JP2007039646A - Method for purifying polyether - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for purifying a polyether, capable of improving productivity and reducing the using amount of an adsorbent. <P>SOLUTION: This method for purifying the polyether comprises a process of neutralizing a crude polyether (d) obtained by the addition polymerization of an active hydrogen-containing compound (b) with an alkylene oxide (c) in the presence of a basic catalyst (a) with an acid, crystallizing the neutralized salt and then filter-treating with a filter, wherein the filter is selected so that the relationship between the mean particle diameter of dispersed particles with a holding particle diameter of the filter satisfies the following formulae (1) and (2): R<SP>1</SP><R<SP>2</SP>(μm)---(1), R<SP>2</SP>-R<SP>1</SP><10 (μm)---(2) [wherein R<SP>1</SP>is the mean particle diameter (μm) of the dispersed particles; and R<SP>2</SP>is the holding particle diameter (μm) of the filter]. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for purifying crude polyether. Specifically, the present invention relates to a method for purifying a crude polyether containing a basic polymerization catalyst.

Usually, a polyether is obtained by addition polymerization of an alkylene oxide to an active hydrogen-containing compound in the presence of a basic catalyst such as potassium hydroxide or sodium methylate. For example, when propylene oxide is used as the alkylene oxide, the amount of the basic catalyst used is 0.1 to 0.5% by weight with respect to the crude polyether. If these basic catalysts remain in the polyether, In order to adversely affect polyurethane resin, cosmetic raw materials, surfactants, lubricants, etc., it is necessary to remove the basic catalyst. Conventionally, as a removal method, a basic catalyst is neutralized with an acidic substance, and the produced neutralized salt is filtered (for example, Patent Document 1), and a basic catalyst is adsorbed and filtered to a solid adsorbent (for example, Patent Document 2) and the like have been proposed.
Japanese Examined Patent Publication No. 38-207442 Japanese Patent Publication No.52-10018

However, in the first method, if a high-concentration acid is added as it is, the polyether will be burnt and deteriorated in quality, so it is necessary to dilute with water and add it. Because it dissolves, when filtering off, the generated salts are insufficiently removed, or even if a filter aid is used, the filter is clogged, requiring much time for filtration and reducing productivity. There is a problem.
In the latter method, the solid alkali adsorbent exhibits high adsorptivity when the alkali concentration is high, but reaches adsorption equilibrium where the alkali concentration is low. 10% is not demonstrated. Therefore, there are problems that a large amount of adsorbent is required and a lot of time is required for the filtration, resulting in high cost, low productivity, and a decrease in the yield of the polyether.
There is a strong demand for a method for purifying a polyether that increases productivity and reduces the amount of adsorbent used.

The inventors of the present invention have arrived at the present invention as a result of intensive studies on a method for purifying crude polyether.
That is, the present invention provides an active hydrogen-containing compound (b) in the presence of a basic catalyst (a).
In the step of neutralizing the crude polyether (d) obtained by addition polymerization of alkylene oxide (c) with acid, further crystallizing the neutralized salt and filtering through a filter, all dispersed particles of 1 μm or less Select a filter that has 1% or less of the dispersed particles and 50% or more of the dispersed particles and the average particle size of the dispersed particles and the retention particle size of the filter satisfy the equations (1) and (2). A method for purifying a crude polyether.
R1 <R2 (μm) (1)
R ₂ −R ₁ <10 (μm) (2)
[Wherein R1 represents the average particle size (μm) of the dispersed particles, and R2 represents the retained particle size (μm) of the filter. ]

The method for purifying the crude polyether of the present invention is simpler and can be purified in a shorter time than the conventional method, and also uses little adsorbent, resulting in less waste. Furthermore, the polyether obtained has a high purity with little oxidative deterioration and little residual alkali, neutralized salt and acid content.

In the present invention, as the basic catalyst (a), alkali metal hydroxides (potassium hydroxide, sodium hydroxide, cesium hydroxide, etc.), alkali metal alcoholates (potassium methylate, sodium methylate, etc.), alkali metal simple substance ( Metal potassium, metal sodium, etc.) and a mixture of two or more of these. Of these, preferred are alkali metal hydroxides and alkali metal alcoholates.

