JPS5845905B2 - Treatment method for galvanized coating surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treatment method for galvanizing, particularly for preventing corrosion and coloring the surface of a hot-dip galvanized coating.

Galvanizing has traditionally been applied to steel materials and products as a long-term corrosion protection method, and it is well known that large structures such as power transmission towers, dam gates, etc. are coated with hot-dip galvanizing. It is.

This anti-corrosion method is far superior to general coating methods, but as air and water pollution progresses, zinc tends to be depleted significantly, and it may not last long like its predecessor. The current situation is that it is no longer possible to expect the anti-corrosion effect.

On the other hand, in order to make the long-term corrosion protection inherent in galvanizing effective, it is necessary to interpose an organic coating on the galvanized surface to prevent contact with corrosive factors such as water and the atmosphere. Furthermore, with the recent increase in the size of structures, there is a strong demand for the need to color and decorate structures from the viewpoint of the need for aviation signs or the aesthetics of harmony with the environment.

For the various reasons mentioned above, various paints such as oil-based paints or synthetic resin-based paints are currently applied to galvanized surfaces.

However, this type of paint has the disadvantage that the paint film peels off or separates from the surface of the galvanized layer at an early stage, and is not always satisfactory.

Furthermore, as structures become larger, repainting for maintenance becomes difficult, so tar epoxy resin paints, tar urethane resin paints, and unsaturated polyester resins are used as top coats in terms of long-term durability and color retention. The use of paints or synthetic resin paints such as epoxy resin enamels and polyurethane resin enamels is being considered, but there is a lack of definitive methods for treating galvanized surfaces to improve the adhesion of these top coats. This is the actual situation.

The present invention seeks to solve the current problems by a treatment method in which a specific coating composition is applied to galvanized surfaces.

That is, the present invention provides a resin composition consisting of (a) 99 to 60% by weight of an epoxy resin containing at least two or more epoxy groups at the end and 1 to 40% by weight of a polyvinyl butyral resin on the surface of the ω galvanized coating.・
・・・・・・・・・100 parts by weight (b) Metallic zinc powder and/or calcium leadate・・・・・・・・・・・・
......10 to 200 parts by weight (c) oxyacid salt,
At least one component selected from metal oxides...
...1 to 150 parts by weight and (d) flat pigment...
. . . Step CB) Coating the primer coating layer by coating and drying a coating composition formed by mixing components in a proportion of 10 to 200 parts by weight The present invention relates to a method for treating the surface of a galvanized coating, which comprises the steps of overcoating at least one layer of various paint layers on the coating layer and drying it to form a coating layer.

The epoxy resin used in the present invention has at least two terminals.
It consists of a mixture of an epoxy resin containing at least three epoxy groups and a crosslinking agent.

Examples of the epoxy resin include linear bisphenol type epoxy resin, methyl-substituted bisphenol type epoxy resin, side chain bisphenol type epoxy resin, phenol novolac type epoxy resin, cresol type epoxy resin, polyphenol type epoxy resin, and aliphatic type epoxy resin. , aromatic type epoxy resins, cycloaliphatic type epoxy resins, ether ester type epoxy resins, etc.

Typical examples of commercially available product names include Epicote (trade name, manufactured by Shell Chemical), Epiclon (trade name, manufactured by Inu Nippon Ink Chemical Industries), and Araldite (trade name, manufactured by Ciba Geigy).

These can be used alone or in combination of two or more to bring out the characteristics of each.

As the crosslinking agent of the present invention, any crosslinking agent that has a group that reacts with the epoxy group or hydroxyl group contained in the epoxy resin molecule and is generally used as a crosslinking agent for epoxy resins may be used.

For example, diethylenetriamine, triethylenetetrane, metaxylylenediamine, metaphenylenediamine,
Aliphatic or aromatic borians such as heterocyclic diamines, secondary or tertiary amines such as dimethylamine methylphenol, tris(dimethylaminomethyl)phenol, piperidine, polyamide resins, amine adducts (generally with amine adducts). In addition to amino compounds such as (2013), incyanate compounds (including blocked incyanate) such as tolylene diisocyanate and hexamethylene diisocyanate, phenolic resins, acid anhydrides, melamine resins, urea resins, and the like.

