JP2000144045A - 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 the new and old galvanized surfaces or the degree of surface treatment which the galvanized surface has undergone by incorporating an epoxy resin, a modified aliphatic polyamine compound blended therewith in a specific ratio and a phenol- modified hydrocarbon resin into a coating composition. SOLUTION: A base resin component comprises an epoxy resin (A) 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 and a phenol-modified hydrocarbon resin (B) having a phenolic hydroxyl group with a hydroxyl number in a range of 50-100 mgKOH/g in an amount of 50-100% by weight in terms of a solids content, based on the weight of the component A, 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 base resin component 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. The composition is suitable for coating onto a galvanized surface.

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 present inventors have previously proposed a highly reactive phenolic paint based on an epoxy resin as a paint for a galvanized surface which has a strong adhesion without being largely influenced by the new or old of the galvanized surface or the degree of surface treatment. A modified epoxy resin coating composition containing a phenol-modified hydrocarbon resin having a hydroxyl group as a modifying resin has been developed.

However, when this modified epoxy resin coating composition is applied to a galvanized surface having various surface conditions and is used in an environment exposed for a long period of time, there remains a problem that the adhesive force slightly decreases. I was

[0008]

Therefore, as a result of further study, it is found that the adhesive force decreases because the cross-linking reaction of the epoxy resin proceeds further during the exposure, and the internal stress generated in the coating film increases. From the experimental result that it is because it becomes too much,
By limiting the mixing ratio of the epoxy resin and the polyamine compound as a curing agent to an appropriate range, it is possible to suppress the occurrence of excessive internal stress, and as a result, it has been found that the adhesive force with the galvanized surface can be maintained for a long time. 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.
The main constituents are an epoxy resin having 0 to 650, a (b) modified aliphatic polyamine compound, and (c) a phenol-modified hydrocarbon resin having a phenolic hydroxyl group and having a hydroxyl value in the range of 50 to 100 mgKOH / g. ,
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]

BEST MODE FOR CARRYING OUT THE INVENTION The modified epoxy resin composition of the present invention comprises (a) an epoxy resin, (c) a phenol-modified hydrocarbon resin having a highly reactive phenolic hydroxyl group, and optionally other components. And (b) a modified aliphatic polyamine compound and, if necessary, other pigments and additives,
It is provided as a two-part coating of a curing agent comprising a solvent.

(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.

In the present invention, various organic and inorganic coloring pigments such as titanium oxide and carbon black, and extenders 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 to impart structural viscosity to the paint, a powdered anti-sagging agent of hydrogenated castor oil type or organic amide type, or these powders are swollen with a solvent such as xylene in advance. An anti-sagging agent on the wax is used.

As additives other than the 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 glycol epoxy solvents, ketone solvents, and alcohol resins used in general epoxy resin paints 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.

[0024]

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 titanium oxide, talc, barium sulfate, and a sagging agent are added thereto, and the mixture is uniformly stirred and mixed with a dissolver to form a mill base. The particles were dispersed by a tabletop disperser so that the degree of dispersion was 30 μm or less by the 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, (b) "ADEKA HARDNER EH-240" (manufactured by Asahi Denka Kogyo KK, solid content: 100%, active hydrogen equivalent: about 76) as a modified aliphatic polyamine compound was used 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. The results are shown in Tables 1 and 2.

[0026]

[Table 1]

[0027]

[Table 2]

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.

* 1 Epicoat # 1001: Bisphenol A type solid epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd., epoxy equivalent: about 490 * 2 Epicoat # 828: Yuka Shell Epoxy Co., Ltd.
Bisphenol A type liquid epoxy resin, epoxy equivalent: about 190 * 3 Epicoat # 834: Yuka Shell Epoxy Co., Ltd.
Bisphenol A type semi-solid epoxy resin, epoxy equivalent: about 240 * 4 Epicoat # 1004: Yuka Shell Epoxy Co., Ltd., bisphenol A type solid epoxy resin, epoxy equivalent: about 980 * 5 Necires EPX-L: NEVCIN Phenol-modified hydrocarbon resin, hydroxyl value: 63 mgKOH / g * 6 Crown Talc C: Matsumura Sangyo Co., Ltd. * 7 Precipitable barium sulfate # 100: Sakai Chemical Industry Co., Ltd.
* 8 γ-glycidoxypropyltrimethoxysilane * 9 Disparone 6900-20X: Kusumoto Kasei Co., Ltd.
* 10 Dispalon OX-77: manufactured by Kusumoto Kasei Co., Ltd. * 11 A mixture of xylene / methyl isobutyl ketone / propylene glycol monomethyl ether = 1/1/1 (weight ratio))

