JP2003128780A - Method for removing organic solvent from oxyalkylene- based polymer solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control polymer deposition at a nozzle part and to stably enable continuous evaporation operation in removing an organic solvent from a polymer solution containing an oxyalkylene-based polymer by using flash operation. SOLUTION: This method comprises, in separating an organic solvent from an oxyalkylene-based polymer solution containing an organic solvent by evaporation, heating the oxyalkylene-based polymer solution to 100 deg.C to 140 deg.C, then feeding the polymer solution to a tank adjusted to normal pressure or above and then adjusting the tank to a reduced pressure condition of <=20 kPa degree of vacuum.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for removing an organic solvent from an oxyalkylene polymer solution containing an oxyalkylene polymer and an organic solvent as main components.

[0002]

As a method for removing an organic solvent from a polymer solution composed of a polymer and an organic solvent, for example, the polymer solution is heated by using a multitubular heat exchanger, and then an atomizer or a spray nozzle is used. A method of flushing in a devolatilizing tank under reduced pressure to remove volatile components (hereinafter referred to as flash evaporation) is disclosed in Japanese Patent Publication No. 48-29797 and is generally used. This method has the advantages that the structure of the evaporator is simpler than that of the thin-film evaporator and the evaporation method having self-renewal property, and the concentration operation can be carried out inexpensively and efficiently.

However, since the oxyalkylene polymer used in the present invention is characterized in that the polymer has high tackiness and low hardness, it has been previously depressurized in the above-mentioned flash evaporation operation as previously reported. When the evaporation operation is carried out directly using an atomizer or a spray nozzle in the devolatilization tank, the concentrated oxyalkylene polymer adheres to the vicinity of the nozzle, making it difficult to carry out the evaporation operation in a stable and continuous manner. was there.

Therefore, it has been desired to develop a method for efficiently removing an organic solvent from a polymer solution containing an oxyalkylene polymer having the above characteristics and an organic solvent to produce a polymer having a small amount of volatile components. In particular, in inexpensive and efficient flash evaporation operation, it has been desired to establish a method capable of preventing the polymer from scaling and clogging near the nozzle outlet and continuously and stably producing the polymer.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to suppress adhesion of a polymer in the vicinity of a nozzle portion when removing an organic solvent from a polymer solution containing an oxyalkylene polymer by a flash evaporation operation. Another object of the present invention is to provide a method for removing an organic solvent, which enables stable and continuous flash evaporation operation.

[0006]

Means for Solving the Problems As a result of earnest studies on a method of efficiently removing an organic solvent from an oxyalkylene polymer solution by flash evaporation, the present inventors have found that
The present invention has been completed by finding a method for suppressing the adhesion of the polymer in the vicinity of the nozzle portion and enabling stable and continuous evaporation operation.

That is, according to the present invention, when the organic solvent is evaporated and separated from the oxyalkylene polymer solution containing the organic solvent, 100 parts of the oxyalkylene polymer solution is used.
C. to 140.degree. C., then the polymer solution is supplied to a tank adjusted to atmospheric pressure or higher, and then the tank is vacuumed to 20.degree.
The present invention relates to a method for removing an organic solvent from an oxyalkylene polymer solution, which is characterized in that a reduced pressure condition of kPa or less is set.

In a preferred embodiment, when the polymer solution is supplied to the tank, a nozzle or a pipe having a hole diameter of 0.5 to 10 mm is used, and the solution discharge pressure of the nozzle or the pipe portion is 0.11. The method relates to the method for removing an organic solvent from the oxyalkylene polymer solution, wherein

In a further preferred embodiment, 35% by weight or more of the organic solvent contained in the polymer solution is separated by evaporation, and the organic solvent is removed from the oxyalkylene polymer solution according to any one of the above. Regarding the method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.

The oxyalkylene polymer in the present invention may be a polymer whose main chain structure has a structure represented by --RO-- as a repeating unit, where R is hydrogen,
Any divalent organic group having 1 to 20 carbon atoms may be used as long as it contains at least one selected from the group consisting of oxygen and nitrogen as a constituent atom. Further, it may be a homopolymer in which all the repeating units are the same, or a copolymer containing two or more kinds of repeating units. Further, the main chain may have a branched structure.

