JPS635046A - Purification of polyether - Google Patents

Abstract

PURPOSE:To facilitate the separation of catalyst, by adding a dissolution solvent and then water to a reaction system to extract an alkaline catalyst in the aqueous phase, separating a polyether phase from the aqueous phase near the critical temperature of the dissolution solvent and coagulating the insoluble polyester to fine particles of the alkaline catalyst. CONSTITUTION:A synthetic polyether is added with a dissolution solvent (e.g. hexane, cyclohexane, benzene, etc.) and then with water to extract alkaline catalyst in the aqueous phase. The reaction system is heated at about the critical temperature of the dissolution solvent to remarkably decrease the viscosity of the polyether phase and eliminate the water emulsion. The aqueous phase is separated as a heavy liquid phase from the polyether phase as a light liquid phase by this treatment and, at the same time, the polyether are coagulated with insoluble polyether as a binder to facilitate the separation of the particle. EFFECT:The yield of purified polyether can be improved and the treatment cost can be remarkably reduced because a complicate operation is unnecessary in the present invention.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] Polyether/v'/'i--Generally, it is synthesized by reacting an alkylene oxide with a compound having active hydrogen under an alkaline catalyst. Therefore, the synthesized polyether)v exhibits alkalinity due to the remaining alkaline catalyst,
In many cases, it cannot be used as is. The present invention relates to a method for efficiently separating and removing a di-alkaline catalyst.

[Conventional technology]

Usually polyethers are processed by post-treatment such as neutralization and removal of this alkaline catalyst.

Refined. These post-treatment methods include 2 methods of neutralizing with a weak acid, 1 method of neutralizing with a strong acid, and removing/j/post-p separation;
There are methods of adsorbing and removing catalysts using activated clay, acid clay, etc., but each method is not perfect, and the product's enlightenment and smudge.

Young wives, lower yields, problems with setting up tubs, and sloppy operations.

There are drawbacks such as.

For example, in the case of an adsorption method, the adsorption performance decreases as the amount of alkali catalyst adsorbed on the adsorbent increases, so it is necessary to regenerate or replace the adsorbent.

It is also necessary to dispose of waste liquid and waste generated at this time. Therefore, these complicated operations increase processing costs, and an efficient separation and purification method is desired.

Also, polyether is liquid at room temperature.

Because it is a highly viscous fluid and the alkaline catalyst is dispersed as submicron particles, it has not been possible to easily separate and purify it using centrifugal separation or gravity sedimentation separation methods alone.

For example, at a temperature of 50''C, the viscosity of polyether is about 400 Cjp, and the gravitational sedimentation rate of 1μ alkali catalyst particles is:

= 2.7 x 10-3 crn/see, 1m
It took about 10 hours to settle, making it impractical.

[Problem that the invention seeks to solve]

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods and provide a method for efficiently and easily separating and removing the alkaline catalyst in polyether in order to obtain high-quality polyether at low cost. It is something to do.

[Means for Solving the Problems] As a result of extensive research, the present inventors have found that when a dissolving solvent is added to and mixed with synthetic polyether, the properties of the polyether change rapidly near the critical state of the dissolving solvent. Based on this finding, the present invention was created.

That is, in the present invention, a dissolving solvent is added to and mixed with a polyether synthesized in the presence of an alkali catalyst, water is further added and mixed to extract the alkali catalyst into the aqueous phase, and then the polyether is synthesized in the vicinity of the critical temperature of the dissolving solvent. Along with phase separation of polyether phase and aqueous phase.

The alkali catalyst particles present in the polyether are separated by gravity sedimentation, and a part of the polyether is selectively agglomerated into the alkali catalyst particles to increase the particle size, and the alkali is separated from the synthetic polyether. and a method for purifying polyether, which comprises removing the dissolving solvent from a mixed solution, and then separating the dissolving solvent and the aqueous phase.

Examples of polyethers to which the present invention can be applied include alkaline catalysts 1 such as caustic potash and caustic soda.

Sodium methylate, potassium methylate.

Examples include all compounds in which alkylene oxide is reacted (added) to a compound having active hydrogen in the presence of metallic sodium, metallic potassium, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc. The active hydrogen-containing compounds include commonly used alcohols, carboxylic acids, phenols, amines, etc., and the alkylene oxides include one or more of ethylene oxide, propylene oxide, and styrene oxide. can be given.

Further, the dissolving solvent to which the present invention can be applied is as follows.

