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| PATENT EXAMPLES |
A sebacic acid prepolymer was prepared by refluxing 60 grams of sebacic acid with 250 ml of acidic anhydride under nitrogen for 90 minutes. The excess acetic anhydride was evaporated from the prepolymer which was then recrystallized from toluene. The crystals were then filtered and recrystallized in a mixture of petroleum ether and anhydrous diethyl ether. The white crystals were then separated by filtration and dried under vacuum. EXAMPLE VI A high molecular weight copolymer of phenylene dipropionic acid and sebacic acid in a ratio of 20:80 was prepared using the sebacic acid prepolymer as prepared in Example I above. A phenylenedipropionic prepolymer was prepared by adding 60 grams of phenylenedipropionic acid to 500 ml boiling acidic anhydride under dry argon and refluxed for 60 minutes. The excess acetic anhydride is removed by an evaporator at 60 degrees C. to yield a white solid which was recrystallized from 30 ml toluene at 0 degrees C. The crystals are then extracted with 200 ml of a diethyl ether and petroleum ether (1:1) mixture for five hours at room temperature. The pure crystals are dried under vacuum under calcium chloride to yield 61 grams of prepolymer with a melting point of 74 to 75 degrees C. The resulting 0.91 gram of PDP prepolymer is mixed with 3.28 grams of the sebacic acid prepolymer at 180 degrees C under high vacuum (less than 10.sup.-2 mm Hg) for 90 minutes. The resulting high molecular weight polyanhydride had a melting point of 56 to 59 degrees C., a weight average molecular weight of 84,920 and an intrinsic viscosity of 0.68 dl/g and a composition of PDP:SA (20:80). |
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