Specific examples of R include --CH _2- , --C ₂ H
_{4 -, - C 3 H 6} -, - C 4 H 8 -, - C 5 H 10 -, - C 6 H 4
_{-, - C 6 H 12 -} , - C 7 H 14, -C 8 H 16 -, C 9 H 18,
_{-C 10 H 20 -, - CH} (CH 3) -, - CH 2 -CH (C
_{H 3) -, - CH 2} -CH (CH 3) -CH 2 -, - C 2 H 4
_{-CH (CH 3) -, -} CH 2 -C 6 H 4 -, - CH 2 -C 6
Examples include groups such as H ₄ —CH ₂ — and —C ₂ H ₄ —C ₆ H ₄ —. Among them, —CH ₂ — and —C ₂ H ₄ are easy to synthesize.
—, —CH ₂ —CH (CH ₃ ) — is preferable, and —CH ₂ —CH (CH ₃ ) — is particularly preferable because of easy availability of raw materials.

The oxyalkylene polymer in the present invention can be obtained, for example, by ring-opening polymerization of a monoepoxide in the presence of an initiator and a catalyst.

Specific examples of the initiator include ethylene glycol, propylene glycol, butanediol, hexamethylene glycol, methallyl alcohol, bisphenol A, hydrogenated bisphenol A, neopentyl glycol, polybutadiene diol, diethylene glycol, triethylene glycol, polyethylene. Dihydric alcohols such as glycol and polypropylene glycol, polypropylene triol, polypropylene tetraol, dipropylene glycol, glycerin, trimethylol methane, trimethylol propane, pentaerythritol and other polyhydric alcohols and various oligomers having multiple hydroxyl groups. To be

Specific examples of the monoepoxide include ethylene oxide, propylene oxide, α-butylene oxide, β-butylene oxide, hexene oxide, cyclohexene oxide, styrene oxide,
Alkylene oxides such as α-methylstyrene oxide, and alkyl glycidyl ethers such as methyl glycidyl ether, ethyl glycidyl ether, isopropyl glycidyl ether and butyl glycidyl ether,
Examples thereof include allyl glycidyl ethers and aryl glycidyl ethers.

As the catalyst, there are already known alkali catalysts such as KOH and NaOH, acidic catalysts such as trifluoroborane-etherate, and complex metal cyanide complex catalysts such as aluminoporphyrin metal complex and cobalt zinc cyanide-glyme complex catalyst. Things are used. In particular, it is preferable to use the double metal cyanide complex catalyst because it causes few side reactions, but other catalysts may be used.

In addition to the above method, for example, oxyalkyl
The main chain skeleton of the ren-based polymer is a hydroxyl-terminated oxyalkylene
Of a basic compound such as KOH, NaOH,
KOCH₃, NaOCH₃In the presence of etc.
Alkyl genide, eg CH ₂Cl₂, CH₂Br₂Etc.
It can also be obtained by chain extension or the like. Also bifunctional
The hydroxyl group end group is
Examples include a method of chain extension of a xyalkylene polymer.
It

The molecular weight of the oxyalkylene polymer of the present invention is not particularly limited, but the number average molecular weight in terms of polystyrene in gel permeation chromatography (GPC) is 1,000 to 100,000. It is preferable that it is more preferably 3,000 to 25,000. If the number average molecular weight is less than 1,000, the desired quality cannot be obtained, and if it exceeds 100,000, the viscosity of the polymer becomes too high and handling tends to be difficult, which is not preferable.

The oxyalkylene polymer solution used in the present invention is not particularly limited as long as it is a solution in which an oxyalkylene polymer is dissolved in an organic solvent.

Known organic solvents can be used, for example, aliphatic, alicyclic or aromatic hydrocarbon solvents, ether solvents, and halides thereof can be preferably used. Specific examples thereof include butane, pentane, hexane, heptane, octane, nonane, decane, dodecane, cyclohexane, cyclopentane, benzene, toluene, xylene, butanol, pentanol, methyl ether, ethyl ether, isopropyl ether, Examples thereof include methylene chloride, methylchloroform, carbon tetrachloride, dichlorodifluoromethane, perchloroethylene, benzene-based solvents or toluene-based solvents substituted with one or more chlorine atoms, bromine atoms and / or iodine atoms. It is not limited. These may be used alone or in combination of two or more.

In order to isolate the oxyalkylene polymer from the polymer solution, it is necessary to remove the organic solvent by evaporation operation.

The flash evaporation operation itself can be applied to polymers other than the oxyalkylene polymer, but in the oxyalkylene polymer in which the tackiness and the deterioration of the fluidity are remarkably exhibited as the evaporation progresses. In the thin-film evaporator and the evaporation method having self-renewal property, increasing the size of the equipment is a big problem in actual production. Therefore, the flash evaporation method alone or the method of combining the evaporator and the flash evaporation method is required. Be advantageous.

Next, the removal of the organic solvent will be described with reference to the accompanying drawings, but the present invention is not limited to these drawings.

