JP4646587B2 - Rubber composition and pneumatic radial tire for aircraft using the same - Google Patents

Description

  The present invention relates to a rubber composition and a pneumatic radial tire for an aircraft using the rubber composition, and is particularly excellent in heat aging resistance of a portion of a bead portion that contacts a rim flange, hardly cracks, and greatly improves safety. The present invention relates to an improved pneumatic radial tire for aircraft.

  Aircraft radial radial tires used for aircraft, linear motor cars, and the like rotate at a significantly higher speed and bear a higher load than takeoff and landing tires compared to truck and bus tires. For this reason, pneumatic radial tires for airplanes are required to have a failure such as a burst even when rotating at a much higher speed and bearing a higher load than ordinary tires for trucks and buses. Aircraft radial radial tires are generally reused after being rehabilitated (hereinafter referred to as “retread”) from a tread rubber that contacts the ground for economic reasons. Therefore, in the pneumatic radial tire for aircraft, not only the initial safety, but also the surface crack of the bead portion caused by the heat aging phenomenon after traveling has become a problem. In particular, when a failure occurs, the rubber composition applied to the periphery of the case and bead of a tire, which can lead to a serious accident, must have high strength even under high speed and high load (large deformation). It is requested.

  In addition, pneumatic radial tires for aircraft can reduce the number of carcass plies and reduce weight compared to conventional tires with a bias structure, but at the same time when traveling under high-speed and high-load conditions. Due to heat aging, there is a problem that a rubber crack failure occurs in the periphery of the bead part, particularly in the surface part of the bead part, and there is concern about the influence on the carcass inside the bead part.

  On the other hand, Japanese Patent Application Laid-Open No. 2003-320820 (Patent Document 1) applies a highly elastic rubber composition to a portion of the bead portion that contacts the rim flange to prevent surface deformation, and before heat aging. A countermeasure for preventing the occurrence of cracks by applying a rubber composition having a large elongation at the time of cutting has been proposed.

JP 2003-320820 A

  However, even in the tire described in Japanese Patent Application Laid-Open No. 2003-320820, the rubber composition used in the portion that contacts the rim flange is subjected to an aging phenomenon due to heat as it continues to run and the number of rehabilitation progresses, and crack failure occurs. Has occurred.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, the portion of the bead portion that contacts the rim flange is excellent in heat aging resistance, is less prone to cracking, and has significantly improved safety. It is to provide a pneumatic radial tire for use. Moreover, the other object of this invention is to provide the rubber composition applied to the member which contacts the rim flange of this pneumatic radial tire for aircraft.

  As a result of diligent studies to achieve the above object, the present inventor has found that a specific amount of HAF grade carbon black is blended with a specific rubber component at a specific portion in contact with the rim flange of a pneumatic radial tire for aircraft. By applying the composition, the heat aging resistance of the part can be improved and the occurrence of cracks can be suppressed, and as a result, the safety of pneumatic radial tires for aircraft can be greatly improved. The invention has been completed.

  That is, the rubber composition of the present invention is a rubber composition applied to a member that comes into contact with the rim flange of an aircraft pneumatic radial tire, and is 30 to 50% by mass of natural rubber and / or synthetic polyisoprene rubber. -It is characterized by blending 45-60 parts by weight of HAF grade carbon black with 100 parts by weight of a rubber component comprising 70-50% by weight of polybutadiene rubber having a 1,4 bond content of 94% or more. .

  In the rubber composition of the present invention, the polybutadiene rubber is a polymer obtained by polymerizing 1,3-butadiene using a cobalt compound or a neodymium compound as a polymerization catalyst, and has a weight average molecular weight (Mw) and a number. The polydispersity (Mw / Mn) represented by the ratio to the average molecular weight (Mn) is preferably 4.3 or less.

  Further, the rubber composition of the present invention preferably has a tensile stress at 100% elongation of vulcanized rubber obtained by vulcanization at 145 ° C. for 30 minutes of 2.4 MPa or more, and 2.5 to 3.5 MPa. More preferably, the elongation at break after heat aging at 100 ° C. for 48 hours as a vulcanized rubber obtained by vulcanization at 145 ° C. for 30 minutes is preferably 300% or more.

