WO2014148435A1 - PRODUCTION METHOD OF AQUEOUS SOLUTION OF α-SULFO FATTY ACID ALKYL ESTER SALT - Google Patents

Abstract

This method involves dissolving a solid substance containing α-sulfo fatty acid alkyl ester salt in water of a temperature Ts(°C) to produce an aqueous solution of the α-sulfo fatty acid alkyl ester salt, wherein the heat absorption peak area S1 of the solid substance at 50°C-130°C observed during thermal analysis by differential scanning thermal analyzer is 50% or greater than the heat absorption peak area S2 at 0°C-130°C, and, defining Tmax (°C) as the heat absorption peak top temperature of the heat flow maximum value observed during thermal analysis of the solid substance by differential scanning thermal analyzer, the temperature Ts (°C) has the following relation with the temperature Tmax (°C). Tmax-5 ≦ Ts ≦ Tmax+5

Description

Method for producing α-sulfo fatty acid alkyl ester salt aqueous solution

The present invention relates to a method for producing an aqueous α-sulfo fatty acid alkyl ester salt solution.
This application claims priority based on Japanese Patent Application No. 2013-055531 filed in Japan on March 18, 2013, the contents of which are incorporated herein by reference.

Α-sulfo fatty acid alkyl ester salt (hereinafter also referred to as “α-SF salt”), which is an anionic surfactant, has excellent detergency, good biodegradability, and little impact on the environment. It is highly evaluated for its performance as a cleaning material, and it is widely used especially for garment detergents.
When blending α-SF salt into a liquid detergent, it is common to prepare an aqueous solution of α-SF salt and mix the aqueous solution with other materials for ease of blending and handling. Is. When preparing an aqueous solution of α-SF salt, for example, a paste containing a high concentration of α-SF salt by using fatty acid methyl ester as a starting material, followed by sulfonation, esterification, neutralization, etc. And the paste is dissolved in water (for example, see Patent Document 1).

International Publication No. 2008/75770

However, an aqueous solution of α-SF salt has a problem that, for example, precipitation occurs under a low temperature condition of about 10 to 20 ° C. and fluidity is lowered. Such an α-SF salt aqueous solution is difficult to handle, and has problems such as being difficult to mix with other materials and not being added at a uniform concentration when producing a liquid detergent.

An object of the present invention is to provide a method for producing an α-SF salt aqueous solution in which α-SF salt is hardly precipitated even under low temperature conditions.

As a result of intensive studies, the present inventor dissolved an α-SF salt-containing solid that was confirmed to be in a specific crystal state by thermal analysis using a differential scanning calorimeter (DSC) in water at a specific temperature. The aqueous solution obtained in this way was found to be less likely to precipitate α-SF salt even under low temperature conditions, and the present invention was completed.

The present invention has the following configuration.
That is,
A method for producing an α-sulfo fatty acid alkyl ester salt aqueous solution by dissolving a solid material containing an α-sulfo fatty acid alkyl ester salt in water at a temperature Ts (° C.), wherein the solid is a differential scanning calorimeter. The heat absorption peak area S1 at 50 ° C. to 130 ° C. observed when performing a thermal analysis at 50 ° C. to 130 ° C. is 50% or more and 100% or less with respect to the heat absorption peak area S 2 at 0 ° C. to 130 ° C., and the temperature Ts ( ° C) is the temperature Tmax (° C) when the heat absorption peak top temperature of the maximum heat flow rate observed when the solid is thermally analyzed by a differential scanning calorimeter is Tmax (° C). A method for producing an α-sulfo fatty acid alkyl ester salt aqueous solution having the following relationship therebetween.
Tmax-5 ≦ Ts ≦ Tmax + 5

According to the method for producing an α-sulfo fatty acid alkyl ester salt (hereinafter sometimes referred to as α-SF salt) aqueous solution of the present invention, an α-SF salt aqueous solution in which precipitation of α-SF salt is unlikely to occur even under low temperature conditions. Can be manufactured.

1 is a schematic configuration diagram showing an example of an α-SF salt production system according to the present invention. 3 is an X-ray diffraction chart of an α-SF salt-containing solid substance (hereinafter also referred to as a metastable solid) (m) in a metastable crystalline state. It is a DSC chart which shows the thermal analysis result in a differential scanning calorimeter about an example of metastable solid (m) (Example 1). 6 is a DSC chart showing thermal analysis results with a differential scanning calorimeter for an example of an α-SF salt-containing solid in a stable state (hereinafter also referred to as stable solid) (s). It is a DSC chart which shows the thermal analysis result in a differential scanning calorimeter about the stable solid (s) obtained by crystallizing the metastable solid (m) of FIG. 3 (Example 1). It is a schematic diagram which shows the base line used as a reference | standard in order to calculate endothermic amount, and the method of peak division.

The present invention is a method for producing an α-SF salt aqueous solution by dissolving a solid containing an α-SF salt in water. In the present invention, as a solid matter dissolved in water, the heat absorption peak area S1 at 50 ° C. to 130 ° C. observed when thermal analysis is performed with a differential scanning calorimeter is the heat absorption peak area S2 at 0 ° C. to 130 ° C. Therefore, a solid in a specific stable crystal state (hereinafter also referred to as “stable state”) that is 50% or more and 100% or less is used. And the temperature of the water which dissolves the said solid substance is controlled to specific temperature.
Hereinafter, a process (I) (hereinafter also referred to as process (I)) for obtaining a solid substance containing an α-SF salt in a flaky state and the like described above using a fatty acid alkyl ester as a starting material, and the α-SF The present invention will be described in detail by exemplifying a production method having a step (II) of dissolving a salt-containing solid in water at a specific temperature (hereinafter also referred to as step (II)).

<Process (I)>
In step (I), first, an α-SF salt-containing solid (m) in a metastable crystalline state (hereinafter also referred to as “metastable state”) is prepared (step (I-1)), and then Then, the α-SF salt-containing solid (m) is crystallized to obtain an α-SF salt-containing solid (s) in a stable state (step (I-2)).
That is, the step (I) comprises the step (I-1) of preparing the α-SF salt-containing solid (m) in a metastable crystalline state and the adjusted α-SF salt-containing solid (m). Crystallization to obtain an α-SF salt-containing solid (s) in a stable state (I-2).
Hereinafter, the α-SF salt-containing solid (m) in a metastable state may be referred to as a metastable solid (m). In addition, the α-SF salt-containing solid (s) in a stable state may be referred to as a stable solid (s).

The metastable solid (m) and the stable solid (s) can be distinguished by thermal analysis using a differential scanning calorimeter.
As will be described in detail later, the metastable solid (m) has a heat absorption peak area at 50 ° C. to 130 ° C. observed during thermal analysis with a differential scanning calorimeter, and a heat absorption peak area at 0 ° C. to 130 ° C. In contrast, the solid is 0% or more and less than 50%.
On the other hand, in the stable solid (s), the heat absorption peak area S1 at 50 ° C. to 130 ° C. observed when thermal analysis is performed with a differential scanning calorimeter is compared with the heat absorption peak area S2 at 0 ° C. to 130 ° C. The heat absorption peak top temperature Tmax (° C.) of the maximum heat flow rate observed when thermal analysis is performed with a differential scanning calorimeter is 50 ° C. or more and 130 ° C. or less. It is a solid.
The ratio of “heat absorption peak area S1 at 50 ° C. to 130 ° C.” to “heat absorption peak area S2 at 0 ° C. to 130 ° C.” defined in the present invention is determined by using a differential scanning calorimeter. It can be determined by putting the object of analysis into the sample, raising the temperature at a predetermined rate of temperature rise, and measuring the endothermic and exothermic amounts. At this time, an exothermic peak may be observed at 0 ° C. to 130 ° C. In this case, a value obtained by subtracting the absolute value of the exothermic peak from the endothermic amount of the endothermic peak at 50 ° C. or higher is 50 It is assumed that the heat absorption peak area S1 is in the range from 1 to 130 ° C. Similarly, for the heat absorption peak area S2 at 0 ° C. to 130 ° C., a value obtained by subtracting the absolute value of the exothermic peak from the endothermic amount of the endothermic peak is used as the total endothermic amount.
Note that a baseline serving as a reference for calculating the endothermic amount is defined by a straight line connecting straight portions before and after the endothermic peak. From the schematic diagram shown in FIG. 6, those skilled in the art can easily understand how to determine the baseline and split the peak.

[Step (I-1)]
In step (I-1), a sulfonation treatment in which the fatty acid alkyl ester is sulfonated with a sulfonation gas; an esterification treatment in which a lower alcohol is added to the sulfonated product obtained by the sulfonation treatment and esterification; and an esterification treatment An α-SF salt-containing paste by performing neutralization treatment for neutralizing the esterified product obtained in step 1; and bleaching treatment for bleaching the neutralized product obtained by neutralization treatment, which is performed as necessary Get. Next, the paste is heated and concentrated to obtain a concentrated product; cooling and solidifying the concentrated product to obtain a cooled solidified product such as a plate; and crushing to crush the cooled solidified product. Process. As a result, α-SF salt-containing solid flakes (m) in a metastable state are obtained.
That is, the step (I-1) includes a sulfonation treatment in which a fatty acid alkyl ester is sulfonated with a sulfonation gas; and an esterification treatment in which a lower alcohol is added to the sulfonated product obtained by the sulfonation treatment to perform esterification. A neutralization treatment for neutralizing the esterified product obtained by the esterification treatment; a concentration treatment for obtaining a concentrated product by heating and concentrating the paste containing α-SF salt obtained by the neutralization treatment; Cooling and solidifying the product by cooling and solidifying the product to obtain a cooled solidified product; and crushing treatment for crushing the cooled and solidified product obtained by the cooling and solidifying treatment.
The step (I-1) may further include a bleaching treatment for bleaching the neutralized product obtained by the neutralization treatment.
The “paste-like” here means a semi-solid state with fluidity.
“Flake” means a flaky solid.

(Sulfonation treatment)
The sulfonation treatment is preferably carried out by bringing a fatty acid alkyl ester into contact with a sulfonated gas in the presence of a coloring inhibitor such as sodium sulfate to sulfonate the fatty acid alkyl ester (gas contact operation), thereby producing α-sulfo. This is a treatment for obtaining a sulfonated product containing a fatty acid alkyl ester (hereinafter also referred to as “α-SF acid”). The coloring inhibitor may be added by an esterification treatment in addition to the sulfonation treatment.