In the present invention, for example, it is preferable to use an evaporator as shown in FIG.

The evaporator of FIG. 1 includes: 1: polymer solution supply tank, 2: liquid feed pump, 3: polymer solution heating device, 4:
It consists of a flash evaporator, 5: flash nozzle, 6: vacuum pump, 7: solvent condenser, 8: recovery solvent receiving tank.

3: The polymer solution heating device is not particularly limited as long as it has a function of raising the temperature of the polymer to a desired temperature, and various types such as plate type or multitubular heat exchangers can be used. Things can be used. Alternatively, it is possible to heat the polymer solution supply tank by installing a jacket or coil. The heating medium is also not particularly limited, and steam, heating oil or the like can be used. By using such a heating device, the polymer solution is heated to 100-140.
It is preferable to heat at a temperature of 120 to 140 ° C. If the heating temperature is lower than 100 ° C, the amount of heat required for evaporation of the solvent tends to be insufficient, and as a result, the evaporation efficiency tends to decrease. On the other hand, if the heating temperature exceeds 140 ° C, thermal degradation of the oxyalkylene polymer may occur. It is not preferable because it is present.

The heated polymer solution is sent to the 4: flash evaporator via the 5: flash nozzle. When feeding the polymer solution, pressure feeding can be used in addition to the 2: liquid feeding pump. In the case of pressure feeding, either an inert gas such as nitrogen or the vapor pressure of the organic solvent contained in the polymer solution may be used.

When the heated polymer solution is supplied to the flash evaporator under reduced pressure, evaporation of the organic solvent occurs in the flash nozzle, and the concentrated oxyalkylene polymer is deposited, resulting in nozzle clogging. Often occur. For this reason, it is preferable that the flash nozzle has a pressurized system in which evaporation does not occur.

To realize such a condition,
At the start of the supply of the polymer solution, it is preferable to set the pressure inside the flash evaporator to atmospheric pressure or higher, more preferably 0.11 MPa or higher. Under such conditions, the evaporation operation is started without the precipitation of the polymer in the pipe. On the contrary, when the pressure is lower than the atmospheric pressure, the evaporation of the organic solvent is started by the time the supply of the polymer solution is stabilized, particularly when the evaporation is started before the inside of the nozzle is filled with the polymer solution, as a result, It is not preferable because the polymer may be precipitated and the nozzle may be clogged.

After the supply of the polymer solution is stabilized, it is preferable to subsequently operate the flash evaporator under a reduced pressure condition of 20 kPa or less, more preferably a reduced pressure condition of 5 kPa or less to start the evaporation of the organic solvent. When the pressure of the flash evaporator exceeds 20 kPa, the solvent evaporation rate decreases, which is not preferable.

The discharge pressure of the oxyalkylene polymer solution is preferably in the range of 0.11 to 1.1 MPa, more preferably 0.3 to 0.6 MPa. If the discharge pressure of the polymer solution is less than 0.11 MPa, the progress of evaporation to the inside of the nozzle tends to cause clogging of the nozzle, and conversely, if it exceeds 1.1 MPa, the discharge rate of the polymer solution tends to be high. It is not preferable because it is too large and the polymer solution easily adheres to the wall of the can due to scattering and splashing of the liquid in the flash evaporation can. The polymer solution attached to the can wall remains on the can wall as the organic solvent evaporates, which causes a decrease in the recovery rate.

Further, in order to stably hold the pressure, it is preferable that the tip portion of the flash nozzle has a hole diameter in the range of 0.5 to 10 mm, more preferably 1 to 5 mm. If the hole diameter of the tip portion is less than 0.5 mm, the nozzle tends to be clogged even within the above pressure range, and conversely, if it exceeds 10 mm, the discharge rate of the polymer solution is increased even within the above pressure range. Since it is large and the problem of polymer adhesion to the wall surface tends to occur, it is not preferable. The shape of the tip of the pipe is not particularly limited.
As shown in FIG. 3, it may be a general tapered one or a simple straight pipe.

The material to be used may be steel or stainless steel, but may be appropriately selected in consideration of the temperature, pressure and solvent resistance to be used. When a metal is used, by coating the inside of the pipe and the vicinity of the tip with a fluororesin, the adhesion of the polymer to the nozzle can be further reduced and stable evaporation can be achieved.

