Process for production of 2,3,3′,4′-biphenyltetracarboxylic dianhydride
View Patent ↗A process for producing 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA), comprising dehydrating 2,3,3′,4′-biphenyltetracarboxylic acid in an inert gas atmosphere under heating at 180 to 195° C. is disclosed. This process produces high-purity a-BPDA which is suitable for production of a polyimide.
1. A process for producing 2,3,3′,4′-biphenyltetracarboxylic dianhydride in powder form, comprising a step of dehydrating 2,3,3′, 4′-biphenyltetracarboxylic acid in an inert gas atmosphere under heating to no more than 195° C. for sufficient time to complete dehydration;
wherein, prior to the step of dehydrating under heating, the water content of 2,3, 3′,4′-biphenyltetracarboxylic acid is reduced to 10% or less.
2. A process for producing 2,3,3′,4′-biphenyltetracarboxylic dianhydride in powder form, comprising:
a crystallization step of subjecting an organic solvent solution of a reaction product mixture containing 2,3,3′,4′-biphenyltetracarboxylic acid tetraester, to a crystallization operation to obtain crystals of 2,3,3′,4′-biphenyltetracarboxylic acid tetraester having a purity of 95% or higher,
a step of hydrolyzing the crystals to obtain 2,3,3′,4′-biphenyltetracarboxylic acid, and
a step of dehydrating the 2,3,3′,4′-biphenyltetracarboxylic acid by heating to a temperature not exceeding 195° to obtain 2,3,3′,4′-biphenyltetracarboxylic dianhydride,
wherein the 2,3,3′,4′-biphenyltetracarboxylic dianhydride obtained, when polymerized with 4, 4′-diaminodiphenyl ether at equal moles at a monomer concentration of 10% by mass at 25° C. for 4.5 hours in a N-methylpyrrolidone solvent, gives a polyamic acid showing a logarithmic viscosity of 1.0 or larger as measured in a 0.5 g/100 ml N-methyl-2-pyrrolidone solution at 30° C., wherein after reducing the water content of 2,3, 3′,4′-biphenyltetracarboxylic acid to 10% or less, the dehydration step is carried out by heating at a temperature not exceeding 195° C. in an inert gas atmosphere for sufficient time to complete dehydration.
3. The process as claimed in claim 2 , wherein the dehydration step is carried out using a Hensehel mixer.
4. A process as claimed in claim 2 , wherein the crystallization comprises:
a first crystallization sub-step of obtaining crystals of a 2,3,3′,4′-biphenyltetracarboxylic acid tetraester having a purity of 95% or higher,
a sub-step of dissolving the crystals in an organic solvent, and
a second crystallization sub-step of obtaining crystals of a 2,3,3′,4′-biphenyltetracarboxylic acid tetraester having a higher purity.
5. A process as claimed in claim 2 , wherein the hydrolysis is carried out under applied pressure with heating, using neither acid nor alkali.
6. A process as claimed in claim 5 , wherein the hydrolysis is carried out under the conditions of a temperature of 150 to 250° C. and a pressure of 0.2 to 3 MPa.
7. A process as claimed in claim 5 , wherein, after the hydrolysis, crystallization is carried out to obtain crystals of 2,3,3′,4′-biphenyltetracarboxylic acid.
8. A process as claimed in clam 2 , wherein the reaction product mixture is obtained from reaction product of a dimerization reaction of an o-phthalic acid diester.
9. A process as claimed in claim 2 , wherein the content of 2,3,3′,4′-biphenyltetracarboxylic acid tetraester in the reaction product mixture is 10 to 95% by mass and the ratio of 3, 4, 3′, 4′-biphenyltetracarboxylic acid tetraester/2,3,3′,4′-biphenyltetracarboxylic acid tetraester is 0.5/1 or less.
10. A process as claimed in claim 1 , wherein the content of impurities in 2,3,3′,4′-biphenyltetracarboxylic dianhydride is 0.6% by mass or less.
11. A process as claimed in claim 2 , wherein the content of impurities in 2,3,3′,4′-biphenyltetracarboxylic dianhydride is 0.6% by mass or less.
12. A process as claimed in claim 1 , wherein the content of iron in 2,3,3′,4′-biphenyltetracarboxylic dianhydride is 1 ppm or less.
13. A process as claimed in claim 2 , wherein the content of iron in 2,3,3′,4′-biphenyltetracarboxylic dianhydride is 1 ppm or less.
14. A process as claimed in claim 1 , wherein a median particle size of the powder of 2,3,3′,4′-biphenyltetracarboxylic dianhydride is 100 μm or less.
15. A process as claimed in claim 2 , wherein a median particle size of the powder of 2,3,3′,4′-biphenyltetracarboxylic dianhydride is 100 μm or less.
16. A process as claimed in claim 1 , wherein a median particle size of the powder of 2,3,3′,4′-biphenyltetracarboxylic dianhydride is 50 μm or less.
17. A process as claimed in claim 2 , wherein a median particle size of the powder of 2,3,3′,4′-biphenyltetracarboxylic dianhydride is 50 μm or less.