  The active hydrogen-containing compound (b) is not limited as long as it generates a cyclic ether ring-opening adduct by reaction with alkylene oxide. For example, a hydroxyl group-containing compound, a carboxyl group-containing compound, a thiol group-containing compound, phosphorus Acid compounds; compounds having two or more active hydrogen-containing functional groups in the molecule; and mixtures of two or more of these. Further, those obtained by adding the above cyclic ethers to these active hydrogen-containing compounds can be used as initiators as long as active hydrogen is present.

Examples of the hydroxyl group-containing compound include water, monovalent alcohol, 2 to 8 valent polyhydric alcohol, phenols, and 2 to 8 valent polyhydric phenols.
Specifically, monohydric alcohols such as methanol, ethanol, butanol, octanol; ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methylpentanediol , Dihydric alcohols such as diethylene glycol, neopentyl glycol, 1,4-bis (hydroxymethyl) cyclohexane, 1,4-bis (hydroxyethyl) benzene, 2,2-bis (4,4′-hydroxycyclohexyl) propane; Trivalent alcohols such as glycerin and trimethylolpropane; 4- to 8-valent pentose such as pentaerythritol, diglycerin, α-methylglucoside, sorbitol, xylit, mannitol, dipentaerythritol, glucose, fructose, sucrose Phenols such as phenol and cresol; polyphenols such as pyrogallol, catechol and hydroquinone; bisphenols such as bisphenol A, bisphenol F and bisphenol S; polybutadiene polyols; castor oil-based polyols; ) Polyfunctional (2-100) polyols such as polymers and polyvinyl alcohols.
Examples of the polybutadiene polyol include those having a 1,2-vinyl structure, those having a 1,2-vinyl structure and a 1,4-trans structure, and those having a 1,4-trans structure. The ratio of the 1,2-vinyl structure and the 1,4-trans structure can be changed in various ways, and for example, the molar ratio is 100: 0 to 0: 100. The polybutadiene glycol (4) includes homopolymers and copolymers (styrene butadiene copolymer, acrylonitrile butadiene copolymer, etc.), and hydrogenated products thereof (hydrogenation rate: for example, 20 to 100%).
Castor oil-based polyols include castor oil and modified castor oil (castor oil modified with a polyhydric alcohol such as trimethylolpropane and pentaerythritol).

Examples of carboxyl group-containing compounds include aliphatic monocarboxylic acids such as acetic acid and propionic acid; aromatic monocarboxylic acids such as benzoic acid; aliphatic polycarboxylic acids such as succinic acid and adipic acid; phthalic acid, terephthalic acid and trimellit Examples thereof include aromatic polycarboxylic acids such as acids; polycarboxylic acid polymers (functional group number: 2 to 100) such as (co) polymers of acrylic acid.
Examples of the polythiol compound of the thiol group-containing compound include divalent to octavalent polyvalent thiols. Specific examples include ethylenedithiol, propylenedithiol, 1,3-butylenedithiol, 1,4-butanedithiol, 1,6-hexanedithiol, 3-methylpentanedithiol, and the like.
Examples of phosphoric acid compounds include phosphoric acid, phosphorous acid, and phosphonic acid.

  Of these, preferred are hydroxyl group-containing compounds, more preferred are polyhydric alcohols, and particularly preferred are propylene glycol and glycerin.

Examples of the alkylene oxide (c) include ethylene oxide, propylene oxide, butylene oxide, and styrene oxide. Of these, propylene oxide is preferred.
The number of moles of alkylene oxide (c) added to the active hydrogen-containing compound (b) is preferably 1 to 300 moles, more preferably 10 to 250 moles, particularly preferably 20 to 160 moles per mole of active hydrogen. is there.
Examples of the method for adding (c) include, but are not limited to, single addition, random addition when two or more kinds of (c) are used, and block addition. Single addition is preferred.

The amount of the basic catalyst (a) used is preferably 0.1 to 0.5% by weight, more preferably 0.1 to 0.3% by weight, based on the crude polyether.
In the case of adding any of the above alkylene oxides, the temperature is preferably 80 to 160 ° C., the pressure is preferably 0 to 0.5 MPa, and the reaction time is preferably 3 to 10 hours. .
The crude polyether thus obtained preferably contains 0.1 to 0.5% by weight of the basic catalyst (a).

