JPH026346B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing α-sulfofatty acid esters, and more particularly to a method for producing pale-colored, highly pure α-sulfofatty acid esters that are useful as surfactants. α-Sulfo fatty acid ester salt obtained by neutralizing α-sulfo fatty acid ester has characteristics such as good hard water resistance, excellent penetration ability, and is mild to the skin. It is useful as a surfactant or a wetting agent. As a method for producing α-sulfo fatty acid ester salts, for example, Japanese Patent Publication No. 52-2890 discloses that a fatty acid ester is allowed to flow down in a thin film, the first step of sulfonation is carried out at 50 to 80°C, and the first stage is sulfonated at 95 to 150°C. A method for carrying out the second stage sulfonation was described in
Publication No. 53-2419 describes fatty acid ester in the form of a thin film.
The first stage of sulfonation is carried out at a temperature of 40-70°C,
A method has been reported in which the excess SO ₃ and by-product gas are then separated and removed, and then the reaction is completed at 60 to 90°C. However, sulfonation of fatty acid esters has a slow reaction rate and requires high temperature, high molar ratio, and long reaction time to complete the sulfonation reaction, which has the disadvantage that the color tone of the sulfonated product obtained is significantly inferior. It was hot. On the mechanism of sulfonation of fatty acid esters, see AJ Stirton, JAOCS, 39 , 490.
(1962), etc., fatty acid esters
Reacts with SO ₃ to form SO ₃ 2-molecule adduct

[Formula] is formed, and it is thought that this decomposes into ₃ molecules of SO and α-sulfo fatty acid ester during ripening. The present inventors also conducted research on the sulfonation mechanism of fatty acid esters, and similar to Stirton et al.
We have deduced the following mechanism for forming SO ₃ bimolecular adducts. As described above, sulfonation of fatty acids proceeds in two steps: formation of an SO ₃ 2-molecule adduct from the fatty acid ester, and decomposition of the SO ₃ 2-molecule adduct into SO ₃ and α-sulfofatty acid ester. The formation of SO ₃ 2-molecule adducts from fatty acid esters in the first stage progresses relatively quickly, but the decomposition of SO ₃ 2-molecule adducts in the second stage is slow and requires heating and aging. Sometimes, color deterioration due to significant discoloration occurs. On the other hand, α-sulfo fatty acid ester

[Formula] has good solubility in water and has excellent detergency and hard water resistance, but it is an α-sulfo fatty acid salt with cleaved ester bonds.

