JPS5951252B2 - Lecithin purification method - Google Patents

Description

[Detailed description of the invention] The present invention relates to dispersion of magnetic powder for, for example, magnetic recording media.

The present invention relates to a lecithin purification method suitable for use in obtaining lecithin used as a pharmaceutical agent. Previously, in Japanese Patent Application No. 73424/1984, the present applicant improved the dispersibility of magnetic powder by using high-purity lecithin as a pretreatment for the magnetic powder, thereby increasing the residual magnetic flux density. The present invention has provided a magnetic recording medium and a method for manufacturing the same, which can obtain a magnetic recording medium with improved Br, squareness ratio Rs, and packing density ρ, as well as excellent surface properties and wear resistance.

A method of pre-treating magnetic powder with lecithin has been proposed before the above application, but the lecithin used in this case is commercially available lecithin, that is, crude lecithin, or commercially available lecithin is washed with acetone to obtain crude lecithin. Lecithin from which neutral fats and fatty acids have been removed (hereinafter referred to as acetone-purified lecithin) is used, but the dispersion effect of magnetic powder was insufficient no matter which method was used.

As a result of various experimental studies, the inventors of the above-mentioned application found that commercially available crude lecithin and acetone-purified lecithin actually have low purity, with crude lecithin having a purity of about 10% or less; Even lecithin is at most about 20% or less, and since these lecithins contain many impurities, it is difficult for this lecithin to completely coat the surface of the magnetic powder as a monomolecular layer, and the surface active ability of lecithin is fully exerted. It was confirmed that the dispersion effect was insufficient due to the inability to do so. That is, since crude lecithin or acetone-purified lecithin contains many impurities, it was thought that these impurities inhibited the adsorption of lecithin molecules to the surface of the magnetic powder. Therefore, in the invention of the above application, based on the above-mentioned considerations, lecithin with particularly high purity, i.e., with a purity of 30% or more, preferably 50% or more, more preferably 9
A material with a purity close to 100% of 5% or more is used, and by doing so, it has been possible to obtain a magnetic recording medium with excellent magnetic and mechanical properties as described above. As described above, magnetic recording media with excellent characteristics can be obtained by using high-purity lecithin as a pretreatment for magnetic powder in magnetic recording media. Cadmium chloride is used in the purification process to produce lecithin, and since cadmium chloride is a pollutant, it is not desirable to use such a lecithin purification method industrially.

The present invention provides a novel lecithin purification method that enables industrial purification of highly pure lecithin without causing pollution. First, in order to facilitate understanding of the present invention, a conventional method that can be applied as a normal lecithin purification method will be explained.

In this case, commercially available lecithin, that is, crude lecithin such as egg lecithin or soybean lecithin, is washed with acetone to remove neutral fats and fatty acids, and a precipitate consisting of phospholipids and proteins is obtained, which is dried.

Next, the lucitin component was extracted from this precipitate with 95% ethanol (the remainder being water). That is, lecithin is dissolved in a 95% ethanol aqueous solution and precipitated impurities such as protein and cephalin are removed. Then, a 50% cadmium chloride solution was added dropwise to the ethanol in which this lecithin was dissolved to purify a white colloidal precipitate consisting of a double salt of lecithin and cadmium chloride, which was then washed with acetone.
Filter and vacuum dry at 40°C or lower (be careful when using cadmium chloride in this way). Next, this double salt is placed in a liquid separation load and dissolved in chloroform. Add 30% ethanol to this, shake, and then let stand.
In this way, cadmium chloride CdCl is added to ethanol. dissolves, leaving lecithin in chloroform, which is
Since its specific gravity is lower than that of ethanol, when it is allowed to stand still, it forms two layers, ethanol in the upper layer and chloroform in the lower layer. Then, take out this lower layer of chloroform from the lower end of the separation load, add ethanol to this chloroform solution again, and repeat the same operation three times in total. Next, the chloroform solution in which lecithin remains and impurities have been removed is evaporated to dryness using a rotary evaporator.
In this way, transparent yellow highly purified lecithin is obtained. Although high purity lecithin can be obtained by the purification method as described above, this method causes pollution problems due to the use of cadmium chloride as described above.

The present invention aims to provide a novel lecithin purification method that avoids the use of such a cadmium chloride solution and avoids pollution problems.

That is, in the present invention, commercially available crude lecithin, such as egg lecithin or soybean lecithin, is washed with acetone, extracted with water-free 100% ethanol or a lower alcohol such as methanol, and zinc chloride is added thereto. A precipitate is obtained from which lecithin is separated.

Next, examples of the present invention will be given.

Example: 700g of Ajinomoto egg lecithin (crude lecithin), 3
Neutral fats and fatty acids are removed by washing with acetone (1) to obtain a precipitate consisting of phospholipids and proteins, which is then dried.

The yield of the precipitate at this time, that is, acetone-purified lecithin, was 4
It was 00gr. Next, the lecithin component is extracted from this precipitate with 1000 cc of 100% ethanol. That is,
Dissolve lecithin in ethanol and remove precipitated impurities such as protein and kephalin. The extract concentration in the ethanol solution at this time was 5.5 gr/100 cc. Then, add 60% zinc chloride (ZnCl) to ethanol in which this lecithin was dissolved. The solution is added dropwise to form a white colloidal precipitate consisting of a double salt of lecithin and zinc chloride, which is washed with acetone, filtered, and vacuum dried at 40°C or lower. Next, put this double salt into a separation load and add 200
Dissolve in cc of chloroform (CHCl3). Add 200cc of 30% ethanol to this and shake, then
Leave it still. In this way, ZnCl2 dissolves in ethanol and lecithin remains in chloroform. As mentioned above, this ethanol has a lower specific gravity than chloroform, so when it is allowed to stand still, two layers are formed: ethanol in the upper layer and chloroform in the lower layer. Then, take out the lower layer of chloroform from the lower end of the separation load, add ethanol to the chloroform solution again, and repeat the same operation three times. To complete the reaction, remove a portion of this ethanol solution and
Add silver nitrate AgNO to this. It was confirmed by dropping a white precipitate of silver chloride (AgCl). Next, the chloroform solution in which lecithin remains and impurities have been removed is evaporated to dryness using a rotary evaporator.
In this way, 35 gr of transparent yellow high purity lecithin was obtained in the same manner as described above. The purity of lecithin obtained through this purification was confirmed to be 94.9%. In the above example, the lecithin component was extracted from the acetone-purified lecithin with 100% ethanol, but when using pure ethanol like this, for example, as in the case of the conventional method described above, It is advantageous in its extract purity compared to extraction with 95% ethanol.

