JPH0753874B2 - Method for stabilizing palm kernel oil fatty acid alkyl ester - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to the stabilization of palm kernel oil fatty acid alkyl esters to produce colorless reaction products.

[Prior Art] Both palm oil and palm kernel oil are important natural starting materials for industrial production of oleochemical products. Such natural starting materials are usually converted prior to their chemical treatment to the triglycerides present, to the corresponding fatty acid esters with lower monohydric alcohols, in particular the corresponding methyl esters. The methyl ester or fatty acid methyl ester mixture is obtained directly by transesterifying the triglyceride with methanol or indirectly by decomposing the triglyceride into fatty acids and glycerin and then esterifying the fatty acid or fatty acid mixture to produce an alkyl ester. be able to.

Comparing the quality of the starting materials after storage by observing, inter alia, storage stability, oxidative stability, stabilizing effect, and their effect on the color of the reaction product, palm oil or its reaction product was found to be palm kernel oil. And that it behaves significantly better than its reaction product. Palm oil is much more stable to oxidation than palm kernel oil. The same applies to their methyl esters or methyl ester mixtures.
This may be due in part to the slightly higher iodine value of palm kernel oil than that of palm oil. Both palm kernel oil and coconut oil contain natural antioxidants, especially in the form of α-tocotrienol. Palm oil contains significantly more antioxidants (> 30ppm) than palm kernel oil (etch.
H. Behringer et al., Fette, Seifen, Anstric
h-mittel), 78, (1976), pp. 228-231).

Palm oil and coconut oil fatty acid methyl ester are typically stable to autoxidation for several months at room temperature, which is not the case for palm kernel oil fatty acid methyl ester. We were able to show that palm kernel oil and palm kernel oil fatty acid methyl ester absorb oxygen significantly faster than palm oil and palm oil fatty acid methyl ester. Corresponding studies have found that palm kernel oil alone absorbs 10 to 25 cultures of palm oil. In the accelerated aging test (in this test, the oxygen absorption amount of natural fats and oils and their derivatives is measured by a Warburg pressure gauge as an indicator of the oxidation behavior of natural fats and oils), before the apparent onset of oxygen absorption, the palm kernel is started. Oil induction time
Although it was on the order of 10 to 20 hours at 80 ℃, no measurable oxygen absorption occurred after 50 to 90 hours in the comparative test using coconut oil.

Due to this significant difference in the properties of palm kernel oil (and its derivatives) and palm oil (and its derivatives),
The extent to which each starting material and / or its reaction product is damaged during storage, shipping and / or processing is very different.

OBJECT OF THE INVENTION The object of the present invention is to improve the undesired instability of palm kernel oil fatty acid alkyl esters. But,
Basic experiments that supplement the natural antioxidant deficiency of palm kernel oil fatty acid alkyl esters by the addition of known antioxidants have surprisingly shown that sufficient reaction products are not readily available. It was

A measure of how suitable a natural fat is as a raw material is its lightness, whether it is a soap solution (obtained by alkali saponification of the corresponding fatty acid methyl ester or fatty acid methyl ester mixture) or fatty acid dimethanolamine (fatty acid methyl ester). Obtained by amination decomposition of the ester starting material). Brightness is an important parameter for the stability of the feedstock and the methyl esters produced from it.

Thus, more particularly the object of the present invention is to stabilize palm kernel oil fatty acid alkyl esters, in particular palm kernel oil fatty acid C ₁ -C ₄ alkyl esters, against undesired effects during storage in the presence of air. In the reaction (1), the stored oleochemical starting material gives a reaction product having a colorless property with no color deterioration. In the present invention, "colorless" is understood to indicate the color stability during each reaction step and corresponds to the known and acceptable color stability of normal quality coconut oil and its reaction products.
That is, it is an object of the present invention to produce palm kernel oil, especially palm kernel oil fatty acid alkyl ester, which is comparable in processing and processing to the corresponding coconut oil based material.

The tests carried out to this end have surprisingly found that the selection of specific antioxidants known per se gives the desired results. The use of other oxidative stabilizers, which in common chemistry can be considered to be exactly equivalent in strength, does not lead to the desired results, especially in the colorlessness of the reaction product of palm kernel oil fatty acid methyl ester.

[Configuration of the Invention] That is, the present invention is 3,5-di -tert.- consists butyl-4-hydroxytoluene (BHT), relates to a stabilizer of C ₁ -C ₄ alkyl esters of palm kernel oil fatty acids.

Palm kernel oil fatty acid C _{1 by} adding very small amount of BHT
-C ₄ alkyl esters a long period at room temperature (e.g. 2 months also) may stabilize (then alkanolamides or soaps are prepared may be stabilized with a degree as shown the desired good brightness) that found It was Further description of the desired brightness is given in the examples below.

Palm kernel oil obtained in varying qualities or impaired to varying degrees during shipping or storage can be stabilized according to the invention by adding small amounts of BHT to form starting materials according to suitable criteria. More importantly, the corresponding palm kernel oil fatty acid alkyl esters of different origin can be stabilized as well. In this connection, the stabilizing additives used according to the invention are added to the fatty acid methyl ester or the fatty acid methyl ester mixture immediately after preparation, or the insufficient fatty acid alkyl ester mixture is purified (preferably by repeated distillation). ) It is desirable to directly stabilize the distillate in addition to the previous.

When other known antioxidants are used instead of the stabilizers used according to the invention, the desired colorlessness of the reaction products of palm kernel oil fatty acid methyl esters is surprisingly not achieved. For example, the use of 2-tert.-butylhydroquinone, butylated hydroxyanisole or gallic acid propyl ester does not achieve the stabilizing effect required in the present invention. Hydrolysis products of tert.-butylhydroquinone, derivatives and propyl gallate and diethanolamide give high brightness. When using a relatively large amount of butylated hydroxyanisole (eg 500 ppm or more), the initial ken number is only high (undesirable),
After long-term storage, the color number of diethanolamide also becomes high, which is not desirable.

The stabilizers used according to the invention are generally effective at concentrations below 500 ppm, more particularly below 300 ppm, relative to the stabilized starting material. In the present invention, BHT is only 10-100 pp
m, more particularly at a concentration of only about 20-50 ppm gives completely satisfactory results. When using metal containers (eg steel tanks) for storage, add metal ion complexing agents (eg citric acid, ascorbic acid or ascorbic acid fatty alcohol esters, especially ascorbic acid palmitate) to the material to be stabilized. Is advantageous.

The palm kernel oil fatty acid alkyl esters to be stabilized according to the invention are obtained by subjecting palm kernel oils to lipolysis according to known methods and then esterifying the resulting fatty acid mixture with the corresponding lower alcohols or corresponding palm kernel oils. Obtained by direct transesterification with alcohol.
The alcohol component of the palm kernel oil fatty acid alkyl ester preferably comprises methanol. Typically, palm acid component of kernel oil fatty acid alkyl ester for further chemical processing, preferably composed cull only C ₁₂ -C ₁₈ fatty acids. For this purpose, so-called first-running fatty acids having 6 to 10 carbon atoms are usually separated from the free fatty acid mixture by fractional distillation in the case of direct esterification. If obtained by replacing the palm kernel oil fatty acid alkyl esters, unwanted esters of C ₆ -C ₁₂ fatty acids are removed from the ester mixture by distillation after transesterification. In principle, this method can of course also be applied to ester mixtures obtained from palm kernel oil fatty acid mixtures by direct esterification without prior fractionation of the fatty acids. That is, in a special aspect, the present invention provides
In particular obtained by esterifying palm kernel oil fatty acids having 12 to 18 carbon atoms with methanol or by transesterifying palm kernel oil with methanol and, if desired, separating C ₁₂ -C ₁₈ fatty acid esters Palm kernel oil fatty acid methyl ester, especially a mixture of C ₁₂ -C ₁₈ fatty acid methyl ester, and di-to prepare a colorless reaction product.
3,5-tert.-butyl-4-hydroxytoluene and /
Alternatively, it relates to a composition containing 500 ppm or less of tocopherol.

Examples In the following examples, the following properties are used as a measure of the stability of palm kernel oil fatty acid esters: peroxide value (PO
Value), carbonyl value (CO value), saponification value brightness (SCV) and diethanolamide brightness (DEACV). These properties were measured as follows.

Peroxide value (PO value) PO value was measured by Wheeler's method (DGF-Einheits methode
n) C-VI 6a (84), Wissen Shaftricher Ferlaks Gezelshaft Mb Her
schaftliche Verlagsgesellchaft mbH), Stuttgart (1950-1984)). In this method, an ester sample is reacted with potassium iodide in a mixture of chloroform and glacial acetic acid at room temperature and the iodine produced by the peroxide present is titrated with sodium thiosulfate (indicator: starch solution). PO value (mVal O ₂ / kg) formula: [In the formula, a = sodium thiosulfate solution consumption (ml), N
= Normality of sodium thiosulfate solution, E = sample weight (g). ] To calculate.

Carbonyl number (CO value) CO value was also measured by DGF-Ein Heights Methode (see C-V18 (58)). In this method, an ester sample is heated to reflux temperature with a 0.5N aqueous alcoholic hydroxylamine hydrochloride solution for a relatively long period of time. The free hydrogen chloride in the cooled mixture is then titrated with 0.5N alcoholic sodium hydroxide solution (indicator: pyridine / bromophenol blue). Formula for CO value: [In the formula, a = 0.5N sodium hydroxide solution consumption (ml),
E = weight of sample (g). ] To calculate.

Saponification Brightness (SCV) To measure SCV, 10 g of fatty acid ester is heated to reflux temperature for 1 hour with 100 ml of 1N methanolic potassium hydroxide solution. The SCV of the cooled sample was measured using a Lovibond colorimeter (L
ovibond Tintometer) 5 1/4 "-absorbent tube. The red and yellow brightness of good quality esters is <1.0 and <5 respectively.

Diethanolamide Lightness (DEACV) To measure DEACV, equivalent amounts of fatty acid ester and diethanolamine are reacted with each other at 85 ° C. for 5 hours in the presence of 1% by weight of total sodium methyl. The liberated methanol is distilled off continuously. The DEACV of the cooled reaction product is measured in a 5 1/4 "-absorption tube on a Lovibond colorimeter. The diethanolamide brightness is <1.5 red and <15 (gardner brightness <3. Equivalent) can be considered sufficient.

In addition, in the examples, examples in which no stabilizer is added and examples in which a stabilizer other than BHT are used are comparative examples.

Examples 1 and 2 Palm kernel oil was hydrolyzed in an autoclave at 220 ° C. After washing away the glycerin, most of the C ₆ -C ₁₀ fatty acids were distilled off from the resulting fatty acid mixture, substantially eliminating C ₁₂ -C
_A mixture of ₁₈ fatty acids was left.

The obtained C ₁₂ -C ₁₈ palm kernel oil fatty acid mixture was treated under normal pressure with
In an autoclave at 0 ° C for 2 hours, methanol (weight ratio
1: 1). Methanol and water of reaction were distilled from the resulting mixture. By repeating the reaction with excess methanol and distillation twice, a mixture of C ₁₂ -C ₁₈ palm kernel oil fatty acid methyl ester having the following properties was obtained: acid number 0.3; saponification number about 238; iodine. Value 18.

PO, CO, SCV and DEA of freshly distilled ester
CV was measured. To the ester sample, 10 ppm of 3,5-di-tert.-butyl-4-hydroxytoluene (BHT; commercial product) or 50 ppm of α-tocopherol (DL; 99%; commercial product) was added as a stabilizer. These samples and samples without added stabilizers (about 500 ml each) were stored in the dark in 500 ml wide mouth flasks with loose screw closures at about 20 ° C. for 6 weeks in the dark. Then, the value was measured again.

