JPH01258777A - Formation of corrosion preventive coating film on rusted surface - Google Patents

Abstract

PURPOSE:To form a superior corrosion preventive coating film on a rust layer on the surface of a metal by coating the rust layer with epoxy resin coating material contg. a silane coupling agent and by fixing the silane coupling agent on the rust layer and the surface of the metal with water in the rust layer. CONSTITUTION:A rust layer on the surface of a metal is coated with epoxy resin coating material contg. a silane coupling agent. This silane coupling agent slowly causes an alcohol removal reaction in the presence of water contained in the rust layer and moisture in the air. A silanol group is reproduced and causes a condensation reaction with hydroxyl groups on the rust layer and the surface of the metal, so the silane coupling agent is fixed by firm chemical bonding to the rust layer and the surface of the metal. Since another functional group of the silane coupling agent reacts with epoxy resin, the epoxy resin coating material penetrates into the rule layer and is well adsorbed on the rust layer to considerably improve the adhesion of the resulting coating film to the rust layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a novel anti-corrosion coating method for metal surfaces having a rust layer.

Conventional technologies and their challenges Traditionally, long-term corrosion protection for steel materials and steel structures has been achieved using epoxy resin paints, polyurethane paints, chlorinated rubber paints, vinyl chloride resin paints, and zinc powder using epoxy resin or ethyl silicate as a binder. Containing paints, etc. are widely used. Among these paints, epoxy resin paints are used as anticorrosive paints for metals in a wide range of fields due to their excellent anticorrosion performance. However, in order for this epoxy resin paint to exhibit excellent anti-corrosion performance over a long period of time, it is necessary to use a power tool, a power brush, or a blasting process to completely remove the rust present on the metal surface. It is necessary to apply the coating sufficiently, and if this surface treatment is not performed, the adhesion of the epoxy resin paint to the metal base will be poor, and the anticorrosion performance will be significantly reduced.

On the other hand, when applying the above-mentioned surface treatment to the metal to be coated, the generation of dust, noise, etc. is unavoidable, and these generation causes pollution,
This is undesirable from a sanitary perspective, and therefore an anticorrosive coating method that omit the metal surface treatment, that is, an anticorrosive coating method that can be applied directly to a metal surface with a rust layer and provides excellent adhesion and anticorrosion performance, has been developed. This has great advantages not only in terms of pollution and hygiene, but also in the ability to omit the painting process, and its development is strongly desired.

However, in the past, various methods have been proposed in which corrosion prevention is achieved by directly applying paint to a metal surface having a rust layer. For example, there is a method of using a paint film-forming element consisting mainly of processed dry resin, alkyd resin, phenol resin, etc., alone or in any combination thereof, and with the addition of anti-corrosion pigments. has insufficient water resistance and corrosion resistance, and also has poor solvent resistance, making it impossible to apply top coats with excellent corrosion resistance such as epoxy resin-based, urethane resin-based, and vinyl resin-based paints that contain solvents with strong dissolving power. There is a drawback. Another method is to apply a paint using moisture-curing isocyanate-based resin to the rusted surface, but this paint generates carbon dioxide gas during the curing reaction, resulting in the formation of many pinholes in the paint film, resulting in long-term corrosion resistance. What are your shortcomings? Furthermore, recently, it has been proposed to use a paint consisting of a precondensate of an epoxy resin and a phenol resin, a polyamine, and a polyamide curing agent (Japanese Unexamined Patent Publication No. 56-14
(See Publication No. 9466). However, when this paint is used, the moisture contained in the rust layer is sealed by the paint film and remains as it is, so rust continues to grow under the paint film, eventually forming blistering rust or black rust. There are drawbacks to doing so.

Means for Solving the Problems Therefore, the present inventor has devised a method that uses an epoxy resin with excellent anti-corrosion properties to enable direct painting on a metal surface with a rust layer without any pretreatment, and which overcomes the drawbacks of the conventional methods described above. As a result of extensive research to develop an anti-corrosion coating method that does not require metal surface treatment, we have discovered that by adding a silane coupling agent to epoxy resin paint, an excellent anti-corrosion coating film can be formed without the need for metal surface treatment. They discovered this and completed the present invention.