Specifically, for example, the following method is used.
First, for example, 92 kg of fatty acid alkyl ester is charged into a reaction tank having a capacity of 200 to 4000 L, and heated at a temperature at which the fatty acid alkyl ester melts, for example, about 70 ° C. to obtain a raw material liquid phase. Next, a sulfonated gas is preferably added to the raw material liquid phase at a constant flow rate (for example, preferably 10 m / sec or more, more preferably 50 to 200 m / sec. If it is less than 10 m / sec, bubbles may become large. The total amount added is, for example, 1.2 moles with respect to the fatty acid alkyl ester, and a plurality of bubbles are generated from the gas sparger. Disperse air bubbles uniformly. When the sulfonation treatment is performed in the presence of a coloring inhibitor, the particles of the coloring inhibitor are uniformly dispersed in the raw material liquid phase by this rotation.
The amount of the coloring inhibitor used is preferably 0.25% to 10% with respect to the fatty acid alkyl ester, for example.
Specifically, as the coloring inhibitor, sodium sulfate is preferable.
Here, “uniform” means a state in which particles are floating without being settled.

The fatty acid alkyl ester is represented by the following formula (1).
R ¹ —CH ₂ —COOR ² (1)

(1) In the formula, R ¹ is a linear or branched alkyl group or alkenyl group having 8 to 20 carbon atoms, and R ² is a linear or branched alkyl group having 1 to 6 carbon atoms. It is.
R ¹ preferably has 10 to 18 carbon atoms, and more preferably 10 to 16 carbon atoms. That is, the carbon number of the acyl group (R ¹ —CH ₂ —CO—) of the fatty acid alkyl ester is preferably from 12 to 20, and more preferably from 12 to 18. R ² preferably has 1 to 3 carbon atoms.
As the fatty acid alkyl ester, a fatty acid methyl ester is preferable.
As the fatty acid methyl ester, for example, when the total mass of the fatty acid methyl ester is 100% by mass, the fatty acid methyl ester having 12 carbon atoms is 0.1 to 0.3% by mass, and the fatty acid methyl ester having 14 carbon atoms is 0.00. 7 to 1.2% by mass, fatty acid methyl ester having 16 carbon atoms, 66.0 to 89.5% by mass, fatty acid methyl ester having 18 carbon atoms, 9.5 to 32.0% by mass, and fatty acid having 20 or more carbon atoms It may be a mixture of fatty acid methyl esters, which may contain methyl esters.

Fatty acid alkyl esters are animal fats and oils derived from beef tallow, fish oil, lanolin and the like; vegetable fats and oils derived from coconut oil, palm oil, soybean oil and the like; synthetic fatty acid alkyl esters derived from the oxo method of α-olefins Any of these may be used and is not particularly limited.
Specifically, as the fatty acid alkyl ester, alkyl laurate such as methyl laurate, ethyl laurate, and propyl laurate; alkyl myristate such as methyl myristate, ethyl myristate, propyl myristate; methyl palmitate, Palmitic acid alkyl esters such as ethyl palmitate and propyl palmitate; Stearic acid alkyl esters such as methyl stearate, ethyl stearate and propyl stearate; Fatty acid alkyl ester; hydrogenated fish oil fatty acid methyl, hydrogenated fish oil fatty acid ethyl, hydrogenated fish oil fatty acid alkyl ester, etc .; coconut oil fatty acid methyl, coconut oil fatty acid ethyl, coconut oil fatty acid Palm oil fatty acid alkyl esters such as lopil; Palm oil fatty acid alkyl esters such as palm oil fatty acid methyl, palm oil fatty acid ethyl, palm oil fatty acid propyl; Palm kernel oil fatty acid methyl, palm kernel oil fatty acid ethyl, palm kernel oil fatty acid propyl, etc. A palm kernel oil fatty acid alkyl ester etc. can be illustrated.
One or more of these can be used.

A fatty acid alkyl ester having a lower iodine value, which is an index of unsaturation, is desirable in terms of both color tone and odor, and the iodine value is preferably 0.5 or less, more preferably 0.2 or less.

When the fatty acid alkyl ester and the sulfonated gas come into contact with each other in the sulfonation treatment, first, a reaction in which SO ₃ is inserted into the alkoxy group of the fatty acid alkyl ester occurs, and a single molecule adduct in which one molecule of SO ₃ is added is generated. Furthermore, it reacts with SO ₃ to introduce a sulfone group at the α-position, thereby producing a bimolecular adduct in which bimolecular SO ₃ is added. Finally, SO ₃ inserted into the alkoxy group is eliminated, and the following formula ( 2) (α-sulfo fatty acid alkyl ester; hereinafter also referred to as “α-SF acid”) is formed. In products obtained by sulfonation (sulfonated products), in addition to α-SF acid, SO ₃ monomolecular adduct, SO ₃ bimolecular adduct, unreacted fatty acid alkyl ester and other by-products Things are included.

R ¹ —CH (SO ₃ H) —COOR ² (2)
(2) wherein, ^{R 1} is the same as ^{R 1} in formula (1), ^{R 2} is the same as ^{R 2} in formula (1).

The sulfonating gas, e.g., SO ₃ gas; gas diluted to SO ₃ gas generated from the SO ₃ gas or oleum with dehumidified air;; SO ₃ gas generated from fuming sulfuric acid, and the like.
The total amount of the sulfonated gas added is at least 1 mol, preferably 1.0 to 2.0 mol, more preferably 1.1 to 1.5 mol relative to the fatty acid alkyl ester.

The rotational speed of the stirrer is preferably, for example, a peripheral speed at the tip of the stirring blade of the stirring blade provided in the stirrer is 0.5 to 6.0 m / sec, and is 2.0 to 5.0 m / sec. More preferably. When the peripheral speed is 0.5 m / sec or more, a sufficient effect of dispersing bubbles is obtained, and the reaction rate is also excellent. When the peripheral speed is 6.0 m / sec or less, the power consumption can be suppressed. Further, by rotating while maintaining the peripheral speed of the tip of the stirring blade within the above-mentioned preferable numerical range, it is possible to sufficiently react even in the ripening operation described later.
Examples of the shape of the stirring blade include a six-blade inclined paddle (up-pumping in the case of 200 L, blade diameter 240 mmφ) and the like.

The reaction temperature in the gas contact operation of the sulfonation treatment is a temperature at which the fatty acid alkyl ester has fluidity, and is not less than the melting point of the fatty acid alkyl ester, preferably not less than the melting point and not more than 70 ° C. above the melting point. It is preferable that
The introduction time of the sulfonation gas in the sulfonation treatment is about 10 minutes to 300 minutes, and preferably about 60 minutes to 240 minutes.

The sulfonation method may be any sulfonation method such as a falling film type sulfonation method or a batch type sulfonation method. In addition, as a sulfonation reaction method, a tank-type reaction, a film reaction, a tubular gas-liquid mixed phase reaction, or the like is used. When using a coloring inhibitor, it is preferable to contact the sulfonated gas in a state in which the coloring inhibitor is uniformly dispersed in the raw material. Therefore, in the batch-type sulfonation method, a tank reaction method is suitable. .

In the sulfonation treatment, an aging operation can be provided as necessary after the gas contact operation described above. From the viewpoint of improving the yield of the finally obtained α-SF salt, it is preferable to provide an aging operation.
That is, the sulfonation treatment preferably includes a gas contact operation and an aging operation.
The aging operation is a step of promoting the desorption of SO ₃ from the bimolecular adduct generated by the gas contact operation while maintaining the predetermined temperature after the gas contact operation.
The ripening operation can be performed, for example, by continuously stirring in the reaction tank subjected to the gas contact operation. The rotational speed of the agitator may be the same as or different from the rotational speed in the contact operation. When a film-type reaction, a tube-type gas-liquid mixed phase reaction, or the like is used for the gas contact operation, the sulfonated product may be transferred to another tank reactor and aged.

The reaction temperature (aging temperature) in the aging operation is preferably in the range of 70 to 100 ° C., for example. When the aging temperature is 70 ° C. or higher, the reaction proceeds rapidly, and when it is 100 ° C. or lower, coloring is also suppressed.
The reaction time (aging time) in the aging operation is preferably determined in the range of 1 minute to 120 minutes, for example.

(Esterification treatment)
In the esterification treatment, a lower alcohol is added to the sulfonated product (the product of the sulfonation treatment) obtained by the sulfonation treatment after the sulfonation treatment (gas contact operation and aging operation carried out as necessary). In this process, the sulfonated product is esterified to cause a reaction (ester reaction) to produce an α-SF acid.

As described above, the sulfonated product obtained by the sulfonation treatment includes, in addition to α-SF acid, a monomolecular adduct of SO ₃ , a bimolecular adduct of SO ₃ , an unreacted fatty acid alkyl ester, and other By-products are included. Among these, when the bimolecular adduct of SO ₃ is neutralized, it becomes an α-sulfo fatty acid dialkali salt, which may have a lower cleaning effect than α-SF salt in a low temperature environment. For this reason, it is necessary to make the content of the bimolecular adduct of SO ₃ as low as possible in the detergent application. Performing esterification process, by generating a alpha-SF acids from bimolecular adduct SO _3, can be lowered content of bimolecular adduct SO _3, a further improvement in the yield of alpha-SF salt Can be planned.
The esterification treatment is performed, for example, by a method in which a lower alcohol is added to the sulfonated product and stirred while maintaining a predetermined temperature (eg, 50 ° C. to 100 ° C.). The rotational speed of the stirrer is preferably, for example, a peripheral speed at the tip of the stirring blade of the stirring blade provided in the stirrer is 0.5 to 6.0 m / sec, and is 2.0 to 5.0 m / sec. More preferably. When the peripheral speed is 0.5 m / sec or more, the added lower alcohol can be uniformly mixed, and the reactivity is excellent. When the peripheral speed is 6.0 m / sec or less, the power consumption can be suppressed.

The lower alcohol used in the esterification treatment is preferably an alcohol having 1 to 6 carbon atoms. Among them, an alcohol having the same carbon number as that of the alcohol residue of the starting fatty acid alkyl ester is preferable. Specifically, methanol is mentioned.
The amount of the lower alcohol added is preferably 0.5 to 50-fold mol, more preferably 0.8 to 2-fold mol based on the bimolecular adduct of SO ₃ contained in the sulfonated product. If it is more than the lower limit of this addition amount, a sufficient addition effect can be obtained. Even if the lower alcohol is added in excess of the upper limit, the esterification reaction does not proceed any further.
In addition, the amount of the bimolecular adduct of SO ₃ contained in the sulfonated product can be quantified by a high performance liquid chromatograph or the like.

For example, the bimolecular adduct of SO ₃ is contained in an amount of 5 to 50% by mass with respect to the total mass of the sulfonated product obtained by the sulfonation treatment, and when methanol is added as the lower alcohol, the amount of methanol added is The amount is preferably 0.25 to 250 parts by mass, more preferably 0.4 to 10 parts by mass with respect to 100 parts by mass of the compound.

The reaction temperature in the esterification treatment is 50 ° C to 100 ° C, preferably 50 ° C to 90 ° C. The reaction time in the esterification treatment is preferably determined in the range of 5 minutes to 120 minutes.

(Neutralization treatment)
The neutralization treatment is a treatment for obtaining a neutralized product by neutralizing the esterified product obtained by the esterification treatment with an alkaline substance such as an alkaline aqueous solution. By performing the neutralization treatment, α-SF salt is formed from α-SF acid in the esterified product.

In the α-SF salt, a counter ion that forms a salt may be any counter ion that forms a water-soluble salt with the following ions.
R ¹ —CH (CO—O—R ² ) —SO ₃ ^—
Examples of the water-soluble salt include alkali metal salts such as sodium salt and potassium salt; alkaline earth metal salts such as calcium salt; ammonium salt; ethanolamine salt and the like.

The neutralization treatment can be performed, for example, by bringing the esterified product into contact with an alkaline aqueous solution.
Examples of the alkaline aqueous solution include an aqueous solution capable of forming the above-mentioned water-soluble salt, for example, an aqueous solution of an alkali metal hydroxide such as sodium hydroxide; an aqueous solution of an alkali metal carbonate; an alkaline earth metal water. An aqueous solution of oxide; an aqueous solution of ammonia; an aqueous solution of ethanolamine and the like.

The concentration of the anionic surfactant described later in 100% by mass of the neutralized product obtained by the neutralization treatment is determined so that both the production efficiency in obtaining the neutralized product and the handleability of the neutralized product are excellent.
Such an anionic surfactant concentration is preferably 60% by mass to 80% by mass, more preferably 62% by mass to 75% by mass, when the total mass of the neutralized product is 100% by mass. If the concentration of the aqueous alkaline solution used for the neutralization treatment is too thin, the amount of the aqueous alkaline solution required for neutralization increases, resulting in an increase in the amount of water in the resulting neutralized product, and the anion interface. The activator concentration is lowered.
The concentration of the alkaline aqueous solution used for the neutralization treatment is preferably 2% to 50%.

The “anionic surfactant concentration” is the concentration of an anionic compound having a function as a surfactant. The anionic compound in the present embodiment includes an α-SF salt, which is a cleaning active ingredient, and α-SF. This corresponds to a by-product α-sulfo fatty acid dialkali salt having a function as a surfactant as well as a salt. Therefore, the “anionic surfactant concentration” in this embodiment is the total concentration of the α-SF salt that is a cleaning active ingredient and the α-sulfo fatty acid dialkali salt (di-salt) that is one of by-products. is there.
The anionic surfactant concentration can be determined by a titration method or the like.

In addition, the mass ratio of α-SF salt and α-sulfo fatty acid dialkali salt in the neutralized product is from the viewpoints of manufacturability when obtaining the neutralized product, handling properties, and quality when blended into a liquid product. When the total mass of the α-SF salt and the α-sulfo fatty acid dialkali salt is 100% by mass, the α-sulfo fatty acid dialkali salt is preferably 0% by mass or more and 10% by mass or less.

The neutralization temperature is preferably 30 ° C to 140 ° C, more preferably 50 ° C to 140 ° C, and further preferably 50 ° C to 80 ° C.
The neutralization time is preferably 5 minutes to 60 minutes, more preferably 20 minutes to 60 minutes.
The pH during neutralization is preferably in the acidic or weak alkaline range (pH 4 to 9 at 30 ° C. to 140 ° C.) in order to prevent hydrolysis of the α-SF salt formed. Outside this range, the ester bond of the α-sulfo fatty acid alkyl ester salt may be easily cleaved.

In addition, in the neutralization treatment, in order to prevent hydrolysis of the produced α-SF salt and the production of by-products associated therewith, it is possible to avoid a radical neutralization operation and perform a mild neutralization treatment as much as possible. preferable. An example of such neutralization treatment is a loop neutralization method. In the above method, a part of the neutralized neutralized product (recycled neutralized product) is circulated in a looped pipe (recycle loop), and the recycled neutralized product is unneutralized after the esterification treatment. It is the system which adds to the product of this and neutralizes.
In the loop neutralization method, neutralization may be performed, for example, by bringing an alkaline aqueous solution into contact with a mixture of a recycled neutralized product and an unneutralized product, or a recycled neutralized product and an unneutralized product. You may carry out by mixing a product and aqueous alkali solution instantaneously under the strong shearing force.

The amount of the recycle neutralized product added is preferably 5 to 25 times by mass and more preferably 10 to 20 times by mass with respect to the total mass of the unneutralized product and the alkaline aqueous solution. When the ratio of the added amount of the recycled neutralized product to the total amount of the unneutralized product and the aqueous alkali solution, that is, the recycling ratio is 5 or more, the effect of suppressing the formation of by-products is excellent, and it is 25 mass times or less. Manufacturing efficiency is improved.

The neutralization treatment can be performed by using a solid metal carbonate or hydrogen carbonate in addition to using an alkaline aqueous solution.
In particular, neutralization with solid metal carbonate (concentrated soda ash) is preferable because concentrated soda ash is less expensive than other alkalis. Further, when neutralization with a solid metal carbonate is performed, when mixed with the product, the amount of water contained in the mixture is small and hardly alkaline, and the heat of neutralization at the time of neutralization is reduced to metal water. Since it is lower than that of the oxide, hydrolysis of the α-SF salt can be suppressed, which is advantageous.

Examples of the metal carbonate or hydrogen carbonate include anhydrous salts such as sodium carbonate, potassium carbonate, ammonium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate, hydrated salts, or mixtures thereof.

(Bleaching treatment)
After the neutralization treatment, a bleaching treatment may be performed as necessary. By performing the bleaching treatment, the colored product produced until the neutralization treatment is bleached, and an α-SF salt having a good color tone can be obtained.
The bleaching treatment can be carried out by adding a bleaching agent to the neutralized product obtained by the neutralizing treatment. As the bleaching agent, for example, an aqueous solution of hydrogen peroxide is preferably used.
The concentration of hydrogen peroxide in the bleaching agent can be determined in consideration of the water content in the bleaching process, the reaction time (bleaching time), or the reaction temperature (bleaching temperature) in the bleaching process. Hydrogen peroxide is preferably 30% by mass to 50% by mass with respect to the total mass of the aqueous solution.

The added amount of the bleaching agent is 0 with respect to 100 parts by mass of the anionic surfactant (total of α-SF salt and α-sulfo fatty acid dialkali salt (di-salt)) in the neutralized product. The range is preferably 1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and still more preferably 0.1 to 3 parts by mass.

The bleaching temperature can be determined in consideration of the concentration of hydrogen peroxide in the bleaching agent, the amount of bleaching agent added, and the bleaching time. For example, the bleaching temperature is preferably determined within the range of 50 ° C to 120 ° C. More preferably, it is determined in the range of ˜90 ° C. When it is at least the lower limit of the above range, an increase in the viscosity of the bleached product is suppressed, and the production suitability such as transfer and stirring is excellent. If it is below the upper limit of the above range, the α-SF salt is hardly hydrolyzed, the deterioration of the color tone of the α-SF salt is suppressed, and the cleaning effect may be lower than that of the α-SF salt in a low temperature environment. The formation of certain di-salts is also reduced.
The bleaching time can be determined in consideration of the concentration of hydrogen peroxide in the bleaching agent, the amount of bleaching agent added, and the bleaching temperature. For example, it is preferably determined in the range of 30 minutes to 600 minutes, and 60 minutes. More preferably, it is determined in the range of ˜480 minutes.

As a bleaching method in the bleaching treatment, for example, a neutralized product is charged into a reaction vessel, and a bleaching agent is added and mixed while maintaining a predetermined temperature. Further, for example, there is a method in which a circulation system for returning a part of the bleached product obtained in the reaction tank to the reaction tank is provided, a neutralized product is added to the circulation system, and then a bleaching agent is added.
Another example is loop-type bleaching. Specifically, there is a method in which a neutralized product and a bleaching agent are added to the circulation line while circulating a part of the neutralized product mixed with the bleaching agent. Can be mentioned.
Furthermore, after adding and mixing a bleaching agent, the bleaching reaction may be advanced by a flow tube method.
The bleaching treatment may be performed on the sulfonated product.

Thus, the paste containing α-SF salt (viscous composition containing α-SF salt) is obtained by performing sulfonation treatment, esterification treatment, neutralization treatment, and bleaching treatment as necessary. Is obtained. The paste containing the α-SF salt may further contain an α-sulfo fatty acid dialkali salt.
The anionic surfactant concentration and the single concentration of α-SF salt in the paste are preferably within the concentration range described for the neutralized product, although depending on the amount of bleach used.

Among the above-described processes, the sulfonation process, the esterification process, and the neutralization process can be performed using, for example, the manufacturing system of FIG.
The production system shown in FIG. 1 includes a tank reactor equipped with a reaction tank 1 and a stirrer 4, an esterification reaction tank 31 connected to an outlet 1a of the reaction tank 1 via a line 21, and an esterification reaction tank. 31 and a recycle loop 32 connected via a line 23.

An SO ₃ gas introduction line 8 and an exhaust gas line 10 are connected to the upper portion of the reaction tank 1 so that SO ₃ gas can be supplied into the reaction tank 1 or discharged from the reaction tank 1. Yes.
As the esterification reaction tank 31, a continuous multistage stirring tank 31a and a buffer 31b having three mixing spaces are used. An alcohol supply line 26 is connected to the continuous multistage agitation tank 31a so that lower alcohol can be supplied to the continuous multistage agitation tank 31a.

The recycle loop 32 includes a neutralization line 32a whose ends are connected to the line 23 and the line 24, and a circulation line 32b branched from both ends of the neutralization line 32a. Two mixers 32c and 32d are provided on the neutralization line 32a. An alkaline aqueous solution supply line 27 is connected to a portion between the mixer 32c and the mixer 32d. Alkaline aqueous solution can be supplied to this. In addition, a pump 32e and a heat exchanger 32f are provided on the circulation line 32b so that the neutralized product can be cooled.

When the sulfonation treatment, the esterification treatment and the neutralization treatment are performed using such a production system, first, the fatty acid alkyl ester as a raw material is charged into the reaction tank 1. While stirring with the stirrer 4, the internal temperature of the reaction tank 1 is raised to a predetermined reaction temperature. Next, a sulfonated gas is introduced into the raw material liquid phase from the SO ₃ gas introduction line 8. Sulfonating gas from SO ₃ gas inlet line 8, is introduced into the reaction vessel 1 via the SO ₃ gas inlet line 8 leading end connected to a gas sparger (not shown), the raw material liquid phase by a stirrer 4 scatter.
After introducing the sulfonated gas into the raw material liquid phase and stirring, it is preferable to maintain the interior of the reaction vessel 1 at a predetermined temperature and perform aging after introducing the sulfonated gas.
In this way, the sulfonation treatment is performed.

Next, the sulfonated product is introduced into the continuous multistage agitation tank 31a, and lower alcohol is supplied from the alcohol supply line 26 and mixed. And the obtained mixture is hold | maintained by the continuous multistage stirring tank 31a and the buffer 31b for a predetermined time at predetermined temperature.
In this way, the esterification treatment is performed.

Thereafter, the obtained product (esterified product) is supplied to the neutralization line 32 a of the recycle loop 32 through the line 23.
The esterified product is neutralized by supplying an alkaline aqueous solution from the alkali supply line 27, and a part of the obtained neutralized product is circulated through the circulation line 32b and cooled by the heat exchanger 32f. Add to the unneutralized esterified product in 32a. This is mixed by the mixer 32c and then neutralized in the same manner as described above.
In this way, neutralization is performed.

Thus, for example, by using the production system of FIG. 1 and performing sulfonation treatment, esterification treatment and neutralization treatment, an α-SF salt-containing paste can be obtained. Thereafter, an α-SF salt-containing paste with improved color tone can be obtained by further performing a bleaching treatment as necessary.

(Concentration treatment)
Subsequently, the obtained α-SF salt-containing paste is heated and concentrated to carry out a concentration treatment to obtain a concentrated product. In the concentration treatment, for example, a thin film evaporator (for example, an evaporator manufactured by Sakura Seisakusho, Exeva manufactured by Shinko Pantech Co., Ltd., a control company manufactured by Hitachi, Ltd., a Wiped Film Evaporator manufactured by Valestra Co., Ltd.) or the like is used. Then, the paste containing α-SF salt is heated. The water content of the concentrated product can be adjusted by controlling the heating temperature and the heating time.
The heating temperature depends mainly on the carbon number of the acyl group of the α-SF salt contained in the paste, but is usually 100 ° C to 150 ° C, preferably 110 ° C to 140 ° C. The heating time is usually 0.15 seconds to 10 minutes, preferably 0.3 seconds to 10 minutes. The melting and concentration of the α-SF salt-containing paste can be performed by using a heat medium such as steam in a jacket portion of a thin film evaporator or the like.
The water content of the concentrated product is preferably 0.5% to 10%.
The concentrated product thus obtained may be subjected to the next cooling and solidification treatment as it is, or after the concentrated product is once cooled and solidified, it is heated again and melted, and this may be subjected to the next cooling and solidification treatment. Good.

(Cooling solidification process)
In the cooling and solidification treatment, for example, a belt type cooler (for example, a double belt cooler manufactured by Nippon Belting Co., Ltd., an NR type double belt cooler, a double belt cooling system manufactured by Sandvik Co., Ltd.), or a drum type. By using a cooler (for example, drum flaker manufactured by Katsuragi Kogyo Co., Ltd., drum fraker FL manufactured by Mitsubishi Materials Techno Co., Ltd.) and cooling the α-SF salt-containing paste while forming it into a plate shape. A plate-like cooled and solidified product is obtained. Among them, a belt type cooler is preferable from the viewpoint of handling, and further, from the viewpoint of cooling efficiency, two metal plates are provided on the upper and lower sides, and the concentrated product is spread and cooled on the lower metal plate. The belt type cooler is preferable.

In the cooling and solidification treatment, the concentrated product in a molten state is cooled to a melting point or lower, and at this time, the crystalline state of the α-SF salt-containing solid can be made metastable by rapidly cooling at a high cooling rate. . Specifically, for example, a concentrated product at 100 ° C. to 150 ° C. is cooled to 0 ° C. to 40 ° C. within 3 minutes, preferably 10 seconds to 1 minute. When cooled rapidly, the productivity is also excellent. The melting point can be measured with a differential scanning calorimeter.
The metastable solid (m) obtained in this way is considered to have become a solid due to supercooling of the liquid crystal state. When the metastable solid (m) of the α-SF salt-containing solid is subjected to X-ray diffraction, as shown in FIG. 2, peak tops are observed at intervals of 20 to 30 mm, 10 to 15 mm, and 3 to 5 mm. An X-ray diffraction chart having three diffraction peaks as shown in FIG. 2 is obtained.
FIG. 2 is an X-ray diffraction chart of the metastable solid (m) produced in Example 1 described later.

Such a metastable solid (m) is generally difficult to form from a high-purity α-SF salt (that is, an α-SF salt having a purity of 99% or more). However, as described above, the fatty acid alkyl ester is used as a starting material. The α-SF salt-containing solid obtained through each treatment usually contains by-products such as methyl sulfate metal salt and fatty acid sulfonate metal salt. When such a by-product is included, the α-SF salt-containing solid tends to be in a metastable state.

Note that α-SF salts are known to take various crystal states. For example, stable crystals of sodium 2-sulfopalmitic acid methyl ester include crystalline states of anhydrous, dihydrate, pentahydrate, and hydrate. The melting point of the anhydride is 112 ° C. and the melting point of the dihydrate is reported to be 70 ° C. (see M. Fujiwara, et.al, Langmuir, 13, p3345 (1997)).

When obtaining a plate-like solid by cooling solidification treatment, the thickness is not particularly limited, but from the viewpoint of performing efficient treatment in the next crushing treatment, crushing provided in a crusher used for crushing treatment It is preferable to determine in consideration of the length of the bar. The crusher is generally configured to include a columnar rotating shaft and a crushing rod extending outward from the circumferential surface of the rotating shaft.
Specifically, the thickness of the plate-like solid is preferably 0.05 times or more and 0.30 times or less of the length of the crushing rod, and is 0.1 times or more and 0.28 times or less. More preferably. In addition, when the thickness of the plate-like solid is 1 to 3 mm, the length of the crushing rod is preferably 10 mm or more and 150 mm or less, and more preferably 15 mm to 100 mm. When the length of the cracking bar is not less than the lower limit of the above range, sufficient cracking power is obtained, and a flake-like α-SF salt-containing solid (m) excellent in fluidity and the like is obtained.

When a plurality of crushing bars are provided for one rotating shaft, the lengths of the crushing bars may not be the same. In that case, the thickness of the plate-like solid is determined based on the length of the shortest crushing bar. Specifically, the length of the shortest crushing rod is preferably 3 times or more and 120 times or less of the average thickness of the plate-like solid, and is 3.5 times or more and 100 times or less. More preferably. On the other hand, the length of the longest crushing rod is preferably 12 times or more and 250 times or less, more preferably 20 times to 200 times the average thickness of the plate-like solid.
The thickness of the plate-like solid can be controlled, for example, by setting the clearance between the input pulleys of the belt type cooler.
In addition, "plate-shaped solid average thickness" here means the average value of the thickness measured in arbitrary 10 or more places in a plate-shaped solid.

(Crushing process)
The crushing treatment can be performed by bringing the cooled solidified product into contact with a crushing rod of a crusher. The tip peripheral speed of the crushing rod is preferably 0.3 to 3.5 m / s, and more preferably 1.0 to 3.0 m / s. When the amount is not less than the lower limit of the above range, sufficient crushing force can be obtained, and as a result, a flake-like α-SF salt-containing solid (m) excellent in fluidity and the like can be obtained. On the other hand, if the amount is not more than the upper limit of the above range, the crushing force does not become excessive, and the resulting α-SF salt-containing solid matter (m) becomes difficult to generate dust.

The rotating shaft of the crusher is usually cylindrical, and preferably has an outer diameter of 40 to 60 mm and an axial length of 550 to 650 mm. The rotating shaft is preferably formed of a material such as SUS from the viewpoint of preventing corrosion. The rotating shaft may be cylindrical.

As described above, the length of the crushing bar is preferably determined in relation to the thickness of the plate-like solid.
The orientation of the axis of the crushing bar with respect to the axis of the rotation axis may or may not be vertical. Moreover, it is preferable that a plurality of crushing rods are arranged side by side along the axial direction of the rotating shaft.
The tip of the crushing bar may be flat or pointed. There is no restriction | limiting in the cross-sectional shape cut | disconnected by the surface perpendicular | vertical with respect to the axis | shaft of a crushing rod, For example, a circle, a square, and a triangle are mentioned. In addition, the quadrangle | tetragon and a triangle here include the shape by which the top part is cut off with the straight line or the curve.
The crushing rod is also preferably made of a material such as SUS from the viewpoint of preventing corrosion, like the rotating shaft.

As a crusher, when one crushing part is composed of one rotating shaft and one or more crushing rods provided on the rotating shaft, even if a crusher having one crushing part is used, Although a crusher having two or more crushing units may be used, crushing can be efficiently performed by using a crusher having two or more crushing units.