* 12 The surface having a metallic luster within one week after plating is degreased with a thinner for epoxy paint. * 13 White rust generated on the plated surface after 6 months of outdoor exposure is completely removed with a # 280 sandpaper and polished until a metallic luster appears. * 14 White rust that has been removed from the plated surface after 6 months of outdoor exposure by using a # 280 sandpaper. * 15 Plated surface after 6 months of outdoor exposure, degreased with thinner for epoxy paint while leaving white rust.

As a result, Example (1) and Comparative Example (1)
In comparison with (2), it was confirmed that when the equivalent weight of the epoxy resin (a) was smaller than 350, the adhesion to the galvanized surface after aging decreased. Comparison between Example (1) and Comparative Example (3) shows that (a) the equivalent of epoxy resin is 6
If it is greater than 50, the solid content of the paint will decrease,
It has been confirmed that it becomes difficult to apply a thick film, or that the amount of solvent in the coating increases, which does not meet the demands of the low VOC era in recent years.

[Example (2) and Comparative Example (4),
(5), (6)] In the same manner as in Example (1), Example (2) and Comparative Examples (5), (6)
The paint of (7) was prepared, and the adhesion to the galvanized surface was tested based on the difference between the old and new surface treatments. The mixing ratio of (a) the epoxy resin and (c) the modified hydrocarbon resin was 66.7 in each of Example (2) and Comparative Examples (5), (6) and (7).
%. The base material of the paint was adjusted in the same manner as in Example (1).

As the curing agent, "ADEKA HARDNER EH-220" (manufactured by Asahi Denka Kogyo Sangyo Co., Ltd.) as a modified aliphatic polyamine compound in Example (2) and Comparative Examples (4) and (5) was used. Solid content: 100%, active hydrogen equivalent: about 7
6) was used as it was. In Comparative Example (7), the modified polyamidoamine “Sunmide X-2700” (manufactured by Sanwa Chemical Industry Co., Ltd., solid content: 70%, active hydrogen equivalent (s
oid): 168).

The mixing ratio to the epoxy resin was 0.6 equivalent in Example (2) and Comparative Example (7). In Comparative Example (5), 0.3 equivalent was used, and in Comparative Example (6), 0.8 equivalent was used. The volume ratio of the pigment to the solid content of the mixed paint is 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 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. Table 3 shows the results.
It is shown in Table 4.

[0035]

[Table 3]

[0036]

[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.

As a result, Example (2) and Comparative Example (4)
If the mixing ratio of (a) the epoxy resin and (b) the modified aliphatic polyamine compound is smaller or larger than the range of 0.5 to 0.7 equivalent in comparison with (5), the aging after coating is longer. It was confirmed that the adhesion to the galvanized surface was reduced. In addition, by comparing Example (2) and Comparative Example (6), it was confirmed that even when the modified polyamidoamine was used as the curing agent, the adhesion to the galvanized surface similarly decreased over time. .

[0039]

According to the present invention, it is possible to obtain a modified epoxy resin paint having a stable adhesive property without being affected by the new or old galvanized surface and the degree of surface treatment, to protect the galvanized coating and to protect the steel structure. Can be protected for a long time.

Claims (1)

[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;
A phenol-modified hydrocarbon resin in the range of 100 to 100 mgKOH / g as a main component, and a mixing ratio of (a) the epoxy resin and (b) the modified aliphatic polyamine compound is 0.5 to 0.7 equivalent. A modified epoxy resin coating composition comprising: