Sealing material composition and tire using same

Abstract

The present invention provides a sealing material composition that constitutes a sealing layer of a pneumatic tire having the sealing layer on the inner surface of the tire, the sealing material composition being characterized by containing (A) a rubber component, (B) a vulcanization accelerator, and (C) sulfur, the rubber component (A) comprises 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, and the vulcanization accelerator (B) / sulfur (C) has a mass ratio of 2.5 or more.

Description

Sealing material compositions and tires using them Technical Field

[0001] This invention relates to sealing material compositions and tires using the same. Background Technology

[0002] Among pneumatic tires, there are known pneumatic tires in which a sealing layer is provided radially inside the inner liner of the tread. In such pneumatic tires, when a foreign object such as a nail pierces the tread, a sealant composition flows into the through hole, thereby achieving a seal, suppressing the reduction of air pressure, and maintaining driving stability.

[0003] As examples of the aforementioned sealing material composition, patent documents 1 to 4 are disclosed, for example.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5646474

[0007] Patent Document 2: Japanese Patent No. 5651109

[0008] Patent Document 3: Japanese Patent No. 5525522

[0009] Patent Document 4: Japanese Patent No. 5738897 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The sealing material composition is required to have flowability to ensure a seal and not to peel off due to deterioration caused by driving. It was determined that the peeling was caused by cross-linking and curing of the sealing material composition due to deterioration, resulting in reduced adhesion, and that shrinkage of the sealing material composition was also a contributing factor.

[0012] However, in the aforementioned prior art, there is still room for improvement regarding initial or deteriorated liquidity and the aforementioned stripping.

[0013] The purpose of this invention is to solve the above-mentioned problems and provide a sealing material composition that can ensure proper flowability at the initial stage or after deterioration, and can also effectively suppress peeling after deterioration, and a tire made using the sealing material composition.

[0014] Problem-solving methods

[0015] Through repeated and in-depth research, the inventors discovered that, relative to rubber components with specific compositions, a sealing material composition in which a specific mixing ratio of the vulcanization accelerator and sulfur is used can solve the aforementioned problems, thus completing the present invention.

[0016] That is, the present invention is a sealing material composition constituting the sealing layer of a pneumatic tire having a sealing layer on the inner surface of the tire.

[0017] Its characteristic is that it includes:

[0018] (A) Rubber components,

[0019] (B) Vulcanization accelerators, and

[0020] (C) Sulfur,

[0021] The ratio of the above-mentioned (B) vulcanization accelerator to the above-mentioned (C) sulfur (by mass) is 2.5 or more, and the rubber component of (A) is composed of...

[0022] 50-100 parts by weight of natural rubber and / or synthetic isoprene rubber, and

[0023] 0 to 50 parts by weight of styrene-butadiene copolymer rubber, butadiene rubber, or mixtures thereof

[0024] constitute.

[0025] Invention Effects

[0026] The sealing material composition of the present invention, relative to a rubber component consisting of (A) 50-100 parts by weight of "natural rubber and / or synthetic isoprene rubber" and 0-50 parts by weight of "styrene-butadiene copolymer rubber, butadiene rubber or mixtures thereof", incorporates (B) a vulcanization accelerator and (C) sulfur, and sets the (B) vulcanization accelerator / (C) sulfur (mass ratio) to be 2.5 or more. By setting the (B) vulcanization accelerator / (C) sulfur (mass ratio) to be 2.5 or more, appropriate flowability can be ensured initially or after deterioration. Furthermore, it can be deduced that, for example, even if the sealing material composition undergoes cross-linking and curing with time-related deterioration, the softness of the natural rubber and / or synthetic isoprene rubber, which is the main component of the rubber component (A), can compensate for the cross-linking and curing, thereby suppressing the reduction of adhesive strength and shrinkage of the sealing material composition, and also sufficiently suppressing peeling after deterioration. Detailed Implementation

[0027] The present invention will now be described in more detail.

[0028] (A) Rubber composition

[0029] The rubber component (A) used in this invention is primarily composed of natural rubber (NR) and / or synthetic isoprene rubber (IR). Additionally, the rubber component (A) can be blended with styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), or mixtures thereof. Furthermore, the rubber component (A) can be end-modified with amines, amides, silyl groups, alkoxysilyl groups, carboxyl groups, hydroxyl groups, etc., and can also be epoxidized.

[0030] There is no particular limitation on the weight-average molecular weight (Mw) of the rubber component (A), but considering the superior 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.

[0031] In addition, in this specification, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) are standard polystyrene conversion values ​​obtained by gel permeation chromatography (GPC).

[0032] The rubber component (A) used in this invention, when set as 100 parts by weight, contains 50 to 100 parts by weight of NR and / or IR, preferably 50 to 80 parts by weight, and 0 to 50 parts by weight of SBR, BR or mixtures thereof, preferably 20 to 50 parts by weight.

[0033] (B) Vulcanization accelerator and (C) sulfur

[0034] As the (B) vulcanization accelerator used in this invention, examples include known sulfenamide-based, thiazole-based, guanidine-based, thiourea-based, dithiocarbamate-based, xanthate-based, and thiuram-based vulcanization accelerators, etc., wherein, from the viewpoint of improving the effect of this invention, one or more selected from sulfenamide-based vulcanization accelerators and thiazole-based vulcanization accelerators are preferred.

[0035] The sealing material composition of the present invention can also undergo dynamic cross-linking because it is mixed with (C) sulfur.

[0036] (Mixing ratio of the sealing material composition)

[0037] In the sealing material composition of the present invention, the amount of (B) vulcanization accelerator mixed relative to 100 parts by weight of (A) rubber component is, for example, 1 to 5 parts by weight, preferably 1 to 4 parts by weight, and more preferably 1 to 3 parts by weight.

[0038] Furthermore, in the sealing material composition of the present invention, the amount of sulfur (C) mixed with 100 parts by weight of rubber component (A) is, for example, less than 0.5 parts by weight, preferably 0.1 to 0.4 parts by weight, and more preferably 0.15 to 0.3 parts by weight.

[0039] Furthermore, in the sealing material composition of the present invention, the ratio of the above-mentioned (B) vulcanization accelerator to the above-mentioned (C) sulfur (mass ratio) must be 2.5 or more. If the ratio is less than 2.5, adequate flowability after initial or deterioration cannot be sufficiently ensured, and peeling after deterioration cannot be sufficiently suppressed. The ratio of the above-mentioned (B) vulcanization accelerator to the above-mentioned (C) sulfur (mass ratio) is preferably 5 or more, more preferably 10 or more, and particularly preferably 10 to 20.

[0040] Within the preferred range of the above-mentioned mixing ratios, the effects of the present invention can be better realized.

[0041] From the viewpoint of improving effectiveness, the sealing material composition of the present invention preferably contains magnesium oxide, and the BET specific surface area of ​​magnesium oxide is more preferably 20-200 m². 2 / g. The BET specific surface area of ​​magnesium oxide is the specific surface area of ​​magnesium oxide determined by nitrogen adsorption according to the one-point method of JIS Z8830.

[0042] The amount of magnesium oxide mixed in the above-mentioned compound is, for example, less than 1.0 parts by mass relative to 100 parts by mass of the rubber component (A) above, preferably 0.1 to 0.5 parts by mass.

[0043] In a preferred form, the sealing material composition of the present invention can be mixed with a tackifier. Examples of tackifiers include hydrocarbon resins. Examples of hydrocarbon resins include aromatic hydrocarbon resins or saturated or unsaturated aliphatic hydrocarbon resins manufactured by polymerizing components obtained from the distillation, decomposition, modification, etc., of crude oil. Examples of petroleum resins include C5 series petroleum resins (aliphatic petroleum resins polymerized from fractions such as isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, and pentene), C9 series petroleum resins (aromatic petroleum resins polymerized from fractions such as α-methylstyrene, o-vinyltoluene, m-vinyltoluene, and p-vinyltoluene), and C5C9 copolymer petroleum resins.

[0044] Furthermore, the glass transition temperature (Tg) of the hydrocarbon resin is preferably higher than 0°C. By specifying Tg in this way, fluidity is improved. The glass transition temperature (Tg) referred to in this invention is the temperature at the midpoint of the transition region, measured by differential scanning calorimetry (DSC) at a heating rate of 20°C / min.

[0045] More preferably, the Tg is above 30°C and below 90°C.

[0046] Furthermore, the number-average molecular weight of the hydrocarbon resin is preferably between 400 and 2000. Having a number-average molecular weight within this range improves adhesive strength.

[0047] The amount of the hydrocarbon resin mixed with the rubber component (A) is preferably 10 to 90 parts by mass, and more preferably 20 to 60 parts by mass, relative to 100 parts by mass of the rubber component (A).

[0048] Furthermore, the sealing material composition of the present invention, as a preferred form, can be mixed with an inorganic filler. Examples of inorganic fillers include one or more selected from calcium carbonate, talc, and clay.

