JP2008024672A - METHOD FOR PRODUCING alpha-SULFOFATTY ACID ALKYL ESTER SALT - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which an α-sulfofatty acid alkyl ester salt excellent in a color tone can be produced using a falling-film reactor. <P>SOLUTION: The method comprises a sulfonation process for sulfonating a fatty acid alkyl ester containing ≤0.5 mass% glycerol and its derivatives under a condition in which a coloring suppressant is absent by using the falling-film reactor, an aging process for carrying out an aging treatment by bringing the product prepared in the sulfonation process to contact with the coloring suppressant hardly soluble in the fatty acid alkyl ester in 0.1-10 mass% of the product within 30 minutes from discharge of the product from the falling-film reactor, an esterification process for esterifying the product prepared in the aging process using a 1-6C alcohol, a neutralization process for neutralizing the product prepared in the esterification process and a bleaching process for bleaching the product prepared in the neutralization process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an α-sulfo fatty acid alkyl ester salt.

A neutralized salt of a sulfonated product of a fatty acid alkyl ester is generally called an α-sulfo fatty acid alkyl ester salt. It is a surfactant that has good water resistance and biodegradability, has excellent detergency, and is mild to the skin. It is a natural raw material system that can be recycled from the viewpoint of resources, and is advantageous in terms of cost, and is also regarded as important from the viewpoint of protecting the global environment.
As a method for producing an α-sulfo fatty acid alkyl ester salt, the fatty acid alkyl ester is sulfonated using SO ₃ gas or the like to obtain an α-sulfo fatty acid alkyl ester, and the α-sulfo fatty acid alkyl ester is neutralized with an alkali. The method is common.
The mechanism of sulfonation of fatty acid alkyl esters is illustrated by the following reaction scheme. Is first inserted is SO ₃ alkoxy group moiety of the fatty acid alkyl esters, generated by SO ₃ one molecule adduct, further introduces SO ₃ in the position α of SO ₃ per molecule adduct SO ₃ bimolecular adduct Generate. Finally, SO ₃ SO ₃ inserted into the alkoxy group portion of the bimolecular adducts release the α- sulfofatty acid alkyl esters are produced de.
In the reaction scheme of the above sulfonation, but to the step of creating SO ₃ bimolecular adduct reaction proceeds rapidly, the step of creating α- sulfofatty acid alkyl esters from SO ₃ bimolecular adduct reaction rate very Very late. Therefore, currently, by providing an aging step after sulfonation, to promote desorption of SO ₃ from SO ₃ bimolecular adduct it has been conducted.
And the alpha-sulfo fatty-acid alkylester salt is manufactured by neutralizing the produced | generated alpha-sulfo fatty-acid alkylester with an alkali.

However, the α-sulfo fatty acid alkyl ester salt obtained as described above usually has a remarkable coloring. Coloring is inconvenient for use as a cleaning agent.
Therefore, in order to improve the color tone of the α-sulfo fatty acid alkyl ester salt, bleaching is generally performed before or after the alkali neutralization step.
Moreover, in order to improve the color tone of the α-sulfo fatty acid alkyl ester salt, a method of performing a sulfonation step and / or an aging step in the presence of a coloring inhibitor has also been proposed (see, for example, Patent Documents 1 to 3). The coloring inhibitor is usually added to the raw material liquid from the initial stage of the sulfonation reaction for reasons such as excellent coloring suppression effect and less labor.

By the way, as the sulfonation method of fatty acid alkyl ester, there are a method using a falling film reactor, a so-called film reactor, and a batch method using a tank reactor. Among these, the method using a falling film reactor has good production efficiency and is currently mainstream in the world.
JP-A-9-216863 JP 2001-2633 A JP 2001-64248 A

However, when using a falling film reactor, it is difficult to obtain an α-sulfo fatty acid alkyl ester salt having an excellent color tone even if a coloring inhibitor is used. The cause is as follows. That is, in the case of using a falling film reactor, usually a thin film is formed by flowing a raw material liquid containing a raw material (fatty acid alkyl ester), and the thin film is brought into contact with SO ₃ gas or the like to effect sulfonation. Is called. Since the coloring inhibitor is usually hardly dissolved in the raw material liquid, it is dispersed in the raw material liquid in a particle state. Therefore, if a color inhibitor is added to the raw material liquid before sulfonation, the color inhibitor particles may be clogged and clogged in the gap portion when the raw material is supplied from a narrow gap to form a thin film. Even in a thin film, the uneven distribution of the coloring inhibitor results in an inhomogeneous film, and a sufficient coloring suppressing effect cannot be obtained.
Conventionally, even if a color inhibitor is added in the aging step after the sulfonation step, a sufficient color suppression effect is usually not obtained.
This invention is made | formed in view of the said situation, Comprising: It aims at providing the manufacturing method which can manufacture the alpha-sulfo fatty-acid alkylester salt excellent in the color tone using the falling film type reactor.

As a result of intensive studies, the present inventors have used glycerin and a fatty acid alkyl ester whose content is a predetermined amount or less as a raw material, and sulfonated the fatty acid alkyl ester using a falling film reactor. The inventors have found that the above-mentioned problems can be solved by bringing them into contact with a predetermined amount of a coloring inhibitor within a predetermined time and ripening them, thereby completing the present invention.
That is, the present invention sulfonates a fatty acid alkyl ester having a glycerin and its derivative content of 0.5% by mass or less using a falling film reactor under the condition that no coloring inhibitor is present. A sulfonation step;
The product obtained in the sulfonation step, and a coloring inhibitor hardly soluble in the fatty acid alkyl ester in an amount of 0.1 to 10% by mass of the product, the product is the falling film reactor. A maturing step in which the maturing process is performed within 30 minutes after being discharged from the
An esterification step of performing an esterification treatment on the product obtained in the aging step using an alcohol having 1 to 6 carbon atoms;
A neutralization step for neutralizing the product obtained in the esterification step;
And a bleaching step of bleaching a product obtained in the neutralization step.

  According to the method for producing an α-sulfo fatty acid alkyl ester salt of the present invention, an α-sulfo fatty acid alkyl ester salt having excellent color tone can be produced using a falling film reactor.

