JPS5845365B2 - Tires with improved durability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tire whose durability is improved by reinforcing it with a steel cord layer which has excellent fatigue resistance.

In recent years, radial tires that use steel cord as the tire belt material or carcass material have developed, and together with improvements in tread rubber quality, the wear resistance of tires has improved dramatically, and the wear life of tires has been significantly extended. It has become a thing.

The steel cord used in such tires has a so-called layered structure, in which two or more filaments plated on the surface with a copper-zinc alloy, so-called brass, are twisted together, and then several or more strands are further twisted together. Steel cords and steel cords with a so-called layered structure in which a plurality of filaments are arranged concentrically and twisted together are widely used.

When a tire using a steel cord like the one mentioned above receives a cut on its surface, rainwater enters from the canted area, rainwater enters from the inner surface of the tire when the tire is stored outdoors, or rubber is added. The gas generated in the sulfur and the moisture that permeates into the rubber due to the heat generated during running becomes water vapor and condenses in the internal gaps of the steel cord, causing the steel cord to rust or corrode and reduce its fatigue resistance. It is known that this has the disadvantage of causing early tire failure.

This is because the rubber used to embed steel cords must have crack growth resistance at the ends of the cord, so the amount of softener blended should be as small as possible, and the amount of filler blended as high as possible to increase reinforcing properties. It is necessary to.

However, meeting these requirements increases the viscosity of the rubber, which makes it difficult for the rubber to penetrate into the inside of the cord during the vulcanization process.Especially in a layered structure, where the filaments are in linear contact with each other, this tendency tends to increase. is especially serious.

In order to solve these drawbacks, the applicant of the present invention has proposed that before rubberizing the steel cord with a calender, as described in Japanese Patent Application No. 54-90948, the steel cord is treated with a solvent that is compatible with rubber. We proposed to fill the inside of the steel cord with rubber by treating it with a rubber dipping solution containing dissolved unvulcanized rubber.

However, this method not only complicates the process and may lead to a decrease in productivity, but also leaves room for improvement in fatigue resistance.

In order to solve the above-mentioned problem, the present inventors have
An embedded rubber whose viscosity was reduced by blending liquid low molecular weight polyisoprene described in Japanese Patent No. 4-36385 was investigated.

However, the invention disclosed in JP-A No. 54-36385 was made solely for the purpose of improving the adhesion between rubber and metals such as cord-shaped and plate-shaped brass materials and steel materials. According to the inventors' research,
When rubber whose viscosity has been lowered by blending liquid low molecular weight polyisoprene described in JP-A No. 54-36385 is used as embedded rubber, such rubber will invade the internal voids of the cord and cause damage to some extent. Although the effect is effective and it is satisfactory for industrial products such as belts and hoses, the fatigue resistance has not reached the target level as a steel cord layer of tires used under harsh conditions due to the recent increase in speed. I have confirmed that it cannot be improved.

On the other hand, the surface of steel cords for tires is often plated with brass in order to improve adhesion with rubber, and the above-mentioned Japanese Patent Application Laid-Open No. 5436385 also mentions that metals constituting composite bodies with rubber are Brass and brass-plated metals are said to be preferred.

Under such circumstances, a steel cord whose surface is peeled using a ternary alloy of brass and cobalt has recently been proposed in Japanese Patent Application Laid-Open No. 54-89940.

The purpose is to improve the drawability of brass-plated steel cord to prevent wire breakage and plating wear-off during the wire thinning process.

However, according to the knowledge and experience of the present inventors, it is clear that the corrosion resistance of an alloy made by adding cobalt to brass is improved, so a prototype tire was manufactured using a steel cord plated with this ternary alloy. When examined, it was found that there was almost no significant difference in fatigue resistance from brass-plated steel cord.

Therefore, when we investigated the cause of this in detail, we found that when manufacturing a steel cord coated with the copper-zinc-cobalt ternary alloy mentioned above, the ternary alloy is harder than brass, so plating islands and plating fall off during wire drawing. It was confirmed that the iron base was exposed on the surface of the cord, and the original corrosion resistance was hindered due to this.

That is, to date, the reality is that there is no tire that is reinforced with a steel cord reinforcing layer that satisfies fatigue resistance and has an excellent durability life.

