JPH10323616A - Manufacture of outer surface coated cast iron pipe and outer surface coated cast iron pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form at a low temperature a paint film which is excellent in adhesion to substrate, impact resistance, flexibility, etc., good in corrosion resistance, finish properties by a method wherein powder coating material composed of a specific composition is applied to an outer surface of a cast iron pipe. SOLUTION: An amount of a phenolic hydroxyl group of a hardener of 200-800 g/eq average phenolic hydroxyl group equivalent, being a compound expressed by the formula 1 is 0.5 to 1.2 equivalent to 1 equivalent of an epoxy group of bisphenol A type epoxy resin of 600 to 2000 g/eq epoxy equivalent at 75 to 128 deg.C softening point. Further, an amount of dicyandiamide to the hardener is 3 to 20 wt.%. Powder coating material wherein an amount of imidazole cure accelerator and/or imidazoline cure accelerator to an amount of the hardener is 0.1 to 15.0 wt.%, is applied onto an outer surface of a cast iron pipe. Thereby, a paint film which is excellent in adhesion to a substrate, impact resistance, flexibility, etc., and good in corrosion resistance, and finish properties can be formed at a low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
A method of producing an externally coated cast iron pipe formed by coating a coating film with excellent impact resistance, flexibility, etc., good corrosion resistance and finish, on the outer surface of the cast iron pipe using powder paint that can be baked at low temperature. The present invention relates to a manufactured exterior painted cast iron pipe.

[0002]

2. Description of the Related Art Conventionally, cast iron pipes have been used for water supply and sewerage, industrial water supply, agricultural water,
It is widely used as a piping material for gas. Cast iron pipes are classified into straight pipes, deformed pipes, and joining parts such as press rings according to their forms, but are collectively referred to herein as cast iron pipes.

[0003] The outer surface of the cast iron pipe is coated with an epoxy-based, acrylic-based or polyester-based anti-corrosion paint at room temperature for drying at room temperature. It is desired to streamline the coating process, such as shortening the drying and hardening curing time (reducing the curing place), and to improve the coating work environment. In addition, the corrosion resistance of the damaged portion of the paint film due to the impact during transportation or burial of the painted cast iron tube is also an object to be improved.

Therefore, a coating film having excellent adhesion to a substrate, impact resistance, flexibility, etc., and excellent corrosion resistance and finish is formed on the outer surface of a cast iron pipe by using a powder coating which can be baked at a low temperature. There is a need for a method to do this.

As a technique for applying a powder coating material to a cast iron pipe, for example, Japanese Patent Publication No. 62-28193 discloses a solid epoxy resin (a) having a softening point of 60 to 150 ° C. and an epoxy equivalent of 400 to 2,000, an amine, Amin adduct,
Polyamide, polyamide adduct, acid group-containing polyester, polyvalent carboxylic acid, acid anhydride, dicyandiamide,
A curing agent (b) selected from imidazoles and the like, and at least 40 parts of a silica-based inorganic filler (c) per 100 parts (parts by weight, hereinafter the same) of the epoxy resin (a) are blended if necessary. Powder I, comprising a coloring agent and extender pigment (d), and a mixture of the pulverized product of the component (b) and a part of the component (c) and / or a part of the component (d).
An epoxy resin-based powder coating obtained by mixing 0 parts or less and 80 parts or more of powder II obtained by mixing, melting, kneading, and pulverizing the component (a) with the remaining components (c) and (d). It has been disclosed.

[0006] The epoxy resin-based powder coating is water-resistant.
Boiling water resistance, salt water resistance, impact resistance, abrasion resistance, flexibility
It gives a coating film with excellent smoothness, has excellent storage stability, and has excellent dispersion, such as an epoxy resin-based powder coating, in which the dispersion of each component in the coating is uniform and the coating film performance does not vary. Despite its performance, 230 ℃ of steel plate at the time of painting
Have to be preheated and baked.

[0007] Japanese Patent Publication No. 40066 discloses a coating composition which has improved the disadvantages of high-temperature preheating at the time of coating, in which 100 parts of a curable resin composed of a polyepoxy compound and a polycarboxy compound are imidazoline as a curing accelerator. A resin composition for powder coating containing 0.01 to 3 parts of a reaction product of a base compound and a carboxylic acid is disclosed.

