JP2006213784A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve service life of a pneumatic radial tire by suppressing oxidative degradation of a rubber composition due to heat generation of a shoulder part and accumulation of heat. <P>SOLUTION: In a pneumatic radial tire in which a belt under pad 5 extending in the circumferential direction of the tire T1 is arranged between the end of a belt layer 1 of the shoulder part 4 and a carcass ply layer 2, the belt under pad 5 comprises a rubber composition containing 0.5-2 pts.wt. of styrenated diphenylamine and 0.5-2 pts.wt. of resorcinol or its derivative each based on 100 pts.wt. of natural rubber and hexamethylenetetramine or a melamine derivative of 0.5-2 times by pts.wt. of the resorcinol or its derivative. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire that has improved durability life by suppressing deterioration of rubber properties due to heat generation at the tire shoulder and its thermal history.

  The shoulder portion of large radial tires generates large amounts of heat due to bending and strain during driving, and the oxygen deterioration phenomenon due to its thermal history causes the rubber composition to lose its fracture characteristics and the strength and elasticity associated with curing. Crack generation and growth are promoted.

  In particular, the lower belt pad extending in the tire circumferential direction between the end of the belt layer inside the shoulder and the carcass ply layer receives heat from both the belt layer and the carcass ply layer while being bent and strained. Deterioration of the deterioration phenomenon is fast due to easy accumulation, and due to deterioration of the pad rubber, due to adhesion failure between the rubber cords of each member, particularly between the steel cord layer of the belt ply or carcass ply and the pad rubber, or internal rubber destruction of the pad under the belt itself In addition, belt separation and carcass ply separation from the belt end were generated, and the durable life of the tire was reduced.

Conventionally, in order to solve such problems, countermeasures have been taken by increasing the amount of an amine-based anti-aging agent for preventing oxidation in the rubber composition of the under-belt pad. In addition, it has been proposed to improve durability by improving the adhesive strength between the pad rubber and the belt or carcass ply layer by blending resorcin or a resorcin derivative and its methylene donor into the pad under the belt (Patent Document). 1).
JP-A-10-204214

  However, when the amount of these amine-based antioxidants is increased, the deterioration prevention effect due to the increase becomes extremely negligible when the content exceeds a certain range. Further, when a large amount of the anti-aging agent is contained in this way, not only the cost increases, but also problems such as a decrease in the elastic modulus of the rubber and contamination due to blooming of the anti-aging agent arise.

  In addition, by adding resorcin or a resorcin derivative and its methylene donor to the rubber composition, it is possible to improve the adhesive strength with the ply layer, but there is a limit to the prevention of oxidative deterioration of the rubber properties against heat generation. There is a need for high-level rubber properties that can cope with harsh usage conditions such as higher performance, higher loads, and continuous running.

  That is, the present invention suppresses the deterioration of the rubber composition constituting the inside of the shoulder due to heat generation and heat accumulation in the shoulder portion of the pneumatic radial tire, while sufficiently maintaining the fracture characteristics of the rubber composition, An object of the present invention is to improve the durability life of a pneumatic radial tire by suppressing a change in elastic modulus due to rubber curing.

  As a result of intensive studies in view of the above problems, the inventors of the present application contain a suitable amount of styrenated diphenylamine and, at the same time, contain resorcin or a resorcin derivative, and a hexamethylenetetramine or a melamine derivative, thereby receiving a heat history. The present inventors have found that the composition is effective in suppressing oxidative deterioration of the composition and maintaining the adhesive strength between the pad rubber and the carcass ply layer.

  The pneumatic radial tire of 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 layer end portion of a tire shoulder portion and a carcass ply layer, and 100 parts by weight of natural rubber In contrast, 0.5 to 2 parts by weight of styrenated diphenylamine, 0.5 to 2 parts by weight of resorcin or resorcin derivative, and 0.5 to 2 parts of the resorcin or resorcin derivative content of hexamethylenetetramine or melamine derivative. A rubber composition containing 2 parts by weight is used.

  The pneumatic radial tire of the present invention uses a rubber composition in which an antioxidant and an adhesive resin are used in combination on an under belt pad to sufficiently cure the rubber while maintaining sufficient fracture characteristics even under conditions of thermal oxidation. It is possible to sufficiently suppress the change in the elastic modulus due to the above and improve the adhesive strength of the belt ply layer, the carcass ply layer and the pad rubber to prevent separation, thereby improving the durability life of the tire.

  The pneumatic radial tire of 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 layer end portion of a tire shoulder portion and a carcass ply layer. Between the pad and the carcass ply layer, 0.5 to 2 parts by weight of styrenated diphenylamine, 0.5 to 2 parts by weight of resorcin or a resorcin derivative, and hexamethylenetetramine or 100 parts by weight of natural rubber An intermediate rubber layer using a rubber composition containing a melamine derivative in an amount of 0.5 to 2 parts by weight of the resorcin or resorcin derivative content is provided.

