JP2007131573A - Production method of polyoxyethylene alkyl ether sulfate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method of a polyoxyethylene alkyl ether sulfate, whereby production of 1,4-dioxane can be reduced through a simple operation. <P>SOLUTION: The production method comprises a sulfation reaction step wherein a polyoxyethylene alkyl ether is brought into contact with gas containing sulfur trioxide to sulfate the polyoxyethylene alkyl ether, a coagulation step wherein a reaction product of the sulfation reaction step is cooled and solidified at a cooling rate of ≥1°C/sec and a neutralization step wherein the solidified reaction product is neutralized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a polyoxyethylene alkyl ether sulfate.

Polyoxyethylene alkyl ether sulfate is used as an anionic surfactant in various applications such as liquid detergents and shampoos.
As a method for producing polyoxyethylene alkyl ether sulfate, the reaction product is neutralized by contacting with polyoxyethylene alkyl ether and sulfur trioxide (hereinafter abbreviated as SO ₃ ) containing gas for sulfation. In general, a method in which the sulfate is converted into a sulfate.
In the production of such polyoxyethylene alkyl ether sulfates, it has hitherto been a problem that 1,4-dioxane is produced as a byproduct. In the production of 1,4-dioxane, 1,4-dioxane is contained as an impurity in the resulting polyoxyethylene alkyl ether sulfate.

For this reason, various studies have been made so far in order to reduce the production of 1,4-dioxane as much as possible for the production method of polyoxyethylene alkyl ether sulfate.
For example, Patent Document 1 discloses a method in which polyoxyalkyl ether is sulfated, the resulting alkyl ether sulfuric acid is evaporated in a thin film to remove 1,4-dioxane, and then neutralized.
Patent Document 2 discloses a method in which thin-film sulfation is performed at a maximum temperature of 70 ° C. or less, preferably 45 to 60 ° C., and a SO ₃ / raw material (polyoxyethylene alkyl ether) molar ratio of 0.95 to 0.99. Proposed.
Patent Document 3 discloses a method for suppressing 1,4-dioxane production by adding a small amount of a carboxylic acid amide oxyethylate to an alkanoloxyethylate.
In Patent Document 4, the SO ₃ / raw material molar ratio is set to 0.95 to 1.0, thin film sulfation is performed at a maximum reaction temperature of 70 ° C. or less, and the temperature of the sulfate after gas-liquid separation is 40 ° C. or less. And a method for neutralizing the sulfate within 3 minutes after gas-liquid separation has been proposed.
Patent Document 5 discloses a method for suppressing the production of 1,4-dioxane by performing a sulfation reaction at a low temperature or by performing a sulfation reaction at a high temperature and then rapidly cooling to a temperature of about room temperature. Has been proposed.
JP-A 63-246357 Japanese Unexamined Patent Publication No. 01-19055 Japanese Patent Laid-Open No. 02-4436 JP 2001-151746 A JP 2001-188776 A

However, the invention disclosed in Patent Document 1 requires a thin film evaporation facility, a decompression facility, and the like. Further, the reaction product must be exposed to an inert gas stream, which is disadvantageous in terms of time and energy.
In the invention disclosed in Patent Document 2, there is a difference in effect depending on the raw material supply amount and the reaction apparatus, and a stable result may not be obtained. Further, the SO ₃ / raw material molar ratio is small and the reaction rate tends to decrease.
In the invention disclosed in Patent Document 3, it is necessary to add the third component, and there is a problem that it is mixed as an impurity in the product.
Moreover, according to the invention disclosed by patent documents 4-5, the production | generation of 1, 4- dioxane can be reduced by simple operation compared with the past. However, there is a demand for a method for producing a polyoxyethylene alkyl ether sulfate capable of further reducing the production of 1,4-dioxane in manufacturers and users of surfactants.
This invention is made | formed in view of the said situation, Comprising: The manufacturing method of the polyoxyethylene alkyl ether sulfate which can reduce the production | generation of 1, 4- dioxane by simple operation is provided.

