JP5193865B2 - Method for producing α-sulfo fatty acid alkyl ester salt - Google Patents

Description

The present invention relates to a method for producing an α-sulfo fatty acid alkyl ester salt.
This application claims priority based on Japanese Patent Application No. 2006-201073 for which it applied on July 24, 2006, and uses the content here.

  The neutralized salt of a sulfonated compound of a fatty acid alkyl ester is generally also called an α-sulfo fatty acid alkyl ester salt. α-Sulfo fatty acid alkyl ester salt is a hard surfactant with good hard water resistance and biodegradability, excellent cleaning power, and mild to the skin. It is advantageous and is regarded as important in terms of protecting the global environment.

As a method for producing an α-sulfo fatty acid alkyl ester salt, a method in which a fatty acid alkyl ester is sulfonated to obtain an α-sulfo fatty acid alkyl ester, and the α-sulfo fatty acid alkyl ester is generally neutralized with an alkali.
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, a bleaching treatment is generally performed before or after the alkali neutralization step to improve the color tone of the α-sulfo fatty acid alkyl ester salt (see, for example, Patent Documents 1 to 3).
Thus, in general, the α-sulfo fatty acid alkyl ester salt is produced by performing a bleaching step in addition to a sulfonation step, an aging step, and an alkali neutralization step.

  However, the method for producing an α-sulfo fatty acid alkyl ester salt as described above has a problem that by-products such as α-sulfo fatty acid and α-sulfo fatty acid dialkali salt are easily generated. If such a by-product is present in a large amount, the performance of the α-sulfo fatty acid alkyl ester salt as a surfactant may be deteriorated, and it is required to suppress the production of the by-product.

It is well known that the operation conditions of neutralization have a great influence on the formation of by-products, but as a result of investigation, it has been found that the bleaching treatment conditions also have a great influence. That is, compared with bleaching under acidic conditions currently practiced industrially, bleaching near neutrality has a high bleaching temperature and a long time because the reaction proceeds slowly due to the low activity of the bleaching agent. Since bleaching time is required, it has not yet been put into practical use.
Furthermore, according to the inventors' research, it has been found that the bleaching treatment near neutrality requires a high bleaching temperature and a long bleaching time, and thus causes a problem of hydrolysis of the ester bond. However, the bleaching treatment near neutrality is basically very low in hydrolyzability of α-sulfo fatty acid alkali ester salts compared to bleaching under acidic conditions. If it is possible, a high-quality bleached product may be finally obtained.

Therefore, it is considered that performing the bleaching process in as short a time as possible is effective in suppressing the formation of by-products, and even if the bleaching time is simply shortened, a sufficient bleaching effect cannot be obtained. In addition, if the bleaching temperature is increased to obtain a sufficient bleaching effect in a short bleaching process, the amount of the bleaching agent that is effectively decomposed due to the decomposition of the bleaching agent is reduced, and hydrolysis is promoted. The amount of generation increases.
In addition, a reaction method in which a bleaching agent is added in portions for the purpose of supplying a necessary amount of the bleaching agent with the progress of the bleaching reaction may be considered, but as a result of the experiment, the method of adding in a divided manner is good. It turned out that it was not possible to obtain a bleached product of a correct color.

In Patent Document 3, by performing the sulfonation step in the presence of a coloring inhibitor, an α-sulfo fatty acid alkyl ester in which coloring is suppressed is obtained, and the α-sulfo fatty acid alkyl ester is neutralized and bleached. Proposed. According to this production method, since the coloring of the α-sulfo fatty acid alkyl ester salt itself before bleaching is suppressed, it is considered that the bleaching treatment time is short.
However, the level of color tone required for α-sulfo fatty acid alkyl ester salts is high, and further improvement in color tone is required.
JP 9-12533 A JP 2001-128852 A JP 2001-64248 A

The present invention has been made in view of the above circumstances, and can produce an α-sulfo fatty acid alkyl ester salt excellent in color tone and suppressed by-product formation even in a short bleaching time. It aims to provide a method.

  As a result of extensive investigations, the present inventors have controlled the temperature conditions during bleaching by a specific procedure, or controlled the reaction temperature and the reaction amount of the bleaching agent within a specific range as the bleaching reaction proceeds. As a result, the inventors have found that the above problems can be solved, and have completed the present invention.

That is, the present invention provides a sulfonation step for sulfonating a fatty acid alkyl ester, an aging step for aging a sulfonated compound obtained in the sulfonation step, and an aging compound obtained in the aging step, An esterification step in which esterification treatment is performed using 1 to 6 alcohols, a neutralization step in which the esterified compound obtained in the esterification step is neutralized to obtain a neutralized product, and the neutralized product is bleached And a bleaching step for obtaining a bleached product,
In the bleaching step, the start temperature of the bleaching reaction is set to 70 to 76 ° C., the start temperature is increased to the maximum temperature of 85 to 100 ° C. within 20 to 240 minutes from the start of the reaction, and the maximum temperature is set to 20 to 360 ° C. Provided is a method for producing an α-sulfo fatty acid alkyl ester salt, which is held for a minute and then lowered to an end temperature of 55 to 75 ° C.

The present invention also includes a sulfonation step for sulfonating a fatty acid alkyl ester, an aging step for aging a sulfonated compound obtained in the sulfonation step, and an aging compound obtained in the aging step, An esterification step in which esterification treatment is performed using 1 to 6 alcohols, a neutralization step in which the esterified compound obtained in the esterification step is neutralized to obtain a neutralized product, and the neutralized product is bleached And a bleaching step for obtaining a bleached product,
In the bleaching step, the reaction is started by adding a bleaching agent to the neutralized product at a reaction start temperature of 70 to 76 ° C., and the consumption of bleaching agent from the start of the reaction is 30 to 60% by mass (addition amount) The temperature is increased to a maximum temperature of 85 to 100 ° C. so that the bleaching agent consumes 25 to 35% by mass (addition amount) of the bleaching agent, and then the remaining of the bleaching agent is maintained. Provided is a method for producing an α-sulfo fatty acid alkyl ester salt, wherein the reaction temperature is lowered to a reaction end temperature of 55 to 75 ° C. so that the amount is 0.1 to 15% by mass (addition amount). To do.

According to the method for producing an α-sulfo fatty acid alkyl ester salt of the present invention, compared with a general bleaching method, even with a small amount of bleaching agent and a short bleaching time, the color tone is excellent, and by-products are produced. An α-sulfo fatty acid alkyl ester salt whose production is suppressed can be produced.
That is, in the constant temperature reaction, which is a general bleaching method, if the temperature is lowered in order to suppress the formation of by-products such as α-sulfo fatty acid dialkali salt, the progress of the bleaching reaction is delayed and the progress of the bleaching reaction is accelerated. Therefore, when the temperature is raised, decomposition of the bleaching agent is promoted, and a bleached product having a good color tone cannot be obtained.

In particular, when hydrogen peroxide is used as a bleaching agent, decomposition is promoted when a trace amount of metal eluted from a pipe or the like is present in the system, so that it is easily affected.
On the other hand, as in the present invention, the bleaching is decomposed by starting at a low temperature in the early stage of bleaching and increasing the temperature while leaving a lot of bleaching agent in the latter half when the bleaching progress is slow. It can be suppressed as much as possible to obtain a bleached product having a good color tone.

  In the present invention, “coloring of α-sulfo fatty acid alkali ester is a polymer called polysulfonated product during sulfonation reaction, and this polymer is easily bleached due to its molecular size. By bleaching the parts that are present and easily bleached by the time the maximum temperature is reached, and bleaching the parts that are difficult to bleach while maintaining the maximum temperature, the bleaching efficiency is improved and the bleaching product with a good color tone is finally obtained. It was completed based on the hypothesis that it can be obtained.

It is a schematic block diagram which shows an example of the manufacturing apparatus used suitably for this invention. It is a schematic block diagram which shows an example of the manufacturing apparatus used suitably for this invention. It is a schematic block diagram which shows an example of the continuous bleaching pipe | tube suitably used for this invention. It is the graph which compared the bleaching conditions in the bleaching process of this invention, and the conventional bleaching conditions. It is the graph which showed the time transition of the bleaching agent consumption in the bleaching process of this invention. It is the graph which showed the time transition of the color tone of the bleached product in the bleaching process of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Falling film reactor 2a ... Outlet of falling film reactor 3 ... Cyclone 4 ... Aging reaction tank 5 ... Esterification reaction tank 6 ... Recycling loop 7 ... Stirring tank 8 ... Continuous bleaching tube 9 ... Stirring tank 10 ... Storage tank 11 ... Stirring tank 12a ... Tank reactor 12b ... Tank reactor 12c ... Tank reactor 13 ... Aging reactor 14 ... Esterification reactor 21 ... Line 22 ... Distribution pipe 23 ... Line 24 ... Line 25 ... Line 26 ... Line 31 ... Gas supply line 32 ... Raw material supply line 33 ... Alcohol supply line 34 ... Alkaline supply line 35 ... Bleach supply line

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.
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 ester (I)).

[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 laurate, ethyl laurate or propyl laurate; methyl myristate, ethyl myristate or propyl myristate; methyl palmitate, ethyl palmitate or propyl palmitate; methyl stearate, ethyl stearate or Hardened beef tallow fatty acid methyl, hardened beef tallow fatty acid ethyl or hardened beef tallow fatty acid propyl; Hardened fish oil fatty acid methyl, hardened fish oil fatty acid ethyl or hardened fish oil fatty acid propyl; Palm oil fatty acid methyl, coconut oil fatty acid ethyl or coconut oil fatty acid propyl; Examples include oil fatty acid methyl, palm oil fatty acid ethyl or palm oil fatty acid propyl; palm kernel oil fatty acid methyl, palm kernel oil fatty acid ethyl or palm kernel oil fatty acid propyl.
Any one of these fatty acid alkyl esters may be used alone, or two or more thereof may be used in combination.

  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.

For sulfonation of fatty acid alkyl esters, methods generally used for sulfonation can be used. For example, double-tube type or multi-tube type falling film reactors, tank reactors, etc. use can be carried out by contacting the fatty acid alkyl ester, and a SO ₃ gas containing SO _3.
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, SO ₃ one molecule adduct (I') from the following formula (I ") with SO ₃ bimolecular adduct represented (I") is generated, SO ₃ bimolecular adduct ( The α-sulfo fatty acid alkyl ester represented by the following general formula (II) is produced from I ″).

[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 it is 30% by volume or less, the sulfonation reaction is unlikely to be excessive, the formation of by-products can be suppressed, and deterioration of the color tone of a sulfonated compound such as an α-sulfo fatty acid alkyl ester can also 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, the amount to be 1.1 to 1.3 times mole 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. 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 time is preferably 5 to 180 seconds, and more preferably 5 to 60 seconds, when a falling film reactor is used as the sulfonation reactor. If the reaction time is less than 180 seconds 5 seconds, and a good SO ₃ gas absorption has an advantage of sulfonic acid having excellent color tone obtained, long and SO ₃ gas absorbed than less than 5 seconds or 180 seconds There is a possibility that a problem occurs that the color tone deteriorates or the deterioration of the color tone is promoted. Moreover, when using a tank reactor, 10 minutes-6 hours are preferable, and 10 minutes-4 hours are more preferable. When the reaction time is 10 minutes or more and 6 hours or less, SO ₃ gas absorption is good and there is an advantage that a sulfonic acid excellent in color tone can be obtained, but when it is less than 10 minutes or longer than 6 hours, SO ₃ gas absorption is excellent. There is a possibility that the problem of deterioration or deterioration of color tone may occur.

After the sulfonation reaction, the product (sulfonated compound) is discharged from the outlet (extraction port) of the sulfonation reactor.
Since the sulfonated compound is usually discharged together with the gas in the sulfonation 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.

<Aging process>
Next, the sulfonated compound obtained in the sulfonation step is subjected to aging treatment to prepare an aging compound. The sulfonated compound usually includes an α-sulfo fatty acid alkyl ester itself, an intermediate such as a by-product SO ₃ bimolecular adduct, a trace amount of unreacted substances, and the like. 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” refers to maintaining the sulfonated compound at a predetermined aging temperature and 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. When it is 20 minutes or more and 240 minutes or less, SO ₃ gas absorption is good and there is an advantage that a sulfonic acid excellent in color tone can be obtained, but when it is less than 20 minutes or longer than 240 minutes, SO ₃ gas absorption is deteriorated. Or, there is a risk that the color tone deterioration is promoted.

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 performed using a continuous multistage stirring tank having two or more partitioned mixing spaces, since it is easy to reduce unevenness of the aging treatment. In such a continuous multistage agitation tank, the sulfonated compound stays in each mixing space for a certain amount of time and then is supplied to the next mixing space. Therefore, the residence time when viewed as the entire continuous multistage agitation tank, that is, the aging time Non-uniformity is reduced.

<Coloring inhibitor>
In the present invention, the sulfonation step and / or the aging step described above are preferably performed in the presence of a coloring inhibitor. Thereby, coloring of (alpha) -sulfo fatty-acid alkylester can be suppressed. Therefore, the color tone of the obtained α-sulfo fatty acid alkyl ester salt is further improved.
As a coloring inhibitor, it is preferable to use a poorly soluble one in the fatty acid alkyl ester.

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. When the content exceeds 10% by mass, the content of the coloring inhibitor in the sulfonated compound or the ripened compound is increased, and the content (purity) of the α-sulfo fatty acid alkyl ester salt in the sulfonated compound or the ripened compound is relatively high. Decreases. The addition amount of the coloring inhibitor is preferably 1 to 10% by mass, more preferably 3 to 7% by mass, based on the amount of fatty acid alkyl ester used.
The color inhibitor may be used by mixing with a raw material before the sulfonation step or at the initial stage of the sulfonation step, and after the sulfonation step, before the aging step or during the aging step, the sulfonated compound is added. They may be added and mixed.

<Esterification process>
Next, the aging compound 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 step, when the SO ₃ bimolecular adduct, which is an intermediate, remains in the mature compound, esterification of the alkoxy group portion of the SO ₃ bimolecular adduct proceeds as follows. To do. 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.

[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 aging compound, the aging compound is neutralized as it is without performing the esterification step, and an α-sulfo fatty acid dialkali as shown in the following general formula (III) Salt is easily generated. Although this 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 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.

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 ripening compound and holding it at a predetermined reaction temperature for a predetermined reaction time.
The reaction temperature is preferably 50 to 100 ° C, more preferably 50 to 90 ° C. When the reaction temperature is 50 ° C. or more and 100 ° C. or less, there is an advantage that a sulfonic acid excellent in the reaction rate and color tone can be obtained. There is a risk that this will occur.
The reaction time is preferably 5 to 180 minutes, more preferably 10 to 60 minutes. If the reaction time is 5 minutes or more and 180 minutes or less, there is an advantage that a sulfonic acid excellent in the reaction rate and color tone can be obtained. If the reaction time is less than 5 minutes or longer than 180 minutes, the reaction rate is lowered or the deterioration of the color tone is promoted. There is a risk that this will occur.

  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 R2 in formula (I)) is preferred, and an alcohol having the same alkyl group as the alkyl group in the alcohol residue is used. More preferred.
1-10 mass% is preferable with respect to 100 mass% of aging compounds, 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.

  In the present invention, the sulfonation reaction rate of the product (esterified compound) obtained in the esterification step is preferably 95 mol% or more, and more preferably 97 mol% or more. Thereby, the production | generation of a by-product can be suppressed and the yield of (alpha) -sulfo fatty-acid alkylester salt improves.

Here, the sulfonation reaction rate means the ratio (%) of the compound having a C—S bond in the esterified compound.
The compound having a CS bond includes all α-sulfo fatty acid alkyl esters which are target compounds, SO ₃ bimolecular adducts, and by-products (methyl sulfate, etc.) having a CS bond. Is included.

The sulfonation reaction rate can be calculated from the concentration of the esterified compound analyzed by high performance liquid chromatography (HPLC), the concentration of the unreacted raw material (fatty acid alkyl ester) in the esterified compound.
The sulfonation reaction rate can be adjusted, for example, by adjusting the amount of SO ₃ to be reacted with the fatty acid alkyl ester, the reaction temperature and time in the aging step and the esterification step, and the like. For example, the greater the amount of SO _3, the higher the sulfonation reaction rate. Further, the longer the reaction time, the higher the sulfonation reaction rate.

<Neutralization process>
Next, the esterification compound is neutralized to form an α-sulfo fatty acid alkyl ester salt from the α-sulfo fatty acid alkyl ester in the esterified compound. 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.

[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 water-soluble salts include alkali metal salts such as sodium salts and potassium salts; alkaline earth metal salts such as calcium salts; ammonium salts; ethanolamine salts and the like.

Neutralization can be performed, for example, by bringing an esterified compound into contact with an aqueous alkali 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 preferably 50% by mass or less, and more preferably 15 to 50% by mass. Hydrolysis of the produced α-sulfo fatty acid alkyl ester salt can be suppressed when the amount is 50% by mass or less. Moreover, adjustment of the active ingredient (AI) density | concentration in the product (neutralized product) obtained by neutralization as it is 15 mass% or more is easy. The neutralized product has a lower viscosity as the AI concentration is lower, and the viscosity tends to be higher as the AI concentration is higher.

  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 this invention, AI density | concentration is calculated | required as a total density | concentration of the alpha-sulfo fatty-acid alkylester salt in a product, and the alpha-sulfo fatty-acid dialkali salt which is one of a by-product.

  The AI concentration (neutralized product AI) 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. In particular, the neutralized product AI is more preferably 60 to 80% by mass and even more preferably 62 to 75% by mass because the viscosity is moderately low and the production efficiency and handling properties are excellent.

The neutralized product AI means that the α-sulfo fatty acid alkyl ester and the α-sulfo fatty acid disulfonic acid in the neutralized product are completely neutralized with an alkali agent, and the α-sulfo fatty acid alkyl ester salt and α-sulfo acid are respectively obtained. The total content (mass%) of the α-sulfo fatty acid alkyl ester salt and the α-sulfo fatty acid dialkali salt in the neutralized product when the fatty acid dialkali salt is considered to be produced.
Here, when a plurality of metal ions (for example, Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ ) that can be counter ions of the neutralized salt are present in the neutralized product, the molecular weight of the salt is It shall be calculated by dividing by the number of moles of metal salt present.

30-140 degreeC is preferable, as for the reaction temperature in a neutralization process, 50-140 degreeC is more preferable, and 30-80 degreeC is further more preferable. When the reaction temperature is 30 ° C. or higher and 140 ° C. or lower, there is an advantage that an α-sulfo fatty acid alkyl ester salt that suppresses decomposition and is excellent in storage stability is obtained, but when it is less than 30 ° C. or higher than 140 ° C. There is a possibility that the degradation may be promoted or the pH may be lowered during storage.
The neutralization time is preferably 5 to 60 minutes, and more preferably 20 to 60 minutes. When the neutralization time is 5 minutes or more and 60 minutes or less, there is an advantage that an α-sulfo fatty acid alkyl ester salt that suppresses decomposition and is excellent in storage stability can be obtained, but when it is less than 5 minutes or longer than 60 minutes There is a possibility that the degradation may be promoted or the pH may be lowered during storage.

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, and pH 5 to 7 is particularly preferable. Outside this range, the ester bond of the α-sulfo fatty acid alkyl ester salt may be easily cleaved.
In addition, pH at the time of neutralization means the numerical value which adjusted neutralized material AI so that it might become 10 mass%, and was measured on the conditions of temperature 25 degreeC.

In addition, in the neutralization process, in order to prevent hydrolysis of the produced α-sulfo fatty acid alkyl ester salt and generation of by-products accompanying it, avoid radical neutralization and perform neutralization as gentle as possible. Is preferred.
An example of such neutralization treatment is a loop neutralization method. This method circulates a part of the neutralized neutralized product (recycled neutralized product) in a looped pipe (recycled loop), and the recycled neutralized product after circulation is converted to unneutralized esterification. In this method, neutralization is performed by adding the compound.

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 esterified compound. The neutralized esterified compound and the alkaline aqueous 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 of the total amount of the unneutralized esterified compound and the aqueous alkali solution. The ratio of the added amount of the recycled neutralized product to the total amount of the unneutralized esterified compound and the aqueous alkali 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. Will improve.

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 neutralized product obtained in the neutralization step is bleached to prepare a bleached product (bleached product).
In the bleaching process, the start temperature, the maximum temperature and the end temperature of the bleaching reaction, the bleach consumption from the start temperature to the maximum temperature, the bleach consumption while being held at the maximum temperature, and The remaining amount of the bleaching agent at the end of the reaction and the time for maintaining the maximum temperature from the start temperature (maximum temperature retention time) are controlled within a specific range to bleach the neutralized product.

  The starting temperature of the bleaching reaction is in the range of 55 to 80 ° C, preferably 55 to 75 ° C, more preferably 60 to 70 ° C. If the starting temperature exceeds 80 ° C., there is a concern that hydrolysis of the neutralized product proceeds, and if it is less than 55 ° C., the fluidity of the neutralized product is poor, which causes a problem in handling.

In the bleaching reaction, the temperature is controlled gradually from the start temperature until the maximum temperature is reached. The maximum temperature is in the range of 85 to 100 ° C, preferably 85 to 95 ° C, and more preferably 85 to 90 ° C. If the maximum temperature is less than 85 ° C, a sufficient bleaching effect cannot be obtained. On the other hand, when the temperature exceeds 100 ° C., the bleaching agent self-decomposes and the bleaching efficiency decreases.
The end temperature is in the range of 55 to 80 ° C, preferably 55 to 75 ° C, and more preferably 60 to 70 ° C. If the end temperature exceeds 80 ° C., there is a concern that hydrolysis of the neutralized product proceeds, and if it is less than 55 ° C., the fluidity of the neutralized product is poor, which causes handling problems such as transfer to the next step.

As for the temperature of the bleached product, when a continuous bleaching tube is used in the apparatus, it is preferable to install a temperature sensor that can continuously take in at an arbitrary position.
The temperature is preferably controlled by utilizing the heat of decomposition of the bleach. If the temperature cannot be controlled only by using decomposition heat, it is necessary to heat or remove heat. In this method, for example, when a continuous bleaching tube is used, an arbitrary warm water is passed through the jacket so that the bleaching temperature becomes a predetermined temperature. It is also possible to control the temperature by installing a heat exchanger in the middle.

  The time from the start temperature to the maximum temperature is 20 to 240 minutes, preferably 30 to 180 minutes, and more preferably 40 to 120 minutes. When the time exceeds 240 minutes, although depending on the temperature, there is a concern that hydrolysis of the α-sulfo fatty acid alkyl ester salt in the neutralized product and consumption of the bleaching agent increase. In addition, when the temperature rise time is less than 20 minutes, that is, when the temperature is raised to the maximum temperature at once in less than 20 minutes, the bleaching agent, particularly hydrogen peroxide, decomposes and bleaching is actually used for bleaching. Since the amount of the agent is reduced, a sufficient bleaching effect cannot be obtained.

  The time for maintaining the maximum temperature is 20 to 360 minutes, preferably 30 to 360 minutes, and more preferably 60 to 240 minutes. If the time for maintaining the maximum temperature exceeds 360 minutes, depending on the temperature, there is a concern about hydrolysis of the α-sulfo fatty acid alkyl ester salt in the neutralized product. It does not proceed and a sufficient bleaching effect cannot be obtained.

  The amount of bleaching agent consumed from the starting temperature to the maximum temperature is 30 to 60% by mass (addition amount), preferably 35 to 55% by mass (addition amount), and 40 to 50% by mass (addition amount). Amount) is more preferred. If the amount of bleaching agent consumed in the time from the start temperature to the maximum temperature is 30% by mass (additional amount) or less, the bleaching reaction to the maximum temperature does not proceed sufficiently and a sufficient bleaching effect is obtained. I can't. On the other hand, when the amount is 60% by mass (addition amount) or more, the bleaching reaction while maintaining the maximum temperature does not proceed sufficiently, and a sufficient bleaching effect cannot be obtained.

  The amount of bleaching agent consumed while maintaining the maximum temperature is 25 to 35% by mass (addition amount), preferably 27 to 33% by mass (addition amount), and more preferably 29 to 31% by mass (addition amount). preferable. If the amount of the bleaching agent while maintaining the maximum temperature is 25% by mass (addition amount) or less, the bleaching reaction does not proceed sufficiently and a sufficient bleaching effect cannot be obtained. On the other hand, when it is 35% by mass or more (addition amount) or more, it is difficult to control to a predetermined temperature due to heat generated by decomposition of the bleaching agent.

  The sum of the time for raising the temperature from the start of the reaction to the maximum temperature and the holding time at the maximum temperature is preferably 240 minutes to 540 minutes, more preferably 300 minutes to 480 minutes, and more preferably 360 minutes to 420 minutes. If the sum of the time for raising the temperature from the start of the reaction to the maximum temperature and the holding time at the maximum temperature is 240 minutes or less, the bleaching reaction does not proceed sufficiently and a sufficient bleaching effect cannot be obtained. Moreover, when it is 540 minutes or more, depending on the temperature, there is a concern about hydrolysis of the α-sulfo fatty acid alkyl ester salt in the neutralized product.

  The amount of the remaining bleach when the reaction temperature is lowered to the reaction end temperature of 55 to 80 ° C. is 0.1 to 15% by mass (addition amount), and 0.5 to 10% by mass (vs. Addition amount) is preferable, and 1 to 5% by mass (addition amount) is more preferable. If the amount of bleaching agent remaining when the reaction temperature is lowered to the reaction end temperature is 0.1% by mass or less (addition amount), the color tone may deteriorate over time. On the other hand, when the amount is 15% by mass (addition amount) or more, for example, when a bleaching agent is used, foaming may occur due to decomposition of the bleaching agent over time. When hydrogen peroxide is used as a bleaching agent, hydrogen peroxide is decomposed over time, and oxygen gas generated during decomposition causes foaming. In order to prevent foaming due to decomposition of the bleaching agent, it is desirable that the volume expansion coefficient (hereinafter referred to as expansion coefficient) of the bleached product from the end of the bleaching reaction to 24 hours later is set to 200% or less.

In the present invention, the time for reducing the maximum temperature to the end temperature needs to be within 24 hours. This is because if the temperature is left for more than 24 hours without lowering, the decomposition of the bleaching agent proceeds. The time is preferably within 12 hours, and more preferably 3 to 6 hours. When this time is 3 hours or more, general cooling equipment can be used, and when it is 6 hours or less, the production efficiency is good.
The cooling method is not particularly limited, and a general method can be used. For example, it may be allowed to cool to 55 to 80 ° C. in an atmosphere of 80 ° C. or lower, preferably 10 to 40 ° C.

More specifically, the bleaching step can be carried out, for example, by mixing a neutralized product and a bleaching agent and treating the mixture under the above temperature conditions.
As the bleaching agent, for example, peroxides such as hydrogen peroxide, persulfate, peracetic acid, percarbonate, and perborate can be used, and hydrogen peroxide is particularly preferable. The bleaching agent is added in the form of an aqueous solution.

As a density | concentration of the bleaching agent to be used, 35-60 mass% in a pure part is preferable. If it is 35% by mass or more and 60% by mass or less, there is an advantage that there is a margin in the range that can be added and safe handling is possible, but if it is less than 35% by mass or more than 60% by mass, the added amount increases and physical properties deteriorate And there is a risk that the risk of handling increases.
The addition amount of the bleaching agent is preferably 0.05 to 5% by mass with respect to 100% by mass of the neutralized AI. If it is 0.05% by mass or more and 5% by mass or less, there is an advantage that an α-sulfo fatty acid ester salt having excellent physical properties and excellent physical properties can be obtained, but if it is less than 0.05% by mass or more than 5% by mass, bleaching is performed. May cause a disadvantage that the process does not proceed or the physical properties deteriorate.

  The amount of bleach used depends on the color of the neutralized product. The color tone of the neutralized product is measured using a Kret photoelectric photometer. For example, if it is 500 (5% KLETT) or less, 1% by mass is appropriate, if it is 500 to 1000 (5% KLETT), 2% by mass is appropriate, and if it is 1000 to 1500 (5% KLETT). 3% by weight is suitable. However, the amount used is not limited to this.

  The color tone of the final product after bleaching is similarly measured using a Krett photometer. It is preferable that the color tone of the final product is less than 50 (5% KLETT). When it exceeds 100 (5% KLETT), it becomes brown, when it is 50 to 100 (5% KLETT), it becomes dark yellow, and when it is less than 50 (5% KLETT), it turns from white to light yellow.

In the present invention, the bleaching step is preferably performed using a continuous bleaching tube.
Here, the “bleaching pipe” is a pipe having a function of maintaining the temperature in the pipe at a predetermined temperature, similarly to the flow pipe. When the desired bleaching temperature is set, the bleaching object passes through the bleaching pipe. Over time, the bleaching reaction proceeds to become a bleached product.
A “continuous bleaching tube” is a bleaching tube having two or more compartments.

FIG. 3 is a schematic configuration diagram of an example of a continuous bleaching tube preferably used in the present invention.
The continuous bleaching pipe 41 shown in FIG. 3 has a configuration in which six independent bleaching pipes (hereinafter referred to as divided pipes) 42a to 42f are connected in series via connection pipes 43a to 43e. Jacket heaters 44a to 44f and a temperature sensor (not shown) are provided around each of the divided pipes 42a to 42f, and the temperature can be adjusted for each divided pipe. Further, from each of the dividing tubes 42a to 42f, a sample in the dividing tube can be collected, and the progress level of bleaching can be confirmed.