Since the objects of the present invention are generally large steel materials and large steel products, the chemical reaction between the epoxy resin and the crosslinking agent proceeds at normal humidity or forced drying, and is accompanied by a chemical reaction with the epoxy group. Amino compounds are most preferred.

The feature of the present invention, as described below, is that at least one component selected from oxyacid salts and metal oxides contained in the composition chemically reacts with the galvanized surface, improving the adhesion of the coating film. It is about giving.

In particular, when phosphate is used as an essential component and at least one component selected from other oxygen salts and metal oxides is used, phosphoric acid and epoxy resin and polyvinyl This is preferable because it forms a chelate bond with the hydroxyl group in the butyral resin, giving it the effect of imparting strong adhesion.

Therefore, when mixing a crosslinking agent into the mixture of the epoxy resin and polyvinyl butyral resin of the present invention, if the crosslinking agent has a property that involves a chemical reaction with the hydroxyl group in the resin composition, the resin composition It is preferable to adjust the amount of the crosslinking agent to an equivalent amount or less to allow the hydroxyl groups in the resin composition molecules to remain.

The polyvinyl butyral resin of the present invention has an average polymerization degree of 25
0-2000, preferably 250-1.000. The degree of butyralization is 57 to 75 mol%, preferably 57 to 70 mol%.

The mixing ratio of the epoxy resin and polyvinyl butyral resin of the present invention is 99 to 60% by weight of the epoxy resin and 1 to 40% by weight of the polyvinyl butyral resin, preferably the former is 9% by weight.
5 to 80% by weight, and 5 to 20% by weight of the latter.

In the present invention, the purpose of using polyvinyl butyral resin is to further promote chelate bonding with the phosphate contained in the composition, impart long-term flexibility to the coating film, and improve adhesion to the galvanized surface. This is to make it stronger.

The adhesion of paint films to active non-ferrous metal surfaces such as galvanized metal surfaces is not as good as that of steel surfaces, and with epoxy resins, the hardness of the paint film increases as the crosslinking density increases due to the progress of chemical reactions. However, the combination of polyvinyl butyral resin, which is a high molecular weight thermoplastic resin, as in the present invention, is extremely effective in alleviating the deterioration of the coating film. be.

The effect of adding the above-mentioned polyvinyl butyral resin increases as the amount increases, but if the amount exceeds the above range, it is not preferable because it may lead to a decrease in the water resistance of the coating film, deterioration in painting workability, etc.

The metal zinc powder and/or calcium leadate used in the present invention may be any of those commonly used for paints.

The amount of this component added to ioo parts by weight of the resin composition is 10
-200 parts by weight, preferably 30-150 parts by weight.

The effect of the metal zinc powder and calcium leadate of the present invention is to stabilize and maintain the long-term adhesion of the coating film, and to provide a buffering effect between the galvanized surface and the coating film to provide an adhesion support effect. Conceivable.

In the present invention, the use of calcium leadate or a combination of calcium leadate and metal zinc powder has a long-lasting effect on adhesion.

When using a combination of metallic zinc powder and calcium leadate, the mixing ratio of calcium leadate and metallic zinc powder is 80% for the former.
~40% by weight and 20-60% by weight of the latter are most effective.

If the amount of at least one component selected from metal zinc powder and calcium leadate used in the present invention is less than 10 parts by weight, there will be no sustained effect on paint film adhesion, and if it is more than 200 parts by weight, adhesion tends to be impaired. It is in.

Oxygen acid salts used in the present invention include chromic acid, phosphoric acid (including condensed phosphoric acid), boric acid, molybdic acid, phosphomolybdic acid, silicomolybdic acid, tungstic acid, phosphotungstic acid, silicotungstic acid, etc. It is a salt consisting of an acid and various metals.

For example, strontium chromate, calcium chromate, lead chromate, zinc chromate, zinc chromate, zinc molybdate, calcium molybdate, zinc tungstate, calcium tungstate, magnesium tungstate, zinc phosphate, lead orthophosphate, lead pyrophosphate, Lead metaphosphate, aluminum phosphate, silver orthophosphate, silver pyrophosphate, silver oxyphosphate, zinc tetraborate,
Zinc metaborate, lead metaborate, lead tetraborate, barium metaborate, etc. can be used.

