DD140670A1 - PROCESS FOR PREPARING IMPROVED STARTS - Google Patents

Abstract

The invention relates to a process for the preparation of improved Starch substances that allow Pölyätheralkohole with a preferred molecular weight with low polydispersity and as possible uniform functionality. The recovered polyether alcohols become rigid polyurethanes with improved mechanical properties Properties processed. The aim of the invention is an economical To develop processes for the preparation of these improved starter substances, that is in an existing discontinuous process let realize. The process for producing the improved Startsubstanzen is characterized in that the glycoside formation with a certain ratio of the aldehyde group-containing monosaccharides begun to diol or ethereal diol and by regulation of pH of the Reaktionsgemisohes at defined points of fixation the degree of conversion and inactivation of the catalyst with a slight excess of basic substances is interrupted and Avoiding or removing interfering starting materials and intermediates become.

Description

_the invention

Process for the preparation of improved starter substances Field of application of the invention

The invention relates to a process for the preparation of improved starter substances which are suitable for the preparation of defined alkylene oxide adducts of glycosides based on aldehyde-containing monosaccharides and diols or ether diols.

Characteristic of the known technical solution

The reaction of polyols with organic polyisocyanates to give polyurethanes is known. In addition to polyester alcohols, especially polyether alcohols based on alcohols or amines are used as polyols. Depending on the intended use of the polyether alcohols, certain starter substances having the most favorable functionality for processing into polyurethanes are used for their preparation.

For the preparation of rigid polyurethanes are triols z. As glycerol, trimethylolpropane or hexanetriol, tetrols such as pentaerythritol, pentols such as xylitol or hexols, z. B ₁ sorbitol used as starting substances for polyether alcohols.

In order to improve properties of polyurethanes, such as cell structure and increase in heat resistance, are used in

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certain cases alkylene oxide adducts of alkyl glycosides used.

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By reaction of acetohalogen sugar, sugar acetals or sugar anhydrides, a laboratory production of glycosides is possible. Practically, Fischer's synthesis has long been accomplished by contacting aliphatic alcohols with the candidate saccharide and adding HCl as a catalyst. Dehydration produces the glycoside, usually the mixture of the = c and p forms. Under Fischer's working conditions, where mono-alcohols and moderately high temperatures and subsequent purification are used, pure compounds can be obtained. However, this procedure can not be effectively transferred to industrial conditions, since either significant product losses or non-uniform products result, the latter especially in the transition to polyhydric alcohols.

According to DT-AS 1468435 and DT-OS 1595066 MethyIglukosid and according to DT-OS 1443556 other monoglucosides such as ethyl, propyl and butyl glucoside are used as the starting substance. They are either obtained from by-products or prepared by the Fischer synthesis of glucose and the corresponding alcohol and polymerized in the presence of an alkaline catalyst with propylene oxide. For a large-scale production of starting substances for polyether alcohols suitable for polyurethane production, such products obtained by the Fischer reaction are often unsuitable, since only lower monofunctional alcohols are used and the resulting glucosides have only 4 hydroxyl groups for further reaction with alkylene oxides.

A process with higher yields and the recovery of higher functional products is described in FP 1450706. For the reaction, glucose and glycol are stirred in the presence of acidic catalysts for a long time and heated. As a result of the reaction, mixtures of glucosides are obtained

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be subjected to the alkylene oxide addition. The result is a predetermined by the conditions of Glukosidsynthese Polyätheralkohol mixture.

Glucosides show the typical behavior of the acetals, they are formed in acidic medium and decomposed, they are stable in the alkaline region. This allows their use for anionic alkylene oxide Urasetzung. The cleavage of the glucosides, their tendency to form further adducts is a major drawback to this French patent cited above. The long heating in the acidic region at temperatures of 100 C - 140 C, in addition to the elimination of glycol to a Diglukosidbildung or reactions to form di- and trisaccharides. Depending on the implementation and choice of synthesis conditions, a mixture of different condensation products in different composition is obtained. Pur further reaction with alkylene oxides is therefore an alternating starting mixture available and the resulting polyether alcohols are also of different composition. This has a negative effect on the utilization of the polyether alcohols to give polyurethanes. In US Pat. No. 3,640,998, after the formation of a lower alkyl glucoside by the Fischer method, a reaction mixture is also prepared by a transacetalization with a higher monofunctional alcohol. In addition to the glucoside, a number of oligosaccharides form. This mixture is reacted by means of alkaline catalysts with ethylene oxide. The products made according to the American patent are used as surfactants. For this purpose, the presence of the mixture of glucoside and oligosaccharides is very advantageous, for processing into polyurethanes, the above-mentioned disadvantages.

Object of the invention

The aim of the invention is to provide an economical method of

To develop position of improved starter substances that Sieb, realize in an existing batch process.

Explanation of the essence of the invention

The invention is based on the object of developing a process for the preparation of improved starter substances which are suitable for the preparation of defined alkylene oxide adducts of glycosides based on aldehyde-group-containing monosaccharides and diols or ethereal diols.

According to the invention, the object is achieved in that the formation of glycosides is started with a specific ratio of the aldehyde group-containing monosaccharides: diol or ether diol and interrupted by regulating the pH of the reaction mixture at defined stages to fix the degree of conversion and inactivate the catalyst with basic substances and interfering starting materials and intermediates are removed or avoided.

In the formation of glycosides, the starting point is a monosaccharide: diol or ether diol ratio of 4: 1 to 1:10, preferably 2: 1 to 1: 5.

As aldehyde group monosaccharides are preferably pentoses such as xylose, lyxose, arabinose, ribose, and hexoses such as glucose, mannose, altrose _s and used.

As diols or ether diols are preferably used ethylene glycol, propylene glycol and diethylene glycol.

The aldehyde group-containing monosaccharides and diols or

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Ether diols are reacted with acidic catalysts such as HCl, H ₂ PO ₂ , H ₂ SO ₄ , Lewis acids or cation exchangers, the acids being in an amount of 100 ppm-1000 ppm, preferably 500 ppm and the ion exchangers in an amount of 1%. - 10%, based on the Monosaccharideenge be added. The reaction is carried out at temperatures of 90 ^° C.-150 ^° C., preferably 110 ^° C.-130 ^° C. The water of reaction is removed by conventional methods such as vacuum distillation, azeotropic distillation or stirring in water-binding agents. Upon reaching a certain reaction stage, which is characterized by a reduction value of 2-5, the reaction is stopped so that the reaction mixture is brought to pH> 9 by means of basic substances. The reduction value is determined by redox titration with Fehling's solution. The pH is measured from the aqueous methanolic solution of the glucoside by means of glass electrodes. The substances used for terminating the reaction in a limited excess to the stoichiometric amount are alkalis, alkaline earths or amines, preferably alkali metal hydroxides, alkali metal hydrides or alkali metal alkoxides, eg. KOH, ITaOH. These substances bring to a standstill by inactivating the catalyst which allows glucoside formation and their presence in limited excess, the condensation reaction and any transacetalisations. The basic substances also remain during the subsequent removal of interfering starting materials and intermediates, such as excess diol or ether diol, residual water of reaction and substances resulting from inactivation, by distillation or stripping by inert gas in the reaction product and also avoid the formation of oligosaccharides, the represent particularly lacking intermediates. The inactivation is carried out at elevated temperature, preferably at 80 ° - 130 ⁰ C is performed.

By the method according to the invention, by selecting the monosaccharide: diol or ether diol ratios, uniform starter substances which are pure according to the requirements

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Starter for the conversion to polyether alcohols can be obtained. This preparation of uniform starting substances is the particular advantage of the process.

The implementation of the improved starting substances is carried out with conventional alkylene oxides -As propylene oxide and / or ethylene oxide in a known Weise'bei temperatures of 100 ⁰ C 150 ⁰ C and pressures of from 1 atm - 12 atm. Due to the known composition of the starter substance, it is possible to

) Preferred molecular weight with low polydispersity and as uniform as possible functionality of the polyether alcohol to control. If appropriate, the starting substance can be deliberately varied by admixing one or more starting additives, such as alcohols, saccharide and / or aminohydroxy compounds having at least trifunctional groups. The catalysts used for the alkoxylation of the glucoside are basic substances, preferably KOH, UaOH, amines. It is quite possible that the basic substances used to inactivate the glucoside forming catalyst in slight excess, which remain during the removal of the interfering starting materials and intermediates in the reaction product, in the preparation of the polyether alcohols

^{J continue to act} as a catalyst and thereby eliminating a further addition of the catalyst for the Polyäthersynthese.

The basic catalyst is optionally separated with inorganic or organic acids or acidic salts by means of acidic sorbents by conventional methods of crude and polyether. The unreacted alkylene oxide and water present in the polyether alcohol are distilled off at temperatures of 100 ⁰ C - 120 ⁰ C in vacuo and then the solid salt is removed by filtration through known filter media. The polyether alcohols obtained are processed with organic isocyanates to give rigid polyurethanes with improved mechanical properties.

The invention will be explained in more detail below with reference to five exemplary embodiments:

In the accompanying drawings show:

Figure 1: molecular weight distribution according to PP 1450 706, which is determined by gel permeation chromatography.

Figure 2: molecular weight distribution according to the invention>, method by gel permeation chromatography

is determined.

Figure 3ϊ molecular weight distribution according to the method of the invention, which is determined by gel permeation chromatography.

Ausführungsbei game 1; (Comparative Example according to FP 1450 706)

In a flask equipped with a thermometer, stirrer and distillation column, 692 parts of monoethylene glycol, 1800 parts of glucose and 3 parts of 33% aqueous HCl are introduced. The mixture is slowly heated to 110 ⁰ C and stirred. After reaching the temperature J chen, the internal pressure is slowly reduced to 12 torr and driven off the reaction water through a column. The resulting viscous product mixture consists of approximately 15 % monoethylene glycol, 56 % glucoside and 29 % disaccharide / diglucoside (FIG. 1).

800 parts of this Glukosidgemisches and 6.4 parts of potassium carbonate are reacted in the autoclave with 1420 propylene oxide. The resulting polyether alcohol is used to make a rigid polyurethane foam.

Embodiment 2:

A 6 l flask with packed column dephlegmator is provided with

124Og of ethylene glycol and 1 g of 35% aqueous HCl filled. Under nitrogen, the contents are heated and gradually 1000 g of glucose are stirred into the diol. After reaching 120 ⁰ C bottom temperature and complete dissolution of glucose, the contents are stirred under vacuum for 5 hours. The water is separated via the dephlegmator. At a reduction value of 3> 5, the reaction mixture is cooled to 90 ⁰ G. Subsequently, the catalyst is inactivated with 10 g of KOH (as aqueous solution) and the reaction is interrupted at this point. The KOH is stirred into the reaction mixture and after examination of a sample shows a pH of 9.4 · The unreacted ethylene glycol and other interfering constituents are then distilled off at a temperature of 120 C and under vacuum. The obtained Hydroxyäthylglukosid has a residual glycol content of 2 % and a content of 97% monoglucoside and 1 % disaccharide / diglucoside (Figure 2).

Embodiment 3

760 g of propylene glycol, 1 g of 80% H ₃ PO ₄ and 1000 g of glucose are heated with stirring and nitrogen in a 6 1-K-olben. The reaction mixture is stirred at 130 ^° C. and 20 torr for 5 hours. Thereafter, another 1 g of 80% HJ? 0. added and the mixture stirred at the above parameters for a further 5 hours. The water of reaction is withdrawn continuously and the content of free glucose is examined every hour. After reaching the reducing power of 4.0, the vacuum is released by means of nitrogen and the reaction is stopped by adding 2 g of KOH and stirring it at 130.degree. This thus fixed reaction mixture is freed in 3 hours at temperatures of 13O ⁰ Q and a vacuum of 10 Torr of interfering starting materials and intermediates. The resulting high-viscosity substance consists of 96 % monoglucoside, 2 % residual content of diol and 2 % higher molecular weight compounds such as diglucoside and oligosaccharides.

Execution Example 4:

In a flask, 750 g of diethylene glycol, 2000 g of glucose and 2 g of 35% aqueous HCl are introduced under nitrogen spraying. While stirring, the temperature is raised to 120 ° C. After the glucose is clearly dissolved, vacuum is applied and at 20 Torr, the water of reaction forming continuously withdrawn. The progress of the reaction is monitored by controls on the level of free glucose. At a reducing power of 1.5, the catalyst is inactivated by addition and stirring of 10 g of KOH. The reaction mixture then has a pH of 10.0. At 140 ⁰ C and 5 Torr this reaction mixture is freed from unwanted starting materials and especially intermediates. The product obtained consists of 95 % disaccharide / diglucoside, 1 % monoglucoside, 2 % higher oligosaccharides and a residual content of 2 % ether diol (FIG. 3). For the alkoxylation to the polyether alcohol, it is not necessary to add an alkaline catalyst since this would lead to inactivation and fixation during the Glukosidherstellung added KOH present in a sufficient also for the reaction to the polyether alcohol in the glucoside.

Ausfühungsb eispie1 5 '.

In this example, the further implementation of the improved substances will be described.

A 1.0 liter autoclave is filled with 200 g of monoglucoside according to Example 2 and purged with nitrogen. After reaching the reaction temperature of 120 ⁰ C, 400 ml of propylene oxide are metered in 2 hours at constant temperature. After completion of the dosing, the stirring is continued until a constant pressure is reached. The polyether mixture is cooled to 80 ⁰ G. For this purpose, 5 % of water (based on the Rohpolyäthergev / icht) and 94 % of the stoichiometry H-PO, (80% aqueous solution) are introduced to neutralize the KOH. Afterwards

subtracted from all volatiles. By filtration through filter media, the salt is separated. The obtained polyether has the following characteristics:

Hydroxyl number = 450 mg KOH / g acid number = 0.1 mg KOH / g pH = 7.1

and is suitable for the production of rigid polyurethanes.

Statement of Bezu used gszeiche n

FIG. 1:

II = disaccharide / diglucoside

III = monoglucoside

IV s = ethylene glycol

FIG. 2:

II = disaccharide / diglucoside

III = monoglucoside

IV = ethylene glycol

FIG. 3:

I ss Higher Oligosaccharides

II = disaccharide / diglucoside

III S = monoglucoside

IV = ether diol

17. FEß. 197 H. ^ ο υ 5 V ^

Claims (4)

Erfindimgsansprüche 1. A process for the preparation of improved starting substances, which are suitable for the production of defined Alkylenoxidaddukte of glycosides based on aldehydgruppenhaltigen monosaccharides and diols or ether diols, characterized in that the glycoside formation with a certain ratio of aldehyde group-containing monosaccharides: diol or ether diol started and by Control of the pH of the reaction mixture at defined stages to fix the degree of conversion and inactivation of the catalyst with a small excess of b-> Bischen substances is interrupted and disturbing starting and intermediates are avoided or removed · 2. The method according to item 1, characterized in that the glycoside formation at a monosaccharide: diol or ether diol ratio of 4: 1 to 1: 10, preferably 2: to 1: 5, is started. 3. The method according to item 1, characterized in that at pH values of 2-5 as a measure of the achievement of specific conversion stages of glycoside formation with known basic substances, a pH V / ert> 9 is set. 4 »method according to item 1, characterized in that as basic substances for inactivating the catalyst and terminating the reaction alkali or _e alkaline earth hydroxides, hydrides, alcoholates or amines used and these are present in a limited excess compounds optionally used as catalysts. verifiable calculations