JPH0957866A - Method and apparatus or repairing polyolefin-coated steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability for the repair of the damaged part having a large area and arriving at the steel surface and to conduct the excellent repair that no peeling occurs by heating a polyolefin coating layer to the temper ature of the specific range with respect to the melting point of the polyolefin by far infrared rays. SOLUTION: The polyolefin coating layer of the periphery of a damaged part is coated with adhesive for polyolefin. The adhesive and the coating layer are melted and brought into close contact with one another by heating by far infrared rays. Then, the layer is coated with urethane resin or epoxy resin repairing paint. In this case, the heating is conducted on the layer at the surface temperature T of the range of (M=20 deg.C)<=T<=(M+40 deg.C) of the melting point M of the polyolefin. A far infrared heater 20 is obtained by coupling a plurality of solid heaters (cast with aluminum 25) coupled via a movable tie member 21. The heater 20 can easily repair a steel tube having a radius of curvature or a coated steel material having a bent such as a steel sheet pipe. A heating power source cable 23 and a temperature sensor 22 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for repairing a damaged coating film of various polyolefin-coated steel materials such as a polyolefin-coated heavy-corrosion-proof steel sheet pile, a steel pipe pile or a line pipe generated during transportation or installation. After coating the urethane and epoxy repair paints and polyolefin adhesive layer with high adhesiveness on the polyolefin coating layer around the part, and using a far infrared heater to melt and adhere the special adhesive and the base material polyolefin, the above repair is performed. The present invention relates to a method for repairing polyolefin, which is characterized in that a repair paint is applied and repaired.

[0002]

2. Description of the Related Art Civil engineering steels such as steel sheet piles, steel pipe piles, and line pipes are required to have long-term durability. Therefore, they are highly durable and reliable polyolefins, especially polyethylene resins, room temperature curing type and heat curing type urethane resins. The use of heavy-duty anti-corrosion steel materials coated with a paint or an epoxy resin paint with a thick film of 1 mm or more is increasing. It is generally accepted that such a coated steel material is excellent in corrosion resistance because it is coated in a controlled factory such as a mill maker. However, handling during transportation or installation may cause damage to the coating film, resulting in coating film defects.

In an epoxy resin-coated or urethane resin-coated steel material, etc., the surface of the base material resin coating itself is active, so during the process of curing after coating with the same type of repair coating material, the base material around the steel surface and the defect portion is treated. Since a strong adhesion with the material coating is formed, there is no problem that a highly durable repair can be easily performed by a coating method similar to normal coating.

[0004]

However, in the case of a polyolefin resin-coated steel material such as polyethylene, since polyolefin does not have a polar group that contributes to adhesion, repair of epoxy resin or urethane resin having high adhesion to the steel surface is required. Adhesion with the steel surface is not a problem if you use a paint for
Adhesion with the base material polyolefin around the defect is extremely poor, and a gap is created between the base material polyolefin and the repair paint over time, corrosion gradually progresses and the repair agent eventually peels off, and the epoxy resin coating Alternatively, a simple repair method such as urethane resin coating cannot be performed. FIG. 3 illustrates this, and shows a cross section of the repaired portion. When the repair material 3 such as epoxy resin or urethane resin is attached to the damaged portion of the polyolefin coating 2 applied on the steel material 1, the shape 4 immediately after the repair is a complete shape, but it is used for a long time. After that, as shown in the shape 5 after use, the space between the repair agent 3 and the polyolefin coating 2 is peeled off,
Water, oxygen ions, etc. 6 enter from this peeling portion, peeling progresses, and finally the repair material peels off.

Therefore, as shown in FIG. 4, a polyolefin stick 11 of the same type as the base material polyolefin is used, and the mixture is melted and integrated by heating with a burner such as a hot air gun 12 (stick method: the steel surface is generally exposed. If it is a small area that does not exist) or apply a sealant 13 etc. on the exposed steel surface as shown in FIG. 5, attach a polyethylene patch sheet 14 of the same type as the base material polyolefin, and attach the aluminum foil. A method for repairing a defective portion by heating the base material polyolefin and the polyolefin patch sheet 14 for repair by heating with a burner through the like (patch method: generally a relatively large area where the steel surface is exposed) In the case of) is carried out.
(For example, JP 61-170586 A, JP 2
No. 14137).

In the case of repairing a small area where the steel surface is not exposed, there is no problem because a relatively stable performance can be obtained by the stick method and workability at the site is good, but the steel surface In the case of a large exposed area, (a) it takes about 20 minutes to 1 hour to repair one place, and the repair work efficiency is poor, and (b) there are large variations due to individual differences and lack of reliability, etc. Therefore, a simple and reliable repair method, which replaces the stick method or the patch method, has been desired.

The present invention was developed in view of such circumstances, and an object thereof is to provide a repair method for a polyolefin-coated steel material and an apparatus therefor.

[0008]

DISCLOSURE OF THE INVENTION The inventors of the present invention have a problem when applying a repair by a paint type such as an epoxy resin coating and a urethane resin coating to a polyolefin coating. Focusing only on the adhesiveness to the base material polyolefin, we have diligently studied a method of activating the surface of the base material polyolefin around the defect part by some method to improve the adhesiveness to the paint type repair agent.

As a result, an active chlorinated polyolefin having an adhesive property with a polyolefin and having a surface after coating, an unsaturated dicarboxylic acid and an ethylene-vinyl acetate copolymer (EV
The graft polymer of A), the graft polymer of an unsaturated dicarboxylic acid and an ethylene-ethyl acrylate copolymer (EEA), or one or more of these graft polymers substituted with chlorine, A paint-type polyolefin primer dissolved in an inducing solvent such as toluene, or a polyolefin primer in which a chlorosulphonated polyolefin vulcanizing agent is added in addition to these components to crosslink After coating the surface of the base material polyolefin, only the coating surface layer is heated and melt-adhered by a far infrared heater between a temperature lower than the melting point of the base material polyolefin by 20 ° C. and a temperature higher than the melting point by 40 ° C. to significantly improve the adhesive strength. I found that.

The present invention relates to a method of repairing a damaged portion of a coating film of a polyolefin-coated steel material, wherein an adhesive for polyolefin is applied on the polyolefin coating layer around the damaged portion and the adhesive and the polyolefin coating are applied by far infrared heating. A method for repairing a polyolefin-coated steel material, which comprises melt-adhering the layers and then applying a urethane resin-based or epoxy resin-based repair coating material.

After imparting adhesion to the surface of the polyolefin, a two-component type polyurethane-based repair paint or epoxy-based repair paint is applied for repair. Examples of the adhesive for polyolefin include chlorinated polyolefin, graft polymer of unsaturated dicarboxylic acid and ethylene-vinyl acetate copolymer, graft polymer of unsaturated dicarboxylic acid and ethylene-ethyl acrylate copolymer, and graft polymerization thereof. Those containing one or more selected from the group of those obtained by substituting chlorine with chlorine are preferable.

Further, it is preferable that the far-infrared ray heating is carried out in such a manner that the surface temperature T on the polyolefin coating layer is in the range of (M-20 ° C.) ≦ T ≦ (M + 40 ° C.) with respect to the melting point M of the polyolefin. As an apparatus of the present invention capable of suitably carrying out the above method, an apparatus for repairing a damaged coating film of a polyolefin-coated steel material, which is 20 to 50 m
A repair device for a polyolefin-coated steel material, comprising: a plurality of far-infrared heaters having a width of m, each heater being movably connected to each other, and having a magnet fixed to the repair steel material.

[0013]

The steel materials for civil engineering to which the present invention is applied include steel sheet piles, steel pipe piles, line pipes, gas pipes, water pipes, corrugated pipes and liner plates. As the polyolefin coating resin, low density polyethylene (LDPE), high density polyethylene (HDPE),
Examples thereof include linear low density polyethylene (LLDPE), crosslinked polyethylene, polyethylene resin such as ultra-high molecular weight polyethylene developed in recent years, polypropylene resin, and polybutene resin.

As a primer for polyolefin, chlorinated polyethylene, chlorinated polypropylene, a graft polymer of EVA with unsaturated dicarboxylic acid, a graft polymer of EEA with unsaturated dicarboxylic acid, or a chlorine-substituted product of these graft polymers. A paint-type polyolefin primer containing one or more of these, dissolved in an organic solvent such as toluene, and chlorosulphonated polyolefin and a vulcanizing agent in addition to these components for crosslinking. It is a characteristic primer for polyolefins and the like.

