Process for radiation cured conjugated diene-vinyl aromatic hydrocarbon block copolymers

Abstract

In a process of curing epoxidized polymers of conjugated dienes which contain aromatic moieties by exposing the polymers to ultraviolet radiation in the presence of a photoinitiator, the improvement which comprises reducing the amount of irradiation necessary to achieve an effective cure by adding a small but effective amount of a photosensitizer which absorbs UV radiation in a wavelength range which is not obscured by the polymer to the polymer prior to or during irradiation.

We claim: 
     
       1. In a process of curing epoxidated polymers of conjugated dienes which contain aromatic moieties by exposing the polymers or a formulation containing such polymers to ultraviolet radiation in the presence of a photoinitiator, the improvement which comprises reducing the amount of irradiation necessary to achieve an effective cure by adding from 0.05 to 0.5 parts per hundred polymer of a photosensitizer which absorbs UV radiation in a wavelength range which is not obscured by the polymer to the polymer prior to or during irradiation. 
     
     
       2. The process of claim 1 wherein the photosensitizer absorbs UV radiation in the range of 300 to 450 nm. 
     
     
       3. The process of claim 2 wherein the photosensitizer is selected from the group consisting of thioxanthone and its alkyl- and halo-derivatives. 
     
     
       4. The process of claim 2 wherein the photoinitiator is an aryl iodonium salt. 
     
     
       5. The process of claim 2 wherein the photoinitiator is an aryl sulfonium salt. 
     
     
       6. The process of claim 2 wherein the photoinitiator is an alkyl-aryl iodonium salt. 
     
     
       7. The process of claim 2 wherein the photosensitizer is perylene, thioxanthone, alkyl-thioxanthones, and halo-thioxanthones. 
     
     
       8. The process of claim 1 wherein the polymer contains monovinyl aromatic monomers. 
     
     
       9. The process of claim 1 wherein the polymer is an epoxidized star polymer containing aromatic coupling agents. 
     
     
       10. In a process of curing a formulation containing at least one epoxidized polymer of a conjugated diene and at least one additive which absorbs UV radiation in the range of 200 to 350 nm, the improvement which comprises reducing the amount of irradiation necessary to achieve and effective cure by adding from 0.05 to 0.5 weight percent of the informulation of a photosensitizer which absorbs UV radiation in a wavelength. 
     
     
       11. The process of claim 10 wherein the photosensitizer absorbs UV radiation in the range of 300 to 450 nm. 
     
     
       12. The process of claim 11 wherein the photosensitizer is selected from the group consisting of thioxanthone and its alkyl- and halo-derivatives. 
     
     
       13. The process of claim 11 wherein the photoinitiator is an aryl iodonium salt. 
     
     
       14. The process of claim 11 wherein the photoinitiator is an aryl sulfonium salt. 
     
     
       15. The process of claim 11 wherein the photoinitiator is an alkyl-aryl iodonium salt. 
     
     
       16. The process of claim 11 wherein the photosensitizer is perylene, thioxanthone, alkyl-thioxanthones, and halo-thioxanthones.