JPS6349501A - Radial tire - Google Patents

Abstract

PURPOSE:To suppress the deterioration of adhesion between a steel cord and a coating rubber by setting the dimension and sulfur content in a tread rubber layer, steel belt layer, and the rubber sheet layer interposed therebetween so as to be set within the specific conditions. CONSTITUTION:When the distance between a steel belt layer 2a positioned on a tread rubber layer 1 side and the boundary surface X1 between a steel cord 3a and a rubber sheet layer 7 is set a1, width of the steel belt 2a is set WS, width of the rubber sheet 7 is set WR, thickness is set a2, total sulfur content in the tread rubber layer 1 is set ST, total sulfur in the coating rubber 4 in the steel belt layer is set SC, and the total sulfur in the rubber sheet is set SR, the following conditions shall be satisfied; 0.2mm<=a1<=0.8mm, (0.8XWS)<=WR, 0.3<a2<1.2mm, 0.6mm<(a1+a2)<2.0mm, 1.0wt%<ST, 2.8wt%< SC<3.6wt%, (1.8XST)<SC, (0.8XSC)<=SR<=(1.2XSC).

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a radial tire for vehicles, and more specifically, to a radial tire for vehicles, and more specifically to a radial tire with improved adhesion between a steel cord constituting a steel belt layer and coated rubber. in,
This relates to radial tires that can withstand harsh operating conditions such as high temperatures and high temperatures.

[Prior art]

-C. One of the factors that influences the durability of radial tires with a steel belt layer used for passenger cars, trucks, buses, etc. is the adhesion between the steel cord that makes up the steel belt layer and the coated rubber. It will be done.

In order to improve the adhesion between the steel cord of the steel belt layer and the coated rubber, for example, the steel cord is plated with brass, as described on page 122 of ``Points for selecting rubber materials (published by the Japanese Standards Association)''. A method has been used in which a cobalt salt of an organic acid is added to the coated rubber.

However, tires are made up of many parts other than the steel belt layer, such as the tread and carcass, and each has a different rubber composition, so compounding agents that can migrate in the rubber, such as sulfur and oil, interfere with each other, and the steel belt Even if the composition of the coated rubber layer is optimized in advance, the composition may change when the product is formed through molding and vulcanization, and the desired adhesion may not be achieved.

Particularly, in a tire having two or more steel belt layers T4, adhesion tends to deteriorate on the surface of the steel cord of the steel belt layer closest to the tread (hereinafter referred to as the last belt layer) facing the tread side. The main reason for this is that it is the closest to moisture entering from the outside of the tire, and because it is closest to the tread, there is a large transfer of oil, sulfur, accelerators, etc. to the coat rubber.

As a countermeasure against this problem, conventional methods have been used to protect the last belt layer by newly providing an undertread between the last belt layer and the tread.

For example, JP-A-54-132904, JP-A-55
-127207 publication, Japanese Patent Application Laid-Open No. 57-4407,
JP-A No. 5F3-76308, JP-A No. 58-116
There are publications such as No. 204. In particular, JP-A No. 57-4407 states that the cause of the decrease in adhesion is that the sulfur compound in the coat rubber transfers to the tread, and that an undertread with a high sulfur content is effective. .

However, even if these methods of providing an undertread are used, the adhesion between the steel cord and rubber can only be improved until the tire is new, and it is sufficient to prevent the deterioration of adhesion when the usage conditions are high or high. It couldn't be prevented.

The first reason is that during the stock period from when a green tire is molded to when it is vulcanized, the compounding agent transfers between the trend and undertread, changing the undertread layer and achieving the desired effect. This is something that cannot be done.

In addition, in the normal tire manufacturing process, the tread is manufactured using an extruder.
It is extruded at a high temperature of around 00°C and is bonded to the undertread, which is made into a sheet with a calendar roll or extruded with an extruder, before cooling, but the migration of the compounding ingredients is rapid at higher temperatures than room temperature, so it takes a short time. The composition of the undertread changes.

