JPH067000B2 - Inner coated steel pipe for water supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an inner surface coated steel pipe used for water supply equipment. More specifically, the present invention relates to an inner coated steel pipe for waterworks, which has excellent water resistance, adhesion, and impact resistance and does not affect water quality at all.

[Conventional technology]

Conventionally, it is known that an epoxy resin is excellent as a coating film forming resin. However, it has a weak point that the water resistance is poor. In order to enhance the water resistance, steel pipes coated with tar epoxy resin paint or tar urethane resin paint have been used for steel pipes for sewerage as well as steel pipes for sewerage. These steel pipes have excellent water resistance, adhesion, and impact resistance, have been used for a long time, and have a track record of use. However, recently, it has been desired to develop a steel pipe for waterworks whose inner surface is coated with a new type of paint that does not contain tar.

The tar in the tar-epoxy resin coating material has a function as a coating material modifier that imparts water resistance to the coating film and also imparts flexibility, plasticity, and adhesion to the substrate. Japanese Patent Publication No. 58-
The ones described in JP-B No. 25,348, JP-B No. 58-46,134 and JP-A No. 55-36,263 are known. What is described in these publications is a liquid low-polymerization product of a monomer containing isopropenyltoluene. This is an excellent modifier when used by blending with paints for other purposes, but when used for waterworks,
There is a problem as described below.

It is also known to use scaly pigments as paint-blending pigments. In particular, it is used for coating the inner surface of slurry transportation pipes that require abrasion resistance. However, it has never been used in connection with the coating modifier of the present invention for an internally coated steel pipe for waterworks that has no slurry or the like.

[Problems to be solved by the invention]

The object of the present invention is to replace the tar epoxy resin-coated steel pipe and the tar urethane resin-coated steel pipe, which have been widely used in steel pipes for conventional waterworks, with the problem that the epoxy resin-coated steel pipe and the urethane resin-coated steel pipe are weak in water resistance. To strengthen the water resistance, strengthen the adhesion with the substrate, plasticize the coating film,
An object of the present invention is to develop a modifier which gives flexibility and does not contain tar, and to provide a steel pipe having a paint containing the modifier coated on its inner surface.

In order to give the coating film flexibility and flexibility, there is a means to add a plasticizer to the paint components, but in general, the plasticizer is a low molecular weight substance, and it has the problem of being dissolved in water and impairing the water quality. It is not preferable. Although a polymer substance has to be used as a component that does not impair the water quality characteristics, this causes a problem that the coating film cannot be provided with flexibility. It is possible to use a substance having a chain structure of aliphatic carbon atoms such as rubber, but these have a problem that they are incompatible with the epoxy resin.

Chroman resins and petroleum resins are resins that do not dissolve in water, have excellent water resistance, and have a molecular weight in the middle of high and low molecular weight, and are suitable for the above purpose, but conventional oil-based paints, Although a modified resin having a degree of compatibility with an alkyd resin paint has been obtained, there is a problem that this modified resin also has a poor compatibility with an epoxy resin.

When the liquid low-polymerization product of isopropenyltoluene is used as a modifier, potassium permanganate consumption in a water dissolution test, taste,
There is a problem that it is not preferable in terms of odor. In addition, if a modifier that imparts flexibility and flexibility is added to the coating film, the cohesive force, tensile strength, and elongation of the coating film may be reduced.

It is a test of a coating film of an inner surface coated steel pipe for waterworks, and there are a temperature gradient test and a water vapor permeability test described below as indicators of long-term durability, but the amount of the modifier of the present invention added to the coating film is too small. However, there has been a problem that the test does not pass even if the amount is too large.

Usually, an extender pigment is added to the paint, but if the blending ratio of this pigment is too low, neither the temperature gradient test nor the water vapor permeability test will pass, and if it is too large, the water vapor permeability test result will also deteriorate. It has occurred.

Therefore, the object of the present invention is to adjust the mixing ratio of the cross-linking resin component of the coating film, the modifier, and the extender pigment to comprehensively prevent corrosion,
Providing internally coated steel pipes for waterworks with coatings that meet requirements such as adhesion, chemical resistance, water quality suitability, weather resistance, compatibility between components, temperature gradient test suitability, steam permeability test characteristics, impact test suitability, etc. It is to be.

Generally, the thicker the coating, the better the anticorrosion and chemical resistance of the coating. However, from the viewpoint of improving the efficiency of coating, if the thick coating property that enables thick coating by one coating is improved, the viscosity of the coating becomes high and the coating workability deteriorates. Another object of the present invention is to provide an inner surface coated steel pipe for waterworks, which is coated with a paint having good thick coating properties while maintaining good coating workability.

[Means for solving problems]

The present inventors have conducted research to solve the above problems, epoxy resin is suitable as a cross-linking resin component of the coating film from the viewpoint of water resistance, corrosion resistance, coating workability, water quality characteristics, cost, etc. There, water resistance is imparted to this coating film, and as a modifier for imparting plasticity and flexibility, a low-polymerization degree resin such as a chroman resin or a petroleum resin is modified to have good compatibility with an epoxy resin, In order to improve the cohesive strength, tensile strength, and elongation of the coating film, a scale-like pigment is blended with a part of the extender pigment, and in order to improve the thick coating property, a spring modification imparting agent is added, and a cross-linking resin is further added. The inventors have found that the problems can be solved by adjusting the blending ratio of the components, the modifier and the extender pigment, and completed the present invention.

That is, the present invention relates to (1) a group consisting of a coumarone resin, an aliphatic petroleum resin, an aromatic petroleum resin, a dicyclopentadiene petroleum resin, and a xylene resin with respect to a total amount of 100 parts by weight of an epoxy resin and an amine curing agent. 40 to 100 parts by weight of a coating modifier having a hydroxyl value of 50 to 300, which is one or more resins selected from the above, and 10 of scale-like pigments.
Content of 100 to 200 parts by weight of an extender pigment of 35 to 35% by weight, 100 parts by weight of fatty acid amide wax as a denaturation modifier, 50 to 150 parts by weight of oxidized polyethylene wax, and 150 to 300 parts by weight of organic bentonite. Is an inner surface coated steel pipe for waterworks, in which an epoxy resin paint containing 0.5 to 1.5 parts by weight as a main component is coated on the inner surface of the steel pipe with respect to 100 parts by weight of the main component of the paint before adding a curing agent, (2) The inner surface coated steel pipe for waterworks as described in (1) above, wherein the epoxy resin is a reaction product of bisphenol A and epichlorohydrin, (3) the scale-like pigment is one selected from mica, MIO and glass flakes, or The above (1), (2) consisting of two or more
An inner surface coated steel pipe for waterworks.

The above epoxy resin refers to the following epoxy resin itself, and the amine curing agent refers to the organic amine compound itself.

As the epoxy resin, a reaction product of one or more selected from bisphenol A, bisphenol F and bisphenol AD with epichlorohydrin can be used, but a bisphenol A type epoxy resin is most preferable. The resin of this type may be liquid or solid, and may be used in combination. When only liquid is used, the hardness of the coating film is improved, but it is preferable to use both liquid and solid from the viewpoints of interlayer adhesion and temperature gradient test. As the amine-based cured product, a modified polyamine-based, amine adduct-based, polyamide-based, polyamide adduct-based amine-based curing agent can be used, and the modified polyamine-based curing agent is particularly preferable in terms of corrosion resistance and water quality.

As the coating modifier, one or more resins selected from the group consisting of coumarone resin, aliphatic petroleum resin, aromatic petroleum resin, dicyclopentadiene petroleum resin and xylene resin are used as epoxy resin. In order to improve the compatibility of the above, a resin having a phenolic hydroxyl group or an alcoholic hydroxyl group introduced therein is used. The hydroxyl value is 50 to 3
00 is a suitable range. When it is less than 50, the compatibility with the epoxy resin is poor, and when it exceeds 300, the water resistance is poor.

When the paint modifier of the present invention is added to the epoxy resin paint,
Although the water resistance, plasticity, and flexibility of the coating film are improved, the problem arises that the cohesive force, tensile strength, and elongation of the coating film decrease. In order to solve this, 10 to 35 parts by weight of the scaly pigment is added to 100 parts by weight of the extender pigment. This improves the tensile strength and elongation of the coating film. Examples of the flaky pigment include mica, MIO, glass flakes, and the like, and mica is excellent in terms of toning of the paint and improvement of the amount of adhesion. If the scaly pigment is less than 10% by weight in the pigment, the effect of increasing tensile strength and elongation cannot be exerted on the coating film, and if it exceeds 35% by weight, the viscosity of the coating composition increases and the coatable viscosity cannot be maintained.

