JP6215141B2 - Run flat tire - Google Patents

Description

  The present invention relates to a run flat tire.

  There is a pneumatic tire called a run-flat tire that can travel a certain distance even when the air pressure inside the tire is reduced to 0 kPa due to a failure such as puncture. As a technique for enabling run-flat running with such an internal pressure lowered, it is known to reinforce the sidewall portion by providing a side reinforcing rubber portion on the inner surface of the sidewall portion (Patent Literature). 1 and 2).

  In such a side reinforcing type run flat tire, a high rigidity rubber is used for the side reinforcing rubber portion in order to suppress deformation of the tire during the run flat running. However, since the temperature of the side reinforcing rubber portion becomes high during run flat running, the rigidity of the side reinforcing rubber portion is lowered and the run flat durability is lowered. On the other hand, if the rigidity reduction of the side reinforcing rubber portion at high temperature is suppressed, the stress applied to the bead portion during run-flat running increases. Therefore, separation may occur between the high-hardness bead filler and the low-hardness carcass ply rubber, and the run-flat durability may be reduced.

  In Patent Document 3, in order to increase the adhesion between the bead filler and the carcass ply, a natural rubber cement layer containing a larger amount of sulfur than the bead filler and the carcass ply may be provided. It is disclosed. In Patent Document 4, a rubber layer is provided between the bead filler and the carcass ply to suppress separation, and the sulfur content of the rubber layer is made smaller than the sulfur content of the carcass ply rubber. Is disclosed. However, none of these are related to run-flat tires, and there is no disclosure that the rubber layer has a sulfur content greater than that of carcass ply rubber and less than that of bead fillers.

JP 2006-282913 A JP 2008-189911 A Japanese Patent Laid-Open No. 06-270616 JP 2012-224678 A

  An object of the present invention is to provide a run flat tire excellent in run flat durability.

  A run flat tire according to the present invention includes a tread portion, a pair of sidewall portions extending radially inward from both ends of the tread portion, and a pair of bead portions provided radially inward of the sidewall portion. A pair of annular bead cores provided in the bead portion, a carcass ply made of a carcass cord and a covering rubber extending in a toroidal shape between the pair of bead cores, and provided on an outer periphery of the bead core. A bead filler, a side reinforcing rubber portion provided on the side wall portion to reinforce the side wall portion, and a rubber layer interposed between the bead filler and the carcass ply. The side reinforcing rubber part has a ratio (M50H / M50N) of a tensile stress (M50H) at 50% elongation at a measurement temperature of 100 ° C to a tensile stress (M50N) at 50% elongation at a measurement temperature of 23 ° C of 1. It consists of a rubber composition that is 0 or more and 1.3 or less. In the rubber composition for a rubber layer, a mass ratio of styrene butadiene rubber in a rubber component is larger than the rubber composition for bead filler and smaller than the rubber composition for coated rubber, and 100 mass of the rubber component. The amount of sulfur added to the part is less than the rubber composition for bead filler and more than the rubber composition for coated rubber.

  According to the present invention, the rubber layer is formed between the bead filler and the carcass ply while forming the side reinforcing rubber portion using a rubber composition having a tensile stress at a high temperature equal to or higher than that at a normal temperature. As described above, the amount of styrene-butadiene rubber and the amount of sulfur are defined. Therefore, during run flat running, excessive deformation of the sidewall portion can be suppressed, and separation between the bead filler and the carcass ply can be suppressed, and therefore run flat durability can be improved. .

Half sectional view of a run flat tire according to an embodiment Sectional view of the test piece used for the adhesion test between the carcass ply and the bead filler Cross-sectional view of the test road used to evaluate the passability

  As shown in FIG. 1, a run flat tire according to one embodiment is a pneumatic radial tire for passenger cars, and includes a tread portion (1) and a pair of left and right sidewall portions (2) extending radially inward from both ends thereof. ) And a pair of left and right bead portions (3) provided radially inward of the sidewall portion (2). An annular bead core (4) is embedded in each of the pair of bead portions (3). In the figure, CL indicates the tire equator. In this example, the tire has a symmetrical structure with respect to the tire equator CL.

