CS254212B1 - Method of deionization and bleaching of polyethers - Google Patents

Abstract

A method for deionizing and decolorizing polyethers based on ethylene oxide * and / or propylene oxide is provided; to be a raw material for the preparation of polyurethanes. In this process, the polyethers are neutralized with the acid in an amount of at least 1 molequivale per mole equivalent per mole of base in the polyether, calculated on the acid dissociation constant greater than 10-7, without addition of solvents, optionally adding magnesium oxide or hydroxide to the ipolytether. a quantity greater than 0.1% by weight, calculated on the polyether, and after homogenisation of the suspension, the solid of polyether is deposited.

Description

The invention relates to a method of deionization and decolorization of polyethers based on ethylene oxide and/or polypropylene oxide so that they can also be a raw material for the preparation of polyurethanes.

Polyetherdiols are most often prepared by addition, or polyaddition, of alkylene oxides with a number of carbon atoms of 2 and 3 to alcohols, diols to polyols, amines, phenols, etc., i.e. to substances with reactive hydrogens. The synthesis is carried out at an elevated temperature, usually around 120 °C, and at a pressure corresponding to the pressure of the alkylene oxide at a given temperature. The most commonly used catalysts are alkali metal hydroxides, sodium hydroxide or potassium hydroxide. After the reaction is complete, which is manifested by the reaction of the alkylene oxide and the subsequent decrease in pressure, it is necessary to remove the alkaline catalyst, i.e. sodium or potassium ions, from the environment so that the concentration of these ions is below

5.10 ^-4 % wt. (5 ppm). At the same time, the product should have an acid number below 0.2 mg KOH/g" ¹ , the pH of the solution should be 6 to 7.0 and, for the widest possible application of the product, the product should be water-clear and colorless, if possible.

The method of removing ions from polyethers is widely described in the patent literature and can be generally summarized into the following groups:

1. Neutralization of alkali metal ions with inorganic or organic acids in the presence of water. Upon evaporation of the water, the salts are separated by filtration.

2. Neutralization of alkali metal ions with inorganic or organic acids in the presence of water and an organic solvent.

3. By extraction of alkali metal hydroxides with water after dilution with an organic solvent.

4. Extraction of salts formed by the hydrolysis of hydroxides with acids, with water after dilution with an organic solvent.

5. We capture metal hydroxides on solid carriers created by impregnation with inorganic acids.

The disadvantage of the latter methods is that during purification the polyol is mixed with water or an organic solvent which must be removed from the finished product. While in the case of purification of water-insoluble polyethers it is possible to remove the main portion of water as a separate phase, or with a substantial portion of salt, it is necessary to evaporate the organic solvent or use a special filtration device to remove the emulsion.

The above procedure therefore not only prolongs the time required for cleaning polyethers, but is also energy-intensive and increases the need for steam or heat, which is particularly evident in the case of water-soluble polyetherdiols. In addition, although the above procedures remove alkali metal ions, the products remain in color as they come out of the polyaddition autoclave.

A low-energy process suitable for deionization of water-soluble polymers was also developed (No. AO 241409). The process also addresses the decolorization of the product, but it used an expensive adsorbent, activated carbon, for decolorization.

For the above reasons, it was necessary to find a suitable process that would be technologically feasible and also solve the above-mentioned problems. The above-mentioned shortcomings have been solved according to the present invention, according to which the method of deionization and decolorization of polyethers based on ethylene oxide and/or propylene oxide, by neutralization with polybasic acids, especially phosphoric or oxalic acid, is carried out in such a way that the polyethers are neutralized with acid in an amount of at least 1 molar equivalent per 1 mole of base in the polyether, calculated for an acid dissociation constant greater than 10 ^-7 , preferably 1.10 to

1.20 moles of phosphoric acid, or 0.55 to 0.70 moles of oxalic acid per 1 mole of base, without the addition of solvents, optionally adding magnesium oxide or hydroxide to the polyether in an amount greater than 0.1% by weight, calculated on the polyether, and after homogenizing the suspension by stirring mechanically or with gas, the solid portion is removed from the polyether.

