Pressure-sensitive adhesives with mixed photocrosslinking system
The present disclosure provides a method of providing an adhesive composition comprising the steps of combining crosslinkable composition including: a) a (meth)acryloyl monomer mixture with the b) photocrosslinking agent mixture, and irradiating with UVC radiation to polymerize and crosslink the composition.
1. A method of preparing a (meth)acrylate adhesive composition comprising:
a) providing a (meth)acryloyl monomer mixture and a photoinitiator,
b) irradiating the mixture with UVA to partially polymerize the monomer mixture to a syrup copolymer;
c) adding additional photoinitiator and optionally a multifunctional (meth)acrylate, followed by;
d) combining the syrup polymer of steps b) or c) with a photocrosslinking mixture comprising:
i) a benzophenone photocrosslinker, and
ii) an anthraquinone photocrosslinker and/or a thioxanthone photocrosslinker;
e) irradiating the mixture with UVA radiation and
f) irradiating the mixture with UVC radiation to further crosslink the copolymer.
2. The method of claim 1 , wherein the step of irradiating with UVA and UVC is concurrent.
3. The method of claim 1 , wherein the step of irradiating with UVA and UVC is consecutive.
4. The method of claim 1 wherein the step of irradiating comprises irradiating first with a UVA source at 315 to 400 nanometers, then with a UVC source at 100 to 280 nanometers.
5. The method of claim 1 wherein the photocrosslinking mixture comprises
1) 5 to 50 wt. % benzophenone photocrosslinker, and
2) 50 to 95 wt. % of either an anthraquinone photocrosslinker or a thioxanthone photocrosslinkers.
6. The method of claim 1 wherein the photocrosslinking mixture comprises
1) 20 to 50 wt. % benzophenone photocrosslinker, and
2) 50 to 80 wt. % of either an anthraquinone photocrosslinker or a thioxanthone photocrosslinkers.
7. The method of claim 1 where the photocrosslinking mixture comprises 0.01 to 10 wt. % relative to the (meth)acryloyl monomer mixture.
8. The method of claim 1 where the photocrosslinking mixture comprises 0.1 to 5 wt. % relative to the (meth)acryloyl monomer mixture.
9. The method of claim 1 wherein the photocrosslinking mixture comprises a benzophenone photocrosslinker, and an anthraquinone photocrosslinker.
10. The method of claim 1 wherein the photocrosslinking mixture comprises a benzophenone photocrosslinker and a thioxanthone photocrosslinker.
11. The method of claim 1 wherein the photocrosslinking mixture comprises a benzophenone photocrosslinker, a thioxanthone photocrosslinker, and an anthraquinone photocrosslinker.
12. The method of claim 1 wherein the a (meth)acryloyl monomer mixture comprises:
i. 85 to 99.5 parts by weight of an (meth)acrylic acid ester of non-tertiary alcohol;
ii. 0.5 to 15 parts by weight of an acid functional ethylenically unsaturated monomer;
iii. 0 to 10 parts by weight of a non-acid functional, ethylenically unsaturated polar monomer;
iv. 0 to 5 parts vinyl monomer; and
v. 0 to 5 parts of a multifunctional (meth)acrylate;
based on 100 parts by weight total monomer.
13. The method of claim 1 wherein the (meth)acryloyl comonomer mixture comprises 0.01 to 5 parts of the multifunctional (meth)acrylate, based on 100 parts total monomers.
14. The method of claim 1 , wherein the monomer mixture further comprises a chain transfer agent.