One-pack type aqueous rust-preventive coating composition

Abstract

To provide an aqueous rust-preventive coating composition having excellent storage stability while improving rust-preventive properties of a coating film.SOLUTION: A one-pack type aqueous rust-preventive coating composition includes an aqueous resin compound containing carboxyl group, rust-preventive agent, crosslinking agent having water solubility and / or water dispersibility, and aqueous medium. Then, crosslinking agent is 1 to 10 pts.wt. for 100 pts.wt. of the aqueous resin compound. As the aqueous resin compound, at least one of acrylic polymer, styrene acrylic polymer and urethane-based polymer containing carboxyl group can be used. As the rust-preventive agent, at least one of phosphoric acid-based rust-preventive agent, molybdic acid-based rust-preventive agent, tungstic acid-based rust-preventive agent, organic metal salt-based rust-preventive agent and phosphorous acid / hypophosphorous acid-based rust-preventive agent can be used. Aqueous solution and / or water dispersion of polycarbodiimide can be used as crosslinking agent.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to one-component and water-based (aqueous) anti-rust coating compositions. [Background technology]

[0002] Conventionally, various anti-rust coating agents have been used to cover metal materials to prevent rust. Most of these anti-rust coating agents are oil-based coating agents, and the large amount of organic solvent contained in these coating agents is undesirable in terms of workability and safety, and can also be a source of environmental pollution. Therefore, in recent years, there has been an increasing demand to switch to water-based coating agents.

[0003] Water-based coating agents include those that use epoxy resin, acrylic resin, urethane resin, etc. as the resin component and incorporate various rust inhibitors into the resin component. However, such water-based coating agents have a problem in that they are inferior in rust prevention to oil-based coating agents.

[0004] For example, Patent Document 1 discloses an aqueous coating material containing an aqueous epoxy resin emulsion and a crosslinking agent, and improves rust prevention by blending a specific powder component. Patent Document 2 discloses a crosslinking agent composition for aqueous resins containing a hydrophobic crosslinking agent, a water-soluble organic compound, an oil-based medium, and an aqueous medium, and an aqueous resin composition containing this crosslinking agent composition for aqueous resins and an aqueous resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-001315 [Patent Document 2] Patent Publication No. 2021-102717 Summary of the Invention [Problem to be solved by the invention]

[0006] There is room for improvement in terms of rust prevention and storage stability in the aqueous coating material described in Patent Document 1 and the aqueous resin composition described in Patent Document 2. An object of the present invention is to provide a water-based rust-preventive coating composition that improves the rust prevention of a coating film and has excellent storage stability. [Means for solving the problem]

[0007] The one-liquid water-based anticorrosive coating composition of the present invention contains a water-based resin compound containing a carboxyl group, a rust inhibitor, a crosslinking agent having water-solubility and / or water-dispersibility, and a water-based medium, and the crosslinking agent is present in an amount of 1 to 10 parts by weight per 100 parts by weight of the water-based resin compound.

[0008] As the aqueous resin compound, at least one of an acrylic polymer, a styrene acrylic polymer, and a urethane polymer containing a carboxyl group can be used.

[0009] As the rust inhibitor, at least one of phosphoric acid-based rust inhibitors, molybdic acid-based rust inhibitors, tungstic acid-based rust inhibitors, organometallic salt-based rust inhibitors, and phosphorous acid / hypophosphorous acid-based rust inhibitors can be used.

[0010] As the crosslinking agent, an aqueous solution and / or an aqueous dispersion of polycarbodiimide can be used.

[0011] The aqueous resin compound preferably has an acid value of 5 to 30 mgKOH / g, and a pH of 7 to 9. Effect of the Invention

[0012] According to the present invention, it is possible to improve the storage stability while improving the rust prevention properties of the coating film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Anti-rust coating composition) The anti-rust coating composition of the present invention has an anti-rust function and is a one-liquid type and water-based (aqueous) coating composition (i.e., one-liquid water-based anti-rust coating composition). The anti-rust coating composition contains a water-based resin compound containing a carboxyl group, a rust inhibitor, a crosslinking agent having water-solubility or water-dispersibility, and an aqueous medium. The content of the crosslinking agent is 1 to 10 parts by weight relative to 100 parts by weight of the water-based resin compound.

[0014] The above-mentioned anti-rust coating composition is applied to an object to form a coating film, thereby improving the anti-rust properties of the coating film. In addition, even if the anti-rust coating composition is stored for a long period of time, the anti-rust properties of the coating film can be guaranteed (hereinafter referred to as "storage stability"). In addition, since the anti-rust coating composition can be dried at room temperature to form a coating film, a heat treatment for drying can be omitted. Each component contained in the anti-rust coating composition will be described below. Note that the notation "A to B" described below means A or more and B or less.

[0015] (Water-based resin compound) The water-based resin compound is a water-based resin compound containing a carboxyl group as an active hydrogen group, and is dispersed in a water-based medium. The water-based resin compound itself may be in a state of being dispersed in a water-based medium (water-soluble), or the water-based resin compound may be in a state of being dispersed in a water-based medium as an emulsion (water-dispersible). When producing the emulsion, a known emulsifier can be appropriately used.

[0016] Examples of the water-based resin compound include acrylic polymers containing carboxyl groups, styrene acrylic polymers containing carboxyl groups, and urethane polymers containing carboxyl groups. The water-based resin compound can be used alone or in combination with multiple types. There are multiple types of acrylic polymers, and one type can be used alone or in combination with multiple types. There are multiple types of styrene acrylic polymers, and one type can be used alone or in combination with multiple types. There are multiple types of urethane polymers, and one type can be used alone or in combination with multiple types.

[0017] The above-mentioned polymers (acrylic, styrene-acrylic, and urethane) can be obtained by polymerizing monomers using a polymerization initiator. Examples of the monomer that can be used include methacrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, styrene, 2-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene, divinylbenzene, phenyl(meth)acrylate, benzyl(meth)acrylate, methyl(meth)acrylate, ethyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, t-butyl(meth)acrylate, n-amyl(meth)acrylate, isoamyl(meth)acrylate, n-hexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl(meth)acrylate, decyl(meth)acrylate, dodecyl(meth)acrylate, octadecyl(meth)acrylate, and cyclohexyl(meth)acrylate. These monomers can be used alone or in combination of two or more to obtain the above-mentioned polymer.

[0018] As the polymerization initiator, for example, persulfates such as ammonium persulfate, sodium persulfate, potassium persulfate, etc., and organic peroxides such as benzoyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate, tert-butyl octoate, acetyl peroxide, etc. These polymerization initiators can be used alone or in combination.

[0019] The urethane polymer is a polyurethane resin that is dispersed in water and exists as a water-soluble or emulsion. The polyurethane resin may be a single type or a combination of two or more types.

[0020] Examples of commercially available urethane polymers include Superflex 126, Superflex 130, Superflex 150, Superflex 420, and Superflex 460 (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Takelac W-6010, Takelac W-6020, Takelac W-6061, Takelac W-405, Takelac W-605, Takelac WS-5000, and Takelac WS-4000 (all manufactured by Mitsui Chemicals, Inc.). Note that Superflex and Takelac are registered trademarks.

[0021] The acid value of the aqueous resin compound is preferably 5 to 30 mgKOH / g. The acid value is a value expressed by mg of potassium hydroxide equivalent to the moles of acid groups contained in 1 g of the aqueous resin compound, and can be measured according to the provisions of JIS K0070 (1992). By setting the acid value to 5 to 30 mgKOH / g, the rust prevention property and storage stability of the rust-preventive coating composition can be further improved.