This composition is excellent in that it is sufficiently crosslinked and cured at a low temperature and in a short time (15 minutes at 150 to 160 ° C. in the examples) and gives a coating film having an excellent appearance. There is a drawback that sufficient adhesion cannot be obtained and the desired corrosion resistance cannot be obtained.

Japanese Patent Application Laid-Open No. 7-224234 discloses an epoxy resin 1 having an epoxy equivalent of 400 to 1300.
An epoxy powder coating material comprising 100 parts, 1 to 20 parts of an organic acid hydrazide and 10 to 100 parts of silica powder having an average particle diameter of 5 to 50 μm, and to which imidazoles, imidazolines and the like may be added if necessary. Melting time at 10 ℃
Epoxy powder coatings for the inner surface of cast iron pipes exhibiting a viscous behavior having a minimum viscosity of 100 poise or less and a curable angle of 1.5 or more for up to 180 seconds are disclosed.

This powder coating is a coating having excellent performance of suppressing pinholes in the coating film while having basic properties such as water resistance, but when used for coating the outer surface of a cast iron pipe, There is a disadvantage that the impact resistance and the bending property are insufficient.

That is, in the case of a cast iron pipe coated with a conventional powder coating, a coating film having excellent adhesion to a substrate, impact resistance, flexibility, and the like, and having good corrosion resistance and finish is produced at a low temperature. The fact is that they cannot be formed.

Since the cast iron tube has a very large heat capacity, it is an important issue for bake-type paints to save energy by using low-temperature baking or utilizing residual heat during inner surface coating.

In order to satisfy such a low-temperature baking property, it is necessary to enhance the curability of the powder coating. For example, as an epoxy resin used as a main component of the powder coating, a solid bisphenol A type is used. For epoxy resin,
A technique of using a novolak epoxy resin in combination is known.

However, in this case, although the curability is improved, there is a problem in that the physical properties of the coating film, for example, the adhesion to the substrate are reduced.

[0015]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems of the prior art, and as a result, completed the present invention.

That is, according to the present invention, the softening point is 75 to 12
The formula (I) is based on 1 equivalent of the epoxy group of the bisphenol A type epoxy resin (A) having an epoxy equivalent of 600 to 2200 g / eq at 8 ° C.

[0017]

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A compound represented by the formula: wherein m is 1 to 4 and having an average phenolic hydroxyl equivalent of 200 to 80.
The amount of the phenolic hydroxyl group of the curing agent (B) of 0 g / eq is 0.5 to 1.2 equivalents, and the amount of the dicyandiamide (C) to the curing agent (B) is 3 to 20% (% by weight,
The same applies hereinafter), and the amount of the imidazole-based curing accelerator and / or the imidazoline-based curing accelerator (D) is 0.1 to 15.0% based on the amount of the curing agent (B). A method for producing an externally coated cast iron pipe wherein the paint is applied to the outer surface of the cast iron pipe (Claim 1), wherein the temperature at which the powder paint is applied to the outer surface of the cast iron pipe is 140 to 180 ° C.
The powder coating composition further comprises an inorganic filler (E) comprising a bisphenol A type epoxy resin (A), a curing agent (B), a dicyandiamide (C) and a curing accelerator (D). 3. The method according to claim 1, wherein the powder coating contains 0 to 100% of the total amount (claim 3), wherein the powder coating material is a bisphenol A type epoxy resin (A), a curing agent (B), and dicyandiamide (C). And a curing reaction agent (D) produced by a precursor reaction, wherein the precursor reaction product has a gel time of 10 to 40 seconds when heated at 200 ° C. by the method of ISO 8130-6. The present invention relates to a method according to claim 1, 2 or 3 (claim 4), and an externally coated cast iron pipe obtained by the method according to claim 1, 2, 3 or 4 (claim 5).

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the softening point is 75 to
Epoxy group 1 of bisphenol A type epoxy resin (A) having an epoxy equivalent of 600 to 2200 g / eq at 128 ° C.
With respect to the equivalent, the general formula (I):

[0020]

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Wherein m is from 1 to 4 wherein the average phenolic hydroxyl equivalent is from 200 to 80.
The amount of the phenolic hydroxyl group of the curing agent (B) of 0 g / eq is 0.5 to 1.2 equivalents, and the amount of the dicyandiamide (C) to the curing agent (B) is 3 to 20%; And a powder coating in which the amount of the imidazole-based curing accelerator and / or the amount of the imidazoline-based curing accelerator (D) is 0.1 to 15.0% based on the amount of the curing agent (B).

Bisphenol A type epoxy resin (A)
Is a component used as a base resin of the powder coating, and has a softening point of 75 to 128 ° C., and more preferably 90 to 110 ° C.
At 200C, the epoxy equivalent is from 600 to 2200 g / eq, further from 650 to 1100 g / eq, for example, bisphenol A (2,2-bis (4-hydroxyphenyl)
Propylene) is reacted with epihalohydrin such as epichlorohydrin to produce a low-molecular-weight epoxy resin, and then is subjected to addition polymerization of bisphenol A to adjust to a desired molecular weight (two-step method).

When the softening point of the bisphenol A type epoxy resin (A) is lower than 75 ° C., the powder coatings are liable to be fused to each other during storage of the powder coatings. And the coating film formation (140) utilizing the residual heat at the time of low-temperature baking or inner coating, which is the object of the present invention.
To 180 ° C.). When the epoxy equivalent of the bisphenol A type epoxy resin (A) is less than 600 g / eq, generally, the molecular weight becomes small and the softening temperature becomes low.
When q exceeds q, the molecular weight generally increases and the softening temperature increases.

The base resin of the powder coating used in the present invention is:
It is a bisphenol A type epoxy resin having good adhesion, flexibility and chemical resistance, and having a softening point and an epoxy equivalent as described above, so that it has good adhesion, flexibility and chemical resistance. It is difficult for powder coatings to fuse with each other during storage.
A powder coating with good finish can be obtained at a low temperature of 80 ° C.

Specific examples of the bisphenol A type epoxy resin (A) include, for example, a commercial product, Toto Kasei Co., Ltd.
Epototo YD-014 (epoxy equivalent 900-1)
000 g / eq, softening point 91-102 ° C.), Epototo YD-017 (epoxy equivalent 1750-2100 g / e)
q, softening point 117-127 ° C), Epotote YD-90
4 (epoxy equivalent 900-1000 g / eq, softening point 9
6-107 ° C.), Epototh YD-907 (epoxy equivalent 1300-1700 g / eq, softening point 117-127)
° C), Yuka Shell Epoxy Co., Ltd. Epicoat 100
3F (epoxy equivalent 700-800 g / eq, softening point about 96 ° C.), Epicoat 1004F (epoxy equivalent 875
~ 975 g / eq, softening point about 103 ° C), Epicoat 1
005F (epoxy equivalent 950-1050 g / eq, softening point about 107 ° C.), Araldite XAC5007 manufactured by Ciba-Geigy Japan (epoxy equivalent 600-700 g)
/ Eq, softening point about 90 ° C), Araldite GT7004
(Epoxy equivalent of 730 to 830 g / eq, softening point of about 10
0 ° C), Araldite GT7097 (epoxy equivalent 16
50 to 2000 g / eq, softening point of about 120 ° C.). These may be used alone or in combination of two or more. Among them, Epicoat 1003F, Epicoat 1005F, and the like are preferable from the viewpoint of the finish (leveling property) in low-temperature baking.

The general formula (I) used in the present invention:

[0027]

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A compound having a phenolic hydroxyl group equivalent of 200 to 800 g / eq (curing agent (B)) represented by the formula (where m is 1 to 4) is used as a curing agent for bisphenol A type epoxy resin (A). It is a component to be performed. Since the curing agent (B) is used as the curing agent, flexibility can be imparted to the cured coating film. In addition, since the phenolic hydroxyl group equivalent is 200 to 800 g / eq, the coating material has a high softening point and is hardly blocked during storage, but has high reactivity and good low-temperature curability. When the average phenolic hydroxyl group equivalent is less than 200 g / eq, the softening point of the coating material decreases, blocking between powder coating materials easily occurs during storage, and when it exceeds 800 g / eq, the reactivity decreases, Low temperature curing becomes difficult.