The second reason is that in tires that have a nylon belt layer between the steel belt layer and the tread to improve high-speed durability and steering performance, the last belt layer is not directly protected by the undertread layer, but instead Since it comes into contact with the nylon belt layer, it is obvious that no improvement in adhesion can be expected.

Furthermore, when using a tread containing a large amount of sulfenamide accelerator, for example, adhesion inhibiting substances are transferred from the tread rubber to the coat rubber when running at high temperatures, and this, combined with the tread shape and coat rubber composition, causes Deterioration of adhesion is also a major cause.

As a result of detailed study on the decrease in adhesion between steel cord and coated rubber under high temperature and high humidity, the present inventors found that a mechanism whereby some substance diffuses from the trend part toward the steel belt layer and destroys the adhesive layer. The conclusion was that it is possible.

Although it is not clear what kind of substance destroys the adhesive layer, it is possible to vulcanize a tire with no grooves on the tread (slick pattern tire) and put it in a high-temperature oven to age. When a peel test is performed, adhesion deterioration is observed in a hollow-like manner, whereas when a tire with no grooves is regrooved after vulcanization and an aging and peel test is performed under the same conditions, it shows that the grooves have deteriorated. Adhesive deterioration of the steel belt layer is less likely to occur. This phenomenon occurs when some substance migrates from the tread rubber to the steel belt layer at high temperatures and the tread becomes thick, so if a large amount of material migrates, the deterioration is significant; It can be explained that if no migration occurs, deterioration is unlikely to occur. In addition, the more the vulcanization accelerator contained in the tread rubber composition, the more likely it is that adhesive deterioration occurs, so it is assumed that the substance that destroys the adhesive layer is either the vulcanization accelerator itself or amines that are decomposed products of the accelerator. ing. In other words, deterioration of adhesion can be prevented by more actively trapping this adhesion inhibiting substance without physically transferring it to the belt coat rubber. As a result of intensive study on the above issues, we have arrived at the present invention.

[Purpose of the invention]

Therefore, the present invention effectively prevents the adhesion between the steel cords constituting the steel belt layer and the coated rubber from deteriorating due to moisture, and makes it possible to sufficiently withstand running even under harsh environments, especially at high temperatures. The purpose is to provide a radial tire with

[Structure of the invention]

Therefore, the radial tire of the present invention has a raw material rubber of 100%
A rubber sheet layer is interposed between a tread rubber layer containing 0.5 parts by weight or more of a sulfenamide vulcanization accelerator and a small (2 or more) steel belt layer. The distance between the steel cord of the steel heald layer located on the rubber layer side and the interface between this steel belt layer and the rubber sheet layer is a, the width of the steel belt layer located on the tread rubber layer side is WS, The width of the rubber sheet layer is W8, the thickness of the rubber sheet layer is al, the total zeol content of the tread rubber layer is 8 teeth, the total zeol content of the coated rubber of the steel belt layer is Sc, and the total zeol content of the rubber sheet layer is Sc. When the zeolite content is SR, the following conditions are satisfied, and the rubber sheet layer is free of resorcin or a resorcin/formaldehyde initial condensate.
．． It is constituted by blending 5 to 4.0% by weight.

0.211≦a, ≦0.8 m, (0.8X W s) ≦WR, 0,3<
az<1.2mm.

0, 61 meetings < (al + a, )
<2.0 1 box, 1.0% by weight<SC, 2.8% by weight<
s, <3.6 wt%, (1,8x ST) < Sc,
(0,8×Sc)≦SR≦(1,2×Sc).

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a partially cross-sectional explanatory diagram of an example of the radial tire of the present invention. In Fig. 1, 1 is a tread rubber layer, 2 is a tread rubber layer;
Reference characters a and 2b indicate steel belt layers provided inside the tread rubber layer 1, and the steel belt layers 2a and 2b are composed of a plurality of steel cords 3a and 3b and a coated rubber 4. Further, the steel belt layer 2a,
On the inside of 2b, a carcass layer 5 and a liner N6 are sequentially laminated. Steel belt layers 2a, 2b
A rubber sheet layer 7 of the same thickness and of the same type as the coat rubber is interposed between the steel belt layer 2a and the tread rubber N1.

