EP4314161A1

EP4314161A1 - Corn wax oxidates and esterification products

Info

Publication number: EP4314161A1
Application number: EP22719236.6A
Authority: EP
Inventors: Philipp KRATZER
Original assignee: Clariant International Ltd
Current assignee: Clariant International Ltd
Priority date: 2021-03-30
Filing date: 2022-03-25
Publication date: 2024-02-07
Also published as: EP4067436A1; KR20230162701A; WO2022207517A1; CN117083348A; BR112023016356A2

Abstract

The invention relates to bright corn wax oxidates, to a process for their production and to their use for agricultural or forestry purposes, as an additive in plastic processing, in care products, in printing inks and/or in paints, and to saponified or estered corn wax oxidates produced by saponifying or estering the described corn wax oxidates.

Description

Corn wax oxidates and esterification products

The invention relates to light-colored corn wax oxidates, a process for producing these oxidation products of corn wax and their use for agricultural or forestry purposes, as an additive in plastics processing, in care products, in printing inks and/or in paints. Also provided are saponified and esterified corn wax oxidates produced by the saponification or esterification of the corn wax oxidates according to the invention.

The oxidation of fossil and non-fossil natural waxes with chromic sulfuric acid has been known since the beginning of the 20th century and has been carried out technically using fossil montan waxes since 1927 in the "Gersthofen process", which is still used today. In addition to fossil montan wax, renewable natural waxes such as e.g. B. Carnauba wax and candelilla wax oxidize. A process for chromic acid oxidation of carnauba wax is described in DE-A 10231886. Natural carnauba waxes (fat grey, type 4; medium yellow, prime yellow and pile, types 3 to 1) and raw montan wax (black) are clearly dark in colour. Oxidation with chromic sulfuric acid leads to lighter wax products.

However, when natural waxes are oxidized with chromic acid, the wax esters are split and the wax alcohols formed are oxidized in situ to form wax acids. The acid number is a measure of the content of free wax acids. The typical conversions of such oxidations are in the range of 50-90% based on the ester groups.

DE-A1 10 2013 007638 discloses a process for producing an acid wax with a defined acid number, in which a mixture of natural wax esters and alpha-olefins is oxidized with a chromic sulfuric acid. The natural wax esters are selected from the group consisting of rice husk wax, carnauba wax, sunflower wax and sugar cane wax. DE-A1 10 2018 116113 shows a process for producing a natural wax oxidate by a two-stage oxidation process, with rice bran wax or sunflower wax being used as starting materials.

EP-A1 3 102 292 discloses the production of an oxidate from rice bran wax and montan wax by treatment with a chromic sulfuric acid.

US-A 4083 731 discloses the production of montan and bark wax oxidate in which montan and bark wax is oxidized at 110°C with a mixture of chromium trioxide and concentrated sulfuric acid.

In addition to the desired lightening, the natural waxes bleached in this way have a higher saponification number and higher acid number than the unbleached waxes.

High acid numbers often have the advantageous effect that the natural wax oxidates can be separated more easily from by-products after oxidation, since the separation of the organic phase containing the wax oxidates from the aqueous phase containing chromium salts and other water-soluble reaction products is favored. In the case of low acid numbers, on the other hand, it was observed that the phase separation often takes place only very slowly or, under certain circumstances, not at all. If there is no or very slow phase separation, it is often not possible to reliably isolate and purify the natural wax oxidates without great effort.

Larger amounts of chromic sulfuric acid are required to achieve high acid numbers, which allow efficient phase separation, than to achieve low acid numbers, which means that larger amounts of chromium salt waste are also produced. Avoiding large amounts of waste is desirable from both an economic and ecological point of view.

Typically, phase separations are made more difficult at low acid numbers if the natural waxes used have a high oil content, pre-treatment such as de-oiling may often be necessary before oxidation. Under certain circumstances, large amounts of solvents may be required for this, which is likewise both economically and ecologically disadvantageous.

In order to obtain products with a low acid number from the natural wax oxidates with a high acid number, the acid number of the wax oxidates can be reduced after the by-products have been separated off, e.g. by esterification of the acids contained in the wax and/or wax oxidate with alcohols. As a result, further synthesis steps are required to achieve natural wax oxidates with low acid numbers even after the oxidation, which also results in economic and ecological disadvantages. Particularly when natural wax oxidates with a low acid number are required for certain applications, it would be advantageous not to use large amounts of chromic sulfuric acid and then lower the acid number by esterification, and to avoid using large amounts of solvent before oxidation.

One object of the present invention is to provide a process for producing a natural wax oxidate by means of chromic sulfuric acid oxidation of a natural wax, in which, after oxidation, the natural wax oxidate can be isolated over a wide acid number range.

It was surprisingly found that after the chromosulfuric acid oxidation of natural waxes, isolation and purification of the natural wax oxides is possible despite low acid numbers if corn wax is used as the natural wax, even if the corn wax has a relatively high oil content.

One subject of the invention is a process for preparing a corn wax oxidate (O), comprising the steps: i) providing a corn wax (MW), ii) providing a mixture (M) of chromium trioxide and sulfuric acid; iii) performing the oxidation of the corn wax (MW) by reacting the corn wax (MW) with the mixture (M) to obtain a corn wax oxidate (O); iv) ending the reaction and allowing the reaction mixture obtained in step iii) to stand until the organic phase has separated from the aqueous phase; v) separation of the organic phase; vi) optionally removing residues containing chromium compounds from the organic phase to obtain the corn wax oxidate (O) in a purified form; vii) optionally repeating the sequence of steps ii) to vi), using the corn wax oxidate (O), optionally in purified form, instead of the corn wax (MW).

With this method, light-colored natural wax oxidates based on corn wax, corn wax oxidates (O), which have an acid number in the range from about 10 to about 170 mg KOFI/g, can be obtained directly without the need for further steps after isolation set the acid number.

It was found that when using corn waxes (MW) as the starting material, the formation of a clear phase boundary between the organic phase and the aqueous phase in step iv) in the process according to the invention can already be observed regularly at an acid number of about 10 mg KOFI/g . With acid numbers in the range from 20 to 50 mg KOFI/g, a clear phase boundary can usually be seen within a period of less than 1 minute in step iv) of the process according to the invention. With acid numbers above 50 mg KOFI/g, a clear phase boundary can often already be seen within a period of less than 10 seconds in step iv) of the process according to the invention. The times given here were observed under conditions as given in the examples. In the case of significantly larger reaction batches, the times can vary, but are then also significantly shorter than with oxidates of other natural waxes, which are produced under otherwise the same conditions.

The phase boundary at low to medium acid numbers can be clearly seen even if the corn wax used has a relatively high oil content. In contrast, with rice bran wax oxidates, under otherwise identical conditions, the phases often only separate from an acid number of approx. 20 mg KOFI/g, and only at a low oil content of < 5% by weight, often only at oil contents < 2 wt%. at In montan waxes, phase separation often only takes place above an acid number of approx. 50 mg KOH/g.

Another object of the invention is a corn wax oxidate (O) that can be prepared by reacting corn wax (MW) with a mixture of chromium trioxide and sulfuric acid.

It is possible to further modify the corn wax oxidates (O) of the invention, for example to further adjust their acid number after preparation of the corn wax oxidate (O) and/or to change other properties, for example by esterification or saponification.

The esterification is usually carried out with alcohols, often with polyvalent alcohols such as ethylene glycol, butylene glycol, glycerol, diglycerol, trimethylolpropane, ethylene glycol, pentaerythritol or sorbitol.

A further object of the invention is therefore an esterified corn wax oxidate (E) which can be prepared by reacting the corn wax oxidate (O) according to the invention with an alcohol, preferably a polyhydric alcohol, particularly preferably ethylene glycol, butylene glycol, glycerol or pentaerythritol.

The saponification is usually carried out using basic metal salts, frequently using alkali metal hydroxides and/or alkaline earth metal hydroxides. Another subject of the invention is therefore a saponified corn wax oxidate (V), which can be prepared by reacting the corn wax oxidate (O) according to the invention or the esterified corn wax oxidate (E) according to the invention with a basic metal salt, preferably an alkali metal hydroxide and/or alkaline earth metal hydroxide, particularly preferably with Ca(OH )2.

Another object of the invention is the use of the corn wax oxidate (O) according to the invention, the esterified corn wax oxidate (E) according to the invention or the saponified corn wax oxidate (V) according to the invention for agricultural or forestry purposes, as an additive in plastics processing, in care products, in printing inks and/or or in paints. The invention also relates to the use of corn wax (MW) for the production of a natural wax oxidate by oxidation with a mixture of chromium trioxide and sulfuric acid.

Cornwax is typically obtained from crude corn oil through multiple processing steps, including basic digestion of the corn oil and multiple purification steps using chemical, thermal, and/or mechanical separation processes. Such a process, in which waxes are separated from crude vegetable oils such as corn oil as an undesirable by-product (approx. 60-90% by weight), is disclosed in US 4,272,447.

According to information from the Food and Agriculture Organization FAO, corn is one of the most widely produced cereals. Around 1,147 million tons of corn were harvested worldwide in 2018.

When processing raw corn, especially the corn oil obtained from it, corn wax is produced in large quantities as a by-product. Due to the high production figures and the wide geographical distribution, corn wax is therefore an economically interesting natural wax.

The chemical composition of corn wax has not yet been fully clarified, despite numerous analytical studies with inconsistent findings. What is certain, however, is the composition of the wax body from wax esters. In "The composition of corn wax" RL Shriner (Journal of the American Chemical Society, 1927, 49, 1290-1294) describes that corn wax consists at least in part of myricyl alcohol esters of C22 and C24 fatty acids. In "Wax Analysis of Vegetable Oils Using Liquid Chromatography on a Double-Adsorbent Layer of Silica Gel and Silver Nitrate-Impregnated Silica Gel" G. Henon states (Journal of the American Oil Chemists' Society 2001 , 78, 401 -410), that corn wax from crude corn oil can have carbon chain lengths of 44 to 58 carbon atoms. The corn wax esters mainly consist of monoesters of long-chain, saturated, unbranched monocarboxylic acids with long-chain, unbranched, aliphatic monoalcohols (hereinafter also referred to as "genuine esters"). Predominant in the acid part are the corn wax esters arachinic, behenic and lignoceric acid with chain lengths C20, C22 and C24, and in the alcohol part of the corn wax esters with chain lengths C24, C26, C28, C30 and C32. In addition, the wax can contain free fatty acids and other components such as squalene, phospholipids and steryl esters.

The level of wax esters in refined and deoiled cornwax is typically greater than 97% by weight. In non-deoiled corn wax, the wax ester content can be as low as 50% by weight, depending on the corn oil content. Other variable components of corn wax to be regarded as “minor quantity components” are the “dark substances”, which are not specified in more detail, squalene and the so-called “gum component”. These components tend to result in product quality that varies in color and applicability and is difficult to reproduce.

The usual technique for lightening the brown corn waxes is the classic bleaching with hydrogen peroxide. Corn waxes bleached with hydrogen peroxide are yellowish and largely correspond to the starting waxes in terms of their ester content and acid number. Such types are mainly offered on the market as de-oiled and refined corn waxes, but since the small-quantity components remain in the product, their product quality also fluctuates.

Corn wax oxidates with a lower acid number than the starting wax can be produced using the oxidation process described in DE 2546791 B by passing air through at elevated temperature. Accordingly, these have an acid number below 10 mg KOFI/g, since the acid number of a raw corn wax is below this value.

The process according to the invention makes it possible to produce light-colored corn wax oxidates (O) which, in comparison with bleaching with hydrogen peroxide, have the same product quality. The corn wax oxidates (O) produced by the process according to the invention usually have iodine color numbers measured according to DIN 6162 (2014) of less than 8 and yellowness indices measured according to ASTM E 313-20 of less than 50. It was found, however, that a suitable Selecting the process parameters for the oxidation of corn wax in a targeted manner iodine color numbers, measured according to DIN 6162 (2014) of less than 6, often less than 5, for example less than 2, and yellowness indices, measured according to ASTM E 313-20 of less than 40, often less than 30, for example less than 15 can be achieved.

At the same time, needle penetration numbers, measured according to DIN 51579 (2010), of less than 10 mm ¹ , often less than 6 mm ¹ , for example less than 4 mm ¹ , are achieved, which is particularly advantageous for applications in which hard waxes are required.

The method according to the invention and the products according to the invention based on corn wax are described in more detail below.

The process according to the invention for producing a corn wax oxidate (O) comprises the steps (or consists of the steps): ii) providing a corn wax (MW), ii) providing a mixture (M) of chromium trioxide and sulfuric acid; iii) performing the oxidation of the corn wax (MW) by reacting the corn wax (MW) with the mixture (M) to obtain a corn wax oxidate (O); iv) ending the reaction and allowing the reaction mixture obtained in step iii) to stand until the organic phase has separated from the aqueous phase; v) separation of the organic phase; vi) optionally removing residues containing chromium compounds from the organic phase in order to obtain the corn wax oxidate (O) in a purified form; vii) optionally repeating the sequence of steps ii) to vi) once or several times, using the corn wax oxidate (O), optionally in purified form, instead of the corn wax (MW).

The corn wax (MW) provided in step i) can be any corn wax.

If a low to medium acid number of the corn wax oxidate (O) is desired, for example 50 mg KOFI/g or lower, the corn wax (MW) can have a proportion of multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having 8 to 20 carbon atoms, from to up to 25% by weight, preferably up to 15% by weight, more preferably up to 10% by weight, preferably up to 5% by weight, particularly preferably up to 3% by weight, based on the total weight of corn wax (MW). Typically, the cornwax (MW) has a level of multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having from 8 to 20 carbon atoms greater than 0.1% by weight.

In this case, the desired proportion of multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having 8 to 20 carbon atoms can already be present in the raw corn wax, but can also be adjusted by pretreating the corn wax. Preferably, the portion is already present in the raw corn wax (MW). In this case it is preferred that the cornwax (MW) is not pretreated.

If, on the other hand, the proportions of multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having 8 to 20 carbon atoms are well above 25% by weight, it can be advantageous to pretreat the corn wax (MW) before providing it in step i). In this case, it is advantageous if the pre-treatment does not include saponification of the esters contained in the corn wax (MW).

Instead, extraction of the multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having from 8 to 20 carbon atoms with one or more organic solvents is preferred, the extraction is carried out until the desired proportion of multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having 8 to 20 carbon atoms is reached. Any organic solvent that can dissolve oils and fats is suitable for this purpose, for example ethyl acetate or acetone, preferably ethyl acetate.

The multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having 8 to 20 carbon atoms are preferably di- and tri-glycerides of aliphatic carboxylic acids having 8 to 20 carbon atoms, especially oils naturally present in corn , especially corn oil.

Accordingly, extraction with an organic solvent can involve de-oiling. In this case, the proportion of multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having 8 to 20 carbon atoms can also be referred to as the oil content of the corn wax.

Preferably, the cornwax (MW), regardless of the proportion of multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having from 8 to 20 carbon atoms in the raw state, is never pretreated prior to oxidation by saponification.

Preferred are corn waxes (MW) comprising a mixture of linear esters having a total number average carbon chain length of from 45 to 55 atoms, preferably from 47 to 53 carbon atoms. Furthermore, corn waxes (MW) are preferred, which comprises a mixture of linear esters, of which at least 30% by mass, preferably at least 40% by mass, particularly preferably at least 50% by mass, have a total carbon chain length of at most 52 carbon atoms, preferably of have 40 to 52 carbon atoms.

Furthermore, the corn wax (MW) preferably has an acid number of less than 20 mg KOH/g, more preferably less than 15 mg KOH/g, preferably less than 10 mg KOH/g, particularly preferably from 1 to 8 mg KOH/g on. In addition, the corn wax (MW) preferably has a saponification number of less than 150 mg KOH/g, more preferably less than 120 mg KOH/g, preferably from 30 to 100 mg KOH/g, particularly preferably from 60 to 95 mg KOH/g.

The mixture (M) of chromium trioxide and sulfuric acid provided in step ii) can be any mixture as long as it is capable of oxidizing oxidizable components of corn wax. Such mixtures of chromium trioxide and sulfuric acid are often also referred to as chromosulphuric acid. The sulfuric acid is preferably concentrated sulfuric acid with a sulfuric acid content of at least 90% by weight, preferably at least 96% by weight, particularly preferably at least 99% by weight. This can optionally be fuming sulfuric acid, i.e. additionally contain sulfur trioxide. The concentration of chromium trioxide in the mixture (M) is preferably 50 to 200 g/l, particularly preferably 70 to 150 g/l, very particularly preferably 80 to 120 g/l.

In step iii) of the process according to the invention, the corn wax (MW) is oxidized by reacting the corn wax (MW) with the mixture (M) in order to obtain a corn wax oxidate (O). The reaction is preferably carried out with stirring and at a temperature of from 70 to 200.degree. C., more preferably from 80 to 150.degree. C., preferably from 90 to 140.degree. C., particularly preferably from 105 to 130.degree.

The weight ratio of the total chromium trioxide used to the corn wax used (MW) is preferably from 1:6 to 3:1, in particular from 1:5 to 2:1, particularly preferably from 2:5 to 6:5. When the ratio is less than 1:6, the level of oxidation is too low to cause significant lightening of the cornwax. If the ratio is greater than 3:1, the cleavage of the ester bonds takes place to a particularly large extent, so that, depending on the other conditions, it can be more difficult to maintain the desired acid numbers in the product. When carrying out step vii) of the process according to the invention, the weight ratio of chromium trioxide used to corn wax used (MW) is preferably less than 6:5 each time step iii) is carried out. This step iii) can optionally be subdivided into several steps. For example, step iii) can include presenting the mixture (M) and then adding the corn wax (MW). Alternatively, step iii) may include introducing the corn wax (MW) and then adding the mixture (M). In these cases, the respective second component (MW) or (M) can be added, for example, in portions, continuously or in a batch, preferably in portions or continuously, particularly preferably in portions.

In embodiments in which the reaction in step iii) is carried out at a temperature of 70 to 200°C, the temperature of the corn wax (MW) and/or the mixture (M) can optionally deviate from the reaction temperature during the addition and only after C., more preferably from 80 to 150.degree. C., preferably from 90 to 140.degree. C., particularly preferably from 105 to 130.degree. C., after the addition of the second component has taken place.

For example, the temperature during the addition can be from 60 to 150.degree. C., preferably from 70 to 130.degree. C., particularly preferably from 80 to 110.degree. Preferably, the corn wax (MW) is in molten form during addition.

In one embodiment, the provided mixture (M) of chromium trioxide and sulfuric acid is presented and heated to a temperature of 60 to 150 ° C, preferably from 70 to 130 ° C, particularly preferably 80 to 110 ° C, and the corn wax (MW) in solid state added in portions. After the addition is complete, the temperature is adjusted to 70 to 200° C., preferably from 80 to 150° C., preferably from 90 to 140° C., particularly preferably from 105 to 130° C., and the oxidation is carried out.

In another embodiment, the provided mixture (M) of chromium trioxide and sulfuric acid is introduced and heated to a temperature of 60 to 130°C, and the corn wax (MW) in a molten state, preferably at a temperature of 60 to 150°C, preferably from 70 to 130 °C, especially preferably 80 to 110 ° C, added in portions. After the addition is complete, the temperature is adjusted to 70 to 200° C., preferably from 80 to 150° C., preferably from 90 to 140° C., particularly preferably from 105 to 130° C., and the oxidation is carried out.

In a further embodiment, the corn wax (MW) is initially taken and melted at a temperature of 60 to 150° C., preferably 70 to 130° C., particularly preferably 80 to 110° C., and the mixture (M) of chromium trioxide and sulfuric acid is melted in portions not tempered added. After the addition is complete, the temperature is adjusted to 70 to 200° C., preferably from 80 to 150° C., preferably from 90 to 140° C., particularly preferably from 105 to 130° C., and the oxidation is carried out.

In another embodiment, the corn wax (MW) is initially taken and melted at a temperature of 60 to 150° C., preferably 70 to 130° C., particularly preferably 80 to 110° C., and the mixture (M) of chromium trioxide and sulfuric acid in portions added hot, preferably at a temperature of 60 to 150 °C, preferably from 70 to 130 °C, particularly preferably 80 to 110 °C. After the addition is complete, the temperature is adjusted to 70 to 200° C., preferably from 80 to 150° C., preferably from 90 to 140° C., particularly preferably from 105 to 130° C., and the oxidation is carried out.

In a further embodiment, corn wax (MW) and the mixture (M) of chromium trioxide and sulfuric acid are initially introduced together at room temperature and slowly raised to a temperature of 70 to 200° C., preferably 80 to 150° C., preferably 90 to 140° C , particularly preferably heated from 105 to 130 ° C, and carried out the oxidation at this temperature.

At least the oxidation at 70 to 200° C., 80 to 150° C., 90 to 140° C., or 105 to 130° C., preferably also the addition of the corn wax (MW) and/or the mixture (M) takes place with stirring . The stirring can be done in any way, for example with a mechanically operated stirrer, or a magnetically operated stirrer. Preferably, stirring is done with a mechanically operated stirrer, particularly preferably with a mechanically operated stirrer comprising a KPG stirrer.

The stirring speed in step iii) is preferably in a range from 100 to 500 rpm (revolutions per minute), more preferably from 120 to 300 rpm, most preferably from 170 to 250 rpm, since at a stirring speed below 100 rpm, the mixing required for efficient oxidation might not be present and at a stirring speed of more than 500 rpm there is an increased risk of the formation of an emulsion that can no longer be separated.

The oxidation of the corn wax in step iii) preferably takes place over a period of at least 30 minutes, more preferably 45 minutes to 12 hours, even more preferably 1 to 8 hours, preferably 2 to 5 hours, particularly preferably 3 to 4.5 hours .

In addition, it is advantageous if no oxidation promoters are added to the reaction mixture of corn wax (MW) and mixture (M), since these can often lead to cleavage of the ester bonds and therefore can increase the acid number in the corn wax oxidate (O).

Preferably, therefore, no oxidation promoters, in particular no oxidation promoters such as emulsifiers (e.g. alkanesulfonates, fluorinated alkanesulfonates), surfactants, polymeric surfactants, nitrogen-containing cationic surfactants, phase transfer catalysts, Fenton reagents, metal salts, hydrochloric acid or the like are used in the oxidation.

After the desired reaction time has been reached, the reaction is ended in step iv) and the reaction mixture is allowed to stand until the organic phase has separated from the aqueous phase. By "terminating the reaction" it is meant that stirring is stopped and heating is stopped. Here, the separation of the floating organic phase, containing the corn wax oxidate (O), from the sinking aqueous phase, containing sulfuric acid and chromium compounds, begins. Optionally, before the reaction mixture is left to stand, it can be transferred to a device in which, after the organic phase has been separated from the aqueous phase, the organic phase can be separated off more easily. An example of such a device is a separating funnel. Other devices for this purpose are known to those skilled in the art and applicable here.

The time required to reach the phase boundary depends on the acid number. Surprisingly, it was observed for the process according to the invention that the organic phase was separated from the aqueous phase by a clear phase boundary shortly after the “end of the reaction” in step iv). With acid numbers in the range of 20-50 mg KOH/g, a clear phase boundary could be observed with a separation time of less than 1 minute. With acid numbers > 50 mg KOH/g this was the case within a few seconds.

The formation of a phase boundary after the "end of the reaction" could even be observed at very low acid numbers of around 10 mg KOH/g and is rather atypical for waxes oxidized by chromic sulfuric acid. Thus, due to the synthesis procedure described, a phase boundary can only be observed in rice waxes from an acid number of approx. 20 mg KOH/g and in montan waxes only from an acid number of approx. 50 mg KOH/g under otherwise identical conditions. This is a clear advantage of corn wax oxidates (O) compared to oxidates of other natural waxes from both an economic and an ecological point of view.

In step v), the organic phase containing the corn wax oxidate is separated off. This can be done, for example, using a separating funnel. Alternatively, the floating organic phase can be skimmed off using appropriate technical means.

It is also possible to pour off the organic phase over the edge of the vessel. Ways of separating organic phases from aqueous phases after a phase separation are known in principle to the person skilled in the art and can be used here. Furthermore, the separated organic phase containing the corn wax oxidate can optionally be worked up further in step vi) in order to remove residues containing chromium compounds from the organic phase and thus obtain the corn wax oxidate in purified form.

The work-up can be carried out in any way that is suitable for separating polar and/or water-soluble substances from organic substances. For example, the organic phase can be chromatographically purified or filtered through silica gel.

Residues containing chromium compounds are preferably removed by washing the organic phase with an aqueous solution of oxalic acid and/or sulfuric acid. Alternatively, residues containing chromium compounds can preferably be removed by washing the organic phase with water. Alternatively, residues containing chromium compounds can preferably be removed by centrifuging the organic phase.

“Washing” here means the mixing of the organic phase with the respective agent for washing and subsequent phase separation according to steps iv) and v).

In a preferred embodiment, residues containing chromium compounds are removed by washing the organic phase once or multiple times with an aqueous solution of oxalic acid and sulfuric acid, followed by washing the organic phase once or multiple times with water.

In a further preferred embodiment, residues containing chromium compounds are removed by washing the organic phase once or several times with an aqueous solution of oxalic acid and sulfuric acid, followed by centrifuging the organic phase. In a further preferred embodiment, residues containing chromium compounds are removed by washing the organic phase once or several times with water, followed by centrifuging the organic phase.

In a particularly preferred embodiment, residues containing chromium compounds are removed by washing the organic phase once or multiple times with an aqueous solution of oxalic acid and sulfuric acid, followed by washing the organic phase once or multiple times with water, followed by centrifuging the organic phase.

Optionally, in step vii), the sequence of steps ii) to vi) can be repeated, using the corn wax oxidate (O), optionally in purified form, instead of the corn wax (MW). Preferably, the sequence of steps ii) to vi) is not repeated.

In a preferred embodiment, the process according to the invention is a process for preparing corn wax oxidates (O) comprising the steps: i) providing a corn wax (MW), preferably a de-oiled corn wax (MW); ii) providing a mixture (M) of chromium trioxide and sulfuric acid; iii) carrying out the oxidation of the corn wax (MW) by reacting the corn wax (MW) with the mixture (M) while stirring and at a temperature of 70 to 200°C, preferably 80 to 150°C, preferably 90 to 140° C, more preferably from 105 to 130°C to obtain a corn wax oxidate (O); iv) ending the reaction and allowing the reaction mixture obtained in step iii) to stand until the organic phase has separated from the aqueous phase; v) separation of the organic phase; vi) optionally removing residues containing chromium compounds from the organic phase in order to obtain the corn wax oxidate (O) in a purified form; vii) optionally repeating the sequence of steps ii) to vi), using the corn wax oxidate (O), optionally in purified form, instead of the corn wax (MW), the oxidation in step iii) being preferred over a period of at least 30 minutes 45 minutes to 12 hours, more preferably 1 to 8 hours, preferably from 2 to 5 hours, most preferably from 3 to 4.5 hours.

In this embodiment, particularly targeted iodine color numbers, measured according to DIN 6162 (2014) of less than 6, often less than 5, for example less than 2, and/or yellowness indices, measured according to ASTM E 313-20 of less than 40, often less than 30, for example less than 15 can be achieved.

Another subject of the invention is a corn wax oxidate (O) obtainable by reacting corn wax (MW) with a mixture (M) of chromium trioxide and sulfuric acid. The corn wax oxidate (O) preferably has an acid number which is greater than that of the corn wax used (MW).

The corn wax oxidate (O) according to the invention preferably has an acid number, measured according to ISO 2114 (2002), from about 10 to about 170 mg KOFI/g, more preferably from 10 to 140 mg KOFI/g, more preferably from 11 to 130 mg KOFI/ g, even more preferably from 15 to 110 mg KOFI/g. In one embodiment, the corn wax oxidate (O) according to the invention has an acid number of about 10 to below 20 mg KOH/g.

In an alternative embodiment, the corn wax oxidate (O) according to the invention has an acid number of about 20 to about 50 mg KOFI/g. In a further alternative embodiment, the corn wax oxidate (O) according to the invention has an acid number, measured according to ISO 2114 (2002), of more than 50 to about 170 mg KOFI/g. In a further embodiment, the corn wax oxidate according to the invention (O) has an acid number of less than 140 mg KOFI/g, preferably less than 110 mg KOFI/g, more preferably less than 60 mg KOH/g, particularly preferably less than 40 mg KOH/g, particularly preferably less than 20 mg KOH/g.

Depending on the degree of conversion of the esters, the corn wax oxidate according to the invention contains genuine esters (C42-C60). "Genuine esters" are understood here to mean residual portions of the wax esters originally present in the raw wax that are not affected by the reaction.

Another subject of the invention is a corn wax oxidate (O) with an acid number, measured according to ISO 2114 (2002), from about 10 to about 170 mg KOH/g, the ratio of the proportion by weight of the genuine wax ester of 46 carbon atoms to the proportion by weight of the genuien wax ester of 52 carbon atoms is greater than 1. This corn wax oxidate (O) can be prepared by a process according to claim 1.

The corn wax oxidate (O) according to the invention is preferably characterized in that the acid number of the corn wax oxidate (O) is greater than that of the corn wax (MW).

Furthermore, the corn wax oxidate (O) according to the invention, in particular if it was produced using a process according to claim 1, preferably has an iodine color number of less than 6, more preferably less than 5, even more preferably less than 3, preferably less than 2, particularly preferably less than 1.5 (measured according to DIN 6162 (2014)). Alternatively, the corn wax oxidate (O) according to the invention preferably has a yellowness index of less than 50, more preferably less than 30, even more preferably less than 20, preferably less than 15, particularly preferably less than 10 (measured according to ASTM E 313 - 20).

The corn wax oxidate (O) according to the invention also preferably has a proportion of multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having 8 to 20 carbon atoms of less than 5% by weight, more preferably less than 3% by weight, most preferably less as 1% by weight based on the total weight of the corn wax oxidate (O). In one embodiment, the corn wax oxidate (O) contains a) from 3 to 40% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic carboxylic acids having from 8 to 36 carbon atoms; b) from 0% to 10% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic alcohols having from 24 to 36 carbon atoms; c) from 0 to 5% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic dicarboxylic acids having from 10 to 30 carbon atoms; d) 30 to 97% by weight, based on the total weight of the corn wax oxidate (O), genuine esters having 40 to 66 carbon atoms; and e) 0 to 30% by weight, based on the total weight of the corn wax oxidate (O), other natural components contained in the corn wax, the sum of a), b), c), d) and e) being 100% by weight. % based on the total weight of the corn wax oxidate (O).

In a preferred embodiment, the corn wax oxidate (O) contains a) 3 to 15% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic carboxylic acids having 8 to 36 carbon atoms; b) from 0% to 7% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic alcohols having from 24 to 36 carbon atoms; c) from 0% to 4% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic dicarboxylic acids having from 10 to 30 carbon atoms; d) 65 to 97% by weight, based on the total weight of the corn wax oxidate (O), genuine esters having 40 to 66 carbon atoms; and e) 0 to 15% by weight, based on the total weight of the corn wax oxidate (O), other natural components contained in the corn wax, the sum of a), b), c), d) and e) being 100% by weight. % based on the total weight of the corn wax oxidate (O).

In a preferred embodiment, the corn wax oxidate (O) contains a) 3 to 10% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic carboxylic acids having 8 to 36 carbon atoms; b) from 0% to 5% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic alcohols having from 24 to 36 carbon atoms; c) from 0 to 3% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic dicarboxylic acids having from 10 to 30 carbon atoms; d) 75 to 97% by weight, based on the total weight of the corn wax oxidate (O), genuine esters having 40 to 66 carbon atoms; and e) 0 to 15% by weight, based on the total weight of the corn wax oxidate (O), other natural components contained in the corn wax, the sum of a), b), c), d) and e) being 100% by weight. % based on the total weight of the corn wax oxidate (O).

The invention also provides a corn wax oxidate (O) with an acid number of less than 50 mg KOH/g and a proportion of multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having 8 to 20 carbon atoms of less than 5% by weight, based on the total weight of cornwax oxidate (O) containing: a) from 3% to 25% by weight, based on the total weight of cornwax oxidate (O), of free aliphatic carboxylic acids having from 8 to 36 carbon atoms; b) from 0% to 10% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic alcohols having from 24 to 36 carbon atoms; c) from 0 to 5% by weight, based on the total weight of the corn wax oxidate (O), of free aliphatic dicarboxylic acids having from 10 to 30 carbon atoms; d) 50 to 97% by weight, based on the total weight of the corn wax oxidate (O), genuine esters having 40 to 66 carbon atoms; and e) 0 to 15% by weight, based on the total weight of the corn wax oxidate (O), other natural components contained in the corn wax, the sum of a), b), c), d) and e) being 100% by weight. % based on the total weight of the corn wax oxidate (O).

Lignoceric acid is preferably present in the corn wax oxidate (O) at a maximum of 5% by weight, particularly preferably at a maximum of 3% by weight, based on the total weight of the corn wax oxidate (O). The weight fractions and chain length distributions can be measured, for example, using gas chromatography.

Furthermore, the corn wax oxidates according to the invention typically have a dropping point, measured according to DIN ISO 2176 (1997), between 70.degree. C. and 90.degree. C., preferably between 75.degree. C. and 80.degree.

The corn wax oxidates according to the invention preferably have a needle penetration number (NPZ) measured according to DIN 51579 (2010) of less than 10 mm ^-1 , preferably less than 6 mm ^-1 , particularly preferably less than 4 mm ^-1 , very particularly preferably less than 3 mm ^-1 .

The oxidation of the corn wax preferably increases the saponification number measured according to DIN ISO 3681 (2019) by at most 70%, preferably by at most 40%, particularly preferably by at most 30%. The increase in the saponification number can be explained mechanistically by the cleavage of the wax esters and the subsequent oxidation of the wax alcohols to acids. In addition, some unsaturated carbon-carbon bonds are split by the oxidizing agent and also oxidized to acids.

The saponification number is therefore also a measure of the oxidation that has actually taken place, in contrast to saponification, in which the saponification number does not change, as is known, and in contrast to other bleaching processes, in which the product only becomes lighter. For example, the bleaching of corn wax with hydrogen peroxide does not bring about any chemical modification of the wax in the sense of the invention, since here only discoloring impurities and secondary components are removed without the actual wax structure being changed.

The corn wax oxidate (O) according to the invention is typically characterized by particularly good thermal stability, measured according to DIN 51006 (2005) with a mass loss of less than 50%, preferably less, until a temperature of 300° C. (heating rate: 5° C./min) is reached 20%, particularly preferably less than 10%. Another subject of the invention is an esterified corn wax oxidate (E) produced by esterification or reaction of the corn wax oxidate (O) described above with an alcohol. Preferred alcohols are polyhydric alcohols, for example ethylene glycol, butylene glycol, glycerol, diglycerol, trimethylolpropane, pentaerythritol or sorbitol, etc.. In the esterification, a weight ratio of alcohol to corn wax oxidate (O) of 1:100 to 1:5 is particularly preferred 1:50 to 1:10, very particularly preferably 1:20 to 1:12.

In addition to the renewable raw material base, the esterified products are preferably characterized by particularly good thermal stability, measured according to DIN 51006 (2005) with a mass loss of less than 15% before a temperature of 300° C. (heating rate: 5° C./min) is reached less than 10% off. The esterified products preferably have an acid number of less than 40 mg KOH/g, particularly preferably less than 30 mg KOH/g, very particularly preferably less than 20 mg KOH/g The invention also relates to the use of the corn wax oxidates according to the invention (O ) or the saponified corn wax oxidates according to the invention (V) or the esterified corn wax oxidates according to the invention (E) for agricultural or forestry purposes, as an additive in the

Plastics processing, in care products, in printing inks and/or in paints.

Another object of the invention is a saponified corn wax oxidate (V) produced by saponifying the above-described corn wax oxidate (O) or the above-described esterified corn wax oxidate (E) with a basic metal salt selected from the group consisting of metal hydroxides (e.g. NaOH, KOH, Ca( OH)2 and Zn(OH)2, etc.), metal oxides (e.g. CaO, etc.), metal carbonates (e.g. Na2CO3, CaC03, etc.) or with aqueous bases (e.g. NaOH, KOH, etc.). Alkali metal hydroxides and/or alkaline earth metal hydroxides, in particular NaOH, KOH and/or Ca(OH) 2 , are preferred. Ca(OH) 2 is very particularly preferred.

In the hydrolysis, a weight ratio of basic metal salt to corn wax oxidate (O) of from 1:100 to 1:5, particularly preferably from 1:50 to 1:10, is preferably chosen. Corresponding manufacturing instructions can be found, for example, in DE4019167 or in EP1010728. In addition to the renewable raw material base, the saponified products are preferably characterized by particularly good thermal stability, measured according to DIN 51006 (2005) with a mass loss of less than 10% until a temperature of 300° C. is reached (heating rate: 5° C./min). less than 5% off. The hydrolyzed products preferably have an acid number of less than 40 mg KOH/g, more preferably less than 25 mg KOH/g, most preferably less than 15 mg KOH/g

Another subject of the invention is the use of corn wax (MW) for the production of a natural wax oxidate by oxidation with a mixture (M) of chromium trioxide and sulfuric acid. The invention is explained in more detail by the following examples, Figures 1-3 and claims.

Substance characterization The standard methods listed in Table 1, which are also used in the characterization of montan waxes and montan wax derivatives, are used to determine the characteristics of corn wax, corn wax oxidates and other corn wax derivatives. Table 1

The chain length distributions of the components of the corn wax oxidates were determined using gas chromatography. Wax acids and wax alcohols with carbon chain lengths between C6 and C36 served as comparison substances.

Wax esters with C44 to C58 were prepared by combining the model substances. In order to identify the peaks of the gas chromatograms of the corn waxes, a defined quantity of the individual components was added to a wax sample and a clear increase in the area of the corresponding peak was observed. The measurement conditions are shown in Table 2.

Table 2

The raw materials used were two different corn waxes (MW 1-2) as examples according to the invention and two rice bran waxes (RBW 1-2) as comparative examples Sugar cane wax (ZRW) and a carnauba wax (CW), each used in the raw state. The raw properties of the corn waxes and the comparative waxes are shown in Table 3.

The rice bran waxes were chosen in such a way that their acid numbers, saponification numbers and oil contents have values that are between those of the corn waxes used. The acid numbers of sugar cane wax and carnauba wax are naturally higher than the acid number of corn wax or rice bran wax. Table 3 (Methods, abbreviations and units in Table 1)

^* Comparative example

Examples 1 to 8 and Comparative Examples 9 to 15

The amount of chromium trioxide given in Table 4 was placed in 96% sulfuric acid (concentration: 100 g CrO 3 /L) and heated to 100° C. in a 3 L reaction vessel with stirrer, temperature sensor, dropping funnel and reflux condenser. Then melted (90°C) natural wax in the raw state was added in portions. The temperature of the reaction mixture was adjusted to 110° C. and stirred with a KPG stirrer at about 200 rpm for 4 h. Heating and stirring were stopped. As soon as the phases have separated, the aqueous phase was separated off. This operation is carried out twice in Examples 3 and 7, and three times in Example 8. In Examples 9, 10, 12, 14 and 15 (Comparative Examples) no phase separation took place. Accordingly, the properties of the natural wax oxidates could not be examined.

The organic phase was freed from chromium residues by washing with an aqueous solution of oxalic acid and sulfuric acid and then by washing with water, drained into warm centrifuge tubes and centrifuged. The oxidation conditions and properties of the corn wax oxidates are given in Table 4.

The chain length distribution measured for Example 2 is shown in Figure 1 and for Example 7 in Figure 2, with free acids shown with open bars and esters with filled bars.

The chain length distribution of the esters in the corn wax used (open bars) is shown in FIG. The number average chain length was determined to be 50 carbons.

In comparison, FIG. 3 also shows the chain length distribution of a rice bran wax with a number-average chain length of 53 carbon atoms (filled bars). The carbon chain length is plotted on the abscissa, and the proportion of the particular carbon chain length in the total chain length distribution in mass % is plotted on the ordinate, determined in each case from the peak areas of the gas chromatogram.

It can be seen from Examples 1 to 8 that the corn wax oxidates have a light inherent color with an iodine color number of less than 5 and a yellowness index of less than 30. At the same time, acid numbers were achieved in a wide range, ranging from a very low value of 11 mg KOFI/g to a high value of 128 mg KOFI/g.

In contrast, in Comparative Examples 9, 10, 12, 14 and 15 in which rice bran wax, cane wax and carnauba wax were used, phase separation did not occur, so that no product could be isolated. This is surprising, since the acid number, the saponification number, the oil content and the amount of natural wax used, which was used for comparison purposes, are close to the corresponding values for the corn wax used. Although phase separation was observed in Comparative Examples 11 and 13, this lasted 300 minutes in the case of rice bran wax, despite the relatively low oil content (4.3% by weight) and the relatively high acid number of the product (35 mg KOH/g). (5 hours) lasted. With similar acid numbers of the rice bran wax oxidate (27 and 36 mg KOH/g), the phase separation in Examples 4 and 5 took place much faster despite the significantly higher oil content of the corn wax (9.7% by weight). In the case of the sugar cane wax, it took 10 minutes for phase separation despite the relatively high acid number of the product (47 mg KOH/g). No phase separation at all could be observed with carnauba wax. At the same time, much better iodine color numbers and yellowness indices of the corn wax oxidates were observed.

Table 4:

^* Comparative example

Table 4 (continued):

^* Comparative example Table 4 (continued):

From this it can be seen that the chromo-sulfuric acid oxidation of corn wax (MW) can produce a wider range of high-quality natural wax oxidates than is usual with rice bran wax, sugar cane wax or carnauba wax.

Examples 16 to 19:

The corn wax oxidates from Examples 3, 5, 6 and 7 are melted under a nitrogen atmosphere in a 1 L reaction vessel with stirrer, temperature sensor, dropping funnel and reflux condenser, and the amount of Ca(OH) 2 given in Table 5 is added. The reaction mixture is stirred until the stated acid number is reached and then the reaction mixture is pressure-filtered while hot.

Table 5

From Examples 16 to 19 it can be seen that saponified products with low acid numbers of less than 15 mg KOH/g can be produced by saponification of the corn wax oxidates with Ca(OH) 2 , which are particularly suitable for applications which require high thermal stability .

Examples 20 to 22

The corn wax oxidate from example 7 is melted under a nitrogen atmosphere in a 1 l reaction vessel fitted with a stirrer, temperature sensor, dropping funnel and reflux condenser, and the amount of alcohol and 0.1 g of methanesulfonic acid given in Table 6 are added. The reaction mixture is stirred until the stated acid number is reached, the water formed is distilled off and the reaction mixture is then pressure-filtered while hot. Table 6

From Examples 20 to 22 it can be seen that esterified products with low acid numbers of less than 20 mg KOH/g can be easily prepared by esterification of the corn wax oxidates with ethylene glycol, glycerol or pentaerythritol, which are particularly suitable for applications that require high thermal stability make..

Claims

patent claims

1. A process for preparing corn wax oxidates (O comprising the steps of: i) providing a corn wax (MW), ii) providing a mixture (M) of chromium trioxide and sulfuric acid; iii) performing the oxidation of the corn wax (MW) by reacting the corn wax (MW) with the mixture (M) to obtain a corn wax oxidate (O); iv) ending the reaction and allowing the reaction mixture obtained in step iii) to stand until the organic phase has separated from the aqueous phase; v) separation of the organic phase; vi) optionally removing residues containing chromium compounds from the organic phase in order to obtain the corn wax oxidate (O) in a purified form; vii) optionally repeating the sequence of steps ii) to vi), using the corn wax oxidate (O), optionally in purified form, instead of the corn wax (MW).

2. The method according to claim 1, wherein the corn wax oxidate (O) has an increased acid number compared to the starting material.

3. The method according to claim 1 or 2, wherein in the method no further

Waxes other than corn wax can be used.

4. Process according to at least one of claims 1 to 3, wherein the weight ratio of total chromium trioxide used to corn wax used (MW) is from 1:6 to 3:1.

5. The method according to at least one of claims 1 to 4, wherein the removal of residues containing chromium compounds is carried out according to step vi) and comprises at least one, preferably at least two, particularly preferably all of steps via), vib) or vic): via) washing the organic phase with an aqueous solution of oxalic acid and/or sulfuric acid; vib) washing the organic phase with water; vic) centrifuging the organic phase.

6. The method according to any one of claims 1 to 5, wherein the corn wax (MW) has a content of multiple esters formed from polyhydric alcohols and aliphatic carboxylic acids having 8 to 20 carbon atoms of up to 25% by weight.

7. The method according to at least one of claims 1 to 6, wherein the sulfuric acid is a concentrated sulfuric acid with a sulfuric acid content of at least 90 wt .-%.

8. The method according to at least one of claims 1 to 7, wherein the reaction in step iii) is carried out with stirring and at a temperature of 70 to 200 ° C.

9. The method according to at least one of claims 1 to 8, wherein the concentration of chromium trioxide in the mixture (M) is from 50 to 200 g/l.

10. The method according to at least one of claims 1 to 9, wherein the oxidation in step iii) takes place over a period of at least 30 minutes, preferably over a period of 1 to 8 hours, particularly preferably from 2 to 5 hours, very particularly preferably from 3 to 4.5 is carried out.

11. The method according to at least one of claims 1 to 10, wherein the corn wax (MW) has an acid number, measured according to ISO 2114 (2002), of less than 20 mg KOH/g.

12. Corn wax oxidate (O) obtainable by reacting corn wax (MW) with a mixture (M) of chromium trioxide and sulfuric acid.

13. Corn wax oxidate (O) according to claim 12, obtainable by a process according to at least one of claims 1 to 11.

14. Corn wax oxidate (O) according to claim 12 or 13, wherein the corn wax oxidate has an acid number, measured according to ISO 2114 (2002), of about 10 to about 170 mg KOH/g.

15. Corn wax oxidate (O) having an acid number of about 10 to about 170 mg KOH/g, wherein the ratio of the weight fraction of the genuine esters with 46 carbon atoms to the weight fraction of the genuine esters with 52 carbon atoms is greater than 1.

16. Esterified corn wax oxidate (E) obtainable by reacting the

Corn wax oxidate (O) according to at least one of Claims 12 to 15 with an alcohol, preferably a polyhydric alcohol, particularly preferably ethylene glycol, butylene glycol, glycerol, diglycerol, trimethylolpropane, pentaerythritol or sorbitol.

17. Saponified corn wax oxidate (V) obtainable by saponifying the corn wax oxidate (O) according to any one of claims 12 to 15 or the esterified corn wax oxidate (E) according to claim 16 with a basic metal salt, preferably an alkali metal hydroxide and/or alkaline earth metal hydroxide, in particular preferably Ca(OH)2.

18. Use of the corn wax oxidate (O) according to at least one of claims 12 to 15, the saponified corn wax oxidate (V) according to claim 16 or the esterified corn wax oxidate (E) according to claim 17 for agricultural or forestry purposes, as an additive in plastics processing, in care products, in printing inks and/or in paints.

19. Use of corn wax (MW) for producing a natural wax oxidate by oxidation with a mixture (M) of chromium trioxide and sulfuric acid.