Table 1 shows the extract and extract purity when the ethanol concentration was 95% and 100%. Next, we will discuss the precipitation state when the Zncl2 solution concentration is changed in the above-mentioned 100% ethanol extraction. As a suspension, the precipitate becomes viscous and difficult to separate.On the other hand, when the concentration is increased, preferably from 30% to 60%, the precipitate becomes white and clearly forms, making it difficult to separate. It was confirmed that cleaning becomes easier.

Further, Table 2 shows the purity and yield for each Zncl2 concentration with respect to the Zncl2 aqueous solution concentration for the samples (Samples Nos. 1, 2, and 3). Note that the yield here is a relative value with the maximum value of pure lecithin produced as 1.

As is clear from Table 2, if the Zncl2 aqueous solution concentration is 30% or more, there is no significant difference in purity or yield, but industrially, the Zncl2 aqueous solution concentration is The concentration is preferably high, and more preferably 50% or more.

Next, since the concentration of the ethanol extract when purifying the double salt by adding the ZnCl2 aqueous solution is thought to affect the purity of lecithin, this will be discussed.

As shown in the figure, it can be seen that the purity with respect to the concentration of the ethanol extract decreases as the concentration increases. This is thought to be due to co-precipitation of impurities, and in order to obtain lecithin of sufficiently high purity, it seems appropriate to keep the ethanol concentration as high as possible. In other words, it is considered desirable to use ethanol with a high concentration of 95% or more, which provides an extract concentration of 5 to 10%. However, this concentration is selected depending on the intended use of the purified lecithin. The experimental conditions here are that the 100% ethanol extract was concentrated or diluted to adjust its concentration, and then purified by precipitation with a 60% ZnCl2 aqueous solution. In the above example, the decomposition of a double salt consisting of lecithin-Zncl2 and the extraction of lecithin were performed using a 30% ethanol solution-chloroform system.
Taloloform is a type 1 organic solvent and is harmful, so if this is to be avoided, cyclohexane or xylene can be used in place of chloroform.

In this case, 60%
After dropping the ZnCl2 solution and drying the resulting precipitate,
Dissolved in cyclohexane (approximately 20%) during the separation loading,
Table 3 shows the purity obtained by adding ethanol solutions of various concentrations to separate the layers and collecting the cyclohexane layer. Purity is affected by the number of extractions, and naturally, the greater the number of extractions, the more ZnCl in the double salt.

Although the removal rate and purity are improved, if the amount is less than 30% ethanol or only water, it is difficult to separate from the beginning and emulsification occurs. And sample No. of Table 3. In cases 4 and 5, the number of extractions could be up to three times. In this case, its purity is about 90%
He confirmed that it will be secured soon. Further, Table 4 shows the results when xylene was used instead of chloroform. This xylene is also relatively easy to emulsify, and in particular, at concentrations other than those in Table 4, such as 30% ethanol or less, severe emulsification occurs from the first time, making it impossible to separate it.

However, as is clear from Tables 3 and 4 above, it was found that cyclohexane or xylene could be used in place of chloroform. Furthermore, it has been found that even if methanol is used as the extraction alcohol in this case, almost the same effect as in the case of ethanol can be obtained.

For example, cyclohexane-2 with 100% methanol
It was confirmed that lecithin with a purity of 89% was obtained in a single extraction. In addition, ZnCl. The double salt of lecithin is harmless, and the purity of lecithin at this stage is as high as 86.4%.
Since the impurity in this is ZnCl, which has no surface-active effect, in some cases lecithin in this state can be used, for example, as a dispersant for pre-treatment of magnetic powder for magnetic tape. As an extraction solvent for acetone-purified lecithin, in addition to ethanol, methanol, which is cheaper than ethanol, can also be used. For example, methanol ( MeOH/Gr)1
500 cc of 00% was stirred for 3 hours, extracted, and then filtered and separated.

This extract had an extract concentration of 7.8 gr/100 cc and an extraction purity of 64.2%. Incidentally, in the case of ethanol, the extract concentration was 5.5 gr/100 cc and the extract purity was 76%. Then, ZnCl was added to this methanol extraction solution. Table 5 shows the results of extracting the precipitate produced by dropping the solution with chloroform-30% ethanol. As is clear from this table, the purity is lower than when using ethanol, but this is because ZnC
l.

This means that a considerable amount of impurities are also co-precipitated during the purification of the precipitate. However, depending on the purpose of use of lecithin, it shows a sufficiently higher purity than commercially available lecithin, so it is practical depending on the purpose of use.

[Brief explanation of drawings]

The figure is a measurement curve diagram of purity versus ethanol extraction concentration, which is used to explain the present invention.

Claims (1)

[Claims] 1. A method for purifying lecithin, which comprises washing crude lecithin with acetone and separating lecithin from a precipitate obtained by adding zinc chloride to the extract with lower alcohol.