JP2000282379A - Stranded wire of rustproof-coated pc steel and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stranded wire of rustproof-coated PC steel excellent in rustproofness without having a curl caused by winding when it is used by pulling out from a drum-wound state, and its production. SOLUTION: This twisted wire has a structure in which the inside of stranded wires, i.e., a space between a core wire and side wires and the outer surfaces of the stranded wires are filled and coated with an internal resin 2 comprising an ethylene-acrylic acid copolymer resin, an ethylene-methacrylic acid copolymer resin or their mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rust-proof coated PC steel strand used for prestressed concrete or a cable-stayed bridge, and a method for producing the same.

[0002]

2. Description of the Related Art As a method for preventing rust of PC steel strands used for prestressed concrete and cable-stayed bridges, Japanese Patent Application Laid-Open No. Hei 6-260,1992 is used.
Although there is a method using an epoxy resin as disclosed in Japanese Patent No. 504818, the resin is filled up to the inside of the twisted wire, and the resin is firmly adhered to the core wire and the side wire. Moisture penetrated from the terminal portion or the pinhole of the resin coating layer does not spread in the longitudinal direction of the wire, and exhibits a very excellent rust prevention effect. However, because it uses hard resin, when pulling out from the drum winding state and using it,
In some cases, the wire was curled due to the curl and it was difficult to construct the wire.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 8-42061, there is a method of filling and covering a gap between a core wire and a side wire and an outer surface of the side wire with a polyethylene resin. Although the above-mentioned winding habit hardly occurs,
Since the adhesiveness between the core wire and the side wire and the resin is weak, the moisture that has penetrated from the terminal portion or the pinhole of the resin coating layer is more likely to spread in the longitudinal direction of the wire as compared with those using the epoxy resin, and the rust prevention effect Was inferior.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rust-proof coated PC steel stranded wire which has no curl when used after being pulled out of a drum and is excellent in rust resistance, and a method for producing the same. Is an issue.

[0005]

Means for Solving the Problems The present inventors have conducted various studies on a method for preventing rusting of a PC steel strand, and as a result, found that the inside of the strand, that is, the gap between the core wire and the side wire, and the The outer surface of the wire is filled and covered with ethylene-acrylic acid copolymer resin, ethylene-methacrylic acid copolymer resin, or a resin composed of a mixture of these, so that the wire is drawn out of the drum wound state and used for winding. It has been found that a rust-proof coated PC steel wire having no habit and excellent in rust resistance can be obtained, and the present invention has been completed.
FIG. 1 shows a rust-proof coated PC steel strand having the above structure.

In the present invention, a thermoplastic resin is used. Examples of the ethylene-acrylic acid copolymer resin include "Primacol" manufactured by Dow Chemical Japan Co., Ltd. and "Novatech EAA" manufactured by Nippon Polychem Co., Ltd. Similarly, as the ethylene-methacrylic acid copolymer resin, “Nucrel” manufactured by DuPont-Mitsui Polychemicals Ltd. can be mentioned.

The present inventors have also studied the method for producing the rust-proof coated PC steel strand of the present invention diligently, and have found that a method having good characteristics can be produced with good productivity by the following method. That is, the temperature of the PC steel strand is 150 to 300 ° C.
After heating in, while gradually loosening partly,
The thermoplastic resin is adhered to the loosened position by extrusion molding, and by returning the mating state before the resin is solidified, the gap between the core wire and the side wire is filled, and the outer peripheral surface of the twisted wire is covered. At the same time, the excess resin is removed by a dice so that the resin remains on the outer peripheral surface of the wire at 100 to 400 μm. At this time, the inner diameter of the die is 0.2 to 0.8 mm larger than the outer diameter of the wire than the PC steel, and the thickness of the die is preferably 2 mm or less.

Further, a PC steel stranded wire in which each side wire is in contact with the core wire and the minimum gap distance between the side wires is 150 μm or more,
The PC steel strand is heated to 150 ° C to 300 ° C and passed through the crosshead part of a resin extruder.
The thermoplastic resin heated to 300 ° C is pressurized to 150 kgf / cm ² or more to simultaneously fill the gap between the core wire and the side wire and cover the outer peripheral surface of the stranded wire. The excess resin is removed by a die so as to leave. At this time, the inner diameter of the die is 0.2 to 0.8 mm larger than the outer diameter of the wire than the PC steel, and the thickness of the die is preferably 2 mm or less.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the gap inside the stranded wire, that is, the gap between the core wire and the side wire, and the outer peripheral surface of the stranded wire are made of ethylene-acrylic acid copolymer resin or ethylene-methacrylic acid copolymer. Filling and coating with a resin or a resin composed of a mixture of these, to obtain a rust-proof coated PC steel wire that has no curl when used by being pulled out of the drum and used for rust prevention Can be.

The above resin is moderately flexible and easily deformable, and is excellent in adhesion to a PC steel wire. For this reason, even when the stranded wire using the resin is bent at an acute angle, the resin is stretched without absorbing the core wire and the side wire and the resin is stretched to absorb deformation and suppress curl.

