JPH0348229B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an anticorrosion coating composition, and more particularly to an anticorrosion coating composition that provides a coating that inhibits corrosion of steel in a corrosive environment containing hydrogen sulfide, oxygen, and water. The anticorrosive coating composition of the present invention is suitable for coating steel materials in chemical plants or tanks that handle hydrogen sulfide or in which hydrogen sulfide is mixed as an impurity, or in transportation pipelines and stations for natural gas, oil, etc., in which hydrogen sulfide is mixed. It can be suitably used. BACKGROUND ART AND PROBLEMS TO BE SOLVED BY THE INVENTION It is well known that hydrogen sulfide (H ₂ S) is highly reactive and easily forms sulfides, especially with various metals. In particular, due to the unique reactivity of H ₂ S in steel materials, so-called hydrogen sulfide corrosion occurs, which deteriorates the strength of steel materials, unlike corrosion of general metals, and many accidents have been reported. Regarding the causes of these hydrogen sulfide cracks, see Nishimura, Kurisu, and Otani, "Journal of the Welding Society," 32 [6], 478-489.
(1963), hydrogen sulfide is basically the same as hydrogen embrittlement, and hydrogen sulfide forms sulfides on the steel surface and only acts as a catalyst for hydrogen absorption by the steel. be. It is also stated that cathodic protection is ineffective as a method for preventing these sulfide cracks, and that some of them cause embrittlement and softening of the coating film, so it is relatively effective if an appropriate one is selected. Therefore, a coating material for preventing hydrogen sulfide cracking must first have the ability to control the formation of sulfides on the steel surface. Such anti-corrosion performance is also necessary for coating materials in corrosive environments where the concentration of hydrogen sulfide is low and hydrogen sulfide does not reach the surface. In other words, when hydrogen sulfide passes through the coating along with water and oxygen and generates sulfide on the steel surface, the bond between the coating material and the steel material is broken, and as a result, the coating material peels off from the steel surface. This is because the anti-corrosion function is lost.
Of course, there is no problem if a suitable coating material prevents hydrogen sulfide, oxygen, and water from entering, but gas and water will eventually permeate through any coating and reach the steel material. Conventional general coating materials in general environments use materials that are relatively difficult for water or oxygen to permeate, i.e., binders such as polyethylene and epoxy resin, and are mainly designed to suppress anode corrosion reactions when water penetrates. It has been designed to prevent the metal to be coated (mostly iron) from dissolving by incorporating metals that have a greater tendency to ionize than iron. A typical example of this type of paint is zinc-rich paint for cathodic protection, which contains a high concentration of zinc in the coating film. Even paints such as epoxy resin paints, vinyl chloride resin paints, and phenol resin paints, which generally have excellent corrosion resistance or chemical resistance and have a proven track record, including this zinc-rich paint, are susceptible to H ₂ S in corrosive environments. The presence of H ₂ S will significantly reduce its anticorrosion performance, and it will be used in environments with high concentrations of H 2 S, such as oil country tubular goods or chemical plants that handle H ₂ S or where H ₂ S is present as an impurity.
Accidents caused by hydrogen sulfide leaks have occurred in tanks, etc.
Conventional coating materials designed to prevent corrosion caused by oxygen and water cannot be said to be effective in preventing corrosion in a corrosive environment containing HS. Structure of the Invention An example of a conventionally known anticorrosive paint composition is one described in JP-A-55-165967.
This paint basically contains a resol-type phenol-modified epoxy resin as the main resin component, and generally forms a hard film, making it impossible to obtain a bendable film, which is one of the properties aimed at in the present invention. Also, corrosion due to oxygen and water or H ₂ S
Corrosion occurs only after these corrosion factors penetrate the coating and reach the steel material. This penetration of corrosion factors into the coating occurs through the pigment-binder interface. Therefore, in order to control the permeation of these corrosion factors through the paint film, it is necessary to strengthen the interaction with the binder on the surface of the pigment particles. This means that there is an optimal pigment depending on the type of resin that is the binder, and even if the pigment of the present invention, which will be described later, is applied as it is to the paint disclosed in JP-A-55-165967, it will not be possible to obtain the desired pigment. In fact, the anticorrosion performance may actually worsen. This is as shown in Comparative Example 5 below, in which a resin synthesized based on Example 1 of JP-A-55-165967 was used as the binder resin. As is clear from these results, because a resol-type phenol-modified epoxy resin is used as the binder resin, sufficient results in bendability cannot be obtained, and the expected effects in salt spray resistance and H ₂ S resistance are not achieved. do not have. 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 weakens the interaction with the resol-type phenol-modified epoxy resin. Conceivable. Means for Solving the Problems and Their Effects According to the present invention: () (a) Epoxy equivalent obtained by addition reaction of bisphenol A having 1 to 2 oxirane rings per molecule and epihalohydrin; is 180~
100 parts by weight of a vehicle consisting of (b) a polyamide amine consisting of an aliphatic diamine and a dimer acid, in which the ratio of the epoxy resin to the polyamide amine is 0.8/1 to 1.4/1 in terms of reaction equivalent; At least one filler selected from the group of carbon black, titanium oxide, aluminum powder, silicon oxide, aluminum oxide and magnesium oxide and inert to hydrogen sulfide 50 to 200
Parts by weight, () The water soluble content is 0.3% or less and the pH of the dissolved water is 6.0 to 7.0.