In particular, when the first crushing portion (sometimes referred to as “pre-rotor”) is coarsely crushed, and then the second crushing portion (also referred to as “pin rotor”) is finely crushed, Since crushing strength without excess and deficiency can be given, it is preferable.
Further, the first crushing portion is composed of one cylindrical rotating shaft having a diameter of 50 mm and a length of 580 mm and 20 crushing rods provided on the outer peripheral surface. The crushing rod has a diameter of 14 mm and a long length. It has a cylindrical shape with a length of 60 mm and has one end attached so as to extend outward in the radial direction, and the crushing rods are arranged on the outer peripheral surface of the rotating shaft at intervals of 90 ° in the rotating direction. It is preferable to constitute a crushing rod row (that is, each crushing rod row is composed of four crushing rods). The first and fifth crushing bar rows are respectively arranged in the vicinity of 65 mm from one end of the rotating shaft, and the second crushing bar row adjacent to the first crushing bar row and the third crushing bar row adjacent to the second crushing bar row. The fourth cracking rod row adjacent to the cracking rod row and the third cracking rod row is approximately equidistant in the longitudinal direction of the rotating shaft between the first cracking rod row and the fifth cracking rod row, respectively. It is preferable that each crushing rod is arranged so as to be shifted by 45 ° in the rotation direction in the adjacent crushing rod rows.
The second crushing portion is composed of one cylindrical rotating shaft having a diameter of 110 mm and a length of 580 mm and 81 crushing rods provided on the outer peripheral surface, and the crushing rod has a diameter of 9 mm and a length. It has a cylindrical shape of 20 mm, and one end thereof is attached to the rotating shaft so as to extend radially outward. The crushing rods are arranged at 120 ° intervals in the rotating direction on the outer peripheral surface of the rotating shaft. It is preferable that a crushing bar row is constructed (that is, each crushing bar row is composed of three crushing rods). In a first pair composed of a first crushing bar row arranged near 30 mm from one end of the rotating shaft and a second crushing bar row adjacent thereto, the first crushing bar row and the second crushing bar The crushing rods are arranged so that the crushing rods are shifted by 60 ° in the rotation direction, and from the third crushing rod row adjacent to the second crushing rod row and the fourth crushing rod row adjacent thereto. Also in the second pair configured, like the first pair, the third cracking bar row and the fourth cracking rod row are arranged so that the cracking rod rows are shifted by 60 ° in the rotation direction. The crushing rods of the first crushing bar row and the crushing rods of the third crushing rod row are arranged so as to be shifted by 5 ° in the rotation direction, and from the fifth crushing rod row to the 27th crushing rod row. Similarly, it is preferable that odd-numbered columns and even-numbered columns form a pair, and the odd-numbered columns in each pair are arranged in the rotational direction so as to be shifted by 5 ° from the adjacent odd-numbered columns.
As a crusher provided with such a 1st crushing part and a 2nd crushing part, the crusher by Nippon Belting Co., Ltd. is mentioned, for example.

The contact between the cooled solidified material and the crushing rod may be carried out by conveying the cooled solidified material such as a plate-shaped solid material at a constant speed toward the rotating shaft provided with the crushing rod. The cooled solidified product may be moved by rotating the rotating shaft provided with the crushing rod, but it is preferable to transport and contact the cooled solidified product at a constant speed. . The conveying speed at that time is preferably 0.005 to 0.6 times, more preferably 0.01 to 0.5 times the tip peripheral speed of the crushing rod. The distance between the rotating shaft and the cooled solidified product at the time of contact is such that the tip of the shortest crushing rod provided on the rotating shaft is about 1/4 of the thickness of the plate-like solid material, preferably 1 It is preferable to set the distance to reach about / 2.

Thus, by the step (I-1) of performing the sulfonation treatment to the crushing treatment, a flaky α-SF salt-containing solid (m) in a metastable state is obtained.

[Step (I-2)]
In the step (I-2), the α-SF salt-containing solid (m) in the metastable state obtained in the above step (I-1) is crystallized. Thereby, an α-SF salt-containing solid (s) in a stable state is obtained.
Examples of the crystallization method include the following methods (i) to (iii).
(I) An α-SF salt-containing solid substance (m) in a metastable state (hereinafter sometimes referred to as a metastable solid (m)) is maintained at a pressure of 30 ° C. or more and 20000 Pa or less for at least 48 hours. Method (hereinafter, also referred to as method (i)).
(Ii) The melt obtained by melting the metastable solid (m) is an α-SF salt-containing solid (s) (hereinafter referred to as “stable”) that is not lower than the melting point of the metastable solid (m) and is in a stable state. A method of maintaining the solid for 5 minutes or more at a temperature below the melting point of the stable solid (s) (hereinafter sometimes referred to as method (ii)).
(Iii) With respect to the melt obtained by melting the metastable solid (m), a shear of 100 (1 / s) or more at a temperature not lower than the melting point of the metastable solid (m) and not higher than 80 ° C. A method of applying a shearing force at a speed (hereinafter sometimes referred to as method (iii)).
That is, in step (I-2), (i) the flaky α-SF salt-containing solid matter (m) obtained in step (I-1) is at least 48 at a pressure of 30 ° C. or more and 20000 Pa or less. Maintaining the time, (ii) melting the flaky α-SF salt-containing solid material (m) obtained in the step (I-1), and adding the molten product obtained by melting the flaky α-SF salt Maintaining for at least 5 minutes at a temperature not lower than the melting point of the solid (m) and not higher than the melting point of the α-SF salt-containing solid (s) in a stable state, or (iii) the flaky shape With respect to the melt obtained by melting the α-SF salt-containing solid (m), at a temperature not lower than the melting point of the flaky α-SF salt-containing solid (m) and not higher than 80 ° C. Including applying a shear force at a shear rate of 100 (1 / s) or more.

Note that the melting points of the metastable solid (m) and the stable solid (s) can be determined in advance by thermal analysis using a differential scanning calorimeter. The melting points of the metastable solid (m) and the stable solid (s) vary depending on the number of carbon atoms of R ¹ and R ^{2 in} the above formula (1).

Hereinafter, methods (i) to (iii) will be described.
(Method (i))
In the method (i), the metastable solid (m) is maintained at a pressure of 30 ° C. or more and 20000 Pa or less for at least 48 hours.
When the temperature is less than 30 ° C., crystallization proceeds, but the rate is very slow. Therefore, it is preferable to maintain the temperature at 30 ° C. or higher and 40 ° C. or lower. Within this range, since the metastable solid (m) does not melt and fuse, solidification during the maintenance for 48 hours or more can be suppressed.
The maintenance temperature need not be a constant temperature as long as it is 30 ° C. or higher. For example, the maintenance temperature may be intermittently heated and cooled. The method for maintaining the temperature is not particularly limited, and examples thereof include a method in which a metastable solid (m) is placed in a container and its external environment is adjusted to a conditional temperature, or the container itself is adjusted to a conditional temperature. Moreover, the method of flowing the airflow of condition temperature inside a container may be used.
As a container, a silo, a flexible container bag, a drum can, a craft bag, a polyethylene bag, etc. can be used.

The pressure is 20000 Pa or less, preferably 12000 Pa or less, more preferably 500 to 8000 Pa, and still more preferably 3000 Pa to 7000 Pa. If it is 20000 Pa or less, the metastable solid (m) is difficult to solidify.
The pressure referred to here is the pressure at the bottom of the container and is defined by the following equation.
Pressure [Pa] = Packing mass [kg] × g [m / s ² ] / Container bottom area [m ² ]
In the above formula, g is gravitational acceleration.
When the container is filled with the metastable solid (m), it is naturally inevitable that pressure is applied to the bottom of the container due to its own weight. Therefore, it is preferable to adjust the shape, filling amount, and the like of the container so that the pressure is within the above range.

When the maintenance time is 48 hours or more, the conversion from the metastable solid (m) to the stable solid (s) proceeds sufficiently. If the maintenance time is excessively long, it leads to a decrease in the factory operation rate and the like, and preferably 72 hours or more and 6 weeks or less.
While maintaining the metastable solid (m) under the above-mentioned conditions, the metastable solid (m) may be put in a container to be in a sealed state or an open state, but if it is in an open state, there is a possibility of moisture absorption. Therefore, it is better to avoid contact with moist air.

The most preferable method (i) is a condition in which the temperature is maintained at 3000 Pa to 7000 Pa for 200 hours to 700 hours at a temperature of 30 ° C. to 35 ° C. Since the stable solid (s) thus obtained has a high melting point of 50 ° C. or higher, it is difficult to melt even when stored at a high temperature.

(Method (ii))
In the method (ii), the melt obtained by melting the metastable solid (m) is used for 5 minutes or more at a temperature not lower than the melting point of the metastable solid (m) and not higher than the melting point of the stable solid (s). maintain.
In the case of the α-SF salt obtained from the fatty acid alkyl ester of the above formula (1), specifically, it is preferably maintained at a temperature of 40 ° C. or more and less than 90 ° C., and is maintained at a temperature of 50 ° C. or more and less than 80 ° C. More preferably. When the temperature is within the above range, the metastable solid (m) is easily converted to the stable solid (s) in a short time. Further, when the maintenance time is within the above range, the metastable solid (m) is surely converted into the stable solid (s).
The most preferred method (ii) is a condition of maintaining at a temperature of 55 ° C. to 75 ° C. for 10 minutes to 500 minutes.

(Method (iii))
In the method (iii), the melt obtained by melting the metastable solid (m) is 100 (1 / s) at a temperature not lower than the melting point of the metastable solid (m) and not higher than 80 ° C. A shear force is applied at the above shear rate.
In the above method (ii), the metastable solid (m) melt was converted to a stable state by maintaining it at a predetermined temperature for a predetermined time, but in the method (iii), instead of maintaining the predetermined time, a shear force give. By applying a shearing force, the transition to a stable state is accelerated.

The means for applying the shearing force is not particularly limited, and examples thereof include various kneading apparatuses and extrusion granulating apparatuses. Specifically, KRC Kneader, Mazzoni S.K. p. Commercial products such as Milling Producer manufactured by a can be used.
The shear rate is defined by shear rate = blade tip speed / clearance, and is 100 (1 / s) or more and 10000 (1 / s) or less, 150 (1 / s) or more and 7000 (1 / s) or less. Is preferably 200 (1 / s) or more and 5000 (1 / s) or less.
When it is 100 (1 / s) or more, the stirring treatment is sufficient, and the metastable solid (m) is reliably converted to the stable solid (s).
The time for applying the shearing force is preferably 5 seconds or more and less than 5 minutes. When it is above the lower limit of the above range, the metastable solid (m) is sufficiently converted to a stable solid (s), and when it is below the upper limit of the above range, a large apparatus (kneading device, extrusion granulator, etc. ) Is not necessary.
The most preferable method (iii) is a condition in which a shear force is applied at a shear rate of 200 to 5000 (1 / s) at a temperature of 55 to 75 ° C.