In order to exhibit the above characteristics, it is necessary that the resin has a low elastic modulus and good elongation. Polyolefin resins have relatively low elastic modulus, good elongation, and low cost. However, general polyethylene hardly adheres to PC steel wires and cannot be used. Therefore, as a result of examining various adhesive polyolefin resins, ethylene-acrylic acid copolymer resin or ethylene-methacrylic acid copolymer resin has low cost, low elasticity, good elongation, and excellent adhesion to PC steel wire. I found something. In addition, these resins showed a small decrease in adhesive strength even after immersion in salt water.

Japanese Patent Application Laid-Open No. 5-163796 discloses a method using a polyethylene-based polyolefin resin having a functional group, typically "Admer" manufactured by Mitsui Chemicals, Inc. The polyolefin resin is expensive and has good initial adhesive strength, but has a large decrease in adhesive strength after immersion in salt water, failing to obtain sufficient corrosion resistance.

In the present invention, it is effective that the thickness of the resin at the peak of the outer peripheral surface of the wire is 400 μm or less. Hereinafter, the thickness of the resin is the thickness at the peak of the outer peripheral surface of the wire. When it exceeds 400 μm, when embedded in concrete and pulled, the total elongation of the resin is large,
It is not suitable when the pull-out strength is low and adhesion to concrete is important.

[0014]

EXAMPLES (Example 1) PC steel strands heated to 250 ° C. were partially loosened sequentially, and Dow Chemical Japan-made “Primacol” was adhered to the loosened portions by extrusion molding, and the twist was returned. . Subsequently, the excess resin on the outer surface was removed through a die having an inner diameter of 0.6 mm larger than the outer diameter of the PC steel strand and a thickness of 2 mm to reduce the resin layer thickness to 300 μm.
m. As described above, the rust preventive coated PC having the structure shown in FIG.
A steel strand was obtained.

Table 1 shows the evaluation results of the produced rust-proof coated PC steel strands.

[0016]

[Table 1]

The curl is determined by measuring the amount of curling of the rust-proof coated PC steel strand before winding on the drum and after holding it for one month by winding it on a drum having a diameter of 1 m, as shown in FIG.
Was evaluated. Corrosion resistance is determined by observing the PC steel wire by spraying salt water on a 15 cm long rust-prevention coated PC steel stranded wire with pinholes, both ends sealed with resin for 1000 hours, then removing the coating resin. evaluated. Also,
The adhesive strength between the resin and the PC steel wire before and 100 hours after the salt spray was evaluated by the force required to peel off the resin coating having a width of 5 mm. Adhesive strength is determined by embedding a wire from rust-proof coated PC steel into cubic concrete with a side of 20 cm and curing the concrete. It was evaluated by the value divided by the surface area of the steel strand.

As shown in Table 1, the obtained rust-proof coated PC
The steel strand had a small winding habit and was excellent in corrosion resistance and adhesion.

(Example 2) By setting the core wire diameter to 5.35 mm and the outer diameter of each of the six side wires to 5.02 mm, a PC steel stranded wire having a gap between side wires of 160 μm was heated to 250 ° C. After that, the resin was extruded through a crosshead portion of a resin extrusion molding machine, and heated to 200 ° C. to 300 ° C., and Dow Chemical Japan-made “Primacol” was pressurized to 150 kgf / cm ² , and the PC steel stranded wire was removed from the side line gap. The resin was filled and the outer peripheral surface was covered. Then, the inner diameter is 0.6 mm larger than the outer diameter of the PC steel strand, and the excess resin on the outer surface is removed through a die having a thickness of 2 mm to remove the rust-proof coated PC steel strand having a resin layer thickness of 300 μm. Obtained. Rust-proof coated PC manufactured
The steel strand was evaluated in the same manner as in Example 1. As shown in Table 1, the obtained rust-proof coated PC steel strand had a small curl and was excellent in corrosion resistance and adhesion.

(Comparative Example 1) After heating a PC steel strand to 250 ° C., the strand was partially loosened sequentially, and “Primacol” manufactured by Dow Chemical Japan was adhered to the loosened portion by extrusion molding. After that, the matching state was returned to the original state. Continuously, the inner diameter is 1.0
Excess resin on the outer surface was removed through a die having a thickness of 2 mm and a thickness of 2 mm to obtain a rust-proof coated PC steel wire having a resin layer thickness of 500 μm. The produced rust-proof coated PC steel strand was evaluated in the same manner as in Example 1. As shown in Table 1,
The obtained rust-proof coated PC steel strand had a small winding habit and was excellent in corrosion resistance, but was poor in adhesion.

Comparative Example 2 A strand of PC steel heated to 250 ° C. was partially loosened sequentially, and powder epoxy resin E90 manufactured by Nippon Paint Co. was applied to the loosened portion by electrostatic coating, melted, and the twist was returned. And further heated at 250 ° C. for 1 minute. As described above, a rust-proof coated PC steel wire was obtained in which the gap between the core wire and the side wire and the outer peripheral surface of the side wire were completely filled and covered. The produced rust-proof coated PC steel strand was evaluated in the same manner as in Example 1. As shown in Table 1, the obtained rust-proof coated PC steel strand was excellent in corrosion resistance and adhesion, but poor in curl.

(Comparative Example 3) After heating a PC steel strand to 250 ° C, the strand was partially relaxed sequentially, and a polyethylene polyolefin “Admer” having a functional group manufactured by Mitsui Chemicals, Inc. was used in the relaxed portion. After being attached by extrusion, the mating state was returned to the original state. Subsequently, the inner diameter is 0.6 mm larger than the outer diameter of the PC steel strand, and the thickness is 2 mm.
Excess resin on the outer surface was removed through a die having a thickness of 300 mm to obtain a rust-proof coated PC steel wire having a resin layer thickness of 300 μm. The produced rust-proof coated PC steel strand was evaluated in the same manner as in Example 1. As shown in Table 1, the obtained rust-proof coating P
The C steel strand had a small winding habit, but was inferior in corrosion resistance.

(Comparative Example 4) After heating a PC steel stranded wire to 250 ° C, the strand was partially loosened sequentially, and the loosened portion was subjected to polyethylene “HIZEX53” manufactured by Mitsui Chemicals, Inc.
05E "was adhered by extrusion, and then returned to the original state. Subsequently, the excess resin on the outer surface was removed through a die having an inner diameter of 0.6 mm larger than the outer diameter of the PC steel strand and a thickness of 2 mm to reduce the resin layer thickness to 300 μm.
A wire was obtained from a rust-proof coated PC steel having a length of m. The produced rust-proof coated PC steel strand was evaluated in the same manner as in Example 1. Table 1
As shown in the above, the obtained anticorrosion-coated PC steel strand had a small winding habit, but was inferior in corrosion resistance and adhesion.

[0024]

As described above, according to the present invention,
By limiting the resin, this rust-proof coated PC steel strand is
It has a small winding habit when used by being pulled out from the drum winding state, and has excellent rust prevention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a rust-proof coated PC steel stranded wire according to the present invention.

FIG. 2 is an explanatory view of a curl test method.

[Explanation of symbols]

 1: PC steel wire 2: Resin 3: Rust-proof coated PC steel wire

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) E04C 5/08 E04C 5/08 // B29K 23:00 105: 22 705: 00 B29L 31:10 (72) Inventor Tsuyoshi Yoshioka 1-1-1, Kunyokita, Itami-shi, Hyogo Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Toshiro Hirohata 1-3-1, Shimaya, Konohana-ku, Osaka-shi, Osaka Sumitomo Electric Industries, Ltd. Osaka In the factory (72) Inventor Yasuji Ogaki 1-3-1 Shimaya, Konohana-ku, Osaka-shi, Osaka Sumitomo Electric Industries, Ltd. Osaka Works F-term (reference) 2E164 AA02 AA11 AA31 3B153 AA09 AA32 AA45 AA47 CC13 CC19 CC52 DD22 FF02 FF03 GG07 GG40 4E070 AA01 AB12 BD00 BG06 4F207 AA03 AG14 AH43 AH46 AP15 AR12 KA01 KA17 KB18 KF01 KJ05 KM16

Claims (4)

[Claims] 1. A stranded wire, a gap between a core wire and a side wire, and an outer peripheral surface of the stranded wire are ethylene-acrylic acid copolymer resin,
Or a rust-proof coated PC steel strand filled and coated with an ethylene-methacrylic acid copolymer resin or a resin comprising a mixture thereof. 2. The thickness of the ethylene-acrylic acid copolymer resin, the ethylene-methacrylic acid copolymer resin, or a mixture thereof at the peak of the outer peripheral surface of the stranded wire is 100 to 400.
The rust-proof coated PC steel strand according to claim 1, wherein the diameter is μm. 3. After heating the PC strand, partially twisting the strands, extruding a thermoplastic resin at the loosened position by extrusion, and then returning the twisted state to the original state. Filling the gap between the core wire and the side wire, and simultaneously covering the outer peripheral surface of the stranded wire, and then removing excess resin with a die so as to leave a predetermined resin on the outer peripheral surface of the wire. Manufacturing method of rust-proof coated PC steel strand. 4. A PC steel stranded wire having a side wire in contact with a core wire and a minimum gap distance between side wires of 150 μm or more is heated, passed through a crosshead portion of a resin extruder, and heated thermoplastic resin is applied. By pressing, filling the gap between the core wire and the side wire, and simultaneously covering the outer peripheral surface of the stranded wire,
A rust-proof coating PC characterized by removing excess resin with a die so as to leave a predetermined resin on the outer peripheral surface of the wire.
Manufacturing method of steel strand.