Process to polymerize AB-PBO monomer phosphate salts

Details Process to polymerize AB-PBO monomer phosphate salts Process to polymerize AB-PBO monomer phosphate salts

1990-06-29

1993-05-11

Kight, III, John

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From phenol, phenol ether, or inorganic phenolate

528167, 528176, 528179, 528183, 528184, 528206, 528207, C08G 6300, C08G 6302, C08G 7902

Patent

active

052101711

ABSTRACT:
AB-polybenzoxazole monomer, such as 3-amino-4-hydroxybenzoic acid, can be synthesized in high yields from a hydroxy-benzoic acid or related compound in a three-step process of (1) nitration, (2) hydrolysis of the ester, and (3) reduction of the nitro moiety. The monomer is conveniently recovered as a phosphate salt in high purity by precipitating and recrystallizing from a phosphoric acid solution. The monomer may be polymerized in high concentrations in polyphosphoric acid containing high levels of P.sub.2 O.sub.5 to yield a high molecular weight polymer without dehydrohalogenation.

REFERENCES:
patent: 4772678 (1988-09-01), Sybert
Imai et al., "Polybenzazoles," 83 Makromol. Chem. 179 (1965).
Wolfe, "Polybenzothiazoles and Polybenzoxazoles," 11 Encyclopedia Poly. Sci. & Tech., 601.

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