It can be confirmed by thermal analysis using a differential scanning calorimeter that the metastable solid (m) has been crystallized and converted to the stable solid (s) by the methods (i) to (iii) described above.
For example, in the case of α-sulfo fatty acid methyl ester salt (MES) produced from a mixture of carbon atoms of R ¹ in the above formula (1) having 14 and 16, when the metastable solid (m) is subjected to thermal analysis, As shown in FIG. 3, a heat absorption (melting) peak having a peak top at about 40 ° C. to 50 ° C. and appearing in a temperature range of about 35 ° C. to 55 ° C. is observed. In this case, since the heat absorption in the region of 50 ° C. or higher is small, the heat absorption peak area at 50 ° C. to 130 ° C. is less than 50% with respect to the heat absorption peak area at 0 ° C. to 130 ° C.
On the other hand, when the stable solid (s) after crystallization is subjected to thermal analysis, for example, as shown in FIGS. 4 and 5, the peak in the vicinity of about 40 ° C. to 50 ° C. is reduced to about 50 ° C. or more (about 50 ° C. A plurality of peaks are observed in a region of about 70 ° C. and about 70 ° C. to 90 ° C.). In this case, the heat absorption peak area S1 at 50 ° C. to 130 ° C. is 50% or more with respect to the heat absorption peak area S2 at 0 to 130 ° C.
Thus, it can be understood that the stable solid (s) exhibits a heat absorption peak at a higher temperature and is more stable in the high temperature region than the metastable solid (m).
3 shows the thermal analysis result of the metastable solid (m) obtained in Example 1 described later, and FIG. 5 shows the stability obtained by crystallizing the metastable solid (m) of Example 1. It is a thermal analysis result of solid (s).

The moisture content of the stable solid (s) is preferably 10% by mass or less, and more preferably 5% by mass or less. The lower limit is preferably 0.5% by mass. That is, the moisture content of the stable solid (s) is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 5% by mass or less.
When the moisture content is within the above range, the storage stability of the stable solid (s) is excellent, and the adhesiveness is hardly increased even at a low temperature. Therefore, the handling property at the time of storage and transportation of the stable solid (s) is improved.
In the case of the stable solid (s) of MES, when the moisture content is low, the absolute value of the heat endothermic peak around 70 ° C. to 90 ° C. tends to increase.

As the differential scanning calorimeter, any of a commercially available general differential scanning calorimeter can be used either an input compensation type or a heat flux type. Specifically, for example, commercially available products such as “Diamond DSC” manufactured by PerkinElmer and “EXSTAR 6000” manufactured by Seiko Instruments Inc. can be used. A sample pan made of aluminum or stainless steel is used as a sample pan to put the sample. The temperature raising rate is preferably 1 to 2 ° C./min. Noise can be suppressed when the rate of temperature increase is equal to or higher than the lower limit value of the above range, and a fine peak can be detected without any problem when the temperature rising rate is equal to or lower than the upper limit value of the above range.

Note that the heat absorption peak area S1 at 50 ° C. to 130 ° C. and the heat absorption peak area S2 at 0 ° C. to 130 ° C. are determined by using “automatic division integration” using software attached to the differential scanning calorimeter. Each can be obtained by performing processing.
When an exothermic peak is observed at 50 ° C. to 130 ° C., the value obtained by subtracting the absolute value of the exothermic peak area from the heat absorption peak area at 50 ° C. to 130 ° C. is S1. Similarly, when an exothermic peak is observed at 0 ° C. to 130 ° C., the value obtained by subtracting the absolute value of the exothermic peak area from the heat absorption peak area at 0 ° C. to 130 ° C. is S2.

<Process (II)>
In step (II), the stable solid (s) obtained in step (I) is dissolved in water to produce an α-SF salt aqueous solution.
Here, the temperature of water that dissolves the stable solid (s) is Ts (° C.), and the heat absorption peak of the maximum heat flow rate observed when the stable solid (s) is subjected to thermal analysis with a differential scanning calorimeter. When the top temperature is Tmax (° C.), the water temperature Ts (° C.) is determined so that the temperature Ts (° C.) and the temperature Tmax (° C.) have the following relationship.

Tmax-5 ≦ Ts ≦ Tmax + 5

Specifically, first, a stable solid (s) to be dissolved is subjected to thermal analysis with a differential scanning calorimeter to obtain a temperature Tmax (° C.). Then, the temperature Ts (° C.) of the water is adjusted within ± 5 ° C. of the temperature Tmax (° C.), and the stable solid (s) is added to the temperature-adjusted water while stirring.
For example, in the DSC chart shown in FIG. 4, since the heat absorption peak top temperature Tmax (° C.) of the maximum heat flow rate is 88 ° C., the water temperature Ts (° C.) is adjusted to the range of 83 ° C. to 93 ° C. Then, a stable solid (s) is added to water and dissolved. In the DSC chart shown in FIG. 5, since the heat absorption peak top temperature Tmax (° C.) of the maximum heat flow rate is 60 ° C., the water temperature Ts (° C.) is adjusted to the range of 55 ° C. to 65 ° C. Then, a stable solid (s) is added to water and dissolved.

More preferably, the temperature Ts (° C.) of the water is determined so that the temperature Ts (° C.) and the temperature Tmax (° C.) have the following relationship.

Tmax-2 ≦ Ts ≦ Tmax + 2

As described above, the temperature Ts (° C.) of water when the stable solid (s) is dissolved is adjusted according to the heat absorption peak top temperature Tmax (° C.) of the maximum heat flow rate of the stable solid (s) to be dissolved. By doing so, for example, an α-SF salt aqueous solution which is less likely to precipitate even under low temperature conditions of about 10 ° C. to 20 ° C. and has excellent low temperature stability can be obtained. An α-SF salt aqueous solution excellent in low-temperature stability is easy to handle and is well mixed with other materials when a liquid detergent is produced.
The effect of improving the low-temperature stability is obtained in a wide range of α-SF salt aqueous solution concentrations. The anionic surfactant concentration of the α-SF salt aqueous solution is preferably 3 with respect to the total mass of the α-SF salt aqueous solution. When the content is in the range of 5% by mass to 25% by mass, more preferably in the range of 5% by mass to 20% by mass, the effect of improving the low temperature stability is remarkably obtained.

The reason why an α-SF salt aqueous solution excellent in low-temperature stability can be obtained by dissolving the stable solid (s) in water at a specific temperature is not necessarily clear, but the heat absorption peak at the maximum heat flow rate is not clear. It is considered that when the stable solid (s) is dissolved in water within a temperature range of ± 5 ° C. from the top temperature Tmax (° C.), the structure of the stable solid (s) in the aqueous solution is stabilized. . In water outside the range of ± 5 ° C from the heat absorption peak top temperature Tmax (° C) of the maximum heat flow rate, the structural balance in the aqueous solution of the stable solid (s) tends to be lost, thereby causing crystallization, that is, precipitation. It will be easier.
In particular, when the stable solid (s) contains by-product methyl sulfate metal salt or fatty acid sulfonate metal salt or has a distribution in the carbon number of acyl groups (α- In the case of a mixture of SF salts), the crystal structure of the stable solid (s) is complicated. In that case, it is considered that the structure of the α-SF salt in the aqueous solution also changes in a complex manner depending on the crystalline state at the time of dissolution. It is considered that the effect of stabilizing the structure of the stable solid (s) in the aqueous solution becomes remarkable by dissolving in water.

An α-SF salt-containing solid that does not satisfy the condition that the heat absorption peak area S1 at 50 ° C. to 130 ° C. is 50% or more of the heat absorption peak area S2 at 0 ° C. to 130 ° C. is dissolved in water. In this case, even if the temperature of water is set within a range of ± 5 ° C. from the heat absorption peak top temperature Tmax (° C.) of the maximum heat flow rate, the low temperature stability of the obtained aqueous solution is not improved.
This is presumably because the structure of the α-SF salt in an aqueous solution is not stable when dissolved in water in a metastable state where the structure of the α-SF salt is not stable.

Other embodiments of the method for producing the aqueous α-sulfo fatty acid alkyl ester salt solution of the present invention include:
A step (I) of obtaining a solid α-SF salt-containing solid in a stable state using a fatty acid alkyl ester as a starting material, and a step (II) of dissolving the α-SF salt-containing solid in water at a temperature Ts (° C.) Including
The step (I) includes a step (I-1) of preparing an α-SF salt-containing solid (m) in a metastable crystalline state, and the adjusted α-SF salt-containing solid (m) is crystallized. And obtaining the α-SF salt-containing solid (s) in the stable state (I-2),
Step (I-1) includes a sulfonation treatment in which the fatty acid alkyl ester is sulfonated with a sulfonation gas; an esterification treatment in which a lower alcohol is added to the sulfonated product obtained by the sulfonation treatment to perform esterification; A neutralization treatment for neutralizing the esterified product obtained by the esterification treatment; a bleaching treatment for bleaching the neutralized product obtained by the neutralization treatment; and an α-SF salt-containing paste obtained by the bleaching treatment Heating and concentrating to obtain a concentrated product; cooling and solidifying the concentrated product to obtain a cooled solidified product; and crushing the cooled and solidified product obtained by the cooling and solidifying treatment. Crushing treatment,
In the step (I-2), (i) the flaky α-SF salt-containing solid (m) obtained in the step (I-1) is at least 48 hours at a pressure of 30 ° C. or more and 20000 Pa or less. (Ii) melting the flaky α-SF salt-containing solid material (m) obtained in step (I-1) to obtain the melt obtained by melting the flaky α-SF salt Maintaining for at least 5 minutes at a temperature not lower than the melting point of the solid (m) and not higher than the melting point of the α-SF salt-containing solid (s) in a stable state, or (iii) the flaky α -With respect to the melt obtained by melting the SF salt-containing solid (m), at a temperature not lower than the melting point of the flaky α-SF salt-containing solid (m) and not higher than 80 ° C. Applying a shear force at a shear rate of (1 / s) or more,
In the step (II), the α-SF salt-containing solid (s) in the stable state has a heat absorption peak area S1 at 50 ° C. to 130 ° C. observed when thermal analysis is performed with a differential scanning calorimeter. , 50% or more with respect to the heat absorption peak area S2 at 0 ° C. to 130 ° C.,
The temperature Ts (° C.) is the temperature Tmax (° C.) when the heat absorption peak top temperature of the maximum heat flow rate observed when the solid matter is thermally analyzed by a differential scanning calorimeter is Tmax (° C.). And the following relationship:
A method for producing an aqueous α-sulfo fatty acid alkyl ester salt solution can be mentioned.
Tmax-5 ≦ Ts ≦ Tmax + 5

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Used raw materials>
(1) Fatty acid methyl ester Fatty acid methyl esters (A-1) to (A-4) were used. Table 1 shows the carbon number distribution of these acyl groups.

