Two-Component Structural Adhesives
The present invention is directed toward an adhesive composition comprising: a first component; and a second component that chemically reacts with the first component, the second component comprising: a polythiol curing agent; and an alkanolamine. Also disclosed are methods of forming a bond between two substrates and adhesive bonds.
1 . An adhesive composition comprising:
a first component; and
a second component that chemically reacts with the first component, the second component comprising:
a polythiol curing agent; and
an alkanolamine.
2 . The adhesive composition of claim 1 , wherein the first component comprises one or more epoxy-containing compounds.
3 . The adhesive composition of claim 1 , wherein the first component further comprises core-shell rubber particles.
4 . The adhesive composition of claim 1 , wherein the polythiol curing agent is present in the second component in an amount sufficient to provide a ratio of epoxide functional groups from the first component to thiol functional groups from the second component of 1.1:1 to 5:1.
5 . The adhesive composition of claim 1 , wherein the polythiol curing agent comprises pentaerythritol tetra-3-mercaptopropionate.
6 . The adhesive composition of claim 1 , wherein the weight ratio of polythiol curing agent to alkanolamine is 1:1 to 22:1.
7 . The adhesive composition of claim 1 , wherein the alkanolamine comprises triethanolamine.
8 . The adhesive composition of claim 1 , wherein the alkanolamine is present in the second component of the adhesive composition in an amount of at least 0.5% by weight, based on the total weight of the second component.
9 . The adhesive composition of claim 1 , further comprising a first-step curing catalyst comprising a cyclic tertiary amine.
10 . The adhesive composition of claim 1 , wherein the adhesive composition further comprises a second-step curing catalyst, wherein the second-step curing catalyst preferably comprises a heat-activated latent curing catalyst.
11 . The adhesive composition of claim 1 , wherein the adhesive composition is substantially free of a color change indicator, aromatic amine curing catalysts and/or silane.
12 . The adhesive composition of claim 1 , wherein the adhesive composition cures by a two-step curing process, wherein a first-step comprises that at least a portion of the first component and the second component chemically react when mixed to partially cure the adhesive composition without activation from an external energy source, wherein the second-step comprises application of an external energy source to the adhesive composition to further cure the adhesive composition, wherein the external energy source of the second-step preferably comprises application of an external heat source to heat the adhesive composition to a temperature of at least 110° C. for a period of at least 30 minutes.
13 . The adhesive composition of claim 12 , wherein the adhesive composition after the first-step has a lap shear of at least 1.0 MPa as measured according to test method ASTM D1002-10 by an Instron model 5567 in tensile mode and/or wherein the adhesive composition after the second-step has a lap shear of at least 5.0 MPa as measured according to test method ASTM D1002-10 by an Instron model 5567 in tensile mode.
14 . A method for forming a bond between two substrates comprising:
applying the adhesive composition of claim 1 to a first substrate;
contacting a second substrate to the adhesive composition such that the adhesive composition is located between the first substrate and the second substrate; and
curing the adhesive composition by a two-step curing process.
15 . The method of claim 14 , wherein the first substrate and second substrate comprise components of an automobile frame.