JPS624076B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aqueous coating composition with excellent rust-preventing ability that contains zinc phosphate and zinc ferrite as rust-preventing pigments. Conventionally, various antirust paints have been used for the purpose of preventing rust on steel structures such as steel towers, ships, and bridges.
However, most of them are oil-based paints,
The content is boiled oil, an oil-based varnish in which natural resin is mixed with boiled oil, or a synthetic resin varnish such as alkyd resin as a vehicle, and pigments such as iron oxide, titanium oxide, zinc oxide, calcium carbonate, etc. are kneaded into the vehicle. Naturally, it contains an organic solvent as a volatile component. Although the organic solvents contained in these paints not only volatilize and harm the health of painting workers, but also pose a risk of explosion or fire when painting steel structures where welding work is often performed, they are not desirable. do not have. In addition, oxides, hydroxides, and sulfates of lead, copper, and chromium are often mixed in to increase the rust-preventing ability, but these pigments are subject to the Air Pollution Control Act, Water Pollution Control Act, and Waste Disposal Control Act. These pigments are regulated as hazardous substances by law, and great care must be taken when handling paints containing these toxic pigments, making painting work difficult. On the other hand, due to these current deficiencies, anticorrosive paints containing non-polluting pigments such as molybdates, phosphates, and borates in an aqueous vehicle are commercially available, but these paints cannot be applied to iron, especially those that have not been sufficiently pretreated. It is hardly used because it has poor adhesion to iron surfaces and its anti-corrosion ability is significantly inferior to that of the oil-based paint. The present invention solves the above-mentioned conventional drawbacks, and provides a water-based paint composition that has excellent adhesion and rust prevention ability without impairing the working environment when painting steel structures such as steel towers, ships, and bridges. This is what we provide. That is, the antirust water-based paint composition of the present invention has the following properties:
Solid content of the resin in a vehicle mainly composed of styrene/acrylic acid ester copolymer resin emulsion
5 to 100 parts by weight of zinc phosphate composite and 5 to 100 parts of zinc ferrite as anti-rust pigments per 100 parts by weight.
It is characterized by containing 100 parts by weight. The styrene/acrylic acid ester copolymer resin emulsion (hereinafter referred to as styrene/acrylic emulsion) used in the present invention is a suspension polymerization of styrene and acrylic acid ester in an aqueous medium. Acid esters include acrylic acid methyl, ethyl, n-propyl, iso
-propyl, n-butyl, iso-butyl, sec-butyl, n-amyl, iso-amyl, n-hexyl, n-hebutyl, oxohebutyl, n-octyl, 2-ethylexyl, n-nonio, oxononyl, n-decyl , oxodecyl, etc. In particular, in the structure of the present invention, alkyl esters having 1 to 6 carbon atoms are preferable, and styrene includes styrene, 0-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, 2,4-dimethylstyrene, etc. , 5-dimethylstyrene, p-chlorostyrene, α-methylstyrene, and the like. One or more of each of the above-mentioned acrylic ester components and styrene components are selected and copolymerized, and the composition ratio is not particularly limited, but in the configuration of the present invention, the styrene component is is preferably 5 to 60% by weight. In addition to the above-described components of the styrene-acrylic emulsion of the present invention, a copolymerizable third component may be appropriately introduced as long as the gist of the present invention is not impaired. Such ingredients include vinyl acetate, acrylonitrile, vinylidene chloride, ethylene, vinyl versatility, acrylamide ethyl methacrylate, methyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl methacrylate, butadiene, maleic acid, Itaconic acid, etc. can be used alone or in combination, but the amount depends on the acrylic and
It is desirable that the amount is 10% (weight ratio) or less based on the styrene component. In the present invention, the zinc phosphate composites used as one of the rust-preventive pigments include zinc phosphate/aluminum, silicate/zinc phosphate, titanic acid/zinc phosphate, and silicate/zinc phosphate. ·aluminum,
Examples include silicic acid/zinc phosphate/aluminum/calcium, zinc/aluminum polyphosphate, silicic acid/zinc/aluminum polyphosphate, etc., and these can be used alone or in combination of two or more. The method for producing these zinc phosphate composites is, for example, by combining an aqueous solution containing zinc ions and aluminum ions (zinc chloride, aluminum chloride, zinc nitrate, etc.) with an alkali metal or ammonium phosphate solution at a temperature of up to 100°C. Sedimentation is allowed to occur, optionally with stirring, and the resulting suspension is maintained at a temperature of up to 100° C. for up to about 10 hours, optionally with stirring. Afterwards, the pigment suspension is washed and filtered,
It is obtained by firing and pulverizing at 200°C to 400°C for 2 hours. For example, a method for producing a composite of silicate and phosphate involves precipitating an aqueous solution containing zinc ions and a carbonate or sodium salt solution of phosphoric acid and silicic acid with stirring as required. The resulting suspension is maintained at a temperature of up to 100° C. for up to about 10 hours, with stirring if necessary. Thereafter, the pigment suspension is washed, filtered, calcined at 200°C to 400°C for 2 hours, and pulverized. Further, zinc ferrite used as another rust-preventive pigment in the present invention is a ferrimagnetic material having a spinel structure and has a chemical formula of ZnFe ₂ O ₄ . The rust-preventing water-based paint composition of the present invention contains a styrene-acrylic emulsion containing a zinc phosphate composite and zinc ferrite, and the proportion thereof is based on 100 parts by weight of the solid content of the emulsion resin.
