JPS60131303A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To check the generation of heat as well as to improve high-speed durability, by making up a belt layer with an adhesive rubber composition of high elastic modulus, high breakdown strength and high breakdown elasticity specifically compounded with a steel cord, in case of a pneumatic tire consisting of a two-ply structural tread. CONSTITUTION:A sulfur 3-7pts.wt., an organic acid cobalt chloride 0.5-5pts.wt. and a carbon 40-70pts.wt. being more than iodine absorption 100g/kg and less than DBP oil absorption 95cm<2>/100g are blended to a 100pts.wt. of natural rubber or the like, while a rubber composition, whose 100% modulus is 40-70kg/ cm<2>, breakdown strength 200kg/cm<2> or more, breakdown elasticity 300% or more after vulcanization, is made prepare, and thereby a belt layer 4 of a two- ply structural tread part 5 is formed. With this constitution, the generation of heat inside a tire is checked and high-speed durability is improvable.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air multi-layer tire in which an adhesive rubber composition having good adhesion to steel cords, high modulus of elasticity, high breaking strength, and high breaking elongation is used in the belt layer. .

With the spread of highway maintenance, there is an increasing demand for first-speed air conditioners. In particular, high-load tires such as truck and support fan tires are required to have high load durability at high speeds, and conventional bias tires are now being replaced by radial tires. The belt layer of a radial tire uses multiple plies with embedded steel cords to maintain high rigidity, and the steel cords are arranged in such a way that they intersect between the plies, so the internal pressure is low. If shearing occurs between the plies of the leakage belt layer during bridge plating and one row is continued for a long time, ply separation may occur between the plies of the belt layer, particularly at both ends of the belt layer, leading to breakage. Conventionally, attempts have been made to modify the design of tire structural factors such as tread radius, belt layer structure, and carcass profile as a method of reducing distortion.

Until now, the required characteristics of the embedded rubber in the belt layer are that it has good adhesion with the steel cord, and that the hardness and modulus of the rubber are high because the highly rigid steel cord is embedded. Buried rubber with a high modulus can be said to be effective in reducing strain during driving, but on the other hand, the belt layer exhibits constant strain behavior when momentary high loads are applied during cornering or braking. Therefore, the buried rubber is required to have high elongation and strength. However, the commonly used embedded rubbers with high hardness and modulus have low elongation and are not necessarily strong, which may actually accelerate destruction. Therefore, the present inventors have developed a rubber composition that has high hardness and modulus, excellent elongation and strength, and has good adhesive properties as an embedded rubber for the belt layer.

However, this type of composition has the disadvantage that it generates a large amount of heat due to dynamic strain during running. Particularly during high-speed running, the temperature of the belt layer increases, which not only reduces the modulus and fracture resistance of the rubber, but also promotes oxidative deterioration of the rubber. On the other hand, conventionally, in order to reduce distortion and suppress heat generation, a two-layer structure is used in which the tread rubber is on the ground contact side, the cap rubber is on the belt layer side, and the base rubber is on the belt layer side, and a highly resilient rubber is used as the base rubber. It is proposed that. By employing the above-mentioned rubber composition in the belt layer of such a structure, heat generation is suppressed and high-speed durability is greatly improved.
This discovery led to the present invention.

In the present invention, the abrasion-resistant calt layer on the tread contact surface side contains 3 to 7 parts by weight of sulfur, 0.5 to 5 parts by weight of organic acid cobalt salt, and an iodine film based on 100 parts by weight of rubber. The amount is 110g/kg or more, and the DBP oil absorption is 95cnl/
If 40 to 0 parts by weight of carbs are added, which is less than 100g, the 100% modulus will be 40 to 70kg/carS.
砿1 blue strong melon is 200kg/d or more, breaking elongation is 3tei 0%
This is a pneumatic tire characterized by actually using the above-mentioned steel cord and a rubber composition with good adhesion.

Next, embodiments of the radial tire of the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional view of the radial tire of the present invention. In the figure, the radial tire (1) of the present invention is made up of a reinforcing ply in which the cord is arranged at an angle of approximately 90° to the red-conducting surface of the tire.
a toroidal carcass ply layer (3) fixed to the carcass plug layer, a belt layer (4) made of steel cord reinforcing the crown portion of this carcass plug layer (1), and a tread rubber layer disposed outside the belt layer (4). (5) and the right pair of sidewall parts (6,). Here, the tread rubber layer (5) has a composite structure of a cap rubber (7) placed on the ground contact side and a base rubber (8) placed adjacent to the top of the belt layer.

As mentioned above, the base rubber (8) suppresses heat generation due to deformation of the belt layer, especially its edges, and disperses and relieves stress, and it is necessary to completely cover at least the edges of the belt layer. The belt layer is arranged in such a shape that it is thickest at the end of the belt layer and gradually decreases in thickness toward the center of the tread and a portion of the shoulder. The base rubber can be arranged as long as it covers at least the ends of the belt layer.It can be formed with a uniform thickness from part of one shoulder to part of the other shoulder, or it can be separated at the center of the tread and y-dove. (However, it is preferable to arrange the base rubber so that part of the shoulder is not exposed on the outside back surface.) Further, the cap rubber requires a volume greater than the entire volume. In Fig. 2, the arc of the innermost belt ply (BL) and both ends of the belt layer (9
) to the extension line of the upper arc (BE) is defined as the total tire volume (VT), the cap rubber volume (V c ) is 040% to 90%.
% range. The cap rubber must have properties such as abrasion resistance and wet grip, but the
If it is less than %, these properties will deteriorate, and if wear progresses further, there is a problem that the base rubber will be directly exposed.

On the other hand, if it exceeds 90%, no heat generation suppression effect can be expected.

It is desirable that the dynamic characteristics of the cap rubber, base rubber, and belt-embedded rubber have the following relationships.

E1≦E3゜E2′≦E3゜Here, E1′: Dynamic elastic modulus of cap rubber E1”
: Loss modulus of elasticity of cap rubber E2゛: Dynamic modulus of elasticity of base rubber E2'' : Loss modulus of elasticity of base rubber E3° : Dynamic modulus of elasticity of belt embedded rubber E,' :
Loss modulus of elasticity of belt-embedded rubber Note that the dynamic properties are measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho ■ at a frequency of 107, an amplitude of 1%, and an initial strain of 12% at a temperature of 70°C. By specifying the cap rubber, base comb, and belt embedded rubber, heat generation at the tread/rod portion can be suppressed, and strain in the belt layer can be more effectively alleviated. In particular, the base rubber near the buried comb of the belt, which has high rigidity, generates a large amount of heat due to compressive strain.
El')2≧E, "/ (E,')" to suppress the heat generation of the base rubber, while E2"/(E,')2≦E,"(
E! We have taken care to ensure that the base rubber is too hard, which could lead to damage to the embedded rubber in the belt.

The carcass is made of a cord with high elasticity such as aramid or steel at the tire equator, and the angle is approximately 90 degrees.
The belt layer (4) is constructed by laminating four steel cord plies in which the cords are arranged at an angle of 10 to 30 degrees with respect to the tire equator.

In addition, in the region sandwiched between the belt layer end (4E) and the carcass (3), a belt layer end (4E) is attached along the shape of the belt layer end (4E).
Cushion rubber (10) with decreasing thickness is arranged on both sides of the belt layer, and this cushion rubber (10) is made of a highly resilient rubber composition, such as Resilience 55, in order to prevent rubber peeling at the end of the belt layer and suppress heat generation. % or more is used.

Next, in the present invention, rubber 100 is used as embedded rubber in the belt layer.
3 to 7 parts by weight of sulfur, 0 parts by weight of organic acid cobalt salt
．． 5 to 5 parts by weight, and 40 to 70 parts by weight of carbon having an iodine adsorption amount of 110 g/kg or more and a DBP oil absorption amount of 95 cnf/100 g or less.

First, the rubbers used in the present invention are non-polar synthetic rubbers such as natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber (SBR), and copolymer rubber of olefins and non-conjugated dienes. For example, EPDM
SEPT) or a mixture thereof.

Next, the organic acid cobalt salt used in the present invention includes cobalt naphthenate, cobalt oleate, cobalt maleinate, cobalt stearate, etc., and cobalt naphthenate is particularly preferred. Organic acid cobalt salt is rubber 100
It is contained in an amount of 0.5 to 5 parts by weight. This organic acid cobalt salt contributes to the adhesion to the steel cord, and if it is less than 0.5 parts by weight, the adhesion is low;
The adhesive strength of vulcanized rubber to steel cord after heat aging exceeds the weight part! qHas a negative impact.

The amount of carbon used in this invention is 5.0 to 70 parts by weight per 100 parts by weight of rubber. Here, carbon is
The iodine adsorption amount is 110 g/kg or more, the DBP oil absorption amount is 95 cIIl/100 g or less, and the particle size is relatively small and the particles are well connected.・The type and amount of carbore are as described above. The reason for selecting Yayoku is to maintain high modulus and breaking strength of the rubber composition after vulcanization and to improve adhesion to steel cords.

So-called soft carbon with large particle size can achieve sufficient modulus and strength! The same applies when the amount of carbon is less than 50 parts by weight. On the other hand, if the coupon exceeds 70 parts by weight, sufficient elongation cannot be obtained, and the scorch time becomes short, making processing difficult. For the same reason, 3 to 7 parts by weight of sulfur is added. If it is less than 3 parts by weight, the modulus and strength after vulcanization will be low, and if it exceeds 7 parts by weight, the elongation will not be sufficient and the blooming of sulfur in the unvulcanized rubber will be intense, making it impractical.

