Acid catalyzed, toughened epoxy adhesives

• US 4,846,905 A
• Filed: 04/06/1988
• Issued: 07/11/1989
• Est. Priority Date: 04/06/1988
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Tarbutton, Kent S., Robins, Janis
• Primary Examiner(s): Nielsen, Earl
• Application Number:
  US07/178,148
• Time in Patent Office: 461 Days
• Field of Search: 525/65, 525/119, 525/122, 528/92, 528/110
• US Class Current: 525/65
• CPC Class Codes: C08G 59/62 Alcohols or phenols
• CPC Class Codes: C08G 59/686 containing nitrogen
• CPC Class Codes: C08L 2666/04 Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• CPC Class Codes: C08L 63/00 Compositions of epoxy resins; Compositions of derivatives of epoxy resins

Abstract

Disclosed is a thermally-curable, one-part epoxy adhesive composition comprising: (1) a glycidyl ether epoxide having a048477475 n epoxy functionality grater than one and a molecular weight between about 150 and 10,000; (2) a catalyst comprising (i) an acid of the formula H⁺ SbF₅ X^- wherein X is halogen, hydroxy, or --OR where --OR is the residue of an aliphatic or aromatic alcohol having a molecular weight less than about 10,000 and (ii) N,N-diethyl-o-toluidine; (3) an aliphatic or non-aromatic cyclic polyol having about 2 to 18 carbon atoms, at least two hydroxy groups of which are primary or secondary, and being free of electron-withdrawing substituents, amine substituents, or large substituents that cause steric hindrance in the α-position in relation to the carbon attached to the methylol group of the polyol; and (4) a toughening agent that does not react with the epoxide during curing and has an epoxide compatible component and an epoxide incompatible component.

Claims

1. A thermally-curable, one-part epoxy adhesive composition comprising:

(1) a glycidyl ether epoxide having an epoxy functionality greater than one and a molecular weight between about 150 and 10,000;

(2) a catalyst comprising (i) an acid of the formula H⁺ SbF₅ X^- wherein X is halogen, hydroxy, or --OR where --OR is the residue of an aliphatic or aromatic alcohol having a molecular weight less than about 10,000 and (ii) N,N- diethyl-o-toluidine;

(3) an aliphatic or non-aromatic cyclic polyol having about 2 to 18 carbon atoms, at least two hydroxy groups of which are primary or secondary, and being free of electron-withdrawing substituents, amine substituents, or large substituents that cause steric hindrance in the α

-position in relation to the carbon attached to the methylol group of the polyol; and

(4) a toughening agent that does not react with the epoxide during curing and has an epoxide compatible component and an epoxide incompatible component.

2. The composition of claim 1 wherein the polyol is present in an amount sufficient to provide an hydroxy to epoxy ratio between about 0.5:

1 and 1.1;

1.

3. The composition of claim 2 wherein said hydroxy to epoxy ratio is between about 0.7:

1 and 0.8;

1.

4. The composition of claim 1 wherein the molar ratio of said acid to N,N-diethyl-o-toluidine is between about 1:

1.5 and 1;

10.

5. The composition of claim 4 wherein said molar ratio is between about 1:

2 and 1;

6.

6. The composition of claim 1 wherein said toughening agent is present at between about 3% and 35% by weight of the epoxide.

7. The composition of claim 1 wherein said toughening agent is a polymeric compound having both a rubbery phase and a thermoplastic phase.

8. The composition of claim 7 wherein said toughening agent is a graft polymer having a polymerized, diene, rubbery core and a shell grafted thereto of an acrylic acid ester, a methacrylic acid ester, a monovinyl aromatic hydrocarbon, or a mixture thereof.

9. The composition of claim 8 wherein said rubbery core comprises polymerized butadiene or a polymerized mixture of butadiene and styrene.

10. The composition of claim 9 wherein said shell comprises a methacrylic acid ester.

11. The composition of claim 10 wherein said methacrylic acid ester comprises a lower alkyl substituted methacrylate.

12. The composition of claim 9 wherein said shell comprises a monovinyl aromatic hydrocarbon.

13. The composition of claim 12 wherein said hydrocarbon is selected from styrene, alpha-methylstyrene, vinyltoluene, vinylxylene, ethylvinylbenzene, isopropylstyrene, chlorostyrene, dichlorostyrene, and ethylchlorostyrene.

14. The composition of claim 7 wherein said toughening agent is a core-shell polymer wherein the core is a rubbery polyacrylate polymer having a glass transition temperature below about 0°

C. and the shell is grafted thereto and is a thermoplastic polyacrylate polymer having a glass transition temperature above about 25°

C.

15. The composition of claim 14 wherein said core is selected from polybutylacrylate and polyisooctylacrylate and said shell is polymethylmethacrylate.

16. The composition of claim 7 wherein said toughening agent is an elastomeric particle having a T_g below about 25°

C. that is a polymerized mixture of free-radical polymerizable monomers and a polymeric stabilizer that is soluble in the epoxide.

17. The composition of claim 1 wherein X is the residue of an alkylene glycol.

18. The composition of claim 1 wherein X is 2-(2-hydroxyethoxy)ethoxy.

19. The composition of claim 1 wherein said polyol is an alkylene glycol.

20. The composition of claim 1 wherein said polyol is 1,4-cyclohexanedimethanol.

21. The composition of claim 1 wherein said epoxide has a molecular weight between about 300 and 1,000.

22. The composition of claim 1 wherein said epoxide is a diglycidyl ether of bisphenol A or a diglycidyl ether of bisphenol F.