  Here, the tensile stress at 100% elongation of the rubber composition is a value before heat aging of the vulcanized rubber obtained by vulcanizing the rubber composition at 145 ° C. for 30 minutes, The elongation at break is a value after the vulcanized rubber is heat-aged at 100 ° C. for 48 hours, and these values are measured before and after the heat aging treatment of the JIS # 3 type test piece made of the vulcanized rubber. This is a value measured by performing a tensile test in accordance with JIS K 6251 later.

  Further, the pneumatic radial tire for aircraft according to the present invention is a pneumatic radial tire for aircraft in which a plurality of carcass plies are arranged between a pair of left and right bead portions, and the bead in a state in which a specified internal pressure is filled by mounting on a standard rim. When the height of the rim flange is H with respect to the base position, a surface rubber layer exposed to the outside of the tire and a base rubber layer located on the back side of the surface rubber layer are arranged at least in the range of 0.5H to 1.5H. And the rubber composition is applied to the surface rubber layer.

  In a preferred example of the pneumatic radial tire for aircraft according to the present invention, a rubber composition having a tensile stress at 100% elongation of 2.9 MPa or more is applied to the base rubber layer. In this case, it is possible to prevent the surface rubber layer from becoming relatively hard, and to prevent heat damage in the base rubber layer. In addition, the value of the tensile stress at 100% elongation of the rubber composition used for the base rubber layer is based on JIS K 6251 without heat aging the vulcanized rubber obtained by vulcanization at 145 ° C. for 30 minutes. It is the value measured by conducting a tensile test.

  In the pneumatic radial tire for aircraft according to the present invention, the maximum thickness of the surface rubber layer is preferably 2.0 mm or more and less than 4.5 mm, and more preferably 2.5 mm or more and 3.5 mm or less. In this case, deformation of the surface rubber layer can be sufficiently suppressed while sufficiently improving the crack resistance of the surface rubber layer.

  According to the present invention, by applying a rubber composition in which a specific amount of HAF grade carbon black is blended with a specific rubber component at a site that comes into contact with the rim flange, the heat aging resistance of the site is improved and cracks are prevented. It is possible to provide a pneumatic radial tire for an aircraft that is extremely safe and has reduced occurrence.

  Hereinafter, the pneumatic radial tire for aircraft according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional view showing an example of a bead portion of an aircraft pneumatic radial tire according to the present invention. In the illustrated tire, a carcass 2 composed of a plurality of carcass plies is disposed between a pair of left and right bead portions 1 (the left side is not shown), and the bead core 3 embedded in the bead portion 1 has a tire radial outer side. The bead filler 4 is disposed. Although the carcass 2 in the illustrated example has a structure wound around the bead core 3 from the inner side in the tire width direction toward the outer side, the structure of the carcass 2 is not limited to this. The carcass 2 is composed of a plurality of carcass plies, but the number is not particularly limited as long as the number is plural.

  In addition, a rim base rubber 5 is disposed at a portion of the bead portion 1 that is in contact with the rim base of the standard rim R on the innermost side in the tire radial direction, and is further attached to the standard rim R and filled with a specified internal pressure. The surface rubber layer 6 exposed to the outside of the tire is disposed in the range of at least 0.5H to 1.5H of the tire when the rim flange height of the standard rim R is H with respect to the bead base position A of the tire. A base rubber layer 7 is disposed on the back side of the rubber layer 6 (inner side in the tire width direction) and on the outer side in the tire width direction of the carcass 2. The surface rubber layer 6 and the base rubber layer 7 form a rim cushion rubber layer 8. Forming.

  Here, the standard rim is described in the yearbook (2001 version) of the American Tire and Rim Association, Inc., and the bead base position A is: This is the position specified by the intersection of the extension line of the bead seat of the rim on which the bead base is mounted and the extension line of the rim flange (standard rim width dimension line).

  Further, a side rubber 9 is disposed on the outer side in the tire radial direction of the rim cushion rubber layer 8, and the side rubber 9 forms a sidewall portion (not shown) of the tire together with the carcass 2 and the like. Furthermore, it continues to the tread part (not shown). In the pneumatic radial tire for aircraft according to the present invention, the structure of the sidewall portion and the tread portion and the members used are not particularly limited.

