# US 10,870,765 B2 · Aqueous coating composition and method for forming a coating film

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- Number: US 10,870,765 B2
- Document ID: US10870765B2
- Status: Granted
- Kind: B2
- Application number: 16/066,113
- Filed: 2016-12-27
- Published: 2020-09-10
- Granted: 2020-12-22
- Earliest claimed: 2015-12-28
- Assignees: Nippon Paint Automotive Coatings Co., Ltd.
- Applicants: Nippon Paint Automotive Coatings Co., Ltd.
- Inventors: Miho Nishioka; Makoto Shimizu
- Web page: https://patentgrep.com/patent/US10870765B2

## CPC

- C09D 5/02: Emulsion paints {including aerosols}
- B05D 7/14: to metal, e.g. car bodies (involving a chemical reaction between the metal and the coating C23)
- B05D 7/542: {the two layers being cured or baked together}
- C08G 18/80: Masked polyisocyanates
- C08K 5/29: Compounds containing {one or more} carbon-to-nitrogen double bonds
- C09D 7/63: organic
- C09D 7/65: macromolecular (C09D7/41-C09D7/48 take precedence)
- C09D 133/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof
- C09D 133/08: Homopolymers or copolymers of acrylic acid esters
- C09D 133/14: of esters containing halogen, nitrogen, sulfur or oxygen atoms in addition to the carboxy oxygen
- C09D 167/02: Polyesters derived from dicarboxylic acids and dihydroxy compounds (C09D167/06 takes precedence)
- C09D 175/04: Polyurethanes
- B05D 3/102: {Pretreatment of metallic substrates (C23C takes precedence)}
- B05D 7/532: {the two layers being cured or baked together, i.e. wet on wet}
- B05D 2202/10: based on Fe
- B05D 2203/00: Other substrates
- B05D 2401/20: Aqueous dispersion or solution
- B05D 2502/005: modified
- B05D 2503/00: Polyurethanes
- B05D 2505/50: Polyimides
- C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)
- B05D: PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL (conveying articles or workpieces through baths of liquid B65G, e.g. B65G49/02)
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)

## Abstract

The objective of the present invention is to provide an aqueous coating composition which has excellent curability at low temperatures. The present invention provides an aqueous coating composition which contains an aqueous resin having a hydroxyl group and a carboxyl group (A), a water-dispersible blocked polyisocyanate compound (B), a hydrophilicized carbodiimide compound (C), and an aqueous polyurethane resin (D), wherein the aqueous resin having a hydroxyl group and a carboxyl group (A) has a hydroxyl value of 80 to 200 mgKOH/g and an acid value of 10 to 40 mgKOH/g in terms of resin solid content, the aqueous polyurethane resin (D) has a glass transition point (Tg) of −50° C. or less, and a cured film of the aqueous polyurethane resin (D) has an elongation at break of 400% or more at −20° C.

## Claims

### Claim 1

An aqueous coating composition comprising:
an aqueous resin having a hydroxyl group and a carboxyl group (A),
a water-dispersible blocked polyisocyanate compound (B),
a hydrophilicized carbodiimide compound (C), and
an aqueous polyurethane resin (D),
wherein
the aqueous resin having a hydroxyl group and a carboxyl group (A) has a hydroxyl value of 80 to 200 mgKOH/g and an acid value of 10 to 40 mgKOH/g in terms of resin solid content,
the hydrophilicized carbodiimide compound (C) is a compound represented by formula (I), (II), or (III) below,
the aqueous polyurethane resin (D) has a glass transition point (Tg) of −50° C. or less, and
a cured film of the aqueous polyurethane resin (D) has an elongation at break of 400% or more at −20° C.,
wherein X is a bifunctional organic group having at least one carbodiimide group, Y is each same or different structure resulting from elimination of a hydroxyl group from a polyalkylene glycol monoalkyl ether, and Z is a structure resulting from elimination of a hydroxyl group from a bifunctional polyol having a number-average molecular weight of 200 to 5,000,
wherein each X is a bifunctional organic group having at least one carbodiimide group, Y is each same or different structure resulting from elimination of a hydroxyl group from a polyalkylene glycol monoalkyl ether, R0 is hydrogen, a methyl group or an ethyl group, each R1 is an alkylene group having 4 or less carbon atoms, n is 0 or 1, and each m is a number from 0 to 60,
wherein X is a bifunctional organic group having at least one carbodiimide group, and Y is each same or different structure resulting from elimination of a hydroxyl group from a polyalkylene glycol monoalkyl ether.