The method for producing a polyoxyethylene alkyl ether sulfate of the present invention that solves the above problems includes a sulfation reaction step of sulfating the polyoxyethylene alkyl ether by contacting the polyoxyethylene alkyl ether and an SO ₃ -containing gas. ,
A solidification step of cooling and solidifying the reaction product of the sulfation reaction step at a cooling rate of 1 ° C./second or more;
And a neutralization step of neutralizing the reaction product after the solidification.

  According to the method for producing a polyoxyethylene alkyl ether sulfate of the present invention, the production of 1,4-dioxane can be reduced by a simple operation.

Hereinafter, the present invention will be described in more detail.
<Sulphation reaction process>
In this step, the polyoxyethylene alkyl ether is brought into contact with the SO ₃ containing gas. Thereby, polyoxyethylene alkyl ether reacts with SO ₃ and is sulfated.

As the raw material polyoxyethylene alkyl ether, a material corresponding to the target polyoxyethylene alkyl ether sulfate may be used. In the present invention, it is preferable to use a polyoxyethylene alkyl ether represented by the following general formula (I).
_{RO- (C 2 H 4 O)} n -H ... (I)
In the formula, R represents a linear or branched alkyl group having 8 to 20 carbon atoms, and n represents a number of 1 to 20.
The alkyl group of R may be linear or branched, and the carbon number of the alkyl group of R is preferably 10-18, and particularly preferably 12-14.
n is the average addition mole number of ethylene oxide (average ethylene oxide addition mole number), and 1,4-dioxane tends to be less likely to be generated as n is smaller. As n, 1-5 are preferable and 1-3 are especially preferable.
Polyoxyethylene alkyl ether may be used individually by 1 type, and may use 2 or more types of mixtures.

As the SO ₃ -containing gas, the SO ₃ gas itself may be used, but since a sulfation reaction occurs uniformly, a diluted gas obtained by diluting the SO ₃ gas with an inert gas such as dehumidified air or nitrogen is used. It is preferable.
The SO ₃ concentration in the SO ₃ -containing gas is preferably 1 to 30% by volume, more preferably 1 to 20% by volume, and further preferably 2 to 10% by volume. When the SO ₃ concentration is 30% by volume or less, the sulfation reaction occurs uniformly without partial excess reaction, and the color of the reaction product is good. When the SO ₃ concentration is 1% by volume or more, the use amount of the dilution gas as a whole is small, and the amount of exhaust gas can be reduced.

The amount of SO ₃ containing gas, the molar ratio of SO ₃ and the polyoxyethylene alkyl ether, an amount comprised within the range of SO ₃ / polyoxyethylene alkyl ether = 0.95-1.05 is preferred, 0. An amount that falls within the range of 98 to 1.02 is more preferable. When it is 1.05 or less, 1,4-dioxane tends to be hardly generated, and the amount of 1,4-dioxane in the reaction product at the end of the sulfation step can be reduced. When it is 0.95 or more, the reaction rate of polyoxyethylene alkyl ether and SO ₃ is good.
Here, the “reaction rate” means the ratio (%) of consumed (sulfated) polyoxyethylene alkyl ether in the raw material polyoxyethylene alkyl ether.

The method for bringing the polyoxyethylene alkyl ether and the SO ₃ -containing gas into contact with each other is not particularly limited, and can be carried out using, for example, a known gas-liquid reactor, such as a tank reactor or a thin film reactor. . However, the reaction time when the tank reactor is used is usually 30 to 60 minutes, which takes longer than 5 to 30 seconds, which is the normal reaction time when the thin film reactor is used. There is a concern that 1,4-dioxane may increase during the progress, and it is preferable to use a thin film reactor.
As the thin film reactor, for example, a falling thin film reactor, a rising thin film reactor, a tubular gas-liquid mixed phase flow reactor, or the like can be used.
Among the thin film reactors, a falling film reactor is preferable from the viewpoints of reaction efficiency and coloring.

