JPH036191B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an inner-coated steel pipe used for pipelines or other piping for the purpose of transporting natural gas or other gases containing hydrogen sulfide. (Prior Art) Conventionally, coatings such as tar epoxy and pure epoxy have been used as anticorrosion coatings on the inner surfaces of steel pipes for the purpose of gas transportation. However, due to resource depletion in recent years, natural gas containing hydrogen sulfide has been mined and transported, and even if deflow treatment is performed midway through, transportation continues with a small amount of hydrogen sulfide remaining as an impurity. A lot of things happened. As an anti-corrosion paint for hydrogen sulfide, JP-A-Sho
No. 55-165967 describes this coating material, which basically contains a resol type phenol-modified epoxy resin as the main resin component. (Problems to be solved by the invention) When the coating film of conventional coated steel is in a humid environment and contains hydrogen sulfide, the hydrogen sulfide and water permeate through the coating and cause corrosion of the steel at the adhesive interface between the coating and the steel. (hereinafter referred to as under-film corrosion), an iron sulfide film was formed, and the adhesion of the paint film quickly deteriorated, resulting in a loss of anticorrosion performance. In other words, when hydrogen sulfide and water pass through the coating film and sulfide is generated on the steel surface, the bond between the coating film and the steel material is broken.
As a result, the coating film peels off from the steel surface and loses its anticorrosion function. In this case, there is no problem if you use a coating that can completely prevent the intrusion of hydrogen sulfide and water, but in reality, with any coating, sooner or later hydrogen sulfide and water will pass through the coating and reach the steel surface. Resulting in. Conventional general coatings in general environments use materials that are relatively impermeable to water or oxygen, i.e., binders such as polyethylene and epoxy resins, and they also use binders such as polyethylene and epoxy resins to suppress the anodic corrosion reaction when water enters. It was designed to prevent corrosion of the steel material being coated, mainly by blending metals that have a greater ionization tendency than iron. A typical example of this type of paint is zinc-rich paint, which contains a high concentration of zinc in the coating film. In addition to this zinc-rich paint, epoxy resin paints, vinyl chloride resin paints, and other paints that have excellent corrosion resistance and chemical resistance and have a proven track record
Even in paints such as phenolic resin paints, when hardened hydrogen is generated in the corrosive environment, the anticorrosion performance of the paints is significantly reduced. Accidents of hydrogen sulfide cracking in steel materials have occurred in environments where hydrogen sulfide is highly concentrated, such as oil country tubular goods or chemical plants and tanks where hydrogen sulfide is handled or where hydrogen sulfide is present as an impurity. Conventional coatings designed to prevent corrosion caused by oxygen and water cannot be said to be effective in inhibiting corrosion in a corrosive environment containing hydrogen sulfide. Furthermore, as an example of a conventionally known anticorrosive paint against hydrogen sulfide, there is one described in JP-A-55-165967, but this paint basically contains a resol type phenol-modified epoxy resin as the main resin component. This generally results in a hard coating film, and there is a problem in that excellent bendability, which is the desired performance of the present invention, cannot be obtained. Corrosion occurs only after these corrosive factors, whether oxygen and water or hydrogen sulfide and water, penetrate the coating and reach the steel material.
The permeation of these corrosion factors within the coating film often occurs through the interface between the pigment and the binder. Therefore, in order to control the permeation of these corrosion factors through the paint film, it is necessary to strengthen the affinity with the binder on the surface of the pigment particles. Therefore, there is an optimal pigment depending on the type of resin that is the binder.
Even when applied to the paint disclosed in Japanese Patent Publication No. 55-165967, it does not necessarily show the expected effect, and in fact, the anticorrosion performance deteriorates. This is as shown in Comparative Example 5, which will be described later, in which a resin synthesized based on Example 1 of JP-A-55-16597 was used as the binder resin. As is clear from these results, when a resol-type phenol-modified epoxy resin is used as the binder resin, good bending properties cannot be obtained, and the expected effects in salt water spray resistance and hydrogen sulfide resistance are not achieved. This fact is due to the fact that the pigments selected in the present invention have a small water-soluble content and the slightly acidic nature of the dissolved water with a pH of 6 to 7, which weakens their affinity with the resol type phenol-modified epoxy resin. It seems to be. (Objective of the Invention) The present invention has excellent corrosion resistance even in an environment containing hydrogen sulfide without impairing the corrosion resistance in the normal environment of conventional inner-coated steel pipes, that is, an environment where water and oxygen are the main corrosion factors. This is an attempt to obtain a highly durable internally coated steel pipe for gas transportation. (Means for Solving the Problem) That is, the present invention uses a polyamide containing a bisphenol type epoxy resin having 1 to 2 oxirane rings per molecule and having an epoxy equivalent of 400 to 1400 as a main component, and consisting of an aliphatic diamine and a dimer acid. Amine 2
Using a polyamide amine adduct obtained by reacting 1 mole of bisphenol type epoxy resin with an epoxy equivalent of 180 to 1400 to 4 moles as a curing agent, the ratio of the epoxy resin to the polyamide amine adduct is 0.8/1 to 1.4/ in terms of reaction equivalent. 50 to 200 parts by weight of a filler inert to hydrogen sulfide per 100 parts by weight of the vehicle of 1, and the pH of the dissolved water with a water soluble content of 0.3% or less.
A high quality paint composition characterized in that the inner surface is coated with a two-component type coating composition that can be cured at room temperature and is characterized by containing 3 to 40 parts by weight of a rust-preventive pigment with a corrosion resistance of 6.0 to 7.0 in the main agent and/or curing agent. Durable inner-coated steel pipe for gas transportation. In a preferred embodiment, (a) the filler inert to hydrogen sulfide is at least one selected from the group consisting of carbon black, titanium oxide, aluminum powder, silicon oxide, aluminum oxide, and magnesium oxide. The above-mentioned highly durable internally coated steel pipe for gas transportation is characterized by: (b) The above-mentioned highly durable inner-coated steel pipe for gas transportation, characterized in that the anticorrosive pigment is an oxide of at least one metal selected from the group of Ba, Zn, Cr, Mo, and Al. (c) The above-mentioned highly durable inner-coated steel pipe for gas transportation, characterized in that the rust-preventive pigment is at least one selected from the group of barium chromate, zinc chromate ZTO, and aluminum phosphomolybdate. (d) The highly durable inner-coated steel pipe for gas transportation, characterized in that the aliphatic diamine is xylylene diamine. Next, the present invention will be explained with reference to FIG. 1. After the inner surface of the steel pipe 1 is cleaned by a blast treatment or the like, it has excellent anti-corrosion performance not only in a normal corrosive environment but also in a gas containing hydrogen sulfide. This is a highly durable inner-coated steel pipe for gas transportation, characterized by coating it with a paint and curing it to form a coating film 2. The anticorrosive paint used to form this coating film 2 will be explained in detail below. The vehicle (binder component) of the anticorrosive paint used in the present invention is an epoxy resin having an epoxy equivalent of 400 to 1400 obtained by the addition reaction of bisphenol A having 1 to 2 oxirane rings per molecule and epihalohydrin. Resin, polyamide amine consisting of aliphatic diamine and dimer acid, and bisphenol type epoxy resin in 2/1 to 4/
It consists of a compound obtained by reacting at a reaction molar ratio of 1 (so-called polyamide amine adduct). Such an epoxy resin is represented by the following structural formula. This resin is commonly called diglycidyl ether of bisphenol A. Although this has two oxirane rings per molecule in its structural formula, products with such a structure do not generally exist. That is, if the epoxy resin has the above structural formula, the epoxy equivalent must be one half of the average molecular weight, but the epoxy equivalent of a normal epoxy resin is smaller than this. In other words, not all of the terminal ends are oxirane rings, and generally some functional groups such as α-diol hydrolyzable chlorine are present. In this sense, the epoxy resin is designed to have the above structure, but in reality, epoxy resins having 1 to 2 oxirane rings per molecule can be used in the present invention. Specifically, "Epicote" (Yuka Ciel Epoxy Co., Ltd.), "Epotote" (Toto Kasei Co., Ltd.)
