Thixotropic cyanoacrylate compositions

Abstract

Cyanoacrylate compositions which employ fumed silicas treated with polydimethylsiloxane or trialkoxyalkylsilane are stable and exhibit an unexpectedly high thixotropic ratio. Such compositions are useful in adhesive applications or, when stabilized so as to prevent polymerizaton in contact with moisture, in latent fingerprint developing applications.

I claim: 
     
       1. In a composition comprising an α-cyanoacrylate ester monomer and a thixotropic agent, the improvement comprising that said composition is a non-flowable gel, said thixotropic agent is present in an amount of 12% or less and is a fumed silica having a surface treated with a trialkoxyalkylsilane and the said composition has a 2.5 RPM Brookfield viscosity of about 1×10 5  or greater. 
     
     
       2. A composition as in claim 1 wherein the silica surface is treated with trimethoxyoctysilane. 
     
     
       3. A composition as in claim 1 comprising an organic polymer dissolved in said monomer. 
     
     
       4. A composition as in claim 3 wherein said polymer is selected from polyvinyl acetate polymers and copolymers, polyacrylates, polymethacrylates and polycyanoacrylates. 
     
     
       5. A composition as in claim 1 stabilized so as to be nonpolymerizable on contact with moisture. 
     
     
       6. A composition as in claim 3 wherein said polymer is present at levels of between 1 and 15% by weight. 
     
     
       7. A composition as in claim 6 wherein said polymer is present at levels of between 3 and 10% by weight. 
     
     
       8. A composition as in claim 7 wherein said polymer is polymethylmethacrylate. 
     
     
       9. A composition as in claim 1 wherein said silica is present in an amount between about 4 and 8% by weight. 
     
     
       10. A composition as in claim 9 wherein said silica is present in an amount of about 6% by weight. .Iadd. 
     
     
       11.  A composition as in claim 1 wherein the composition viscosity is about 1×10 5 . .Iaddend. .Iadd.12. A composition comprising: an α-cyanoacrylate ester monomer; between 1 and 15% of a polymeric thickener; and   an amount less than 12% by weight of the composition of a trimethoxyoctylsilane treated fumed silica effective to form a thixotropic gel. .Iaddend. .Iadd.13. A composition comprising:   an α-cyanoacrylate ester monomer;   between 1 and 15% of a polymeric thickener; and   an amount in the range of about 4%-8% by weight of the composition of a trimethoxyoctylsilane treated silica, said amount of silica effective to form a thixotropic gel. .Iaddend. .Iadd.14. A composition comprising:   an α-cyanoacrylate ester monomer;   between 1 and 15% of a polymeric thickener; and   a trimethoxyoctylsilane treated silica having a surface area of about 150 m 2  /gm in an amount, less than 12% by weight of the composition, effective to form a thixotropic gel. .Iaddend. .Iadd.15. A composition as in claim 12 wherein the polymeric thickener is polymethylmethacrylate. .Iaddend. .Iadd.16. A composition as in claim 13 wherein said polymeric thickener is polymethylmethacrylate and is present in the range of about   
     
     
        3%-10%. .Iaddend. .Iadd.17.  A composition as in claim 16 wherein the monomer is methyl or ethyl cyanoacrylate. .Iaddend. .Iadd.18. A composition consisting essentially of: methyl or ethyl cyanoacrylate;   between 1 and 15% by weight of the composition of polymethylmethacrylate; and   about 4-8% by weight of the composition of a trimethoxyoctylsilane treated silica. .Iaddend. .Iadd.19. A composition as in claim 18 which also includes a polymerization stabilizer. .Iaddend.