PAINT COMPOSITION, COATED ARTICLE, AND METHOD FOR FORMING CURED FILM

Abstract

Provided is a paint composition that can be easily manufactured and provides a cured film having excellent hardness, chemical resistance, antifouling properties, and weather resistance, the paint composition comprising: 100 parts by mass of (A) one or more polyols selected from acrylic polyols, polyester polyols, and polyether polyols; 0.5 to 20 parts by mass of (B) a silane coupling agent having an isocyanurate skeleton; and 5 to 100 parts by mass of (C) an organopolysiloxane represented by formula (I)

(SiO.sub.4/2).sub.a(R.sup.1SiO.sub.3/2).sub.b(R.sup.1.sub.2SiO.sub.2/2).sub.c(R.sup.1.sub.3SiO.sub.1/2).sub.d(R.sup.2O.sub.1/2).sub.e(I)

(wherein, each R.sup.1 independently denotes a substituted or unsubstituted C1-12 monovalent hydrocarbon group, R.sup.2 denotes a hydrogen atom or a C1-6 alkyl group, a, b, c, and d are numbers satisfying 0a1, 0b1, 0c0.5, 0d1, a+b+c+d=1, and 0.5<(a+b)1, and e is a number satisfying 0<e4).

Claims

1. A coating composition comprising (A) 100 parts by weight of one or two or more polyols selected from the group consisting of an acrylic polyol, a polyester polyol, and a polyether polyol, (B) 0.5 to 20 parts by weight of a silane coupling agent having an isocyanurate skeleton, and (C) 5 to 100 parts by weight of an organopolysiloxane represented by the following formula (I):
[Chem. 1]
(SiO.sub.4/2).sub.a(R.sup.1SiO.sub.3/2).sub.b(R.sup.1.sub.2SiO.sub.2/2).sub.c(R.sup.1.sub.3SiO.sub.1/2).sub.d(R.sup.2O.sub.1/2).sub.e(I) wherein R.sup.1 is each independently a C.sub.1-C.sub.12 substituted or unsubstituted monovalent hydrocarbon group, R.sup.2 is a hydrogen atom or a C.sub.1-C.sub.6 alkyl group, a, b, c, and d are numbers satisfying 0a1, 0b1, 0c0.5, 0d<1, a+b+c+d=1, and 0.5<(a+b)1, and e is a number satisfying 0<e4.

2. The coating composition of claim 1 wherein the component (A) is an acrylic polyol, a polyester polyol, or both of them.

3. The coating composition of claim 1 wherein the component (B) is a compound represented by the following formula (II): ##STR00003## wherein R.sup.3 is each independently a C.sub.1-C.sub.20 alkylene group, R.sup.4 is each independently a C.sub.1-C.sub.12 substituted or unsubstituted monovalent hydrocarbon group, each R.sup.5 is a hydrogen atom or a C.sub.1-C.sub.8 alkyl group, and f is each independently 0, 1, or 2.

4. The coating composition of claim 1 wherein in formula (I), R.sup.1 is each independently a C.sub.1-C.sub.8 alkyl group, a C.sub.2-C.sub.8 alkenyl group, a C.sub.6-C.sub.10 aryl group, or a C.sub.7-C.sub.10 aralkyl group.

5. The coating composition of claim 4 wherein in formula (I), R.sup.1 is each independently a methyl group, an ethyl group, or a phenyl group.

6. The coating composition of claim 1 wherein in formula (I), the C.sub.1-C.sub.6 alkyl group accounts for at least 80% of the total number of R.sup.2.

7. The coating composition of claim 1 wherein in formula (I), a is 0<a1.

8. The coating composition of any ono of claim 1 wherein in formula (I), d is 0.

9. The coating composition of claim 1 wherein the component (C) has a kinematic viscosity of 1 to 200 mm.sup.2/s at 25 C.

10. The coating composition of claim 1 further comprising (D) a curing catalyst.

11. A method for preparing the coating composition of claim 1, the method comprising mixing the components (A) to (C) at 10 C. to 40 C.

