Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Treatment with particular chemical
Reexamination Certificate
2000-06-01
2001-03-27
Barts, Samuel (Department: 1621)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Treatment with particular chemical
Reexamination Certificate
active
06207010
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for the preparation of iminodisuccinic acid alkali metal salts by reaction of maleic acid and ammonia in an aqueous medium in the presence of alkali metal hydroxides and working up thereof. The resulting products can be employed as complexing agents for alkaline earth metal and heavy metal ions in the fields of detergents and cleaning compositions, pharmaceuticals, cosmetics, agriculture, electroplating, building materials, textiles and paper. In these fields, use as a water softener, bleaching agent stabilizer, trace nutrient fertilizer and setting retarder is to be emphasized in particular. The invention furthermore relates to the use of iminodisuccinic acid alkali metal salts in papermaking.
Complexing agents have been employed in large amounts for years. Many complexing agents customary to date, such as ethylenediaminetetracetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA) and various phosphonates, are not biodegradable or are biodegradable to only a limited degree, remobilize heavy metals in surface waters and can even enter drinking water treatment, since they are adsorbed neither in sewage sludges nor in soils. Phosphates are complexing agents which contribute towards eutrophication of surface waters. Summarizing, these are ecotoxicological properties which are found to be a disadvantage nowadays.
It is therefore an important object to develop complexing agents which do not have the ecotoxicological disadvantages to date. Iminodisuccinic acid is thus a complexing agent which shows a ready biodegradability and therefore has an ecotoxicological advantage over the complexing agents to date.
In the future, however, not only will the product properties of chemicals which chiefly enter the environment after use be examined critically under the aspects described, but also the preparation processes. It was thus surprising that an environmentally relevant preparation process could also be found for a chemical which is currently not yet available industrially and has environmentally relevant properties.
For iminodisuccinic acid, the following preparation possibilities based on maleic anhydride or maleic acid and ammonia are known to date: GB 1 306 331 describes the preparation of iminodisuccinic acid from maleic acid and ammonia in a molar ratio of 2:3 to 2:5 at temperatures of 60 to 155° C. For working up, either hydrochloric acid or sodium hydroxide solution are added. In SU 0 639 863, iminodisuccinic acid is prepared from maleic acid and ammonia at a molar ratio of 2:0.8 to 2:1 and temperatures of 110 to 130° C. in the presence of alkali metal hydroxides. JP 6/329 606 describes a three-stage process for the preparation of iminodisuccinic acid. A maleic acid derivative is first reacted with ammonia in an aqueous medium. Alkali metal or alkaline earth metal hydroxides are then added. In the third process stage, a so-called maturation process follows. JP 6/329 607 also describes a three-stage process for the preparation of iminodisuccinic acid. In the first stage, a maleic acid derivative is again first reacted with ammonia in an aqueous medium. Alkali metal or alkaline earth metal hydroxides are then added in the second stage. In the third stage, after addition of a further maleic acid derivative, the reaction is continued. It is expressly stated in this patent application that maleic anhydride, maleic acid or maleic acid ammonium salt are employed as maleic acid derivatives. The desired reaction is said to take place hardly at all with metal salts of maleic acid, so that the aim cannot be achieved.
It is all the more astonishing that, according to the invention, maleic acid and ammonia can be reacted in an advantageous manner to give iminodisuccinic acid in high yields precisely in the presence of alkali metal hydroxides.
SUMMARY OF THE INVENTION
The invention therefore relates to a process for the preparation of iminodisuccinic acid alkali metal salts, which is characterized in that maleic anhydride (MA), alkali metal hydroxide (MeOH), ammonia (NH
3
) and water are reacted in a molar ratio of MA:MeOH:NH
3
:H
2
O=2:0.1-4:1.1-6:5-30 at temperatures of 70-170° C., under pressures of 1-80 bar over reaction times of 0.1-100 h, ammonia and water are distilled off from the reaction mixture at temperatures of 50-170° C. under pressures of 0.1-50 bar in the course of 0.1-50 h, with the addition of water and 0-4 mol of MeOH per 2 mol of MA originally employed, and after the distillation water is added in amount such that the solution formed contains a solids content of 5-60%, based on the total weight of the solution.
DESCRIPTION OF THE INVENTION
In the process according to the invention, water, alkali metal hydroxide (MeOH), maleic anhydride (MA) and ammonia (NH
3
) are metered into a reactor and the maleic acid salt formed is reacted at the reaction temperatures (T) and over the reaction times (t) mentioned. Ammonia is then distilled off as a mixture with water, with the addition of water and, if appropriate, further MeOH. After this distillation, the product is adjusted to an expedient concentration by addition of water. If appropriate, this product solution can be subjected to a clarifying filtration. Me here denotes Li, Na or K, preferably Na or K, particularly preferably Na.
The process according to the invention has the advantage that it can be carried out both discontinuously and continuously, and a high degree of profitability can be achieved here. This state of affairs is of great importance, since in spite of all advantages, environmentally friendly products are also only competitive if they can be prepared under corresponding economic conditions. The process according to the invention produces no waste, since after distillation of the ammonia, which can be recycled and further processed and, if appropriate, employed again, the product which remains is used completely. According to OECD 301 E, this product is moreover readily biodegradable. Economy and ecology are combined with one another in the process and product in a hitherto unknown manner.
In the process according to the invention, MA, water and alkali metal hydroxide are first mixed with one another in a molar ratio of MA:MeOH:water=2:0.1-4:5-30, it being possible for different metering variants to be carried out. Thus, MA can first be converted into the corresponding maleic acid salts with water via the maleic acid stage, or alternatively directly with aqueous alkali metal hydroxide solution. The second metering variant has proved to be advantageous for technical and chemical reasons. With this it is possible to prepare particularly concentrated maleic acid salt solutions of low secondary component content in a simple manner. These slightly yellowish solutions contain the possible secondary components fumaric acid and malic acid in only small amounts. The maleic acid salt is thus used in the further process with yields of >92%, preferably >95%, particularly preferably >98% of the theoretical amount.
In respect of a continuous process procedure, continuous and simultaneous metering of MA and alkali metal hydroxide solutions into an initially introduced maleic acid salt solution has proved to be particularly advantageous. Even very pure and also colorless solutions can be obtained with equally high yields in this manner.
Preferably, MA and MeOH are employed in a molar ratio of 2:0.5-3.9, particularly preferably 2:0.9-3.5, especially preferably 2:1.5-3.1.
Preferably, MA and NH3 are employed in a molar ratio of 2:1.2-5.5, particularly preferably 2:1.5-4.5, especially preferably 2:1.9-3.5.
Preferably, MA and H
2
O are employed in a molar ratio of 2:5.5-25, particularly preferably 2:6-20, especially preferably 2:6.5-15.
The maleic acid salt is prepared from MA, MeOH and water at temperatures of at least 60° C., for example at 60-130° C., preferably at 70-120° C., particularly preferably at 80-115° C., at which rapid and complete reaction of the MA is ensured and at which a stirrability and pumpabili
Dobert Frank
Groth Torsten
Joentgen Winfried
Roick Thomas
Wagner Paul
Barts Samuel
Bayer Aktiengesellschaft
Eyl Diderico van
Gil Joseph C.
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