JP4646770B2 - Steel cord and automotive tire - Google Patents

Description

  The present invention relates to a steel cord used as an embedded reinforcing material for rubber products such as an automobile tire and an automobile tire using the steel cord.

  In order to prevent the entire vehicle from bouncing when the automobile steps on the bumps on the road, the effect of distorting the surface that contacts the road surface of the tire to absorb unevenness (so-called “envelope effect”) It is necessary to increase the torque so that the entire tire is not distorted. For this reason, a steel cord having a high stretchability (that is, a large elongation until breakage) is used as a steel cord embedded in an outer layer portion of a reinforcing layer (breaker or belt) between a carcass and a tread on the outer periphery of the tire. The so-called “high elongation code”) is used. The high elongation cord (H / E cord) used for such purposes has a total elongation to break (elongation to break) of 4% or more, preferably 5% or more (3% or less for ordinary steel cords). It is required to be.

  In addition, the high elongation cord not only has a high total elongation, but also has a primary elongation that is easy to stretch at low loads, and gradually increases its rigidity as the load increases. Thus, it is necessary that the total elongation at break (elongation to break) is 4% or more, preferably 5% or more. Further, since the cord is embedded in the tire, it is indispensable that the entire surface of the cord is covered with rubber and that the rubber enters the cord without any gap.

  However, conventional steel cords have a high elongation of not less than 4%, preferably not less than 5%, and a suitable primary elongation in the low-load region. However, it is not possible to satisfy all the conditions necessary for the high elongation cord to be used by being embedded in the outer layer portion of the reinforcing layer of an automobile tire, which is excellent in rubber penetration.

  Among the conditions for the high elongation cord, the total elongation of 4% or more, preferably 5% or more can be realized by adopting a steel cord having a multi-layer twist (n × m structure). However, in the multi-layer twist (n × m structure), since the strands are in close contact with each other, a closed gap is formed at the center of the strand, rubber penetration is poor, and the gap at the center of the strand remains as it is during tire molding. End up.

  Further, as a single-layer twisted high elongation cord, a cord having a total elongation of 4% or more and 5% or more is known by making the twist pitch smaller than the conventional one (for example, Patent Documents). 1).

  However, the conventional single layer twisted high elongation cord has a very small twist pitch coefficient (twist pitch / cord diameter) of 5 to 10 (the twist pitch coefficient of a general cord is about 20), and the number of twists is high. Therefore, productivity is poor, and therefore, a large number of stranding machines are required, which not only requires equipment costs but also consumes a large amount of energy.

  In addition, since this conventional single-layer twisted high elongation cord is tightly twisted, the gap through which the rubber can enter is small, and the rubber does not easily enter the center of the cord. The so-called 1 × n (n = 3 to 8) steel cord in which 3 to 8 strands (steel filaments) are twisted into a single layer structure has a straw-shaped space in the longitudinal direction of the cord, In the case of the closed twist in which the strands are closely twisted so as to closely contact each other, the gap at the center of the cord is closed. In this case, for example, when the steel cord becomes a composite with rubber in the tire molding process, if the rubber does not penetrate to the gap in the cord central portion and the cord central portion remains as a hollow portion, Moisture that has entered the inside of the cord penetrates into the hollow space in the center of the cord that has become a hollow part, which penetrates the inside of the cord in the longitudinal direction due to capillary action, and as a result, corrosion proceeds from the inside of the cord, resulting in steel. It may deteriorate the fatigue resistance of the cord and shorten the tire life.

  As a cord that is excellent in rubber penetration by single layer twisting, in order to ensure rubber penetration, a steel cord with an open structure in which strands shaped in a circular spiral are loosely twisted so that the strands do not adhere to each other (so-called “ Open code "). Since this cord has an open structure, high extensibility can be obtained without reducing the twist pitch. However, since open cords are stretched greatly with a small load due to loose twisting, handling workability is very poor, and the cords are removed from the reel in the process of sandwiching the cords in the manufacture of tires with rubber sheets (called calendar process) The cord stretches with a small tension when it is unwound, and the gap between the strands disappears. The cord is sandwiched between the rubber sheets in that state, so the cord and rubber are integrated with heat and pressure in the subsequent vulcanization process. When the processing is performed, the gap between the strands is closed, so that the rubber cannot enter the inside of the cord, and a gap that is not filled with rubber remains in the tire.