  In the tire, at least one carcass ply (5) extending in a toroidal shape is embedded between the pair of bead cores (4). In this example, the number of carcass plies (5) is one, but two or more may be provided. The carcass ply (5) extends from the tread portion (1) through the sidewall portion (2) to the bead portion (3), and the end portion of the carcass ply (5) around the bead core (4) in the bead portion (3). It is locked by turning back. In this example, the end portion of the carcass ply (5) is folded around the bead core (4) from the inner side in the tire width direction to the outer side and locked. The carcass ply (5) includes a carcass cord made of an organic fiber cord or the like and a covering rubber that covers the carcass cord. The carcass cords are arranged substantially at right angles to the tire circumferential direction. An inner liner layer (6) for maintaining air pressure is provided on the tire inner surface side of the carcass ply (5).

  Between the main body part (5A) of the carcass ply (5) and the folded part (5B), a bead filler (7) made of hard rubber is provided on the outer periphery (ie, radially outer peripheral side) of the bead core (4). It has been. The bead filler (7) has a triangular cross section in which the width gradually decreases toward the radially outer side.

  Each of the pair of sidewall portions (2) is provided with a side reinforcing rubber portion (8) also called a side pad in order to increase the rigidity thereof. The side reinforcing rubber part (8) is disposed on the tire inner surface side of the carcass ply (5) in the side wall part (2). In this example, the carcass ply (5) and the inner liner layer (6) It is sandwiched. The side reinforcing rubber portion (8) is thick at the central portion in the radial direction of the side wall portion (2), and is gradually thinned from the central portion toward the tread portion (1) side and the bead portion (3) side. In the tire meridian cross section shown in FIG. 1, a crescent-shaped cross section is formed.

  The side reinforcing rubber portion (8) extends inward in the radial direction beyond the tip (ie, radially outer end) of the bead filler (7). Accordingly, the side reinforcing rubber portion (8) and the bead filler (7) have an overlap in the tire radial direction, and the side reinforcing rubber portion (8) and the bead filler (7) of the carcass ply (5) are overlapped in this overlapping portion. It is adjacent to the main body (5A).

  A belt (10) comprising at least two belt plies is arranged between the carcass ply (5) and the tread rubber portion (9) on the radially outer peripheral side of the carcass ply (5) in the tread portion (1). Has been. A belt reinforcing layer (11) is provided on the outer peripheral side of the belt (10).

In the run flat tire according to the present embodiment, the side reinforcing rubber portion (8) that reinforces the sidewall portion (2) is formed using a rubber composition having a novel physical property that improves run flat durability. . In the rubber composition, the tensile stress at 50% elongation at a measurement temperature of 23 ° C. is M50N, the tensile stress at 50% elongation at a measurement temperature of 100 ° C. is M50H, and the ratio of both is M50H / M50N. Satisfy the relationship. That is, the rubber composition constituting the side reinforcing rubber portion (8) satisfies the following relationship in physical properties of vulcanized rubber.
1.0 ≦ M50H / M50N ≦ 1.3
As a result, a side reinforcing rubber portion (8) having the same physical properties is obtained, and while maintaining the running performance during normal running (for example, saddle riding performance), the deformation of the side wall during run flat running is suppressed. Flat durability can be improved.

  More specifically, in a rubber composition with a high hardness generally used for a side reinforcing rubber portion of a run flat tire, the elastic modulus decreases at a high temperature. In this embodiment, this relationship is reversed to correspond to a run flat running time. A rubber composition is used in which the tensile stress at high temperature (100 ° C.) is equal to or higher than the tensile stress at normal temperature (23 ° C.) corresponding to normal running. When M50H / M50N is 1.0 or more, it is possible to suppress run-down durability and improve run-flat durability. More preferably, the tensile stress at high temperature is higher than the tensile stress at normal temperature, that is, M50H / M50N> 1.0, and more preferably, M50H / M50N is 1.1 or more. On the other hand, if M50H / M50N is too large, the rigidity at high temperatures becomes too high and runflat durability is impaired. M50H / M50N is preferably less than 1.3, more preferably 1.2 or less.