,
"Araldite" (Ciba Geigy), "Epicron"
(Dainippon Ink & Chemicals Co., Ltd.) is a commercially available epoxy resin having an epoxy equivalent of 400 to 1,400 and a molecular weight of 800 to 3,000. For example, if manufactured by Yuka Ciel Epoxy Co., Ltd., Epicote 1001 has n=2.0 and an average molecular weight of 900.
and epoxy equivalent of 450-500, Epicoat
1004 has n=3.7, average molecular weight 1400 and epoxy equivalent weight 900-1000. If the epoxy equivalent is less than 400, the reactivity will be high, the pot life will be short, and the workability will be poor. In addition, in this case, the cured product becomes brittle and API
Does not pass standard bending test. Furthermore, if the epoxy equivalent exceeds 1400, the reaction at room temperature becomes extremely slow and the viscosity becomes too high, making coating difficult. One of the curing agents, polyamide amine, has the general formula here [In the formula, A is

【formula】

or -(CH ₂ )n ^- (n=2 to 12)], and 2 to 4 moles of polyamidoamine obtained from an aliphatic diamine and dimer acid, and a bisphenol type epoxy with an epoxy equivalent of 180 to 1400. Obtained by reacting 1 mole of resin. Dimer acid, which is one component of this polyamide amine duct, can be obtained by heating and polymerizing unsaturated fatty acids in natural oils and fats. In this heating polymerization,
Although linoleic acid is commonly used, any fatty acid with unsaturated double bonds can be used. ). As the aliphatic diamine which is the second component of the polyamide amine adduct, xylylene diamine, ethylene diamine, hexamethylene diamine, bisauminopropyl-tetraoxaspiro undecane, etc. can be used. In addition, aromatic amines such as phenylene diamine, diamine diphenylmethane, and diaminodiphenylsulfonate, or menthanediamine, diethylene triamine,
Compounds having three or more amino groups in the molecule, such as triethylenetetramine, are not very practical because they tend to gel when producing polyamidoamine. The polyamidoamine, which is the product of the previous step of the polyamidoamine adduct, is the product of the aliphatic diamine 2
It can be easily obtained by heating and condensing mol and 1 mol of dimer acid at 120 to 180°C. A specific example is "Vermicide" (Henkel Japan Ltd.). The third component of the polyamide amine adduct, the bisphenol type epoxy resin, needs to have an epoxy equivalent weight of 180-1400, preferably 180-500. If the epoxy equivalent of the epoxy resin exceeds 1400, the adduct reaction becomes difficult. Furthermore, if the epoxy equivalent is less than 180, the number of epoxy groups per molecule will decrease, making it impossible to obtain the desired hardness and flexibility of the coating film. The polyamide adduct can be obtained by reacting an aliphatic diamine and a dimer acid in a conventional manner, then adding an epoxy resin to the reaction system and reacting in a conventional manner. Generally, when painting the inner surface of steel pipes,
Requires very large-scale equipment. for example,
As described in Japanese Unexamined Patent Publication No. 56-95960, Utility Model Publication No. 58-27813, etc., a paint discharging device with various devises is inserted into the hollow part of the steel pipe, and a hose leading to it is connected from one end of the long steel pipe to the paint supply device. It is common to connect. Therefore, painting the inside of steel pipes requires a large amount of paint at one time, and since it requires large-scale equipment, it takes time to repair any problems that occur, so the paint needs to have a long pot life. Become. That is, when the main agent and curing agent are mixed, a reaction begins, and the viscosity increases to such a degree that it cannot be discharged by a coating device, and finally gelation occurs. Pot life refers to the time from when the main component and curing agent are mixed in a two-component paint until the paint cannot be discharged normally. API that standardizes the inner coating of natural gas line pipes
(American Petroleum Institute) requires a pot life of 8 hours or more. In order to create a two-component paint with such a long pot life, the primary amine of the amine class is reacted with an epoxy resin in advance to convert it into a secondary amine. It is possible to delay the reaction time of Although the effect of extending the pot life by forming into an adduct in this way is well known, the present invention is characterized in that the adduct raw material is selected so that the adduct product and the cured product of the epoxy resin have excellent practical performance. Dimer acid, which is a raw material for the polyamide amine adduct, which is one of the vehicle components of the anticorrosive paint in the present invention, overcomes the hard and brittle properties of general epoxy resin amine cured products, and is particularly useful for the aliphatic diamine adduct, which is another raw material. When reacted with the resin, it acts to give a cured resin that is hard and flexible, and has the properties of a so-called elastomer. The compounding ratio of this epoxy resin and polyamide amine adduct is 0.8/1 to 1.4/1 in terms of equivalent ratio, preferably 0.8/1 to 1.4/1.
Must be 1.2/1. If this ratio is less than 0.8/1, the coating film will become too soft and the anticorrosion performance such as water resistance will also deteriorate. On the other hand, if the blending ratio exceeds 1.4/1, the coating film will become hard and brittle, and its anticorrosion properties such as water resistance will also deteriorate. Next, examples of fillers for the anticorrosive paint in the present invention include carbon black, titanium oxide, aluminum powder, silicon oxide, aluminum oxide,
One or more fillers that are inert to hydrogen sulfide, such as magnesium oxide, can be selected and used. In addition, Ba, which has a water-soluble content of 0.3% or less and a pH of dissolved water of 6.0 to 7.0, is used as a rust-preventing pigment.
Contains as an essential component a compound whose main agent is one or more oxides of Zn, Cr, Mo, and Al. These fillers and antirust pigments both have a common property that they have a small water-soluble content of 0.3 or less and are relatively stable against hydrogen sulfide. Here, the water soluble content and the pH of the dissolved water were measured by a method used in a general pigment test. That is, the water-soluble content was determined based on JIS-5101 by boiling 5 g of pigment in 200 c.c. of water for 5 minutes and determining the weight change. Also, the PH of the dissolved water
boiled 5 g of pigment in 100 c.c. of distilled water for 1 hour, kneaded it with water to form a paste, and measured the pH after 24 hours. The purpose of the filler is to provide color and strengthen the coating, and its addition must not at least worsen corrosion caused by water and oxygen, or corrosion in the presence of hydrogen sulfide. . Hunke is JOCCA magazine, volume 50,
942 (1967) discusses water as a corrosion factor and explains the mechanism by which water permeates through the paint film, but in both cases, water attacks the interface between the binder and filler or pigment, causing the permeation to occur. I'm awake. In the present invention, a filler has been selected that has strong affinity at the interface between the binder and filler, is difficult for water, oxygen, or hydrogen sulfide to attack this interface, and is difficult for these substances to accumulate at the interface.
