Photolytically induced redox curable compositions
Photolytically induced redox curable compositions, which show a delayed onset of cure resulting in controllable “open times” for the end user consumer, are provided. These compositions are activated by exposure to electromagnetic radiation, such as UV/VIS radiation with a wavelength in the range of 254-470 nm, but show a commercially meaningful “open time” prior to cure. This property is particularly attractive when opaque substrates and/or substrates with low transmissivity are to be assembled.
1. A photolytically induced RedOx curable composition, comprising:
(a) a RedOx curable component selected from vinyl ethers, alkenyl ethers, (meth)acrylates and combinations thereof;
(b) a metallocene-containing photoinitiator;
(c) a peroxide; and
(d) an acidic activator component.
2. The composition of claim 1 , wherein the photoinitiator is selected from the group consisting of ferrocenium- and ruthenium-containing photoinitiators.
3. The composition of claim 1 , wherein the peroxide is t-butyl perbenzoate.
4. The composition of claim 1 , wherein the acidic activator component is a member selected from the group consisting of (meth)acrylic acid; maleic acid; fumaric acid; cinnamic acid; cyanoacetic acid; barbituric acid; 1,3-dimethylbarbituric acid; malonic acid; methylmalonic acid; mono-ethyl malonate; 2-acetylcyclohexanone; ethyl cyanoacetate; acetylacetone; acetoacetic acid; ethyl acetoacetate; dihydroresorcinol; 1,3-diketones; 1,3,5-triketones; β-ketoesters; ascorbic acid; citric acid; phenolic compounds; pyruvic acid; mono-ethyl fumarate; mono-butyl maleate; mono-2-(methacryloyloxy)ethyl maleate; tocopheol, tannic acid and derivatives and combinations thereof.
5. The composition of claim 1 , wherein the composition cures within a period of time of 30 seconds to 10 minutes after exposure to UV-radiation at a wavelength of 254 to 470 nm.
6. The composition according to claim 1 , wherein the acidic activator component comprises one or more of ascorbic acid or derivative thereof and tocopherol.
7. The composition according to claim 1 , wherein the acidic activator component comprises the combination of ascorbic acid or derivative thereof, tocopherol and tannic acid.
8. The composition according to claim 1 , wherein the photoinitiator is represented by
wherein Me is Fe or Ru; R 1 and R 2 may or may not be present, but when present may individually be selected from the group consisting of alkyl of from 1 to 5 carbon atoms, halogen, hydroxyl, and carboxyl; and X is an anion.
9. The composition according to claim 1 , wherein the photoinitiator has a core cation represented by
10. The composition according to claim 1 , wherein the photoinitiator is used in an amount within the range of about 0.1 to about 2 percent by weight of the total composition.
11. A method for attaching one substrate to another substrate, comprising the steps of:
applying a composition according to claim 1 to a first substrate;
activating the composition prior to or after application thereof through exposure to radiation in the electromagnetic spectrum; and
positioning the other substrate onto the first substrate; and
optionally, curing the composition at a temperature between 60 and 140° C.