Adhesive compositions for easy application and improved durability
View Patent ↗The present invention is directed to an adhesive composition comprising a crosslinkable acrylic copolymer, a multi-functionalized crosslinkable oligomer and a photoinitiator wherein the partially cured composition exhibits excellent wet out characteristics as reflected in a tan delta value of at least 0.4, preferably greater than 0.5, more preferable greater than 0.6 as measured at 20° C. resulting from a first curing stage, and the fully cured composition exhibits an improved stiffness and temperature resistance as reflected in a storage elastic modulus of at least 175,000 Pa at 20° C. and a shear adhesion failure temperature of at least 425° F. (218.3° C.) at 1 Kg/in 2 (0.155 Kg/cm 2 ), respectively, which result from a second sequential curing stage.
1. A fully cured crosslinked adhesive composition comprising:
(a) a benzophenone-functionalized crosslinked acrylic copolymer; and
(b) a multi-functionalized crosslinked oligomer having a functional moiety selected from the group consisting of acrylate, epoxy, hydroxy, and combinations thereof;
wherein the composition is free of a mono-functionalized oligomer and:
(i) the acrylic copolymer is crosslinked with itself, and
(ii) the oligomer is crosslinked with itself, and the fully cured composition has a storage modulus value of at least 175,000 Pa at 20° C., a shear adhesion failure temperature of at least 425° F. (218.3° C.) at 1 Kg/in 2 (0.155 Kg/cm 2 ), a heated shear value at 160° C. of greater than 10,000 minutes and a peel force value of at least 3.2 lb./in.
2. The composition as defined in claim 1 wherein the acrylic copolymer is a solvent-free benzophenone-functionalized acrylic copolymer.
3. The composition as defined in claim 1 wherein the acrylic copolymer is polymerized from 2-ethylhexyl acrylate or butyl acrylate.
4. The composition as defined in claim 1 wherein the acrylic copolymer is crosslinked by exposure to light having a wavelength substantially less than 300 nm.
5. The composition as defined in claim 1 wherein the oligomer comprises a urethane oligomer having an acrylate functional moiety.
6. The composition as defined in claim 1 wherein the oligomer is present in an amount of at least 10% by weight relative to the dry weight of the acrylic copolymer.
7. The composition as defined in claim 1 wherein the oligomer is crosslinked by exposure to light having a wavelength substantially greater than 300 nm.
8. The composition as defined in claim 1 wherein the oligomer is crosslinked by exposure to light having a wavelength of between 320 to 440 nm.
9. The composition as defined in claim 1 wherein the fully cured composition has a tan delta value of less than 0.8 as measured at 20° C.
10. The composition as defined in claim 1 wherein the fully cured composition has a room temperature shear adhesion value of least 200 hours at 10 lb./in 2 (4.5 Kg/cm 2 ).
11. The composition as defined in claim 1 wherein the fully cured composition has a visible light transmission of between 80 to 100%.
12. A fully cured adhesive composition comprising:
(a) a solvent-free benzophenone-functionalized crosslinked acrylic copolymer which is polymerized from 2-ethylhexyl acrylate or butyl acrylate;
a multi-functionalized crosslinked urethane oligomer having an acrylate functional moiety; wherein the oligomer is present in an amount of at least 10% by weight relative to the dry weight of the acrylic copolymer;
and wherein the composition is free of a mono-functionalized oligomer and:
(i) the acrylic copolymer is crosslinked with itself, and
(ii) the oligomer is crosslinked with itself and the fully cured composition has a storage modulus value of at least 175,000 Pa at 20° C., a shear adhesion failure temperature of at least 425° F. (218.3° C.) at 1 Kg/in 2 (0.155 Kg/cm 2 ), a heated shear value at 160° C. of greater than 10,000 minutes and a peel force value of at least 3.2 lb./in.
13. The composition as defined in claim 12 wherein the fully cured composition has a tan delta value of less than 0.8 as measured at 20° C. after the second curing stage.
14. The composition as defined in claim 12 wherein the fully cured composition has a room temperature shear adhesion value of least 200 hours at 10 lb./in 2 (4.5 Kg/cm 2 ) after the second curing stage.
15. The composition as defined in claim 12 wherein the fully cured composition has a visible light transmission of between 80 to 100%.
16. A partially cured adhesive composition comprising:
(a) a benzophenone-functionalized crosslinked acrylic copolymer;
(b) a multi-functionalized crosslinkable oligomer comprising a functional moiety selected from the group consisting of acrylate, epoxy, hydroxy, and combinations thereof;
(c) a photoinitiator which initiates polymerization of the oligomer; and
wherein the composition is free of a mono-functionalized oligomer; the acrylic copolymer is crosslinked with itself; and the partially cured composition has a tan δ value greater than 0.6 as measured at 20° C.
17. A partially cured adhesive composition as defined in claim 16 , wherein said oligomer is adapted for crosslinking with itself by a radiation curing stage to produce a fully cured composition having a storage modulus value of at least 175,000 Pa at 20° C., a shear adhesion failure temperature of at least 425° F. (218.3° C.) at 1 Kg/in 2 (0.155 Kg/cm 2 ), a heated shear value at 160° C. of greater than 10,000 minutes and a peel force value of at least 3.2 lb./in.
18. A partially cured adhesive composition as defined in claim 16 , wherein the acrylic copolymer is a solvent-free benzophenone-functionalized acrylic copolymer.
19. A partially cured adhesive composition as defined in claim 16 , wherein the acrylic copolymer is polymerized from 2-ethylhexyl acrylate or butyl acrylate.
20. A partially cured adhesive composition as defined in claim 16 , wherein the acrylic copolymer is crosslinked by exposure to light having a wavelength substantially less than 300 nm.
21. A partially cured adhesive composition as defined in claim 16 , wherein the oligomer comprises a urethane oligomer having an acrylate functional moiety.
22. A partially cured adhesive composition as defined in claim 16 , wherein the oligomer is present in an amount of at least 10% by weight relative to the dry weight of the acrylic copolymer.
23. A partially cured adhesive composition as defined in claim 16 , wherein the photoinitiator is present in an amount of between 0.5 to 5% by weight relative to the dry weight of the acrylic copolymer.
24. A partially cured adhesive composition as defined in claim 16 , wherein the photoinitiator is selected from the group consisting of acetophenone, aryl phosphineoxides, aryl sulfonium and aryl iodonium salts of hexafluorophophate, benzyl/benzoin, benzophenone, thioxanthone, and combination thereof.
25. A method for making an adhesive composition comprising:
(i) crosslinking an acrylic copolymer with itself in a first curing stage in the presence of
(a) a multi-functionalized oligomer having a functional moiety selected from the group of acrylate, epoxy, hydroxy, and combinations thereof; and
(b) a photoinitiator adapted for irradiative polymerization of the oligomer;
to produce a partially cured composition having a tan δ value greater than 0.6 as measured at 20° C., wherein the composition is free of a mono-functionalized oligomer.
26. A method for making an adhesive composition, as defined in claim 25 , further comprising an additional step of:
(ii) crosslinking the oligomer with itself in the partially cured composition of step (i) in a second sequential radiation curing stage to produce a fully cured composition having a storage modulus value of at least 175,000 Pa at 20° C., a shear adhesion failure temperature of at least 425° F. (218.3° C.) at 1 Kg/in 2 (0.155 Kg/cm 2 ), a heated shear value at 160° C. of greater than 10,000 minutes and a peel force value of at least 3.2 lb./in.
27. A method for making an adhesive composition, as defined in claim 25 , wherein said acrylic copolymer is benzophenone-functionalized.
28. A method for making an adhesive composition, as defined in claim 25 , wherein the acrylic copolymer is a solvent-free benzophenone-functionalized acrylic copolymer.
29. A method for making an adhesive composition, as defined in claim 25 , wherein the acrylic copolymer is polymerized from 2-ethylhexyl acrylate or butyl acrylate.
30. A method for making an adhesive composition, as defined in claim 25 , wherein the acrylic copolymer is crosslinked during the first curing stage by exposure to light having a wavelength less than 300 nm.
31. A method for making an adhesive composition, as defined in claim 25 , wherein the oligomer comprises a urethane oligomer having an acrylate functional moiety.
32. A method for making an adhesive composition, as defined in claim 25 , wherein the oligomer is present in an amount of at least 10% by weight relative to the dry weight of the acrylic copolymer.
33. A method for making an adhesive composition, as defined in claim 25 , wherein in the photoinitiator is present in an amount of between 0.5 to 5% by weight relative to the dry weight of the acrylic copolymer.
34. A method for making an adhesive composition, as defined in claim 26 , wherein the oligomer is crosslinked during the second curing stage by exposure to light having a wavelength greater than 300 nm.
35. A method for making an adhesive composition, as defined in claim 26 , wherein the oligomer is crosslinked during the second curing stage by exposure to light having a wavelength of between 320 to 440 nm.
36. A method for making an adhesive composition, as defined in claim 26 , wherein the fully cured composition has a tan delta value of less than 0.8 as measured at 20° C.
37. A method for making an adhesive composition, as defined in claim 26 , wherein the fully cured composition has a room temperature shear adhesion value of least 200 hours at 10 lb./in 2 (4.5 Kg/cm 2 ).
38. A method for making an adhesive composition, as defined in claim 25 , wherein the photoinitiator is selected from the group consisting of acetophenone, aryl phosphineoxides, aryl sulfonium and aryl iodonium salts of hexafluorophophate, benzyl/benzoin, benzophenone, thioxanthone, and combination thereof.
39. A method for making an adhesive composition, as defined in claim 26 , wherein the fully cured composition has a visible light transmission of between 80 to 100%.