JPH0521950B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field The present invention relates to a coating composition for underwater coating, and more specifically, it is used for coating underwater parts of marine structures, etc., underwater or water-wet surfaces such as spray zones, and has excellent coating workability and corrosion inhibiting effects. The present invention relates to a coating composition having the following properties. Prior Art Compositions containing epoxy resins and polyamine resins as resin components are well known, but due to their strong hydrophobicity, they have poor wettability on hydrophilic coated surfaces. A method of adding polyester resin, which is more hydrophilic than epoxy resin, as a modifier to adjust the hydrophilic/hydrophobic ratio, or a polycarboxylic acid amine salt having oleic acid or polyoxyalkylene groups in the epoxy-polyamine resin system. A method of adding surfactants such as the following has been proposed. These methods can improve the wettability of the coated surface to some extent, but they are still insufficient. Especially when the composition has a viscosity of 50 poise or less, the composition applied in water will aggregate and will not coat the coated surface uniformly. The problem is that it cannot be covered. Problems to be Solved by the Invention Therefore, the wettability of an epoxy resin coating composition containing a curing agent to a water-wet surface is greatly improved, and even at low viscosity, the surface to be coated can be coated easily and uniformly in water. There is a need for a coating composition for underwater coating that can exhibit a corrosion inhibiting effect, and it is an object of the present invention to meet this problem. Means for Solving the Problems According to the present invention, the above object includes an epoxy resin and a polyamine resin or a polyamide resin as resin components, and has the formula:

[Formula] or (In the formula, R is an alkyl group having 6 to 20 carbon atoms, and n is a positive integer of 0 or 2 to 5.) Add 0.1 to 4.0% of the total composition by weight of the metal salt or amine salt of phosphoric acid mono- or diester represented by %
This can be achieved by using a coating composition for underwater painting that contains the following. The epoxy resin used in the present invention has the following formula: (In the formula, Z is -H, _-CH3 , _-C2H5 ) A resin having _at least one glycidyl ether group in the molecule, typical examples thereof include bisphenol. Diglycidyl ether of A, diglycidyl ether of bisphenol F, phenol novolac epoxy resin, diglycidyl ether of alkylene oxide adducts of bisphenols, other carboxylic acids, amines
Alternatively, phosphoric acid-modified bisphenol A diglycidyl ether or the like can be used. In addition, a curing agent commonly used for epoxy resins is blended into this epoxy resin as a curing agent, and these can be, for example, aliphatic polyamines, aromatic polyamines, alicyclic polyamines, polyamides, polymercaptans, etc., but especially polyamides, etc. Alternatively, a polyamine resin is preferable. These resins are usually used in a ratio of 0.5 to 2.0 equivalents of active hydrogen of amine or mercaptan to 1 equivalent of epoxy group of the epoxy resin, and are provided as a two-component paint, which is uniformly mixed and applied at the time of use. However, the present invention is characterized in that a specific alkyl phosphate is blended into the coating composition in an amount of 0.1 to 4.0% by weight based on the total composition. When the present inventors added various surfactants to improve the wettability of epoxy resin paints to water-wet surfaces, they were very surprised to find that almost no noticeable improvement effect was obtained. We have found that only certain alkyl phosphates can specifically significantly improve wettability. That is, in the present invention, the formula

[Formula] or (In the formula, R is an alkyl group having 6 to 20 carbon atoms, and n is a positive integer of 0 or 2 to 5.) A metal salt or amine salt of phosphoric acid mono- or diester represented by 0.1-4.0% by weight of the product, preferably 0.2-1.5% by weight
It is added at a ratio of Such additives can be incorporated into the epoxy resin component or the polyamide or polyamine resin component of the two-component epoxy resin coating, or alternatively, they can be added directly to the mixed system of these resin components prior to use.
If the amount added is less than 0.1% by weight of the total composition, the wettability to the coated surface will be poor and the corrosion inhibiting effect will be insufficient.
On the other hand, if it exceeds 4.0% by weight, the hydrophilicity of the paint becomes too large and the paint begins to emulsify in water, resulting in a tendency for workability and water resistance of the cured film to deteriorate, both of which are undesirable. As already mentioned, the present inventors have tried adding various surfactants to the system consisting of an epoxy resin and a curing agent. agents, polyoxyethylene alkyl phenyl ethers, etc., zwitterionic surfactants such as alkyl betaines, etc.
Anionic surfactants such as alkylbenzene sulfonates, alkyl sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, sorbitan monopalmitate, fatty acid salts, etc. are all ineffective, and metal salts of the above-mentioned phosphoric acid mono- or diesters, etc. It has been discovered that alkali metal salts, alkaline earth metal salts, or amine salts such as triethanolamine salts can specifically significantly improve wettability. Although it is not fully understood why these salts bring about the effect of significantly improving wettability, the present inventors have investigated the interfacial tension with water and the lamella length of the resin liquid in water as shown below. It is believed that the characteristics of these representative phosphate ester salts contribute to the improvement of wettability. That is, bisphenol A diglycidyl ether with an epoxy equivalent of 190 as an epoxy resin varnish.
Hysol SAS296 with 70 parts by weight and non-reactive diluent
(Aromatic hydrocarbon diluent, Nippon Petrochemical) using a mixture of 30 parts by weight and the additive to be tested.
When 1.5 parts by weight is mixed and further mixed with water, the liquid is separated into a lower layer of resin varnish and an upper layer of water. Liquid temperature 20℃
So, here is the dynometer (BYK-Chemie)
GmbH) platinum ring is inserted, 1.5mm/
The interfacial tension (maximum tension) with water is measured by raising the ring at a speed of 1 minute, and the length of the thin film of varnish attached to the ring from the point showing the maximum tension until it breaks is measured as the lamella length. , all of the additives used in the present invention exhibit an interfacial tension between the resin varnish and water of 4 dynes/cm or more and a lamella length of 0.2 or less, whereas most of the surfactants mentioned above exhibit a value of 0.2 or less. The interfacial tension of something is 4 dynes/cm
It has been found that the lamella length is less than 4 dynes/cm and the lamella length is greater than 0.2 cm. The paint composition for underwater painting according to the present invention may contain pigments and aggregates used in conventional underwater curable paints as appropriate. The pigments and aggregates used have a coloring function and are also used to prevent the coating material from floating due to the difference in specific gravity with water when painting in water, and preferably have a high specific gravity and excellent corrosion resistance. . For example, titanium oxide, zinc oxide, iron oxide, aluminum oxide, aluminum powder, barium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, talc, clay, kaolin, mica, graphite, silica,
Examples include diatomaceous earth and asbestos. Examples of the aggregate include silica sand, glass lake, aras fiber, synthetic fiber, 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 a thixotropic agent, a silane coupling agent, and an inhibitor, a non-reactive diluent for adjusting viscosity, a solvent, and the like can be added to the coating composition. The paint composition for underwater painting according to the present invention includes steel materials,
It can be easily applied with a brush, roller, trowel, etc. to wet surfaces such as concrete or in a splash zone, and has the following advantages compared to conventional epoxy-based underwater curing paints. That is, the wettability to the surface to be coated is significantly improved, and even a low-viscosity composition has good coating workability. The corrosion resistance of the coating film is improved due to the great corrosion inhibiting effect of the alkyl phosphate. As mentioned above, the paint composition for underwater painting of the present invention has excellent coating workability underwater and on wet surfaces, and the formed coating film has a large anticorrosion effect over a long period of time, and is suitable for coating underwater and wet surfaces such as marine structures. Suitable as a coating material. 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◎…100% of the surface to be coated can be coated with one stroke with a spatula
