DE2500241A1 - Liquid surfactant hydroxy ester mixture - specified polyols reacted with aliphatic acid then with aliphatic acid - Google Patents

Abstract

A surfactant compsn. comprises a mixt. of a hydroxyesters which are condensn. prods. of (a) 1 mol. of triethanolamine, glycerol, trimethylolpropane or pentaerythritol or a mixt. of these with (b) 1-2 mols. of a satd. 16-26C aliphatic or cycloaliphatic carboxylic acid or their mixtx. and (c) 0.1-0.9 mol., pref. 0.1-0.7 mol. of a 3-10C aliphatic dicarboxylic acid or a mixt. of these. The prods. are used as emulsifying agents for prepg. water in oil emulsions and find application in the prepn. of fibres or lubricants and in cosmetic and pharmaceutical applicns. The compsns. are easily prepd. and economic. Avoiding the use of unsatd. acids frequently used in prods. of this nature, avoids the disagreeable smell and tendency to oxidise of these prods.

Description

Surface-active, liquid, hydroxyl-containing ester mixtures and a Process for their preparation The invention relates to surface-active, liquid, Hydroxyl-containing ester mixtures, consisting of condensation products of 1 mol of triethanolamine with 1 to 2 moles of a saturated branched chain, aliphatic or cycloaliphatic Carboxylic acid with 16 to 26 carbon atoms or mixtures thereof from 0.1 to 0.5 mol, preferably 0.1 to 0.3 moles of an aliphatic straight or branched chain dicarboxylic acid with 3 to 10 carbon atoms or mixtures thereof with a hydroxyl number of 50 bit 250, a saponification number from 150 to 250 and an acid number below 5, preferably under 1, and a method for their preparation.

The invention aims in particular at surface-active substances, in particular a liquid water-in-oil emulsifier (W / O emulsifier) from technical accessible starting materials after a simple, economically not very expensive Winning procedure. The products are used in both cosmetic and pharmaceutical applications Area, preferably in W / O emulsions, as well as in the technical field, for example, when sizing and preparing fibers or as leather oiling middle.

Liquid emulsifiers with the lowest possible freezing points and with An HLB value (Hydrophil Lipophil Balance) of 3 to 7 is used for stable emulsions preferred and are easier to handle than pasty, viscous or semi-solid Emulsions.

The selection of liquid W / O emulsifiers is in contrast to the large ones The range of O / W emulsifiers is not large. The W / O emulsifiers on the market are predominantly unsaturated fatty acid, especially oleic acid esterification products such as sorbitol oleate, pentaerythritoleate, polyethylene glycol monooleate, glyceryl polyricinolate and polyglycerol ricinolate, as well as wool wax and dease derivatives which lead to oxidation tend, and have a distinctly unpleasant odor. Perfuming a W / O emulsion is made by using pre-emulsifiers on the basis of unsaturated Fatty acids, which are relatively easily subject to rancidity, are problematic.

The task of the invention was development and economic Production of a surface-active substance, in particular a new W / O emulsifier, the one poisonous emulsion stability both at elevated temperature and below the freezing point and if possible in liquid form - for the purpose of easier handling - present as an odorless and light-colored surface-active product target.

It has now been found that a liquid, odorless, colored light-colored and emulsion-stabilizing, surface-active product that has the disadvantages, such as unpleasant smell, color, tough consistency, the previously available W / O emulsifiers on the basis of unsaturated fatty acid esterification products does not contain, if you have 1 mole of triethanolamine with 1 to 2 moles of a saturated branched chain, aliphatic or cycloaliphatic monocarboxylic acid with 16 to 26 carbon atoms or their mixtures at 100 to 220 ° C, preferably under vacuum to form hydroxyl-containing Partial esters are esterified until an acid number below 50, preferably below 1, is reached is and at the same time with their formation or thereafter the hydroxyl-containing Partial ester with 0.1 to 0.5 mol, preferably 0.1 to 0.3 mol of an aliphatic straight or branched chain dicarboxylic acid with 3 to 10 carbon atoms, mixtures thereof or anhydrides condensed at 100 to 220 ° C, preferably under vacuum, to one Acid number below 5, preferably below 1, is reached and the crude product in the usual way Way discolored and deodorized.

The production is preferably taught according to claims 3 to 5.

Once the dicarboxylic acids or their anhydrides have been added very preferably slowly, especially after cooling to temperatures of 100 to 14000 esterified with an only slow increase in temperature of 8-1200 per hour.

A similar slow esterification is triethanolamine with high proportions in the range of 1 mole to 1 to 1.2 moles of monocarboxylic acid is recommended. This will be Resins old by-products secured avoided.

The condensation products represent mixtures in which a link of the partial ester molecules by the dicarboxylic acids, depending on the molar ratios takes place to a greater or lesser extent, both the molecule being a dicarboxylic acid by esterification of both carboxyl groups on two different triethanolamine partial esters can be bound, as well as a bond of a molecule of triethanolamine partial ester can take place on two different molecules of a dicarboxylic acid.

As far as the production takes place in a vacuum, a vacuum up to about 20 Torr can be used.

In the preparation of the condensation products are generally no esterification catalysts required but common esterification resp. Transesterification catalysts ie alkyl titanates, p-toluenesulfonic acids and quaternary ammonium salts can be used in amounts of 0.1 to 1%.

The required saturated, branched ketti, gen acids are through catalytic treatment in the heat of unsaturated fatty acids or oils that contain such fatty acids, for example linseed, rapeseed and fish oil, The dimeric and trimeric fatty acids that are also formed are separated off. The production of saturated, cyclic carboxylic acids by alkalizing Linseed oil in aqueous media was described by R E. Beal, R.A. Eisenhaur and V.Æ. Sohns, J. At the. Oil. Chem.

Soc. Vol 42 1115 (1965) describe in detail.

The used for the condensation of triethanolamine partial esters Dicarboxylic acids can be straight-chain or branched.

For example, malonic acid, succinic acid, fumaric acid, glutaric acid, Aedipic acid, sebacic acid, 2-ethylsuccinic acid, dimethylglutaric acid or trimethyladipic acid as well as their anhydrides. In the technical field you can use maleic acid or maleic anhydride or with branched-chain dicarboxylic acids or their anhydrides-condensed Use triethanolamine partial esters.

The condensation products of the triethanolamine partial esters developed according to the invention with aliphatic dicarboxylic acids are characterized by special advantages: 1. They are odorless, light, clear liquids with a cloud point of approx. -5 ° C; they are soluble in vase oils, paraffin oil, fatty alcohols, waxes, natural Fats and oils and are characterized by good distribution in the fat phase Processing off.

2. The exact setting of a desired HLB value for W / O emulsions is possible by adjusting the degree of condensation with changing proportions of aliphatic Dicarboxylic acid. The HLB value itself is a measure of the ratio of hydrophilic ones to lipophilic groups in the emulsifier molecule. The HL3 value of the emulsifiers according to the invention can be adjusted by changing the triethanolamine partial esters Produces proportions of monocarboxylic acids with 1- 26 C atoms and these in turn with changing proportions of dicarboxylic acids with 3 bi3 10 atoms condensed and thereby the The HLB value varies in such a way that each fat base to be emulsified has a specific one can assign optimal HLB value required for this fat phase. Here finds as the proportion of dicarboxylic acid increases, the HLB value decreases.

3. Oxidation stability against atmospheric oxygen when the emulsifier is stored or emulsions made therefrom.

The saturated used according to the invention for the preparation of the partial esters branched-chain acids and the condensation products produced under mild conditions are largely stable to oxidation. So-called isostearic acid is preferably used a, obtained by catalytic treatment of linseed oil fatty acids (manufacturer Unilever-Emery N.Y., Gouda / Holland) with a titer of 90C, an iodine number below 7, a saponification number from 180 to 197 and an acid number from 175 to 191. This isostearic acid is a mixture of numerous isomeric, preferably methyl-branched C18 fatty acids with low iodine numbers, which have a good resistance to oxidation. ( H. Janistyn Handbook of Cosmetics and Fragrances (1969), Volume 1, p.533).

Instead of isostenric acid, an easily accessible one can also be used Mixture of iso acids of chain length 22 with proportions of acids of other chain length use which in a corresponding manner such as isostearic acid from erucic acid Rapeseed oil can be obtained.

An interaction with any active ingredients to be incorporated into Cosmetics and pharmacy is used due to the saturated nature of the isostearic acid to exclude.

Triethanolamine and products made from it, e.g. salts, esters and addition products are used universally as surface-active substances and are also commercially available in stabilized form. Dicarboxylic acids, succinic anhydride, Succinic acid, fumaric acid, malonic acid, glutaric acid, adipic acid, sebacic acid, are produced on an industrial scale, and their quality and purity are satisfactory.

Succinic acid and fumaric acid are present in the human body, in which they occur as an intermediate in the citric acid cycle. Is fumaric acid an edible acid and used in the USA as a substitute for fruit acid.

Many of these dicarboxylic acids also occur in nature, e.g. Malonic acid, glutaric acid and adipic acid are found in the juice of the sugar tart. Thus t are the raw materials that are used in the products manufactured according to the invention are harmless to health.

To avoid discoloration, nitrogen can be added during the esterification Pass it through the reaction mixture and additionally add Attis carbon. After conventional deodorization, for example by means of steam and bleaching with fuller's earth under vacuum you get a perfect, light, odorless one Product, without detectable peroxide content.

4. Storage stability of W / O emulsions using the according to the invention developed condensation products.

The quality of an emulsifier, especially a W / O emulsifier, can be determined from the stability of the emulsions made from them. In the case of W / O emulsions, this stability test is preferably carried out at elevated temperatures carried out as a short-term test. This is where the quality of an emulsifier comes through Oil or water separation and / or by reversing the phase to the O / W emulsion (slope the conductivity), which are according to the invention for use as emulsifiers condensation products of the triethanolamine particle esters developed for the production of W / O emulsions with aliphatic straight and branched chain dicarboxylic acids showed in the them here; o produced W / O emulsions at 2500 after 6 months, at 40 ° C after 3 months and at 55 ° C after 2 weeks no water excretion, hardly any oil excretion and no significant change in conductivity with regard to a phase transition to O / W emulsion. These have the same good properties in terms of durability the W / O emulsions were also able to perform in the rocking test belonging to the stability test can be determined in the temperature range of -15 ° C or -20 ° C.

From the consistency behavior that developed from the according to the invention Emulsifiers produced emulsion can be concluded that with increasing degree of condensation i.e. increasing molar proportion of dicarboxylic acids, the viscosity of the emulsion decreases in such a way that the consistency of the cream can be adjusted.

This same phenomenon could occur with the use of dicarboxylic acids can be observed in the partial ester condensates with increasing number of CH2 groups.

The following examples explain the invention in more detail without it However, to be limited.

Example 1 In a 10 liter three-necked flask equipped with a stirrer, water separator, Thermometer and gas inlet tube, a mixture of 5112 g ( 18 mol) isostearic acid (type 5681 from Unilever-Emery) and 2682 g (18 mol ) Triethanolamine with stirring and simultaneous passage of four nitrogen Hours of heat at 200 ° C and the resulting water of reaction removed at the same time. The key figures for the ester produced in this way can be found in Table 1 below.

Example 1 a 1000 g of the triethanolamine partial ester prepared in Example 1 with 40 g of malonic acid in a 2 liter three-necked flask equipped with a stirrer, thermometer, gas inlet tube and water separator is provided, under a nitrogen atmosphere for four hours at 140 Further esterified up to 1800C (temperature increase 10 ° C / hour).

Example 2 Analogously to Example 1 a, 1000 g of triethanolamine partial esters, prepared according to Example 1, mixed with 20 g of succinic anhydride.

Example 3 Analogously to Example 1a, 1000 g of triethanolamine partial esters are used Esterified with 40 g of succinic anhydride.

Example 4 Analogously to Example 1a, 1000 g of triethanolamine partislester are used Esterified with 60 g of succinic anhydride.

Example 5 1000 g of triethinolamine partial esters are obtained analogously to Example 1a Esterified with 80 g of succinic anhydride.

Example 6 Analogously to Example 1a, 1000 g of triethanolamine partial esters are used Esterified with 50 g of fumaric acid.

Example 7 1000 g of triethanolamine partial esters are obtained analogously to Example 1a Esterified with 60 g of adipic acid.

Example 8 Analogously to Example 1a, 1000 g of triethanolamine partial esters are obtained Esterified with 60 g of sebacic acid.

Example 9 A mixture of 1107 g (3.9 mol) isostearic acid, 447 g (3.0 mol) triethanolamine and 30 g ( 0.3 mol) succinic anhydride in the presence of 0.15 g butyl titanate as a catalyst as well as 3 g activated charcoal with intensive stirring and nitrogen atmosphere for six hours heated to 100 to 160 ° C (temperature increase 10 ° C / h). The resulting reaction water is removed at 20 torr. The ester mixture obtained is then heated to 160.degree deodorized for one hour and bleached with 1% fuller's earth at 1000C for one hour and then filtered in a pressure filter.

Example 10 Analogously to Example 9, an ester mixture is prepared, however the amount of succinic anhydride used is 60 g instead of 30 g.

Example 11 Analogously to Example 9, an ester mixture with 90 g of amber is produced acid anhydride produced.

Example 12 A mixture of 1275 g (4.5 mol) of isostearic acid, 447 grams (3.0 moles) of triethonolamine, 33 grams (0.33 moles) of succinic anhydride and 2 g of A-tohle is under intensive stirring and a nitrogen atmosphere for six hours (Temperature increase 1000 / h) heated from 100 ° C to 160 ° C and the water of reaction ex removed at 20 torr. The resulting ester mixture is deodorized for one hour at 160 ° C, with 1, bleached fuller's earth and filtered in a pressure filter.

Example 13 Analogously to Example 12, an ester mixture with 66 g is used instead made of 33 g, succinic anhydride.

Example 14 With intensive stirring and a nitrogen atmosphere an ester mixture of 1135 g (4 mol) isostearic acid, 298 (2.0 mol) tri: -ithanolariin, 27 g (0.27 mol) of succinic anhydride, 0.15 g of butyl titanate and 3 a A-Eohle in three hours at 140-160 ° C, and 20 Torr produced, after which an hour Deodorization at 160 ° C., bleaching and pressure filtration follow.

Example 15 With vigorous stirring and a nitrogen atmosphere, a Ester mixture of 620 g (2 mol) of a branched-chain C18 and C22 iso acid, the in the thermal treatment of erucic acid-containing Bapool analogous to the production of isostearic acid was obtained, 298 g (2 mol) of triethanolamine and 27 g (0.15 mol) of trimethyladipic acid, 0.1 g of butyl titanate and 2 g of activated carbon in six hours at 140 to 160 ° C (temperature rise 10 ° C / h) and 20 Torr, After which a one hour deodorization at 160 ° C, a bleaching and a Pressure filtration follows.

Properties and key figures of the ester mixtures according to the examples len can be found in the following table.

Table 1 IS = isostearic acid or iso-C22 acid TEA = triethanolamine chemical and physical data of the examples listed under 1 to 15: Ex. Molar ratio proportion Dicarbon- SZ VZ OHZ HLB value Density Viscosi- cloud point TEA: IS acid g / 100 g Par- # 0.5 at 25 ° C at ° C according to DIN tialester 25 ° C cP 51383 1 1: 1.0 ------- 0.5 138 252 6.0 0.952 197.8 -10 1a 1: 1.0 1 g malonic acid 0.6 154 222 5.8 0.957 210.0 -10 2 1: 1.0 2 g succinic acid- 0.8 152 224 5.4 0.959 226.4-8 anhydride 3 1: 1.0 4 g "0.8 173 200 3.8 0.965 266.4-7 4 1: 1.0 6 g "0.4 201 160 1.8 0.972 335.8 - 6 5 1: 1.0 8 g" 0.5 223 139 0.6 0.979 418.7 - 6 6 1: 1.0 5 g fumaric acid 0.6 188 180 3.0 0.965 335.5 - 6 7 1: 1.0 6 g adipic acid 0.6 178 196 3.2 0.967 266.5 - 8 8 1: 1.0 6 g sebacic acid 0.9 170 200 3.3 0.960 276.4 -10 9 1: 1.3 2 g succinic anhydride 0.4 174 150 3.0 0.951 195.7-8 10 1: 1.3 4 g "0.6 193 130 2.0 0.957 239.5 - 6 11 1: 1.3 6 g" 0.7 212 122 0.6 0.965 298.7-6 12 1: 1.5 2 g succinic anhydride 0.5 173 149 2.4 0.945 181.0-8 0.3 195 110 1.6 0.950 212.5 - 5 13 1: 1.5 4 g "14 1: 2.0 2 g succinic acid 0.9 189 62 2.0 0.934 151.5-5 anhydride 15 1: 1.0 3 g trimethyladi- 0.7 143 238 3.0 0.972 282.4-6 pinic acid Example 16 (emulsion tests) The condensation products of the triethanolamine isostearic acid partial esters developed according to the invention with aliphatic straight or branched chain dicarboxylic acids can, as from the Examples listed can be seen (Table 1), with an appropriate reaction procedure and with coordination of the proportions of the individual reactants in their The degree of condensation or the proportion of free OH groups can be varied and determined, whereby every desired HLB value for W / O emulsifiers can be achieved.

