Latent hardener, process for producing the same, and adhesive containing latent hardener

Abstract

A latent curing agent ( 30 ) of the present invention includes a core member ( 31 ) and a capsule ( 37 ) covering up the surface of the core member ( 31 ). The core member ( 31 ) includes a secondary particle ( 32 ) and a curing agent ( 35 ) retained in a gap ( 38 ) of the secondary particle ( 32 ). The curing agent ( 35 ) is liquid at ambient temperature. When the capsule ( 37 ) is destructed so that the curing agent ( 35 ) is emitted into an adhesive, the curing agent ( 35 ) is mixed with other ingredients in the adhesive. A metal alcoholate which is liquid at ambient temperature or a metal chelate which is liquid at ambient temperature is used as the curing agent ( 35 ), while a silane coupling agent is added to the adhesive. A reaction takes place between the curing agent ( 35 ) and the silane coupling agent to yield cations. By these cations, the epoxy resin undergoes cation in polymerization. Since the cation generating reaction proceeds at a temperature lower than in the case of the conventional adhesive, curing proceeds more promptly and at a lower temperature than in the case of the conventional adhesive.

1 . A latent curing agent comprising a core member containing a curing agent, and a capsule which covers up said core member, said curing agent being emitted to outside from said core member on destruction of said capsule, wherein said core member has a plurality of particles and said curing agent is retained between gaps of said particles.  
     
     
         2 . The latent curing agent according to  claim 1  wherein said plural particles coalesce together to form a secondary particle.  
     
     
         3 . The latent curing agent according to  claim 2  wherein the average particle size of each particle making up the secondary particle is equal to or greater than 0.1 μm and equal to or less than 1.0 μm; and 
 wherein the average particle size of said secondary particle is equal to or greater than 1 μm and equal to or less than 20 μm.    
     
     
         4 . The latent curing agent according to  claim 1  wherein the particle forming said secondary particle is a resin particle.  
     
     
         5 . The latent curing agent according to  claim 4  wherein the resin making up the resin particles is a urea formalin resin.  
     
     
         6 . The latent curing agent according to  claim 1  wherein the weight of the curing agent retained in said capsule is equal to or greater than 15 wt % of the weight of said secondary particle.  
     
     
         7 . The latent curing agent according to  claim 1  wherein the curing agent is one or both of a metal chelate and a metal alcoholate.  
     
     
         8 . The latent curing agent according to  claim 7  wherein the metal chelate is one or both of an aluminum chelate or a titanium chelate.  
     
     
         9 . The latent curing agent according to  claim 8  wherein the metal alcoholate is formed of one or both of an aluminum alcoholate and a titanium alcoholate as main ingredient.  
     
     
         10 . A latent curing agent comprising a core member containing a curing agent, and a capsule which covers up said core member, said curing agent being emitted to outside from said core member on destruction of said capsule, wherein said core member has a porous particle and said curing agent is retained in said porous particle.  
     
     
         11 . The latent curing agent according to  claim 10  wherein said porous particle is formed of zeolite.  
     
     
         12 . The latent curing agent according to  claim 10  wherein the weight of said curing agent retained in said capsule is equal to or greater than 15 wt % of the weight of said porous particle.  
     
     
         13 . The latent curing agent according to  claim 10  wherein the curing agent is one or both of a metal chelate and a metal alcoholate.  
     
     
         14 . The latent curing agent according to  claim 13  wherein the metal chelate is one or both of an aluminum chelate and a titanium chelate.  
     
     
         15 . The latent curing agent according to  claim 14  wherein the metal alcoholate is formed of one or both of an aluminum alcoholate and a titanium alcoholate as main ingredient.  
     
     
         16 . A method for the preparation of a latent curing agent comprising: 
 a mixing step of mixing a carrier having a gap in its inner structure and a liquid curing agent to form a core member made up by said carrier and said curing agent retained in said carrier;    a depositing step of mixing said core member and a capsule resin particle to cause the capsule resin particle to be deposited on the surface of said core member; and    a fusing step of fusing said capsule resin particle, deposited to said core member, to form a capsule covering up the surface of said core member.    
     
     
         17 . The method for the preparation of a latent curing agent according to  claim 16  wherein said carrier is rinsed after said mixing step.  
     
     
         18 . The method for the preparation of a latent curing agent according to  claim 16  wherein said fusing step is carried out by stirring the core member to which is affixed said capsule resin particle.  
     
     
         19 . An adhesive comprising: 
 a thermosetting resin;    a silane coupling agent; and    a latent curing agent including a core member containing a curing agent, and a capsule which covers up said core member, said curing agent being emitted to outside from said core member on destruction of said capsule, said core member having a plurality of particles and said curing agent is retained between gaps of said particles.    
     
     
         20 . An adhesive comprising: 
 a thermosetting resin;    a silane coupling agent; and    a latent curing agent including a core member containing a curing agent and a capsule which covers up said core member, said curing agent being emitted to outside from said core member on destruction of said capsule, said core member having a porous particle and said curing agent is retained in said porous particle.