  And, as a steel cord having excellent rubber penetration, it has a 1 × n structure composed of n (n = 3 to 8) strands, and at least one strand is a habit due to shaping for twisting. There has also been proposed a steel cord for reinforcing rubber products, which has different small spiral bends and has a substantially oval cross section (see Patent Document 2). However, even in the case of this cord, it is necessary to reduce the twist pitch in order to increase the total elongation, the productivity is poor, a large number of stranding machines are required, the equipment cost is high, and the energy consumption is also large. .

  In addition, by using at least one strand of steel cord consisting of 3 or more strands as a zigzag strand, it is also proposed to form a gap that allows the rubber material to penetrate and improve rubber penetration. (For example, see Patent Document 3). Since this steel cord has many locations where the strands come into contact with each other, unlike the open cord where adjacent strands are separated from each other, the contact portion suppresses the reduction of the gap due to tension, and at the time of low load Elongation is reduced. Moreover, this steel cord can obtain high extensibility by attaching all the strands in a zigzag shape. However, when steel cords (called “zigzag cords”) in which all the strands are attached in a zigzag shape and the total elongation (elongation to break) is to be increased to 5% or more, the zigzag attachment becomes large (pitch and There is a problem that the twist is disturbed and the fatigue resistance is lowered due to the twist disorder. A zigzag wrinkle is a two-dimensional wave type machined with gears and the like, and has a bent portion, but when bending stress is applied (when this cord is used for tire reinforcement, bending stress is always applied due to road surface unevenness. However, there is also a problem that stress is concentrated on the bent portion, thereby reducing fatigue resistance.

JP-A-1-250483 No. 7-30714 JP-A-2-307994

  Therefore, it has high extensibility, has a moderate primary elongation in the low load range, has excellent rubber penetration, and can suppress the equipment cost and production energy consumption, thereby preventing a decrease in productivity. It is an object to provide a steel cord suitable as a high elongation cord to be used by embedding it in an embedded reinforcing material for rubber products, particularly an outer layer of a reinforcing layer of an automobile tire, and an automobile tire using the steel cord.

The steel cord of the present invention is a 1 × n open structure in which n strands (n = 3 to 8) are each formed into a flat spiral shape and twisted to form a gap between the strands in a single layer. The twisted cord has a substantially elliptical cross section, and all the strands have a spiral shape with a smaller wave height and pitch than that of the twisted shape. A steel cord for reinforcing rubber products in which the cross-sectional shape of each of the strands is substantially elliptical, and there are two or more types of spiral-like strands, and the spiral shape of at least one strand habit Unlike spiral habit of other wires, characterized major axis ratio 1.3 to 4.0 der Rukoto diameter to the minor diameter of the cross-sectional shape of the spiral habit of the wires is substantially elliptical And

  Since this steel cord has an open structure and each strand has a spiral-like bend, the elongation is large, and the total elongation until breakage is 4% or more, preferably 5 without breaking the pitch. % High elongation can be obtained. Therefore, productivity does not decrease, it is not necessary to increase the number of stranding machines, and energy consumption does not increase. Further, even if the gap between the strands is reduced in the low load region, a spiral habit remains, and rubber penetration is ensured.

  In addition, since the strands with spiral wrinkles that are three-dimensional wave type have a larger elongation than those with zigzag wrinkles that are two-dimensional wave types, it is necessary to increase the wave height of the wrinkles as in the case of zigzag wrinkles The shape can be stabilized and the twisting disturbance can be reduced. Therefore, a decrease in fatigue resistance due to twisting disturbance can be reduced. In addition, the spiral-shaped habit does not have a bent portion where bending stress is concentrated, and there is little deterioration in fatigue due to concentration of bending stress.

  This steel cord has two or more types of spiral strands of strands, and the spiral elongation of at least one strand is different from the spiral strands of other strands. It can be suppressed from becoming too large, has an appropriate primary elongation in the low load area, and gradually increases the rigidity of rigidity as the load increases. The total elongation at break (elongation to break) Of 4% or more, preferably 5% or more.

