A significant improvement in a process to produce epichlorohydrin through the use of glycerin as renewable feedstock is presented. The glycerin to epichlorohydrin (GTE) process proceeds in two chemical steps. In the first step, glycerin is hydrochlorinated with hydrogen chloride gas at elevated temperature and pressure to a mixture of 1,3-DCH (1,3-dichlorohydrin, 1,3-dichloropropan-2-ol) and 2,3-DCH (2,3-dichlorohydrin, 2,3-dichloropropan-1-ol), using a carboxylic acid catalyst. In the second step, the mixture of dichlorohydrins is converted to epichlorohydrin with a base. This solventless process represents an economically and environmentally advantageous, atom-efficient process to an existing commodity chemical that can employ a renewable resource for its primary feedstock.

No abstract

The mechanism of poly(p-phenylenebenzoxazole) formation from terephthalic acid (TA) and diaminodihydroxybenzene dihydrochloride (DADHB) in polyphosphoric acid (PPA) was studied. The solubility of TA in PPA with 86% P2O5 content was determined to be 0.02% at 100 °C and 0.06% at 140 °C. Dissolved TA existed as three species, TA, α-(4-carboxybenzoyl)-ω-hydroxypoly(oxyphosphinico), and α,α‘-[1,4-phenylenebis(carbonyl)]bis[ω-hydroxypoly(oxyphosphinico)]. DADHB also reacts with PPA, and DADHB, α-(2,4-diamino-5-hydroxyphenyl)-ω-hydroxypoly(oxyphosphinico), and α,α‘-(4,6-diamino-1,3-phenylene)bis[(ω-hydroxypoly(oxyphosphinico)] were found. During the course of polymerization, conversion of DADHB was higher than that of TA. NMR, IR, and mass spectroscopy characterization of PBO oligomer and its product with benzoic-carboxy-13C acid suggested both chain ends were capped with DADHB, which is different from oligomers of conventional AA plus BB step-growth polymers. An unprecedented polymerization mechanism is proposed to account for this unusual oligomer structure and the remarkable fact that high molecular weight PBO was obtained even when 5% excess of one of the monomers, TA, was used. The reactivities of the two functional groups in DADHB toward carboxylic acid to form benzoxazole in PPA were different.

No abstract

Poly(p‐phenylenebenzobisoxazole) (PBO) fiber with polyphenylene sulfide (PPS) pendent groups was made to improve PBO fiber compressive strength by crosslinking. PPS moieties allowed the polymeric network to crosslink at heat‐treatment temperatures at which PBO does not thermally degrade. PBO‐PPS fiber heat‐treated for 30 s at 600°C did not dissolve or break up in methanesulfonic acid. Compressive strength of crosslinked fiber was about 20% better than that of unmodified PBO fiber. In another experiment, 10 mol % of 2,5‐diphenylsulfideterephthalic acid was incorporated into PBO fiber. The side chain of one phenyl sulfide unit was too short to enhance crosslinking, and the fiber had about the same compressive strength as unmodified PBO fiber. © 1995 John Wiley & Sons, Inc.