Adhesive Compositions For Easy Application and Improved Durability

• US 20120277341A1
• Filed: 07/11/2012
• Published: 11/01/2012
• Est. Priority Date: 08/03/2009
• Status: Active Grant

• Current Assignee: Morgan Adhesives Company (Amcor Plc)
• Original Assignee: Curwood Incorporated (Amcor Plc)
• Inventors: Smith, Timothy Michael, McMaster, Gary Allan
• Granted Patent: US 8,686,060 B2
• Time in Patent Office: Days
• US Class Current: 522/64
• CPC Class Codes: A61K 6/887 Compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: C08F 2/48 by ultraviolet or visible light
• CPC Class Codes: C08F 2/50 with sensitising agents
• CPC Class Codes: C08G 18/672 Esters of acrylic or alkyl acrylic acid having only one group containing active hydrogen
• CPC Class Codes: C08G 2170/40 Compositions for pressure-sensitive adhesives
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 2666/04 Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• CPC Class Codes: C08L 33/08 Homopolymers or copolymers of acrylic acid esters
• CPC Class Codes: C08L 33/14 of esters containing halogen, nitrogen, sulfur, or oxygen atoms in addition to the carboxy oxygen
• CPC Class Codes: C09J 133/08 Homopolymers or copolymers of acrylic acid esters
• CPC Class Codes: C09J 133/14 of esters containing halogen, nitrogen, sulfur or oxygen atoms in addition to the carboxy oxygen
• CPC Class Codes: C09J 2301/302 the adhesive being pressure-sensitive, i.e. tacky at temperatures inferior to 30°C

Abstract

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/in² (0.155 Kg/cm²), respectively, which result from a second sequential curing stage.

Claims

1. An adhesive composition comprising:

(a) a benzophenone-functionalized crosslinkable 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 and has;

(i) a first radiation curing stage wherein the acrylic copolymer is crosslinked with itself and the partially cured composition exhibits a tan δ

value greater than 0.6 as measured at 20°

C., and

(ii) a second sequential radiation curing stage wherein the oligomer is crosslinked with itself and the fully cured composition exhibits 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/in² (0.155 Kg/cm²), 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 further comprising 2-ethylhexyl acrylate or butyl acrylate comonomers.

4. The composition as defined in claim 1 wherein the acrylic copolymer is crosslinked during the first curing stage by exposure to light having a wavelength substantially less than 300 nm.

5. The composition as defined in claim 1 wherein the oligomer comprises an acrylate functional moiety and a urethane monomer or comonomer.

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 photoinitiator is present in an amount of between 0.5 to 5% by weight relative to the dry weight of the acrylic copolymer.

8. The composition as defined in claim 1 wherein the oligomer is crosslinked during the second curing stage by exposure to light having a wavelength substantially greater than 300 nm.

9. The composition as defined in claim 1 wherein the oligomer is crosslinked during the second curing stage by exposure to light having a wavelength of between 320 to 440 nm.

10. The composition as defined in claim 1 wherein the fully cured composition exhibits a tan delta value of less than 0.8 as measured at 20°

C. after the second curing stage.

11. The composition as defined in claim 1 wherein the fully cured composition exhibits a room temperature shear adhesion value of least 200 hours at 10 lb./in² (4.5 Kg/cm²) after the second curing stage.

12. The composition as defined in claim 1 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.

13. The composition as defined in claim 1 wherein the fully cured composition exhibits a visible light transmission of between 80 to 100%.

14. An adhesive composition comprising:

(a) a solvent-free benzophenone-functionalized crosslinkable acrylic copolymer comprising 2-ethylhexyl acrylate or butyl acrylate comonomers;

(b) a multi-functionalized crosslinkable oligomer comprising an acrylate functional moiety and a urethane monomer or comonomer;

wherein the oligomer is present in an amount of at least 10% by weight relative to the dry weight of the acrylic copolymer;

(c) a photoinitiator which initiates polymerization of the oligomer and is present in an amount of between 0.5 to 5% by weight relative to the dry weight of the acrylic copolymer; and

wherein the composition is free of a mono-functionalized oligomer and has;

(i) a first radiation curing stage wherein the acrylic copolymer is crosslinked with itself and the partially cured composition exhibits a tan δ

value greater than 0.6 as measured at 20°

C., and

(ii) a second sequential radiation curing stage wherein the oligomer is crosslinked with itself and the fully cured composition exhibits 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/in² (0.155 Kg/cm²), 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.

15. The composition as defined in claim 14 wherein the acrylic copolymer is crosslinked during the first curing stage by exposure to light having a wavelength substantially less than 300 nm.

16. The composition as defined in claim 14 wherein the oligomer is crosslinked during the second curing stage by exposure to light having a wavelength substantially greater than 300 nm.

17. The composition as defined in claim 14 wherein the oligomer is crosslinked during the second curing stage by exposure to light having a wavelength of between 320 to 440 nm.

18. The composition as defined in claim 14 wherein the fully cured composition exhibits a tan delta value of less than 0.8 as measured at 20°

C. after the second curing stage.

19. The composition as defined in claim 14 wherein the fully cured composition exhibits a room temperature shear adhesion value of least 200 hours at 10 lb./in² (4.5 Kg/cm²) after the second curing stage.

20. The composition as defined in claim 14 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.

21. The composition as defined in claim 14 wherein the fully cured composition exhibits a visible light transmission of between 80 to 100%.