Process of preparing high molecular weight polyamide with recovery of diamine and return of same to polymerization system
AssigneeC/O E. I. Du Pont de Nemours & Co.
InventorValdis Ansis Augstkalns
Life of this patent
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Abstract
In the preparation of high molecular weight polyamides, vaporization of the organic diamine employed results in its loss. The effect of the loss can be reduced by collecting the vapor given off during the evaporation and/or polymerization steps, condensing it, passing the condensate through a selected ion-exchange resin, and obtaining the diamine by contacting the resin with either a strong inorganic acid or an aqueous solution of an organic dicarboxylic acid used in making high molecular weight polyamides depending upon the resin employed. When the diacid is used, the salt so obtained can be used in preparing high molecular weight polyamides.
Claims7
In the process for preparing a fiber-forming or moldable polyamide from an aqueous solution of a polyamide-forming salt of an organic diamine and an organic dicarboxylic acid wherein the salt is concentrated and polymerized, during which steam and organic diamine are vented from the evaporation and polymerization equipment;
- the improvement which comprises in sequence
- 1. collection and condensing vented vapor to form an aqueous solution of organic diamine condensate,
- 2. contacting the condensate of the vented vapor with the hydrogen form of a carboxylic cation-exchange resin which has a strength sufficient to recover said organic diamine from an aqueous solution thereof,
- 3. contacting the resin employed in step (2) with an organic dicarboxylic acid of the type employed in making said polyamide to form an aqueous solution of organic diamine-organic dicarboxylic acid salt,
- 4. collecting the aqueous solution obtained in step (3), and
- 5. adding the solution from step (4) to the salt preparation facility of said polymerization equipment.
Dependencies are inferred from the claim text.