DD210461A1 - METHOD FOR CLEANING BASIC, LOW-MOLECULAR POLYETHERAL CARBOHINS - Google Patents

Abstract

The invention relates to a process for purifying basic low molecular weight polyether alcohols. The polyether alcohols purified by this process are mainly suitable for the preparation of polyurethanes. The invention has for its object to develop a process for the purification of basic low molecular weight polyether alcohols by combining main cleaning and post-purification. According to the invention, this object is achieved in that the basic polyether alcohol before the main cleaning with an amount of water corresponding to a water content after the acid addition of 0.5% to 10%, based on the amount of polyether used, and an amount of acid in the amount of 50% mixed to 100% of the stoichiometric reaction, mixed intensively for 1 h to 2 h at temperatures of 60 degrees C to 100 degrees C, if necessary, partially Entwaessert and resulting salts are removed, after which a small amount of water can be recycled and under Combination of added Saeuremenge from the main cleaning with the residence time in the ion exchange after-cleaning the pre-purified polyether alcohol successively treated with cation and anion exchangers or only with cation exchanger and then distilled.

Description

Title of the invention

Process for purifying basic low molecular weight polyether alcohols

Field of application of the invention

The invention relates to a process for purifying basic low molecular weight polyether alcohols. The polyether alcohols purified by this process are suitable for all known uses, mainly for use in polyurethanes.

Characteristic of the known technical solutions

In the preparation of polyether alcohols by addition of alkylene oxides to starter substances basic compounds such as alkali metal hydroxide or Srdalkalihydroxid be used as catalysts «The resulting in the alkoxylation polyether containing · each added amount of catalyst and must therefore for further use, especially in the reaction with Isocyanates to polyurethanes , be garached. Various methods are known with the aid of which basic catalyst residues can be removed from the polyether alcohol. Sine series method works on the method of neutralization with inorganic or organic acids or with acidic salts. The resulting water and other volatile compounds are removed by distillation or stripping with inert gas, the precipitated salts are filtered off. Other known methods work

by the method of ion exchange. In this case, the polyether alcohols are mixed with a solvent or solvent mixture of in particular water and an organic solvent, such as methanol, in order to lower the viscosity and increase the ion permeability, and then to exchange the ions. The solvent is used in a relatively large proportion, in particular 750 % of the amount of polyether alcohol used, and removed by distillation after ion exchange The catalyst is removed by using a specific cation exchanger or, more frequently, by combining cation and anion exchangers Cleaning methods are known, wonaeh - by precipitating certain amounts of catalyst, acid catalysts are removed and a residual removal is carried out with addition of cation and anion exchange ^ To reduce viscosity of the polyether alcohol water and / or certain amounts of methanol are added and the ion exchange in particular realized by exchange columns.

Aim of the invention;

The aim of the invention is to develop a process for purifying basic low molecular weight polyether alcohols without addition of organic solvents. ,

presentation; the essence of the invention

The invention has for its object to provide a method for. Purification of basic low molecular weight polyether alcohols by combining main and post-purification to develop. According to the invention, the object is achieved in that the basic polyether alcohol before the main cleaning with a specially adapted amount of water and acid and mixed intensively for neutralization '1 h to 2 h at tempera doors of 60 ⁰ C to 100 ⁰ G is mixed intensively 50 % to 100% of the stoichiometric conversion of acid are added to the intended effectiveness of the main cleaning and the acid used for this purpose. At the same time, the amount of water