  In the pneumatic radial tire for aircraft according to the present invention, it is necessary to dispose the surface rubber layer 6 exposed to the outside of the tire in a range of at least 0.5H to 1.5H. Here, when the arrangement position of the surface rubber layer 6 is made narrower than the range of 0.5H to 1.5H, a rubber boundary portion is located at the contact portion between the tire and the rim flange, so that cracks may occur during manufacturing. is there.

  The surface rubber layer 6 includes a rubber component 100 comprising 30 to 50% by mass of natural rubber and / or synthetic polyisoprene rubber and 70 to 50% by mass of polybutadiene rubber having a cis-1,4 bond content of 94% or more. A rubber composition formed by blending 45 to 60 parts by mass of HAF grade carbon black with respect to parts by mass is applied. The rubber composition of this composition has a sufficiently high tensile stress before heat aging and has a sufficiently large elongation at break after heat aging. Therefore, by applying the rubber composition to the surface rubber layer 6, surface rubber can be obtained. The heat aging resistance of the layer 6 can be improved to suppress the occurrence of cracks, and the safety of the pneumatic radial tire for aircraft can be greatly improved.

  The rubber component of the rubber composition for the surface rubber layer 6 is a polybutadiene rubber (natural rubber (NR) and / or synthetic polyisoprene rubber (IR) 30 to 50% by mass and a cis-1,4 bond content of 94% or more. BR) 70 to 50% by mass is required. When the proportion of natural rubber and / or synthetic polyisoprene rubber in the rubber component is less than 30% by mass, that is, when the proportion of polybutadiene rubber having a cis-1,4 bond content of 94% or more exceeds 70% by mass, elongation at break Will fall. On the other hand, if the proportion of polybutadiene rubber having a cis-1,4 bond content of 94% or more in the rubber component is less than 50% by mass, that is, if the proportion of natural rubber and / or synthetic polyisoprene rubber exceeds 50% by mass, Wear of the surface rubber is promoted.

  The polybutadiene rubber used in the rubber composition must have a cis-1,4 bond content of 94% or more. If the polybutadiene rubber used has a cis-1,4 bond content of less than 94%, the crack resistance is lowered. The cis-1,4 bond content of the polybutadiene rubber can be measured by, for example, an infrared method (Morello method).

  The polybutadiene rubber having a cis-1,4 bond content of 94% or more can be produced by a known method, and a commercially available product can be used, but a cobalt (Co) compound or a neodymium (Nd) compound is used as a polymerization catalyst. It is preferable to use a polymer obtained by polymerizing 1,3-butadiene. Here, the cobalt compound is not particularly limited, and examples thereof include cobalt octoate, cobalt naphthenate, cobalt benzoate, cobalt acetylacetonate, cobalt acetoacetate complex, and the neodymium compound. Is not particularly limited, and examples thereof include neodymium tri-2-ethylhexanoate, neodymium trineodecanoate, a complex compound of these with acetylacetone, and neodymium tri-n-butoxide.

  As the high cis polybutadiene rubber, it is preferable to use a polymer having a polydispersity (Mw / Mn) represented by a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 4.3 or less. . The polydispersity (Mw / Mn) indicates the sharpness of the molecular weight distribution, and the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polybutadiene rubber are determined as values in terms of polystyrene using, for example, GPC. be able to.

  The rubber composition for the surface rubber layer 6 contains, as a reinforcing filler, 45-60 parts by mass of HAF grade carbon black with respect to 100 parts by mass of the rubber component. If the blending amount of the HAF grade carbon black is less than 45 parts by mass with respect to 100 parts by mass of the rubber component, the elongation at the time of cutting of the rubber composition is improved, but the rigidity is lowered. The tensile stress at the time decreases and deformation of the surface rubber layer 6 cannot be prevented. On the other hand, when the amount exceeds 60 parts by mass, the rigidity of the rubber composition is improved, but the elongation at break after thermal aging is decreased. Therefore, the occurrence of cracks in the surface rubber layer 6 cannot be sufficiently suppressed. Here, examples of the HAF grade carbon black include N330, N339, and the like.