Hereinafter, the present invention will be described in more detail.
<Sulfonation step>
First, a sulfonation step of sulfonating a fatty acid alkyl ester that is a raw material is performed.
In the present invention, it is necessary to use a fatty acid alkyl ester having a glycerin and its derivative content of 0.5% by mass or less. When the content is 0.5% by mass or less, coloring in the sulfonation step can be effectively suppressed, and the color tone of the obtained α-sulfo fatty acid alkyl ester salt is improved. The content of glycerin and its derivatives in the fatty acid alkyl ester is preferably 0.2% by mass or less, more preferably 0.1% by mass or less.
Content of glycerol and its derivative (s) is a ratio (mass%) of the total amount of glycerol and its derivative in fatty-acid alkylester.
Examples of glycerin derivatives include fatty acid monoglycerin esters, fatty acid diglycerin esters, and fatty acid triglycerin esters.
The content of glycerin and its derivatives can be measured, for example, using gas chromatography, based on the method described in “Introduction to Lipid Analysis”, Society Press, pages 226-228.

  As the fatty acid alkyl ester, a commercially available product or a synthesized product may be used as long as the content of glycerin and its derivative is 0.5% by mass or less. In addition, by washing a fatty acid alkyl ester having a glycerin and its derivative content of more than 0.5% by mass with a solvent that dissolves glycerin and its derivative, such as water, the content of glycerin and its derivative is reduced. You may use it as 0.5 mass% or less.

  The fatty acid alkyl ester preferably has an iodine value of 0.5 or less, and more preferably 0.2 or less. The lower the iodine value, the more effectively the coloration in the sulfonation step can be reduced, and the color tone of the resulting α-sulfo fatty acid alkyl ester salt becomes better. Moreover, the odor of the α-sulfo fatty acid alkyl ester salt is also suppressed. Particularly, those having an iodine value of 0.2 or less have a particularly good color tone as compared with those having an iodine value exceeding 0.2.

  More specifically, examples of the fatty acid alkyl ester include fatty acid alkyl esters represented by the following general formula (I) (hereinafter sometimes referred to as fatty acid alkyl esters (I)).

［式中、Ｒ^１は炭素数６〜２４の直鎖または分岐鎖状のアルキル基またはアルケニル基を表し、Ｒ^２は炭素数１〜６の直鎖または分岐鎖状のアルキル基を表す。］

[Wherein, R ¹ represents a linear or branched alkyl group or alkenyl group having 6 to 24 carbon atoms, and R ² represents a linear or branched alkyl group having 1 to 6 carbon atoms. ]

The alkyl group for R ¹ may be linear or branched, and preferably has 8 to 22 carbon atoms, more preferably 10 to 18 carbon atoms.
The alkenyl group for R ¹ may be linear or branched, and preferably has 8 to 22 carbon atoms, more preferably 10 to 18 carbon atoms.
R ¹ is preferably an alkyl group. That is, the α-sulfo fatty acid alkyl ester salt is preferably an α-sulfo saturated fatty acid alkyl ester salt.
The alkyl group for R ² may be linear or branched, and preferably has 1 to 3 carbon atoms, more preferably 1 or 2.

Specific examples of fatty acid alkyl esters include animal fats derived from beef tallow, fish oil lanolin, etc .; plant fats derived from palm oil, palm oil, soybean oil, etc .; synthesis derived from the oxo method of α-olefins Examples include fatty acid alkyl esters. More specifically, methyl, ethyl or propyl laurate; methyl, ethyl or propyl myristate; methyl, ethyl or propyl palmitate; methyl stearate, ethyl or propyl; hydrogenated beef tallow fatty acid methyl, ethyl or propyl; hydrogenated fish oil fatty acid Examples thereof include methyl, ethyl or propyl; palm oil fatty acid methyl, ethyl or propyl; palm oil fatty acid methyl, ethyl or propyl; palm kernel oil fatty acid methyl, ethyl or propyl and the like.
Any one of these fatty acid alkyl esters may be used alone, or two or more thereof may be used in combination.

The sulfonation of the fatty acid alkyl ester is carried out using a falling film reactor under conditions where no color inhibitor is present.
As the falling film reactor, those generally used for sulfonation reaction can be used. For example, a double-tube type falling film reactor (such as TO reactor manufactured by Lion Corporation), multi-tube type A falling thin film reactor (made by Valestra Co., Ltd.) and the like can be mentioned.

The sulfonation of the fatty acid alkyl ester can be carried out by bringing the raw material liquid containing the fatty acid alkyl ester into contact with the SO ₃ gas containing SO ₃ in the falling film reactor.
When the fatty acid alkyl ester is brought into contact with SO ₃ gas, an SO ₃ single-molecule adduct in which SO ₃ is inserted into the alkoxy group portion of the fatty acid alkyl ester is first generated. Next, SO ₃ is inserted into the α-position of the SO ₃ monomolecular adduct to produce an SO ₃ bimolecular adduct. Thereafter, SO ₃ is eliminated from the alkoxy group part of the SO ₃ bimolecular adduct to produce an α-sulfo fatty acid alkyl ester.
More specifically, the fatty acid alkyl ester (I) will be described as an example. As shown below, the fatty acid alkyl ester (I) is converted to an SO ₃ monomolecular adduct represented by the following general formula (I ′) ( I ') is generated, the SO ₃ one molecule adduct (I'"SO ₃ bimolecular adduct represented by) (I" following formulas) (I) is produced, the SO ₃ bimolecular addition The α-sulfo fatty acid alkyl ester represented by the following general formula (II) is produced from the body (I ″).

［式中、Ｒ^１およびＲ^２は、それぞれ、上記式（Ｉ）中のＲ^１およびＲ^２と同じである。］

[Wherein, R ¹ and R ² are the same as R ¹ and R ² in the formula (I), respectively. ]

In this sulfonation reaction scheme, the reaction proceeds promptly until the SO ₃ bimolecular adduct formation stage. SO ₃ generation phase of α- sulfofatty acid alkyl esters from bimolecular adduct is very slow reaction rate, and thereafter, by performing the aging step, desorption of SO ₃ from SO ₃ bimolecular adduct promote Is done.