The reaction temperature is preferably 40 to 70 ° C, more preferably 40 to 60 ° C, and still more preferably 40 to 50 ° C. When the temperature is 40 ° C. or higher, the reaction efficiency between polyoxyethylene alkyl ether and SO ₃ is high, and a high reaction rate can be achieved in a short reaction time. When it is 70 ° C. or lower, 1,4-dioxane tends to be hardly generated, and production of 1,4-dioxane in the reaction product until the coagulation step is performed can be suppressed.
When the sulfation reaction step is performed under relatively high conditions such as the above reaction temperature, 1,4-dioxane tends to increase if the reaction product of the sulfation reaction is left as it is after the sulfation reaction. Therefore, it is preferable to perform the coagulation step immediately after the sulfation reaction is completed.

<Coagulation process>
Next, the reaction product obtained in the sulfation reaction step is cooled and solidified at a cooling rate of 1 ° C./second or more. Thereby, the production | generation of 1, 4- dioxane can be suppressed effectively.
In the solidification of the reaction product, the reaction product is cooled to a temperature below the freezing point of the reaction product, that is, sulfated polyoxyethylene alkyl ether (hereinafter sometimes referred to as sulfate). Can be performed.
For example, in the above general formula (I), when R is a linear alkyl group having 12 to 14 carbon atoms and n is a sulfate of polyoxyethylene alkyl ether having 2 to 3, or a mixture thereof, the freezing point is Under normal pressure (1 atm), the temperature is about −8 to −2 ° C., for example, when cooled to −10 ° C. or lower, the sulfated oxide is in a solidified state.

Here, the “freezing point of the sulfate” is the highest temperature at which the sulfate changes from a liquid to a solid and loses its fluidity.
The freezing point of sulfate can be measured in accordance with “11. Freezing point measurement method” described in “Cosmetic raw material standards” (Pharmaceutical Daily Newspaper, New Edition, pages 419-420) If it is expected that the cooling medium used will be dry ice and ethanol instead of water).
That is, the measurement of the freezing point of sulfate can be performed as follows.
[apparatus]
The apparatus shown in FIG. 3 is used. Each code | symbol in FIG. 3 has the following meaning.
A: Glass-made air outer wall (both inner and outer walls are clouded and silicon oil is applied)
B: Sample container ((hard) glass test tube, except for the portion in contact with the sample, clouded with silicone oil applied to both walls of the tube, inserted into A, and fixed with a cork screw.)
C: Mark D: Glass bath E: Glass stir bar (diameter 3 mm, lower end in a ring with an outer diameter of 18 mm)
F: Thermometer No. 4, 5 or 6 G: Thermometer No. 1 H: Auxiliary thermometer Use thermometer No. 1 so that the mercury bulb is at the center of the sample top and F reading (freezing point) To.
[Operation]
Put the sample up to the marked line C of the sample container B. In a glass bath D, water (cooling medium) having a temperature lower by 10 to 15 ° C. than the expected freezing point is added. However, if the freezing point is expected to be lower than 15 ° C., dry ice and ethanol are used as the cooling medium.
Place B in the sample, attach a thermometer F, auxiliary thermometer H, and glass stirring rod E, and insert it into the glass air outer sheath A, and cool the sample to a temperature 5 ° C higher than the expected freezing point. Then, gently move E up and down at a rate of 20 times per minute and read the temperature every 30 seconds. When solidification has started, stop stirring and read the temperature t ° C. at which the difference between at least four consecutive readings is within 0.2 ° C. with the F reading, and the H reading t ′ ° C. at that time. After reading and calculating the freezing point T ° C according to the following equation, the average value is taken as the freezing point.
When undercooled, the inner wall of B is rubbed with E to promote solidification. When freezing begins, stop stirring and read the temperature every 10 seconds, read the F reading t ° C and the H reading t '° C when it remains constant for 1 minute, and set the freezing point T ° C It is calculated by the following formula.
T = t + 0.00015 (t−t ′) (t−t ″)
In the formula, t ″ is the frequency of F on the upper surface of the sample when t ° C. is read. If there is no F scale at that point, extrapolate.

