JP2007186736A - Method for manufacturing metallic wire, metallic cord for reinforcing rubber product, and vehicle tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a metallic wire, which can sufficiently inhibit the adhesiveness of the metallic wire to a rubber product from deteriorating due to aging in a humid and hot environment without degrading a wire-drawability of the metallic wire; also to provide a metallic cord for reinforcing the rubber product and a vehicle tire. <P>SOLUTION: The method for manufacturing the metallic wire 2 which composes the metallic cord for reinforcing the rubber product comprises the steps of: firstly forming a Cu plating layer 6 and a Zn plating layer 7 on the surface of a metallic base wire 3; and then thermally diffusing the Cu plating layer 6 and the Zn plating layer 7 into each other to form a brass plating layer 4 on the surface of the metallic base wire 3. In the plating step, the Cu plating layer 6 and the Zn plating layer 7 are formed on the surface of the metallic base wire 3 so that a Cu content can be 51 to 61 wt.% of the brass plating layer 4 after having been solidified. Subsequently, an iron phosphate coating film 8 is formed on the surface of the brass plating layer 4 by electrolytically chemical-conversion-treating the brass plating layer 4. Subsequently, the metallic wire 2 having the iron phosphate coating film 8 formed thereon is wire-drawn. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a metal wire obtained by applying a brass plating layer to the surface of a metal element wire, and a metal cord for reinforcing rubber articles formed using the metal wire and a vehicle tire.

  As a reinforcing member for rubber articles such as automobile tires, metal cords having an excellent reinforcing effect have been frequently used. Such metal cords for reinforcing rubber articles generally have a structure in which a plurality of metal wires are twisted together. As a method for producing a metal wire for forming a metal cord for reinforcing rubber articles, for example, a method described in Patent Document 1 is known.

In the one described in Patent Document 1, first, a Cu plating layer and a Zn plating layer are formed on the surface of a steel wire, and thermal diffusion treatment is performed, so that a Cu-Zn alloy layer having a Cu content ratio of 55% or more (brass plating) Layer). Then, the coated steel wire is immersed in a phosphating solution, and a phosphate containing a predetermined amount of phosphorus is adhered to the surface of the coated steel wire. Thereafter, the coated steel wire is drawn.
Japanese Patent Publication No. 7-8917

  In the above prior art, the Cu content ratio of the brass plating layer is set to 55% or more, but this lower limit level is a β phase having a low ductility as a crystal structure. For this reason, when the Cu content ratio of the brass plating layer is about 55%, the wire drawing workability of the coated steel wire is deteriorated. On the other hand, when the Cu content ratio of the brass plating layer is increased, there is a problem that wet heat adhesiveness and aging adhesiveness to rubber articles (hereinafter referred to as wet heat / aging adhesiveness) are lowered.

  In the above prior art, a phosphate containing a predetermined amount of phosphorus is adhered to the surface of the coated steel wire for the purpose of suppressing a decrease in wet heat and aged adhesion to rubber articles. However, when a severe wire drawing process is subsequently performed or when a plurality of coated steel wires are twisted, the brass plating layer may be rubbed or peeled off. In this case, since the amount of phosphorus present on the surface of the coated steel wire becomes non-uniform, the effect of suppressing the deterioration of wet heat and aging adhesiveness is not sufficiently exhibited.

  An object of the present invention is to provide a metal wire manufacturing method and a metal cord for reinforcing a rubber article that can sufficiently suppress a decrease in wet heat and aged adhesiveness of the metal wire to a rubber article without impairing the drawing workability of the metal wire. And providing tires for vehicles.

  The present invention relates to a method for producing a metal wire by applying a brass plating layer made of a Cu-Zn alloy on the surface of a metal strand, and forming a Cu plating layer and a Zn plating layer on the surface of the metal strand. A step of forming a brass plating layer on the surface of the metal wire by thermal diffusion, and a step of forming a phosphate coating on the surface of the brass plating layer by subjecting the brass plating layer to a chemical conversion coating treatment by electrolysis. In the step of forming the brass plating layer, the Cu plating layer and the Zn plating layer are formed on the surface of the metal element wire so that the Cu content ratio of the brass plating layer is 51 to 61 wt%. It is a feature.