The shape and the like of the evaporator can be freely selected as long as it matches the operating temperature and pressure. However, the inner diameter D of the evaporator is limited by the amount of treatment, and the solvent evaporation amount per unit time of the evaporator is usually 500 kg / m ²
It is necessary to design so as to be less than / h. If the evaporation operation is performed in a range of a larger evaporation amount than this, the phenomenon of entrainment of the polymer particles easily occurs, which is not preferable. Also,
In order to suppress entrainment of droplets, the inlet of the solvent recovery line consisting of 6: vacuum pump, 7: solvent condenser,
It is preferably installed at the top of the evaporator.

Further, if the solvent vapor is condensed in the evaporator, a phenomenon such as impregnation of the polymer after evaporation may occur and the evaporation efficiency may be lowered. Therefore, it is preferable to keep the temperature of the evaporator itself to such an extent that condensation of solvent vapor can be prevented.

6: The vacuum pump can be used without limitation as long as it has an evacuation capacity capable of holding the evaporator at 20 kPa or less with respect to the throughput of the polymer solution. This is because the solvent evaporation amount in flash evaporation is determined by the polymer solution supply amount, the supply temperature and the flash evaporator internal pressure.

Further, the presence of an antioxidant during the flash evaporation operation from the polymer solution makes it possible to suppress the quality deterioration due to the thermal decomposition of the polymer. These antioxidants may be dissolved at the stage of polymer solution.

The above-mentioned antioxidant is a phenolic antioxidant having a function of a radical chain inhibitor, for example, 2,6-.
Di-tert-butyl-p-cresol, 2,6-di-
tert-butylphenol, 2,4-dimethyl-6-
tert-butylphenol, 2,2'-methylenebis
(4-methyl-6-tert-butylphenol), 4,
4'-butylidene bis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6)
-Tert-butylphenol), tetrakis [methylene-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane, 1,1,3-tris
(2-Methyl-4-hydroxy-5-tert-butylphenyl) butane and the like can be used.

Similarly, as a radical chain inhibitor, an amine-based antioxidant such as phenyl-β-naphthylamine,
α-naphthylamine, N, N′-di-sec-butyl-
p-phenylenediamine, phenothiazine, N, N'-
Diphenyl-p-phenylenediamine and the like can be used, but are not limited thereto.

The amount of the antioxidant added is preferably 0.001 to 10 parts by weight with respect to 100 parts by weight of the oxyalkylene polymer. If the amount is less than 0.001 part by weight, the effect of the antioxidant is lowered, and if it exceeds 10 parts by weight, the product quality may be adversely affected, which is not preferable.

When the organic solvent is evaporated from the oxyalkylene polymer solution containing the organic solvent by using the above-described evaporation device and evaporation conditions,
Suppresses the adhesion of the polymer in the vicinity of the nozzle and enables stable and continuous flash evaporation operation, evaporating and separating 35% by weight or more of the organic solvent contained in the polymer solution, and further 70% by weight or more. It becomes possible to stably evaporate and separate.

[0042]

The present invention will be described in more detail with reference to the following examples. It should be noted that the present invention is not limited to these examples and can be appropriately modified and implemented within the scope of the present invention.

Prior to the examples, the analytical measuring method used in the present invention will be described below. (Measurement of residual solvent) Equipment used: Shimadzu Corporation Gas Chromatography GC-1
7A Separation column: Porapack QS Carrier gas: Nitrogen (150 kPa) Separation conditions: Initial temperature 100 ° C., 6.5 minutes hold, heating rate 15 ° C./min, final temperature 140 ° C., 8 minutes hold, injection temperature 200 ° C., detector Temperature 200
℃ Sample preparation: Polymer about 0.5g, Diluting solvent Acetone about 5
g, standard sample ethanol about 0.01 g. (Production Example 1) Propylene oxide was polymerized using polypropylene glycol as an initiator and a zinc hexacyanocobaltate complex catalyst to obtain a hydroxyl group-terminated polyether oligomer. Subsequently, a methanol solution of sodium methoxide was added to the hydroxyl group-terminated polyether oligomer to distill off methanol, and 3-chloro-1-
Propene was added to convert the terminal hydroxyl groups to allyl groups to obtain crude polyether A. Then, the polymer solution mixed at a ratio of crude polyether A / n-hexane = 100/230 (weight ratio) was supplied to a one-column five-stage high-speed stirring type stirring tank having a turbine blade with an edge, and at the same time ion-exchanged water was supplied. Is supplied at a ratio of crude polyether A / ion-exchanged water = 100/220 (weight ratio), and a salt by-produced in the process of obtaining crude polyether A is extracted into ion-exchanged water at a blade tip speed of 15 m / s. Processed. The treatment liquid was subsequently separated with a separation plate type continuous centrifuge (centrifugal force of 9000 G) to obtain a polymer solution. (Examples 1 and 2) The polymer solution obtained in Production Example 1 was flash-evaporated using the evaporation equipment shown in FIG. About 5 L of the polymer solution was charged into a jacketed polymer solution supply tank, and heating medium oil was circulated through the jacket to raise the temperature. Liquid temperature is 124 ° C (Example 1), 125 ° C
After becoming constant in (Example 2), the internal pressure of the polymer solution supply tank was adjusted to 0.6 MPa with nitrogen gas. The flash nozzle installed in the evaporator was equipped with a fluororesin coating nozzle having a hole diameter of 1 mm. The polymer solution was supplied to the flash evaporator which was opened to normal pressure for about 5 seconds, and after confirming that the solution pressure was 0.6 MPa, the vacuum pump was started and the evaporation operation was continued for about 10 minutes. During the evaporation operation, the degree of vacuum is 3.33 kPa (Example 1), 20.00
It was kept at kPa (Example 2). No clogging of the nozzle was confirmed during the evaporation operation. After completion of the evaporation operation, the polymer solution at the bottom of the evaporator was recovered. No polymer adhesion was confirmed on the side wall of the can. The amount of solvent remaining in the polymer solution was quantified by gas chromatography. The amount of residual solvent in the polymer solution was 17.1% by weight (Example 1) and 29.3% by weight (Example 2), respectively, and the evaporation rate based on the total solvent was 75.5%. (Example 1) was 58.0% (Example 2).