A two-component anticorrosive paint composition substantially free of phosphoric acid, consisting of 3 to 40 parts by weight of an anticorrosive pigment of things are provided. The vehicle (binder component) used in the anticorrosive coating composition of the present invention contains 1 to 2
An epoxy resin with an epoxy equivalent of 180 to 2,500 obtained by the addition reaction of bisphenol A having 3 oxyquiran rings and epihalohydrin, and a polyamide amine consisting of an aliphatic diamine and a dimer acid in a ratio of 0.8/1 to 1.4/1. It is a compound formed by reacting at a reaction equivalent ratio. Such epoxy resin is represented by the following structural formula, This resin is commonly called diglycidyl ether of bisphenol A. Structurally, it has two oxirane rings per molecule, but products with this structure generally do not exist. That is, if the epoxy resin has the above structural formula, the average molecular weight must be twice the epoxy equivalent, but it generally has a considerably small value. In other words, not all of the terminal ends are oxirane rings, but some functional groups such as α-diol hydrolyzable chlorine are generally present. In this sense, it has a linear structure as shown above, and although it was originally designed to have the above structure, in reality it has 1 to 2 oxirane rings per molecule, making it difficult for epoxy resins to function properly. It can be used in the invention. Specifically, “Epicote”
(Yuka Ciel Epoxy Co., Ltd.), "Epototh" (Toto Kasei Co., Ltd.), "Araldite" (Ciba Kaigyu Co., Ltd.), "Epicron" (Dainippon Ink & Chemicals Co., Ltd.), etc. are commercially available brands. So, the epoxy equivalent is 180 ~
2500, it is appropriate to use an epoxy resin with a molecular weight of 380 to 3000. For example, Epicoat 828 manufactured by Yuka Ciel Epoxy Co., Ltd. has n=0, average molecular weight 380, and epoxy equivalent weight 184 to 194, and Epicoat 1001
is n=2.0, average molecular weight 900 and epoxy equivalent weight 450
~500, Epicote 1004 has n=3.7, average molecular weight 1400 and epoxy equivalent weight 900-1000, and Epicote 1007 has n=8.8, average molecular weight 2900 and epoxy equivalent weight 1750-2100. On the other hand, aliphatic diamines, such as polyamide amines consisting of xylylene diamine and dimer acid,
Typically [In the formula, A is

【formula】 −(CH ₂ ) _o − n=2 to 12]. Dimer acid, which is the acid component of such polyamide amine, can be obtained by heating and polymerizing unsaturated fatty acids in natural oils and fats. Linoleic acid is most commonly used in this cyclization thermal polymerization, but basically any fatty acid with unsaturated double bonds can be used. "Versa Dim" (Henkel Japan Ltd.) is an example. Examples of the aliphatic diamine that is the other component include xylylene diamine, ethylene diamine, hexamethylene diamine, bis-aminopropyl-tetraoxaspiroundecane, etc., which have an aromatic skeleton;
Although various structures such as alkyl groups or heterocyclic structures can be used, aliphatic diamines are most suitable as the type of amine. Aromatic amines such as phenylene diamine, diaminodiphenylmethane, diaminodiphenyl sulfone, or menthanediamine diethylenetriamine, triethylenetetramine, etc.
Compounds having more than one amino group are not very practical because they tend to gel when producing polyamide. This polyamide amine can be easily obtained by heating and condensing 2 moles of the aliphatic diamine and 1 mole of dimoic acid at 120°C to 180°C.
Specifically, “Versamide” (manufactured by Henkel Japan)
can be mentioned. These bisphenol A-based epoxy resin and polyamide amine containing dimer acid are prepared separately before film formation, and mixed immediately before use.
Once coated, a chemical reaction occurs at room temperature, forming a strong film. If it is necessary to adjust the curing reaction rate depending on the type of object to be coated or the coating process, a portion of these two binder components may be precondensed in advance to remove all of the primary amine of the polyamide amine. It can be converted into a secondary amine and used. This is a common use of epoxy resins as amine adduct hardeners with amine hardeners. That is, the general formula You may prepare in the form shown below. In any case, a part of the cured product is precondensed in advance, and the cured structure as a film is the same as that formed by the present invention. The epoxy resin, one of the binder components, needs to have a linear structure and an epoxy equivalent of 180 to 2,500, preferably 350 to 1,900, as shown in the above structural formula. If the epoxy resin is less than 180, a compound as shown by the basic structural formula described above cannot be produced. That is, in the above formula, when n=0, the epoxy equivalent is around 180. Furthermore, if the epoxy equivalent exceeds 2,500, the intended reaction at room temperature will not occur, and the viscosity will become too high, making it difficult to form a film. Dimer acid, which is a raw material for polyamide amine, which is another component of the vehicle component of the anticorrosive coating composition of the present invention, overcomes the hard and brittle properties of general epoxy resin amine cured products, and is especially another raw material. When reacted with diamine, it acts to give a cured resin that is hard and flexible, and has the properties of a so-called elastomer. Its specific properties indicate excellent performance in terms of bendability of the film. The blending ratio of this binder component is the number of equivalents of epoxy group/the number of equivalents of active hydrogen of polyamide amine = 0.8/1 ~
It should be 1.4/1, preferably 0.8/1 to 1.2/1. If this ratio is less than 0.8/1, the cured product will be too soft and its anticorrosion properties such as water resistance will deteriorate. On the other hand, if it exceeds 1.4/1, it becomes hard and brittle, and also deteriorates corrosion resistance such as water resistance. Fillers that are inert to hydrogen sulfide (hereinafter simply referred to as fillers) used in the coating composition of the present invention include carbon black, titanium oxide, aluminum powder, silicon oxide, aluminum oxide, and magnesium oxide. One or more fillers selected from the group may be mentioned. In addition, we use Ba, Zu, Cr, Mo, and Al as anti-corrosion pigments with a water-soluble content of 0.3% or less and a pH of 6.0 to 7.0 in the dissolved water.
Contains as an essential component a compound mainly composed of one or more oxides. These fillers and rust-preventing pigments have a common property that they have a small water-soluble content of 0.3 or less, and are relatively stable against H ₂ S, which is the original purpose. Here, when measuring the PH of the water-soluble content and dissolved water, the water-soluble content is JIS-K.
-5101 22, PH performed JIS-K-5101 24.
The purpose of the filler is to color the film and strengthen the film.
Corrosion caused by general water and oxygen, or
Addition of H ₂ S must not at least worsen corrosion in an environment where it is present, and must improve anti-corrosion performance. Hunke discusses water as a corrosion factor in JOCCA, Vol. 50, p. 942 (1967),
The mechanism of permeation through the film is explained, but in all cases, permeation occurs due to water attacking the interface between the binder and filler pigment. In the present invention, the interaction at the interface between the binder and these fillers or antirust pigments is strong,
In addition, a material was selected that is difficult for water, oxygen, or H ₂ S to attack and accumulate at this interface. In particular, the water-soluble content is small,
We considered that the essential condition for not weakening the interaction at this interface is to cause as little reaction as possible to HS with respect to H ₂ S. Although it has not been demonstrated that low water-soluble content and low reactivity with H ₂ S do not weaken interfacial interactions, at least fillers or rust-preventive pigments that meet these conditions The coating using the .
It was confirmed that even after immersion in H ₂ S saturated water, it exhibited very excellent performance. If water or H ₂ S attacks the pigment surface and dissolves the pigment, or if it reacts with H 2 S, water or H ₂ S will enter the interface with the binder.
H ₂ S will accumulate more easily. This facilitates the supply of water or H ₂ S, which is a corrosion factor, to the surface of the steel material, leading to a significant deterioration in anticorrosion performance. In other words, a coating film using pigments and fillers with low water-soluble content and low reactivity with H ₂ S can maintain anticorrosion performance. On the other hand, anticorrosive pigments are generally metal salts with a high water-soluble content and a greater tendency to ionize than iron, and are used for their ability to suppress anode corrosion reactions. However, in a system where corrosive factors including water, oxygen, and _H2S coexist, being easily soluble in water produces metal ions, and when attacked by _H2S , the sulfide of that metal is immediately released. will be formed. This weakens the interfacial interaction between the binder and these anti-rust pigments,
As a result, the corrosion reaction under the coating is accelerated. In other words, the necessary requirements for anticorrosive pigments are that they are difficult to react with H ₂ S and are also difficult to dissolve in water. Furthermore, it is preferable that the pH of the aqueous solution in which these pigments are slightly dissolved is slightly acidic, with a pH of 6 to 7.
H ₂ S exhibits slight acidity when dissolved in water. On the other hand, if the anticorrosive pigments in the coating dissolve in water and exhibit an alkaline pH, they will serve to attract more H ₂ S water, which is slightly acidic, which is disadvantageous for anticorrosion properties. On the other hand, if the pH is less than 6, corrosion of steel will occur in an acidic region, and a low pH will itself promote corrosion, which is undesirable. Preferred antirust 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 .P ₂ O ₅ .Al ₂ O ₃ ), and the like. These amounts are based on the weight of the binder component.
With respect to 100 parts by weight, the amount of the filler is 50 to 200 parts by weight, and the amount of the antirust pigment is 3 to 40 parts by weight. If the amount of filler is less than 50 parts by weight, it is not practical in terms of film strength.
Impact and bending properties deteriorate. In addition, the amount of binder exceeding 200 parts by weight is less than the amount of filler, which is not desirable because the binder is insufficient and a uniform film cannot be formed, causing defects such as pinholes, and the physical properties are insufficient. do not have. Next, if the amount of the rust preventive pigment is less than 3 parts by weight, the rust preventive property will be insufficient;
If it exceeds 40 parts by weight, even if the water-soluble content is suppressed to 0.3% or less, the absolute amount of the rust-preventing pigment dissolved in water will increase, and the rust-preventing property will deteriorate, which is not preferable. In addition to the above-mentioned essential components, the anticorrosive coating composition according to the present invention may contain appropriate additives such as anti-cissing agents, anti-sagging agents, and spreading agents. Further, in order to improve the workability for forming a film, solvents may be added as necessary. EXAMPLES The present invention will be explained in more detail with reference to Examples below, but it goes without saying that the scope of the present invention is not limited to these Examples. Example 1 Synthesis of polyamide amine () 576 g of Versadime #216 (manufactured by Henkel Japan, acid value 195) (equivalent to 1 mole as a calculated value) was placed in a three-necked flask equipped with a Kueller dehydrator and a stirrer.
560 g (theoretical value) and 120 g (2 moles) of ethylenediamine were charged, and the mixture was gradually heated and stirred. temperature
The temperature was raised from 160°C to 200°C over about 4 hours, and the water generated by the reaction was dehydrated using a Cuellar dehydrator. When the theoretical amount of water, 36g, had been dehydrated, the acid value of the resin was measured. After confirming that the acid value was 3 or less, the reaction was terminated. The amine active hydrogen equivalent of the produced polyamide amine () was 107. Example 2 Synthesis of polyamide amine () 576g of Versadime #216 using the same equipment as Example 1
(1 mol) and xylylenediamine 272g (2 mol)
While stirring, the temperature was increased from 160℃ to 200℃ for about 3 hours, while constantly removing reaction water from the system.
The reaction was terminated after confirming that approximately 36 g of water had come out of the system and that the acid value was 3 or less. The amine active hydrogen equivalent of the obtained polyamide amine () was 141. Example 3 Preparation of paint Parts by weight of components (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 ZTO (water soluble content 0.3% or less, PH
6.8 11.0 Disparon 4200-20 (Filction agent) (manufactured by Kyoeisha) 0.8 100.0 (Curing agent) Polyamide amine () 7.1 (Epoxy group/active hydrogen = 1:1) The above formulation was mixed with xylene/butyl cellosolve/methyl isobutyl ketone/n- Butanol (50/30/
10/10) was dissolved in 120 parts by weight of a mixed solvent, and a film with a thickness of 60 to 80 μm was coated on a steel plate by airless coating. The steel plate used was a 70 x 150 x 0.8 mm blank steel plate polished with #400 paper.