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The amount of water can be added together with the acid or before the amount of acid and it is thus adjusted to a water content of the acid amount of O ₃ 5 % to 10 % of the amount of polyether used. The water and acid are thoroughly mixed with the crude polyether alcohol after addition. At very high alkali contents and added amounts of water <? 5% , it is possible to perform at this stage of the purification process or by stripping with inert gas, wherein the residual water content after distillation was measured > 0.5 % . The resulting in the main purification salts are removed from the reaction mixture. This is realized by pressure or suction filtration. Sub-combination of added acid and water quantity from the main purification of the pre-purified polyether with certain residence time with cation and Anionenaustaäseher or successively _o treated only with cation exchanger. Before this subsequent purification, a small amount of water up to the water content <C10 % of the treated amount of polyether alcohol can be added to the mixture. The ion-exchange with ion exchanger can be carried out continuously in which the polyether alcohol / water mixture to be purified is passed over exchanger columns and the reaction time can be controlled by the Polyetheralkohoiza or -ablauf. But the post-purification can also be carried out batchwise, ¹ where 'the' ion exchanger is introduced into the polyether alcohol mixture to be treated, certain time remains therein, stirred for contacting and removed by filtration. 'The purified polyether alcohol is purified by distillation after the lonenaustauscherreinigung Stripping with inert gas freed from the water content.

The inventive method has the advantage that low molecular weight polyether alcohols, which can not be completely rid of the catalyst ions due to their high solubility in salt, can be completely purified. Due to the combination of added amount of water and acid from the main cleaning with the residence time in the ion exchanger after-cleaning was despite low water content in the polyether and without the addition of methanol or similar organic Lö-

a very fast and complete ion exchange. Since only the water mixtures customary for acid purification are used for the post-purification according to the invention, distillation or drying with customary parameters is also possible.

The invention will be explained in more detail below with reference to two exemplary embodiments.

Embodiment 1

In a 2 1 flask equipped with thermometer, reflux condenser and stirrer, 1 l of low molecular weight polyether alcohol based on ethylene glycol and propylene oxide. filled with a total alkalinity of 0.15 % KOH, inertized with nitrogen and heated to a temperature of 80 ⁰ C. For the main cleaning 90 g EJ) and 1.4 ml H-PO, conc. filled and thoroughly mixed by means of stirrer within 2 hours at the set temperature with Rohpolyetheralkohol. The mixture is partially dewatered by means of stripping and nitrogen, the resulting salts are filtered off and the polyether alcohol for Ilachreaktion after addition of 5 g of cation and 5 g of anion exchanger for 0.5 h. at a temperature of 50 G intensively mixed with the ion exchangers, filtered and finally distilled. This results in a polyether alcohol with the following characteristics;

Acid value = 0.05 mg KOH / g ph value = 7.1 k ⁺ content = 5 ppm

Exemplary embodiment 2

1 l low molecular weight polyether alcohol based on glycerol and propylene oxide is charged with a total alkalinity of 0.1 % KOH, rendered inert with nitrogen and heated to a temperature of SO ⁰ C in a 2 l flask with thermometer, reflux condenser and hour. For the main cleaning are successively 10 g HpO and 0.95 g H ^ PO, conc. filled and within 1 h

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intensively mixed. The resulting Salae be abfiltrieri and the polyether alcohol for further purification with 10 g of cation and anion exchanger 10g for 1 hour at a temperature of 50 ⁰ C brought intensively into contact with the ion exchangers, filtered and finally distilled. The result is a Polyetheralkchol with the following bacterial counts:

acid number = O , 01 mg KOH / g PH value = 6 , 9 k ⁺ content »3 PDI η

Claims (1)

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invention claim A process for the addition of .basic low molecular weight polyether alcohols by combination of main cleaning with organic and / or inorganic acids or addition of acidic salts and ion exchange after purification and subsequent distillation, characterized in that the basic polyether alcohol before the main cleaning with an amount of water which is a water content after the acid addition of 0.5 % to 10%, based on the Polyetheralkoholinenge used and an amount of acid in the amount of 50 % to 100 % of the stoichiometric reaction, for neutralization for 1 h to 2 h at temperatures of 60 ⁰ C to 100 ⁰ C intensively mixed, if necessary, partially dehydrated vjird. and resulting salts are removed, after which, if necessary, a small amount of water can be added again and treated with combination of added amount of acid from the main cleaning with the residence time in the ion exchange final purification of the prepurified polyether alcohol successively with cation and anion exchangers bzis, only with cation exchanger _e