||||||||||||||| US005208298A United States Patent (19) 11 Patent Number: 5,208,298 Chung et al. (45) Date of Patent: May 4, 1993 (54) STABLE SOLUTION OF POLYBENZMIDAZOLE AND FOREIGN PATENT DOCUMENTS POLYSULFONS BLENDS 0240302 10/1987 European Pat. Off. (75) Inventors: Tai-Shung Chung, Randolph; Arthur 91/04300 4/1991 PCT Int'l Appl. G. Schlask, Roselle Park; Dieter Primary Examiner-Paul R. Michl Kurschus, Bayville, all of N.J. Assistant Examiner-Tae H. Yoon (73) Assignee: Hoechst Celanese Corp., Somerville, Attorney, Agent, or Firm-J. M. Hunter, Jr. N.J. (57) ABSTRACT (21) Appl. No.: 865,386 A stable solution of polybenzinidazole resin containing 22) Filed: Apr. 8, 1992 from approximately 10 to approximately 35 weight 51 Int. Cl. ...................... C08L 77/06; C08L 81/06; percent of resins and from approximately 65 to approxi CO8L 79/04 mately 90 weight percent of a suitable solvent, the resins (52) U.S. C. .................................... 525/435; 524/606; consist of from approximately 70 to approximately 95 524/609, 524/612; 525/540; 525/906 weight percent of polybenzimidazole and from approxi (58) Field of Search ............... 524/606, 609, 612, 720; mately 5 to approximately 30 weight percent of polysul 525/435, 540,906 fone, wherein the solution is substantially free of or ganic salt. The solution is useful for the production of (56) References Cited films, fibers and molded articles exhibiting enhanced U.S. PATENT DOCUMENTS mechanical properties. 3,441,640 4/1969 Santangelo .......................... 524/422 4,340,697 7/1982 Aya et al. ............................ 525/906 20 Claims, 4 Drawing Sheets U.S. Patent May 4, 1993 Sheet 1 of 4 5,208,298 C N C un C. C C C cru cro r to O C () o CO C l d Cad ae - 2. l CP C U. wn Ol m god O O s d. S. s Cd Co Cd Cd ea Co Cd u v ur U.S. Patent May 4, 1993 Sheet 2 of 4 5,208,298 07 08 XWBH8(X)NOIIWONOTE U.S. Patent May 4, 1993 Sheet 3 of 4 5,208,298 0007 0070 w 0G) 06 09 BTISNB1SÍTI??OW(0/6) 5,208,298 1. 2 the Solution, wherein the solution is substantially free of STABLE SOLUTION OF POLYBENZMIDAZOLE organic salt. AND POLYSULFONS BLENDS Another embodiment of the invention is directed to a fiber prepared from a stable solution of polyben FIELD OF THE INVENTION Zinidazole resin solution consisting of from approxi The present invention relates to a stable solution of mately 10 to approximately 35 weight percent of the aromatic polybenzimidazole and polysulfone resins resin and from approximately 65 to approximately 90 which is substantially free of organic salts. The solution weight percent of a suitable solvent, based on the total is useful for the production of films, fibers and molded weight of the solution, the resin component consisting articles. O essentially of from approximately 70 to approximately 95 weight percent of polybenzimidazole resin and from BACKGROUND ART approximately 5 to approximately 30 weight percent of Aromatic polybenzimidazoles are a unique class of polysulfone resin, based on the total weight of the res intractable, i.e., not melt processable, organic polymers ins, wherein the resins solution is substantially free of which are high temperature resistant, as well as chemi 15 organic salts, by the process of: cal and oxidative resistant. Because these polymers are (a) preparing a stable solution of polybenzimidazole not melt processable, it is difficult to form them into resin consisting of from approximately 10 to approxi film, fibers and molded articles. To enhance the melt mately 35 weight percent of resin and from approxi processability, reduce the cost of products made there mately 65 to approximately 90 weight percent of a suit from, and moisture takeup of the finished product, poly able solvent, based on the total weight of the solution, benzimidazole is often blended with a tractable poly the resin consisting of from approximately 70 to approx mer. One useful tractable polymers useful for blending imately 95 weight percent of polybenzimidazole and with polybenzimidazole is aromatic polysulfones. How from approximately 5 to approximately 30 weight per ever, desirable mechanical and thermal properties are significantly reduced by the addition of these melt pro 25 cent of polysulfone, based on the total weight of the cessable polymers; the degree of reduction is usually resins present in the solution, wherein the solution is proportional to the weight percent of the melt process substantially free of organic salts; able polymer addition. Blends of polybenzimidazole (b) fabricating a fiber from the solution under sub and polysulfone are generally prepared by a process stantially moisture-free conditions; known as solution blending. Solution blending involves 30 (c) evaporating the solvent from the fiber; dissolving both polymers in a suitable solvent to form a (d) washing