  When the mixture of the neutralized product and the bleaching agent is supplied to the continuous bleaching tube 41, the mixture moves in each divided tube while staying for a certain period of time. Therefore, in the continuous bleaching tube 41, the above-described temperature control can be easily performed by considering the residence time in each dividing tube and individually setting the temperature of each dividing tube.

  The bleaching step is preferably performed under the conditions of pH of 4 to 79, preferably 5 to 7. Thereby, the alpha-sulfo fatty acid alkyl ester salt of favorable color tone is obtained, suppressing a hydrolysis. This pH can be finely adjusted by adjusting the pH in the neutralization step or by adding an acid or an alkali agent. In addition, pH at the time of neutralization means the numerical value which adjusted the AI density | concentration so that it might become 10%, and was measured on the conditions of temperature 25 degreeC.

Hereinafter, preferred embodiments of the production method of the present invention will be described with reference to the drawings.
<First aspect>
FIG. 1 is a schematic configuration diagram of a manufacturing apparatus suitably used in this embodiment.
The production apparatus shown in FIG. 1 includes a falling film reactor 2, a cyclone 3 connected to the falling film reactor 2 via a line 21, and an aging connected to the cyclone 3 via a flow pipe 22. Reaction tank 4, esterification reaction tank 5 connected to this aging reaction tank 4 via line 23, recycle loop 6 connected to this esterification reaction tank 5 via line 24, and this recycle loop 6 And a stirring tank 7 connected via a line 25, and a continuous bleaching tube 8 connected to the stirring tank 7 via a line 26.

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 the coloring inhibitor is connected to the first continuous multistage agitation tank 4 a to which the flow pipe 22 is connected, and the coloring inhibitor can be supplied from the storage tank 10.
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 alkali supply line 34 is connected to a portion of the neutralization line 6a between the mixer 6c and the mixer 6d. An aqueous alkaline solution can be supplied into the 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.
In this example, the continuous bleaching pipe 8 is composed of five divided pipes and four connecting pipes connecting them. In the continuous bleaching tube 8, the temperature of the bleaching object passing through the continuous bleaching tube 8 and the holding time thereof can be adjusted by adjusting the temperature for each individual divided tube.

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 SO ₃ gas and a raw material liquid containing a fatty acid alkyl ester are supplied from the upper part of the falling film reactor 2, the SO ₃ gas and the thin film of the raw material liquid are passed from the upper part to the lower part of the falling film reactor 2. Come into contact with each other and the sulfonation reaction proceeds.
The reaction product (sulfonated compound) is discharged from the falling film reactor 2 and separated into gas and liquid by the cyclone 3, and then introduced into the first continuous multistage agitation tank 4a and brought into contact with the coloring inhibitor. Aging is performed in the first continuous multistage stirring tank 4a and the second continuous multistage stirring tank 4b.

Next, the aging compound after aging is supplied to the continuous multistage agitation tank 5a, and alcohol having 1 to 6 carbon atoms is supplied from the alcohol supply line 33 and mixed. After the obtained mixture is held in the continuous multistage agitation tank 5 a and the agitation tank 5 b for a predetermined time at a predetermined temperature, the obtained esterified compound is supplied to the recycle loop 6 through a line 24.
The esterified compound 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 compound in line 6a. This is mixed by the mixer 6c and then neutralized in the same manner as described above.

  After neutralization, the obtained neutralized product 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. Supply to the bleaching tube 8. Using this continuous bleaching tube 8, the temperature of the mixture is set to 55 to 80 ° C., the temperature is reached to 85 to 100 ° C. in 20 to 240 minutes, and the temperature is maintained for 20 to 360 minutes for bleaching. The obtained bleached product is discharged from the continuous bleaching tube 8 or from the continuous bleaching tube 8 and cooled in the stirring tank 9 by cooling or the like, and the temperature is lowered to 55 to 80 ° C. Thereby, the target alpha-sulfo fatty acid alkyl ester salt (bleached product) is obtained.

<Second aspect>
FIG. 2 is a schematic configuration diagram of a manufacturing apparatus suitably used in this embodiment. In addition, in this manufacturing apparatus, what has the structure similar to the manufacturing apparatus shown in FIG. 1 attaches | subjects the same code | symbol, and abbreviate | omits the detailed description.

The production apparatus shown in FIG. 2 includes a stirring tank 11, three tank reactors 12a to 12c, a stirring tank-type aging reaction tank 13, a stirring tank-type esterification reaction tank 14, a recycle loop 6, The stirring tank 7, the continuous bleaching tube 8, and the stirring tank 9 are roughly configured.
A raw material liquid supply line 32 is connected to the stirring tank 11. In the stirring tank 11, the raw material liquid containing the fatty acid alkyl ester supplied to the stirring tank 11 through the raw material liquid supply line 32 and the coloring inhibitor are mixed, and the obtained mixed liquid is supplied to the tank reactors 12a to 12c. It can be done.

Gas supply lines 31 (for convenience, only those connected to the tank reactor 12a are shown and the others are not shown) are connected to the upper portions of the three tank reactors 12a to 12c. Through these, SO ₃ gas can be supplied to the tank reactors 12a to 12c.
The tank reactors 12a to 12c and the aging reaction tank 13 are each provided with a circulation line connecting the bottom and the upper part, and heat exchangers 15a to 15d are installed on the circulation lines, respectively. Has been. Therefore, in the sulfonation step and / or the aging step, a part of the reaction tank is extracted from the bottom, cooled by a heat exchanger on the circulation line, and returned to the reactor from the top of the tank reactor and circulated again. By doing so, an excessive increase in the reaction temperature in the tank reactor can be prevented.
An alcohol supply line 33 is connected to the esterification reaction tank 14 so that alcohol having 1 to 6 carbon atoms can be supplied to the esterification reaction tank 14.

The production of the α-sulfo fatty acid alkyl ester salt using the production apparatus shown in FIG. 2 can be performed, for example, as follows.
First, a raw material (fatty acid alkyl ester) and a coloring inhibitor are introduced into the stirring tank 11 from the raw material supply line 32 to prepare a solid-liquid mixed phase, which is charged into each of the tank reactors 12a to 12c. Next, SO ₃ gas is introduced from the gas supply line 31 and brought into contact with the mixed liquid-solid liquid mixed phase. At this time, in order to prevent an excessive increase in the reaction temperature due to heat generated by contact between the raw material and the sulfonated gas, a part of the solid-liquid mixed phase is removed from the circulation line provided at the bottom of the tank reactors 12a to 12c. It may be extracted and cooled by heat exchangers 15a to 15c provided in the middle of the circulation line, and returned to the upper part of the tank reactors 12a to 12c and circulated again.

Next, the sulfonated compounds in the tank reactors 12a to 12c are supplied to the aging reaction tank 13 and maintained at a predetermined temperature to perform the aging process.
After completion of the aging step, the aging compound in the aging reaction tank 13 is supplied to the esterification reaction tank 14, and alcohol having 1 to 6 carbon atoms is supplied from the alcohol supply line 33 and mixed. After the obtained mixture is held in the esterification reaction tank 14 at a predetermined temperature for a predetermined time, the obtained esterified compound is supplied to the recycle loop 6 through a line 24.

  Thereafter, the target α-sulfo fatty acid alkyl ester salt (bleached product) is obtained by neutralization and bleaching in the same manner as in the first embodiment.