Purification is performed on the crude polyether. First, water is added to and mixed with the crude polyether, heated, and neutralized with mineral acid. The pH at this time is preferably 5.0 to 9.0, and particularly preferably 7.0 to 9.0.
The amount of water to be added is preferably 0.1 to 5.0% by weight, more preferably 1.0 to 3.5% by weight, based on the crude polyether (d).
If it is 0.1% by weight or more, the alcoholate of the polyether can be sufficiently hydrolyzed, and the crystallization time does not increase significantly. If it is 5.0% by weight or less, water can be sufficiently dissolved in the polyether and the two layers are not separated, and the crystallization time does not increase significantly.
Moreover, it is preferable that the gas phase oxygen concentration is 0.1 vol% or less through an inert gas before the treatment. When the gas phase oxygen concentration is 0.1 vol% or less, the polyether is not easily oxidized, the peroxide value is not increased, and the aldehyde is hardly generated. Alkali metal hydroxides are carbonated by carbon dioxide and are eluted without being adsorbed by the method using an adsorbent. However, the carbonate of the present invention is also crystallized, and the efficiency is improved even when the gas phase oxygen concentration is high. Can remove alkali well.

The heating temperature is preferably 80 to 98 ° C, more preferably 90 to 95 ° C. When the temperature is 80 ° C. or higher, the subsequent filtration rate is increased. The heating time only needs to reach 80 to 98 ° C, and 1 to 5 minutes is sufficient.
The acid that neutralizes the alkali is preferably a mineral acid such as phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, or hydrosilicofluoric acid, and more preferably phosphoric acid, sulfuric acid, or hydrochloric acid. The amount of the mineral acid to be added is preferably 0.5 to 1.0 mol, more preferably 0.8 to 1.0 mol with respect to the basic catalyst. When the amount is 0.5 mol or more, the subsequent crystallization is completed in a short time, and the neutralized salt grows large and becomes easy to filter. If it is less than 1.0 mol, the acid is not mixed into the purified polyether, and an adsorbent for removing the acid is hardly required.

After neutralization with mineral acid, crystallization is subsequently carried out. As the crystallization method, preferably <1> a method of adding a hardly soluble solid aromatic carboxylic acid to water or crude polyether (b), <2> a method of crystallization by dehydration under heating and reduced pressure. is there. More preferred is a method of adding the aromatic carboxylic acid <1> that allows crystallization in a short time. Aromatic carboxylic acids have the role of crystallizing agents that crystallize neutralized salts with mineral acids in a short time. Examples of the aromatic carboxylic acid include aromatic monocarboxylic acids such as benzoic acid; aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, trimellitic acid, and naphthalenedicarboxylic acid. The addition amount is preferably 0.1 or more with respect to the basic catalyst. More preferably, it is 0.3-0.5 mol. At 0.1 mol or more, the neutralized salt can be crystallized greatly in a short time.
Dispersed particles crystallized in the crystallization step are 1 μm or less of the total dispersed particles.
%, And the average particle size (R1) is preferably 10 μm or more, more preferably 15 μm or more.

The average particle size of the solid aromatic carboxylic acid compound is preferably 10 μm or more. More preferably, it is 20 μm or more. If it is 10 μm or more, crystallization is completed in a short time, and the neutralized salt grows large and is easy to filter.

Filtration may be either pressure filtration or vacuum filtration, but pressure filtration is preferred because it is easy to prevent oxygen contamination. The retained particle diameter (R2) of the filter is preferably 10 to 40 μm as long as the formula (1) and the formula (2) are satisfied. Furthermore, the thing of 20-30 micrometers is preferable. If it is 10 μm or more, it can be filtered smoothly without clogging the filter, a cake layer with good filterability is formed on the filter surface, and there is little polyether remaining in the cake, improving the yield. Moreover, if it is 40 micrometers or less, a filter layer with favorable filterability will be formed in the filter surface, without causing filtration leakage, and a transparent liquid will be obtained in a short time.
R1 <R2 (μm) (1)
R ₂ −R ₁ <10 (μm) (2)
[Wherein R1 represents the average particle size (μm) of the dispersed particles, and R2 represents the retained particle size (μm) of the filter. ]

The material of the filter is not particularly limited. For example, paper, polypropylene, polytetrafluoroethylene, polyester, polyphenylene sulfide, acrylic, meta-aramid and the like can be mentioned, but paper and polypropylene are preferable.

