JPH10226760A - Powder coating material for inner surface of cast iron pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder coating material for the inner surface of a cast iron pipe which is excellent in effects on reducing the consumption of the residual chlorine in tap water. SOLUTION: A powder coating material for coating the inner surface of a cast iron pipe is prepd. by incorporating silica having an average particle size of 1-50μm into the same without incorporating a nitrogen-base curative and by adjusting the gel time (stringiness method) at 180 deg.C to 10-200sec. Pref. examples of a powder coating material contg. no nitrogen-base curative are an epoxy powder coating material contg. 100 pts.wt. epoxy resin having an epoxy equivalent of 400-2,000 and 2-30 pts.wt. acid anhydride curative; an acrylic powder coating material contg. 100 pts.wt. acrylic resin having an epoxy equivalent of 250-1,000 and 4-50 pts.wt. polycarboxylic acid curative; and an acrylic- epoxy hybrid powder coating material contg. an epoxy resin having an epoxy equivalent of 400-2,000 and an acrylic resin having an acid value of 10-200 in an equivalent ratio of epoxy group to carboxyl group of (1:0.6)-(1:1.6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder coating for the inner surface of a cast iron pipe, and more particularly to a powder coating used for coating the inner surface of a cast iron pipe for water supply. , "Tap water" means "tap water") and a powder coating excellent in the effect of suppressing the consumption of residual chlorine required.

[0002]

2. Description of the Related Art Heretofore, as a paint to be applied to the inner surface of a cast iron pipe, an epoxy powder paint using a nitrogen-based hardener such as an imidazoline-based, hydrazide-based, amide-based, dicyandiamide-based, or imidazole-based has been used. Was.

However, when the epoxy powder coating using the above-mentioned nitrogen-based hardener is applied to the inner surface of a cast iron pipe for water supply, the nitrogen atoms contained in the hardener reduce the chlorine ion concentration in the tap water. There is a problem that the water quality at the terminal consumption stage of the tap water is reduced due to the reduction.

[0004]

SUMMARY OF THE INVENTION The present invention solves the problems of the paint used for coating the inner surface of the conventional cast iron pipe for water supply as described above, and has an effect of suppressing the consumption of residual chlorine in tap water. An object is to provide an excellent powder coating for the inner surface of a cast iron pipe.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a method for removing residual chlorine in tap water by using a powder coating containing no nitrogen-based hardener as a powder coating used for coating the inner surface of a cast iron pipe for water supply. While suppressing consumption, average particle size 1 ~
Including 50 μm of silica and one of the above powder coatings
By adjusting the gel time (stringing method) at 80 ° C. to 10 to 200 seconds, it is possible to solve the problem that is likely to occur due to non-use of the nitrogen-based curing agent.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The powder coating for an inner surface of a cast iron pipe of the present invention is constituted by a powder coating not containing a nitrogen-based hardener.
Preferred examples thereof include, for example, 100 parts by weight of an epoxy resin having an epoxy equivalent of 400 to 2000, 2 to 30 parts by weight of an acid anhydride-based curing agent, and silica having an average particle diameter of 1 to 50 μm. An epoxy powder coating material whose gel time (stringing method) at 180 ° C. is adjusted to 10 to 200 seconds, and a polycarboxylic carboxylic curing agent 4 based on 100 parts by weight of an acrylic resin having an epoxy equivalent of 250 to 1000
Containing silica having an average particle diameter of 1 to 50 μm, and having a gel time (stringing method) at 180 ° C. of 10
Acrylic powder paint having an acid value of 10 to 200 with respect to 100 parts by weight of an epoxy resin having an epoxy equivalent of 400 to 2000 and an epoxy group: carboxyl equivalent ratio of 1: 0. 6-1: 1.6
And an average particle diameter of 1 to 50 μm.
Gel time at 180 ° C containing m of silica (stringing method)
And an acrylic-epoxy hybrid powder paint adjusted to 10 to 200 seconds.

[0007] Examples of the epoxy resin serving as the base resin of the epoxy powder coating include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, halogenated bisphenol A type epoxy resin, and halogenated novolak type epoxy resin. Resins, terephthalic acid epoxy resins, etc., may be used alone or in combination of two or more.

In these epoxy resins, the epoxy equivalent is preferably from 400 to 2,000 for the following reason. That is, when the epoxy equivalent of the epoxy resin is less than 400, the reactivity of the epoxy powder coating becomes strong, so that the gel time thereof becomes faster with time, pinholes are likely to be generated, or the fixability may be increased. There is. Further, when the epoxy equivalent of the epoxy resin exceeds 2,000, the reactivity of the epoxy powder coating decreases, the effect of suppressing the generation of pinholes decreases, or the Erichsen value becomes 1 mm or less, and May not be able to follow the deformation of the cast iron pipe, and the coating film may be cracked.

