DE10250429A1 - Working up polyether-polyol from alkali-catalysed alkoxylation of alcohol, amine or carboxylic acid involves adding protonatable or protonated nitrogen compounds as crystallisation promoters before filtration - Google Patents

Abstract

Protonatable or protonated nitrogen-containing inorganic and/or organic compounds are used as crystallisation promoters in a method for working up polyether-polyols obtained by the alkali-catalysed reaction of alkylene oxides with starters such as alcohols, amines and carboxylic acids. A method for working up polyether-polyols obtained by the alkali-catalysed reaction of alkylene oxides (AO) with starter molecules (e.g. alcohols, amines, carboxylic acids), followed by neutralisation with mineral acid or organic acid (optionally in presence of antioxidants), evaporation of water and addition of mineral filter aids, in which protonatable or protonated nitrogen-containing inorganic and/or organic compounds (I) are used as crystallisation promoters.

Description

The invention relates to a Process for the preparation of polyether polyols by alkaline Catalysis can be made.

Polyethers by alkaline catalysis can be produced mixed with an acid for working up become. The corresponding is then formed in a neutralization reaction Salt. When using watery acids is followed by the Removal of the water brought about a crystallization in order the final work-up step to separate the salt that has formed.

That the neutralization and refurbishment process is in the interest of process optimization, for example WO-A-01/88015. At the center of the investigation is the finding that work up the basic polyether without using it apart from adsorption reagents (magnesium silicate (p. 11 line 28)) filter aids (p. 6 lines 3 to 8). Furthermore, the Water content in each step of the process is <2% (p. 9 lines 15 ff). The fact that that 95% of the resulting salt is in the form of small particles (p. 11 lines 32 ff) and thus do not lead to the typical caking. Become the process conditions described here have not been observed, so receives products with low potassium (5 ppm K) and not detectable amounts of sodium, but occur in the equipment larger caking on (p. 14 lines 25 ff).

In DD-A-230 537 The goal is to produce reproducible grain sizes in the salt suspension. The base-catalyzed polyethers are worked up in such a way that a progressive increase in salt deposits from batch to batch is to be prevented in the reaction vessel.

The salt deposits are thereby Prevents water from flowing out of the reaction vessel first remaining salt precipitate from the previous batch and solved becomes. Then the resulting alkaline solution is cleaned with the resulting salt solution Mixed polyol. The alkaline polyol is then neutralized with the help of mineral acids and evaporates the volatile Ingredients. The polyol salt mixture is made in a known manner worked up. In Example 2 using the procedure described here 800 kg of water and 118 kg of a 75% phosphoric acid added. So a total of 829.5 kg water to 16,000 kg alkaline Polyether, corresponding to 5.2% water. However, the authors report of the fact that "... in emptied container stick to the stirrer and some on the container walls Crystals. On the bottom of the container there is a thin one Salt layer ... "(Example 2).

In CN-A-1229806 describes a process for working up polyether polyols, which likewise comprises the steps of neutralization, drying and dewatering, followed by circulation filtration.

The core of this application is the setting the water content to less than 1% during the neutralization process and the addition of a water-containing inorganic salt as a seed. Furthermore a phenol derivative is used as an antioxidant. In addition, an absorbent is used.

WO-A-02/10252 also relates the processing of polyether polyols. It becomes a purification process described by polyether polyols, in which the polyols are first neutralized or not neutralized, be brought into contact with an aqueous solution containing a contains organic salt. This solution is mixed with the polyol and exposed to a temperature around to form a two-phase system from polyol phase and aqueous salt phase. Subsequently the salt phase is discarded.

According to the description of patent WO-A-01/88015, the prior art with regard to the raw polyether mixture to be processed can be summarized as follows:
P. 9 line 5 ff: "... Thus, when phosphoric acid is used alkali metal phosphate is the salt formed upon combination of polyol reaction product and acid. The expression" alkali metal phosphate "as used in this connection refers to salt comprising both alkali metal and phosphate and hence include alkali metal dihydrogen phosphate, dialkali metal monohydrogen phosphate and trialkali metal phosphate. Normally, the dihydrogen phosphate will constitute the bulk of the alakli metal phosphate ... ".

In summary, it comes with the Polyether work-up of the raw polyether mixture to the following Problems:

• 1.) targeted control of particle formation;
• 2.) Reduction or avoidance of salt caking in the apparatus;
• 3.) Reduction and equalization from Salt content in the filtered polyether mixture;
• 4.) Avoidance of product cloudiness through, for example, finely dispersed salts and thus also avoidance multiple filtrations to obtain clear polyethers.

Surprisingly it was found that by adding nitrogen-containing inorganic or organic compounds (ammonium salts, ammonia, amines) Salzvergröberung while of the crystallization process occurs.

In a first embodiment, the invention relates to a process for processing Po lyether polyols, which are obtainable by alkaline catalysis of alcohols with an alkylene oxide, by subsequent neutralization with a mineral acid, if appropriate in the presence of mineral filtration aids and antioxidants, followed by evaporation of the water, which is characterized in that protonatable or protonated as a crystallization aid uses nitrogenous inorganic and / or organic compounds.

The basic catalyzed polyether is with the help of strong mineral acids (e.g. phosphoric acid) or organic acids neutralized so that at the end of the neutralization reaction the pH is ≤ 7. With the addition of the acidic compounds, water and dosed an antioxidant.

The crystallization aids are for example before the water is evaporated in solid or dissolved form, optionally also added in gas form. After a reasonable Salzrührzeit one begins with the distillation of all volatile components Apply vacuum and heat to 150 ° C. The forming salt polyether Suspension can be Filter clearly with high filter outputs. There is no salt build-up in the cauldron.

The amount of nitrogenous Crystallization aid is added, preferably amounts to 50 up to 1,000 ppm (based on the total batch).

Particularly preferred in the sense of The present invention is selected as a crystallization aid from ammonia, Ammonium salts, mixtures of ammonium salts or ammonia with alkaline earth metal salts, alkanolamines, cyclic amines, acyclic amines and their derivatives.

As ammonium salts in the sense of the present The invention is particularly suitable for phosphate salts, in particular the diammonium hydrogen phosphate. 350 ppm are particularly preferred Diammonium hydrogen phosphate, based on the total batch. The alkaline earth metal salts, which are used in addition to the nitrogen-containing crystallization aid can be are preferably selected from the chlorides. Particularly preferred in Magnesium chloride is for the purposes of the present invention.

The salt coarsening works in particular when applied to sodium dihydrogen phosphate, potassium dihydrogen phosphate or a mixture of potassium and sodium dihydrogen phosphate.

The weight ratio is preferably the Crystallization aid for alkali metal and / or alkaline earth metal salts adjusted so that the nitrogen-containing crystallization aids in an amount of 0.1 to 1.5 mmol / 25 mmol alkali metal and / or Alkaline earth metal salts used.

Surprisingly leads the Adding the substoichiometric Amount of crystallization aid for efficient crystallization.

Diammonium hydrogen phosphate is preferably used, the main constituents of the salts formed, such as potassium dihydrogen phosphate, Sodium dihydrogen phosphate and sodium / potassium dihydrogen phosphate mixed salt, when removing water, crystallize in coarse form.

Leave the polyether salt suspensions filter yourself with high filter performance. The filtered polyethers are blank. The processing equipment is free of salt caking.

EXAMPLES

In the following, attempts to Polyether workup described.

The work-up was checked for success by the determined filtration performance (in kg / m ² h) at 2 bar / RT. The reference test was always the comparison test in which the filtration performance was determined without the addition of crystallization aids.

All attempts to process the Polyether salt-water mixture were made with the one described below Mixing performed. This mixture corresponds to the general description of the raw polyether mixture from the patent WO-A-01/88015 p.9 line 5 ff.

Mixture used, referred to as BPE-M:
18.05 kg of butanol-started propylene oxide-containing polyether with an average molecular weight of 1,800 g / mol (referred to as filtrate), 139 g of potassium dihydrogenphosphate (1.02 mol), 1,085 g of water (5.6% by weight based on the total batch ) and 67 g sodium dihydrogen phosphate (0.56 mol).

Examples / comparative examples:

General implementation of the Tries:

To 300 g of the salt-containing polyether mixture the examples / comparative example were 0.12 g (0.04% by weight) the crystallization aid (see table) added. Passing through of nitrogen protective gas was heated to 125 ° C. at 35 mbar. All volatile Components were distilled off from the batch. After 2 h the vacuum is broken, the mixture is cooled and filtered.

The filtration was carried out at RT and 2 bar pressure over commercially available filter plates (HS1600 from Seitz-Schenk, the filter layer made of cellulose, natural diatomaceous earth and perlites has a water flow of about 275 1 / m ² / min (at 100 kPa), a mass per unit area of 1,240 g / m ² and a thickness of about 3.7 mm ).

The filter performance was determined by determining the filter quantity, filter area and filter time and stated in kg / m ² h. All correspondingly characterized polyethers were clear and showed no turbidity.

Result:

In the table are the examples / comparative examples and the associated Results reproduced. In addition to the filtration performance, that is Baking behavior shown.

If the amount of crystallization aid added 0.04% by weight, this is stated in the table.

Table:

Claims (7)

Process for working up polyether polyols which can be obtained by alkaline catalysis of starters (alcohols, amines, carboxylic acids etc.) with an alkylene oxide, by subsequent neutralization with a mineral acid or an organic acid, if appropriate in the presence of antioxidants, followed by evaporation of the Water, followed by the addition of mineral filtration aids, characterized in that protonatable or protonated nitrogenous inorganic and / or organic compounds are used as crystallization aids. A method according to claim 1, characterized in that the nitrogen-containing crystallization aid at a pH of ≤ 7 in fixed or loosened Admits form. A method according to claim 1 or 2, characterized in that that the nitrogen-containing crystallization aid in a lot from 10 to 5,000 ppm, based on the total batch. Especially an amount of 50 to 1,000 ppm of nitrogen is preferred Crystallization aid used. Method according to one of claims 1 to 3, characterized in that that one selects the nitrogenous crystallization aid Ammonia, ammonium salts, mixtures of ammonium salts and / or ammonia with alkaline earth metal salts, alkanolamines, cyclic amines, acyclic Amines and their derivatives individually or as a mixture with one another. A method according to claim 4, characterized in that the ammonium salt used is phosphate salts, especially diammonium hydrogen phosphate. A method according to claim 4 or 5, characterized in that that alkaline earth metal chlorides are used, especially magnesium chloride. Method according to one of claims 4 to 6, characterized in that that the nitrogen-containing crystallization aid in a lot from 0.1 to 1.5 mmol per 25 mmol alkali metal and / or alkaline earth metal salt.