JPS6358722B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a pneumatic tire with significantly improved durability by applying a steel cord having a filament made of an amorphous alloy of a predetermined composition to at least the inner layer of the pneumatic tire. It is related to tires. In recent years, tires have been required to have a high level of performance in terms of running life, high-speed running performance, safety, etc., and in response to these demands, pneumatic tires using steel cords have been developed. Compared to organic fibers, this steel cord has less strength loss due to heat history, and steel cord tires are highly durable even when running continuously at high speeds for long periods of time.
It is widely used in passenger cars and long-distance transportation trucks. However, this steel cord also has the problem of reduced strength due to rust, and various solutions have been proposed in the past. A typical example of this is the improvement of the plating of the steel filament constituting the steel cord. For example, in JP-A-49-102002, the surface steel filament is coated with brass plating in consideration of adhesion to rubber. ,
There is a description that the steel filament for the core is coated with galvanized, which is relatively resistant to rust. However, the steel filament becomes fatigued while the tire is running, and the plating is scraped off due to the fretting phenomenon (a phenomenon in which the filaments rub against each other and are worn away), so the present invention shows that improvement by plating cannot achieve the rust prevention effect. It was confirmed by the following people. Therefore, in order to increase the rust prevention effect, there is no choice but to use a rust-resistant filament material itself, and if an amorphous alloy that is resistant to rust and has better corrosion resistance than stainless steel can be used for steel cords for tires. , it is possible to prevent the steel cord from deteriorating in strength due to rust, and is expected to improve the durability of the tire. Furthermore, amorphous alloys have a tensile strength of 200 to 320 Kg/mm2 compared to the crystalline alloys (high carbon steel) used in current steel cords, which are 350 to 350 kg/ ^mm2 .
High at 450Kg/mm ² and specific gravity compared to the current 7.8g/cm ³
Since it is as low as 6.7 to 7.2 g/cm ³ , it is possible to reduce the weight of the tire. In this regard, Japanese Patent Publications No. 45401/1982 and Japanese Patent Publication No. 1243/1983 are published as attempts to apply Fe-based amorphous alloys to tires. These disclose technologies for linear Fe-based amorphous alloys characterized by containing 1% or more of Cu in the metal composition, but they have the following technical problems. In other words, the addition of Cu to Fe-based amorphous alloys increases the Tg of the alloy.
This results in a decrease in the point and makes it extremely difficult to amorphize during manufacturing. In other words, linear amorphous alloys obtained by rapid cooling at the usual cooling rate of about 10 ⁵ °C/second have a wire diameter of 20μ or less,
If the wire diameter is larger than that, the crystal phase will be mixed in and the wire will become brittle.
Even if the cooling rate is increased, the wire diameter will only get smaller and smaller, and it will still fall far short of the minimum wire diameter of 100 to 150μ, which is the minimum wire diameter that can withstand practical use as a filament for steel cord for tire reinforcement. It was unsuitable for tire applications. Furthermore, it is well known that the addition of Cu to Fe-based amorphous alloys reduces the strength compared to the addition of other transition metals, and therefore, as a steel cord for reinforcing tires, it cannot withstand high deformation input. Also, it does not have sufficient performance against repeated bending stress, and from this point of view it cannot be put to practical use. On the other hand, as an example of applying Fe-based amorphous alloys to things other than tires, amorphous alloy materials such as Fe-PB-based and Fe-Si-B-based have been known as transformer materials for utility poles. However, this linear amorphous alloy has a thickness of about 30 to 50μ at most, and its strength is low and its adhesion to rubber is insufficient, making it unsuitable for use as a filament for tire reinforcing cords. It was hot. The present inventors have conducted extensive research with the aim of solving the above technical problem and developing a tire with improved durability by making it possible to apply an amorphous alloy to steel cords for reinforcing tires. As a result, by specifying the composition of the amorphous alloy, it was possible to form a filament that