The SO ₃ gas, an inert gas such as dehumidified air or nitrogen, SO ₃ gas diluted to SO ₃ concentration 1-30% by volume is preferably used. When the SO ₃ concentration is 1% by volume or more, the volume of the SO ₃ gas falls within an appropriate range, and a reactor having a relatively small capacity can be used. When the amount is 30% by volume or less, the sulfonation reaction is unlikely to be excessive, generation of by-products can be suppressed, and deterioration of the color tone of a sulfonated product such as α-sulfo fatty acid alkyl ester can be prevented.
The amount of SO ₃ gas, the amount of SO ₃ in the SO ₃ gas is preferably the amount to be 1.0 to 2.0 times the moles of fatty acid alkyl esters, a 1.1 to 1.3-fold molar The amount is more preferable, and an amount of 1.15 to 1.25 times mol is more preferable. When the amount is 1.0 times or more, the sulfonation reaction proceeds sufficiently. When the amount is 2.0 times or less, excessive sulfonation reaction can be suppressed, and coloring of the reaction product due to local heat can be prevented. Can be suppressed.

The reaction temperature in the sulfonation reaction may be a temperature at which the fatty acid alkyl ester has fluidity, and generally, a temperature within the range of the melting point + 70 ° C. is applied from the melting point of the fatty acid alkyl ester. For example, in the case of the fatty acid alkyl ester (I) described above, the reaction temperature is usually preferably 50 to 120 ° C, and more preferably 60 to 90 ° C. The reaction pressure is from atmospheric pressure to 50 kPa (gauge).
The reaction time is preferably 5 to 180 seconds, and more preferably 5 to 60 seconds.

After the sulfonation reaction, the product is discharged from the outlet (removal port) of the falling film reactor.
At this time, since the product is usually discharged together with the gas in the falling film reactor, it is preferable to perform gas-liquid separation with a dust collector such as a cyclone after the discharge.
During gas-liquid gas separated by the separation (gas), typically, it contains SO _X gas or reaction mist. These are preferably collected and removed by an electric dust collector or a filter. Further, SO ₂ remaining in the exhaust gas may be removed through an alkali scrubber as necessary. An alkali scrubber is a kind of wet acidic gas absorption device, and is a device that neutralizes and collects an acidic gas contained in a gas by passing it through an aqueous alkaline solution.

In the present invention, the sulfonation reaction rate at the outlet of the falling film reactor of the product obtained in the sulfonation step is preferably 70 mol% or less. Thereby, the effect of the coloring inhibitor brought into contact with the product after the sulfonation step is sufficiently exhibited, and an α-sulfo fatty acid alkyl ester salt having an excellent color tone is obtained.
Here, the sulfonation reaction rate means the ratio (%) of the compound having a C—S bond in the product when discharged from the outlet of the falling film reactor.
The compound having a C—S bond has a C—S bond, such as the above-mentioned SO ₃ bimolecular adduct and by-products (such as methyl sulfate), in addition to the target compound α-sulfo fatty acid alkyl ester. Everything is included.
The sulfonation reaction rate is determined by analyzing the product collected from the outlet of the falling film reactor by high performance liquid chromatography (HPLC) to determine the concentration of unreacted raw material (fatty acid alkyl ester) in the product, It can be calculated from the concentration.
The sulfonation reaction rate can be adjusted, for example, by adjusting the amount of SO ₃ reacted with the fatty acid alkyl ester. For example, the greater the amount of SO ₃ , the higher the sulfonation reaction rate. Specifically, when SO ₃ is used in an amount of 1.2 mol times that of the fatty acid alkyl ester, the sulfonation reaction rate varies depending on the reaction conditions such as reaction temperature and reaction time, but is usually 55 to 60 mol%. When 1.4 mol times the amount is used, it is usually less than 70%.

<Aging process>
Next, an aging treatment of the product obtained in the sulfonation step is performed. The product obtained in the sulfonation step usually contains an α-sulfo fatty acid alkyl ester itself, an intermediate such as a by-product SO ₃ bimolecular adduct, and a small amount of unreacted product. . By performing the aging process, desorption of SO ₃ from SO ₃ bimolecular adduct is accelerated to improve the yield of α- sulfofatty acid alkyl esters, also the formation of by-products can be suppressed.
Here, “ripening treatment” means holding the product at a predetermined aging temperature for a predetermined aging time.
The aging temperature is preferably 70 to 100 ° C, more preferably 70 to 90 ° C. When the aging temperature is 70 ° C. or higher, the reaction proceeds rapidly, and when it is 100 ° C. or lower, coloring is unlikely to occur.
The aging time is preferably 20 to 240 minutes, more preferably 30 to 120 minutes, and further preferably 40 to 100 minutes.
The aging treatment can be performed using a general stirring tank or a flow pipe.
The “flow pipe” is a pipe having a function of maintaining a predetermined temperature for a predetermined time by passing it through a pipe at a constant temperature with a constant flow velocity.
The aging treatment is particularly preferably carried out using a continuous multistage agitation tank having two or more partitioned mixing spaces because it is preferable to reduce unevenness of the aging treatment. In such a continuous multistage agitation tank, the product stays in each mixing space for a certain period of time and then is supplied to the next mixing space. Therefore, the residence time when viewed as a whole continuous multistage agitation tank, that is, uneven aging time Less.

The aging is carried out in the presence of a coloring inhibitor hardly soluble in the fatty acid alkyl ester in an amount of 0.1 to 10% by mass of the product.
Here, in the present invention, the “coloring inhibitor hardly soluble in fatty acid alkyl ester” means that the solubility in 100 g of fatty acid alkyl ester (raw material) used is 1 g or less at 25 ° C.
As the coloring inhibitor, it is preferable to use inorganic sulfates and / or organic acid salts having monovalent metal ions. In particular, inorganic sulfates are highly effective in inhibiting coloration, are often inexpensive, and are further incorporated into detergents. Therefore, when producing α-sulfo fatty acid alkyl ester salts for use in detergents, inorganic sulfates must be α -Preferred because it does not need to be removed from the sulfo fatty acid alkyl ester salt.
Examples of monovalent metal ions include sodium ions, potassium ions, and lithium ions.
Examples of the inorganic sulfate include sodium sulfate, potassium sulfate, lithium sulfate and the like. As the inorganic sulfate, an anhydrous salt is particularly preferable, and anhydrous sodium sulfate (sodium salt) is particularly preferable.
Examples of the organic acid salt include sodium formate, potassium formate, and sodium acetate.
The coloring inhibitor is preferably powdery. In particular, those having an average particle size of 250 μm or less are preferable, and 100 μm or less is more preferable. Such a color inhibitor has a large surface area, a large contact area with the raw material liquid, an improved dispersibility in the raw material liquid, and a sufficient color suppression effect. The lower limit of the average particle diameter is preferably 1 μm or more, more preferably 10 μm or more, taking account of ease of handling, availability, and the like.
A coloring inhibitor may be used individually by 1 type, and may use 2 or more types together.
The addition amount of the coloring inhibitor needs to be within a range of 0.1 to 10% by mass with respect to the amount of the fatty acid alkyl ester used as a raw material. When the amount is less than 0.1% by mass, the coloring suppression effect cannot be obtained. If it exceeds 10% by mass, the content of the coloring inhibitor in the product increases, and the content (purity) of the α-sulfo fatty acid alkyl ester salt in the product relatively decreases. 1-10 mass% is preferable with respect to the usage-amount of a fatty-acid alkylester, and, as for the addition amount of a coloring inhibitor, 3-7 mass% is more preferable.

The product obtained in the sulfonation step and the color inhibitor are brought into contact within 30 minutes after the product is discharged from the falling film reactor. The state of the color inhibitor used for contact may be in the form of a powder, but it is preferably dispersed in a small amount of raw material and supplied in a liquid form for more uniform contact. When the time until contact is longer than 30 minutes, the effect of the color inhibitor is not sufficiently exhibited, and the product is markedly colored. This is presumed to be due to some reaction that causes significant coloration if it remains in contact with the color inhibitor for more than 30 minutes after being discharged from the falling film reactor.
The shorter the time from the discharge of the product to the contact with the coloring inhibitor is, the shorter it is, preferably within 25 minutes, more preferably within 20 minutes, and particularly preferably within 10 minutes. The shorter the time is, the better the effect of the present invention is.

<Esterification process>
Next, the product obtained in the aging step is subjected to esterification using an alcohol having 1 to 6 carbon atoms. Thereby, the yield of (alpha) -sulfo fatty-acid alkylester improves and the production | generation of a by-product is also suppressed.
In this esterification process, the product after the aging step, if the SO ₃ bimolecular adduct intermediates is left, as follows, an alkoxy group portion of the SO ₃ bimolecular adduct Esterification proceeds. That is, elimination of the SO ₃ inserted into the alkoxy group part of the SO ₃ bimolecular adduct (I ″) and transesterification proceeds by alcohol (R ³ —OH), and the following general formula (II ′) Thus, the yield of α-sulfo fatty acid alkyl ester is improved.

［式中、Ｒ^１およびＲ^２は、それぞれ、上記式（Ｉ）中のＲ^１およびＲ^２と同じであり、Ｒ^３は炭素数１〜６のアルキル基である。］

[Wherein, R ¹ and R ² are the same as R ¹ and R ² in the formula (I), respectively, and R ³ is an alkyl group having 1 to 6 carbon atoms. ]

Further, when the SO ₃ bimolecular adduct remains in the product after the aging step, the product is neutralized as it is without performing the esterification step, as shown in the following general formula (III) α-sulfo fatty acid dialkali salt is easily formed. Although the α-sulfo fatty acid dialkali salt has a function as a surfactant, its performance is lower than that of the α-sulfo fatty acid alkyl ester salt, and when it is present in a large amount in the final product (product), The detergency, water solubility and the like of the α-sulfo fatty acid alkyl ester salt may be reduced, and as a result, the performance of the detergent or the like in which the product is used may be deteriorated.
In this invention, the production | generation of the alpha-sulfo fatty-acid dialkali salt which is one of a by-product can be suppressed by performing an esterification process.
Thus, the yield of α-sulfo fatty acid alkyl ester salt is improved, and the production of by-products is suppressed, whereby the yield of α-sulfo fatty acid alkyl ester salt is improved.

［式中、Ｒ^１は、上記式（Ｉ）中のＲ^１と同じである。］

Wherein, ^{R 1} is the same as ^{R 1} in the formula (I). ]

The esterification treatment can be performed, for example, by adding an alcohol having 1 to 6 carbon atoms to the product after the aging step, and maintaining this for a predetermined reaction time at a predetermined reaction temperature.
The reaction temperature is preferably 50 to 100 ° C, more preferably 50 to 90 ° C.
The reaction time is preferably 5 to 180 minutes, more preferably 10 to 60 minutes.
The esterification treatment can be performed using a general stirring tank or a flow pipe as in the aging step, and a continuous multistage having two or more partitioned mixing spaces in order to narrow the residence time distribution. It is preferable to use a stirring tank.
The alcohol may be linear or branched and is preferably a monohydric alcohol. In particular, an alcohol having a carbon number equal to the carbon number of the alcohol residue of the starting fatty acid alkyl ester (for example, the carbon number of R ² in formula (I)) is preferred, and has the same alkyl group as the alkyl group in the alcohol residue. Alcohol is more preferred.
1-10 mass% is preferable with respect to 100 mass% of products after aging, and, as for the addition amount of alcohol, 2-5 mass% is more preferable. When the addition amount of the alcohol is 1% by mass or more, the effect of the esterification treatment is sufficiently obtained, and when it is 10% by mass or less, there is no need to perform a step of recovering the excess lower alcohol, which is efficient. is there.

<Neutralization process>
Next, the product obtained in the esterification step is neutralized. Thereby, the α-sulfo fatty acid alkyl ester salt is produced from the α-sulfo fatty acid alkyl ester in the product. For example, when the fatty acid alkyl ester (I) is used as a raw material, an α-sulfo fatty acid alkyl ester salt (IV) represented by the following general formula (IV) is mainly produced.

［式中、Ｒ^１およびＲ^２は、それぞれ、上記式（Ｉ）中のＲ^１およびＲ^２と同じであり、Ｍは対イオンを示す。］

[Wherein, R ¹ and R ² are the same as R ¹ and R ^{2 in} formula (I), respectively, and M represents a counter ion. ]

Any counter ion of M may be used as long as it forms a water-soluble salt with 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.

Neutralization can be performed, for example, by bringing the product after the esterification step into contact with an alkaline aqueous solution.
Any alkaline aqueous solution may be used as long as it can form a target salt, for example, a compound capable of forming M in the above general formula (I). For example, an alkali metal hydroxide such as sodium hydroxide can be used. And alkali metal carbonates, alkaline earth metal hydroxides, ammonia, ethanolamine and the like.
The concentration of the alkaline aqueous solution is adjusted to be the AI concentration of the following neutralized product.
Here, “AI” is a compound having a function as a surfactant contained in a product. The product obtained by the production method of the present invention usually contains an α-sulfo fatty acid dialkali salt as a by-product in addition to the α-sulfo fatty acid alkyl ester salt. The α-sulfo fatty acid dialkali salt also has a function as a surfactant, like the α-sulfo fatty acid alkyl ester salt. Therefore, in the present invention, the AI concentration is determined as the total concentration of the α-sulfo fatty acid alkyl ester salt and the α-sulfo fatty acid dialkali salt, which is one of the by-products.
The AI concentration in the neutralized product is preferably 10 to 80% by mass. Manufacturing efficiency improves that it is 10 mass% or more, and it is excellent in handling property in it being 80 mass% or less. Particularly, since the viscosity is moderately low and the production efficiency and handling properties are excellent, the AI concentration is more preferably 60 to 80% by mass, and further preferably 62 to 75% by mass.

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

In addition, in the neutralization step, in order to prevent hydrolysis of the produced α-sulfo fatty acid alkyl ester salt and the production of by-products accompanying it, avoid radical neutralization and perform mild neutralization as much as possible. Is preferred.
An example of such neutralization treatment is a loop neutralization method. In this method, a part of the neutralized neutralized product (recycled neutralized product) is circulated in a looped pipe (recycled loop), and the recycled neutralized product is unneutralized after the esterification step. 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. The sum product and the aqueous alkali solution may be mixed instantaneously under a strong shearing force.
The added amount of the recycled neutralized product is preferably 5 to 25 times by mass, more preferably 10 to 20 times by mass, the total amount of the unneutralized product and the aqueous alkali solution. The ratio of the added amount of the recycle neutralized product to the total amount of the unneutralized product and the alkaline aqueous solution, that is, the recycle ratio is 5 or more, the by-product formation suppression effect is excellent, and the production efficiency is 25 or less. improves.

The neutralization step 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. In addition, when neutralized with solid metal carbonate, when mixed with the product, the amount of water contained in the mixture is small and it becomes difficult to become strongly alkaline. Therefore, the hydrolysis of the α-sulfo fatty acid alkyl ester 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, and ammonium hydrogen carbonate, hydrated salts, and mixtures thereof.

<Bleaching process>
Next, the product (neutralized product) obtained in the neutralization step is bleached.
The bleaching step can be performed by a conventional method, for example, by mixing a neutralized product and a bleaching agent and maintaining the mixture at a predetermined bleaching temperature and a predetermined bleaching time.
As the bleaching agent, for example, an aqueous solution of hydrogen peroxide, hypochlorite or the like is preferably used.
The amount of the bleach used is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, based on AI.
The bleaching temperature may be a temperature suitable for the bleach used. For example, when hydrogen peroxide is used, 50 to 140 ° C is preferable, and 80 to 140 ° C is more preferable. Moreover, when using hypochlorous acid, 30-80 degreeC is preferable.
The bleaching time may be carried out until the desired color tone is bleached, and is practically about 30 minutes to 7 days.
The bleaching step is preferably performed under the condition of pH 4-9. Thereby, the outstanding bleaching effect is exhibited and the alpha-sulfo fatty-acid alkylester salt of a favorable color tone is obtained.

Hereinafter, preferred embodiments of the production method of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a manufacturing apparatus 1 that is preferably used in the present embodiment.
The production apparatus shown in FIG. 1 includes a falling film reactor 2, a cyclone 3 connected to an outlet 2a of the falling film reactor 2 via a line 21, and a cyclone 3 connected to the cyclone 3 via a flow pipe 22. An aging reaction tank 4, an esterification reaction tank 5 connected to the aging reaction tank 4 via a line 23, a recycle loop 6 connected to the esterification reaction tank 5 via a line 24, A stirring tank 7 connected to the recycle loop 6 via a line 25 and a bleaching tube 8 connected to the stirring tank 7 via a line 26 are schematically configured.

A gas supply line 31 and a raw material liquid supply line 32 are connected to the upper part of the falling film reactor 2 through which a SO ₃ gas and a raw material liquid containing a fatty acid alkyl ester are supplied. The reactor 2 can be supplied.
The aging reaction tank 4 is composed of a first continuous multistage stirring tank 4a having three mixing spaces and a second continuous multistage stirring tank 4b having three mixing spaces. A storage tank 10 for storing a coloring inhibitor is connected to the first continuous multistage agitation tank 4a to which the flow pipe 22 is connected, so that the coloring inhibitor can be supplied in powder form from the storage tank 10. It has become. Here, if necessary, the apparatus can also be supplied in a liquid state in which a coloring inhibitor is dispersed in the raw material.
The esterification reaction tank 5 includes a continuous multistage stirring tank 5a having three mixing spaces and a stirring tank 5b. An alcohol supply line 33 is connected to the continuous multistage agitation tank 5a so that alcohol having 1 to 6 carbon atoms can be supplied to the continuous multistage agitation tank 5a.
The recycle loop 6 includes a neutralization line 6a having ends connected to the line 24 and the line 25, and a circulation line 6b branched from both ends of the neutralization line 6a. Two mixers 6c and 6d are provided on the neutralization line, and an alkaline aqueous solution supply line 34 is connected to a portion of the neutralization line 6a between the mixer 6c and the mixer 6d. An aqueous alkali solution can be supplied into the sum line 6a. A heat exchanger 6e is provided on the circulation line 6b so that the neutralized product can be cooled.
A mixer 26 a is provided on the line 26, and a bleaching agent supply line 35 is connected to a portion of the line 26 between the stirring tank 7 and the mixer 26 a.

The production of an α-sulfo fatty acid alkyl ester salt using the production apparatus shown in FIG. 1 can be performed, for example, as follows.
First, when a raw material liquid containing SO ₃ gas and a fatty acid alkyl ester containing 0.5% by mass or less of glycerin and its derivatives is supplied from the upper part of the falling film reactor 2, the falling film reactor 2 From the upper part to the lower part, the SO ₃ gas and the thin film of the raw material liquid come into contact with each other, so that the sulfonation reaction proceeds.
The reaction product (sulfonated product) is discharged from the outlet 2a of the falling film reactor 2, gas-liquid separated at the cyclone 3, and then discharged within 30 minutes after being discharged at the outlet 2a. It introduce | transduces into the tank 4a, is made to contact with a coloring inhibitor, and is aged in the 1st continuous multistage stirring tank 4a and the 2nd continuous multistage stirring tank 4b.
Next, the product after aging (aged product) is introduced into the continuous multistage agitation tank 5a, and alcohol having 1 to 6 carbon atoms is supplied from the alcohol supply line 33 and mixed. The obtained mixture is held in the continuous multistage stirring tank 5a and the stirring tank 5b for a predetermined time at a predetermined temperature, and then the obtained product (esterified product) is supplied to the recycle loop 6 through the line 24. .
The esterified product is neutralized by supplying an alkaline aqueous solution from the alkali supply line 34, and a part of the obtained neutralized product is circulated through the circulation line 6b and cooled by the heat exchanger 6e. Add to unneutralized esterified product in 6a. This is mixed by the mixer 6c and then neutralized in the same manner as described above.
After neutralization, the neutralized product obtained is supplied to the line 26 via the line 25 and the stirring tank 7 and mixed with the bleach supplied from the bleach supply line 35 by the mixer 26a, and then the mixture is bleached. It supplies to the pipe | tube 8 and a bleaching reaction is advanced as predetermined | prescribed bleaching temperature. Thereby, the target alpha-sulfo fatty acid alkyl ester salt (bleached product) is obtained.

<Other optional steps>
In this invention, you may perform the heating process which heat-processes a neutralized material after performing the said neutralization process and before performing a bleaching process. When the heating step is performed, the color tone of the obtained product is further improved.
The heat treatment can be performed by heating the neutralized product to a predetermined temperature and holding the temperature for a predetermined time, and the heating temperature is preferably 70 ° C. or higher, more preferably 70 to 120 ° C. The heating time is preferably 0.5 hours to 7 days, more preferably 1 hour to 5 days, and further preferably 2 to 24 hours.

  The α-sulfo fatty acid alkyl ester salt produced as described above may be used as a product as it is, or may be used for preparing a liquid detergent composition or the like. Moreover, it may shape | mold into shapes, such as a powder form, a granular form, flake form, and a noodle form, and may be used for preparation of a powder detergent composition, a solid detergent, etc.

According to the production method of the present invention, it is possible to produce an α-sulfo fatty acid alkyl ester salt with little coloration and good color tone.
Moreover, according to the manufacturing method of this invention, sulfonation reaction can also be performed stably.
Therefore, the α-sulfo fatty acid alkyl ester salt produced by the production method of the present invention is not only excellent in color tone but also excellent in quality stability, and is useful as a raw material used in cleaning compositions and the like. .

Hereinafter, the present invention will be described more specifically with reference to examples.
The measurement methods used in the following examples and comparative examples are as follows.
<Measuring method of content of glycerin and its derivative in raw material>
The content of glycerin and its derivatives in the raw material is 3% OV-1 (manufactured by Nippon Chromatography Co., Ltd.), 50 → 300 ° C., 12 ° C./min, based on Introductory Lipid Analysis Method p226-228 Perform gas chromatography under conditions and calculate by area ratio.

<Measurement method of sulfonation reaction rate in product>
0.02, 0.1, and 0.2 g of standard materials (fatty acid methyl ester) to be used are accurately weighed in a 50 ml volumetric flask, methanol is added up to the marked line, and dissolved using ultrasonic waves. After dissolution, cool to about 25 ° C. and use this as the standard solution. About 2 ml of this standard solution is filtered using a 0.45 μm chromatographic disk, followed by high performance liquid chromatography under the following measurement conditions, and a calibration curve is created from the peak area.
(High-performance liquid chromatography measurement conditions)
Apparatus: LC-10AT (manufactured by Shimadzu Corporation).
Column: Inertsil ODS-2 (manufactured by GL Sciences).
Column temperature: 40 ° C.
Detector: differential refractive index detector RID-6A (manufactured by Shimadzu Corporation).
Mobile _{phase: H 2 O / CH 3 OH} = 5/95 ( volume ratio) mixed solution.
-Flow rate: 1.0 mL / min.
Injection volume: 100 μL.

  A sample (product at the outlet of the reactor or product after esterification) (5.0 g) is accurately weighed into a 50 ml volumetric flask, methanol is added up to the marked line, and dissolved using ultrasonic waves. After dissolution, the solution is cooled to about 25 ° C. and used as a test solution. About 2 ml of this 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, and the unreacted sample solution was analyzed using the calibration curve prepared above. Obtain the concentration of the raw material. The concentration of the reacted raw material is obtained from the concentration of the unreacted raw material, and the ratio of the reacted raw material (sulfonation reaction rate (mass%)) in the used raw material is calculated from the value.

<Measurement method of color tone>
The color tone is measured with a Krett photoelectric photometer using a 40 mm optical path length, No42 blue filter for an aqueous solution having a pure component (AI) concentration of 5 mass%.

<Measurement method of bleached product composition>
[AI concentration (total concentration of α-sulfo fatty acid methyl ester sodium salt and α-sulfo fatty acid disodium salt (di-Na salt)]]
Weigh accurately 0.3 g of the bleached product into a 200 ml volumetric flask, add ion-exchanged water (distilled water) up to the marked line, and dissolve with ultrasound. After dissolution, it is cooled to about 25 ° C., 5 ml of this is taken into a titration bottle with a whole pipette, 25 ml of MB indicator (methylene blue) and 15 ml of chloroform are added, and further 5 ml of a 0.004 mol / l benzethonium chloride solution is added. Titrate with 0.002 ml / l sodium alkylbenzene sulfonate solution. In the titration, the titration bottle is stoppered and shaken vigorously and allowed to stand, and the end point is the point where both layers have the same color tone against a white plate. Similarly, a blank test (the same test as above except that no bleached product is used) is performed, and the concentration is calculated from the difference in titer.

[Proportion of di-Na salt in AI]
Di-Na salt standards 0.02, 0.05, 0.1 g are accurately weighed into a 200 ml volumetric flask, about 50 ml of water and about 50 ml of ethanol are added and dissolved using ultrasound. After dissolution, the solution is cooled to about 25 ° C., and methanol is accurately added up to the marked line to make a standard solution. About 2 ml of this standard solution is filtered using a 0.45 μm chromatographic disk, followed by high performance liquid chromatography under the following measurement conditions, and a calibration curve is created from the peak area.
(High-performance liquid chromatography measurement conditions)
Apparatus: 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: 0.7% sodium perchlorate in H ₂ O / CH ₃ OH = 1/4 (volume ratio) solution.
-Flow rate: 1.0 mL / min.
Injection volume: 100 μL.

Next, 1.5 g of the bleached product is accurately weighed into a 200 ml volumetric flask, and about 50 ml of water and about 50 ml of ethanol are added and dissolved using ultrasonic waves. After dissolution, the solution is cooled to about 25 ° C., and methanol is 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, then analyzed by high performance liquid chromatography under the same measurement conditions as described above, and the di-Na salt in the sample solution was prepared using the calibration curve prepared above. Determine the concentration.
From the calculated di-Na salt concentration and the AI concentration determined above, the ratio (mass%) of the di-Na salt in AI is calculated.

[Sodium salt concentration and methyl sulfate concentration (mass%)]
Weigh 0.02, 0.04, 0.1, 0.2g each of the standard products of methyl sulfate and mirabilite accurately into a 200 ml volumetric flask, add ion-exchanged water (distilled water) to the marked line, To dissolve. After dissolution, cool to about 25 ° C. and use this as the standard solution. About 2 ml of this standard solution is filtered using a 0.45 μm chromatographic disk, followed by ion chromatography under the following measurement conditions, and a calibration curve is created from the peak areas of methyl sulfate and mirabilite standard solution.
(Ion chromatography measurement conditions)
Apparatus: DX-500 (manufactured by Nippon Dionex).
Detector: Electric conductivity detector CD-20 (manufactured by Nippon Dionex).
-Pump: IP-25 (manufactured by Nippon Dionex).
Oven: LC-25 (manufactured by Nippon Dionex).
-Integrator: C-R6A (manufactured by Shimadzu Corporation).
Separation column: AS-12A (manufactured by Nippon Dionex).
Guard column: AG-12A (manufactured by Nippon Dionex).
Eluent: 2.5 mM Na ₂ CO ₃ /2.5 mM NaOH / 5 vol% acetonitrile aqueous solution.
-Eluent flow rate: 1.3 mL / min.
・ Regeneration liquid: pure water.
Column temperature: 30 ° C.
-Loop volume: 25 μL.

Next, 0.3 g of the bleached product 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 is 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, analyzed by ion chromatography under the same measurement conditions as above, and using the calibration curve prepared above, the concentration of methyl sulfate and sodium sulfate in the sample solution were analyzed. The concentration is obtained, and the methyl sulfate concentration and the sodium sulfate concentration (mass%) in the sample are calculated.
From the calculated methyl sulfate concentration and mirabilite concentration and the AI concentration determined above, the ratio of methyl sulfate concentration and mirabilite concentration to the AI concentration (% vs. AI) is calculated.

<Examples 1-4 and Comparative Examples 1-2 (Preparation of α-sulfo fatty acid alkyl ester salt-containing paste)>
(Preparation of raw material (fatty acid methyl ester))
A fatty acid methyl ester prepared by the following procedure was used as a raw material.
RBD palm stearin was esterified with methanol (35% vs. RBD palm stearin) using caustic soda (0.21% vs. RBD palm stearin) as a catalyst at 80 ° C. for 60 minutes to obtain a crude esterified product.
The crude esterified product was washed with water to reduce the content of glycerin and its derivatives remaining in the crude esterified product, and then distilled, and the iodine value was reduced by hydrogenating this in the following procedure. A fatty acid methyl ester (hereinafter referred to as a raw material) used as a raw material was obtained.
In addition, RBD palm stearin is a RBD process (purification: refine, bleach: bleach, deodorization: dedar) for the solid content (palm stearin) after wintering (crystallization and solid-liquid separation) of palm oil. Oil.
In the obtained raw material, the carbon chain length ratio of the alkyl group of the fatty acid was C14 / C16 / C18 = 1/60/39 (mass ratio).
Moreover, at the time of the said water washing, content of the glycerol and its derivative to reduce was adjusted by changing the quantity and washing | cleaning time of the water to be used. Table 1 shows the contents of glycerin and its derivatives in the fatty acid methyl ester after hydrogenation.
According to a conventional method, the above hydrogenation treatment is carried out by adding 0.1% by mass of trade name SO-850 (manufactured by Sakai Chemical Co., Ltd.) as a hydrogenation catalyst with respect to the fatty acid methyl ester, at 170 ° C. for 1 hour, The pressure was 0.64 MPa (gauge pressure). After the hydrogenation treatment, the catalyst was removed by filtration. Table 1 shows the iodine value of each raw material.

Using the fatty acid methyl ester obtained as a raw material, an α-sulfo fatty acid alkyl ester salt was produced by the following procedure using a production apparatus having the same structure as the production apparatus shown in FIG.
(Sulfonation process)
As the falling film reactor 2, the falling film reactor shown in Table 1 (hereinafter sometimes simply referred to as the reactor 2) was used. The SO ₃ gas, an SO ₂ with dry air (dew point -55 ° C.) was used as the SO ₃ by catalytic oxidation.
The raw material and SO ₃ gas diluted so as to have an SO ₃ concentration of 8% by dry air were supplied from the upper part to the lower part of the reactor 2 so as to contact in parallel flow. At this time, the SO ₃ gas was supplied so that the amount of SO ₃ was 1.2 mol times the amount of the raw material. The reaction temperature in the reactor 2 was 80 ° C., the reaction time was 15 seconds, and the reaction pressure was 10 kPa (gauge).
The reaction product was discharged from the outlet 2a at the bottom of the reactor 2. The sulfonation reaction rate was measured for the discharged reaction product. The results are shown in Table 1.
At this time, the exhaust gas discharged together with the reaction product is gas-liquid separated from the reaction product by the cyclone 3, and then collected by an electric dust collector (not shown), and further, an alkali scrubber (not shown). After SO ₂ was removed by, it was released into the atmosphere.

