JP3469356B2 - Steel cord for reinforcing rubber articles and pneumatic tire using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord for reinforcing rubber articles such as automobile tires and conveyor belts, and a pneumatic tire using the same.

[0002]

2. Description of the Related Art Conventionally, in a rubber product reinforced with a steel cord, there has been a problem that the durability life of the product is shortened due to corrosion of the steel cord filament due to moisture invading the product.

For example, a steel cord used for a belt layer of a tire has a cavity in the steel cord, and when the tire tread is damaged to reach the belt,
Moisture that has entered the belt may be transmitted through the cavities in the steel cord to drastically reduce the corrosion resistance, reduce the adhesive force between the rubber and the steel cord in that portion, and cause a separation phenomenon.

Therefore, in order to prevent such corrosion propagation, a structure of a steel cord has been proposed in which the filament gap of the steel cord is maintained by pressure vulcanization and the rubber sufficiently penetrates into the cord through the gap. (JP-A-60-38208, JP-A-59-179)
No. 0, JP-A-56-131404). However, each of the steel cord structures disclosed in these publications has a problem that the cord strength, the cord weight increase, the cord productivity, the rubber permeability, and the sufficient corrosion propagation resistance cannot be obtained at the same time.

Further, in order to achieve both the above technically repelling characteristics, one core filament is spirally shaped, and 5, 6, 7, and 8 sheath filaments are respectively arranged on the outer periphery of the core filament, so that the rubber penetration property is improved. In order to obtain sufficient corrosion propagation resistance, the molding rate and pitch differ depending on the number of sheaths, and the direction of the helix is regulated to improve productivity, ensure rubber penetration, and maintain a large cord strength. However, a steel cord having improved corrosion propagation resistance has been proposed (JP-A-5-186979). However, since the steel cord has a circular cord cross-section arrangement, an increase in the cord thickness due to the molding of the cord filament is a constraint condition, and the gauge of the cord diameter cannot be reduced and the rubber layer cannot be thinned. There is a problem.

Further, the rubber material surely penetrates between the strands to form a complete composite body, which is repeatedly buckled to cause buckling and does not easily cause fretting wear, thereby improving rigidity and fatigue resistance. A steel cord has also been proposed (Japanese Utility Model Laid-Open No. 6-29993). However, in this steel cord, since the core filament diameter is large, depending on the filament arrangement, a portion that comes into contact with the core is likely to occur, so rubber does not penetrate due to variations in manufacturing, and sufficient corrosion propagation resistance can be obtained. There is a problem in that there is nothing.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a tire for automobiles and a conveyor belt which are excellent in rubber penetration and corrosion resistance in both the spiral direction of the core filament and the twist direction of the sheath in different directions or in the same direction. An object of the present invention is to provide a steel cord for reinforcing a rubber article such as a steel cord and a pneumatic tire using the same.

[0008]

The inventors of the present invention have made earnest studies in view of the above-mentioned problems of the prior art, and as a result, have determined that the core filament has a specific structure and the core filament molding pitch, sheath filament pitch, and cord longitudinal direction. By specifying the relationship between the core filament shape and the sheath circumscribing shape range and their numerical relative relationship in a vertical cross-sectional locus, a steel cord for reinforcing rubber articles that is excellent in rubber penetration and corrosion propagation and air using the same Succeeding in obtaining a filled tire, the present invention has been completed. That is, (1) the steel cord for reinforcing a rubber article of the present invention comprises one core steel filament and n (n = 5 to 8) sheath filaments arranged around the core steel filament. The core filament has a cross-sectional locus drawn by the core filament in the direction perpendicular to the longitudinal direction of the cord in an elliptical shape or a shape close to an ellipse.
The ratio Oc (Oc = a / b) of the major axis a and the minor axis b of the ellipse is in the range of 1.1 ≦ Oc ≦ 2.3, and the amplitude Lc of the molding of the core filament and the strand diameter dc.
The molding ratio Rc (Lc / dc) represented by the following equation is expressed by the following equation with respect to each of the number of sheaths, and in the case of 5 sheath filaments, 0.12 ≦ Rc ≦
1.0, with 6 sheath filaments, 0.15 ≦ Rc ≦
1.2, in the case of 7 sheath filaments, 0.18 ≦ Rc ≦
1.5, in the case of 8 sheath filaments, 0.21 ≦ Rc ≦
1.8, and the pitch Pd of the molding of the core filament is in the range of 3.0 dc / 0.34 ≦ Pd ≦ 8.0 dc / 0.34.

(2) In the above (1), the pitch Ps of the six sheath filaments is within the range of 1.0Pd≤Ps≤8.0Pd with respect to the core filament pitch Pd, and the six sheath filaments are included. The circumscribed shape of the sheath filament in the direction perpendicular to the longitudinal direction of the cord of the filament is an ellipse or a shape close thereto, and the ratio Os (Os = c / d) of the major axis c and the minor axis d of the ellipse is 1. A steel cord for reinforcing a rubber article, which is in the range of 1 ≦ Os ≦ 2.0. (3) The carbon content is 0.80 to 0.85% by weight
The steel cord for reinforcing rubber articles according to (1) or (2). (4) Core filament diameter dc and sheath filament diameter d
The steel cord for reinforcing a rubber article according to any one of the above (1) to (3), wherein s is substantially dc = ds. (5) In a pneumatic tire having a belt layer having a steel cord inside a tread portion, the steel cord is the rubber article reinforcing steel cord according to any one of (1) to (4). A pneumatic tire characterized by the following.

[0010]

In the steel cord for reinforcing rubber articles according to claims 1 to 4 of the present invention, the cross section locus of the core filament in the direction perpendicular to the longitudinal direction of the cord is elliptical or a shape close to the ellipse, and the sheath filament is circumscribed. The shape of the cord is elliptical or close to the ellipse, and the cord itself is a flat cord. It can prevent the cord thickness from increasing due to molding, can be thin gauge, can make the rubber layer thin, and has good rubber permeability. Therefore, the corrosion propagation resistance is improved. Further, in the pneumatic tire according to claim 5 of the present invention, since the steel cord satisfying the above-mentioned rubber permeability and corrosion propagation resistance is used for the belt layer, the durability of the belt layer is significantly improved. (This point will be described in detail in Examples).

The contents of the present invention will be described below. As the steel cord for reinforcing rubber articles of the present invention, for example, as shown in FIGS. 1 (a) and 1 (b), one core steel filament 10 and six core steel filaments 11 arranged around the core steel filament 11 are provided. Sheath filament 11, 11 ...
The core filament 10 has a cross-sectional locus drawn by the filament in the direction perpendicular to the longitudinal direction of the cord, which is an ellipse or a shape close to the ellipse, and the ratio Oc (Oc (Oc) of the major axis a and the minor axis b of the ellipse. = A / b, hereinafter "O
c ”) is in the range of 1.1 ≦ Oc ≦ 2.30, and the molding ratio Rc (Lc represented by the ratio of the molding amplitude Lc of the core filament to the strand diameter dc of the core filament 10). / Dc) is the sheath filament 11,
11 ... 6 are in the range of 0.15 ≦ Rc ≦ 1.2 and the core filament molding pitch Pc is 3.0 dc / 0.34 ≦ Pc ≦ 8.0 dc / 0. A steel cord A for reinforcing rubber articles in the range of 34 is mentioned.

In the present invention, the major axis a and the minor axis b of the ellipse perpendicular to the longitudinal direction of the cord of the core filament 10 are used.
The ratio Oc of the cords is set in the range of 1.1 ≦ Oc ≦ 2.30 and the outer shape of the sheath filament is elliptical or a shape close to the ellipse to flatten the cord itself, thereby preventing an increase in cord thickness due to molding. In addition, the gauge can be made thinner, the rubber layer is made thinner, the permeability of rubber is improved, and the corrosion propagation resistance is improved. When the ratio Oc of the major axis a to the minor axis b of the ellipse is less than 1.1, rubber permeability to the cord and corrosion propagation resistance cannot be obtained, and when Oc exceeds 2.30, it becomes difficult in manufacturing, and thus it is preferable. Absent.