  Hydrotalcite-based adsorbents (for example, Kyoward 500, Kyoward 1000, Kyoward 2000, etc. <all manufactured by Kyowa Chemical Industry Co., Ltd.>), diatomaceous earth, etc. are used to prevent filtration leakage during filtration and to adjust pH. Filter aids (for example, Radiolite 600, Radiolite 800, Radiolite 900 <all manufactured by Showa Chemical Industry Co., Ltd.>) may be used. The amount of these used is preferably 0.01 to 0.2% by weight based on the crude polyether, and the average particle size is preferably 10 to 100 μm. When it is 10 μm or more, the filtration rate is fast and the production capacity is good. If it is 100 μm or less, the adsorptive power does not decrease, and neutralized salts and acids do not elute. The obtained filtrate is dehydrated at 90 to 160 ° C. under reduced pressure (100 kPa or less). The method may be a batch method or a shower ring method.

By the method of the present invention, a polyether having a residual alkali, neutralized salt, and acid content of 1 ppm or less can be obtained in a simple and short time.
The method of the present invention is preferably performed in the absence of oxygen, and the gas phase oxygen concentration is 1000 ppm or less, preferably 500 ppm or less. If it is 1000 ppm or less, the polyether is difficult to be oxidized, and as a result, it is difficult to be colored.

EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to this.
The average particle size of the dispersed particles was measured by diluting 100 times with the same kind of purified polyether using a particle size distribution analyzer LA-750 manufactured by Horiba.
The pH was measured by the method described in Section 6.9 of the JIS K1557 polyether test method for polyurethane [about 14 vol% solution of isopropanol alcohol / water (10/6 volume ratio) mixture].
The acid value was measured by the potentiometric titration method in Section 6.6 of the JIS test method. In addition, the part in an Example is a weight part.
The residual base concentration was measured based on the CPR measurement method in Section 6.8 of the JIS test method and converted as an alkali metal hydroxide.
The volatile matter was measured by gas chromatograph, or by reacting an acid and back titrating unreacted acid.
The neutralized salt was measured by measuring the alkali metal concentration with ICP (Inductively Coupled Plasma Emission Spectrometer) and the difference from the alkali content of the residual base.

Production Example 1
In a 1 KL high-pressure gas reaction facility, 150 kg of glycerin propylene oxide adduct (hydroxyl value converted molecular weight 600) and 2 kg of potassium hydroxide were charged, followed by vacuum dehydration at 120 ° C. for 60 minutes. Next, the temperature was raised to 100 to 130 ° C., 635 kg of propylene oxide was injected in about 8 hours, and the reaction was continued for 2 hours at the same temperature until the volatile content became 0.1% or less. d-1).
The potassium concentration of the crude polyether d-1 was 2,550 ppm.

Production Example 2
In a 1 KL high-pressure gas reaction facility, 90 kg of glycerin propylene oxide adduct (hydroxyl value converted molecular weight 600) and 2.2 kg of potassium hydroxide were charged, and after vacuum substitution, vacuum dehydration was performed at 120 ° C. for 60 minutes. Next, the temperature is raised to 100 to 130 ° C., 680 kg of propylene oxide is injected in about 8 hours, and then 125 kg of ethylene oxide is injected in about 2 hours. The reaction was continued for a time to obtain a liquid crude polyether (hereinafter referred to as crude polyether d-2) having an increased HLB. The caustic potash concentration of the crude polyether d-2 was 2,460 ppm.