Since the formula [formula] has extremely poor water solubility, detergency, and hard water resistance, the secondary effects of the α-sulfo fatty acid salt must be avoided as much as possible. Since this α-sulfofatty acid salt is produced as a by-product during alkali neutralization of the SO ₃ bimolecular adduct, heating and aging steps to decompose the SO ₃ bimolecular adduct into α-sulfofatty acid ester and SO ₃ are essential. Therefore, prevention of color tone deterioration during heat aging was an important problem to be solved in order to produce pale-colored α-sulfo fatty acid ester salts. We have developed the above sulfonate color tone and SO ₃ 2
It was found that there is an important relationship between the amount of molecular adducts and the amount of molecular adducts. The first stage of the sulfonation reaction is carried out under mild reaction conditions in which absorption of SO ₃ is the main activity. Under these conditions, SO ₃ 2-molecule adducts are mainly formed, and the coloration of the sulfonated product is very small. However, when heated and aged to a reaction rate of 95% or higher, which can be preferably used as a surfactant, significant coloring occurs. As a result of our pursuit of the cause of this coloring, the present inventors found that the SO ₃ 2-molecule adduct decomposes, producing α-sulfo fatty acid ester and SO ₃ as products, and this SO ₃ reacts with unreacted fatty acid ester. On the other hand, dehydrogenation of the alkyl group was caused and coloration was promoted. Therefore, as a result of further research, the present inventors found that by adjusting the amount of the SO ₃ bimolecular adduct in the sulfonated product and completing the sulfonation reaction at a relatively high temperature, a light color and a high reaction rate could be achieved. It has been found that it is possible to obtain α-fatty acid esters with a high concentration of α-fatty acid esters. That is, the α-sulfo fatty acid ester of the present invention is characterized by including the following four steps. (1) First step General formula RCH ₂ COOR' (wherein, R has 6 to 6 carbon atoms
20 alkyl group, R' has 1 to 6 carbon atoms
represents a molar group of ) per mole of fatty acid ester, diluted with inert gas.
40-80 °C using 1.0-1.5 mol of 15% _SO3 by volume
A step of sulfonating the fatty acid with. (2) Second step (a) The reaction product obtained in the first step and (b) the content of SO ₃ bimolecular adduct of fatty acid ester, which is 10 to 30 times the amount of this reaction product, is 20 A second step of mixing with a liquid mainly composed of α-sulfo fatty acid ester in an amount of not more than % by weight. (3) Third step A step of separating the mixture from the second step into a liquid phase and a gas phase. (4) Fourth step The liquid phase obtained in the third step is heated to 80 to 100℃.
A process of aging for 10 to 30 minutes. Each step will be explained in more detail below. The first step is a step aimed at gentle sulfonation at a relatively low temperature and absorption of SO ₃ gas into fatty acid ester. The fatty acid ester targeted by the present invention has the general formula
RCH ₂ COOR′. Here, R is C ₈ ~
a C ₂₀ alkyl group, preferably a C ₁₂ to C ₁₈ straight chain or branched alkyl group, and R′ is a C ₁ to C ₆ alkyl group, preferably a C ₁ to C ₃ straight chain or branched alkyl group It is. These fatty acid esters include animal fats and oils derived from beef tallow, fish oil, lanolin, etc., vegetable fats and oils derived from coconut oil, palm oil, soybean oil, etc.
It may be any synthetic fatty acid ester derived from the oxo method of olefin, and is not particularly limited. Examples include methyl, ethyl or propyl laurate, methyl or ethyl palmitate, methyl or ethyl stearate, methyl or ethyl hydrogenated beef tallow, methyl or ethyl coconut oil, methyl or ethyl palm oil, hydrogenation. Examples include methyl or ethyl fish oil fatty acids, methyl or ethyl lanophosphate, and the like. These may be used alone or in combination, and in order to improve the color tone of the sulfonated product, it is better that the iodine value is as low as possible.
Preferably it is 1 or less. Sulfonation methods include thin film sulfonation method,
Any method such as tank-type sulfonation method can be used, but
A thin film sulfonation method is preferred from the viewpoint of reducing coloring of the target product. As a sulfonating agent, anhydrous SO ₃ diluted to 1 to 15% by volume with dry nitrogen or an inert gas such as air can be used. Also, SO ₃ gas generated by sulfur combustion can be heated over a V ₂ O ₅ catalyst. It can also be used to convert it into SO ₃ gas. Moreover, SO ₃ gas is used in an amount of 1.0 to 1.5 mol based on the fatty acid ester. 1.0
If it is less than 1.5, a sufficient reaction rate will not be obtained, and if it exceeds 1.5, no particular effect will be obtained, and on the contrary, problems such as coloring of the product and treatment of excess gas will occur. The first step, sulfonation, is carried out at 40-80°C. If the temperature is below 40°C, sufficient reaction will not take place, and if it exceeds 80°C, side reactions such as cleavage of ester bonds will occur, which is undesirable. Further, the contact time in the first step is suitably about 5 to 30 seconds. In the second step, in order to adjust the amount of the SO ₃ 2-molecule adduct of the fatty acid ester in the reaction product obtained in the first step, the reaction product is mixed with α-sulfonate in an amount 10 to 30 times this amount. This is a step of mixing a composition (liquid) mainly consisting of a fatty acid ester. The liquid phase of the first step mainly contains α-sulfo fatty acid ester.