Thus, according to the present invention, on a metal surface having a rust layer,
A metal having a rust layer characterized in that an epoxy resin paint containing a silane coupling agent is applied, and then the silane coupling agent in the epoxy resin paint, the rust layer, and the metal surface are fixed by moisture in the rust layer. A method of anti-corrosion coating of a surface is provided.

The reason that the epoxy resin paint can be applied directly to the rusted surface without any pretreatment as in the present invention is due to the use of a silane coupling agent as a rust layer fixing agent. The agent gradually causes a dealcoholization reaction depending on the moisture contained in the rust layer and the humidity in the air, reproduces the silanol group, and further causes a condensation reaction with the hydroxyl groups on the rust and metal surface, and the silane coupling agent It is strongly chemically bonded and fixed to the rust layer and metal surface.

Since the other functional group of the silane coupling agent reacts with the epoxy resin, the epoxy resin paint can sufficiently penetrate and adsorb into the rust layer, and its adhesion to the rust layer is also very good. In addition, since the alcohols produced during the curing reaction process volatilize out of the coating film together with the organic solvent, they do not cause pinholes and there is no risk of impairing the anticorrosion properties of the coating film.

Furthermore, the water contained in the rust layer is consumed in the curing reaction of the epoxy resin paint as described above, so the rust layer is firmly fixed inside by the cured paint film without any water present. Rust growth is completely stopped. The cured coating film thus formed completely blocks out external corrosive substances, preventing corrosion, and has excellent solvent resistance, so it can be coated with various top coats. .

That is, the above-mentioned features of the present invention are that, in the case of epoxy resin paints for which it was conventionally unthinkable to directly apply a rust layer to a metal surface, by using an epoxy resin paint containing a silane coupling agent, This was achieved for the first time and cannot be obtained using conventional epoxy resin paints.

The metal to which the method of the present invention is preferably applied is usually steel, but it can also be applied to non-ferrous metals.

The silane coupling agent-containing epoxy resin paint used in the present invention will be described below.

Examples of epoxy resins used in the paint include the known epoxy resins described in Chapter 2 of "Epoxy Resins" by Kuniyuki Hashimoto, published by Nikkan Kogyo Shimbun, 1969, among which 1 molecule Those having at least 2 or more epoxy groups, preferably 2 to 5 epoxy groups per epoxy group, and which are bonded by carbon chains of organic residues containing these epoxy groups or carbon chains interrupted by oxygen atoms are preferably used. In particular, those having an average molecular weight of about 350 to about 3,000 and an epoxy equivalent of about 80 to about 1,000 are preferred.

Examples of suitable epoxy resins include epoxy resins obtained by reacting polyhydric alcohols, polyhydric phenols, etc. with excess epichlorohydrin or alkylene oxide. Examples of polyhydric alcohols include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, glycerin, neopentyl glycol, butylene glycol, hexanediol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, diglycidyl, sorbitol, etc. , as a polyhydric phenol, 2.2-
Bis(4-hydroxyphenyl)propane (bisphenol A), halogenated bisphenol A, 4,4-dihydroxyphenylmethane (bisphenol F), tris(4-hydroxyphenyl)propane, resorcinol, tetrahydroxyphenylethane, novolac type polyhydric These include phenol, cresol type polyhydric phenol, etc. Examples of epoxy resins other than these that can be used in the present invention include 1,2.3-)lis(2,3-epoxypropoxy)
Glycidyl adducts of propane, aniline or aniline derivatives (such as orthotoluidine), glycidyl esters such as phthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, epoxidized soybean oil, etc. .

As the curing agent for the above-mentioned epoxy resin, all the usual curing agents for epoxy resins can be used, such as aliphatic polyamine, modified aliphatic polyamine, modified aromatic polyamine, alicyclic polyamine, and modified alicyclic polyamine. , polyamides, amino resins, carboxylic acids, mercaptans, and the like.

The ratio of the curing agent used is usually about 0.5 to 2 equivalents of active hydrogen groups per 1 equivalent of epoxy groups.

In the present invention, as the silane coupling agent, one represented by the following formula is preferably used.