<Example 1>
Put 800 kg of crude polyether (d-1) in a 1 KL treatment tank (sealed tank equipped with a stirrer), change the oxygen concentration in the gas phase to 400 ppm by nitrogen substitution, 12 kg of ion-exchange water and 2.6 kg of 75% phosphoric acid aqueous solution ( 0.55 mol) with respect to the basic catalyst as phosphoric acid, stirred at 90 ° C. for 5 minutes, and then 1.6 kg of terephthalic acid having an average particle size of 40 μm (0.27 mol with respect to the basic catalyst) was added, Stirring was performed for 20 minutes. The average particle diameter (R1) of the dispersed particles of the precipitated crystals was 25 μm, particles of 1 μm or less were 0.1%, and particles of 10 μm or more were 83%. Using a spatula filter (horizontal filter plate type pressure filter) with a capacity of about 80L and a filtration area of 1m2, pressurize under nitrogen with a filter cloth (manufactured by Shikishima Campus Co., Ltd.) with a retained particle size (R2) of 29μm as a filter. (0.1 MPa) Filtration was circulated. After 5 minutes of filtration, a clear liquid was obtained, and the time required to filter 800 kg was 90 minutes. The filtrate was circulated and dehydrated at 160 ° C. with a film evaporator to obtain a colorless and transparent purified polyether.
The residual base concentration of the purified polyether was 0.2 ppm, the acid value was 0.001, and no neutralized salt was detected. The amount of waste after filtration (total amount of neutralized salt, adsorbent, filter aid, and polyether oil supply) was 0.80% by weight relative to the crude polyether. The total time of the neutralization step, the crystallization step, and the filtration step was 150 minutes.

<Example 2>
Neutral crystallization was performed in the same manner except that the crude polyether (d-1) in Example 1 was replaced with (d-2) and the amount of ion-exchanged water was 25.6 kg.
The average particle diameter (R1) of the dispersed particles of the precipitated crystals was 20 μm, 1 μm or less was 0.1%, 10 μm or more was 78%. Using a Spackler filter (horizontal filter plate type pressure filter) with a capacity of about 80L and a filtration area of 1m2, pressurize under nitrogen with a non-woven fabric (manufactured by Chubu Filter Co., Ltd.) with a reserved particle size (R2) of 25μm (0) .1 MPa) Filtration was circulated. A clear liquid was obtained after 5 minutes of filtration, and the time required to filter 800 kg was 100 minutes. The filtrate was circulated and dehydrated at 160 ° C. with a film evaporator to obtain a colorless and transparent purified polyether.
The residual base concentration of the purified polyether was 0.3 ppm, the acid value was 0.002, and no neutralized salt was detected. The amount of waste after filtration was 1.17% by weight relative to the crude polyether. The total time including the neutralization step, the crystallization step, and the filtration step was 170 minutes.

<Example 3>
Put 800 kg of crude polyether (d-1) in a 1 KL treatment tank (sealed tank equipped with a stirrer), make the oxygen concentration in the gas phase 400 ppm by purging with nitrogen, 12 kg of ion-exchange water and 4.67 kg of 75% phosphoric acid aqueous solution ( 1.0 mol) was added as phosphoric acid to the basic catalyst, and dehydration was performed at 90 ° C. under reduced pressure. In this method, it took 6 hours for crystallization. At this time, the average particle diameter (R ₁ ) was 10 μm, particles of 1 μm or less were 0.1%, and particles of 10 μm or more were 62%. Using a spatula filter (horizontal filter plate type pressure filter) with a capacity of about 80 L and a filtration area of 1 m ² , pressurize under nitrogen with a filter paper (manufactured by Azumi Filter Paper Co., Ltd.) with a reserved particle size (R ₂ ) of 14 μm. (0.1 MPa) Filtration was circulated. After 5 minutes of filtration, a clear liquid was obtained, and the time required to filter 800 kg was 90 minutes. The filtrate was circulated and dehydrated at 160 ° C. with a film evaporator to obtain a colorless and transparent purified polyether.
The residual base concentration of the purified polyether was 0.2 ppm, the acid value was 0.001, and no neutralized salt was detected. The amount of waste after filtration was 0.80% by weight relative to the crude polyether. The total time of the neutralization step, the crystallization step, and the filtration step was 460 minutes.