<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. The heating temperature is preferably 70 ° C. or higher, and 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, an α-sulfo fatty acid alkyl ester having an excellent color tone and suppressing the formation of by-products by effectively causing a bleaching agent to act on a bleaching reaction even in a short bleaching time. A salt can be produced.
Since the coloring mechanism itself of the α-sulfo fatty acid alkyl ester salt is unknown, the reason why the above-mentioned effect is obtained is not clear, but in the early and late stages of the bleaching process, a mixture of neutralized product and bleaching agent It is presumed that some bleaching agent remains in the inside. That is, conventionally, bleaching is generally performed by heating to a maximum temperature at a stretch and maintaining that temperature. In this case, the bleaching agent is consumed at an early stage of the bleaching reaction with high bleaching efficiency. In the latter stage of bleaching when the bleaching efficiency is low, it is presumed that no bleaching agent remained and this reduced the bleaching effect.

In contrast, in the present invention, the bleaching temperature is increased from a specific start temperature to a specific maximum temperature at a specific temperature increase time, held for a specific time, and cooled to reduce the bleaching efficiency. It is considered that a certain amount of bleaching agent remains even in the later stage, whereby a high bleaching effect can be obtained by a short bleaching treatment.
Further, in detail, as described above, the colored product is a polymer having a different molecular weight. Depending on the size of the molecule, there are those that are easily bleached and those that are difficult to bleach. It can be presumed that the reaction efficiency of the bleaching agent was improved by bleaching at a low temperature where the self-decomposition of the agent is low and bleaching a portion that is difficult to bleach at a high temperature.

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.

<Measurement method of sulfonation reaction rate in product>
As a raw material to be used, 0.02, 0.1, and 0.2 g of fatty acid methyl ester standard products are accurately weighed into 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)
Device: LC-10AT (manufactured by Shimadzu Corporation)
Column: Inertsil ODS-2 (manufactured by GL Sciences Inc.)
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 (sulfonated compound or esterified compound) (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>
For the color tone, an aqueous solution having a pure content (AI) concentration of 5% by mass of a sample was measured with No. 40 mm optical path length. Measure with a Kret photoelectric meter using a 42 blue filter.

<Measurement of residual hydrogen peroxide>
Weigh accurately 2.0 g of the bleached product into a 200 ml Erlenmeyer flask and add 50 ml of 1N sulfuric acid to dissolve completely. After dissolution, 0.5 g of potassium iodide is added, an air-cooled tube is connected to the Erlenmeyer flask, and immersed in a boiling water bath for 30 minutes. After 30 minutes, remove from the warm bath, cool to room temperature and titrate with 0.1N sodium thiosulfate. At that time, the starch solution is used as an indicator. From the obtained titer, the amount of residual hydrogen peroxide is quantified using the following formula.
Residual hydrogen peroxide (%) = A × 0.1 × F × 0.017 × 100 / S
A: 0.1N sodium thiosulfate titration (ml)
F: Factor of 0.1N sodium thiosulfate S: Sample amount of sample (g)

<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 and 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 (made by Nippon Dionex)
Detector: Electrical conductivity detector CD-20 (manufactured by Nippon Dionex)
Pump: IP-25 (made 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% (volume) acetonitrile aqueous solution Eluent flow rate: 1.3 mL / min
Regenerating solution: 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 and then analyzed by ion chromatography under the same measurement conditions as described above. 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.

[PH of neutralized product]
The AI concentration of the neutralized product is measured and diluted with distilled water so that the AI concentration becomes 10%. After dilution, the sample is completely dissolved using ultrasonic waves, etc., adjusted to 25 ° C. using constant temperature water or a constant temperature bath, and measured using a pH meter.

<Examples 1-6, Comparative Examples 1-6 (Preparation of paste containing α-sulfo fatty acid alkyl ester salt)>
(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 using methanol (35% vs. RBD palm stearin) with caustic soda (0.21% vs. RBD palm stearin) as a catalyst at 80 ° C. for 60 minutes to obtain a crude esterified compound. .
The crude esterified compound is washed with water to reduce the content of glycerin and its derivatives remaining in the crude esterified compound, and then the carbon chain length ratio of the fatty acid alkyl group is C14 / C16 / C18 = 1. Distilled to be / 60/39 (mass ratio). The iodine value was reduced by hydrogenating this in the following procedure, and fatty acid methyl ester (hereinafter referred to as 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 (crystallizing at solid temperature and solid-liquid separation) palm oil. Oil.
The hydrogenation treatment is carried out according to a conventional method by adding 0.1% by mass of a 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. I went there. After the hydrogenation treatment, the catalyst was removed by filtration. The iodine value of the obtained raw material was 0.02 mg-I2 / g.

Using the obtained fatty acid methyl ester as a raw material, an α-sulfo fatty acid alkyl ester salt was produced by the following procedure.
(Sulfonation process / ripening process)
In Example 1 and Comparative Example 1, a stirred tank reactor 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.
After charging the raw material and 5 parts by mass of finely powdered sodium sulfate with an average particle size of 40-50 μm with respect to 100 parts by mass of the raw material in the tank, SO ₃ gas diluted to 8% with dry air is used as SO ₃ / raw material. Was blown over 3 hours so that the molar ratio was 1.2, and the sulfonation reaction was carried out. The obtained sulfonated compound was then aged by stirring in a stirring tank at 80 ° C. for 30 minutes. The exhaust gas was mist collected by a Cottrell dust collector, and after SO ₂ was removed by an alkali scrubber, it was released to the atmosphere.

In Examples 2 to 6 and Comparative Examples 2 to 6, a multitubular falling film reactor 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 SO ₃ / raw material molar ratio was set to 1.2, and SO ₃ gas diluted to 8% with the raw material and dry air was supplied so as to contact in parallel flow from the top to the bottom of the reactor. The reaction temperature in the reactor 2 was 80 ° C., and the reaction time was 15 seconds.
At this time, the exhaust gas discharged together with the sulfonated compound is gas-liquid separated from the sulfonated compound with a cyclone, and then collected with a cottrel dust collector, and after SO ₂ is removed with an alkali scrubber, the exhaust gas is discharged into the atmosphere. Was released.
After gas-liquid separation in a cyclone, the sulfonated compound discharged from the multi-tubular falling film reactor is added with 5 parts by mass of finely powdered sodium sulfate having an average particle size of 40-50 μm per 100 parts by mass of the raw material. The mixture was supplied to the continuous multistage agitation tank 4a and aged at a temperature of 80 ° C. for an average of 90 minutes.

(Esterification process)
Next, in Examples 1 to 6 and Comparative Examples 1 to 6, the aging compound after aging was supplied to the continuous multistage stirring tank 5a, and at the same time, 3% by mass of methanol was continuously added to the aging compound. The esterification treatment was performed by supplying and maintaining at a temperature of 80 ° C. and an average residence time of 30 minutes. Here, the industrial grade (water | moisture content of 1000 ppm or less) was used for methanol.
About the obtained esterified compound, the sulfonation reaction rate (sulfonation rate after esterification) and the color tone were measured. As a result, the sulfonation reaction rate after esterification in Example 1 and Comparative Example 1 was 99%, and the color tone was 900 (5% KLETT). In Examples 2 to 6 and Comparative Examples 2 to 6, the sulfonation reaction rate after esterification was 98%, and the color tone was 1100 (5% KLETT).

(Neutralization process)
Next, the esterified compound after completion of esterification was neutralized by supplying it to the recycle loop 6 of FIG.
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 68% 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 compound, 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 controlled at 70 ° C. by a heat exchanger in the recycle loop 6. The internal pressure of the recycle loop 6 was 0.4 MPa.
The color tone of the obtained neutralized product was measured. As a result, the color tone of the neutralized product in Example 1 was 850 (5% KLETT). The color tone of the neutralized product in Examples 2-6 and Comparative Examples 1-6 was 1000 (5% KLETT). The pH of the neutralized product was 6.2.