  In a metal wire formed by forming a brass plating layer on the surface of a metal element wire, when the Cu content ratio of the brass plating layer is 63 wt% or more, the crystal structure of the brass plating layer is a relatively soft and ductile α phase. Or, since it becomes the (α + β) phase, the wire drawing workability of the metal wire is improved, but there is a problem that the wet heat and aging adhesion of the metal wire to the rubber article is lowered.

  Therefore, in the present invention, the Cu plating layer and the Zn plating layer are formed on the surface of the metal strand so that the Cu content ratio of the brass plating layer is 61 wt% or less, and is thermally diffused. Thereby, the fall of the wet heat and aged adhesiveness of the metal wire with respect to a rubber article can be suppressed.

  However, if the Cu content ratio of the brass plating layer is too low, the β and γ layers are deposited as the crystal structure of the brass plating layer, and the brass plating layer becomes hard and brittle. Sexuality deteriorates. Specifically, when drawing a metal wire, the metal wire is pulled out with a die in a state in which a drawing lubricant is adhered to the surface of the metal wire, but the brass plating layer is hard. If it is brittle, it tends to adversely affect the die, such as damage. As a result, the surface properties of the metal wire after drawing are deteriorated, and in the worst case, the metal wire is broken.

  Therefore, in the present invention, the Cu plating layer and the Zn plating layer are formed on the surface of the metal wire so as to be thermally diffused so that the Cu content ratio of the brass plating layer is 51 wt% or more. Thereby, it is possible to obtain a brass plating layer having a minimum necessary hardness that is currently conceivable for wire drawing of a metal wire using a die. Moreover, after forming a brass plating layer on the surface of the metal wire, a phosphate coating is formed on the surface of the brass plating layer by subjecting the brass plating layer to a chemical conversion coating treatment by electrolysis. In this way, unlike the case where a so-called non-electrolytic conversion film treatment is performed in which a brass plating layer is immersed in a phosphating solution to form a phosphate film, a phosphate film is uniformly formed on the surface of the brass plating layer. Will come to be. Accordingly, when the metal wire is drawn, damage or the like is less likely to occur in the die, so that the drawability of the metal wire can be improved.

  Preferably, in the step of forming the phosphate film, an iron phosphate film is formed on the surface of the brass plating layer. In a material for reinforcing rubber articles that dislikes wire surface residues, wet (liquid) lubricants are frequently used as wire drawing lubricants. Further, zinc phosphate is generally used as the phosphate film, but this zinc phosphate is not compatible with the wet lubricant. For this reason, when a zinc phosphate film is formed on the surface of the brass plating layer, there is a possibility that the wire drawing workability of the metal wire is deteriorated. On the other hand, iron phosphate has an affinity for a wet drawing lubricant, and hardly causes any trouble in the formation of a film. Therefore, it is most preferable to form an iron phosphate film as the phosphate film.

At this time, it is preferable to subject the brass plating layer to a chemical conversion film treatment by electrolysis so that the adhesion amount of the iron phosphate film is 5 to 40 mg / m ² . In this case, since the amount of iron phosphate coating deposited is not too small, an increase in the frictional resistance between the metal wire and the die, which is generated when the metal wire is drawn, can be sufficiently suppressed. This reliably prevents the metal wire from being seized or broken. In addition, since the amount of iron phosphate coating attached is not too large, the iron phosphate coating is unlikely to remain on the surface of the metal wire after wire drawing. Thereby, the fall of the initial adhesiveness of the metal wire with respect to a rubber article can fully be suppressed.

  Moreover, the metal cord for reinforcing rubber articles of the present invention is formed by twisting together using the metal wire manufactured by the above-described metal wire manufacturing method. By adopting the above-described method for producing a metal wire as described above, the wire drawing processability of the metal wire is improved and the decrease in wet heat and aged adhesion of the metal wire to the rubber article is sufficiently suppressed. .