  In addition to the rubber component and HAF grade carbon black, the rubber composition for the surface rubber layer 6 is a compounding agent usually used in the rubber industry, such as stearic acid, zinc white, anti-aging agent, vulcanization accelerator. Vulcanization accelerators, vulcanizing agents, and the like can be appropriately selected and blended within a range that does not impair the object of the present invention, and commercially available products can be used as these blending agents. In addition, the said rubber composition can be manufactured by mix | blending HAF grade carbon black and the various compounding agents selected suitably as needed to a rubber component, kneading | mixing, heating, and extruding.

  The rubber composition for the surface rubber layer 6 is vulcanized at 145 ° C. for 30 minutes to give a vulcanized rubber, and has an elongation at break of 300% or more after the vulcanized rubber is heat-aged at 100 ° C. for 48 hours. It is preferable. If a rubber composition having an elongation at cutting after heat aging of less than 300% is used for the surface rubber layer 6, it becomes impossible to sufficiently suppress the occurrence of cracks in the surface rubber layer 6.

  The rubber composition for the surface rubber layer 6 preferably has a tensile stress at 100% elongation of 2.4 MPa or more as a vulcanized rubber obtained by vulcanization at 145 ° C. for 30 minutes, and is 2.5 to 3.5 MPa. More preferably. If a rubber composition having a tensile stress at 100% elongation before heat aging of less than 2.4 MPa is used for the surface rubber layer 6, deformation of the surface rubber layer 6 cannot be prevented.

  The surface rubber layer 6 preferably has a maximum thickness of 2.0 mm or more and less than 4.5 mm, and more preferably 2.5 mm or more and 3.5 mm or less. If the maximum thickness of the surface rubber layer 6 is less than 2.0 mm, the effect of improving the crack resistance of the surface rubber layer 6 is insufficient, while if it is 4.5 mm or more, the deformation of the rubber becomes remarkable.

  On the other hand, a rubber composition having a tensile stress at 100% elongation of 2.9 MPa or more is preferably applied to the base rubber layer 7 of the rim cushion rubber layer 8. When the tensile stress at 100% elongation of the rubber composition applied to the base rubber layer 7 is less than 2.9 MPa, the surface rubber layer 6 becomes relatively hard, and the base rubber layer 7 is heat-resistant.

  The pneumatic radial tire for aircraft of the present invention is not particularly limited except that the above rubber composition is used for the surface rubber layer 6, and can be manufactured according to a conventional method. Further, as the gas filled in the pneumatic radial tire for an aircraft, an inert gas such as nitrogen, argon, helium, etc. can be used in addition to air having normal or oxygen partial pressure adjusted. The pneumatic radial tire for aircraft of the present invention can be used for a linear motor car as well as an aircraft.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  A rubber composition was prepared according to the formulation shown in Table 1, and the rubber composition was vulcanized at 145 ° C. for 30 minutes to prepare a JIS # 3 type test piece. Next, the test piece was subjected to a tensile test according to JIS K 6251, and the tensile stress at 100% elongation before heat aging was measured. Moreover, after carrying out the heat aging of the test piece similar to the above for 48 hours at 100 degreeC, the tension test was done based on JISK6251 and the elongation at the time of cutting after heat aging was measured. The results are shown in Table 1.

  Next, the rubber composition was applied to the surface rubber layer 6 to prototype a pneumatic radial tire for aircraft having a bead portion having the structure shown in FIG. The size of the prototype tire is APR 50 × 20.0R22 32PR, and the position of the surface rubber layer is in the range of 0.5H to 1.5H with respect to the rim flange height H. The maximum thickness was 3.0 mm, and a rubber composition having a tensile stress at 3.0% elongation of 3.0 MPa was applied to the base rubber layer 7. The tires obtained were stored in a 100 ° C incubator for 48 hours, then attached to a drum tester and approved by the US Aviation Administration (FAA) under the standard internal pressure of 220 psi (1520 kPa). One cycle of “TSO-C62 d” was performed, the number of cracks in the surface rubber of the bead portion after the test and the deformation state of the rubber were visually determined, and further, the presence or absence of destruction of the base rubber layer was examined. The results are shown in Table 1.