In Example 2, the C ₁₂ -C ₁₈ palm kernel oil fatty acid methyl esters prepared by the method and stabilized again BHT10ppm. The results are shown in Table 1.

Example 3 C ₁₂ -C ₁₈ palm kernel oil fatty acid methyl ester (PO value 40, CO value 0.6) stored for 6 weeks or longer was distilled twice. The total residue was 3.7% by weight. The acid value of the distillate was 0.3, the saponification value was 241 and the iodine value was 14.

PO, CO, SCV and DEA of freshly distilled ester
CV was measured. 3,5-di-tert.-butyl-4-hydroxytoluene (BHT; commercial product) 10 ppm and 50 ppm, α-tocopherol (99%; commercial product) 50 ppm and soybean oil tocopherol mixture (γ-tocopherol 50% by weight as main component) % Content; commercial product) 50 ppm as substance to be used according to the invention, as well as 2-tert.-butylhydroquinone (TBH
Q; commercial product) 50 ppm and 2-tert.-butylhydroxyanisole (BHA; commercial product) 50 ppm were added to the ester samples as control substances. These samples and samples without stabilizers (each about 500 ml) were stored in a 500 ml wide mouth flask with loose screw closure at about 20 ° C. for 4 weeks in the dark. Then, the value was measured again. Second result
Shown in the table.

As can be seen from Table 2, even palm kernel oil fatty acid methyl esters already impaired by oxidation can be effectively stabilized by the substance to be used according to the invention after redistillation, even after long-term storage, Colored reaction products can be obtained from stabilized esters rather than from unstabilized esters.

Example 4 Stabilized and unstabilized samples of the C ₁₂ -C ₁₈ palm kernel oil fatty acid methyl ester described in Example 1 and as a control.
A sample of C ₁₂ -C ₁₈ coconut oil fatty acid methyl ester (acid value 0.3; saponification value 240; iodine value 11) was subjected to an accelerated aging test using a Barbulg pressure gauge (Laboratoriumstechnik fr Biochemi.
ker), edited by B. Keil and Z. Solmova, by Akademische Feleraks Gezelschaft Gäst & Portich (Akademis)
che Verlagsgesellschaft Geest & Portig) KG, Leipzig, 1965, pp. 247-249).

In this test, oxygen was applied to the sample (3 g) at 80 ° C., and the oxygen absorption amount was continuously measured. The following samples were tested: A) Palm kernel oil fatty acid methyl ester (without stabilizer) B) Palm kernel oil fatty acid methyl ester + BHT10ppm, C) Palm kernel oil fatty acid methyl ester + BHT50ppm, D) Palm oil fatty acid methyl ester (The stabilizer is not included.) The results are shown in FIG. It can be seen that addition of 50 ppm of BHT sufficiently stabilizes palm kernel oil fatty acid methyl ester to the extent that palm oil fatty acid methyl ester is comparable.

[Brief description of drawings]

 FIG. 1 is a graph showing the results of Example 4.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Horst Baumann Federal Republic of Germany 5653 Reichlingen, Vogelbalte No. 17 (72) Inventor Hartwich Schutt Germany 4000 Deutzseldorf Fu-Benrath, Haydn Schuttraasse 50 (72) ) Inventor Harald Ballis, Germany Federal Republic of Germany 4000 Deutzseldorf 13, Einschtäinschttraasse 4 (56) References JP-A-55-69688 (JP, A) JP-A-53-73206 (JP, A) Special Kai 55-54400 (JP, A) Oil Chemistry Vol. 28, No. 10 (1979), P. 747-759

Claims (4)

[Claims] _1. Stabilizer of a C ₁ -C ₄ alkyl ester of palm kernel oil fatty acid consisting of 3,5-di-tert.-butyl-4-hydroxytoluene. 2. The stabilizer according to claim 1, which is used at a concentration of 500 ppm or less. 3. The stabilizer according to claim 1, wherein the alkyl ester is a methyl ester. 4. The stabilizer according to claim 1, wherein the alkyl ester is a mixture of methyl ester of palm kernel oil fatty acid having 12 to 18 carbon atoms.