The compound represented by the general formula (I) may contain unreacted bisphenol A. When bisphenol A is contained, the content is high, and is 30% with respect to the total of the compound represented by the general formula (I) and bisphenol A. When bisphenol A is contained, the curing agent (B) (mixture of the compound represented by the general formula (I) and bisphenol A) has a phenolic hydroxyl equivalent of 200 to 8 as described above.
00 g / eq.

The compound represented by the general formula (I) can be obtained, for example, by reacting a bisphenol A type epoxy resin with bisphenol A.

Those having m of less than 1 in the general formula (I) cannot be present because a bisphenol type epoxy resin is used as a raw material. On the other hand, if m exceeds 4, the reaction tends to proceed too much during the synthesis, making the synthesis difficult.

Specific examples of the curing agent (B) include TH-4100 (a phenolic hydroxyl equivalent of about 725 g / eq, a softening point of about 110 ° C.) manufactured by Toto Kasei Co., Ltd., which is a commercially available product.
Epicure 171 (phenolic hydroxyl equivalent: 200-286 g / eq, softening point: about 80 ° C.), Epicure 170 (phenolic hydroxyl equivalent: 286-400 g / eq, softening point: about 90 ° C.) manufactured by Yuka Shell Epoxy Co., Ltd. can give. These may be used alone or in combination of two or more. Among them, EpiCure 170 is preferable from the viewpoint of storage stability and finish (leveling property).

Dicyandiamide (C) has the formula:

[0034]

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Is a component used as a curing agent for the bisphenol A type epoxy resin (A), and is used in combination with the curing agent (B). By using dicyandiamide (C) in combination with the curing agent (B), it is possible to improve the adhesion to the substrate and obtain a powder coating having high corrosion resistance.

The powder coating used in the present invention may further contain an imidazole-based curing accelerator and / or an imidazoline-based curing accelerator (D) in order to improve low-temperature baking properties.
Is included. The imidazole-based curing accelerator and the imidazoline-based curing accelerator have a general formula:

[0037]

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Wherein R ¹ is a hydrogen atom, for example, an alkyl group having 1 to 17 carbon atoms such as a methyl group or an ethyl group, a phenyl group, and R ² is a hydrogen atom or a methyl group. As a specific example, 2MZ (2-methylimidazole) manufactured by Shikoku Chemical Industry Co., Ltd.
PZ (2-phenylimidazole), C ₁₁ Z (2-undecyl imidazole), C ₁₇ Z (2-heptadecyl imidazole), 2MZL (2- methyl imidazoline), 2
E · 4MZL (2-ethyl-4-methylimidazoline)
And so on. These may be used alone or in combination of two or more. Of these, 2M
Z is preferred from the viewpoint of the curing acceleration function.

The amount of the phenolic hydroxyl group of the curing agent (B) per one equivalent of the epoxy group of the bisphenol A type epoxy resin (A) in the powder coating used in the present invention is 0.1%.
5 to 1.2 equivalents, further 0.5 to 1.0 equivalents,
And the amount of dicyandiamide (C) with respect to the curing agent (B) is 3 to 20%. Further, the amount of the imidazole-based curing accelerator and / or the imidazoline-based curing accelerator (D) relative to the curing agent (B) is 0.1 to 15.0%, and more preferably 0.5 to 10%. Curing agent (B) for 1 equivalent of epoxy group of bisphenol A type epoxy resin (A)
When the amount of the phenolic hydroxyl group is less than 0.5 equivalent, a sufficiently cured product cannot be obtained, and mechanical strength such as impact resistance becomes poor. On the other hand, if it exceeds 1.2 equivalents, unreacted curing agent remains in the coating film, resulting in poor curability. On the other hand, if the amount of dicyandiamide (C) is less than 3% with respect to the curing agent (B), the expected adhesion to the substrate cannot be obtained, and the cathode peelability in the corrosion resistance test is not improved. On the other hand, if it exceeds 20%, curing shrinkage strain is generated, which adversely affects the appearance of the coating film such as gloss. Further, when the amount of the curing accelerator (D) with respect to the curing agent (B) is less than 0.1%, the curing is not promoted, and when the amount exceeds 15.0%, the reactivity becomes too high and blocking occurs. And storage stability becomes poor.

The powder coating used in the present invention may further contain an inorganic filler (E) such as an extender such as calcium carbonate, barium sulfate or silica.