(1) The present invention is effective for tires in which the tread rubber layer 1 contains 0.5 parts by weight or more of a sulfenamide vulcanization accelerator per 100 parts by weight of raw rubber.

Here, the sulfenamide vulcanization accelerator is, for example, N
, N-dicyclohexyl-2-benzothiazolesulfenamide, N-cyclohexyl-2-benzothiazolesulfenamide, N-oxydiethylene-2-benzothiazolesulfenamide, N,N-diisopropyl-2- Benzothiazole sulfenamide, N-te
rt-butyl-2-benzothiazolesulfenamide and the like.

(2) In the present invention, the average distance between the steel cord 3a of the last belt N2a and the steel cord 3b of the steel belt H2b adjacent to the last belt layer 2a is d.
1 Boundary surface X on the tread rubber layer 1 side of the last belt N2a
The distance from 1 to the surface of the steel cord 3a closest to the rubber seal layer 7 is aI, the total sulfur content of the tread rubber layer 1 is Sa, the steel belt layers 2a, 2b (the total sulfur content of D coated rubber 4 is sc) , 0.6 w≦d≦
1. Ow, aI≦0.8mm,
ST>1.0 weight 11%, 2.8 weight%<Se<3
．． 6% by weight, tires with 1.8
3. The width of the rubber sheet layer is WSl, the thickness of the rubber sheet layer is 32, the total sulfur content of the rubber sheet layer is SR, and 0.8XS.
c≦s, ≦1.2xsc, 0.8xWS≦w, l
, 0.31m<az<1.2n% 0.6mm
<(a++az)<2.0■ By disposing the rubber sheet jiJ7 on the tread rubber layer 1 side of the last belt N2a, the decrease in adhesion can be suppressed to some extent.

Here, when d is 0.6 mm or less, the peeling force between the steel belt layers decreases, and when d is 1.0 mm or more, the tread separation resistance at high speeds decreases. Sulfur migration occurs due to the difference in sulfur concentration between the two rubber compositions that are in contact with the interface Xl, so if Sc is 2.8% by weight or less and sc/sT is 1.8 or less, adhesive deterioration due to migration is unlikely to occur. Become. Moreover, if SC is 1.0% by weight or less or Sc is 3.6% by weight or more, the adhesiveness between the tread rubber layer and the interface X + , X z between the steel belt N2a decreases. The transition from the steel belt [2a to the tread rubber layer 1 occurs at the boundary surface, so al is 0.8
mm or more, virtually no decrease in sulfur concentration occurs near the surface of the steel wire, and no decrease in adhesion occurs.

The rubber sheet layer 7 for suppressing sulfur migration preferably covers the entire width Ws of the last bell) Jif2a, and needs to cover at least 80% of the area.

When the thickness N2 of the rubber sheet layer 7 is 0.3 fl or less, it is rolled,
The bonding process becomes difficult, and if it exceeds 1.2n, the tread separation resistance decreases, so preferably 0.35Im≦a2≦0.8, and the combined thickness of Al and N2 (a++az) is 0. , 6** or less, the effect of suppressing migration is small, and if it is 2.0 or more, tread separation resistance decreases. Since sulfur migration is caused by a difference in sulfur concentration, the total sulfur content SCl of the rubber sheet layer 7 needs to be 100±20% of the total sulfur content of the steel belt layers 2a, 2b.

The rubber sheet layer 7 can be formed by a conventional method using an extruder, a calendar, or the like.

When the tread rubber N1 and the steel belts N2a and 2b are combined in the green tire molding process, the rubber sheet N7 is the tread rubber layer 1 of the last belt layer 2a.
Since the rubber sheet layer 7 needs to be placed on the side surface, the rubber sheet layer 7 can be pasted on the molding drum in the green tire molding process, or it can be pasted on the last bell layer 2a in advance. good.