  Cooling needs to be performed at a cooling rate of 1 ° C./second or more, preferably 5 ° C./second or more, more preferably 8 ° C./second or more. The larger the cooling rate, the more the generation of 1,4-dioxane during cooling is suppressed. The upper limit of the cooling rate is not particularly limited, but it is practically 10 ° C./second or less because it is difficult to actually increase the cooling rate and leads to cost increase.

  The cooling means is not particularly limited and can be cooled by a conventionally known method. For example, after completion of the reaction in a thin film reactor, a method of obtaining a reaction product solidified in a flaky shape by continuously cooling with a rotary chiller (Japan Vacuum Technology K / K) etc. and peeling from the rotating surface. There is.

<Neutralization process>
Next, the reaction product after solidification in the coagulation step is neutralized. Thereby, polyoxyethylene alkyl ether sulfate is produced.

Neutralization can be performed by bringing the reaction product into contact with an alkali.
The reaction product to be neutralized may be in a solidified state or in a dissolved state. When the solidified reaction product is brought into contact with the alkali, the reaction heat of the neutralization reaction (neutralization heat) is generated, so the reaction product dissolves from the part in contact with the alkali, and the neutralization proceeds gradually. To do.
Examples of the alkali include alkali metal or alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, and calcium hydroxide, carbonates, bicarbonates, organic amines, and ammonia.
These alkalis are usually used as an aqueous solution. The alkali concentration in the aqueous alkali solution is not particularly limited and is appropriately selected depending on the type of alkali.

  Neutralization can be performed by, for example, a method of adding a reaction product to an aqueous alkaline solution, a method of adding an aqueous alkaline solution to a reaction product, or the like. In the present invention, a method of adding a reaction product to an alkaline aqueous solution is preferable. When the reaction product is a liquid, it is preferable to add the reaction product of the sulfation reaction dropwise, and when it is a solid, It is preferable to add in the form of flakes or powders.

Neutralization is not particularly limited, but is preferably performed within 30 minutes and more preferably within 20 minutes after completion of the sulfation reaction in the sulfation reaction step. By carrying out within 30 minutes, the production of 1,4-dioxane is further suppressed.
Here, the time when the sulfation reaction is completed means the time when the target reaction rate is secured, and the target reaction rate is preferably 97% or more.

  The temperature condition in the neutralization step is preferably 70 ° C. or less and more preferably 50 ° C. or less in order to prevent thermal decomposition of the produced polyoxyethylene alkyl ether sulfate. Although there is no restriction | limiting in particular as a lower limit, Since cooling takes the cost for suppressing the temperature rise by the heat of neutralization, 20 degreeC or more is practical.

  Whether or not the reaction product has been neutralized, that is, whether or not the polyoxyethylene alkyl ether sulfate has become a sulfate can be confirmed by measuring the pH of the reaction product in the liquid state. Neutralization is usually performed so that the pH is about 5-9.

The type of polyoxyethylene alkyl ether sulfate produced by the production method of the present invention is not particularly limited, and may be, for example, a polyoxyethylene alkyl ether sulfate conventionally proposed as an anionic surfactant.
Examples of the salt include alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as magnesium salt and calcium salt, organic amine salts such as triethanolamine salt, ammonium salt and the like. The type of these salts can be selected by selecting the type of alkali used in the neutralization step.

