Solvent free low-melt viscosity imide oligomers and thermosetting polymide composites

Abstract

This invention relates to the composition and a solvent-free process for preparing novel imide oligomers and polymers specifically formulated with effective amounts of a dianhydride such as 2,3,3′,4-biphenyltetra carboxylic dianydride (a-BPDA), at least one aromatic diamine and an endcapped of 4-phenylethynylphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260-280° C. When the imide oligomer melt is cured at about 371° C. in a press or autoclave under 100-500 psi, the melt resulted in a thermoset polyimide having a glass transition temperature (T g ) equal to and above 310° C. A novel feature of this process is that the monomers; namely the dianhydrides, diamines and the endcaps, are melt processable to form imide oligomers at temperatures ranging between 232-280° C. (450-535° F.) without any solvent. These low-melt imide oligomers can be easily processed by resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM) or the resin infusion process with fiber preforms e.g. carbon, glass or quartz preforms to produce polyimide matrix composites with 288-343° C. (550-650° F.) high temperature performance capability. This invention relates to compositions and a solvent-free reaction process for preparing imide oligomers and polymers specifically derived from effective amounts of dianhydrides such as 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA), at least one aromatic polyamine and an end-cap such as 4-phenylethynyphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260° C.-280° C.

1. Process for preparing low-melt viscosity imide oligomers derived from a solvent-free reaction of stoichiometric effective amounts of at least one asymmetric dianhydride having the formula: 
       
         
           
           
               
               
           
         
       
       wherein X is selected from the group consisting of nil, C═O, —CH 2  and oxygen, and at least one aromatic diamine having the formula: 
       
         
           
           
               
               
           
         
       
       wherein Y is a aromatic radical selected from the group to consisting of 
       
         
           
           
               
               
           
         
       
       and an endcap selected from the group consisting of 4-phenylethynylphthalic anhydride and cis-5-norbornene-endo-2,3-dicarboxylic anhydride. 
     
     
       2. The process of  claim 1  wherein effective amounts of an additive selected from the group consisting of 4-phenylethynyldiphenyl methane and diphenylacetylene is added to the solvent-free reaction. 
     
     
       3. The solvent-free reaction process of  claim 2  wherein the reaction temperature ranges from about 232°-280° C. 
     
     
       4. The solvent-free reaction process of  claim 1  wherein at least one of the dianhydrides is 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       5. The solvent-free reaction process of  claim 1  wherein at least one of the dianhydrides is 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       6. The solvent-free reaction process of  claim 1  wherein at least one of the dianhydrides is 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       7. The solvent-free reaction process of  claim 1  wherein the Y radical of the diamine has the formula: 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       8. The solvent-free reaction process of  claim 1  wherein the Y radical of the diamine has the formula: 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       9. The solvent-free reaction process of  claim 1  wherein the Y radical of the diamine has the formula: 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       10. The solvent-free reaction process of  claim 1  wherein the Y radical of the diamine has the formula: 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       11. The solvent-free reaction process of  claim 1  wherein the Y radical of the diamine has the formula: 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       12. The solvent-free reaction process of  claim 1  wherein the Y radical of the diamine has the formula: 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       13. The solvent-free reaction process of  claim 1  wherein the endcap is 4-phenylethynylphthalic anhydride. 
     
     
       14. The solvent-free reaction process of  claim 1  wherein the endcap is cis-5-norbornene-endo-2,3-dicarboxylic anhydride. 
     
     
       15. The solvent-free reaction process of  claim 13  wherein the reaction temperatures range from about 232° C. to 280° C. to obtain imidize oligomers having a low-melt viscosity of about 1-60 poises at 260°-280° C., and a cure glass-transition temperature of about 310°-380° C. 
     
     
       16. The thermosetting imidized resins or  claim 15  cured with a fiber preform at temperatures ranging from about 650° to 700° F. to obtain thermosetting polyimide matrix-composites having a T g  ranging from about 310°-380° C. 
     
     
       17. The thermosetting polyimide matrix composites of  claim 16  wherein the fiber preform is carbon, glass, or a synthetic fiber preform. 
     
     
       18. The imide oligomers obtained by the solvent-free process of  claim 1  cured by resin-transfer molding at temperatures ranging from about 650° to 700° F., to obtain thermosetting polyimides having a T g  ranging from about 310°-380° C. 
     
     
       19. Imide oligomers obtained by the solvent-free process of  claim 1  cured at temperatures ranging from about 650° to 700° F. to obtain thermosetting polyimides having a T g  ranging from about 310°-380° C. 
     
     
       20. Imide oligomers obtained by the solvent-free process of  claim 1 . 
     
     
       21. A process for preparing low-melt viscosity imide oligomers which comprises reacting in a solvent-free media at temperatures ranging from about 232° C. to 270° C. an effective amount of an asymmetric dianhydride having the formula: 
       
         
           
           
               
               
           
         
       
       wherein X is selected from the group consisting of nil, C═O, —CH 2  and oxygen, and at least one diamine having a formula selected from the group consisting of: 
       
         
           
           
               
               
           
         
       
       and 
       
         
           
           
               
               
           
         
       
       wherein the Y radicals are either the same or different and are selected from the group consisting of nil, CH 2 , C 2 H 4 , C═O, and oxygen, and a reactive end-cap selected from the group consisting of 4-phenylethynylphthalic anhydride and cis-5-norbornene-endo-2,3-dicarboxylic anhydride. 
     
     
       22. The process of claim 21 wherein the Y radical of at least one of the diamines is C═O. 
     
     
       23. The process of claim 21 wherein the diamines comprise three rings and the reactive end-cap is selected from the group consisting of 4-phenylethynylphthalic anhydride and cis-5-norbornene-endo-2,3-dicarboxylic anhydride. 
     
     
       24. The process of claim 21, further comprising subsequently curing said oligomers at temperatures of about 700° F. to obtain thermosetting polyimide resins having a T g  greater than 330° C. 
     
     
       25. The process of claim 21 wherein the end-cap is 4-phenylethynylphthalic anhydride. 
     
     
       26. The process of claim 21 wherein the end-cap is cis-5-norbornene-endo-2,3-dicarboxylic anhydride. 
     
     
       27. The process of claim 21 wherein said imide oligomers exhibit a low-melt viscosity of about 1-60 poise at 260° C.-280° C. 
     
     
       28. The process of claim 21, further comprising curing said oligomers with fibers at temperatures ranging from about 260° C.-280° C. to obtain thermosetting polyimide-matrix composites. 
     
     
       29. The process of claim 28 wherein the fibers are selected from the group consisting of carbon, glass, quartz and synthetic fibers. 
     
     
       30. Imide oligomers obtained by the process of claim 21. 
     
     
       31. A thermosetting polyimide resin obtained by the process of claim 24. 
     
     
       32. A thermosetting polyimide-matrix composite obtained by the process of claim 28. 
     
     
       33. A thermosetting polyimide-matrix composite obtained by the process of claim 29. 
     
     
       34. Imide oligomers obtained by the process of claim 21, wherein said oligomers exhibit a low-melt viscosity of about 1-60 poise at 260° C.-280° C.