CS273474B1 - Method of epoxy resins' low-viscous reactive solvent preparation - Google Patents

Abstract

The invention is based on the use of a low-viscous epoxy resin reactive solvent prepared by boiling a mixture of cycloaliphatic ketones with monoethanolamine in a molar ratio of 1 : 1 under azeotropic water removal with the help of cyclohexane (or toluene), whereupon cyclohexane (or toluene) is distilled off the reaction mixture under normal pressure and the overhead distillates under a pressure of 3.33 kPa to a temperature of 90 degrees C, whereas cycloaliphatic ketones are understood as a mixture of 2, 3 and 4 methylcyclohexanones and cyclohexanone containing ketones of 70 to 89 % by weight.

Description

The present invention relates to a process for the preparation of a low viscosity reactive solvent of epoxy resins based on condensates of monoethanolamine of monoethanolamine.

To ensure good processability of epoxy resins, their lowest viscosity is required. This depends on the temperature, the relative molecular weight of the resin, its reactivity and the hardener, etc. In general, a reduction in viscosity can be achieved by the addition of low molecular weight substances. Organic solvents are volatile from the mixture. Glycidyl ether reactive solvents increase hardener consumption, increase exotherm and are harmful to health. Dibutylphthalate thinners have a high viscosity, often insufficient resistance to dry heat and various chemicals. Recently, benzyl alcohol has been used in the construction industry, but it reduces the heat resistance. The low viscosity results in better processability and bubble escape from the composition, easier mold filling and higher refillable. The optimum reactive solvent should have a strong dilution effect, guaranteed by its low viscosity up to 25 mPa · s at 25 ° C and low molecular weight at the highest possible boiling point. However, in order to maintain the original properties, the addition of the reactive solvent is as low as possible. An important requirement for a reactive solvent is that it contains a reactive group to participate in the cure while being as toxic as possible. Reactive solvents often increase the heat of reaction by their own reaction. In the case of, for example, acrylates, the double bond reacts 4 times faster with amines than epoxy resins, thereby limiting the size of possible casting or complicating technological conditions. The most effective reactive solvent is styrene. However, its use is abandoned for health reasons. Glycidyl ethers in turn have harmful effects on the skin and mucous membranes. Also, acrylates damage the respiratory mucosa. The danger of acrylates is strongly dependent on the molecular weight of the acrylates; the liquid causes skin inflammations, especially during long-term exposure. Conventional Diana epoxides provide curing with conventional hardeners solid, rigid, sometimes even brittle materials, which, in conjunction with materials with different volumetric thermal expansion, have considerable internal stress and often lead to cracking of the products. These drawbacks are particularly evident when applied to products of larger sizes with insufficient resistance to low temperatures, impact, etc. The use of reactive solvents usually results in flexibility.

We have now found that some of these problems can be solved by using a low-viscosity reactive solvent of epoxy pigs, obtainable by reacting cycloaliphatic ketones with ethanolamine in a 1: 1 molar ratio in the presence of cyclohexane or toluene as solvents for azeotropic drainage, then cyclohexane (toluene) under normal pressure and the rest under pressure

3.33 kPa to 90 ° C. Cycloaliphatic ketones are understood to mean a technical mixture of 2,3 and 4-methylcyclohexanones having a ketone content of 70 to 89% by weight. based on methylcyclohexanone. The product is a pale brown to reddish brown liquid with slight haze and mild turpentic odor. By dissolving in the epoxy resin, the haze disappears completely. The amine number ranges from 290 to 380, the viscosity at 25 ° C ranges from 0.014 to 0.021 Pa.s.

The reactive solvent thus obtained can be incorporated into the compositions as a separate component or as a solution thereof in an epoxy resin or hardener. Due to the low reactivity of the secondary amine group with the epoxy group, a slow increase in viscosity has to be expected.

The advantage of the solution according to the invention is to obtain a reactive solvent with low viscosity, which brings better processability and reduced viscosity of epoxy resins, furthermore health safety during further manipulation and the compositions in which it is contained.

