Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1999-02-22
2001-02-27
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S322000, C528S323000, C528S324000, C528S329100, C528S331000, C528S332000, C528S336000, C528S347000
Reexamination Certificate
active
06194538
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel process for preparing polyamides from aminonitriles and water at elevated temperature and elevated pressure.
BACKGROUND OF INVENTION
U.S. Pat. No. 2,245,129 describes a batchwise two-step preparation of polycaprolactam from &ohgr;-aminocapronitrile (“ACN”) and water at a temperature within the range from 150 to 300° C., governed by a specific temperature program as a function of the amount of water added, and a pressure of not more than 30 bar. The disadvantages of this process are the long reaction times (20 h in step 1), the low viscosity of the resulting polycaproplactam and the high level of volatile bases (essentially primary acid amides) compared with a polycaprolactam prepared from caprolactam.
DE-C 35 34 817, U.S. Pat. Nos. 4,568,736 and 4,629,776 partly solve the problems described in U.S. Pat. No. 2,245,129 by the use of phosphorus- and sulfur-containing catalysts. The use of the catalysts mentioned improves the low space-time yield of the process described in U.S. Pat. No. 2,245,129. However, the level of volatile bases in all the products prepared by the abovementioned processes is still too high, so that the polyamides are difficult to process and have a reduced carboxyl end group number. The stoichiometric discrepancy between the amino and carboxyl end groups in the products of the abovementioned processes is responsible for their showing an insufficient degree of polymerization and a slow increase in molecular weight during tempering. Furthermore, complete removal of the catalysts is virtually impossible, so that the chemical and physical behavior of the polymers prepared using the catalysts, such as type and quantity of end groups or snap-off behavior during spinning, is adversely affected.
EP-A 479 306 proposes, in relation to the reaction of ACN with water to give polycaprolactam, to remove ammonia and water continuously, by decompressing, once a reaction temperature from 200 to 260° C. has been attained and at the same time to add water continuously while selecting a pressure within the range from 14 to 24×10
6
Pa (14 to 24 bar).
EP-A 65 291 describes a continuous process for preparing nylon-6,6 from dinitriles and diamines. Molecular weight building takes place by polycondensation.
Caprolactam is not produced as an intermediate, which it is in the polymerization of ACN. Thus, because the reactions are different, the process of EP-A 65 291 is not applicable to the present problem.
It is an object of the present invention to provide a process for preparing polyamides from aminonitriles with improved hydrolysis of the reactants, especially of the acid amide groups, and thus a higher carboxyl end group content. The molecular weight increase during the polymerization and the temperability of the product are improved in this way, compared with prior art processes.
We have found that this object is achieved by a process for preparing a polyamide by reaction of at least one aminonitrile with water, which comprises:
(1) reacting at least one aminonitrile with water at a temperature from 100 to 360° C. and a pressure from 0.1 to 35×10
6
Pa to obtain a reaction mixture,
(2) further reacting the reaction mixture at a temperature from 150 to 400° C. and a pressure which is lower than the pressure in step 1, the temperature and the pressure being selected so as to obtain a first gas phase and a first liquid or a first solid phase or a mixture of first solid and first liquid phase, and the first gas phase is separated from the first liquid or the first solid phase or from the mixture of first liquid and first solid phase, and
(3) admixing the first liquid or the first solid phase or the mixture of first liquid and first solid phase with a gaseous or liquid phase comprising water at a temperature from 150 to 360° C. and a pressure from 0.1 to 30×10
6
Pa to obtain a product mixture.
The present invention further provides a process for preparing a polyamide by reaction of at least one aminonitrile with water, which comprises:
(1) reacting at least one aminonitrile with water at a temperature from 100 to 360° C. and a pressure from 0.1 to 35×10
6
Pa to obtain a reaction mixture,
(2) further reacting the reaction mixture at a temperature from 150 to 400° C. and a pressure which is lower than the pressure in step 1, the temperature and the pressure being selected so as to obtain a first gas phase and a first liquid or a first solid phase or a mixture of first solid and first liquid phase, and the first gas phase is separated from the first liquid or the first solid phase or from the mixture of first liquid and first solid phase, and
(3) admixing the first liquid or the first solid phase or the mixture of first liquid and first solid phase with a gaseous or liquid phase comprising water at a temperature from 150 to 360° C. and a pressure from 0.1 to 30×10
6
Pa to obtain a product mixture,
(4) postcondensing the product mixture at a temperature from 200 to 350° C. and a pressure which is lower than the pressure of step 3, the temperature and pressure being selected so as to obtain a second, water- and ammonia-comprising gas phase and a second liquid or second solid phase or a mixture of second liquid and second solid phase, which each comprise the polyamide.
The present invention further provides a process for preparing a polyamide by reaction of at least one aminonitrile with water, which comprises:
(1) reacting at least one aminonitrile with water at a temperature from 100 to 360° C. and a pressure from 0.1 to 35×10
6
Pa to obtain a reaction mixture,
(2) further reacting the reaction mixture at a temperature from 150 to 400° C. and a pressure which is lower than the pressure in step 1, the temperature and the pressure being selected so as to obtain a first gas phase and a first liquid or a first solid phase or a mixture of first solid and first liquid phase, and the first gas phase is separated from the first liquid or the first solid phase or from the mixture of first liquid and first solid phase, and
(4) postcondensing the first liquid or first solid phase or the mixture of first liquid and first solid phase at a temperature from 200 to 350° C. and a pressure which is lower than the pressure of step 3, the temperature and pressure being selected so as to obtain a second, water- and ammonia-comprising gas phase and a second liquid or second solid phase or a mixture of second liquid and second solid phase, which each comprise the polyamide.
The aminonitrile can be in principle any aminonitrile, ie., any compound having both at least one amino group and at least one nitrile group. &ohgr;-Aminonitriles are preferred, especially &ohgr;-aminoalkyl nitrites having from 4 to 12 carbon atoms, more preferably from 4 to 9 carbon atoms, in the alkylene moiety, or aminoalkylaryl nitrites having from 8 to 13 carbon atoms, preferred aminoalkylaryl nitrites being aminoalkylaryl nitrites which have an alkyl spacer of at least one carbon atom between the aromatic unit and the amino and nitrile group. Especially preferred aminoalkylaryl nitriles are those which have the amino group and nitrile group in the 1,4 position relative to each other.
The &ohgr;-aminoalkyl nitrile used is preferably a linear &ohgr;-aminoalkyl nitrile in which the alkylene moiety (—CH
2
—) preferably contains from 4 to 12 carbon atoms, more preferably from 4 to 9 carbon atoms, such as 6-amino-1-cyanopentane (6-aminocapronitrile), 7-amino-1-cyanohexane, 8-amino-1-cyanoheptane, 9-amino-1-cyanooctane, 10-amino-1-cyanononane, particularly preferably 6-aminocapronitrile.
6-Aminocapronitrile is customarily obtained by hydrogenation of adiponitrile according to known methods, described for example in DE-A 836,938, DE-A 848,654 or U.S. Pat. No. 5,151,543.
Of course, it is also possible to use mixtures of a plurality of aminonitriles or mixtures of an aminonitrile with further comonomers, for example caprolactam or the below-defined mixture.
In a particular embodiment, especially if copolyamides are to be prepared, the following mi
Harder Wolfgang
Keller Dieter
Krauss Dieter
Ludwig Alfons
Mohrschladt Ralf
BASF - Aktiengesellschaft
Hampton-Hightower P.
Keil & Weinkauf
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