can be used as a filament for steel cords, and steel cords with this filament applied at least to the inner layer can be used as belts and carcass ply materials for pneumatic tires. It has been confirmed that the above object can be achieved by applying the invention to at least one of the following, and the present invention has been achieved. Therefore, the pneumatic tire of the present invention contains Ni and/or Co: 1 to 20 at%, Si: 5 at% to B: 20 at%, and (Si+B): 10 to 30 at%, with the remainder being substantially Fe. A steel cord having a filament made of an amorphous metal having the composition applied to at least the inner layer side is applied to at least one of a belt and a carcass ply material of a pneumatic tire. The reason for adding the transition metals Ni and/or Co in the above composition of the amorphous alloy of the present invention is to consider the adhesion with the rubber composition when applied to tires as described above, and the semimetal element Si and B are added to improve the ability to form an amorphous state. Therefore, the contents of Ni and /Co as well as Si and B are limited in terms of adhesive strength and ability to form an amorphous state. That is, if the Ni and/or Co content is less than 1 at%, the adhesive strength will decrease, and if it exceeds 20 at%, the filament strength will decrease. If the total content of Si and B is less than 10 at% and exceeds 30 at%, the ability to form an amorphous state deteriorates. In the present invention, Ni and/or Co are added as transition metal elements from the viewpoint of adhesion between the steel cord and the rubber composition. In addition, as semimetallic elements, P-C and Si-B systems are preferable from a practical range in terms of manufacturing, but when used in tire reinforcing cords, the heat generation temperature of tires at high speeds reaches 150 to 200°C, so metal materials are preferred. Since stability is required, a Si--B type material with good thermal stability is most preferable. In this case, the mixing ratio of Si and B is 1 to 20 at%, Si: 5 at% to B: 20 at%, and (Si + B): 10 to 30 at%. Improves strength after fatigue. Among these, the case where the Si content is 10 at% and the B content is 12 to 13 at% is easiest to manufacture. Here, "easy to manufacture" means that a filament with a larger wire diameter can be obtained at the same cooling rate. In the present invention, the steel cord used for reinforcing the tire belt and carcass ply material may have any of a layered structure, a double-twisted structure, a bundle-twisted structure, and a single-twisted structure. In either of these twisted structures, it is most preferable to apply an amorphous alloy to all constituent filaments, but the same corrosion-resistant (rust-preventing) effect can be obtained even if the amorphous alloy is applied only to the inner layer filaments. can get. This is because when steel cords are used in tires, the surface filaments of the steel cords are completely covered with the coating rubber composition (filler rubber), so they are not affected by moisture or corrosive gases during tire vulcanization. Although it is not easily corroded, the inner layer filament is not completely covered with the rubber composition, so it is easily affected by moisture and corrosive gas, and the inner layer filament always corrodes first, which causes the steel cord to break. Here, a case will be described in which the amorphous alloy is applied only to the inner layer filament. For steel cords with a layered structure, this applies to the core and inner sheath. For example, as shown in Figure 1 (3+9+
15) In the +1 twisted structure, the core filament,
It consists of a first sheath filament 2, a second sheath filament 3, and a wrapping wire 4. Among these, when applying an amorphous alloy filament to the inner layer side, it is applied to only 1, only 2, or both 1 and 2. There are three application methods for both. However, in order to increase the rust prevention effect, it is desirable to apply it to both the core filament 1 and the first sheath filament 2. Similarly, (3+9)× shown in Figure 2
For steel cords with a twist structure of 0.160+1×0.120, there is a method that applies only to core filament 1. The same applies to steel cords with a bundled structure.
For example, in the twisted structure of 1×28+1 in FIG. 3, there are cases where only 5 of the innermost filament 5, inner layer filament 6, and surface filament 7 are applied, and cases where it is applied to both 5 and 6 (other than 7). The latter is preferable from the viewpoint of rust prevention effect. In steel cords with a double-strand structure, the core strands are 8 and 1, respectively, as shown in the case of a strand structure of 7×4+1 in FIG. 4, a strand structure of 7×7 in FIG. 5, and a strand structure of 3×7 in FIG. An amorphous alloy filament may be applied to the core filament 10 in the surface strand 9. When amorphous alloy filaments are used only on the inner layer side, the surface filaments are usually made of high carbon steel wire that is brushed. In this case, the composition of the brass plating has a Cu/Zn ratio of 7/3 to
