JPH026345B2 - - 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 wetting agent. Linear alkylbenzenes, higher alcohols, higher alcohol ethoxylates, α-olefins, etc., which are known as anionic surfactants, have high reactivity, and by the sulfonation method using SO ₃ as the sulfonating agent, surfactants can be converted into surfactants in an almost equimolar reaction. Conventionally, sulfonated products with a reaction rate of 95% or more can be obtained, which can be used satisfactorily as a sulfonated product. However, fatty acid esters have poor reactivity and can be used as sulfonating agents with an equimolar or more amount of SO ₃ (usually
(approximately 1.2 times the molar amount), which posed several problems to be solved. For example, in Japanese Patent Publication No. 39-20842, the first
65-90 of SO ₃ required for reaction at below 70 °C in stage
% and the remaining SO ₃ at 70℃ or higher in the second stage.
A two-stage method for sulfonating fatty acid esters is disclosed. Also, special public service 39-28635
The publication discloses a two-stage sulfonation method in which SO ₃ is first dissolved at a low temperature, then the temperature is raised to cause a 50% reaction, and then the reaction is carried out continuously at 70° C. or higher. Furthermore, Japanese Patent Publication No. 52-2890 describes a method in which a fatty acid ester is allowed to flow down in a thin film, the first stage of sulfonation is carried out at 50 to 80°C, and the second stage of sulfonation is carried out at 95 to 150°C. It was also published in 1973-
Publication No. 2419 discloses that fatty acid esters are prepared in the form of a thin film of 40~
A method has been reported in which the first stage of sulfonation is carried out at a temperature of 70°C, then the excess SO ₃ and by-product gas are separated and removed, and then the reaction is completed at 60 to 90°C. However, since the sulfonation reaction rate of fatty acid esters is slow, high temperatures, high molar ratios of SO ₃ , and long reaction times are required to complete the reaction, resulting in coloration of the resulting sulfonated products.
Glauber's salt and alkyl sulfate are produced as by-products, and the conventional method described above has not been able to satisfactorily solve this problem. The reason for the poor reactivity of fatty acid esters is that fatty acid esters react with SO ₃ in two molecules, as seen in AJ Stirton, JAOCS.39, 490 (1962) and Nagayama et al., Oil Chemistry, 24: 395 (1975). ,
SO ₃ bimolecular adduct

