JP2006176608A - Method for producing fatty acids - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a rapid filtration rate while maintaining separation efficiency in a method for producing target fatty acids by naturally fractionating the fatty acids, and filtering the product. <P>SOLUTION: The method for producing the saturated fatty acids and the unsaturated fatty acids by melting raw material fatty acids, cooling the melted fatty acids to precipitate crystals, and filtering the precipitates uses a surface filtration filter medium having an aperture corresponding to the particle diameters of accumulated 5-60 mass% from the small size side based on a volume particle size distribution of the precipitated crystals as the filter medium at the filtration operation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for efficiently separating saturated fatty acids and unsaturated fatty acids from a mixture of fatty acids by natural fractionation.

  Fatty acids are widely used as intermediate raw materials for foods such as monoglycerides and diglycerides, additives for various other industrial products, and intermediate raw materials. Such fatty acids are generally produced by hydrolyzing vegetable oils such as rapeseed oil and soybean oil and animal oils such as beef tallow by a high pressure method or an enzymatic decomposition method. However, the fatty acids produced by simply hydrolyzing animal and vegetable oils as described above are not necessarily suitable as industrial raw materials with the same fatty acid composition. That is, it is necessary to separate into unsaturated fatty acids and saturated fatty acids depending on the purpose of use.

  Therefore, adjustment of the fatty acid composition is necessary to obtain the desired fatty acid. In general, solvent fractionation and wetting agent fractionation methods are used for the separation of fatty acids, but these methods have high separation efficiency (yield), but are not limited to equipment investment, recovery of solvent and wetting agent aqueous solution, etc. It has the problem of running costs. On the other hand, the natural fractionation method (solvent-free method) without using a solvent is an inexpensive fractionation method, and an emulsifier (crystal adjuster) such as polyglycerin fatty acid ester is also used to reduce the filtration rate, which has been regarded as a problem. ) Is used (see Patent Document 1).

  In order to efficiently separate the particles to be filtered, the filter medium in the filtration step generally determines the pore size by determining the particle size of the particles to be filtered. In general, in order to achieve the purpose of trapping solids using a filter medium, the pore diameter of the pores of the filter medium is smaller than the particle diameter of the solid to be separated, or the particles are cross-linked onto the pores and the size of the pores. Is required to be narrowed (see Non-Patent Document 1). Further, the filter medium is roughly classified into a surface filter medium and an internal filter medium. In general, in the surface filtration, the separated particle diameter is inevitably substantially equal to the pore diameter (see Non-Patent Document 2), and the pore diameter of the surface filter material is the object to be filtered. Although it is necessary to make it smaller than the minimum particle diameter of particle | grains, when a hole diameter is too small, filtration resistance will become large and filtration efficiency will fall. Moreover, in internal filtration (depth filtration), although it is possible to make the pore diameter larger than the particle diameter of the filtration target particles (see Non-Patent Document 2), by accumulating the filtration target particles inside the filter medium, There is a problem that the filtration efficiency decreases as the filtration proceeds, and the portion accumulated in the filter medium is wasted.

Japanese Patent Laid-Open No. 11-106782 Theory and Calculation of Chemical Equipment (2nd edition) Sangyo Tosho Co., Ltd. Satoshi Ishikawa et al., “Analysis of Particle Separation Mechanism of Metal Nonwoven Filter Media Based on Stochastic Model”, Chemical Engineering, 2004, Vol. 30, No. 5, p.604-

  As described above, the filtering step has a theoretical limit, and thus has been performed with a certain degree of compromise in terms of efficiency. Moreover, even in the technique using a crystal modifier in the process of naturally separating saturated fatty acid and unsaturated fatty acid from a mixture of fatty acids, the above-mentioned compromise has to be set to low efficiency conditions. Therefore, in such a case, if further efficiency of filtration can be achieved, there are great advantages in terms of stable production and cost.

  Accordingly, an object of the present invention is to achieve a faster filtration rate while maintaining the separation efficiency in a method for producing a desired fatty acid by naturally separating and filtering the fatty acid.

  As a result of examining the above problems, the present inventor has found that when filtering the surface of fatty acid crystals, the pore size of the filter medium is increased to a level that cannot be conventionally adopted compared to the particle size of the filtration target. It has been found that there is no filtration leakage within the range, whereby the filtration rate can be improved while maintaining the filtration efficiency.

  That is, the present invention is a method for producing saturated fatty acids and unsaturated fatty acids by melting raw material fatty acids and then cooling them to cool and filtering them, and depositing them as filter media in the filtration operation The present invention provides a method for producing saturated fatty acids and unsaturated fatty acids using a surface filtration medium having a pore size corresponding to a cumulative particle size of 5 to 60% by mass with respect to the volume particle size distribution of crystals.

  According to the present invention, in the separation of saturated fatty acids and unsaturated fatty acids by the natural separation method of fatty acids, the separation efficiency after crystal precipitation can be increased and the filtration rate can be increased. Shortening can be achieved.

[Definition]
In the present invention, the “natural fractionation method” means that the raw fatty acids to be treated do not contain the amount of water to be phase-separated and do not use a solvent, and are cooled with stirring as necessary to precipitate solid components. After that, the solid-liquid separation is performed. “Surface filtration” refers to filtration that captures solid particles on the surface of the filter medium. “Saturated fatty acid ratio” refers to a value measured by gas chromatography, and “transparent melting point” refers to a value measured by a standard oil analysis test method (2.2.4.1-1996).

[Raw fatty acids]
In the present invention, the raw fatty acids subject to separation of saturated fatty acids and unsaturated fatty acids are produced by hydrolyzing vegetable oils such as rapeseed oil and soybean oil and animal oils such as beef tallow by a high pressure method or an enzymatic decomposition method. . The method of the present invention is more effective when the amount of fatty acid in the raw fatty acids is 50% by mass or more, particularly 85% by mass or more, and partial glycerides may be present. Further, as the raw material fatty acids, palmitic acid in fatty acid composition, the ratio of saturated fatty acids such as stearic acid (C ₁₂ ~C ₂₂₎ is 5 to 60 wt%, in particular those of the 8-50 wt% preferred. For example, fatty acids derived from vegetable oils such as soybean oil and palm oil can be used.

(Crystal modifier)
The natural fractionation method in the present invention is preferably performed by adding a crystal modifier to the raw fatty acids before the precipitation of crystals. The crystal modifier is not particularly limited, but is preferably a polyhydric alcohol fatty acid ester, which is a food additive, sucrose fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, organic acid monoglyceride, glycerin fatty acid ester, polyglycerin fatty acid ester Among them, polyglycerol fatty acid ester is preferable. Particularly preferred polyglycerin fatty acid esters in the present invention include those having a transparent melting point in the range represented by the following formula (1).

                  0.38x + 13≤y≤0.54x + 44 (1)

[X: raw fatty acids fatty saturated fatty acids in the composition (C ₁₂ -C ₂₂₎ Ratio (wt%)
y: transparent melting point of polyglycerol fatty acid ester (° C.)]

  A more preferable range of the transparent melting point (y) is 0.38x + 19 ≦ y ≦ 0.54x + 40, and a particularly preferable range is 0.38x + 28 ≦ y ≦ 0.54x + 36. The transparent melting point (y) of the polyglycerol fatty acid ester is preferably higher than the transparent melting point of the raw fatty acids.

  In addition, the average degree of polymerization of glycerin in the polyglycerin fatty acid ester is preferably 5 or more, particularly 8 to 30 in terms of obtaining a crystallized state that is easy to filter. The fatty acid in the polyglycerol fatty acid ester is preferably composed of a saturated or unsaturated fatty acid having 10 to 22 carbon atoms, particularly 12 to 18 carbon atoms, from the viewpoint of adjusting the transparent melting point of the polyglycerol fatty acid ester. Although the said fatty acid may be comprised with a single fatty acid, what is comprised with the mixed fatty acid is preferable from the point of obtaining the crystalline state especially easy to filter. As the polyglycerol fatty acid ester, a commercially available product can be used, or it may be synthesized by an esterification reaction between polyglycerol and a fatty acid. In the esterification reaction of polyglycerin and fatty acid, an alkali catalyst such as sodium hydroxide is added to these mixtures, and esterification is performed directly at 200 to 260 ° C. under an inert gas stream such as nitrogen, using an enzyme. Any method such as a method may be used.

  Two or more kinds of crystal modifiers may be used in combination, and the addition amount is preferably 0.001 to 5% by weight, particularly about 0.05 to 1% by weight, based on the raw fatty acids.

(Temperature adjustment)
The crystal modifier is preferably mixed and dissolved at a temperature higher than the transparent melting point of the polyglycerol fatty acid ester so that it can be completely dissolved in the raw fatty acids. The cooling time and cooling temperature after this mixing and dissolution vary depending on the amount of raw material, cooling capacity, etc., and may be appropriately selected depending on the composition of raw fatty acids. For example, in the case of soybean fatty acid, it takes 1 to 30 hours, preferably about 3 to 20 hours up to -3 ° C. In the case of rapeseed fatty acid, it is 1 to 30 hours, preferably 3 to 20 hours up to 2 ° C. The cooling may be a batch process or a continuous process. Thereby, a saturated fatty acid is obtained as a solid part, and an unsaturated fatty acid is obtained as a liquid part, respectively. The cooling operation is preferably performed under conditions such that the average grain size of the precipitated crystals is 100 μm or more, particularly 150 μm or more.

(Crystal grain size measurement)
The method for measuring the particle size of crystals in the solid part is not particularly limited, and examples thereof include microscopy. Microscopy is a method of measuring the size and number of particles, but the size can be measured by a constant direction diameter (interval when two parallel lines in an arbitrary constant direction are circumscribed on each particle). (Theory and calculation of chemical machinery, 2nd edition, by Saburo Kamei, p.464). In addition, the volume-based particle size distribution can be easily calculated by considering it as a spherical particle having a constant direction diameter as a representative length, and is further substantially equal to the mass-based particle size distribution by regarding the specific gravity of the particle as constant. It will be a thing.

[Surface filtration media]
In the present invention, a surface filtration method is employed as a solid-liquid separation method. Although it does not specifically limit as a filter material of a surface filtration system, A filter cloth, a woven wire mesh, a notch wire, a punching metal, etc. are mentioned. As the surface filtration media, those having a pore size corresponding to a particle size of 5 to 60% by mass cumulatively from the small side with respect to the volume particle size distribution of the precipitated crystals are used from the viewpoint of compatibility between separation efficiency and filtration rate. Preferably, those having a pore size corresponding to a particle size of 10 to 50% by mass, more preferably 10 to 40% by mass are used. The thickness of the filter medium is preferably 1.5 mm or less, particularly 1 mm or less from the viewpoint of reducing internal filtration resistance, and preferably 0.1 mm or more from the viewpoint of strength.

  Here, the pore diameter of the filter medium can be determined by the bubble point method (JIS K 3832). The bubble point method is a widely used method for measuring the maximum pore size of filter media. That is, a liquid (water or alcohol) that has a known density and surface tension and that wets the filter medium well is absorbed in the pores of the filter medium in advance, and air pressure is applied from the back side of the film to observe the generation of bubbles on the film surface. Measure the minimum pressure (bubble point). The pore diameter (d) can be estimated from the relational expression between the surface tension (γ) of the liquid and the bubble point shown below.

d = (4γcosθ) / ΔP
[D [m]: pore diameter, θ: contact angle between membrane material and solvent (0 ° in the case of completely wetted solvent (isopropyl alcohol)), γ [N / m]: surface tension of solvent, ΔP [Pa]: (Bubble point pressure)

  In general, in the surface filtration method, the separated particle size is inevitably substantially equal to the pore size of the filter medium. Therefore, in order to avoid leakage during filtration, a pore size smaller than the minimum particle size distribution size of the precipitated particles is usually employed. On the other hand, in the present invention, there is no leakage during filtration despite the use of a filter medium having a large pore size corresponding to a cumulative 5 to 60% by mass from the small side with respect to the volume particle size distribution of the precipitated particles. The filtration rate can be improved while maintaining the above.

  In the following examples, the fatty acid composition and the saturated fatty acid ratio are measured by gas chromatography, the transparent melting point of the fatty acid is measured by the standard oil analysis test method (2.2.4.1-1996), and the pore size of the filter medium is the bubble point. Measured by the method.

[Preparation of raw fatty acids]
The fats and oils shown in Table 1 were hydrolyzed by a conventional method to prepare raw fatty acids. Table 1 shows the fatty acid composition, saturated fatty acid ratio (% by mass), and fatty acid concentration of the fatty acid used.

[Fatty acid fractionation]
To the crystallization tank, 30 kg of raw fatty acid shown in Table 1 and 45 g of polyglycerin fatty acid ester (decaglycerin ester) shown in Table 2 are added and dissolved uniformly at 80 ° C. Next, the mixture was cooled to 30 ° C. for 1 hour while being stirred at 30 rpm, then cooled to −3 ° C. at a cooling rate of 3 ° C./h, and aged for 3 hours. Then, it was pumped to the tank before filtration. The crystal grain size distribution was measured by taking a slurry from a pre-filtration tank and microscopically. The results are shown in Table 3. The slurry is extracted from the pre-filtration tank, and filtered with 0.03 MPa using various filter cloths shown in Table 4 (filtration area 39 cm ² ) to obtain a liquid part (unsaturated fatty acid) and a solid part (crystal part; saturated fatty acid). Sorted into Results of measuring filtration time, liquid part yield and fatty acid composition of liquid part and solid part (ratio of C _{12 to} C ₂₂ saturated fatty acid) necessary to obtain 500 mL of filtrate, and observing the state of the filtrate Table 4 shows.

  As is clear from Table 4, when the filtering operation was performed using a filter medium having a pore size corresponding to a particle size of 5 to 60% by mass from the small side with respect to the volume particle size distribution of the crystals, the filtration time was fast, Since the liquid part quality does not change, it can be seen that saturated fatty acids and unsaturated fatty acids can be naturally separated in a short time and in high yield. On the other hand, when a filter medium having a pore diameter corresponding to a particle size of less than 5% by mass is used from the small side with respect to the volume particle size distribution of the crystal, the filtration rate is slow, which is not preferable, and the accumulation exceeds 60% by weight. In this case, the quality of the liquid part is deteriorated due to crystal filtration leakage, which is not preferable.

Claims (3)

  This is a method for producing saturated fatty acids and unsaturated fatty acids by precipitating crystals by melting the raw fatty acids and then cooling them, and filtering them to obtain a volume particle size distribution of the crystals to be precipitated as filter media in the filtration operation. On the other hand, a method for producing saturated fatty acids and unsaturated fatty acids using a surface filter medium having a pore size corresponding to a particle size of 5 to 60% by mass from the small side.   2. The production method according to claim 1, wherein a polyglycerin fatty acid ester is added and mixed before the crystals are precipitated.   The method according to claim 1 or 2, wherein the average particle size of the crystals is 100 µm or more.