R' S i (OR) 3 [wherein R' represents an organic functional group such as an amino group, mercapto group, vinyl group, or epoxy group, and OR represents a functional group such as an alkoxy group. ] As a preferred specific example,
Vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, vinylacetosilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltris(β-methoxyethoxysilane),
β-(3,4-Epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyljethoxysilane, N-β-(aminoethyl)γ-aminopropyltri Methoxysilane, N-β-(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, bis(trimethylsilano)amine, N Examples include -phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane.

In particular, aminosilane-based, mercaptosilane-based, and epoxysilane-based silane coupling agents are preferred, and more specifically, γ-glycidoxypropyltrimethoxysilane,
N-β-(aminoethyl)γ-aminopropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane are mentioned.

The amount of the silane coupling agent added to the paint is about 0.1 to 20 parts by weight per 100 parts by weight of the total ffi (solid content) of the epoxy resin and its curing agent in the paint, and 1 part by weight. ~10 parts by weight is preferred. If the blending ratio of the silane coupling agent is less than 0.1 part by weight,
If the amount exceeds 20 parts by weight, the effect of fixing the rust layer will be insufficient, and if the amount is more than 20 parts by weight, the cured coating will not have sufficient mechanical strength, which is not preferred.

Solvents used in epoxy resin paints include aromatic hydrocarbons such as toluene and xylene; acetone, methyl ethyl ketone, and methyl isobutyl ketone (hereinafter referred to as M
IBK), diisobutyl ketone, and other ketones; esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, cellosolve, and cellosolve acetate. The amount used is about 200 parts by weight or less per 100 parts by weight of the total amount (solid content) of the epoxy resin and curing agent.

Epoxy resin paints can be easily prepared by simultaneously mixing the above components by any known means, but in some cases a silane coupling agent may be mixed in just before use of the paint.

In addition to the above components, the epoxy resin paint may contain conventionally used pigments, additives, plasticizers, etc., as desired, in an amount of 200 parts per 100 parts by weight of the total amount (solid content) of the epoxy resin and curing agent. It can be added as appropriate within a range of about parts by weight or less.

The epoxy resin paint can be applied by conventionally known painting means such as spray painting and brush painting. Although the metal surface of the object to be coated has a rust layer for the purpose of the present invention, it is necessary to remove the floating rust during coating.

If floating rust is not removed, there is a drawback that the adhesion of the anticorrosive coating is reduced.

The amount of the epoxy resin paint to be applied is not particularly limited, but generally has a dry film thickness of about 30 to about 500 microns, preferably about 60 to about 300 microns.

In the applied epoxy resin paint, the silane coupling agent gradually causes a dealcoholization reaction with the rust layer and moisture in the air, reproduces the silanol group, and then undergoes a condensation reaction with the hydroxyl groups on the rust and metal surface. This causes the silane coupling agent to form a strong chemical bond with rust and metal surfaces. Since the other functional group of the silane coupling agent reacts with the epoxy resin or curing agent, it is possible to firmly fix the rust layer and exhibit excellent anticorrosion performance.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Note that parts indicate "parts by weight."

Example 1 A silane coupling agent was mixed with an epoxy resin in the following blended parts (solid content, the same hereinafter) and dispersed in a paint mill for 20 minutes to form a base. A curing agent was mixed into the obtained base at the following mixing ratio.

Base [Epicote 828J (epoxy resin, 28 parts manufactured by Shell Kagaku Co., Ltd.) Red iron (manufactured by Toda Kogyo Co., Ltd.) 10 parts Talc (manufactured by Nippon Nameshi Co., Ltd.) 30 parts Xylene: //MIBK=1/1 20 parts This epoxy resin paint is applied to shot-blasted steel plates and shot-blasted steel plates that are exposed outdoors for two months to generate rust, and then the floating rust is removed to a dry film thickness of about 100 μm.
It was air spray painted to look like this. The results of the coating film performance test of the obtained coating film are shown in Table 1 below. When the chain plate was painted, the corrosion resistance was dramatically improved compared to Comparative Example 1.

Furthermore, even on rust-free shot blasted steel plates, the epoxy resin exhibits its inherent excellent corrosion resistance, similar to the comparative example.

Example 2 A base was prepared by dispersing the following blended parts by the method shown in Example 1. The silane coupling agent was mixed with the curing agent together with xylene in the following proportions. This base and curing agent were mixed in the following proportions to prepare a paint.

