JPH03115473A - Water-base anticorrosive point for galvanized steel - Google Patents

Abstract

PURPOSE:To obtain the title paint for temporarily preventing white rust, capable of improving the corrosion resistance of galvanized steel while retaining the metallic gloss by incorporating a chromium pigment, a calcium plumbate pigment, etc., into a water-soluble, water-suspendible or water-emulsifiable acrylic, vinyl acetate or epoxy-modified polyester resin. CONSTITUTION:A water-soluble, water-suspendible or water-emulsifiable resin (having a pH of 7 to 10, preferably 8 to 9, selected from amony acrylic, vinyl ester, and epoxy-modified polyester resins) is mixed with 0.1-2vol.% pigment (selected from a chromium pigment and a calcium plumbate pigment) to give a water-base anticorrosive paint for galvanized steel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water-based anticorrosive coating for galvanized steel. The anticorrosive paint of the present invention is used to temporarily prevent white rust on galvanized steel materials, such as water pipes, road lighting poles, guardrail building materials, steel towers, and bridges.

[Conventional technology]

Temporary rust prevention methods for galvanized steel include applying a drying oil varnish made of alkyd resin to form a hardened film, passivating the galvanized surface through chemical conversion treatment, or a combination of both. There are known ways to do this.

Specifically, in the method of forming a cured film using a general drying oil varnish, organic solvents evaporate into the atmosphere, becoming a source of air pollution, and furthermore, creating a sanitary problem for the working environment. Ta. In addition, in the method of chemical conversion treatment,
Compared to coatings using organic films, corrosion resistance is insufficient, and there are also problems such as coloring of the plating.

In order to solve these problems, several attempts have been made to form an organic film using a water-based resin that contains a small amount of organic solvent and whose volatile components are mostly water to achieve temporary rust prevention.
Attempts are being made.

For example, JP-A-55-116768 describes a coating composition for preventing zinc white rust, which contains aluminum dihydrogen tripolyphosphate and a fast-acting corrosive (eg, zinc chloride, ammonium chloride, etc.).

JP-A-57-53571 describes a water-soluble resin for temporary rust prevention of galvanized copper plates, which is obtained by introducing a phosphoric acid group into a thermoplastic water-dilutable acrylic resin containing a carboxyl group. JP-A-62-169870 has (a)
An emulsion in which a neutralized maleated resin is dispersed in water, (b) a nitrogen-containing unsaturated monomer as a copolymerization component (
meth) acrylic pigment dispersion resin, (C) anticorrosive pigment, (
d) Other pigments, (e) Aqueous medium, and) Amphipathic a.
Water-based anticorrosion paints containing a melt are described. JP-A-1-156398 discloses acrylic, vinyl acrylic or acrylic styrene copolymers, lubricating additives, zinc group elements, chromium group elements, etc. as multifunctional films for zinc and zinc alloys plated on steel materials. A membrane comprising a soluble complex of one or more polyvalent cations selected from zirconium group elements and vanadium group elements is described. special fair 1
Publication No. 25347 states that when a baking color clear paint containing a metal complex type spirit dye is applied to a thermosetting acrylic/urea resin on a chromium-plated surface, it has a high reflectivity and high dimensional appearance. It is stated that a good film can be obtained.

[Problem to be Solved by the Invention] Therefore, the problem to be solved by the present invention is to maintain the metallic luster of zinc plating, that is, to prevent the occurrence of white rust, and to develop a low-pollution paint. It is an object of the present invention to solve the above problems using a composition.

Water-based resins are being studied in order to achieve low-pollution properties in coating compositions, but water-based resins basically have a high affinity with water, and their corrosion resistance under wet conditions is lower than that of drying oils. He was several steps inferior.

Therefore, the present invention provides a water-based anticorrosive paint for galvanized steel, which improves the corrosion resistance of the above-mentioned water-based resin under wet conditions while retaining the metallic luster of galvanized steel, and which is particularly intended for rust prevention when wet. The purpose is to

[Means for Solving the Problems] That is, according to the present invention, one or more types selected from the group consisting of water-soluble, water-Qi-based or water-emulsifiable acrylic resins, vinyl acetate resins, and epoxy-modified polyester resins. One or more pigments selected from the group of chromium pigments and calcium lead acid pigments are added to the resin at a pigment volume concentration of O, 1 to 2.
Provided is a water-based anticorrosive paint for galvanized steel containing %.

Galvanized steel materials to be coated with the anticorrosive paint of the present invention include:
Materials in the shape of plates, tubes, rods, and combinations thereof;
Examples include processed products and products. In addition, "galvanizing" is called galvanizing in English.
ng).

There are two methods for galvanizing steel sheets: hot-dip galvanizing and electrogalvanizing.For shapes other than steel sheets, there is also a diffusion coating method (for zinc, sheradizing). ) Thermal spraying method is also used. Continuous electroplating methods are used to apply thin zinc plating as part of a composite anti-corrosion coating. In recent years, zinc-nickel (Zn-Ni) has become thinner and has excellent corrosion resistance.
, zinc-iron (Zn-Fe), zinc-aluminum (Zn
-AI), those plated with alloys such as zinc-cobalt (Zn-Co) to a thickness of 5 μm or less have been commercialized. When zinc solidifies, a crystal pattern called a spangle is formed, and in order to enlarge this pattern and give it luster, a small amount of tin or antimony is sometimes added to the zinc bath.

Temporary rust prevention in the present invention means that the galvanized surface is prevented from undergoing chemical changes during storage and transportation, making it corrosion resistant.

When galvanized steel is used in the atmosphere, a dense zinc oxide film is formed on the surface of the plating layer, which gradually loses its luster. The reason why zinc plating exhibits excellent corrosion resistance is that this dense oxide film blocks the atmosphere and protects the underlying zinc.White rust does not refer to this protective oxide film, but to white bulky rust. Glue occurs on the surface and refers to a condition that resembles chalk powder adhering to it.

White rust occurs when the shiny zinc plating layer gets wet with rain or dew and is exposed to an environment where it does not dry easily.
This does not occur when plated steel is immersed in water.

When substances that corrode zinc, such as acidic substances, alkaline substances, organic acids, and salt, adhere to the plating surface, noticeable white rust occurs, and this occurs particularly frequently when the zinc is exposed to seawater during marine transportation.

White rust is basic zinc carbonate (2ZnCO* + 3Zn
(OH)z.H2O) is said to be the main component, and an example of its composition is as follows.

Zn(OH)z-55%, ZnCQ-z-40%
, 11.0-5% Moisture is always involved in the occurrence of white rust,
This moisture may come from rainwater or droplets, but it is also often from condensation.

White rust occurs when part of the plating layer is dry and part wet, and when the boundary line does not move for a long time, it occurs on the wet side of the plating layer adjacent to the boundary line. is often seen. When the dry/wet boundary moves over a long period of time, the area where white rust occurs becomes large.

Water droplets play an important role in the generation of white rust. Even a small amount of water droplets contain salts and conduct electricity, and since the outer periphery of the water droplet is in contact with the air, more oxygen in the air is dissolved than the inside, and in such conditions a phenomenon called oxygen concentration battery occurs. As a result of this action, the zinc surface in contact with the center of the water droplet has a lower potential than the zinc surface in contact with the outer boundary of the water droplet, and as a result, zinc near the center is ionized and elutes into the water, producing hydroxyl groups and carbonate ions. It is thought that the zinc carbonate turns into basic zinc carbonate, which deposits on the surface and causes white rust.

Water-based resins that can be used in the present invention include the aforementioned acrylic resins, vinyl acetate resins, and epoxy-modified polyester resins.

These resins are used in the form of an aqueous solution, aqueous suspension, or an aqueous emulsion. The p++ of these aqueous resin solutions is preferably about 7 to 10 for the stability of the rust preventive in the paint.
Those having a pH of 8 to 9 are more preferable.

When the pu of the aqueous resin solution is less than 7, the stability of the rust preventive agent decreases, and there is a risk that the rust preventive agent will precipitate, making it difficult to obtain a stable dispersion.

Further, the iron may corrode in the ungalvanized steel frame or in the galvanized pinhole portions, causing red rust, which is undesirable. In addition, if the PL of the aqueous resin solution exceeds 10, although the dispersion stability of the rust preventive agent is good, the resin itself tends to be easily hydrolyzed by alkali, and the zinc plating of the object to be coated may be damaged by the paint solution. dissolved by
There is also a risk of damaging the metallic luster.

Water-based acrylic resins include main monomers consisting of alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhegysyl (meth)acrylate. Other comonomers such as (meth)acrylic acid, maleic acid, itaconic acid, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, acrylamide, N-methylolacrylamide, styrene,
It is a polymer formed by copolymerizing vinyltoluene, acrylonitrile, vinyl acetate, vinyl persate, etc.

Synthesis of these polymers is usually carried out by a general polymerization method. A method in which monomers are emulsified in the presence of an emulsifier and then emulsion polymerized in an aqueous medium using a polymerization initiator to directly obtain an emulsion. A method in which an emulsion is obtained by post-emulsifying in an aqueous solvent, or a method in which a solution polymerized with a hydrophilic solvent is partially neutralized with ammonia or a suitable amine to make it water-soluble to obtain an aqueous solution. , a method to obtain an aqueous suspension by reducing the neutralized portion, and the like.

Water-based epoxy polyester resins include polyphenols such as bisphenol A1 bisphenol F and bisphenol AD, novolac resins, condensates of polyhydroxybenzenes such as resorcinol and catechol, and their derivatives with epichlorohydrin or methylepichlorohydrin, and polyphenols such as butadiene and isoprene. An alkyd resin synthesized from a polyhydric alcohol and a polybasic acid is modified with an epoxy compound such as an epoxide of an olefin compound or an epoxide of an alicyclic compound, and is partially neutralized with ammonia or a suitable amine to form an aqueous solution. , water suspension.

Moreover, unneutralized substances can be emulsified in water using an emulsifier. The above polyhydric alcohols include dihydric alcohols such as ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6-hexane glycol, and dipropylene glycol, and trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane. , pentaerythritol, dipentaerythritol, etc. are also used. Examples of the polybasic acids include phthalic anhydride, isophthalic acid, terephthalic acid, sebacic acid,
Dibasic acids such as fumaric acid, itaconic acid, and phthalic anhydride, tribasic acids such as trimellitic anhydride and methylcyclohexenetricarboxylic acid, and tetrabasic acids such as pyromellitic anhydride are used.

For example, carboxyl-modified styrene-butadiene copolymer latex, carboxy-modified acrylonitrile-butadiene copolymer latex, carboxy-modified chlorobutane latex, carboxy-modified methyl methacrylate
Ethylene such as butadiene copolymer latex, carboxy-modified butyl rubber latex, carboxy-modified polybutadiene latex, carboxy-modified styrene, (meth)acrylate, saturated carboxylic acid vinyl ester, (meth)acrylonitrile, crotonic acid ester, dimaleate, sifumarate, shitaconate, etc. In aqueous emulsions of synthetic resins containing carboxyl groups, such as copolymer emulsions of sexually unsaturated monomers, compounds with the general formula MHz (CH □C)lzNH
)-C) t2clIzNliz (in the formula, n represents an integer of 0 or 1 or more) to an aqueous emulsion of a polyion complex obtained by mixing polyphenols such as bisphenol A1 bisphenol F, Novolac resins, condensates of polyhydroxybenzene and its derivatives such as resorcinol and catechol, and epichlorohydrin or methylepichlorohydrin, epoxidized products of diolefin compounds such as butadiene and isoprene, and epoxidized products of alicyclic compounds; Epoxide compounds toluene, xylene,
Dissolved in hydrophobic solvents such as benzene, gasoline, kerosene, ligroin, tetralin, decalin, turpentine oil, alkylbenzene, halogenated hydrocarbons, chlorobenzene, chlorotoluene, ketones, hydrophobic ethers, various phthalates, and various adipates. This is a one-component epoxy resin aqueous emulsion, which is obtained by dispersing the epoxy resin in the aqueous emulsion using an emulsifier in the aqueous emulsion, or by adding a surfactant that does not react with the polyepoxide compound.

Further, the aqueous vinyl acetate resin is conventionally known, and preferred are vinyl acetate homopolymer aqueous emulsions, ethylene-vinyl acetate copolymer aqueous emulsions, and other vinyl acetate copolymer aqueous emulsions.

The rust preventive pigment used in the present invention must basically satisfy the following requirements.

i) It has a rust preventive effect on zinc plating.

ii) Within the blending amount that produces the rust-preventive effect, it has a range that does not impair the metallic luster and silver color of zinc plating, such as coloration and opacity, when formed into a coating film.

In order to satisfy these two requirements, the present invention:
Chromium-based pigments, especially chromate-based anticorrosive pigments, and lead-based pigments, especially calcium leadate are preferred. With other anti-corrosion pigments, in order to achieve the desired anti-corrosive power, it is necessary to incorporate large amounts, which causes the coating to become colored and even more opaque, making it impossible to achieve the objective of the present invention. It cannot be used to do this. In other words, chromates such as strontium chromate, zinc chromate, barium chromate, and potassium chromate and calcium leadate are suitable for achieving the desired rust prevention ability and providing a transparent coating film. and a combination system of both. These anticorrosive pigments made of chromate and calcium leadate have a pigment volume of 4 degrees (pigment volume) relative to the resin solid content.
Volume Concentration, hereafter p.
(abbreviated as vc) must be blended so that it is 0.1 to 2%. If the PVC of chromate-based rust-preventive pigments, seasick calcium, and pigments made from a combination thereof is less than 0.1% PVC, the rust-preventing power will be insufficient, and if it exceeds 2% PVC, the paint film will be colored, and the purpose It is not possible to obtain an anticorrosive paint.

The anticorrosive paint of the present invention further includes a dispersant, if necessary.
Additives such as antifoaming agents and film-forming aids may also be added.