As other extender pigments, extender pigments usually used in paints such as talc, kaolin, calcium carbonate, barite can be used.

In the present invention, in order to obtain a coating having good thick coating characteristics while maintaining good coating workability, a salt modification imparting agent is added. Examples of the salt modification imparting agent include silicone type, castor oil type, fatty acid amide wax, oxidized polyethylene wax, and organic bentonite type. The amount of addition is 0.5 to 100 parts by weight of the main component of the coating material before adding the curing agent.
1.5 parts by weight is preferred. If it is less than 0.5 part by weight, the increase in the amount of adhesion cannot be obtained, and if it exceeds 1.5 parts by weight, the effect is saturated and it is uneconomical. Fatty acid amide wax, in terms of increase of adhesion amount, maintenance of denaturation over time, and interlayer adhesion,
The combined use of oxidized polyethylene wax and organic bentonite is excellent. With respect to 100 parts by weight of the fatty acid amide wax, 50 to 150 parts by weight of polyethylene oxide wax and 150 to 300 parts by weight of organic bentonite wax are preferable. If the amount of the fatty acid amide wax is larger than this ratio, the amount of adhesion will be increased, but there will be a decrease in aging and a decrease in interlayer adhesion. When the amount of the oxidized polyethylene wax is large, the interlaminar adhesion can be improved, but the effect of increasing the amount of the deposited polyethylene becomes small, and the browning deterioration with time occurs. When the amount of organic bentonite is large, it is possible to maintain the aging modification and improve the interlayer adhesion.
It cannot be expected that the adhesion amount will increase. That is, there are three types of optimum blending ratio ranges.

Further, the epoxy resin coating material to be coated on the steel pipe for water supply of the present invention has a total amount of the epoxy resin and the amine-based curing agent, the coating material modifying agent, the extender pigment, and the walnut modifying agent in the optimum mixing ratio range.

40 to 100 parts by weight of the paint modifier is subjected to a temperature gradient test with respect to 100 parts by weight of the total amount of the epoxy resin and the amine-based curing agent,
The water vapor permeability of the coating film is in the optimum range. If it is less than 40 parts by weight, the period until blistering occurs in the temperature gradient test becomes short and the value of water vapor permeability becomes large. Again 100
When the amount is more than 40 parts by weight, the same result is obtained when the amount is less than 40 parts by weight.

Also for extender pigments, the optimum range is 100 to 200 parts by weight. If it is less than 100 parts by weight, the number of days until blistering occurs in the temperature gradient test is short, and the water vapor permeability becomes large. If it exceeds 200 parts by weight, the water vapor permeability will increase.

Further, as the paint, in addition to the above main components, a coloring pigment, various additives and a solvent which are usually used are added and dispersed to obtain a paint. The inner surface of the steel pipe is subjected to rusting, after degreasing treatment, if necessary, after coating with a shop primer, a curing agent is mixed immediately before coating, and coating is performed by air spraying by a centrifugal coating method to obtain an inner coated steel pipe for waterworks.

The above-mentioned temperature gradient test and water vapor permeability test are tests of the coating film of the inner surface coated steel pipe for waterworks and are indicators of long-term durability.

The temperature gradient test is a test in which the coating film side is dipped in water of 60 ° C. and the steel plate side is dipped in water of 15 ° C. to see the occurrence of blisters, that is, blistering, but there is no blistering for 15 days. Things are indicators.

In the water vapor permeability test, the coating film was peeled off, and it was measured by the number of g of the water vapor permeated for 24 hours per 1 m ² per 100 μm of the coating film. It is measured by a water vapor permeability measuring device manufactured by Lyssy. The index is 14 g / m ² · 24 hr · 100μ or less.

As an evaluation of the inner surface coated steel pipe of the present invention, JWWAK-11
There are 5 standards (Japan Waterworks Association standards), and the coating film performance and the dissolution test in water are evaluated separately. As the physical properties of the coating film,
The case of a steel pipe is estimated for the coating film normally applied to a steel plate. The coating film of the coated steel pipe of the present invention passes standards such as a bending test of 38 mm or more, a direct peeling area of 3 cm ² or less in an impact test, and a characteristic of not peeling indirectly. The tar epoxy resin paint JISK-5664 is also applied.
Passes the corrosion resistance test (alkali resistance, acid resistance, volatile oil resistance, salt spray resistance, moat resistance, etc.). For example, as the chemical resistance, there is no abnormality when immersed in 5% sulfuric acid, 5% caustic soda solution and No. 3 volatile oil for 30 days. In the salt spray test (30 days) of JWWA K-115, there was no abnormality, the adhesion with the shop primer was 25 to 27 kg / cm ² , and the interlayer adhesion was also good.

Even in the dissolution test for water, which is essential as a water supply paint, JW was performed under the drying conditions of 20 ° C × 75% RH × 30 days.
WA K-115 less turbidity 0.5 degrees of water is a standard chromaticity 1 degree or less, KM _n O ₄ consumption 2.0ppm or less, phenols 0.005ppm below, amine, without Jian detection, odor, All of the internally coated steel pipes for waterworks according to the present invention have passed the standard with no taste abnormality, and have obtained results.

[Action]

As a coating film for internally coated steel pipes for waterworks, epoxy resin coating film is weak in water resistance, flexibility, coumarone resin modified by giving a hydroxyl value so as to be compatible with epoxy resin, which is poor in flexibility, Solving the problem by blending a modifying agent composed of petroleum resin and xylene resin, the cohesive force, tensile strength, and elongation of the coating film caused by the blending of the modifying agent are reduced.
Solved by the binding effect of the mixture of scale-like pigments, and by the combination effect of this modifier and extender pigments including scale-like pigments, it is compatible with the temperature gradient test and water vapor permeability test required for internally coated steel pipes for waterworks. I am letting you.

The difficulty of thick coatability due to the addition of modifiers, etc. is improved by improving the thick coatability while lowering the viscosity during coating by blending a browning modifier.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples.

Wall thickness 1 whose inner surface was cleaned by grid blasting
The following paint was centrifugally applied by air spray to the inner surface of a water pipe having a diameter of 4.3 mm, an outer diameter of 1.826 mm and a length of 12 m.

As an epoxy resin, AER331, AE manufactured by Asahi Kasei
R661 was used, and a modified polyamine, Fuji Chair 4030 manufactured by Fuji Kasei was used as a curing agent.

As a paint modifier, a phenol-modified coumarone resin (manufactured by Shin Nisshin Chemical) having a hydroxyl value of 60 and a softening point of 110 ° C or a dicyclopentadiene-based petroleum resin (Quinton 1 manufactured by Nippon Zeon Co., Ltd.)
700) was used. As the extender pigment, mica having an average particle diameter of 30 to 45 μ was used as the scaly pigment, and talc was used as the other extender pigment.

If the hydroxyl value of the phenol-modified coumarone resin is 50,
It was not compatible with the epoxy resin. Also, the hydroxyl value is 350
In this case, the peeling width of the cross cut portion in the salt spray test was 8 mm, and the water resistance was deteriorated.

As the solvent, toluene and isopropyl alcohol were used for the main component other than the curing agent, and toluene and isopropyl alcohol were used for the curing agent.

As a siliency modification imparting agent, a fatty acid amide wax is 0.2% by weight, 0.2% by weight of oxidized polyethylene, and
0.6% by weight of organic bentonite was used.

As a comparative example, a case in which a flake pigment mica is not used is shown for each case where a phenol-modified coumarone resin or a dicyclopentadiene-based petroleum resin is used as a modifier.

The blending ratio and the coating film physical properties are shown in Table 1.

In Example 1- (1), 40 parts by weight of (Example 3) and 100 parts by weight of (Example 4), where the phenol-modified coumarone resin is 100 parts by weight of epoxy resin + amine curing agent,
The results of the temperature gradient test, which is the most severe test of water resistance, are shown in Table 1- (2) when 35 parts by weight of Comparative Example 3 and 110 parts by weight of Comparative Example 4 are used.

In Example 1- (1), 100 parts by weight of (Example 5), (Example 6), and 20 parts by weight of the extender pigments of talc and mica are defined as 100 parts by weight of the epoxy resin + amine curing agent.
0 parts by weight, (Comparative Example 5) 90 parts by weight, (Comparative Example 6) 22
Table 1- (3) shows the results of the temperature gradient test in the case of 0 part by weight.

