JP2009299219A - Method for producing rubber steel cord composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a rubber-steel cord composite material which prevents deterioration in durability caused by a coating amount of unvulcanized rubber, degradation in fatigue resistance and workability and stably obtains excellent durability and fatigue resistance. <P>SOLUTION: In producing a rubber-steel cord composite material of two-layer twisting structure by coating the circumferences of core made by twisting one or a plurality of filaments with unvulcanized rubber, twisting a plurality of filaments to become a sheath while forming gaps between the filaments, in the cross-section of the cord, when the area of region enclosed by the circumscribed circle of the core and the contour lines of the core is A and the cross-section area of the coating layer of the unvulcanized rubber coating the core is B, the unvulcanized rubber is coated under conditions that the areas A and B satisfy the following formula: A&le;B&le;5A. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a rubber-steel cord composite used for reinforcing a rubber article, and particularly to stably produce a rubber-steel cord composite excellent in fatigue resistance and durability.

  Various properties are required for rubber cords, especially steel cords for reinforcing tires, and particularly for applications in severe usage environments, improvements in durability and fatigue resistance are required.

  Therefore, conventionally, various methods have been proposed to improve the durability and fatigue resistance of the steel cord. For example, it is known to provide a gap between sheath filaments by making the core filament diameter of the cord and the diameter of the sheath filament different as in the case of different diameter cords, or by thinning out the number of sheath filaments.

  That is, by providing a gap between the sheath filaments, the so-called rubber penetration property, in which rubber enters the steel cord through the gap during vulcanization in the tire manufacturing process, is improved. As a result, wear due to the filaments contacting and rubbing is prevented, and corrosion of the steel cord due to moisture entering the inside of the steel cord from the trauma generated in the tire and propagation of corrosion are suppressed, The durability and fatigue resistance of the steel cord are improved.

  However, when the cords are of different diameters or the sheath filaments are thinned out, the arrangement of the sheath filaments tends to be biased when manufacturing the steel cords, and it is difficult to provide a uniform gap between the sheath filaments. If the gaps between the sheath filaments are non-uniform, rubber intrusion into the gaps becomes non-uniform during vulcanization, resulting in deterioration of durability and fatigue resistance.

As a solution to the above problem, Patent Document 1 discloses a technique for manufacturing an elastomer composite steel cord by coating an unvulcanized rubber (elastomer) around a core prior to twisting of a sheath filament at the time of manufacturing a steel cord. Has proposed.
JP 2002-266266 A

  However, in the above technique, if the amount of unvulcanized rubber coated around the core is too small, a region not filled with rubber is formed in the hollow portion between the core filament and the sheath filament. As a result, at the time of vulcanization, the rubber does not sufficiently enter the hollow region, and the infiltration of moisture cannot be avoided, so that the expected durability cannot be obtained.

  On the other hand, when the rubber coating amount is too large, excess rubber protrudes to the outer periphery of the steel cord, and twist distortion occurs during the production of the steel cord, so that the fatigue resistance is lowered. In addition, in the rewind process of subdividing into another spool of a predetermined length for shipping, during the work of unwinding the pre-wound cord, the wound steel cords will be caught by excess rubber, It causes workability deterioration.

In addition, in Patent Document 2, after forming a core by twisting a plurality of strands, the core is coated with unvulcanized rubber in advance, and a rubber coating layer is formed around the core, A steel cord has been proposed in which anti-wear particles are attached to the outer periphery of a rubber coating layer.
JP 2004-190199 A

  However, the steel cord proposed in Patent Document 2 is the same as in Patent Document 1, when the hollow region between the core filament and the sheath filament is not filled with unvulcanized rubber, or when excess rubber protrudes from the outer periphery of the steel cord. was there. Further, since the anti-adhesion particles are attached to the outer periphery of the rubber coating layer, there is a problem that the anti-adhesion particles adversely affect the adhesion between the steel cord and the rubber in the vulcanization process of tire manufacture.

  The present invention solves the above-mentioned problems, and prevents the deterioration of durability due to the coating amount of the unvulcanized rubber, the fatigue resistance, the deterioration of workability, and the excellent durability and fatigue resistance. It is an object of the present invention to provide an advantageous method for producing a steel cord capable of stably obtaining the steel cord.

  The inventor has intensively studied to solve the above problems. As a result, when coating unvulcanized rubber around the core during the manufacture of steel cords, strictly adjusting the amount of rubber coverage advantageously contributes to a stable improvement in durability and fatigue resistance. As a result, the present invention has been completed.