* 1 RSS # 3
* 2 Ube Industries, BR150L, using cobalt catalyst, cis-1,4 bond content = 95%, Mw / Mn = 3.3
* 3 JSR, BR01, using nickel catalyst, cis-1,4 bond content = 94%, Mw / Mn = 4.2
* 4 N339
* 5 Nouchi 6C, N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd.
* 6 Ouchi Shinsei Chemical Co., Ltd., Noxeller NS, Nt-butyl-2-benzothiazolylsulfenamide

  As is clear from Table 1, the rubber compositions of Comparative Examples 1 and 2 have too much carbon black, and the rubber composition of Comparative Example 3 has a too high proportion of polybutadiene rubber (that is, natural composition). Since the ratio of rubber is too low), the elongation at break after thermal aging is insufficient, and the tires of Comparative Examples 1 to 3 in which these rubber compositions are applied to the surface rubber layer are cracked on the bead surface. Had occurred. Further, in the tire of Comparative Example 1, destruction of the base rubber layer was also observed. Furthermore, although the rubber composition of Comparative Example 4 has a sufficiently large elongation at the time of cutting after heat aging, the amount of carbon black is too small, so that the tensile stress at 100% elongation is small. In the tire of Comparative Example 4 in which was applied to the surface rubber layer, deformation was observed in the bead portion.

  On the other hand, since the rubber compositions of Examples 1 to 3 are rubber compositions formulated according to the present invention, sufficient tensile stress at 100% elongation (before heat aging) and elongation at break (before cutting) In the tires of Examples 1 to 3 in which these rubber compositions are applied to the surface rubber layer, the occurrence of cracks on the surface of the bead portion is prevented, and Deformation was also prevented.

It is a fragmentary sectional view showing an example of the bead part of the pneumatic radial tire for airplanes of the present invention.

Explanation of symbols

1 Bead part 2 Carcass 3 Bead core 4 Bead filler 5 Rim base rubber 6 Surface rubber layer 7 Base rubber layer 8 Rim cushion rubber layer 9 Side rubber R Standard rim A Bead base position H Rim flange height

Claims (7)

In an aircraft pneumatic radial tire in which a plurality of carcass plies are arranged between a pair of left and right bead portions, the height of the rim flange is set to H with reference to the bead base position in a state of being mounted on a standard rim and filled with a specified internal pressure. A surface rubber layer exposed to the outside of the tire and a base rubber layer located on the back side of the surface rubber layer are disposed in a range of at least 0.5H to 1.5H, and natural rubber and / or The vulcanization rate according to ASTM D1765-01 is applied to 100 parts by mass of rubber component consisting of 30-50% by mass of synthetic polyisoprene rubber and 70-50% by mass of polybutadiene rubber having a cis-1,4 bond content of 94% or more. It is a standard, and the average nitrogen surface area of 70~99m ² / g
It is characterized by blending 45-60 parts by mass of carbon black,
Pneumatic aircraft characterized by applying a rubber composition characterized in that the tensile stress at 100% elongation of vulcanized rubber obtained by vulcanization at 145 ° C for 30 minutes is 2.4 MPa or more and 3.4 MPa Radial tire. The polybutadiene rubber is a polymer obtained by polymerizing 1,3-butadiene using a cobalt compound or a neodymium compound as a polymerization catalyst, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). 2. The pneumatic radial tire for an aircraft according to claim 1, wherein the polydispersity (Mw / Mn) represented by the formula is 4.3 or less.   The vulcanized rubber obtained by vulcanizing at 145 ° C for 30 minutes has a tensile stress at 100% elongation of 2.4 MPa or more and vulcanized rubber obtained by vulcanizing at 145 ° C for 30 minutes at 48 ° C. The pneumatic radial tire for aircraft according to claim 1, wherein an elongation at break after time heat aging is 300% or more.   The pneumatic radial tire for an aircraft according to any one of claims 1 to 3, wherein a rubber composition having a tensile stress at 100% elongation of 2.9 MPa or more is applied to the base rubber layer.   The pneumatic radial tire for aircraft according to any one of claims 1 to 3, wherein the maximum thickness of the surface rubber layer is 2.0 mm or more and less than 4.5 mm.   The pneumatic radial tire for aircraft according to claim 5, wherein the maximum thickness of the surface rubber layer is 2.5 mm or more and 3.5 mm or less. The vulcanization rate according to ASTM D1765-01 is standard, and the carbon black having an average nitrogen surface area of 70 to 99 m ² / g is either N330 or N339. Pneumatic radial tire for aircraft.

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