It is thought that this is to form [Formula]. Therefore, in order to obtain a sulfonated product with a reaction rate of 95% or more that can be satisfactorily used as a surfactant, the presence of an excess amount of SO ₃ is essential. It goes without saying that SO ₃ used in excess will cause significant coloring during the sulfonation reaction, and in order to be used as a surfactant, it must be neutralized with an alkali agent such as an aqueous alkali metal hydroxide solution, aqueous ammonia, or ethanolamine. When forming the ester salt, undesirable by-products are produced that do not take part in the reaction. The present inventors also conducted extensive studies on the sulfonation mechanism of fatty acid esters, and found that the above-mentioned by-products were
We have come to the conclusion that this is a by-product due to the following mechanism during neutralization of the SO ₃ 2-molecule adduct with an alkaline agent. Sulfates such as alkyl sulfate salts and Glauber's salts can cause non-uniformity due to crystallization of by-products at low temperatures when used as liquid detergents, and can cause poor powder properties, especially when used as granular detergents. The problem was that its hygroscopicity caused a decrease in fluidity, severely restricting its range of use. The present inventors have conducted intensive studies on a method for sulfonating fatty acid esters that solves the above-mentioned drawbacks all at once. As a result, the inventors have found that by sulfonating fatty acid esters through the following three steps, there is less coloring and less generation of by-products. It was discovered that sulfo fatty acid esters can be obtained. (1) 1st 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 an alkyl group. ) for 1 mole _of fatty acid ester represented by
A step of sulfonating the fatty acid ester at 80°C. (2) Second step A step of separating the reaction product from the first step into a liquid phase and a gas phase, that is, a liquid phase mainly consisting of the sulfonated product of the fatty acid ester after sulfonation and the unreacted fatty acid ester, A process of separating gas and liquid from an inert gas and a gas phase mainly consisting of SO ₃ gas. (3) 3rd step The liquid phase from the 2nd step is 10~200Torr, 90~
A process of heating at 150℃ and aging under reduced pressure. Each step will be explained in more detail below. The first step is a step aimed at mild 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; be. These fatty acid esters include animal fats and fats derived from beef tallow, fish oil, and lanolin, vegetable fats and fats derived from coconut oil, palm oil, soybean oil, etc., and α-
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 of the tank-type sulfonation methods can be employed, but the 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 ₂ gas generated by sulfur combustion is 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 problems such as disposal of excess gas will arise. 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. The second step is a step of separating the reaction products from the first step into gas and liquid, and the 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 first step, and in this sense, it is preferable to separate by mechanical means such as a cyclone. The third step is a step in which the liquid phase from the second step is aged under reduced pressure and at a relatively high temperature to complete the sulfonation reaction, and the excess dissolved SO ₃ is forcibly removed. Depressurization is performed at 10-200 Torr. If the temperature exceeds 200 Torr, side reactions cannot be effectively prevented, resulting in coloring of the product and increase in by-products.
Further, no particular effect is observed even if the pressure is reduced to less than 10 Torr. Aging temperature is 90-150℃, preferably 100-120℃
It is. If the temperature is less than 90°C, the reaction will be slow to complete, and if it exceeds 150°C, the product will become colored. Further, the appropriate aging time is about 5 seconds to 5 minutes, preferably 10 seconds to 2 minutes, and more preferably 20 to 40 seconds. By treating the α-sulfo fatty acid ester obtained in the third step with an appropriate alkaline agent, such as an alkali metal hydroxide, ammonia, or ethanolamine, an α-sulfo fatty acid ester salt useful as a surfactant can be obtained. It will be done. As explained above, according to the present invention, it is possible to obtain α-sulfo fatty acid ester with a light color and high purity. Examples and Comparative Examples Hardened beef tallow fatty acid methyl ester (average molecular weight
290, iodine value 0.3) was sulfonated with SO ₃ diluted to 5% by volume with air under the conditions listed in Table 1 (first step), and the reaction product was immediately introduced into a cyclone for gas-liquid separation. (second step), the liquid phase was aged under the conditions listed in Table 1 (third step), and dissolved excess SO ₃ was separated. Immediately reduce 3rd process emissions by 5%
It was neutralized to pH 6.5 with NOOH aqueous solution. The properties of the obtained neutralized product were measured using the following method.
Shown in the table. (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 convert to an activator concentration of 5%. (2) Reaction rate Reaction rate (%) = A + B / C × 100 A: Number of moles of α-sulfo fatty acid ester salt B: Number of moles of α-sulfo fatty acid salt C: Number of moles of raw material fatty acid ester (3) Glauber's salt 95 % ethanol solution was centrifuged, decanted three times, dried at 105°C for 30 minutes, and weighed. Glauber's salt content (%) = D / E + F × 100 D; Weight of 95% ethanol insoluble matter E; Weight of α-sulfo fatty acid ester salt F; Weight of α-sulfo fatty acid salt (4) Methyl sulfate Methyl sulfate (%) =G-(H+E+F+I+J)/E+F×100 G; Weight of neutralized product H; Weight of water E, F; Same as above I; Unreacted fatty acid ester J; Weight of mirabilite

【table】

【table】

Claims (1)

[Claims] 1 General formula RCH ₂ COOR' (in the formula, 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
A first step of sulfonating the fatty acid ester with
A second step of separating the reaction product obtained in the first step into a gas phase and a liquid phase, and a second step of aging the liquid phase under reduced pressure and heating at 10 to 200 Torr and 90 to 150°C. A method for producing an α-sulfo fatty acid ester, the method comprising three steps.