JPS6041705B2 - Coating type metal surface treatment composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating type metal surface treatment composition, and in particular to the production of metal materials that have been surface treated in advance to have coating adhesion on metal surfaces after degreasing treatment and corrosion resistance after painting. The object of the present invention is to provide a coated metal surface treatment composition for use in the treatment of metal surfaces.

Conventionally, phosphate treatment, chromate treatment, etc. have been carried out as anti-corrosion or paint preparation treatment for this type of degreased metal surface. It is necessary to remove the reactive processing liquid adhering to the processing object. Therefore, the wastewater discharged from the water washing process for removing the treated solution contains harmful substances and naturally requires treatment from a pollution standpoint, which increases the cost of wastewater treatment equipment and its operating costs. There were flaws. In addition, chromate treatment based on chromic acid, dichromic acid, or its salts is inexpensive and has excellent anticorrosion properties, but it has the disadvantage of causing paint film adhesion problems due to changes over time. The issue of adverse effects on the human body and destruction of nature has been brought into focus, and at the same time, the management standards for the use of chromic acids have become stricter.As with phosphate treatment, chromate treatment must be washed with water immediately after treatment to prevent it from adhering to the treated object. Because it is necessary to constantly remove reactive processing liquids,
It is necessary to treat the wastewater discharged from the water washing process, and as mentioned above, there is a drawback that the cost of wastewater treatment equipment and operating costs are high. In order to solve these problems, metal fabricators are increasingly using surface-treated metal materials such as surface-treated steel sheets. There are two characteristics that this surface-treated metal material must have:
1. No rust should be observed during the period from manufacture at a mill manufacturer to use by a metal fabricator for at least 1 hour, preferably 6 hours or more, in an accelerated salt spray test.

2. Excellent paint film adhesion and paint corrosion resistance.In particular, dirt such as oil that adheres due to pressing or cutting is usually cleaned by metal fabricators using alkaline cleaning, so the paint film adhesion remains strong even after alkaline cleaning. It also needs to have corrosion resistance after painting.

Although the use of surface-treated metal materials frees metal fabricators from the burden of wastewater treatment, chromate-treated metal materials, as well as phosphate-treated metal sulfur, are subject to chromate removal during the sealing process. Because of its use, contamination due to hexavalent chromium elution during the cleaning process of metal fabricators could not be avoided. On the other hand, mill manufacturers that produce surface-treated metal materials still have problems with wastewater treatment and hexavalent chromium contamination due to surface treatment.

Therefore, it has been desired to develop a coating-drying type metal surface treatment composition that does not contain chromium and is used to produce surface-treated metal materials.

As a coating type metal surface treatment method, Japanese Patent Publication No. 44-13562
It is known to utilize a composite coating method of silica and phosphoric acid as shown in , but this method had the disadvantage of poor alkali cleaning resistance.

As a result of various studies to eliminate the above-mentioned conventional drawbacks, the present inventors have found that a coating type metal surface treatment composition containing silica, PO4, and an anionic water-soluble resin with an acid value of 400 or more improves the corrosion resistance of metal surfaces. The present invention was completed by discovering that it is possible to produce a surface-treated metal material that has good paint film adhesion, post-painting corrosion resistance, and paint film adhesion after alkali cleaning, and post-painting corrosion resistance.

The most preferred silica used in the present invention is Aerosil (registered trademark Nippon Aerosil Co., Ltd.), which is a highly dispersed silica produced by a gas phase method. Examples include removed silica sol (for example, registered trademark Snowtex, manufactured by Nissan Chemical Co., Ltd.).

When solid silica such as Aerosil is used, it is uniformly dispersed in colloidal form in water using a dispersion device such as a high-speed dissolper.

The amount of silica used is 5-200y/', preferably 10-200y/'
100y/e, it is difficult to form a film below 5g/';
00y/' or more, the film is likely to peel off after formation. PO4 used in the present invention includes orthophosphoric acid or light or heavy metal salts of orthophosphoric acid such as aluminum phosphate, aluminum biphosphate, nickel phosphate, cobalt phosphate, zinc phosphate, ammonium phosphate and phosphoric acid. Alkali metal salts such as sodium and potassium phosphate are not preferred.

