# US 10,865,271 B2 · Epoxy compositions and surfacing films therefrom

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- Number: US 10,865,271 B2
- Document ID: US10865271B2
- Status: Granted
- Kind: B2
- Application number: 16/006,659
- Filed: 2018-06-12
- Published: 2018-10-11
- Granted: 2020-12-15
- Earliest claimed: 2009-12-29
- Assignees: 3M Innovative Properties Company
- Applicants: 3M Innovative Properties Company
- Inventors: Scott A. Boyd; Dmitriy Salnikov; David T. Amos
- Web page: https://patentgrep.com/patent/US10865271B2

## CPC

- C08G 59/4021: {Ureas; Thioureas; Guanidines; Dicyandiamides}
- C08G 59/4042: {Imines; Imides}
- C08L 63/00: Compositions of epoxy resins; Compositions of derivatives of epoxy resins
- C08L 79/00: Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen or carbon only, not provided for in groups C08L61/00 - C08L77/00
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)

## Abstract

A composition is provided comprising: a) a curable epoxy resin; and b) 0.01-30% by weight of a polycarbodiimide according to Formula I: R—{—N═C═N—R—}n—N═C═N—R (I) wherein n is an integer between 0 and 100, and wherein each R is independently selected from aromatic and aliphatic groups which contain between 1 and 24 carbons and which are optionally substituted, typically comprising 0.1-20% by weight of the polycarbodiimide. In some embodiments the present disclosure provides sheet materials made of such cured, uncured or partially cured materials. In some embodiments these compositions may be useful in making surfacing films for composite parts and may demonstrate good paint stripper resistance and microcrack resistance.

## Claims

### Claim 1

A method of increasing paint stripper resistance and microcrack resistance of a fiber-matrix composite part, the method comprising:
disposing onto an outermost surface of an uncured fiber-composite matrix a composition comprising:
a curable oxazolidone ring-containing epoxy resin; and
1-3% by weight of a mono- or polycarbodiimide according to Formula I:
R{N═C=N—R-}n-N=C=N—R (I)
wherein n is an integer between 0 and 100 and wherein each R is independently selected from aromatic and aliphatic groups which contain between 1 and 24 carbons; and
curing the composition and uncured fiber-composite matrix to obtain a fiber-matrix composite part with a surfacing film thereon having increased paint stripper resistance and microcrack resistance.

### Claim 2 (depends on 1)

The method according to claim 1 wherein n is at least 1.

### Claim 3 (depends on 1)

The method according to claim 1 wherein n is at least 2.

### Claim 4 (depends on 1)

The method according to claim 1 wherein R contains between 3 and 12 carbons.

### Claim 5 (depends on 1)

The method according to claim 1 wherein all R groups are aromatic.

### Claim 6 (depends on 1)

The method according to claim 1 wherein all R groups are selected from the group consisting of phenyl, toluyl, phenylene and methyl-phenylene.

### Claim 7 (depends on 1)

The method according to claim 1 wherein the surfacing film is a cured-in component of the composite part forming the outer surface of the composite part.

### Claim 8 (depends on 7)

The method according to claim 7 wherein the composition is applied to a layup tool prior to being disposed onto the outermost surface of the uncured fiber-composite matrix.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the composition and uncured fiber-composite matrix are cured by autoclaving.

### Claim 10 (depends on 1)

The method according to claim 1, wherein the composition is disposed on a release liner and dried prior to disposing the composition onto the outermost surface of the uncured fiber-composite matrix.

### Claim 11 (depends on 1)

The method of claim 1 wherein the uncured fiber-composite matrix comprises one or more plies of pre-impregnated carbon fiber.

### Claim 12 (depends on 1)

The method according to claim 1, wherein the surfacing film has an exposed surface and further comprising the step of applying a paint to the exposed surface.

### Claim 13 (depends on 1)

The method according to claim 1 wherein the composition disposed on the uncured fiber-composite matrix as a sheet having a thickness of less than 0.5 mm.