The metal oxides used in the present invention are oxides of chromium, molybdenum, tungsten, manganese, etc.

For example, chromium trioxide, molybdenum trioxide, tungsten trioxide, manganese dioxide, etc. can be used.

These oxyacid salts and metal oxides described above can be used alone or in a mixture in any proportion.

In particular, when the above-mentioned phosphate is used as an essential component and is used in combination with at least one component selected from other oxyacids or metal oxides, the phosphoric acid produced by its hydrolysis becomes an oxyacid or Since it is thought that a chelate compound is formed between the hydroxyl groups in the epoxy resin and the polyvinyl butyral resin via the metal ions in the metal oxide, the use of that combination is most preferred.

The amounts of the oxyacid salts and metal oxides used in the present invention vary depending on their respective reactivity to the galvanized surface, corrosion resistance, etc., and vary accordingly. It is used in an amount of 1 to 150 parts by weight, preferably 5 to 100 parts by weight.

In the above, if the amount of the oxyacid salt or metal oxide is less than 1 part by weight, no effect of forming a chemical conversion film or forming a chelate on the galvanized surface can be expected.

On the other hand, if the amount exceeds 150 parts by weight, the adhesion of the coating film to the zinc plating tends to be impaired.

In the present invention, phosphate is an essential component, and at least one selected from other oxygen salts and metal oxides other than phosphate is used.
As mentioned above, it is most effective to use a combination of phosphoric acid and phosphoric acid, but the preferred mixing ratio of phosphate and other oxysaccharides and metal oxides is that the former is the most effective. The latter is 95-30% by weight and 5-70% by weight.

As the flat pigment of the present invention, for example, flat iron oxide (M
icaceous iron oxide), flat aluminum powder, mica, glass flakes, mica, flat lead powder, etc., and these can be used alone or in combination of two or more.

The effect of the flat pigment in the present invention is to impart appropriate roughness to the surface of the primer coating layer and to strengthen the interlayer adhesion with the top coating layer.

In general, the coating hardness of polypolymer resin-based paints increases as the crosslinking density progresses, and delamination tends to occur unless the top coat is applied at relatively short intervals.
As mentioned above, by imparting appropriate roughness to the surface of the primer coating film using the flat pigment, it is possible to obtain the effect of extending the interval between overcoatings of the topcoat without limit, and the greatest effect of the present invention is that the primer coating Different types of paints such as cool epoxy resin paints, tar urethane resin paints, and unsaturated polyester resin paints can be applied over the film layer.

In particular, a coating film obtained from a combination of different types of paints exhibits a remarkable anticorrosion effect when the coated object is placed in an environment where it is submerged in water.

Recently, from the perspective of long-term corrosion protection, there are many cases in which structures are coated with galvanized coating and then coated with thick-film paints such as cool epoxy resin paints, tar urethane resin paints, and unsaturated polyester resin paints. Since these paints originally have poor adhesion to the galvanized surface, a primer coating layer made of epoxy resin, which has good adhesion to the galvanized surface, is usually interposed.

However, when different types of paint films are overcoated, the adhesion between the films is generally poor, and in harsh environments such as submersion in water, water can penetrate between the paint layers over many years. However, there was a tendency for defects such as peeling of the paint film and blistering between the primer paint layer and the top coat layer.

In the present invention, the above-mentioned defects are improved by incorporating a flat pigment into the coating film to strengthen the mutual adhesion between the primer coating layer and the top coating layer.

The preferred content of the flat pigment of the present invention is 10 to 200
Parts by weight, more preferably 50 to 150 parts by weight.

In the present invention, if the amount of the flat pigment exceeds 200 parts by weight, the surface roughness of the coating film is too large and tends to foam when overcoated, while if it is less than 10 parts by weight,
There is no effect of imparting roughness to the surface of the coating film.

As described above, the present invention includes at least one component selected from a resin composition, metal zinc powder, and calcium leadate, and at least one component selected from an oxyacid salt and a metal oxide, each in the above-described quantitative ratio. By using a coating composition that has been made to last, it is possible to obtain a coating film that has strong adhesion to the surface of the galvanized coating and whose effect lasts for a long time. This imparts strong adhesion to the membrane.

