JPH0521949B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field The present invention relates to an underwater curable epoxy coating composition, more specifically, the main ingredient is an epoxy resin with excellent adhesion and water resistance, which is used for coating underwater areas and tidal zones such as marine structures, ports, and river facilities. The present invention relates to a coating composition. Prior Art Various types of paints have been known as underwater curing paints. Among these, compositions made by adding pigments to epoxy-polyamide resins take advantage of the polyamide resin's surfactant ability and are designed to easily wet the surface to be coated in water, but the polyamide resin dissolves in water. It easily dissolves into water in an uncured state, so to prevent this, it is necessary to increase the viscosity of the paint using pigments or the like. However, this viscosity reduces the wettability with the surface to be coated and significantly impairs coating workability. Furthermore, the adhesion of the cured film to the surface to be coated and the corrosion resistance are not sufficient, and long-term practical use cannot be expected. On the other hand, compositions prepared by adding pigments to epoxy-polyamine resins generally have strong hydrophobic properties and have poor wettability on the hydrophilic surface to be coated, and for this reason a number of improvement techniques have been proposed. For example, there are methods of adjusting the hydrophilic/hydrophobic balance using surfactants and the like to improve wettability with the surface to be coated, but this has not yet led to improved adhesion of the cured film. Furthermore, the use of surfactants has the problem of reducing water resistance. As another technique, attempts have been made to modify epoxy resins with phosphoric acid, but there are problems with the adhesion of the cured film. Problems to be Solved by the Invention Therefore, there is a need for an underwater-curable epoxy coating composition that can be easily coated on a surface to be coated in water, has excellent adhesion of the cured film, and can withstand long-term corrosion protection. It is an object of the present invention to provide a composition. Means for Solving the Problems According to the present invention, in order to achieve the above object,
A two-component type characterized by containing a carboxylic acid-modified epoxy resin obtained by reacting an epoxy resin with a polyhydric carboxylic acid having at least one hydroxyl group in the molecule, and a polyamide resin or a polyamine resin as resin components. A water-curable epoxy coating composition is provided. In the present invention, a polar group is introduced into the molecule by reacting a portion of the epoxy resin with carboxylic acid without losing the excellent coating performance and curability of the epoxy resin, thereby achieving improved adhesion. It will be done. The carboxylic acid-modified epoxy resin used in the present invention can be produced from an epoxy resin and a polyhydric carboxylic acid having at least one hydroxyl group in the molecule, and usually both of these are added per equivalent of epoxy group in the epoxy resin. The reaction is carried out such that the carboxyl group of the carboxylic acid is in a proportion of 0.01 to 0.5 equivalent, preferably 0.01 to 0.3 equivalent. Carboxyl group is 0.01
If it is less than an equivalent amount, paint workability and adhesion of the cured film tend to deteriorate, and if it exceeds 0.5 equivalent, the viscosity increases, both of which are undesirable. The reaction temperature is usually about 50 to 150°C. Further, 0.1% or less of tertiary amine may be added as a reaction accelerator if necessary. Although a solvent is not necessarily required in this reaction, the reaction may be carried out in the presence of a solvent. Examples of solvents used in this case include aromatic solvents, ketone solvents, ether solvents, etc. The amount of these solvents used is usually about 5 to 50 parts by weight per 100 parts by weight of the target carboxylic acid-modified epoxy resin. It is. The carboxylic acid-modified epoxy resin thus obtained is usually liquid, but if it is solid, it is preferably used after being dissolved with a diluent.
The epoxy equivalent is 4000 or less, preferably about 190 to 500. The epoxy resin used as a raw material in the present invention has the following formula: (In the formula, Z is -H, -CH ₃ , -C ₂ H ₅ ) having at least one glycidyl ether group in the molecule, and representative examples thereof include, for example, bisphenol A. Preferred examples include diglycidyl ether of bisphenol F, diglycidyl ether of phenol novolak epoxy resin, and diglycidyl ether of alkylene oxide adducts of bisphenols. In the present invention, polyhydric carboxylic acids having at least one hydroxyl group in the molecule are used as the carboxylic acids used for modifying the epoxy resin, and in particular, malic acid, tartaric acid, and citric acid have at least one hydroxyl group in the molecule. Dicarboxylic acids and tricarboxylic acids having a hydroxyl group are preferred. In the present invention, ordinary curing agents for epoxy resins are used as curing agents for the above-mentioned carboxylic acid-modified epoxy resins, such as aliphatic polyamines,
They may be aromatic polyamines, alicyclic polyamines, polyamides, polymercaptans, etc., but polyamide resins and polyamine resins are particularly preferred. The amount of these curing agents used is also the amount used as a normal curing agent, and usually about 0.5 to 2.0 equivalents of amine equivalent in the case of polyamine and active hydrogen equivalent of mercaptan in the case of polymercaptan are used per equivalent of epoxy group. Bye. Further, the underwater curable epoxy coating composition according to the present invention may optionally contain pigments and aggregates used in conventional underwater curable coatings. The pigments and aggregates used not only have a coloring function but also prevent the coating material from floating due to the difference in specific gravity with water when painting in water, and those with high specific gravity and excellent corrosion resistance are used. preferable. For example, titanium oxide, zinc oxide, iron oxide, aluminum oxide, aluminum powder, barium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate,
Examples include talc, clay, kaolin, mica, graphite, silica, diatomaceous earth, and asbestos. Examples of the aggregate include silica sand, glass flakes, glass fibers, synthetic fibers, natural or artificial micasias iron oxide, and the like. The blending amount of the pigment and aggregate is preferably 60% or less as the volume concentration of the pigment and aggregate in the entire composition. Furthermore, if desired, modifiers such as surfactants, thixotropic agents, silane coupling agents, and inhibitors may be added to the coating composition.
It is also possible to add non-reactive diluents, solvents, etc. for viscosity adjustment. The underwater curable epoxy coating composition according to the present invention can be easily applied underwater to steel materials, concrete, etc. with a brush, roller, trowel, etc., and has the following advantages compared to conventional epoxy underwater curable coatings. have It has good wettability with the surface to be coated and has excellent painting workability. Excellent adhesion of cured film. It is an electrically high resistance film and has excellent corrosion resistance. As mentioned above, the underwater curable epoxy coating composition of the present invention has excellent underwater coating workability, and the formed coating film has a large anti-corrosion effect over a long period of time, making it suitable for coating spray zones and submerged areas of marine structures. It is suitable as a material for EXAMPLES The present invention will be explained in more detail by showing Examples and Comparative Examples below. In the examples and comparative examples,
All parts are by weight. The evaluation method in Examples and Comparative Examples is as follows. Underwater painting workability ◎...The surface to be coated can be coated with one stroke with a spatula.
Condition where 100% coverage is possible ○...The coated surface is coated twice with a spatula.
Condition in which 100% coverage is possible △... Condition in which 100% of the surface to be coated can be covered by 3 to 5 strokes with a spatula ×... Condition in which the surface to be coated can be covered in 6 or more strokes with a spatula To the surface to be coated Visually observe the contact surface of the cured film with the surface to be coated. ○...Less than 14゜△...45゜~90゜ ×...Better adhesion than 90゜ Remaining coating area by goblin test at 10mm intervals ◎...95% or more ○...94~80% △... ...79 to 50% ×...49% or less Electrical resistance of the coating Film AC electrical resistance value of the coating Measurement conditions: Electrode area 50cm ² , frequency 1kHz Measuring equipment: CJA-3 type anticorrosive coating tester (Shindenshi Kogyo Co., Ltd.) Examples 1 to 9 The epoxy resins and carboxylic acids shown in Table 1 were mixed, 0.05% of N,N-dimethylbenzylamine was added as a reaction accelerator, and the reaction was carried out at 130°C for 3 hours to form a carboxylic acid. An acid-modified epoxy resin was obtained. 100 parts of the resin, 10 parts of titanium oxide, 50 parts of talc,
A paint was prepared by mixing 30 parts of glass flakes, blending a curing agent in the proportions shown in Table 1, and adding an appropriate amount of a non-reactive diluent (Hysol SAS296, manufactured by Nippon Petrochemicals) as a viscosity modifier. A water-curable epoxy coating composition was prepared. However, in Example 8, the above pigment was not added and it was used as a clear. A steel plate with a thickness of 3.2 mm that has been rusted in seawater for one year and treated with St-3 (according to SIS05-5900) with a wire brush is used as the substrate to be coated, and the above-mentioned underwater-curable epoxy coating composition is applied in seawater. The coating was applied to a thickness of approximately 3 mm using a spatula, and its underwater coating workability and wettability to the surface to be coated were evaluated. Furthermore, the adhesiveness and electrical resistance of the cured film after one year of immersion were measured. The above results are shown in Table 1. Comparative Example 1 A paint was manufactured according to the formulation of MIL-P-28579 (YD), and the same evaluation as in the example was performed using the paint. The results are shown in Table 2. Comparative Example 2 A comparative composition was prepared by mixing 100 parts of bisphenol A diglycidyl ether (epoxy equivalent: 190) with the same pigment formulation as in the example in the same proportion, and adding a curing agent in the proportion shown in Table 2. Obtained. Table 2 shows the results of the same evaluation as in Examples using this composition. Comparative Example 3 100 parts of bisphenol A diglycidyl ether (epoxy equivalent: 190) and 2 parts of orthophosphoric acid were mixed and reacted at 80°C for 5 hours to obtain a phosphoric acid-modified epoxy resin. Comparative compositions were obtained by mixing 100 parts of the resin with the same proportions of pigments as in the examples, and blending curing agents in the proportions shown in Table 2. Table 2 shows the results of the same evaluation as in Examples using this composition. Comparative Example 4 Two alkylbenzenesulfonates were added to Comparative Example 2.
A comparative composition was obtained. Table 2 shows the results of the same evaluation as in Examples using this composition. Comparative Example 5 Two parts of oleic acid was mixed with Comparative Example 2 to obtain a comparative composition. Table 2 shows the results of the same evaluations as in Examples using this composition.

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Claims (1)

[Claims] 1. A carboxylic acid-modified epoxy resin obtained by reacting an epoxy resin with a polyhydric carboxylic acid having at least one hydroxyl group in the molecule, and a polyamide resin or a polyamine resin as resin components. Characteristic underwater curable epoxy paint composition. 2 Carboxylic acid-modified epoxy resin is obtained by reacting an epoxy resin with a polyhydric carboxylic acid having at least one hydroxyl group in the molecule in an amount such that the ratio of carboxyl groups to 1 equivalent of epoxy group is 0.01 to 0.5 equivalents. The composition according to claim 1, which is a resin comprising: