm, wherein an amount of the hollow body is 0.1 to 100 pts.mass relative to 100 pts.mass of the rubber component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A known pneumatic tire has 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 exerting sealing properties and suppressing a decrease in air pressure, thereby enabling the tire to continue running. The sealant material compositions are disclosed in, for example, Patent Documents 1 to 4 listed below. Furthermore, Patent Document 5 below discloses a foam sealing compound containing a sealing gel, a resin, and a natural or synthetic rubber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5646474 [Patent Document 2] Patent No. 5651109 [Patent Document 3] Patent No. 5525522 [Patent Document 4] Patent No. 5738897 [Patent Document 5] Special Publication No. 2020-507640 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional technology has room for improvement in sealing performance for through holes formed when a foreign object such as a nail penetrates the tread portion. Specifically, to improve sealing performance, the sealant composition needs to flow into the through holes and have appropriate flow properties so that it does not flow toward the center of the tire tread in the width direction when the tire is running. However, the conventional technology has not been able to meet this requirement, and improvement is needed. An object of the present invention is to provide a sealant composition that can solve the above problems and also reduce road noise by having sound absorption properties, and a tire using the same. [Means for solving the problem]

[0005] As a result of extensive research, the present inventors have discovered that the above-mentioned problems can be solved by a sealant composition in which hollow bodies having specific true specific gravity and average particle size are blended with a rubber component having a specific composition, and have been able to complete the present invention.

[0006] That is, the present invention provides 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 natural rubber, synthetic isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, or a mixture thereof; and (B) A hollow body having a true specific gravity of 0.3 or less and an average particle size of 20 μm to 200 μm. and the amount of the hollow bodies blended relative to 100 parts by mass of the rubber component is 0.1 to 100 parts by mass. The present invention provides a sealant material composition characterized by the above-mentioned. The present invention also provides a tire using the sealant material composition. [Effects of the Invention]

[0007] The sealant composition of the present invention includes (A) a rubber component consisting of natural rubber, synthetic isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, or a mixture thereof, and (B) hollow bodies having a true specific gravity of 0.3 or less and an average particle size of 20 μm to 200 μm. The blending amount of the hollow bodies is 0.1 to 100 parts by mass per 100 parts by mass of the rubber component. This allows the hollow bodies to easily flow into holes formed when a foreign object such as a nail penetrates the tread, while maintaining appropriate flow properties that prevent the hollow bodies from flowing toward the center of the tire tread width during tire operation. This results in excellent sealing properties. Furthermore, the blending of hollow bodies having a specific true specific gravity and average particle size provides sound absorption properties to the tire, thereby reducing road noise. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 10 is a diagram for explaining measurement of the amount of deformation. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will now be described in further detail. (A) Rubber component The rubber component (A) used in the present invention is made of natural rubber (NR), synthetic isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), or a mixture thereof. Among these, from the viewpoint of excellent sealing properties and sound absorption properties, the rubber component (A) is preferably made 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. The rubber component (A) may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, or the like, or may be epoxidized. The weight average molecular weight (Mw) of the (A) rubber component is not particularly limited, but in order to obtain better 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 number average molecular weight (Mn) are values ​​calculated as standard polystyrene obtained by gel permeation chromatography (GPC) measurement.

[0010] 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, when the total is taken as 100 parts by mass.

[0011] (B) Hollow body The hollow body (B) used in the present invention is hollow and preferably spherical, and examples thereof include inorganic hollow bodies such as glass balloons, hollow silica, shirasu balloons, fly ash balloons, and ceramic balloons; and resin hollow bodies. Examples of resin hollow bodies include resin hollow bodies having an outer shell made of a phenolic resin, urea resin, polystyrene resin, polyvinylidene chloride, or acrylonitrile copolymer (e.g., a copolymer of acrylonitrile and methacrylonitrile, or a copolymer of acrylonitrile and a vinyl monomer copolymerizable with acrylonitrile, such as butadiene or styrene). Among these, resin hollow bodies are preferred from the viewpoints that the outer shell is less likely to crack, the hollow body maintains its shape, and the sound absorption properties are excellent.