the fiber with a non-solvent; and polybenzimidazole-containing dope. The dope can be (e) drying the fiber at a low temperature utilized to form films or fibers by conventional tech The resins solution is stable for long periods of time, and niques, or the resins blend can be precipitated out of fibers produced from the solution exhibit enhanced solution utilizing a non-solvent. The precipitate can be 35 mechanical and thermal properties which make them dried to form a particulate blend which is useful for useful as flame retardant materials. forming molded articles and the like. BRIEF DESCRIPTION OF THE DRAWINGS When solution of polybenzimidazole and polysulfone in the range of from approximately 1 to approximately While the specification concludes with claims partic 99 weight percent of polybenzimidazole and approxi ularly pointing out and distinctly claiming the present mately 1 to approximately 99 weight percent of polysul invention, it is believed that the present invention will fone are dissolved in a suitable solvent, the polyben be better understood from the following description in zimidazole will separate out of the solution after a short conjunction with the accompanying drawings in which: period of time unless it is stabilized with an organic salt, FIG. 1 is a graph of the viscosities of various weight e.g., lithium chloride. While the addition of a stabilizer 45 ratios of stable solutions containing 21 weight percent has lengthened the time of solution stability, it has re of polybenzimidazole and polysulfone resins dissolved sulted in the adverse effecting the mechanical and ther in N,N'-dimethylacetamide solutions; mal properties of fibers spun from the dope. It has now FIG. 2 is a graph of the break elongation of dry-spun been discovered that solutions of polybenzimidazole fibers prepared from a stable solution containing 80 and polysulfone within the range of approximately 10 to 50 weight percent polybenzimidazole and 20 weight per approximately 35 weight percent of polysulfone and cent polysulfone; approximately 65 to approximately 90 weight percent FIG. 3 is a graph of the tensile modulus of dry-spun of polybenzimidazole which are substantially free of fibers prepared from a stable solution containing 80 organic salts are stable for long periods of time without weight percent polybenzimidazole and 20 weight per phase separation. Fibers produced from the solution 55 cent polysulfone; and exhibit enhanced mechanical and thermal properties. FIG. 4 is a graphical representation of the tensile strength of dry-spun fibers prepared from a stable solu SUMMARY OF THE INVENTION tion containing 80 weight percent polybenzimidazole The present invention is directed to a stable solution and 20 weight percent polysulfone. of polybenzimidazole resin consisting of from approxi mately 10 to approximately 35 weight percent of resin DETAILED DESCRIPTION OF THE and from approximately 65 to approximately 90 weight INVENTION percent of a suitable solvent, based on the total weight Generally, the aromatic polybenzimidazole useful in of the solution, the resin component consisting of from the present invention may be any polybenzimidazole approximately 70 to approximately 95 weight percent 65 resins known to those skilled in the art. Typical poly of polybenzimidazole (PBI) and from approximately 5 mers of this class and their preparation are more fully to approximately 30 weight percent of polysulfone described in U.S. Pat. No. 2,895,946; U.S. Pat. No. (PS), based on the total weight of the resins present in 26,065; and the Journal of Polymer Science, Vol. 50, 5,208,298 3 4. pages 511-539 (1961), which are herein incorporated by poly-2,2'-(m-phenylene)-5,5'-dicbenzimidazole) sul reference in their entirety. These polybenzinidazoles fone; consist essentially of recurring units of the Formulae I poly-2,2'-(m-phenylene)-5,5'-di(benzimidazole) meth and II: ane; Formula I is: poly-2,2'-(m phenylene)-5',5'-di(benzimidazole) propane-2,2; and poly-2,2'-(m-phenylene)-5,5'-di(benzimidazole) ethylene-1,2; where the double bonds of the ethylene groups are O intact in the final polymer. A preferred polybenzirpidazole for use in the present invention is poly-2,2'-(n-phenylene)-5,5'-biben wherein Ari represents a tetravalent aromatic moiety zimidazole, the recurring unit of which is: having the formula: 15 N N A. W C C V / 20 N H h Processes for preparing the aromatic polyben IOOL 25 Zimidazoles of the invention are described in U.S. Pat. Nos. 3,441,640; 3,433,772; 3,509,108; 3,549,603; wherein R1 is O, SO2, CH-CH, C(CF3)2 or (CH2) and 3,526,693; 3,552,389; 3,619,453; 3,671,491; 3,969,430; wherein x is an integer of from 1 to 4; and Ar2 represents and 4,020,142 all of which are herein incorporated by a divalent aromatic moiety having the formula: reference in their entirety.