<Comparative Example 1>
Put 800 kg of crude polyether (d-1) in a 1 KL treatment tank (sealed tank equipped with a stirrer), change the oxygen concentration in the gas phase to 400 ppm by nitrogen substitution, 12 kg of ion-exchange water and 4.67 kg of 75% phosphoric acid aqueous solution ( 1.0 mol) was added as phosphoric acid to the basic catalyst, and dehydration was performed at 90 ° C. under reduced pressure. In this method, it took 6 hours for crystallization. The average particle diameter (R ₁ ) at this time was 10 μm. 0.4 kg of “Radiolite 800” (manufactured by Showa Kagaku Kogyo; diatomaceous earth filter aid) is added to this, and a spatula filter (horizontal filter type pressure filter) with a capacity of about 80 L and a filtration area of 1 m ² is used. The filtration was performed by circulating pressure (0.1 MPa) under nitrogen with a filter cloth (manufactured by Shikishima Campus Co., Ltd.) having a retained particle diameter (R ₂ ) of 29 μm as a filter. A transparent liquid was obtained after 10 minutes of filtration, and the time required to filter 800 kg was 110 minutes. The filtrate was circulated and dehydrated at 160 ° C. with a film evaporator to obtain a colorless and transparent purified polyether.
The residual base concentration of the purified polyether was 0.5 ppm, the acid value was 0.12, and the neutralized salt was 38 ppm. The amount of waste after filtration was 0.82% by weight relative to the crude polyether. The total time including the neutralization step, the crystallization step, and the filtration step was 500 minutes.

<Comparative example 2>
Put 800 kg of crude polyether (d-1) in a 1 KL treatment tank (sealed tank with a stirrer), make the gas phase oxygen concentration 450 ppm by nitrogen substitution, 12 kg of ion-exchanged water and 4.46 kg of 35% hydrochloric acid aqueous solution ( Hydrochloric acid (1.2 mol) with respect to the basic catalyst), and 1.6 kg of “KYOWARD 1000” (hydrotalcite acid adsorbent, manufactured by Kyowa Chemical Industry Co., Ltd.) was added and dehydrated under reduced pressure at 90 ° C. for 4 hours. went. The average particle size (R ₁ ) at this time was 13 μm. This "Radiolite 800" (product of Showa Chemical Co., diatomaceous earth filter aid) was added 0.4 kg, a volume of about 80L, spa Klar filter having a filtration area of 1 m ² (the horizontal filter plates type pressure filter) used, Filtration was performed under pressure (0.1 MPa) under nitrogen using a filter cloth (manufactured by Shikishima Campus Co., Ltd.) having a retained particle size (R ₂ ) of 29 μm as a filter. A transparent liquid was obtained after 10 minutes of filtration, and the time required to filter 800 kg was 200 minutes. The filtrate was circulated and dehydrated at 160 ° C. with a film evaporator to obtain a colorless and transparent purified polyether. The purified polyether had a residual base concentration of 0.2 ppm, an acid value of 0.01, and Cl ions by ion chromatography. Was detected at 6 ppm. The amount of waste after filtration was 0.98% by weight relative to the crude polyether. The total time of the neutralization step, the crystallization step, and the filtration step was 460 minutes.

<Comparative Example 3>
Put 800 kg of crude polyether (d-1) in a 1 KL treatment tank (sealed tank with a stirrer), change the oxygen concentration in the gas phase to 450 ppm by nitrogen substitution, add 16 kg of ion-exchanged water, 4.8 kg of magnesium silicate (manufactured by Kyowa Chemical Industry Co., Ltd.) (0.6 wt% with respect to the crude polyether) was added, and the oxygen concentration in the gas phase was again 450 ppm by nitrogen substitution, followed by stirring at 90 ° C. for 10 minutes. At this time, the average particle diameter (R ₁ ) was 17 μm. To this, 0.4 kg of “Radiolite 800” (manufactured by Showa Chemical Industry Co., Ltd .; diatomaceous earth filter aid) is used, and a spatula filter (horizontal filter type pressure filter) with a capacity of about 80 L and a filtration area of 1 m ² is used. Filtration was performed under pressure (0.1 MPa) under nitrogen using a filter cloth (manufactured by Shikishima Campus Co., Ltd.) having a retained particle size (R ₂ ) of 29 μm as a filter. Even after 10 minutes of filtration, a transparent liquid was not obtained, and 1 kg of “Radiolite 800” was further added to continue filtration. After 10 minutes, a clear liquid was obtained, and the time required for filtering 800 kg was 100 minutes. The filtrate was circulated and dehydrated at 160 ° C. with a film evaporator to obtain a colorless and transparent purified polyether.
The residual base concentration of the purified polyether was 16 ppm.
The amount of waste after filtration was 1.8% by weight relative to the crude polyether. The total time including the neutralization step, the crystallization step, and the filtration step was 240 minutes.