Furthermore, in a tire having a nylon belt layer between the last belt FJ 2 a and the tread rubber layer 1, by arranging the rubber sheet layer 7 that satisfies the above conditions between the last belt N2a and the nylon belt layer, A similar effect can be obtained. That is, one or more nylon belt layers may be placed on the rubber sheet layer 7.

(3) Furthermore, in the present invention, the rubber sheet layer 7
0.5 to 4.0% by weight, preferably 0.5 to 3.0% by weight of resorcin or resorcin/formaldehyde initial condensate.
Add 0% by weight.

This traps adhesion inhibitors and minimizes adhesion deterioration at high temperatures. The blending amount of resorcin or resorcin/formaldehyde initial condensate is 0.5
If it is less than 4.0% by weight, it will not be effective (if it exceeds 4.0% by weight, the breaking strength will drop significantly and the heat generated during running will be high,
Durability is poor and undesirable.

The resorcinol/formaldehyde initial condensate is a compound represented by the following structural formula.

Product names include Sumikanol 620 (Sumai Kagaku), Penacolite Resin B-18s (KOPPERS)
etc. can be mentioned.

Examples and comparative examples are shown below.

Examples and comparative tires are 155S for passenger cars with two steel belt layers.
Using R13 size, the steel cord has a copper content of approximately 63
% brass plating was used, and the coating rubber for the tread rubber and steel belt layer was the one in Table 1 below, and the tread rubber was blended with 0.78 parts by weight of N-cyclohexyl-2benzothiazole sulfenamide be. In addition, the total sulfur content was measured by the method of JIS K6350,
d = 0, 8 **, a 1 = 0.4 ui, WI
I=WH. The rubber sheet layer was applied to the last belt in advance and then molded into a green tire.

The compounding contents (A to ■) of the rubber sheet layer are shown in Table 2.

A does not contain resorcinol or resorcinol/formaldehyde initial condensate, and BG contains resorcinol/formaldehyde initial condensate in order of 0.3, 0.5, 1.0.
2.0.3.0.4.0% by weight was added, H was A with 3.0% by weight of resorcin added, ■ was added with a reduced amount of sulfur and 3.0% by weight of resorcin was added. It is something.

In Table 3, standard example 1 is a tire with normal specifications,
Comparative Example 1 is a tire with a I+ a t =0.95 fin and a rubber sheet layer that does not contain resorcin and an initial condensate of resorcin/formaldehyde, and Comparative Example 2 is a tire in which a rubber sheet layer of Comparative Example 1 is provided with a rubber sheet layer that does not contain resorcin/formaldehyde initial condensate. This is a tire to which 0.3% by weight of the initial condensate was added. Comparative Example 9 is a tire having a rubber sheet layer having an a++aZ of 0.65 s weight and containing no resorcin and a resorcin/formaldehyde initial condensate, and Comparative Example 11 is a tire with a rubber sheet layer of Comparative Example 9 with a reduced amount of sulfur compounded. , and added 3.0% by weight of resorcinol. In Examples 3 to 8, 3tIl of resorcinol formaldehyde was added to the rubber sheet layer so that ai + at = 0.95.
Sequentially shrink the metal by 0.5°1.0.2.0.3.0.4.0
This is a tire in which rubber sheet layers are arranged in different amounts by weight. Example 10 is a tire in which a rubber sheet layer containing 3.0% by weight of resorcin was added to the rubber sheet layer of Comparative Example 9.

Each tire was vulcanized immediately after molding in the same manner as in a normal tire manufacturing process.

The prototype tire was tested 7 times to see the effects of heat and moisture.
Two conditions: one in which the product is left in a steam oven at 0°C and 98% humidity for 30 days, and the other in which it is left in an air oven at 100°C for 72 hours and then left in a steam oven at 70°C and 98% humidity for another 30 days. It deteriorated. The adhesion between the steel cord of the last belt layer and the coated rubber was evaluated by performing a peel test between the tread rubber and the last belt layer and determining the rubber coverage of the steel cord after peeling.