In the present invention, in addition to the above-mentioned essential components, it is also possible to add other resins that are compatible with the coating composition within a range that does not impair the object of the present invention.

If desired, rust preventive pigments, extender pigments such as talc and silica, coloring pigments such as iron oxide, carbon black, and titanium oxide, bituminous materials such as asphalt, tar, and pitch, anti-settling agents, anti-sag agents, and interfaces. Additives such as activators and surface conditioners, coupling agents to further enhance the adhesion of coatings,
Chelate compounds, solvents, etc. can also be added.

In addition, in the case where an organic solvent system other than water is used as a solvent in the present invention, at least one kind is added to assist in the elution or hydrolysis of metal ions of oxyacid salts and/or metal oxides in the composition. It is preferable that the composition contains 3% by weight or less of water based on the above alcoholic solvent or solvent.

In the method of the present invention, a coating composition having the above composition is applied to a galvanized surface by a known method such as a brush, spray, or roller to obtain a dry film thickness of about 10 to 300 microns, and then the epoxy resin is applied. After the crosslinking agent undergoes a chemical reaction and the coating film is cured under conditions necessary for drying the coating film, at least one or more coating film is coated with the primer using any paint depending on the use and purpose of the structure. A laminated film is obtained by overcoating the coating layer and drying it.

The coating film obtained by the treatment method of the present invention exhibits strong durability against long-term submergence and exposure, and has stable adhesion over a long period of time without peeling or detaching in a short period of time unlike in conventional methods. It is something that you have.

Next, the specific effects of the present invention will be shown by examples. In addition, "parts" or "%" in the examples and comparative examples are "parts by weight" or "parts by weight".
% by weight.

Example 1 An epoxy resin composition obtained by mixing the epoxy resin and the crosslinking agent in equivalent amounts using a linear bisphenol type epoxy resin having an epoxy equivalent of 450 to 500 and a polyamide resin having an active hydrogen equivalent of 150 as a crosslinking agent; Average degree of polymerization 2
60 and polyvinyl butyral resin having a degree of butyralization of 60 mol % were combined to prepare a coating composition having the composition shown in Table 1.

(Table 2) For comparison, compositions outside the scope of the present invention were also prepared in the same manner.

The resulting composition was adjusted to a viscosity suitable for brush coating using a mixed solvent of methyl isobutyl ketone and n-butyl alcohol (1:1 (weight ratio)) as needed, and a dry film was applied to the hot-dip galvanized surface. A brimer coating layer was obtained by brush coating to a thickness of 80 microns.

Then, it was dried for 7 days at 20° C. and 75% RH and exposed outdoors.

After 6 months, 12 parts of chloroprene (molecular weight approximately 10,000), 5 parts of chlorinated paraffin, and long oil alkyd resin varnish (phthalic anhydride content: 24%, linseed oil content: 65%) were applied to the surface of the primer coating layer as a top coat. %, non-volatile content 70%) 8 parts, talc 25 parts, iron oxide 15 parts, 15%
A chlorinated rubber system obtained by mixing and dispersing 10 parts of a lead naphthenate dryer, 0.2 parts of a 5% cobalt nanthenate dryer, 0.3 parts of a 5% manganese naphthenate dryer, and 33.5 parts of xylene has a dry film thickness. Apply two coats of 40 microns at 24-hour intervals to achieve a thickness of 80 microns, and store at 20°C.
, and was dried for 7 days under conditions of 75% RH and subjected to a comparative test.

Example 2 Average polymerization with an epoxy resin composition obtained by mixing the epoxy resin and the crosslinking agent in equivalent amounts using a linear bisphenol type epoxy resin having an epoxy equivalent of 900 to 1000 and a polyamide resin having an active hydrogen equivalent of 150 as a crosslinking agent. degree about 60
A coating composition having the composition shown in Table 3 was prepared by combining polyvinyl butyral resin with a degree of butyralization of 0 and 72 mol %.

For comparison, a composition outside the scope of the present invention was also prepared in the same manner.