  Furthermore, the vehicle tire of the present invention is characterized in that a rubber material is reinforced by the above-described metal cord for reinforcing rubber articles. Thus, by using the metal cord for reinforcing rubber articles obtained by the above-described metal wire manufacturing method, the metal wire for the rubber article reinforcing metal cord has good wire drawing workability, and the metal for the vehicle tire is used. The wet heat / aging adhesiveness of the wire is sufficiently suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the wet heat and aged adhesiveness of the metal wire with respect to a rubber article can fully be suppressed, without impairing the wire drawing workability of a metal wire. This makes it possible to stabilize the bonding performance between the obtained metal cord for reinforcing a rubber article and a rubber article such as a vehicle tire.

  Hereinafter, preferred embodiments of a metal wire manufacturing method, a metal cord for reinforcing rubber articles, and a vehicle tire according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a vehicle tire provided with an embodiment of a metal cord for reinforcing rubber articles according to the present invention. In the figure, a vehicle tire 30 includes a tire body 31, and the tire body 31 includes a tread portion 33 and a pair of sidewall portions 33 extending inward in the tire radial direction from both ends of the tread portion 32. Yes. A carcass 34 and a two-layer belt portion 35 are embedded in the tire body 31. The carcass 34 is provided from the tread portion 32 to each sidewall portion 33. The belt portion 35 is provided on the outer side in the tire radial direction of the carcass 34 in the tread portion 32.

  As shown in FIG. 2, the belt portion 35 is formed by covering a plurality of rubber article reinforcing metal cords 1 in parallel with a rubber material 36 in a state where a plurality of metal cords 1 for reinforcing rubber articles are arranged in parallel. It will be. The metal cord 1 for reinforcing rubber articles is used as a reinforcing material for the vehicle tire 30. As the rubber material 36, it is desirable to use a material having better adhesiveness than the rubber forming the tire body 31.

  FIG. 3 is a perspective view of the metal cord 1 for reinforcing rubber articles, and FIG. 4 is an enlarged cross-sectional view of the metal cord 1 for reinforcing rubber articles. In each figure, the metal cord 1 for reinforcing rubber articles is formed by twisting three metal wires 2A to 2C in a spiral shape. The metal wires 2 </ b> A to 2 </ b> C have a metal strand 3 made of a steel wire and a brass plating layer 4 made of a Cu—Zn alloy formed on the surface of the metal strand 3.

  As shown in FIGS. 3 and 5, the metal wire 2 </ b> A is formed with bent corrugated portions 5 at a pitch finer than the twist pitch of the metal wire 2 </ b> A. Such a corrugated part 5 is not formed in the metal wires 2B and 2C. By forming the bent corrugated portion 5 in the metal wire 2A, gaps are formed at predetermined intervals between the metal wire 2A and the metal wires 2B and 2C. For this reason, when manufacturing the vehicle tire 30 in which the metal cord 1 for reinforcing rubber articles is built, the degree of rubber penetration into the metal cord 1 for reinforcing rubber articles 1 is increased. Therefore, corrosion of the metal cord for reinforcing rubber articles 1 due to water intrusion from the damaged portion of the vehicle tire 30 can be suppressed.

  Next, a process of manufacturing the metal wires 2A to 2C (hereinafter referred to as the metal wire 2) will be described with reference to FIGS. First, the brass plating layer 4 made of a Cu—Zn alloy is formed on the surface of the metal wire 3 made of a steel wire.

  Specifically, the metal wire 3 is immersed in a copper plating bath, and the Cu plating layer 6 is formed on the surface of the metal wire 3. And the metal strand 3 in which this Cu plating layer 6 was formed is immersed in a zinc plating bath, and the Zn plating layer 7 is formed on the Cu plating layer 6 (process 51 of FIG. 6). As the copper plating bath, for example, a copper pyrophosphate bath or a copper sulfate bath is used, and as the zinc plating bath, for example, a zinc sulfate bath is used.