The drying conditions were 20°C x 10 days + 50°C x 24 hours. API-RP-5L- improves dry coating adhesion, hardness, bending, salt spray properties, and methanol water immersion.
The test was conducted according to 2. Furthermore, it was immersed in saturated H ₂ S water at 30° C. for 500 hours to perform an adhesion test to examine its H ₂ S resistance. The results were as shown in Table 1. Example 4 Parts by weight of paint preparation ingredients (main agent) Epicote #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 () 9.8 (Epoxy group/active hydrogen = 0.8/1) A coating material was prepared according to the above formulation, and the same tests as in Example 3 were conducted. The results were as shown in Table 1. Example 5 Preparation of paint (main ingredient) 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 (Curing agent) Polyamide amine ( ) 8.7 (Epoxy group/active hydrogen = 0.9/1) A coating material was prepared according to the above formulation, and the same test as in Example 3 was conducted. The results were as shown in Table 1. Comparative Example 1 The same experiment as in Example 3 was conducted using iron oxide red, which easily reacts with hydrogen sulfide, instead of titanium oxide. The results were as shown in Table 1. Example 6 Preparation of paint Parts by weight of components (main agent) Epicoat #1001 18.7 Epototh YD-017 2.9 Talc 28.2 Titanium oxide 27.3 Zinc chromate ZTO 10.2 Disparon 4200-20 0.7 88.0 (Curing agent) Adduct of polyamidoamine () and Epicoat #1001 Product (reaction equivalent ratio polyamide amine ()/
Epicoat 1001 = 2/1) 22.0 (Epoxy group/active hydrogen = 1.2/1) In Example 3, 14.9 g of epoxy in the base resin and polyamide amine () were added in advance as a curing agent according to a conventional method.
An adduct preliminarily reacted with 7.1g of the above was used.
However, (epoxy group/active hydrogen) in the binder
The ratio was set to 1.2/1. The results were as shown in Table 1. Comparative Example 2 In Example 3, zinc chromate type C (ZnO・K ₂ CrO ₄・
ZnCrO ₄ ) (PH6.8, water soluble content 8%) was used. The results were as shown in Table 1. Comparative Example 3 Parts by Weight of Ingredients (Main Agent) Epicoat #1001 29.2 Epotote YD-017 2.6 Disparon 4200-20 0.8 32.6 (Curing Agent) Polyamide Amine () 7.1 A paint with the above composition was prepared and the same test as in Example 3 was conducted. Summer. The results were as shown in Table 1. Comparative Example 4 In Example 3, the curing agent was xylylene diamine 2.3
The experiment was conducted in place of g. The results were as shown in Table 1. Comparative Example 5 A similar experiment was carried out in Example 6 by replacing the epoxy resin component in the main resin with a resol-type phenolic resin precondensate of the epoxy resin condensed as in Example 1 of JP-A-55-165967. Ta. The results were as shown in Table 1. The expected performance in terms of bendability and hydrogen sulfide resistance could not be obtained. This is thought to be the result of a weak interface between the zinc chromate ZTO used as the anticorrosion pigment and the resol type phenolic resin precondensate of the epoxy resin that is the binder.

【table】

【table】

Claims (1)

[Claims] 1 () (a) The epoxy equivalent obtained by the addition reaction of bisphenol A having 1 to 2 oxirane rings per molecule and epihalohydrin is
180 to 2500, and (b) a polyamide amine consisting of an aliphatic diamine and a dimer acid, the vehicle having a reaction equivalent ratio of epoxy resin to polyamide amine of 0.8/1 to 1.4/1.
100 parts by weight, () 50 to 200 parts by weight of at least one filler selected from the group of carbon black, titanium oxide, aluminum powder, silicon oxide, aluminum oxide, and magnesium oxide and inert to hydrogen sulfide.
Parts by weight, () The water soluble content is 0.3% or less and the pH of the dissolved water is 6.0 to 7.0.
A two-component anticorrosive paint composition substantially free of phosphoric acid, consisting of 3 to 40 parts by weight of a rust preventive pigment of thing. 2. The anticorrosive paint composition according to claim 1, wherein the anticorrosive pigment is an oxide of at least one metal selected from the group of Ba, Zn, Cr, Mo, and AI. 3. The anticorrosive paint composition according to claim 1, wherein the anticorrosive pigment is at least one selected from the group of barium chromate, zinc chromate ZTO type, and aluminum phosphomolybdate. 4. The anticorrosive coating composition according to claim 1, wherein the aliphatic diamine is xylylene diamine.