Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-11-19
2003-05-27
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S323000, C528S324000, C528S312000, C528S315000, C528S320000, C528S332000, C528S335000, C528S336000
Reexamination Certificate
active
06569988
ABSTRACT:
This invention relates to a process for producing polyamides from hexamethylenediamine, aminocapronitrile and a dicarboxylic acid.
The hydrogenation of adiponitrile in the presence of catalysts has been extensively described. For instance, DE-A-196 31 521 describes the catalytic hydrogenation of pentenenitrile in the presence of carbon monoxide. The resulting mixtures of 6-aminocapronitrile and hexamethylenediamine, after their separation, may be further converted to produce nylon 6 and nylon 66. DE-A-43 19 134, for example, discloses a process whereby aminocaproic acid can be reacted in the presence of heterogeneous catalysts to form caprolactam, which in turn is used as monomer for producing nylon 6. Hexamethylenediamine and also adipic acid are also monomeric building blocks for nylon 66.
Another possibility is the direct hydrolytic polymerization of aminocapronitrile, in which case aminocapronitrile may be reacted with water in the presence of catalysts, cf. DE-A-197 09 390.
The disadvantage with existing processes for producing nylon 6 and nylon 66 from aminocapronitrile and hexamethylenediamine is the fact that, after the hydrogenation, the two components have to be used separately in the respective polymerizations. In addition, the monomers have to be of high purity, which generally necessitates an energy- and cost-intensive separation.
It an object of the present invention to provide a process for producing polyamides by using adiponitrile hydrogenation products in a convenient polymerization, not involving a separation after the hydrogenation.
We have found that this object is achieved according to the invention by a process for producing polyamides, which comprises reacting a mixture comprising hexamethylenediamine and aminocapronitrile and obtained from the hydrogenation of adiponitrile with water and a dicarboxylic acid. Preferably, the hydrogenation mixture used comes directly from the hydrogenation stage and has not been subjected to any further purification. The process provides polyamides based on aminonitriles, adipic acid and hexamethylenediamine.
A hydrogenation mixture of 6-aminocapronitrile and hexamethylenediamine can be converted into polyamide mixtures by reacting it in the presence of bifunctional acids such as adipic acid or terephthalic acid in a plurality of steps or stages which are characterized by certain temperatures and pressures.
A multiplicity of hydrogenation mixtures can be used. According to the invention, the molar ratio of 6-amino-capronitrile and hexamethylenediamine in the hydrogenation mixture is preferably in the range from 1:99 to 99:1, preferably from 5:95 to 95:5, particularly preferably from 10:90 to 90:10. The aminocapronitrile-hexamethylenediamine mixture is customarily obtained by hydrogenating adiponitrile according to known processes as described for example in DE-A 836,938, DE-A 848,654 or U.S. Pat. No. 5,151,543. It is also possible to use mixtures of various aminonitriles and diamines.
If desired, the reaction mixture may have added to it, at every reaction stage of the process according to the invention, chain-extending, -branching and -regulating substances known to one skilled in the art, for example mono-, bi- and trifunctional compounds, UV and heat stabilizers, pigments, processing aids, flame retardants, dyes or impact modifiers, as described for example in DE-A-197 09 390.
Chain-extending, -branching and -regulating substances are preferably added to the reaction mixture before, during or after the first reaction stage, whereas pigments, processing aids and dyes are preferably added to the mixture after the stages which include catalyst fixed beds.
According to the invention, the hydrogenation mixture can be converted into polyamide together with water and at least one bifunctional acid in various embodiments of the process. According to the invention, the sequence of steps described hereinbelow takes place either batchwise, i.e., in succession in a single reactor, or continuously, i.e., in successive reactors. It is also possible to carry out some of the steps continuously and the rest batchwise.
A preferred process comprises the steps of:
(1) mixing of the hydrogenation mixture of hexamethylenediamine and aminocapronitrile with water and a dicarboxylic acid to form a reaction mixture and subsequent conversion at a temperature in the range from 90 to 300° C. and a pressure at which the reaction mixture constitutes a single liquid phase,
(2) further conversion of the conversion mixture of step (1) at a temperature in the range from 230 to 400° C. and a pressure at which a liquid and a gaseous phase are obtained, separation of the gaseous phase from the liquid phase, and
(3) postcondensation of the product mixture at a temperature of from 250 to 310° C. and a pressure which is lower than the pressure in step (2).
The steps will now be described in more detail.
(1) The hydrogenation mixture is completely mixed with a bifunctional acid, preferably with adipic acid, and water, for example with the aid of static mixers or in a stirred tank which may also serve as a feed vessel. The acid content is determined as a function of the hexamethylenediamine concentration and is preferably from 50 to 150 mol %, particularly preferably from 90 to 110 mol %, based on the molar amount of hexamethylenediamine used. According to the invention, water is used in a molar ratio of aminocapronitrile to water in the range from 1:1 to 1:6, particularly preferably from 1:1 to 1:4, most preferably from 1:1 to 1:3, preference being given to using water in excess, based on the aminocapronitrile present in the hydrogenation mixture.
The conversion of the reaction mixture takes place at temperatures in the range from 90 to 300° C., preferably from 150 to 230° C. The pressure in this reaction step is preferably selected so that the mixture constitutes a single liquid phase. The reactor used may for example be a flow tube. The residence time in this reaction stage is up to 10 hours, preferably from 0.1 to 3 hours, particularly preferably from 0.1 to 1 hour.
(2) Further conversion of the conversion mixture of step 1 at a temperature in the range from 230 to 400° C., preferably from 250 to 280° C., at such a pressure that a liquid phase and a gaseous phase are obtained and the gaseous phase can be separated from the liquid phase. The residence time in this reaction stage depends on the water content of the mixture, on the reaction temperature and the reactor pressure and on the degree of polymerization desired for the product at the end of the reaction time. It is up to 10 hours, preferably in the range from 0.1 to 5 hours, particularly preferably from 0.1 to 3 hours.
The removal of the gas phase may be effected by the use of stirred or unstirred separating tanks or tank batteries and by the use of evaporator apparatuses, for example by means of circulatory evaporators or thin-film evaporators, as by filmtruders, or by means of annular disk reactors, which ensure an enlarged phase interface. In certain circumstances, recirculation of the reaction mixture or the use of a loop reactor may be necessary to enlarge the phase interface. Furthermore, the removal of the gas phase may be furthered by the addition of water vapor or inert gas into the liquid phase.
If the degree of polymerization is sufficient, then the polymer melt obtained can be discharged from the second stage, for example by means of a gear pump, cooled in a waterbath and further processed in subsequent process steps known to one skilled in the art, for example by extrusion, extraction, pigmenting, tempering.
In a possible embodiment of the second process step, the pressure corresponds to the equilibrium vapor pressure of water at the preselected temperature, so that water separation from the reaction mixture is possible over a finite period of for example 100 minutes. High degrees of polymerization or product viscosities, however, then require a further, third stage enabling an effective condensation of the reaction mixture at low pressures.
(3) The removal of the resulting water of con
Hildebrandt Volker
Krauss Dieter
Leemann Martin
Mohrschladt Ralf
BASF - Aktiengesellschaft
Hampton-Hightower P.
Keil & Weinkauf
LandOfFree
Method for the production of polyamides does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the production of polyamides, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the production of polyamides will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3044447