Liquid photopolymer useful in fabricating printing plates which are resistant to solvent based ink

Abstract

A polymer based on the reaction of an excess of diisocyanate with saturated polyolefine diols to form an oligomer and further reaction of the oligomer with hydroxyacrylates or hydroxymethacrylates is discussed. The polymer is then blended with ethylenically unsaturated monomers and a photoinitiator to produce a photosensitive composition which is useful in fabricating printing plates.

What is claimed is:  
     
         1 . A photosensitive resin composition comprising: 
 a). an ethylenically unsaturated polyurethane prepolymer of the following structure:    Y—XP—X n Y     wherein P is a saturated polyolefine;     wherein X is independently selected from the group consisting of aromatic diisocyanates and aliphatic diisocyanates;     wherein Y is a terminal group which has an ethylenically active portion at the outer end of said group; and     wherein n is an integer of from 1 to 20;    b). at least one ethylenically unsaturated monomer; and    c). at least one photopolymerization initiator.    
     
     
         2 . A photosensitive resin composition of  claim 1  wherein P is selected from the group consisting of hydrogenated polybutadienes, hydrogenated polyisoprenes, and hydrogenated, copolymers of butadiene with styrene.  
     
     
         3 . A photosensitive resin composition of  claim 1  wherein Y is independently selected from the group consisting of acrylates and methacrylates.  
     
     
         4 . A photosensitive resin composition of  claim 1  wherein the terminal group is polypropylene glycol monomethacrylate.  
     
     
         5 . A photosensitive composition of  claim 1  wherein the unsaturated polyurethane prepolymer is prepared by reacting an excess of a diisocyanate with diols selected from the group consisting of saturated polyolefine diols, a mixture of saturated polyolefine diols with unsaturated polyolefine diols, a mixture of saturated polyolefine diols with short chain diols, and a mixture of saturated polyolefine diols with polyester diols, to form an oligomer, and further reaction of the oligomer with a compound selected from the group consisting of hydroxy acrylates and hydroxymethacrylates.  
     
     
         6 . A photosensitive composition of  claim 1  wherein the prepolymer has a molecular weight greater than 3,000.  
     
     
         7 . A photosensitive resin composition of  claim 1  wherein the monomer comprises a mixture of monomers having one ethylenic group and monomers having more than one ethylenic group.  
     
     
         8 . A photosensitive composition of  claim 5  wherein the diols comprise a mixture of saturated polyolefine diols with short chain diols and wherein the short chain diols comprise less than 15 percent by weight of the total diols.  
     
     
         9 . A photosensitive composition according to  claim 8  wherein the monomer comprises a mixture of monomers having one ethylenic group and monomers having more than one ethylenic groups.  
     
     
         10 . A process for fabricating a printing plate, said process comprising: 
 a). selectively contacting a photosensitive resin composition comprising: 
 1) an ethylenically unsaturated polyurethane prepolymer of the following structure:  
 Y—XP—X n Y  
  wherein P is a saturated polyolefine;  
  wherein X is independently selected from the group consisting of aromatic diisocyanates and aliphatic diisocyanates;  
  wherein Y is a terminal group which has an ethylenically active portion at the outer end of said group; and  
  wherein n is an integer of from 1 to 20;  
 2) at least one ethylenically unsaturated monomer; and  
 3) at least one photopolymerization initiator; with actinic radiation; and  
   b) developing away any unpolymerized photosensitive resin.    
     
     
         11 . A process according to  claim 10  wherein P is selected from the group consisting of hydrogenated polybutadienes, hydrogenated polyisoprenes, and hydrogenated copolymers of butadiene with styrene.  
     
     
         12 . A process according to  claim 10  wherein Y is independently selected from the group consisting of acrylates and methacrylates.  
     
     
         13 . A process according to  claim 10  wherein the terminal group is polypropylene glycol monomethacrylate.  
     
     
         14 . A process according to  claim 10  wherein the unsaturated polyurethane prepolymer is prepared by reacting an excess of a diisocyanate with diols selected from the group consisting of saturated polyolefine diols, a mixture of saturated polyolefine diols with unsaturated polyolefine diols, a mixture of saturated polyolefine diols with short chain diols, and a mixture of saturated polyolefine diols with polyester diols, to form an oligomer, and further reaction of the oligomer with a compound selected from the group consisting of hydroxy acrylates and hydroxymethacrylates.  
     
     
         15 . A process according to  claim 10  wherein the prepolymer has a molecular weight greater than 3,000.  
     
     
         16 . A process according to  claim 10  wherein the monomer comprises is a mixture of monomers having one ethylenic group and monomers having more than one ethylenic group.  
     
     
         17 . A process according to  claim 14  wherein the diols comprise a mixture of saturated polyolefine diols with short claim diols and wherein the short claim diols comprise less than 15 percent by weight of the total diols.  
     
     
         18 . A process according to  claim 17  wherein the monomer comprises a mixture of monomers having one ethylenic group and monomers having more than one ethylenic group.  
     
     
         19 . A method of forming an ethylenically unsaturated polyurethane prepolymer comprising: 
 a) reacting an excess of a diisocyanate with diols selected from the group consisting of saturated polyolefine diols, a mixture of saturated polydefine diols with unsaturated polyolefine diols, a mixture of saturated polyolefine diols with short claim diols and a mixture of saturated polyolefine diols with polyester diols, to form an oligomer; and    b) further reacting the oligomer with a compound selected from the group consisting of hydroxyacrylates, hydroxymethacrylates and mixtures thereof.    
     
     
         20 . A method according to  claim 19  wherein the diols comprise a mixture of saturated polyolefine diols with short chain diols and wherein the short chain diols comprise less than 15 percent by weight of the total diols.  
     
     
         21 . A printing plate comprising the photochemical reaction product of: 
 (a) an ethylenically unsaturated polyurethane prepolymer which prepolymer was prepared by: 
 1). reacting an excess of a diisocyanate with diols selected from the group consisting of saturated polyolefine diols, a mixture of saturated polyolefine diols with unsaturated polyolefine diols, a mixture of saturated polyolefine diols with short chain diols and a mixture of saturated polyolefine diols with polyester diols, to form an oligomer; and  
 2). further reacting the oligomer with a compound selected from the group consisting of hydroxyacrylates, hydroxymethacrylates and mixtures thereof;  
   (b) at least one ethylenically unsaturated monomer; and    (c) at least one photopolymerization initiator.