(Aging process)
Next, the reaction product discharged from the outlet 2a of the reactor 2 is held in the cyclone 3 and the flow pipe 22 at 80 ° C. for the time shown in Table 1, and then continuously multistage together with the coloring inhibitor shown in Table 1. The mixture was supplied to the stirring tank 4a and aged by being retained in the continuous multistage stirring tank 4a and the continuous multistage stirring tank 4b at a temperature of 80 ° C. for an average of 90 minutes. At this time, the average residence time of the reaction product in the cyclone 3 was 7 minutes.

(Esterification process)
Next, the reaction product after aging is supplied to the continuous multistage agitation tank 5a, and at the same time, 4% by mass of methanol is continuously supplied to the reaction product, the temperature is 80 ° C., and the average residence time is The esterification treatment was performed by maintaining the condition for 30 minutes. Here, the industrial grade (water | moisture content of 1000 ppm or less) was used for methanol.
About the reaction product obtained at this time, the sulfonation reaction rate (sulfonation rate after esterification) and the color tone (color after esterification) were measured. The results are shown in Table 1.

(Neutralization process)
Next, the reaction product (esterified product) after completion of esterification was supplied to the recycle loop 6 for neutralization.
For the neutralization, an alkaline aqueous solution in which 48% by mass of industrial grade caustic soda was diluted with clean water was used. At this time, the caustic soda was diluted such that the caustic soda concentration in the alkaline aqueous solution was 66 to 70% by mass in the neutralized product neutralized with the alkaline aqueous solution.
A part of the neutralized product was circulated through the recycle loop 6, mixed with the esterified product, and neutralized again. At this time, neutralization was performed at a recycle ratio of 20 while maintaining the pH of the recycled neutralized product at 5-7. The neutralization temperature was 75 to 80 ° C., and the pressure inside the recycle loop 6 was 0.4 MPa.

(Bleaching process)
Next, subsequent to neutralization, bleaching was performed using an industrial grade hydrogen peroxide solution having a purity of 35% by mass.
For bleaching, the neutralized product and the hydrogen peroxide solution were mixed in the mixer 7, introduced into the aging tube 8 at a temperature of 80 ° C., held at the same temperature for 3 hours, and then discharged from the aging tube 8.
The amount of hydrogen peroxide added was 1.0% by mass with respect to 100% by mass of the neutralized product.
The color tone (bleached product color) of the pasty product (bleached product) after being discharged from the aging tube 8 and kept at 80 ° C. for 12 hours was measured.
Further, as the composition of the bleached product, the AI concentration in the bleached product, the ratio of the di-Na salt in AI, the concentration of sodium sulfate and the methyl sulfate concentration in the bleached product were measured. The results are shown in Table 1.

In Table 1, * 1 to * 4 have the following meanings.
* 1: Total amount of glycerin, fatty acid monoglyceride, fatty acid diglyceride, and fatty acid triglyceride.
* 2: A is a multi-tube falling film type sulfonation reactor, and B is a double-tube falling film type sulfonation reactor.
* 3: C is finely powdered sodium sulfate (average particle size of 40 to 50 μm), and D is sodium acetate (average particle size of 100 to 200 μm).
* 4: The addition amount is a ratio (mass%) to 100 parts by mass of the reaction product obtained by the sulfonation step.

As is clear from the above results, the bleached products produced in Examples 1 to 5 were less colored and excellent in color tone. In addition, the color tone (color after esterification) of the esterified product as the intermediate product was also suppressed from being colored as compared with the comparative example.
On the other hand, Comparative Example 1 using a raw material with a glycerin and its derivative content exceeding 0.5% by mass, and a comparison in which the time from discharge of the reactor outlet to contact with the coloring inhibitor was 30 minutes In Examples 2 and 3 (3 is a sulfonation reaction rate of 70 mol% or more at the outlet of the thin film reactor), both the esterified product and the bleached product were markedly colored.

It is a schematic block diagram which shows an example of the manufacturing apparatus used for this invention.

Explanation of symbols

2 ... falling film reactor, 2a ... outlet of falling film reactor, 3 ... cyclone, 4 ... maturation reaction tank, 5 ... esterification reaction tank, 6 ... recycle loop, 7 ... stirring tank, 8 ... bleaching tube, DESCRIPTION OF SYMBOLS 9 ... Stirring tank, 10 ... Storage tank, 21 ... Line, 22 ... Distribution pipe, 23-26 ... Line, 31 ... Gas supply line, 32 ... Raw material supply line, 33 ... Alcohol supply line, 34 ... Alkaline supply line, 35 ... bleach supply line.

Claims (3)

A sulfonation step of sulfonating a fatty acid alkyl ester having a content of glycerin and a derivative thereof of 0.5% by mass or less using a falling film reactor under the condition that no coloring inhibitor is present;
The product obtained in the sulfonation step, and a coloring inhibitor hardly soluble in the fatty acid alkyl ester in an amount of 0.1 to 10% by mass of the product, the product is the falling film reactor. A maturing step in which the maturing process is performed within 30 minutes after being discharged from the
An esterification step of performing an esterification treatment on the product obtained in the aging step using an alcohol having 1 to 6 carbon atoms;
A neutralization step for neutralizing the product obtained in the esterification step;
And a bleaching step of bleaching the product obtained in the neutralization step. A method for producing an α-sulfo fatty acid alkyl ester salt.   The method for producing an α-sulfo fatty acid alkyl ester salt according to claim 1, wherein the product obtained in the sulfonation step has a sulfonation reaction rate of 70 mol% or less at the outlet of the falling film reactor. The manufacturing method of the alpha-sulfo fatty-acid alkylester salt of Claim 1 which uses the inorganic sulfate and / or organic acid salt which have a monovalent metal ion as said coloring inhibitor.

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