Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-06-08
2001-08-14
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S332000, C528S495000, C528S497000, C528S50200C, C528S503000
Reexamination Certificate
active
06274698
ABSTRACT:
This invention relates to a (continuous) process for the transformation of ammonium aspartate into aspartic acid, and to a continuous process for the production of polysuccinimide by a polycondensation step of ammonium aspartate thus obtained.
According to the state of the art, two major routes exist to prepare polysuccinimide
the polycondensation of maleic anhydride with ammonia, resulting in a polycondensate composed of D- and L-anhydroaspartimide building blocks. Typical examples of this process are described in a.o. EP 256366, EP 578451, U.S. Pat. No. 5,410,017 or EP 612784.
the polycondensation of aspartic acid or precursors thereof, such as ammonium aspartate. This reaction is performed with or without catalyst addition. Typical examples of this process are described in a.o. U.S. Pat. No. 3,846,380, EP 406623, U.S. Pat. No. 5,219,986, WO 9214753, or EP 578448.
Polysuccinimide is used as a starting material for the production of polyaspartic acid, which finds application a.o. as Ca scavengers in detergents.
When using maleic anhydride as the starting compound, a D,L-polyaspartic acid is obtained after the alkaline hydrolysis of the corresponding polysuccinimide. This polycondensate has a less good biodegradability than the polycondensates of L-aspartic acid.
The L-aspartic acid used in the preparation of L-polyaspartic acid is obtained via the bioconversion of fumaric or maleic acid, or salts thereof. During these bioconversion reactions ammonium fumarate is contacted with an aspartame enzyme system, while ammonium maleate is contacted with a maleate isomerase/aspartase enzyme system. These transformations can be conducted in batch or continuously. A continuous process is e.g. described in GB 2084155, EP 89165 or DE 2835874, where ammonium fumarate is reacted over a column containing an immobilised aspartase-producing micro-organism. The resulting ammonium aspartate solution can then be transformed into an aspartic acid solution followed by the crystallisation of the corresponding acid.
Several methods are described for the recovery of crystalline aspartic acid. The standard method for obtaining crystalline aspartic acid comprises the addition of sulfuric acid to the ammonium aspartate solution. This method allows the formation of ammonium sulfate and aspartic acid. After crystallisation of the aspartic acid the ammonium sulfate residue is recovered and used as fertiliser.
Another method for recovering aspartic acid is described in EP 588674 and consists in the addition of fumaric acid to the ammonium aspartate solution. The major advantage of this method resides in the fact that no by-product is formed because ammonia is recovered as ammonium fumarate when using fumaric acid as the neutralising agent.
The major disadvantage of this method resides in the fact that the transformation of ammonium aspartate into ammonium fumarate is time consuming and discontirnous.
An improvement of the above process is described in EP 678499. This application describes the use of an alcoholic solution of fumaric acid which is added to an ammonium aspartate solution. The formation of aspartic acid crystals indeed takes less time but a residual solution of ammonium fumarate in aqueous alcohol is obtained. The alcohol, such as ethanol or methanol, must first be removed before the ammonium fumarate solution can be further processed to ammonium aspartate.
A further method for obtaining aspartic acid out of ammonium aspartate is described in JP 07/330696. Here the ammonium aspartate solution is heated which results in the decomposition of the ammonium salt into aspartic acid and ammonia, which is evaporated together with the water. This method is quite energy consuming (because hot water has to be supplied continuously and then evaporated) while the ammonium aspartate is not completely converted into aspartic acid.
The conversion of ammonium aspartate into polysuccinimide is for instance described in DE 4429108. This patent application discloses the formation of polysuccinimide by evaporating a solution of ammonium aspartate at 80° C. to dry, followed by a 4 hour heat treatment at 180-220° C. During this heating a foam is produced which is milled to a fine powder. This powder is then further polycondensed to the final polysuccinimide.
Continuous methods for preparing polysuccinimide from aspartic acid, with or without catalyst are described in e.g. U.S. Pat. No. 5,449,748, WO 9605241, EP 646615 and EP 578449.
From the prior art it can thus be concluded that a continuous transformation of fumarate into aspartate is known, and also a continuous transformation of aspartic acid into polysuccinimide. A continuous transformation of ammonium aspartate into aspartic acid would therefore be very interesting because then a continuous process for obtaining polysuccinimide out of fumaric acid would become possible.
Applicants have now succeeded in the development of a continuous process for preparing aspartic acid from ammonium aspartate and hence for preparing polysuccinimide out of fumaric acid or maleic acid.
The invention thus specifically relates to a process for the (continuous) preparation of aspartic acid by decomposition of ammonium aspartate, in which a concentrated aqueous solution of ammonium aspartate is constantly introduced into a diluent in which water has a low solubility, which diluent is maintained at a temperature at which ammonium aspartate decomposes into aspartic acid and ammonia and in which the water and the formed ammonia and aspartic acid are continuously removed, preferably at a rate substantially corresponding to the rate of introducing the ammonium aspartate solution into the diluent.
According to a preferred feature of the invention the aqueous solution has a concentration of at least 25% by weight of ammonium aspartate. More concentrated solutions, in particular solutions with at least 50% (such as 50-60%) by weight of ammonium aspartate are more economical and therefore prefered.
According to another preferred aspect of the invention the solubility of water in the used diluent is less than 2% by weight, preferably less than 1%. Its temperature is appropriately maintained at a temperature above 130° C., preferably between 130 and 160° C., most preferably between 140 and 150° C.
In selecting the diluent, preference is to be given to those having a boiling point of at least 165° C., preferably between 190 and 300° C. Particularly suitable classes of solvents are higher alcohols, higher aliphatic hydrocarbons, higher aromatic hydrocarbons, higher alkyl ethers and high boiling aromatic ethers.
Preferred diluents are decanol, dodecanol, decaline, tetraline, and phenyl linear or branched C
10
-C
20
-alkanes.
According to a further preferred feature of the invention the rate of introduction of the aqueous ammonium aspartate solution and/or the rate of removal of the water, ammonia and aspartic acid is such that the formation of a twoliquid phase system is prevented.
According to still another preferred feature of the invention the content of aspartic acid crystals in the reaction medium during the continuous process is at least 10% by weight of the amount of diluent used.
The invention also specifically relates to a continuous process for preparing polysuccinimide starting from fumaric or maleic acid and ammonia, involving the said continuous process for preparing aspartic acid from ammonium aspartate.
This continuous process for preparing polysuccinimide according to the invention comprises the following process steps:
reaction of fumaric or maleic acid with ammonia to prepare ammonium fumarate or maleate,
continuous bioconversion of the ammonium fumarate or ammonium maleate respectively into an aqueous ammonium aspartate solution, using immobilised aspartase or fumarate isomerase/aspartase respectively containing micro-organisms,
concentrating the aqueous solution,
continuously introducing the concentrated aqueous solution of ammonium aspartate into a diluent in which water has a low solubility, which diluent is maintained at a temperature at which ammonium aspartate decomposes i
Cami Pierre
Eyal Aharon
Lecomte Didier
Vitner Aher
Amylum Europe N.V.
Truong Duc
Tungol Maria Parrish
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