[Formula] SO ₃ 2-molecule adduct of fatty acid ester

Contains [Formula] and unreacted fatty acid ester. The amount of the SO ₃ two-molecule adduct of the fatty acid ester in the liquid phase varies depending on the reaction conditions, but is usually 50 wt% or more.
Therefore, a liquid mainly composed of fatty acid esters containing 20 wt % or less of SO ₃ 2-molecule adducts of fatty acid esters is added. The third step is a step of separating gas and liquid from the mixture obtained in the second step, in which inert gas and unabsorbed
SO ₃ is removed. Although the gas-liquid separation means is not particularly limited, it is preferable to separate the gas and liquid immediately after the completion of the second step, and in this sense, separation is preferably performed by mechanical means such as a cyclone. The fourth step is to prepare the liquid phase in which the content of SO ₃ 2-molecule adduct of fatty acid ester has been adjusted as described above.
In the step of aging at 80 to 100°C for 10 to 30 minutes, the amount of bimolecular adduct is controlled, so coloring is prevented and a pale α-sulfo fatty acid ester is obtained.
If the ripening or temperature does not reach the above-mentioned lower limit, the reaction will not be fully completed, and if it exceeds the upper limit, the product will become colored. By treating the aged product obtained in the fourth step with a suitable alkaline agent such as an alkali metal hydroxide, ammonia, ethanolamine, etc., an α-sulfo fatty acid ester salt useful as a surfactant can be obtained. As described above, in the present invention, the amount of SO ₃ 2-molecule adduct is adjusted after the first step, but the reaction product obtained after the fourth step of the present invention is used as the composition necessary for this. By recycling this after the first step, the present invention can be carried out efficiently. Of course, separately adjusted α-
This does not preclude the use of liquid products containing sulfofatty acid esters. FIG. 1 is a flowchart for carrying out the above-mentioned recycling. The product from the 4th step is mainly composed of α-sulfo fatty acid ester and contains 20 wt% or less of SO ₃ 2-molecule adduct, which is added to the reaction product (liquid phase amount) from the 1st step by 10 to The purpose of the second step is achieved by recycling 30 times the amount and mixing immediately. At the beginning of the start-up of the equipment, the waste from the ripening process (fourth process) is recycled to the recycling system 11.
(Actually, it can constitute part to all of the ripening device.) After this amount reaches the recycled amount, it is recycled from line 12 to the downstream stage of the first stage sulfonation (first step). After that, the same amount of α-sulfo fatty acid ester (including 20 wt% or less of bimolecular adducts) as the amount discharged from the first step was added.
is taken from line 13. By neutralizing this with an alkali agent, an α-sulfo fatty acid salt can be obtained. The SO ₃ 2-molecule adduct content in the sulfonation mixture can be measured by NMR using the solvent and absorption magnetic field as shown below.