In the present invention, six sheath filaments 11 are provided around the core steel filament 10, but the number of the sheath filaments 11 is not limited to 6, but is 5, 7 or 8. it can. When the number of the sheath filaments 11 is 4 or less, sufficient cord strength cannot be obtained, and when the number of the sheath filaments 11 is 9 or more, workability at the time of manufacturing is deteriorated and
It is not preferable because sufficient rubber permeability and corrosion propagation resistance cannot be obtained.

When the number of the sheath filaments 11 is 6, the shaping ratio Rc (Lc / dc) represented by the ratio of the helical shaping amplitude Lc to the strand diameter dc of the core filament 10 is the sheath. Filament 11, 1
By setting the range of 0.15 ≦ Rc ≦ 1.2 for 6 pieces of 1 ..., it is possible to improve the rubber permeability, improve the cord strength, and improve Workability can be improved. In the present invention, in consideration of rubber permeability, cord strength, and workability during manufacturing, the range of the molding ratio Rc varies depending on the number of sheath filaments 11. When the number of sheath filaments 11 is 5, 0.12 ≦
Rc ≦ 1.0, when the number of the sheath filaments 11 is 0.18 ≦
Rc ≦ 1.5, and when eight sheath filaments 11 are used, 0.21 ≦
It is preferable that Rc ≦ 1.8.

Further, according to the present invention, the pitch Pc of the spiral die forming is 3.0 dc / 0.34≤Pc≤8.0.
It is set in the range of dc / 0.34. The pitch Pc is 3.
When it is less than 0 dc / 0.34, sufficient rubber permeability cannot be obtained, and when the pitch Pc exceeds 8.0 dc / 0.34, sufficient corrosion propagation resistance cannot be obtained, which is not preferable.

When the number of the sheath filaments 11 is 6, the pitch Ps of the 6 sheath filaments is relative to the core filament pitch Pd.
1.0Pd ≦ Ps ≦ 8.0Pd, and 6
The circumscribed shape of the sheath filament in the direction perpendicular to the longitudinal direction of the cord of the sheath filament is an elliptical shape or a shape close to the elliptic shape, and the major axis c and the minor axis d of the ellipse.
It is more preferable that the ratio Os (Os = c / d) is 1.1 ≦ Os ≦ 2.0 (see FIG. 1A). The range of 1.0 Pd ≦ Ps ≦ 8.0 Pd and the above 1.1
By setting the range of ≦ Os ≦ 2.0, workability during manufacturing can be improved, and sufficient rubber permeability and corrosion propagation resistance can be obtained.

It is preferable that the spiral direction of the core filament of the steel cord is the same as the sheath twisting direction, and by making the spiral direction of the core filament the same as the sheath twisting direction, the workability during manufacturing is further improved. Can be improved. In particular, in the case where the spiral direction of the core filament is the same as the sheath twist direction, the pitch Pc of the spiral shaping is 3.0 dc / 0.34 ≦ Pc ≦ 6.6 in order to achieve the object of the present invention. 0 dc /
The range Oc is preferably in the range of 0.34, and the ratio Oc of the major axis a and the minor axis b of the ellipse of the cross section drawn by the spiral is 1.2.
The range of ≦ Oc ≦ 2.0 is preferable.

When the carbon content of the steel cord is 0.80 to 0.85% by weight, the strength of the steel cord can be further secured and the weight can be reduced. Furthermore, by making the core filament diameter dc and the sheath filament diameter ds substantially dc = ds, workability during manufacturing is further improved, and
Sufficient rubber penetration and corrosion propagation resistance can be obtained.

The steel cord for reinforcing a rubber article of the present invention thus constructed is a reinforcing material for a tire such as a carcass of an automobile tire, a belt layer, a bead portion reinforcing layer, or the like.
It is preferably used as a reinforcing material for a conveyor belt.