That is, if the entire surface of the steel cord on the tread side was covered with the coated rubber, the rubber coverage was determined to be 100%, and if the steel cord was exposed without any coating rubber attached, the rubber coverage was determined to be 0%.

As a result of experiments under the above conditions, the rubber coverage of new tires that have not been affected by heat or moisture is good, but the rubber coverage of tires left at 70℃ and 98% humidity for 30 days is a standard example. 1 shows a considerable decrease, and Comparative Example 9 also shows a decrease. That is, if the rubber sheet layer 7 is not present, the adhesive deterioration is significant, but even if the rubber sheet layer 7 is present, the adhesive deterioration cannot be prevented if the coat gauge is thin.

Furthermore, when looking at the rubber coverage after 72 hours in air at 100°C and 30 days at 70°C and 98% humidity, Comparative Example 1 was 2.9°.
Adhesive deterioration is significant. The results of Comparative Example 1 show that even if rubber sheet N7 with the optimum coat gauge and sulfur composition is placed, adhesive deterioration cannot be prevented unless the initial condensate of resorcinol/formaldehyde is placed. Furthermore, from Comparative Example 2, it can be seen that there is no effect if the amount of the resorcinol-formaldehyde initial condensate is small. Comparative Example 11 shows that even if an appropriate amount of resorcinol-formaldehyde initial condensate is blended, the effect is small when the amount of sulfur blended is small and the sheet gauge is thin.

It can be seen that Examples 3 to 8 showed less adhesion deterioration than the corresponding standard examples and comparative examples, and the effect was realized when the resorcinol/formaldehyde initial condensate was contained in an amount of 0.5 to 4.0% by weight. . Furthermore, from Example 10, even if the thickness of the rubber sheet layer becomes thin, if the sulfur content is optimized, 3.0% by weight of resorcinol can be added to the rubber sheet layer 7 to a satisfactory level. It can be seen that adhesive deterioration can be prevented.

〔Effect of the invention〕

As explained above, the radial tire of the present invention can be used at high temperatures,
Since there is less deterioration of the adhesion between the steel cord of the steel belt layer and the coated rubber under high humidity conditions, it has the advantage of reducing failures of radial tires used under harsh operating conditions such as high temperatures.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional explanatory view of an example of the radial tire of the present invention. DESCRIPTION OF SYMBOLS 1... Tread rubber layer, 2a, 2b... Steel belt layer, 3a, 3b... Steel cord, 4...
Coat rubber, 5... carcass layer, 6... liner layer,
7...Rubber sheet layer. Figure 1

Claims (1)

[Claims] 1. Between a tread rubber layer containing 0.5 parts by weight or more of a sulfenamide vulcanization accelerator per 100 parts by weight of raw rubber and at least two or more steel belt layers. In a tire with a rubber sheet layer interposed, the distance between the steel cord of the steel belt layer located closest to the tread rubber layer and the interface between this steel belt layer and the rubber sheet layer is a_1, and the tread rubber layer The width of the steel belt layer located on the side is W_S, the width of the rubber sheet layer is W_R, the thickness of the rubber sheet layer is a_2, the total sulfur content of the tread rubber layer is S_T, and the coating rubber of the steel belt layer is When the total sulfur content is S_C and the total sulfur content of the rubber sheet layer is S_R, the following conditions are satisfied, and 0.
A radial tire characterized by containing 5 to 4.0% by weight. 0.2mm≦a_1≦0.8mm, (0.8×W_S)≦W_R, 0.3<a_2<1.2
mm, 0.6mm<(a_1+a_2)<2.0mm,
1.0 wt%<S_T, 2.8 wt%<S_C<3.6
Weight%, (1.8×S_T)<S_C, (0.8×S_
C)≦S_R≦(1.2×S_C). 2. The radial tire according to claim 1, wherein at least one nylon belt layer is disposed between the tread rubber layer and the rubber sheet layer.