As the method for manufacturing the anticorrosive paint of the present invention, a method commonly used for manufacturing paints can be used. More specifically, for example, the anticorrosive pigment may be wetted with water in advance, and the required amount may be added to the resin solution and stirred.

The film thickness to achieve the anti-corrosion power and transparency that is the goal of the present invention is 5 to 2.
It is 0 μm, preferably 10 to 20 μm. If the film thickness is less than 5 μm, the surface of the object to be coated may not be completely covered, and rust will occur in the uncovered areas. Furthermore, if the film thickness exceeds 20 μm, a colored window may be formed, which is not preferable.

The anticorrosive paint of the present invention can be applied normally using a brush, roller, airless spray, air spray, etc. Furthermore, it is possible to apply a top coat on this paint, if necessary. As the top coat, it is also possible to use epoxy, urethane, acrylic, or other paints normally used for anticorrosion purposes, or paints intended for aesthetic purposes.

〔Example] Hereinafter, the present invention will be explained in more detail based on Examples.

Removed soil (preparation of paint) Cypinol NPX-407024 in a stainless steel container
Add 5g of strontium chromate and 75g of water, mix for 5 minutes with a dispenser, mix 7.6g of strontium chromate and 200g of water so that the pre-prepared PvC is 2%, and add a slurry. 20 with Disper
A paint was prepared by mixing for 0 minutes.

(Preparation of coating film) Apply the coating to a hot-dip galvanized steel sheet preheated to 60°C using a bar coater #30 to a film thickness of 10 to 15 μm, and after drying at 20°C for 124 hours, perform an appearance test and a Tsuruto spray test ( 48 hours) and a moisture resistance test (48 hours).

In Examples, compositions of Examples 2 to 11 in Table 1 were prepared in the same manner as in Example 1, and tested.

- Cans 112.13 and 14 The compositions of Examples 12 to 14 in Table 1 were applied to electrogalvanized T1 plates, prepared in the same manner as in Example 1, and tested.

Konosou〃11-3 Example 1 except that the antirust pigment of Example 1.4.6 was removed.
It was prepared and tested in the same manner.

↓ LL12 Mutual ↓ It was prepared and tested in the same manner as in Example 1, except that the PvC of strontium chromate N in Example 1 was changed.

This product was prepared and tested in the same manner as in Example 1, except that the type and amount of the rust-preventing pigment in Example 1 was changed.

1 Consideration 1 A rust preventive clear using an organic solvent type alkyd resin was prepared and used as a reference example.

Table 1 shows the formulations of the compositions used in each Example and Comparative Example.

*1 *2 *3 *4 *5 *6 *7 *8 *9 *10 *11 Cypinol NPX-4070 (manufactured by Saiden Chemical Co., Ltd.: Styrene acrylic copolymer emulsion solid content concentration: 45
%, pH 8.8 Cypinol NPX-8431 (manufactured by Saiden Chemical ■: Styrene acrylic copolymer aqueous solution Solid content concentration: 45%,
pH 8.5 Cypinol S-9000 (manufactured by Saiden Chemical ■) Vinyl acetate emulzidine Solid content concentration 745%, p) 18.5 Cypinol NPX-7368 (manufactured by Saiden Chemical ■: Eboxy ester emulsion Solid content concentration: 45%, p
H8,5 Strontium chromate (manufactured by Kikuchi Color ■) Zinc chromate (manufactured by Kikuchi Color ■) Barium chromate (manufactured by Kikuchi Color ■) Calcium chromate (manufactured by Kikuchi Color ■) Organic solvent-based alkyd resin paint for rust prevention of zinc plating (Japan) Calcium leadate (manufactured by Kikuchi Color ■) Aluminum phosphomolybdate (manufactured by Kikuchi Color ■) Table 11 Fruit (Test method) Appearance: Visual visual resistance to spraying; JIS K54007.8 Test time: 48 hours Moisture resistance, JIS K22464.32.1 test time
48 hours As shown in Table 2, according to the present invention, a temporary rust-preventing clear for galvanizing that has anti-corrosion performance equivalent to that of the conventional one can be obtained using a water-based resin, and furthermore, the coated galvanized steel sheet has a zinc metallic luster. No change in hue due to coloring was observed.

[Effects of the Invention] As is clear from the above test results, the water-based anticorrosive paint composition of the present invention enables temporary rust prevention of zinc plating with low pollution and similar to conventional methods.

Claims (1)

[Claims] 1. One or more resins selected from the group of water-soluble, water-suspended or water-emulsifiable acrylic resins, vinyl acetate resins, and epoxy-modified polyester resins, and selected from the group of chromium pigments and calcium lead acid pigments. 1. A water-based anticorrosive paint for galvanized steel, characterized in that the water-based anticorrosive paint contains one or more types of pigments in a pigment volume concentration of 0.1 to 2%.