Finish for glass fabrics used for reinforcing epoxy structures

Abstract

A composition and method for selectively increasing the resin flow and gel time of an epoxy resin that fills the capillary region between filaments in fiberglass yarns making up a woven fabric. The composition and method are used in the lamination of fiberglass reinforced composites such as copper clad laminates for circuit boards and reduces the occurrence of voids in the capillary region.

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         13 . The method of  claim 23  wherein the glass fabric that is used for reinforcing an epoxy resin article is prepared by the steps of: 
 a) providing fabric woven from glass fiber;  
 b) cleaning said fabric to remove sizing and other deposits on the surface of the filaments in the glass fiber;  
 c) preparing a bath for said fabric comprising water and at least one cationic amino-silane coupling agent.  
 d) immersing said cleaned fabric in said bath;  
 e) removing the fabric from the bath and removing excess bath solution;  
 f) drying the fabric;  
 g) immersing the finish and dried fabric in a solution of a weak acid;  
 h) drying the fabric.  
 
     
     
         14 . The method of  claim 16  wherein the bath comprises at least one additional silane coupling agent, namely, a chloro-silane coupling agent and the boric acid is present in the range from about 0.1% to 5% of the combined weight of said coupling agents.  
     
     
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         16 . The method of  claim 13  wherein said weak acid is boric acid.  
     
     
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         23 . In the method of making an epoxy resin article reinforced by multifilament, fiberglass fabric, the improvement which comprises providing a latent catalyst inhibitor on the surfaces of the filaments of the fiberglass fabric.  
     
     
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         26 . An epoxy resin article made by the method of  claim 23  and having a substantially reduced number of voids in the space between filaments in the multifilament fiberglass fabric.  
     
     
         27 . The epoxy resin article of  claim 26  wherein the article is a circuit board.