Claims
- 1. A method for preparing an aromatic benzoxazole polymer having repeating units of the formula ##STR7## wherein Ar is ##STR8## wherein R is an alkyl group having 8 to 12 carbon atoms, which comprises reacting 4,4'-hexafluoroisopropylidene bis-(2-aminophenol) with an aromatic dicarboxylic acid selected from the group consisting of isophthalic acid, terephthalic acid, 2,5-pyridine dicarboxylic acid, 2,6-pyridine dicarboxylic acid and a 2,5-bis(alkoxy) terephthalic acid of the formula ##STR9## wherein R is an alkyl group having 8 to 12 carbon atoms, under reaction conditions in a reaction medium consisting essentially of a halogenated hydrocarbon solvent and a dehydrating agent, and recovering said polymer.
- 2. The method of claim 1 wherein said solvent is o-dichlorobenzene.
- 3. The method of claim 1 wherein said dehydrating agent is trimethylsilyl polyphosphate.
- 4. The method of claim 1 wherein said reaction is carried out at a temperature of about 150.degree. to 225.degree. C. for about 10 to 100 hours.
- 5. The method of claim 4 wherein said dicarboxylic acid is 2,5-bis(oxy-n-decyl) terephthalic acid, wherein said solvent is o-dichlorobenzene, wherein said dehydrating agent is trimethylsilyl polyphosphate, and wherein said reaction conditions are 160.degree. C. for 48 hours followed by 185.degree. C. for 24 hours.
- 6. The method of claim 4 wherein said dicarboxylic acid is isophthalic acid, wherein said solvent is o-dichlorobenzene, wherein said dehydrating agent is trimethylsilyl polyphosphate, and wherein said reaction conditions are 160.degree. C. for 24 hours followed by 185.degree. C. for 24 hours.
- 7. The method of claim 4 wherein said dicarboxylic acid is terephthalic acid, wherein said solvent is o-dichlorobenzene, wherein said dehydrating agent is trimethylsilyl polyphosphate, and wherein said reaction conditions are 160.degree. C. for 24 hours followed by 185.degree. C. for 24 hours.
- 8. The method of claim 4 wherein said dicarboxylic acid is 2,5-pyridine dicarboxylic acid, wherein said solvent is o-dichlorobenzene, wherein said dehydrating agent is trimethylsilyl polyphosphate, and wherein said reaction conditions are 160.degree. C. for 24 hours followed by 185.degree. C. for 24 hours.
- 9. The method of claim 4 wherein said dicarboxylic acid is 2,6-pyridine dicarboxylic acid, wherein said solvent is o-dichlorobenzene, wherein said dehydrating agent is trimethylsilyl polyphosphate, and wherein said reaction conditions are 160.degree. C. for 24 hours followed by 185.degree. C. for 24 hours.
RIGHTS OF THE GOVERNMENT
The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the Payment of any royalty.
This invention relates to thermoplastic aromatic benzoxazole Polymers and to a method for synthesizing these polymers.
In recent years, there has been considerable interest in the utilization of thermoplastics as matrices in fiber reinforced composites. Thermoplastic matrices offer the possibility of lower fabrication costs of advanced structures, as compared to thermosetting resins. Such cost reductions are possible because, in general, faster and less expensive manufacturing procedures can be employed when using thermoplastic materials. In the past, one major drawback to the use of high performance thermoplastics as matrix resins has been the very high temperatures required for fabrication due to the high glass transition temperatures of these materials.
Aromatic benzoxazole polymers are excellent candidates for use in high temperature applications due to their excellent thermooxidative stability. These materials have, however, received minimal consideration as thermoplastic materials, generally, or as thermoplastic matrices, specifically, due to their relatively high glass transition temperatures. Such high glass transition temperatures make fabrication without degradation of the polymer extremely difficult.
Accordingly, it is an object of the present invention to provide aromatic benzoxazole polymers having relatively low glass transition temperatures.
It is another object of this invention to provide a method for preparing these polymers.
Other objects and advantages of the present invention will be apparent to those skilled in the art.
In accordance with the present invention, there is provided an aromatic benzoxazole polymer having repeating units of the formula ##STR4## wherein Ar is ##STR5## wherein R is an alkyl group having 8 to 12 carbon atoms.
The polymers of this invention are prepared by the polycondensation of 4,4'-hexafluoroisopropylidene bis-(2-aminophenol) with a dicarboxylic acid selected from the group consisting of isophthalic acid, terephthalic acid, 2,5-pyridine dicarboxylic acid, 2,6-pyridine dicarboxylic acid and a 2,5-bis(alkoxy) terephthalic acid of the formula ##STR6## wherein R is an alkyl group having 8 to 12 carbon atoms, in a suitable reaction medium containing a suitable dehydrating agent.
The 2,5-bis(alkoxy) terephthalic acid may be prepared as described in Reinhardt and Unroe, application Serial No. 07/241,646, filed of even date, now U.S. Pat. No. 4,871,712 which is incorporated by reference.
The polycondensation reaction is carried out in a halogenated hydrocarbon which is a solvent for the monomers. Suitable solvents include dichlorobenzene, tolylchloride, dichlorotoluene, trichlorobenzene and the like. Suitable dehydrating agents include P.sub.2 O.sub.5, POCl.sub.3, PCl.sub.5, trifluoroacetic anhydride-pyridine, trimethylsilyl polyphosphate (PPSE) and thionyl chloride. The presently preferred reaction medium is o-dichlorobenzene together with a non-acidic dehydrating agent, preferably trimethylsilyl polyphosphate (PPSE).
The polycondensation reaction is carried out at a temperature of about 150.degree. C. to 225.degree. C. for about 10 to 100 hours. It is convenient to employ a stepped heating schedule, e.g. about 150.degree. C. to 180.degree. C. for about 10 to 60 hours followed by about 170.degree. C. to 225.degree. C. for about 10 to 36 hours.
At the end of the reaction period, the reaction mixture is cooled to about room temperature. The polymer may then be recovered from the reaction mixture by any conventional technique, such as by pouring the reaction mixture into a non-solvent for the polymer, such as methanol.
The polymers of the present invention are useful as matrix materials in fiber reinforced composites and as hosts for molecular composites.
US Referenced Citations (1)
| Number |
Name |
Date |
Kind |
| 4820793 |
Imai et al. |
Apr 1989 |
|
Foreign Referenced Citations (2)
| Number |
Date |
Country |
| 3707125 |
Oct 1987 |
DEX |
| 26876 |
Dec 1967 |
JPX |
Patent Grant
4931532