For example, the formation conditions of the Cu plating layer 6 include a concentration of copper pyrophosphate liquid of 56 to 120 g / liter, a plurality of copper plating bath treatment tanks and more than a zinc plating bath treatment tank, and a treatment current. the density and 2.0~20.0A / dm ^2. The formation conditions of the Zn plating layer 7 include a zinc sulfate solution concentration of 60 to 200 g / liter, a plurality of zinc plating baths, and a processing current density of 3.0 to 30.0 A / dm ^2. And

  Subsequently, by heating the metal wire 3 on which the Cu plating layer 6 and the Zn plating layer 7 are formed at a predetermined temperature (for example, about 520 ° C.), the Cu plating layer 6 and the Zn plating layer 7 are thermally diffused. Then, the brass plating layer 4 is formed on the surface of the metal wire 3, and the brass plating layer 4 is subsequently solidified by water cooling or the like, and then the wire surface oxide is removed by pickling with dilute nitric acid or the like (step 52 in FIG. 6). ).

  In the above steps, the Cu plating layer 6 and the Zn plating layer 7 are formed on the surface of the metal element wire 3 so that the Cu content ratio of the brass plating layer 4 after solidification is 51 to 61 wt%, preferably 51 to 57 wt%. Are formed in order. Here, when the Cu plating layer 6 and the Zn plating layer 7 are thermally diffused, the brass content of the brass plating layer 4 is not uniform as a whole, but a gradient is provided. For this reason, the Cu content ratio of the brass plating layer 4 here is expressed as an average value. Also, the Cu content ratio of the brass plating layer 4 is set so that the adhesion amount of the Cu plating layer 6 and the adhesion amount of the Zn plating layer 7 are within the range of the formation conditions of the Cu plating layer 6 and the Zn plating layer 7 described above. It can be easily done by adjusting.

  In the formation of the brass plating layer 4 by the above thermal diffusion method, first, the Zn plating layer 7 may be formed on the surface of the metal wire 3, and the Cu plating layer 6 may be formed on the Zn plating layer 7. .

Subsequently, an iron phosphate film 8 is formed on the surface of the brass plating layer 4 by subjecting the brass plating layer 4 to a chemical conversion film treatment by electrolysis (step 53 in FIG. 6). Specifically, for example, by using a solution for forming a phosphate film containing a predetermined amount of iron ions, phosphate ions and nitrate ions as an electrolytic solution, and passing a current with the metal wire 3 as a cathode, brass plating is performed. An iron phosphate film 8 is formed on the surface of the layer 4. At this time, for example, the electrolytic solution treatment tank is one or a plurality of tanks, and the treatment current density is 2.5 to 25.0 A / dm ² .

  Subsequently, wire drawing is performed on the metal wire 2 obtained by the chemical conversion film treatment by electrolysis (step 54 in FIG. 6). Specifically, as shown in FIG. 8, the diameter of the metal wire 2 is reduced by drawing the metal wire 2 obtained by the chemical conversion film treatment through a plurality of dies 9 (only one is shown in FIG. 8). Make it thinner. At this time, in order to improve the slidability of the metal wire 2 with respect to the die 9, the wire drawing is performed in a state where the wire drawing lubricant is adhered to the surface of the metal wire 2. As the wire drawing lubricant, a wet (liquid) lubricant is used.

  As described above, the metal wire 2 having a desired diameter having the brass plating layer 4 on the surface is obtained. In addition, since the iron phosphate film 8 formed on the outermost surface of the metal wire 2 is sequentially removed by wire drawing, the iron phosphate film 8 is hardly present on the surface of the metal wire 2 after the wire drawing. Then, the above-described metal cord for reinforcing rubber articles 1 is formed by subjecting a plurality (three in this case) of such metal wires 2 to twisting (step 55 in FIG. 6). ).

