JP2002038082A - Paint composition and painted metal plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition and a coated metal plate having equivalent rust resistance and moisture resistance without using a chromate-based rust-preventive pigment which is not preferable on environmental issues. SOLUTION: A first constitution is (A) a film-forming resin composition containing a hydroxyl group-containing polyester and / or epoxy resin, (B) an amino resin and / or a blocked polyisocyanate compound, and (C1) calcium ion exchangeability. And (C2) at least one selected from the group consisting of (C2) a rust preventive pigment containing a phosphate, a rust preventive pigment containing a phosphite, and a rust preventive pigment containing a molybdate salt. A coating composition comprising at least one kind of rust-preventive pigment, wherein the second composition is a coating metal sheet obtained by applying the coating composition as a primer to the surface of a metal sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition having excellent corrosion resistance and moisture resistance, and a coated metal sheet provided with the coating composition as a primer.

[0002]

2. Description of the Related Art A coated metal sheet (pre-coated metal sheet) is formed by coating a metal sheet which has been subjected to a chemical conversion treatment such as a phosphate treatment or a chromate treatment onto a base coat or a top coat which is a resin composition for a thermosetting film. It is used as a structural material for home appliances, office equipment, building materials, furniture, etc. by performing molding such as pressing without requiring a painting process on the demand side. Since corrosion progresses from scratches on the processed part and scratches on the coating film surface, chromate-based rust-preventive pigments are used for the undercoat paint on the pre-coated metal plate. However, hexavalent chromium is generated from the chromate-based rust-preventive pigment, which is not preferable in terms of environmental problems.

As a composition using a pigment containing no hexavalent chromium, for example, JP-A-11-222575 discloses a coating composition having calcium ion-exchanged amorphous silica. In addition, when used as a primer, the moisture resistance was insufficient. In addition, JP
JP-149278A proposes a rust-preventive pigment composition comprising a combination of aluminum dihydrogen tripolyphosphate and a zinc compound, the particle surfaces of which are coated with a metal compound, but the corrosion protection is still insufficient. Satisfactory performance has not always been obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a coating composition and a coated metal sheet which are excellent in rust resistance and moisture resistance without using a chromate-based rust-preventive pigment as described above.

[0005]

Means for Solving the Problems A first constitution of the present invention for solving the above-mentioned problems comprises (A) a hydroxyl group-containing polyester and / or epoxy resin, (B) an amino resin and / or a blocked polyisocyanate compound. A film-forming resin composition containing (C1) calcium ion-exchangeable amorphous silica, and (C2) a rust-preventive pigment containing phosphate,
A paint composition comprising at least one rust-preventive pigment selected from the group consisting of a phosphite-containing rust-preventive pigment and molybdate-containing rust-preventive pigment.

[0006] In a first aspect of the present invention, the phosphate, phosphite and molybdate are at least one selected from the group consisting of zinc, calcium, magnesium and aluminum. A coating composition comprising the above metal phosphates, phosphites and molybdates. Further, the ratio of (C1) :( C2) is 5:
95 to 30:70.

A second constitution of the present invention is that (A) a film-forming resin composition containing a hydroxyl group-containing polyester and / or epoxy resin, (B) an amino resin and / or a blocked polyisocyanate compound, and (C1) calcium At least one selected from the group consisting of ion-exchangeable amorphous silica, and (C2) a rust-preventive pigment containing phosphate, a rust-preventive pigment containing phosphite, and a rust-preventive pigment containing molybdate acid. A coating composition containing one or more rust-preventive pigments,
Chemically treated galvanized steel sheet, zinc aluminum alloy plated steel sheet, aluminum plated steel sheet, stainless steel sheet,
This is a coated metal plate characterized by being applied as a primer on the surface of a metal plate such as an aluminum plate.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The coating composition of the present invention comprises (A) a hydroxyl group-containing resin, (B) a curing agent, (C1) a calcium ion-exchangeable amorphous silica, and (C2) a phosphate. The main component is at least one rust-preventive pigment selected from the group consisting of rust-preventive pigments containing phosphites, rust-preventive pigments containing phosphites, and rust-preventive pigments containing molybdate.

