# US 11,111,394 B2 · Primer coating composition and method for forming coating film

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- Number: US 11,111,394 B2
- Document ID: US11111394B2
- Status: Granted
- Kind: B2
- Application number: 16/072,934
- Filed: 2017-01-26
- Published: 2019-01-31
- Granted: 2021-09-07
- Earliest claimed: 2016-01-27
- Assignees: Nippon Paint Automotive Coatings Co., Ltd.
- Applicants: Nippon Paint Automotive Coatings Co., Ltd.
- Inventors: Hiromi Fujimoto
- Web page: https://patentgrep.com/patent/US11111394B2

## CPC

- C09D 5/002: {Priming paints (C09D5/08 takes precedence)}
- B05D 7/14: to metal, e.g. car bodies (involving a chemical reaction between the metal and the coating C23)
- B05D 7/24: for applying particular liquids or other fluent materials
- C08F 8/20: Halogenation
- C08F 255/02: on to polymers of olefins having two or three carbon atoms
- C08G 18/797: {containing carbodiimide and/or uretone-imine groups}
- C09D 123/00: Coating compositions based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Coating compositions based on derivatives of such polymers
- C09D 123/26: modified by chemical after-treatment
- C09D 151/06: grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond
- C09D 163/00: Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
- C09D 175/04: Polyurethanes
- 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)
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS

## Abstract

The present invention relates to a primer coating composition including an aqueous polyolefin-based resin (A), an aqueous epoxy resin (B), a hydrophilicized-modified carbodiimide compound (C), and an aqueous polyurethane resin (D), in which the aqueous polyolefin-based resin (A) includes an aqueous polypropylene-based resin having a weight-average molecular weight of 50,000 to 200,000, and the hydrophilicized-modified carbodiimide compound (C) is a hydrophilicized-modified carbodiimide compound (C) having a prescribed structure.

## Claims

### Claim 1

A primer coating composition comprising:
an aqueous polyolefin-based resin (A);
an aqueous epoxy resin (B);
a hydrophilicized-modified carbodiimide compound (C); and
an aqueous polyurethane resin (D),
wherein
the aqueous polyolefin-based resin (A) comprises an aqueous polypropylene-based resin having a weight-average molecular weight of 50,000 to 200,000,
a content of the hydrophilicized-modified carbodiimide compound (C) is 3 to 10 parts by mass based on 100 parts by mass of the resin solid content of the primer coating composition, and
the hydrophilicized-modified carbodiimide compound (C) is a compound represented by a formula (I), (II) or (III) below:
YOCONH—X—NHCOO—Z—OCONH—X—NHCOOY (I)
wherein Xs are each a bifunctional organic group having at least one carbodiimide group, Ys are identical or different structures each 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 Xs are each a bifunctional organic group having at least one carbodiimide group, Ys are identical or different structures each resulting from elimination of a hydroxyl group from a polyalkylene glycol monoalkyl ether, R0 is hydrogen, a methyl group or an ethyl group, R1 is an alkylene group having 4 or less carbon atoms, n is 0 or 1, and m is 0 to 60,
YOCONH—X—NHCOOY (III)
wherein X is a bifunctional organic group having at least one carbodiimide group, and Ys are identical or different structures each resulting from elimination of a hydroxyl group from a polyalkylene glycol monoalkyl ether.

### Claim 2 (depends on 1)

The primer coating composition according to claim 1, wherein a content of the aqueous polyolefin-based resin (A) is 15 to 60 parts by mass based on 100 parts by mass of a resin solid content of the primer coating composition.

### Claim 3 (depends on 1)

The primer coating composition according to claim 1, wherein the hydrophilicized-modified carbodiimide compound (C) represented by the formula (III) is a compound defined below:
YOCONH—X—NHCOOY (III)
wherein X is a bifunctional organic group having at least one carbodiimide group, and Ys are identical or different structures selected from (i) or (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 4 (depends on 3)

The primer coating composition according to claim 3, wherein
in the hydrophilicized-modified carbodiimide compound (C) represented by the formula (III), one Y is (i) and another Y is (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 5 (depends on 1)

The primer coating composition according to claim 1, wherein
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.

### Claim 6 (depends on 1)

The primer coating composition according to claim 1, wherein a content of the aqueous polyurethane resin (D) is 15 parts by mass or more based on 100 parts by mass of the resin solid content of the primer coating composition.

### Claim 7 (depends on 1)

The primer coating composition according to claim 1, wherein the content of the aqueous polyurethane resin (D) is 25 parts by mass or more and 45 parts by mass or less based on 100 parts by mass of the resin solid content of the primer coating composition.

### Claim 8 (depends on 1)

The primer coating composition according to claim 1, wherein a content of the aqueous epoxy resin (B) is 20 parts by mass or more and 50 parts by mass or less based on 100 parts by mass of the resin solid content of the primer coating composition.

### Claim 9 (depends on 1)

A method for forming a coating film, the method comprising a step of applying the primer coating composition according to claim 1 to an object to be coated, and heating the primer coating composition to 70° C. to 120° C. to form a primer coating film.

### Claim 10 (depends on 9)

The method for forming a coating film according to claim 9, further comprising a step of forming at least one coating film selected from an intermediate coating film, a base coating film and a clear coating film on the primer coating film.

### Claim 11 (depends on 9)

The method for forming a coating film according to claim 9, wherein the object to be coated comprises a steel plate part and a resin part.