JP2015113381A - Coating material composition for metal conduit and metal conduit produced by applying the same thereto - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin coating material composition for a metal conduit that has excellent in dryability and has low odor without impairing various functions required of a coating material for a metal conduit and to provide a metal conduit produced by applying the epoxy resin coating material composition thereto.SOLUTION: An epoxy resin coating material composition for a metal conduit, preferably, for a part of a metal conduit in contact with water, comprises as essential components a silane coupling agent and a glycol ether solvent. In the coating material composition, preferably, the content of the silane coupling agent is 1-5 wt% and the content of the glycol ether solvent is 1-20 wt%. The metal conduit is produced by applying the epoxy resin coating material composition for a metal conduit thereto.

Description

  The present invention relates to an epoxy resin coating composition for metal tubes and a metal tube formed by applying the coating composition. More specifically, the present invention applies a low odor type coating composition excellent in drying property for cast iron pipes used as waterworks pipes and the like, and the coating composition to a wetted part, particularly a cut pipe end face. Related to the cast iron pipe.

  Generally, metal pipes such as cast iron pipes and steel pipes are used for transporting and storing drinking water such as water pipes and water storage pipes. In recent years, with increasing interest in water, safer and better quality tap water has been demanded. For this reason, in order to deliver not only highly purified water but also high-quality water as it is in the water supply business, construction of a higher-level water pipe system is being promoted.

  Against this backdrop, ductile cast iron pipes used for water pipes are also increasingly used for epoxy resin powder coatings with excellent corrosion resistance and hygiene on the inner surface. Even if it is used, the water quality will be adversely affected if appropriate measures are not taken during construction. For example, it is difficult to ensure a sufficient drying time when a cut tube is used at a construction site in order to adjust the length of the tube and repair coating is performed. For this reason, the conventional paint for coating the inner surface of the pipe is insufficiently dried, which may cause a problem in terms of anticorrosion performance and odor, and may impair the corrosion resistance and hygiene of the entire pipeline.

  As a solution to this, anticorrosion rubber in which the end face of the cut tube is covered with a rubber cover has been put into practical use.

  Regarding cast iron pipes for water supply, it is clearly stated in the Japan Water Works Association Standard JWWA K 139 that "the water quality after passing the water, especially odors must be taken into consideration before it is shipped to the factory" Specific values such as toluene 0.2 mg / L or less and xylene 0.4 mg / L or less are listed as values. From the viewpoint of countermeasures for odors, solvent-based paints use organic solvents such as toluene and xylene, as well as solvents consisting of alkylcyclohexanes having 9 to 10 carbon atoms, and their combination is intended to promote solvent volatilization. However, a xylene-free composition has not been achieved, and it has not been put into practical use (Patent Document 2).

JP2013-2520A JP 2011-6612 A

  The present invention provides a coating composition for a metal tube with a low environmental load that can further reduce the drying time while suppressing the solvent odor without impairing various functions required for the coating for a metal tube, and a metal tube formed by applying the coating composition. The purpose is to provide.

  In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result of the anticorrosion treatment for metal pipes, the epoxy resin coating composition for metal pipes contains a silane coupling agent and a glycol ether solvent as essential components. Thus, the present inventors have found that the drying time can be significantly shortened with a xylene-free composition and that the function as an anticorrosion treatment coating can be sufficiently exhibited even with a thin film thickness, and the present invention has been completed.

  That is, the present invention relates to an epoxy resin coating composition for metal pipes, which contains a silane coupling agent and a glycol ether solvent as essential components.

  The coating composition of the present invention is preferably for a wetted part of a metal tube.

  In the coating composition of the present invention, the content of the silane coupling agent is preferably 1 to 5% by weight.

  In the coating composition of the present invention, the content of the glycol ether solvent is preferably 1 to 20% by weight.

  In the coating composition of the present invention, the metal pipe to be applied is preferably a water supply pipe.

  The present invention also relates to an epoxy resin coating composition for metal pipes, which comprises a silane coupling agent and a glycol ether solvent as essential components and coated with the coating composition.

  In the metal tube of the present invention, the application region is preferably a wetted part.

  The metal pipe of the present invention is preferably a cast iron pipe, and the application region is a cut end face of the pipe.

  According to the coating composition of the present invention, the coating composition for metal pipes such as adhesion, corrosion resistance, concealability, water resistance, and long-term durability can be made into a thin film without impairing various functions required, and the coating has a strong odor. Without using a volatile organic solvent such as xylene, the drying time of the coating film can be greatly shortened. Thereby, painting work efficiency improves and it can utilize for not only repair uses, such as a cut tube end face repair in an installation field, but various uses. In addition, it can be used as an overcoat for various standard coatings.

  The coating composition of the present invention is an epoxy resin coating composition for metal pipes, and is characterized by containing a silane coupling agent and a glycol ether solvent as essential components.

<Metal tube and coating area>
The metal tube to which the coating composition of the present invention is applied is not particularly limited as long as it is made of metal, and examples thereof include metal tubes such as cast iron tubes, steel tubes, and copper tubes. The surface of the metal tube may be subjected to a ground treatment such as epoxy, latex, or zinc spraying. The use of the metal pipe of the present invention is not particularly limited for use in water and sewage, for storage of water, etc., but considering the further effect of washing the coating composition of the present invention with water, drinking water for water supply, storage, etc. The cast iron pipe for use is particularly preferred.

  Specifically, cast iron pipes are widely used for water and sewage pipes and the like, and are used in various environments. However, in order to adjust the length of the pipe, a process called a cut pipe is performed at the installation site. Since the iron portion is exposed on the cut surface of the cut tube, and the coating of the inner surface and the outer surface of the tube is also affected, the exposed end surface of the cut portion of the iron portion and its surroundings are several millimeters to several centimeters, for example, about 1 mm to about Repair painting is required for 5mm. The epoxy resin coating composition of the present invention having excellent drying properties and taking measures against odor can be particularly preferably used on the end face of the cut tube, which is a cut surface at that time.

  In the present invention, the term “cut tube end face” means, of course, a cut surface, but may also mean a region including a pipe outer surface and a pipe inner surface of several millimeters to several centimeters around the cut surface.

  In addition, the coating composition of the present invention can be used not only for the end face of the cut pipe but also for repairs used in places where other iron surfaces are exposed, and furthermore, for the coating of joint parts between pipes. Can also be used.

  Cast iron pipes are widely used in water and sewage pipes and the like, and are often used in various embedded environments. In particular, improvements in durability and corrosion resistance of the pipe outer surface are required. Therefore, for example, a zinc-based primer defined in Japan Ductile Iron Pipe Association Standard JDPA Z 2010 “Ductile Cast Iron Pipe Synthetic Resin Coating” is often used as the anticorrosive layer on the outer surface of the pipe. In addition, as a top coat for a zinc-based primer, for example, a paint defined in Japan Water Works Association Standard JWWA K 139 “Ductile Cast Iron Pipe Synthetic Resin Paint for Waterworks” is often used. The coating composition of the present invention can also be used as this top coat.

  On the other hand, the inner surface of the cast iron pipe is often subjected to epoxy resin powder coating or mortar lining in order to maintain high corrosivity and durability against long-term water flow.

  Since the coating composition of the present invention has good coating with various coating materials, it repairs the exposed part of the cut pipe end face and iron part of the cast iron pipe coated as described above on the pipe outer surface and pipe inner surface. It can be suitably used for use.

  The application area of the coating composition of the present invention in the metal tube is not particularly limited, and can be used for coating both the inner surface and the outer surface of the metal tube. In view of obtaining the effect of washing the coating composition with water, the coating composition is preferably used for a wetted part of a metal pipe, that is, for a wetted part of a cast iron pipe for drinking water such as for waterworks or for storing water.

  In this specification, the “water-contact part of a metal pipe” means a part that comes into contact with water in use. Specifically, when connecting not only the inner surface of a water pipe or a water storage pipe but also a metal pipe. Includes a portion of the connecting portion that contacts water. That is, the cut pipe end face and the joint part as described above are also included in the water contact portion, require the same anticorrosion treatment as the outer surface of the pipe, and come into contact with water in use. Accordingly, particularly preferable application areas of the coating composition of the present invention include, for example, a cut end face and a joint portion of a cast iron pipe used for a water pipe. Moreover, the area | region containing a cut-tube end surface is the most preferable from the meaning which can fully exhibit the quick-drying property of the coating composition of this invention.

<Epoxy resin>
As the epoxy resin, various polyepoxy compounds known in this technical field can be used, and examples thereof include bisphenol type epoxy resins obtained by reaction of bisphenols with epichlorohydrin. Specifically, it is obtained by reacting an epoxy resin consisting of a reaction product of epichlorohydrin and bisphenol A, an epoxy resin consisting of a reaction product of epichlorohydrin and bisphenol F, or a fatty acid with these epoxy resins. And modified epoxy resins such as amine-modified epoxy resins obtained by reacting amines such as alkanolamines and urethane-modified epoxy resins obtained by reacting with polyisocyanate compounds. Of these, bisphenol A type epoxy resins of epichlorohydrin and bisphenol A and modified epoxy resins thereof are preferred, and amine modified resins are more preferred from the viewpoints of drying properties, adhesion, and corrosion resistance.

  The weight average molecular weight of the epoxy resin is preferably in the range of 10,000 to 70,000. When the weight average molecular weight is less than 10,000, there are problems in adhesion, drying properties, physical properties of the coating film, and the like. When the weight average molecular weight is more than 70,000, there are problems in solubility, coating, and spray coating workability.

<Silane coupling agent>
The silane coupling agent used in the present invention is used for improving the adhesion to a metal tube, and specific examples thereof are not particularly limited. For example, vinyltrimethoxysilane, vinyltriethoxysilane are used. Vinyl-based alkoxysilanes such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldi Epoxy alkoxysilanes such as ethoxysilane and 3-glycidoxypropyltriethoxysilane; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxyp Methacrylic alkoxysilane such as pyrtriethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-aminopropyltri Methoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl)- Amino alkoxysilanes such as 2-aminoethyl-3-aminopropyltrimethoxysilane, ureido alkoxysilanes such as 3-ureidopropyltriethoxysilane, and sulfide alkoxysilanes such as bis (triethoxysilylpropyl) tetrasulfide. And the like. Of these, amino-based alkoxysilanes and epoxy-based alkoxysilanes are preferable from the viewpoint of interaction with the epoxy resin, and 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane are most preferable. These silane coupling agents can be used alone or in admixture of two or more.

  The content of the silane coupling agent in the coating composition of the present invention is preferably 1.0% by weight or more, more preferably 1.5% by weight or more, and most preferably 2.5% by weight or more. % By weight or less is preferable, 4.5% by weight or less is more preferable, and 3.0% by weight or less is most preferable. When the content of the silane coupling agent is less than 1% by weight, there is a tendency that the effect of improving the adhesion cannot be obtained. When the content is more than 5.0% by weight, there is a problem in the paint storage stability, and the gel is stored during storage. There is a case. Moreover, it is expensive as a raw material, and the paint unit price becomes high.

<Glycol ether solvent>
The glycol ether solvent used in the present invention is not particularly limited. For example, propylene glycol monoether such as propylene glycol monomethyl ether (PGMME), propylene glycol monoethyl ether, propylene glycol monopropyl ether, ethylene glycol monomethyl, and the like. Examples thereof include ethylene glycol monoethers such as ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether; diethylene glycol monoethers such as diethylene glycol monoethyl ether and diethylene glycol monobutyl ether. Among these, propylene glycol monoether, particularly PGMME, is preferable from the viewpoints of epoxy resin solubility and evaporation rate (dryability, coating workability). These solvents can be used alone or in admixture of two or more.

  The content of the glycol ether solvent in the coating composition of the present invention is preferably 1.0% by weight or more, more preferably 2.0% by weight or more, preferably 20.0% by weight or less, and 10.0% by weight. % Or less is more preferable. If the content of the glycol ether solvent is less than 1.0% by weight, the effect tends to be hardly exerted. If the content is more than 20.0% by weight, the durability and drying properties of the coating film are adversely affected. There is.

<Other solvents>
The coating composition of the present invention may contain other water-soluble solvent (a). Such a solvent is not particularly limited, but is a lower alcohol such as ethyl alcohol, isopropyl alcohol (IPA), Sec-butyl alcohol, t-butyl alcohol; methyl ethyl ketone; propylene glycol; water such as monoethylene glycol. For example, a solvent that dissolves in water at a miscibility level is preferable, for example, a solvent that dissolves in water at a mixing level. Moreover, the thing with the weak odor of the solvent itself is more preferable. These solvents can be used alone or in admixture of two or more.

