JP2009248769A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reversion resistance and thermal aging resistance while maintaining low heat-generation property and adhesive fracture resistance in a belt lower pad often subjected to repetitive load during traveling. <P>SOLUTION: In the pneumatic radial tire T1 including the belt lower pad 5 extending in the tire circumferential direction between a belt 1 end portion of a shoulder part 4 and a carcass ply 2, as the belt lower pad 5, a rubber composition comprising 25-45 pts.wt. of carbon black and 2-5 pts.wt. of sulfur relative to 100 pts.wt. of diene-based rubber, resorcinol or its derivative, a hexamethylenetetramine or a melamine derivative, and 0.1-1.0-times pts.wt. of 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane based on the sulfur is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire having an improved belt lower pad provided on a tire shoulder.

  In general, the shoulder portion of a large radial tire is provided with a rubber member called a belt lower pad that extends in the tire circumferential direction between the belt end portion and the carcass ply, and these members are complicated. It is configured in combination. The lower belt pad has a role to relieve the shear stress between the belt end and the carcass ply, and is easily subjected to repeated loads during traveling, and is a member adjacent to the belt and carcass ply, so it has low heat generation. In addition, there is a demand for adhesive fracture resistance (that is, characteristics that can withstand adhesive fracture between the belt and the carcass ply).

  Therefore, resorcin or resorcin derivative and its methylene donor hexamethylenetetramine or melamine derivative are blended to suppress interfacial breakage with carcass ply, or styrenated diphenylamine is blended to suppress thermal oxidative degradation. (See Patent Documents 1 and 2 below).

  On the other hand, vulcanization of natural rubber, etc. with sulfur is known to cause reversion (reversion of vulcanization). Among tire members, especially those that contain a lot of natural rubber as a rubber component are thermally stable during vulcanization. If the property is not good, there is a problem that rubber deterioration after becoming a tire is large and durability is impaired.

  For this reason, in a belt-under-pad having a natural rubber as a main component as a rubber component, it is required to improve the reversion resistance and the heat aging resistance while maintaining the low heat generation property and the adhesive fracture resistance. However, when resorcin or a derivative thereof is blended in order to improve the adhesive fracture resistance, the heat aging resistance is lowered, and thus it is actually not possible to meet such a requirement.

  In addition, in order to prevent reversion, compounding 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane is conventionally known for rubber compositions for tire treads (the following patent document). 3). However, the tread is a good surface layer portion around the heat at the time of tire vulcanization molding, and the above compound is used to prevent over-vulcanization. Therefore, in addition to the situation under the belt under the belt disposed inside the tire, the tread rubber composition generally has a small amount of sulfur and does not contain any adhesive resin. Are clearly different in structure.

  Patent Document 4 below discloses that the above compound is blended in a tire cord covering rubber composition, but the cord covering rubber composition has a deformation amount at the time of tire use as compared to a pad under the belt. Low heat build-up is not taken into account because it is small, so a large amount of carbon black is blended in order to ensure reinforcement rather than low heat build-up, and the belt under pad clearly has the structure and required performance Is different.

Thus, although it has been conventionally known that 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane is used, by adding a predetermined amount in a pad under the belt, low exothermic property and It has not been known that reversion resistance and heat aging resistance can be dramatically improved while maintaining adhesive fracture resistance.
JP-A-10-204214 JP 2006-213784 A JP 2005-263892 A JP 2003-82586 A

  The present invention has been made in view of the above points, and is provided between a belt end portion and a carcass ply, and has low heat build-up and adhesive fracture resistance in a belt lower pad that is susceptible to repeated load during traveling. It is an object to improve reversion resistance and heat aging resistance while maintaining.

  As a result of intensive studies in view of the above problems, the present inventors have found that, in the rubber composition of the under-belt pad, 1,6-, together with a phenolic compound or phenolic resin and hexamethylenetetramine or melamine derivative as its methylene donor. It has been found that it is effective to add a predetermined amount of bis (N, N-dibenzylthiocarbamoyldithio) hexane, and the present invention has been achieved.

  That is, the pneumatic radial tire according to the present invention is a pneumatic radial tire in which a belt lower pad extending in the tire circumferential direction is disposed between a belt end portion of a tire shoulder portion and a carcass ply. The phenolic resin containing 25 to 45 parts by weight of carbon black and 2 to 5 parts by weight of sulfur with respect to 100 parts by weight of the diene rubber, and phenol compounds or phenol compounds condensed with formaldehyde, and methylene thereof Containing hexamethylenetetramine or a melamine derivative as a donor, and further containing 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane in an amount of 0.1 to 1.0 parts by weight of the sulfur. A rubber composition is used.

  According to the present invention, in a rubber composition for a belt under pad, a predetermined amount of 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane is blended with each of the above components, so that it is required as a belt under pad. The reversion resistance and the heat aging resistance can be drastically improved while maintaining the low exothermic property and the adhesive fracture resistance, and the vulcanization speed can be increased. Therefore, the durability at the shoulder portion can be improved while improving the vulcanization productivity of the pneumatic radial tire.

  FIG. 1 is an enlarged cross-sectional view of a main part of a tire T1 showing one embodiment of a pneumatic radial tire of the present invention. Reference numeral 1 denotes a belt made of a steel cord. In the figure, four belt layers are laminated. Reference numeral 2 denotes one carcass ply in which steel cords are radially arranged, reference numeral 3 denotes a tread rubber, reference numeral 4 denotes a shoulder portion, and reference numeral 5 denotes a belt lower pad.

  The belt lower pad 5 is formed of a belt-like rubber member having a substantially triangular cross section disposed between the end portion of the belt 1 and the carcass ply 2 and between the carcass ply 2 and the tread rubber 3 in the shoulder portion 4. It is arranged along the entire circumference in the tire circumferential direction on both sides.

  The under-belt pad 5 includes (A) a diene rubber, (B) carbon black, (C) sulfur, (D) a phenolic resin obtained by condensing a phenolic compound or a phenolic compound with formaldehyde, E) A rubber composition containing hexamethylenetetramine or a melamine derivative as the methylene donor and (F) 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane is used.

  Examples of the diene rubber blended as the rubber component (A) in the rubber composition include natural rubber, isoprene rubber, styrene butadiene rubber, and polybutadiene rubber. Among these, natural rubber having excellent destructive properties is preferably used. Therefore, the rubber component is a diene rubber having natural rubber as a main component, that is, natural rubber alone, or 50% by weight or more of natural rubber. A blend with a diene rubber is preferred.

  The carbon black as the component (B) is not particularly limited, and grades generally used for the belt lower pad 5 such as HAF, FEF, and GPF can be used. The carbon black is preferably blended in an amount of 25 to 45 parts by weight with respect to 100 parts by weight of the diene rubber. Thus, by reducing the blending amount of carbon black, it is possible to suppress the heat generation of the belt lower pad 5 that is easily deformed when the tire is used, and to impart low heat generation properties. In addition, when there are few compounding quantities of carbon black than 25 weight part, it is inferior to reinforcement.

  The sulfur component (C) is blended in an amount of 2 to 5 parts by weight with respect to 100 parts by weight of the diene rubber, and by blending in a larger amount than the tread rubber, the belt 1 as the belt lower pad 5 or Adhesiveness to the carcass ply 2 can be enhanced. That is, when the amount of sulfur is less than 2 parts by weight, the adhesiveness is poor. On the other hand, when the amount of sulfur exceeds 5 parts by weight, the vulcanization rate becomes slow, the flexibility is impaired, and the heat resistance is deteriorated.

  The component (D) is a methylene acceptor corresponding to the methylene donor of the component (E), and can improve adhesion to the belt or carcass ply by reacting with the methylene group of the methylene donor.

  The phenol compounds include phenol, resorcin, or alkyl derivatives thereof. Alkyl derivatives include derivatives of relatively long-chain alkyl groups such as nonylphenol and octylphenol, as well as methyl group derivatives such as cresol and xylenol. The phenol compound may contain an acyl group such as an acetyl group as a substituent.

  In addition, phenolic resins obtained by condensing phenolic compounds with formaldehyde include resorcin-formaldehyde resins, phenolic resins (that is, phenol-formaldehyde resins), cresol resins (that is, cresol-formaldehyde resins), and a plurality of phenols. Formaldehyde resins made of compounds are included. These are uncured resins that have liquid or heat fluidity.

  Among these, from the viewpoint of compatibility with the rubber component and other components, and the denseness and reliability of the resin after curing, the component (D) is preferably resorcin or a resorcin derivative. A condensed formalin resin is preferred.

  (D) It is preferable that the compounding quantity of the phenolic compound or phenol-type resin of a component is 0.5-3 weight part with respect to 100 weight part of diene rubbers, More preferably, it is 0.5-2 weight part. is there. When the blending amount of the component (D) is too small, the adhesiveness is inferior. On the other hand, when the amount is too large, the low heat buildup is impaired and the durability is inferior.

  The component (E) is a methylene donor that reacts and cures the component (D), and hexamethylenetetramine or a melamine derivative is used. As the melamine derivative, for example, methylol melamine, a partially etherified product of methylol melamine, a condensate of melamine, formaldehyde, and methanol is used, and among them, hexamethoxymethyl melamine is particularly preferable.

  The compounding amount of the hexamethylenetetramine or melamine derivative as the component (E) is an amount sufficient to cause sufficient reaction and curing with respect to the component (D), specifically, the compounding amount of the component (D). It is preferable that it is 0.5-2 times weight part. If the blending amount is less than 0.5 parts by weight, sufficient reaction and curing cannot be performed. Conversely, if it exceeds 2 parts by weight, physical properties of the rubber composition may be deteriorated. .

  Component (F) 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane is a reversion-resistant crosslinking agent, and is 0.1 to 1.% relative to the amount of component (C) sulfur. 0 times by weight is blended. By blending the compound of component (F), the reversion resistance can be improved, and heat aging by blending the component (D) without impairing the low heat build-up and adhesive fracture resistance. The heat aging resistance can be improved by canceling the deterioration of the property. When the blending amount of the component (F) is less than 0.1 times the amount, such an effect cannot be sufficiently exhibited. Conversely, when the amount is more than 1.0 times, the scorch property is inferior. Fatigue resistance decreases. The amount of component (F) is more preferably 0.1 to 0.5 parts by weight, and still more preferably 0.2 to 0.5 parts by weight of the amount of sulfur.

  In the rubber composition used for the belt lower pad 5, in addition to the above-described components, various additives generally blended in this type of rubber composition can be arbitrarily blended, and the blending amount is also It can be a general amount. Examples of the additive to be arbitrarily blended include other fillers such as silica, softener, zinc white, stearic acid, anti-aging agent, vulcanization accelerator and the like, and in a range not contrary to the object of the present invention. It can mix | blend suitably.

  The rubber composition can be prepared by kneading using a commonly used Banbury mixer, kneader, or other mixer, and is suitably used as the belt under-pad 5 for large pneumatic radial tires such as trucks, buses, and light trucks. The pneumatic radial tire T1 can be manufactured by molding and vulcanizing according to a conventional method.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

  According to the composition shown in the following Tables 1 and 2, the rubber compositions of Examples 1 to 6 and Comparative Examples 1 to 5 were kneaded using a closed Banbury mixer. Details of each component in the table are as follows.

・ Natural rubber: RSS # 3,
・ Carbon black: HAF, “Seast 300” manufactured by Tokai Carbon Co., Ltd.
P-phenylenediamine: “Santflex 6PPD” manufactured by Flexis,
・ Styrenated diphenylamine: “LAS-P” manufactured by Seiko Chemical Industries,
Resorcin-alkylphenol-formalin resin: “SUMIKANOL 620” manufactured by Sumitomo Chemical Co., Ltd.
Hexamethoxymethyl melamine: “Cyretz 963L (HMMM)” manufactured by Mitsui Cytec
Insoluble sulfur: “Cristex HS OT-20” (80% by weight is sulfur content) manufactured by Flexis,
・ Vulcanization accelerator NS: “Noxeller NS-P” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Thiocarbamoyl compound: 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane, “Vulcuren VP KA9188” manufactured by LANXESS.