% coverage ○…2 strokes with a spatula will cover the surface to be coated 100%
% coverage △... Condition where 100% of the coated surface can be covered by 3 to 5 or more strokes with a spatula ×... 100% coverage of the coated surface by 6 or more strokes with a spatula
100% coverage condition Wettability to coated surface Visually observe the contact angle of the cured film applied with a spatula to the coated surface. ○...Smaller than 45°△...45°~90° ×...Larger than 90° Electrical resistance of coating film Electrical resistance value measurement conditions: Electrode area 50cm ² , frequency 1kHz Measuring device: CJA-3 type anticorrosive coating film Test device (Shindenshi Kogyo) Corrosion inhibition effect A bare steel plate was immersed in a solution in which 0.25% by weight of a surfactant was dissolved or dispersed in seawater, and evaluation was made based on the state of rust on the steel plate after 7 days. ○...No rust △...0.03-1% rust x...1% or more rust Example 1-3 Bisphenol A diglycidyl ether with epoxy equivalent of 190, Electrostripper N (registered trade name, C ₈ higher alkyl) Mixture of triethanolamine salts of phosphoric acid mono- and diesters (Kao Atlas), titanium oxide, talc, and glass flakes were added to the coating liquid in the proportions shown in Table 1. A paint containing a curing agent and an appropriate amount of a non-reactive diluent (Hysol SAS296, Nippon Petrochemical) as a viscosity modifier was used as an underwater coating composition. A 3.2mm thick steel plate that has been rusted in seawater for one year,
Using a steel plate treated with St3 (according to SIS05-5900) with a wire brush as the object to be coated, the above underwater coating composition was applied to a thickness of approximately 3 mm with a spatula in seawater, and the underwater coating workability and surface to be coated were evaluated. The wettability to was evaluated. Furthermore, the electrical resistance was measured after one month of immersion. The above results are shown in Table 1. Example 4 Bisphenol A diglycidyl ether, (epoxy equivalent: 190), alkyl phosphate (Electrostripper N, Kao Atlas), and modified aliphatic polyamine (Fujikyure 5405, Fuji Kasei)
The clears were combined in the formulation shown in Table 1 to form a coating composition for underwater coating (35 poise/25°C), and the underwater coating workability and wettability to the coated surface were evaluated. The results are shown in Table 1. Comparative Example 1 Evaluations were made in the same manner as in Examples 1 to 3 using a comparative composition in which a curing agent was combined with a coating liquid in which the alkyl phosphate was removed from Examples 1 to 3. The results are shown in Table 1. Comparative Example 2 Evaluations were made in the same manner as in Examples 1 to 3 using a comparative composition in which a coating liquid containing an increased amount of alkyl phosphate and a curing agent were combined compared to Examples 1 to 3. The results are shown in Table 1. Comparative Examples 3 to 6 Comparative compositions using the surfactants shown in Table 1 instead of the alkyl phosphate in Example 4 were evaluated in the same manner as in Example 4. The results are shown in Table 1. Furthermore, the corrosion inhibition effects of alkyl phosphates were compared with those of other surfactants. The results are shown in Table 2. Furthermore, the fact that various surfactants other than those of the present invention cannot achieve the purpose of the invention is shown as reference material.

【table】

【table】

【table】

[Table] *…Effect of surfactant on underwater painting workability, same as Example 4
It was evaluated using Clear.

Claims (1)

[Claims] 1. Contains an epoxy resin and a polyamine resin or a polyamide resin as resin components, and as a surfactant, bisphenol A diglycidyl ether with an epoxy equivalent of 190 and a non-reactive aromatic hydrocarbon diluent of 70 : Mix 1.5 parts by weight with 30 parts by weight mixture and further mix with water to create a separated layer of resin varnish and water. At a liquid temperature of 20℃, insert a platinum ring of a dynometer and ring at a speed of 1.5 mm/min. When the interfacial tension between water and resin varnish is measured by increasing An expression [formula] that has the following properties, or (In the formula, R is an alkyl group having 6 to 20 carbon atoms, and n is a positive integer of 0 or 2 to 5.) Add 0.1 to 4.0% of the total composition by weight of the metal salt or amine salt of phosphoric acid mono- or diester represented by %
A coating composition for underwater painting containing.