One-component toughened epoxy adhesives with improved adhesion to oily surfaces and high wash-off resistance

Patent metadata

Field	Value
Publication number	US-11034869-B2
Application number	US-202016936628-A
Country	US
Kind code	B2
Filing date	Jul 23, 2020
Priority date	Sep 10, 2015
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

Epoxy adhesives include a latent curing agent, a reactive toughener having capped isocyanate groups, and certain urea compounds. The toughener is made by chain extending and capping a mixture of isocyanate-terminated prepolymers. The prepolymers include an isocyanate-terminated polyether and an isocyanate-terminated diene polymer. The adhesives have excellent wash-off resistance and excellent ability to adhere to oily substrates.

First claim

The invention claimed is:

1. A method for adhering a first oily substrate to a second substrate, comprising
1) forming a layer of a one-component epoxy adhesive comprising in admixture:

A) at least 25 weight percent, based on the weight of the adhesive, of one or more non-rubber-modified epoxy resins;
B) 5 to 45 weight percent, based on the weight of the composition, of a reactive elastomeric toughener having capped isocyanate groups, which reactive elastomeric toughener includes a chain-extended and then isocyanate-capped mixture of i) a 1000 to 10,000 number average molecular weight isocyanate-terminated polyether and ii) a 1000 to 10,000 number average molecular weight isocyanate-terminated diene polymer;
C) one or more latent epoxy curing agents in an amount sufficient to cure the adhesive; and
D) 0.1 to 5 weight percent, based on the weight of the adhesive, of at least one urea compound having one or more urea groups and a molecular weight per urea group of up to 250, the adhesive being devoid of an aminophenol curing accelerator,
at a bondline between the first oily substrate and the second substrate to form an assembly that includes the first and second substrates each in contact with the adhesive composition at the bondline; then
2) degreasing the assembly to remove oil from the first oily substrate; and then
3) heating the degreased assembly to an elevated temperature to cure the adhesive.

2. The method of claim 1 , wherein the urea compound is polyurea corresponding to a reaction product of an aromatic polyisocyanate with a dialkyl amine.

3. The method of claim 2 , wherein the urea compound corresponds to a reaction product of an aliphatic polyisocyanate with a dialkyl amine.

4. The method of claim 3 wherein the urea compound is isophorone bis(dimethyl urea).

5. The method of claim 2 wherein the urea compound is one or more of 2,4′- and/or 4,4′-methylene bis(phenyl dimethyl urea) and 2,4- and/or 2,6-toluene bis(dimethyl urea).

6. The method of claim 1 , wherein the latent epoxy curing agent includes dicyanamide.

7. The method of claim 1 , wherein the toughener is made in a process that includes the steps of chain-extending the mixture of the isocyanate-terminated polyether and the isocyanate-terminated diene polymer and then capping the remaining isocyanate groups of the chain-extended material.

8. The method of claim 1 , wherein the isocyanate groups of the isocyanate-terminated polyether and the isocyanate-terminated diene polymer are aliphatic isocyanate groups.

9. The method of claim 1 , wherein the capped isocyanate groups of the toughener are capped with a monophenol or an aminophenol.

10. The method of claim 1 which further comprises the steps of:
1-A): after step 1) and before step 2), fastening the assembly using mechanical means, by spot-curing one or more portions of the adhesive composition, or both, to maintain the substrates and adhesive in a fixed position relative to each other, wherein at least a portion of the adhesive remains uncured; and
2-A): after step 2) and before step 3), contacting the fastened assembly with a heat-curable coating to form a coated and fastened assembly.

11. The method of claim 10 wherein the heat-curable coating is cured in step 3).

12. The method of claim 10 or 11 , wherein the degreasing step 2) is performed at a temperature of at least 50° C.

Assignees

• Ddp Specialty Electronic Materials Us Llc

Inventors

• Lutz Andreas
• Schneider Daniel
• Flueckiger Jeannine

Classifications

• C08G18/755

  and at least one isocyanate or isothiocyanate group linked to a secondary carbon atom of the cycloaliphatic ring, e.g. isophorone diisocyanate · CPC title

• C09J163/00 Primary

  Adhesives based on epoxy resins; Adhesives based on derivatives of epoxy resins · CPC title

• C08G18/4854

  Polyethers containing oxyalkylene groups having four carbon atoms in the alkylene group · CPC title

• C08G65/33348

  containing isocyanate group · CPC title

• C08G18/10

  Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step · CPC title