JP2002103356A - Pretreatment method for coating zinc-plated steel pipe and other steel products with synthetic resin and method for producing resin coated steel pipe and other steel products - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pretreatment method for coating a zinc-hot-dipped or zinc-electroplated steel pipe and steel with a synthetic resin in which the thickness of the coat can be set freely, the peeling of the coat is prevented, and the finish of the coat is beautiful and a method for producing the coated products. SOLUTION: The method includes a process (a) in which the steel is degreased and etched, a process (b) in which the degreased, etched steel is washed with water, a process (c) in which the washed steel is dried, a process (d) the dried steel is coated with a primer, a process (e) in which the steel coated with the primer is dried, a process (f) in which the dried steel is heated, a process (g) in which the heated steel is coated with the synthetic resin, and a process (h) in which the coated steel is cooled with water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a pretreatment method for coating a steel pipe or other steel material coated with hot-dip galvanized or electro-galvanized steel with a synthetic resin, and a method for coating a steel pipe or other steel material hot-dip galvanized or electro-galvanized. The present invention relates to a synthetic resin coating method.

[0002]

2. Description of the Related Art Carbon steel pipes are generally used for pipes used in piping lines and the like. Although carbon steel pipes are superior in durability to general steel pipes, chemicals, Under severe natural conditions, such as a place that is charged or a place that is exposed to salt damage such as near the sea, the quality is significantly deteriorated. Steel pipes with a longer service life are required for piping and the like in concrete of intelligent buildings, which are difficult to replace and are almost impossible to replace.

[0003] The above-mentioned pre-coating of steel pipes and other steel materials used in piping under severe natural conditions and in concrete of an intelligent building which is almost impossible to repair or replace is required to ensure adhesion. For example, a method of first removing a metal oil film, rust, dirt, and the like, followed by applying a primer, and coating a synthetic resin is used as a base.

[0004] In general, a method for coating a steel pipe or other steel with a synthetic resin is as follows: degreasing → water washing → pickling → water washing → hot water washing → drying → primer (adhesion promoter) application → drying → heating → polyamide resin coating → water cooling → steel pipe In case the inner rust inhibitor is applied → inspection → packing →
Through many steps of completion, synthetic resin-coated steel pipes have been manufactured. Steel pipes and other steel materials produced by this method have the drawback that they can be coated by chemical treatment and the heating temperature cannot be set higher, and the coating film is difficult to apply because the coating film is difficult to remove. Processing under severe conditions such as press working was impossible.

On the other hand, synthetic resin coating on hot-dip galvanized, electrogalvanized steel pipes and other steel materials has an unstable factor due to chemical conversion treatment, and a sufficient film thickness cannot be obtained even with synthetic resin coating. Was. In addition, since the thickness of the synthetic resin coating is small, there is a problem that it is impossible to cut the disk, screw the outer surface, and grip with a pipe wrench.

[0006]

DISCLOSURE OF THE INVENTION The present invention has the above problems, that is, the thickness of a hot-dip galvanized or electro-galvanized steel pipe or other steel-made synthetic resin coating can be freely set, and the present invention is not limited to press working. Pre-treatment method for synthetic resin coating of hot-dip galvanized, electro-galvanized steel pipes and other steel materials with beautiful finish even when used in buildings and other places without causing film peeling even under severe conditions, and synthesis To produce resin-coated steel pipes and other steel materials.

[0007]

Means for Solving the Problems In order to solve the above problems, the inventors have conducted intensive studies and as a result, the thickness of the hot-dip galvanized, electro-galvanized steel pipe and other steel materials can be freely set, and the press can be performed. Even under severe conditions such as processing, the film does not peel off, and even when used in buildings and other places, it is a method of producing a beautifully finished synthetic resin coated steel pipe and other synthetic resin coated steel materials. In addition to completing the method that can be performed in the process, hot-dip galvanizing,
The present inventors have succeeded in simply performing a method of coating a synthetic resin on a steel pipe or other steel material subjected to electrogalvanization, and solved the above-described problem.

A first feature of the present invention is a pretreatment method for applying a synthetic resin film to a hot dip galvanized, electrogalvanized steel pipe or other steel material, which comprises the following steps. a. Degreasing and etching of hot dip galvanized, electro galvanized steel pipes and other steel materials, b. Washing the degreased and etched steel pipe and other steel materials with water, c. Drying the washed steel pipe and other steel materials.

[0009] It is difficult to apply a synthetic resin coating to hot-dip galvanized or electrogalvanized steel pipes and other steel materials. If these are to be coated with a synthetic resin, they are subjected to a chemical conversion treatment with phosphoric acid and then to a synthetic resin coating. Have been done. However, in the chemical conversion treatment with phosphoric acid, a strong adhesion was not obtained, and a sufficient film thickness could not be obtained. The method of the present invention does not require this chemical conversion treatment, and has a feature that the film thickness can be freely adjusted.

As pretreatment steps for applying a synthetic resin coating to ordinary steel pipes and other steel materials, the steps of degreasing the steel pipes and other steel materials, the steps of rinsing, the steps of pickling, the steps of rinsing,
The process includes a hot water washing process and a drying process.

In the degreasing / etching step performed here, the metal material is degreased with an alkali degreasing agent containing sodium hydroxide, sodium silicate or a surfactant, and then washed with water, and then acidified with hydrochloric acid, sulfuric acid or the like. After the washing, a step of washing away the acid by washing with water, further washing with hot water, and drying is adopted.

[0013] Degreasing is a process for removing oil films such as rolling oil and rust-preventive oil that have adhered to the metal material. Pickling neutralizes alkali residues adhered during degreasing and further removes metal rust and the like. This is a process for dissolving and removing the metal material to clean the surface of the metal material and to obtain uniform properties without unevenness.

In the above-described pretreatment process of the hot dip galvanized and electrogalvanized steel pipes and other steel materials according to the present invention, the pickling process and the drying process are performed in comparison with the above-described processing processes of ordinary steel pipes and steel materials. 2 is omitted.

A second feature of the present invention is that, in the degreasing / etching step, sodium hydroxide, sodium silicate, sodium carbonate, sodium phosphate, a water-soluble titanium salt,
The purpose is to degrease and etch hot dip galvanized, electro galvanized steel pipes and other steel materials using a degreasing agent containing a nonionic surfactant.

[0015] That is, in the degreasing stage, in the case of general steel pipes and other steel materials, in the pretreatment step, a strong alkali degreasing agent, a weak alkali degreasing agent, an emulsion degreasing agent or a solvent is used as a degreasing agent. Various degreasing methods such as electrolytic degreasing, spray degreasing, immersion degreasing, ultrasonic degreasing, and beta degreasing are performed.

If the pH value of the degreasing agent is too high, the metal material tends to corrode. Therefore, it is necessary to consider a certain limit of the pH value depending on the metal material. 10, aluminum: 10, tin: 11, brass: 11.5.

On the other hand, the degreasing agent used in the present invention comprises 1 to 30% of sodium hydroxide and 20 to 60% of sodium silicate.
%, Sodium carbonate 16-48%, sodium phosphate 2.6-7.
8%, a water-soluble titanium salt of 1.5 to 4.5%, and a nonionic surfactant of 5 to 15% are mixed, and this solution is used as a stock solution. When used, this stock solution is used as a 1-6% aqueous solution. When this degreasing agent is used, not only hot-dip galvanizing and electrogalvanizing materials can be degreased, but also etching can be performed at the same time.

The sodium salt such as caustic soda, sodium silicate, sodium carbonate, sodium phosphate and the like may be a potassium salt. As the water-soluble titanium salt, titanium phosphate, titanium sulfate and the like are usually used. .

The nonionic surfactant is also called a nonionic surfactant and includes polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester. Oxyethylene sorbitol fatty acid ester,
Examples thereof include glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene glyceride, and alkyl alkanolamide.

The processing temperature for degreasing / etching using an alkaline degreasing agent is 10 ° C. to 80 ° C., preferably 50 ° C. to 6 ° C.
At 0 ° C., the immersion time is 5 minutes to 60 minutes, preferably 30 minutes to
Perform for 40 minutes. Next, it is washed with water and dried. The drying may be natural drying or forced drying.

A third feature of the present invention is a method for coating a steel pipe or other steel material coated with hot-dip galvanized or electrogalvanized steel, which comprises the following steps: a. Degreasing and etching of hot dip galvanized, electro galvanized steel pipes and other steel materials, b. Washing the degreased and etched steel pipe and other steel materials with water, c. Drying the washed steel pipe and other steel materials; d. Applying a primer to the dried steel pipe or other steel material, e. Drying the steel pipe or other steel material coated with the primer, f.
Heating the dried steel pipe or other steel material; g. Coating the heated steel pipe or other steel material with a synthetic resin, h. A method of water-cooling a steel pipe or other steel material coated with the synthetic resin, wherein the method comprises a step of subjecting the hot-dip galvanized or electrogalvanized steel pipe or other steel material to a synthetic resin-coated steel pipe or other steel material.

The method of coating a synthetic resin on a normal steel pipe or other steel material is as follows: degreasing → water washing → pickling → water washing → hot water washing → drying → primer application → drying → heating → nylon coating → water cooling → internal rust inhibitor This is performed in each step of coating. On the other hand, in the case of the hot-dip galvanized steel pipe or electrogalvanized steel pipe or other steel material of the present invention, by using an alkaline degreaser containing a nonionic surfactant, the acid pickling, water washing, hot water washing, Also, each step of applying the inner rust preventive agent could be omitted, and the process was shortened and the finish was satisfactory.

The above-mentioned pickling, water washing and hot water washing are omitted, and in the hot-dip galvanized, electrogalvanized steel pipe and other synthetic resin coating steps after degreasing, water washing and drying, primer coating is first performed. The primer preferably has an adhesive property to both the tubular body and the thermoplastic resin powder to be welded, and has a property of not being thermally degraded at the time of welding, such as a modified polyamideamine-curable epoxy resin or a polychloroprene phenol resin. The synthetic resin primer is used on the inner surface or outer surface of the tubular body, or is dipped to form a primer layer.

Other primers include acrylate resin, polychloroprene resin, polyamideamine-curable epoxy resin, acid amideamine-curable epoxy resin, aromatic polyamine-curable epoxy resin, vinyl acetate resin, polyolefin resin, urethane resin, Epoxy phenol resins and the like can be exemplified.

A step of allowing the tube coated with the synthetic resin primer to air dry at room temperature for at least 30 minutes and at most 120 hours to cure the primer layer; After the surface is dried and before it is completely cured, without preheating the tube on the primer layer formed on the tube, polyethylene also discharged from the spray gun by the combustion flame of the mixed gas discharged from the spray gun, There is a method in which a thermoplastic resin powder of polypropylene or ethylene-vinyl acetate copolymer is heated and melted, and a droplet-shaped thermoplastic resin powder is sprayed on the inner surface or outer surface of the tube. To perform thermal spraying of thermoplastic resin powder,
By rotating the spray gun with respect to the tube, or by rotating the tube with the spray gun close to the tube, and moving the spray gun in the axial direction of the tube at the same time, the inner surface of the tube Alternatively, it is performed by a method of forming a plastic anticorrosive film having a desired thickness on the outer surface.

After applying the primer, the powder coating of the synthetic resin after drying includes polyethylene, nylon, epoxy,
Resins such as saponified ethylene vinyl acetate copolymer, polybutene, polyamide, polytetrafluoroethylene, polyfluoroethylene propylene, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and polyvinylidene fluoride can be exemplified.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The practice of the method of the present invention will be specifically described below, but the present invention is not limited to the following examples. Hot dip galvanized steel pipe 10 shown in FIG.
As chemicals used for degreasing / etching, sodium hydroxide 5.0%, sodium silicate 42.0%, sodium carbonate 34.0%
%, Sodium phosphate 6.0%, a water-soluble titanium salt 3.0%, and a nonionic surfactant 10.0% were used as a 3% aqueous solution. Degreasing / etching processing temperature is 10 ℃
C. to 80.degree. C., preferably 50 to 60.degree. C., and the immersion time is 5 minutes to 60 minutes, preferably 30 minutes to 40 minutes. The pH of this aqueous solution was 12.4, and the galvanized steel pipe was degreased and etched at 50 ° C. for 30 minutes.

Next, the hot-dip galvanized steel pipe is degreased and etched, and the rinsing step is performed by a dipping method in the present invention. Drying after washing with water was performed by natural drying, but drying may be forcibly performed.

The primer coating of the hot-dip galvanized or electroplated steel pipe after the completion of the pretreatment is performed by a dipping method, a spraying method, or the like. In the present invention, the coating is performed by a dipping method. After the application of the primer, the dried hot-dip galvanized steel pipe was powder-coated with a polyamide resin (nylon 12).

FIG. 1 is a perspective view of a hot-dip galvanized steel pipe 10 coated with a polyamide resin according to the pretreatment method and the synthetic resin coating method of the present invention. As shown in FIG. 2, 11 is a steel pipe, 12 is a galvanized layer, 13 is a primer layer, and the outermost layer 14 is a polyamide resin layer.

FIG. 3 is a sectional view of an electrogalvanized steel material 20 similarly coated with a polyamide resin by the pretreatment method and the synthetic resin coating method of the present invention. , 22 are galvanized layers, 23 is a primer layer, and the outermost layer 24 is a polyamide resin layer.

[0032]

According to the conventional method, it is difficult to apply a synthetic resin coating to a steel pipe or other steel material which is hot-dip galvanized or electrogalvanized. The synthetic resin can be easily coated by the manufacturing method.

Further, the synthetic resin-coated steel pipe and other steel materials produced by the method of the present invention have a strong adhesive force which cannot be obtained by the conventional method, and a thick film can be coated.
Enables plastic working such as bending and pressing. According to the method of the present invention, hot-dip galvanized nylon 12 resin coated, electrogalvanized steel pipe and other steel materials, the coating is difficult to peel off,
The life of the piping has been significantly extended.

Also, hot-dip galvanizing, which has been conventionally performed,
Compared with the method of coating a galvanized steel pipe or other steel with a synthetic resin, the chemical conversion step can be omitted, so that the pretreatment time can be shortened, the film thickness can be freely adjusted, and the finish can be satisfied.

[0035]

[Brief description of the drawings]

FIG. 1 is a perspective view of a steel pipe.

FIG. 2 is a sectional view of a steel pipe.

FIG. 3 is a sectional view of a steel material.

[Explanation of symbols]

 10: Synthetic resin coated steel pipe 11: Steel pipe 12: Galvanized layer 13: Primer layer 14: Polyamide resin layer 20: Synthetic resin coated steel 21: Steel 22: Zinc plated layer 23: Primer layer 24: Polyamide resin layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29K 105: 22 B29K 105: 22 B29L 23:00 B29L 23:00 F term (Reference) 4D075 BB18Z BB24X BB65X BB66X CA47 DA15 DA23 DB02 DB05 4F205 AD12 AD27 AD29 AD33 AD34 AG03 AG08 GA05 GB01 GB11 GC10 GE02 GE21 GF01 GF25 GN07 GN13 GN18 4K053 PA02 PA08 PA18 RA22 RA25 RA27 RA28 RA66 TA08 ZA10

Claims (3)

[Claims] 1. A pretreatment method for coating a hot-dip galvanized or electrogalvanized steel pipe or other steel material with a synthetic resin, comprising the following steps: a. Degreasing and etching of hot dip galvanized, electro galvanized steel pipes and other steel materials, b. Washing the degreased and etched steel pipe and other steel materials with water, c. Drying the washed steel pipe and other steel materials. 2. A hot-dip galvanizing method using a sodium hydroxide, a sodium silicate, a sodium carbonate, a sodium phosphate, a water-soluble titanium salt and an alkali degreasing agent containing a nonionic surfactant in the degreasing / etching step. The pretreatment method according to claim 1, wherein the plated steel pipe and other steel materials are degreased and etched. 3. A method for producing a hot-dip galvanized or electro-galvanized synthetic resin-coated steel pipe or a synthetic resin-coated steel material, comprising the following steps: a. Degreasing and etching of hot dip galvanized, electro galvanized steel pipes and other steel materials, b. Washing the degreased and etched steel pipe and other steel materials with water, c. Drying the washed steel pipe or other steel material; d. Applying a primer to the dried steel pipe or other steel material; e. Drying the steel pipe or other steel material coated with the primer, f. Heating the dried steel pipe or other steel material; g. Coating the heated steel pipe or other steel material with a synthetic resin, h. A step of water-cooling the steel pipe or other steel material coated with the synthetic resin.