JPH051019A - Production of sodium n-alkylaminoethanesulfonate - Google Patents

Abstract

PURPOSE:To provide a production process of N-alkylaminoethanesulfonic acid sodium salt capable of remarkably suppressing production of by-products and substantially requiring no purification process, thees having an extremely excellent economical efficiency. CONSTITUTION:An aqueous solution of sodium hydrogensulfite controlled to pH>=4.4 is reacted with ethylene oxide at <=80 deg.C to produce an aqueous solution of sodium isethionate. The aqueous solution of sodium isethionate in which the total content of sulfite and hydrogensulfite ingredients is <=1.0wt.% (expressed in terms of SO2) based on sodium isethionate is reacted with an alkylamine at 150-300 deg.C to produce an N-alkylaminoethanesulfonic acid sodium salt. Then, unreacted alkylamine is recovered from the resultant reaction mixture by distillation at liquid temperature of the reaction mixture of <=175 deg.C and further water is removed by distillation so as to become the concentration of the objective N-alkylaminoethanesulfonic acid sodium salt above a required product level by the concentration and the deposited solid is removed by filtration to provide the high-quality N-alkylaminoethanesulfonic acid sodium salt water solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a production process for obtaining sodium N-alkylaminoethanesulfonate, which is useful as a raw material for surfactants, pH buffers and the like, in high quality.

[0002]

2. Description of the Related Art Commercially produced sodium N-alkylaminoethanesulfonates include sodium isethionate, ethylene glycol, sodium ethanedisulfonate and N-alkylaminobis (sodium ethanesulfonate) as organic impurities. However, it mainly contains sodium sulfate as an inorganic impurity and various other unknown compounds.

N-alkylaminoethanesulfonic acid and its sodium salt are used for various purposes. Among them, when they are used as raw materials for products such as hair care products and body shampoos that come into direct contact with the human body, they are products. It is desirable that the type and amount of impurities contained in the product be kept as low as possible.

Further, the concentration of the products currently on the market is about 40% by weight, but it is desired that the concentration is higher in terms of transportation cost and the like. However, the impurity level of the commercially available product is considerably high, and when the concentration of sodium N-alkylaminoethanesulfonate is 40% by weight or more, crystal precipitation of organic electrolyte and inorganic electrolyte having relatively low solubility in water. Causes clouding or phase separation. Therefore, product handling troubles are caused and the product value is significantly impaired. As for the product sodium N-alkylaminoethanesulfonate, the items required in terms of quality include appearance such as hue and chromaticity, odor, etc., but as is clear from the above description, it is highly pure. More desired.

Purification of sodium N-alkylaminoethanesulfonate is not easy because of the physical and chemical properties of this compound. As one of the refining methods, there is disclosed a method in which a mineral acid is added to the sodium organic sulfonate to make it into a sulfonic acid type, which is once taken out by crystallization to remove various impurities (West German Patent No. 11222540, No. 1).
157234, JP-A-61-22061). Although high-purity products can be obtained by these methods, a large amount of inorganic salts such as sodium sulfate are produced, and thus an apparatus and operation for separating and removing them are required. Furthermore, new measures for waste treatment due to organic substances adhering to the inorganic salt are required. As described above, the addition of a new refining step causes an increase in equipment cost, and inevitably complicates the solid handling operation during plant operation.

[0006]

In order to industrially produce sodium N-alkylaminoethanesulfonate, which is inexpensive and excellent in quality, it is necessary to produce by-products as much as possible in the reaction step for producing the substance. Optimization of the suppression reaction is desired.

The present inventors have reviewed the individual reaction steps in order to obtain a high-quality and high-concentration sodium N-alkylaminoethanesulfonate aqueous solution containing a small amount of impurities, and as a result of studying the improvement of the process, the present invention was conducted. Has been completed.

[0008]

That is, according to the present invention, when sodium N-alkylaminoethanesulfonate is produced from sodium bisulfite, ethylene oxide, and alkylamine as main raw materials, a) pH is adjusted to 4.4 or more. Ethylene oxide was introduced into the aqueous sodium bisulfite solution at a molar ratio of ethylene oxide / sodium bisulfite of 0.95 to 1.05, and the reaction was carried out at a temperature of 80 ° C. or lower to produce a sodium isethionate aqueous solution. b) Alkylamine and alkylamine / sodium isethionate mol are added to the above sodium isethionate aqueous solution in which the total content of the sulfite and bisulfite components is 1.0% by weight or less based on sodium isethionate (SO ₂ conversion). Add 150 to 300 so that the ratio becomes 8 to 20
The reaction is carried out at a temperature of ℃ to produce sodium N-alkylaminoethanesulfonate c) Unreacted alkylamine is obtained from the obtained reaction mixture,
The reaction mixture is recovered by distillation at a liquid temperature of 175 ° C. or lower d) Further, water is distilled off and concentrated so that the concentration of the target product sodium N-alkylaminoethanesulfonate is equal to or higher. Filtration is a method for producing a high-quality sodium N-alkylaminoethanesulfonate aqueous solution, which comprises the steps a) to e).

The present invention will be described in detail below.

In the production of sodium isethionate by the reaction of ethylene oxide and sodium bisulfite, the pH is
An aqueous sodium bisulfite solution adjusted to 4.4 or more, preferably 4.5 to 5.0 is used. When the reaction is started at a pH of less than 4.4, the amount of ethylene glycol by-product increases. Even if the reaction is started from the region where the pH exceeds 5, there is no particular problem in terms of the generation of organic impurities, and even if these conditions are selectively adopted, there is practically no problem. However, at the end of the reaction, the alkali concentration in the system becomes high, and an operation for removing the excess alkali content is required in the subsequent step, and no advantage can be found.

Ethylene oxide is used in a molar ratio of 0.95 to 1.05, preferably 0.99 to sodium bisulfite.
Used in the range of 1.03. If the amount of ethylene oxide is too large, the amount of water-soluble organic impurities derived from an excessive amount of ethylene oxide is increased as a by-product. On the other hand, if the amount is too small, the excess sulfite component causes an undesirable side reaction product in the next step.

The reaction temperature is 80 ° C. or lower, preferably 40 to
It is 70 ° C. If the temperature is too high, the amount of ethylene glycol by-product increases, and if it is too low, the amount of ethylene glycol by-product can be suppressed, but a sufficient reaction rate cannot be obtained and it takes a long time to complete the reaction.

The sodium isethionate aqueous solution obtained as described above is subjected to a reaction with an alkylamine in the next step and converted to the desired sodium N-alkylaminoethanesulfonate. In this reaction, the sulfite component (bisulfite ion and sulfite ion) present in the aqueous solution of sodium isethionate is 1 wt% or less, preferably 0.5 wt% or less (SO ₂ conversion, based on the weight of sodium isethionate). It is essential that there be. The sulfite component causes sodium ethanedisulfonate as a by-product, resulting in deterioration of storage stability of the product. For example, in the case of producing sodium N-methylaminoethanesulfonate by reacting methylamine with sodium isethionate, when the total content of the sulfite and bisulfite components is 1% by weight, the amount of sodium ethanedisulfonate by-product is Is about 2.
5% (based on the weight of sodium N-methylaminoethanesulfonate). This value is almost the same level as or lower than the products currently on the market, but it is desirable to further reduce the impurity content level in order to obtain a higher quality product. More preferably, it is desired to use an aqueous solution of sodium isethionate having a total content of the sulfite and bisulfite components of 0.5% by weight or less. That is, the amount of sodium ethanedisulfonate by-product is about 1.5% by weight or less (based on the weight of sodium N-methylaminoethanesulfonate), and it can be said that such selection of conditions is extremely preferable in terms of final product quality.

The sodium isethionate obtained by the method of the present invention has a reduced content of sodium sulfite or sodium bisulfite. If the content is not sufficiently reduced, oxygen-containing gas such as air is used. It is possible to convert the sulfurous acid component into a sulfate ion to render it harmless by sufficiently contacting it with or by performing an oxidation treatment by adding various oxidizing agents such as hydrogen peroxide and alkali metal persulfate.

The alkylamine used for the reaction with sodium isethionate is a monoalkylamine having a C ₁ -C ₈ alkyl group or a cycloalkyl group. Specific examples include methylamine, ethylamine, propylamine, butylamine, cyclohexylamine and the like. The amount used is 5 to 3 with respect to sodium isethionate.
The molar ratio is 0 times, preferably 8 to 20 times.

The reaction temperature is 150 to 300 ° C, preferably 190 to 270 ° C.

In this reaction, it is essential to obtain a sufficient conversion rate of sodium isethionate in order to obtain a high quality product, and the reaction time therefor is 3 to 10 hours in a preferable temperature range. At that time, the reaction pressure becomes 50 to 100 Kg / cm ² G. The unreacted alkylamine is then distilled off, i.e. generally by flash distillation. Here, it is important to carry out the operation at a temperature of the reaction mixture of 175 ° C. or lower. If the temperature is too high, a decomposition reaction of sodium N-alkylaminoethanesulfonate occurs, so that the amount of undesired by-products increases and the quality deteriorates. N-obtained as described above
The aqueous solution of sodium alkylaminoethane sulfonate is further concentrated to a desired product concentration or higher. At this time, when solids are generated due to the precipitation of the contained impurities, they are removed by a simple operation such as centrifugation. In addition, the amount of solids generated at this time is also small.

After this operation, water is added to the obtained filtrate to adjust the concentration to a desired value to obtain a product sodium N-alkylaminoethanesulfonate aqueous solution. Further, the obtained filtrate can be directly used as a product. For example, product concentration 40
When it is at least 50% by weight, it is concentrated to at least 45% by weight, preferably at least 50% by weight to remove precipitated impurities such as sodium sulfate and sodium ethanedisulfonate.

The sodium N-alkylaminoethanesulfonate, which is the object of the present invention, generally has a C _{1 to} C ₈ alkyl group and a cycloalkyl group, for example, N-methyl, N-ethyl. , N-propyl, N-butyl, N-cyclohexyl, etc. are exemplified by sodium aminoethanesulfonate.

[0020]

INDUSTRIAL APPLICABILITY The aqueous solution of sodium N-alkylaminoethanesulfonate produced by the method of the present invention has a very low level of impurities, and thus is essentially economical without requiring a purification step. Can provide the manufacturing process. Sodium sulfate and sodium ethanedisulfonate in the product are unfavorable compounds that easily precipitate in an aqueous solution and impair the stability of the product over time. In that respect, the product obtained by the production process of the present invention has excellent storage stability even as a high-concentration product having a sodium N-alkylaminoethanesulfonate concentration of 50% by weight or more. Further, it is possible to obtain a high-concentration aqueous solution having a sodium N-alkylaminoethanesulfonate concentration of 60% by weight, and it can be expected to reduce the transportation cost by increasing the concentration of the product.

[0021]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.
The concentrations in the examples are all wt%.

Example 1 Commercially available sodium bisulfite powder 2777 g was added to water 5149.
9 g of 24% aqueous sodium hydroxide solution
Was added to adjust the pH of the solution to 4.5. The SO ₂ content measured by iodometric titration was 23.18%.

Obtained aqueous sodium bisulfite solution 795
4 g was charged into a magnetic stirring type 10 liter autoclave, and the inside of the reaction system was replaced with nitrogen. After heating and stirring were started to bring the temperature of the content liquid to 40 ° C., 1303 g of ethylene oxide collected in a pressure vessel was intermittently injected with nitrogen over 2 hours while controlling the reaction temperature to 50 to 60 ° C. After that, aging was performed for 1 hour. The obtained reaction mixture was analyzed by liquid chromatography to find that sodium isethionate was 45.4% and ethylene glycol was 0.44.
%, 0.20% of sodium sulfate was contained. The unreacted sulfite and bisulfite components were 0.3% (SO ₂ conversion) based on sodium isethionate.

Obtained aqueous solution of sodium isethionate 1
Charge 845g and 6154g of 40% methylamine aqueous solution to a magnetic stirring type 10 liter autoclave.
The reaction was carried out at 0 ° C for 4 hours. At this time, the reaction pressure is 75 kg
/ Cm < ² > G. After the reaction is completed, the reaction mixture is heated to 170 ° C.
After cooling to room temperature, the valve of the autoclave was opened and unreacted methylamine was distilled off. After the distillation and recovery of methylamine from the reaction mixture was completed, the reaction solution was extracted from the autoclave and transferred to a 10 liter round bottom flask equipped with a glass bead packed column with a height of 30 cm for simple distillation, a thermometer and a stirrer. Further, water was distilled off under reduced pressure, and the mixture was concentrated while being removed from the system. When the temperature of the content liquid reached 118 ° C., the concentration operation was completed and the mixture was allowed to cool to room temperature. Then, the precipitated impurities were removed by centrifugal filtration.

The obtained filtrate was analyzed by liquid chromatography to find that sodium N-methylaminoethanesulfonate 59.8%, N-methylaminobis (sodium ethanesulfonate) 1.1%, ethylene glycol 0.54 %, Sodium ethanedisulfonate 0.44
%, Sodium sulfate 0.26% and sodium isethionate 0.29%.

Water was added to this solution to prepare a sodium N-methylaminoethanesulfonate concentration of 57.0%. As a result of a storage stability test for one month at room temperature, no white turbidity or the like was observed and the stability was very good.

Claims (1)

Claims: 1. When producing sodium N-alkylaminoethane sulfonate from sodium bisulfite, ethylene oxide, and alkylamine as main raw materials, a) bisulfite adjusted to pH 4.4 or higher. Ethylene oxide is introduced into a sodium aqueous solution so that the ethylene oxide / sodium bisulfite molar ratio is 0.95 to 1.05, and the reaction is carried out at a temperature of 80 ° C. or lower to produce a sodium isethionate aqueous solution b) Sulfurous acid Alkylamine was added to the above sodium isethionate aqueous solution having a total content of the salt and bisulfite components of 1.0% by weight or less (calculated as SO ₂ ) based on sodium isethionate, and the alkylamine / sodium isethionate molar ratio was 8%. ~ 20 to 150-300
The reaction is carried out at a temperature of ℃ to produce sodium N-alkylaminoethanesulfonate c) Unreacted alkylamine is obtained from the obtained reaction mixture,
The reaction mixture is collected at a liquid temperature of 175 ° C. or lower by distillation d) Further, the target product is distilled off and concentrated so that the concentration of sodium N-alkylaminoethanesulfonate is not less than e) The precipitated solid is removed. Filter. A method for producing a high-quality sodium N-alkylaminoethanesulfonate aqueous solution, which comprises the steps a) to e) above.