(Bleaching process)
Subsequent to neutralization, bleaching was performed using an industrial grade hydrogen peroxide solution having a purity of 35% by mass. The amount of hydrogen peroxide added was 1.5% by mass of hydrogen peroxide with respect to 100% by mass of the neutralized product (2.2% with respect to AI).
In Examples 1 to 3 and Comparative Examples 1 to 3, bleaching was performed by thoroughly mixing the neutralized product at 70 ° C. obtained in the neutralization step with hydrogen peroxide at room temperature in a beaker for 1 minute. The mixture was placed in a thermostatic bath where the temperature could be controlled, and bleaching was performed by adjusting the starting temperature shown in Tables 1 and 2 and the time until the temperature of the mixture reached the maximum temperature, the maximum temperature, and the maximum temperature holding time. The temperature of the bleached product was measured by inserting a temperature sensor directly into the bleached product (paste).

  Moreover, in Examples 4-6 and Comparative Examples 4-6, after neutralizing 70 degreeC neutralized material and normal temperature hydrogen peroxide water in a line mixer, it is the same as that of what was shown in FIG. It was introduced into a continuous bleaching tube (the residence time of each divided tube was about 30 minutes, respectively) of the configuration (however, the number of divided tubes was changed according to the time until reaching the maximum temperature and the maximum temperature holding time). In this continuous bleaching tube, the temperature of each divided tube is set so as to reach the target temperature at the target time, that is, the start temperature shown in Tables 1-2, the time until the temperature of the mixture reaches the maximum temperature, the maximum temperature, Bleaching was carried out by adjusting so as to satisfy the maximum temperature holding time.

After maintaining the maximum temperature for the time shown in Tables 1-2, the bleached product was cooled to the end temperature shown in Tables 1-2 by allowing to cool.
The color tone of the pasty bleached product 24 hours after the start of bleaching (at the first start temperature after mixing with hydrogen peroxide) 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 Tables 1-2.

As is clear from the above results, the bleached products produced in Examples 1 to 6 were less colored and excellent in color tone. In addition, the amount of di-Na salt as a by-product was small.
On the other hand, Comparative Example 1 in which the time to reach the maximum temperature was 300 minutes and Comparative Example 6 in which the maximum temperature holding time was 480 minutes had a large amount of di-Na salt produced. Comparative Example 2 in which the time to reach the maximum temperature is 10 minutes, Comparative Examples 3 to 4 in which the maximum temperature is outside the range of 85 to 100 ° C., and Comparative Example 5 in which the maximum temperature holding time is 10 minutes are Although the color tone value of the Japanese product was the same level as in Examples 1 to 6, the color tone value of the bleached product was higher than that of Examples 1 to 6, and the color tone was poor. This result indicates that the bleaching reaction did not proceed sufficiently.
Thus, in Examples 1-6, the bleaching time comparable to Comparative Examples 1-5, and in a shorter time than Comparative Example 6, while suppressing the production of by-products, an excellent bleaching effect was obtained. Obtained.

<Examples 7 to 18 and Comparative Examples 7 to 18 (Preparation of α-sulfo fatty acid alkyl ester salt-containing paste)>
(Preparation of raw material (fatty acid methyl ester))
Fatty acid methyl ester in the same procedure as in Examples 1 to 6 and Comparative Examples 1 to 6 except that the carbon chain length ratio of the alkyl group of the fatty acid was C16 / C18 = 90/10 (mass%). Was prepared.

Using the obtained fatty acid methyl ester as a raw material, an α-sulfo fatty acid alkyl ester salt was produced by the following procedure.
(Sulfonation process / ripening process)
In Example 7 and Comparative Example 7, a stirred tank reactor was used, and sulfonation and aging were performed in the same procedure as in Example 1 and Comparative Example 1.

  In Examples 8 to 18 and Comparative Examples 8 to 18, sulfonating and aging were performed in the same procedure as in Examples 2 to 6 and Comparative Examples 2 to 6 using a multi-tube falling film reactor.

(Esterification process)
Next, in Examples 7-18 and Comparative Examples 7-18, esterification was performed in the same procedure as in Examples 1-6 and Comparative Examples 1-6.
About the obtained esterified compound, the sulfonation reaction rate (sulfonation rate after esterification) and the color tone were measured. As a result, the sulfonation reaction rate after esterification in Example 7 and Comparative Example 7 was 99%, and the color tone was 400 (5% KLETT). In Examples 8 to 18 and Comparative Examples 8 to 18, the sulfonation reaction rate after esterification was 98%, and the color tone was 500 (5% KLETT).

(Neutralization process)
Next, the esterified compound after completion of esterification was supplied to the recycle loop 6 of FIG. 1 and neutralized by the same procedure as in Examples 1-6 and Comparative Examples 1-6.
The color tone of the obtained neutralized product was measured. As a result, the color tone of the neutralized product in Example 7 and Comparative Example 7 was 350 (5% KLETT). The color tone of the neutralized product in Examples 8 to 18 and Comparative Examples 8 to 18 was 450 (5% KLETT). The pH of the neutralized product was 6.2.

(Bleaching process)
Subsequent to neutralization, bleaching was performed using an industrial grade hydrogen peroxide solution having a purity of 35% by mass. In Examples 7 to 8 and Comparative Examples 7 to 8, in the same procedure as in Examples 1 to 3 and Comparative Examples 1 to 3, the starting temperature shown in Tables 3 to 4 and the temperature of the mixture reached the maximum temperature. Bleaching was performed by adjusting the time, maximum temperature, and maximum temperature holding time.

  Moreover, in Examples 9-18 and Comparative Examples 9-18, in the same procedure as Examples 9-18 and Comparative Examples 9-18, the starting temperature shown in Tables 3-4 and the temperature of the mixture reach the maximum temperature. Bleaching was carried out by adjusting the time until the maximum time and the maximum temperature holding time.

After holding the maximum temperature for the time shown in Tables 3-4, the bleached product was cooled to the end temperature shown in Tables 3-4 by standing to cool.
The color tone of the pasty bleached product 24 hours after the start of bleaching (at the first start temperature after mixing with hydrogen peroxide) 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 Tables 3-4.

As is clear from the above results, the bleached products produced in Examples 7 to 18 were less colored, excellent in color tone, and small in expansion rate during storage. In addition, the amount of di-Na salt as a by-product was small.
On the other hand, Comparative Example 8 in which the time to reach the maximum temperature is 300 minutes, Comparative Example 10 in which the maximum temperature is 110 ° C., and Comparative Example 12 in which the maximum temperature holding time is 480 minutes are large in the amount of di-Na salt produced. It was. Further, Comparative Example 7 in which the time to reach the maximum temperature was 10 minutes, Comparative Example 9 in which the maximum temperature was 80 ° C., Comparative Example 11 in which the maximum holding time was 10 minutes, and the hydrogen peroxide consumption at the maximum temperature was 20%. Comparative Example 13 with respect to the addition amount, Comparative Example 14 with a hydrogen peroxide consumption at the maximum temperature of 40% vs. addition amount, and Comparative Example 15 with a residual hydrogen peroxide amount at the end of the reaction of 0.05% vs. addition amount Although the color tone value of the neutralized product was the same level as in Examples 7 to 18, the color tone value of the bleached product was higher than that of Examples 7 to 18, and the color tone was poor. This result indicates that the bleaching reaction did not proceed sufficiently.

Further, Comparative Example 17 in which the hydrogen peroxide addition amount was 0.04% vs. AI was worse in color tone than Example 17, and Comparative Example 18 in which the hydrogen peroxide addition amount was 6% vs. AI was from Example 18. Also, the expansion rate during storage increased.
Thus, in Examples 7-18, the outstanding bleaching effect was acquired on the same bleaching conditions as Comparative Examples 7-18, suppressing the production | generation of a by-product.