6/4 is good. In addition, the present inventors also investigated coating rubber compositions for belts and carcass plies in order to improve the adhesion of amorphous alloys as tire reinforcing cords. If 2 parts by weight or more and 7 parts by weight or less of sulfur and 1 part or more and 5 parts by weight or less of a metal salt of an organic carboxylic acid or a mixture thereof are contained based on 100 parts by weight, the composition of the amorphous alloy and coating rubber can be improved. It was also found that the adhesiveness with objects increases synergistically. Here, diene rubber refers to natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber,
One type of polybutadiene or a mixture thereof. The organic carboxylic acid is a resin acid such as rosin acid or tall oil acid, a fatty acid such as stearic acid, palmitic acid, or oleic acid, or naphthenic acid. The metal used in the metal salt of the organic carboxylic acid is preferably a transition metal element, Ni, Co, Mo, Cr, or Mn, and among these, Co and Ni are particularly preferred. The present invention will be explained in more detail below with reference to Examples and Reference Examples. In the examples, thermal stability, initial strength, strength retention after running, fatigue strength retention after running, and adhesiveness after running were evaluated as follows. Evaluation method: Thermal stability: Each cord is held at 250°C in the air before being applied to tires, and the time until ductility disappears due to structural relaxation or crystallization of the amorphous phase and it begins to become brittle is measured. do. The longer this time, the better the thermal stability. The loss of ductility was determined by 180° tight bending of the sample. Initial strength: 10 cords were taken out from the belt section or carcass ply section of a new tire, and their strength was measured using a tensile tester and the average value was taken. The tension test conditions were a chuck distance of 200 mm and a tension speed of 20 mm/min. Post-running strength retention rate: After running on a general road, the post-running strength was determined in the same manner as the initial strength, and the obtained value was divided by the initial strength to determine the retention rate. Expressed in (%). Fatigue strength retention rate after running: First, the initial fatigue strength (fatigue limit) was determined by taking out a cord from a new tire and performing a rotary bending fatigue test in the same manner as when measuring strength. Then, after driving on general roads for 100,000 km, we took out the cord and measured the fatigue strength after driving in the same way.
The retention rate for initial fatigue strength is expressed. Note that the rotating bending fatigue conditions are for sample lengths of 70 to 100 mm.
The rotation speed is 3000 rpm, and the stress is changed depending on the curvature applied to the sample. Fatigue strength (fatigue limit) is
The highest stress that does not cause breakage is shown in ¹⁰⁶ cycles. Adhesiveness after driving: Width 50mm from the tire belt or carcass ply after driving on general roads.
A sample with a length of 200 mm was cut out and the peel resistance between the rubber and the cord (according to JIS-6301) was measured. The results are shown in Kg/book. Example 1 Alloy base materials having the three compositions of composition numbers a, c, and g shown in Table 1 were appropriately melted at a temperature of 1000 to 1400°C in a secret melting furnace, and the molten metal was brought to high pressure through a nozzle. The material was injected into a cylindrical steel plate and rapidly cooled inside a cylindrical steel plate rotating at high speed to obtain an amorphous alloy filament with a round wire cross section and a wire diameter of 0.175 mm. For comparison, composition numbers h, i
Similarly, a filament was made on a trial basis, but when the wire diameter exceeded 20 μm, the desired 0.175 mm amorphous alloy filament could not be obtained because crystals were mixed in and the wire became brittle. The above amorphous alloy filaments having composition numbers a, c, and g were twisted in four types of twisting structures as shown in Table 2. Twisted structure A has two types a and c, and twisted structure B has c and c types.
G2 types and twisted structures C and D were each trial-produced with composition c1 type.