  By the way, in the conventional metal cord for reinforcing rubber articles having a metal wire on which a brass plating layer is formed, the Cu content ratio of the brass plating layer is about 63 to 68 wt%. In this case, the crystal structure of the brass plating layer is an α phase or (α + β) phase that is relatively soft and rich in ductility, so that the initial adhesion of the metal cord to the rubber article is improved. The wet heat and aged adhesion of metal cords are reduced. As a countermeasure, in order to suppress the corrosion of Cu, which is a cause of lowering of adhesiveness, Cu is not exposed on the outermost surface of the metal wire by controlling the temperature of thermal diffusion, or the brass plating layer is made of Co, Ni or the like. Although adding a plating third element or attaching a chemical composition to the brass plating layer can be mentioned, none of them has led to fundamental measures. In order to reduce the amount of Cu on the outermost surface of the metal wire, the amount of Cu adhesion before thermal diffusion may be reduced as a whole. However, when the Cu content ratio of the brass plating layer is lower than 63 wt%, brass plating after solidification is performed. The crystal structure of the layer is changed from the (α + β) phase to the β layer, resulting in a hard and brittle brass plating layer, which deteriorates the wire drawing workability of the metal wire.

  Therefore, in the present embodiment, the Cu plating layer 6 and the Zn plating layer 7 are formed on the surface of the metal wire 3 so that the Cu content ratio of the brass plating layer 4 after solidifying by thermal diffusion is 51 to 61 wt%. A predetermined amount of the iron phosphate coating 8 is formed on the surface of the brass plating layer 4 by forming and thermally diffusing it and subjecting the brass plating layer 4 to a chemical conversion coating treatment by electrolysis.

  By setting the Cu content ratio of the brass plating layer 4 to 51 to 61 wt%, the Cu content of the brass plating layer 4 in the metal wire 2 is less than that of the conventional metal cord for reinforcing rubber articles. The resulting corrosion of the brass plating layer 4 is suppressed. Thereby, compared with the conventional metal cord for reinforcing rubber articles, wet heat and aging adhesion of the metal wire 2 to the rubber article can be enhanced. Here, the reason why the lower limit of the Cu content ratio is set to 51 wt% is to ensure the minimum necessary hardness as the brass plating layer 4 when the metal wire 2 is drawn using the die 9.

  Here, when the phosphate film is formed by a non-electrolytic conversion film process, that is, a process in which the metal wire 2 is immersed in a solution for forming a phosphate film, the phosphate film is uniformly attached to the brass plating layer. Is difficult. For this reason, when a metal wire having such a phosphate coating is drawn through a die, the frictional resistance between the metal wire and the die is locally increased, which causes damage to the die. Sometimes. In this case, not only the life of the die is shortened, but also the surface properties of the metal wire after drawing are deteriorated, and in the worst case, the metal wire is disconnected.

  On the other hand, in this embodiment, as a method for forming the iron phosphate film 8 on the surface of the brass plating layer 4, the iron phosphate film 8 is uniformly formed on the surface of the brass plating layer 4 by using a chemical conversion film treatment by an electrolytic method. It can be formed stably. Accordingly, when the metal wire 2 on which such an iron phosphate film 8 is formed is drawn through the die 9, the frictional resistance between the metal wire 2 and the die 9 is reduced. Is reduced and the life of the die 9 is extended. Moreover, since the wire drawing workability of the metal wire 2 is improved, the surface property of the metal wire 2 after the drawing is improved and the disconnection of the metal wire 2 can be prevented.

  The phosphate film formed on the brass plating layer 4 is the iron phosphate film 8 as follows. That is, in the wire drawing of the metal wire 2, a wet wire drawing lubricant is used as described above, but metal ions (Cu, Zn, etc.) contained in the wet wire drawing lubricant are constant. If the amount is exceeded, the wire drawing lubricant will deteriorate. When the phosphate coating is a zinc phosphate coating, Zn contained in the zinc phosphate coating may drop and ionize during wire drawing, which will accelerate the deterioration of the wire drawing lubricant. The wire drawing processability of the wire is impaired. In addition, it is conceivable that the phosphate film is a manganese phosphate film, a cobalt phosphate film, or the like. However, since manganese phosphate, cobalt phosphate, and the like are difficult to be coated, the cost increases to obtain a desired film amount. On the other hand, iron phosphate is effective as a phosphate film to be formed on the brass plating layer 4 because it has good affinity with a wet wire drawing lubricant and hardly interferes with film formation.