The present inventors conducted intensive research with the aim of solving the above-mentioned drawbacks, and found that steel cords coated with a specific copper-cobalt-zinc ternary alloy were treated with buried rubber mixed with a specific liquid rubber. It has been found that the coating provides a steel cord with synergistically improved fatigue resistance, and that tires reinforced using the same have significantly improved durability life, leading to the achievement of the present invention.

Accordingly, the tire with improved durability of the present invention uses a steel cord made from a filament whose surface is plated with a ternary copper-cobalt-zinc alloy, with a rubber composition containing 5 to 25 parts by weight of the rubber component. It is characterized by being reinforced by a cord layer embedded in a rubber composition of liquid polyisoprene having a molecular weight of ~go, ooo, and vulcanized.

In the present invention, the composition of the copper-cobalt-zinc ternary alloy used to plate the steel cord is 58 to 75% copper by weight and 0 cobalt, considering adhesion with rubber and wire drawability.
．． A composition of 5 to 10 weight rice cakes and a zinc 15 to 41.5 weight rice cake is preferable, and particularly preferable is copper 60 to 70 weight φ, cobal weight-fu weight ratio, and zinc 23 to 31 weight weight.

In addition, the thickness of the plating is preferably 0.05 to 0.40μ,
Particularly preferred is 0.12 to 0.40μ.

In the present invention, the molecular weight is io or oo as described above.

An embedded rubber composition containing 5 to 25 parts by weight of liquid polyisoprene of ~so,ooo in the polymer component is used.

The molecular weight of liquid polyisoprene is 10,000~so,o
The reason why liquid polyisoprene is limited to oo is because it is co-vulcanized with other diene rubbers, so when unvulcanized it lowers the viscosity of the embedded rubber composition, and during the vulcanization process it very easily penetrates into the internal gaps of the steel cord. Although the embedded rubber composition is allowed to penetrate and does not affect the physical properties of the rubber after vulcanization, if the molecular weight is less than io or ooo, the viscosity of the embedded rubber composition becomes too low, resulting in poor workability. As the molecular weight deteriorates, the physical properties after vulcanization also deteriorate. On the other hand, if the molecular weight exceeds so or ooo, it is impossible to achieve the viscosity reduction necessary for the rubber to penetrate into the internal voids of the steel cord, which is the objective of the present invention. It is.

Moreover, the reason why the content of liquid polyisoprene is set in the range of 5 to 25 parts by weight of the rubber component in the embedded rubber composition is that if it is less than 5 parts by weight, the effect of the present invention cannot be achieved even remotely, and if it exceeds 25 parts by weight. Both cases are undesirable, since workability is significantly deteriorated and practicality is lost as described above.

Furthermore, liquid polyisoprene has 1,2-bonds and 3-bonds to improve crosslinking reactivity during vulcanization and fracture properties after vulcanization.
, 4-bonds in an amount of 5 to IO by weight.

In the present invention, the rubber components other than liquid polyisoprene contained in the embedded rubber composition are preferably natural rubber, synthetic polyisoprene rubber, polybutadiene rubber, and styrene-butadiene copolymer rubber. Among these, natural rubber and base polyisoprene rubber are particularly preferred from the viewpoint of heat generation properties and crack growth resistance.

The steel cord used in the present invention may have any twisted structure as long as it can be used for tires. Therefore, such a steel cord may be used as a belt, carcass, chafer or side part It can also be used as a reinforcing layer or the like.

It is also desirable that all of the filaments occupying the steel cord be coated with the ternary alloy mentioned above, but in some cases only some of the filaments may be coated with the ternary alloy.
It may also be a steel cord plated with an original alloy.

The present invention will be explained in more detail below with reference to Reference Examples and Examples.

Reference Example Compound Al~ having the composition shown in Table 1 (shown in parts by weight)
Various embedded rubber compositions of No. 4 were prepared.

Steel cord A has a twisted structure plated with copper-zinc (63/37) alloy to a thickness of 0.20μ (I X3 + 9 + 15) XO,1
75+1 steel cord, and steel cord B as copper-cobalt-zinc (6515/30) alloy with 0.
A steel cord of the same twisted structure plated to a thickness of 20μ was prepared.

A total of 8 types of rubberized cord layers were made by embedding steel cord A and steel cord B in various embedding rubber compositions of the above formulations A1 to 4 under normal tire manufacturing conditions,
Then it was vulcanized.