In particular, the essential conditions for not weakening the affinity of this interface are that the water-soluble content is small and that it does not react with hydrogen sulfide. Although it has not been demonstrated that the low water-soluble content and low reactivity with hydrogen sulfide do not weaken the affinity of the interface,
Paint films using fillers that meet at least these conditions show excellent performance in normal rust prevention tests, such as salt spray resistance, water resistance, and salt water resistance, and also exhibit excellent performance when immersed in hydrogen sulfide saturated water. It has been confirmed that it shows excellent performance. Specific examples of such fillers include carbon black, titanium oxide, aluminum powder, silicon oxide aluminum oxide, elemental magnesium oxide, MgO・SiO ₂・Al ₂ O ₃ called talc, and Al ₂ called clay. O ₃・SiO ₂ , mica K ₂ O・
Composites such as Al ₂ O ₃ and SiO ₂ can be used, but other fillers can also be used as long as they can perform the above-mentioned functions. On the other hand, regarding anti-corrosive pigments, general anti-rust pigments are salts of metals that have a high water-soluble content and have a greater tendency to ionize than iron, and their ability to suppress anodic corrosion reactions is utilized. However, in a corrosive environment containing hydrogen sulfide and water, being easily soluble in water creates metal ions, which when attacked by hydrogen sulfide immediately form sulfides of that metal. This weakens the affinity of the interface between the binder and these anticorrosion pigments, and as a result, corrosion reactions under the coating film are accelerated. In other words, the anti-corrosion pigment must be difficult to react with hydrogen sulfide and difficult to dissolve in water. Furthermore, it is preferable that the aqueous solution in which these pigments are slightly dissolved has a slightly acidic pH of 6 to 7. Hydrogen sulfide is slightly acidic when dissolved in water. On the other hand, if the anti-rust pigment in the paint film dissolves in water and the pH becomes alkaline,
It plays the role of attracting more hydrogen sulfide, which is slightly acidic, and impairs anti-corrosion performance. On the other hand, if the pH is less than 6, corrosion of the steel material will be accelerated, which is not preferable. Preferred rust-preventive pigments that satisfy these conditions include, for example, barium chromate (BaCrO _{4 )} , zinc chromate ZTO type (ZnCrO ₄ .
4Zn(OH) ₂ ), aluminum phosphomolybdate (MoO ₃ C・P ₂ O ₅・Al ₂ O ₃ ), and the like. These amounts are based on the weight of the binder component.
To 100 parts by weight, the filler is 50 to 200 parts by weight, and the antirust pigment is 3 to 40 parts by weight. If the amount of filler is less than 50 parts by weight, the strength of the coating film will be low, resulting in poor impact and bending properties. Furthermore, if the amount of the filler exceeds 200 parts by weight, the binder will be insufficient and a uniform film will not be formed, resulting in defects such as pinholes and deterioration of physical properties, which is not preferable. Next, if the amount of the rust preventive pigment is less than 3 parts by weight, the anticorrosion performance will be insufficient, and if it exceeds 40 parts by weight, even if the water-soluble content is suppressed to 0.3% or less, the amount of the rust preventive pigment that dissolves in water will be insufficient. If the absolute amount increases, the anticorrosion performance will deteriorate, which is undesirable. The anticorrosive paint according to the present invention may contain appropriate additives such as an anti-cissing agent, an anti-sagging agent, and a spreading agent in addition to the essential components described above. In addition, in order to improve painting workability, it can also be blended with solvents as necessary. Furthermore, if necessary, it is also possible to add other epoxy equivalent or nopolac type epoxy resins within 10% of the amount of the claimed epoxy resin. (Examples) Hereinafter, the present invention will be explained in more detail according to Examples. Example 1 After cleaning the inner surface of an SGP steel pipe with an outer diameter of 8.91 mm, a wall thickness of 4.2 mm, and a length of 3 m by sandplast treatment, the following anticorrosive paint was applied using an airless paint sprayer equipped with a pole gun and cured at room temperature. and thickness 60~
A coating film of 80μ was formed. Ingredients of anti-corrosion paint Main agent Epicoat #1001 (epoxy equivalent: 450) (manufactured by Yuka Ciel Epoxy Co., Ltd.) 29.2 Epotote YD-017 (epoxy equivalent: 2200) (manufactured by Toto Kasei Co., Ltd.) 2.6 Talc 30.5 Titanium oxide 25.9 Zinc chromate ( Water soluble content 0.3% or less, PH6.8)
11.0 Disparon 4200-20 (flow agent) (manufactured by Kyoeisha) 0.8 100.0 Curing agent polyamide amine adduct () 17.2 17.2 (ratio of equivalent number of epoxy equivalent and polyamide amine adduct = 1:1) Solvent xylene 60 Butyl cellosolve 36 Methyl isobutyl Ketone 12 n-butanol 12 120 The above polyamide amine adduct () was synthesized by the method shown below. Synthesis method of polyamide amine adduct () In a three-necked flask equipped with a Küller dehydrator and a stirrer, add 576 g of Versadime #216 (acid value 195, made by Henkel Japan) (equivalent to 1 mole as a calculated value, theoretical value is 560 g). 120 g (2 mol) of ethylenediamine was charged and stirred while gradually heating. Raise the temperature from 160℃ to 200℃ over about 4 hours,
During this time, the water produced by the reaction was condensed in a cueller and removed from the reaction system, and when the theoretical value of 36 g of water had been dehydrated, the acid value of the resin was measured and confirmed that the acid value was 3 or less. After confirming this, the reaction was completed.