  In each rubber composition, as a common compound, 5 parts by weight of oil (“JOMO Process NC-140” manufactured by Japan Energy Co., Ltd.) and zinc white (“Zinc Hana 3” manufactured by Mitsui Mining & Mining Co., Ltd.) per 100 parts by weight of diene rubber No. ") and 5 parts by weight of stearic acid (manufactured by Kao Corporation) were added.

  Each rubber composition obtained was evaluated for scorch properties, vulcanization speed, reversion resistance, heat aging resistance, and heat generation. Further, a trial tire (tire size: 11R22.5) of a pneumatic radial tire shown in FIG. 1 in which each rubber composition was applied to an under-belt pad was manufactured, and adhesion fracture resistance and drum durability were evaluated. Each evaluation method is as follows, and the results are shown in Tables 1 and 2.

Scorch resistance: in conformity with JIS K6300, using a L-shaped rotor, was measured scorch time _{t 35} (minute) when measured at 125 ° C..

- vulcanization rate: in conformity with JIS K6300, using a L-shaped rotor, was measured scorch time _{t 50} (minute) when measured at 0.99 ° C..

-Reversion resistance: Measured at 180 ° C. using an L-shaped rotor in accordance with JIS K6300, the time Δt ₁₀ (min) until the torque decreases by 10% from the maximum value (MH) Was measured. It means that it is excellent in reversion resistance, so that a numerical value is large.

Heat aging resistance: Each rubber composition was vulcanized at 150 ° C. for 30 minutes to prepare a test sample. The test piece was aged in a gear oven at 90 ° C. for 96 hours. Was used to conduct a tensile test in accordance with JIS K6251 (using No. 3 type dumbbell) and measure 100% modulus. The measured value after aging was determined as a percentage of the unaged measured value and was defined as the 100% modulus change rate. The smaller the value, the better the heat aging resistance.

Low exothermic property: Each rubber composition was vulcanized at 150 ° C. for 30 minutes to prepare a test sample. Each sample was subjected to a spectrometer manufactured by Toyo Seiki Co., Ltd. at a temperature of 60 ° C., a frequency of 50 Hz, and an initial strain of 10%. Tan δ was measured at a dynamic strain of 2%. It displays with the index | exponent which set the value of the comparative example 2 to 100, and shows that it is excellent in low heat generation property, so that a numerical value is small.

-Adhesive fracture resistance: A prototype tire was mounted on the rear wheel of a high-speed long-distance bus, and after traveling 200,000 km (highway usage rate = 90%), the tire was disassembled and the carcass ply was taken out and adjacent to the pad under the belt The ratio of the rubber adhering to the ply cord at the site was visually determined and displayed as the ply cord-rubber adhesion rate. It shows that it is excellent in adhesive fracture resistance (ply separation resistance), so that a numerical value is large.

Drum durability: Using an indoor drum testing machine equipped with a steel drum with a diameter of 1.7 m, and for each prototype tire, the air pressure was 100% as specified in JIS D4230, the test speed was 40 km / h, and the tire load load Starting from 140% of the JIS regulations, the load was increased by 10% every 150 hours, and a running test was conducted until a failure occurred in the tire. Based on the distance traveled until the failure of the tire of Comparative Example 2 as a reference, “x” indicates that the travel distance until the failure occurs is 10% or more shorter than that of Comparative Example 2, and “10” indicates that the travel distance is 10% or longer and is superior. “O” was evaluated as “Δ” for an equivalent within 10%.