The advantage of the process according to the invention is the simplicity of the process, minimal heat requirement and practically in one stage ensuring the deionization of the product, the required acid number of the product, pH, and color of the product without the need for increased pressure, long reaction time, multiple dilution, evaporation, or extraction procedures.

The process can be carried out directly in the reactor in which the main reaction took place.

In the first stage of the process, it is important to know the amount of catalyst used. This is known by weighing it, or it can be obtained by filtering the sample after degassing the autoclave with an inert gas.

The required amount of phosphoric acid used is 1.0 mole to 1.05 mole of acid per mole of hydroxide, due to the dissociation constant of phosphoric acid to the first stage of 7.5.10 ^-3 , the second stage of 6.2.1 CT ⁸ , and the third stage of 4.8.10 ^-12 at a temperature of 25 °C.

When using oxalic acid, due to the fact that the dissociation constants to the first and second stages 5.9.10 ^-2 , or 6.4.10~ ⁵ are greater than 10 ^{-7 ,} it is necessary to use 0.5 moles of oxalic acid per 1 mole of NaOH or KOH, respectively.

The correct dosage of acid can be checked, in addition to weighing, also by pH after homogenization of the polyether. The pH of the polyether is measured in a 3:2 mixture of alcohol and water, where 2 g of polyether is dissolved in 20 cm ³ of the mixture at room temperature.

If the pH of the polyether is not below pH 8 (5.5 to 6.5), it is necessary to take another sample (homogeneity control, samples) and repeat the procedure. If the pH does not decrease, this indicates a low addition of acid. In that case, it is necessary to add another acid in the amount of 5% to the original addition of acid. After homogenizing the polyether, repeat the determination.

If the desired pH (5.5 to 6.5) is reached, this indicates the binding of sodium or potassium ions in the form of salts.

Excess acid is preferably removed by adding magnesium oxide or hydroxide. In this case, it is necessary to add such an amount of magnesium oxide to the solution that the pH of the solution is in the range of 6.5 to 8.0. The addition of excess magnesium is not a problem during the forced processing of the polyol, since it is removed by filtration with potassium or hydrogen, but the excess is not necessary. Magnesium oxide, as we surprisingly found out, has, in addition to the neutralizing effect, also a significant decolorizing effect on the polyether. In the case that the polyether sample is still tolerably colored after neutralization of the base with acids, the applicable procedure (addition of magnesium) is not necessary; This is especially not necessary when using oxalic acid, the use of which has the advantage that the acid number of the polyether polyol does not increase when overdosing in an anhydrous environment.

The application of acids is advantageous even before the hot solution is heated after degassing the autoclave and removing oxiranes residues, e.g. by purging the autoclave with nitrogen, or inert gas, or using a vacuum. After adding the acid, the polyether is homogenized either by stirring, or circulating with a pump, or by purging the batch under vacuum with a weak air stream. At a temperature of 80 to 120°C, acids can be successfully applied, and with good homogenization of the solution, only 5 minutes are sufficient for deionization of the polyether (under laboratory conditions).

The application of acid or MgO under heat is essential both for the reasons of removing the water of crystallisation produced by neutralisation and introduced into the process with phosphoric acid or phosphoric acid by evaporation and for the reasons of subsequent filtration. Here, due to the reduced viscosity of the polyether, filtration takes place quickly.

In this case, poor filtration (slow) may indicate that the product has a pH above 8, i.e. that the amount of added acid is low. In an alkaline environment, the filtration time is significantly longer.

Oxide, or. magnesium hydroxide can be added to the sample after the addition of acid, but it is also possible to apply it before the addition of acids. As a result of the very low dissociation of the above-mentioned magnesium compounds, the acid reacts preferentially with alkali metal hydroxides and binds them in the polymers in the form of insoluble salts. In this case, when using magnesium compounds, it is also possible to overdose the acids based on the calculated content of alkali metal hydroxides. (preferably by 10%), while there is no risk of increasing the acid number of the polyether due to the binding of excess acids in the form of magnesium salts. However, this procedure. safely achieves the removal of. hydrogen ions,.,resp. potassium from polyethers.

The advantage of this process is therefore the discovery of a simple process for the preparation of polyethers suitable for the preparation of linear polyurethanes (when using polyetherdiols), where the desired colorlessness of the products can be obtained simultaneously with deionization.