That is, the gist configuration of the present invention is as follows.
(1) After coating the core of untwisted one or more filaments with unvulcanized rubber, twist the two or more filaments that form the sheath with a gap between each filament and twist the two layers In manufacturing the steel cord having the structure, in the cross section of the cord, the area of the region surrounded by the circumscribed circle of the core and the outline of the core is A, and the cross-sectional area of the unvulcanized rubber coating layer coated on the core is B. When A and B are the following formulas A ≦ B ≦ 5A
A method for producing a rubber-steel cord composite, characterized in that unvulcanized rubber is coated under conditions satisfying In addition, the filament which comprises a core by twisting here is what is called a core filament, and the filament used as a sheath is what is called a sheath filament.

(2) The method for producing a rubber-steel cord composite according to (1), wherein the means for forming a gap between the plurality of filaments serving as the sheath adjusts the number of sheath filaments.

  In accordance with the present invention, the amount of unvulcanized rubber coated around the core is strictly adjusted to suppress the occurrence of twist turbulence and the penetration of moisture into the steel cord during the production of the rubber-steel cord composite. As a result, a rubber-steel cord composite excellent in durability and fatigue resistance can be stably obtained.

Hereinafter, the manufacturing method of the rubber-steel cord composite of the present invention will be specifically described with reference to the drawings. FIG. 1 shows a production facility for a rubber-steel cord composite suitable for use in the practice of the present invention.
In the figure, reference numeral 1 denotes a core of a cord, and the core 1 may be a core composed of a single filament or a core obtained by twisting a plurality of filaments in advance. Reference numeral 2 denotes a sheath filament, and a plurality of the sheath filaments 2 constitute a sheath of a rubber-steel cord composite. 3 is an unwinding device for the core 1, 4 is an unwinding device for the sheath filament 2, and 5 is an unvulcanized rubber coating device. The unvulcanized rubber coating device 5 allows the core to be 1 is coated with an unvulcanized rubber 6. 7 is a wire concentrator for converging the core 1 and the sheath filament 2, and 8 is a stranded wire machine for twisting the core 1 and the sheath filament 2 coated with the unvulcanized rubber 6. A combined rubber-steel cord composite is shown.

  In the apparatus shown in FIG. 1, the core 1 is first guided to the wire concentrator 7, and the unvulcanized rubber 6 is coated around the core 1 by the unvulcanized rubber coating apparatus 5 in the middle. A plurality of sheath filaments 2 unwound from the unwinding device 4 are supplied to the wire concentrator 7, and the sheath filaments 2 are in close contact with each other around the core 1 covered with the unvulcanized rubber 6 described above. Focus so as not to. Next, the obtained bundled body is twisted with a twisting machine 8 to obtain a rubber-steel cord composite 9 having a two-layer twist structure as shown in FIG.

Now, in the present invention, it is important to strictly adjust the coating amount of the unvulcanized rubber to be coated within the appropriate range for the rubber-steel cord composite described above. That is, in the cross section of the core shown in FIG. 3A, the area of the area surrounded by the circumcircle of the core (indicated by the phantom line in the figure) and the outline of the core (indicated by the bold line in the figure) is A, Also, in the cross section of the core and the unvulcanized rubber coating layer shown in FIG. 3B, the cross sectional area of the unvulcanized rubber coating layer coated on the core (the region indicated by the horizontal line in the figure) is B. For these A and B, the following formula A ≦ B ≦ 5A
It is important to satisfy this relationship. More preferably, the range is A ≦ B ≦ 4A.

  That is, when the area B is less than the area A (B <A), the amount of unvulcanized rubber present in the hollow portion between the core filament and the sheath cannot be said to be sufficient, so that even by rubber penetration during subsequent vulcanization Since the hollow portion does not completely disappear and the infiltration of moisture is inevitable, the expected durability cannot be obtained. On the other hand, when the area B exceeds the area 5A (B> 5A), excess rubber that cannot be accommodated in the hollow region between the core filament and the sheath protrudes in large quantities from the outer peripheral surface of the cord, and thus twisting disturbance occurs when the cord is twisted, As a result, fatigue resistance decreases. In addition, in the calendar process of manufacturing the rubber sheet, the wound cords are attracted by the excess rubber during the work of arranging the cords that have been wound in advance in parallel, which leads to deterioration in workability.

  On the other hand, if the coating amount of the unvulcanized rubber is adjusted to the range of A ≦ B ≦ 5A that satisfies the requirements of the present invention, the hollow region of the cord can be filled with the unvulcanized rubber. Durability can be obtained stably. In addition, since the twisting disturbance that occurs during twisting of the cords can be avoided, the expected fatigue resistance can be stably obtained, and in addition, the wound cords can be caught by excess rubber. Therefore, deterioration of workability can be prevented.

Next, a means for forming a gap between a plurality of filaments serving as a sheath is not particularly limited, but a method of adjusting the number of sheath filaments is advantageous from the viewpoint of simplicity.
Here, the gap between the sheath filaments is preferably about 0.03 to 0.11 mm.

  The optimum relationship between the area B and the area A varies depending on the outer diameter of the cord, the interval between the sheath filaments, etc. However, it is important to keep the amount of excess rubber protruding to a small amount and satisfy this requirement. Thus, it is important to determine an appropriate relationship between the area B and the area A in the range of A ≦ B ≦ 5A.

