PROCESS FOR THE PREPARATION OF PARTIAL ESTERS WITH EMULSIFYING EFFECT

Abstract: Partial esters of glycerine condensates with carboxylic acids of the type present in natural triglycerides are conventionally prepared by heating a mixture of a glycerine condensate or glycerine condensates and one or more fatty acids or a natural fat to a high temperature in the presence of a basic catalyst, and this reacton proceeds without formation of undesired by-products when the reaction is performed in tertiary butyl alcohol as solvent. The partial esters are used as emulsifiers within the food and stimulant industry. Particularly a glycerine condensate and triglyceride are used as starting materials in a weight ratio of about 20 - 70:80 - 30, using preferably 0.1 -0.5 liters of tertiary butyl alcohol per 450 g of combined starting materials.

Description: PROCESS FOR THE PREPARATION OF PARTIAL ESTERS WITH EMULSIFYING EFFECT . The present invention relates to a process for the preparation of partial esters of glycerine condensates with carboxylic acids of the type present in natural triglycerides , that is , fatty acids of 4 - 26 carbon atoms , in the following designated "C 4 _ 26 fatty acids" . Partial esters of the above-mentioned type which, in addition to the esterified hydroxy groups, contain free hydroxy groups , are of great commercial importance as emulsifiers in the food and stimu¬ lant industry, for example for the preparation of baking mixes , margarine, minarine, mayonnaise and salads , and as emulsifiers for use in technical emulsions or emulsions for use within agriculture, e . g. "calf milk" . Such partial esters useful as emulsifiers are conventionally pro¬ duced in a commercial scale by heating a mixture of on the one hand a glycerine condensate or glycerine condensates and on the other hand one or more fatty acids or a natural fat, that is , a material substantially consisting of triglycerides , to a high tempera¬ ture of the order of 200 - 260 C , often in the presence of a basic catalyst such as sodium hydroxide . However, at the high tempera¬ ture employed, by-products may be formed which impart, to the resulting material, an undesired colour and flavour and which may be undesired from the point of view of nutrition . According to the invention , it has now been found that in the preparation of partial esters of glycerine condensates with C 4 ?fi fatty acids by reacting glycerine condensates with fatty acid glyce- rides, exceRent results are obtained when the reaction is performed using tertiary butyl alcohol as solvent. The invention is based on this recognition and relates to a process for preparing partial esters of glycerine condensates with C - „ fi fatty acids by reacting glycerine condensates with fatty acid glyce- rides in the presence of a basic catalyst, which process is characte rized in that the reaction is performed using tertiary butyl alcohol as solvent. In comparison with products prepared at high temperature without the use of solvent, the products prepared by the process according to the invention are distinguished by improved colour, odour and flavour, and their emulsifying effect is particularly good. Further¬ more, in the process according to the invention, no further conden- sation of the glycerine condensate material used takes place; in the conventional high-temperature method, such further condensation does take place, which, i.a. , means that the possible uses of the non-esterified glycerine condensate material separated after the reaction are limited, and the continuous condensation per se makes an effective control of the process difficult, which makes it more difficult to obtain as weU- defined products as by the process ac¬ cording to the invention . Furthermore, it has been found that particularly good yields may be obtained by the esterification by the process according to the invention . Besides , it has been found that tertiary butyl alcohol can be removed effectively from the esters formed, which is of considerable importance for a product which is to be. used in nutrients at a time when, to an increasing degree, consumers and authorities caR for nutrients being free of foreign substances . As fatty acid glyceride starting material may, for example, be used fats or fat mixtures (triglycerides) and diglycerides or diglyceride mixtures, and the fats or fat mixtures may also naturaRy contain or be mixed with major or minor amounts of diglycerides . The diglyceride materials may be the result of other productions of for example emulsifiers . Monoglycerides may also be contained in the starting material. In the process of the invention, a natural fat is usuaRy used which may have been treated chemicaRy, e . g. refined or completely or partiaRy hardened. Examples of suitable fats may be ox taRow, butterfat, lard, herring oR, whale oR, palm fat, cocoa butter and vegetable oRs such as rape oR, peanut oR, soya oR and coconut oR, and these fats mentioned as examples may be refined and, as regards the oRs , completely or partiaRy hardened . The expression "glycerine condensates" is herein taken to mean products which are formed by coupling of two or more molecules of glycerine with water separation . These glycerine condensates , stRl containing free hydroxy groups , may be constituted by for example 2 - 10 glycerine units and wRl usuaRy be in the form of mixtures containing fractions of different chain lengths , usuaRy also contain¬ ing monomer glycerine . Glycerine condensates may, e . g. , be pre¬ pared by heating glycerine to a relatively high temperature in the presence of a basic catalyst, thereby usuaRy obtaining complex mixtures of viscosities of more than 300 centipoise, measured at 60 C, and very interesting mixtures of this type have viscosities in the range of 700 - 1400 centipoise, measured at 60 C, but also materials of higher viscosities may be interesting starting materials in the process according to the invention. By the process according to the invention it is possible to use a starting material which in addition to glycerine condensates (with their optional content of monomer glycerine) , contains minor amounts of added monomer glycerine, just as propylene glycol may be contained in the starting material. A special feature of the process according to the invention is that a glycerine condensate material of a quite specific character or composition may be used to yield products of a corresponding specific character or composition as in the process according to the present invention , in contrast to the conventional process , no further condensation of the glycerine condensate material takes place . As the reesterification reaction performed according to the inven¬ tion is sensitive to water, the starting materials and the alcohol material used should be substantiaRy water-free . As mentioned above, the process according to the invention is performed in the presence of a basic catalyst . An alkali etal base such as sodium hydroxide, sodium carbonate , Rthium hydroxide , potassium hydroxide or potassium carbonate or mixtures thereof are preferably used as a catalyst. For most purposes it is preferred to use sodium hydroxide or potassium carbonate , which both have a good catalytic effect with respect to the reesterification reaction . OMPI _ Suitably, the process of the invention may be performed by heating the reaction mixture, for example to at least 60 C, especiaRy at least 70 C and preferably at the boRing point under reflux, but it is also possible to work at a temperature level which is above the boRing point of tertiary butyl alcohol, then using an overpressure; hereby, shorter reaction times are obtained. Like the subsequent treatments of the product the reaction may be performed in batches or continuously . Subsequent to the reaction, which is normaRy completed in less than 1 hour, the basic catalyst is normaRy neutralized, for example with phosphoric acid, and tertiary butyl alcohol is evaporated, suitably on a thin layer evaporator. The remaining mixture wiR usuaRy separate into a glycerine condensate phase and a fatty phase consisting, to a major extent, of the reaction product. The fatty phase may, e . g. , be separated from the glycerine condensate phase by centrifuging or decanting and may per se be the desired end product as it shows exceRent emulsifying properties . The glycerine condensate material dissolved in the product may, if desired, be removed, e . g. by selectively dissolving the ester com¬ ponent of the product, that is , the desή-ed emulsifier-active reac¬ tion product, in a suitable solvent, for example a hydrocarbon, and separating the glycerine condensate material insoluble in the solvent, whereafter the ester product may be worked up , e . g. , by evaporation of the solvent. Removal of the glycerine condensate component by washing with water and/or aqueous Rquids , e .g . , aqueous saRne solutions in a manner known per se, is also possible. Such a washing wiR simultaneously remove practicaRy quantitatively any residues of tertiary butyl alcohol. Any residues of tertiary butyl alcohol may also be removed practicaRy quantitatively by vigorous vacuum treatment, for example in a thin layer evaporator . If desired, also the ester product per se may be fractionated in a known manner, for example to obtain fractions with specific desired properties , which fractionation may be performed by means of solvents , for example by recrystaRisation . OMPI IPO By the process according to the invention interesting products are obtained by using, as starting materials , a glycerine condensate and triglyceride in a weight ratio of about 20 - 70: 80 - 30. Pro¬ ducts of great commercial importance are obtained, when the weight ratio of glycerine condensate to triglyceride is 40 - 65 : 60 - 35. Suitably, 0.4 - 4 parts by volume of tertiary butyl alcohol per part by weight of the combined starting materials are used, and it is especiaRy preferred to use 0. 1 - 0.5 Hters , particularly 0. 15 - 0.4 Hters , of tertiary butyl alcohol per 450 g of the combined starting materials . Here , the catalyst is suitably sodium hydroxide, and the best results are obtained when this is added in an amount of 0.5 - 10 g per 450 g of the combined starting materials , but the added amount of basic catalyst must, of course , be adjusted to the pH of the glycerine condensate material, which may in itself contain a base originating from the preparation of the material. The process according to the invention is further Rlustrated in the foRowing examples : Example 1. 607.5 g of glycerine condensate with a viscosity, measured at 70 C , of 500 centipoise, and 742.5 g of soya oR are used as start¬ ing materials . 6 g of sodium hydroxide are used as catalyst, and 750 ml of tertiary butyl alcohol are used as solvent. In a reaction tank provided with reflux condenser and steam jacket the sodium hydroxide is firstly dissolved in the glycerine condensate with stirring and heating to 120 - 130 C for 35 minutes, and thereafter the other components mentioned are added . The whole mixture is heated to the reflux temperature (89 - 96°) and thereafter kept at this temperature with reflux for 60 minutes . (After refluxing for 50 minutes the mixture is completely clear) . Thereafter, the reaction mixture is neutraRzed with 10.05 ml of 86% phosphoric acid, and then it is fRtered and evaporated on a rotary evaporator at 130 - 140 C and a pressure of about 30 mm Hg abs . After decanting from glycerine condensate precipitated by standing, a fat phase of 1163 g with a saponification value of 128.0 , an acid value of 7.8 and a pH of 3.8 is obtained. Example 2. 202.5 g of glycerine condensate with a viscosity, measured at 70°C, of 500 centipoise, and 247.5 g of coconut oR are used as starting materials . 2 g of sodium hydroxide are used as catalyst, and 250 ml of tertiary butyl alcohol are used as solvent. In a reaction tank provided with reflux condenser and steam jacket the sodium hydroxide is firstly dissolved in the glycerine condensate with stirring and heating to 120 - 130°C for 30 minutes . There¬ after the other components mentioned are added, whereafter the temperature is raised untR the mixture is boRing, and at this temperature (90 - 96 C) refluxing is performed for 60 minutes . After refluxing for 22 minutes , the reaction mixture is completely clear. After the reaction is completed, the mixture is neutralized with 3.35 ml of 86% phosphoric acid and thereafter fRtered, and the fRtrate is evaporated in a rotary evaporator at 130 - 140 C and a pressure of about 30 mm Hg abs . The fat phase totals 423 g and has a saponification value of 152.8, an acid value of 7.9 and a pH value of 4.0. Example 3. InitiaRy, butterfat was prepared from unleavened butter, heating the latter to about 80 C and leaving it at this temperature for 45 minutes and thereafter decanting the fat phase and evaporating twice on thin layer evaporator at 130°C and 40 mm Hg abs . The foRowing recipe was used: 3.7 kg of polyglycerine condensate, viscosity 500 centipoise at 70 C 37 g of sodium hydroxide OMPI 4.5 kg of butterfat 3.7 kg of tertiary butyl alcohol. InitiaRy, the sodium hydroxide was dissolved in the poly glycerine at 130 C with stirring for 45 minutes , thereafter the other compo¬ nents were added, and the reaction was performed at 88 - 93 C with reflux for 70 minutes . After neutraRzation with 58 ml of 86% phosphoric acid, the product was finaRy evaporated several times on thin layer evaporator. Before the last two evaporations , a water amount totalling 5% of the product was added . The yield was 7.25 kg of product with a saponification value of 138.7, an acid value of 7.0, and a pH of 3.8. The product had a nice yeRow colour and showed a paste-Rke consistency after crystaRisation . Example 4. The foRowing recipe was used: 18 kg of glycerine condensate , viscosity 500 centipoise at 70°C 22 kg of fuRy hardened taRow 178 g of sodium hydroxide 22.2 Hters of tertiary butyl alcohol. InitiaRy, the sodium hydroxide was dissolved in the glycerine -o condensate at 130 - 135 C with stirring for 45 minutes , and there¬ after the melted taRow and tertiary butyl alcohol were added, and the mixture was heated to reflux temperature (88 - 95°C) and kept at this temperature for 65 minutes and thereafter neutralized with 298 ml of 86% phosphoric acid, whereafter the solvent was evaporated on thin layer evaporator, and the precipitated glycerine condensate was separated . The resulting product had a saponification value of 129.3, an acid value of 8.5, and a pH of 4.9 OMPI Comparison example . A polyglycerine ester is prepared at high temperature (known art) according to the foRowing recipe : 22.5 kg of glycerine condensate, viscosity 500 centi¬ poise at 70 C 27.5 kg of fuRy hardened taRow 222 g of sodium hydroxide . AR of the raw materials are from the same batch as in Example 4. InitiaRy, the sodium hydroxide was dissolved in the glycerine con¬ densate with stirring for 45 minutes at 130 - 135 C, and thereafter the melted taRow was added, and the mixture was heated to 240 C and kept at this temperature for 1 hour. After cooling to 220 C, the reaction product was neutralized with 3.72 ml of 86% phosphoric acid and further cooled to about 160 C, whereafter the undissolved glycerol condensate was separated . The ester thus produced has a saponification value of 140.4, an acid value of 8.7, and a pH of 6.1. Comparison with Example 4 shows that the sapontfication value of the product prepared in tertiary butyl alcohol (Example 4) is signi- ficantly low τ er than that of the product prepared at high temperature which shows a better esterification by the process in tertiary butyl alcohol. OMPI

Claims: Patent claims. 1. A process for the preparation of partial esters of glycerine condensates with C._ ( , fatty acids by reacting glycerine condensates with fatty acid glycerides in the presence of a basic catalyst, c h a r a c t e r i z e d in that the reaction is performed in tertiary butyl alcohol as solvent. 2. A process as claimed in claim 1, c h a r a c t e r i z e d in that an aRcaHmetal base is used as basic catalyst. 3. A process as claimed in claim 2, c ha r a c t e r i z e d in that sodium hydroxide or potassium carbonate is used as aRcaHmetal base. 4. A process as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that the weight ratio of glycerine condensate to fatty acid glyceride material is about 20 - 70:80 - 30. 5. A process as claimed in claim 4, c h a r a c t e r i z e d in that the ratio is 40 - 65:60 - 35. 6. A process as claimed in any one of the preceding claims, c h a r a c t e r i z e d by using 0.4 - 4 parts by volume of tert¬ iary butyl alcohol per part by weight of the combined starting materials. 7. A process as claimed in claim 6, c h a r a c t e r i z e d by using 0.1 - 0.5 Hter of tertiary butyl alcohol per 450 g of the combined starting materials. 8. A process as claimed in any one of the preceding claims, c h a r a c t e r i z e d by using butterfat as triglyceride material. OMPI

Inventors: DREYER J, SCHOU H
Applicants: DREYER J, NEXUS APS, SCHOU H
Application year: 1979
Main classification: C07C69
IPC codes: B01F17, C11C3