JPS6245571A - Method of purifying alkyl sulfuric ester salt - Google Patents

Abstract

PURPOSE:To purify the titled compound useful as a dentifrice, etc., in a light color without causing deterioration in fragrance, by drying in vacuum aqueous slurry or powder of the titled compound which contains a specific amount of an inorganic salt based on a corresponding amount of a surface active agent so that an unreacted oil component is evaporated and removed. CONSTITUTION:Aqueous slurry or powder of an alkyl sulfuric ester salt (A for short) which contains <=1% inorganic salt based on a corresponding amount of a surface active agent is dried in vacuum and an unreacted oil component is evaporated and removed, to give a purified alkyl sulfuric ester salt having <=1% unreacted oil component and <=1% inorganic salt. An alkyl sulfuric ester salt shown by the formula ROSO3M (R is 8-18C alkyl; M is alkali metal, etc.,) is preferable as the component A.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for purifying an alkyl sulfate salt.

More specifically, the present invention provides a method for industrially producing a highly pure and light-colored alkyl sulfate ester salt at low cost.

[Conventional technology]

It is well known that alkyl sulfate ester salts have been used as foaming agents for toothpastes, emulsifying and dispersing agents, raw materials for cosmetics, and raw materials for detergents.

Among these, when alkyl sulfate salts are used as foaming agents for toothpastes or raw materials for cosmetics and cosmetics, inorganic salts and unreacted oils contained in the alkyl sulfate salts,
Color, odor, etc. often pose problems during use. For example, when used as a foaming agent for tooth brushing, mirabilite or common salt present as an inorganic salt may have a bitter or undesirable taste. In addition, the presence of unreacted oil imparts raw material odor, oxidation odor, malodor, unpleasant taste, and skin irritation. A similar problem arises when used as a raw material for cosmetics or cosmetics.

Therefore, such inorganic salts or unreacted oil must be removed from the surfactant product as much as possible.

The inorganic salts, unreacted oil content, and color of conventional alkyl sulfate salts depend on the reaction conditions under which they are produced, e.g.
When manufacturing using O3 gas, the shape of the reactor, SO
, partial pressure, reaction temperature, SO.

It is greatly influenced by the excess rate, etc.

Usually, in the most economical sulfation/neutralization method in terms of yield, the inorganic salt in the alkyl sulfate salt is about 1% and the unreacted oil content is about 2%. The amounts of these unreacted acids and unreacted oils are determined by the SOz excess rate during sulfation.

In general, it is possible to reduce the S(h excess rate as much as possible during sulfation) to reduce the amount of H, SO, derived from excess S03, and in turn, it is possible to reduce the amount of inorganic salts after neutralization. It is also possible to reduce the amount to about 0.1 to 0.5% per surfactant equivalent.However, increasing the SO3 excess rate during sulfation to increase the reaction rate and reduce the unreacted oil content is Currently known sulfation methods can only reduce the amount of unreacted oil to 0.5 to 1% per surfactant equivalent, accompanied by a significant increase in product coloration, yield, and inorganic acid content. These things are true for chlorosulfonic acid and lI23O.
The same applies to the case of sulfating with other sulfating agents such as No. 4.

Usually, acetone, ethers, isopropanol are used as means to remove these non-alkaline salts and unreacted oil components.7. A solvent extraction method using a polar solvent such as ethanol or methanol, a cytopolar solvent such as hexane or toluene, or a solvent crystallization method is used. However, since the solubility of inorganic salts and unreacted oil in these solvents is different, it is difficult to remove inorganic salts and unreacted oil at the same time, and as mentioned earlier, the SO3 molar ratio (excess It is impractical to lower the reaction rate) and remove only unreacted oil by solvent extraction, or to use a combination of two separation methods: one for removing inorganic salts and one for removing unreacted oil.

[Problem that the invention seeks to solve]

Regardless of the separation method, the use of solvents;
Limited availability of solvents, need for extraction efficiency and solvent recovery, and.

If the used solvent is not completely removed from the product, there will be problems such as a solvent odor remaining in the product, so if it is used industrially, there are disadvantages such as high cost. It has been desired to develop a method for industrially producing sulfate ester salts at low cost.

[Means for solving problems]

The present inventors solved the above-mentioned drawbacks, and improved efficiency with simple operation.
As a result of intensive research to find a method for purifying alkyl sulfate salts, the present invention has been completed.

That is, in the present invention, an aqueous slurry or powder of an alkyl sulfate ester salt having an inorganic salt content of 1% or less based on the surfactant equivalent is dried under vacuum to remove unreacted oil by evaporation to form an interface. The present invention relates to a method for purifying an alkyl sulfate ester salt, which is characterized by refining the unreacted oil content to 1% or less and the inorganic salt content to 1% or less based on the amount equivalent to the activator.

The alkyl sulfate salt used in the present invention includes:
Those represented by the general formula RO3O3M are preferred. Here, R represents a carbon y, alkyl group having 8 to 18 carbon atoms, and the gate represents an alkali metal or an alkaline earth metal. This alkyl sulfate ester salt is obtained by sulfating and neutralizing natural alcohol derived from animal and vegetable oils such as beef tallow or coconut oil, or synthetic alcohol derived from petroleum, by a known method. The neutralizing agent used is an aqueous solution of an alkali metal hydroxide such as caustic soda or potassium hydroxide, or an aqueous solution or slurry of an alkaline earth metal hydroxide such as magnesium hydroxide or calcium hydroxide.

The inorganic salt in the alkyl sulfate ester salt obtained by sulfation and neutralization by a known method is usually 0.1 to 2%, depending on the sulfation method.

In the present invention, as the alkyl sulfate ester salt having an inorganic salt content of 1% or less based on the surfactant equivalent, one obtained during sulfation and neutralization of alcohol may be used as it is, or one obtained after neutralization may be used. , those obtained by separating the inorganic salt without using an organic solvent can be used. For example, when reacting using gaseous SO, it is possible to freeze the inorganic salt produced after neutralization by lowering the excess SO3. Other purification methods for removing inorganic salts from the alkyl sulfate ester salt obtained by sulfation and neutralization may also be considered. As mentioned above, purification methods using organic solvents are not the object of the present invention.

The following method can be considered as a method for removing an inorganic salt from an aqueous alkyl sulfate salt solution.

(1) Cooling the aqueous solution of the alkyl sulfate salt to crystallize the alkyl sulfate salt. That is, in this case, since inorganic salts such as mirabilite and common salt migrate to the aqueous phase due to their solubility in water, the method involves solid-liquid separation of the crystallized alkyl sulfate ester salt.

(2) A method of desalting an aqueous solution of an alkyl sulfate salt by means such as ultrafiltration or diffusion dialysis.

It is possible to desalt by the above method.

When desalting is carried out using method (1), water is evaporated in the next drying step. If a product containing few inorganic salts is produced by the method (2) or sulfation/neutralization, a method such as regular spray drying is used. That is, the drying method varies depending on the water content of the aqueous alkyl sulfate salt solution or paste.

However, no matter which method (1) or (2) is used, it is difficult to remove unreacted oil, and it is necessary to evaporate and remove unreacted oil in the next step of vacuum drying. Further, in the vacuum drying process, in view of the characteristic bubbling of aqueous alkyl sulfate salt solutions, when performing vacuum drying, it is necessary to use a spray-dried powder or a paste separated by crystallization.

Furthermore, the temperature during drying is limited due to thermal decomposition or thermal hydrolysis of the alkyl sulfate salt. In other words, the decomposition of alkyl sulfate ester salts is usually slightly affected by the alkyl chain length, but if the temperature exceeds 100"C, decomposition occurs rapidly, so the temperature during drying should be kept below 100°C, preferably below 80°C. However, most of the unreacted oil content is unreacted higher alcohol as a raw material, and the vapor pressure during drying is low, making normal vacuum drying difficult.For example, lauryl sulfate ester salt In the case of , most of the unreacted oil is lauryl alcohol, and its vapor pressure at 80°C is Q,3 Torr, and at 90°C it is 0.65 Torr.However, the unreacted oil in the lauryl sulfate salt is The reaction oil content has a drying temperature of 8
It can be easily removed at 0° C. and a pressure of 10 Torr. That is,
They discovered that unreacted oil can be easily removed by evaporation at a pressure higher than the vapor pressure of unreacted oil, and completed the present invention.

Incidentally, during vacuum drying, a chelating agent such as EDTA, citric acid, phosphoric acid or a salt thereof, a PL+ buffering agent such as benzoic acid or baking soda, an antibacterial agent, etc. may be added.

〔Effect of the invention〕

The highly purified alkyl sulfate ester salt obtained by the method of the present invention, which contains a small amount of inorganic salt and unreacted oil, is light in color and has very little odor.

According to the method of the present invention, a highly pure alkyl sulfate salt is obtained as a powder, but it can also be used after being dissolved in water again.

Furthermore, the obtained highly purified alkyl sulfate ester salt has no deterioration in oral odor and can be used as a raw material for cosmetics, cosmetics, and toothpaste.

〔Example〕

Examples of the present invention will be shown below, but the present invention is not limited to these Examples.

Note that parts in the examples are parts by weight.

Example 1 An alcohol having an average carbon number of 12 was sulfated using a continuous thin film sulfation apparatus, and then neutralized using a caustic soda aqueous solution in a conventional manner to form an aqueous slurry of sodium alkyl sulfate (surfactant fraction: 29. 0%, mirabilite 0.25%, and unreacted oil 0.65%). After diluting 1 part of the obtained slurry with 4 parts of water, it was poured into a stirred tank type crystallizer with scraped walls and cooled from 35°C to 5°C to obtain needle-like or rod-like (approx. lll111
A crystal with a length of 1) was obtained. Crystallization begins at about 15°C, but is cooled to 5°C to increase yield. The aqueous slurry that has been cooled and crystallized is centrifuged to remove the crystalline portion (surfactant fraction: 69.0%, Glauber's salt: 0.03%, unreacted oil: 1.0%).
0%) and an aqueous phase.

The crystal part is dried using a vacuum stirring dryer (manufactured by earth machine metal side, internal volume 2
5.5 ff), and was dried at a pressure of 30 Torr and a temperature of the outer cylinder of the dryer at 70°C. After drying for 5 hours, the powder in the system was sampled and analyzed, and the surfactant content was 98.4%, Glauber's salt was 0.04%, unreacted oil was 0.86%, and water was 0.71%. . Further increase the pressure by 5
Torr was adjusted and vacuum drying was continued for 5 hours, and the surfactant content was 99.8%, mirabilite 0.04%, unreacted oil 0.05%, and moisture 0110%. There was no increase, indicating that there was no decomposition due to heat. After drying, the vacuum dryer was discharged to obtain highly pure sodium alkyl sulfate in a yield of 98%.

Example 2 An alcohol having an average carbon number of 14 was sulfated using a continuous thin-film sulfation apparatus using 5O30.95 mol per mol of alcohol, and then neutralized using a caustic soda aqueous solution in a conventional manner to obtain an alkyl A sodium sulfate ester aqueous slurry (surfactant fraction: 25.0%, Glauber's salt: 0.05%, unreacted oil: 0.8%) was obtained. The obtained slurry was introduced into a spray drying tower and spray-dried with a hot air temperature of 200°C and an exhaust air temperature of 90°C1 raw rice feed 2.0OOA/Hr. When analyzed, it was found that the surfactant content was 98.2% and the mirabilite content was 0.2%. 2%, unreacted oil 0.6%, and water 1.0%. Furthermore, this powder was dried in a vacuum stirring dryer (manufactured by Doyo Machine Metal 0@, internal volume 25.5
After drying for 5 hours at a pressure of 5 Torr and a temperature of the outer cylinder of the dryer of 80°C, it was discharged and analyzed, and the surfactant content was 99.0% and Glauber's salt was 0.2%. , unreacted oil content was 0.2%, water content was 0.6%, and highly pure sodium alkyl sulfate was obtained with a yield of 95%. or,
The mirabilite content did not increase, indicating that there was no decomposition due to heat.

Example 3 Lauryl alcohol having an average carbon number of 12 was sulfated with chlorosulfonic acid, and then neutralized with caustic soda to form an aqueous slurry of sodium alkyl sulfate (surfactant fraction 3).
0.0%, mirabilite 0.70%, common salt 0.50%, unreacted oil 0.80%). Add 1 part of the resulting slurry to 2 parts of water.
After diluting with 5 parts, it was passed through an Asahi Kasei ultrafiltration membrane (polyacrylonitrile type, molecular weight cut off 6000, membrane area 0.2 resistance). The mother liquor was circulated and the filtrate was continuously discharged. Analysis of the mother liquor after 10 hours revealed that the surfactant content was 12.6% and that mirabilite was 0.
．． 09%, salt 0.02%, and unreacted oil 0.37%. This mother liquor was spray-dried to obtain a powder containing 97.1% surface activity, 0.68% mirabilite, 0.15% common salt, 0.60% unreacted oil, and 1.5% water. Next, this powder was dried in a vacuum stirring dryer (manufactured by Doyo Machine Metal ■, internal volume 25cm).
．． After drying for 10 hours at a pressure of 30 Torr and a temperature of the outer barrel of the dryer of 70°C, the pressure was further adjusted to 5 Torr and dried for 5 hours.

When the obtained powder was analyzed, it was found that the surface activity ratio was 99.7.
%, mirabilite 0.70%, salt 0.13%, unreacted oil 0.
30%, water content 0.10%, and highly pure sodium alkyl sulfate was obtained with a yield of 90%.

In addition, mirabilite and common salt did not increase, indicating that there was no decomposition due to heat.

Claims (1)

[Claims] 1. An aqueous slurry or powder of an alkyl sulfate salt containing 1% or less of an inorganic salt based on the surfactant equivalent is dried under vacuum to remove unreacted oil by evaporation. , per surfactant equivalent, unreacted oil content 1% or less, inorganic salt 1%
A method for purifying an alkyl sulfate ester salt, which is characterized by the following purification. 2. The alkyl sulfate ester salt containing 1% or less of inorganic salt based on the surfactant equivalent is obtained during sulfation and neutralization of alcohol, or after neutralization without using an organic solvent. The method according to claim 1, which is obtained by separating an inorganic salt. 3. The method according to claim 1, wherein the inorganic salt is an alkali metal salt or an alkaline earth metal salt. 4. The method according to claim 1, wherein the alkyl sulfate salt has an average carbon number of 8 to 18.