Radiation curable printing ink composition

Abstract

The invention is a radiation curable printing ink composition comprising a liquid viscous epoxidized diene polymer and a pigment. Preferred diene polymers are block copolymers comprising at least interior and exterior diene blocks wherein the exterior diene blocks contain a greater concentration of di-, tri-, and tetrasubstituted olefinic epoxides than the interior blocks and wherein the copolymer contains from 0.1 to 3.0 Meq of olefinic epoxides per gram of copolymer and the peak molecular weights as determined by gel permeation chromatography of the exterior blocks of from 300 to 2000 and the peak molecular weights as determined by gel permeation chromatography of the interior blocks are from 2,000 to 10,000. In another preferred embodiment, the polymer is a star polymer having a random distribution of from 0.5 to 5 Meq of di-, tri-, and tetrasubstituted olefinic epoxides per gram of polymer and greater than four arms wherein the peak molecular weights as determined by gel permeation chromatography of the arms are from 1500 to 15,000.

We claim: 
     
       1. A radiation curable printing ink composition comprising a liquid viscous diene block polymer wherein a portion of the olefinic double bonds in the diene are epoxidized and a pigment. 
     
     
       2. The composition of claim 1 wherein the polymer is a block copolymer comprising at least interior and exterior diene blocks wherein the exterior diene blocks contain a greater concentration of di-, tri- and tetrasubstituted olefinic epoxides than the interior blocks and wherein the copolymer contains from 0.1 to 3.0 Meq of olefinic epoxides per gram of copolymer and the peak molecular weights as determined by gel permeation chromatography of the exterior blocks are from 300 to 2000 and the peak molecular weights as determined by gel permeation chromatography of the interior blocks are from 2000 to 10,000. 
     
     
       3. The composition of claim 2 wherein the external diene block is 1,4-polyisoprene and the internal diene block is polybutadiene. 
     
     
       4. The composition of claim 2 wherein the external diene block is 1,4-polybutadiene and the internal diene block is 1,2-polybutadiene. 
     
     
       5. The composition of claim 2 wherein the polymer is hydrogenated such that less than 1 Meq of olefinic double bonds per gram of polymer remain in the block copolymer. 
     
     
       6. The composition of claim 5 wherein the ratio of the amount of epoxy in the external blocks to that in the internal blocks is at least 3:1. 
     
     
       7. The composition of claim 1 wherein the polymer is crosslinked through at least some of the epoxy functionality by exposure to radiation. 
     
     
       8. The composition of claim 2 wherein the copolymer is crosslinked through at least some of the epoxy functionality by exposure to radiation. 
     
     
       9. The composition of claim 2 wherein the block copolymer is of the formula   (A-B).sub.k or A-(B-A).sub.j     wherein A is an exterior diene block; and   wherein B is an interior diene block; and   wherein j is 1 to 6 and k is 2 to 6.   
     
     
       10. The composition of claim 9 wherein the copolymer is hydrogenated such that less than 1Meq of olefinic double bonds per gram of polymer remain in the copolymer. 
     
     
       11. The composition of claim 9 wherein the copolymer is crosslinked through at least some of the epoxy functionality by exposure to radiation. 
     
     
       12. The composition of claim 2 wherein block copolymer is of the formula   D.sub.n -X-C.sub.r     wherein D is A-B-M p  or (A-B) j  -M p  or A-(B-A) j  -M p  ; and   wherein A is an exterior diene block; and   wherein B is an interior diene block; and   wherein C is a block or multiblock segment which has a peak molecular weight as determined by gel permeation chromatography of 100 to 18,000 and comprises A, B or methacrylate or mixtures thereof but is not identical to D; and   wherein the B block may contain a monoalkenyl aromatic hydrocarbon monomer and the A blocks may comprise up to 99% of a monoalkenyl aromatic hydrocarbon monomer; and   wherein M is a miniblock of a monomer selected form the group consisting of vinyl aromatic hydrocarbons and dienes and which has a peak molecular weight as determined by gel permeation chromatography of 50 to 3000; and   wherein X is a coupling agent or coupling monomers or initiator, j is 1 to 6, n≧2, r≧0, n≧r, n+r ranges from 3 to 100 and p is 0 or 1.   
     
     
       13. The composition of claim 12 wherein the polymer is hydrogenated such that less than 1 Meq of olefinic double bonds per gram of polymer remain in the copolymer. 
     
     
       14. The block copolymer of claim 12 wherein the copolymer is crosslinked through at least some of the epoxy functionality by exposure to radiation. 
     
     
       15. The composition of claim 1 wherein the polymer is a star polymer having a random distribution of from 0.5 to 5 Meq of di-, tri- and tetrasubstituted olefinic epoxides per gram of polymer and greater than 4 arms wherein the peak molecular weights as determined by gel permeation chromatography of the arms are from 1500 to 15,000. 
     
     
       16. The composition of claim 15 wherein the arms are primarily 1,4-polyisoprene. 
     
     
       17. The composition of claim 15 wherein the arms are primarily 1,4-polybutadiene. 
     
     
       18. The composition of claim 15 wherein the polymer is hydrogenated such that less than 1Meq of olefinic double bonds per gram of polymer remain in the polymer. 
     
     
       19. The composition of claim 15 wherein the polymer is crosslinked through at least some of the epoxy functionality by exposure to radiation. 
     
     
       20. The composition of claim 15 wherein the star polymer is of the formula   D.sub.n -X-C.sub.r     wherein D is (A-M p ); and   wherein A is a block comprising at least one diene and the peak molecular weight as determined by gel permeation chromatography of A is from 1,500 to 15,000; and   wherein C is a block or multiblock segment which has a peak molecular weight as determined by gel permeation chromatography of 50 to 15,000 and comprises at least one diene or vinyl aromatic hydrocarbon or methacrylate or combinations thereof but is not identical to D; and   wherein the A blocks may comprise up to 99% of a monoalkenyl aromatic hydrocarbon monomer; and   wherein M is a miniblock of a monomer selected from the group consisting of vinyl aromatic hydrocarbons and dienes and has a peak molecular weight as determined by gel permeation chromatography of 50 to 1000; and   wherein X is a coupling agent or coupling monomers or initiator, n≧2, r≧0, n≧r, n+r ranges from greater than 4 to 100 and p is 0 or 1.   
     
     
       21. The composition of claim 20 wherein the polymer is hydrogenated such that less than 1 Meq of olefinic double bonds per gram of polymer remain in the copolymer. 
     
     
       22. The composition of claim 20 wherein the polymer is crosslinked through at least some of the epoxy functionality by exposure to radiation.