  Steel cords that have the same spiral strands and that can achieve a total elongation of 4% or more, preferably 5% or more, have a primary elongation that is too large. The originally necessary reinforcement function cannot be demonstrated. In other words, in this case, when the cord is stretched under a load, the cord first stretches so that the looseness (gap between the strands) is eliminated, and at the same time, the strands of the strands are removed and straightened. , The strand itself stretches, and finally breaks. At that time, if the strands of the strands (wave height, pitch) are the same, each strand stretches the same amount at the same time. (Next elongation) increases. For this reason, this steel cord cannot provide the necessary reinforcing function, and the steering stability and life of the tire are reduced. On the other hand, in the steel cord of the present invention, since the stranding of the strands is different, all the strands are stretched at the initial stage of the low load region, but when it is more than that, the stretched strands have not been stretched yet. It becomes a state in which the strands are mixed, and resistance against elongation is generated. Therefore, the primary elongation can be prevented from becoming excessively large, and it has an appropriate primary elongation portion in the low load region, and gradually increases the rigidity of the elongation as the load increases. The total elongation (elongation to break) can be 4% or more, preferably 5% or more.

  In addition, the steel cord has a substantially cross-sectional shape of the cord and a substantially spiral cross-sectional shape of the strand of wire, so that the short diameter side dimension of the entire cord can be reduced, and the short length of the steel cord can be reduced. By arranging the radial side in the thickness direction of the rubber of the tire, the thickness of the tire can be reduced. Moreover, the rigidity in the tire radial direction is thereby reduced, and the effect of absorbing irregularities when the projection is stepped on during traveling is increased.

  In addition, since the steel cord has a substantially elliptical cross-sectional shape, the frequency with which at least two adjacent strands contact at least one end on the major axis side of the cord increases, and the strands move freely. Therefore, it is possible to prevent the gap between the strands from decreasing due to the external pressure caused by the rubber flow generated when the steel cord is embedded in the rubber and vulcanized, and the rubber can be reliably infiltrated. As a result, fatigue resistance is improved.

  In addition, this steel cord has a substantially elliptical cross-sectional shape and a substantially elliptical cross-sectional shape of the strands of the wire, so that the twisted wire effect is sufficiently exerted and the fatigue resistance is improved. . The extensibility of the cord, that is, the total elongation until breaking, can be increased by increasing the wave height of the spiral-shaped bead of each strand. The cord in which is twisted is an aggregate of spiral strands, and the twisted wire effect is not sufficiently exhibited, and sufficient fatigue resistance cannot be obtained.

  Here, for example, the spiral beak has a substantially elliptical cross-sectional shape with substantially the same minor axis and a different major axis for each type. That is, the wave heights of the spiral-like strands of the strands are set to have substantially the same diameter at the short diameter portion and different diameters at the long diameter portion. Thereby, the strands can be brought into contact with each other at the minor axis portion to exert or hold the twisted wire effect.

In the steel cord of the present invention , the ratio of the major axis to the minor axis of the spiral cross-sectional shape of each strand that is substantially elliptical is 1.3 to 4.0 . If the ratio of the major axis to the minor axis (major axis / minor axis) of the cross-sectional shape of the spiral spiral of the strand is less than 1.3, the total elongation is 4% or more, preferably 5% or more cannot be obtained. On the other hand, when the major axis / minor axis exceeds 4.0, the arrangement of the strands during twisting is disturbed, and twisting and flattening become difficult.

  The automobile tire according to the present invention is characterized in that the steel cord having the above configuration is embedded in rubber as a reinforcing material. This tire has a great effect of absorbing irregularities at the outer periphery of the tire when the automobile steps on the protrusion on the traveling road so that the entire automobile does not bounce. Moreover, the fatigue resistance of the steel cord is high and the tire life is long.

  As described above, according to the present invention, it has a high elongation property, has an appropriate primary elongation portion in a low load region, has excellent rubber penetration, and suppresses equipment costs and production energy consumption. It is possible to provide a steel cord that can prevent a decrease in productivity, and an automobile tire using the steel cord.

  FIG. 1 is a cross-sectional view of a steel cord according to an embodiment of the present invention. In this steel cord, n strands (n = 3 to 8) having a strand diameter of 0.20 to 0.45 mm are each formed into a flat spiral shape so that a gap is formed between the strands in a single layer. In addition to the twisted 1xn (1x5 in the illustrated example) open twisted structure, the cord cross-sectional shape is substantially elliptical, and apart from the habit of shaping for twisting, It has a spiral-like bevel with a smaller wave height and pitch than the bend formed by twisting, and each element wire has two or more types of spiral-like bends, and at least one of the strand-like bends is another strand. Unlike the spiral bevel, the cross-sectional shape of each of these strands is a steel cord having a substantially elliptical shape.