It is preferable to use a material that has the ability to dissolve polyether at room temperature and is easy to recover and handle.Also, since the temperature near the critical state is used, the critical temperature should be set in consideration of the thermal decomposition temperature or thermal alteration temperature of the polyether. Preferably, the temperature is 300°C or less. Table 1 shows typical dissolving solvents.

Table 1. Dissolving solvent pentane a6.1 196.6 3,
9.3 Hexane 68.7 234.7
29.9 Hebutane 98.4 267.0
27.0 octane 125.7 296.2
24.6 Cyclohexane 80 281.
0 40.4 Benzene 80.1 288
,5 47.7 Propane -42,196,8
42,0 Butane -0,5152,037,5 [Operation] The sedimentation rate of particles is expressed by the Stokene equation below.

U: Sedimentation velocity ρ, density of two particles ρ: density of liquid Dp, particle diameter μ: viscosity of liquid g: gravitational acceleration From the above equation, sedimentation rate is proportional to the square of the particle diameter, so it increases as the particle size increases. It can be seen that the gravitational sedimentation rate increases greatly, and sedimentation separation accelerates greatly.

Here, the solubility of polyether in a dissolving solvent decreases rapidly near the critical temperature of the dissolving solvent, and polyether with a large molecular weight selectively undergoes phase separation and does not dissolve in the dissolving solvent. Fine particles of the alkali catalyst in polyether can be easily separated by agglomerating them using the insoluble polynye T/L/ as a binder and increasing the particle size.

Furthermore, by adding the dissolving solvent under conditions near the critical temperature, there is an effect of reducing liquid viscosity μ and liquid density ρ, (1)
According to the formula, there is a synergistic effect of increasing the sedimentation velocity U as the particle size increases.

In addition, by adding water to polyether, it was possible to easily extract the alkali catalyst in polyether into the aqueous phase, but the aqueous phase formed an extremely stable emulsion with the polyether, and the aqueous phase It was difficult to separate the and polyether phases.

The present invention has the effect of promoting phase separation between the aqueous phase and the polyether phase by adding a dissolving solvent to the mixed phase near the critical temperature. That is, by adding a dissolving solvent near the critical temperature, the viscosity of the polyether phase decreases significantly and the specific gravity also decreases.The water emulsion disappears due to the increase in the difference in specific gravity with water, and the aqueous phase becomes heavy. As a liquid phase, polyether rapidly separates into a light liquid phase.

Therefore, according to the present invention, the alkali catalyst can be easily extracted into the aqueous phase, and the aqueous phase and the polyether phase can be easily phase-separated, making it possible to recover polyether that does not substantially contain the alkali catalyst. It has become possible.

Here, the amount of ascites added should be at least 5 times the saturated concentration of the alkali catalyst in water, but in order to increase the contact efficiency between the ascites and the alkali catalyst, it is necessary to add the ascites/L/1 part by weight of the alkali catalyst. It is preferable to add at least 0.01 part by weight. Particularly preferably 0.01 to 0.
The range is 10.

Addition of 0.10 or more simply increases the amount of water used, which is economically undesirable.

The amount of the dissolving solvent added is particularly preferably 2 to 4 parts by weight per 1 part by weight of Boliete/V. If it is less than 2 parts by weight, the viscosity and specific gravity of the liquid will not be sufficiently reduced and the sedimentation rate will be low, which is not preferable.

The operating pressure may be sufficient as long as it is sufficient to prevent the dissolving solvent from vaporizing, and is preferably in the range from the critical pressure of the dissolving solvent to twice the critical pressure. A pressure higher than this is undesirable as it increases costs.

The operating temperature should also be close to the critical temperature at which the rate of diffusion of the dissolving solvent into the polyether is high. Particularly preferably, the temperature should be at least 80° C. below the critical temperature and 50° C. above the critical temperature. However, it should be below the thermal decomposition or thermal alteration temperature of the polyether. The critical temperature is 50°
If the temperature is higher than C, the density of the dissolving solvent decreases rapidly and the solubility decreases, so the recovery rate of the poly(I) ether decreases, which is not preferable. In order to increase the density while remaining in this state, it is necessary to increase the pressure to several times the critical pressure or more, which is economically disadvantageous.

In the above-mentioned desired temperature range, a part of the polyethyl is rapidly phase-separated, and coagulation and sedimentation separation of the alkali fine particles can be promoted.

It has also been found that it is sufficient to obtain the phase-separated polyether in an amount several times that of the alkali fine particles, and the loss of the polyether can be ignored.

