	US 12,305,083 B1
	Two-part epoxy adhesive with working life color change indicator
Zachary J. Thompson, Woodbury, MN (US); Jay S. Schlechte, Oakdale, MN (US); Charlotte C. Clark, Minneapolis, MN (US); and Erin A. Suchara, Minneapolis, MN (US)
Assigned to 3M Innovative Properties Company, St. Paul, MN (US)
Appl. No. 18/856,309
Filed by 3M INNOVATIVE PROPERTIES COMPANY, St. Paul, MN (US)
PCT Filed Jun. 14, 2023, PCT No. PCT/IB2023/056171 § 371(c)(1), (2) Date Oct. 11, 2024, PCT Pub. No. WO2023/242782, PCT Pub. Date Dec. 21, 2023.
Claims priority of provisional application 63/352,797, filed on Jun. 16, 2022.
Int. Cl. C09J 163/00 (2006.01); C08G 59/50 (2006.01); C08G 59/56 (2006.01); C09J 5/00 (2006.01); C09J 11/04 (2006.01); C09J 11/06 (2006.01); C09J 11/08 (2006.01); B32B 15/092 (2006.01); B32B 27/18 (2006.01); B32B 27/20 (2006.01); B32B 27/26 (2006.01); B32B 27/38 (2006.01)

CPC C09J 163/00 (2013.01) [C09J 5/00 (2013.01); C09J 11/04 (2013.01); C09J 11/06 (2013.01); C09J 11/08 (2013.01); C09J 2400/166 (2013.01)]

15 Claims

1. A two-part epoxy adhesive comprising:

a Part A comprising, based on the total weight of components a) and b):

a) 99.5 to 99.99 weight percent of at least one curable epoxy resin;

b) 0.01 to 0.5 weight percent of at least one pH indicator dye exhibiting an abrupt color change from colorless to a color in the pH range of 8.0-10.6; and

a Part B comprising, based on the total weight of components c)-f):

c) 89 to 97 weight percent of at least one aliphatic primary polyamine;

d) 1 to 3 weight percent of at least one tris(2,4,6-dialkylaminoalkyl) phenol having from 13 to 24 carbon atoms;

e) 1 to 3 weight percent of at least one aliphatic tertiary 1,3-bis(N,N-dialkyl-aminoalkyl) urea having from 6 to 24 carbon atoms; and

f) 1 to 5 weight percent at least one of an alkali metal nitrate and an alkaline earth nitrate,

wherein the ratio of the total combined weight of components a) and b) to the total combined weight of components c)-f) is in the range 1.0 to 1.5.

9. A reaction product prepared by mixing Part A and of Part B of the two-part epoxy adhesive of claim 1.

11. The reaction product of claim 9, wherein the reaction product is flowable and curable, and wherein the reaction product is capable of undergoing a visible color change that indicates curing has advanced to a predetermined working life endpoint of the reaction product.

12. A method of bonding two substrates, the method comprising:

disposing the reaction product of claim 11 between first and second substrates prior to said undergoing the visible color change; and

sufficiently curing the reaction product to form an adhesive bond between the first and second substrates.

13. The method of claim 12, wherein at least one of the first and second substrates comprises steel.