Examples of the acid anhydride-based curing agent for curing the epoxy resin include phthalic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, hymic anhydride, and hymic anhydride, Benzophenone tetracarboxylic acid, ethylene glycol bis trimellitate, maleic anhydride-styrene copolymer and the like can be mentioned.

The amount of the acid anhydride-based curing agent is preferably 2 to 30 parts by weight based on 100 parts by weight of the epoxy resin. If the amount of the acid anhydride-based curing agent is less than 2 parts by weight based on 100 parts by weight of the epoxy resin, a sufficient cross-linking density cannot be obtained, and therefore, long-term corrosion resistance and adhesion may not be obtained. If the amount of the acid anhydride-based curing agent is more than 30 parts by weight based on 100 parts by weight of the epoxy resin, the amount of the curing agent is too large, the molecular weight of the cured coating film becomes small, and the number of unreacted acid groups is large. As a result, the water resistance may decrease.

The acrylic resin used as the base resin of the acrylic powder coating has an epoxy equivalent of 250 to 1
000 is preferable, and the Japan Water Works Association Standard (JWW
Acrylonitrile prohibited in A) is not used. Examples of usable monomers include ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, and methacrylic acid. Examples include methyl, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, styrene, acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, and glycidyl acrylate. Can be

The reason why the epoxy equivalent of the acrylic resin is preferably 250 to 1000 is as follows. That is, when the epoxy equivalent of the acrylic resin is less than 250, the reactivity of the acrylic powder coating may be too strong to gel at the time of coating preparation, or the gel time of the coating may be extremely short, resulting in poor storage stability. If the epoxy equivalent of the acrylic resin exceeds 1,000, the reactivity of the acrylic powder coating decreases, the effect of suppressing the generation of pinholes decreases, or the Erichsen value becomes 1 mm or less, and the coating film becomes cast iron. There is a possibility that it becomes impossible to follow the deformation of the tube, and cracks may occur in the coating film.

Examples of the polycarboxylic acid curing agent used as a curing agent for the acrylic resin include adipic acid, sebacic acid, azelaic acid, dodecane diacid, succinic acid, OSK-DA SL-20 [trade name, Okamura Oil Co., Ltd.], OSK-DA SL-16 [trade name, Okamura Oil Co., Ltd.], OSK-DA UL-16 [trade name,
Okamura Oil Co., Ltd.] and OSK-DA UL-20 [trade name, manufactured by Okamura Oil Co., Ltd.].

The compounding amount of the polycarboxylic acid curing agent is as follows:
The amount is preferably 4 to 50 parts by weight based on 100 parts by weight of the acrylic resin. If the amount of the polycarboxylic acid-based curing agent is less than 4 parts by weight based on 100 parts by weight of the acrylic resin, a sufficient cross-linking density cannot be obtained, and therefore, sufficient corrosion resistance and adhesion may not be obtained. If the compounding amount of the polyvalent carboxylic acid-based curing agent is more than 50 parts by weight based on 100 parts by weight of the acrylic resin, too much curing agent may cause gelation at the time of coating preparation, or the gel time may become extremely short and stored. There is a possibility that the stability is deteriorated.

As the epoxy resin serving as the base resin of the acrylic-epoxy hybrid powder coating, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resin, halogenated bisphenol A type epoxy resin, halogenated novolak type epoxy resin, terephthalic acid epoxy resin, and the like. These may be used alone or in combination of two or more.

The epoxy resin serving as the base resin of the acrylic-epoxy hybrid powder coating preferably has an epoxy equivalent of 400 to 2,000 for the following reason. That is, when the epoxy equivalent of the epoxy resin is less than 400, the reactivity of the acrylic-epoxy hybrid powder coating becomes stronger, so that the gel time becomes faster with time, and pinholes are easily generated or the sticking property is reduced. May be stronger. Also,
When the epoxy equivalent of the epoxy resin exceeds 2,000, the reactivity of the acrylic-epoxy hybrid powder coating decreases, the effect of suppressing the generation of pinholes decreases, and the Erichsen value becomes 1 mm or less, and the coating film becomes thin. May not be able to follow the deformation of the cast iron pipe, and the coating film may be cracked.

The acrylic resin in the acrylic-epoxy hybrid powder coating has an acid value of 10
It is preferably from 200 to 200. When the acid value of the acrylic resin is less than 10, the number of functional groups is too small to obtain a sufficient crosslink density, so that the coating film becomes brittle, and when the acid value of the acrylic resin exceeds 200, the reactivity becomes low. Becomes too large to cause gelation during preparation of the coating material, or the gel time of the coating material becomes extremely short, resulting in poor storage stability. In addition, the molecular weight of the cured coating film becomes small, so that the coating film may become brittle.

The mixing ratio of the epoxy resin to the acrylic resin in the acrylic-epoxy hybrid powder coating composition is 1: 0.6 in the equivalent ratio of epoxy group to carboxyl group.
It is preferable that the amount be in the range of １1 to 1.6.
This is for the following reason. That is, when the mixing ratio of the acrylic resin is less than the above range, crosslinking is not sufficiently performed, so that there is a possibility that long-term corrosion resistance and adhesion may not be secured, and the mixing ratio of the acrylic resin is higher than the above range. Similarly, since crosslinking is not sufficiently performed, there is a possibility that long-term corrosion resistance and adhesion cannot be ensured.

Further, in any of the powder coatings, silica having an average particle size of 1 to 50 μm is contained. This is because it has an action of suppressing the generation of pinholes based on vaporized components such as air and moisture contained in the tube holes.

The silica having an average particle diameter of 1 to 50 μm is
100 parts by weight of the base resin of each powder coating (that is, epoxy resin for epoxy powder coating, acrylic resin for acrylic powder coating, and epoxy resin and acrylic resin for acrylic-epoxy hybrid powder coating) 10
It is preferably from 100 to 100 parts by weight. If the amount of the silica is less than 10 parts by weight based on 100 parts by weight of the base resin, a sufficient effect of suppressing pinhole generation and an effect of preventing blistering due to a temperature gradient cannot be obtained. If the amount is more than 100 parts by weight with respect to 100 parts by weight of the base resin, the melt viscosity of the powder coating becomes high, so that a sufficient effect of suppressing pinhole generation cannot be obtained.

In each of the above powder coatings, in addition to the above components,
Further, a coloring pigment, an extender, a leveling agent, an anti-dripping agent, a catalyst and the like can be appropriately added.

Examples of the coloring pigment include titanium oxide (TiO ₂ ) and carbon black.
Examples of the extender include talc, calcium carbonate, barium sulfate, and the like. Examples of the leveling agent include Acronal (trade name,
Acrylic oligomer-based leveling agent, manufactured by BASF),
Modflow powder (trade name, acrylic oligomer-based leveling agent, manufactured by Monsanto Co., Ltd.) and the like, and examples of the anti-dripping agent include fine powder silica, Aerosil 200 (trade name, manufactured by Nippon Aerosil Co., Ltd.) and the like. . The catalyst promotes the reaction between the epoxy resin and the acrylic resin when preparing the acrylic-epoxy hybrid powder coating, or cure reaction when the epoxy resin is cured with an acid anhydride-based curing agent, if necessary. However, JWWA does not permit the use of phosphorus-based catalysts, so when using catalysts, it is necessary to use imidazole-based or imidazoline-based nitrogen-containing catalysts. However, in the case of a catalyst, unlike a nitrogen-based curing agent, one having a low nitrogen content is used,
Even if the amount used is large, it is as small as 1 part by weight or less with respect to 100 parts by weight of the resin, so that the consumption of residual chlorine is not substantially affected.

The powder coating of the present invention is prepared, for example, by dry-blending the above-mentioned base resin such as epoxy resin and acrylic resin, curing agent, silica and the like with a Henschel mixer and melt-kneading with a co-kneader or the like. Will be Then, the obtained mixture is pulverized by a hammer mill or the like, and coarse particles are cut by a sieve, and used as a powder coating.

The powder coating of the present invention must have a gel time at 180 ° C. (stringing method) adjusted to 10 to 200 seconds. When the gel time at 180 ° C. (stringing method) is shorter than 10 seconds, gelation occurs at the time of preparation of the coating material, and the storage stability is deteriorated due to aging during storage, and the gel time at 180 ° C. (stringing method). Is 200
If the time is longer than seconds, it becomes impossible to sufficiently suppress the generation of pinholes based on vaporized components such as air and moisture contained in the holes of the cast iron tube.

[0025]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Examples 1 to 10 and Comparative Examples 1 to 3 Examples 1 to 10 and Comparative Example 1 have the compositions shown in Tables 1 to 4.
~ 3 powder coatings were prepared. The unit of the numerical value of each component in the table is parts by weight. In addition, details of products indicated by a product name or the like in the table are described after a table in which they are first displayed, and the description thereof is omitted in subsequent tables.

[0027]

[Table 1]

* 1: Epototo YD-013 (trade name) Epoxy resin with an epoxy equivalent of 860 manufactured by Toto Kasei Co., Ltd. * 2: Epomic R-304K (trade name) Epoxy equivalent 920 manufactured by Mitsui Petrochemical Industries, Ltd. * 3: Fine Dick A-223S (trade name) Acrylic resin with an epoxy equivalent of 630 manufactured by Dainippon Ink and Chemicals, Inc.

* 4: Almatex PD-6200 (trade name) Acrylic resin with an epoxy equivalent of 720 manufactured by Mitsui Toatsu Chemicals, Inc. * 5: Joncryl SCX-839 (trade name) Acid value 105 manufactured by Johnson Polymer Co. Acrylic resin for hybrids * 6: Trimellitic anhydride An acid anhydride curing agent manufactured by Mitsubishi Gas Chemical Co., Ltd. * 7: Dotecanedioic acid A polycarboxylic acid curing agent manufactured by Ube Industries, Ltd.

* 8: Mini Zeal 15 μm (trade name) Silica with an average particle diameter of 15 μm manufactured by US Silica * 9: Chiona 575 (trade name) Titanium white manufactured by SCM CHEMICALS * 10: Mitsubishi Carbon # 45 (trade name) Furnace type carbon manufactured by Mitsubishi Carbon Corporation * 11: Acronal LR8820 (trade name) Acrylic oligomer-based leveling agent manufactured by BASF

[0031]

[Table 2]

* 12: Epomic R-392 (trade name) Epoxy resin with an epoxy equivalent of 550 manufactured by Mitsui Petrochemical Industry Co., Ltd. * 13: Epomic R-363 (trade name) Epoxy manufactured by Mitsui Petrochemical Industry Co., Ltd. Epoxy resin with an equivalent weight of 740 * 14: Johnsoncryl SCX-817 (trade name) Acrylic resin for hybrid with an acid value of 55 manufactured by Johnson Polymer * 15: Johnsoncryl SCX-819 (trade name) Acid value of 75 manufactured by Johnson Polymer Acrylic resin for hybrid

* 16: Johncryl SCX-804 (trade name) Acrylic resin for hybrid having an acid value of 15 manufactured by Johnson Polymer * 17: BYK-360P (trade name) Powder leveling agent adsorbed on silica manufactured by BYK * 18: Actilon NXJ-60 (trade name) Propyl imidazole catalyst manufactured by Shinthrone (content: 60% by weight)

[0034]

[Table 3]

* 19: Epotote YD-012PK
(Trade name) Epoxy resin with an epoxy equivalent of 740 manufactured by Toto Kasei Co., Ltd. * 20: Tetrahydrophthalic anhydride, an acid anhydride curing agent manufactured by Shin Nippon Rika Co., Ltd. * 21: TMEG500 (trade name) Shin Nippon Rika Anhydride curing agent [Ethylene glycol-bis (anhydrotrimellitate)] * 22: Pestagon B-31 (trade name) Humids imidazoline catalyst

[0036]

[Table 4]

* 23: Dicyandiamide, a nitrogen-based curing agent manufactured by Nippon Carbide Industry Co., Ltd. * 24: 2-Phenylimidazoline, a nitrogen-based curing agent manufactured by Shikoku Chemicals, Inc. * 25: Adipic dihydrazide Nippon Hydrazine Industry Co., Ltd. Made, nitrogen-based curing agent

The above-mentioned powder coating is prepared by dry blending each component with a Henschel mixer (manufactured by Mitsui Miike Seisakusho Co., Ltd.) and melt-kneading with a co-kneader (manufactured by Buss Co., Ltd.). Nibaudaru Co., Ltd.], and coarse particles were cut with a 60-mesh sieve to obtain a powder coating having an average particle diameter of 50 μm. In addition,
The above Examples 4 to 8 are acrylic-epoxy hybrid powder coatings. The equivalent ratio of epoxy group: carboxyl group in these coatings is 1: 1 in Example 4, and 5 in Example 5.
Is 1: 0.75, Example 6 is 1: 1 and Example 7 is 1:
1, Example 8 is 1: 1.

Examples 1 to 10 prepared as described above
The gel time (stringing method) at 180 ° C. of the powder coatings of Comparative Examples 1 to 3 was measured. The measuring method is as follows,
The measurement results are shown in Tables 5 to 8 below.

Gel Time Measurement Method 100 mg of each of the above powder coatings was placed on a hot plate kept at a constant temperature of 180 ° C. Starting from the point when the whole was melted, the powder coating was pulled upward at regular intervals while stirring with a spatula. The time until the molten paint no longer pulls the string is measured, and it is defined as a gel time (second).

Further, the above Examples 1 to 10 and Comparative Example 1
The Erichsen value and the residual chlorine consumption of the powder coatings Nos. 1 to 3 were measured. The measurement methods are as follows, and the measurement results are shown in Tables 5 to 8 below.

Measurement method of Erichsen value Each powder coating material was applied to a shot blasted surface of a cold-rolled steel plate having a thickness of 2 mm and a size of 70 mm × 150 mm so as to have an average film thickness of 200 μm, and baked in a furnace at 180 ° C. for 20 minutes. After preparing a coated plate and cooling the coated plate, JIS-K-54
00 Extrude until a crack appears in the coating film according to the Erichsen test specified in 8.2.2, and let it be the Erichsen value.

Method for measuring residual chlorine consumption Each powder coating material was applied to both sides of a cold-rolled steel sheet having a thickness of 0.8 mm and a size of 70 mm × 150 mm so that the average film thickness was 200 μm each, and the coating was performed at 180 ° C. for 20 minutes. Baking to make a coated plate.

Next, 1 liter of tap water adjusted with sodium hypochlorite so that the residual chlorine concentration becomes 1.0 ppm was placed in a glass beaker having an internal volume of 1 liter, and the coating area was reduced to 500 cm ² in the tap water. The coated plate is immersed in such a way that it becomes sealed.

After standing in a dark place at 20 ° C. for 24 hours, the consumption of residual chlorine in the immersion water was measured according to JWWA-K-139-1992.
Measure based on

The above evaluation results are summarized in Tables 5 to 8. Table 5 shows the evaluation results of Examples 1 to 4, Table 6 shows the evaluation results of Examples 5 to 8, and Table 7 Examples 9-1
0 shows the evaluation results, and Table 8 shows the evaluation results of Comparative Examples 1 to 3.

[0047]

[Table 5]

[0048]

[Table 6]

[0049]

[Table 7]

[0050]

[Table 8]

As is clear from the comparison between the evaluation results of Examples 1 to 10 shown in Tables 5 to 7 and the evaluation results of Comparative Examples 1 to 3 shown in Table 8, Examples 1 to 10 As compared with No. 3, the consumption of residual chlorine was small. Further, Examples 1 to
No. 10 is JWWW with an Erichsen value of 3.0 to 5.0 mm.
It was within an appropriate range that satisfied the requirement of an Erichsen value of 3.0 mm or more specified in AG-112, and showed that the coating film could sufficiently follow even when the cast iron tube was deformed.

[0052]

As described above, according to the present invention, a powder coating for the inner surface of a cast iron pipe excellent in the effect of suppressing the consumption of residual chlorine required for tap water can be provided.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C09D 133/14 C09D 133/14 163/00 163/00 (72) Inventor Shuichi Onizuka 2-41-1, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture No. Kawakami Paint Co., Ltd. (72) Inventor Kenji Suda 2-41-1, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Inside Kawakami Paint Co., Ltd. (72) Inventor Yasuhiro Tsuchiya 2-41-1, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture No. Kawakami Paint Co., Ltd.

Claims (2)

[Claims] 1. A powder coating containing no nitrogen-based curing agent, comprising silica having an average particle size of 1 to 50 μm, and having a temperature of 180 ° C.
Wherein the gel time (stringing method) is adjusted to 10 to 200 seconds. 2. A powder coating containing no nitrogen-based curing agent,
Epoxy resin 100 having an epoxy equivalent of 400 to 2000
Epoxy powder paint containing 2 to 30 parts by weight of acid anhydride-based curing agent with respect to parts by weight, epoxy equivalent of 250 to 1000
Acrylic powder paint containing 4 to 50 parts by weight of a polycarboxylic acid-based curing agent with respect to 100 parts by weight of acrylic resin, or epoxy resin 100 having an epoxy equivalent of 400 to 2000
An acrylic resin having an acid value of 10 to 200 with respect to parts by weight is used in an equivalent ratio of epoxy group: carboxyl group of 1: 0.6 to 1:
The powder coating for an inner surface of a cast iron pipe according to claim 1, which is an acrylic-epoxy hybrid powder coating containing 1.6 or less.