JPH0417076B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a steel cord used by being embedded in various rubber products to be vulcanized and molded, such as tires and belts for belt conveyors. (Prior art) There are five requirements for this type of steel cord: first, reinforcement, second, corrosion resistance, third, shape retention, fourth, durability, and fifth. This is the bondability with rubber products. As well-known representative examples, the steel cord proposed in JP-A No. 55-136534 and the steel cord proposed in JP-A-59-136534 are
There is a steel cord proposed in Publication No. 1790. The former is constructed with a twisted structure as shown in Figure 7 with a large degree of irregularity in the shape of the cord, and this large degree of shape irregularity can raise the bondability between the cord and the rubber product to a certain level. However, regarding shape retention, there is a problem that it easily loses its shape due to external pressure during vulcanization, which not only has a negative effect on bonding properties, but also causes indentations between the wires when the shape collapses. . Furthermore, regarding durability,
Due to the repeated application of severe external pressure, the wires rub against each other and internal wear progresses quickly, and the formation of indentations between the wires is also significant, causing rapid fatigue and shortening the lifespan of rubber products. It is easily corroded by water and moisture that enters through cracks or pores, and moisture in the air, and there is also a problem that it is inferior in terms of contact resistance. The latter, as shown in Figure 8, consists of several single wires or strands twisted together so that they are located approximately concentrically with a distance between each other to form an open cord. In principle, the wires are arranged so that they do not come into contact with the single wire or strands, and the rubber penetrates between the wires and strands to provide a certain degree of bonding. However, since it is originally an open cord type, each single wire or strand has a degree of freedom, and due to the external pressure during vulcanization, there are parts where the rubber penetrates intensively, parts where it does not, and parts where it does not penetrate at all. There is a problem in that the properties are unbalanced both in the circumferential direction and in the length direction. Due to this degree of freedom, there are problems with shape retention, the occurrence of dents between wires, and durability problems such as shortened life due to rapid progress of internal wear.
There are problems with contact resistance and reinforcing properties due to the occurrence of impressions. In addition, there is a tire cord (Japanese Patent Publication No. 11325/1983) in which the core wire is made of a non-metallic wire with the same tensile strength as the metal wire as a cord with improved reinforcing properties. There is a space between each adjacent metal strand, a space between a metal strand and a non-metal core, and a core space in each metal strand, which is not intended to be eliminated. Because of this structure, it has the same problems as the conventional example described above, that is, it has poor contact resistance and durability. Similarly, with improved reinforcing properties,
A tire cord in which a part of the stranded wires are replaced with glass fiber or polyamide fiber filaments of the same thickness (Japanese Patent Application Laid-open No. 119356/1983)
However, there was no original intention to eliminate the existence of space, and the structure is such that a core space exists between each adjacent line, so as before,
It has the disadvantage of poor contact resistance and durability. Additionally, there is a steel cord (Japanese Patent Application Laid-Open No. 128384/1984) which aims to improve the corrosion resistance, durability, and bondability. This product has a twisted structure in which a core is made of vulcanized rubber that can be bonded to the covering rubber, and a plurality of wires are arranged around the outer periphery of the core.By twisting the core and wires together, The core is pressed and deformed so that it has a twisted cross-sectional structure in which the inner space of the strands and the spaces between the strands are closely spaced. However, in order to eliminate internal voids, the core is pressed and deformed with the strands, so the twisted cross-sectional form of the strands changes due to the resistance when pressing the core, causing the cord to deteriorate. In a twisted cross-sectional configuration in which there are differences in the degree of bonding and tensile strength between the core and the covering rubber at each part in the longitudinal direction, or where the twisted wires are in contact with each other, the core may be attached to the corner portions of adjacent wires. If the core does not fit in completely and gaps remain, there are problems with contact resistance and durability. (Problems to be Solved by the Invention) The present invention solves all of the above-mentioned problems, namely reinforcing properties, anti-corrosion properties, shape retention properties, durability, and bonding properties. Our goal is to complete a steel cord that is superior by ensuring that the gap is filled in and eliminated, regardless of the structure of the steel cord. (Means for Solving the Problems) In order to achieve the above-mentioned problems, the present invention has a steel cord that is embedded in advance in a rubber product to be vulcanized and molded, by filling at least the core space with a core. , formed and bonded with a reinforcing material that has the required tensile strength and heat resistance above the vulcanization temperature, and a binding member made of synthetic fiber or rubbery polymer compound that becomes semi-molten below the vulcanization temperature. The steel cord is constructed by covering or impregnating the material with a reinforcing material, and the bonding material is semi-melted at the vulcanization temperature of the rubber product and is formed into a single wire or an outline shape in the cross section of the core space between the strands. It is characterized by (Function) The reinforcing material of the core filled in the core space reinforces and improves the tensile force of the cord, while the binding material semi-melts during vulcanization of the rubber product.
The core space is used as a mold to form the outer shape of the core space in cross section, filling the core space and penetrating to the outside to maintain the shape of the cord, improve contact resistance, and improve bonding properties. (Example) Steel cord A is a single-layer wire, such as 1×3, 1×4, 1×5, etc., in which three or more single strands 1 are twisted together, and a plurality of strands 2 are twisted together. Multilayer wire e.g. 3+6, 3+9, 7×4
etc., and at least the core space 3 is filled with the core 4. The core 4 consists of a reinforcing material 4a and a bonding material 4b coated or impregnated with the reinforcing material 4a.
a is made of, for example, a metal that does not semi-melt during vulcanization of the rubber product and has the required tensile strength, or a lightweight chemical or synthetic fiber;
The bonding material 4b is made of a synthetic fiber or a rubber-like polymer compound treated or untreated with RFL (resorcinol, formalin, latex) having a semi-melting point lower than the vulcanization temperature of the rubber product. This core 4 is filled in the core space 3 in the form of one or more bundled or stranded wires, and during vulcanization, the binding material 4b semi-melts and completely fills the core space 3, and becomes a single wire or strand. In between, it leaks evenly from the inside to the outside, and fuses and binds with the rubber that invades from the outside to the inside around the cord. In this case, if the bonding material 4b is made of a rubber-like polymer compound, it is useful because it has high fusion strength because it is made of the same material as the rubber product. In addition, when the bonding material 4b is selected from a material whose melting point is lower than the vulcanization temperature, it melts and fills the core space 3 to the smallest detail, and evenly leaks from the inside to the outside between the single wires or strands. It fuses with the rubber around the cord to create an even stronger bond. FIG. 4 shows an embodiment in which the space 5 formed between the core wire portion and the outer wire portion is also filled with the core 4, and the portion filled with the core 4 is not limited to the core space portion 3 only. Further, the core 4 filled in the space 5 may be only the bonding material 4b. FIG. 6 shows an embodiment in which a core 4 is filled in place of the strand-like core shown in FIG. 4, and similarly, the strand-like core shown in FIG. It is also free to carry out filling the core 4. The reinforcing material 4a is made of metal or chemical or synthetic fiber that has a heat resistance of 170 degrees or more, and is selected from the following examples of high tensile strength and low tensile strength according to the application. The fibers include composite fibers of each single fiber or a combination thereof.

