JP2008297667A - Steel cord, method for producing same and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel card that improves handleability and rubber adhesiveness while controlling core removal without formation of a core filament and improving rubber penetrability into the inside of the cord. <P>SOLUTION: The steel cord S1 or S2 of 1+5 structure or 1+6 structure is obtained by twisting five or six sheath filaments 2 around one unformed core filament 1. At least a part of the core filament 1 is coated with a vulcanized rubber 3, twisted sheath filaments 2 are bonded through the vulcanized rubber 3 to the coated core filament 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a steel cord, a method for manufacturing the same, and a pneumatic tire using the steel cord. More specifically, the present invention relates to a steel cord and a pneumatic tire using the same. The present invention relates to a steel cord capable of improving adhesion to rubber, a method for producing the same, and a pneumatic tire using the steel cord.

  For example, steel cords are used for reinforcing layers such as a pneumatic tire for passenger cars and a belt layer of a heavy duty pneumatic tire used for trucks, buses, and the like. Among such steel cords, there are steel cords of 1 + 5 structure or 1 + 6 structure in which five or six sheath filaments are twisted around one core filament. Steel cords of this structure generally have poor rubber penetration into the interior, and so-called core dislodgement, in which the core filament of the core partially jumps out during cutting and traveling of the steel cord, is likely to occur.

  Therefore, the core filament is shaped into a wave shape to prevent the core from coming off and improve the rubber penetration into the inside. However, when the core filament is brazed in this way, the initial elongation increases, so the belt In a tire using such a steel cord as a layer, the growth of the tire outer diameter during high-speed running cannot be effectively suppressed.

  Conventionally, the present applicant has proposed a steel cord in which a core filament is coated with an unvulcanized rubber as an improved technology of the steel cord (see, for example, Patent Document 1). When this technology is applied to a 1 + 5 structure or 1 + 6 structure steel cord, the core filament can be suppressed without brazing and the rubber penetration into the inside can be improved, and the elongation of the steel cord is small. There is an advantage that the growth of the tire outer diameter during traveling can be effectively suppressed.

However, there was room for further improvement such as unvulcanized rubber oozing out on the surface of the steel cord during the work, difficulty in handling such as stickiness, and decreased adhesion to rubber.
JP 2002-363875 A

  An object of the present invention is to provide a steel cord capable of improving handling properties and adhesion to rubber while suppressing core removal without brazing the core filament and improving rubber penetration into the inside, and its production It is to provide a method and a pneumatic tire.

  The steel cord of the present invention that achieves the above object is a steel cord of 1 + 5 structure or 1 + 6 structure in which 5 or 6 sheath filaments are twisted around one unbrazed core filament, A portion is covered with vulcanized rubber and bonded and bonded, and the sheath filament is bonded and bonded to the core filament through the vulcanized rubber.

  The method for producing a steel cord according to the present invention is a method for producing the above-described steel cord, wherein at least a part of one unbrazed core filament is coated with unvulcanized rubber, and the core filament coated with the rubber is used. It is characterized in that five or six sheath filaments are twisted around each other, a cord obtained by twisting the sheath filaments is wound on a reel, and then heated to vulcanize the unvulcanized rubber.

  The pneumatic tire of the present invention is characterized by having a reinforcing layer in which the above-described steel cords are arranged.

  According to the above-described steel cord of the present invention, since the core filament and the sheath filament are bonded via the vulcanized rubber, the core filament is partially ejected when the steel cord is cut or run. While this can be prevented, vulcanized rubber is already present inside the core filament and sheath filament, which can improve the problem of rubber penetration into the interior that occurs when manufacturing rubber products with this steel cord. it can.

  In addition, since vulcanized rubber is interposed between the core filament and the sheath filament, there is no problem that unvulcanized rubber oozes out on the surface of the steel cord during handling of the steel cord, and handling properties are improved. be able to.

  Furthermore, the surface of the core filament and the sheath filament is usually plated to ensure adhesion with rubber. If unvulcanized rubber is interposed between the core filament and the sheath filament, the unvulcanized rubber will be removed. The plating is gradually damaged by the influence of the accelerator in the rubber and the initial adhesion and further the water-resistant adhesion are lowered. However, since the present invention is a vulcanized rubber, such problems can be avoided and good adhesion to the rubber can be maintained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of the steel cord of the present invention. This steel cord S1 has a 1 + 5 structure including one core filament (non-brazed core filament) 1 that is not brazed and five sheath filaments 2 arranged around the core filament 1. Yes.