At this time, it is preferable to perform the chemical conversion film treatment by an electrolytic method so that the adhesion amount of the iron phosphate film 8 after the chemical conversion film treatment is 5 to 40 mg / m ² . By making the adhesion amount of the iron phosphate film 8 5 mg / m ² or more, when the metal wire 2 is drawn, the frictional resistance between the metal wire 2 and the die 9 increases, It is possible to reliably prevent disconnection. Moreover, since the adhesion amount of the iron phosphate film 8 is 40 mg / m ² or less, the iron phosphate film 8 formed on the surface of the brass plating layer 4 is almost eliminated after the drawing process of the metal wire 2. A decrease in the initial adhesiveness to the rubber article can be suppressed.

  As described above, according to the present embodiment, it is possible to sufficiently suppress a decrease in wet heat and aged adhesion of the metal wire 2 to the rubber article without impairing the wire drawing workability of the metal wire 2. As a result, a decrease in wet heat and aged adhesion of the rubber article reinforcing metal cord 1 to the vehicle tire can be sufficiently suppressed, so that stable adhesion between the vehicle tire 30 and the rubber article reinforcing metal cord 1 is ensured. It becomes possible to do.

  Next, the Example about the manufacturing method of the metal wire which concerns on this invention is described below. Actually, after forming a Cu plating layer and a Zn plating layer on the surface of the metal wire and thermally diffusing them to form a brass plating layer, the wire drawing is performed by a wet wire drawing machine having 20 to 22 dies. Went. As the metal wire, a steel wire equivalent to JIS standard SWRS 82A was used. Moreover, the wire diameter of the metal wire before wire drawing is 1.50 mm, and the wire diameter of the final metal wire after wire drawing is 0.27 mm.

Specifically, a plurality of types of samples as described in Table 1 were manufactured. In Table 1, the samples of Comparative Examples 1 to 4 do not form a phosphate film on the surface of the brass plating layer, and the samples of Comparative Examples 5 and 6 are brass plated using a chemical conversion film treatment by an electrolytic method. A zinc phosphate film is formed on the surface of the layer, and the samples of Examples 1 to 7 are obtained by forming an iron phosphate film on the surface of the brass plating layer by using a chemical conversion film treatment by an electrolytic method. The production conditions for each sample are as shown in Table 1. In addition, in the chemical conversion film treatment by the electrolytic method, when the current is increased in order to increase the amount of the phosphate film deposited, the resistance increases and the treatment current density increases. Moreover, the phosphate film amount in Table 1 is the film amount before wire drawing.

  For Comparative Examples 1 to 6 and Examples 1 to 7, when the wire drawing speed of the wet wire drawing machine was set to 200 m / min, 400 m / min, 600 m / min, and 800 m / min, the metal wire was drawn. It was confirmed whether or not the metal wire was broken. The results are as shown in Table 1.

  In Comparative Examples 1 and 2, since the Cu content ratio of the brass plating layer is as high as 63% and 66%, respectively, even when the wire drawing is performed at a wire drawing speed of 800 m / min, no disconnection of the metal wire occurs. . Further, in Comparative Examples 4 and 6, the Cu content ratio of the brass plating layer is a little as low as 61%. Therefore, when wire drawing is performed at a wire drawing speed of 800 m / min, the metal wire is disconnected. In Examples 2 to 5 in which the Cu content ratio was the same and the wire drawing was performed at the same wire drawing speed, no disconnection of the metal wire occurred. Moreover, in Comparative Examples 3 and 5, since the Cu content ratio of the brass plating layer is further reduced to 57%, when wire drawing is performed at a wire drawing speed of 400 m / min, disconnection of the metal wire occurs. However, in Example 6 where the Cu content ratio was the same and the wire drawing was performed at the same wire drawing speed, no breakage of the metal wire occurred. Furthermore, in Example 7, even though the Cu content ratio of the brass plating layer was further reduced to 54%, the metal wire was broken even when the wire drawing was performed at a wire drawing speed of 400 m / min. Not.

