Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-03-28
2003-03-11
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S170000, C528S312000, C528S313000, C528S322000, C528S323000, C528S324000, C528S331000, C528S332000
Reexamination Certificate
active
06531570
ABSTRACT:
The present invention relates to accelerants and processes for producing polyamides from aminonitriles and water, in particular at elevated temperature and elevated pressure.
U.S. Pat. No. 4,629,776 describes a catalytic process for producing polyamides from &ohgr;-aminonitriles such as &ohgr;-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 practically not possible 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 &ohgr;-aminonitriles. The &ohgr;-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
5
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. Titanium dioxide can be used, for example. The catalyst is used in the form of extrudates, for example.
Existing processes provide inadequate space-time yields in some instances and a molecular weight buildup which could do with improvement. In addition, the product is not always obtained in the requisite purity.
DE-A-197 09 390 and DE-A-198 04 023, both unpublished at the priority date of the present invention, describe the use of heterogeneous metal oxide catalysts in the reaction of aminonitriles with water to form polyamide. The advantage is that the fixed bed catalyst used is completely removable from the reaction mixture or the end product and the product properties are not adversely affected. However, the use of the fixed bed catalyst is subject to constraints if pigmented reaction mixtures are used, since the catalyst solids may blind and hence may lose their catalytic effect.
It is an object of the present invention to provide an accelerant for producing polyamides from aminonitriles and water and an improved process which leads to products which are not impaired by the accelerant. More particularly, the product and processing properties and the purity of the end product shall not be reduced.
We have found that this object is achieved according to the invention by using lactams, aminocarboxylic acids or their mixtures as accelerants or cocatalysts in the production of polyamides from aminonitriles and water.
The lactams, aminocarboxylic acids or mixtures thereof are preferably used in an amount of from 0.1 to 20% by weight, based on the aminonitrile quantity. They may be used together with metal oxide fixed bed catalysts as described hereinbelow.
We have found that this object is additionally achieved according to the invention by a process for producing a polyamide by reaction of at least one aminonitrile with water, which comprises the following steps:
(1) reacting at least one aminonitrile with water at a temperature from 90 to 400° C. and a pressure from 0.1 to 35×10
6
Pa, which reaction can be carried out in the presence of a Brönsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide, 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, which reaction can be carried out in the presence of a Brönsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide, the temperature and 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 370° C. and a pressure from 0.1 to 30×10
6
Pa, optionally in the presence of the above catalyst, to obtain a product mixture, wherein the reaction is carried out in at least one of steps (1) and (2) in the presence of lactams, aminocarboxylic acids or mixtures thereof in an amount of from 0.1 to 20% by weight, based on the amount of aminonitrile used.
Preferably, the above process additionally comprises the following step:
(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 continuous process for producing a polyamide by reaction of at least one aminonitrile with water, which comprises the following steps:
(1) reacting at least one aminonitrile with water at a temperature from 90 to 400° C. and a pressure from 0.1 to 35×10
6
Pa, which reaction can be carried out in the presence of a Brönsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide, 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, which reaction can be carried out in the presence of a Brönsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide, the temperature and 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 the 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, wherein the reaction is carried out in at least one of steps (1) and (2) in the presence of lactams, aminocarboxylic acids or mixtures thereof in an amount
Hildebrandt Volker
Mohrschladt Ralf
BASF - Aktiengesellschaft
Hampton-Hightower P.
Keil & Weinkauf
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