[0012] The hollow body (B) used in the present invention has a true specific gravity of 0.3 or less and an average particle size of 20 μm to 200 μm. By satisfying these conditions, the sealant composition can be endowed with appropriate flowability and excellent sound absorption properties. The true specific gravity is preferably 0.1 or less, and more preferably 0.01 to 0.1. The average particle size is preferably 20 μm to 100 μm. The true specific gravity and average particle size can be measured by known methods. For example, the true specific gravity can be measured by the liquid displacement method, and the average particle size can be measured as the median diameter (D50: particle size at 50% of the cumulative particle size distribution) measured by laser diffraction.

[0013] (C) sulfur and (D) vulcanization accelerator The sealant composition of the present invention preferably further contains (C) sulfur and (D) a vulcanization accelerator. Vulcanization with these components allows the sealant composition to easily flow into the formed through-holes and provides it with appropriate flowability so that it does not flow toward the center of the tire tread width direction during tire running. Examples of the vulcanization accelerator (D) used in the present invention include known sulfenamide-based, thiazole-based, guanidine-based, thiourea-based, dithiocarbamate-based, xanthogenate-based, and thiuram-based vulcanization accelerators, and among these, from the viewpoint of improving the effects of the present invention, one or more selected from sulfenamide-based vulcanization accelerators and thiazole-based vulcanization accelerators are preferred. The sealant composition of the present invention is also capable of dynamic crosslinking because it contains sulfur (C).

[0014] (Mixing ratio of sealant composition) In the sealant composition of the present invention, the blending amount of the (B) hollow bodies is 0.1 to 100 parts by mass per 100 parts by mass of the (A) rubber component. From the viewpoint of improving the effects of the present invention, the blending amount of the (B) hollow bodies is preferably 0.1 to 50 parts by mass, more preferably 1 to 30 parts by mass, per 100 parts by mass of the (A) rubber component. When (C) sulfur and (D) vulcanization accelerator are compounded, the compounding amount thereof is preferably 1 part by mass or more, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the (A) rubber component. The amount of (C) sulfur mixed is preferably 0.1 to 0.5 parts by mass, and more preferably 0.1 to 0.4 parts by mass, per 100 parts by mass of the (A) rubber component. The compounding amount of the vulcanization accelerator (D) is preferably 1 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component (A). In the sealant composition of the present invention, the blending ratio of (C) sulfur and (D) vulcanization accelerator is preferably 2.5 or more, more preferably 5 to 20, in terms of vulcanization accelerator / sulfur (mass ratio), from the viewpoint of improving the effects of the present invention.

[0015] The sealant composition of the present invention can 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. The glass transition temperature (Tg) of the hydrocarbon resin is preferably higher than 0°C. By specifying the 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 when a thermogram is measured by differential scanning calorimetry (DSC) at a heating 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 hydrocarbon resin is preferably 400 to 2000. By having the number average molecular weight in this range, adhesive strength is improved. The amount of the hydrocarbon resin added is preferably 10 to 90 parts by mass, and more preferably 20 to 60 parts by mass, per 100 parts by mass of the rubber component (A).

[0016] (Other ingredients) The sealant 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 antioxidant, and carbon black. Such additives can be kneaded into a composition by a general method, and the amounts of these additives may be conventional amounts as long as they do not contradict the object of the present invention. When a plasticizer is compounded, the amount is preferably 20 to 90 parts by mass per 100 parts by mass of the rubber component (A).

[0017] The sealant material composition of the present invention is preferably such that when a sample of the sealant material composition having a thickness of 1.2 mm is placed on parallel plates having a diameter of 8 mm and a shear stress of 3000 Pa is applied in the rotational direction of the parallel plates for 60 minutes, the deformation of the sample is 7000% or less. The deformation amount of the sample is measured under the following conditions. Measurement equipment: TA Instruments ARES-G2 dynamic viscoelasticity measuring instrument Jig: 8mm diameter parallel plate Sample thickness: 1.2 mm Shear stress: 3000Pa Duration: 60 minutes

[0018] Hereinafter, the measurement of the deformation amount of the sample will be described with reference to FIG. The measuring device has, as its main components, a rotatable jig 1 and a jig 2 facing jig 1. Jigs 1 and 2 are equipped with parallel plates 12 and 14, respectively. First, a sample S made of the sealant material composition and having a thickness of 1.2 mm is placed on parallel plate 12 having a diameter of 8 mm, and sample S is fixed between parallel plate 12 and another parallel plate 14. The thickness of sample S is 1.2 mm. Only parallel plate 12 is rotated, and a shear stress of 3000 Pa is applied in the direction of rotation for 60 minutes, and the deformation (strain) of sample S after 60 minutes is measured. The temperature in the measurement chamber is set to 80°C.