CS 273474 Bl

The basic raw material for the preparation of the reactive solvent is technical methylcyclohexanone. It is available in two grades, but always as a mixture of its three isomers (2, 3, 4) and cyclohexanone (2 to 10% by weight). Cresols (up to 0.3% by weight), higher cycloaliphatic ketones, cyclohexane and cyclohexene (1% by weight) are all present in small amounts. Both qualities differ in the content of ketones in the said mixture from 70 to 89% by weight. The remainder (30 to 5 wt.%) Is methylcyclohexanol (mixture of isomers 2,3 and 4).

Technical methylcyclohaxanone is refluxed with conventional grade monoethanolamine under azeotropic dewatering with cyclohexane or toluene until the theoretical amount of water is separated. The starting ketones with ethanolamine are used in a 1: 1 molar ratio, based on the ketone content, the reaction proceeds quantitatively.

After the solvent has been distilled off, a small proportion of the ancestors is distilled off to 90 ° C at

3.33 kPa.

The formation of N-hydroxyethylimines and oxazolidines is known from the general reactions of the carbonyl group with 1,2-aminoalcohols. In the case of the reaction of cycloaliphatic ketones with ethanolamine, the products will be of the same type. The composition of the reaction mixture is not known, nor is the procedure by which the complicated reaction mixture can be analyzed.

For some applications, it is preferred that the reactive solvent contain a greater proportion of the reactive groups than is achieved by the process described. This can be solved by adding cyclohexanone to the starting ketone feedstock as seen in Example 3.

Example. 1

451 g (2.9 mol) of technical cyclohexanone with a ketone content of 72% by weight. 177 g (2.9 mol) of ethanolamine are boiled under azeotropic dewatering using 150 g of cyclohexane. The reaction is complete after separation of the theoretical amount of water (53 mL for 3 h). Most of the cyclohexanone was distilled off under normal pressure, and the front portion was distilled off under pressure

3.33 kPa to 90 ° 0 (36 g). 540 g of a light red-brown product are obtained with slight turbidity and terpenic odor. Amine number: 300.3 mg KOH / 1 g, Viscosity at 25 ° C: 0.0194 Pa.s. Homogenization of 90 g of epoxy resin having an average molecular weight of 388, a viscosity of 15.9 Pa.s / 25 ° C and 10 g of the product gives a resin with a viscosity of 2.79 Pa.s / 25 ° 0,

Example 2 ^R

392 g (2.9 mol) of technical methylcyclohexenone and a ketone content of 83% by weight; 177 g (2.9 mol) of ethanolamine are boiled under azeotropic dewatering using 150 g of cyclohexane. By following the procedure of Example 1, 477 g of a light brown product with a slight turbidity and terpenic odor are obtained. Amine number: 341.1 mg KOH / 1 g. Viscosity: 0.0174 Pa.s / 25 ° C. Homogenization of 90 g of epoxide resin having an average molecular weight of 395, a viscosity of 16.3 Pa.s / 25 ° C and 10 g of product yields a resin with a viscosity of 2.86 Pa.s / 25 ° 0.

Example 3

A mixture of 248 g (2.5 mol) of cyclohexanone (99%), 202 g (1.5 mol) of technical methyloyclohexanone (83%) and 244 g of ethanolamine (4 mol) was boiled under azeotropic dewatering of the reaction mixture. After 72 ml of water had been separated off, 578 g of a pinkish terpanic color product were obtained as described in Example 1. Amine number: 380.7 mg

KOH / 1 g, Viscosity: 0.0207 Pa.s / 25 ° C. Homogenization of 90 g of epoxy resin

CS _t 273474 Bl £

With a mean molecular weight of 400, a viscosity of 17.1 Pa.s at 25 ° C and 10 g of product, a resin having a viscosity of 3 »22 Pa.s / 25 ° C is obtained,

Claims (1)

SUBJECT OF THE INVENTION A process for preparing a low viscosity reactive solvent of epoxy resins, characterized in that a 1: 1 molar ratio of cycloallphatic ketones β monoethanolamine is boiled under azeotropic dewatering with cyclobexane or toluene, after which the cyclohexane or toluene are distilled off under normal pressure. 3.33 kPa to 90 ° C, wherein ee by cycloaliphatic ketones means a mixture of 2,3 and 4-methylcyclohexanones and an cyclohexanone having a ketone content of 70 to 89% by weight.