JPS58112808A - Pneumatic tyre - Google Patents

Abstract

PURPOSE:To prevent separation of the end part of a breaker and the end part of a carcass in the case of a tyre using steel cord, by utilizing specifically composed rubber of natural rubber group as protective rubber surrounding said end parts. CONSTITUTION:Compound rubber obtained through blending 100pts.wt. elastomer with less than 20wt% natural rubber or synthetic rubber of diene group and further mixing it with carbon black HAF-LS50-90pts.wt., sulfur 4.5-10pts.wt., naphthenic acid cobalt 0.02-0.8pts.wt. and N,N-dicyclohexyl-2-benzo thiazole sulphen amide 0.5-2.0pts.wt. is used as protective rubber 5 for covering and protecting the end part of the steel cord breaker 1 and a turnup end part 6 of a steel cord carcass ply. Thus, exfoliation of the end parts of both the breaker and the carcass can be prevented and traveling durability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire, and more specifically, the present invention relates to a pneumatic tire, and more specifically, by using a specific rubber composition for the protective rubber surrounding the steel breaker end and the carcass end, the protective rubber has high elasticity. The present invention relates to a pneumatic tire which has high suction strength and high adhesion, prevents a decrease in breaking strength due to moisture absorption during unvulcanization, and prevents carcass edge separation and carcass edge separation.

In recent years, the required performance of automobile tires has diversified as vehicles have become larger and faster speeds have been achieved due to the construction of expressways.
Durability under harsh conditions is increasingly required. In response to these demands, radial bright tires have been developed in which steel cords are used for the breaker or the breaker and carcass.

However, tires with steel cords in the breaker and carcass have a drawback in that so-called separation, such as peeling, is likely to occur during running due to the ends of the steel cords being a source of generation.

Generally, one layer of a breaker consists of at least two layers,
Since this breaker layer has high rigidity, strain tends to concentrate at both ends of the breaker where the thickness decreases in the direction of the bead, and separation tends to occur with these ends becoming the core of fracture. In order to compensate for this drawback, a method is generally used in which both ends of the breaker are wrapped with protective rubber having a high elastic modulus, thereby relaxing the rigid fault at both ends of the breaker and reducing local strain.

FIG. 1 is a sectional view of a tire having a steel cord breaker and carcass, and FIG. 2 is an enlarged sectional view of a portion of the breaker.

In the figure, 1 indicates a steel cord breaker, 12 indicates a steel cord carcass, 6 indicates a chafer 14, a bead core, and 5 indicates a protective rubber. The breaker 1 is composed of four pieces, and their terminal parts are surrounded by a protective rubber 5.

On the other hand, a radial tire that uses steel cords for the carcass ply has at least one carcass ply with cords arranged at approximately 90 degrees to the tire circumferential direction, and ends at a position where it is folded back around the bead core. The folded end of the carcass ply is located near the joint between the flexible sidewall made of thin side rubber and the strongly hardened bead, so the carcass ply folded end is located near the joint between the flexible sidewall made of thin side rubber and the strongly hardened bead. Local strain concentrates at the terminal portion, and separation is likely to occur at this terminal portion. In order to compensate for this drawback, a common method is to wrap the folded end portion of the carcass ply in protective rubber to prevent separation.

FIG. 3 is an enlarged sectional view of the tire bead portion.

In the figure, the carcass 2 is folded back around a bead core 4, and its end portion 6 is surrounded by protective rubber.

Conventionally, high elastic modulus rubber was used to wrap and protect the end of the steel breaker and the folded end of the steel cord carcass ply, which was made by blending 40 to 70 parts by weight of highly reinforcing carbon black with 100 parts by weight of a polymer mainly composed of natural rubber. However, such rubber compositions are still insufficient in terms of adhesion to steel cords, high breaking strength, etc., and furthermore, if they absorb moisture while unvulcanized, their tensile strength, elongation at break, etc. There was a drawback that physical properties deteriorated.

The present inventors conducted extensive studies to solve the above-mentioned problems, and as a result, they arrived at the present invention.

Accordingly, an object of the present invention is to provide a pneumatic tire that is free from peeling at the breaker end and carcass end and has excellent running durability.

That is, the present invention uses natural rubber or a diene-based synthetic rubber in addition to natural rubber as a protective rubber that surrounds one end of the steel cord breaker and the folded end of the steel coat carcass in a tire using a steel cord for the breaker or carcass. Elastomer 1 blended with 20% by weight or less
00 parts by weight, carbon black HAF-LS
50 to 90 parts by weight, 4.5 to 10 parts by weight of sulfur, 0.02 to 0.8 parts by weight of cobalt naphthenate (in terms of Co), and N
.

The gist of the present invention is to use a rubber composition containing 0.5 to 2.0 parts by weight of N-dicyclohexyl-2-benzothiazolesulfenamide. The elastomer used for the rubber that wraps and protects the end portion of - and the folded end portion of the steel cord carcass ply is an elastomer selected from natural rubber or a rubber blended with natural rubber and diene-based synthetic rubber at 20 parts by weight or less.

Regarding the effects of combining a large amount of sulfur with a cobalt organic acid and N,N-dicyclohexyl-2-benzothiazole (hereinafter referred to as vulcanization accelerator DZ), Japanese Patent Application No. 1983-16
As disclosed in No. 6738, Uzi elastic modulus,
Although it is possible to obtain high breaking and strong cutting properties, it has not yet been possible to obtain satisfactory adhesive strength, low heat generation properties, etc. As a result of further research, the present inventors found that the physical properties obtained by press vulcanization in a laboratory using the same unvulcanized rubber,
When we compared the physical properties obtained by cutting and removing from the tire after molding and curing the tire, we found that although the heat history was set to be the same as that of laboratory press vulcanization and tire vulcanization, It has been found that the rubber with the above-mentioned properties has lower tensile strength at break. Further investigation into the cause of this revealed that during the tire manufacturing process, after unvulcanized rubber is processed into a sheet or extruded, it is left for several hours to several tens of hours before being molded into a tire. It was discovered that unvulcanized rubber absorbs moisture from the air inside the factory, resulting in a decrease in its breaking strength. Particularly in the case of tire constituent materials that are important for tire running durability and have a small cross-sectional shape, such as the protective rubber that surrounds the end of a steel cord breaker or breaker layer and the folded end of a steel cord carcass or carcass layer. It was discovered that the decrease in rupture strength properties due to moisture absorption during unvulcanization is closely related to the decrease in tire running durability.

It has also been found that this decrease in physical properties at break due to moisture absorption of unvulcanized rubber can be significantly improved by using cobalt naphthenate as the organic acid cobalt and HAF-LS as the carbon black.

Furthermore, when naphthenic acid fupart, accelerator DZ, and carbon black HAF-LS are combined, a rubber with high adhesive strength to steel cord, excellent breaking strength, high elastic modulus, and low heat build-up can be obtained. was also found.

The carbon black HAF-LS used in the present invention has an iodine adsorption amount of 70 to 90 mW/? , oil absorption is 60~8
0 d/1oof carbon black powder.

The amount of carbon black HAF-LS added must be 50 to 90 parts by weight per 100 parts by weight of the elastomer. If it is less than 50 parts by weight, the elastic modulus of the rubber composition will decrease, and if it exceeds 90 parts by weight, it will become highly exothermic.

The amount of sulfur added is 4.5 to 10 parts by weight per 10 parts by weight of the elastomer; if it is less than 4.5 parts by weight, it is difficult to obtain a high elastic modulus rubber, and if it is more than 10 parts by weight, the breaking strength properties will decrease. When unvulcanized rubber is used, sulfur fumes are intense and impractical.

The amount of accelerator DZ added is preferably 0.5 parts by weight or more, preferably 0.6 to 1.5 parts by weight, per 100 parts by weight of the elastomer. If it is less than 0.5 part by weight, heat generation is high and is inappropriate.

The amount of cobalt naphthenate added is 0.02 to 0.8 parts by weight, preferably 0.1 to 0.4 parts by weight of cobalt element per 100 parts by weight of the elastomer. Therefore,
For example, when cobalt naphthenate with a cobalt content of 10% is used, 0.0% cobalt naphthenate is used per 100 parts by weight of the elastomer.
2 to 8 parts by weight, preferably 1 to 4 parts by weight. If the cobalt element content is less than 0.02 parts by weight, it is difficult to obtain good adhesion to the steel cord, and if it is more than 0.8 parts by weight, the strength at break decreases.

Other chemicals other than those mentioned above, such as softeners and anti-aging agents, can be added according to conventional methods.

The rubber composition having the above composition is used as a protective rubber to surround the ends of the steel cord precursor and the folded ends of the steel cord carcass ply, and is sheeted with a roll or extruded into a predetermined shape with a tube. Compared to conventional tires, the pneumatic tires used for this purpose are less likely to cause separation, so their running durability can be significantly improved.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example: For 100 parts by weight of natural rubber, each compounding agent shown in Table 1 was mixed in parts by weight, and further, 2 parts by weight of stearic acid, 6 parts by weight of zinc white, 1 part by weight of anti-aging agent, and 3 parts by weight of softener. Physical property test results of a rubber composition compounded with , and the breaker end part and carcass ply shown in the attached diagram for a 1000-2014PR type tire in which the breaker consists of four steel cord layers and a steel cord carcass ply layer. The above rubber composition (unvulcanized rubber) was extruded into a predetermined shape using a tuber to create a protective rubber that surrounds the folded end portion of the tire, and a tire was manufactured using this and the running durability was evaluated. are also shown.

The measurement method for each value in Table 1 is as follows.