As described above, in the method for producing polyoxyethylene alkyl ether sulfate of the present invention, 1,4-dioxane is produced by a simple method in which the reaction product of the sulfation reaction step is rapidly cooled and solidified. Can be effectively suppressed. Therefore, the obtained polyoxyethylene alkyl ether sulfate has a reduced content of 1,4-dioxane. According to the present invention, for example, a polyoxyethylene having a 1,4-dioxane content of 20 ppm or less is used. An alkyl ether sulfate can be obtained.
The content of 1,4-dioxane contained in the polyoxyethylene alkyl ether sulfate can be measured by a known method such as gas chromatography.

Furthermore, in the present invention, even when sulfation is performed at a relatively high temperature of 40 ° C. or higher, the production of 1,4-dioxane can be effectively reduced. Therefore, polyoxyethylene alkyl ether sulfate can be obtained with a high reaction rate.
Further, since a simple operation of solidifying the sulfate is sufficient, it does not require a large-scale facility such as a thin film evaporation facility or a decompression facility, which is advantageous in terms of energy. Further, it is not necessary to strictly control the ratio of the raw material to sulfur trioxide.
Furthermore, unlike the invention disclosed in Patent Document 3, it is not necessary to add the third component, so that a polyoxyethylene alkyl ether sulfate with less impurities can be obtained.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these.
In the following examples and comparative examples, the following materials were used.
“Polyoxyethylene alkyl ethers of natural alcohols mainly composed of C ₁₂ and ₁₄ ”: Natural alcohols (trade names: Alcohols having 12 carbon atoms in the alkyl group and alcohols having 14 carbon atoms in the alkyl group) CO1214, manufactured by P & G)) with an average of 2 or 3 moles of ethylene oxide (EO) added.
“Polyoxyethylene alkyl ether of a synthetic alcohol mainly composed of C12 and ₁₃ ”: a synthetic alcohol (trade name: a mixture of an alcohol having an alkyl group having 12 carbon atoms and an alcohol having an alkyl group having 13 carbon atoms) Neodol 23 (manufactured by Shall)) with an average of 2 or 3 moles of ethylene oxide (EO) added.
"Sodium hydroxide": Flake caustic soda (Asahi Glass Co., Ltd.)

  As described in paragraph [0014], the freezing point of the sulfate of each polyoxyethylene alkyl ether is “11. Freezing point” described in “Cosmetic Raw Material Standards” (Pharmaceutical Daily Report, pages 419-420). Measurement was performed according to “Measurement Method”.

Further, the amount of 1,4-dioxane in the reaction product was determined by the following measuring method.
<Measurement method of 1,4-dioxane>
About 15 g of the reaction product is precisely weighed in a 100 ml volumetric flask, and a sample prepared by measuring up with ethanol is subjected to gas chromatography under the following measurement conditions. Separately, a 1,4-dioxane reagent is diluted with ethanol. The amount of 1,4-dioxane in the sample was quantified using the calibration curve created using the test solution for the calibration curve created in the above, and the amount of 1,4-dioxane in the reaction product was determined from the result.
[Gas chromatography measurement conditions]
-Device used: Capillary gas chromatography (Device name: HP5890, manufactured by Hewlett-Packard Company)
Column: DB-WAX (manufactured by J & W Scientific, length 30 m, inner diameter (ID): 0.25 mm, film thickness: 0.25 μm)
・ Temperature program: Holding time 40 ° C. 10 minutes → 30 ° C./min. Heating up to 200 ° C. 10 minutes ・ Carrier gas: Helium (adjusted to have a linear velocity of 30 cm / sec)
-Detector: FID, temperature 200 ° C
・ Sample injection volume: 1μL
-Split ratio: [30: 1]