  From these experimental results, when an iron phosphate film is formed on the surface of the brass plating layer using a chemical film treatment by an electrolytic method, the wire drawing workability of the metal wire is improved and the metal wire is less likely to break. Conceivable.

  Moreover, about Comparative Examples 1-6 and Examples 1-7, the test piece for adhesive evaluation was created, and the test of the wet heat and aged adhesiveness in the metal cord with respect to rubber articles was done using this test piece. .

  Specifically, three metal wires manufactured at a drawing speed of 400 m / min were twisted twice with a twisting and twisting machine to form a metal cord having a structure as shown in FIG. In addition, about the metal wire of the comparative examples 3 and 5, the metal cord was produced using the favorable part of the metal wire until it broke.

  Moreover, the test piece 10 for adhesive evaluation as shown in FIG. 9 was produced as follows. That is, the metal cord 11 produced as described above is cut into about 140 mm, and the metal cord 11 is placed on a rubber sheet 12 having a width of 49 mm without any gap, and another rubber sheet 13 is covered with a sandwich. Then, heat vulcanization was performed under the initial adhesive vulcanization condition of 165 ° C. for 18 minutes to obtain a test piece 10.

  And after leaving this test piece 10 to stand in the oven of the humid heat atmosphere of temperature 80 degreeC and humidity 95% for 1 day (24h), 3 days (72h), 5 days (150h), 7 days (168h), it is not left untreated A peel test of the test piece 10 was performed including (for initial bonding).

  Specifically, a cut 14 is made in each of 5 mm inner portions from both sides of the test piece 10 so that the peeling width W of the test piece 10 is 40 mm, thereby forming a rectangular rubber gripping portion 15. Note that cellophane (registered trademark: not shown) is affixed in advance to a portion corresponding to the rubber gripping portion 15 on the cord / rubber interface of the rubber sheet 13 so as not to be bonded to the metal cord 11. Then, the boundary surface K between the metal cord 11 and the rubber sheet 13 is peeled off at a speed of 100 mm / min in a state where the rubber grip 15 and the one end side portion of the rubber sheet 12 are sandwiched by the tensile testing machine 16. Thus, the adhesion of the metal cord 11 to the test piece 10 which is a rubber article was evaluated.

At this time, the adhesiveness of the peeling surface K of the test piece 10 was evaluated based on the area where the metal cord 11 was covered with rubber. The evaluation criteria are as follows.
5 points: Rubber coverage of metal cord is about 100%
4.5 points: Rubber coverage of metal cord is about 90-99%
4 points: About 80-89% of rubber coverage of metal cord
3.5 points: About 70-79% of rubber coverage of metal cord
3 points: About 60-69% of rubber coverage of metal cord
2.5 points: Rubber coverage of metal cord is about 50-59%
2 points: Rubber coverage of metal cord is about 40-49%
1.5 points: Rubber coverage of metal cord is about 30-39%
1 point: Rubber coverage of metal cord is less than about 30%

  The test results of the adhesion property of the metal cord are as shown in Table 1. In Comparative Examples 1 and 2, since the Cu content ratio of the brass plating layer is as high as 63% and 66%, respectively, the initial adhesiveness is good, but the wet heat and aged adhesiveness are considerably lowered with the passage of time. Yes. Moreover, in Comparative Examples 4 and 6, since the Cu content ratio of the brass plating layer is a little lower 61%, compared with Comparative Examples 1 and 2, a decrease in wet heat and aged adhesiveness is suppressed, In Examples 1 to 5 having the same Cu content ratio, a decrease in wet heat and aged adhesiveness is further suppressed. Moreover, in Comparative Examples 3 and 5, since the Cu content ratio of the brass plating layer is further reduced to 57%, a decrease in wet heat / aging adhesiveness is suppressed as compared with Comparative Examples 4 and 6, In Example 6 in which the Cu content ratio is the same, the decrease in wet heat / aging adhesiveness is further suppressed. Furthermore, in Example 7, since the Cu content ratio of the brass plating layer is sufficiently low as 54%, a decrease in wet heat and aged adhesiveness is suppressed as compared with Examples 1-6.