[Table] The bonding material 4b is made of polyurethane, polyethylene, etc., which becomes semi-molten at a temperature of 160 degrees or less.
A synthetic resin such as polypropylene or a rubbery polymer compound such as butyl rubber, which is selected depending on the application. In the above-mentioned embodiment, the steel cord A can be reduced in weight at once, especially when the reinforcing material 4a is made of chemical or synthetic fibers with a light specific gravity, excluding metals with a heavy specific gravity. (Effects of the invention) (a) Corrosion resistance The reinforcing material of the core filled in the core space reinforces and improves the tensile force of the cord, while the binding material semi-melts during vulcanization of the rubber product. Since the core space is molded into a mold to have the outer cross-sectional shape of the core space, the core space can be reliably and quickly filled with the connecting member regardless of its cross-sectional configuration. As a result, it is possible to prevent air, moisture, and moisture from entering the core space, that is, the cord, and the corrosion-proofing ability is high. (b) Shape retention Since the connecting member is semi-molten and formed into a similar shape corresponding to the cross-sectional shape of the core space, the twisted cross-sectional configuration of the single wire or strand does not change, and the original twisted cross-sectional configuration is maintained. The cord maintains its shape well, and the degree of bonding between the connecting member and the rubber at each longitudinal section of the cord is constant and stable, and there is no difference in the tensile strength of the cord at each longitudinal section. Each part has balanced tensile strength. C. Durability The binding member is semi-molten and formed into a similar shape corresponding to the cross-sectional shape of the core space, and fills between the single wires or strands, thereby preventing the single wires or strands from rubbing against each other and causing severe damage. The progression of internal wear due to external pressure was significantly slowed down, and the impressions between the wires were reduced, resulting in particularly improved fatigue resistance. (d) Reinforcement property It has excellent contact resistance, shape retention, and durability, and the strength of the cord itself is not impaired, and the cord has the original reinforcing effect. E. Bonding property When the rubber product is vulcanized, the bonding material semi-melts and fills the core space, and also penetrates between the single wires or strands evenly from the inside to the outside, and penetrates from the outside to the inside around this bonding material and the cord. The rubber is fused to each other and has good bonding strength with uniform bonding in both the circumferential direction and the length direction. F. Improving reinforcing properties The reinforcing material fills the core space as part of the core and reinforces the cord with its own tensile force, and depending on the selection of the material, it has a strong reinforcing effect. G As shown below, this is a steel cord that has improved corrosion resistance, shape retention, durability, reinforcing properties, bonding properties, and reinforcing properties all at once. With a single layer such as ×5, the cord diameter can be made smaller than before with the same strength.

[Brief explanation of drawings]

FIG. 1 is a radial cross-sectional view showing an embodiment of the steel cord of the present invention. FIGS. 2 to 6 are radial cross-sectional views showing other embodiments. 7 and 8 show a conventional example, with FIG. 7 being a front view and FIG. 8 being a radial sectional view. In the figure, A is a steel cord, 3 is a core space, and 4 is a steel cord.
is the core, 4a is the reinforcing material, and 4b is the binding material.

Claims (1)

[Scope of Claims] 1. In a steel cord that is embedded in advance in a rubber product to be vulcanized, at least the core space is filled with a core, and the core is heated to a temperature above the above-mentioned vulcanization temperature with a required tensile strength. It is made of a reinforcing material that has a heat resistance of A steel cord characterized in that it is semi-molten depending on the vulcanization temperature of the product and is formed into a single wire or a cross-sectional outline shape of the core space between the strands. 2. The steel cord according to claim 1, wherein the reinforcing material has a tensile strength of 270 kg/mm2 or more. 3. The steel cord according to claim 1, wherein the reinforcing material has a tensile strength of 269 kg/mm2 or less. 4. Claims 1 to 3, wherein the reinforcing material has a heat resistance of 170 degrees or more.
Any steel cord listed in section. 5. Any steel cord according to claims 1 to 4, wherein the bonding material is in a semi-molten state at 160 degrees or less. 6. Any steel cord according to claims 1 to 5, wherein the reinforcing material is made of metal. 7. Any steel cord according to claims 1 to 5, wherein the reinforcing material is made of chemical or synthetic fiber.