  The tensile stress (M50H) at 50% elongation at a measurement temperature of 100 ° C. of the rubber composition constituting the side reinforcing rubber part is 3.5 MPa or more, which increases the rigidity of the side wall part at high temperature, It is preferable for improving flat durability. The lower limit of M50H is more preferably 4.0 MPa or more. Further, the upper limit of M50H is not particularly limited, but is preferably 5.5 MPa or less, more preferably 5.3 MPa or less. By setting such an upper limit, the rigidity becomes too high at high temperatures. Therefore, it is possible to improve the run-flat durability by suppressing the side wall portion from becoming difficult to bend. The tensile stress (M50N) at 50% elongation at a measurement temperature of 23 ° C. of the rubber composition is not particularly limited, but is 3.0 to 5.0 MPa in order to maintain good running performance during normal running. More preferably, the lower limit is 3.5 MPa or more, and the upper limit is 4.5 MPa or less.

  In the side reinforcing rubber part (8), various rubber compositions having a physical property of the vulcanized rubber can be used by blending a rubber component made of a diene rubber with a filler. A rubber composition for a side reinforcing rubber part according to an embodiment is obtained by blending a rubber component containing natural rubber (NR) and polybutadiene rubber (BR) with a phenol-based thermosetting resin and a methylene donor as a curing agent thereof. The mass ratio of the blending amount of the phenolic thermosetting resin with respect to the methylene donor is 1.5 times or more.

  The natural rubber and polybutadiene rubber as the rubber component are not particularly limited, and those generally used in the rubber industry can be used. The blending ratio of the two in the rubber component is not particularly limited. For example, the natural rubber may be 20 to 70% by mass or 30 to 60% by mass. 30-80 mass% may be sufficient as polybutadiene rubber, and 40-70 mass% may be sufficient as it. The tear resistance can be improved by increasing the content of natural rubber, and the bending fatigue resistance can be improved by increasing the content of polybutadiene rubber.

  The rubber component may be composed only of natural rubber and polybutadiene rubber, but other diene rubbers may be blended. Other rubbers are not particularly limited, and examples thereof include styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and chloroprene rubber (CR).

  As the phenol-based thermosetting resin, a thermosetting resin obtained by condensing at least one phenol compound selected from the group consisting of phenol, resorcin, and alkyl derivatives thereof with an aldehyde such as formaldehyde is used. , High hardness can be achieved. In addition to methyl group derivatives such as cresol and xylenol, the alkyl derivatives include derivatives of relatively long chain alkyl groups such as nonylphenol and octylphenol. Specific examples of the phenolic thermosetting resin include an unmodified phenolic resin (straight phenolic resin) obtained by condensing phenol and formaldehyde, an alkyl-substituted phenolic resin obtained by condensing alkylphenol such as cresol, xylenol, and octylphenol with formaldehyde, Various novolak type phenol resins such as resorcin-formaldehyde resin obtained by condensing resorcin and formaldehyde, and resorcin-alkylphenol co-condensed formaldehyde resin obtained by condensing resorcin, alkylphenol and formaldehyde are exemplified. Further, for example, an oil-modified novolak phenol resin modified with at least one oil selected from the group consisting of cashew nut oil, tall oil, rosin oil, linole oil, oleic acid and linolenic acid can also be used. Any one of these phenol-based thermosetting resins may be used, or two or more thereof may be used in combination.

  Hexamethylenetetramine and / or melamine derivatives are used as the methylene donor to be blended as a curing agent for the phenol-based thermosetting resin. Examples of the melamine derivative include at least one selected from the group consisting of hexamethoxymethyl melamine, hexamethylol melamine pentamethyl ether, and polyvalent methylol melamine. Among these, as a methylene donor, hexamethoxymethyl melamine and / or hexamethylene tetramine are preferable, and hexamethoxymethyl melamine is more preferable.

  The blending amount (A) of the phenol-based thermosetting resin is A / B ≧ 1.5 in terms of mass ratio with the blending amount (B) of the methylene donor. If the proportion of the methylene donor as the curing agent is too large, the rubber crosslinking system may be adversely affected. By using it at an appropriate ratio, it becomes easy to set the ratio of M50H / M50N within the above range, and the effect of suppressing deformation during run-flat running can be enhanced and the run-flat durability can be improved. A / B is more preferably 2.0 or more, and further preferably 2.5 or more. The upper limit of A / B is preferably 7.0 or less, more preferably 5.0 or less, and still more preferably 4.0 or less.