  This steel cord is embedded in an outer layer portion of a reinforcing layer (breaker or belt) between a carcass and a tread as a reinforcing material for an automobile tire, for example.

  FIG. 1 shows an example of a steel cord of this embodiment having a 1 × 5 structure in which five strands 1, 2, 3, 4, and 5 having strand diameters of 0.20 to 0.45 mm are twisted together. A steel cord is schematically shown.

  In the example shown in FIG. 1, all the strands 1, 2, 3, 4, and 5 are different in spiral shape, and there are five types of spiral shape. In FIG. 1, alternate long and short dash lines 11, 12, 13, 14, and 15 indicate spiral cross-sectional shapes of the strands 1, 2, 3, 4, and 5. As shown in the drawing, the spiral bends of the steel wires 1, 2, 3, 4 and 5 of this steel cord have the same minor axis of the substantially elliptical cross-sectional shapes 11, 12, 13, 14, and 15, and the major axis is long. Different for each type.

  The spiral shape of each of the strands 1, 2, 3, 4, 5, which is substantially elliptical, is the ratio of the major axis to the minor axis of the cross-sectional shapes 11, 12, 13, 14, 15 (major axis / minor axis). Is set to 1.3 to 4.0. The ratio of the major axis to the minor axis (major axis / minor axis) of the substantially elliptical cross-sectional shape 10 of the cord is also set to 1.3 to 4.0.

  This steel cord has an open structure, and each of the strands 1, 2, 3, 4 and 5 has a spiral crease. Therefore, the steel cord has a large elongation, and even if the pitch is not reduced, the total elongation until breakage is achieved. High extensibility with a degree of 4% or more, preferably 5% or more can be obtained. Therefore, productivity does not decrease, it is not necessary to increase the number of stranding machines, and energy consumption does not increase. Further, even if the gap between the strands is reduced in the low load region, a spiral habit remains, and rubber penetration is ensured.

  In addition, the strands 1, 2, 3, 4 and 5 with a spiral-like shape that is a three-dimensional wave type can stabilize the shape while ensuring high elongation, and can reduce twist disturbance. It is possible to reduce the decrease in fatigue resistance due to the disturbance of the stress, and there is little decrease in fatigue due to the concentration of bending stress.

  And this steel cord has two or more types of spiral bends of the strands 1, 2, 3, 4 and 5, and the spiral bend of at least one strand is different from the spiral beak of other strands. In particular, it is possible to prevent the primary elongation from becoming excessively large due to the difference in the spiral shape of all the strands 1, 2, 3, 4, and 5, and it is possible to suppress an appropriate 1 in a low load region. It has a next elongation part, and gradually increases the rigidity as the load increases, so that the total elongation at break (elongation to break) is 4% or more, preferably 5% or more. it can. FIG. 2 is a stress-elongation diagram (a) of the steel cord of this embodiment and a stress-elongation diagram (b) of the comparative example. The comparative example is an example of a steel cord in which all spiral wires are the same, and when the total elongation of 4% or more, preferably 5% or more can be obtained, the primary elongation is unnecessarily large. Too much, it can not demonstrate the reinforcement function originally required as a steel cord.

  Further, this steel cord has a short cross-sectional shape 10 because the cross-sectional shape 10 of the cord is substantially elliptical and the cross-sectional shapes 11, 12, 13, 14, and 15 of the strands of the strands are substantially elliptical. A diameter side dimension can be made small and the thickness of a tire can be made thin by arrange | positioning a breadth side in the thickness direction of the rubber | gum of a tire. Moreover, the rigidity in the tire radial direction is thereby reduced, and the effect of absorbing irregularities when the projection is stepped on during traveling is increased.

  In addition, since the cross-sectional shape 10 of the cord is substantially elliptical, the steel cord has an increased frequency of contacting at least two adjacent strands at least at one end on the major axis side of the cord. The movement is restricted, so it is possible to prevent the gap between the strands from decreasing due to the external pressure caused by the rubber flow generated when the steel cord is embedded in rubber and vulcanized, and the rubber can be surely intruded. , Thereby improving fatigue resistance.