Next, the vulcanization accelerator used in the present invention is preferably N0BS (N-oxydiethylene, pentthiazyl, sulfenamide). The type of vulcanization accelerator is influenced by the use of the organic acid cobalt salt and the blended amount of sulfur, and within the above-mentioned range of the present invention, it is recommended to use 0.50 to 1.50 of N0BS to improve adhesion to the steel cord. Desirable from point of view.

In the present invention, the steel cord used for the belt layer is preferably a steel cord plated with brass, and the plating components include copper (Cu) and zinc (Zn) in a weight ratio of C.
Those with a u/Zri ratio of 55/45 to 80/20 are generally used, and those with a Cu/Zn ratio of TO/30 are particularly preferred.

In addition, when actually compounding rubber, it is used together with vulcanizing agents, vulcanizing aids, accelerators, fillers, softeners, plasticizers, anti-aging agents, and other processing aids that are used as ordinary rubber compounding agents. Of course, they may be blended.

Next, in the present invention, based on the above-mentioned composition, the 100 modulus after vulcanization is 40 to 70 kg/cnf, and the breaking strength is 200 k.
A rubber having a g/c+d or more and a breaking elongation of 380% or more is used as the embedded rubber for the belt layer. The reason why the 100% modulus is in the range of 40 to 70 kg/cI11 is because cords with high elastic modulus such as steel cords and Kevlar (trade name of DuPont) are used for the cords in the belt layer, so there is a rigidity between the cords and the cords. 100 to avoid forming a step.
% modulus is required to be 40 kg/caf or more, and on the other hand, it is required to be 70 kg/d or less in order not to form a step in rigidity with the adjacent tread rubber. In addition, the belt layer is subjected to deformation strain during internal pressure filling and load loading, but especially at both ends of the belt layer, the gap between the carcass ply and the carcass ply widens, forming a structural fault in this area, causing large deformation strain. Become. Therefore, the embedded rubber in the belt layer has high elongation and strength, that is, the elongation at break is 380% or more,
Moreover, the breaking strength is 200kg/co? The above is necessary.

If these values are not met, the steel cord and rubber will separate, making it impossible to maintain durability.

Therefore, the present invention provides a tire with a two-layer structure of cap rubber and base rubber in the tread portion, by specifying the composition and physical properties of the rubber embedded in the belt layer as described above.
It maintains adhesion with the steel cord and controls peeling between the plies of the belt layer during high-speed running, demonstrating high durability.

The present invention will be described below with reference to Examples.

Example 1 An embedded rubber for a belt layer was evaluated according to the formulation shown in Table 1, and the results are shown in Table 2.

Example 2 A truck bus tire of size 100OR20, 14PR with the cross-sectional structure shown in Fig. 1 was manufactured by adjusting the compounding contents shown in Table 1 as the embedded rubber of the belt layer, and testing the durability of the drum. A test was conducted. Test condition is load 3
．． 5t, speed 70km/h, internal pressure 8.0kgf/cnf. The dynamic elastic modulus (E+') of the cap rubber is 6.
0kgf/cn? , loss modulus (El”) is 8.5 kg
f/cat, what is the dynamic elastic modulus (E 2' ) of the base rubber? 2kgf/cnl loss modulus (Ex”) is 6.0kg
f/cif. The results are shown in Table 3.

From Table 3, it can be seen that the running distance of the examples of the present invention until tire failure was longer than that of the other comparative examples, and that the durability was improved.

[Brief explanation of the drawing]

FIG. 1 is a left half of a sectional view of the tire of the present invention, and FIG. 2 is a partially enlarged view of the tread portion thereof. 1-1--- Tire 7--- Cap rubber 2---
- Bead core 8 - Base rubber 3 - Carcass 10'' Cushion comb 4 - - 1 - Belt layer 5 °° Tread section patent applicant Sumitomo Rubber Industries Co., Ltd. agent Patent attorney Yoshihira Nakamura Figure 1 Figure 2 figure

Claims (4)

[Claims] (1) The tread has a two-layer structure consisting of a wear-resistant cap rubber on the tread side and a highly resilient base rubber on the belt layer side, and the belt layer has a diaphragm 10
Sulfur, 3 to 7 parts by weight, organic acid cobalt salt, 0.5 to 5 parts by weight, iodine adsorption amount is 110 g/k relative to 0 parts by weight.
g or less, Dt3P oil absorption is 95 cJ/100 g or less, contains 40 to 70 parts by weight of alcarphone, and has a 100% modulus after vulcanization of 40 to 70 kg/cIIf: breaking strength is 200 kg/cJ or more, Breaking elongation is 38
A pneumatic tire characterized by using a steel cord having a content of 0% or more and a rubber composition with good adhesion. (2) The tire according to claim 1, wherein the organic acid cobalt is cobalt stearate or cobalt naphthenate. (3) The rubber composition according to claim 1, which contains 60 to 70 parts by weight of carbon. (4) The tire according to claim 1, which has a breaking strength of 250'kg/cIi1 or more.