The active hydrogen equivalent of this polyamide amine was 107. Next, 232 g of a mixed solvent of xylene/n-butanol = 8/2 was added to this reaction system and mixed well, and the reaction system was cooled to 40°C. of 75
% xylene solution) was added dropwise over 4 hours.
After completion, the reaction was further stirred at 40°C for 24 hours to complete the reaction. The obtained polyamide amine () had an active hydrogen equivalent weight of 260 (solid content: 195). The internally coated steel pipe obtained in this way is installed in a gas circulation system, and simulated natural gas containing 10% hydrogen sulfide, 100% relative humidity, and nitrogen gas is added to the interior for 30 minutes.
℃, 1 atm, and flow rate of 5 m/sec. 3
After one year had elapsed, the internally coated steel pipes were removed and changes in the appearance, adhesion, and hardness of the coating were examined. The results are shown in Table 1. The surface is polished with #400 emery paper, 70 mm wide x 150 mm, in accordance with API standard RP5L2, which specifies the quality of the inner surface coating of steel pipes for ordinary natural gas.
Adhesion, hardness, bending, and salt spray tests were conducted on the coated steel plate, which was coated with the above anticorrosive paint using an airless coating machine on a long x 0.8 mm thick steel plate and cured under the conditions of 20℃ x 10 days + 50℃ x 24 hours. We conducted performance tests such as: The results are shown in Table 2. Example 2 Same procedure as Example 1, outer diameter 89.1 mm, wall thickness 4.2 mm,
A 3m long SGP steel pipe was coated with the following anti-corrosion paint.
We created internally coated steel pipes with a film thickness of 60 to 80μ. Ingredients of anti-corrosion paint Base agent Epicoat #1001 38.3 Epotote YD-017 3.4 Clay 39.8 Carbon Black 3.4 Barium chromate (water soluble content > 0.3%, PH6.0) 6.7 Zinc chromate ZTO 7.6 Disparon 4200-20 0.8 100.0 Curing agent polyamide amine adduct () 21.1 21.1 (ratio of equivalent numbers of epoxy resin and epoxy amine adduct = 0.8:1) Solvent xylene 60 Butyl cellosolve 36 Methyl isobutyl ketone 12 n-butanol 12 120 The above polyamide amine adduct ()
was synthesized by the method shown below. Synthesis method of polyamide amine adduct (2017) Put 576 g (1 mol) of Versadime #216 and 272 g (2 mol) of xylene diamine into a three-necked flask equipped with a Cuyler dehydrator and a stirrer, and heat with stirring to 160 g. From ℃ to 200℃ about 3
As the temperature was raised over time and reaction water was constantly removed from the system, approximately 36g of water came out of the system and the acid value was 3.
The reaction was terminated after confirming that the following conditions were met. The active hydrogen equivalent of this polyamide amine was 141. Next, 270 g of xylene/n-butanol = 8/2 mixed solvent was added to this reaction system and mixed well, and after cooling the reaction system to 35°C, 506 g of a separately prepared xylene solution of Epicote #828 was added dropwise over 6 hours. After this was completed, the reaction was further stirred at 35° C. for 2 hours to complete the reaction. The obtained polyamide amine adato () has an active hydrogen equivalent of 195 (solid content).
146). The internally coated steel pipe thus obtained was subjected to a simulated natural gas circulation test and a performance test based on API standards in the same manner as in Example 1. The results are shown in Tables 1 and 2. Example 3 Same procedure as Example 1, outer diameter 89.1 mm, wall thickness 4.2 mm,
A 3m long SGP steel pipe was coated with the following anti-corrosion paint.
An inner steel pipe with a film thickness of 60 to 80μ was created. Main ingredients of anticorrosive paint Epikoat #1001 33.5 Epikoat #828 (epoxy equivalent 190) (manufactured by Yuka Ciel Epoxy Co., Ltd.) 3.0 Talc 35.0 Aluminum piece 14.9 Zinc chromate ZTO 12.7 Disparon 4200-20 0.9 100.0 Hardening agent Polyamide amine adduct () 21.9 21.9 (ratio of equivalent numbers of epoxy and polyamide amine adduct = 0.9:1) Solvent xylene 50 Butyl cellosolve 30 Methyl isobutyl ketone 10 n-butanol 10 100 Regarding the inner surface coated steel pipe thus obtained, Example 1 Similarly, a simulated natural gas circulation test and a performance test based on API standards were conducted. The results are shown in Tables 1 and 2. Comparative Example 1 In Example 1, the same weight part of iron oxide red, which easily reacts with hydrogen sulfide, was used in place of the titanium oxide in the anticorrosive paint, and the same test was conducted. The results are shown in Tables 1 and 2. Comparative Example 2 In Example 1, zinc chromate type C (ZnO・K ₂ CrO ₄・
A similar experiment was conducted using the same parts by weight of ZnCrO ₄ , pH 6.8, water soluble content 8%). The results are shown in Tables 1 and 2. Comparative Example 3 In Example 1, the same experiment was conducted using the following anticorrosive paint instead of the anticorrosive paint.
The results are shown in Tables 1 and 2. Ingredients of anti-corrosion paint Base agent Epicoat #1001 29.2 Epotote YD-017 2.6 Dispatron 4200-20 0.8 32.6 Curing agent polyamide amine adduct () 17.2 17.2 Solvent xylene 60 Butyl cellosolve 36 Methyl isobutyl ketone 12 n-butanol 12 120 Comparison Example 4 A similar experiment was conducted in Example 1 except that the curing agent in the anticorrosive paint was replaced with 2.3 parts by weight of xylene diamine. The results are shown in Tables 1 and 2. Comparative Example 5 A similar experiment was carried out in Example 4 except that the epoxy resin component in the base resin was replaced with a resol type phenolic resin precondensate of an epoxy resin condensed as in the example of JP-A-55-165967. The results are shown in Tables 1 and 2.

[Table] I went.

[Table] As is clear from the examples described above, all of the inner-coated steel pipes according to the present invention showed no change in the appearance of the coating film in the three-year simulated natural gas circulation test, and the adhesion of the coating film and The hardness has also been maintained at the original level, and it has excellent durability in gases containing hydrogen sulfide. Also, in performance tests based on API standards, all of the internally coated steel pipes according to the present invention satisfied the specified values, and had sufficient performance even in a normal gas atmosphere and during transportation and storage. In addition, all of the anticorrosive paints of the present invention have a long pot life of 8 hours or more, and have a long pot life of 8 hours or more.
Meets the standards. On the other hand, as shown in Comparative Examples 1 to 3, inner-coated steel pipes using fillers or anti-rust pigments and inner-coated steel pipes without fillers or anti-rust pigments, which easily react with hydrogen sulfide, In a simulated natural gas circulation test, the appearance of the paint film was discolored.
Since adhesion and coating hardening are significantly reduced, it has insufficient anticorrosion performance in gases containing hydrogen sulfide. In addition, when xylylene diamine alone is used as a curing agent, as shown in Comparative Example 4, the flexibility of the coating film is insufficient, and the pot life is shortened, in addition to not satisfying the API standard regarding bendability. Because it is very short, painting workability at the factory is poor. Therefore, in order to achieve the objects of the present invention, it is necessary to use a polyamidoamine adduct consisting of an aliphatic diamine, a dimer acid and an epoxy resin. Furthermore, as shown in Comparative Example 5, the inner surface coated steel pipe using the anticorrosive composition described in JP-A No. 55-165967 did not have sufficient flexibility of the coating.
Does not meet API standard bendability requirements. (Effects of the invention) As described above in detail, the coating film of conventional anti-corrosion inner coated steel pipes deteriorates in a short period of time in a gas atmosphere containing hydrogen sulfide, and it is said that they are resistant to hydrogen sulfide. However, the internally coated steel pipe according to the present invention contains 10% hydrogen sulfide, has a relative humidity of 100%, and a temperature of 30°C. In addition to showing no deterioration of the coating film even after 3 years in a simulated natural gas circulation test at ℃ and 1 atm, it satisfies all the required values for each performance test stipulated in API standard RP5L2, and is free from hydrogen sulfide. It not only has excellent anticorrosion performance against atmospheres containing carbon dioxide, but also excellent anticorrosion performance and ease of handling in normal environments during transportation and storage. Further, since the anticorrosive paint according to the present invention has a long pot life, the workability of painting the inner surface of steel pipes in a factory is also excellent.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an internally coated steel pipe according to the present invention. 1: Steel pipe, 2: Paint film.

Claims (1)

[Scope of Claims] 1. Based on 2 to 4 moles of polyamide amine consisting of an aliphatic diamine and a dimer acid, the base material is a bisphenol type epoxy resin having 1 to 2 oxirane rings per molecule and having an epoxy equivalent of 400 to 1400. Using a polyamide amine adduct obtained by reacting 1 mole of bisphenol type epoxy resin with an epoxy equivalent of 180 to 1400 as a curing agent, the ratio of the epoxy resin to the polyamide amine adduct is 0.8/1 to 0.8/1 in terms of reaction equivalent.
50 to 200 parts by weight of a filler inert to hydrogen sulfide per 100 parts by weight of a 1.4/1 vehicle and 3 to 3 parts of a rust preventive pigment with a water soluble content of 0.3% or less and a dissolved water pH of 6.0 to 7.0. 1. A highly durable inner-coated steel pipe for gas transportation, the inner surface of which is coated with a two-component coating composition that can be cured at room temperature and contains 40 parts by weight of a base agent and/or a curing agent. 2. Claim No. 2, characterized in that the filler inert to hydrogen sulfide is at least one selected from the group of carbon black, titanium oxide, aluminum powder, silicon oxide, aluminum oxide, and magnesium oxide. Highly durable internally coated steel pipe for gas transportation according to item 1. 3. Highly durable gas transport material according to claim 1, wherein the rust-preventing pigment is an oxide of at least one metal selected from the group of Ba, Zn, Cr, Mo, and Al. Internally painted steel pipe. 4. The highly durable inner surface for gas transport according to claim 1, wherein the rust-preventing pigment is at least one selected from the group of barium chromate, zinc chromate ZTO type, and aluminum phosphomolybdate. Painted steel pipe. 5. The highly durable inner-coated steel pipe for gas transportation according to claim 1, wherein the aliphatic diamine is xylylene diamine.