CS218835B1 - Process for the preparation of trivalent chromium complexes with organic acids - Google Patents

Abstract

The invention relates to a method for preparing complexes of trivalent chromium with organic acids, dissolved in non-polar solvents. These complexes are intended primarily for catalysis of the reaction of carboxylic acids with epoxides. The essence of the preparation method consists in melting chromium trichloride with an organic acid having 3-30 carbon atoms in the molecule, or with a mixture of such organic acids, in a molar ratio of 1:2 to 1:5 at a temperature of 100-250 °C. The melting continues until water and hydrogen chloride escape. After the reaction is complete, the melt is cooled and the product is isolated either directly in the form of a paste, or further processed into a powder, or dissolved in a high-molecular solvent or plasticizer to form a solution. If a solution of the complex is to be obtained, it is advantageous to add a high-boiling solvent with a boiling point of 200-350°C to the reaction mixture before the actual melting.

Description

The invention relates to a method for preparing complexes of trivalent chromium with organic acids, soluble in non-polar solvents. These complexes are intended primarily for catalyzing the reaction of carboxylic acids with epoxides.

The reaction between epoxides and organic acids yields beta-hydroxyesters as the product.

This reaction is industrially important, especially for di- or polyfunctional epoxides and di- or polyfunctional organic acids, because long-chain beta-hydroxyesters are formed, which can be used as paint raw materials or casting resins using di- or polyfunctional organic acids with 2-12 carbon atoms, or as rubber-like materials using di- or polyfunctional organic acids of polyolefinic character with 10-1000 carbon atoms, e.g. the so-called carboxyl-terminated liquid rubbers,

Without the presence of a catalyst, the reaction is very slow and is not industrially applicable. As catalysts for the above reaction, tertiary amines, phosphines, stibines and bismuthines, quaternary ammonium and phosphonium salts and hydroxides, thialcohols and thioethers, anexes, boron trifluoride and its adducts with ethers and amines are known. From chromium-based substances, various chromium soaps with aliphatic or naphthenic acids and mono and polynuclear complexes of trivalent chromium with substituted salicylic acids are used.

Chromium soaps, prepared in the classical way by precipitation of soluble chromium salts with soluble salts of organic acids, are very slightly soluble or insoluble in a mixture of organic acids with epoxides and are characterized by very low catalytic activity. It is more advantageous to use chromium complexes based on substituted salicylic acid, which do not cause, for example, homopolymerization of epoxides as tertiary amines and are catalytically very effective; however, their preparation is relatively expensive and difficult and they exhibit a certain induction period during the reaction.

The above-mentioned shortcomings are eliminated by the method of preparing complexes of trivalent chromium with organic acids according to the invention, the essence of which consists in melting chromium trichloride with an organic acid having 3-30 carbon atoms in the molecule, or with a mixture of such organic acids, at a temperature of 100-250 °C in a molar ratio of 1:2 to 1:5.

The melting continues until water and hydrogen chloride are released. After the reaction is complete, the melt is cooled and the product is isolated either directly in the form of a paste, or further processed into a powder, or dissolved in a high-molecular organic solvent or plasticizer to form a solution. In the latter case — isolation of the reaction product in the form of a solution — it is advantageous to add a high-boiling solvent, with a boiling point

200—350 °C, into the reaction mixture before melting begins. The complex solution is then available immediately after the reaction is complete.

Of the organic acids with 3-30 carbon atoms in the molecule, butyric, isobutyric, propionic, valeric, isovaleric, pivalic, caproic, caprylic, pelargonic, capric, undecyl, lauric, myristic, enanthic, palmitic, stearic, arachic, cyclohexanecarboxylic, acrylic, methacrylic, crotonic, elaidic, oleic, sorbic, linoleic, phenylacetic, naphthylacetic, benzoic, toluic, salicylic, diisopropylsalicylic, dimethylsalicylic, diethylsalicylic, methylethylsalicylic, cinnamic, hydrocinnamic, mesitylene, triphenylacetic, naphthoic, anthracenecarboxylic, etc. are particularly suitable for use in the preparation method according to the invention, in a molar ratio of chromium chloride to organic acid of 1:2 to 1:5. Several acids can also be used in any mutual ratio.

As high-boiling solvents, the following are used: -octane, isooctane, gasoline, kerosene, nonane, decane, undecane, dodecane, toluene, ethylbenzene, xylene, cumene, pseudocumene, mesitylene, indane, -diphenylmethane, chlorobenzene, dichlorobenzene, nitrobenzene, triphenylphosphate, tributylphosphate, tricreoylphosphate, amisol, dimethylsuccinate, diethylsuccinate, dibutylsuccinate, diethyloxalate, dimethyladipate, dioctyladipate, diethyladipate, dibutyladipate, dimethylphthalate, diethylphthalate, dibutylphthalate, dioctylphthalate, etc., or mixtures of the aforementioned solvents.

• - Testing of the catalytic activity of the product was carried out by determining the time required to reduce the original concentration of caproic acid (1 M) by half (t 1/2) during its reaction with phenylglycidyl ether (1 M) in a toluene solution in the presence of 1.5% by weight of the tested catalyst at 70 degrees Celsius. The loss of caproic acid depending on the concentration was monitored by titrating an aliquot of the reaction mixture with a 0.1 M solution of potassium hydroxide in ethanol against phenolphthalein as an indicator. The half-lives of the model reaction using the catalyst according to the invention were comparable or in many cases lower than the half-lives of the model reaction using diisopropylsalicylic acid complexes. The catalysts prepared according to the invention also did not show an induction period, or showed an induction period shorter than the conventional diisopropylsalicylic acid complexes.

The complexes prepared according to the invention are also stable for a long time, only the complexes of palmitic and stearic acid changed over time to a less active form, poorly soluble in non-polar organic solvents, which is probably caused by the transition of the complex to the form of chromium soap. Effective catalysts are also formed by mixtures of various organic acids with chromium trichloride at temperatures in the range of 100-250 °C, which allows the use of commercially available industrial acid mixtures for their preparation. In some applications, the liquid form of the catalyst may be more advantageous, which is obtained ^either by dissolving the solid product in an organic solvent, or by carrying out the reaction in the presence of a higher-boiling organic solvent or a plasticizer. The most active catalysts were formed at a molar ratio of chromium trichloride — organic acid of 1 : 3, violation of this ratio in both directions led to a decrease in catalytic activity. Determination of the molecular weight of the products by vapor osmometry showed that multinuclear complexes are formed.

Example 1

A mixture of 26.6 g (0.1 mol] of chromium trichloride hexahydrate and 0.3 mol of organic acid was melted in a porcelain dish until water and hydrogen chloride escaped. Then the melting was extended for another 30 minutes and after cooling the reaction mixture a waxy product or a solid green melt was obtained, which was crushed to a gray-green powder. The individual melting conditions and catalytic activity of the products are given in the following table:

acid total melting time (h) melting temperature (°c) catalytic activity t _1/2 (min)

butter 1.5 160 14 buttermilk 1.5 160 13 kapron 2 180 9 capryi 2 160 13 caprine 2 180 27 laurel 2 160 33 palmitic 3 180 75 stearate 2 180 28 oil 3 180 250 diesel loctite 3 180 24 diisopropylsalicylic acid 3 120 32 Example 2 where was the water leaking? and hydrogen chloride about 30—60 min and then the melting continued for 60 min. A mixture of 26.6 g 0.1 mol chloride hexahydrate After cooling, the product was -crushed into powder- chromium with a mixture acids A, B, C were green powder, whose catalytic activity melted in porcelain bowl at 160 °C until is shown in the following table: acid (mol) catalytic activity A B c t 1/2 (min)

naphtha oleate (0.1) caprylic (0.15) butyric (0.1) capric (0.2) lauric (0.15) capronic (0.1) ·* caprylic (0.1)

Example 3

A mixture of 26.6 g (0.1 mol) of chromium trichloride hexahydrate, 34.8 g (0.3 mol) of caproic acid and 40 g of dioctylphthalate was heated to 160 °C until hydrogen chloride was released (30 min). It was then heated for another 1 h at the above temperature and, after cooling, a dark green viscous solution was obtained, which, when determining the catalytic activity in a model reaction, showed T 1/2 = 16 min.

The chromium complexes prepared according to the invention can be used to catalyze the reaction between organic acids and epoxides of all types, i.e. monofunctional and polyfunctional, possibly containing other functional groups, and to prepare both low molecular weight beta-hydroxyesters and high molecular weight substances used as epoxy-based varnishes, epoxy casting resins or elastomers. The reaction proceeds poorly or does not proceed at all in a polar environment and therefore must be carried out ^either without a solvent or using non-polar organic solvents.

In addition to their main use as catalysts for the reaction between epoxides and organic acids, the complexes of trivalent iron with organic acids prepared by the method according to the invention can also be used to increase the conductivity of non-polar solvents used for the preparation of various solutions, such as polymer solutions applied mainly as adhesives. The increase in conductivity here prevents the formation of static electricity charges and possible discharges during individual stages of the technological preparation process - e.g. during mixing, kneading, etc. This reduces the risk of fire in these operations.

Claims (2)

SUBJECT Process for the preparation of chromium (III) complexes with organic acids soluble in non-polar organic solvents, in particular for the catalysis of the reaction of carboxylic acids with epoxides, characterized in that it melts at a temperature of 100-250 ° C in a molar ratio of 1: 2 to 1: 5 chromium trichloride with an organic acid having a carbon number of 3-30 or a mixture of such organic acids until water and hydrogen chloride escape, after which the melt is cooled and the reaction product is isolated in the form of a paste, powder or solution. 2. A process according to claim 1, wherein the reaction mixture is treated with a solvent having a boiling point of 200-350 [deg.] C. prior to melting, and the reaction product is obtained immediately after completion of the reaction and cooled as a solution thereof.