The amount of phosphoric acid used is 1 to 50 y/e1, preferably 2 to 25
f/f, and if it is less than 1y/', the corrosion resistance after painting will deteriorate, and if it is more than 50y/e, the corrosion resistance after painting will deteriorate.

The aqueous resin used in the present invention is an anionic water-soluble resin such as polyacrylic acid, vinyl maleic acid copolymer, methyl vinyl maleic acid copolymer, styrene maleic acid copolymer, etc., and has an acid value of 400 or more and is unneutralized. It has water solubility in the state.

The maleic anhydride copolymer is used after ring-opening with water to make it water-soluble. Since a resin having an acid value of less than 400 does not dissolve in an unneutralized state, it becomes insoluble at pH1 to 5 of the composition of the present invention and cannot be used. The amount of this water-soluble resin used is 0.5 to 50
da/' is preferably 1 to 259/e.

Below 0.5y/e, corrosion resistance when unpainted, coating adhesion,
Also, the adhesion of the coating after alkali cleaning and the corrosion resistance after painting deteriorate, and if it exceeds q/e, the corrosion resistance after painting deteriorates.

The composition of the present invention has a pH in the range of 5 to 5, and below the PH1, it shows corrosiveness to the material metal, and at a pH above 5, the phosphate or the metal salt of the anionic water-soluble resin precipitates and the solution composition changes. This results in a deterioration of all character.

The coating type metal surface treatment composition of the present invention can be prepared by the following method.

First, in an aqueous solution of 20 to 75% by weight orthophosphoric acid, ,Al
, Nl, CO, Zn, and other oxides, hydroxides, carbonates, or phosphates are calculated and added so as to finally have a predetermined pH, thereby preparing an acidic phosphoric acid aqueous solution of the metal.

Gradually add 10% to 10% by weight of an anionic water-soluble resin while stirring to make it homogeneous, and then disperse Aerosil using a high-speed dissolver or mix silica sol such as Snotex using a propeller stirrer to make it homogeneous. After that, the mixture was diluted to a predetermined concentration using ion-exchanged water. The conditions for using the composition of the present invention are as follows: After coating the metal surface from which dirt such as oil and fat has been removed using a method such as a roll coater, curtain coater, air gun spray, or electrostatic coating, a wet film weight of 1 to 20 q/Tl is applied. It may be dried by evaporating moisture using a dryer such as hot air drying.

If the weight of the wet film is less than 1y/d, it is difficult to completely cover the metal surface, and if it is more than 20y/T7I, the coating solution flows, which not only tends to cause uneven coating during drying, but also requires excessive drying equipment. capacity or drying time. As explained above, the composition of the present invention is applied directly after degreasing the metal surface to impart coating film adhesion and post-coating corrosion resistance. Since it is possible to produce metal materials that do not require the use of metals, and there is no need for the commonly performed phosphate treatment or chromate treatment, it is natural that post-treatment, i.e., reactive treatment liquids attached to the metal surface, be performed. This eliminates the process of washing away wastewater with water, eliminates the process of treating wastewater containing harmful substances due to the washing process, and eliminates the need for wastewater treatment equipment and the various costs associated therewith.

The present invention will be explained below with reference to Examples.

Example 1 The surface of a commercially available electrogalvanized steel sheet (coating amount: 20 y/d, dimensions: 0.03 cm x 20 cm x 30 cTn) was wiped clean with acetone, and then Composition 1 of the present invention described below was applied thereto.

Composition 1 of the present invention 75% orthophosphoric acid 13.9y/Ez
nOl. 6 Methyl vinyl ether maleic anhydride copolymer 8y/e Aerosil #20060 PH2.5 Coating is done with a roll coater, the method is reverse coating, mesh rolls are used as metering rolls, and wet coating is performed by adjusting the roll spacing. The coating was applied so that the weight of the film was 5y/a.

Immediately thereafter, it was dried at 120° C. for 35 seconds in an open hot air drying system. The plate temperature at this time was 70°C. Control example 1
As a result, composition 1 of the present invention was treated in the same manner as in Example 1, except that the methyl vinyl ether maleic anhydride copolymer was removed.

As control example 2, a commercially available electrogalvanized steel sheet (plating amount 2
(0q/d1 dimensions: 0.03 cm x 20α x 30α) The surface was cleaned by wiping with acetone, washed with water, and subjected to chemical conversion treatment with the following chromate treatment solution. Chromate treatment liquid composition Chromic anhydride 10y/e Orthophosphoric acid 1 Silica hydrofluoric acid
2 Chromium carbonate
1 〃Sulfuric acid 0.5〃pH2. with zinc carbonate. The conditions for the chemical conversion treatment were as follows: spraying at a treatment temperature of 40°C for 5 seconds, immediately washing with water to remove the reactive chromate treatment solution adhering to the treated surface, and drying with a dryer.

When measured using fluorescent X-rays, the amount of chromium deposited was 13mg/
It was d. The electrogalvanized copper plates treated in Example 1, Comparative Example 1, and Comparative Example 2 were JISZ coated without being coated.
A salt water spray test based on 237L was conducted to measure the time until white rust appeared. The results are shown in Table 1. The alkyd melamine paint was applied to the electrogalvanized steel sheets treated in Example 1, Comparative Example 1, and Comparative Example 2 by the Parcoat method, and after setting for 2 minutes, it was baked in a hot air circulating system at an ambient temperature of 140°C for 2 powders. A coated plate with a coating film thickness of 30±2 microns was obtained. Table 2 shows the results of a coating film adhesion test and a salt spray test performed on these coated plates. Example 1
The electrolytic galvanized steel sheets treated in Control Example 1 and Control Example 2 were treated with an alkaline cleaning solution (registered trademark Fine Cleaner 432, Nippon Parkerizing Co., Ltd., concentration 20 da/l).
) at 60°C for 12 minutes using a spray method, followed by washing with water for 1 hour and drying with a hair dryer. Table 2 also shows the results of the paint film adhesion test and the salt spray test of the product coated in exactly the same manner as above. Paint film adhesion test 7rrt. with Erichsen tester. /7TI. After extrusion, Cellotape (registered trademark, Nichiban Co., Ltd.) was pressed onto the extruded portion, left for 1 minute, and then rapidly peeled off, and the peeling state of the coating film was scored using the following five-point scale.

5 points Salt water spray test on painted board with no paint film peeling A cross cut was made on the painted board to reach the base metal using an NT cutter, and after conducting a salt water spray test based on JIS Z237L for 120 hours, it was washed with water, dried, and Sellotape was crimped on the painted surface. After being allowed to stand for 1 minute, it was rapidly peeled off, and the degree of peeling of the blisters from the cross-cut area was scored using the following 5-point method.

5 points No peeling Example 2 First commercially available cold rolled steel 1SG3141 (Dimensions 0.06cm x 2
After cleaning the surface (0α x 30 cm) by wiping it with acetone, the composition 2 of the present invention described below was applied.

Composition 2 of the present invention, pH 2.2, was applied using a roll coater using reverse coating, using a mesh roll as the metering roll, and adjusting the roll spacing so that the weight of the wet film was 10y/Rrl. .

Immediately thereafter, it was dried for 2 hours at 120'C5 in an open hot air circulation system. The plate temperature at this time was 70°C. As Control Example 3, the same treatment as in Example 2 was carried out, except that polyacrylic acid was removed from Composition 2 of the present invention.

As control example 4, commercially available cold-rolled steel first 1SG3141 (dimensions 0
．． 06cm x 20cm x 30c7rL) After cleaning the surface by wiping it with acetone, spraying it for 2 minutes at 50'C with an iron phosphate treatment solution consisting of 10 da/' ammonium dihydrogen phosphate, immediately washing it with water, and then drying it. A chrome seal was applied by spraying an aqueous solution of chromic acid (old da/f) and orthophosphoric acid (0.05 y/f) at 50°C, followed by drying with a dryer.

The unpainted cold-rolled steel sheets treated in Example 2, Comparative Example 3, and Comparative Example 4 were subjected to a salt spray test based on JIS Z237l to measure the time until red rust appeared.

The results are shown in Table 3. Alkyd melamine coating was applied to the cold-rolled steel sheets treated in Example 2, Comparative Example 3, and Comparative Example 4 using the Parcoat method, and after setting the two powders, the two powders were heated in an open hot air circulation system at an atmosphere and temperature of 140°C. A coated plate with a baked coating film thickness of 30±2 microns was obtained.

Table 4 shows the results of a coating film adhesion test and a salt spray test conducted on these coated plates. The cold-rolled steel sheets treated in Example 2, Comparative Example 3, and Comparative Example 4 were washed with an alkaline cleaning solution (Fine Cleaner 4326, 20y/e) for 60 minutes.
After washing with a spray method for 2 minutes, it was washed with water for 15 seconds and dried with a dryer.

Table 4 also shows the results of the coating film adhesion test and the salt spray test of this product coated in exactly the same manner as above.

Test conditions and scoring criteria are the same as in Example 1.
Example 3 Commercially available pure aluminum plate (dimensions 0.03 cm x 20 cm x 30
cm) After cleaning the surface by wiping it with acetone, soak it in a 1% aqueous solution of caustic soda at 60°C for 10 minutes to remove the oxide film.
After immersion for a second, immediately after washing with water, drying with a dryer and cooling, the following composition of the present invention 3 was applied.

Composition of the present invention 375% orthophosphoric acid
7y/' coating was done using a roll coater using a natural coat, using a mesh roll as the metering roll, adjusting the roll spacing to achieve a wet film weight of 10y/'.
It was applied so that it became d.

After this, immediately open the hot air circulation system to 120'C3 [shares]
Dry for a while. The plate temperature at this time was 70°C. Control example 5
As a result, composition 3 of the present invention was treated in the same manner as in Example 3, except that the methyl vinyl ether maleic anhydride copolymer was removed.

As control example 6, a commercially available pure aluminum plate (dimensions 0.03 cm x
After wiping the surface (20 cm x 30 cm) with acetone to clean it, it was immersed in a 1% caustic soda aqueous solution at 60'C to remove the oxide film, and then immediately washed with water and subjected to chemical conversion treatment with the following chromate solution. Composition of chromate treatment liquid Adjustment to pH 2 with aluminum hydroxide Conditions for chemical conversion treatment were treatment at a treatment temperature of 40°C for 5 seconds by spray method, immediately after treatment, washing with water and drying with a dryer.

When measured using fluorescent X-rays, the amount of chromium deposited was 16 mg/I. The unpainted pure aluminum plates treated in Example 3, Comparative Example 5, and Comparative Example 6 were subjected to a salt spray test based on JIS Z237l to measure the time it took for white rust to develop.

The results are shown in Table 5. Alkitudramine paint was applied to the pure aluminum plates treated according to Example 3, Comparative Example 5, and Comparative Example 6 using the Parcoat method, and after setting the two powders, a hot air circulation system was opened at an ambient temperature of 140'C for 25 minutes. Baking was performed to obtain a coated plate with a coating thickness of 30±2 microns.

Table 6 shows the results of a coating film adhesion test and a salt spray test performed on these coated plates. The pure aluminum plates treated in Example 3, Comparative Example 5, and Comparative Example 6 were treated with an alkaline cleaning solution (Fine Cleaner #432eK concentration 20q).
/e) at 60° C. for 2 minutes using a spout method, followed by washing with water for 15 seconds and drying with a hair dryer. Table 6 also shows the results of the paint film adhesion test and the salt spray test of the product coated in exactly the same manner as above. Salt water spray time 36Ct
The test conditions and scoring criteria were the same as in Example 1, except for the f interval.

Claims (1)

[Claims] 1 Silica 5-200g/l and PO_41-50g/l
l and an anionic water-soluble resin with an acid value of 400 or more from 0.5 to
A coating type metal surface treatment composition containing 50 g/l and having a pH in the range of 1 to 5.