[0022] The pH of the water-based resin compound (emulsion) is preferably 7 to 9. A neutralizing agent, which is a basic organic compound such as ammonia, can be used to adjust the pH. By adjusting the pH of the water-based resin compound (emulsion) to 7 to 9, the storage stability of the rust-preventive coating composition can be easily ensured. When ammonia is added, the volatilization speed of ammonia is appropriate, so that the crosslinking reaction (curing speed) caused by a sudden drop in pH is suppressed, and the crosslinking reaction occurs after the water in the coating film volatilizes. This allows the formation of a dense coating film and improves rust prevention.

[0023] (rust inhibitor) The rust inhibitor may be any agent that exhibits rust-preventing properties. For example, phosphoric acid-based rust inhibitors, molybdic acid-based rust inhibitors, tungstic acid-based rust inhibitors, organometallic salt-based rust inhibitors, and phosphorous acid / hypophosphorous acid-based rust inhibitors are preferably used. These rust inhibitors may be used alone or in combination.

[0024] Examples of phosphate-based rust inhibitors include phosphate compounds such as zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, barium phosphate, and magnesium phosphate; polyphosphate compounds such as zinc polyphosphate, iron polyphosphate, and aluminum polyphosphate; silicon phosphate; titanium phosphate; and organic modified products and / or hydrates of these.

[0025] Examples of the molybdic acid-based rust inhibitors include molybdic acid compounds such as zinc molybdate, aluminum molybdate, calcium molybdate, and barium molybdate; phosphomolybdic acid compounds such as zinc phosphomolybdate, calcium phosphomolybdate, aluminum phosphomolybdate, and zinc aluminum phosphomolybdate; and organic modified products and / or hydrates thereof.

[0026] Examples of tungstic acid-based rust inhibitors include tungstic acid compounds such as zinc tungstate, aluminum tungstate, calcium tungstate, barium tungstate, and organic modified products and / or hydrates of these compounds.

[0027] Examples of the organometallic salt-based rust inhibitor include zinc salts of organic nitro compounds and zinc salts of zinc butanoate.

[0028] Examples of phosphorous acid / hypophosphite-based rust inhibitors include lead phosphite, zinc phosphite, magnesium phosphite, manganese phosphite, iron hypophosphite, and calcium hypophosphite.

[0029] The content of the rust inhibitor is preferably 1 to 10 parts by weight, and more preferably 2 to 5 parts by weight, based on 100 parts by weight of the aqueous resin compound. If the content of the rust inhibitor is less than 1 part by weight or exceeds 10 parts by weight, the rust prevention properties tend to decrease.

[0030] (Crosslinking agent) The crosslinking agent is water-soluble and / or water-dispersible, and as the crosslinking agent, for example, an aqueous solution and / or an aqueous dispersion of polycarbodiimide containing a carbodiimide group in the molecule can be used. Commercially available products include Carbodilite® V02, V-02-L2, V04, V05, V10, E01, E02, E03A, E04, and E05 (manufactured by Nisshinbo Chemical Co., Ltd.).

[0031] The content of the crosslinking agent (solid content) is 1 to 10 parts by mass when the water-based resin compound is 100 parts by mass. The content of the crosslinking agent is preferably 2 to 8 parts by mass. When the content of the crosslinking agent exceeds 10 parts by mass, the rust-preventive properties of the coating film and the storage stability of the anti-rust coating composition tend to decrease, and the adhesion and abrasion resistance of the coating film tend to decrease. On the other hand, when the content of the crosslinking agent is less than 1 part by mass, the rust-preventive properties of the coating film and the storage stability of the anti-rust coating composition tend to decrease, and the appearance of the coating film tends to be impaired and the durable adhesion tends to decrease.

[0032] (aqueous medium) The aqueous medium may be water or a hydrophilic organic solvent. In consideration of the environmental load and cost reduction, a medium containing water is preferred, and a medium containing 50 parts by weight or more of water is preferred.

[0033] Examples of the hydrophilic organic solvent include alcohols, ethers, ketones, esters, etc., which have hydrophilicity. One type may be used alone, or two or more types may be used in combination.

[0034] Examples of hydrophilic alcohols include methanol, isopropanol, n-butanol, 2-ethylhexyl alcohol, ethylene glycol, propylene glycol, etc. Examples of hydrophilic ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, propylene glycol monoethyl ether, 3-methoxy-3-methylbutanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, tetrahydrofuran, etc.

[0035] Examples of hydrophilic ketones include acetone, etc. Examples of hydrophilic esters include ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, etc.

[0036] (Other additives) In addition to the above-mentioned components, other components can be added to the anticorrosive coating composition. Examples of these components include zinc oxide, carbon black, lamp black, bone black, graphite, black iron oxide, cobalt black, copper manganese iron black, molybdate orange, permanent red, permanent carmine, anthraquinone red, perylene red, quinacridone red, yellow iron oxide, titanium yellow, fast yellow, benzimidazolone yellow, cobalt green, phthalocyanine green, ultramarine blue, Prussian blue, cobalt blue, phthalocyanine blue, and quinacridone bio. Examples of additives include color pigments such as red, dioxazine violet, aluminum pigments, and pearl pigments, film-forming aids, thickeners, leveling agents, coupling agents, plasticizers such as dioctyl phthalate (DOP), butyl benzyl phthalate (BBP), dibutyl phthalate (DBP), diisodecyl phthalate (DIDP), dioctyl terephthalate (DOTP), and dioctyl adipate (DOA), antifreeze agents, pH adjusters, preservatives, antifungal agents, anti-algae agents, antibacterial agents, dispersants, defoamers, UV absorbers, light stabilizers, antioxidants, and water.

[0037] (Method of applying anti-rust coating composition) When applying the anticorrosive coating composition to an object, a known applicator can be used. Examples of applicators include sprays, rollers, and brushes. Examples of objects include chassis of automobiles, buses, and trucks, transport containers, large steel plates and processed materials such as steel materials for construction and springs, and cast iron and processed materials such as cast iron pipes and pulleys.

[0038] The amount of the anticorrosive coating composition to be applied can be determined appropriately depending on the object, but is preferably 0.05 to 0.8 kg / m 2 It is preferable to set the density to 0.08 to 0.5 kg / m 2It is more preferable to apply the anti-rust coating composition once. The number of times the anti-rust coating composition is applied can be determined appropriately depending on the object, but is preferably 1 to 3 times. When applying, the anti-rust coating composition can be diluted appropriately as necessary. After applying the anti-rust coating composition to the object, the composition can be dried at room temperature (preferably 0 to 50°C, more preferably 5 to 45°C), and can also be heated as necessary. EXAMPLES

[0039] As emulsions of water-based resin compounds, emulsion polymers A to C described below were prepared.

[0040] (Emulsion polymer A) A glass reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen gas inlet tube was charged with 1.3 parts by weight of an anionic emulsifier, 0.5 parts by weight of a nonionic emulsifier, and 130 parts by weight of ion-exchanged water, and the mixture was heated to 80°C under a nitrogen stream.

[0041] Next, a monomer mixture consisting of 37.7 parts by weight of n-butyl acrylate, 60 parts by weight of styrene, and 2.3 parts by weight of methacrylic acid, and 0.5 parts by weight of ammonia persulfate dissolved and dispersed in 10 parts by weight of ion-exchanged water were dropped over 5 hours. Then, the mixture was left at 80°C for 2 hours to complete the reaction. Next, after cooling to room temperature, 14% ammonia water was used to adjust the pH to 8.5 and the resin component (water-based resin compound) to 40 parts by weight, thereby obtaining an emulsion polymer A (styrene acrylic polymer). The acid value of the resin component (water-based resin compound) contained in the emulsion polymer A was measured and found to be 15 mgKOH / g.

