Epoxy resin composition

Abstract

According to this invention, an epoxy resin composition is provided with a finely dispersed phase of an elastomeric block copolymer having at least one block of a hydrogenated conjugated diene connected to at least one block of a carboxylated monoalkenyl aromatic hydrocarbon. The block copolymers are dispersed in the epoxy resin by emulsifying the carboxylated block copolymer and blending the emulsion with the epoxy resin. The block copolymer is emulsified from a relatively non-polar solvent such as tetrahydrofuran using gradual addition of a polar solvent such as water or an alcohol. The dispersed rubber particles have an average diameter between 0.05 and 0.20 microns.

We claim: 
     
       1. A process to prepare an epoxy resin composition comprising the steps of: emulsifying a block copolymer from a solvent solution by addition of a more polar solvent, the block copolymer comprising at least one block of a monalkenyl aromatic hydrocarbon connected to at least one selectively hydrogenated block of a conjugated diene wherein the block copolymer is modified by incorporating one or more carboxylic acid groups selectively into the mon-alkenyl aromatic blocks; and combining the block copolymer with an epoxy resin.   
     
     
       2. The process of claim 1 wherein the block copolymer is emulsified from tetrahydrofuran and the polar solvent is water or an alcohol. 
     
     
       3. The process of claim 1 wherein the block copolymer consists of one selectively carboxylated block of styrene and one selectively hydrogenated block of isoprene. 
     
     
       4. A process to prepare an epoxy resin composition, comprising the steps of: emulsifying a block copolymer by addition of a polar solvent to a solution of the block copolymer in a less polar solvent, the block copolymer consisting of one selectively carboxylated block of a monoalkenyl aromatic hydrocarbon connected to one selectively hydrogenated block of a conjugated diene wherein the block copolymer is modified by incorporating one or more carboxylic acid groups selectively into the monoalkenyl aromatic blocks; and   combining the emulsion of the block copolymer with an epoxy resin, wherein the selectively carboxylated block of the block copolymer has sufficient acid groups to prevent agglomeration of the block copolymer in the epoxy resin composition.   
     
     
       5. The process of claim 4 further comprising the step of removing all solvents from the epoxy resin composition to form a solvent-free epoxy resin composition. 
     
     
       6. The process of claim 4 wherein the block copolymer is a carboxylated polystyrene-hydrogenated polyisoprene diblock copolymer having from 4.0 to 10.0 percent by polystyrene weight of acid groups selectively grafted to the polystyrene block. 
     
     
       7. The process of claim 4 wherein the epoxy resin is a polyglycidyl ether of bisphenol A. 
     
     
       8. The process of claim 4 wherein the epoxy resin is a polyglycidyl ether of bisphenol F.