[Table] Also, you can easily find it as follows. Neutralize the sulfonated mixture with a 1-2% dilute alkaline aqueous solution, add ethanol to the resulting neutralized product to make a 90%-ethanol aqueous solution, adjust the pH to 10-11, and then adjust the pH to 40-50. Heat to ℃ and centrifuge. Next, add 90%-ethanol to the residue and heat it again at 40-50℃.
After heating to
After dissolving in water, diluting with pure water and titrating by methylene blue method, the α-sulfo fatty acid salt content is calculated using the following formula. SO ₃ bimolecular adduct (%) = α-sulfofatty acid salt (g)
× (molecular weight of SO ₃ bimolecular adduct / molecular weight of α-sulfo fatty acid salt) / amount of sulfonation mixture used for neutralization (g) × 100 Example 1 Thin film reactor (made of glass, inner diameter 6 mm, length 1.2
m) as the first reactor, extremely hardened beef tallow fatty acid methyl ester (average molecular weight 290, iodine value:
0.5) was reacted at an SO ₃ molar ratio of 1.3 and a reaction temperature of 50°C.
This sulfonated product is recycled and mixed with α-sulfo fatty acid ester from the second reactor in an amount 10 times the amount of this sulfonated product at the outlet of the first reactor, and this mixture is passed through a gas/liquid separator to inert gas. , unabsorbed
After separating the SO ₃ gas, it was introduced into the second reactor, heated by a heat exchanger, and aged at 90° C. for 30 minutes. An amount corresponding to the amount injected from the first reactor of this α-sulfo fatty acid ester was discharged to form a product.
The content of SO ₃ 2-molecule adduct of α-sulfo fatty acid ester in this product was 16 wt%. The color tone and reaction rate are as shown in Table 1. Example 2 The same procedure as in Example 1 was carried out except that the amount of recycled α-sulfo fatty acid ester from the second reactor was 20 times the amount and the aging temperature of the second reactor was 100°C.
The α-sulfo fatty acid ester obtained in this example
The content of the SO ₃ bimolecular adduct was 12 wt%, and its color tone and reaction rate are as shown in Table 1. Example 3 The same procedure as in Example 1 was carried out except that the amount of recycled α-sulfo fatty acid ester from the second reactor was 30 times the amount, the aging temperature of the second reactor was 100°C, and the time was 15 minutes. . The content of the SO ₃ 2-molecule adduct of α-sulfo fatty acid ester obtained in this example was 14 wt%.
The color tone and reaction rate are as shown in Table 1. Example 4 The reaction was carried out in the same manner as in Example 1, except that the reaction temperature in the first reactor was 40° C., and the amount of recycled α-sulfo fatty acid ester from the second reactor was 20 times the amount. The content of the SO ₃ 2-molecule adduct of α-sulfo fatty acid ester obtained in this example was 16 wt%, and its color tone and reaction rate are as shown in Table 1. Example 5 The reaction temperature in the first reactor was 80°C, the amount of recycled α-sulfo fatty acid ester from the second reactor was 20 times the amount, and the aging temperature in the second reactor was 80°C.
The same procedure as in Example 1 was carried out except that. The content of the SO ₃ 2-molecule adduct of α-sulfo fatty acid ester obtained in this example was 14 wt%, and its color tone and reaction rate are as shown in Table 1. Comparative Example 1 The same procedure as in Example 1 was carried out except that the α-sulfo fatty acid ester from the second reactor in the method of the present invention was not recycled. The content of the SO ₃ bimolecular adduct of α-sulfo fatty acid ester obtained in this comparative example was 25 wt%, and its color tone and
The reaction rate is shown in Table-1. Comparative Example 2 The same procedure as in Example 1 was carried out except that the amount of α-sulfo fatty acid ester recycled from the second reactor in the method of the present invention was also 5 times the amount. The content of the SO ₃ 2-molecule adduct of α-sulfo fatty acid ester obtained in this comparative example was 23 wt%, and its color tone and reaction rate are as shown in Table 1. Comparative Example 3 The amount of α-sulfo fatty acid ester recycled from the second reactor in the method of the present invention was set to 5 times the amount,
The same procedure as in Example 1 was conducted except that the aging temperature in the second reactor was 100° C. and the aging time was 5 minutes. The content of the SO ₃ two-molecule adduct of α-sulfo fatty acid ester obtained in this comparative example was 26 wt%, and its color tone and reaction rate are as shown in Table 1. Comparative Example 4 Reaction temperature in the first reactor in the method of the present invention: 90
The reaction was carried out in the same manner as in Example 1, except that the temperature was changed to 20.degree. The content of the SO ₃ bimolecular adduct of α-sulfo fatty acid ester obtained in this comparative example is
Although the concentration was 13 wt%, as shown in Table 1, significant coloration was observed in terms of color tone. In addition, in the table, the color tone was measured as follows. (1) Color Tone Measured with a Klett Summerson photometer using a No. 42 blue filter at an activator concentration of 0.5% and an optical path length of 40 mm, and the measured value was multiplied by 10 to give an activator concentration of 5%.
It was converted into

[Table]

[Brief explanation of drawings]

FIG. 1 is a flow diagram showing an embodiment of the present invention.

Claims (1)

[Claims] 1. General formula RCH ₂ COOR' (wherein R has 6 to 6 carbon atoms)
20 alkyl group, and R' represents an alkyl group having 1 to 6 carbon atoms. ) for 1 mole of fatty acid ester, diluted with inert gas.
40-80 °C using _SO3 gas 1.0-1.5 mol% by volume
The first step is to sulfonate the fatty acid ester, and the content of the reaction product obtained in the first step and the SO ₃ bimolecular adduct of the fatty acid ester in an amount of 10 to 30 times that of this reaction product is 20 a second step of mixing the mixture with a liquid mainly consisting of α-sulfo fatty acid ester in an amount of % by weight or less; a third step of separating the mixture obtained in the second step into a liquid phase and a gas phase; A method for producing an α-sulfo fatty acid ester, comprising a fourth step of aging the liquid phase obtained in the third step at 80 to 100°C for 10 to 30 minutes. 2. The manufacturing method according to claim 1, wherein a part of the product from the fourth step is recycled and used as the liquid mainly composed of α-sulfo fatty acid ester in the second step.