Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-07-25
2001-09-11
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S312000, C528S319000, C528S320000, C528S322000, C528S323000, C528S324000
Reexamination Certificate
active
06288207
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a continuous process for producing polyamides from aminonitriles and water at elevated temperature and elevated pressure.
RELATED PRIOR ART
U.S. Pat. No. 4,629,776 describes a catalytic process for producing polyamides from w-aminonitriles such as w-amino-capronitrile (ACN). ACN is reacted with water in the presence of a catalytic amount of an oxidized sulfur compound as catalyst. Sulfuric acid is an example of the catalyst used.
U.S. Pat. No. 4,568,736 describes a similar catalytic process for producing polyamides. The catalyst used in this case is an oxygen-containing phosphorus compound, phosphoric acid or a phosphonic acid.
Complete removal of catalyst is virtually impossible in either process. The presence of catalyst in the polymer can hinder the building of high molecular weight polymers and compromise later processing operations, for example spinning. Moreover, the level of volatiles in the polymers obtained is high, so that the polyamides are difficult to process.
EP-A-0 479 306 describes the production of polyamides from w-aminonitriles. The w-aminonitriles are reacted with water in the presence of an oxygen-containing phosphorus compound as catalyst. Once a reaction temperature from 200 to 260° C. has been obtained, ammonia and water are continuously removed by decompressing and at the same time water is continuously added, the pressure being selected within the range from 14 to 24×10
6
Pa (14-24 bar).
DE-A-43 39 648 relates to a process for producing caprolactam by reacting aminocarbonitriles with water in the liquid phase using heterogeneous catalysts. Suitable heterogeneous catalysts include acidic, basic or amphoteric oxides of the elements of main groups 2, 3 and 4 of the Periodic Table. Titaniurn dioxide can be used, for example. The catalyst is used in the form of extrudates, for example.
BRIEF SUMMARY OF THE INVENTION
A continuous reaction requires intensive transverse mixing within the tubular reactors used, to even out concentration and temperature gradients. In addition, any axial backmixing should be as low as possible. Only effective suppression of axial backmixing, or axial dispersion, makes it possible to achieve a plug flow profile which guarantees a narrow residence time distribution and a defined equal residence time for all volume elements in the tubular reactor.
REFERENCES:
patent: 4568736 (1986-02-01), Curatolo et al.
patent: 4629776 (1986-12-01), Curatolo et al.
patent: 5109104 (1992-04-01), Mark
patent: 5151543 (1992-09-01), Ziemecki
patent: 5646277 (1997-07-01), Fuchs et al.
patent: 5739324 (1998-04-01), Fuchs et al.
patent: 43 39 648 (1995-05-01), None
patent: 197 09 390 (1998-09-01), None
patent: 227 866 (1987-07-01), None
patent: 479 306 (1992-04-01), None
patent: WO 98/08889 (1998-03-01), None
Hildebrandt Volker
Krauss Dieter
Mohrschladt Ralf
BASF - Aktiengesellschaft
Hampton-Hightower P.
Keil & Weinkauf
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