To the excellent properties of the inventively produced, surface-active, liquid, hydroxyl-containing ester mixtures - in particular the to show the extremely beneficial effect of the dicarboxylic acids - were the ester mixtures listed in the examples in their emulsifying effect with two commercially available emulsifiers, e.g. pentaerythritol monooleate or sorbitan sesquioleate compared. Three different types of fat bases were chosen. Manufactured the emulsions were prepared by the following procedure.

In principle, the aqueous phase heated to 70 ° C. was kept constant intensive stirring within 5 minutes into the equally warm, oily phase that at the same time containing the emulsifier, added and within 60 minutes to 25 ° C cooled down.

To bring about a comparison of the different emulsifiers the emulsions produced in this way are tested for stability at 25 ° C., 40 ° C. and 55 ° C., respectively Subjected to 6, 4 months and 2 weeks respectively.

The storage of the manufactured emulsions at different temperatures was divided as follows: 1. Sample - storage at room temperature for 6 months in polystyrene vessels when completely filled 2nd sample - storage at 4000 for 3rd Months in screw-top jars with 80% filling. 3rd sample - storage at 55 ° C for 2 weeks in screw-top jars with 80% inger filling 4th sample - Teu freezing cycle: the sample was stored for 16 h at −150 ° C. and then for 8 h at + 20 ° C. Assessment of the decomposition phenomena that occur during the storage test (not during the tan / freeze cycles ) occurred, the following symbols were used: 0 = perfect I = low oil separation - max. 0.5 vol .-% II = weak oil separation - approx. 0.5 - 1.0 vol .-% III = stronger Oil separation - approx. 1.0 - 1.5% by volume (+) = W / O-stable water-in-oil emulsion (-) = O / W unstable water-in-oil emulsion or oil-in-water emulsion for the thaw / freeze cycles (G.A. Nowak, Seifen-Öle-Fette-Wachse, 92, No. 3/1966) was the number of cycles entered in Tab. 2 and 3, which did not show any signs of decomposition, at the thaw / freeze cycles occurred in each case, while in the others Storage oil separation was observed.

Table 2 Emulsion type A fat base Vaseline (Pharmaline V-15 DÄB 7) Composition of the emulsions: Fat base 1: 27 parts by weight of Vaseline 3 Parts by weight of the emulsifiers of Examples 1 to 15 water phase: 0.3 part by weight of MgSO4 3.0 parts by weight of glycerol 0.2 part by weight of propyl p-hydroxybenzoate 66.5 parts by weight Water Example 6 months 3 months 2 weeks thaw-freeze cycles No. 25 ° C 40 ° C 55 ° C -13 ° C (16h 20 ° C (8h pentserythritol- 0 (+) I (-) II (-) 4x monooleate sorbitan sesquio- O (+) I (+) II (+) 8 x leat 1 0 (+) I (+) II (+) 6x 1 a O (+) G (+) o (+) 12 x 2 0 (+) O (+) o (+) 12 x 3 to all: all: 0 (+) 10 x 15 O (+) 0 (+) some some I (+) 8 x example 17 Manufacture of a gel-like adsorption pad and its use as an oreme base.

The emulsifiers produced in Examples 1 to 15 were in their emulsion-stabilizing effect in an application example of an adsorption base compared.

Composition of the emulsion: 35 parts by weight adsorption base (fat base 2) 65 parts by weight of aqueous phase (62.5 parts by weight of water, 0.3 part by weight of MgSO4, 0.2 parts by weight propyl p-hydroxybenzoate, 2.0 parts by weight sorbitol) composition and preparation of the adsorption base: fat base 2: 40 parts by weight of paraffin oil 35 parts by weight MIGLYOL 812 R (manufacturer Dynamit Nobel) 7 parts by weight BENTONE 27 R (Titan Society, Leverkusen) or 34 3 parts by weight propylene glycol 15 parts by weight of the emulsifiers according to Examples 1 to 15 The components of the adsorption base are stirred vigorously at 12,000 for 1 h. After cooling to 80 ° C, 35 parts by weight the gel-like additive base with 65 parts by weight, aqueous phase heated to 80 ° C with constant stirring.