  Thus, the said subject can be solved also by arrange | positioning the intermediate | middle rubber layer which consists of the said rubber composition between a belt lower pad and a carcass ply layer. In this case, the intermediate rubber layer is used for thermal oxidation while suppressing internal heat generation at the shoulder portion and improving bending fatigue resistance by using a rubber composition that emphasizes low exothermic property for the belt lower pad and has appropriate flexibility. Deterioration can be prevented and the adhesion between the carcass ply and the pad rubber can be secured to improve the durability of the tire.

  The pneumatic radial tire of the present invention is characterized in that the rubber composition further contains a P-phenylenediamine-based antioxidant.

  With this configuration, it is possible to further suppress deterioration of rubber physical properties under thermal oxidation conditions.

  According to the present invention, the rubber composition constituting the belt lower pad suppresses thermal oxidative deterioration, sufficiently maintains the breaking characteristics of the pad rubber, suppresses a change in elastic modulus due to rubber curing, and By maintaining the adhesive strength with the carcass ply layer, the durability life of the pneumatic radial tire can be improved.

(First embodiment)
FIG. 1 is a half sectional view of a tire T1 showing a first 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 plies are laminated. 2 is a carcass ply in which steel cords are radially arranged, 3 is a tread rubber, 4 is a shoulder portion, and 5 is 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 pneumatic radial tire T1 according to the present invention uses a rubber composition in which the natural rubber is a rubber component and the styrenated diphenylamine and resorcin or a resorcin derivative, hexamethylenetetramine or a melamine derivative are used in the lower belt pad 5 of the present invention. It is done.

  The styrenated diphenylamine used in the rubber composition acts as an antioxidant for preventing oxidative deterioration of the rubber composition that receives a thermal history, and is 0.5 to 2 parts by weight with respect to 100 parts by weight of the natural rubber component. Blended.

  Styrenated diphenylamine is a group of compounds having a structure in which one or more styrene monomers are added to each benzene ring of diphenylamine. As this styrenated diphenylamine, an antioxidant for rubber described in JP-A-9-53070 can be preferably used.

  If the content of this styrenated diphenylamine is less than 0.5 parts by weight, a sufficient effect of preventing thermal oxidative deterioration cannot be obtained, and oxidative deterioration of rubber and embrittlement due to progress of cross-linking proceed. On the other hand, if the content of styrenated diphenylamine exceeds 2 parts by weight, not only will the cost increase, but the elastic modulus of the rubber will significantly decrease, which may cause separation and decrease in durability. Problems such as contamination due to the problem also occur.

  The rubber composition used in the present invention contains 0.5 to 2 parts by weight of resorcin or a resorcin derivative as an adhesive resin with respect to 100 parts by weight of the natural rubber component.

  By using resorcin or a resorcin derivative, the thermal oxidative degradation is suppressed by a synergistic effect with the styrenated diphenylamine, and the elastic modulus of the rubber is maintained in an appropriate range, and the coating for the tire cord covering the belt and the carcass ply. The adhesive strength with rubber can be improved, and not only initial adhesiveness but also heat and moisture heat resistant adhesiveness can be maintained, and adhesive performance such as separation can be suppressed while maintaining adhesive performance for a long period of time.

  Resorcin derivatives include resorcin / formaldehyde resins obtained by condensing resorcin and formaldehyde, but phenol-based resins such as phenol / formaldehyde resins and cresol / formaldehyde resins obtained by condensing phenols (phenol, cresol, etc.) and aldehydes. It can also be used. Resorcin derivatives containing resorcin or alkylphenol are preferred from the viewpoint of compatibility with rubber components and other components, and the density and reliability of the resin after curing, and examples of resorcin derivatives include resorcin / alkylphenol co-condensed formalin resins. it can.

  If the content of the resorcin or resorcin derivative is less than 0.2 parts by weight, the effect of suppressing thermal oxidation deterioration cannot be sufficiently obtained, the rubber physical properties cannot be sufficiently improved, and good adhesive properties are also obtained. I can't get it. That is, the elastic modulus of the rubber changes due to long-term use or accelerated deterioration, and the fracture characteristics cannot be sufficiently maintained, resulting in a decrease in durability. On the other hand, if the content exceeds 2 parts by weight, the heat resistance of the rubber composition deteriorates and the elastic modulus increases and becomes brittle.

  In the rubber composition according to the present invention, hexamethylenetetramine or melamine derivative is blended in 0.5 to 2 times by weight of resorcin or resorcin derivative content as a methylene donor for reacting and curing resorcin or resorcin derivative. The

  As the melamine derivative, for example, a partially etherified product of methylolmelamine, a compound in which a reaction product of melamine and formalin is methoxylated with methanol, etc. are used. Among them, the number of bound formalins per molecule of melamine is 4 to 6, Is preferably a mixture of 2 to 6 and a monomer content of 60 to 90%.

  The content of the hexamethylenetetramine or melamine derivative is at least an amount sufficient to cause sufficient reaction and curing with respect to the resorcin, etc., and when the content is less than 0.5 times by weight of resorcin, etc. Does not allow sufficient reaction and curing. On the other hand, when the content exceeds 2 parts by weight, the physical properties of the rubber composition are lowered.

  In the above rubber composition, other antioxidants that further improve the antioxidant can be used in combination, and aromatic secondary amines, among them, P-phenylenediamine antioxidants are preferred, and styrenation The combined use with diphenylamine can further improve the antioxidant effect of the rubber composition.

  The P-phenylenediamine-based antioxidant is a proton-donating antioxidant (radical chain inhibitor or primary anti-aging agent) that captures radicals by a proton-donating mechanism, like styrenated diphenylamine, and its content Is 0.5 to 2 parts by weight per 100 parts by weight of the rubber component. If the content is less than 0.5 parts by weight, the combined effect of the antioxidant is small. If the content exceeds 2 parts by weight, the rubber elastic modulus is excessive as in the case of adding excessive styrenated diphenylamine. There is a possibility that problems such as a decrease in temperature and blooming of antioxidants may occur.

  The rubber composition used in the present invention contains 20 to 80 parts by weight of a rubber reinforcing filler with respect to 100 parts by weight of the rubber component. In general, carbon black or silica is used as a reinforcing filler, and these can be used alone or in combination. The silica content when carbon black and silica are used in combination is suitably in the range of 10 to 40 parts by weight. You can choose.

  In the rubber composition used in the present invention, in addition to the antioxidant and the adhesive resin component, various compounding agents generally blended in a tire rubber composition can be arbitrarily blended in the natural rubber component. The blending amount can also be a general amount. As a compounding agent arbitrarily blended, for example, a vulcanizing agent, a vulcanization accelerator, a softening agent, zinc white, stearic acid, wax, an anti-aging agent, a processing aid and the like are appropriately blended within a range not contrary to the object of the present invention. can do.

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

(Second Embodiment)
FIG. 2 is a half sectional view of a tire T2 showing a second embodiment of the pneumatic radial tire of the present invention. The main structure of the tire T2 is the same as that of the tire T1, and the configuration around the belt lower pad 6 in the shoulder portion 4 is different from that of the first embodiment.

  In other words, reference numeral 1 is a belt, 2 is a carcass ply, 3 is a tread rubber, 4 is a shoulder portion, 6 is a belt lower pad, 7 is an intermediate rubber disposed between the belt lower pad 6 and the carcass ply layer 2. Is a layer.

  The intermediate rubber layer 7 is a rubber layer disposed between the belt lower pad 6 and the carcass ply 2, along with the belt lower pad 6 having a substantially triangular cross section along the entire circumference in the tire circumferential direction on both sides of the tire cross section. It is arranged.

  In the tire T2 of the present embodiment, a rubber composition containing the styrenated diphenylamine described in the first embodiment, a resorcin or resorcin derivative, and a hexamethylenetetramine or melamine derivative is used for the intermediate rubber layer 7.

  By disposing this rubber layer 7, the thermal oxidation deterioration between the belt lower pad 6 and the carcass ply 2 is suppressed, the rubber physical properties of the boundary portion are maintained, and the adhesion strength with the carcass ply layer is maintained and the tire is maintained. It is possible to improve the durability.

  Hereinafter, although the rubber composition and pneumatic radial tire concerning this invention are demonstrated based on an Example, this invention is not limited to these Examples.

  In the blending contents (parts by weight) shown in Table 1, with respect to 100 parts by weight of natural rubber (RSS3), styrenated diphenylamine, P-phenylenediamine-based antioxidant, and adhesive resin as the following antioxidants As a resorcinol and a melamine derivative, the following compounding agent (parts by weight) was blended as a common blending component, and the rubber compositions of Examples 1 to 4 and Comparative Examples 1 to 3 were kneaded using a closed Banbury mixer. .

[Antioxidants, adhesive resins]
Styrenated diphenylamine: manufactured by Seiko Chemical Industry, LAS-P
・ P-phenylenediamine anti-aging agent: manufactured by Monsanto, Santoflex 6PPD
Resorcin: manufactured by Sumitomo Chemical Co., Ltd. Melamine derivative (hexamethoxymethylmelamine): Mitsui Cytec, Cyretz 963L

[Common ingredients (blending amount)]
Carbon black: 40 parts by weight (Showa Cabot, Show Black N326)
・ Zinc flower: 10 parts by weight (Mitsui Metal Mining Co., Ltd., Zinc flower No. 3)
・ Vulcanization accelerator DZ: 1 part by weight (manufactured by Ouchi Shinsei Chemical, Noxeller DZ-G)
・ Sulfur: 5 parts by weight (manufactured by Shikoku Chemicals Co., Ltd., Mucron OT-20F)

  For each rubber composition, the thermal oxidation deterioration performance was evaluated by the tensile elongation at break and the 100% modulus change rate, and the drum of the pneumatic radial tire shown in FIG. Durability was evaluated. The results are shown in Table 1.

[Tensile test]
In accordance with JIS K6251, a tensile test was performed using an autograph manufactured by Shimadzu Corporation (using No. 3 dumbbell), and then the tensile test piece was left in a constant temperature dryer adjusted to 90 ° C. for 96 hours to conduct a tensile test after aging. went. With respect to the elongation at break and 100% modulus, the measured value after aging was obtained as a percentage of the measured value before aging, and the elongation at break and the rate of change in 100% modulus were obtained. The larger the numerical value, the better the elongation at break. The smaller the numerical value, the better the 100% modulus change rate.

[Drum durability]
A trial tire of size 11R22.5, in which each rubber composition is applied to the under belt pad, was produced, and an indoor drum tester equipped with a steel drum having a diameter of 1.7 m was used. The air pressure was 10% as specified in JIS D4230. Then, the test speed was set to 40 km / h, the tire load was started from 140% of the JIS standard, and the load was increased by 10% every 150 hours until a failure occurred in the tire. Comparative Example 1 Based on the distance traveled until the failure of the tire as a reference, “X” indicates that the distance traveled to the failure is inferior by 10% or more compared to Comparative Example 1, “×” indicates that the travel distance is 10% or longer and excellent. ".

  As shown in Table 1, in Examples 1 to 4, the elongation at break is maintained at 48% or more to suppress the oxidative deterioration of the pad under the belt, and the change rate of 100% modulus (elastic modulus) is suppressed to 175% or less. I was able to. In particular, when a P-phenylenediamine anti-aging agent is used in combination, the elongation at break can be maintained at 50% or more, the rate of change in 100% modulus can be kept small, and separation from the belt and carcass ply can be prevented. The drum durability can be improved, and the effect of increasing the amount of styrenated diphenylamine is clearly shown.

  On the other hand, in Comparative Example 2 in which styrenated diphenylamine was used alone, an antioxidant effect was not obtained, and in Comparative Example 3 in which an adhesive resin was not contained even when a P-phenylenediamine-based antioxidant was used in combination, 100% modulus was obtained. The increase could not be suppressed, resulting in poor durability.

  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.

1 is a half sectional view of a tire showing an embodiment of the present invention. It is a half sectional view of a tire showing other embodiments of the present invention.

Explanation of symbols

T1, T2 ... Pneumatic radial tire 1 ... Belt 2 ... Carcass 3 ... Tread 4 ... Shoulder 5, 6 ... Belt under pad 7 ... Intermediate rubber layer

Claims (3)

In a pneumatic radial tire in which a belt lower pad extending in the tire circumferential direction is arranged between a belt layer end portion of a tire shoulder portion and a carcass ply layer,
In the belt under pad,
0.5 to 2 parts by weight of styrenated diphenylamine, 0.5 to 2 parts by weight of resorcin or resorcin derivative, and hexamethylenetetramine or melamine derivative to the resorcin or resorcin derivative content with respect to 100 parts by weight of natural rubber A pneumatic radial tire characterized by using a rubber composition containing 0.5 to 2 parts by weight of the above. In a pneumatic radial tire in which a belt lower pad extending in the tire circumferential direction is arranged between a belt layer end portion of a tire shoulder portion and a carcass ply layer,
Between the belt lower pad and the carcass ply layer,
0.5 to 2 parts by weight of styrenated diphenylamine, 0.5 to 2 parts by weight of resorcin or resorcin derivative, and hexamethylenetetramine or melamine derivative to the resorcin or resorcin derivative content with respect to 100 parts by weight of natural rubber A pneumatic radial tire characterized in that an intermediate rubber layer using a rubber composition containing 0.5 to 2 parts by weight of the rubber composition is provided. The pneumatic composition according to claim 1 or 2, wherein the rubber composition further contains 0.5 to 2 parts by weight of a P-phenylenediamine-based antioxidant for 100 parts by weight of natural rubber. Radial tire.

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