  Although the compounding quantity of a phenol type thermosetting resin is not specifically limited, It is preferable that it is 1-20 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 1-10 mass parts. Moreover, the compounding quantity of a methylene donor is although it does not specifically limit, It is preferable that it is 0.2-10 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 0.5-5 mass parts.

  You may mix | blend a quinoline-type anti-aging agent and at least 1 type of anti-aging agent other than a quinoline-type anti-aging agent in the rubber composition for side reinforcement rubber parts. By blending these two or more anti-aging agents, run flat durability can be improved.

  Examples of the quinoline antioxidant include 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ) and 6-ethoxy-2,2,4-trimethyl-1,2-dihydro- Examples include at least one selected from the group consisting of quinoline (ETMDQ).

  Other anti-aging agents used in combination with quinoline anti-aging agents include, for example, aromatic secondary amine-based anti-aging agents, phenol-based anti-aging agents, sulfur-based anti-aging agents, and phosphite-based anti-aging agents. And at least one antiaging agent selected from the group consisting of:

  Examples of the aromatic secondary amine type antioxidant include N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (6PPD), N-isopropyl-N′-phenyl-p- Phenylenediamine (IPPD), N, N'-diphenyl-p-phenylenediamine (DPPD), N, N'-di-2-naphthyl-p-phenylenediamine (DNPD), N- (3-methacryloyloxy-2- P-phenylenediamine-based antioxidants such as hydroxypropyl) -N′-phenyl-p-phenylenediamine, N-cyclohexyl-N′-phenyl-p-phenylenediamine; p- (p-toluenesulfonylamido) diphenylamine, 4 , 4′-bis (α, α-dimethylbenzyl) diphenylamine (CD), octylated diphenylamine Down (ODPA), diphenylamine-based antiaging agent such as styrenated diphenylamine; N- phenyl-1-naphthylamine (PAN), such as naphthylamine antioxidant such as N- phenyl-2-naphthylamine (PBN), and the like. Any of these may be used alone or in combination of two or more.

  Examples of the phenol-based anti-aging agent include monophenol-based anti-aging agents such as 2,6-di-tert-butyl-4-methylphenol (DTBMP) and styrenated phenol (SP); 2,2′-methylene- Bis (4-methyl-6-tert-butylphenol) (MBMBP), 2,2′-methylene-bis (4-ethyl-6-tert-butylphenol) (MBETB), 4,4′-butylidene-bis (3- Bisphenol-based antioxidants such as methyl-6-tert-butylphenol) (BBMTBP) and 4,4′-thio-bis (3-methyl-6-tert-butylphenol) (TBMTBP); 2,5-di-tert- Butylhydroquinone (DBHQ), 2,5-di-tert-amylhydroquinone (DAHQ), etc. Examples include idroquinone anti-aging agents. Any of these may be used alone or in combination of two or more.

  Examples of the sulfur-based antioxidant include benzimidazole-based antioxidants such as 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, and zinc salt of 2-mercaptobenzimidazole; dithiocarbamate salts such as nickel dibutyldithiocarbamate Anti-aging agents; thiourea-based anti-aging agents such as 1,3-bis (dimethylaminopropyl) -2-thiourea and tributylthiourea; and organic thioacids such as dilauryl thiodipropionate. Examples of the phosphite antioxidant include tris (nonylphenyl) phosphite. Any of these may be used alone or in combination of two or more.

  Among other antiaging agents used in combination with the quinoline type antiaging agent, among them, aromatic secondary amine type antiaging agents are preferable, and p-phenylenediamine type antiaging agents are more preferable.

  The blending amount of the quinoline anti-aging agent is preferably 20% by mass or more with respect to the total blending amount of the anti-aging agent, and the effect of improving the run flat durability can be enhanced. More preferably, it is 25 mass% or more, More preferably, it is 30 mass% or more. The upper limit of this ratio is preferably 80% by mass or less, and more preferably 75% by mass or less. The total blending amount of the anti-aging agent, that is, the total blending amount of the quinoline anti-aging agent and the other anti-aging agent is preferably 1 to 10 parts by mass, more preferably 100 parts by mass of the rubber component. Is 1.5-7 parts by mass, more preferably 2-5 parts by mass. The compounding amount of the quinoline antioxidant is preferably 0.2 to 8 parts by mass, more preferably 0.5 to 4 parts by mass with respect to 100 parts by mass of the rubber component.