Further, the pneumatic tire of the present invention uses a steel cord having the above-mentioned rubber permeability and corrosion propagation resistance in the belt layer having the steel cord, and by using this steel cord, the belt layer The durability of can be greatly improved. The belt layers may be, for example, 1 layer, 2 layers, 3 layers, 4 layers depending on the applications such as pneumatic radial tires for passenger cars and pneumatic tires for heavy loads.
The structure can have more than one layer, and the number of steel cords to be driven into the belt layer is appropriately set depending on the application of the pneumatic tire and the like.

[0021]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but it goes without saying that the present invention is not limited to these Examples.

(Examples 1 to 12 and Comparative Examples 1 to 10) As shown in Tables 1 and 2 below, with respect to Examples 1 to 12 and Comparative Examples 1 to 10, the core die attachment ratio Rc and the core helix were obtained, respectively. The pitch Pc, the cord structure, the core wire diameter dc, the core-to-shear surface ellipticity ratio Oc, the sheath wire diameter ds, the sheath twist pitch Ps, the core type spiral direction, the steel cord having the sheath twist direction, and the sheath filament 6 In the case of the book (cord structure 1 + 6), a size of 10,000 R2 further including a belt layer (interlaced belt layer) including a steel cord in which the sheath cross-section ellipticity ratio Os (c / d) is specified.
No. 0 truck and bus radial tires were prototyped, and corrosion resistance (separation resistance) and cord strength of each tire were evaluated. The results are shown in Table 1 below.
It shows in Table 2.

The corrosion propagation resistance (separation resistance) and the cord strength were measured by the following methods. Corrosion Propagation Resistance (Separation Resistance) Corrosion propagation resistance is taken out by taking 100 mm of the belt cord with the rubber covered from the tire, coating the side surface with silicone sealant, and then applying 10% NaOH to one end of the cord.
Immerse the solution in the aqueous solution only from the cut surface, and then pick up the rubber after immersion for 24 hours with pliers and peel it off.
The exposed part of the metal is the corrosion propagation part, and its length (mm)
Evaluated by The smaller the length (mm), the better the corrosion propagation resistance.

Cord strength Measured in accordance with the steel tire cord test method of JIS G3510.

[0025]

[Table 1]

[0026]

[Table 2]

(Consideration of Tables 1 and 2) In Examples 1 to 12 shown in Table 1, the core-forming rate Rc, the core-forming pitch Pc,
The core cross-sectional ellipticity ratio Oc falls within the scope of the present invention.
Seen individually, Examples 1 and 2 have a code structure of 1 + 5.
It is understood that sufficient corrosion propagation resistance is obtained. In Examples 3 to 10, the code structure is 1 + 6, and it can be seen that sufficient corrosion propagation resistance is obtained in this case as well. Further, Examples 9 and 10 are cases in which the molding direction of the core is different from the sheath twisting direction,
In this case as well, it can be seen that sufficient corrosion propagation resistance is obtained. Example 11 has a code structure of 1 + 7, and Example 1
No. 2 has a code structure of 1 + 8, and it can be seen that sufficient corrosion propagation resistance is obtained also in these cases.

On the other hand, Comparative Examples 1 to 1 shown in Table 2
Reference numeral 10 denotes the core type attachment ratio Rc, the core type attachment pitch Pc, the core cross-section ellipticity ratio Oc, and the ellipticity ratio O of the outer tangent to the sheath filament.
Any of s falls outside the scope of the present invention. In Comparative Example 1, the code structure is 1 + 5, the cross-sectional locus drawn by the core mold is circular, and it is understood that the corrosion propagation resistance is inferior at 60 mm when the core mold attaching direction is the same direction as the sheath twisting direction. Comparative Examples 2 to 6 are examples in which the cord structure is 1 + 6, and the core die attaching direction and the sheath twisting direction are the same direction, and it can be seen that the corrosion propagation resistance is significantly inferior to the Examples. In Comparative Examples 2 and 5, the cross sectional locus drawn by the core mold is a circle, and in Comparative Examples 3 and 4, it is an ellipse, but the ratio Os of the major axis c and the minor axis d of the ellipse in the circumscribed shape of the sheath filament is Os. Is a small example, and in Comparative Example 6, the locus of the cross section drawn by the circumscribed shape of the sheath filament is elliptical, but Os is small, and
Since the spiral pitch Pc of the core is as long as 8.0, it can be seen that the corrosion propagation resistance is poor. In Comparative Examples 7 and 8, the cord structures are 1 + 7 and 1 + 8, respectively, and the cross-sectional loci drawn by the core die are circles, and it is understood that the corrosion propagation resistance is 100 mm, which is poor. In Comparative Examples 9 and 10, the code structures are 1 + 7 and 1 + 8, respectively, and the cross-sectional loci drawn by the core mold are elliptical, but it can be seen that when Os is small, the corrosion propagation resistance is inferior.

[0029]

According to the present invention described in claims 1 to 4,
It has good productivity and is very useful as a rubber reinforcing material. Further, it can improve the durability of rubber composites such as tires and conveyor belts, and can greatly improve the service life thereof. A steel cord for reinforcing rubber articles is provided. Particularly, with the steel cord for reinforcing rubber articles according to the second aspect, the durability and the service life can be greatly improved. According to the present invention as set forth in claim 5, the use of the steel cord satisfying the rubber permeability and the corrosion propagation resistance as set forth in any one of claims 1 to 4 in the belt layer makes A pneumatic tire having significantly improved durability is provided.

[Brief description of drawings]

FIG. 1 shows an example of a steel cord for reinforcing a rubber article of the present invention, (a) is a sectional view thereof, and (b) is a side view showing an example of a sheath filament.

[Explanation of symbols]

A Steel cord for reinforcing rubber articles 10 core filament 11 sheath filament

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) D07B 1/06-1/10 B29D 30/38-30/46 B60C 9/00-9/30 B60C 15/00-15 / 06 D07B 1/16

Claims (5)

(57) [Claims] 1. A core steel filament and n core steel filaments arranged around the core steel filament (n
= 5 to 8), the core filament has an elliptical shape or a shape close to an elliptical shape in the cross section locus drawn by the core filament in the direction perpendicular to the longitudinal direction of the cord. And the short axis b ratio O
c (Oc = a / b) is in the range of 1.1 ≦ Oc ≦ 2.3, and the amplitude Lc of the molding of the core filament and the strand diameter dc.
The molding ratio Rc (Lc / dc) represented by the following equation is expressed by the following equation with respect to each of the number of sheaths, and in the case of 5 sheath filaments, 0.12 ≦ Rc ≦
1.0, with 6 sheath filaments, 0.15 ≦ Rc ≦
1.2, in the case of 7 sheath filaments, 0.18 ≦ Rc ≦
1.5, in the case of 8 sheath filaments, 0.21 ≦ Rc ≦
1.8, and the pitch Pd of the molding of the core filament is in the range of 3.0 dc / 0.34 ≦ Pd ≦ 8.0 dc / 0.34, for reinforcing a rubber article. Steel cord. 2. The pitch Ps of six sheath filaments according to claim 1, wherein the pitch Ps of the six sheath filaments is P.
It is in the range of 1.0Pd ≦ Ps ≦ 8.0Pd with respect to d, and the circumscribed shape of the sheath filaments in the direction perpendicular to the cord longitudinal direction of the six sheath filaments is an ellipse or a shape close thereto. A steel cord for reinforcing rubber articles, characterized in that the ratio Os (Os = c / d) of the major axis c and the minor axis d of the ellipse is in the range of 1.1 ≦ Os ≦ 2.0. 3. Carbon content of 0.80 to 0.85% by weight
The steel cord for reinforcing rubber articles according to claim 1 or 2. 4. The core filament diameter dc and the sheath filament diameter ds are substantially dc = ds.
The steel cord for reinforcing a rubber article according to any one of 3 above. 5. A pneumatic tire provided with a belt layer having a steel cord inside a tread portion, wherein the steel cord is the steel cord for reinforcing rubber articles according to any one of claims 1 to 4. Pneumatic tire characterized by.