Epoxy adhesive having improved impact resistance

Abstract

In the preparation of an improved adhesive composition, a first reaction product is prepared by the reaction at an elevated temperature of a) 30 to 50 wt-% of an epoxy resin, solid at room temperature, which was prepared from bisphenol A and/or bisphenol F and epichlorohydrin with an epoxide equivalent weight of 400 to 700, b) 10 to 25 wt-% of an epoxy resin, liquid at room temperature, prepared from bisphenol A and/or bisphenol F and epichlorohydrin with an epoxide equivalent weight of 150 to 220, c) 35 to 50 wt-% amino-terminated polyethylene and/or polypropylene glycols and d) a carboxyl-terminated butadiene-nitrile rubber. The first reaction product is mixed with an acrylate terminated urethane resin, glass microspheres, expandable hollow plastic microspheres and a latent curing agent to make an adhesive composition which is pumpable at room temperature and capable of expansion to about 100% with high impact resistance after curing.

What is claimed is:  
     
         1 . A curable adhesive which comprises: 
 A) a prepolymer reaction mixture of 
 (a) epoxy resin or resins prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 150 to about 700;and  
 (b) an amino-terminated polyalkylene glycol, or a carboxyl terminated butadiene nitrile resin, or mixtures thereof;  
   B) an acrylate terminated urethane resin; and    C) a latent curing agent.    
     
     
         2 . A curable adhesive of  claim 1  which comprises an expanding agent to expand the adhesive during curing.  
     
     
         3 . A curable adhesive of  claim 2  wherein the expanding agent comprises expanded or expandable hollow plastic microspheres.  
     
     
         4 . A curable adhesive of  claim 1  in which the acrylate-terminated urethane resin comprises the reaction product of an isocyanate terminated urethane prepolymer and an isocyanate reactive acrylate or methacrylate.  
     
     
         5 . A curable adhesive of  claim 4  in which the isocyanate terminated prepolymer is prepared by reacting a polyfunctional isocyanate with a polyol.  
     
     
         6 . A curable adhesive of  claim 5  in which the polyfunctional isocyanate is an aromatic diisocyanate.  
     
     
         7 . The curable adhesive of  claim 5  in which the number average molecular weight of the polyol is from about 400 to about 4000.  
     
     
         8 . The curable adhesive of  claim 5  in which the number average molecular weight of the polyol is from about 700 to about 2000.  
     
     
         9 . The curable adhesive of  claim 4  in which the isocyanate terminated urethane prepolymer is prepared by reacting polypropylene glycol or polytetramethylene glycol and an isocyanate selected from the group consisting of 2,4 toluenediisocyanate, 2,6-toluenediisocyanate, 2,6 -toluenediisocyanate, 2,4 -toluenediisocyanate, methylenediphenyldiisocyanate, isophoronediisocyanate, hexamethylenediisocyanate, paraphenylenediisocyanate and mixtures thereof.  
     
     
         10 . The curable adhesive of  claim 4  in which the isocyanate reactive acrylates and methacrylates are selected from the group consisting of hydroxy alkylacrylates and hydroxyalkyl methacrylates.  
     
     
         11 . The curable adhesive of  claim 4  in which the isocyanate reactive acrylate or methacrylate is derived from a C 2 -C 8  alcohol.  
     
     
         12 . A curable adhesive composition comprising :a pre-reacted reaction product of 
 A) a pre-reacted reaction product of 
 (a) about 0.5 to about 1 equivalent of an epoxy resin which is solid at room temperature prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 400 to about 700;  
 (b) about 0.5 to about 1 equivalent of an epoxy resin which is liquid at room temperature prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 150 to about 220; and  
 (c) about 0.125 to about 0.5 equivalent of an amino-terminated polyalkylene glycol selected from the group consisting of polyethylene and polypropylene glycols; wherein said epoxy resins (a) and (b) are present in an amount such that a stoichiometric excess of at least 1 equivalent of epoxy groups over the amino groups is provided, said amino-terminated polyalkylene glycol comprising 
 i) a linear amino-terminated polyethylene glycol, or  
 ii) a linear amino-terminated polypropylene glycol, or,  
 iii) a linear amino-terminated polyethylene glycol and a trifunctional amino-terminated polypropylene glycol;  
 
 wherein about 4 to about 40% of the epoxy equivalents of the total epoxy resin component are replaced by an adduct of dimeric fatty acides on epoxy resins prepared from diglycidyl ethers of bisphenol A or F, or by an adduct of carboxyl-terminated butadiene-nitrile rubber on epoxy resins prepared from diglycidyl ethers of bisphenol A or F;  
   B) an acrylate terminated urethane resin which comprises the reaction product of an isocyanate terminated urethane prepolymer and an isocyanate reactive acrylate or methacrylate;    C) a latent curing agent; and    D) an expanding agent comprising hollow plastic microspheres.    
     
     
         13 . A curable adhesive composition which comprises: 
 A) a reaction product of a polyepoxide resin having at least two 1,2-epoxy groups per molecule with polyoxy alkylene amine and, optionally, an adduct of carboxy terminated butadiene-nitrile rubber (BNR);    B) an acrylate terminated urethane resin; and    C) a latent curing agent.    
     
     
         14 . A curable adhesive which comprises: 
 A) a prepolymer reaction mixture of 
 (a) an epoxy resin, an epoxy resin which is solid at room temperature prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 400 to about 700;  
 (b) an epoxy resin which is liquid at room temperature prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 150 to about 220; and  
 (c) an amino-terminated polyalkylene glycol selected from the group consisting of polyethylene and polypropylene glycols, or a carboxyl terminated butadienenitrile resin, or mixtures thereof;  
   B) an acrylate-terminated urethane resin;    C) a latent curing agent; and    D) an expanding agent comprising hollow microspheres.    
     
     
         15 . A method of making a composite article which comprises: contacting a surface with a curable adhesive which comprises: 
 A) a prepolymer reaction mixture of 
 (a) epoxy resin or resins prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 150 to about 700;  
 (b) an amino-terminated polyalkylene glycol selected from the group consisting of polyethylene and polypropylene glycols, or a carboxyl terminated butadiene nitrile resin, or mixtures thereof,  
   B) an acrylate-terminated urethane resin; and    C) a latent curing agent; and curing the adhesive in contact with the surface to prepare a composite article.    
     
     
         16 . The method of  claim 15  in which the surface is metal or plastic.  
     
     
         17 . The method of  claim 15  in which at least two surfaces are contacted with the curable adhesive and cured in contact therewith.  
     
     
         18 . The method of  claim 15  in which the curable adhesive is flowed into contact with the surface at a temperature between about 10 and about 50 degrees C.  
     
     
         19 . The method of  claim 15  in which the curable adhesive is flowed into contact with the surface at a temperature between about 20 and about 40 degrees C.  
     
     
         20 . The method of  claim 15  in which the curable adhesive contains hollow plastic microspheres.