When the inorganic filler (E) is blended, the blending amount is based on the total amount of the bisphenol A type epoxy resin (A), the curing agent (B), dicyandiamide (C) and the curing accelerator (D). 100% or less, furthermore 0 to 5
A range of 0% is preferred. If the amount of the inorganic filler (E) exceeds 100%, the melt viscosity increases, the wettability with the substrate decreases, and in this case, the adhesion tends to be poor. In addition, the formation of a continuous coating film tends to be difficult.

In the powder coating used in the present invention, various fired coloring pigments such as carbon black, titanium white, and red iron oxide may be added in addition to the inorganic filler (E). Further, a thermoplastic resin such as a flow regulator at the time of melting, an anti-repellent agent, and a petroleum resin may be blended.

In the present invention, the powder coating is applied to the outer surface of a cast iron tube, preferably a coating film is formed (baked) at 140 to 180 ° C., to produce an outer surface coated cast iron tube.

The cast iron tube is generally 75 to 2600 mm
It is important from the viewpoint of energy saving that φ is generally large, such as 10 mm or more in wall thickness, large in heat capacity, and low in the temperature during baking. The powder coating used in the present invention is, for example, 8 to 16 minutes at 140 ° C. and 2 hours at 160 ° C.
It can be cured at a low temperature and in a short time of 1 to 2 minutes at 180 ° C. for 4 minutes, which is preferable from the viewpoint of energy saving. When curing, it may be baked and cured,
When the inner surface of a cast iron pipe is coated with an epoxy resin powder coating or the like, the outer coating film can be cured by the residual heat.

Further, a coating film having a film thickness of usually 60 to 200 μm can be formed by a usual method such as electrostatic powder coating or fluid immersion coating. If necessary, the cast iron pipe may be subjected to a pre-painting treatment such as a shot blast treatment before painting. In the case of post-baking, the baking conditions are usually 15
It is about 5 to 20 minutes at 0 to 200 ° C.

In order to improve the low-temperature curability of the powder coating used in the present invention, if necessary, a bisphenol A type epoxy resin (A), a curing agent (B) and a curing agent (C) may be used.
The precursor reaction may be performed in the presence of the curing accelerator (D).

The precursor reaction is carried out in advance in a range where the powder coating can be obtained, so that the unreacted functional groups remaining are reduced as much as possible because it is difficult to react during the film forming process. This is to make it printable. In other words, it is carried out to increase the reactivity of the functional groups involved in the reaction to maximize the performance of the cured coating film and to enable low-temperature baking. In this sense, by the precursor reaction,
It is preferable to adjust the gel time of the paint when heated at 200 ° C. to 10 to 40 seconds by the method of ISO 8130-6. If the gel time is shorter than 10 seconds, the reaction will proceed too much and the melt viscosity will increase, resulting in poor adhesion to the substrate and poor coating film appearance. On the other hand, when the time exceeds 40 seconds, the expected low-temperature curability becomes insufficient.

The precursor reaction can be carried out by controlling the temperature of the extruder at 85 to 110 ° C. and adjusting the residence time of the extruder during the production of the paint. Moreover, after extrusion, it can be carried out by a method of aging at a temperature of about 40 to 80 ° C.

According to the production method of the present invention as described above, a coating film having excellent adhesion, impact resistance, flexibility, etc., good corrosion resistance, and good finish is formed on the outer surface of a cast iron tube by baking at a low temperature. Can be.

The thus produced outer surface coated cast iron pipe of the present invention is obtained by forming a coating film having a thickness of usually 60 to 200 μm from the powder coating used in the present invention on the outer surface of the cast iron pipe. Yes, it has desirable characteristics as described above.

As a preferred embodiment of the production method of the present invention, taking a deformed tube as an example, first, the inner surface of the deformed tube preheated to about 200 ° C. is powder-coated, and after the coating is completed, the inner surface is masked if necessary. Then, with respect to one equivalent of the epoxy group of the bisphenol A type epoxy resin (A) having a softening point of 75 to 128 ° C. and an epoxy equivalent of 600 to 2200 g / eq, the general formula (I):

[0052]

Embedded image

Wherein m is from 1 to 4 wherein the average phenolic hydroxyl equivalent is from 200 to 80.
The amount of the phenolic hydroxyl group of the curing agent (B) of 0 g / eq is 0.5 to 1.2 equivalents, and the amount of the dicyandiamide (C) to the curing agent (B) is 3 to 20%; A powder coating in which the amount of the imidazole-based curing accelerator and / or the amount of the imidazoline-based curing accelerator (D) is 0.1 to 15.0% based on the amount of the curing agent (B); A powder paint having a gel time of 10 to 40 seconds when heated at 200 ° C. is applied to the outer surface of a cast iron pipe at about 160 ° C. by the method of ISO 8130-6, and 140 to 160
A method of forming a coating film at a temperature of ° C. In this case, since the powder coating on the inner and outer surfaces can be performed in a continuous process, productivity can be improved in terms of energy saving and space saving.

[0054]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments.

The raw materials used below are shown in Table 1.

[0056]

[Table 1]

The evaluation methods performed below are summarized below.

(Finishability) Painted ductile cast iron members manufactured in Examples and Comparative Examples described later were used. The painted surface of the painted ductile cast iron member was visually evaluated according to the following criteria.

◎: Smoothness with little unevenness ：: Smoothness with unevenness か な り: Slightly unevenness and poor smoothness ×: Extremely unevenness and extremely poor smoothness

(Corrosion resistance) The coated ductile cast iron members manufactured in the following Examples and Comparative Examples were subjected to a 1
Make a straight wound (length 10cm) on the book, JIS K
The maximum value of the cathode peeling width after 500 hours under the conditions of the salt water spray test of 9.1 of 5400 was evaluated according to the following criteria.

：: less than 5 mm on one side from the cut wound Δ: 5 mm or more and less than 10 mm on one side from the cut wound ×: 10 mm or more on one side from the cut wound

(Impact resistance) Painted ductile cast iron members manufactured in Examples and Comparative Examples described later were used.

20 ° C. on the painted side of the painted ductile cast iron member
And DuPont impact test (1/2 inch (impact part) x 50)
0 g (load) × 50 cm (height)), and the state of the coating film at the impact portion was evaluated according to the following criteria.

：: Damage of the coating film only at the impact portion Δ: Damage of the coating film at the impact portion and floating of the coating film at a portion other than the impact portion ×: Damage of the coating film at the impact portion and peeling of the coating film around the impact portion

(Curability) A gauze containing methyl ethyl ketone was lightly applied to the coating films produced in Examples and Comparative Examples to be described later, and the coating film was reciprocated 10 times so as to be wiped. did.

◎: No abnormality ：: There is a slight trace on the coating film, but there is no loss of gloss. ：: No dissolution of the coating film is observed, but gloss disappears.

(Bending resistance) Tin plate (150 × 50 ×
0.3 mm) was polished using ^# 180 paper to obtain a test piece.

A powder coating was applied to the test piece to a thickness of about 100 μm.
And baked at 160 ° C. for 10 minutes.

The bending resistance test was conducted according to JIS K 5400, 8.1 (bending resistance), and the diameter of the mandrel of the bending tester was 10 m.
m and evaluated according to the following criteria.

：: No cracking or peeling was observed in the coating film ×: Cracking or peeling occurred in the coating film

(Water Quality Test) A double-sided frosted glass (200 × 70 × 2 mm) having flat sides was used as a test piece. A test piece was coated with a powder coating material on both sides and at an end in a size of 120 × 70 mm on one side, and dried in a drying oven at an ambient temperature of 180 ° C. for 15 minutes.
Bake for a minute.

The test was performed according to the method of JWWA K-139 and evaluated.

：: All items passed ×: Some items failed

Production Example 1 (Production of Powder Coating) 100 parts of Epicoat 1005F, Epicure 170
34 parts, cyanide amide (manufactured by Nippon Carbide Co., Ltd.)
3.4 parts, 2 parts MZ (Shikoku Chemical Industry Co., Ltd.) 0.7 parts,
2.0 parts of Mitsubishi Carbon MA100 (carbon black manufactured by Mitsubishi Chemical Corporation), 20.0 parts of barium sulfate, and 0.6 part of Acronal 4F were mixed with a Super Mixer Co., Ltd.
(Kawada Seisakusho) to make a granular uniform mixture, and then using a co-kneader (manufactured by Swissbus) to adjust the shaft rotation speed so that the passage time is 45 seconds at a casing temperature of 95 ° C and a shaft temperature of 35 ° C. A precursor reaction was performed simultaneously with the melt mixing. After cooling, it was pulverized using an ACM pulverizer (manufactured by Hosokawa Micron Co., Ltd.) so as to have an average particle size of 35 μm to prepare a powder coating.

Production Example 2 (Production of Powder Coating) After extruding using a co-kneader in Production Example 1,
Further, the molten mixture was kept at 50 ° C. for 24 hours,
After aging by the method of SO 8130-6 so that the gel time of the coating when heated at 200 ° C. became 15 seconds, the coating was pulverized so that the average particle diameter became 35 μm to prepare a powder coating.

Example 1 A ductile cast iron member (70 × 150 × 20 mm) was subjected to a shot blast treatment to obtain SSPC-SP5 (white metal). The treated plate is heated at 170 ° C in a baking furnace.
The powder paint obtained in Production Example 1 was immediately applied to the ductile cast iron member taken out of the baking furnace by electrostatic spray coating so that the coating thickness became 100 μm.
It was left in a room at 25 ° C. to form a cured coating film. The coating was started when the temperature of the ductile cast iron member was 160 ° C, and the temperature at the end of the coating was 155 ° C.

Examples 2 to 8 and Comparative Examples 1 to 4 Painted ductile cast iron members were prepared in the same manner as in Example 1 by using paints having the compositions shown in Table 2 and manufactured in the same manner as in Production Example 1. The performance was evaluated. Table 2 shows the results.

Example 9 A coated ductile cast iron member was prepared in the same manner as in Example 1 using the paint prepared by the method of Production Example 2 with the composition shown in Table 2, and the performance was evaluated. Table 2 shows the results.

[0079]

[Table 2]

[0080]

According to the present invention, when an externally coated cast iron pipe is manufactured by the method of the present invention, it is possible to bake a coating film having excellent adhesion to a substrate, impact resistance, flexibility, etc., and good corrosion resistance and finish at a low temperature. it can.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C09D 5/03 C09D 5/03 163/02 163/02 (72) Inventor Masahiko Saito 1-12-1, Kitahorie, Nishi-ku, Osaka-shi, Osaka No. 19 Kurimoto Iron Works Co., Ltd. (72) Inventor Yoshisada Michiura 1-112 Kitahorie, Nishi-ku, Osaka-shi, Osaka No. 19 Kurimoto Iron Works Co., Ltd. No. 17 Nippon Paint Co., Ltd.

Claims (5)

[Claims] 1. A bisphenol A type epoxy resin (A) having a softening point of 75 to 128 ° C. and an epoxy equivalent of 600 to 2200 g / eq per 1 equivalent of an epoxy group of the general formula (I): (Wherein m is 1 to 4), wherein the curing agent (B) has an average phenolic hydroxyl equivalent of 200 to 800 g / eq and the amount of phenolic hydroxyl groups is 0.5 to 1.
2 equivalents, the amount of dicyandiamide (C) is 3 to 20% by weight based on the amount of the curing agent (B), and the amount of the imidazole-based curing accelerator and / or the amount of the imidazoline-based curing accelerator (D) is A method for producing an externally coated cast iron pipe, characterized in that a powder coating material having an amount of 0.1 to 15.0% by weight based on the amount of the curing agent (B) is applied to the outer surface of the cast iron pipe. 2. The method according to claim 1, wherein the temperature at which the powder coating is applied to the outer surface of the cast iron pipe is 140 to 180 ° C. 3. The powder coating composition further comprises an inorganic filler (E) based on the total amount of bisphenol A epoxy resin (A), curing agent (B), dicyandiamide (C) and curing accelerator (D). The production method according to claim 1, wherein the content is 0 to 100% by weight. 4. The powder coating material is a precursor reaction product produced by a precursor reaction of a bisphenol A epoxy resin (A), a curing agent (B), a dicyandiamide (C) and a curing accelerator (D). The precursor reaction product is IS
The method according to claim 1, 2 or 3, wherein the coating has a gel time of 10 to 40 seconds when heated at 200C according to the method of O8130-6. 5. An externally coated cast iron pipe obtained by the method according to claim 1, 2, 3 or 4.