  Further, this steel cord has a twisted wire effect because the cross-sectional shape 10 of the cord is substantially elliptical and the cross-sectional shapes 11, 12, 13, 14, and 15 of the strands of the strands are substantially elliptical. It is fully demonstrated and fatigue resistance is improved.

  In addition, the steel cord has a spiral shape of the strands 1, 2, 3, 4, and 5 but has a substantially elliptical cross-sectional shape 1, 2, 3, 4, and 5 with substantially the same short diameter and a long diameter. By changing each one (the wave height is approximately the same diameter in the short diameter portion and different in diameter in the long diameter portion), the strands can be brought into contact with each other at the short diameter portion to exhibit or maintain the twisted wire effect.

  Further, as described above, the steel cord has a long diameter with respect to the short diameter of the spiral cross-sectional shapes 11, 12, 13, 14, 15 of the strands 1, 2, 3, 4, 5 that are substantially elliptical. The ratio (major axis / minor axis) is 1.3 to 4.0. When the major axis / minor axis is less than 1.3, a total elongation of 5% or more cannot be obtained. This is because, when the diameter exceeds 4.0, the arrangement of the strands during twisting is disturbed, making it difficult to perform twisting and flattening.

  This steel cord is embedded in the outer layer of the reinforcing layer (breaker or belt) between the carcass and tread of an automobile tire as a reinforcing material. Absorb and function so that the entire car does not bounce. Moreover, the fatigue resistance of the steel cord is high, and the tire life is improved.

  In the above embodiment, an example of a steel cord having a 1 × 5 structure has been described. However, the present invention is applied to a steel cord having a 1 × 3, 1 × 4, 1 × 6, 1 × 7, or 1 × 8 structure. Can also be applied.

  In the above embodiment, an example of a steel cord in which spirals of all the strands 1, 2, 3, 4, and 5 are different from each other has been described. Spiral habits need not be different. It is only necessary that each strand has two or more types of spiral bends, and the spiral bend of at least one strand is different from the spiral bends of other strands.

  Moreover, in the said embodiment, the short diameter of the spiral cross section 11, 12, 13, 14, 15 of each strand 1, 2, 3, 4, 5 is substantially the same, and the long diameter differs for every kind. However, the major axis of each of the strands 1, 2, 3, 4, 5 has substantially the same major axis and the minor axis is different for each type. Is also possible. Moreover, the wave heights of the spiral-shaped bead of each of the strands 1, 2, 3, 4, and 5 can be substantially the same on the long diameter side and the short diameter side, and the pitch can be different.

  The steel cord of the present invention can also be applied as an embedded reinforcing material for rubber products other than automobile tires.

  Table 1 shows two types of steel cords (“Example 1” and “Example 2”) of the examples of the present invention using the same material strands, and the major axis / minor axis of the spiral spiral of the strands. Samples of Comparative Example 1 ("Comparative Example") and 2 Conventional Examples ("Conventional Example 1" and "Conventional Example 2") with different ratios of the major axis / minor axis of the cord are prepared and after rubber coating The results of comparative tests on the properties of elongation, fatigue resistance, rubber penetration, productivity and processing energy consumption after vulcanization are shown.

  “Example 1” is a steel cord having a 1 × 5 structure according to the present invention in which a strand of 0.30 mm diameter is used and the strands of all the strands are different. / Minor axis) is 0.60 mm / 0.37 mm, 0.65 mm / 0.36 mm, 1.24 mm / 0.37 mm, 0.90 mm / 0.36 mm, 1.37 mm / 0.36 mm, and the twist pitch is 15 mm. The cord diameter (major axis / minor axis) is 1.76 mm / 0.76 mm, and the twist pitch coefficient (twist pitch / cord diameter) is 11.9.

  “Example 2” is a steel cord having a 1 × 8 structure according to the present invention using a 0.30 mm-diameter strand, in which the strands of all the strands are different, and the spiral height of each strand (long diameter) / Minor axis) is 0.68 mm / 0.50 mm, 1.61 mm / 0.49 mm, 0.82 mm / 0.50 mm, 1.28 mm / 0.50 mm, 1.85 mm / 0.51 mm, 1.75 mm / 0.50mm, 0.65mm / 0.49mm, 1.98mm / 0.50mm, twist pitch 18mm, cord diameter (major / minor) 2.52mm / 0.82mm, twist pitch coefficient (twist pitch / cord (Diameter) is 10.8.

