Curing agents for cationically curable compositions

Abstract

Novel catalyst systems in cationically curable compositions provide colorless cationically cured compositions with improved degree of cure and thermal stability. The curable composition comprises at least one cationically curable monomer and a curing agent comprising Photocurative A or Photocurative B. Photocurative A comprises an effective amount of an accelerating photochemically active salt comprising a photochemically active cation and an accelerating anion, and an effective amount of an inhibiting non-photochemically active salt comprising a non-photochemically active cation and an inhibiting anion. Photocurative B comprises an effective amount of an inhibiting photochemically active salt comprising a photochemically active cation and an inhibiting anion, and an effective amount of an accelerating non-photochemically active salt comprising a non-photochemically active cation and an accelerating anion. The inhibiting and accelerating salts in photocuratives A and B are defined by photo differential scanning calorimetry (pDSC) and thermal differential scanning calorimetry (tDSC). The compositions are useful, for example, as optically colorless or low color coatings, adhesives, encapsulants, and sealants for optical and electronic applications.

1 . A cured polymer comprising the reaction product of a photocurable composition comprising: 
 a) at least one cationically curable monomer, and    b) a curing agent comprising Photocurative A or Photocurative B, wherein 
 Photocurative A comprises  
 1) an effective amount of an accelerating photochemically active salt comprising a photochemically active cation and an accelerating anion, and  
 2) an effective amount of an inhibiting non-photochemically active salt comprising a non-photochemically active cation and an inhibiting anion; and  
 Photocurative b comprises  
 1) an effective amount of an inhibiting photochemically active salt comprising a photochemically active cation and an inhibiting anion, and  
 2) an effective amount of an accelerating non-photochemically active salt comprising a non-photochemically active cation and an accelerating anion; 
 wherein the inhibiting and accelerating anions are defined by photo differential scanning calorimetry (pdsc) and thermal differential scanning calorimetry (tdsc) such that anions of triarylsulfonium salts that have a total dsc exotherm energy value of 0 to 300 joules per gram (J/g) are classified as inhibiting anions, and anions of triarylsulfonium salts that have a total dsc exotherm energy value greater than 300 to 750 joules per gram (J/g) are classified as accelerating anions;  
 said cured polymer being a high performance colorless or low color polymer:  
 
   
     
     
         2 . The cured polymer according to  claim 1  having a T g  measured by dynamic mechanical analysis (DMA) at 1 Hz at least 10° C. higher than a corresponding polymer cured by a conventional curative.  
     
     
         3 . The cured polymer according to  claim 1  wherein said inhibiting photochemically active salt of said curable composition inhibiting photochemically active salt has a total DSC exotherm energy in the range of 0 to 250 J/g.  
     
     
         4 . The cured polymer according to  claim 1  wherein said wherein said inhibiting photochemically active salt of said curable composition has a total DSC exotherm energy in the range of 0 to 200 J/g.  
     
     
         5 . The cured polymer according to  claim 1  wherein said accelerating photochemically active salt of said curable composition has a total DSC exotherm energy in the range of greater than 300 to 750 J/g.  
     
     
         6 . The cured polymer according to  claim 1  wherein said accelerating photochemically active salt of said curable composition has a total DSC exotherm energy in the range of 325 to 600 J/g.  
     
     
         7 . The cured polymer according to  claim 1  wherein said accelerating photochemically active salt of said curable composition has a total DSC exotherm energy in the range of 350 to 500 J/g.  
     
     
         8 . The cured polymer according to  claim 1  wherein said cationically curable monomer of said curable composition is selected from the group consisting of 1,2-, 1,3-, and 1,4-cyclic ethers (also designated as 1,2-, 1,3-, and 1,4-epoxides), vinyl ethers, N-vinyl compounds, ethylenically unsaturated hydrocarbons, cyclic formals, and cyclic organosiloxanes.  
     
     
         9 . The cured polymer according to  claim 1  wherein said cationically curable monomer of said curable composition is selected from the group consisting of epoxy monomers and vinyl ethers.  
     
     
         10 . The cured polymer according to  claim 1  wherein said cationically curable monomer of said curable composition is an epoxy monomer.  
     
     
         11 . The cured polymer according to  claim 1  wherein said curable composition further comprises a free radically polymerizable monomer.  
     
     
         12 . The cured polymer according to  claim 1  wherein said curable composition further comprises one or more mono- or poly-alcohols or blends thereof.  
     
     
         13 . The cured polymer according to  claim 1  wherein said free radically polymerizable monomer of said curable composition is an acrylate or methacrylate.  
     
     
         14 . The cured polymer according to  claim 1  wherein said curable composition comprises a bifunctional monomer comprising of at least one cationically polymerizable functionality or a functionality that copolymerizes with a cationically curable monomer.  
     
     
         15 . The curable polymer according to  claim 14  wherein said bifunctional monomer of said curable composition comprises at least one free-radically curable functionality.  
     
     
         16 . The cured polymer according to  claim 1  wherein said accelerating photochemically active salt of Photocurative A of said curable composition comprising a photochemically active cation and an accelerating anion is selected from the group consisting of iodonium, sulfonium, and cationic organometallic salts of AsF 6   − , SbF 6   − , CF 3 SO 3   − , HC(SO 2 CF 3 ) 2   − , C(SO 2 CF 3 ) 3   − , N(SO 2 CF 3 ) 2   − , tetra(pentafluorophenyl)borate, and tetra(3,5-bistrifluoromethylphenyl)borate.  
     
     
         17 . The cured polymer according to  claim 1  wherein said inhibiting non-photochemically active salt of said curable composition comprising a non-photoactive cation and an inhibiting anion is selected from the group consisting of tetraalkylammonium, phosphonium, pyridinium, benzothiazolium, benzooxazolium, Li + , Na + , K + , Cs + , and Ca +2  salts of BF 4   − , PF 6   − , p-toluenesulfonate, and tetraphenylborates.  
     
     
         18 . The cured polymer according to  claim 1  wherein said inhibiting photochemically active salt of Photocurative B of said curable composition comprising a photochemically active cation and an inhibiting anion is selected from the group consisting of iodonium, sulfonium, and organometallic salts of BF 4   − , PF 6   − , p-toluenesulfonate, and tetraphenylborates.  
     
     
         19 . The cured polymer according to  claim 1  wherein said accelerating non-photochemically active salt of Photocurative B of said curable composition comprising a non-photochemically active cation and an accelerating anion is selected from the group consisting of tetraalkylammonium, phosphonium, pyridinium, benzothiazolium, benzooxazolium, Li + , Na + , K + , Cs + , and Ca +2  salts of AsF 6   − , SbF 6   − , CF 3 SO 3   − , C(SO 2 CF 3 ) 3   − , HC(SO 2 CF 3 ) 2   − , CF 3 SO 3   − , N(SO 2 CF 3 ) 2 −, tetra(pentafluorophenyl)borate, and tetra(3,5-bisfluoromethylphenyl)borate.  
     
     
         20 . The cured polymer according to  claim 1  wherein said inhibiting anion of said photochemically active salt of said curable composition is selected from the group consisting of BF 4   − , PF 6   − , tetraphenylborate, and p-toluenesulfonate.  
     
     
         21 . The cured polymer according to  claim 1  wherein said photochemically active salt of said curable composition is present in the range of 0.01 to 20% based on the weight of total monomer.  
     
     
         22 . The cured polymer according to  claim 1  wherein said non-photochemically active salt of said curable composition is present in the range of 0.01 to 10% based on the weight of total monomer.  
     
     
         23 . The cured polymer according to  claim 11  wherein said curable composition further comprises a free radical initiator.