### Claim 2 (depends on 1)

The aqueous coating composition according to claim 1, wherein a content of the hydrophilicized carbodiimide compound (C) is 1 to 8% by mass in terms of a resin solid content of the aqueous coating composition.

### Claim 3 (depends on 1)

The aqueous coating composition according to claim 1, wherein the aqueous resin (A) comprises an acrylic emulsion having a number-average molecular weight of 10,000 to 80,000.

### Claim 4 (depends on 1)

The aqueous coating composition according to claim 1, wherein the hydrophilicized carbodiimide compound (C) represented by the formula (III) above is a compound below,
wherein X is a bifunctional organic group having at least one carbodiimide group, and Y is each same or different structure selected from (i) and (ii) below:
(i) a structure resulting from elimination of a hydroxyl group from a polyethylene glycol monoalkyl ether in which an alkyl group having 1 to 3 carbon atoms is ether-linked to an end of a polyethylene oxide unit having a repeat number of 6 to 20,
(ii) a structure resulting from elimination of a hydroxyl group from a polypropylene glycol monoalkyl ether in which an alkyl group having 1 to 8 carbon atoms is ether-linked to an end of a polypropylene oxide unit having a repeat number of 4 to 60.

### Claim 5 (depends on 4)

The aqueous coating composition according to claim 4, wherein in the hydrophilicized carbodiimide compound (C) represented by the formula (III) above,
one Y is the (i) and another Y is the (ii), and
a ratio of the structure (i) to the structure (ii) is within a range of (i):(ii)=1:0.7 to 1:8.

### Claim 6 (depends on 1)

The aqueous coating composition according to claim 1, wherein a content of the aqueous polyurethane resin (D) is 15% by mass or more in terms of the resin solid content of the aqueous coating composition.

### Claim 7 (depends on 1)

The aqueous coating composition according to claim 1, wherein a content of the aqueous polyurethane resin (D) is 30% by mass or more and 40% by mass or less in terms of the resin solid content of the aqueous coating composition.

### Claim 8 (depends on 1)

The aqueous coating composition according to claim 1, wherein a content of the aqueous polyurethane resin (D) is 15% by mass or more and less than 30% by mass in terms of the resin solid content of the aqueous coating composition.

### Claim 9 (depends on 1)

The aqueous coating composition according to claim 1, wherein
a content of the water-dispersible blocked polyisocyanate compound (B) is 10 to 25% by mass in terms of the resin solid content of the aqueous coating composition, and
a content of the hydrophilicized carbodiimide compound (C) is 1.5 to 7% by mass in terms of the resin solid content of the aqueous coating composition.

### Claim 10 (depends on 1)

The aqueous coating composition according to claim 1, wherein a mass ratio of the content of the water-dispersible blocked polyisocyanate compound (B) to the content of the hydrophilicized carbodiimide compound (C) in terms of the resin solid content of the aqueous coating composition is (B):(C)=25:1 to 1.25:1.

### Claim 11 (depends on 1)

A method for forming a coating film in use of an aqueous coating composition, wherein the method comprises:
a coating step of applying the aqueous coating composition according to claim 1 to an object to be coated to form a coating film, and
a curing step of curing the resulting coating film at 70 to 100° C.

### Claim 12 (depends on 11)

The method for forming a coating film according to claim 11, wherein
the coating step comprises:
a first coating step of applying the aqueous coating composition, wherein a content of the aqueous polyurethane resin (D) is 30% by mass or more and 40% by mass or less in terms of the resin solid content of the aqueous coating composition, onto an object to be coated to form a first coating film, and
a second application step of applying the aqueous coating composition, wherein a content of the aqueous polyurethane resin (D) is 15% by mass or more and less than 30% by mass in terms of the resin solid content of the aqueous coating composition, onto the first coating film to form a second coating film.

### Claim 13 (depends on 11)

The method for forming a coating film according to claim 11, wherein the object to be coated includes a steel plate part and a resin part.