Two step preparation of random polyoxadiazole copolymer and articles resulting therefrom
View Patent ↗In a preparation of random polyoxadiazole copolymer by reaction of a mixture of oleum, hydrazine sulfate, terephthalic acid, and isophthalic acid, the improvement requires the addition of oleum in more than one step.
1. In a process for preparing a random copolyoxadiazole from a mixture containing oleum, hydrazine sulfate, terephthalic acid, and para-oriented aromatic diacid;
wherein the improvement comprises oleum addition in more than one step, comprising:
(a) combining hydrazine sulfate, terepthalic acid and para-oriented aromatic diacid,
(b) adding to (a) oleum in an amount not greater than 3 molar equivalent of sulfur trioxide based on moles of hydrazine with temperature of the oleum controlled to not greater than 50 degrees Celsius until dissolution occurs of oleum, hydrazine sulfate, terephthalic acid, and para-oriented aromatic diacid followed by heating in a range of 100 to 150 degrees Celsius with stirring until viscosity plateaus,
(c) adding a further amount of oleum to complete the reaction to prepare the random copolyoxadiazole.
2. The process of claim 1 wherein the total amount of sulfur trioxide is in a range from 5 to 6 molar equivalents based on the moles of hydrazine.
3. The process of claim 1 wherein hydrazine sulfate expressed as hydrazine is present in an amount from 95 to 100 mole percent in comparison to a total number of moles of terephthalic acid and at least one additional para-oriented aromatic diacid.
4. The process of claim 1 wherein terepthalic acid and at least one additional para-oriented aromatic diacid are present in an amount from 65 to 90 mole percent and 35 to 10 mole percent respectively.
5. The process of claim 1 with a solution temperature in a range from 100 to 150 degrees Celsius following dissolution.
6. The process of claim 1 wherein oleum is added in more than two steps.
7. The process of claim 1 wherein the additional para-oriented aromatic diacid comprises 4,4′-oxybis(benzoic acid).
8. The process of claim 1 wherein the additional para-oriented aromatic diacid comprises 4,4′-azobenzenedicarboxylic acid.
9. The process of claim 1 wherein the additional para-oriented aromatic diacid comprises 4,4′-stilbenedicarboxylic acid.
10. The process of claim 1 wherein the additional para-oriented aromatic diacid comprises 1,4′-phenylenediacrylic acid.
11. The process of claim 1 wherein the additional para-oriented aromatic diacid comprises 2,6-naphthalene dicarboxylic acid.
12. The process of claim 1 wherein the additional para-oriented aromatic diacid comprises 4,4′-biphenyldicarboxylic acid.
13. The process of claim 1 wherein the viscosity of the solution plateaus in step (b) in a time period after about 30 to 75 minutes of heating.