Process and device for producing polyamides, with optimized flow guidance

Patent metadata

Field	Value
Publication number	US-10584204-B2
Application number	US-201615547950-A
Country	US
Kind code	B2
Filing date	Feb 2, 2016
Priority date	Feb 4, 2015
Publication date	Mar 10, 2020
Grant date	Mar 10, 2020

Abstract

A process for producing polyamides makes flow guidance within the process more efficient. In some respects, the process is based on the polymerization of lactam to a polyamide-containing polymer melt, the subsequent granulation of the polymer melt to polyamide granules using granulation liquid, and the subsequent extraction of monomeric and oligomeric constituents from the PA granules in an extraction column. In some examples, a temperature of the granulation liquid before being fed into an extraction liquid stream is lower than a temperature of the extraction liquid stream before the granulation liquid is fed into the extraction liquid stream. The invention relates also to a device for carrying out processes such as this one.

First claim

What is claimed is:

1. A process for producing polyamides with optimized flow guidance, the process comprising:
polymerizing lactam to a polyamide-containing polymer melt;
granulating the polyamide-containing polymer melt to PA granules using granulation liquid;
extracting monomeric and oligomeric constituents from the PA granules in an extraction column, wherein the PA granules are guided countercurrently to an extraction liquid stream; and
feeding at least a portion of the granulation liquid into the extraction liquid stream at at least one infeed point of the extraction column to adjust a temperature and a lactam concentration of the extraction liquid stream, wherein the at least one infeed point comprises ten infeed points at most, wherein if the at least one infeed point comprises more than one infeed point the infeed points are disposed at different heights of the extraction column,
wherein a content of lactam and oligomeric constituents in the granulation liquid before the granulation liquid is fed into the extraction liquid stream is lower than a content of at least one of lactam or oligomeric constituents in the extraction liquid stream before the granulation liquid is fed in, wherein the content of the at least one of the lactam or oligomeric constituents in the granulation liquid before the granulation liquid is fed into the extraction liquid stream is from 0.1% by weight to 5.0% by weight.

2. The process of claim 1 wherein a temperature of the granulation liquid before being fed into the extraction liquid stream is lower than the temperature of the extraction liquid stream before the granulation liquid is fed in.

3. The process of claim 2 wherein the temperature of the granulation liquid before being fed into the extraction liquid stream is from 10° C. to 50° C.

4. The process of claim 2 wherein the temperature of the granulation liquid before being fed into the extraction liquid stream is from 15° C. to 40° C.

5. The process of claim 1 wherein the at least one infeed point of the extraction column comprises between one and four infeed points.

6. The process of claim 1 further comprising measuring and adjusting an amount of granulation liquid fed into the extraction liquid stream.

7. The process of claim 1 wherein the granulation liquid contains at least one of lactam or oligomeric constituents, the process further comprising:
providing the granulation liquid by way of a granulation liquid circuit;
feeding demineralized water into the granulation liquid circuit;
measuring a content of the at least one of lactam or oligomeric constituents in the granulation liquid; and
adjusting an amount of the demineralized water fed into the granulation liquid circuit based on the measured content of the at least one of lactam or oligomeric constituents in the granulation liquid so as to keep the content of the at least one of lactam or oligomeric constituents in the granulation liquid within a range.

8. The process of claim 1 further comprising pre-extracting in a pre-extraction column after the granulating and before the extracting, wherein after the extracting the extraction liquid stream is discharged from the extraction column and fed to the pre-extraction column and guided countercurrently to the PA granules.

9. The process of claim 1 further comprising discharging the extraction liquid stream from the extraction column after the extraction.

10. The process of claim 9 wherein no additional granulation liquid from another source is fed to a collecting tank for evaporation.

Assignees

• Uhde Inventa Fischer Gmbh
• Thyssenkrupp Ag
• Uhde High Pressure Tech Gmbh

Inventors

• Königsmann Bernd

Classifications

• C08G69/16 Primary

  Preparatory processes · CPC title

• C08G69/46

  Post-polymerisation treatment · CPC title

• B01D11/0284

  Multistage extraction · CPC title

• B01D2011/002

  Counter-current extraction · CPC title

• B29B9/065 Primary

  under-water, e.g. underwater pelletizers · CPC title