The mixture is stirred until the mass has cooled and a smooth cream is obtained.

Table 3 shows results of the stability test.

Table 3 Example 6 months, 3 months, 2 weeks of thaw-freeze cycles No. 25 ° C 40 ° C 55 ° C -15 ° C (16h) / pentaerythritol- 20 ° C (8h) monooleate ° (+) I (-) III (-) 4 x sorbitan sesquioleate o (+) I (+) II (+) 8 x 1 o (+) o (+) II (-) 6x 1a O (+) O (+) O (+) 10x 2 o (+) 0 (+ ) 0 (+) 12 x 3 o (+) o (+) o (+) 12 x 4 to all all o (+) 10 x 15 o (+) 0 (+) some some I (+) 8 x Example 18 The emulsifier produced in Example 2 was used in its emulsion-stabilizing Effect tested within a W / O lotion as an application example: composition of the emulsion: 33 parts by weight of fat base 3 67 parts by weight of aqueous phase (0.3 part by weight NgSO4, 0.2 part by weight of p-hydroxy-benzoic acid propyl ester, 3.0 parts by weight of 70% sorbitol solution, 63.5 parts by weight of water) Composition and preparation of the fat base 3: 45.0 Parts by weight of paraffin oil 30.0 parts by weight of MIGLYOL R 812 (manufacturer Dynamit Nobel) 20.0 Parts by weight of the emulsifier developed in Example 2 2.0 parts by weight Bentone R 27 (Titangesellschaft, Leverkusen) 3.0 parts by weight propylene glycol The components the bed base 3 are stirred vigorously at 12,000 for 1 h. After cooling down 80 ° C, 33 parts by weight of the fat base are heated to 80 ° C with 67 parts by weight aqueous phase is cooled to 25 ° C. for at least 1 h with constant stirring. The received When stored for 2 weeks at 40 ° C., W / O lotion does not show any oil deposition or any Phase transition.

Claims (5)

Claims 1. Surface-active, liquid, hydrocyclic ester mixtures, consisting of from condensation products of 1 mole of triethanolamine with 1 to 2 moles of a saturated one branched-chain, aliphatic or cycloaliphatic monocarboxylic acid with 16 up to 26 carbon atoms or mixtures thereof from 0.1 to 0.5 mol, preferably 0.1 to 0.3 Mol, of an aliphatic dicarboxylic acid with 3 to 10 carbon atoms or mixtures thereof with a hydroxyl number of 50 to 250, a saponification number of 150 to 250 and an acid number below 5. 2. Process for the production of surface-active, liquid, hydroxyl-containing Ester mixtures according to Claim 1, characterized in that 1 mol of triethanolamine with 1 to 2 moles of a saturated branched chain, aliphatic or cycloaliphatic Nonocarboxylic acid with 16 to 26 carbon atoms or mixtures thereof at 100 to 220 ° C., preferably Esterified under vacuum to hydroxyl-containing partial esters until an acid number is below 50, preferably below 1, is reached and simultaneously with its formation or subsequently thereon the hydroxyl-containing partial esters with 0.1 to 0.5 mol, preferably 0.1 to 0.3 mol of an aliphatic straight or branched chain dicarboxylic acid with 3 to 10 carbon atoms, their mixtures or anhydrides at 100 to 220 ° d, preferably below Vacuum condenses until an acid number below 5, preferably below 1, is reached and the crude product in dblicher Way discolored and deodorized. 3. The method according to claim 2, characterized in that the hydroxyl-containing partial esters in the absence of the dicarboxylic acids, their mixtures or anhydrides preferably at 160 to 18,000 and then their with condensed the dicarboxylic acids. 4. The method according to claim 2, characterized in that one triethanolamine with monocarboxylic acid and dicarboxylic acids, their mixture or anhydrides at the same time at 100 to 200 ° C, preferably at 120 to 16000, slowly esterified under vacuum, until an acid number below 5, preferably below 1, is reached. 5. The method according to any one of claims 2 to 4, characterized in that that the temperature of the reaction mixture in the presence of the dicarboxylic acids or their anhydrides slowly increased by about 8 to 1200, preferably 9 to 1100, per hour will.