In Table 1- (1), regarding the content of the scale-like pigment in the extender pigment, an example near the upper limit of the range of 10 to 35% by weight is described in Example 1, and an example near the lower limit is described in Example 2. ,
As a comparative example, with respect to the extender pigment, in the case of 8% by weight (Comparative Example 7) and 40% by weight (Comparative Example 8), the tensile strength, the elongation and the degree of deterioration of Erichsen of the coating film are shown in Table 1. −
Shown in (4).

Using the coating material prepared in this example, the denaturing agent was changed and the inner surface was cleaned by grit blasting in the same manner as in Table 1 to have a wall thickness of 14.3 mm and an outer diameter of 1.826 mm.
Table 2 shows the results of centrifugal coating by air spraying on the inner surface of a 12 m long steel pipe for water supply, and examination of the maximum amount of adhesion, interlayer adhesion, and deterioration of aging deterioration.

As a result, the range of 0.5 to 1.5% by weight is effective as the agent for imparting denaturation when the modifying material and extender pigment of the present invention is used, but especially fatty acid amide wax, oxidized polyethylene wax, organic It is clear that the combination of bentonite is the most preferable, and the ratio thereof is preferably 1: 1: 2 to 3. Only with the fatty acid amide wax, the interlayer adhesion is slightly inferior, and the aging deterioration is also observed. Only the organic bentonite type has a slight decrease in the maximum deposition amount. In Example L in which 0.5% by weight or less, that is, 0.4% by weight of the main ingredient was added, the increase in the maximum adhesion amount was slight. As a comparative example, in the case where no salt modification imparting agent was added at all, the amount of adhesion was small and thick coatability was not obtained.

Tables 3 and 4 show the test results of the water-coated inner surface coated steel pipes of the examples with respect to the Japan Waterworks Association standards and the like. All satisfy the standards.

[Advantages of the Invention] The internally coated steel pipe for waterworks of the present invention is a tar-epoxy resin internally coated steel pipe which has been conventionally used without using tar, due to the binding effect of the unique modifier of the present invention and the scaly pigment. In comparison with tar urethane resin inner surface coated steel pipes, the coating properties were superior or inferior.

Even the dissolution test in water completely satisfied the standard of JWWA K-115. It is an extremely useful invention in practice as an internally coated steel pipe for waterworks.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masaaki Uehara 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Stock Company, Kimitsu Works (72) Inventor ▲ Sokita Yoshida 690 Tsuyazaki, Tsuyazaki, Munakata-gun, Fukuoka (72) ) Inventor Hiroshi Kido 4-7-6-303 Nakai, Kokurakita-ku, Kitakyushu-shi, Fukuoka (72) Inventor Kazuhiro Masunaga 1-35 Sachimachi, Ashiya-cho, Onga-gun, Fukuoka (56) Reference JP-A-52-76335 (JP, A)

Claims (3)

[Claims] 1. A total amount 1 of epoxy resin and amine curing agent.
One part or two or more kinds of resin selected from the group consisting of coumarone resin, aliphatic petroleum resin, aromatic petroleum resin, dicyclopentadiene petroleum resin, and xylene resin, and having a hydroxyl value of 50 per 100 parts by weight. To 300 parts by weight of the coating modifier, 100 to 200 parts by weight of an extender pigment containing 10 to 35% by weight of a scaly pigment, and 100 parts by weight of a fatty acid amide wax as a salt modification agent, to an oxidized polyethylene wax. 0.5 to 100 parts by weight of the main component of the coating material before adding the curing agent to the salt-modifying agent consisting of 50 to 150 parts by weight and organic bentonite 150 to 300 parts by weight.
An inner surface coated steel pipe for waterworks, which is obtained by coating the inner surface of the steel pipe with an epoxy resin paint whose main component is about 1.5 parts by weight. 2. The internally coated steel pipe for water supply according to claim 1, wherein the epoxy resin is a reaction product of bisphenol A and epichlorohydrin. 3. The internally coated steel pipe for waterworks according to claim 1 or 2, wherein the flaky pigment is one or more selected from mica, M10 and glass flakes.