In order to examine the degree of rubber penetration into the internal gaps of these rubberized cord layers, we used a Heck type air permeation measuring device to evacuate the air in the chamber with a vacuum pump until the scale of the mercury column showed 380 mm. The pump was stopped, then the air cock was opened, and the time until the scale of the mercury column showed 370 mm was determined.

The longer this time, the more difficult it is for air to pass through the internal gaps of the cord, thus indicating that the amount of tacom entering the internal gaps of the cord is large.

Note that there was no difference in the degree of rubber penetration between steel cord A and steel cord B.

The obtained results are also listed in Table 1 using steel cord Bl.

Next, the above eight types of rubberized cord layers were used as samples with a length of 220 plates and a width of 50 mm, and for these samples,
Using a salt spray tester, spray 5% NaCt at a spray pressure of 1.
kg/- onto the sample in a tank at 40°C, and the bending angle ±
The samples were bent at 40° and 40 cpm of bending.

Next, the cord was taken out and subjected to a tensile test to examine the bending fatigue resistance of the cord.

The results were evaluated using the strength retention rate (multiple) based on the pre-measured cord strength before bending fatigue.
As shown in the figure.

Figure 1 shows the results for steel cord A and steel cord B buried with the embedding rubber composition of formulation A2, and for comparison, steel cord A and steel cord buried with the embedding rubber composition of formulation AI. The results for B are shown.

Similarly, FIGS. 2 and 3 show the results obtained with the embedded rubber compositions of Compound Layer 3 and Compound Layer 4, respectively, in comparison with the results obtained with the embedded rubber composition of Compound AI.

From FIGS. 1 to 3, when using the embedded rubber composition of formulation 711L1 that does not contain liquid polyisoprene,
There is almost no difference in bending fatigue resistance between steel cord A and steel cord B, but when using the embedded rubber composition of compound layers 2 to 4 containing liquid polyisoprene, the bending fatigue resistance It can be seen that steel cord B is significantly improved synergistically over steel cord A.

Example A conventional tire A using a rubber layer in which steel cord A was embedded in an embedded rubber composition of compound AI as a carcass of a steel radial tire with a tire size of 11-22.5.
Comparative tire B1 using a cord layer in which steel cord B was embedded in the embedded rubber composition of compound layer 1 Steel cord A
Comparative tire C using a cord layer embedded with the embedding rubber composition of blend A4 and tire D of the present invention using a cord layer embedded with steel cord B in the embedding rubber composition of blend A4 were prototyped. The durable life of the tires was evaluated.

The evaluation method was to remove the inner liner in a width of 50 mm along the radial direction of the tire, fill the inner surface of the tire with water, and run the tire at 30,000/im under a JI8100% load.

After running, the cord was removed from the carcass, and the strength retention rate was determined in the same manner as the reference example.

The results obtained are shown in Figure 4. As is clear from Figure 4,
It can be seen that tire D of the present invention has a synergistically improved durability life.

[Brief explanation of drawings]

Figures 1, 2, and 3 are diagrams showing the relationship between the strength retention rate of the cord and the number of bending cycles of the rubberized cord layer sample, and Figure 4 is the 11-22.5 radial tire of the example. It is a graph showing the strength retention rate of the cord.

Claims (1)

[Scope of Claims] 1. A steel cord consisting of a filament whose surface is plated with a ternary copper-cobalt-zinc alloy is coated with a steel cord having a weight of 5 to 25% of the rubber portion in the rubber composition for 10,000 to 10,000 seconds.
Reinforced by a cord layer embedded with a rubber composition of liquid polyisoprene having a molecular weight of o, ooo,
A tire with improved durability, characterized by being made by vulcanization. 2 As a g-type polyisoprene, 1,2-bond and 3
, 4-bonds in an amount of 5 to 10 by weight, according to claim 1, wherein the tire has an improved durability life. 3 The composition of the copper-cobalt-zinc ternary alloy is copper 58-75
Weight φ, Kobal) 0.5 to 10 weight, Zinc 15 to 41
．． 5. A tire with improved durability according to claim 1 or 2, which has a weight of 5. 4 The thickness of the copper-cobalt-zinc ternary alloy plating is 0.
05 to 0.40μ. A tire with improved durability life according to claim 1.2 or 3. 5. Claims 1, 2. containing natural rubber and/or synthetic polyisoprene rubber in the embedded rubber composition.
A tire with improved durability as described in item 3 or 4.