Method of making aromatic dihydroxy diacid dihalides and precipitates resulting therefrom
View Patent ↗A method of making an aromatic dihydroxy diacid dihalide comprises forming a solution of an aromatic dihydroxy diacid in a solvent, contacting the aromatic dihydroxy diacid solution with a halogenating agent; heating the solution under an inert atmosphere to convert from 50 and 100 percent of the aromatic dihydroxy diacid to aromatic dihydroxy diacid dihalide, wherein the time required for the conversion is less than 4 hours, and removing at least a portion of the solvent.
1. A method of making an aromatic dihydroxy diacid dihalide, comprising:
a) forming a solution of an aromatic dihydroxy diacid in a cyclic ether solvent with the provisio that the dihydroxy diacid dichloride formed in step (c) is soluble in the solvent;
b) contacting the aromatic dihydroxy diacid solution with a halogenating agent;
c) heating the solution under an inert atmosphere to convert from 50 to 100 weight percent of the aromatic dihydroxy diacid to aromatic dihydroxy diacid dihalide wherein the time for the conversion is less than 4 hours, and
d) removing at least a portion of the cyclic ether solvent.
2. The method of claim 1 wherein the aromatic dihydroxy diacid is selected from the group consisting of 2,5-dihydroxy-terephthalic acid, 1,5-dihydroxy-2,6-naphthalene dicarboxylic acid, 2,6-dihydroxy-1,5-naphthalene dicarboxylic acid, and mixtures thereof.
3. The method of claim 2 , wherein the solvent comprises tetrahydrofuran, tetrahydropyran, or mixtures thereof.
4. The method of claim 1 , wherein the halogenating agent is selected from the group consisting of thionyl chloride, thionyl bromide, phosgene, chlorine, bromine and mixtures thereof.
5. The method of claim 1 , wherein the halogenating agent is present in a stoichiometric excess based on the amount needed to convert 100 percent of the aromatic diacid to aromatic dihydroxy diacid dihalide.
6. The method of claim 1 comprising the further steps:
e) combining dihydroxy diacid dihalide resulting from step (c) with a further solvent for the dihalide which does not dissolve at least a portion of the remaining components;
f) recovering dihydroxy diacid dihalide from the solvent of step (e).
7. The method of claim 6 , wherein the dihydroxy diacid dihalide is recovered as a solid from the solvent solution of step (e).
8. The method of claim 6 wherein the solvent of step (e) is selected from the group consisting of hexane, heptane, and mixtures thereof.
9. A purified aromatic dihydroxy diacid dihalide composition containing 1 to 25 weight percent aliphatic solvent when stored at about 25 degrees Celsius under Nitrogen atmosphere for 168 hours results in less than 1 percent of the aromatic dihydroxy diacid dihalide self polymerizing.
10. The purified dihydroxy diacid dihalide composition on claim 9 wherein the solvent comprises hexane or heptane.