Method and product for improved ceramic fiber reinforced and filled thermoplastic and thermosetting resin systems
BACKGROUND OF THE INVENTION 
     The present invention relates to an improved method and product for creating fiber reinforced and/or filled thermoplastic and/or thermosetting resin systems. More particularly, the present invention is directed to such resin systems which are usable in higher temperature applications. 
     Glass fiber reinforced resin systems are widely used today for everything from boat hulls, automobile bodies, toys, sliding boards and the like. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved product and method of manufacturing a resin system which may be utilized in high temperature applications in everything from porcelain veneers and replacement teeth in dentistry to components used in connection with combustion engines. The present invention provides improved temperature characteristics for all types of industrial uses of reinforced resin systems. 
     Briefly, in accordance with the present invention, a method and product are disclosed for providing improved ceramic fiber reinforced and filled thermoplastic and thermosetting resin systems, wherein the ceramic fiber material is first etched with hydrofluoric acid, acidulated phosphate fluoride or other suitable etchant to produce a roughened surface on the ceramic fiber material which promotes adhesion. Such roughened surface of the ceramic fiber provides improved bonding for additional strength. The etched ceramic fiber material, which may take various forms, is then silanated with a silane coupling agent and utilized in the production of a reinforced resin system which may be utilized in high temperature applications. 
     The term ceramic fiber is defined and used herein broadly to include various high temperature glassy type fibers which may be made from pure or substantially pure silica, various silicates, metal oxides and various other fibers provided with a coating or treatment of silica on their surface. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to a method and product for improved ceramic fiber reinforced and filled thermoplastic and thermosetting resin systems, wherein the ceramic fiber material is first etched to produce a roughened surface on the ceramic fiber material. In other words, the etching produces microporosities in the surface of the ceramic material. In the presently preferred embodiments of the invention, the ceramic fiber material is etched with either hydrofluoric acid or 1.23% acidulated phosphate fluoride (or other suitable percentage). However, it is understood that other etchants, such as hot phosphoric acid, may be utilized which function in the same way to produce the same result. 
     The ceramic fiber material may be woven, braided or knitted cloth, uniform or random mesh, rope, thread or any other material made of ceramic fibers. The resins may be any of the various thermoplastic or thermosetting resins. However, in view of the particular application, wherein the ceramic reinforced resin system may be utilized in higher temperature settings, the resin should be selected to have suitable temperature characteristics. 
     The etched ceramic fiber material is then silanated with an organo-functional silane. Some examples of organo-functional silanes are vinyltrichlorosilane, vinyltriethoxy-silane, vinyl-tris(beta-methoxyethoxy)silane, gamma-MethacryloxyPropyltrimethyoxysilane, beta-(3,4-Epoxycyclohexyl)-ethyltrimethoxysilane, gamma-Glycidoxypropyltrimethoxysilane, gamma-Aminopropyltriethoxysilane, and N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane. However, it is understood that other silane coupling agents may be used in practicing the present invention. 
     The organo-functional silanes act as coupling agents between the ceramic fiber material and the composite resin. A chemical bridge between the coupling agents and the ceramic substrates requires both a reactive silane and a reactive site on the ceramic surface. The number and arrangement of the reactive sites on the ceramic surface is increased by the etching process described herein. 
     Any suitable ceramic fiber material may be utilized in practicing the invention. The term &#34;ceramic fibers&#34; is used herein throughout broadly to cover all fibers which are referred to as ceramic fibers. These include, but are not limited to, fibers made from substantially pure or pure silica, various silicates, metal oxides and other fibers, such as carbon, which are coated or provided with a silica treatment on their surface. Some examples of ceramic fibers which may be utilized in the practicing of the present invention include aluminosilicate fibers and zirconia fibers. Such fibers are commercially available from Imperial Chemical Industries, Ltd. (&#34;ICI&#34;) of Wilmington, Del. Other ceramic fibers which are currently available include high grade ceramic fibers sold under the trademark Nextel™ by 3M Corporation. One example of the composition of Nextel™ fibers is, by weight, 62% aluminum oxide (Al 2  O 3 ), 14% boron oxide (B 2  O 3 ) and 24% silicon dioxide (SiO 2 ). Another example of ceramic fibers usable in practicing the present invention are those sold by JPS Glass Fabrics, a division of JPS Converter and Industrial Corporation of Slater, South Carolina, under the trademark Astroquartz™. The Astroquartz™ ceramic fibers are comprised of substantially pure silica (99.5% SiO 2 ). These are sometimes referred to as quartz fibers. An example of a fiber treated with silica on its surface is a carbon fiber treated with silica on its surface and sold under the trademark Nicalon™ commercially available from Nippon Carbon Co. of Japan, that is, it has a surface of ceramic material and a core of a different material. 
     In accordance with the present invention, a product and the method of providing improved ceramic fiber reinforced and filled resin systems are disclosed. The etched and silanated ceramic fiber may utilized in thermoplastic or thermosetting resins. The ceramic fiber material, whether it is in the form of a cloth, mesh, rope, thread or the like, is first etched to roughen its surface, which roughening may be observed under a microscope and may be described as microporosities. The etching may be performed using either hydrofluoric acid, 1.23% acidulated phosphate fluoride or any other suitable etchant. Any suitable silane coupling agent and particularly the organo-functional silanes may be utilized, and these include vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris(beta-methoxyethoxy)silane, gamma-methacryloxypropyltrimethoxysilane, beta-(3,4-Epoxycyclohexyl)-ethyltrimethoxysilane, gamma-Glycidoxypropyltrimethoxysilane, gamma-Aminopropyltriethoxysilane, and N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane. 
     In a preferred embodiment, it is contemplated that the product of the ceramic fiber material may be provided in pre-etched form. That is, ceramic fiber woven material, mesh, rope or thread may be first treated with hydrofluoric acid and sold in that form for use in the production of an etched silanated ceramic fiber reinforced product. The ceramic fiber may be pre-etched and pre-silanated as sold. 
     The product and/or method of the present invention have wide application in various areas of industry, medicine and dentistry. The present invention may be used in any application of a fiber reinforced resin system, and is particularly useful where the reinforced resin system may be subjected to temperatures in excess of those appropriate for a fiberglass reinforced resin system. These include various components and parts in manufacturing processes, combustion engines, aerospace and various other applications. 
     In addition, the product and/or method of the present invention have specific application in the field of prosthetic dentistry, and more particularly, in the field of restorative and splinting operations in the field of dentistry using various reinforced resin systems. Attention is directed to my previously issued patent, U.S. Pat. No. 5,098,304, regarding the use in dentistry of composite resin reinforced systems, the subject matter of which is incorporated herein by reference the same as if set forth at length. Since reinforced resin systems made in accordance with the present invention may be heated to well in excess of one thousand degrees Fahrenheit, porcelain replacement teeth, which are required to be fired in ovens, may be formed utilizing the ceramic fiber reinforced resin systems of the present invention. 
     In view of the above, the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.