(A) The hydroxyl group-containing resin is selected from a polyester resin and an epoxy resin. Polyester resin
A hydroxyl group-containing polyester having a number average molecular weight of preferably from 2,000 to 25,000, more preferably from 3,000 to 20,000. The epoxy resin has a number average molecular weight of 20
00 to 25000, more preferably 3000
It is a hydroxyl group-containing epoxy resin having a molecular weight of up to 20,000.

The polyester resin can be obtained from a polyhydric alcohol and a polybasic acid by a known esterification method. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, hydrogenated bisphenol, and EO and PO addition of bisphenol A. Product, glycerin, trimethylolethane, trimethylolpropane,
Pentaerythritol and the like. Polybasic acids include phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, azelaic acid, sebacic acid, maleic anhydride, fumaric acid, trimellitic anhydride, and pyromellitic anhydride. And the like. If necessary, a monobasic acid such as benzoic acid or p-tert-butylbenzoic acid can be used in combination.

Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and novolak type epoxy resin.

(B) The curing agent is an amino resin and / or a block isocyanate compound. Examples of the amino resin include, but are not particularly limited to, a melamine resin, a benzoguanamine resin, and a urea resin. Of the above amino resins, melamine resins are preferred, and alkyl etherified melamine resins and mixed alkyl etherified melamine resins are more preferred. Examples of the alkyl etherified melamine resin include a methyl etherified resin etherified with methyl alcohol, n-butanol, a butyl etherified melamine resin etherified with iso-butanol, and a mixed etherified melamine resin of methyl ether and butyl ether. . Examples of the methyl etherified melamine resin include Cymel 300, 301, 303, 325, and 3
50 (all manufactured by Mitsui Cytec), Super Beckamine L-105-60 (manufactured by Dainippon Ink and Chemicals),
Sumimar M-100, M-55 (all manufactured by Sumitomo Chemical) and the like. As the butyl etherified melamine resin, Super Beckamine L110-60, L-
109-60, L-117-60, L-127-60
(All manufactured by Dainippon Ink and Chemicals), Uban 20S
B, 20SE60 (manufactured by Mitsui Chemicals, Inc.) and the like. Cymel 235 as the mixed etherified melamine resin,
231, 236, 266, 267 (all are Mitsui Cytec), Nikarac MX500 (manufactured by Sanwa Chemical), Sumimar M-66B (manufactured by Sumitomo Chemical) and the like.

These melamine resins can be used alone or as a mixture of two or more. When a melamine resin is used as a curing agent, usually, a hydroxyl group-containing resin 100
The melamine resin is preferably 10 to 50 parts by weight (solid content) with respect to the weight part (solid content). More preferably 15 to 3
5 parts by weight (solid content).

When the melamine resin is used as a curing agent, it is preferable to use a curing catalyst. As the catalyst, an acid catalyst is used, and aromatic sulfonic acids such as p-toluenesulfonic acid, dodecylbenzenesulfone, and dinonylnaphthalenedisulfonic acid, and amine salts thereof are preferably used. The amount of the catalyst used is 0.5 to 3 parts by weight based on 100 parts by weight of the total of the solid content of the hydroxyl group-containing resin and the melamine resin.

The above-mentioned blocked isocyanate compound is a compound obtained by blocking an isocyanate group of an isocyanate compound with a suitable blocking agent. Examples of the blocked isocyanate compound include aromatic polyisocyanates such as toluene diisocyanate, 4,4-diphenylmethane diisocyanate and xylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; hydrogenated xylene diisocyanate; Additives 4,4 diphenylmethane diisocyanate, isophorone diisocyanates, adducts with trimethylolpropane, etc., and polymers such as isocyanurates. Examples of the blocking agent include phenol-based blocking agents such as phenol and cresol, oxime-based blocking agents such as methyl ethyl ketoxime, acetoxime and benzophenone oxime, lactam-based blocking agents such as ε-caprolactam and γ-butyrolactam, methanol, ethanol,
Examples include alcohol-based blocking agents such as butanol and cyclohexanol, active methylene compound-based blocking agents such as diethyl malonate and ethyl acetoacetate, and urea-based blocking agents such as thiourea. Particularly, oxime-based blocking agents, lactam-based blocking agents, and active methylene compound-based blocking agents are preferred. Commercially available blocked isocyanate compounds include Desmodur BL3370, BL4265, B
L3175, BL3272, Sumidur BL3175
(Manufactured by Sumitomo Bayer Urethane), Takenate B-830,
B-820NSU, B-842N, B-846N (manufactured by Takeda Pharmaceutical) Burnock D-500, D-550, DB-9
80K, B3-867 (manufactured by Dainippon Ink and Chemicals), and the like. When a blocked isocyanate compound is used as a curing agent, usually, 10 to 50 parts by weight (solid content) of a melamine resin is preferred, more preferably 15 to 35 parts by weight (based on 100 parts by weight (solid content) of a hydroxyl group-containing resin). Solids).