Next, an example of an embodiment of v purification (1) according to the present invention will be explained with reference to the process diagram shown in FIG.

In FIG. 1, l is a synthetic polyether supply line, 2
4 is a dissolution solvent circulation line, 4 is a gravity sedimentation separation tank, 5 is an alkali catalyst discharge line, 6 is a supernatant liquid, 7 is a separation tank, 8 is a purified polyether line, and 9 is a water supply line.

From the lower part 5 of the gravity sedimentation separation tank 4, the agglomerated sediment of the phase-separated polyether and the alkali fine particles and the aqueous phase are extracted, and from the upper part 6, the polyether containing substantially no alkali fine particles and the dissolved polyether are extracted. The solvent is removed as an overflow liquid, and the polyether in the overflow, the dissolved solvent and water are introduced into a separation tank 7 and separated.

For the separation tank 7, any of the evaporative separation method, the self-steam PE condensation method, or the supercritical separation method can be used, and the method can be determined based on safety.

〔Example〕

Next, the effects of the present invention will be explained in more detail using actual gun examples.

29 g of KOH was added as a catalyst to 500 g of glycerin, and 1200 g of propylene oxide was reacted by a conventional method.

Next, 3 times the amount of n-hexane and 0
．． Add 0.5 times the amount of water, charge it into a vertical auto-kump, raise the temperature to 175°C without stirring, leave it for 30 minutes, collect the supernatant from the side, and from the supernatant, n-hexane and Water was separated by distillation to recover high quality polyether.

The KOH concentration in the polyether was 50 ppm, which was sufficiently purified compared to the KOH concentration in the raw material, which was 1:160 ppm.

The yield of the polyether was 99. Qwt%.

[Comparative example]

Table 1 shows comparative examples in which the type of dissolving solvent, amount of water added, and operating temperature were changed in Example 1.

In Table 1, Case 1 is an example in which no dissolving solvent or water was added, Case 2 is an example in which the effect of extracting the alkali catalyst into the aqueous phase was not obtained without adding water, and Case 14 is an example in which the effect of extracting the alkali catalyst into the aqueous phase was not obtained. Operating temperature is 290'C due to high critical temperature of 345°C
This is an example in which the removal effect of KOH decreased because there was too much temperature difference between the two. Raising the operating temperature higher than this is undesirable as it causes thermal decomposition of the polyether. Slow 17 is an example in which the removal effect of KOf( was not obtained because the operating temperature was too low at 50°C, and &18 is an example in which the operating temperature was too high at 300°C, resulting in thermal decomposition of polyether and 9° purified polyester. This is an example in which the recovery rate of ether was significantly reduced. [Effects of the Invention] As detailed above, the present invention adds a dissolving solvent and water to a polyether containing an alkali catalyst, and dissolves the polyether into the dissolving solvent. The solubility of the solvent is controlled by temperature near the critical temperature of the dissolving solvent.

By increasing the rate of sedimentation separation of the alkaline catalyst.

The alkali catalyst is coagulated and sedimented and separated, and the alkali catalyst is extracted into the aqueous phase, and the aqueous phase and polyether phase are phase separated in the presence of a dissolving solvent, making it possible to improve the yield of purified polyether and substantially eliminate the alkali catalyst. The purpose of the present invention is to provide a method for producing purified polyether that does not contain. Furthermore, since no complicated operations are required, processing costs can be reduced to a large extent.

[Brief explanation of drawings]

FIG. 1 shows an example of an embodiment of the present invention.
FIG. 2 is a process flow diagram of a purification method. DESCRIPTION OF SYMBOLS 1...Synthetic polyether supply line, 2...Dissolving solvent circulation line, 4...Gravity sedimentation separation tank, 5...Alkali catalyst and water discharge line, 6...Supernatant liquid (overflow liquid) ) line, 7...separation tank, 8...purified polyether line, 9...water supply line Akatsuki

Claims (1)

[Claims] A dissolving solvent is added to and mixed with the polyether synthesized in the presence of an alkali catalyst, water is further added and mixed to extract the alkali catalyst into the aqueous phase, and then the polyether phase and the water are mixed near the critical temperature of the dissolving solvent. In addition to phase separation of the phases, the alkaline catalyst particles remaining in the polyether are separated by gravity sedimentation, and a part of the polyether is selectively agglomerated into the alkali catalyst particles to increase the particle size. . A method for purifying polyether, which comprises removing the alkali from a mixed solution of the synthetic polyether and the dissolving solvent, and then separating the dissolving solvent and the aqueous phase.