12. A cured coating formed from the coating composition of claim 1.

13. A coated article comprising a substrate and the cured coating of claim 12 formed on at least one surface of the substrate directly or via at least one other layer.

14. A method for forming a cured coating on a substrate, comprising applying the coating composition of claim 1 to at least one surface of a substrate directly or via at least one other layer, and then curing the coating composition.

Description

EXAMPLES

[0148] Examples and Comparative Examples are given below for further illustrating the invention although the invention is not limited thereto. It is noted that the hydroxyl value is measured by a neutralization titration method in accordance with JIS K 0070:1992. The weight average molecular weight is measured by gel permeation chromatography (GPC, HLC-8220 manufactured by Tosoh Corp.) using tetrahydrofuran (THF) as developing solvent. The nonvolatile content is measured by a nonvolatile residue test method after drying by heating at 105 C. for 3 hours on an aluminum petri dish according to JIS K 5601-1-2:2008. The kinematic viscosity is measured at 25 C. with a Cannon-Fenske viscometer. The constitution ratio of siloxane units in component (C) is calculated from the measurement results of .sup.1H-NMR and .sup.29Si-NMR spectroscopy.

[1] Preparation of Coating Composition

Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-4

[0149] Coating compositions (i) to (xi) were prepared by mixing the following components at 25 C. in the compositional ratios (weight ratio) given in Table 1.

<Component (A)>

[0150] (A-1): Acrydic A-801P (acrylic polyol, nonvolatile content: 50% by weight, hydroxyl value: 50 mgKOH/g, manufactured by DIC Corporation) [0151] (A-2): Burnock D-220 (polyester polyol, nonvolatile content: 100% by weight, hydroxyl value: 147 mgKOH/g, manufactured by DIC Corporation)

<Component (B)>

[0152] (B): KBM-9659 (tris-(trimethoxylylpropyl) isocyanurate, manufactured by Shin-Etsu Chemical Co., Ltd.)

<Component (C)>

[0153] (C-1): An organopolysiloxane represented by formula (I) wherein a=0.8, b=0.2, c=0, d=0, e=0.26, R.sup.1=methyl or phenyl (the proportion of the number of phenyl groups in the total number of R.sup.1: 20%), and R.sup.2=methyl (nonvolatile content: 87% by weight, weight average molecular weight: 1,000, kinematic viscosity at 25 C.: 5 mm.sup.2/s, manufactured by Shin-Etsu Chemical Co., Ltd.) [0154] (C-2): An organopolysiloxane represented by formula (I) wherein a=0.1, b=0.6, c=0.3, d=0, e=0.24, R.sup.1=methyl or phenyl (proportion of the number of phenyl groups in the total number of R.sup.1: 30%), and R.sup.2=methyl (nonvolatile content: 96% by weight, weight average molecular weight: 1,800, kinematic viscosity at 25 C.: 100 mm.sup.2/s, manufactured by Shin-Etsu Chemical Co., Ltd.)

<Component (D)>

[0155] (D): Neostann U-830 (dioctyltin, manufactured by Nitto Kasei Co., Ltd.)

<Component (E)>

[0156] (E): Ethyl acetate/butyl acetate mixed solvent (weight ratio: 1:1)

TABLE-US-00001 TABLE 1 Composition Example Comparative Example (parts by weight) 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-1 1-2 1-3 1-4 Coating composition (i) (ii) (iii) (iv) (v) (vi) (vii) (viii) (ix) (x) (xi) (A-1) 200 200 200 200 200 200 200 200 200 200 (A-2) 100 (B) 5 20 0.5 5 0.5 5 5 0.1 0.5 50 10 (C-1) 50 100 20 100 10 50 50 5 50 150 (C-2) 50 (D) 0.2 0.2 0.1 0.2 0 0.2 0.2 0.2 0.2 0.2 0.2 (E) 10 10 5 10 20 10 10 10 10 10

[2] Preparation and Evaluation of Coated Article

Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-4

[0157] Each of the coating compositions (i) to (xi) of Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-4 was applied onto a metal substrate by flow coating so as to give a dry coating thickness of 30 m, and heated at 150 C. for 1 hour to form a coating.

[0158] The coated articles were evaluated for coating appearance, rubbing test, pencil hardness, antifouling test, and accelerated weather resistance, with the results shown in Table 2.

(1) Coating Appearance

[0159] On visual observation, a sample having a uniform coating surface and free of asperities due to agglomerates or cracks is rated acceptable (), and a sample having a non-uniform coating surface and blushing, asperities due to agglomerates, and/or cracks is rated unacceptable (x).

(2) Rubbing Test

[0160] Bemcot M-3II (area: 4 cm.sup.2, manufactured by Asahi Kasei Corporation) was immersed in acetone. The surface was rubbed back and forth 30 times under a load of 500 gf. After the rubbing test, the coating appearance was evaluated by visual observation. [0161] : No substantial changes are observed as compared with the coating appearance before the test. [0162] : Slight stripping and whitening were observed as compared with the coating appearance before the test. [0163] x: Significant stripping and whitening were observed as compared with the coating appearance before the test.

(3) Pencil Hardness

[0164] The pencil hardness was measured under a load of 750 g according to JIS K 5600-5-4. A hardness of F or higher was rated as acceptable.

(4) Antifouling Test

[0165] A line was drawn on a test surface with an oil-based permanent marker (organic solvent-type marker, trade name: McKee Extra Fine, manufactured by Zebra Co., Ltd.). After being left to stand for 3 hours, it was evaluated whether or not the line could be wiped off with Bemcot M-3II (area: 4 cm.sup.2, manufactured by Asahi Kasei Corporation) immersed in a mixed solvent of ethanol/toluene (weight ratio: 1/1). After completion of the test, the amount of ink remaining on the coating was visually observed and evaluated in three grades. [0166] : No substantial changes are observed as compared with the initial sample. [0167] : Ink remains slightly as compared with the initial sample. [0168] x: Ink remains significantly as compared with the initial sample.

(5) Accelerated Weather Resistance

[0169] In the accelerated weathering test, a super-accelerated weathering tester (Eye Super UV tester manufactured by Iwasaki Electric Co., Ltd.) was used. The test piece was a polyester-coated steel plate (0.8 mm70 mm60 mm). The test included 30 cycles with one cycle consisting of 3 hours of irradiation (UV intensity: 90 mW, black panel temperature: 63 C., 70% RH), 4 hours of darkening (black panel temperature: 63 C., 70% RH), and 3 hours of dewing (black panel temperature: 30 C., 90% RH) to a total of 10 hours. After the test, the coating was visually observed for swell, cracks, stripping, and gloss changes and evaluated in three grades. [0170] : No substantial changes are observed as compared with the initial sample. [0171] : Some gloss clouding is observed as compared with the initial sample. [0172] x: Substantial gloss clouding, cracks, and stripping are observed as compared with the initial sample.

TABLE-US-00002 TABLE 2 Example Comparative Example 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-1 2-2 2-3 2-4 Coating composition (i) (ii) (iii) (iv) (v) (vi) (vii) (viii) (ix) (x) (xi) Coating appearance X Rubbing test X Pencil hardness H F H 2H F H F H HB B 2H Antifouling test Accelerated X X weather resistance

[0173] As is evident from Table 2, the coatings obtained in Examples 2-1 to 2-7 were excellent in chemical resistance, hardness, antifouling properties, and weather resistance.

[0174] In contrast, the coating of Comparative Example 2-1 using the composition containing a short amount of component (B) was insufficient in chemical resistance, antifouling properties, and weather resistance. The coating of Comparative Example 2-3 using the composition containing an excess of component (B) was inferior in hardness.

[0175] The coating of Comparative Example 2-2 using the composition containing a short amount of component (C) was insufficient in chemical resistance, hardness, antifouling property, and weather resistance. The coating of Comparative Example 2-4 using the composition containing an excess of component (C) had an uneven coating surface and was inferior in chemical resistance and weather resistance.