  Further, in the present invention, it is preferable not to include a water-insoluble low-volatile solvent such as xylene from the viewpoint of odor control.

  In addition to the glycol ether solvent and the water-soluble solvent (a), the solvent may contain other solvents usually used in the field of metal tube paints, such as hydrocarbons such as toluene and cyclohexane; ethyl acetate, acetic acid Esters such as butyl and propylene glycol monomethyl ether acetate; ketones such as methyl isobutyl ketone and cyclohexanone; alcohols such as 1-butanol and isobutanol; ethyl-3-ethoxypropionate (EEP: trade name, manufactured by Eastman Kodak Company) ) And the like. These are used singly or in admixture of two or more in consideration of workability, paint stability, solubility, evaporation rate, safety, legal regulations and the like.

<Other ingredients>
In addition to the above components, the coating composition of the present invention may contain known pigments, additives, curing agents and the like as long as they do not affect the water quality, if necessary.

  In the coating composition of the present invention, it is desirable to adjust the thixotropic coefficient during coating to 2.0 to 5.0 in order to ensure coating workability. If the thixotropic coefficient of viscosity at coating is less than 2.0, the required film thickness cannot be applied due to sagging in dip coating, and if it exceeds 5.0, the fluidity (leveling property) decreases during spray coating. The finished appearance of is reduced. The thixotropic coefficient is mainly adjusted by the viscosity modifier and the type and amount of the pigment. Generally, in order to ensure the coating film performance, the thixotropy is determined after the pigment type and amount are determined. A method of adding a viscosity modifier to the shortage is taken.

  Moreover, it is preferable that the coating composition of this invention adjusts the coating-material non-volatile content at the time of coating to 25 to 55 weight%, in order to ensure coating workability | operativity. The paint non-volatile content is the weight of the paint component that remains after the paint component is volatilized or evaporated when the paint is heated under certain conditions, expressed as a percentage of the original weight of the paint. This means a solid content or pigment in a resin. If the non-volatile content during coating is less than 25% by weight, thick film coating becomes difficult in dip coating, and if it exceeds 55% by weight, the viscosity becomes too high. .

  The pigment used in the metal pipe coating composition of the present invention is for imparting sufficient colorability to the coating, and the content is not particularly limited, but is contained in the coating composition in an amount of 10 to 40% by weight. The content is preferably 15 to 35% by weight.

  Examples of the pigment include titanium oxide, iron oxide, carbon black (for example, trade name MA100, manufactured by Mitsubishi Chemical Corporation), cyanine blue, cyanine green, and the like; calcium carbonate, talc, barium sulfate (for example, Tsuchiya Kaolin) Kogyo Co., Ltd., average particle size of 0.5 μm, etc.), extender pigments such as clay; antirust pigments such as zinc phosphate, calcium phosphate, aluminum phosphomolybdate, and the like. These may be used alone or in combination of two or more if necessary.

  Other additives include defoamers made of silicone and organic polymers; surface conditioners made of silicone and organic polymers; viscosity modifiers made of amide wax and organic bentonite (sagging agents); silica, alumina, etc. Matting agents comprising: Dispersing agents comprising polycarboxylates, etc .; UV absorbers comprising benzophenone, hindered amine light stabilizers, phenolic antioxidants, etc .; known additives such as waxes . These can be used alone or in admixture of two or more if necessary.

  The coating composition of the present invention is preferably a one-pack type resin composition from the viewpoint of quick drying and improved workability.

<One-pack type epoxy resin paint>
When the coating composition of the present invention is a one-pack type epoxy resin coating, the Japan Ductile Iron Pipe Association Standard JDPA Z 2010 “Ductile Cast Iron Pipe Synthetic Resin Coating” is stipulated in the February 12, 2009 revision. .1 In addition to the above-mentioned epoxy resin, silane coupling agent, glycol ether solvent and other components described above, the following resins and modifications are applicable as long as they do not impair the effects of the present invention. Components such as agents and additives can also be added.

  Examples of such resins include acrylate or methacrylate copolymers containing styrene, vinyl acetate or butadiene, xylene resins, toluene resins, cyclopentadiene resins, coumarone indene resins, carboxylated acrylic modified SBR resins, and the like.

  Examples of the modifier include acrylate or methacrylate copolymer containing styrene, vinyl acetate or butadiene, coumarone indene resin, xylene resin, toluene resin, cyclopentadiene resin, carboxylated acrylic modified SBR resin and the like.

  Additives include acrylic copolymer, sodium salt of acrylic acid and maleic acid copolymer, acrylic polymer, organosilane, dimethylpolysiloxane, amide wax, xanthan gum, modified cellulose compound, cellulose acetate butyrate, hydroxyethyl cellulose, Aluminum stearate, cobalt naphthenate, zinc naphthenate, mineral oil, petrolatum, sodium dodecylbenzenesulfonate, poly (oxyethylene) alkyl ether, polyoxyalkylene fatty acid ester, 1,2-benzisothiazolin-3-one, bromonitro Examples include alcohol compounds, dicyclohexyl phthalate, methyl ethyl ketoxime, aqueous ammonia, N, N′-dimethylaminoethanol, and triethylamine.

<Method for producing coating composition>
For the production of the coating composition for metal pipes of the present invention, equipment conventionally used for coating production is used. The production method is not particularly limited. For example, after adding a pigment, an additive (pigment dispersant, viscosity modifier, etc.), a solvent, etc. to a commercially available epoxy resin or epoxy resin varnish, a dispersion treatment is performed using a roll mill, SG mill, disper, etc. By doing so, a desired coating composition can be obtained.

  The method for applying the coating composition for a metal pipe of the present invention to the metal pipe is not particularly limited, but it is applied by a method such as brush coating, roller coating, air spray coating, airless spray coating, dip coating or shower coat coating.

  The thickness of the applied coating film is preferably 150 μm or less, more preferably 100 μm to 50 μm. If it is thinner than 50 μm, durability and corrosion resistance may not be sufficient, and if it is thicker than 150 μm, drying property and low odor may not be sufficient.

  In the metal tube to which the coating composition of the present invention is applied, a highly volatile solvent such as toluene in the coating is first volatilized. Even if the water-soluble solvent remains in the coating film, it is eluted when the inside of the tube is washed. At that time, it is discharged together with the remaining volatile solvent such as toluene. Therefore, even if it is used for a water pipe or a water storage pipe, the solvent odor is hardly perceived from the water in contact with the coating film, and of course, there is an effect that the water quality is not adversely affected.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

  The coating composition produced in the following examples is based on the Japan Ductile Iron Pipe Association Standard JDPA Z 2010 “Ductile Cast Iron Pipe Synthetic Resin Coating” 4.1.1 epoxy resin paint defined in the February 12, 2009 revision. It is equivalent.

The detail of the component used in the Example and the comparative example is shown below.
-Epoxy resin varnish: solid content 40 wt% = amine-modified epoxy resin (weight average molecular weight of about 30000), solvent content 60 wt% = MEK (methyl ethyl ketone): TL (toluene): IPA (isopropyl alcohol): PMA (propylene glycol monomethyl) Mixture and pigment of ether acetate) = 18: 24: 12: 6 Pigment: Titanium oxide / carbon black / calcium carbonate (extreme pigment) / zinc phosphate rust preventive pigment (weight% in the composition is 10% each) .0 / trace amount / 18.2 / 4.3)
Silane coupling agent: 3-glycidoxypropyltrimethoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.)
・ PGMME: Propylene glycol monomethyl ether

Examples 1-7 and Comparative Examples 1-3
The components were mixed according to the composition shown in Table 1, and further dispersed to about 30 μm or less using a normal pigment dispersing apparatus to prepare each coating composition.

  About each obtained coating composition, the following tests were done and the performance as a coating composition and the performance of the coating film obtained were evaluated.

(1) Medium-resistant salt sprayability To confirm the long-term durability of the coating film, JIS K 5600-7-1 (General coating test method-Part 7: Long-term durability of the coating film-Section 1: Medium resistance) The test was carried out according to the basic salt sprayability.

  Each coating material produced in Examples 1 to 7 and Comparative Examples 1 to 3 was applied to a polished steel plate (150 × 100 mm) with a brush coating of 50 μm. And the crosscut was given with the cutter knife, the sodium chloride aqueous solution (5%) was sprayed, and the external appearance was observed. When no abnormalities in the appearance such as white rust, red rust and blisters were observed, no abnormality was found, and when any one of those abnormalities was observed, it was regarded as abnormal. In addition, it was not made into the observation object within 2 mm each of the both sides of a crosscut.

The results are shown in Table 1.
◎: No abnormality for 300 hours ○: No abnormality for 200 hours ○ △: No abnormality for 170 hours △: No abnormality for 120 hours ×: Abnormality for 120 hours

(2) Drying property The test was performed according to JIS K 5600-1-1 (Paint General Test Method—Part 1: General Rules—Section 1: Test General (Conditions and Methods)). Each coating material produced in Examples 1 to 7 and Comparative Examples 1 to 3 was spray-coated on one side of a polished steel plate (200 × 100 mm) by 50 μm. Then, the coated surface of the test piece was faced up, the plate was leveled and placed in a constant temperature and humidity room (temperature 23 ° C., humidity 50%), and the dry state was evaluated. What was hardened and dried within 10 minutes was marked with ○, and what was not hardened and dried within 10 minutes was marked with x. The results are shown in Table 1.

(3) Workability It was confirmed that there was no hindrance to brush application according to JIS K 5600-1-1 (5 to 40 ° C.). Brushed paint was applied to one side of a polished soft steel plate (500 × 200 × 1 mm), and the coating amount was applied once so that the dry film thickness was 50 μm, and workability was evaluated.
The results are shown in Table 1.
○: No problem in brush handling, △: Slight brush handling, x: Bad brush handling

(4) Odor test (leaching test)
Each paint produced in Examples 1 to 7 and Comparative Examples 1 to 3 was applied to a glass plate (200 × 70 × 2 mm) made of double-sided ground glass by brush coating with a thickness of 50 μm. And according to the JWWA Z108 water supply equipment-leaching test method, what dried the coated glass plate for 7 days was each immersed in 1 L of test water for 16 hours, and the odor in test water was evaluated. The water contact area was set to 15 cm ² / L. The results are shown in Table 1.

The evaluation standard of odor is as follows.
○: Odorless △: Weak odor ×: Odor

  From Table 1, in Examples 1-7, compared with Comparative Examples 1 and 2, it was confirmed that both of them were excellent in neutral salt sprayability and long-term durability was good. In Examples 1 to 7, it was confirmed that both the workability and the leachability were good and the odor was reduced as compared with Comparative Examples 1 and 3.

  From these results, it can be seen that when the silane coupling agent and the glycol ether solvent are used in combination in the epoxy resin coating, a low odor coating composition having good workability, drying properties and corrosion resistance can be obtained.

Example 8
The epoxy resin paint having the composition of Example 3 was cut from a ductile cast iron pipe (outer diameter: 68 mm, inner diameter: 56 mm) coated with zinc rich primer and synthetic resin paint as a pipe outer surface coating and epoxy resin powder coating as a pipe inner surface coating. 50 μm was applied to the tube end surface (cross section and tube outer surface side 2 mm, tube inner surface side 2 mm) by brush painting.

  About the obtained cast iron pipe, the appearance of the painted surface is not particularly problematic, and the water passage time is 30 minutes after painting and satisfies the tap water quality standard (TOC is 3 mg / L or less, no odor) in TOC and odor, Furthermore, there was no problem in the recognizability with the tube outer surface coating and the tube inner surface coating, and it was good.

Claims (8)

An epoxy resin coating composition for metal pipes, comprising a silane coupling agent and a glycol ether solvent as essential components. The coating composition according to claim 1, which is used for a wetted part of a metal tube. The coating composition according to claim 1 or 2, wherein the content of the silane coupling agent is 1 to 5% by weight. The coating composition according to any one of claims 1 to 3, wherein the content of the glycol ether solvent is 1 to 20% by weight. The coating composition according to any one of claims 1 to 4, wherein the metal pipe is a water supply pipe. The metal pipe which apply | coated the coating composition of any one of Claims 1-5. The metal pipe according to claim 6, wherein the application region is a wetted part. The metal pipe according to claim 6 or 7, wherein the metal pipe is a cast iron pipe and the application region is a cut end face of the pipe.