JP2008201841A - Pneumatic tire for emergency - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a pneumatic tire for emergency, satisfying both improvement in weather resistance and lightening. <P>SOLUTION: The pneumatic tire for emergency equipped with a cap tread part is formed by using a rubber composition comprising (A) (i) 15-45 wt.% of an ethylene-propylene-diene terpolymer rubber having a diene component content of ≥5 wt.% and <13 wt.% and (ii) 85-55 wt.% of a diene-based rubber except a halogenated butyl rubber, (B) 50-100 pts.wt. based on 100 pts.wt. of the rubber component (A) of carbon black having a nitrogen absorption specific surface area of 65-150 m<SP>2</SP>/g and (C) 0.5-1.5 pts.wt. based on 100 pts.wt. of the rubber component (A) of an amine-based antioxidant. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an emergency pneumatic tire. More specifically, the present invention relates to an emergency pneumatic tire that has improved weather resistance, particularly ozone crack resistance, and reduced weight.

  Emergency pneumatic tires installed in passenger cars, minivans, etc. have been stored in the trunk in the past, but nowadays they are often installed outside the vehicle for the purpose of securing the interior space. Therefore, in emergency pneumatic tires, weather resistance, particularly ozone crack resistance is also regarded as important.

  On the other hand, the emergency pneumatic tire itself is also stored for the purpose of temporary use when the standard tire used in normal driving becomes unusable due to a failure such as puncture. Unlike so-called “ground tires”, which are standard tires mounted on vehicles for the purpose of reducing space and weight, they are generally narrower, thinner, and relatively simple in structure. "Emergency pneumatic tires" are being used.

  In the T type emergency pneumatic tire having the structural features as described above, the ground tire is used to support a load equivalent to that of the ground tire even though the tread layer is thin and easily distorted for weight reduction. Therefore, it is required to have higher ozone crack resistance than a ground tire. Therefore, it is necessary to increase durability as well as weight reduction for emergency pneumatic tires, and there is an increasing demand for achieving both weather resistance, particularly ozone crack resistance, and weight reduction. Further, since the T-type emergency pneumatic tire has a narrow width, higher grip performance is required in order to ensure steering stability. Furthermore, T-type emergency pneumatic tires are thin and simple for the purpose of weight reduction, so the temperature at 0 ° C. is related to the breaking strength related to the durability of the tire at the practical level and the grip performance of the tire. It is required to secure a loss tangent (tan δ) at.

  Prior art documents related to the invention of this application include the following.

JP 2005-139352 A JP 2005-153604 A Japanese Patent Publication No. 6-18950 Japanese Patent No. 8-20202 Japanese Patent No. 2629295 JP 11-301210 A JP 2001-181458 A

  As described above, in the technical field, there is an increasing demand for both improvement in weather resistance, particularly ozone crack resistance, and weight reduction for emergency pneumatic tires. Accordingly, an object of the present invention is to provide an emergency pneumatic tire that achieves improved weather resistance, particularly ozone crack resistance and weight reduction.

The object is to provide (A) (i) 15 to 45% by weight of an ethylene-propylene-diene terpolymer rubber having a diene component content of 5% by weight or more and less than 13% by weight, and (ii) a halogenated butyl rubber. A rubber component consisting of 85 to 55% by weight of diene rubber excluding, and (B) 50 to 100 parts by weight of a nitrogen adsorption specific surface area of 65 to 150 m ² / g with respect to 100 parts by weight of the rubber component (A). A cap tread portion formed by using a rubber composition containing a certain carbon black and (C) 0.5 to 1.5 parts by weight of an amine-based antioxidant for 100 parts by weight of the rubber component (A). Achieved by an emergency pneumatic tire with According to the present invention, resistance to ozone cracking due to long-term mounting outside the vehicle and weight reduction are realized at a high level.

  The rubber component (A) used in the rubber composition used for forming the cap tread portion in the emergency pneumatic tire of the present invention has (i) a diene component content of 5 wt% or more and 13 wt%. Less than ethylene-propylene-diene terpolymer rubber (EPDM) and (ii) diene rubber excluding halogenated butyl rubber. The ethylene-propylene-diene terpolymer rubber (A) (i) may have any diene component content of 5 wt% or more and less than 13 wt%. Specific examples of the diene rubber that can be used as the component (A) (ii) in the present invention include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), chloroprene rubber. (CR), acrylonitrile butadiene rubber (NBR), etc. are mentioned, These can be used individually or in combination of 2 or more types.

  The blending amount of the ethylene-propylene-diene terpolymer rubber (A) (i) is a diene rubber excluding the ethylene-propylene-diene terpolymer rubber (A) (i) and halogenated butyl rubber ( A) 15 to 45% by weight based on the total amount with (ii). The blending amount of the diene rubber (A) (ii) is based on the total amount of the ethylene-propylene-diene terpolymer rubber (A) (i) and the diene rubber (A) (ii). 85 to 55% by weight. When the blending amount of the ethylene-propylene-diene terpolymer rubber (A) (i) is less than 15% by weight of the rubber component (A), improvement of ozone crack resistance at low and high temperatures When the effect is small and the amount exceeds 45% by weight of the rubber component (A), the ozone crack resistance at low and high temperatures is improved, but the breaking strength is lowered. When the content of the diene component of the ethylene-propylene-diene terpolymer rubber (A) (i) is less than 5% by weight, ozone crack resistance at high temperatures is lowered.

The component (B) contained in the rubber composition used for forming the cap tread portion in the emergency pneumatic tire of the present invention has a nitrogen adsorption specific surface area (N ₂ SA) of 65 to 150 m ² / g. Carbon black. When the nitrogen adsorption specific surface area of carbon black (B) is less than 65 m ² / g, the breaking strength and tan δ at 0 ° C. are insufficient, while when the nitrogen adsorption specific surface area exceeds 150 m ² / g. This is not preferable because processability is deteriorated and raw material costs are increased. The compounding quantity of carbon black (B) is 50-100 weight part with respect to 100 weight part of said rubber components (A). When the compounding amount of carbon black (B) is less than 50 parts by weight with respect to rubber component (A), tan δ is insufficient, while when it exceeds 100 parts by weight with respect to rubber component (A) In addition, ozone crack resistance and breaking strength at low temperatures are reduced.

  Examples of the amine anti-aging agent (C) that can be included in the rubber composition used to form the cap tread portion in the emergency pneumatic tire of the present invention include N-phenyl-N′-1, 3-dimethylbutyl-p-phenylenediamine (abbreviation: 6PPD), N-phenyl-N′-isopropyl-p-phenylenediamine (abbreviation: IPPD), N, N′-diphenyl-p-phenylenediamine (abbreviation: DPPD) P, p′-dioctyldiphenylamine (abbreviation: ODPA), p, p′-dicumyldiphenylamine (abbreviation: DCDP), 2,2,4-trimethyl-1,2-dihydroquinoline polymer (abbreviation: TMDQ), 6 -Ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (abbreviation: ETMDQ) and the like. The amine-based antioxidant (C) is blended in the rubber composition of the present invention in an amount of 0.5 to 1.5 parts by weight with respect to 100 parts by weight of the rubber component (A). If the compounding amount of the amine-based anti-aging agent (C) is less than 0.5 parts by weight, the ozone crack resistance is insufficient, while if it exceeds 1.5 parts by weight, it is added to the rubber composition. The amine-based anti-aging agent leached out to the tire surface, and the tire surface turns brown, and the appearance of the tire deteriorates.

  Next, with reference to FIGS. 1 and 2, an emergency pneumatic tire using the rubber composition in the cap tread portion will be described. FIG. 1 is a tire meridian direction sectional view showing a preferred embodiment of an emergency pneumatic tire of the present invention. In FIG. 1, the carcass layer 4 is mounted on the bead cores 5 and 5 'and the bead fillers 7 and 7' in the pair of left and right bead portions 3 and 3 'via the side walls 2 and 2'. The carcass layer 4 includes an outer carcass layer 4a and an inner carcass layer 4b. In this figure, between the tread 1 and the outer carcass layer 4a, two breakers (belt layers) 6 are arranged over the circumference of the tire in the tire circumferential direction. As will be described later, the tread 1 includes a cap tread portion 1a and an under tread portion 1b. A crown portion is formed by the tread 1, the breaker 6, and the carcass layer 4 inside thereof. A groove 8 is provided in the tread 1 over the tire circumferential direction.

  FIG. 2 is a partial enlarged cross-sectional view of the emergency pneumatic tire of the present invention, in which FIG. As shown in FIG. 2, the tread 1 includes a cap tread portion 1a and an under tread portion 1b. In this invention, since the said rubber composition shows the weather resistance, breaking strength, and grip performance which were improved with sufficient balance, the thickness of the tread 1 can be made thin compared with a regular tire. Specifically, the thickness from the groove bottom 10 of the groove 8 provided in the tread 1 to the breaker 6 (to the outer carcass layer 4a when the breaker 6 is not disposed) is 3 mm or less, preferably 1 to 3 mm. The groove depth of the groove 8 can be 4 mm or less, preferably 2 to 4 mm.

  A vulcanizing agent such as sulfur is also blended in the rubber composition for a tread of an emergency pneumatic tire according to the present invention. When sulfur is used as the vulcanizing agent, for example, powder sulfur or the like, which is well known in the rubber compounding technical field, can be used. It can be a general blending amount.

  The rubber composition used for forming the cap tread of the emergency pneumatic tire according to the present invention includes a filler (silica, etc.), a plasticizer, a softener, and a vulcanizing agent in addition to the above compounding agents. An auxiliary agent, a vulcanization accelerator, a vulcanization retarder, an anti-aging agent, and / or other various additives generally used in the rubber compounding technical field can be blended. The blending amount of these additives can also be a conventional general blending amount as long as the object of the present invention is not violated.

  Furthermore, the said rubber composition can be manufactured by mixing said each component using a well-known rubber kneading machine (for example, a roll, a Banbury mixer, a kneader etc.).

  Although the present invention will be described in more detail with reference to comparative examples and examples described below, the technical scope of the present invention is not limited to these examples.

Comparative Examples 1-13 and Examples 1-8
In accordance with the composition shown in Tables 1 and 2 below, a vulcanization accelerator and components other than sulfur are mixed for 5 minutes using a 70 liter closed Banbury mixer, released from the mixer at 150 ° C., and then vulcanized with an open roll. Agents and sulfur were mixed to obtain rubber compositions of Comparative Examples 1 to 13 and Examples 1 to 8. Next, physical properties of these rubber compositions were evaluated by the following test methods.

Footnotes in Table 1 and Table 2:
(1) Nipol 1712 manufactured by Nippon Zeon Co., Ltd. (Amount of oil: 37.5 parts by weight of aromatic oil with respect to 100 parts by weight of rubber)
(2) Nipol 1502 manufactured by Nippon Zeon Co., Ltd. (non-oil exhibition)
(3) Nipol BR1220 (non-oil exhibition) manufactured by Nippon Zeon Co., Ltd.
(4) Bromobutyl X2 from Lanxess Rubber
(5) Esprene 505A manufactured by Sumitomo Chemical Co., Ltd. (ethylene content 50%, propylene content 40.5%, diene content 9.5%)
(6) EPT3091 manufactured by Mitsui Chemicals, Inc. (ethylene content 61%, propylene content 33.5%, diene content 5.5%)
(7) EPT1070 manufactured by Mitsui Chemicals (ethylene content 57%, propylene content 39%, diene content 4%)
(8) Ethylene-propylene copolymer rubber EPT1045 (ethylene content 51%, propylene content 49%) manufactured by Mitsui Chemicals, Inc.
(9) Esprene 586 manufactured by Sumitomo Chemical Co., Ltd. (ethylene content 66%, propylene content 21.5%, diene content 12.5%)
(10) Toast Carbon's seast KH (N339, nitrogen adsorption specific surface area 93 m ² / g)
(11) Show black N330 manufactured by Cabot Japan (nitrogen adsorption specific surface area 75 m ² / g)
(12) Show Black N550 manufactured by Cabot Japan (nitrogen adsorption specific surface area 42 m ² / g)
(13) Three types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.
(14) Industrial stearic acid manufactured by NOF Corporation
(15) Nocrack 6C (N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry
(16) Sannoc made by Ouchi Shinsei Chemical Industry
(17) Extract 4 made by Showa Shell Sekiyu
(18) Oil-treated sulfur from Hosoi Chemical Industry
(19) Noxeller CZ-G (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry
(20) Noxeller D (1,3-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry

Test Method (1) Breaking Strength Each rubber composition of the above comparative examples and examples was press vulcanized at 160 ° C. for 30 minutes in a 15 cm × 15 cm × 0.2 cm mold to obtain a vulcanized rubber sheet. A No. 3 dumbbell test piece was punched from the vulcanized rubber sheet, and the stress at break (breaking strength) was measured in accordance with JIS K6251. The greater the index value, the greater the breaking strength. If the rupture strength becomes too small, the tire may be damaged by contact with the mounting bracket to the vehicle.

(2) Loss tangent (tan δ):
The rubber compositions of the above comparative examples and examples were press vulcanized in a 15 cm × 15 cm × 0.2 cm mold at 160 ° C. for 30 minutes to obtain a vulcanized rubber sheet. According to JIS K6394, the loss tangent (tan δ) was determined using a viscoelastic spectrometer under the conditions of a temperature of 0 ° C., a frequency of 20 Hz, an average strain of 10%, and a strain amplitude of 2%. If the value of the loss tangent (tan δ) is 90 or more, the grip performance of the rubber composition after vulcanization is practically acceptable.

(3) (a) Ozone crack resistance (rubber test piece):
The rubber compositions of the above comparative examples and examples were press vulcanized at 160 ° C. for 30 minutes in a 15 cm × 15 cm × 0.2 cm mold to obtain a vulcanized rubber sheet, and a test piece was obtained from the vulcanized rubber sheet. It produced and tested based on JISK6259. The test piece was placed in a test tank maintained at an ozone concentration of 50 pphm and allowed to stand at a temperature of −20 ° C. for 96 hours, and then the ozone crack resistance was evaluated. Furthermore, a similar test was performed under the same conditions except that the temperature was changed to 50 ° C. The evaluation of ozone crack resistance is expressed as the minimum strain (critical strain) when a crack is visually confirmed on the surface of the test piece under the conditions of static elongation strain of 10%, 20%, 30%, 40% and 50%. It was. The case where no crack occurred even at 50% was expressed as NC. In the case of NC, or the greater the critical strain, the better the ozone crack resistance.
(B) Ozone crack resistance (tire):
A test tire of size T135 / 70D16 using each rubber composition of the above comparative examples and examples as a cap tread was produced, the test tire was assembled, the air pressure was 420 kPa, and the ozone concentration was maintained at 50 pphm. The sample was placed in a test tank and allowed to stand at −20 ° C. for 96 hours, and then the ozone crack resistance was evaluated. Furthermore, a similar test was performed under the same conditions except that the temperature was changed to 50 ° C. The evaluation of ozone crack resistance was performed by visually confirming the presence or absence of cracks.

(4) Appearance Each rubber composition of the above comparative examples and examples was press vulcanized in a 15 cm × 15 cm × 0.2 cm mold at 160 ° C. for 30 minutes to produce a test piece, which was filled with air, temperature The sample was placed in a thermostatic bath set at 50 ° C. and allowed to stand for 96 hours, and then the presence or absence of discoloration on the surface of the test piece, which is characteristic of leaching of the antioxidant, was visually confirmed.

  The rubber composition of Comparative Example 1 is not preferable because ozone cracks cannot be confirmed with the naked eye and is excellent in ozone crack resistance. However, in the appearance test, the color changes to brown and there is a concern about ambient contamination.

  The rubber composition of Comparative Example 2 has the same formulation as that of Comparative Example 1 except that the blending amount of the antioxidant is changed from 2.75 parts by weight to 0.50 parts by weight. Although the appearance was improved as compared with Comparative Example 1, the ozone crack resistance at −20 ° C. and 50 ° C. deteriorated.

  The rubber composition of Comparative Example 3 was obtained by replacing part of the non-oil-extended SBR constituting the rubber component with brominated butyl rubber (Br-IIR), and the ozone crack resistance was insufficient.

  The rubber compositions of Examples 1 to 3 are those in which EPDM (A) (i) is blended with the rubber component within the scope of the present invention, and the breaking strength and tan δ (0 ° C.) in comparison with Comparative Example 1 are It was kept at a practical level and exhibited good ozone crack resistance and appearance.

  In the rubber composition of Comparative Example 4, the blending amount of the anti-aging agent was 0.30 parts by weight below the range defined in the present invention, and the ozone crack resistance at 50 ° C. was lowered.

  In the rubber composition of Comparative Example 5, the blending amount of the anti-aging agent was 2.00 parts by weight exceeding the range defined in the present invention, and the color changed to brown to an extent that was not acceptable in the appearance test.

  In the rubber composition of Comparative Example 6, the EPDM blending amount was 10.00 parts by weight below the range defined in the present invention, and the ozone crack resistance at −20 ° C. and 50 ° C. was lowered.

  The rubber composition of Comparative Example 7 was such that the blending amount of EPDM was 50.00 parts by weight exceeding the range specified in the present invention, and the ozone crack resistance at −20 ° C. and 50 ° C. was improved. However, the decrease in breaking strength was large.

  The rubber composition of Comparative Example 8 has the same formulation as that of the rubber composition of Example 1 except that a part of the non-oil-extended SBR is replaced with brominated butyl. The ozone cracking property decreased.

  Examples 4 and 5 have the same formulation as the rubber composition of Example 1 except that 40 parts by weight of EPDM having a different composition was blended. Improved as well.

  The rubber compositions of Comparative Examples 9 and 10 were blended with 40 parts by weight of EPDM and EPM having a diene content of less than 5% by weight, respectively, and the ozone crack resistance at 50 ° C. decreased.

  The rubber compositions of Examples 6 to 8 were blended with carbon black having a blending amount and a nitrogen adsorption specific surface area within the range of the present invention, and exhibited practically high breaking strength, tan δ and good ozone crack resistance. .

  The rubber composition of Comparative Example 11 was blended with carbon black having a nitrogen adsorption specific surface area outside the range specified in the present invention. Although the ozone crack resistance was improved, the breaking strength and tan δ were deteriorated.

  The rubber compositions of Comparative Examples 12 and 13 are those in which carbon black is blended in a blending amount outside the range specified in the present invention, and it is possible to achieve both break strength, tan δ, and ozone crack resistance at a practical level. There wasn't.

  From the above evaluation results, in order to achieve good ozone crack resistance, practical level grip performance (tan δ) and breaking strength at the same time, it is necessary to make the rubber composition formula satisfy the scope of the present invention. It turns out that it is.

FIG. 1 is a cross-sectional view of an emergency pneumatic tire according to a preferred embodiment of the present invention. FIG. 2 is a partially enlarged cross-sectional view of an emergency pneumatic tire according to a preferred embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread 1a Cap tread part 1b Under tread part 2, 2 'Side wall 3, 3' Bead part 4 Carcass layer 4a Outer carcass layer 4b Inner carcass layer 5, 5 'Bead core 6 Breaker 7, 7' Bead filler 8 Groove 9 Shoulder Part 10 Groove bottom

Claims (2)

(A) (i) 15 to 45% by weight of an ethylene-propylene-diene terpolymer rubber having a diene component content of 5% by weight or more and less than 13% by weight and (ii) a diene rubber excluding a halogenated butyl rubber A rubber component consisting of 85 to 55% by weight, and (B) a carbon black having a nitrogen adsorption specific surface area of 65 to 150 m ² / g of 50 to 100 parts by weight with respect to 100 parts by weight of the rubber component (A) And (C) an emergency provided with a cap tread portion formed by using a rubber composition containing 0.5 to 1.5 parts by weight of an amine anti-aging agent with respect to 100 parts by weight of the rubber component (A). Pneumatic tires.   The emergency pneumatic tire according to claim 1, wherein the cap tread portion has a groove having a depth of 4 mm or less, and a thickness from the groove bottom to the breaker or the outermost carcass layer is 3 mm or less. .

Images