A rubber-steel cord composite having a structure of 3 × 8 × 0.22 mm was produced using the production equipment shown in FIG. At that time, as shown in Table 1, the coating amount of the unvulcanized rubber, the coating amount of the unvulcanized rubber, which is changed in various ways, is represented by the area B shown in FIG. The area B is indicated by a relative ratio with the area A.
The durability of the tire comprising the rubber-steel cord composite thus obtained and the fatigue resistance and workability of the rubber-steel cord composite were investigated. The results are also shown in Table 1.

  The durability of the tires was determined by making a plurality of tires of size 11R22.5 using a plurality of types of rubber-steel cord composites shown in Table 1, and making each tire into a rim of size 8.25 × 22.5. It evaluated by using the tire wheel which attached. Specifically, a high internal pressure / high load load (internal pressure: 900 kPa (relative pressure) and load load: 58.8 kPa) is applied to each tire wheel, running on a drum tester, and the bead part breaks down. The time until the occurrence was measured, the result in Conventional Example 1 was expressed as an index with 100, and the others as relative values, and the whole was subjected to relative evaluation. The results are shown in Table 1, and the larger the value, the better the durability of the tire.

  The fatigue resistance of the rubber-steel cord composite was determined by applying A method (Firestone method) of compression / bending fatigue strength test according to JIS L 1017 to a vulcanized rubber sheet with a roller having a radius of curvature of 15 mm. The number of times of bending until the vulcanized rubber sheet broke was measured, and this measurement was evaluated by indexing. In addition, the conventional example 1 is indexed as 100, and the higher the numerical value, the better the fatigue resistance. Here, the vulcanized rubber sheet was produced by vulcanizing under pressure and heating into a rubber sheet in which a plurality of cords were arranged at equal intervals so that the cords were parallel to each other and embedded in the rubber.

  The workability was evaluated based on the following criteria for the degree of cord-to-corrugation due to excess rubber protruding after winding the rubber-steel cord composite. In this evaluation, ◎ (double circle) is the same situation as normal work, ○ (maru) is a situation where there is no problem in workability, although there is some excess rubber surplus, △ (sankaku) Shows a situation where excessive rubber protrudes in a large amount on the outer peripheral surface of the rubber-steel cord composite, and the cords are stuck to each other, thereby hindering workability.

  From the results of Table 1, in Invention Examples 1 to 3, where the coating amount (area B) of the unvulcanized rubber satisfies the range of A ≦ B ≦ 5A, the durability of the tire and the fatigue resistance of the rubber-steel cord composite It can be seen that the workability can be obtained stably and the deterioration of workability can be prevented. In particular, in Comparative Examples 1 and 2 that satisfy A ≦ B ≦ 4A, the durability of the tire and the fatigue resistance of the rubber-steel cord composite were significantly improved. On the other hand, in the conventional example in which the area B of the unvulcanized rubber coating layer is less than the area A and Comparative Example 1, the hollow region of the rubber-steel cord composite could not be sufficiently filled with unvulcanized rubber. A decrease in tire durability was inevitable. On the other hand, in Comparative Example 2 in which the area B exceeds 5 A, a large amount of excess rubber caused twisting of the steel cord, resulting in a decrease in fatigue resistance of the rubber-steel cord composite. In addition, excessive rubber protruded in large amounts on the outer peripheral surface of the rubber-steel cord composite, and the wound cords were attracted to each other, so that workability was inevitably deteriorated.

It is a figure which shows the manufacturing equipment of a rubber-steel cord composite suitable for implementation of this invention. It is a figure which shows the cross section of a code | cord | chord. It is a figure which shows the cross section (b) of the cross section (a) of a core, and a core and an unvulcanized rubber coating layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core 2 Sheath filament 3 Core unwinding device 4 Sheath filament unwinding device 5 Unvulcanized rubber coating device 6 Unvulcanized rubber 7 Wire concentrator 8 Stranding machine 9 Rubber-steel cord composite

Claims (2)

A two-layer twisted rubber structure in which a core obtained by twisting one or a plurality of filaments is coated with unvulcanized rubber, and then a plurality of filaments serving as a sheath are twisted with a gap between the filaments. -In producing the steel cord composite, in the cross section of the cord, the area of the region surrounded by the circumcircle of the core and the outline of the core is A, and the cross-sectional area of the unvulcanized rubber coating layer coated on the core is When B, A and B are represented by the following formulas A ≦ B ≦ 5A
A method for producing a rubber-steel cord composite, characterized in that unvulcanized rubber is coated under conditions satisfying   2. The method for producing a rubber-steel cord composite according to claim 1, wherein the means for forming a gap between the plurality of filaments serving as the sheath is to adjust the number of sheath filaments.

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