Each of the obtained compositions was adjusted to a viscosity suitable for brush coating using a mixed solvent consisting of methyl isobutyl ketone:n-butyl alcohol-1:1 (Li amount ratio) as needed, and then applied to the hot-dip galvanized surface. The primer coating layer was coated with a brush to a dry film thickness of 60 microns and left to dry for 48 hours at 20° C. and 75% RH to obtain a primer coating layer.

Next, as a top coat, 30 parts of an epoxy resin composition prepared by mixing an epoxy resin with an epoxy equivalent of 450 to 500 and a polyamine adduct with an active hydrogen equivalent of 180 in an equivalent amount;
A tar epoxy resin paint consisting of 20 parts of coal tar pitch, 20 parts of talc, 3 parts of anti-sagging agent, 15 parts of xylene, 5 parts of methyl isobutyl ketone, and 7 parts of n-butyl alcohol was airless sprayed to a dry film thickness of 300 microns. It was painted, dried for 7 days under conditions of 20° C. and 75% RH, and then subjected to a comparative test.

Comparative Experiment 1 Using the test pieces of the invention samples A1 to 14 and comparative sample layers 1 to 12, a cutter knife was used to test the adhesion of the coating film to the initial galvanized surface. 11 vertical and 11 horizontal cutting lines that cross at right angles reaching the galvanized surface are made at intervals to form 100 squares.

Next, cellophane tape was pressed onto the squares, and the cellophane tape was instantly peeled off, and the remaining number of squares was expressed as a percentage.Meanwhile, another test piece was immersed in 3% saline solution for 6 months. After soaking, take out the specimen and observe the coating surface.
After confirming the presence or absence of coating film defects and abnormalities, the test piece is left at room temperature for 24 hours to allow moisture in the coating film to scatter.

Next, the adhesion quality of the coating film of the same test piece after long-term immersion is determined by the same procedure and determination method as in the initial adhesion test.

The test results obtained are shown in the table 4 to Table 7.

Comparative Experiment 2 Using the specimens of the invention samples A15 to 19 and comparative samples AI3 to AI16 obtained as described above, a cutter knife was used to test the adhesion of the coating film to the initial galvanized surface. Using this method, 11 vertical and 11 horizontal cutting lines reaching the galvanized surface at 2n width intervals and crossing at right angles were inserted into the coating film to form 100 squares.

Next, cellophane tape was pressed onto the squares, the tape was instantly peeled off, and the number of squares remaining was expressed as a percentage.

On the other hand, another test piece was immersed in a 3% saline solution for 3 years, and then the test piece was taken out and the coating surface was observed.
After confirming the presence or absence of coating film defects and abnormalities, the test piece is left at room temperature for 24 hours to allow moisture in the coating film to scatter.

Next, the adhesion of the coating film after long-term immersion is determined by the same treatment and determination method as in the initial adhesion test.

The results are shown in Tables 8 and 9.

It is clear from the comparative experiment results table that the coating layer obtained by the treatment method of the present invention not only has an excellent adhesion effect to the galvanized surface, but also has excellent mutual adhesion with the top coat. be.

Therefore, the corrosion-proofing effect of the coating film is excellent, and it is possible to protect the galvanized surface for a long time.

Claims (1)

[Scope of Claims] 1(A) On the surface of the galvanized coating, (a) consisting of 99 to 60% by weight of an epoxy resin containing at least two or more epoxy groups at the terminal and 1 to 40% by weight of a polyvinyl butyral resin. Resin composition...
......100 parts by weight, (b) Metallic zinc powder and/or calcium leadate...
・・・・・・・・・・・・・・・・・・10～200
parts by weight, (c) at least one component selected from oxyacid salts and metal oxides...1 to 150 parts by weight, and (d) oblate pigments...10 to 200 parts by weight. (6) forming at least one layer of various paints on the primer coating layer; (6) forming a primer coating layer on the primer coating layer; A method for treating the surface of galvanized coatings, which consists of the process of overcoating and drying to form a laminated film. 2. At least one component selected from the oxysaccharides and metal oxides has a phosphate as an essential component, and at least one component selected from the oxysaccharides and metal oxides other than the phosphates.
The method for treating the surface of a galvanized coating according to claim 1, wherein the galvanized coating is a seed component. 3. The method for treating the surface of a galvanized coating according to claim 1, wherein the flat pigment is flat iron oxide.