The amount of the zinc phosphate composite is 5 to 100 parts by weight, and the zinc ferrite is 5 to 100 parts by weight, and more preferably the total amount of the zinc phosphate composite and zinc ferrite is 150 parts by weight or less. . As a result of intensive research, the present inventors discovered that the styrene
It has been discovered that when a zinc phosphate composite and zinc ferrite coexist in the acrylic emulsion at the above-mentioned mixing ratio, the weather resistance, rust prevention ability, adhesion, etc. of the paint film applied to iron surfaces can be satisfied. If the compounding ratio of the zinc phosphate composite and zinc ferrite is below the above range, the rust prevention ability will be poor, and if it is above the range, the weather resistance of the coating film will deteriorate. Furthermore, if only either the zinc phosphate composite or the zinc ferrite is applied, the anti-corrosion ability of the conventional oil-based paint mentioned above is significantly inferior. Although the mechanism by which the coexistence of the two types of rust preventive pigments significantly improves the rust preventive ability is not clear, the effect is clear from the results of Examples described later. The method for producing the rust-preventive water-based paint composition of the present invention includes:
Zinc phosphate composite and zinc ferrite powder are made into a slurry in an aqueous medium using a dispersing agent and a dispersing device such as a ball mill, sand mill, high speed mill, colloid mill, or stirring device, and then water-soluble This is achieved by adding and mixing the styrene/acrylic emulsion after a viscosity adjustment step using a polymer or the like. As the dispersant for the rust preventive pigment, anionic or nonionic dispersants used in general water-based paints can be used alone or in combination. Water-soluble polymers used in the viscosity adjustment process include cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose, as well as polyvinyl alcohol, casein, guar gum,
Carrageenan, sodium alginate, polyacrylic acid amide, or synthetic resins such as acrylic resins, epoxy resins, and polyester resins, either alone or as copolymers, may be modified to be water-soluble. Commercially available such water-soluble synthetic resins include Aloron 5 (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.) and Watersol S-302 (manufactured by Dainippon Ink Chemical Co., Ltd.). In addition to the above-mentioned additives, various additives can be added to the rust-preventing aqueous paint composition of the present invention as long as they do not impair the object of the present invention. These additives include fillers such as calcium carbonate, talc, kaolin, bentonite, silica powder, barium sulfate, mica, zinc white, titanium oxide, and aluminum hydroxide, or pigments, as well as preservatives,
Anti-bacterial agents, wetting agents, film-forming aids (e.g., butyl carbitol acetate, benzyl alcohol, etc.), freeze stabilizers (e.g., ethylene glycol), antifoaming agents, flashlast inhibitors (e.g., sodium nitrite, etc.) etc. can be included as appropriate. Furthermore, the coating material of the present invention can be diluted with water to an appropriate viscosity if necessary, and applied by a known general method such as brush coating, roller coating, or spray coating. As mentioned above, since the rust-preventing water-based paint composition of the present invention is water-based, there is no risk of explosion or fire even if welding work is being carried out nearby when painting steel structures, and the paint composition is water-based. Not only can it be easily diluted with water, it does not contain any harmful pigments such as lead, copper, or chromium, so it does not harm the health of workers, and it is also more functional than conventional products. It has anti-corrosion ability equivalent to or better than that of oil-based paint. Next, the anticorrosive water-based coating composition of the present invention will be explained in detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. All compounding ratios in the Examples and Comparative Examples shown below are expressed in parts by weight. Example 1 Tap water 100 Anionic dispersant 5 Nonionic wetting agent 5 Antifoaming agent 2 Calcium carbonate 50 Zinc ferrite 100 Zinc/aluminum phosphate 100 Preservative 2 Coating agent 35 Added sequentially according to the above compounding ratio. After stirring at high speed for 30 minutes in a pot using a high-speed mill to sufficiently disperse the pigments, 50 parts of 2% hydroxyethyl cellulose was added, and then the styrene/acrylic ester copolymer resin was stirred at low speed. 500 parts of emulsion (50%) was added and mixed with stirring to produce a rust-preventive water-based paint composition of the present invention. The method for producing the styrene/acrylic acid ester copolymer resin emulsion (50%) used in this example is as follows. First, a monomer composition of 83 parts of ethyl acrylate, 15 parts of styrene, and 2 parts of methacrylic acid was mixed with 2 parts of anionic surfactant sodium dodecylbenzenesulfonate, 0.3 parts of ammonium persulfate, and 100 parts of water. Then, polymerization was carried out in a conventional manner at 70°C for 5 hours to obtain a polymer emulsion with a solid content concentration of 50%, and the pH was adjusted to 7.0 with aqueous ammonia. Then, the coating composition was applied to a mild steel plate using a bar coater to a film thickness of 50 mm, dried in a room at 20° C. and 65% RH for 7 days, and then tested. The results are shown in Table 3. Examples 2 to 8 Coating compositions were obtained in the same manner as in Example 1 according to the compounding ratios shown in Table 1 below, and were similarly subjected to post-coating tests. The results are shown in Table 3.

[Table] Comparative Examples 1 to 8 Coating compositions were obtained in the same manner as in Example 1 according to the compounding ratios shown in Table 2 below, and then subjected to comparative tests after coating. The results are shown in Table 3.

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Claims (1)

[Claims] 1. 5 to 100 parts by weight of a zinc phosphate composite as a rust-preventing pigment and 5 parts by weight of zinc ferrite to 100 parts by weight of the resin solid content in a vehicle mainly composed of a styrene/acrylic acid ester copolymer resin emulsion. A rust-preventing aqueous paint composition characterized by containing up to 100 parts by weight.