  A filler such as carbon black and / or silica can be blended in the rubber composition for the side reinforcing rubber part. It is preferable that the compounding quantity of a filler is 20-100 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 30-80 mass parts, More preferably, it is 50-70 mass parts. As the filler, carbon black alone or a blend of carbon black and silica is preferable, and carbon black is more preferable. In addition, the value of the tensile stress of the rubber composition can be adjusted by the type and blending amount of the filler.

  The carbon black is not particularly limited. For example, ISAF class (N200 series), HAF class (N300 series), FEF class (N500 series), GPF class (N600 series) (both ASTM grade) are used. More preferably, it is FEF grade.

  In addition to the above components, the side reinforcing rubber part rubber composition includes various additives commonly used in tire rubber compositions such as oil, zinc white, stearic acid, wax, vulcanizing agent, and vulcanization accelerator. Can be blended. Here, examples of the vulcanizing agent include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the blending amount thereof is 100 parts by mass of the rubber component. It is preferable that it is 0.1-10 mass parts with respect to it, More preferably, it is 0.5-8 mass parts, More preferably, it is 1-5 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 0.5-5 mass parts.

  The rubber composition for the side reinforcing rubber part can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. Moreover, the side reinforcement rubber part (8) which consists of this rubber composition can be formed by vulcanization-molding a tire at 140-180 degreeC, for example according to a conventional method. When the rubber composition is used, the phenolic thermosetting resin and the methylene donor are blended in the above mass ratio, and two or more antiaging agents including a quinoline antiaging agent are blended. It is easy to set the ratio of M50H / M50N within the above range by increasing the tensile stress at, and the run-flat durability can be remarkably improved.

  In the run flat tire according to the present embodiment, as shown in FIG. 1, a rubber layer (12) interposed between the bead filler (7) and the carcass ply (5) is provided. In this example, the rubber layer (12) is formed by placing a rubber tape between the main body (5A) of the carcass ply (5) and the bead filler (7). The layer (12) is provided along the inner side surface in the tire width direction of the bead filler (7). The rubber layer (12) is provided over the entire height direction (tire radial direction) of the bead filler (7).

  Although not shown, the rubber layer (12) may be provided along the outer side surface of the bead filler (7) in the tire width direction. In this case, the rubber layer (12) is a folded portion of the carcass ply (5). (5B) and the bead filler (7). Moreover, you may provide along both the tire width direction inner side surface and outer side surface of a bead filler (7). Preferably, the rubber layer (12) is provided along the inner side surface in the tire width direction of the bead filler (7) as shown in FIG. 1, and the bead portion adjacent to the highly rigid side reinforcing rubber portion (8) ( The failure at the time of run-flat running in 3) can be more effectively suppressed.

  The thickness of a rubber layer (12) is not specifically limited, For example, 0.5-2.0 mm may be sufficient and 0.8-1.5 mm may be sufficient.

  In the present embodiment, the rubber layer (12) is formed using a rubber composition that satisfies the following relationships (i) and (ii). That is, in the rubber composition for the rubber layer, (i) the mass ratio of the styrene butadiene rubber (SBR) in the rubber component is larger than the rubber composition for the bead filler and more than the rubber composition for the covering rubber of the carcass ply. It is small, and (ii) the amount of sulfur compounded with respect to 100 parts by mass of the rubber component is less than the rubber composition for bead filler and more than the rubber composition for coated rubber.

  For (i) above, the mass ratio of SBR in the rubber component of the rubber composition for the rubber layer is Mr (mass%), the mass ratio of the rubber composition for bead filler is Mb (mass%), When the mass ratio of the rubber composition for rubber is Mp (mass%), Mb <Mr <Mp. Thus, by setting the SBR ratio of the rubber layer (12) to a value between the rubber compositions on both sides thereof, the rubber layer (12) can be applied to the coated rubber and bead filler (7) of the adjacent carcass ply (5). And the separation between the carcass ply (5) and the bead filler (7) during run-flat running can be suppressed.

  The rubber component of the bead filler rubber composition is preferably composed of natural rubber or natural rubber and SBR, and may not contain SBR. The mass ratio Mb of SBR in the rubber component is preferably 25% by mass or less. Therefore, in one embodiment, the rubber component is composed of 75 to 100% by mass of natural rubber and 25 to 0% by mass of SBR, more preferably natural. The rubber is 85 to 100% by mass and SBR is 15 to 0% by mass. The rubber component of the rubber composition for covering rubber of the carcass ply is preferably composed of natural rubber and SBR. In one embodiment, the rubber component is composed of 50 to 75% by mass of natural rubber and 50 to 25% by mass of SBR. The rubber component of the rubber composition for the rubber layer is preferably composed of natural rubber and SBR. In one embodiment, the rubber component is composed of 70 to 95% by mass of natural rubber and 30 to 5% by mass of SBR, more preferably. They are 80-95 mass% natural rubber and 20-5 mass% SBR.

  About said (ii), the sulfur compounding quantity with respect to 100 mass parts of rubber components in the rubber composition for rubber layers is made into Sr (mass part), and the sulfur compounding quantity with respect to 100 mass parts of rubber components in the rubber composition for bead filler is made into Sb ( Sb> Sr> Sp, where Sp (mass part) is the sulfur content relative to 100 parts by mass of the rubber component in the rubber composition for coated rubber. Thus, by setting the amount of sulfur as a cross-linking agent in the rubber layer (12) to a value between the rubber compositions on both sides thereof, the rubber layer (12) can be coated with the covering rubber of the adjacent carcass ply (5) and Adhesiveness with the bead filler (7) is improved, and separation between the carcass ply (5) and the bead filler (7) during run-flat running can be suppressed. Here, the sulfur blending amount is a net sulfur amount blended as a vulcanizing agent and does not include a sulfur component contained in the vulcanization accelerator or the like. Examples of sulfur as a vulcanizing agent include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

  3-10 mass parts is preferable and, as for the sulfur compounding quantity Sb of the rubber composition for bead fillers, 5-8 mass parts is more preferable. 0.5-7 mass parts is preferable and, as for the sulfur compounding quantity Sp of the rubber composition for coating rubber, 1-4 mass parts is more preferable. 1-8 mass parts is preferable and, as for sulfur compounding quantity Sr of the rubber composition for rubber layers, 2-6 mass parts is more preferable.

  A filler can be blended in the rubber composition for the bead filler, the covering rubber, and the rubber layer. The filler is preferably composed mainly of carbon black, and silica may be used in combination with carbon black. The blending amount of the filler may be, for example, 30 to 120 parts by mass or 40 to 100 parts by mass with respect to 100 parts by mass of the rubber component. Moreover, various additives, such as oil, zinc white, a stearic acid, anti-aging agent, a vulcanization accelerator, can be mix | blended with these rubber compositions. In addition, the above-described phenolic thermosetting resin may be blended in the bead filler rubber composition, and high rigidity can be achieved. The compounding quantity of a phenol type thermosetting resin is not specifically limited, 1-20 mass parts may be sufficient with respect to 100 mass parts of rubber components, and 5-15 mass parts may be sufficient. These rubber compositions can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll or other mixer.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

[Preparation and evaluation of rubber composition]
Using a Banbury mixer, according to the formulation (parts by mass) shown in Table 1 below, first, in the first step (non-pro mixing step), components other than sulfur, vulcanization accelerator and methylene donor are added and mixed (discharge temperature) = 160 ° C.) Then, in the second step (final mixing step), sulfur, a vulcanization accelerator, and a methylene donor were added and mixed (discharge temperature = 100 ° C.) in the second step (for the side reinforcing rubber part). A rubber composition was prepared. Similarly, a rubber composition for a rubber layer is prepared according to the formulation (parts by mass) shown in Table 2 below, and the rubber composition for bead filler and carcass ply coating rubber is prepared according to the formulation (parts by mass) shown in Table 3 below. Was prepared.

