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Browse Prior Art Database

Purification of Pyromellitic Dianhydride

IP.com Disclosure Number: IPCOM000083439D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Duran, J: AUTHOR [+2]

Abstract

A sample of pyromellitic dianhydride was recrystallized from reagent grade methyl ethyl ketone (MEK), three times, with a yield of approx. 25%. The MEK was first passed over a column of Al(2)O(3). It was then distilled over calcium hydride to reduce the water content.

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Purification of Pyromellitic Dianhydride

A sample of pyromellitic dianhydride was recrystallized from reagent grade methyl ethyl ketone (MEK), three times, with a yield of approx. 25%. The MEK was first passed over a column of Al(2)O(3). It was then distilled over calcium hydride to reduce the water content.

The sample was then vacuum dried overnight at room temperature. It was then sublimed in a vacuum at 180 degrees C at a pressure of 1 x 10/6/ torr.

Next the sample was loaded into an 11 mm PYREX* tube, 30 inches in length. The tube was evacuated and backfilled to a pressure of 600 mm with oxygen and water-free nitrogen gas. The sample was then carefully melted to form a solid ingot about 25" long. The tube was reevacuated and again backfilled with 600 mm N(2) and flame tipped.

The sample tube was then passed through 25 zones (on zone refiner). The width of the molten zones was held to approx. 1/2" and moved along at a rate of 1-1/2" per hour. About 1-1/2" of black residue at the bottom of the tube was then removed. The sample was reloaded into a second tube, using the same procedure as described in paragraph 3 above.

The sample was then (important) heated in 4" segments to near boiling while in the tube, in order to "dissolve" small brown particles which did not previously zone refine down (or up). The small particles are soluble in the solvent (PMDA) at higher than melt temperatures (approx. 284 degrees C).

The sample was then passed through an additional 75...