In addition, in order to compare the bleaching conditions of the present invention and the prior art, the bleaching conditions (gradient heating) of Example 8 are round, and as a conventional technique, the same neutralized product and bleach as in Example 8 are used, FIG. 4 shows a graph in which the bleaching conditions when the bleaching reaction is performed at a constant temperature of 70 ° C. are plotted as triangles, and similarly the bleaching conditions when the bleaching reaction is performed at a constant temperature of 90 ° C. are plotted as squares.
Similarly, FIG. 5 shows a graph showing the time transition of the bleaching agent consumption under the bleaching conditions, and FIG. 6 shows a graph showing the time transition of the color tone under the bleaching conditions.

<Example 19 and Comparative Example 19 (Preparation of α-sulfo fatty acid alkyl ester salt-containing paste)>
(Preparation of raw material (fatty acid methyl ester))
Fatty acid methyl ester in the same procedure as in Examples 1 to 6 and Comparative Examples 1 to 6, except that the carbon chain length ratio of the alkyl group of the fatty acid was C16 / C18 = 80/20 (mass%). Was prepared.

Using the obtained fatty acid methyl ester as a raw material, an α-sulfo fatty acid alkyl ester salt was produced by the following procedure.
(Sulfonation process / ripening process)
In Example 19 and Comparative Example 19, sulfonation and aging were performed in the same procedure as in Example 1 and Comparative Example 1, using a stirred tank reactor.

(Esterification process)
Next, in Example 19 and Comparative Example 19, esterification was performed in the same procedure as in Examples 1 to 6 and Comparative Examples 1 to 6.
About the obtained esterified compound, the sulfonation reaction rate (sulfonation rate after esterification) and the color tone were measured. As a result, the sulfonation reaction rate after esterification in Example 19 and Comparative Example 19 was 99%, and the color tone was 600 (5% KLETT).

(Neutralization process)
Next, the esterified compound after completion of esterification was supplied to the recycle loop 6 of FIG. 1 and neutralized by the same procedure as in Examples 1-6 and Comparative Examples 1-6.
The color tone of the obtained neutralized product was measured. As a result, the color tone of the neutralized product in Example 19 and Comparative Example 19 was 550 (5% KLETT). The pH of the neutralized product was 6.2.

(Bleaching process)
Subsequent to neutralization, the same procedure as in Examples 4 to 6 and Comparative Examples 4 to 6 is used, and the start temperature shown in Table 5, the time until the temperature of the mixture reaches the maximum temperature, the maximum temperature, and the maximum temperature holding time are satisfied. Bleaching was carried out by adjusting as follows.

After maintaining the maximum temperature for the time shown in Table 5, the bleached product was allowed to cool to the end temperature shown in Table 5.
The color tone of the pasty bleached product 24 hours after the start of bleaching (at the first start temperature after mixing with hydrogen peroxide) 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 5.

As is clear from the above results, the bleached product produced in Example 19 was less colored, excellent in color tone, and low in expansion during storage. In addition, the amount of di-Na salt as a by-product was small.
On the other hand, in Comparative Example 19 where the maximum temperature was 80 ° C., although the color tone value of the neutralized product was the same level as in Example 19, the value of the bleached product was higher than that in Example 19, and the color tone was higher. It was bad. This result indicates that the bleaching reaction did not proceed sufficiently.
Thus, in Example 19, the outstanding bleaching effect was acquired on the bleaching conditions comparable as the comparative example 19, suppressing the production | generation of a by-product.

In the present invention, in the bleaching step, the initial stage where the progress of bleaching is early is performed from a low temperature, and the temperature is raised in the state where many bleaches are left in the latter half where the progress of bleaching is slow, so that the decomposition of the bleaching agent is suppressed, A bleached product having a good color tone can be obtained. According to the method of the present invention, it is possible to produce an α-sulfo fatty acid alkyl ester salt that is excellent in color tone and suppressed by-product formation even with a small amount of bleach and a short bleaching time.

Claims (10)

A sulfonation step for sulfonating a fatty acid alkyl ester, an aging step for aging a sulfonated compound obtained in the sulfonation step, and an alcohol having 1 to 6 carbon atoms with respect to the aging compound obtained in the aging step. An esterification step using an esterification treatment, a neutralization step of neutralizing the esterified compound obtained in the esterification step to obtain a neutralized product, and bleaching the neutralized product to obtain a bleached product A bleaching process,
In the bleaching step, the start temperature of the bleaching reaction is set to 70 to 76 ° C., the start temperature is increased to the maximum temperature of 85 to 100 ° C. within 20 to 240 minutes from the start of the reaction, and the maximum temperature is set to 20 to 360 ° C. A method for producing an α-sulfo fatty acid alkyl ester salt, which is held for a minute and then lowered to an end temperature of 55 to 75 ° C.   2. The method for producing an α-sulfo fatty acid alkyl ester salt according to claim 1, wherein in the bleaching step, the sum of the time for raising the reaction temperature from the reaction start temperature to the highest temperature and the holding time for the highest temperature is 240 to 540 minutes. .   The manufacturing method of the alpha-sulfo fatty-acid alkylester salt of Claim 1 which performs the said bleaching process using a continuous bleaching pipe | tube.   2. The α-sulfo according to claim 1, wherein a bleaching agent is further added in the bleaching step, and the added amount of the bleaching agent is 0.05 to 5% by mass of the bleaching agent with respect to 100% by mass of the neutralized AI. A method for producing a fatty acid alkyl ester salt.   The manufacturing method of the alpha-sulfo fatty-acid alkylester salt of Claim 1 which performs the said sulfonation process and / or the said aging process in presence of a coloring inhibitor. A sulfonation step for sulfonating a fatty acid alkyl ester, an aging step for aging a sulfonated compound obtained in the sulfonation step, and an alcohol having 1 to 6 carbon atoms with respect to the aging compound obtained in the aging step. An esterification step using an esterification treatment, a neutralization step of neutralizing the esterified compound obtained in the esterification step to obtain a neutralized product, and bleaching the neutralized product to obtain a bleached product A bleaching process,
In the bleaching step, the reaction is started by adding a bleaching agent to the neutralized product at a reaction start temperature of 70 to 76 ° C., and the consumption of bleaching agent from the start of the reaction is 30 to 60% by mass (addition amount) The temperature is increased to a maximum temperature of 85 to 100 ° C. so that the bleaching agent consumes 25 to 35% by mass (addition amount) of the bleaching agent, and then the remaining of the bleaching agent is maintained. A method for producing an α-sulfo fatty acid alkyl ester salt, characterized in that the reaction temperature is lowered to a reaction end temperature of 55 to 75 ° C. so that the amount is 0.1 to 15% by mass (addition amount).   The manufacturing method of the alpha-sulfo fatty-acid alkylester salt of Claim 6 which performs the said bleaching process using a continuous bleaching pipe | tube.   The method for producing an α-sulfo fatty acid alkyl ester salt according to claim 6, wherein the addition amount of the bleaching agent is 0.05 to 5% by mass with respect to 100% by mass of the neutralized product AI.   The method for producing an α-sulfo fatty acid alkyl ester salt according to claim 6, wherein the sulfonation step and / or the aging step is performed in the presence of a coloring inhibitor.   The method for producing an α-sulfo fatty acid alkyl ester salt according to claim 9, wherein an inorganic sulfate and / or organic acid salt having a monovalent metal ion is used as the coloring inhibitor.