Allied Corporation

Allied Chemical Corporation

Joseph D DeCaprio

William B Fisher

Lamberto Crescentini

Roy J Lilley, Jr

Stanley D Lazarus

Richard Eugene Mayer

John W Wagner

Ronald K Nilsen

Webb B Blackman, Jr

This invention is a method of purifying crude caprolactam. The improved method comprises taking a portion of a process stream of crude caprolactam having low boiling impurities and distilling the stream in the presence of water by fractional distillation into an overhead containing water and low boiling impurities and bottoms of caprolactam having improved purity and low water content. The improvement also comprises taking a low water content stream of crude caprolactam having low boiling impurities and adding water to the stream and distilling the stream by fractional distillation as described above.

Removal of light impurities from caprolactam by distillation with water

This invention is a method to recover caprolactam from a combined stream of mother liquor from a caprolactam crystallizer and other lactam containing aqueous streams, the improvement comprising steam distilling the combined stream at a temperature of from between about 180.degree. C. to 235.degree. C. in the absence of any depolymerization agent such as phosphoric acid; so that the residue from the steam distilling remains fluid; relatively low levels of caprolactam remain in the residue; less residue is generated; the recovered caprolactam has improved high quality; and losses of caprolactam due to side reactions are reduced.

Recovery of caprolactam from process residues

This invention is the method to recover caprolactam from a concentrated nylon 6 chip wash water containing water, cyclic oligomer, and caprolactam. The method comprises feeding the concentrated wash water to a wiped-film evaporator operated at a temperature of from about 200.degree. C. to 300.degree. C. and a pressure from about 10 to about 250 Torr, thereby separating the wash water into (a) an overhead stream of water and caprolactam and (b) a bottom stream of caprolactam and cyclic oligomers, then recovering the caprolactam from the overhead stream. The caprolactam in the bottom stream can also be recovered, and the cyclic oligomers depolymerized to caprolactam for recovery.

Recovery of caprolactam from nylon 6 oligomers

The esterification of an aromatic dicarboxylic acid with an alkylene glycol containing 2 to 10 carbon atoms is described under conditions of direct esterification wherein the resultant polyester has low ether content. The dicarboxylic acid is esterified with the alkylene glycol in the presence of a compound of the formula ##STR1## wherein M is H, an alkali metal selected from the group consisting of lithium, sodium and potassium or an alkaline earth metal selected from the group calcium and magnesium.

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Hopewell, VA, United States of America

Joseph D DeCaprio