The detail of each component in Tables 1-3 is as follows.
・ NR: Natural rubber, RSS No. 3 ・ BR: “BR01” manufactured by JSR Corporation
・ SBR: "SBR1502" manufactured by JSR Corporation
・ Carbon black: N550, “Seast SO” manufactured by Tokai Carbon Corporation
・ Oil: “JOMO Process NC140” manufactured by JX Nippon Oil & Energy Sun Energy Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Phenolic resin: Oil-modified novolak-type phenolic resin, "Sumilite Resin PR13349" manufactured by Sumitomo Bakelite Co., Ltd.
・ Zinc flower: "Zinc flower No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent 1: N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine, “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Anti-aging agent 2: 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), “ANTAGE RD” manufactured by Kawaguchi Chemical Industry Co., Ltd.
・ Vulcanization accelerator 1: “Noxeller NS-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization accelerator 2: “Rhenogran HEXA-80 / SBR” manufactured by Rhein Chemie Japan
・ Methylene donor: hexamethoxymethylmelamine, “CYREZ 964RPC” manufactured by Mitsui Cytec Co., Ltd.
Sulfur: Shikoku Chemicals Co., Ltd. “Muclon OT-20” (sulfur content 80 mass%, oil content 20 mass%).

  About the rubber composition for the side reinforcing rubber part, using a test piece having a thickness of 2 mm vulcanized at 160 ° C. for 25 minutes, the tensile stress (M50N) at 50% elongation at 23 ° C. and 100 ° C. by the following method Tensile stress (M50H) at 50% elongation was measured and the ratio of both (M50H / M50N) was determined.

  -Tensile stress at 50% elongation at 23 ° C: Conforms to JIS K6251. About the dumbbell-shaped No. 3 type test piece, the tensile test was implemented at room temperature 23 degreeC, and the tensile stress at the time of 50% elongation was calculated | required.

  -Tensile stress at 50% elongation at 100 ° C: Conforms to JIS K6251. After holding a dumbbell-shaped No. 3 specimen in a thermostatic bath at 100 ° C for 1 hour or longer, a tensile test is carried out in a 100 ° C atmosphere with a tensile tester equipped with a thermostatic bath. Tensile stress at 50% elongation Asked.

  As shown in Table 1, in Formulation 1, which is a control, M50H / M50N, which is a ratio of normal temperature to high temperature tensile stress, was 0.9, and the rigidity decreased at high temperatures. In Formulation 2, the increase in carbon black and the addition of phenolic resin and methylene donor to Formulation 1 resulted in no decrease in tensile stress at high temperatures, but the increase in rigidity was too great, and M50H / M50N was It exceeded 1.3. On the other hand, while blending a predetermined amount of a phenolic resin and a methylene donor and blending two or more anti-aging agents including a quinoline anti-aging agent, the mixing stresses at high temperatures increase M50H. / M50N ratio could be in the range of 1.1 to 1.2.

[Production and evaluation of tires]
As shown in Table 4, the rubber composition for side reinforcing rubber part described in Table 1, the rubber composition for rubber layer described in Table 2, and the rubber composition for bead filler and coated rubber described in Table 3 are as shown in Table 4. 1 was used, and a radial tire having a tire size: 245 / 40ZR18 having the structure shown in FIG. 1 was vulcanized and molded according to a conventional method. About each tire, all the structures other than the side reinforcement rubber part, the bead filler, and the covering rubber were made common. As for the carcass ply (5), a rayon cord 1840 dtex / 3 was driven to make one ply at 21/25 mm, and the thickness of the covering rubber was 1.0 mm. The thickness of the rubber layer (12) was 1.0 mm.

  Moreover, in order to evaluate the adhesiveness of a bead filler and a carcass ply, the test piece for an adhesive test shown in FIG. 2 was produced. The evaluation method is as follows.

  ・ Adhesiveness: Each rubber composition for rubber layer, bead filler and coated rubber is processed into a rubber sheet having a thickness of 1 mm, and as shown in FIG. 2, the coated rubber (21), rubber layer (22) and bead An unvulcanized sample for adhesion test was prepared by laminating the filler (23) in this order. The unvulcanized sample was vulcanized at 160 ° C. for 30 minutes to obtain a test piece (20). Using an autograph “DCS500” manufactured by Shimadzu Corporation, the gripping margin of the coated rubber (21a) and the bead filler A peeling test was conducted by pulling the margin (23a) away from each other, and the average peeling force per 10 mm width was determined. It was displayed as an index with the average peel force value of Comparative Example 1 produced without sandwiching the rubber layer as 100. The larger the number, the higher the adhesion.

  Each tire obtained was evaluated for run-flat durability and overriding performance. Each evaluation method is as follows.