(A-1): Trade name “Edenor ME C16-80 MY” manufactured by Emery. Fatty acid methyl ester which originated from palm oil, was esterified, added and mixed with methyl ester of acyl group having 16 carbon atoms in a predetermined ratio, hydrogenated, and subjected to total distillation (bottom cut).
(A-2): “Pastel M16 (Fatty acid methyl ester manufactured by Lion Corporation)” and “Pastel M18 (Fatty acid methyl ester manufactured by Lion Corporation)” have the carbon number of the acyl group shown in Table 1. As a mixed mixture.
(A-3): “Pastel M16 (Fatty acid methyl ester manufactured by Lion Corporation)” and “Pastel M18 (Fatty acid methyl ester manufactured by Lion Corporation)” have the carbon number of the acyl group shown in Table 1. As a mixed mixture.
(A-4): Trade name “Edenor ME C16-60 MY” manufactured by Emery. Fatty acid methyl ester which originated from palm oil, was esterified, added and mixed with methyl ester of acyl group having 16 carbon atoms in a predetermined ratio, hydrogenated, and subjected to total distillation (bottom cut).

(2) Sulfonated gas: A gas produced by catalytic oxidation of SO ₂ using dry air (dew point −55 ° C.).
(3) Methanol (used in esterification treatment): Industrial grade (water content 1000 ppm or less).
(4) Caustic soda (used in neutralization treatment): Caustic soda obtained by diluting an industrial grade product (concentration of 48% by mass) with clean water.
(5) Hydrogen peroxide solution (used in bleaching treatment): Industrial grade hydrogen peroxide solution (35% by mass concentration: Junsei Chemical Co., Ltd.).

In Production Examples 1 to 4, steps (I-1) and (I-2) were performed as follows, and α-SF salt-containing solids (B-1) to (B-4) which are stable solids (s) ) Were produced respectively. In Production Example 5, an α-SF salt-containing solid (B-5) that is a metastable solid (m) was produced. In the step (I-1), the sulfonation treatment to the neutralization treatment were performed using the production system having the configuration shown in FIG.

(Production Example 1): Production of α-SF salt-containing solid (B-1) [Step (I-1)] (Sulfonation treatment)
100 parts by mass of the fatty acid methyl ester (A-1) was charged into the tank-type sulfonation reactor, and a sulfonation gas was added at a reaction molar ratio (SO ₃ / fatty acid methyl ester) = 1.2, and sulfonation ( Gas contact operation) (80 ° C., 240 minutes). Thereafter, the mixture was transferred to an esterification tank and subjected to an aging operation (80 ° C., 20 minutes), and then 5 parts by mass of sodium sulfate was added over 15 minutes to 100 parts by mass of the fatty acid methyl ester (A-1). The mixture was stirred for 20 minutes from the start of sodium sulfate addition. A sulfonated product was thus obtained.
The esterification tank is a jacketed agitation tank (10% dish-type end plate, 4 baffle plates) having an inner diameter of 600 mm and a container depth of 816 mm, and uses an agitating blade composed of 6 inclined turbine blades to flow downward. It was installed as follows. The stirring rotation speed was 277 rpm.

(Esterification treatment)
3 parts by mass of methanol (1.5 times mol with respect to the bimolecular adduct of SO ₃ ) was added to 100 parts by mass of the sulfonated product obtained by the sulfonation treatment, and esterification (80 ° C., 75 minutes) To obtain an esterified product.

(Neutralization treatment)
Next, the product obtained by the esterification treatment is added simultaneously and continuously with a 30% by mass aqueous sodium hydroxide solution in the vicinity of the stirring blade of the mixer, and mixed by stirring to perform a neutralization reaction. A sulfo fatty acid methyl ester salt (neutralized product) was produced. The neutralized product was prepared so that the temperature of the obtained neutralized product was 80 ° C. and pH around 6.0. The pH was measured directly on the neutralized product (stock solution, 80 ° C.) flowing through the neutralization line with a pH meter (SHDM-135: manufactured by Toa DKK Co., Ltd.) installed in the neutralization line.

(Bleaching treatment)
Next, this neutralized product is fed at a feed rate of 180 to 200 kg / hr to a circulation loop type bleaching agent mixing line having a circulation line having a heat exchanger, and 35% hydrogen peroxide solution is added to the sulfonated product. 3.5 to 11.5 kg / hr depending on color tone (1 to 3% by mass with respect to AI (active ingredient: α-sulfo fatty acid alkyl ester salt)), and bleach mixed from the circulation line The neutralized product (preliminary bleached product) and hydrogen peroxide solution were mixed thoroughly (1% by mass if 5% KLETT was 500 or less, 2% by mass if 5% KLETT was 500 to 1000, If the 5% KLETT is 1000 to 1500, it is 3% by mass, and 5% KLETT means that the obtained 5% by mass solution of α-sulfo fatty acid methyl ester salt is 40 mm optical path length, No. 42 -It means the value of color tone measured with a Krett photometer using a filter.)
The amount of loop circulation was 15 times the amount of neutralized product newly added to the preliminary bleached product, and the pressure in the circulation loop pipe was 4 kg / cm ² . The temperature of the circulation loop was adjusted to 80 ° C. with a heat exchanger, and the residence time of the circulation loop was 10 minutes.
Subsequently, this was introduced into a bleaching line of a distribution pipe system not shown, and the bleaching proceeded. As the bleaching line, a jacketed double tube with adjustable temperature and pressure was used. The flow of the bleaching agent mixture was a piston flow, the pressure was 4 kg / cm ² , the maximum temperature was adjusted to 80 ° C. or more, and the residence time was 180 minutes.
Thus, an α-SF salt-containing solid paste was obtained.

(Concentration treatment)
Subsequently, the obtained α-SF salt-containing solid paste was introduced into a vacuum thin film evaporator (heat transfer surface: 4 m ² , manufactured by Ballestra) at 200 kg / hr, the inner wall heating temperature was 100 ° C. to 160 ° C., and the degree of vacuum was 0. The solution was concentrated at 01 to 0.03 MPa and taken out as a concentrate (melt) at a temperature of 100 to 130 ° C.
A part of the concentrated product obtained here was cooled, and the concentration of α-SF salt contained in the concentrated product was measured by a methylene blue (MB) back titration method described in JIS K3362 as described later. did. The concentrations of disodium salt (Di-Na), sodium methyl sulfate (MeSO ₄ Na), and sodium sulfate (Na ₂ SO ₄ ) were measured by liquid chromatography as described later.

(Cooling solidification treatment and crushing treatment)
The resulting concentrated product is cooled from 100 ° C. to 130 ° C. to 20 ° C. to 30 ° C. in 0.5 minutes using a belt cooler (manufactured by Nippon Belting Co., Ltd.), and is a plate of metastable solid (m). A solid was obtained.
Thereafter, the plate-like solid was crushed using a crusher (manufactured by Nippon Belting Co., Ltd.) to obtain a flaky MES metastable solid (m).

[Step (I-2)]
The method (i) described above was employed to convert the metastable solid (m) to a stable solid (s). Specifically, based on a test using a flexible container bag, a polyethylene inner bag is put into a 430 L polypropylene flexible container bag (manufactured by Furuta Shoten), and obtained in step (I-1). 200 kg of flaky MES metastable solid (m) was added and allowed to stand at the temperature and pressure shown in Table 2 for the period shown in Table 2. In this way, an α-SF salt-containing solid (B-1) which is a stable solid (s) was obtained. Table 2 shows the analysis results of the obtained α-SF salt-containing solid (B-1).
Further, the α-SF salt-containing solid (B-1) was subjected to thermal analysis with a differential scanning calorimeter as described later, and 50 ° C. to 130 ° C. with respect to the heat absorption peak area S 2 at 0 ° C. to 130 ° C. Ratio of heat absorption peak area S1 at ° C .: The heat absorption peak top temperature Tmax (° C.) of the observed maximum heat flow rate was determined. The results are shown in Table 3.

(Production Example 2): Production of α-SF salt-containing solid (B-2) Production Example 1 except that fatty acid methyl ester (A-2) was used instead of fatty acid methyl ester (A-1). Each step was performed in the same manner to obtain an α-SF salt-containing solid (B-2). Table 2 shows the analysis results of the obtained α-SF salt-containing solid (B-2). In addition, the α-SF salt-containing solid (B-2) was subjected to thermal analysis with a differential scanning calorimeter in the same manner as in Production Example 1, and 50% of the heat absorption peak area S2 at 0 ° C. to 130 ° C. The ratio of the heat absorption peak area S1 in the range from 0 ° C. to 130 ° C .; the heat absorption peak top temperature Tmax (° C.) of the maximum observed heat flow rate was determined. The results are shown in Table 3.

(Production Example 3): Production of α-SF salt-containing solid (B-3) Production Example 1 except that fatty acid methyl ester (A-3) was used instead of fatty acid methyl ester (A-1). Each step was performed in the same manner to obtain an α-SF salt-containing solid (B-3). Table 2 shows the analysis results of the resulting α-SF salt-containing solid (B-3). Further, the α-SF salt-containing solid (B-3) was subjected to thermal analysis with a differential scanning calorimeter in the same manner as in Production Example 1, and 50% of the heat absorption peak area S2 at 0 ° C. to 130 ° C. The ratio of the heat absorption peak area S1 in the range from 0 ° C. to 130 ° C .; the heat absorption peak top temperature Tmax (° C.) of the maximum observed heat flow rate was determined. The results are shown in Table 3.

(Production Example 4): Production of α-SF salt-containing solid (B-4) Production Example 1 except that fatty acid methyl ester (A-4) was used instead of fatty acid methyl ester (A-1). Each step was performed in the same manner to obtain an α-SF salt-containing solid (B-4). Table 2 shows the analysis results of the resulting α-SF salt-containing solid (B-4). In addition, the α-SF salt-containing solid (B-4) was subjected to thermal analysis with a differential scanning calorimeter in the same manner as in Production Example 1, and 50% of the heat absorption peak area S2 at 0 ° C. to 130 ° C. The ratio of the heat absorption peak area S1 in the range from 0 ° C. to 130 ° C .; the heat absorption peak top temperature Tmax (° C.) of the maximum observed heat flow rate was determined. The results are shown in Table 3.

