Two stage methods for processing adhesives and related compositions
Methods for forming melt processable, actinic radiation polymerizable and crosslinkable adhesives are described. In certain versions, the adhesives or pre-adhesive compositions include two initiators and are polymerized and/or crosslinked by exposure to actinic radiation such as UV light or electron beam radiation. Also described are pre-adhesive compositions including polymerizable monomers, articles including the adhesives, and various methods and systems related to the adhesives and their application. In addition, various apparatuses are described for polymerizing or crosslinking the compositions.
1. A method of forming an adhesive, the method comprising:
providing a composition comprising at least one monomer, a first actinic radiation initiator, and a second actinic radiation initiator, wherein the second initiator is substantially non-photoactive at activation wavelength(s) of the first initiator;
at least partially polymerizing the composition by exposing the composition to radiation comprising wavelengths corresponding to the activation wavelength(s) of the first initiator;
at least partially crosslinking the composition to thereby form the adhesive by exposing the composition to radiation comprising wavelengths corresponding to the activation wavelength(s) of the second initiator;
wherein at least one of the first and the second initiators is a polymerizable monomer containing a photoinitiator moiety,
wherein upon activation of the first initiator the at least one monomer polymerizes to form a pre-adhesive, and
wherein at least one of the first and second initiators is an activatable photoinitiator moiety covalently bound to the pre-adhesive polymer backbone.
2. The method of claim 1 wherein the at least partially polymerizing the composition is performed by irradiating the composition with UV radiation.
3. The method of claim 1 wherein the at least partially polymerizing the composition is performed by irradiating the composition with electron beam radiation.
4. The method of claim 1 wherein the at least partially crosslinking the composition is performed by irradiating the composition with UV radiation.
5. The method of claim 1 wherein the at least partially crosslinking the composition is performed by irradiating the composition with electron beam radiation.
6. The method of claim 1 wherein the the pre-adhesive composition comprises controlled architecture polymers comprising a reactive functional group.
7. The method of claim 6 wherein the controlled architecture polymers exhibit an apportionment ratio of the reactive functional group between two blocks of the polymer within a range of from 1.1:1 to 10,000:1.
8. The method of claim 1 wherein the composition is free of solvents.
9. The method of claim 1 wherein the second initiator is an activatable photoinitiator moiety covalently bound to the pre-adhesive polymer backbone.
10. The method of claim 1 wherein the pre-adhesive exhibits a viscosity within a range of from 1,000 cps to 80,000 cps at a temperature within a range of from 110′ C to 180° C.
11. The method of claim 1 wherein the pre-adhesive exhibits a viscosity within a range of from 30,000 cps to 40,000 cps at a temperature within a range of from 120° C. to 140° C.
12. The method of claim 1 wherein the pre-adhesive exhibits a viscosity within a range of from 40,000 cps to 50,000 cps at a temperature within a range of from 120° C. to 140° C.
13. The method of claim 1 wherein the pre-adhesive exhibits a viscosity within a range of from 1,000 cps to 15,000 cps at a temperature within a range of from 110° C. to 130° C.
14. The method of claim 1 wherein the pre-adhesive comprises at least 95% solids.
15. A method of forming an adhesive, the method comprising:
providing a composition comprising at least one monomer, a first actinic radiation initiator, and a second actinic radiation initiator, wherein the second initiator is substantially non-photoactive at activation wavelength(s) of the first initiator;
at least partially polymerizing the composition by exposing the composition to radiation comprising wavelengths corresponding to the activation wavelength(s) of the first initiator;
at least partially crosslinking the composition to thereby form the adhesive by exposing the composition to radiation comprising wavelengths corresponding to the activation wavelength(s) of the second initiator;
wherein at least one of the first and the second initiators is a polymerizable monomer containing a photoinitiator moiety,
wherein upon activation of the first initiator the at least one monomer polymerizes to form a pre-adhesive, and
wherein the second initiator is an activatable photoinitiator moiety covalently bound to the pre-adhesive polymer backbone.