[0042] (Emulsion polymer B) Emulsion polymer B (acrylic polymer) was produced by the same production method as emulsion polymer A. Here, a monomer mixture consisting of 39 parts by weight of n-butyl acrylate, 60 parts by weight of methyl methacrylate, and 1 part by weight of methacrylic acid was used as the monomer mixture. The acid value of the resin component (water-based resin compound) contained in emulsion mixture B was measured and found to be 6.5 mgKOH / g.

[0043] (Emulsion polymer C) Emulsion polymer C (styrene acrylic polymer) was produced by the same production method as emulsion polymer A. Here, as the monomer mixture, a monomer mixture consisting of 36 parts by weight of n-butyl acrylate, 60 parts by weight of styrene, and 4 parts by weight of methacrylic acid was used. In addition, the pH was adjusted to 7.5 using 14% ammonia water. The acid value of the resin component (water-based resin compound) contained in emulsion polymer C was measured and found to be 26 mgKOH / g.

[0044] (rust inhibitor) As a rust inhibitor, a phosphomolybdic acid compound (LF Bousei MC-400WK by Kikuchi Color Co., Ltd.) was prepared.

[0045] (Crosslinking agent) An aqueous polycarbodiimide solution (Polycarbodilite V-02-L2, Nisshinbo Chemical Co., Ltd.) was prepared as crosslinking agent A. An aqueous polycarbodiimide solution (Polycarbodilite E-02, Nisshinbo Chemical Co., Ltd.) was prepared as crosslinking agent B. Both crosslinking agents A and B had a solid content of 40 parts by weight.

[0046] (solvent) As the solvent A, denatured alcohol (Econol L, manufactured by Imazu Pharmaceutical Co., Ltd.) was prepared. As the solvent B, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate was prepared.

[0047] (Pigments) A carbon black processed pigment (AF Black U-14, Dainichiseika Color & Chemicals Mfg. Co., Ltd.) was prepared as pigment A. Furthermore, silica gel (Mizukasil P-707, Mizusawa Kagaku Kogyo Co., Ltd.) was prepared as pigment B.

[0048] (Plasticizer / Water) As the plasticizer, diisodecyl phthalate was prepared, and as the water, ion-exchanged water was prepared.

[0049] (Anti-rust coating composition) Using the above-mentioned components, anti-rust coating compositions of Examples 1 to 6 and Comparative Examples 1 and 2 were produced. Table 1 below shows the components and their contents contained in the anti-rust coating compositions of Examples 1 to 6 and Comparative Examples 1 and 2. The anti-rust coating compositions of Examples 1 to 6 and Comparative Examples 1 and 2 were prepared by mixing the components shown in Table 1 below. In Table 1 below, the numbers in parentheses indicate the contents of each component (rust inhibitor and solid content of crosslinking agent) when the resin component (water-based resin compound) contained in each emulsion polymer A to C is taken as 100 parts by weight.

[0050] [Table 1]

[0051] (Evaluation of rust prevention) The rust-preventive properties were evaluated by normal evaluation and post-storage evaluation, which will be described below.

[0052] (Normal rating) The rust-preventive coating compositions (Examples 1 to 6 and Comparative Examples 1 and 2) were applied to a steel plate (manufactured by Paltec Co., Ltd.) and dried (at room temperature) to form a coating film having a thickness of 50±1 μm. Next, after leaving the plate in an atmosphere of 20°C and 65% RH for 7 days, the coating film was cross-cut using a cutter knife, and a back seal was applied to the area of ​​the steel plate other than the coating film.

[0053] In this state, a salt spray test was conducted in accordance with the provisions of JIS K5600-7-1 (1999). Specifically, the steel plate on which the coating film was formed was placed in a salt spray tank and salt water was sprayed onto the steel plate. At 168 hours, 336 hours, and 500 hours after the start of salt water spraying, the areas other than the cross cuts were observed to evaluate the state of rust formation. The evaluation criteria will be described later.

[0054] (Post-storage evaluation) The rust-preventive coating compositions (Examples 1 to 6 and Comparative Examples 1 and 2) were stored at 40°C for 30 days, and then the stored rust-preventive coating compositions were applied to a steel plate (manufactured by Paltec Co., Ltd.) and dried (at room temperature) to form a coating film having a thickness of 50±1 μm. The plate was then left to stand for 7 days under an atmosphere of 20°C and 65% RH. The coating film was then cross-cut using a cutter knife, and a back seal was applied to the area of ​​the steel plate other than the coating film.

[0055] In this state, a salt spray test was conducted in accordance with the provisions of JIS K5600-7-1 (1999). Specifically, the steel plate on which the coating film was formed was placed in a salt spray tank and salt water was sprayed onto the steel plate. At 168 hours, 336 hours, and 500 hours after the start of salt water spraying, the areas other than the cross cuts were observed to evaluate the state of rust formation. The evaluation criteria will be described later.

[0056] In the normal evaluation and post-storage evaluation described above, a three-level evaluation (◯, △, ×) was performed based on the evaluation criteria described below. Evaluation: No rust was observed in areas other than the cross cuts. Evaluation: △: Slight rust is observed in areas other than the cross cuts. Evaluation: ×: Rust is evident in areas other than the cross cuts.

[0057] The results of the normal evaluation and the post-storage evaluation are shown in Table 2 below.

[0058] [Table 2]

[0059] As can be seen from Table 2 above, in the normal evaluation, in Examples 1 to 6, even after 500 hours had passed, no rust was observed or only slight rust occurred. On the other hand, in Comparative Examples 1 and 2, it was confirmed that rust had noticeably occurred after 336 hours had passed. In Comparative Examples 1 and 2, since rust had noticeably occurred after 336 hours had passed, the evaluation after 500 hours was omitted ("-" in Table 2 above). In this way, it was confirmed that Examples 1 to 6 have excellent rust prevention properties.

[0060] On the other hand, in the post-storage evaluation, in Examples 1 to 6, even after 500 hours had passed, no rust was observed or only slight rust occurred. On the other hand, in Comparative Example 2, rust was significantly generated after only 168 hours had passed, and in Comparative Example 1, rust was significantly generated after 336 hours had passed. In Comparative Examples 1 and 2, rust was significantly generated after 336 hours had passed, so the evaluation after 500 hours was omitted ("-" in Table 2 above).

[0061] As described above, it was confirmed that the anti-rust coating compositions of Examples 1 to 6 had excellent anti-rust properties even after long-term (30 days) storage. That is, it was confirmed that the anti-rust coating compositions were able to maintain excellent anti-rust properties even after storage, and had excellent storage stability.

Claims

1. a water-based resin compound containing a carboxyl group; Rust inhibitors and A crosslinking agent having water-solubility and / or water-dispersibility; An aqueous medium, A one-liquid water-based anticorrosive coating composition, characterized in that the crosslinking agent is contained in an amount of 1 to 10 parts by weight per 100 parts by weight of the water-based resin compound.

2. 2. The one-component water-based anticorrosive coating composition according to claim 1, wherein the water-based resin compound is at least one of an acrylic polymer, a styrene-acrylic polymer, and a urethane polymer, each of which contains a carboxyl group.

3. 2. The one-component water-based rust-preventive coating composition according to claim 1, wherein the rust inhibitor is at least one of a phosphoric acid-based rust inhibitor, a molybdic acid-based rust inhibitor, a tungstic acid-based rust inhibitor, an organometallic salt-based rust inhibitor, and a phosphorous acid / hypophosphorous acid-based rust inhibitor.

4. 2. The one-component water-based anticorrosive coating composition according to claim 1, wherein the crosslinking agent is an aqueous solution and / or an aqueous dispersion of polycarbodiimide.

5. The acid value of the aqueous resin compound is 5 to 30 mgKOH / g, 2. The one-liquid water-based anticorrosive coating composition according to claim 1, wherein the water-based resin compound has a pH of 7 to 9.

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