[0019] In the present invention, the deformation amount is more preferably 1000 to 5000%. To achieve the deformation amount of the sample, the total amount of sulfur and vulcanization accelerator and the amount of vulcanization accelerator may be adjusted to fall within the above-mentioned preferred range. The deformation amount can also be adjusted by adding a plasticizer. The sealant composition of the present invention having the above deformation amount can be more easily flown into the formed through-holes and can be further imparted with suitable flowability so that the composition does not flow toward the center of the tire tread width direction during tire running.

[0020] 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 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, the sealant that constitutes the sealant layer flows into the hole, thereby preventing a decrease in air pressure and allowing the vehicle to continue driving. The sealant layer preferably has a thickness of 2 mm to 6 mm. [Example]

[0021] 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."

[0022] Examples 1 to 5 and Comparative Examples 1 to 2 The components (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 resulting 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. The resulting sealant material was examined for the following properties.

[0023] Test tire production A pneumatic tire having a tire size of 255 / 45R19, 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 radially inner side of the inner liner layer in the tread portion, was used to produce various test tires by attaching the various sealant materials described above as the sealant layer.

[0024] Sealing performance evaluation The test tire was mounted on an SUV (2400cc class vehicle), the air pressure was set to 230kPa, and the load was set to 100% of the maximum load. A φ4mm nail was pierced into the shoulder of the test tire, and after removing the nail and leaving it for 1 hour, the air pressure of the test tire was measured and evaluated according to the following criteria. 〇: 200kPa or more △: 150kPa or more and less than 200kPa ×: Less than 150 kPa

[0025] Flowability evaluation The test tire was mounted on an SUV (2400cc class vehicle), the air pressure was set to 230 kPa, and the vehicle was driven at 200 km / h for 1 hour. After that, the degree of flow from the edge of the sealant layer of the test tire was checked and evaluated according to the following evaluation criteria. ◎: Within 0.5cm 〇: 0.5 to less than 1 cm △: 1cm or more but less than 2cm ×: 2cm or more

[0026] Sound absorption evaluation The test tire was mounted on an SUV (2400cc class vehicle), and the tire was air-pressurized to 230 kPa, with a load of 100% of the maximum load, and sound absorption was evaluated. The sound absorption was evaluated by a sensory evaluation by the driver. The results were expressed as an index, with the value of Comparative Example 1 being 100. A higher index indicates better sound absorption.

[0027] The deformation of the sealant was measured by the method described above.

[0028] The results are shown in Table 1.

[0029] [Table 1]

[0030] *1:NR(SIR20) *2: SBR (Nipol 1502 manufactured by Nippon Zeon Co., Ltd.) *3: Tackifier (ENEOS Corporation T-REZ RC115, C5 petroleum resin) *4: Naphthenic oil (Idemitsu Kosan Co., Ltd. Diana Process Oil NP250 (naphthenic process oil)) *5: Sulfur (Kinka brand oil-filled 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: Hollow body 1 (F-65DE manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd., acrylonitrile polymer, average particle size 40 to 60 μm, true specific gravity 0.030 ± 0.005) *8: Hollow body 2 (F-80DE manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd., acrylonitrile polymer, average particle size 90-130 μm, true specific gravity 0.020 ± 0.005) *9: Hollow body 3 (MFL-100MCA manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd., acrylonitrile polymer / calcium carbonate, average particle size 60-70 μm, true specific gravity 0.12 ± 0.02)

[0031] The results in Table 1 show that the sealant material composition of each Example contains (A) a rubber component consisting of natural rubber, synthetic isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, or a mixture thereof, and (B) hollow bodies having a true specific gravity of 0.3 or less and an average particle size of 20 μm to 200 μm, and the blending amount of the hollow bodies is 0.1 to 100 parts by mass per 100 parts by mass of the rubber component. Therefore, the sealant material composition has appropriate flow properties that allow the sealant material composition to easily flow into a through hole formed when a foreign object such as a nail penetrates the tread, and does not flow toward the center of the tire tread in the width direction when the tire is running, and also has excellent sound absorption properties. In contrast, in Comparative Example 1, no hollow bodies (B) were blended, and therefore no sound absorbing effect was observed. In Comparative Example 2, the blending amount of (B) hollow bodies exceeded the upper limit specified by the present invention, and therefore the sealing property deteriorated.

[0032] The present invention includes the following embodiments. Embodiment 1: A sealant material composition constituting 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 natural rubber, synthetic isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, or a mixture thereof; and (B) A hollow body having a true specific gravity of 0.3 or less and an average particle size of 20 μm to 200 μm. and the amount of the hollow bodies blended relative to 100 parts by mass of the rubber component is 0.1 to 100 parts by mass. A sealant material composition characterized by: Embodiment 2: The sealant material composition according to embodiment 1, wherein the hollow body (B) is a resin hollow body. Embodiment 3: 3. The sealant material composition according to claim 1 or 2, wherein the rubber component comprises 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. Embodiment 4: 4. The sealant material composition according to any one of embodiments 1 to 3, further comprising (C) sulfur and (D) a vulcanization accelerator. Embodiment 5: The sealant material composition according to embodiment 4, wherein the total amount of the (C) sulfur and the (D) vulcanization accelerator is 1 part by mass or more per 100 parts by mass of the rubber component. Embodiment 6: 6. The sealant material composition according to embodiment 4 or 5, wherein the blending ratio of the (C) sulfur and the (D) vulcanization accelerator is 2.5 or more in terms of the vulcanization accelerator / sulfur (mass ratio). Embodiment 7: 7. The sealant material composition according to any one of embodiments 1 to 6, wherein the true specific gravity of the (B) hollow body is 0.1 or less. Embodiment 8: 8. The sealant material composition according to any one of embodiments 1 to 7, wherein a sample made of the sealant material composition and having a thickness of 1.2 mm is placed on parallel plates having a diameter of 8 mm, and when a shear stress of 3000 Pa is applied in the rotational direction of the parallel plates for 60 minutes, the sample deforms by 7000% or less. Embodiment 9: A tire using the sealant material composition according to any one of the first to eighth embodiments. Embodiment 10: 10. The tire according to embodiment 9, wherein the sealant material composition has a thickness of 2 to 6 mm. [Explanation of symbols]

[0033] 1, 2 Jig 12, 14 Parallel Plate

Claims

1. A sealant material composition constituting 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 natural rubber, synthetic isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, or a mixture thereof; and (B) A hollow body having a true specific gravity of 0.3 or less and an average particle size of 20 μm to 200 μm. and the amount of the hollow bodies blended per 100 parts by mass of the rubber component is 0.1 to 100 parts by mass. A sealant material composition characterized by:

2. 2. The sealant material composition according to claim 1, wherein the hollow body (B) is a resin hollow body.

3. 2. The sealant material composition according to claim 1, wherein the rubber component comprises 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.

4. 2. The sealant material composition according to claim 1, further comprising (C) sulfur and (D) a vulcanization accelerator.

5. 5. The sealant material composition according to claim 4, wherein the total amount of the sulfur (C) and the vulcanization accelerator (D) is 1 part by mass or more per 100 parts by mass of the rubber component.

6. 5. The sealant material composition according to claim 4, wherein the blending ratio of the sulfur (C) and the vulcanization accelerator (D) is 2.5 or more in terms of the vulcanization accelerator / sulfur (mass ratio).

7. 2. The sealant material composition according to claim 1, wherein the hollow body (B) has a true specific gravity of 0.1 or less.

8. The sealant material composition according to claim 1, characterized in that a sample made of the sealant material composition and having a thickness of 1.2 mm is placed on parallel plates having a diameter of 8 mm, and when a shear stress of 3000 Pa is applied in the rotational direction of the parallel plates for 60 minutes, the deformation of the sample is 7000% or less.

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

10. 10. The tire according to claim 9, wherein the sealant material composition has a thickness of 2 to 6 mm.

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