  The entire outer peripheral surface of the core filament 1 is covered with a vulcanized rubber 3, and five sheath filaments 2 are twisted around the core filament 1 covered with the vulcanized rubber 3. The vulcanized rubber 3 is vulcanized and bonded to the core filament 1 and the five sheath filaments 2 through a heating process (vulcanization process) described later, and the five sheath filaments 2 twisted together are vulcanized. The core filament 1 is adhesively bonded via the vulcanized rubber 3.

  FIG. 2 shows another embodiment of the steel cord of the present invention. This steel cord S2 is obtained by arranging six sheath filaments 2 in the steel cord S1 described above. That is, the steel cord S2 of FIG. 2 includes 1 + 6 including one core filament (non-brazed core filament) 1 that is not brazed and six sheath filaments 2 arranged around the core filament 1. It has a structure.

  The entire outer peripheral surface of the core filament 1 is covered with a vulcanized rubber 3, and six sheath filaments 2 are twisted around the core filament 1 covered with the vulcanized rubber 3. The vulcanized rubber 3 is vulcanized and bonded to the core filament 1 and the six sheath filaments 2 through a heating process (vulcanization process) described later, and the six sheath filaments 2 twisted together are vulcanized. The core filament 1 is adhesively bonded via the vulcanized rubber 3.

  Hereinafter, a method of manufacturing the steel cord S1 shown in FIG. 1 will be described with reference to FIGS. 3 and 4, 11 is a covering portion for extruding unvulcanized rubber to cover the core filament 1, 12 is a twisting portion for twisting the sheath filament 2, and 14 is a cord twisting the sheath filament 2. A winding unit for winding 4 around the reel 15, and a heating unit for heating the cord 4.

  First, one long core filament 1 that is not wound is wound around a reel (not shown), is continuously pulled out, transported in the direction indicated by the arrow, and supplied to the covering unit 11. The entire outer peripheral surface of the core filament 1 is covered with unvulcanized rubber while passing through the covering portion 11. The core filament 1 </ b> A covered with the unvulcanized rubber 3 ′ is then supplied to the twisting unit 12.

  On the other hand, five sheath filaments 2 drawn continuously from a reel (not shown) are also supplied to the twisting section 12, where they are spirally wound around the core filament 1A covered with the unvulcanized rubber 3 '. Combined. The cord 4 obtained by twisting the sheath filament 2 is conveyed and continuously wound around the reel 15 of the winding unit 14.

  Here, the cord 4 is wound on the reel 15 for the following reason. That is, the cord 4 is heated in the next step, but the surface of the cord 4 is oxidized by the heating and an oxide is generated on the surface, which causes a decrease in adhesiveness. By winding the cord 4 on the reel 15 in this way, the inside of the reel 15 is difficult to transmit air, and the amount of oxide generated on the surface of the cord 4 can be suppressed.

  When the winding on the reel 15 is completed, the cord 4 wound on the reel 15 of the winding unit 14 is accommodated in the heating unit 16 and the cord 4 is heated as shown in FIG. Thereby, the unvulcanized rubber 3 ′ covering the core filament 1 is vulcanized, and a long steel cord S 1 in which the core filament 1 and the five sheath filaments 2 are vulcanized and bonded via the vulcanized rubber 3 is obtained. . The heating of the cord 4 is preferably performed in a nitrogen atmosphere in order to further suppress oxidation of the steel cord surface.

  The steel cord S2 shown in FIG. 2 can be manufactured in the same manner as described above except that the six sheath filaments 2 are supplied to the twisted portion 12 instead of the five sheath filaments 2 described above.

  FIG. 5 shows an example of a pneumatic tire using the steel cords S1 and S2 described above. In FIG. 5, 21 is a tread portion, 22 is a sidewall portion, 23 is a bead portion, and TE is a tire equatorial plane. In this pneumatic tire, a carcass layer 24 is extended between the left and right bead portions 23, and both end portions of the pneumatic tire are sandwiched between bead cores 25 embedded in the bead portions 23 so that bead fillers 26 are sandwiched from the inner side in the tire axial direction. It is folded back. A plurality of belt layers 27 are provided on the outer peripheral side of the carcass layer 24 of the tread portion 21.

  The belt layer 27 is configured by embedding steel cords (not shown) inclined with respect to the tire circumferential direction in a rubber layer, and the steel cord S1 or S2 described above is used for the steel cord of the belt layer 27. . The steel cords S1 and S2 are not limited to the belt layer 27 that functions as a reinforcing layer of the tire, and can be used for any reinforcing layer that functions to reinforce the tire and in which the steel cords are arranged.

  The pneumatic tire can be manufactured by forming a green tire having a reinforcing layer (belt layer 27 in the example of FIG. 5) in which steel cords S1 or S2 are arranged and vulcanizing it.

  According to the above-described steel cords S1 and S2 of the present invention, since the core filament 1 and the sheath filament 2 are bonded and bonded via the vulcanized rubber, the core filament 1 is cut when the steel cords S1 and S2 are cut or run. It is possible to prevent the occurrence of core loss that partially protrudes. Since the vulcanized rubber already exists between the core filament 1 and the sheath filament 2, the problem of rubber penetration into the interior can be improved.

  Further, since the vulcanized rubber is interposed between the core filament 1 and the sheath filament 2, there is no problem that the unvulcanized rubber oozes out on the surface of the steel cord during the operation, and good handling properties are obtained. be able to.

  Further, the surfaces of the core filament 1 and the sheath filament 2 are generally plated to ensure adhesion with rubber. When an unvulcanized rubber is interposed between the core filament 1 and the sheath filament 2, the plating is gradually damaged by the influence of an accelerator in the unvulcanized rubber and the initial adhesiveness and further the water-resistant adhesiveness are lowered. Although a problem arises, since it is a vulcanized rubber in the present invention, there is no such problem, and good adhesion to rubber can be ensured.

  In the pneumatic tire using the steel cords S1 and S2 for the belt layer 17 described above, even if the tread portion 1 reaches the belt layer 17, it is possible to prevent moisture from penetrating into the steel cord of the belt layer 17. Therefore, the corrosion propagation resistance of the belt layer 17 can be improved.

  In addition, since the core filament 1 is not brazed, the elongation of the steel cords S1 and S2 is reduced, so that the growth of the tire outer diameter during high-speed running can be suppressed. Therefore, the edge separation resistance of the belt layer 17 can be improved.

  The steel cords S1 and S2 described above can be preferably used as a steel cord for a reinforcing layer of a pneumatic tire as described above. However, the present invention is not limited to this, and other rubber products having a reinforcing layer in which steel cords are arranged, for example, Further, it can be suitably used for rubber products to which a dynamic load is applied, such as a conveyor belt and a track belt.

  In the embodiment described above, the steel cords S1 and S2 are configured so that the entire outer peripheral surface of the core filament 1 is covered with vulcanized rubber. However, the entire outer peripheral surface of the core filament 1 is not necessarily vulcanized rubber depending on the use and necessity. It is not necessary to cover the outer peripheral surface of the core filament 1 at least partially, or the outer peripheral surface of the core filament 1 can be intermittently coated with vulcanized rubber in the longitudinal direction. Preferably, the entire outer peripheral surface of the core filament 1 is covered with vulcanized rubber as in the above-described embodiment.

  The production of the steel cord in which at least a part of the outer peripheral surface of the core filament 1 is partially covered with the vulcanized rubber 3 may be performed by covering at least a part of the core filament 1 with the unvulcanized rubber 3 ′. In the case of the long core filament 1 described above, the core filament 1 passing through the covering portion 11 is intermittently covered with unvulcanized rubber 3 'according to the length used in the product, and the use thereof. It suffices that at least a part of the length to be formed is covered with the unvulcanized rubber 3 ′.

  In the present invention, the steel cords S1 and S2 are limited to the 1 + 5 structure and the 1 + 6 structure. However, the core sheath problem 2 does not occur when the number of the sheath filaments 2 is four, and the shape is unstable when the number is seven. This is because it is not suitable for rubber products such as tires to which dynamic loads are applied.

  Inventive steel cords 1 to 3 (Examples 1 to 3) and comparative steel cords (Comparative Examples 1 and 2) having configurations shown in Table 1 were produced. Each steel cord is a cord in which the core filament is not brazed.

  When each of these test cords was subjected to an evaluation test of anti-corrosion resistance, initial adhesiveness and handling property by the method shown below, the results shown in Table 1 were obtained.

Core removal resistance The core portion of each test cord having a length of 50 mm was pulled out with pliers, and the ease of pulling out was evaluated in four stages: ◎, ○, Δ, and ×. ◎ indicates that the core filament is not pulled out and has very good anti-coring property, ○ indicates that the core filament is slightly pulled out but has good anti-coring property, and △ indicates that the core filament is pulled out relatively easily, and the anti-coring property X means that the core filament can be pulled out easily and the anti-corrosion resistance is very poor.

