JP2013060536A - Aqueous emulsion coating material and coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous emulsion coating material including a metallic zinc powder and an aqueous emulsion binder, using water as the main solvent, wherein aggregation of the metallic zinc powder and gelling of the coating material are suppressed by improving dispersion stability of the metallic zinc powder, and coating workability is improved by suppressing generation of hydrogen gas.SOLUTION: This aqueous emulsion coating material includes at least one aqueous emulsion binder selected from an aqueous solution of a water-soluble resin and an aqueous dispersion of a water-dispersible resin, a water-soluble polymer compound, a metallic zinc powder and an organic solvent.

Description

  The present invention relates to a water-based emulsion paint and a coating method. More specifically, the present invention relates to a water-based emulsion paint containing metallic zinc powder and a coating method using the water-based emulsion paint.

  Since zinc has an excellent antirust effect on iron, paints containing metallic zinc powder have been developed and widely used. Examples of such paints include zinc rich paint and zinc paint. Zinc rich paint is used for, for example, a large-scale structure in which steel materials such as housing members, bridges, tanks, plants, ships, etc. are frequently used. On the other hand, the zinc paint is used as, for example, a galvanized repair paint, a repair paint for welded parts, and the like. Among these, the cured film formed by zinc rich paint has a very large content of metal zinc powder of usually 70% by weight or more, and exhibits a very excellent rust prevention effect for various members including iron.

  The zinc rich paint is roughly classified into an inorganic zinc rich paint using ethyl silicate as a binder and an organic zinc rich paint using an epoxy resin as a binder. The inorganic zinc-rich paint is quick-drying, and its cured film contains 80% by weight or more of metallic zinc powder, and exhibits an excellent rust prevention effect due to the synergistic effect of the metallic zinc powder and the binder. In addition, the organic zinc rich paint has a good antirust effect and is excellent in painting workability. For example, it can be easily applied with a brush. Furthermore, the cured film has high adhesion to the surface of the member containing iron and adhesion to the top coat.

  Each of these zinc rich paints contains an organic solvent as a solvent. From the viewpoints of environmental protection, ensuring worker safety, and VOC (volatile organic compound) regulations, some or all of the solvent is water. Water-based zinc rich paints have been demanded, and various proposals have been made.

  For example, an aqueous zinc rich paint containing a chelating agent such as alkali silicate, metallic zinc powder, ethylenediaminetetraacetic acid and water (see Patent Document 1), an aqueous zinc rich containing alkaline silicate, metallic zinc powder, flaky silica and water. Paint (see Patent Document 2), water-based emulsion of epoxy resin, water-based zinc-rich paint containing metal zinc powder and amine curing agent (refer to Patent Document 3), aqueous solution containing alkali silicate, ammonium ion and halogen ion, and metal zinc Water-based zinc rich paint containing powder (see Patent Document 4) and the like.

  On the other hand, it is known to add cellulose ethers such as carboxymethylcellulose as a thickener to various coating materials. Examples of the combined use of metallic zinc powder and cellulose ethers include metallic zinc powder, binder resin, calcium carbonate whisker and organic solvent, and as a binder, partially hydrolyzed polyalkyl silicate or a modified product thereof and cellulose ethers An inorganic zinc-rich paint using a mixture of these is proposed (see Patent Document 5).

JP 2005-154557 A JP 2006-160776 A JP 2008-272666 A JP 2009-249490 A JP 11-293200 A

  In the water-based zinc rich paints described in Patent Documents 1 to 4, the metal zinc powder and the binder alkali silicate or epoxy resin coexist in water. Under such coexistence, the dispersibility of the metal zinc powder in the paint is lowered, and inconveniences such as aggregation of the metal zinc powder and gelation of the paint are likely to occur. Applying paint with such inconvenience to the surface of the member and drying the resulting coating to form a cured film results in variations in the film thickness of the cured film, and the surface of the cured film becomes uneven, The rust prevention effect may be partially insufficient.

  In addition, since zinc is an amphoteric metal and the binder has acidity or alkalinity, there is a problem that metal zinc powder reacts with the binder in the presence of water to generate hydrogen gas. For this reason, bubbles of hydrogen gas are easily generated in the coating film made of the water-based zinc rich paint described in Patent Documents 1 to 4. Since hydrogen gas bubbles float on the surface of the coating film and crack, crater-like depressions and cracks are generated on the surface of the cured film obtained by drying the coating film. As a result, the mechanical strength and durability of the cured film are locally reduced, which causes a decrease in the rust prevention effect of the cured film and shortens the service life. In addition, the depressions and cracks impair the smoothness of the cured film surface.

  Furthermore, when forming a topcoat cured film on the surface of the cured film, depressions and cracks on the surface of the cured film are caused by variations in the film thickness of the topcoat cured film, a decrease in adhesion between the cured film and the topcoat cured film, It causes a decrease in mechanical strength and durability.

  On the other hand, Patent Document 5 only describes that the metallic zinc powder, the binder resin, and the cellulose ether coexist in an organic solvent, and the metallic zinc powder, the binder resin, and the cellulose ether coexist in water. There is no mention or suggestion.

  The object of the present invention includes metallic zinc powder and binder resin, and despite the use of water as the main solvent, the aggregation of metallic zinc powder, gelation of paint and generation of hydrogen gas are suppressed, and the coating workability is excellent. A water-based emulsion paint is provided.

  The present inventors have conducted extensive research in view of the problems of the prior art. As a result, the combined use of water-based emulsion binders, water-soluble polymer compounds, metallic zinc powder, and organic solvents reduces the content of organic solvents, suppresses the aggregation of metallic zinc powder and gelation of paint, and enables painting. It was found that a paint having good workability can be obtained. Furthermore, the inventors of the present invention have a function in which the water-soluble polymer compound has a function of suppressing aggregation of metal zinc powder and a function of suppressing generation of hydrogen due to a reaction between an aqueous emulsion binder and metal zinc powder. As a result, the present invention was completed.

That is, the aqueous emulsion paint of the present invention contains at least one aqueous emulsion binder selected from an aqueous solution of a water-soluble resin and an aqueous dispersion of a water-dispersible resin, a water-soluble polymer compound, metallic zinc powder, and an organic solvent. It is characterized by.
A preferable aqueous emulsion paint of the present invention is obtained by mixing a liquid containing an aqueous emulsion binder and a water-soluble polymer compound with a liquid containing metal zinc powder and an organic solvent.
Another preferable water-based emulsion paint of the present invention is obtained by mixing a liquid containing metal zinc powder, a water-soluble polymer compound and an organic solvent, and a water-based emulsion binder.

In the water-based emulsion paint of the present invention, the amount of water contained in the water-based emulsion binder is preferably the same as or more than the amount of the organic solvent.
In the water-based emulsion paint of the present invention, 0.1 to 500 parts by weight of metal zinc powder, 0.01 to 20 parts by weight of a water-soluble polymer compound, and 0% of organic solvent with respect to 100 parts by weight of the resin solid content of the water-based emulsion binder. More preferably, the amount of water contained in the water-based emulsion binder is 1 to 20 times the content of the organic solvent.
In the water-based emulsion paint of the present invention, the metal zinc powder preferably has a volume average particle size of 0.1 μm to 100 μm.

In the water-based emulsion paint of the present invention, the water-soluble polymer compound is preferably at least one selected from cellulose ethers and polyvinyl alcohol.
The water-soluble polymer compound is preferably a cellulose ether, and the cellulose ether is at least one selected from the group consisting of methylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxyethylcellulose, and carboxymethylcellulose. Is more preferable.
The number average molecular weight of the water-soluble polymer compound is more preferably 8000 to 75000.

  In a preferred form of the aqueous emulsion paint of the present invention, the aqueous emulsion binder is an aqueous dispersion of a water-dispersible resin, and the aqueous dispersion of the water-dispersible resin is an aqueous emulsion of a silicone resin. Such a cured film of the water-based emulsion paint has heat resistance at a temperature of 200 ° C to 400 ° C.

  The water-based emulsion paint of a preferred form of the present invention comprises 100 parts by weight of an aqueous dispersion of a silicone resin (resin solid content) and 0.01 to 20 parts by weight of a water-soluble polymer compound having a number average molecular weight of 8000 to 75000. And a liquid containing 0.1 to 500 parts by weight of metal zinc powder and 0.1 to 100 parts by weight of an organic solvent, and the amount of water contained in the aqueous dispersion is It is characterized by being 1 to 20 times the amount of the solvent.

Further, the coating method of the present invention includes a liquid containing at least one water-based emulsion binder selected from an aqueous solution of a water-soluble resin and an aqueous dispersion of a water-dispersible resin, a water-soluble polymer compound, a metal zinc powder, and an organic solvent. The resulting aqueous emulsion paint is applied to the surface of a member containing iron, and the obtained coating film is dried.
Another aspect of the coating method of the present invention is a method comprising at least one aqueous emulsion selected from a liquid containing metallic zinc powder, a water-soluble polymer compound and an organic solvent, an aqueous solution of a water-soluble resin, and an aqueous dispersion of a water-dispersible resin. A binder is mixed, and the obtained aqueous emulsion paint is applied to the surface of a member containing iron, and the obtained coating film is dried.
The member to which the water-based emulsion paint is applied is preferably a member that is exposed to a temperature of 200 ° C to 400 ° C.

  The water-based emulsion paint of the present invention has good dispersibility of the metal zinc powder and other components in spite of coexistence of metal zinc powder and acidic or alkaline water-based emulsion vine in the presence of water. Aggregation of metallic zinc powder and gelation of paint do not occur, generation of hydrogen gas is further suppressed, and excellent workability is achieved. More specifically, even if the water-based emulsion paint of the present invention is allowed to stand at a temperature of 40 ° C. for 24 hours, no hydrogen is generated, and metal zinc aggregation and paint gelation do not occur.

  For this reason, the water-based emulsion paint of the present invention has excellent coating workability, can be easily applied by simple operations such as roller coating and brush coating, has little variation in film thickness, has a dense structure, A cured film with high mechanical strength can be formed. Moreover, the surface of the cured film formed from the water-based emulsion paint of the present invention has very few defects such as crater-like depressions and cracks.

  The coating method of this invention can form a cured film efficiently on the member surface containing iron by using the said water-system emulsion coating material.

  The water-based emulsion paint of the present invention contains at least one water-based emulsion binder selected from an aqueous solution of a water-soluble resin and an aqueous dispersion of a water-dispersible resin, a water-soluble polymer compound, metallic zinc powder, and an organic solvent.

  As the aqueous emulsion binder, an aqueous solution of a water-soluble resin and an aqueous dispersion of a water-dispersible resin are used. Here, the water-soluble resin and the water-dispersible resin are not particularly limited as long as they are water-soluble and / or water-dispersible resins, but alkyd resins, aminoalkyd resins, melamine resins, silicone resins, urea resins, phenols. It is preferably at least one selected from the group consisting of resin, acrylic resin, epoxy resin, polybutadiene, fiber derivative resin, benzoguanamine resin, vinyl resin, urethane resin, polyamide, polyester, and polyacrylic resin.

  Among these resins, a silicone resin that is a water-dispersible resin is preferable from the viewpoint of further improving the heat resistance of a cured film formed from a paint. As a water-based emulsion binder, a cured film formed from a water-based emulsion paint containing a water-based emulsion of a silicone resin has high heat resistance and, for example, does not change even when exposed to a temperature of about 200 ° C to 400 ° C. High antirust performance. Moreover, an epoxy resin is preferable from the viewpoint of further improving the corrosion resistance of the cured film formed from the paint.

  The content of the water-soluble resin or water-dispersible resin in the water-based emulsion binder, that is, the resin solid content is preferably 10 to 60% by weight, more preferably 30 to 50% by weight, based on the total amount of the water-based emulsion binder. By setting the resin solid content in the above range, the water content and the organic solvent content in the water-based emulsion paint of the present invention are in an appropriate ratio, and the generation of hydrogen by the water-soluble polymer compound The suppression effect can be sufficiently exhibited. Moreover, the coating workability of the water-based emulsion paint of the present invention is further improved.

  If the solid content is less than 10% by weight, the workability of the water-based emulsion paint of the present invention on the surface of the article is lowered, and a cured film having high strength and durability tends to be unable to be formed. If the solid content exceeds 60% by weight, the solubility of the water-soluble resin or the water-dispersibility of the water-dispersible resin is lowered, and these precipitates tend to occur.

  The amount of water contained in the water-based emulsion binder is preferably the same as or greater than the amount of organic solvent described later, and more preferably 1 to 20 times the amount of organic solvent. As a result, the water-based emulsion paint has a low organic solvent content and is highly safe for the environment and workers. Further, when the amount of water and the amount of the organic solvent are within the above ranges, the water-soluble polymer compound suppresses the reaction between the aqueous emulsion binder and the metal zinc powder and suppresses the aggregation of the metal zinc powder. The effect is further enhanced and the generation of hydrogen is further reduced.

  The water-soluble polymer compound is not particularly limited as long as it is a polymer compound having water solubility, but at least one selected from cellulose ethers and polyvinyl alcohol is preferable. That is, a water-soluble polymer compound having a plurality of hydroxyl groups is preferable. The water-soluble polymer compound may be used in the form of an aqueous solution. By making such a water-soluble polymer compound present in the water-based emulsion paint of the present invention, generation of hydrogen gas due to the reaction between the water-based emulsion binder and metal zinc powder is suppressed.

  Among the water-soluble polymer compounds, cellulose ethers are preferable. Although it does not specifically limit as cellulose ethers, It is preferable that it is at least 1 sort (s) chosen from the group which consists of methylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxyethylcellulose, and carboxymethylcellulose. Among these cellulose ethers, carboxymethyl cellulose, methyl cellulose and the like are preferable from the viewpoint of achieving both the effect of suppressing the generation of hydrogen and the coating workability of the water-based emulsion paint at a high level.

  The number average molecular weight of the water-soluble polymer compound is preferably 8000 to 75000. When the water-soluble polymer compound has a number average molecular weight in the above range, the effect of suppressing the generation of hydrogen gas is enhanced, and the coating workability of the aqueous emulsion paint on the member containing iron can be further improved. When the number average molecular weight is significantly lower than 8000, the effect of suppressing the generation of hydrogen gas tends to be insufficient. When the number average molecular weight greatly exceeds 75,000, the effect of suppressing the generation of hydrogen gas becomes insufficient and the coating workability of the water-based emulsion paint tends to be lowered.

  The amount of the water-soluble polymer compound used is not particularly limited, but is preferably 0.01 to 20 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the resin solid content of the aqueous emulsion binder. Preferably they are 0.5 weight part or more and less than 5 weight part. By using the water-soluble polymer compound within the above range, the effect of suppressing the generation of hydrogen is enhanced, and the coating workability of the water-based emulsion paint is also good. When the amount of the water-soluble polymer compound used is less than 0.01 part by weight, the effect of suppressing the generation of hydrogen tends to be insufficient. On the other hand, when the amount of the water-soluble polymer compound used exceeds 20 parts by weight, the coating workability of the water-based emulsion paint tends to be remarkably lowered.

  As the metal zinc powder, metal zinc powder of various shapes such as granular, spherical, and scale-like materials that have been used in the field of zinc rich paint and zinc paint can be used without any particular limitation. The volume average particle size of the metallic zinc powder is preferably 0.1 to 100 μm, more preferably 3 to 40 μm. Thereby, the dispersion stability in the coating material of metallic zinc powder can be improved, and aggregation of metallic zinc powder can be suppressed.

  When the volume average particle diameter of the metal zinc powder is significantly less than 0.1 μm, the effect of suppressing the generation of hydrogen by the water-soluble polymer compound is lowered, and hydrogen tends to be generated. Furthermore, the dispersion stability of the metal zinc powder in the water-based emulsion paint is lowered, and the metal zinc powder tends to agglomerate and the paint gels. If the volume average particle size of the metallic zinc powder exceeds 100 μm, the denseness of the cured film (zinc film) formed from the water-based emulsion paint is impaired, and local variations occur in the state of the structure of the cured film, resulting in a cured film. There is a tendency that the service life of the product becomes shorter.

  The volume average particle diameter of the metal zinc powder was measured using a Multisizer 3 (manufactured by Beckman Coulter) and gently stirred in a beaker filled with ISOTON 2 (manufactured by Beckman Coulter, Inc .: measurement electrolyte). After the metallic zinc powder is dropped with a spoid and the reading of the densitometer on the main body screen is adjusted to around 10%, the measurement can be performed using a 400 μm aperture.

  The amount of metallic zinc powder used is preferably 0.1 to 500 parts by weight, more preferably 30 to 300 parts by weight, based on 100 parts by weight of the resin solid content of the aqueous emulsion binder. If the amount of metallic zinc powder used is significantly less than 0.1 parts by weight, a cured film having high strength and durability tends not to be formed. If the amount of metallic zinc powder used is significantly greater than 500 parts by weight, there is a tendency that hydrogen generation cannot be sufficiently suppressed. Moreover, there exists a tendency for the coating workability | operativity of a water-system emulsion paint to fall.

  By appropriately adjusting the amount of metallic zinc powder used, the water-based emulsion paint can be made into a zinc rich paint, and further can be made into a zinc paint. The zinc rich paint is a paint capable of forming a cured film having a high zinc content such that the zinc content in the cured film exceeds 70% by weight, and preferably exceeds 80% by weight. Zinc paint is a paint that can form a cured film with a zinc content of about 20 to 70% by weight. For example, zinc paint repair paints, galvanized surfaces of cars, construction scaffolding materials, various industrial machines, etc. Can be used as a paint for repairing corrosion-resistant undercoats and welds.

  As the organic solvent, an organic solvent conventionally used in the field of zinc rich paint can be used without particular limitation, but ketone solvents, aromatic hydrocarbon solvents, alcohol solvents, ester solvents, acetate solvents, It is preferably at least one selected from the group consisting of petroleum solvents and glycol ether solvents.

  Specific examples of the ketone solvent include acetone, methyl ethyl ketone, and the like. Specific examples of the aromatic hydrocarbon solvent include benzene, toluene, xylene and the like. Specific examples of the alcohol solvent include methanol, ethanol, n-propanol, isopropanol and n-butanol. Specific examples of the ester solvent include ethyl formate, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, tret-butyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone. . Specific examples of the acetate solvent include methyl acetate and ethyl acetate. Specific examples of the petroleum solvent include petroleum ether, petroleum benzine, ligroin and the like. Specific examples of the glycol ether solvent include diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether, and the like.

  Among these organic solvents, glycol ether solvents are preferable from the viewpoint of further suppressing aggregation of metal zinc powder and gelation of the paint in the water-based emulsion paint.

  The amount of the organic solvent used is not particularly limited and can be appropriately selected according to the amount of metal zinc powder used. Preferably, it is 0.1 to 100 parts by weight with respect to 100 parts by weight of the resin solid content of the aqueous emulsion binder. More preferably, it is 0.1 to 50 parts by weight. When the amount of the organic solvent used is less than 0.1 parts by weight, the treatment of the metal zinc powder with the organic solvent becomes insufficient, and there is a tendency for each component, particularly the aggregation of the metal zinc powder and the gelation of the paint to occur. . When the amount of the organic solvent used exceeds 100 parts by weight, the environment and workers tend to be loaded.

  The water-based emulsion paint of the present invention can further contain a general additive for rust preventive paint. Examples of such additives include an anti-sagging agent, a pigment, an inorganic corrosion inhibitor, and an organic corrosion inhibitor.

Specific examples of the sagging inhibitor include amorphous silica, colloidal calcium carbonate, organic bentonite, hydrogenated castor oil, aliphatic amides, higher fatty acids, microgel particles, and the like.
Specific examples of pigments include, for example, talc, mica, barium sulfate, clay, calcium carbonate, zinc white, titanium white, bengara, zinc phosphate, aluminum phosphate, barium metaborate, aluminum molybdate, and iron phosphide. Can be mentioned.

  Specific examples of inorganic corrosion inhibitors include molybdates such as zinc molybdate, calcium molybdate and zinc phosphomolybdate, tungstates such as zinc tungstate and calcium tungstate, zinc chromate and basic chromic acid. Chromic acid compounds such as lead, strontium chromate, zinc chromate, basic lead compounds such as basic lead sulfate and basic lead carbonate, metaborates such as barium metaborate, metasilicate compounds such as calcium metasilicate, nitrite, Examples include polyphosphoric acid.

Specific examples of the organic corrosion inhibitor include carboxylic acids such as oleic acid, dimer acid, and naphthenic acid, carboxylic acid metal soaps, sulfonates, amine salts, and esters.
Each of these additives can be used alone or in combination of two or more.

  The aqueous emulsion paint of the present invention is preferably a two-component paint. For example, immediately before application to the surface of a member containing iron, the aqueous system of the present invention is mixed by mixing the liquid A containing an aqueous emulsion binder and a water-soluble polymer compound with the liquid B containing metallic zinc powder and an organic solvent. It is preferred to prepare an emulsion paint. At this time, the mixing ratio of the liquid A and the liquid B is appropriately adjusted so that the content of each component is within the above-described ranges.

  Liquid A can be prepared, for example, by mixing an aqueous emulsion binder and a water-soluble polymer compound. The water contained in the liquid A is water contained in the aqueous solution of the water-soluble resin or the aqueous dispersion of the water-dispersible resin. However, the water can be added as long as the preferable characteristics of the aqueous emulsion paint of the present invention are not impaired. It doesn't matter.

  The liquid B can be prepared, for example, by mixing metallic zinc powder and an organic solvent, and uniformly dispersing the metallic zinc powder in the organic solvent. Further, a water-soluble polymer compound may be added to the B liquid. Thus, before bringing the metal zinc powder into contact with the aqueous emulsion binder, it is preferable to mix the metal zinc powder and the organic solvent so that the organic solvent adheres to the surface of the metal zinc powder. Thereby, the dispersion stability of the metal zinc powder in the water-based emulsion paint of the present invention is further improved, and the aggregation of the metal zinc powder and the gelation of the paint are less likely to occur. The anti-corrosive additive may be added to either the liquid A or the liquid B, and may further be added to the aqueous emulsion paint of the present invention after the liquid A and the liquid B are mixed.

The aqueous emulsion paint of the present invention can also be prepared by mixing an aqueous emulsion binder and a liquid C containing a water-soluble polymer compound, metallic zinc powder and an organic solvent. Liquid C can be prepared, for example, by mixing a water-soluble polymer compound, metallic zinc powder, and an organic solvent. A water-soluble polymer compound may be added to the water-based emulsion binder. By bringing the metal zinc powder into contact with a water-soluble polymer compound and an organic solvent before the aqueous emulsion binder comes into contact with the metal zinc powder, the effect of suppressing the dispersion stability of the metal zinc powder in the paint and the generation of hydrogen. Is further increased. The anti-corrosive additive may be added to either the water-based emulsion binder or the liquid C, and may further be added to the water-based emulsion paint of the present invention after the water-based emulsion binder and the liquid C are mixed. .
In preparing the water-based emulsion paint of the present invention, it may be prepared by adding water so that the amount of water is 1 to 20 times the amount of the organic solvent.

  The water-based emulsion paint of the present invention thus obtained not only has an excellent rust prevention performance, but also contains a large amount of water equal to or more than an organic solvent, so that it can protect the environment and safety for workers. It is also useful in terms. Furthermore, the cured film made of the water-based emulsion paint of the present invention has excellent adhesion to the surface of the article. The water-based emulsion paint of the present invention can be used as a rust preventive paint such as zinc rich paint and zinc paint.

  The coating method of the present invention is characterized in that the aqueous emulsion paint obtained above is applied to the surface of an article containing iron, and the obtained coating film is dried to form a cured film containing metallic zinc powder. And Application of the aqueous emulsion paint to the article containing iron is preferably within 8 hours, more preferably within 3 hours, immediately after mixing liquid A and liquid B, and immediately after mixing aqueous emulsion binder and liquid C. It is good to carry out. If it exceeds 8 hours immediately after mixing, the dispersion stability of the metallic zinc powder and the like in the water-based emulsion paint is lowered, and aggregation and precipitation of the metallic zinc powder and the like tend to occur. Such agglomeration or precipitation tends to lower the coating workability and locally reduce the mechanical strength of the cured film, the adhesion to the article surface, the antirust performance, and the like.

  In addition, as a method for applying the water-based emulsion paint, any of the methods for applying the liquid to the solid surface can be adopted, but considering the good workability of the water-based emulsion paint, brush coating, roll brush coating, Application methods such as roll coating, air spray, and airless spray are preferred.

  The member containing iron is not particularly limited as long as it is a component made of a material containing iron, such as steel. For example, housing members, bridges, tanks, plants, ships, various vehicles, construction scaffolding materials, steel making facilities, petroleum Examples include large-scale structural members that use a lot of steel materials such as refining equipment. Among these, for example, members exposed to high temperatures of 200 ° C. to 400 ° C., such as steel making facilities and petroleum refining facilities, are preferable. Further, the water-based emulsion paint of the present invention is not limited to large structural members, but is used for repairing zinc plating in articles having galvanized surfaces and damaged parts of the galvanized parts or articles having welds. It can also be used as a protective paint for welds.

  The drying temperature of the water-based emulsion coating film applied to the surface of the article containing iron is not particularly limited, and may be left at room temperature, and the liquid component in the coating film is volatilized by heating. May be. However, since the water-based emulsion paint of the present invention is efficiently dried at room temperature, it is usually not necessary to heat it. The thickness of the cured film thus formed is appropriately selected according to the type of the article containing iron, but is usually about 10 to 150 μm, preferably about 30 to 60 μm. As a result, a cured film containing metal zinc powder, excellent in durability and antirust performance against iron, and having high adhesion to the article surface is formed.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
(Examples 1-6 and Comparative Example 1)
(1) Preparation of liquid A Methyl cellulose (water-soluble polymer compound) in a water-based emulsion containing 50% by weight of a silicone resin in a blending ratio (parts by weight) shown in Table 1 below with respect to 100 parts by weight of resin solids , Manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 8000) and abbreviated as “MC” in Table 1 below) were dispersed and dissolved to prepare liquids A of Examples 1 to 6 and Comparative Example 1. In Comparative Example 1, methylcellulose is not used.

(2) Preparation of solution B Metal zinc powder (Honjo Chemical Co., Ltd., shape: granular, volume average particle size: 20 μm) 30 parts by weight and diethylene glycol monomethyl ether (organic solvent) 5 parts by weight were mixed. A liquid (metal zinc powder slurry) was prepared. Water: organic solvent (weight ratio) = 10: 1.

(3) Preparation of water-based emulsion paint The liquid A and the liquid B obtained above were mixed at a weight ratio of 1: 1 to prepare water-based emulsion paints of Examples 1 to 6 and Comparative Example 1.

(Example 7)
The same procedure as in Example 3 was used except that carboxymethylcellulose (water-soluble polymer compound, manufactured by Nippon Paper Chemicals Co., Ltd., number average molecular weight 8000, abbreviated as “CMC” in Table 1 below) was used instead of methylcellulose. A water-based emulsion paint was prepared.

(Evaluation of aggregation and sedimentation state of metallic zinc powder)
The paints obtained in Examples 1 to 7 and Comparative Example 1 were allowed to stand for 20 minutes immediately after mixing of the liquid A and the liquid B, and then the agglomeration and settling state of the metal zinc powder in each paint was visually observed. And evaluated as follows. The results are shown in Table 1.

(Double-circle): The aggregate and precipitation have not arisen.
A: Agglomerates having a weak cohesive force are produced, but are easily and uniformly dispersed by stirring.
Δ: Aggregation occurs in the entire paint, and the coagulation force of the upper agglomerate is weak, but precipitation with strong cohesion force occurs at the bottom.
X: Aggregation occurs in the entire coating material, an agglomerate having a strong cohesive force is formed at the top, and a precipitate having a strong cohesive force is generated at the bottom.

(Evaluation of liquid level of coating film and generation of hydrogen gas)
Each paint obtained in Examples 1 to 7 and Comparative Example 1 was placed in a 1-liter glass beaker, and the liquid surface state of the paint and the generation state of hydrogen gas were visually observed and evaluated as follows. The results are shown in Table 1.

A: No generation of bubbles is observed, and there is no change in the liquid level.
○: Generation of bubbles is slightly observed.
Δ: It can be confirmed that some of the generated bubbles are crushed at the liquid level.
X: It can be confirmed that a large amount of bubbles are generated and the liquid surface is crushed violently.

(Evaluation of paint workability)
The paints obtained in Examples 1 to 7 and Comparative Example 1 were applied to the iron plate surface with a roller brush, the coating workability of each paint was examined, and evaluated as follows. The results are shown in Table 1.

A: Coating with a roller brush is easy, the coating film surface is flat and the coating film is uniform.
○: Painting with a roller brush is easy, but the surface of the coating film is crusty.
(Triangle | delta): Attention is required for the painting by a roller brush, and the thin dispersion | variation has arisen in the thickness of the coating film.
X: Cannot be painted with a roller brush.

  From Table 1, a water-based emulsion of metal zinc powder is prepared by mixing a liquid A containing an aqueous emulsion binder and a water-soluble polymer compound with a liquid B containing metal zinc powder and an organic solvent. It is clear that the dispersion stability in the paint is improved. Further, from comparison between Examples 1 to 7 and Comparative Example 1, the water-soluble polymer compound has an effect of increasing the dispersion stability of the metal zinc powder and an effect of suppressing the generation of hydrogen. Is clear.

  Further, from the comparison between Examples 1 to 6 (particularly Examples 2 to 4) and Comparative Example 1, by containing a predetermined amount of methylcellulose (CM), the generation of hydrogen gas is suppressed, and the coating workability is increased. It is clear that an aqueous emulsion paint excellent in the above can be obtained. Moreover, even when using carboxymethylcellulose (CMC) instead of methylcellulose as the water-soluble polymer compound from Example 7, the dispersion stability of components such as metallic zinc powder is good, the generation of hydrogen gas is suppressed, and coating is performed. It is clear that a water-based emulsion paint excellent in workability can be obtained.

  In addition, from the results of Examples 2 to 4, if the content of the water-soluble polymer compound is 0.5 parts by weight or more and less than 5 parts by weight with respect to 100 parts by weight of the resin solid content, It can be seen that a water-based emulsion paint that can satisfy the dispersion stability, the effect of suppressing the generation of hydrogen gas, and the coating workability at a high level can be obtained.

  The water-based emulsion paints of Examples 2 to 4 and Comparative Example 1 were applied to the surface of the sand plast steel plate by air spray, the obtained coating film was dried indoors for 3 days, and further exposed outdoors for 7 days. A cured film having a thickness of 50 μm was prepared. The surface of the cured film was visually observed. The cured films of Examples 2 to 4 had a substantially uniform film thickness, and there were no crater-like depressions or cracks on the surface, and the surfaces were smooth. On the other hand, the cured film of Comparative Example 1 had different film thicknesses, and many crater-like depressions existed on the surface, and the surface was uneven.

  Furthermore, after putting the cured film of Examples 2-4 into a 300 degreeC thermostat and preserve | saving for 3 days, it took out and examined the external appearance, but a crack etc. did not generate | occur | produce in a cured film, and peeling of a cured film was also recognized. There wasn't. And after this, it became clear that rust did not occur on the surface of the iron plate on which the cured film was formed, and the rust prevention performance was maintained.

Claims (14)

  An aqueous emulsion paint comprising at least one aqueous emulsion binder selected from an aqueous solution of a water-soluble resin and an aqueous dispersion of a water-dispersible resin, a water-soluble polymer compound, metallic zinc powder, and an organic solvent.   The water-based emulsion paint of Claim 1 obtained by mixing the liquid containing the said water-based emulsion binder and the said water-soluble polymer compound, and the liquid containing the said metal zinc powder and the said organic solvent.   The water-based emulsion paint according to claim 1, obtained by mixing the metal zinc powder, a liquid containing the water-soluble polymer compound and the organic solvent, and the water-based emulsion binder.   The water-based emulsion paint according to any one of claims 1 to 3, wherein the amount of water contained in the water-based emulsion binder is equal to or greater than the amount of the organic solvent.   0.1 to 500 parts by weight of the metal zinc powder, 0.01 to 20 parts by weight of the water-soluble polymer compound, and 0.1 to 100 parts of the organic solvent with respect to 100 parts by weight of the resin solid content of the aqueous emulsion binder. 5. The water-based emulsion paint according to claim 4, wherein the water-based emulsion paint is contained in an amount of 1 part to 20 times the amount of the organic solvent.   The water-based emulsion paint according to any one of claims 1 to 5, wherein the metal zinc powder has a volume average particle size of 0.1 to 100 µm.   The water-based emulsion paint according to any one of claims 1 to 6, wherein the water-soluble polymer compound is at least one selected from cellulose ethers and polyvinyl alcohol.   The water-soluble polymer compound is the cellulose ether, and the cellulose ether is at least one selected from the group consisting of methyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose. 8. A water-based emulsion paint according to 7.   The water-based emulsion paint according to any one of claims 1 to 8, wherein the water-soluble polymer compound has a number average molecular weight of 8000 to 75000.   The aqueous emulsion paint according to any one of claims 1 to 9, wherein the aqueous emulsion binder is an aqueous dispersion of a silicone resin, and the cured film has heat resistance at a temperature of 200 ° C to 400 ° C. .   A liquid containing 100 parts by weight of an aqueous dispersion of a silicone resin (resin solid content) and 0.01 to 20 parts by weight of a water-soluble polymer compound having a number average molecular weight of 8000 to 75000, and metal zinc powder 0.1 to 500 parts by weight Part and a liquid containing 0.1 to 100 parts by weight of an organic solvent, and the amount of water contained in the aqueous dispersion is 1 to 20 times the amount of the organic solvent. paint.   A liquid containing at least one water-based emulsion binder selected from an aqueous solution of a water-soluble resin and an aqueous dispersion of a water-dispersible resin and a water-soluble polymer compound, and a liquid containing a metal zinc powder and an organic solvent, The coating method which apply | coats the obtained water-based emulsion coating material to the surface of the member containing iron, and dries the obtained coating film.   A liquid containing metal zinc powder, a water-soluble polymer compound and an organic solvent was mixed with at least one aqueous emulsion binder selected from an aqueous solution of a water-soluble resin and an aqueous dispersion of a water-dispersible resin. A coating method in which a water-based emulsion paint is applied to the surface of a member containing iron and the resulting coating film is dried.   The coating method according to claim 12 or 13, wherein the member is a member exposed to a temperature of 200 ° C to 400 ° C.