When the above-mentioned blocked isocyanate compound is used as a curing agent, it is preferable to use a curing catalyst.
As the curing catalyst, organotin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dioctyltin diacetate, and dibutyltin oxide are suitable. The amount of the catalyst used is preferably 0.05 to 0.5 part by weight based on 100 parts by weight of the total of the solid content of the hydroxyl group-containing resin and the blocked isocyanate compound.

As the rust preventive pigment, (C1) calcium ion exchangeable amorphous silica and (C2) a rust preventive pigment containing a phosphate, a rust preventive pigment containing a phosphite, and molybdic acid are contained. And at least one rust-preventive pigment selected from the group consisting of rust-preventive pigments. When these pigments are used alone, performance that cannot be achieved is obtained.

Calcium ion exchangeable amorphous silica is a non-toxic rust preventive pigment obtained by ion exchange of calcium ions into porous silica gel powder. H that has passed through the coating
+ Ion-exchanges with Ca + in the coating film, and released Ca +
Is believed to protect the metal surface and exhibit a rust-preventive action. As calcium ion exchangeable amorphous silica,
Shielddex 303, AC-3, AC-5 (WR
Grace & Co), Shielddex (Fuji Silysia) and the like.

The phosphate is a non-toxic rust-preventive pigment, and the phosphate is preferably a phosphate of one or more metals selected from the group consisting of zinc, calcium, magnesium and aluminum. It is thought that the phosphate ions that gradually elute and the metal ions on the metal surface react with the moisture that enters from the outside, forming a passive film with good adhesion, protecting the metal surface and exhibiting rust prevention. ing.

As the rust preventive pigment mainly composed of phosphate,
Zinc phosphate-based LF dyes D-1, ZP-50S
(Manufactured by Kikuchi Color Co., Ltd.), calcium phosphate-based LF brush CP-Z (manufactured by Kikuchi Color), magnesium phosphate-based LF brush MZP-500 (manufactured by Kikuchi Color), aluminum phosphate-based LF brush CRFC
-1 (made by Kikuchi Color) and the like.

Phosphite is a non-toxic rust-preventive pigment. As the phosphite, phosphite of one or more metals selected from the group consisting of zinc, calcium, magnesium and aluminum is used. preferable. The eluted phosphite ions capture the oxygen that penetrates into the coating film, and the phosphorous acid is oxidized to phosphoric acid, which reacts with the metal ions on the metal surface to form a complex compound. To protect the metal surface,
It is believed to have a rust-preventing effect.

As the rust preventive pigment mainly composed of phosphite,
Zinc phosphite-based EXPERT NP-1500, NP
-1600 (manufactured by Toho Pigment), calcium phosphite-based E
XPERT NP-1000, NP-1020C (manufactured by Toho Pigment Co., Ltd.)
TNP-1100, NP-1102 (manufactured by Toho Pigment Co., Ltd.) and the like.

Molybdate is a non-toxic pigment, and the molybdate is preferably a molybdate of one or more metals selected from the group consisting of zinc, calcium, magnesium and aluminum. It is thought that molybdate ions, which gradually elute, and metal ions on the metal surface react with the moisture that enters from the outside to form a passive film with good adhesion, protecting the metal surface and exhibiting rust prevention. I have.

As a rust preventive pigment mainly composed of molybdate, zinc molybdate-based LF-Boss M-PSN
(Made by Kikuchi Color), calcium molybdate-based LF
Bosei MC-400WR (Kikuchi Color), aluminum molybdate-based LF Bosei PM-30
0, PM-308 (made by Kikuchi Color) and the like.

(C1) A calcium ion-exchange amorphous silica, and (C2) a rust-preventive pigment containing a phosphate, a rust-preventive pigment containing a phosphite, and a rust-preventive pigment containing molybdic acid. By using at least one or more kinds of rust-preventive pigments selected from the following group, both rust-preventive properties and moisture resistance can be achieved. The ratio (weight ratio) of (C1) and (C2), that is, (C1) :( C2) is 5:95 to 30: 7.
0 is preferable, and 10: 90-2 is more preferable.
5:75. The total of the above (C1) and (C2) is 15 to 100 with respect to 100 parts (solid content) of the hydroxyl group-containing resin.
Preferably, the amount is from 25 to 75 parts by weight.

(D) As other additives, the composition of the present invention may contain, if necessary, a coloring agent such as an organic solvent, a dye, an organic pigment, an inorganic pigment, or a metal pigment, a dispersant, an anti-settling agent, and a leveling agent. , Etc. can be added.

The coating composition of the present invention is used as a primer on a surface of a metal plate such as a galvanized steel plate, a zinc-aluminum alloy-plated steel plate, an aluminum-plated steel plate, a stainless steel plate, or an aluminum plate which has been subjected to a chemical conversion treatment. Applied. As a coating method, coating can be performed by a known method such as roll coater coating, spray coating, or brush coating. The thickness of the dried coating film is not particularly limited, but is preferably 1 to 10 μm. The coated metal plate is heated to an ultimate plate temperature of 180 to 23.
Bake to 0 ° C. After applying the primer coating in this manner, a top coat is applied. As the top coating, known coatings such as polyester resin, silicone-modified polyester resin, silicon-modified acrylic resin, and fluororesin can be used. As the painting method,
Coating can be performed by a known method such as roll coater coating, spray coating, or brush coating. The thickness of the dried coating film is not particularly limited, but is preferably 10 to 20 μm. The coated metal plate is baked so that the reached plate temperature becomes 180 to 250 ° C.

[0028]

The present invention will be described below in detail with reference to examples. All parts and percentages in the examples are on a weight basis.

(Example 1) Super Beckolite M68
267 parts (solid content: 80 parts) of 01-30 (a polyester resin solution having a solid content of 30%, manufactured by Dainippon Ink and Chemicals, number average molecular weight is about 15,000), Shielddex C-30
3 (manufactured by WR Grace & Co., calcium ion-exchangeable amorphous silica), 4 parts, LF Dose D-
1 (Taica, zinc phosphate based rust preventive pigment) 36 parts, titanium white 20 parts and appropriate amount of 1/1 (weight ratio) mixed solvent of Solvesso 100 (Esso Petroleum, aromatic mixed solvent) and cyclohexanone And mix with a glass bead mill.
Time dispersed. It was confirmed by a particle gauge that the particle size was 10 μm or less. Then Super Beckamine L10
53.3 (manufactured by Dainippon Ink and Chemicals, methylated melamine resin having a solid content of 60%) 33.3 parts (solid content: 20 parts) and Nailure 5225 (manufactured by King Industries, amine salt of dodecylbenzenesulfonic acid, effective Ingredient 25
%), Add 1 part and mix uniformly.
The viscosity was adjusted to about 100 seconds (Ford cup # 4/25 ° C.) to obtain a coating composition. The obtained paint was applied to a chromate-treated hot-dip galvanized steel sheet (zinc adhesion amount: 45 g / m2) having a thickness of 0.5 mm using a bar coater to obtain a dry film thickness of 5 μm.
m, and baked at a reached plate temperature of 200 ° C. Next, a polyester-based overcoat (“SRF05” manufactured by Dainippon Ink and Chemicals, Inc.) was applied using a bar coater to a dry film thickness of 15 μm.
Baking was done.

(Examples 2 to 27, Comparative Examples 1 to 4)
Except for the paint compounding ratio shown in 4, the same as in Example 1
A coating composition was obtained. The compounding amounts shown in Tables 1 to 4 are indicated by the amount of solid content or the amount of active ingredient (parts by weight).

Next, a coated steel sheet was prepared in the same manner as in Example 1. Hereinafter, the components used in Tables 1 to 4 will be described. -Epicron 9055-40AX: manufactured by Dainippon Ink and Chemicals, bisphenol A type epoxy resin solution, solid content 40
%, Number average molecular weight of the resin is about 5,200. Death module BL4265: manufactured by Sumitomo Bayer Urethane, oxime block of isocyanurate of isophorone diisocyanate, solid content 65%. Formate TK-1: an organic tin-based dissociation catalyst manufactured by Takeda Pharmaceutical, solid content 10%. * EXPERT NP-1500: a zinc phosphite-based rust preventive pigment manufactured by Toho Pigment. -LF-Bosei M-PSN: manufactured by Kikuchi Color, a zinc molybdate-based rust preventive pigment.

With respect to the coated plate obtained as described above,
The corrosion resistance and moisture resistance were evaluated according to the following evaluation criteria.

(Corrosion Resistance) A coated plate is cut into a size of 50 × 150 mm, and a cross cut reaching a base is provided at substantially the center. This test plate was subjected to a salt spray test for 750 hours in accordance with JIS Z2371. The maximum swollen width of the cross cut portion was measured. Evaluation was made according to the following criteria. ：: No swelling was observed in the cross cut portion. ：: The maximum swollen width on one side of the cut portion is less than 1 mm. Δ: The maximum swollen width on one side of the cut portion is 1 mm or more and less than 5 mm. X: The maximum swollen width on one side of the cut portion is 5 mm or more.

(Moisture resistance) A coated plate is cut into a size of 50 × 150 mm and used as a test piece. JIS K540
A moisture resistance test was performed according to the rotary method of the humidity resistance test of No. 0. The swelling of the flat part of the test piece was evaluated according to the evaluation criteria of ASTM D714. ◎: No blistering ○: 8F △: 8M, 6F ×: 8MD or more, 6M or more

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

EFFECT OF THE INVENTION The coating composition of the present invention is useful as a primer coating because it has excellent corrosion resistance and moisture resistance. Further, since it does not contain hexavalent chromium, there is no environmental problem. Since the metal plate of the present invention has the above characteristics,
It can be usefully used as a pre-coated metal.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C09D 5/08 C09D 5/08 161/20 161/20 163/00 163/00 175/04 175/04 175 / 06 175/06 (72) Inventor Atsushi Miyagaki 1-4-1-220 Shozuzawa, Itabashi-ku, Tokyo F-term (reference) 4D075 AE03 CA33 CA38 DA06 DB02 EA02 EA05 EB33 EB35 EB38 EB45 EB56 EC03 EC15 4J038 DA142 DA162 DA172 DB061 DB071 DD041 DD121 DD191 DG111 DG161 DG221 DG301 HA246 HA416 HA446 KA05 KA08 MA14 NA03 NA04 NA27 PC02

Claims (4)

[Claims] 1. A film-forming resin composition containing (A) a hydroxyl group-containing polyester and / or epoxy resin, (B) an amino resin and / or a blocked polyisocyanate compound, and (C1) a calcium ion-exchangeable amorphous silica. ,
And (C2) at least one or more rust-preventive pigments selected from the group consisting of phosphate-containing rust-preventive pigments, phosphite-containing rust-preventive pigments, and molybdate-containing rust-preventive pigments A coating composition comprising: 2. The coating composition according to claim 1, wherein the salt is at least one metal salt selected from the group consisting of zinc, calcium, magnesium and aluminum. 3. The ratio of (C1) :( C2) is 5:95.
The coating composition according to claim 1 or 2, wherein the ratio is up to 30:70. 4. A film-forming resin composition containing (A) a hydroxyl group-containing polyester and / or epoxy resin, (B) an amino resin and / or a blocked polyisocyanate compound, and (C1) calcium ion-exchangeable amorphous silica. ,
And (C2) at least one rust-preventive pigment selected from the group consisting of a rust-preventive pigment containing a phosphate, a rust-preventive pigment containing a phosphite, and a rust-preventive pigment containing molybdate acid. A coated metal plate, wherein the coating composition contained is applied as a primer to the surface of the metal plate.