The specific process of the invention is given in the examples, which do not exclude other possible combinations.

Example 1’

Polyetherdiol prepared by block polyaddition of ethylene oxide to diethylene glycol and subsequent polyaddition of propylene oxide to the resulting polyethylene glycol at a temperature of 120 ^° C using 0.25% by weight of potassium hydroxide.

The amount of individual components was chosen to produce a semi-synthetic polymer with a molecular weight of 1000 with 50% by weight of ethoxymer units.

Analysis of the product showed a potassium hydroxide content of 0.2% by weight by direct filtration and 0.25% by weight by indirect filtration.

The results of the application of various amounts of phosphoric acid (in the form of 85% by weight) or oxalic acid (dihydrate) are summarized in Table 1.

As can be seen from the results summarized in Table 1, deionization of polyether diode 1000/50 can be performed with acid, phosphoric acid, and oxalic acid, even without the presence of solvents, for a period of 10 and 30 minutes, respectively, provided that the appropriate amount of acids is used.

Effect of the amount of acid used on the properties of the purified polyether

Table 1

Type Considerable Quantity Product

acids Temperature (°C) Time (min) (mol acid/acidity no. contents K+ ppm Na ⁺ PH /mol KOH) (mg KOH/g) H3PO-1 120 10 0.895 0.066 343.0 22.0 7.8 H3PO4 120 10 0.972 0.099 297 11.5 6.9 H3PO1 120 10 1,050 0.130 8.7 0.4 6.4 H3PO4 120 10 1,128 0.235 < 4.0 < 0.4 4.9 H3PO4 120 10 1,206 0.453 < 4.0 < 0.4 4.3 H2C2O4 80 30 0.498 0.050 314 18.9 H2C2O4 80 30 0.533 — 89 3.3 — H2C2O4 80 30 0.569 0.15 < 4.0 < 0.4 6.00 H2C2O4 80 30 0.640 0.16 < 4.0 < 0.4 5.08 H2C2O4 80 30 0.712 0.15 < 4.0 < 0.4 3.10 H2C2O4 80 30 0.783 0.16 < 4.0 < 0.4 6.0 H2C2O4 100 30 0.854 0.08 < 4.0 < 0.4 — H2C2O4 100 30 0.961 0.09 < 4.0 < 0.4 — H2C2O1 100 30 1,032 0.13 < 4.0 < 0.4 —_ H2C2O4 100 30 1,103 0.15 < 4.0 < 0.4

In this case, even a double overdose of acid did not affect the acid number and this was at a suitable level for use in polyurethanes.

In order to measure the effect of time on deionization, the effect of acid exposure time on deionization was measured in the laboratory with good sample mixing. The results are listed in Table 2.

Table 2

Effect of reaction time on qualitative parameters of obtained polyetherdiol 1000/50

Type of acid Quantity (mol. , mol' ¹ ) Precipitation No. of acidity (mg KOH . g ¹ Product PH temperature (°C) time (min.) contents K+ ppm Na+ H2C2O4 0.640 80 5 0.123 < 4.0 < 0.4 6.0 H2C2O4 0.640 80 10 0.105 < 4.0 < 0.4 6.0 H2C2O4 0.640 80 20 0.114 < 4.0 < 0.4 6.1 H2C2O4 0.640 80 30 0.127 < 4.0 < 0.4 6.2 H2C2O4 0.640 80 60 0.113 < 4.0 < 0.4 6.1 H2C2O4 0.640 80 120 0.105 < 4.0 < 0.4 6.3 H2C2O4 0.640 80 180 0.092 < 4.0 < 0.4 6.1 H2C2O4 0.640 80 240 0.114 < 4.0 < 0.4 6.0 H2C2O4 0.640 120 5 0.13 < 4.0 < 0.4 5.7 H2C2O4 0.640 120 60 0.12 < 4.0 < 0.4 5.8 H2C2O4 0.640 120 120 0.13 < 4.0 < 0.4 5.6 H2C2O1 0.640 120 180 0.21 < 4.0 < 0.4 5.3 H2C2O4 0.640 120 240 0.22 < 4.0 < 0.4 5.1 H3PO4* 1,167 80 5 0.115 < 4.0 < 0.4 7.0 H3PO4* 1,167 80 30 0.123 < 4.0 < 0.4 6.2 H3PO4* 1,167 80 60 0.141 < 4.0 < 0.4 6.3 H3PO4* 1,167 80 120 0.143 < 4.0 < 0.4 6.3 H3PO4* 1,167 80 180 0.133 < 4.0 < 0.4 6.4 H3PO4* 0.168 80 240 0.145 < 4.0 < 0.4 5.8 H3PO4 0.168 80 30 0.338 < 4.0 < 0.4 4.5

Note:

* After the reaction, the indicated time, magnesium oxide was added to the suspension in an amount of 0.1 mole per mole of phosphoric acid used as an additive at a temperature of 80 ^° C and filtered off after 20 minutes of stirring. Parallel experiment with a reaction time of 30 minutes, without the addition of magnesium oxide — acid number 0.338 and pH 4.5, last line, Table 2. When following the color solution for different periods of thermal stress using air for stirring the mixture, it was observed that the samples discolored during the reaction, with the discoloring being higher at a temperature of 120 °C.

The effect of the amount of magnesium oxide used on the adjustment of the acid number in the case of an overdose of phosphoric acid is summarized in Table 3.

Effect of the amount of magnesium oxide on the properties of polyetherdiol 1,000/50

Type of acid Quantity (mol mol ^-1 ) Amount of MgO (mol mol ^-1 ) acidity number (mgKOH.g ^-1 ) Product K ⁺ content PPm Na+ PH H3PO4 1,563 0.0 1,176 < 4.0 < 0.4 3.82 H3PO4 1,563 0.144 0.990 < 4.0 < 0.4 3.88 H3PO4 1,563 0.288 0.784 < 4.0 < 0.4 4.14 II3PO4 1,563 0.576 -0.575 < 4.0 < 0.4 4.15 H3.PO4 1,563 1,152 0.133 < 4.0 < 0.4 5.40 H3PO4 1,130 0.0 0.248 < 4.0 < 0.4 4.50 H3PO4 1,130 0.144 0.191 < 4.0 < 0.4 4.90 I-Í3PO4 1.130 0.288 0.112 < 4.0 < 0.4 5.90 H3PO4 1.130 0.576 0.047 < 4.0 < 0.4 7.93

The procedure in Table 4 was followed after 10 minutes of reaction at 20°C (after acidification), magnesium oxide was added to the mixture and after 10 minutes of stirring the solid product was separated by filtration. The determinations were made in the filtrate.

As can be seen from the results summarized in the table, magnesium oxide reduces the acid number and adjusts the pH of the solution as needed, while its application also causes the solution to discolor.

Example 2

The polyether polyol prepared by the sequential addition of ethylene oxide and propylene oxide to glycol had a molecular weight of 2,000 and an ethylene glycol unit content of 30% by weight.

The product contained 0.3% by mass. sodium hydroxide.

For deionization, phosphoric acid was used in an amount of 1.13 moles per mole of sodium hydroxide. In order to achieve an acid number below 0.15 mg KOH per 1 g of polyetherdiol, a combination with the application of magnesium hydroxide was tested. The tests were carried out at a temperature of 80 °C in such a way that in the first case, phosphoric acid was applied first for 30 minutes and then magnesium hydroxide for 20 minutes. In the second case, the application of phosphoric acid and magnesium oxide was done together and after 30 minutes of reaction, the precipitate was separated by filtration. The acid number, pH and concentration of hydrogen and potassium were determined in the filtrates. When 0.82 moles of magnesium hydroxide were applied per mole of phosphoric acid, approximately the same values were determined in both cases. Acid number

0.10 mg KOH/g, pil 6.1 and sodium and potassium concentrations below 1 ppm.

Example 1.a d 3

Polyetherdiols, type statistical polyadduct of propylene oxide. and ethylene oxide with a content of 0.23 percent by weight. KOH and mol. weight/content of ethylene glycol in the molecule type 1 200/75; when applying 0.55 mole of oxalic acid per mole of potassium hydroxide at. temperature 120 °C for 30 min. at. evaporation on a rotary evaporator, an acid number of 0.14 mg/g was achieved, hydrogen content 1.1 ppm, potassium content 0.8 ppm, water content 0.05% by weight.

In the case that the mixture was not distilled, it contained 1.2% water, which was reflected by an acid number of 2.17 mg KOH/g. In this case, 0.0 mol. of magnesium oxide per mol of oxalic acid was added to the filtrate. After 30 minutes of heating at a temperature of 120 °C, the acid content decreased to 0.11 mg. g ^-1 .

The polyether diol, block type PEP 1 200/30, was deionized using phosphoric acid at 1.20 mol/mol KOH, at 120 ^C C for 30 minutes of stirring.

The unionized product had a sum of (K -j- Na) ions below 2 ppm, but an acid number of 0.442 KOH/g and a pH of 4.68. After the addition of 0.5 moles of MgO per mole of phosphoric acid, an acid number of 0.16, a pH of 6.1, and a decrease in light absorption at 440 nm from 75 to 100 nm were achieved. Example 4

Oxalic acid was used for the deionization of polyether polyols prepared on the basis of trimethylolpropane by the addition of a mixture of ethylene oxide and propylene oxide so that they contained 0, 20, 40 and 60% of ethoxamer units in the molecule and a molecular weight of about 3,500. The KOH content determined in the products ranged from 2.16 to 2.29 mg/g. A 10% excess of oxalic or phosphoric acid (i.e. 0.55 Table 4 and 1.10 mol/mol KOH, respectively) was used for deionization. The procedure was applied at a temperature of 120 °C, while the mixing of 500 g of samples lasted 30 minutes. After the specified time, the solution was filtered and the acid number, Na and K ion content and pH were determined.

The results were summarized in Table 4.

Effect of deionization of trimethylolpropane-based polyether polyols containing 0 to 60 wt. % ethylene glycol ether in the molecule at a temperature of 120 °C and 30 minutes exposure

Type Acid used MgO Product

polyether species amount (mole/ /mole) (mole/ /mole) Acid number (mg.g ^-1 ) contents On PPm K PH Slovaprop 48/20 H3PO4. 1.15 0.0 0.34 2.2 4.2 5.6 48/20 H2C2O4 0.55 0.0 0.22 1.0 1.8 6.6 48/40 H3PO4 1.10 0.0 0.20 5.7 16.0 6.7 48/40 H2C2O4* 0.60 0.0 0.29 1.2 2.4 6.8 48/60 H3PO4 1.10 0.0 0.28 2.9 5.4 5.5 48/60 H2C2O4 0.55 0.0 0.26 1.3 3.6 5.7 48/20 H3PO4 1.20· 0.50 0.15 1.2 2.4 6.4 48/40 H3P04- 1.20 0.50 0.11 1.1 3.0 6.2 48/60 H3PO4 1.20' 0.50 0.15 1.0 2.2 6.6

Note:

* poor filtration, therefore increased oxalic acid

Since the polyether polyols mentioned showed a high sodium and potassium content when using a 10% excess of phosphoric acid, it was necessary to increase the acid content to a 20% excess, with the acidity being at the desired level after the application of magnesium oxide. The vessel was evacuated during heating to remove water.

Example 5'

A copolyether based on ethylene oxide and propylene oxide with a molecular weight of 1200 with 30% by weight of ethylene oxide units, a potassium hydroxide content of 1.2 mg KOH/g, a color at 440 μ of 26% extinction relative to distilled water, was deionized with 0.55 moles of oxalic acid per 1 mole of potassium hydroxide determined.

After filtration, a light transmittance of 51% was achieved, pH 7.0®, acid number: 0.135 mg. . g ^-1 . Deionization was carried out at a temperature of 100 degrees Celsius for 30 minutes.

Application of 0.5 wt. % magnesium oxide to the feed,! increased the extraction to i 69·· %> pH 8.18, net acidity 0.09 mg KOH/g,

In the case of application of 0.73 moles of oxalic acid/mole of determined potassium hydroxide at a temperature of 120 °C for 30 minutes, after filtration the extinction was 84%, pH 5.95, acid number 0.25, K 4- Na ion content < 2.0 ppm. With the addition of 1% by weight to the batch of magnesium oxide, an extraction of 96%, pH 7.10, acid number 0.14 mg. g ^-1 : With the addition of 2.5% by weight of magnesium oxide after application of oxalic acid, a pH of 7.11 was achieved, extinction i 98%, acid number 0.021 mg. . g ^_1 . Application of magnesium oxide at a temperature of 120 °C was 30 minutes.

Claims (1)

2542121112 contained 0, 20, 40 and 60% of ethoxamer units per molecule, and molecular weight of about 3,500 was used, and oxalic acid was used. The KOH content of the products ranged from 2.16 to 2.29 mg / g. A 10% excess of oxalic acid was used for deionization, respectively. phosphorous (i.e., 0.55Table 4 and 1.10 moles / mol KOH). The application of the procedure was carried out at a temperature of 120 ° C, with the stirring of 500 g of the samples taking 30 minutes. After the given cane, the solution was filtered and the acid value was determined, the Na and K content and the ipH content. The results are summarized in Table 4. Effect of deionization of trimethylolpropane-based polyether polyols containing 0 to 60 wt. Ethylene glycol ether in the molecule at 120 ° C and 30 minutes exposure Type Used MgO product Polyether product type amount (mole / / mole) (mole / mole) acid number (mg.g-1) content Na PPm K PH Slovaprop 48/20 H3PO4. 1.15 0.0 0.34 2.2 4.2 5.6 48/20 H2C2O4 0.55 0.0 0.22 1.0 1.8 6.6 48/40 H3PO4 1.10 0.0 0.20 5.7 16.0 6.7 48/40 H2C2O4 * 0.60 0.0 0.29 1.2 2.4 6.8 48/60 H3PO4 1.10 0.0 0.28 2, 9 5.4 5.5 48/60 H2C2O4 0.55 0.0 0.26 1.3 3.6 5.7 48/20 H3PO4 1.20 · 0.50 0.15 1.2 2.4 6 , 4 48/40 H3P04- 1,20 0,50 0,11 1,1 3,0 6,2 48/60 H3PO4 1,20 '0,50 0,15 1,0 2,2 6,6 Note: Poor Filtration, therefore Increasing Oxalic Acid Since the polyetherpolyols have a high sodium and potassium content when using a 10% excess of phosphoric acid, the acid content has to be increased to 26% excess with the addition of oxide feverish was the acidity of the desirable level. During heating, the water was evacuated. Example 5 * Ethylene oxide / propylene oxide copolyether of mol. weight 1200 with 30 wt. of ethylene oxide units, a potassium hydroxide content of 1.2 mg KOH / g, a coloring of 440 µl of 26% extinction with distilled water, was deionized with 0.55 mol of oxalic acid per mole of determined potassium hydroxide. After filtration, a 51% light strength was obtained, pH 7.06, acid value: 0.135 mg / g. The deionization was carried out at 100 degrees Celsius in 30 minutes. Extraction increased to 69% of pH8.18, pure acidity of 0.09 mg KOH / g, by application of 0.73 mol of oxalic acid / mole of determined potassium hydroxide at 120 ° C in 30 minutes, filtration was extinction of 84 %, pH 5.95, purity 0.25, K 4 Na ions content <2.0 ppm. With the addition of 1% by weight of magnesium oxide, extraction was 96%, pH 7.10, acid number 0.14 With the addition of 2.5% by weight of magnesium oxide after the addition of oxalic acid, a pH of 7.11, an extinction of 98%, an acidity of 0.021 mg, g_1 was achieved. G was 30 minutes The method of deionization and decolorization of ethylene oxide and / or propylene oxide-based polyethers by neutralizing polyhydric acids elixirs, in particular phosphoric acid or oxalic acid, characterized in that the polyetherys are neutralized with an acid in an amount of at least 1 mole-equivalent per mole of base in a polyether, calculated on the acid dissociation constant greater than 10-7, preferably from about 10-7% by weight. From 1.10 to 1.20 mole of phosphoric acid, or from 0.55 to 0.70 mole of oxalic acid per mole of base, without the addition of solvents, optionally adding an oxide or magnesium hydroxide to the polyether as 0.1% by weight, calculated on the polyether after homogenisation of the suspension by stirring mechanically or by gas, is removed from the solid polyether.