【table】

[Table] For comparison, the Cu/Zn ratio of the same wire diameter is 7/3.
Brass plated crystalline high carbon steel wire currently in use, twisted in the same way as B, C, D, E (Fig. 1),
F (Fig. 4) and G (Fig. 3). Among the above, the thermal stability of the amorphous alloy steel cord was measured. The above nine types of twisted cords were applied to the belt layer of a TBR1000-R20 steel radial tire, and a tire prototype was made. As the coating rubber composition, composition No. 1 shown in Table 5 of Reference Examples below was used. In addition to measuring the initial strength of the steel cords of these new tires, we also evaluated their strength retention and adhesion after driving on public roads for 100,000 km. The outermost cord of the belt was sampled both when it was new and after it had been driven. In addition, the above 9 types of twisted cords can be used for TBR1000-
We applied this to the carcass ply layer of a steel radial tire called R20 and made a tire prototype. Similarly, the initial strength of the steel cord of a new tire was measured, and the strength retention rate, fatigue strength retention rate, and adhesion were evaluated after driving on general roads for 100,000 km. The results are shown in Table 3.

[Table] Example 2 Alloy base materials having the three composition numbers a, c, and g shown in Table 1 were melted in the same manner as in Example 1, and rapidly cooled to form a wire with a round cross section and a wire diameter of 0.160. mm and wire diameter 0.120
Two types of amorphous alloy filaments of mm were obtained. From this filament, (3+9)×0.160 shown in Figure 2
We prototyped a steel cord with a +1×0.120 layer twist structure. As the coating rubber composition, composition No. 1 shown in Table 5 of the following reference examples was used. For composition number a, an amorphous alloy filament is applied only to the core, and the sheath (surface filament) and wrapping wire are made of currently used crystalline high carbon steel wire that is brass-plated with a Cu/Zn ratio of 7/3. did.
Thermal stability was measured for the amorphous alloy steel cord. For composition numbers c and g, amorphous alloy filaments were used for all filaments. For comparison, a steel cord made of currently used crystalline high carbon steel wire with the same twist structure and a Cu/Zn ratio of 7/3 was also prepared and designated as sample No. 13. The above four types of twisted cords were applied to the belt layer of a steel radial tire for passenger cars of size 165SR13, and a tire was prototyped. In addition to measuring the initial strength of the steel cord of a new tire, we also evaluated the strength retention rate, fatigue strength retention rate, and adhesion after driving on public roads for 50,000 km. The results obtained are shown in Table 4.

[Table] By using the steel cord made of the amorphous alloy of the present invention according to Examples 1 and 2, the strength loss of the steel cord due to corrosion is significantly improved compared to the brass-plated crystalline steel cord, and the adhesiveness is also at the same level. It is understood that this will significantly improve tire durability. Reference Example The amorphous alloy steel cord of Sample No. 1 (composition number C, twist structure number B) of Example 1 was embedded in various coating rubber compositions shown in Table 5 and heated at 145°C x 60°C.
After partial pressure vulcanization, one side of the rubber layer was polished until the cord surface was exposed, and a peel test was conducted according to JIS-K-6301 to calculate the adhesive strength per cord. As for heat aging conditions, the sample was left at 120° C. for 50 hours with the gear open before polishing. The results are shown in Table 5. It is understood that when the organic carboxylic acid metal salt is 1 to 5 parts by weight and the sulfur is 2 to 7 parts by weight, initial adhesive strength, adhesive strength after heat aging, and retention of adhesive strength after heat aging are all improved. .

[Table] Diamine

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views of an example of a layer-twisted steel cord used in the present invention, FIG. 3 is a cross-sectional view of an example of bundle-twisted steel cord used in the present invention, and FIGS. 4 and 5. and FIG. 6 are cross-sectional views of a double-stranded steel cord used in the present invention. 1...Core filament, 2...First sheath filament, 3...Second sheath filament, 4
...wrapping wire.

Claims (1)

[Claims] 1 Ni and/or Co: 1 to 20 at%, Si: 5 at% or more and B: 20 at% or less, and (Si+B): 10 to 30 at%, with the remainder being substantially Fe. A pneumatic tire characterized in that a steel cord having a filament made of an amorphous alloy applied to at least the inner layer side is applied to at least one of a belt and a carcass ply material of the pneumatic tire. 2. A pneumatic tire according to claim 1, wherein a steel cord in which the amorphous alloy is applied to all filaments is applied to at least one of a belt and a carcass ply material of the pneumatic tire.