  Run-flat durability: A drum testing machine made of steel with a smooth surface and having a diameter of 1700 mm was used. The tire internal pressure was 0 kPa, and the load was 65% of the load capacity corresponding to the load index. After increasing the speed to 80 km / h in 5 minutes from the start of the test, the vehicle was run at 80 km / h until a failure occurred. The distance traveled until the failure occurred was indexed with the tire of Comparative Example 1 as 100. The larger the number, the better the run flat durability.

  ・ Saddle overpassability: A test road having a cross-sectional shape shown in FIG. 2 simulating a standard road ridge by mounting a test tire built in a standard rim with an internal pressure of 200 kPa on the front wheel of the test vehicle (height difference of the ridge h = 20 mm) Thus, sensory evaluation was carried out on the overpassability of the tire. The items that could easily get over the kite were marked with ○, those that were slightly difficult to get over were marked with △, and those that were very difficult to get over were marked with ×.

  The results are as shown in Table 4. In Comparative Example 1, although M50H / M50N of the side reinforcing rubber part is within the specified range, since no rubber layer is provided between the bead filler and the carcass ply, the adhesiveness at the interface between them is low, and the run flat durability It was inferior to. In Comparative Example 2, although a rubber layer was provided, the amount of sulfur blended was less than that of the coated rubber, and the adhesion between the bead filler and the carcass ply was inferior. In Comparative Example 3, the SBR mass ratio of the rubber layer was too large, and the adhesion and run-flat durability were greatly deteriorated. In Comparative Example 4, the SBR mass ratio of the rubber layer was too small, and the effect of improving adhesion and run-flat durability could not be obtained. In Comparative Example 5, the amount of sulfur compounded in the rubber layer was too large, and the adhesion and run flat durability were greatly deteriorated. In Comparative Examples 6 and 7, although the adhesive property was excellent by providing the prescribed rubber layer, the M50H / M50N of the side reinforcing rubber part was out of the range of 0.9 or 1.4. The flat durability was inferior. On the other hand, run flat durability can be remarkably improved without impairing the saddle riding performance when it is Examples 1 to 7 that satisfy both the M50H / M50N of the side reinforcing rubber part and the regulations of the rubber layer. It was.

DESCRIPTION OF SYMBOLS 1 ... Tread part, 2 ... Side wall part, 3 ... Bead part, 5 ... Carcass ply, 7 ... Bead filler, 8 ... Side reinforcement rubber part, 12 ... Rubber layer

Claims (4)

A tread portion, a pair of sidewall portions extending radially inward from both ends of the tread portion, and a pair of bead portions provided radially inward of the sidewall portion,
A pair of annular bead cores provided in the bead part; a carcass ply made of a carcass cord and a covering rubber extending in a toroidal shape between the pair of bead cores; a bead filler provided on an outer periphery of the bead core; A side reinforcing rubber portion that is provided in the sidewall portion and reinforces the sidewall portion, and a rubber layer that is interposed between the bead filler and the carcass ply,
The side reinforcing rubber part has a ratio (M50H / M50N) of a tensile stress (M50H) at 50% elongation at a measurement temperature of 100 ° C to a tensile stress (M50N) at 50% elongation at a measurement temperature of 23 ° C of 1. A rubber composition that is 0 or more and 1.3 or less,
In the rubber composition for a rubber layer, a mass ratio of styrene butadiene rubber in a rubber component is larger than the rubber composition for bead filler and smaller than the rubber composition for coated rubber, and 100 mass of the rubber component. The sulfur content relative to the part is less than the rubber composition for the bead filler and more than the rubber composition for the coated rubber,
Run flat tire.   The run-flat tire according to claim 1, wherein a tensile stress (M50H) at 50% elongation at a measurement temperature of 100 ° C of the rubber composition constituting the side reinforcing rubber portion is 3.5 MPa or more.   The rubber composition constituting the side reinforcing rubber part is formed by blending a rubber component containing natural rubber and polybutadiene rubber with a phenol-based thermosetting resin and a methylene donor as a curing agent thereof, The run-flat tire according to claim 1 or 2, wherein a mass ratio of a blending amount of the phenol-based thermosetting resin with respect to the methylene donor is 1.5 times or more.   The rubber composition constituting the side reinforcing rubber portion is further formed by blending a quinoline anti-aging agent and at least one anti-aging agent other than the quinoline anti-aging agent. Run flat tire.

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