Initial Adhesiveness The prepared steel cord was allowed to stand for 30 days under conditions of a temperature of 35 ° C. and a humidity of 65%, and then an embedded test piece for a rubber adhesion test was produced according to JIS G3510, and an adhesion test was performed. The results were evaluated in four stages, ◎, ○, Δ, and ×. ◎ means very good adhesion, ○ means good adhesion, Δ means slightly poor adhesion, and × means that adhesion is greatly inferior.

Handling property Handling property was evaluated in two stages of ○ and × from the ease of handling of each test code. ○ means that there are no problems and X means that the test code is sticky and the codes are in close contact with each other.

  From Table 1, it can be seen that the steel cord of the present invention has good anti-coring properties, initial adhesiveness and handling properties.

  The tire size is 295 / 75R22.5, the tire structure is the same as in FIG. 5, and the steel cords 1 to 3 (Examples 1 to 3) of the first embodiment and the comparative steel cords 1 and 2 (Comparative Examples 1 and 2) ) Were used for the belt layer, respectively. In the test tire 5, the test tire 6 in which the core filament was brazed into a corrugated shape was produced.

  Each of these test tires was mounted on a standard rim, and the following methods were used to evaluate the tire outer diameter growth, the edge separation resistance of the belt layer, and the corrosion propagation resistance of the steel cord used for the belt layer. The results shown in Table 2 were obtained.

Tire Outer Diameter Growth Each test tire was filled with a specified air pressure, and after running a real vehicle of 50,000 km, the tire outer diameter at the groove bottom was measured, and the amount of growth from a new article was obtained. The results are shown as an index with the test tire 6 as 100. A smaller index value means less outer diameter growth.

Edge separation resistance Each test tire is mounted on a vehicle with a pneumatic pressure of 760 kPa, and after running a real vehicle of 100,000 km, each test tire is disassembled, and the amount of peeling at the edge of the No. 3 belt layer is measured over the entire circumference. The maximum peel amount (mm) was determined. The results are shown as an index with the test tire 6 as 100. The smaller the index value, the better the belt edge separation resistance.

Corrosion resistance propagation resistance The surface of a 20 cm steel cord taken out from each test tire is covered with a sealant material, dried, then cut at both ends, and one end of the steel cord is immersed in 20% salt water for 5 days and then taken out from the salt water. The peel length of the core filament and the sheath filament was measured. The results are indicated by an index with the test tire 5 being 100. The larger the index value, the better the corrosion propagation resistance.

  From Table 2, the test tires 1 to 3 using the steel cord of the present invention for the belt layer have good tire outer diameter growth, edge separation resistance of the belt layer, and corrosion propagation resistance of the steel cord. Recognize.

It is an expanded sectional view showing one embodiment of the steel cord of the present invention. It is an expanded sectional view showing other embodiments of the steel cord of the present invention. It is explanatory drawing which shows the manufacturing method of a steel cord. It is explanatory drawing which shows the process of heating. It is a half sectional view showing an example of a pneumatic tire using a steel cord of the present invention for a belt layer.

Explanation of symbols

1 Core filament (non-brazed core filament)
2 sheath filament 3 vulcanized rubber 3 'unvulcanized rubber 4 cord 11 covering portion 12 twisted portion 15 reel 16 heating portion S1, S2 steel cord 27 belt layer (reinforcing layer)

Claims (5)

  In a 1 + 5 structure or 1 + 6 structure steel cord in which 5 or 6 sheath filaments are twisted around one unbrazed core filament, at least a part of the core filament is covered with vulcanized rubber and adhesively bonded. A steel cord obtained by bonding the sheath filament to the core filament through the vulcanized rubber.   The steel cord according to claim 1, wherein the entire outer peripheral surface of the core filament is covered with vulcanized rubber.   The method of manufacturing a steel cord according to claim 1, wherein at least a part of one unbrazed core filament is coated with unvulcanized rubber, and five or six are wound around the rubber-coated core filament. A method of manufacturing a steel cord, in which a sheath filament is twisted and a cord in which the sheath filament is twisted is wound on a reel and then heated to vulcanize the unvulcanized rubber.   The method for producing a steel cord according to claim 3, wherein heating is performed in a nitrogen atmosphere.   A pneumatic tire having a reinforcing layer in which the steel cord according to claim 1 is arranged.

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