(1) To measure the physical properties of vulcanized rubber, unvulcanized rubber was rolled into a sheet with a roll, a vulcanized sheet was created under vulcanization conditions of 150°C for 30 minutes, and the sheet was punched out with a JIS No. 3 dumbbell.
A tensile test was conducted according to -K-6301.

(2) Heat measurement is typically performed using a Gutdrich 7 rexometer, which is used in the rubber industry, according to ASTM D-623.
Evaluation was made using BC (Heat Build Up). That is, the specimen was vulcanized into a cylindrical specimen with a diameter of 17.8 m and a height of 25 m.
f, the degree of heat generation was measured after 25 minutes at a dynamic strain of 22.5% and a rotational speed of 180 rpm.

(3) Evaluation of adhesive strength with steel cord is performed using AST
According to MD2229, a brass-plated steel cord with a 3+9+15 structure was used to evaluate the pull-out force and residual rubber coverage (%).

(4) Moisture content is determined by rolling unvulcanized rubber into a sheet with rolls, cutting it into a 4611 x 451 square piece, and measuring 30
The specimens were left for 48 hours in a chamber controlled at 85% relative humidity and evaluated as the change in weight before and after being left in the chamber, that is, weight increase moisture content. Physical property evaluation after moisture absorption was performed using the physical property evaluation sheet at the same time for 30 minutes.
After being left in a chamber at a temperature of 85% relative humidity, it was vulcanized and its physical properties were evaluated.

(5) Tire running durability is 70 Krr on drum
The vehicle was run continuously at y'hr, and the load was increased at regular intervals to evaluate the travel distance (Km) until tire separation occurred.

In addition, each tire immediately after processing and after being left for 48 hours after processing,
Immediately after processing, the running durability of the molded and vulcanized tire was evaluated immediately after extrusion processing, and after being left for 48 hours after processing, the running durability of the molded and vulcanized tire was evaluated after being left in the manufacturing factory for 48 hours after extrusion processing. was evaluated.

(Margin below this page) In Table 1, A is related to the present invention, B, C, D
, E, F, and G are for comparison. A and B are comparisons of carbon black HAP-LS and HAF. A and C are comparisons between accelerators DZ and OBS, A and D are carbon black/accelerator combinations, HAF-LS/I)Z
and HAFloBS, A and E are comparisons of fupart naphthenate and cobalt stearate, A and F are accelerator D.
Regarding the amount of Z, 0.7 parts by weight and 14 parts by weight of vO are compared, and A and G represent the comparison between 7 parts by weight and 4 parts by weight of sulfur.

From the test results in Table 1, the rubber composition containing the high sulfur compound according to the present invention, a large amount of carbon black HAF-LS, cobalt in naphthene, and the vulcanization accelerator DZ has an initial physical property of 1. In addition to being advantageous in terms of vulcanization properties after moisture absorption in unvulcanized rubber, there is little decrease in breaking strength even though the g & wetness ratio of each composition is the same.
It can be seen that high adhesive strength can be maintained.

In the case of F and G, which are the same blended compositions, the accelerator DZ was 0.
F containing 4 parts by weight generates a high amount of heat, while G containing only 4 parts by weight of sulfur is advantageous in terms of strength at break, but has low adhesive strength. In addition, tire running durability evaluation was conducted when the tire was molded and vulcanized immediately after extrusion processing to minimize the influence of moisture in the air during unvulcanization, and when the tire was molded and vulcanized immediately after extrusion processing. From the running durability evaluation results of tires molded and vulcanized after being left unused, it was found that the running durability level of the tire in which the rubber composition A according to the present invention was applied as the protective rubber at one end of the steel breaker and the folded end of the steel carcass was high. Furthermore, after extrusion processing, the running durability level changes less depending on whether or not the unvulcanized rubber is left alone.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a pneumatic tire, FIG. 2 is a partially enlarged sectional view of a breaker of the pneumatic tire, and FIG. 3 is an enlarged sectional view of a ped part of the pneumatic tire. DESCRIPTION OF SYMBOLS 1... Steel cord breaker-52... Steel cord carcass, 6... Chafer-14... Heat core, 5... Protective rubber, 6... Carcass folded end part. Agent: Patent Attorney Makoto Ogawa − Patent Attorney: Ken Noguchi Patent Attorney: Kazuhiko Saishita

Claims (1)

[Claims] In a tire using a steel cord for the breaker or carcass, 20% of natural rubber or diene-based synthetic rubber is added to natural rubber as a protective rubber that surrounds one end of the steel cord breaker and the folded end of the steel cord carcass.
% by weight or less per 100 parts by weight of the blended elastomer, 50 to 90 parts by weight of carbon black HAF-LS, 4.5 to 10 parts by weight of sulfur, and 0.0 parts by weight of cobal naphthenate).
02 to 0.8 parts by weight (in terms of Co) and N,N-dicyclohexyl-2-benzothiazolesulfenamide 0
．． A pneumatic tire characterized by using a rubber composition containing 5 to 2.0 parts by weight of the rubber composition.