  As shown in the above table, in Comparative Example 1, since the resorcin derivative and the melamine derivative, which are adhesive resins, were not blended, the adhesive fracture resistance was inferior and the drum durability was also inferior. In Comparative Example 2, the adhesive fracture resistance was improved by blending an adhesive resin with respect to Comparative Example 1, but the heat aging resistance was reduced. In Comparative Example 3, the decrease in the heat aging resistance was improved and the vulcanization rate was improved as compared with Comparative Example 2 by reducing the amount of sulfur, but the scorch property and low exothermic property deteriorated, There was also no improvement in drum durability.

  On the other hand, Example 1 in which 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane as the component (F) was mixed with a part of sulfur and the amount of sulfur was added as it was. According to Example 2, the reversion resistance and the heat aging resistance are drastically ensured as compared with Comparative Example 2 which is excellent in the adhesion fracture resistance, while maintaining the same adhesion fracture resistance and maintaining low heat generation. Had improved. In particular, the deterioration of the heat aging resistance of Comparative Example 2 due to the blending of the resorcin derivative was completely cancelled, and the heat aging resistance could be further improved than that of Comparative Example 1. In addition, the scorch property was not deteriorated, the vulcanization speed was increased, and the drum durability was also improved. The same applies to Example 3 in which the amount of sulfur was increased with respect to Example 1 and the component (F) was reduced.

  On the other hand, in Example 4 in which the amount of sulfur was reduced and the component (F) was increased as compared with Example 1, the low heat build-up was improved as compared with Example 1, but the fatigue resistance was slightly lowered. It was slightly inferior in durability and was comparable to Comparative Example 2. Other performances were excellent as in Example 1.

  In Example 5 in which the compounding amount of the adhesive resin was reduced with respect to Example 1, the low exothermic property could be improved while securing other performances almost equal to those of Example 1. Moreover, in Example 6 which changed the anti-aging agent, the improvement effect was recognized also in the low exothermic property, improving the adhesive fracture resistance further.

  In Comparative Example 4 in which the blending amount of the component (F) is too small, no effect of improving reversion resistance and heat aging resistance was observed. In Comparative Example 5 in which the amount of the component (F) is too large, although the reversion resistance and the heat aging resistance were excellent, the scorch property was inferior and the fatigue resistance was lowered. The drum durability was comparable to that of Comparative Example 2.

  As described above, after blending a predetermined amount of carbon black and sulfur with the diene rubber containing natural rubber as a main component and blending the predetermined adhesive resin, 1,6-bis (N, N -By adding a predetermined amount of dibenzylthiocarbamoyldithio) hexane, while maintaining low heat build-up and adhesion fracture resistance, the vulcanization speed is increased, and reversion resistance and heat aging resistance are dramatically improved. It is possible to improve the durability of the pad under the belt and to increase the life of the tire and to improve the vulcanization productivity.

  The pneumatic radial tire of the present invention is used for light trucks including large vehicles such as trucks and buses, and is particularly suitable for vehicles used under heavy load conditions involving long distances and continuous running.

It is a principal part expanded sectional view of the tire which shows one Embodiment of this invention.

Explanation of symbols

T1 ... Pneumatic radial tire 1 ... Belt 2 ... Carcass ply 3 ... Tread 4 ... Shoulder 5 ... Belt belt pad

Claims (2)

In a pneumatic radial tire in which a belt lower pad extending in the tire circumferential direction is arranged between a belt end portion of a tire shoulder portion and a carcass ply,
In the belt under pad,
A phenolic resin containing 25 to 45 parts by weight of carbon black and 2 to 5 parts by weight of sulfur with respect to 100 parts by weight of a diene rubber, and a phenolic compound or a phenolic compound condensed with formaldehyde, and a methylene donor thereof A rubber composition containing the hexamethylenetetramine or melamine derivative as a further, and further containing 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane in an amount of 0.1 to 1.0 parts by weight of the sulfur. Using things,
Pneumatic radial tire.   The rubber composition contains the phenolic compound or phenolic resin in an amount of 0.5 to 3 parts by weight with respect to 100 parts by weight of the diene rubber, and the hexamethylenetetramine or melamine derivative contains the phenolic compound or The pneumatic radial tire according to claim 1, containing 0.5 to 2 parts by weight of phenolic resin.

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