The chlorinated polyolefin is mainly used for adhesion to polyethylene, polypropylene and the like, and the graft polymer of unsaturated carboxylic acid and EVA or the graft polymer of unsaturated carboxylic acid and EEA is mainly used for paints and resins. Contributes to adhesion with repair paint. Further, the chlorosulfonated polyolefin can be crosslinked with a vulcanizing agent to improve the strength of the adhesive itself, but if it is added in a large amount, the adhesiveness with the polyolefin and the repair paint is lowered. Therefore, the compounding amount of chlorinated polyolefin is 5 to 50 parts by weight, unsaturated carboxylic acid and EVA.
It is preferable that the blending amount of the graft polymer of 1) or the graft polymer of unsaturated carboxylic acid and EEA is 5 to 50 parts by weight, and the blending amount of the chlorosulfonated polyolefin is 5 to 30 parts by weight.

If the amount is out of this range, the adhesiveness to the polyolefin or the repair coating is lowered, or the strength of the adhesive layer itself is lowered. As the post-heating temperature after applying the above-mentioned polyolefin adhesive to the polyolefin, the surface temperature T ° C of the polyolefin is preferably in the range of (M-20 ° C) ≦ T ≦ (M + 40 ° C) with respect to the melting point M. . If post-heating is performed at a temperature lower than (M-20 ° C), sufficient adhesion cannot be obtained. Also, (M + 40
If post-heating is performed in a temperature range above (° C),
It is not preferable because it has a bad effect such as deterioration of the leveling property of the surface.

A partial schematic view of the far infrared heater 20 of the embodiment of the present invention is shown in FIG. This far infrared heater 20 has 5
The rod heater 24 of 00W is cast with aluminum 25,
Far infrared radiation paint is applied to the heating portion 26 of the aluminum 25. Far-infrared radiation paints are commercially available, such as W-500 manufactured by Okitsumo. At one end of the far-infrared heater 20, a magnet 27 fixed to the repair steel material is provided. The fixing portion can be expanded and contracted by the expansion and contraction mechanism 27. FIG. 1 is an overall view of a far-infrared heater 20, in which a plurality of solid state heaters (cast by aluminum 25) are connected via a movable connecting member 21 as shown in FIG. This far-infrared heater 20 can easily repair a coated steel material having a radius of curvature such as a steel pipe or a bent portion such as a steel sheet pile. In FIG. 1, 23 is a heating power cable, 22
Is a temperature sensor. As the movable tie member 21, a material that can withstand a maximum temperature of 330 ° C., for example, Nichias fine flex cloth F31711t = 2 is used.

[0018]

EXAMPLES The results of repairing a polyethylene-coated steel sheet pile that is actually used for earth retaining using the repairing apparatus and the repair coating material of the present invention will be described below. In the evaluation test, a steel sheet pile was cut out from the sample in a width direction of 10 cm,
The following test is carried out with the end face being exposed, and the peeling state of the end face and the adhesiveness retention ratio by the pull-off method for the adhesion between polyethylene and the coating agent (adhesive strength after test / adhesive strength before test × 100 %).

Anticorrosion test method 1: Salt spray test (5% Na
Cl, 35 ° C.) 90 days Anticorrosion test method 2: Salt water immersion test (3% NaCl, 50
90 ° C.) 90 days [Example 1] As the adhesive, low chlorinated polyethylene 1 was used.
2 parts, unsaturated dicarboxylic acid-EVA graft copolymer 8
Parts, 60 parts of chlorosulphonated polyethylene, vulcanizing agent 2
100 parts of titanium oxide, based on 0 parts of resin solids,
A mixture of 200 parts of toluene was used.

Crosslinked low density polyethylene was used as the polyolefin for heavy corrosion protection. After applying the adhesive on the polyolefin, the surface of the polyolefin was heated to 120 ° C. with a far infrared heater, allowed to cool, and then a two-component room temperature curable urethane repair paint was applied to obtain a test material. [Example 2] Unsaturated dicarboxylic acid-EVA as an adhesive
An adhesive was used in which 100 parts of titanium oxide and 200 parts of toluene were blended with respect to a resin solid content consisting of 20 parts of a graft polymer, 60 parts of chlorosulphonated polyethylene, and 20 parts of a vulcanizing agent. Other than that, a two-component urethane repair paint was applied under the same conditions as in Example 1 to obtain a test material.

[Example 3] The same adhesive as in Example 1 was used except that non-crosslinked LLDPE (linear low-density polyethylene) was used as the heavy-duty anticorrosion polyolefin, and after heating under the same post-heating conditions, A two-component urethane paint was applied to obtain a test material. [Example 4] A two-pack type epoxy resin paint was applied as a repair paint under the same conditions as in Example 1 for the adhesive, the post-heating conditions, and the polyolefin resin to obtain a test sample.

Comparative Example 1 The cross-linked polyethylene resin was coated with the adhesive for polyolefin of Example 1 at room temperature, and then a two-pack type urethane coating material for repair was coated to obtain a test material. [Comparative Example 2] The adhesive for polyolefin of Example 1 was coated on a crosslinked polyethylene resin at 60 ° C, and then a urethane resin for repair was coated to obtain a test material.

Comparative Example 3 1 part of chlorinated polypropylene,
1 part of unsaturated dicarboxylic acid, 75 parts of chlorosulphonated polyolefin, and 23 parts of vulcanizing agent relative to the resin solid content,
A mixture of 100 parts of titanium oxide and 200 parts of toluene was used. Crosslinked low-density polyethylene was used as the heavy-corrosion-proof polyolefin. After heating the surface of the polyolefin to 180 ° C., a repair two-component urethane paint was applied to obtain a test material.

[Comparative Example 4] As an adhesive, 100 parts of titanium oxide and 20 parts of toluene were added to a resin solid content consisting of 60 parts of chlorinated polypropylene and 40 parts of unsaturated dicarboxylic acid.
A mixture of 0 parts was used. The post-heating conditions and the polyolefin resin were the same as in Example 1, and a two-component type urethane paint for repair was applied as a repair paint to obtain a test material.

Table 1 shows the results of various tests of the above Examples and Comparative Examples. From these experiments, the reliability of repairing a large-scaled flaw reaching a steel surface, which has been difficult in the past, is improved by the adhesive and the apparatus.

[0026]

[Table 1]

[0027]

EFFECTS OF THE INVENTION According to the present invention, when repairing a coating film damaged portion of various polyolefin-coated steel materials such as polyolefin-coated heavy corrosion-resistant steel sheet piles, steel pipe piles or line pipes generated during transportation, installation, etc. Since the polyolefin of the material is melt-adhered, the reliability of repairing a large-scale scratch reaching a steel surface, which has been difficult to repair in the past, is improved, and excellent repair without peeling can be performed.

[Brief description of drawings]

FIG. 1 is an overall perspective view of a main part of a heating device according to an embodiment.

FIG. 2 is a partial schematic view of the heating device of the embodiment, (a)
It is a top view, (b) side view, (c) front view.

FIG. 3 is an explanatory diagram of peeling for repairing a coating film.

FIG. 4 is an explanatory diagram of a conventional switch method.

FIG. 5 is an explanatory diagram of a conventional patch rate method.

[Explanation of symbols] 1 steel material 2 polyolefin coating 3 repair agent 4 shape immediately after repair 5 shape after use 6 water, oxygen ions, etc. 11 stick 12 hot air gun 13 sheetant 14 patch sheet 20 heating device 21 connecting member 22 temperature sensor 23 Heating power cable 24 Rod heater 25 Aluminum 26 Heating part 27 Magnet

Claims (4)

[Claims] 1. A method for repairing a damaged portion of a coating film of a polyolefin-coated steel material, wherein an adhesive for polyolefin is applied onto the polyolefin coating layer around the damaged portion, and the adhesive and the polyolefin coating layer are heated by far-infrared heating. A method for repairing a polyolefin-coated steel material, which comprises applying a urethane resin-based or epoxy resin-based repair paint after melt-adhesion. 2. The polyolefin adhesive is a chlorinated polyolefin, a graft polymer of an unsaturated dicarboxylic acid and an ethylene-vinyl acetate copolymer, a graft polymer of an unsaturated dicarboxylic acid and an ethylene-ethyl acrylate copolymer, and The method for repairing a polyolefin-coated steel material according to claim 1, which comprises one or more selected from the group of chlorine-substituted graft polymers. 3. The far-infrared heating is performed by setting a surface temperature T on the polyolefin coating layer to a melting point M of the polyolefin within a range of (M−20 ° C.) ≦ T ≦ (M + 40 ° C.). A method for repairing a polyolefin-coated steel material according to claim 1 or 2. 4. A device for repairing a damaged coating film of a polyolefin-coated steel material, comprising a plurality of far-infrared heaters having a width of 20 to 50 mm, wherein the heaters are individually movably connected to each other. A repair device for a polyolefin-coated steel material, which is equipped with a magnet for fixing.