<Comparative example 4>
Put 800 kg of crude polyether (d-1) in a 1 KL treatment tank (sealed tank with a stirrer), change the oxygen concentration in the gas phase to 450 ppm by nitrogen substitution, add 16 kg of ion-exchanged water, 16 kg of aluminum silicate (manufactured by Kyowa Chemical Industry Co., Ltd.) (2.0% by weight based on the crude polyether) was added, and the oxygen concentration in the gas phase was 450 ppm again by nitrogen substitution, followed by stirring at 90 ° C. for 10 minutes. The average particle size (R ₁ ) at this time was 60 μm. To this, 0.4 kg of “Radiolite 800” (manufactured by Showa Chemical Industry Co., Ltd .; diatomaceous earth filter aid) is used, and a spatula filter (horizontal filter type pressure filter) with a capacity of about 80 L and a filtration area of 1 m ² is used. As a filter, pressure (0.1 MPa) filtration was circulated under a nitrogen filter paper (manufactured by Azumi Filter Paper Co., Ltd.) having a retained particle diameter (R ₂ ) of 6 μm. A clear liquid was obtained after 5 minutes of filtration, and the time required to filter 800 kg was 150 minutes. The filtrate was circulated and dehydrated at 160 ° C. with a film evaporator to obtain a colorless and transparent purified polyether.
The residual base concentration of the purified polyether was 1.5 ppm. The amount of waste after filtration was 5% by weight relative to the crude polyether. The total time including the neutralization step, the crystallization step, and the filtration step was 180 minutes.

<Comparative Example 5>
Put 800 kg of crude polyether (d-1) in a 1 KL treatment tank (sealed tank equipped with a stirrer), make the oxygen concentration in the gas phase 400 ppm by purging with nitrogen, 12 kg of ion-exchange water and 4.67 kg of 75% phosphoric acid aqueous solution ( 1.0 mol) was added as phosphoric acid to the basic catalyst, and dehydration was performed at 90 ° C. under reduced pressure. In this method, it took 6 hours for crystallization. The average particle diameter (R ₁ ) at this time was 10 μm. Using a spatula filter (horizontal filter plate type pressure filter) with a capacity of about 80 L and a filtration area of 1 m ² , pressurize under nitrogen with a filter paper (manufactured by Azumi Filter Paper Co., Ltd.) with a reserved particle size (R ₂ ) of 6 μm. (0.1 MPa) Filtration was circulated. A transparent liquid was obtained immediately after filtration, but the time required to filter 800 kg was 300 minutes.
The filtrate was circulated and dehydrated at 160 ° C. with a film evaporator to obtain a colorless and transparent purified polyether. The residual base concentration of the purified polyether was 0.2 ppm, the acid value was 0.001, and no neutralized salt was detected. The amount of waste after filtration was 0.80% by weight relative to the crude polyether. The total time of the neutralization step, the crystallization step, and the filtration step was 660 minutes.

Since the purified polyether obtained by the method for purifying a polyether of the present invention has high purity, it can be suitably used as a raw material for polyurethane foams, resins, surfactants, cosmetics and the like.

Claims (1)

The crude polyether (d) obtained by addition polymerization of the alkylene oxide (c) to the active hydrogen-containing compound (b) in the presence of the basic catalyst (a) is neutralized with an acid, and a neutralized salt is crystallized. Then, in the step of filtering with a filter, the relationship between the average particle size of the dispersed particles and the retained particle size of the filter is 1% or less of the dispersed particles is 1% or less of the total dispersed particles and 50% or more of the dispersed particles are 10% or more. A method for purifying a crude polyether, wherein a filter satisfying the formulas (1) and (2) is selected and filtered.
R1 <R2 (μm) (1)
R ₂ −R ₁ <10 (μm) (2)
[Wherein R1 represents the average particle size (μm) of the dispersed particles, and R2 represents the retained particle size (μm) of the filter. ]