  The “comparative example” is a 1 × 5 structure using a strand having a diameter of 0.30 mm and different in the spiral shape of all the strands, and the ratio of the major axis / minor axis of the spiral shape of the strand is different from that of the present invention. Steel cords that are different (some are out of the range of 1.3 to 4.0), and the ratio of the major axis / minor axis of the cord is different (out of the range of 1.3 to 4.0). The wave height (major axis / single axis) of the spiral-shaped habit is 1.42 mm / 0.52 mm, 2.43 mm / 0.52 mm, 1.69 mm / 0.51 mm, 2.13 mm / 0.52 mm, 1.31 mm / 0, respectively. The twist pitch is 15 mm, the cord diameter (major axis / minor axis) is 3.09 mm / 0.76 mm, and the twist pitch coefficient (twist pitch / cord diameter) is 7.8.

  “Conventional example 1” is a conventional single unit having a 1 × 5 structure in which a twist pitch coefficient (twist pitch / cord diameter) is extremely small (twist pitch / cord diameter = 6.4) using a 0.30 mm diameter strand. A layered high elongation cord (see Patent Document 1), the twist pitch is 5.5 mm, the cord diameter is 0.85 mm, and the twist pitch coefficient (twist pitch / cord diameter) is 6.4.

  “Conventional Example 2” is a 4 × 4 multi-layer steel cord using a 0.20 mm diameter strand, the twist pitch (strand twist pitch / cord twist pitch) is 3.5 mm / 7 mm, and the cord diameter Is 1.46 mm and the twist pitch coefficient (twist pitch / cord diameter) is 4.8.

In Table 1, “Rubber coverage” (rubber penetration) indicates that a cord is embedded in rubber under a tensile load of 50 N, vulcanized, then the cord is taken out, the cord is disassembled, and a certain length is observed. The ratio of the length of the traced contact with the rubber material to the observed length is displayed as a percentage, and the “Rotating Bending Life Index” is the bending of the cord into a substantially U shape in the Hunter-type fatigue test. (In this case, the bending shape is set so that a stress of 150 kg / mm ² is applied to the maximum curvature point of the cord), and the total number of rotations until the vicinity of the maximum curvature point breaks is shown. Yes, "Production index per unit time per unit" is an index display where the production efficiency per unit time is "conventional example 1" as 100. "Energy consumption index for stranded wire processing" is unit production Consumption per hit That the ratio of the energy is obtained by exponential display the "conventional example 1" as 100.

  From the results of this comparative test (Table 1), the steel cords of Examples 1 and 2 impair the elongation (total elongation), fatigue resistance (rotational bending life index), and rubber penetration (rubber coverage). Thus, it can be seen that productivity (production index per unit time per twister) can be improved and consumption of processing energy (energy consumption index of stranded wire processing) can be reduced.

It is sectional drawing of the steel cord of 1 * 5 structure of embodiment of this invention. It is the stress-elongation diagram (a) of the steel cord of embodiment of this invention, and the stress-elongation diagram (b) of a comparative example.

Explanation of symbols

1, 2, 3, 4, 5 Strand 10 Cross section of cord 11, 12, 13, 14, 15 Cross section of spiral spiral of strand

Claims (3)

An open strand of 1 × n structure in which n strands (n = 3 to 8) are each formed into a flat spiral shape and twisted so that a gap is formed between the strands in a single layer. Each of the strands has a spiral shape with a wave height and a pitch smaller than that of the shape formed by twisting, in addition to the shape formed by twisting. A steel cord for reinforcing rubber products having a cross-sectional shape of a spiral shape of a wire that is substantially elliptical, and the spiral shape of at least one strand is another strand when there are two or more types of the spiral shape the Unlike spiral habit, steel cord diameter ratio to the minor diameter of the cross-sectional shape of the spiral habit of the wires is substantially elliptical and wherein 1.3 to 4.0 der Rukoto. 2. The steel cord according to claim 1, wherein the spiral beak has a substantially elliptical cross-sectional shape with substantially the same minor axis and a different major axis for each type. An automobile tire characterized in that the steel cord according to claim 1 or 2 is embedded in rubber as a reinforcing material.

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