  From such an experimental result, it is thought that the fall of the wet heat and aged adhesiveness of the metal cord with respect to a rubber article is suppressed by making Cu content ratio of a brass plating layer into 51-61 wt%.

  Here, in the test results shown in Table 1, the lower the Cu content ratio of the brass plating layer, the lower the initial adhesiveness of the metal cord to the rubber article. This is because the compounded rubber sheets 12 and 13 (test piece 10) prepared according to the above were used. Improvement of the initial adhesiveness of the low Cu ratio metal cord can be achieved by adding a vulcanization accelerator to the conventional product.

  By the above examples, the Cu ratio of the brass plating layer after thermal diffusion is set to 51 to 61 wt%, and the brass plating layer is subjected to a chemical conversion film treatment by an electrolytic method, thereby drawing a metal wire. The effect of the present invention was demonstrated that the decrease in wet heat and aged adhesion of the metal wire to the rubber article can be sufficiently suppressed without impairing the properties.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the metal cord 1 for reinforcing rubber articles is embedded in the vehicle tire 30, but the metal cord for reinforcing rubber articles of the present invention is not limited to the vehicle tire, but includes a conveyor belt and a hose. It can also be applied as a reinforcing material for rubber articles such as.

  Moreover, in the said embodiment, although the metal cord 1 for rubber article reinforcement was comprised with three metal wires 2A-2C, as a metal cord for rubber article reinforcement, you may comprise only with one metal wire. Alternatively, a plurality of metal wires may be used.

It is sectional drawing which shows the vehicle tire provided with one Embodiment of the metal cord for rubber article reinforcement which concerns on this invention. It is sectional drawing of the belt part shown in FIG. It is a perspective view of the metal cord for rubber article reinforcement shown in FIG. It is an expanded sectional view of the metal cord for rubber article reinforcement shown in FIG. It is a side view which shows one of the three metal wires shown in FIG. It is a flowchart which shows the procedure which manufactures the metal wire and metal cord which are shown in FIG. It is sectional drawing which shows the process of forming a brass plating layer and an iron phosphate film | membrane in order on the surface of the metal strand shown in FIG. It is sectional drawing which shows the method of wire-drawing the metal wire shown in FIG. It is a figure which shows the test method of wet heat and aged adhesiveness of the metal wire with respect to a rubber article.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Metal cord for rubber article reinforcement, 2, 2A-2C ... Metal wire, 3 ... Metal element wire, 4 ... Brass plating layer, 6 ... Cu plating layer, 7 ... Zn plating layer, 8 ... Iron phosphate film (phosphate) Coating), 30 ... Vehicle tire.

Claims (5)

A method for producing a metal wire, wherein a brass plating layer made of a Cu-Zn alloy is applied to the surface of a metal wire,
Forming the brass plating layer on the surface of the metal strand by forming a Cu plating layer and a Zn plating layer on the surface of the metal strand and thermally diffusing the same;
Forming a phosphate film on the surface of the brass plating layer by subjecting the brass plating layer to a chemical conversion film treatment by electrolysis,
In the step of forming the brass plating layer, the Cu plating layer and the Zn plating layer are formed on the surface of the metal wire so that the Cu content ratio of the brass plating layer is 51 to 61 wt%. A method for producing a metal wire.   2. The method of manufacturing a metal wire according to claim 1, wherein in the step of forming the phosphate film, an iron phosphate film is formed on the surface of the brass plating layer. Wherein as amount of adhering iron phosphate coating is 5 to 40 mg / m ^2, the production method of the metal wire of claim 2, wherein applying a chemical conversion coating treatment by the electrolysis to the brass plating layer.   A metal cord for reinforcing rubber articles, characterized by being formed using a metal wire manufactured by the method for manufacturing a metal wire according to any one of claims 1 to 3.   A vehicle tire comprising a rubber material reinforced with the metal cord for reinforcing rubber articles according to claim 4.

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