Base: Epicoat 100IJ (300 parts epoxy resin manufactured by Shell Chemical Co., Ltd.) Red iron (manufactured by Toda Kogyo Co., Ltd.) 7 parts Talc (manufactured by Nippon Talc Co., Ltd.) 28 parts xylene/M
IBK=1/1 15 parts hardening agent [Persamide 140J (polyamide resin 5 parts resin, manufactured by Henkel Hakusui Co., Ltd.) "Toray Silicone 5H-6020J 2 parts (γ
-(2-aminoethyl)aminopropyltrimethoxysilane (manufactured by Toray Silicone Co., Ltd.) xylene 13 parts This paint was applied in the same manner as in Example 1.

Table 1 shows the results of the coating film performance test of the obtained coating film. Example 1 even if a silane coupling agent is added to the curing agent
Similarly, corrosion resistance has improved dramatically.

Example 3 A silane coupling agent was dispersed in the following proportions by the method shown in Example 1, and mixed with a curing agent to prepare a paint.

Base "Epicote 100IJ (300 parts epoxy resin manufactured by Shell Chemical Co., Ltd.) [Toray Silicone 5H-6030J 3 parts (γ
- Methacryloxypropyltrimethoxysilane, manufactured by Toray Silicone Co., Ltd.) Red iron (manufactured by Toda Kogyo Co., Ltd.) 7 parts talc (Japan Talc (Japan Talc)
Co., Ltd.) 28 parts xylene/MIBK=1
/1 27 parts hardening agent [Persamide 140J (polyamide resin 5 parts resin, manufactured by Henkel Hakusui Co., Ltd.) This paint was applied in the same manner as in Example 1.

Table 1 shows the results of the coating film performance test of the obtained coating film. Even if the type of epoxy resin was different, the corrosion resistance was dramatically improved as in Example 1.

Example 4 A base was prepared by dispersing the following blended parts using the method shown in Example 1. A curing agent was mixed with this base in the following proportions to prepare a paint. Immediately before applying this paint, a silane coupling agent was mixed in the following proportions.

Red iron (manufactured by Toda Kogyo Co., Ltd.) 10 parts Talc (manufactured by Nippon Nameshi Co., Ltd.) 30 parts Xylene/M
IBK=1/1 20 parts This paint was used in Example 1
Painted in the same way.

Table 1 shows the results of the coating film performance test of the obtained coating film. Even if the silane coupling agent is not added to the base or hardener in advance, by adding it to the paint before painting, it is possible to dramatically improve corrosion resistance as in Examples 1 and 2. became.

Comparative Example 1 The following proportions were dispersed by the method shown in Example] and used as a base. Mix a curing agent with this base in the following proportions,
It was made into paint.

Base [Epicote 828J (epoxy resin 28 parts resin, manufactured by Shell Kagaku Co., Ltd.) Red iron (manufactured by Toda Kogyo Co., Ltd.) 10 parts Talc (manufactured by Nippon Talc Co., Ltd.) 30 parts xylene/MIBK = 1/1 22 parts of this The paint was applied in the same manner as in Example 1.

Table 1 shows the results of the coating film performance test of the obtained coating film.

The test results for each example and comparative example are shown in Table 1.

In Table 1, notes 1 to 3 indicate the following: Note 1: Exposed outdoors for 6 months in a seaside area.

Note 2: ◎...No rust at all. ○...1% of the painted board
Black rust has formed in the following areas. △...Black rust develops in an area of 5% or less.

Note 3: Subjected to two-cross cut tape test.

◎...No peeling at all. O: Peeling occurs on an area of 5% or less of the painted plate. △...Area of 30% or less 1 x 8.

As is clear from the above test results, the epoxy resin paint applied by the anticorrosive coating method of the present invention reacts with the moisture in the chains, so it has good penetration and adsorption into the rust layer, and has excellent adhesion to the rust surface. The cured coating exhibits the excellent anti-corrosion properties inherent to epoxy resin coatings on rusted surfaces.

(that's all)

Claims (1)

[Claims] (1) Apply an epoxy resin paint containing a silane coupling agent to the metal surface that has a rust layer, and then fix the silane coupling agent in the epoxy resin paint, the rust layer, and the metal surface with the moisture in the rust layer. A method for forming an anticorrosion coating on a rust surface, characterized by: