JP2000144046A - Modified epoxy resin-based coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain stabilized adhesion to a galvanized surface for a long period of time without being affected by the surface conditions, for example, the difference between a new and an old galvanized surfaces or the degree of surface treatment which the galvanized surface has undergone and still maintain good adhesion even if a flaw occurs in the coating film by incorporating an epoxy resin, a modified aliphatic polyamine compound, a phenol-modified hydrocarbon resin and a rust preventive pigment into a coating composition. SOLUTION: A main agent comprises (A) an epoxy resin constituting the main skeleton of a bisphenol A type, a bisphenol F type or a bisphenol AD type and having an epoxy equivalent of 350-650, a phenol-modified hydrocarbon resin having a phenolic hydroxyl group with a hydroxyl number in a range of 50-100 mgKOH/g and a rust preventive pigment containing as a component a metal or a salt thereof having a lesser ionization tendency than a zinc ion, and other pigments, additives and solvents which may be optionally blended. A modified epoxy resin-based coating composition is provided as a two-pack coating composition by blending the main agent with a curing agent comprising a modified aliphatic polyamine compound having an equivalent ratio of the polyamine compound to the component A of 0.5-0.7, and other pigments, additives and solvents which may be optionally blended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modified epoxy resin paint composition mainly used for coating galvanized steel structures, panels, guardrails, steel towers, steel pipes, and other galvanized surfaces, and nonferrous metal surfaces such as aluminum. It is about things.

[0002]

2. Description of the Related Art Conventionally, as a paint for a galvanized surface, when the galvanized surface has a new metallic luster, an etching primer comprising a vinyl butyral resin and phosphoric acid after a degreasing treatment is mainly used. . Since this coating has a thin coating film thickness of about 8 to 10 μm and is inferior in anticorrosion performance and is also limited in hue, it is applied on at least two or more layers of an intermediate coating and a top coating. And used for use.

[0003] Further, when the metallic luster of the plated surface has been lost or white rust has occurred after a long time after plating, the surface of the plated surface is treated with kelenium, and then a main agent comprising an epoxy resin and a hydrocarbon resin is added. In many cases, a modified epoxy resin paint using a polyamine compound as a curing agent is applied. However, in this case, if the coating is not applied after completely removing impurities such as white rust and oil from the plated surface with a mechanical tool such as a disk sander, sandpaper or sweep blast, or by hand tools, coating with the galvanized surface will not be possible. It is difficult to ensure good adhesion.

[0004] Further, even if such a modified epoxy resin coating has a certain degree of good adhesion to the galvanized surface at the initial stage of coating, the adhesion may decrease over time and may naturally come off. Very much.

[0005]

As described above, with regard to coating on a galvanized surface, it is necessary to use a different degree of surface treatment and a different paint or coating system according to the new and old of the plated surface. It is also difficult to accurately determine the degree of old and new. In addition, when painting on a construction site, it may be difficult to perform a sufficient undercoating process, and it is said that zinc is always a concern for adhesion during the period when the coating is being used immediately after painting. This is the actual state of painting on the plated surface.

[0006] The inventors of the present invention have developed an epoxy resin-based paint for a galvanized surface which has a strong adhesiveness which is not greatly affected by the new and old of the galvanized surface and the degree of surface treatment, and which has a long term from the initial stage of coating. A phenol-modified hydrocarbon resin having a highly reactive phenolic hydroxyl group is blended as a modifying resin, and a modified aliphatic polyamine compound as a curing agent is blended in an amount of 0.5 to 0.7 equivalent to an epoxy resin. A modified epoxy resin coating composition was developed.

[0007] However, this modified epoxy resin coating composition can maintain good adhesion for a long period of time even in a high-temperature and high-humidity environment if the coating film is in a healthy state. When the wound reaches, the problem that adhesion is reduced from around the wound remains.

[0008]

Accordingly, as a result of further study, it has been found that a zinc-plated surface can be formed on a coating film by adding a rust-preventive pigment containing a metal having a lower ionization tendency than zinc or a salt thereof as a component. The present inventors have found that good adhesion can be maintained even when scratches reaching up to are obtained, and the present invention has been completed.

That is, according to the present invention, (a) the main skeleton is bisphenol A type, bisphenol F type or bisphenol AD type, and their epoxy equivalent is 35.
(B) a modified aliphatic polyamine compound, (c) a phenol-modified hydrocarbon resin having a phenolic hydroxyl group and a hydroxyl value in the range of 50 to 100 mgKOH / g, and (d) zinc. Also contains a metal with a low ionization tendency or its salt as a rust preventive pigment,
A modified epoxy resin coating composition, wherein the mixing ratio of (a) the epoxy resin and (b) the modified aliphatic polyamine compound is 0.5 to 0.7 equivalent.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The modified epoxy resin coating composition of the present invention comprises (a) an epoxy resin, (c) a phenol-modified hydrocarbon resin having a highly reactive phenolic hydroxyl group,
(D) a rust-preventive pigment containing a metal or a salt thereof having a lower ionization tendency than zinc as a component, and other pigments, additives, and a main component comprising a solvent, which are blended as necessary;
It is provided as a two-pack coating of a modified aliphatic polyamine compound and a curing agent comprising other pigments, additives, and a solvent to be blended as required.

(A) As the epoxy resin, bisphenol A type, bisphenol F type or bisphenol A
D-type epoxy resin is preferable, and the epoxy equivalent is 350.
To 650, which are generally used for paints, are preferred. In a liquid or semi-solid epoxy resin having an epoxy equivalent of less than 350, even if the amount of the curing agent is adjusted, the molecular weight between crosslinks is small, and as a result, the internal stress increases, leading to a decrease in the adhesive force in the long term. It is not suitable. In the case of a resin having an epoxy equivalent greater than 650, a large amount of an organic solvent is required to adjust the coating viscosity to a suitable coating viscosity, so that it is difficult to obtain a thick coating. It does not meet the current demand for a low VOC, low-process system and is not preferred.

The modified aliphatic polyamine compound (b) used as a curing agent for the epoxy resin is a diamine or a polyamine having two or more primary amino groups in its molecular skeleton.

As a curing agent for the epoxy resin, a modified aliphatic polyamine obtained by reacting an excessively low molecular weight aliphatic polyamine or meta-xylylenediamine with a low-viscosity liquid epoxy resin, or the above-mentioned low molecular weight amine Is generally used, for example, a modified polyamidoamine obtained by reacting the compound with phthalic anhydride or dimer acid.

However, the modified polyamidoamine has a large allowable range of mixing ratio with the epoxy resin, and the cured coating film obtained is said to be highly flexible, but unreacted carboxylic acid remaining in the resin. Is not suitable for this purpose because it reacts with zinc to form fragile zinc soaps and inhibits adhesion.

The mixing ratio of the epoxy resin and the modified aliphatic polyamine compound is preferably 0.5 to 0.7 in equivalent ratio.
When the blending ratio of the modified aliphatic polyamine compound is less than 0.5 equivalent, a dense coating film cannot be obtained due to insufficient crosslinking, the anticorrosion performance as a single film is inferior, and various topcoat paints are used. There is a problem with the performance of the system when overcoated. On the other hand, if the mixing ratio is more than 0.7 equivalent, the curing reaction further proceeds during use, the coating film shrinks, internal stress is generated, and the adhesion to the galvanized surface is undesirably reduced.

The modified aliphatic polyamine compound preferably has an active hydrogen equivalent of less than 300 in view of the mixing ratio with the epoxy resin, the viscosity, etc. Absent.

(C) The modified hydrocarbon resin is a phenol-modified hydrocarbon resin having a highly reactive phenolic hydroxyl group in the molecule and has a hydroxyl value of 50 to 100 mg KO.
H / g is used. Hydroxyl value is 50mgKOH
If it is less than / g, the effect of improving the adhesion to the galvanized surface is insufficient, and if it is more than 100 mgKOH / g, there is a problem in compatibility with the epoxy resin,
A stable paint cannot be obtained.

The mixing ratio of the phenol-modified hydrocarbon resin to the epoxy resin is 50 to 50 in terms of solid content.
100% is preferred. When the compounding ratio is less than 50%, the effect of improving the adhesion to the galvanized surface is insufficient, and when the mixing ratio is more than 100%, the compatibility with the epoxy resin is reduced, and the It is not preferable because stability becomes poor.

(D) As the rust preventive pigment, a pigment containing a metal or a salt thereof having a lower ionization tendency than zinc is used. Metals having a lower ionization tendency than zinc include C
a, Sr, K, Na, Mg, and Al. Among them, those used as rust preventive pigments include aluminum tripolyphosphate, calcium phosphate, calcium molybdate, and molybdenum phosphorus. Aluminum acid-based, cyanamide zinc-calcium-based, aluminum flake, and the like.

The mixing ratio of these rust preventive pigments is 100
5 parts or more, more desirably 10 parts or more are preferable in the part. If the compounding ratio is less than 5 parts, the effect of preventing a decrease in adhesion is small, which is not preferable. On the other hand, there is no particular upper limit on the amount of addition, but it may be determined in consideration of the price.

As the rust preventive pigments, those containing lead or chromium as a main component have been conventionally used, but these pigments are not preferable because of their harmfulness. In addition to the above-mentioned non-polluting rust-preventive pigments, there are zinc phosphate-based, zinc phosphite-based, barium metaborate-based, and strontium metaborate-based pigments. Barium borate-based pigments are not preferred because they are inferior to the rust-preventive pigments mentioned above. In addition, strontium metaborate-based strontium itself belongs to heavy metals, and it is not preferable to use it in a paint.

In the present invention, various organic and inorganic coloring pigments such as titanium oxide and carbon black, and extender pigments such as clay, kaolin, talc, calcium carbonate, barium sulfate and silica sand are blended as the pigments. can do.

As the anti-sagging agent added for imparting structural viscosity to the paint, a powdered anti-sagging agent of hydrogenated castor oil type or organic amide type, or these powders are swelled in advance with a solvent such as xylene. An anti-sagging agent on the wax is used.

As additives other than those described above, pigment treating agents such as antifoaming agents, silane coupling agents, dispersants, and wetting agents can be used as required.

As the solvent, aromatic hydrocarbon solvents such as toluene and xylene, and those used in general epoxy resin coatings such as glycol ethers, ketones and alcohols can be used as they are.

Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited thereto.

[0027]

Examples [Example (1) and Comparative Example (1),
(2), (3)] The coatings of Example (1) and Comparative Examples (1), (2), (3) were prepared with the formulations shown in Table 1, and the state of the coatings was evaluated. The mixing ratio of the modified hydrocarbon resin (c) to the epoxy resin (a) was set to 66.7%. (A) Epoxy resin or its solution and (c) modified hydrocarbon resin are mixed, and (d) rust preventive pigment, titanium oxide, talc, barium sulfate and anti-sagging agent are added thereto and uniformly mixed with a dissolver. This was used as a mill base, which was dispersed using a desktop disperser such that the degree of dispersion was 30 μm or less by a linear method. A silane coupling agent, an antifoaming agent, and the remaining solvent were added to and mixed with the dispersed mill base to obtain a main component of a paint.

As the curing agent, "ADEKA HARDNER EH-240" (manufactured by Asahi Denka Kogyo KK, solid content: 100%, active hydrogen equivalent: about 76) was used as a modified aliphatic polyamine compound as it was. . The mixing ratio to the epoxy resin was 0.6 equivalent. The volume ratio of the pigment to the solid content of the mixed paint was standardized to about 37%. The mixed paint was applied to the galvanized surfaces having different surface conditions with a brush so that the dry film thickness became 50 μm, and dried at room temperature for 7 days. The initial degree of adhesion due to the difference between the new and old galvanized surfaces and the surface treatment is 2 mm
Evaluation was made by a cross-cut tape test at intervals. In addition, the painted test plate was subjected to JIS B-77
Adhesion after 1000 hours using a sunshine carbon arc lamp type weather resistance tester specified in No. 53 was similarly evaluated. Further, an X-shaped cut (X cut) reaching the galvanized surface is made in the coating film with a cutter knife, and JIS K-5
The salt water resistance test (SST) specified in 400.9.1 was 5
After performing for 00 hours, the peeling degree from the X-cut portion was evaluated. The results are shown in Tables 1 and 2.

[0029]

[Table 1]

[0030]

[Table 2]

Unless otherwise specified, numerical values in the tables represent parts by weight. ○ mark: Each cut is thin and smooth at both ends, and there is no peeling at the intersection of the cut and at a glance, or there is a slight peeling at the intersection of the cut and no peel at a glance of the square. , The area of the missing part is 5 of the total square area
%. Δ mark: Both sides of the cut and the intersection are peeled off and the width is wide, and the area of the defective portion is within 5 to 35% of the entire square area. X: The width of the peeling due to the cut is wider than that of the triangle, and the area of the defective portion is 35% or more of the total square area. Rank A: No peeling or no intersection at the X point, and slight peeling at the X-cut part. Rank B: In any direction from the intersection of the X-cut part.
There is peeling within 0 mm. Rank C: Most of the X-cut portion where the tape has been peeled off, or the X-cut portion has come off more than the X-cut portion.

* 1 Epicoat # 1001: Bisphenol A type solid epoxy resin, manufactured by Yuka Shell Epoxy Co., Ltd., epoxy equivalent: about 490 * 2 Necires EPX-L: manufactured by NEVCIN, phenol-modified hydrocarbon resin, hydroxyl value: 63 mg KOH / g * 3 LF-Bosei PM-300C: manufactured by Kikuchi Color Co., Ltd., aluminum phosphomolybdate * 4 Crown talc C: manufactured by Matsumura Sangyo Co., Ltd. * 5 Precipitable barium sulfate # 100: Sakai Chemical Industry Co., Ltd.
* 6 γ-glycidoxypropyltrimethoxysilane * 7 Disparone 6900-20X: Kusumoto Kasei Co., Ltd.
* 8 Dispalon OX-77: manufactured by Kusumoto Kasei Co., Ltd. * 9 Xylene / methyl isobutyl ketone / propylene glycol monomethyl ether = 1/1/1 (weight ratio)
Mixture)

* 10 A surface having a metallic luster within one week after plating is degreased with a thinner for epoxy paint. * 11 White rust generated on the plated surface after 6 months of outdoor exposure is completely removed with a # 280 sandpaper and polished until metallic luster appears. * 12 White rust that has formed on the plated surface after 6 months of outdoor exposure is removed using a # 280 sandpaper. * 13 Plated surface after 6 months of outdoor exposure, degreased with a thinner for epoxy paint, leaving the generated white rust.

As a result, Examples (1), (2) and (3)
In comparison with Comparative Examples (1) and (2), (d) the rust-preventive pigment was not blended, or if the blending amount was small, the peeling from the X-cut portion after the salt water resistance test increased, and (D) It was confirmed that when 5 parts or more of the rust preventive pigment was blended, the adhesion of the X-cut portion was also good.

[Examples (4) and (5) and Comparative Examples (3), (4) and (5)] In the same manner as in Example (1),
The paints of Examples (4) and (5) and Comparative Examples (3), (4) and (5) were prepared with the formulations shown in Table 3, and the adhesion to the galvanized surface was tested by the difference between the old and new surface treatments. did.
The mixing ratio of (a) the epoxy resin and (c) the modified hydrocarbon resin is 66.7% as in the previous case. The base material of the paint was adjusted in the same manner as in Example (1).

As the curing agent, (b) Adeka Hardener EH-220 (manufactured by Asahi Denka Kogyo KK, solid content: 100%, active hydrogen equivalent: about 76) as a modified aliphatic polyamine compound is used as it is. Was.

The mixing ratio to the epoxy resin was all 0.6 equivalent. The volume ratio of the pigment to the solid content of the mixed paint was standardized to about 37%. The mixed paint has a dry film thickness of 50
It was applied to a galvanized surface having a different surface state with a brush so as to have a thickness of μm, and dried at room temperature for 7 days. The degree of adhesion due to the difference between the new and old galvanized surfaces and the surface treatment was evaluated by a cross cut tape test at 2 mm intervals. Further, assuming an exposed environment, the coated test plate was subjected to a sunshine carbon arc lamp type weather resistance tester specified in JIS B-7753 for 1000 hours, and the adhesion was similarly evaluated. An X-shaped cut (X-cut) that reaches the galvanized surface of the coating
With a cutter knife, JIS K-5400.9.
After performing the salt water resistance test (SST) specified in 1 for 500 hours, the degree of peeling from the X-cut portion was evaluated. The results are shown in Tables 3 and 4.

[0038]

[Table 3]

[0039]

[Table 4]

Unless otherwise specified, numerical values in the table represent parts by weight. ○ mark: Each cut is thin and smooth at both ends, and there is no peeling at the intersection of the cut and at a glance, or there is a slight peeling at the intersection of the cut and no peel at a glance of the square. , The area of the missing part is 5 of the total square area
%. Δ mark: Both sides of the cut and the intersection are peeled off and the width is wide, and the area of the defective portion is within 5 to 35% of the entire square area. X: The width of the peeling due to the cut is wider than that of the triangle, and the area of the defective portion is 35% or more of the total square area. Rank A: No peeling or no intersection at the X point, and slight peeling at the X-cut part. Rank B: In any direction from the intersection of the X-cut part.
There is peeling within 0 mm. Rank C: Most of the X-cut portion where the tape has been peeled off, or the X-cut portion has come off more than the X-cut portion.

* 14 K White # 84: manufactured by Teika Co., Ltd.
Aluminum tripolyphosphate * 15 LF Bowsei CP-Z: Kikuchi Color Co., Ltd., calcium phosphate type * 16 LF Bowsei ZP-SB: Kikuchi Color Co., Ltd.
Zinc phosphate * 17 BUSAN 11M-1: Barium metaborate based on Sakai Chemical Industry Co., Ltd. * 18 Calcium plumbate: Calcium leadate based on Sakai Chemical Industry Co., Ltd.

As a result, a comparison between Examples (4) and (5) and Comparative Examples (3), (4) and (5) shows that (d) the metal as a component of the rust preventive pigment has a higher ionization tendency than zinc. It was confirmed that when was noble, the effect of suppressing the decrease in adhesion after the anticorrosion test was small.

[0043]

According to the present invention, it is possible to obtain a modified epoxy resin paint having a stable adhesion without being affected by the new or old galvanized surface or the degree of surface treatment. Good adhesion to the surface, protection of galvanization, and long-term corrosion protection of steel structures.

Continued on the front page F term (reference) 4J038 CR021 CR022 DB061 DB062 DB392 DH002 GA09 HA066 HA246 HA306 HA426 KA03 KA06 MA07 NA03 PB05 PC02

Claims (2)

[Claims] (A) an epoxy resin having a main skeleton of bisphenol A type, bisphenol F type or bisphenol AD type, having an epoxy equivalent of 350 to 650, (b) a modified aliphatic polyamine compound,
(C) having a phenolic hydroxyl group and having a hydroxyl value of 50;
(D) a phenol-modified hydrocarbon resin in the range of from 100 mgKOH / g, (d) a metal having a lower ionization tendency than zinc or a salt thereof as a rust preventive pigment, (a) an epoxy resin and (b) a modified aliphatic polyamine compound A modified epoxy resin coating composition, wherein the mixing ratio of the modified epoxy resin coating composition is 0.5 to 0.7 equivalent. (D) the component of a metal or a salt thereof constituting the rust preventive pigment is one or more selected from Ca, Sr, K, Na, Mg and Al, and has a lower ionization tendency than zinc. The modified epoxy resin coating composition according to claim 1, wherein the modified epoxy resin coating composition is a suitable metal.