[0049] The amount of the inorganic filler mixed with the above is preferably 1 to 20 parts by mass relative to 100 parts by mass of the rubber component (A) above, and more preferably 5 to 15 parts by mass.

[0050] (Other ingredients)

[0051] The sealing material composition of the present invention can be mixed with various additives other than the above-mentioned components, such as vulcanizing or crosslinking agents, vulcanizing or crosslinking accelerators, zinc oxide, anti-aging agents, and plasticizers. These additives can be mixed using conventional methods to form the composition, and the mixing amounts of these additives can be conventional mixing amounts as long as they do not deviate from the purpose of the present invention. In addition, when mixing with plasticizers, the amount is preferably 20 to 90 parts by weight relative to 100 parts by weight of the rubber component (A) above.

[0052] The sealing material composition of the present invention can be provided as a sealing layer on the radially inner side of the inner liner of the tread layer of a pneumatic tire. This sealing layer can be formed by bonding a sheet-shaped sealing material composed of the sealing material composition of the present invention around the entire inner surface of the tire. Alternatively, the sealing layer can be formed by spirally bonding a rope-like or strip-shaped sealing material composed of the sealing material composition of the present invention to the inner surface of the tire. The sealing material can be a sulfide. When a foreign object such as a nail pierces the tread layer, the sealing material forming the sealing layer flows into the through-hole, suppressing the reduction of air pressure and maintaining driving stability. The sealing layer has a thickness of, for example, 0.5 mm to 5.0 mm.

[0053] Example

[0054] The present invention will be further described below by way of examples and comparative examples, but the present invention is not limited to the following examples. In addition, in the following examples, "parts" means "parts by mass".

[0055] Examples 1-15 and Comparative Examples 1-2

[0056] In the formulation (parts by weight) shown in Table 1, the rubber composition was obtained by mixing in a 1.7-liter closed Banbury mixer for 40 minutes. The obtained rubber composition was then vulcanized under pressure at 180°C for 10 minutes in a specified mold to obtain a sealant with a thickness of 3 mm. Hereinafter, the obtained sealant will be referred to as the initial sealant.

[0057] Furthermore, the initial sealing material obtained above was subjected to hygrothermal degradation under the following conditions. Hereinafter, the resulting sealing material will be referred to as the hygrothermal-degraded sealing material.

[0058] Humid heat deterioration conditions: temperature 70℃, relative humidity 96%, period 30 days

[0059] The following characteristics were investigated regarding the initial sealant and the sealant after damp heat degradation.

[0060] Liquidity (creep)

[0061] Creep testing was performed under the following conditions.

[0062] Measuring device: ARES-G2 dynamic viscoelasticity measuring instrument manufactured by TA Instruments.

[0063] Fastener: Parallel plate with a diameter of 8mm

[0064] Sample thickness: 1.2 mm

[0065] Shear stress: 3000 Pa

[0066] Time: 60 minutes

[0067] If the creep coefficient is below 100, the degree of solidification is high, the fluidity is reduced, and the seal cannot be maintained. Conversely, if the creep coefficient is above 9000, there is excessive fluidity, which can lead to problems such as leakage towards the center of the tire tread in the width direction during driving. Furthermore, creep is measured in percentages (%).

[0068] Liquidity and divestiture (real-world vehicle evaluation)

[0069] The pneumatic tire has a size of 215 / 55R17 and includes a tread portion, a pair of sidewall portions, and a pair of bead portions. A sealing layer made of sealing material is provided on the radially inner side of the inner liner of the tread portion. Various test tires are manufactured by attaching this sealing material as the sealing layer. The resulting test tires are then subjected to the following tests. Furthermore, the newly manufactured test tire is referred to as the initial test tire, and the test tire that has undergone the aforementioned damp-heat degradation treatment is referred to as the damp-heat degradation post-test tire.

[0070] Liquidity (Real Vehicle Evaluation)

[0071] The test tire was assembled on a 17×7J rim and mounted on a roller tester. After 80 hours of high-flexure testing at an air pressure of 160 kPa, a load of 8.5 kN, and a speed of 80 km / h, the flow and peeling states of the sealant were investigated. The evaluation results were as follows: A 3 mm sealant thickness that decreased to less than 1.5 mm at various locations from the end of the sealant was considered to be flowing. No flow was observed at 0.5 cm from the end of the sealant, marked with "◎"; no flow was observed at 1 cm from the end of the sealant, marked with "○"; flow was observed at 1 cm from the end of the sealant and not at 2 cm, marked with "△"; and flow was observed at 2 cm from the end of the sealant, marked with "×".

[0072] Peelability

[0073] After the above fluidity (real-vehicle evaluation) test, a visual inspection is conducted to check for any peeling of the sealant. Peeling performance is assessed on the test tires after they have undergone damp and heat degradation.

[0074] The results are shown in Table 1.

[0075] [Table 1]

[0076]

[0077] *1: NR (SIR20)

[0078] *2: SBR (Nipol1502 manufactured by Japan ZEON Co., Ltd.)

[0079] *3: Hydrocarbon resin (ENEOS Co., Ltd. T-REZ RC115, C5 petroleum resin)

[0080] *4: Petroleum-based cycloalkane oil (Diana Process oil NP250 manufactured by Idemitsu Kosan Co., Ltd.)

[0081] *5: Sulfur (Made by Tsurumi Chemical Industry Co., Ltd., using finely powdered sulfur in Kinka printing ink)

[0082] *6: Sulphamide-based vulcanization accelerator CZ (NOCCELER CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.)

[0083] *7: Sulphamide-based vulcanization accelerator NS (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name NOCCELERNS-P)

[0084] *8: Thiazole-based vulcanization accelerator DM (SANCELER DM-PO manufactured by Sanshin Chemical Industry Co., Ltd.)

[0085] *9: Calcium carbonate (manufactured by Maruo Calcium Co., Ltd.)

[0086] *10: Magnesium oxide-1 (manufactured by Kyowa Chemical Industry Co., Ltd., Kyowamag 30, BET specific surface area = 42m²) 2 / g)

[0087] *11: Magnesium oxide-2 (Kyowa Mag150, manufactured by Kyowa Chemical Industry Co., Ltd., BET specific surface area = 144 m²) 2 / g)

[0088] As can be seen from the results in Table 1, the sealing material compositions of each embodiment contain (A) a rubber component consisting of 50 to 100 parts by weight of natural rubber and / or synthetic isoprene rubber, and 0 to 50 parts by weight of styrene-butadiene copolymer rubber, butadiene rubber, or mixtures thereof, (B) a vulcanization accelerator, and (C) sulfur. The ratio of (B) vulcanization accelerator to (C) sulfur (by weight) is 2.5 or more. Therefore, it is possible to ensure appropriate flowability at the initial stage or after deterioration, and to sufficiently suppress peeling after deterioration.

[0089] In contrast, in Comparative Example 1, since the ratio of (B) vulcanization accelerator to (C) sulfur (by mass) was 2.0, the fluidity deteriorated after damp heat degradation in the actual vehicle evaluation. In addition, peeling of the sealant was also observed after damp heat degradation.

[0090] In Comparative Example 2, the ratio of (B) vulcanization accelerator to (C) sulfur (by mass) was 1.7, resulting in a deterioration in the initial sealant's flowability in terms of creep and real-vehicle evaluation.

[0091] The present invention includes the following embodiments.

[0092] Embodiment 1: A sealing material composition constituting the sealing layer of a pneumatic tire having a sealing layer on the inner surface of the tire, characterized in that it comprises (A) a rubber component, (B) a vulcanization accelerator, and (C) sulfur.

[0093] The rubber component (A) is composed of

[0094] 50-100 parts by weight of natural rubber and / or synthetic isoprene rubber, and

[0095] 0 to 50 parts by weight of styrene-butadiene copolymer rubber, butadiene rubber, or mixtures thereof

[0096] constitute,

[0097] The ratio of (B) vulcanization accelerator to (C) sulfur is 2.5 or more by mass.

[0098] Embodiment 2: The sealing material composition as described in Embodiment 1, characterized in that the (B) vulcanization accelerator is a sulfenamide and / or thiazole vulcanization accelerator.

[0099] Embodiment 3: The sealing material composition as described in Embodiment 1 or 2, characterized in that the ratio of (B) vulcanization accelerator to (C) sulfur is 5 or more by mass.

[0100] Embodiment 4: The sealing material composition according to any one of Embodiments 1 to 3, characterized in that the ratio of (B) vulcanization accelerator to (C) sulfur is 10 or more by mass.

[0101] Embodiment 5: The sealing material composition according to any one of Embodiments 1 to 4, characterized in that the sealing material composition further contains magnesium oxide, and the amount of magnesium oxide mixed in is less than 1.0 part by mass relative to 100 parts by mass of the rubber component.

[0102] Embodiment 6: The sealing material composition according to any one of Embodiments 1 to 5, characterized in that the amount of (C) sulfur mixed in is less than 0.5 parts by mass relative to 100 parts by mass of the rubber component.

[0103] Embodiment 7: The sealing material composition according to any one of Embodiments 1 to 6, characterized in that the sealing material composition further contains a hydrocarbon resin as a tackifier, and the amount of the hydrocarbon resin is 10 to 90 parts by mass relative to 100 parts by mass of the rubber component (A).

[0104] Embodiment 8: The sealing material composition according to any one of Embodiments 1 to 7, characterized in that the sealing material composition further contains one or more selected from calcium carbonate, talc and clay as an inorganic filler.

[0105] Embodiment 9: A sealing material composition according to any one of Embodiments 1 to 8, characterized in that, when the total amount of the (A) rubber component is set at 100 parts by mass, the (A) rubber component is composed of...

[0106] 50-80 parts by weight of natural rubber and / or synthetic isoprene rubber, and

[0107] 20 to 50 parts by weight of styrene-butadiene copolymer rubber, butadiene rubber, or mixtures thereof

[0108] constitute.

[0109] Embodiment 10: The sealing material composition according to any one of Embodiments 1 to 9, characterized in that the (B) vulcanization accelerator is a sulfenamide-based vulcanization accelerator.

[0110] Embodiment 11: A sealing material composition according to any one of Embodiments 1 to 10, characterized in that the sealing material composition further comprises magnesium oxide, wherein the BET specific surface area of ​​the magnesium oxide is 20 to 200 m². 2 / g.

[0111] Embodiment 12: The sealing material composition according to any one of Embodiments 1 to 11, characterized in that the sealing material composition further contains a hydrocarbon resin as a tackifier, wherein the hydrocarbon resin is a petroleum-based resin.

[0112] Embodiment 13: A tire that uses the sealing material composition described in any one of Embodiments 1 to 12.

Claims

1. A sealing material composition, which constitutes the sealing layer of a pneumatic tire having a sealing layer on the inner surface of the tire, characterized in that, The product comprises (A) a rubber component, (B) a vulcanization accelerator and (C) sulfur, wherein the (A) rubber component consists of 50 to 100 parts by weight of natural rubber and / or synthetic isoprene rubber, and 0 to 50 parts by weight of styrene-butadiene copolymer rubber, butadiene rubber or mixtures thereof, and the ratio of the (B) vulcanization accelerator to the (C) sulfur is 2.5 or more by weight.

2. The sealing material composition according to claim 1, characterized in that, The (B) vulcanization accelerator is a sulfenamide and / or thiazole vulcanization accelerator.

3. The sealing material composition according to claim 1, characterized in that, The ratio of (B) vulcanization accelerator to (C) sulfur is 5 or more by mass.

4. The sealing material composition according to claim 1, characterized in that, The ratio of (B) vulcanization accelerator to (C) sulfur is 10 or more by mass.

5. The sealing material composition according to claim 1, characterized in that, The sealing material composition also contains magnesium oxide, and the amount of magnesium oxide mixed in is less than 1.0 part by weight relative to 100 parts by weight of the rubber component.

6. The sealing material composition according to claim 1, characterized in that, The amount of sulfur (C) mixed in is less than 0.5 parts by mass relative to 100 parts by mass of the rubber component.

7. The sealing material composition according to claim 1, characterized in that, The sealing material composition also contains a hydrocarbon resin as a tackifier, and the amount of the hydrocarbon resin is 10 to 90 parts by weight relative to 100 parts by weight of the rubber component (A).

8. The sealing material composition according to claim 1, characterized in that, The sealing material composition also contains one or more selected from calcium carbonate, talc and clay as inorganic fillers.

9. The sealing material composition according to claim 1, characterized in that, When the total of the rubber component (A) is set to 100 parts by mass, the rubber component (A) consists of 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 mixtures thereof.

10. The sealing material composition according to claim 1, characterized in that, The (B) vulcanization accelerator is a sulfenamide-based vulcanization accelerator.

11. The sealing material composition according to claim 1, characterized in that, The sealing material composition further contains magnesium oxide, wherein the BET specific surface area of ​​the magnesium oxide is 20-200 m². 2 / g.

12. The sealing material composition according to claim 1, characterized in that, The sealing material composition also contains a hydrocarbon resin as a tackifier, wherein the hydrocarbon resin is a petroleum-based resin.

13. A tire that uses the sealing material composition of claim 1.

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