The results are shown in Table 1.

[0045]

[Table 1]

(Comparative Examples 1 to 3) Polymer temperature and evaporator vacuum degree were 70 ° C. and 46.66 kPa (Comparative Example 1), respectively.
112 ° C., 46.66 kPa (Comparative Example 2) and 88
C., 33.33 kPa (Comparative Example 3), and Example 1
The same experiment as in ~ 2 was performed. In all cases, clogging of the nozzle and adhesion of polymer to the can wall were not confirmed. The results of measuring the amount of solvent remaining in the polymer solution are shown in Table 2. Since the supply temperature of the polymer solution is low and the pressure in the flash evaporator is high, the amount of residual solvent in the polymer solution is 55% by weight in all cases.
Above all, the solvent evaporation rate was 25% or less in all cases.

[0047]

[Table 2]

Comparative Example 4 Example 1 was repeated except that the polymer solution was supplied to a flash evaporator having a vacuum degree of 9.33 kPa.
The same experiment was performed. In about 10 seconds, the resin adhered to the tip of the nozzle and the solution could not be supplied. (Comparative Example 5) Polymer solution pressure was 1.6 MPa with nitrogen gas.
The same experiment as in Example 1 was carried out except that the adjustment was made to. After the evaporation was completed, the adhesion to the can wall was confirmed.

[0049]

[Table 3]

[0050]

By using the evaporation method of the present invention,
When the organic solvent is removed from the polymer solution containing the oxyalkylene polymer by flash evaporation, the adhesion of the polymer at the nozzle portion is suppressed, and stable and continuous evaporation operation is possible.

[Brief description of drawings]

FIG. 1 is an example of a schematic diagram of an evaporation method used in the present invention.

FIG. 2 is a schematic diagram of an experimental apparatus used in Examples and Comparative Examples of the present invention.

[Explanation of symbols] 1: Polymer solution supply tank 2: Liquid delivery pump 3: Polymer solution heating device 4: Flash evaporator 5: Flash nozzle 6: Vacuum pump 7: Solvent condenser 8: Collected solvent receiving tank 9: Heat medium device 10: Polymer solution thermometer 11: Polymer solution pressure gauge 12: Flash evaporator pressure gauge

Claims (3)

[Claims] 1. When the organic solvent is evaporated and separated from the oxyalkylene polymer solution containing the organic solvent, the oxyalkylene polymer solution is heated to 100 ° C. to 140 ° C. and then adjusted to atmospheric pressure or higher. A method for removing an organic solvent from an oxyalkylene polymer solution, which comprises supplying a polymer solution to a tank and then subjecting the tank to a reduced pressure condition of a vacuum degree of 20 kPa or less. 2. When supplying a polymer solution to a tank, a nozzle or a pipe having a hole diameter of 0.5 to 10 mm is used, and the discharge pressure of the solution at the nozzle or the pipe portion is 0.1.
The method for removing an organic solvent from an oxyalkylene polymer solution according to claim 1, wherein the method is 1 to 1.1 MPa. 3. The method for removing an organic solvent from an oxyalkylene polymer solution according to claim 1, wherein 35% by weight or more of the organic solvent contained in the polymer solution is separated by evaporation.