[Examples 1 to 3, Comparative Examples 1 to 4]
A polyoxyethylene alkyl ether of natural alcohol mainly composed of C12 and ₁₄ (average number of moles of added ethylene oxide 3, average molecular weight = 466, freezing point when sulfated: −6 ° C.) is used as a raw material under the following conditions: The sulfation reaction was carried out.
[Sulphation reaction conditions]
SO ₃ -containing gas: A gas diluted with air so that the SO ₃ concentration becomes 4% by volume.
· SO ₃ containing gas consumption: 1.00 times the molar amount of the starting material as SO ₃ (polyoxyethylene alkyl ether / SO ₃ (molar ratio) = 1.00).
-Reactor: Flowing thin film reactor (made of cylindrical glass, inner diameter 6 mm, length 1200 mm).
-Reaction temperature: 50 degreeC.
Reaction time: 5 to 10 seconds The reaction rate of the sulfation reaction is 97%, and the amount of 1,4-dioxane in the neutralized product (sulfate) when the obtained sulfate is immediately neutralized (vs. Sulfate (unit: ppm) was 15 ppm.

Subsequently, the obtained sulfate was cooled to the ultimate temperature shown in Table 1 at the cooling rate shown in Table 1 and solidified. The cooling rate was selected from various cryogens (dry ice / ethanol at a cooling rate of 10 ° C./second, calcium chloride hexahydrate / ice at 5 ° C./second, salt / at 1 ° C./second and 0.5 ° C./second). Ice).
20 minutes after the completion of the sulfation reaction, the solution was neutralized by adding small pieces of solidified sulfate to a 4% by mass aqueous sodium hydroxide solution. The temperature during neutralization was maintained at 50 ° C. or lower. The completion of neutralization was confirmed with a pH test paper.
The amount of 1,4-dioxane (based on sulfate: unit ppm) in the obtained reaction product (sulfate (polyoxyethylene alkyl ether sodium sulfate)) was measured, and the results are shown in Table 1.

[Examples 2-6, Comparative Examples 5-8]
Implemented except using polyoxyethylene alkyl ether of natural alcohol mainly composed of C12 and ₁₄ (average number of moles of added ethylene oxide 2, average molecular weight = 422, freezing point: -5 ° C) The sulfation reaction was carried out in the same manner as in Example 1.
The reaction rate of the sulfation reaction is 97%, and the amount of 1,4-dioxane in the neutralized product (sulfate) when the obtained sulfate is immediately neutralized (to sulfate: unit ppm) is It was 15 ppm.

Subsequently, the obtained sulfate was cooled to the ultimate temperature shown in Table 2 at the cooling rate shown in Table 2 and solidified.
20 minutes after the completion of the sulfation reaction, the reaction product was neutralized in the same manner as in the example. The amount of 1,4-dioxane (based on sulfate: unit ppm) in the obtained reaction product (sulfate) was measured, and the results are shown in Table 2.

[Examples 7 to 9, Comparative Examples 9 to 12]
Implemented except that polyoxyethylene alkyl ether of synthetic alcohol mainly composed of C12 and ₁₃ (average number of moles of added ethylene oxide 3, average molecular weight = 456, freezing point when sulfated: -6 ° C) was used as a raw material. The sulfation reaction was carried out in the same manner as in Example 1.
The reaction rate of the sulfation reaction is 97%, and the amount of 1,4-dioxane in the neutralized product (sulfate) when the obtained sulfate is immediately neutralized (to sulfate: unit ppm) is It was 15 ppm.

Next, the obtained sulfate was cooled to the ultimate temperature shown in Table 3 at the cooling rate shown in Table 3 and solidified.
20 minutes after the completion of the sulfation reaction, the reaction product was neutralized in the same manner as in the example. The amount of 1,4-dioxane in the reaction product (sulfate) (sulfate: unit ppm) was measured, and the results are shown in Table 3.

[Examples 10 to 12, Comparative Examples 13 to 16]
Implemented except that polyoxyethylene alkyl ether of synthetic alcohol mainly composed of C12 and ₁₃ (average number of moles of added ethylene oxide 2, average molecular weight = 412, freezing point when sulfated: −5 ° C.) was used as a raw material. The sulfation reaction was carried out in the same manner as in Example 1.
The reaction rate of the sulfation reaction is 97%, and the amount of 1,4-dioxane in the neutralized product (sulfate) when the obtained sulfate is immediately neutralized (to sulfate: unit ppm) is It was 15 ppm.