(Production Example 5): Production of α-SF salt-containing solid (B-5) which is a metastable solid (m) Each of the steps was carried out in the same manner as in Production Example 1, and α-SF salt-containing solid (B- 5) was obtained. However, concentration treatment was performed, and step (I-2) was not performed. Table 2 shows the analysis results of the resulting α-SF salt-containing solid (B-5). In addition, the α-SF salt-containing solid (B-5) was subjected to thermal analysis with a differential scanning calorimeter in the same manner as in Production Example 1, and 50% of the heat absorption peak area S2 at 0 ° C. to 130 ° C. The ratio of the heat absorption peak area S1 in the range from 0 ° C. to 130 ° C .; the heat absorption peak top temperature Tmax (° C.) of the maximum observed heat flow rate was determined. The results are shown in Table 3.

The analysis was performed by the following method.
(1) Moisture measurement The moisture was measured using a Karl Fischer moisture meter ("MKC-210" manufactured by Kyoto Electronics Industry Co., Ltd.). Specifically, 10 mg to 100 mg of sample was completely dissolved in Karl Fischer reagent at 15 to 25 ° C., and measurement was started. The measurement was automatically stopped as the electrode reaction ended. The amount of sample input was input to the Karl Fischer moisture meter touch panel to calculate the amount of moisture.

(2) Anionic surfactant concentration (% by mass)
0.3 g of a sample was accurately weighed into a 200 mL volumetric flask, and ion-exchanged water (distilled water) was added up to the marked line and dissolved by ultrasonic waves. After dissolution, cool to about 25 ° C., take 5 mL of the solution with a whole pipette into a titration bottle, add 25 mL of MB (methylene blue) indicator and 15 mL of chloroform, and then add 5 mL of a 0.004 mol / L benzethonium chloride solution. Titrated with 0.002 mol / L sodium alkylbenzene sulfonate solution. In each titration, the titration bottle was capped and shaken vigorously, then allowed to stand, and the end point was the point where both layers had the same color tone against a white plate. Similarly, a blank test (the same test as described above except that no sample was used) was performed, and the anionic surfactant concentration was calculated from the difference in titer. Here, as described above, the anionic surfactant concentration is the total concentration of the α-SF salt, which is a cleaning active ingredient, and the α-sulfo fatty acid dialkali salt (di-salt), which is one of by-products. It is.

(3) Ratio of α-sulfo fatty acid disodium salt in anionic surfactant Standard product of α-sulfo fatty acid disodium salt (hereinafter also referred to as “Di-Na”) 0.02, 0.05, 0. 1 g was accurately weighed into a 200 mL volumetric flask, about 50 mL of water and about 50 mL of ethanol were added and dissolved using ultrasonic waves. After dissolution, the mixture was cooled to about 25 ° C., and methanol was accurately added up to the marked line to obtain a standard solution.
About 2 mL of this standard solution was filtered using a 0.45 μm chromatographic disk, followed by high performance liquid chromatographic analysis under the following measurement conditions to prepare a calibration curve from the peak area.

Next, 1.5 g of the α-SF salt-containing solid was accurately weighed into a 200 mL volumetric flask, and about 50 mL of water and about 50 mL of ethanol were added and dissolved using ultrasonic waves. After dissolution, the mixture was cooled to about 25 ° C., and methanol was accurately added up to the marked line to make a test solution.
About 2 mL of the test solution was filtered using a 0.45 μm chromatographic disk and then analyzed by high performance liquid chromatography under the same measurement conditions as described above. The concentration of Di-Na in the sample solution was analyzed using the calibration curve prepared above. Asked.
In Table 2, the concentration of Di-Na when the anionic surfactant concentration is 100% by mass is described as “Di-Na amount in 100% by mass of anionic surfactant”.

(High-performance liquid chromatographic analysis measurement conditions)
・ Device: LC-6A (manufactured by Shimadzu Corporation) ・ Column: Nucleosil 5SB (manufactured by GL Sciences Inc.) ・ Column temperature: 40 ° C. ・ Detector: Differential refractive index detector RID-6A (manufactured by Shimadzu Corporation) ・ Mobile phase: 0 0.7% sodium perchlorate in H ₂ O / CH ₃ OH = 1/4 (volume ratio) solution Flow rate: 1.0 mL / min.・ Injection volume: 100 μL

(4) Sodium sulfate concentration and methyl sulfate concentration (mass%)
Accurately weigh 0.02, 0.04, 0.1, and 0.2 g of sodium sulfate and methyl sulfate, respectively, into a 200 mL volumetric flask, add ion-exchanged water (distilled water) to the marked line, It was dissolved using sonic waves. After dissolution, the mixture was cooled to about 25 ° C. and used as a standard solution. About 2 mL of this standard solution was filtered using a 0.45 μm chromatographic disk, followed by ion chromatographic analysis under the following measurement conditions, and a calibration curve was created from the peak areas of the sodium sulfate and methyl sulfate standard solutions.
Next, 0.3 g of a measurement sample is accurately weighed into a 200 mL volumetric flask, ion-exchanged water (distilled water) is added up to the marked line, and dissolved using ultrasonic waves. After dissolution, the solution was cooled to about 25 ° C. and used as a test solution. About 2 mL of the test solution was filtered using a 0.45 μm chromatographic disk and then analyzed by an ion chromatograph under the same measurement conditions as described above. Using the prepared calibration curve, the methyl sulfate concentration and sodium sulfate concentration in the sample solution were analyzed. The sodium sulfate and methyl sulfate concentrations (mass%) in the sample were calculated.

(Ion chromatographic analysis and measurement conditions)-Device: DX-500 (Nippon Dionex)-Detector: Electrical conductivity detector CD-20 (Nippon Dionex)-Pump: IP-25 (Nippon Dionex)・ Oven: LC-25 (made by Nippon Dionex) ・ Integrator: C-R6A (made by Shimadzu Corporation) ・ Separation column: AS-12A (made by Nippon Dionex) ・ Guard column: AG-12A (Japan) Manufactured by Dionex Co., Ltd.)-Eluent: 2.5 mM Na ₂ CO ₃ /2.5 mM NaOH / 5% (volume) acetonitrile aqueous solution-eluent flow rate: 1.3 mL / min.・ Regeneration solution: Pure water ・ Column temperature: 30 ° C. ・ Loop volume: 25 μL

(5) Thermal analysis with a differential scanning calorimeter A Perkin Elmer Diamond DSC was used as a differential scanning calorimeter. 20 g of the sample was pulverized with a trio blender (manufactured by Trio Science), 5-30 mg of the sample was put in an aluminum sample pan, heated from 0 ° C. to 130 ° C. at a rate of 2 ° C./min, and subjected to thermal analysis. .
S1 × 100 / S2 was determined from the heat absorption peak area S1 at 50 ° C. to 130 ° C. and the heat absorption peak area S2 at 0 ° C. to 130 ° C. The area S1 and the area S2 were obtained by performing an “automatic division integration” process using software attached to the differential scanning calorimeter. When an exothermic peak is observed at 50 ° C. to 130 ° C., the value obtained by subtracting the absolute value of the exothermic peak area from the heat absorption peak area at 50 ° C. to 130 ° C. is S1, and the exothermic peak is generated at 0 to 130 ° C. When a peak was observed, the value obtained by subtracting the absolute value of the exothermic peak area from the heat absorption peak area at 0 ° C. to 130 ° C. was defined as S2.

(Examples 1 to 10, Comparative Examples 1 to 7)
In each Example and each Comparative Example, as shown in Table 3, the α-SF salt-containing solids (B-1) to (B-5) obtained in each Production Example were dissolved in water, and 2.5 kg An α-SF salt-containing aqueous solution was prepared. Here, the amount of the α-SF salt-containing solids (B-1) to (B-5) dissolved in water is such that the concentration of the anionic surfactant in the obtained α-SF salt-containing aqueous solution is the value shown in Table 3. Decided to be.
For dissolution, a 5 L beaker, a stirring motor, a 45-degree inclined paddle (9 cm), a baffle plate (4 sheets), and the like were used. Specifically, water is put into a beaker and heated, and after confirming that a predetermined temperature (Ts (° C.)) has been reached, the rotation speed of the stirring motor is set to 262 rpm and the α-SF salt is contained. Solids (B-1) to (B-5) were added to water. The solution was stirred until it could be visually confirmed that it was completely dissolved to obtain each aqueous solution.
Temperature Ts (° C.) of water at the time of dissolution, heat absorption peak top temperature Tmax (° C.) of the maximum heat flow rate observed by thermal analysis of α-SF salt-containing solids (B-1) to (B-5) Table 3 shows the difference between Tmax (° C.) and Ts (° C.) (Tmax−Ts (° C.)).
The obtained α-SF salt-containing aqueous solution was sampled in a glass bottle with a capacity of 200 ml and allowed to stand in a thermostatic bath at 18 ° C. The appearance after 24 hours of standing was confirmed and evaluated in the following four stages. The results are shown in Table 3.
A: Transparent B: Slight cloudiness C: Precipitation was observed, but the aqueous solution was fluid.
D: Precipitation is observed, and there is no fluidity of the aqueous solution.

As shown in Table 3, each example employs a stable solid (s) of an α-SF salt-containing solid, which is dissolved in water at an appropriate temperature to obtain an aqueous solution. Excellent stability. On the other hand, in each comparative example where the temperature of water is not appropriate, the α-SF salt to be dissolved is not a stable solid (s), or both of them, an aqueous solution excellent in low-temperature stability cannot be obtained. It was.

The method for producing an α-sulfo fatty acid alkyl ester salt aqueous solution of the present invention is extremely important industrially because it can produce an α-SF salt aqueous solution that hardly causes precipitation even under low temperature conditions.

Claims (1)

1. A method for producing an α-sulfo fatty acid alkyl ester salt aqueous solution by dissolving a solid containing an α-sulfo fatty acid alkyl ester salt in water at a temperature Ts (° C.),
   The solid matter has a heat absorption peak area S1 at 50 ° C. to 130 ° C. observed when thermal analysis is performed with a differential scanning calorimeter, which is 50% or more of the heat absorption peak area S2 at 0 ° C. to 130 ° C. Yes,
   The temperature Ts (° C.) is the temperature Tmax (° C.) when the heat absorption peak top temperature of the maximum heat flow rate observed when the solid matter is thermally analyzed by a differential scanning calorimeter is Tmax (° C.). And an aqueous α-sulfo fatty acid alkyl ester salt solution having the following relationship:
   Tmax-5 ≦ Ts ≦ Tmax + 5

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