Next, the obtained sulfate was cooled to the ultimate temperature shown in Table 4 at the cooling rate shown in Table 4 and solidified.
20 minutes after the completion of the sulfation reaction, the reaction product was neutralized in the same manner as in the example. The amount of 1,4-dioxane (relative to sulfate: unit ppm) in the obtained reaction product (sulfate) was measured, and the result is shown in Table 4.

  As shown in the above results, an increase in 1,4-dioxane could be suppressed by setting the cooling rate to 1 ° C./s or more and setting the sulfate to the freezing point or less.

[Evaluation Test 1]
The difference in the amount of 1,4-dioxane produced due to the residence temperature of the sulfate after completion of the sulfation step was evaluated by the following procedure.
Example 1 Polyoxyethylene alkyl ether of synthetic alcohol mainly composed of C12 and ₁₃ (average number of moles of added ethylene oxide 3, average molecular weight = 466, freezing point when sulfated: −6 ° C.) was used as a raw material. The sulfation reaction was carried out in the same manner as above.
The obtained sulfate is held at a residence temperature of −10 ° C., 30 ° C., 40 ° C. or 50 ° C., a small amount is sampled every 5 minutes from the end of the reaction, neutralization is performed, and 1 in the obtained sulfate The time course of the amount of 1,4-dioxane (ppm vs. sulfate) was measured. Since the production of 1,4-dioxane stops by neutralization, the time from the completion of the reaction until neutralization becomes the residence time. In addition, about the example of -10 degreeC, 30 degreeC, and 40 degreeC, after completion | finish of reaction, it cooled to each temperature with the cooling rate of 5 degree-C / sec. The results are shown in FIG.
As shown in FIG. 1, when the sulfur oxide was set to −10 ° C. below the freezing point, the increase rate of 1,4-dioxane was 0.01 ppm to sulfate / min, and the production of 1,4-dioxane was almost I found out.
Thus, it was found that by solidifying the sulfate, the by-product of 1,4-dioxane after the completion of the reaction can be significantly suppressed as compared to the case where the reaction is not solidified.

[Evaluation Test 2]
About the reaction product (sulfate) obtained in Example 1 and Comparative Examples 1 to 3, the amount of 1,4-dioxane (ppm vs. sulfate) 30 minutes after the completion of the reaction was determined.
The log [1,4-dioxane increase (ppm vs. sulfate)] obtained from this value is taken on the vertical axis, the temperature reached (° C.) is taken on the horizontal axis, and the intersection is shown in FIG.
As shown in FIG. 2, it was found that Comparative Examples 1 to 3 in which the sulfated oxide remained liquid were arranged almost on the same straight line, and there was a correlation between the temperature and the amount of 1,4-dioxane. It was. On the other hand, in Example 1 in which the sulfated oxide was solidified, it was not on the straight line, and it was found that the production of 1,4-dioxane was remarkably suppressed.

  From the results of Evaluation Tests 1 and 2, it was confirmed that there was a significant difference in the 1,4-dioxane formation inhibitory effect between the case of solidifying the sulfate and the case of not solidifying the sulfate.

It is a graph which shows the difference of the production amount of 1, 4- dioxane by the residence temperature of the reaction composition (sulfur oxide) after completion | finish of a sulfation process. It is a graph which shows the relationship between the ultimate temperature in a coagulation process, and a 1, 4- dioxane production amount. It is the schematic of the apparatus used for the measurement of a freezing point.

Claims (1)

A sulfation reaction step of contacting the polyoxyethylene alkyl ether and sulfur trioxide-containing gas to sulfate the polyoxyethylene alkyl ether;
A solidification step of cooling and solidifying the reaction product of the sulfation reaction step at a cooling rate of 1 ° C./second or more;
And a neutralizing step of neutralizing the reaction product after the solidification. A method for producing a polyoxyethylene alkyl ether sulfate.

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